TY - JOUR. T1 - Chronic exposure to adenosine receptor agonists and antagonists reciprocally regulates the A1 adenosine receptor-adenylyl cyclase system in cerebellar granule cells. AU - Hettinger-Smith, Barbara D.. AU - Leid, Mark. AU - Murray, Thomas F.. PY - 1996/11. Y1 - 1996/11. N2 - Chronic treatment with the adenosine receptor antagonist caffeine evokes an up-regulation of A1 adenosine receptors and increased coupling of the receptor to G proteins in rat brain membranes. However, chronic agonist exposure has not been explored. Primary cultures of cerebellar granule cells were exposed chronically to A1 adenosine receptor agonists and antagonists. Exposure to the A1 adenosine receptor agonist N6-cyclopentyladenosine resulted in (1) a time- and concentration-dependent reduction in the density of receptors labeled by 1,3[3H]dipropyl-8-cyclopentylxanthine, (2) an enhanced ability of guanyl nucleotides to decrease the fraction of A1 adenosine receptor sites displaying high affinity for ...
Intravenously administered adenosine is rapidly cleared from the circulation via cellular uptake, primarily by erythrocytes and vascular endothelial cells. This process involves a specific transmembrane nucleoside carrier system that is reversible, nonconcentrative, and bidirectionally symmetrical. Intracellular adenosine is rapidly metabolized either via phosphorylation to adenosine monophosphate by adenosine kinase, or via deamination to inosine by adenosine deaminase in the cytosol. Since adenosine kinase has a lower Km and Vmax than adenosine deaminase, deamination plays a significant role only when cytosolic adenosine saturates the phosphorylation pathway. Inosine formed by deamination of adenosine can leave the cell intact or can be degraded to hypoxanthine, xanthine, and ultimately uric acid. Adenosine monophosphate formed by phosphorylation of adenosine is incorporated into the high-energy phosphate pool. While extracellular adenosine is primarily cleared by cellular uptake with a ...
Adenosine is a candidate sleep substance. It can be both a distress signal of importance in pathology and a physiological regulator. Key factors in determining which of these possibilities pertain are: (i) the number of receptors expressed, and (ii) the mechanisms that establish extracellular adenosine levels. The roles of adenosine are studied by means of antagonists and/or animals (mostly mice) with targeted deletions of receptors or enzymes involved in adenosine metabolism. Whereas adaptive changes in the genetically modified mice can occur for the physiologically important effects, such adaptive changes are less likely to occur in situations where adenosine acts as a distress signal. The relevance to sleep will be covered only in general terms in this review and will be covered in other contributions to this volume.
Adenosine is a nucleoside that is composed of adenine and d-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. For instance, adenosine plays an important role in energy transfer - as adenosine triphosphate (ATP) and adenosine diphosphate (ADP). It also plays a role in signal transduction as cyclic adenosine monophosphate, cAMP. Adenosine itself is both a neurotransmitter and potent vasodilator. When administered intravenously, adenosine causes transient heart block in the AV node. Because of the effects of adenosine on AV node-dependent supraventricular tachycardia, adenosine is considered a class V antiarrhythmic agent ...
Having the ability to modulate lymphocyte entry into the central nervous system (CNS) would benefit patients with neuroinflammatory diseases. We have previously shown that extracellular adenosine regulates CNS entry of lymphocytes during experimental autoimmune encephalomyelitis (EAE), the animal model for the CNS inflammatory disease multiple sclerosis. For instance, while extracellular adenosine levels are vastly increased following inflammatory cellular damage (from the hydrolysis of released cytoplasimic ATP by CD39 and CD73), mice lacking CD73 or given adenosine receptor (AR) antagonists have significantly reduced CNS lymphocyte entry during EAE. We now show through detailed genetic studies that AR signaling regulates lymphocyte migration into the CNS though induction of CX3CL1, a specialized chemokine that acts as both an adhesion molecule and chemoattractant for lymphocytes, monocytes, and NK cells. We show that AR signaling is necessary and sufficient to induce CNS expression of CX3CL1 ...
Vasodilator stress with adenosine or dipyridamole is an alternative to exercise stress with myocardial perfusion imaging for the detection of coronary artery disease. Although the safety of adenosine and dipyridamole has been well established, undesirable side effects including chest pain, headache, dyspnea, and atrioventricular conduction abnormalities do occur in a majority of patients.1-4 In addition, both adenosine and dipyridamole produce severe bronchoconstriction when given to asthmatics. Because of its ultrashort half-life, adenosine must be administered by a constant IV infusion.. Whereas adenosine-induced coronary vasodilatation is mediated primarily by stimulation of the A2A receptor subtype on vascular smooth muscle, the side effects described above are believed to be caused by stimulation of 1 or more of the other 3 adenosine receptor subtypes, A1, A2B, and A3.5 The discovery of highly selective and relatively short-acting adenosine receptor A2A agonists6-9 has opened the ...
