thioinosine and 8-(4-((2-aminoethyl)aminocarbonylmethyloxy)phenyl)-1-3-dipropylxanthine

Previously, we have shown that hydrogen peroxide (H2O2) and glucose deprivation (GD) induced ATP loss and cell death in astrocytes. Here, we reported that adenosine and related purine nucleos(t)ides recovered cellular ATP level and completely prevented the cell death in rat primary astrocytes co-treated with H2O2 and glucose deprivation. Time- and concentration-dependently, H2O2 induced cell death and ATP loss in glucose-deprived astrocytes. Adenosine or ATP prevented both astrocytic death and ATP loss caused by H2O2/GD in dose-dependent manner. Further, inhibition of adenosine deamination or transport with erythro-9-(-hydroxy-3-nonyl)adenosine or S-(4-nitrobenzyl)-6-thioinosine largely attenuated the protective effect of adenosine. Other purine nucleos(t)ides such as inosine, guanosine, ADP, AMP, ITP and GTP also showed similar protective effects. Adenosine or ATP also blocked the mitochondrial dysfunction and glutathione (GSH) depletion in H2O2-treated glucose-deprived astrocytes. The present results suggest that adenosine and related purine nucleos(t)ides may protect astrocytes from H2O2 and glucose deprivation induced the potentiated death by restoration of cellular ATP level.

Topics: Adenine; Adenosine; Analysis of Variance; Animals; Animals, Newborn; Astrocytes; Benzimidazoles; Carbocyanines; Cell Death; Cells, Cultured; Dose-Response Relationship, Drug; Drug Interactions; Glucose; Hydrogen Peroxide; In Vitro Techniques; L-Lactate Dehydrogenase; Membrane Potentials; Mitochondria; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Purines; Rats; Rats, Sprague-Dawley; Theobromine; Thioinosine; Time Factors; Xanthines

The aim of this study was to determine whether endogenous adenosine has antiarrhythmic effects on ischemia-induced ventricular tachyarrhythmias. We therefore modulated the effect of endogenous adenosine in isolated rat hearts using four different approaches. First, interstitial adenosine was elevated by metabolic inhibition with either EHNA (erythro-9-(2-hydroxy-3-nonly)adenine) or acadesine [5-amino-1-beta-D-imidazole-4-carboxamide). Second, cardiac effects of A1 adenosine receptors were allosterically enhanced with PD81,723 (2-amino-4,5-dimethyl-3-thienyl)[3-(trifluoromethyl)phenyl]-methanone . Third, endogenous adenosine release was suppressed with NBMPR (S-(4-nitrobenzyl)-6-thioinosine), and fourth, adenosine receptor subtypes were blocked with antagonists of different selectivity. Regional ischemia, induced by coronary artery ligation, caused ventricular fibrillation of a reproducible kind in about 20% of untreated hearts with a low calcium concentration in the perfusion medium (0.80 mmol/l CaCl2) and in about 75% with high calcium (1.85 mmol/l) within an observation period of 30 min. At high calcium, EHNA (1 and 10 micromol/l) and acadesine (500 micromol/l) suppressed the occurrence of ventricular fibrillation from 68% (controls) to 47%, 33% and 38%, respectively. Conversely, PD81,723 (10 micromol/l) did not influence the occurrence of ventricular fibrillation. At low calcium, NBMPR (0.1 and 1 micromol/l) resulted in a concentration-dependent rise of ventricular fibrillation from 13% (controls) to 40% and 57%, respectively. The adenosine receptor antagonists theophylline (100 micromol/l), XAC (Xanthine Amine Congener; 1 micromol/l) and 8-PT (8-phenyltheophylline; 1 micromol/l) caused a rise in the occurrence of ventricular fibrillation from 25%, 15% and 18% (controls) to 57%, 39% and 44%, respectively, and the selective A2a receptors antagonist CSC (8-(3-chlorostyryl)caffeine; 5 micromol/l) from 20% to 56%. Conversely, the selective A1 receptor blocker DPCPX (8-cyclopentyl-1,3-dipropyl-xanthine; 1 micromol/l) was ineffective. NBMPR or EHNA concentration-dependent suppressed or increased ischemia-induced adenosine overflow, respectively, in a concentration-dependent manner, whereas the adenosine receptor antagonists did not influence adenosine overflow. We conclude that endogenous adenosine is an antiarrhythmic mediator accumulating in acute ischemic myocardium to a level which effectively decreases the occurrence of ventricular fibrillation by an A2

Topics: Adenine; Adenosine; Aminoimidazole Carboxamide; Animals; Caffeine; Creatine Kinase; Electrocardiography; Enzyme Inhibitors; Hypoxanthine; Inosine; Male; Myocardial Ischemia; Myocardium; Perfusion; Rats; Rats, Wistar; Reperfusion Injury; Ribonucleosides; Theophylline; Thioinosine; Thiophenes; Time Factors; Ventricular Fibrillation; Xanthines

The adhesion of leukocytes to the endothelium of postcapillary venules hallmarks a key event in ischemia-reperfusion injury. Adenosine has been shown to protect from postischemic reperfusion injury, presumably through inhibition of postischemic leukocyte-endothelial interaction. This study was performed to investigate in vivo by which receptors the effect of adenosine on postischemic leukocyte-endothelium interaction is mediated. The hamster dorsal skinfold model and fluorescence microscopy were used for intravital investigation of red cell velocity, vessel diameter, and leukocyte-endothelium interaction in postcapillary venules of a thin striated skin muscle. Leukocytes were stained in vivo with acridine orange (0.5 mg kg-1 min-1 i.v.). Parameters were assessed prior to induction of 4 h ischemia to the muscle tissue and 0.5 h, 2 h, and 24 h after reperfusion. Adenosine, the adenosine A1-selective agonist 2-chloro-N6-cyclopentyladenosine (CCPA), the A2-selective agonist CGS 21,680, the non-selective adenosine receptor antagonist xanthine amine congener (XAC), and the adenosine uptake blocker S-(p-nitrobenzyl)-6-thioinosine (NBTI) were infused via jugular vein starting 15 min prior to release of ischemia until 0.5 h after reperfusion. Adenosine and CGS 21,680 significantly reduced postischemic leukocyte-endothelium interaction 0.5 h after reperfusion (p less than 0.01), while no inhibitory effect was observed with CCPA. Coadministration of XAC blocked the inhibitory effects of adenosine. Infusion of NBTI alone effectively decreased postischemic leukocyte-endothelium interaction. These findings indicate that adenosine reduces post-ischemic leukocyte-endothelium interaction via A2 receptor and suggest a protective role of endogenous adenosine during ischemia-reperfusion.

Topics: Adenosine; Animals; Cell Adhesion; Cricetinae; Endothelium, Vascular; Ischemia; Leukocytes; Mesocricetus; Muscles; Phenethylamines; Receptors, Purinergic; Reperfusion Injury; Thioinosine; Xanthines