Antiapoptosis and mitochondrial effect of pioglitazone preconditioning in the ischemic/reperfused heart of rat

Purpose Pioglitazone, used clinically in the treatment of type 2 diabetes mellitus, has been implicated as a regulator of cellular inflammatory and ischemic responses. The present study examined whether pioglitazone could inhibit cadiocyte apoptosis and reduce mitochondrial ultrastructure injury and membrane potential loss in the ischemic/reperfused heart of the rat. Furthermore, we investigated whether the protective effect of pioglitazone was related to opening of the mitochondrial(ATP)-sensitive potassium channels. Methods Adult male Sprague-Dawley rats were subjected to 30 min of ischemia followed by 4 h of reperfusion. At 24 h before ischemia, rats were randomized to receive 0.9% saline, 5-hydroxydecanoate (5-HD, 10 mg kg(-1), i.v.)plus pioglitazone (3mg kg(-1), i.v.) or pioglitazone (3 mg kg(-1),i.v.). One group served as sham control. We investigated mitochondrial structure, apoptosis rate and Bcl-2, Bax and Caspase-3 proteins by immunohistochemistry staining. RTPCR was used to determine the expression of P38MAPK mRNA and JNKmRNA. Western blotting was used to measure the expression of P38MAPK, JNK and NF kappa B P65. A second group of rats were randomly divided into shamoperated, ischemia/reperfusion (I/R), pioglitazone treatment, 5-HD+pioglitazone and 5-HD groups and the size of myocardial infarction was determined. Primary cultured cardiomyocytes of neonatal Sprague-Dawley rats were divided into control, hypoxia reoxygenation, different concentrations centrations of pioglitazone and 5-HD+pioglitazone groups. JC-1 staining flowcytometry was used to examine mitochondrial membrane potential (Delta psi m). Results Pioglitazone decreased mitochondrial ultrastructural damage compared to I/R, and reduced infarct size from 34.93 +/- 5.55% (I/R) to 20.24 +/- 3.93% (P<0.05). Compared with the I/R group, the apoptosis rate and positive cell index (PCI) of Bax and Caspase-3 proteins in the pioglitazone group were significantly decreased (P<0.05), while the PCI of Bcl-2 protein was increased (P<0.05). There was no significant difference between the I/R and 5-HD+pioglitazone groups. Compared with the sham-operated group, the expression of P38MAPK mRNA, JNK mRNA and protein of P38MAPK, JNK and NF kappa B P65 in I/R was increased (P<0.05). Pioglitazone did inhibit the increase in expressions vs I/R (P<0.05). The rate of loss Delta psi m cells in the pioglitazone group was significantly lower than in the hypoxia reoxygenation group, while the addition of 5-HD inhibited the effect of pioglitazone. Conclusion Pioglitazone inhibited cadiocyte apoptosis and reduced mitochondrial ultrastructure injury and membrane potential loss in the ischemic/reperfused heart of rat. These protective effects of pioglitazone may be related to opening mitochondrial(ATP)-sensitive potassium channels.