A concise synthesis of a series of N6-substituted adenosines with bicyclo[3.2.1]octan-6-yl and polycyclic N6-substituents has been developed. The adenosine A1 receptor (A1R) affinity and potency of these compounds was initially assessed using competitive binding assays and cyclic adenosine monophosphate (cAMP) accumulation assays in DDT1 MF-2 cells. The potency and receptor subtype selectivity of selected examples was further evaluated by measuring their effects on cAMP accumulation at all human adenosine receptor subtypes expressed in CHO cells. The results of these assays indicated that all of the synthesised N6-substituted adenosines are full agonists at A1R and activate this receptor selectively over the other adenosine receptor subtypes. The two standout compounds in terms of potency were N6-(3-thiabicyclo[3.2.1]octan-6-yl)adenosine and N6-(cubanylmethyl)adenosine with EC50 values at human A1R of 2.3 nM and 1.1 nM, respectively. The cubanylmethyl derivative in particular proved to be highly ...
We examined how the endogenous anticonvulsant adenosine might influence gamma-aminobutyric acid type A (GABA(A)) receptor stability and which adenosine receptors (ARs) were involved. Upon repetitive activation (GABA 500 microM), GABA(A) receptors, microtransplanted into Xenopus oocytes from neurosurgically resected epileptic human nervous tissues, exhibited an obvious GABA(A)-current (I(GABA)) run-down, which was consistently and significantly reduced by treatment with the nonselective adenosine receptor antagonist CGS15943 (100 nM) or with adenosine deaminase (ADA) (1 units/ml), that inactivates adenosine. It was also found that selective antagonists of A2B (MRS1706, 10 nM) or A3 (MRS1334, 30 nM) receptors reduced I(GABA) run-down, whereas treatment with the specific A1 receptor antagonist DPCPX (10 nM) was ineffective. The selective A2A receptor antagonist SCH58261 (10 nM) reduced or potentiated I(GABA) run-down in approximately 40% and approximately 20% of tested oocytes, respectively. The ...
Introduction: Prior studies demonstrate that ischemic preconditioning (IP) alters adenosine metabolism. The significance of this effect is not fully understood, but evidence suggests that reduction in extracellular adenosine may represent use as an alternative fuel. Transformation into AMP/ADP may also replenish intracellular total adenine nucleotides (TAN), improving the potential high-energy phosphate bonds available in cells facing ischemia. In both cases, adenosine supports cell energy requirements and may be a key component of IPs protective mechanisms. There are no previous studies of brain adenosine in human patients undergoing remote IP.. Methods: In adults with aneurysmal subarachnoid hemorrhage (SAH), 3-4 remote IP sessions were conducted on non-consecutive days, 4-12 days after hemorrhage. Each session consisted of 4 5-min cycles of lower extremity blood pressure cuff inflation to 30mmHg above systolic blood pressure, followed by 5-min reperfusion. Patients had microdialysis (MD) ...
To the Editor: Recently, Jeremias et al1 reported their studies comparing the vasodilator action of intracoronary injected adenosine with ATP in 6 healthy mongrel dogs. On the basis of a dose-response curve ranging from 10 to 100 μg, the authors conclude that adenosine and ATP are approximately equipotent vasodilators. Neither substance could induce maximal vasodilation, as assessed with postischemic hyperemia. Similar results were obtained by Kato et al2 in the human coronary vasculature using a single dose of adenosine and ATP (20 μg), without comparison with postischemic hyperemia. Both groups conclude that adenosine and ATP are equipotent coronary vasodilators and suggest that the ATP-induced vasodilation is caused by its degradation to AMP and adenosine, with subsequent stimulation of adenosine A2 receptors. We disagree their conclusions for the following 2 reasons:. 1. Equimolar doses of ATP and adenosine should be compared. The molecular weight of ATP is roughly twice that of adenosine ...
