A Novel, Inexpensive Method to Monitor, Record, and Analyze Breathing Behavior During Normobaric Hypoxia Generated by the Reduced Oxygen Breathing Device.

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Temme, Leonard A; St Onge, Paul; Adams, Mark; Still, David L; Statz, Jonathan K; Williams, Steven T

2017-03-01

Since hypoxia remains one of the most important physiological hazards the aviation environment poses, military aviators are trained to recognize symptoms of hypoxia in order to implement appropriate safety procedures and countermeasures when hypoxia occurs. A widely used commercial instrument for hypoxia training, demonstration, and research is the Reduced Oxygen Breathing Device (ROBD). Here we describe a novel, inexpensive method to use the ROBD's breathing loop pressure (BLP) to measure respiration rate, a critically important response parameter for hypoxia. The ROBD can be controlled by a computer to export several variables including BLP, via the ROBD's RS232 port. An archived database was reanalyzed to assess the BLP data. New instrumentation added independent measures of respiration and expired oxygen and carbon dioxide; these measures were integrated with the ROBD output. Analysis of the archived data showed that the BLP reflected realistic breathing patterns. The new instrumentation integrated well with the ROBD, and independently supported the potential of the BLP as a valid measure of respiration. The ROBD's BLP data may provide a basis for a reliable, sensitive measure of respiration that is available at no additional cost. Reprint & Copyright © 2017 Association of Military Surgeons of the U.S.

Chemical Activation of the Hypoxia-Inducible Factor Reversibly Reduces Tendon Stem Cell Proliferation, Inhibits Their Differentiation, and Maintains Cell Undifferentiation.

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Menon, Alessandra; Creo, Pasquale; Piccoli, Marco; Bergante, Sonia; Conforti, Erika; Banfi, Giuseppe; Randelli, Pietro; Anastasia, Luigi

2018-01-01

Adult stem cell-based therapeutic approaches for tissue regeneration have been proposed for several years. However, adult stem cells are usually limited in number and difficult to be expanded in vitro, and they usually tend to quickly lose their potency with passages, as they differentiate and become senescent. Culturing stem cells under reduced oxygen tensions (below 21%) has been proposed as a tool to increase cell proliferation, but many studies reported opposite effects. In particular, cell response to hypoxia seems to be very stem cell type specific. Nonetheless, it is clear that a major role in this process is played by the hypoxia inducible factor (HIF), the master regulator of cell response to oxygen deprivation, which affects cell metabolism and differentiation. Herein, we report that a chemical activation of HIF in human tendon stem cells reduces their proliferation and inhibits their differentiation in a reversible and dose-dependent manner. These results support the notion that hypoxia, by activating HIF, plays a crucial role in preserving stem cells in an undifferentiated state in the "hypoxic niches" present in the tissue in which they reside before migrating in more oxygenated areas to heal a damaged tissue.

Chemical Activation of the Hypoxia-Inducible Factor Reversibly Reduces Tendon Stem Cell Proliferation, Inhibits Their Differentiation, and Maintains Cell Undifferentiation

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Alessandra Menon

2018-01-01

Full Text Available Adult stem cell-based therapeutic approaches for tissue regeneration have been proposed for several years. However, adult stem cells are usually limited in number and difficult to be expanded in vitro, and they usually tend to quickly lose their potency with passages, as they differentiate and become senescent. Culturing stem cells under reduced oxygen tensions (below 21% has been proposed as a tool to increase cell proliferation, but many studies reported opposite effects. In particular, cell response to hypoxia seems to be very stem cell type specific. Nonetheless, it is clear that a major role in this process is played by the hypoxia inducible factor (HIF, the master regulator of cell response to oxygen deprivation, which affects cell metabolism and differentiation. Herein, we report that a chemical activation of HIF in human tendon stem cells reduces their proliferation and inhibits their differentiation in a reversible and dose-dependent manner. These results support the notion that hypoxia, by activating HIF, plays a crucial role in preserving stem cells in an undifferentiated state in the “hypoxic niches” present in the tissue in which they reside before migrating in more oxygenated areas to heal a damaged tissue.

Exercise Improves Mood State in Normobaric Hypoxia.

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Seo, Yongsuk; Fennell, Curtis; Burns, Keith; Pollock, Brandon S; Gunstad, John; McDaniel, John; Glickman, Ellen

2015-11-01

The purpose of this study was to quantify the efficacy of using exercise to alleviate the impairments in mood state associated with hypoxic exposure. Nineteen young, healthy men completed Automated Neuropsychological Assessment Metrics-4(th) Edition (ANAM4) versions of the mood state test before hypoxia exposure, after 60 min of hypoxia exposure (12.5% O(2)), and during and after two intensities of cycling exercise (40% and 60% adjusted Vo(2max)) under the same hypoxic conditions. Peripheral oxygen saturation (Spo(2)) and regional cerebral oxygen saturation (rSo(2)) were continuously monitored. At rest in hypoxia, Total Mood Disturbance (TMD) was significantly increased compared to baseline in both the 40% and 60% groups. TMD was significantly decreased during exercise compared to rest in hypoxia. TMD was also significantly decreased during recovery compared to rest in hypoxia. Spo(2) significantly decreased at 60 min rest in hypoxia, during exercise, and recovery compared to baseline. Regional cerebral oxygen saturation was also reduced at 60 min rest in hypoxia, during exercise, and recovery compared to baseline. The current study demonstrated that exercise at 40% and 60% of adjusted Vo(2max) attenuated the adverse effects of hypoxia on mood. These findings may have significant applied value, as negative mood states are known to impair performance in hypoxia. Further studies are needed to replicate the current finding and to clarify the possible mechanisms associated with the potential benefits of exercise on mood state in normobaric hypoxia.

Hypoxia and hypoglycaemia in Ewing's sarcoma and osteosarcoma: regulation and phenotypic effects of Hypoxia-Inducible Factor.

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Knowles, Helen J; Schaefer, Karl-Ludwig; Dirksen, Uta; Athanasou, Nicholas A

2010-07-16

Hypoxia regulates gene expression via the transcription factor HIF (Hypoxia-Inducible Factor). Little is known regarding HIF expression and function in primary bone sarcomas. We describe HIF expression and phenotypic effects of hypoxia, hypoglycaemia and HIF in Ewing's sarcoma and osteosarcoma. HIF-1alpha and HIF-2alpha immunohistochemistry was performed on a Ewing's tumour tissue array. Ewing's sarcoma and osteosarcoma cell lines were assessed for HIF pathway induction by Western blot, luciferase assay and ELISA. Effects of hypoxia, hypoglycaemia and isoform-specific HIF siRNA were assessed on proliferation, apoptosis and migration. 17/56 Ewing's tumours were HIF-1alpha-positive, 15 HIF-2alpha-positive and 10 positive for HIF-1alpha and HIF-2alpha. Expression of HIF-1alpha and cleaved caspase 3 localised to necrotic areas. Hypoxia induced HIF-1alpha and HIF-2alpha in Ewing's and osteosarcoma cell lines while hypoglycaemia specifically induced HIF-2alpha in Ewing's. Downstream transcription was HIF-1alpha-dependent in Ewing's sarcoma, but regulated by both isoforms in osteosarcoma. In both cell types hypoglycaemia reduced cellular proliferation by >or= 45%, hypoxia increased apoptosis and HIF siRNA modulated hypoxic proliferation and migration. Co-localisation of HIF-1alpha and necrosis in Ewing's sarcoma suggests a role for hypoxia and/or hypoglycaemia in in vivo induction of HIF. In vitro data implicates hypoxia as the primary HIF stimulus in both Ewing's and osteosarcoma, driving effects on proliferation and apoptosis. These results provide a foundation from which to advance understanding of HIF function in the pathobiology of primary bone sarcomas.

Hypoxia in tumors: pathogenesis-related classification, characterization of hypoxia subtypes, and associated biological and clinical implications.

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Vaupel, Peter; Mayer, Arnulf

2014-01-01

Hypoxia is a hallmark of tumors leading to (mal-)adaptive processes, development of aggressive phenotypes and treatment resistance. Based on underlying mechanisms and their duration, two main types of hypoxia have been identified, coexisting with complex spatial and temporal heterogeneities. Chronic hypoxia is mainly caused by diffusion limitations due to enlarged diffusion distances and adverse diffusion geometries (e.g., concurrent vs. countercurrent microvessels, Krogh- vs. Hill-type diffusion geometry) and, to a lesser extent, by hypoxemia (e.g., in anemic patients, HbCO formation in heavy smokers), and a compromised perfusion or flow stop (e.g., due to disturbed Starling forces or intratumor solid stress). Acute hypoxia mainly results from transient disruptions in perfusion (e.g., vascular occlusion by cell aggregates), fluctuating red blood cell fluxes or short-term contractions of the interstitial matrix. In each of these hypoxia subtypes oxygen supply is critically reduced, but perfusion-dependent nutrient supply, waste removal, delivery of anticancer or diagnostic agents, and repair competence can be impaired or may not be affected. This detailed differentiation of tumor hypoxia may impact on our understanding of tumor biology and may aid in the development of novel treatment strategies, tumor detection by imaging and tumor targeting, and is thus of great clinical relevance.

Role of JAK-STAT pathway in reducing cardiomyocytes hypoxia/reoxygenation injury induced by S1P postconditioning.

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Wang, Yuqing; Wang, Dongfei; Zhang, Lizhi; Ye, Fangyu; Li, Mengmeng; Wen, Ke

2016-08-05

This experiment was designed to explore the protection of sphingosine1-phosphate (S1P) postconditioning on rat myocardial cells injured by hypoxia/reoxygenation acting via the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signal pathway. The data showed that S1P could significantly increase cell viability, lower the rate of apoptosis, decrease the content of lactate dehydrogenase (LDH) and caspase3 activity in the culture medium, increase the activity of total superoxide dismutase (T-SOD) and manganese superoxide dismutase (Mn-SOD), reduce the loss of mitochondrial membrane potential and the fluorescence intensity of intracellular calcium, as well as increase the phosphorylation of JAK2 and STAT3 in comparison with the H/R group. When the JAK inhibitor AG490 or the STAT inhibitor stattic were added, the effects of S1P were inhibited. Our date shows that S1P protects H9c2 cells from hypoxia/reoxygenation injury and that the protection by S1P was inhibited by AG490 and stattic. Therefore S1P protects H9c2 cells against hypoxia/reoxygenation injury via the JAK-STAT pathway. Copyright © 2016 Elsevier B.V. All rights reserved.

Hypoxia-Inducible Regulation of a Prodrug-Activating Enzyme for Tumor-Specific Gene Therapy

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Toru Shibata

2002-01-01

Full Text Available Previous studies have suggested that tumor hypoxia could be exploited for cancer gene therapy. Using hypoxia-responsive elements derived from the human vascular endothelial growth factor gene, we have generated vectors expressing a bacterial nitroreductase. (20NTR gene that can activate the anticancer prodrug CB1954. Stable transfectants of human HT1080 tumor cells with hypoxia-inducible vectors were established with G418 selection. Hypoxic induction of NTR protein correlated with increased sensitivity to in vitro exposure of HT 1080 cells to the prodrug. Growth delay assays were performed with established tumor xenografts derived from the same cells to detect the in vivo efficacy of CB1954 conversion to its cytotoxic form. Significant antitumor effects were achieved with intraperitoneal injections of CB1954 both in tumors that express NTR constitutively or with a hypoxia-inducible promoter. In addition, respiration of 10% O2 increased tumor hypoxia in vivo and enhanced the antitumor effects. Taken together, these results demonstrate that hypoxia-inducible vectors may be useful for tumor-selective gene therapy, although the problem of delivery of the vector to the tumors, particularly to the hypoxic cells in the tumors, is not addressed by these studies.

Hypoxia symptoms during altitude training in professional Iranian fighter pilots.

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Alagha, Babak; AhmadBeygi, Shervin; Ahmadbeigy, Shervin; Moosavi, Seyed Ali Javad; Jalali, Seyed Mahmood

2012-01-01

Susceptibility to hypoxia is influenced by a multitude of factors, including fatigue, physical activity, illnesses, ambient temperature, rate of ascent, destination altitude, medications, and alcohol. Anecdotally, several reports have been made regarding changes in the form of hypoxia presentation in Iranian fighter pilots in the absence of these factors. This study focused specifically on the effect of pilot age on susceptibility to hypoxia and its initial presentation. We assumed that a pilot's age may increase his susceptibility to hypoxia and consequently reduce the amount of time it takes for hypoxia to present. Because our literature review did not reveal any previous study addressing the possible relationship between age and susceptibility to hypoxia, the purpose of this study is to address and clarify this relationship. In this retrospective study, we collected information from Iranian fighter pilots (n = 30) through an anonymous questionnaire in 2000. The form of hypoxia presentation of each subject was evaluated during five altitude chamber training (ACT) sessions that were conducted routinely from 1972 to 1984. To enhance the accuracy of the study's results, confounding factors such as prior hypoxia experience in an ACT session have been taken into consideration. The results revealed a statistically significant relationship between age and a change in the form of hypoxia presentation in our subjects. Increased age reduced the amount of time before the first individual hypoxia symptom appeared (P < .000002). Although having previous hypoxia experience may help pilots to recognize their symptoms earlier, its effect was not statistically significant (P < .18). A few changes in the nature of individual symptoms were observed; however, we did not find a meaningful statistical correlation between pilot age and change in the nature of symptoms. Susceptibility ot hypoxia increases with pilot age. Copyright © 2012 Air Medical Journal Associates. Published by

Intramucosal–arterial PCO 2 gap fails to reflect intestinal dysoxia in hypoxic hypoxia

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Dubin, Arnaldo; Murias, Gastón; Estenssoro, Elisa; Canales, Héctor; Badie, Julio; Pozo, Mario; Sottile, Juan P; Barán, Marcelo; Pálizas, Fernando; Laporte, Mercedes

2002-01-01

Introduction An elevation in intramucosal–arterial PCO 2 gradient (ΔPCO 2) could be determined either by tissue hypoxia or by reduced blood flow. Our hypothesis was that in hypoxic hypoxia with preserved blood flow, ΔPCO 2 should not be altered. Methods In 17 anesthetized and mechanically ventilated sheep, oxygen delivery was reduced by decreasing flow (ischemic hypoxia, IH) or arterial oxygen saturation (hypoxic hypoxia, HH), or no intervention was made (sham). In the IH group (n = 6), blood...

Hypoxia and hypoglycaemia in Ewing's sarcoma and osteosarcoma: regulation and phenotypic effects of Hypoxia-Inducible Factor

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Dirksen Uta

2010-07-01

Full Text Available Abstract Background Hypoxia regulates gene expression via the transcription factor HIF (Hypoxia-Inducible Factor. Little is known regarding HIF expression and function in primary bone sarcomas. We describe HIF expression and phenotypic effects of hypoxia, hypoglycaemia and HIF in Ewing's sarcoma and osteosarcoma. Methods HIF-1α and HIF-2α immunohistochemistry was performed on a Ewing's tumour tissue array. Ewing's sarcoma and osteosarcoma cell lines were assessed for HIF pathway induction by Western blot, luciferase assay and ELISA. Effects of hypoxia, hypoglycaemia and isoform-specific HIF siRNA were assessed on proliferation, apoptosis and migration. Results 17/56 Ewing's tumours were HIF-1α-positive, 15 HIF-2α-positive and 10 positive for HIF-1α and HIF-2α. Expression of HIF-1α and cleaved caspase 3 localised to necrotic areas. Hypoxia induced HIF-1α and HIF-2α in Ewing's and osteosarcoma cell lines while hypoglycaemia specifically induced HIF-2α in Ewing's. Downstream transcription was HIF-1α-dependent in Ewing's sarcoma, but regulated by both isoforms in osteosarcoma. In both cell types hypoglycaemia reduced cellular proliferation by ≥ 45%, hypoxia increased apoptosis and HIF siRNA modulated hypoxic proliferation and migration. Conclusions Co-localisation of HIF-1α and necrosis in Ewing's sarcoma suggests a role for hypoxia and/or hypoglycaemia in in vivo induction of HIF. In vitro data implicates hypoxia as the primary HIF stimulus in both Ewing's and osteosarcoma, driving effects on proliferation and apoptosis. These results provide a foundation from which to advance understanding of HIF function in the pathobiology of primary bone sarcomas.

Combining hypobaric hypoxia or hyperbaric oxygen postconditioning with memantine reduces neuroprotection in 7-day-old rat hypoxia-ischemia.

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Gamdzyk, Marcin; Ziembowicz, Apolonia; Bratek, Ewelina; Salinska, Elzbieta

2016-10-01

Perinatal hypoxia-ischemia causes brain injury in neonates, but a fully successful treatment to prevent changes in the brain has yet to be developed. The aim of this study was to evaluate the effect of combining memantine treatment with HBO (2.5 ATA) or HH (0.47 ATA) on neonatal hypoxia-ischemia brain injury. 7-day old rats were subjected to hypoxia-ischemia (H-I) and treated with combination of memantine and HBO or HH. The brain damage was evaluated by examination of infarct area and the number of apoptotic cells in CA1 region of hippocampus. Additionally, the level of reactive oxygen species (ROS) was measured. Memantine, HBO or HH postconditioning applied at short time (1-6h) after H-I, and repeated for two subsequent days, resulted in significant neuroprotection. The reduction in ipsilateral hemisphere weight deficit and in the size of infarct area was observed 14days after H-I. A reduction in apoptosis and ROS level was also observed. Combining memantine with HBO or HH resulted in a loss of neuroprotection. Our results show that, combining HBO or HH postconditioning with memantine produce no additive increase in the neuroprotective effect. On the contrary, combining the treatments resulted in lower neuroprotection in comparison to the effects of memantine, HBO or HH alone. Copyright © 2016 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Targeted expression of heme oxygenase-1 prevents the pulmonary inflammatory and vascular responses to hypoxia

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Minamino, Tohru; Christou, Helen; Hsieh, Chung-Ming; Liu, Yuxiang; Dhawan, Vijender; Abraham, Nader G.; Perrella, Mark A.; Mitsialis, S. Alex; Kourembanas, Stella

2001-07-01

Chronic hypoxia causes pulmonary hypertension with smooth muscle cell proliferation and matrix deposition in the wall of the pulmonary arterioles. We demonstrate here that hypoxia also induces a pronounced inflammation in the lung before the structural changes of the vessel wall. The proinflammatory action of hypoxia is mediated by the induction of distinct cytokines and chemokines and is independent of tumor necrosis factor- signaling. We have previously proposed a crucial role for heme oxygenase-1 (HO-1) in protecting cardiomyocytes from hypoxic stress, and potent anti-inflammatory properties of HO-1 have been reported in models of tissue injury. We thus established transgenic mice that constitutively express HO-1 in the lung and exposed them to chronic hypoxia. HO-1 transgenic mice were protected from the development of both pulmonary inflammation as well as hypertension and vessel wall hypertrophy induced by hypoxia. Significantly, the hypoxic induction of proinflammatory cytokines and chemokines was suppressed in HO-1 transgenic mice. Our findings suggest an important protective function of enzymatic products of HO-1 activity as inhibitors of hypoxia-induced vasoconstrictive and proinflammatory pathways.

Loss aversion and hypoxia: less loss aversion in oxygen-depleted environment.

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Pighin, Stefania; Bonini, Nicolao; Savadori, Lucia; Hadjichristidis, Constantinos; Schena, Federico

2014-03-01

Hypoxia, the deprivation of adequate oxygen supply, constitutes a direct threat to survival by disrupting cardiovascular or respiratory homeostasis and eliciting a respiratory distress. Although hypoxia has been shown to increase brain vulnerability and impair basic cognitive functions, only one study has examined its effect on decision-making. The present study examined the effect of mild hypoxia on individual's loss aversion, that is, the tendency to be more affected by losses than equal sized gains. A sample of 26 participants were asked to either accept or reject a series of mixed gambles once in an oxygen-depleted environment (14.1% oxygen concentration) and once in a normoxic environment (20.9% oxygen concentration). Each gamble involved a 50-50 chance of winning or losing specified amounts of money. Mild hypoxia decreased loss aversion: on average in the normoxic condition participants accepted gambles if the gain was at least 2.4 times as large as the loss, whereas in the oxygen-depleted condition participants accepted gambles if the gain was at least 1.7 times as large as the loss. Mild hypoxia may push individuals to be less cautious in daily decisions that involve a trade-off between a gain and a loss.

GABA accumulating neurons are relatively resistant to chronic hypoxia in vitro: An autoradiographic study

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Sher, P.K.; Hu, S.

1990-01-01

Whether there is preferential loss of certain types of nerve cells or specific cellular functions after hypoxic or ischemic insults remains unclear. To evaluate this phenomenon in vitro, the vulnerability of GABAergic neurons to hypoxia was investigated both quantitatively and with autoradiography. Immature neuronal cortical cultures obtained from fetal mice were subjected to chronic hypoxia (5% O2) for 24 h or 48 h and then returned to the normoxic condition for 48 h. The shorter hypoxic exposure resulted in significantly reduced numbers of neurons in comparison to the longer exposure and also to controls (29% and 26%, respectively; p less than 0.001). LDH efflux, a reliable indicator of cell damage, also was higher after the shorter exposure insult. Nevertheless, in these same 24 h hypoxic cultures there was prominent sparing of those neurons which accumulate GABA: by 48 h of recovery GABAergic neurons constituted 29.3 +/- 2.0% of the remaining neuronal population in comparison to 11.6 +/- 0.6 and 14.4 +/- 0.8% for controls and 48 h hypoxia, respectively; (p less than 0.001). Although total GABA uptake per neuron was significantly decreased after both types of insult, there was a concomitant increase in glial GABA uptake (i.e., that which could be displaced by beta-alanine). These observations suggest that certain GABAergic cortical neurons are relatively more resistant to chronic hypoxia than the general neuronal population and that depression of overall neuronal GABA uptake may be associated with enhanced glial GABA uptake

Chitosan-shelled oxygen-loaded nanodroplets abrogate hypoxia dysregulation of human keratinocyte gelatinases and inhibitors: New insights for chronic wound healing

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Khadjavi, Amina [Dipartimento di Neuroscienze, Università di Torino, Torino (Italy); Magnetto, Chiara [Istituto Nazionale di Ricerca Metrologica (INRIM), Torino (Italy); Panariti, Alice [Dipartimento di Scienze della Salute, Università di Milano Bicocca, Monza (Italy); Argenziano, Monica [Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Torino (Italy); Gulino, Giulia Rossana [Dipartimento di Oncologia, Università di Torino, Torino (Italy); Rivolta, Ilaria [Dipartimento di Scienze della Salute, Università di Milano Bicocca, Monza (Italy); Cavalli, Roberta [Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Torino (Italy); Giribaldi, Giuliana [Dipartimento di Oncologia, Università di Torino, Torino (Italy); Guiot, Caterina [Dipartimento di Neuroscienze, Università di Torino, Torino (Italy); Prato, Mauro, E-mail: mauro.prato@unito.it [Dipartimento di Neuroscienze, Università di Torino, Torino (Italy); Dipartimento di Scienze della Sanità Pubblica e Pediatriche, Università di Torino, Torino (Italy)

2015-08-01

Background: : In chronic wounds, efficient epithelial tissue repair is hampered by hypoxia, and balances between the molecules involved in matrix turn-over such as matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are seriously impaired. Intriguingly, new oxygenating nanocarriers such as 2H,3H-decafluoropentane-based oxygen-loaded nanodroplets (OLNs) might effectively target chronic wounds. Objective: : To investigate hypoxia and chitosan-shelled OLN effects on MMP/TIMP production by human keratinocytes. Methods: : HaCaT cells were treated for 24 h with 10% v/v OLNs both in normoxia or hypoxia. Cytotoxicity and cell viability were measured through biochemical assays; cellular uptake by confocal microscopy; and MMP and TIMP production by enzyme-linked immunosorbent assay or gelatin zymography. Results: : Normoxic HaCaT cells constitutively released MMP-2, MMP-9, TIMP-1 and TIMP-2. Hypoxia strongly impaired MMP/TIMP balances by reducing MMP-2, MMP-9, and TIMP-2, without affecting TIMP-1 release. After cellular uptake by keratinocytes, nontoxic OLNs abrogated all hypoxia effects on MMP/TIMP secretion, restoring physiological balances. OLN abilities were specifically dependent on time-sustained oxygen diffusion from OLN core. Conclusion: : Chitosan-shelled OLNs effectively counteract hypoxia-dependent dysregulation of MMP/TIMP balances in human keratinocytes. Therefore, topical administration of exogenous oxygen, properly encapsulated in nanodroplet formulations, might be a promising adjuvant approach to promote healing processes in hypoxic wounds. - Highlights: • Hypoxia impairs MMP9/TIMP1 and MMP2/TIMP2 balances in HaCaT human keratinocytes. • Chitosan-shelled oxygen-loaded nanodroplets (OLNs) are internalised by HaCaT cells. • OLNs are not toxic to HaCaT cells. • OLNs effectively counteract hypoxia effects on MMP/TIMP balances in HaCaT cells. • OLNs appear as promising and cost-effective therapeutic tools for hypoxic

Chitosan-shelled oxygen-loaded nanodroplets abrogate hypoxia dysregulation of human keratinocyte gelatinases and inhibitors: New insights for chronic wound healing

International Nuclear Information System (INIS)

Khadjavi, Amina; Magnetto, Chiara; Panariti, Alice; Argenziano, Monica; Gulino, Giulia Rossana; Rivolta, Ilaria; Cavalli, Roberta; Giribaldi, Giuliana; Guiot, Caterina; Prato, Mauro

2015-01-01

Background: : In chronic wounds, efficient epithelial tissue repair is hampered by hypoxia, and balances between the molecules involved in matrix turn-over such as matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are seriously impaired. Intriguingly, new oxygenating nanocarriers such as 2H,3H-decafluoropentane-based oxygen-loaded nanodroplets (OLNs) might effectively target chronic wounds. Objective: : To investigate hypoxia and chitosan-shelled OLN effects on MMP/TIMP production by human keratinocytes. Methods: : HaCaT cells were treated for 24 h with 10% v/v OLNs both in normoxia or hypoxia. Cytotoxicity and cell viability were measured through biochemical assays; cellular uptake by confocal microscopy; and MMP and TIMP production by enzyme-linked immunosorbent assay or gelatin zymography. Results: : Normoxic HaCaT cells constitutively released MMP-2, MMP-9, TIMP-1 and TIMP-2. Hypoxia strongly impaired MMP/TIMP balances by reducing MMP-2, MMP-9, and TIMP-2, without affecting TIMP-1 release. After cellular uptake by keratinocytes, nontoxic OLNs abrogated all hypoxia effects on MMP/TIMP secretion, restoring physiological balances. OLN abilities were specifically dependent on time-sustained oxygen diffusion from OLN core. Conclusion: : Chitosan-shelled OLNs effectively counteract hypoxia-dependent dysregulation of MMP/TIMP balances in human keratinocytes. Therefore, topical administration of exogenous oxygen, properly encapsulated in nanodroplet formulations, might be a promising adjuvant approach to promote healing processes in hypoxic wounds. - Highlights: • Hypoxia impairs MMP9/TIMP1 and MMP2/TIMP2 balances in HaCaT human keratinocytes. • Chitosan-shelled oxygen-loaded nanodroplets (OLNs) are internalised by HaCaT cells. • OLNs are not toxic to HaCaT cells. • OLNs effectively counteract hypoxia effects on MMP/TIMP balances in HaCaT cells. • OLNs appear as promising and cost-effective therapeutic tools for hypoxic

Response of skeletal muscle mitochondria to hypoxia.

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Hoppeler, Hans; Vogt, Michael; Weibel, Ewald R; Flück, Martin

2003-01-01

This review explores the current concepts relating the structural and functional modifications of skeletal muscle mitochondria to the molecular mechanisms activated when organisms are exposed to a hypoxic environment. In contrast to earlier assumptions it is now established that permanent or long-term exposure to severe environmental hypoxia decreases the mitochondrial content of muscle fibres. Oxidative muscle metabolism is shifted towards a higher reliance on carbohydrates as a fuel, and intramyocellular lipid substrate stores are reduced. Moreover, in muscle cells of mountaineers returning from the Himalayas, we find accumulations of lipofuscin, believed to be a mitochondrial degradation product. Low mitochondrial contents are also observed in high-altitude natives such as Sherpas. In these subjects high-altitude performance seems to be improved by better coupling between ATP demand and supply pathways as well as better metabolite homeostasis. The hypoxia-inducible factor 1 (HIF-1) has been identified as a master regulator for the expression of genes involved in the hypoxia response, such as genes coding for glucose transporters, glycolytic enzymes and vascular endothelial growth factor (VEGF). HIF-1 achieves this by binding to hypoxia response elements in the promoter regions of these genes, whereby the increase of HIF-1 in hypoxia is the consequence of a reduced degradation of its dominant subunit HIF-1a. A further mechanism that seems implicated in the hypoxia response of muscle mitochondria is related to the formation of reactive oxygen species (ROS) in mitochondria during oxidative phosphorylation. How exactly ROS interfere with HIF-1a as well as MAP kinase and other signalling pathways is debated. The current evidence suggests that mitochondria themselves could be important players in oxygen sensing.

Brain blood flow and blood pressure during hypoxia in the epaulette shark Hemiscyllium ocellatum, a hypoxia-tolerant elasmobranch.

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Söderström, V; Renshaw, G M; Nilsson, G E

1999-04-01

The key to surviving hypoxia is to protect the brain from energy depletion. The epaulette shark (Hemiscyllium ocellatum) is an elasmobranch able to resist energy depletion and to survive hypoxia. Using epi-illumination microscopy in vivo to observe cerebral blood flow velocity on the brain surface, we show that cerebral blood flow in the epaulette shark is unaffected by 2 h of severe hypoxia (0.35 mg O2 l-1 in the respiratory water, 24 C). Thus, the epaulette shark differs from other hypoxia- and anoxia-tolerant species studied: there is no adenosine-mediated increase in cerebral blood flow such as that occurring in freshwater turtles and cyprinid fish. However, blood pressure showed a 50 % decrease in the epaulette shark during hypoxia, indicating that a compensatory cerebral vasodilatation occurs to maintain cerebral blood flow. We observed an increase in cerebral blood flow velocity when superfusing the normoxic brain with adenosine (making sharks the oldest vertebrate group in which this mechanism has been found). The adenosine-induced increase in cerebral blood flow velocity was reduced by the adenosine receptor antagonist aminophylline. Aminophylline had no effect upon the maintenance of cerebral blood flow during hypoxia, however, indicating that adenosine is not involved in maintaining cerebral blood flow in the epaulette shark during hypoxic hypotension.

cGMP-Phosphodiesterase Inhibition Prevents Hypoxia-Induced Cell Death Activation in Porcine Retinal Explants.

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Lorena Olivares-González

Full Text Available Retinal hypoxia and oxidative stress are involved in several retinal degenerations including diabetic retinopathy, glaucoma, central retinal artery occlusion, or retinopathy of prematurity. The second messenger cyclic guanosine monophosphate (cGMP has been reported to be protective for neuronal cells under several pathological conditions including ischemia/hypoxia. The purpose of this study was to evaluate whether the accumulation of cGMP through the pharmacological inhibition of phosphodiesterase (PDE with Zaprinast prevented retinal degeneration induced by mild hypoxia in cultures of porcine retina. Exposure to mild hypoxia (5% O2 for 24h reduced cGMP content and induced retinal degeneration by caspase dependent and independent (PARP activation mechanisms. Hypoxia also produced a redox imbalance reducing antioxidant response (superoxide dismutase and catalase activities and increasing superoxide free radical release. Zaprinast reduced mild hypoxia-induced cell death through inhibition of caspase-3 or PARP activation depending on the cell layer. PDE inhibition also ameliorated the effects of mild hypoxia on antioxidant response and the release of superoxide radical in the photoreceptor layer. The use of a PKG inhibitor, KT5823, suggested that cGMP-PKG pathway is involved in cell survival and antioxidant response. The inhibition of PDE, therefore, could be useful for reducing retinal degeneration under hypoxic/ischemic conditions.

Cold shock protein YB-1 is involved in hypoxia-dependent gene transcription

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Rauen, Thomas; Frye, Bjoern C.; Wang, Jialin; Raffetseder, Ute; Alidousty, Christina; En-Nia, Abdelaziz; Floege, Jürgen; Mertens, Peter R.

2016-01-01

Hypoxia-dependent gene regulation is largely orchestrated by hypoxia-inducible factors (HIFs), which associate with defined nucleotide sequences of hypoxia-responsive elements (HREs). Comparison of the regulatory HRE within the 3′ enhancer of the human erythropoietin (EPO) gene with known binding motifs for cold shock protein Y-box (YB) protein-1 yielded strong similarities within the Y-box element and 3′ adjacent sequences. DNA binding assays confirmed YB-1 binding to both, single- and double-stranded HRE templates. Under hypoxia, we observed nuclear shuttling of YB-1 and co-immunoprecipitation assays demonstrated that YB-1 and HIF-1α physically interact with each other. Cellular YB-1 depletion using siRNA significantly induced hypoxia-dependent EPO production at both, promoter and mRNA level. Vice versa, overexpressed YB-1 significantly reduced EPO-HRE-dependent gene transcription, whereas this effect was minor under normoxia. HIF-1α overexpression induced hypoxia-dependent gene transcription through the same element and accordingly, co-expression with YB-1 reduced HIF-1α-mediated EPO induction under hypoxic conditions. Taken together, we identified YB-1 as a novel binding factor for HREs that participates in fine-tuning of the hypoxia transcriptome. - Highlights: • Hypoxia drives nuclear translocation of cold shock protein YB-1. • YB-1 physically interacts with hypoxia-inducible factor (HIF)-1α. • YB-1 binds to the hypoxia-responsive element (HRE) within the erythropoietin (EPO) 3′ enhancer. • YB-1 trans-regulates transcription of hypoxia-dependent genes such as EPO and VEGF.

Ubiquitination is absolutely required for the degradation of hypoxia-inducible factor - 1 alpha protein in hypoxic conditions

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Wang, Ronghai; Zhang, Ping; Li, Jinhang; Guan, Hongzai; Shi, Guangjun

2016-01-01

The hypoxia-inducible factor (HIF) is recognized as the master regulator of hypoxia response. HIF-α subunits expression are tightly regulated. In this study, our data show that ts20 cells still expressed detectable E1 protein even at 39.5° C for 12 h, and complete depletion of E1 protein expression at 39.5° C by siRNA enhanced HIF-1α and P53 protein expression. Further inhibition of E1 at 39.5 °C by siRNA, or E1 inhibitor Ube1-41 completely blocked HIF-1α degradation. Moreover, immunoprecipitations of co-transfection of HA-ubiquitin and FLAG–HIF–1α plasmids directly confirmed the involvement of ubiquitin in the hypoxic degradation of HIF-1α. Additionally, hypoxic HIF-1 α degradation is independent of HAF, RACK1, sumoylation or nuclear/cytoplasmic localization. Taken together, our data suggest that constitutive HIF-1α protein degradation in hypoxia is absolutely ubiquitination-dependent, and unidentified E3 ligase may exist for this degradation pathway. - Highlights: • HIF-1α protein is constitutively degraded in hypoxic conditions. • Requirement of ubiquitination for HIF-1α degradation in hypoxia. • Hypoxic HIF-1α degradation is independent of HAF, RACK1, sumoylation or nuclear/cytoplasmic localization.

Ubiquitination is absolutely required for the degradation of hypoxia-inducible factor - 1 alpha protein in hypoxic conditions

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Wang, Ronghai [Department of Urology, Linzi District People' s Hospital, Zibo, 255400 (China); Zhang, Ping, E-mail: zpskx001@163.com [Department of Gynecology, Qingdao Municipal Hospital, Qingdao, 266011 (China); Li, Jinhang [Department of Gynecology, Qingdao Municipal Hospital, Qingdao, 266011 (China); Guan, Hongzai [Laboratory Department, School of Medicine, Qingdao University, Qingdao, 266071 (China); Shi, Guangjun, E-mail: qdmhshigj@yahoo.com [Department of Hepatobiliary Surgery, Qingdao Municipal Hospital, Qingdao, 266071 (China)

2016-01-29

The hypoxia-inducible factor (HIF) is recognized as the master regulator of hypoxia response. HIF-α subunits expression are tightly regulated. In this study, our data show that ts20 cells still expressed detectable E1 protein even at 39.5° C for 12 h, and complete depletion of E1 protein expression at 39.5° C by siRNA enhanced HIF-1α and P53 protein expression. Further inhibition of E1 at 39.5 °C by siRNA, or E1 inhibitor Ube1-41 completely blocked HIF-1α degradation. Moreover, immunoprecipitations of co-transfection of HA-ubiquitin and FLAG–HIF–1α plasmids directly confirmed the involvement of ubiquitin in the hypoxic degradation of HIF-1α. Additionally, hypoxic HIF-1 α degradation is independent of HAF, RACK1, sumoylation or nuclear/cytoplasmic localization. Taken together, our data suggest that constitutive HIF-1α protein degradation in hypoxia is absolutely ubiquitination-dependent, and unidentified E3 ligase may exist for this degradation pathway. - Highlights: • HIF-1α protein is constitutively degraded in hypoxic conditions. • Requirement of ubiquitination for HIF-1α degradation in hypoxia. • Hypoxic HIF-1α degradation is independent of HAF, RACK1, sumoylation or nuclear/cytoplasmic localization.

Hypoxia and hypoglycaemia in Ewing's sarcoma and osteosarcoma: regulation and phenotypic effects of Hypoxia-Inducible Factor

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Knowles, Helen J; Schaefer, Karl-Ludwig; Dirksen, Uta; Athanasou, Nicholas A

2010-01-01

Hypoxia regulates gene expression via the transcription factor HIF (Hypoxia-Inducible Factor). Little is known regarding HIF expression and function in primary bone sarcomas. We describe HIF expression and phenotypic effects of hypoxia, hypoglycaemia and HIF in Ewing's sarcoma and osteosarcoma. HIF-1α and HIF-2α immunohistochemistry was performed on a Ewing's tumour tissue array. Ewing's sarcoma and osteosarcoma cell lines were assessed for HIF pathway induction by Western blot, luciferase assay and ELISA. Effects of hypoxia, hypoglycaemia and isoform-specific HIF siRNA were assessed on proliferation, apoptosis and migration. 17/56 Ewing's tumours were HIF-1α-positive, 15 HIF-2α-positive and 10 positive for HIF-1α and HIF-2α. Expression of HIF-1α and cleaved caspase 3 localised to necrotic areas. Hypoxia induced HIF-1α and HIF-2α in Ewing's and osteosarcoma cell lines while hypoglycaemia specifically induced HIF-2α in Ewing's. Downstream transcription was HIF-1α-dependent in Ewing's sarcoma, but regulated by both isoforms in osteosarcoma. In both cell types hypoglycaemia reduced cellular proliferation by ≥ 45%, hypoxia increased apoptosis and HIF siRNA modulated hypoxic proliferation and migration. Co-localisation of HIF-1α and necrosis in Ewing's sarcoma suggests a role for hypoxia and/or hypoglycaemia in in vivo induction of HIF. In vitro data implicates hypoxia as the primary HIF stimulus in both Ewing's and osteosarcoma, driving effects on proliferation and apoptosis. These results provide a foundation from which to advance understanding of HIF function in the pathobiology of primary bone sarcomas

Atherosclerotic renal artery stenosis is associated with elevated cell cycle arrest markers related to reduced renal blood flow and postcontrast hypoxia.

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Saad, Ahmed; Wang, Wei; Herrmann, Sandra M S; Glockner, James F; Mckusick, Michael A; Misra, Sanjay; Bjarnason, Haraldur; Lerman, Lilach O; Textor, Stephen C

2016-11-01

Atherosclerotic renal artery stenosis (ARAS) reduces renal blood flow (RBF), ultimately leading to kidney hypoxia and inflammation. Insulin-like growth factor binding protein-7 (IGFBP-7) and tissue inhibitor of metalloproteinases-2 (TIMP-2) are biomarkers of cell cycle arrest, often increased in ischemic conditions and predictive of acute kidney injury (AKI). This study sought to examine the relationships between renal vein levels of IGFBP-7, TIMP-2, reductions in RBF and postcontrast hypoxia as measured by blood oxygen level-dependent (BOLD) magnetic resonance imaging. Renal vein levels of IGFBP-7 and TIMP-2 were obtained in an ARAS cohort (n= 29) scheduled for renal artery stenting and essential hypertensive (EH) healthy controls (n = 32). Cortical and medullary RBFs were measured by multidetector computed tomography (CT) immediately before renal artery stenting and 3 months later. BOLD imaging was performed before and 3 months after stenting in all patients, and a subgroup (N = 12) underwent repeat BOLD imaging 24 h after CT/stenting to examine postcontrast/procedure levels of hypoxia. Preintervention IGFBP-7 and TIMP-2 levels were elevated in ARAS compared with EH (18.5 ± 2.0 versus 15.7 ± 1.5 and 97.4 ± 23.1 versus 62.7 ± 9.2 ng/mL, respectively; Pblood flow (r = -0.59, P= 0.004). These data demonstrate elevated IGFBP-7 and TIMP-2 levels in ARAS as a function of the degree of reduced RBF. Elevated baseline IGFBP-7 levels were associated with protection against postimaging hypoxia, consistent with 'ischemic preconditioning'. Despite contrast injection and stenting, AKI in these high-risk ARAS subjects with elevated IGFBP-7/TIMP-2 was rare and did not affect long-term kidney function. © The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.

Hypoxic hypoxia as a means of modifying radiosensibility

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Neumeister, K.; Niemiec, C.; Bolck, M.; Jahns, J.; Kamprad, F.; Arnold, P.; Johannsen, U.; Koch, F.; Mehlhorn, G.

1977-01-01

Following an overview of the various possibilities of creating hypoxia in mammals, the problem of reducing radioresistance of hypoxic tumor cells is treated. Furthermore, the results of irradiation experiments with mice, rats and pigs breathing hypoxic mixtures of O 2 and N 2 are given and discussed with a view to applying hypoxic hypoxia in the radiotherapy of human tumors. (author)

The yeast genome may harbor hypoxia response elements (HRE).

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Ferreira, Túlio César; Hertzberg, Libi; Gassmann, Max; Campos, Elida Geralda

2007-01-01

The hypoxia-inducible factor-1 (HIF-1) is a heterodimeric transcription factor activated when cells are submitted to hypoxia. The heterodimer is composed of two subunits, HIF-1alpha and the constitutively expressed HIF-1beta. During normoxia, HIF-1alpha is degraded by the 26S proteasome, but hypoxia causes HIF-1alpha to be stabilized, enter the nucleus and bind to HIF-1beta, thus forming the active complex. The complex then binds to the regulatory sequences of various genes involved in physiological and pathological processes. The specific regulatory sequence recognized by HIF-1 is the hypoxia response element (HRE) that has the consensus sequence 5'BRCGTGVBBB3'. Although the basic transcriptional regulation machinery is conserved between yeast and mammals, Saccharomyces cerevisiae does not express HIF-1 subunits. However, we hypothesized that baker's yeast has a protein analogous to HIF-1 which participates in the response to changes in oxygen levels by binding to HRE sequences. In this study we screened the yeast genome for HREs using probabilistic motif search tools. We described 24 yeast genes containing motifs with high probability of being HREs (p-value<0.1) and classified them according to biological function. Our results show that S. cerevisiae may harbor HREs and indicate that a transcription factor analogous to HIF-1 may exist in this organism.

The radiation response of cells recovering after chronic hypoxia

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Kwok, T.T.; Sutherland, R.M.

1989-01-01

Experiments were performed to study the influence of hypoxic pretreatment on the radiation response of A431 human squamous carcinoma cells. Reaeration for 10 min after chronic hypoxia (greater than 2 h) was found to enhance the radiosensitivity of A431 cells, and the maximal effect was seen for those cells reaerated after 12 h of hypoxia. The radiosensitivity enhancement for reaerated cells after 12 h of hypoxia was maximized by 5 min after the return to aerobic conditions and reached the control level by 12 h of reaeration. This enhanced radiosensitive state was characterized by a reduced shoulder region and increased slope of the radiation dose-response curve for cells in both the exponential and plateau phases of growth. There was a slight increase in the number of G1 and decrease in the number of S and G2 + M cells for both exponential- and plateau-phase cultures following 12 h hypoxic treatment. Although growth inhibition induced by 12 h of hypoxia was seen for cells in the exponential phase, there was no cell number change in the plateau-phase culture after hypoxia. Plating efficiency (PE) of cells in both growth phases was reduced by 30% after hypoxia. Furthermore, in the exponential-phase culture, the extent of reduction in PE after hypoxia was similar among cells in different phases of the cell cycle. Although S-phase cells in exponentially growing cultures were relatively more resistant to radiation than G1 and G2 + M cells, the cell age-response pattern was the same whether the cells had been aerobic or hypoxic before reaeration and irradiation. Furthermore, the enhancement ratio associated with reaeration after 12 h of hypoxia for these three subpopulations of cells was 1.3. Our results indicate that the increase in radiosensitivity due to reaeration after chronic hypoxia is unlikely to be related to the changes of cell cycle stage and growth phase during hypoxic treatment

Molecular characterization and mRNA expression of two key enzymes of hypoxia-sensing pathways in eastern oysters Crassostrea virginica (Gmelin): Hypoxia-inducible factor α (HIF-α) and HIF-prolyl hydroxylase (PHD)

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Piontkivska, Helen; Chung, J. Sook; Ivanina, Anna V.; Sokolov, Eugene P.; Techa, Sirinart; Sokolova, Inna M.

2010-01-01

Oxygen homeostasis is crucial for development, survival and normal function of all metazoans. A family of transcription factors called hypoxia-inducible factors (HIF) is critical in mediating the adaptive responses to reduced oxygen availability. The HIF transcription factor consists of a constitutively expressed β subunit and an oxygen-dependent α subunit; the abundance of the latter determines the activity of HIF and is regulated by a family of O2- and Fe2+-dependent enzymes prolyl hydroxylases (PHDs). Currently very little is known about the function of this important pathway and the molecular structure of its key players in hypoxia-tolerant intertidal mollusks including oysters, which are among the animal champions of anoxic and hypoxic tolerance and thus can serve as excellent models to study the role of HIF cascade in adaptations to oxygen deficiency. We have isolated transcripts of two key components of the oxygen sensing pathway - the oxygen-regulated HIF-α subunit and PHD - from an intertidal mollusk, the eastern oyster Crassostrea virginica, and determined the transcriptional responses of these two genes to anoxia, hypoxia and cadmium (Cd) stress. HIF-α and PHD homologs from eastern oysters C. virginica show significant sequence similarity and share key functional domains with the earlier described isoforms from vertebrates and invertebrates. Phylogenetic analysis shows that genetic diversification of HIF and PHD isoforms occurred within the vertebrate lineage indicating functional diversification and specialization of the oxygen-sensing pathways in this group, which parallels situation observed for many other important genes. HIF-α and PHD homologs are broadly expressed at the mRNA level in different oyster tissues and show transcriptional responses to prolonged hypoxia in the gills consistent with their putative role in oxygen sensing and the adaptive response to hypoxia. Similarity in amino acid sequence, domain structure and transcriptional

Analysis of hypoxia and hypoxia-like states through metabolite profiling.

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Julie E Gleason

Full Text Available In diverse organisms, adaptation to low oxygen (hypoxia is mediated through complex gene expression changes that can, in part, be mimicked by exposure to metals such as cobalt. Although much is known about the transcriptional response to hypoxia and cobalt, little is known about the all-important cell metabolism effects that trigger these responses.Herein we use a low molecular weight metabolome profiling approach to identify classes of metabolites in yeast cells that are altered as a consequence of hypoxia or cobalt exposures. Key findings on metabolites were followed-up by measuring expression of relevant proteins and enzyme activities. We find that both hypoxia and cobalt result in a loss of essential sterols and unsaturated fatty acids, but the basis for these changes are disparate. While hypoxia can affect a variety of enzymatic steps requiring oxygen and heme, cobalt specifically interferes with diiron-oxo enzymatic steps for sterol synthesis and fatty acid desaturation. In addition to diiron-oxo enzymes, cobalt but not hypoxia results in loss of labile 4Fe-4S dehydratases in the mitochondria, but has no effect on homologous 4Fe-4S dehydratases in the cytosol. Most striking, hypoxia but not cobalt affected cellular pools of amino acids. Amino acids such as aromatics were elevated whereas leucine and methionine, essential to the strain used here, dramatically decreased due to hypoxia induced down-regulation of amino acid permeases.These studies underscore the notion that cobalt targets a specific class of iron proteins and provide the first evidence for hypoxia effects on amino acid regulation. This research illustrates the power of metabolite profiling for uncovering new adaptations to environmental stress.

The tyrosine phosphatase SHP-1 regulates hypoxia inducible factor-1α (HIF-1α protein levels in endothelial cells under hypoxia.

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Stefan K Alig

Full Text Available The tyrosine phosphatase SHP-1 negatively influences endothelial function, such as VEGF signaling and reactive oxygen species (ROS formation, and has been shown to influence angiogenesis during tissue ischemia. In ischemic tissues, hypoxia induced angiogenesis is crucial for restoring oxygen supply. However, the exact mechanism how SHP-1 affects endothelial function during ischemia or hypoxia remains unclear. We performed in vitro endothelial cell culture experiments to characterize the role of SHP-1 during hypoxia.SHP-1 knock-down by specific antisense oligodesoxynucleotides (AS-Odn increased cell growth as well as VEGF synthesis and secretion during 24 hours of hypoxia compared to control AS-Odn. This was prevented by HIF-1α inhibition (echinomycin and apigenin. SHP-1 knock-down as well as overexpression of a catalytically inactive SHP-1 (SHP-1 CS further enhanced HIF-1α protein levels, whereas overexpression of a constitutively active SHP-1 (SHP-1 E74A resulted in decreased HIF-1α levels during hypoxia, compared to wildtype SHP-1. Proteasome inhibition (MG132 returned HIF-1α levels to control or wildtype levels respectively in these cells. SHP-1 silencing did not alter HIF-1α mRNA levels. Finally, under hypoxic conditions SHP-1 knock-down enhanced intracellular endothelial reactive oxygen species (ROS formation, as measured by oxidation of H2-DCF and DHE fluorescence.SHP-1 decreases half-life of HIF-1α under hypoxic conditions resulting in decreased cell growth due to diminished VEGF synthesis and secretion. The regulatory effect of SHP-1 on HIF-1α stability may be mediated by inhibition of endothelial ROS formation stabilizing HIF-1α protein. These findings highlight the importance of SHP-1 in hypoxic signaling and its potential as therapeutic target in ischemic diseases.

Cognitive responses to hypobaric hypoxia: implications for aviation training

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Neuhaus C

2014-11-01

Full Text Available Christopher Neuhaus,1,2 Jochen Hinkelbein2,31Department of Anesthesiology, Heidelberg University Hospital, Ruprecht Karls University of Heidelberg, Heidelberg, 2Emergency Medicine and Air Rescue Working Group, German Society of Aviation and Space Medicine (DGLRM, Munich, 3Department of Anesthesiology and Intensive Care Medicine, University Hospital of Cologne, Cologne, GermanyAbstract: The aim of this narrative review is to provide an overview on cognitive responses to hypobaric hypoxia and to show relevant implications for aviation training. A principal element of hypoxia-awareness training is the intentional evocation of hypoxia symptoms during specific training sessions within a safe and controlled environment. Repetitive training should enable pilots to learn and recognize their personal hypoxia symptoms. A time span of 3–6 years is generally considered suitable to refresh knowledge of the more subtle and early symptoms especially. Currently, there are two different technical approaches available to induce hypoxia during training: hypobaric chamber training and reduced-oxygen breathing devices. Hypoxia training for aircrew is extremely important and effective, and the hypoxia symptoms should be emphasized clearly to aircrews. The use of tight-fitting masks, leak checks, and equipment checks should be taught to all aircrew and reinforced regularly. It is noteworthy that there are major differences in the required quality and quantity of hypoxia training for both military and civilian pilots.Keywords: cognitive response, aviation training, pilot, hypoxia, oxygen, loss of consciousness

Perinatal Hypoxia and Ischemia in Animal Models of Schizophrenia

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Dimitri Hefter

2018-03-01

Full Text Available Intrauterine or perinatal complications constitute a major risk for psychiatric diseases. Infants who suffered from hypoxia–ischemia (HI are at twofold risk to develop schizophrenia in later life. Several animal models attempt to reproduce these complications to study the yet unknown steps between an insult in early life and outbreak of the disease decades later. However, it is very challenging to find the right type and severity of insult leading to a disease-like phenotype in the animal, but not causing necrosis and focal neurological deficits. By contrast, too mild, repetitive insults may even be protective via conditioning effects. Thus, it is not surprising that animal models of hypoxia lead to mixed results. To achieve clinically translatable findings, better protocols are urgently needed. Therefore, we compare widely used models of hypoxia and HI and propose future directions for the field.

Quercetin suppresses hypoxia-induced accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) through inhibiting protein synthesis.

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Lee, Dae-Hee; Lee, Yong J

2008-10-01

Quercetin, a ubiquitous bioactive plant flavonoid, has been shown to inhibit the proliferation of cancer cells and induce the accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha) in normoxia. In this study, under hypoxic conditions (1% O(2)), we examined the effect of quercetin on the intracellular level of HIF-1alpha and extracellular level of vascular endothelial growth factor (VEGF) in a variety of human cancer cell lines. Surprisingly, we observed that quercetin suppressed the HIF-1alpha accumulation during hypoxia in human prostate cancer LNCaP, colon cancer CX-1, and breast cancer SkBr3 cells. Quercetin treatment also significantly reduced hypoxia-induced secretion of VEGF. Suppression of HIF-1alpha accumulation during treatment with quercetin in hypoxia was not prevented by treatment with 26S proteasome inhibitor MG132 or PI3K inhibitor LY294002. Interestingly, hypoxia (1% O(2)) in the presence of 100 microM quercetin inhibited protein synthesis by 94% during incubation for 8 h. Significant quercetin concentration-dependent inhibition of protein synthesis and suppression of HIF-1alpha accumulation were observed under hypoxic conditions. Treatment with 100 microM cycloheximide, a protein synthesis inhibitor, replicated the effect of quercetin by inhibiting HIF-1alpha accumulation during hypoxia. These results suggest that suppression of HIF-1alpha accumulation during treatment with quercetin under hypoxic conditions is due to inhibition of protein synthesis. (c) 2008 Wiley-Liss, Inc.

Modulation of radioprotective effects of respiratory hypoxia by changing the duration of hypoxia before irradiation and by combining hypoxia and administration of hemopoiesis-stimulating agents

International Nuclear Information System (INIS)

Vacek, A.; Hofer, M.

2001-01-01

Aim: Analysis of radioprotective effect of respiratory hypoxia on hemopoietic tissue and enhancement of this effect by hemopoietic activation. Material and methods: In mice breathing hypoxic gas mixture during total body gamma irradiation the recovery of pluripotent and committed granulocyte-macrophage progenitor cells and animal lethality were determined. Results: In mice forced to breathe 10% O 2 and 8% O 2 during irradiation, the oxygen tension in the spleen decreased to 40% and 20%, respectively, of control values. Hypoxia mitigated the lethal effect of gamma-rays and improved the recovery of hemopoiesis in compartments of pluripotent and committed progenitor cells. Enhancement of the proliferative activity in hemopoietic tissue by a cytokine (rmGM-CSF) or an immunomodulator (dextran sulfate) increased the effect of hypoxic radioprotection, while elimination of proliferative cells by hydroxyurea decreased the radioprotective effect. Adaptation of experimental animals to hypoxic conditions was found to reduce the radioprotective effect without influencing tissue partial oxygen pressure lowered by hypoxic conditions. Conclusion: The data presented confirm the radioprotective effect of 10% and 8% O 2 respiratory hypoxia on hemopoiesis. These findings may represent a way out for further experimental and clinical research aimed at considering differential protection of various tissues by hypoxia. (orig.) [de

Small interfering RNA targeting HIF-1{alpha} reduces hypoxia-dependent transcription and radiosensitizes hypoxic HT 1080 human fibrosarcoma cells in vitro

Energy Technology Data Exchange (ETDEWEB)

Staab, Adrian [Wuerzburg Univ. (Germany). Dept. of Radiation Oncology; Paul Scherrer Institute (PSI), Villigen (Switzerland); Fleischer, Markus [Wuerzburg Univ. (Germany). Dept. of Radiation Oncology; Wuerzburg Univ. (Germany). Medical Clinic II; Loeffler, Juergen; Einsele, Herrmann [Wuerzburg Univ. (Germany). Medical Clinic II; Said, Harun M.; Katzer, Astrid; Flentje, Michael [Wuerzburg Univ. (Germany). Dept. of Radiation Oncology; Plathow, Christian [Freiburg Univ. (Germany). Dept. of Nuclear Medicine; Vordermark, Dirk [Wuerzburg Univ. (Germany). Dept. of Radiation Oncology; Halle-Wittenberg Univ. (Germany). Dept. of Radiation Oncology

2011-04-15

Background: Hypoxia inducible factor-1 has been identified as a potential target to overcome hypoxia-induced radioresistance The aim of the present study was to investigate whether selective HIF-1 inhibition via small interfering RNA (siRNA) targeting hypoxia-inducible factor 1{alpha} (HIF-1{alpha}) affects hypoxia-induced radioresistance in HT 1080 human fibrosarcoma cells. Material and Methods: HIF-1{alpha} expression in HT 1080 human fibrosarcoma cells in vitro was silenced using HIF-1{alpha} siRNA sequence primers. Quantitative real-time polymerase chain reaction assay was performed to quantify the mRNA expression of HIF-1{alpha}. HIF-1{alpha} protein levels were studied by Western blotting at 20% (air) or after 12 hours at 0.1% O{sub 2} (hypoxia). Cells were assayed for clonogenic survival after irradiation with 2, 5, or 10 Gy, under normoxic or hypoxic conditions in the presence of HIF-1{alpha}-targeted or control siRNA sequences. A modified oxygen enhancement ratio (OER') was calculated as the ratio of the doses to achieve the same survival at 0.1% O{sub 2} as at ambient oxygen tensions. OER' was obtained at cell survival levels of 50%, 37%, and 10%. Results: HIF-1{alpha}-targeted siRNA enhanced radiation treatment efficacy under severely hypoxic conditions compared to tumor cells treated with scrambled control siRNA. OER was reduced on all survival levels after treatment with HIF-1{alpha}-targeted siRNA, suggesting that inhibition of HIF-1 activation by using HIF-1{alpha}-targeted siRNA increases radiosensitivity of hypoxic tumor cells in vitro. Conclusion: Inhibition of HIF-1 activation by using HIF-1{alpha}-targeted siRNA clearly acts synergistically with radiotherapy and increase radiosensitivity of hypoxic cells in vitro. (orig.)

Small interfering RNA targeting HIF-1α reduces hypoxia-dependent transcription and radiosensitizes hypoxic HT 1080 human fibrosarcoma cells in vitro

International Nuclear Information System (INIS)

Staab, Adrian; Fleischer, Markus; Wuerzburg Univ.; Loeffler, Juergen; Einsele, Herrmann; Said, Harun M.; Katzer, Astrid; Flentje, Michael; Plathow, Christian; Vordermark, Dirk; Halle-Wittenberg Univ.

2011-01-01

Background: Hypoxia inducible factor-1 has been identified as a potential target to overcome hypoxia-induced radioresistance The aim of the present study was to investigate whether selective HIF-1 inhibition via small interfering RNA (siRNA) targeting hypoxia-inducible factor 1α (HIF-1α) affects hypoxia-induced radioresistance in HT 1080 human fibrosarcoma cells. Material and Methods: HIF-1α expression in HT 1080 human fibrosarcoma cells in vitro was silenced using HIF-1α siRNA sequence primers. Quantitative real-time polymerase chain reaction assay was performed to quantify the mRNA expression of HIF-1α. HIF-1α protein levels were studied by Western blotting at 20% (air) or after 12 hours at 0.1% O 2 (hypoxia). Cells were assayed for clonogenic survival after irradiation with 2, 5, or 10 Gy, under normoxic or hypoxic conditions in the presence of HIF-1α-targeted or control siRNA sequences. A modified oxygen enhancement ratio (OER') was calculated as the ratio of the doses to achieve the same survival at 0.1% O 2 as at ambient oxygen tensions. OER' was obtained at cell survival levels of 50%, 37%, and 10%. Results: HIF-1α-targeted siRNA enhanced radiation treatment efficacy under severely hypoxic conditions compared to tumor cells treated with scrambled control siRNA. OER was reduced on all survival levels after treatment with HIF-1α-targeted siRNA, suggesting that inhibition of HIF-1 activation by using HIF-1α-targeted siRNA increases radiosensitivity of hypoxic tumor cells in vitro. Conclusion: Inhibition of HIF-1 activation by using HIF-1α-targeted siRNA clearly acts synergistically with radiotherapy and increase radiosensitivity of hypoxic cells in vitro. (orig.)

Acute physical exercise under hypoxia improves sleep, mood and reaction time.

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de Aquino-Lemos, Valdir; Santos, Ronaldo Vagner T; Antunes, Hanna Karen Moreira; Lira, Fabio S; Luz Bittar, Irene G; Caris, Aline V; Tufik, Sergio; de Mello, Marco Tulio

2016-02-01

This study aimed to assess the effect of two sessions of acute physical exercise at 50% VO2peak performed under hypoxia (equivalent to an altitude of 4500 m for 28 h) on sleep, mood and reaction time. Forty healthy men were randomized into 4 groups: Normoxia (NG) (n = 10); Hypoxia (HG) (n = 10); Exercise under Normoxia (ENG) (n = 10); and Exercise under Hypoxia (EHG) (n = 10). All mood and reaction time assessments were performed 40 min after awakening. Sleep was reassessed on the first day at 14 h after the initiation of hypoxia; mood and reaction time were measured 28 h later. Two sessions of acute physical exercise at 50% VO2peak were performed for 60 min on the first and second days after 3 and 27 h, respectively, after starting to hypoxia. Improved sleep efficiency, stage N3 and REM sleep and reduced wake after sleep onset were observed under hypoxia after acute physical exercise. Tension, anger, depressed mood, vigor and reaction time scores improved after exercise under hypoxia. We conclude that hypoxia impairs sleep, reaction time and mood. Acute physical exercise at 50% VO2peak under hypoxia improves sleep efficiency, reversing the aspects that had been adversely affected under hypoxia, possibly contributing to improved mood and reaction time.

Hypoxia Room

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Federal Laboratory Consortium — The Hypoxia Room is a 8x8x8 ft. clear vinyl plastic and aluminum frame construction enclosure located within USAREIM laboratory 028. The Hypoxia Room (manufactured...

Hypoxia silences retrotrapezoid nucleus respiratory chemoreceptors via alkalosis.

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Basting, Tyler M; Burke, Peter G R; Kanbar, Roy; Viar, Kenneth E; Stornetta, Daniel S; Stornetta, Ruth L; Guyenet, Patrice G

2015-01-14

In conscious mammals, hypoxia or hypercapnia stimulates breathing while theoretically exerting opposite effects on central respiratory chemoreceptors (CRCs). We tested this theory by examining how hypoxia and hypercapnia change the activity of the retrotrapezoid nucleus (RTN), a putative CRC and chemoreflex integrator. Archaerhodopsin-(Arch)-transduced RTN neurons were reversibly silenced by light in anesthetized rats. We bilaterally transduced RTN and nearby C1 neurons with Arch (PRSx8-ArchT-EYFP-LVV) and measured the cardiorespiratory consequences of Arch activation (10 s) in conscious rats during normoxia, hypoxia, or hyperoxia. RTN photoinhibition reduced breathing equally during non-REM sleep and quiet wake. Compared with normoxia, the breathing frequency reduction (Δf(R)) was larger in hyperoxia (65% FiO2), smaller in 15% FiO2, and absent in 12% FiO2. Tidal volume changes (ΔV(T)) followed the same trend. The effect of hypoxia on Δf(R) was not arousal-dependent but was reversed by reacidifying the blood (acetazolamide; 3% FiCO2). Δf(R) was highly correlated with arterial pH up to arterial pH (pHa) 7.5 with no frequency inhibition occurring above pHa 7.53. Blood pressure was minimally reduced suggesting that C1 neurons were very modestly inhibited. In conclusion, RTN neurons regulate eupneic breathing about equally during both sleep and wake. RTN neurons are the first putative CRCs demonstrably silenced by hypocapnic hypoxia in conscious mammals. RTN neurons are silent above pHa 7.5 and increasingly active below this value. During hyperoxia, RTN activation maintains breathing despite the inactivity of the carotid bodies. Finally, during hypocapnic hypoxia, carotid body stimulation increases breathing frequency via pathways that bypass RTN. Copyright © 2015 the authors 0270-6474/15/350527-17$15.00/0.

Chronic intermittent hypoxia induces atherosclerosis via activation of adipose angiopoietin-like 4.

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Drager, Luciano F; Yao, Qiaoling; Hernandez, Karen L; Shin, Mi-Kyung; Bevans-Fonti, Shannon; Gay, Jason; Sussan, Thomas E; Jun, Jonathan C; Myers, Allen C; Olivecrona, Gunilla; Schwartz, Alan R; Halberg, Nils; Scherer, Philipp E; Semenza, Gregg L; Powell, David R; Polotsky, Vsevolod Y

2013-07-15

Obstructive sleep apnea is a risk factor for dyslipidemia and atherosclerosis, which have been attributed to chronic intermittent hypoxia (CIH). Intermittent hypoxia inhibits a key enzyme of lipoprotein clearance, lipoprotein lipase, and up-regulates a lipoprotein lipase inhibitor, angiopoietin-like 4 (Angptl4), in adipose tissue. The effects and mechanisms of Angptl4 up-regulation in sleep apnea are unknown. To examine whether CIH induces dyslipidemia and atherosclerosis by increasing adipose Angptl4 via hypoxia-inducible factor-1 (HIF-1). ApoE(-/-) mice were exposed to intermittent hypoxia or air for 4 weeks while being treated with Angptl4-neutralizing antibody or vehicle. In vehicle-treated mice, hypoxia increased adipose Angptl4 levels, inhibited adipose lipoprotein lipase, increased fasting levels of plasma triglycerides and very low density lipoprotein cholesterol, and increased the size of atherosclerotic plaques. The effects of CIH were abolished by the antibody. Hypoxia-induced increases in plasma fasting triglycerides and adipose Angptl4 were not observed in mice with germline heterozygosity for a HIF-1α knockout allele. Transgenic overexpression of HIF-1α in adipose tissue led to dyslipidemia and increased levels of adipose Angptl4. In cultured adipocytes, constitutive expression of HIF-1α increased Angptl4 levels, which was abolished by siRNA. Finally, in obese patients undergoing bariatric surgery, the severity of nocturnal hypoxemia predicted Angptl4 levels in subcutaneous adipose tissue. HIF-1-mediated increase in adipose Angptl4 and the ensuing lipoprotein lipase inactivation may contribute to atherosclerosis in patients with sleep apnea.

Hypoxia tolerance in coral-reef triggerfishes (Balistidae)

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Wong, Corrie C.; Drazen, Jeffrey C.; Callan, Chatham K.; Korsmeyer, Keith E.

2018-03-01

Despite high rates of photosynthetic oxygen production during the day, the warm waters of coral reefs are susceptible to hypoxia at night due to elevated respiration rates at higher temperatures that also reduce the solubility of oxygen. Hypoxia may be a challenge for coral-reef fish that hide in the reef to avoid predators at night. Triggerfishes (Balistidae) are found in a variety of reef habitats, but they also are known to find refuge in reef crevices and holes at night, which may expose them to hypoxic conditions. The critical oxygen tension ( P crit) was determined as the point below which oxygen uptake could not be maintained to support standard metabolic rate (SMR) for five species of triggerfish. The triggerfishes exhibited similar levels of hypoxia tolerance as other coral-reef and coastal marine fishes that encounter low oxygen levels in their environment. Two species, Rhinecanthus rectangulus and R. aculeatus, had the lowest P crit ( 3.0 kPa O2), comparable to the most hypoxia-tolerant obligate coral-dwelling gobies, while Odonus niger and Sufflamen bursa were moderately tolerant to hypoxia ( P crit 4.5 kPa), and Xanthichthys auromarginatus was intermediate ( P crit 3.7 kPa). These differences in P crit were not due to differences in oxygen demand, as all the species had a similar SMR once mass differences were taken into account. The results suggest that triggerfish species are adapted for different levels of hypoxia exposure during nocturnal sheltering within the reef.

Pharmacological inhibition of dynamin II reduces constitutive protein secretion from primary human macrophages.

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Maaike Kockx

Full Text Available Dynamins are fission proteins that mediate endocytic and exocytic membrane events and are pharmacological therapeutic targets. These studies investigate whether dynamin II regulates constitutive protein secretion and show for the first time that pharmacological inhibition of dynamin decreases secretion of apolipoprotein E (apoE and several other proteins constitutively secreted from primary human macrophages. Inhibitors that target recruitment of dynamin to membranes (MiTMABs or directly target the GTPase domain (Dyngo or Dynole series, dose- and time- dependently reduced the secretion of apoE. SiRNA oligo's targeting all isoforms of dynamin II confirmed the involvement of dynamin II in apoE secretion. Inhibition of secretion was not mediated via effects on mRNA or protein synthesis. 2D-gel electrophoresis showed that inhibition occurred after apoE was processed and glycosylated in the Golgi and live cell imaging showed that inhibited secretion was associated with reduced post-Golgi movement of apoE-GFP-containing vesicles. The effect was not restricted to macrophages, and was not mediated by the effects of the inhibitors on microtubules. Inhibition of dynamin also altered the constitutive secretion of other proteins, decreasing the secretion of fibronectin, matrix metalloproteinase 9, Chitinase-3-like protein 1 and lysozyme but unexpectedly increasing the secretion of the inflammatory mediator cyclophilin A. We conclude that pharmacological inhibitors of dynamin II modulate the constitutive secretion of macrophage apoE as a class effect, and that their capacity to modulate protein secretion may affect a range of biological processes.

Hypofractionation results in reduced tumor cell kill compared to conventional fractionation for tumors with regions of hypoxia.

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Carlson, David J; Keall, Paul J; Loo, Billy W; Chen, Zhe J; Brown, J Martin

2011-03-15

Tumor hypoxia has been observed in many human cancers and is associated with treatment failure in radiation therapy. The purpose of this study is to quantify the effect of different radiation fractionation schemes on tumor cell killing, assuming a realistic distribution of tumor oxygenation. A probability density function for the partial pressure of oxygen in a tumor cell population is quantified as a function of radial distance from the capillary wall. Corresponding hypoxia reduction factors for cell killing are determined. The surviving fraction of a tumor consisting of maximally resistant cells, cells at intermediate levels of hypoxia, and normoxic cells is calculated as a function of dose per fraction for an equivalent tumor biological effective dose under normoxic conditions. Increasing hypoxia as a function of distance from blood vessels results in a decrease in tumor cell killing for a typical radiotherapy fractionation scheme by a factor of 10(5) over a distance of 130 μm. For head-and-neck cancer and prostate cancer, the fraction of tumor clonogens killed over a full treatment course decreases by up to a factor of ∼10(3) as the dose per fraction is increased from 2 to 24 Gy and from 2 to 18 Gy, respectively. Hypofractionation of a radiotherapy regimen can result in a significant decrease in tumor cell killing compared to standard fractionation as a result of tumor hypoxia. There is a potential for large errors when calculating alternate fractionations using formalisms that do not account for tumor hypoxia. Copyright © 2011 Elsevier Inc. All rights reserved.

Hypoxia induces epithelial-mesenchymal transition via activation of SNAI1 by hypoxia-inducible factor -1α in hepatocellular carcinoma

International Nuclear Information System (INIS)

Zhang, Lin; Feng, Xiaobin; Dong, Jiahong; Qian, Cheng; Huang, Gang; Li, Xiaowu; Zhang, Yujun; Jiang, Yan; Shen, Junjie; Liu, Jia; Wang, Qingliang; Zhu, Jin

2013-01-01

High invasion and metastasis are the primary factors causing poor prognosis of patients with hepatocellular carcinoma (HCC). However, the molecular mechanisms underlying these biological behaviors have not been completely elucidated. In this study, we investigate the molecular mechanism by which hypoxia promotes HCC invasion and metastasis through inducing epithelial-mesenchymal transition (EMT). The expression of EMT markers was analyzed by immunohistochemistry. Effect of hypoxia on induction of EMT and ability of cell migration and invasion were performed. Luciferase reporter system was used for evaluation of Snail regulation by hypoxia-inducible factor -1α (HIF-1α). We found that overexpression of HIF-1α was observed in HCC liver tissues and was related to poor prognosis of HCC patients. HIF-1α expression profile was correlated with the expression levels of SNAI1, E-cadherin, N-cadherin and Vimentin. Hypoxia was able to induce EMT and enhance ability of invasion and migration in HCC cells. The same phenomena were also observed in CoCl2-treated cells. The shRNA-mediated HIF-1α suppression abrogated CoCl2-induced EMT and reduced ability of migration and invasion in HCC cells. Luciferase assay showed that HIF-1α transcriptional regulated the expression of SNAI1 based on two hypoxia response elements (HREs) in SNAI1 promoter. We demonstrated that hypoxia-stabilized HIF1α promoted EMT through increasing SNAI1 transcription in HCC cells. This data provided a potential therapeutic target for HCC treatment

Human erythropoietin response to hypocapnic hypoxia, normocapnic hypoxia, and hypocapnic normoxia

DEFF Research Database (Denmark)

Klausen, T; Christensen, H; Hansen, J M

1996-01-01

exposed to 2 h each of hypocapnic hypoxia, normocapnic hypoxia, hypocapnic normoxia, and normal breathing of room air (control experiment). During the control experiment, serum-EPO showed significant variations (ANOVA P = 0.047) with a 15% increase in mean values. The serum-EPO measured in the other...... (10% Co2 with 10% O2) to the hypoxic gas mixture. This elicited an increased ventilation, unaltered arterial pH and haemoglobin oxygen affinity, a lower degree of hypoxia than during hypocapnic hypoxia, and no significant changes in serum-EPO (ANOVA P > 0.05). Hypocapnic normoxia, produced...

Glycine reduces tissue lipid peroxidation in hypoxia-reoxygenation-induced necrotizing enterocolitis in rats

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Meyer Karine Furtado

2006-01-01

Full Text Available PURPOSE: To assess the protective effect of glycine in an experimental model of Neonatal Necrotizing Enterocolitis (NEC. METHODS: Fifty (50 neonatal Wistar rats, from a litter of six female rats and weighing 4 to 6 grams, were used. Five animals were cannibalized and the 45 remaining were distributed into three groups: the G1 normal control group (n=12; the G2 Group (n=16, of animals that underwent hypoxia-reoxygenation (HR; the G3 Group of animals (n=17 that underwent HR following a 5% intraperitoneal glycine infusion. The animals underwent hypoxia in a CO2 chamber receiving an air flow of 100% CO2 for 5 minutes and reoxygenation receiving an O2 flow at 100% for 5 minutes. One centimeter long small bowel and colon segments were prepared for histological analysis. The rest of the bowel was removed in a block and frozen at minus 80degreesC for homogenization and determination of tissue malondialdehyde (MDA. Tissue lesions were classified as Grade 0 to Grade 5, according to the level of damaged mucosa. RESULTS: The animals in Group G1 had levels of small bowel and colon lesion significantly smaller as compared to the animals in Groups G2 and G3. The G2 group had mean MDA values significantly higher than the animals in the G1 (p = .015 and G3 (p=0.021 groups. MDA values did not differ significantly (p = 0.992 for the animals in groups G1 and G3. CONCLUSION: Glycine reduces tissue MDA levels (a measurement of lipid peroxidation following HR in neonatal rats.

The Effects of Portulaca oleracea on Hypoxia-Induced Pulmonary Edema in Mice.

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Yue, Tan; Xiaosa, Wen; Ruirui, Qi; Wencai, Shi; Hailiang, Xin; Min, Li

2015-03-01

Portulaca oleracea L. (PO) is known as "a vegetable for long life" due to its antioxidant, anti-inflammatory, and other pharmacological activities. However, the protective activity of the ethanol extract of PO (EEPO) against hypoxia-induced pulmonary edema has not been fully investigated. In this study, we exposed mice to a simulated altitude of 7000 meters for 0, 3, 6, 9, and 12 h to observe changes in the water content and transvascular leakage of the mouse lung. It was found that transvascular leakage increased to the maximum in the mouse lung after 6 h exposure to hypobaric hypoxia. Prophylactic administration of EEPO before hypoxic exposure markedly reduced the transvascular leakage and oxidative stress, and inhibited the upregulation of NF-kB in the mouse lung, as compared with the control group. In addition, EEPO significantly reduced the levels of proinflammatory cytokines and cell adhesion molecules in the lungs of mice, as compared with the hypoxia group. Our results show that EEPO can reduce initial transvascular leakage and pulmonary edema under hypobaric hypoxia conditions.

