sr-144528 and Myocardial-Infarction

1 The purpose of this study was to determine whether endocannabinoids can protect the heart against ischaemia and reperfusion. 2 Rat isolated hearts were exposed to low-flow ischaemia (0.5-0.6 ml min(-1)) and reperfusion. Functional recovery as well as CK and LDH overflow into the coronary effluent were monitored. Infarct size was determined at the end of the experiments. Phosphorylation levels of p38, ERK1/2, and JNK/SAPK kinases were measured by Western blots. 3 None of the untreated hearts recovered from ischaemia during the reperfusion period. Perfusion with either 300 nM palmitoylethanolamide (PEA) or 300 nM 2-arachidonoylglycerol (2-AG), but not anandamide (up to 1 micro M), 15 min before and throughout the ischaemic period, improved myocardial recovery and decreased the levels of coronary CK and LDH. PEA and 2-AG also reduced infarct size. 4 The CB(2)-receptor antagonist, SR144528, blocked completely the cardioprotective effect of both PEA and 2-AG, whereas the CB(1)-receptor antagonist, SR141716A, blocked partially the effect of 2-AG only. In contrast, both ACEA and JWH015, two selective agonists for CB(1)- and CB(2)- receptors, respectively, reduced infarct size at a concentration of 50 nM. 5 PEA enhanced the phosphorylation level of p38 MAP kinase during ischaemia. PEA perfusion doubled the baseline phosphorylation level of ERK1/2, and enhanced its increase upon reperfusion. The cardioprotective effect of PEA was completely blocked by the p38 MAP kinase inhibitor, SB203580, and significantly reduced by the ERK1/2 inhibitor, PD98059, and the PKC inhibitor, chelerythrine. 6 In conclusion, endocannabinoids exert a strong cardioprotective effect in a rat model of ischaemia-reperfusion that is mediated mainly through CB(2)-receptors, and involves p38, ERK1/2, as well as PKC activation.

Topics: Amides; Animals; Arachidonic Acids; Biomarkers; Blotting, Western; Camphanes; Cannabinoid Receptor Modulators; Endocannabinoids; Ethanolamines; Glycerides; Heart; Imidazoles; L-Lactate Dehydrogenase; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; p38 Mitogen-Activated Protein Kinases; Palmitic Acids; Piperidines; Protein Kinase C; Pyrazoles; Pyridines; Rats; Rats, Sprague-Dawley; Rimonabant; Signal Transduction

We have found that intravenous administration of cannabinoid receptor (CB) agonist HU-210 (0.05 mg/kg), increases cardiac resistance against arrhythmogenic effect of epinephrine, aconitine, coronary artery occlusion and reperfusion in rats. Pretreatment with CB2-receptor antagonist, SR144528 (1 mg/kg), completely abolished the antiarrhythmic effect of HU-210. However this effect of HU-210 was not attenuated by pretreatment with CB1-receptor antagonist, SR141716A (3 mg/kg). We also found that HU-210 (0.05 mg/kg) decreased the relationship between infarction size and area of ischemia. It is concluded that CB2 receptor stimulation promotes an increase in the cardiac resistance against arrhythmogenic influences and probably increases myocardial tolerance of both ischemic and reperfusion damages in rats.

Topics: Aconitine; Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Arterial Occlusive Diseases; Camphanes; Cannabinoids; Coronary Artery Disease; Dronabinol; Epinephrine; Male; Myocardial Infarction; Myocardial Reperfusion Injury; Piperidines; Pyrazoles; Rats; Rats, Wistar; Receptor, Cannabinoid, CB2; Receptors, Cannabinoid; Receptors, Drug; Rimonabant

We have investigated the involvement of the endocannabinoid system in the delayed cardioprotection conferred by heat stress preconditioning in the isolated rat heart.. Rats were divided into eight groups (n=7 in each group), subjected to either heat stress (42 degrees C for 15 min, HS groups) or sham anaesthesia (Sham groups). Twenty-four hours later, their hearts were isolated, retrogradely perfused, and subjected to a 30-min occlusion of the left coronary artery followed by 120 min of reperfusion. Some hearts were perfused with either SR 141716 (a cannabinoid CB(1) receptor antagonist, 1 microM), SR 144528 (a CB(2) receptor antagonist, 1 microM) or L-NAME (a NOS inhibitor, 3 microM) 5 min before ischaemia and during the ischaemic period.. The infarct size-reducing effect conferred by heat stress (35.7+/-1.8% in Sham to 14.1+/-0.6% in HS groups) was not altered by the perfusion of SR 141716 (11.2+/-1.5%) but was abolished by both SR 144528 (36.6+/-1.6%) and L-NAME (32.0+/-4.4%). In hearts from non-heat-stressed rats, perfusion with SR 141716 (32.8+/-1.6%), SR 144528 (33.4+/-2.2%) and L-NAME (31.6+/-2.9%) had no effect on infarct size.. These results suggest an involvement of endocannabinoids, acting through CB(2) receptors, and NO in the cardioprotection conferred by heat stress against myocardial ischaemia. The possible interaction between both mediators of the heat stress response remains to be determined.

Topics: Analysis of Variance; Animals; Camphanes; Cannabinoid Receptor Modulators; Cannabinoids; Endocannabinoids; Fever; Ischemic Preconditioning, Myocardial; Male; Myocardial Infarction; Myocardium; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Perfusion; Piperidines; Pyrazoles; Rats; Rats, Wistar; Receptor, Cannabinoid, CB2; Receptors, Cannabinoid; Receptors, Drug; Rimonabant; Time Factors