Intra- and extracellular adenosine levels rise in response to physiological stimuli and with metabolic/energetic perturbations, inflammatory challenge and tissue injury. Extracellular adenosine engages members of the G-protein coupled adenosine receptor (AR) family to mediate generally beneficial acute and adaptive responses within all constituent cells of the heart. In this way the four AR sub-types - A1, A2A, A2B, and A 3Rs - regulate myocardial contraction, heart rate and conduction, adrenergic control, coronary vascular tone, cardiac and vascular growth, inflammatory-vascular cell interactions, and cellular stress-resistance, injury and death. The AR sub-types exert both distinct and overlapping effects, and may interact in mediating these cardiovascular responses. The roles of the ARs in beneficial modulation of cardiac and vascular function, growth and stress-resistance render them attractive therapeutic targets. However, interactions between ARs and with other receptors, and their ubiquitous
Adenosine is an important mediator of the endogenous defense against ischemia-induced injury in the heart. Adenosine can achieve cardioprotection by mediating the effect of ischemic preconditioning and by protecting against myocyte injury when it is present during the infarct-producing ischemia. A novel adenosine A3 receptor can mediate this protective function. One approach to achieve cardioprotection is to enhance myocardial sensitivity to the endogenous adenosine by increasing the number of adenosine receptors instead of administering an adenosine receptor agonist. The objective of the present study was to investigate whether genetic manipulation of the cardiac myocyte, achieved by gene transfer and overexpression of the human A3 receptor cDNA, renders the myocytes resistant to the deleterious effect of ischemia. Prolonged hypoxia with glucose deprivation, causing myocyte injury and adenosine release, was used to simulate ischemia in cultured chick embryo ventricular myocytes. During simulated
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We have demonstrated previously that both acute and chronic oral administration of adenosine have novel functions such as anti-hypertensive effects and improved hyperlipidaemia in stroke-prone spontaneously hypertensive rats (SHRSP) fed a normal diet. The purpose of the present study was to investigate the effect of adenosine administration on metabolic syndrome-related parameters in SHRSP fed a high-fat diet. Six-week-old rats were divided into three groups, and were administered either water (control) or adenosine (10 or 100 mg/l) for 8 weeks. During this period, the rats had free access to a high-fat diet based on AIN-93M. The results showed that hypertension, plasma lipid, NO, insulin, glucose and urinary 8-hydroxy-2-deoxyguanosine levels improved significantly in both adenosine groups. The mRNA expression levels of genes involved in anti-oxidative activity and adenosine receptors were also altered in the adenosine groups. Administration of adenosine also increased plasma adiponectin ...
Cyclic 3, 5-[14C]AMP was measured in platelets that had first been incubated with [14C]adenine. Maximum increases of 2-4-fold were observed 0.5 min after addition of 10-40 µM adenosine. Smaller increases were obtained with higher concentrations of adenosine. In 0.5-min incubations 2-chloroadenosine was less effective than adenosine at concentrations below 20 µM and more effective at concentrations above 100 µM. Incorporation of 1-10 µM adenosine into platelets was inhibited at least 96% by p-nitrobenzylthioguanosine without any effect on the increase in cyclic [14C]AMP caused by these concentrations of adenosine, suggesting that adenosine acts at an extracellular site. With higher adenosine concentrations, p-nitrobenzylthioguanosine was less effective in inhibiting incorporation of adenosine but blocked the decline in cyclic [14C]AMP levels observed on increasing the adenosine concentration above 40 µM. This inhibitory effect of high adenosine concentrations on the accumulation of cyclic ...
Each type of adenosine receptor has different functions, although with some overlap.[3] For instance, both A1 receptors and A2A play roles in the heart, regulating myocardial oxygen consumption and coronary blood flow, while the A2A receptor also has broader anti-inflammatory effects throughout the body.[4] These two receptors also have important roles in the brain,[5] regulating the release of other neurotransmitters such as dopamine and glutamate,[6][7][8] while the A2B and A3 receptors are located mainly peripherally and are involved in processes such as inflammation and immune responses. Most older compounds acting on adenosine receptors are nonselective, with the endogenous agonist adenosine being used in hospitals as treatment for severe tachycardia (rapid heart beat),[9] and acting directly to slow the heart through action on all four adenosine receptors in heart tissue,[10] as well as producing a sedative effect through action on A1 and A2A receptors in the brain. Xanthine derivatives ...
Regadenoson produced higher stress MBF than dipyridamole and adenosine (3.58 ± 0.58 vs. 2.81 ± 0.67 vs. 2.78 ± 0.61 ml/min/g, p = 0.0009 and p = 0.0008 respectively). Regadenoson had a much higher heart rate response than adenosine and dipyridamole respectively (95 ± 11 vs. 76 ± 13 vs. 86 ± 12 beats/ minute) When stress MBF was adjusted for heart rate, there were no differences between regadenoson and adenosine (37.8 ± 6 vs. 36.6 ± 4 μl/sec/g, p = NS), but differences between regadenoson and dipyridamole persisted (37.8 ± 6 vs. 32.6 ± 5 μl/sec/g, p = 0.03). The unadjusted MPR was higher with regadenoson (3.11 ± 0.63) when compared with adenosine (2.7 ± 0.61, p = 0.02) and when compared with dipyridamole (2.61 ± 0.57, p = 0.04). Similar to stress MBF, these differences in MPR between regadenoson and adenosine were abolished when adjusted for heart rate (2.04 ± 0.34 vs. 2.12 ± 0.27, p = NS), but persisted between regadenoson and dipyridamole (2.04 ± 0.34 vs. 1.77 ± 0.33, p = ...
