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Sample records for adenosine receptor agonist

  1. Adenosine A(2A) receptor dynamics studied with the novel fluorescent agonist Alexa488-APEC.

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    Brand, Frank; Klutz, Athena M; Jacobson, Kenneth A; Fredholm, Bertil B; Schulte, Gunnar

    2008-08-20

    G protein-coupled receptors, such as the adenosine A(2A) receptor, are dynamic proteins, which undergo agonist-dependent redistribution from the cell surface to intracellular membranous compartments, such as endosomes. In order to study the kinetics of adenosine A(2A) receptor redistribution in living cells, we synthesized a novel fluorescent agonist, Alexa488-APEC. Alexa488-APEC binds to adenosine A(2A) (K(i)=149+/-27 nM) as well as A(3) receptors (K(i)=240+/-160 nM) but not to adenosine A(1) receptors. Further, we characterized the dose-dependent increase in Alexa488-APEC-induced cAMP production as well as cAMP response element binding (CREB) protein phosphorylation, verifying the ligand's functionality at adenosine A(2A) but not A(2B) receptors. In live-cell imaging studies, Alexa488-APEC-induced adenosine A(2A) receptor internalization, which was blocked by the competitive reversible antagonist ZM 241385 and hyperosmolaric sucrose. Further, internalized adenosine A(2A) receptors co-localized with clathrin and Rab5, indicating that agonist stimulation promotes adenosine A(2A) receptor uptake through a clathrin-dependent mechanism to Rab5-positive endosomes. The basic characterization of Alexa488-APEC described here showed that it provides a useful tool for tracing adenosine A(2A) receptors in vitro.

  2. Indirect modulation of dopamine D2 receptors as potential pharmacotherapy for schizophrenia: I. Adenosine agonists.

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    Dixon, D A; Fenix, L A; Kim, D M; Raffa, R B

    1999-04-01

    To review preclinical and clinical information related to pharmacologic modulation of dopamine D2 receptors as potential novel antipsychotic therapy. Specifically, to summarize the data that suggest a modulatory action of adenosine A2A receptors on dopamine D2 receptors and, therefore, a possible rational role of adenosine A2A agonists as novel antipsychotic agents. Primary and review articles were identified by MEDLINE search (from 1966 to May 1998) and through secondary sources. All of the articles identified from the data sources were evaluated and all information deemed relevant was included in this review. For all of the older and many of the newer antipsychotic agents, there is a strong correlation between clinical antipsychotic activity and affinity for dopamine D2 receptors. Unfortunately, dopamine D2 receptors are believed to also be involved in the adverse effect profile of these agents. The indirect modulation of dopamine D2 receptors, rather than direct block, might produce antipsychotic effects without the usual adverse reactions. Several lines of evidence from animal studies suggest that the use of selective A2A agonists might represent a novel approach to the treatment of psychoses. Dopamine receptor modulation might represent a novel antipsychotic approach or adjunct therapy. The data regarding adenosine agonists (particularly selective A2A receptor agonists) are inconclusive at the present time. Direct clinical demonstration of effectiveness is required.

  3. Therapeutic efficacy of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) against organophosphate intoxication

    NARCIS (Netherlands)

    Bueters, T.J.H.; Groen, B.; Danhof, M.; IJzerman, A.P.; Helden, H.P.M. van

    2002-01-01

    The objective of the present study was to investigate whether reduction of central acetylcholine (ACh) accumulation by adenosine receptor agonists could serve as a generic treatment against organophosphate (OP) poisoning. The OPs studied were tabun (O-ethyl-N-dimethylphosphoramidocyanidate), sarin

  4. Capadenoson, a clinically trialed partial adenosine A1receptor agonist, can stimulate adenosine A2Breceptor biased agonism.

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    Baltos, Jo-Anne; Vecchio, Elizabeth A; Harris, Matthew A; Qin, Cheng Xue; Ritchie, Rebecca H; Christopoulos, Arthur; White, Paul J; May, Lauren T

    2017-07-01

    The adenosine A 2B receptor (A 2B AR) has been identified as an important therapeutic target in cardiovascular disease, however in vitro and in vivo targeting has been limited by the paucity of pharmacological tools, particularly potent agonists. Interestingly, 2-((6-amino-3,5-dicyano-4-(4-(cyclopropylmethoxy)phenyl)-2-pyridinyl)thio)acetamide (BAY60-6583), a potent and subtype-selective A 2B AR agonist, has the same core structure as 2-amino-6-[[2-(4-chlorophenyl)-1,3-thiazol-4-yl]methylsulfanyl]-4-[4-(2-hydroxyethoxy)phenyl]pyridine-3,5-dicarbonitril (capadenoson). Capadenoson, currently classified as an adenosine A 1 receptor (A 1 AR) partial agonist, has undergone two Phase IIa clinical trials, initially in patients with atrial fibrillation and subsequently in patients with stable angina. Capadenoson has also been shown to decrease cardiac remodeling in an animal model of advanced heart failure and a capadenoson derivative, neladenoson bialanate, recently entered clinical development for the treatment of chronic heart failure. The therapeutic effects of capadenoson are currently thought to be mediated through the A 1 AR. However, the ability of capadenoson to stimulate additional adenosine receptor subtypes, in particular the A 2B AR, has not been rigorously assessed. In this study, we demonstrate that capadenoson does indeed have significant A 2B AR activity in physiologically relevant cells, cardiac fibroblasts and cardiomyocytes, which endogenously express the A 2B AR. Relative to the non-selective adenosine receptor agonist NECA, capadenoson was a biased A 2B AR agonist with a preference for cAMP signal transduction over other downstream mediators in cells with recombinant and endogenous A 2B AR expression. These findings suggest the reclassification of capadenoson as a dual A 1 AR/A 2B AR agonist. Furthermore, a potential A 2B AR contribution should be an important consideration for the future clinical development of capadenoson-like therapeutics, as the A

  5. The adenosine A2A receptor agonist CGS 21680 exhibits antipsychotic-like activity in Cebus apella monkeys

    DEFF Research Database (Denmark)

    Andersen, M B; Fuxe, K; Werge, T

    2002-01-01

    The adenosine A2A receptor agonist CGS 21680 has shown effects similar to dopamine antagonists in behavioural assays in rats predictive for antipsychotic activity, without induction of extrapyramidal side-effects (EPS). In the present study, we examined whether this functional dopamine antagonism...... showed a functional anti-dopaminergic effect in Cebus apella monkeys without production of EPS. This further substantiates that adenosine A2A receptor agonists may have potential as antipsychotics with atypical profiles....

  6. Synthesis of novel apio carbocyclic nucleoside analogues as selective a(3) adenosine receptor agonists.

    Science.gov (United States)

    Lee, Jeong A; Moon, Hyung Ryong; Kim, Hea Ok; Kim, Kyung Ran; Lee, Kang Man; Kim, Bum Tae; Hwang, Ki Jun; Chun, Moon Woo; Jacobson, Kenneth A; Jeong, Lak Shin

    2005-06-24

    On the basis of the biological activity of neplanocin A and apio-dideoxyadenosine (apio-ddA), novel apio-neplanocin A analogues 5a-d, combining the properties of two nucleosides, were stereoselectively synthesized. The apio moiety of the target nucleosides 5a-d was stereoselectively introduced by treating lactol 10 with 37% formaldehyde in the presence of potassium carbonate. The carbasugar moiety of neplanocin A was successively built by exposing diene 12 on a Grubbs catalyst in methylene chloride. The final nucleosides 5a-d were synthesized from the condensation of the glycosyl donor 14 with nucleic bases under the standard Mitsunobu conditions. Similarly, apio-aristeromycin 6 and (N)-apio-methanocarbaadenosine 7 were derived from the common intermediate 13 using catalytic hydrogenation and Simmons-Smith cyclopropanation as key steps. All of the final nucleosides 5a-d, 6, and 7 did not show significant inhibitory activity against S-adenosylhomocysteine hydrolase (SAH) up to 100 muM, maybe due to the absence of the secondary hydroxyl group at the C3'-position, which should be oxidized by cofactor-bound NAD(+). However, apio-neplanocin A (5a) showed potent and highly selective binding affinity (K(i) = 628 +/- 69 nM) at the A(3) adenosine receptor without any binding affinity at the A(1) and A(2A) adenosine receptors. In conclusion, we have first developed novel carbocyclic nucleosides with unnatural apio-carbasugars using stereoselective hydroxymethylation and RCM reaction and also discovered a new template of human A(3) adenosine receptor agonist, which play a great role in developing new A(3) adenosine receptor agonist as well as in identifying the binding site of the receptor.

  7. Structural Probing and Molecular Modeling of the A3 Adenosine Receptor: A Focus on Agonist Binding

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    Antonella Ciancetta

    2017-03-01

    Full Text Available Adenosine is an endogenous modulator exerting its functions through the activation of four adenosine receptor (AR subtypes, termed A1, A2A, A2B and A3, which belong to the G protein-coupled receptor (GPCR superfamily. The human A3AR (hA3AR subtype is implicated in several cytoprotective functions. Therefore, hA3AR modulators, and in particular agonists, are sought for their potential application as anti-inflammatory, anticancer, and cardioprotective agents. Structure-based molecular modeling techniques have been applied over the years to rationalize the structure–activity relationships (SARs of newly emerged A3AR ligands, guide the subsequent lead optimization, and interpret site-directed mutagenesis (SDM data from a molecular perspective. In this review, we showcase selected modeling-based and guided strategies that were applied to elucidate the binding of agonists to the A3AR and discuss the challenges associated with an accurate prediction of the receptor extracellular vestibule through homology modeling from the available X-ray templates.

  8. Structural Probing and Molecular Modeling of the A₃ Adenosine Receptor: A Focus on Agonist Binding.

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    Ciancetta, Antonella; Jacobson, Kenneth A

    2017-03-11

    Adenosine is an endogenous modulator exerting its functions through the activation of four adenosine receptor (AR) subtypes, termed A₁, A2A, A2B and A₃, which belong to the G protein-coupled receptor (GPCR) superfamily. The human A₃AR (hA₃AR) subtype is implicated in several cytoprotective functions. Therefore, hA₃AR modulators, and in particular agonists, are sought for their potential application as anti-inflammatory, anticancer, and cardioprotective agents. Structure-based molecular modeling techniques have been applied over the years to rationalize the structure-activity relationships (SARs) of newly emerged A₃AR ligands, guide the subsequent lead optimization, and interpret site-directed mutagenesis (SDM) data from a molecular perspective. In this review, we showcase selected modeling-based and guided strategies that were applied to elucidate the binding of agonists to the A₃AR and discuss the challenges associated with an accurate prediction of the receptor extracellular vestibule through homology modeling from the available X-ray templates.

  9. Indirect basal ganglia pathway mediation of repetitive behavior: attenuation by adenosine receptor agonists.

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    Tanimura, Yoko; Vaziri, Sasha; Lewis, Mark H

    2010-06-26

    Repetitive behaviors are diagnostic for autism and common in related neurodevelopmental disorders. Despite their clinical importance, underlying mechanisms associated with the expression of these behaviors remain poorly understood. Our lab has previously shown that the rates of spontaneous stereotypy in deer mice (Peromyscus maniculatus) were negatively correlated with enkephalin content, a marker of striatopallidal but not striatonigral neurons. To investigate further the role of the indirect basal ganglia pathway, we examined neuronal activation of the subthalamic nucleus (STN) using cytochrome oxidase (CO) histochemistry in high- and low-stereotypy mice. CO activity in STN was significantly lower in high-stereotypy mice and negatively correlated with the frequency of stereotypy. In addition, exposure to environmental enrichment, which attenuated stereotypy, normalized the activity of STN. Co-administration of the adenosine A(2A) receptor agonist CGS21680 and the A(1) receptor agonist CPA attenuated stereotypy dose-dependently. The significant reduction associated with the lowest dose of the drug combination tested was due to its effects on mice with lower baseline levels of stereotypy. Higher doses of the drug combination were required to show robust behavioral effects, and presumably requisite activation of the indirect pathway, in high-stereotypy mice. These findings support that decreased indirect pathway activity is linked to the expression of high levels of stereotypy in deer mice and that striatal A(1) and A(2A) receptors may provide promising therapeutic targets for the treatment of repetitive behaviors in neurodevelopmental disorders.

  10. Interactions of purified bovine brain A1-adenosine receptors with G-proteins. Reciprocal modulation of agonist and antagonist binding.

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    Freissmuth, M; Selzer, E; Schütz, W

    1991-05-01

    The bovine brain A1-adenosine receptor was purified 8000-fold by affinity chromatography on xanthine-amine-congener (XAC)-Sepharose. Addition of a 120-fold molar excess of a purified bovine brain G-protein preparation (Go,i a mixture of Go and Gi, containing predominantly Go) decreases the Bmax of the binding of the antagonist radioligand [3H]XAC to the receptor. This decrease is observed not only after insertion into phospholipid vesicles but also in detergent solution, and is reversed by GTP analogues. In the presence of Go,i, about 20 and 40% of the receptors display guanine-nucleotide-sensitive high-affinity binding of the agonist radioligand (-)-N6-3-([125I]iodo-4-hydroxyphenylisopropyl)adenosine after reconstitution into lipid vesicles and in detergent solution, respectively. The ability of Go,i to enhance agonist binding and decrease antagonist binding is concentration-dependent, with a half-maximal effect occurring at approximately 10-fold molar excess of G-proteins over A1-adenosine receptors. In the presence of the receptor, the rate of guanosine 5'-[gamma-[35S]thio]triphosphate (GTP[35S]) binding to Go,i is accelerated. This rate is further enhanced if the receptor is activated by the agonist (-)(R)-N6-phenylisopropyladenosine, whereas the antagonist XAC decreases the association rate of GTP[35S] to levels observed in the absence of receptor. These results show (1) that detergent removal is not a prerequisite for the observation of coupling between the A1-adenosine receptor and Go,i, and (2) that the regulatory effect of G-proteins on antagonist binding to the A1-adenosine receptor can be reconstituted by using purified components.

  11. Selective adenosine A2A receptor agonists and antagonists protect against spinal cord injury through peripheral and central effects

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    Esposito Emanuela

    2011-04-01

    Full Text Available Abstract Background Permanent functional deficits following spinal cord injury (SCI arise both from mechanical injury and from secondary tissue reactions involving inflammation. Enhanced release of adenosine and glutamate soon after SCI represents a component in the sequelae that may be responsible for resulting functional deficits. The role of adenosine A2A receptor in central ischemia/trauma is still to be elucidated. In our previous studies we have demonstrated that the adenosine A2A receptor-selective agonist CGS21680, systemically administered after SCI, protects from tissue damage, locomotor dysfunction and different inflammatory readouts. In this work we studied the effect of the adenosine A2A receptor antagonist SCH58261, systemically administered after SCI, on the same parameters. We investigated the hypothesis that the main action mechanism of agonists and antagonists is at peripheral or central sites. Methods Spinal trauma was induced by extradural compression of SC exposed via a four-level T5-T8 laminectomy in mouse. Three drug-dosing protocols were utilized: a short-term systemic administration by intraperitoneal injection, a chronic administration via osmotic minipump, and direct injection into the spinal cord. Results SCH58261, systemically administered (0.01 mg/kg intraperitoneal. 1, 6 and 10 hours after SCI, reduced demyelination and levels of TNF-α, Fas-L, PAR, Bax expression and activation of JNK mitogen-activated protein kinase (MAPK 24 hours after SCI. Chronic SCH58261 administration, by mini-osmotic pump delivery for 10 days, improved the neurological deficit up to 10 days after SCI. Adenosine A2A receptors are physiologically expressed in the spinal cord by astrocytes, microglia and oligodendrocytes. Soon after SCI (24 hours, these receptors showed enhanced expression in neurons. Both the A2A agonist and antagonist, administered intraperitoneally, reduced expression of the A2A receptor, ruling out the possibility that the

  12. A Structure-Activity Relationship Study of Bitopic N6-Substituted Adenosine Derivatives as Biased Adenosine A1 Receptor Agonists.

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    Aurelio, Luigi; Baltos, Jo-Anne; Ford, Leigh; Nguyen, Anh T N; Jörg, Manuela; Devine, Shane M; Valant, Celine; White, Paul J; Christopoulos, Arthur; May, Lauren T; Scammells, Peter J

    2018-02-15

    Herein, we investigate the structure-activity relationships of a series of compounds derived from the bitopic N6-substituted adenosine derivative 1, a previously reported biased ligand at the A1 adenosine receptor. Modifications were made to the orthosteric adenosine pharmacophore, the linker and the allosteric 2-amino-3-benzoylthiophene pharmacophore to probe the structure-activity relationships, both in terms of the effect of these modifications on biased signalling as well as receptor subtype selectivity. Modification of the orthosteric pharmacophore at the 2- or 5'-positions resulted in a significant loss of bias away from calcium mobilization that was observed for 1. Interestingly, increasing the linker length by one additional carbon resulted in approximately 10-fold increase in bias away from calcium mobilization, while reducing the linker length by one carbon trended towards a reduction in bias. In terms of the allosteric pharmacophore, the trifluoromethylphenyl substituent on the thiophene ring appears to be crucial for the biased signaling away from calcium mobilization.

  13. [Proteomics analysis of adenosine A1 receptor agonist-induced delayed myocardial protection in rabbits].

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    Zhou, Jianmei; Zou, Dingquan; Ran, Ke; Chang, Yetian

    2011-10-01

    To investigate the changes of myocardial protein expression profiles in 2-chloro-N6-cyclopentyladenosine (CCPA), an adenosine A1 receptor agonist-induced delayed myocardial protection in New Zealand rabbits . A total of 8 rabbits were randomly divided into a CCPA group (CCPA group) and a normal saline group (NS group). CCPA and NS were infused into rabbits in the CCPA group and the NS group respectively. Twenty-four hours later, the rabbits were subjected to 30 min left anterior descending coronary artery occlusion and were reperfused for 2 hours, then the ischemic zone tissues of left ventricle were sampled for proteomic analysis.A total of 12 other New Zeland rabbits were divided into a sham group (Sham group), a normal saline group (NS group) and a CCPA group (CCPA group). The expression of αB-crystalline, one of the differential proteins, was confirmed by Western blot. Analysis of two dimensional gel electrophoresis showed that the expression of 55 protein spots were different between the two groups, 17 protein spots were preliminarily identified with the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and Mascot and Expasy bioinformatics software. These proteins included stress proteins, metabolism-associated proteins, signal transduction pathway-related proteins, ionophorous proteins, immunity-associated proteins, and so on. Western blot showed that the expression of αB-crystalline was significantly up-regulated in the CCPA group. The myocardial protein expression profiles are changed markedly in the preconditioning late phase of CCPA .The differential proteins might be involved in the delayed cardioprotection induced by CCPA.

  14. The hybrid molecule, VCP746, is a potent adenosine A2B receptor agonist that stimulates anti-fibrotic signalling.

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    Vecchio, Elizabeth A; Chuo, Chung Hui; Baltos, Jo-Anne; Ford, Leigh; Scammells, Peter J; Wang, Bing H; Christopoulos, Arthur; White, Paul J; May, Lauren T

    2016-10-01

    We have recently described the rationally-designed adenosine receptor agonist, 4-(5-amino-4-benzoyl-3-(3-(trifluoromethyl)phenyl)thiophen-2-yl)-N-(6-(9-((2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxylmethyl)tetrahydro-furan-2-yl)-9H-purin-6-ylamino)hexyl)benzamide (VCP746), a hybrid molecule consisting of an adenosine moiety linked to an adenosine A1 receptor (A1AR) allosteric modulator moiety. At the A1AR, VCP746 mediated cardioprotection in the absence of haemodynamic side effects such as bradycardia. The current study has now identified VCP746 as an important pharmacological tool for the adenosine A2B receptor (A2BAR). The binding and function of VCP746 at the A2BAR was rigorously characterised in a heterologous expression system, in addition to examination of its anti-fibrotic signalling in cardiac- and renal-derived cells. In FlpInCHO cells stably expressing the human A2BAR, VCP746 was a high affinity, high potency A2BAR agonist that stimulated Gs- and Gq-mediated signal transduction, with an apparent lack of system bias relative to prototypical A2BAR agonists. The distinct agonist profile may result from an atypical binding mode of VCP746 at the A2BAR, which was consistent with a bivalent mechanism of receptor interaction. In isolated neonatal rat cardiac fibroblasts (NCF), VCP746 stimulated potent inhibition of both TGF-β1- and angiotensin II-mediated collagen synthesis. Similar attenuation of TGF-β1-mediated collagen synthesis was observed in renal mesangial cells (RMC). The anti-fibrotic signalling mediated by VCP746 in NCF and RMC was selectively reversed in the presence of an A2BAR antagonist. Thus, we believe, VCP746 represents an important tool to further investigate the role of the A2BAR in cardiac (patho)physiology. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Effects of adenosine and a selective A2A adenosine receptor agonist on hemodynamic and thallium-201 and technetium-99m-sestaMIBI biodistribution and kinetics.

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    Mekkaoui, Choukri; Jadbabaie, Farid; Dione, Donald P; Meoli, David F; Purushothaman, Kailasnath; Belardinelli, Luiz; Sinusas, Albert J

    2009-10-01

    The purpose of this study was to compare a selective A(2A) adenosine receptor agonist (regadenoson) with adenosine in clinically relevant canine models with regard to effects on hemodynamics and thallium-201 ((201)Tl) and technetium-99m ((99m)Tc)-sestaMIBI biodistribution and kinetics. The clinical application of vasodilator stress for perfusion imaging requires consideration of the effects of these vasodilating agents on systemic hemodynamics, coronary flow, and radiotracer uptake and clearance kinetics. Sequential imaging and arterial blood sampling was performed on control, anesthetized closed-chest canines (n = 7) to evaluate radiotracer biodistribution and kinetics after either a bolus administration of regadenoson (2.5 microg/kg) or 4.5-min infusion of adenosine (280 microg/kg). The effects of regadenoson on coronary flow and myocardial radiotracer uptake were then evaluated in an open-chest canine model of a critical stenosis (n = 7). Results from ex vivo single-photon emission computed tomography were compared with tissue well-counting. The use of regadenoson compared favorably with adenosine in regard to the duration and magnitude of the hemodynamic effects and the effect on (201)Tl and (99m)Tc-sestaMIBI biodistribution and kinetics. The arterial blood clearance half-time was significantly faster for (99m)Tc-sestaMIBI (regadenoson: 1.4 +/- 0.03 min; adenosine: 1.5 +/- 0.08 min) than for (201)Tl (regadenoson: 2.5 +/- 0.16 min, p adenosine: 2.7 +/- 0.04 min, p regadenoson stress was significantly greater than the relative perfusion defect with (99m)Tc-sestaMIBI (0.69 +/- 0.03%, p regadenoson produced a hyperemic response comparable to a standard infusion of adenosine. The biodistribution and clearance of both (201)Tl and (99m)Tc-sestaMIBI during regadenoson were similar to adenosine vasodilation. Ex vivo perfusion images under the most ideal conditions permitted detection of a critical stenosis, although (201)Tl offered significant advantages over (99m

  16. Extracellular Loop 2 of the Adenosine A1 Receptor Has a Key Role in Orthosteric Ligand Affinity and Agonist Efficacy.

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    Nguyen, Anh T N; Baltos, Jo-Anne; Thomas, Trayder; Nguyen, Toan D; Muñoz, Laura López; Gregory, Karen J; White, Paul J; Sexton, Patrick M; Christopoulos, Arthur; May, Lauren T

    2016-12-01

    The adenosine A 1 G protein-coupled receptor (A 1 AR) is an important therapeutic target implicated in a wide range of cardiovascular and neuronal disorders. Although it is well established that the A 1 AR orthosteric site is located within the receptor's transmembrane (TM) bundle, prior studies have implicated extracellular loop 2 (ECL2) as having a significant role in contributing to orthosteric ligand affinity and signaling for various G protein-coupled receptors (GPCRs). We thus performed extensive alanine scanning mutagenesis of A 1 AR-ECL2 to explore the role of this domain on A 1 AR orthosteric ligand pharmacology. Using quantitative analytical approaches and molecular modeling, we identified ECL2 residues that interact either directly or indirectly with orthosteric agonists and antagonists. Discrete mutations proximal to a conserved ECL2-TM3 disulfide bond selectively affected orthosteric ligand affinity, whereas a cluster of five residues near the TM4-ECL2 juncture influenced orthosteric agonist efficacy. A combination of ligand docking, molecular dynamics simulations, and mutagenesis results suggested that the orthosteric agonist 5'-N-ethylcarboxamidoadenosine binds transiently to an extracellular vestibule formed by ECL2 and the top of TM5 and TM7, prior to entry into the canonical TM bundle orthosteric site. Collectively, this study highlights a key role for ECL2 in A 1 AR orthosteric ligand binding and receptor activation. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

  17. Separation of on-target efficacy from adverse effects through rational design of a bitopic adenosine receptor agonist.

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    Valant, Celine; May, Lauren T; Aurelio, Luigi; Chuo, Chung Hui; White, Paul J; Baltos, Jo-Anne; Sexton, Patrick M; Scammells, Peter J; Christopoulos, Arthur

    2014-03-25

    The concepts of allosteric modulation and biased agonism are revolutionizing modern approaches to drug discovery, particularly in the field of G protein-coupled receptors (GPCRs). Both phenomena exploit topographically distinct binding sites to promote unique GPCR conformations that can lead to different patterns of cellular responsiveness. The adenosine A1 GPCR (A1AR) is a major therapeutic target for cardioprotection, but current agents acting on the receptor are clinically limited for this indication because of on-target bradycardia as a serious adverse effect. In the current study, we have rationally designed a novel A1AR ligand (VCP746)--a hybrid molecule comprising adenosine linked to a positive allosteric modulator--specifically to engender biased signaling at the A1AR. We validate that the interaction of VCP746 with the A1AR is consistent with a bitopic mode of receptor engagement (i.e., concomitant association with orthosteric and allosteric sites) and that the compound displays biased agonism relative to prototypical A1AR ligands. Importantly, we also show that the unique pharmacology of VCP746 is (patho)physiologically relevant, because the compound protects against ischemic insult in native A1AR-expressing cardiomyoblasts and cardiomyocytes but does not affect rat atrial heart rate. Thus, this study provides proof of concept that bitopic ligands can be designed as biased agonists to promote on-target efficacy without on-target side effects.

  18. Methodical Challenges and a Possible Resolution in the Assessment of Receptor Reserve for Adenosine, an Agonist with Short Half-Life

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    Judit Zsuga

    2017-05-01

    Full Text Available The term receptor reserve, first introduced and used in the traditional receptor theory, is an integrative measure of response-inducing ability of the interaction between an agonist and a receptor system (consisting of a receptor and its downstream signaling. The underlying phenomenon, i.e., stimulation of a submaximal fraction of receptors can apparently elicit the maximal effect (in certain cases, provides an opportunity to assess the receptor reserve. However, determining receptor reserve is challenging for agonists with short half-lives, such as adenosine. Although adenosine metabolism can be inhibited several ways (in order to prevent the rapid elimination of adenosine administered to construct concentration–effect (E/c curves for the determination, the consequent accumulation of endogenous adenosine biases the results. To address this problem, we previously proposed a method, by means of which this bias can be mathematically corrected (utilizing a traditional receptor theory-independent approach. In the present investigation, we have offered in silico validation of this method by simulating E/c curves with the use of the operational model of agonism and then by evaluating them using our method. We have found that our method is suitable to reliably assess the receptor reserve for adenosine in our recently published experimental setting, suggesting that it may be capable for a qualitative determination of receptor reserve for rapidly eliminating agonists in general. In addition, we have disclosed a possible interference between FSCPX (8-cyclopentyl-N3-[3-(4-(fluorosulfonylbenzoyloxypropyl]-N1-propylxanthine, an irreversible A1 adenosine receptor antagonist, and NBTI (S-(2-hydroxy-5-nitrobenzyl-6-thioinosine, a nucleoside transport inhibitor, i.e., FSCPX may blunt the effect of NBTI.

  19. Methodical Challenges and a Possible Resolution in the Assessment of Receptor Reserve for Adenosine, an Agonist with Short Half-Life.

    Science.gov (United States)

    Zsuga, Judit; Erdei, Tamas; Szabó, Katalin; Lampe, Nora; Papp, Csaba; Pinter, Akos; Szentmiklosi, Andras Jozsef; Juhasz, Bela; Szilvássy, Zoltán; Gesztelyi, Rudolf

    2017-05-19

    The term receptor reserve, first introduced and used in the traditional receptor theory, is an integrative measure of response-inducing ability of the interaction between an agonist and a receptor system (consisting of a receptor and its downstream signaling). The underlying phenomenon, i.e., stimulation of a submaximal fraction of receptors can apparently elicit the maximal effect (in certain cases), provides an opportunity to assess the receptor reserve. However, determining receptor reserve is challenging for agonists with short half-lives, such as adenosine. Although adenosine metabolism can be inhibited several ways (in order to prevent the rapid elimination of adenosine administered to construct concentration-effect (E/c) curves for the determination), the consequent accumulation of endogenous adenosine biases the results. To address this problem, we previously proposed a method, by means of which this bias can be mathematically corrected (utilizing a traditional receptor theory-independent approach). In the present investigation, we have offered in silico validation of this method by simulating E/c curves with the use of the operational model of agonism and then by evaluating them using our method. We have found that our method is suitable to reliably assess the receptor reserve for adenosine in our recently published experimental setting, suggesting that it may be capable for a qualitative determination of receptor reserve for rapidly eliminating agonists in general. In addition, we have disclosed a possible interference between FSCPX (8-cyclopentyl- N³ -[3-(4-(fluorosulfonyl)benzoyloxy)propyl]- N ¹-propylxanthine), an irreversible A₁ adenosine receptor antagonist, and NBTI (S-(2-hydroxy-5-nitrobenzyl)-6-thioinosine), a nucleoside transport inhibitor, i.e., FSCPX may blunt the effect of NBTI.

  20. The adenosine A2A receptor agonist CGS 21680 exhibits antipsychotic-like activity in Cebus apella monkeys

    DEFF Research Database (Denmark)

    Andersen, M B; Fuxe, K; Werge, T

    2002-01-01

    and lack of EPS in rodents could also be observed in non-human primates. We investigated the effects of CGS 21680 on behaviours induced by D-amphetamine and (-)-apomorphine in EPS-sensitized Cebus apella monkeys. CGS 21680 was administered s.c. in doses of 0.01, 0.025 and 0.05 mg/kg, alone...... and in combination with D-amphetamine and (-)-apomorphine. The monkeys were videotaped after drug administration and the tapes were rated for EPS and psychosis-like symptoms. CGS 21680 decreased apomorphine-induced behavioural unrest, arousal (0.01-0.05 mg/kg) and stereotypies (0.05 mg/kg) while amphetamine...... showed a functional anti-dopaminergic effect in Cebus apella monkeys without production of EPS. This further substantiates that adenosine A2A receptor agonists may have potential as antipsychotics with atypical profiles....

  1. Characterization of biochemical effects of CGS 21680C, an A2-adenosine receptor agonist, in the mammalian ventricle.

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    Bokník, P; Neumann, J; Schmitz, W; Scholz, H; Wenzlaff, H

    1997-12-01

    Effects of a putative A2-adenosine receptor agonist 2-[(p-2-carboxyethyl)-phenethylamino]-5'-N-ethyl-carboxamide-adeno sine (CGS 21680C) on force of contraction, protein phosphorylation, cyclic adenosine monophosphate (cAMP) content, and the activity of phosphodiesterase (PDE) isoenzymes in guinea pig ventricular (GPV) preparations were studied. CGS 21680C (1-100 microM) did not affect force of contraction in isolated electrically driven papillary muscles and was ineffective in increasing phosphorylation of phospholamban (PLB) and the inhibitory subunit of troponin (TnI) in [32P]-labeled GPV cardiomyocytes. However, under the same conditions, CGS 21680C (10 microM) increased cAMP content from 4.3 +/- 0.2 to 13.0 +/- 0.6 pmol/mg protein, and this effect was completely abolished by A2-adenosine receptor antagonist 9-chloro-2-(2-furanyl)-5,6-dihydro-1,2,4-triazolo-(1,5-c)quinazolin++ +-5-imine (CGS 15943A). CGS 21680C (10 microM) inhibited PDE isoenzymes I, II, III, IV by 7.0, 8.3, 4.7, and 23.2%, respectively. Similarly, rolipram (100 microM), a selective PDE IV inhibitor, increased cAMP content from 4.4 +/- 0.3 to 7.2 +/- 0.3 pmol/mg protein without affecting the phosphorylation state of PLB and TnI. We conclude that CGS 21680C increases cAMP content in GPV cardiomyocytes by activation of adenylyl cyclase or in part by inhibition of PDE IV activity. The increase in cAMP content by CGS 21680C or rolipram is ineffective in increasing phosphorylation of PLB and TnI. These results support the concept of compartments for cAMP or protein kinase A or both in cardiomyocytes that are not coupled to phosphorylation and contractility.

  2. An A2A adenosine receptor agonist, ATL313, reduces inflammation and improves survival in murine sepsis models

    Directory of Open Access Journals (Sweden)

    Linden Joel

    2008-10-01

    Full Text Available Abstract Background The pathophysiology of sepsis is due in part to early systemic inflammation. Here we describe molecular and cellular responses, as well as survival, in A2A adenosine receptor (AR agonist treated and untreated animals during experimental sepsis. Methods Sepsis was induced in mice by intraperitoneal inoculation of live bacteria (Escherichia coli or Staphylococcus aureus or lipopolysaccharide (LPS. Mice inoculated with live bacteria were treated with an A2A AR agonist (ATL313 or phosphate buffered saline (PBS, with or without the addition of a dose of ceftriaxone. LPS inoculated mice were treated with ATL313 or PBS. Serum cytokines and chemokines were measured sequentially at 1, 2, 4, 8, and 24 hours after LPS was administered. In survival studies, mice were followed until death or for 7 days. Results There was a significant survival benefit in mice infected with live E. coli (100% vs. 20%, p = 0.013 or S. aureus (60% vs. 20%, p = 0.02 when treated with ATL313 in conjunction with an antibiotic versus antibiotic alone. ATL313 also improved survival from endotoxic shock when compared to PBS treatment (90% vs. 40%, p = 0.005. The serum concentrations of TNF-α, MIP-1α, MCP-1, IFN-γ, and IL-17 were decreased by ATL313 after LPS injection (p p p Conclusion Further studies are warranted to determine the clinical utility of ATL313 as a novel treatment for sepsis.

  3. Selectivity is species-dependent: Characterization of standard agonists and antagonists at human, rat, and mouse adenosine receptors

    National Research Council Canada - National Science Library

    Alnouri, Mohamad Wessam; Jepards, Stephan; Casari, Alessandro; Schiedel, Anke C; Hinz, Sonja; Müller, Christa E

    2015-01-01

    Adenosine receptors (ARs) have emerged as new drug targets. The majority of data on affinity/potency and selectivity of AR ligands described in the literature has been obtained for the human species...

  4. Detection of coronary stenosis with myocardial contrast echocardiography using regadenoson, a selective adenosine A2A receptor agonist.

    Science.gov (United States)

    Le, D Elizabeth; Bragadeesh, Thanjavur; Zhao, Yan; Wang, Yue-Gang; Zha, Daogang; Kaul, Sanjiv

    2012-04-01

    Regadenoson is comparable to adenosine in pharmacologic radionuclide stress tests but has not been studied with stress myocardial contrast echocardiography. This study assessed the haemodynamic profile and ability of regadenoson, a novel selective A(2A) receptor agonist, to detect coronary artery stenosis during myocardial contrast echocardiography. Myocardial contrast echocardiography was performed to measure myocardial blood volume, myocardial blood flow velocity, and total regional myocardial blood flow before and after administration of regadenoson (5 µg kg(-1), 10 s bolus) in 10 open-chest dogs with mild-to-moderate coronary stenosis that was not flow limiting at rest. Regadenoson decreased blood pressure but did not change heart rate. It increased coronary blood flow significantly (P regadenoson. No arrhythmias were noted with regadenoson either prior to or during myocardial contrast echocardiography. Regadenoson can be used as a vasodilator stress agent with myocardial contrast echocardiography to detect the presence of physiologically significant coronary stenosis. The optimum time for image acquisition was 3-10 min after drug administration.

  5. A New Class of Fluorinated A2A Adenosine Receptor Agonist with Application to Last-Step Enzymatic [18 F]Fluorination for PET Imaging.

    Science.gov (United States)

    Lowe, Phillip T; Dall'Angelo, Sergio; Mulder-Krieger, Thea; IJzerman, Adriaan P; Zanda, Matteo; O'Hagan, David

    2017-11-02

    The A2A adenosine receptor belongs to a family of G-coupled protein receptors that have been subjected to extensive investigation over the last few decades. Due to their prominent role in the biological functions of the heart, lungs, CNS and brain, they have become a target for the treatment of illnesses ranging from cancer immunotherapy to Parkinson's disease. The imaging of such receptors by using positron emission tomography (PET) has also been of interest, potentially providing a valuable tool for analysing and diagnosing various myocardial and neurodegenerative disorders, as well as offering support to drug discovery trials. Reported herein are the design, synthesis and evaluation of two new 5'-fluorodeoxy-adenosine (FDA)-based receptor agonists (FDA-PP1 and FDA-PP2), each substituted at the C-2 position with a terminally functionalised ethynyl unit. The structures enable a synthesis of 18 F-labelled analogues by direct, last-step radiosynthesis from chlorinated precursors using the fluorinase enzyme (5'-fluoro-5'-deoxyadenosine synthase), which catalyses a transhalogenation reaction. This delivers a new class of A2A adenosine receptor agonist that can be directly radiolabelled for exploration in PET studies. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Adenosine receptor neurobiology: overview.

    Science.gov (United States)

    Chen, Jiang-Fan; Lee, Chien-fei; Chern, Yijuang

    2014-01-01

    Adenosine is a naturally occurring nucleoside that is distributed ubiquitously throughout the body as a metabolic intermediary. In the brain, adenosine functions as an important upstream neuromodulator of a broad spectrum of neurotransmitters, receptors, and signaling pathways. By acting through four G-protein-coupled receptors, adenosine contributes critically to homeostasis and neuromodulatory control of a variety of normal and abnormal brain functions, ranging from synaptic plasticity, to cognition, to sleep, to motor activity to neuroinflammation, and cell death. This review begun with an overview of the gene and genome structure and the expression pattern of adenosine receptors (ARs). We feature several new developments over the past decade in our understanding of AR functions in the brain, with special focus on the identification and characterization of canonical and noncanonical signaling pathways of ARs. We provide an update on functional insights from complementary genetic-knockout and pharmacological studies on the AR control of various brain functions. We also highlight several novel and recent developments of AR neurobiology, including (i) recent breakthrough in high resolution of three-dimension structure of adenosine A2A receptors (A2ARs) in several functional status, (ii) receptor-receptor heterodimerization, (iii) AR function in glial cells, and (iv) the druggability of AR. We concluded the review with the contention that these new developments extend and strengthen the support for A1 and A2ARs in brain as therapeutic targets for neurologic and psychiatric diseases. © 2014 Elsevier Inc. All rights reserved.

  7. Polyamidoamine (PAMAM) Dendrimer Conjugates of Clickable Agonists of the A3 Adenosine Receptor and Coactivation of the P2Y14 Receptor by a Tethered Nucleotide

    Energy Technology Data Exchange (ETDEWEB)

    Tosh, Dilip, K. [National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health; Yoo, Lena S. [National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health; Chinn, Moshe [National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health; Hong, Kunlun [ORNL; Kilbey, II, S Michael [ORNL; Barrett, Matthew O. [University of North Carolina School of Medicine; Fricks, Ingrid P. [University of North Carolina School of Medicine; Harden, T. Kendall [University of North Carolina School of Medicine; Jacobson, Kenneth A. [National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health

    2010-01-01

    We previously synthesized a series of potent and selective A{sub 3} adenosine receptor (AR) agonists (North-methanocarba nucleoside 5{prime}-uronamides) containing dialkyne groups on extended adenine C2 substituents. We coupled the distal alkyne of a 2-octadiynyl nucleoside by Cu(I)-catalyzed 'click' chemistry to azide-derivatized G4 (fourth-generation) PAMAM dendrimers to form triazoles. A{sub 3}AR activation was preserved in these multivalent conjugates, which bound with apparent Ki of 0.1-0.3 nM. They were substituted with nucleoside moieties, solely or in combination with water-solubilizing carboxylic acid groups derived from hexynoic acid. A comparison with various amide-linked dendrimers showed that triazole-linked conjugates displayed selectivity and enhanced A{sub 3}AR affinity. We prepared a PAMAM dendrimer containing equiproportioned peripheral azido and amino groups for conjugation of multiple ligands. A bifunctional conjugate activated both A{sub 3} and P2Y{sub 14} receptors (via amide-linked uridine-5{prime}-diphosphoglucuronic acid), with selectivity in comparison to other ARs and P2Y receptors. This is the first example of targeting two different GPCRs with the same dendrimer conjugate, which is intended for activation of heteromeric GPCR aggregates. Synergistic effects of activating multiple GPCRs with a single dendrimer conjugate might be useful in disease treatment.

  8. Adenosine receptors as drug targets — what are the challenges?

    Science.gov (United States)

    Chen, Jiang-Fan; Eltzschig, Holger K.; Fredholm, Bertil B.

    2014-01-01

    Adenosine signalling has long been a target for drug development, with adenosine itself or its derivatives being used clinically since the 1940s. In addition, methylxanthines such as caffeine have profound biological effects as antagonists at adenosine receptors. Moreover, drugs such as dipyridamole and methotrexate act by enhancing the activation of adenosine receptors. There is strong evidence that adenosine has a functional role in many diseases, and several pharmacological compounds specifically targeting individual adenosine receptors — either directly or indirectly — have now entered the clinic. However, only one adenosine receptor-specific agent — the adenosine A2A receptor agonist regadenoson (Lexiscan; Astellas Pharma) — has so far gained approval from the US Food and Drug Administration (FDA). Here, we focus on the biology of adenosine signalling to identify hurdles in the development of additional pharmacological compounds targeting adenosine receptors and discuss strategies to overcome these challenges. PMID:23535933

  9. Interactions of purified bovine brain A1-adenosine receptors with G-proteins. Reciprocal modulation of agonist and antagonist binding.

    OpenAIRE

    Freissmuth, M.; Selzer, E.; Schütz, W.

    1991-01-01

    The bovine brain A1-adenosine receptor was purified 8000-fold by affinity chromatography on xanthine-amine-congener (XAC)-Sepharose. Addition of a 120-fold molar excess of a purified bovine brain G-protein preparation (Go,i a mixture of Go and Gi, containing predominantly Go) decreases the Bmax of the binding of the antagonist radioligand [3H]XAC to the receptor. This decrease is observed not only after insertion into phospholipid vesicles but also in detergent solution, and is reversed by GT...

  10. Partial agonism of theophylline-7-riboside on adenosine receptors

    NARCIS (Netherlands)

    IJzerman, A. P.; van der Wenden, E. M.; von Frijtag Drabbe Künzel, J. K.; Mathôt, R. A.; Danhof, M.; Borea, P. A.; Varani, K.

    1994-01-01

    Theophylline-7-riboside was evaluated as a partial agonist for rat adenosine receptors. Radioligand binding experiments were performed on both A1 and A2a adenosine receptors, using several methodologies to discriminate between agonists and antagonists. Mainly from thermodynamic data it was concluded

  11. Partial Adenosine A1 Agonist in Heart Failure.

    Science.gov (United States)

    Dinh, Wilfried; Albrecht-Küpper, Barbara; Gheorghiade, Mihai; Voors, Adriaan A; van der Laan, Michael; Sabbah, Hani N

    2017-01-01

    Adenosine exerts a variety of physiological effects by binding to cell surface G-protein-coupled receptor subtypes, namely, A1, A2a, A2b, and A3. The central physiological role of adenosine is to preclude tissue injury and promote repair in response to stress. In the heart, adenosine acts as a cytoprotective modulator, linking cardiac function to metabolic demand predominantly via activation of adenosine A1 receptors (A1Rs), which leads to inhibition of adenylate cyclase activity, modulation of protein kinase C, and opening of ATP-sensitive potassium channels. Activation of myocardial adenosine A1Rs has been shown to modulate a variety of pathologies associated with ischemic cardiac injury, including arrhythmogenesis, coronary and ventricular dysfunction, apoptosis, mitochondrial dysfunction, and ventricular remodeling. Partial A1R agonists are agents that are likely to elicit favorable pharmacological responses in heart failure (HF) without giving rise to the undesirable cardiac and extra-cardiac effects observed with full A1R agonism. Preclinical data have shown that partial adenosine A1R agonists protect and improve cardiac function at doses that do not result in undesirable effects on heart rate, atrioventricular conduction, and blood pressure, suggesting that these compounds may constitute a valuable new therapy for chronic HF. Neladenoson bialanate (BAY1067197) is the first oral partial and highly selective A1R agonist that has entered clinical development for the treatment of HF. This review provides an overview of adenosine A1R-mediated signaling in the heart, summarizes the results from preclinical and clinical studies of partial A1R agonists in HF, and discusses the potential benefits of these drugs in the clinical setting.

  12. An adenosine A3 receptor agonist inhibits DSS-induced colitis in mice through modulation of the NF-κB signaling pathway

    Science.gov (United States)

    Ren, Tianhua; Tian, Ting; Feng, Xiao; Ye, Shicai; Wang, Hao; Wu, Weiyun; Qiu, Yumei; Yu, Caiyuan; He, Yanting; Zeng, Juncheng; Cen, Junwei; Zhou, Yu

    2015-01-01

    The role of the adenosine A3 receptor (A3AR) in experimental colitis is controversial. The A3AR agonist N6-(3-iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA) has been shown to have a clinical benefit, although studies in A3AR-deficient mice suggest a pro-inflammatory role. However, there are no studies on the effect of 2-Cl-IB-MECA and the molecular mechanism of action of A3AR in murine colitis models in vivo. Is it the same as that observed in vitro? The interaction between 2-CL-IB-MECA and A3AR in a murine colitis model and the signaling pathways associated with this interaction remain unclear. Here we demonstrate a role for the NF-κB signaling pathway and its effect on modifying the activity of proinflammatory factors in A3AR-mediated biological processes. Our results demonstrated that A3AR activation possessed marked effects on experimental colitis through the NF-κB signaling pathway. PMID:25762375

  13. ( sup 3 H)CGS 21680, a selective A2 adenosine receptor agonist directly labels A2 receptors in rat brain

    Energy Technology Data Exchange (ETDEWEB)

    Jarvis, M.F.; Schulz, R.; Hutchison, A.J.; Do, U.H.; Sills, M.A.; Williams, M. (CIBA-GEIGY Corporation, Summit, NJ (USA))

    1989-12-01

    In the present study, the binding of a highly A2-selective agonist radioligand, (3H)CGS 21680 (2-(p-(2-carboxyethyl)-phenethylamino)-5'-N-ethylcarboxamido adenosine) is described. (3H)CGS 21680 specific binding to rat striatal membranes was saturable, reversible and dependent upon protein concentration. Saturation studies revealed that (3H)CGS 21680 bound with high affinity (Kd = 15.5 nM) and limited capacity (apparent Bmax = 375 fmol/mg of protein) to a single class of recognition sites. Estimates of ligand affinity (16 nM) determined from association and dissociation kinetic experiments were in close agreement with the results from the saturation studies. (3H)CGS 21680 binding was greatest in striatal membranes with negligible specific binding obtained in rat cortical membranes. Adenosine agonists ligands competed for the binding of 5 nM (3H)CGS 21680 to striatal membranes with the following order of activity; CGS 21680 = 5'-N-ethylcarboxamidoadenosine greater than 2-phenylaminoadenosine (CV-1808) = 5'-N-methylcarboxamidoadenosine = 2-chloroadenosine greater than R-phenylisopropyladenosine greater than N6-cyclohexyladenosine greater than N6cyclopentyltheophylline greater than S-phenylisopropyladenosine. The nonxanthine adenosine antagonist, CGS 15943A, was the most active compound in inhibiting the binding of (3H)CGS 21680. Other adenosine antagonists inhibited binding in the following order; xanthine amine congener = 1,3-dipropyl-8-(2-amino-4-chloro)phenylxanthine greater than 1,3-dipropyl-8-cyclopentylxanthine greater than 1,3-diethyl-8-phenylxanthine greater than 8-phenyltheophylline greater than 8-cyclopentyltheophylline = xanthine carboxylic acid congener greater than 8-parasulfophenyltheophylline greater than theophylline greater than caffeine.

  14. Sickle cell vaso-occlusion causes activation of iNKT cells that is decreased by the adenosine A2A receptor agonist regadenoson.

    Science.gov (United States)

    Field, Joshua J; Lin, Gene; Okam, Maureen M; Majerus, Elaine; Keefer, Jeffrey; Onyekwere, Onyinye; Ross, Ainsley; Campigotto, Federico; Neuberg, Donna; Linden, Joel; Nathan, David G

    2013-04-25

    Adenosine A2A receptor (A2AR) agonists reduce invariant natural killer T (iNKT) cell activation and decrease inflammation in sickle cell disease (SCD) mice. We conducted a phase 1 trial of the A2AR agonist regadenoson in adults with SCD. The target dose was 1.44 μg/kg/h. iNKT cell activation was evaluated using antibodies targeting the p65 subunit of nuclear factor-κB (phospho-NF-κB p65), interferon-γ (IFN-γ), and A2AR. Regadenoson was administered to 27 adults with SCD. We examined 21 patients at steady state and 6 during painful vaso-occlusive crises (pVOC). iNKT cell activation was also measured in 14 African-American controls. During pVOC, the fraction of iNKT cells demonstrating increased phospho-NF-κB p65 and A2AR expression was significantly higher compared with controls (P regadenoson during pVOC, phospho-NF-κB p65 activation in iNKT cells decreased compared to baseline by a median of 48% (P = .03) to levels similar to controls and steady-state SCD. No toxicities were identified. Infusional regadenoson administered to adults with SCD at 1.44 μg/kg/h during pVOC decreases activation of iNKT cells without toxicity.

  15. Glutamate receptor agonists

    DEFF Research Database (Denmark)

    Vogensen, Stine Byskov; Greenwood, Jeremy R; Bunch, Lennart

    2011-01-01

    The neurotransmitter (S)-glutamate [(S)-Glu] is responsible for most of the excitatory neurotransmission in the central nervous system. The effect of (S)-Glu is mediated by both ionotropic and metabotropic receptors. Glutamate receptor agonists are generally a-amino acids with one or more...... stereogenic centers due to strict requirements in the agonist binding pocket of the activated state of the receptor. By contrast, there are many examples of achiral competitive antagonists. The present review addresses how stereochemistry affects the activity of glutamate receptor ligands. The review focuses...... mainly on agonists and discusses stereochemical and conformational considerations as well as biostructural knowledge of the agonist binding pockets, which is useful in the design of glutamate receptor agonists. Examples are chosen to demonstrate how stereochemistry not only determines how the agonist...

  16. Adenosine A2A  receptor agonist prevents cardiac remodeling and dysfunction in spontaneously hypertensive male rats after myocardial infarction

    Directory of Open Access Journals (Sweden)

    da Silva JS

    2017-03-01

    Full Text Available Jaqueline S da Silva,1 Daniele Gabriel-Costa,1 Roberto T Sudo,1 Hao Wang,2 Leanne Groban,2 Emanuele B Ferraz,3 José Hamilton M Nascimento,3 Carlos Alberto M Fraga,1 Eliezer J Barreiro,1 Gisele Zapata-Sudo1 1Research Program Development of Drugs, Institute of Biomedical Sciences, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; 2Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, NC, USA; 3Institute of Biophysics Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil Background: This work evaluated the hypothesis that 3,4-methylenedioxybenzoyl-2- thienylhydrazone (LASSBio-294, an agonist of adenosine A2A  receptor, could be beneficial for preventing cardiac dysfunction due to hypertension associated with myocardial infarction (MI. Methods: Male spontaneously hypertensive rats (SHR were randomly divided into four groups (six animals per group: sham-operation (SHR-Sham, and myocardial infarction rats (SHR-MI were treated orally either with vehicle or LASSBio-294 (10 and 20 mg.kg-1.d-1 for 4 weeks. Echocardiography and in vivo hemodynamic parameters measured left ventricle (LV structure and function. Exercise tolerance was evaluated using a treadmill test. Cardiac remodeling was accessed by LV collagen deposition and tumor necrosis factor α expression. Results: Early mitral inflow velocity was significantly reduced in the SHR-MI group, and there was significant recovery in a dose-dependent manner after treatment with LASSBio-294. Exercise intolerance observed in the SHR-MI group was prevented by 10 mg.kg-1.d-1 of LASSBio-294, and exercise tolerance exceeded that of the SHR-Sham group at 20 mg.kg-1.d-1. LV end-diastolic pressure increased after MI, and this was prevented by 10 and 20 mg.kg-1.d-1 of LASSBio-294. Sarcoplasmic reticulum Ca2+ ATPase levels were restored in a dose-dependent manner after treatment with LASSBio-294. Fibrosis and inflammatory processes were also

  17. A3 adenosine receptor agonist prevents the development of paclitaxel-induced neuropathic pain by modulating spinal glial-restricted redox-dependent signaling pathways.

    Science.gov (United States)

    Janes, Kali; Esposito, Emanuela; Doyle, Timothy; Cuzzocrea, Salvatore; Tosh, Dillip K; Jacobson, Kenneth A; Salvemini, Daniela

    2014-12-01

    Chemotherapy-induced peripheral neuropathy accompanied by chronic neuropathic pain is the major dose-limiting toxicity of several anticancer agents including the taxane paclitaxel (Taxol). A critical mechanism underlying paclitaxel-induced neuropathic pain is the increased production of peroxynitrite in spinal cord generated in response to activation of the superoxide-generating enzyme, NADPH oxidase. Peroxynitrite in turn contributes to the development of neuropathic pain by modulating several redox-dependent events in spinal cord. We recently reported that activation of the Gi/Gq-coupled A3 adenosine receptor (A3AR) with selective A3AR agonists (ie, IB-MECA) blocked the development of chemotherapy induced-neuropathic pain evoked by distinct agents, including paclitaxel, without interfering with anticancer effects. The mechanism or mechanisms of action underlying these beneficial effects has yet to be explored. We now demonstrate that IB-MECA attenuates the development of paclitaxel-induced neuropathic pain by inhibiting the activation of spinal NADPH oxidase and two downstream redox-dependent systems. The first relies on inhibition of the redox-sensitive transcription factor (NFκB) and mitogen activated protein kinases (ERK and p38) resulting in decreased production of neuroexcitatory/proinflammatory cytokines (TNF-α, IL-1β) and increased formation of the neuroprotective/anti-inflammatory IL-10. The second involves inhibition of redox-mediated posttranslational tyrosine nitration and modification (inactivation) of glia-restricted proteins known to play key roles in regulating synaptic glutamate homeostasis: the glutamate transporter GLT-1 and glutamine synthetase. Our results unravel a mechanistic link into biomolecular signaling pathways employed by A3AR activation in neuropathic pain while providing the foundation to consider use of A3AR agonists as therapeutic agents in patients with chemotherapy-induced peripheral neuropathy. Copyright © 2014

  18. CF101, An Agonist to the A3 Adenosine Receptor, Enhances the Chemotherapeutic Effect of 5-Fluorouracil in a Colon Carcinoma Murine Model

    Directory of Open Access Journals (Sweden)

    Sara Bar-Yehuda

    2005-01-01

    Full Text Available NF-κB and the upstream kinase PKB/Akt are highly expressed in chemoresistance tumor cells and may hamper the apoptotic pathway. CF101, a specific agonist to the A3 adenosine receptor, inhibits the development of colon carcinoma growth in cell cultures and xenograft murine models. Because CF101 has been shown to downregulate PKB/Akt and NF-κB protein expression level, we presumed that its combination with chemotherapy will enhance the antitumor effect of the cytotoxic drug. In this study, we utilized 3-[4,5Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT and colony formation assays and a colon carcinoma xenograft model. It has been shown that a combined treatment of CF101 and 5-fluorouracil (5-FU enhanced the cytotoxic effect of the latter on HCT-116 human colon carcinoma growth. Downregulation of PKB/Akt, NF-κB, and cyclin D1, and upregulation of caspase-3 protein expression level were observed in cells and tumor lesions on treatment with a combination of CF101 and 5-FU. Moreover, in mice treated with the combined therapy, myelotoxicity was prevented as was evidenced by normal white blood cell and neutrophil counts. These results show that CF101 potentiates the cytotoxic effect of 5-FU, thus preventing drug resistance. The myeloprotective effect of CF101 suggests its development as an add-on treatment to 5-FU.

  19. Regadenoson, a selective A2A adenosine receptor agonist, causes dose-dependent increases in coronary blood flow velocity in humans.

    Science.gov (United States)

    Lieu, Hsiao D; Shryock, John C; von Mering, Gregory O; Gordi, Toufigh; Blackburn, Brent; Olmsted, Ann W; Belardinelli, Luiz; Kerensky, Richard A

    2007-07-01

    Regadenoson is a selective A2A adenosine receptor agonist and vasodilator used to increase the heterogeneity of distribution of coronary blood flow during myocardial perfusion imaging. This study characterized the dose dependence of regadenoson-induced coronary hyperemia. An open-label, dose-escalation study of regadenoson (10-500 microg, rapid intravenous bolus) was performed in 34 subjects; in 4 additional subjects, the effect of aminophylline to reverse the response to regadenoson was determined. Intracoronary peak blood flow velocity in either the left anterior descending or left circumflex artery was measured by continuous Doppler signal recording, heart rate, central aortic blood pressure, and adverse effects were recorded. Regadenoson increased peak blood flow velocity by up to 3.4-fold in a dose-dependent manner. The mean duration of the increase in flow velocity of 2.5-fold or greater caused by 400 to 500 microg of regadenoson was 2.3 to 2.4 minutes. Regadenoson (400-500 microg) increased heart rate by up to 21 +/- 6 beats/min and decreased systolic blood pressure (-5 +/- 8 mm Hg to -24 +/- 16 mm Hg) and diastolic blood pressure (-8 +/- 4 mm Hg to -15 +/- 14 mm Hg). Aminophylline (100 mg) attenuated the increase in peak flow velocity but not tachycardia caused by 400 microg of regadenoson. The results of this study demonstrate the utility of regadenoson as a coronary vasodilator for myocardial perfusion imaging.

  20. Repetitive stimulation of adenosine A1 receptors in vivo : Changes in receptor numbers, G-proteins and A1 receptor agonist-induced hypothermia

    NARCIS (Netherlands)

    Roman, Viktor; Keijser, Johannes; Luiten, Paul G. M.; Meerlo, Peter

    2008-01-01

    Adenosine is an important neuromodulator and neuroprotective molecule, which is produced in the brain as a function of neuronal activity, coupling energy expenditure to energy supply. Under conditions of increased need and reduced availability of energy, including hypoxia and prolonged wakefulness,

  1. Safety of regadenoson, an adenosine A2A receptor agonist for myocardial perfusion imaging, in mild asthma and moderate asthma patients: a randomized, double-blind, placebo-controlled trial.

    Science.gov (United States)

    Leaker, Brian R; O'Connor, B; Hansel, Trevor T; Barnes, Peter J; Meng, Lixen; Mathur, Vandana S; Lieu, Hsiao D

    2008-01-01

    Patients with reactive airways are at risk for adenosine-induced bronchoconstriction, mediated via A(2B) and/or A(3) adenosine receptors. To examine the effects of regadenoson, a selective adenosine A(2A) receptor agonist, on airway resistance, we conducted a randomized, double-blind, placebo-controlled crossover trial in asthmatic patients with a positive adenosine monophosphate challenge test. The mean ratio of the forced expiratory volume in 1 second (FEV(1)) at each tested time point relative to the baseline FEV(1) was significantly higher after treatment with regadenoson compared with placebo from 10 to 60 minutes after treatment. One patient had a substantial but asymptomatic FEV(1) reduction (-36.2%) after regadenoson that reversed spontaneously. The most common adverse events with regadenoson were tachycardia (66%), dizziness (53%), headache (45%), and dyspnea (34%). The mean heart rate significantly increased with regadenoson (maximum of +10.4 beats/min) versus placebo. In this pilot safety study of 48 patients with mild or moderate asthma who had bronchial reactivity to adenosine monophosphate, regadenoson was safe and well tolerated.

  2. Flow cytometry application for studies on adenosine A2A receptors expression.

    Science.gov (United States)

    Wójcik, Tomasz; Bereta, Michał; Faron-Górecka, Agata; Dziedzicka-Wasylewska, Marta; Kieć-Kononowicz, Katarzyna

    2008-01-01

    Adenosine A2A receptors belong to the heptaspanning membrane receptors family A, also known as G protein-coupled receptors. In human brain they are highly expressed in striatum, where they co-exist and co-function with adenosine A1, glutamate mGlu5 and dopamine D2 receptors. As glutaminergic neurotransmission modulators in GABAergic enkephalinergic neurons, adenosine A2A receptors are attractive targets for new, alternative therapies of neurodegenerative disorders, like Parkinson's disease and Huntington's disease. The aim of the research was to obtained fluorescently tagged adenosine A2A receptors. Gene encoding human adenosine A2A receptor was inserted into plasmid pEYFP-N1, bearing enhanced yellow fluorescent protein (EYFP). The construct was expressed in HEK 293 cells. Fluorescence was observed by flow cytometry and epifluorescence microscopy. Functional ligand binding properties were investigated by saturation binding analysis of adenosine A2A receptors specific agonist [3H] CGS 21680.

  3. Role of A3 adenosine receptor in diabetic neuropathy.

    Science.gov (United States)

    Yan, Heng; Zhang, Enshui; Feng, Chang; Zhao, Xin

    2016-10-01

    Neuropathy is the most common diabetic complication. Although the A1 and A2A adenosine receptors are important pharmacological targets in alleviating diabetic neuropathy, the role of the A3 adenosine receptor remains unknown. Because the A3 adenosine receptor regulates pain induced by chronic constriction injury or chemotherapy, its stimulation might also attenuate diabetic neuropathy. This study examines the effects of systemic treatment with the A3 adenosine receptor agonist 1-deoxy-1-[6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-N-methyl-β-d-ribofuranuronamide (IB-MECA) on diabetic neuropathy and explores the putative mechanisms underlying its pharmacological effects. We show that IB-MECA alleviated mechanical hyperalgesia and thermal hypoalgesia in mice 2 weeks but not 4 weeks after streptozocin (STZ) treatment. Furthermore, IB-MECA prevented the reduction in sciatic motor nerve conduction velocity and sensory nerve conduction velocity in diabetic mice 2 weeks but not 4 weeks after STZ treatment. Similarly, IB-MECA inhibited the activation of nuclear factor-κB and decreased the generation of tumor necrosis factor-α in the spinal cord of mice 2 weeks but not 4 weeks after STZ treatment. These phenomena were associated with reduction of A3 adenosine receptor expression in the spinal cord after long-term diabetes. Our results suggest that the A3 adenosine receptor plays a critical role in regulating diabetic neuropathy and that reduction in A3 adenosine receptor expression/function might contribute to the progression of diabetic neuropathy. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  4. Adenosine activates brown adipose tissue and recruits beige adipocytes via A2A receptors

    DEFF Research Database (Denmark)

    Gnad, Thorsten; Scheibler, Saskia; von Kügelgen, Ivar

    2014-01-01

    therapies based on cold exposure or β-adrenergic agonists are clinically not feasible, alternative strategies must be explored. Purinergic co-transmission might be involved in sympathetic control of BAT and previous studies reported inhibitory effects of the purinergic transmitter adenosine in BAT from...... hamster or rat. However, the role of adenosine in human BAT is unknown. Here we show that adenosine activates human and murine brown adipocytes at low nanomolar concentrations. Adenosine is released in BAT during stimulation of sympathetic nerves as well as from brown adipocytes. The adenosine A2A...... receptor is the most abundant adenosine receptor in human and murine BAT. Pharmacological blockade or genetic loss of A2A receptors in mice causes a decrease in BAT-dependent thermogenesis, whereas treatment with A2A agonists significantly increases energy expenditure. Moreover, pharmacological stimulation...

  5. Emerging GLP-1 receptor agonists

    DEFF Research Database (Denmark)

    Lund, Asger; Knop, Filip K; Vilsbøll, Tina

    2011-01-01

    Introduction: Recently, glucagon-like peptide-1 receptor (GLP-1R) agonists have become available for the treatment of type 2 diabetes. These agents exploit the physiological effects of GLP-1, which is able to address several of the pathophysiological features of type 2 diabetes. GLP-1R agonists...

  6. Adenosine A2B-receptor-mediated cyclic AMP accumulation in primary rat astrocytes.

    OpenAIRE

    Peakman, M C; Hill, S. J.

    1994-01-01

    1. The effects of adenosine receptor agonists and antagonists on the accumulation of cyclic AMP have been investigated in primary cultures of rat astrocytes. 2. Adenosine A2-receptor stimulation caused a concentration-dependent increase in the accumulation of [3H]-cyclic AMP in cells prelabelled with [3H]-adenine. The rank order of agonist potencies was 5'-N-ethylcarboxamidoadenosine (NECA; EC50 = 1 microM) > adenosine (EC50 = 5 microM) > 2-chloroadenosine (EC50 = 20 microM) >> CGS 21680 (EC5...

  7. Evidence for constitutively-active adenosine receptors at mammalian motor nerve endings

    OpenAIRE

    Searl, Timothy J; Silinsky, Eugene M

    2012-01-01

    A study was made to determine if constitutively active adenosine receptors are present at mouse motor nerve endings. In preparations blocked by low Ca2+ / high Mg2+ solution, 8-cyclopentyl-1,3,dipropylxanthine (CPX, 10–100 nM), which has been reported to be both an A1 adenosine receptor antagonist and inverse agonist, produced a dose-dependent increase in the number of acetylcholine quanta released by a nerve impulse. Adenosine deaminase, which degrades ambient adenosine into its inactive con...

  8. Mast cell adenosine receptors function: a focus on the A3 adenosine receptor and inflammation

    Directory of Open Access Journals (Sweden)

    Noam eRudich

    2012-06-01

    Full Text Available Adenosine is a metabolite, which has long been implicated in a variety of inflammatory processes. Inhaled adenosine provokes bronchoconstriction in asthmatics or chronic obstructive pulmonary disease (COPD patients, but not in non-asthmatics. This hyper responsiveness to adenosine appears to be mediated by mast cell activation. These observations have marked the receptor that mediates the bronchoconstrictor effect of adenosine on mast cells, as an attractive drug candidate. Four subtypes (A1, A2a, A2b and A3 of adenosine receptors have been cloned and shown to display distinct tissue distributions and functions. Animal models have firmly established the ultimate role of the A3 adenosine receptor (A3R in mediating hyper responsiveness to adenosine in mast cells, although the influence of the A2b adenosine receptor was confirmed as well. In contrast, studies of the A3R in humans have been controversial. In this review, we summarize data on the role of different adenosine receptors in mast cell regulation of inflammation and pathology, with a focus on the common and distinct functions of the A3R in rodent and human mast cells. The relevance of mouse studies to the human is discussed.

  9. Structural Mapping of Adenosine Receptor Mutations

    DEFF Research Database (Denmark)

    Jespers, Willem; Schiedel, Anke C; Heitman, Laura H

    2018-01-01

    The four adenosine receptors (ARs), A1, A2A, A2B, and A3, constitute a subfamily of G protein-coupled receptors (GPCRs) with exceptional foundations for structure-based ligand design. The vast amount of mutagenesis data, accumulated in the literature since the 1990s, has been recently supplemente...

  10. Modulation of bladder function by luminal adenosine turnover and A1 receptor activation

    Science.gov (United States)

    Prakasam, H. Sandeep; Herrington, Heather; Roppolo, James R.; Jackson, Edwin K.

    2012-01-01

    The bladder uroepithelium transmits information to the underlying nervous and musculature systems, is under constant cyclical strain, expresses all four adenosine receptors (A1, A2A, A2B, and A3), and is a site of adenosine production. Although adenosine has a well-described protective effect in several organs, there is a lack of information about adenosine turnover in the uroepithelium or whether altering luminal adenosine concentrations impacts bladder function or overactivity. We observed that the concentration of extracellular adenosine at the mucosal surface of the uroepithelium was regulated by ecto-adenosine deaminase and by equilibrative nucleoside transporters, whereas adenosine kinase and equilibrative nucleoside transporters modulated serosal levels. We further observed that enriching endogenous adenosine by blocking its routes of metabolism or direct activation of mucosal A1 receptors with 2-chloro-N6-cyclopentyladenosine (CCPA), a selective agonist, stimulated bladder activity by lowering the threshold pressure for voiding. Finally, CCPA did not quell bladder hyperactivity in animals with acute cyclophosphamide-induced cystitis but instead exacerbated their irritated bladder phenotype. In conclusion, we find that adenosine levels at both surfaces of the uroepithelium are modulated by turnover, that blocking these pathways or stimulating A1 receptors directly at the luminal surface promotes bladder contractions, and that adenosine further stimulates voiding in animals with cyclophosphamide-induced cystitis. PMID:22552934

  11. Adenosine receptor modulation of seizure susceptibility in rats

    Energy Technology Data Exchange (ETDEWEB)

    Szot, P.

    1987-01-01

    Adenosine is considered to be a neuromodulator or cotransmitter in the periphery and CNS. This neuromodulatory action of adenosine may be observed as an anticonvulsant effect. Dose-response curves for R-phenylisopropyladenosine (PIA), cycohexyladenosine (CHA), 2-chloroadenosine (2-ClAdo), N-ethylcarboxamidoadenosine (NECA) and S-PIA were generated against PTZ seizure thresholds in the rat. The rank order of potency for adenosine agonists to elevate PTZ seizure threshold was R-PIA > 2-ClAdo > NECA > CHA > S-PIA. R-PIA was approximately 80-fold more potent than S-PIA. This 80-fold difference in potency between the diasteriomers of PIA was consistent with an A{sub 1} adenoise receptor-mediated response. The anticonvulsant action of 2-ClAdo was reversed by pretreatment with theoplylline. Chronic administration of theophylline significantly increased the specific binding of {sup 3}H-cyclohexyladenosine in membranes of the cerebral cortex and cerebellum of the rat. Chronic exposure to theophylline produced a significant increase in the densities of both the high- and low-affinity forms of A{sub 1} adenosine receptors in the cerebral cortex.

  12. The Role of Adenosine Receptors in Psychostimulant Addiction

    Directory of Open Access Journals (Sweden)

    Inmaculada Ballesteros-Yáñez

    2018-01-01

    Full Text Available Adenosine receptors (AR are a family of G-protein coupled receptors, comprised of four members, named A1, A2A, A2B, and A3 receptors, found widely distributed in almost all human body tissues and organs. To date, they are known to participate in a large variety of physiopathological responses, which include vasodilation, pain, and inflammation. In particular, in the central nervous system (CNS, adenosine acts as a neuromodulator, exerting different functions depending on the type of AR and consequent cellular signaling involved. In terms of molecular pathways and second messengers involved, A1 and A3 receptors inhibit adenylyl cyclase (AC, through Gi/o proteins, while A2A and A2B receptors stimulate it through Gs proteins. In the CNS, A1 receptors are widely distributed in the cortex, hippocampus, and cerebellum, A2A receptors are localized mainly in the striatum and olfactory bulb, while A2B and A3 receptors are found at low levels of expression. In addition, AR are able to form heteromers, both among themselves (e.g., A1/A2A, as well as with other subtypes (e.g., A2A/D2, opening a whole range of possibilities in the field of the pharmacology of AR. Nowadays, we know that adenosine, by acting on adenosine A1 and A2A receptors, is known to antagonistically modulate dopaminergic neurotransmission and therefore reward systems, being A1 receptors colocalized in heteromeric complexes with D1 receptors, and A2A receptors with D2 receptors. This review documents the present state of knowledge of the contribution of AR, particularly A1 and A2A, to psychostimulants-mediated effects, including locomotor activity, discrimination, seeking and reward, and discuss their therapeutic relevance to psychostimulant addiction. Studies presented in this review reinforce the potential of A1 agonists as an effective strategy to counteract psychostimulant-induced effects. Furthermore, different experimental data support the hypothesis that A2A/D2 heterodimers are

  13. Hydrogen sulfide inhibits A2A adenosine receptor agonist induced β-amyloid production in SH-SY5Y neuroblastoma cells via a cAMP dependent pathway.

    Directory of Open Access Journals (Sweden)

    Bhushan Vijay Nagpure

    Full Text Available Alzheimer's disease (AD is the leading cause of senile dementia in today's society. Its debilitating symptoms are manifested by disturbances in many important brain functions, which are influenced by adenosine. Hence, adenosinergic system is considered as a potential therapeutic target in AD treatment. In the present study, we found that sodium hydrosulfide (NaHS, an H2S donor, 100 µM attenuated HENECA (a selective A2A receptor agonist, 10-200 nM induced β-amyloid (1-42 (Aβ42 production in SH-SY5Y cells. NaHS also interfered with HENECA-stimulated production and post-translational modification of amyloid precursor protein (APP by inhibiting its maturation. Measurement of the C-terminal APP fragments generated from its enzymatic cleavage by β-site amyloid precursor protein cleaving enzyme 1 (BACE1 showed that NaHS did not have any significant effect on β-secretase activity. However, the direct measurements of HENECA-elevated γ-secretase activity and mRNA expressions of presenilins suggested that the suppression of Aβ42 production in NaHS pretreated cells was mediated by inhibiting γ-secretase. NaHS induced reductions were accompanied by similar decreases in intracellular cAMP levels and phosphorylation of cAMP responsive element binding protein (CREB. NaHS significantly reduced the elevated cAMP and Aβ42 production caused by forskolin (an adenylyl cyclase, AC agonist alone or forskolin in combination with IBMX (a phosphodiesterase inhibitor, but had no effect on those caused by IBMX alone. Moreover, pretreatment with NaHS significantly attenuated HENECA-elevated AC activity and mRNA expressions of various AC isoforms. These data suggest that NaHS may preferentially suppress AC activity when it was stimulated. In conclusion, H2S attenuated HENECA induced Aβ42 production in SH-SY5Y neuroblastoma cells through inhibiting γ-secretase via a cAMP dependent pathway.

  14. Adenosine receptor ligands on cancer therapy: A review of Patent Literature.

    Science.gov (United States)

    Diniz, Carmen; Sousa, Joana Beatriz; Fresco, Paula; Goncalves, Jorge

    2017-11-07

    Adenosine is a purine, with an adenine group and a ribose sugar, formed endogenously by ATP catabolism both intracellularly and extracellularly. Among the medicinal features of adenosine and of its receptors (A1, A2A, A2B and A3), anticancer activity has been an intense field of research. The anticancer potential of adenosine receptor ligands has been brought forefront of research and evidenced in innumerous research articles and patents. The present review focuses on the patent literature from 2002 onwards (2002-2017). Patents were searched and downloaded from the open access patent data bases and available online. A significant number of patents (65) have been published on adenosine receptor ligands claiming anticancer activity, or presenting new methods of preparation or of treatment thereof from 2002-2017 (May). From these, 35 were published highlighting the promising attributes of compounds/methods to fight cancer. Most of the compounds act as adenosine A3 receptor agonists, while others act as antagonists for the other adenosine receptor subtypes. The signaling events triggered by activation of adenosine A3 receptor or by blockade of adenosine A1, A2A and A2B receptors can reverse an environment pro-cancer to an anti-cancer in the body. The promising anticancer effects mediated by adenosine receptor ligands put them in the forefront as new drug candidates. The present compilation can be worthy to medicinal chemists, pharmacologists, biochemists and other researchers focusing on the putative anticancer activity of adenosine receptor ligands. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  15. Structure-Based Rational Design of Adenosine Receptor Ligands.

    Science.gov (United States)

    Gutiérrez-de-Terán, Hugo; Sallander, Jessica; Sotelo, Eddy

    2017-01-01

    The family of adenosine receptors (ARs) is focus of several medicinal chemistry programs aimed to find new potent and selective drugs. Each receptor subtype has been proposed as a relevant drug target in the treatment of, e.g., cardiovascular or inflammatory diseases, asthma or Parkinson's disease. Until recently, most of these efforts have been dominated by ligand-based or empirical approaches. However, the latest advances in G protein-coupled receptor (GPCR) crystallography allowed for a thorough structural characterization of the A2AAR subtype, which has been crystalized with a number of agonists and antagonists. Consequently, the ligand discovery of AR ligands has been enriched with a number of structure-based approaches. These include the generation of higher-confident homology models for the remaining AR subtypes, virtual screening identification of novel chemotypes, structure-based lead-optimization programs, rationalization of selectivity profiles, or the structural characterization of novel binding sites that enable the design of novel allosteric modulators. Computational methodologies have importantly contributed to the success of these structure-based approaches, and the recent advances in the field are also analyzed in this review. We conclude that the design of adenosine receptor ligands has improved dramatically with the consideration of structure- based approaches, which is paving the way to a better understanding of the biology and pharmacological modulation of this relevant family of receptors.

  16. Targeting adenosine receptors in the development of cardiovascular therapeutics.

    NARCIS (Netherlands)

    Riksen, N.P.; Rongen, G.A.P.J.M.

