Pioglitazone attenuates myocardial ischemia-reperfusion injury via up-regulation of ERK and COX-2.

Our previous study demonstrated that the peroxisome proliferator-activated receptor (PPAR) γ agonist, pioglitazone (PIO), may be cardioprotective against ischemia-reperfusion injury; however, modulation of p42/p44 extracellular signal-regulated kinases (ERK1/2) and cyclooxygenase (COX)-2 by PIO in the myocardium with respect to ischemia-reperfusion (I/R) is only partially understood. We determined if PIO reduces I/R-induced apoptosis in cardiomyocytes, and whether or not this protective effect is due to modulation of ERK1/2 and COX-2. Sixty male Sprague-Dawley rats were randomized and assigned to 1 of 6 groups: I/R; I/R + PIO (5 mg•kg(-1)•day(-1)); I/R + PIO (10 mg•kg(-1)•day(-1)); I/R + PIO (10 mg•kg(-1)•day(-1)) + the ERK1/2 inhibitor, PD98059; I/R + PIO ( 10 mg•kg(-1)•day(-1)) + GW9662;and I/R + PD98059. Rats underwent 30 min of myocardial ischemia and 120 min of reperfusion, and then hearts were harvested for analysis. RT-PCR and Western blotting were performed to detect expression of ERK1/2 and COX-2. The number of TUNEL-positive cardiomyocytes and NEC in the PIO groups (5 and 10 mg•kg(-1)•day(-1)) was much lower than the I/R group. The cardioprotective effect of PIO was abrogated by PD98059 and GW9662. Phosphorylation of ERK1/2 and COX-2 was increased in the PIO-treated group compared with the I/R group. GW9662 reversed the expression of ERK1/2 and COX- 2 phosphorylation induced by PIO. PD98059 reversed the expression of COX-2 induced by PIO. PIO was shown to be cardioprotective in an I/R injury model in rats via inhibition of cardiomyocyte apoptosis. PIO limited the infarct size in a PPAR-γ-dependent manner. These results show that PIO triggers the MAPK signaling pathway involving ERK1/2 using COX-2 as the downstream target.