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In the central nervous system, the nucleoside adenosine regulates neuronal activity by modulating the actions of other neurotransmitter systems, thereby influencing many different physiological processes and behaviors. Adenosinergic mechanisms are especially important in fine-tuning glutamatergic neurotransmission. Astrocytic release of adenosine triphosphate and its subsequent extracellular breakdown provides adenosine to drive homeostatic sleep. Acute ethanol (alcohol) exposure increases extracellular adenosine, which mediates the ataxic and hypnotic/sedative effects of alcohol, while chronic ethanol exposure leads to downregulated adenosine signaling that underlies insomnia, a major predictor of relapse. Adenosine gates glutamatergic input to the circadian clock located in the suprachiasmatic nucleus of the hypothalamus, modulating both photic (light-induced) and nonphotic (behaviorally-induced) synchronization of circadian activity rhythms. A recent study using mice lacking the equilibrative ...
Adenosine mediates many physiological functions via activation of extracellular receptors. The modulation of cell growth by adenosine was found to be receptor-mediated. In A431 cells adenosine evoked a biphasic response in which a low concentration (~10 μM) produced inhibition of colony formation but at higher concentrations (up to 100 μM) this inhibition was progressively reversed. Evidence for the involvement of A1 (inhibitory) and A2 (stimulatory) adenosine receptors in regulating cell growth of these tumor cells was obtained through plating efficiency studies based on the relative potency of adenosine agonists and antagonists. When both A1 and A2 receptors were blocked, colony formation or growth was not inhibited at low concentrations of adenosine but was inhibited at high adenosine concentrations ...
The initial studies to test the hypothesis that adenosine release mediates the anti-inflammatory effects of methotrexate were performed in vitro. In these studies, methotrexate treatment increased adenosine release from cultured endothelial cells and fibroblasts and the adenosine released diminished stimulated neutrophil adhesion to the monolayers of cultured cells (Cronstein et al., 1991). Subsequent in vivo studies confirmed the hypothesis that adenosine mediates the anti-inflammatory effects of methotrexate; pharmacologically relevant doses of methotrexate induce intracellular AICAR accumulation in splenocytes, increase adenosine concentrations in inflammatory exudates, and diminish leukocyte accumulation at an inflamed site (Cronstein et al., 1993). Moreover, the increase in exudate adenosine concentration was responsible for the anti-inflammatory effects of the drug since adenosine receptor antagonists or adenosine deaminase, an enzyme which converts adenosine to the receptor-inactive ...
Our work demonstrates that human endothelial cells of disparate origin are characterized by differential expression of adenosine receptor subtypes. HUVECs express mRNA for A2A and A2B receptors at a ratio of 10:1, and this preferential gene expression agrees well with the typical pharmacological phenotype of A2A receptor-mediated simulation of adenylate cyclase by adenosine analogs. Using complementary techniques, RT-PCR, and gene expression array, we found that A1 and A3 adenosine receptors are not expressed in HUVECs. Previous studies in HUVECs have suggested a potential role of A1 receptor in maintaining endothelial barrier function4 and of A1 and A3 receptors in modulation of tissue factors expression.6 The apparent contradiction between these results and ours can be explained by the use of nonselective concentrations of adenosine receptor ligands in previous studies.. HMEC-1 also express only A2A and A2B mRNA, but in contrast to HUVECs, they express predominantly A2B receptor mRNA, with a ...
Adenosine receptors (AR) belong to the G-protein coupled receptor family. There are four receptor subtypes: A1, A2A, A2B e A3. Adenosine receptor subtypes show a different distribution in the organism and are implicated in several physiopathological processes. In particular, antagonists towards A1AR are promising in the treatment of cognitive disorders. A2A antagonists seem to be involved in decrease the neurological impairment observed in Parkinson’s disease. A2B antagonists are potential therapeutic agents in asthma and diabetes. Finally, antagonists at the A3AR could be implicated in tumor growth inhibition and in glaucoma treatment. The crystallographic structure acquisition of the human A2A receptor allowed the design of new AR antagonists by the help of computational techniques. Our group is focused on the synthesis of new adenosine receptor antagonists (particularly towards A2A and A3) for their potential therapeutic use, but also as tools for pharmacological investigations on ...