    2012-01-01

    Adenosine receptor stimulation has negative inotropic and dromotropic actions, reduces cardiac ischemia-reperfusion injury and remodeling, and prevents cardiac arrhythmias. In the vasculature, adenosine modulates vascular tone, reduces infiltration of inflammatory cells and generation of foam cells,

  17. Adenosine promotes alternative macrophage activation via A2A and A2B receptors

    Science.gov (United States)

    Csóka, Balázs; Selmeczy, Zsolt; Koscsó, Balázs; Németh, Zoltán H.; Pacher, Pál; Murray, Peter J.; Kepka-Lenhart, Diane; Morris, Sidney M.; Gause, William C.; Leibovich, S. Joseph; Haskó, György

    2012-01-01

    Adenosine has been implicated in suppressing the proinflammatory responses of classically activated macrophages induced by Th1 cytokines. Alternative macrophage activation is induced by the Th2 cytokines interleukin (IL)-4 and IL-13; however, the role of adenosine in governing alternative macrophage activation is unknown. We show here that adenosine treatment of IL-4- or IL-13-activated macrophages augments the expression of alternative macrophage markers arginase-1, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), and macrophage galactose-type C-type lectin-1. The stimulatory effect of adenosine required primarily A2B receptors because the nonselective adenosine receptor agonist 5′-N-ethylcarboxamidoadenosine (NECA) increased both arginase activity (EC50=261.8 nM) and TIMP-1 production (EC50=80.67 nM), and both pharmacologic and genetic blockade of A2B receptors prevented the effect of NECA. A2A receptors also contributed to the adenosine augmentation of IL-4-induced TIMP-1 release, as both adenosine and NECA were less efficacious in augmenting TIMP-1 release by A2A receptor-deficient than control macrophages. Of the transcription factors known to drive alternative macrophage activation, CCAAT-enhancer-binding protein β was required, while cAMP response element-binding protein and signal transducer and activator of transcription 6 were dispensable in mediating the effect of adenosine. We propose that adenosine receptor activation suppresses inflammation and promotes tissue restitution, in part, by promoting alternative macrophage activation.—Csóka, B., Selmeczy, Z., Koscsó, B., Németh, Z. H., Pacher, P., Murray, P. J., Kepka-Lenhart, D., Morris S. M., Jr., Gause, W. C., Leibovich, S. J., Haskó, G. Adenosine promotes alternative macrophage activation via A2A and A2B receptors. PMID:21926236

  18. Synthesis and biological evaluation of a new series of 2-amino-3-aroyl thiophene derivatives as agonist allosteric modulators of the A1 adenosine receptor. A position-dependent effect study.

    Science.gov (United States)

    Romagnoli, Romeo; Baraldi, Pier Giovanni; Lopez-Cara, Carlota; Cruz-Lopez, Olga; Moorman, Allan R; Massink, Arnault; IJzerman, Adriaan P; Vincenzi, Fabrizio; Borea, Pier Andrea; Varani, Katia

    2015-08-28

    The 2-amino-3-(p-chlorobenzoyl)thiophene scaffold has been widely employed as a pharmacophore for the identification of small molecules acting as allosteric modulators at the adenosine A1 receptor. A new series of 2-amino-3-(p-chlorobenzoyl)-4-benzyl-5-arylthiophene derivatives, characterized by the absence as well as the presence of electron-releasing or electron-withdrawing groups on the phenyl ring at the 4- and 5-positions of the thiophene ring, were identified as positive allosteric enhancers at the adenosine A1 receptor in binding (saturation, competition and dissociation kinetics) and functional assays. To better understand the positional requirements of substituents on the 2-amino-3-(p-chlorobenzoyl)thiophene core, the corresponding regioisomeric 4-aryl-5-benzylthiophene analogues were synthesized and found to possess reduced allosteric enhancer activity. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  19. The role of muscarinic receptors in the beneficial effects of adenosine against myocardial reperfusion injury in rats.

    Directory of Open Access Journals (Sweden)

    Lei Sun

    Full Text Available Adenosine, a catabolite of ATP, displays a wide variety of effects in the heart including regulation of cardiac response to myocardial ischemia and reperfusion injury. Nonetheless, the precise mechanism of adenosine-induced cardioprotection is still elusive. Isolated Sprague-Dawley rat hearts underwent 30 min global ischemia and 120 min reperfusion using a Langendorff apparatus. Both adenosine and acetylcholine treatment recovered the post-reperfusion cardiac function associated with adenosine and muscarinic receptors activation. Simultaneous administration of adenosine and acetylcholine failed to exert any additive protective effect, suggesting a shared mechanism between the two. Our data further revealed a cross-talk between the adenosine and acetylcholine receptor signaling in reperfused rat hearts. Interestingly, the selective M(2 muscarinic acetylcholine receptor antagonist methoctramine significantly attenuated the cardioprotective effect of adenosine. In addition, treatment with adenosine upregulated the expression and the maximal binding capacity of muscarinic acetylcholine receptor, which were inhibited by the selective A(1 adenosine receptor antagonist 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX and the nitric oxide synthase inhibitor N(ω-nitro-L-arginine methyl ester (L-NAME. These data suggested a possible functional coupling between the adenosine and muscarinic receptors behind the observed cardioprotection. Furthermore, nitric oxide was found involved in triggering the response to each of the two receptor agonist. In summary, there may be a cross-talk between the adenosine and muscarinic receptors in ischemic/reperfused myocardium with nitric oxide synthase might serve as the distal converging point. In addition, adenosine contributes to the invigorating effect of adenosine on muscarinic receptor thereby prompting to regulation of cardiac function. These findings argue for a potentially novel mechanism behind the adenosine

  20. Adenosine Receptor Stimulation Improves Glucocorticoid-Induced Osteoporosis in a Rat Model.

    Science.gov (United States)

    Pizzino, Gabriele; Irrera, Natasha; Galfo, Federica; Oteri, Giacomo; Atteritano, Marco; Pallio, Giovanni; Mannino, Federica; D'Amore, Angelica; Pellegrino, Enrica; Aliquò, Federica; Anastasi, Giuseppe P; Cutroneo, Giuseppina; Squadrito, Francesco; Altavilla, Domenica; Bitto, Alessandra

    2017-01-01

    Glucocorticoid-induced osteoporosis (GIO) is a secondary cause of bone loss. Bisphosphonates approved for GIO, might induce jaw osteonecrosis; thus additional therapeutics are required. Adenosine receptor agonists are positive regulators of bone remodeling, thus the efficacy of adenosine receptor stimulation for treating GIO was tested. In a preventive study GIO was induced in Sprague-Dawley rats by methylprednisolone (MP) for 60 days. Animals were randomly assigned to receive polydeoxyribonucleotide (PDRN), an adenosine A2 receptor agonist, or PDRN and DMPX (3,7-dimethyl-1-propargylxanthine, an A 2 antagonist), or vehicle (0.9% NaCl). Another set of animals was used for a treatment study, following the 60 days of MP-induction rats were randomized to receive (for additional 60 days) PDRN, or PDRN and DMPX (an adenosine A2 receptor antagonist), or zoledronate (as control for gold standard treatment), or vehicle. Control animals were administered with vehicle for either 60 or 120 days. Femurs were analyzed after treatments for histology, imaging, and breaking strength analysis. MP treatment induced severe bone loss, the concomitant use of PDRN prevented the developing of osteoporosis. In rats treated for 120 days, PDRN restored bone architecture and bone strength; increased b-ALP, osteocalcin, osteoprotegerin and stimulated the Wnt canonical and non-canonical pathway. Zoledronate reduced bone resorption and ameliorated the histological features, without significant effects on bone formation. Our results suggest that adenosine receptor stimulation might be useful for preventing and treating GIO.

  1. Adenosine Receptor Stimulation Improves Glucocorticoid-Induced Osteoporosis in a Rat Model

    Directory of Open Access Journals (Sweden)

    Gabriele Pizzino

    2017-09-01

    Full Text Available Glucocorticoid-induced osteoporosis (GIO is a secondary cause of bone loss. Bisphosphonates approved for GIO, might induce jaw osteonecrosis; thus additional therapeutics are required. Adenosine receptor agonists are positive regulators of bone remodeling, thus the efficacy of adenosine receptor stimulation for treating GIO was tested. In a preventive study GIO was induced in Sprague-Dawley rats by methylprednisolone (MP for 60 days. Animals were randomly assigned to receive polydeoxyribonucleotide (PDRN, an adenosine A2 receptor agonist, or PDRN and DMPX (3,7-dimethyl-1-propargylxanthine, an A2 antagonist, or vehicle (0.9% NaCl. Another set of animals was used for a treatment study, following the 60 days of MP-induction rats were randomized to receive (for additional 60 days PDRN, or PDRN and DMPX (an adenosine A2 receptor antagonist, or zoledronate (as control for gold standard treatment, or vehicle. Control animals were administered with vehicle for either 60 or 120 days. Femurs were analyzed after treatments for histology, imaging, and breaking strength analysis. MP treatment induced severe bone loss, the concomitant use of PDRN prevented the developing of osteoporosis. In rats treated for 120 days, PDRN restored bone architecture and bone strength; increased b-ALP, osteocalcin, osteoprotegerin and stimulated the Wnt canonical and non-canonical pathway. Zoledronate reduced bone resorption and ameliorated the histological features, without significant effects on bone formation. Our results suggest that adenosine receptor stimulation might be useful for preventing and treating GIO.

  2. Adenosine A2A Receptors Modulate Acute Injury and Neuroinflammation in Brain Ischemia

    Directory of Open Access Journals (Sweden)

    Felicita Pedata

    2014-01-01

    Full Text Available The extracellular concentration of adenosine in the brain increases dramatically during ischemia. Adenosine A2A receptor is expressed in neurons and glial cells and in inflammatory cells (lymphocytes and granulocytes. Recently, adenosine A2A receptor emerged as a potential therapeutic attractive target in ischemia. Ischemia is a multifactorial pathology characterized by different events evolving in the time. After ischemia the early massive increase of extracellular glutamate is followed by activation of resident immune cells, that is, microglia, and production or activation of inflammation mediators. Proinflammatory cytokines, which upregulate cell adhesion molecules, exert an important role in promoting recruitment of leukocytes that in turn promote expansion of the inflammatory response in ischemic tissue. Protracted neuroinflammation is now recognized as the predominant mechanism of secondary brain injury progression. A2A receptors present on central cells and on blood cells account for important effects depending on the time-related evolution of the pathological condition. Evidence suggests that A2A receptor antagonists provide early protection via centrally mediated control of excessive excitotoxicity, while A2A receptor agonists provide protracted protection by controlling massive blood cell infiltration in the hours and days after ischemia. Focus on inflammatory responses provides for adenosine A2A receptor agonists a wide therapeutic time-window of hours and even days after stroke.

  3. Adenosine inhibits neutrophil vascular endothelial growth factor release and transendothelial migration via A2B receptor activation.

    LENUS (Irish Health Repository)

    Wakai, A

    2012-02-03

    The effects of adenosine on neutrophil (polymorphonuclear neutrophils; PMN)-directed changes in vascular permeability are poorly characterized. This study investigated whether adenosine modulates activated PMN vascular endothelial growth factor (vascular permeability factor; VEGF) release and transendothelial migration. PMN activated with tumour necrosis factor-alpha (TNF-alpha, 10 ng\\/mL) were incubated with adenosine and its receptor-specific analogues. Culture supernatants were assayed for VEGF. PMN transendothelial migration across human umbilical vein endothelial cell (HUVEC) monolayers was assessed in vitro. Adhesion molecule receptor expression was assessed flow cytometrically. Adenosine and some of its receptor-specific analogues dose-dependently inhibited activated PMN VEGF release. The rank order of potency was consistent with the affinity profile of human A2B receptors. The inhibitory effect of adenosine was reversed by 3,7-dimethyl-1-propargylxanthine, an A2 receptor antagonist. Adenosine (100 microM) or the A2B receptor agonist 5\\'-N-ethylcarboxamidoadenosine (NECA, 100 microM) significantly reduced PMN transendothelial migration. However, expression of activated PMN beta2 integrins and HUVEC ICAM-1 were not significantly altered by adenosine or NECA. Adenosine attenuates human PMN VEGF release and transendothelial migration via the A2B receptor. This provides a novel target for the modulation of PMN-directed vascular hyperpermeability in conditions such as the capillary leak syndrome.

  4. Endogenous Receptor Agonists: Resolving Inflammation

    Directory of Open Access Journals (Sweden)

    Gerhard Bannenberg

    2007-01-01

    Full Text Available Controlled resolution or the physiologic resolution of a well-orchestrated inflammatory response at the tissue level is essential to return to homeostasis. A comprehensive understanding of the cellular and molecular events that control the termination of acute inflammation is needed in molecular terms given the widely held view that aberrant inflammation underlies many common diseases. This review focuses on recent advances in the understanding of the role of arachidonic acid and ω-3 polyunsaturated fatty acids (PUFA–derived lipid mediators in regulating the resolution of inflammation. Using a functional lipidomic approach employing LC-MS-MS–based informatics, recent studies, reviewed herein, uncovered new families of local-acting chemical mediators actively biosynthesized during the resolution phase from the essential fatty acids eicosapentaenoic acid (EPA and docosahexaenoic acid (DHA. These new families of local chemical mediators are generated endogenously in exudates collected during the resolution phase, and were coined resolvins and protectins because specific members of these novel chemical families control both the duration and magnitude of inflammation in animal models of complex diseases. Recent advances on the biosynthesis, receptors, and actions of these novel anti-inflammatory and proresolving lipid mediators are reviewed with the aim to bring to attention the important role of specific lipid mediators as endogenous agonists in inflammation resolution.

  5. Emerging GLP-1 receptor agonists

    DEFF Research Database (Denmark)

    Lund, Asger; Knop, Filip K; Vilsbøll, Tina

    2011-01-01

    and liraglutide, as well as the emerging GLP-1R agonists including the long-acting compounds. Expert opinion: An emerging therapeutic trend toward initial or early combination therapy with metformin- and incretin-based therapy is anticipated for patients with type 2 diabetes. GLP-1-based therapy has so far proven...... safe and tolerable. The determination of which incretin-based therapy to choose necessitates comparisons between the various GLP-1R agonists. The available GLP-1R agonists cause sustained weight loss and clinical relevant improvement of glycemic control. The long-acting GLP-1R agonists in late...

  6. Small-molecule AT2 receptor agonists

    DEFF Research Database (Denmark)

    Hallberg, Mathias; Sumners, Colin; Steckelings, U Muscha

    2017-01-01

    The discovery of the first selective, small-molecule ATR receptor (AT2R) agonist compound 21 (C21) (8) that is now extensively studied in a large variety of in vitro and in vivo models is described. The sulfonylcarbamate derivative 8, encompassing a phenylthiofen scaffold is the drug-like agonist...

  7. Adenosine 2A receptor agonism: A single intrathecal administration attenuates motor paralysis in experimental autoimmune encephalopathy in rats

    NARCIS (Netherlands)

    Loram, L.C.; Strand, K.A.; Taylor, F.R.; Sloane, E.; van Dam, A.M.; Rieger, J.; Maier, S.F.; Watkins, L.R.

    2015-01-01

    A single intrathecal dose of adenosine 2A receptor (A2AR) agonist was previously reported to produce a multi-week reversal of allodynia in two different models of neuropathic pain in addition to downregulating glial activation markers in the spinal cord. We aimed to determine whether a

  8. Structural determinants of efficacy at A3 adenosine receptors: modification of the ribose moiety.

    Science.gov (United States)

    Gao, Zhan-Guo; Jeong, Lak Shin; Moon, Hyung Ryong; Kim, Hea Ok; Choi, Won Jun; Shin, Dae Hong; Elhalem, Eleonora; Comin, Maria J; Melman, Neli; Mamedova, Liaman; Gross, Ariel S; Rodriguez, Juan B; Jacobson, Kenneth A

    2004-03-01

    We have found previously that structural features of adenosine derivatives, particularly at the N6- and 2-positions of adenine, determine the intrinsic efficacy as A3 adenosine receptor (AR) agonists. Here, we have probed this phenomenon with respect to the ribose moiety using a series of ribose-modified adenosine derivatives, examining binding affinity and activation of the human A3 AR expressed in CHO cells. Both 2'- and 3'-hydroxyl groups in the ribose moiety contribute to A3 AR binding and activation, with 2'-OH being more essential. Thus, the 2'-fluoro substitution eliminated both binding and activation, while a 3'-fluoro substitution led to only a partial reduction of potency and efficacy at the A3 AR. A 5'-uronamide group, known to restore full efficacy in other derivatives, failed to fully overcome the diminished efficacy of 3'-fluoro derivatives. The 4'-thio substitution, which generally enhanced A3 AR potency and selectivity, resulted in 5'-CH2OH analogues (10 and 12) which were partial agonists of the A3 AR. Interestingly, the shifting of the N6-(3-iodobenzyl)adenine moiety from the 1'- to 4'-position had a minor influence on A3 AR selectivity, but transformed 15 into a potent antagonist (16) (Ki = 4.3 nM). Compound 16 antagonized human A3 AR agonist-induced inhibition of cyclic AMP with a K(B) value of 3.0 nM. A novel apio analogue (20) of neplanocin A, was a full A3 AR agonist. The affinities of selected, novel analogues at rat ARs were examined, revealing species differences. In summary, critical structural determinants for human A3 AR activation have been identified, which should prove useful for further understanding the mechanism of receptor activation and development of more potent and selective full agonists, partial agonists and antagonists for A3 ARs.

  9. Subtype selective kainic acid receptor agonists

    DEFF Research Database (Denmark)

    Bunch, Lennart; Krogsgaard-Larsen, Povl

    2009-01-01

    (S)-Glutamic acid (Glu) is the major excitatory neurotransmitter in the mammalian central nervous system, activating the plethora of glutamate receptors (GluRs). In broad lines, the GluRs are divided into two major classes: the ionotropic Glu receptors (iGluRs) and the metabotropic Glu receptors (m......GluRs). Within the iGluRs, five subtypes (KA1, KA2, iGluR5-7) show high affinity and express full agonist activity upon binding of the naturally occurring amino acid kainic acid (KA). Thus these receptors have been named the KA receptors. This review describes all-to our knowledge-published KA receptor agonists...

  10. Mechanism of A2 adenosine receptor activation. I. Blockade of A2 adenosine receptors by photoaffinity labeling

    Energy Technology Data Exchange (ETDEWEB)

    Lohse, M.J.; Klotz, K.N.; Schwabe, U.

    1991-04-01

    It has previously been shown that covalent incorporation of the photoreactive adenosine derivative (R)-2-azido-N6-p-hydroxy-phenylisopropyladenosine ((R)-AHPIA) into the A1 adenosine receptor of intact fat cells leads to a persistent activation of this receptor, resulting in a reduction of cellular cAMP levels. In contrast, covalent incorporation of (R)-AHPIA into human platelet membranes, which contain only stimulatory A2 adenosine receptors, reduces adenylate cyclase stimulation via these receptors. This effect of (R)-AHPIA is specific for the A2 receptor and can be prevented by the adenosine receptor antagonist theophylline. Binding studies indicate that up to 90% of A2 receptors can be blocked by photoincorporation of (R)-AHPIA. However, the remaining 10-20% of A2 receptors are sufficient to mediate an adenylate cyclase stimulation of up to 50% of the control value. Similarly, the activation via these 10-20% of receptors occurs with a half-life that is only 2 times longer than that in control membranes. This indicates the presence of a receptor reserve, with respect to both the extent and the rate of adenylate cyclase stimulation. These observations require a modification of the models of receptor-adenylate cyclase coupling.

  11. Muscimol as an ionotropic GABA receptor agonist.

    Science.gov (United States)

    Johnston, Graham A R

    2014-10-01

    Muscimol, a psychoactive isoxazole from Amanita muscaria and related mushrooms, has proved to be a remarkably selective agonist at ionotropic receptors for the inhibitory neurotransmitter GABA. This historic overview highlights the discovery and development of muscimol and related compounds as a GABA agonist by Danish and Australian neurochemists. Muscimol is widely used as a ligand to probe GABA receptors and was the lead compound in the development of a range of GABAergic agents including nipecotic acid, tiagabine, 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol, (Gaboxadol(®)) and 4-PIOL.

  12. Discovery of LAS101057: A Potent, Selective, and Orally Efficacious A2B Adenosine Receptor Antagonist.

    Science.gov (United States)

    Eastwood, Paul; Esteve, Cristina; González, Jacob; Fonquerna, Silvia; Aiguadé, Josep; Carranco, Inés; Doménech, Teresa; Aparici, Mònica; Miralpeix, Montserrat; Albertí, Joan; Córdoba, Mónica; Fernández, Raquel; Pont, Mercè; Godessart, Núria; Prats, Neus; Loza, María Isabel; Cadavid, María Isabel; Nueda, Arsenio; Vidal, Bernat

    2011-03-10

    The structure-activity relationships for a series of pyrazine-based A2B adenosine receptor antagonists are described. From this work, LAS101057 (17), a potent, selective, and orally efficacious A2B receptor antagonist, was identified as a clinical development candidate. LAS101057 inhibits agonist-induced IL-6 production in human fibroblasts and is active in an ovalbumin (OVA)-sensitized mouse model after oral administration, reducing airway hyperresponsiveness to methacholine, Th2 cytokine production, and OVA-specific IgE levels.

  13. Protective effect of adenosine receptors against lipopolysaccharide-induced acute lung injury

    Science.gov (United States)

    Gorshkov, Boris; Varn, Matthew N.; Zemskova, Marina A.; Zemskov, Evgeny A.; Sridhar, Supriya; Lucas, Rudolf; Verin, Alexander D.

    2014-01-01

    Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) affect 200,000 people a year in the USA. Pulmonary vascular and specifically endothelial cell (EC) barrier compromise is a hallmark of these diseases. We have recently shown that extracellular adenosine enhances human pulmonary (EC) barrier via activation of adenosine receptors (ARs) in cell cultures. On the basis of these data, we hypothesized that activation of ARs might exert barrier-protective effects in a model of ALI/ARDS in mice. To test this hypothesis, we examined the effects of pre- and posttreatment of adenosine and 5′-N-ethylcarboxamidoadenosine (NECA), a nonselective stable AR agonist, on LPS-induced lung injury. Mice were given vehicle or LPS intratracheally followed by adenosine, NECA, or vehicle instilled via the internal jugular vein. Postexperiment cell counts, Evans Blue Dye albumin (EBDA) extravasation, levels of proteins, and inflammatory cytokines were analyzed. Harvested lungs were used for histology and myeloperoxidase studies. Mice challenged with LPS alone demonstrated an inflammatory response typical of ALI. Cell counts, EBDA extravasation, as well as levels of proteins and inflammatory cytokines were decreased in adenosine-treated mice. Histology displayed reduced infiltration of neutrophils. NECA had a similar effect on LPS-induced vascular barrier compromise. Importantly, posttreatment with adenosine or NECA recovers lung vascular barrier and reduces inflammation induced by LPS challenge. Furthermore, adenosine significantly attenuated protein degradation of A2A and A3 receptors induced by LPS. Collectively, our results demonstrate that activation of ARs protects and restores vascular barrier functions and reduces inflammation in LPS-induced ALI. PMID:24414256

  14. The role of glial adenosine receptors in neural resilience and the neurobiology of mood disorders

    NARCIS (Netherlands)

    Calker, D; Biber, K

    2005-01-01

    Adenosine receptors were classified into A(1)- and A(2)-receptors in the laboratory of Bernd Hamprecht more than 25 years ago. Adenosine receptors are instrumental to the neurotrophic effects of glia cells. Both microglia and astrocytes release after stimulation via adenosine receptors factors that

  15. Characterization of the binding of a novel nonxanthine adenosine antagonist radioligand, ( sup 3 H)CGS 15943, to multiple affinity states of the adenosine A1 receptor in the rat cortex

    Energy Technology Data Exchange (ETDEWEB)

    Jarvis, M.F.; Williams, M.; Do, U.H.; Sills, M.A. (CIBA-GEIGY Corp., Summit, NJ (USA))

    1991-01-01

    The triazoloquinazoline CGS 15943 is the first reported nonxanthine adenosine antagonist that has high affinity for brain adenosine receptors. In the present study, the binding of (3H) CGS 15943 to recognition sites in rat cortical membranes was characterized. Saturation experiments revealed that (3H)CGS 15943 labeled a single class of recognition sites with high affinity and limited capacity. Competition studies revealed that the binding of (3H)CGS 15943 was consistent with the labeling of brain adenosine A1 receptors. Adenosine agonists inhibited 1 nM (3H)CGS 15943 binding with the following order of activity N6-cyclopentyladenosine (IC50 = 15 nM) greater than 2-chloroadenosine greater than (R)-N6-phenylisopropyladenosine greater than 5'-N6-ethylcarboxamidoadenosine greater than (S)N6-phenylisopropyladenosine greater than CGS 21680 greater than CV 1808 (IC50 greater than 10,000 nM). The potency order for adenosine antagonists was CGS 15943 (IC50 = 5 nM) greater than 8-phenyltheophylline greater than 1,3-dipropyl-8-(4-amino-2-chloro)phenylxanthine greater than 1,3-diethyl-8-phenylxanthine greater than theophylline = caffeine (IC50 greater than 10,000 nM). Antagonist inhibition curves were steep and best described by a one-site binding model. In contrast, adenosine A1 agonist competition curves were shallow, as indicated by Hill coefficients less than unity. Computer analysis revealed that these inhibition curves were best described by a two-site binding model. Agonist competition curves generated in the presence of 1 mM GTP resulted in a rightward shift and steepening of the inhibition-concentration curves, whereas antagonist binding was not altered in the presence of GTP. The complex binding interactions found with adenosine agonists indicate that (3H)CGS 15943 labels both high and low affinity components of the adenosine A1 receptor in the rat cortex.

  16. Effect of an inhaled adenosine A(2A) agonist on the allergen-induced late asthmatic response

    NARCIS (Netherlands)

    Luijk, B.; van den Berge, M.; Kerstjens, H. A. M.; Postma, D. S.; Cass, L.; Sabin, A.; Lammers, J. -W. J.

    Background: Adenosine receptor activation is suggested to play a role in asthmatic airway inflammation. Inhibition of adenosine receptors may have an effect on the late asthmatic response (LAR) after allergen inhalation and this mechanism could offer a potential new treatment in asthma. Methods: We

  17. Adenosine inhibits renin release from juxtaglomerular cells via an A1 receptor-TRPC-mediated pathway

    Science.gov (United States)

    Ortiz-Capisano, M. Cecilia; Atchison, Douglas K.; Harding, Pamela; Lasley, Robert D.

    2013-01-01

    Renin is synthesized and released from juxtaglomerular (JG) cells. Adenosine inhibits renin release via an adenosine A1 receptor (A1R) calcium-mediated pathway. How this occurs is unknown. In cardiomyocytes, adenosine increases intracellular calcium via transient receptor potential canonical (TRPC) channels. We hypothesized that adenosine inhibits renin release via A1R activation, opening TRPC channels. However, higher concentrations of adenosine may stimulate renin release through A2R activation. Using primary cultures of isolated mouse JG cells, immunolabeling demonstrated renin and A1R in JG cells, but not A2R subtypes, although RT-PCR indicated the presence of mRNA of both A2AR and A2BR. Incubating JG cells with increasing concentrations of adenosine decreased renin release. Different concentrations of the adenosine receptor agonist N-ethylcarboxamide adenosine (NECA) did not change renin. Activating A1R with 0.5 μM N6-cyclohexyladenosine (CHA) decreased basal renin release from 0.22 ± 0.05 to 0.14 ± 0.03 μg of angiotensin I generated per milliliter of sample per hour of incubation (AngI/ml/mg prot) (P renin. Reducing extracellular calcium with EGTA increased renin release (0.35 ± 0.08 μg AngI/ml/mg prot; P renin inhibition by CHA (0.28 ± 0.06 μg AngI/ml/mg prot; P renin release by 55%, and blocked the inhibitory effect of CHA. Repeating these experiments in JG cells from A1R knockout mice using CHA or NECA demonstrated no effect on renin release. However, RT-PCR showed mRNA from TRPC isoforms 3 and 6 in isolated JG cells. Adding the TRPC blocker SKF-96365 reversed CHA-mediated inhibition of renin release. Thus A1R activation results in a calcium-dependent inhibition of renin release via TRPC-mediated calcium entry, but A2 receptors do not regulate renin release. PMID:23884142

  18. Stimulation of endothelial adenosine A1 receptors enhances adhesion of neutrophils in the intact guinea pig coronary system.

    Science.gov (United States)

    Zahler, S; Becker, B F; Raschke, P; Gerlach, E

    1994-09-01

    The primary aim was to determine the action of pathophysiologically relevant adenosine concentrations (0.1-1 microM) on adhesion of neutrophils to coronary endothelium. Further aims were to evaluate the nature and localisation of the adenosine receptor involved, and to assess the effect of endogenous adenosine. Adhesion was studied in isolated perfused guinea pig hearts by determining the number of cells emerging in the coronary effluent after intracoronary bolus injections of 600,000 neutrophils prepared from guinea pig or human blood. The system was characterised by the use of the proadhesive stimulus thrombin. A 5 min infusion of adenosine (0.1-0.3 microM) or the A1 receptor agonist N6-cyclopentyladenosine (CPA, 0.01 microM) significantly increased adhesion from about 20% (control) to 30%. This effect was prevented by the A1 receptor antagonist dipropyl-8-cyclopentylxanthine (DPCPX, 0.1 microM). It was not diminished by cessation of adenosine infusion 90 s prior to neutrophil injection. At a higher concentration of adenosine (1 microM), adhesion did not seem to be enhanced. However, coinfusion of the A2 receptor antagonist 3,7-dimethyl-1-propargylxanthine (DMPX, 0.1 microM) with 1 microM adenosine unmasked the A1 action, adhesion rising to 39%. Adenosine had a quantitatively identical effect on adhesion of human neutrophils. Total ischaemia of 15 min duration raised adhesion of subsequently applied neutrophils to 35%. This effect was completely blocked by DPCPX, as well as by ischaemic preconditioning (3 x 3 min). Preconditioning raised initial postischaemic coronary effluent adenosine from about 0.8 microM to 1.5 microM. The findings suggest a bimodal participation of adenosine in the development of postischaemic dysfunction by an endothelium dependent modulation of neutrophil adhesion. Stimulation occurs via endothelial A1 receptors at submicromolar adenosine levels, whereas cardioprotection by adenosine may in part relate to the use of pharmacologically high

  19. Synthesis and evaluation of N⁶-substituted apioadenosines as potential adenosine A₃ receptor modulators.

    Science.gov (United States)

    Toti, Kiran S; Moss, Steven M; Paoletta, Silvia; Gao, Zhan-Guo; Jacobson, Kenneth A; Van Calenbergh, Serge

    2014-08-01

    Adenosine receptors (ARs) trigger signal transduction pathways inside the cell when activated by extracellular adenosine. Selective modulation of the A₃AR subtype may be beneficial in controlling diseases such as colorectal cancer and rheumatoid arthritis. Here, we report the synthesis and evaluation of β-D-apio-D-furano- and α-D-apio-L-furanoadenosines and derivatives thereof. Introduction of a 2-methoxy-5-chlorobenzyl group at N(6) of β-D-apio-D-furanoadenosine afforded an A₃AR antagonist (10c, Ki=0.98 μM), while a similar modification of an α-D-apio-L-furanoadenosine gave rise to a partial agonist (11c, Ki=3.07 μM). The structural basis for this difference was examined by docking to an A₃AR model; the antagonist lacked a crucial interaction with Thr94. Published by Elsevier Ltd.

  20. Synthesis and Evaluation of N6-Substituted Apioadenosines as Potential Adenosine A3 Receptor Modulators

    Science.gov (United States)

    Toti, Kiran S.; Moss, Steven M.; Paoletta, Silvia; Gao, Zhan-Guo; Jacobson, Kenneth A.; Van Calenbergh, Serge

    2014-01-01

    Adenosine receptors (ARs) trigger signal transduction pathways inside the cell when activated by extracellular adenosine. Selective modulation of the A3AR subtype may be beneficial in controlling diseases such as colorectal cancer and rheumatoid arthritis. Here, we report the synthesis and evaluation of β-D-apio-D-furano- and α-D-apio-L-furanoadenosines and derivatives thereof. Introduction of a 2-methoxy-5-chlorobenzyl group at N6 of β-D-apio-D-furanoadenosine afforded an A3AR antagonist (10c, Ki = 0.98 μM), while a similar modification of an α-D-apio-L-furanoadenosine gave rise to a partial agonist (11c, Ki = 3.07 μM). The structural basis for this difference was examined by docking to an A3AR model; the antagonist lacked a crucial interaction with Thr94. PMID:24931275

  1. Partial adenosine A1 receptor agonism: a potential new therapeutic strategy for heart failure.

    Science.gov (United States)

    Greene, Stephen J; Sabbah, Hani N; Butler, Javed; Voors, Adriaan A; Albrecht-Küpper, Barbara E; Düngen, Hans-Dirk; Dinh, Wilfried; Gheorghiade, Mihai

    2016-01-01

    Heart failure (HF) represents a global public health and economic problem associated with unacceptable rates of death, hospitalization, and healthcare expenditure. Despite available therapy, HF carries a prognosis comparable to many forms of cancer with a 5-year survival rate of ~50%. The current treatment paradigm for HF with reduced ejection fraction (EF) centers on blocking maladaptive neurohormonal activation and decreasing cardiac workload with therapies that concurrently lower blood pressure and heart rate. Continued development of hemodynamically active medications for stepwise addition to existing therapies carries the risk of limited tolerability and safety. Moreover, this treatment paradigm has thus far failed for HF with preserved EF. Accordingly, development of hemodynamically neutral HF therapies targeting primary cardiac pathologies must be considered. In this context, a partial adenosine A1 receptor (A1R) agonist holds promise as a potentially hemodynamically neutral therapy for HF that could simultaneous improve cardiomyocyte energetics, calcium homeostasis, cardiac structure and function, and long-term clinical outcomes when added to background therapies. In this review, we describe the physiology and pathophysiology of HF as it relates to adenosine agonism, examine the existing body of evidence and biologic rationale for modulation of adenosine A1R activity, and review the current state of drug development of a partial A1R agonist for the treatment of HF.

  2. Imidazo[1,2-α]pyridines possess adenosine A1 receptor affinity for the potential treatment of cognition in neurological disorders.

    Science.gov (United States)

    Lefin, Roslyn; van der Walt, Mietha M; Milne, Pieter J; Terre'Blanche, Gisella

    2017-09-01

    Previous research has shown that bicyclic 6:5-fused heteroaromatic compounds with two N-atoms have variable degrees of adenosine A1 receptor antagonistic activity. Prompted by this imidazo[1,2-α]pyridine analogues were synthesized and evaluated for their adenosine A1 and A2A receptor affinity via radioligand binding studies and subjected to a GTP shift assay to determine its adenosine A1 receptor agonistic or antagonistic functionality. Imidazo[1,2-α]pyridine, the parent scaffold, was found devoid of affinity for the adenosine A1 and A2A receptors. The influence of substitution on position C2 showed no improvement for either adenosine A1 or A2A receptor affinity. The addition of an amino or a cyclohexylamino group to position C3 also showed no improvement of adenosine A1 or A2A receptor affinity. Surprisingly para-substitution on the phenyl ring at position C2 in combination with a cyclohexylamino group at position C3 led to adenosine A1 receptor affinity in the low micromolar range with compound 4d showing: (1) the highest affinity for the adenosine A1 receptor with a Ki value of 2.06µM and (2) adenosine A1 receptor antagonistic properties. This pilot study concludes that para-substituted 3-cyclohexylamino-2-phenyl-imidazo[1,2-α]pyridine analogues represent an interesting scaffold to investigate further structure-activity relationships in the design of novel imidazo[1,2-α]pyridine-based adenosine A1 receptor antagonists for the treatment of neurodegenerative disorders. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Small-Animal PET Study of Adenosine A(1) Receptors in Rat Brain : Blocking Receptors and Raising Extracellular Adenosine

    NARCIS (Netherlands)

    Paul, Soumen; Khanapur, Shivashankar; Rybczynska, Anna A.; Kwizera, Chantal; Sijbesma, Jurgen W. A.; Ishiwata, Kiichi; Willemsen, Antoon T. M.; Elsinga, Philip H.; Dierckx, Rudi A. J. O.; van Waarde, Aren

    2011-01-01

    Activation of adenosine A(1) receptors (A(1)R) in the brain causes sedation, reduces anxiety, inhibits seizures, and promotes neuroprotection. Cerebral A(1)R can be visualized using 8-dicyclopropylmethyl-1-C-11-methyl-3-propyl-xanthine (C-11-MPDX) and PET. This study aims to test whether C-11-MPDX

  4. John Daly Lecture: Structure-guided Drug Design for Adenosine and P2Y Receptors

    Directory of Open Access Journals (Sweden)

    Kenneth A. Jacobson

    2015-01-01

    Full Text Available We establish structure activity relationships of extracellular nucleosides and nucleotides at G protein-coupled receptors (GPCRs, e.g. adenosine receptors (ARs and P2Y receptors (P2YRs, respectively. We synthesize selective agents for use as pharmacological probes and potential therapeutic agents (e.g. A3AR agonists for neuropathic pain. Detailed structural information derived from the X-ray crystallographic structures within these families enables the design of novel ligands, guides modification of known agonists and antagonists, and helps predict polypharmacology. Structures were recently reported for the P2Y12 receptor (P2Y12R, an anti-thrombotic target. Comparison of agonist-bound and antagonist-bound P2Y12R indicates unprecedented structural plasticity in the outer portions of the transmembrane (TM domains and the extracellular loops. Nonphosphate-containing ligands of the P2YRs, such as the selective P2Y14R antagonist PPTN, are desired for bioavailability and increased stability. Also, A2AAR structures are effectively applied to homology modeling of closely related A1AR and A3AR, which are not yet crystallized. Conformational constraint of normally flexible ribose with bicyclic analogues increased the ligand selectivity. Comparison of rigid A3AR agonist congeners allows the exploration of interaction of specific regions of the nucleoside analogues with the target and off-target GPCRs, such as biogenic amine receptors. Molecular modeling predicts plasticity of the A3AR at TM2 to accommodate highly rigidified ligands. Novel fluorescent derivatives of high affinity GPCR ligands are useful tool compounds for characterization of receptors and their oligomeric assemblies. Fluorescent probes are useful for characterization of GPCRs in living cells by flow cytometry and other methods. Thus, 3D knowledge of receptor binding and activation facilitates drug discovery.

  5. Species difference in the G protein selectivity of the human and bovine A1-adenosine receptor.

    Science.gov (United States)

    Jockers, R; Linder, M E; Hohenegger, M; Nanoff, C; Bertin, B; Strosberg, A D; Marullo, S; Freissmuth, M

    1994-12-23

    The purified bovine brain A1-adenosine receptor has previously been shown to discriminate among closely related G protein alpha-subunits. To obtain analogous information for the human receptor, the cDNA coding for the human A1-adenosine receptor was inserted into a plasmid placing the synthesis of the receptor protein under the control of the MalE promoter. Following induction by maltose, active receptor accumulated in Escherichia coli membranes. Binding of the antagonist 8-[3H]cyclopentyl-1,3-dipropylxanthine to E. coli membranes (KD approximately 2 nM, Bmax approximately 0.2-0.4 pmol/mg) showed the appropriate pharmacological profile. Incubation of E. coli membranes with purified Go,i-reconstituted guanine nucleotide-sensitive high affinity binding of the agonist (-)[125I] N6-3-(iodo-4-hydroxyphenylisopropyl)adenosine to the receptor (KD approximately 1 nM). In the presence of purified beta gamma-subunit, the recombinant receptor interacted equally well with the recombinant G protein alpha-subunits Gi alpha-1, Gi alpha-2, Gi alpha-3; G(o) alpha displayed a lower affinity for the receptor while Gs alpha was inactive. Parallel experiments were carried out in bovine and human brain membranes pretreated with N-ethylmaleimide to inactivate the endogenous G(o)/Gi proteins; Gi alpha-3 was most potent in reconstituting 125I-HPIA binding to bovine membranes, while Gi alpha-1, Gi alpha-2, and G(o) alpha displayed similar affinities. However, in human membranes, Gi alpha-1, Gi alpha-2, and Gi alpha-3, were equipotent and high concentrations of G(o) alpha were required to promote 125I-HPIA binding. These observations show (i) that functional human A1-adenosine receptors were synthesized in E. coli; (ii) that the pattern of G protein coupling is identical for the recombinant human A1-receptor and its counterpart in the native membrane; (iii) and that species differences between bovine and human receptor exist not only in their pharmacological profile but also in their G

  6. Binding mode similarity measures for ranking of docking poses: a case study on the adenosine A2A receptor

    Science.gov (United States)

    Anighoro, Andrew; Bajorath, Jürgen

    2016-06-01

    We report an investigation designed to explore alternative approaches for ranking of docking poses in the search for antagonists of the adenosine A2A receptor, an attractive target for structure-based virtual screening. Calculation of 3D similarity of docking poses to crystallographic ligand(s) as well as similarity of receptor-ligand interaction patterns was consistently superior to conventional scoring functions for prioritizing antagonists over decoys. Moreover, the use of crystallographic antagonists and agonists, a core fragment of an antagonist, and a model of an agonist placed into the binding site of an antagonist-bound form of the receptor resulted in a significant early enrichment of antagonists in compound rankings. Taken together, these findings showed that the use of binding modes of agonists and/or antagonists, even if they were only approximate, for similarity assessment of docking poses or comparison of interaction patterns increased the odds of identifying new active compounds over conventional scoring.

  7. Creatine, similarly to ketamine, affords antidepressant-like effects in the tail suspension test via adenosine A₁ and A2A receptor activation.

    Science.gov (United States)

    Cunha, Mauricio P; Pazini, Francis L; Rosa, Julia M; Ramos-Hryb, Ana B; Oliveira, Ágatha; Kaster, Manuella P; Rodrigues, Ana Lúcia S

    2015-06-01

    The benefits of creatine supplementation have been reported in a broad range of central nervous systems diseases, including depression. A previous study from our group demonstrated that creatine produces an antidepressant-like effect in the tail suspension test (TST), a predictive model of antidepressant activity. Since depression is associated with a dysfunction of the adenosinergic system, we investigated the involvement of adenosine A1 and A2A receptors in the antidepressant-like effect of creatine in the TST. The anti-immobility effect of creatine (1 mg/kg, po) or ketamine (a fast-acting antidepressant, 1 mg/kg, ip) in the TST was prevented by pretreatment of mice with caffeine (3 mg/kg, ip, nonselective adenosine receptor antagonist), 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (2 mg/kg, ip, selective adenosine A1 receptor antagonist), and 4-(2-[7-amino-2-{2-furyl}{1,2,4}triazolo-{2,3-a}{1,3,5}triazin-5-yl-amino]ethyl)-phenol (ZM241385) (1 mg/kg, ip, selective adenosine A2A receptor antagonist). In addition, the combined administration of subeffective doses of creatine and adenosine (0.1 mg/kg, ip, nonselective adenosine receptor agonist) or inosine (0.1 mg/kg, ip, nucleoside formed by the breakdown of adenosine) reduced immobility time in the TST. Moreover, the administration of subeffective doses of creatine or ketamine combined with N-6-cyclohexyladenosine (CHA) (0.05 mg/kg, ip, selective adenosine A1 receptor agonist), N-6-[2-(3,5-dimethoxyphenyl)-2-(methylphenyl)ethyl]adenosine (DPMA) (0.1 mg/kg, ip, selective adenosine A2A receptor agonist), or dipyridamole (0.1 μg/mouse, icv, adenosine transporter inhibitor) produced a synergistic antidepressant-like effect in the TST. These results indicate that creatine, similarly to ketamine, exhibits antidepressant-like effect in the TST probably mediated by the activation of both adenosine A1 and A2A receptors, further reinforcing the potential of targeting the purinergic system to the management of mood disorders.

  8. Adenosine A(3) receptor-induced CCL2 synthesis in cultured mouse astrocytes

    NARCIS (Netherlands)

    Wittendorp, MC; Boddeke, HWGM; Biber, K

    During neuropathological conditions, high concentrations of adenosine are released, stimulating adenosine receptors in neurons and glial cells. It has recently been shown that stimulation of adenosine receptors in glial cells induces the release of neuroprotective substances such as NGF, S-100beta,

  9. Elevated adenosine signaling via adenosine A2B receptor induces normal and sickle erythrocyte sphingosine kinase 1 activity

    Science.gov (United States)

    Sun, Kaiqi; Zhang, Yujin; Bogdanov, Mikhail V.; Wu, Hongyu; Song, Anren; Li, Jessica; Dowhan, William; Idowu, Modupe; Juneja, Harinder S.; Molina, Jose G.; Blackburn, Michael R.; Kellems, Rodney E.

    2015-01-01

    Erythrocyte possesses high sphingosine kinase 1 (SphK1) activity and is the major cell type supplying plasma sphingosine-1-phosphate, a signaling lipid regulating multiple physiological and pathological functions. Recent studies revealed that erythrocyte SphK1 activity is upregulated in sickle cell disease (SCD) and contributes to sickling and disease progression. However, how erythrocyte SphK1 activity is regulated remains unknown. Here we report that adenosine induces SphK1 activity in human and mouse sickle and normal erythrocytes in vitro. Next, using 4 adenosine receptor-deficient mice and pharmacological approaches, we determined that the A2B adenosine receptor (ADORA2B) is essential for adenosine-induced SphK1 activity in human and mouse normal and sickle erythrocytes in vitro. Subsequently, we provide in vivo genetic evidence that adenosine deaminase (ADA) deficiency leads to excess plasma adenosine and elevated erythrocyte SphK1 activity. Lowering adenosine by ADA enzyme therapy or genetic deletion of ADORA2B significantly reduced excess adenosine-induced erythrocyte SphK1 activity in ADA-deficient mice. Finally, we revealed that protein kinase A-mediated extracellular signal-regulated kinase 1/2 activation functioning downstream of ADORA2B underlies adenosine-induced erythrocyte SphK1 activity. Overall, our findings reveal a novel signaling network regulating erythrocyte SphK1 and highlight innovative mechanisms regulating SphK1 activity in normal and SCD. PMID:25587035

  10. Allosteric interactions across native adenosine-A3 receptor homodimers: quantification using single-cell ligand-binding kinetics

    OpenAIRE

    May, Lauren T.; Bridge, Lloyd J.; Stoddart, Leigh A.; Briddon, Stephen J.; Hill, Stephen J

    2011-01-01

    A growing awareness indicates that many G-protein-coupled receptors (GPCRs) exist as homodimers, but the extent of the cooperativity across the dimer interface has been largely unexplored. Here, measurement of the dissociation kinetics of a fluorescent agonist (ABA-X-BY630) from the human A1 or A3 adenosine receptors expressed in CHO-K1 cells has provided evidence for highly cooperative interactions between protomers of the A3-receptor dimer in single living cells. In the absence of competiti...

  11. Enhanced cellular adenosine uptake limits adenosine receptor stimulation in patients with hyperhomocysteinemia.

    NARCIS (Netherlands)

    Riksen, N.P.; Rongen, G.A.; Boers, G.H.J.; Blom, H.J.; Broek, P.H.H. van den; Smits, P.

    2005-01-01

    OBJECTIVE: Endogenous adenosine has several cardioprotective effects. We postulate that in patients with hyperhomocysteinemia increased intracellular formation of S-adenosylhomocysteine decreases free intracellular adenosine. Subsequently, facilitated diffusion of extracellular adenosine into cells

  12. Adenosine receptor control of cognition in normal and disease.

    Science.gov (United States)

    Chen, Jiang-Fan

    2014-01-01

    Adenosine and adenosine receptors (ARs) are increasingly recognized as important therapeutic targets for controlling cognition under normal and disease conditions for its dual roles of neuromodulation as well as of homeostatic function in the brain. This chapter first presents the unique ability of adenosine, by acting on the inhibitory A1 and facilitating A2A receptor, to integrate dopamine, glutamate, and BNDF signaling and to modulate synaptic plasticity (e.g., long-term potentiation and long-term depression) in brain regions relevant to learning and memory, providing the molecular and cellular bases for adenosine receptor (AR) control of cognition. This led to the demonstration of AR modulation of social recognition memory, working memory, reference memory, reversal learning, goal-directed behavior/habit formation, Pavlovian fear conditioning, and effort-related behavior. Furthermore, human and animal studies support that AR activity can also, through cognitive enhancement and neuroprotection, reverse cognitive impairments in animal models of Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, and schizophrenia. Lastly, epidemiological evidence indicates that regular human consumption of caffeine, the most widely used psychoactive drug and nonselective AR antagonists, is associated with the reduced cognitive decline in aging and AD patients, and with the reduced risk in developing PD. Thus, there is a convergence of the molecular studies revealing AR as molecular targets for integrating neurotransmitter signaling and controlling synaptic plasticity, with animal studies demonstrating the strong procognitive impact upon AR antagonism in normal and disease brains and with epidemiological and clinical evidences in support of caffeine and AR drugs for therapeutic modulation of cognition. Since some of adenosine A2A receptor antagonists are already in phase III clinical trials for motor benefits in PD patients with remarkable safety profiles

  13. Adenosine A3 receptor activation is neuroprotective against retinal neurodegeneration.

    Science.gov (United States)

    Galvao, Joana; Elvas, Filipe; Martins, Tiago; Cordeiro, M Francesca; Ambrósio, António Francisco; Santiago, Ana Raquel

    2015-11-01

    Death of retinal neural cells, namely retinal ganglion cells (RGCs), is a characteristic of several retinal neurodegenerative diseases. Although the role of adenosine A3 receptor (A3R) in neuroprotection is controversial, A3R activation has been reported to afford protection against several brain insults, with few studies in the retina. In vitro models (retinal neural and organotypic cultures) and animal models [ischemia-reperfusion (I-R) and partial optic nerve transection (pONT)] were used to study the neuroprotective properties of A3R activation against retinal neurodegeneration. The A3R selective agonist (2-Cl-IB-MECA, 1 μM) prevented apoptosis (TUNEL(+)-cells) induced by kainate and cyclothiazide (KA + CTZ) in retinal neural cultures (86.5 ± 7.4 and 37.2 ± 6.1 TUNEL(+)-cells/field, in KA + CTZ and KA + CTZ + 2-Cl-IB-MECA, respectively). In retinal organotypic cultures, 2-Cl-IB-MECA attenuated NMDA-induced cell death, assessed by TUNEL (17.3 ± 2.3 and 8.3 ± 1.2 TUNEL(+)-cells/mm(2) in NMDA and NMDA+2-Cl-IB-MECA, respectively) and PI incorporation (ratio DIV4/DIV2 3.3 ± 0.3 and 1.3 ± 0.1 in NMDA and NMDA+2-Cl-IB-MECA, respectively) assays. Intravitreal 2-Cl-IB-MECA administration afforded protection against I-R injury decreasing the number of TUNEL(+) cells by 72%, and increased RGC survival by 57%. Also, intravitreal administration of 2-Cl-IB-MECA inhibited apoptosis (from 449.4 ± 37.8 to 207.6 ± 48.9 annexin-V(+)-cells) and RGC loss (from 1.2 ± 0.6 to 8.1 ± 1.7 cells/mm) induced by pONT. This study demonstrates that 2-Cl-IB-MECA is neuroprotective to the retina, both in vitro and in vivo. Activation of A3R may have great potential in the management of retinal neurodegenerative diseases characterized by RGC death, as glaucoma and diabetic retinopathy, and ischemic diseases. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Interaction of purified bovine brain A1-adenosine receptors with guanine nucleotide-binding proteins of human platelet membranes following reconstitution.

    Science.gov (United States)

    Munshi, R; Linden, J

    1990-08-01

    A1-adenosine receptors and associated guanine nucleotide-binding proteins (G proteins) have been co-purified from bovine cerebral cortex by agonist affinity chromatography [J. Biol. Chem. 264:14853-14859 (1989)]. In this study we have reconstituted purified bovine brain A1 receptors into human platelet membranes that contain A2- but no detectable A1-adenosine receptors. The recovery of reconstituted receptors was assessed from the binding of the antagonist radioligand [125I]3-(4-amino-3-iodo)phenethyl-1-propyl-8-cyclopentyl-xanthine and ranged from 32 to 84%. Coupling of reconstituted A1 receptors to platelet G proteins was evaluated by measurement of the high affinity binding of an agonist radioligand, 125I-aminobenzyladenosine, to receptor-G protein complexes and by stereospecific photoaffinity labeling of a 35,000-Da receptor polypeptide with the agonist photoaffinity label 125I-azidobenzyladenosine. Fifty percent of receptors reconstituted into platelet membranes bound agonists with high affinity, indicative of coupling to platelet G proteins. Reconstituted A1 receptors bound various ligands with affinities characteristic of A1 receptors of bovine brain. Although platelets contain both pertussis toxin-sensitive and -insensitive G proteins, reconstituted high affinity agonist binding was almost completely abolished by treatment of platelet membranes with guanosine 5'-3-O-(thio)triphosphate, pertussis toxin, N-ethylmaleimide, or heparin. Following reconstitution, A1 receptors could be resolubilized in complexes with platelet G proteins. The data suggest that marked species differences in the binding affinity of ligands to adenosine receptors result from differences in the receptors rather than membrane structure or G proteins and, further, that A1 receptors couple selectively and tightly to pertussis toxin-sensitive G proteins.

  15. Adenosine A2A receptors in ventral striatum, hypothalamus and nociceptive circuitry. Implications for drug addiction, sleep and pain

    Science.gov (United States)

    Ferré, S.; Diamond, I.; Goldberg, S.R.; Yao, L.; Hourani, S.M.O.; Huang, Z.L.; Urade, Y.; Kitchen, I.

    2007-01-01

    Adenosine A2A receptors localized in the dorsal striatum are considered as a new target for the development of antiparkinsonian drugs. Co-administration of A2A receptor antagonists has shown a significant improvement of the effects of L-DOPA. The present review emphasizes the possible application of A2A receptor antagonists in pathological conditions other than parkinsonism, including drug addiction, sleep disorders and pain. In addition to the dorsal striatum, the ventral striatum (nucleus accumbens) contains a high density of A2A receptors, which presynaptically and postsynaptically regulate glutamatergic transmission in the cortical glutamatergic projections to the nucleus accumbens. It is currently believed that molecular adaptations of the cortico-accumbens glutamatergic synapses are involved in compulsive drug seeking and relapse. Here we review recent experimental evidence suggesting that A2A antagonists could become new therapeutic agents for drug addiction. Morphological and functional studies have identified lower levels of A2A receptors in brain areas other than the striatum, such as the ventrolateral preoptic area of the hypothalamus, where adenosine plays an important role in sleep regulation. Although initially believed to be mostly dependent on A1 receptors, here we review recent studies that demonstrate that the somnogenic effects of adenosine are largely mediated by hypothalamic A2A receptors. A2A receptor antagonists could therefore be considered as a possible treatment for narcolepsy and other sleep-related disorders. Finally, nociception is another adenosine-regulated neural function previously thought to mostly involve A1 receptors. Although there is some conflicting literature on the effects of agonists and antagonists, which may partly be due to the lack of selectivity of available drugs, the studies in A2A receptor knockout mice suggest that A2A receptor antagonists might have some therapeutic potential in pain states, in particular where

  16. Molecular Vibration-Activity Relationship in the Agonism of Adenosine Receptors

    Directory of Open Access Journals (Sweden)

    Hyun Keun Chee

    2013-12-01

    Full Text Available The molecular vibration-activity relationship in the receptor-ligand interaction of adenosine receptors was investigated by structure similarity, molecular vibration, and hierarchical clustering in a dataset of 46 ligands of adenosine receptors. The resulting dendrogram was compared with those of another kind of fingerprint or descriptor. The dendrogram result produced by corralled intensity of molecular vibrational frequency outperformed four other analyses in the current study of adenosine receptor agonism and antagonism. The tree that was produced by clustering analysis of molecular vibration patterns showed its potential for the functional classification of adenosine receptor ligands.

  17. The 1976C>T polymorphism in the adenosine A2A receptor gene does not affect the vasodilator response to adenosine in humans in vivo

    NARCIS (Netherlands)

    Riksen, N.P.; Franke, B.; Broek, P. van den; Smits, P.; Rongen, G.A.

    2007-01-01

    The 1976C>T polymorphism in the adenosine A2A receptor gene (ADORA2A) modulates the psychological response to administration of the adenosine receptor antagonist caffeine. We quantified the vascular response to adenosine and caffeine to determine the relevance of this variant allele in the

  18. Co-purification of A1 adenosine receptors and guanine nucleotide-binding proteins from bovine brain.

    Science.gov (United States)

    Munshi, R; Linden, J

    1989-09-05

    A1 adenosine receptors and guanine nucleotide-binding proteins (G proteins) solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate have been co-purified from bovine cerebral cortex. A portion of solubilized receptors which displays high affinity GTP-sensitive agonist binding (40-50%) adheres tightly to agonist affinity columns composed of N6-aminobenzyladenosine-agarose. A1 adenosine receptors and G proteins are rapidly and selectively coeluted from agonist columns by the addition of 8-p-sulfophenyltheophylline, but only in combination with Mg2+-GTP or N-ethylmaleimide, agents which lower the affinity of receptors for agonists. Purified receptors and G protein alpha-subunits can be detected with the potent A1-selective antagonist radioligand, [125I]3-(4-amino-3-iodo)phenethyl-1-propyl-8-cyclopentylxanthine (125I-BW-A844U) and [35S]guanosine 5'-3-O-(thio)triphosphate [( 35S]GTP gamma S), respectively. Pretreatment of solubilized receptors with 0.1 mM N-ethylmaleimide or 0.1 mM R-phenylisopropyladenosine abolishes adsorption of receptors and G proteins to affinity columns. Following removal of 8-p-sulfophenyltheophylline and GTP, purified receptors bind agonists (2 sites) and antagonists (1 site) with affinities similar to crude soluble receptors and typical of A1 receptors. Some receptors may be denatured as a result of purification since only 23% of the radioligand binding sites which adhere to the affinity column can be detected in the eluate. The Bmax of purified receptors, 820 +/- 100 pmol/mg protein (n = 3) is 1800-fold higher than crude soluble receptors. The specific activity of [35S]GTP gamma S binding sites in affinity column eluates is 4640 pmol/mg protein. Assuming a 1:1 stoichiometry, this specific activity indicates that receptor-G protein complexes are greater than 50% pure following affinity chromatography. The photoaffinity labeled purified receptor was identified by polyacrylamide gel electrophoresis as a single band with a

  19. Methylthioadenosine reprograms macrophage activation through adenosine receptor stimulation.

    Directory of Open Access Journals (Sweden)

    Peter A Keyel

    Full Text Available Regulation of inflammation is necessary to balance sufficient pathogen clearance with excessive tissue damage. Central to regulating inflammation is the switch from a pro-inflammatory pathway to an anti-inflammatory pathway. Macrophages are well-positioned to initiate this switch, and as such are the target of multiple therapeutics. One such potential therapeutic is methylthioadenosine (MTA, which inhibits TNFα production following LPS stimulation. We found that MTA could block TNFα production by multiple TLR ligands. Further, it prevented surface expression of CD69 and CD86 and reduced NF-KB signaling. We then determined that the mechanism of this action by MTA is signaling through adenosine A2 receptors. A2 receptors and TLR receptors synergized to promote an anti-inflammatory phenotype, as MTA enhanced LPS tolerance. In contrast, IL-1β production and processing was not affected by MTA exposure. Taken together, these data demonstrate that MTA reprograms TLR activation pathways via adenosine receptors to promote resolution of inflammation.

  20. The mouse brain adenosine A(1) receptor : functional expression and pharmacology

    NARCIS (Netherlands)

    Wittendorp, MC; Kunzel, JVD; Ijzerman, AP; Boddeke, HWGM; Biber, K

    2004-01-01

    The adenosinergic system is involved in many important physiological functions. Adenosine exerts its extracellular effects through four types of G-protein-coupled receptors: A(1), A(2A), A(2B) and A(3). Adenosine acts as an important regulator of metabolic processes. In the brain adenosine mediates

  1. Thrombopoietin-receptor agonists in haematological disorders

    DEFF Research Database (Denmark)

    Gudbrandsdottir, S.; Hasselbalch, H.; Frederiksen, H.

    2012-01-01

    The objective of this study was to investigate the use of thrombopoietin-receptor agonists (TPO-ra) in patients with refractory primary immune thrombocytopenia (ITP) as well as off-label use of TPO-ra in Danish haematology departments. Hospital medical records from 32 of the 39 patients having...... received TPO-ra from 2009 to 1 May 2011 were available for data collection and included in the study. Of these patients, 15 received TPO-ra for refractory primary ITP, 7 for secondary ITP (chronic lymphatic leukaemia, systemic lupus erythematosus, Evans syndrome, human immunodeficiency virus and celiac...... disease) and 10 were treated for non-ITP (chemotherapy-induced, acute myeloid leukaemia, myelodysplastic syndrome, hereditary spherocytosis and suspected chemically induced thrombocytopenia). Initial response to TPO-ra defined as platelet counts >30×10/l after 4 weeks of treatment was found in 59...

  2. Combining GLP-1 receptor agonists with insulin

    DEFF Research Database (Denmark)

    Holst, Jens Juul; Vilsbøll, T

    2013-01-01

    Due to the increasing prevalence of type 2 diabetes mellitus (T2DM), the emergent trend towards diagnosis in younger patients and the progressive nature of this disease, many more patients than before now require insulin to maintain glycaemic control. However, there is a degree of inertia among...... physicians and patients regarding the initiation and intensification of insulin therapy, in part due to concerns about the associated weight gain and increased risk of hypoglycaemia. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) increase insulin release and suppress glucagon secretion in a glucose......, compared with insulin, the antihyperglycaemic efficacy of GLP-1RAs is limited. The combination of a GLP-1RA and insulin might thus be highly effective for optimal glucose control, ameliorating the adverse effects typically associated with insulin. Data from clinical studies support the therapeutic...

  3. Insulin restores L-arginine transport requiring adenosine receptors activation in umbilical vein endothelium from late-onset preeclampsia.

    Science.gov (United States)

    Salsoso, R; Guzmán-Gutiérrez, E; Sáez, T; Bugueño, K; Ramírez, M A; Farías, M; Pardo, F; Leiva, A; Sanhueza, C; Mate, A; Vázquez, C; Sobrevia, L

    2015-03-01

    Preeclampsia is associated with impaired placental vasodilation and reduced endothelial nitric oxide synthase (eNOS) activity in the foetoplacental circulation. Adenosine and insulin stimulate vasodilation in endothelial cells, and this activity is mediated by adenosine receptor activation in uncomplicated pregnancies; however, this activity has yet to be examined in preeclampsia. Early onset preeclampsia is associated with severe placental vasculature alterations that lead to altered foetus growth and development, but whether late-onset preeclampsia (LOPE) alters foetoplacental vascular function is unknown. Vascular reactivity to insulin (0.1-1000 nmol/L, 5 min) and adenosine (1 mmol/L, 5 min) was measured in KCl-preconstricted human umbilical vein rings from normal and LOPE pregnancies using a wire myograph. The protein levels of human cationic amino acid transporter 1 (hCAT-1), adenosine receptor subtypes, total and Ser¹¹⁷⁷- or Thr⁴⁹⁵-phosphorylated eNOS were detected via Western blot, and L-arginine transport (0-1000 μmol/L L-arginine, 3 μCi/mL L-[³H]arginine, 20 s, 37 °C) was measured in the presence or absence of insulin and adenosine receptor agonists or antagonists in human umbilical vein endothelial cells (HUVECs) from normal and LOPE pregnancies. LOPE increased the maximal L-arginine transport capacity and hCAT-1 and eNOS expression and activity compared with normal conditions. The A(2A) adenosine receptor (A(2A)AR) antagonist ZM-241385 blocked these effects of LOPE. Insulin-mediated umbilical vein ring relaxation was lower in LOPE pregnancies than in normal pregnancies and was restored using the A(2A)AR antagonist. The reduced foetoplacental vascular response to insulin may result from A(2A)AR activation in LOPE pregnancies. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Adenosine through the A2A adenosine receptor increases IL-1β in the brain contributing to anxiety

    Science.gov (United States)

    Chiu, Gabriel S.; Darmody, Patrick T.; Walsh, John P.; Moon, Morgan L.; Kwakwa, Kristin A.; Bray, Julie K.; McCusker, Robert H.; Freund, Gregory G.

    2014-01-01

    Anxiety is one of the most commonly reported psychiatric conditions, but its pathogenesis is poorly understood. Ailments associated with activation of the innate immune system, however, are increasingly linked to anxiety disorders. In adult male mice, we found that adenosine doubled caspase-1 activity in brain by a pathway reliant on ATP-sensitive potassium (KATP) channels, protein kinase A (PKA) and the A2A adenosine receptor (AR). In addition, adenosine-dependent activation of caspase-1 increased interleukin (IL)-1β in the brain by two-fold. Peripheral administration of adenosine in wild-type (WT) mice led to a 2.3-fold increase in caspase-1 activity in the amygdala and to a 33% and 42% reduction in spontaneous locomotor activity and food intake, respectively, that were not observed in caspase-1 knockout (KO), IL-1 receptor type 1 (IL-1R1) KO and A2A AR KO mice or in mice administered a caspase-1 inhibitor centrally. Finally, adenosine administration increased anxiety-like behaviors in WT mice by 28% in the open field test and by 55% in the elevated zero-maze. Caspase-1 KO mice, IL-1R1 KO mice, A2A AR KO mice and WT mice treated with the KATP channel blocker, glyburide, were resistant to adenosine-induced anxiety-like behaviors. Thus, our results indicate that adenosine can act as an anxiogenic by activating caspase-1 and increasing IL-1β in the brain. PMID:24907587

  5. Probing Biased/Partial Agonism at the G Protein-Coupled A2B Adenosine Receptorˇ

    Science.gov (United States)

    Gao, Zhan-Guo; Balasubramanian, Ramachandran; Kiselev, Evgeny; Wei, Qiang; Jacobson, Kenneth A.

    2014-01-01

    G protein-coupled A2B adenosine receptor (AR) regulates numerous important physiological functions, but its activation by diverse A2BAR agonists is poorly profiled. We probed potential partial and/or biased agonism in cell lines expressing variable levels of endogenous or recombinant A2BAR. In cAMP accumulation assays, both 5′-substituted NECA and C2-substituted MRS3997 are full agonists. However, only 5′-substituted adenosine analogs are full agonists in calcium mobilization, ERK1/2 phosphorylation and β-arrestin translocation. A2BAR overexpression in HEK293 cells markedly increased the agonist potency and maximum effect in cAMP accumulation, but less in calcium and ERK1/2. A2BAR siRNA silencing was more effective in reducing the maximum cAMP effect of non-nucleoside agonist BAY60-6583 than NECA's. A quantitative ‘operational model’ characterized C2-substituted MRS3997 as either balanced (cAMP accumulation, ERK1/2) or strongly biased agonist (against calcium, β-arrestin). N6-Substitution biased against ERK1/2 (weakly) and calcium and β-arrestin (strongly) pathways. BAY60-6583 is ERK1/2-biased, suggesting a mechanism distinct from adenosine derivatives. BAY60-6583, as A2BAR antagonist in MIN-6 mouse pancreatic β cells expressing low A2BAR levels, induced insulin release. This is the first relatively systematic study of structure-efficacy relationships of this emerging drug target. PMID:24853985

  6. Adenosine transiently modulates stimulated dopamine release in the caudate putamen via A1 receptors

    Science.gov (United States)

    Ross, Ashley E.; Venton, B. Jill

    2014-01-01

    Adenosine modulates dopamine in the brain via A1 and A2A receptors, but that modulation has only been characterized on a slow time scale. Recent studies have characterized a rapid signaling mode of adenosine that suggests a possible rapid modulatory role. Here, fast-scan cyclic voltammetry was used to characterize the extent to which transient adenosine changes modulate stimulated dopamine release (5 pulses at 60 Hz) in rat caudate putamen brain slices. Exogenous adenosine was applied and dopamine concentration monitored. Adenosine only modulated dopamine when it was applied 2 or 5 s before stimulation. Longer time intervals and bath application of 5 µM adenosine did not decrease dopamine release. Mechanical stimulation of endogenous adenosine 2s before dopamine stimulation also decreased stimulated dopamine release by 41 ± 7 %, similar to the 54 ± 6 % decrease in dopamine after exogenous adenosine application. Dopamine inhibition by transient adenosine was recovered within 10 minutes. The A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) blocked the dopamine modulation, whereas dopamine modulation was unaffected by the A2A receptor antagonist SCH 442416. Thus, transient adenosine changes can transiently modulate phasic dopamine release via A1 receptors. These data demonstrate that adenosine has a rapid, but transient, modulatory role in the brain. PMID:25219576

  7. Structure-Activity Analysis of Biased Agonism at the Human Adenosine A3 Receptor.

    Science.gov (United States)

    Baltos, Jo-Anne; Paoletta, Silvia; Nguyen, Anh T N; Gregory, Karen J; Tosh, Dilip K; Christopoulos, Arthur; Jacobson, Kenneth A; May, Lauren T

    2016-07-01

    Biased agonism at G protein-coupled receptors (GPCRs) has significant implications for current drug discovery, but molecular determinants that govern ligand bias remain largely unknown. The adenosine A3 GPCR (A3AR) is a potential therapeutic target for various conditions, including cancer, inflammation, and ischemia, but for which biased agonism remains largely unexplored. We now report the generation of bias "fingerprints" for prototypical ribose containing A3AR agonists and rigidified (N)-methanocarba 5'-N-methyluronamide nucleoside derivatives with regard to their ability to mediate different signaling pathways. Relative to the reference prototypical agonist IB-MECA, (N)-methanocarba 5'-N-methyluronamide nucleoside derivatives with significant N(6) or C2 modifications, including elongated aryl-ethynyl groups, exhibited biased agonism. Significant positive correlation was observed between the C2 substituent length (in Å) and bias toward cell survival. Molecular modeling suggests that extended C2 substituents on (N)-methanocarba 5'-N-methyluronamide nucleosides promote a progressive outward shift of the A3AR transmembrane domain 2, which may contribute to the subset of A3AR conformations stabilized on biased agonist binding. U.S. Government work not protected by U.S. copyright.

  8. Control of cannabinoid CB1 receptor function on glutamate axon terminals by endogenous adenosine acting at A1 receptors.

    Science.gov (United States)

    Hoffman, Alexander F; Laaris, Nora; Kawamura, Masahito; Masino, Susan A; Lupica, Carl R

    2010-01-13

    Marijuana is a widely used drug that impairs memory through interaction between its psychoactive constituent, Delta-9-tetrahydrocannabinol (Delta(9)-THC), and CB(1) receptors (CB1Rs) in the hippocampus. CB1Rs are located on Schaffer collateral (Sc) axon terminals in the hippocampus, where they inhibit glutamate release onto CA1 pyramidal neurons. This action is shared by adenosine A(1) receptors (A1Rs), which are also located on Sc terminals. Furthermore, A1Rs are tonically activated by endogenous adenosine (eADO), leading to suppressed glutamate release under basal conditions. Colocalization of A1Rs and CB1Rs, and their coupling to shared components of signal transduction, suggest that these receptors may interact. We examined the roles of A1Rs and eADO in regulating CB1R inhibition of glutamatergic synaptic transmission in the rodent hippocampus. We found that A1R activation by basal or experimentally increased levels of eADO reduced or eliminated CB1R inhibition of glutamate release, and that blockade of A1Rs with caffeine or other antagonists reversed this effect. The CB1R-A1R interaction was observed with the agonists WIN55,212-2 and Delta(9)-THC and during endocannabinoid-mediated depolarization-induced suppression of excitation. A1R control of CB1Rs was stronger in the C57BL/6J mouse hippocampus, in which eADO levels were higher than in Sprague Dawley rats, and the eADO modulation of CB1R effects was absent in A1R knock-out mice. Since eADO levels and A1R activation are regulated by homeostatic, metabolic, and pathological factors, these data identify a mechanism in which CB1R function can be controlled by the brain adenosine system. Additionally, our data imply that caffeine may potentiate the effects of marijuana on hippocampal function.

  9. Influence of the adenosine A1 receptor on blood pressure regulation and renin release

    DEFF Research Database (Denmark)

    Brown, Russell D.; Thorén, Peter; Steege, Andreas

    2006-01-01

    The present study was performed to investigate the role of adenosine A1 receptors in regulating blood pressure in conscious mice. Adenosine A1-receptor knockout (A1R-/-) mice and their wild-type (A1R+/+) littermates were placed on standardized normal-salt (NS), high-salt (HS), or salt-deficient (SD....... The elevated plasma renin concentrations found in the A1R-/- mice could also result in increased blood pressure. Our results confirm that adenosine, acting through the adenosine A1 receptor, plays an important role in regulating blood pressure, renin release, and sodium excretion....

  10. Elevated Adenosine Induces Placental DNA Hypomethylation Independent of A2B Receptor Signaling in Preeclampsia.

    Science.gov (United States)

    Huang, Aji; Wu, Hongyu; Iriyama, Takayuki; Zhang, Yujin; Sun, Kaiqi; Song, Anren; Liu, Hong; Peng, Zhangzhe; Tang, Lili; Lee, Minjung; Huang, Yun; Ni, Xin; Kellems, Rodney E; Xia, Yang

    2017-07-01

    Preeclampsia is a prevalent pregnancy hypertensive disease with both maternal and fetal morbidity and mortality. Emerging evidence indicates that global placental DNA hypomethylation is observed in patients with preeclampsia and is linked to altered gene expression and disease development. However, the molecular basis underlying placental epigenetic changes in preeclampsia remains unclear. Using 2 independent experimental models of preeclampsia, adenosine deaminase-deficient mice and a pathogenic autoantibody-induced mouse model of preeclampsia, we demonstrate that elevated placental adenosine not only induces hallmark features of preeclampsia but also causes placental DNA hypomethylation. The use of genetic approaches to express an adenosine deaminase minigene specifically in placentas, or adenosine deaminase enzyme replacement therapy, restored placental adenosine to normal levels, attenuated preeclampsia features, and abolished placental DNA hypomethylation in adenosine deaminase-deficient mice. Genetic deletion of CD73 (an ectonucleotidase that converts AMP to adenosine) prevented the elevation of placental adenosine in the autoantibody-induced preeclampsia mouse model and ameliorated preeclampsia features and placental DNA hypomethylation. Immunohistochemical studies revealed that elevated placental adenosine-mediated DNA hypomethylation predominantly occurs in spongiotrophoblasts and labyrinthine trophoblasts and that this effect is independent of A2B adenosine receptor activation in both preeclampsia models. Extending our mouse findings to humans, we used cultured human trophoblasts to demonstrate that adenosine functions intracellularly and induces DNA hypomethylation without A2B adenosine receptor activation. Altogether, both mouse and human studies reveal novel mechanisms underlying placental DNA hypomethylation and potential therapeutic approaches for preeclampsia. © 2017 American Heart Association, Inc.

  11. DMPD: Shaping of monocyte and macrophage function by adenosine receptors. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 17056121 Shaping of monocyte and macrophage function by adenosine receptors. Hasko ...G, Pacher P, Deitch EA, Vizi ES. Pharmacol Ther. 2007 Feb;113(2):264-75. Epub 2006 Sep 14. (.png) (.svg) (.html) (.csml) Show Shapi...ng of monocyte and macrophage function by adenosine receptors. PubmedID 17056121 Title Shapi

  12. Genetically Controlled Upregulation of Adenosine A(1) Receptor Expression Enhances the Survival of Primary Cortical Neurons

    NARCIS (Netherlands)

    Serchov, Tsvetan; Atas, Hasan-Cem; Normann, Claus; van Calker, Dietrich; Biber, Knut

    2012-01-01

    Adenosine has a key endogenous neuroprotective role in the brain, predominantly mediated by the adenosine A(1) receptor (A(1)R). This has been mainly explored using pharmacological tools and/or receptor knockout mice strains. It has long been suggested that the neuroprotective effects of A(1)R are

  13. A3 Adenosine Receptor Allosteric Modulator Induces an Anti-Inflammatory Effect: In Vivo Studies and Molecular Mechanism of Action

    Directory of Open Access Journals (Sweden)

    Shira Cohen

    2014-01-01

    Full Text Available The A3 adenosine receptor (A3AR is overexpressed in inflammatory cells and in the peripheral blood mononuclear cells of individuals with inflammatory conditions. Agonists to the A3AR are known to induce specific anti-inflammatory effects upon chronic treatment. LUF6000 is an allosteric compound known to modulate the A3AR and render the endogenous ligand adenosine to bind to the receptor with higher affinity. The advantage of allosteric modulators is their capability to target specifically areas where adenosine levels are increased such as inflammatory and tumor sites, whereas normal body cells and tissues are refractory to the allosteric modulators due to low adenosine levels. LUF6000 administration induced anti-inflammatory effect in 3 experimental animal models of rat adjuvant induced arthritis, monoiodoacetate induced osteoarthritis, and concanavalin A induced liver inflammation in mice. The molecular mechanism of action points to deregulation of signaling proteins including PI3K, IKK, IκB, Jak-2, and STAT-1, resulting in decreased levels of NF-κB, known to mediate inflammatory effects. Moreover, LUF6000 induced a slight stimulatory effect on the number of normal white blood cells and neutrophils. The anti-inflammatory effect of LUF6000, mechanism of action, and the differential effects on inflammatory and normal cells position this allosteric modulator as an attractive and unique drug candidate.

  14. Discovery of the First Selective, Nonpeptidic Orexin 2 Receptor Agonists.

    Science.gov (United States)

    Heifetz, Alexander; Bodkin, Mike J; Biggin, Philip C

    2015-10-22

    In this issue, Nagase and colleagues report the discovery of the first selective nonpeptidic orexin 2 receptor (OX2R) agonists. The discovery of these OX2R selective agonists opens up new avenues for therapies related to the activation of the orexin system, especially with respect to the treatment of sleep disorders such as narcolepsy.

