Diabetes mellitus has been known to mitigate ischemic or pharmacologic preconditioning in ischemia-reperfusion injuries. Remifentanil is a widely used opioid in cardiac anesthesia that possesses a cardioprotective effect against ischemia-reperfusion. We evaluated whether diabetes affected remifentanil preconditioning induced cardioprotection in ischemia-reperfusion rat hearts in view of anti-apoptotic pathways of survival and Ca2+ homeostasis. Streptozotocin-induced, diabetic rats and age-matched wild-type Sprague-Dawley rats were subjected to a left anterior descending coronary artery occlusion for 30 min followed by 1 h of reperfusion. Each diabetic and wild-type rat was randomly assigned to the sham, ischemia-reperfusion only, or remifentanil preconditioning group. Myocardial infarct size, activities of ERK1/2, Bcl2, Bax and cytochrome c, and gene expression influencing Ca2+ homeostasis were assessed. Remifentanil preconditioning significantly reduced myocardial infarct size compared to ischemia-reperfusion only in wild-type rats but not in diabetic rats. Remifentanil preconditioning increased expression of ERK1/2 and anti-apoptotic protein Bcl-2 and decreased expression of pro-apoptotic proteins, Bax and cytochrome c, compared to ischemia-reperfusion only in wild-type rats. In diabetic rat hearts, however, remifentanil preconditioning failed to recover the phosphorylation state of ERK1/2 and to repress apoptotic signaling. In addition, diabetes minimized remifentanil induced modulation of abnormal changes in sarcoplasmic reticulum genes and proteins in ischemia-reperfusion rat hearts. In conclusion, diabetes mitigated remifentanil induced cardioprotection against ischemia-reperfusion, which might be associated with reduced recovery of the activities of proteins involved in anti-apoptotic pathways including ERK1/2 and the abnormal expression of sarcoplasmic reticulum genes as a result of ischemia-reperfusion in rat hearts.
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