Summary 1. The effect of the adenosine A2 receptor (AdoA2R) agonist N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)-ethyl]adenosine (DPMA) on adenosine A1 receptor (AdoA1R)-mediated negative inotropic responses was investigated in rat heart. 2. Hearts from male Wistar rats (250-350 g) were perfused with Krebs-Henseleit solution at constant flow in non-recirculating Langendorff mode. Hearts were paced at 5 Hz (5 ms duration, supramaximal voltage) via ventricular electrodes. After 30 min equilibration, (R)-N6-phenylisopropyl adenosine (R-PIA) concentration-response curves were constructed in the absence or presence of DPMA. 3. In paced hearts, R-PIA induced concentration-dependent decreases in triple product (heart rate נpeak systolic developed pressure נdP?/?dtmax), which were significantly attenuated by 1 nmol?/?L DPMA with a shift in pEC50 from 8.0 ᠰ.5 (n = 9) in control hearts to 6.63 ᠱ.03 (n = 5) in treated tissues (P , 0.05). The AdoA2AR antagonist 8-(3-chlorostyryl)caffeine (1 ...
TY - JOUR. T1 - Modulating P1 Adenosine Receptors in Disease Progression of SOD1G93A Mutant Mice. AU - Armida, Monica. AU - Matteucci, Alessandra. AU - Pèzzola, Antonella. AU - Baqi, Younis. AU - Müller, Christa E. AU - Popoli, Patrizia. AU - Potenza, Rosa Luisa. PY - 2019/5. Y1 - 2019/5. N2 - Amyotrophic lateral sclerosis (ALS) is a fatal progressing neurodegenerative disease; to date, despite the intense research effort, only two therapeutic options, with very limited effects, are available. The purinergic system has been indicated as a possible new therapeutic target for ALS, but the results are often contradictory and generally confused. The present study was designed to determine whether P1 adenosine receptor ligands affected disease progression in a transgenic model of ALS. SOD1G93A mice were chronically treated, from presymptomatic stage, with a selective adenosine A2A receptor agonist (CGS21680), antagonist (KW6002) or the A1 receptor antagonist DPCPX. Body weight, motor performance ...
P>Adenosine is a well-described anti-inflammatory modulator of immune responses within peripheral tissues. Extracellular adenosine accumulates in inflamed and damaged tissues and inhibits the effector functions of various immune cell populations, including CD8 T cells. However, it remains unclear whether extracellular adenosine also regulates the initial activation of naive CD8 T cells by professional and semi-professional antigen-presenting cells, which determines their differentiation into effector or tolerant CD8 T cells, respectively. We show that adenosine inhibited the initial activation of murine naive CD8 T cells after alpha CD3/CD28-mediated stimulation. Adenosine caused inhibition of activation, cytokine production, metabolic activity, proliferation and ultimately effector differentiation of naive CD8 T cells. Remarkably, adenosine interfered efficiently with CD8 T-cell priming by professional antigen-presenting cells (dendritic cells) and semi-professional antigen-presenting cells ...
The review summarizes data evaluating the role of adenosine receptor signaling in murine hematopoietic functions. The studies carried out utilized either non-selective activation of adenosine receptors induced by elevation of extracellular adenosine or by administration of synthetic adenosine analogs having various proportions of selectivity for a particular receptor. Numerous studies have described stimulatory effects of non-selective activation of adenosine receptors, manifested as enhancement of proliferation of cells at various levels of the hematopoietic hierarchy. Subsequent experimental approaches, considering the hematopoiesis-modulating action of adenosine receptor agonists with a high level of selectivity to individual adenosine receptor subtypes, have revealed differential effects of various adenosine analogs. Whereas selective activation of A(1) receptors has resulted in suppression of proliferation of hematopoietic progenitor and precursor cells, that of A(3) receptors has led to ...
Recent evidence suggests that ethanol initially causes an increase in receptor-dependent cAMP levels, followed by heterologous desensitization of receptors coupled to GS after chronic exposure. Here we investigated the role of adenosine in mediating these responses. We found that ethanol caused accumulation of extracellular adenosine in NG108-15 and S49 lymphoma cells. This adenosine activated adenosine receptors to increase intracellular cAMP levels. The addition of adenosine deaminase, to degrade accumulated extracellular adenosine, or isobutyl-methylxanthine, an adenosine receptor antagonist, completely blocked ethanol-induced increases in cAMP levels in NG108-15 cells. Chronic exposure of NG108-15 and S49 wild type cells to ethanol resulted in heterologous desensitization of adenosine receptor- and prostaglandin E1 receptor-dependent cAMP signal transduction. Coincubation of NG108-15 and S49 wild type cells with adenosine deaminase and ethanol for 48 hr prevented heterologous ...