  15. Adenosine receptor antagonists for cognitive dysfunction: a review of animal studies.

    Science.gov (United States)

    Takahashi, Reinaldo Naoto; Pamplona, Fabricio Alano; Prediger, Rui Daniel Schroder

    2008-01-01

    Over the last decade, adenosine receptors in the central nervous system have been implicated in the modulation of cognitive functions. Despite the general view that endogenous adenosine modulates cognition through the activation of adenosine A1 receptors, evidence is now emerging on a possible role of A2A receptors in learning and memory. The present review attempts to examine results reported in different studies using diverse animal models, to provide a comprehensive picture of the recent evidence of a relationship between adenosinergic function and memory deficits. The present data suggest that caffeine (a nonselective adenosine receptor antagonist) and selective adenosine A2A receptor antagonists can improve memory performance in rodents evaluated through different tasks. They might also afford protection against memory dysfunction elicited in experimental models of aging, Alzheimer's disease, Parkinson's disease and, in spontaneously hypertensive rats (SHR), a putative genetic model of attention deficit hyperactivity disorder (ADHD).

  16. Nicotine receptor partial agonists for smoking cessation

    Directory of Open Access Journals (Sweden)

    Kate Cahill

    Full Text Available BACKGROUND: Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist and reducing smoking satisfaction (acting as an antagonist. OBJECTIVES: The primary objective of this review is to assess the efficacy and tolerability of nicotine receptor partial agonists, including cytisine, dianicline and varenicline for smoking cessation. SEARCH METHODS: We searched the Cochrane Tobacco Addiction Group's specialised register for trials, using the terms ('cytisine' or 'Tabex' or 'dianicline' or 'varenicline' or 'nicotine receptor partial agonist' in the title or abstract, or as keywords. The register is compiled from searches of MEDLINE, EMBASE, PsycINFO and Web of Science using MeSH terms and free text to identify controlled trials of interventions for smoking cessation and prevention. We contacted authors of trial reports for additional information where necessary. The latest update of the specialized register was in December 2011. We also searched online clinical trials registers. SELECTION CRITERIA: We included randomized controlled trials which compared the treatment drug with placebo. We also included comparisons with bupropion and nicotine patches where available. We excluded trials which did not report a minimum follow-up period of six months from start of treatment. DATA COLLECTION AND ANALYSIS: We extracted data on the type of participants, the dose and duration of treatment, the outcome measures, the randomization procedure, concealment of allocation, and completeness of follow-up. The main outcome measured was abstinence from smoking at longest follow-up. We used the most rigorous definition of abstinence, and preferred biochemically validated rates where they were reported. Where appropriate we pooled risk ratios (RRs, using the Mantel-Haenszel fixed-effect model. MAIN RESULTS: Two recent cytisine trials (937 people

  17. Differential inhibition of noradrenaline release mediated by inhibitory A₁-adenosine receptors in the mesenteric vein and artery from normotensive and hypertensive rats.

    Science.gov (United States)

    Rocha-Pereira, C; Sousa, J B; Vieira-Rocha, M S; Fresco, P; Gonçalves, J; Diniz, C

    2013-03-01

    Mesenteric arteries and veins are densely innervated by sympathetic nerves and are crucial in the regulation of peripheral resistance and capacitance, respectively, thus, in the control of blood pressure. Presynaptic adenosine receptors are involved in vascular tonus regulation, by modulating noradrenaline release from vascular postganglionic sympathetic nerve endings. Some studies also suggest that adenosine receptors (AR) may have a role in hypertension. We aim at investigating the role of presynaptic adenosine receptors in mesenteric vessels and establish a relationship between their effects (in mesenteric vessels) and hypertension, using the spontaneously hypertensive rats (SHR) as a model of hypertension. Adenosine receptor-mediated modulation of noradrenaline release was investigated through the effects of selective agonists and antagonists on electrically-evoked [(3)H]-noradrenaline overflow. CPA (A1AR selective agonist: 1-100 nM) inhibited tritium overflow, but the inhibition was lower in SHR mesenteric vessels. IB-MECA (A3AR selective agonist: 1-100 nM) also inhibited tritium overflow but only in WKY mesenteric veins. CGS 21680 (A2AAR selective agonist: up to 100 nM) failed to facilitate noradrenaline release in mesenteric veins, from both strains, but induced a similar facilitation in the mesenteric arteries. NECA (non-selective AR agonist: 1, 3 and 10μM), in the presence of A1 (DPCPX, 20 nM) and A3 (MRS 1523, 1 μM) AR selective antagonists, failed to change tritium overflow. In summary, the modulatory effects mediated by presynaptic adenosine receptors were characterized, for the first time, in mesenteric vessels: a major inhibition exerted by the A1 subtype in both vessels; a slight inhibition mediated by A3 receptors in mesenteric vein; a facilitation mediated by A2A receptors only in mesenteric artery (from both strains). The less efficient prejunctional adenosine receptor mediated inhibitory effects can contribute to an increase of noradrenaline in

  18. GABAA receptor partial agonists and antagonists

    DEFF Research Database (Denmark)

    Krall, Jacob; Balle, Thomas; Krogsgaard-Larsen, Niels

    2015-01-01

    antagonists and describes the development of potent antagonists from partial agonists originally derived from the potent GABAAR agonist muscimol. In this process, several heterocyclic aromatic systems have been used in combination with structural models in order to map the orthosteric binding site...

  19. Quantification of adenosine A(1) receptor biased agonism: Implications for drug discovery.

    Science.gov (United States)

    Baltos, Jo-Anne; Gregory, Karen J; White, Paul J; Sexton, Patrick M; Christopoulos, Arthur; May, Lauren T

    2016-01-01

    Adenosine A1 receptor (A1AR) stimulation is a powerful protective mechanism in cerebral and cardiac ischemia-reperfusion injury. Despite this, therapeutic targeting of the A1AR for the treatment of ischemia-reperfusion injury has been largely unsuccessful, as high concentrations of prototypical A1AR agonists impart significant hemodynamic effects, particularly pronounced bradycardia, atrioventricular block and hypotension. Exploiting the phenomenon of biased agonism to develop ligands that promote A1AR cytoprotection in the absence of adverse hemodynamic effects remains a relatively unexplored, but exciting, approach to overcome current limitations. In native systems, the atypical A1AR agonists VCP746 and capadenoson retain cytoprotective signaling in the absence of bradycardia, a phenomenon suggestive of biased agonism. The current study used pharmacological inhibitors to investigate A1AR mediated cytoprotective signal transduction in a CHO FlpIn cell background, thus identifying candidate pathways for quantitative bias profiling, including cAMP, extracellular signal-regulated kinases 1 and 2 and Akt1/2/3. Subsequently, effects on cell survival and the bias profile of VCP746 and capadenoson were determined and compared to that of the prototypical A1AR agonists, NECA, R-PIA, MeCCPA and CPA. We found that prototypical agonists do not display significant bias for any of the pathways assessed. In contrast, VCP746 and capadenoson show significant bias away from calcium mobilization relative to all pathways tested. These studies demonstrate that quantitative "fingerprinting" of biased agonism within a model system can enable ligands to be clustered by their bias profile, which in turn may be predictive of preferential physiologically relevant in vivo pharmacology. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Locomotor activation by theacrine, a purine alkaloid structurally similar to caffeine: involvement of adenosine and dopamine receptors.

    Science.gov (United States)

    Feduccia, Allison A; Wang, Yuanyuan; Simms, Jeffrey A; Yi, Henry Y; Li, Rui; Bjeldanes, Leonard; Ye, Chuangxing; Bartlett, Selena E

    2012-08-01

    Purine compounds, such as caffeine, have many health-promoting properties and have proven to be beneficial in treating a number of different conditions. Theacrine, a purine alkaloid structurally similar to caffeine and abundantly present in Camellia kucha, has recently become of interest as a potential therapeutic compound. In the present study, theacrine was tested using a rodent behavioral model to investigate the effects of the drug on locomotor activity. Long Evans rats were injected with theacrine (24 or 48 mg/kg, i.p.) and activity levels were measured. Results showed that the highest dose of theacrine (48 mg/kg, i.p.) significantly increased locomotor activity compared to control animals and activity remained elevated throughout the duration of the session. To test for the involvement of adenosine receptors underlying theacrine's motor-activating properties, rats were administered a cocktail of the adenosine A₁ agonist, N⁶-cyclopentyladenosine (CPA; 0.1 mg/kg, i.p.) and A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS-21680; 0.2 mg/kg, i.p.). Pre-treatment with theacrine significantly attenuated the motor depression induced by the adenosine receptor agonists, indicating that theacrine is likely acting as an adenosine receptor antagonist. Next, we examined the role of DA D₁ and D₂ receptor antagonism on theacrine-induced hyperlocomotion. Both antagonists, D₁R SCH23390 (0.1 or 0.05 mg/kg, i.p.) and D₂R eticlopride (0.1 mg/kg, i.p.), significantly reduced theacrine-stimulated activity indicating that this behavioral response, at least in part, is mediated by DA receptors. In order to investigate the brain region where theacrine may be acting, the drug (10 or 20 μg) was infused bilaterally into nucleus accumbens (NAc). Theacrine enhanced activity levels in a dose-dependent manner, implicating a role of the NAc in modulating theacrine's effects on locomotion. In addition, theacrine did not induce locomotor

  1. Activation of A(2) adenosine receptors dilates cortical efferent arterioles in mouse

    DEFF Research Database (Denmark)

    Al-Mashhadi, Rozh H; Skøtt, Ole; Vanhoutte, Paul M

    2009-01-01

    Adenosine can induce vasodilatation and vasoconstriction of the renal afferent arteriole of the mouse. We determined here its direct effect on efferent arterioles of mouse kidneys. Using isolated-perfused cortical efferent arterioles, we measured changes in luminal diameter in response to adenosine....... Extraluminal application of adenosine and cyclohexyladenosine had no effect on the luminal diameter. When the vessels were constricted by the thromboxane mimetic U46619, application of adenosine and 5'-N-ethylcarboxamido-adenosine dilated the efferent arterioles in a dose-dependent manner. We also found...... that the adenosine-induced vasodilatation was inhibited by the A(2)-specific receptor blocker 3,7-dimethyl-1-propargylxanthine. In the presence of this inhibitor, adenosine failed to alter the basal vessel diameter of quiescent efferent arterioles. Using primer-specific polymerase chain reaction we found...

  2. Constitutive activity of the A2A adenosine receptor and compartmentalised cyclic AMP signalling fine-tune noradrenaline release.

    Science.gov (United States)

    Ibrisimovic, Edin; Drobny, Helmut; Yang, Qiong; Höfer, Thomas; Boehm, Stefan; Nanoff, Christian; Schicker, Klaus

    2012-12-01

    Neuroblastoma SH-SY5Y (SH) cells endogenously express A(2A) adenosine receptors and can be differentiated into a sympathetic neuronal phenotype, capable of depolarisation-dependent noradrenaline release. Using differentiated SH culture, we here explored the link between A(2A)-receptor signalling and neurotransmitter release. In response to the receptor agonist CGS21680, the cells produced cyclic AMP (cAMP), and when depolarised, they released increased amounts of noradrenaline. An A(2A)-receptor antagonist, XAC, as well as an inhibitor of cAMP-dependent protein kinase A (PKA), H89, depressed agonist-dependent release. In the presence of XAC or H89, noradrenaline release was found to be below basal values. This suggested that release facilitation also owes to constitutive receptor activity. We demonstrate that even in the absence of an agonist, the native A(2A)-receptor stimulated cAMP production, leading to the activation of PKA and enhanced noradrenaline release. Ancillary, non-cAMP-dependent effects of the receptor (i.e. phosphorylation of CREB, of Rabphilin3A) were refractory to constitutive activation. PKA-dependent facilitation of noradrenaline release was recapitulated with membrane-permeable 8-Br-cAMP; in addition to facilitation, 8-Br-cAMP caused marked inhibition of release, an effect not observed upon receptor activation. Inhibition by receptor-independent cAMP was likely due to suppression of voltage-dependent calcium current (VDCC) and increased activity of Src-family kinases. Receptor-mediated release facilitation was reproduced in the presence of tetrodotoxin (blocking action potentials); hence, the signalling occurred at the active zone comprising release sites. Our findings thus support (1) presynaptic localisation of the A(2A)-receptor and (2) suggest that compartmentalised pathways transmit cAMP signalling in order to facilitate depolarisation-dependent neurotransmitter release.

  3. MELATONIN DAN MELATONIN RECEPTOR AGONIST SEBAGAI PENANGANAN INSOMNIA PRIMER KRONIS

    Directory of Open Access Journals (Sweden)

    Ni Luh Putu Ayu Maha Iswari

    2013-04-01

    Full Text Available Melatonin is a hormone that has an important role in the mechanism of sleep. Hypnotic effects of melatonin and melatonin receptor agonist are mediated via MT1 and MT2 receptors, especially in circadian rhythm pacemaker, suprachiasmatic nucleus, which is worked on the hypothalamic sleep switch. This mechanism is quite different with the GABAergic drugs such as benzodiazepine. Agonist melatonin triggers the initiation of sleep and normalize circadian rhythms so that makes it easier to maintain sleep. The main disadvantage of melatonin in helping sleep maintenance on primary insomnia is that the half life is very short. The solution to this problem is the use of prolonged-release melatonin and melatonin receptor agonist agents such as ramelteon. Melatoninergic agonist does not cause withdrawal effects, dependence, as well as cognitive and psychomotor disorders as often happens on the use of benzodiazepine.  

  4. Human Monocyte Recognition of Adenosine-Based Cyclic Dinucleotides Unveils the A2a Gαs Protein-Coupled Receptor Tonic Inhibition of Mitochondrially Induced Cell Death

    Science.gov (United States)

    Pont, Frédéric; Bétous, Delphine; Ravet, Emmanuel; Ligat, Laetitia; Lopez, Frédéric; Poupot, Mary; Poirot, Marc; Pérouzel, Éric; Tiraby, Gérard; Verhoeyen, Els

    2014-01-01

    Cyclic dinucleotides are important messengers for bacteria and protozoa and are well-characterized immunity alarmins for infected mammalian cells through intracellular binding to STING receptors. We sought to investigate their unknown extracellular effects by adding cyclic dinucleotides to the culture medium of freshly isolated human blood cells in vitro. Here we report that adenosine-containing cyclic dinucleotides induce the selective apoptosis of monocytes through a novel apoptotic pathway. We demonstrate that these compounds are inverse agonist ligands of A2a, a Gαs-coupled adenosine receptor selectively expressed by monocytes. Inhibition of monocyte A2a by these ligands induces apoptosis through a mechanism independent of that of the STING receptors. The blockade of basal (adenosine-free) signaling from A2a inhibits protein kinase A (PKA) activity, thereby recruiting cytosolic p53, which opens the mitochondrial permeability transition pore and impairs mitochondrial respiration, resulting in apoptosis. A2a antagonists and inverse agonist ligands induce apoptosis of human monocytes, while A2a agonists are antiapoptotic. In vivo, we used a mock developing human hematopoietic system through NSG mice transplanted with human CD34+ cells. Treatment with cyclic di-AMP selectively depleted A2a-expressing monocytes and their precursors via apoptosis. Thus, monocyte recognition of cyclic dinucleotides unravels a novel proapoptotic pathway: the A2a Gαs protein-coupled receptor (GPCR)-driven tonic inhibitory signaling of mitochondrion-induced cell death. PMID:25384972

  5. Regulation of hippocampal cannabinoid CB1 receptor actions by adenosine A1 receptors and chronic caffeine administration: implications for the effects of Δ9-tetrahydrocannabinol on spatial memory.

    Science.gov (United States)

    Sousa, Vasco C; Assaife-Lopes, Natália; Ribeiro, Joaquim A; Pratt, Judith A; Brett, Ros R; Sebastião, Ana M

    2011-01-01

    The cannabinoid CB(1) receptor-mediated modulation of γ-aminobutyric acid (GABA) release from inhibitory interneurons is important for the integrity of hippocampal-dependent spatial memory. Although adenosine A(1) receptors have a central role in fine-tuning excitatory transmission in the hippocampus, A(1) receptors localized in GABAergic cells do not directly influence GABA release. CB(1) and A(1) receptors are the main targets for the effects of two of the most heavily consumed psychoactive substances worldwide: Δ(9)-tetrahydrocannabinol (THC, a CB(1) receptor agonist) and caffeine (an adenosine receptor antagonist). We first tested the hypothesis that an A(1)-CB(1) interaction influences GABA and glutamate release in the hippocampus. We found that A(1) receptor activation attenuated the CB(1)-mediated inhibition of GABA and glutamate release and this interaction was manifested at the level of G-protein activation. Using in vivo and in vitro approaches, we then investigated the functional implications of the adenosine-cannabinoid interplay that may arise following chronic caffeine consumption. Chronic administration of caffeine in mice (intraperitoneally, 3 mg/kg/day, for 15 days, >12 h before trials) led to an A(1)-mediated enhancement of the CB(1)-dependent acute disruptive effects of THC on a short-term spatial memory task, despite inducing a reduction in cortical and hippocampal CB(1) receptor number and an attenuation of CB(1) coupling with G protein. A(1) receptor levels were increased following chronic caffeine administration. This study shows that A(1) receptors exert a negative modulatory effect on CB(1)-mediated inhibition of GABA and glutamate release, and provides the first evidence of chronic caffeine-induced alterations on the cannabinoid system in the cortex and hippocampus, with functional implications in spatial memory.

  6. A comprehensive comparative review of adenosine diphosphate receptor antagonists.

    Science.gov (United States)

    Oh, Erin Y; Abraham, Teena; Saad, Nasser; Rapp, Jonathan H; Vastey, Fabienne L; Balmir, Eric

    2012-02-01

    Thrombosis risk necessitates dual antiplatelet therapy with aspirin and an adenosine diphosphate (ADP) receptor antagonist, in patients who have acute coronary syndrome. Current guidelines emphasize the critical role of dual antiplatelet therapy in both medical management and invasive strategy, especially in patients undergoing percutaneous coronary intervention. With the availability of multiple ADP-receptor antagonists, it is crucial to select the most appropriate agent for each patient. The pertinent trials were identified through a MEDLINE search, in addition to a manual search from the articles retrieved. This review examines the differences between clopidogrel, prasugrel and ticagrelor in terms of their pharmacological/pharmacokinetic properties, clinical efficacy, drug interactions and safety parameters. Prasugrel and ticagrelor exhibit greater platelet inhibition and superior efficacy compared with clopidogrel, at the expense of higher bleeding risk. Prasugrel and ticagrelor should be preferred over clopidogrel in patients who are at a high risk of thrombotic events with low risk of bleeding. Additionally, these two agents may offer advantage over clopidogrel in those patients who might have risk for drug resistance due to CYP2C19 polymorphism. In selecting the ideal agent for patients, clinicians should tailor the antiplatelet regimen by considering individual risk factors and medication characteristics.

  7. Adenosine A3 Receptor Suppresses Prostate Cancer Metastasis by Inhibiting NADPH Oxidase Activity

    Directory of Open Access Journals (Sweden)

    Sarvesh Jajoo

    2009-11-01

    Full Text Available Prostate cancer is the most commonly diagnosed and second most lethal malignancy in men, due mainly to a lack of effective treatment for the metastatic disease. A number of recent studies have shown that activation of the purine nucleoside receptor, adenosine A3 receptor (A3AR, attenuates proliferation of melanoma, colon, and prostate cancer cells. In the present study, we determined whether activation of the A3AR reduces the ability of prostate cancer cells to migrate in vitro and metastasize in vivo. Using severe combined immunodeficient mice, we show that proliferation and metastasis of AT6.1 rat prostate cancer cells were decreased by the administration of A3AR agonist N6-(3-iodobenzyl adenosine-5′-N-methyluronamide. In vitro studies show that activation of A3AR decreased high basal nicotinamide adenine dinucleotide phosphate (NADPH oxidase activity present in these cells, along with the expression of Rac1 and p47phox subunits of this enzyme. Inhibition of NADPH oxidase activity by the dominant-negative RacN17 or short interfering (siRNA against p47phox reduced both the generation of reactive oxygen species and the invasion of these cells on Matrigel. In addition, we show that membrane association of p47phox and activation of NADPH oxidase is dependent on the activity of the extracellular signal-regulated kinase (ERK1/2 mitogen-activated protein kinase pathway. We also provide evidence that A3AR inhibits ERK1/2 activity in prostate cancer cells through inhibition of adenylyl cyclase and protein kinase A. We conclude that activation of the A3AR in prostate cancer cells reduces protein kinase A-mediated stimulation of ERK1/2, leading to reduced NADPH oxidase activity and cancer cell invasiveness.

  8. High salt diet exacerbates vascular contraction in the absence of adenosine A₂A receptor.

    Science.gov (United States)

    Pradhan, Isha; Zeldin, Darryl C; Ledent, Catherine; Mustafa, Jamal S; Falck, John R; Nayeem, Mohammed A

    2014-05-01

    High salt (4% NaCl, HS) diet modulates adenosine-induced vascular response through adenosine A(2A) receptor (A(2A)AR). Evidence suggests that A(2A)AR stimulates cyp450-epoxygenases, leading to epoxyeicosatrienoic acids (EETs) generation. The aim of this study was to understand the vascular reactivity to HS and underlying signaling mechanism in the presence or absence of A(2A)AR. Therefore, we hypothesized that HS enhances adenosine-induced relaxation through EETs in A(2A)AR⁺/⁺, but exaggerates contraction in A(2A)AR⁻/⁻. Organ bath and Western blot experiments were conducted in HS and normal salt (NS, 0.18% NaCl)-fed A(2A)AR⁺/⁺ and A(2A)AR⁻/⁻ mice aorta. HS produced concentration-dependent relaxation to non-selective adenosine analog, NECA in A(2A)AR⁺/⁺, whereas contraction was observed in A(2A)AR⁻/⁻ mice and this was attenuated by A₁AR antagonist (DPCPX). CGS 21680 (selective A(2A)AR agonist) enhanced relaxation in HS-A(2A)AR⁺/⁺ versus NS-A(2A)AR⁺/⁺, which was blocked by EETs antagonist (14,15-EEZE). Compared with NS, HS significantly upregulated the expression of vasodilators A(2A)AR and cyp2c29, whereas vasoconstrictors A₁AR and cyp4a in A(2A)AR⁺/⁺ were downregulated. In A(2A)AR⁻/⁻ mice, however, HS significantly downregulated the expression of cyp2c29, whereas A₁AR and cyp4a were upregulated compared with A(2A)AR⁺/⁺ mice. Hence, our data suggest that in A(2A)AR⁺/⁺, HS enhances A(2A)AR-induced relaxation through increased cyp-expoxygenases-derived EETs and decreased A₁AR levels, whereas in A(2A)AR⁻/⁻, HS exaggerates contraction through decreased cyp-epoxygenases and increased A₁AR levels.

  9. TPO receptor agonist for chronic idiopathic thrombocytopenic purpura.

    Science.gov (United States)

    Zeng, Yan; Duan, Xin; Xu, Jiajun; Ni, Xun

    2011-07-06

    Chronic idiopathic thrombocytopenic purpura (ITP) is an acquired autoimmune disorder that is characterized predominantly by a low platelet count. Thrombopoietin (TPO) receptor agonists increase production of platelets by stimulating the TPO receptor in people with chronic ITP. To determine the efficacy and safety of TPO receptor agonists in chronic ITP patients. We searched MEDLINE (from 1950 to March 2011), EMBASE (from 1974 to March 2011), and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 3) to identify all randomized trials in chronic ITP. We also contacted authors of included studies and TPO receptor agonists manufacturers. Randomized controlled trials (RCTs) comparing TPO receptor agonists alone, or in combination with other drugs, to placebo, no treatment, other drugs, splenectomy or another TPO receptor agonist in patients with chronic ITP. Two review authors independently screened papers, extracted data and assessed the risk of bias in the included studies. Six trials with 808 patients were included. Five studies compared TPO receptor agonists with placebo (romiplostim: 100, eltrombopag: 299, placebo: 175); one study compared TPO receptor agonists with standard of care (SOC) (romiplostim: 157; SOC: 77). SOC included a variety of therapies, such as glucocorticoid, anti-D immune globulin, intravenous immune globulin, rituximab, azathioprine, and so on. Overall survival, one of our primary outcomes, was not studied by these RCTs and we could not estimate number needed to treat (NNT). Another primary outcome, improving significant bleeding events, did not reveal any significant differences between the TPO receptor agonists group and the control group (placebo or SOC) (versus placebo risk ratio (RR) 0.48, 95% confidence interval (CI) 0.20 to 1.15; versus SOC RR 0.49, 95% CI 0.15 to 1.63).For secondary outcomes, TPO receptor agonists statistically significantly improved overall platelet response (versus placebo RR

  10. Caffeine, Adenosine Receptors and Estrogen in Toxin Models of Parkinson's Disease

    National Research Council Canada - National Science Library

    Schwarzschild, Michael A; Xu, Kui

    2008-01-01

    Continued progress has been made toward each of the Specific Aims (SAs) 1 and 2 (SA 3 completed) of our research project, Caffeine, adenosine receptors and estrogen in toxin models of Parkinson's disease...

  11. Identification of Two New Cholesterol Interaction Sites on the A2A Adenosine Receptor.

    Science.gov (United States)

    Rouviere, Eric; Arnarez, Clément; Yang, Lewen; Lyman, Edward

    2017-12-05

    By mole, cholesterol is the most abundant component of animal cell plasma membranes. Many membrane proteins have been shown to be functionally dependent on cholesterol, several of which have also been shown to bind cholesterol at well-defined locations on their membrane-facing surface. In this work, a combination of coarse-grained "Martini" and all-atom simulations are used to identify two, to our knowledge, new cholesterol-binding sites on the A2A adenosine receptor, a G-protein-coupled receptor that is a target for the treatment of Parkinson's disease. One of the sites is also observed to bind cholesterol in several recent, high-resolution crystal structures of the protein, and in the simulations, interacts with cholesterol only when bound to the inverse agonist ZM241385. Cataloguing cholesterol-binding sites is a vital step in the effort to understand cholesterol-dependent function of membrane proteins. Given that cholesterol content in plasma membranes varies with cell type and on administration of widely prescribed pharmaceuticals, such as statins, understanding cholesterol-dependent function is an important step toward exploiting membrane compositional variation for therapeutic purposes. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  12. Principles of agonist recognition in Cys-loop receptors

    Directory of Open Access Journals (Sweden)

    Timothy eLynagh

    2014-04-01

    Full Text Available Cys-loop receptors are ligand-gated ion channels that are activated by a structurally diverse array of neurotransmitters, including acetylcholine, serotonin, glycine and GABA. After the term chemoreceptor emerged over 100 years ago, there was some wait until affinity labeling, molecular cloning, functional studies and X-ray crystallography experiments identified the extracellular interface of adjacent subunits as the principal site of agonist binding. The question of how subtle differences at and around agonist-binding sites of different Cys-loop receptors can accommodate transmitters as chemically diverse as glycine and serotonin has been subject to intense research over the last three decades. This review outlines the functional diversity and current structural understanding of agonist-binding sites, including those of invertebrate Cys-loop receptors. Together, this provides a framework to understand the atomic determinants involved in how these valuable therapeutic targets recognize and bind their ligands.

  13. Adenosine A2B receptor-mediated leukemia inhibitory factor release from astrocytes protects cortical neurons against excitotoxicity

    Directory of Open Access Journals (Sweden)

    Moidunny Shamsudheen

    2012-08-01

    Full Text Available Abstract Background Neuroprotective and neurotrophic properties of leukemia inhibitory factor (LIF have been widely reported. In the central nervous system (CNS, astrocytes are the major source for LIF, expression of which is enhanced following disturbances leading to neuronal damage. How astrocytic LIF expression is regulated, however, has remained an unanswered question. Since neuronal stress is associated with production of extracellular adenosine, we investigated whether LIF expression in astrocytes was mediated through adenosine receptor signaling. Methods Mouse cortical neuronal and astrocyte cultures from wild-type and adenosine A2B receptor knock-out animals, as well as adenosine receptor agonists/antagonists and various enzymatic inhibitors, were used to study LIF expression and release in astrocytes. When needed, a one-way analysis of variance (ANOVA followed by Bonferroni post-hoc test was used for statistical analysis. Results We show here that glutamate-stressed cortical neurons induce LIF expression through activation of adenosine A2B receptor subtype in cultured astrocytes and require signaling of protein kinase C (PKC, mitogen-activated protein kinases (MAPKs: p38 and ERK1/2, and the nuclear transcription factor (NF-κB. Moreover, LIF concentration in the supernatant in response to 5′-N-ethylcarboxamide (NECA stimulation was directly correlated to de novo protein synthesis, suggesting that LIF release did not occur through a regulated release pathway. Immunocytochemistry experiments show that LIF-containing vesicles co-localize with clathrin and Rab11, but not with pHogrin, Chromogranin (CgA and CgB, suggesting that LIF might be secreted through recycling endosomes. We further show that pre-treatment with supernatants from NECA-treated astrocytes increased survival of cultured cortical neurons against glutamate, which was absent when the supernatants were pre-treated with an anti-LIF neutralizing antibody. Conclusions

  14. No Effect of Nutritional Adenosine Receptor Antagonists on Exercise Performance in the Heat

    Science.gov (United States)

    2008-11-01

    358–363, 1996. 11. Cook NC, Samman S. Flavonoids —chemistry, metabolism, cardiopro- tective effects, and dietary sources. Nutr Biochem 7: 66–76, 1996...metabolism and health effects of dietary flavonoids in man. Biomed Pharmacother 51: 305–310, 1997. R400 ADENOSINE RECEPTOR ANTAGONISM AND EXERCISE IN THE HEAT...Interactions of flavonoids with adenosine receptors. J Med Chem 39: 781–788, 1996. 35. MacRae HS, Mefferd KM. Dietary antioxidant supplementation com

  15. Inosine Released from Dying or Dead Cells Stimulates Cell Proliferation via Adenosine Receptors.

    Science.gov (United States)

    Chen, Jin; Chaurio, Ricardo A; Maueröder, Christian; Derer, Anja; Rauh, Manfred; Kost, Andriy; Liu, Yi; Mo, Xianming; Hueber, Axel; Bilyy, Rostyslav; Herrmann, Martin; Zhao, Yi; Muñoz, Luis E

    2017-01-01

    Many antitumor therapies induce apoptotic cell death in order to cause tumor regression. Paradoxically, apoptotic cells are also known to promote wound healing, cell proliferation, and tumor cell repopulation in multicellular organisms. We aimed to characterize the nature of the regenerative signals concentrated in the micromilieu of dead and dying cells. Cultures of viable melanoma B16F10 cells, mouse fibroblasts, and primary human fibroblast-like synoviocytes (FLS) in the presence of dead and dying cells, their supernatants (SNs), or purified agonists and antagonists were used to evaluate the stimulation of proliferation. Viable cell quantification was performed by either flow cytometry of harvested cells or by crystal violet staining of adherent cells. High-performance liquid chromatography and liquid chromatography coupled with mass spectrometry of cell SNs were deployed to identify the nature of growth-promoting factors. Coimplantation of living cells in the presence of SNs collected from dead and dying cells and specific agonists was used to evaluate tumor growth in vivo. The stimulation of proliferation of few surviving cells by bystander dead cells was confirmed for melanoma cells, mouse fibroblasts, and primary FLS. We found that small soluble molecules present in the protein-free fraction of SNs of dead and dying cells were responsible for the promotion of proliferation. The nucleoside inosine released by dead and dying cells acting via adenosine receptors was identified as putative inducer of proliferation of surviving tumor cells after irradiation and heat treatment. Inosine released by dead and dying cells mediates tumor cell proliferation via purinergic receptors. Therapeutic strategies surmounting this pathway may help to reduce the rate of recurrence after radio- and chemotherapy.

  16. Inosine Released from Dying or Dead Cells Stimulates Cell Proliferation via Adenosine Receptors

    Directory of Open Access Journals (Sweden)

    Yi Zhao

    2017-04-01

    Full Text Available IntroductionMany antitumor therapies induce apoptotic cell death in order to cause tumor regression. Paradoxically, apoptotic cells are also known to promote wound healing, cell proliferation, and tumor cell repopulation in multicellular organisms. We aimed to characterize the nature of the regenerative signals concentrated in the micromilieu of dead and dying cells.MethodsCultures of viable melanoma B16F10 cells, mouse fibroblasts, and primary human fibroblast-like synoviocytes (FLS in the presence of dead and dying cells, their supernatants (SNs, or purified agonists and antagonists were used to evaluate the stimulation of proliferation. Viable cell quantification was performed by either flow cytometry of harvested cells or by crystal violet staining of adherent cells. High-performance liquid chromatography and liquid chromatography coupled with mass spectrometry of cell SNs were deployed to identify the nature of growth-promoting factors. Coimplantation of living cells in the presence of SNs collected from dead and dying cells and specific agonists was used to evaluate tumor growth in vivo.ResultsThe stimulation of proliferation of few surviving cells by bystander dead cells was confirmed for melanoma cells, mouse fibroblasts, and primary FLS. We found that small soluble molecules present in the protein-free fraction of SNs of dead and dying cells were responsible for the promotion of proliferation. The nucleoside inosine released by dead and dying cells acting via adenosine receptors was identified as putative inducer of proliferation of surviving tumor cells after irradiation and heat treatment.ConclusionInosine released by dead and dying cells mediates tumor cell proliferation via purinergic receptors. Therapeutic strategies surmounting this pathway may help to reduce the rate of recurrence after radio- and chemotherapy.

  17. [Effects of GLP-1 receptor agonists on carbohydrate metabolism control].

    Science.gov (United States)

    Fernández-García, José Carlos; Colomo, Natalia; Tinahones, Francisco José

    2014-09-01

    Glucagon-like peptide-1 (GLP-1) receptor agonists are a new group of drugs for the treatment of type 2 diabetes mellitus (DM2). In the present article, we review the available evidence on the efficacy of GLP-1 receptor agonists as glucose-lowering agents, their place in therapeutic algorithms, and the clinical factors associated with a favorable treatment response. Finally, we describe the clinical characteristics of patients who may benefit from these drugs. Copyright © 2014 Elsevier España, S.L.U. All rights reserved.

  18. Effects of A1 receptor agonist/antagonist on spontaneous seizures in pilocarpine-induced epileptic rats.

    Science.gov (United States)

    Amorim, Beatriz Oliveira; Hamani, Clement; Ferreira, Elenn; Miranda, Maísa Ferreira; Fernandes, Maria José S; Rodrigues, Antonio M; de Almeida, Antônio-Carlos G; Covolan, Luciene

    2016-08-01

    Adenosine is an endogenous anticonvulsant that activates pre- and postsynaptic adenosine A1 receptors. A1 receptor agonists increase the latency for the development of seizures and status epilepticus following pilocarpine administration. Although hippocampal adenosine is increased in the chronic phase of the pilocarpine model, it is not known whether the modulation of A1 receptors may influence the frequency of spontaneous recurrent seizures (SRS). Here, we tested the hypothesis that the A1 receptor agonist RPia ([R]-N-phenylisopropyladenosine) and the A1 antagonist DPCPX (8-Cyclopentyl-1,3-dipropylxanthine) administered to chronic pilocarpine epileptic rats would respectively decrease and increase the frequency of SRS and hippocampal excitability. Four months after Pilo-induced SE, chronic epileptic rats were video-monitored for the recording of SRS before (basal) and after a 2-week treatment with RPia (25μg/kg) or DPCPX (50μg/kg). Following sacrifice, brain slices were studied with electrophysiology. We found that rats given RPia had a 93% nonsignificant reduction in the frequency of seizures compared with their own pretreatment baseline. In contrast, the administration of DPCPX resulted in an 87% significant increase in seizure rate. Nontreated epileptic rats had a similar frequency of seizures along the study. Corroborating our behavioral data, in vitro recordings showed that slices from animals previously given DPCPX had a shorter latency to develop epileptiform activity, longer and higher DC shifts, and higher spike amplitude compared with slices from nontreated Pilo controls. In contrast, smaller spike amplitude was recorded in slices from animals given RPia. In summary, the administration of A1 agonists reduced hippocampal excitability but not the frequency of spontaneous recurrent seizures in chronic epileptic rats, whereas A1 receptor antagonists increased both. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Interactions of the bovine brain A1-adenosine receptor with recombinant G protein alpha-subunits. Selectivity for rGi alpha-3.

    Science.gov (United States)

    Freissmuth, M; Schütz, W; Linder, M E

    1991-09-25

    The ability of the bovine brain A1-adenosine receptor to discriminate between different G protein subtypes was tested using G protein alpha-subunits synthesized in Escherichia coli (rG alpha-subunits). When combined with a 3-fold molar excess of beta gamma-subunit purified from bovine brain and used at high concentrations, all three subtypes of rGi alpha (rGi alpha-1, rGi alpha-2, and rGi alpha-3) and rGo alpha were capable of reconstituting guanine nucleotide-sensitive high-affinity binding of the agonist radioligand (-)-N6-3-[125I] (iodo-4-hydroxyphenylisopropyl) adenosine ([125I]HPIA) to the purified A1-adenosine receptor (Kd approximately 1.2 nM). Titration of the A1-adenosine receptor with increasing amounts of rG alpha revealed a approximately 10-fold higher affinity for rGi alpha-3 compared with rGi alpha-1, rGi alpha-2, and rGo alpha. This selectivity was also observed in the absence of beta gamma. Other alpha-subunits (rGs alpha-s, rGs alpha-L, rGs alpha PT, and rGz alpha) did not promote [125I]HPIA binding to the purified receptor. In N-ethylmaleimide-treated bovine brain membranes, rGi alpha-3 was the only rG alpha-subunit capable of reconstituting high-affinity agonist binding. Similarly, rGi alpha-3 competed potently with rGo alpha for activation by the agonist-liganded A1-adenosine receptor, whereas a approximately 50-fold molar excess of rGo alpha was required to quench the receptor-mediated release of [alpha-32P]GDP from rGi alpha-3. Hence, in spite of the extensive homology between alpha-subunits belonging to the Gi/Go group, the A1-adenosine receptor appears to discriminate between the subtypes. This specificity is likely to govern transmembrane signaling pathways in vivo.

  20. Deletion of presynaptic adenosine A1 receptors impairs the recovery of synaptic transmission after hypoxia.

    Science.gov (United States)

    Arrigoni, E; Crocker, A J; Saper, C B; Greene, R W; Scammell, T E

    2005-01-01

    Adenosine protects neurons during hypoxia by inhibiting excitatory synaptic transmission and preventing NMDA receptor activation. Using an adeno-associated viral (AAV) vector containing Cre recombinase, we have focally deleted adenosine A(1) receptors in specific hippocampal regions of adult mice. Recently, we found that deletion of A(1) receptors in the CA1 area blocks the postsynaptic responses to adenosine in CA1 pyramidal neurons, and deletion of A(1) receptors in CA3 neurons abolishes the presynaptic effects of adenosine on the Schaffer collateral input [J Neurosci 23 (2003) 5762]. In the current study, we used this technique to delete A(1) receptors focally from CA3 neurons to investigate whether presynaptic A(1) receptors protect synaptic transmission from hypoxia. We studied the effects of prolonged (1 h) hypoxia on the evoked field excitatory postsynaptic potentials (fEPSPs) in the CA1 region using in vitro slices. Focal deletion of the presynaptic A(1) receptors on the Schaffer collateral input slowed the depression of the fEPSPs in response to hypoxia and impaired the recovery of the fEPSPs after hypoxia. Delayed responses to hypoxia linearly correlated with impaired recovery. These findings provide direct evidence that the neuroprotective role of adenosine during hypoxia depends on the rapid inhibition of synaptic transmission by the activation of presynaptic A(1) receptors.

  1. Unique interaction pattern for a functionally biased ghrelin receptor agonist

    DEFF Research Database (Denmark)

    Sivertsen, Bjørn Behrens; Lang, Manja; Frimurer, Thomas M.

    2011-01-01

    Based on the conformationally constrained D-Trp-Phe-D-Trp (wFw) core of the prototype inverse agonist [D-Arg(1),D-Phe(5),D-Trp(7,9),Leu(11)]substance P, a series of novel, small, peptide-mimetic agonists for the ghrelin receptor were generated. By using various simple, ring-constrained spacers...... connecting the D-Trp-Phe-D-Trp motif with the important C-terminal carboxyamide group, 40 nm agonism potency was obtained and also in one case (wFw-Isn-NH(2), where Isn is isonipecotic acid) ~80% efficacy. However, in contrast to all previously reported ghrelin receptor agonists, the piperidine-constrained w......Fw-Isn-NH(2) was found to be a functionally biased agonist. Thus, wFw-Isn-NH(2) mediated potent and efficacious signaling through the Ga(q) and ERK1/2 signaling pathways, but in contrast to all previous ghrelin receptor agonists it did not signal through the serum response element, conceivably the Ga(12...

  2. An adenosine A(2A) agonist injected in the nucleus of the solitary tract prolongs the laryngeal chemoreflex by a GABAergic mechanism in decerebrate piglets.

    Science.gov (United States)

    Duy, Philip M; Xia, Luxi; Bartlett, Donald; Leiter, J C

    2010-07-01

    Hyperthermic prolongation of the laryngeal chemoreflex (LCR) in decerebrate piglets is prevented or reversed by GABA(A) receptor antagonists and adenosine A(2A) (Ad-A(2A)) receptor antagonists administered in the nucleus of the solitary tract (NTS). Therefore, we tested the hypothesis that enhanced GABA(A) activity and administration of the Ad-A(2A) agonist, CGS-21680, would prolong the LCR in normothermic conditions. We studied 46 decerebrate piglets ranging from 3 to 8 postnatal days of age. Focal injection into the NTS of 100 nl of 0.5 m nipecotic acid, a GABA reuptake inhibitor, significantly (P < 0.05) prolonged the LCR in normothermic conditions in 10 of 11 animals tested. Injecting 100 nl of 5-12.5 microm CGS-21680 unilaterally or bilaterally into the NTS also prolonged the LCR in normothermic conditions (n = 15), but the effect was smaller than that of unilateral injection of nipecotic acid. Systemic administration of the GABA(A) receptor antagonist, bicuculline, prevented the CGS-21680-dependent prolongation of the LCR in normothermic animals (n = 11). We conclude that thermal prolongation of the LCR depends on a thermally sensitive process or set of neurons in the NTS, which, when activated by elevated brain temperature, enhances adenosinergic and GABAergic function in the region of the NTS. These results emphasize the importance of a thermally sensitive integrative site in the dorsal medulla that, along with sites in the ventral medulla, determine the response to laryngeal chemoreflex stimulation.

  3. Gingerols: a novel class of vanilloid receptor (VR1) agonists

    Science.gov (United States)

    Dedov, Vadim N; Tran, Van H; Duke, Colin C; Connor, Mark; Christie, MacDonald J; Mandadi, Sravan; Roufogalis, Basil D

    2002-01-01

    Gingerols, the pungent constituents of ginger, were synthesized and assessed as agonists of the capsaicin-activated VR1 (vanilloid) receptor. [6]-Gingerol and [8]-gingerol evoked capsaicin-like intracellular Ca2+ transients and ion currents in cultured DRG neurones. These effects of gingerols were blocked by capsazepine, the VR1 receptor antagonist. The potency of gingerols increased with increasing size of the side chain and with the overall hydrophobicity in the series. We conclude that gingerols represent a novel class of naturally occurring VR1 receptor agonists that may contribute to the medicinal properties of ginger, which have been known for centuries. The gingerol structure may be used as a template for the development of drugs acting as moderately potent activators of the VR1 receptor. PMID:12411409

  4. Melatonin receptor agonists: new options for insomnia and depression treatment.

    Science.gov (United States)

    Spadoni, Gilberto; Bedini, Annalida; Rivara, Silvia; Mor, Marco

    2011-12-01

    The circadian nature of melatonin (MLT) secretion, coupled with the localization of MLT receptors to the suprachiasmatic nucleus, has led to numerous studies of the role of MLT in modulation of the sleep-wake cycle and circadian rhythms in humans. Although much more needs to be understood about the various functions exerted by MLT and its mechanisms of action, three therapeutic agents (ramelteon, prolonged-release MLT, and agomelatine) are already in use, and MLT receptor agonists are now appearing as new promising treatment options for sleep and circadian-rhythm related disorders. In this review, emphasis has been placed on medicinal chemistry strategies leading to MLT receptor agonists, and on the evidence supporting therapeutic efficacy of compounds undergoing clinical evaluation. A wide range of clinical trials demonstrated that ramelteon, prolonged-release MLT and tasimelteon have sleep-promoting effects, providing an important treatment option for insomnia and transient insomnia, even if the improvements of sleep maintenance appear moderate. Well-documented effects of agomelatine suggest that this MLT agonist offers an attractive alternative for the treatment of depression, combining efficacy with a favorable side effect profile. Despite a large number of high affinity nonselective MLT receptor agonists, only limited data on MT₁ or MT₂ subtype-selective compounds are available up to now. Administration of the MT₂-selective agonist IIK7 to rats has proved to decrease NREM sleep onset latency, suggesting that MT₂ receptor subtype is involved in the acute sleep-promoting action of MLT; rigorous clinical studies are needed to demonstrate this hypothesis. Further clinical candidates based on selective activation of MT₁ or MT₂ receptors are expected in coming years. © 2010 Blackwell Publishing Ltd.

  5. Principles of agonist recognition in Cys-loop receptors

    DEFF Research Database (Denmark)

    Lynagh, Timothy Peter; Pless, Stephan Alexander

    2014-01-01

    diverse as glycine and serotonin has been subject to intense research over the last three decades. This review outlines the functional diversity and current structural understanding of agonist-binding sites, including those of invertebrate Cys-loop receptors. Together, this provides a framework...

  6. Pyrazolodiazepine derivatives with agonist activity toward Drosophila RYamide receptor.

    Science.gov (United States)

    Yoon, Yeu Kyung; Kim, Jung Ha; Kim, Jeong-Hyun; Kwon, Jae-Young; Kim, Yong-Chul; Kim, Young-Joon; Park, Zee-Yong

    2016-10-15

    The neuropeptide Y (NPY)-like signaling is conserved broadly in many animal species, and implicated in diverse biological functions, particularly those associated with feeding and metabolism. In Drosophila, three G protein coupled receptors (GPCRs) are closely related to the vertebrate NPY receptors: RYamide receptor (RYa-R) CG5811, neuropeptide F receptor (NPFR) CG1147 and short neuropeptide F receptor (sNPF-R) CG7395. Here, we screened 442 compounds of the pyrazolodiazepine analogs library, and identified four synthetic small compounds that activate the RYa-R, but not other two receptors. Their maximum activity is about 40% of the endogenous ligand, Drosophila RYamide-1, indicating they are partial agonists. Structural comparisons of these agonists identified an active core structure, characterized by phenylalanine and lysine fused pyrazolodiazepine skeletons, which can be utilized as a lead structure for further development of more potent drugs active on mammalian NPYRs. Identification of small compound agonists selective on RYa-R of the genetically amenable insect model will facilitate future efforts to understand biological functions of RYa-R, a GPCR conserved in many species. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. A1 adenosine receptor inhibition of cyclic AMP formation and radioligand binding in the guinea-pig cerebral cortex.

    Science.gov (United States)

    Alexander, S P; Curtis, A R; Kendall, D A; Hill, S J

    1994-12-01

    1. A1 adenosine receptors were investigated by radioligand binding and functional studies in slices and particulate preparations from guinea-pig cerebral cortex. 2. Binding of the adenosine receptor antagonist radioligand, 8-cyclopentyl-[3H]-1,3-dipropylxanthine (DPCPX) to guinea-pig cerebral cortical membranes exhibited high density (1410 +/- 241 fmol mg-1 protein) and high affinity (Kd 3.8 +/- 0.3 nM). 3. [3H]-DPCPX binding to guinea-pig cerebral cortical membranes was displaced in a monophasic manner by adenosine receptor antagonists with the rank order of affinity (Ki values, nM): DPCPX (6) < xanthine amine congener (XAC, 153) < PD 115,199 (308). 4. Agonist displacement of [3H]-DPCPX binding was biphasic and exhibited the following rank order at the low affinity site (Ki values): 2-chloro-N6-cyclopentyl-adenosine (CCPA, 513 nM) = N6-R-phenylisopropyladenosine (R-PIA, 526 nM) = N6-cyclopentyladenosine (CPA, 532 nM) < 2-chloroadenosine (2CA, 3.2 microM) = 5'-N-ethylcarboxamidoadenosine (NECA, 4.6 microM) < N6-S-phenylisopropyladenosine (S-PIA, 19.9 microM). 5. In cerebral cortical slices, [3H]-DPCPX binding was displaced by antagonists and agonists in an apparently monophasic manner with the rank order of affinity (Ki values, nM): DPCPX (14) < XAC (45) < R-PIA (266) < PD 115,199 (666) < S-PIA (21000). 6. Cyclic AMP accumulation stimulated by 30 microM forskolin in guinea-pig cerebral cortical slices was inhibited by R-PIA, CCPA and CPA up to 1 microM in a concentration-dependent fashion with IC50 values of 14, 18, and 22 nM, respectively. All three analogues inhibited the forskolin response to a similar extent (82-93% inhibition). NECA, S-PTA and 2CA failed to inhibit the forskolin response, but rather enhanced the accumulation of cyclic AMP at concentrations of 100 nM or greater, presumably through activation of A2b adenosine receptors coupled to stimulation of cyclic AMP accumulation in guinea-pig cerebral cortical slices.7. The inhibition of forskolin

  8. Computational study of the molecular mechanisms of caffeine action: Caffeine complexes with adenosine receptors

    Science.gov (United States)

    Poltev, V. I.; Rodríguez, E.; Grokhlina, T. I.; Deriabina, A.; Gonzalez, E.

    To understand the molecular basis of the principal biological action of the caffeine (CAF), the molecular mechanics calculations of possible complexes between CAF and the fragments of human A1 adenosine receptor were performed. The fragments were selected after considerations of the CAF molecular structure and its possible interactions, as well as after an analysis of the extensive bibliography on the structure, biological role, site-directed mutagenesis, and the modeling of the adenosine receptors. The minimum energy configurations of these complexes were obtained using two different computer programs with different force fields. The most favorable configurations correspond to the formation of two hydrogen bonds between the CAF molecule and hydrophilic amino acid residues of the fragments of transmembrane domains of the receptor. These configurations are supposed to contribute to CAF blocking of the adenosine receptors. They will be used later for the construction of model CAF complexes with two transmembrane domains simultaneously.

  9. Complex formation and functional interaction between adenosine A1 receptor and type-1 metabotropic glutamate receptor

    Directory of Open Access Journals (Sweden)

    Yuji Kamikubo

    2015-07-01

    Full Text Available The adenosine A1 receptor (A1R is a G protein-coupled receptor (GPCR for adenosine, a ubiquitous neuromodulator, and thus regulates neuronal excitability, as well as arousal and sensitivity to pain. In addition, we have previously described a new mode of action for A1R: in cerebellar Purkinje cells, its activation attenuates neuronal responses to glutamate, as mediated by the type-1 metabotropic glutamate receptor (mGluR1. mGluR1 is also a GPCR, and elicits such responses as long-term depression of the postsynaptic response to glutamate, a cellular basis for cerebellar motor learning. Here, we explore in greater detail the interaction between A1R and mGluR1 using non-neuronal cells. Co-immunoprecipitation and Förster resonance energy transfer (FRET analysis reveal that A1R and mGluR1 form a complex. Furthermore, we found that mGluR1 activation inhibits A1R signaling, as measured by changes in intracellular cAMP. These findings demonstrate that A1R and mGluR1 have the intrinsic ability to form a heteromeric complex and mutually modulate signaling. This interaction may represent a new form of intriguing GPCR-mediated cellular responses.

  10. REDUCTION OF ADENOSINE-A1-RECEPTORS IN THE PERFORANT PATHWAY TERMINAL ZONE IN ALZHEIMER HIPPOCAMPUS

    NARCIS (Netherlands)

    JAARSMA, D; SEBENS, JB; KORF, J

    1991-01-01

    The cells of origin of the perforant pathway are destroyed in Alzheimer's disease (AD). In rat the adenosine A1-receptors are specifically localized on the perforant path terminals in the molecular layer of the dentate gyrus. In the present study the density of A1-receptors in the hippocampus of

  11. Targeting Adenosine A2A Receptors in Parkinson’s Disease

    Science.gov (United States)

    2006-11-01

    1Facultad de Ciencias Químicas BUAP and 2Centro de Estudios Regionales UAY. *(ilhlimon@siu.buap.mx). Background: The A2A receptors antagonists have been...Funded by: FCQ- BUAP . Targeting Adenosine A2A Receptors in Parkinson’s Disease and Other CNS Disorders May 17 - 19, 2006 Boston

  12. Modulation of Adenosine Receptors by [60]Fullerene Hydrosoluble Derivative in SK-N-MC Cells

    Science.gov (United States)

    2011-01-01

    The most known fullerenes are spherical carbon compounds composed of 60 carbon atoms. C60 fullerenes have shown biochemical and biomedical properties in the last years such as as blockade of apoptosis and neuroprotection. The nucleoside adenosine has a neuroprotective role mainly due to inhibition of glutamate release, which is a neurotransmitter related to excitotoxicity and cell death. In the present work, we have determined the presence of adenosine receptors in SK-N-MC cells, a neuroepithelioma human cell line, and analyzed the effect of fullerenes in these receptors by using radioligand binding, immunoblotting, and quantitative real time PCR assays. Results demonstrated that SK-N-MC cells endogenously express adenosine receptors. Fullerene exposure of these cells did not affect cell viability measured by MTT reduction assay. However, adenosine A1 and A2A receptors were both increased in SK-N-MC cells after treatment. These results suggest for the first time the modulation of adenosine receptors after C60 fullerenes exposure. PMID:22816023

  13. G protein-coupled receptor inactivation by an allosteric inverse-agonist antibody

    Science.gov (United States)

    Hino, Tomoya; Arakawa, Takatoshi; Iwanari, Hiroko; Yurugi-Kobayashi, Takami; Ikeda-Suno, Chiyo; Nakada-Nakura, Yoshiko; Kusano-Arai, Osamu; Weyand, Simone; Shimamura, Tatsuro; Nomura, Norimichi; Cameron, Alexander D.; Kobayashi, Takuya; Hamakubo, Takao; Iwata, So; Murata, Takeshi

    2011-01-01

    G protein-coupled receptors (GPCRs) are the largest class of cell-surface receptors, and these membrane proteins exist in equilibrium between inactive and active states.1-13 Conformational changes induced by extracellular ligands binding to GPCRs result in a cellular response through the activation of G-proteins. The A2A adenosine receptor (A2AAR) is responsible for regulating blood flow to the cardiac muscle and is important in the regulation of glutamate and dopamine release in the brain.14 In this study, we have successfully raised a mouse monoclonal antibody against human A2AAR that prevents agonist but not antagonist binding to the extracellular ligand-binding pocket. The structure of the A2AAR-antibody Fab fragment (Fab2838) complex reveals that the fragment, unexpectedly, recognises the intracellular surface of A2AAR and that its complementarity determining region, CDR-H3, penetrates into the receptor. CDR-H3 is located in a similar position to the G-protein C-terminal fragment in the active opsin structure1 and to the CDR-3 of the nanobody in the active β2 adrenergic receptor structure2 but locks the A2AAR in an inactive conformation. These results shed light on a novel strategy to modulate GPCR activity. PMID:22286059

  14. Structure of the agonist-bound neurotensin receptor.

    Science.gov (United States)

    White, Jim F; Noinaj, Nicholas; Shibata, Yoko; Love, James; Kloss, Brian; Xu, Feng; Gvozdenovic-Jeremic, Jelena; Shah, Priyanka; Shiloach, Joseph; Tate, Christopher G; Grisshammer, Reinhard

    2012-10-25

    Neurotensin (NTS) is a 13-amino-acid peptide that functions as both a neurotransmitter and a hormone through the activation of the neurotensin receptor NTSR1, a G-protein-coupled receptor (GPCR). In the brain, NTS modulates the activity of dopaminergic systems, opioid-independent analgesia, and the inhibition of food intake; in the gut, NTS regulates a range of digestive processes. Here we present the structure at 2.8 Å resolution of Rattus norvegicus NTSR1 in an active-like state, bound to NTS(8-13), the carboxy-terminal portion of NTS responsible for agonist-induced activation of the receptor. The peptide agonist binds to NTSR1 in an extended conformation nearly perpendicular to the membrane plane, with the C terminus oriented towards the receptor core. Our findings provide, to our knowledge, the first insight into the binding mode of a peptide agonist to a GPCR and may support the development of non-peptide ligands that could be useful in the treatment of neurological disorders, cancer and obesity.

  15. Adenosine Receptor Stimulation by Polydeoxyribonucleotide Improves Tissue Repair and Symptomology in Experimental Colitis.

    Science.gov (United States)

    Pallio, Giovanni; Bitto, Alessandra; Pizzino, Gabriele; Galfo, Federica; Irrera, Natasha; Squadrito, Francesco; Squadrito, Giovanni; Pallio, Socrate; Anastasi, Giuseppe P; Cutroneo, Giuseppina; Macrì, Antonio; Altavilla, Domenica

    2016-01-01

    Activation of the adenosine receptor pathway has been demonstrated to be effective in improving tissue remodeling and blunting the inflammatory response. Active colitis is characterized by an intense inflammatory reaction resulting in extensive tissue damage. Symptomatic improvement requires both control of the inflammatory process and repair and remodeling of damaged tissues. We investigated the ability of an A2A receptor agonist, polydeoxyribonucleotide (PDRN), to restore tissue structural integrity in two experimental colitis models using male Sprague-Dawley rats. In the first model, colitis was induced with a single intra-colonic instillation of dinitrobenzenesulfonic acid (DNBS), 25 mg diluted in 0.8 ml 50% ethanol. After 6 h, animals were randomized to receive either PDRN (8 mg/kg/i.p.), or PDRN + the A2A antagonist [3,7-dimethyl-1-propargylxanthine (DMPX); 10 mg/kg/i.p.], or vehicle (0.8 ml saline solution) daily. In the second model, dextran sulfate sodium (DSS) was dissolved in drinking water at a concentration of 8%. Control animals received standard drinking water. After 24 h animals were randomized to receive PDRN or PDRN+DMPX as described above. Rats were sacrificed 7 days after receiving DNBS or 5 days after DSS. In both experimental models of colitis, PDRN ameliorated the clinical symptoms and weight loss associated with disease as well as promoted the histological repair of damaged tissues. Moreover, PDRN reduced expression of inflammatory cytokines, myeloperoxidase activity, and malondialdehyde. All these effects were abolished by the concomitant administration of the A2A antagonist DMPX. Our study suggests that PDRN may represent a promising treatment for improving tissue repair during inflammatory bowel diseases.

  16. ADENOSINE RECEPTOR STIMULATION BY POLYDEOXYRIBONUCLEOTIDE IMPROVES TISSUE REPAIR AND SYMPTOMOLOGY IN EXPERIMENTAL COLITIS.

    Directory of Open Access Journals (Sweden)

    Giovanni Pallio

    2016-08-01

    Full Text Available Activation of the adenosine receptor pathway has been demonstrated to be effective in improving tissue remodelling and blunting the inflammatory response. Active colitis is characterized by an intense inflammatory reaction resulting in extensive tissue damage. Symptomatic improvement requires both control of the inflammatory process and repair and remodelling of damaged tissues. We investigated the ability of an A2A receptor agonist, polydeoxyribonucleotide (PDRN, to restore tissue structural integrity in two experimental colitis models using male Sprague-Dawley rats. In the first model, colitis was induced with a single intra-colonic instillation of dinitro-benzene-sulfonic acid (DNBS, 25mg diluted in 0.8ml 50% ethanol. After 6 hrs, animals were randomized to receive either PDRN (8mg/kg/i.p., or PDRN + the A2A antagonist (DMPX; 10mg/kg/i.p., or vehicle (0.8 ml saline solution daily. In the second model, dextran sodium sulphate (DSS was dissolved in drinking water at a concentration of 8%. Control animals received standard drinking water. After 24 hrs animals were randomized to receive PDRN or PDRN+DMPX as described above. Rats were sacrificed 7 days after receiving DNBS or 5 days after DSS. In both experimental models of colitis, PDRN ameliorated the clinical symptoms and weight loss associated with disease as well as promoted the histological repair of damaged tissues. Moreover, PDRN reduced expression of inflammatory cytokines, myeloperoxydase activity, and malondialdheyde. All these effects were abolished by the concomitant administration of the A2a antagonist DMPX. Our study suggests that PDRN may represent a promising treatment for improving tissue repair during inflammatory bowel diseases.

  17. IL-4 amplifies the pro-inflammatory effect of adenosine in human mast cells by changing expression levels of adenosine receptors.

    Directory of Open Access Journals (Sweden)

    Xiaoyang Hua

    Full Text Available Adenosine inhalation produces immediate bronchoconstriction in asthmatics but not in normal subjects. The bronchospastic effect of adenosine is largely mediated through adenosine-induced mast cell activation, the mechanism of which is poorly understood due to limitations in culturing human primary mast cells. Here, we show that human umbilical cord blood -derived mast cells incubated with the Th2 cytokine IL-4 develop increased sensitivity to adenosine. Potentiation of anti-IgE- induced and calcium ionophore/PMA-induced degranulation was augmented in mast cells cultured with IL-4, and this effect was reduced or abolished by pre-treatment with A(2BsiRNA and selective A(2B receptor antagonists, respectively. IL-4 incubation resulted in the increased expression of A(2B and reduced expression of A(2A adenosine receptors on human mast cells. These results suggest that Th2 cytokines in the asthmatic lung may alter adenosine receptor expression on airway mast cells to promote increased responsiveness to adenosine.

  18. IL-4 Amplifies the Pro-Inflammatory Effect of Adenosine in Human Mast Cells by Changing Expression Levels of Adenosine Receptors

    Science.gov (United States)

    Hua, Xiaoyang; Chason, Kelly D.; Patel, Janki Y.; Naselsky, Warren C.; Tilley, Stephen L.

    2011-01-01

    Adenosine inhalation produces immediate bronchoconstriction in asthmatics but not in normal subjects. The bronchospastic effect of adenosine is largely mediated through adenosine-induced mast cell activation, the mechanism of which is poorly understood due to limitations in culturing human primary mast cells. Here, we show that human umbilical cord blood -derived mast cells incubated with the Th2 cytokine IL-4 develop increased sensitivity to adenosine. Potentiation of anti-IgE- induced and calcium ionophore/PMA-induced degranulation was augmented in mast cells cultured with IL-4, and this effect was reduced or abolished by pre-treatment with A2BsiRNA and selective A2B receptor antagonists, respectively. IL-4 incubation resulted in the increased expression of A2B and reduced expression of A2A adenosine receptors on human mast cells. These results suggest that Th2 cytokines in the asthmatic lung may alter adenosine receptor expression on airway mast cells to promote increased responsiveness to adenosine. PMID:21966389

  19. GIRK channel activation via adenosine or muscarinic receptors has similar effects on rat atrial electrophysiology

    DEFF Research Database (Denmark)

    Wang, Xiaodong; Liang, Bo; Skibsbye, Lasse

    2013-01-01

    G protein-coupled inwardly rectifying K+ channels (GIRK) are important in the regulation of heart rate and atrial electrophysiology. GIRK channels are activated by G protein-coupled receptors, including muscarinic M2 receptors and adenosine A1 receptors. The aim of this study was to characterize...... and compare the electrophysiological effects of acetylcholine (ACh) and adenosine on GIRK channels in rat atria. Action potential duration at 90% repolarization (APD90), effective refractory period (ERP), and resting membrane potential (RMP) were investigated in isolated rat atria by intracellular recordings....... Both the adenosine analog N6-cyclopentyladenosine (CPA) and ACh profoundly shortened APD90 and ERP and hyperpolarized the RMP. No additive or synergistic effect of CPA and ACh coapplication was observed. To antagonize GIRK channel activation, the specific inhibitor rTertiapin Q (TTQ) was applied...

  20. Induction of TRPV1 desensitization by a biased receptor agonist.

    Science.gov (United States)

    Wang, Elaine E; Li, Hui; Wang, Shu; Chuang, Alexander Y; Chuang, Huai-hu

    2011-01-01

    Selective suppression of hyperactive sensory neurons is an attractive strategy for managing pathological pain. Blocking Na(+) channels to eliminate action potentials and desensitizing transduction channels can both reduce sensory neuron excitability. The novel synthetic vanilloid ligand cap-ET preserves agonist activation of intracellular Ca(2+) signals and large organic cation transport but loses effective electric current induction. Cap-ET can therefore be used to deliver the membrane impermeable Na(+) channel blocker QX-314 to substantially inhibit voltage-activated Na(+) currents. We explored, besides facilitating entry of organic cationic therapeutics, whether cap-ET can also produce receptor desensitization similar to the natural agonist capsaicin. Using the YO-PRO-1 based fluorescent dye uptake assay, we found that cap-ET effectively triggered Ca(2+) dependent desensitization of TRPV1 when the receptor was pre-sensitized with the surrogate oxidative chemical phenylarsine oxide (PAO), suggesting an alternative use of permanently charged cationic capsaicinoids in differential neuronal silencing.

  1. Bradykinin and adenosine receptors mediate desflurane induced postconditioning in human myocardium: role of reactive oxygen species

    Directory of Open Access Journals (Sweden)

    Gérard Jean-Louis

    2010-07-01

    Full Text Available Abstract Background Desflurane during early reperfusion has been shown to postcondition human myocardium, in vitro. We investigated the role of adenosine and bradykinin receptors, and generation of radical oxygen species in desflurane-induced postconditioning in human myocardium. Methods We recorded isometric contraction of human right atrial trabeculae hanged in an oxygenated Tyrode's solution (34 degrees Celsius, stimulation frequency 1 Hz. After a 30-min hypoxic period, desflurane 6% was administered during the first 5 min of reoxygenation. Desflurane was administered alone or with pretreatment of N-mercaptopropionylglycine, a reactive oxygen species scavenger, 8-(p-Sulfophenyltheophylline, an adenosine receptor antagonist, HOE140, a selective B2 bradykinin receptor antagonist. In separate groups, adenosine and bradykinin were administered during the first minutes of reoxygenation alone or in presence of N-mercaptopropionylglycine. The force of contraction of trabeculae was recorded continuously. Developed force at the end of a 60-min reoxygenation period was compared (mean ± standard deviation between the groups by a variance analysis and post hoc test. Results Desflurane 6% (84 ± 6% of baseline enhanced the recovery of force after 60-min of reoxygenation as compared to control group (51 ± 8% of baseline, P N-mercaptopropionylglycine (54 ± 3% of baseline, 8-(p-Sulfophenyltheophylline (62 ± 9% of baseline, HOE140 (58 ± 6% of baseline abolished desflurane-induced postconditioning. Adenosine (80 ± 9% of baseline and bradykinin (83 ± 4% of baseline induced postconditioning (P vs control, N-mercaptopropionylglycine abolished the beneficial effects of adenosine and bradykinin (54 ± 8 and 58 ± 5% of baseline, respectively. Conclusions In vitro, desflurane-induced postconditioning depends on reactive oxygen species production, activation of adenosine and bradykinin B2 receptors. And, the cardioprotective effect of adenosine and bradykinin

  2. Improving the developability profile of pyrrolidine progesterone receptor partial agonists

    Energy Technology Data Exchange (ETDEWEB)

    Kallander, Lara S.; Washburn, David G.; Hoang, Tram H.; Frazee, James S.; Stoy, Patrick; Johnson, Latisha; Lu, Qing; Hammond, Marlys; Barton, Linda S.; Patterson, Jaclyn R.; Azzarano, Leonard M.; Nagilla, Rakesh; Madauss, Kevin P.; Williams, Shawn P.; Stewart, Eugene L.; Duraiswami, Chaya; Grygielko, Eugene T.; Xu, Xiaoping; Laping, Nicholas J.; Bray, Jeffrey D.; Thompson, Scott K. (GSKPA)

    2010-09-17

    The previously reported pyrrolidine class of progesterone receptor partial agonists demonstrated excellent potency but suffered from serious liabilities including hERG blockade and high volume of distribution in the rat. The basic pyrrolidine amine was intentionally converted to a sulfonamide, carbamate, or amide to address these liabilities. The evaluation of the degree of partial agonism for these non-basic pyrrolidine derivatives and demonstration of their efficacy in an in vivo model of endometriosis is disclosed herein.

  3. Receptor antagonist and selective agonist derivatives of mouse interleukin-2.

    OpenAIRE

    Zurawski, S M; Zurawski, G

    1992-01-01

    Mouse interleukin-2 (mIL-2) proteins with substitutions at two residues (D34 and Q141) that interact specifically with different signalling subunits (respectively, beta and gamma) of the IL-2 receptor (IL-2R) were examined using several in vitro cellular assays. Proteins with specific substitutions at both residues were partial agonists and their maximal responses varied widely in different IL-2-responsive cell types. Two of these cell types had comparable numbers of IL-2R and similar affinit...

  4. A2BR adenosine receptor modulates sweet taste in circumvallate taste buds.

    Directory of Open Access Journals (Sweden)

    Shinji Kataoka

    Full Text Available In response to taste stimulation, taste buds release ATP, which activates ionotropic ATP receptors (P2X2/P2X3 on taste nerves as well as metabotropic (P2Y purinergic receptors on taste bud cells. The action of the extracellular ATP is terminated by ectonucleotidases, ultimately generating adenosine, which itself can activate one or more G-protein coupled adenosine receptors: A1, A2A, A2B, and A3. Here we investigated the expression of adenosine receptors in mouse taste buds at both the nucleotide and protein expression levels. Of the adenosine receptors, only A2B receptor (A2BR is expressed specifically in taste epithelia. Further, A2BR is expressed abundantly only in a subset of taste bud cells of posterior (circumvallate, foliate, but not anterior (fungiform, palate taste fields in mice. Analysis of double-labeled tissue indicates that A2BR occurs on Type II taste bud cells that also express Gα14, which is present only in sweet-sensitive taste cells of the foliate and circumvallate papillae. Glossopharyngeal nerve recordings from A2BR knockout mice show significantly reduced responses to both sucrose and synthetic sweeteners, but normal responses to tastants representing other qualities. Thus, our study identified a novel regulator of sweet taste, the A2BR, which functions to potentiate sweet responses in posterior lingual taste fields.

  5. A2BR Adenosine Receptor Modulates Sweet Taste in Circumvallate Taste Buds

    Science.gov (United States)

    Yang, Dan; Shultz, Nicole; Vandenbeuch, Aurelie; Ravid, Katya; Kinnamon, Sue C.; Finger, Thomas E.

    2012-01-01

    In response to taste stimulation, taste buds release ATP, which activates ionotropic ATP receptors (P2X2/P2X3) on taste nerves as well as metabotropic (P2Y) purinergic receptors on taste bud cells. The action of the extracellular ATP is terminated by ectonucleotidases, ultimately generating adenosine, which itself can activate one or more G-protein coupled adenosine receptors: A1, A2A, A2B, and A3. Here we investigated the expression of adenosine receptors in mouse taste buds at both the nucleotide and protein expression levels. Of the adenosine receptors, only A2B receptor (A2BR) is expressed specifically in taste epithelia. Further, A2BR is expressed abundantly only in a subset of taste bud cells of posterior (circumvallate, foliate), but not anterior (fungiform, palate) taste fields in mice. Analysis of double-labeled tissue indicates that A2BR occurs on Type II taste bud cells that also express Gα14, which is present only in sweet-sensitive taste cells of the foliate and circumvallate papillae. Glossopharyngeal nerve recordings from A2BR knockout mice show significantly reduced responses to both sucrose and synthetic sweeteners, but normal responses to tastants representing other qualities. Thus, our study identified a novel regulator of sweet taste, the A2BR, which functions to potentiate sweet responses in posterior lingual taste fields. PMID:22253866

  6. Insulin-increased L-arginine transport requires A(2A adenosine receptors activation in human umbilical vein endothelium.

    Directory of Open Access Journals (Sweden)

    Enrique Guzmán-Gutiérrez

    Full Text Available Adenosine causes vasodilation of human placenta vasculature by increasing the transport of arginine via cationic amino acid transporters 1 (hCAT-1. This process involves the activation of A(2A adenosine receptors (A(2AAR in human umbilical vein endothelial cells (HUVECs. Insulin increases hCAT-1 activity and expression in HUVECs, and A(2AAR stimulation increases insulin sensitivity in subjects with insulin resistance. However, whether A(2AAR plays a role in insulin-mediated increase in L-arginine transport in HUVECs is unknown. To determine this, we first assayed the kinetics of saturable L-arginine transport (1 minute, 37°C in the absence or presence of nitrobenzylthioinosine (NBTI, 10 µmol/L, adenosine transport inhibitor and/or adenosine receptors agonist/antagonists. We also determined hCAT-1 protein and mRNA expression levels (Western blots and quantitative PCR, and SLC7A1 (for hCAT-1 reporter promoter activity. Insulin and NBTI increased the extracellular adenosine concentration, the maximal velocity for L-arginine transport without altering the apparent K(m for L-arginine transport, hCAT-1 protein and mRNA expression levels, and SLC7A1 transcriptional activity. An A2AAR antagonist ZM-241385 blocked these effects. ZM241385 inhibited SLC7A1 reporter transcriptional activity to the same extent in cells transfected with pGL3-hCAT-1(-1606 or pGL3-hCAT-1(-650 constructs in the presence of NBTI + insulin. However, SLC7A1 reporter activity was increased by NBTI only in cells transfected with pGL3-hCAT-1(-1606, and the ZM-241385 sensitive fraction of the NBTI response was similar in the absence or in the presence of insulin. Thus, insulin modulation of hCAT-1 expression and activity requires functional A(2AAR in HUVECs, a mechanism that may be applicable to diseases associated with fetal insulin resistance, such as gestational diabetes.

  7. Adenosine receptors regulate gap junction coupling of the human cerebral microvascular endothelial cells hCMEC/D3 by Ca2+influx through cyclic nucleotide-gated channels.

    Science.gov (United States)

    Bader, Almke; Bintig, Willem; Begandt, Daniela; Klett, Anne; Siller, Ina G; Gregor, Carola; Schaarschmidt, Frank; Weksler, Babette; Romero, Ignacio; Couraud, Pierre-Olivier; Hell, Stefan W; Ngezahayo, Anaclet

    2017-04-15

    Gap junction channels are essential for the formation and regulation of physiological units in tissues by allowing the lateral cell-to-cell diffusion of ions, metabolites and second messengers. Stimulation of the adenosine receptor subtype A 2B increases the gap junction coupling in the human blood-brain barrier endothelial cell line hCMEC/D3. Although the increased gap junction coupling is cAMP-dependent, neither the protein kinase A nor the exchange protein directly activated by cAMP were involved in this increase. We found that cAMP activates cyclic nucleotide-gated (CNG) channels and thereby induces a Ca 2+ influx, which leads to the increase in gap junction coupling. The report identifies CNG channels as a possible physiological link between adenosine receptors and the regulation of gap junction channels in endothelial cells of the blood-brain barrier. The human cerebral microvascular endothelial cell line hCMEC/D3 was used to characterize the physiological link between adenosine receptors and the gap junction coupling in endothelial cells of the blood-brain barrier. Expressed adenosine receptor subtypes and connexin (Cx) isoforms were identified by RT-PCR. Scrape loading/dye transfer was used to evaluate the impact of the A 2A and A 2B adenosine receptor subtype agonist 2-phenylaminoadenosine (2-PAA) on the gap junction coupling. We found that 2-PAA stimulated cAMP synthesis and enhanced gap junction coupling in a concentration-dependent manner. This enhancement was accompanied by an increase in gap junction plaques formed by Cx43. Inhibition of protein kinase A did not affect the 2-PAA-related enhancement of gap junction coupling. In contrast, the cyclic nucleotide-gated (CNG) channel inhibitor l-cis-diltiazem, as well as the chelation of intracellular Ca 2+ with BAPTA, or the absence of external Ca 2+ , suppressed the 2-PAA-related enhancement of gap junction coupling. Moreover, we observed a 2-PAA-dependent activation of CNG channels by a combination of

  8. Safety of regadenoson, a selective adenosine A2A agonist, in patients with chronic obstructive pulmonary disease: A randomized, double-blind, placebo-controlled trial (RegCOPD trial).

    Science.gov (United States)

    Thomas, Gregory S; Tammelin, Bruce R; Schiffman, George L; Marquez, Rudy; Rice, Deborah L; Milikien, Douglas; Mathur, Vandana

    2008-01-01

    Patients with reactive airways are at risk for adenosine-induced bronchoconstriction, mediated via A(2B) and/or A(3) adenosine receptors. In this randomized, double-blind, placebo-controlled crossover trial, we examined the safety of regadenoson, a selective adenosine A(2A) receptor agonist, in patients with moderate chronic obstructive pulmonary disease (COPD) (n = 38) and patients with severe COPD (n = 11) with a baseline mean forced expiratory volume in 1 second (FEV(1)) of 1.74 +/- 0.50 L and 1.0 +/- 0.35 L, respectively, 37% of whom had dyspnea during activities of daily living. Patients receiving glucocorticoids or oxygen and those with pretreatment wheezing were included. Short-acting bronchodilators were withheld for at least 8 hours before treatment. No differences emerged between regadenoson and placebo on multiple lung function parameters, including repeated FEV(1) and forced vital capacity, respiratory rate, pulmonary examinations, and oxygen saturation. The mean maximum decline in FEV(1) was 0.11 +/- 0.02 L and 0.12 +/- 0.02 L (P = .55) in patients after regadenoson and placebo, respectively, and new-onset wheezing was observed in 6% and 12%, respectively (P = .33). No patient required acute treatment with bronchodilators or oxygen. This pilot study showed the overall safety of regadenoson in 49 compromised outpatients with clinically stable moderate and severe chronic obstructive pulmonary disease.