Effects of continuous hypoxia on energy metabolism in cultured cerebro-cortical neurons.

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Malthankar-Phatak, Gauri H; Patel, Anant B; Xia, Ying; Hong, Soonsun; Chowdhury, Golam M I; Behar, Kevin L; Orina, Isaac A; Lai, James C K

2008-09-10

Mechanisms underlying hypoxia-induced neuronal adaptation have not been fully elucidated. In the present study we investigated glucose metabolism and the activities of glycolytic and TCA cycle enzymes in cerebro-cortical neurons exposed to hypoxia (3 days in 1% of O2) or normoxia (room air). Hypoxia led to increased activities of LDH (194%), PK (90%), and HK (24%) and decreased activities of CS (15%) and GDH (34%). Neurons were incubated with [1-(13)C]glucose for 45 and 120 min under normoxic or hypoxic (120 min only) conditions and 13C enrichment determined in the medium and cell extract using 1H-{13C}-NMR. In hypoxia-treated neurons [3-(13)C]lactate release into the medium was 428% greater than in normoxia-treated controls (45-min normoxic incubation) and total flux through lactate was increased by 425%. In contrast glucose oxidation was reduced significantly in hypoxia-treated neurons, even when expressed relative to total cellular protein, which correlated with the reduced activities of the measured mitochondrial enzymes. The results suggest that surviving neurons adapt to prolonged hypoxia by up-regulation of glycolysis and down-regulation of oxidative energy metabolism, similar to certain other cell types. The factors leading to adaptation and survival for some neurons but not others remain to be determined.

Alginate Microencapsulation of Human Islets Does Not Increase Susceptibility to Acute Hypoxia

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I. K. Hals

2013-01-01

Full Text Available Islet transplantation in diabetes is hampered by the need of life-long immunosuppression. Encapsulation provides partial immunoprotection but could possibly limit oxygen supply, a factor that may enhance hypoxia-induced beta cell death in the early posttransplantation period. Here we tested susceptibility of alginate microencapsulated human islets to experimental hypoxia (0.1–0.3% O2 for 8 h, followed by reoxygenation on viability and functional parameters. Hypoxia reduced viability as measured by MTT by 33.8±3.5% in encapsulated and 42.9±5.2% in nonencapsulated islets (P<0.2. Nonencapsulated islets released 37.7% (median more HMGB1 compared to encapsulated islets after hypoxic culture conditions (P<0.001. Glucose-induced insulin release was marginally affected by hypoxia. Basal oxygen consumption was equally reduced in encapsulated and nonencapsulated islets, by 22.0±6.1% versus 24.8±5.7%. Among 27 tested cytokines/chemokines, hypoxia increased the secretion of IL-6 and IL-8/CXCL8 in both groups of islets, whereas an increase of MCP-1/CCL2 was seen only with nonencapsulated islets. Conclusion. Alginate microencapsulation of human islets does not increase susceptibility to acute hypoxia. This is a positive finding in relation to potential use of encapsulation for islet transplantation.

Hypoxia inducible factor 3α plays a critical role in alveolarization and distal epithelial cell differentiation during mouse lung development.

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Yadi Huang

Full Text Available Lung development occurs under relative hypoxia and the most important oxygen-sensitive response pathway is driven by Hypoxia Inducible Factors (HIF. HIFs are heterodimeric transcription factors of an oxygen-sensitive subunit, HIFα, and a constitutively expressed subunit, HIF1β. HIF1α and HIF2α, encoded by two separate genes, contribute to the activation of hypoxia inducible genes. A third HIFα gene, HIF3α, is subject to alternative promoter usage and splicing, leading to three major isoforms, HIF3α, NEPAS and IPAS. HIF3α gene products add to the complexity of the hypoxia response as they function as dominant negative inhibitors (IPAS or weak transcriptional activators (HIF3α/NEPAS. Previously, we and others have shown the importance of the Hif1α and Hif2α factors in lung development, and here we investigated the role of Hif3α during pulmonary development. Therefore, HIF3α was conditionally expressed in airway epithelial cells during gestation and although HIF3α transgenic mice were born alive and appeared normal, their lungs showed clear abnormalities, including a post-pseudoglandular branching defect and a decreased number of alveoli. The HIF3α expressing lungs displayed reduced numbers of Clara cells, alveolar epithelial type I and type II cells. As a result of HIF3α expression, the level of Hif2α was reduced, but that of Hif1α was not affected. Two regulatory genes, Rarβ, involved in alveologenesis, and Foxp2, a transcriptional repressor of the Clara cell specific Ccsp gene, were significantly upregulated in the HIF3α expressing lungs. In addition, aberrant basal cells were observed distally as determined by the expression of Sox2 and p63. We show that Hif3α binds a conserved HRE site in the Sox2 promoter and weakly transactivated a reporter construct containing the Sox2 promoter region. Moreover, Hif3α affected the expression of genes not typically involved in the hypoxia response, providing evidence for a novel

Hypoxia Decreases Invasin-Mediated Yersinia enterocolitica Internalization into Caco-2 Cells.

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Zeitouni, Nathalie E; Dersch, Petra; Naim, Hassan Y; von Köckritz-Blickwede, Maren

2016-01-01

Yersinia enterocolitica is a major cause of human yersiniosis, with enterocolitis being a typical manifestation. These bacteria can cross the intestinal mucosa, and invade eukaryotic cells by binding to host β1 integrins, a process mediated by the bacterial effector protein invasin. This study examines the role of hypoxia on the internalization of Y. enterocolitica into intestinal epithelial cells, since the gastrointestinal tract has been shown to be physiologically deficient in oxygen levels (hypoxic), especially in cases of infection and inflammation. We show that hypoxic pre-incubation of Caco-2 cells resulted in significantly decreased bacterial internalization compared to cells grown under normoxia. This phenotype was absent after functionally blocking host β1 integrins as well as upon infection with an invasin-deficient Y. enterocolitica strain. Furthermore, downstream phosphorylation of the focal adhesion kinase was also reduced under hypoxia after infection. In good correlation to these data, cells grown under hypoxia showed decreased protein levels of β1 integrins at the apical cell surface whereas the total protein level of the hypoxia inducible factor (HIF-1) alpha was elevated. Furthermore, treatment of cells with the HIF-1 α stabilizer dimethyloxalylglycine (DMOG) also reduced invasion and decreased β1 integrin protein levels compared to control cells, indicating a potential role for HIF-1α in this process. These results suggest that hypoxia decreases invasin-integrin-mediated internalization of Y. enterocolitica into intestinal epithelial cells by reducing cell surface localization of host β1 integrins.

Prolonged hypoxia increases survival even in Zebrafish (Danio rerio showing cardiac arrhythmia.

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Renate Kopp

Full Text Available Tolerance towards hypoxia is highly pronounced in zebrafish. In this study even beneficial effects of hypoxia, specifically enhanced survival of zebrafish larvae, could be demonstrated. This effect was actually more pronounced in breakdance mutants, which phenotypically show cardiac arrhythmia. Breakdance mutants (bre are characterized by chronically reduced cardiac output. Despite an about 50% heart rate reduction, they become adults, but survival rate significantly drops to 40%. Normoxic bre animals demonstrate increased hypoxia inducible factor 1 a (Hif-1α expression, which indicates an activated hypoxic signaling pathway. Consequently, cardiovascular acclimation, like cardiac hypertrophy and increased erythrocyte concentration, occurs. Thus, it was hypothesized, that under hypoxic conditions survival might be even more reduced. When bre mutants were exposed to hypoxic conditions, they surprisingly showed higher survival rates than under normoxic conditions and even reached wildtype values. In hypoxic wildtype zebrafish, survival yet exceeded normoxic control values. To specify physiological acclimation, cardiovascular and metabolic parameters were measured before hypoxia started (3 dpf, when the first differences in survival rate occurred (7 dpf and when survival rate plateaued (15 dpf. Hypoxic animals expectedly demonstrated Hif-1α accumulation and consequently enhanced convective oxygen carrying capacity. Moreover, bre animals showed a significantly enhanced heart rate under hypoxic conditions, which reached normoxic wildtype values. This improvement in convective oxygen transport ensured a sufficient oxygen and nutrient supply and was also reflected in the significantly higher mitochondrial activity. The highly optimized energy metabolism observed in hypoxic zebrafish larvae might be decisive for periods of higher energy demand due to organ development, growth and increased activity. However, hypoxia increased survival only during a

Acetazolamide during acute hypoxia improves tissue oxygenation in the human brain.

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Wang, Kang; Smith, Zachary M; Buxton, Richard B; Swenson, Erik R; Dubowitz, David J

2015-12-15

Low doses of the carbonic anhydrase inhibitor acetazolamide provides accelerated acclimatization to high-altitude hypoxia and prevention of cerebral and other symptoms of acute mountain sickness. We previously observed increases in cerebral O2 metabolism (CMRO2 ) during hypoxia. In this study, we investigate whether low-dose oral acetazolamide (250 mg) reduces this elevated CMRO2 and in turn might improve cerebral tissue oxygenation (PtiO2 ) during acute hypoxia. Six normal human subjects were exposed to 6 h of normobaric hypoxia with and without acetazolamide prophylaxis. We determined CMRO2 and cerebral PtiO2 from MRI measurements of cerebral blood flow (CBF) and cerebral venous O2 saturation. During normoxia, low-dose acetazolamide resulted in no significant change in CBF, CMRO2 , or PtiO2 . During hypoxia, we observed increases in CBF [48.5 (SD 12.4) (normoxia) to 65.5 (20.4) ml·100 ml(-1)·min(-1) (hypoxia), P effect was improved cerebral tissue PtiO2 during acute hypoxia [11.4 (2.7) (hypoxia) to 16.5 (3.0) mmHg (hypoxia + acetazolamide), P effect, low-dose acetazolamide is effective at the capillary endothelium, and we hypothesize that local interruption in cerebral CO2 excretion accounts for the improvements in CMRO2 and ultimately in cerebral tissue oxygenation during hypoxia. This study suggests a potentially pivotal role of cerebral CO2 and pH in modulating CMRO2 and PtiO2 during acute hypoxia. Copyright © 2015 the American Physiological Society.

Hypoxia and hypoxia mimetics decrease aquaporin 5 (AQP5 expression through both hypoxia inducible factor-1α and proteasome-mediated pathways.

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Jitesh D Kawedia

Full Text Available The alveolar epithelium plays a central role in gas exchange and fluid transport, and is therefore critical for normal lung function. Since the bulk of water flux across this epithelium depends on the membrane water channel Aquaporin 5 (AQP5, we asked whether hypoxia had any effect on AQP5 expression. We show that hypoxia causes a significant (70% decrease in AQP5 expression in the lungs of mice exposed to hypoxia. Hypoxia and the hypoxia mimetic, cobalt, also caused similar decreases in AQP5 mRNA and protein expression in the mouse lung epithelial cell line MLE-12. The action of hypoxia and cobalt on AQP5 transcription was demonstrated by directly quantifying heternonuclear RNA by real-time PCR. Dominant negative mutants of Hypoxia Inducible Factor (HIF-1α and HIF-1α siRNA blocked the action of cobalt, showing that HIF-1α is a key component in this mechanism. The proteasome inhibitors, lactacystin or proteasome inhibitor-III completely abolished the effect of hypoxia and cobalt both at the protein and mRNA level indicating that the proteasome pathway is probably involved not only for the stability of HIF-1α protein, but for the stability of unidentified transcription factors that regulate AQP5 transcription. These studies reveal a potentially important physiological mechanism linking hypoxic stress and membrane water channels.

Hypoxia and Hypoxia Mimetics Decrease Aquaporin 5 (AQP5) Expression through Both Hypoxia Inducible Factor-1α and Proteasome-Mediated Pathways

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Kawedia, Jitesh D.; Yang, Fan; Sartor, Maureen A.; Gozal, David; Czyzyk-Krzeska, Maria; Menon, Anil G.

2013-01-01

The alveolar epithelium plays a central role in gas exchange and fluid transport, and is therefore critical for normal lung function. Since the bulk of water flux across this epithelium depends on the membrane water channel Aquaporin 5 (AQP5), we asked whether hypoxia had any effect on AQP5 expression. We show that hypoxia causes a significant (70%) decrease in AQP5 expression in the lungs of mice exposed to hypoxia. Hypoxia and the hypoxia mimetic, cobalt, also caused similar decreases in AQP5 mRNA and protein expression in the mouse lung epithelial cell line MLE-12. The action of hypoxia and cobalt on AQP5 transcription was demonstrated by directly quantifying heternonuclear RNA by real-time PCR. Dominant negative mutants of Hypoxia Inducible Factor (HIF-1α) and HIF-1α siRNA blocked the action of cobalt, showing that HIF-1α is a key component in this mechanism. The proteasome inhibitors, lactacystin or proteasome inhibitor-III completely abolished the effect of hypoxia and cobalt both at the protein and mRNA level indicating that the proteasome pathway is probably involved not only for the stability of HIF-1α protein, but for the stability of unidentified transcription factors that regulate AQP5 transcription. These studies reveal a potentially important physiological mechanism linking hypoxic stress and membrane water channels. PMID:23469202

Hypoxia promotes uveal melanoma invasion through enhanced Notch and MAPK activation.

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Laura Asnaghi

Full Text Available The transcriptional response promoted by hypoxia-inducible factors has been associated with metastatic spread of uveal melanoma. We found expression of hypoxia-inducible factor 1α (HIF-1α protein in well-vascularized tumor regions as well as in four cell lines grown in normoxia, thus this pathway may be important even in well-oxygenated uveal melanoma cells. HIF-1α protein accumulation in normoxia was inhibited by rapamycin. As expected, hypoxia (1% pO2 further induced HIF-1α protein levels along with its target genes VEGF and LOX. Growth in hypoxia significantly increased cellular invasion of all 5 uveal melanoma lines tested, as did the introduction of an oxygen-insensitive HIF-1α mutant into Mel285 cells with low HIF-1α baseline levels. In contrast, HIF-1α knockdown using shRNA significantly decreased growth in hypoxia, and reduced by more than 50% tumor invasion in four lines with high HIF-1α baseline levels. Pharmacologic blockade of HIF-1α protein expression using digoxin dramatically suppressed cellular invasion both in normoxia and in hypoxia. We found that Notch pathway components, including Jag1-2 ligands, Hes1-Hey1 targets and the intracellular domain of Notch1, were increased in hypoxia, as well as the phosphorylation levels of Erk1-2 and Akt. Pharmacologic and genetic inhibition of Notch largely blocked the hypoxic induction of invasion as did the pharmacologic suppression of Erk1-2 activity. In addition, the increase in Erk1-2 and Akt phosphorylation by hypoxia was partially reduced by inhibiting Notch signaling. Our findings support the functional importance of HIF-1α signaling in promoting the invasive capacity of uveal melanoma cells in both hypoxia and normoxia, and suggest that pharmacologically targeting HIF-1α pathway directly or through blockade of Notch or Erk1-2 pathways can slow tumor spread.

Cobaltous chloride and hypoxia inhibit aryl hydrocarbon receptor-mediated responses in breast cancer cells

International Nuclear Information System (INIS)

Khan, Shaheen; Liu Shengxi; Stoner, Matthew; Safe, Stephen

2007-01-01

The aryl hydrocarbon receptor (AhR) is expressed in estrogen receptor (ER)-positive ZR-75 breast cancer cells. Treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces CYP1A1 protein and mRNA levels and also activates inhibitory AhR-ERα crosstalk associated with hormone-induced reporter gene expression. In ZR-75 cells grown under hypoxia, induction of these AhR-mediated responses by TCDD was significantly inhibited. This was not accompanied by decreased nuclear AhR levels or decreased interaction of the AhR complex with the CYP1A1 gene promoter as determined in a chromatin immunoprecipitation assay. Hypoxia-induced loss of Ah-responsiveness was not associated with induction of hypoxia-inducible factor-1α or other factors that sequester the AhR nuclear translocation (Arnt) protein, and overexpression of Arnt under hypoxia did not restore Ah-responsiveness. The p65 subunit of NFκB which inhibits AhR-mediated transactivation was not induced by hypoxia and was primarily cytosolic in ZR-75 cells grown under hypoxic and normoxic conditions. In ZR-75 cells maintained under hypoxic conditions for 24 h, BRCA1 (an enhancer of AhR-mediated transactivation in breast cancer cells) was significantly decreased and this contributed to loss of Ah-responsiveness. In cells grown under hypoxia for 6 h, BRCA1 was not decreased, but induction of CYP1A1 by TCDD was significantly decreased. Cotreatment of ZR-75 cells with TCDD plus the protein synthesis inhibitor cycloheximide for 6 h enhanced CYP1A1 expression in cells grown under hypoxia and normoxia. These results suggest that hypoxia rapidly induces protein(s) that inhibit Ah-responsiveness and these may be similar to constitutively expressed inhibitors of Ah-responsiveness (under normoxia) that are also inhibited by cycloheximide

Cytoprotective effects of atmospheric-pressure plasmas against hypoxia-induced neuronal injuries

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Yan, Xu; Meng, Zhaozhong; Ouyang, Jiting; Qiao, Yajun; Li, Jiaxin; Jia, Mei; Yuan, Fang; (Ken Ostrikov, Kostya

2018-02-01

Atmospheric pressure plasma jet (APPJ) has recently been the focus of cytoprotective research due to the physiological roles of ROS and RNS. In the current study, we investigated the effect of APPJ treatment on the hypoxia (1% oxygen) induced cell injuries. SH-SY5Y cells were treated by APPJ for different duration and incubated in normoxic condition (20% oxygen) for 5 h followed by 24 h hypoxia treatment. Cell viability was evaluated by lactate dehydrogenase (LDH) release and further monitored using the electric cell-substrate impedance sensing (ECIS) system after APPJ treatment. Results showed that APPJ could reduce cell injuries after 24 h hypoxia, which was consistent with the ECIS results. Furthermore, extracellular NO and H2O2 production was significantly increased with the APPJ treatment. It was also interesting to find that APPJ treatment reduced SH-SY5Y cells proliferation in the hypoxic microenvironment during the first 20 h of hypoxia. Although more work was still need to clarify whether the cell viability maintenance was related to the cell proliferation during hypoxia, our results provide the first evidence of real-time cell viability changes after APPJ treatment under both normoxic and hypoxic conditions, which could provide evidence for the neuroprotective applications of APPJ.

Reducing body fat with altitude hypoxia training in swimmers: role of blood perfusion to skeletal muscles.

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Chia, Michael; Liao, Chin-An; Huang, Chih-Yang; Lee, Wen-Chih; Hou, Chien-Wen; Yu, Szu-Hsien; Harris, M Brennan; Hsu, Tung-Shiung; Lee, Shin-Da; Kuo, Chia-Hua

2013-02-28

Swimmers tend to have greater body fat than athletes from other sports. The purpose of the study was to examine changes in body composition after altitude hypoxia exposure and the role of blood distribution to the skeletal muscle in swimmers. With a constant training volume of 12.3 km/day, young male swimmers (N = 10, 14.8 ± 0.5 years) moved from sea-level to a higher altitude of 2,300 meters. Body composition was measured before and after translocation to altitude using dual-energy X-ray absorptiometry (DXA) along with 8 control male subjects who resided at sea level for the same period of time. To determine the effects of hypoxia on muscle blood perfusion, total hemoglobin concentration (THC) was traced by near-infrared spectroscopy (NIRS) in the triceps and quadriceps muscles under glucose-ingested and insulin-secreted conditions during hypoxia exposure (16% O2) after training. While no change in body composition was found in the control group, subjects who trained at altitude had unequivocally decreased fat mass (-1.7 ± 0.3 kg, -11.4%) with increased lean mass (+0.8 ± 0.2 kg, +1.5%). Arterial oxygen saturation significantly decreased with increased plasma lactate during hypoxia recovery mimicking 2,300 meters at altitude (~93% versus ~97%). Intriguingly, hypoxia resulted in elevated muscle THC, and sympathetic nervous activities occurred in parallel with greater-percent oxygen saturation in both muscle groups. In conclusion, the present study provides evidence that increased blood distribution to the skeletal muscle under postprandial condition may contribute to the reciprocally increased muscle mass and decreased body mass after a 3-week altitude exposure in swimmers.

Intermittent hypoxia training in prediabetes patients: Beneficial effects on glucose homeostasis, hypoxia tolerance and gene expression.

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Serebrovska, Tetiana V; Portnychenko, Alla G; Drevytska, Tetiana I; Portnichenko, Vladimir I; Xi, Lei; Egorov, Egor; Gavalko, Anna V; Naskalova, Svitlana; Chizhova, Valentina; Shatylo, Valeriy B

2017-09-01

The present study aimed at examining beneficial effects of intermittent hypoxia training (IHT) under prediabetic conditions. We investigate the effects of three-week IHT on blood glucose level, tolerance to acute hypoxia, and leukocyte mRNA expression of hypoxia inducible factor 1α (HIF-1α) and its target genes, i.e. insulin receptor, facilitated glucose transporter-solute carrier family-2, and potassium voltage-gated channel subfamily J. Seven healthy and 11 prediabetic men and women (44-70 years of age) were examined before, next day and one month after three-week IHT (3 sessions per week, each session consisting 4 cycles of 5-min 12% O 2 and 5-min room air breathing). We found that IHT afforded beneficial effects on glucose homeostasis in patients with prediabetes reducing fasting glucose and during standard oral glucose tolerance test. The most pronounced positive effects were observed at one month after IHT termination. IHT also significantly increased the tolerance to acute hypoxia (i.e. SaO 2 level at 20th min of breathing with 12% O 2 ) and improved functional parameters of respiratory and cardiovascular systems. IHT stimulated HIF-1α mRNA expression in blood leukocytes in healthy and prediabetic subjects, but in prediabetes patients the maximum increase was lagged. The greatest changes in mRNA expression of HIF-1α target genes occurred a month after IHT and coincided with the largest decrease in blood glucose levels. The higher expression of HIF-1α was positively associated with higher tolerance to hypoxia and better glucose homeostasis. In conclusion, our results suggest that IHT may be useful for preventing the development of type 2 diabetes. Impact statement The present study investigated the beneficial effects of intermittent hypoxia training (IHT) in humans under prediabetic conditions. We found that three-week moderate IHT induced higher HIF-1α mRNA expressions as well as its target genes, which were positively correlated with higher tolerance

Hypoxia and anemia: factors in decreased sensitivity to radiation therapy and chemotherapy?

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Harrison, Louis; Blackwell, Kimberly

2004-01-01

Hypoxia is a common feature of solid tumors that occurs across a wide variety of malignancies. Hypoxia and anemia (which contributes to tumor hypoxia) can lead to ionizing radiation and chemotherapy resistance by depriving tumor cells of the oxygen essential for the cytotoxic activities of these agents. Hypoxia may also reduce tumor sensitivity to radiation therapy and chemotherapy through one or more indirect mechanisms that include proteomic and genomic changes. These effects, in turn, can lead to increased invasiveness and metastatic potential, loss of apoptosis, and chaotic angiogenesis, thereby further increasing treatment resistance. Investigations of the prognostic significance of pretreatment tumor oxygenation status have shown that hypoxia (oxygen tension [pO(2)] value effect of hypoxia on standard cancer treatment, a variety of hypoxia- and anemia-targeted therapies have been studied in an effort to improve therapeutic effectiveness and patient outcomes. Early evidence from experimental and clinical studies suggests the administration of recombinant human erythropoietin (rHuEPO) may enhance the effectiveness of radiation therapy and chemotherapy by increasing hemoglobin levels and ameliorating anemia in patients with disease- or treatment-related anemia. However, further research is needed in the area of hypoxia-related treatment resistance and its reversal.

The role of hypoxia inducible factor 1 (HIF-1) in hypoxia induced apoptosis

NARCIS (Netherlands)

Greijer, A.E.; Wall, E. van der

2004-01-01

Apoptosis can be induced in response to hypoxia. The severity of hypoxia determines whether cells become apoptotic or adapt to hypoxia and survive. A hypoxic environment devoid of nutrients prevents the cell undergoing energy dependent apoptosis and cells become necrotic. Apoptosis regulatory

Effects of hypoxia and hypercapnia on geniohyoid contractility and endurance.

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Salmone, R J; Van Lunteren, E

1991-08-01

Sleep apnea and other respiratory diseases produce hypoxemia and hypercapnia, factors that adversely affect skeletal muscle performance. To examine the effects of these chemical alterations on force production by an upper airway dilator muscle, the contractile and endurance characteristics of the geniohyoid muscle were examined in situ during severe hypoxia (arterial PO2 less than 40 Torr), mild hypoxia (PO2 45-65 Torr), and hypercapnia (PCO2 55-80 Torr) and compared with hyperoxic-normocapnic conditions in anesthetized cats. Muscles were studied at optimal length, and contractile force was assessed in response to supramaximal electrical stimulation of the hypoglossal nerve (n = 7 cats) or geniohyoid muscle (n = 2 cats). There were no significant changes in the twitch kinetics or force-frequency curve of the geniohyoid muscle during hypoxia or hypercapnia. However, the endurance of the geniohyoid, as reflected in the fatigue index (ratio of force at 2 min to initial force in response to 40-Hz stimulation at a duty cycle 0.33), was significantly reduced by severe hypoxia but not by hypercapnia or mild hypoxia. In addition, the downward shift in the force-frequency curve after the repetitive stimulation protocol was greater during hypoxia than hyperoxia, especially at higher frequencies. In conclusion, the ability of the geniohyoid muscle to maintain force output during high levels of activation is adversely affected by severe hypoxia but not mild hypoxia or hypercapnia. However, none of these chemical perturbations affected muscle contractility acutely.

Role of hypoxia and hypoxia inducible factor in physiological and pathological conditions

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Mozhgan Jahani

2017-11-01

Full Text Available Introduction: Organisms are exposed to oxygen deprivation (Hypoxia in various physiological and pathological conditions. There are different conserve evolutionary responses to counterview with this stress that primary transcriptional response to stress related to hypoxia is interceded by hypoxia-inducible factor (HIF-1 in mammals. This factor can regulate different genes that have essential roles in adaptation to this condition. In this review, the role of this factor in physiological and pathological conditions under hypoxic condition has been evaluated after examining structural features and regulation characteristics of HIF-1. Methods: First, articles related to the keywords of hypoxia and HIF-1 (from 1991-2016 were searched from valid databases such as Springer Link, Google Scholar, PubMed and Science direct. Then, the articles correlated with hypoxia, HIF-1 and their roles in physiological and pathological conditions (120 articles were searched and just 64 articles were selected for this study. Result: According to studies, there are different genes in cells and organs that can be regulated by HIF-1. Activation of genes expression by this protein occurs through its linkage to cis-acting of 50 base pair hypoxia response element (HRE region located in their promotor and enhancer. Depending on circumstances, activation of these genes can be beneficial or harmful. Conclusion: Activation of different genes in hypoxia by HIF-1 has different effects on physiological and pathological conditions. Therefore, HIF-1, as a hypoxia-inducible factor in hypoxic conditions, plays an essential role in the adaptation of cells and organs to changes related to the presence of oxygen.

Vitamin E supplementation inhibits muscle damage and inflammation after moderate exercise in hypoxia.

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Santos, S A; Silva, E T; Caris, A V; Lira, F S; Tufik, S; Dos Santos, R V T

2016-08-01

Exercise under hypoxic conditions represents an additional stress in relation to exercise in normoxia. Hypoxia induces oxidative stress and inflammation as mediated through tumour necrosis factor (TNF)-α release that might be exacerbated through exercise. In addition, vitamin E supplementation might attenuate oxidative stress and inflammation resulting from hypoxia during exercise. The present study aimed to evaluate the effects of vitamin E supplementation (250 mg) on inflammatory parameters and cellular damage after exercise under hypoxia simulating an altitude of 4200 m. Nine volunteers performed three sessions of 60 min of exercise (70% maximal oxygen uptake) interspersed for 1 week under normoxia, hypoxia and hypoxia after vitamin E supplementation 1 h before exercise. Blood was collected before, immediately after and at 1 h after exercise to measure inflammatory parameters and cell damage. Percentage oxygen saturation of haemoglobin decreased after exercise and recovered 1 h later in the hypoxia + vitamin condition (P exercise (P exercise in hypoxia increased interleukin (IL)-6, TNF-α, IL-1ra and IL-10 immediately after exercise (P exercise in hypoxia without supplementation (P exercise reduces cell damage markers after exercise in hypoxia and changes the concentration of cytokines, suggesting a possible protective effect against inflammation induced by hypoxia during exercise. © 2016 The British Dietetic Association Ltd.

Dexamethasone impairs hypoxia-inducible factor-1 function

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Wagner, A.E.; Huck, G.; Stiehl, D.P.; Jelkmann, W.; Hellwig-Buergel, T.

2008-01-01

Hypoxia-inducible factor-1 (HIF-1) is a heterodimeric transcription-factor composed of α- and β-subunits. HIF-1 is not only necessary for the cellular adaptation to hypoxia, but it is also involved in inflammatory processes and wound healing. Glucocorticoids (GC) are therapeutically used to suppress inflammatory responses. Herein, we investigated whether GC modulate HIF-1 function using GC receptor (GR) possessing (HepG2) and GR deficient (Hep3B) human hepatoma cell cultures as model systems. Dexamethasone (DEX) treatment increased HIF-1α levels in the cytosol of HepG2 cells, while nuclear HIF-1α levels and HIF-1 DNA-binding was reduced. In addition, DEX dose-dependently lowered the hypoxia-induced luciferase activity in a reporter gene system. DEX suppressed the hypoxic stimulation of the expression of the HIF-1 target gene VEGF (vascular endothelial growth factor) in HepG2 cultures. DEX did not reduce hypoxically induced luciferase activity in HRB5 cells, a Hep3B derivative lacking GR. Transient expression of the GR in HRB5 cells restored the susceptibility to DEX. Our study discloses the inhibitory action of GC on HIF-1 dependent gene expression, which may be important with respect to the impaired wound healing in DEX-treated patients

Knockdown of hypoxia-inducible factor-1 alpha reduces proliferation, induces apoptosis and attenuates the aggressive phenotype of retinoblastoma WERI-Rb-1 cells under hypoxic conditions.

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Xia, Tian; Cheng, Hao; Zhu, Yu

2014-01-01

Hypoxia-inducible factor-1 alpha (HIF-1α) plays a critical role in tumor cell adaption to hypoxia by inducing the transcription of numerous genes. The role of HIF-1α in malignant retinoblastoma remains unclear. We analyzed the role of HIF-1α in WERI-Rb-1 retinoblastoma cells under hypoxic conditions. CoCl2 (125 mmol/L) was added to the culture media to mimic hypoxia. HIF-1α was silenced using siRNA. Gene and protein expression were measured by semi-quantitative RT-PCR and Western blotting. Cell cycle and apoptosis were analyzed by flow cytometry. Cell proliferation, adhesion and invasion were assayed using MTT, Transwell invasion, and cell adhesion assays respectively. Hypoxia significantly upregulated HIF-1α protein expression and the HIF-1α target genes VEGF, GLUT1, and Survivin mRNA. HIF-1α mRNA expression was not affected by hypoxia. Transfection of the siRNA expression plasmid pRNAT-CMV3.2/Neo-HIF-1α silenced HIF-1α by approximately 80% in hypoxic WERI-Rb-1 cells. The knockdown of HIF-1α under hypoxic conditions downregulated VEGF, GLUT1, and Survivin mRNA. It also inhibited proliferation, promoted apoptosis, induced the G0/G1 phase cell cycle arrest, and reduced the adhesion and invasion of WERI-Rb-1 cells. HIF-1α plays a major role in the survival and aggressive phenotype of retinoblastoma cells under hypoxic conditions. Targeting HIF-1α may be a promising therapeutic strategy for human malignant retinoblastoma.

Preclinical evidence of mitochondrial nicotinamide adenine dinucleotide as an effective alarm parameter under hypoxia

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Shi, Hua; Sun, Nannan; Mayevsky, Avraham; Zhang, Zhihong; Luo, Qingming

2014-01-01

Early detection of tissue hypoxia in the intensive care unit is essential for effective treatment. Reduced nicotinamide adenine dinucleotide (NADH) has been suggested to be the most sensitive indicator of tissue oxygenation at the mitochondrial level. However, no experimental evidence comparing the kinetics of changes in NADH and other physiological parameters has been provided. The aim of this study is to obtain the missing data in a systematic and reliable manner. We constructed four acute hypoxia models, including hypoxic hypoxia, hypemic hypoxia, circulatory hypoxia, and histogenous hypoxia, and measured NADH fluorescence, tissue reflectance, cerebral blood flow, respiration, and electrocardiography simultaneously from the induction of hypoxia until death. We found that NADH was not always the first onset parameter responding to hypoxia. The order of responses was mainly affected by the cause of hypoxia. However, NADH reached its alarm level earlier than the other monitored parameters, ranging from several seconds to >10 min. As such, we suggest that the NADH can be used as a hypoxia indicator, although the exact level that should be used must be further investigated. When the NADH alarm is detected, the body still has a chance to recover if appropriate and timely treatment is provided.

Mechanisms Causing Hypoxia in the Baltic Sea at Different Spatial and Temporal Scales

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Conley, D. J.; Carstensen, J.; Gustafsson, B.; Slomp, C. P.

2016-02-01

A number of synthesis efforts have documented the world-wide increase in hypoxia, which is primarily driven by nutrient inputs with consequent organic matter enrichment. Physical factors including freshwater or saltwater inputs, stratification and temperature also play an important role in causing and sustaining hypoxia. The Baltic Sea provides an interesting case study to examine changes in oxygen dynamics over time because of the diversity of the types of hypoxia that occur, which ranges from episodic to seasonal hypoxia to perennial hypoxia. Hypoxia varies spatially across the basin with differences between open water bottoms and coastal systems. In addition, the extent and intensity of hypoxia has also varied greatly over the history of the basin, e.g. the last 8000 years. We will examine the mechanisms causing hypoxia at different spatial and temporal scales. The hydrodynamical setting is an important governing factor controlling possible time scales of hypoxia, but enhanced nutrient fluxes and global warming amplify oxygen depletion when oxygen supply by physical processes cannot meet oxygen demands from respiration. Our results indicate that climate change is counteracting management efforts to reduce hypoxia. We will address how hypoxia in the Baltic Sea is terminated at different scales. More importantly, we will explore the prospects of getting rid of hypoxia with the nutrient reductions that have been agreed upon by the countries in the Baltic Sea basin and discuss the time scales of improvement in bottom water oxygen conditions.

Hypoxia activated EGFR signaling induces epithelial to mesenchymal transition (EMT.

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Ashish Misra

Full Text Available Metastasis is a multi-step process which requires the conversion of polarized epithelial cells to mesenchymal cells, Epithelial-Mesenchymal Transition (EMT. EMT is essential during embryonic morphogenesis and has been implicated in the progression of primary tumors towards metastasis. Hypoxia is known to induce EMT; however the molecular mechanism is still poorly understood. Using the A431 epithelial cancer cell line, we show that cells grown under hypoxic conditions migrated faster than cells grown under normal oxygen environment. Cells grown under hypoxia showed reduced adhesion to the extracellular matrix (ECM probably due to reduced number of Vinculin patches. Growth under hypoxic conditions also led to down regulation of E-cadherin and up regulation of vimentin expression. The increased motility of cells grown under hypoxia could be due to redistribution of Rac1 to the plasma membrane as opposed to increased expression of Rac1. EGF (Epidermal Growth Factor is a known inducer of EMT and growth of A431 cells in the absence of oxygen led to increased expression of EGFR (EGF Receptor. Treatment of A431 cells with EGF led to reduced cell adhesion to ECM, increased cell motility and other EMT characteristics. Furthermore, this transition was blocked by the monoclonal antibody Cetuximab. Cetuximab also blocked the hypoxia-induced EMT suggesting that cell growth under hypoxic conditions led to activation of EGFR signaling and induction of EMT phenotype.

Decreased "ineffective erythropoiesis" preserves polycythemia in mice under long-term hypoxia.

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Harada, Tomonori; Tsuboi, Isao; Hirabayashi, Yukio; Kosaku, Kazuhiro; Naito, Michiko; Hara, Hiroyuki; Inoue, Tohru; Aizawa, Shin

2015-05-01

Hypoxia induces innumerable changes in humans and other animals, including an increase in peripheral red blood cells (polycythemia) caused by the activation of erythropoiesis mediated by increased erythropoietin (EPO) production. However, the elevation of EPO is limited and levels return to normal ranges under normoxia within 5-7 days of exposure to hypoxia, whereas polycythemia continues for as long as hypoxia persists. We investigated erythropoiesis in bone marrow and spleens from mouse models of long-term normobaric hypoxia (10 % O2) to clarify the mechanism of prolonged polycythemia in chronic hypoxia. The numbers of erythroid colony-forming units (CFU-E) in the spleen remarkably increased along with elevated serum EPO levels indicating the activation of erythropoiesis during the first 7 days of hypoxia. After 14 days of hypoxia, the numbers of CFU-E returned to normoxic levels, whereas polycythemia persisted for >140 days. Flow cytometry revealed a prolonged increase in the numbers of TER119-positive cells (erythroid cells derived from pro-erythroblasts through mature erythrocyte stages), especially the TER119 (high) CD71 (high) population, in bone marrow. The numbers of annexin-V-positive cells among the TER119-positive cells particularly declined under chronic hypoxia, suggesting that the numbers of apoptotic cells decrease during erythroid cell maturation. Furthermore, RT-PCR analysis showed that the RNA expression of BMP-4 and stem cell factor that reduces apoptotic changes during erythroid cell proliferation and maturation was increased in bone marrow under hypoxia. These findings indicated that decreased apoptosis of erythroid cells during erythropoiesis contributes to polycythemia in mice during chronic exposure to long-term hypoxia.

Fatty Acid Biosynthesis Inhibition Increases Reduction Potential in Neuronal Cells under Hypoxia

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Stephen A Brose

2016-11-01

Full Text Available Recently, we have reported a novel neuronal specific pathway for adaptation to hypoxia through increased fatty acid (FA biosynthesis (FAS followed by esterification into lipids. However, the biological role of this pathway under hypoxia remains to be elucidated. In the presented study, we have tested our hypothesis that activation of FAS maintains reduction potential and reduces lactoacidosis in neuronal cells under hypoxia. To address this hypothesis, we measured the effect of FAS inhibition on NADH2+/NAD+ and NADPH2+/NADP+ ratios, and lactic acid levels in neuronal SH-SY5Y cells exposed to normoxic and hypoxic conditions. FAS inhibitors, TOFA (inhibits Acetyl-CoA carboxylase and cerulenin (inhibits FA synthase, increased NADH2+/NAD+ and NADPH2+/NADP+ ratios under hypoxia. Further, FAS inhibition increased lactic acid under both normoxic and hypoxic conditions, and caused cytotoxicity under hypoxia but not normoxia. These results indicate that FA may serve as hydrogen acceptors under hypoxia, thus supporting oxidation reactions including anaerobic glycolysis. These findings may help to identify a radically different approach to attenuate hypoxia related pathophysiology in the nervous system including stroke.

Fatty Acid Biosynthesis Inhibition Increases Reduction Potential in Neuronal Cells under Hypoxia.

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Brose, Stephen A; Golovko, Svetlana A; Golovko, Mikhail Y

2016-01-01

Recently, we have reported a novel neuronal specific pathway for adaptation to hypoxia through increased fatty acid (FA) biosynthesis followed by esterification into lipids. However, the biological role of this pathway under hypoxia remains to be elucidated. In the presented study, we have tested our hypothesis that activation of FA synthesis maintains reduction potential and reduces lactoacidosis in neuronal cells under hypoxia. To address this hypothesis, we measured the effect of FA synthesis inhibition on [Formula: see text]/NAD + and [Formula: see text]/NADP + ratios, and lactic acid levels in neuronal SH-SY5Y cells exposed to normoxic and hypoxic conditions. FA synthesis inhibitors, TOFA (inhibits Acetyl-CoA carboxylase) and cerulenin (inhibits FA synthase), increased [Formula: see text]/NAD + and [Formula: see text]/NADP + ratios under hypoxia. Further, FA synthesis inhibition increased lactic acid under both normoxic and hypoxic conditions, and caused cytotoxicity under hypoxia but not normoxia. These results indicate that FA may serve as hydrogen acceptors under hypoxia, thus supporting oxidation reactions including anaerobic glycolysis. These findings may help to identify a radically different approach to attenuate hypoxia related pathophysiology in the nervous system including stroke.

Dynamics and distribution of natural and human-caused hypoxia

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Rabalais, N. N.; Díaz, R. J.; Levin, L. A.; Turner, R. E.; Gilbert, D.; Zhang, J.

2010-02-01

often. The consequences of global warming and climate change are effectively uncontrollable at least in the near term. On the other hand, the consequences of eutrophication-induced hypoxia can be reversed if long-term, broad-scale, and persistent efforts to reduce substantial nutrient loads are developed and implemented. In the face of globally expanding hypoxia, there is a need for water and resource managers to act now to reduce nutrient loads to maintain, at least, the current status.

Ageing and cardiorespiratory response to hypoxia.

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Lhuissier, François J; Canouï-Poitrine, Florence; Richalet, Jean-Paul

2012-11-01

The risk of severe altitude-induced diseases is related to ventilatory and cardiac responses to hypoxia and is dependent on sex, age and exercise training status. However, it remains unclear how ageing modifies these physiological adaptations to hypoxia. We assessed the physiological responses to hypoxia with ageing through a cross-sectional 20 year study including 4675 subjects (2789 men, 1886 women; 14-85 years old) and a longitudinal study including 30 subjects explored at a mean 10.4 year interval. The influence of sex, training status and menopause was evaluated. The hypoxia-induced desaturation and the ventilatory and cardiac responses to hypoxia at rest and exercise were measured. In men, ventilatory response to hypoxia increased (P ageing. Cardiac response to hypoxia was blunted with ageing in both sexes (P ageing. These adaptive responses were less pronounced or absent in post-menopausal women (P ageing in men while cardiac response is blunted with ageing in both sexes. Training aggravates desaturation at exercise in hypoxia, improves the ventilatory response and limits the ageing-induced blunting of cardiac response to hypoxia. Training limits the negative effects of menopause in cardiorespiratory adaptations to hypoxia.

Valuing Ecosystem Services with Fishery Rents: A Lumped-Parameter Approach to Hypoxia in the Neuse River Estuary

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Larry B. Crowder

2011-11-01

Full Text Available Valuing ecosystem services with microeconomic underpinnings presents challenges because these services typically constitute nonmarket values and contribute to human welfare indirectly through a series of ecological pathways that are dynamic, nonlinear, and difficult to quantify and link to appropriate economic spatial and temporal scales. This paper develops and demonstrates a method to value a portion of ecosystem services when a commercial fishery is dependent on the quality of estuarine habitat. Using a lumped-parameter, dynamic open access bioeconomic model that is spatially explicit and includes predator-prey interactions, this paper quantifies part of the value of improved ecosystem function in the Neuse River Estuary when nutrient pollution is reduced. Specifically, it traces the effects of nitrogen loading on the North Carolina commercial blue crab fishery by modeling the response of primary production and the subsequent impact on hypoxia (low dissolved oxygen. Hypoxia, in turn, affects blue crabs and their preferred prey. The discounted present value fishery rent increase from a 30% reduction in nitrogen loadings in the Neuse is $2.56 million, though this welfare estimate is fairly sensitive to some parameter values. Surprisingly, this number is not sensitive to initial conditions.

Simulated reduction of hypoxia in the northern Gulf of Mexico due to phosphorus limitation

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Arnaud Laurent

2014-02-01

Full Text Available Abstract Excess nutrient loading from the Mississippi-Atchafalaya River system promotes the seasonal development of hypoxic bottom waters on the Louisiana shelf with detrimental effects on the benthic fauna. In the Mississippi River plume, primary production becomes phosphorus-limited between May and July at the peak of nutrient loading, displacing a portion of primary production and depositional fluxes westward. Here we quantitatively assessed, for the first time, the effect of phosphorus limitation on hypoxia development in the Mississippi-Atchafalaya River plume using a realistic physical-biogeochemical model. Results indicate that, despite a redistribution of respiration processes toward the western shelf, phosphorus limitation does not promote a westward expansion or relocation of hypoxia, as previously speculated. Rather, the onset of hypoxia was delayed and the size of the hypoxic zone reduced. Sensitivity experiments showed that this feature is robust in our model. Results from simulations with altered river input indicate that, despite phosphorus limitation, the co-reduction of nitrogen and phosphorus loads remains the best strategy to reduce hypoxia. Yet, even though nutrient load reductions have an immediate effect on hypoxia in this analysis, a 50% reduction in both nutrients will not be sufficient to meet the Gulf Hypoxia action plan goal of a 5·103 km2 hypoxic area.

Is decision making in hypoxia affected by pre-acclimatisation? A randomized controlled trial.

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Niedermeier, Martin; Weisleitner, Andreas; Lamm, Claus; Ledochowski, Larissa; Frühauf, Anika; Wille, Maria; Burtscher, Martin; Kopp, Martin

2017-05-01

Decision making is impaired in hypoxic environments, which may have serious or even lethal consequences for mountaineers. An acclimatisation period prior to high altitude exposures may help to overcome adverse effects of hypoxia. Thus, we investigated possible effects of short-term pre-acclimatisation on decision making in hypoxia. In a randomized controlled study design, 52 healthy participants were allocated to a hypoxia group (HG: short-term pre-acclimatisation by the use of intermittent hypoxia 7×1h at F i O 2 =12.6%, equivalent to 4500m) or a control group (CG: sham pre-acclimatisation 7×1h at F i O 2 =20.9%, equivalent to 600m). The number of risky decisions was assessed using the Game of Dice Task at four time points during a 12-hours stay in hypoxia (F i O 2 =12.6%). 42 (HG: 27, CG: 25) participants completed the study. The number of risky decisions was significantly (p=0.048 as determined by 4×2 ANCOVA) reduced in the hypoxia group compared to the control group, partial η 2 =0.11, when the age-effect on decision making was controlled. Self-reported positive affective valence prior to decision making was negatively related to the number of risky decisions, rdecision making in hypoxia in a positive way and might be considered as a risk-reducing preparation method prior to exposures to hypoxic environments. Positive affective states seem to have a medium-sized protective effect against risky decision making. Copyright © 2017 Elsevier Inc. All rights reserved.

Alginate Microencapsulation of Human Islets Does Not Increase Susceptibility to Acute Hypoxia

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Hals, I. K.; Rokstad, A. M.; Strand, B. L.; Oberholzer, J.; Grill, V.

2013-01-01

Islet transplantation in diabetes is hampered by the need of life-long immunosuppression. Encapsulation provides partial immunoprotection but could possibly limit oxygen supply, a factor that may enhance hypoxia-induced beta cell death in the early posttransplantation period. Here we tested susceptibility of alginate microencapsulated human islets to experimental hypoxia (0.1–0.3% O2 for 8 h, followed by reoxygenation) on viability and functional parameters. Hypoxia reduced viability as measured by MTT by 33.8 ± 3.5% in encapsulated and 42.9 ± 5.2% in nonencapsulated islets (P microencapsulation of human islets does not increase susceptibility to acute hypoxia. This is a positive finding in relation to potential use of encapsulation for islet transplantation. PMID:24364039

Pimonidazole: a novel hypoxia marker for complementary study of tumor hypoxia and tumor biology

International Nuclear Information System (INIS)

Varia, Mahesh A.; Kennedy, Andrew S.; Calkins-Adams, Dennise P.; Rinker, Lillian; Novotny, Debra; Fowler, Wesley C.; Raleigh, James A.

1997-01-01

Purpose/Objectives: Tumor hypoxia appears to be associated with treatment resistance and with gene expression that may lead to hypoxia-mediated selection of tumor cells as a source for cell growth and metastases. The objective of this study was to develop complementary techniques of hypoxia detection with molecular markers of cell proliferation and metastases in order to investigate the role of tumor hypoxia in tumor biology. Materials and Methods: Pimonidazole is a 2-nitroimidazole which is reductively-activated and becomes covalently bound to thiol-containing proteins only in hypoxic cells. These adducts can be detected using immunohistochemistry, enzyme linked immunosorbent assay or flow cytometry as a measure of hypoxia in tumors. Quantitative immunohistochemical analysis has been completed for five patients with squamous cell carcinoma of the cervix who were given pimonidazole hydrochloride (0.5 g/m 2 intravenously) followed by cervical biopsies 24 hours later. Informed consent was obtained according to a protocol approved by the Institutional Review Board. A minimum of 3 random biopsies were obtained from the tumors and at least four sections examined from each biopsy site. Formalin fixed, paraffin embedded tissue sections were immunostained for pimonidazole binding using a mouse monoclonal antibody. Commercially available monoclonal antibodies were used to detect cell proliferation markers MIB-1 (Ki-67) and to detect vascular endothelial growth factor (VEGF) in tumor cells in contiguous sections. The extent of immunostaining was expressed as the percent of immunostained to total tumor cells as determined by Chalkley point counting. Results: No clinical toxicities were associated with pimonidazole infusion. Immunostaining with pimonidazole antibody was observed in all patients indicating the presence of tumor hypoxia. Qualitatively there is little or no overlap between the areas of hypoxia and proliferation. Quantitative data tabulated below show the

Migraine induced by hypoxia

DEFF Research Database (Denmark)

Arngrim, Nanna; Schytz, Henrik Winther; Britze, Josefine

2016-01-01

in the visual cortex were measured by proton magnetic resonance spectroscopy. The circumference of cranial arteries was measured by 3 T high-resolution magnetic resonance angiography. Hypoxia induced migraine-like attacks in eight patients compared to one patient after sham (P = 0.039), aura in three...... and possible aura in 4 of 15 patients. Hypoxia did not change glutamate concentration in the visual cortex compared to sham, but increased lactate concentration (P = 0.028) and circumference of the cranial arteries (P ... suggests that hypoxia may provoke migraine headache and aura symptoms in some patients. The mechanisms behind the migraine-inducing effect of hypoxia should be further investigated....

Determinants of maximal oxygen uptake in severe acute hypoxia

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Calbet, J A L; Boushel, Robert Christopher; Rådegran, G

2003-01-01

To unravel the mechanisms by which maximal oxygen uptake (VO2 max) is reduced with severe acute hypoxia in humans, nine Danish lowlanders performed incremental cycle ergometer exercise to exhaustion, while breathing room air (normoxia) or 10.5% O2 in N2 (hypoxia, approximately 5,300 m above sea......: 1) reduction of PiO2, 2) impairment of pulmonary gas exchange, and 3) reduction of maximal cardiac output and peak leg blood flow, each explaining about one-third of the loss in VO2 max....

Oxidative stress and apoptosis after acute respiratory hypoxia and reoxygenation in rat brain

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Debora Coimbra-Costa

2017-08-01

Full Text Available Acute hypoxia increases the formation of reactive oxygen species (ROS in the brain. However, the effect of reoxygenation, unavoidable to achieve full recovery of the hypoxic organ, has not been clearly established. The aim of the present study was to evaluate the effects of exposition to acute severe respiratory hypoxia followed by reoxygenation on the evolution of oxidative stress and apoptosis in the brain. We investigated the effect of in vivo acute severe normobaric hypoxia (rats exposed to 7% O2 for 6 h and reoxygenation in normoxia (21% O2 for 24 h or 48 h on oxidative stress markers, the antioxidant system and apoptosis in the brain. After respiratory hypoxia we found increased levels of HIF-1α expression, lipid peroxidation, protein oxidation and nitric oxide in brain extracts. Antioxidant defence systems such as superoxide dismutase (SOD, reduced glutathione (GSH and glutathione peroxidase (GPx and the reduced/oxidized glutathione (GSH/GSSG ratio were significantly decreased in the brain. After 24 h of reoxygenation, oxidative stress parameters and the anti-oxidant system returned to control values. Regarding the apoptosis parameters, acute hypoxia increased cytochrome c, AIF and caspase 3 activity in the brain. The apoptotic effect is greatest after 24 h of reoxygenation. Immunohistochemistry suggests that CA3 and dentate gyrus in the hippocampus seem more susceptible to hypoxia than the cortex. Severe acute hypoxia increases oxidative damage, which in turn could activate apoptotic mechanisms. Our work is the first to demonstrate that after 24 h of reoxygenation oxidative stress is attenuated, while apoptosis is maintained mainly in the hippocampus, which may, in fact, be the cause of impaired brain function. Keywords: Antioxidants, Apoptosis, Normobaric hypoxia, Oxidative stress, Reoxygenation

A genetically encoded biosensor for visualising hypoxia responses in vivo

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Tvisha Misra

2017-02-01

Full Text Available Cells experience different oxygen concentrations depending on location, organismal developmental stage, and physiological or pathological conditions. Responses to reduced oxygen levels (hypoxia rely on the conserved hypoxia-inducible factor 1 (HIF-1. Understanding the developmental and tissue-specific responses to changing oxygen levels has been limited by the lack of adequate tools for monitoring HIF-1 in vivo. To visualise and analyse HIF-1 dynamics in Drosophila, we used a hypoxia biosensor consisting of GFP fused to the oxygen-dependent degradation domain (ODD of the HIF-1 homologue Sima. GFP-ODD responds to changing oxygen levels and to genetic manipulations of the hypoxia pathway, reflecting oxygen-dependent regulation of HIF-1 at the single-cell level. Ratiometric imaging of GFP-ODD and a red-fluorescent reference protein reveals tissue-specific differences in the cellular hypoxic status at ambient normoxia. Strikingly, cells in the larval brain show distinct hypoxic states that correlate with the distribution and relative densities of respiratory tubes. We present a set of genetic and image analysis tools that enable new approaches to map hypoxic microenvironments, to probe effects of perturbations on hypoxic signalling, and to identify new regulators of the hypoxia response.

Activity of the hypoxia-activated prodrug, TH-302, in preclinical human acute myeloid leukemia models.

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Portwood, Scott; Lal, Deepika; Hsu, Yung-Chun; Vargas, Rodrigo; Johnson, Megan K; Wetzler, Meir; Hart, Charles P; Wang, Eunice S

2013-12-01

Acute myeloid leukemia (AML) is an aggressive hematologic neoplasm. Recent evidence has shown the bone marrow microenvironment in patients with AML to be intrinsically hypoxic. Adaptive cellular responses by leukemia cells to survive under low oxygenation also confer chemoresistance. We therefore asked whether therapeutic exploitation of marrow hypoxia via the hypoxia-activated nitrogen mustard prodrug, TH-302, could effectively inhibit AML growth. We assessed the effects of hypoxia and TH-302 on human AML cells, primary samples, and systemic xenograft models. We observed that human AML cells and primary AML colonies cultured under chronic hypoxia (1% O2, 72 hours) exhibited reduced sensitivity to cytarabine-induced apoptosis as compared with normoxic controls. TH-302 treatment resulted in dose- and hypoxia-dependent apoptosis and cell death in diverse AML cells. TH-302 preferentially decreased proliferation, reduced HIF-1α expression, induced cell-cycle arrest, and enhanced double-stranded DNA breaks in hypoxic AML cells. Hypoxia-induced reactive oxygen species by AML cells were also diminished. In systemic human AML xenografts (HEL, HL60), TH-302 [50 mg/kg intraperitoneally (i.p.) 5 times per week] inhibited disease progression and prolonged overall survival. TH-302 treatment reduced the number of hypoxic cells within leukemic bone marrows and was not associated with hematologic toxicities in nonleukemic or leukemic mice. Later initiation of TH-302 treatment in advanced AML disease was as effective as earlier TH-302 treatment in xenograft models. Our results establish the preclinical activity of TH-302 in AML and provide the rationale for further clinical studies of this and other hypoxia-activated agents for leukemia therapy. ©2013 AACR.

Hypoxia decreases creatine uptake in cardiomyocytes, while creatine supplementation enhances HIF activation.

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Santacruz, Lucia; Arciniegas, Antonio Jose Luis; Darrabie, Marcus; Mantilla, Jose G; Baron, Rebecca M; Bowles, Dawn E; Mishra, Rajashree; Jacobs, Danny O

2017-08-01

Creatine (Cr), phosphocreatine (PCr), and creatine kinases (CK) comprise an energy shuttle linking ATP production in mitochondria with cellular consumption sites. Myocytes cannot synthesize Cr: these cells depend on uptake across the cell membrane by a specialized creatine transporter (CrT) to maintain intracellular Cr levels. Hypoxia interferes with energy metabolism, including the activity of the creatine energy shuttle, and therefore affects intracellular ATP and PCr levels. Here, we report that exposing cultured cardiomyocytes to low oxygen levels rapidly diminishes Cr transport by decreasing V max and K m Pharmacological activation of AMP-activated kinase (AMPK) abrogated the reduction in Cr transport caused by hypoxia. Cr supplementation increases ATP and PCr content in cardiomyocytes subjected to hypoxia, while also significantly augmenting the cellular adaptive response to hypoxia mediated by HIF-1 activation. Our results indicate that: (1) hypoxia reduces Cr transport in cardiomyocytes in culture, (2) the cytoprotective effects of Cr supplementation are related to enhanced adaptive physiological responses to hypoxia mediated by HIF-1, and (3) Cr supplementation increases the cellular ATP and PCr content in RNCMs exposed to hypoxia. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Overexpression of Hypoxia-Inducible Factor-1α Exacerbates Endothelial Barrier Dysfunction Induced by Hypoxia

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Pei Wang

2013-09-01

Full Text Available Background/Aims: The mechanisms involved in endothelial barrier dysfunction induced by hypoxia are incompletely understood. There is debate about the role of hypoxia-inducible factor-1α (HIF-1α in endothelial barrier disruption. The aim of this study was to investigate the effect of genetic overexpression of HIF-1α on barrier function and the underlying mechanisms in hypoxic endothelial cells. Methods: The plasmid pcDNA3.1/V5-His-HIF-1α was stably transfected into human endothelial cells. The cells were exposed to normoxia or hypoxia. The mRNA and protein expressions of HIF-1α were detected by RT-PCR and Western blot respectively. The barrier function was assessed by measuring the transendothelial electrical resistance (TER. The Western blot analysis was used to determine the protein expression of glucose transporter-1 (GLUT-1, zonular occludens-1 (ZO-1, occludin, and myosin light chain kinase (MLCK in endothelial cells. The mRNA expression of proinflammatory cytokines was detected by qRT-PCR. Results: Genetic overexpression of HIF-1α significantly increased the mRNA and protein expression of HIF-1α in endothelial cells. The overexpression of HIF-1α enhanced the hypoxia-induced increase of HIF-1α and GLUT-1 protein expression. HIF-1α overexpression not only exacerbated hypoxia-induced endothelial barrier dysfunction but also augmented hypoxia-induced up-regulation of MLCK protein expression. HIF-1α overexpression also enhanced IL-1β, IL-6 and TNF-α mRNA expression. Conclusion: We provide evidence that genetic overexpression of HIF-1α aggravates the hypoxia-induced endothelial barrier dysfunction via enhancing the up-regulation of MLCK protein expression caused by hypoxia, suggesting a potential role for HIF-1α in the pathogenesis of endothelial barrier dysfunction in hypoxia.

Diacetoxyscirpenol as a new anticancer agent to target hypoxia-inducible factor 1

Science.gov (United States)

Choi, Yong-Joon; Shin, Hyun-Woo; Chun, Yang-Sook; Leutou, Alain Simplice; Son, Byeng Wha; Park, Jong-Wan

2016-01-01

Hypoxia activates hypoxia-inducible factor 1, which promotes the progression of malignancy by stimulating angiogenesis and by augmenting the ability of tumors to survive. Thus, HIF-1 is one of the most compelling targets for treating cancers. The aim of this study was to find a small molecule that inhibits HIF-1 under hypoxia in cancer cells. 7,280 compounds in a chemical library were tested in a cancer cell line expressing luciferase HIF-dependently. Through three rounds of screening, we finally picked up a compound that originates from a marine bacterium parasitizing red alga. The antibiotic potently inhibited HIF-1 expression and its transcriptional activity in cancer cells exposed to hypoxia. Through two-step fractionation, diacetoxyscirpenol was purified and identified as a HIF-inhibiting ingredient. Mechanistically, diacetoxyscirpenol inhibits the synthesis of HIF-1α protein and also interferes with the dimerization of HIF-1α and ARNT. It attenuates HIF-mediated gene expression in cancer cells exposed to hypoxia, and by doing so reduces tumorigenic and angiogenic potentials of cancer cells. More importantly, diacetoxyscirpenol retarded tumor growth in mice, and reduced HIF-1α expression and vascular formation in the tumors. Overall, diacetoxyscirpenol is considered a potential drug deregulating the HIF-1 signaling pathway, and it could be beneficially employed for treating malignant tumors with hypoxic microenvironment. PMID:27613833

Effects of copper, hypoxia and acute temperature shifts on mitochondrial oxidation in rainbow trout (Oncorhynchus mykiss) acclimated to warm temperature

International Nuclear Information System (INIS)

Sappal, Ravinder; Fast, Mark; Stevens, Don; Kibenge, Fred; Siah, Ahmed; Kamunde, Collins

2015-01-01

Highlights: • Warm acclimation reduced the electron transport system (ETS) efficiency. • Warm acclimation altered the effects of acute temperature shift, hypoxia and Cu on ETS. • Warm acclimation increased thermal sensitivity of state 3 and reduced that of state 4. • Cu stimulated while hypoxia inhibited ETS respiratory activity. • Interactions of Cu and hypoxia on the ETS and plasma metabolites were antagonistic. - Abstract: Temperature fluctuations, hypoxia and metals pollution frequently occur simultaneously or sequentially in aquatic systems and their interactions may confound interpretation of their biological impacts. With a focus on energy homeostasis, the present study examined how warm acclimation influences the responses and interactions of acute temperature shift, hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperature for 3 weeks followed by exposure to environmentally realistic levels of Cu and hypoxia for 24 h. Subsequently, mitochondrial electron transport system (ETS) respiratory activity supported by complexes I–IV (CI–IV), plasma metabolites and condition indices were measured. Warm acclimation reduced fish condition, induced aerobic metabolism and altered the responses of fish to acute temperature shift, hypoxia and Cu. Whereas warm acclimation decelerated the ETS and increased the sensitivity of maximal oxidation rates of the proximal (CI and II) complexes to acute temperature shift, it reduced the thermal sensitivity of state 4 (proton leak). Effects of Cu with and without hypoxia were variable depending on the acclimation status and functional index. Notably, Cu stimulated respiratory activity in the proximal ETS segments, while hypoxia was mostly inhibitory and minimized the stimulatory effect of Cu. The effects of Cu and hypoxia were modified by temperature and showed reciprocal antagonistic interaction on the ETS and plasma

Effects of copper, hypoxia and acute temperature shifts on mitochondrial oxidation in rainbow trout (Oncorhynchus mykiss) acclimated to warm temperature

Energy Technology Data Exchange (ETDEWEB)

Sappal, Ravinder [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Fast, Mark [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Stevens, Don [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Kibenge, Fred [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada); Siah, Ahmed [British Columbia Centre for Aquatic Health Sciences, 871A Island Highway, Campbell River, British Columbia V9W 2C2 (Canada); Kamunde, Collins, E-mail: ckamunde@upei.ca [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3 (Canada)

2015-12-15

Highlights: • Warm acclimation reduced the electron transport system (ETS) efficiency. • Warm acclimation altered the effects of acute temperature shift, hypoxia and Cu on ETS. • Warm acclimation increased thermal sensitivity of state 3 and reduced that of state 4. • Cu stimulated while hypoxia inhibited ETS respiratory activity. • Interactions of Cu and hypoxia on the ETS and plasma metabolites were antagonistic. - Abstract: Temperature fluctuations, hypoxia and metals pollution frequently occur simultaneously or sequentially in aquatic systems and their interactions may confound interpretation of their biological impacts. With a focus on energy homeostasis, the present study examined how warm acclimation influences the responses and interactions of acute temperature shift, hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperature for 3 weeks followed by exposure to environmentally realistic levels of Cu and hypoxia for 24 h. Subsequently, mitochondrial electron transport system (ETS) respiratory activity supported by complexes I–IV (CI–IV), plasma metabolites and condition indices were measured. Warm acclimation reduced fish condition, induced aerobic metabolism and altered the responses of fish to acute temperature shift, hypoxia and Cu. Whereas warm acclimation decelerated the ETS and increased the sensitivity of maximal oxidation rates of the proximal (CI and II) complexes to acute temperature shift, it reduced the thermal sensitivity of state 4 (proton leak). Effects of Cu with and without hypoxia were variable depending on the acclimation status and functional index. Notably, Cu stimulated respiratory activity in the proximal ETS segments, while hypoxia was mostly inhibitory and minimized the stimulatory effect of Cu. The effects of Cu and hypoxia were modified by temperature and showed reciprocal antagonistic interaction on the ETS and plasma

Long-term exposure to hypoxia inhibits tumor progression of lung cancer in rats and mice

International Nuclear Information System (INIS)

Yu, Lunyin; Hales, Charles A

2011-01-01

Hypoxia has been identified as a major negative factor for tumor progression in clinical observations and in animal studies. However, the precise role of hypoxia in tumor progression has not been fully explained. In this study, we extensively investigated the effect of long-term exposure to hypoxia on tumor progression in vivo. Rats bearing transplanted tumors consisting of A549 human lung cancer cells (lung cancer tumor) were exposed to hypoxia for different durations and different levels of oxygen. The tumor growth and metastasis were evaluated. We also treated A549 lung cancer cells (A549 cells) with chronic hypoxia and then implanted the hypoxia-pretreated cancer cells into mice. The effect of exposure to hypoxia on metastasis of Lewis lung carcinoma in mice was also investigated. We found that long-term exposure to hypoxia a) significantly inhibited lung cancer tumor growth in xenograft and orthotopic models in rats, b) significantly reduced lymphatic metastasis of the lung cancer in rats and decreased lung metastasis of Lewis lung carcinoma in mice, c) reduced lung cancer cell proliferation and cell cycle progression in vitro, d) decreased growth of the tumors from hypoxia-pretreated A549 cells, e) decreased Na + -K + ATPase α1 expression in hypoxic lung cancer tumors, and f) increased expression of hypoxia inducible factors (HIF1α and HIF2α) but decreased microvessel density in the lung cancer tumors. In contrast to lung cancer, the growth of tumor from HCT116 human colon cancer cells (colon cancer tumor) was a) significantly enhanced in the same hypoxia conditions, accompanied by b) no significant change in expression of Na + -K + ATPase α1, c) increased HIF1α expression (no HIF2α was detected) and d) increased microvessel density in the tumor tissues. This study demonstrated that long-term exposure to hypoxia repressed tumor progression of the lung cancer from A549 cells and that decreased expression of Na + -K + ATPase was involved in hypoxic

Hypoxia-induced cytotoxic drug resistance in osteosarcoma is independent of HIF-1Alpha.

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Jennifer Adamski

Full Text Available Survival rates from childhood cancer have improved dramatically in the last 40 years, such that over 80% of children are now cured. However in certain subgroups, including metastatic osteosarcoma, survival has remained stubbornly poor, despite dose intensive multi-agent chemotherapy regimens, and new therapeutic approaches are needed. Hypoxia is common in adult solid tumours and is associated with treatment resistance and poorer outcome. Hypoxia induces chemotherapy resistance in paediatric tumours including neuroblastoma, rhabdomyosarcoma and Ewing's sarcoma, in vitro, and this drug resistance is dependent on the oxygen-regulated transcription factor hypoxia inducible factor-1 (HIF-1. In this study the effects of hypoxia on the response of the osteosarcoma cell lines 791T, HOS and U2OS to the clinically relevant cytotoxics cisplatin, doxorubicin and etoposide were evaluated. Significant hypoxia-induced resistance to all three agents was seen in all three cell lines and hypoxia significantly reduced drug-induced apoptosis. Hypoxia also attenuated drug-induced activation of p53 in the p53 wild-type U2OS osteosarcoma cells. Drug resistance was not induced by HIF-1α stabilisation in normoxia by cobalt chloride nor reversed by the suppression of HIF-1α in hypoxia by shRNAi, siRNA, dominant negative HIF or inhibition with the small molecule NSC-134754, strongly suggesting that hypoxia-induced drug resistance in osteosarcoma cells is independent of HIF-1α. Inhibition of the phosphoinositide 3-kinase (PI3K pathway using the inhibitor PI-103 did not reverse hypoxia-induced drug resistance, suggesting the hypoxic activation of Akt in osteosarcoma cells does not play a significant role in hypoxia-induced drug resistance. Targeting hypoxia is an exciting prospect to improve current anti-cancer therapy and combat drug resistance. Significant hypoxia-induced drug resistance in osteosarcoma cells highlights the potential importance of hypoxia as a target

Metabolic Plasticity Enables Circadian Adaptation to Acute Hypoxia in Zebrafish Cells

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Adolf M. Sandbichler

2018-04-01

Full Text Available Background/Aims: Reduced oxygen availability, hypoxia, is frequently encountered by organisms, tissues and cells, in aquatic environments as well as in high altitude or under pathological conditions such as infarct, stroke or cancer. The hypoxic signaling pathway was found to be mutually intertwined with circadian timekeeping in vertebrates and, as reported recently, also in mammals. However, the impact of hypoxia on intracellular metabolic oscillations is still unknown. Methods: For determination of metabolites we used Multilabel Reader based fluorescence and luminescence assays, circadian levels of Hypoxia Inducible Factor 1 alpha and oxidized peroxiredoxins were semi quantified by Western blotting and ratiometric quantification of cytosolic and mitochondrial H2O2 was achieved with stable transfections of a redox sensitive green fluorescent protein sensor into zebrafish fibroblasts. Circadian oscillations of core clock gene mRNA´s were assessed using realtime qPCR with subsequent cosine wave fit analysis. Results: Here we show that under normoxia primary metabolic activity of cells predominately occurs during day time and that after acute hypoxia of two hours, administrated immediately before each sampling point, steady state concentrations of glycolytic key metabolites such as glucose and lactate reveal to be highly rhythmic, following a circadian pattern with highest levels during the night periods and reflecting the circadian variation of the cellular response to hypoxia. Remarkably, rhythms in glycolysis are transferred to cellular energy states under normoxic conditions, so that ADP/ATP ratios oscillate as well, which is the first evidence for cycling ADP/ATP pools in a metazoan cell line to our knowledge. Furthermore, the hypoxia induced alterations in rhythms of glycolysis lead to the alignment of three major cellular redox systems, namely the circadian oscillations of NAD+/NADH and NADP+/NADPH ratios and of increased nocturnal levels

Temporal responses of coastal hypoxia to nutrient loading and physical controls

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W. M. Kemp

2009-12-01

Full Text Available The incidence and intensity of hypoxic waters in coastal aquatic ecosystems has been expanding in recent decades coincident with eutrophication of the coastal zone. Worldwide, there is strong interest in reducing the size and duration of hypoxia in coastal waters, because hypoxia causes negative effects for many organisms and ecosystem processes. Although strategies to reduce hypoxia by decreasing nutrient loading are predicated on the assumption that this action would reverse eutrophication, recent analyses of historical data from European and North American coastal systems suggest little evidence for simple linear response trajectories. We review published parallel time-series data on hypoxia and loading rates for inorganic nutrients and labile organic matter to analyze trajectories of oxygen (O₂ response to nutrient loading. We also assess existing knowledge of physical and ecological factors regulating O₂ in coastal marine waters to facilitate analysis of hypoxia responses to reductions in nutrient (and/or organic matter inputs. Of the 24 systems identified where concurrent time series of loading and O₂ were available, half displayed relatively clear and direct recoveries following remediation. We explored in detail 5 well-studied systems that have exhibited complex, non-linear responses to variations in loading, including apparent "regime shifts". A summary of these analyses suggests that O₂ conditions improved rapidly and linearly in systems where remediation focused on organic inputs from sewage treatment plants, which were the primary drivers of hypoxia. In larger more open systems where diffuse nutrient loads are more important in fueling O₂ depletion and where climatic influences are pronounced, responses to remediation tended to follow non-linear trends that may include hysteresis and time-lags. Improved understanding of hypoxia remediation requires that future studies use

Hypoxia targeting copper complexes

International Nuclear Information System (INIS)

Dearling, J.L.

1998-11-01

The importance and incidence of tumour hypoxia, its measurement and current treatments available, including pharmacological and radiopharmacological methods of targeting hypoxia, are discussed. A variety of in vitro and in vivo methods for imposing hypoxia have been developed and are reviewed. Copper, its chemistry, biochemistry and radiochemistry, the potential for use of copper radionuclides and its use to date in this field is considered with particular reference to the thiosemicarbazones. Their biological activity, metal chelation, in vitro and in vivo studies of their radiocopper complexes and the potential for their use as hypoxia targeting radiopharmaceuticals is described. The reduction of the copper(II) complex to copper(l), its pivotal importance in their biological behaviour, and the potential for manipulation of this to effect hypoxia selectivity are described. An in vitro method for assessing the hypoxia selectivity of radiopharmaceuticals is reported. The rapid deoxygenation and high viability of a mammalian cell culture in this system is discussed and factors which may affect the cellular uptake of a radiopharmaceutical are described. The design, synthesis and complexation with copper and radiocopper of a range of bis(thiosemicarbazones) is reported. Synthesis of these compounds is simple giving high yields of pure products. The characteristics of the radiocopper complexes ( 64 Cu) including lipophilicity and redox activity are reported (reduction potentials in the range -0.314 - -0.590 V). High cellular uptakes of the radiocopper complexes of the ligands, in hypoxic and normoxic EMT6 and CHO320 cells, were observed. Extremes of selectivity are shown ranging from the hypoxia selective 64 Cu(II)ATSM to normoxic cell selective 64 Cu(II)GTS. The selectivities observed are compared with the physico chemical characteristics of the complexes. A good correlation exists between selectivity of the complex and its Cu(II)/Cu(I) reduction potential, with hypoxia

Weakening of the radioprotective action of gas hypoxia with growth of ascitic tumors

Energy Technology Data Exchange (ETDEWEB)

Aytmagambetova, B Z; Shmakova, N L; Fadeyeva, T A

1975-06-27

It was shown previously that moderate hypoxia induced by breathing oxygen-poor air (5 percent O/sub 2/) reduces the lethal effect of the total irradiation of mice, while with local irradiation of tumors reduction of tumor growth rate is even more marked in hypoxia-protected animals than with irradiation of mice in normal air. This suggests the possible therapeutic application of hypoxia. It was found that acute gas hypoxia strongly retards radiation damage to bone marrow, both qualitatively (type of cells affected) and quantitatively. In addition, a definite weakening of the protective effect of hypoxia was observed, this being proportional to increase in tumor size. Planned future tests involving direct dynamic measurement of oxygen stress as a function of amount of ascites are expected to supply further information on reduction of radiosensitivity of normal tissues and on the selective intensification of tumor regression. Graphic data accompany the paper. (JPRS)

Systemic Hypoxia Changes the Organ-Specific Distribution of Vascular Endothelial Growth Factor and Its Receptors

Science.gov (United States)

Marti, Hugo H.; Risau, Werner

1998-12-01

Vascular endothelial growth factor (VEGF) plays a key role in physiological blood vessel formation and pathological angiogenesis such as tumor growth and ischemic diseases. Hypoxia is a potent inducer of VEGF in vitro. Here we demonstrate that VEGF is induced in vivo by exposing mice to systemic hypoxia. VEGF induction was highest in brain, but also occurred in kidney, testis, lung, heart, and liver. In situ hybridization analysis revealed that a distinct subset of cells within a given organ, such as glial cells and neurons in brain, tubular cells in kidney, and Sertoli cells in testis, responded to the hypoxic stimulus with an increase in VEGF expression. Surprisingly, however, other cells at sites of constitutive VEGF expression in normal adult tissues, such as epithelial cells in the choroid plexus and kidney glomeruli, decreased VEGF expression in response to the hypoxic stimulus. Furthermore, in addition to VEGF itself, expression of VEGF receptor-1 (VEGFR-1), but not VEGFR-2, was induced by hypoxia in endothelial cells of lung, heart, brain, kidney, and liver. VEGF itself was never found to be up-regulated in endothelial cells under hypoxic conditions, consistent with its paracrine action during normoxia. Our results show that the response to hypoxia in vivo is differentially regulated at the level of specific cell types or layers in certain organs. In these tissues, up- or down-regulation of VEGF and VEGFR-1 during hypoxia may influence their oxygenation after angiogenesis or modulate vascular permeability.

Zinc promotes the death of hypoxic astrocytes by upregulating hypoxia-induced hypoxia-inducible factor-1alpha expression via poly(ADP-ribose) polymerase-1.

