miR-30e-3p Promotes Cardiomyocyte Autophagy and Inhibits Apoptosis via Regulating Egr-1 during Ischemia/Hypoxia

Background: Microvascular obstruction (MVO) can result in coronary microcirculation embolism and myocardial microinfarction. Myocardial injury induced by MVO is characterized by continuous ischemia and hypoxia of cardiomyocytes. Autophagy and apoptosis are closely associated with various cardiovascular diseases. Based on our previous study, we observed a decrease in miR-30e-3p expression and an increase in Egr-1 expression in a rat coronary microembolization model. However, the specific function of miR-30e-3p in regulating autophagy and apoptosis in an ischemia/hypoxia (IH) environment remains to be deciphered. We exposed cardiomyocytes to an IH environment and then determined whether miR-30e-3p was involved in promoting cardiomyocyte autophagy and inhibiting apoptosis by regulating Egr-1.

Methods: Cardiomyocytes were isolated from rats for our in vitro study. miR-30e-3p was either overexpressed or inhibited by transfection with lentiviral vectors into cardiomyocytes. 3-Methyladenine (3-MA) was used to inhibit autophagy. RT-qPCR and western blotting were used to determine the expression levels of miR-30e-3p, Egr-1, and proteins related to the autophagy and apoptosis process. Autophagic vacuoles and autophagic flux were evaluated using transmission electron microscopy (TEM) and confocal microscopy, respectively. Cardiomyocyte viability was evaluated using the MTS assay. Cell injury was assessed by lactate dehydrogenase (LDH) leakage, and apoptosis was determined by flow cytometry.

Results: Both miR-30e-3p expression and autophagy were significantly inhibited, and apoptosis was increased in cardiomyocytes after 9 hours of IH exposure. Overexpression of miR-30e-3p increased autophagy and inhibited apoptosis, as well as suppressed Egr-1 expression and decreased cell injury. In addition, inhibition of miR-30e-3p reduced autophagy and increased apoptosis and cell injury.

Conclusions: miR-30e-3p may be involved in promoting cardiomyocyte autophagy and inhibiting apoptosis by indirectly regulating Egr-1 expression in an IH environment.