MicroRNA-1249 regulates the apoptosis of myocardial cells in rats with chronic intermittent hypoxia by autophagy

Abstract

Objective: To investigate the regulation and possible mechanism of microRNA (miR)-1249 on myocardial apoptosis in chronic intermittent hypoxia rats. Methods: A total of 16male SD rats aged 8 weeks were randomly divided into 2 groups by the random number table: normoxia control group and chronic intermittent hypoxia group (CIH) (n=8 each). The CIH group was exposed to intermittent hypoxia every day from 9: 00 to 17: 00 for 8 consecutive weeks, while the control group received the same frequency of pulse air. Hemodynamic values were measured via a cannula inserted into right common carotid artery. The expressions of miR-1249 and microtubule-associated protein light chain 3 (LC3) mRNA were observed by real-time PCR. The expressions of LC3 and Cleaved Caspase-3 were detected by Western bolt. TUNEL staining was performed to detect myocardial apoptosis. The rat cardiomyocyte cell H9C2 was divided into normoxia group, intermittent hypoxia (IH) group and miR-1249 inhibitor transfected and IH treatment group (inhibitor group). At the end of the experiment, the activation of LC3 protein in each group of cells was determined. Results: Compared with normoxia control group, left ventricle end diastolic pressure (LVEDP) increased [(4.6±0.4) vs (2.2±0.1) mmHg (1 mmHg=0.133 kPa)], left ventricular systolic pressure (LVSP) , maximal rate of pressure decline (-dp/dtmax), and maximal rate of pressure development (+ dp/dtmax) decreased in CIH group [(92.7±4.1) vs (135.3±3.2) mmHg, (4 247±108) vs (7 626±235) mmHg/s, and (3 168±105) vs (6 028±81) mmHg/s] (all P<0.001). The expression of miR-1249 and LC3 mRNA were significantly higher in CIH group than that in normoxia control group (all P<0.001), and a positive correlation was found between the expression of LC3 mRNA and miR-1249. The expression of LC3 and Cleaved Caspase-3 protein in myocardial tissue of CIH rats were significantly higher than that of the normoxia control group (all P<0.001). The proportion of myocardial cell apoptosis in CIH rats was significantly higher than that in the normoxia control group [(23.84±4.94)% vs (2.93±0.73)%] (P<0.001). The activation of LC3 in myocardial cells of inhibitor group was significantly lower than that of IH group, but higher than that in normoxia group. Conclusions: CIH could induce LC3 by raising the expression of miR-1249, and then induce the activation of apoptosis protein Caspase3. It ultimately induces myocardial apoptosis.