The role of C-reactive protein in ischemia/reperfusion injury and preconditioning in a rat model of myocardial infarction

For the first time the involvement of C-Reactive protein (CRP) in early (acute) and delayed ischemic (IPC) and pharmacological (chemical) preconditioning (CPC) in an in vivo model of rat myocardial infarction was presented. Acute IPC was produced by three 5 minute occlusion (ischemia) periods interspersed with 5 minute reperfusion, followed by 30 minute occlusion of the left coronary artery and 2 hour reperfusion injury. Acute CPC was produced by a k-opioid receptor agonist U50488H (5 mg/kg) applied i.v. 15 minutes before 30 minute ischemia/ 2 hour reperfusion. Delayed preconditioning was produced by 30 minute ischemia/ 2 hour reperfusion, induced 24 hour after either ischemic or pharmacological preconditioning. The myocardial ischemia/reperfusion injury was evaluated on the basis of total and cardiac creatine kinase isoenzyme activity, functional recovery of the heart (ECG), infarct size (% IS/RA) and mortality at the end of the experiments. The results obtained showed that: k-opioid receptor agonist U50488H mimics both the acute and delayed IPC in the above experimental protocol; Both acute IPC and most probably CPC act by opening of K(ATP) channels (the effects were blocked by nonspecific ATP-sensitive K channel blocker glybenclamide), and via activation of protein kinase C (a selective protein kinase C inhibitor chelerythrine blocked the efects); C-reactive protein (CRP) was significantly elevated by 54% in non-preconditioned acute ischemia/reperfusion injury. The elevation was more pronounced (82% increase) 24 hour after non-preconditioned ischemia/reperfusion injury. It reflected very well the increase in cardiac isoenzymes, infarct size and mortality of the rats, and can be used as a marker of the severity of myocardial injury in this model; The increase of CRP was prevented by both IPC and CPC in early, and especially in late preconditioning. This confirms the involvement of CRP as a marker in cardiac ischemic/reperfusion injury. It was concluded that in addition to the established involvement of adenosine, bradykinin, opioid and other receptors, a suppression of myocardial CRP/complement production might be involved in the biological mechanism of preconditioning. This could be a promising perspective in clinical interventions against ischemia/reperfusion injuries of the heart.