  9. Activation of Adenosine Receptor A2A Increases HSC Proliferation and Inhibits Death and Senescence by Down-regulation of p53 and Rb

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    Md. Kaimul eAhsan

    2014-04-01

    Full Text Available Background & Aims: During fibrosis hepatic stellate cells (HSC undergo activation, proliferation and senescence but the regulation of these important processes is poorly understood. The adenosine A2A receptor (A2A is known to be present on HSC, and its activation results in liver fibrosis. In this study, we tested if A2A has a role in the regulation of HSC proliferation, apoptosis, senescence, and the relevant molecular mechanism.Methods: The ability of adenosine to regulate p53 and Rb protein levels, proliferation, apoptosis and senescence was tested in the human HSC cell line LX-2 and rat primary HSC.Results: Adenosine receptor activation down-regulates p53 and Rb protein levels, increases BrdU incorporation and increases cell survival in LX-2 cells and in primary rat HSC. These effects of NECA were reproduced by an adenosine A2A receptor specific agonist (CGS21680 and blocked by a specific antagonist (ZM241385. By day twenty-one of culture primary rat HSC entered senescence and expressed -gal which was significantly inhibited by NECA. Furthermore, NECA induced down regulation of p53 and Rb and Rac1, and decreased phosphorylation of p44-42 MAP Kinase in LX-2 cells and primary rat HSC. These effects were reproduced by the cAMP analog 8-Bromo-cAMP, and the adenylyl cyclase activator forskolin, and were blocked by PKA inhibitors.Conclusions: These results demonstrate that A2A receptor regulates a number of HSC fate decisions and induces greater HSC proliferation, reduces apoptosis and senescence by decreasing p53 and Rb through cAMP-PKA/Rac1/p38 MAPK pathway. This provides a mechanism for adenosine induced HSC regulation and liver fibrosis.

  10. An adenosine A2A agonist injected in the nucleus of the solitary tract prolongs the laryngeal chemoreflex by a GABAergic mechanism in decerebrate piglets

    Science.gov (United States)

    Duy, Philip M.; Xia, Luxi; Bartlett, Donald; Leiter, J.C.

    2010-01-01

    Hyperthermic prolongation of the laryngeal chemoreflex (LCR) in decerebrate piglets is prevented or reversed by gamma-aminobutyric acid A (GABAA) receptor antagonists and adenosine A2A (Ad-A2A) receptor antagonists administered in the nucleus of the solitary tract (NTS). Therefore, we tested the hypothesis that enhanced GABAA activity and administration of the Ad-A2A agonist, CGS-21680, would prolong the LCR under normothermic conditions. We studied 46 decerebrate piglets ranging from 3 to 8 post-natal days of age. Focal injection into the NTS of 100 nl of 0.5 M nipecotic acid, a GABA reuptake inhibitor, significantly (P < 0.05) prolonged the LCR under normothermic conditions in 10 of 11 animals tested. Injecting 100 nl of 5–12.5 microM CGS-21680 unilaterally or bilaterally into the NTS also prolonged the LCR under normothermic conditions (n=15), but the effect was smaller than the effect of unilateral injection of nipecotic acid. Systemic administration of the GABAA receptor antagonist, bicuculline, prevented the CGS-21680-dependent prolongation of the LCR in normothermic animals (n = 11). We conclude that thermal prolongation of the LCR depends on a thermally sensitive process or set of neurons in the NTS, which, when activated by elevated brain temperature, enhance adenosinergic and GABAergic function in the region of the NTS. These results emphasize the importance of a thermally sensitive integrative site in the dorsal medulla that, along with sites in the ventral medulla, determine the response to laryngeal chemoreflex stimulation. PMID:20418346

  11. Effects of melanocortin 1 receptor agonists in experimental nephropathies.

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    Annika Lindskog Jonsson

    Full Text Available Nephrotic syndrome, characterized by massive proteinuria, is caused by a large group of diseases including membranous nephropathy (MN and focal segmental glomerulosclerosis (FSGS. Although the underlying mechanisms are beginning to unravel, therapy is unspecific and far from efficient. It has been suggested that adrenocorticotropic hormone (ACTH has beneficial effects in patients with MN and possibly in other nephrotic diseases. We have previously reported that ACTH may act directly on podocytes through the melanocortin 1 receptor (MC1R. In the present study, we evaluate the effect of highly specific MC1R agonists in two different nephrotic disease models. Experimental MN: Passive Heymann nephritis (PHN was induced in rats that were treated for four weeks with MS05, a selective MC1R agonist, or saline. The degree of albuminuria was significantly reduced over time and the effect was sustained one week after treatment withdrawal (p<0.05. Experimental FSGS: Based on a dose-response study, two doses of adriamycin were used for induction of nephropathy in Balb/c mice. Mice were treated with either a synthetic MC1R agonist (BMS-470539, with α-melanocyte stimulating hormone (α-MSH or with saline. There was no beneficial effect of treatment. In summary, MC1R agonists reduce albuminuria and improve morphology in experimentally induced MN whereas they have no effect in experimental FSGS. The results illustrate the differences in these podocytopathies in terms of signaling mechanisms underlying proteinuria, and progression of disease.

  12. Agonist Binding to Chemosensory Receptors: A Systematic Bioinformatics Analysis

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    Fabrizio Fierro

    2017-09-01

    Full Text Available Human G-protein coupled receptors (hGPCRs constitute a large and highly pharmaceutically relevant membrane receptor superfamily. About half of the hGPCRs' family members are chemosensory receptors, involved in bitter taste and olfaction, along with a variety of other physiological processes. Hence these receptors constitute promising targets for pharmaceutical intervention. Molecular modeling has been so far the most important tool to get insights on agonist binding and receptor activation. Here we investigate both aspects by bioinformatics-based predictions across all bitter taste and odorant receptors for which site-directed mutagenesis data are available. First, we observe that state-of-the-art homology modeling combined with previously used docking procedures turned out to reproduce only a limited fraction of ligand/receptor interactions inferred by experiments. This is most probably caused by the low sequence identity with available structural templates, which limits the accuracy of the protein model and in particular of the side-chains' orientations. Methods which transcend the limited sampling of the conformational space of docking may improve the predictions. As an example corroborating this, we review here multi-scale simulations from our lab and show that, for the three complexes studied so far, they significantly enhance the predictive power of the computational approach. Second, our bioinformatics analysis provides support to previous claims that several residues, including those at positions 1.50, 2.50, and 7.52, are involved in receptor activation.

  13. In Vivo PET Imaging of Adenosine 2A Receptors in Neuroinflammatory and Neurodegenerative Disease

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    Anna Vuorimaa

    2017-01-01

    Full Text Available Adenosine receptors are G-protein coupled P1 purinergic receptors that are broadly expressed in the peripheral immune system, vasculature, and the central nervous system (CNS. Within the immune system, adenosine 2A (A2A receptor-mediated signaling exerts a suppressive effect on ongoing inflammation. In healthy CNS, A2A receptors are expressed mainly within the neurons of the basal ganglia. Alterations in A2A receptor function and expression have been noted in movement disorders, and in Parkinson’s disease pharmacological A2A receptor antagonism leads to diminished motor symptoms. Although A2A receptors are expressed only at a low level in the healthy CNS outside striatum, pathological challenge or inflammation has been shown to lead to upregulation of A2A receptors in extrastriatal CNS tissue, and this has been successfully quantitated using in vivo positron emission tomography (PET imaging and A2A receptor-binding radioligands. Several radioligands for PET imaging of A2A receptors have been developed in recent years, and A2A receptor-targeting PET imaging may thus provide a potential additional tool to evaluate various aspects of neuroinflammation in vivo. This review article provides a brief overview of A2A receptors in healthy brain and in a selection of most important neurological diseases and describes the recent advances in A2A receptor-targeting PET imaging studies.

  14. Dopamine receptor agonists modulate voluntary alcohol intake independently of individual levels of alcohol intake in rats

    OpenAIRE

    Spoelder, Marcia; Annemarie M Baars; Rotte, Marthe D.; Vanderschuren, Louk J.M.J.; Lesscher, Heidi M. B.

    2016-01-01

    RATIONALE: Individual susceptibility to alcohol use disorder has been related to functional changes in dopaminergic neurotransmission. OBJECTIVES: The aim of the current work was to assess the effects of selective dopamine D1 and D2 receptor agonists and antagonists on alcohol consumption in rats that differ in individual levels of alcohol intake. METHODS: The effects of the dopamine D1 receptor agonist SKF 82958, the dopamine D1 receptor antagonist SCH 23390, the dopamine D2 receptor agonist...

  15. NCS-1 associates with adenosine A2A receptors and modulates receptor function

    Directory of Open Access Journals (Sweden)

    Gemma eNavarro

    2012-04-01

    Full Text Available Modulation of G protein-coupled receptor (GPCR signalling by local changes in intracellular calcium concentration is an established function of Calmodulin which is known to interact with many GPCRs. Less is known about the functional role of the closely related neuronal EF-hand Ca2+-sensor proteins that frequently associate with calmodulin targets with different functional outcome. In the present study we aimed to investigate if a target of calmodulin – the A2A adenosine receptor, is able to associate with two other neuronal calcium binding proteins, namely NCS-1 and caldendrin. Using bioluminescence resonance energy transfer and co-immunoprecipitation experiments we show the existence of A2A - NCS-1 complexes in living cells whereas caldendrin did not associate with A2A receptors under the conditions tested. Interestingly, NCS-1 binding modulated downstream A2A receptor intracellular signalling in a Ca2+-dependent manner. Taken together this study provides further evidence that neuronal Ca2+-sensor proteins play an important role in modulation of GPCR signalling.

  16. Untangling dopamine-adenosine receptor-receptor assembly in experimental parkinsonism in rats

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    Víctor Fernández-Dueñas

    2015-01-01

    Full Text Available Parkinson’s disease (PD is a dopaminergic-related pathology in which functioning of the basal ganglia is altered. It has been postulated that a direct receptor-receptor interaction – i.e. of dopamine D2 receptor (D2R with adenosine A2A receptor (A2AR (forming D2R-A2AR oligomers – finely regulates this brain area. Accordingly, elucidating whether the pathology prompts changes to these complexes could provide valuable information for the design of new PD therapies. Here, we first resolved a long-standing question concerning whether D2R-A2AR assembly occurs in native tissue: by means of different complementary experimental approaches (i.e. immunoelectron microscopy, proximity ligation assay and TR-FRET, we unambiguously identified native D2R-A2AR oligomers in rat striatum. Subsequently, we determined that, under pathological conditions (i.e. in a rat PD model, D2R-A2AR interaction was impaired. Collectively, these results provide definitive evidence for alteration of native D2R-A2AR oligomers in experimental parkinsonism, thus conferring the rationale for appropriate oligomer-based PD treatments.

  17. Newer GLP-1 receptor agonists and obesity-diabetes.

    Science.gov (United States)

    Brown, Emily; Cuthbertson, Daniel J; Wilding, John P

    2018-02-01

    Obesity is a major risk factor for type 2 diabetes and may complicate type 1 diabetes. In parallel with the global epidemic of obesity, the incidence of type 2 diabetes is increasing exponentially. To reverse these alarming trends, weight loss becomes a major therapeutic priority in prevention and treatment of type 2 diabetes. Given that glucagon-like peptide-1 receptor agonists (GLP-1 RAs) improve glycaemic control and cause weight loss, they are receiving increasing attention for the treatment of diabetes-obesity. This review discusses current and emerging therapeutic options with GLP-1 RAs and considers the next generation of novel peptide co-agonists with the potential for improved therapeutic outcomes in obesity and type 2 diabetes. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Trace Amine-Associated Receptor 1 Agonists as Narcolepsy Therapeutics.

    Science.gov (United States)

    Black, Sarah W; Schwartz, Michael D; Chen, Tsui-Ming; Hoener, Marius C; Kilduff, Thomas S

    2017-11-01

    Narcolepsy, a disorder of rapid eye movement (REM) sleep, is characterized by excessive daytime sleepiness and cataplexy, a loss of muscle tone triggered by emotional stimulation. Current narcolepsy pharmacotherapeutics include controlled substances with abuse potential or drugs with undesirable side effects. As partial agonists at trace amine-associated receptor 1 (TAAR1) promote wakefulness in mice and rats, we evaluated whether TAAR1 agonism had beneficial effects in two mouse models of narcolepsy. In the first experiment, male homozygous B6-Taar1 tm1(NLSLacZ)Blt (Taar1 knockout) and wild-type mice were surgically implanted to record electroencephalogram, electromyogram, locomotor activity, and body temperature, and the efficacy of the TAAR1 agonist, RO5256390, on sleep/wake and physiological parameters was determined. In the second experiment, the effects of the TAAR1 full agonist RO5256390 and partial agonist RO5263397 on sleep/wake, locomotor activity, body temperature, and cataplexy were assessed in two mouse narcolepsy models. RO5256390 profoundly reduced rapid eye movement sleep in wild-type mice; these effects were eliminated in Taar1 knockout mice. The TAAR1 partial agonist RO5263397 also promoted wakefulness and suppressed nonrapid eye movement sleep. Both compounds reduced body temperature in the two narcolepsy models at the highest doses tested. Both TAAR1 compounds also mitigated cataplexy, the pathognomonic symptom of this disorder, in the narcolepsy models. The therapeutic benefit was mediated through a reduction in number of cataplexy episodes and time spent in cataplexy. These results suggest TAAR1 agonism as a new therapeutic pathway for treatment of this orphan disease. The common underlying mechanism may be the suppression of rapid eye movement sleep. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  19. Attenuated renovascular constrictor responses to angiotensin II in adenosine 1 receptor knockout mice

    DEFF Research Database (Denmark)

    Hansen, Pernille B; Hashimoto, Seiji; Briggs, Josie

    2003-01-01

    In the present experiments we examined the renovascular constrictor effects of ANG II in the chronic and complete absence of A1 adenosine receptors (A1AR) using mice with targeted deletion of the A1AR gene. Glomerular filtration rate (GFR) was not different between A1AR +/+ and A1AR -/- mice unde...

  20. Pyrazolo Derivatives as Potent Adenosine Receptor Antagonists: An Overview on the Structure-Activity Relationships

    Directory of Open Access Journals (Sweden)

    Siew Lee Cheong

    2011-01-01

    Full Text Available In the past few decades, medicinal chemistry research towards potent and selective antagonists of human adenosine receptors (namely, A1, A2A, A2B, and A3 has been evolving rapidly. These antagonists are deemed therapeutically beneficial in several pathological conditions including neurological and renal disorders, cancer, inflammation, and glaucoma. Up to this point, many classes of compounds have been successfully synthesized and identified as potent human adenosine receptor antagonists. In this paper, an overview of the structure-activity relationship (SAR profiles of promising nonxanthine pyrazolo derivatives is reported and discussed. We have emphasized the SAR for some representative structures such as pyrazolo-[4,3-e]-1,2,4-triazolo-[1,5-c]pyrimidines; pyrazolo-[3,4-c] or -[4,3-c]quinolines; pyrazolo-[4,3-d]pyrimidinones; pyrazolo-[3,4-d]pyrimidines and pyrazolo-[1,5-a]pyridines. This overview not only clarifies the structural requirements deemed essential for affinity towards individual adenosine receptor subtypes, but it also sheds light on the rational design and optimization of existing structural templates to allow us to conceive new, more potent adenosine receptor antagonists.

  1. Angiotensin receptor agonistic autoantibodies and hypertension: preeclampsia and beyond.

    Science.gov (United States)

    Xia, Yang; Kellems, Rodney E

    2013-06-21

    Hypertensive disorders are life-threatening diseases with high morbidity and mortality, affecting billions of individuals worldwide. A multitude of underlying conditions may contribute to hypertension, thus the need for a plethora of treatment options to identify the approach that best meets the needs of individual patients. A growing body of evidence indicates that (1) autoantibodies that bind to and activate the major angiotensin II type I (AT₁) receptor exist in the circulation of patients with hypertensive disorders, (2) these autoantibodies contribute to disease pathophysiology, (3) antibody titers correlate to the severity of the disease, and (4) efforts to block or remove these pathogenic autoantibodies have therapeutic potential. These autoantibodies, termed AT₁ agonistic autoantibodies have been extensively characterized in preeclampsia, a life-threatening hypertensive condition of pregnancy. As reviewed here, these autoantibodies cause symptoms of preeclampsia when injected into pregnant mice. Somewhat surprisingly, these auto antibodies also appear in 3 animal models of preeclampsia. However, the occurrence of AT₁ agonistic autoantibodies is not restricted to pregnancy. These autoantibodies are prevalent among kidney transplant recipients who develop severe transplant rejection and malignant hypertension during the first week after transplantation. AT₁ agonistic autoantibodies are also highly abundant among a group of patients with essential hypertension that are refractory to standard therapy. More recently these autoantibodies have been seen in patients with the autoimmune disease, systemic sclerosis. These 3 examples extend the clinical impact of AT₁ agonistic autoantibodies beyond pregnancy. Research reviewed here raises the intriguing possibility that preeclampsia and other hypertensive conditions are autoimmune diseases characterized by the presence of pathogenic autoantibodies that activate the major angiotensin receptor, AT₁. These

  2. Effects of TRA-418, a novel TP-receptor antagonist, and IP-receptor agonist, on human platelet activation and aggregation.

    Science.gov (United States)

    Miyamoto, Mitsuko; Yamada, Naohiro; Ikezawa, Shiho; Ohno, Michihiro; Otake, Atsushi; Umemura, Kazuo; Matsushita, Teruo

    2003-11-01

    [4-[2-(1,1-Diphenylethylsulfanyl)-ethyl]-3,4-dihydro-2H-benzo[1,4]oxazin-8-yloxy]-acetic acid N-Methyl-d-glucamine salt (TRA-418) has both thromboxane A2 (TP)-receptor antagonist and prostacyclin (IP)-receptor agonist properties. The present study examined the advantageous effects of TRA-418 based on the dual activities, over an agent having either activity alone and also the difference in the effects of TRA-418 and a glycoprotein alphaIIb/beta3 integrin (GPIIb/IIIa) inhibitor. TRA-418 inhibited platelet GPIIb/IIIa activation as well as P-selectin expression induced by adenosine 5'-diphosphate, thrombin receptor agonist peptide 1-6 (Ser-Phe-Leu-Leu-Arg-Asn-NH2), and U-46619 in the presence of epinephrine (U-46619+ epinephrine). TRA-418 also inhibited platelet aggregation induced by those platelet-stimulants in Ca2+ chelating anticoagulant, citrate and in nonchelating anticoagulant, d-phenylalanyl-l-prolyl-l-arginyl-chloromethyl ketone (PPACK). The TP-receptor antagonist SQ-29548 inhibited only U-46619+epinephrine-induced GPIIb/IIIa activation, P-selectin expression, and platelet aggregation. The IP-receptor agonist beraprost sodium inhibited platelet activation. Beraprost also inhibited platelet aggregation induced by platelet stimulants we tested in citrate and in PPACK. The GPIIb/IIIa inhibitor abciximab blocked GPIIb/IIIa activation and platelet aggregation. However, abciximab showed slight inhibitory effects on P-selectin expression. TRA-418 is more advantageous as an antiplatelet agent than TP-receptor antagonists or IP-receptor agonists separately used. TRA-418 showed a different inhibitory profile from abciximab in the effects on P-selectin expression.

  3. N-methyl-D-aspartic acid receptor agonists

    DEFF Research Database (Denmark)

    Madsen, U; Frydenvang, Karla Andrea; Ebert, B

    1996-01-01

    (R,S)-2-Amino-2-(3-hydroxy-5-methyl-4-isoxazolyl)acetic acid [(R,S)-AMAA, 4] is a potent and selective agonist at the N-methyl-D-aspartic acid (NMDA) subtype of excitatory amino acid receptors. Using the Ugi "four-component condensation" method, the two diastereomers (2R)- and (2S)-2-[3-(benzyloxy......) showed peak affinity for [3H]AMPA receptor sites (IC50 = 72 +/- 13 microM) and was shown to be a more potent inhibitor of [3H]CPP binding (IC50 = 3.7 +/- 1.5 microM) than (S)-AMAA (9) (IC50 = 61 +/- 6.4 microM). Neither enantiomer of AMAA affected [3H]kainic acid receptor binding significantly...

  4. Dopamine D3 receptor agonists as pharmacological tools.

    Science.gov (United States)

    Kassel, S; Schwed, J S; Stark, H

    2015-09-01

    Dysregulation of the dopaminergic innervation in the central nervous system plays a key role in different neurological disorders like Parkinson´s disease, restless legs syndrome, schizophrenia etc. Although dopamine D3 receptors have been recognized as an important target in these diseases, their full pharmacological properties need further investigations. With focus on dopamine D3 receptor full agonists, this review has divided the ergoline and non-ergoline ligands in dissimilar chemical subclasses describing their pharmacodynamic properties on different related receptors, on species differences and their functional properties on different signaling mechanism. This is combined with a short description of structure-activity relationships for each class. Therefore, this overview should support the rational choice for the optimal compound selection based on affinity, selectivity and efficacy data in biochemical and pharmacological studies. Copyright © 2014 Elsevier B.V. and ECNP. All rights reserved.

  5. Adenosine A2B receptor: from cell biology to human diseases

    Science.gov (United States)

    Sun, Ying; Huang, Pingbo

    2016-08-01

    Extracellular adenosine is a ubiquitous signaling molecule that modulates a wide array of biological processes. Recently, significant advances have been made in our understanding of A2B adenosine receptor (A2BAR). In this review, we first summarize some of the general characteristics of A2BAR, and then we describe the multiple binding partners of the receptor, such as newly identified α-actinin-1 and p105, and discuss how these associated proteins could modulate A2BAR’s functions, including certain seemingly paradoxical functions of the receptor. Growing evidence indicates a critical role of A2BAR in cancer, renal disease, and diabetes, in addition to its importance in the regulation of vascular diseases and lung disease. Here, we also discuss the role of A2BAR in cancer, renal disease, and diabetes and the potential of the receptor as a target for treating these three diseases.

  6. The impact of changes in UK classification of the synthetic cannabinoid receptor agonists in 'Spice'.

    Science.gov (United States)

    Dargan, Paul I; Hudson, Simon; Ramsey, John; Wood, David M

    2011-07-01

    Spice is the iconic brand name of a smokeable herbal mixture containing synthetic cannabinoid receptor agonists. It has been available on the Internet/in head shops in Europe since at least 2006. The synthetic cannabinoid receptor agonist constituents of Spice were classified in the UK as Class B agents in December 2009. This study assessed the impact of this legislation on the synthetic cannabinoid receptor agonists present in Spice products and whether new synthetic cannabinoid receptor agonists outside of the legislation are now available. Spice products were bought, prior to and after the change in the UK legislation, from a range of Internet legal high websites selling to UK consumers. Products were analysed using liquid chromatography high-resolution tandem mass spectrometry (LCMSMS). Identification of the synthetic cannabinoid receptor agonist(s) detected was made by comparison to existing databases or by 'in silico' methods. Sixteen products were purchased prior to the UK control of synthetic cannabinoid receptor agonists; all contained at least one synthetic cannabinoid receptor agonist. 20 products were purchased after the UK control; no active compounds were detected in 3 (15%). The remaining 17 (85%) all contained at least one classified synthetic cannabinoid receptor agonist. Additionally, 2 synthetic cannabinoid receptor agonists not covered under current UK generic legislation (AM-694 and the 'novel Belarus compound') were detected. Despite the UK 'Spice' classification, classified synthetic cannabinoid receptor agonists continue to be supplied over the Internet to UK users. Furthermore, new synthetic cannabinoid receptor agonists not covered by the legislation are appearing. Consideration needs to be given to reviewing the UK legislation so that suppliers cannot circumvent it by supplying legal alternatives to the classified synthetic cannabinoid receptor agonists. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Characterization of a novel nonpeptide vasopressin V2-agonist, OPC-51803, in cells transfected human vasopressin receptor subtypes

    Science.gov (United States)

    Nakamura, Shigeki; Yamamura, Yoshitaka; Itoh, Shuji; Hirano, Takahiro; Tsujimae, Kenji; Aoyama, Masashi; Kondo, Kazumi; Ogawa, Hidenori; Shinohara, Tomoichi; Kan, Keizo; Tanada, Yoshihisa; Teramoto, Shuji; Sumida, Takumi; Nakayama, Sunao; Sekiguchi, Kazuo; Kambe, Toshimi; Tsujimoto, Gozoh; Mori, Toyoki; Tominaga, Michiaki

    2000-01-01

    We discovered the first nonpeptide arginine-vasopressin (AVP) V2-receptor agonist, OPC-51803. Pharmacological properties of OPC-51803 were elucidated using HeLa cells expressing human AVP receptor subtypes (V2, V1a and V1b) and compared with those of 1-desamino-8-D-arginine vasopressin (dDAVP), a peptide V2-receptor agonist.OPC-51803 and dDAVP displaced [3H]-AVP binding to human V2- and V1a-receptors with Ki values of 91.9±10.8 nM (n=6) and 3.12±0.38 nM (n=6) for V2-receptors, and 819±39 nM (n=6) and 41.5±9.9 nM (n=6) for V1a-receptors, indicating that OPC-51803 was about nine times more selective for V2-receptors, similar to the selectivity of dDAVP. OPC-51803 scarcely displaced [3H]-AVP binding to human V1b-receptors even at 10−4 M, while dDAVP showed potent affinity to human V1b-receptors with the Ki value of 13.7±3.2 nM (n=4).OPC-51803 concentration-dependently increased cyclic adenosine 3′, 5′-monophosphate (cyclic AMP) production in HeLa cells expressing human V2-receptors with an EC50 value of 189±14 nM (n=6). The concentration-response curve for cyclic AMP production induced by OPC-51803 was shifted to the right in the presence of a V2-antagonist, OPC-31260.At 10−5 M, OPC-51803 did not increase the intracellular Ca2+ concentration ([Ca2+]i) in HeLa cells expressing human V1a-receptors. On the other hand, dDAVP increased [Ca2+]i in HeLa cells expressing human V1a- and V1b-receptors in a concentration-dependent fashion.From these results, OPC-51803 has been confirmed to be the first nonpeptide agonist for human AVP V2-receptors without agonistic activities for V1a- and V1b-receptors. OPC-51803 may be useful for the treatment of AVP-deficient pathophysiological states and as a tool for AVP researches. PMID:10780976

  8. Overlapping binding site for the endogenous agonist, small-molecule agonists, and ago-allosteric modulators on the ghrelin receptor

    DEFF Research Database (Denmark)

    Holst, Birgitte; Frimurer, Thomas M; Mokrosinski, Jacek

    2009-01-01

    A library of robust ghrelin receptor mutants with single substitutions at 22 positions in the main ligand-binding pocket was employed to map binding sites for six different agonists: two peptides (the 28-amino-acid octanoylated endogenous ligand ghrelin and the hexapeptide growth hormone......, and PheVI:23 on the opposing face of transmembrane domain (TM) VI. Each of the agonists was also affected selectively by specific mutations. The mutational map of the ability of L-692,429 and GHRP-6 to act as allosteric modulators by increasing ghrelin's maximal efficacy overlapped with the common....... It is concluded that although each of the ligands in addition exploits other parts of the receptor, a large, common binding site for both small-molecule agonists--including ago-allosteric modulators--and the endogenous agonist is found on the opposing faces of TM-III and -VI of the ghrelin receptor....

  9. Endogenous activation of adenosine A1 receptors promotes post-ischemic electrocortical burst suppression

    DEFF Research Database (Denmark)

    Ilie, A; Ciocan, D; Constantinescu, A O

    2009-01-01

    . Several lines of evidence suggest that BS reflects an impairment of neocortical connectivity. Here we tested in vivo whether synaptic depression by adenosine A1 receptor (A1R) activation contributes to BS patterns following GCI. Male Wistar rats were subjected to 1, 5 or 10 min of GCI using a "four......-min GCI the effect of DPCPX was only apparent on the initial fast decay of the BS ratio. These data suggest that endogenous adenosine release promotes BS patterns during reperfusion following transient cerebral ischemia. Furthermore, the endogenous A1R activation may be the primary underlying cause...

  10. Adenosine receptors in rat and human pancreatic ducts stimulate chloride transport

    DEFF Research Database (Denmark)

    Novak, Ivana; Hede, Susanne; Hansen, Mette

    2007-01-01

    these could be involved in secretory processes, which involve cystic fibrosis transmembrane regulator (CFTR) Cl(-) channels or Ca(2+)-activated Cl(-) channels and [Formula: see text] transporters. Reverse transcriptase polymerase chain reaction analysis on rat pancreatic ducts and human duct cell......, it was found that 58% of PANC-1 cells responded to adenosine, whereas only 9% of CFPAC-1 cells responded. Adenosine elicited Ca(2+) signals only in a few rat and human duct cells, which did not seem to correlate with Cl(-) signals. A(2A) receptors were localized in the luminal membranes of rat pancreatic ducts...

  11. Cardiovascular safety and benefits of GLP-1 receptor agonists

    DEFF Research Database (Denmark)

    Dalsgaard, Niels B; Brønden, Andreas; Lauritsen, Tina Vilsbøll

    2017-01-01

    INTRODUCTION: Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs) constitute a class of drugs for the treatment of type 2 diabetes, and currently, six different GLP-1RAs are approved. Besides improving glycemic control, the GLP-1RAs have other beneficial effects such as weight loss...... and a low risk of hypoglycemia. Treatment with the GLP-1RA lixisenatide has been shown to be safe in patients with type 2 diabetes and recent acute coronary syndrome. Furthermore, liraglutide and semaglutide have been shown to reduce cardiovascular (CV) disease (CVD) risk in type 2 diabetes patients...

  12. Stimulation of endothelial adenosine Al receptors enhances adhesion of neutrophils in the intact guinea pig coronary system

    OpenAIRE

    Zahler, Stefan; Becker, Bernhard F.; Raschke, P.; Gerlach, E.

    1994-01-01

    Objective: The primary aim was to determine the action of pathophysiologically relevant adenosine concentrations (0.1-1 μM) on adhesion of neutrophils to coronary endothelium. Further aims were to evaluate the nature and localisation of the adenosine receptor involved. and to assess the effect of endogenous adenosine. Methods: Adhesion was studied in isolated perfused guinea pig hearts by determining the number of cells emerging in the coronary effluent after intracoronary bolus injections...

  13. Fluorescent agonists for the Torpedo nicotinic acetylcholine receptor.

    Science.gov (United States)

    Krieger, Florian; Mourot, Alexandre; Araoz, Romulo; Kotzyba-Hibert, Florence; Molgó, Jordi; Bamberg, Ernst; Goeldner, Maurice

    2008-05-05

    We have synthesized a series of fluorescent acylcholine derivatives carrying different linkers that vary in length and structure and connect the acylcholine unit to the environment-sensitive fluorophores 7-(diethylamino)coumarin-3-carbonyl (DEAC) or N-(7-nitrobenz-2-oxa-1,3-diazol-yl) (NBD). The pharmacological properties of the fluorescent analogues were investigated on heterologously expressed nicotinic acetylcholine receptor (nAChR) from Torpedo californica and on oocytes transplanted with nAChR-rich Torpedo marmorata membranes. Agonist action strongly depends on the length and the structure of the linker. One particular analogue, DEAC-Gly-C6-choline, showed partial agonist behavior with about half of the maximum response of acetylcholine, which is at least 20 times higher than those observed with previously described fluorescent dansyl- and NBD-acylcholine analogues. Binding of DEAC-Gly-C6-choline to Torpedo nAChR induces a strong enhancement of fluorescence intensity. Association and displacement kinetic experiments revealed dissociation constants of 0.5 nM for the alphadelta-binding site and 15.0 nM for the alphagamma-binding site. Both the pharmacological and the spectroscopic properties of this agonist show great promise for characterizing the allosteric mechanism behind the function of the Torpedo nAChR, as well as for drug-screening studies.

  14. Lipid- and polyion complex-based micelles as agonist platforms for TNFR superfamily receptors.

    Science.gov (United States)

    Gilbreth, Ryan N; Novarra, Shabazz; Wetzel, Leslie; Florinas, Stelios; Cabral, Horacio; Kataoka, Kazunori; Rios-Doria, Jonathan; Christie, Ronald J; Baca, Manuel

    2016-07-28

    Receptor clustering is important for signaling among the therapeutically relevant TNFR superfamily of receptors. In nature, this clustering is driven by trimeric ligands often presented in large numbers as cell surface proteins. Molecules capable of driving similar levels of clustering could make good agonists and hold therapeutic value. However, recapitulating such extensive clustering using typical biotherapeutic formats, such as antibodies, is difficult. Consequently, generating effective agonists of TNFR superfamily receptors is challenging. Toward addressing this challenge we have used lipid- and polyion complex-based micelles as platforms for presenting receptor-binding biologics in a multivalent format that facilitates receptor clustering and imparts strong agonist activity. We show that receptor-binding scFvs or small antibody mimetics that have no agonist activity on their own can be transformed into potent agonists through multivalent presentation on a micelle surface and that the activity of already active multivalent agonists can be enhanced. Using this strategy, we generated potent agonists against two different TNFR superfamily receptors and mouse tumor model studies demonstrate that these micellar agonists have therapeutic efficacy in vivo. Due to its ease of implementation and applicability independent of agonist molecular format, we anticipate that this strategy could be useful for developing agonists to a variety of receptors that rely on clustering to signal. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Abolished tubuloglomerular feedback and increased plasma renin in adenosine A1 receptor deficient mice

    DEFF Research Database (Denmark)

    Brown, R.; Ollerstam, A.; Johansson, B.

    2001-01-01

    The hypothesis that adenosine acting on adenosine A1 receptors (A1R) regulates several renal functions and mediates tubuloglomerular feedback (TGF) was examined using A1R knockout mice. We anesthetized knockout, wild-type, and heterozygous mice and measured glomerular filtration rate, TGF response...... greater in the A1R knockout mice [74.2 +/- 14.3 milli-Goldblatt units (mGU)/ml] mice compared with the wild-type and A1R+/- mice (36.3 +/- 8.5 and 34.1 +/- 9.6 mGU/ml), respectively. The results demonstrate that adenosine acting on A1R is required for TGF and modulates renin release....

  16. [Safety and tolerability of GLP-1 receptor agonists].

    Science.gov (United States)

    Soldevila, Berta; Puig-Domingo, Manel

    2014-09-01

    Glucagon-like peptide-1 receptor agonists (GLP-1ra) are a new group of drugs with a glucose-lowering action due to their incretin effect. The GLP-1 receptor is expressed in various human tissues, which could be related to the pleiotropic effects of human GLP-1, as well as to the adverse effects described in patients treated with GLP-1ra. The risk of hypoglycaemia is low, which is one of the main considerations in the safety of this family of compounds and is also important to patients with diabetes. The most frequent adverse effect is nausea, which usually occurs at the start of treatment and is transient in 20-60% of affected patients. This article also reviews the information available on antibody formation, the potential effect on the thyroid gland, and the controversial association between this group of drugs with pancreatitis and cancer. Copyright © 2014 Elsevier España, S.L.U. All rights reserved.

  17. Helminthosporic acid functions as an agonist for gibberellin receptor.

    Science.gov (United States)

    Miyazaki, Sho; Jiang, Kai; Kobayashi, Masatomo; Asami, Tadao; Nakajima, Masatoshi

    2017-11-01

    Helminthosporol was isolated from a fungus, Helminthosporium sativum, as a natural plant growth regulator in 1963. It showed gibberellin-like bioactivity that stimulated the growth of the second leaf sheath of rice. After studying the structure-activity relationship between the compound and some synthesized analogs, it was found that helminthosporic acid (H-acid) has higher gibberellin-like activity and chemical stability than helminthosporol. In this study, we showed that (1) H-acid displays gibberellin-like activities not only in rice but also in Arabidopsis, (2) it regulates the expression of gibberellin-related genes, (3) it induces DELLA degradation through binding with a gibberellin receptor (GID1), and (4) it forms the GID1-(H-acid)-DELLA complex to transduce the gibberellin signal in the same manner as gibberellin. This work shows that the H-acid mode of action acts as an agonist for gibberellin receptor.

  18. Modulation of neuroimmunity by adenosine and its receptors: Metabolism to mental illness

    Science.gov (United States)

    Chiu, Gabriel S.; Freund, Gregory G.

    2014-01-01

    Adenosine is a pleiotropic bioactive with potent neuromodulatory properties. Due to its ability to easily cross the blood-brain barrier, it can act as a signaling molecule between the periphery and the brain. It functions through four (A1, A2A, A2B, and A3) cell surface G protein-coupled adenosine receptors (AR) that are expressed in some combination on nearly all cells types within the CNS. By regulating the activity of adenylyl cyclase and changing the intracellular concentration of cAMP, adenosine can alter neuronal function and neurotransmission. A variety of illnesses related to metabolic dysregulation, such as type 1 diabetes and Alzheimer’s disease, are associated with an elevated serum concentration of adenosine and a pathogenesis rooted in inflammation. This review describes the accepted physiologic function of adenosine in neurological disease and explores its new potential as a peripheral to central danger signal that can activate the neuroimmune system and contribute to symptoms of sickness and psychopathologies. PMID:25308443

  19. Nucleus accumbens neurotransmission and effort-related choice behavior in food motivation: effects of drugs acting on dopamine, adenosine, and muscarinic acetylcholine receptors.

    Science.gov (United States)

    Nunes, Eric J; Randall, Patrick A; Podurgiel, Samantha; Correa, Mercè; Salamone, John D

    2013-11-01

    Mesolimbic dopamine (DA) is a critical component of the brain circuitry regulating behavioral activation and effort-related processes. Although nucleus accumbens (NAc) DA depletions or antagonism leave aspects of appetite and primary food motivation intact, rats with impaired DA transmission reallocate their instrumental behavior away from food-reinforced tasks with high response requirements, and instead select less effortful food-seeking behaviors. Previous work showed that adenosine A2A antagonists can reverse the effects of DA D2 antagonists on effort-related choice, and that stimulation of adenosine A2A receptors produces behavioral effects that are similar to those induced by DA antagonism. The present review summarizes the literature on the role of NAc DA and adenosine in effort-related processes, and also presents original data on the effects of local stimulation of muscarinic acetylcholine receptors in NAc core. Local injections of the muscarinic agonist pilocarpine directly into NAc core produces shifts in effort-related choice behavior similar to those induced by DA antagonism or A2A receptor stimulation, decreasing lever pressing but increasing chow intake in rats responding on a concurrent fixed ratio/chow feeding choice task. In contrast, injections into a neostriatal control site dorsal to the NAc were ineffective. The actions of pilocarpine on this task were attenuated by co-administration of the muscarinic antagonist scopolamine. Thus, drugs that act on DA, adenosine A2A, and muscarinic receptors regulate effort-related choice behavior, which may have implications for the treatment of psychiatric symptoms such as psychomotor slowing, fatigue or anergia that can be observed in depression and other disorders. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Regulation of lung surfactant secretion by the A sub 2 adenosine receptor

    Energy Technology Data Exchange (ETDEWEB)

    Gilfillan, A.M.; Gobran, L.I.; Rooney, S.A. (Yale Univ. School of Medicine, New Haven, CT (USA))

    1987-05-01

    The authors previously reported that adenosine (A) stimulates secretion of phosphatidylcholine (PC), the major component of surfactant, in type II pneumocytes. To determine how this effect is mediated we examined the effect of P{sub 1} purinoceptor agonists -N{sup 6}-phenylisoprpyl-A (PIA), 5{prime}-N-ethylcarboxyamido-A (NECA), 2-chloro-A (CA) - and antagonists - theophylline (T) and 8-phenyltheophylline (8PT) - on PC secretion and cAMP levels in type II cells isolated from the adult rat. The cells were preincubated with {sup 3}H-choline for 20 h, transferred to fresh medium and incubated {plus minus} test agents for 1.5 h after which {sup 3}H-PC in the cells and medium was measured. A and its analogs stimulated PC secretion in a dose-dependent manner. At the optimal concentration (A, 1 mM; analogs, 0.01 mM) secretion was stimulated approx. 2-fold from a basal rate of 0.08-1.02% of total PC in the medium after 1.5 h. The potency order was NECA>CA=L-PIA>A>D-PIA. The EC{sub 50} for NECA was 8.9 {times} 10{sup {minus}8}M. The effect of NECA was significantly inhibited by 8PT (0.01 mM) and T (0.05 mM). NECA, A and L-PIA increased cellular cAMP levels 34, 12 and 8 fold, respectively, from a basal level of 0.23-0.28 pmol/10{sup 6} cells. These data suggest that the A{sub 2} subtype of the P{sub 1} receptor mediates the effect of A. In newborn rabbits, lung lavage PC increased form 24.1 {plus minus} 1.6 ug P/g lung dry wt at 0 h to 62.6 {plus minus} 7.7 after breathing for 3 h (n=13). 8PT (15 mg/kg, i.m.) at 0 h decreased the PC content at 3 h by 29% to 44.4 {plus minus} 5.1 ug/g. This suggests a functional role for the P{sub 1} receptor in lung surfactant secretion.

  1. Caffeine promotes anti-tumor immune response during tumor initiation: Involvement of the adenosine A2A receptor.

    Science.gov (United States)

    Eini, Hadar; Frishman, Valeria; Yulzari, Robert; Kachko, Leonid; Lewis, Eli C; Chaimovitz, Cidio; Douvdevani, Amos

    2015-11-01

    Epidemiologic studies depict a negative correlation between caffeine consumption and incidence of tumors in humans. The main pharmacological effects of caffeine are mediated by antagonism of the adenosine receptor, A2AR. Here, we examine whether the targeting of A2AR by caffeine plays a role in anti-tumor immunity. In particular, the effects of caffeine are studied in wild-type and A2AR knockout (A2AR(-/-)) mice. Tumor induction was achieved using the carcinogen 3-methylcholanthrene (3-MCA). Alternatively, tumor cells, comprised of 3-MCA-induced transformed cells or B16 melanoma cells, were inoculated into animal footpads. Cytokine release was determined in a mixed lymphocyte tumor reaction (MLTR). According to our findings, caffeine-consuming mice (0.1% in water) developed tumors at a lower rate compared to water-consuming mice (14% vs. 53%, respectively, p=0.0286, n=15/group). Within the caffeine-consuming mice, tumor-free mice displayed signs of autoimmune alopecia and pronounced leukocyte recruitment intocarcinogen injection sites. Similarly, A2AR(-/-) mice exhibited reduced rates of 3-MCA-induced tumors. In tumor inoculation studies, caffeine treatment resulted in inhibition of tumor growth and elevation in proinflammatory cytokine release over water-consuming mice, as depicted by MLTR. Addition of the adenosine receptor agonist, NECA, to MLTR resulted in a sharp decrease in IFNγ levels; this was reversed by the highly selective A2AR antagonist, ZM241385. Thus, immune response modulation through either caffeine or genetic deletion of A2AR leads to a Th1 immune profile and suppression of carcinogen-induced tumorigenesis. Taken together, our data suggest that the use of pharmacologic A2AR antagonists may hold therapeutic potential in diminishing the rate of cancer development. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. The GS Protein-coupled A2a Adenosine Receptor Controls T Cell Help in the Germinal Center.

    Science.gov (United States)

    Abbott, Robert K; Silva, Murillo; Labuda, Jasmine; Thayer, Molly; Cain, Derek W; Philbrook, Phaethon; Sethumadhavan, Shalini; Hatfield, Stephen; Ohta, Akio; Sitkovsky, Michail

    2017-01-27

    T follicular helper (TFH) cells have been shown to be critically required for the germinal center (GC) reaction where B cells undergo class switch recombination and clonal selection to generate high affinity neutralizing antibodies. However, detailed knowledge of the physiological cues within the GC microenvironment that regulate T cell help is limited. The cAMP-elevating, Gs protein-coupled A2a adenosine receptor (A2aR) is an evolutionarily conserved receptor that limits and redirects cellular immunity. However, the role of A2aR in humoral immunity and B cell differentiation is unknown. We hypothesized that the hypoxic microenvironment within the GC facilitates an extracellular adenosine-rich milieu, which serves to limit TFH frequency and function, and also promotes immunosuppressive T follicular regulatory cells (TFR). In support of this hypothesis, we found that following immunization, mice lacking A2aR (A2aRKO) exhibited a significant expansion of T follicular cells, as well as increases in TFH to TFR ratio, GC T cell frequency, GC B cell frequency, and class switching of GC B cells to IgG1. Transfer of CD4 T cells from A2aRKO or wild type donors into T cell-deficient hosts revealed that these increases were largely T cell-intrinsic. Finally, injection of A2aR agonist, CGS21680, following immunization suppressed T follicular differentiation, GC B cell frequency, and class switching of GC B cells to IgG1. Taken together, these observations point to a previously unappreciated role of GS protein-coupled A2aR in regulating humoral immunity, which may be pharmacologically targeted during vaccination or pathological states in which GC-derived autoantibodies contribute to the pathology. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  3. Therapeutic applications of TRAIL receptor agonists in cancer and beyond

    Science.gov (United States)

    Amarante-Mendes, Gustavo P.; Griffith, Thomas S.

    2016-01-01

    TRAIL/Apo-2L is a member of the TNF superfamily first described as an apoptosis-inducing cytokine in 1995. Similar to TNF and Fas ligand, TRAIL induces apoptosis in caspase-dependent manner following TRAIL death receptor trimerization. Because tumor cells were shown to be particularly sensitive to this cytokine while normal cells/tissues proved to be resistant along with being able to synthesize and release TRAIL, it was rapidly appreciated that TRAIL likely served as one of our major physiologic weapons against cancer. In line with this, a number of research laboratories and pharmaceutical companies have attempted to exploit the ability of TRAIL to kill cancer cells by developing recombinant forms of TRAIL or TRAIL receptor agonists (e.g., receptor-specific mAb) for therapeutic purposes. In this review article we will describe the biochemical pathways used by TRAIL to induce different cell death programs. We will also summarize the clinical trials related to this pathway and discuss possible novel uses of TRAIL-related therapies. In recent years, the physiological importance of TRAIL has expanded beyond being a tumoricidal molecule to one critical for a number of clinical settings — ranging from infectious disease and autoimmunity to cardiovascular anomalies. We will also highlight some of these conditions where modulation of the TRAIL/TRAIL receptor system may be targeted in the future. PMID:26343199

  4. Co-administration of delta- and mu-opioid receptor agonists promotes peripheral opioid receptor function

    OpenAIRE

    Schramm, Cicely L.; Honda, Christopher N.

    2010-01-01

    Enhancement of peripheral opioid analgesia following tissue injury or inflammation in animal models is well-documented, but clinical results of peripheral opioid therapy remain inconsistent. Previous studies in the central nervous system have shown that co-administration of μ- and δ-opioid receptor agonists can enhance analgesic outcomes; however, less is known about the functional consequences of opioid receptor interactions in the periphery. The present study examines the effects of intrapl...

  5. The alleged dopamine D1 receptor agonist SKF 83959 is a dopamine D1 receptor antagonist in primate cells and interacts with other receptors.

    Science.gov (United States)

    Andringa, G; Drukarch, B; Leysen, J E; Cools, A R; Stoof, J C

    1999-01-01

    So far, no clear correlation has been found between the effects of dopamine D1 receptor agonists on motor behavior in primate models of Parkinson's disease and their ability to stimulate adenylate cyclase in rats, the benzazepine SKF 83959 (3-methyl-6-chloro-7,8-hydroxy-1-[3-methylphenyl]-2,3,4,5-tetrahydro-]H- 3-benzazepine) being the most striking example. Since this discrepancy might be attributed to: (A) the different species used to study these effects or (B) the interaction of SKF 83959 with other catecholamine receptors, the aims of this study were: (1) to study the ability of SKF 83959 to stimulate adenylate cyclase in cultured human and monkey glial cells equipped with dopamine D1 receptors and (2) to evaluate the affinity for and the functional interaction of SKF 83959 with other catecholamine receptors. Binding studies revealed that SKF 83959 displayed the highest affinity for the dopamine D1 receptor (pKi=6.72) and the alpha2-adrenoceptor (pKi=6.41) and moderate affinity for the dopamine D2 receptor and the noradrenaline transporter. In monkey and human cells, SKF 83959 did not stimulate cyclic adenosine monophosphate (cAMP) formation to a significant extent, but antagonized very potently the dopamine-induced stimulation of cAMP formation in both cell types. The compound stimulated basal dopamine outflow and inhibited depolarization-induced acetylcholine release only at concentrations > 10 microM. Finally, SKF 83959 concentration dependently increased electrically evoked noradrenaline release, indicating that it had alpha2-adrenoceptor blocking activity and interfered with the noradrenaline transporter. In conclusion, SKF 83959 is a potent dopamine D1 receptor and alpha2-adrenoceptor antagonist. Thus, the anti-parkinsonian effects of SKF 83959 in primates are not mediated by striatal dopamine D1 receptors coupled to adenylate cyclase in a stimulatory way.

  6. Adenosine AA Receptor Antagonists Do Not Disrupt Rodent Prepulse Inhibition: An Improved Side Effect Profile in the Treatment of Parkinson's Disease

    Directory of Open Access Journals (Sweden)

    Carina J. Bleickardt

    2012-01-01

    Full Text Available Parkinson's disease (PD is characterized by loss of dopaminergic neurons in the substantia nigra. Current treatments for PD focus on dopaminergic therapies, including L-dopa and dopamine receptor agonists. However, these treatments induce neuropsychiatric side effects. Psychosis, characterized by delusions and hallucinations, is one of the most serious such side effects. Adenosine A2A receptor antagonism is a nondopaminergic treatment for PD with clinical and preclinical efficacy. The present studies assessed A2A antagonists SCH 412348 and istradefylline in rodent prepulse inhibition (PPI, a model of psychosis. Dopamine receptor agonists pramipexole (0.3–3 mg/kg, pergolide (0.3–3 mg/kg, and apomorphine (0.3–3 mg/kg significantly disrupted PPI; ropinirole (1–30 mg/kg had no effect; L-dopa (100–300 mg/kg disrupted rat but not mouse PPI. SCH 412348 (0.3–3 mg/kg did not disrupt rodent PPI; istradefylline (0.1–1 mg/kg marginally disrupted mouse but not rat PPI. These results suggest that A2A antagonists, unlike dopamine agonists, have an improved neuropsychiatric side effect profile.

  7. Comparison of the Effects of Adenosine A1 Receptors Activity in CA1 Region of the Hippocampus on Entorhinal Cortex and Amygdala Kindled Seizures in Rats

    Directory of Open Access Journals (Sweden)

    A. Heidarianpour

    2008-10-01

    Full Text Available Introduction & Objective: In the CNS, adenosine is known to suppress repetitive neuronal Firing, suggesting a role as an endogenous modifier of seizures. Indeed, intracerebral adenosine concentrations rise acutely during seizure activity and are thought to be responsible for terminating seizures and establishing a period of post-ictal refractoriness. However, it is unclear whether this suppression results from a general depression of brain excitability or through action on particular sites critical for the control of after discharge generation and/or seizure development and propagation. In this regard, comparison of the effects of adenosine A1 receptors of CA1 (region of the ‎hippocampus on entorhinal cortex and amygdala kindled seizures was ‎investigated in this study. Materials & Methods: In this experimental study, Animals were kindled by daily electrical stimulation of amygdale (group A or entorhinal cortex (group B. In the fully kindled animals, N6-‎cyclohexyladenosine (CHA;1 and 10 M; a selective adenosine A1 receptoragonist and 1,3-dimethyl-8-cyclohexylxanthine(CPT;1 ‎µ‎M; a selective ‎adenosine A1 receptors antagonist were microinfused bilaterally into the CA1 ‎region of hippocampus (1l/2min and animals were stimulated at 5 and 15 minutes after drug ‎injection. All animals were received artificial cerebrospinal fluid, 24 h before ‎each drug injection and this result were used as control. Results: The seizure parameters were measured at 5 and 15min post injection. Obtained data showed that CHA at concentrations of 10 ‎µ‎M reduced ‎entorhinal cortex and amygdala after discharge and stage5 seizure durations and ‎increased stage4 latency. CHA at concentration 1‎µ‎M significantly alters ‎seizure parameters of group A but not effect on group B. Intrahippocampal (CA1 region pretreatment of CPT (1 ‎µ‎M before CHA abolished the effects of CHA on seizure parameters.Conclusion: It ‎may be

  8. Excessive penile norepinephrine level underlies impaired erectile function in adenosine A1 receptor deficient mice.

    Science.gov (United States)

    Ning, Chen; Qi, Lin; Wen, Jiaming; Zhang, Yujin; Zhang, Weiru; Wang, Wei; Blackburn, Michael; Kellems, Rodney; Xia, Yang

    2012-10-01

    Penile erection is a complex neurovascular physiological event controlled by multiple factors and signaling pathways. A considerable amount of evidence indicates that adenosine plays a significant role in cavernosal smooth muscle relaxation. However, the specific role of adenosine and its receptors in erectile physiology and pathology is not fully understood. To determine the role of the adenosine A1 receptor (ADORA1) in penile erection. Adenosine A1 receptor deficient (Adora1-/-) mice and aged-matched wild-type (WT) mice were utilized. We evaluated the in vivo erectile function by measuring the intracavernosal pressure (ICP) in response to cavernous nerve stimulation (CNS). Enzyme-linked immunosorbent assay was used to measure the norepinephrine (NE) plasma concentration in the corpus cavernosum and systemic circulation. We also evaluated the myosin light chain phosphorylation (p-MLC) in penile tissue pre- and post-CNS. The main outcome measurement of this research was the evaluation of in vivo erectile response to CNS by measuring the ICP in Adora1-/- mice and WT mice and to identify the localization and specific neuron types of ADORA1 expression by dual immunostaining and immunofluorescence co-localization. In vivo, both the ratio of CNS-induced Maximum ICP to mean arterial pressure and CNS-induced slope in Adora1-/- mice were significantly lower than WT mice. At the cellular level in penile tissue, we determined that ADORA1 was highly abundant in neuronal cells. During penile erection, Adora1-/- mice exhibited a higher level of NE plasma concentration in the penis than WT mice. And WT mice had a significantly greater reduction in p-MLC compared to Adora1-/- mice. Our results show that ADORA1 is enriched on neuron cells where it functions to control NE release. Activation of this receptor during penile erection results in reduced NE release and reduced cavernosal smooth muscle contraction, therefore facilitating penile erection. © 2012 International Society for

  9. Adenosine A2B receptor blockade slows growth of bladder and breast tumors.

    Science.gov (United States)

    Cekic, Caglar; Sag, Duygu; Li, Yuesheng; Theodorescu, Dan; Strieter, Robert M; Linden, Joel

    2012-01-01

    The accumulation of high levels of adenosine in tumors activates A(2A) and A(2B) receptors on immune cells and inhibits their ability to suppress tumor growth. Deletion of adenosine A(2A) receptors (A(2A)ARs) has been reported to activate antitumor T cells, stimulate dendritic cell (DC) function, and inhibit angiogenesis. In this study, we evaluated the effects of intermittent intratumor injection of a nonselective adenosine receptor antagonist, aminophylline (AMO; theophylline ethylenediamine) and, for the first time to our knowledge, a selective A(2B)AR antagonist, ATL801. AMO and ATL801 slowed the growth of MB49 bladder and 4T1 breast tumors in syngeneic mice and reduced by 85% metastasizes of breast cancer cells from mammary fat to lung. Based on experiments with A(2A)AR(-/-) or adenosine A(2B) receptor(-/-) mice, the effect of AMO injection was unexpectedly attributed to A(2B)AR and not to A(2A)AR blockade. AMO and ATL801 significantly increased tumor levels of IFN-γ and the IFN-inducible chemokine CXCL10, which is a ligand for CXCR3. This was associated with an increase in activated tumor-infiltrating CXCR3(+) T cells and a decrease in endothelial cell precursors within tumors. Tumor growth inhibition by AMO or ATL801 was eliminated in CXCR3(-/-) mice and RAG1(-/-) mice that lack mature T cells. In RAG1(-/-) mice, A(2B)AR deletion enhanced CD86 expression on CD11b(-) DCs. Bone marrow chimera experiments demonstrated that CXCR3 and A(2B)AR expression on bone marrow cells is required for the antitumor effects of AMO. The data suggest that blockade of A(2B)ARs enhances DC activation and CXCR3-dependent antitumor responses.

  10. Toll-Like Receptor 9 Agonists for Cancer Therapy.

    Science.gov (United States)

    Melisi, Davide; Frizziero, Melissa; Tamburrino, Anna; Zanotto, Marco; Carbone, Carmine; Piro, Geny; Tortora, Giampaolo

    2014-08-04

    The immune system has acquired increasing importance as a key player in cancer maintenance and growth. Thus, modulating anti-tumor immune mediators has become an attractive strategy for cancer treatment. Toll-like receptors (TLRs) have gradually emerged as potential targets of newer immunotherapies. TLR-9 is preferentially expressed on endosome membranes of B-cells and plasmacytoid dendritic cells (pDC) and is known for its ability to stimulate specific immune reactions through the activation of inflammation-like innate responses. Several synthetic CpG oligonucleotides (ODNs) have been developed as TLR-9 agonists with the aim of enhancing cancer immune surveillance. In many preclinical models, CpG ODNs were found to suppress tumor growth and proliferation both in monotherapy and in addition to chemotherapies or target therapies. TLR-9 agonists have been also tested in several clinical trials in patients with solid tumors. These agents showed good tolerability and usually met activity endpoints in early phase trials. However, they have not yet been demonstrated to significantly impact survival, neither as single agent treatments, nor in combination with chemotherapies or cancer vaccines. Further investigations in larger prospective studies are required.

  11. Toll-Like Receptor 9 Agonists for Cancer Therapy

    Directory of Open Access Journals (Sweden)

    Davide Melisi

    2014-08-01

    Full Text Available The immune system has acquired increasing importance as a key player in cancer maintenance and growth. Thus, modulating anti-tumor immune mediators has become an attractive strategy for cancer treatment. Toll-like receptors (TLRs have gradually emerged as potential targets of newer immunotherapies. TLR-9 is preferentially expressed on endosome membranes of B-cells and plasmacytoid dendritic cells (pDC and is known for its ability to stimulate specific immune reactions through the activation of inflammation-like innate responses. Several synthetic CpG oligonucleotides (ODNs have been developed as TLR-9 agonists with the aim of enhancing cancer immune surveillance. In many preclinical models, CpG ODNs were found to suppress tumor growth and proliferation both in monotherapy and in addition to chemotherapies or target therapies. TLR-9 agonists have been also tested in several clinical trials in patients with solid tumors. These agents showed good tolerability and usually met activity endpoints in early phase trials. However, they have not yet been demonstrated to significantly impact survival, neither as single agent treatments, nor in combination with chemotherapies or cancer vaccines. Further investigations in larger prospective studies are required.

  12. Synthetic and computer assisted analysis of the pharmacophore for agonists at benzodiazepine receptors.

    Science.gov (United States)

    Diaz-Arauzo, H; Koehler, K F; Hagen, T J; Cook, J M

    1991-01-01

    In order to employ rational drug design in the discovery of selective benzodiazepine receptor agonists and inverse agonists, pharmacophore/receptor models for both these activities must first be established. Recently, a pharmacophore for the inverse agonist site has been formulated employing the most recent receptor mapping techniques (22). The continuation of this approach to the pharmacophore for agonist ligands has permitted a definition of this site independently of the inverse agonist model. The agonist pharmacophore/receptor contains two hydrogen bond donating sites of interaction (H1 and H2) located about 6.5 A from each other, as well as three areas of lipophilic interaction (L1-L3). The areas L1 and L2 are critical for agonist activity; moreover, some ligands also require an interaction in a third lipophilic area termed L3. This is in agreement with previous work (12-23). In addition, an area of negative steric interaction (S1) between the ligand and receptor-binding protein is defined. In regard to the pharmacophore, it was established that the alignment rule for agonist beta-carbolines is different from that which elicits inverse agonist activity. Consideration of the pharmacophore has resulted in the synthesis of a new beta-carboline 16 which elicits agonist activity. This ligand 16 not only satisfied the requirements of the pharmacophore, but more importantly it elicited both anticonvulsant and anxiolytic activity, but was devoid of the myorelaxant/ataxic properties associated with the benzodiazepines.

  13. A Unified Model of the GABA(A) Receptor Comprising Agonist and Benzodiazepine Binding Sites

    DEFF Research Database (Denmark)

    Kongsbak, Kristine Grønning; Bergmann, Rikke; Sørensen, Pernille Louise

    2013-01-01

    We present a full-length a1b2c2 GABA receptor model optimized for agonists and benzodiazepine (BZD) allosteric modulators. We propose binding hypotheses for the agonists GABA, muscimol and THIP and for the allosteric modulator diazepam (DZP). The receptor model is primarily based on the glutamate...

  14. Sumatriptan (5-HT1D receptor agonist) does not exacerbate symptoms in obsessive compulsive disorder

    NARCIS (Netherlands)

    Pian, KLH; Westerberg, HGM; van Megen, HJGM; den Boer, JA

    1998-01-01

    The non-selective serotonin (5-HT) receptor agonist meta-chlorophenylpiperazine (mCPP) has been reported to elicit symptoms in patients with obsessive compulsive disorder (OCD). MK-212, another nonselective 5-HT receptor agonist, does not seem to induce obsessive compulsive symptoms in OCD patients.

  15. Benzodiazepine agonist and inverse agonist actions on GABAA receptor-operated chloride channels. II. Chronic effects of ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Buck, K.J.; Harris, R.A. (Univ. of Colorado Health Sciences Center, Denver (USA))

    1990-05-01

    Mice were made tolerant to and dependent on ethanol by administration of a liquid diet. Gamma-aminobutyric acid (GABA) receptor-dependent uptake of 36Cl- by mouse cortical microsacs was used to study the actions of benzodiazepine (BZ) agonists and inverse agonists. Chronic exposure to ethanol attenuated the ability of a BZ agonist, flunitrazepam, to augment muscimol-stimulated uptake of 36Cl- and enhanced the actions of BZ inverse agonists, Ro15-4513 (ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo(1,4)-benzodiazepine - 3-carboxylate) and DMCM (methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate), to inhibit GABAA receptor-operated chloride channels. Augmentation of chloride flux by pentobarbital was not reduced by chronic ethanol exposure. Attenuation of flunitrazepam efficacy was transient and returned to control levels within 6 to 24 hr after withdrawal from ethanol, but increased sensitivity to Ro15-4513 was observed as long as 8 days after withdrawal. Chronic exposure to ethanol did not alter (3H)SR 95531 (2-(3'-carbethoxy-2'propyl)-3-amino-6-p-methoxyphenylpyridazinium bromide) binding to low-affinity GABAA receptors or muscimol stimulation of chloride flux; and did not alter (3H)Ro15-4513 or (3H)flunitrazepam binding to central BZ receptors or allosteric modulation of this binding by muscimol (i.e., muscimol-shift). These results suggest that chronic exposure to ethanol reduces coupling between BZ agonist sites and the chloride channel, and may be responsible for the development of cross-tolerance between ethanol and BZ agonists. In contrast, coupling between BZ inverse agonist sites and the chloride channel is increased.

  16. Use of thrombopoietin receptor agonists in childhood immune thrombocytopenia

    Directory of Open Access Journals (Sweden)

    Angelica Maria Garzon

    2015-08-01

    Full Text Available Most children with immune thrombocytopenia (ITP will have spontaneous remission regardless of therapy, while about 20% will go on to have chronic ITP. In those children with chronic ITP who need treatment, standard therapies for acute ITP may have adverse effects that complicate their long term use. Thus, alternative treatment options are needed for children with chronic ITP. Thrombopoietin receptor agonists (TPO-RA have been shown to be safe and efficacious in adults with ITP, and represent a new treatment option for children with chronic ITP. One TPO-RA, eltrombopag, is now approved for children. Clinical trials in children are ongoing and data is emerging on safety and efficacy. This review will focus on the physiology of TPO-RA, their clinical use in children, as well as the long term safety issues that need to be considered when using these agents

  17. Adenosine A

    National Research Council Canada - National Science Library

    Vallon, Volker; Schroth, Jana; Satriano, Joseph; Blantz, Roland C; Thomson, Scott C; Rieg, Timo

    2009-01-01

    ...'). Here, experiments were performed in adenosine A receptor knockout mice (A R-/-), which lack an immediate TGF response, to determine whether A Rs are essential for early diabetic hyperfiltration and the salt paradox. Methods...

  18. Combining a GLP-1 receptor agonist and basal insulin: study evidence and practical considerations.

    Science.gov (United States)

    Carris, Nicholas W; Taylor, James R; Gums, John G

    2014-12-01

    Most patients with diabetes mellitus require multiple medications to achieve glycemic goals. Considering this and the increasing incidence of type 2 diabetes worldwide, the need for effective combination therapy is pressing. Basal insulin and glucagon-like peptide 1 (GLP-1) receptor agonists are frequently used to treat type 2 diabetes. Though both classes of medication are exclusively injectable, which may cause initial hesitation from providers, evidence for their combined use is substantial. This review summarizes the theoretical benefit, supporting evidence, and implementation of a combined basal insulin-GLP-1 receptor agonist regimen. Basal insulin added to a GLP-1 receptor agonist reduces hemoglobin A1c (HbA1c) without weight gain or significantly increased hypoglycemia. A GLP-1 receptor agonist added to basal insulin reduces HbA1c and body weight. Compared with the addition of meal-time insulin to basal insulin, a GLP-1 receptor agonist produces similar or greater reduction in HbA1c, weight loss instead of weight gain, and less hypoglycemia. Gastrointestinal adverse events are common with GLP-1 receptor agonists, especially during initiation and titration. However, combination with basal insulin is not expected to augment expected adverse events that come with using a GLP-1 receptor agonist. Basal insulin can be added to a GLP-1 receptor agonist with a slow titration to target goal fasting plasma glucose. In patients starting a GLP-1 receptor agonist, the dose of basal insulin should be decreased by 20 % in patients with an HbA1c ≤8 %. The evidence from 15 randomized prospective studies supports the combined use of a GLP-1 receptor agonist with basal insulin in a broad range of patients with uncontrolled type 2 diabetes.

  19. Adenosine A2a receptors and O2 sensing in development

    Science.gov (United States)

    2011-01-01

    Reduced mitochondrial oxidative phosphorylation, via activation of adenylate kinase and the resulting exponential rise in the cellular AMP/ATP ratio, appears to be a critical factor underlying O2 sensing in many chemoreceptive tissues in mammals. The elevated AMP/ATP ratio, in turn, activates key enzymes that are involved in physiologic adjustments that tend to balance ATP supply and demand. An example is the conversion of AMP to adenosine via 5′-nucleotidase and the resulting activation of adenosine A2A receptors, which are involved in acute oxygen sensing by both carotid bodies and the brain. In fetal sheep, A2A receptors associated with carotid bodies trigger hypoxic cardiovascular chemoreflexes, while central A2A receptors mediate hypoxic inhibition of breathing and rapid eye movements. A2A receptors are also involved in hypoxic regulation of fetal endocrine systems, metabolism, and vascular tone. In developing lambs, A2A receptors play virtually no role in O2 sensing by the carotid bodies, but brain A2A receptors remain critically involved in the roll-off ventilatory response to hypoxia. In adult mammals, A2A receptors have been implicated in O2 sensing by carotid glomus cells, while central A2A receptors likely blunt hypoxic hyperventilation. In conclusion, A2A receptors are crucially involved in the transduction mechanisms of O2 sensing in fetal carotid bodies and brains. Postnatally, central A2A receptors remain key mediators of hypoxic respiratory depression, but they are less critical for O2 sensing in carotid chemoreceptors, particularly in developing lambs. PMID:21677265

  20. Overcoming the blood-brain barrier for delivering drugs into the brain by using adenosine receptor nanoagonist.

    Science.gov (United States)

    Gao, Xihui; Qian, Jun; Zheng, Shuyan; Changyi, Yinzhi; Zhang, Jianping; Ju, Shenghong; Zhu, Jianhua; Li, Cong

    2014-04-22

    The extremely low permeability of the blood-brain barrier (BBB) poses the greatest impediment in the treatment of central nervous system (CNS) diseases. Recent work indicated that BBB permeability can be up-regulated by activating A2A adenosine receptor (AR), which temporarily increases intercellular spaces between the brain capillary endothelial cells. However, due to transient circulation lifetime of adenosine-based agonists, their capability to enhance brain delivery of drugs, especially macromolecular drugs, is limited. In this work, a series of nanoagonists (NAs) were developed by labeling different copies of A2A AR activating ligands on dendrimers. In vitro transendothelial electrical resistance measurements demonstrated that the NAs increased permeability of the endothelial cell monolayer by compromising the tightness of tight junctions, the key structure that restricts the entry of blood-borne molecules into the brain. In vivo imaging studies indicated the remarkably up-regulated brain uptake of a macromolecular model drug (45 kDa) after intravenous injection of NAs. Autoradiographic imaging showed that the BBB opening time-window can be tuned in a range of 0.5-2.0 h by the NAs labeled with different numbers of AR-activating ligands. By choosing a suitable NA, it is possible to maximize brain drug delivery and minimize the uncontrollable BBB leakage by matching the BBB opening time-window with the pharmacokinetics of a therapeutic agent. The NA-mediated brain drug delivery strategy holds promise for the treatment of CNS diseases with improved therapeutic efficiency and reduced side-effects.

  1. Identification of a naturally occurring retinoid X receptor agonist from Brazilian green propolis.

    Science.gov (United States)

    Nakashima, Ken-Ichi; Murakami, Tohru; Tanabe, Hiroki; Inoue, Makoto

    2014-10-01

    Brazilian green propolis (BGP), a resinous substance produced from Baccharis dracunculifolia by Africanized honey bees (Apis mellifera), is used as a folk medicine. Our present study explores the retinoid X receptor (RXR) agonistic activity of BGP and the identification of an RXR agonist in its extract. RXRα agonistic activity was evaluated using a luciferase reporter gene assay. Isolation of the RXRα agonist from the ethanolic extract of BGP was performed using successive silica gel and a reversed phase column chromatography. The interaction between the isolated RXRα agonist and RXRα protein was predicted by a receptor-ligand docking simulation. The nuclear receptor (NR) cofactor assay was used to estimate whether the isolated RXRα agonist bound to various NRs, including RXRs and peroxisome proliferator-activated receptors (PPARs). We further examined its effect on adipogenesis in 3T3-L1 fibroblasts. We identified drupanin as an RXRα agonist with an EC50 value of 4.8 ± 1.0 μM. Drupanin activated three RXR subtypes by a similar amount and activated PPARγ moderately. Additionally, drupanin induced adipogenesis and elevated aP2 mRNA levels in 3T3-L1 fibroblasts. Drupanin, a component of BGP, is a novel RXR agonist with slight PPARγ agonistic activity. This study revealed for the first time that BGP activates RXR and drupanin is an RXR agonist in its extract. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Excess adenosine in murine penile erectile tissues contributes to priapism via A2B adenosine receptor signaling

    Science.gov (United States)

    Mi, Tiejuan; Abbasi, Shahrzad; Zhang, Hong; Uray, Karen; Chunn, Janci L.; Xia, Ling Wei; Molina, Jose G.; Weisbrodt, Norman W.; Kellems, Rodney E.; Blackburn, Michael R.; Xia, Yang

    2008-01-01

    Priapism, abnormally prolonged penile erection in the absence of sexual excitation, is associated with ischemia-mediated erectile tissue damage and subsequent erectile dysfunction. It is common among males with sickle cell disease (SCD), and SCD transgenic mice are an accepted model of the disorder. Current strategies to manage priapism suffer from a poor fundamental understanding of the molecular mechanisms underlying the disorder. Here we report that mice lacking adenosine deaminase (ADA), an enzyme necessary for the breakdown of adenosine, displayed unexpected priapic activity. ADA enzyme therapy successfully corrected the priapic activity both in vivo and in vitro, suggesting that it was dependent on elevated adenosine levels. Further genetic and pharmacologic evidence demonstrated that A2B adenosine receptor–mediated (A2BR-mediated) cAMP and cGMP induction was required for elevated adenosine–induced prolonged penile erection. Finally, priapic activity in SCD transgenic mice was also caused by elevated adenosine levels and A2BR activation. Thus, we have shown that excessive adenosine accumulation in the penis contributes to priapism through increased A2BR signaling in both Ada–/– and SCD transgenic mice. These findings provide insight regarding the molecular basis of priapism and suggest that strategies to either reduce adenosine or block A2BR activation may prove beneficial in the treatment of this disorder. PMID:18340377

  3. Effect of adenosine1-receptor blockade on renin release from rabbit isolated perfused juxtaglomerular apparatus

    DEFF Research Database (Denmark)

    Weihprecht, H; Lorenz, J N; Schnermann, J

    1990-01-01

    ,3-dipropylxanthine (CPX) on renin release from single isolated rabbit JGAs with macula densa perfused. The A1-receptor agonist, N6-cyclohexyladenosine (CHA), applied in the bathing solution at 10(-7) M, was found to inhibit renin secretion, an effect that was completely blocked by adding CPX (10(-5) M) to the bath...

  4. Diminution of contractile response by kappa-opioid receptor agonists in isolated rat ventricular cardiomyocytes is mediated via a pertussis toxin-sensitive G protein.

    Science.gov (United States)

    Wenzlaff, H; Stein, B; Teschemacher, H

    1998-09-01

    Opioids directly decrease the contractile response of isolated ventricular cardiomyocytes to electrical stimulation. To investigate whether these effects are mediated via GTP-binding G(i/o) proteins we examined the influence of pertussis toxin on the effects of the kappa-opioid receptor agonist trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benz eneacetamide (U-50,488) methanesulphonate and on the as yet undescribed effects of the opioid peptide dynorphin A (1-8) on contraction. In isolated, electrically driven, rat ventricular cardiomyocytes both agents concentration dependently reduced cell shortening within 15 min, decreasing the contractile response by 79+/-4% (n=5) and 62+/-2% (n=6) of control values at maximal effective concentrations of 10 microM (U-50,488) and 1 microM [dynorphin A (1-8)], respectively. Pertussis toxin pre-treatment (200 ng/ml; 4.5-5 h) completely abolished the effects of U-50,488 and dynorphin A (1-8) on the contractile response, indicating that these effects are mediated via G(i/o) proteins. In addition, the non-selective opioid receptor antagonist (-)-naloxone and the kappa-opioid receptor antagonist nor-binaltorphimine antagonized the effects of U-50,488 and dynorphin A (1-8) on the contractile response. Furthermore, the mu- and delta-opioid receptor agonist (D-Ala2, D-Leu5)-enkephalin (DADLE) had no effects on contraction. These results indicate that the decrease in cell shortening is due to stimulation of kappa-opioid receptors. The direct effect of kappa-opioid receptor agonists on the contractile response thus represents an additional mechanism for decreasing cardiac contractility, besides the M-cholinoceptor- or adenosine receptor-mediated pathway. It is conceivable that increased release of endogenous dynorphins from the heart during hypoxia may protect the heart in a similar manner to adenosine.

  5. Adenosine elicits an eNOS-independent reduction in arterial blood pressure in conscious mice that involves adenosine A(2A) receptors

    DEFF Research Database (Denmark)

    Andersen, Henrik; Jaff, Mohammad G; Høgh, Ditte

    2011-01-01

    Aims:  Adenosine plays an important role in the regulation of heart rate and vascular reactivity. However, the mechanisms underlying the acute effect of adenosine on arterial blood pressure in conscious mice are unclear. Therefore, the present study investigated the effect of the nucleoside on mean...... arterial blood pressure (MAP) and heart rate (HR) in conscious mice. Methods:  Chronic indwelling catheters were placed in C57Bl/6J (WT) and endothelial nitric oxide synthase knock-out (eNOS(-/-) ) mice for continuous measurements of MAP and HR. Using PCR and myograph analysis involment of adenosine...... receptors was investigated in human and mouse renal blood vessels Results:  Bolus infusion of 0.5 mg/kg adenosine elicited significant transient decreases in MAP (99.3±2.3 to 70.4±4.5 mmHg) and HR (603.2±18.3 to 364.3±49.2 min(-1) ) which were inhibited by the A(2A) receptor antagonist ZM 241385. Activation...

  6. Discovery of Potent and Highly Selective A2B Adenosine Receptor Antagonist Chemotypes.

    Science.gov (United States)

    El Maatougui, Abdelaziz; Azuaje, Jhonny; González-Gómez, Manuel; Miguez, Gabriel; Crespo, Abel; Carbajales, Carlos; Escalante, Luz; García-Mera, Xerardo; Gutiérrez-de-Terán, Hugo; Sotelo, Eddy

    2016-03-10

    Three novel families of A2B adenosine receptor antagonists were identified in the context of the structural exploration of the 3,4-dihydropyrimidin-2(1H)-one chemotype. The most appealing series contain imidazole, 1,2,4-triazole, or benzimidazole rings fused to the 2,3-positions of the parent diazinone core. The optimization process enabled identification of a highly potent (3.49 nM) A2B ligand that exhibits complete selectivity toward A1, A2A, and A3 receptors. The results of functional cAMP experiments confirmed the antagonistic behavior of representative ligands. The main SAR trends identified within the series were substantiated by a molecular modeling study based on a receptor-driven docking model constructed on the basis of the crystal structure of the human A2A receptor.

  7. Mast cells are directly activated by contact with cancer cells by a mechanism involving autocrine formation of adenosine and autocrine/paracrine signaling of the adenosine A3 receptor.

