Introduction: Ischemic preconditioning (IPC) is an adaptive response of the heart to stress resulting in cardioprotection in following Ischiemia/reperfusion(I/R) injury. I/R injury induces hydrolysis of membrane phospholipids to arachidonic acids (AA) and AA is metabolised by cyclooxygenases (COXs), lipoxygenases (LOXs), and cytochrome P450 (CYPs) enzymes. It’s been well known that (4.PGE2 and PGI2 by) COX-2 mediates of cardioprotective effects through PI3K-Akt signaling pathways in IPC. Recent studies suggest that overexpression of CYP2C induce COX-2 expression and epoxyeicosatrienoic acids (EETs) mediate cardioprotection during I/R injury, however, the relation between CYPs and COX-2 in IPC is poorly understood. Therefore, we examine the role of CYP2J3, which is considered as major epoxygenase in heart, COX-2 and its metabolites in IPC.
Meothods: IPC was achieved by 2 cycles of each 5 minutes ischemia and reperfusion before sustained 45 minutes I/R injury (1. in Langendorff mode) (n=5, each group). CYPs and COX-2 inhibitors were added to (2.the perfusion buffer) 20 min before IPC. LDH and infarct size was measured at 30 min and at 45 min after reperfusion. CYP2J3 and COX-2 expression were determined by westernblot and RT-PCR. AA metabolites were measured by liquid-chromatography mass spectrometry (LC-MS).
Results: CYP2J3 expression was down-regulated in I/R injury, whereas its activity were recovered by IPC (3. which associated with an increased COX-2 expression). CYP2J3 expression was suppressed by EET antagonist EEZE and CYP epoxygenase inhibitor MS-PPOH, however, COX-2 expression was not affected by EEZE but reduced by MS-PPOH. The LDH and infarct size were reduced corresponding to COX-2 expression.
Conclusion: I/R injury reduced CYP2J3 expression and enhanced by IPC. COX-2 expression was inhibited by CYP epoxygenase inhibitor MS-PPOH and COX-2 inhibitors. These data indicated that the enhanced activity of CYP epoxygenase is prerequisite for COX-2 mediated cardioprotection in IPC.
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