Science.gov (United States)

Pan, Rong; Chen, Chen; Liu, Wen-Lan; Liu, Ke-Jian

2013-07-01

Pathological release of excess zinc ions has been implicated in ischemic brain cell death. However, the underlying mechanisms remain to be elucidated. In stroke, ischemia-induced zinc release and hypoxia-inducible factor-1 (HIF-1) accumulation concurrently occur in the ischemic tissue. The present study tests the hypothesis that the presence of high intracellular zinc concentration is a major cause of modifications to PARP-1 and HIF-1α during hypoxia, which significantly contributes to cell death during ischemia. Primary cortical astrocytes and C8-D1A cells were exposed to different concentrations of zinc chloride. Cell death rate and protein expression of HIF-1 and Poly(ADP-ribose) polymerase (PARP)-1 were examined after 3-h hypoxic treatment. Although 3-h hypoxia or 100 μM of zinc alone did not induce noticeable cytotoxicity, their combination led to a dramatic increase in astrocytic cell death in a zinc-concentration-dependent manner. Exposure of astrocytes to hypoxia for 3 h remarkably increased the levels of intracellular zinc and HIF-1α protein, which was further augmented by added exogenous zinc. Notably, HIF-1α knockdown blocked zinc-induced astrocyte death. Moreover, knockdown of PARP-1, another important protein in the response of hypoxia, attenuated the overexpression of HIF-1α and reduced the cell death rate. Our studies show that zinc promotes hypoxic cell death through overexpression of the hypoxia response factor HIF-1α via the cell fate determine factor PARP-1 modification, which provides a novel mechanism for zinc-mediated ischemic brain injury. © 2013 John Wiley & Sons Ltd.

Screening of hypoxia-inducible genes in sporadic ALS.

LENUS (Irish Health Repository)

Cronin, Simon

2008-10-01

Genetic variations in two hypoxia-inducible angiogenic genes, VEGF and ANG, have been linked with sporadic amyotrophic lateral sclerosis (SALS). Common variations in these genes may reduce the levels or functioning of their products. VEGF and ANG belong to a larger group of angiogenic genes that are up-regulated under hypoxic conditions. We hypothesized that common genetic variation across other members of this group may also predispose to sporadic ALS. To screen other hypoxia-inducible angiogenic genes for association with SALS, we selected 112 tagging single nucleotide polymorphisms (tgSNPs) that captured the common genetic variation across 16 VEGF-like and eight ANG-like hypoxia-inducible genes. Screening for association was performed in 270 Irish individuals with typical SALS and 272 ethnically matched unrelated controls. SNPs showing association in the Irish phase were genotyped in a replication sample of 281 Swedish sporadic ALS patients and 286 Swedish controls. Seven markers showed association in the Irish. The one modest replication signal observed in the Swedish replication sample, at rs3801158 in the gene inhibin beta A, was for the opposite allele vs. the Irish cohort. We failed to detect association of common variation across 24 candidate hypoxia-inducible angiogenic genes with SALS.

Signaling hypoxia by hypoxia-inducible factor protein hydroxylases: a historical overview and future perspectives

Science.gov (United States)

Bishop, Tammie; Ratcliffe, Peter J

2014-01-01

By the early 1900s, the close matching of oxygen supply with demand was recognized to be a fundamental requirement for physiological function, and multiple adaptive responses to environment hypoxia had been described. Nevertheless, the widespread operation of mechanisms that directly sense and respond to levels of oxygen in animal cells was not appreciated for most of the twentieth century with investigators generally stressing the regulatory importance of metabolic products. Work over the last 25 years has overturned that paradigm. It has revealed the existence of a set of “oxygen-sensing” 2-oxoglutarate dependent dioxygenases that catalyze the hydroxylation of specific amino acid residues and thereby control the stability and activity of hypoxia-inducible factor. The hypoxia-inducible factor hydroxylase pathway regulates a massive transcriptional cascade that is operative in essentially all animal cells. It transduces a wide range of responses to hypoxia, extending well beyond the classical boundaries of hypoxia physiology. Here we review the discovery and elucidation of these pathways, and consider the opportunities and challenges that have been brought into focus by the findings, including new implications for the integrated physiology of hypoxia and therapeutic approaches to ischemic/hypoxic disease. PMID:27774477

Combining Optical Reporter Proteins with Different Half-lives to Detect Temporal Evolution of Hypoxia and Reoxygenation in Tumors

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Pierre Danhier

2015-12-01

Full Text Available Here we have developed a hypoxia response element driven imaging strategy that combined the hypoxia-driven expression of two optical reporters with different half-lives to detect temporal changes in hypoxia and hypoxia inducible factor (HIF activity. For this purpose, human prostate cancer PC3 cells were transfected with the luciferase gene fused with an oxygen-dependent degradation domain (ODD-luc and a variant of the enhanced green fluorescent protein (EGFP. Both ODD-luciferase and EGFP were under the promotion of a poly-hypoxia-response element sequence (5xHRE. The cells constitutively expressed tdTomato red fluorescent protein. For validating the imaging strategy, cells were incubated under hypoxia (1% O2 for 48 hours and then reoxygenated. The luciferase activity of PC3-HRE-EGFP/HRE-ODD-luc/tdtomato cells detected by bioluminescent imaging rapidly decreased after reoxygenation, whereas EGFP levels in these cells remained stable for several hours. After in vitro validation, PC3-HRE-EGFP/HRE-ODD-luc/tdtomato tumors were implanted subcutaneously and orthotopically in nude male mice and imaged in vivo and ex vivo using optical imaging in proof-of-principle studies to demonstrate differences in optical patterns between EGFP expression and bioluminescence. This novel "timer" imaging strategy of combining the short-lived ODD-luciferase and the long-lived EGFP can provide a time frame of HRE activation in PC3 prostate cancer cells and will be useful to understand the temporal changes in hypoxia and HIF activity during cancer progression and following treatments including HIF targeting strategies.

Tumor Hypoxia: Causative Mechanisms, Microregional Heterogeneities, and the Role of Tissue-Based Hypoxia Markers.

Science.gov (United States)

Vaupel, Peter; Mayer, Arnulf

Tumor hypoxia is a hallmark of solid malignant tumor growth, profoundly influences malignant progression and contributes to the development of therapeutic resistance. Pathogenesis of tumor hypoxia is multifactorial, with contributions from both acute and chronic factors. Spatial distribution of hypoxia within tumors is markedly heterogeneous and often changes over time, e.g., during a course of radiotherapy. Substantial changes in the oxygenation status can occur within the distance of a few cell layers, explaining the inability of currently used molecular imaging techniques to adequately assess this crucial trait. Due to the possible importance of tumor hypoxia for clinical decision-making, there is a great demand for molecular tools which may provide the necessary resolution down to the single cell level. Exogenous and endogenous markers of tumor hypoxia have been investigated for this purpose. Their potential use may be greatly enhanced by multiparametric in situ methods in experimental and human tumor tissue.

CNS hypoxia is more pronounced in murine cerebral than noncerebral malaria and is reversed by erythropoietin

DEFF Research Database (Denmark)

Hempel, Casper; Combes, Valery; Hunt, Nicholas Henry

2011-01-01

observed in mice without CM, and hypoxia seemed to be confined to neuronal cell somas. PARP-1-deficient mice were not protected against CM, which argues against a role for cytopathic hypoxia. Erythropoietin therapy reversed the development of CM and substantially reduced the degree of neural hypoxia......Cerebral malaria (CM) is associated with high mortality and risk of sequelae, and development of adjunct therapies is hampered by limited knowledge of its pathogenesis. To assess the role of cerebral hypoxia, we used two experimental models of CM, Plasmodium berghei ANKA in CBA and C57BL/6 mice....... These findings demonstrate cerebral hypoxia in malaria, strongly associated with cerebral dysfunction and a possible target for adjunctive therapy....

Neuroprotective effect of peroxiredoxin 6 against hypoxia-induced retinal ganglion cell damage

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Kumar Anil

2010-10-01

Full Text Available Abstract Background The ability to respond to changes in the extra-intracellular environment is prerequisite for cell survival. Cellular responses to the environment include elevating defense systems, such as the antioxidant defense system. Hypoxia-evoked reactive oxygen species (ROS-driven oxidative stress is an underlying mechanism of retinal ganglion cell (RGC death that leads to blinding disorders. The protein peroxiredoxin 6 (PRDX6 plays a pleiotropic role in negatively regulating death signaling in response to stressors, and thereby stabilizes cellular homeostasis. Results We have shown that RGCs exposed to hypoxia (1% or hypoxia mimetic cobalt chloride display reduced expression of PRDX6 with higher ROS expression and activation of NF-κB. These cells undergo apoptosis, while cells with over-expression of PRDX6 demonstrate resistance against hypoxia-driven RGC death. The RGCs exposed to hypoxia either with 1% oxygen or cobalt chloride (0-400 μM, revealed ~30%-70% apoptotic cell death after 48 and 72 h of exposure. Western analysis and real-time PCR showed elevated expression of PRDX6 during hypoxia at 24 h, while PRDX6 protein and mRNA expression declined from 48 h onwards following hypoxia exposure. Concomitant with this, RGCs showed increased ROS expression and activation of NF-κB with IkB phosphorylation/degradation, as examined with H2DCF-DA and transactivation assays. These hypoxia-induced adverse reactions could be reversed by over-expression of PRDX6. Conclusion Because an abundance of PRDX6 in cells was able to attenuate hypoxia-induced RGC death, the protein could possibly be developed as a novel therapeutic agent acting to postpone RGC injury and delay the progression of glaucoma and other disorders caused by the increased-ROS-generated death signaling related to hypoxia.

Hypoxia inhibits the growth, differentiation and bone-forming capacity of rat osteoblasts

International Nuclear Information System (INIS)

Utting, J.C.; Robins, S.P.; Brandao-Burch, A.; Orriss, I.R.; Behar, J.; Arnett, T.R.

2006-01-01

We investigated the effect of hypoxia on rat osteoblast function in long-term primary cultures. Reduction of pO 2 from 20% to 5% and 2% decreased formation of mineralized bone nodules 1.7-fold and 11-fold, respectively. When pO 2 was reduced further to 0.2%, bone nodule formation was almost abolished. The inhibitory effect of hypoxia on bone formation was partly due to decreased osteoblast proliferation, as measured by 3 H-thymidine incorporation. Hypoxia also sharply reduced osteoblast alkaline phosphatase (ALP) activity and expression of mRNAs for ALP and osteocalcin, suggesting inhibition of differentiation to the osteogenic phenotype. Hypoxia did not increase the apoptosis of osteoblasts but induced a reversible state of quiescence. Transmission electron microscopy revealed that collagen fibrils deposited by osteoblasts cultured in 2% O 2 were less organized and much less abundant than in 20% O 2 cultures. Furthermore, collagen produced by hypoxic osteoblasts contained a lower percentage of hydroxylysine residues and exhibited an increased sensitivity to pepsin degradation. These data demonstrate the absolute oxygen requirement of osteoblasts for successful bone formation and emphasize the importance of the vasculature in maintaining bone health. We recently showed that hypoxia also acts in a reciprocal manner as a powerful stimulator of osteoclast formation. Considered together, our results help to explain the bone loss that occurs at the sites of fracture, tumors, inflammation and infection, and in individuals with vascular disease or anemia

Disruption of the Serotonergic System after Neonatal Hypoxia-Ischemia in a Rodent Model

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Kathryn M. Buller

2012-01-01

Full Text Available Identifying which specific neuronal phenotypes are vulnerable to neonatal hypoxia-ischemia, where in the brain they are damaged, and the mechanisms that produce neuronal losses are critical to determine the anatomical substrates responsible for neurological impairments in hypoxic-ischemic brain-injured neonates. Here we describe our current work investigating how the serotonergic network in the brain is disrupted in a rodent model of preterm hypoxia-ischemia. One week after postnatal day 3 hypoxia-ischemia, losses of serotonergic raphé neurons, reductions in serotonin levels in the brain, and reduced serotonin transporter expression are evident. These changes can be prevented using two anti-inflammatory interventions; the postinsult administration of minocycline or ibuprofen. However, each drug has its own limitations and benefits for use in neonates to stem damage to the serotonergic network after hypoxia-ischemia. By understanding the fundamental mechanisms underpinning hypoxia-ischemia-induced serotonergic damage we will hopefully move closer to developing a successful clinical intervention to treat neonatal brain injury.

Three hours of intermittent hypoxia increases circulating glucose levels in healthy adults.

Science.gov (United States)

Newhouse, Lauren P; Joyner, Michael J; Curry, Timothy B; Laurenti, Marcello C; Man, Chiara Dalla; Cobelli, Claudio; Vella, Adrian; Limberg, Jacqueline K

2017-01-01

An independent association exists between sleep apnea and diabetes. Animal models suggest exposure to intermittent hypoxia, a consequence of sleep apnea, results in altered glucose metabolism and fasting hyperglycemia. However, it is unknown if acute exposure to intermittent hypoxia increases glucose concentrations in nondiabetic humans. We hypothesized plasma glucose would be increased from baseline following 3 h of intermittent hypoxia in healthy humans independent of any effect on insulin sensitivity. Eight (7M/1F, 21-34 years) healthy subjects completed two study visits randomized to 3 h of intermittent hypoxia or continuous normoxia, followed by an oral glucose tolerance test. Intermittent hypoxia consisted of 25 hypoxic events per hour where oxygen saturation (SpO 2 ) was significantly reduced (Normoxia: 97 ± 1%, Hypoxia: 90 ± 2%, P  0.05). In contrast, circulating glucose concentrations were increased after 3 h of intermittent hypoxia when compared to baseline (5.0 ± 0.2 vs. 5.3 ± 0.2 mmol/L, P = 0.01). There were no detectable changes in insulin sensitivity following intermittent hypoxia when compared to continuous normoxia, as assessed by the oral glucose tolerance test (P > 0.05). Circulating glucose is increased after 3 h of intermittent hypoxia in healthy humans, independent of any lasting changes in insulin sensitivity. These novel findings could explain, in part, the high prevalence of diabetes in patients with sleep apnea and warrant future studies to identify underlying mechanisms. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Dynamics and distribution of natural and human-caused hypoxia

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N. N. Rabalais

2010-02-01

strengthened stratification alone, from increased surface water temperature as the global climate warms, is sufficient to worsen hypoxia where it currently exists and facilitate its formation in additional waters. Increased precipitation that increases freshwater discharge and flux of nutrients will result in increased primary production in the receiving waters up to a point. The interplay of increased nutrients and stratification where they occur will aggravate and accelerate hypoxia. Changes in wind fields may expand oxygen minimum zones onto more continental shelf areas. On the other hand, not all regions will experience increased precipitation, some oceanic water temperatures may decrease as currents shift, and frequency and severity of tropical storms may increase and temporarily disrupt hypoxia more often.

The consequences of global warming and climate change are effectively uncontrollable at least in the near term. On the other hand, the consequences of eutrophication-induced hypoxia can be reversed if long-term, broad-scale, and persistent efforts to reduce substantial nutrient loads are developed and implemented. In the face of globally expanding hypoxia, there is a need for water and resource managers to act now to reduce nutrient loads to maintain, at least, the current status.

Selective vulnerability in brain hypoxia

DEFF Research Database (Denmark)

Cervos-Navarro, J.; Diemer, Nils Henrik

1991-01-01

Neuropathology, selective vulnerability, brain hypoxia, vascular factors, excitotoxicity, ion homeostasis......Neuropathology, selective vulnerability, brain hypoxia, vascular factors, excitotoxicity, ion homeostasis...

Obstructive sleep apnea: role of intermittent hypoxia and inflammation.

Science.gov (United States)

May, Anna M; Mehra, Reena

2014-10-01

Obstructive sleep apnea results in intermittent hypoxia via repetitive upper airway obstruction leading to partial or complete upper airway closure, apneas and hypopneas, respectively. Intermittent hypoxia leads to sympathetic nervous system activation and oxidative stress with a resultant systemic inflammatory cascade. The putative mechanism by which obstructive sleep apnea has been linked to numerous pathologic conditions including stoke, cardiovascular disease, hypertension, and metabolic derangements is through these systemic effects. Treatment of obstructive sleep apnea appears to reduce systemic markers of inflammation and ameliorates the adverse sequelae of this disease. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

In vivo characterization of a reporter gene system for imaging hypoxia-induced gene expression.

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Carlin, Sean; Pugachev, Andrei; Sun, Xiaorong; Burke, Sean; Claus, Filip; O'Donoghue, Joseph; Ling, C Clifton; Humm, John L

2009-10-01

To characterize a tumor model containing a hypoxia-inducible reporter gene and to demonstrate utility by comparison of reporter gene expression to the uptake and distribution of the hypoxia tracer (18)F-fluoromisonidazole ((18)F-FMISO). Three tumors derived from the rat prostate cancer cell line R3327-AT were grown in each of two rats as follows: (1) parental R3327-AT, (2) positive control R3327-AT/PC in which the HSV1-tkeGFP fusion reporter gene was expressed constitutively, (3) R3327-AT/HRE in which the reporter gene was placed under the control of a hypoxia-inducible factor-responsive promoter sequence (HRE). Animals were coadministered a hypoxia-specific marker (pimonidazole) and the reporter gene probe (124)I-2'-fluoro-2'-deoxy-1-beta-d-arabinofuranosyl-5-iodouracil ((124)I-FIAU) 3 h prior to sacrifice. Statistical analysis of the spatial association between (124)I-FIAU uptake and pimonidazole fluorescent staining intensity was then performed on a pixel-by-pixel basis. Utility of this system was demonstrated by assessment of reporter gene expression versus the exogenous hypoxia probe (18)F-FMISO. Two rats, each bearing a single R3327-AT/HRE tumor, were injected with (124)I-FIAU (3 h before sacrifice) and (18)F-FMISO (2 h before sacrifice). Statistical analysis of the spatial association between (18)F-FMISO and (124)I-FIAU on a pixel-by-pixel basis was performed. Correlation coefficients between (124)I-FIAU uptake and pimonidazole staining intensity were: 0.11 in R3327-AT tumors, -0.66 in R3327-AT/PC and 0.76 in R3327-AT/HRE, confirming that only in the R3327-AT/HRE tumor was HSV1-tkeGFP gene expression associated with hypoxia. Correlation coefficients between (18)F-FMISO and (124)I-FIAU uptakes in R3327-AT/HRE tumors were r=0.56, demonstrating good spatial correspondence between the two tracers. We have confirmed hypoxia-specific expression of the HSV1-tkeGFP fusion gene in the R3327-AT/HRE tumor model and demonstrated the utility of this model for the

In vivo characterization of a reporter gene system for imaging hypoxia-induced gene expression

International Nuclear Information System (INIS)

Carlin, Sean; Pugachev, Andrei; Sun Xiaorong; Burke, Sean; Claus, Filip; O'Donoghue, Joseph; Ling, C. Clifton; Humm, John L.

2009-01-01

Purpose: To characterize a tumor model containing a hypoxia-inducible reporter gene and to demonstrate utility by comparison of reporter gene expression to the uptake and distribution of the hypoxia tracer 18 F-fluoromisonidazole ( 18 F-FMISO). Methods: Three tumors derived from the rat prostate cancer cell line R3327-AT were grown in each of two rats as follows: (1) parental R3327-AT, (2) positive control R3327-AT/PC in which the HSV1-tkeGFP fusion reporter gene was expressed constitutively, (3) R3327-AT/HRE in which the reporter gene was placed under the control of a hypoxia-inducible factor-responsive promoter sequence (HRE). Animals were coadministered a hypoxia-specific marker (pimonidazole) and the reporter gene probe 124 I-2'-fluoro-2'-deoxy-1-β-D-arabinofuranosyl-5-iodouracil ( 124 I-FIAU) 3 h prior to sacrifice. Statistical analysis of the spatial association between 124 I-FIAU uptake and pimonidazole fluorescent staining intensity was then performed on a pixel-by-pixel basis. Utility of this system was demonstrated by assessment of reporter gene expression versus the exogenous hypoxia probe 18 F-FMISO. Two rats, each bearing a single R3327-AT/HRE tumor, were injected with 124 I-FIAU (3 h before sacrifice) and 18 F-FMISO (2 h before sacrifice). Statistical analysis of the spatial association between 18 F-FMISO and 124 I-FIAU on a pixel-by-pixel basis was performed. Results: Correlation coefficients between 124 I-FIAU uptake and pimonidazole staining intensity were: 0.11 in R3327-AT tumors, -0.66 in R3327-AT/PC and 0.76 in R3327-AT/HRE, confirming that only in the R3327-AT/HRE tumor was HSV1-tkeGFP gene expression associated with hypoxia. Correlation coefficients between 18 F-FMISO and 124 I-FIAU uptakes in R3327-AT/HRE tumors were r=0.56, demonstrating good spatial correspondence between the two tracers. Conclusions: We have confirmed hypoxia-specific expression of the HSV1-tkeGFP fusion gene in the R3327-AT/HRE tumor model and demonstrated the utility of

Hypoxia-Related Hormonal Appetite Modulation in Humans during Rest and Exercise: Mini Review

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Tadej Debevec

2017-05-01

Full Text Available Obesity is associated with numerous chronic ailments and represents one of the major health and economic issues in the modernized societies. Accordingly, there is an obvious need for novel treatment approaches. Recently, based on the reports of reduced appetite and subsequent weight loss following high-altitude sojourns, exposure to hypoxia has been proposed as a viable weight-reduction strategy. While altitude-related appetite modulation is complex and not entirely clear, hypoxia-induced alterations in hormonal appetite modulation might be among the key underlying mechanisms. The present paper summarizes the up-to-date research on hypoxia/altitude-induced changes in the gut and adipose tissue derived peptides related to appetite regulation. Orexigenic hormone ghrelin and anorexigenic peptides leptin, glucagon-like peptide-1, peptide YY, and cholecystokinin have to-date been investigated as potential modulators of hypoxia-driven appetite alterations. Current evidence suggests that hypoxia can, especially acutely, lead to decreased appetite, most probably via reduction of acylated ghrelin concentration. Hypoxia-related short and long-term changes in other hormonal markers are more unclear although hypoxia seems to importantly modulate leptin levels, especially following prolonged hypoxic exposures. Limited evidence also suggests that different activity levels during exposures to hypoxia do not additively affect hormonal appetite markers. Although very few studies have been performed in obese/overweight individuals, the available data indicate that hypoxia/altitude exposures do not seem to differentially affect appetite regulation via hormonal pathways in this cohort. Given the lack of experimental data, future well-controlled acute and prolonged studies are warranted to expand our understanding of hypoxia-induced hormonal appetite modulation and its kinetics in health and disease.

Cancer cell-associated cytoplasmic B7–H4 is induced by hypoxia through hypoxia-inducible factor-1α and promotes cancer cell proliferation

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Jeon, You-Kyoung [Department of Microbiology and Immunology, Inje University College of Medicine, Busan 614-735 (Korea, Republic of); Advanced Research Center for Multiple Myeloma, Inje University College of Medicine, Busan 614-735 (Korea, Republic of); Park, Sae-Gwang; Choi, Il-Whan [Department of Microbiology and Immunology, Inje University College of Medicine, Busan 614-735 (Korea, Republic of); Lee, Soo-Woong [Advanced Research Center for Multiple Myeloma, Inje University College of Medicine, Busan 614-735 (Korea, Republic of); Lee, Sang Min [Department of Internal Medicine, Division of Hematology/Oncology, Busan Paik Hospital, Inje University, Busan 614-735 (Korea, Republic of); Choi, Inhak, E-mail: miccih@inje.ac.kr [Department of Microbiology and Immunology, Inje University College of Medicine, Busan 614-735 (Korea, Republic of); Advanced Research Center for Multiple Myeloma, Inje University College of Medicine, Busan 614-735 (Korea, Republic of)

2015-04-03

Aberrant B7–H4 expression in cancer tissues serves as a novel prognostic biomarker for poor survival in patients with cancer. However, the factor(s) that induce cancer cell-associated B7–H4 remain to be fully elucidated. We herein demonstrate that hypoxia upregulates B7–H4 transcription in primary CD138{sup +} multiple myeloma cells and cancer cell lines. In support of this finding, analysis of the Multiple Myeloma Genomics Portal (MMGP) data set revealed a positive correlation between the mRNA expression levels of B7–H4 and the endogenous hypoxia marker carbonic anhydrogenase 9. Hypoxia-induced B7–H4 expression was detected in the cytoplasm, but not in cancer cell membranes. Chromatin immunoprecipitation analysis demonstrated binding of hypoxia-inducible factor-1α (HIF-1α) to proximal hypoxia-response element (HRE) sites within the B7–H4 promoter. Knockdown of HIF-1α and pharmacological inhibition of HIF-1α diminished B7–H4 expression. Furthermore, knockdown of cytoplasmic B7–H4 in MCF-7 decreased the S-phase cell population under hypoxia. Finally, MMGP analysis revealed a positive correlation between the transcript levels of B7–H4 and proliferation-related genes including MKI67, CCNA1, and Myc in several patients with multiple myeloma. Our results provide insight into the mechanisms underlying B7–H4 upregulation and its role in cancer cell proliferation in a hypoxic tumor microenvironment. - Highlights: • Hypoxia upregulates B7–H4 transcription and protein expression. • Hypoxia-induced B7–H4 is detected in the cytoplasm, but not on membrane. • ChIP assay reveals a binding of HIF-1α to B7–H4 promoter at HRE site. • Knockdown and pharmacological inhibition of HIF-1α reduce B7–H4 expression. • B7–H4 knockdown decrease the number of cells in S-phase of cell cycle.

Nuclear orphan receptor TLX induces Oct-3/4 for the survival and maintenance of adult hippocampal progenitors upon hypoxia.

Science.gov (United States)

Chavali, Pavithra Lakshminarasimhan; Saini, Ravi Kanth Rao; Matsumoto, Yoshiki; Ågren, Hans; Funa, Keiko

2011-03-18

Hypoxia promotes neural stem cell proliferation, the mechanism of which is poorly understood. Here, we have identified the nuclear orphan receptor TLX as a mediator for proliferation and pluripotency of neural progenitors upon hypoxia. We found an enhanced early protein expression of TLX under hypoxia potentiating sustained proliferation of neural progenitors. Moreover, TLX induction upon hypoxia in differentiating conditions leads to proliferation and a stem cell-like phenotype, along with coexpression of neural stem cell markers. Following hypoxia, TLX is recruited to the Oct-3/4 proximal promoter, augmenting the gene transcription and promoting progenitor proliferation and pluripotency. Knockdown of Oct-3/4 significantly reduced TLX-mediated proliferation, highlighting their interdependence in regulating the progenitor pool. Additionally, TLX synergizes with basic FGF to sustain cell viability upon hypoxia, since the knockdown of TLX along with the withdrawal of growth factor results in cell death. This can be attributed to the activation of Akt signaling pathway by TLX, the depletion of which results in reduced proliferation of progenitor cells. Cumulatively, the data presented here demonstrate a new role for TLX in neural stem cell proliferation and pluripotency upon hypoxia.

Nuclear Orphan Receptor TLX Induces Oct-3/4 for the Survival and Maintenance of Adult Hippocampal Progenitors upon Hypoxia*

Science.gov (United States)

Chavali, Pavithra Lakshminarasimhan; Saini, Ravi Kanth Rao; Matsumoto, Yoshiki; Ågren, Hans; Funa, Keiko

2011-01-01

Hypoxia promotes neural stem cell proliferation, the mechanism of which is poorly understood. Here, we have identified the nuclear orphan receptor TLX as a mediator for proliferation and pluripotency of neural progenitors upon hypoxia. We found an enhanced early protein expression of TLX under hypoxia potentiating sustained proliferation of neural progenitors. Moreover, TLX induction upon hypoxia in differentiating conditions leads to proliferation and a stem cell-like phenotype, along with coexpression of neural stem cell markers. Following hypoxia, TLX is recruited to the Oct-3/4 proximal promoter, augmenting the gene transcription and promoting progenitor proliferation and pluripotency. Knockdown of Oct-3/4 significantly reduced TLX-mediated proliferation, highlighting their interdependence in regulating the progenitor pool. Additionally, TLX synergizes with basic FGF to sustain cell viability upon hypoxia, since the knockdown of TLX along with the withdrawal of growth factor results in cell death. This can be attributed to the activation of Akt signaling pathway by TLX, the depletion of which results in reduced proliferation of progenitor cells. Cumulatively, the data presented here demonstrate a new role for TLX in neural stem cell proliferation and pluripotency upon hypoxia. PMID:21135096

Andrographolide protects mouse astrocytes against hypoxia injury by promoting autophagy and S100B expression

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Juan Du

2018-04-01

Full Text Available Andrographolide (ANDRO has been studied for its immunomodulation, anti-inflammatory, and neuroprotection effects. Because brain hypoxia is the most common factor of secondary brain injury after traumatic brain injury, we studied the role and possible mechanism of ANDRO in this process using hypoxia-injured astrocytes. Mouse cortical astrocytes C8-D1A (astrocyte type I clone from C57/BL6 strains were subjected to 3 and 21% of O2 for various times (0–12 h to establish an astrocyte hypoxia injury model in vitro. After hypoxia and ANDRO administration, the changes in cell viability and apoptosis were assessed using CCK-8 and flow cytometry. Expression changes in apoptosis-related proteins, autophagy-related proteins, main factors of JNK pathway, ATG5, and S100B were determined by western blot. Hypoxia remarkably damaged C8-D1A cells evidenced by reduction of cell viability and induction of apoptosis. Hypoxia also induced autophagy and overproduction of S100B. ANDRO reduced cell apoptosis and promoted cell autophagy and S100B expression. After ANDRO administration, autophagy-related proteins, S-100B, JNK pathway proteins, and ATG5 were all upregulated, while autophagy-related proteins and s100b were downregulated when the jnk pathway was inhibited or ATG5 was knocked down. ANDRO conferred a survival advantage to hypoxia-injured astrocytes by reducing cell apoptosis and promoting autophagy and s100b expression. Furthermore, the promotion of autophagy and s100b expression by ANDRO was via activation of jnk pathway and regulation of ATG5.

Intermittent hypoxia in childhood: the harmful consequences versus potential benefits of therapeutic uses

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Tatiana V. Serebrovskaya

2015-05-01

Full Text Available Intermittent hypoxia often occurs in early infancy in both preterm and term infants and especially at 36 to 44 weeks postmenstrual age. These episodes of intermittent hypoxia could result from sleep-disordered breathing or may be temporally unrelated to apnea or bradycardia events. There are numerous reports indicating adverse effects of intermittent hypoxia on development, behavior, academic achievement and cognition in children with sleep apnea syndrome. It remains uncertain the exact causative relationship between the neurocognitive and behavioral morbidities and intermittent hypoxia and/or its associated sleep fragmentation. On the other hand, well-controlled and moderate intermittent hypoxia conditioning/training has been used in sick children for treating their various forms of bronchial asthma, allergic dermatoses, autoimmune thyroiditis, cerebral palsy, and obesity. This review article provides an updated and impartial analysis on the currently available evidence in supporting either side of the seemingly contradictory scenarios. We wish to stimulate a comprehensive understanding of such a complex physiological phenomenon as intermittent hypoxia, which may be accompanied by other confounding factors (e.g. hypercapnia, polycythemia, in order to prevent or reduce its harmful consequences, while maximize its potential utility as an effective therapeutic tool in pediatric patients.

Metabolic Plasticity Enables Circadian Adaptation to Acute Hypoxia in Zebrafish Cells.

Science.gov (United States)

Sandbichler, Adolf M; Jansen, Bianca; Peer, Bettina A; Paulitsch, Monika; Pelster, Bernd; Egg, Margit

2018-01-01

Reduced oxygen availability, hypoxia, is frequently encountered by organisms, tissues and cells, in aquatic environments as well as in high altitude or under pathological conditions such as infarct, stroke or cancer. The hypoxic signaling pathway was found to be mutually intertwined with circadian timekeeping in vertebrates and, as reported recently, also in mammals. However, the impact of hypoxia on intracellular metabolic oscillations is still unknown. For determination of metabolites we used Multilabel Reader based fluorescence and luminescence assays, circadian levels of Hypoxia Inducible Factor 1 alpha and oxidized peroxiredoxins were semi quantified by Western blotting and ratiometric quantification of cytosolic and mitochondrial H2O2 was achieved with stable transfections of a redox sensitive green fluorescent protein sensor into zebrafish fibroblasts. Circadian oscillations of core clock gene mRNA´s were assessed using realtime qPCR with subsequent cosine wave fit analysis. Here we show that under normoxia primary metabolic activity of cells predominately occurs during day time and that after acute hypoxia of two hours, administrated immediately before each sampling point, steady state concentrations of glycolytic key metabolites such as glucose and lactate reveal to be highly rhythmic, following a circadian pattern with highest levels during the night periods and reflecting the circadian variation of the cellular response to hypoxia. Remarkably, rhythms in glycolysis are transferred to cellular energy states under normoxic conditions, so that ADP/ATP ratios oscillate as well, which is the first evidence for cycling ADP/ATP pools in a metazoan cell line to our knowledge. Furthermore, the hypoxia induced alterations in rhythms of glycolysis lead to the alignment of three major cellular redox systems, namely the circadian oscillations of NAD+/NADH and NADP+/NADPH ratios and of increased nocturnal levels of oxidized peroxiredoxins, resulting in a highly

Hypoxia and metastasis in an orthotopic cervix cancer xenograft model

International Nuclear Information System (INIS)

Chaudary, Naz; Mujcic, Hilda; Wouters, Bradly G.; Hill, Richard P.

2013-01-01

Background: Hypoxia can promote tumor metastasis by mechanisms that are believed to result from changes in gene expression. The current study examined the role of putative metastatic genes regulated by cyclic hypoxia in relation to metastasis formation in orthotopic models of cervix cancer. Methods: Orthotopic tumors derived from ME180 human cervix cancer cells or from early generation human cervix cancer xenografts were exposed to cyclic hypoxic conditions during growth in vivo and tumor growth and lymphnode metastases were monitored. Expression of the chemokine receptor CXCR4 and various genes in the Hedgehog (Hh) pathway were inhibited using genetic (inducible shRNA vs CXCR4) small molecule (AMD3100) or antibody (5E1) treatment (CXCR4 and Hh genes, respectively) during tumor growth. Results: As reported previously, exposure of tumor bearing mice to cyclic hypoxia caused a reduction of tumor growth but a large increase in metastasis. Inhibition of CXCR4 or Hh gene activity during tumor growth further reduced primary tumor size and reduced lymphatic metastasis to levels below those seen in control mice exposed to normoxic conditions. Conclusion: Blocking CXCR4 or Hh gene expression are potential therapeutic pathways for improving cervix cancer treatment

VHL-mediated hypoxia regulation of cyclin D1 in renal carcinoma cells.

Science.gov (United States)

Bindra, Ranjit S; Vasselli, James R; Stearman, Robert; Linehan, W Marston; Klausner, Richard D

2002-06-01

Renal cell carcinoma is associated with mutation of the von Hippel-Lindau (VHL) tumor suppressor gene. Cell lines derived from these tumors cannot exit the cell cycle when deprived of growth factors, and the ability to exit the cell cycle can be restored by the reintroduction of wild-type protein VHL (pVHL). Here, we report that cyclin D1 is overexpressed and remains inappropriately high in during contact inhibition in pVHL-deficient cell lines. In addition, hypoxia increased the expression of cyclin D1 specifically in pVHL-negative cell lines into which pVHL expression was restored. Hypoxic-induction of cyclin D1 was not observed in other pVHL-positive cell lines. This suggests a model whereby in some kidney cell types, pVHL may regulate a proliferative response to hypoxia, whereas the loss of pVHL leads to constitutively elevated cyclin D1 and abnormal proliferation under normal growth conditions.

The effect of hypobaric hypoxia on multichannel EEG signal complexity.

Science.gov (United States)

Papadelis, Christos; Kourtidou-Papadeli, Chrysoula; Bamidis, Panagiotis D; Maglaveras, Nikos; Pappas, Konstantinos

2007-01-01

The objective of this study was the development and evaluation of nonlinear electroencephalography parameters which assess hypoxia-induced EEG alterations, and describe the temporal characteristics of different hypoxic levels' residual effect upon the brain electrical activity. Multichannel EEG, pO2, pCO2, ECG, and respiration measurements were recorded from 10 subjects exposed to three experimental conditions (100% oxygen, hypoxia, recovery) at three-levels of reduced barometric pressure. The mean spectral power of EEG under each session and altitude were estimated for the standard bands. Approximate Entropy (ApEn) of EEG segments was calculated, and the ApEn's time-courses were smoothed by a moving average filter. On the smoothed diagrams, parameters were defined. A significant increase in total power and power of theta and alpha bands was observed during hypoxia. Visual interpretation of ApEn time-courses revealed a characteristic pattern (decreasing during hypoxia and recovering after oxygen re-administration). The introduced qEEG parameters S1 and K1 distinguished successfully the three hypoxic conditions. The introduced parameters based on ApEn time-courses are assessing reliably and effectively the different hypoxic levels. ApEn decrease may be explained by neurons' functional isolation due to hypoxia since decreased complexity corresponds to greater autonomy of components, although this interpretation should be further supported by electrocorticographic animal studies. The introduced qEEG parameters seem to be appropriate for assessing the hypoxia-related neurophysiological state of patients in the hyperbaric chambers in the treatment of decompression sickness, carbon dioxide poisoning, and mountaineering.

Hypoxia-inducible factor-1α induces multidrug resistance protein in colon cancer

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Lv Y

2015-07-01

Full Text Available Yingqian Lv, Shan Zhao, Jinzhu Han, Likang Zheng, Zixin Yang, Li Zhao Department of Oncology, The Second Hospital, Hebei Medical University, Shijiazhuang, Hebei Province, People’s Republic of China Abstract: Multidrug resistance is the major cause of chemotherapy failure in many solid tumors, including colon cancer. Hypoxic environment is a feature for all solid tumors and is important for the development of tumor resistance to chemotherapy. Hypoxia-inducible factor (HIF-1α is the key transcription factor that mediates cellular response to hypoxia. HIF-1α has been shown to play an important role in tumor resistance; however, the mechanism is still not fully understood. Here, we found that HIF-1α and the drug resistance-associated gene multidrug resistance associated protein 1 (MRP1 were induced by treatment of colon cancer cells with the hypoxia-mimetic agent cobalt chloride. Inhibition of HIF-1α by RNA interference and dominant-negative protein can significantly reduce the induction of MRP1 by hypoxia. Bioinformatics analysis showed that a hypoxia response element is located at -378 to -373 bp upstream of the transcription start site of MRP1 gene. Luciferase reporter assay combined with mutation analysis confirmed that this element is essential for hypoxia-mediated activation of MRP gene. Furthermore, RNA interference revealed that HIF-1α is necessary for this hypoxia-driven activation of MRP1 promoter. Importantly, chromatin immunoprecipitation analysis demonstrated that HIF-1α could directly bind to this HRE site in vivo. Together, these data suggest that MRP1 is a downstream target gene of HIF-1α, which provides a potential novel mechanism for HIF-1α-mediated drug resistance in colon cancer and maybe other solid tumors as well. Keywords: hypoxia, hypoxia-inducible factor-1α, multidrug resistance associated protein, transcriptional regulation, chemotherapy tolerance

Lack of bcr and abr promotes hypoxia-induced pulmonary hypertension in mice.

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Min Yu

Full Text Available Bcr and Abr are GTPase activating proteins that specifically downregulate activity of the small GTPase Rac in restricted cell types in vivo. Rac1 is expressed in smooth muscle cells, a critical cell type involved in the pathogenesis of pulmonary hypertension. The molecular mechanisms that underlie hypoxia-associated pulmonary hypertension are not well-defined.Bcr and abr null mutant mice were compared to wild type controls for the development of pulmonary hypertension after exposure to hypoxia. Also, pulmonary arterial smooth muscle cells from those mice were cultured in hypoxia and examined for proliferation, p38 activation and IL-6 production. Mice lacking Bcr or Abr exposed to hypoxia developed increased right ventricular pressure, hypertrophy and pulmonary vascular remodeling. Perivascular leukocyte infiltration in the lungs was increased, and under hypoxia bcr-/- and abr-/- macrophages generated more reactive oxygen species. Consistent with a contribution of inflammation and oxidative stress in pulmonary hypertension-associated vascular damage, Bcr and Abr-deficient animals showed elevated endothelial leakage after hypoxia exposure. Hypoxia-treated pulmonary arterial smooth muscle cells from Bcr- or Abr-deficient mice also proliferated faster than those of wild type mice. Moreover, activated Rac1, phosphorylated p38 and interleukin 6 were increased in these cells in the absence of Bcr or Abr. Inhibition of Rac1 activation with Z62954982, a novel Rac inhibitor, decreased proliferation, p38 phosphorylation and IL-6 levels in pulmonary arterial smooth muscle cells exposed to hypoxia.Bcr and Abr play a critical role in down-regulating hypoxia-induced pulmonary hypertension by deactivating Rac1 and, through this, reducing both oxidative stress generated by leukocytes as well as p38 phosphorylation, IL-6 production and proliferation of pulmonary arterial smooth muscle cells.

Andrographolide inhibits hypoxia-induced hypoxia-inducible factor 1α and endothelin 1 expression through the heme oxygenase 1/CO/cGMP/MKP-5 pathways in EA.hy926 cells.

Science.gov (United States)

Lin, Hung-Chih; Su, Shih-Li; Lin, Wan-Chun; Lin, Ai-Hsuan; Yang, Ya-Chen; Lii, Chong-Kuei; Chen, Haw-Wen

2018-03-01

Andrographolide is a potent anti-inflammatory agent found in Andrographis paniculata. Endothelin 1 (ET-1) is an endothelium-derived vasoconstrictor with pro-inflammatory properties secreted in response to hypoxia. Mitogen-activated protein kinase phosphatase 5 (MKP-5) is a dual-specificity phosphatase that dephosphorylates threonine and tyrosine residues of MAPKs. We showed previously that hypoxia-induced HIF-1α expression and ET-1 secretion are dependent on p38 MAPK in EA.hy926 cells. Here, we investigate what role MKP-5 plays in andrographolide's inhibition of hypoxia-induced expression of HIF-1α and ET-1. Hypoxic conditions were created using the hypoxia-mimetic agent CoCl 2 . Andrographolide enhanced HO-1 and MKP-5 expression and cellular cGMP content in addition to inhibiting hypoxia-induced ROS generation. Concomitantly, the HO-1 byproduct CO and the cGMP analogue 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) increased MKP-5 expression, and pretreatment with CO and 8-Br-cGMP inhibited hypoxia-induced HIF-1α and ET-1 expression. Transfection of HO-1 siRNA or pretreatment with the HO-1 inhibitor ZnPP-9 or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a specific inhibitor of soluble guanylate cyclase, reduced andrographolide-induced MKP-5 expression. Moreover, silencing MKP-5 or treatment with the phosphatase inhibitor vanadate abrogated andrographolide's suppressing hypoxia-induced p38 MAPK activation and HIF-1α expression. The inhibition of hypoxia-induced HIF-1α and ET-1 expression by andrographolide is likely associated with HO-1/CO/cGMP/MKP-5 pathways, which is involved in inhibiting hypoxia-induced p38 MAPK activation. © 2017 Wiley Periodicals, Inc.

Comparative and Experimental Studies on the Genes Altered by Chronic Hypoxia in Human Brain Microendothelial Cells

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Eugenia Mata-Greenwood

2017-05-01

Full Text Available Background : Hypoxia inducible factor 1 alpha (HIF1A is a master regulator of acute hypoxia; however, with chronic hypoxia, HIF1A levels return to the normoxic levels. Importantly, the genes that are involved in the cell survival and viability under chronic hypoxia are not known. Therefore, we tested the hypothesis that chronic hypoxia leads to the upregulation of a core group of genes with associated changes in the promoter DNA methylation that mediates the cell survival under hypoxia.Results : We examined the effect of chronic hypoxia (3 days; 0.5% oxygen on human brain micro endothelial cells (HBMEC viability and apoptosis. Hypoxia caused a significant reduction in cell viability and an increase in apoptosis. Next, we examined chronic hypoxia associated changes in transcriptome and genome-wide promoter methylation. The data obtained was compared with 16 other microarray studies on chronic hypoxia. Nine genes were altered in response to chronic hypoxia in all 17 studies. Interestingly, HIF1A was not altered with chronic hypoxia in any of the studies. Furthermore, we compared our data to three other studies that identified HIF-responsive genes by various approaches. Only two genes were found to be HIF dependent. We silenced each of these 9 genes using CRISPR/Cas9 system. Downregulation of EGLN3 significantly increased the cell death under chronic hypoxia, whereas downregulation of ERO1L, ENO2, adrenomedullin, and spag4 reduced the cell death under hypoxia.Conclusions : We provide a core group of genes that regulates cellular acclimatization under chronic hypoxic stress, and most of them are HIF independent.

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen

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Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten Joan

2013-01-01

Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen sa...... activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology.......Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen...... saturation alters wave activity; (2) glial Ca(2+) waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus...

Hypoxia as a Biomarker and for Personalized Radiation Oncology

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Vordermark, Dirk; Horsman, Michael R

2016-01-01

Tumor hypoxia is a clinically relevant cause of radiation resistance. Direct measurements of tumor oxygenation have been performed predominantly with the Eppendorf histograph and these have defined the reduced prognosis after radiotherapy in poorly oxygenated tumors, especially head-and-neck canc...

Hypoxia and hypoxia inducible factor-1α are required for normal endometrial repair during menstruation.

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Maybin, Jacqueline A; Murray, Alison A; Saunders, Philippa T K; Hirani, Nikhil; Carmeliet, Peter; Critchley, Hilary O D

2018-01-23

Heavy menstrual bleeding (HMB) is common and debilitating, and often requires surgery due to hormonal side effects from medical therapies. Here we show that transient, physiological hypoxia occurs in the menstrual endometrium to stabilise hypoxia inducible factor 1 (HIF-1) and drive repair of the denuded surface. We report that women with HMB have decreased endometrial HIF-1α during menstruation and prolonged menstrual bleeding. In a mouse model of simulated menses, physiological endometrial hypoxia occurs during bleeding. Maintenance of mice under hyperoxia during menses decreases HIF-1α induction and delays endometrial repair. The same effects are observed upon genetic or pharmacological reduction of endometrial HIF-1α. Conversely, artificial induction of hypoxia by pharmacological stabilisation of HIF-1α rescues the delayed endometrial repair in hypoxia-deficient mice. These data reveal a role for HIF-1 in the endometrium and suggest its pharmacological stabilisation during menses offers an effective, non-hormonal treatment for women with HMB.

Hypoxia-Inducible Factor Pathway Inhibition Resolves Tumor Hypoxia and Improves Local Tumor Control After Single-Dose Irradiation

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Helbig, Linda [OncoRay–National Center for Radiation Research in Oncology, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden (Germany); Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden (Germany); Koi, Lydia [OncoRay–National Center for Radiation Research in Oncology, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden (Germany); Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden (Germany); Deutsches Konsortium für Translationale Krebsforschung, Site Dresden, Dresden (Germany); Brüchner, Kerstin [Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden (Germany); Institute of Radiooncology Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Gurtner, Kristin [Department of Radiation Oncology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden (Germany); Hess-Stumpp, Holger; Unterschemmann, Kerstin [Global Drug Discovery, Bayer Pharma, Berlin (Germany); Pruschy, Martin [Radiation Oncology, University of Zurich, Zurich (Switzerland); and others

2014-01-01

Purpose: To study the effects of BAY-84-7296, a novel orally bioavailable inhibitor of mitochondrial complex I and hypoxia-inducible factor 1 (HIF-1) activity, on hypoxia, microenvironment, and radiation response of tumors. Methods and Materials: UT-SCC-5 and UT-SCC-14 human squamous cell carcinomas were transplanted subcutaneously in nude mice. When tumors reached 4 mm in diameter BAY-84-7296 (Bayer Pharma AG) or carrier was daily administered to the animals. At 7 mm tumors were either excised for Western blot and immunohistologic investigations or were irradiated with single doses. After irradiation animals were randomized to receive BAY-84-7296 maintenance or carrier. Local tumor control was evaluated 150 days after irradiation, and the dose to control 50% of tumors (TCD{sub 50}) was calculated. Results: BAY-84-7296 decreased nuclear HIF-1α expression. Daily administration of inhibitor for approximately 2 weeks resulted in a marked decrease of pimonidazole hypoxic fraction in UT-SCC-5 (0.5% vs 21%, P<.0001) and in UT-SCC-14 (0.3% vs 19%, P<.0001). This decrease was accompanied by a significant increase in fraction of perfused vessels in UT-SCC-14 but not in UT-SCC-5. Bromodeoxyuridine and Ki67 labeling indices were significantly reduced only in UT-SCC-5. No significant changes were observed in vascular area or necrosis. BAY-84-7296 before single-dose irradiation significantly decreased TCD{sub 50}, with an enhancement ratio of 1.37 (95% confidence interval [CI] 1.13-1.72) in UT-SCC-5 and of 1.55 (95% CI 1.26-1.94) in UT-SCC-14. BAY-84-7296 maintenance after irradiation did not further decrease TCD{sub 50}. Conclusions: BAY-84-7296 resulted in a marked decrease in tumor hypoxia and substantially reduced radioresistance of tumor cells with the capacity to cause a local recurrence after irradiation. The data suggest that reduction of cellular hypoxia tolerance by BAY-84-7296 may represent the primary biological mechanism underlying the observed enhancement of

Effects of manganese and hypoxia on coelomocyte renewal in the echinoderm, Asterias rubens (L.)

International Nuclear Information System (INIS)

Oweson, Carolina; Li Chenghua; Soederhaell, Irene; Hernroth, Bodil

2010-01-01

Manganese (Mn) is a naturally abundant metal and particularly so in soft-bottom oceanic sediments where it generally occurs bound in a four-valent colloidal state as MnO 2 . When hypoxic conditions occur in bottom waters, the metal reduces to the bioavailable ion Mn 2+ and can reach concentrations known to have immunotoxic effects in the crustacean Nephrops norvegicus, reducing numbers of circulating haemocytes as a consequence. However, we have previously shown that Mn seems to have a contrasting effect on the echinoderm Asterias rubens in which it triggers the proliferation of haematopoietic cells and increases coelomocyte numbers. Since elevated Mn levels mostly co-occur with hypoxia in nature, here we investigated whether hypoxia has a negative effect on haematopoiesis. Proliferation and differentiation of coelomocytes and cells in the coelomic epithelium of A. rubens were compared after 3 days of exposure to realistic levels of Mn, hypoxia or a combination of these two parameters. We can confirm that Mn elevated numbers of coelomocytes and increased proliferation of epithelial cells, but hypoxia did not affect these levels. However, hypoxia did affect differentiation of these cells as judged by investigating the expression of a Runt domain transcription factor, which was also cloned and sequenced. Through comparative quantification using a real time PCR technique, we found that exposure to hypoxia had a clearly stimulating effect on mRNA expression of Runt gene in both coelomocytes and epithelial cells. These results indicate that during hypoxic conditions the composition of coelomocyte sub-populations changed.

Hepcidin: A Critical Regulator Of Iron Metabolism During Hypoxia

Science.gov (United States)

2011-01-01

inducible factor (HIF)/hypoxia response element ( HRE ) system, as well as recent evidence indicating that localized adipose hypoxia due to obesity may...mechanisms by which hypoxia affects hepcidin expression, to include a review of the hypoxia inducible factor (HIF)/hypoxia response element ( HRE ) system, as...a battery of genes are induced by the hypoxia inducible factor (HIF)/hypoxia response element ( HRE ) system. The HIF system senses O2 levels through

Hypoxia training: symptom replication in experienced military aircrew.

Science.gov (United States)

Johnston, Ben J; Iremonger, Gareth S; Hunt, Sheena; Beattie, Elizabeth

2012-10-01

Military aircrew are trained to recognize the signs and symptoms of hypoxia in a safe environment using a variety of methods to simulate altitude. In order to investigate the effectiveness of hypoxia training, this study compared the recall of hypoxia symptoms in military aircrew between two consecutive hypobaric chamber hypoxia training sessions conducted, on average, 4.5 yr apart. Previously trained subjects completed a questionnaire immediately before and after they underwent refresher hypoxia training and recorded the occurrence, order, and severity of symptoms experienced. Responses from refresher training were compared with their recall of symptoms experienced during previous training. There was no difference in the recall of most hypoxia symptoms between training sessions. Slurred speech was recalled more frequently from previous training compared to refresher training (14 vs. 4 subjects), whereas hot/cold flushes were recalled less frequently from previous training compared to refresher training (5 vs. 17 subjects). There was a statistically significant difference in overall hypoxia score (10.3 vs. 8.3), suggesting that from memory subjects may underestimate the level of hypoxia experienced in previous training. A high level of similarity between the recall of previously experienced hypoxia symptoms and recent experience supports the effectiveness of hypoxia training. These results replicate the finding of a 'hypoxia signature' reported by a previous study. Small differences in the recall of some symptoms and in overall hypoxia score highlight the importance of drawing attention to the more subtle symptoms of early hypoxia, and of using training techniques which optimize aircrew recall.

THE EFFECT OF HYPOXIA ON THE MAXIMUM MATABOLIC RATE AND SPECIFIC DYNAMIC ACTION IN ATLANTIC COD Gadus morhua

DEFF Research Database (Denmark)

Steffensen, John Fleng

2010-01-01

John Fleng Steffensen' and Anders Drud Jordan Aquaculture 2010 - San Diego - Physiological Insights Towards Improving Fish Culture. Hypoxia is an increasing problem in coastal near areas and estuaries. Hypoxia can also be a problem in aquaculture systems with a high degree of recirculating water...... reduced the Scope for Activity by 55 % in nonnoxia. In hypoxia the effect was more pronounced with a 69 % reduction of the scope for activity. In conclusion hypoxia prolong the postabsorptive state of fi sh by limiting the peak metabolic rate, causing that less food is assimilated over a certain period...

Body temperature depression and peripheral heat loss accompany the metabolic and ventilatory responses to hypoxia in low and high altitude birds.

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Scott, Graham R; Cadena, Viviana; Tattersall, Glenn J; Milsom, William K

2008-04-01

The objectives of this study were to compare the thermoregulatory, metabolic and ventilatory responses to hypoxia of the high altitude bar-headed goose with low altitude waterfowl. All birds were found to reduce body temperature (T(b)) during hypoxia, by up to 1-1.5 degrees C in severe hypoxia. During prolonged hypoxia, T(b) stabilized at a new lower temperature. A regulated increase in heat loss contributed to T(b) depression as reflected by increases in bill surface temperatures (up to 5 degrees C) during hypoxia. Bill warming required peripheral chemoreceptor inputs, since vagotomy abolished this response to hypoxia. T(b) depression could still occur without bill warming, however, because vagotomized birds reduced T(b) as much as intact birds. Compared to both greylag geese and pekin ducks, bar-headed geese required more severe hypoxia to initiate T(b) depression and heat loss from the bill. However, when T(b) depression or bill warming were expressed relative to arterial O(2) concentration (rather than inspired O(2)) all species were similar; this suggests that enhanced O(2) loading, rather than differences in thermoregulatory control centres, reduces T(b) depression during hypoxia in bar-headed geese. Correspondingly, bar-headed geese maintained higher rates of metabolism during severe hypoxia (7% inspired O(2)), but this was only partly due to differences in T(b). Time domains of the hypoxic ventilatory response also appeared to differ between bar-headed geese and low altitude species. Overall, our results suggest that birds can adjust peripheral heat dissipation to facilitate T(b) depression during hypoxia, and that bar-headed geese minimize T(b) and metabolic depression as a result of evolutionary adaptations that enhance O(2) transport.

Microenvironmental oxygen partial pressure in acute myeloid leukemia: Is there really a role for hypoxia?

Science.gov (United States)

Rieger, Christina T; Fiegl, Michael

2016-07-01

Reduced oxygen partial pressure (pO2) has been recognized as being relevant in hematopoiesis and the pathophysiology of malignant diseases. Although hypoxic (meaning insufficient supply of oxygen) and anoxic areas are present and of pathophysiologic importance (by hypoxia-induced pathways such as HiF1α) in solid tumors, this may not be true for (malignant) hematologic cells. Hematopoiesis occurs in the stem cell niche, which is characterized, among other things, by extremely low pO2. However, in contrast to solid tumors, in this context, the low pO2 is physiological and this feature, among others, is shared by the malignant stem cell niche harboring leukemia-initiating cells. Upon differentiation, hematopoietic cells are constantly exposed to changes in pO2 as they travel throughout the human body and encounter arterial and venous blood and migrate into oxygen-carrier-free tissue with low pO2. Hematologic malignancies such as acute myeloid leukemia (AML) make little difference in this respect and, whereas low oxygen is the usual environment of AML cells, recent evidence suggests no role for real hypoxia. Although there is no evidence that AML pathophysiology is related to hypoxia, leukemic blasts still show several distinct biological features when exposed to reduced pO2: they down- or upregulate membrane receptors such as CXCR4 or FLT3, activate or inhibit intracellular signaling pathways such as PI3K, and specifically secrete cytokines (IL-8). In summary, reduced pO2 should not be mistaken for hypoxia (nor should it be so called), and it does not automatically induce hypoxia-response mechanisms; therefore, a strict distinction should be made between physiologically low pO2 (physoxia) and hypoxia. Copyright © 2016 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc. All rights reserved.

Regulation of mRNA translation influences hypoxia tolerance

International Nuclear Information System (INIS)

Koritzinsky, M.; Wouters, B.G.; Koumenis, C.

2003-01-01

Hypoxia is a heterogenous but common characteristic of human tumours and poor oxygenation is associated with poor prognosis. We believe that the presence of viable hypoxic tumor cells reflects in part an adaptation and tolerance of these cells to oxygen deficiency. Since oxidative phosphorylation is compromized during hypoxia, adaptation may involve both the upregulation of glycolysis as well as downregulation of energy consumption. mRNA translation is one of the most energy costly cellular processes, and we and others have shown that global mRNA translation is rapidly inhibited during hypoxia. However, some mRNAs, including those coding for HIF-1 α and VEGF, remain efficiently translated during hypoxia. Clearly, the mechanisms responsible for the overall inhibition of translation during hypoxia does not compromize the translation of certain hypoxia-induced mRNA species. We therefore hypothesize that the inhibition of mRNA translation serves to promote hypoxia tolerance in two ways: i) through conservation of energy and ii) through differential gene expression involved in hypoxia adaptation. We have recently identified two pathways that are responsible for the global inhibition of translation during hypoxia. The phosphorylation of the eukaryotic initiation factor eIF2 α by the ER resident kinase PERK results in down-regulation of protein synthesis shortly after the onset of hypoxia. In addition, the initiation complex eIF4F is disrupted during long lasting hypoxic conditions. The identification of the molecular pathways responsible for the inhibition of overall translation during hypoxia has rendered it possible to investigate their importance for hypoxia tolerance. We have found that mouse embryo fibroblasts that are knockout for PERK and therefore not able to inhibit protein synthesis efficiently during oxygen deficiency are significantly less tolerant to hypoxia than their wildtype counterparts. We are currently also investigating the functional significance

Stress response of lead-exposed rainbow trout (Oncorhynchus mykiss) during swimming performance and hypoxia challenges

Energy Technology Data Exchange (ETDEWEB)

Phillips, K.A. [National Biological Service, La Crosse, WI (United States)]|[Univ. of Wisconsin, La Crosse, WI (United States); Caldwell, C.A. [National Biological Service, La Crosse, WI (United States); Sandheinrich, M.B. [Univ. of Wisconsin, La Crosse, WI (United States)

1995-12-31

Contaminants often invoke a stress response in aquatic organisms, and may compromise their capacity to respond to secondary stressors. This may reduce growth, reproduction and survival. The authors objectives were to assess the effects of lead and secondary stressors on hematology and blood chemistry of rainbow trout. After a 7 to 8-week aqueous exposure to Pb(100{micro}g/L), rainbow trout were challenged with forced swimming or hypoxia. Lead significantly reduced concentrations of 5-aminolevulinic acid dehydratase (ALAD), but not other constituents in the blood. Lead did not affect the swimming endurance of the fish. Hematocrit, mean cell hemoglobin content, and mean cell volume were significantly lower in Pb-exposed trout following the swimming challenge. Although hypoxia resulted in increased hematocrit and plasma glucose concentrations, there were no significant differences between the Pb and control groups. Hypoxia did not affect plasma chloride concentrations, although concentrations increased in Pb-exposed trout. There was no difference in lactic acid concentrations between Pb-exposed and control fish after forced swimming or hypoxia.

Limited effects of exogenous glucose during severe hypoxia and a lack of hypoxia-stimulated glucose uptake in isolated rainbow trout cardiac muscle

Science.gov (United States)

Becker, Tracy A.; DellaValle, Brian; Gesser, Hans; Rodnick, Kenneth J.

2013-01-01

SUMMARY We examined whether exogenous glucose affects contractile performance of electrically paced ventricle strips from rainbow trout under conditions known to alter cardiomyocyte performance, ion regulation and energy demands. Physiological levels of d-glucose did not influence twitch force development for aerobic preparations (1) paced at 0.5 or 1.1 Hz, (2) at 15 or 23°C, (3) receiving adrenergic stimulation or (4) during reoxygenation with or without adrenaline after severe hypoxia. Contractile responses to ryanodine, an inhibitor of Ca2+ release from the sarcoplasmic reticulum, were also not affected by exogenous glucose. However, glucose did attenuate the fall in twitch force during severe hypoxia. Glucose uptake was assayed in non-contracting ventricle strips using 2-[3H] deoxy-d-glucose (2-DG) under aerobic and hypoxic conditions, at different incubation temperatures and with different inhibitors. Based upon a lack of saturation of 2-DG uptake and incomplete inhibition of uptake by cytochalasin B and d-glucose, 2-DG uptake was mediated by a combination of facilitated transport and simple diffusion. Hypoxia stimulated lactate efflux sixfold to sevenfold with glucose present, but did not increase 2-DG uptake or reduce lactate efflux in the presence of cytochalasin B. Increasing temperature (14 to 24°C) also did not increase 2-DG uptake, but decreasing temperature (14 to 4°C) reduced 2-DG uptake by 45%. In conclusion, exogenous glucose improves mechanical performance under hypoxia but not under any of the aerobic conditions applied. The extracellular concentration of glucose and cold temperature appear to determine and limit cardiomyocyte glucose uptake, respectively, and together may help define a metabolic strategy that relies predominantly on intracellular energy stores. PMID:23685969

IBMX protects human proximal tubular epithelial cells from hypoxic stress through suppressing hypoxia-inducible factor-1α expression.

Science.gov (United States)

Hasan, Arif Ul; Kittikulsuth, Wararat; Yamaguchi, Fuminori; Musarrat Ansary, Tuba; Rahman, Asadur; Shibayama, Yuki; Nakano, Daisuke; Hitomi, Hirofumi; Tokuda, Masaaki; Nishiyama, Akira

2017-09-15

Hypoxia predisposes renal fibrosis. This study was conducted to identify novel approaches to ameliorate the pathogenic effect of hypoxia. Using human proximal tubular epithelial cells we showed that a pan-phosphodiesterase (PDE) inhibitor, 3-isobutyl-1-methylxanthine (IBMX) dose and time dependently downregulated hypoxia-inducible factor 1α (HIF-1α) mRNA expression, which was further augmented by addition of a transcriptional inhibitor, actinomycin D. IBMX also increased the cellular cyclic adenosine monophosphate (cAMP) level. Luciferase assay showed that blocking of protein kinase A (PKA) using H89 reduced, while 8-Br-cAMP agonized the repression of HIF-1α promoter activity in hypoxic condition. Deletion of cAMP response element binding sites from the HIF-1α promoter abrogated the effect of IBMX. Western blot and immunofluorescent study confirmed that the CoCl 2 induced increased HIF-1α protein in whole cell lysate and in nucleus was reduced by the IBMX. Through this process, IBMX attenuated both CoCl 2 and hypoxia induced mRNA expressions of two pro-fibrogenic factors, platelet-derived growth factor B and lysyl oxidase. Moreover, IBMX reduced production of a mesenchymal transformation factor, β-catenin; as well as protected against hypoxia induced cell-death. Taken together, our study showed novel evidence that the PDE inhibitor IBMX can downregulate the transcription of HIF-1α, and thus may attenuate hypoxia induced renal fibrosis. Copyright © 2017 Elsevier Inc. All rights reserved.

Role of the AMPKgamma3 isoform in hypoxia-stimulated glucose transport in glycolytic skeletal muscle

DEFF Research Database (Denmark)

Deshmukh, Atul S; Glund, Stephan; Tom, Robby Z

2009-01-01

, phosphorylation of CaMKII, AMPK, ACC, and TBC1D1/D4 as well as isoform-specific AMPK activity was determined. Basal and hypoxia-mediated phosphorylation of CaMKII, AMPK, and ACC as well as alpha1- and alpha2-associated AMPK activity was comparable between AMPKgamma3-KO and wild-type mice. KN-93 reduced hypoxia...

Proteins modulation in human skeletal muscle in the early phase of adaptation to hypobaric hypoxia

DEFF Research Database (Denmark)

Vigano, A.; Ripamonti, M.; Palma, S. De

2008-01-01

High altitude hypoxia is a paraphysiological condition triggering redox status disturbances of cell organization leading, via oxidative stress, to proteins, lipids, and DNA damage. In man, skeletal muscle, after prolonged exposure to hypoxia, undergoes mass reduction and alterations at the cellul......, whereas the mammalian target of rapamycin (mTOR), a marker of protein synthesis, was reduced Udgivelsesdato: 2008/11...

A preclinical model for noninvasive imaging of hypoxia-induced gene expression; comparison with an exogenous marker of tumor hypoxia

Energy Technology Data Exchange (ETDEWEB)

Wen Bixiu; Burgman, Paul; Zanzonico, Pat; O' Donoghue, Joseph; Li, Gloria C.; Ling, C. Clifton [Memorial Sloan-Kettering Cancer Center, Department of Medical Physics, New York (United States); Cai Shangde; Finn, Ron [Memorial Sloan-Kettering Cancer Center, Department of Radiology, New York (United States); Serganova, Inna [Memorial Sloan-Kettering Cancer Center, Department of Neurology, New York (United States); Blasberg, Ronald; Gelovani, Juri [Memorial Sloan-Kettering Cancer Center, Department of Radiology, New York (United States); Memorial Sloan-Kettering Cancer Center, Department of Neurology, New York (United States)

2004-11-01

Hypoxia is associated with tumor aggressiveness and is an important cause of resistance to radiation therapy and chemotherapy. Assays of tumor hypoxia could provide selection tools for hypoxia-modifying treatments. The purpose of this study was to develop and characterize a rodent tumor model with a reporter gene construct that would be transactivated by the hypoxia-inducible molecular switch, i.e., the upregulation of HIF-1. The reporter gene construct is the herpes simplex virus 1-thymidine kinase (HSV1-tk) fused with the enhanced green fluorescent protein (eGFP) under the regulation of an artificial hypoxia-responsive enhancer/promoter. In this model, tumor hypoxia would up-regulate HIF-1, and through the hypoxia-responsive promoter transactivate the HSV1-tkeGFPfusion gene. The expression of this reporter gene can be assessed with the {sup 124}I-labeled reporter substrate 2'-fluoro-2'-deoxy-1-{beta}-d-arabinofuranosyl-5-iodouracil ({sup 124}I-FIAU), which is phosphorylated by the HSV1-tk enzyme and trapped in the hypoxic cells. Animal positron emission tomography (microPET) and phosphor plate imaging (PPI) were used in this study to visualize the trapped {sup 124}I-FIAU, providing a distribution of the hypoxia-induced molecular events. The distribution of {sup 124}I-FIAU was also compared with that of an exogenous hypoxic cell marker, {sup 18}F-fluoromisonidazole (FMISO). Our results showed that {sup 124}I-FIAU microPET imaging of the hypoxia-induced reporter gene expression is feasible, and that the intratumoral distributions of {sup 124}I-FIAU and {sup 18}F-FMISO are similar. In tumor sections, detailed radioactivity distributions were obtained with PPI which also showed similarity between {sup 124}I-FIAU and {sup 18}F-FMISO. This reporter system is sufficiently sensitive to detect hypoxia-induced transcriptional activation by noninvasive imaging and might provide a valuable tool in studying tumor hypoxia and in validating existing and future

Hypoxia-Inducible Factor Pathway Inhibition Resolves Tumor Hypoxia and Improves Local Tumor Control After Single-Dose Irradiation

International Nuclear Information System (INIS)

Helbig, Linda; Koi, Lydia; Brüchner, Kerstin; Gurtner, Kristin; Hess-Stumpp, Holger; Unterschemmann, Kerstin; Pruschy, Martin

2014-01-01

Purpose: To study the effects of BAY-84-7296, a novel orally bioavailable inhibitor of mitochondrial complex I and hypoxia-inducible factor 1 (HIF-1) activity, on hypoxia, microenvironment, and radiation response of tumors. Methods and Materials: UT-SCC-5 and UT-SCC-14 human squamous cell carcinomas were transplanted subcutaneously in nude mice. When tumors reached 4 mm in diameter BAY-84-7296 (Bayer Pharma AG) or carrier was daily administered to the animals. At 7 mm tumors were either excised for Western blot and immunohistologic investigations or were irradiated with single doses. After irradiation animals were randomized to receive BAY-84-7296 maintenance or carrier. Local tumor control was evaluated 150 days after irradiation, and the dose to control 50% of tumors (TCD 50 ) was calculated. Results: BAY-84-7296 decreased nuclear HIF-1α expression. Daily administration of inhibitor for approximately 2 weeks resulted in a marked decrease of pimonidazole hypoxic fraction in UT-SCC-5 (0.5% vs 21%, P 50 , with an enhancement ratio of 1.37 (95% confidence interval [CI] 1.13-1.72) in UT-SCC-5 and of 1.55 (95% CI 1.26-1.94) in UT-SCC-14. BAY-84-7296 maintenance after irradiation did not further decrease TCD 50 . Conclusions: BAY-84-7296 resulted in a marked decrease in tumor hypoxia and substantially reduced radioresistance of tumor cells with the capacity to cause a local recurrence after irradiation. The data suggest that reduction of cellular hypoxia tolerance by BAY-84-7296 may represent the primary biological mechanism underlying the observed enhancement of radiation response. Whether this mechanism contributes to the improved outcome of fractionated chemoradiation therapy warrants further investigation

Effects of Acute Systemic Hypoxia and Hypercapnia on Brain Damage in a Rat Model of Hypoxia-Ischemia.

Directory of Open Access Journals (Sweden)

Wanchao Yang

Full Text Available Therapeutic hypercapnia has the potential for neuroprotection after global cerebral ischemia. Here we further investigated the effects of different degrees of acute systemic hypoxia in combination with hypercapnia on brain damage in a rat model of hypoxia and ischemia. Adult wistar rats underwent unilateral common carotid artery (CCA ligation for 60 min followed by ventilation with normoxic or systemic hypoxic gas containing 11%O2,13%O2,15%O2 and 18%O2 (targeted to PaO2 30-39 mmHg, 40-49 mmHg, 50-59 mmHg, and 60-69 mmHg, respectively or systemic hypoxic gas containing 8% carbon dioxide (targeted to PaCO2 60-80 mmHg for 180 min. The mean artery pressure (MAP, blood gas, and cerebral blood flow (CBF were evaluated. The cortical vascular permeability and brain edema were examined. The ipsilateral cortex damage and the percentage of hippocampal apoptotic neurons were evaluated by Nissl staining and terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL assay as well as flow cytometry, respectively. Immunofluorescence and western blotting were performed to determine aquaporin-4 (AQP4 expression. In rats treated with severe hypoxia (PaO2 50 mmHg, hypercapnia protected against these pathophysiological changes. Moreover, hypercapnia treatment significantly reduced brain damage in the ischemic ipsilateral cortex and decreased the percentage of apoptotic neurons in the hippocampus after the CCA ligated rats were exposed to mild or moderate hypoxemia (PaO2 > 50 mmHg; especially under mild hypoxemia (PaO2 > 60 mmHg, hypercapnia significantly attenuated the expression of AQP4 protein with brain edema (p < 0.05. Hypercapnia exerts beneficial effects under mild to moderate hypoxemia and augments detrimental effects under severe hypoxemia on brain damage in a rat model of hypoxia-ischemia.

Protein S-glutathionylation induced by hypoxia increases hypoxia-inducible factor-1α in human colon cancer cells.

Science.gov (United States)

Jeon, Daun; Park, Heon Joo; Kim, Hong Seok

2018-01-01

Hypoxia is a common characteristic of many types of solid tumors. Intratumoral hypoxia selects for tumor cells that survive in a low oxygen environment, undergo epithelial-mesenchymal transition, are more motile and invasive, and show gene expression changes driven by hypoxia-inducible factor-1α (HIF-1α) activation. Therefore, targeting HIF-1α is an attractive strategy for disrupting multiple pathways crucial for tumor growth. In the present study, we demonstrated that hypoxia increases the S-glutathionylation of HIF-1α and its protein levels in colon cancer cells. This effect is significantly prevented by decreasing oxidized glutathione as well as glutathione depletion, indicating that S-glutathionylation and the formation of protein-glutathione mixed disulfides is related to HIF-1α protein levels. Moreover, colon cancer cells expressing glutaredoxin 1 are resistant to inducing HIF-1α and expressing hypoxia-responsive genes under hypoxic conditions. Therefore, S-glutathionylation of HIF-1α induced by tumor hypoxia may be a novel therapeutic target for the development of new drugs. Copyright © 2017 Elsevier Inc. All rights reserved.

Ubiquitination is absolutely required for the degradation of hypoxia-inducible factor--1 alpha protein in hypoxic conditions.

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Wang, Ronghai; Zhang, Ping; Li, Jinhang; Guan, Hongzai; Shi, Guangjun

2016-01-29

The hypoxia-inducible factor (HIF) is recognized as the master regulator of hypoxia response. HIF-α subunits expression are tightly regulated. In this study, our data show that ts20 cells still expressed detectable E1 protein even at 39.5° C for 12 h, and complete depletion of E1 protein expression at 39.5° C by siRNA enhanced HIF-1α and P53 protein expression. Further inhibition of E1 at 39.5 °C by siRNA, or E1 inhibitor Ube1-41 completely blocked HIF-1α degradation. Moreover, immunoprecipitations of co-transfection of HA-ubiquitin and FLAG-HIF-1α plasmids directly confirmed the involvement of ubiquitin in the hypoxic degradation of HIF-1α. Additionally, hypoxic HIF-1 α degradation is independent of HAF, RACK1, sumoylation or nuclear/cytoplasmic localization. Taken together, our data suggest that constitutive HIF-1α protein degradation in hypoxia is absolutely ubiquitination-dependent, and unidentified E3 ligase may exist for this degradation pathway. Copyright © 2016 Elsevier Inc. All rights reserved.

Uncoupling protein-2 mRNA expression in mice subjected to intermittent hypoxia

Directory of Open Access Journals (Sweden)

Luciana Rodrigues Vieira

2015-04-01

Full Text Available Objective: To investigate the effect of intermittent hypoxia-a model of obstructive sleep apnea (OSA-on pancreatic expression of uncoupling protein-2 (UCP2, as well as on glycemic and lipid profiles, in C57BL mice. Methods: For 8 h/day over a 35-day period, male C57BL mice were exposed to intermittent hypoxia (hypoxia group or to a sham procedure (normoxia group. The intermittent hypoxia condition involved exposing mice to an atmosphere of 92% N and 8% CO2 for 30 s, progressively reducing the fraction of inspired oxygen to 8 ± 1%, after which they were exposed to room air for 30 s and the cycle was repeated (480 cycles over the 8-h experimental period. Pancreases were dissected to isolate the islets. Real-time PCR was performed with TaqMan assays. Results: Expression of UCP2 mRNA in pancreatic islets was 20% higher in the normoxia group than in the hypoxia group (p = 0.11. Fasting serum insulin was higher in the hypoxia group than in the normoxia group (p = 0.01. The homeostasis model assessment of insulin resistance indicated that, in comparison with the control mice, the mice exposed to intermittent hypoxia showed 15% lower insulin resistance (p = 0.09 and 21% higher pancreatic β-cell function (p = 0.01. Immunohistochemical staining of the islets showed no significant differences between the two groups in terms of the area or intensity of α- and β-cell staining for insulin and glucagon. Conclusions: To our knowledge, this is the first report of the effect of intermittent hypoxia on UCP2 expression. Our findings suggest that UCP2 regulates insulin production in OSA. Further study of the role that UCP2 plays in the glycemic control of OSA patients is warranted.

Hypoxia-Inducible Factor 3 Is an Oxygen-Dependent Transcription Activator and Regulates a Distinct Transcriptional Response to Hypoxia

Directory of Open Access Journals (Sweden)

Peng Zhang

2014-03-01

Full Text Available Hypoxia-inducible factors (HIFs play key roles in the cellular response to hypoxia. It is widely accepted that whereas HIF-1 and HIF-2 function as transcriptional activators, HIF-3 inhibits HIF-1/2α action. Contrary to this idea, we show that zebrafish Hif-3α has strong transactivation activity. Hif-3α is degraded under normoxia. Mutation of P393, P493, and L503 inhibits this oxygen-dependent degradation. Transcriptomics and chromatin immunoprecipitation analyses identify genes that are regulated by Hif-3α, Hif-1α, or both. Under hypoxia or when overexpressed, Hif-3α binds to its target gene promoters and upregulates their expression. Dominant-negative inhibition and knockdown of Hif-3α abolish hypoxia-induced Hif-3α-promoter binding and gene expression. Hif-3α not only mediates hypoxia-induced growth and developmental retardation but also possesses hypoxia-independent activities. Importantly, transactivation activity is conserved and human HIF-3α upregulates similar genes in human cells. These findings suggest that Hif-3 is an oxygen-dependent transcription factor and activates a distinct transcriptional response to hypoxia.