    Science.gov (United States)

    Gorzalczany, Yaara; Akiva, Eyal; Klein, Ofir; Merimsky, Ofer; Sagi-Eisenberg, Ronit

    2017-07-01

    Mast cells (MCs) constitute an important part of the tumor microenvironment (TME). However, their underlying mechanisms of activation within the TME remain poorly understood. Here we show that recapitulating cell-to-cell contact interactions by exposing MCs to membranes derived from a number of cancer cell types, results in MC activation, evident by the increased phosphorylation of the ERK1/2 MAP kinases and Akt, in a phosphatidylinositol 3-kinase dependent fashion. Activation is unidirectional since MC derived membranes do not activate cancer cells. Stimulated ERK1/2 phosphorylation is strictly dependent on the ecto enzyme CD73 that mediates autocrine formation of adenosine, and is inhibited by knockdown of the A3 adenosine receptor (A3R) as well as by an A3R antagonist or by agonist-stimulated down-regulation of the A3R. We also show that cancer cell mediated triggering upregulates expression and stimulates secretion of interleukin 8 from the activated MCs. These findings provide evidence for a novel mode of unidirectional crosstalk between MCs and cancer cells implicating direct activation by cancer cells in MC reprogramming into a pro tumorigenic profile. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Adenosine Receptors As Drug Targets for Treatment of Pulmonary Arterial Hypertension

    Directory of Open Access Journals (Sweden)

    Allan K. N. Alencar

    2017-12-01

    Full Text Available Pulmonary arterial hypertension (PAH is a clinical condition characterized by pulmonary arterial remodeling and vasoconstriction, which promote chronic vessel obstruction and elevation of pulmonary vascular resistance. Long-term right ventricular (RV overload leads to RV dysfunction and failure, which are the main determinants of life expectancy in PAH subjects. Therapeutic options for PAH remain limited, despite the introduction of prostacyclin analogs, endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and soluble guanylyl cyclase stimulators within the last 15 years. Through addressing the pulmonary endothelial and smooth muscle cell dysfunctions associated with PAH, these interventions delay disease progression but do not offer a cure. Emerging approaches to improve treatment efficacy have focused on beneficial actions to both the pulmonary vasculature and myocardium, and several new targets have been investigated and validated in experimental PAH models. Herein, we review the effects of adenosine and adenosine receptors (A1, A2A, A2B, and A3 on the cardiovascular system, focusing on the A2A receptor as a pharmacological target. This receptor induces pulmonary vascular and heart protection in experimental models, specifically models of PAH. Targeting the A2A receptor could potentially serve as a novel and efficient approach for treating PAH and concomitant RV failure. A2A receptor activation induces pulmonary endothelial nitric oxide synthesis, smooth muscle cell hyperpolarization, and vasodilation, with important antiproliferative activities through the inhibition of collagen deposition and vessel wall remodeling in the pulmonary arterioles. The pleiotropic potential of A2A receptor activation is highlighted by its additional expression in the heart tissue, where it participates in the regulation of intracellular calcium handling and maintenance of heart chamber structure and function. In this way, the activation of A2A

  9. A3 Adenosine Receptors Modulate Hypoxia-inducible Factor-1a Expression in Human A375 Melanoma Cells

    Directory of Open Access Journals (Sweden)

    Stefania Merighi

    2005-10-01

    Full Text Available Hypoxia-inducible factor-1 (HIF-1 is a key regulator of genes crucial to many aspects of cancer biology. The purine nucleoside, adenosine, accumulates within many tissues under hypoxic conditions, including that of tumors. Because the levels of both HIF-1 and adenosine are elevated within the hypoxic environment of solid tumors, we investigated whether adenosine may regulate HIF-1. Here we show that, under hypoxic conditions (< 2% 02, adenosine upregulates HIF-1α protein expression in a dose-dependent and timedependent manner, exclusively through the A3 receptor subtype. The response to adenosine was generated at the cell surface because the inhibition of A3 receptor expression, by using small interfering RNA, abolished nucleoside effects. A3 receptor stimulation in hypoxia also increases angiopoietin-2 (Ang-2 protein accumulation through the induction of HIF-1α. In particular, we found that A3 receptor stimulation activates p44/p42 and p38 mitogen-activated protein kinases, which are required for A3-induced increase of HIF-1a and Ang-2. Collectively, these results suggest a cooperation between hypoxic and adenosine signals that ultimately may lead to the increase in HIF-1-mediated effects in cancer cells.

  10. Adenosine A(1) Receptors in the Central Nervous System : Their Functions in Health and Disease, and Possible Elucidation by PET Imaging

    NARCIS (Netherlands)

    Paul, S.; Elsinga, P. H.; Ishiwata, K.; Dierckx, R. A. J. O.; van Waarde, A.

    2011-01-01

    Adenosine is a neuromodulator with several functions in the central nervous system (CNS), such as inhibition of neuronal activity in many signaling pathways. Most of the sedating, anxiolytic, seizure-inhibiting and protective actions of adenosine are mediated by adenosine A(1) receptors (A(1)R) on

  11. Inhibition of A2A Adenosine Receptor Signaling in Cancer Cells Proliferation by the Novel Antagonist TP455

    Directory of Open Access Journals (Sweden)

    Stefania Gessi

    2017-12-01

    Full Text Available Several evidences indicate that the ubiquitous nucleoside adenosine, acting through A1, A2A, A2B, and A3 receptor (AR subtypes, plays crucial roles in tumor development. Adenosine has contrasting effects on cell proliferation depending on the engagement of different receptor subtypes in various tumors. The involvement of A2AARs in human A375 melanoma, as well as in human A549 lung and rat MRMT1 breast carcinoma proliferation has been evaluated in view of the availability of a novel A2AAR antagonist, with high affinity and selectivity, named as 2-(2-furanyl-N5-(2-methoxybenzyl[1,3]thiazolo[5,4-d]pyrimidine-5,7-diammine (TP455. Specifically, the signaling pathways triggered in the cancer cells of different origin and the antagonist effect of TP455 were investigated. The A2AAR protein expression was evaluated through receptor binding assays. Furthermore, the effect of A2AAR activation on cell proliferation at 24, 48 and 72 hours was studied. The selective A2AAR agonist 2-p-(2-carboxyethylphenethylamino-5′-N-ethylcarboxamidoadenosine hydrochloride (CGS21680, concentration-dependently induced cell proliferation in A375, A549, and MRMT1 cancer cells and the effect was potently antagonized by the A2AAR antagonist TP455, as well as by the reference A2AAR blocker 4-(2-[7-amino-2-(2-furyl[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethylphenol (ZM241385. As for the signaling pathway recruited in this response we demonstrated that, by using the specific inhibitors of signal transduction pathways, the effect of A2AAR stimulation was induced through phospholipase C (PLC and protein kinase C-delta (PKC-δ. In addition, we evaluated, through the AlphaScreen SureFire phospho(p protein assay, the kinases enrolled by A2AAR to stimulate cell proliferation and we found the involvement of protein kinase B (AKT, extracellular regulated kinases (ERK1/2, and c-Jun N-terminal kinases (JNKs. Indeed, we demonstrated that the CGS21680 stimulatory effect on kinases was

  12. Antinociceptive effects of mixtures of mu opioid receptor agonists and cannabinoid receptor agonists in rats: impact of drug and fixed-dose ratio.

    Science.gov (United States)

    Maguire, David R; France, Charles P

    2017-11-25

    Pain is a significant clinical problem, and there is a need for effective pharmacotherapies with fewer adverse effects than currently available drugs (e.g., mu opioid receptor agonists). Cannabinoid receptor agonists enhance the antinociceptive effects of mu opioid receptor agonists, but it remains unclear which drugs and in what proportion will yield the most effective and safest treatments. The antinociceptive effects of the mu opioid receptor agonists etorphine and morphine alone and in combination with the cannabinoid receptor agonists Δ9-THC and CP55940 were studied in male Sprague-Dawley rats (n=16) using a warm water tail withdrawal procedure. The ratio of opioid to cannabinoid (3:1, 1:1, and 1:3) varied for each mixture. Drugs administered alone or as pairwise mixtures of an opioid and a cannabinoid dose-dependently increased tail withdrawal latency. Mixtures with morphine produced supra-additive (CP55940) and additive (Δ9-THC) effects, whereas mixtures with etorphine and either cannabinoid were sub-additive. The interactions were not different among ratios for a particular mixture. The nature of the interaction between opioids and cannabinoids with regard to antinociceptive effects varies with the particular drugs in the mixture, which can have implications for designing combination therapies for pain. Copyright © 2017. Published by Elsevier B.V.

  13. The adenosine A2B receptor is involved in anion secretion in human pancreatic duct Capan-1 epithelial cells

    DEFF Research Database (Denmark)

    Hayashi, M.; Inagaki, A.; Novak, Ivana

    2016-01-01

    − channels important for anion secretion, we herein performed experiments on Capan-1, a human pancreatic duct cell line, using open-circuit Ussing chamber and gramicidin-perforated patch-clamp techniques. The luminal addition of adenosine increased the negative transepithelial potential difference (Vte...... antagonist, PSB 603, inhibited the response of Isc to adenosine. Immunohistochemical analysis showed that the A2A and A2B receptors colocalized with Ezrin in the luminal membranes of Capan-1 monolayers and in rat pancreatic ducts. Adenosine elicited the whole-cell Cl− currents in guinea pig duct cells...

  14. The effect of cannabidiol on ischemia/reperfusion-induced ventricular arrhythmias: the role of adenosine A1 receptors.

    Science.gov (United States)

    Gonca, Ersöz; Darıcı, Faruk

    2015-01-01

    Cannabidiol (CBD) is a nonpsychoactive phytocannabinoid with anti-inflammatory activity mediated by enhancing adenosine signaling. As the adenosine A1 receptor activation confers protection against ischemia/reperfusion (I/R)-induced ventricular arrhythmias, we hypothesized that CBD may have antiarrhythmic effect through the activation of adenosine A1 receptor. Cannabidiol has recently been shown to suppress ischemia-induced ventricular arrhythmias. We aimed to research the effect of CBD on the incidence and the duration of I/R-induced ventricular arrhythmias and to investigate the role of adenosine A1 receptor activation in the possible antiarrhythmic effect of CBD. Myocardial ischemia and reperfusion was induced in anesthetized male rats by ligating the left anterior descending coronary artery for 6 minutes and by loosening the bond at the coronary artery, respectively. Cannabidiol alone was given in a dose of 50 µg/kg, 10 minutes prior to coronary artery occlusion and coadministrated with adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) in a dose of 100 µg/kg, 15 minutes prior to coronary artery occlusion to investigate whether the antiarrhythmic effect of CBD is modified by the activation of adenosine A1 receptors. The experimental groups were as follows: (1) vehicle control (n = 10), (2) CBD (n = 9), (3) DPCPX (n = 7), and (4) CBD + DPCPX group (n = 7). Cannabidiol treatment significantly decreased the incidence and the duration of ventricular tachycardia, total length of arrhythmias, and the arrhythmia scores compared to control during the reperfusion period. The DPCPX treatment alone did not affect the incidence and the duration of any type of arrhythmias. However, DPCPX aborted the antiarrhythmic effect of CBD when it was combined with it. The present results demonstrated that CBD has an antiarrhythmic effect against I/R-induced arrhythmias, and the antiarrhythmic effect of CBD may be mediated through the activation of adenosine

  15. Cordycepin Increases Nonrapid Eye Movement Sleep via Adenosine Receptors in Rats

    Directory of Open Access Journals (Sweden)

    Zhenzhen Hu

    2013-01-01

    Full Text Available Cordycepin (3′-deoxyadenosine is a naturally occurring adenosine analogue and one of the bioactive constituents isolated from Cordyceps militaris/Cordyceps sinensis, species of the fungal genus Cordyceps. It has traditionally been a prized Chinese folk medicine for the human well-being. Because of similarity of chemical structure of adenosine, cordycepin has been focused on the diverse effects of the central nervous systems (CNSs, like sleep regulation. Therefore, this study was undertaken to know whether cordycepin increases the natural sleep in rats, and its effect is mediated by adenosine receptors (ARs. Sleep was recorded using electroencephalogram (EEG for 4 hours after oral administration of cordycepin in rats. Sleep architecture and EEG power spectra were analyzed. Cordycepin reduced sleep-wake cycles and increased nonrapid eye movement (NREM sleep. Interestingly, cordycepin increased θ (theta waves power density during NREM sleep. In addition, the protein levels of AR subtypes (A1, A2A, and A2B were increased after the administration of cordycepin, especially in the rat hypothalamus which plays an important role in sleep regulation. Therefore, we suggest that cordycepin increases theta waves power density during NREM sleep via nonspecific AR in rats. In addition, this experiment can provide basic evidence that cordycepin may be helpful for sleep-disturbed subjects.

  16. Recovery sleep after extended wakefulness restores elevated A1 adenosine receptor availability in the human brain.

    Science.gov (United States)

    Elmenhorst, David; Elmenhorst, Eva-Maria; Hennecke, Eva; Kroll, Tina; Matusch, Andreas; Aeschbach, Daniel; Bauer, Andreas

    2017-04-18

    Adenosine and functional A1 adenosine receptor (A1AR) availability are supposed to mediate sleep-wake regulation and cognitive performance. We hypothesized that cerebral A1AR availability after an extended wake period decreases to a well-rested state after recovery sleep. [(18)F]CPFPX positron emission tomography was used to quantify A1AR availability in 15 healthy male adults after 52 h of sleep deprivation and following 14 h of recovery sleep. Data were additionally compared with A1AR values after 8 h of baseline sleep from an earlier dataset. Polysomnography, cognitive performance, and sleepiness were monitored. Recovery from sleep deprivation was associated with a decrease in A1AR availability in several brain regions, ranging from 11% (insula) to 14% (striatum). A1AR availabilities after recovery did not differ from baseline sleep in the control group. The degree of performance impairment, sleepiness, and homeostatic sleep-pressure response to sleep deprivation correlated negatively with the decrease in A1AR availability. Sleep deprivation resulted in a higher A1AR availability in the human brain. The increase that was observed after 52 h of wakefulness was restored to control levels during a 14-h recovery sleep episode. Individuals with a large increase in A1AR availability were more resilient to sleep-loss effects than those with a subtle increase. This pattern implies that differences in endogenous adenosine and A1AR availability might be causal for individual responses to sleep loss.

  17. Synergistic Action of Presynaptic Muscarinic Acetylcholine Receptors and Adenosine Receptors in Developmental Axonal Competition at the Neuromuscular Junction.

    Science.gov (United States)

    Nadal, Laura; Garcia, Neus; Hurtado, Erica; Simó, Anna; Tomàs, Marta; Lanuza, Maria Angel; Cilleros, Victor; Tomàs, Josep Maria

    2016-01-01

    The development of the nervous system involves the initial overproduction of synapses, which promotes connectivity. Hebbian competition between axons with different activities leads to the loss of roughly half of the overproduced elements and this refines connectivity. We used quantitative immunohistochemistry to investigate, in the postnatal day 7 (P7) to P9 neuromuscular junctions, the involvement of muscarinic receptors (muscarinic acetylcholine autoreceptors and the M1, M2, and M4 subtypes) and adenosine receptors (A1 and A2A subtypes) in the control of axonal elimination after the mouse levator auris longus muscle had been exposed to selective antagonists in vivo. In a previous study we analyzed the role of each of the individual receptors. Here we investigate the additive or occlusive effects of their inhibitors and thus the existence of synergistic activity between the receptors. The main results show that the A2A, M1, M4, and A1 receptors (in this order of ability) delayed axonal elimination at P7. M4 produces some occlusion of the M1 pathway and some addition to the A1 pathway, which suggests that they cooperate. M2 receptors may modulate (by allowing a permissive action) the other receptors, mainly M4 and A1. The continued action of these receptors (now including M2 but not M4) finally promotes axonal loss at P9. All 4 receptors (M2, M1, A1, and A2A, in this order of ability) are necessary. The M4 receptor (which in itself does not affect axon loss) seems to modulate the other receptors. We found a synergistic action between the M1, A1, and A2A receptors, which show an additive effect, whereas the potent M2 effect is largely independent of the other receptors (though can be modulated by M4). At P9, there is a full mutual dependence between the A1 and A2A receptors in regulating axon loss. In summary, postnatal axonal elimination is a regulated multireceptor mechanism that involves the cooperation of several muscarinic and adenosine receptor subtypes.

  18. Caffeine May Reduce Perceived Sweet Taste in Humans, Supporting Evidence That Adenosine Receptors Modulate Taste.

    Science.gov (United States)

    Choo, Ezen; Picket, Benjamin; Dando, Robin

    2017-09-01

    Multiple recent reports have detailed the presence of adenosine receptors in sweet sensitive taste cells of mice. These receptors are activated by endogenous adenosine in the plasma to enhance sweet signals within the taste bud, before reporting to the primary afferent. As we commonly consume caffeine, a powerful antagonist for such receptors, in our daily lives, an intriguing question we sought to answer was whether the caffeine we habitually consume in coffee can inhibit the perception of sweet taste in humans. 107 panelists were randomly assigned to 2 groups, sampling decaffeinated coffee supplemented with either 200 mg of caffeine, about the level found in a strong cup of coffee, or an equally bitter concentration of quinine. Participants subsequently performed sensory testing, with the session repeated in the alternative condition in a second session on a separate day. Panelists rated both the sweetened coffee itself and subsequent sucrose solutions as less sweet in the caffeine condition, despite the treatment having no effect on bitter, sour, salty, or umami perception. Panelists were also unable to discern whether they had consumed the caffeinated or noncaffeinated coffee, with ratings of alertness increased equally, but no significant improvement in reaction times, highlighting coffee's powerful placebo effect. This work validates earlier observations in rodents in a human population. © 2017 Institute of Food Technologists®.

  19. Physical origins of remarkable thermostabilization by an octuple mutation for the adenosine A2a receptor

    Science.gov (United States)

    Kajiwara, Yuta; Ogino, Takahiro; Yasuda, Satoshi; Takamuku, Yuuki; Murata, Takeshi; Kinoshita, Masahiro

    2016-07-01

    It was experimentally showed that the thermal stability of a membrane protein, the adenosine A2a receptor, was remarkably enhanced by an octuple mutation. Here we theoretically prove that the energy decrease arising from the formation of protein intramolecular hydrogen bonds and the solvent-entropy gain upon protein folding are made substantially larger by the mutation, leading to the remarkable enhancement. The solvent is formed by hydrocarbon groups constituting nonpolar chains of the lipid bilayer within a membrane. The mutation modifies geometric characteristics of the structure so that the solvent crowding can be reduced to a larger extent when the protein folds.

  20. Fluorinated Adenosine A2A Receptor Antagonists Inspired by Preladenant as Potential Cancer Immunotherapeutics

    Directory of Open Access Journals (Sweden)

    Gengyang Yuan

    2017-01-01

    Full Text Available Antagonism of the adenosine A2A receptor on T cells blocks the hypoxia-adenosinergic pathway to promote tumor rejection. Using an in vivo immunoassay based on the Concanavalin A mouse model, a series of A2A antagonists were studied and identified preladenant as a potent lead compound for development. Molecular modeling was employed to assist drug design and subsequent synthesis of analogs and those of tozadenant, including fluorinated polyethylene glycol PEGylated derivatives. The efficacy of the analogs was evaluated using two in vitro functional bioassays, and compound 29, a fluorinated triethylene glycol derivative of preladenant, was confirmed as a potential immunotherapeutic agent.

  1. B1 but not B2 bradykinin receptor agonists promote DU145 prostate ...

    African Journals Online (AJOL)

    both vital for cancer growth and progression. Objectives: To investigate the effect of two bradykinin receptor (B1R and B2R) agonists on growth and motility of prostate tumour (DU145) and micro-vascular endothelial cells (dMVECs). Methods: Increasing concentrations of selective B1R and B2R agonists were added to ...

  2. Hydrogen/Deuterium Exchange Reveals Distinct Agonist/Partial Agonist Receptor Dynamics within the intact Vitamin D Receptor/Retinoid X Receptor Heterodimer

    Science.gov (United States)

    Zhang, Jun; Chalmers, Michael J.; Stayrook, Keith R.; Burris, Lorri L.; Garcia-Ordonez, Ruben D.; Pascal, Bruce D.; Burris, Thomas P.; Dodge, Jeffery A.; Griffin, Patrick R.

    2010-01-01

    Summary Regulation of nuclear receptor (NR) activity is driven by alterations in the conformational dynamics of the receptor upon ligand binding. Previously we demonstrated that hydrogen/deuterium exchange (HDX) can be applied to determine novel mechanism of action of PPARγ ligands and in predicting tissue specificity of selective estrogen receptor modulators. Here we applied HDX to probe the conformational dynamics of the ligand binding domain (LBD) of the vitamin D receptor (VDR) upon binding its natural ligand 1α,25-dihydroxyvitamin D3 (1,25D3), and two analogs, alfacalcidol and ED-71. Comparison of HDX profiles from ligands in complex with the LBD with full-length receptor bound to its cognate receptor retinoid X receptor (RXR) revealed unique receptor dynamics that could not be inferred from static crystal structures. These results demonstrate that ligands modulate the dynamics of the heterodimer interface as well as providing insight into the role of AF-2 dynamics in the action of VDR partial agonists. PMID:20947021

  3. TC299423, a Novel Agonist for Nicotinic Acetylcholine Receptors

    Directory of Open Access Journals (Sweden)

    Teagan R. Wall

    2017-09-01

    Full Text Available (E-5-(Pyrimidin-5-yl-1,2,3,4,7,8-hexahydroazocine (TC299423 is a novel agonist for nicotinic acetylcholine receptors (nAChRs. We examined its efficacy, affinity, and potency for α6β2∗ (α6β2-containing, α4β2∗, and α3β4∗ nAChRs, using [125I]-epibatidine binding, whole-cell patch-clamp recordings, synaptosomal 86Rb+ efflux, [3H]-dopamine release, and [3H]-acetylcholine release. TC299423 displayed an EC50 of 30–60 nM for α6β2∗ nAChRs in patch-clamp recordings and [3H]-dopamine release assays. Its potency for α6β2∗ in these assays was 2.5-fold greater than that for α4β2∗, and much greater than that for α3β4∗-mediated [3H]-acetylcholine release. We observed no major off-target binding on 70 diverse molecular targets. TC299423 was bioavailable after intraperitoneal or oral administration. Locomotor assays, measured with gain-of-function, mutant α6 (α6L9′S nAChR mice, show that TC299423 elicits α6β2∗ nAChR-mediated responses at low doses. Conditioned place preference assays show that low-dose TC299423 also produces significant reward in α6L9′S mice, and modest reward in WT mice, through a mechanism that probably involves α6(non-α4β2∗ nAChRs. However, TC299423 did not suppress nicotine self-administration in rats, indicating that it did not block nicotine reinforcement in the dosage range that was tested. In a hot-plate test, TC299423 evoked antinociceptive responses in mice similar to those of nicotine. TC299423 and nicotine similarly inhibited mouse marble burying as a measure of anxiolytic effects. Taken together, our data suggest that TC299423 will be a useful small-molecule agonist for future in vitro and in vivo studies of nAChR function and physiology.

  4. Adenosine Receptors as a Biological Pathway for the Anti-Inflammatory and Beneficial Effects of Low Frequency Low Energy Pulsed Electromagnetic Fields

    Directory of Open Access Journals (Sweden)

    Katia Varani

    2017-01-01

    Full Text Available Several studies explored the biological effects of low frequency low energy pulsed electromagnetic fields (PEMFs on human body reporting different functional changes. Much research activity has focused on the mechanisms of interaction between PEMFs and membrane receptors such as the involvement of adenosine receptors (ARs. In particular, PEMF exposure mediates a significant upregulation of A2A and A3ARs expressed in various cells or tissues involving a reduction in most of the proinflammatory cytokines. Of particular interest is the observation that PEMFs, acting as modulators of adenosine, are able to increase the functionality of the endogenous agonist. By reviewing the scientific literature on joint cells, a double role for PEMFs could be hypothesized in vitro by stimulating cell proliferation, colonization of the scaffold, and production of tissue matrix. Another effect could be obtained in vivo after surgical implantation of the construct by favoring the anabolic activities of the implanted cells and surrounding tissues and protecting the construct from the catabolic effects of the inflammatory status. Moreover, a protective involvement of PEMFs on hypoxia damage in neuron-like cells and an anti-inflammatory effect in microglial cells have suggested the hypothesis of a positive impact of this noninvasive biophysical stimulus.

  5. Potent achiral agonists of the ghrelin (growth hormone secretagogue) receptor. Part I: Lead identification.

    Science.gov (United States)

    Heightman, Tom D; Scott, Jackie S; Longley, Mark; Bordas, Vincent; Dean, David K; Elliott, Richard; Hutley, Gail; Witherington, Jason; Abberley, Lee; Passingham, Barry; Berlanga, Manuela; de Los Frailes, Maite; Wise, Alan; Powney, Ben; Muir, Alison; McKay, Fiona; Butler, Sharon; Winborn, Kim; Gardner, Christopher; Darton, Jill; Campbell, Colin; Sanger, Gareth

    2007-12-01

    High throughput screening combined with efficient datamining and parallel synthesis led to the discovery of a novel series of indolines showing potent in vitro ghrelin receptor agonist activity and acceleration of gastric emptying in rats.

  6. Agonists of fibroblast growth factor receptor induce neurite outgrowth and survival of cerebellar granule neurons

    DEFF Research Database (Denmark)

    Li, Shizhong; Christensen, Claus; Køhler, Lene B

    2009-01-01

    Fibroblast growth factor receptor (FGFR) signaling is pivotal in the regulation of neurogenesis, neuronal differentiation and survival, and synaptic plasticity both during development and in adulthood. In order to develop low molecular weight agonists of FGFR, seven peptides, termed hexafins...

  7. The importance of the adenosine A(2A) receptor-dopamine D(2) receptor interaction in drug addiction.

    Science.gov (United States)

    Filip, M; Zaniewska, M; Frankowska, M; Wydra, K; Fuxe, K

    2012-01-01

    Drug addiction is a serious brain disorder with somatic, psychological, psychiatric, socio-economic and legal implications in the developed world. Illegal (e.g., psychostimulants, opioids, cannabinoids) and legal (alcohol, nicotine) drugs of abuse create a complex behavioral pattern composed of drug intake, withdrawal, seeking and relapse. One of the hallmarks of drugs that are abused by humans is that they have different mechanisms of action to increase dopamine (DA) neurotransmission within the mesolimbic circuitry of the brain and indirectly activate DA receptors. Among the DA receptors, D(2) receptors are linked to drug abuse and addiction because their function has been proven to be correlated with drug reinforcement and relapses. The recognition that D(2) receptors exist not only as homomers but also can form heteromers, such as with the adenosine (A)(2A) receptor, that are pharmacologically and functionally distinct from their constituent receptors, has significantly expanded the range of potential drug targets and provided new avenues for drug design in the search for novel drug addiction therapies. The aim of this review is to bring current focus on A(2A) receptors, their physiology and pharmacology in the central nervous system, and to discuss the therapeutic relevance of these receptors to drug addiction. We concentrate on the contribution of A(2A) receptors to the effects of different classes of drugs of abuse examined in preclinical behavioral experiments carried out with pharmacological and genetic tools. The consequences of chronic drug treatment on A(2A) receptor-assigned functions in preclinical studies are also presented. Finally, the neurochemical mechanism of the interaction between A(2A) receptors and drugs of abuse in the context of the heteromeric A(2A)-D(2) receptor complex is discussed. Taken together, a significant amount of experimental analyses provide evidence that targeting A(2A) receptors may offer innovative translational strategies

  8. Cerebral A{sub 1} adenosine receptors (A{sub 1}AR) in liver cirrhosis

    Energy Technology Data Exchange (ETDEWEB)

    Boy, Christian [Research Centre Juelich, Brain Imaging Centre West, Institute of Medicine, Juelich (Germany); University Hospital Essen, Department of Nuclear Medicine, Essen (Germany); Meyer, Philipp T. [Research Centre Juelich, Brain Imaging Centre West, Institute of Medicine, Juelich (Germany); University Hospital Aachen, Department of Nuclear Medicine, Aachen (Germany); Kircheis, Gerald; Haussinger, Dieter [University of Duesseldorf, Clinic for Gastroenterology, Hepatology and Infectiology, Duesseldorf (Germany); Holschbach, Marcus H.; Coenen, Heinz H. [Research Centre Juelich, Institute of Nuclear Chemistry, Juelich (Germany); Herzog, Hans; Elmenhorst, David [Research Centre Juelich, Brain Imaging Centre West, Institute of Medicine, Juelich (Germany); Kaiser, Hans J. [University Hospital Aachen, Department of Nuclear Medicine, Aachen (Germany); Zilles, Karl [Research Centre Juelich, Brain Imaging Centre West, Institute of Medicine, Juelich (Germany); C. and O. Vogt Institute of Brain Research, Duesseldorf (Germany); Bauer, Andreas [Research Centre Juelich, Brain Imaging Centre West, Institute of Medicine, Juelich (Germany); University of Duesseldorf, Department of Neurology, Duesseldorf (Germany)

    2008-03-15

    The cerebral mechanisms underlying hepatic encephalopathy (HE) are poorly understood. Adenosine, a neuromodulator that pre- and postsynaptically modulates neuronal excitability and release of classical neurotransmitters via A{sub 1} adenosine receptors (A{sub 1}AR), is likely to be involved. The present study investigates changes of cerebral A{sub 1}AR binding in cirrhotic patients by means of positron emission tomography (PET) and [{sup 18}F]CPFPX, a novel selective A{sub 1}AR antagonist. PET was performed in cirrhotic patients (n = 10) and healthy volunteers (n = 10). Quantification of in vivo receptor density was done by Logan's non-invasive graphical analysis (pons as reference region). The outcome parameter was the apparent binding potential (aBP, proportional to B{sub max}/K{sub D}). Cortical and subcortical regions showed lower A{sub 1}AR binding in cirrhotic patients than in controls. The aBP changes reached statistical significance vs healthy controls (p < 0.05, U test with Bonferroni-Holm adjustment for multiple comparisons) in cingulate cortex (-50.0%), precentral gyrus (-40.9%), postcentral gyrus (-38.6%), insular cortex (-38.6%), thalamus (-32.9%), parietal cortex (-31.7%), frontal cortex (-28.6), lateral temporal cortex (-28.2%), orbitofrontal cortex (-27.9%), occipital cortex (-24.6), putamen (-22.7%) and mesial temporal lobe (-22.4%). Regional cerebral adenosinergic neuromodulation is heterogeneously altered in cirrhotic patients. The decrease of cerebral A{sub 1}AR binding may further aggravate neurotransmitter imbalance at the synaptic cleft in cirrhosis and hepatic encephalopathy. Different pathomechanisms may account for these alterations including decrease of A{sub 1}AR density or affinity, as well as blockade of the A{sub 1}AR by endogenous adenosine or exogenous xanthines. (orig.)

  9. GLP-1 receptor agonists and heart failure in diabetes.

    Science.gov (United States)

    Scheen, André J

    2017-04-01

    The prevalence of heart failure (HF) is increasing in patients with type 2 diabetes (T2D), and glucose-lowering agents have distinctive effects on the risk of developing HF that requires hospitalization. Such an increased risk has been consistently reported with thiazolidinediones (glitazones) and perhaps also with the dipeptidyl peptidase (DPP)-4 inhibitor saxagliptin (at least in SAVOR - TIMI 53), whereas a markedly decreased risk was highlighted with the sodium - glucose cotransporter type 2 (SGLT2) inhibitor empagliflozin in EMPA-REG OUTCOME. Yet, the effects of glucagon-like peptide-1 receptor agonists (GLP-1RAs) on myocardial function remain controversial. Whereas some promising observations have been reported in various animal models, the effects of GLP-1RAs on myocardial function in humans are more heterogeneous, while the positive effect on left ventricular ejection fraction (LVEF), if any, appears to be inconsistent and rather modest in most patients with HF. However, no increased risk of hospitalization for HF has been reported with GLP-1RAs in meta-analyses of phase-II/III trials (exenatide, albiglutide, dulaglutide, liraglutide), demonstrating the safety of this pharmacological class, and such findings have been confirmed by three large prospective cardiovascular outcome trials (ELIXA with lixisenatide, LEADER with liraglutide and SUSTAIN-6 with semaglutide). In particular, LEADER reported a trend towards a reduction in HF hospitalization (-13%, P = 0.14), together with a significant reduction in cardiovascular and all-cause mortality in patients with T2D at risk of cardiovascular disease. These results are reassuring in the face of the somewhat negative results of the FIGHT trial, which evaluated the effects of liraglutide in patients with advanced HF and low LVEF, such that further studies and caution are now required when using this agent to treat such patients in clinical practice. © 2017 Elsevier Masson SAS. All rights reserved.

  10. Prolonging survival of corneal transplantation by selective sphingosine-1-phosphate receptor 1 agonist.

    Directory of Open Access Journals (Sweden)

    Min Gao

    Full Text Available Corneal transplantation is the most used therapy for eye disorders. Although the cornea is somewhat an immune privileged organ, immune rejection is still the major problem that reduces the success rate. Therefore, effective chemical drugs that regulate immunoreactions are needed to improve the outcome of corneal transplantations. Here, a sphingosine-1-phosphate receptor 1 (S1P1 selective agonist was systematically evaluated in mouse allogeneic corneal transplantation and compared with the commonly used immunosuppressive agents. Compared with CsA and the non-selective sphingosine 1-phosphate (S1P receptor agonist FTY720, the S1P1 selective agonist can prolong the survival corneal transplantation for more than 30 days with a low immune response. More importantly, the optimal dose of the S1P1 selective agonist was much less than non-selective S1P receptor agonist FTY720, which would reduce the dose-dependent toxicity in drug application. Then we analyzed the mechanisms of the selected S1P1 selective agonist on the immunosuppression. The results shown that the S1P1 selective agonist could regulate the distribution of the immune cells with less CD4+ T cells and enhanced Treg cells in the allograft, moreover the expression of anti-inflammatory cytokines TGF-β1 and IL-10 unregulated which can reduce the immunoreactions. These findings suggest that S1P1 selective agonist may be a more appropriate immunosuppressive compound to effectively prolong mouse allogeneic corneal grafts survival.

  11. Would calcium or potassium channels be responsible for cardiac arrest produced by adenosine and ATP in the right atria of Wistar rats?

    Science.gov (United States)

    Camara, Henrique; Rodrigues, Juliano Quintella Dantas; Alves, Gabriel Andrade; da Silva Junior, Edilson Dantas; Caricati-Neto, Afonso; Garcia, Antônio G; Jurkiewicz, Aron

    2015-12-05

    Autonomic nerves release ATP, which is processed into adenosine in the synaptic cleft. Adenosine and ATP exert a negative chronotropic effect in the heart. This study aims to evaluate adenosine and P2 receptors and cellular signalling in cardiac arrest produced by purines in the heart. Right atria of adult Wistar rats were used to evaluate the effects of adenosine, ATP and CPA (an adenosine A1 receptor agonist), in the presence and absence of DPCPX, an adenosine A1 receptor antagonist. Effects of adenosine A2 and A3 receptors agonists and antagonists were also investigated. Finally, involvement of calcium and potassium channels in these responses was assessed using BayK 8644 and 4-Aminopyridine. Cumulative concentration-effect curves of adenosine and CPA resulted in a negative chronotropic effect culminating in cardiac arrest at 1000μM (adenosine) and 1µM (CPA). Furthermore, ATP produced a negative chronotropic effect at 1-300µM and cardiac arrest at 1000μM in the right atrium. ATPγS (a non-hydrolysable analogue of ATP) reduced chronotropism only. The effects of adenosine, CPA and ATP were inhibited by DPCPX, a selective adenosine A1 receptor antagonist. The selective adenosine A2 and A3 receptors antagonists did not alter the chronotropic response of adenosine. 4-Aminopyridine, a blocker of potassium channels at 10mM, prevented the cardiac arrest produced by adenosine and ATP, while BayK 8644, activator of calcium channels, did not prevent cardiac arrest. Adenosine A1 receptor activation by adenosine and ATP produces cardiac arrest in the right atrium of Wistar rats predominantly through activation of potassium channels. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Anesthetic Cardioprotection: The Role of Adenosine

    Science.gov (United States)

    Bonney, Stephanie; Hughes, Kelly; Eckle, Tobias

    2014-01-01

    Brief periods of cardiac ischemia and reperfusion exert a protective effect against subsequent longer ischemic periods, a phenomenon coined ischemic preconditioning. Similar, repeated brief episodes of coronary occlusion and reperfusion at the onset of reperfusion, called post-conditioning, dramatically reduce infarct sizes. Interestingly, both effects can be achieved by the administration of any volatile anesthetic. In fact, cardio-protection by volatile anesthetics is an older phenomenon than ischemic pre- or post-conditioning. Although the mechanism through which anesthetics can mimic ischemic pre- or post-conditioning is still unknown, adenosine generation and signaling are the most redundant triggers in ischemic pre- or postconditioning. In fact, adenosine signaling has been implicated in isoflurane-mediated cardioprotection. Adenosine acts via four receptors designated as A1, A2a, A2b, and A3. Cardioprotection has been associated with all subtypes, although the role of each remains controversial. Much of the controversy stems from the abundance of receptor agonists and antagonists that are, in fact, capable of interacting with multiple receptor subtypes. Recently, more specific receptor agonists and new genetic animal models have become available paving way towards new discoveries. As such, the adenosine A2b receptor was shown to be the only 1 of the adenosine receptors whose cardiac expression is induced by ischemia in both mice and humans and whose function is implicated in ischemic pre- or post-conditioning. In the current review, we will focus on adenosine signaling in the context of anesthetic cardioprotection and will highlight new discoveries, which could lead to new therapeutic concepts to treat myocardial ischemia using anesthetic preconditioning. PMID:24502579

  13. Differential expression of a(2a), A(1)-adenosine and D(2)-dopamine receptor genes in rat peripheral arterial chemoreceptors during postnatal development.

    Science.gov (United States)

    Gauda, E B; Northington, F J; Linden, J; Rosin, D L

    2000-07-28

    The sensitivity of peripheral arterial chemoreceptors in the carotid body to hypoxia increases with postnatal maturation. Carotid sinus nerve activity is augmented by adenosine binding to A(2a)-adenosine receptors and attenuated by dopamine binding to D(2)-dopamine receptors. In this study, we used in situ hybridization histochemistry to determine the change in the levels of mRNA expression for A(2a) and A(1)-adenosine receptors and D(2)-dopamine receptors in the rat carotid body. We also investigated the cellular distribution and possible colocalization of these receptor mRNAs and tyrosine hydroxylase (TH) mRNAs during the first 2 weeks of postnatal development. By using immunohistocytochemistry, we detected A(2a)-adenosine receptor protein in the carotid body and petrosal ganglion. We found that A(2a)-adenosine receptor mRNA and protein are expressed in the carotid body in animals at 0, 3, 6 and 14 postnatal days. The level of A(2a)-adenosine receptor mRNA expression significantly decreased by 14 postnatal days (P<0.02 vs. day 0) while D(2)-dopamine receptor mRNA levels significantly increased by day 3 and remained greater than D(2)-dopamine receptor mRNA levels at day 0 (P<0.001 all ages vs. day 0). TH mRNA was colocalized in cells in the carotid body with A(2a) adenosine receptor and D(2)-dopamine receptor mRNAs. A(1)-adenosine receptor mRNA was not expressed in the carotid body at any of the ages examined. In the petrosal ganglion, A(1)-adenosine receptor mRNA was abundantly expressed in numerous cells, A(2a)-adenosine receptor mRNA was expressed in a moderate number of cells while D(2)-dopamine receptor mRNA was seen in a few cells in the rostral petrosal ganglion. In conclusion, using in situ hybridization histochemistry, we have shown that mRNA for both the excitatory, A(2a)-adenosine receptor, and the inhibitory, D(2)-dopamine receptor, is developmentally regulated in presumably type I cells in the carotid body which may contribute to the maturation of

  14. Functional plasticity of the N/OFQ-NOP receptor system determines analgesic properties of NOP receptor agonists

    Science.gov (United States)

    Schröder, W; Lambert, D G; Ko, M C; Koch, T

    2014-01-01

    Despite high sequence similarity between NOP (nociceptin/orphanin FQ opioid peptide) and opioid receptors, marked differences in endogenous ligand selectivity, signal transduction, phosphorylation, desensitization, internalization and trafficking have been identified; underscoring the evolutionary difference between NOP and opioid receptors. Activation of NOP receptors affects nociceptive transmission in a site-specific manner, with antinociceptive effects prevailing after peripheral and spinal activation, and pronociceptive effects after supraspinal activation in rodents. The net effect of systemically administered NOP receptor agonists on nociception is proposed to depend on the relative contribution of peripheral, spinal and supraspinal activation, and this may depend on experimental conditions. Functional expression and regulation of NOP receptors at peripheral and central sites of the nociceptive pathway exhibits a high degree of plasticity under conditions of neuropathic and inflammatory pain. In rodents, systemically administered NOP receptor agonists exerted antihypersensitive effects in models of neuropathic and inflammatory pain. However, they were largely ineffective in acute pain while concomitantly evoking severe motor side effects. In contrast, systemic administration of NOP receptor agonists to non-human primates (NHPs) exerted potent and efficacious antinociception in the absence of motor and sedative side effects. The reason for this species difference with respect to antinociceptive efficacy and tolerability is not clear. Moreover, co-activation of NOP and μ-opioid peptide (MOP) receptors synergistically produced antinociception in NHPs. Hence, both selective NOP receptor as well as NOP/MOP receptor agonists may hold potential for clinical use as analgesics effective in conditions of acute and chronic pain. PMID:24762001

  15. Modulatory effects by CB1 receptors on rat spinal locomotor networks after sustained application of agonists or antagonists.

    Science.gov (United States)

    Veeraraghavan, P; Nistri, A

    2015-09-10

    Sustained administration of cannabinoid agonists acting on neuronal CB1 receptors (CB1Rs) are proposed for treating spasticity and chronic pain. The impact of CB1Rs on mammalian locomotor networks remains, however, incompletely understood. To clarify how CB1Rs may control synaptic activity and locomotor network function, we used the rat spinal cord in vitro which is an advantageous model to investigate locomotor circuit mechanisms produced by the local central pattern generator. Neither the CB1 agonist anandamide (AEA) nor the CB1R antagonist AM-251 evoked early (3-24h largely impaired locomotor network activity induced by DR stimuli or neurochemicals, and depressed disinhibited bursting without changing reflex amplitude or inducing neurotoxicity even if CB1R immunoreactivity was lowered in the central region. Since CB1R activation usually inhibits cyclic adenosine monophosphate (cAMP) synthesis, we investigated how a 24-h application of AEA or AM-251 affected basal or forskolin-stimulated cAMP levels. While AEA decreased them in an AM-251-sensitive manner, AM-251 per se did not change resting or stimulated cAMP. Our data suggest that CB1Rs may control the circuit gateway regulating the inflow of sensory afferent inputs into the locomotor circuits, indicating a potential site of action for restricting peripheral signals disruptive for locomotor activity. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

  16. A Modular Dual-Labeling Scaffold That Retains Agonistic Properties for Somatostatin Receptor Targeting.

    Science.gov (United States)

    Ghosh, Sukhen C; Rodriguez, Melissa; Carmon, Kendra S; Voss, Julie; Wilganowski, Nathaniel L; Schonbrunn, Agnes; Azhdarinia, Ali

    2017-11-01

    Fluorescence-guided surgery is an emerging imaging technique that can enhance the ability of surgeons to detect tumors when compared with visual observation. To facilitate characterization, fluorescently labeled probes have been dual-labeled with a radionuclide to enable cross-validation with nuclear imaging. In this study, we selected the somatostatin receptor imaging agent DOTATOC as the foundation for developing a dual-labeled analog. We hypothesized that a customized dual-labeling approach with a multimodality chelation (MMC) scaffold would minimize steric effects of dye conjugation and retain agonist properties. Methods: An MMC conjugate (MMC-TOC) was synthesized on solid-phase and compared with an analog prepared using conventional methods (DA-TOC). Both analogs were conjugated to IRDye 800 using copper-free click chemistry. The resulting compounds, MMC(IR800)-TOC and DA(IR800)-TOC, were labeled with Cu and 64 Cu and tested in vitro in somatostatin receptor subtype 2-overexpressing HEK-293 cells to assess agonist properties, and in AR42J rat pancreatic cancer cells to determine receptor binding characteristics. Multimodality imaging was performed in AR42J xenografts. Results: Cu-MMC(IR800)-TOC demonstrated higher potency for cyclic adenosine monophosphate inhibition (half maximal effective concentration [EC 50 ]: 0.21 ± 0.18 vs. 1.38 ± 0.54 nM) and receptor internalization (EC 50 : 41.9 ± 29.8 vs. 455 ± 299 nM) than Cu-DA(IR800)-TOC. Radioactive uptake studies showed that blocking with octreotide caused a dose-dependent reduction in 64 Cu-MMC(IR800)-TOC uptake whereas 64 Cu-DA(IR800)-TOC was not affected. In vivo studies revealed higher tumor uptake for 64 Cu-MMC(IR800)-TOC than 64 Cu-DA(IR800)-TOC (5.2 ± 0.2 vs. 3.6 ± 0.4 percentage injected dose per gram). In vivo blocking studies with octreotide reduced tumor uptake of 64 Cu-MMC(IR800)-TOC by 66%. Excretion of 64 Cu-MMC(IR800)-TOC was primarily through the liver and spleen whereas 64 Cu-DA(IR800)-TOC

  17. A2A adenosine receptor antagonism enhances synaptic and motor effects of cocaine via CB1 cannabinoid receptor activation.

    Directory of Open Access Journals (Sweden)

    Alessandro Tozzi

    Full Text Available BACKGROUND: Cocaine increases the level of endogenous dopamine (DA in the striatum by blocking the DA transporter. Endogenous DA modulates glutamatergic inputs to striatal neurons and this modulation influences motor activity. Since D2 DA and A2A-adenosine receptors (A2A-Rs have antagonistic effects on striatal neurons, drugs targeting adenosine receptors such as caffeine-like compounds, could enhance psychomotor stimulant effects of cocaine. In this study, we analyzed the electrophysiological effects of cocaine and A2A-Rs antagonists in striatal slices and the motor effects produced by this pharmacological modulation in rodents. PRINCIPAL FINDINGS: Concomitant administration of cocaine and A2A-Rs antagonists reduced glutamatergic synaptic transmission in striatal spiny neurons while these drugs failed to produce this effect when given in isolation. This inhibitory effect was dependent on the activation of D2-like receptors and the release of endocannabinoids since it was prevented by L-sulpiride and reduced by a CB1 receptor antagonist. Combined application of cocaine and A2A-R antagonists also reduced the firing frequency of striatal cholinergic interneurons suggesting that changes in cholinergic tone might contribute to this synaptic modulation. Finally, A2A-Rs antagonists, in the presence of a sub-threshold dose of cocaine, enhanced locomotion and, in line with the electrophysiological experiments, this enhanced activity required activation of D2-like and CB1 receptors. CONCLUSIONS: The present study provides a possible synaptic mechanism explaining how caffeine-like compounds could enhance psychomotor stimulant effects of cocaine.

  18. Stereostructure-activity studies on agonists at the AMPA and kainate subtypes of ionotropic glutamate receptors

    DEFF Research Database (Denmark)

    Johansen, Tommy N; Greenwood, Jeremy R; Frydenvang, Karla Andrea

    2003-01-01

    (S)-Glutamic acid (Glu), the major excitatory neurotransmitter in the central nervous system, operates through ionotropic as well as metabotropic receptors and is considered to be involved in certain neurological disorders and degenerative brain diseases that are currently without any satisfactory...... therapeutic treatment. Until recently, development of selective Glu receptor agonists had mainly been based on lead compounds, which were frequently naturally occurring excitants structurally related to Glu. These Glu receptor agonists generally contain heterocyclic acidic moieties, which has stimulated...... the use of bioisosteric replacement approaches for the design of subtype-selective agonists. Furthermore, most of these leads are conformationally restricted and stereochemically well-defined Glu analogs. Crystallization of the agonist binding domain of the GluR2 subunit of the (RS)-2-amino-3-(3-hydroxy-5...

  19. A2A Adenosine Receptor Antagonism Reverts the Blood-Brain Barrier Dysfunction Induced by Sleep Restriction.

    Directory of Open Access Journals (Sweden)

    Gabriela Hurtado-Alvarado

    Full Text Available Chronic sleep restriction induces blood-brain barrier disruption and increases pro-inflammatory mediators in rodents. Those inflammatory mediators may modulate the blood-brain barrier and constitute a link between sleep loss and blood-brain barrier physiology. We propose that adenosine action on its A2A receptor may be modulating the blood-brain barrier dynamics in sleep-restricted rats. We administrated a selective A2A adenosine receptor antagonist (SCH58261 in sleep-restricted rats at the 10th day of sleep restriction and evaluated the blood-brain barrier permeability to dextrans coupled to fluorescein (FITC-dextrans and Evans blue. In addition, we evaluated by western blot the expression of tight junction proteins (claudin-5, occludin, ZO-1, adherens junction protein (E-cadherin, A2A adenosine receptor, adenosine-synthesizing enzyme (CD73, and neuroinflammatory markers (Iba-1 and GFAP in the cerebral cortex, hippocampus, basal nuclei and cerebellar vermis. Sleep restriction increased blood-brain barrier permeability to FITC-dextrans and Evans blue, and the effect was reverted by the administration of SCH58261 in almost all brain regions, excluding the cerebellum. Sleep restriction increased the expression of A2A adenosine receptor only in the hippocampus and basal nuclei without changing the expression of CD73 in all brain regions. Sleep restriction reduced the expression of tight junction proteins in all brain regions, except in the cerebellum; and SCH58261 restored the levels of tight junction proteins in the cortex, hippocampus and basal nuclei. Finally, sleep restriction induced GFAP and Iba-1 overexpression that was attenuated with the administration of SCH58261. These data suggest that the action of adenosine on its A2A receptor may have a crucial role in blood-brain barrier dysfunction during sleep loss probably by direct modulation of brain endothelial cell permeability or through a mechanism that involves gliosis with subsequent

  20. A2A Adenosine Receptor Antagonism Reverts the Blood-Brain Barrier Dysfunction Induced by Sleep Restriction.

    Science.gov (United States)

    Hurtado-Alvarado, Gabriela; Domínguez-Salazar, Emilio; Velázquez-Moctezuma, Javier; Gómez-González, Beatriz

    2016-01-01

    Chronic sleep restriction induces blood-brain barrier disruption and increases pro-inflammatory mediators in rodents. Those inflammatory mediators may modulate the blood-brain barrier and constitute a link between sleep loss and blood-brain barrier physiology. We propose that adenosine action on its A2A receptor may be modulating the blood-brain barrier dynamics in sleep-restricted rats. We administrated a selective A2A adenosine receptor antagonist (SCH58261) in sleep-restricted rats at the 10th day of sleep restriction and evaluated the blood-brain barrier permeability to dextrans coupled to fluorescein (FITC-dextrans) and Evans blue. In addition, we evaluated by western blot the expression of tight junction proteins (claudin-5, occludin, ZO-1), adherens junction protein (E-cadherin), A2A adenosine receptor, adenosine-synthesizing enzyme (CD73), and neuroinflammatory markers (Iba-1 and GFAP) in the cerebral cortex, hippocampus, basal nuclei and cerebellar vermis. Sleep restriction increased blood-brain barrier permeability to FITC-dextrans and Evans blue, and the effect was reverted by the administration of SCH58261 in almost all brain regions, excluding the cerebellum. Sleep restriction increased the expression of A2A adenosine receptor only in the hippocampus and basal nuclei without changing the expression of CD73 in all brain regions. Sleep restriction reduced the expression of tight junction proteins in all brain regions, except in the cerebellum; and SCH58261 restored the levels of tight junction proteins in the cortex, hippocampus and basal nuclei. Finally, sleep restriction induced GFAP and Iba-1 overexpression that was attenuated with the administration of SCH58261. These data suggest that the action of adenosine on its A2A receptor may have a crucial role in blood-brain barrier dysfunction during sleep loss probably by direct modulation of brain endothelial cell permeability or through a mechanism that involves gliosis with subsequent inflammation and

  1. A2A Adenosine Receptor Antagonism Reverts the Blood-Brain Barrier Dysfunction Induced by Sleep Restriction

    Science.gov (United States)

    Hurtado-Alvarado, Gabriela; Domínguez-Salazar, Emilio; Velázquez-Moctezuma, Javier

    2016-01-01

    Chronic sleep restriction induces blood-brain barrier disruption and increases pro-inflammatory mediators in rodents. Those inflammatory mediators may modulate the blood-brain barrier and constitute a link between sleep loss and blood-brain barrier physiology. We propose that adenosine action on its A2A receptor may be modulating the blood-brain barrier dynamics in sleep-restricted rats. We administrated a selective A2A adenosine receptor antagonist (SCH58261) in sleep-restricted rats at the 10th day of sleep restriction and evaluated the blood-brain barrier permeability to dextrans coupled to fluorescein (FITC-dextrans) and Evans blue. In addition, we evaluated by western blot the expression of tight junction proteins (claudin-5, occludin, ZO-1), adherens junction protein (E-cadherin), A2A adenosine receptor, adenosine-synthesizing enzyme (CD73), and neuroinflammatory markers (Iba-1 and GFAP) in the cerebral cortex, hippocampus, basal nuclei and cerebellar vermis. Sleep restriction increased blood-brain barrier permeability to FITC-dextrans and Evans blue, and the effect was reverted by the administration of SCH58261 in almost all brain regions, excluding the cerebellum. Sleep restriction increased the expression of A2A adenosine receptor only in the hippocampus and basal nuclei without changing the expression of CD73 in all brain regions. Sleep restriction reduced the expression of tight junction proteins in all brain regions, except in the cerebellum; and SCH58261 restored the levels of tight junction proteins in the cortex, hippocampus and basal nuclei. Finally, sleep restriction induced GFAP and Iba-1 overexpression that was attenuated with the administration of SCH58261. These data suggest that the action of adenosine on its A2A receptor may have a crucial role in blood-brain barrier dysfunction during sleep loss probably by direct modulation of brain endothelial cell permeability or through a mechanism that involves gliosis with subsequent inflammation and

  2. Antinociception by systemically-administered acetaminophen (paracetamol) involves spinal serotonin 5-HT7 and adenosine A1 receptors, as well as peripheral adenosine A1 receptors.

    Science.gov (United States)

    Liu, Jean; Reid, Allison R; Sawynok, Jana

    2013-03-01

    Acetaminophen (paracetamol) is a widely used analgesic, but its sites and mechanisms of action remain incompletely understood. Recent studies have separately implicated spinal adenosine A(1) receptors (A(1)Rs) and serotonin 5-HT(7) receptors (5-HT(7)Rs) in the antinociceptive effects of systemically administered acetaminophen. In the present study, we determined whether these two actions are linked by delivering a selective 5-HT(7)R antagonist to the spinal cord of mice and examining nociception using the formalin 2% model. In normal and A(1)R wild type mice, antinociception by systemic (i.p.) acetaminophen 300mg/kg was reduced by intrathecal (i.t.) delivery of the selective 5-HT(7)R antagonist SB269970 3μg. In mice lacking A(1)Rs, i.t. SB269970 did not reverse antinociception by systemic acetaminophen, indicating a link between spinal 5-HT(7)R and A(1)R mechanisms. We also explored potential roles of peripheral A(1)Rs in antinociception by acetaminophen administered both locally and systemically. In normal mice, intraplantar (i.pl.) acetaminophen 200μg produced antinociception in the formalin test, and this was blocked by co-administration of the selective A(1)R antagonist DPCPX 4.5μg. Acetaminophen administered into the contralateral hindpaw had no effect, indicating a local peripheral action. When acetaminophen was administered systemically, its antinociceptive effect was reversed by i.pl. DPCPX in normal mice; this was also observed in A(1)R wild type mice, but not in those lacking A(1)Rs. In summary, we demonstrate a link between spinal 5-HT(7)Rs and A(1)Rs in the spinal cord relevant to antinociception by systemic acetaminophen. Furthermore, we implicate peripheral A(1)Rs in the antinociceptive effects of locally- and systemically-administered acetaminophen. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  3. Overexpression of Adenosine A2A Receptors in Rats: Effects on Depression, Locomotion, and Anxiety

    Science.gov (United States)

    Coelho, Joana E.; Alves, Pedro; Canas, Paula M.; Valadas, Jorge S.; Shmidt, Tatiana; Batalha, Vânia L.; Ferreira, Diana G.; Ribeiro, Joaquim A.; Bader, Michael; Cunha, Rodrigo A.; do Couto, Frederico Simões; Lopes, Luísa V.

    2014-01-01

    Adenosine A2A receptors (A2AR) are a sub-type of receptors enriched in basal ganglia, activated by the neuromodulator adenosine, which interact with dopamine D2 receptors. Although this reciprocal antagonistic interaction is well-established in motor function, the outcome in dopamine-related behaviors remains uncertain, in particular in depression and anxiety. We have demonstrated an upsurge of A2AR associated to aging and chronic stress. Furthermore, Alzheimer’s disease patients present A2AR accumulation in cortical areas together with depressive signs. We now tested the impact of overexpressing A2AR in forebrain neurons on dopamine-related behavior, namely depression. Adult male rats overexpressing human A2AR under the control of CaMKII promoter [Tg(CaMKII-hA2AR)] and aged-matched wild-types (WT) of the same strain (Sprague-Dawley) were studied. The forced swimming test (FST), sucrose preference test (SPT), and the open-field test (OFT) were performed to evaluate behavioral despair, anhedonia, locomotion, and anxiety. Tg(CaMKII-hA2AR) animals spent more time floating and less time swimming in the FST and presented a decreased sucrose preference at 48 h in the SPT. They also covered higher distances in the OFT and spent more time in the central zone than the WT. The results indicate that Tg(CaMKII-hA2AR) rats exhibit depressive-like behavior, hyperlocomotion, and altered exploratory behavior. This A2AR overexpression may explain the depressive signs found in aging, chronic stress, and Alzheimer’s disease. PMID:24982640

  4. Overexpression of adenosine A2A receptors in rats: effects on depression, locomotion and anxiety

    Directory of Open Access Journals (Sweden)

    Joana E Coelho

    2014-06-01

    Full Text Available Adenosine A2A receptors (A2AR are a sub-type of receptors enriched in basal ganglia, activated by the neuromodulator adenosine, which interact with dopamine D2 receptors. Although this reciprocal antagonistic interaction is well established in motor function, the outcome in dopamine-related behaviors remains uncertain, in particular in depression and anxiety. We have demonstrated an upsurge of A2AR associated to aging and chronic stress. Furthermore, Alzheimer’s disease patients present A2AR accumulation in cortical areas together with depressive signs. We now tested the impact of overexpressing A2AR in forebrain neurons on dopamine related behavior, namely depression. Adult male rats overexpressing human A2AR under the control of CaMKII promoter [Tg(CaMKII-hA2AR] and aged-matched wild-types (WT of the same strain (Sprague-Dawley were studied. The forced swimming test (FST, sucrose preference test (SPT and the open-field test (OFT were performed to evaluate behavioral despair, anhedonia, locomotion and anxiety. Tg(CaMKII-hA2AR animals spent more time floating and less time swimming in the FST and presented a decreased sucrose preference at 48h in the SPT. They also covered higher distances in the OFT and spent more time in the central zone than the WT. The results indicate that Tg(CaMKII-hA2AR rats exhibit depressive-like behavior, hyperlocomotion and altered exploratory behavior. This A2AR overexpression may explain the depressive signs found in aging, chronic stress and Alzheimer’s disease.

  5. Interactions between Delta(9)-tetrahydrocannabinol and mu opioid receptor agonists in rhesus monkeys: discrimination and antinociception.

    Science.gov (United States)

    Li, Jun-Xu; McMahon, Lance R; Gerak, Lisa R; Becker, Ginger L; France, Charles P

    2008-08-01

    Opioid receptor agonists can enhance some effects of cannabinoid receptor agonists, and cannabinoid receptor agonists can enhance some effects of opioid receptor agonists; however, the generality of these interactions is not established. This study examined interactions between the discriminative stimulus and antinociceptive effects of mu opioid receptor agonists and Delta(9)-tetrahydrocannabinol (THC) in rhesus monkeys. Neither heroin nor morphine (intravenous (i.v.) or subcutaneous (s.c.)) altered the discriminative stimulus effects of THC in monkeys (n = 5) discriminating 0.1 mg/kg THC i.v. In contrast, THC (s.c.) markedly attenuated the discriminative stimulus effect of morphine and heroin in nondependent monkeys (n = 4) discriminating 1.78 mg/kg morphine s.c. Doses of THC that attenuated the discriminative stimulus effects of morphine in nondependent monkeys failed to modify the discriminative stimulus effects of morphine in morphine-dependent (5.6 mg/kg/12 h) monkeys (n = 4) discriminating 0.0178 mg/kg naltrexone s.c. THC also failed to modify the discriminative stimulus effects of naltrexone in morphine-dependent monkeys or the effects of midazolam in monkeys (n = 4) discriminating 0.32 mg/kg midazolam s.c. Doses of THC (s.c.) that attenuated the discriminative stimulus effects of morphine in nondependent monkeys enhanced the antinociceptive effects of morphine (s.c.) in nondependent monkeys. While mu receptor agonists did not alter the discriminative stimulus effects of THC, THC altered the effects of mu receptor agonists in a context-dependent manner. That the same doses of THC enhance, attenuate, or do not affect morphine, depending on the condition, suggests that attenuation of morphine by THC can result from perceptual masking rather than common pharmacodynamic mechanisms or pharmacokinetic interactions.

  6. Neuronal transporter and astrocytic ATP exocytosis underlie activity-dependent adenosine release in the hippocampus

    Science.gov (United States)

    Wall, Mark J; Dale, Nicholas

    2013-01-01

    The neuromodulator adenosine plays an important role in many physiological and pathological processes within the mammalian CNS. However, the precise mechanisms of how the concentration of extracellular adenosine increases following neural activity remain contentious. Here we have used microelectrode biosensors to directly measure adenosine release induced by focal stimulation in stratum radiatum of area CA1 in mouse hippocampal slices. Adenosine release was both action potential and Ca2+ dependent and could be evoked with low stimulation frequencies and small numbers of stimuli. Adenosine release required the activation of ionotropic glutamate receptors and could be evoked by local application of glutamate receptor agonists. Approximately 40% of stimulated-adenosine release occurred by translocation of adenosine via equilibrative nucleoside transporters (ENTs). This component of release persisted in the presence of the gliotoxin fluoroacetate and thus results from the direct release of adenosine from neurons. A reduction of adenosine release in the presence of NTPDase blockers, in slices from CD73−/− and dn-SNARE mice, provides evidence that a component of adenosine release arises from the extracellular metabolism of ATP released from astrocytes. This component of release appeared to have slower kinetics than the direct ENT-mediated release of adenosine. These data suggest that activity-dependent adenosine release is surprisingly complex and, in the hippocampus, arises from at least two distinct mechanisms with different cellular sources. PMID:23713028

  7. Adenosine receptors: regulatory players in the preservation of mitochondrial function induced by ischemic preconditioning of rat liver.

    Science.gov (United States)

    Duarte, Filipe V; Amorim, João A; Varela, Ana T; Teodoro, João S; Gomes, Ana P; Cunha, Rodrigo A; Palmeira, Carlos M; Rolo, Anabela P

    2017-06-01

    Although adenosine A1 receptors (A1R) have been associated to ischemic preconditioning (IPC), direct evidence for their ability to preserve mitochondrial function upon hepatic preconditioning is still missing and could represent a novel strategy to boost the quality of liver transplants. We tested if the A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) prevented IPC in the liver and if the A1R agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) might afford a pharmacological preconditioning. Livers underwent a 120 min of 70% warm ischemia and 16 h of reperfusion (I/R), and the IPC group underwent a 5-min ischemic episode followed by a 10-min period of reperfusion before I/R. DPCPX or CCPA was administered intraperitoneally 2 h before IPC or I/R. The control of mitochondrial function emerged as the central element affected by IPC and controlled by endogenous A1R activation. Thus, livers from IPC- or CCPA-treated rats displayed an improved oxidative phosphorylation with higher state 3 respiratory rate, higher respiratory control ratio, increased ATP content, and decreased lag phase. IPC and CCPA also prevented the I/R-induced susceptibility to calcium-induced mitochondrial permeability transition, the rate of reactive oxygen species (ROS) generation, and the decreased mitochondrial content of phospho-Ser(9) GSK-3β. DPCPX abrogated these effects of IPC. These implicate the control of GSK-3β activity by Akt-mediated Ser(9)-GSK-3β phosphorylation preserving the efficiency of oxidative phosphorylation and ROS-mediated cell death in the ability of A1R activation to mimic IPC in the liver. In conclusion, the parallel between IPC and A1R-mediated preconditioning also paves the way to consider a putative therapeutic use of the later in liver transplants.

  8. Ultraslow Water-Mediated Transmembrane Interactions Regulate the Activation of A2A Adenosine Receptor

    Science.gov (United States)

    Lee, Yoonji; Kim, Songmi; Choi, Sun; Hyeon, Changbong

    2016-09-01

    Water molecules inside G-protein coupled receptor have recently been spotlighted in a series of crystal structures. To decipher the dynamics and functional roles of internal waters in GPCR activity, we studied A$_{\\text{2A}}$ adenosine receptor using $\\mu$sec-molecular dynamics simulations. Our study finds that the amount of water flux across the transmembrane (TM) domain varies depending on the receptor state, and that the water molecules of the TM channel in the active state flow three times slower than those in the inactive state. Depending on the location in solvent-protein interface as well as the receptor state, the average residence time of water in each residue varies from $\\sim\\mathcal{O}(10^2)$ psec to $\\sim\\mathcal{O}(10^2)$ nsec. Especially, water molecules, exhibiting ultraslow relaxation ($\\sim\\mathcal{O}(10^2)$ nsec) in the active state, are found around the microswitch residues that are considered activity hotspots for GPCR function. A continuous allosteric network spanning the TM domain, arising from water-mediated contacts, is unique in the active state, underscoring the importance of slow waters in the GPCR activation.

  9. Bioassay directed identification of natural aryl hydrocarbon-receptor agonists in marmalade

    NARCIS (Netherlands)

    Ede, van K.I.; Li, A.; Antunes Fernandes, E.C.; Mulder, P.P.J.; Peijnenburg, A.A.C.M.; Hoogenboom, L.A.P.

    2008-01-01

    Citrus fruit and citrus fruit products, like grapefruit, lemon and marmalade were shown to contain aryl hydrocarbon receptor (AhR) agonists, as detected with the DR CALUX® bioassay. This is of interest regarding the role of the Ah-receptor pathway in the adverse effects of dioxins, PCBs and other

  10. Tweaking agonist efficacy at N-methyl-D-aspartate receptors by site-directed mutagenesis

    DEFF Research Database (Denmark)

    Hansen, Kasper B; Clausen, Rasmus P; Bjerrum, Esben J

    2005-01-01

    The structural basis for partial agonism at N-methyl-D-aspartate (NMDA) receptors is currently unresolved. We have characterized several partial agonists at the NR1/NR2B receptor and investigated the mechanisms underlying their reduced efficacy by introducing mutations in the glutamate binding si...

  11. Evaluation of potential agonist radioligands for imaging dopamine D2/3 receptors

    NARCIS (Netherlands)

    van Wieringen, J.P.

    2015-01-01

    Imaging dopamine receptors with PET and SPECT can shed light on the nature of neuropsychiatric disorders which are characterized by disturbances in dopamine D2/3 receptor functioning. Agonist radioligands are considered superior to antagonists because they are more sensitive to detect dopamine

  12. The sphingosine 1-phosphate receptor agonist FTY720 is neuroprotective after cuprizone-induced CNS demyelination

    NARCIS (Netherlands)

    Slowik, A.; Schmidt, T.; Beyer, C.; Amor, S.; Clarner, T.; Kipp, M.

    2015-01-01

    Background and Purpose Modulation of the sphingosine 1-phosphate receptor is an approved treatment for relapsing multiple sclerosis because of its anti-inflammatory effect of retaining lymphocytes within the lymph nodes. Here, we evaluated the potential of an agonist at this receptor, FTY720

  13. Prejunctional and peripheral effects of the cannabinoid CB1 receptor inverse agonist rimonabant (SR 141716)

    NARCIS (Netherlands)

    van Diepen, Hester; Schlicker, Eberhard; Michel, Martin C.

    2008-01-01

    Rimonabant is an inverse agonist specific for cannabinoid receptors and selective for their cannabinoid-1 (CB1) subtype. Although CB1 receptors are more abundant in the central nervous system, rimonabant has many effects in the periphery, most of which are related to prejunctional modulation of

  14. beta-agonist-induced constitutive beta(2)-adrenergic receptor activity in bovine tracheal smooth muscle

    NARCIS (Netherlands)

    de Vries, B; Meurs, H; Roffel, AF; Elzinga, CRS; Hoiting, BH; de Vries, MML; Zaagsma, J

    2000-01-01

    1 According to the two state receptor model, the beta (2)-adrenergic receptor (beta (2)-AR) isomerizes between an inactive state and a constitutively active state, which couples to the stimulatory G-protein in the absence of agonist. In bovine tracheal smooth muscle (BTSM), we investigated the

  15. Serotonin 2A receptor agonist binding in the human brain with [C]Cimbi-36

    DEFF Research Database (Denmark)

    Ettrup, A.; da Cunha-Bang, S.; McMahon, Barry P.

    2014-01-01

    [C]Cimbi-36 was recently developed as a selective serotonin 2A (5-HT) receptor agonist radioligand for positron emission tomography (PET) brain imaging. Such an agonist PET radioligand may provide a novel, and more functional, measure of the serotonergic system and agonist binding is more likely...... than antagonist binding to reflect 5-HT levels in vivo. Here, we show data from a first-in-human clinical trial with [C]Cimbi-36. In 29 healthy volunteers, we found high brain uptake and distribution according to 5-HT receptors with [C]Cimbi-36 PET. The two-tissue compartment model using arterial input...... significantly decreased [C]Cimbi-36 binding in all cortical regions with no effects in cerebellum. These results confirm that [C]Cimbi-36 binding is selective for 5-HT receptors in the cerebral cortex and that cerebellum is an appropriate reference tissue for quantification of 5-HT receptors in the human brain...

  16. Chronic sleep restriction induces long-lasting changes in adenosine and noradrenaline receptor density in the rat brain.

    Science.gov (United States)

    Kim, Youngsoo; Elmenhorst, David; Weisshaupt, Angela; Wedekind, Franziska; Kroll, Tina; McCarley, Robert W; Strecker, Robert E; Bauer, Andreas

    2015-10-01

    Although chronic sleep restriction frequently produces long-lasting behavioural and physiological impairments in humans, the underlying neural mechanisms are unknown. Here we used a rat model of chronic sleep restriction to investigate the role of brain adenosine and noradrenaline systems, known to regulate sleep and wakefulness, respectively. The density of adenosine A1 and A2a receptors and β-adrenergic receptors before, during and following 5 days of sleep restriction was assessed with autoradiography. Rats (n = 48) were sleep-deprived for 18 h day(-1) for 5 consecutive days (SR1-SR5), followed by 3 unrestricted recovery sleep days (R1-R3). Brains were collected at the beginning of the light period, which was immediately after the end of sleep deprivation on sleep restriction days. Chronic sleep restriction increased adenosine A1 receptor density significantly in nine of the 13 brain areas analysed with elevations also observed on R3 (+18 to +32%). In contrast, chronic sleep restriction reduced adenosine A2a receptor density significantly in one of the three brain areas analysed (olfactory tubercle which declined 26-31% from SR1 to R1). A decrease in β-adrenergic receptors density was seen in substantia innominata and ventral pallidum which remained reduced on R3, but no changes were found in the anterior cingulate cortex. These data suggest that chronic sleep restriction can induce long-term changes in the brain adenosine and noradrenaline receptors, which may underlie the long-lasting neurocognitive impairments observed in chronic sleep restriction. © 2015 European Sleep Research Society.

  17. Chronic sleep restriction induces long-lasting changes in adenosine and noradrenaline receptor density in the rat brain

    Science.gov (United States)

    WEISSHAUPT, ANGELA; WEDEKIND, FRANZISKA; KROLL, TINA; MCCARLEY, ROBERT W.

    2015-01-01

    SUMMARY Although chronic sleep restriction frequently produces long-lasting behavioural and physiological impairments in humans, the underlying neural mechanisms are unknown. Here we used a rat model of chronic sleep restriction to investigate the role of brain adenosine and noradrenaline systems, known to regulate sleep and wakefulness, respectively. The density of adenosine A1 and A2a receptors and β-adrenergic receptors before, during and following 5 days of sleep restriction was assessed with autoradiography. Rats (n = 48) were sleep-deprived for 18 h day–1 for 5 consecutive days (SR1–SR5), followed by 3 unrestricted recovery sleep days (R1–R3). Brains were collected at the beginning of the light period, which was immediately after the end of sleep deprivation on sleep restriction days. Chronic sleep restriction increased adenosine A1 receptor density significantly in nine of the 13 brain areas analysed with elevations also observed on R3 (+18 to +32%). In contrast, chronic sleep restriction reduced adenosine A2a receptor density significantly in one of the three brain areas analysed (olfactory tubercle which declined 26–31% from SR1 to R1). A decrease in b-adrenergic receptors density was seen in substantia innominata and ventral pallidum which remained reduced on R3, but no changes were found in the anterior cingulate cortex. These data suggest that chronic sleep restriction can induce long-term changes in the brain adenosine and noradrenaline receptors, which may underlie the long-lasting neurocognitive impairments observed in chronic sleep restriction. PMID:25900125

  18. Novel Alexa Fluor-488 Labeled Antagonist of the A2A Adenosine Receptor: Application to a Fluorescence Polarization-Based Receptor Binding Assay

    Science.gov (United States)

    Kecskés, Miklós; Kumar, T. Santhosh; Yoo, Lena; Gao, Zhan-Guo; Jacobson, Kenneth A.

    2010-01-01

    Fluorescence polarization (FP) assay has many advantages over the traditional radioreceptor binding studies. We developed an A2A adenosine receptor (AR) FP assay using a newly synthesized fluorescent antagonist of the A2AAR (MRS5346), a pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine derivative conjugated to the fluorescent dye Alexa Fluor-488. MRS5346 displayed a Ki value of 111±16 nM in radioligand binding using [3H]CGS21680 and membranes prepared from HEK293 cells stably expressing the human A2AAR. In a cyclic AMP functional assay, MRS5346 was shown to be an A2AAR antagonist. MRS5346 did not show any effect on A1 and A3 ARs in binding or the A2BAR in a cyclic AMP assay at 10 μM. Its suitability as a fluorescent tracer was indicated in an initial observation of an FP signal following A2AAR binding. The FP signal was optimal with 20 nM MRS5346 and 150 μg protein/mL HEK293 membranes. The association and dissociation kinetic parameters were readily determined using this FP assay. The Kdvalue of MRS5346 calculated from kinetic parameters was 16.5 ± 4.7 nM. In FP competition binding experiments using MRS5346 as a tracer, Ki values of known AR agonists and antagonists consistently agreed with Ki values from radioligand binding. Thus, this FP assay, which eliminates using radioisotopes, appears to be appropriate for both routine receptor binding and high-throughput screening with respect to speed of analysis, displaceable signal and precision. The approach used in the present study could be generally applicable to other GPCRs. PMID:20438717

  19. Novel Alexa Fluor-488 labeled antagonist of the A(2A) adenosine receptor: Application to a fluorescence polarization-based receptor binding assay.

    Science.gov (United States)

    Kecskés, Miklós; Kumar, T Santhosh; Yoo, Lena; Gao, Zhan-Guo; Jacobson, Kenneth A

    2010-08-15

    Fluorescence polarization (FP) assay has many advantages over the traditional radioreceptor binding studies. We developed an A(2A) adenosine receptor (AR) FP assay using a newly synthesized fluorescent antagonist of the A(2A)AR (MRS5346), a pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine derivative conjugated to the fluorescent dye Alexa Fluor-488. MRS5346 displayed a K(i) value of 111+/-16nM in radioligand binding using [(3)H]CGS21680 and membranes prepared from HEK293 cells stably expressing the human A(2A)AR. In a cyclic AMP functional assay, MRS5346 was shown to be an A(2A)AR antagonist. MRS5346 did not show any effect on A(1) and A(3) ARs in binding or the A(2B)AR in a cyclic AMP assay at 10microM. Its suitability as a fluorescent tracer was indicated in an initial observation of an FP signal following A(2A)AR binding. The FP signal was optimal with 20nM MRS5346 and 150microg protein/mL HEK293 membranes. The association and dissociation kinetic parameters were readily determined using this FP assay. The K(d) value of MRS5346 calculated from kinetic parameters was 16.5+/-4.7nM. In FP competition binding experiments using MRS5346 as a tracer, K(i) values of known AR agonists and antagonists consistently agreed with K(i) values from radioligand binding. Thus, this FP assay, which eliminates using radioisotopes, appears to be appropriate for both routine receptor binding and high-throughput screening with respect to speed of analysis, displaceable signal and precision. The approach used in the present study could be generally applicable to other GPCRs. Published by Elsevier Inc.

  20. Adenosine-diphosphate (ADP) receptor antagonists for the prevention of cardiovascular disease in type 2 diabetes mellitus (Review)

    NARCIS (Netherlands)

    Valentine, N.; Laar, F.A. van de; Driel, M.L. van

    2012-01-01

    BACKGROUND: Cardiovascular disease (CVD) is the most prevalent complication of type 2 diabetes with an estimated 65% of people with type 2 diabetes dying from a cause related to atherosclerosis. Adenosine-diphosphate (ADP) receptor antagonists like clopidogrel, ticlopidine, prasugrel and ticagrelor

  1. Synthesis and Properties of a New Water-Soluble Prodrug of the Adenosine A2A Receptor Antagonist MSX-2

    Directory of Open Access Journals (Sweden)

    Christa E. Müller

    2008-02-01

    Full Text Available The compound L-valine-3-{8-[(E-2-[3-methoxyphenylethenyl]-7-methyl-1-propargylxanthine-3-yl}propyl ester hydrochloride (MSX-4 was synthesized as an aminoacid ester prodrug of the adenosine A2A receptor antagonist MSX-2. It was found to bestable in artificial gastric acid, but readily cleaved by pig liver esterase.