Treatment with an adenosine uptake inhibitor attenuates glomerulonephritis in mice.: This study evaluated the effects of KF24345 (3-[1-(6,7-diethoxy-2-morpholin
Activation of protein kinase C (PKC) via adenosine receptors is known to be involved in the cardioprotection of ischemic preconditioning (IPC). Specifically, activation of PKCε is critical for cardioprotection. There is ample evidence that PKCε resides in cardiac mitochondria. However, the signals that promote translocation of PKCε are largely unknown. The present study was designed to determine whether and how adenosine receptor activation induces translocation of PKCε to mitochondria. Freshly isolated adult rat cardiac myocytes and rat heart-derived H9c2 were used in the study. Immunofluorescence imaging of isolated mitochondria showed that PKCε but not PKCδ was localized in mitochondria and this mitochondrial localization of PKCε was significantly increased by adenosine treatment. The adenosine-induced increase in PKCε-positive mitochondria was largely prevented not only by PKC inhibitor chelerythrine, but also by the HSP90 inhibitor geldanamycin and by siRNA targeting HSP90. ...
The adenosine A3 receptor, also known as ADORA3, is an adenosine receptor, but also denotes the human gene encoding it. Adenosine A3 receptors are G protein-coupled receptors that couple to Gi/Gq and are involved in a variety of intracellular signaling pathways and physiological functions. It mediates a sustained cardioprotective function during cardiac ischemia, it is involved in the inhibition of neutrophil degranulation in neutrophil-mediated tissue injury, it has been implicated in both neuroprotective and neurodegenerative effects, and it may also mediate both cell proliferation and cell death[citation needed]. Recent publications demonstrate that adenosine A3 receptor antagonists (SSR161421) could have therapeutic potential in bronchial asthma (17,18). Multiple transcript variants encoding different isoforms have been found for this gene. An adenosine A3 receptor agonist (CF-101) is in clinical trials for the treatment of rheumatoid arthritis. In a mouse model of infarction the A3 ...
In the current study, the combination of T62 and clonidine produced a synergistic interaction in rats with incisional pain. Synergy usually indicates that the two drugs have different final pathways to produce their effect, although other levels of interaction, such as altered drug disposition, can also be responsible. We did not measure tissue concentrations of drugs, so we cannot exclude a pharmacokinetic mechanism of synergy in the current study. Nonetheless, the observation of synergy is somewhat surprising if, as indicated by studies with spinal nerve ligation, the effect of T62 relies entirely on stimulating spinal norepinephrine release, which acts on α2adrenoceptors. One would in that case expect an additive interaction, and intrathecal adenosine and clonidine do interact additively in spinal-ligated rats. 14 In contrast, a synthetic adenosine agonist interacts synergistically with clonidine in acute thermal nociception tests in normal rats. 20 In addition, idazoxan only partially ...
... -First A2A Adenosine Receptor Agonist Approved for Use as Pharmacolo... Stress Agent in Myocardial Perfusion Imaging- ...PALO ALTO Calif. and DEERFIELD Ill. April 10 FirstCall/...Lexiscan is the first A2A adenosine receptor agonist shown to be safe...,CV,Therapeutics,and,Astellas,Announce,FDA,Approval,for,Lexiscan(TM),(regadenoson),Injection,biological,advanced biology technology,biology laboratory technology,biology device technology,latest biology technology
Synonyms for adenosine 5'-diphosphate in Free Thesaurus. Antonyms for adenosine 5'-diphosphate. 1 synonym for adenosine diphosphate: ADP. What are synonyms for adenosine 5'-diphosphate?
Synonyms for adenosine triphosphatase test in Free Thesaurus. Antonyms for adenosine triphosphatase test. 2 words related to adenosine: biochemistry, nucleoside. What are synonyms for adenosine triphosphatase test?
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Adenosine is a key metabolite involved in metabolic hyperemia in many vascular beds including coronary circulation, cerebral circulation, and skeletal muscle circulation.1 The roles of adenosine in vasculature are most prominent during hypoxia, ischemia, and reactive hyperemia.1 One important action of adenosine is to induce endothelium-dependent vasorelaxation.1-4 It is previously shown that, at least in some arteries, such as skeletal muscle arteries, a rise in [Ca2+]i is required for the endothelium-dependent vasorelaxation in response to adenosine.3-5 In the present study, we explored the possible role of CNG channels in adenosine-induced Ca2+ influx in vascular endothelial cells. Our results show that the adenosine-induced Ca2+ influx was markedly reduced by CNG-specific inhibitors L-cis-diltiazem and LY-83583 in H5V cells and in the primary cultured BAECs. Whole cell patch clamp recorded an adenosine-induced current that was sensitive to L-cis-diltiazem in both cell types. Furthermore, a ...
