am-630 and Myocardial-Ischemia

Anandamide, one of the endocannabinoids, has been reported to exhibit cardioprotective properties, particularly in its ability to limit the damage produced by ischemia reperfusion injury. However, the mechanisms underlying the effect are not well known. This study is to investigate whether anandamide alter Na(+)/Ca(2+) exchanger and the intracellular free Ca(2+) concentration ([Ca(2+)]i).. Na(+)/Ca(2+) exchanger current (I(NCX)) was recorded and analysed by using whole-cell patch-clamp technique and [Ca(2+)]i was measured by loading myocytes with the fluorescent Ca(2+) indicator Fura-2/AM.. We found that I(NCX) was enhanced significantly after perfusion with simulated ischemic external solution; [Ca(2+)]i was also significantly increased by simulated ischemic solution. The reversal potential of I(NCX) was shifted to negative potentials in simulated ischemic external solution. Anandamide (1-100 nM) failed to affect I(NCX) and [Ca(2+)]i in normal solution. However, anandamide (1-100 nM) suppressed the increase in INCX in simulated ischemic external solution concentration-dependently and normalized INCX reversal potential. Furthermore, anandamide (100 nM) significantly attenuated the increase in [Ca(2+)]i in simulated ischemic solution. Blocking CB1 receptors with the specific antagonist AM251 (500 nM) failed to affect the effects of anandamide on I(NCX) and [Ca(2+)]i in simulated ischemic solution. CB2 receptor antagonist AM630 (100 nM) eliminated the effects of anandamide on I(NCX) and [Ca(2+)]i in simulated ischemic solution, and CB2 receptor agonist JWH133 (100 nM) simulated the effects of anandamide that suppressed the increase in I(NCX) and [Ca(2+)]i in simulated ischemic solution. In addition, pretreatment with the Gi/o-specific inhibitor pertussis toxin (PTX, 500 ng/ml) eliminated the effects of anandamide and JWH133 on I(NCX) in simulated ischemic solution.. Collectively, these findings suggest that anandamide suppresses calcium overload through inhibition of I(NCX) during perfusion with simulated ischemic solution; the effects may be mediated by CB2 receptor via PTX-sensitive Gi/o proteins. This mechanism is importantly involved in the anti-ischemia injury caused by endocannabinoids.

Topics: Aniline Compounds; Animals; Arachidonic Acids; Calcium; Cannabinoids; Cell Separation; Endocannabinoids; GTP-Binding Protein alpha Subunits, Gi-Go; Heart Ventricles; Indoles; Intracellular Space; Ion Channel Gating; Male; Myocardial Ischemia; Myocytes, Cardiac; Pertussis Toxin; Phenyl Ethers; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB2; Sodium-Calcium Exchanger; Solutions

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.. Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.. WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.. This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Topics: Animals; Benzoxazines; Cannabinoids; Cardiotonic Agents; Coronary Vessels; Diabetes Mellitus, Type 2; Heart; Heart Rate; Indoles; Male; Morpholines; Myocardial Ischemia; Myocardial Reperfusion Injury; Naphthalenes; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Piperidines; Pyrazoles; Rats; Rats, Zucker; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2