  2. Inverse agonistic activity of antihistamines and suppression of histamine H1 receptor gene expression.

    Science.gov (United States)

    Mizuguchi, Hiroyuki; Ono, Shohei; Hattori, Masashi; Fukui, Hiroyuki

    2012-01-01

    Histamine H(1) receptor (H1R) expression influences the severity of allergy symptoms. We examined the effect of inverse agonists on H1R gene expression. Two inverse agonists (carebastine and mepyramine), but not the neutral antagonist oxatomide, decreased inositol phosphate accumulation. The inverse agonists also decreased H1R gene expression and down-regulated H1R mRNA below basal expression, while basal H1R mRNA expression was maintained after oxatomide treatment. These results suggest that inverse agonists more potently alleviate allergy symptoms by not only inhibiting stimulus-induced up-regulation of H1R gene expression but also by suppressing basal histamine signaling through their inverse agonistic activity.

  3. Adenosine A(2a) receptor stimulation prevents hepatocyte lipotoxicity and non-alcoholic steatohepatitis (NASH) in rats.

    Science.gov (United States)

    Imarisio, Chiara; Alchera, Elisa; Sutti, Salvatore; Valente, Guido; Boccafoschi, Francesca; Albano, Emanuele; Carini, Rita

    2012-09-01

    NEFA (non-esterified 'free' fatty acid)-mediated lipotoxicity plays a critical role in the pathogenesis of NASH (non-alcoholic steatohepatitis). In the light of the growing need for new therapeutic options for NASH, we investigated the action of A2aR (adenosine A(2a) receptor) stimulation against lipotoxicity. The effects of the A(2a)R agonist CGS21680 [2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxyamidoadenosine] were evaluated 'in vitro' in liver cells exposed to SA (stearic acid) and 'in vivo' in rats with NASH induced by 8 weeks of feeding with an MCD diet (methionine/choline-deficient diet). In cultured hepatocytes, SA promoted apoptosis by inducing MKK4 (mitogen-activated protein kinase kinase 4)/SEK1 (stress-activated protein kinase/extracellular-signal-regulated kinase kinase-1) and JNK-1/2 (c-Jun N-terminal kinase-1/2) activation. CGS21680 addition prevented JNK-1/2 activation and reduced apoptosis without interfering with lipid accumulation. CGS21680 action required PI3K (phosphoinositide 3-kinase)/Akt-mediated block of MKK4/SEK1. Consistently, PI3K inhibition with wortmannin abolished the cytoprotective action of CGS21680 and reverted MKK4 inhibition. SA lipotoxicity was also prevented by transfecting HTC cells with a specific MKK4/SEK1 siRNA (small interfering RNA). In rats receiving the MCD diet, the development of NASH was associated with MKK4/SEK1 and JNK-1/2 activation. CGS21680 (0.5 mg/kg of body weight, intraperitoneal) administration to MCD-fed rats prevented JNK-1/2 activation by acting on MKK4/SEK1. CGS21680 also effectively reduced NASH-associated ALT (alanine aminotransferase) release, hepatocyte apoptosis, liver inflammation and fibrosis without affecting hepatic steatosis. Taken together, these results demonstrate that, by inhibiting JNK-1/2, A(2a)R stimulation reduces lipotoxicity and ameliorates NASH, giving a rationale to investigate A(2a)R agonists as possible new therapeutic agents in preventing fatty liver progression to NASH.

  4. PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR (PPAR) AGONISTS AS PROMISING NEW MEDICATIONS FOR DRUG ADDICTION: PRECLINICAL EVIDENCE

    Science.gov (United States)

    Foll, Bernard Le; Ciano, Patricia Di; Panlilio, Leigh V.; Goldberg, Steven R.; Ciccocioppo, Roberto

    2013-01-01

    This review examines the growing literature on the role of peroxisome proliferator-activated receptors (PPARs) in addiction. There are two subtypes of PPAR receptors that have been studied in addiction: PPAR-α and PPAR-γ. The role of each PPAR subtype in common models of addictive behavior, mainly pre-clinical models, is summarized. In particular, studies are reviewed that investigated the effects of PPAR-α agonists on relapse, sensitization, conditioned place preference, withdrawal and drug intake, and effects of PPAR-γ agonists on relapse, withdrawal and drug intake. Finally, studies that investigated the effects of PPAR agonists on neural pathways of addiction are reviewed. Taken together this preclinical data indicates that PPAR agonists are promising new medications for drug addiction treatment. PMID:23614675

  5. Common genetic polymorphisms of adenosine A2A receptor do not influence response to regadenoson.

    Science.gov (United States)

    Berlacher, Mark; Mastouri, Ronald; Philips, Santosh; Skaar, Todd C; Kreutz, Rolf P

    2017-04-01

    Hemodynamic response to regadenoson varies greatly, and underlying mechanisms for variability are poorly understood. We hypothesized that five common variants of adenosine A2A receptor (ADORA2A) are associated with altered response to regadenoson. Consecutive subjects (n = 357) undergoing resting regadenoson nuclear stress imaging were enrolled. Genotyping was performed using Taqman-based assays for rs5751862, rs2298383, rs3761422, rs2267076 and rs5751876. There was no significant difference in heart rate or blood pressure between different genotypes following regadenoson administration. There was also no significant difference in myocardial ischemia detected by nuclear perfusion imaging as defined by summed difference score, or in self-reported side effects among the genotypes tested. The common A2A variants studied are not associated with variability in hemodynamic response to regadenoson or variability in detection of ischemia with nuclear perfusion stress imaging.

  6. The RegEx trial: a randomized, double-blind, placebo- and active-controlled pilot study combining regadenoson, a selective A(2A) adenosine agonist, with low-level exercise, in patients undergoing myocardial perfusion imaging.

    Science.gov (United States)

    Thomas, Gregory S; Thompson, Randall C; Miyamoto, Michael I; Ip, Tze K; Rice, Deborah L; Milikien, Douglas; Lieu, Hsiao D; Mathur, Vandana S

    2009-01-01

    Although vasodilator stress myocardial perfusion imaging (MPI) is increasingly performed with exercise, adenosine A(2A) receptor agonists have not been studied with exercise. To determine the safety of administering regadenoson during exercise and, secondarily, to evaluate image quality, patient acceptance, and detection of perfusion defects. Patients requiring pharmacologic MPI received a standard adenosine-supine protocol (AdenoSup, n = 60) and were then randomized (2:1) in a double-blind manner to low-level exercise with bolus intravenous injection of regadenoson (RegEx, n = 39) or placebo (PlcEx, n = 21). Adverse events occurred in 95%, 77%, and 33% of patients receiving AdenoSup, RegEx, and PlcEx, respectively. Peak heart rate was 13 beats per minute (bpm) and 21 bpm greater following RegEx compared to that following PlcEx and AdenoSup, respectively (P = .006 and or = 20 mm Hg showed no important differences between RegEx and PlcEx. No occurrences of 2nd degree or higher AV block were observed following RegEx or PlcEx; one patient developed 2nd degree AV block following AdenoSup. The mean heart-to-liver and heart-to-gut ratios were improved on RegEx vs AdenoSup: 0.85 (0.34) vs 0.65 (0.26), P regadenoson with low-level exercise is feasible, well tolerated, and associated with fewer side effects compared to AdenoSup.

  7. Adenosine A2B receptor blockade slows growth of bladder and breast tumors1

    Science.gov (United States)

    Cekic, Caglar; Sag, Duygu; Li, Yuesheng; Theodorescu, Dan; Strieter, Robert M.; Linden, Joel

    2011-01-01

    The accumulation of high levels of adenosine in tumors activates A2A and A2B receptors on immune cells and inhibits their ability to suppress tumor growth. Deletion of A2AARs has been reported to activate anti-tumor T cells, stimulates DC function and inhibits angiogenesis. Here we evaluated the effects of intermittent intratumor injection of a non-selective adenosine receptor antagonist, aminophylline (AMO, theophylline ethylenediamine) and, for the first time, a selective A2BAR antagonist, ATL801. AMO and ATL801 slowed the growth of MB49 bladder and 4T1 breast tumors in syngeneic mice, and reduced by 85% metastasizes of breast cancer cells from mammary fat to lung. Based on experiments with A2AAR−/− or A2BAR−/− mice, the effect of AMO injection was unexpectedly attributed to A2BAR and not to A2AAR blockade. AMO and ATL801 significantly increased tumor levels of IFNγ and the interferon-inducible chemokine CXCL10, which is a ligand for CXCR3. This was associated with an increase in activated tumor-infiltrating CXCR3+ T cells and a decrease in endothelial cell precursors within tumors. Tumor growth inhibition by AMO or ATL801 was eliminated in CXCR3−/− mice and in RAG1−/− mice that lack mature T cells. In RAG1−/− mice A2BAR deletion enhanced CD86 expression on CD11b- DCs. Bone marrow chimera experiments demonstrated that CXCR3 and A2BAR expression on bone marrow cells are required for the anti-tumor effects of AMO. The data suggest that blockade of A2BARs enhances DC activation and CXCR3-dependent anti-tumor responses. PMID:22116822

  8. Free Fatty Acid Receptor 1 (FFA1/GPR40) Agonists

    DEFF Research Database (Denmark)

    Christiansen, Elisabeth; Due-Hansen, Maria E; Urban, Christian

    2012-01-01

    FFA1 (GPR40) is a new target for treatment of type 2 diabetes. We recently identified the potent FFA1 agonist TUG-469 (5). Inspired by the structurally related TAK-875, we explored the effects of a mesylpropoxy appendage on 5. The appendage significantly lowers lipophilicity and improves metabolic...

  9. Purinergic agonist induction of metallothionein.

    Science.gov (United States)

    Xiong, X; Garrett, S H; Arizono, K; Brady, F O

    1992-10-01

    Metallothionein (MT) protein is readily induced in vivo in rat liver by adenosine and adenosine agonists (2-chloroadenosine, 5-(N-ethyl) carboxamido adenosine, and 5-chloro-5-deoxyadenosine). These presumably operate via AMP/adenosine receptors of the P1 (A2) type, which use the cAMP pathway. ATP was ineffective as an inducer for MT. 2-Chloroadenosine was the most effective inducer (7.27-fold at 11 hr). This induction was blockable by the adenosine antagonists, caffeine and theophylline. MT protein induction by 2-chloroadenosine in primary cultured rat hepatocytes was modest (1.55-fold), but this was also blocked by theophylline. MT mRNA induction was assessed using dot blot and Northern gel assays. Large inductions by 2-chloroadenosine (5.1- to 41-fold) were seen, and these were detectable as early as 2 hr in vivo. Two rat hepatoma cell lines (EC3 and 2M) were studied in vitro. Modest inductions of MT mRNA were seen: 2.10-fold for EC3 and 4.12-fold for 2M. Our studies implicate the potential role of the purinergic system in the modulation of transcription of MT genes in rat liver. The sources of adenosine in vivo that might cause induction of MT mRNA and protein are not well defined, but adenosine may be important as a signal in stress response situations involving tissue damage, such as ischemia, hypoxia, and hemorrhagic shock.

  10. Role of dopamine receptor agonists in the treatment of early Parkinson's disease.

    Science.gov (United States)

    Bonuccelli, Ubaldo; Del Dotto, Paolo; Rascol, Olivier

    2009-12-01

    In the last two decades, the usefulness of dopamine receptor agonists in the symptomatic treatment of Parkinson' disease (PD) has been demonstrated in many randomized controlled clinical trials. The initial role of such compounds as an adjunctive therapy to L-dopa to improve motor fluctuations has now expanded to the treatment of early PD as initial monotherapy. The rationale for the use of dopamine receptor agonists in early disease is to delay or reduce the incidence of motor complications resulting from long-term L-dopa therapy, probably by virtue of less pulsatile stimulation of postsynaptic dopamine receptors. Indeed, controlled trials with both ergot and non-ergot dopamine receptor agonists, such as cabergoline, pergolide, pramipexole and ropinirole, have shown lower risk of motor fluctuations and dyskinesias than with L-dopa, when used as monotherapy in early PD patients. The benefit of agonists in preventing motor complications is, however, balanced by a smaller effect on motor symptoms compared with L-dopa. Moreover, a greater incidence of side-effects, particularly somnolence, hallucinations and leg oedema, occurs with dopamine receptor agonists. Because of the risk of fibrotic reactions, ergot derivatives (bromocriptine, cabergoline, and pergolide) are not recommended as first-line antiparkinsonian medication. In younger patients, who are usually more prone to developing L-dopa-induced motor complications, the initial treatment with dopamine receptor agonists can be recommended. Further pharmacological refinement of PD management with these drugs may result from new formulations of old drugs, such as once-daily prolonged-release ropinirole, or new agonists, such as the rotigotine patch, that can allow more continuous dopaminergic stimulation and improve patient compliance with the drug treatment. Theoretically, another advantage of dopamine receptor agonists is the potential for a neuroprotective effect, through many different mechanisms of actions

  11. Click-Chemistry-Mediated Synthesis of Selective Melanocortin Receptor 4 Agonists.

    Science.gov (United States)

    Palmer, Daniel; Gonçalves, Juliana P L; V Hansen, Louise; Wu, Boqian; Hald, Helle; Schoffelen, Sanne; Diness, Frederik; Le Quement, Sebastian T; Nielsen, Thomas E; Meldal, Morten

    2017-10-24

    The melanocortin receptor 4 (MC4R) subtype of the melanocortin receptor family is a target for therapeutics to ameliorate metabolic dysfunction. Endogenous MC4R agonists possess a critical pharmacophore (HFRW), and cyclization of peptide agonists often enhances potency. Thus, 17 cyclized peptides were synthesized by solid phase click chemistry to develop novel, potent, selective MC4R agonists. Using cAMP measurements and a transcriptional reporter assay, we observed that several constrained agonists generated by a cycloaddition reaction displayed high selectivity (223- to 467-fold) toward MC4R over MC3R and MC5R receptor subtypes without compromising agonist potency. Significant variation was also observed between the EC50 values for the two assays, with robust levels of reporter expression measured at lower concentrations than those effecting appreciable increases in cAMP levels for the majority of the compounds tested. Collectively, we characterized significant elements that modulate the activity of the core pharmacophore for MC4R and provide a rationale for careful assay selection for agonist screening.

  12. GLP-1 receptor agonists or DPP-4 inhibitors: how to guide the clinician?

    Science.gov (United States)

    Scheen, André J

    2013-12-01

    Pharmacological treatment of type 2 diabetes has been enriched during recent years, with the launch of incretin therapies targeting glucagon-like peptide-1 (GLP-1). Such medications comprise either GLP-1 receptor agonists, with short (one or two daily injections: exenatide, liraglutide, lixisenatide) or long duration (one injection once weekly: extended-released exenatide, albiglutide, dulaglutide, taspoglutide); or oral compounds inhibiting dipeptidyl peptidase-4 (DPP-4), the enzyme that inactives GLP-1, also called gliptins (sitagliptin, vildagliptin, saxagliptin, linagliptin, alogliptin). Although both pharmacological approaches target GLP-1, important differences exist concerning the mode of administration (subcutaneous injection versus oral ingestion), the efficacy (better with GLP-1 agonists), the effects on body weight and systolic blood pressure (diminution with agonists versus neutrality with gliptins), the tolerance profile (nausea and possibly vomiting with agonists) and the cost (higher with GLP-1 receptor agonists). Both agents may exert favourable cardiovascular effects. Gliptins may represent a valuable alternative to a sulfonylurea or a glitazone after failure of monotherapy with metformin while GLP-1 receptor agonists may be considered as a good alternative to insulin (especially in obese patients) after failure of a dual oral therapy. However, this scheme is probably too restrictive and modalities of using incretins are numerous, in almost all stages of type 2 diabetes. Physicians may guide the pharmacological choice based on clinical characteristics, therapeutic goals and patient's preference. Copyright © 2013. Published by Elsevier Masson SAS.

  13. Alpha/sub 1/ receptor coupling events initiated by methoxy-substituted tolazoline partial agonists

    Energy Technology Data Exchange (ETDEWEB)

    Wick, P.; Keung, A.; Deth, R.

    1986-03-01

    A series of mono- and dimethyoxy substituted tolazoline derivatives, known to be partial agonists at the alpha/sub 1/ receptor, were compared with the ..cap alpha../sub 1/ selective full agonist phenylephrine (PE) on isolated strips of rabbit aorta Agonist activity was evaluated in contraction, /sup 45/Ca influx, /sup 45/Ca efflux, and /sup 32/P-Phospholipid labelling studies. Maximum contractile responses for the 2-, 3-, and 3, 5- methoxy substituted tolazoline derivatives (10/sup -5/M) were 53.8, 67.6 and 99.7% of the PE (10/sup -5/M) response respectively. These same partial agonists caused a stimulation of /sup 45/Ca influx to the extent of 64, 86, and 95% of the PE response respectively. In /sup 45/Ca efflux studies, (a measure of the intracellular Ca/sup +2/ release) the tolazolines caused: 30%, 63%, and 78% of the PE stimulated level. /sup 32/P-Phosphatidic acid (PA) labelling was measured as an index of PI turnover after ..cap alpha../sub 1/ receptor stimulation. Compared to PE, the 2-, 3-, and 3,5- methoxy substituted tolazoline derivatives caused 22, 46, and 72% PA labelling. The above values are all in reasonable accord with the rank order or agonist activity shown in maximum contractile responses. The results of this investigation suggest that partial agonists stimulate ..cap alpha.. receptor coupling events at a level which is quantitatively comparable to their potencies in causing contraction of arterial smooth muscle.

  14. Triazoloquinazolines as Human A3 Adenosine Receptor Antagonists: A QSAR Study

    Directory of Open Access Journals (Sweden)

    Dae-Sil Lee

    2006-11-01

    Full Text Available Multiple linear regression analysis was performed on the quantitative structure-activity relationships (QSAR of the triazoloquinazoline adenosine antagonists for human A3receptors. The data set used for the QSAR analysis encompassed the activities of 33triazoloquinazoline derivatives and 72 physicochemical descriptors. A template moleculewas derived using the known molecular structure for one of the compounds when bound tothe human A2B receptor, in which the amide bond was in a cis-conformation. All the testcompounds were aligned to the template molecule. In order to identify a reasonable QSARequation to describe the data set, we developed a multiple linear regression program thatexamined every possible combination of descriptors. The QSAR equation derived from thisanalysis indicates that the spatial and electronic effects is greater than that of hydrophobiceffects in binding of the antagonists to the human A3 receptor. It also predicts that a largesterimol length parameter is advantageous to activity, whereas large sterimol widthparameters and fractional positive partial surface areas are nonadvatageous.

  15. Leishmania infantum Parasites Subvert the Host Inflammatory Response through the Adenosine A2A Receptor to Promote the Establishment of Infection

    OpenAIRE

    Lima, Mikhael H. F.; Sacramento, Lais A.; Gustavo F.S. Quirino; Marcela D Ferreira; Luciana Benevides; Santana, Alynne K. M.; Fernando Q Cunha; Almeida, Roque P; Silva, João S.; Vanessa Carregaro

    2017-01-01

    Adenosine is an endogenously released purine nucleoside that signals through four widely expressed G protein-coupled receptors: A1, A2A, A2B, and A3. Of these, A2AR is recognized as mediating major adenosine anti-inflammatory activity. During cutaneous leishmaniasis, adenosine induces immunosuppression, which promotes the establishment of infection. Herein, we demonstrated that A2AR signaling is exploited by Leishmania infantum parasites, the etiologic agent that causes Visceral Leishmaniasis...

  16. Cefminox, a Dual Agonist of Prostacyclin Receptor and Peroxisome Proliferator-Activated Receptor-Gamma Identified by Virtual Screening, Has Therapeutic Efficacy against Hypoxia-Induced Pulmonary Hypertension in Rats

    Directory of Open Access Journals (Sweden)

    Jingwen Xia

    2018-02-01

    Full Text Available Prostacyclin receptor (IP and peroxisome proliferator-activated receptor-gamma (PPARγ are both potential targets for treatment of pulmonary arterial hypertension (PAH. Expression of IP and PPARγ decreases in PAH, suggesting that screening of dual agonists of IP and PPARγ might be an efficient method for drug discovery. Virtual screening (VS of potential IP–PPARγ dual-targeting agonists was performed in the ZINC database. Ten of the identified compounds were further screened, and cefminox was found to dramatically inhibit growth of PASMCs with no obvious cytotoxicity. Growth inhibition by cefminox was partially reversed by both the IP antagonist RO113842 and the PPARγ antagonist GW9662. Investigation of the underlying mechanisms of action demonstrated that cefminox inhibits the protein kinase B (Akt/mammalian target of rapamycin (mTOR signaling pathway through up-regulation of the expression of phosphatase and tensin homolog (PTEN, which is inhibited by GW9662, and enhances cyclic adenosine monophosphate (cAMP production in PASMCs (which is inhibited by RO113842. In a rat model of hypoxia-induced pulmonary hypertension, cefminox displayed therapeutic efficacy not inferior to that of the prostacyclin analog iloprost or the PPARγ agonist rosiglitazone. Our results identified cefminox as a dual agonist of IP and PPARγ that significantly inhibits PASMC proliferation by up-regulation of PTEN and cAMP, suggesting that it has potential for treatment of PAH.

  17. Anticonvulsant activity of some vanilloid receptor agonists | Awad ...

    African Journals Online (AJOL)

    Background: Vanilloid receptors 1 (VR 1), a group of transient receptor potential channels family was cloned in 1997. They were found to be a potential target for treatment of different acute and chronic pain disorder. Recently these receptors were reported to be involved in several pathological conditions. Objectives: The ...

  18. Adenosine A1 receptor-mediated inhibition of in vitro prolactin secretion from the rat anterior pituitary

    Directory of Open Access Journals (Sweden)

    D.L.W. Picanço-Diniz

    2006-11-01

    Full Text Available In previous studies, we demonstrated biphasic purinergic effects on prolactin (PRL secretion stimulated by an adenosine A2 agonist. In the present study, we investigated the role of the activation of adenosine A1 receptors by (R-N6-(2-phenylisopropyladenosine (R-PIA at the pituitary level in in vitro PRL secretion. Hemipituitaries (one per cuvette in five replicates from adult male rats were incubated. Administration of R-PIA (0.001, 0.01, 0.1, 1, and 10 µM induced a reduction of PRL secretion into the medium in a U-shaped dose-response curve. The maximal reduction was obtained with 0.1 µM R-PIA (mean ± SEM, 36.01 ± 5.53 ng/mg tissue weight (t.w. treatment compared to control (264.56 ± 15.46 ng/mg t.w.. R-PIA inhibition (0.01 µM = 141.97 ± 15.79 vs control = 244.77 ± 13.79 ng/mg t.w. of PRL release was blocked by 1 µM cyclopentyltheophylline, a specific A1 receptor antagonist (1 µM = 212.360 ± 26.560 ng/mg t.w., whereas cyclopentyltheophylline alone (0.01, 0.1, 1 µM had no effect. R-PIA (0.001, 0.01, 0.1, 1 µM produced inhibition of PRL secretion stimulated by both phospholipase C (0.5 IU/mL; 977.44 ± 76.17 ng/mg t.w. and dibutyryl cAMP (1 mM; 415.93 ± 37.66 ng/mg t.w. with nadir established at the dose of 0.1 µM (225.55 ± 71.42 and 201.9 ± 19.08 ng/mg t.w., respectively. Similarly, R-PIA (0.01 µM decreased (242.00 ± 24.00 ng/mg t.w. the PRL secretion stimulated by cholera toxin (0.5 mg/mL; 1050.00 ± 70.00 ng/mg t.w.. In contrast, R-PIA had no effect (468.00 ± 34.00 ng/mg t.w. on PRL secretion stimulation by pertussis toxin (0.5 mg/mL; 430.00 ± 26.00 ng/mg t.w.. These results suggest that inhibition of PRL secretion after A1 receptor activation by R-PIA is mediated by a Gi protein-dependent mechanism.

  19. [Development of chronic myelogenous leukemia during treatment with TPO receptor agonist for ITP].

    Science.gov (United States)

    Hattori, Hideki; Kuwayama, Maki; Takamori, Hiroyuki; Nishiura, Nobuko; Karasuno, Takahiro

    2014-12-01

    We report a 77-year-old Japanese man with idiopathic thrombocytopenic purpura (ITP) which developed into chronic myelogenous leukemia (CML) during treatment with eltrombopag, a thrombopoetin (TPO) receptor agonist, because the disease was refractory to prednisolone. Eltrombopag can induce a good reaction in terms of the platelet count. However, CML in the chronic phase developed in about 19 months in our present case. Dasatinib was administered because he had diabetes. However, a blastic crisis immediately occurred. He died despite switching to Nilotinib. Recently, the occurrence of myelofibrosis and hematological malignancies due to long-term use of TPO receptor agonists has become a concern. This is the first report of a TPO receptor agonist possibly contributing to CML onset and crisis.

  20. Assembly of high-affinity insulin receptor agonists and antagonists from peptide building blocks

    Science.gov (United States)

    Schäffer, Lauge; Brissette, Renee E.; Spetzler, Jane C.; Pillutla, Renuka C.; Østergaard, Søren; Lennick, Michael; Brandt, Jakob; Fletcher, Paul W.; Danielsen, Gillian M.; Hsiao, Ku-Chuan; Andersen, Asser S.; Dedova, Olga; Ribel, Ulla; Hoeg-Jensen, Thomas; Hertz Hansen, Per; Blume, Arthur J.; Markussen, Jan; Goldstein, Neil I.

    2003-04-01

    Insulin is thought to elicit its effects by crosslinking the two extracellular -subunits of its receptor, thereby inducing a conformational change in the receptor, which activates the intracellular tyrosine kinase signaling cascade. Previously we identified a series of peptides binding to two discrete hotspots on the insulin receptor. Here we show that covalent linkage of such peptides into homodimers or heterodimers results in insulin agonists or antagonists, depending on how the peptides are linked. An optimized agonist has been shown, both in vitro and in vivo, to have a potency close to that of insulin itself. The ability to construct such peptide derivatives may offer a path for developing agonists or antagonists for treatment of a wide variety of diseases.

  1. Optimisation of in silico derived 2-aminobenzimidazole hits as unprecedented selective kappa opioid receptor agonists

    DEFF Research Database (Denmark)

    Sasmal, Pradip K; Krishna, C Vamsee; Sudheerkumar Adabala, S

    2015-01-01

    Kappa opioid receptor (KOR) is an important mediator of pain signaling and it is targeted for the treatment of various pains. Pharmacophore based mining of databases led to the identification of 2-aminobenzimidazole derivative as KOR agonists with selectivity over the other opioid receptors DOR...... and MOR. A short SAR exploration with the objective of identifying more polar and hence less brain penetrant agonists is described herewith. Modeling studies of the recently published structures of KOR, DOR and MOR are used to explain the receptor selectivity. The synthesis, biological evaluation and SAR...... of novel benzimidazole derivatives as KOR agonists are described. The in vivo proof of principle for anti-nociceptive effect with a lead compound from this series is exemplified....

  2. Ghrelin receptor inverse agonists: identification of an active peptide core and its interaction epitopes on the receptor

    DEFF Research Database (Denmark)

    Holst, Birgitte; Lang, Manja; Brandt, Erik

    2006-01-01

    [D-Arg1,D-Phe5,D-Trp7,9,Leu11]Substance P functions as a low-potency antagonist but a high-potency full inverse agonist on the ghrelin receptor. Through a systematic deletion and substitution analysis of this peptide, the C-terminal carboxyamidated pentapeptide wFwLX was identified as the core...... structure, which itself displayed relatively low inverse agonist potency. Mutational analysis at 17 selected positions in the main ligand-binding crevice of the ghrelin receptor demonstrated that ghrelin apparently interacts only with residues in the middle part of the pocket [i.e., between transmembrane...... upon both AspII:20 and GluIII:09. The identified pharmacophore can possibly serve as the basis for targeted discovery of also nonpeptide inverse agonists for the ghrelin receptor....

  3. Identification of adiponectin receptor agonist utilizing a fluorescence polarization based high throughput assay.

    Directory of Open Access Journals (Sweden)

    Yiyi Sun

    Full Text Available Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (--arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases.

  4. Identification of Adiponectin Receptor Agonist Utilizing a Fluorescence Polarization Based High Throughput Assay

    Science.gov (United States)

    Sun, Yiyi; Zang, Zhihe; Zhong, Ling; Wu, Min; Su, Qing; Gao, Xiurong; Zan, Wang; Lin, Dong; Zhao, Yan; Zhang, Zhonglin

    2013-01-01

    Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (-)-arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases. PMID:23691032

  5. Small-molecule agonists for the glucagon-like peptide 1 receptor

    DEFF Research Database (Denmark)

    Knudsen, Lotte Bjerre; Kiel, Dan; Teng, Min

    2007-01-01

    The peptide hormone glucagon-like peptide (GLP)-1 has important actions resulting in glucose lowering along with weight loss in patients with type 2 diabetes. As a peptide hormone, GLP-1 has to be administered by injection. Only a few small-molecule agonists to peptide hormone receptors have been...... described and none in the B family of the G protein coupled receptors to which the GLP-1 receptor belongs. We have discovered a series of small molecules known as ago-allosteric modulators selective for the human GLP-1 receptor. These compounds act as both allosteric activators of the receptor...

  6. Induction of TRPV1 desensitization by a biased receptor agonist

    OpenAIRE

    Wang, Elaine E; Li, Hui; Wang, Shu; Chuang, Alexander Y; Chuang, Huai-hu

    2011-01-01

    Selective suppression of hyperactive sensory neurons is an attractive strategy for managing pathological pain. Blocking Na+ channels to eliminate action potentials and desensitizing transduction channels can both reduce sensory neuron excitability. The novel synthetic vanilloid ligand cap-ET preserves agonist activation of intracellular Ca2+ signals and large organic cation transport but loses effective electric current induction. Cap-ET can therefore be used to deliver the membrane impermeab...

  7. Receptor structure-based discovery of non-metabolite agonists for the succinate receptor GPR91.

    Science.gov (United States)

    Trauelsen, Mette; Rexen Ulven, Elisabeth; Hjorth, Siv A; Brvar, Matjaz; Monaco, Claudia; Frimurer, Thomas M; Schwartz, Thue W

    2017-12-01

    Besides functioning as an intracellular metabolite, succinate acts as a stress-induced extracellular signal through activation of GPR91 (SUCNR1) for which we lack suitable pharmacological tools. Here we first determined that the cis conformation of the succinate backbone is preferred and that certain backbone modifications are allowed for GPR91 activation. Through receptor modeling over the X-ray structure of the closely related P2Y1 receptor, we discovered that the binding pocket is partly occupied by a segment of an extracellular loop and that succinate therefore binds in a very different mode than generally believed. Importantly, an empty side-pocket is identified next to the succinate binding site. All this information formed the basis for a substructure-based search query, which, combined with molecular docking, was used in virtual screening of the ZINC database to pick two serial mini-libraries of a total of only 245 compounds from which sub-micromolar, selective GPR91 agonists of unique structures were identified. The best compounds were backbone-modified succinate analogs in which an amide-linked hydrophobic moiety docked into the side-pocket next to succinate as shown by both loss- and gain-of-function mutagenesis. These compounds displayed GPR91-dependent activity in altering cytokine expression in human M2 macrophages similar to succinate, and importantly were devoid of any effect on the major intracellular target, succinate dehydrogenase. These novel, synthetic non-metabolite GPR91 agonists will be valuable both as pharmacological tools to delineate the GPR91-mediated functions of succinate and as leads for the development of GPR91-targeted drugs to potentially treat low grade metabolic inflammation and diabetic complications such as retinopathy and nephropathy. Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

  8. The GABAA receptor agonist THIP is neuroprotective in organotypic hippocampal slice cultures

    DEFF Research Database (Denmark)

    Kristensen, Bjarne Winther; Noraberg, Jens; Zimmer, Jens

    2003-01-01

    The potential neuroprotective effects of the GABA(A) receptor agonists THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) and muscimol, and the selective GluR5 kainate receptor agonist ATPA ((RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl)propanoic acid), which activates GABAergic interneu......, while muscimol (100-1000 microM) and ATPA (1-3 microM) were without effect. The results demonstrate that direct GABA(A) agonism can mediate neuroprotection in the hippocampus in vitro as previously suggested in vivo....

  9. Reports of pathological gambling, hypersexuality, and compulsive shopping associated with dopamine receptor agonist drugs.

    Science.gov (United States)

    Moore, Thomas J; Glenmullen, Joseph; Mattison, Donald R

    2014-12-01

    Severe impulse control disorders involving pathological gambling, hypersexuality, and compulsive shopping have been reported in association with the use of dopamine receptor agonist drugs in case series and retrospective patient surveys. These agents are used to treat Parkinson disease, restless leg syndrome, and hyperprolactinemia. To analyze serious adverse drug event reports about these impulse control disorders received by the US Food and Drug Administration (FDA) and to assess the relationship of these case reports with the 6 FDA-approved dopamine receptor agonist drugs. We conducted a retrospective disproportionality analysis based on the 2.7 million serious domestic and foreign adverse drug event reports from 2003 to 2012 extracted from the FDA Adverse Event Reporting System. Cases were selected if they contained any of 10 preferred terms in the Medical Dictionary for Regulatory Activities (MedDRA) that described the abnormal behaviors. We used the proportional reporting ratio (PRR) to compare the proportion of target events to all serious events for the study drugs with a similar proportion for all other drugs. We identified 1580 events indicating impulse control disorders from the United States and 21 other countries:710 fordopamine receptor agonist drugs and 870 for other drugs. The dopamine receptor agonist drugs had a strong signal associated with these impulse control disorders (n = 710; PRR = 277.6, P < .001). The association was strongest for the dopamine agonists pramipexole (n = 410; PRR = 455.9, P < .001) and ropinirole (n = 188; PRR = 152.5, P < .001), with preferential affinity for the dopamine D3 receptor. A signal was also seen for aripiprazole, an antipsychotic classified as a partial agonist of the D3 receptor (n = 37; PRR = 8.6, P < .001). Our findings confirm and extend the evidence that dopamine receptor agonist drugs are associated with these specific impulse control disorders. At present

  10. Adenosine signaling promotes neuronal, catecholaminergic differentiation of primary neural crest cells and CNS-derived CAD cells.

    Science.gov (United States)

    Bilodeau, Matthew L; Ji, Ming; Paris, Maryline; Andrisani, Ourania M

    2005-07-01

    In neural crest (NC) cultures cAMP signaling is an instructive signal in catecholaminergic, sympathoadrenal cell development. However, the extracellular signals activating the cAMP pathway during NC cell development have not been identified. We demonstrate that in avian NC cultures, evidenced by tyrosine hydroxylase expression and catecholamine biosynthesis, adenosine and not adrenergic signaling, together with BMP2, promotes sympathoadrenal cell development. In NC cultures, addition of the adenosine receptor agonist NECA in the presence of BMP2 promotes sympathoadrenal cell development, whereas the antagonist CGS 15943 or the adenosine degrading enzyme adenosine deaminase (ADA) suppresses TH expression. Importantly, NC cells express A2A and A2B receptors which couple with Gsalpha increasing intracellular cAMP. Employing the CNS-derived catecholaminergic CAD cell line, we also demonstrate that neuronal differentiation mediated by serum withdrawal is further enhanced by treatment with IBMX, a cAMP-elevating agent, or the adenosine receptor agonist NECA, acting via cAMP. By contrast, the adenosine receptor antagonist CGS 15943 or the adenosine degrading enzyme ADA inhibits CAD cell neuronal differentiation mediated by serum withdrawal. These results support that adenosine is a physiological signal in neuronal differentiation of the CNS-derived catecholaminergic CAD cell line and suggest that adenosine signaling is involved in NC cell development in vivo.

  11. Interleukin-24 as a target cytokine of environmental aryl hydrocarbon receptor agonist exposure in the lung.

    Science.gov (United States)

    Luo, Yueh-Hsia; Kuo, Yu-Chun; Tsai, Ming-Hsien; Ho, Chia-Chi; Tsai, Hui-Ti; Hsu, Chin-Yu; Chen, Yu-Cheng; Lin, Pinpin

    2017-06-01

    Exposure to environmental aryl hydrocarbon receptor (AhR) agonists, such as halogenated aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), has great impacts on the development of various lung diseases. As emerging molecular targets for AhR agonists, cytokines may contribute to the inflammatory or immunotoxic effects of environmental AhR agonists. However, general cytokine expression may not specifically indicate environmental AhR agonist exposure. By comparing cytokine and chemokine expression profiles in human lung adenocarcinoma cell line CL5 treated with AhR agonists and the non-AhR agonist polychlorinated biphenyl (PCB) 39, we identified a target cytokine of environmental AhR agonist exposure of in the lungs. Thirteen cytokine and chemokine genes were altered in the AhR agonists-treated cells, but none were altered in the PCB39-treated cells. Interleukin (IL)-24 was the most highly induced gene among AhR-modulated cytokines. Cotreatment with AhR antagonist completely prevented IL-24 induction by AhR agonists in the CL5 cells. Knockdown AhR expression with short-hairpin RNA (shRNA) significantly reduced benzo[a]pyrene (BaP)-induced IL-24 mRNA levels. We further confirmed that gene transcription, but not mRNA stability, was involved in IL-24 upregulation by BaP. Particulate matter (PM) in the ambient air contains some PAHs and is reported to activate AhR. Oropharyngeal aspiration of PM significantly increased IL-24 levels in lung epithelia and in bronchoalveolar lavage fluid of mice 4weeks after treatment. Thus, our data suggests that IL-24 is a pulmonary exposure target cytokine of environmental AhR agonists. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Phosphopeptide mapping of cholecystokinin receptors on agonist-stimulated native pancreatic acinar cells.

    Science.gov (United States)

    Ozcelebi, F; Miller, L J

    1995-02-17

    The cholecystokinin (CCK) receptor on the rat pancreatic acinar cell is a G protein-coupled receptor that is phosphorylated in response to homologous and heterologous agonist stimulation. In this work we have studied the stoichiometry of receptor phosphorylation and have utilized one-dimensional phosphopeptide mapping after cyanogen bromide cleavage to demonstrate that the third intracellular loop is the predominant domain of phosphorylation of this receptor in response to these treatments. Of the average 5 mol of phosphate/mol of receptor, greater than 95% was on the third loop, with the remainder residing on the carboxyl-terminal tail. Serine residues were the site of greater than 95% of phosphorylation, with threonine representing the remainder, and no phosphotyrosine was detected. Further, we have utilized two-dimensional phosphopeptide mapping after subtilisin cleavage to identify differing sites of CCK receptor phosphorylation which are dependent on the agonist utilized to stimulate this cell. Both qualitative and quantitative differences in phosphorylation sites were observed after acinar cell stimulation with different protein kinase C agonists. Further, distinct phosphopeptides on the map were identified as representing substrate(s) of a staurosporine-insensitive kinase activity stimulated only by receptor occupation with native CCK and were felt to represent site(s) of action of a member of the G protein-coupled receptor kinase family. This represents a sensitive and powerful approach that is applicable to sparse receptors residing in their native cellular environment to assess possible differences in patterns of phosphorylation which may be important in agonist-specific receptor regulation.

  13. Striatal pre- and postsynaptic profile of adenosine A(2A receptor antagonists.

    Directory of Open Access Journals (Sweden)

    Marco Orru

    2011-01-01

    Full Text Available Striatal adenosine A(2A receptors (A(2ARs are highly expressed in medium spiny neurons (MSNs of the indirect efferent pathway, where they heteromerize with dopamine D(2 receptors (D(2Rs. A(2ARs are also localized presynaptically in cortico-striatal glutamatergic terminals contacting MSNs of the direct efferent pathway, where they heteromerize with adenosine A(1 receptors (A(1Rs. It has been hypothesized that postsynaptic A(2AR antagonists should be useful in Parkinson's disease, while presynaptic A(2AR antagonists could be beneficial in dyskinetic disorders, such as Huntington's disease, obsessive-compulsive disorders and drug addiction. The aim or this work was to determine whether selective A(2AR antagonists may be subdivided according to a preferential pre- versus postsynaptic mechanism of action. The potency at blocking the motor output and striatal glutamate release induced by cortical electrical stimulation and the potency at inducing locomotor activation were used as in vivo measures of pre- and postsynaptic activities, respectively. SCH-442416 and KW-6002 showed a significant preferential pre- and postsynaptic profile, respectively, while the other tested compounds (MSX-2, SCH-420814, ZM-241385 and SCH-58261 showed no clear preference. Radioligand-binding experiments were performed in cells expressing A(2AR-D(2R and A(1R-A(2AR heteromers to determine possible differences in the affinity of these compounds for different A(2AR heteromers. Heteromerization played a key role in the presynaptic profile of SCH-442416, since it bound with much less affinity to A(2AR when co-expressed with D(2R than with A(1R. KW-6002 showed the best relative affinity for A(2AR co-expressed with D(2R than co-expressed with A(1R, which can at least partially explain the postsynaptic profile of this compound. Also, the in vitro pharmacological profile of MSX-2, SCH-420814, ZM-241385 and SCH-58261 was is in accordance with their mixed pre- and postsynaptic profile

  14. The Quintiles Prize Lecture 2004. The identification of the adenosine A2B receptor as a novel therapeutic target in asthma.

    Science.gov (United States)

    Holgate, Stephen T

    2005-08-01

    Adenosine is a powerful bronchoconstrictor of asthmatic, but not normal, airways. In vitro studies on isolated human mast cells and basophils revealed that adenosine and selective analogues augmented inflammatory mediator release from mast cells by stimulating A(2) receptors. Pharmacological blockade of mast cell mediator release in vivo also attenuated adenosine-induced bronchoconstriction, as did theophylline, by adenosine A(2) receptor antagonism. Further in vitro studies revealed that the asthmatic response to adenosine is likely to be mediated via the A(2B) subtype which is selectively antagonised by enprofylline. Studies in animal models, especially mice, have shown a close synergistic interaction between adenosine, Th2 and airway remodelling responses. The recent description of A(2B) receptors on human airway smooth muscle cells that mediate cytokine and chemokine release and induce differentiation of fibroblasts into myofibroblasts strengthens the view that adenosine maybe more than an inflammatory mediator in asthma but also participates in airway wall remodelling in this disease. These data have provided a firm basis for developing adenosine A(2B) receptor antagonists as a new therapeutic approach to this disease.

  15. The Quintiles Prize Lecture 2004: The identification of the adenosine A2B receptor as a novel therapeutic target in asthma

    Science.gov (United States)

    Holgate, Stephen T

    2005-01-01

    Adenosine is a powerful bronchoconstrictor of asthmatic, but not normal, airways. In vitro studies on isolated human mast cells and basophils revealed that adenosine and selective analogues augmented inflammatory mediator release from mast cells by stimulating A2 receptors. Pharmacological blockade of mast cell mediator release in vivo also attenuated adenosine-induced bronchoconstriction, as did theophylline, by adenosine A2 receptor antagonism. Further in vitro studies revealed that the asthmatic response to adenosine is likely to be mediated via the A2B subtype which is selectively antagonised by enprofylline. Studies in animal models, especially mice, have shown a close synergistic interaction between adenosine, Th2 and airway remodelling responses. The recent description of A2B receptors on human airway smooth muscle cells that mediate cytokine and chemokine release and induce differentiation of fibroblasts into myofibroblasts strengthens the view that adenosine maybe more than an inflammatory mediator in asthma but also participates in airway wall remodelling in this disease. These data have provided a firm basis for developing adenosine A2B receptor antagonists as a new therapeutic approach to this disease. PMID:15980878

  16. Increased Signaling via Adenosine A(1) Receptors, Sleep Deprivation, Imipramine, and Ketamine Inhibit Depressive-like Behavior via Induction of Homer1a

    NARCIS (Netherlands)

    Serchov, Tsvetan; Clement, Hans-Willi; Schwarz, Martin K.; Iasevoli, Felice; Tosh, Dilip K.; Idzko, Marco; Jacobson, Kenneth A.; de Bartolomeis, Andrea; Normann, Claus; Biber, Knut; van Calker, Dietrich

    2015-01-01

    Major depressive disorder is among the most commonly diagnosed disabling mental diseases. Several non-pharmacological treatments of depression upregulate adenosine concentration and/or adenosine A(1) receptors (A(1)R) in the brain. To test whether enhanced A(1)R signaling mediates antidepressant

  17. Structural Requirements of N-Substituted Spiropiperidine Analogues as Agonists of Nociceptin/Orphanin FQ Receptor

    Directory of Open Access Journals (Sweden)

    Ling Yang

    2011-12-01

    Full Text Available The nociceptin/orphanin FQ (NOP receptor is involved in a wide range of biological functions, including pain, anxiety, depression and drug abuse. Especially, its agonists have great potential to be developed into anxiolytics. In this work, both the ligand- and receptor-based three-dimensional quantitative structure–activity relationship (3D-QSAR studies were carried out using comparative molecular field analysis (CoMFA and comparative molecular similarity indices analysis (CoMSIA techniques on 103 N-substituted spiropiperidine analogues as NOP agonists. The resultant optimal ligand-based CoMSIA model exhibited Q2 of 0.501, R2ncv of 0.912 and its predictive ability was validated by using an independent test set of 26 compounds which gave R2pred value of 0.818. In addition, docking analysis and molecular dynamics simulation (MD were also applied to elucidate the probable binding modes of these agonists. Interpretation of the 3D contour maps, in the context of the topology of the active site of NOP, provided insight into the NOP-agonist interactions. The information obtained from this work can be used to accurately predict the binding affinity of related agonists and also facilitate the future rational design of novel agonists with improved activity.

  18. Effects of cannabinoid and vanilloid receptor agonists and their interaction on learning and memory in rats.

    Science.gov (United States)

    Shiri, Mariam; Komaki, Alireza; Oryan, Shahrbanoo; Taheri, Masoumeh; Komaki, Hamidreza; Etaee, Farshid

    2017-04-01

    Despite previous findings on the effects of cannabinoid and vanilloid systems on learning and memory, the effects of the combined stimulation of these 2 systems on learning and memory have not been studied. Therefore, in this study, we tested the interactive effects of cannabinoid and vanilloid systems on learning and memory in rats by using passive avoidance learning (PAL) tests. Forty male Wistar rats were divided into the following 4 groups: (1) control (DMSO+saline), (2) WIN55,212-2, (3) capsaicin, and (4) WIN55,212-2 + capsaicin. On test day, capsaicin, a vanilloid receptor type 1 (TRPV1) agonist, or WIN55,212-2, a cannabinoid receptor (CB1/CB2) agonist, or both substances were injected intraperitoneally. Compared to the control group, the group treated with capsaicin (TRPV1 agonist) had better scores in the PAL acquisition and retention test, whereas treatment with WIN55,212-2 (CB1/CB2 agonist) decreased the test scores. Capsaicin partly reduced the effects of WIN55,212-2 on PAL and memory. We conclude that the acute administration of a TRPV1 agonist improves the rats' cognitive performance in PAL tasks and that a vanilloid-related mechanism may underlie the agonistic effect of WIN55,212-2 on learning and memory.

  19. Platelet adenosine diphosphate receptor antagonists: ticlopidine to ticagrelor—a long continuing journey

    Science.gov (United States)

    Kaul, Upendra; Mansoor, Aijaz H.

    2012-01-01

    Platelet aggregation plays a central role in the pathogenesis of atherothrombosis. Platelet adenosine diphosphate (ADP) receptor antagonists (ticlopidine, clopidogrel, prasugrel, and ticagrelor) are a major advance in the treatment of atherothrombotic diseases, especially acute coronary syndromes (ACS). Ticlopidine was the first thienopyridine introduced into clinical practice, but its potentially serious haematological side-effects limited its use and it was quickly eclipsed by clopidogrel. Clinical trials established aspirin plus clopidogrel as the standard dual anti-platelet therapy in patients with ACS and patients undergoing percutaneous coronary intervention (PCI) with stenting. Clopidogrel was found to have pharmacokinetic and pharmacodynamic limitations. Prasugrel is the next approved thienopyridine that has shown superior efficacy in ACS patients undergoing PCI in comparison to clopidogrel, although at the cost of a higher bleeding risk. Ticagrelor is the latest non-thienopyridine ADP receptor blocker that is potent, effective, reversible, and relatively safer as compared to clopidogrel. Both prasugrel and ticagrelor are more potent than clopidogrel. The data so far suggests that ticagrelor has a wider applicability in usage in patients with ACS as compared to prasugrel. Prasugrel however seems to be better tolerated. Search is on for newer more potent but safer anti-platelet agents. PMID:22572427

  20. Platelet adenosine diphosphate receptor antagonists: ticlopidine to ticagrelor-a long continuing journey.

    Science.gov (United States)

    Kaul, Upendra; Mansoor, Aijaz H

    2012-01-01

    Platelet aggregation plays a central role in the pathogenesis of atherothrombosis. Platelet adenosine diphosphate (ADP) receptor antagonists (ticlopidine, clopidogrel, prasugrel, and ticagrelor) are a major advance in the treatment of atherothrombotic diseases, especially acute coronary syndromes (ACS). Ticlopidine was the first thienopyridine introduced into clinical practice, but its potentially serious haematological side-effects limited its use and it was quickly eclipsed by clopidogrel. Clinical trials established aspirin plus clopidogrel as the standard dual anti-platelet therapy in patients with ACS and patients undergoing percutaneous coronary intervention (PCI) with stenting. Clopidogrel was found to have pharmacokinetic and pharmacodynamic limitations. Prasugrel is the next approved thienopyridine that has shown superior efficacy in ACS patients undergoing PCI in comparison to clopidogrel, although at the cost of a higher bleeding risk. Ticagrelor is the latest non-thienopyridine ADP receptor blocker that is potent, effective, reversible, and relatively safer as compared to clopidogrel. Both prasugrel and ticagrelor are more potent than clopidogrel. The data so far suggests that ticagrelor has a wider applicability in usage in patients with ACS as compared to prasugrel. Prasugrel however seems to be better tolerated. Search is on for newer more potent but safer anti-platelet agents. Copyright © 2012 Cardiological Society of India. Published by Elsevier B.V. All rights reserved.

  1. High-Performance Prediction of Human Estrogen Receptor Agonists Based on Chemical Structures

    Directory of Open Access Journals (Sweden)

    Yuki Asako

    2017-04-01

    Full Text Available Many agonists for the estrogen receptor are known to disrupt endocrine functioning. We have developed a computational model that predicts agonists for the estrogen receptor ligand-binding domain in an assay system. Our model was entered into the Tox21 Data Challenge 2014, a computational toxicology competition organized by the National Center for Advancing Translational Sciences. This competition aims to find high-performance predictive models for various adverse-outcome pathways, including the estrogen receptor. Our predictive model, which is based on the random forest method, delivered the best performance in its competition category. In the current study, the predictive performance of the random forest models was improved by strictly adjusting the hyperparameters to avoid overfitting. The random forest models were optimized from 4000 descriptors simultaneously applied to 10,000 activity assay results for the estrogen receptor ligand-binding domain, which have been measured and compiled by Tox21. Owing to the correlation between our model’s and the challenge’s results, we consider that our model currently possesses the highest predictive power on agonist activity of the estrogen receptor ligand-binding domain. Furthermore, analysis of the optimized model revealed some important features of the agonists, such as the number of hydroxyl groups in the molecules.

  2. High-Performance Prediction of Human Estrogen Receptor Agonists Based on Chemical Structures.

    Science.gov (United States)

    Asako, Yuki; Uesawa, Yoshihiro

    2017-04-23

    Many agonists for the estrogen receptor are known to disrupt endocrine functioning. We have developed a computational model that predicts agonists for the estrogen receptor ligand-binding domain in an assay system. Our model was entered into the Tox21 Data Challenge 2014, a computational toxicology competition organized by the National Center for Advancing Translational Sciences. This competition aims to find high-performance predictive models for various adverse-outcome pathways, including the estrogen receptor. Our predictive model, which is based on the random forest method, delivered the best performance in its competition category. In the current study, the predictive performance of the random forest models was improved by strictly adjusting the hyperparameters to avoid overfitting. The random forest models were optimized from 4000 descriptors simultaneously applied to 10,000 activity assay results for the estrogen receptor ligand-binding domain, which have been measured and compiled by Tox21. Owing to the correlation between our model's and the challenge's results, we consider that our model currently possesses the highest predictive power on agonist activity of the estrogen receptor ligand-binding domain. Furthermore, analysis of the optimized model revealed some important features of the agonists, such as the number of hydroxyl groups in the molecules.

  3. Discovery of novel acetanilide derivatives as potent and selective beta3-adrenergic receptor agonists.

    Science.gov (United States)

    Maruyama, Tatsuya; Onda, Kenichi; Hayakawa, Masahiko; Matsui, Tetsuo; Takasu, Toshiyuki; Ohta, Mitsuaki

    2009-06-01

    In the search for potent and selective human beta3-adrenergic receptor (AR) agonists as potential drugs for the treatment of obesity and noninsulin-dependent (type II) diabetes, a novel series of acetanilide-based analogues were prepared and their biological activities were evaluated at the human beta3-, beta2-, and beta1-ARs. Among these compounds, 2-pyridylacetanilide (2f), pyrimidin-2-ylacetanilide (2u), and pyrazin-2-ylacetanilide (2v) derivatives exhibited potent agonistic activity at the beta3-AR with functional selectivity over the beta1- and beta2-ARs. In particular, compound 2u was found to be the most potent and selective beta3-AR agonist with an EC(50) value of 0.11 microM and no agonistic activity for either the beta1- or beta2-AR. In addition, 2f, 2u, and 2v showed significant hypoglycemic activity in a rodent diabetic model.

  4. Design and synthesis of small molecule agonists of EphA2 receptor.

    Science.gov (United States)

    Petty, Aaron; Idippily, Nethrie; Bobba, Viharika; Geldenhuys, Werner J; Zhong, Bo; Su, Bin; Wang, Bingcheng

    2018-01-01

    Ligand-independent activation of EphA2 receptor kinase promotes cancer metastasis and invasion. Activating EphA2 receptor tyrosine kinase with small molecule agonist is a novel strategy to treat EphA2 overexpressing cancer. In this study, we performed a lead optimization of a small molecule Doxazosin that was identified as an EphA2 receptor agonist. 33 new analogs were developed and evaluated; a structure-activity relationship was summarized based on the EphA2 activation of these derivatives. Two new derivative compounds 24 and 27 showed much improved activity compared to Doxazosin. Compound 24 possesses a bulky amide moiety, and compound 27 has a dimeric structure that is very different to the parental compound. Compound 27 with a twelve-carbon linker of the dimer activated the kinase and induced receptor internalization and cell death with the best potency. Another dimer with a six-carbon linker has significantly reduced potency compared to the dimer with a longer linker, suggesting that the length of the linker is critical for the activity of the dimeric agonist. To explore the receptor binding characteristics of the new molecules, we applied a docking study to examine how the small molecule binds to the EphA2 receptor. The results reveal that compounds 24 and 27 form more hydrogen bonds to EphA2 than Doxazosin, suggesting that they may have higher binding affinity to the receptor. Published by Elsevier Masson SAS.

  5. A cation-π interaction at a phenylalanine residue in the glycine receptor binding site is conserved for different agonists

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Hanek, Ariele P; Price, Kerry L

    2011-01-01

    Cation-π interactions have been demonstrated to play a major role in agonist-binding in Cys-loop receptors. However, neither the aromatic amino acid contributing to this interaction nor its location is conserved among Cys-loop receptors. Likewise, it is not clear how many different agonists of a ...

  6. Hide and seek: a comparative autoradiographic in vitro investigation of the adenosine A3 receptor

    Energy Technology Data Exchange (ETDEWEB)

    Haeusler, D.; Fuchshuber, F.; Girschele, F.; Hacker, M.; Wadsak, W.; Mitterhauser, Markus [Medical University of Vienna, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Grassinger, L. [University of Applied Sciences Wiener Neustadt, Department of Biomedical Analytics, Wiener Neustadt (Austria); Hoerleinsberger, W.J. [Medical University of Vienna, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); University of Vienna, Cognitive Science Research Platform, Vienna (Austria); Hoeftberger, R.; Leisser, I. [Medical University of Vienna, Institute of Neurology, Vienna (Austria); Shanab, K.; Spreitzer, H. [University of Vienna, Department of Drug and Natural Product Synthesis, Vienna (Austria); Gerdenitsch, W. [Medical University of Vienna, Institute of Biomedicinal Research, Vienna (Austria)

    2015-05-01

    Since the adenosine A3 receptor (A3R) is considered to be of high clinical importance in the diagnosis and treatment of ischaemic conditions (heart and brain), glaucoma, asthma, arthritis, cancer and inflammation, a suitable and selective A3R PET tracer such as [{sup 18}F]FE rate at SUPPY would be of high clinical value for clinicians as well as patients. A3R was discovered in the late 1990s, but there is still little known regarding its distribution in the CNS and periphery. Hence, in autoradiographic experiments the distribution of A3R in human brain and rat tissues was investigated and the specific binding of the A3R antagonist FE rate at SUPPY and MRS1523 compared. Immunohistochemical staining (IHC) experiments were also performed to validate the autoradiographic findings. For autoradiographic competition experiments human post-mortem brain and rat tissues were incubated with [{sup 125}I]AB-MECA and highly selective compounds to block the other adenosine receptor subtypes. Additionally, IHC was performed with an A3 antibody. Specific A3R binding of MRS1523 and FE rate at SUPPY was found in all rat peripheral tissues examined with the highest amounts in the spleen (44.0 % and 46.4 %), lung (44.5 % and 45.0 %), heart (39.9 % and 42.9 %) and testes (27.4 % and 29.5 %, respectively). Low amounts of A3R were found in rat brain tissues (5.9 % and 5.6 %, respectively) and human brain tissues (thalamus 8.0 % and 9.1 %, putamen 7.8 % and 8.2 %, cerebellum 6.0 % and 7.8 %, hippocampus 5.7 % and 5.6 %, caudate nucleus 4.9 % and 6.4 %, cortex 4.9 % and 6.3 %, respectively). The outcome of the A3 antibody staining experiments complemented the results of the autoradiographic experiments. The presence of A3R protein was verified in central and peripheral tissues by autoradiography and IHC. The specificity and selectivity of FE rate at SUPPY was confirmed by direct comparison with MRS1523, providing further evidence that [{sup 18}F]FE rate at SUPPY may be a suitable A3 PET

  7. New 4-Functionalized Glutamate Analogues Are Selective Agonists at Metabotropic Glutamate Receptor Subtype 2 or Selective Agonists at Metabotropic Glutamate Receptor Group III

    DEFF Research Database (Denmark)

    Huynh, Tri H. V.; Erichsen, Mette N.; Tora, Amelie S.

    2016-01-01

    The metabotropic glutamate (Glu) receptors (mGluRs) play key roles in modulating excitatory neurotransmission in the brain. In all, eight subtypes have been identified and divided into three groups, group I (mGlu1,5), group II (mGlu2,3), and group III (mGlu4,6–8). In this article, we present a L-...... a selective agonist activity profile at mGlu2 (EC50 in the micromolar range), whereas 2c/2d were both selective agonists at group III, subtypes mGlu4,6,8. In general, 2d was 20-fold more potent than 2c and potently activated mGlu4,6,8 in the low–mid nanomolar range.......The metabotropic glutamate (Glu) receptors (mGluRs) play key roles in modulating excitatory neurotransmission in the brain. In all, eight subtypes have been identified and divided into three groups, group I (mGlu1,5), group II (mGlu2,3), and group III (mGlu4,6–8). In this article, we present a L-2......,4-syn-substituted Glu analogue, 1d, which displays selective agonist activity at mGlu2 over the remaining mGluR subtypes. A modeling study and redesign of the core scaffold led to the stereoselective synthesis of four new conformationally restricted Glu analogues, 2a–d. Most interestingly, 2a retained...

  8. Harnessing glucagon-like peptide-1 receptor agonists for the pharmacological treatment of overweight and obesity.

    Science.gov (United States)

    Burcelin, R; Gourdy, P

    2017-01-01

    Over the past 30 years, there has been a dramatic rise in global obesity prevalence, resulting in significant economic and social consequences. Attempts to develop pharmacological agents to treat obesity have met with many obstacles including the lack of long-term effectiveness and the potential for adverse effects. Historically, there have been limited treatment options for overweight and obesity; however, since 2012, a number of new drugs have become available. A number of peptides produced in the gut act as key mediators of the gut-brain axis, which is involved in appetite regulation. This review discusses the role of the gut-brain axis in appetite regulation with special focus on glucagon-like peptide-1. Liraglutide 3.0 mg, a glucagon-like peptide-1 receptor agonist that targets this pathway, is now approved for the treatment of obesity and overweight (body mass index ≥27 kg/m2 ) with comorbidities such as type 2 diabetes, high blood pressure, high cholesterol or obstructive sleep apnoea. In addition, other glucagon-like peptide-1 receptor agonists offer promise for obesity management in the future. This review examines how glucagon-like peptide-1 receptor agonists promote weight loss and summarizes the clinical data on weight loss with glucagon-like peptide-1 receptor agonists. © 2016 The Authors Obesity Reviews published by John Wiley & Sons Ltd on behalf of World Obesity Federation.

  9. Non-Acidic Free Fatty Acid Receptor 4 Agonists with Antidiabetic Activity

    DEFF Research Database (Denmark)

    Goncalves de Azavedo, Carlos M. B. P.; Watterson, Kenneth R; Wargent, Ed T

    2016-01-01

    The free fatty acid receptor 4 (FFA4 or GPR120) has appeared as an interesting potential target for the treatment of metabolic disorders. At present, most FFA4 ligands are carboxylic acids that are assumed to mimic the endogenous long-chain fatty acid agonists. Here, we report preliminary structu...

  10. Novel non-indolic melatonin receptor agonists differentially entrain endogenous melatonin rhythm and increase its amplitude

    NARCIS (Netherlands)

    Drijfhout, W.J; de Vries, J.B; Homan, E.J; Brons, H.F; Copinga, S; Gruppen, G; Beresford, I.J M; Hagan, R.M; Grol, Cor; Westerink, B.H.C.

    1999-01-01

    In this study we have examined the ability of melatonin and four synthetic melatonin receptor agonists to entrain endogenous melatonin secretion in rats, free running in constant darkness. The circadian melatonin profile was measured by trans-pineal microdialysis, which not only reveals the time of

  11. B1 but not B2 bradykinin receptor agonists promote DU145 prostate ...

    African Journals Online (AJOL)

    Background: The kallikrein-kinin system (KKS) is an endogenous pathway involved in angiogenesis and tumourigenesis, both vital for cancer growth and progression. Objectives: To investigate the effect of two bradykinin receptor (B1R and B2R) agonists on growth and motility of prostate tumour (DU145) and ...

  12. Dopamine D1 receptor-agonist interactions: A mutagenesis and homology modeling study.

    Science.gov (United States)

    Mente, Scot; Guilmette, Edward; Salafia, Michelle; Gray, David

    2015-01-01

    The dopamine D1 receptor is a G protein-coupled receptor that regulates intracellular signaling via agonist activation. Although the number of solved GPCR X-ray structures has been steadily increasing, still no structure of the D1 receptor exists. We have used site-directed mutagenesis of 12 orthosteric vicinity residues of possible importance to G protein-coupled activation to examine the function of prototypical orthosteric D1 agonists and partial agonists. We find that residues from four different regions of the D1 receptor make significant contributions to agonist function. All compounds studied, which are catechol-amines, are found to interact with the previously identified residues: the conserved D103(3.32), as well as the trans-membrane V serine residues. Additional key interactions are found for trans-membrane VI residues F288(6.51), F289(6.52) and N292(6.55), as well as the extra-cellular loop residue L190(ECL2). Molecular dynamics simulations of a D1 homology model have been used to help put the ligand-residue interactions into context. Finally, we considered the rescaling of fold-shift data as a method to account for the change in the size of the mutated side-chain and found that this rescaling helps to relate the calculated ligand-residue energies with observed experimental fold-shifts. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Mechanism of partial agonist action at the NR1 subunit of NMDA receptors.

    Science.gov (United States)

    Inanobe, Atsushi; Furukawa, Hiroyasu; Gouaux, Eric

    2005-07-07

    Partial agonists produce submaximal activation of ligand-gated ion channels. To address the question of partial agonist action at the NR1 subunit of the NMDA receptor, we performed crystallographic and electrophysiological studies with 1-aminocyclopropane-1-carboxylic acid (ACPC), 1-aminocyclobutane-1-carboxylic acid (ACBC), and 1-aminocyclopentane-1-carboxylic acid (cycloleucine), three compounds with incrementally larger carbocyclic rings. Whereas ACPC and ACBC partially activate the NMDA receptor by 80% and 42%, respectively, their cocrystal structures of the NR1 ligand binding core show the same degree of domain closure as found in the complex with glycine, a full agonist, illustrating that the NR1 subunit provides a new paradigm for partial agonist action that is distinct from that of the evolutionarily related GluR2, AMPA-sensitive receptor. Cycloleucine behaves as an antagonist and stabilizes an open-cleft conformation. The NR1-cycloleucine complex forms a dimer that is similar to the GluR2 dimer, thereby suggesting a conserved mode of subunit-subunit interaction in AMPA and NMDA receptors.

  14. Differential Effects of Cannabinoid Receptor Agonist on Social Discrimination and Contextual Fear in Amygdala and Hippocampus

    Science.gov (United States)

    Segev, Amir; Akirav, Irit

    2011-01-01

    We examined whether the cannabinoid receptor agonist WIN55,212-2 (WIN; 5 [mu]g/side) microinjected into the hippocampus or the amygdala would differentially affect memory processes in a neutral vs. an aversive task. In the aversive contextual fear task, WIN into the basolateral amygdala impaired fear acquisition/consolidation, but not retrieval.…

  15. Unraveling the high- and low-sensitivity agonist responses of nicotinic acetylcholine receptors

    DEFF Research Database (Denmark)

    Harpsøe, Kasper; Ahring, Philip K; Christensen, Jeppe K

    2011-01-01

    for the observation of two distinct agonist sensitivities. Using different expression ratios of mammalian a4 and ß2 subunits and concatenated constructs, we demonstrate that a biphasic response is an intrinsic functional property of the (a4)(3)(ß2)(2) receptor. In addition to two high-sensitivity sites at a4ß2...

  16. Treatment potential of the GLP-1 receptor agonists in type 2 diabetes mellitus

    DEFF Research Database (Denmark)

    Østergaard, L; Frandsen, Christian S.; Madsbad, S

    2016-01-01

    Over the last decade, the discovery of glucagon-like peptide 1 receptor agonists (GLP-1 RAs) has increased the treatment options for patients with type 2 diabetes mellitus (T2DM). GLP-1 RAs mimic the effects of native GLP-1, which increases insulin secretion, inhibits glucagon secretion, increases...

  17. Dopamine receptor agonists modulate voluntary alcohol intake independently of individual levels of alcohol intake in rats

    NARCIS (Netherlands)

    Spoelder, M.; Baars, A.M.; Rotte, M.D.; Vanderschuren, L.J.; Lesscher, H.M.

    2016-01-01

    RATIONALE: Individual susceptibility to alcohol use disorder has been related to functional changes in dopaminergic neurotransmission. OBJECTIVES: The aim of the current work was to assess the effects of selective dopamine D1 and D2 receptor agonists and antagonists on alcohol consumption in rats

  18. Biostructural and pharmacological studies of bicyclic analogues of the 3-isoxazolol glutamate receptor agonist ibotenic acid

    DEFF Research Database (Denmark)

    Frydenvang, Karla Andrea; Pickering, Darryl S; Greenwood, Jeremy R

    2010-01-01

    We describe an improved synthesis and detailed pharmacological characterization of the conformationally restricted analogue of the naturally occurring nonselective glutamate receptor agonist ibotenic acid (RS)-3-hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-7-carboxylic acid (7-HPCA, 5) at A...

  19. Atypical antipsychotic-like effects of the dopamine D-3 receptor agonist, (+)-PD 128,907

    NARCIS (Netherlands)

    Witkin, J; Gasior, M; Acri, J; Beekman, M; Thurkauf, A; de Boer, Peter; Wikstrom, H; Dijkstra, D

    1998-01-01

    Anti-schizophrenia agents with improved efficacy and side-effect profiles are required. A dopamine D-3 receptor agonist, R-(+)-trans-3,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano[4,3-b]-1,4-oxazin-9-ol HCl ((+)-PD 128,907), displayed an atypical antipsychotic profile comparable to that of

  20. The angiotensin type 2 receptor agonist Compound 21 elicits cerebroprotection in endothelin-1 induced ischemic stroke

    DEFF Research Database (Denmark)

    Joseph, Jason P; Mecca, Adam P; Regenhardt, Robert W

    2014-01-01

    Evidence indicates that angiotensin II type 2 receptors (AT2R) exert cerebroprotective actions during stroke. A selective non-peptide AT2R agonist, Compound 21 (C21), has been shown to exert beneficial effects in models of cardiac and renal disease, as well as hemorrhagic stroke. Here, we...

  1. Effects of glucagon-like peptide-1 (GLP-1) receptor agonists on cardiovascular risk factors

    DEFF Research Database (Denmark)

    Dalsgaard, Niels B; Vilsbøll, Tina; Knop, Filip K

    2017-01-01

    trials for diabetes therapies. To determine if different glucagon-like peptide-1 receptor agonists (GLP-1RAs) had varying effects on these CV risk factors, we reviewed 16 head-to-head trials directly comparing GLP-1RAs that included at least one of the five factors. Few trials reported statistical...

  2. Recombinant ecto-5'-nucleotidase (CD73 has long lasting antinociceptive effects that are dependent on adenosine A1 receptor activation

    Directory of Open Access Journals (Sweden)

    Zylka Mark J

    2010-04-01

    Full Text Available Abstract Background Ecto-5'-nucleotidase (NT5E, also known as CD73 hydrolyzes extracellular adenosine 5'-monophosphate (AMP to adenosine in nociceptive circuits. Since adenosine has antinociceptive effects in rodents and humans, we hypothesized that NT5E, an enzyme that generates adenosine, might also have antinociceptive effects in vivo. Results To test this hypothesis, we purified a soluble version of mouse NT5E (mNT5E using the baculovirus expression system. Recombinant mNT5E hydrolyzed AMP in biochemical assays and was inhibited by α,β-methylene-adenosine 5'-diphosphate (α,β-me-ADP; IC50 = 0.43 μM, a selective inhibitor of NT5E. mNT5E exhibited a dose-dependent thermal antinociceptive effect that lasted for two days when injected intrathecally in wild-type mice. In addition, mNT5E had thermal antihyperalgesic and mechanical antiallodynic effects that lasted for two days in the complete Freund's adjuvant (CFA model of inflammatory pain and the spared nerve injury (SNI model of neuropathic pain. In contrast, mNT5E had no antinociceptive effects when injected intrathecally into adenosine A1 receptor (A1R, Adora1 knockout mice. Conclusion Our data indicate that the long lasting antinociceptive effects of mNT5E are due to hydrolysis of AMP followed by activation of A1R. Moreover, our data suggest recombinant NT5E could be used to treat chronic pain and to study many other physiological processes that are regulated by NT5E.

  3. Key Modulatory Role of Presynaptic Adenosine A2A Receptors in Cortical Neurotransmission to the Striatal Direct Pathway

    Directory of Open Access Journals (Sweden)

    César Quiroz

    2009-01-01

    Full Text Available Basal ganglia processing results from a balanced activation of direct and indirect striatal efferent pathways, which are controlled by dopamine D1 and D2 receptors, respectively. Adenosine A2A receptors are considered novel antiparkinsonian targets, based on their selective postsynaptic localization in the indirect pathway, where they modulate D2 receptor function. The present study provides evidence for the existence of an additional, functionally significant, segregation of A2A receptors at the presynaptic level. Using integrated anatomical, electrophysiological, and biochemical approaches, we demonstrate that presynaptic A2A receptors are preferentially localized in cortical glutamatergic terminals that contact striatal neurons of the direct pathway, where they exert a selective modulation of corticostriatal neurotransmission. Presynaptic striatal A2A receptors could provide a new target for the treatment of neuropsychiatric disorders.

  4. Anticonvulsant effect of cannabinoid receptor agonists in models of seizures in developing rats.

    Science.gov (United States)

    Huizenga, Megan N; Wicker, Evan; Beck, Veronica C; Forcelli, Patrick A

    2017-09-01

    Although drugs targeting the cannabinoid system (e.g., CB1 receptor agonists) display anticonvulsant efficacy in adult animal models of seizures/epilepsy, they remain unexplored in developing animal models. However, cannabinoid system functions emerge early in development, providing a rationale for targeting this system in neonates. We examined the therapeutic potential of drugs targeting the cannabinoid system in three seizure models in developing rats. Postnatal day (P) 10, Sprague-Dawley rat pups were challenged with the chemoconvulsant methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) or pentylenetetrazole (PTZ), after treatment with either CB1/2 mixed agonist (WIN 55,212-2), CB1 agonist (arachidonyl-2'-chloroethylamide [ACEA]), CB2 agonist (HU-308), CB1 antagonist (AM-251), CB2 antagonist (AM-630), fatty acid amide hydrolase inhibitor (URB-597), or G protein-coupled receptor 55 agonist (O-1602). P20 Sprague-Dawley pups were challenged with DMCM after treatment with WIN, ACEA, or URB. Finally, after pretreatment with WIN, P10 Sprague-Dawley rats were challenged against acute hypoxia-induced seizures. The mixed CB1/2 agonist and the CB1-specific agonist, but no other drugs, displayed anticonvulsant effects against clonic seizures in the DMCM model. By contrast, both CB1 and CB2 antagonism increased seizure severity. Similarly, we found that the CB1/2 agonist displayed antiseizure efficacy against acute hypoxia-induced seizures (automatisms, clonic and tonic-clonic seizures) and tonic-clonic seizures evoked by PTZ. Anticonvulsant effects were seen in P10 animals but not P20 animals. Early life seizures represent a significant cause of morbidity, with 30-40% of infants and children with epilepsy failing to achieve seizure remission with current pharmacotherapy. Identification of new therapies for neonatal/infantile epilepsy syndromes is thus of high priority. These data indicate that the anticonvulsant action of the CB system is specific to CB1

  5. ATP induced vasodilatation and purinergic receptors in the human leg: roles of nitric oxide, prostaglandins and adenosine

    DEFF Research Database (Denmark)

    Mortensen, Stefan P; Gonzalez-Alonso, Jose; Bune, Laurids

    2009-01-01

    Plasma adenosine-5'-triphosphate (ATP) is thought to contribute to the local regulation of skeletal muscle blood flow. Intravascular ATP infusion can induce profound limb muscle vasodilatation, but the purinergic receptors and downstream signals involved in this response remain unclear. This study...... investigated: 1) the role of nitric oxide (NO), prostaglandins and adenosine as mediators of ATP induced limb vasodilation and 2) the expression and distribution of purinergic P2 receptors in human skeletal muscle. Systemic and leg hemodynamics were measured before and during 5-7 min of femoral intra.......05) and was associated with a parallel lowering in leg vascular conductance and cardiac output and a compensatory increase in leg O2 extraction. Infusion of theophylline did not alter the ATP induced leg hyperemia or systemic variables. Real time PCR analysis of the mRNA content from the vastus lateralus muscle of 8...

  6. Early Cessation of Adenosine Diphosphate Receptor Inhibitors Among Acute Myocardial Infarction Patients Treated With Percutaneous Coronary Intervention

    DEFF Research Database (Denmark)

    Fosbøl, Emil L; Ju, Christine; Anstrom, Kevin J

    2016-01-01

    treated with percutaneous coronary intervention discharged alive on ADPri therapy from 233 United States TRANSLATE-ACS study (Treatment With Adenosine Diphosphate Receptor Inhibitors: Longitudinal Assessment of Treatment Patterns and Events After Acute Coronary Syndrome) participating hospitals......BACKGROUND: Guidelines recommend the use of adenosine diphosphate receptor inhibitor (ADPri) therapy for 1 year postacute myocardial infarction; yet, early cessation of therapy occurs frequently in clinical practice. METHODS AND RESULTS: We examined 11 858 acute myocardial infarction patients...... ADPri cessation included physician-recommended discontinuation (54%), as well as patient self-discontinuation, because of cost (19%), medication side effects (9%), and procedural interruption (10%). Using a time-dependent covariate model, early cessation of ADPri therapy was associated with increased...