Effects of adenosine receptor agonists of the A1, A2A and A3 subtypes on the proinflammatory activity of human neutrophils in ...
In this study and previously (24), we have demonstrated that blockade of the A2AAR with an A2A-specific AR antagonist protected mice from EAE by hindering lymphocyte entry into the brain and spinal cord of wild-type mice. This finding was unexpected, as this function of adenosine, that is, mediating lymphocyte migration into the CNS, was previously unknown. Furthermore, the facts that adenosine suppresses the immune response and resolves inflammation (2) are at odds with the finding that blockade of the A2AAR, which mediates the preponderance of adenosines suppressive and anti-inflammatory functions (2), protects mice from EAE (24). The purpose of this study was to delineate adenosines role in the immune response from its function in mediating immune cell migration into the CNS via the A2A receptor.. We show that A2AAR−/− mice developed more severe EAE than did their wild-type counterparts. This severe disease was characterized in the CNS by increased numbers of lymphocytes and activated ...
Adenosine A1 and A2 receptors are widely distributed in the brain and spinal cord and represent a non-opiate target for pain management. Activated spinal A1 receptors inhibit sensory transmission by inhibiting the slow ventral root potential, which is the C-fiber-evoked excitatory response associated with nociception. Adenosine may inhibit intrinsic neurons through an increase in K+ conductance and presynaptic inhibition of sensory nerve terminals to inhibit the release of substance P and perhaps glutamate. Although adenosine A3 receptors are not found in the nervous system, adenosine is also known to have anti-inflammatory properties that may contribute to pain relief in the peripheral setting of inflammation ...
Adenosine is a modulator of many physiological and pathophysiological processes in the central nervous system (CNS). Blockade of the adenosine receptors A1ARs and A2AARs has shown beneficial neuroprotective effects in animal models and in clinical studies of Parkinsonss disease (PD) and Alzheimers disease (AD). Furthermore, selective inhibitors of the monoamine oxidase A (MAO-A) are applied as adjunctive therapeutics for PD, as they protect the brains of PD patients from oxidative stress. Nevertheless, there is still no satisfactory multitarget drug approach which inhibits MAO-A and the two adenosine receptors A1ARs and A2AARs. This invention provides newly designed tricyclic xanthine derivatives which allow overcoming this problem. A variety of 69 derivatives were prepared and evaluated in radioligand binding studies at adenosine receptors and for their ability to inhibit monoamine oxidases. Potent dual-target-directed A1/A2A adenosine receptor antagonists were identified. Several compounds ...
Results: Preliminary results from 24 patients demonstrate that symptomatic adenosine administration was successful in identifying true effective biventricular paced beats. This has allowed us to identify patients with fusion beats. 8 patients were non-responders to CRT, whereas 16 patients were responders. 50% (n= 4) of non-responders and 12.5% (n= 2) of responders had definite electrocardiography (ECG) changes through the symptomatic adenosine administration, showing that a percentage of the paced beats counted by the CRT device may in fact be fusion beats. Figure 1 shows the clear change in the morphology of the QRS complex in one of the non-responders ...
A series of new 2-alkynyl and 2-cycloalkynyl derivatives of adenosine-5-N-ethyluronamid(NECA) and of N-ethyl-l-deoxy-l-(6-amino-2-hexynyl-9H-purin-9-yl)-b-D-ribofuranuronamid(1e, HENECA), bearing hydroxy, amino, chloro, and cyano groups in the side chain, were synthesized. The compounds were studied in binding and functional assays to assess their potency for the A2 compared to A1 adenosine receptor. The presence of an a-hydroxyl group in the alkynyl chain of NECA derivatives accounts for the A2 agonist potency, leading to compounds endowed with sub-nanomolar affinity in binding studies. However, these analogues also possess good A1 receptor affinity resulting in low A2 selectivity. From functional experiments the 4-hydroxy-l-butynyl(6) and the 4-(2-tetrahydro-2H-pyranyloxy)-l-butynyl (16) derivatives appear to be very potent in inducing vasorelaxation without appreciable effect on heart rate. The new compounds were also tested as inhibitors of platelet aggregation induced by ADP. ...
