Down-regulation of Xist and Mir-7a-5p improves LPS-induced myocardial injury

Background: X-inactive specific transcript (Xist) is a lncRNA, which plays a significant role in X-chromosome inactivation, regulates cell proliferation in tumor cells, and inhibits apoptosis in acute myocardial infarction. On the other hand, miR-7a-5p is involved in cardiomyocytes injury in myocardial ischemia/reperfusion. However, their roles in LPS-induced damage remain unclear. Objectives: This study aimed at using siRNA transfection and lentivirus infection to regulate the expression of xist and miR-7a-5p, and to evaluate their effects on LPS-induced myocardial damage. Method: Mice cardiomyocytes (MCM) cells were divided into six groups, namely the control group, the LPS group, the LPS + lncRNA^- group, the LPS + lncRNA⁺ group, the LPS + miRNA^- group, and the LPS + miRNA⁺ group. Quantitative real-time PCR (qRT-PCR) was performed to assay for the RNA expressions of xist, miR-7a-5p, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and recombinant mitochondrial transcription factor A (Tfam) in all the groups. The ATP level was determined using the adenosine triphosphate (ATP) assay kit according to the manufacturer's instructions. Flow cytometry was performed to estimate the level of apoptosis and proliferation in cells in each group. Results: The level of xist in the myocardial cells was markedly higher in the LPS group compared with the control group; however, it was reduced in the LPS+ lncRNA^- group. There was no significant difference in the expression of xist among the LPS+miRNA^-, LPS+miRNA⁺, and LPS groups. Moreover, the expression of mir-7a-5p was significantly reduced in myocardial cells in the LPS group, and moderately reduced in the LPS+ miRNA^- group, but remarkably elevated in the LPS+ miRNA⁺ group (P<0.05). The expression of mir-7a-5p was comparably similar in the LPS+ lncRNA^- group, LPS+ lncRNA⁺ group, and LPS groups. Further, the levels of PGC-1a, and Tfam were determined. In the LPS group, the expression of PGC-1α was significantly reduced but elevated in the LPS+lncRNA^- and LPS+ miRNA^- groups (P<0.05). There was no significant difference in the level of PGC-1α among the LPS, LPS+ lncRNA⁺, and LPS+ miRNA⁺ groups. The expression of Tfam was markedly reduced in the LPS group (P < 0.05), but elevated after the suppression of xist and mir-7a-5p. The expression of Tfam was not significantly different among the LPS group, LPS+ lncRNA⁺ and LPS+ miRNA⁺ groups. Notably, overexpression of mir-7a-5p had a mild effect on the expression of Tfam in the LPS+ miRNA⁺ group compared with the control group. Besides, ATP expression in the LPS group was markedly reduced, but elevated after the inhibition of xist and mir-7a-5p. Suppressing the expression of xist or mir-7a-5p resulted in reduced cell apoptosis and increased cell proliferation. Conclusions: In this study, we established that down-regulation of xist and mir-7a-5p reduces apoptosis in response to LPS.