  7. FRET-based detection of M1 muscarinic acetylcholine receptor activation by orthosteric and allosteric agonists.

    Directory of Open Access Journals (Sweden)

    Danijela Markovic

    Full Text Available Muscarinic acetylcholine receptors (mAChRs are 7-transmembrane, G protein-coupled receptors that regulate a variety of physiological processes and represent potentially important targets for therapeutic intervention. mAChRs can be stimulated by full and partial orthosteric and allosteric agonists, however the relative abilities of such ligands to induce conformational changes in the receptor remain unclear. To gain further insight into the actions of mAChR agonists, we have developed a fluorescently tagged M(1 mAChR that reports ligand-induced conformational changes in real-time by changes in Förster resonance energy transfer (FRET.Variants of CFP and YFP were inserted into the third intracellular loop and at the end of the C-terminus of the mouse M(1 mAChR, respectively. The optimized FRET receptor construct (M(1-cam5 was expressed stably in HEK293 cells.The variant CFP/YFP-receptor chimera expressed predominantly at the plasma membrane of HEK293 cells and displayed ligand-binding affinities comparable with those of the wild-type receptor. It also retained an ability to interact with Gα(q/11 proteins and to stimulate phosphoinositide turnover, ERK1/2 phosphorylation and undergo agonist-dependent internalization. Addition of the full agonist methacholine caused a reversible decrease in M(1 FRET (F(EYFP/F(ECFP that was prevented by atropine pre-addition and showed concentration-dependent amplitude and kinetics. Partial orthosteric agonists, arecoline and pilocarpine, as well as allosteric agonists, AC-42 and 77-LH-28-1, also caused atropine-sensitive decreases in the FRET signal, which were smaller in amplitude and significantly slower in onset compared to those evoked by methacholine.The M(1 FRET-based receptor chimera reports that allosteric and orthosteric agonists induce similar conformational changes in the third intracellular loop and/or C-terminus, and should prove to be a valuable molecular reagent for pharmacological and structural

  8. Structurally related nucleotides as selective agonists and antagonists at P2Y1 receptors

    Science.gov (United States)

    Jacobson, Kenneth A.; Moro, Stefano; Hoffmann, Carsten; Kim, Yong-Chul; Kim, Hak Sung; Ravi, R. Gnana; Harden, T. Kendall; Boyer, José L.

    2015-01-01

    The P2Y1 receptor responds to adenine nucleotides and is present in platelets, heart, smooth muscles prostate, ovary, and brain. A selective antagonist may be useful as an antithrombotic agent. We have analyzed the binding site of this G protein-coupled receptor using ligand design, site-directed mutagenesis, and homology modeling based on rhodopsin. We have designed and synthesized a series of deoxyadenosine 3′,5′-bisphosphate derivatives that act as antagonists, or, in some cases with small structural changes, as agonists or partial agonists. The 2-position accommodates Cl or thioethers, whereas the N6-position is limited to Me or Et. 2′-Substitution with OH or OMe increases agonist efficacy over 2′-H. Using molecular modeling of the binding site, the oxygen atoms of the ribose moiety were predicted to be non-essential, i.e. no specific H-bonds with the receptor protein appear in the model. We have, therefore, substituted this moiety with carbocylics, smaller and larger rings, conformationally constrained rings, and acyclics, with retention of affinity for the receptor. With simplified pharmacophores we are exploring the steric and electronic requirements of the receptor binding site, and the structural basis of receptor activation. PMID:11347970

  9. Adenosine and dialysis hypotension

    NARCIS (Netherlands)

    Franssen, CMF

    In this issue, Imai et al. report the results of a double-blind placebo-controlled study on the effect of an adenosine A1 receptor antagonist, FK352, on the incidence of dialysis hypotension in hypotension-prone patients. This Commentary discusses the use of selective adenosine A1 receptor

  10. Effects of caffeine on behavioral and inflammatory changes elicited by copper in zebrafish larvae: Role of adenosine receptors.

    Science.gov (United States)

    Cruz, Fernanda Fernandes; Leite, Carlos Eduardo; Kist, Luiza Wilges; de Oliveira, Giovanna Medeiros; Bogo, Maurício Reis; Bonan, Carla Denise; Campos, Maria Martha; Morrone, Fernanda Bueno

    2017-04-01

    This study investigated the effects of caffeine in the behavioral and inflammatory alterations caused by copper in zebrafish larvae, attempting to correlate these changes with the modulation of adenosine receptors. To perform a survival curve, 7dpf larvae were exposed to 10μM CuSO 4 , combined to different concentrations of caffeine (100μM, 500μM and 1mM) for up to 24h. The treatment with copper showed lower survival rates only when combined with 500μM and 1mM of caffeine. We selected 4 and 24h as treatment time-points. The behavior evaluation was done by analyzing the traveled distance, the number of entries in the center, and the length of permanence in the center and the periphery of the well. The exposure to 10μM CuSO 4 plus 500μM caffeine at 4 and 24h changed the behavioral parameters. To study the inflammatory effects of caffeine, we assessed the PGE 2 levels by using UHPLC-MS/MS, and TNF, COX-2, IL-6 and IL-10 gene expression by RT-qPCR. The expression of adenosine receptors was also evaluated with RT-qPCR. When combined to copper, caffeine altered inflammatory markers depending on the time of exposure. Adenosine receptors expression was significantly increased, especially after 4h exposure to copper and caffeine together or separately. Our results demonstrated that caffeine enhances the inflammation induced by copper by decreasing animal survival, altering inflammatory markers and promoting behavioral changes in zebrafish larvae. We also conclude that alterations in adenosine receptors are related to those effects. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Computational Prediction and Biochemical Analyses of New Inverse Agonists for the CB1 Receptor.

    Science.gov (United States)

    Scott, Caitlin E; Ahn, Kwang H; Graf, Steven T; Goddard, William A; Kendall, Debra A; Abrol, Ravinder

    2016-01-25

    Human cannabinoid type 1 (CB1) G-protein coupled receptor is a potential therapeutic target for obesity. The previously predicted and experimentally validated ensemble of ligand-free conformations of CB1 [Scott, C. E. et al. Protein Sci. 2013 , 22 , 101 - 113 ; Ahn, K. H. et al. Proteins 2013 , 81 , 1304 - 1317] are used here to predict the binding sites for known CB1-selective inverse agonists including rimonabant and its seven known derivatives. This binding pocket, which differs significantly from previously published models, is used to identify 16 novel compounds expected to be CB1 inverse agonists by exploiting potential new interactions. We show experimentally that two of these compounds exhibit inverse agonist properties including inhibition of basal and agonist-induced G-protein coupling activity, as well as an enhanced level of CB1 cell surface localization. This demonstrates the utility of using the predicted binding sites for an ensemble of CB1 receptor structures for designing new CB1 inverse agonists.

  12. Adenosine A2a receptor induces GDNF expression by the Stat3 signal in vitro.

    Science.gov (United States)

    Ke, Rong-Hu; Xiong, Ji; Liu, Ying

    2012-11-14

    Adenosine A2a receptor (A2aR) is believed to play a role in a number of physiological responses and pathological conditions. Our group has shown previously that A2aR-activated astrocytes occurred following oxygen-glucose deprivation. However, the relationship between A2aR and neurotrophins is poorly understood. Here, we investigate the effect of A2aR on glial cell line-derived neurotrophic factor (GDNF) expression in rat brain astrocyte-2 (RBA-2) cells by quantitative PCR and western blot. We established a stable A2aR-overexpressing cell line and found that A2aR induced GDNF expression both at mRNA and protein levels. A2aR-selective antagonist Sch58261 decreased GDNF expression in a dose-dependent manner with increased activation of Stat3. The Stat3 inhibitor reversed the effect of Sch58261 on GDNF expression. Therefore, these data indicate that A2aR induces GDNF expression by the Stat3 pathway, which provides a new insight into the function of A2aR in cerebral ischemia and neuroprotection.

  13. The A2B adenosine receptor modulates pulmonary hypertension associated with interstitial lung disease.

    Science.gov (United States)

    Karmouty-Quintana, Harry; Zhong, Hongyan; Acero, Luis; Weng, Tingting; Melicoff, Ernestina; West, James D; Hemnes, Anna; Grenz, Almut; Eltzschig, Holger K; Blackwell, Timothy S; Xia, Yang; Johnston, Richard A; Zeng, Dewan; Belardinelli, Luiz; Blackburn, Michael R

    2012-06-01

    Development of pulmonary hypertension is a common and deadly complication of interstitial lung disease. Little is known regarding the cellular and molecular mechanisms that lead to pulmonary hypertension in patients with interstitial lung disease, and effective treatment options are lacking. The purpose of this study was to examine the adenosine 2B receptor (A(2B)R) as a regulator of vascular remodeling and pulmonary hypertension secondary to pulmonary fibrosis. To accomplish this, cellular and molecular changes in vascular remodeling were monitored in mice exposed to bleomycin in conjunction with genetic removal of the A(2B)R or treatment with the A(2B)R antagonist GS-6201. Results demonstrated that GS-6201 treatment or genetic removal of the A(2B)R attenuated vascular remodeling and hypertension in our model. Furthermore, direct A(2B)R activation on vascular cells promoted interleukin-6 and endothelin-1 release. These studies identify a novel mechanism of disease progression to pulmonary hypertension and support the development of A(2B)R antagonists for the treatment of pulmonary hypertension secondary to interstitial lung disease.

  14. Modulation of oral movements by intranigral 5-hydroxytryptamine receptor agonists in the rat.

    Science.gov (United States)

    Liminga, U; Johnson, A E; Andrén, P E; Gunne, L M

    1993-10-01

    Bilateral infusion of 5-hydroxytryptamine (5-HT) agonists into the substantia nigra pars reticulata (SNr) of awake rats was shown to influence oral behavior. The 5-HT1A agonist (R)-8-hydroxy-2-(di-propylamino)- tetralin (8-OH-DPAT) (1.3-13 nmol on each side) produced a dose-dependent depression of vacuous chewing movements (VCMs) that lasted about 20 min. The (R)-8-OH-DPAT-induced depression of VCMs was blocked by the simultaneous intranigral infusion of a specific 5-HT1A antagonist [(-)-(S)-5-fluoro-8-hydroxy-2-(dipropylamino)tetralin HCl (UH-301)], which had no effect when given alone. Another 5-HT1A agonist [(5-methoxy-N,N-dimethyltryptamine hydrogen oxalate (5-MeO-DMT)] also reduced VCM frequencies. Intranigral infusion of the nonspecific 5-HT-agonists 1-(3-triflouro-methylphenyl) piperazine (TFMPP) and 1(m-chlorophenyl)-piperazine (mCPP) and a 5-HT3 agonist [2-methyl-5-hydroxytryptamine (2-Me-5-HT)] increased VCM after 5- to 10-nmol doses. Another 5-HT3 agonist (1-phenylbiguanide) and a 5-HT2 agonist [1-(4-bromophenyl-2,5-dimethoxy)-2-aminopropane (DOB)] had no significant effect. As most 5-HT receptors in the SNr are of the 5-HT1B subtype, these results suggest that the increased VCM frequency was mediated via nigral 5-HT1B receptors. The importance of 5-HTergic mechanisms in the development of drug-induced dyskinesias is discussed.

  15. Characterization of the 5-HT7 receptor. Determination of the pharmacophore for 5-HT7 receptor agonism and CoMFA-based modeling of the agonist binding site

    NARCIS (Netherlands)

    Vermeulen, ES; Schmidt, AW; Sprouse, JS; Wikstrom, HV; Grol, CJ

    2003-01-01

    On the basis of a set of 20 diverse 5-HT7 receptor agonists, the pharmacophore for 5-HT7 receptor agonism was determined. Additionally two CoMFA models were developed, based on different alignments of the agonists. Both models show good correlations between experimental and predictive pK(i) values

  16. Ah receptor agonist activity in frequently consumed food items

    NARCIS (Netherlands)

    Waard, de W.J.; Aarts, J.M.M.J.G.; Peijnenburg, A.A.C.M.; Kok, de T.M.C.M.; Schooten, van F.J.; Hoogenboom, L.A.P.

    2008-01-01

    The aryl hydrocarbon receptor (AhR) receives much attention for its role in the toxicity of dioxins and dioxin-like polychlorinated biphenyls. However, many other compounds have also been reported to bind and activate AhR, of which natural food components are of special interest from a human health

  17. Synthesis and enantiopharmacology of new AMPA-kainate receptor agonists

    DEFF Research Database (Denmark)

    Conti, P; De Amici, M; De Sarro, G

    1999-01-01

    , and the rat cortical wedge preparation. CIP-A showed a good affinity for both 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) and kainic acid (KAIN) receptors. These results were confirmed in the cortical slice model where CIP-A displayed an EC(50) value very close to that of AMPA...

  18. The use of anchored agonists of phagocytic receptors for cancer immunotherapy: B16-F10 murine melanoma model.

    Directory of Open Access Journals (Sweden)

    Tereza Janotová

    Full Text Available The application of the phagocytic receptor agonists in cancer immunotherapy was studied. Agonists (laminarin, molecules with terminal mannose, N-Formyl-methioninyl-leucyl-phenylalanine were firmly anchored to the tumor cell surface. When particular agonists of phagocytic receptors were used together with LPS (Toll-like receptor agonist, high synergy causing tumour shrinkage and a temporary or permanent disappearance was observed. Methods of anchoring phagocytic receptor agonists (charge interactions, anchoring based on hydrophobic chains, covalent bonds and various regimes of phagocytic agonist/LPS mixture applications were tested to achieve maximum therapeutic effect. Combinations of mannan/LPS and f-MLF/LPS (hydrophobic anchors in appropriate (pulse regimes resulted in an 80% and 60% recovery for mice, respectively. We propose that substantial synergy between agonists of phagocytic and Toll-like receptors (TLR is based on two events. The TLR ligand induces early and massive inflammatory infiltration of tumors. The effect of this cell infiltrate is directed towards tumor cells, bearing agonists of phagocytic receptors on their surface. The result of these processes was effective killing of tumor cells. This novel approach represents exploitation of innate immunity mechanisms for treating cancer.

  19. Kinetics of agonist-induced intrinsic fluorescence changes in the Torpedo acetylcholine receptor.

    Science.gov (United States)

    Kawai, Hideki; Raftery, Michael A

    2010-05-01

    The nicotinic acetylcholine receptor from Torpedo electric organs is a ligand-gated ion channel that undergoes conformational transitions for activation and/or desensitization. Earlier work suggested that intrinsic fluorescence changes of the receptor monitors kinetic transitions toward the high-affinity, desensitized state. Here, using highly purified membrane preparations to minimize contaminating fluorescence, we examined kinetic mechanisms of the receptor as monitored by its intrinsic fluorescence. Fluorescence changes were specific to the receptor as they were blocked by alpha-bungarotoxin and were induced by agonists, but not by the antagonist hexamethonium. Acetylcholine, carbamylcholine and suberyldicholine showed only one kinetic phase with relatively fast rates (t(1/2) = 0.2-1.2 s). Effective dissociation constants were at least an order of magnitude higher than the high affinity, equilibrium binding constants for these agonists. A semirigid agonist isoarecolone-methiodide, whose activation constant was approximately 3-fold lower than acetylcholine, induced an additional slow phase (t(1/2) = 4.5-9 s) with apparent rates that increased and then decreased in a concentration dependent manner, revealing a branched mechanism for conformational transitions. We propose that the intrinsic fluorescence changes of the receptor describe a process(es) toward a fast desensitization state prior to the formation of the high affinity state.

  20. Identification of the antiarrhythmic drugs amiodarone and lorcainide as potent H3 histamine receptor inverse agonists.

    Science.gov (United States)

    Del Tredici, Andria L; Ma, Jian-Nong; Piu, Fabrice; Burstein, Ethan S

    2014-01-01

    Use of molecular pharmacology to reprofile older drugs discovered before the advent of recombinant technologies is a fruitful method to elucidate mechanisms of drug action, expand understanding of structure-activity relationships between drugs and receptors, and in some cases, repurpose approved drugs. The H3 histamine receptor is a G-protein-coupled receptor (GPCR) primarily expressed in the central nervous system where among many things it modulates cognitive processes, nociception, feeding and drinking behavior, and sleep/wakefulness. In binding assays and functional screens of the H3 histamine receptor, the antiarrhythmic drugs lorcainide and amiodarone were identified as potent, selective antagonists/inverse agonists of human and rat H3 histamine receptors, with relatively little or no activity at over 20 other monoamine GPCRs, including H1, H2, and H4 receptors. Potent antagonism of H3 receptors was unique to amiodarone and lorcainide of 20 antiarrhythmic drugs tested, representing six pharmacological classes. These results expand the pharmacophore of H3 histamine receptor antagonist/inverse agonists and may explain, in part, the effects of lorcainide on sleep in humans.

  1. A Novel Non-Peptidic Agonist of the Ghrelin Receptor with Orexigenic Activity In vivo

    Science.gov (United States)

    Pastor-Cavada, Elena; Pardo, Leticia M.; Kandil, Dalia; Torres-Fuentes, Cristina; Clarke, Sarah L.; Shaban, Hamdy; McGlacken, Gerard P.; Schellekens, Harriet

    2016-11-01

    Loss of appetite in the medically ill and ageing populations is a major health problem and a significant symptom in cachexia syndromes, which is the loss of muscle and fat mass. Ghrelin is a gut-derived hormone which can stimulate appetite. Herein we describe a novel, simple, non-peptidic, 2-pyridone which acts as a selective agonist for the ghrelin receptor (GHS-R1a). The small 2-pyridone demonstrated clear agonistic activity in both transfected human cells and mouse hypothalamic cells with endogenous GHS-R1a receptor expression. In vivo tests with the hit compound showed significant increased food intake following peripheral administration, which highlights the potent orexigenic effect of this novel GHS-R1a receptor ligand.

  2. Highly selective and potent agonists of sphingosine-1-phosphate 1 (S1P1) receptor.

    Science.gov (United States)

    Vachal, Petr; Toth, Leslie M; Hale, Jeffrey J; Yan, Lin; Mills, Sander G; Chrebet, Gary L; Koehane, Carol A; Hajdu, Richard; Milligan, James A; Rosenbach, Mark J; Mandala, Suzanne

    2006-07-15

    Novel series of sphingosine-1-phosphate (S1P) receptor agonists were developed through a systematic SAR aimed to achieve high selectivity for a single member of the S1P family of receptors, S1P1. The optimized structure represents a highly S1P1-selective and efficacious agonist: S1P1/S1P2, S1P1/S1P3, S1P1/S1P4>10,000-fold, S1P1/S1P5>600-fold, while EC50 (S1P1) <0.2 nM. In vivo experiments are consistent with S1P1 receptor agonism alone being sufficient for achieving desired lymphocyte-lowering effect.

  3. High constitutive signaling of the ghrelin receptor--identification of a potent inverse agonist

    DEFF Research Database (Denmark)

    Holst, Birgitte; Cygankiewicz, Adam; Jensen, Tine Halkjaer

    2003-01-01

    Ghrelin is a GH-releasing peptide that also has an important role as an orexigenic hormone-stimulating food intake. By measuring inositol phosphate turnover or by using a reporter assay for transcriptional activity controlled by cAMP-responsive elements, the ghrelin receptor showed strong, ligand......-independent signaling in transfected COS-7 or human embryonic kidney 293 cells. Ghrelin and a number of the known nonpeptide GH secretagogues acted as agonists stimulating inositol phosphate turnover further. In contrast, the low potency ghrelin antagonist, [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-substance P was surprisingly...... found to be a high potency (EC50 = 5.2 nm) full inverse agonist as it decreased the constitutive signaling of the ghrelin receptor down to that observed in untransfected cells. The homologous motilin receptor functioned as a negative control as it did not display any sign of constitutive activity...

  4. A successful treatment of buprenorphine withdrawal with the dopamine receptor agonist pramipexole.

    Science.gov (United States)

    Makhinson, Michael; Gomez-Makhinson, Juliana

    2014-01-01

    Buprenorphine, used for treating opioid dependence, may have a withdrawal syndrome requiring treatment. Modulation of the dopamine system, which has been implicated in opioid withdrawal, may be a target for withdrawal for opioids such as buprenorphine. A case is reported of a buprenorphine withdrawal syndrome with predominant symptoms of restlessness that were resistant to clonidine and benzodiazepines. It was successfully treated with the dopamine agonist pramipexole. Dopamine receptor agonists may have a place in the treatment of restlessness associated with opioid withdrawal and may have value for the broader spectrum of opioid withdrawal symptoms. © American Academy of Addiction Psychiatry.

  5. Agonist antagonist interactions at the rapidly desensitizing P2X3 receptor.

    Directory of Open Access Journals (Sweden)

    Nick Helms

    Full Text Available P2X3 receptors (P2XRs, as members of the purine receptor family, are deeply involved in chronic pain sensation and therefore, specific, competitive antagonists are of great interest for perspective pain management. Heretofore, Schild plot analysis has been commonly used for studying the interaction of competitive antagonists and the corresponding receptor. Unfortunately, the steady-state between antagonist and agonist, as a precondition for this kind of analysis, cannot be reached at fast desensitizing receptors like P2X3R making Schild plot analysis inappropriate. The aim of this study was to establish a new method to analyze the interaction of antagonists with their binding sites at the rapidly desensitizing human P2X3R. The patch-clamp technique was used to investigate the structurally divergent, preferential antagonists A317491, TNP-ATP and PPADS. The P2X1,3-selective α,β-methylene ATP (α,β-meATP was used as an agonist to induce current responses at the wild-type (wt P2X3R and several agonist binding site mutants. Afterwards a Markov model combining sequential transitions of the receptor from the closed to the open and desensitized mode in the presence or absence of associated antagonist molecules was developed according to the measured data. The P2X3R-induced currents could be fitted correctly with the help of this Markov model allowing identification of amino acids within the binding site which are important for antagonist binding. In conclusion, Markov models are suitable to simulate agonist antagonist interactions at fast desensitizing receptors such as the P2X3R. Among the antagonists investigated, TNP-ATP and A317491 acted in a competitive manner, while PPADS was identified as a (pseudoirreversible blocker.

  6. Isolation and characterization of coronary endothelial and smooth muscle cells from A1 adenosine receptor-knockout mice

    OpenAIRE

    Teng, Bunyen; Ansari, Habib R.; Oldenburg, Peter J.; Schnermann, J.; Mustafa, S. Jamal

    2005-01-01

    Mice have been used widely in in vivo and in vitro cardiovascular research. The availability of knockout mice provides further clues to the physiological significance of specific receptor subtypes. Adenosine A1 receptor (A1AR)-knockout (A1KO) mice and their wild-type (A1WT) controls were employed in this investigation. The heart and aortic arch were carefully removed and retroinfused with enzyme solution (1 mg/ml collagenase type I, 0.5 mg/ml soybean trypsin inhibitor, 3% BSA, and 2% antibiot...

  7. Novel 4-thiazolidinone derivatives as agonists of benzodiazepine receptors

    OpenAIRE

    Faizi, Mehrdad; Jahani, Reza; Ebadi, Seyed Abbas; Tabatabai, Sayyed Abbas; Rezaee, Elham; Lotfaliei, Mehrnaz; Amini, Mohsen; Almasirad, Ali

    2017-01-01

    A new series of 4-chloro-N-(2-(substitutedphenyl)-4-oxothiazolidin-3-yl)-2-phenoxybenzamide derivatives were designed, synthesized and biologically evaluated as anticonvulsant agents. The designed compounds have the main essential functional groups for binding to the benzodiazepine receptors and 4-thiazolidinone ring as an anticonvulsant pharmacophore. Some of the new synthesized compounds showed considerable anticonvulsant activity in electroshock and pentylenetetrazole-induced lethal convul...

  8. Astrocytic Lrp4 (Low-Density Lipoprotein Receptor-Related Protein 4) Contributes to Ischemia-Induced Brain Injury by Regulating ATP Release and Adenosine-A2AR (Adenosine A2A Receptor) Signaling.

    Science.gov (United States)

    Ye, Xin-Chun; Hu, Jin-Xia; Li, Lei; Li, Qiang; Tang, Fu-Lei; Lin, Sen; Sun, Dong; Sun, Xiang-Dong; Cui, Gui-Yun; Mei, Lin; Xiong, Wen-Cheng

    2018-01-01

    Lrp4 (low-density lipoprotein receptor-related protein 4) is predominantly expressed in astrocytes, where it regulates glutamatergic neurotransmission by suppressing ATP release. Here, we investigated Lrp4's function in ischemia/stroke-induced brain injury response, which includes glutamate-induced neuronal death and reactive astrogliosis. The brain-specific Lrp4 conditional knockout mice (Lrp4 GFAP-Cre ), astrocytic-specific Lrp4 conditional knockout mice (Lrp4 GFAP-creER ), and their control mice (Lrp4 f/f ) were subjected to photothrombotic ischemia and the transient middle cerebral artery occlusion. After ischemia/stroke, mice or their brain samples were subjected to behavior tests, brain histology, immunofluorescence staining, Western blot, and quantitative real-time polymerase chain reaction. In addition, primary astrocytes and neurons were cocultured with or without oxygen and glucose deprivation and in the presence or absence of the antagonist for adenosine-A 2A R (adenosine A2A receptor) or ATP-P2X7R (P2X purinoceptor 7) signaling. Gliotransmitters, such as glutamate, d-serine, ATP, and adenosine, in the condition medium of cultured astrocytes were also measured. Lrp4, largely expressed in astrocytes, was increased in response to ischemia/stroke. Both Lrp4 GFAP-Cre and Lrp4 GFAP-creER mice showed less brain injury, including reduced neuronal death, and impaired reactive astrogliosis. Mechanistically, Lrp4 conditional knockout in astrocytes increased ATP release and the production of ATP derivative, adenosine, which were further elevated by oxygen and glucose deprivation. Pharmacological inhibition of ATP-P 2 X 7 R or adenosine-A 2A R signaling diminished Lrp4 GFAP-creER 's protective effect. The astrocytic Lrp4 plays an important role in ischemic brain injury response. Lrp4 deficiency in astrocytes seems to be protective in response to ischemic brain injury, likely because of the increased ATP release and adenosine-A 2A R signaling. © 2017 American Heart

  9. Cannabidiol is a partial agonist at dopamine D2High receptors, predicting its antipsychotic clinical dose.

    Science.gov (United States)

    Seeman, P

    2016-10-18

    Although all current antipsychotics act by interfering with the action of dopamine at dopamine D2 receptors, two recent reports showed that 800 to 1000 mg of cannabidiol per day alleviated the signs and symptoms of schizophrenia, although cannabidiol is not known to act on dopamine receptors. Because these recent clinical findings may indicate an important exception to the general rule that all antipsychotics interfere with dopamine at dopamine D2 receptors, the present study examined whether cannabidiol acted directly on D2 receptors, using tritiated domperidone to label rat brain striatal D2 receptors. It was found that cannabidiol inhibited the binding of radio-domperidone with dissociation constants of 11 nm at dopamine D2High receptors and 2800 nm at dopamine D2Low receptors, in the same biphasic manner as a dopamine partial agonist antipsychotic drug such as aripiprazole. The clinical doses of cannabidiol are sufficient to occupy the functional D2High sites. it is concluded that the dopamine partial agonist action of cannabidiol may account for its clinical antipsychotic effects.

  10. Distinct Signaling Cascades Elicited by Different Formyl Peptide Receptor 2 (FPR2 Agonists

    Directory of Open Access Journals (Sweden)

    Fabio Cattaneo

    2013-04-01

    Full Text Available The formyl peptide receptor 2 (FPR2 is a remarkably versatile transmembrane protein belonging to the G-protein coupled receptor (GPCR family. FPR2 is activated by an array of ligands, which include structurally unrelated lipids and peptide/proteins agonists, resulting in different intracellular responses in a ligand-specific fashion. In addition to the anti-inflammatory lipid, lipoxin A4, several other endogenous agonists also bind FPR2, including serum amyloid A, glucocorticoid-induced annexin 1, urokinase and its receptor, suggesting that the activation of FPR2 may result in potent pro- or anti-inflammatory responses. Other endogenous ligands, also present in biological samples, include resolvins, amyloidogenic proteins, such as beta amyloid (Aβ-42 and prion protein (Prp106–126, the neuroprotective peptide, humanin, antibacterial peptides, annexin 1-derived peptides, chemokine variants, the neuropeptides, vasoactive intestinal peptide (VIP and pituitary adenylate cyclase activating polypeptide (PACAP-27, and mitochondrial peptides. Upon activation, intracellular domains of FPR2 mediate signaling to G-proteins, which trigger several agonist-dependent signal transduction pathways, including activation of phospholipase C (PLC, protein kinase C (PKC isoforms, the phosphoinositide 3-kinase (PI3K/protein kinase B (Akt pathway, the mitogen-activated protein kinase (MAPK pathway, p38MAPK, as well as the phosphorylation of cytosolic tyrosine kinases, tyrosine kinase receptor transactivation, phosphorylation and nuclear translocation of regulatory transcriptional factors, release of calcium and production of oxidants. FPR2 is an attractive therapeutic target, because of its involvement in a range of normal physiological processes and pathological diseases. Here, we review and discuss the most significant findings on the intracellular pathways and on the cross-communication between FPR2 and tyrosine kinase receptors triggered by different FPR2

  11. Monoterpenoids induce agonist-specific desensitization of transient receptor potential vanilloid-3 (TRPV3) ion channels.

    Science.gov (United States)

    Sherkheli, Muhammad Azhar; Benecke, Heike; Doerner, Julia Franca; Kletke, Olaf; Vogt-Eisele, A K; Gisselmann, Guenter; Hatt, Hanns

    2009-01-01

    Transient receptor potential vanilloid-3 (TRPV3) is a thermo-sensitive ion channel expressed in skin keratinocytes and in a variety of neural cells. It is activated by warmth as well as monoterpenoids including camphor, menthol, dihydrocarveol and 1,8-cineol. TRPV3 is described as a putative nociceptor and previous studies revealed sensitization of the channel during repeated short-term stimulation with different agonists. In the present investigation TRPV3 was transiently expressed in either Xenopus oocytes or HEK293 cells. Whole-cell voltage-clamp techniques were used to characterize the behavior of TRPV3 when challenged with different agonists. Similarly, a human keratinocyte-derived cell line (HaCaT cells) was used to monitor the behavior of native TRPV3 when challenged with different agonists. We report here that prolonged exposure (5-15 minutes) of monoterpenoids results in agonist-specific desensitization of TRPV3. Long-term exposure to camphor and 1,8-cineol elicits desensitizing currents in TRPV3 expressing oocytes, whereas the non-terpenoid agonist 2-APB induces sustained currents. Agonist-specific desensitization of endogenous TRPV3 was also found in HaCaT cells, which may be taken as a representative for the native system. Terpenoids have a long history of use in therapeutics, pharmaceuticals and cosmetics but knowledge about underpinning molecular mechanisms is incomplete. Our finding on agonist-induced desensitization of TRPV3 by some monoterpenoids displays a novel mechanism through which TRP channels could be functionally modulated. Desensitization of TRPV3 channels might be the molecular basis of action for some of the medicinal properties of camphor and 1,8-cineol.

  12. A2A adenosine receptor antagonists to weaken the hypoxia-HIF-1α driven immunosuppression and improve immunotherapies of cancer.

    Science.gov (United States)

    Hatfield, Stephen M; Sitkovsky, Michail

    2016-08-01

    Hypoxic and adenosine rich tumor microenvironments represent an important barrier that must be overcome to enable T and NK cells to reject tumors. The A2A adenosine receptor (A2AR) on activated immune cells was identified as a critical and non-redundant mediator of physiological immunosuppression. Observations showing that tumor-protecting A2AR also suppress and redirect the anti-tumor immune response pointed to the importance of inhibiting this pathway to improve cancer immunotherapy. We advocated (i) blocking immunosuppressive adenosine-A2AR-cAMP-mediated intracellular signaling by A2AR antagonists and (ii) weakening hypoxia-HIF-1α-mediated accumulation of extracellular adenosine by oxygenation agents that also inhibits CD39/CD73 adenosine-generating enzymes. In view of commencing clinical trials of synthetic A2AR antagonists in combination with cancer immunotherapies, we discuss their promise and exclusion criteria. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Peroxisome proliferator-activated receptor-delta agonist ameliorated inflammasome activation in nonalcoholic fatty liver disease.

    Science.gov (United States)

    Lee, Hyun Jung; Yeon, Jong Eun; Ko, Eun Jung; Yoon, Eileen L; Suh, Sang Jun; Kang, Keunhee; Kim, Hae Rim; Kang, Seoung Hee; Yoo, Yang Jae; Je, Jihye; Lee, Beom Jae; Kim, Ji Hoon; Seo, Yeon Seok; Yim, Hyung Joon; Byun, Kwan Soo

    2015-12-07

    To evaluate the inflammasome activation and the effect of peroxisome proliferator-activated receptors (PPAR)-δ agonist treatment in nonalcoholic fatty liver disease (NAFLD) models. Male C57BL/6J mice were classified according to control or high fat diet (HFD) with or without PPAR-δ agonist (GW) over period of 12 wk [control, HFD, HFD + lipopolysaccharide (LPS), HFD + LPS + GW group]. HepG2 cells were exposed to palmitic acid (PA) and/or LPS in the absence or presence of GW. HFD caused glucose intolerance and hepatic steatosis. In mice fed an HFD with LPS, caspase-1 and interleukin (IL)-1β in the liver were significantly increased. Treatment with GW ameliorated the steatosis and inhibited overexpression of pro-inflammatory cytokines. In HepG2 cells, PA and LPS treatment markedly increased mRNA of several nucleotide-binding and oligomerization domain-like receptor family members (NLRP3, NLRP6, and NLRP10), caspase-1 and IL-1β. PA and LPS also exaggerated reactive oxygen species production. All of the above effects of PA and LPS were reduced by GW. GW also enhanced the phosphorylation of AMPK-α. PPAR-δ agonist reduces fatty acid-induced inflammation and steatosis by suppressing inflammasome activation. Targeting the inflammasome by the PPAR-δ agonist may have therapeutic implication for NAFLD.

  14. Enhanced neurodegeneration after a high dose of methamphetamine in adenosine A3 receptor null mutant mice.

    Science.gov (United States)

    Shen, H; Luo, Y; Yu, S-J; Wang, Y

    2011-10-27

    Previous reports have indicated that adenosine A3 receptor (A3R) knockout mice are more sensitive to ischemic or hypoxic brain injury. The purpose of this study was to examine if suppression of A3R expression is associated with increase in sensitivity to injury induced by a high dose of methamphetamine (Meth). Adult male A3R null mutant (-/-) mice and their controls (+/+) were injected with four doses (2 h apart) of Meth (10 mg/kg) or saline. Animals were placed in a behavioral activity chamber, equipped with food and water, for 52 h starting from one day after injections. The first 4 h were used for studying exploratory behaviors, and the next 48 h were used to measure locomotor activity. High doses of Meth equally reduced the 4-h exploratory behavior in -/- and +/+ mice. Meth suppressed locomotor activity between 4 and 52 h in both groups, with a greater reduction being found in the -/- mice. Brain tissues were collected at 3 days after the Meth or saline injections. Meth treatment reduced striatal dopamine (DA) levels in both +/+ and -/- mice with an increase in 3,4-dihydroxyphenylacetic acid (DOPAC)/DA ratio being found only in -/- animals. Meth also significantly increased ionized calcium-binding adaptor molecule 1 (Iba-1) and cleaved caspase-3 level in striatum, as well as Iba-1 and TNFα mRNA expression in nigra in -/-, compared to +/+, mice. Previous studies have shown that pharmacological suppression of vesicular monoamine transport 2 (VMAT2) by reserpine enhanced Meth toxicity by increasing cytosolic DA and inflammation. A significant reduction in striatal VMAT2 expression was found in -/- mice compared to +/+ mice, suggesting that increase in sensitivity to Meth injury in -/- mice may be related to a reduction in VMAT2 expression in these mice. In conclusion, our data suggest that A3R -/- mice are more sensitive to high doses of Meth. Published by Elsevier Ltd.

  15. Long-term treatment with the beta-3 adrenoceptor agonist, mirabegron ameliorates detrusor overactivity and restores cyclic adenosine monophosphate (cAMP) levels in obese mice.

    Science.gov (United States)

    Calmasini, Fabiano B; de Oliveira, Mariana G; Alexandre, Eduardo C; da Silva, Fábio H; da Silva, Carmem P V; Candido, Tuany Z; Antunes, Edson; Mónica, Fabíola Z

    2017-08-01

    To evaluate the effects of the beta-3 adrenoceptor agonist, mirabegron in a mouse model of detrusor overactivity induced by obesity. C57BL/6 male mice were fed with standard chow or high-fat diet for 12 weeks. Lean and obese mice were treated orally with mirabegron (10 mg/kg/day) from the last 2 weeks of diet. Cystometric evaluations, functional assays, protein expression for phosphodiesterase type 4 (PDE4), and cyclic adenosine monophosphate (cAMP) measurement were carried out. In obese mice the body weight, epididymal fat mass, fasting glucose, and low-density lipoprotein (LDL) levels were higher (P < 0.001) than in the lean mice. A reduction of 34% and 54% and an increase of 35% in the epididimal fat, LDL, and HDL levels (P < 0.05), respectively, were observed in the obese group treated with mirabegron, whereas no changes were seen in the lipid profile from lean mice. Obese group showed irregular micturition pattern, characterized by significant increases in frequency and non-void contractions. Carbachol, potassium chloride, and electrical-field stimulation induced detrusor smooth muscle (DSM) contractions, which were greater in bladders from obese mice than from lean mice. Two-week treatment with mirabegron restored all the contractile response alterations in the DSM. Basal intracellular levels of cAMP were reduced (68%), whereas PDE4 protein expression was increased (54%) in bladder from obese mice. Mirabegron restored the cAMP levels in obese bladder, without changing the PDE4 expression. Mirabegron was able to completely restore the urinary alterations seen in the bladder from obese mice. © 2016 Wiley Periodicals, Inc.

  16. Agonist activity of LSD and lisuride at cloned 5HT2A and 5HT2C receptors.

    Science.gov (United States)

    Egan, C T; Herrick-Davis, K; Miller, K; Glennon, R A; Teitler, M

    1998-04-01

    Evidence from studies with phenylisopropylamine hallucinogens indicates that the 5HT2A receptor is the likely target for the initiation of events leading to hallucinogenic activity associated with LSD and related drugs. Recently, lisuride (a purported non-hallucinogenic congener of LSD) was reported to be a potent antagonist at the 5HT2C receptor and an agonist at the 5HT2A receptor. LSD exhibited agonist activity at both receptors. These data were interpreted as indicating that the 5HT2C receptor might be the initiating site of action for hallucinogens. To test this hypothesis, recombinant cells expressing 5HT2A and 5HT2C receptors were used to determine the actions of LSD and lisuride. LSD and lisuride were potent partial agonists at 5HT2A receptors with EC50 values of 7.2 nM and 17 nM, respectively. Also, LSD and lisuride were partial agonists at 5HT2C receptors with EC50 values of 27 nM and 94 nM, respectively. We conclude that lisuride and LSD have similar actions at 5HT2A and 5HT2C receptors in recombinant cells. As agonist activity at brain 5HT2A receptors has been associated with hallucinogenic activity, these results indicate that lisuride may possess hallucinogenic activity, although the psychopharmacological effects of lisuride appear to be different from the hallucinogenic effects of LSD.

  17. Comparison of the effects of the GABAB receptor positive modulator BHF177 and the GABAB receptor agonist baclofen on anxiety-like behavior, learning, and memory in mice

    OpenAIRE

    Li, Xia; Risbrough, Victoria B.; Cates-Gatto, Chelsea; Kaczanowska, Katarzyna; Finn, M. G.; Roberts, Amanda J; Markou, Athina

    2013-01-01

    γ-Aminobutyric acid B (GABAB) receptor activation is a potential therapeutic approach for the treatment of drug addiction, pain, anxiety, and depression. However, full agonists of this receptor induce side-effects, such as sedation, muscle relaxation, tolerance, and cognitive disruption. Positive allosteric modulators (PAMs) of the GABAB receptor may have similar therapeutic effects as agonists with superior side-effect profiles. The present study behaviorally characterized N-([1R,2R,4S]-bicy...

  18. Immunoactive effects of cannabinoids: considerations for the therapeutic use of cannabinoid receptor agonists and antagonists

    Science.gov (United States)

    Greineisen, William E.; Turner., Helen

    2013-01-01

    The active constituents of Cannabis sativa have been used for centuries as recreational drugs and medicinal agents. Today, marijuana is the most prevalent drug of abuse in the United States and, conversely, therapeutic use of marijuana constituents are gaining mainstream clinical and political acceptance. Given the documented contributions of endocannabinoid signaling to a range of physiological systems, including cognitive function, and the control of eating behaviors, it is unsurprising that cannabinoid receptor agonists and antagonists are showing significant clinical potential. In addition to the neuroactive effects of cannabinoids, an emerging body of data suggests that both endogenous and exogenous cannabinoids are potently immunoactive. The central premise of this review article is that the immunological effects of cannabinoids should be considered in the context of each prescribing decision. We present evidence that the immunological effects of cannabinoid receptor agonists and antagonists are highly relevant to the spectrum of disorders for which cannabinoid therapeutics are currently offered. PMID:20219697

  19. Therapeutic Effects of Melatonin Receptor Agonists on Sleep and Comorbid Disorders

    Directory of Open Access Journals (Sweden)

    Moshe Laudon

    2014-09-01

    Full Text Available Several melatonin receptors agonists (ramelteon, prolonged-release melatonin, agomelatine and tasimelteon have recently become available for the treatment of insomnia, depression and circadian rhythms sleep-wake disorders. The efficacy and safety profiles of these compounds in the treatment of the indicated disorders are reviewed. Accumulating evidence indicates that sleep-wake disorders and co-existing medical conditions are mutually exacerbating. This understanding has now been incorporated into the new Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5. Therefore, when evaluating the risk/benefit ratio of sleep drugs, it is pertinent to also evaluate their effects on wake and comorbid condition. Beneficial effects of melatonin receptor agonists on comorbid neurological, psychiatric, cardiovascular and metabolic symptomatology beyond sleep regulation are also described. The review underlines the beneficial value of enhancing physiological sleep in comorbid conditions.

  20. Treatment of type 2 diabetes with glucagon-like peptide-1 receptor agonists

    DEFF Research Database (Denmark)

    Hansen, K B; Knop, F K; Holst, Jens Juul

    2009-01-01

    The incretin system is an area of great interest for the development of new therapies for the management of type 2 diabetes. Existing antidiabetic drugs are often insufficient at getting patients to glycaemic goals. Furthermore, current treatment modalities are not able to prevent the continued...... ongoing decline in pancreatic beta-cell function and, lastly, they have a number of side effects including hypoglycaemia and weight gain. Glucagon-like peptide-1 (GLP-1) receptor agonists are a new class of pharmacological agents, which improve glucose homeostasis in a multifaceted way. Their effects...... of hypoglycaemia with GLP-1 receptor agonists is low, the compounds have clinically relevant effects on body weight, and data are suggesting beneficial effects on cardiovascular risk factors. Exenatide was released in 2005 for the treatment of type 2 diabetes and liraglutide is expected to be approved by the Food...

  1. Theophylline, adenosine receptor antagonist prevents behavioral, biochemical and neurochemical changes associated with an animal model of tardive dyskinesia.

    Science.gov (United States)

    Bishnoi, Mahendra; Chopra, Kanwaljit; Kulkarni, Shrinivas K

    2007-01-01

    Tardive dyskinesia is considered to be the late onset adverse effect of prolonged administration of typical neuroleptic drugs. Adenosine is now widely accepted as the major inhibitory neuromodulators in the central nervous system besides GABA. Antagonists of A2A receptors are known to confer protection against neuronal damage caused by toxins and reactive oxygen species. The present study investigated the effect of adenosine receptor antagonist, theophylline (25 and 50 mg/kg, ip) in an animal model of tardive dyskinesia by using different behavioral (orofacial dyskinetic movements, stereotypy, locomotor activity, % retention), biochemical (lipid peroxidation, reduced glutathione levels, antioxidant enzyme levels (SOD and catalase)) and neurochemical (neurotransmitter levels) parameters. Chronic administration of haloperidol (1 mg/kg ip for 21 days) significantly increased vacuous chewing movements (VCMs), tongue protrusions, facial jerking in rats which was dose-dependently inhibited by theophylline. Chronic administration of haloperidol also resulted in the increased dopamine receptor sensitivity as evidenced by increased locomotor activity and stereotypic rearing. Further, it also decreased % retention time in elevated plus maze paradigm. Pretreatment with theophylline reversed these behavioral changes. Chronic administration of haloperidol also induced oxidative damage in all the brain regions which was prevented by theophylline, especially in the striatum. Chronic administration of haloperidol resulted in a decrease in dopamine levels which was reversed by treatment with theophylline (at higher doses). The findings of the present study suggested the involvement of adenosinergic receptor system in the development of tardive dyskinesia and possible therapeutic potential of theophylline in this disorder.

  2. Perinatal caffeine, acting on maternal adenosine A(1 receptors, causes long-lasting behavioral changes in mouse offspring.

    Directory of Open Access Journals (Sweden)

    Olga Björklund

    Full Text Available BACKGROUND: There are lingering concerns about caffeine consumption during pregnancy or the early postnatal period, partly because there may be long-lasting behavioral changes after caffeine exposure early in life. METHODOLOGY/PRINCIPAL FINDINGS: We show that pregnant wild type (WT mice given modest doses of caffeine (0.3 g/l in drinking water gave birth to offspring that as adults exhibited increased locomotor activity in an open field. The offspring also responded to cocaine challenge with greater locomotor activity than mice not perinatally exposed to caffeine. We performed the same behavioral experiments on mice heterozygous for adenosine A(1 receptor gene (A(1RHz. In these mice signaling via adenosine A(1 receptors is reduced to about the same degree as after modest consumption of caffeine. A(1RHz mice had a behavioral profile similar to WT mice perinatally exposed to caffeine. Furthermore, it appeared that the mother's genotype, not offspring's, was critical for behavioral changes in adult offspring. Thus, if the mother partially lacked A(1 receptors the offspring displayed more hyperactivity and responded more strongly to cocaine stimulation as adults than did mice of a WT mother, regardless of their genotype. This indicates that long-term behavioral alterations in the offspring result from the maternal effect of caffeine, and not a direct effect on fetus. WT offspring from WT mother but having a A(1R Hz grandmother preserved higher locomotor response to cocaine. CONCLUSIONS/SIGNIFICANCE: We suggest that perinatal caffeine, by acting on adenosine A(1 receptors in the mother, causes long-lasting behavioral changes in the offspring that even manifest themselves in the second generation.

  3. Comparative pharmacokinetics and pharmacodynamics of platelet adenosine diphosphate receptor antagonists and their clinical implications.

    Science.gov (United States)

    Floyd, Christopher N; Passacquale, Gabriella; Ferro, Albert

    2012-07-01

    Over the last two decades or more, anti-platelet therapy has become established as a cornerstone in the treatment of patients with ischaemic cardiovascular disease, since such drugs effectively reduce arterial thrombotic events. The original agent used in this context was aspirin (acetylsalicylic acid) but, with the advent of adenosine diphosphate (ADP) receptor antagonists, the use of dual anti-platelet therapy has resulted in further improvement in cardiovascular outcomes when compared with aspirin alone. The first group of platelet ADP receptor antagonists to be developed was the thienopyridine class, which comprise inactive pro-drugs that require in vivo metabolism to their active metabolites before exerting their inhibitory effect on the P2Y(12) receptor. Clopidogrel has been the principal ADP receptor antagonist in use over the past decade, but is limited by variability in its in vivo inhibition of platelet aggregation (IPA). The pharmacokinetics of clopidogrel are unpredictable due to their vulnerability to multiple independent factors including genetic polymorphisms. Expression of the 3435T/T genetic variant encoding the MDR1 gene for the P-glycoprotein efflux transporter results in a significantly reduced maximum drug concentration and area under the plasma concentration-time curve as intestinal absorption of clopidogrel is reduced; and the expression of the mutant *2 allele of CYP2C19 results in similar pharmacokinetic effects as the two cytochrome P450 (CYP)-mediated steps required for the production of the active metabolite of clopidogrel are impaired. These variable pharmacokinetics lead to erratic pharmacodynamics and cannot reliably be overcome with increased dosing. Both prasugrel, a third-generation thienopyridine, and ticagrelor, a cyto-pentyl-triazolo-pyrimidine, have more predictable pharmacokinetics and enhanced pharmacodynamics than clopidogrel. Neither appears to be affected by the same genetic polymorphisms as clopidogrel; prasugrel requires

  4. Heterocyclic acetamide and benzamide derivatives as potent and selective beta3-adrenergic receptor agonists with improved rodent pharmacokinetic profiles.

    Science.gov (United States)

    Goble, Stephen D; Wang, Liping; Howell, K Lulu; Bansal, Alka; Berger, Richard; Brockunier, Linda; DiSalvo, Jerry; Feighner, Scott; Harper, Bart; He, Jiafang; Hurley, Amanda; Hreniuk, Donna; Parmee, Emma; Robbins, Michael; Salituro, Gino; Sanfiz, Anthony; Streckfuss, Eric; Watkins, Eloisa; Weber, Ann E; Struthers, Mary; Edmondson, Scott D

    2010-03-15

    A series of amide derived beta(3)-adrenergic receptor (AR) agonists is described. The discovery and optimization of several series of compounds derived from 1, is used to lay the SAR foundation for second generation beta(3)-AR agonists for the treatment of overactive bladder. Copyright 2010 Elsevier Ltd. All rights reserved.

  5. Nonpeptide orexin type-2 receptor agonist ameliorates narcolepsy-cataplexy symptoms in mouse models

    OpenAIRE

    Irukayama-Tomobe, Yoko; Ogawa, Yasuhiro; Tominaga, Hiromu; Ishikawa, Yukiko; Hosokawa, Naoto; Ambai, Shinobu; Kawabe, Yuki; Uchida, Shuntaro; Nakajima, Ryo; Saitoh, Tsuyoshi; Kanda, Takeshi; Vogt, Kaspar; Sakurai, Takeshi; Nagase, Hiroshi; Yanagisawa, Masashi

    2017-01-01

    Narcolepsy-cataplexy is a debilitating disorder characterized by excessive daytime sleepiness (sleep attacks) and cataplexy, a sudden bilateral loss of muscle tone often triggered by emotion. The disease is caused by a selective loss of hypothalamic neurons producing the neuropeptide orexin. Currently, only symptomatic therapies are available for narcolepsy. Here, we examine the pharmacological effect of YNT-185, a nonpeptide, selective agonist for the orexin type-2 receptor in mouse models o...

  6. The pharmacology of imepitoin: the first partial benzodiazepine receptor agonist developed for the treatment of epilepsy.

    Science.gov (United States)

    Rundfeldt, Chris; Löscher, Wolfgang

    2014-01-01

    Although benzodiazepines (BZDs) offer a wide spectrum of antiepileptic activity against diverse types of epileptic seizures, their use in the treatment of epilepsy is limited because of adverse effects, loss of efficacy (tolerance), and development of physical and psychological dependence. BZDs act as positive allosteric modulators of the inhibitory neurotransmitter GABA by binding to the BZD recognition site ("BZD receptor") of the GABAA receptor. Traditional BZDs such as diazepam or clonazepam act as full agonists at this site, so that one strategy to resolve the disadvantages of these compounds would be the development of partial agonists with lower intrinsic efficacy at the BZD site of the GABAA receptor. Several BZD site partial or subtype selective compounds, including bretazenil, abecarnil, or alpidem, have been developed as anxioselective anxiolytic drugs, but epilepsy was not a target indication for such compounds. More recently, the imidazolone derivatives imepitoin (ELB138) and ELB139 were shown to act as low-affinity partial agonists at the BZD site of the GABAA receptor, and imepitoin was developed for the treatment of epilepsy. Imepitoin displayed a broad spectrum of anticonvulsant activity in diverse seizure and epilepsy models at tolerable doses, and, as expected from its mechanism of action, lacked tolerance and abuse liability in rodent and primate models. The more favorable pharmacokinetic profile of imepitoin in dogs versus humans led to the decision to develop imepitoin for the treatment of canine epilepsy. Based on randomized controlled trials that demonstrated antiepileptic efficacy and high tolerability and safety in epileptic dogs, the drug was recently approved for this indication in Europe. Hopefully, the favorable profile of imepitoin for the treatment of epilepsy in dogs will reactivate the interest in partial BZD site agonists as new treatments for human epilepsy.

  7. Lorcaserin: a selective serotonin receptor (5-HT2C) agonist for the treatment of obesity

    OpenAIRE

    Bhaven C. Kataria

    2012-01-01

    Lorcaserin is a selective serotonin receptor (5-HT2C) agonist that recently received the U.S. Food and Drug Administration (FDA) approval for chronic weight management. The efficacy of this drug in reducing body weight and improving metabolic parameters of obese patients has been demonstrated in three phase-3 clinical trials. The available evidence indicates that this drug does not show heart valve abnormalities, and the treatment improves the risk factors for type 2 diabetes and cardiovascul...

  8. Crystal structures of agonist-bound human cannabinoid receptor CB1.

    Science.gov (United States)

    Hua, Tian; Vemuri, Kiran; Nikas, Spyros P; Laprairie, Robert B; Wu, Yiran; Qu, Lu; Pu, Mengchen; Korde, Anisha; Jiang, Shan; Ho, Jo-Hao; Han, Gye Won; Ding, Kang; Li, Xuanxuan; Liu, Haiguang; Hanson, Michael A; Zhao, Suwen; Bohn, Laura M; Makriyannis, Alexandros; Stevens, Raymond C; Liu, Zhi-Jie

    2017-07-27

    The cannabinoid receptor 1 (CB1) is the principal target of the psychoactive constituent of marijuana, the partial agonist Δ(9)-tetrahydrocannabinol (Δ(9)-THC). Here we report two agonist-bound crystal structures of human CB1 in complex with a tetrahydrocannabinol (AM11542) and a hexahydrocannabinol (AM841) at 2.80 Å and 2.95 Å resolution, respectively. The two CB1-agonist complexes reveal important conformational changes in the overall structure, relative to the antagonist-bound state, including a 53% reduction in the volume of the ligand-binding pocket and an increase in the surface area of the G-protein-binding region. In addition, a 'twin toggle switch' of Phe200(3.36) and Trp356(6.48) (superscripts denote Ballesteros-Weinstein numbering) is experimentally observed and appears to be essential for receptor activation. The structures reveal important insights into the activation mechanism of CB1 and provide a molecular basis for predicting the binding modes of Δ(9)-THC, and endogenous and synthetic cannabinoids. The plasticity of the binding pocket of CB1 seems to be a common feature among certain class A G-protein-coupled receptors. These findings should inspire the design of chemically diverse ligands with distinct pharmacological properties.

  9. Beta-Adrenergic Receptors and Mechanisms in Asthma: The New Long-Acting Beta-Agonists

    Directory of Open Access Journals (Sweden)

    Robert G Townley

    1996-01-01

    Full Text Available The objective is to review β-adrenergic receptors and mechanisms in the immediate and late bronchial reaction in asthma and the new long-acting β-agonist. This will be discussed in light of the controversy of the potential adverse effect of regular use of long-acting β-agonists. We studied the effect of formoterol on the late asthmatic response (LAR and airway inflammation in guinea-pigs. Formoterol suppressed the LAR, antigen-induced airway inflammation and hyperresponsiveness, although isoproterenol failed to inhibit these parameters. β-Adrenergic hyporesponsiveness, and cholinergic and a- adrenergic hyperresponsiveness have been implicated in the pathogenesis of asthma. A decrease in β-adrenoreceptor function can result either from exogenously administered β-agonist or from exposure to allergens resulting in a late bronchial reaction. There is increasing evidence that eosinophils, macrophages, and lymphocytes which are of primary importance in the late bronchial reaction are also modulated by β2- adrenoreceptors. In functional studies of guinea-pig or human isolated trachea and lung parenchyma, PAF and certain cytokines significantly reduced the potency of isoproterenol to reverse methacholine- or histamine-induced contraction. The effect of glucocorticoids on pulmonary β-adrenergic receptors and responses suggests an important role for glucocorticoids to increase β-adrenergic receptors and responsiveness.

  10. Radiosynthesis and evaluation of 11C-CIMBI-5 as a 5-HT2A receptor agonist radioligand for PET

    DEFF Research Database (Denmark)

    Ettrup, Anders; Palner, Mikael; Gillings, Nicolas

    2010-01-01

    PET tracers would, however, enable imaging of the active, high-affinity state of receptors, which may provide a more meaningful assessment of membrane-bound receptors. In this study, we radiolabel the high-affinity 5-HT(2A) receptor agonist 2-(4-iodo-2,5-dimethoxyphenyl)-N-(2-[(11)C-OCH(3...

  11. IOP-Lowering Effect of ONO-9054, A Novel Dual Agonist of Prostanoid EP3 and FP Receptors, in Monkeys

    National Research Council Canada - National Science Library

    Yamane, Shinsaku; Karakawa, Tomohiro; Nakayama, Satoshi; Nagai, Kazufumi; Moriyuki, Kazumi; Neki, Shinichi; Suto, Fumitaka; Kambe, Tohru; Hirota, Yasushi; Kawabata, Kazuhito

    2015-01-01

    The purpose of this study was to determine whether a better IOP reduction can be observed in conscious, normotensive monkeys treated with ONO-9054, a novel dual EP3 and FP receptor agonist, compared...

  12. Role of protein kinase A in the inhibition of human mast cell histamine release by β-adrenergic receptor agonists

    Directory of Open Access Journals (Sweden)

    Toshinobu Kato

    2002-01-01

    Conclusions: The present results suggest that PKA activation induced by β-adrenergic receptor agonists plays a crucial role in inhibiting IgE-mediated histamine release from human cultured mast cells through suppressing PKC translocation.

  13. Adenosine dysfunction in epilepsy

    Science.gov (United States)

    Boison, Detlev

    2011-01-01

    Extracellular levels of the brain’s endogenous anticonvulsant and neuroprotectant adenosine largely depend on an astrocyte-based adenosine cycle, comprised of ATP release, rapid degradation of ATP into adenosine, and metabolic reuptake of adenosine through equilibrative nucleoside transporters and phosphorylation by adenosine kinase (ADK). Changes in ADK expression and activity therefore rapidly translate into changes of extracellular adenosine, which exerts its potent anticonvulsive and neuroprotective effects by activation of pre- and postsynaptic adenosine A1 receptors. Increases in ADK increase neuronal excitability, whereas decreases in ADK render the brain resistant to seizures and injury. Importantly, ADK was found to be overexpressed and associated with astrogliosis and spontaneous seizures in rodent models of epilepsy, as well as in human specimen resected from patients with hippocampal sclerosis and temporal lobe epilepsy. Several lines of evidence indicate that overexpression of astroglial ADK and adenosine deficiency are pathological hallmarks of the epileptic brain. Consequently, adenosine augmentation therapies constitute a powerful approach for seizure prevention, which is effective in models of epilepsy that are resistant to conventional antiepileptic drugs. The adenosine kinase hypothesis of epileptogenesis suggests that adenosine dysfunction in epilepsy undergoes a biphasic response: An acute surge of adenosine that can be triggered by any type of injury might contribute to the development of astrogliosis via adenosine receptor –dependent and –independent mechanisms. Astrogliosis in turn is associated with overexpression of ADK, which was shown to be sufficient to trigger spontaneous recurrent electrographic seizures. Thus, ADK emerges as a promising target for the prediction and prevention of epilepsy. PMID:22700220

  14. Time-Dependent Protection of CB2 Receptor Agonist in Stroke.

    Directory of Open Access Journals (Sweden)

    Seong-Jin Yu

    Full Text Available Recent studies have indicated that type 2 cannabinoid receptor (CB2R agonists reduce neurodegeneration after brain injury through anti-inflammatory activity. The purpose of this study was to examine the time-dependent interaction of CB2R and inflammation in stroke brain. Adult male rats were subjected to right middle cerebral artery occlusion (MCAo. CB2R mRNA expression was significantly elevated >20 fold on day 2, peaked >40-fold on day 5, and normalized on day 10 post-stroke. Inflammatory markers IBA1 and TLR4 were significantly upregulated 15 fold until day 5 after MCAo. Because of the delayed upregulation of CB2R and IBA1, we next treated animals daily with CB2R agonist AM1241 or anti-inflammatory PPAR-γ agonist pioglitazone from 2 to 5 days after MCAo. Delayed treatment with pioglitazone significantly reduced abnormal neurological scores and body asymmetry as well as brain infarction in stroke animals. No behavioral improvement or reduction in brain infarction was found in animals receiving AM1241. Pioglitazone, but not AM1241, significantly reduced IBA1 expression in the stroke cortex, suggesting that delayed treatment with AM1241 failed to alter ischemia-mediated IBA-1 upregulation. In contrast, pretreatment with AM1241 significantly reduced brain infarction and neurological deficits. In conclusion, our data support a time-dependent neuroprotection of CB2 agonist in an animal model of stroke. Delayed post- treatment with PPAR-γ agonist induced behavioral recovery and microglial suppression; early treatment with CB2R agonist suppressed neurodegeneration in stroke animals.

  15. Therapeutic potential of α7 nicotinic receptor agonists to regulate neuroinflammation in neurodegenerative diseases

    Science.gov (United States)

    Foucault-Fruchard, Laura; Antier, Daniel

    2017-01-01

    Neurodegenerative diseases, such as Alzheimer's, Parkinson's and Huntington's diseases, are all characterized by a component of innate immunity called neuroinflammation. Neuronal loss and neuroinflammation are two phenomena closely linked. Hence, the neuroinflammation is a relevant target for the management of the neurodegenerative diseases given that, to date, there is no treatment to stop neuronal loss. Several studies have investigated the potential effects of activators of alpha 7 nicotinic acetylcholine receptors in animal models of neurodegenerative diseases. These receptors are widely distributed in the central nervous system. After activation, they seem to mediate the cholinergic anti-inflammatory pathway in the brain. This anti-inflammatory pathway, first described in periphery, regulates activation of microglial cells considered as the resident macrophage population of the central nervous system. In this article, we shortly review the agonists of the alpha 7 nicotinic acetylcholine receptors that have been evaluated in vivo and we focused on the selective positive allosteric modulators of these receptors. These compounds represent a key element to enhance receptor activity only in the presence of the endogenous agonist. PMID:29089979

  16. Therapeutic potential of α7 nicotinic receptor agonists to regulate neuroinflammation in neurodegenerative diseases

    Directory of Open Access Journals (Sweden)

    Laura Foucault-Fruchard

    2017-01-01

    Full Text Available Neurodegenerative diseases, such as Alzheimer's, Parkinson's and Huntington's diseases, are all characterized by a component of innate immunity called neuroinflammation. Neuronal loss and neuroinflammation are two phenomena closely linked. Hence, the neuroinflammation is a relevant target for the management of the neurodegenerative diseases given that, to date, there is no treatment to stop neuronal loss. Several studies have investigated the potential effects of activators of alpha 7 nicotinic acetylcholine receptors in animal models of neurodegenerative diseases. These receptors are widely distributed in the central nervous system. After activation, they seem to mediate the cholinergic anti-inflammatory pathway in the brain. This anti-inflammatory pathway, first described in periphery, regulates activation of microglial cells considered as the resident macrophage population of the central nervous system. In this article, we shortly review the agonists of the alpha 7 nicotinic acetylcholine receptors that have been evaluated in vivo and we focused on the selective positive allosteric modulators of these receptors. These compounds represent a key element to enhance receptor activity only in the presence of the endogenous agonist.

  17. Adenosine-induced neuroprotection : involvement of glia cells and cytokines

    NARCIS (Netherlands)

    Wittendorp, Maria Catharina

    2004-01-01

    Adenosine is released during pathological conditions and has significant neuroprotective effects mainly by stimulating adenosine A1 receptors in neurons. These neuroprotective effects are increased following upregulation of adenosine A1 receptors. Much research has been performed to enhance the

  18. The role of the A2a receptor agonist, regadenoson, in modulating hepatic artery flow in the porcine small-for-size liver graft.

    Science.gov (United States)

    Zhu, Xiaocheng; Shiba, Hiroaki; Fung, John J; Wang, Lian-Fu; Arakawa, Yusuke; Irefin, Samuel; Demetris, Anthony J; Kelly, Dympna M

    2012-05-01

    Hepatic artery vasoconstriction plays a major role in the pathophysiology of the small-for-size (SFS) liver graft injury and is reversed by adenosine. The A2a adenosine receptor (AR) has been suggested to be one of the key receptors that modulate hepatic hemodynamic changes. The aim of the study is to define the effects of the A2a AR agonist, regadenoson, in modulating hepatic artery flow (HAF) in SFS liver grafts of a porcine model. Seven female recipient pigs (66-70 kg) receiving 20% liver grafts were treated with regadenoson, 0.1 ug/kg/min starting on POD1 (n = 7). Results were compared with those with untreated 20% liver grafts (n= 8). The recipients were observed for 14 d. Hepatic artery flow (HAF) and portal vein flow (PVF) were recorded. Liver biopsies and serum samples were also taken at the designed time points through postoperative day (POD)14. Dose-response curves of regadenoson established 0.1 ug/kg/min as the most effective dose of regadenoson for maintaining an increase in HAF. No adverse effects were seen with regadenoson infusion. HAF immediately increased by up to 2.2-fold after regadenoson infusion. The levels of daily average of HAF and percentage of HAF in total liver blood flow were 34.5% and 41.8%, respectively, higher in the regadenoson group than in the untreated group. Histologic scores of hepatic artery spasm and bile duct necrosis were significantly lower in the regadenoson group than in the untreated group (P = 0.01 and 0.04, respectively). The complication rates of hepatic artery thrombosis and gastrointestinal bleeding were lower in the regadenoson group than in the untreated group (0/7, 0% versus 2/8, 25% and 0/7, 0% versus 2/8 and 25%, respectively). The 14-d survival rates were 4/7 (57.1 %) in regadenoson group compared with 2/8 (25%) in the untreated group. Adenosine A2a AR agonist, regadenoson, increases HAF in the recipients of SFS grafts with modest improvements in outcome. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. Comparative receptor surface analysis of agonists for tyramine receptor which inhibit sex-pheromone production in Plodia interpunctella.

    Science.gov (United States)

    Hirashima, A; Eiraku, T; Kuwano, E; Eto, M

    2004-03-01

    The quantitative structure-activity relationship (QSAR) of a set of 29 agonists for tyramine (TA) receptor responsible for the inhibition of sex-pheromone production in Plodia interpunctella, was analyzed using comparative receptor surface analysis (CoRSA). Using the common steric and electrostatic features of the most active members of a series of compounds, CoRSA generated a virtual receptor model, represented as points on a surface complementary to the van der Waals or Wyvill steric surface of the aligned compounds. Three-dimensional energetics descriptors were calculated from receptor surface model (RSM)/ligand interaction and these three-dimensional descriptors were used in genetic partial least squares data analysis to generate a QSAR model, giving a 3D QSAR with r(2)=0.969 for calibration and CV- r(2)=0.635 for the leave-one-out cross validation.

  20. Regulation of Cardiovascular Development by Adenosine and Adenosine-Mediated Embryo Protection

    OpenAIRE

    Rivkees, Scott A; Wendler, Christopher C.

    2012-01-01

    Few signaling molecules have the potential to influence the developing mammal as the nucleoside adenosine. Adenosine levels increase rapidly with tissue hypoxia and inflammation. Adenosine antagonists include the methlyxanthines caffeine and theophylline. The receptors that transduce adenosine action are the A1, A2a, A2b, and A3 adenosine receptors (ARs). We examined how adenosine acts via A1ARs to influence embryo development.

  1. Beyond glucose lowering: glucagon-like peptide-1 receptor agonists, body weight and the cardiovascular system.

    Science.gov (United States)

    Vergès, B; Bonnard, C; Renard, E

    2011-12-01

    Glucagon-like peptide-1 (GLP-1) belongs to the incretin hormone family: in the presence of elevated blood glucose, it stimulates insulin secretion and inhibits glucagon production. In addition, GLP-1 slows gastric emptying. GLP-1 secretion has also been reported to potentially affect patients with type 2 diabetes (T2DM) compared with non-diabetics and, as enzymatic inactivation by dipeptidyl peptidase-4 (DPP-4) shortens the GLP-1 half-life to a few minutes, GLP-1 receptor agonists such as exenatide twice daily (BID) and liraglutide have been developed, and have become part of the management of patients with T2DM. This review focuses on the potential beneficial effects of these compounds beyond those associated with improvements in blood glucose control and weight loss, including changes in the cardiovascular and central nervous systems. This was a state-of-the-art review of the literature to evaluate the relationships between GLP-1, GLP-1 receptor agonists, weight and the cardiovascular system. GLP-1 receptor agonists improve glucose control and do not significantly increase the risk of hypoglycaemia. Also, this new class of antidiabetic drugs was shown to favour weight loss. Mechanisms may involve central action, direct action by reduction of food intake and probably indirect action through slowing of gastric emptying. The relative importance of each activity remains unclear. Weight loss may improve cardiovascular outcomes in patients with T2DM, although GLP-1 receptor agonists may have other direct and indirect effects on the cardiovascular system. Reductions in myocardial infarct size and improvements in cardiac function have been seen in animal models. Beneficial changes in cardiac function were also demonstrated in patients with myocardial infarcts or heart failure. Indirect effects could involve a reduction in blood pressure and potential effects on oxidation. However, the mechanisms involved in the pleiotropic effects of GLP-1 receptor agonists have yet to

  2. Ractopamine, a livestock feed additive, is a full agonist at trace amine-associated receptor 1.

    Science.gov (United States)

    Liu, Xuehong; Grandy, David K; Janowsky, Aaron

    2014-07-01

    Ractopamine (RAC) is fed to an estimated 80% of all beef, swine, and turkey raised in the United States. It promotes muscle mass development, limits fat deposition, and reduces feed consumption. However, it has several undesirable behavioral side effects in livestock, especially pigs, including restlessness, agitation, excessive oral-facial movements, and aggressive behavior. Numerous in vitro and in vivo studies suggest RAC's physiological actions begin with its stimulation of β1- and β2-adrenergic receptor-mediated signaling in skeletal muscle and adipose tissue; however, the molecular pharmacology of RAC's psychoactive effects is poorly understood. Using human cystic fibrosis transmembrane conductance regulator (hCFTR) chloride channels as a sensor for intracellular cAMP, we found that RAC and p-tyramine (TYR) produced concentration-dependent increases in chloride conductance in oocytes coexpressing hCFTR and mouse trace amine-associated receptor 1 (mTAAR1), which was completely reversed by the trace amine-associated receptor 1 (TAAR1)-selective antagonist EPPTB [N-(3-ethoxyphenyl)-4-pyrrolidin-1-yl-3-trifluoromethylbenzamide]. Oocytes coexpressing hCFTR and the human β2-adrenergic receptor showed no response to RAC or TYR. These studies demonstrate that, contrary to expectations, RAC is not an agonist of the human β2-adrenergic receptor but rather a full agonist for mTAAR1. Since TAAR1-mediated signaling can influence cardiovascular tone and behavior in several animal models, our finding that RAC is a full mTAAR1 agonist supports the idea that this novel mechanism of action influences the physiology and behavior of pigs and other species. These findings should stimulate future studies to characterize the pharmacological, physiological, and behavioral actions of RAC in humans and other species exposed to this drug. U.S. Government work not protected by U.S. copyright.

  3. Role of prucalopride, a serotonin (5-HT4 receptor agonist, for the treatment of chronic constipation

    Directory of Open Access Journals (Sweden)

    Banny S Wong

    2010-05-01

    Full Text Available Banny S Wong, Noriaki Manabe, Michael CamilleriClinical Enteric Neuroscience Translational and Epidemiological Research (C.E.N.T.E.R., Mayo Clinic, Rochester, Minnesota, USAAbstract: Constipation affects up to a quarter of the population in developed countries and is associated with poor quality of life and significant economic burden. Many patients with chronic constipation are dissatisfied with current therapy due to lack of long-term efficacy or side effects. Previous nonselective 5-hydroxytryptamine receptor 4 (5-HT4 agonists have been associated with significant interactions with other receptors (5-HT1B, 5-HT1D, and 5-HT2B for tegaserod; hERG for cisapride, leading to adverse cardiovascular events resulting in withdrawal of these drugs from the market. Prucalopride is a novel gastrointestinal prokinetic agent. It acts as a high affinity, highly-selective 5-HT4 agonist. Its efficacy in patients with chronic constipation has been demonstrated in several phase II and phase III clinical trials showing significant improvements in bowel transit, bowel function, gastrointestinal symptoms, and quality of life, with benefit maintained for up to 24 months in open label, multicenter, follow-up studies. Prucalopride’s high selectivity for the 5-HT4 receptor may explain its favorable safety and tolerability profiles, even in elderly subjects with stable cardiovascular disease. Prucalopride is a well tolerated and efficacious prokinetic medication that should enhance the treatment of chronic constipation unresponsive to first-line treatments.Keywords: prucalopride, 5-HT4 agonist, serotonin agonist, efficacy, prokinetic

  4. Collybolide is a novel biased agonist of κ-opioid receptors with potent antipruritic activity

    Science.gov (United States)

    Gupta, Achla; Gomes, Ivone; Bobeck, Erin N.; Fakira, Amanda K.; Massaro, Nicholas P.; Sharma, Indrajeet; Cavé, Adrien; Hamm, Heidi E.; Parello, Joseph

    2016-01-01

    Among the opioid receptors, the κ-opioid receptor (κOR) has been gaining considerable attention as a potential therapeutic target for the treatment of complex CNS disorders including depression, visceral pain, and cocaine addiction. With an interest in discovering novel ligands targeting κOR, we searched natural products for unusual scaffolds and identified collybolide (Colly), a nonnitrogenous sesquiterpene from the mushroom Collybia maculata. This compound has a furyl-δ-lactone core similar to that of Salvinorin A (Sal A), another natural product from the plant Salvia divinorum. Characterization of the molecular pharmacological properties reveals that Colly, like Sal A, is a highly potent and selective κOR agonist. However, the two compounds differ in certain signaling and behavioral properties. Colly exhibits 10- to 50-fold higher potency in activating the mitogen-activated protein kinase pathway compared with Sal A. Taken with the fact that the two compounds are equipotent for inhibiting adenylyl cyclase activity, these results suggest that Colly behaves as a biased agonist of κOR. Behavioral studies also support the biased agonistic activity of Colly in that it exhibits ∼10-fold higher potency in blocking non–histamine-mediated itch compared with Sal A, and this difference is not seen in pain attenuation by these two compounds. These results represent a rare example of functional selectivity by two natural products that act on the same receptor. The biased agonistic activity, along with an easily modifiable structure compared with Sal A, makes Colly an ideal candidate for the development of novel therapeutics targeting κOR with reduced side effects. PMID:27162327

  5. Adenosine A1 receptor antagonist mitigates deleterious effects of sleep deprivation on adult neurogenesis and spatial reference memory in rats.

    Science.gov (United States)

    Chauhan, G; Ray, K; Sahu, S; Roy, K; Jain, V; Wadhwa, M; Panjwani, U; Kishore, K; Singh, S B

    2016-11-19

    Sleep deprivation (SD) upsurges intracellular levels of adenosine, impairs adult neuronal cell proliferation (NCP) and cognition while caffeine, a non-selective adenosine A1 receptor (A1R) antagonist improves cognition and adult NCP during SD. We examined the selective antagonistic effects of adenosine A1R using 8-cyclopentyl-1,3-dimethylxanthine (8-CPT) on impairment of spatial reference memory and adult NCP during 48h SD. Adult male Sprague Dawley rats were sleep deprived for 48h, using an automatic cage vibrating stimulus based on animal activity. Spatial reference memory was tested as a measure of cognitive performance employing Morris Water Maze. Rats were given 8-CPT dissolved in 50% dimethyl sulfoxide (DMSO), twice daily (10mg/kg, i.p.) along with 5-bromo-2-deoxyuridine (BrdU) (50mg/kg/day, i.p.). The rats treated with 8-CPT showed significantly short mean latency and path-length to reach the platform compared to the SD rats. Consistent with these findings, 8-CPT-treated group was found to have significantly increased the number of BrdU, Ki-67 and doublecortin (DCX) positive cells. However, no significant difference was seen in NeuN expression in the Dentate Gyrus (DG). Brain-derived neurotropic factor (BDNF) expression in the DG and CA1 region was observed to decrease significantly after SD and be rescued by 8-CPT treatment. Furthermore, latency to reach platform showed a negative correlation with number of BrdU, DCX type-1 cells and BDNF expression in DG. Thus, it may be concluded that treatment with 8-CPT, an adenosine A1R antagonist during SD mitigates SD induced decline in spatial reference memory and adult NCP possibly via up regulation of BDNF levels in DG and CA1 regions. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

  6. A2B adenosine receptor contributes to penile erection via PI3K/AKT signaling cascade-mediated eNOS activation

    Science.gov (United States)

    Wen, Jiaming; Grenz, Almut; Zhang, Yujin; Dai, Yingbo; Kellems, Rodney E.; Blackburn, Michael R.; Eltzschig, Holger K.; Xia, Yang

    2011-01-01

    Normal penile erection is under the control of multiple factors and signaling pathways. Although adenosine signaling is implicated in normal and abnormal penile erection, the exact role and the underlying mechanism for adenosine signaling in penile physiology remain elusive. Here we report that shear stress leads to increased adenosine release from endothelial cells. Subsequently, we determined that ecto-5′-nucleotidase (CD73) is a key enzyme required for the production of elevated adenosine from ATP released by shear-stressed endothelial cells. Mechanistically, we demonstrate that shear stress-mediated elevated adenosine functions through the adenosine A2B receptor (A2BR) to activate the PI3K/AKT signaling cascade and subsequent increased endothelial nitric oxide synthase (eNOS) phosphorylation. These in vitro studies led us to discover further that adenosine was induced during sustained penile erection and contributes to PI3K/AKT activation and subsequent eNOS phosphorylation via A2BR signaling in intact animal. Finally, we demonstrate that lowering adenosine in wild-type mice or genetic deletion of A2BR in mutant mice significantly attenuated PI3K/AKT activation, eNOS phosphorylation, and subsequent impaired penile erection featured with the reduction of ratio of maximal intracavernosal pressure to systemic arterial pressure from 0.49 ± 0.03 to 0.41 ± 0.05 and 0.38 ± 0.04, respectively (both Ppenile erection via PI3K/AKT-dependent eNOS activation. These studies suggest that this signaling pathway may be a novel therapeutic target for erectile disorders.—Wen, J., Grenz, A., Zhang, Y., Dai, Y., Kellems, R. E., Blackburn, M. R., Eltzschig, H. K., Xia, Y. A2B adenosine receptor contributes to penile erection via PI3K/AKT signaling cascade-mediated eNOS activation. PMID:21566208

  7. Novel Zn2+ Modulated GPR39 Receptor Agonists Do Not Drive Acute Insulin Secretion in Rodents.

    Directory of Open Access Journals (Sweden)

    Ola Fjellström

    Full Text Available Type 2 diabetes (T2D occurs when there is insufficient insulin release to control blood glucose, due to insulin resistance and impaired β-cell function. The GPR39 receptor is expressed in metabolic tissues including pancreatic β-cells and has been proposed as a T2D target. Specifically, GPR39 agonists might improve β-cell function leading to more adequate and sustained insulin release and glucose control. The present study aimed to test the hypothesis that GPR39 agonism would improve glucose stimulated insulin secretion in vivo. A high throughput screen, followed by a medicinal chemistry program, identified three novel potent Zn2+ modulated GPR39 agonists. These agonists were evaluated in acute rodent glucose tolerance tests. The results showed a lack of glucose lowering and insulinotropic effects not only in lean mice, but also in diet-induced obese (DIO mice and Zucker fatty rats. It is concluded that Zn2+ modulated GPR39 agonists do not acutely stimulate insulin release in rodents.