Adenine Ribose 3 Phosphate groups ATP Adenosine ATP Structure ATP = Adenosine TriPhosphate High Energy Bonds ADP ATP Energy Energy Adenosine diphosphate (ADP) + Phosphate
Adenosine mediates its pysiological effects through four G protein-coupled receptors (A1, A2A, A2B and A3). A large number of agonists with high affinity at A1, A2A, A3 adenosine receptors and moderate affinity at A2B receptor have been developed over the years. Many compounds originally thought to be selective for the A1 or A2A subtypes later turned to be also potent agonists at more recently discovered A3 receptor. Owing to he great interest in A1 agonists as neuroprotective, antilipolytic, antiarrhythmic, and antinociceptive agents, there is a need for novel agonists with high potency and selectivity at this receptor subtype to avoid side effects due to the stimulation of the other subtypes. We discovered that the substitution of the hydrogen in 2-position of the ribose moiety of the A1 selective agonist CCPA with a methyl group (2-Me-CCPA) reduces the affinity at human A2A and A3 receptors, thus increasing the selectivity for A1 subtype [1]. In this communication we report on the affinity ...
Breakdown of excessive amounts of adenosine triphosphate (ATP), the main energy source of a cell, leads to the formation of extracellular adenosine, an important signaling molecule involved in multiple pathways that regulate neuronal and immunological function. Adenosine is either actively produced by certain cells or is released from damaged tissue, particularly when cells are starved of oxygen. Adenosine levels are tightly regulated at all points throughout its production, release, uptake and degradation, and disruptions in control that result in excessively high levels are associated with a number of human pathologies, including severe combined immunodeficiency (SCID).. The diversity in the regulation and function of adenosine (both of which differ in a tissue- and cell-specific manner) means that it has been difficult to unravel its exact role at the molecular level. In addition, data obtained in vitro, or in tissue culture, might not be relevant to whole organisms, and mammalian model ...
Cyclic AMP; 35-cyclic AMP; 6-(6-Amino-9H-purin-9-yl)tetrahydro-4H-furo[3,2-d][1,3,2]dioxaphosphinine-2,7-diol 2-oxide; Acrasin; Adenosine 3,5-cyclic monophosphate; Adenosine 3,5-cyclic phosphate; Adenosine 3,5-cyclophosphate; Adenosine 3,5-monophosphate; Adenosine 3,5-cyclic monophosphorate; Adenosine 3,5-cyclic monophosphoric acid; Adenosine cyclic monophosphate; Cyclic 3,5-AMP; Cyclic 3,5-adenylate; Cyclic 3,5-adenylic acid; Cyclic adenosine 3,5-phosphate; adenosine cyclic-monophosphate; adenosine-cyclic-phosphate; adenosine-cyclic-phosphoric-acid; ...
Cyclic AMP; 35-cyclic AMP; 6-(6-Amino-9H-purin-9-yl)tetrahydro-4H-furo[3,2-d][1,3,2]dioxaphosphinine-2,7-diol 2-oxide; Acrasin; Adenosine 3,5-cyclic monophosphate; Adenosine 3,5-cyclic phosphate; Adenosine 3,5-cyclophosphate; Adenosine 3,5-monophosphate; Adenosine 3,5-cyclic monophosphorate; Adenosine 3,5-cyclic monophosphoric acid; Adenosine cyclic monophosphate; Cyclic 3,5-AMP; Cyclic 3,5-adenylate; Cyclic 3,5-adenylic acid; Cyclic adenosine 3,5-phosphate; adenosine cyclic-monophosphate; adenosine-cyclic-phosphate; adenosine-cyclic-phosphoric-acid; ...
Title: Adenosine and ATP Receptors in the Brain. VOLUME: 11 ISSUE: 8. Author(s):Geoffrey Burnstock, Bertil B. Fredholm and Alexei Verkhratsky. Affiliation:Autonomic Neuroscience Centre, University College Medical School, London, Rowland Hill Street, London NW3 2PF; UK.. Keywords:Ischaemia, CNS, glia, neurones, neurodegeneration, neuropathology, purinergic transmission, nucleotide receptors, presynaptic neuromodulation, P2X receptors, Purinergic signalling, purinoceptors, Parkinsons disease, P2 receptors. Abstract: There is a widespread presence of both adenosine (P1) and P2 nucleotide receptors in the brain on both neurones and glial cells. Adenosine receptors play a major role in presynaptic neuromodulation, while P2X receptors are involved in fast synaptic transmission and synaptic plasticity. P2Y receptors largely mediate presynaptic activities. Both P1 and P2 receptors participate in neurone-glia interactions. Purinergic signalling is involved in control of cerebral vascular tone and ...