Effects of ration size and hypoxia on specific dynamic action in the cod

DEFF Research Database (Denmark)

Jordan, Anders D; Steffensen, John F

2007-01-01

We present the first data on the effect of hypoxia on the specific dynamic action (SDA) in a teleost fish. Juvenile cod (Gadus morhua) were fed meals of 2.5% and 5% of their wet body mass (BM) in normoxia (19.8 kPa Po(2)) and 5% BM in hypoxia (6.3 kPa Po(2)). Reduced O(2) availability depressed...... the postprandial peaks of oxygen consumption, and to compensate for this, the total SDA duration lasted 212.0+/-20 h in hypoxia, compared with 95.1+/-25 h in normoxia. The percentage of energy associated with the meal digestion and assimilation (SDA coefficient) was equivalent between the different feeding rations...

Effect of endothelin antagonism on apnea frequency following chronic intermittent hypoxia.

Science.gov (United States)

Donovan, Lucas M; Liu, Yuzhen; Weiss, J Woodrow

2014-04-01

Chronic hypoxia increases the hypoxic ventilatory response (HVR). Augmented HVR contributes to central apneas seen in heart failure and complex sleep apnea. Endothelin receptor (ETR) antagonism decreases carotid body afferent activity following chronic intermittent hypoxia (CIH). We speculated ETR antagonism would reduce HVR and apneas following CIH. HVR and apneas were measured after exposure to CIH and room air sham (SHAM). ETR blocker Ambrisentan was administered via the chow of CIH-exposed animals from days 1 to 12 of CIH (CIH/AMB). A separate crossover group was exposed to CIH and fed normal chow (placebo) days 1-6, and Ambrisentan days 7-12 (CIH/PLA-AMB). SHAM and CIH/PLA animals were fed placebo days 1-12. The CIH/AMB and CIH/PLA-AMB rats had reduced HVR compared to CIH/PLA, similar HVR compared to sham exposed animals, and reduced apnea frequency compared to CIH/PLA animals. The reduced HVR and post-hypoxic apneas resulting from Ambrisentan administration suggests ETR antagonists may have utility in reducing central apneas following CIH. Copyright © 2014 Elsevier B.V. All rights reserved.

Hypoxia during pregnancy in rats leads to the changes of the cerebral white matter in adult offspring

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Wang, Lingxing; Cai, Ruowei; Lv, Guorong; Huang, Ziyang; Wang, Zhenhua

2010-01-01

The aim of the present study is to evaluate the effect of reduced fetal oxygen supply on cerebral white matter in the adult offspring and further assess its susceptibility to postnatal hypoxia and high-fat diet. Based on a 3 x 2 full factorial design consisting of three factors of maternal hypoxia, postnatal high-fat diet, and postnatal hypoxia, the ultrastructure of myelin, axon and capillaries were observed, and the expression of myelin basic protein (MBP), neurofilament-H+L(NF-H+L), and glial fibrillary acidic protein (GFAP) was analyzed in periventricular white matter of 16-month-old offspring. Demyelination, injured axon and damaged microvasculars were observed in maternal hypoxia offspring. The main effect of maternal hypoxia lead to decreased expression of MBP or NF-H+L, and increased expression of GFAP (all P < 0.05). Moreover, there was positive three-way interaction among maternal hypoxia, high-fat diet and postnatal hypoxia on MBP, NF-H+L or GFAP expression (all P < 0.05). In summary, our results indicated that maternal hypoxia during pregnancy in rats lead to changes of periventricular white matter in adult offspring, including demyelination, damaged axon and proliferated astroglia. This effect was amplified by high-fat diet and postnatal hypoxia.

Hypoxic pretreatment protects against neuronal damage of the rat hippocampus induced by severe hypoxia.

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Gorgias, N; Maidatsi, P; Tsolaki, M; Alvanou, A; Kiriazis, G; Kaidoglou, K; Giala, M

1996-04-01

The present study investigates whether under conditions of successive hypoxic exposures pretreatment with mild (15% O(2)) or moderate (10% O(2)) hypoxia, protects hippocampal neurones against damage induced by severe (3% O(2)) hypoxia. The ultrastructural findings were also correlated with regional superoxide dismutase (SOD) activity changes. In unpretreated rats severe hypoxia induced ultrastructural changes consistent with the aspects of delayed neuronal death (DND). However, in preexposed animals hippocampal damage was attenuated in an inversely proportional way with the severity of the hypoxic pretreatment. The ultrastructural hypoxic tolerance findings were also closely related to increased regional SOD activity levels. Thus the activation of the endogenous antioxidant defense by hypoxic preconditioning, protects against hippocampal damage induced by severe hypoxia. The eventual contribution of increased endogenous adenosine and/or reduced excitotoxicity to induce hypoxic tolerance is discussed.

Tissue hypoxia during ischemic stroke: adaptive clues from hypoxia-tolerant animal models.

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Nathaniel, Thomas I; Williams-Hernandez, Ashley; Hunter, Anan L; Liddy, Caroline; Peffley, Dennis M; Umesiri, Francis E; Imeh-Nathaniel, Adebobola

2015-05-01

The treatment and prevention of hypoxic/ischemic brain injury in stroke patients remain a severe and global medical issue. Numerous clinical studies have resulted in a failure to develop chemical neuroprotection for acute, ischemic stroke. Over 150 estimated clinical trials of ischemic stroke treatments have been done, and more than 200 drugs and combinations of drugs for ischemic and hemorrhagic strokes have been developed. Billions of dollars have been invested for new scientific breakthroughs with only limited success. The revascularization of occluded cerebral arteries such as anti-clot treatments of thrombolysis has proven effective, but it can only be used in a 3-4.5h time frame after the onset of a stroke, and not for every patient. This review is about novel insights on how to resist tissue hypoxia from unconventional animal models. Ability to resist tissue hypoxia is an extraordinary ability that is not common in many laboratory animals such as rat and mouse models. For example, we can learn from a naked mole-rat, Chrysemys picta, how to actively regulate brain metabolic activity to defend the brain against fluctuating oxygen tension and acute bouts of oxidative stress following the onset of a stroke. Additionally, a euthermic arctic ground squirrel can teach us how the brain of a stroke patient can remain well oxygenated during tissue hypoxia with no evidence of cellular stress. In this review, we discuss how these animals provide us with a system to gain insight into the possible mechanisms of tissue hypoxia/ischemia. This issue is of clinical significance to stroke patients. We describe specific physiological and molecular adaptations employed by different animals' models of hypoxia tolerance in aquatic and terrestrial environments. We highlight how these adaptations might provide potential clues on strategies to adapt for the clinical management of tissue hypoxia during conditions such as stroke where oxygen demand fails to match the supply. Copyright

Stromal Expression of Hypoxia Regulated Proteins Is an Adverse Prognostic Factor in Colorectal Carcinomas

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Arjen H. G. Cleven

2007-01-01

Full Text Available Background: Hypoxia modifies the phenotype of tumors in a way that promotes tumor aggressiveness and resistance towards chemotherapy and radiotherapy. However, the expression and influence of hypoxia-regulated proteins on tumor biology are not well characterized in colorectal tumors. We studied the role of protein expression of hypoxia-inducible factor (HIF-1α, HIF-2α, carbonic anhydrase 9 (CA9 and glucose transporter 1 (GLUT1 in patients with colorectal adenocarcinomas. Methods: Expression of HIF-1α, HIF-2α, CA9 and GLUT1 was quantified by immunohistochemistry in 133 colorectal adenocarcinomas. The expression of hypoxia markers was correlated with clinicopathological variables and overall patient survival. Results: Expression of these hypoxia markers was detected in the epithelial compartment of the tumor cells as well as in tumor-associated stromal cells. Although tumor cells frequently showed expression of one or more of the investigated hypoxia markers, no correlation among these markers or with clinical response was found. However, within the tumor stroma, positive correlations between the hypoxia markers HIF-2α, CA9 and GLUT1 were observed. Furthermore expression of HIF-2α and CA9 in tumor-associated stroma were both associated with a significantly reduced overall survival. In the Cox proportional hazard model, stromal HIF-2α expression was an independent prognostic factor for survival. Conclusion: These observations show, that expression of hypoxia regulated proteins in tumor-associated stromal cells, as opposed to their expression in epithelial tumor cells, is associated with poor outcome in colorectal cancer. This study suggests that tumor hypoxia may influence tumor-associated stromal cells in a way that ultimately contributes to patient prognosis.

Hypoxia induces adipogenic differentitation of myoblastic cell lines

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Itoigawa, Yoshiaki [Tohoku University School of Medicine, Sendai (Japan); Juntendo University School of Medicine, Tokyo (Japan); Kishimoto, Koshi N., E-mail: kishimoto@med.tohoku.ac.jp [Tohoku University School of Medicine, Sendai (Japan); Okuno, Hiroshi; Sano, Hirotaka [Tohoku University School of Medicine, Sendai (Japan); Kaneko, Kazuo [Juntendo University School of Medicine, Tokyo (Japan); Itoi, Eiji [Tohoku University School of Medicine, Sendai (Japan)

2010-09-03

Research highlights: {yields} C2C12 and G8 myogenic cell lines treated by hypoxia differentiate into adipocytes. {yields} The expression of C/EBP{beta}, {alpha} and PPAR{gamma} were increased under hypoxia. {yields} Myogenic differentiation of C2C12 was inhibited under hypoxia. -- Abstract: Muscle atrophy usually accompanies fat accumulation in the muscle. In such atrophic conditions as back muscles of kyphotic spine and the rotator cuff muscles with torn tendons, blood flow might be diminished. It is known that hypoxia causes trans-differentiation of mesenchymal stem cells derived from bone marrow into adipocytes. However, it has not been elucidated yet if hypoxia turned myoblasts into adipocytes. We investigated adipogenesis in C2C12 and G8 murine myogenic cell line treated by hypoxia. Cells were also treated with the cocktail of insulin, dexamethasone and IBMX (MDI), which has been known to inhibit Wnt signaling and promote adipogenesis. Adipogenic differentiation was seen in both hypoxia and MDI. Adipogenic marker gene expression was assessed in C2C12. CCAAT/enhancer-binding protein (C/EBP) {beta}, {alpha} and peroxisome proliferator activating receptor (PPAR) {gamma} were increased by both hypoxia and MDI. The expression profile of Wnt10b was different between hypoxia and MDI. The mechanism for adipogenesis of myoblasts in hypoxia might be regulated by different mechanism than the modification of Wnt signaling.

Reflex bradycardia does not influence oxygen consumption during hypoxia in the European eel (Anguilla anguilla)

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Iversen, Nina Kerting; McKenzie, David; Malte, H.

2010-01-01

the bradycardia on oxygen consumption (MO2), standard metabolic rate (SMR) and the critical oxygen partial pressure for regulation of SMR in hypoxia (Pcrit) in European eels Anguilla anguilla (mean ± SEM mass 528 ± 36 g; n = 14). Eels were instrumented with a Transonic flow probe around the ventral aorta......Most teleost fish reduce heart rate when exposed to acute hypoxia. This hypoxic bradycardia has been characterised for many fish species, but it remains uncertain whether this reflex contributes to the maintenance of oxygen uptake in hypoxia. Here we describe the effects of inhibiting...

4-Guanidino-n-butyl syringate (Leonurine, SCM 198) protects H9c2 rat ventricular cells from hypoxia-induced apoptosis.

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Liu, Xin-hua; Chen, Pei-fang; Pan, Li-long; Silva, Ranil De; Zhu, Yi-zhun

2009-11-01

In the present study, we examined the ability of a chemically synthesized compound based on the structure of leonurine, a phytochemical component of Herba leonuri, to protect H9c2 rat ventricular cells from apoptosis induced by hypoxia and serum deprivation, as a model of ischemia. The results revealed a concentration-dependent increase in cell viability associated with leonurine treatment, accompanied by a consistent decline in lactate dehydrogenase leakage into the culture medium. The fraction of annexin V-fluorescein isothiocyanate-positive cells was increased by hypoxia but reduced by leonurine. These changes were associated with increased expression of the antiapoptotic gene, Bcl-2, and reduced expression of the proapoptotic gene, Bax. Leonurine also reduced the cytosolic Ca overload induced by hypoxia. These results suggest that leonurine elicits potent cardioprotective effects in H9c2 cells, and these effects may be mediated by inhibition of intracellular Ca overload and apoptosis during hypoxia.

Effect of hypoxia on the activity and binding of glycolytic and associated enzymes in sea scorpion tissues

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Lushchak V.I.

1998-01-01

Full Text Available The effect of hypoxia on the levels of glycogen, glucose and lactate as well as the activities and binding of glycolytic and associated enzymes to subcellular structures was studied in brain, liver and white muscle of the teleost fish, Scorpaena porcus. Hypoxia exposure decreased glucose levels in liver from 2.53 to 1.70 µmol/g wet weight and in muscle led to its increase from 3.64 to 25.1 µmol/g wet weight. Maximal activities of several enzymes in brain were increased by hypoxia: hexokinase by 23%, phosphoglucoisomerase by 47% and phosphofructokinase (PFK by 56%. However, activities of other enzymes in brain as well as enzymes in liver and white muscle were largely unchanged or decreased during experimental hypoxia. Glycolytic enzymes in all three tissues were partitioned between soluble and particulate-bound forms. In several cases, the percentage of bound enzymes was reduced during hypoxia; bound aldolase in brain was reduced from 36.4 to 30.3% whereas glucose-6-phosphate dehydrogenase fell from 55.7 to 28.7% bound. In muscle PFK was reduced from 57.4 to 41.7% bound. Oppositely, the proportion of bound aldolase and triosephosphate isomerase increased in hypoxic muscle. Phosphoglucomutase did not appear to occur in a bound form in liver and bound phosphoglucomutase disappeared in muscle during hypoxia exposure. Anoxia exposure also led to the disappearance of bound fructose-1,6-bisphosphatase in liver, whereas a bound fraction of this enzyme appeared in white muscle of anoxic animals. The possible function of reversible binding of glycolytic enzymes to subcellular structures as a regulatory mechanism of carbohydrate metabolism is discussed.

FoxO3A promotes metabolic adaptation to hypoxia by antagonizing Myc function

DEFF Research Database (Denmark)

Jensen, Kim Steen; Binderup, Tina; Jensen, Klaus Thorleif

2011-01-01

Exposure of metazoan organisms to hypoxia engages a metabolic switch orchestrated by the hypoxia-inducible factor 1 (HIF-1). HIF-1 mediates induction of glycolysis and active repression of mitochondrial respiration that reduces oxygen consumption and inhibits the production of potentially harmful...... tumour tissue in vivo and that FoxO3A short-hairpin RNA (shRNA)-expressing xenograft tumours are decreased in size and metabolically changed. Our findings define a novel mechanism by which FoxO3A promotes metabolic adaptation and stress resistance in hypoxia....... reactive oxygen species (ROS). Here, we show that FoxO3A is activated in hypoxia downstream of HIF-1 and mediates the hypoxic repression of a set of nuclear-encoded mitochondrial genes. FoxO3A is required for hypoxic suppression of mitochondrial mass, oxygen consumption, and ROS production and promotes...... cell survival in hypoxia. FoxO3A is recruited to the promoters of nuclear-encoded mitochondrial genes where it directly antagonizes c-Myc function via a mechanism that does not require binding to the consensus FoxO recognition element. Furthermore, we show that FoxO3A is activated in human hypoxic...

Teleosts in hypoxia : Aspects of anaerobic metabolism

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Van den Thillart, G.; van Waarde, Aren

1985-01-01

Moderate hypoxia can be tolerated by many fish species, while only some species survive severe hypoxia or anoxia. Hypoxia usually activates anaerobic glycolysis, which may be temporary when the animals are able to improve their oxygen extraction capacity. Switching over to aerobic metabolism allows

Hypoxia Impacts on Food Web Linkages in a Pelagic Ecosystem

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Sato, M.; Horne, J. K.; Parker-Stetter, S. L.; Essington, T.; Keister, J. E.; Moriarty, P.; Li, L.

2016-02-01

Low dissolved oxygen (DO), or hypoxia, causes significant disturbances on aquatic organisms, but the consequences for key food web linkages is not well understood. Here, we tested how the intensity of low DO events governs the degree of spatial overlap between pelagic zooplanktivorous fish and their zooplankton prey, fish feeding rates, and community compositions of zooplankton. We hypothesized that the greater sensitivity of fish to DO compared to zooplankton would lead to diminished spatial overlap at moderate DO and reduced feeding rates of fish, while severe hypoxia would amplify spatial overlap by preventing zooplankton from using deep refuge habitats leading to increased fish feeding rates. We also hypothesized shifts in zooplankton community composition towards less energetically profitable taxa such as small copepods and gelatinous species. We used a combination of multifrequency acoustic and net sampling for detecting distributions and abundance of zooplankton and pelagic fish in Hood Canal, WA, a seasonally hypoxic fjord. We employed a sampling design which paired hypoxic regions of Hood Canal with normoxic regions sampled prior to, during, and after the onset of hypoxia in two years. Contrary to our hypotheses, we found that fish and zooplankton did not change their horizontal and vertical distributions during periods and in locations with low DO levels. Consequently, the vertical overlap between fish and zooplankton did not change with DO. Fish feeding rates and the dominant zooplankton prey did not change with hypoxia events. The apparent resilience of fish to low DO in our system may be explained by decreased metabolic oxygen demand due to cool temperatures, increased availability and accessibility to their prey in low DO waters, or potential increase in predation risk at shallower depth. This study highlights the importance of both temperature and DO, instead of hypoxia threshold alone, in evaluating the impacts of hypoxia on pelagic communities.

Menadione and ethacrynic acid inhibit the hypoxia-inducible factor (HIF) pathway by disrupting HIF-1α interaction with p300.

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Na, Yu-Ran; Han, Ki-Cheol; Park, Hyunsung; Yang, Eun Gyeong

2013-05-17

Hypoxia is a general characteristic of most solid malignancies and intimately related to neoplastic diseases and cancer progression. Homeostatic response to hypoxia is primarily mediated by hypoxia inducible factor (HIF)-1α that elicits transcriptional activity through recruitment of the CREB binding protein (CBP)/p300 coactivator. Targeted blockade of HIF-1α binding to CBP/p300 would thus constitute a novel approach for cancer treatment by suppressing tumor angiogenesis and metastasis. Here, we identified inhibitors against the interaction between HIF-1α and p300 by a fluorescence polarization-based assay employing a fluorescently-labeled peptide containing the C-terminal activation domain of HIF-1α. Two small molecule inhibitors, menadione (MD) and ethacrynic acid (EA), were found to decrease expression of luciferase under the control of hypoxia-responsive elements in hypoxic cells as well as to efficiently block the interaction between the full-length HIF-1α and p300. While these compounds did not alter the expression level of HIF-1α, they down-regulated expression of a HIF-1α target vascular endothelial growth factor (VEGF) gene. Considering hypoxia-induced VEGF expression leading to highly aggressive tumor growth, MD and EA may provide new scaffolds for development of tumor therapeutic reagents as well as tools for a better understanding of HIF-1α-mediated hypoxic regulation. Copyright © 2013 Elsevier Inc. All rights reserved.

Epidermal growth factor receptor inhibition reduces angiogenesis via hypoxia-inducible factor-1α and Notch1 in head neck squamous cell carcinoma.

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Wei-Ming Wang

Full Text Available Angiogenesis, a marker of cancer development, affects response to radiotherapy sensibility. This preclinical study aims to understand the receptor tyrosine kinase-mediated angiogenesis in head neck squamous cell carcinoma (HNSCC. The receptor tyrosine kinase activity in a transgenic mouse model of HNSCC was assessed. The anti-tumorigenetic and anti-angiogenetic effects of cetuximab-induced epidermal growth factor receptor (EGFR inhibition were investigated in xenograft and transgenic mouse models of HNSCC. The signaling transduction of Notch1 and hypoxia-inducible factor-1α (HIF-1α was also analyzed. EGFR was overexpressed and activated in the Tgfbr1/Pten deletion (2cKO mouse model of HNSCC. Cetuximab significantly delayed tumor onset by reducing tumor angiogenesis. This drug exerted similar effects on heterotopic xenograft tumors. In the human HNSCC tissue array, increased EGFR expression correlated with increased HIF-1α and micro vessel density. Cetuximab inhibited tumor-induced angiogenesis in vitro and in vivo by significantly downregulating HIF-1α and Notch1. EGFR is involved in the tumor angiogenesis of HNSCC via the HIF-1α and Notch1 pathways. Therefore, targeting EGFR by suppressing hypoxia- and Notch-induced angiogenesis may benefit HNSCC therapy.

Increased accumulation of hypoxia-inducible factor-1α with reduced transcriptional activity mediates the antitumor effect of triptolide

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Li Zheng

2010-10-01

Full Text Available Abstract Background Hypoxia-inducible factor-1α (HIF-1α, a critical transcription factor to reduced O2 availability, has been demonstrated to be extensively involved in tumor survival, aggressive progression, drug resistance and angiogenesis. Thus it has been considered as a potential anticancer target. Triptolide is the main principle responsible for the biological activities of the Traditional Chinese Medicine tripterygium wilfordii Hook F. Triptolide possesses great chemotherapy potential for cancer with its broad-spectrum anticancer, antiangiogenesis, and drug-resistance circumvention activities. Numerous biological molecules inhibited by triptolide have been viewed as its possible targets. However, the anticancer action mechanisms of triptolide remains to be further investigated. Here we used human ovarian SKOV-3 cancer cells as a model to probe the effect of triptolide on HIF-1α. Results Triptolide was observed to inhibit the proliferation of SKOV-3 cells, and meanwhile, to enhance the accumulation of HIF-1α protein in SKOV-3, A549 and DU145 cells under different conditions. Triptolide did not change the kinetics or nuclear localization of HIF-1α protein or the 26 S proteasome activity in SKOV-3 cells. However, triptolide was found to increase the levels of HIF-1α mRNA. Unexpectedly, the HIF-1α protein induced by triptolide appeared to lose its transcriptional activity, as evidenced by the decreased mRNA levels of its target genes including VEGF, BNIP3 and CAIX. The results were further strengthened by the lowered secretion of VEGF protein, the reduced sprout outgrowth from the rat aorta rings and the inhibitory expression of the hypoxia responsive element-driven luciferase reporter gene. Moreover, the silencing of HIF-1α partially prevented the cytotoxicity and apoptosis triggered by triptolide. Conclusions The potent induction of HIF-1α protein involved in its cytotoxicity, together with the suppression of HIF-1 transcriptional

Acclimatory responses of the Daphnia pulex proteome to environmental changes. I. Chronic exposure to hypoxia affects the oxygen transport system and carbohydrate metabolism

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Madlung Johannes

2009-04-01

Full Text Available Abstract Background Freshwater planktonic crustaceans of the genus Daphnia show a remarkable plasticity to cope with environmental changes in oxygen concentration and temperature. One of the key proteins of adaptive gene control in Daphnia pulex under hypoxia is hemoglobin (Hb, which increases in hemolymph concentration by an order of magnitude and shows an enhanced oxygen affinity due to changes in subunit composition. To explore the full spectrum of adaptive protein expression in response to low-oxygen conditions, two-dimensional gel electrophoresis and mass spectrometry were used to analyze the proteome composition of animals acclimated to normoxia (oxygen partial pressure [Po2]: 20 kPa and hypoxia (Po2: 3 kPa, respectively. Results The comparative proteome analysis showed an up-regulation of more than 50 protein spots under hypoxia. Identification of a major share of these spots revealed acclimatory changes for Hb, glycolytic enzymes (enolase, and enzymes involved in the degradation of storage and structural carbohydrates (e.g. cellubiohydrolase. Proteolytic enzymes remained constitutively expressed on a high level. Conclusion Acclimatory adjustments of the D. pulex proteome to hypoxia included a strong induction of Hb and carbohydrate-degrading enzymes. The scenario of adaptive protein expression under environmental hypoxia can be interpreted as a process to improve oxygen transport and carbohydrate provision for the maintenance of ATP production, even during short episodes of tissue hypoxia requiring support from anaerobic metabolism.

Assessing and addressing the re-eutrophication of Lake Erie: central basin hypoxia

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Scavia, Donald; Allan, J. David; Arend, Kristin K.; Bartell, Steven; Beletsky, Dmitry; Bosch, Nate S.; Brandt, Stephen B.; Briland, Ruth D.; Daloğlu, Irem; DePinto, Joseph V.; Dolan, David M.; Evans, Mary Anne; Farmer, Troy M.; Goto, Daisuke; Han, Haejin; Höök, Tomas O.; Knight, Roger; Ludsin, Stuart A.; Mason, Doran; Michalak, Anna M.; Richards, R. Peter; Roberts, James J.; Rucinski, Daniel K.; Rutherford, Edward; Schwab, David J.; Sesterhenn, Timothy M.; Zhang, Hongyan; Zhou, Yuntao

2014-01-01

Relieving phosphorus loading is a key management tool for controlling Lake Erie eutrophication. During the 1960s and 1970s, increased phosphorus inputs degraded water quality and reduced central basin hypolimnetic oxygen levels which, in turn, eliminated thermal habitat vital to cold-water organisms and contributed to the extirpation of important benthic macroinvertebrate prey species for fishes. In response to load reductions initiated in 1972, Lake Erie responded quickly with reduced water-column phosphorus concentrations, phytoplankton biomass, and bottom-water hypoxia (dissolved oxygen 2) requires cutting total phosphorus loads by 46% from the 2003–2011 average or reducing dissolved reactive phosphorus loads by 78% from the 2005–2011 average. Reductions to these levels are also protective of fish habitat. We provide potential approaches for achieving those new loading targets, and suggest that recent load reduction recommendations focused on western basin cyanobacteria blooms may not be sufficient to reduce central basin hypoxia to 2000 km2.

Circulating levels of cell-derived microparticles are reduced by mild hypobaric hypoxia: data from a randomised controlled trial.

Science.gov (United States)

Ayers, Lisa; Stoewhas, Anne-Christin; Ferry, Berne; Latshang, Tsogyal D; Lo Cascio, Christian M; Sadler, Ross; Stadelmann, Katrin; Tesler, Noemi; Huber, Reto; Achermann, Peter; Bloch, Konrad E; Kohler, Malcolm

2014-05-01

Hypoxia is known to induce the release of microparticles in vitro. However, few publications have addressed the role of hypoxia in vivo on circulating levels of microparticles. This randomised, controlled, crossover trial aimed to determine the effect of mild hypoxia on in vivo levels of circulating microparticles in healthy individuals. Blood was obtained from 51 healthy male volunteers (mean age of 26.9 years) at baseline altitude (490 m) and after 24 and 48 h at moderate altitude (2,590 m). The order of altitude exposure was randomised. Flow cytometry was used to assess platelet-poor plasma for levels of circulating microparticles derived from platelets, endothelial cells, leucocytes, granulocytes, monocytes, red blood cells and procoagulant microparticles. Mean (standard deviation) oxygen saturation was significantly lower on the first and second day after arrival at 2,590 m, 91.0 (2.0) and 92.0 (2.0) %, respectively, compared to 490 m, 96 (1.0) %, p microparticles (annexin V+ -221/μl 95 % CI -370.8/-119.0, lactadherin+ -202/μl 95 % CI -372.2/-93.1), platelet-derived microparticles (-114/μl 95 % CI -189.9/-51.0) and red blood cell-derived microparticles (-81.4 μl 95 % CI -109.9/-57.7) after 48 h at moderate altitude was found. Microparticles derived from endothelial cells, granulocytes, monocytes and leucocytes were not significantly altered by exposure to moderate altitude. In healthy male individuals, mild hypobaric hypoxia, induced by a short-term stay at moderate altitude, is associated with lower levels of procoagulant microparticles, platelet-derived microparticles and red blood cell-derived microparticles, suggesting a reduction in thrombotic potential.

Glycogen synthesis is induced in hypoxia by the hypoxia-inducible factor and promotes cancer cell survival

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Joffrey ePelletier

2012-02-01

Full Text Available The hypoxia-inducible factor 1 (HIF-1, in addition to genetic and epigenetic changes, is largely responsible for alterations in cell metabolism in hypoxic tumor cells. This transcription factor not only favors cell proliferation through the metabolic shift from oxidative phosphorylation to glycolysis and lactic acid production but also stimulates nutrient supply by mediating adaptive survival mechanisms. In this study we showed that glycogen synthesis is enhanced in non-cancer and cancer cells when exposed to hypoxia, resulting in a large increase in glycogen stores. Furthermore, we demonstrated that the mRNA and protein levels of the first enzyme of glycogenesis, phosphoglucomutase1 (PGM1, were increased in hypoxia. We showed that induction of glycogen storage as well as PGM1 expression were dependent on HIF-1 and HIF-2. We established that hypoxia-induced glycogen stores are rapidly mobilized in cells that are starved of glucose. Glycogenolysis allows these hypoxia-preconditioned cells to confront and survive glucose deprivation. In contrast normoxic control cells exhibit a high rate of cell death following glucose removal. These findings point to the important role of hypoxia and HIF in inducing mechanisms of rapid adaptation and survival in response to a decrease in oxygen tension. We propose that a decrease in pO2 acts as an alarm that prepares the cells to face subsequent nutrient depletion and to survive.

Glycogen Synthesis is Induced in Hypoxia by the Hypoxia-Inducible Factor and Promotes Cancer Cell Survival

Energy Technology Data Exchange (ETDEWEB)

Pelletier, Joffrey; Bellot, Grégory [Institute of Developmental Biology and Cancer Research, CNRS-UMR 6543, Centre Antoine Lacassagne, University of Nice-Sophia Antipolis, Nice (France); Gounon, Pierre; Lacas-Gervais, Sandra [Centre Commun de Microscopie Appliquée, University of Nice-Sophia Antipolis, Nice (France); Pouysségur, Jacques; Mazure, Nathalie M., E-mail: mazure@unice.fr [Institute of Developmental Biology and Cancer Research, CNRS-UMR 6543, Centre Antoine Lacassagne, University of Nice-Sophia Antipolis, Nice (France)

2012-02-28

The hypoxia-inducible factor 1 (HIF-1), in addition to genetic and epigenetic changes, is largely responsible for alterations in cell metabolism in hypoxic tumor cells. This transcription factor not only favors cell proliferation through the metabolic shift from oxidative phosphorylation to glycolysis and lactic acid production but also stimulates nutrient supply by mediating adaptive survival mechanisms. In this study we showed that glycogen synthesis is enhanced in non-cancer and cancer cells when exposed to hypoxia, resulting in a large increase in glycogen stores. Furthermore, we demonstrated that the mRNA and protein levels of the first enzyme of glycogenesis, phosphoglucomutase1 (PGM1), were increased in hypoxia. We showed that induction of glycogen storage as well as PGM1 expression were dependent on HIF-1 and HIF-2. We established that hypoxia-induced glycogen stores are rapidly mobilized in cells that are starved of glucose. Glycogenolysis allows these “hypoxia-preconditioned” cells to confront and survive glucose deprivation. In contrast normoxic control cells exhibit a high rate of cell death following glucose removal. These findings point to the important role of hypoxia and HIF in inducing mechanisms of rapid adaptation and survival in response to a decrease in oxygen tension. We propose that a decrease in pO{sub 2} acts as an “alarm” that prepares the cells to face subsequent nutrient depletion and to survive.

Glycogen Synthesis is Induced in Hypoxia by the Hypoxia-Inducible Factor and Promotes Cancer Cell Survival

International Nuclear Information System (INIS)

Pelletier, Joffrey; Bellot, Grégory; Gounon, Pierre; Lacas-Gervais, Sandra; Pouysségur, Jacques; Mazure, Nathalie M.

2012-01-01

The hypoxia-inducible factor 1 (HIF-1), in addition to genetic and epigenetic changes, is largely responsible for alterations in cell metabolism in hypoxic tumor cells. This transcription factor not only favors cell proliferation through the metabolic shift from oxidative phosphorylation to glycolysis and lactic acid production but also stimulates nutrient supply by mediating adaptive survival mechanisms. In this study we showed that glycogen synthesis is enhanced in non-cancer and cancer cells when exposed to hypoxia, resulting in a large increase in glycogen stores. Furthermore, we demonstrated that the mRNA and protein levels of the first enzyme of glycogenesis, phosphoglucomutase1 (PGM1), were increased in hypoxia. We showed that induction of glycogen storage as well as PGM1 expression were dependent on HIF-1 and HIF-2. We established that hypoxia-induced glycogen stores are rapidly mobilized in cells that are starved of glucose. Glycogenolysis allows these “hypoxia-preconditioned” cells to confront and survive glucose deprivation. In contrast normoxic control cells exhibit a high rate of cell death following glucose removal. These findings point to the important role of hypoxia and HIF in inducing mechanisms of rapid adaptation and survival in response to a decrease in oxygen tension. We propose that a decrease in pO 2 acts as an “alarm” that prepares the cells to face subsequent nutrient depletion and to survive.

Angiotensin-(1-7 relieved renal injury induced by chronic intermittent hypoxia in rats by reducing inflammation, oxidative stress and fibrosis

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W. Lu

Full Text Available We aimed to study the renal injury and hypertension induced by chronic intermittent hypoxia (CIH and the protective effects mediated by angiotensin 1-7 [Ang(1-7]. We randomly assigned 32 male Sprague-Dawley rats (body weight 180-200 g to normoxia control, CIH, Ang(1-7-treated normoxia, and Ang(1-7-treated CIH groups. Systolic blood pressure (SBP was monitored at the start and end of each week. Renal sympathetic nerve activity (RSNA was recorded. CTGF and TGF-β were detected by immunohistochemistry and western blotting. Tissue parameters of oxidative stress were also determined. In addition, renal levels of interleukin-6, tumor necrosis factor-α, nitrotyrosine, and hypoxia-inducible factor-1α were determined by immunohistochemistry, immunoblotting, and ELISA. TUNEL assay results and cleaved caspase 3 and 12 were also determined. Ang(1-7 induced a reduction in SBP together with a restoration of RSNA in the rat model of CIH. Ang(1-7 treatment also suppressed the production of reactive oxygen species, reduced renal tissue inflammation, ameliorated mesangial expansion, and decreased renal fibrosis. Thus, Ang(1-7 treatment exerted renoprotective effects on CIH-induced renal injury and was associated with a reduction of oxidative stress, inflammation and fibrosis. Ang(1-7 might therefore represent a promising therapy for obstructive sleep apnea-related hypertension and renal injury.

Hypoxia: From Placental Development to Fetal Programming.

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Fajersztajn, Lais; Veras, Mariana Matera

2017-10-16

Hypoxia may influence normal and different pathological processes. Low oxygenation activates a variety of responses, many of them regulated by hypoxia-inducible factor 1 complex, which is mostly involved in cellular control of O 2 consumption and delivery, inhibition of growth and development, and promotion of anaerobic metabolism. Hypoxia plays a significant physiological role in fetal development; it is involved in different embryonic processes, for example, placentation, angiogenesis, and hematopoiesis. More recently, fetal hypoxia has been associated directly or indirectly with fetal programming of heart, brain, and kidney function and metabolism in adulthood. In this review, the role of hypoxia in fetal development, placentation, and fetal programming is summarized. Hypoxia is a basic mechanism involved in different pregnancy disorders and fetal health developmental complications. Although there are scientific data showing that hypoxia mediates changes in the growth trajectory of the fetus, modulates gene expression by epigenetic mechanisms, and determines the health status later in adulthood, more mechanistic studies are needed. Furthermore, if we consider that intrauterine hypoxia is not a rare event, and can be a consequence of unavoidable exposures to air pollution, nutritional deficiencies, obesity, and other very common conditions (drug addiction and stress), the health of future generations may be damaged and the incidence of some diseases will markedly increase as a consequence of disturbed fetal programming. Birth Defects Research 109:1377-1385, 2017.© 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Constitutively active RAS signaling reduces 1,25 dihydroxyvitamin D-mediated gene transcription in intestinal epithelial cells by reducing vitamin D receptor expression.

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DeSmet, Marsha L; Fleet, James C

2017-10-01

High vitamin D status is associated with reduced colon cancer risk but these studies ignore the diversity in the molecular etiology of colon cancer. RAS activating mutations are common in colon cancer and they activate pro-proliferative signaling pathways. We examined the impact of RAS activating mutations on 1,25 dihydroxyvitamin D (1,25(OH) 2 D)-mediated gene expression in cultured colon and intestinal cell lines. Transient transfection of Caco-2 cells with a constitutively active mutant K-RAS (G12 V) significantly reduced 1,25(OH) 2 D-induced activity of both a human 25-hydroxyvitamin D, 24 hydroxyase (CYP24A1) promoter-luciferase and an artificial 3X vitamin D response element (VDRE) promoter-luciferase reporter gene. Young Adult Mouse Colon (YAMC) and Rat Intestinal Epithelial (RIE) cell lines with stable expression of mutant H-RAS had suppressed 1,25(OH) 2 D-mediated induction of CYP24A1 mRNA. The RAS effects were associated with lower Vitamin D receptor (VDR) mRNA and protein levels in YAMC and RIE cells and they could be partially reversed by VDR overexpression. RAS-mediated suppression of VDR levels was not due to either reduced VDR mRNA stability or increased VDR gene methylation. However, chromatin accessibility to the VDR gene at the proximal promoter (-300bp), an enhancer region at -6kb, and an enhancer region located in exon 3 was significantly reduced in RAS transformed YAMC cells (YAMC-RAS). These data show that constitutively active RAS signaling suppresses 1,25(OH) 2 D-mediated gene transcription in colon epithelial cells by reducing VDR gene transcription but the mechanism for this suppression is not yet known. These data suggest that cancers with RAS-activating mutations may be less responsive to vitamin D mediated treatment or chemoprevention. Copyright © 2017 Elsevier Ltd. All rights reserved.

Losartan reduces the immediate and sustained increases in muscle sympathetic nerve activity after hyperacute intermittent hypoxia.

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Jouett, Noah P; Moralez, Gilbert; Raven, Peter B; Smith, Michael L

2017-04-01

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxemia, which produces elevations in sympathetic nerve activity (SNA) and associated hypertension in experimental models that persist beyond the initial exposure. We tested the hypotheses that angiotensin receptor blockade in humans using losartan attenuates the immediate and immediately persistent increases in 1 ) SNA discharge and 2 ) mean arterial pressure (MAP) after hyperacute intermittent hypoxia training (IHT) using a randomized, placebo-controlled, repeated-measures experimental design. We measured ECG and photoplethysmographic arterial pressure in nine healthy human subjects, while muscle SNA (MSNA) was recorded in seven subjects using microneurography. Subjects were exposed to a series of hypoxic apneas in which they inhaled two to three breaths of nitrogen, followed by a 20-s apnea and 40 s of room air breathing every minute for 20 min. Hyperacute IHT produced substantial and persistent elevations in MSNA burst frequency (baseline: 15.3 ± 1.8, IHT: 24 ± 1.5, post-IHT 20.0 ± 1.3 bursts/min, all P 0.70). This investigation confirms the role of angiotensin II type 1a receptors in the immediate and persistent sympathoexcitatory and pressor responses to IHT. NEW & NOTEWORTHY This study demonstrates for the first time in humans that losartan, an angiotensin receptor blocker (ARB), abrogates the acute and immediately persistent increases in muscle sympathetic nerve activity and arterial pressure in response to acute intermittent hypoxia. This investigation, along with others, provides important beginning translational evidence for using ARBs in treatment of the intermittent hypoxia observed in obstructive sleep apnea patients. Copyright © 2017 the American Physiological Society.

Hypoxia and hypoxia-inducible factors as regulators of T cell development, differentiation, and function

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McNamee, Eóin N.; Johnson, Darlynn Korns; Homann, Dirk

2014-01-01

Oxygen is a molecule that is central to cellular respiration and viability, yet there are multiple physiologic and pathological contexts in which cells experience conditions of insufficient oxygen availability, a state known as hypoxia. Given the metabolic challenges of a low oxygen environment, hypoxia elicits a range of adaptive responses at the cellular, tissue, and systemic level to promote continued survival and function. Within this context, T lymphocytes are a highly migratory cell type of the adaptive immune system that frequently encounters a wide range of oxygen tensions in both health and disease. It is now clear that oxygen availability regulates T cell differentiation and function, a response orchestrated in large part by the hypoxia-inducible factor transcription factors. Here, we discuss the physiologic scope of hypoxia and hypoxic signaling, the contribution of these pathways in regulating T cell biology, and current gaps in our understanding. Finally, we discuss how emerging therapies that modulate the hypoxic response may offer new modalities to alter T cell function and the outcome of acute and chronic pathologies. PMID:22961658

Hepcidin: A Critical Regulator of Iron Metabolism during Hypoxia

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Korry J. Hintze

2011-01-01

Full Text Available Iron status affects cognitive and physical performance in humans. Recent evidence indicates that iron balance is a tightly regulated process affected by a series of factors other than diet, to include hypoxia. Hypoxia has profound effects on iron absorption and results in increased iron acquisition and erythropoiesis when humans move from sea level to altitude. The effects of hypoxia on iron balance have been attributed to hepcidin, a central regulator of iron homeostasis. This paper will focus on the molecular mechanisms by which hypoxia affects hepcidin expression, to include a review of the hypoxia inducible factor (HIF/hypoxia response element (HRE system, as well as recent evidence indicating that localized adipose hypoxia due to obesity may affect hepcidin signaling and organismal iron metabolism.

Gene Expression Programs in Response to Hypoxia: Cell Type Specificity and Prognostic Significance in Human Cancers.

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2006-01-01

Full Text Available BACKGROUND: Inadequate oxygen (hypoxia triggers a multifaceted cellular response that has important roles in normal physiology and in many human diseases. A transcription factor, hypoxia-inducible factor (HIF, plays a central role in the hypoxia response; its activity is regulated by the oxygen-dependent degradation of the HIF-1alpha protein. Despite the ubiquity and importance of hypoxia responses, little is known about the variation in the global transcriptional response to hypoxia among different cell types or how this variation might relate to tissue- and cell-specific diseases. METHODS AND FINDINGS: We analyzed the temporal changes in global transcript levels in response to hypoxia in primary renal proximal tubule epithelial cells, breast epithelial cells, smooth muscle cells, and endothelial cells with DNA microarrays. The extent of the transcriptional response to hypoxia was greatest in the renal tubule cells. This heightened response was associated with a uniquely high level of HIF-1alpha RNA in renal cells, and it could be diminished by reducing HIF-1alpha expression via RNA interference. A gene-expression signature of the hypoxia response, derived from our studies of cultured mammary and renal tubular epithelial cells, showed coordinated variation in several human cancers, and was a strong predictor of clinical outcomes in breast and ovarian cancers. In an analysis of a large, published gene-expression dataset from breast cancers, we found that the prognostic information in the hypoxia signature was virtually independent of that provided by the previously reported wound signature and more predictive of outcomes than any of the clinical parameters in current use. CONCLUSIONS: The transcriptional response to hypoxia varies among human cells. Some of this variation is traceable to variation in expression of the HIF1A gene. A gene-expression signature of the cellular response to hypoxia is associated with a significantly poorer prognosis

The role of hypoxia, p53, and apoptosis in human cervical carcinoma pathogenesis

International Nuclear Information System (INIS)

Kim, Charlotte Y.; Tsai, Mitchell H.; Osmanian, Cynthia; Calkins, Dennise P.; Graeber, Thomas G.; Greenspan, David L.; Kennedy, Andrew S.; Rinker, Lillian H.; Varia, Mahesh A.; DiPaolo, Joseph A.; Peehl, Donna M.; Raleigh, James A.; Giaccia, Amato J.

1997-01-01

, ionizing radiation did not stimulate p53 accumulation or apoptosis in these cells. Cervical epithelial cells containing the intact HPV 16 genome also exhibited hypoxia induced apoptosis. Hypoxia stimulated p53 induction but not apoptosis in cell lines derived from human cervical squamous cell carcinomas, indicating that these cell lines have acquired further genetic alterations independent of p53 which reduced their apoptotic sensitivity to hypoxia. Furthermore, E6 and E7 infected cervical epithelial cells subjected to multiple rounds of hypoxia followed by aerobic recovery achieved resistance to hypoxia induced apoptosis, indicating that hypoxia could directly select for cells with diminished apoptotic sensitivity. In situ, hypoxia and apoptosis were found to co-localize in tumors of patients with advanced clinical stage. Conclusion: Expression of viral oncoproteins in human cervical epithelial cells can increase their sensitivity to hypoxia-induced apoptosis. Hypoxia can select for variants that have lost their apoptotic potential and hypoxia correlates spatially with apoptosis in human cervical carcinoma biopsies. Therefore, these results implicate a role for hypoxia-mediated selection in human tumor progression and can in part explain the aggressiveness of cervical carcinomas with low p0 2 values

Modification of bacterial cell survival by postirradiation hypoxia

Energy Technology Data Exchange (ETDEWEB)

Vexler, F B; Eidus, L Kh

1986-01-27

It is shown that postirradiation hypoxia affects the survival of E.coli. Hypoxic conditions immediately after a single-dose irradiation diminish cell survival in nutrient medium. Increasing time intervals between irradiation and hypoxia decrease the efficiency of the latter, while 1 h after irradiation hypoxia does not modify the survival of irradiated cells. These findings reveal that the mechanisms of action of postirradiation hypoxia on eu- and prokaryotic cells are similar.

[18F]-FMISO PET study of hypoxia in gliomas before surgery: correlation with molecular markers of hypoxia and angiogenesis

Energy Technology Data Exchange (ETDEWEB)

Bekaert, Lien [CHU de Caen, Department of Neurology, Caen (France); Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, Caen (France); CHU de Caen, Department of Neurosurgery, Caen (France); CHU de Caen, Service de Neurochirurgie, Caen (France); Valable, Samuel; Collet, Solene; Bordji, Karim; Petit, Edwige; Bernaudin, Myriam [Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, Caen (France); Lechapt-Zalcman, Emmanuele [Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, Caen (France); CHU de Caen, Department of Pathology, Caen (France); Ponte, Keven [CHU de Caen, Department of Neurosurgery, Caen (France); Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, Caen (France); Constans, Jean-Marc [Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, Caen (France); CHU de Caen, Department of Neuroradiology, Caen (France); Levallet, Guenaelle [CHU de Caen, Department of Pathology, Caen (France); Branger, Pierre [CHU de Caen, Department of Neurology, Caen (France); Emery, Evelyne [CHU de Caen, Department of Neurosurgery, Caen (France); Manrique, Alain [CHU de Caen, Department of Nuclear Medicine, Caen (France); Barre, Louisa [Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/LDM-TEP group, Caen (France); Guillamo, Jean-Sebastien [CHU de Caen, Department of Neurology, Caen (France); Normandie Univ, UNICAEN, CEA, CNRS, ISTCT/CERVOxy Group, Caen (France); CHU de Nimes, Department of Neurology, Nimes (France)

2017-08-15

Hypoxia in gliomas is associated with tumor resistance to radio- and chemotherapy. However, positron emission tomography (PET) imaging of hypoxia remains challenging, and the validation of biological markers is, therefore, of great importance. We investigated the relationship between uptake of the PET hypoxia tracer [18F]-FMISO and other markers of hypoxia and angiogenesis and with patient survival. In this prospective single center clinical study, 33 glioma patients (grade IV: n = 24, III: n = 3, and II: n = 6) underwent [18F]-FMISO PET and MRI including relative cerebral blood volume (rCBV) maps before surgery. Maximum standardized uptake values (SUVmax) and hypoxic volume were calculated, defining two groups of patients based on the presence or absence of [18F]-FMISO uptake. After surgery, molecular quantification of CAIX, VEGF, Ang2 (rt-qPCR), and HIF-1α (immunohistochemistry) were performed on tumor specimens. [18F]-FMISO PET uptake was closely linked to tumor grade, with high uptake in glioblastomas (GB, grade IV). Expression of biomarkers of hypoxia (CAIX, HIF-1α), and angiogenesis markers (VEGF, Ang2, rCBV) were significantly higher in the [18F]-FMISO uptake group. We found correlations between the degree of hypoxia (hypoxic volume and SUVmax) and expression of HIF-1α, CAIX, VEGF, Ang2, and rCBV (p < 0.01). Patients without [18F]-FMISO uptake had a longer survival time than uptake positive patients (log-rank, p < 0.005). Tumor hypoxia as evaluated by [18F]-FMISO PET is associated with the expression of hypoxia markers on a molecular level and is related to angiogenesis. [18F]-FMISO uptake is a mark of an aggressive tumor, almost always a glioblastoma. Our results underline that [18F]-FMISO PET could be useful to guide glioma treatment, and in particular radiotherapy, since hypoxia is a well-known factor of resistance. (orig.)

Hypoxia causes IL-8 secretion, Charcot Leyden crystal formation, and suppression of corticosteroid-induced apoptosis in human eosinophils.

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Porter, L M; Cowburn, A S; Farahi, N; Deighton, J; Farrow, S N; Fiddler, C A; Juss, J K; Condliffe, A M; Chilvers, E R

2017-06-01

Inflamed environments are typically hypercellular, rich in pro-inflammatory cytokines, and profoundly hypoxic. While the effects of hypoxia on neutrophil longevity and function have been widely studied, little is known about the consequences of this stimulus on eosinophils. We sought to investigate the effects of hypoxia on several key aspects of eosinophil biology, namely secretion, survival, and their sensitivity to glucocorticosteroids (GCS), agents that normally induce eosinophil apoptosis. Eosinophils derived from patients with asthma/atopy or healthy controls were incubated under normoxia and hypoxia, with or without glucocorticoids. Activation was measured by flow cytometry, ELISA of cultured supernatants, and F-actin staining; apoptosis and efferocytosis by morphology and flow cytometry; and GCS efficacy by apoptosis assays and qPCR. Hypoxic incubation (3 kPa) caused (i) stabilization of HIF-2α and up-regulation of hypoxia-regulated genes including BNIP3 (BCL2/adenovirus E1B 19-kDa protein-interacting protein 3) and GLUT1 (glucose transporter 1); (ii) secretion of pre-formed IL-8, and Charcot Leyden crystal (CLC) formation, which was most evident in eosinophils derived from atopic and asthmatic donors; (iii) enhanced F-actin formation; (iv) marked prolongation of eosinophil lifespan (via a NF-κB and Class I PI3-kinase-dependent mechanism); and (v) complete abrogation of the normal pro-apoptotic effect of dexamethasone and fluticasone furoate. This latter effect was evident despite preservation of GCS-mediated gene transactivation under hypoxia. These data indicate that hypoxia promotes an eosinophil pro-inflammatory phenotype by enhancing eosinophil secretory function, delaying constitutive apoptosis, and importantly, antagonizing the normal pro-apoptotic effect of GCS. As eosinophils typically accumulate at sites that are relatively hypoxic, particularly during periods of inflammation, these findings may have important implications to understanding the

Effect of dead space on breathing stability at exercise in hypoxia.

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Hermand, Eric; Lhuissier, François J; Richalet, Jean-Paul

2017-12-01

Recent studies have shown that normal subjects exhibit periodic breathing when submitted to concomitant environmental (hypoxia) and physiological (exercise) stresses. A mathematical model including mass balance equations confirmed the short period of ventilatory oscillations and pointed out an important role of dead space in the genesis of these phenomena. Ten healthy subjects performed mild exercise on a cycloergometer in different conditions: rest/exercise, normoxia/hypoxia and no added dead space/added dead space (aDS). Ventilatory oscillations (V˙E peak power) were augmented by exercise, hypoxia and aDS (Pspace. This underlines opposite effects observed in heart failure patients and normal subjects, in which added dead space drastically reduced periodic breathing and sleep apneas. It also points out that alveolar ventilation remains very close to metabolic needs and is not affected by an added dead space. Clinical Trial reg. n°: NCT02201875. Copyright © 2017 Elsevier B.V. All rights reserved.

Hypoxia, hypoxia-inducible transcription factor, and macrophages in human atherosclerotic plaques are correlated with intraplaque angiogenesis

NARCIS (Netherlands)

Sluimer, Judith C.; Gasc, Jean-Marie; van Wanroij, Job L.; Kisters, Natasja; Groeneweg, Mathijs; Sollewijn Gelpke, Maarten D.; Cleutjens, Jack P.; van den Akker, Luc H.; Corvol, Pierre; Wouters, Bradly G.; Daemen, Mat J.; Bijnens, Ann-Pascale J.

2008-01-01

We sought to examine the presence of hypoxia in human carotid atherosclerosis and its association with hypoxia-inducible transcription factor (HIF) and intraplaque angiogenesis. Atherosclerotic plaques develop intraplaque angiogenesis, which is a typical feature of hypoxic tissue and expression of

Targeting hypoxic microenvironment of pancreatic xenografts with the hypoxia-activated prodrug TH-302.

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Lohse, Ines; Rasowski, Joanna; Cao, Pinjiang; Pintilie, Melania; Do, Trevor; Tsao, Ming-Sound; Hill, Richard P; Hedley, David W

2016-06-07

Previous reports have suggested that the hypoxic microenvironment provides a niche that supports tumor stem cells, and that this might explain clinical observations linking hypoxia to metastasis. To test this, we examined the effects of a hypoxia-activated prodrug, TH-302, on the tumor-initiating cell (TIC) frequency of patient-derived pancreatic xenografts (PDX).The frequencies of TIC, measured by limiting dilution assay, varied widely in 11 PDX models, and were correlated with rapid growth but not with the levels of hypoxia. Treatment with either TH-302 or ionizing radiation (IR), to target hypoxic and well-oxygenated regions, respectively, reduced TIC frequency, and the combination of TH-302 and IR was much more effective in all models tested. The combination was also more effective than TH-302 or IR alone controlling tumor growth, particularly treating the more rapidly-growing/hypoxic models. These findings support the clinical utility of hypoxia targeting in combination with radiotherapy to treat pancreatic cancers, but do not provide strong evidence for a hypoxic stem cell niche.

Cardiovascular, respiratory and metabolic responses to temperature and hypoxia of the winter frog Rana catesbeiana

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Rocha P.L.

1997-01-01

Full Text Available The objective of the present study was to determine the effects of hypoxia and temperature on the cardiovascular and respiratory systems and plasma glucose levels of the winter bullfrog Rana catesbeiana. Body temperature was maintained at 10, 15, 25 and 35oC for measurements of breathing frequency, heart rate, arterial blood pressure, metabolic rate, plasma glucose levels, blood gases and acid-base status. Reducing body temperature from 35 to 10oC decreased (P<0.001 heart rate (bpm from 64.0 ± 3.1 (N = 5 to 12.5 ± 2.5 (N = 6 and blood pressure (mmHg (P<0.05 from 41.9 ± 2.1 (N = 5 to 33.1 ± 2.1 (N = 6, whereas no significant changes were observed under hypoxia. Hypoxia-induced changes in breathing frequency and acid-base status were proportional to body temperature, being pronounced at 25oC, less so at 15oC, and absent at 10oC. Hypoxia at 35oC was lethal. Under normoxia, plasma glucose concentration (mg/dl decreased (P<0.01 from 53.0 ± 3.4 (N = 6 to 35.9 ± 1.7 (N = 6 at body temperatures of 35 and 10oC, respectively. Hypoxia had no significant effect on plasma glucose concentration at 10 and 15oC, but at 25oC there was a significant increase under conditions of 3% inspired O2. The arterial PO2 and pH values were similar to those reported in previous studies on non-estivating Rana catesbeiana, but PaCO2 (37.5 ± 1.9 mmHg, N = 5 was 3-fold higher, indicating increased plasma bicarbonate levels. The estivating bullfrog may be exposed not only to low temperatures but also to hypoxia. These animals show temperature-dependent responses that may be beneficial since during low body temperatures the sensitivity of most physiological systems to hypoxia is reduced

NFAT5 is activated by hypoxia: role in ischemia and reperfusion in the rat kidney.

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Sandra Villanueva

Full Text Available The current hypothesis postulates that NFAT5 activation in the kidney's inner medulla is due to hypertonicity, resulting in cell protection. Additionally, the renal medulla is hypoxic (10-18 mmHg; however there is no information about the effect of hypoxia on NFAT5. Using in vivo and in vitro models, we evaluated the effect of reducing the partial pressure of oxygen (PO(2 on NFAT5 activity. We found that 1 Anoxia increased NFAT5 expression and nuclear translocation in primary cultures of IMCD cells from rat kidney. 2 Anoxia increased transcriptional activity and nuclear translocation of NFAT5 in HEK293 cells. 3 The dose-response curve demonstrated that HIF-1α peaked at 2.5% and NFAT5 at 1% of O(2. 4 At 2.5% of O(2, the time-course curve of hypoxia demonstrated earlier induction of HIF-1α gene expression than NFAT5. 5 siRNA knockdown of NFAT5 increased the hypoxia-induced cell death. 6 siRNA knockdown of HIF-1α did not affect the NFAT5 induction by hypoxia. Additionally, HIF-1α was still induced by hypoxia even when NFAT5 was knocked down. 7 NFAT5 and HIF-1α expression were increased in kidney (cortex and medulla from rats subjected to an experimental model of ischemia and reperfusion (I/R. 7 Experimental I/R increased the NFAT5-target gene aldose reductase (AR. 8 NFAT5 activators (ATM and PI3K were induced in vitro (HEK293 cells and in vivo (I/R kidneys with the same timing of NFAT5. 8 Wortmannin, which inhibits ATM and PI3K, reduces hypoxia-induced NFAT5 transcriptional activation in HEK293 cells. These results demonstrate for the first time that NFAT5 is induced by hypoxia and could be a protective factor against ischemic damage.

The usability of a 15-gene hypoxia classifier as a universal hypoxia profile in various cancer cell types

DEFF Research Database (Denmark)

Sørensen, Brita Singers; Knudsen, Anders Bisgård; Wittrup, Catja Foged

2015-01-01

genes, with BNIP3 not being upregulated at hypoxic conditions in 3 out of 6 colon cancer cell lines, and ALDOA in OE21 and FAM162A and SLC2A1 in SW116 only showing limited hypoxia induction. Furthermore, in the esophagus cell lines, the normoxic and hypoxic expression levels of LOX and BNIP3 were below...... the tissue type dependency of hypoxia induced genes included in a 15-gene hypoxic profile in carcinoma cell lines from prostate, colon, and esophagus cancer, and demonstrated that in vitro, with minor fluctuations, the genes in the hypoxic profile are hypoxia inducible, and the hypoxia profile may......BACKGROUND AND PURPOSE: A 15-gene hypoxia profile has previously demonstrated to have both prognostic and predictive impact for hypoxic modification in squamous cell carcinoma of the head and neck. This gene expression profile may also have a prognostic value in other histological cancer types...

Cycling hypoxia: A key feature of the tumor microenvironment.

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Michiels, Carine; Tellier, Céline; Feron, Olivier

2016-08-01

A compelling body of evidence indicates that most human solid tumors contain hypoxic areas. Hypoxia is the consequence not only of the chaotic proliferation of cancer cells that places them at distance from the nearest capillary but also of the abnormal structure of the new vasculature network resulting in transient blood flow. Hence two types of hypoxia are observed in tumors: chronic and cycling (intermittent) hypoxia. Most of the current work aims at understanding the role of chronic hypoxia in tumor growth, response to treatment and metastasis. Only recently, cycling hypoxia, with spatial and temporal fluctuations in oxygen levels, has emerged as another key feature of the tumor environment that triggers different responses in comparison to chronic hypoxia. Either type of hypoxia is associated with distinct effects not only in cancer cells but also in stromal cells. In particular, cycling hypoxia has been demonstrated to favor, to a higher extent than chronic hypoxia, angiogenesis, resistance to anti-cancer treatments, intratumoral inflammation and tumor metastasis. These review details these effects as well as the signaling pathway it triggers to switch on specific transcriptomic programs. Understanding the signaling pathways through which cycling hypoxia induces these processes that support the development of an aggressive cancer could convey to the emergence of promising new cancer treatments. Copyright © 2016 Elsevier B.V. All rights reserved.

Hypoxia and Its Acid-Base Consequences: From Mountains to Malignancy.

Science.gov (United States)

Swenson, Erik R

Hypoxia, depending upon its magnitude and circumstances, evokes a spectrum of mild to severe acid-base changes ranging from alkalosis to acidosis, which can alter many responses to hypoxia at both non-genomic and genomic levels, in part via altered hypoxia-inducible factor (HIF) metabolism. Healthy people at high altitude and persons hyperventilating to non-hypoxic stimuli can become alkalotic and alkalemic with arterial pH acutely rising as high as 7.7. Hypoxia-mediated respiratory alkalosis reduces sympathetic tone, blunts hypoxic pulmonary vasoconstriction and hypoxic cerebral vasodilation, and increases hemoglobin oxygen affinity. These effects and others can be salutary or counterproductive to tissue oxygen delivery and utilization, based upon magnitude of each effect and summation. With severe hypoxia either in the setting of profound arterial hemoglobin desaturation and reduced O2 content or poor perfusion (ischemia) at the global or local level, metabolic and hypercapnic acidosis develop along with considerable lactate formation and pH falling to below 6.8. Although conventionally considered to be injurious and deleterious to cell function and survival, both acidoses may be cytoprotective by various anti-inflammatory, antioxidant, and anti-apoptotic mechanisms which limit total hypoxic or ischemic-reperfusion injury. Attempts to correct acidosis by giving bicarbonate or other alkaline agents under these circumstances ahead of or concurrent with reoxygenation efforts may be ill advised. Better understanding of this so-called "pH paradox" or permissive acidosis may offer therapeutic possibilities. Rapidly growing cancers often outstrip their vascular supply compromising both oxygen and nutrient delivery and metabolic waste disposal, thus limiting their growth and metastatic potential. However, their excessive glycolysis and lactate formation may not necessarily represent oxygen insufficiency, but rather the Warburg effect-an attempt to provide a large amount

Association between hypoxia and perinatal arterial ischemic stroke: a meta-analysis.

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Lili Luo

Full Text Available Perinatal arterial ischemic stroke (AIS occurs in an estimated 17 to 93 per 100000 live births, yet the etiology is poorly understood. Although investigators have implicated hypoxia as a potential cause of AIS, the role of hypoxia in AIS remains controversial. The aim of this study was to estimate the association between perinatal hypoxia factors and perinatal arterial ischemic stroke through a meta-analysis of published observational studies.A systematic search of electronically available studies published through July 2013 was conducted. Publication bias and heterogeneity across studies were evaluated and summary odds ratios (ORs and 95% confidence intervals (CIs were calculated with fixed-effects or random-effects models.A total of 8 studies describing the association between perinatal hypoxia factors and neonatal arterial ischemic stroke (AIS met inclusion criteria, and 550 newborns with AIS were enrolled. The associations were found for AIS: preeclampsia (OR 2.14; 95% CI, 1.25 to 3.66, ventouse delivery (OR 2.23; 95% CI, 1.26 to 3.97, fetal heart rate abnormalities (OR 6.30; 95% CI, 3.84 to 10.34, reduced fetal movement (OR 5.35; 95% CI, 2.17 to 13.23, meconium-stained liquor (OR 3.05; 95% CI, 2.02 to 4.60, low Apgar score (OR 5.77; 95% CI, 1.66 to 20.04 and resuscitation at birth (OR 4.59; 95% CI, 3.23 to 6.52. Our data did not show any significant change of the mean risk estimate for oxytocin induction (OR 1.33; 95% CI, 0.84 to 2.11 and low arterial umbilical cord ph (OR 4.63; 95% CI 2.14 to 9.98.There is a significant association between perinatal hypoxia factors and AIS. The result indicates that perinatal hypoxia maybe one of causes of AIS. Large scale prospective clinical studies are still warranted.

2-Iminobiotin Superimposed on Hypothermia Protects Human Neuronal Cells from Hypoxia-Induced Cell Damage: An in Vitro Study

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Karina Zitta

2018-01-01

Full Text Available Perinatal asphyxia represents one of the major causes of neonatal morbidity and mortality. Hypothermia is currently the only established treatment for hypoxic-ischemic encephalopathy (HIE, but additional pharmacological strategies are being explored to further reduce the damage after perinatal asphyxia. The aim of this study was to evaluate whether 2-iminobiotin (2-IB superimposed on hypothermia has the potential to attenuate hypoxia-induced injury of neuronal cells. In vitro hypoxia was induced for 7 h in neuronal IMR-32 cell cultures. Afterwards, all cultures were subjected to 25 h of hypothermia (33.5°C, and incubated with vehicle or 2-IB (10, 30, 50, 100, and 300 ng/ml. Cell morphology was evaluated by brightfield microscopy. Cell damage was analyzed by LDH assays. Production of reactive oxygen species (ROS was measured using fluorometric assays. Western blotting for PARP, Caspase-3, and the phosphorylated forms of akt and erk1/2 was conducted. To evaluate early apoptotic events and signaling, cell protein was isolated 4 h post-hypoxia and human apoptosis proteome profiler arrays were performed. Twenty-five hour after the hypoxic insult, clear morphological signs of cell damage were visible and significant LDH release as well as ROS production were observed even under hypothermic conditions. Post-hypoxic application of 2-IB (10 and 30 ng/ml reduced the hypoxia-induced LDH release but not ROS production. Phosphorylation of erk1/2 was significantly increased after hypoxia, while phosphorylation of akt, protein expression of Caspase-3 and cleavage of PARP were only slightly increased. Addition of 2-IB did not affect any of the investigated proteins. Apoptosis proteome profiler arrays performed with cellular protein obtained 4 h after hypoxia revealed that post-hypoxic application of 2-IB resulted in a ≥ 25% down regulation of 10/35 apoptosis-related proteins: Bad, Bax, Bcl-2, cleaved Caspase-3, TRAILR1, TRAILR2, PON2, p21, p27, and phospho

Hypoxia-Activated Prodrug TH-302 Targets Hypoxic Bone Marrow Niches in Preclinical Leukemia Models.

Science.gov (United States)

Benito, Juliana; Ramirez, Marc S; Millward, Niki Zacharias; Velez, Juliana; Harutyunyan, Karine G; Lu, Hongbo; Shi, Yue-Xi; Matre, Polina; Jacamo, Rodrigo; Ma, Helen; Konoplev, Sergej; McQueen, Teresa; Volgin, Andrei; Protopopova, Marina; Mu, Hong; Lee, Jaehyuk; Bhattacharya, Pratip K; Marszalek, Joseph R; Davis, R Eric; Bankson, James A; Cortes, Jorge E; Hart, Charles P; Andreeff, Michael; Konopleva, Marina

2016-04-01

To characterize the prevalence of hypoxia in the leukemic bone marrow, its association with metabolic and transcriptional changes in the leukemic blasts and the utility of hypoxia-activated prodrug TH-302 in leukemia models. Hyperpolarized magnetic resonance spectroscopy was utilized to interrogate the pyruvate metabolism of the bone marrow in the murine acute myeloid leukemia (AML) model. Nanostring technology was used to evaluate a gene set defining a hypoxia signature in leukemic blasts and normal donors. The efficacy of the hypoxia-activated prodrug TH-302 was examined in the in vitro and in vivo leukemia models. Metabolic imaging has demonstrated increased glycolysis in the femur of leukemic mice compared with healthy control mice, suggesting metabolic reprogramming of hypoxic bone marrow niches. Primary leukemic blasts in samples from AML patients overexpressed genes defining a "hypoxia index" compared with samples from normal donors. TH-302 depleted hypoxic cells, prolonged survival of xenograft leukemia models, and reduced the leukemia stem cell pool in vivo In the aggressive FLT3/ITD MOLM-13 model, combination of TH-302 with tyrosine kinase inhibitor sorafenib had greater antileukemia effects than either drug alone. Importantly, residual leukemic bone marrow cells in a syngeneic AML model remain hypoxic after chemotherapy. In turn, administration of TH-302 following chemotherapy treatment to mice with residual disease prolonged survival, suggesting that this approach may be suitable for eliminating chemotherapy-resistant leukemia cells. These findings implicate a pathogenic role of hypoxia in leukemia maintenance and chemoresistance and demonstrate the feasibility of targeting hypoxic cells by hypoxia cytotoxins. ©2015 American Association for Cancer Research.

The multi-level impact of chronic intermittent hypoxia on central auditory processing.

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Wong, Eddie; Yang, Bin; Du, Lida; Ho, Wai Hong; Lau, Condon; Ke, Ya; Chan, Ying Shing; Yung, Wing Ho; Wu, Ed X

2017-08-01

During hypoxia, the tissues do not obtain adequate oxygen. Chronic hypoxia can lead to many health problems. A relatively common cause of chronic hypoxia is sleep apnea. Sleep apnea is a sleep breathing disorder that affects 3-7% of the population. During sleep, the patient's breathing starts and stops. This can lead to hypertension, attention deficits, and hearing disorders. In this study, we apply an established chronic intermittent hypoxemia (CIH) model of sleep apnea to study its impact on auditory processing. Adult rats were reared for seven days during sleeping hours in a gas chamber with oxygen level cycled between 10% and 21% (normal atmosphere) every 90s. During awake hours, the subjects were housed in standard conditions with normal atmosphere. CIH treatment significantly reduces arterial oxygen partial pressure and oxygen saturation during sleeping hours (relative to controls). After treatment, subjects underwent functional magnetic resonance imaging (fMRI) with broadband sound stimulation. Responses are observed in major auditory centers in all subjects, including the auditory cortex (AC) and auditory midbrain. fMRI signals from the AC are statistically significantly increased after CIH by 0.13% in the contralateral hemisphere and 0.10% in the ipsilateral hemisphere. In contrast, signals from the lateral lemniscus of the midbrain are significantly reduced by 0.39%. Signals from the neighboring inferior colliculus of the midbrain are relatively unaffected. Chronic hypoxia affects multiple levels of the auditory system and these changes are likely related to hearing disorders associated with sleep apnea. Copyright © 2017 Elsevier Inc. All rights reserved.

Protective effect of Edaravone against hypoxia-induced cytotoxicity in osteoblasts MC3T3-E1 cells.

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Cao, Bo; Chai, Chunxiang; Zhao, Sishun

2015-12-01

Edaravone is a newly developed clinical medicine for the treatment of acute cerebral infarction. Reduced blood supply to bones (hypoxia) has been involved in the pathological development of osteoporosis. In this study, we investigated the effect of Edaravone and its latent mechanism on hypoxia-induced cell toxicity in MC3T3-E1 cells. Cell viability was determined by the 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Intracellular reactive oxygen species (ROS) and nitric oxide (NO) were determined by the fluorescence dyes 2',7'-dichlorofluorescein diacetate (DCFH-DA) and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA), respectively. mRNA and proteins were determined by real-time polymerase chain reaction and Western blot analysis, respectively. Edaravone significantly restored the hypoxia-induced reduction of MC3T3-E1 cell viability and inhibited lactate dehydrogenase release. In addition, we found that Edaravone inhibits the generation of ROS and NO. Hoechst staining results indicated that the nuclear condensation characteristic of apoptosis was increased in MC3T3-E1 cells after hypoxia exposure, which was significantly suppressed by Edaravone treatment. Mechanistically, we found that Edaravone markedly reduced the expression of cleaved caspase-3 and blunted the release of cytochrome c. These findings strongly suggested that Edaravone suppresses hypoxia-induced cytotoxicity in MC3T3-E1 cells. The pleiotropic effects of Edaravone on hypoxia exposure in osteoblasts suggest potential antiosteoporosis mechanisms of Edaravone. © 2015 International Union of Biochemistry and Molecular Biology.

Symbiodinium mitigate the combined effects of hypoxia and acidification on a noncalcifying cnidarian

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Klein, Shannon G.

2017-04-08

Anthropogenic nutrient inputs enhance microbial respiration within many coastal ecosystems, driving concurrent hypoxia and acidification. During photosynthesis, Symbiodinium spp., the microalgal endosymbionts of cnidarians and other marine phyla, produce O and assimilate CO and thus potentially mitigate the exposure of the host to these stresses. However, such a role for Symbiodinium remains untested for noncalcifying cnidarians. We therefore contrasted the fitness of symbiotic and aposymbiotic polyps of a model host jellyfish (Cassiopea sp.) under reduced O (~2.09 mg/L) and pH (~ 7.63) scenarios in a full-factorial experiment. Host fitness was characterized as asexual reproduction and their ability to regulate internal pH and Symbiodinium performance characterized by maximum photochemical efficiency, chla content and cell density. Acidification alone resulted in 58% more asexual reproduction of symbiotic polyps than aposymbiotic polyps (and enhanced Symbiodinium cell density) suggesting Cassiopea sp. fitness was enhanced by CO-stimulated Symbiodinium photosynthetic activity. Indeed, greater CO drawdown (elevated pH) was observed within host tissues of symbiotic polyps under acidification regardless of O conditions. Hypoxia alone produced 22% fewer polyps than ambient conditions regardless of acidification and symbiont status, suggesting Symbiodinium photosynthetic activity did not mitigate its effects. Combined hypoxia and acidification, however, produced similar numbers of symbiotic polyps compared with aposymbiotic kept under ambient conditions, demonstrating that the presence of Symbiodinium was key for mitigating the combined effects of hypoxia and acidification on asexual reproduction. We hypothesize that this mitigation occurred because of reduced photorespiration under elevated CO conditions where increased net O production ameliorates oxygen debt. We show that Symbiodinium play an important role in facilitating enhanced fitness of Cassiopea sp. polyps, and

Mitochondrial Reactive Oxygen Species Trigger Hypoxia-Induced Transcription

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Chandel, N. S.; Maltepe, E.; Goldwasser, E.; Mathieu, C. E.; Simon, M. C.; Schumacker, P. T.

1998-09-01

Transcriptional activation of erythropoietin, glycolytic enzymes, and vascular endothelial growth factor occurs during hypoxia or in response to cobalt chloride (CoCl2) in Hep3B cells. However, neither the mechanism of cellular O2 sensing nor that of cobalt is fully understood. We tested whether mitochondria act as O2 sensors during hypoxia and whether hypoxia and cobalt activate transcription by increasing generation of reactive oxygen species (ROS). Results show (i) wild-type Hep3B cells increase ROS generation during hypoxia (1.5% O2) or CoCl2 incubation, (ii) Hep3B cells depleted of mitochondrial DNA (ρ 0 cells) fail to respire, fail to activate mRNA for erythropoietin, glycolytic enzymes, or vascular endothelial growth factor during hypoxia, and fail to increase ROS generation during hypoxia; (iii) ρ 0 cells increase ROS generation in response to CoCl2 and retain the ability to induce expression of these genes; and (iv) the antioxidants pyrrolidine dithiocarbamate and ebselen abolish transcriptional activation of these genes during hypoxia or CoCl2 in wild-type cells, and abolish the response to CoCl2 in ρ 0 cells. Thus, hypoxia activates transcription via a mitochondria-dependent signaling process involving increased ROS, whereas CoCl2 activates transcription by stimulating ROS generation via a mitochondria-independent mechanism.

Suppression of the expression of hypoxia-inducible factor-1α by RNA interference alleviates hypoxia-induced pulmonary hypertension in adult rats.

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Li, Ying; Shi, Bo; Huang, Liping; Wang, Xin; Yu, Xiaona; Guo, Baosheng; Ren, Weidong

2016-12-01

Hypoxia-inducible factor-1α (HIF-1α) has been implicated in the pathogenesis of hypoxic pulmonary hypertension (PH). However, the potential clinical value of HIF-1α as a therapeutic target in the treatment of PH has not yet been evaluated. In this study, an animal model of hypoxia-induced PH was established by exposing adult rats to 10% O2 for 3 weeks, and the effects of the lentivirus-mediated delivery of HIF-1α short hairpin RNA (shRNA) by intratracheal instillation prior to exposure to hypoxia on the manifestations of hypoxia-induced PH were assessed. The successful delivery of HIF-1α shRNA into the pulmonary arteries effectively suppressed the hypoxia-induced upregulation of HIF-1α, accompanied by the prominent attenuation the symptoms associated with hypoxia-induced PH, including the elevation of pulmonary arterial pressure, hypertrophy and hyperplasia of pulmonary artery smooth muscle cells (PASMCs), as well as the muscularization of pulmonary arterioles. In addition, the knockdown of HIF-1α in cultured rat primary PASMCs significantly inhibited the hypoxia-induced acceleration of the cell cycle and the proliferation of the PASMCs, suggesting that HIF-1α may be a direct mediator of PASMC hyperplasia in hypoxia-induced PH. In conclusion, this study demonstrates the potent suppressive effects of HIF-1α shRNA on hypoxia-induced PH and PASMC hyperplasia, providing evidence for the potential application of HIF-1α shRNA in the treatment of hypoxic PH.

