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Previously, we have identified ZFAS1 as a potential new long non-coding RNA (lncRNA) biomarker of acute myocardial infarction (MI) and as a sarcoplasmic reticulum Ca2+-ATPase 2a (SERCA2a) inhibitor, causing intracellular Ca2+ overload and contractile dysfunction in a mouse model of MI. In the current study, we aimed to evaluate the effects of ZFAS1 on the apoptosis of cardiomyocytes in the MI mouse model. Knockdown of endogenous ZFAS1 by virus-mediated silencing shRNA or siZFAS1 partially abrogated the ischemia-induced apoptosis of cardiomyocytes. Overexpression of ZFAS1 in normal cardiomyocytes reduced the cell viability, similar to that observed in hypoxia-treated cardiomyocytes. Moreover, ZFAS1 cardiac-specific knock-in mice showed impaired cardiac function, adversely altered Ca2+ homeostasis, repressed expression and activities of SERCA2a, and increased apoptosis. At the subcellular level, ZFAS1 induced mitochondrial swelling and showed a pronounced decrease in mitochondrial membrane potential. At the molecular level, ZFAS1 activated the mitochondria apoptosis pathway, which could be nearly abolished by a calcium chelator. The effects of ZFAS1 were readily reversible upon knockdown of this lncRNA. Notably, ZFAS1-FD (only functional domain) mimicked the effects of full-length ZFAS1 in regulation of cardiomyocyte apoptosis. In conclusion, our study shows that ZFAS1, an endogenous SERCA2a inhibitor, induces mitochondria-mediated apoptosis via cytosolic Ca2+ overload. Therefore, anti-ZFAS1 might be considered a new therapeutic strategy for protecting cardiomyocytes from MI-induced apoptosis.

Ischemia-reperfusion (I/R) injury is a major side effect of the reperfusion treatment of the ischemic heart. Few therapies are available for the effective prevention of this injury caused by the oxidative stress-induced cardiomyocyte apoptosis. Metformin was shown to have a potential cardiac protective effect and ability to reduce cardiac events, but the exact mechanism remains unclear. Here, we aimed to confirm and investigate the mechanisms underlying potential metformin activity against I/R injury in response to oxidative stress. We determined that the expression of miR-1a-3p was significantly increased in neonatal rat ventricular cells (NRVCs), which were exposed to H2O2in vitro and in the hearts of mice that underwent the I/R injury. MiR-1a-3p was shown to target the 3′ UTR of GRP94, which results in the accumulation of un- or misfolded proteins, leading to the endoplasmic reticulum (ER) stress. The obtained results demonstrated that C/EBP β directly induces the upregulation of miR-1a-3p by binding to its promoter. Furthermore, as a direct allosteric AMPK activator, metformin was shown to activate AMPK and significantly reduce C/EBP β and miR-1a-3p levels compared with those in the control group. In conclusion, metformin protects cardiomyocytes against H2O2 damage through the AMPK/C/EBP β/miR-1a-3p/GRP94 pathway, which indicates that metformin may be applied for the treatment of I/R injury.

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