Effects of exercise preconditioning on NLRP3 and mitochondrial fission in isoproterenol-induced myocardial infarcted rats

Myocardial infarction is a common disease that causes morbidity and mortality in human. Exercise training is an effective strategy to improve cardioprotection. The signaling pathways of exercise preconditioning on the reduction of MI-induced cardiac injuries is one of the topics that has attracted a lot of attention. The purpose of this study was to investigate the effects of exercise preconditioning on cardiac damage and dynamin-related protein 1 (Drp1) as an effective factor for activating the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) following myocardial infarction (MI). Twenty male Wistar rats were randomly divided into 4 groups of high-intensity interval training + myocardial infarction (HIIT + MI), control + myocardial infarction (CON + MI), HIIT, and sham. Training groups performed 4 weeks (5 days per week) of HIIT. The training protocol consisted of 10*1-min running intervals were separated by a 2-min rest. The training intensity varied every week. For induction of MI, an injection of isoproterenol was used. Creatine kinase-myoglobin binding (CK-MB), lactate dehydrogenase (LDH), Drp1, and NLRP3 gene expression were measured. The results of the present study showed that CK-MB and LDH in CON + MI group were significantly higher than in the HIIT + MI group (P ˂ 0.05). Myocardial infarction results in a significant increase in Drp1 gene expression in the CON + MI and HIIT + MI groups relative to the sham group. The expression of the Drp1 gene was lower in the HIIT + MI group than in the CON + MI group, but it was insignificant. Moreover, NLRP3 in the CON + MI group had a remarkable increase compared with HIIT + MI, HIIT, and sham groups (P ˃ 0.05). Four weeks of exercise preconditioning reduced injury and necrosis in cardiac tissue and can increase cardioprotection. Although NLRP3 inflammasome was reduced due to exercise training, it had no significant decrease in Drp1 expression which may indicate the need for a longer training period.