  8. Repeated exposure to the κ-opioid receptor agonist salvinorin A modulates extracellular signal-regulated kinase and reward sensitivity.

    Science.gov (United States)

    Potter, David N; Damez-Werno, Diane; Carlezon, William A; Cohen, Bruce M; Chartoff, Elena H

    2011-10-15

    Repeated exposure to drugs of abuse and stress increase dynorphin, a κ opioid receptor (KOR) ligand, in the nucleus accumbens (NAc). Acute KOR activation produces dysphoria that might contribute to addictive behavior. How repeated KOR activation modulates reward circuitry is not understood. We used intracranial self-stimulation (ICSS), a method that provides a behavioral index of reward sensitivity, to measure the effects of repeated administration of the KOR agonist salvinorin A (salvA) (2 mg/kg) on the reward-potentiating effects of cocaine (5.0 mg/kg). In separate rats, we measured the effects of salvA on activation of extracellular signal regulated kinase (ERK), cyclic adenosine monophosphate (cAMP) response element binding protein, and c-Fos within the NAc. SalvA had biphasic effects on reward: an immediate effect was to decrease the rewarding impact of ICSS, whereas a delayed effect was to increase the rewarding impact of ICSS. Repeated salvA produced a net decrease in the reward-potentiating effects of cocaine. In the NAc, both acute and repeated salvA administration increased phosphorylated ERK, whereas only acute salvA increased c-Fos and repeated salvA increased phosphorylated cAMP response element binding protein. The KOR antagonist nor-binaltorphimine (20 mg/kg) blocked the immediate and delayed effects of salvA and prolonged the duration of cocaine effects in ICSS. Repeated salvA might trigger opponent processes such that "withdrawal" from the dysphoric effects of KOR activation is rewarding and decreases the net rewarding valence of cocaine. The temporal effects of salvA on ERK signaling suggest KOR-mediated engagement of distinct signaling pathways within the NAc that might contribute to biphasic effects on reward sensitivity. Copyright © 2011 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  9. A role for a specific cholesterol interaction in stabilizing the Apo configuration of the human A(2A) adenosine receptor.

    Science.gov (United States)

    Lyman, Edward; Higgs, Chris; Kim, Byungchan; Lupyan, Dmitry; Shelley, John C; Farid, Ramy; Voth, Gregory A

    2009-12-09

    The function of G-protein-coupled receptors is tightly modulated by the lipid environment. Long-timescale molecular dynamics simulations (totaling approximately 3 mus) of the A(2A) receptor in cholesterol-free bilayers, with and without the antagonist ZM241385 bound, demonstrate the instability of helix II in the apo receptor in cholesterol-poor membrane regions. We directly observe that the effect of cholesterol binding is to stabilize helix II against a buckling-type deformation, perhaps rationalizing the observation that the A(2A) receptor couples to G protein only in the presence of cholesterol (Zezula and Freissmuth, 2008). The results suggest a mechanism by which the A(2A) receptor may function as a coincidence detector, activating only in the presence of both cholesterol and agonist. We also observed a previously hypothesized conformation of the tryptophan "rotameric switch" on helix VI in which a phenylalanine on helix V positions the tryptophan out of the ligand binding pocket.

  10. Role of Adenosine Signaling on Pentylenetetrazole-Induced Seizures in Zebrafish

    Science.gov (United States)

    Siebel, Anna Maria; Menezes, Fabiano Peres; Capiotti, Katiucia Marques; Kist, Luiza Wilges; Schaefer, Isabel da Costa; Frantz, Juliana Zanetti; Bogo, Maurício Reis; Da Silva, Rosane Souza

    2015-01-01

    Abstract Adenosine is a well-known endogenous modulator of neuronal excitability with anticonvulsant properties. Thus, the modulation exerted by adenosine might be an effective tool to control seizures. In this study, we investigated the effects of drugs that are able to modulate adenosinergic signaling on pentylenetetrazole (PTZ)-induced seizures in adult zebrafish. The adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) decreased the latency to the onset of the tonic-clonic seizure stage. The adenosine A1 receptor agonist cyclopentyladenosine (CPA) increased the latency to reach the tonic-clonic seizure stage. Both the adenosine A2A receptor agonist and antagonist, CGS 21680 and ZM 241385, respectively, did not promote changes in seizure parameters. Pretreatment with the ecto-5′nucleotidase inhibitor adenosine 5′-(α,β-methylene) diphosphate (AMPCP) decreased the latency to the onset of the tonic-clonic seizure stage. However, when pretreated with the adenosine deaminase (ADA) inhibitor, erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA), or with the nucleoside transporter (NT) inhibitors, dipyridamole and S-(4-Nitrobenzyl)-6-thioinosine (NBTI), animals showed longer latency to reach the tonic-clonic seizure status. Finally, our molecular analysis of the c-fos gene expression corroborates these behavioral results. Our findings indicate that the activation of adenosine A1 receptors is an important mechanism to control the development of seizures in zebrafish. Furthermore, the actions of ecto-5′-nucleotidase, ADA, and NTs are directly involved in the control of extracellular adenosine levels and have an important role in the development of seizure episodes in zebrafish. PMID:25560904

  11. Muscarinic receptor agonists stimulate matrix metalloproteinase 1-dependent invasion of human colon cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Raufman, Jean-Pierre, E-mail: jraufman@medicine.umaryland.edu [Division of Gastroenterology and Hepatology, University of Maryland School of Medicine, Baltimore, MD (United States); Cheng, Kunrong; Saxena, Neeraj; Chahdi, Ahmed; Belo, Angelica; Khurana, Sandeep; Xie, Guofeng [Division of Gastroenterology and Hepatology, University of Maryland School of Medicine, Baltimore, MD (United States)

    2011-11-18

    Highlights: Black-Right-Pointing-Pointer Muscarinic receptor agonists stimulated robust human colon cancer cell invasion. Black-Right-Pointing-Pointer Anti-matrix metalloproteinase1 antibody pre-treatment blocks cell invasion. Black-Right-Pointing-Pointer Bile acids stimulate MMP1 expression, cell migration and MMP1-dependent invasion. -- Abstract: Mammalian matrix metalloproteinases (MMPs) which degrade extracellular matrix facilitate colon cancer cell invasion into the bloodstream and extra-colonic tissues; in particular, MMP1 expression correlates strongly with advanced colon cancer stage, hematogenous metastasis and poor prognosis. Likewise, muscarinic receptor signaling plays an important role in colon cancer; muscarinic receptors are over-expressed in colon cancer compared to normal colon epithelial cells. Muscarinic receptor activation stimulates proliferation, migration and invasion of human colon cancer cells. In mouse intestinal neoplasia models genetic ablation of muscarinic receptors attenuates carcinogenesis. In the present work, we sought to link these observations by showing that MMP1 expression and activation plays a mechanistic role in muscarinic receptor agonist-induced colon cancer cell invasion. We show that acetylcholine, which robustly increases MMP1 expression, stimulates invasion of HT29 and H508 human colon cancer cells into human umbilical vein endothelial cell monolayers - this was abolished by pre-incubation with atropine, a non-selective muscarinic receptor inhibitor, and by pre-incubation with anti-MMP1 neutralizing antibody. Similar results were obtained using a Matrigel chamber assay and deoxycholyltaurine (DCT), an amidated dihydroxy bile acid associated with colon neoplasia in animal models and humans, and previously shown to interact functionally with muscarinic receptors. DCT treatment of human colon cancer cells resulted in time-dependent, 10-fold increased MMP1 expression, and DCT-induced cell invasion was also blocked by pre

  12. Blockade of alcohol's amnestic activity in humans by an alpha5 subtype benzodiazepine receptor inverse agonist.

    Science.gov (United States)

    Nutt, David J; Besson, Marie; Wilson, Susan J; Dawson, Gerard R; Lingford-Hughes, Anne R

    2007-12-01

    Alcohol produces many subjective and objective effects in man including pleasure, sedation, anxiolysis, plus impaired eye movements and memory. In human volunteers we have used a newly available GABA-A/benzodiazepine receptor inverse agonist that is selective for the alpha5 subtype (a5IA) to evaluate the role of this subtype in mediating these effects of alcohol on the brain. After pre-treatment with a5IA, we found almost complete blockade of the marked impairment caused by alcohol (mean breath concentration 150mg/100ml) of word list learning and partial but non-significant reversal of subjective sedation without effects on other measures such as intoxication, liking, and slowing of eye movements. This action was not due to alterations in alcohol kinetics and so provides the first proof of concept that selectively decreasing GABA-A receptor function at a specific receptor subtype can offset some actions of alcohol in humans. It also supports growing evidence for a key role of the alpha5 subtype in memory. Inverse agonists at other GABA-A receptor subtypes may prove able to reverse other actions of alcohol, and so offer a new approach to understanding the actions of alcohol in the human brain and in the treatment of alcohol related disorders in humans.

  13. Withdrawal reactions following cessation of central alpha-adrenergic receptor agonists.

    Science.gov (United States)

    Reid, J L; Campbell, B C; Hamilton, C A

    1984-01-01

    Interruption of long-term treatment with alpha 2-adrenergic receptor agonists may be associated with reversal of their hemodynamic effects, clinical and biochemical evidence of increased peripheral sympathetic activity, and behavioral responses similar to those seen after narcotic or alcohol withdrawal. Reactions are most commonly observed after short-acting imidazoline drugs such as clonidine and tiamenidine. Reactions are less common after longer acting agents such as guanfacine. A new management approach to withdrawal has been evaluated, which uses a combination of alpha 1-blockade (prazosin) and cardioselective beta-blockade (atenolol) together with a benzodiazepine (chlordiazepoxide). Withdrawal reactions were not observed in eight patients in whom clonidine was withdrawn under cover of these agents. The mechanism of the withdrawal reaction may involve agonist-induced down regulation of alpha 2-adrenergic receptor affinity, number, or both. Experimental studies with the irreversible alpha-antagonist phenoxybenzamine on the turnover of alpha 2-receptors suggest that recovery of receptor number may be much slower in the brain than in the periphery.

  14. Arotinolol is a weak partial agonist on beta 3-adrenergic receptors in brown adipocytes.

    Science.gov (United States)

    Zhao, J; Golozoubova, V; Cannon, B; Nedergaard, J

    2001-07-01

    Arotinolol, a clinically used alpha/beta-adrenergic blocker, has been demonstrated to be an anti-obesity agent. The anti-obesity effect of arotinolol was suggested to be the result of direct activation of thermogenesis in brown-fat cells. We tested the ability of arotinolol to stimulate thermogenesis (oxygen consumption) in isolated brown-fat cells and in intact animals. Arotinolol stimulated thermogenesis in brown-fat cells isolated from mouse and hamster. A relatively low sensitivity to the beta-adrenergic antagonist propranolol (pK(B) approximately 6) indicated that arotinolol interacted with the beta3-adrenergic receptor. On the beta3-receptor, arotinolol was a very weak (EC50 approximately 20 microM) and only partial (approximately 50%) agonist, but arotinolol also demonstrated the properties of being a beta3-receptor antagonist with a pK(B) of 5.7. In intact animals, only the antagonistic action of arotinolol could be observed. Because arotinolol is only a very weak and partial agonist on the beta3-receptors, direct stimulation of thermogenesis in brown adipose tissue is unlikely to be sufficient to cause significant weight loss. It may be necessary to invoke additional pathways to explain the anti-obesity effects of chronic treatment with arotinolol.

  15. Studies with [{sup 11}C]alprazolam: an agonist for the benzodiazepine receptor

    Energy Technology Data Exchange (ETDEWEB)

    Dobbs, Frank R.; Banks, William; Fleishaker, Joseph C.; Valentine, Alan D.; Kinsey, Berma M.; Franceschini, Mark P.; Digenis, George A.; Tewson, Timothy J

    1995-05-01

    We have built a system for the synthesis of high specific activity carbon-11 alprazolam (Xanax), a high affinity agonist for the benzodiazepine receptor. The system produces 30-40 mCi of the compound with a specific activity of >12,000 Ci per millimole. Using this compound we have performed PET studies on 6 normal subjects and studied the cerebral influx and efflux of the compound. The uptake in the brain was low, approx. 1% of the administered dose. However, the levels of the compound in the circulation at early time points are heavily affected by the specific activity of the tracer, i.e. when pharmacologically active doses are used as blocking doses the concentration of radioactive material is higher in the circulation and more material enters the brain. We attribute this to a depot effect where the compound is trapped in saturatable sites in an organ, probably the lungs, and is slowly released over time. In the presence of blocking doses of agonist, the compound washes out of the brain more quickly suggesting that some blockade of the receptors is occurring. However, the pharmacological activity of the compound does not permit the administration of enough material to ensure complete receptor blockade. The compound shows definite signs of acting as a receptor binding ligand but the unusual pharmacokinetics complicate the interpretation of the data.

  16. Renoprotective Effects of AVE0991, a Nonpeptide Mas Receptor Agonist, in Experimental Acute Renal Injury

    Science.gov (United States)

    Barroso, Lívia Corrêa; Silveira, Kátia Daniela; Lima, Cristiano Xavier; Borges, Valdinéria; Bader, Michael; Rachid, Milene; Santos, Robson Augusto Souza; Souza, Danielle Gloria; Simões e Silva, Ana Cristina; Teixeira, Mauro Martins

    2012-01-01

    Renal ischemia and reperfusion (I/R) is the major cause of acute kidney injury in hospitalized patients. Mechanisms underlying reperfusion-associated injury include recruitment and activation of leukocytes and release of inflammatory mediators. In this study, we investigated the renal effects of acute administration of AVE0991, an agonist of Mas, the angiotensin-(1–7) receptor, the angiotensin-(1–7) receptor, in a murine model of renal I/R. Male C57BL/6 wild-type or Mas−/− mice were subjected to 30 min of bilateral ischemia and 24 h of reperfusion. Administration of AVE0991 promoted renoprotective effects, as seen by improvement of function, decreased tissue injury, prevention of local and remote leucocyte infiltration, and release of the chemokine, CXCL1. I/R injury was similar in WT and Mas−/− mice, suggesting that endogenous activation of this receptor does not control renal damage under baseline conditions. In conclusion, pharmacological interventions using Mas receptor agonists may represent a therapeutic opportunity for the treatment of renal I/R injury. PMID:22319645

  17. Renoprotective Effects of AVE0991, a Nonpeptide Mas Receptor Agonist, in Experimental Acute Renal Injury

    Directory of Open Access Journals (Sweden)

    Lívia Corrêa Barroso

    2012-01-01

    Full Text Available Renal ischemia and reperfusion (I/R is the major cause of acute kidney injury in hospitalized patients. Mechanisms underlying reperfusion-associated injury include recruitment and activation of leukocytes and release of inflammatory mediators. In this study, we investigated the renal effects of acute administration of AVE0991, an agonist of Mas, the angiotensin-(1–7 receptor, the angiotensin-(1–7 receptor, in a murine model of renal I/R. Male C57BL/6 wild-type or Mas−/− mice were subjected to 30 min of bilateral ischemia and 24 h of reperfusion. Administration of AVE0991 promoted renoprotective effects, as seen by improvement of function, decreased tissue injury, prevention of local and remote leucocyte infiltration, and release of the chemokine, CXCL1. I/R injury was similar in WT and Mas−/− mice, suggesting that endogenous activation of this receptor does not control renal damage under baseline conditions. In conclusion, pharmacological interventions using Mas receptor agonists may represent a therapeutic opportunity for the treatment of renal I/R injury.

  18. Blockade of A2b Adenosine Receptor Reduces Tumor Growth and Immune Suppression Mediated by Myeloid-Derived Suppressor Cells in a Mouse Model of Melanoma

    Directory of Open Access Journals (Sweden)

    Raffaella Iannone

    2013-12-01

    Full Text Available The A2b receptor (A2bR belongs to the adenosine receptor family. Emerging evidence suggest that A2bR is implicated in tumor progression in some murine tumor models, but the therapeutic potential of targeting A2bR in melanoma has not been examined. This study first shows that melanoma-bearing mice treated with Bay 60-6583, a selective A2bR agonist, had increased melanoma growth. This effect was associated with higher levels of immune regulatory mediators interleukin-10 (IL-10 and monocyte chemoattractant protein 1 (MCP-1 and accumulation of tumor-associated CD11b positive Gr1 positive cells (CD11b+Gr1+ myeloid-derived suppressor cells (MDSCs. Depletion of CD11b+Gr1+ cells completely reversed the protumor activity of Bay 60-6583. Conversely, pharmacological blockade of A2bR with PSB1115 reversed immune suppression in the tumor microenvironment, leading to a significant melanoma growth delay. PSB1115 treatment reduced both levels of IL-10 and MCP-1 and CD11b+Gr1+ cell number in melanoma lesions. These effects were associated with higher frequency of tumor-infiltrating CD8 positive (CD8+ T cells and natural killer T (NKT cells and increased levels of T helper 1 (Th1-like cytokines. Adoptive transfer of CD11b+Gr1+ cells abrogated the antitumor activity of PSB1115. These data suggest that the antitumor activity of PSB1115 relies on its ability to lower accumulation of tumor-infiltrating MDSCs and restore an efficient antitumor T cell response. The antitumor effect of PSB1115 was not observed in melanoma-bearing nude mice. Furthermore, PSB1115 enhanced the antitumor efficacy of dacarbazine. These data indicate that A2bR antagonists such as PSB1115 should be investigated as adjuvants in the treatment of melanoma.

  19. Influence of agonist efficacy and receptor phosphorylation on antagonist affinity measurements: differences between second messenger and reporter gene responses.

    Science.gov (United States)

    Baker, Jillian G; Hall, Ian P; Hill, Stephen J

    2003-09-01

    The ability of an antagonist to bind to a receptor is an innate property of that ligand-receptor chemical interaction. Provided no change in the antagonist or receptor chemical nature occurs, this affinity should remain constant for a given antagonist-receptor interaction, regardless of the agonists used. This fundamental assumption underpins the classification of receptors. Here, measurements of beta2-adrenoceptor-mediated cAMP accumulation and cAMP response-element (CRE)-mediated reporter-gene transcription revealed differences in antagonist affinity that depended upon agonist incubation time and the efficacy of the competing agonist. In cAMP accumulation studies (10-min agonist incubation), antagonist affinities were the same regardless of the agonist used. The CRE-reporter gene assay (5 h of incubation) antagonist affinities were 10-fold lower in the presence of isoprenaline and adrenaline than when salbutamol or terbutaline were present (e.g., log KD propranolol -8.65 +/- 0.08, n = 22, and -9.68 +/- 0.07, n = 17, for isoprenaline and salbutamol-induced responses, respectively). Isoprenaline and adrenaline were more efficacious in functional studies, and their ability to internalize GFP-tagged human beta2-adrenoceptors. Longer-term cAMP studies also showed significant differences in KD values moving toward that seen with gene transcription. Agonist-dependent differences in antagonist affinity were reduced for reporter-gene responses when a phosphorylation-deficient mutant of the beta2-adrenoceptor was used. This study suggests that high-efficacy agonists induce a chemical modification in beta2-adrenoceptors (via phosphorylation) that reduces antagonist affinities. Because reporter-gene assays are used for high-throughput screening in drug discovery, less efficacious or partial agonists may be more reliable than highly efficacious agonists when reporter-gene techniques are used to estimate antagonist affinity.

  20. Synthetic cannabinoid receptor agonists inhibit tumor growth and metastasis of breast cancer

    Science.gov (United States)

    Qamri, Zahida; Preet, Anju; Nasser, Mohd W.; Bass, Caroline E.; Leone, Gustavo; Barsky, Sanford H.; Ganju, Ramesh K.

    2014-01-01

    Cannabinoids have been reported to possess antitumorogenic activity. Not much is known, however, about the effects and mechanism of action of synthetic nonpsychotic cannabinoids on breast cancer growth and metastasis. We have shown that the cannabinoid receptors CB1 and CB2 are overexpressed in primary human breast tumors compared with normal breast tissue. We have also observed that the breast cancer cell lines MDA-MB231, MDA-MB231-luc, and MDA-MB468 express CB1 and CB2 receptors. Furthermore, we have shown that the CB2 synthetic agonist JWH-133 and the CB1 and CB2 agonist WIN-55,212-2 inhibit cell proliferation and migration under in vitro conditions. These results were confirmed in vivo in various mouse model systems. Mice treated with JWH-133 or WIN-55,212-2 showed a 40% to 50% reduction in tumor growth and a 65% to 80% reduction in lung metastasis. These effects were reversed by CB1 and CB2 antagonists AM 251 and SR144528, respectively, suggesting involvement of CB1 and CB2 receptors. In addition, the CB2 agonist JWH-133 was shown to delay and reduce mammary gland tumors in the polyoma middle T oncoprotein (PyMT) transgenic mouse model system. Upon further elucidation, we observed that JWH-133 and WIN-55,212-2 mediate the breast tumor-suppressive effects via a coordinated regulation of cyclooxygenase-2/ prostaglandin E2 signaling pathways and induction of apoptosis. These results indicate that CB1 and CB2 receptors could be used to develop novel therapeutic strategies against breast cancer growth and metastasis. PMID:19887554

  1. Endogenous activation of adenosine A(1) receptors accelerates ischemic suppression of spontaneous electrocortical activity

    DEFF Research Database (Denmark)

    Ilie, Andrei; Ciocan, Dragos; Zagrean, Ana-Maria

    2006-01-01

    Cerebral ischemia induces a rapid suppression of spontaneous brain rhythms prior to major alterations in ionic homeostasis. It was found in vitro during ischemia that the rapidly formed adenosine, resulting from the intracellular breakdown of ATP, may inhibit synaptic transmission via the A(1...

  2. Diadenosine diphosphate (Ap₂A) delays neutrophil apoptosis via the adenosine A2A receptor and cAMP/PKA pathway.

    Science.gov (United States)

    Pliyev, Boris K; Dimitrieva, Tatyana V; Savchenko, Valery G

    2014-10-01

    Diadenosine polyphosphates have been shown to inhibit neutrophil apoptosis, but mechanisms of the antiapoptotic effect are not known. Diadenosine diphosphate (Ap2A) is the simplest naturally occurring diadenosine polyphosphate, and its effect on neutrophil apoptosis has not previously been investigated. Here we report that Ap2A delays spontaneous apoptosis of human neutrophils, and the effect is reversed by the adenosine A2A receptor antagonists SCH442416 and ZM241385. Ap2A induced an elevation of intracellular cAMP and the elevation was blocked by the adenosine A2A receptor antagonists. The antiapoptotic effect of Ap2A was abrogated by 2',5'-dideoxyadenosine, an inhibitor of adenylyl cyclase, and Rp-8-Br-cAMPS, an inhibitor of type I cAMP-dependent protein kinase A (PKA). Together, these results demonstrate that Ap2A delays neutrophil apoptosis via the adenosine A2A receptor and cAMP/PKA signaling axis.

  3. Prospects for Creation of Cardioprotective and Antiarrhythmic Drugs Based on Opioid Receptor Agonists.

    Science.gov (United States)

    Maslov, Leonid N; Khaliulin, Igor; Oeltgen, Peter R; Naryzhnaya, Natalia V; Pei, Jian-Ming; Brown, Stephen A; Lishmanov, Yury B; Downey, James M

    2016-09-01

    It has now been demonstrated that the μ, δ1 , δ2 , and κ1 opioid receptor (OR) agonists represent the most promising group of opioids for the creation of drugs enhancing cardiac tolerance to the detrimental effects of ischemia/reperfusion (I/R). Opioids are able to prevent necrosis and apoptosis of cardiomyocytes during I/R and improve cardiac contractility in the reperfusion period. The OR agonists exert an infarct-reducing effect with prophylactic administration and prevent reperfusion-induced cardiomyocyte death when ischemic injury of heart has already occurred; that is, opioids can mimic preconditioning and postconditioning phenomena. Furthermore, opioids are also effective in preventing ischemia-induced arrhythmias. © 2016 Wiley Periodicals, Inc.

  4. Lixisenatide, a novel GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus

    DEFF Research Database (Denmark)

    Christensen, Mikkel; Knop, Filip K; Holst, Jens Juul

    2009-01-01

    Lixisenatide, under development by sanofi-aventis, is a novel human glucagon-like peptide-1 receptor (GLP-1R) agonist for the treatment of type 2 diabetes mellitus (T2DM; non-insulin dependent diabetes). The structure of lixisenatide, based on exendin-4(1-39) modified C-terminally with six Lys...... of the anticipated effects of lixisenatide on glycemic measures and weight; favorable results would place lixisenatide for consideration among other GLP-1R agonists in the treatment armamentarium for T2DM....... residues, is able to withstand physiological degradation by dipeptidyl peptidase IV. In vitro, lixisenatide bound to human GLP-1R with a greater affinity than native human GLP-1 (7-36 amide). In various in vitro and in vivo models of T2DM, lixisenatide improved glycemic measures and demonstrated promising...

  5. Liver X Receptor Agonists Inhibit the Phospholipid Regulatory Gene CTP: Phosphoethanolamine Cytidylyltransferase-Pcyt2

    Directory of Open Access Journals (Sweden)

    Lin Zhu

    2008-01-01

    Full Text Available Metabolic pulse-chase experiments demonstrated that 25-hydroxycholesterol (25-OH, the endogenous activator of the liver X receptor (LXR, significantly reduced the biosynthesis of phosphatidylethanolamine via CDP-ethanolamine (Kennedy pathway at the step catalyzed by CTP: phosphoethanolamine cytidylyltransferase (Pcyt2. In the mouse embryonic fibroblasts C3H10T1/2, the LXR synthetic agonist TO901317 lowered Pcyt2 promoter-luciferase activity in a concentration-dependent manner. Furthermore, 25-OH and TO901317 reduced mouse Pcyt2 mRNA and protein levels by 35–60%. The inhibitory effects of oxysterols and TO901317 on the Pcyt2 promoter function, mRNA and protein expression were conserved in the human breast cancer cells MCF-7. These studies identify the Pcyt2 gene as a novel target whereby LXR agonists may indirectly modulate inflammatory responses and atherosclerosis.

  6. Efficacy and Safety of GLP-1 Receptor Agonists for Type 2 Diabetes Mellitus Treatment: Systematic Review

    Directory of Open Access Journals (Sweden)

    Ana Paula Martins

    2016-04-01

    Full Text Available Introduction: Glucagon-like peptide analogues are a new class of drugs used in the treatment of type 2 diabetes mellitus that mimic the endogenous hormone glucagon-like peptide 1. Glucagon-like peptide 1 regulates glucose levels by stimulating glucose-dependent insulin secretion, suppressing glucagon secretion, delayed gastric emptying and promoting satiety. The individualized treatment of type 2 diabetes mellitus, using various glucagon--like peptide receptor agonists, has recently been described and the interest related to these drugs continues to grow. Objectives: To review the efficacy and safety of glucagon-like peptide 1 agonists in patients with inadequately controlled type 2 diabetes mellitus on metformin alone, highlighting their added value in therapeutic use comparatively to second line oral therapies used in type 2 diabetes mellitus. Methods: Studies were obtained from electronic searches of The Cochrane Library and PubMed. Randomized controlled trials were selected if they were at least 8 weeks in duration; compared a glucagon-like peptide 1 analogue with an oral anti-diabetic agent in patients experiencing inadequate glycemic control with metformin monotherapy; and reported hemoglobin A1c data in non-pregnant adults with type 2 diabetes mellitus. Results: Of 72 potentially relevant articles identified, 23 were retrieved for detailed evaluation and 10 met the inclusion criteria. The majority of glucagon-like peptide 1 agonists showed equivalent or superior efficacy than most active comparators for reducing hemoglobin A1c, with a greater proportion of patients achieving hemoglobin A1c <7%. Glucagon-like peptide 1 agonists also showed extra-glycemic effects such as weight loss and the reduction of important cardiovascular parameters. Side effects included gastrointestinal complications, mainly nausea, vomiting and diarrhea. The incidence of hypoglycemia was less common for this class of agents. Conclusion: Glucagon-like peptide 1

  7. Disruption of agonist and ligand activity in an AMPA glutamate receptor splice-variable domain deletion mutant.

    Science.gov (United States)

    Johnson, Wayne D; Parandaman, Vijaya; Onaivi, Emmanuel S; Taylor, Robert E; Akinshola, B Emmanuel

    2008-07-30

    The mechanisms by which agonists and other ligands bind ligand-gated ion channels are important determinants of function in neurotransmitter receptors. The partial agonist, kainic acid (KA) activates a less desensitized, and more robust AMPA receptor (AMPAR) current than full agonists, glutamate or AMPA. Cyclothiazide (CTZ), the allosteric modulator of AMPARs, potentiates receptor currents by inhibiting receptor desensitization resulting from agonist activation. We have constructed an AMPAR GluR1 subunit deletion mutant GluR1L3T(Delta739-784) by deleting the splice-variable "flip/flop" region of the L3 domain in the wild-type receptor and compared its function to that of the wild-type GluR1 receptor and an AMPAR substitution mutant GluR1A782N. When compared to GluR1, the potency of glutamate activation of GluR1L3T was increased, in contrast to a decrease in potency of activation and reduced sensitivity to optimal concentrations of KA. Furthermore, GluR1L3T was totally insensitive to CTZ potentiation of KA and glutamate-activated currents in Xenopus laevis oocytes. The potency of glutamate and KA activation of GluR1A782N was not significantly different from that of the wild-type GluR1 receptor although the mutant receptor currents were more sensitive to CTZ potentiation than the wild-type receptor current. This result is an indication that glutamate and KA binding to the agonist (S1/S2) domain on AMPAR can be modulated by an expendable splice-variable region of the receptor. Moreover, the effect of the allosteric modulator, CTZ on agonist activation of AMPAR can also be modified by a non-conserved amino acid residue substitution within the splice-variable "flip/flop" region.

  8. Ghrelin receptor (GHS-R1A) agonists show potential as interventive agents during aging.

    Science.gov (United States)

    Smith, Roy G; Sun, Yuxiang; Jiang, Hong; Albarran-Zeckler, Rosie; Timchenko, Nikolai

    2007-11-01

    Administration of an orally active agonist (MK-0677) of the growth hormone secretagogue receptor (GHS-R1a) to elderly subjects restored the amplitude of endogenous episodic growth hormone (GH) release to that of young adults. Functional benefits include increased lean mass and bone density and modest improvements in strength. In old mice, a similar agonist partially restored function to the thymus and reduced tumor cell growth and metastasis. Treatment of old mice with the endogenous GHS-R1a agonist ghrelin restored a young liver phenotype. The mechanism involves inhibition of cyclin D3:cdk4/cdk6 activity and increased protein phosphatase-2A (PP2A) activity in liver nuclei, which stabilizes the dephosphorylated form of the transcription factor C/EBPalpha preventing the age-dependent formation of the C/EBPalpha-Rb-E2F4-Brm nuclear complex. By inhibiting formation of this complex, repression of E2F target genes is de-repressed and C/EBPalpha regulated expression of Pepck, a regulator of gluconeogenesis, is normalized, thereby restoring a young liver phenotype. In the brain, aging is associated with decline in dopamine function. We investigated the potential neuromodulatory role of GHS-R1a on dopamine action. Neurons were identified in the hippocampus, cortex, substantia nigra, and ventral tegmental areas that coexpressed GHS-R1a and dopamine receptor subtype-1 (D1R). Cell culture studies showed that, in the presence of ghrelin and dopamine, GHS-R and D1R form heterodimers, which modified G-protein signal transduction resulting in amplification of dopamine signaling. We speculate that aging is associated with deficient endogenous ghrelin signaling that can be rescued by intervention with GHS-R1a agonists to improve quality of life and maintain independence.

  9. Excess adenosine A2B receptor signaling contributes to priapism through HIF-1α mediated reduction of PDE5 gene expression

    Science.gov (United States)

    Ning, Chen; Wen, Jiaming; Zhang, Yujin; Dai, Yingbo; Wang, Wei; Zhang, Weiru; Qi, Lin; Grenz, Almut; Eltzschig, Holger K.; Blackburn, Michael R.; Kellems, Rodney E.; Xia, Yang

    2014-01-01

    Priapism is featured with prolonged and painful penile erection and is prevalent among males with sickle cell disease (SCD). The disorder is a dangerous urological and hematological emergency since it is associated with ischemic tissue damage and erectile disability. Here we report that phosphodiesterase-5 (PDE5) gene expression and PDE activity is significantly reduced in penile tissues of two independent priapic models: SCD mice and adenosine deaminase (ADA)-deficient mice. Moreover, using ADA enzyme therapy to reduce adenosine or a specific antagonist to block A2B adenosine receptor (ADORA2B) signaling, we successfully attenuated priapism in both ADA−/− and SCD mice by restoring penile PDE5 gene expression to normal levels. This finding led us to further discover that excess adenosine signaling via ADORA2B activation directly reduces PDE5 gene expression in a hypoxia-inducible factor-1α (HIF-1α)-dependent manner. Overall, we reveal that excess adenosine-mediated ADORA2B signaling underlies reduced penile PDE activity by decreasing PDE5 gene expression in a HIF-1α-dependent manner and provide new insight for the pathogenesis of priapism and novel therapies for the disease.—Ning, C., Wen, J., Zhang, Y., Dai, Y., Wang, W., Zhang, W., Qi, L., Grenz, A., Eltzschig, H. K., Blackburn, M. R., Kellems, R. E., Xia, Y. Excess adenosine A2B receptor signaling contributes to priapism through HIF-1α mediated reduction of PDE5 gene expression. PMID:24614760

  10. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    Science.gov (United States)

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease.

  11. Revealing a steroid receptor ligand as a unique PPAR[gamma] agonist

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Shengchen; Han, Ying; Shi, Yuzhe; Rong, Hui; Zheng, Songyang; Jin, Shikan; Lin, Shu-Yong; Lin, Sheng-Cai; Li, Yong (Pitt); (Xiamen)

    2012-06-28

    Peroxisome proliferator-activated receptor gamma (PPAR{gamma}) regulates metabolic homeostasis and is a molecular target for anti-diabetic drugs. We report here the identification of a steroid receptor ligand, RU-486, as an unexpected PPAR{gamma} agonist, thereby uncovering a novel signaling route for this steroid drug. Similar to rosiglitazone, RU-486 modulates the expression of key PPAR{gamma} target genes and promotes adipocyte differentiation, but with a lower adipogenic activity. Structural and functional studies of receptor-ligand interactions reveal the molecular basis for a unique binding mode for RU-486 in the PPAR{gamma} ligand-binding pocket with distinctive properties and epitopes, providing the molecular mechanisms for the discrimination of RU-486 from thiazolidinediones (TZDs) drugs. Our findings together indicate that steroid compounds may represent an alternative approach for designing non-TZD PPAR{gamma} ligands in the treatment of insulin resistance.

  12. Anti-tumor Activity of Toll-Like Receptor 7 Agonists

    Directory of Open Access Journals (Sweden)

    Huju Chi

    2017-05-01

    Full Text Available Toll-like receptors (TLRs are a class of pattern recognition receptors that play a bridging role in innate immunity and adaptive immunity. The activated TLRs not only induce inflammatory responses, but also elicit the development of antigen specific immunity. TLR7, a member of TLR family, is an intracellular receptor expressed on the membrane of endosomes. TLR7 can be triggered not only by ssRNA during viral infections, but also by immune modifiers that share a similar structure to nucleosides. Its powerful immune stimulatory action can be potentially used in the anti-tumor therapy. This article reviewed the anti-tumor activity and mechanism of TLR7 agonists that are frequently applied in preclinical and clinical investigations, and mainly focused on small synthetic molecules, including imiquimod, resiquimod, gardiquimod, and 852A, etc.

  13. Conversion of agonist site to metal-ion chelator site in the beta(2)-adrenergic receptor

    DEFF Research Database (Denmark)

    Elling, C E; Thirstrup, K; Holst, Birgitte

    1999-01-01

    effect of, for example Cu(2+), and in several cases increased the affinity of the ions for the agonistic site. Wash-out experiments and structure-activity analysis indicated, that the high-affinity chelators and the metal ions bind and activate the mutant receptor as metal ion guided ligand complexes...... in the mutant receptors not by normal catecholamine ligands but instead either by free zinc ions or by zinc or copper ions in complex with small hydrophobic metal-ion chelators. Chelation of the metal ions by small hydrophobic chelators such as phenanthroline or bipyridine protected the cells from the toxic....... Because of the well-understood binding geometry of the small metal ions, an important distance constraint has here been imposed between TM-III and -VII in the active, signaling conformation of 7TM receptors. It is suggested that atoxic metal-ion chelator complexes could possibly in the future be used...

  14. Development of betulinic acid as an agonist of TGR5 receptor using a new in vitro assay

    Directory of Open Access Journals (Sweden)

    Lo SH

    2016-08-01

    Full Text Available Shih-Hsiang Lo,1,2 Kai-Chung Cheng,3 Ying-Xiao Li,3,4 Chin-Hong Chang,4,5 Juei-Tang Cheng,4,6 Kung-Shing Lee7,8 1Division of Cardiology, Department of Internal Medicine, Zhongxing Branch of Taipei City Hospital, 2Department of History and Geography, University of Taipei, Taipei, Taiwan; 3Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan; 4Department of Medical Research, 5Department of Neurosurgery, Chi-Mei Medical Center, Yong Kang, 6Institute of Medical Science, College of Health Science, Chang Jung Christian University, Tainan, 7Department of Surgery, Pingtung Hospital, 8Division of Neurosurgery, Department of Surgery, Kaohsiung Medical University Chung-Ho Memorial Hospital, School of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan Background: G-protein-coupled bile acid receptor 1, also known as TGR5 is known to be involved in glucose homeostasis. In animal models, treatment with a TGR5 agonist induces incretin secretion to reduce hyperglycemia. Betulinic acid, a triterpenoid present in the leaves of white birch, has been introduced as a selective TGR5 agonist. However, direct activation of TGR5 by betulinic acid has not yet been reported. Methods: Transfection of TGR5 into cultured Chinese hamster ovary (CHO-K1 cells was performed to establish the presence of TGR5. Additionally, TGR5-specific small interfering RNA was employed to silence TGR5 in cells (NCI-H716 cells that secreted incretins. Uptake of glucose by CHO-K1 cells was evaluated using a fluorescent indicator. Amounts of cyclic adenosine monophosphate and glucagon-like peptide were quantified using enzyme-linked immunosorbent assay kits. Results: Betulinic acid dose-dependently increases glucose uptake by CHO-K1 cells transfected with TGR5 only, which can be considered an alternative method instead of radioligand binding assay. Additionally, signals coupled to TGR5 activation are also

  15. Adenosine A(2A) receptor gene (ADORA2A) variants may increase autistic symptoms and anxiety in autism spectrum disorder.

    Science.gov (United States)

    Freitag, Christine M; Agelopoulos, Konstantin; Huy, Ellen; Rothermundt, Matthias; Krakowitzky, Petra; Meyer, Jobst; Deckert, Jürgen; von Gontard, Alexander; Hohoff, Christa

    2010-01-01

    Autism spectrum disorders (ASDs) are heterogeneous disorders presenting with increased rates of anxiety. The adenosine A(2A) receptor gene (ADORA2A) is associated with panic disorder and is located on chromosome 22q11.23. Its gene product, the adenosine A(2A) receptor, is strongly expressed in the caudate nucleus, which also is involved in ASD. As autistic symptoms are increased in individuals with 22q11.2 deletion syndrome, and large 22q11.2 deletions and duplications have been observed in ASD individuals, in this study, 98 individuals with ASD and 234 control individuals were genotyped for eight single-nucleotide polymorphisms in ADORA2A. Nominal association with the disorder was observed for rs2236624-CC, and phenotypic variability in ASD symptoms was influenced by rs3761422, rs5751876 and rs35320474. In addition, association of ADORA2A variants with anxiety was replicated for individuals with ASD. Findings point toward a possible mediating role of ADORA2A variants on phenotypic expression in ASD that need to be replicated in a larger sample.

  16. Immunomodulatory impact of the A2A adenosine receptor on the profile of chemokines produced by neutrophils

    Science.gov (United States)

    McColl, Shaun R.; St-Onge, Mireille; Dussault, Andrée-Anne; Laflamme, Cynthia; Bouchard, Line; Boulanger, Jean; Pouliot, Marc

    2010-01-01

    In LPS-stimulated human neutrophils, engagement of the adenosine A2A receptor selectively prevented the expression and release of TNF-α, MIP-1α/CCL3, MIP-1β/CCL4, MIP-2α/CXCL2, and MIP-3α/CCL20. In mice lacking the A2A receptor, granulocytes that migrated into the air pouch 4 h after LPS injection expressed higher mRNA levels of TNF-α, MIP-1α, and MIP-1β than PMNs from wild-type mice. In mononuclear cells present in the air pouch 72 h after LPS injection, expression of IL-1β, TNF-α, IL-6, and MCP-2/CCL6 was higher in A2AR knockout mice. In addition to highlighting neutrophils as an early and pivotal target for mediating adenosine anti-inflammatory activities, these results identify TNF-α and the MIP chemokine family as gene products whose expression is pivotally affected by activation of A2AR in LPS-activated PMNs. Modulation by A2AR in the production of inflammatory signals by PMNs may thus influence the evolution of an inflammatory response by reducing the activation status of inflammatory cells. PMID:16280366

  17. The effects of the alpha2-adrenergic receptor agonists clonidine and rilmenidine, and antagonists yohimbine and efaroxan, on the spinal cholinergic receptor system in the rat

    DEFF Research Database (Denmark)

    Abelson, Klas S P; Höglund, A Urban

    2004-01-01

    and rilmenidine increased, while yohimbine decreased spinal acetylcholine release. Efaroxan affected acetylcholine release differently depending on concentration. Nicotinic receptor blockade attenuated the effect of all ligands. All ligands showed poor binding affinity for muscarinic receptors. On the other hand......Cholinergic agonists produce spinal antinociception via mechanisms involving an increased release of intraspinal acetylcholine. The cholinergic receptor system interacts with several other receptor types, such as alpha2-adrenergic receptors. To fully understand these interactions, the effects...... of various receptor ligands on the cholinergic system must be investigated in detail. This study was initiated to investigate the effects of the alpha2-adrenergic receptor agonists clonidine and rilmenidine and the alpha2-adrenergic receptor antagonists yohimbine and efaroxan on spinal cholinergic receptors...

  18. Activation of adenosine A₂A receptors suppresses the emission of pro-social and drug-stimulated 50-kHz ultrasonic vocalizations in rats: possible relevance to reward and motivation.

    Science.gov (United States)

    Simola, Nicola; Costa, Giulia; Morelli, Micaela

    2016-02-01

    Rats emit 50-kHz ultrasonic vocalizations (USVs) in response to pleasurable stimuli, and these USVs are considered a tool for investigating reward and motivation. This study aimed to clarify how activity of adenosine A2A receptors, which modulate reward and motivation, influences 50-kHz USV emission in rats. Rats received one of the following treatments in a test cage: (1) acute administration of the A2A receptor agonist CGS 21680 (0.05-0.2 mg/kg, i.p.) during social interactions; (2) long-term amphetamine (1 or 2 mg/kg, i.p.) or morphine (7.5 mg/kg, s.c.) administration on alternate days, alone or with CGS 21680, followed after 7 days of discontinuation by test cage re-exposure, to assess drug-conditioning effects, and thereafter drug challenge; (3) acute administration of the D1/D2 receptor agonist apomorphine (4 mg/kg, i.p.), alone or with CGS 21680; and (4) long-term administration of the non-selective A1/A2A receptor antagonist caffeine (15 mg/kg, i.p.), on alternate days. USVs and locomotor activity were evaluated throughout the treatments. CGS 21680 attenuated 50-kHz USV emission stimulated by social interactions, amphetamine, apomorphine, and morphine, and rats administered CGS 21680 with amphetamine or morphine emitted fewer conditioned 50-kHz USVs upon test cage re-exposure, compared with rats administered amphetamine or morphine alone. Moreover, CGS 21680 administration prevented long-term changes in locomotor activity in amphetamine- and morphine-treated rats. Finally, caffeine had no effect on 50-kHz USVs. These results indicate that activation of A2A receptors attenuates 50-kHz USV emission in rats and further elucidate how these receptors modulate the motivational properties of natural and pharmacological stimuli.

  19. Receptor structure-based discovery of non-metabolite agonists for the succinate receptor GPR91

    Directory of Open Access Journals (Sweden)

    Mette Trauelsen

    2017-12-01

    Conclusions: These novel, synthetic non-metabolite GPR91 agonists will be valuable both as pharmacological tools to delineate the GPR91-mediated functions of succinate and as leads for the development of GPR91-targeted drugs to potentially treat low grade metabolic inflammation and diabetic complications such as retinopathy and nephropathy.

  20. Neuroprotection by caffeine in the MPTP model of parkinson's disease and its dependence on adenosine A2A receptors.

    Science.gov (United States)

    Xu, K; Di Luca, D G; Orrú, M; Xu, Y; Chen, J-F; Schwarzschild, M A

    2016-05-13

    Considerable epidemiological and laboratory data have suggested that caffeine, a nonselective adenosine receptor antagonist, may protect against the underlying neurodegeneration of parkinson's disease (PD). Although both caffeine and more specific antagonists of the A2A subtype of adenosine receptor (A2AR) have been found to confer protection in animal models of PD, the dependence of caffeine's neuroprotective effects on the A2AR is not known. To definitively determine its A2AR dependence, the effect of caffeine on 1-methyl-4-phenyl-1,2,3,6 tetra-hydropyridine (MPTP) neurotoxicity was compared in wild-type (WT) and A2AR gene global knockout (A2A KO) mice, as well as in central nervous system (CNS) cell type-specific (conditional) A2AR knockout (cKO) mice that lack the receptor either in postnatal forebrain neurons or in astrocytes. In WT and in heterozygous A2AR KO mice caffeine pretreatment (25mg/kgip) significantly attenuated MPTP-induced depletion of striatal dopamine. By contrast in homozygous A2AR global KO mice caffeine had no effect on MPTP toxicity. In forebrain neuron A2AR cKO mice, caffeine lost its locomotor stimulant effect, whereas its neuroprotective effect was mostly preserved. In astrocytic A2AR cKO mice, both caffeine's locomotor stimulant and protective properties were undiminished. Taken together, these results indicate that neuroprotection by caffeine in the MPTP model of PD relies on the A2AR, although the specific cellular localization of these receptors remains to be determined. Copyright © 2016 IBRO. All rights reserved.

  1. Structural Determinants for the Binding of Morphinan Agonists to the μ-Opioid Receptor.

    Directory of Open Access Journals (Sweden)

    Xiaojing Cong

    Full Text Available Atomistic descriptions of the μ-opioid receptor (μOR noncovalently binding with two of its prototypical morphinan agonists, morphine (MOP and hydromorphone (HMP, are investigated using molecular dynamics (MD simulations. Subtle differences between the binding modes and hydration properties of MOP and HMP emerge from the calculations. Alchemical free energy perturbation calculations show qualitative agreement with in vitro experiments performed in this work: indeed, the binding free energy difference between MOP and HMP computed by forward and backward alchemical transformation is 1.2±1.1 and 0.8±0.8 kcal/mol, respectively, to be compared with 0.4±0.3 kcal/mol from experiment. Comparison with an MD simulation of μOR covalently bound with the antagonist β-funaltrexamine hints to agonist-induced conformational changes associated with an early event of the receptor's activation: a shift of the transmembrane helix 6 relative to the transmembrane helix 3 and a consequent loss of the key R165-T279 interhelical hydrogen bond. This finding is consistent with a previous proposal suggesting that the R165-T279 hydrogen bond between these two helices indicates an inactive receptor conformation.

  2. Identification of the first surrogate agonists for the G protein-coupled receptor GPR132

    DEFF Research Database (Denmark)

    Shehata, Mohamed A.; Christensen, Hanna Belcik; Isberg, Vignir

    2015-01-01

    GPR132 is an orphan class A G protein-coupled receptor. It has been proposed to be activated by protons and to regulate apoptosis, atherosclerosis and inflammation, but these results are still preliminary. In the current work, we designed and screened a focused compound library using a β-arrestin......GPR132 is an orphan class A G protein-coupled receptor. It has been proposed to be activated by protons and to regulate apoptosis, atherosclerosis and inflammation, but these results are still preliminary. In the current work, we designed and screened a focused compound library using a β......-arrestin recruitment assay, and thereby identified the first disclosed surrogate GPR132 agonist 1 with a potency of 3.4 μM. This constitutes the first available pharmacological tool for the in vitro characterization of the orphan receptor GPR132. The testing of 32 analogs furthermore identified a number of compounds...... with lower activity – of which six were agonists and two were antagonists – that were used to construct preliminary structure–activity relationships. Docking followed by a molecular dynamics simulation of compound 1 in a structural model of GPR132 displayed the putative interactions for the key ligand...

  3. Nicotinic receptor partial agonists alter catecholamine homeostasis and response to nicotine in PC12 cells.

    Science.gov (United States)

    Turcanu, D S; Kirtok, N; Eibl, C; Guendisch, D; LaGamma, E F; Nankova, B B

    2012-05-16

    Repeated stress is a major public health concern where many stress responses are mediated by neuronal nicotinic acetylcholine receptors. In the present study we evaluated the effects of the nicotinic receptor partial agonists, cytisine and its derivative 3-(pyridin-3'-yl)-cytisine (3-pyr-Cyt) on two main biological outputs associated with activation of nAChR-release of neurotransmitters and increase in catecholamine biosynthesis to replenish the releasable pool. We compared these substances to the maximal response triggered by nicotine (full agonist) in PC12 cells. Cytisine, 3-pyr-Cyt or nicotine induced time-, dose- and Ca(2+)-dependent significant release of norepinephrine (NE) into the culture media. These effects were completely inhibited by mecamylamine but not by α-bungarotoxin, and only partially affected by α-conotoxin AulB, consistent with the involvement of α3β4 receptors. Co-application of cytisine (or 3-pyr-Cyt) and nicotine resulted in attenuated nicotine-induced NE release. Cytisine or 3-pyr-Cyt alone induced a modest rise in tyrosine hydroxylase (TH) mRNA levels (index of the cell's catecholamine biosynthetic capacity). We conclude that both, cytisine and 3-pyr-Cyt (i) display typical partial agonist properties at naturally existing ganglionic nAChR (α3β4 and α7 nAChR) with regard to catecholamine homeostasis (i.e. NE release and re-synthesis) and (ii) modulated the effect of nicotine during combined treatment. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  4. Preventing or attenuating amphotericin B nephrotoxicity with dopamine receptor agonists: a literature review

    Directory of Open Access Journals (Sweden)

    Iman Karimzadeh

    2016-09-01

    Full Text Available Nephrotoxicity is generally considered as the most clinically significant and dose-limiting adverse reaction of amphotericin B. Currently, only the clinical effectiveness of salt loading and administering lipid formulations of amphotericin B have been clearly demonstrated to prevent its nephrotoxicity. In this review, we collected the published data related to dopamine receptor agonists in preventing amphotericin B nephrotoxicity. A literature search was conducted by the relevant keywords like ‘‘amphotericin B”, “nephrotoxicity’’, and ‘‘dopamine’’in databases such as Scopus, Medline, Embase and ISI Web of Knowledge. Four relevant articles were considered. Results of all the 3 experimental studies demonstrated that co-administration of dopamine (0.5-10 μg/kg/min as continuous intravenous infusion, SK&F R-105058, a prodrug of fenoldopam (10 mg/kg twice daily, orally or fenoldopam, a relatively selective dopamine receptor type 1 agonist, (0.5 or 1 μg/kg/min as continuous intravenous infusion can at least significantly mitigate the decrease in creatinine clearance caused by amphotericin B. Furthermore, fenoldopam and SK&F R-105058 can also protect against or delay amphotericin B-induced tubular damage. In contrast, the only clinical trial published until now found that simultaneous continuous intravenous infusion of low dose dopamine (3 μg/kg/min had no beneficial effect on the incidence, severity and time onset of developing amphotericin B-induced nephrotoxicity in autologous bone marrow transplant and leukemia patients. Considering the lack of beneficial effects in different settings such as acute kidney injury of any cause, negative results of the only clinical trial, and risk of significant adverse reactions, continuous intravenous infusion of low dose dopamine (1-3 μg/kg/min or selective dopamine receptor type 1 agonists (e.g., fenoldopam currently appears to have no promising clinical role in preventing or attenuating

  5. [Hypocretins and adenosine in the regulation of sleep].

    Science.gov (United States)

    Salín-Pascual, R J

    To review the recent discovery of hypocretins (orexins) and their link to the pathophysiology of narcolepsy and the role of adenosine in the integration of brain metabolism and sleep. The importance of the functions carried out by the hypothalamus in the regulation of sleep and the waking state has been consolidated by the discovery of hypocretins and the role played by cerebral adenosine. Hypocretins are two peptides made up of 33 and 28 amino acids whose neurons are located predominantly in the lateral hypothalamus and surrounding regions. In the Doberman canine narcolepsy model, in which this disease is presented with an autosomal recessive pattern, a mutation was detected in one of the receptors involved in the hypocretin system, namely the hypocretin-2 receptor. Failures in the hypocretin system have been confirmed as a key factor in narcolepsy by other findings in laboratory animals and humans. Adenosine, on the other hand, is accumulated during the waking state as a result of neuronal metabolism and this in turn is related to drowsiness. Sleep episodes lower the levels of this substance in the brain. Adenosine receptor antagonists increase wakefulness (e.g. caffeine), while the agonists promote slow-wave sleep. Hypocretins and adenosine from the hypothalamus perform functions involving the regulation of sleep and wakefulness. Understanding these two systems can have repercussions on clinical problems such as insomnia, hypersomnia and other neuropsychiatric disorders.

  6. Discovery of benzamide analogues as a novel class of 5-HT3 receptor agonists

    DEFF Research Database (Denmark)

    Jørgensen, Charlotte Grube; Frølund, Bente Flensborg; Kehler, Jan

    2011-01-01

    A 5-HT(3) receptor agonist based on a benzamide scaffold was identified in a screening of a small commercial compound library, and an elaborate SAR study originating from this hit was performed. The design, synthesis, and functional characterisation of benzamide analogues at the 5-HT(3) A receptor...

  7. Novel indole and azaindole (pyrrolopyridine) cannabinoid (CB) receptor agonists: design, synthesis, structure-activity relationships, physicochemical properties and biological activity

    NARCIS (Netherlands)

    Blaazer, A.R.; Lange, J.H.M.; van der Neut, M.A.W.; Mulder, A.; den Boon, F.S.; Werkman, T.R.; Kruse, C.G.; Wadman, W.J.

    2011-01-01

    The discovery, synthesis and structure-activity relationship (SAR) of a novel series of cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptor ligands are reported. Based on the aminoalkylindole class of cannabinoid receptor agonists, a biphenyl moiety was introduced as novel lipophilic indole 3-acyl

  8. The muscarinic M1/M4 receptor agonist xanomeline exhibits antipsychotic-like activity in Cebus apella monkeys

    DEFF Research Database (Denmark)

    Andersen, Maibritt B; Fink-Jensen, Anders; Peacock, Linda

    2003-01-01

    Xanomeline is a muscarinic M(1)/M(4) preferring receptor agonist with little or no affinity for dopamine receptors. The compound reduces psychotic-like symptoms in patients with Alzheimer's disease and exhibits an antipsychotic-like profile in rodents without inducing extrapyramidal side effects ...... that xanomeline inhibits D-amphetamine- and (-)-apomorphine-induced behavior in Cebus apella monkeys at doses that do not cause EPS. These data further substantiate that muscarinic receptor agonists may be useful in the pharmacological treatment of psychosis....

  9. Conformational variability of the glycine receptor M2 domain in response to activation by different agonists

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Dibas, Mohammed I; Lester, Henry A

    2007-01-01

    change. Although taurine and beta-alanine were weak partial agonists at the alpha1R19'C glycine receptor, they induced large fluorescence changes. Propofol, which drastically enhanced these currents, did not induce a glycine-like blue shift in the spectral emission peak. The inhibitors strychnine...... and picrotoxin elicited fluorescence and current changes as expected for a competitive antagonist and an open channel blocker, respectively. Glycine and taurine (or beta-alanine) also produced an increase and a decrease, respectively, in the fluorescence of a label attached to the nearby L22'C residue. Thus...

  10. [Dopamine receptor agonists: new forms and new possibilities in the treatment of Parkinson's disease].

    Science.gov (United States)

    Katunina, E A; Titova, N V; Bezdolny, Yu N; Shykkerimov, R K; Gasanov, M G; Burd, S G; Lebedeva, A V; Boiko, A N

    2015-01-01

    Main mechanisms of action of dopamine receptor agonists, efficacy of their use according to the results of earlier clinical trials and possible side-effects are discussed. The authors present their experience of prescription of rotigotine transdermal system in an open study of 30 patients with Parkinson's disease. The duration of the study was 8 weeks. There was a significant improvement of both motor and nonmotor (pain sensations, sleep, mood). The effective dose for treatment of initial stages was 4-6 mg daily and for the full-blown stage - 6-8 mg daily. The tolerability was good.

  11. Attenuated vasodilator effectiveness of protease-activated receptor 2 agonist in heterozygous par2 knockout mice.

    Directory of Open Access Journals (Sweden)

    John C Hennessey

    Full Text Available Studies of homozygous PAR2 gene knockout mice have described a mix of phenotypic effects in vitro and in vivo. However, there have been few studies of PAR2 heterozygous (wild-type/knockout; PAR2-HET mice. The phenotypes of many hemi and heterozygous transgenic mice have been described as intermediates between those of wild-type and knockout animals. In our study we aimed to determine the effects of intermediary par2 gene zygosity on vascular tissue responses to PAR2 activation. Specifically, we compared the vasodilator effectiveness of the PAR2 activating peptide 2-furoyl-LIGRLO-amide in aortas of wild-type PAR2 homozygous (PAR2-WT and PAR2-HET mice. In myographs under isometric tension conditions, isolated aortic rings were contracted by alpha 1-adrenoeceptor agonist (phenylephrine, and thromboxane receptor agonist (U46619 and then relaxation responses by the additions of 2-furoyl-LIGRLO-amide, acetylcholine, and nitroprusside were recorded. A Schild regression analysis of the inhibition by a PAR2 antagonist (GB-83 of PAR2 agonist-induced aortic ring relaxations was used to compare receptor expression in PAR2-WT to PAR2-HET. PAR2 mRNA in aortas was measured by quantitative real-time PCR. In aortas contracted by either phenylephrine or U46619, the maximum relaxations induced by 2-furoyl-LIGRLO-amide were less in PAR2-HET than in the gender-matched PAR2-WT. GB-83 was 3- to 4-fold more potent for inhibition of 2fly in PAR2-HET than in PAR2-WT. PAR2 mRNA content of aortas from PAR2-HET was not significantly different than in PAR2-WT. Acetylcholine- and nitroprusside-induced relaxations of aortas from PAR2-HET were not significantly different than in PAR2-WT and PAR2 knockout. An interesting secondary finding was that relaxations induced by agonists of PAR2 and muscarinic receptors were larger in females than in males. We conclude that the lower PAR2-mediated responses in PAR2-HET aortas are consistent with evidence of a lower quantity of functional

  12. Role of Adenosine Receptor A2A in Traumatic Optic Neuropathies

    Science.gov (United States)

    2015-02-01

    Faculty of Pharmacy, Mansoura University, Mansoura, Egypt d South Western Medical Center, Dallas, TX, USA e Department of Orthopedics , Georgia Regents...Burnstock, 1998). However, the apparently impaired protection in mice with TON reflects that protection by endogenous adenosine is in sufficient and...Liou a,⁎ a Department of Ophthalmology, Georgia Regents University, 30909, USA b Department of Orthopedics , Georgia Regents University, 30909, USA c

  13. Combined action of estrogen receptor agonists and antagonists in two-hybrid recombinant yeast in vitro.

    Science.gov (United States)

    Yang, Rong; Li, Na; Rao, Kaifeng; Ma, Mei; Wang, Zijian

    2015-01-01

    Estrogen receptor (ER) antagonistic chemicals in aquatic environments are believed to influence the binding of both endogenous and exogenous estrogens to ERs in aquatic organisms. Although the combined effects of estrogenic compounds have attracted much scientific concern, little work has been done on the influence of such antiestrogens on the biological effects of estrogens. This study focused on how the presence of different amounts of antagonists affects the results of ER agonist activity tests. To achieve this, three questions were stated and answered in sequence. A two-hybrid recombinant yeast assay mediated by ER was adopted, providing a single mode of action and single target of action for this study. Mixtures created by an ER agonist and three antagonists following the fixed-ratio principle were assessed. The concentration of 17β-estradiol causing maximum induction was set as the fixed dose of estrogen in the antagonist activity test (question 1). When the two classes of chemicals coexisted, antiestrogens, which as a whole behaved according to the concentration addition model (question 2), decreased the response of estrogen and compressed the concentration-response curves along the y-axis in the agonist activity test (question 3). This may cause the estradiol equivalent to be underestimated and potentially mask the action of estrogenic effects in toxicity evaluation of environmental samples. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. E17110 promotes reverse cholesterol transport with liver X receptor β agonist activity in vitro

    Directory of Open Access Journals (Sweden)

    Ni Li

    2016-05-01

    Full Text Available Liver X receptor (LXR plays an important role in reverse cholesterol transport (RCT, and activation of LXR could reduce atherosclerosis. In the present study we used a cell-based screening method to identify new potential LXRβ agonists. A novel benzofuran-2-carboxylate derivative was identified with LXRβ agonist activity: E17110 showed a significant activation effect on LXRβ with an EC50 value of 0.72 μmol/L. E17110 also increased the expression of ATP-binding cassette transporter A1 (ABCA1 and G1 (ABCG1 in RAW264.7 macrophages. Moreover, E17110 significantly reduced cellular lipid accumulation and promoted cholesterol efflux in RAW264.7 macrophages. Interestingly, we found that the key amino acids in the LXRβ ligand-binding domain had distinct interactions with E17110 as compared to TO901317. These results suggest that E17110 was identified as a novel compound with LXRβ agonist activity in vitro via screening, and could be developed as a potential anti-atherosclerotic lead compound.

  15. Peroxisome proliferator-activated receptoragonists attenuate biofilm formation by Pseudomonas aeruginosa.

    Science.gov (United States)

    Bedi, Brahmchetna; Maurice, Nicholas M; Ciavatta, Vincent T; Lynn, K Sabrina; Yuan, Zhihong; Molina, Samuel A; Joo, Myungsoo; Tyor, William R; Goldberg, Joanna B; Koval, Michael; Hart, C Michael; Sadikot, Ruxana T

    2017-08-01

    Pseudomonas aeruginosa is a significant contributor to recalcitrant multidrug-resistant infections, especially in immunocompromised and hospitalized patients. The pathogenic profile of P. aeruginosa is related to its ability to secrete a variety of virulence factors and to promote biofilm formation. Quorum sensing (QS) is a mechanism wherein P. aeruginosa secretes small diffusible molecules, specifically acyl homo serine lactones, such as N-(3-oxo-dodecanoyl)-l-homoserine lactone (3O-C12-HSL), that promote biofilm formation and virulence via interbacterial communication. Strategies that strengthen the host's ability to inhibit bacterial virulence would enhance host defenses and improve the treatment of resistant infections. We have recently shown that peroxisome proliferator-activated receptor γ (PPARγ) agonists are potent immunostimulators that play a pivotal role in host response to virulent P. aeruginosa Here, we show that QS genes in P. aeruginosa (strain PAO1) and 3O-C12-HSL attenuate PPARγ expression in bronchial epithelial cells. PAO1 and 3O-C12-HSL induce barrier derangements in bronchial epithelial cells by lowering the expression of junctional proteins, such as zonula occludens-1, occludin, and claudin-4. Expression of these proteins was restored in cells that were treated with pioglitazone, a PPARγ agonist, before infection with PAO1 and 3O-C12-HSL. Barrier function and bacterial permeation studies that have been performed in primary human epithelial cells showed that PPARγ agonists are able to restore barrier integrity and function that are disrupted by PAO1 and 3O-C12-HSL. Mechanistically, we show that these effects are dependent on the induction of paraoxonase-2, a QS hydrolyzing enzyme, that mitigates the effects of QS molecules. Importantly, our data show that pioglitazone, a PPARγ agonist, significantly inhibits biofilm formation on epithelial cells by a mechanism that is mediated via paraoxonase-2. These findings elucidate a novel role for

  16. Adenosine 2A receptor antagonist prevented and reversed liver fibrosis in a mouse model of ethanol-exacerbated liver fibrosis.

    Directory of Open Access Journals (Sweden)

    Dian J Chiang

    Full Text Available The effect of moderate alcohol consumption on liver fibrosis is not well understood, but evidence suggests that adenosine may play a role in mediating the effects of moderate ethanol on tissue injury. Ethanol increases the concentration of adenosine in the liver. Adenosine 2A receptor (A2AR activation is known to enhance hepatic stellate cell (HSC activation and A2AR deficient mice are protected from fibrosis in mice. Making use of a novel mouse model of moderate ethanol consumption in which female C57BL/6J mice were allowed continued access to 2% (vol/vol ethanol (11% calories or pair-fed control diets for 2 days, 2 weeks or 5 weeks and superimposed with exposure to CCl4, we tested the hypothesis that moderate ethanol consumption increases fibrosis in response to carbon tetrachloride (CCl4 and that treatment of mice with an A2AR antagonist prevents and/or reverses this ethanol-induced increase in liver fibrosis. Neither the expression or activity of CYP2E1, required for bio-activation of CCl4, nor AST and ALT activity in the plasma were affected by ethanol, indicating that moderate ethanol did not increase the direct hepatotoxicity of CCl4. However, ethanol feeding enhanced HSC activation and exacerbated liver fibrosis upon exposure to CCl4. This was associated with an increased sinusoidal angiogenic response in the liver. Treatment with A2AR antagonist both prevented and reversed the ability of ethanol to exacerbate liver fibrosis.Moderate ethanol consumption exacerbates hepatic fibrosis upon exposure to CCl4. A2AR antagonism may be a potential pharmaceutical intervention to decrease hepatic fibrosis in response to ethanol.

  17. Cannabidiol displays unexpectedly high potency as an antagonist of CB1 and CB2 receptor agonists in vitro

    Science.gov (United States)

    Thomas, A; Baillie, G L; Phillips, A M; Razdan, R K; Ross, R A; Pertwee, R G

    2007-01-01

    Background and purpose: A nonpsychoactive constituent of the cannabis plant, cannabidiol has been demonstrated to have low affinity for both cannabinoid CB1 and CB2 receptors. We have shown previously that cannabidiol can enhance electrically evoked contractions of the mouse vas deferens, suggestive of inverse agonism. We have also shown that cannabidiol can antagonize cannabinoid receptor agonists in this tissue with a greater potency than we would expect from its poor affinity for cannabinoid receptors. This study aimed to investigate whether these properties of cannabidiol extend to CB1 receptors expressed in mouse brain and to human CB2 receptors that have been transfected into CHO cells. Experimental approach: The [35S]GTPγS binding assay was used to determine both the efficacy of cannabidiol and the ability of cannabidiol to antagonize cannabinoid receptor agonists (CP55940 and R-(+)-WIN55212) at the mouse CB1 and the human CB2 receptor. Key results: This paper reports firstly that cannabidiol displays inverse agonism at the human CB2 receptor. Secondly, we demonstrate that cannabidiol is a high potency antagonist of cannabinoid receptor agonists in mouse brain and in membranes from CHO cells transfected with human CB2 receptors. Conclusions and implications: This study has provided the first evidence that cannabidiol can display CB2 receptor inverse agonism, an action that appears to be responsible for its antagonism of CP55940 at the human CB2 receptor. The ability of cannabidiol to behave as a CB2 receptor inverse agonist may contribute to its documented anti-inflammatory properties. PMID:17245363

  18. Efficacy and safety of insulin-GLP-1 receptor agonists combination in type 2 diabetes mellitus: a systematic review.

    Science.gov (United States)

    Cimmaruta, D; Maiorino, M I; Scavone, C; Sportiello, L; Rossi, F; Giugliano, D; Esposito, K; Capuano, A

    2016-12-01

    Attaining optimal glycemic targets in patients with type 2 diabetes is often hard and compromised by the shortcomings of the several treatments. Areas covered: When glycemic levels are not adequately controlled, an association of GLP-1 receptor agonists and insulin therapy can be adopted. In order to assess the benefit/risk profile of this combination therapy, a literature search of randomized clinical trials was performed.Eighteen trials matched the inclusion criteria. In 10 studies, GLP-1 receptor agonists were added on to an existing regimen, whereas insulin added to an existing GLP-1 receptor agonists regimen occurred in 2 studies. Six studies compared GLP-1 receptor agonists with short acting insulin as a treatment strategy to intensify basal insulin therapy. Expert opinion: Clinical trials herein reviewed demonstrated the safety and the efficacy of combining GLP-1 receptor agonists with basal insulin, with most studies showing equal or slightly superior efficacy, as compared with the addition of prandial insulin, associated with weight loss and less hypoglycemia.

  19. Adenosine Receptor Activation in the “Trigger” Limb of Remote Pre-Conditioning Mediates Human Endothelial Conditioning and Release of Circulating Cardioprotective Factor(s

    Directory of Open Access Journals (Sweden)

    Hussain Contractor, MBChB, DPhil

    2016-10-01

    Full Text Available Remote ischemic pre-conditioning (rIPC has emerged as a potential mechanism to reduce ischemia-reperfusion injury. Clinical data, however, have been mixed, and its physiological basis remains unclear, although it appears to involve release of circulating factor(s and/or neural pathways. Here, the authors demonstrate that adenosine receptor activation is an important step in initiating human pre-conditioning; that pre-conditioning liberates circulating cardioprotective factor(s; and that exogenous adenosine infusion is able to recapitulate release of this factor. However, blockade of adenosine receptors in ischemic tissue does not block the protection afforded by pre-conditioning. These data have important implications for defining the physiology of human pre-conditioning and its translation to future clinical trials.

  20. Differences in Acute Anorectic Effects of Long-Acting GLP-1 Receptor Agonists in Rats

    Science.gov (United States)

    Sisley, Stephanie; Smith, Kathleen; Sandoval, Darleen A.; Seeley, Randy J.

    2014-01-01

    Long-acting glucagon-like peptide-1 receptor (GLP-1R) agonists have both glucose- and weight-lowering effects. The brain is poised to mediate both of these actions since GLP-1Rs are present in key areas known to control weight and glucose. Although some research has been performed on the effects of exendin-4 in the brain, little data exists on the central effects of liraglutide, a long-acting GLP-1R agonist with much closer structural homology to native GLP-1. In lean, Long-Evans rats, we found that direct intra-third cerebroventricular (i3vt) administration of 0.26 nmol liraglutide caused a 50% reduction in food intake. However, exendin-4 produced the same reduction in food intake with 10-fold greater potency (0.02 nmol). These data are supported by similar c-Fos immunoreactivity in the hypothalamic paraventricular nuclei by exendin-4 as compared to liraglutide despite differing doses. The anorectic effects of both drugs were blocked with i3vt pre-treatment of a GLP-1R competitive antagonist, exendin(9-39), indicating that both drugs required the GLP-1R for their effects. Exendin-4, and not liraglutide, caused hyperglycemia when given i3vt prior to an oral glucose tolerance test, although liraglutide did not lower glucose. Thus, these data show that GLP-1R agonists have differing anorectic potencies in the CNS, which may account for some of their clinical differences. Additionally, we show here that the glucose lowering properties of acute administration of GLP-1R agonists are not accounted for by their central effects. PMID:24879927

  1. GABAA receptor subtype-selective modulators. II. α5-selective inverse agonists for cognition enhancement.

    Science.gov (United States)

    Atack, John R

    2011-01-01

    Benzodiazepine site agonists (such as diazepam) are well-known to impair cognition. Since benzodiazepines exert their effects via modulation of α1-, α2-, α3- and α5-containing GABA(A) receptors, the cognition-impairing effects of diazepam must be associated with one or several of these subtypes. Of these different subtypes, α5-containing GABA(A) receptors represent an attractive option as the "cognition" subtype based upon the preferential localization of these receptors within the hippocampus and the well-established role of the hippocampus in learning and memory. As a result, it is hypothesized that an inverse agonist selective for the α5 subtype should enhance cognition. For example, L-655708, a partial inverse agonist with 50-100-fold higher affinity for the α5 relative to the α1, α2 and α3 subtypes of GABA(A) receptors, enhanced cognitive performance in rats. Unfortunately, however, pharmacokinetic properties of this compound prevented it being developed further. In order to try achieve binding selectivity in a series structurally distinct from the imidazobenzodiazepines, the group at Merck, Sharp & Dohme commenced studies within the triazolopyridazine series. Although a degree of binding selectivity could be achieved (a maximum of 22-125-fold for α5 versus α1, α2 or α3) this approach was dropped in favour of a strategy to identify compounds with either a combination of selective affinity and selective efficacy or purely selective efficacy. With respect to the former, screening of the Merck chemical collection identified a novel, moderately α5-binding selective thiophene series and further optimization of this series produced MRK-536, which demonstrated a modest α5 binding selectivity (~10-fold) as well as α5-efficacy selectivity. However, the structure-activity relationship within this and the analogous tetralone series proved unpredictable and these series were not pursued further. The success of the selective efficacy approach on the α2/

  2. Involvement of the Retinoid X Receptor Ligand in the Anti-Inflammatory Effect Induced by Peroxisome Proliferator-Activated Receptor Agonist In Vivo

    Directory of Open Access Journals (Sweden)

    Atsuki Yamamoto

    2011-01-01

    Full Text Available Peroxisome proliferator-activated receptor γ (PPARγ forms a heterodimeric DNA-binding complex with retinoid X receptors (RXRs. It has been reported that the effect of the PPAR agonist is reduced in hepatocyte RXR-deficient mice. Therefore, it is suggested that the endogenous RXR ligand is involved in the PPARγ agonist-induced anti-inflammatory effect. However, the participation of the RXR ligand in the PPARγ-induced anti-inflammatory effect is unknown. Here, we investigated the influence of RXR antagonist on the anti-inflammatory effect of PPARγ agonist pioglitazone in carrageenan test. In addition, we also examined the influence of PPAR antagonist on the anti-inflammatory effect induced by RXR agonist NEt-3IP. The RXR antagonist suppressed the antiedema effect of PPARγ agonist. In addition, the anti-inflammatory effect of RXR agonist was suppressed by PPARγ antagonist. PPARγ agonist-induced anti-inflammatory effects were reversed by the RXR antagonist. Thus, we showed that the endogenous RXR ligand might contribute to the PPARγ agonist-induced anti-inflammatory effect.

  3. Radiosynthesis and evaluation of 11C-CIMBI-5 as a 5-HT2A receptor agonist radioligand for PET

    DEFF Research Database (Denmark)

    Ettrup, Anders; Palner, Mikael; Gillings, Nic

    2010-01-01

    PET brain imaging of the serotonin 2A (5-hydroxytryptamine 2A, or 5-HT(2A)) receptor has been widely used in clinical studies, and currently, several well-validated radiolabeled antagonist tracers are used for in vivo imaging of the cerebral 5-HT(2A) receptor. Access to 5-HT(2A) receptor agonist...... PET tracers would, however, enable imaging of the active, high-affinity state of receptors, which may provide a more meaningful assessment of membrane-bound receptors. In this study, we radiolabel the high-affinity 5-HT(2A) receptor agonist 2-(4-iodo-2,5-dimethoxyphenyl)-N-(2-[(11)C-OCH(3......)]methoxybenzyl)ethanamine ((11)C-CIMBI-5) and investigate its potential as a PET tracer....

  4. Metal ion-mediated agonism and agonist enhancement in melanocortin MC1 and MC4 receptors

    DEFF Research Database (Denmark)

    Holst, Birgitte; Elling, Christian E; Schwartz, Thue W

    2002-01-01

    -melanocortin stimulating hormone (alpha-MSH) in the MC1 and MC4 receptors, respectively. In the presence of peptide agonist, Zn(II) acted as an enhancer on both receptors, because it shifted the dose-response curves to the left: most pronounced was a 6-fold increase in alpha-MSH potency on the MC1 receptor. The effect...... of the metal ion appeared to be additive, because the maximal cAMP response for alpha-MSH in the presence of Zn(II) was 60% above the maximal response for the peptide alone. The affinity of Zn(II) could be increased through binding of the metal ion in complex with small hydrophobic chelators. The binding...... in the MC1 receptor. Metal ion-chelator complexes having antagonistic properties were also found. An initial attempt to ma