Imaging tumor hypoxia: Blood-borne delivery of imaging agents is fundamentally different in hypoxia subtypes

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Peter Vaupel

2014-03-01

Full Text Available Hypoxic tissue subvolumes are a hallmark feature of solid malignant tumors, relevant for cancer therapy and patient outcome because they increase both the intrinsic aggressiveness of tumor cells and their resistance to several commonly used anticancer strategies. Pathogenetic mechanisms leading to hypoxia are diverse, may coexist within the same tumor and are commonly grouped according to the duration of their effects. Chronic hypoxia is mainly caused by diffusion limitations resulting from enlarged intercapillary distances and adverse diffusion geometries and — to a lesser extent — by hypoxemia, compromised perfusion or long-lasting microregional flow stops. Conversely, acute hypoxia preferentially results from transient disruptions in perfusion. While each of these features of the tumor microenvironment can contribute to a critical reduction of oxygen availability, the delivery of imaging agents (as well as nutrients and anticancer agents may be compromised or remain unaffected. Thus, a critical appraisal of the effects of the various mechanisms leading to hypoxia with regard to the blood-borne delivery of imaging agents is necessary to judge their ability to correctly represent the hypoxic phenotype of solid malignancies.

Vagal activity and oxygen saturation response to hypoxia: Effects of aerobic fitness and rating of hypoxia tolerance

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Tomáš Macoun

2017-10-01

Full Text Available Background: A reduction in the inspired oxygen fraction (FiO2 induces a decline in arterial oxygen saturation (SpO2 and changes of heart rate variability (HRV. It has been shown that SpO2 and HRV responses to similar levels of acute normobaric hypoxia are inter-individual variable. Variable response may be influenced by normoxia reached maximal oxygen uptake (VO2max value. Objective: The primary aim was to assess HRV and the SpO2 response to hypoxia, and examine the association with normoxic VO2max. Methods: Supine HRV and SpO2 were monitored during normobaric hypoxia (FiO2 = 9.6% for 10 minutes in 28 subjects, aged 23.7 ± 1.7 years. HRV was evaluated by using both spectral and time domain HRV analysis. Low frequency (LF, 0.05-0.15 Hz and high frequency (HF, 0.15-0.50 Hz power together with square root of the mean of the squares of the successive differences (rMSSD were calculated and transformed by natural logarithm (Ln. Based on the SpO2 in hypoxia, subjects were divided into Resistant (RG, SpO2 ≥ 70.9%, n = 14 and Sensitive (SG, SpO2 < 70.9%, n = 14 groups. Perceived hypoxia tolerance was self-scored on a 4-level scale. Results: VO2max was higher in SG (62.4 ± 7.2 ml ⋅ kg-1 ⋅ min-1 compared with RG (55.5 ± 7.1 ml ⋅ kg-1 ⋅ min-1, p = .017, d = 0.97. A significant relationship (r = -.45, p = .017 between hypoxic-normoxic difference in SpO2 and normoxic VO2max level was found. Vagal activity (Ln rMSSD was significantly decreased (SG: p < .001, d = 2.64; RG: p < .001, d = 1.22, while sympathetic activity (Ln LF/HF was relatively increased (p < .001, d = -1.40 in only the SG during hypoxia. Conclusions: Results show that subjects with a higher aerobic capacity exhibited a greater decline in SpO2, accompanied by greater autonomic cardiac disturbances during hypoxia. The SpO2 reduction was associated with perceived hypoxia comfort/discomfort. The hypoxia

Hypoxia promotes apoptosis of neuronal cells through hypoxia-inducible factor-1α-microRNA-204-B-cell lymphoma-2 pathway.

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Wang, Xiuwen; Li, Ji; Wu, Dongjin; Bu, Xiangpeng; Qiao, Yong

2016-01-01

Neuronal cells are highly sensitive to hypoxia and may be subjected to apoptosis when exposed to hypoxia. Several apoptosis-related genes and miRNAs involve in hypoxia-induced apoptosis. This study aimed to examine the role of HIF1α-miR-204-BCL-2 pathway in hypoxia-induced apoptosis in neuronal cells. Annexin V/propidium iodide assay was performed to analyze cell apoptosis in AGE1.HN and PC12 cells under hypoxic or normoxic conditions. The expression of BCL-2 and miR-204 were determined by Western blot and qRT-PCR. The effects of miR-204 overexpression or knockdown on the expression of BCL-2 were evaluated by luciferase assay and Western blot under hypoxic or normoxic conditions. HIF-1α inhibitor YC-1 and siHIF-1α were employed to determine the effect of HIF-1α on the up-regulation of miR-204 and down-regulation of BCL-2 induced by hypoxia. Apoptosis assay showed the presence of apoptosis induced by hypoxia in neuronal cells. Moreover, we found that hypoxia significantly down-regulated the expression of BCL-2, and increased the mRNA level of miR-204 in neuronal cells than that in control. Bioinformatic analysis and luciferase reporter assay demonstrated that miR-204 directly targeted and regulated the expression of BCL-2. Specifically, the expression of BCL-2 was inhibited by miR-204 mimic and enhanced by miR-204 inhibitor. Furthermore, we detected that hypoxia induced cell apoptosis via HIF-1α/miR-204/BCL-2 in neuronal cells. This study demonstrated that HIF-1α-miR-204-BCL-2 pathway contributed to apoptosis of neuronal cells induced by hypoxia, which could potentially be exploited to prevent spinal cord ischemia-reperfusion injury. © 2015 by the Society for Experimental Biology and Medicine.

Catalase-loaded cisplatin-prodrug-constructed liposomes to overcome tumor hypoxia for enhanced chemo-radiotherapy of cancer.

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Zhang, Rui; Song, Xuejiao; Liang, Chao; Yi, Xuan; Song, Guosheng; Chao, Yu; Yang, Yu; Yang, Kai; Feng, Liangzhu; Liu, Zhuang

2017-09-01

Aiming at improved therapeutic efficacies, the combination of chemotherapy and radiotherapy (chemo-radiotherapy) has been widely studied and applied in clinic. However, the hostile characteristics of tumor microenvironment such as hypoxia often limit the efficacies in both types of cancer therapies. Herein, catalase (CAT), an antioxidant enzyme, is encapsulated inside liposomes constituted by cisplatin (IV)-prodrug-conjugated phospholipid, forming CAT@Pt (IV)-liposome for enhanced chemo-radiotherapy of cancer. After being loaded inside liposomes, CAT within CAT@Pt (IV)-liposome shows retained and well-protected enzyme activity, and is able to trigger decomposition of H 2 O 2 produced by tumor cells, so as to produce additional oxygen for hypoxia relief. As the result, treatment of CAT@Pt (IV)-liposome induces the highest level of DNA damage in cancer cells after X-ray radiation compared to the control groups. In vivo tumor treatment further demonstrates a remarkably improved therapeutic outcome in chemo-radiotherapy with such CAT@Pt (IV)-liposome nanoparticles. Hence, an exquisite type of liposome-based nanoparticles is developed in this work by integrating cisplatin-based chemotherapy and catalase-induced tumor hypoxia relief together for combined chemo-radiotherapy with great synergistic efficacy, promising for clinical translation in cancer treatment. Copyright © 2017. Published by Elsevier Ltd.

Slit2 ameliorates renal inflammation and fibrosis after hypoxia-and lipopolysaccharide-induced epithelial cells injury in vitro

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Zhou, Xiangjun [Department of Urology, Taihe Hospital, Hubei University of Medicine, Hubei (China); Yao, Qisheng, E-mail: yymcyqs@126.com [Department of Urology, Taihe Hospital, Hubei University of Medicine, Hubei (China); Sun, Xinbo; Gong, Xiaoxin; Yang, Yong; Chen, Congbo [Department of Urology, Taihe Hospital, Hubei University of Medicine, Hubei (China); Shan, Guang [Department of Urology, Renmin Hospital of Wuhan University, Hubei (China)

2017-03-01

Hypoxic acute kidney injury (AKI) is often incompletely repaired and leads to chronic kidney disease (CKD), which is characterized by tubulointerstitial inflammation and fibrosis. The Slit2 family of secreted glycoproteins is expressed in the kidney, it has been shown to exert an anti-inflammatory activity and prevent ischemic renal injury in vivo. However, whether Slit2 reduces renal fibrosis and inflammation after hypoxic and inflammatory epithelial cells injury in vitro remains unknown. In this study, we aimed to evaluate whether Slit2 ameliorated fibrosis and inflammation in two renal epithelial cells line challenged with hypoxia and lipopolysaccharide (LPS). Renal epithelial cells were treated with hypoxia and LPS to induce cell injury. Hoechst staining and Western blot analysis was conducted to examine epithelial cells injury. Immunofluorescence staining and Western blot analysis was performed to evaluate tubulointerstitial fibrosis. Real-time polymerase chain reaction (PCR) tested the inflammatory factor interleukin (IL)−1β and tumor necrosis factor (TNF)-α, and Western blot analysis determined the hypoxia-inducible factor (HIF)−1α, Toll-like receptor 4 (TLR4) and nuclear factor (NF)-κB. Results revealed that hypoxia induced epithelial cells apoptosis, inflammatory factor IL-1β and TNF-α release and tubulointerstitial fibrosis. LPS could exacerbate hypoxia -induced epithelial cells apoptosis, IL-1β and TNF-α release and fibrosis. Slit2 reduced the expression of fibronectin, the rate of epithelial cell apoptosis, and the expression of inflammatory factor. Slit2 could also inhibit the expression of TLR4 and NF-κB, but not the expression of HIF-1α. Therefore, Slit2 attenuated inflammation and fibrosis after LPS- and hypoxia-induced epithelial cells injury via the TLR4/NF-κB signaling pathway, but not depending on the HIF-1α signaling pathway. - Highlights: • Slit2 ameliorates inflammation after hypoxia-and LPS-induced epithelial cells injury

Restraint stress intensifies interstitial K+ accumulation during severe hypoxia

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Christian eSchnell

2012-03-01

Full Text Available Chronic stress affects neuronal networks by inducing dendritic retraction, modifying neuronal excitability and plasticity, and modulating glial cells. To elucidate the functional consequences of chronic stress for the hippocampal network, we submitted adult rats to daily restraint stress for three weeks (6 h/day. In acute hippocampal tissue slices of stressed rats, basal synaptic function and short-term plasticity at Schaffer collateral/CA1 neuron synapses were unchanged while long-term potentiation was markedly impaired. The spatiotemporal propagation pattern of hypoxia-induced spreading depression episodes was indistinguishable among control and stress slices. However, the duration of the extracellular direct current (DC potential shift was shortened after stress. Moreover, K+ fluxes early during hypoxia were more intense, and the postsynaptic recoveries of interstitial K+ levels and synaptic function were slower. Morphometric analysis of immunohistochemically stained sections suggested hippocampal shrinkage in stressed rats, and the number of cells that are immunoreactive for GFAP (glial fibrillary acidic protein was increased in the CA1 subfield indicating activation of astrocytes. Western blots showed a marked downregulation of the inwardly rectifying K+ channel Kir4.1 in stressed rats. Yet, resting membrane potentials, input resistance and K+-induced inward currents in CA1 astrocytes were indistinguishable from controls. These data indicate an intensified interstitial K+ accumulation during hypoxia in the hippocampus of chronically stressed rats which seems to arise from a reduced interstitial volume fraction rather than impaired glial K+ buffering. One may speculate that chronic stress aggravates hypoxia-induced pathophysiological processes in the hippocampal network and that this has implications for the ischemic brain.

Intermittent Hypoxia Causes Inflammation and Injury to Human Adult Cardiac Myocytes.

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Wu, Jing; Stefaniak, Joanna; Hafner, Christina; Schramel, Johannes Peter; Kaun, Christoph; Wojta, Johann; Ullrich, Roman; Tretter, Verena Eva; Markstaller, Klaus; Klein, Klaus Ulrich

2016-02-01

Intermittent hypoxia may occur in a number of clinical scenarios, including interruption of myocardial blood flow or breathing disorders such as obstructive sleep apnea. Although intermittent hypoxia has been linked to cardiovascular and cerebrovascular disease, the effect of intermittent hypoxia on the human heart is not fully understood. Therefore, in the present study, we compared the cellular responses of cultured human adult cardiac myocytes (HACMs) exposed to intermittent hypoxia and different conditions of continuous hypoxia and normoxia. HACMs were exposed to intermittent hypoxia (0%-21% O2), constant mild hypoxia (10% O2), constant severe hypoxia (0% O2), or constant normoxia (21% O2), using a novel cell culture bioreactor with gas-permeable membranes. Cell proliferation, lactate dehydrogenase release, vascular endothelial growth factor release, and cytokine (interleukin [IL] and macrophage migration inhibitory factor) release were assessed at baseline and after 8, 24, and 72 hours of exposure. A signal transduction pathway finder array was performed to determine the changes in gene expression. In comparison with constant normoxia and constant mild hypoxia, intermittent hypoxia induced earlier and greater inflammatory response and extent of cell injury as evidenced by lower cell numbers and higher lactate dehydrogenase, vascular endothelial growth factor, and proinflammatory cytokine (IL-1β, IL-6, IL-8, and macrophage migration inhibitory factor) release. Constant severe hypoxia showed more detrimental effects on HACMs at later time points. Pathway analysis demonstrated that intermittent hypoxia primarily altered gene expression in oxidative stress, Wnt, Notch, and hypoxia pathways. Intermittent and constant severe hypoxia, but not constant mild hypoxia or normoxia, induced inflammation and cell injury in HACMs. Cell injury occurred earliest and was greatest after intermittent hypoxia exposure. Our in vitro findings suggest that intermittent hypoxia

Understanding and exploiting the genomic response to hypoxia

International Nuclear Information System (INIS)

Giaccia, A.J.

2003-01-01

The tumor microenvironment influences both therapeutic outcome and malignant progression. Of the many factors that may be altered in the tumor microenvironment, changes in tumor oxygenation have been strongly associated with a lower probability of local tumor control and survival. In vitro studies indicate that cells exposed to a low oxygen environment exhibit multiple phenotypes, including cell-cycle arrest, increased expression of pro-angiogenic genes, increased invasive capacity, increased apoptosis, increased anaerobic metabolism and altered differentiation programs. While the mechanistic basis of hypoxia as an impediment to radiotherapy and chemotherapy is well understood, it is unclear what changes in the cellular phenotype are important in understanding how hypoxia modifies malignant progression. One insight into how hypoxia modulates malignant progression comes from understanding the critical transcriptional regulators of gene expression under hypoxic conditions such as hypoxia inducible factor 1 (HIF-1) as well as changes in gene expression in untransformed and transformed cells. Overall, about 1.5% of the genome is found to be transcriptionally responsive to changes in oxygenation. Most importantly, the coordinated changes in gene expression under hypoxic conditions underscore the physiologic basis for altering gene expression in response to a low oxygen environment. In addition, some hypoxia-induced genes exhibit increased expression after reoxygenation, suggesting that they are regulated both by hypoxia and oxidative stress. Analysis of the genomic response to hypoxia has several therapeutic uses. First, it allows one to ask the question of what the cellular consequences are to inhibition of the transcriptional response to hypoxia such as by targeting the HIF-1 transcription factor. While the effect of loss of HIF-1 in tumors leads to inhibition of tumor growth, it does not eliminate tumors. In fact, studies indicate that inhibition of HIF-1 leads to a

Neutralizing S1P inhibits intratumoral hypoxia, induces vascular remodelling and sensitizes to chemotherapy in prostate cancer

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Ader, Isabelle; Golzio, Muriel; Andrieu, Guillaume; Zalvidea, Santiago; Richard, Sylvain; Sabbadini, Roger A.; Malavaud, Bernard; Cuvillier, Olivier

2015-01-01

Hypoxia promotes neovascularization, increased tumor growth, and therapeutic resistance. The transcription factor, hypoxia-inducible factor 1α (HIF-1α), has been reported as the master driver of adaptation to hypoxia. We previously identified the sphingosine kinase 1/sphingosine 1-phosphate (SphK1/S1P) pathway as a new modulator of HIF-1α under hypoxia. Taking advantage of a monoclonal antibody neutralizing extracellular S1P (sphingomab), we report that inhibition of S1P extracellular signaling blocks HIF-1α accumulation and activity in several cancer cell models exposed to hypoxia. In an orthotopic xenograft model of prostate cancer, we show that sphingomab reduces hypoxia and modifies vessel architecture within 5 days of treatment, leading to increased intratumoral blood perfusion. Supporting the notion that a transient vascular normalization of tumor vessels is the mechanism by which sphingomab exerts its effects, we demonstrate that administration of the antibody for 5 days before chemotherapy is more effective at local tumor control and metastatic dissemination than any other treatment scheduling. These findings validate sphingomab as a potential new normalization agent that could contribute to successful sensitization of hypoxic tumors to chemotherapy. PMID:25915662

Induction of gastrin expression in gastrointestinal cells by hypoxia or cobalt is independent of hypoxia-inducible factor (HIF).

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Xiao, Lin; Kovac, Suzana; Chang, Mike; Shulkes, Arthur; Baldwin, Graham S; Patel, Oneel

2012-07-01

Gastrin and its precursors have been shown to promote mitogenesis and angiogenesis in gastrointestinal tumors. Hypoxia stimulates tumor growth, but its effect on gastrin gene regulation has not been examined in detail. Here we have investigated the effect of hypoxia on the transcription of the gastrin gene in human gastric cancer (AGS) cells. Gastrin mRNA was measured by real-time PCR, gastrin peptides were measured by RIA, and gastrin promoter activity was measured by dual-luciferase reporter assay. Exposure to a low oxygen concentration (1%) increased gastrin mRNA concentrations in wild-type AGS cells (AGS) and in AGS cells overexpressing the gastrin receptor (AGS-cholecystokinin receptor 2) by 2.1 ± 0.4- and 4.1 ± 0.3-fold (P factor hypoxia-inducible factor 1 (HIF-1) or knockdown of either the HIF-1α or HIF-1β subunit did not affect gastrin promoter inducibility under hypoxia indicated that the hypoxic activation of the gastrin gene is likely HIF independent. Mutational analysis of previously identified Sp1 regulatory elements in the gastrin promoter also failed to abrogate the induction of promoter activity by hypoxia. The observations that hypoxia up-regulates the gastrin gene in AGS cells by HIF-independent mechanisms, and that this effect is enhanced by the presence of gastrin receptors, provide potential targets for gastrointestinal cancer therapy.

Unique flexibility in energy metabolism allows mycobacteria to combat starvation and hypoxia.

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Michael Berney

Full Text Available Mycobacteria are a group of obligate aerobes that require oxygen for growth, but paradoxically have the ability to survive and metabolize under hypoxia. The mechanisms responsible for this metabolic plasticity are unknown. Here, we report on the adaptation of Mycobacterium smegmatis to slow growth rate and hypoxia using carbon-limited continuous culture. When M. smegmatis is switched from a 4.6 h to a 69 h doubling time at a constant oxygen saturation of 50%, the cells respond through the down regulation of respiratory chain components and the F1Fo-ATP synthase, consistent with the cells lower demand for energy at a reduced growth rate. This was paralleled by an up regulation of molecular machinery that allowed more efficient energy generation (i.e. Complex I and the use of alternative electron donors (e.g. hydrogenases and primary dehydrogenases to maintain the flow of reducing equivalents to the electron transport chain during conditions of severe energy limitation. A hydrogenase mutant showed a 40% reduction in growth yield highlighting the importance of this enzyme in adaptation to low energy supply. Slow growing cells at 50% oxygen saturation subjected to hypoxia (0.6% oxygen saturation responded by switching on oxygen scavenging cytochrome bd, proton-translocating cytochrome bc1-aa3 supercomplex, another putative hydrogenase, and by substituting NAD+-dependent enzymes with ferredoxin-dependent enzymes thus highlighting a new pattern of mycobacterial adaptation to hypoxia. The expression of ferredoxins and a hydrogenase provides a potential conduit for disposing of and transferring electrons in the absence of exogenous electron acceptors. The use of ferredoxin-dependent enzymes would allow the cell to maintain a high carbon flux through its central carbon metabolism independent of the NAD+/NADH ratio. These data demonstrate the remarkable metabolic plasticity of the mycobacterial cell and provide a new framework for understanding their

Network-based association of hypoxia-responsive genes with cardiovascular diseases

International Nuclear Information System (INIS)

Wang, Rui-Sheng; Oldham, William M; Loscalzo, Joseph

2014-01-01

Molecular oxygen is indispensable for cellular viability and function. Hypoxia is a stress condition in which oxygen demand exceeds supply. Low cellular oxygen content induces a number of molecular changes to activate regulatory pathways responsible for increasing the oxygen supply and optimizing cellular metabolism under limited oxygen conditions. Hypoxia plays critical roles in the pathobiology of many diseases, such as cancer, heart failure, myocardial ischemia, stroke, and chronic lung diseases. Although the complicated associations between hypoxia and cardiovascular (and cerebrovascular) diseases (CVD) have been recognized for some time, there are few studies that investigate their biological link from a systems biology perspective. In this study, we integrate hypoxia genes, CVD genes, and the human protein interactome in order to explore the relationship between hypoxia and cardiovascular diseases at a systems level. We show that hypoxia genes are much closer to CVD genes in the human protein interactome than that expected by chance. We also find that hypoxia genes play significant bridging roles in connecting different cardiovascular diseases. We construct a hypoxia-CVD bipartite network and find several interesting hypoxia-CVD modules with significant gene ontology similarity. Finally, we show that hypoxia genes tend to have more CVD interactors in the human interactome than in random networks of matching topology. Based on these observations, we can predict novel genes that may be associated with CVD. This network-based association study gives us a broad view of the relationships between hypoxia and cardiovascular diseases and provides new insights into the role of hypoxia in cardiovascular biology. (paper)

Recombinant adeno-associated virus-delivered hypoxia-inducible stanniocalcin-1 expression effectively inhibits hypoxia-induced cell apoptosis in cardiomyocytes.

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Shi, Xin; Wang, Jianzhong; Qin, Yan

2014-12-01

Ischemia/hypoxia-induced oxidative stress is detrimental for the survival of cardiomyocytes and cardiac function. Stanniocalcin-1 (STC-1), a glycoprotein, has been found to play an inhibitory role in the production of reactive oxygen species (ROS). Here, we speculated that the overexpression of STC-1 might alleviate oxidative damage in cardiomyocytes under conditions of hypoxia. To control the expression of STC-1 in hypoxia, we constructed a recombinant adeno-associated virus (AAV) carrying the hypoxia-responsive element (HRE) to mediate hypoxia induction. Cardiomyocytes were infected with AAV-HRE-STC-1 and cultured in normoxic or hypoxic conditions, and STC-1 overexpression was only detected in hypoxic cultured cardiomyocytes by using quantitative real-time polymerase chain reaction and Western blot analysis. Using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, AAV-HRE-STC-1 infection was shown to significantly enhance cell survival under hypoxia. Hypoxia-induced cell apoptosis was inhibited by AAV-HRE-STC-1 infection by using the Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide apoptosis assay. Moreover, the proapoptotic protein Caspase-3 and anti-apoptotic protein Bcl-2, which were dysregulated by hypoxia, were reversed by AAV-HRE-STC-1 infection. AAV-HRE-STC-1-mediated STC-1 overexpression markedly inhibited ROS production in cardiomyocytes cultured under hypoxic conditions. AAV-HRE-STC-1 infection significantly upregulated uncoupled protein 3 (UCP3), whereas silencing of UCP3 blocked the inhibitory effect of AAV-HRE-STC-1 on ROS production. In contrast, AAV-HRE-STC-1 infection had no effect on UCP2, and knockdown of UCP2 did not block the inhibitory effect of AAV-HRE-STC-1 on ROS production in the cardiomyocytes cultured under hypoxic conditions. Taken together, STC1 activates antioxidant pathway in cardiomyocytes through the induction of UCP3, implying that AAV-HRE-STC-1 has potential in the treatment of ischemic

Ebselen by modulating oxidative stress improves hypoxia-induced macroglial Müller cell and vascular injury in the retina.

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Tan, Sih Min; Deliyanti, Devy; Figgett, William A; Talia, Dean M; de Haan, Judy B; Wilkinson-Berka, Jennifer L

2015-07-01

Oxidative stress is an important contributor to glial and vascular cell damage in ischemic retinopathies. We hypothesized that ebselen via its ability to reduce reactive oxygen species (ROS) and augment nuclear factor-like 2 (Nrf2) anti-oxidants would attenuate hypoxia-induced damage to macroglial Müller cells and also lessen retinal vasculopathy. Primary cultures of rat Müller cells were exposed to normoxia (21% O2), hypoxia (0.5% O2) and ebselen (2.5 μM) for up to 72 h. Oxygen-induced retinopathy (OIR) was induced in C57BL/6J mice while control mice were housed in room air. Mice received vehicle (saline, 5% dimethyl sulfoxide) or ebselen (10 mg/kg) each day between postnatal days 6-18. In cultured Müller cells, flow cytometry for dihydroethidium revealed that ebselen reduced the hypoxia-induced increase in ROS levels, whilst increasing the expression of Nrf2-regulated anti-oxidant genes, heme oxygenase 1, glutathione peroxidase-1, NAD(P)H dehydrogenase quinone oxidoreductase 1 and glutamate-cysteine ligase. Moreover, in Müller cells, ebselen reduced the hypoxia-induced increase in protein levels of pro-angiogenic and pro-inflammatory factors including vascular endothelial growth factor, interleukin-6, monocyte chemoattractant-protein 1 and intercellular adhesion molecule-1, and the mRNA levels of glial fibrillary acidic protein (GFAP), a marker of Müller cell injury. Ebselen improved OIR by attenuating capillary vaso-obliteration and neovascularization and a concomitant reduction in Müller cell gliosis and GFAP. We conclude that ebselen protects against hypoxia-induced injury of retinal Müller cells and the microvasculature, which is linked to its ability to reduce oxidative stress, vascular damaging factors and inflammation. Agents such as ebselen may be potential treatments for retinopathies that feature oxidative stress-mediated damage to glia and the microvasculature. Copyright © 2015 Elsevier Ltd. All rights reserved.

Progressive hypoxia decouples activity and aerobic performance of skate embryos.

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Di Santo, Valentina; Tran, Anna H; Svendsen, Jon C

2016-01-01

Although fish population size is strongly affected by survival during embryonic stages, our understanding of physiological responses to environmental stressors is based primarily on studies of post-hatch fishes. Embryonic responses to acute exposure to changes in abiotic conditions, including increase in hypoxia, could be particularly important in species exhibiting long developmental time, as embryos are unable to select a different environment behaviourally. Given that oxygen is key to metabolic processes in fishes and aquatic hypoxia is becoming more severe and frequent worldwide, organisms are expected to reduce their aerobic performance. Here, we examined the metabolic and behavioural responses of embryos of a benthic elasmobranch fish, the little skate (Leucoraja erinacea), to acute progressive hypoxia, by measuring oxygen consumption and movement (tail-beat) rates inside the egg case. Oxygen consumption rates were not significantly affected by ambient oxygen levels until reaching 45% air saturation (critical oxygen saturation, S crit). Below S crit, oxygen consumption rates declined rapidly, revealing an oxygen conformity response. Surprisingly, we observed a decoupling of aerobic performance and activity, as tail-beat rates increased, rather than matching the declining metabolic rates, at air saturation levels of 55% and below. These results suggest a significantly divergent response at the physiological and behavioural levels. While skate embryos depressed their metabolic rates in response to progressive hypoxia, they increased water circulation inside the egg case, presumably to restore normoxic conditions, until activity ceased abruptly around 9.8% air saturation.

The dual role of autophagy under hypoxia-involvement of interaction between autophagy and apoptosis.

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Li, Mengmeng; Tan, Jin; Miao, Yuyang; Lei, Ping; Zhang, Qiang

2015-06-01

Hypoxia is one of severe cellular stress and it is well known to be associated with a worse outcome since a lack of oxygen accelerates the induction of apoptosis. Autophagy, an important and evolutionarily conserved mechanism for maintaining cellular homeostasis, is closely related to the apoptosis caused by hypoxia. Generally autophagy blocks the induction of apoptosis and inhibits the activation of apoptosis-associated caspase which could reduce cellular injury. However, in special cases, autophagy or autophagy-relevant proteins may help to induce apoptosis, which could aggravate cell damage under hypoxia condition. In addition, the activation of apoptosis-related proteins-caspase can also degrade autophagy-related proteins, such as Atg3, Atg4, Beclin1 protein, inhibiting autophagy. Although the relationship between autophagy and apoptosis has been known for rather complex for more than a decade, the underlying regulatory mechanisms have not been clearly understood. This short review discusses and summarizes the dual role of autophagy and the interaction and molecular regulatory mechanisms between autophagy and apoptosis under hypoxia.

Insulin protects apoptotic cardiomyocytes from hypoxia/reoxygenation injury through the sphingosine kinase/sphingosine 1-phosphate axis.

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Huan Yu

Full Text Available OBJECTIVE: Experimental and clinical studies have shown that administration of insulin during reperfusion is cardioprotective, but the mechanisms underlying this effect are still unknown. In this study, the ability of insulin to protect apoptotic cardiomyocytes from hypoxia/reoxygenation injury using the sphingosine kinase/sphingosine 1-phosphate axis was investigated. METHODS AND RESULTS: Rat cardiomyocytes were isolated and subjected to hypoxia and reoxygenation. [γ-32P] ATP was used to assess sphingosine kinase activity. Insulin was found to increase sphingosine kinase activity. Immunocytochemistry and Western blot analysis showed changes in the subcellular location of sphingosine kinase 1 from cytosol to the membrane in cardiomyocytes. Insulin caused cardiomyocytes to accumulate of S1P in a dose-dependent manner. FRET efficiency showed that insulin also transactivates the S1P1 receptor. TUNEL staining showed that administration of insulin during reoxygenation could to reduce the rate of reoxygenation-induced apoptosis, which is a requirement for SphK 1 activity. It also reduced the rate of activation of the S1P receptor and inhibited hypoxia/reoxygenation-induced cell death in cardiomyocytes. CONCLUSION: The sphingosine kinase 1/sphingosine 1-phosphate/S1P receptor axis is one pathway through which insulin protects rat cardiomyocytes from apoptosis induced by hypoxia/reoxygenation injury.

Moderate hypoxia influences potassium outward currents in adipose-derived stem cells.

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Mayuri Prasad

Full Text Available Moderate hypoxic preconditioning of adipose-derived stem cells (ASCs enhances properties such as proliferation and secretion of growth factors, representing a valuable strategy to increase the efficiency of cell-based therapies. In a wide variety of cells potassium (K+ channels are key elements involved in the cellular responses to hypoxia, suggesting that ASCs cultured under low oxygen conditions may display altered electrophysiological properties. Here, the effects of moderate hypoxic culture on proliferation, whole-cell currents, and ion channel expression were investigated using human ASCs cultured at 5% and 20% oxygen. Although cell proliferation was greatly enhanced, the dose-dependent growth inhibition by the K+ channel blocker tetraethylammonium (TEA was not significantly affected by hypoxia. Under both normoxic and hypoxic conditions, ASCs displayed outward K+ currents composed by Ca2+-activated, delayed rectifier, and transient components. Hypoxic culture reduced the slope of the current-voltage curves and caused a negative shift in the voltage activation threshold of the whole-cell currents. However, the TEA-mediated shift of voltage activation threshold was not affected by hypoxia. Semiquantitative real-time RT-PCR revealed that expression of genes encoding for various ion channels subunits related to oxygen sensing and proliferation remained unchanged after hypoxic culture. In conclusion, outward currents are influenced by moderate hypoxia in ASCs through a mechanism that is not likely the result of modulation of TEA-sensitive K+ channels.

Redox signaling during hypoxia in mammalian cells

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Kimberly A. Smith

2017-10-01

Full Text Available Hypoxia triggers a wide range of protective responses in mammalian cells, which are mediated through transcriptional and post-translational mechanisms. Redox signaling in cells by reactive oxygen species (ROS such as hydrogen peroxide (H2O2 occurs through the reversible oxidation of cysteine thiol groups, resulting in structural modifications that can change protein function profoundly. Mitochondria are an important source of ROS generation, and studies reveal that superoxide generation by the electron transport chain increases during hypoxia. Other sources of ROS, such as the NAD(PH oxidases, may also generate oxidant signals in hypoxia. This review considers the growing body of work indicating that increased ROS signals during hypoxia are responsible for regulating the activation of protective mechanisms in diverse cell types.

Application of 99Tcm-HL-91 in the hypoxia study of malignant lymphoma

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Li Li; Han Peizhen; Yan Yujun; Wang Yueying; Wang Junqi; Li Meijia

2002-01-01

Objective: 99 Tc m -HL91 is a putative hypoxic tracer probing hypoxia in solid tumors. This study was aimed at investigating the property of the spontaneous IRM-2-ML malignant lymphoma in homozygotic IRM-2 mice, and at testing the applicability of 99 Tc m -HL91 to the imaging of hypoxia in tumors. Methods: Biodistribution of 99 Tc m -HL91 after intravenously injection into normal and tumor-bearing IRM-2 mice was studied by determining blood and tissue levels of radioactivity from 20 to 360 min after injection. Nicotinamide was used to reduce the extent of hypoxia in the tumors. Planar SPECT imaging on normal and tumor-bearing IRM-2 mice was also performed. Results: Tumor load did not significantly influence the retention of 99 Tc m -HL91 in normal organs. 99 Tc m -HL91 was metabolized mainly via the liver and kidney, and was cleared fast from the blood. The tumor-to-blood ratio and tumor-to-muscle ratio continued to increase until 360 min (2.63 +- 0.25 and 3.37 +- 0.22 at 120 min, 3.51 +- 0.17 and 6.44 +- 0.29 at 360 min, respectively). The retention of 99 Tc m -HL91 in the tumor was reduced in mice by treatment with nicotinamide. Planar SPECT imaging showed that tumor could be observed clearly. Conclusion: These results confirm that IRM-2-ML malignant lymphoma possesses the common property of solid tumors,and also indicate that 99 Tc m -HL91 could be used to detect tumor hypoxia

Intermittent hypoxia increases insulin resistance in genetically obese mice.

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Polotsky, Vsevolod Y; Li, Jianguo; Punjabi, Naresh M; Rubin, Arnon E; Smith, Philip L; Schwartz, Alan R; O'Donnell, Christopher P

2003-10-01

Obstructive sleep apnoea, a syndrome that leads to recurrent intermittent hypoxia, is associated with insulin resistance in obese individuals, but the mechanisms underlying this association remain unknown. We utilized a mouse model to examine the effects of intermittent hypoxia on insulin resistance in lean C57BL/6J mice and leptin-deficient obese (C57BL/6J-Lepob) mice. In lean mice, exposure to intermittent hypoxia for 5 days (short term) resulted in a decrease in fasting blood glucose levels (from 173 +/- 11 mg dl-1 on day 0 to 138 +/- 10 mg dl-1 on day 5, P obese mice, short-term intermittent hypoxia led to a decrease in blood glucose levels accompanied by a 607 +/- 136 % (P intermittent hypoxia was completely abolished by prior leptin infusion. Obese mice exposed to intermittent hypoxia for 12 weeks (long term) developed a time-dependent increase in fasting serum insulin levels (from 3.6 +/- 1.1 ng ml-1 at baseline to 9.8 +/- 1.8 ng ml-1 at week 12, P intermittent hypoxia is dependent on the disruption of leptin pathways.

Hypoxia induces mitochondrial mutagenesis and dysfunction in inflammatory arthritis.

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Biniecka, Monika

2012-02-01

OBJECTIVE: To assess the levels and spectrum of mitochondrial DNA (mtDNA) point mutations in synovial tissue from patients with inflammatory arthritis in relation to in vivo hypoxia and oxidative stress levels. METHODS: Random Mutation Capture assay was used to quantitatively evaluate alterations of the synovial mitochondrial genome. In vivo tissue oxygen levels (tPO(2)) were measured at arthroscopy using a Licox probe. Synovial expression of lipid peroxidation (4-hydroxynonenal [4-HNE]) and mitochondrial cytochrome c oxidase subunit II (CytcO II) deficiency were assessed by immunohistochemistry. In vitro levels of mtDNA point mutations, reactive oxygen species (ROS), mitochondrial membrane potential, and markers of oxidative DNA damage (8-oxo-7,8-dihydro-2\\'-deoxyguanine [8-oxodG]) and lipid peroxidation (4-HNE) were determined in human synoviocytes under normoxia and hypoxia (1%) in the presence or absence of superoxide dismutase (SOD) or N-acetylcysteine (NAC) or a hydroxylase inhibitor (dimethyloxalylglycine [DMOG]). Patients were categorized according to their in vivo tPO(2) level (<20 mm Hg or >20 mm Hg), and mtDNA point mutations, immunochemistry features, and stress markers were compared between groups. RESULTS: The median tPO(2) level in synovial tissue indicated significant hypoxia (25.47 mm Hg). Higher frequency of mtDNA mutations was associated with reduced in vivo oxygen tension (P = 0.05) and with higher synovial 4-HNE cytoplasmic expression (P = 0.04). Synovial expression of CytcO II correlated with in vivo tPO(2) levels (P = 0.03), and levels were lower in patients with tPO(2) <20 mm Hg (P < 0.05). In vitro levels of mtDNA mutations, ROS, mitochondrial membrane potential, 8-oxo-dG, and 4-HNE were higher in synoviocytes exposed to 1% hypoxia (P < 0.05); all of these increased levels were rescued by SOD and DMOG and, with the exception of ROS, by NAC. CONCLUSION: These findings demonstrate that hypoxia-induced mitochondrial dysfunction drives

The interactive effect of cooling and hypoxia on forearm fatigue development.

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Lloyd, Alex; Hodder, Simon; Havenith, George

2015-09-01

To examine the effect of separate and combined exposure to hypoxia [normoxia (FIO2 = 0.21) vs. moderate altitude (FIO2 = 0.13)] and temperature [thermoneutral (22 °C) vs. cold (5 °C)] on muscle fatigue development in the forearm, after repeated low-resistance contractions. Eight males were exposed for 70 min to four separate conditions in a balanced order. Conditions were normoxic-thermoneutral (N), hypoxic-thermoneutral, normoxic-cold and hypoxic-cold. After 15-min seated rest, participants carried out intermittent dynamic forearm exercise at 15 % maximal isometric voluntary contraction (MVC) for eight consecutive, 5-min work bouts. Each bout was separated by 110 s rest during which MVC force was collected. When exposed to hypoxia and cold independently, the exercise protocol decreased MVC force of the finger flexors by 8.1 and 13.9 %, respectively, compared to thermoneutral normoxia. When hypoxia and cold were combined, the decrease in MVC force was 21.4 % more than thermoneutral normoxia, reflecting an additive effect and no interaction. EMG relative to force produced during MVC, increased by 2 and 1.2 μV per kg (36 and 23 % of N) for cold and hypoxia, respectively. When the stressors were combined the effect was additive, increasing to 3.1 μV per kg (56 % of N). When compared to exercise in thermoneutral normoxic conditions, both cold and hypoxia significantly reduce brief MVC force output. This effect appears to be of mechanical origin, not a failure in muscle fibre recruitment per se. Additionally, the reduction in force is greater when the stressors are combined, showing an additive effect.

Investigating the complexity of respiratory patterns during recovery from severe hypoxia

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Akay, Metin; Sekine, Noriko

2004-03-01

Progressive hypoxemia in anesthetized, peripherally chemodenervated piglets results in initial depression of the phrenic neurogram (PN) culminating in phrenic silence and, eventually, gasping. These changes reverse after the 30 min reoxygenation (recovery) period. To determine if changes in the PN patterns correspond to changes in temporal patterning, we have used the approximate entropy (ApEn) method to examine the effects of maturation on the complexity of breathing patterns in chemodenervated, vagotomized and decerebrated piglets during severe hypoxia and reoxygenation. The phrenic neurogram in piglets was recorded during eupnea (normal breathing), severe hypoxia (gasping) and recovery from severe hypoxia in 31 piglets (2 35 days). Nonlinear dynamical analysis of the phrenic neurogram was performed using the ApEn method. The mean ApEn values for a recording of five consecutive breaths during eupnea, a few phrenic neurogram signals during gasping, the beginning of the recovery period, and five consecutive breaths at every 5 min interval for the 30 min recovery period were calculated. Our data suggest that gasping resulted in reduced duration of the phrenic neurogram, and the gasp-like patterns exist at the beginning of the recovery. But, the durations of phrenic neurograms during recovery were increased after 10 min postreoxygenation, but were restored 30 min post recovery. The ApEn (complexity) values of the phrenic neurogram during eupnea were higher than those of gasping and the early (the onset of) recovery from severe hypoxia (p < 0.01), but were not statistically different than 5 min post recovery regardless of the maturation stages. These results suggest that hypoxia results in a reversible reconfiguration of the central respiratory pattern generator.

Transcriptomic and proteomic analyses of the Aspergillus fumigatus hypoxia response using an oxygen-controlled fermenter

Science.gov (United States)

2012-01-01

with other pathogenic fungi, the induction of glycolysis and transcriptional down-regulation of the TCA cycle and oxidative phosphorylation appear to major components of the hypoxia response in this pathogenic mold. In addition, a significant induction of the transcripts involved in ergosterol biosynthesis is consistent with previous observations in the pathogenic yeasts Candida albicans and Cryptococcus neoformans indicating conservation of this response to hypoxia in pathogenic fungi. Because ergosterol biosynthesis enzymes also require iron as a co-factor, the increase in iron uptake transcripts is consistent with an increased need for iron under hypoxia. However, unlike C. albicans and C. neoformans, the GABA shunt appears to play an important role in reducing NADH levels in response to hypoxia in A. fumigatus and it will be intriguing to determine whether this is critical for fungal virulence. Overall, regulatory mechanisms of the A. fumigatus hypoxia response appear to involve both transcriptional and post-transcriptional control of transcript and protein levels and thus provide candidate genes for future analysis of their role in hypoxia adaptation and fungal virulence. PMID:22309491

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen

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Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten; Lauritzen, Martin

2012-01-01

Glial calcium (Ca2+) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen saturation alters wave activity; (2) glial Ca2+ waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of...

Macrophage-mediated response to hypoxia in disease

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Tazzyman S

2014-11-01

Full Text Available Simon Tazzyman,1 Craig Murdoch,2 James Yeomans,1 Jack Harrison,1 Munitta Muthana3 1Department of Oncology, 2School of Clinical Dentistry, 3Department of Infection and Immunity, University of Sheffield, Sheffield, UK Abstract: Hypoxia plays a critical role in the pathobiology of various inflamed, diseased tissues, including malignant tumors, atherosclerotic plaques, myocardial infarcts, the synovia of rheumatoid arthritic joints, healing wounds, and sites of bacterial infection. These areas of hypoxia form when the blood supply is occluded and/or the oxygen supply is unable to keep pace with cell growth and/or infiltration of inflammatory cells. Macrophages are ubiquitous in all tissues of the body and exhibit great plasticity, allowing them to perform divergent functions, including, among others, patrolling tissue, combating invading pathogens and tumor cells, orchestrating wound healing, and restoring homeostasis after an inflammatory response. The number of tissue macrophages increases markedly with the onset and progression of many pathological states, with many macrophages accumulating in avascular and necrotic areas, where they are exposed to hypoxia. Recent studies show that these highly versatile cells then respond rapidly to the hypoxia present by altering their expression of a wide array of genes. Here we review the evidence for hypoxia-driven macrophage inflammatory responses in various disease states, and how this influences disease progression and treatment. Keywords: macrophage, hypoxia, inflammation, cytokine

Hypoxia-inducible factor signalling mechanisms in the central nervous system.

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Corcoran, A; O'Connor, J J

2013-08-01

In the CNS, neurones are highly sensitive to the availability of oxygen. In conditions where oxygen availability is decreased, neuronal function can be altered, leading to injury and cell death. Hypoxia has been implicated in a number of central nervous system pathologies including stroke, head trauma and neurodegenerative diseases. Cellular responses to oxygen deprivation are complex and result in activation of short- and long-term mechanisms to conserve energy and protect cells. Failure of synaptic transmission can be observed within minutes following this hypoxia. The acute effects of hypoxia on synaptic transmission are primarily mediated by altering ion fluxes across membranes, pre-synaptic effects of adenosine and other actions at glutamatergic receptors. A more long-term feature of the response of neurones to hypoxia is the activation of transcription factors such as hypoxia-inducible factor. The activation of hypoxia-inducible factor is governed by a family of dioxygenases called hypoxia-inducible factor prolyl 4 hydroxylases (PHDs). Under hypoxic conditions, PHD activity is inhibited, thereby allowing hypoxia-inducible factor to accumulate and translocate to the nucleus, where it binds to the hypoxia-responsive element sequences of target gene promoters. Inhibition of PHD activity stabilizes hypoxia-inducible factor and other proteins thus acting as a neuroprotective agent. This review will focus on the response of neuronal cells to hypoxia-inducible factor and its targets, including the prolyl hydroxylases. We also present evidence for acute effects of PHD inhibition on synaptic transmission and plasticity in the hippocampus. © 2013 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

The impact of hypoxia on oncolytic virotherapy

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Guo ZS

2011-11-01

Full Text Available Z Sheng GuoUniversity of Pittsburgh Cancer Institute and Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USAAbstract: The hypoxic tumor microenvironment plays significant roles in tumor cell metabolism and survival, tumor growth, and progression. Hypoxia modulates target genes in target cells mainly through an oxygen-sensing signaling pathway mediated by hypoxia-inducible factor of transcription factors. As a result, hypoxic tumor cells are resistant to conventional therapeutics such as radiation and chemotherapy. Oncolytic virotherapy may be a promising novel therapeutic for hypoxic cancer. Some oncolytic viruses are better adapted than others to the hypoxic tumor environment. Replication of adenoviruses from both groups B and C is inhibited, yet replication of herpes simplex virus is enhanced. Hypoxia seems to exert little or no effect on the replication of other oncolytic viruses. Vaccinia virus displayed increased cytotoxicity in some hypoxic cancer cells even though viral protein synthesis and transgene expression were not affected. Vesicular stomatitis virus replicated to similar levels in both hypoxic and normoxic conditions, and is effective for killing hypoxic cancer cells. However, vesicular stomatitis virus and reovirus, but not encephalomyocarditis virus, are sensitive to elevated levels of hypoxia-inducible factor-1α in renal cancer cells with the loss of von Hippel–Lindau tumor suppressor protein, because elevated hypoxia-inducible factor activity confers dramatically enhanced resistance to cytotoxicity mediated by vesicular stomatitis virus or reovirus. A variety of hypoxia-selective and tumor-type-specific oncolytic adenoviruses, generated by incorporating hypoxia-responsive elements into synthetic promoters to control essential genes for viral replication or therapeutic genes, have been shown to be safe and efficacious. Hypoxic tumor-homing macrophages can function effectively as carrier

Inflammation and hypoxia in the kidney: friends or foes?

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Haase, Volker H

2015-08-01

Hypoxic injury is commonly associated with inflammatory-cell infiltration, and inflammation frequently leads to the activation of cellular hypoxia response pathways. The molecular mechanisms underlying this cross-talk during kidney injury are incompletely understood. Yamaguchi and colleagues identify CCAAT/enhancer-binding protein δ as a cytokine- and hypoxia-regulated transcription factor that fine-tunes hypoxia-inducible factor-1 signaling in renal epithelial cells and thus provide a novel molecular link between hypoxia and inflammation in kidney injury.

Cutaneous vascular and core temperature responses to sustained cold exposure in hypoxia.

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Simmons, Grant H; Barrett-O'Keefe, Zachary; Minson, Christopher T; Halliwill, John R

2011-10-01

We tested the effect of hypoxia on cutaneous vascular regulation and defense of core temperature during cold exposure. Twelve subjects had two microdialysis fibres placed in the ventral forearm and were immersed to the sternum in a bathtub on parallel study days (normoxia and poikilocapnic hypoxia with an arterial O(2) saturation of 80%). One fibre served as the control (1 mM propranolol) and the other received 5 mM yohimbine (plus 1 mM propranolol) to block adrenergic receptors. Skin blood flow was assessed at each site (laser Doppler flowmetry), divided by mean arterial pressure to calculate cutaneous vascular conductance (CVC), and scaled to baseline. Cold exposure was first induced by a progressive reduction in water temperature from 36 to 23°C over 30 min to assess cutaneous vascular regulation, then by clamping the water temperature at 10°C for 45 min to test defense of core temperature. During normoxia, cold stress reduced CVC in control (-44 ± 4%) and yohimbine sites (-13 ± 7%; both P cooling but resulted in greater reductions in CVC in control (-67 ± 7%) and yohimbine sites (-35 ± 11%) during cooling (both P cooling rate during the second phase of cold exposure was unaffected by hypoxia (-1.81 ± 0.23°C h(-1) in normoxia versus -1.97 ± 0.33°C h(-1) in hypoxia; P > 0.05). We conclude that hypoxia increases cutaneous (non-noradrenergic) vasoconstriction during prolonged cold exposure, while core cooling rate is not consistently affected.

Physiological determinants of human acute hypoxia tolerance.

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2013-11-01

AbstractIntroduction. We investigated possible physiological determinants of variability in hypoxia tolerance in subjects given a 5-minute normobaric exposure to 25,000 ft equivalent. Physiological tolerance to hypoxia was defined as the magnitude of...

Impact of Seasonal Hypoxia on Activity and Community Structure of Chemolithoautotrophic Bacteria in a Coastal Sediment.

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Lipsewers, Yvonne A; Vasquez-Cardenas, Diana; Seitaj, Dorina; Schauer, Regina; Hidalgo-Martinez, Silvia; Sinninghe Damsté, Jaap S; Meysman, Filip J R; Villanueva, Laura; Boschker, Henricus T S

2017-05-15

Seasonal hypoxia in coastal systems drastically changes the availability of electron acceptors in bottom water, which alters the sedimentary reoxidation of reduced compounds. However, the effect of seasonal hypoxia on the chemolithoautotrophic community that catalyzes these reoxidation reactions is rarely studied. Here, we examine the changes in activity and structure of the sedimentary chemolithoautotrophic bacterial community of a seasonally hypoxic saline basin under oxic (spring) and hypoxic (summer) conditions. Combined 16S rRNA gene amplicon sequencing and analysis of phospholipid-derived fatty acids indicated a major temporal shift in community structure. Aerobic sulfur-oxidizing Gammaproteobacteria ( Thiotrichales ) and Epsilonproteobacteria ( Campylobacterales ) were prevalent during spring, whereas Deltaproteobacteria ( Desulfobacterales ) related to sulfate-reducing bacteria prevailed during summer hypoxia. Chemolithoautotrophy rates in the surface sediment were three times higher in spring than in summer. The depth distribution of chemolithoautotrophy was linked to the distinct sulfur oxidation mechanisms identified through microsensor profiling, i.e., canonical sulfur oxidation, electrogenic sulfur oxidation by cable bacteria, and sulfide oxidation coupled to nitrate reduction by Beggiatoaceae The metabolic diversity of the sulfur-oxidizing bacterial community suggests a complex niche partitioning within the sediment, probably driven by the availability of reduced sulfur compounds (H 2 S, S 0 , and S 2 O 3 2- ) and electron acceptors (O 2 and NO 3 - ) regulated by seasonal hypoxia. IMPORTANCE Chemolithoautotrophic microbes in the seafloor are dependent on electron acceptors, like oxygen and nitrate, that diffuse from the overlying water. Seasonal hypoxia, however, drastically changes the availability of these electron acceptors in the bottom water; hence, one expects a strong impact of seasonal hypoxia on sedimentary chemolithoautotrophy. A

Hypoxia induces dilated cardiomyopathy in the chick embryo: mechanism, intervention, and long-term consequences.

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Andrei Tintu

Full Text Available Intrauterine growth restriction is associated with an increased future risk for developing cardiovascular diseases. Hypoxia in utero is a common clinical cause of fetal growth restriction. We have previously shown that chronic hypoxia alters cardiovascular development in chick embryos. The aim of this study was to further characterize cardiac disease in hypoxic chick embryos.Chick embryos were exposed to hypoxia and cardiac structure was examined by histological methods one day prior to hatching (E20 and at adulthood. Cardiac function was assessed in vivo by echocardiography and ex vivo by contractility measurements in isolated heart muscle bundles and isolated cardiomyocytes. Chick embryos were exposed to vascular endothelial growth factor (VEGF and its scavenger soluble VEGF receptor-1 (sFlt-1 to investigate the potential role of this hypoxia-regulated cytokine.Growth restricted hypoxic chick embryos showed cardiomyopathy as evidenced by left ventricular (LV dilatation, reduced ventricular wall mass and increased apoptosis. Hypoxic hearts displayed pump dysfunction with decreased LV ejection fractions, accompanied by signs of diastolic dysfunction. Cardiomyopathy caused by hypoxia persisted into adulthood. Hypoxic embryonic hearts showed increases in VEGF expression. Systemic administration of rhVEGF(165 to normoxic chick embryos resulted in LV dilatation and a dose-dependent loss of LV wall mass. Lowering VEGF levels in hypoxic embryonic chick hearts by systemic administration of sFlt-1 yielded an almost complete normalization of the phenotype.Our data show that hypoxia causes a decreased cardiac performance and cardiomyopathy in chick embryos, involving a significant VEGF-mediated component. This cardiomyopathy persists into adulthood.

Unraveling the role of hypoxia-inducible factor (HIF)-1α and HIF-2α in the adaption process of human microvascular endothelial cells (HMEC-1) to hypoxia: Redundant HIF-dependent regulation of macrophage migration inhibitory factor.

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Hahne, Martin; Schumann, Peggy; Mursell, Mathias; Strehl, Cindy; Hoff, Paula; Buttgereit, Frank; Gaber, Timo

2018-03-01

Hypoxia driven angiogenesis is a prominent feature of tissue regeneration, inflammation and tumor growth and is regulated by hypoxia-inducible factor (HIF)-1 and -2. The distinct functions of HIFs in the hypoxia-induced angiogenesis and metabolic switch of endothelial cells are still unknown and therefore aim of this study. We investigated the role of HIF-1 and -2 in the adaptation of immortalized human microvascular endothelial cells (HMEC-1) to hypoxic conditions (1% O 2 ) in terms of angiogenesis, cytokine secretion, gene expression and ATP/ADP-ratio using shRNA-mediated reduction of the oxygen sensitive α-subunits of either HIF-1 or HIF-2 or the combination of both. Reduction of HIF-1α diminished cellular energy, hypoxia-induced glycolytic gene expression, and angiogenesis not altering pro-angiogenic factors. Reduction of HIF-2α diminished hypoxia-induced pro-angiogenic factors, enhanced anti-angiogenic factors and attenuated angiogenesis not altering glycolytic gene expression. Reduction of both HIFs reduced cell survival, gene expression of glycolytic enzymes and pro-angiogenic factors as compared to the corresponding control. Finally, we identified the macrophage migration inhibitory factor (MIF) to be redundantly regulated by HIF-1 and HIF-2 and to be essential in the process of hypoxia-driven angiogenesis. Our results demonstrate a major impact of HIF-1 and HIF-2 on hypoxia-induced angiogenesis indicating distinct but also overlapping functions of HIF-1 and HIF-2. These findings open new possibilities for therapeutic approaches by specifically targeting the HIF-1 and HIF-2 or their target MIF. Copyright © 2017 Elsevier Inc. All rights reserved.

The role of metformin and resveratrol in the prevention of hypoxia-inducible factor 1α accumulation and fibrosis in hypoxic adipose tissue.

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Li, Xiaole; Li, Jia; Wang, Lulu; Li, Aiyun; Qiu, Zhixia; Qi, Lian-Wen; Kou, Junping; Liu, Kang; Liu, Baolin; Huang, Fang

2016-06-01

Hypoxic activation of hypoxia-inducible factor 1α (HIF-1α) and fibrosis in adipose tissue contribute to adipose dysfunction. This study was designed to investigate the effects of metformin and resveratrol on the regulation of HIF-1α and fibrosis in hypoxic adipose tissue. Mice were fed a high-fat diet to induce hypoxia and fibrosis in adipose tissue; adipose tissue incubated in vitro in 1% O2 showed a similar change. The effects of metformin and resveratrol on hypoxia, HIF-1α accumulation, endoplasmic reticulum stress and gene expressions of extracellular matrix components and pro-inflammatory cytokines were examined. Oral administration of metformin or resveratrol prevented hypoxia and reduced HIF-1α accumulation with dephosphorylation of inositol-requiring enzyme 1α and eukaryotic initiation factor 2α, indicative of suppression of hypoxic HIF-1α activation and endoplasmic reticulum stress. Metformin and resveratrol down-regulated gene expressions of Col3α, Col6α, elastin and lysyl oxidase and thereby reduced collagen deposition in adipose tissue. The increased gene expressions of TNF-α, IL-6, monocyte chemoattractant protein 1 and F4/80 were also down-regulated by metformin and resveratrol. Metformin and resveratrol had similar effects in adipose tissue exposed to 1% O2 . Metformin reduced ATP production and prevented the reduction in oxygen tension in 3T3-L1 cells, suggesting that it prevented hypoxia by limiting oxygen consumption, whereas resveratrol reduced HIF-1α accumulation by promoting its proteasomal degradation via the regulation of AMPK/SIRT1. Hypoxia and fibrosis are early causes of adipose dysfunction in obesity. Both metformin and resveratrol effectively inhibited HIF-1α activation-induced fibrosis and inflammation in adipose tissue, although by different mechanisms. © 2016 The British Pharmacological Society.

Task failure during exercise to exhaustion in normoxia and hypoxia is due to reduced muscle activation caused by central mechanisms while muscle metaboreflex does not limit performance

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Rafael eTorres-Peralta

2016-01-01

Full Text Available To determine whether task failure during incremental exercise to exhaustion (IE is principally due to reduced neural drive and increased metaboreflex activation eleven men (22±2 years performed a 10s control isokinetic sprint (IS; 80 rpm after a short warm-up. This was immediately followed by an IE in normoxia (Nx, PIO2:143 mmHg and hypoxia (Hyp, PIO2:73 mmHg in random order, separated by a 120 min resting period. At exhaustion, the circulation of both legs was occluded instantaneously (300 mmHg during 10 or 60s to impede recovery and increase metaboreflex activation. This was immediately followed by an IS with open circulation. Electromyographic recordings were obtained from the vastus medialis and lateralis. Muscle biopsies and blood gases were obtained in separate experiments. During the last 10s of the IE, pulmonary ventilation, VO2, power output and muscle activation were lower in hypoxia than in normoxia, while pedaling rate was similar. Compared to the control sprint, performance (IS-Wpeak was reduced to a greater extent after the IE-Nx (11% lower P<0.05 than IE-Hyp. The root mean square (EMGRMS was reduced by 38 and 27% during IS performed after IE-Nx and IE-Hyp, respectively (Nx vs. Hyp: P<0.05. Post-ischemia IS-EMGRMS values were higher than during the last 10s of IE. Sprint exercise mean (IS-MPF and median (IS-MdPF power frequencies, and burst duration, were more reduced after IE-Nx than IE-Hyp (P<0.05. Despite increased muscle lactate accumulation, acidification, and metaboreflex activation from 10 to 60s of ischemia, IS-Wmean (+23% and burst duration (+10% increased, while IS-EMGRMS decreased (-24%, P<0.05, with IS-MPF and IS-MdPF remaining unchanged. In conclusion, close to task failure, muscle activation is lower in hypoxia than in normoxia. Task failure is predominantly caused by central mechanisms, which recover to great extent within one minute even when the legs remain ischemic. There is dissociation between the recovery of

Autophagy‑mediated adaptation of hepatocellular carcinoma cells to hypoxia‑mimicking conditions constitutes an attractive therapeutic target.

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Owada, Satoshi; Endo, Hitoshi; Shida, Yukari; Okada, Chisa; Ito, Kanako; Nezu, Takahiro; Tatemichi, Masayuki

2018-04-01

Hepatocellular carcinoma has extremely poor prognosis. In cancerous liver tissues, aberrant proliferation of cancer cells leads to the creation of an area where an immature vascular network is formed. Since oxygen is supplied to cancer tissues through the bloodstream, a part of the tumor is exposed to hypoxic conditions. As hypoxia is known to severely reduce the effectiveness of existing anticancer agents, novel valid therapeutic targets must be identified for the treatment of hepatocellular carcinoma. Generally, autophagy has been reported to play an important role in the adaptation of cancer cells to hypoxia. However, the exact role and significance of this process vary depending on the cancer type, requiring detailed analysis in individual primary tumors and cell lines. In the present study, we examined autophagy induced by cobalt chloride, a hypoxia‑mimicking agent, in hepatocellular carcinoma cells with the aim to evaluate the validity of this process as a potential therapeutic target. We observed that treatment with cobalt chloride induced autophagy, including the intracellular quality control mechanism, in an AMPK‑dependent manner. Furthermore, treatment with autophagy inhibitors (bafilomycin and LY294002) resulted in significant, highly‑selective cytotoxicity and apoptosis activation under hypoxia‑mimicking conditions. The knockdown of AMPK also revealed significant cytotoxicity in hypoxia‑mimicking conditions. These results clearly demonstrated that autophagy, especially mitophagy, was induced by the AMPK pathway when hepatocellular carcinoma cells were subjected to hypoxic conditions and played an important role in the adaptation of these cells to such conditions. Thus, autophagy may constitute an attractive therapeutic target for the treatment of hepatocellular carcinoma.

Hypoxia is increasing in the coastal zone of the Baltic Sea.

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Conley, Daniel J; Carstensen, Jacob; Aigars, Juris; Axe, Philip; Bonsdorff, Erik; Eremina, Tatjana; Haahti, Britt-Marie; Humborg, Christoph; Jonsson, Per; Kotta, Jonne; Lännegren, Christer; Larsson, Ulf; Maximov, Alexey; Medina, Miguel Rodriguez; Lysiak-Pastuszak, Elzbieta; Remeikaité-Nikiené, Nijolé; Walve, Jakob; Wilhelms, Sunhild; Zillén, Lovisa

2011-08-15

Hypoxia is a well-described phenomenon in the offshore waters of the Baltic Sea with both the spatial extent and intensity of hypoxia known to have increased due to anthropogenic eutrophication, however, an unknown amount of hypoxia is present in the coastal zone. Here we report on the widespread unprecedented occurrence of hypoxia across the coastal zone of the Baltic Sea. We have identified 115 sites that have experienced hypoxia during the period 1955-2009 increasing the global total to ca. 500 sites, with the Baltic Sea coastal zone containing over 20% of all known sites worldwide. Most sites experienced episodic hypoxia, which is a precursor to development of seasonal hypoxia. The Baltic Sea coastal zone displays an alarming trend with hypoxia steadily increasing with time since the 1950s effecting nutrient biogeochemical processes, ecosystem services, and coastal habitat.

[Effects of interleukin-18 and hypoxia-inducible factor-1α in serum and gingival tissues of rat model with periodontitis exposed to chronic intermittent hypoxia].

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Wang, Bin; Wang, Xiaoqin

2015-08-01

This study evaluates the expression of interleukin-18 (IL-18) and hypoxia-inducible factor (HIF)-lα in rat periodontitis model exposed to normoxia and chronic intermittent hypoxia (CIH) environments. The possible correlation between periodontitis and obstructive sleep apnea-hypopnea syndrome (OSAHS) was also investigated. Methods: Thirty-two Sprague-Dawley (SD) rats were randomly assigned into four groups: normoxia control, normoxia periodontitis, hypoxia control, and hypoxia periodontitis groups. The periodontitis models were established by ligating the bilateral maxillary second molars and employing high-carbohydrate diets. Rats in hypoxia control and hypoxia periodontitis groups were exposed to CIH treatment mimicking a moderately severe OSAHS condition. All animals were sacrificed after eight weeks, and the clinical periodontal indexes were detected. The levels of IL-18 and HIF-1α in serum and gingival tissues were determined using enzyme-linked immunosorbent assay (ELISA). The correlation between attachment loss (AL) and the levels of IL-18 and HIF-lα in hypoxia periodontitis group was evaluated. The levels of IL-18 and HIF-lα in hypoxia periodontitis group were significantly higher than that in normoxia periodontitis and hypoxia control groups (Pperiodontal tissues, which is correlated with IL-18 and HIF-lα levels.

Feeding rates affect stress and non-specific immune responses of juvenile blunt snout bream Megalobrama amblycephala subjected to hypoxia.

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Li, Xiang-Fei; Xu, Chao; Tian, Hong-Yan; Jiang, Guang-Zhen; Zhang, Ding-Dong; Liu, Wen-Bin

2016-02-01

This study aimed to investigate the effects of feeding rates on stress response, innate immunity and hypoxia resistance of juvenile blunt snout bream Megalobrama amblycephala. Fish were randomly assigned to one of six feeding rates (2, 3, 4, 5, 6 and 7% of body weight/day) for 60 days. Then, fish were subjected to hypoxic conditions and haemato-immunological parameters were analyzed pre- and post-challenge. Low feed ration resulted in decreased liver superoxide dismutase and catalase activities and reduced glutathione contents. Inadequate feeding also adversely affected the immune functions of fish, as was characterized by the relatively low haemato-immunological parameters (including alternative complement (ACH50), myeloperoxidase (MPO), plasma protein profiles and transferring) and high hypoxia-induced mortality. High feed ration did not lead to the improvement in antioxidant capability, immune responses and survival. In addition, plasma cortisol, glucose and transferrin levels as well as lysozyme activities all increased significantly after hypoxia challenge, whereas the opposite was true for plasma ACH50 and MPO activities as well as protein profiles in terms of hypoxia challenge. An interaction between feeding rate and hypoxia was also observed in plasma cortisol, glucose and protein profiles. In conclusion, a feeding rate of 4-5% of body weight/day is optimal to boost the innate immunity of juvenile blunt snout bream. Low ration resulted in decreased antioxidant capability, compromised immune functions and reduced hypoxia resistance, while over feeding did not benefit the health status. Copyright © 2016 Elsevier Ltd. All rights reserved.

HPV E6 and E7 in hypoxia mediated tumorigenesis in cervical epithelial cells

International Nuclear Information System (INIS)

Kim, Charlotte Y.; Tsai, Mitchell; Graeber, Thomas G.; Peehl, Donna M.; Giaccia, Amato J.

1996-01-01

Objective: In our previous work, we found that hypoxia induces apoptosis in oncogenically transformed rodent cells and loss of the p53 tumor suppressor gene significantly reduces hypoxia induced cell death. In this report, we show that transformation of wild-type p53 expressing primary cervical epithelial cells with the E6 and E7 genes from high risk human papillomavirus (HPV) type 16 dramatically enhances their susceptibility to hypoxia induced apoptosis. Materials and Methods: Sub confluent primary normal human cervical epithelial cells and normal human fibroblasts were infected with retroviral vectors containing HPV16 E6 and E7 and the neomycin selectable marker using previously described techniques. Clones were selected and isolated in neomycin containing media. Exponentially growing cells were treated with hypoxia (0.02% O 2 ) using specially designed chambers, irradiated (800 cGy) using a cesium source, or grown under aerobic conditions (20% O 2 ) as a control. After treatment, cells were stained with Hoescht and propidium iodide and viewed with a fluorescent microscope for analysis of apoptotic cells. To determine increase in expression of p53, immuno blots were performed using whole cell extracts. Results: After a 48 hour exposure to hypoxic conditions, 40% of E6 and E7 transformed cervical cells exhibit morphologic features indicative of apoptosis, compared to 5% of untransformed cervical cells. Exposure of HPV E6 and E7 transformed cells to ionizing radiation, however, did not initiate apoptosis. Immunoblot assays show induction of p53 under hypoxic conditions but not by ionizing radiation, indicating that hypoxia is able to induce p53 in the presence of E6 and that hypoxia activates p53 by a pathway which is distinct from that of ionizing radiation. Furthermore, hypoxia did not induce apoptosis in normal human fibroblasts transformed with E6 and E7, suggesting that the cellular response to hypoxia is influenced by the cell type. Conclusion: These results

Optical Imaging of Tumor Hypoxia and Evaluation of Efficacy of a Hypoxia-Targeting Drug in Living Animals

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Hiroshi Harada

2005-07-01

Full Text Available Solid tumors containing more hypoxic regions show a more malignant phenotype by increasing the expression of genes encoding angiogenic and metastatic factors. Hypoxia-inducible factor-1 (HIF-1 is a master transcriptional activator of such genes, and thus, imaging and targeting hypoxic tumor cells where HIF-1 is active are important in cancer therapy. In the present study, HIF-1 activity was monitored via an optical in vivo imaging system by using a luciferase reporter gene under the regulation of an artificial HIF-1-dependent promoter, 5HRE. To monitor tumor hypoxia, we isolated a stable reporter-transfectant, HeLa/5HRE-Luc, which expressed more than 100-fold luciferase in response to hypoxic stress, and observed bioluminescence from its xenografts. Immunohistochemical analysis of the xenografts with a hypoxia marker, pimonidazole, confirmed that the luciferase-expressing cells were hypoxic. Evaluation of the efficacy of a hypoxia-targeting prodrug, TOP3, using this optical imaging system revealed that hypoxic cells were significantly diminished by TOP3 treatment. Immunohistochemical analysis of the TOP3-treated xenografts confirmed that hypoxic cells underwent apoptosis and were removed after TOP3 treatment. These results demonstrate that this model system using the 5HRE-luciferase reporter construct provides qualitative information (hypoxic status of solid tumors and enables one to conveniently evaluate the efficacy of cancer therapy on hypoxia in malignant solid tumors.

Transcriptomic and proteomic analyses of the Aspergillus fumigatus hypoxia response using an oxygen-controlled fermenter

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Barker Bridget M

2012-02-01

components of the hypoxia response in this pathogenic mold. In addition, a significant induction of the transcripts involved in ergosterol biosynthesis is consistent with previous observations in the pathogenic yeasts Candida albicans and Cryptococcus neoformans indicating conservation of this response to hypoxia in pathogenic fungi. Because ergosterol biosynthesis enzymes also require iron as a co-factor, the increase in iron uptake transcripts is consistent with an increased need for iron under hypoxia. However, unlike C. albicans and C. neoformans, the GABA shunt appears to play an important role in reducing NADH levels in response to hypoxia in A. fumigatus and it will be intriguing to determine whether this is critical for fungal virulence. Overall, regulatory mechanisms of the A. fumigatus hypoxia response appear to involve both transcriptional and post-transcriptional control of transcript and protein levels and thus provide candidate genes for future analysis of their role in hypoxia adaptation and fungal virulence.

The role of mRNA translation in the adaptation to hypoxia

International Nuclear Information System (INIS)

Koritzinsky, M.; Wouters, B.G.; Koumenis, C.

2003-01-01

Hypoxia commonly occurs in human tumours and is associated with a poor prognosis. We and others have shown that global mRNA translation is rapidly inhibited during hypoxia. However, some mRNAs, such as those coding for HIF-1 α and VEGF, remain efficiently translated. We therefore hypothesize that the inhibition of mRNA translation serves to promote hypoxia tolerance in two ways: i) through conservation of energy and ii) through differential gene expression involved in hypoxia adaptation. We are investigating the mechanisms responsible for the down regulation of protein synthesis during hypoxia, and how specific mRNAs maintain their ability to be translated under such conditions. Our goal is to understand the significance of these regulatory mechanisms for hypoxia tolerance in vitro and tumor growth in vivo. We have previously shown that one mechanism responsible for inhibiting protein synthesis during hypoxia is the activation of PERK, which inhibits the essential translation factor eIF2 α . Here we show that PERK-/- MEFs are not able to inhibit protein synthesis efficiently during hypoxia and are significantly less tolerant to hypoxia than wt cells. We also show that other mechanisms are important for sustained low protein synthesis during chronic hypoxia. We demonstrate that the eIF4F complex is disrupted during prolonged hypoxia, and that this is mediated by 4E-BP1 and 4E-T. eIF4F is essential for translation which is dependent upon the 5'mRNA cap-structure. These studies therefore indicate a switch from the inhibition of all translation through eIF2 α during acute hypoxia, to the inhibition of only cap-dependent translation during chronic hypoxia. This model predicts the differential induction of genes that can be translated cap-independently during chronic hypoxia, which is consistent with the observed differential translation of HIF-1 α and VEGF. The functional significance of the disruption of the eIF4F complex during hypoxia is currently being addressed

Effect of hypoxia on benthic nutrient fluxes in the northwestern Black Sea

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Friedrich, J.

2012-04-01

, ammonia release from the sediments has been significantly higher than in oxic conditions, while no significant differences were detected in nitrate effluxes. This may be explained by dissimilatory reduction of the nitrate stored in large sulphate reducing bacteria like Beggiatoa (DNRA) leading to high fluxes of ammonia. DNRA might be an important recycling pathway of nitrogen during hypoxia on the Black Sea shelf. Hypoxia triggers also phosphate efflux from the sediment, the flux being marginally significantly higher than during oxic conditions where phosphate adsorbs to iron and manganese oxihydroxides. No clear pattern has been found in the N:P ratios of the nutrient efflux. This study shows that hypoxia supports higher ammonia and phosphate effluxes from the sediment than oxic conditions, making the sediment to a larger source of nutrients for benthic and pelagic productivity. Avoiding man-made hypoxia or anoxia in coastal seas is crucial for maintaining a balanced and functioning ecosystem.

CAROTID BODY POTENTIATION DURING CHRONIC INTERMITTENT HYPOXIA: IMPLICATION FOR HYPERTENSION

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Rodrigo eDel Rio

2014-11-01

Full Text Available Autonomic dysfunction is involved in the development of hypertension in humans with obstructive sleep apnea, and animals exposed to chronic intermittent hypoxia (CIH. It has been proposed that a crucial step in the development of the hypertension is the potentiation of the carotid body (CB chemosensory responses to hypoxia, but the temporal progression of the CB chemosensory, autonomic and hypertensive changes induced by CIH are not known. We tested the hypothesis that CB potentiation precedes the autonomic imbalance and the hypertension in rats exposed to CIH. Thus, we studied the changes in CB chemosensory and ventilatory responsiveness to hypoxia, the spontaneous baroreflex sensitivity (BRS, heart rate variability (HRV and arterial blood pressure in pentobarbital anesthetized rats exposed to CIH for 7, 14 and 21 days. After 7 days of CIH, CB chemosensory and ventilatory responses to hypoxia were enhanced, while BRS was significantly reduced by 2-fold in CIH-rats compared to sham-rats. These alterations persisted until 21 days of CIH. After 14 days, CIH shifted the HRV power spectra suggesting a predominance of sympathetic over parasympathetic tone. In contrast, hypertension was found after 21 days of CIH. Concomitant changes between the gain of spectral HRV, BRS and ventilatory hypoxic chemoreflex showed that the CIH-induced BRS attenuation preceded the HRV changes. CIH induced a simultaneous decrease of the BRS gain along with an increase of the hypoxic ventilatory gain. Present results show that CIH-induced persistent hypertension was preceded by early changes in CB chemosensory control of cardiorespiratory and autonomic function.

Subchronic inhalation of soluble manganese induces expression of hypoxia-associated angiogenic genes in adult mouse lungs

International Nuclear Information System (INIS)

Bredow, Sebastian; Falgout, Melanie M.; March, Thomas H.; Yingling, Christin M.; Malkoski, Stephen P.; Aden, James; Bedrick, Edward J.; Lewis, Johnnye L.; Divine, Kevin K.

2007-01-01

Although the lung constitutes the major exposure route for airborne manganese (Mn), little is known about the potential pulmonary effects and the underlying molecular mechanisms. Transition metals can mimic a hypoxia-like response, activating the hypoxia inducible factor-1 (HIF-1) transcription factor family. Through binding to the hypoxia-response element (HRE), these factors regulate expression of many genes, including vascular endothelial growth factor (VEGF). Increases in VEGF, an important biomarker of angiogenesis, have been linked to respiratory diseases, including pulmonary hypertension. The objective of this study was to evaluate pulmonary hypoxia-associated angiogenic gene expression in response to exposure of soluble Mn(II) and to assess the genes' role as intermediaries of potential pulmonary Mn toxicity. In vitro, 0.25 mM Mn(II) altered morphology and slowed the growth of human pulmonary epithelial cell lines. Acute doses between 0.05 and 1 mM stimulated VEGF promoter activity up to 3.7-fold in transient transfection assays. Deletion of the HRE within the promoter had no effect on Mn(II)-induced VEGF expression but decreased cobalt [Co(II)]-induced activity 2-fold, suggesting that HIF-1 may not be involved in Mn(II)-induced VEGF gene transcription. Nose-only inhalation to 2 mg Mn(II)/m 3 for 5 days at 6 h/day produced no significant pulmonary inflammation but induced a 2-fold increase in pulmonary VEGF mRNA levels in adult mice and significantly altered expression of genes associated with murine angiogenesis. These findings suggest that even short-term exposures to soluble, occupationally relevant Mn(II) concentrations may alter pulmonary gene expression in pathways that ultimately could affect the lungs' susceptibility to respiratory disease

Effect of acute exposure to moderate altitude on muscle power: hypobaric hypoxia vs. normobaric hypoxia.

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Belén Feriche

Full Text Available When ascending to a higher altitude, changes in air density and oxygen levels affect the way in which explosive actions are executed. This study was designed to compare the effects of acute exposure to real or simulated moderate hypoxia on the dynamics of the force-velocity relationship observed in bench press exercise. Twenty-eight combat sports athletes were assigned to two groups and assessed on two separate occasions: G1 (n = 17 in conditions of normoxia (N1 and hypobaric hypoxia (HH and G2 (n = 11 in conditions of normoxia (N2 and normobaric hypoxia (NH. Individual and complete force-velocity relationships in bench press were determined on each assessment day. For each exercise repetition, we obtained the mean and peak velocity and power shown by the athletes. Maximum power (Pmax was recorded as the highest P(mean obtained across the complete force-velocity curve. Our findings indicate a significantly higher absolute load linked to P(max (∼ 3% and maximal strength (1 RM (∼ 6% in G1 attributable to the climb to altitude (P<0.05. We also observed a stimulating effect of natural hypoxia on P(mean and P(peak in the middle-high part of the curve (≥ 60 kg; P<0.01 and a 7.8% mean increase in barbell displacement velocity (P<0.001. No changes in any of the variables examined were observed in G2. According to these data, we can state that acute exposure to natural moderate altitude as opposed to simulated normobaric hypoxia leads to gains in 1 RM, movement velocity and power during the execution of a force-velocity curve in bench press.

Impact of intermittent hypoxia and exercise on blood pressure and metabolic features from obese subjects suffering sleep apnea-hypopnea syndrome.

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González-Muniesa, P; Lopez-Pascual, A; de Andrés, J; Lasa, A; Portillo, M P; Arós, F; Durán, J; Egea, C J; Martinez, J A

2015-09-01

Strategies designed to reduce adiposity and cardiovascular-accompanying manifestations have been based on nutritional interventions conjointly with physical activity programs. The aim of this 13-week study was to investigate the putative benefits associated to hypoxia plus exercise on weight loss and relevant metabolic and cardiorespiratory variables, when prescribed to obese subjects with sleep apnea syndrome following dietary advice. The participants were randomly distributed in the following three groups: control, normoxia, and hypoxia. All the subjects received dietary advice while, additionally, normoxia group was trained under normal oxygen concentration and Hypoxia group under hypoxic conditions. There was a statistically significant decrease in fat-free mass (Kg) and water (%) on the control compared to normoxia group (p hypoxia compared to control group (p hypoxia group showed some specific benefits concerning appetite and cardiometabolic-related measurements as exertion time and diastolic blood pressure, with a therapeutical potential.

Reducing nitrogen export from the corn belt to the Gulf of Mexico: agricultural strategies for remediating hypoxia

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McLellan, Eileen; Robertson, Dale M.; Schilling, Keith; Tomer, Mark; Kostel, Jill; Smith, Douglas G.; King, Kevin

2015-01-01

SPAtially Referenced Regression on Watershed models developed for the Upper Midwest were used to help evaluate the nitrogen-load reductions likely to be achieved by a variety of agricultural conservation practices in the Upper Mississippi-Ohio River Basin (UMORB) and to compare these reductions to the 45% nitrogen-load reduction proposed to remediate hypoxia in the Gulf of Mexico (GoM). Our results indicate that nitrogen-management practices (improved fertilizer management and cover crops) fall short of achieving this goal, even if adopted on all cropland in the region. The goal of a 45% decrease in loads to the GoM can only be achieved through the coupling of nitrogen-management practices with innovative nitrogen-removal practices such as tile-drainage treatment wetlands, drainage–ditch enhancements, stream-channel restoration, and floodplain reconnection. Combining nitrogen-management practices with nitrogen-removal practices can dramatically reduce nutrient export from agricultural landscapes while minimizing impacts to agricultural production. With this approach, it may be possible to meet the 45% nutrient reduction goal while converting less than 1% of cropland in the UMORB to nitrogen-removal practices. Conservationists, policy makers, and agricultural producers seeking a workable strategy to reduce nitrogen export from the Corn Belt will need to consider a combination of nitrogen-management practices at the field scale and diverse nitrogen-removal practices at the landscape scale.

Kinetic modeling in PET imaging of hypoxia

DEFF Research Database (Denmark)

Li, Fan; Jørgensen, Jesper Tranekjær; Hansen, Anders E

2014-01-01

be used for non-invasive mapping of tissue oxygenation in vivo and several hypoxia specific PET tracers have been developed. Evaluation of PET data in the clinic is commonly based on visual assessment together with semiquantitative measurements e.g. standard uptake value (SUV). However, dynamic PET......Tumor hypoxia is associated with increased therapeutic resistance leading to poor treatment outcome. Therefore the ability to detect and quantify intratumoral oxygenation could play an important role in future individual personalized treatment strategies. Positron Emission Tomography (PET) can...... analysis for PET imaging of hypoxia....

Multi-Vitamin B Supplementation Reverses Hypoxia-Induced Tau Hyperphosphorylation and Improves Memory Function in Adult Mice.

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Yu, Lixia; Chen, Yuan; Wang, Weiguang; Xiao, Zhonghai; Hong, Yan

2016-08-04

Hypobaric hypoxia (HH) leads to reduced oxygen delivery to brain. It could trigger cognitive dysfunction and increase the risk of dementia including Alzheimer's disease (AD). The present study was undertaken in order to examine whether B vitamins (B6, B12, folate, and choline) could exert protective effects on hypoxia-induced memory deficit and AD related molecular events in mice. Adult male Kunming mice were assigned to five groups: normoxic control, hypoxic model (HH), hypoxia+vitamin B6/B12/folate (HB), hypoxia+choline (HC), hypoxia+vitamin B6/B12/folate+choline (HBC). Mice in the hypoxia, HB, HC, and HBC groups were exposed to hypobaric hypoxia for 8 h/day for 28 days in a decompression chamber mimicking 5500 meters of high altitude. Spatial and passive memories were assessed by radial arm and step-through passive test, respectively. Levels of tau and glycogen synthase kinase (GSK)-3β phosphorylation were detected by western blot. Homocysteine (Hcy) concentrations were determined using enzymatic cycling assay. Mice in the HH group exhibited significant spatial working and passive memory impairment, increased tau phosphorylation at Thr181, Ser262, Ser202/Thr205, and Ser396 in the cortex and hippocampus, and elevated Hcy levels compared with controls. Concomitantly, the levels of Ser9-phosphorylated GSK-3β were significantly decreased in brain after hypoxic treatment. Supplementations of vitamin B6/B12/folate+choline could significantly ameliorate the hypoxia-induced memory deficits, observably decreased Hcy concentrations in serum, and markedly attenuated tau hyperphosphorylation at multiple AD-related sites through upregulating inhibitory Ser9-phosphorylated GSK-3β. Our finding give further insight into combined neuroprotective effects of vitamin B6, B12, folate, and choline on brain against hypoxia.

Protective action of tetramethylpyrazine on the medulla oblongata in rats with chronic hypoxia.

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Ding, Yan; Hou, Xuefei; Chen, Li; Li, Hui; Tang, Yuhong; Zhou, Hua; Zhao, Shu; Zheng, Yu

2013-01-01

Tetramethylpyrazine (TMP), one of the active ingredients of the Chinese herb Lingusticum Wallichii Frantchat (Chuan Xiong), plays an important role in neuroprotection. However, the protective effect of TMP on the medulla oblongata, the most important region of the brain for cardiovascular and respiratory control, during chronic hypoxia remains unclear. In this study, we examined the neuroprotective effect of TMP on the medulla oblongata after chronic hypoxic injury in rats. Male Sprague-Dawley rats were randomly divided into four groups: control group, TMP group, chronic hypoxia group, and chronic hypoxia+TMP group. Rats were exposed to hypoxia (10% (v/v) O₂) or normoxia for 6 h daily for 14 days. TMP (80 mg/kg) or vehicle (saline) was injected intraperitoneally 30 min before experimentation. Loss of neurons in the pre-Bötzinger complex, the nucleus ambiguus, the nucleus tractus solitarius, the hypoglossal nucleus and the facial nucleus were evaluated by Nissl staining. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured, and apoptosis was monitored using the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method. The level of Bcl-2 mRNA and Bax mRNA was quantitatively measured by RT-PCR analysis. TMP protected Nissl bodies of neurons from injury in all nuclei observed, and reduced the loss of neurons in the nucleus ambiguus, the nucleus tractus solitarius, and the hypoglossal nucleus in rats subjected to chronic hypoxia. TMP upregulated SOD activity and inhibited the increase in MDA content in the medulla oblongata of hypoxic rats. In addition, TMP decreased the rate of apoptosis index (the percentage of apoptotic cells against the total number of cells) in all medullary structures examined, excepting the nucleus ambiguus and inhibited the decrease in Bcl-2 mRNA levels in the medulla oblongata following hypoxia. Our findings indicate that TMP may protect the medullary structures that are involved in

Upregulated copper transporters in hypoxia-induced pulmonary hypertension.

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Adriana M Zimnicka

Full Text Available Pulmonary vascular remodeling and increased arterial wall stiffness are two major causes for the elevated pulmonary vascular resistance and pulmonary arterial pressure in patients and animals with pulmonary hypertension. Cellular copper (Cu plays an important role in angiogenesis and extracellular matrix remodeling; increased Cu in vascular smooth muscle cells has been demonstrated to be associated with atherosclerosis and hypertension in animal experiments. In this study, we show that the Cu-uptake transporter 1, CTR1, and the Cu-efflux pump, ATP7A, were both upregulated in the lung tissues and pulmonary arteries of mice with hypoxia-induced pulmonary hypertension. Hypoxia also significantly increased expression and activity of lysyl oxidase (LOX, a Cu-dependent enzyme that causes crosslinks of collagen and elastin in the extracellular matrix. In vitro experiments show that exposure to hypoxia or treatment with cobalt (CoCl2 also increased protein expression of CTR1, ATP7A, and LOX in pulmonary arterial smooth muscle cells (PASMC. In PASMC exposed to hypoxia or treated with CoCl2, we also confirmed that the Cu transport is increased using 64Cu uptake assays. Furthermore, hypoxia increased both cell migration and proliferation in a Cu-dependent manner. Downregulation of hypoxia-inducible factor 1α (HIF-1α with siRNA significantly attenuated hypoxia-mediated upregulation of CTR1 mRNA. In summary, the data from this study indicate that increased Cu transportation due to upregulated CTR1 and ATP7A in pulmonary arteries and PASMC contributes to the development of hypoxia-induced pulmonary hypertension. The increased Cu uptake and elevated ATP7A also facilitate the increase in LOX activity and thus the increase in crosslink of extracellular matrix, and eventually leading to the increase in pulmonary arterial stiffness.

Gene expression promoted by the SV40 DNA targeting sequence and the hypoxia-responsive element under normoxia and hypoxia

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C.B. Sacramento

2010-08-01

Full Text Available The main objective of the present study was to find suitable DNA-targeting sequences (DTS for the construction of plasmid vectors to be used to treat ischemic diseases. The well-known Simian virus 40 nuclear DTS (SV40-DTS and hypoxia-responsive element (HRE sequences were used to construct plasmid vectors to express the human vascular endothelial growth factor gene (hVEGF. The rate of plasmid nuclear transport and consequent gene expression under normoxia (20% O2 and hypoxia (less than 5% O2 were determined. Plasmids containing the SV40-DTS or HRE sequences were constructed and used to transfect the A293T cell line (a human embryonic kidney cell line in vitro and mouse skeletal muscle cells in vivo. Plasmid transport to the nucleus was monitored by real-time PCR, and the expression level of the hVEGF gene was measured by ELISA. The in vitro nuclear transport efficiency of the SV40-DTS plasmid was about 50% lower under hypoxia, while the HRE plasmid was about 50% higher under hypoxia. Quantitation of reporter gene expression in vitro and in vivo, under hypoxia and normoxia, confirmed that the SV40-DTS plasmid functioned better under normoxia, while the HRE plasmid was superior under hypoxia. These results indicate that the efficiency of gene expression by plasmids containing DNA binding sequences is affected by the concentration of oxygen in the medium.

WE-AB-202-10: Modelling Individual Tumor-Specific Control Probability for Hypoxia in Rectal Cancer

Energy Technology Data Exchange (ETDEWEB)

Warren, S; Warren, DR; Wilson, JM; Muirhead, R; Hawkins, MA; Maughan, T; Partridge, M [University of Oxford, Oxford, Oxfordshire (United Kingdom)

2016-06-15

Purpose: To investigate hypoxia-guided dose-boosting for increased tumour control and improved normal tissue sparing using FMISO-PET images Methods: Individual tumor-specific control probability (iTSCP) was calculated using a modified linear-quadratic model with rectal-specific radiosensitivity parameters for three limiting-case assumptions of the hypoxia / FMISO uptake relationship. {sup 18}FMISO-PET images from 2 patients (T3N0M0) from the RHYTHM trial (Investigating Hypoxia in Rectal Tumours NCT02157246) were chosen to delineate a hypoxic region (GTV-MISO defined as tumor-to-muscle ratio > 1.3) within the anatomical GTV. Three VMAT treatment plans were created in Eclipse (Varian): STANDARD (45Gy / 25 fractions to PTV4500); BOOST-GTV (simultaneous integrated boost of 60Gy / 25fr to GTV +0.5cm) and BOOST-MISO (60Gy / 25fr to GTV-MISO+0.5cm). GTV mean dose (in EQD2), iTSCP and normal tissue dose-volume metrics (small bowel, bladder, anus, and femoral heads) were recorded. Results: Patient A showed small hypoxic volume (15.8% of GTV) and Patient B moderate hypoxic volume (40.2% of GTV). Dose escalation to 60Gy was achievable, and doses to femoral heads and small bowel in BOOST plans were comparable to STANDARD plans. For patient A, a reduced maximum bladder dose was observed in BOOST-MISO compared to BOOST-GTV (D0.1cc 49.2Gy vs 54.0Gy). For patient B, a smaller high dose volume was observed for the anus region in BOOST-MISO compared to BOOST-GTV (V55Gy 19.9% vs 100%), which could potentially reduce symptoms of fecal incontinence. For BOOST-MISO, the largest iTSCPs (A: 95.5% / B: 90.0%) assumed local correlation between FMISO uptake and hypoxia, and approached iTSCP values seen for BOOST-GTV (A: 96.1% / B: 90.5%). Conclusion: Hypoxia-guided dose-boosting is predicted to improve local control in rectal tumors when FMISO is spatially correlated to hypoxia, and to reduce dose to organs-at-risk compared to boosting the whole GTV. This could lead to organ

Mechanisms of c-myc degradation by nickel compounds and hypoxia.

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Qin Li

2009-12-01

Full Text Available Nickel (Ni compounds have been found to cause cancer in humans and animal models and to transform cells in culture. At least part of this effect is mediated by stabilization of hypoxia inducible factor (HIF1a and activating its downstream signaling. Recent studies reported that hypoxia signaling might either antagonize or enhance c-myc activity depending on cell context. We investigated the effect of nickel on c-myc levels, and demonstrated that nickel, hypoxia, and other hypoxia mimetics degraded c-myc protein in a number of cancer cells (A549, MCF-7, MDA-453, and BT-474. The degradation of the c-Myc protein was mediated by the 26S proteosome. Interestingly, knockdown of both HIF-1alpha and HIF-2alpha attenuated c-Myc degradation induced by Nickel and hypoxia, suggesting the functional HIF-1alpha and HIF-2alpha was required for c-myc degradation. Further studies revealed two potential pathways mediated nickel and hypoxia induced c-myc degradation. Phosphorylation of c-myc at T58 was significantly increased in cells exposed to nickel or hypoxia, leading to increased ubiquitination through Fbw7 ubiquitin ligase. In addition, nickel and hypoxia exposure decreased USP28, a c-myc de-ubiquitinating enzyme, contributing to a higher steady state level of c-myc ubiquitination and promoting c-myc degradation. Furthermore, the reduction of USP28 protein by hypoxia signaling is due to both protein degradation and transcriptional repression. Nickel and hypoxia exposure significantly increased the levels of dimethylated H3 lysine 9 at the USP28 promoter and repressed its expression. Our study demonstrated that Nickel and hypoxia exposure increased c-myc T58 phosphorylation and decreased USP28 protein levels in cancer cells, which both lead to enhanced c-myc ubiquitination and proteasomal degradation.

Hypoxia-induced hypothermia mediated by GABA in the rostral parapyramidal area of the medulla oblongata.

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Osaka, T

2014-05-16

Hypoxia evokes a regulated decrease in the body core temperature (Tc) in a variety of animals. The neuronal mechanisms of this response include, at least in part, glutamatergic activation in the lateral preoptic area (LPO) of the hypothalamus. As the sympathetic premotor neurons in the medulla oblongata constitute a cardinal relay station in the descending neuronal pathway from the hypothalamus for thermoregulation, their inhibition can also be critically involved in the mechanisms of the hypoxia-induced hypothermia. Here, I examined the hypothesis that hypoxia-induced hypothermia is mediated by glutamate-responsive neurons in the LPO that activate GABAergic transmission in the rostral raphe pallidus (rRPa) and neighboring parapyramidal region (PPy) of the medulla oblongata in urethane-chloralose-anesthetized, neuromuscularly blocked, artificially ventilated rats. Unilateral microinjection of GABA (15nmol) into the rRPa and PPy regions elicited a prompt increase in tail skin temperature (Ts) and decreases in Tc, oxygen consumption rate (VO2), and heart rate. Next, when the GABAA receptor blocker bicuculline methiodide (bicuculline methiodide (BMI), 10pmol) alone was microinjected into the rRPa, it elicited unexpected contradictory responses: simultaneous increases in Ts, VO2 and heart rate and a decrease in Tc. Then, when BMI was microinjected bilaterally into the PPy, no direct effect on Ts was seen; and thermogenic and tachycardic responses were slight. However, pretreatment of the PPy with BMI, but not vehicle saline, greatly attenuated the hypothermic responses evoked by hypoxic (10%O2-90%N2, 5min) ventilation or bilateral microinjections of glutamate (5nmol, each side) into the LPO. The results suggest that hypoxia-induced hypothermia was mediated, at least in part, by the activation of GABAA receptors in the PPy. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

Embryonic hypoxia programmes postprandial cardiovascular function in adult common snapping turtles (Chelydra serpentina).

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Wearing, Oliver H; Conner, Justin; Nelson, Derek; Crossley, Janna; Crossley, Dane A

2017-07-15

Reduced oxygen availability (hypoxia) is a potent stressor during embryonic development, altering the trajectory of trait maturation and organismal phenotype. We previously documented that chronic embryonic hypoxia has a lasting impact on the metabolic response to feeding in juvenile snapping turtles ( Chelydra serpentina ). Turtles exposed to hypoxia as embryos [10% O 2 (H10)] exhibited an earlier and increased peak postprandial oxygen consumption rate, compared with control turtles [21% O 2 (N21)]. In the current study, we measured central blood flow patterns to determine whether the elevated postprandial metabolic response in H10 turtles is linked to lasting impacts on convective transport. Five years after hatching, turtles were instrumented to quantify systemic ([Formula: see text]) and pulmonary ([Formula: see text]) blood flows and heart rate ( f H ) before and after a ∼5% body mass meal. In adult N21 and H10 turtles, f H was increased significantly by feeding. Although total stroke volume ( V S,tot ) remained at fasted values, this tachycardia contributed to an elevation in total cardiac output ([Formula: see text]). However, there was a postprandial reduction in a net left-right (L-R) shunt in N21 snapping turtles only. Relative to N21 turtles, H10 animals exhibited higher [Formula: see text] due to increased blood flow through the right systemic outflow vessels of the heart. This effect of hypoxic embryonic development, reducing a net L-R cardiac shunt, may support the increased postprandial metabolic rate we previously reported in H10 turtles, and is further demonstration of adult reptile cardiovascular physiology being programmed by embryonic hypoxia. © 2017. Published by The Company of Biologists Ltd.

Endogenous markers of tumor hypoxia. Predictors of clinical radiation resistance?

International Nuclear Information System (INIS)

Vordermark, D.; Brown, J.M.

2003-01-01

Background: Eppendorf electrode measurements of tumor oxygenation have defined an adverse effect of tumor hypoxia on prognosis after radiotherapy and other treatment modalities, in particular in head and neck and cervix carcinomas as well as soft tissue sarcomas. Recently, the immunohistochemical detection of proteins involved in the ''hypoxic response'' of tumor cells has been discussed as a method to estimate hypoxia in clinical tumor specimens. Material and Methods: This review focuses on clinical and experimental data, regarding prognostic impact and comparability with other methods of hypoxia detection, for three proteins suggested as endogenous markers of tumor hypoxia: hypoxia-inducible factor-1α (HIF-1α), carbonic anhydrase 9 (CA 9), and glucose transporter 1 (GLUT1). Results: None of the three potential hypoxia markers is exclusively hypoxia-specific, and in each case protein can be detected under normoxic conditions in vitro. HIF-1α responds rapidly to hypoxia but also to reoxygenation, making this marker quite unstable in the context of clinical sample collection. The perinecrotic labeling pattern typical of chronic hypoxia and a reasonable agreement with injectable hypoxia markers such as pimonidazole have most consistently been described for CA 9. All three markers showed correlation with Eppendorf electrode measurements of tumor oxygenation in carcinoma of the cervix. In nine of 13 reports, among them all three that refer to curative radiotherapy for head and neck cancer, HIF-1α overexpression was associated with poor outcome. CA 9 was an adverse prognostic factor in cervix, head and neck and lung cancer, but not in two other head and neck cancer reports. GLUT1 predicted for poor survival in colorectal, cervix and lung cancer. Conclusion: Endogenous markers have the potential to indicate therapeutically relevant levels of hypoxia within tumors. Clinical trials assessing a marker's ability to predict a benefit from specific hypoxia

Endogenous markers of tumor hypoxia. Predictors of clinical radiation resistance?

Energy Technology Data Exchange (ETDEWEB)

Vordermark, D. [Dept. of Radiation Oncology, Univ. of Wuerzburg (Germany); Dept. of Radiation Oncology, Stanford Univ. School of Medicine, Stanford, CA (United States); Brown, J.M. [Dept. of Radiation Oncology, Stanford Univ. School of Medicine, Stanford, CA (United States)

2003-12-01

Background: Eppendorf electrode measurements of tumor oxygenation have defined an adverse effect of tumor hypoxia on prognosis after radiotherapy and other treatment modalities, in particular in head and neck and cervix carcinomas as well as soft tissue sarcomas. Recently, the immunohistochemical detection of proteins involved in the ''hypoxic response'' of tumor cells has been discussed as a method to estimate hypoxia in clinical tumor specimens. Material and Methods: This review focuses on clinical and experimental data, regarding prognostic impact and comparability with other methods of hypoxia detection, for three proteins suggested as endogenous markers of tumor hypoxia: hypoxia-inducible factor-1{alpha} (HIF-1{alpha}), carbonic anhydrase 9 (CA 9), and glucose transporter 1 (GLUT1). Results: None of the three potential hypoxia markers is exclusively hypoxia-specific, and in each case protein can be detected under normoxic conditions in vitro. HIF-1{alpha} responds rapidly to hypoxia but also to reoxygenation, making this marker quite unstable in the context of clinical sample collection. The perinecrotic labeling pattern typical of chronic hypoxia and a reasonable agreement with injectable hypoxia markers such as pimonidazole have most consistently been described for CA 9. All three markers showed correlation with Eppendorf electrode measurements of tumor oxygenation in carcinoma of the cervix. In nine of 13 reports, among them all three that refer to curative radiotherapy for head and neck cancer, HIF-1{alpha} overexpression was associated with poor outcome. CA 9 was an adverse prognostic factor in cervix, head and neck and lung cancer, but not in two other head and neck cancer reports. GLUT1 predicted for poor survival in colorectal, cervix and lung cancer. Conclusion: Endogenous markers have the potential to indicate therapeutically relevant levels of hypoxia within tumors. Clinical trials assessing a marker's ability to predict a

Effects of Acute Hypoxia and Reoxygenation on Physiological and Immune Responses and Redox Balance of Wuchang Bream (Megalobrama amblycephala Yih, 1955

Directory of Open Access Journals (Sweden)

Nan Chen

2017-06-01

Full Text Available To study Megalobrama amblycephala adaption to water hypoxia, the changes in physiological levels, innate immune responses, redox balance of M.amblycephala during hypoxia were investigated in the present study. When M. amblycephala were exposed to different dissolved oxygen (DO including control (DO: 5.5 mg/L and acute hypoxia (DO: 3.5 and 1.0 mg/L, respectively, hemoglobin (Hb, methemoglobin (MetHb, glucose, Na+, succinatedehydrogenase (SDH, lactate, interferon alpha (IFNα, and lysozyme (LYZ, except hepatic glycogen and albumin gradually increased with the decrease of DO level. When M. amblycephala were exposed to different hypoxia time including 0.5 and 6 h (DO: 3.5 mg/L, and then reoxygenation for 24 h after 6 h hypoxia, Hb, MetHb, glucose, lactate, and IFNα, except Na+, SDH, hepatic glycogen, albumin, and LYZ increased with the extension of hypoxia time, while the above investigated indexes (except albumin, IFNα, and LYZ decreased after reoxygenation. On the other hand, the liver SOD, CAT, hydrogen peroxide (H2O2, and total ROS were all remained at lower levels under hypoxia stress. Finally, Hif-1α protein in the liver, spleen, and gill were increased with the decrease of oxygen concentration and prolongation of hypoxia time. Interestingly, one Hsp70 isoforms mediated by internal ribozyme entry site (IRES named junior Hsp70 was only detected in liver, spleen and gill. Taken together, these results suggest that hypoxia affects M. amblycephala physiology and reduces liver oxidative stress. Hypoxia-reoxygenation stimulates M. amblycephala immune parameter expressions, while Hsp70 response to hypoxia is tissue-specific.

Progress toward overcoming hypoxia-induced resistance to solid tumor therapy

International Nuclear Information System (INIS)

Karakashev, Sergey V; Reginato, Mauricio J

2015-01-01

Hypoxic tumors are associated with poor clinical outcome for multiple types of human cancer. This may be due, in part, to hypoxic cancer cells being resistant to anticancer therapy, including radiation therapy, chemotherapy, and targeted therapy. Hypoxia inducible factor 1, a major regulator of cellular response to hypoxia, regulates the expression of genes that are involved in multiple aspects of cancer biology, including cell survival, proliferation, metabolism, invasion, and angiogenesis. Here, we review multiple pathways regulated by hypoxia/hypoxia inducible factor 1 in cancer cells and discuss the latest advancements in overcoming hypoxia-mediated tumor resistance

Stanniocalcin-2 is a HIF-1 target gene that promotes cell proliferation in hypoxia

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Law, Alice Y.S. [Department of Biology, Hong Kong Baptist University, Kowloon Tong (Hong Kong); Wong, Chris K.C., E-mail: ckcwong@hkbu.edu.hk [Department of Biology, Hong Kong Baptist University, Kowloon Tong (Hong Kong)

2010-02-01

Stanniocalcin-2 (STC2), the paralog of STC1, has been suggested as a novel target of oxidative stress response to protect cells from apoptosis. The expression of STC2 has been reported to be highly correlated with human cancer development. In this study, we reported that STC2 is a HIF-1 target gene and is involved in the regulation of cell proliferation. STC2 was shown to be up-regulated in different breast and ovarian cancer cells, following exposure to hypoxia. Using ovarian cancer cells (SKOV3), the underlying mechanism of HIF-1 mediated STC2 gene transactivation was characterized. Hypoxia-induced STC2 expression was found to be HIF-1{alpha} dependent and required the recruitment of p300 and HDAC7. Using STC2 promoter deletion constructs and site-directed mutagenesis, two authentic consensus HIF-1 binding sites were identified. Under hypoxic condition, the silencing of STC2 reduced while the overexpression of STC2 increased the levels of phosphorylated retinoblastoma and cyclin D in both SKOV3 and MCF7 cells. The change in cell cycle proteins correlated with the data of the serial cell counts. The results indicated that cell proliferation was reduced in STC2-silenced cells but was increased in STC2-overexpressing hypoxic cells. Solid tumor progression is usually associated with hypoxia. The identification and functional analysis of STC2 up-regulation by hypoxia, a feature of the tumor microenvironment, sheds light on a possible role for STC2 in tumors.

Identifying novel hypoxia-associated markers of chemoresistance in ovarian cancer.

LENUS (Irish Health Repository)

McEvoy, Lynda M

2015-01-01

Ovarian cancer is associated with poor long-term survival due to late diagnosis and development of chemoresistance. Tumour hypoxia is associated with many features of tumour aggressiveness including increased cellular proliferation, inhibition of apoptosis, increased invasion and metastasis, and chemoresistance, mostly mediated through hypoxia-inducible factor (HIF)-1α. While HIF-1α has been associated with platinum resistance in a variety of cancers, including ovarian, relatively little is known about the importance of the duration of hypoxia. Similarly, the gene pathways activated in ovarian cancer which cause chemoresistance as a result of hypoxia are poorly understood. This study aimed to firstly investigate the effect of hypoxia duration on resistance to cisplatin in an ovarian cancer chemoresistance cell line model and to identify genes whose expression was associated with hypoxia-induced chemoresistance.

Hypoxia and bicarbonate could limit the expression of iron acquisition genes in Strategy I plants by affecting ethylene synthesis and signaling in different ways.

Science.gov (United States)

García, María J; García-Mateo, María J; Lucena, Carlos; Romera, Francisco J; Rojas, Carmen L; Alcántara, Esteban; Pérez-Vicente, Rafael

2014-01-01

In a previous work, it was shown that bicarbonate (one of the most important factors causing Fe chlorosis in Strategy I plants) can limit the expression of several genes involved in Fe acquisition. Hypoxia is considered another important factor causing Fe chlorosis, mainly on calcareous soils. However, to date it is not known whether hypoxia aggravates Fe chlorosis by affecting bicarbonate concentration or by specific negative effects on Fe acquisition. Results found in this work show that hypoxia, generated by eliminating the aeration of the nutrient solution, can limit the expression of several Fe acquisition genes in Fe-deficient Arabidopsis, cucumber and pea plants, like the genes for ferric reductases AtFRO2, PsFRO1 and CsFRO1; iron transporters AtIRT1, PsRIT1 and CsIRT1; H(+) -ATPase CsHA1; and transcription factors AtFIT, AtbHLH38, and AtbHLH39. Interestingly, the limitation of the expression of Fe-acquisition genes by hypoxia did not occur in the Arabidopsis ethylene constitutive mutant ctr1, which suggests that the negative effect of hypoxia is related to ethylene, an hormone involved in the upregulation of Fe acquisition genes. As for hypoxia, results obtained by applying bicarbonate to the nutrient solution suggests that ethylene is also involved in its negative effect, since ACC (1-aminocyclopropane-1-carboxylic acid; ethylene precursor) partially reversed the negative effect of bicarbonate on the expression of Fe acquisition genes. Taken together, the results obtained show that hypoxia and bicarbonate could induce Fe chlorosis by limiting the expression of Fe acquisition genes, probably because each factor negatively affects different steps of ethylene synthesis and/or signaling. © 2013 Scandinavian Plant Physiology Society.

Acute intermittent hypoxia and rehabilitative training following cervical spinal injury alters neuronal hypoxia- and plasticity-associated protein expression.

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Hassan, Atiq; Arnold, Breanna M; Caine, Sally; Toosi, Behzad M; Verge, Valerie M K; Muir, Gillian D

2018-01-01

One of the most promising approaches to improve recovery after spinal cord injury (SCI) is the augmentation of spontaneously occurring plasticity in uninjured neural pathways. Acute intermittent hypoxia (AIH, brief exposures to reduced O2 levels alternating with normal O2 levels) initiates plasticity in respiratory systems and has been shown to improve recovery in respiratory and non-respiratory spinal systems after SCI in experimental animals and humans. Although the mechanism by which AIH elicits its effects after SCI are not well understood, AIH is known to alter protein expression in spinal neurons in uninjured animals. Here, we examine hypoxia- and plasticity-related protein expression using immunofluorescence in spinal neurons in SCI rats that were treated with AIH combined with motor training, a protocol which has been demonstrated to improve recovery of forelimb function in this lesion model. Specifically, we assessed protein expression in spinal neurons from animals with incomplete cervical SCI which were exposed to AIH treatment + motor training either for 1 or 7 days. AIH treatment consisted of 10 episodes of AIH: (5 min 11% O2: 5 min 21% O2) for 7 days beginning at 4 weeks post-SCI. Both 1 or 7 days of AIH treatment + motor training resulted in significantly increased expression of the transcription factor hypoxia-inducible factor-1α (HIF-1α) relative to normoxia-treated controls, in neurons both proximal (cervical) and remote (lumbar) to the SCI. All other markers examined were significantly elevated in the 7 day AIH + motor training group only, at both cervical and lumbar levels. These markers included vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and phosphorylated and nonphosphorylated forms of the BDNF receptor tropomyosin-related kinase B (TrkB). In summary, AIH induces plasticity at the cellular level after SCI by altering the expression of major plasticity- and hypoxia-related proteins at spinal regions

Intermittent Hypoxia Enhances Functional Connectivity of Midcervical Spinal Interneurons

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Streeter, Kristi A.; Sunshine, Michael D.; Patel, Shreya; Gonzalez-Rothi, Elisa J.; Reier, Paul J.

2017-01-01

Brief, intermittent oxygen reductions [acute intermittent hypoxia (AIH)] evokes spinal plasticity. Models of AIH-induced neuroplasticity have focused on motoneurons; however, most midcervical interneurons (C-INs) also respond to hypoxia. We hypothesized that AIH would alter the functional connectivity between C-INs and induce persistent changes in discharge. Bilateral phrenic nerve activity was recorded in anesthetized and ventilated adult male rats and a multielectrode array was used to record C4/5 spinal discharge before [baseline (BL)], during, and 15 min after three 5 min hypoxic episodes (11% O2, H1–H3). Most C-INs (94%) responded to hypoxia by either increasing or decreasing firing rate. Functional connectivity was examined by cross-correlating C-IN discharge. Correlograms with a peak or trough were taken as evidence for excitatory or inhibitory connectivity between C-IN pairs. A subset of C-IN pairs had increased excitatory cross-correlations during hypoxic episodes (34%) compared with BL (19%; p phrenic motoneurons and excitatory inputs to these “pre-phrenic” cells increased during AIH. We conclude that AIH alters connectivity of the midcervical spinal network. To our knowledge, this is the first demonstration that AIH induces plasticity within the propriospinal network. SIGNIFICANCE STATEMENT Acute intermittent hypoxia (AIH) can trigger spinal plasticity associated with sustained increases in respiratory, somatic, and/or autonomic motor output. The impact of AIH on cervical spinal interneuron (C-IN) discharge and connectivity is unknown. Our results demonstrate that AIH recruits excitatory C-INs into the spinal respiratory (phrenic) network. AIH also enhances excitatory and reduces inhibitory connections among the C-IN network. We conclude that C-INs are part of the respiratory, somatic, and/or autonomic response to AIH, and that propriospinal plasticity may contribute to sustained increases in motor output after AIH. PMID:28751456

HRGFish: A database of hypoxia responsive genes in fishes

Science.gov (United States)

Rashid, Iliyas; Nagpure, Naresh Sahebrao; Srivastava, Prachi; Kumar, Ravindra; Pathak, Ajey Kumar; Singh, Mahender; Kushwaha, Basdeo

2017-02-01

Several studies have highlighted the changes in the gene expression due to the hypoxia response in fishes, but the systematic organization of the information and the analytical platform for such genes are lacking. In the present study, an attempt was made to develop a database of hypoxia responsive genes in fishes (HRGFish), integrated with analytical tools, using LAMPP technology. Genes reported in hypoxia response for fishes were compiled through literature survey and the database presently covers 818 gene sequences and 35 gene types from 38 fishes. The upstream fragments (3,000 bp), covered in this database, enables to compute CG dinucleotides frequencies, motif finding of the hypoxia response element, identification of CpG island and mapping with the reference promoter of zebrafish. The database also includes functional annotation of genes and provides tools for analyzing sequences and designing primers for selected gene fragments. This may be the first database on the hypoxia response genes in fishes that provides a workbench to the scientific community involved in studying the evolution and ecological adaptation of the fish species in relation to hypoxia.

HIF-2α Expression Regulates Sprout Formation into 3D Fibrin Matrices in Prolonged Hypoxia in Human Microvascular Endothelial Cells.

Science.gov (United States)

Nauta, Tessa D; Duyndam, Monique C A; Weijers, Ester M; van Hinsbergh, Victor M W; Koolwijk, Pieter

2016-01-01

During short-term hypoxia, Hypoxia Inducible Factors (particular their subunits HIF-1α and HIF-2α) regulate the expression of many genes including the potent angiogenesis stimulator VEGF. However, in some pathological conditions chronic hypoxia occurs and is accompanied by reduced angiogenesis. We investigated the effect of prolonged hypoxia on the proliferation and sprouting ability of human microvascular endothelial cells and the involvement of the HIFs and Dll4/Notch signaling. Human microvascular endothelial cells (hMVECs), cultured at 20% oxygen for 14 days and seeded on top of 3D fibrin matrices, formed sprouts when stimulated with VEGF-A/TNFα. In contrast, hMVECs precultured at 1% oxygen for 14 days were viable and proliferative, but did not form sprouts into fibrin upon VEGF-A/TNFα stimulation at 1% oxygen. Silencing of HIF-2α with si-RNA partially restored the inhibition of endothelial sprouting, whereas HIF-1α or HIF-3α by si-RNA had no effect. No involvement of Dll4/Notch pathway in the inhibitory effect on endothelial sprouting by prolonged hypoxia was found. In addition, hypoxia decreased the production of urokinase-type plasminogen activator (uPA), needed for migration and invasion, without a significant effect on its inhibitor PAI-1. This was independent of HIF-2α, as si-HIF-2α did not counteract uPA reduction. Prolonged culturing of hMVECs at 1% oxygen inhibited endothelial sprouting into fibrin. Two independent mechanisms contribute. Silencing of HIF-2α with si-RNA partially restored the inhibition of endothelial sprouting pointing to a HIF-2α-dependent mechanism. In addition, reduction of uPA contributed to reduced endothelial tube formation in a fibrin matrix during prolonged hypoxia.

Cuticle ultrastructure, cuticular lipid composition, and gene expression in hypoxia-stressed Arabidopsis stems and leaves.

Science.gov (United States)

Kim, Hyojin; Choi, Dongsu; Suh, Mi Chung

2017-06-01

An increased permeability of the cuticle is closely associated with downregulation of genes involved in cuticular lipid synthesis in hypoxia-stressed Arabidopsis and may allow plants to cope with oxygen deficiency. The hydrophobic cuticle layer consisting of cutin polyester and cuticular wax is the first barrier to protect the aerial parts of land plants from environmental stresses. In the present study, we investigated the role of cuticle membrane in Arabidopsis responses to oxygen deficiency. TEM analysis showed that the epidermal cells of hypoxia-treated Arabidopsis stems and leaves possessed a thinner electron-translucent cuticle proper and a more electron-dense cuticular layer. A reduction in epicuticular wax crystal deposition was observed in SEM images of hypoxia-treated Arabidopsis stem compared with normoxic control. Cuticular transpiration was more rapid in hypoxia-stressed leaves than in normoxic control. Total wax and cutin loads decreased by approximately 6-12 and 12-22%, respectively, and the levels of C29 alkanes, secondary alcohols, and ketones, C16:0 ω-hydroxy fatty acids, and C18:2 dicarboxylic acids were also prominently reduced in hypoxia-stressed Arabidopsis leaves and/or stems relative to normoxic control. Genome-wide transcriptome and quantitative RT-PCR analyses revealed that the expression of several genes involved in the biosynthesis and transport of cuticular waxes and cutin monomers were downregulated more than fourfold, but no significant alterations were detected in the transcript levels of fatty acid biosynthetic genes, BCCP2, PDH-E1α, and ENR1 in hypoxia-treated Arabidopsis stems and leaves compared with normoxic control. Taken together, an increased permeability of the cuticle is closely associated with downregulation of genes involved in cuticular lipid synthesis in hypoxia-stressed Arabidopsis. The present study elucidates one of the cuticle-related adaptive responses that may allow plants to cope with low oxygen levels.

Preserved cardiac mitochondrial function and reduced ischaemia/reperfusion injury afforded by chronic continuous hypoxia: Role of opioid receptors

Czech Academy of Sciences Publication Activity Database

Maslov, L. N.; Naryzhnaya, N. V.; Prokudina, E. S.; Kolář, František; Gorbunov, A. S.; Zhang, Y.; Wang, H.; Tsibulnikov, S.Yu.; Portnichenko, A. G.; Lasukova, T. V.; Lishmanov, Yu. B.

2015-01-01

Roč. 42, č. 5 (2015), s. 496-501 ISSN 1440-1681 R&D Projects: GA ČR(CZ) GAP303/12/1162 Institutional support: RVO:67985823 Keywords : cardioprotection * chronic hypoxia * ischaemia/reperfusion * mitochondrial function * opioid receptors Subject RIV: ED - Physiology Impact factor: 2.004, year: 2015

Assessment of Hypoxia in the Stroma of Patient-Derived Pancreatic Tumor Xenografts

Energy Technology Data Exchange (ETDEWEB)

Lohse, Ines; Lourenco, Corey; Ibrahimov, Emin; Pintilie, Melania [Ontario Cancer Institute and Campbell Family Cancer Research Institute, Princess Margaret Cancer Center, University Health Network, 610 University Ave., Toronto, ON M5G2M9 (Canada); Tsao, Ming-Sound [Ontario Cancer Institute and Campbell Family Cancer Research Institute, Princess Margaret Cancer Center, University Health Network, 610 University Ave., Toronto, ON M5G2M9 (Canada); Department of Pathology, University Health Network, 200 Elizabeth Street, Toronto, ON M5G2C4 (Canada); Department of Laboratory Medicine and Pathobiology, 27 King’s College Circle, University of Toronto, Toronto, ON M5S1A1 (Canada); Hedley, David W., E-mail: david.hedley@uhn.ca [Ontario Cancer Institute and Campbell Family Cancer Research Institute, Princess Margaret Cancer Center, University Health Network, 610 University Ave., Toronto, ON M5G2M9 (Canada); Departments of Medical Biophysics University of Toronto, 610 University Ave., Toronto, ON M5G2M9 (Canada); Departments of Medicine, University of Toronto, 610 University Ave., Toronto, ON M5G2M9 (Canada); Department of Medical Oncology and Hematology, Princess Margaret Cancer Center, 610 University Ave., Toronto, ON M5G2M9 (Canada)

2014-02-26

The unusually dense stroma of pancreatic cancers is thought to play an important role in their biological aggression. The presence of hypoxia is also considered an adverse prognostic factor. Although it is usually assumed that this is the result of effects of hypoxia on the epithelial component, it is possible that hypoxia exerts indirect effects via the tumor stroma. We therefore measured hypoxia in the stroma of a series of primary pancreatic cancer xenografts. Nine patient-derived pancreatic xenografts representing a range of oxygenation levels were labeled by immunohistochemistry for EF5 and analyzed using semi-automated pattern recognition software. Hypoxia in the tumor and stroma was correlated with tumor growth and metastatic potential. The extent of hypoxia varied from 1%–39% between the different models. EF5 labeling in the stroma ranged from 0–20% between models, and was correlated with the level of hypoxia in the tumor cell area, but not microvessel density. Tumor hypoxia correlated with spontaneous metastasis formation with the exception of one hypoxic model that showed disproportionately low levels of hypoxia in the stroma and was non-metastatic. Our results demonstrate that hypoxia exists in the stroma of primary pancreatic cancer xenografts and suggest that stromal hypoxia impacts the metastatic potential.

Chondroprotective effect of zinc oxide nanoparticles in conjunction with hypoxia on bovine cartilage-matrix synthesis.

Science.gov (United States)

Mirza, Eraj Humayun; Pan-Pan, Chong; Wan Ibrahim, Wan Mohd Azhar Bin; Djordjevic, Ivan; Pingguan-Murphy, Belinda

2015-11-01

Articular cartilage is a tissue specifically adapted to a specific niche with a low oxygen tension (hypoxia), and the presence of such conditions is a key factor in regulating growth and survival of chondrocytes. Zinc deficiency has been linked to cartilage-related disease, and presence of Zinc is known to provide antibacterial benefits, which makes its inclusion attractive in an in vitro system to reduce infection. Inclusion of 1% zinc oxide nanoparticles (ZnONP) in poly octanediol citrate (POC) polymer cultured in hypoxia has not been well determined. In this study we investigated the effects of ZnONP on chondrocyte proliferation and matrix synthesis cultured under normoxia (21% O2 ) and hypoxia (5% O2 ). We report an upregulation of chondrocyte proliferation and sulfated glycosaminoglycan (S-GAG) in hypoxic culture. Results demonstrate a synergistic effect of oxygen concentration and 1% ZnONP in up-regulation of anabolic gene expression (Type II collagen and aggrecan), and a down regulation of catabolic (MMP-13) gene expression. Furthermore, production of transcription factor hypoxia-inducible factor 1A (HIF-1A) in response to hypoxic condition to regulate chondrocyte survival under hypoxia is not affected by the presence of 1% ZnONP. Presence of 1% ZnONP appears to act to preserve homeostasis of cartilage in its hypoxic environment. © 2015 Wiley Periodicals, Inc.

Hypoxia, Epithelial-Mesenchymal Transition, and TET-Mediated Epigenetic Changes

Directory of Open Access Journals (Sweden)

Shih-Han Kao

2016-02-01

Full Text Available Tumor hypoxia is a pathophysiologic outcome of disrupted microcirculation with inadequate supply of oxygen, leading to enhanced proliferation, epithelial-mesenchymal transition (EMT, metastasis, and chemo-resistance. Epigenetic changes induced by hypoxia are well documented, and they lead to tumor progression. Recent advances show that DNA demethylation mediated by the Ten-eleven translocation (TET proteins induces major epigenetic changes and controls key steps of cancer development. TET enzymes serve as 5mC (5-methylcytosine-specific dioxygenases and cause DNA demethylation. Hypoxia activates the expression of TET1, which also serves as a co-activator of HIF-1α transcriptional regulation to modulate HIF-1α downstream target genes and promote epithelial-mesenchymal transition. As HIF is a negative prognostic factor for tumor progression, hypoxia-activated prodrugs (HAPs may provide a favorable therapeutic approach to lessen hypoxia-induced malignancy.

Modulation of radioprotective effects of respiratory hypoxia by changing the duration of hypoxia before irradiation and by combining hypoxia and administration of hemopoiesis-stimulating agents

Energy Technology Data Exchange (ETDEWEB)

Vacek, A.; Hofer, M. [Czechoslovak Academy of Sciences, Brno (Czech Republic). Inst. of Biophysics; Tacev, T. [Masaryk Memorial Cancer Inst., Brno (Czechoslovakia)

2001-09-01

Aim: Analysis of radioprotective effect of respiratory hypoxia on hemopoietic tissue and enhancement of this effect by hemopoietic activation. Material and methods: In mice breathing hypoxic gas mixture during total body gamma irradiation the recovery of pluripotent and committed granulocyte-macrophage progenitor cells and animal lethality were determined. Results: In mice forced to breathe 10% O{sub 2} and 8% O{sub 2} during irradiation, the oxygen tension in the spleen decreased to 40% and 20%, respectively, of control values. Hypoxia mitigated the lethal effect of gamma-rays and improved the recovery of hemopoiesis in compartments of pluripotent and committed progenitor cells. Enhancement of the proliferative activity in hemopoietic tissue by a cytokine (rmGM-CSF) or an immunomodulator (dextran sulfate) increased the effect of hypoxic radioprotection, while elimination of proliferative cells by hydroxyurea decreased the radioprotective effect. Adaptation of experimental animals to hypoxic conditions was found to reduce the radioprotective effect without influencing tissue partial oxygen pressure lowered by hypoxic conditions. Conclusion: The data presented confirm the radioprotective effect of 10% and 8% O{sub 2} respiratory hypoxia on hemopoiesis. These findings may represent a way out for further experimental and clinical research aimed at considering differential protection of various tissues by hypoxia. (orig.) [German] Ziel: Analyse von radioprotektiver Wirkung der respiratorischen Hypoxie auf das haematopoetische Gewebe und Verstaerkung dieses Effekts durch Aktivierung der Haematopoese. Material und Methode: Es wurden bei Maeusen, die 10%igen und 8%igen Sauerstoff waehrend der Bestrahlung geatmet haben, die Erholung von pluripotenten und unipotenten Progenitorzellen und das Ueberleben nach einer letalen Strahlendosis untersucht. Ergebnisse: Bei Maeusen, die 10% und 8% Sauerstoff waehrend der Strahlentherapie geatmet haben, sank der Sauerstoffpartialdruck

Decreased extracellular adenosine levels lead to loss of hypoxia-induced neuroprotection after repeated episodes of exposure to hypoxia.

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Mei Cui

Full Text Available Achieving a prolonged neuroprotective state following transient ischemic attacks (TIAs is likely to effectively reduce the brain damage and neurological dysfunction associated with recurrent stroke. HPC is a phenomenon in which advanced exposure to mild hypoxia reduces the stroke volume produced by a subsequent TIA. However, this neuroprotection is not long-lasting, with the effects reaching a peak after 3 days. Therefore, in this study, we investigated the use of multiple episodes of hypoxic exposure at different time intervals to induce longer-term protection in a mouse stroke model. C57BL/6 mice were subjected to different hypoxic preconditioning protocols: a single episode of HPC or five identical episodes at intervals of 3 days (E3d HPC or 6 days (E6d HPC. Three days after the last hypoxic exposure, temporary middle cerebral artery occlusion (MCAO was induced. The effects of these HPC protocols on hypoxia-inducible factor (HIF regulated gene mRNA expression were measured by quantitative PCR. Changes in extracellular adenosine concentrations, known to exert neuroprotective effects, were also measured using in vivo microdialysis and high pressure liquid chromatography (HPLC. Neuroprotection was provided by E6d HPC but not E3d HPC. HIF-regulated target gene expression increased significantly following all HPC protocols. However, E3d HPC significantly decreased extracellular adenosine and reduced cerebral blood flow in the ischemic region with upregulated expression of the adenosine transporter, equilibrative nucleoside transporter 1 (ENT1. An ENT1 inhibitor, propentofylline increased the cerebral blood flow and re-established neuroprotection in E3d HPC. Adenosine receptor specific antagonists showed that adenosine mainly through A1 receptor mediates HPC induced neuroprotection. Our data indicate that cooperation of HIF-regulated genes and extracellular adenosine is necessary for HPC-induced neuroprotection.

Radiation, hypoxia and genetic stimulation: implications for future therapies

International Nuclear Information System (INIS)

Adams, Gerald E.; Hasan, Na'il M.; Joiner, Michael C.

1997-01-01

The cellular stress response, whereby very low doses of cytotoxic agents induce resistance to much higher doses, is an evolutionary defence mechanism and is stimulated following challenges by numerous chemical, biological and physical agents including particularly radiation, drugs, heat and hypoxia. There is much homology in the effects of these agents which are manifest through the up-regulation of various genetic pathways. Low-dose radiation stress influences processes involved in cell-cycle control, signal transduction pathways, radiation sensitivity, changes in cell adhesion and cell growth. There is also homology between radiation and other cellular stress agents, particularly hypoxia. Whereas traditionally, hypoxia was regarded mainly as an agent conferring resistance to radiation, there is now much evidence illustrating the cytokine-like properties of hypoxia as well as radiation. Stress phenomena are likely to be important in risks arising from low doses of radiation. Conversely, exploitation of the stress response in settings appropriate to therapy can be particularly beneficial not only in regard to radiation alone but in combinations of radiation and drugs. Similarly, tissue hypoxia can be exploited in novel ways of enhancing therapeutic efficacy. Bioreductive drugs, which are cytotoxically activated in hypoxic regions of tissue, can be rendered even more effective by hypoxia-induced increased expression of enzyme reductases. Nitric oxide pathways are influenced by hypoxia thereby offering possibilities for novel vascular based therapies. Other approaches are discussed

Hypoxia-inducible factor-1α upregulation in microglia following hypoxia protects against ischemia-induced cerebral infarction.

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Huang, Tao; Huang, Weiyi; Zhang, Zhiqiang; Yu, Lei; Xie, Caijun; Zhu, Dongan; Peng, Zizhuang; Chen, Jiehan

2014-10-01

Activated microglia were considered to be the toxic inflammatory mediators that induce neuron degeneration after brain ischemia. Hypoxia can enhance the expression of hypoxia-inducible factor-1α (HIF-1α) in microglia and cause microglial activation. However, intermittent hypoxia has been reported recently to be capable of protecting the body from myocardial ischemia. We established a high-altitude environment as the hypoxic condition in this study. The hypoxic condition displayed a neuroprotective effect after brain ischemia, and mice exposed to this condition presented better neurological performance and smaller infarct size. At the same time, a high level of HIF-1α, low level of isoform of nitric oxide synthase, and a reduction in microglial activation were also seen in ischemic focus of hypoxic mice. However, this neuroprotective effect could be blocked by 2-methoxyestradiol, the HIF-1α inhibitor. Our finding suggested that HIF-1α expression was involved in microglial activation in vitro and was regulated by oxygen supply. The microglia were inactivated by re-exposure to hypoxia, which might be due to overexpression of HIF-1α. These results indicated that hypoxic conditions can be exploited to achieve maximum neuroprotection after brain ischemia. This mechanism possibly lies in microglial inactivation through regulation of the expression of HIF-1α.

Chronic Prenatal Hypoxia Down-Regulated BK Channel Β1 Subunits in Mesenteric Artery Smooth Muscle Cells of the Offspring

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Bailin Liu

2018-02-01

Full Text Available Background/Aims: Chronic hypoxia in utero could impair vascular functions in the offspring, underlying mechanisms are unclear. This study investigated functional alteration in large-conductance Ca2+-activated K+ (BK channels in offspring mesenteric arteries following prenatal hypoxia. Methods: Pregnant rats were exposed to normoxic control (21% O2, Con or hypoxic (10.5% O2, Hy conditions from gestational day 5 to 21, their 7-month-old adult male offspring were tested for blood pressure, vascular BK channel functions and expression using patch clamp and wire myograh technique, western blotting, and qRT-PCR. Results: Prenatal hypoxia increased pressor responses and vasoconstrictions to phenylephrine in the offspring. Whole-cell currents density of BK channels and amplitude of spontaneous transient outward currents (STOCs, not the frequency, were significantly reduced in Hy vascular myocytes. The sensitivity of BK channels to voltage, Ca2+, and tamoxifen were reduced in Hy myocytes, whereas the number of channels per patch and the single-channel conductance were unchanged. Prenatal hypoxia impaired NS1102- and tamoxifen-mediated relaxation in mesenteric arteries precontracted with phenylephrine in the presence of Nω-nitro-L-arginine methyl ester. The mRNA and protein expression of BK channel β1, not the α-subunit, was decreased in Hy mesenteric arteries. Conclusions: Impaired BK channel β1-subunits in vascular smooth muscle cells contributed to vascular dysfunction in the offspring exposed to prenatal hypoxia.

Hypoxia-based strategies for regenerative dentistry-Views from the different dental fields.

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Müller, Anna Sonja; Janjić, Klara; Lilaj, Bledar; Edelmayer, Michael; Agis, Hermann

2017-09-01

The understanding of the cell biological processes underlying development and regeneration of oral tissues leads to novel regenerative approaches. Over the past years, knowledge on key roles of the hypoxia-based response has become more profound. Based on these findings, novel regenerative approaches for dentistry are emerging, which target cellular oxygen sensors. These approaches include hypoxia pre-conditioning and pharmacologically simulated hypoxia. The increase in studies on hypoxia and hypoxia-based strategies in regenerative dentistry highlights the growing attention to hypoxia's role in regeneration and its underlying biology, as well as its application in a therapeutic setting. In this narrative review, we present the current knowledge on the role of hypoxia in oral tissues and review the proposed hypoxia-based approaches in different fields of dentistry, including endodontics, orthodontics, periodontics, and oral surgery. Copyright © 2017 Elsevier Ltd. All rights reserved.

Region-specific adaptations in determinants of rat skeletal muscle oxygenation to chronic hypoxia.

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Wust, R.C.; Jaspers, R.T.; Heyst, A.F.J. van; Hopman, M.T.E.; Hoofd, L.J.C.; Laarse, W.J. van der; Degens, H.

2009-01-01

Chronic exposure to hypoxia is associated with muscle atrophy (i.e., a reduction in muscle fiber cross-sectional area), reduced oxidative capacity, and capillary growth. It is controversial whether these changes are muscle and fiber type specific. We hypothesized that different regions of the same

Fatty Acid Uptake and Lipid Storage Induced by HIF-1α Contribute to Cell Growth and Survival after Hypoxia-Reoxygenation

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Karim Bensaad

2014-10-01

Full Text Available Summary: An in vivo model of antiangiogenic therapy allowed us to identify genes upregulated by bevacizumab treatment, including Fatty Acid Binding Protein 3 (FABP3 and FABP7, both of which are involved in fatty acid uptake. In vitro, both were induced by hypoxia in a hypoxia-inducible factor-1α (HIF-1α-dependent manner. There was a significant lipid droplet (LD accumulation in hypoxia that was time and O2 concentration dependent. Knockdown of endogenous expression of FABP3, FABP7, or Adipophilin (an essential LD structural component significantly impaired LD formation under hypoxia. We showed that LD accumulation is due to FABP3/7-dependent fatty acid uptake while de novo fatty acid synthesis is repressed in hypoxia. We also showed that ATP production occurs via β-oxidation or glycogen degradation in a cell-type-dependent manner in hypoxia-reoxygenation. Finally, inhibition of lipid storage reduced protection against reactive oxygen species toxicity, decreased the survival of cells subjected to hypoxia-reoxygenation in vitro, and strongly impaired tumorigenesis in vivo. : Bensaad et al. now show that FABP3 and FABP7 are induced by HIF-1α and lead to a significant lipid droplet (LD accumulation in hypoxia. In hypoxia-reoxygenation, ATP production occurs via fatty acid β-oxidation or glycogen degradation in a cell-type-dependent manner, while inhibition of LD formation increases ROS toxicity and decreases cell survival in vitro and strongly impairs tumorigenesis in vivo.

Hypoxia as a biomarker for radioresistant cancer stem cells.

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Peitzsch, Claudia; Perrin, Rosalind; Hill, Richard P; Dubrovska, Anna; Kurth, Ina

2014-08-01

Tumor initiation, growth and relapse after therapy are thought to be driven by a population of cells with stem cell characteristics, named cancer stem cells (CSC). The regulation of their radiation resistance and their maintenance is poorly understood. CSC are believed to reside preferentially in special microenvironmental niches located within tumor tissues. The features of these niches are of crucial importance for CSC self-renewal, metastatic potential and therapy resistance. One of the characteristics of solid tumors is occurrence of less oxygenated (hypoxic regions), which are believed to serve as so-called hypoxic niches for CSC. The purpose of this review was the critical discussion of the supportive role of hypoxia and hypoxia-related pathways during cancer progression and radiotherapy resistance and the relevance for therapeutic implications in the clinic. It is generally known since decades that hypoxia inside solid tumors impedes chemo- and radiotherapy. However, there is limited evidence to date that targeting hypoxic regions during conventional therapy is effective. Nonetheless improved hypoxia-imaging technologies and image guided individualized hypoxia targeted therapy in conjunction with the development of novel molecular targets may be able to challenge the protective effect on the tumor provided by hypoxia.

Radiation-induced hypoxia may perpetuate late normal tissue injury

International Nuclear Information System (INIS)

Vujaskovic, Zeljko; Anscher, Mitchell S.; Feng, Q.-F.; Rabbani, Zahid N.; Amin, Khalid; Samulski, Thaddeus S.; Dewhirst, Mark W.; Haroon, Zishan A.

2001-01-01

Purpose: The purpose of this study was to determine whether or not hypoxia develops in rat lung tissue after radiation. Methods and Materials: Fisher-344 rats were irradiated to the right hemithorax using a single dose of 28 Gy. Pulmonary function was assessed by measuring the changes in respiratory rate every 2 weeks, for 6 months after irradiation. The hypoxia marker was administered 3 h before euthanasia. The tissues were harvested at 6 weeks and 6 months after irradiation and processed for immunohistochemistry. Results: A moderate hypoxia was detected in the rat lungs at 6 weeks after irradiation, before the onset of functional or histopathologic changes. The more severe hypoxia, that developed at the later time points (6 months) after irradiation, was associated with a significant increase in macrophage activity, collagen deposition, lung fibrosis, and elevation in the respiratory rate. Immunohistochemistry studies revealed an increase in TGF-β, VEGF, and CD-31 endothelial cell marker, suggesting a hypoxia-mediated activation of the profibrinogenic and proangiogenic pathways. Conclusion: A new paradigm of radiation-induced lung injury should consider postradiation hypoxia to be an important contributing factor mediating a continuous production of a number of inflammatory and fibrogenic cytokines

Mesenchymal Stem Cells Respond to Hypoxia by Increasing Diacylglycerols.

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Lakatos, Kinga; Kalomoiris, Stefanos; Merkely, Béla; Nolta, Jan A; Fierro, Fernando A

2016-02-01

Mesenchymal stem cells (MSC) are currently being tested clinically for a plethora of conditions, with most approaches relying on the secretion of paracrine signals by MSC to modulate the immune system, promote wound healing, and induce angiogenesis. Hypoxia has been shown to affect MSC proliferation, differentiation, survival and secretory profile. Here, we investigate changes in the lipid composition of human bone marrow-derived MSC after exposure to hypoxia. Using mass spectrometry, we compared the lipid profiles of MSC derived from five different donors, cultured for two days in either normoxia (control) or hypoxia (1% oxygen). Hypoxia induced a significant increase of total triglycerides, fatty acids and diacylglycerols (DG). Remarkably, reduction of DG levels using the phosphatidylcholine-specific phospholipase C inhibitor D609 inhibited the secretion of VEGF and Angiopoietin-2, but increased the secretion of interleukin-8, without affecting significantly their respective mRNA levels. Functionally, incubation of MSC in hypoxia with D609 inhibited the potential of the cells to promote migration of human endothelial cells in a wound/scratch assay. Hence, we show that hypoxia induces in MSC an increase of DG that may affect the angiogenic potential of these cells. © 2015 Wiley Periodicals, Inc.

Mitochondrial Respiration in Insulin-Producing β-Cells: General Characteristics and Adaptive Effects of Hypoxia.

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Hals, Ingrid K; Bruerberg, Simon Gustafson; Ma, Zuheng; Scholz, Hanne; Björklund, Anneli; Grill, Valdemar

2015-01-01

To provide novel insights on mitochondrial respiration in β-cells and the adaptive effects of hypoxia. Insulin-producing INS-1 832/13 cells were exposed to 18 hours of hypoxia followed by 20-22 hours re-oxygenation. Mitochondrial respiration was measured by high-resolution respirometry in both intact and permeabilized cells, in the latter after establishing three functional substrate-uncoupler-inhibitor titration (SUIT) protocols. Concomitant measurements included proteins of mitochondrial complexes (Western blotting), ATP and insulin secretion. Intact cells exhibited a high degree of intrinsic uncoupling, comprising about 50% of oxygen consumption in the basal respiratory state. Hypoxia followed by re-oxygenation increased maximal overall respiration. Exploratory experiments in peremabilized cells could not show induction of respiration by malate or pyruvate as reducing substrates, thus glutamate and succinate were used as mitochondrial substrates in SUIT protocols. Permeabilized cells displayed a high capacity for oxidative phosphorylation for both complex I- and II-linked substrates in relation to maximum capacity of electron transfer. Previous hypoxia decreased phosphorylation control of complex I-linked respiration, but not in complex II-linked respiration. Coupling control ratios showed increased coupling efficiency for both complex I- and II-linked substrates in hypoxia-exposed cells. Respiratory rates overall were increased. Also previous hypoxia increased proteins of mitochondrial complexes I and II (Western blotting) in INS-1 cells as well as in rat and human islets. Mitochondrial effects were accompanied by unchanged levels of ATP, increased basal and preserved glucose-induced insulin secretion. Exposure of INS-1 832/13 cells to hypoxia, followed by a re-oxygenation period increases substrate-stimulated respiratory capacity and coupling efficiency. Such effects are accompanied by up-regulation of mitochondrial complexes also in pancreatic islets

'Molecular switch' vectors for hypoxia- and radiation-mediated gene therapy of cancer

International Nuclear Information System (INIS)

Greco, O.; Marples, B.; Joiner, M.C.; Scott, S.D.

2003-01-01

Intratumoral areas of low oxygen concentration are known to be refractive to radiotherapy treatment. However, this physiological condition can be exploited for selective cancer gene therapy. We have developed a series of synthetic promoters selectively responsive to both hypoxia and ionizing radiation (IR). These promoters contain hypoxia regulatory elements (HREs) from the erythropoietin (Epo), the phosphoglycerate kinase1(PGK1) and vascular endothelial growth factor (VEGF) genes, and/or IR-responsive CArG elements from the Early Growth Response 1 (Egr1) gene. The HRE and CArG promoters were able to regulate expression of reporter and suicide genes in human tumor cells, following corresponding stimulation with hypoxia (0.1% O2) or X-irradiation (5Gy) [Greco et al, 2002, Gene Therapy 9:1403]. Furthermore, the chimeric HRE + CArG promoters could be activated by these stimuli independently or even more significantly when given in combination, with the Epo HRE/CArG promoter proving to be the most responsive and robust. In order to amplify and maintain transgene expression even following withdrawal of the triggering stimuli, we have developed a 'molecular switch' system [Scott et al, 2000, Gene Therapy 7:1121]. This 'switch' system has now been engineered as a single vector molecule, containing HRE and CArG promoters. This new series of HRE/CArG switch vectors have been tested in a herpes simplex thymidine kinase (HSVtk)/ganciclovir (GCV) suicide gene assay. Results indicate that a) higher and more selective tumor cell kill is achieved with the switch when compared with the HRE and CArG promoters directly driving HSVtk expression and b) the Epo HRE/CArG switch vectors appear to function as efficiently as the strong constitutive cytomegalovirus (CMV) promoter construct

The role of wind field induced flow velocities in destratification and hypoxia reduction at Meiling Bay of large shallow Lake Taihu, China.

Science.gov (United States)

Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Wencai; Wang, Jianwei; Gao, Xiaomeng; Khan, Hafiz Osama Sarwar; Pan, Baozhu; Acharya, Kumud

2018-01-01

Wind induced flow velocity patterns and associated thermal destratification can drive to hypoxia reduction in large shallow lakes. The effects of wind induced hydrodynamic changes on destratification and hypoxia reduction were investigated at the Meiling bay (N 31° 22' 56.4″, E 120° 9' 38.3″) of Lake Taihu, China. Vertical flow velocity profile analysis showed surface flow velocities consistency with the wind field and lower flow velocity profiles were also consistent (but with delay response time) when the wind speed was higher than 6.2 m/s. Wind field and temperature found the control parameters for hypoxia reduction and for water quality conditions at the surface and bottom profiles of lake. The critical temperature for hypoxia reduction at the surface and the bottom profile was ≤24.1C° (below which hypoxic conditions were found reduced). Strong prevailing wind field (onshore wind directions ESE, SE, SSE and E, wind speed ranges of 2.4-9.1 m/s) reduced the temperature (22C° to 24.1C°) caused reduction of hypoxia at the near surface with a rise in water levels whereas, low to medium prevailing wind field did not supported destratification which increased temperature resulting in increased hypoxia. Non-prevailing wind directions (offshore) were not found supportive for the reduction of hypoxia in study area due to less variable wind field. Daytime wind field found more variable (as compared to night time) which increased the thermal destratification during daytime and found supportive for destratification and hypoxia reduction. The second order exponential correlation found between surface temperature and Chlorophyll-a (R 2 : 0.2858, Adjusted R-square: 0.2144 RMSE: 4.395), Dissolved Oxygen (R 2 : 0.596, Adjusted R-square: 0.5942, RMSE: 0.3042) concentrations. The findings of the present study reveal the driving mechanism of wind induced thermal destratification and hypoxic conditions, which may further help to evaluate the wind role in eutrophication

Normobaric hypoxia training: the effects of breathing-gas flow rate on symptoms.

Science.gov (United States)

Artino, Anthony R; Folga, Richard V; Vacchiano, Charles

2009-06-01

The U.S. Navy has replaced segments of refresher low-pressure chamber instruction with normobaric hypoxia training using a reduced oxygen breathing device (ROBD). A previous training evaluation revealed that this alternative instructional paradigm is a preferred means of training experienced jet aviators to recognize and recover from hypoxia. However, findings from this earlier work also indicated that air hunger was the most commonly reported symptom during ROBD training. This finding raised concern that air hunger could have resulted from a training artifact caused by the lower breathing-gas flow rate produced by the ROBD when compared to more familiar jet aircraft breathing systems. In an effort to address this issue, a software change was made that increased ROBD mask flow from 30 to 50 L x min(-1) (LPM). The purpose of this retrospective study was to determine if there are differences in the hypoxia symptoms reported by aviators trained on the ROBD upgrade (ROBD-50) compared to those trained on the original device (ROBD-30). Hypoxia training was provided to 156 aviators using the ROBD-50, and survey results were compared to those obtained from 121 aviators trained on the ROBD-30. There was a significant decrease in the number of aviators who reported experiencing air hunger while training on the ROBD-50 (44.2%) as compared to the ROBD-30 (59.4%) [Pearson chi2 (1) = 5.45, P hunger and, therefore, may impact training fidelity.

Enhanced carotid body chemosensory activity and the cardiovascular alterations induced by intermittent hypoxia

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Rodrigo eIturriaga

2014-12-01

Full Text Available The carotid body (CB plays a main role in the maintenance of the oxygen homeostasis. The hypoxic stimulation of the CB increases the chemosensory discharge, which in turn elicits reflex sympathetic, cardiovascular and ventilatory adjustments. An exacerbate carotid chemosensory activity has been associated with human sympathetic-mediated diseases such as hypertension, insulin resistance, heart failure and obstructive sleep apnea (OSA. Indeed, the CB chemosensory discharge becomes tonically hypereactive in experimental models of OSA and heart failure. Chronic intermittent hypoxia (CIH, a main feature of OSA, enhances CB chemosensory baseline discharges in normoxia and in response to hypoxia, inducing sympathetic overactivity and hypertension. Oxidative stress, increased levels of ET-1, Angiotensin II and pro-inflammatory cytokines, along with a reduced production of NO in the CB, have been associated with the enhanced carotid chemosensory activity. In this review, we will discuss new evidence supporting a main role for the CB chemoreceptor in the autonomic and cardiorespiratory alterations induced by intermittent hypoxia, as well as the molecular mechanisms involved in the CB chemosensory potentiation.

Enhanced carotid body chemosensory activity and the cardiovascular alterations induced by intermittent hypoxia

Science.gov (United States)

Iturriaga, Rodrigo; Andrade, David C.; Del Rio, Rodrigo

2014-01-01

The carotid body (CB) plays a main role in the maintenance of the oxygen homeostasis. The hypoxic stimulation of the CB increases the chemosensory discharge, which in turn elicits reflex sympathetic, cardiovascular, and ventilatory adjustments. An exacerbate carotid chemosensory activity has been associated with human sympathetic-mediated diseases such as hypertension, insulin resistance, heart failure, and obstructive sleep apnea (OSA). Indeed, the CB chemosensory discharge becomes tonically hypereactive in experimental models of OSA and heart failure. Chronic intermittent hypoxia (CIH), a main feature of OSA, enhances CB chemosensory baseline discharges in normoxia and in response to hypoxia, inducing sympathetic overactivity and hypertension. Oxidative stress, increased levels of ET-1, Angiotensin II and pro-inflammatory cytokines, along with a reduced production of NO in the CB, have been associated with the enhanced carotid chemosensory activity. In this review, we will discuss new evidence supporting a main role for the CB chemoreceptor in the autonomic and cardiorespiratory alterations induced by intermittent hypoxia, as well as the molecular mechanisms involved in the CB chemosensory potentiation. PMID:25520668

Haemoglobin modulates NO emission and hyponasty under hypoxia-related stress in Arabidopsis thaliana

DEFF Research Database (Denmark)

Hebelstrup, Kim; van Zanten, Martijn; Mandon, Julien

2012-01-01

Nitric oxide (NO) and ethylene are signalling molecules that are synthesized in response to oxygen depletion. Non-symbiotic plant haemoglobins (Hbs) have been demonstrated to act in roots under oxygen depletion to scavenge NO. Using Arabidopsis thaliana plants, the online emission of NO or ethylene...... was directly quantified under normoxia, hypoxia (0.1–1.0% O2), or full anoxia. The production of both gases was increased with reduced expression of either of the Hb genes GLB1 or GLB2, whereas NO emission decreased in plants overexpressing these genes. NO emission in plants with reduced Hb gene expression......-nitrosylated compounds, and it is demonstrated that hypoxia substantially increased the content of S-nitrosylated compounds. A parallel up-regulation of Hb gene expression in the normoxic shoots of the flooded plants may reflect signal transmission from root to shoot via ethylene and a role for Hb in the shoots. Hb gene...

Roles of nitric oxide, nitrite and myoglobin on myocardial efficiency in trout (Oncorthynchus mykiss) and goldfish (Carassius auratus): implications for hypoxia tolerance

DEFF Research Database (Denmark)

Pedersen, Claus Lunde; Faggiano, Serena; Helbo, Signe

2010-01-01

The roles of nitric oxide synthase activity (NOS), nitrite and myoglobin (Mb) in the regulation of myocardial function during hypoxia were examined in trout and goldfish, a hypoxia-intolerant and hypoxia-tolerant species, respectively. We measured the effect of NOS inhibition, adrenaline and nitr......The roles of nitric oxide synthase activity (NOS), nitrite and myoglobin (Mb) in the regulation of myocardial function during hypoxia were examined in trout and goldfish, a hypoxia-intolerant and hypoxia-tolerant species, respectively. We measured the effect of NOS inhibition, adrenaline...... in both trout and goldfish myocardium, with trout showing a significant increase in the O2 utilization efficiency, i.e. the ratio of twitch force to O2 consumption, suggesting an increased anaerobic metabolism. NOS inhibition enhanced myocardial O2 consumption and decreased efficiency, indicating...... that mitochondrial respiration is under a tone of NOS-produced NO. When trout myocardial twitch force and O2 consumption are enhanced by adrenaline, this NO tone disappears. Consistent with its conversion to NO, nitrite reduced O2 consumption and increased myocardial efficiency in trout but not in goldfish...

Protective effect of astrocyte-conditioned medium on neurons following hypoxia and mechanical injury

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YAN Ji-wen

2013-02-01

Full Text Available 【Abstract】Objective: To investigate the protec-tive effect of mouse astrocyte-conditioned medium (ACM on hypoxic and mechanically injured neurons by a cell model in vitro, and to explore the possible mechanism. Methods: The model of hypoxic neuronal injury was caused by 3% O 2 in three-gas incubator. Neurons were cul-tured with ordinary medium or 20% ACM respectively and randomly divided into hypoxic group (hypoxia for 4, 8, 24 h and marked as H4R0, H8R0, H24R0 and hypoxia reoxygenation group (H4R24, H8R24, H24R24. Mechanical injury model was developed by scratching neurons cultured in 20% ACM or ordinary medium to different degrees. Neu-rons in both medium were divided into normal control group, mild, moderate and severe injury groups. The 20% ACM was added 24 h before hypoxia/reoxygenation or mechanical injury. The morphology and survival of neurons were observed and counted by trypan blue staining. The concentration of NO, lactic dehydrogenase (LDH and membrane ATPase activity were detected by corresponding kits. Results: It was showed that 20% ACM can obviously promote the survival rate of hypoxia/reoxygenated neurons and scratched neurons as well. The morphology and num-ber of neurons exposed to hypoxia or scratch injury showed great difference between groups with or without ACM treatment. Compared with control group, the concentration of NO and LDH was much lower in hypoxic/reoxygenated neurons treated with 20% ACM, and the ATPase activity was higher. For the mechanical injury model, neurons with moderate injury also revealed a lower NO and LDH concen-tration than the control group. All the differences were sta-tistically significant (P<0.05. Conclusion: ACM can promote the survival and func-tional recovery of neurons following hypoxia or scratching to a certain degree. The mechanism may be associated with reducing the synthesis and release of NO and LDH as well as increasing the activity of membrane ATPase. Key words: Glial cell line

Zeaxanthin Inhibits Hypoxia-Induced VEGF Secretion by RPE Cells through Decreased Protein Levels of Hypoxia-Inducible Factors-1α

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Richard Rosen

2015-01-01

Full Text Available Hypoxia is the most important stimulus leading to upregulation of VEGF in the retina and this is caused by accumulation of hypoxia-inducible factors-1α (HIF-1α protein. The effects of zeaxanthin, a natural phytochemical, on the VEGF and HIF-1α expression in the primary culture of human retinal pigment epithelial (RPE cells were studied. An in vitro RPE cell hypoxia model was established by placing cells under 1% oxygen pressure or by adding cobalt chloride (CoCl2 to the culture medium. RPE cells and conditioned media were collected from cultures treated with and without zeaxanthin under normoxic and hypoxic conditions. VEGF and HIF-1α protein and RNA levels were measured by ELISA kits and RT-PCR, respectively. Hypoxia caused a significant increase of VEGF expression and accumulation of HIF-1α in RPE cells. Zeaxanthin at 50–150 μM significantly inhibited the expression of VEGF and accumulation of HIF-1α protein caused by hypoxia but did not affect expression of VEGF and HIF-1α under normoxic conditions. This is the first report on the effect of zeaxanthin on VEGF and HIF-1α levels in cultured RPE cells and suggests that zeaxanthin may have potential value in the prevention and treatment of various retinal diseases associated with vascular leakage and neovascularization.

The effects of hypoxia on active ionic transport processes in the gill epithelium of hyperregulating crab, Carcinus maneas.

Science.gov (United States)

Lucu, Čedomil; Ziegler, Andreas

2017-09-01

Effects of hypoxia on the osmorespiratory functions of the posterior gills of the shore crab Carcinus maenas acclimated to 12ppt seawater (DSW) were studied. Short-circuit current (Isc) across the hemilamella (one epithelium layer supported by cuticle) was substantially reduced under exposure to 1.6, 2.0, or 2.5mg O 2 /L hypoxic saline (both sides of epithelium) and fully recovered after reoxygenation. Isc was reduced equally in the epithelium exposed to 1.6mg O 2 /L on both sides and when the apical side was oxygenated and the basolateral side solely exposed to hypoxia. Under 1.6mg O 2 /L, at the level of maximum inhibition of Isc, conductance was decreased from 40.0mScm -2 to 34.7mScm -2 and fully recovered after reoxygenation. Isc inhibition under hypoxia and reduced 86 Rb + (K + ) fluxes across apically located K + channels were caused preferentially by reversible inhibition of basolaterally located and ouabain sensitive Na + ,K + -ATPase mediated electrogenic transport. Reversible inhibition of Isc is discussed as decline in active transport energy supply down regulating metabolic processes and saving energy during oxygen deprivation. In response to a 4day exposure of Carcinus to 2.0mg O 2 /L, hemolymph Na + and Cl - concentration decreased, i.e. hyperosmoregulation was weakened. Variations of the oxygen concentration level and exposure time to hypoxia lead to an increase of the surface of mitochondria per epithelium area and might in part compensate for the decrease in oxygen availability under hypoxic conditions. Copyright © 2017 Elsevier Inc. All rights reserved.

Hypoxia, but not an electrolyte-imbalanced diet, reduces feed intake, growth and oxygen consumption in rainbow trout (Oncorhynchus mykiss)

NARCIS (Netherlands)

Magnoni, Leonardo J.; Eding, Ep; Leguen, Isabelle; Prunet, Patrick; Geurden, Inge; Ozório, Rodrigo O.A.; Schrama, Johan W.

2018-01-01

Oxygen limitation and dietary imbalances are key aspects influencing feed intake (FI) and growth performance in cultured fish. This study investigated the combined effects of hypoxia and dietary electrolyte balance on the growth performance, body composition and nutrient utilization in a rainbow

CONSTITUTIONAL INTERPRETATION OF ROMANIA: POST MODERNITY

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P. RATHNASWAMY

2017-06-01

Full Text Available Austria had in 1920 Constitutional Court followed by Italy in 1946, Germany in 1949, Romania in 1989, South Africa in 1991, and Ethiopia in 1995. Each Constitution has its provisions on the constitutional interpretation. Romania has its own provisions and it is considered here its legality and the best possible measures and recommendations for future. Judicial power is vested in judiciary to interpret constitution, laws, and actions of other organs of government. Judicial review is the function resulted upon judicial power. Political body joins through the appointment of its members in the judicial review and it limits the independence of judiciary. It also reduces the values of separation of powers. Challenges and opportunities of growth and development do influence the spirit of separation of powers and judicial independence. The principle of inherent judicial power in judiciary inducts upon the constitutional interpretation. Thus, the principles of constitutional interpretation are varying in Romania and other similar constitutional courts of Germany, Ethiopia, and Italy but not in South Africa.

TanshinoneIIA and cryptotanshinone protect against hypoxia-induced mitochondrial apoptosis in H9c2 cells.

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Hyou-Ju Jin

Full Text Available Mitochondrial apoptosis pathway is an important target of cardioprotective signalling. Tanshinones, a group of major bioactive compounds isolated from Salvia miltiorrhiza, have been reported with actions against inflammation, oxidative stress, and myocardial ischemia reperfusion injury. However, the actions of these compounds on the chronic hypoxia-related mitochondrial apoptosis pathway have not been investigated. In this study, we examined the effects and molecular mechanisms of two major tanshonones, tanshinone IIA (TIIA and cryptotanshinone (CT on hypoxia induced apoptosis in H9c2 cells. Cultured H9c2 cells were treated with TIIA and CT (0.3 and 3 μΜ 2 hr before and during an 8 hr hypoxic period. Chronic hypoxia caused a significant increase in hypoxia inducible factor 1α expression and the cell late apoptosis rate, which was accompanied with an increase in caspase 3 activity, cytochrome c release, mitochondria membrane potential and expression of pro-apoptosis proteins (Bax and Bak. TIIA and CT (0.3 and 3 μΜ, in concentrations without affecting the cell viability, significantly inhibited the late apoptosis and the changes of caspase 3 activity, cytochrome c release, and mitochondria membrane potential induced by chronic hypoxia. These compounds also suppressed the overexpression of Bax and reduced the ratio of Bax/Bcl-2. The results indicate that TIIA and CT protect against chronic hypoxia induced cell apoptosis by regulating the mitochondrial apoptosis signaling pathway, involving inhibitions of mitochondria hyperpolarization, cytochrome c release and caspase 3 activity, and balancing anti- and pro-apoptotic proteins in Bcl-2 family proteins.

Intermittent hypoxia, cardiovascular disease and obstructive sleep apnoea.

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Turnbull, Chris D

2018-01-01

Obstructive sleep apnoea (OSA) is a common disorder and is associated with cardiovascular disease. Continuous positive airway pressure (CPAP), whilst reducing blood pressure, has not been shown to reduce cardiovascular events when used as a treatment solely for this purpose in patients with previous cardiovascular disease. Developing a better understanding of the mechanisms underlying cardiovascular disease in OSA is important to develop new treatments. Potential causative mechanisms for cardiovascular disease in OSA include arousal induced sympathetic activation, large intrathoracic pressure swings leading to shear stress on the heart and great vessels, and intermittent hypoxia (IH). This review discusses the role of IH, as a major physiological consequence of OSA, in the development of cardiovascular disease.

Silencing of osteopontin promotes the radiosensitivity of breast cancer cells by reducing the expression of hypoxia inducible factor 1 and vascular endothelial growth factor

Institute of Scientific and Technical Information of China (English)

YANG Li; ZHAO Wei; ZUO Wen-shu; WEI Ling; SONG Xian-rang; WANG Xing-wu; ZHENG Gang; ZHENG Mei-zhu

2012-01-01

Background Osteopontin (OPN) is a secreted phosphoglycoprotein (SSP) that is overexpressed in a variety of tumors and was regarded as a molecular marker of tumors.In this study,we intended to demonstrate the role of OPN in human breast cancer cell line MDA-MB-231.Methods Recombinant plasmid expressing small interfering RNA (siRNA) specific to OPN mRNA was transfected into MDA-MB-231 cells to generate the stable transfected cell line MDA-MB-343,and the empty plasmid tansfected cells (MDA-MB-neg) or wildtype MDA-MB-231 cells were used as control cells respectively.Expression of OPN,hypoxia inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) proteins was analyzed by Western blotting analysis.The radiosensitivity of cells was determined by detecting cell apoptosis,cell proliferation and cell senescence.Results HIF-1 and VEGF proteins in MDA-MB-343 cells were significantly downregulated upon the efficient knockdown of OPN expression under either hypoxia or normoxia environment.Moreover,expression of OPN protein was upregualted upon hypoxic culture.Stable OPN-silencing also decreased cell invasion,increased cell apoptosis and cell senescence,as well as reduced clonogenic survival,resulting in increase radiation tolerance.Conclusions Suppression of OPN gene expression can enhance radiosensitivity and affect cell apoptosis in breast cancer cells.OPN seems to be an attractive target for the improvement of radiotherapy.

Hypoxia independent drivers of melanoma angiogenesis

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Svenja eMeierjohann

2015-05-01

Full Text Available Tumor angiogenesis is a process which is traditionally regarded as the tumor`s response to low nutrient supply occurring under hypoxic conditions. However, hypoxia is not a prerequisite for angiogenesis. The fact that even single tumor cells or small tumor cell aggregates are capable of attracting blood vessels reveals the early metastatic capability of tumor cells. This review sheds light on the hypoxia independent mechanisms of tumor angiogenesis in melanoma.

Effects of natural and human-induced hypoxia on coastal benthos

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Levin, L. A.; Ekau, W.; Gooday, A. J.; Jorissen, F.; Middelburg, J. J.; Naqvi, S. W. A.; Neira, C.; Rabalais, N. N.; Zhang, J.

2009-10-01

Coastal hypoxia (defined here as branchial structures, predominate. Large taxa are more sensitive than small taxa to hypoxia. Crustaceans and echinoderms are typically more sensitive to hypoxia, with lower oxygen thresholds, than annelids, sipunculans, molluscs and cnidarians. Mobile fish and shellfish will migrate away from low-oxygen areas. Within a species, early life stages may be more subject to oxygen stress than older life stages. Hypoxia alters both the structure and function of benthic communities, but effects may differ with regional hypoxia history. Human-caused hypoxia is generally linked to eutrophication, and occurs adjacent to watersheds with large populations or agricultural activities. Many occurrences are seasonal, within estuaries, fjords or enclosed seas of the North Atlantic and the NW Pacific Oceans. Benthic faunal responses, elicited at oxygen levels below 2 ml L-1, typically involve avoidance or mortality of large species and elevated abundances of enrichment opportunists, sometimes prior to population crashes. Areas of low oxygen persist seasonally or continuously beneath upwelling regions, associated with the upper parts of oxygen minimum zones (SE Pacific, W Africa, N Indian Ocean). These have a distribution largely distinct from eutrophic areas and support a resident fauna that is adapted to survive and reproduce at oxygen concentrations <0.5 ml L-1. Under both natural and eutrophication-caused hypoxia there is loss of diversity, through attrition of intolerant species and elevated dominance, as well as reductions in body size. These shifts in species composition and diversity yield altered trophic structure, energy flow pathways, and corresponding ecosystem services such as production, organic matter cycling and organic C burial. Increasingly the influences of nature and humans interact to generate or exacerbate hypoxia. A warmer ocean is more stratified, holds less oxygen, and may experience greater advection of oxygen-poor source

Interactive effects of maternal cigarette smoke, heat stress, hypoxia, and lipopolysaccharide on neonatal cardiorespiratory and cytokine responses

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McDonald, Fiona B.; Chandrasekharan, Kumaran; Wilson, Richard J. A.

2016-01-01

Maternal cigarette smoke (CS) exposure exhibits a strong epidemiological association with Sudden Infant Death Syndrome, but other environmental stressors, including infection, hyperthermia, and hypoxia, have also been postulated as important risk factors. This study examines whether maternal CS exposure causes maladaptations within homeostatic control networks by influencing the response to lipopolysaccharide, heat stress, and/or hypoxia in neonatal rats. Pregnant dams were exposed to CS or parallel sham treatments daily for the length of gestation. Offspring were studied at postnatal days 6–8 at ambient temperatures (Ta) of 33°C or 38°C. Within each group, rats were allocated to control, saline, or LPS (200 µg/kg) treatments. Cardiorespiratory patterns were examined using head-out plethysmography and ECG surface electrodes during normoxia and hypoxia (10% O2). Serum cytokine concentrations were quantified from samples taken at the end of each experiment. Our results suggest maternal CS exposure does not alter minute ventilation (V̇e) or heart rate (HR) response to infection or high temperature, but independently increases apnea frequency. CS also primes the inflammatory system to elicit a stronger cytokine response to bacterial insult. High Ta independently depresses V̇e but augments the hypoxia-induced increase in V̇e. Moreover, higher Ta increases HR during normoxia and hypoxia, and in the presence of an immune challenge, increases HR during normoxia, and reduces the increase normally associated with hypoxia. Thus, while most environmental risk factors increase the burden on the cardiorespiratory system in early life, hyperthermia and infection blunt the normal HR response to hypoxia, and gestational CS independently destabilizes breathing by increasing apneas. PMID:27733384

Sickle Mice Are Sensitive to Hypoxia/Ischemia-Induced Stroke but Respond to Tissue-Type Plasminogen Activator Treatment.

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Sun, Yu-Yo; Lee, Jolly; Huang, Henry; Wagner, Mary B; Joiner, Clinton H; Archer, David R; Kuan, Chia-Yi

2017-12-01

The effects of lytic stroke therapy in patients with sickle cell anemia are unknown, although a recent study suggested that coexistent sickle cell anemia does not increase the risk of cerebral hemorrhage. This finding calls for systemic analysis of the effects of thrombolytic stroke therapy, first in humanized sickle mice, and then in patients. There is also a need for additional predictive markers of sickle cell anemia-associated vasculopathy. We used Doppler ultrasound to examine the carotid artery of Townes sickle mice tested their responses to repetitive mild hypoxia-ischemia- and transient hypoxia-ischemia-induced stroke at 3 or 6 months of age, respectively. We also examined the effects of tPA (tissue-type plasminogen activator) treatment in transient hypoxia-ischemia-injured sickle mice. Three-month-old sickle cell (SS) mice showed elevated resistive index in the carotid artery and higher sensitivity to repetitive mild hypoxia-ischemia-induced cerebral infarct. Six-month-old SS mice showed greater resistive index and increased flow velocity without obstructive vasculopathy in the carotid artery. Instead, the cerebral vascular wall in SS mice showed ectopic expression of PAI-1 (plasminogen activator inhibitor-1) and P-selectin, suggesting a proadhesive and prothrombotic propensity. Indeed, SS mice showed enhanced leukocyte and platelet adherence to the cerebral vascular wall, broader fibrin deposition, and higher mortality after transient hypoxia-ischemia. Yet, post-transient hypoxia-ischemia treatment with tPA reduced thrombosis and mortality in SS mice. Sickle mice are sensitive to hypoxia/ischemia-induced cerebral infarct but benefit from thrombolytic treatment. An increased resistive index in carotid arteries may be an early marker of sickle cell vasculopathy. © 2017 American Heart Association, Inc.

Hypoxia-induced retinopathy model in adult zebrafish

DEFF Research Database (Denmark)

Cao, Ziquan; Jensen, Lasse D.; Rouhi, Pegah

2010-01-01

Hypoxia-induced vascular responses, including angiogenesis, vascular remodeling and vascular leakage, significantly contribute to the onset, development and progression of retinopathy. However, until recently there were no appropriate animal disease models recapitulating adult retinopathy available....... In this article, we describe protocols that create hypoxia-induced retinopathy in adult zebrafish. Adult fli1: EGFP zebrafish are placed in hypoxic water for 3-10 d and retinal neovascularization is analyzed using confocal microscopy. It usually takes 11 d to obtain conclusive results using the hypoxia......-induced retinopathy model in adult zebrafish. This model provides a unique opportunity to study kinetically the development of retinopathy in adult animals using noninvasive protocols and to assess therapeutic efficacy of orally active antiangiogenic drugs....

In vitro ischemia suppresses hypoxic induction of hypoxia-inducible factor-1α by inhibition of synthesis and not enhanced degradation.

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Karuppagounder, Saravanan S; Basso, Manuela; Sleiman, Sama F; Ma, Thong C; Speer, Rachel E; Smirnova, Natalya A; Gazaryan, Irina G; Ratan, Rajiv R

2013-08-01

Hypoxia-inducible factor (HIF) mediates a broad, conserved adaptive response to hypoxia, and the HIF pathway is a potential therapeutic target in cerebral ischemia. This study investigated the mechanism by which in vitro ischemia (oxygen-glucose deprivation; OGD) affects canonical hypoxic HIF-1α stabilization. We validated the use of a reporter containing the oxygen-dependent degradation domain of HIF-1α fused to firefly luciferase (ODD-luc) to monitor quantitatively distinct biochemical events leading to hypoxic HIF-1α expression or stabilization in a human neuroblastoma cell line (SH-SY5Y). When OGD was imposed following a 2-hr hypoxic stabilization of ODD-luc, the levels of the reporter were reduced, consistent with prior models proposing that OGD enhances HIF prolylhydroxylase (PHD) activity. Surprisingly, PHD inhibitors and proteasome inhibitors do not stabilize ODD-luc in OGD. Furthermore, OGD does not affect the half-life of ODD-luc protein following hypoxia, suggesting that OGD abrogates hypoxic HIF-1α induction by reducing HIF-1α synthesis rather than by enhancing its degradation. We observed ATP depletion under OGD vs. hypoxia and propose that ATP depletion enhances translational suppression, overcoming the selective synthesis of HIF concurrent with global decreases in protein synthesis in hypoxia. Taken together, these findings biochemically characterize a practical reporter for monitoring HIF-1α levels and support a novel model for HIF regulation in an in vitro model of human ischemia. Copyright © 2013 Wiley Periodicals, Inc.

Effect of hypoxia on specific dynamic action and postprandial cardiovascular physiology in rainbow trout (Oncorhynchus mykiss).

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Eliason, Erika J; Farrell, Anthony P

2014-05-01

Fish routinely encounter hypoxic environments, which may have detrimental effects on digestion and performance. The present study measured oxygen consumption (MO2), gastrointestinal blood flow (GBF), cardiac output (Vb) and heart rate (f(H)) in rainbow trout Oncorhynchus mykiss at 10°C-11.5°C while exposed to a 1.5-h step-wise hypoxia treatment (80%, 60% and 40% saturation=16.7, 12.6 and 8.4 kPa, respectively), which began 4 h after being fed 1% of their body mass. GBF and f(H) significantly decreased by 41 and 25%-29%, respectively, at the most severe hypoxia step (40% saturation), while MO2 and Vb were maintained throughout the entire hypoxia exposure. Thus, GBF and f(H) were more sensitive to hypoxia than MO2 or Vb in digesting rainbow trout. Subsequent to the hypoxic exposure, the fish were returned to normoxia and monitored for a total of 50h after feeding. While the magnitude of SDA was unaffected, peak postprandial MO2 was reduced by 17%, and the duration of specific dynamic action (SDA) was prolonged by 6h in hypoxia-treated fish when compared to control fish. In conclusion, digestive performance was compromised both during and after the hypoxic exposure, which could lead to negative effects on growth. Copyright © 2014 Elsevier Inc. All rights reserved.

Hypoxia-induced oxidative base modifications in the VEGF hypoxia-response element are associated with transcriptionally active nucleosomes.

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Ruchko, Mykhaylo V; Gorodnya, Olena M; Pastukh, Viktor M; Swiger, Brad M; Middleton, Natavia S; Wilson, Glenn L; Gillespie, Mark N

2009-02-01

Reactive oxygen species (ROS) generated in hypoxic pulmonary artery endothelial cells cause transient oxidative base modifications in the hypoxia-response element (HRE) of the VEGF gene that bear a conspicuous relationship to induction of VEGF mRNA expression (K.A. Ziel et al., FASEB J. 19, 387-394, 2005). If such base modifications are indeed linked to transcriptional regulation, then they should be detected in HRE sequences associated with transcriptionally active nucleosomes. Southern blot analysis of the VEGF HRE associated with nucleosome fractions prepared by micrococcal nuclease digestion indicated that hypoxia redistributed some HRE sequences from multinucleosomes to transcriptionally active mono- and dinucleosome fractions. A simple PCR method revealed that VEGF HRE sequences harboring oxidative base modifications were found exclusively in mononucleosomes. Inhibition of hypoxia-induced ROS generation with myxathiozol prevented formation of oxidative base modifications but not the redistribution of HRE sequences into mono- and dinucleosome fractions. The histone deacetylase inhibitor trichostatin A caused retention of HRE sequences in compacted nucleosome fractions and prevented formation of oxidative base modifications. These findings suggest that the hypoxia-induced oxidant stress directed at the VEGF HRE requires the sequence to be repositioned into mononucleosomes and support the prospect that oxidative modifications in this sequence are an important step in transcriptional activation.

Hypoxia-responsive ERFs involved in postdeastringency softening of persimmon fruit.

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Wang, Miao-Miao; Zhu, Qing-Gang; Deng, Chu-Li; Luo, Zheng-Rong; Sun, Ning-Jing; Grierson, Donald; Yin, Xue-Ren; Chen, Kun-Song

2017-11-01

Removal of astringency by endogenously formed acetaldehyde, achieved by postharvest anaerobic treatment, is of critical importance for many types of persimmon fruit. Although an anaerobic environment accelerates de-astringency, it also has the deleterious effect of promoting excessive softening, reducing shelf life and marketability. Some hypoxia-responsive ethylene response factors (ERFs) participate in anaerobic de-astringency, but their role in accelerated softening was unclear. Undesirable rapid softening induced by high CO 2 (95%) was ameliorated by adding the ethylene inhibitor 1-MCP (1 μL/L), resulting in reduced astringency while maintaining firmness, suggesting that CO 2 -induced softening involves ethylene signalling. Among the hypoxia-responsive genes, expression of eight involved in fruit cell wall metabolism (Dkβ-gal1/4, DkEGase1, DkPE1/2, DkPG1, DkXTH9/10) and three ethylene response factor genes (DkERF8/16/19) showed significant correlations with postdeastringency fruit softening. Dual-luciferase assay indicated that DkERF8/16/19 could trans-activate the DkXTH9 promoter and this interaction was abolished by a mutation introduced into the C-repeat/dehydration-responsive element of the DkXTH9 promoter, supporting the conclusion that these DkERFs bind directly to the DkXTH9 promoter and regulate this gene, which encodes an important cell wall metabolism enzyme. Some hypoxia-responsive ERF genes are involved in deastringency and softening, and this linkage was uncoupled by 1-MCP. Fruit of the Japanese cultivar 'Tonewase' provide a model for altered anaerobic response, as they lost astringency yet maintained firmness after CO 2 treatment without 1-MCP and changes in cell wall enzymes and ERFs did not occur. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

ANTAGONISM OF PROGESTERONE RECEPTOR SUPPRESSES CAROTID BODY RESPONSES TO HYPOXIA AND NICOTINE IN RAT PUPS

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JOSEPH, V.; NIANE, L. M.; BAIRAM, A.

2013-01-01

We tested the hypothesis that antagonism of progesterone receptor (PR) in newborn rats alters carotid body and respiratory responses to hypoxia and nicotinic receptor agonists. Rats were treated with the PR antagonist mifepristone (daily oral gavage 40 μg/g/d) or vehicle between post-natal days 3 and 15. In 11–14-day-old rats, we used in vitro carotid body/carotid sinus nerve preparation and whole body plethysmography to assess the carotid body and ventilatory responses to hypoxia (65 mmHg in vitro, 10% O2 in vivo) and to nicotinic receptor agonists (as an excitatory modulator of carotid body activity—nicotine 100 μM for in vitro studies, and epibatidine 5 μg/kg, i.p., which mainly acts on peripheral nicotinic receptors, for in vivo studies). The carotid body responses to hypoxia and nicotine were drastically reduced by mifepristone. Compared with vehicle, mifepristone-treated rats had a reduced body weight. The ventilatory response to epibatidine was attenuated; however, the hypoxic ventilatory response was similar between vehicle and mifepristone-treated pups. Immunohistochemical staining revealed that mifepristone treatment did not change carotid body morphology. We conclude that PR activity is a critical factor ensuring proper carotid body function in newborn rats. PMID:22326965

Hypoxia regulates the expression of the neuromedin B receptor through a mechanism dependent on hypoxia-inducible factor-1α.

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Hyun-Joo Park

Full Text Available The neuromedin B receptor (NMB-R, a member of the mammalian bombesin receptor family, is frequently overexpressed in various tumors. In the present study, we found that exposure to hypoxic conditions increases the levels of NMBR mRNA and protein in breast cancer cells, which are tightly regulated by hypoxia-inducible factor-1α (HIF-1α. We confirmed the effect of HIF-1α on NMBR transcription by performing an NMBR promoter-driven reporter assay and then identified a functional hypoxia-responsive element (HRE in the human NMBR promoter region. Further, the binding of HIF-1α to the NMBR promoter was corroborated by electrophoretic mobility shift and chromatin immunoprecipitation assays, which showed that HIF-1α specifically and directly bound to the NMBR promoter in response to hypoxia. Immunohistochemical analysis of a xenograft and a human breast cancer tissue array revealed a significant correlation between NMB-R and HIF-1α expression. Taken together, our findings indicate that hypoxia induces NMB-R expression through a novel mechanism to regulate HIF-1α expression in breast cancer cells.

Anthrax lethal toxin inhibits translation of hypoxia-inducible factor 1α and causes decreased tolerance to hypoxic stress.

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Ouyang, Weiming; Torigoe, Chikako; Fang, Hui; Xie, Tao; Frucht, David M

2014-02-14

Hypoxia is considered to be a contributor to the pathology associated with administration of anthrax lethal toxin (LT). However, we report here that serum lactate levels in LT-treated mice are reduced, a finding inconsistent with the anaerobic metabolism expected to occur during hypoxia. Reduced lactate levels are also observed in the culture supernatants of LT-treated cells. LT inhibits the accumulation of hypoxia-inducible factor (HIF)-1α, a subunit of HIF-1, the master regulator directing cellular responses to hypoxia. The toxin has no effect on the transcription or protein turnover of HIF-1α, but instead it acts to inhibit HIF-1α translation. LT treatment diminishes phosphorylation of eIF4B, eIF4E, and rpS6, critical components of the intracellular machinery required for HIF-1α translation. Moreover, blockade of MKK1/2-ERK1/2, but not p38 or JNK signaling, lowers HIF-1α protein levels in both normoxic and hypoxic conditions, consistent with a role for MKK1 and MKK2 as the major targets of LT responsible for the inhibition of HIF-1α translation. The physiological importance of the LT-induced translation blockade is demonstrated by the finding that LT treatment decreases the survival of hepatocyte cell lines grown in hypoxic conditions, an effect that is overcome by preinduction of HIF-1α. Taken together, these data support a role for LT in dysregulating HIF-1α and thereby disrupting homeostatic responses to hypoxia, an environmental characteristic of certain tissues at baseline and/or during disseminated infection with Bacillus anthracis.

Hypoxia Induces Epithelial-Mesenchymal Transition in Follicular Thyroid Cancer: Involvement of Regulation of Twist by Hypoxia Inducible Factor-1α.

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Yang, Yeon Ju; Na, Hwi Jung; Suh, Michelle J; Ban, Myung Jin; Byeon, Hyung Kwon; Kim, Won Shik; Kim, Jae Wook; Choi, Eun Chang; Kwon, Hyeong Ju; Chang, Jae Won; Koh, Yoon Woo

2015-11-01

Although follicular thyroid cancer (FTC) has a relatively fair prognosis, distant metastasis sometimes results in poor prognosis and survival. There is little understanding of the mechanisms contributing to the aggressiveness potential of thyroid cancer. We showed that hypoxia inducible factor-1α (HIF-1α) induced aggressiveness in FTC cells and identified the underlying mechanism of the HIF-1α-induced invasive characteristics. Cells were cultured under controlled hypoxic environments (1% O₂) or normoxic conditions. The effect of hypoxia on HIF-1α, and epithelial-to-mesenchymal transition (EMT) related markers were evaluated by quantitative real-time PCR, Western blot analysis and immunocytochemistry. Invasion and wound healing assay were conducted to identify functional character of EMT. The involvement of HIF-1α and Twist in EMT were studied using gene overexpression or silencing. After orthotopic nude mouse model was established using the cells transfected with lentiviral shHIF-1α, tissue analysis was done. Hypoxia induces HIF-1α expression and EMT, including typical morphologic changes, cadherin shift, and increased vimentin expression. We showed that overexpression of HIF-1α via transfection resulted in the aforementioned changes without hypoxia, and repression of HIF-1α with RNA interference suppressed hypoxia-induced HIF-1α and EMT. Furthermore, we also observed that Twist expression was regulated by HIF-1α. These were confirmed in the orthotopic FTC model. Hypoxia induced HIF-1α, which in turn induced EMT, resulting in the increased capacity for invasion and migration of cells via regulation of the Twist signal pathway in FTC cells. These findings provide insight into a possible therapeutic strategy to prevent invasive and metastatic FTC.

Late gestational hypoxia and a postnatal high salt diet programs endothelial dysfunction and arterial stiffness in adult mouse offspring.

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Walton, Sarah L; Singh, Reetu R; Tan, Tiffany; Paravicini, Tamara M; Moritz, Karen M

2016-03-01

Gestational hypoxia and high dietary salt intake have both been associated with impaired vascular function in adulthood. Using a mouse model of prenatal hypoxia, we examined whether a chronic high salt diet had an additive effect in promoting vascular dysfunction in offspring. Pregnant CD1 dams were placed in a hypoxic chamber (12% O2) or housed under normal conditions (21% O2) from embryonic day 14.5 until birth. Gestational hypoxia resulted in a reduced body weight for both male and female offspring at birth. This restriction in body weight persisted until weaning, after which the animals underwent catch-up growth. At 10 weeks of age, a subset of offspring was placed on a high salt diet (5% NaCl). Pressurized myography of mesenteric resistance arteries at 12 months of age showed that both male and female offspring exposed to maternal hypoxia had significantly impaired endothelial function, as demonstrated by impaired vasodilatation to ACh but not sodium nitroprusside. Endothelial dysfunction caused by prenatal hypoxia was not exacerbated by postnatal consumption of a high salt diet. Prenatal hypoxia increased microvascular stiffness in male offspring. The combination of prenatal hypoxia and a postnatal high salt diet caused a leftward shift in the stress-strain relationship in both sexes. Histopathological analysis of aortic sections revealed a loss of elastin integrity and increased collagen, consistent with increased vascular stiffness. These results demonstrate that prenatal hypoxia programs endothelial dysfunction in both sexes. A chronic high salt diet in postnatal life had an additive deleterious effect on vascular mechanics and structural characteristics in both sexes. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

Cognition Effects of Low-Grade Hypoxia

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2016-07-01

human short-term memory . Br J Anaesth. 1971; 43(6):548–552. 3. Crow TJ, Kelman GR. Psychological effects of mild acute hypoxia. Br J Anaesth. 1973; 45...Journal Article 3. DATES COVERED (From – To) Jan 2003 – Sep 2005 4. TITLE AND SUBTITLE Cognition Effects of Low-Grade Hypoxia 5a. CONTRACT NUMBER... cognitive function are reported in this paper. The study compared cognitive function during short exposures at four different altitudes. Ninety-one

Snail/beta-catenin signaling protects breast cancer cells from hypoxia attack

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Scherbakov, Alexander M., E-mail: alex.scherbakov@gmail.com [Laboratory of Clinical Biochemistry, Institute of Clinical Oncology, N.N. Blokhin Cancer Research Centre, Kashirskoye sh. 24, Moscow 115478 (Russian Federation); Stefanova, Lidia B.; Sorokin, Danila V.; Semina, Svetlana E. [Laboratory of Molecular Endocrinology, Institute of Carcinogenesis, N.N. Blokhin Cancer Research Centre, Kashirskoye sh. 24, Moscow 115478 (Russian Federation); Berstein, Lev M. [Laboratory of Oncoendocrinology, N.N. Petrov Research Institute of Oncology, St. Petersburg 197758 (Russian Federation); Krasil’nikov, Mikhail A. [Laboratory of Molecular Endocrinology, Institute of Carcinogenesis, N.N. Blokhin Cancer Research Centre, Kashirskoye sh. 24, Moscow 115478 (Russian Federation)

2013-12-10

The tolerance of cancer cells to hypoxia depends on the combination of different factors – from increase of glycolysis (Warburg Effect) to activation of intracellular growth/apoptotic pathways. Less is known about the influence of epithelial–mesenchymal transition (EMT) and EMT-associated pathways on the cell sensitivity to hypoxia. The aim of this study was to explore the role of Snail signaling, one of the key EMT pathways, in the mediating of hypoxia response and regulation of cell sensitivity to hypoxia, using as a model in vitro cultured breast cancer cells. Earlier we have shown that estrogen-independent HBL-100 breast cancer cells differ from estrogen-dependent MCF-7 cells with increased expression of Snail1, and demonstrated Snail1 involvement into formation of hormone-resistant phenotype. Because Snail1 belongs to hypoxia-activated proteins, here we studied the influence of Snail1 signaling on the cell tolerance to hypoxia. We found that Snail1-enriched HBL-100 cells were less sensitive to hypoxia-induced growth suppression if compared with MCF-7 line (31% MCF-7 vs. 71% HBL-100 cell viability after 1% O{sub 2} atmosphere for 3 days). Snail1 knock-down enhanced the hypoxia-induced inhibition of cell proliferation giving the direct evidence of Snail1 involvement into cell protection from hypoxia attack. The protective effect of Snail1 was shown to be mediated, at least in a part, via beta-catenin which positively regulated expression of HIF-1-dependent genes. Finally, we found that cell tolerance to hypoxia was accompanied with the failure in the phosphorylation of AMPK – the key energy sensor, and demonstrated an inverse relationship between AMPK and Snail/beta-catenin signaling. Totally, our data show that Snail1 and beta-catenin, besides association with loss of hormone dependence, protect cancer cells from hypoxia and may serve as an important target in the treatment of breast cancer. Moreover, we suggest that the level of these proteins as well

Disrupting Hypoxia-Induced Bicarbonate Transport Acidifies Tumor Cells and Suppresses Tumor Growth.

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McIntyre, Alan; Hulikova, Alzbeta; Ledaki, Ioanna; Snell, Cameron; Singleton, Dean; Steers, Graham; Seden, Peter; Jones, Dylan; Bridges, Esther; Wigfield, Simon; Li, Ji-Liang; Russell, Angela; Swietach, Pawel; Harris, Adrian L

2016-07-01

Tumor hypoxia is associated clinically with therapeutic resistance and poor patient outcomes. One feature of tumor hypoxia is activated expression of carbonic anhydrase IX (CA9), a regulator of pH and tumor growth. In this study, we investigated the hypothesis that impeding the reuptake of bicarbonate produced extracellularly by CA9 could exacerbate the intracellular acidity produced by hypoxic conditions, perhaps compromising cell growth and viability as a result. In 8 of 10 cancer cell lines, we found that hypoxia induced the expression of at least one bicarbonate transporter. The most robust and frequent inductions were of the sodium-driven bicarbonate transporters SLC4A4 and SLC4A9, which rely upon both HIF1α and HIF2α activity for their expression. In cancer cell spheroids, SLC4A4 or SLC4A9 disruption by either genetic or pharmaceutical approaches acidified intracellular pH and reduced cell growth. Furthermore, treatment of spheroids with S0859, a small-molecule inhibitor of sodium-driven bicarbonate transporters, increased apoptosis in the cell lines tested. Finally, RNAi-mediated attenuation of SLC4A9 increased apoptosis in MDA-MB-231 breast cancer spheroids and dramatically reduced growth of MDA-MB-231 breast tumors or U87 gliomas in murine xenografts. Our findings suggest that disrupting pH homeostasis by blocking bicarbonate import might broadly relieve the common resistance of hypoxic tumors to anticancer therapy. Cancer Res; 76(13); 3744-55. ©2016 AACR. ©2016 American Association for Cancer Research.

Hypoxia-induced p53 modulates both apoptosis and radiosensitivity via AKT

NARCIS (Netherlands)

Leszczynska, K.B.; Foskolou, I.P.; Abraham, A.G.; Anbalagan, S.; Tellier, C.; Haider, S.; Span, P.N.; O'Neill, E.E.; Buffa, F.M.; Hammond, E.M.

2015-01-01

Restoration of hypoxia-induced apoptosis in tumors harboring p53 mutations has been proposed as a potential therapeutic strategy; however, the transcriptional targets that mediate hypoxia-induced p53-dependent apoptosis remain elusive. Here, we demonstrated that hypoxia-induced p53-dependent

Hippocampal mitogen-activated protein kinase activation is associated with intermittent hypoxia in a rat model of obstructive sleep apnea syndrome.

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Zhao, Ya-Ning; Wang, Hong-Yang; Li, Jian-Min; Chen, Bao-Yuan; Xia, Guo; Zhang, Pan-Pan; Ge, Yan-Lei

2016-01-01

generally increased at the late stages under continued hypoxia, but increased at all time-points under the intermittent hypoxia conditions. The two types of hypoxia induced an increase in the MDA content, but a decrease in SOD activity. Marked changes in these two parameters coupled with markedly reduced surviving cells in the hippocampus in a time‑dependent manner were observed in the intermittent hypoxia group in comparison with the continued hypoxia group. OSAS‑induced intermittent hypoxia markedly activated the MAPK signaling pathways, which were triggered by oxidative stress, leading to abnormal expression of downstream Bcl‑2 and Bax, and a severe loss of neural cells in the hippocampus.

Impact of Hypoxia on the Metastatic Potential of Human Prostate Cancer Cells

International Nuclear Information System (INIS)

Dai Yao; Bae, Kyungmi; Siemann, Dietmar W.

2011-01-01

Purpose: Intratumoral hypoxia is known to be associated with radioresistance and metastasis. The present study examined the effect of acute and chronic hypoxia on the metastatic potential of prostate cancer PC-3, DU145, and LNCaP cells. Methods and Materials: Cell proliferation and clonogenicity were tested by MTT assay and colony formation assay, respectively. 'Wound-healing' and Matrigel-based chamber assays were used to monitor cell motility and invasion. Hypoxia-inducible factor 1 alpha (HIF-1α) expression was tested by Western blot, and HIF-1-target gene expression was detected by real-time polymerase chain reaction. Secretion of matrix metalloproteinases (MMPs) was determined by gelatin zymography. Results: When PC-3 cells were exposed to 1% oxygen (hypoxia) for various periods of time, chronic hypoxia (≥24 h) decreased cell proliferation and induced cell death. In contrast, prostate cancer cells exposed to acute hypoxia (≤6 h) displayed increased motility, clonogenic survival, and invasive capacity. At the molecular level, both hypoxia and anoxia transiently stabilized HIF-1α. Exposure to hypoxia also induced the early expression of MMP-2, an invasiveness-related gene. Treatment with the HIF-1 inhibitor YC-1 attenuated the acute hypoxia-induced migration, invasion, and MMP-2 activity. Conclusions: The length of oxygen deprivation strongly affected the functional behavior of all three prostate cancer cell lines. Acute hypoxia in particular was found to promote a more aggressive metastatic phenotype.

Effect of oxygen on cardiac differentiation in mouse iPS cells: role of hypoxia inducible factor-1 and Wnt/beta-catenin signaling.

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Tanya L Medley

Full Text Available BACKGROUND: Disturbances in oxygen levels have been found to impair cardiac organogenesis. It is known that stem cells and differentiating cells may respond variably to hypoxic conditions, whereby hypoxia may enhance stem cell pluripotency, while differentiation of multiple cell types can be restricted or enhanced under hypoxia. Here we examined whether HIF-1alpha modulated Wnt signaling affected differentiation of iPS cells into beating cardiomyocytes. OBJECTIVE: We investigated whether transient and sustained hypoxia affects differentiation of cardiomyocytes derived from murine induced pluripotent stem (iPS cells, assessed the involvement of HIF-1alpha (hypoxia-inducible factor-1alpha and the canonical Wnt pathway in this process. METHODS: Embryoid bodies (EBs derived from iPS cells were differentiated into cardiomyocytes and were exposed either to 24 h normoxia or transient hypoxia followed by a further 13 days of normoxic culture. RESULTS: At 14 days of differentiation, 59 ± 2% of normoxic EBs were beating, whilst transient hypoxia abolished beating at 14 days and EBs appeared immature. Hypoxia induced a significant increase in Brachyury and islet-1 mRNA expression, together with reduced troponin C expression. Collectively, these data suggest that transient and sustained hypoxia inhibits maturation of differentiating cardiomyocytes. Compared to normoxia, hypoxia increased HIF-1alpha, Wnt target and ligand genes in EBs, as well as accumulation of HIF-1alpha and beta-catenin in nuclear protein extracts, suggesting involvement of the Wnt/beta-catenin pathway. CONCLUSION: Hypoxia impairs cardiomyocyte differentiation and activates Wnt signaling in undifferentiated iPS cells. Taken together the study suggests that oxygenation levels play a critical role in cardiomyocyte differentiation and suggest that hypoxia may play a role in early cardiogenesis.

Evaluating Aquatic Life Benefits of Reducing Nutrient Loading to Remediate Episodic and Diel Cycling Hypoxia in a Shallow Hypereutrophic Estuary

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Theoretical linkages between excess nutrient loading, nutrient-enhanced community metabolism (i.e., production and respiration), and hypoxia in estuaries are well-understood. In seasonally-stratified estuaries and coastal systems (e.g., Chesapeake Bay, northern Gulf of Mexico), h...

Hypoxia-induced p53 modulates both apoptosis and radiosensitivity via AKT

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Leszczynska, Katarzyna B.; Foskolou, Iosifina P.; Abraham, Aswin G.; Anbalagan, Selvakumar; Tellier, Céline; Haider, Syed; Span, Paul N.; O’Neill, Eric E.; Buffa, Francesca M.; Hammond, Ester M.

2015-01-01

Restoration of hypoxia-induced apoptosis in tumors harboring p53 mutations has been proposed as a potential therapeutic strategy; however, the transcriptional targets that mediate hypoxia-induced p53-dependent apoptosis remain elusive. Here, we demonstrated that hypoxia-induced p53-dependent apoptosis is reliant on the DNA-binding and transactivation domains of p53 but not on the acetylation sites K120 and K164, which, in contrast, are essential for DNA damage–induced, p53-dependent apoptosis. Evaluation of hypoxia-induced transcripts in multiple cell lines identified a group of genes that are hypoxia-inducible proapoptotic targets of p53, including inositol polyphosphate-5-phosphatase (INPP5D), pleckstrin domain–containing A3 (PHLDA3), sulfatase 2 (SULF2), B cell translocation gene 2 (BTG2), cytoplasmic FMR1-interacting protein 2 (CYFIP2), and KN motif and ankyrin repeat domains 3 (KANK3). These targets were also regulated by p53 in human cancers, including breast, brain, colorectal, kidney, bladder, and melanoma cancers. Downregulation of these hypoxia-inducible targets associated with poor prognosis, suggesting that hypoxia-induced apoptosis contributes to p53-mediated tumor suppression and treatment response. Induction of p53 targets, PHLDA3, and a specific INPP5D transcript mediated apoptosis in response to hypoxia through AKT inhibition. Moreover, pharmacological inhibition of AKT led to apoptosis in the hypoxic regions of p53-deficient tumors and consequently increased radiosensitivity. Together, these results identify mediators of hypoxia-induced p53-dependent apoptosis and suggest AKT inhibition may improve radiotherapy response in p53-deficient tumors. PMID:25961455

Increased oxidative stress and anaerobic energy release, but blunted Thr172-AMPKα phosphorylation, in response to sprint exercise in severe acute hypoxia in humans.

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Morales-Alamo, David; Ponce-González, Jesús Gustavo; Guadalupe-Grau, Amelia; Rodríguez-García, Lorena; Santana, Alfredo; Cusso, Maria Roser; Guerrero, Mario; Guerra, Borja; Dorado, Cecilia; Calbet, José A L

2012-09-01

AMP-activated protein kinase (AMPK) is a major mediator of the exercise response and a molecular target to improve insulin sensitivity. To determine if the anaerobic component of the exercise response, which is exaggerated when sprint is performed in severe acute hypoxia, influences sprint exercise-elicited Thr(172)-AMPKα phosphorylation, 10 volunteers performed a single 30-s sprint (Wingate test) in normoxia and in severe acute hypoxia (inspired Po(2): 75 mmHg). Vastus lateralis muscle biopsies were obtained before and immediately after 30 and 120 min postsprint. Mean power output and O(2) consumption were 6% and 37%, respectively, lower in hypoxia than in normoxia. O(2) deficit and muscle lactate accumulation were greater in hypoxia than in normoxia. Carbonylated skeletal muscle and plasma proteins were increased after the sprint in hypoxia. Thr(172)-AMPKα phosphorylation was increased by 3.1-fold 30 min after the sprint in normoxia. This effect was prevented by hypoxia. The NAD(+)-to-NADH.H(+) ratio was reduced (by 24-fold) after the sprints, with a greater reduction in hypoxia than in normoxia (P exercise in human skeletal muscle is altered in severe acute hypoxia, which abrogated Thr(172)-AMPKα phosphorylation, likely due to lower LKB1 activation by SIRT1.

Baicalin Attenuates Hypoxia-Induced Pulmonary Arterial Hypertension to Improve Hypoxic Cor Pulmonale by Reducing the Activity of the p38 MAPK Signaling Pathway and MMP-9

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Shuangquan Yan

2016-01-01

Full Text Available Baicalin has a protective effect on hypoxia-induced pulmonary hypertension in rats, but the mechanism of this effect remains unclear. Thus, investigating the potential mechanism of this effect was the aim of the present study. Model rats that display hypoxic pulmonary hypertension and cor pulmonale under control conditions were successfully generated. We measured a series of indicators to observe the levels of pulmonary arterial hypertension, pulmonary arteriole remodeling, and right ventricular remodeling. We assessed the activation of p38 mitogen-activated protein kinase (MAPK in the pulmonary arteriole walls and pulmonary tissue homogenates using immunohistochemistry and western blot analyses, respectively. The matrix metalloproteinase- (MMP- 9 protein and mRNA levels in the pulmonary arteriole walls were measured using immunohistochemistry and in situ hybridization. Our results demonstrated that baicalin not only reduced p38 MAPK activation in both the pulmonary arteriole walls and tissue homogenates but also downregulated the protein and mRNA expression levels of MMP-9 in the pulmonary arteriole walls. This downregulation was accompanied by the attenuation of pulmonary hypertension, arteriole remodeling, and right ventricular remodeling. These results suggest that baicalin may attenuate pulmonary hypertension and cor pulmonale, which are induced by chronic hypoxia, by downregulating the p38 MAPK/MMP-9 pathway.

Copper alters hypoxia sensitivity and the behavioural emersion response in the amphibious fish Kryptolebias marmoratus.

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Blewett, Tamzin A; Simon, Robyn A; Turko, Andy J; Wright, Patricia A

2017-08-01

Elevated levels of metals have been reported in mangrove ecosystems worldwide. Mangrove fishes also routinely experience severe environmental stressors, such as hypoxia. In the amphibious fish Kryptolebias marmoratus (mangrove rivulus), a key behavioural response to avoid aquatic stress is to leave water (emersion). We hypothesized that copper (Cu) exposure would increase the sensitivity of this behavioural hypoxia avoidance response due to histopathological effects of Cu on gill structure and function. K. marmoratus were exposed to either control (no added Cu) or Cu (300μg/L) for 96h. Following this period, fish were exposed to an acute hypoxic challenge (decline in dissolved oxygen to ∼0% over 15min), and the emersion response was recorded. Gills were examined for histological changes. Fish exposed to Cu emersed at a higher dissolved oxygen level (7.5±0.6%), relative to the control treatment group (5.8±0.4%). Histological analysis showed that the gill surface area increased and the interlamellar cell mass (ILCM) was reduced following Cu exposure, contrary to our prediction. Overall, these data indicate that Cu induces hypoxia-like changes to gill morphology and increases the sensitivity of the hypoxia emersion response. Copyright © 2017 Elsevier B.V. All rights reserved.

Brain adaptation to hypoxia and hyperoxia in mice

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Laura Terraneo

2017-04-01

Conclusion: Prolonged mild hyperoxia leads to persistent cerebral damage, comparable to that inferred by prolonged mild hypoxia. The underlying mechanism appears related to a model whereby the imbalance between ROS generation and anti-ROS defense is similar, but occurs at higher levels in hypoxia than in hyperoxia.

[Effect of intermittent hypoxia of sleep apnea on embryonic rat cortical neurons in vitro].

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Zhang, Chanjuan; Li, Yanzhong; Wang, Yan

2015-05-01

To investigate the effects of different pattens of intermittent hypoxia on the activity and apoptosis of primary cultured rat embryonic cortical neurons, and to evaluate the role of intermittent hypoxia in the mechanism of obstructive sleep syndrom induced cognitive function loss. The embryonic cerebral cortical neurons were cultured in vitro and were identified by immunofluorescence. Cultured neurons were randomly divided into intermittent hypoxia group, intermittent normal oxygen group, persistent hypoxia group and the control group, and intermittent hypoxia group was divided into five subgroups according to different frequency and time-bound. Neurons were exposed in different modes of hypoxia. MTT colorimetry was used to detect the viability of the neurons, and DAPI colorated measurement was used to calculate the percentages of neuron apoptosis. There were significantly different effects between all subgroups of intermittent hypoxia and the continued hypoxia group on neuronal activity and apoptosis (P Intermittent hypoxia groups with different frequency and time had no difference in neuronal activity and apoptosis (P > 0.05). The effect of intermittent hypoxia was more serious than that of continued hypoxia on neuronal activity and apoptosis; The impact of intermittent hypoxia on neuronal activity and apoptosis may be an important factor in obstructive sleep apnea related cognitive impairment.

Air exposure behavior of the semiterrestrial crab Neohelice granulata allows tolerance to severe hypoxia but not prevent oxidative damage due to hypoxia-reoxygenation cycle.

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de Lima, Tábata Martins; Geihs, Márcio Alberto; Nery, Luiz Eduardo Maia; Maciel, Fábio Everton

2015-11-01

The air exposure behavior of the semi-terrestrial crab Neohelice granulata during severe hypoxia was studied. This study also verified whether this behavior mitigates possible oxidative damage, namely lipoperoxidation, caused by hypoxia and reoxygenation cycles. The lethal time for 50% of the crabs subjected to severe hypoxia (0.5 mgO2 · L(-1)) with free access to air was compared to that of crabs subjected to severe hypoxia without access to air. Crabs were placed in aquaria divided into three zones: water (when the animal was fully submersed), land (when the animal was completely emerged) and intermediate (when the animal was in contact with both environments) zones. Then the crabs were held in this condition for 270 min, and the time spent in each zone was recorded. Lipid peroxidation (LPO) damage to the walking leg muscles was determined for the following four experimental conditions: a--normoxic water with free access to air; b--hypoxic water without access to air; c--hypoxic water followed by normoxic water without air access; and d--hypoxic water with free access to air. When exposed to hypoxic water, N. granulata spent significantly more time on land, 135.3 ± 17.7 min, whereas control animals (exposed to normoxic water) spent more time submerged, 187.4 ± 20.2 min. By this behavior, N. granulata was able to maintain a 100% survival rate when exposed to severe hypoxia. However, N. granulata must still return to water after periods of air exposure (~ 14 min), causing a sequence of hypoxia/reoxygenation events. Despite increasing the survival rate, hypoxia with air access does not decrease the lipid peroxidation damage caused by the hypoxia and reoxygenation cycle experienced by these crabs.

Systemic oxidative-nitrosative-inflammatory stress during acute exercise in hypoxia; implications for microvascular oxygenation and aerobic capacity.

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Woodside, John D S; Gutowski, Mariusz; Fall, Lewis; James, Philip E; McEneny, Jane; Young, Ian S; Ogoh, Shigehiko; Bailey, Damian M

2014-12-01

Exercise performance in hypoxia may be limited by a critical reduction in cerebral and skeletal tissue oxygenation, although the underlying mechanisms remain unclear. We examined whether increased systemic free radical accumulation during hypoxia would be associated with elevated microvascular deoxygenation and reduced maximal aerobic capacity (V̇O2 max ). Eleven healthy men were randomly assigned single-blind to an incremental semi-recumbent cycling test to determine V̇O2 max in both normoxia (21% O2) and hypoxia (12% O2) separated by a week. Continuous-wave near-infrared spectroscopy was employed to monitor concentration changes in oxy- and deoxyhaemoglobin in the left vastus lateralis muscle and frontal cerebral cortex. Antecubital venous blood samples were obtained at rest and at V̇O2 max to determine oxidative (ascorbate radical by electron paramagnetic resonance spectroscopy), nitrosative (nitric oxide metabolites by ozone-based chemiluminescence and 3-nitrotyrosine by enzyme-linked immunosorbent assay) and inflammatory stress biomarkers (soluble intercellular/vascular cell adhesion 1 molecules by enzyme-linked immunosorbent assay). Hypoxia was associated with increased cerebral and muscle tissue deoxygenation and lower V̇O2 max (P exercise-induced increase in oxidative-nitrosative-inflammatory stress, hypoxia per se did not have an additive effect (P > 0.05 versus normoxia). Consequently, we failed to observe correlations between any metabolic, haemodynamic and cardiorespiratory parameters (P > 0.05). Collectively, these findings suggest that altered free radical metabolism cannot explain the elevated microvascular deoxygenation and corresponding lower V̇O2 max in hypoxia. Further research is required to determine whether free radicals when present in excess do indeed contribute to the premature termination of exercise in hypoxia. © 2014 The Authors. Experimental Physiology © 2014 The Physiological Society.

Hif1a inactivation rescues photoreceptor degeneration induced by a chronic hypoxia-like stress.

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Barben, Maya; Ail, Divya; Storti, Federica; Klee, Katrin; Schori, Christian; Samardzija, Marijana; Michalakis, Stylianos; Biel, Martin; Meneau, Isabelle; Blaser, Frank; Barthelmes, Daniel; Grimm, Christian

2018-04-17

Reduced choroidal blood flow and tissue changes in the ageing human eye impair oxygen delivery to photoreceptors and the retinal pigment epithelium. As a consequence, mild but chronic hypoxia may develop and disturb cell metabolism, function and ultimately survival, potentially contributing to retinal pathologies such as age-related macular degeneration (AMD). Here, we show that several hypoxia-inducible genes were expressed at higher levels in the aged human retina suggesting increased activity of hypoxia-inducible transcription factors (HIFs) during the physiological ageing process. To model chronically elevated HIF activity and investigate ensuing consequences for photoreceptors, we generated mice lacking von Hippel Lindau (VHL) protein in rods. This activated HIF transcription factors and led to a slowly progressing retinal degeneration in the ageing mouse retina. Importantly, this process depended mainly on HIF1 with only a minor contribution of HIF2. A gene therapy approach using AAV-mediated RNA interference through an anti-Hif1a shRNA significantly mitigated the degeneration suggesting a potential intervention strategy that may be applicable to human patients.

Human erythropoietin response to hypocapnic hypoxia, normocapnic hypoxia, and hypocapnic normoxia

DEFF Research Database (Denmark)

Klausen, T; Christensen, H; Hansen, J M

1996-01-01

This study investigated the human erythropoietin (EPO) response to short-term hypocapnic hypoxia, its relationship to a normoxic or hypoxic increase of the haemoglobin oxygen affinity, and its suppression by the addition of CO2 to the hypoxic gas. On separate days, eight healthy male subjects were...

Hypoxia-Independent Downregulation of Hypoxia-Inducible Factor 1 Targets by Androgen Deprivation Therapy in Prostate Cancer

Energy Technology Data Exchange (ETDEWEB)

Ragnum, Harald Bull [Department of Radiation Biology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Røe, Kathrine [Department of Radiation Biology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Division of Medicine, Department of Oncology, Akershus University Hospital, Lørenskog (Norway); Holm, Ruth; Vlatkovic, Ljiljana [Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Nesland, Jahn Marthin [Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Medical Faculty, University of Oslo, Oslo (Norway); Aarnes, Eva-Katrine [Department of Radiation Biology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Ree, Anne Hansen [Division of Medicine, Department of Oncology, Akershus University Hospital, Lørenskog (Norway); Medical Faculty, University of Oslo, Oslo (Norway); Flatmark, Kjersti [Department of Tumor Biology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Department of Gastrointestinal Surgery, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Seierstad, Therese [Department of Radiology and Nuclear Medicine, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Faculty of Health Sciences, Buskerud University College, Drammen (Norway); Lilleby, Wolfgang [Department of Oncology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway); Lyng, Heidi, E-mail: heidi.lyng@rr-research.no [Department of Radiation Biology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo (Norway)

2013-11-15

Purpose: We explored changes in hypoxia-inducible factor 1 (HIF1) signaling during androgen deprivation therapy (ADT) of androgen-sensitive prostate cancer xenografts under conditions in which no significant change in immunostaining of the hypoxia marker pimonidazole had occurred. Methods and Materials: Gene expression profiles of volume-matched androgen-exposed and androgen-deprived CWR22 xenografts, with similar pimonidazole-positive fractions, were compared. Direct targets of androgen receptor (AR) and HIF1 transcription factors were identified among the differentially expressed genes by using published lists. Biological processes affected by ADT were determined by gene ontology analysis. HIF1α protein expression in xenografts and biopsy samples from 35 patients receiving neoadjuvant ADT was assessed by immunohistochemistry. Results: A total of 1344 genes showed more than 2-fold change in expression by ADT, including 35 downregulated and 5 upregulated HIF1 targets. Six genes were shared HIF1 and AR targets, and their downregulation was confirmed with quantitative RT-PCR. Significant suppression of the biological processes proliferation, metabolism, and stress response in androgen-deprived xenografts was found, consistent with tumor regression. Nineteen downregulated HIF1 targets were involved in those significant biological processes, most of them in metabolism. Four of these were shared AR and HIF1 targets, including genes encoding the regulatory glycolytic proteins HK2, PFKFB3, and SLC2A1. Most of the downregulated HIF1 targets were induced by hypoxia in androgen-responsive prostate cancer cell lines, confirming their role as hypoxia-responsive HIF1 targets in prostate cancer. Downregulation of HIF1 targets was consistent with the absence of HIF1α protein in xenografts and downregulation in patients by ADT (P<.001). Conclusions: AR repression by ADT may lead to downregulation of HIF1 signaling independently of hypoxic fraction, and this may contribute to

Hypoxia-Independent Downregulation of Hypoxia-Inducible Factor 1 Targets by Androgen Deprivation Therapy in Prostate Cancer

International Nuclear Information System (INIS)

Ragnum, Harald Bull; Røe, Kathrine; Holm, Ruth; Vlatkovic, Ljiljana; Nesland, Jahn Marthin; Aarnes, Eva-Katrine; Ree, Anne Hansen; Flatmark, Kjersti; Seierstad, Therese; Lilleby, Wolfgang; Lyng, Heidi

2013-01-01

Purpose: We explored changes in hypoxia-inducible factor 1 (HIF1) signaling during androgen deprivation therapy (ADT) of androgen-sensitive prostate cancer xenografts under conditions in which no significant change in immunostaining of the hypoxia marker pimonidazole had occurred. Methods and Materials: Gene expression profiles of volume-matched androgen-exposed and androgen-deprived CWR22 xenografts, with similar pimonidazole-positive fractions, were compared. Direct targets of androgen receptor (AR) and HIF1 transcription factors were identified among the differentially expressed genes by using published lists. Biological processes affected by ADT were determined by gene ontology analysis. HIF1α protein expression in xenografts and biopsy samples from 35 patients receiving neoadjuvant ADT was assessed by immunohistochemistry. Results: A total of 1344 genes showed more than 2-fold change in expression by ADT, including 35 downregulated and 5 upregulated HIF1 targets. Six genes were shared HIF1 and AR targets, and their downregulation was confirmed with quantitative RT-PCR. Significant suppression of the biological processes proliferation, metabolism, and stress response in androgen-deprived xenografts was found, consistent with tumor regression. Nineteen downregulated HIF1 targets were involved in those significant biological processes, most of them in metabolism. Four of these were shared AR and HIF1 targets, including genes encoding the regulatory glycolytic proteins HK2, PFKFB3, and SLC2A1. Most of the downregulated HIF1 targets were induced by hypoxia in androgen-responsive prostate cancer cell lines, confirming their role as hypoxia-responsive HIF1 targets in prostate cancer. Downregulation of HIF1 targets was consistent with the absence of HIF1α protein in xenografts and downregulation in patients by ADT (P<.001). Conclusions: AR repression by ADT may lead to downregulation of HIF1 signaling independently of hypoxic fraction, and this may contribute to

Constitutional changes and the dilemmas of constitutionalism

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Arsen Bačić

2009-01-01

Full Text Available The need to develop constitutional mechanisms whose aim is to resolve fundamental relations in society demands the widest possible inclusion of all of society’s active participants in the discussion on the need to adopt or revise the Constitution. The opening of every new round of constitutional changes is of great importance because it always unlocks certain new and important questions. The answers to those questions should be offered by state authority (policy and civil society including science and its disciplines. In this paper, the author mentions several topics which are of interest in the current discussion on the significance of current constitutional changes for the future of the development of constitutionalism and democracy in the Republic of Croatia. These are above all topics of political and legal constitutionalism and suggestions linked to strengthening the independence of judicial powers. The author advocates consistent application of constitutional control and check mechanisms which exclude all insularity of judicial powers in relation to democratic control.

Hypoxia-inducible factors - regulation, role and comparative aspects in tumourigenesis

DEFF Research Database (Denmark)

Hansen, A E; Kristensen, A T; Law, I

2011-01-01

important prognostic information and may help identify potential hypoxia circumventing and targeting strategies. This review summarizes current knowledge on HIF regulation and function in tumour cells and discusses the aspects of using companion animals as comparative spontaneous cancer models. Spontaneous...... tumours in companion animals hold a great research potential for the evaluation and understanding of tumour hypoxia and in the development of hypoxia-targeting therapeutics....

Hypoxia-Induced Autophagy Is Mediated through Hypoxia-Inducible Factor Induction of BNIP3 and BNIP3L via Their BH3 Domains▿ †

OpenAIRE

Bellot, Grégory; Garcia-Medina, Raquel; Gounon, Pierre; Chiche, Johanna; Roux, Danièle; Pouysségur, Jacques; Mazure, Nathalie M.

2009-01-01

While hypoxia-inducible factor (HIF) is a major actor in the cell survival response to hypoxia, HIF also is associated with cell death. Several studies implicate the HIF-induced putative BH3-only proapoptotic genes bnip3 and bnip3l in hypoxia-mediated cell death. We, like others, do not support this assertion. Here, we clearly demonstrate that the hypoxic microenvironment contributes to survival rather than cell death by inducing autophagy. The ablation of Beclin1, a major actor of autophagy,...

Regulation of Cited2 expression provides a functional link between translational and transcriptional responses during hypoxia

International Nuclear Information System (INIS)

Beucken, Twan van den; Magagnin, Michael G.; Savelkouls, Kim; Lambin, Philippe; Koritzinsky, Marianne; Wouters, Bradly G.

2007-01-01

Background and purpose: Protein synthesis rates are greatly reduced under hypoxic conditions as a consequence of an overall inhibition of mRNA translation. Certain specific mRNA species have the ability to escape this general translational repression. At the cellular level this results in differential protein expression during hypoxic conditions. The objective of this study was to characterize the translational regulation of the postulated HIF-1α antagonist Cited2. Materials and methods: DU145 prostate carcinoma cells and mouse embryonic fibroblasts with a homozygous knock-in mutation for eIF2α (S51A) or wild-type eIF2α were exposed to severe hypoxia after which both total mRNA and efficiently translated mRNA were isolated. Quantitative RT-PCR was used to measure and compare changes in transcription (total mRNA) with changes in translation (efficiently translated mRNA fraction). Results: We show using HIF-1α null MEF cells that transcriptional induction of Cited2 during hypoxia is dependent on HIF-1α. Although global mRNA translation is inhibited during hypoxia Cited2 mRNA remains efficiently translated. An evolutionary conserved upstream open reading frame (uORF) in the 5'UTR of Cited2 did not stimulate translation in an eIF2α dependent manner during hypoxia. Conclusions: Selective translation Cited2 by an eIF2α independent mechanism establishes a link between translation and HIF-1 dependent transcription during hypoxia

Tumor hypoxia and reoxygenation: the yin and yang for radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Hong, Beom Ju; Kim, Jong Woo; Jeong, Hoi Bin; Bok, Seo Yeon; Kim, Young Eun; Ahn, G One [Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang (Korea, Republic of)

2016-12-15

Tumor hypoxia, a common feature occurring in nearly all human solid tumors is a major contributing factor for failures of anticancer therapies. Because ionizing radiation depends heavily on the presence of molecular oxygen to produce cytotoxic effect, the negative impact of tumor hypoxia had long been recognized. In this review, we will highlight some of the past attempts to overcome tumor hypoxia including hypoxic radiosensitizers and hypoxia-selective cytotoxin. Although they were (still are) a very clever idea, they lacked clinical efficacy largely because of ‘reoxygenation’ phenomenon occurring in the conventional low dose hyperfractionation radiotherapy prevented proper activation of these compounds. Recent meta-analysis and imaging studies do however indicate that there may be a significant clinical benefit in lowering the locoregional failures by using these compounds. Latest technological advancement in radiotherapy has allowed to deliver high doses of radiation conformally to the tumor volume. Although this technology has brought superb clinical responses for many types of cancer, recent modeling studies have predicted that tumor hypoxia is even more serious because ‘reoxygenation’ is low thereby leaving a large portion of hypoxic tumor cells behind. Wouldn’t it be then reasonable to combine hypoxic radiosensitizers and/or hypoxia-selective cytotoxin with the latest radiotherapy? We will provide some preclinical and clinical evidence to support this idea hoping to revamp an enthusiasm for hypoxic radiosensitizers or hypoxia-selective cytotoxins as an adjunct therapy for radiotherapy.

Kinetic modeling in PET imaging of hypoxia

Science.gov (United States)

Li, Fan; Joergensen, Jesper T; Hansen, Anders E; Kjaer, Andreas

2014-01-01

Tumor hypoxia is associated with increased therapeutic resistance leading to poor treatment outcome. Therefore the ability to detect and quantify intratumoral oxygenation could play an important role in future individual personalized treatment strategies. Positron Emission Tomography (PET) can be used for non-invasive mapping of tissue oxygenation in vivo and several hypoxia specific PET tracers have been developed. Evaluation of PET data in the clinic is commonly based on visual assessment together with semiquantitative measurements e.g. standard uptake value (SUV). However, dynamic PET contains additional valuable information on the temporal changes in tracer distribution. Kinetic modeling can be used to extract relevant pharmacokinetic parameters of tracer behavior in vivo that reflects relevant physiological processes. In this paper, we review the potential contribution of kinetic analysis for PET imaging of hypoxia. PMID:25250200

Effects of hypoxia on the closing pressure of the canine systemic arterial circulation.

Science.gov (United States)

Sylvester, J T; Gilbert, R D; Traystman, R J; Permutt, S

1981-10-01

We studied the relationships among closing pressure (Pc) and indices of systemic arterial resistance (Ra) and compliance (Ca) during hypoxic hypoxia (HH) and carbon monoxide hypoxia (COH) in anesthetized dogs with cardiac bypass and constant ventilation. Closing pressure was measured as the lowest level to which arterial pressure (Pa) fell after inflow to the arterial bed was reduced suddenly to zero. Since the fall of Pa to Pc could be well-described as a single exponential function of time and since Pc was always greater than outflow (venous) pressure. Ra and CA were determined by applying a "vascular waterfall" model to the arterial bed. During HH, Pc increased while Ra and Ca decreased. During COH, Pc and Ra decreased, but Ca did not change. The Pc results indicate that during HH, but not COH, a large portion of the systemic arterial bed experienced a marked increase in vasomotor tone, a qualitative difference that would have been missed if Pc had not been measured. The relationship among Pc, Ra, and Ca during hypoxia suggest these indices may have been determined largely by different portions of the arterial bed in which tone changed independently.

A Prospect and Challenges for Adopting Constitutional Complaint and Constitutional Question in the Indonesian Constitutional Court

OpenAIRE

Faiz, Pan Mohamad

2016-01-01

A jurisdiction of the Indonesian Constitutional Court concerning constitutional adjudication is only limited to review the constitutionality of national law. There is no mechanism for challenging any decision or action made by public authorities that violate fundamental rights enshrined in the Indonesian Constitution. This article argues that constitutional complaint and constitutional question might be adopted as new jurisdictions of the Indonesian Constitutional Court in order to strengthen...

Is hypoxia training good for muscles and exercise performance?

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Vogt, Michael; Hoppeler, Hans

2010-01-01

Altitude training has become very popular among athletes as a means to further increase exercise performance at sea level or to acclimatize to competition at altitude. Several approaches have evolved during the last few decades, with "live high-train low" and "live low-train high" being the most popular. This review focuses on functional, muscular, and practical aspects derived from extensive research on the "live low-train high" approach. According to this, subjects train in hypoxia but remain under normoxia for the rest of the time. It has been reasoned that exercising in hypoxia could increase the training stimulus. Hypoxia training studies published in the past have varied considerably in altitude (2300-5700 m) and training duration (10 days to 8 weeks) and the fitness of the subjects. The evidence from muscle structural, biochemical, and molecular findings point to a specific role of hypoxia in endurance training. However, based on the available performance capacity data such as maximal oxygen uptake (Vo(2)max) and (maximal) power output, hypoxia as a supplement to training is not consistently found to be advantageous for performance at sea level. Stronger evidence exists for benefits of hypoxic training on performance at altitude. "Live low-train high" may thus be considered when altitude acclimatization is not an option. In addition, the complex pattern of gene expression adaptations induced by supplemental training in hypoxia, but not normoxia, suggest that muscle tissue specifically responds to hypoxia. Whether and to what degree these gene expression changes translate into significant changes in protein concentrations that are ultimately responsible for observable structural or functional phenotypes remains open. It is conceivable that the global functional markers such as Vo(2)max and (maximal) power output are too coarse to detect more subtle changes that might still be functionally relevant, at least to high-level athletes.

Seasonal and interannual effects of hypoxia on fish habitat quality in central Lake Erie

Science.gov (United States)

Arend, Kristin K.; Beletsky, Dmitry; DePinto, Joseph; Ludsin, Stuart A.; Roberts, James J.; Rucinski, Daniel K.; Scavia, Donald; Schwab, David J.; Höök, Tomas O.

2011-01-01

1. Hypoxia occurs seasonally in many stratified coastal marine and freshwater ecosystems when bottom dissolved oxygen (DO) concentrations are depleted below 2–3 mg O2 L-1. 2. We evaluated the effects of hypoxia on fish habitat quality in the central basin of Lake Erie from 1987 to 2005, using bioenergetic growth rate potential (GRP) as a proxy for habitat quality. We compared the effect of hypoxia on habitat quality of (i) rainbow smelt, Osmerus mordax mordax Mitchill (young-of-year, YOY, and adult), a cold-water planktivore, (ii) emerald shiner, Notropis atherinoides Rafinesque (adult), a warm-water planktivore, (iii) yellow perch, Perca flavescens Mitchill (YOY and adult), a cool-water benthopelagic omnivore and (iv) round goby Neogobius melanostomus Pallas (adult) a eurythermal benthivore. Annual thermal and DO profiles were generated from 1D thermal and DO hydrodynamics models developed for Lake Erie’s central basin. 3. Hypoxia occurred annually, typically from mid-July to mid-October, which spatially and temporally overlaps with otherwise high benthic habitat quality. Hypoxia reduced the habitat quality across fish species and life stages, but the magnitude of the reduction varied both among and within species because of the differences in tolerance to low DO levels and warm-water temperatures. 4. Across years, trends in habitat quality mirrored trends in phosphorus concentration and water column oxygen demand in central Lake Erie. The per cent reduction in habitat quality owing to hypoxia was greatest for adult rainbow smelt and round goby (mean: -35%), followed by adult emerald shiner (mean: -12%), YOY rainbow smelt (mean: -10%) and YOY and adult yellow perch (mean: -8.5%). 5. Our results highlight the importance of differential spatiotemporally interactive effects of DO and temperature on relative fish habitat quality and quantity. These effects have the potential to influence the performance of individual fish species as well as population dynamics

Tumor microenvironment conditions alter Akt and Na⁺/H⁺ exchanger NHE1 expression in endothelial cells more than hypoxia alone

DEFF Research Database (Denmark)

Pedersen, Anna-Kathrine; Mendes Lopes de Melo, Joana; Mørup, Nina

2017-01-01

Background Chronic angiogenesis is a hallmark of most tumors and takes place in a hostile tumor microenvironment (TME) characterized by hypoxia, low nutrient and glucose levels, elevated lactate and low pH. Despite this, most studies addressing angiogenic signaling use hypoxia as a proxy for tumor...... cells, Akt1 most abundantly. Akt1 protein expression was reduced by TME yet unaffected by hypoxia, while Akt phosphorylation was increased by TME. The Akt loss was partly reversed by MCF-7 human breast cancer cell conditioned medium, suggesting that in vivo, the cancer cell secretome may compensate....../inhibition. Conclusions NHE1 and Akt are downregulated by TME conditions, more potently than by hypoxia alone. This inhibits endothelial cell migration and growth in a manner likely modulated by the cancer cell secretome....

Effects of hypoxia on serum hepatic chemistries of Tibet chicken and ...

African Journals Online (AJOL)

Hypoxia is a major factor that affects the subsistence and development of multicellular organisms. Tibet chicken, as a unique native chicken breed in altiplano, shows genetic adaptation to hypoxia comparing with the breeds at the low altitude. In the present study, to explore effects of hypoxia on chicken fetal livers, eggs of ...

Frequently asked questions in hypoxia research

Directory of Open Access Journals (Sweden)

Wenger RH

2015-09-01

Full Text Available Roland H Wenger,1,2 Vartan Kurtcuoglu,1,2 Carsten C Scholz,1,2 Hugo H Marti,3 David Hoogewijs1,2,4 1Institute of Physiology and Zurich Center for Human Physiology (ZIHP, University of Zurich, 2National Center of Competence in Research “Kidney.CH”, Zurich, Switzerland; 3Institute of Physiology and Pathophysiology, University of Heidelberg, Heidelberg, 4Institute of Physiology, University of Duisburg-Essen, Essen, Germany Abstract: “What is the O2 concentration in a normoxic cell culture incubator?” This and other frequently asked questions in hypoxia research will be answered in this review. Our intention is to give a simple introduction to the physics of gases that would be helpful for newcomers to the field of hypoxia research. We will provide background knowledge about questions often asked, but without straightforward answers. What is O2 concentration, and what is O2 partial pressure? What is normoxia, and what is hypoxia? How much O2 is experienced by a cell residing in a culture dish in vitro vs in a tissue in vivo? By the way, the O2 concentration in a normoxic incubator is 18.6%, rather than 20.9% or 20%, as commonly stated in research publications. And this is strictly only valid for incubators at sea level. Keywords: gas laws, hypoxia-inducible factor, Krogh tissue cylinder, oxygen diffusion, partial pressure, tissue oxygen levels

Hypoxanthine as a measurement of hypoxia.

Science.gov (United States)

Saugstad, O D

1975-04-01

The hypoxanthine concentration in plasma was found to be a sensitive parameter of hypoxia of the fetus and the newborn infant. The plasma level of hypoxanthine in the umbilical cord in 29 newborn infants with normal delivery varied between 0 and 11.0 mumol/liter with a mean of 5.8 mumol/liter, SD 3.0 mumol/liter. Compared with this reference group the hypoxanthine concentration in plasma of the umbilical cord in 10 newborn infants with clinical signs of intrauterine hypoxia during labor was found to be significantly higher, with a range of 11.0-61.5 mumol/liter, with a mean of 25.0 mumol/liter, SD 18.0 mumol/liter. The plasma level of hypoxanthine in two premature babies developing an idiopathic respiratory distress syndrome was monitored. The metabolite was found to be considerably increased, in one of them more than 24 hr after a period of hypoxia necessitating artificial ventilation. The hypoxanthine level in plasma of umbilical arterial blood was followed about 2 hr postpartum in three newborn infants with clinical signs of intrauterine hypoxia. The decrease of the plasma concentration of the metabolite seemed to be with a constant velocity, as it was about 10 mumol/liter/hr in these cases. A new method was used for the determination of hypoxanthine in plasma, based on the principle that PO2 decreased when hypoxanthine is oxidized to uric acid.

Effect of hypoxia on thallium kinetics in cultured chick myocardial cells

International Nuclear Information System (INIS)

Friedman, B.J.; Beihn, R.; Friedman, J.P.

1987-01-01

To assess the effect of hypoxia on cellular thallium-201 ( 201 Tl) uptake and washout independent of coronary flow, we studied thallium kinetics during normoxia and hypoxia in cultured chick ventricular cells. Monolayers of contracting ventricular cells grown on coverslips were placed in a chamber and perfused to asymptote with media containing 201 Tl. Perfusates were equilibrated with 5% CO 2 -95% air or 5% CO 2 -95% nitrogen for normoxia and hypoxia, respectively. Washout thallium kinetics were then observed during perfusion with unlabeled media. Twenty paired experiments were performed, randomly alternating the sequence of normoxia and hypoxia. Pharmacokinetics for thallium were determined by computer using standard formulae. Thallium uptake and washout were best described by assuming that intracellular thallium was contained within a single compartment. Cellular thallium uptake, as well as transfer rate constants for thallium uptake and for thallium washout during normoxia and hypoxia, were compared using paired t-tests. During normoxia and hypoxia, respectively, thallium uptake was 22 +/- 7% and 19 +/- 7% of asymptote (p less than 0.01); the compartmental rate constant for uptake by the cell was 0.16 +/- 0.07 min-1 and 0.15 +/- 0.06 min-1 (N.S.); and the transfer rate constant for washout from the cell was 0.26 +/- 0.06 min-1 and 0.23 +/- 0.05 min-1 (p less than 0.01). We conclude that there was a small (14%) decrease in thallium uptake during hypoxia. The rate of thallium uptake and washout was slightly less during hypoxia, although only the rate of washout was significantly less. These data show that cellular accumulation of thallium and the rate of washout of thallium were minimally decreased by hypoxia independent of blood flow

Oroxylin A regulates glucose metabolism in response to hypoxic stress with the involvement of Hypoxia-inducible factor-1 in human hepatoma HepG2 cells.

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Dai, Qinsheng; Yin, Qian; Wei, Libin; Zhou, Yuxin; Qiao, Chen; Guo, Yongjian; Wang, Xiaotang; Ma, Shiping; Lu, Na

2016-08-01

Metabolic alteration in cancer cells is one of the most conspicuous characteristics that distinguish cancer cells from normal cells. In this study, we investigated the influence and signaling ways of oroxylin A affecting cancer cell energy metabolism under hypoxia. The data showed that oroxylin A remarkably reduced the generation of lactate and glucose uptake under hypoxia in HepG2 cells. Moreover, oroxylin A inhibited HIF-1α expression and its stability. The downstream targets (PDK1, LDHA, and HK II), as well as their mRNA levels were also suppressed by oroxylin A under hypoxia. The silencing or the overexpression of HIF-1α assays suggested that HIF-1α is required for metabolic effect of oroxylin A in HepG2 cells during hypoxia. Furthermore, oroxylin A could reduce the expression of complex III in mitochondrial respiratory chain, and then decrease the accumulation of ROS at moderate concentrations (0-50 µM) under hypoxia, which was benefit for its inhibition on glycolytic activity by decreasing ROS-mediated HIF-1 expression. Besides, oroxylin A didn't cause the loss of MMP under hypoxia and had no obvious effects on the expression of OXPHOS complexes, suggesting that oroxylin A did not affect mitochondrial mass at the moderate stress of oroxylin A. The suppressive effect of oroxylin A on glycolysis led to a significantly repress of ATP generation, for ATP generation mostly depends on glycolysis in HepG2 cells. This study revealed a new aspect of glucose metabolism regulation of oroxylin A under hypoxia, which may contribute to its new anticancer mechanism. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Induction of Gastrin Expression in Gastrointestinal Cells by Hypoxia or Cobalt Is Independent of Hypoxia-Inducible Factor (HIF)

OpenAIRE

Xiao, Lin; Kovac, Suzana; Chang, Mike; Shulkes, Arthur; Baldwin, Graham S.; Patel, Oneel

2012-01-01

Gastrin and its precursors have been shown to promote mitogenesis and angiogenesis in gastrointestinal tumors. Hypoxia stimulates tumor growth, but its effect on gastrin gene regulation has not been examined in detail. Here we have investigated the effect of hypoxia on the transcription of the gastrin gene in human gastric cancer (AGS) cells. Gastrin mRNA was measured by real-time PCR, gastrin peptides were measured by RIA, and gastrin promoter activity was measured by dual-luciferase reporte...

Hypoxia-induced dysfunction of rat diaphragm: role of peroxynitrite.

NARCIS (Netherlands)

Zhu, X.; Heunks, L.M.A.; Versteeg, E.M.M.; Heijden, E. van der; Ennen, L.; Kuppevelt, A.H.M.S.M. van; Vina, J.; Dekhuijzen, P.N.R.

2005-01-01

Oxidants may play a role in hypoxia-induced respiratory muscle dysfunction. In the present study we hypothesized that hypoxia-induced impairment in diaphragm contractility is associated with elevated peroxynitrite generation. In addition, we hypothesized that strenuous contractility of the diaphragm

[Influence of exogenous gamma-aminobutyric acid (GABA) on GABA metabolism and amino acid contents in roots of melon seedling under hypoxia stress].

Science.gov (United States)

Wang, Chun-Yan; Li, Jing-Rui; Xia, Qing-Ping; Wu, Xiao-Lei; Gao, Hong-Bo

2014-07-01

This paper investigated the influence of gamma-aminobutyric acid (GABA) on GABA metabolism and amino acid content under hypoxia stress by accurately controlling the level of dissolved oxygen in hydroponics, using the roots of melon 'Xiyu 1' seedlings as the test material. The results showed that compared with the control, the growth of roots was inhibited seriously under hypoxia stress. Meanwhile, the hypoxia-treated roots had significantly higher activities of glutamate decarboxylase (GAD), glutamate dehydrogenase (GDH), glutamate synthase (GOGAT), glutamine synthetase (GS), alanine aminotransferase (ALT), aspartate aminotransferase (AST) as well as the contents of GABA, pyruvic acid, alanine (Ala) and aspartic acid (Asp). But the contents of glutamic acid (Glu) and alpha-keto glutaric acid in roots under hypoxia stress was obviously lower than those of the control. Exogenous treatment with GABA alleviated the inhibition effect of hypoxia stress on root growth, which was accompanied by an increase in the contents of endogenous GABA, Glu, alpha-keto glutaric acid and Asp. Furthermore, under hypoxia stress, the activities of GAD, GDH, GOGAT, GS, ALT, AST as well as the contents of pyruvic acid and Ala significantly decreased in roots treated with GABA. However, adding GABA and viny-gamma-aminobutyric acid (VGB) reduced the alleviation effect of GABA on melon seedlings under hypoxia stress. The results suggested that absorption of GABA by roots could alleviate the injury of hypoxia stress to melon seedlings. This meant that GABA treatment allows the normal physiological metabolism under hypoxia by inhibiting the GAD activity through feedback and maintaining higher Glu content as well as the bal- ance of carbon and nitrogen.

Hypoxia modifies the feeding preferences of Drosophila. Consequences for diet dependent hypoxic survival

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Frelin Christian

2010-05-01

Full Text Available Abstract Background Recent attention has been given to the relationships between diet, longevity, aging and resistance to various forms of stress. Flies do not simply ingest calories. They sense different concentrations of carbohydrate and protein macronutrients and they modify their feeding behavior in response to changes in dietary conditions. Chronic hypoxia is a major consequence of cardiovascular diseases. Dietary proteins have recently been shown to decrease the survival of chronically hypoxic Drosophila. Whether flies modify their feeding behavior in response to hypoxia is not currently known. This study uses the recently developed capillary feeding assay to analyze the feeding behavior of normoxic and chronically hypoxic Drosophila melanogaster. Results The intakes rates of sucrose and yeast by normoxic or chronically hypoxic flies (5% O2 were analyzed under self selecting and "no choice" conditions. Chronically hypoxic flies fed on pure yeast diets or mixed diets under self selection conditions stopped feeding on yeast. Flies fed on mixed diets under "no choice" conditions reduced their food intakes. Hypoxia did not modify the adaptation of flies to diluted diets or to imbalanced diets. Mortality was assessed in parallel experiments. Dietary yeast had two distinct effects on hypoxic flies (i a repellent action which eventually led to starvation and which was best observed in the absence of dietary sucrose and (ii a toxic action which led to premature death. Finally we determined that hypoxic survivals were correlated to the intakes of sucrose, which suggested that dietary yeast killed flies by reducing their intake of sucrose. The feeding preferences of adult Drosophila were insensitive to NO scavengers, NO donor molecules and inhibitors of phosphodiesterases which are active on Drosophila larvae. Conclusion Chronically hypoxic flies modify their feeding behavior. They avoid dietary yeast which appears to be toxic. Hypoxic survival is

Retinal neuroprotection by hypoxic preconditioning is independent of hypoxia-inducible factor-1 alpha expression in photoreceptors.

Science.gov (United States)

Thiersch, Markus; Lange, Christina; Joly, Sandrine; Heynen, Severin; Le, Yun Zheng; Samardzija, Marijana; Grimm, Christian

2009-06-01

Hypoxic preconditioning stabilizes hypoxia-inducible factor (HIF) 1 alpha in the retina and protects photoreceptors against light-induced cell death. HIF-1 alpha is one of the major transcription factors responding to low oxygen tension and can differentially regulate a large number of target genes. To analyse whether photoreceptor-specific expression of HIF-1 alpha is essential to protect photoreceptors by hypoxic preconditioning, we knocked down expression of HIF-1 alpha specifically in photoreceptor cells, using the cyclization recombinase (Cre)-lox system. The Cre-mediated knockdown caused a 20-fold reduced expression of Hif-1 alpha in the photoreceptor cell layer. In the total retina, RNA expression was reduced by 65%, and hypoxic preconditioning led to only a small increase in HIF-1 alpha protein levels. Accordingly, HIF-1 target gene expression after hypoxia was significantly diminished. Retinas of Hif-1 alpha knockdown animals did not show any pathological alterations, and tolerated hypoxic exposure in a comparable way to wild-type retinas. Importantly, the strong neuroprotective effect of hypoxic preconditioning against light-induced photoreceptor degeneration persisted in knockdown mice, suggesting that hypoxia-mediated survival of light exposure does not depend on an autocrine action of HIF-1 alpha in photoreceptor cells. Hypoxia-mediated stabilization of HIF-2 alpha and phosphorylation of signal transducer and activator of transcription 3 (STAT 3) were not affected in the retinas of Hif-1 alpha knockdown mice. Thus, these factors are candidates for regulating the resistance of photoreceptors to light damage after hypoxic preconditioning, along with several potentially neuroprotective genes that were similarly induced in hypoxic knockdown and control mice.

Severe hypoxia affects exercise performance independently of afferent feedback and peripheral fatigue.

Science.gov (United States)

Millet, Guillaume Y; Muthalib, Makii; Jubeau, Marc; Laursen, Paul B; Nosaka, Kazunori

2012-04-01

To test the hypothesis that hypoxia centrally affects performance independently of afferent feedback and peripheral fatigue, we conducted two experiments under complete vascular occlusion of the exercising muscle under different systemic O(2) environmental conditions. In experiment 1, 12 subjects performed repeated submaximal isometric contractions of the elbow flexor to exhaustion (RCTE) with inspired O(2) fraction fixed at 9% (severe hypoxia, SevHyp), 14% (moderate hypoxia, ModHyp), 21% (normoxia, Norm), or 30% (hyperoxia, Hyper). The number of contractions (performance), muscle (biceps brachii), and prefrontal near-infrared spectroscopy (NIRS) parameters and high-frequency paired-pulse (PS100) evoked responses to electrical muscle stimulation were monitored. In experiment 2, 10 subjects performed another RCTE in SevHyp and Norm conditions in which the number of contractions, biceps brachii electromyography responses to electrical nerve stimulation (M wave), and transcranial magnetic stimulation responses (motor-evoked potentials, MEP, and cortical silent period, CSP) were recorded. Performance during RCTE was significantly reduced by 10-15% in SevHyp (arterial O(2) saturation, SpO(2) = ∼75%) compared with ModHyp (SpO(2) = ∼90%) or Norm/Hyper (SpO(2) > 97%). Performance reduction in SevHyp occurred despite similar 1) metabolic (muscle NIRS parameters) and functional (changes in PS100 and M wave) muscle states and 2) MEP and CSP responses, suggesting comparable corticospinal excitability and spinal and cortical inhibition between SevHyp and Norm. It is concluded that, in SevHyp, performance and central drive can be altered independently of afferent feedback and peripheral fatigue. It is concluded that submaximal performance in SevHyp is partly reduced by a mechanism related directly to brain oxygenation.

Melatonin modulates the fetal cardiovascular defense response to acute hypoxia.

Science.gov (United States)

Thakor, Avnesh S; Allison, Beth J; Niu, Youguo; Botting, Kimberley J; Serón-Ferré, Maria; Herrera, Emilio A; Giussani, Dino A

2015-08-01

Experimental studies in animal models supporting protective effects on the fetus of melatonin in adverse pregnancy have prompted clinical trials in human pregnancy complicated by fetal growth restriction. However, the effects of melatonin on the fetal defense to acute hypoxia, such as that which may occur during labor, remain unknown. This translational study tested the hypothesis, in vivo, that melatonin modulates the fetal cardiometabolic defense responses to acute hypoxia in chronically instrumented late gestation fetal sheep via alterations in fetal nitric oxide (NO) bioavailability. Under anesthesia, 6 fetal sheep at 0.85 gestation were instrumented with vascular catheters and a Transonic flow probe around a femoral artery. Five days later, fetuses were exposed to acute hypoxia with or without melatonin treatment. Fetal blood was taken to determine blood gas and metabolic status and plasma catecholamine concentrations. Hypoxia during melatonin treatment was repeated during in vivo NO blockade with the NO clamp. This technique permits blockade of de novo synthesis of NO while compensating for the tonic production of the gas, thereby maintaining basal cardiovascular function. Melatonin suppressed the redistribution of blood flow away from peripheral circulations and the glycemic and plasma catecholamine responses to acute hypoxia. These are important components of the fetal brain sparing response to acute hypoxia. The effects of melatonin involved NO-dependent mechanisms as the responses were reverted by fetal treatment with the NO clamp. Melatonin modulates the in vivo fetal cardiometabolic responses to acute hypoxia by increasing NO bioavailability. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effects of intermittent hypoxia on running economy.

Science.gov (United States)

Burtscher, M; Gatterer, H; Faulhaber, M; Gerstgrasser, W; Schenk, K

2010-09-01

We investigated the effects of two 5-wk periods of intermittent hypoxia on running economy (RE). 11 male and female middle-distance runners were randomly assigned to the intermittent hypoxia group (IHG) or to the control group (CG). All athletes trained for a 13-wk period starting at pre-season until the competition season. The IHG spent additionally 2 h at rest on 3 days/wk for the first and the last 5 weeks in normobaric hypoxia (15-11% FiO2). RE, haematological parameters and body composition were determined at low altitude (600 m) at baseline, after the 5 (th), the 8 (th) and the 13 (th) week of training. RE, determined by the relative oxygen consumption during submaximal running, (-2.3+/-1.2 vs. -0.3+/-0.7 ml/min/kg, Ptraining phase. Georg Thieme Verlag KG Stuttgart . New York.

Synergistic effects of hypoxia and increasing CO2 on benthic invertebrates of the central Chilean coast

KAUST Repository

Steckbauer, Alexandra

2015-07-10

Ocean acidification (OA) and hypoxic events are an increasing worldwide problem, but the synergetic effects of these factors are seldom explored. However, this synergetic occurrence of stressors is prevalent. The coastline of Chile not only suffers from coastal hypoxia but the cold, oxygen-poor waters in upwelling events are also supersaturated in CO2, a study site to explore the combined effect of OA and hypoxia. We experimentally evaluated the metabolic response of different invertebrate species (2 anthozoans, 9 molluscs, 4 crustaceans, 2 echinoderms) of the coastline of central Chile (33°30′S, 71°37′W) to hypoxia and OA within predicted levels and in a full factorial design. Organisms were exposed to 4 different treatments (ambient, low oxygen, high CO2, and the combination of low oxygen and high CO2) and metabolism was measured after 3 and 6 days. We show that the combination of hypoxia and increased pCO2 reduces the respiration significantly, compared to a single stressor. The evaluation of synergistic pressures, a more realistic scenario than single stressors, is crucial to evaluate the effect of future changes for coastal species and our results provide the first insight on what might happen in the next 100 years.

Synergistic effects of hypoxia and increasing CO2 on benthic invertebrates of the central Chilean coast

KAUST Repository

Steckbauer, Alexandra; Ramajo, Laura; Hendriks, Iris E.; Fernandez, Miriam; Lagos, Nelson A.; Prado, Luis; Duarte, Carlos M.

2015-01-01

Ocean acidification (OA) and hypoxic events are an increasing worldwide problem, but the synergetic effects of these factors are seldom explored. However, this synergetic occurrence of stressors is prevalent. The coastline of Chile not only suffers from coastal hypoxia but the cold, oxygen-poor waters in upwelling events are also supersaturated in CO2, a study site to explore the combined effect of OA and hypoxia. We experimentally evaluated the metabolic response of different invertebrate species (2 anthozoans, 9 molluscs, 4 crustaceans, 2 echinoderms) of the coastline of central Chile (33°30′S, 71°37′W) to hypoxia and OA within predicted levels and in a full factorial design. Organisms were exposed to 4 different treatments (ambient, low oxygen, high CO2, and the combination of low oxygen and high CO2) and metabolism was measured after 3 and 6 days. We show that the combination of hypoxia and increased pCO2 reduces the respiration significantly, compared to a single stressor. The evaluation of synergistic pressures, a more realistic scenario than single stressors, is crucial to evaluate the effect of future changes for coastal species and our results provide the first insight on what might happen in the next 100 years.

Ontogenetic Responses of Calanus chilensis to Hypoxia from Northern Chile (23ºS), Humboldt Current Ecosystem

Science.gov (United States)

Ruz, P. M.; Hidalgo, P.; Escribano, R.; Franco-Cisterna, B.; Yebra, L.; Keister, J. E.

2016-02-01

Eastern Boundary Upwelling Systems are being subjected to expansion, intensification and shoaling of Oxygen Minimum Zones (OMZ's), as a result of ongoing climate change. To understand how dominant epipelagic copepods may respond to stressful conditions induced by low oxygen, we experimentally studied the effect of hypoxia over the stage-specific physiology of Calanus chilensis from the Mejillones Bay (23°S — 70°W), northern Chile, during the winters of 2013 and 2014. Females, eggs and nauplii (NI to NIV) of C. chilensis were incubated under hypoxia ( 0.7 mg O2 L-1) and normoxia ( 8.3 mg O2 L-1) conditions at a constant temperature of 14ºC as to estimate egg production rate (EPR), hatching success (HS) and naupliar growth and development time. Additionally, we estimated survivorship by using Neutral Red technique, and also examined female metabolism by measuring specific activity of the enzymes Aminoacyl-tRNA synthetases (spAARS) (growth index) and the electron transport system (spETS) (potential respiration). Survival of females and EPR were not significantly affected by dissolved oxygen (DO) conditions, coinciding with no significant changes in their metabolism. By contrast, HS was reduced from normoxia (70%) to hypoxia (30%), whereas naupliar growth (NI to NIII) was lower under hypoxia (0.155 ± 0.007 d-1) than normoxia (0.237 ± 0.006 d-1), resulting also in a longer development time, 6.490 ± 0.353 d and 4.238 ± 0.149 d, respectively. Most eggs and nauplii collected at the end of the experiments were alive, although a higher proportion of organisms were recovered in normoxia than hypoxia. Our results revealed stage-specific responses to hypoxia in C. chilensis and the importance of ontogenetic responses to variable levels of oxygenation in the upwelling zone.

High-Intensity Interval Training in Normobaric Hypoxia Leads to Greater Body Fat Loss in Overweight/Obese Women than High-Intensity Interval Training in Normoxia.

Science.gov (United States)

Camacho-Cardenosa, Alba; Camacho-Cardenosa, Marta; Burtscher, Martin; Martínez-Guardado, Ismael; Timon, Rafael; Brazo-Sayavera, Javier; Olcina, Guillermo

2018-01-01

A moderate hypoxic stimulus is considered a promising therapeutic modality for several pathological states including obesity. There is scientific evidence suggesting that when hypoxia and physical activity are combined, they could provide benefits for the obese population. The aim of the present study was to investigate if exposure to hypoxia combined with two different protocols of high-intensity interval exercise in overweight/obese women was more effective compared with exercise in normoxia. Study participants included 82 overweight/obese women, who started a 12 week program of 36 sessions, and were randomly divided into four groups: (1) aerobic interval training in hypoxia (AitH; FiO 2 = 17.2%; n = 13), (2) aerobic interval training in normoxia (AitN; n = 15), (3) sprint interval training in hypoxia (SitH; n = 15), and (4) sprint interval training in normoxia (SitN; n = 18). Body mass, body mass index, percentage of total fat mass, muscle mass, basal metabolic rate, fat, and carbohydrate oxidation, and fat and carbohydrate energy were assessed. Outcomes were measured at baseline (T1), after 18 training sessions (T2), 7 days after the last session (T3), and 4 weeks after the last session (T4). The fat mass in the SitH group was significantly reduced compared with the SitN group from T1 to T3 ( p Fat mass in the AitH group decreased significantly ( p fat mass, with a statistically significant reduction in the hypoxia groups ( p fat oxidation tended to increase and oxidation of carbohydrates tended to decrease in both hypoxia groups, the tendency was reversed in the normoxia groups. Thus, high-intensity interval training under normobaric intermittent hypoxia for 12 weeks in overweight/obese women seems to be promising for reducing body fat content with a concomitant increase in muscle mass.

Susceptibility to hypoxia and breathing control changes after short-term cold exposures

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Lyudmila T. Kovtun

2013-08-01

Full Text Available Background . Hypoxia is the reduction of oxygen availability due to external or internal causes. There is large individual variability of response to hypoxia. Objective . The aim of this study was to define individual and typological features in susceptibility to hypoxia, its interrelation with hypoxic and hypercapnic ventilatory responses (HVR and HCVR, respectively and their changes after cold acclimation. Design . Twenty-four healthy men were tested. HVR and HCVR were measured by the rebreathing method during hypoxic and hypercapnic tests, respectively. These tests were carried out in thermoneutral conditions before and after cold exposures (nude, at 13°C, 2 h daily, for 10 days. Susceptibility to hypoxia (sSaO2 was determined as haemoglobin saturation slope during hypoxic test. Results . It was found that HVR and HCVR significantly increased and susceptibility to hypoxia (sSaO2 tended to decrease after cold acclimation. According to sSaO2 results before cold exposures, the group was divided into 3: Group 1 – with high susceptibility to hypoxia, Group 2 – medium and Group 3 – low susceptibility. Analysis of variances (MANOVA shows the key role of susceptibility to hypoxia and cold exposures and their interrelation. Posterior analysis (Fisher LSD showed significant difference in susceptibility to hypoxia between the groups prior to cold acclimation, while HVR and HCVR did not differ between the groups. After cold acclimation, susceptibility to hypoxia was not significantly different between the groups, while HCVR significantly increased in Groups 1 and 3, HVR significantly increased in Group 3 and HCVR, HVR did not change in Group 2. Conclusions . Short-term cold exposures caused an increase in functional reserves and improved oxygen supply of tissues in Group 1. Cold exposure hypoxia has caused energy loss in Group 3. Group 2 showed the most appropriate energy conservation reaction mode to cold exposures. No relation was found between

Elevation of hypoxia resistance with the use of gutimine

Energy Technology Data Exchange (ETDEWEB)

Vinogradov, V.M.; Pastushenkov, L.V.; Sumina, E.N.

Experimental data demonstrating the protection from the adverse effects of hypoxia offered by the antioxidant gutimine and its analogs are presented. The experiments included preliminary studies of hypoxia resistance and recovery under simulated altitude, studies of circulatory hypoxia in the brain and in intrauterine fetuses, studies of myocardial ischemia during acute and chronic experiments and studies where cardiac, kidney and limb circulation is cut off. The compound was also found to be effective in cases of hemorrhagic hypotension, complex hypoxia in peritonitis, meningococcal meningitis, and the weakening of uterine muscle contractility during prolonged deliveries, and in cranial-cerebral trauma. Mechanisms of the antihypoxic action of gutimine and its analogs have been found to include the reduction of oxygen utilization, the activation of aerobic and anaerobic metabolism, the acceleration of lactate utilization, the inhibition of lipolysis in fat tissue, and stabilization of cell membranes. Clinical observations also support the experimental data.

The cross-tissue metabolic response of abalone (Haliotis midae) to functional hypoxia.

Science.gov (United States)

Venter, Leonie; Loots, Du Toit; Mienie, Lodewyk J; Jansen van Rensburg, Peet J; Mason, Shayne; Vosloo, Andre; Lindeque, Jeremie Z

2018-03-23

Functional hypoxia is a stress condition caused by the abalone itself as a result of increased muscle activity, which generally necessitates the employment of anaerobic metabolism if the activity is sustained for prolonged periods. With that being said, abalone are highly reliant on anaerobic metabolism to provide partial compensation for energy production during oxygen-deprived episodes. However, current knowledge on the holistic metabolic response for energy metabolism during functional hypoxia, and the contribution of different metabolic pathways and various abalone tissues towards the overall accumulation of anaerobic end-products in abalone are scarce. Metabolomics analysis of adductor muscle, foot muscle, left gill, right gill, haemolymph and epipodial tissue samples indicated that South African abalone ( Haliotis midae) subjected to functional hypoxia utilises predominantly anaerobic metabolism, and depends on all of the main metabolite classes (proteins, carbohydrates and lipids) for energy supply. Functional hypoxia caused increased levels of anaerobic end-products: lactate, alanopine, tauropine, succinate and alanine. Also, elevation in arginine levels was detected, confirming that abalone use phosphoarginine to generate energy during functional hypoxia. Different tissues showed varied metabolic responses to hypoxia, with functional hypoxia showing excessive changes in the adductor muscle and gills. From this metabolomics investigation, it becomes evident that abalone are metabolically able to produce sufficient amounts of energy when functional hypoxia is experienced. Also, tissue interplay enables the adjustment of H. midae energy requirements as their metabolism shifts from aerobic to anaerobic respiration during functional hypoxia.This article has an associated First Person interview with the first author of the paper. © 2018. Published by The Company of Biologists Ltd.

The cross-tissue metabolic response of abalone (Haliotis midae to functional hypoxia

Directory of Open Access Journals (Sweden)

Leonie Venter

2018-03-01

Full Text Available Functional hypoxia is a stress condition caused by the abalone itself as a result of increased muscle activity, which generally necessitates the employment of anaerobic metabolism if the activity is sustained for prolonged periods. With that being said, abalone are highly reliant on anaerobic metabolism to provide partial compensation for energy production during oxygen-deprived episodes. However, current knowledge on the holistic metabolic response for energy metabolism during functional hypoxia, and the contribution of different metabolic pathways and various abalone tissues towards the overall accumulation of anaerobic end-products in abalone are scarce. Metabolomics analysis of adductor muscle, foot muscle, left gill, right gill, haemolymph and epipodial tissue samples indicated that South African abalone (Haliotis midae subjected to functional hypoxia utilises predominantly anaerobic metabolism, and depends on all of the main metabolite classes (proteins, carbohydrates and lipids for energy supply. Functional hypoxia caused increased levels of anaerobic end-products: lactate, alanopine, tauropine, succinate and alanine. Also, elevation in arginine levels was detected, confirming that abalone use phosphoarginine to generate energy during functional hypoxia. Different tissues showed varied metabolic responses to hypoxia, with functional hypoxia showing excessive changes in the adductor muscle and gills. From this metabolomics investigation, it becomes evident that abalone are metabolically able to produce sufficient amounts of energy when functional hypoxia is experienced. Also, tissue interplay enables the adjustment of H. midae energy requirements as their metabolism shifts from aerobic to anaerobic respiration during functional hypoxia. This article has an associated First Person interview with the first author of the paper.

Knock-down of hypoxia-induced carbonic anhydrases IX and XII radiosensitizes tumor cells by increasing intracellular acidosis

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Doyen, Jérome [Institute for Research on Cancer and Aging of Nice, CNRS UMR 7284, University of Nice Sophia-Antipolis,, Nice (France); Department of Radiation Oncology, Centre Antoine-Lacassagne, Nice (France); Parks, Scott K. [Institute for Research on Cancer and Aging of Nice, CNRS UMR 7284, University of Nice Sophia-Antipolis,, Nice (France); Marcié, Serge [Department of Radiation Oncology, Centre Antoine-Lacassagne, Nice (France); Pouysségur, Jacques [Institute for Research on Cancer and Aging of Nice, CNRS UMR 7284, University of Nice Sophia-Antipolis,, Nice (France); Centre Scientifique de Monaco (Monaco); Chiche, Johanna, E-mail: chiche@unice.fr [Institute for Research on Cancer and Aging of Nice, CNRS UMR 7284, University of Nice Sophia-Antipolis,, Nice (France)

2013-01-07

The relationship between acidosis within the tumor microenvironment and radioresistance of hypoxic tumor cells remains unclear. Previously we reported that hypoxia-induced carbonic anhydrases (CA) IX and CAXII constitute a robust intracellular pH (pH{sub i})-regulating system that confers a survival advantage on hypoxic human colon carcinoma LS174Tr cells in acidic microenvironments. Here we investigate the role of acidosis, CAIX and CAXII knock-down in combination with ionizing radiation. Fibroblasts cells (-/+ CAIX) and LS174Tr cells (inducible knock-down for ca9/ca12) were analyzed for cell cycle phase distribution and survival after irradiation in extracellular pH{sub o} manipulations and hypoxia (1% O{sub 2}) exposure. Radiotherapy was used to target ca9/ca12-silenced LS174Tr tumors grown in nude mice. We found that diminishing the pH{sub i}-regulating capacity of fibroblasts through inhibition of Na{sup +}/H{sup +} exchanger 1 sensitize cells to radiation-induced cell death. Secondly, the pH{sub i}-regulating function of CAIX plays a key protective role in irradiated fibroblasts in an acidic environment as accompanied by a reduced number of cells in the radiosensitive phases of the cell cycle. Thirdly, we demonstrate that irradiation of LS174Tr spheroids, silenced for either ca9 or both ca9/ca12, showed a respective 50 and 75% increase in cell death as a result of a decrease in cell number in the radioresistant S phase and a disruption of CA-mediated pH{sub i} regulation. Finally, LS174Tr tumor progression was strongly decreased when ca9/ca12 silencing was combined with irradiation in vivo. These findings highlight the combinatory use of radiotherapy with targeting of the pH{sub i}-regulating CAs as an anti-cancer strategy.

Midcervical neuronal discharge patterns during and following hypoxia

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Sandhu, M. S.; Baekey, D. M.; Maling, N. G.; Sanchez, J. C.; Reier, P. J.

2014-01-01

Anatomical evidence indicates that midcervical interneurons can be synaptically coupled with phrenic motoneurons. Accordingly, we hypothesized that interneurons in the C3–C4 spinal cord can display discharge patterns temporally linked with inspiratory phrenic motor output. Anesthetized adult rats were studied before, during, and after a 4-min bout of moderate hypoxia. Neuronal discharge in C3–C4 lamina I–IX was monitored using a multielectrode array while phrenic nerve activity was extracellularly recorded. For the majority of cells, spike-triggered averaging (STA) of ipsilateral inspiratory phrenic nerve activity based on neuronal discharge provided no evidence of discharge synchrony. However, a distinct STA phrenic peak with a 6.83 ± 1.1 ms lag was present for 5% of neurons, a result that indicates a monosynaptic connection with phrenic motoneurons. The majority (93%) of neurons changed discharge rate during hypoxia, and the diverse responses included both increased and decreased firing. Hypoxia did not change the incidence of STA peaks in the phrenic nerve signal. Following hypoxia, 40% of neurons continued to discharge at rates above prehypoxia values (i.e., short-term potentiation, STP), and cells with initially low discharge rates were more likely to show STP (P phrenic motoneuron pool, and these cells can modulate inspiratory phrenic output. In addition, the C3–C4 propriospinal network shows a robust and complex pattern of activation both during and following an acute bout of hypoxia. PMID:25552641

The effects of exercise under hypoxia on cognitive function.

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Soichi Ando

Full Text Available Increasing evidence suggests that cognitive function improves during a single bout of moderate exercise. In contrast, exercise under hypoxia may compromise the availability of oxygen. Given that brain function and tissue integrity are dependent on a continuous and sufficient oxygen supply, exercise under hypoxia may impair cognitive function. However, it remains unclear how exercise under hypoxia affects cognitive function. The purpose of this study was to examine the effects of exercise under different levels of hypoxia on cognitive function. Twelve participants performed a cognitive task at rest and during exercise at various fractions of inspired oxygen (FIO2: 0.209, 0.18, and 0.15. Exercise intensity corresponded to 60% of peak oxygen uptake under normoxia. The participants performed a Go/No-Go task requiring executive control. Cognitive function was evaluated using the speed of response (reaction time and response accuracy. We monitored pulse oximetric saturation (SpO2 and cerebral oxygenation to assess oxygen availability. SpO2 and cerebral oxygenation progressively decreased during exercise as the FIO2 level decreased. Nevertheless, the reaction time in the Go-trial significantly decreased during moderate exercise. Hypoxia did not affect reaction time. Neither exercise nor difference in FIO2 level affected response accuracy. An additional experiment indicated that cognitive function was not altered without exercise. These results suggest that the improvement in cognitive function is attributable to exercise, and that hypoxia has no effects on cognitive function at least under the present experimental condition. Exercise-cognition interaction should be further investigated under various environmental and exercise conditions.

Regulation of HIF prolyl hydroxylases by hypoxia-inducible factors.

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Aprelikova, Olga; Chandramouli, Gadisetti V R; Wood, Matthew; Vasselli, James R; Riss, Joseph; Maranchie, Jodi K; Linehan, W Marston; Barrett, J Carl

2004-06-01

Hypoxia and induction of hypoxia-inducible factors (HIF-1alpha and HIF-2alpha) is a hallmark of many tumors. Under normal oxygen tension HIF-alpha subunits are rapidly degraded through prolyl hydroxylase dependent interaction with the von Hippel-Lindau (VHL) tumor suppressor protein, a component of E3 ubuiquitin ligase complex. Using microarray analysis of VHL mutated and re-introduced cells, we found that one of the prolyl hydroxylases (PHD3) is coordinately expressed with known HIF target genes, while the other two family members (PHD1 and 2) did not respond to VHL. We further tested the regulation of these genes by HIF-1 and HIF-2 and found that siRNA targeted degradation of HIF-1alpha and HIF-2alpha results in decreased hypoxia-induced PHD3 expression. Ectopic overexpression of HIF-2alpha in two different cell lines provided a much better induction of PHD3 gene than HIF-1alpha. In contrast, we demonstrate that PHD2 is not affected by overexpression or downregulation of HIF-2alpha. However, induction of PHD2 by hypoxia has HIF-1-independent and -dependent components. Short-term hypoxia (4 h) results in induction of PHD2 independent of HIF-1, while PHD2 accumulation by prolonged hypoxia (16 h) was decreased by siRNA-mediated degradation of HIF-1alpha subunit. These data further advance our understanding of the differential role of HIF factors and putative feedback loop in HIF regulation. Copyright 2004 Wiley-Liss, Inc.

Crosstalk between nitrite, myoglobin and reactive oxygen species to regulate vasodilation under hypoxia.

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Matthias Totzeck

Full Text Available The systemic response to decreasing oxygen levels is hypoxic vasodilation. While this mechanism has been known for more than a century, the underlying cellular events have remained incompletely understood. Nitrite signaling is critically involved in vessel relaxation under hypoxia. This can be attributed to the presence of myoglobin in the vessel wall together with other potential nitrite reductases, which generate nitric oxide, one of the most potent vasodilatory signaling molecules. Questions remain relating to the precise concentration of nitrite and the exact dose-response relations between nitrite and myoglobin under hypoxia. It is furthermore unclear whether regulatory mechanisms exist which balance this interaction. Nitrite tissue levels were similar across all species investigated. We then investigated the exact fractional myoglobin desaturation in an ex vivo approach when gassing with 1% oxygen. Within a short time frame myoglobin desaturated to 58±12%. Given that myoglobin significantly contributes to nitrite reduction under hypoxia, dose-response experiments using physiological to pharmacological nitrite concentrations were conducted. Along all concentrations, abrogation of myoglobin in mice impaired vasodilation. As reactive oxygen species may counteract the vasodilatory response, we used superoxide dismutase and its mimic tempol as well as catalase and ebselen to reduce the levels of reactive oxygen species during hypoxic vasodilation. Incubation of tempol in conjunction with catalase alone and catalase/ebselen increased the vasodilatory response to nitrite. Our study shows that modest hypoxia leads to a significant nitrite-dependent vessel relaxation. This requires the presence of vascular myoglobin for both physiological and pharmacological nitrite levels. Reactive oxygen species, in turn, modulate this vasodilation response.

Comparing the effect of hypercapnia and hypoxia on the electroencephalogram during wakefulness.

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Wang, David; Yee, Brendon J; Wong, Keith K; Kim, Jong Won; Dijk, Derk-Jan; Duffin, James; Grunstein, Ronald R

2015-01-01

Hypoxia has been postulated as a key mechanism for neurocognitive impairment in sleep-disordered breathing. However, the effect of hypoxia on the electroencephalogram (EEG) is not clear. We examined quantitative EEG recordings from 20 normal volunteers under three 5-min ventilatory control protocols: progressive hypercapnia with iso-hyperoxia (pO2=150mmHg) (Protocol 1), progressive hypercapnia with iso-hypoxia (pO2=50mmHg) (Protocol 2), and progressive hypoxia with a CO2 scrubber in the circuit (Protocol 3). Each protocol started with a 5-min session of breathing room air as baseline. In Protocol 1, compared to its baseline, iso-hyperoxia hypercapnia led to a lower Alpha% and higher Delta/Alpha (D/A) ratio. Similarly, in Protocol 2, the iso-hypoxia hypercapnia induced a higher Delta%, a lower Alpha% and higher D/A ratio. No difference was found in any EEG spectral band including the D/A ratio when Protocols 1 & 2 were compared. In Protocol 3, the Delta%, Alpha% and D/A ratio recorded during hypoxia were not significantly different from baseline. We found that hypercapnia, but not hypoxia, may play a key role in slowing of the EEG in healthy humans. Hypercapnia may be a greater influence than hypoxia on brain neuroelectrical activities. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Identification of Hypoxia-Regulated Proteins Using MALDI-Mass Spectrometry Imaging Combined with Quantitative Proteomics

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Djidja, Marie-Claude; Chang, Joan; Hadjiprocopis, Andreas

2014-01-01

Hypoxia is present in most solid tumors and is clinically correlated with increased metastasis and poor patient survival. While studies have demonstrated the role of hypoxia and hypoxia-regulated proteins in cancer progression, no attempts have been made to identify hypoxia-regulated proteins using...

Protection of Pentoxifylline against Testis Injury Induced by Intermittent Hypobaric Hypoxia

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Chen Yao

2016-01-01

Full Text Available To investigate the effect of pentoxifylline (PTX on spermatogenesis dysfunction induced by intermittent hypobaric hypoxia (IHH and unveil the underlying mechanism, experimental animals were assigned to Control, IHH+Vehicle, and IHH+PTX groups and exposed to 4 cycles of 96 h of hypobaric hypoxia followed by 96 h of normobaric normoxia for 32 days. PTX was administered for 32 days. Blood and tissue samples were collected 7 days thereafter. Serum malondialdehyde levels were used to assess lipid peroxidation; ferric-reducing antioxidant power (FRAP, superoxide dismutase, and catalase and glutathione peroxidase enzyme activities were assessed to determine antioxidant capacity in various samples. Testis histopathology was assessed after hematoxylin-eosin staining by Johnsen’s testicular scoring system. Meanwhile, testosterone synthase and vimentin amounts were assessed by immunohistochemistry. Sperm count, motility, and density were assessed to determine epididymal sperm quality. IHH treatment induced significant pathological changes in testicular tissue and enhanced serum lipid peroxide levels, while reducing serum FRAP, antioxidant enzyme activities, and testosterone synthase expression. Moreover, IHH impaired epididymal sperm quality and vimentin structure in Sertoli cells. Oral administration of PTX improved the pathological changes in the testis. IHH may impair spermatogenesis function of testicular tissues by inducing oxidative stress, but this impairment could be attenuated by administration of PTX.

Hypoxia-inducible transcription factor-1α promotes hypoxia-induced A549 apoptosis via a mechanism that involves the glycolysis pathway

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Luo, FengMing; Liu, XiaoJing; Yan, NaiHong; Li, ShuangQing; Cao, GuiQun; Cheng, QingYing; Xia, QingJie; Wang, HongJing

2006-01-01

Hypoxia-inducible transcription factor-1α (HIF-1α), which plays an important role in controlling the hypoxia-induced glycolysis pathway, is a 'master' gene in the tissue hypoxia response during tumor development. However, its role in the apoptosis of non-small cell lung cancer remains unknown. Here, we have studied the effects of HIF-1α on apoptosis by modulating HIF-1α gene expression in A549 cells through both siRNA knock-down and over-expression. A549 cells were transfected with a HIF-1α siRNA plasmid or a HIF-1α expression vector. Transfected cells were exposed to a normoxic or hypoxic environment in the presence or absence of 25 mM HEPES and 2-deoxyglucose (2-DG) (5 mM). The expression of three key genes of the glycolysis pathway, glucose transporter type 1(GLUT1), phosphoglycerate kinase 1(PGK1), and hexokinase 1(HK1), were measured using real-time RT-PCR. Glycolysis was monitored by measuring changes of pH and lactate concentration in the culture medium. Apoptosis was detected by TUNEL assay and flow cytometry. Knocking down expression of HIF-1α inhibited the glycolysis pathway, increased the pH of the culture medium, and protected the cells from hypoxia-induced apoptosis. In contrast, over-expression of HIF-1α accelerated glycolysis in A549 cells, decreased the pH of the culture medium, and enhanced hypoxia-induced apoptosis. These effects of HIF-1α on glycolysis, pH of the medium, and apoptosis were reversed by treatment with the glycolytic inhibitor, 2-DG. Apoptosis induced by HIF-1α over-expression was partially inhibited by increasing the buffering capacity of the culture medium by adding HEPES. During hypoxia in A549 cells, HIF-1α promotes activity of the glycolysis pathway and decreases the pH of the culture medium, resulting in increased cellular apoptosis

HYPOXIA-ACTIVATED PRO-DRUG TH-302 EXHIBITS POTENT TUMOUR SUPPRESSIVE ACTIVITY AND COOPERATES WITH CHEMOTHERAPY AGAINST OSTEOSARCOMA

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Liapis, Vasilios; Labrinidis, Agatha; Zinonos, Irene; Hay, Shelley; Ponomarev, Vladimir; Panagopoulos, Vasilios; DeNichilo, Mark; Ingman, Wendy; Atkins, Gerald J.; Findlay, David M.; Zannettino, Andrew CW.; Evdokiou, Andreas

2015-01-01

Tumour hypoxia is a major cause of treatment failure for a variety of malignancies. However, tumour hypoxia also offers treatment opportunities, exemplified by the development compounds that target hypoxic regions within tumours. TH-302 is a pro-drug created by the conjugation of 2-nitroimidazole to bromo-isophosphoramide (Br-IPM). When TH-302 is delivered to regions of hypoxia, Br-IPM, the DNA cross linking toxin, is released. In this study we assessed the cytotoxic activity of TH-302 against osteosarcoma cells in vitro and evaluated its anticancer efficacy as a single agent, and in combination with doxorubicin, in an orthotopic mouse model of human osteosarcoma (OS). In vitro, TH-302 was potently cytotoxic to osteosarcoma cells selectively under hypoxic conditions, whereas primary normal human osteoblasts were protected. Animals transplanted with OS cells directly into their tibiae and left untreated developed mixed osteolytic/osteosclerotic bone lesions and subsequently developed lung metastases. TH-302 reduced tumor burden in bone and cooperated with doxorubicin to protect bone from osteosarcoma induced bone destruction, while it also reduced lung metastases. TH-302 may therefore be an attractive therapeutic agent with strong activity as a single agent and in combination with chemotherapy against OS. PMID:25444931

Hypoxia-activated pro-drug TH-302 exhibits potent tumor suppressive activity and cooperates with chemotherapy against osteosarcoma.

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Liapis, Vasilios; Labrinidis, Agatha; Zinonos, Irene; Hay, Shelley; Ponomarev, Vladimir; Panagopoulos, Vasilios; DeNichilo, Mark; Ingman, Wendy; Atkins, Gerald J; Findlay, David M; Zannettino, Andrew C W; Evdokiou, Andreas

2015-02-01

Tumor hypoxia is a major cause of treatment failure for a variety of malignancies. However, tumor hypoxia also offers treatment opportunities, exemplified by the development compounds that target hypoxic regions within tumors. TH-302 is a pro-drug created by the conjugation of 2-nitroimidazole to bromo-isophosphoramide (Br-IPM). When TH-302 is delivered to regions of hypoxia, Br-IPM, the DNA cross linking toxin, is released. In this study we assessed the cytotoxic activity of TH-302 against osteosarcoma cells in vitro and evaluated its anticancer efficacy as a single agent, and in combination with doxorubicin, in an orthotopic mouse model of human osteosarcoma (OS). In vitro, TH-302 was potently cytotoxic to osteosarcoma cells selectively under hypoxic conditions, whereas primary normal human osteoblasts were protected. Animals transplanted with OS cells directly into their tibiae and left untreated developed mixed osteolytic/osteosclerotic bone lesions and subsequently developed lung metastases. TH-302 reduced tumor burden in bone and cooperated with doxorubicin to protect bone from osteosarcoma induced bone destruction, while it also reduced lung metastases. TH-302 may therefore be an attractive therapeutic agent with strong activity as a single agent and in combination with chemotherapy against OS. Crown Copyright © 2014. Published by Elsevier Ireland Ltd. All rights reserved.

An insert-based enzymatic cell culture system to rapidly and reversibly induce hypoxia: investigations of hypoxia-induced cell damage, protein expression and phosphorylation in neuronal IMR-32 cells

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Ying Huang

2013-11-01

Ischemia-reperfusion injury and tissue hypoxia are of high clinical relevance because they are associated with various pathophysiological conditions such as myocardial infarction and stroke. Nevertheless, the underlying mechanisms causing cell damage are still not fully understood, which is at least partially due to the lack of cell culture systems for the induction of rapid and transient hypoxic conditions. The aim of the study was to establish a model that is suitable for the investigation of cellular and molecular effects associated with transient and long-term hypoxia and to gain insights into hypoxia-mediated mechanisms employing a neuronal culture system. A semipermeable membrane insert system in combination with the hypoxia-inducing enzymes glucose oxidase and catalase was employed to rapidly and reversibly generate hypoxic conditions in the culture medium. Hydrogen peroxide assays, glucose measurements and western blotting were performed to validate the system and to evaluate the effects of the generated hypoxia on neuronal IMR-32 cells. Using the insert-based two-enzyme model, hypoxic conditions were rapidly induced in the culture medium. Glucose concentrations gradually decreased, whereas levels of hydrogen peroxide were not altered. Moreover, a rapid and reversible (onoff generation of hypoxia could be performed by the addition and subsequent removal of the enzyme-containing inserts. Employing neuronal IMR-32 cells, we showed that 3 hours of hypoxia led to morphological signs of cellular damage and significantly increased levels of lactate dehydrogenase (a biochemical marker of cell damage. Hypoxic conditions also increased the amounts of cellular procaspase-3 and catalase as well as phosphorylation of the pro-survival kinase Akt, but not Erk1/2 or STAT5. In summary, we present a novel framework for investigating hypoxia-mediated mechanisms at the cellular level. We claim that the model, the first of its kind, enables researchers to rapidly and

Silibinin inhibits hypoxia-induced HIF-1α-mediated signaling, angiogenesis and lipogenesis in prostate cancer cells: In vitro evidence and in vivo functional imaging and metabolomics.

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Deep, Gagan; Kumar, Rahul; Nambiar, Dhanya K; Jain, Anil K; Ramteke, Anand M; Serkova, Natalie J; Agarwal, Chapla; Agarwal, Rajesh

2017-03-01

Hypoxia is associated with aggressive phenotype and poor prognosis in prostate cancer (PCa) patients suggesting that PCa growth and progression could be controlled via targeting hypoxia-induced signaling and biological effects. Here, we analyzed silibinin (a natural flavonoid) efficacy to target cell growth, angiogenesis, and metabolic changes in human PCa, LNCaP, and 22Rv1 cells under hypoxic condition. Silibinin treatment inhibited the proliferation, clonogenicity, and endothelial cells tube formation by hypoxic (1% O 2 ) PCa cells. Interestingly, hypoxia promoted a lipogenic phenotype in PCa cells via activating acetyl-Co A carboxylase (ACC) and fatty acid synthase (FASN) that was inhibited by silibinin treatment. Importantly, silibinin treatment strongly decreased hypoxia-induced HIF-1α expression in PCa cells together with a strong reduction in hypoxia-induced NADPH oxidase (NOX) activity. HIF-1α overexpression in LNCaP cells significantly increased the lipid accumulation and NOX activity; however, silibinin treatment reduced HIF-1α expression, lipid levels, clonogenicity, and NOX activity even in HIF-1α overexpressing LNCaP cells. In vivo, silibinin feeding (200 mg/kg body weight) to male nude mice with 22Rv1 tumors, specifically inhibited tumor vascularity (measured by dynamic contrast-enhanced MRI) resulting in tumor growth inhibition without directly inducing necrosis (as revealed by diffusion-weighted MRI). Silibinin feeding did not significantly affect tumor glucose uptake measured by FDG-PET; however, reduced the lipid synthesis measured by quantitative 1 H-NMR metabolomics. IHC analyses of tumor tissues confirmed that silibinin feeding decreased proliferation and angiogenesis as well as reduced HIF-1α, FASN, and ACC levels. Together, these findings further support silibinin usefulness against PCa through inhibiting hypoxia-induced signaling. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

N and P as ultimate and proximate limiting nutrients in the northern Gulf of Mexico: implications for hypoxia reduction strategies

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K. Fennel

2018-05-01

Full Text Available The occurrence of hypoxia in coastal oceans is a long-standing and growing problem worldwide and is clearly linked to anthropogenic nutrient inputs. While the need for reducing anthropogenic nutrient loads is generally accepted, it is costly and thus requires scientifically sound nutrient-reduction strategies. Issues under debate include the relative importance of nitrogen (N and phosphorus (P as well as the magnitude of the reduction requirements. The largest anthropogenically induced hypoxic area in North American coastal waters (of 15 000 ± 5000 km2 forms every summer in the northern Gulf of Mexico where the Mississippi and Atchafalaya rivers deliver large amounts of freshwater and nutrients to the shelf. A 2001 plan for reducing this hypoxic area by nutrient management in the watershed called for a reduction of N loads. Since then evidence of P limitation during the time of hypoxia formation has arisen, and a dual nutrient-reduction strategy for this system has been endorsed. Here we report the first systematic analysis of the effects of single and dual nutrient load reductions from a spatially explicit physical–biogeochemical model for the northern Gulf of Mexico. The model has been shown previously to skillfully represent the processes important for hypoxic formation. Our analysis of an ensemble of simulations with stepwise reductions in N, P, and N and P loads provides insight into the effects of both nutrients on primary production and hypoxia, and it allows us to estimate what nutrient reductions would be required for single and dual nutrient-reduction strategies to reach the hypoxia target. Our results show that, despite temporary P limitation, N is the ultimate limiting nutrient for primary production in this system. Nevertheless, a reduction in P load would reduce hypoxia because primary production is P limited in the region where density stratification is conducive to hypoxia development, but reductions in N load have

Culture media from hypoxia conditioned endothelial cells protect human intestinal cells from hypoxia/reoxygenation injury.

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Hummitzsch, Lars; Zitta, Karina; Bein, Berthold; Steinfath, Markus; Albrecht, Martin

2014-03-10

Remote ischemic preconditioning (RIPC) is a phenomenon, whereby short episodes of non-lethal ischemia to an organ or tissue exert protection against ischemia/reperfusion injury in a distant organ. However, there is still an apparent lack of knowledge concerning the RIPC-mediated mechanisms within the target organ and the released factors. Here we established a human cell culture model to investigate cellular and molecular effects of RIPC and to identify factors responsible for RIPC-mediated intestinal protection. Human umbilical vein cells (HUVEC) were exposed to repeated episodes of hypoxia (3 × 15 min) and conditioned culture media (CM) were collected after 24h. Human intestinal cells (CaCo-2) were cultured with or without CM and subjected to 90 min of hypoxia/reoxygenation injury. Reverse transcription-polymerase chain reaction, Western blotting, gelatin zymography, hydrogen peroxide measurements and lactate dehydrogenase (LDH) assays were performed. In HUVEC cultures hypoxic conditioning did not influence the profile of secreted proteins but led to an increased gelatinase activity (Pcultures 90 min of hypoxia/reoxygenation resulted in morphological signs of cell damage, increased LDH levels (Pculture model may help to unravel RIPC-mediated cellular events and to identify molecules released by RIPC. Copyright © 2014 Elsevier Inc. All rights reserved.

Dose prescription and treatment planning based on FMISO-PET hypoxia

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Toma-Dasu, Iuliana; Antonovic, Laura; Uhrdin, Johan; Dasu, Alexandru; Nuyts, Sandra; Dirix, Piet; Haustermans, Karin; Brahme, Anders

2012-01-01

Purpose. The study presents the implementation of a novel method for incorporating hypoxia information from PET-CT imaging into treatment planning and estimates the efficiency of various optimization approaches. Its focuses on the feasibility of optimizing treatment plans based on the non-linear conversion of PET hypoxia images into radiosensitivity maps from the uptake properties of the tracers used. Material and methods. PET hypoxia images of seven head-and-neck cancer patients were used to determine optimal dose distributions needed to counteract the radiation resistance associated with tumor hypoxia assuming various scenarios regarding the evolution of the hypoxic compartment during the treatment. A research planning system for advanced studies has been used to optimize IMRT plans based on hypoxia information from patient PET images. These resulting plans were compared in terms of target coverage for the same fulfilled constraints regarding the organs at risk. Results. The results of a planning study indicated the clinical feasibility of the proposed method for treatment planning based on PET hypoxia. Antihypoxic strategies would lead to small improvements in all the patients, but higher effects are expected for the fraction of patients with hypoxic tumors. For these, individualization of the treatment based on hypoxia PET imaging could lead to improved treatment outcome while creating the premises for limiting the irradiation of the surrounding normal tissues. Conclusions. The proposed approach offers the possibility of improved treatment results as it takes into consideration the heterogeneity and the dynamics of the hypoxic regions. It also provides early identification of the clinical cases that might benefit from dose escalation as well as the cases that could benefit from other counter-hypoxic measures

Hypoxia-ischemia and retinal ganglion cell damage

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Charanjit Kaur

2008-08-01

Full Text Available Charanjit Kaur1, Wallace S Foulds2, Eng-Ang Ling11Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; 2Singapore Eye Research Institute, SingaporeAbstract: Retinal hypoxia is the potentially blinding mechanism underlying a number of sight-threatening disorders including central retinal artery occlusion, ischemic central retinal vein thrombosis, complications of diabetic eye disease and some types of glaucoma. Hypoxia is implicated in loss of retinal ganglion cells (RGCs occurring in such conditions. RGC death occurs by apoptosis or necrosis. Hypoxia-ischemia induces the expression of hypoxia inducible factor-1α and its target genes such as vascular endothelial growth factor (VEGF and nitric oxide synthase (NOS. Increased production of VEGF results in disruption of the blood retinal barrier leading to retinal edema. Enhanced expression of NOS results in increased production of nitric oxide which may be toxic to the cells resulting in their death. Excess glutamate release in hypoxic-ischemic conditions causes excitotoxic damage to the RGCs through activation of ionotropic and metabotropic glutamate receptors. Activation of glutamate receptors is thought to initiate damage in the retina by a cascade of biochemical effects such as neuronal NOS activation and increase in intracellular Ca2+ which has been described as a major contributing factor to RGC loss. Excess production of proinflammatory cytokines also mediates cell damage. Besides the above, free-radicals generated in hypoxic-ischemic conditions result in RGC loss because of an imbalance between antioxidant- and oxidant-generating systems. Although many advances have been made in understanding the mediators and mechanisms of injury, strategies to improve the damage are lacking. Measures to prevent neuronal injury have to be developed.Keywords: retinal hypoxia, retinal ganglion cells, glutamate receptors, neuronal injury, retina

Hypoxia-driven angiogenesis: role of tip cells and extracellular matrix scaffolding.

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Germain, Stéphane; Monnot, Catherine; Muller, Laurent; Eichmann, Anne

2010-05-01

Angiogenesis is a highly coordinated tissue remodeling process leading to blood vessel formation. Hypoxia triggers angiogenesis via induction of expression of growth factors such as vascular endothelial growth factor (VEGF). VEGF instructs endothelial cells to form tip cells, which lead outgrowing capillary sprouts, whereas Notch signaling inhibits sprout formation. Basement membrane deposition and mechanical cues from the extracellular matrix (ECM) induced by hypoxia may participate to coordinated vessel sprouting in conjunction with the VEGF and Notch signaling pathways. Hypoxia regulates ECM composition, deposition, posttranslational modifications and rearrangement. In particular, hypoxia-driven vascular remodeling is dynamically regulated through modulation of ECM-modifying enzyme activities that eventually affect both matricellular proteins and growth factor availability. Better understanding of the complex interplay between endothelial cells and soluble growth factors and mechanical factors from the ECM will certainly have significant implications for understanding the regulation of developmental and pathological angiogenesis driven by hypoxia.

Hypobaric Hypoxia Imbalances Mitochondrial Dynamics in Rat Brain Hippocampus

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Khushbu Jain

2015-01-01

Full Text Available Brain is predominantly susceptible to oxidative stress and mitochondrial dysfunction during hypobaric hypoxia, and therefore undergoes neurodegeneration due to energy crisis. Evidences illustrate a high degree of association for mitochondrial fusion/fission imbalance and mitochondrial dysfunction. Mitochondrial fusion/fission is a recently reported dynamic mechanism which frequently occurs among cellular mitochondrial network. Hence, the study investigated the temporal alteration and involvement of abnormal mitochondrial dynamics (fusion/fission along with disturbed mitochondrial functionality during chronic exposure to hypobaric hypoxia (HH. The Sprague-Dawley rats were exposed to simulated high altitude equivalent to 25000 ft for 3, 7, 14, 21, and 28 days. Mitochondrial morphology, distribution within neurons, enzyme activity of respiratory complexes, Δψm, ADP: ATP, and expression of fission/fusion key proteins were determined. Results demonstrated HH induced alteration in mitochondrial morphology by damaged, small mitochondria observed in neurons with disturbance of mitochondrial functionality and reduced mitochondrial density in neuronal processes manifested by excessive mitochondrial fragmentation (fission and decreased mitochondrial fusion as compared to unexposed rat brain hippocampus. The study suggested that imbalance in mitochondrial dynamics is one of the noteworthy mechanisms occurring in hippocampal neurons during HH insult.

Hypoxia-inducible factor-1β (HIF-1β) is upregulated in a HIF-1α-dependent manner in 518A2 human melanoma cells under hypoxic conditions.

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Mandl, Markus; Kapeller, Barbara; Lieber, Roman; Macfelda, Karin

2013-04-26

Solid tumors include hypoxic areas due to excessive cell proliferation. Adaptation to low oxygen levels is mediated by the hypoxia-inducible factor (HIF) pathway promoting invasion, metastasis, metabolic alterations, chemo-resistance and angiogenesis. The transcription factor HIF-1, the major player within this pathway consists of HIF-1α and HIF-1β. The alpha subunit is continuously degraded under normoxia and becomes stabilized under reduced oxygen supply. In contrast, HIF-1β is generally regarded as constitutively expressed and being present in excess within the cell. However, there is evidence that the expression of this subunit is more complex. The aim of this study was to investigate the role of HIF-1β in human melanoma cells. Among a panel of five different cell lines, in 518A2 cells exposed to the hypoxia-mimetic cobalt chloride HIF-1β was rapidly elevated on protein level. Knockdown experiments performed under cobalt chloride-exposure and hypoxia revealed that this effect was mediated by HIF-1α. The non-canonical relationship between these subunits was further confirmed by pharmacologic inhibition of HIF-1α and by expression of a dominant-negative HIF mutant. Overexpression of HIF-1α showed a time delay in HIF-1β induction, thus arguing for HIF-1β de novo synthesis rather than protein stabilization by heterodimerization. A Hen's egg test-chorioallantoic membrane model of angiogenesis and invasion indicated a local expression of HIF-1β and implies a biological relevance of these findings. In summary, this study demonstrates the HIF-1α-dependent regulation of HIF-1β under hypoxic conditions for the first time. The results indicate a novel cell specific mechanism which might prevent HIF-1β to become a limiting factor. Copyright © 2013 Elsevier Inc. All rights reserved.

Cerium oxide nanoparticles protect rodent lungs from hypobaric hypoxia-induced oxidative stress and inflammation

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Arya A

2013-11-01

intraperitoneal injections of low micromole concentration, we successfully localized the nanoceria in rodent lung without any inflammatory response. The lung-deposited nanoceria limited ROS formation, lipid peroxidation, and glutathione oxidation, and prevented oxidative protein modifications like nitration and carbonyl formation during hypobaric hypoxia. We also observed reduced lung inflammation in the nanoceria-injected lungs, supporting the anti-inflammatory properties of nanoceria. Conclusion: Cumulatively, these results suggest nanoceria deposit in lungs, confer protection by quenching noxious free radicals during hypobaric hypoxia, and do not evoke any inflammatory response. Keywords: nanoceria, high altitude, nanomedicine

[Electrophysiological study on rat conduit pulmonary artery smooth muscle cells under normoxia and acute hypoxia].

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Hu, Ying; Zou, Fei; Cai, Chun-Qing; Wu, Hang-Yu; Yun, Hai-Xia; Chen, Yun-Tian; Jin, Guo-En; Ge, Ri-Li

2006-10-25

The present study was designed to investigate the electrophysiological characteristics of rat conduit pulmonary artery smooth muscle cells (PASMCs) and the response to acute hypoxia. PASMCs of the 1st to 2nd order branches in the conduit pulmonary arteries were obtained by enzymatic isolation. The PASMCs were divided into acute hypoxia preconditioned group and normoxia group. Hypoxia solutions were achieved by bubbling with 5% CO2 plus 95% N2 for at least 30 min before cell perfusion. Potassium currents were compared between these two groups using whole-cell patch clamp technique. The total outward current of PASMCs was measured under normoxia condition when iBTX [specific blocking agent of large conductance Ca-activated K(+) (BK(Ca)) channel] and 4-AP [specific blocking agent of delayed rectifier K(+) (K(DR)) channel] were added consequently into bath solution. PASMCs were classified into three types according to their size, shape and electrophysiological characteristics. Type I cells are the smallest with spindle shape, smooth surface and discrete perinuclear bulge. Type II cells show the biggest size with banana-like appearance. Type III cells have the similar size with type I, and present intermediary shape between type I and type II. iBTX had little effect on the total outward current in type I cells, while 4-AP almost completely blocked it. Most of the total outward current in type II cells was inhibited by iBTX, and the remaining was sensitive to 4-AP. In type III cells, the total outward current was sensitive to both iBTX and 4-AP. Acute hypoxia reduced the current in all three types of cells: (1614.8+/-62.5) pA to (892.4+/-33.6) pA for type I cells (Ppotassium current and improves the E(m) in PASMCs. These effects may be involved in the modulation of constriction/relaxation of conduit artery under acute hypoxia. Different distribution of K(DR) and BK(Ca) channels in these three types of PASMCs might account for their different constriction

Effects of natural and human-induced hypoxia on coastal benthos

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L. A. Levin

2009-10-01

Full Text Available Coastal hypoxia (defined here as <1.42 ml L⁻¹; 62.5 μM; 2 mg L⁻¹, approx. 30% oxygen saturation develops seasonally in many estuaries, fjords, and along open coasts as a result of natural upwelling or from anthropogenic eutrophication induced by riverine nutrient inputs. Permanent hypoxia occurs naturally in some isolated seas and marine basins as well as in open slope oxygen minimum zones. Responses of benthos to hypoxia depend on the duration, predictability, and intensity of oxygen depletion and on whether H₂S is formed. Under suboxic conditions, large mats of filamentous sulfide oxidizing bacteria cover the seabed and consume sulfide. They are hypothesized to provide a detoxified microhabitat for eukaryotic benthic communities. Calcareous foraminiferans and nematodes are particularly tolerant of low oxygen concentrations and may attain high densities and dominance, often in association with microbial mats. When oxygen is sufficient to support metazoans, small, soft-bodied invertebrates (typically annelids, often with short generation times and elaborate branchial structures, predominate. Large taxa are more sensitive than small taxa to hypoxia. Crustaceans and echinoderms are typically more sensitive to hypoxia, with lower oxygen thresholds, than annelids, sipunculans, molluscs and cnidarians. Mobile fish and shellfish will migrate away from low-oxygen areas. Within a species, early life stages may be more subject to oxygen stress than older life stages.

Hypoxia alters both the structure and function of benthic communities, but effects may differ with regional hypoxia history. Human-caused hypoxia is generally linked to eutrophication, and occurs adjacent to watersheds with large populations or agricultural activities. Many occurrences are seasonal, within estuaries, fjords or enclosed seas of the North Atlantic and the NW Pacific Oceans. Benthic faunal responses, elicited at oxygen levels below

Hypoxia and Angiogenesis in Endometrioid Endometrial Carcinogenesis

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Nicole Horrée

2007-01-01

Full Text Available Background: Hypoxia-inducible factor 1α (HIF-1α plays an essential role in the adaptive response of cells to hypoxia, triggering biologic events associated with aggressive tumor behavior. Methods: Expression of HIF-1α and proteins in the HIF-1α pathway (Glut-1, CAIX, VEGF in paraffin-embedded specimens of normal (n = 17, premalignant (n = 17 and endometrioid endometrial carcinoma (n = 39 was explored by immunohistochemistry, in relation to microvessel density (MVD. Results: HIF-1α overexpression was absent in inactive endometrium but present in hyperplasia (61% and carcinoma (87%, with increasing expression in a perinecrotic fashion pointing to underlying hypoxia. No membranous expression of Glut-1 and CAIX was noticed in inactive endometrium, in contrast with expression in hyperplasia (Glut-1 0%, CAIX 61%, only focal and diffuse and carcinoma (Glut-1 94.6%, CAIX 92%, both mostly perinecrotically. Diffuse HIF-1α was accompanied by activation of downstream targets. VEGF was significantly higher expressed in hyperplasias and carcinomas compared to inactive endometrium. MVD was higher in hyperplasias and carcinomas than in normal endometrium (p < 0.001. Conclusion: HIF-1α and its downstream genes are increasingly expressed from normal through premalignant to endometrioid adenocarcinoma of the endometrium, paralleled by activation of its downstream genes and increased angiogenesis. This underlines the potential importance of hypoxia and its key regulator HIF-1α in endometrial carcinogenesis.

Caffeine reduces apnea frequency and enhances ventilatory long-term facilitation in rat pups raised in chronic intermittent hypoxia.

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Julien, Cécile A; Joseph, Vincent; Bairam, Aida

2010-08-01

The mechanisms underlying the therapeutic function of caffeine on apneas in preterm neonates are not well determined. To better understand these effects, we exposed rat pups from postnatal d 3-12 to chronic intermittent hypoxia (5% O2/100 s every 10 min; 6 cycles/h followed by 1 h at 21% O2, 24 h/d), a model mimicking hypoxemic exposure in apneic neonates. Then, using whole-body plethysmography, we evaluated minute ventilation, apnea frequency, and duration after i.p injection of caffeine citrate (20 mg/kg) or saline under normoxia and in response to either sustained (FiO2 12%, 20 min) or brief (FiO2 5%, 60 s, total 10 episodes of 8 min each) hypoxia. These tests were used to assess peripheral and central components of hypoxic response. The latter also assessed the ventilatory long-term facilitation during recovery (2 h). Caffeine injection increased minute ventilation under baseline and during recovery. This effect was correlated with a decrease in apnea frequency (not duration). On the contrary, caffeine did not change the ventilatory response to sustained or brief hypoxic exposure. These results suggest that the effects of caffeine on apnea depend on increased central normoxic respiratory drive and enhancement of ventilatory long-term facilitation rather than on higher hypoxic ventilatory response.

Spontaneous calcium waves in Bergman glia increase with age and hypoxia and may reduce tissue oxygen.

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Mathiesen, Claus; Brazhe, Alexey; Thomsen, Kirsten; Lauritzen, Martin

2013-02-01

Glial calcium (Ca(2+)) waves constitute a means to spread signals between glial cells and to neighboring neurons and blood vessels. These waves occur spontaneously in Bergmann glia (BG) of the mouse cerebellar cortex in vivo. Here, we tested three hypotheses: (1) aging and reduced blood oxygen saturation alters wave activity; (2) glial Ca(2+) waves change cerebral oxygen metabolism; and (3) neuronal and glial wave activity is correlated. We used two-photon microscopy in the cerebellar cortexes of adult (8- to 15-week-old) and aging (48- to 80-week-old) ketamine-anesthetized mice after bolus loading with OGB-1/AM and SR101. We report that the occurrence of spontaneous waves is 20 times more frequent in the cerebellar cortex of aging as compared with adult mice, which correlated with a reduction in resting brain oxygen tension. In adult mice, spontaneous glial wave activity increased on reducing resting brain oxygen tension, and ATP-evoked glial waves reduced the tissue O(2) tension. Finally, although spontaneous Purkinje cell (PC) activity was not associated with increased glia wave activity, spontaneous glial waves did affect intracellular Ca(2+) activity in PCs. The increased wave activity during aging, as well as low resting brain oxygen tension, suggests a relationship between glial waves, brain energy homeostasis, and pathology.

Blunted neuronal calcium response to hypoxia in naked mole-rat hippocampus.

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Bethany L Peterson

Full Text Available Naked mole-rats are highly social and strictly subterranean rodents that live in large communal colonies in sealed and chronically oxygen-depleted burrows. Brain slices from naked mole-rats show extreme tolerance to hypoxia compared to slices from other mammals, as indicated by maintenance of synaptic transmission under more hypoxic conditions and three fold longer latency to anoxic depolarization. A key factor in determining whether or not the cellular response to hypoxia is reversible or leads to cell death may be the elevation of intracellular calcium concentration. In the present study, we used fluorescent imaging techniques to measure relative intracellular calcium changes in CA1 pyramidal cells of hippocampal slices during hypoxia. We found that calcium accumulation during hypoxia was significantly and substantially attenuated in slices from naked mole-rats compared to slices from laboratory mice. This was the case for both neonatal (postnatal day 6 and older (postnatal day 20 age groups. Furthermore, while both species demonstrated more calcium accumulation at older ages, the older naked mole-rats showed a smaller calcium accumulation response than even the younger mice. A blunted intracellular calcium response to hypoxia may contribute to the extreme hypoxia tolerance of naked mole-rat neurons. The results are discussed in terms of a general hypothesis that a very prolonged or arrested developmental process may allow adult naked mole-rat brain to retain the hypoxia tolerance normally only seen in neonatal mammals.

Blunted neuronal calcium response to hypoxia in naked mole-rat hippocampus.

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Peterson, Bethany L; Larson, John; Buffenstein, Rochelle; Park, Thomas J; Fall, Christopher P

2012-01-01

Naked mole-rats are highly social and strictly subterranean rodents that live in large communal colonies in sealed and chronically oxygen-depleted burrows. Brain slices from naked mole-rats show extreme tolerance to hypoxia compared to slices from other mammals, as indicated by maintenance of synaptic transmission under more hypoxic conditions and three fold longer latency to anoxic depolarization. A key factor in determining whether or not the cellular response to hypoxia is reversible or leads to cell death may be the elevation of intracellular calcium concentration. In the present study, we used fluorescent imaging techniques to measure relative intracellular calcium changes in CA1 pyramidal cells of hippocampal slices during hypoxia. We found that calcium accumulation during hypoxia was significantly and substantially attenuated in slices from naked mole-rats compared to slices from laboratory mice. This was the case for both neonatal (postnatal day 6) and older (postnatal day 20) age groups. Furthermore, while both species demonstrated more calcium accumulation at older ages, the older naked mole-rats showed a smaller calcium accumulation response than even the younger mice. A blunted intracellular calcium response to hypoxia may contribute to the extreme hypoxia tolerance of naked mole-rat neurons. The results are discussed in terms of a general hypothesis that a very prolonged or arrested developmental process may allow adult naked mole-rat brain to retain the hypoxia tolerance normally only seen in neonatal mammals.

Effects of hypoxia on human cancer cell line chemosensitivity

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2013-01-01

Background Environment inside even a small tumor is characterized by total (anoxia) or partial oxygen deprivation, (hypoxia). It has been shown that radiotherapy and some conventional chemotherapies may be less effective in hypoxia, and therefore it is important to investigate how different drugs act in different microenvironments. In this study we perform a large screening of the effects of 19 clinically used or experimental chemotherapeutic drugs on five different cell lines in conditions of normoxia, hypoxia and anoxia. Methods A panel of 19 commercially available drugs: 5-fluorouracil, acriflavine, bortezomib, cisplatin, digitoxin, digoxin, docetaxel, doxorubicin, etoposide, gemcitabine, irinotecan, melphalan, mitomycin c, rapamycin, sorafenib, thalidomide, tirapazamine, topotecan and vincristine were tested for cytotoxic activity on the cancer cell lines A2780 (ovarian), ACHN (renal), MCF-7 (breast), H69 (SCLC) and U-937 (lymphoma). Parallel aliquots of the cells were grown at different oxygen pressures and after 72 hours of drug exposure viability was measured with the fluorometric microculture cytotoxicity assay (FMCA). Results Sorafenib, irinotecan and docetaxel were in general more effective in an oxygenated environment, while cisplatin, mitomycin c and tirapazamine were more effective in a low oxygen environment. Surprisingly, hypoxia in H69 and MCF-7 cells mostly rendered higher drug sensitivity. In contrast ACHN appeared more sensitive to hypoxia, giving slower proliferating cells, and consequently, was more resistant to most drugs. Conclusions A panel of standard cytotoxic agents was tested against five different human cancer cell lines cultivated at normoxic, hypoxic and anoxic conditions. Results show that impaired chemosensitivity is not universal, in contrast different cell lines behave different and some drugs appear even less effective in normoxia than hypoxia. PMID:23829203

Inflammatory cytokine tumor necrosis factor α suppresses neuroprotective endogenous erythropoietin from astrocytes mediated by hypoxia-inducible factor-2α.

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Nagaya, Yoshiaki; Aoyama, Mineyoshi; Tamura, Tetsuya; Kakita, Hiroki; Kato, Shin; Hida, Hideki; Saitoh, Shinji; Asai, Kiyofumi

2014-12-01

Interest in erythropoietin (EPO) as a neuroprotective mediator has grown since it was found that systemically administered EPO is protective in several animal models of disease. However, given that the blood-brain barrier limits EPO entry into the brain, alternative approaches that induce endogenous EPO production in the brain may be more effective clinically and associated with fewer untoward side-effects. Astrocytes are the main source of EPO in the central nervous system. In the present study we investigated the effect of the inflammatory cytokine tumor necrosis factor α (TNFα) on hypoxia-induced upregulation of EPO in rat brain. Hypoxia significantly increased EPO mRNA expression in the brain and kidney, and this increase was suppressed by TNFα in vivo. In cultured astrocytes exposed to hypoxic conditions for 6 and 12 h, TNFα suppressed the hypoxia-induced increase in EPO mRNA expression in a concentration-dependent manner. TNFα inhibition of hypoxia-induced EPO expression was mediated primarily by hypoxia-inducible factor (HIF)-2α rather than HIF-1α. The effects of TNFα in reducing hypoxia-induced upregulation of EPO mRNA expression probably involve destabilization of HIF-2α, which is regulated by the nuclear factor (NF)-κB signaling pathway. TNFα treatment attenuated the protective effects of astrocytes on neurons under hypoxic conditions via EPO signaling. The effective blockade of TNFα signaling may contribute to the maintenance of the neuroprotective effects of EPO even under hypoxic conditions with an inflammatory response. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Heterogeneous role of the glutathione antioxidant system in modulating the response of ESFT to fenretinide in normoxia and hypoxia.

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Tapiwanashe Magwere

Full Text Available Glutathione (GSH is implicated in drug resistance mechanisms of several cancers and is a key regulator of cell death pathways within cells. We studied Ewing's sarcoma family of tumours (ESFT cell lines and three mechanistically distinct anticancer agents (fenretinide, doxorubicin, and vincristine to investigate whether the GSH antioxidant system is involved in the reduced sensitivity to these chemotherapeutic agents in hypoxia. Cell viability and death were assessed by the trypan blue exclusion assay and annexin V-PI staining, respectively. Hypoxia significantly decreased the sensitivity of all ESFT cell lines to fenretinide-induced death, whereas the effect of doxorubicin or vincristine was marginal and cell-line-specific. The response of the GSH antioxidant system in ESFT cell lines to hypoxia was variable and also cell-line-specific, although the level of GSH appeared to be most dependent on de novo biosynthesis rather than recycling. RNAi-mediated knockdown of key GSH regulatory enzymes γ-glutamylcysteine synthetase or glutathione disulfide reductase partially reversed the hypoxia-induced resistance to fenretinide, and increasing GSH levels using N-acetylcysteine augmented the hypoxia-induced resistance in a cell line-specific manner. These observations are consistent with the conclusion that the role of the GSH antioxidant system in modulating the sensitivity of ESFT cells to fenretinide is heterogeneous depending on environment and cell type. This is likely to limit the value of targeting GSH as a therapeutic strategy to overcome hypoxia-induced drug resistance in ESFT. Whether targeting the GSH antioxidant system in conjunction with other therapeutics may benefit some patients with ESFT remains to be seen.