MicroRNA miR‐378‐3p is an Essential Regulator of Autophagy and Proliferation in Endothelial Cells

Abstract

Background Macroautophagy is a highly conserved cellular process in which cytoplasmic materials are internalized into an autophagosome that later fuses with a lysosome for their degradation and recycling. MicroRNAs (miRNAs) are integral regulators in a variety of cellular processes and are known to regulate autophagy, and miRNA and autophagy both play roles in the regulation of endothelial function. Accordingly, we hypothesize that miRNA miR‐378‐3p is an essential regulator of endothelial autophagy and endothelial function. Methods and Results To test our hypothesis, we cultured human umbilical vein endothelial cells (HUVEC) and confirmed the basal expression of miR‐378‐3p. To determine the effect of autophagy on miR‐378a‐3p, autophagy was genetically (via silencing autophagy‐related gene ATG7) and pharmacologically (via chloroquine treatment) inhibited in HUVECs, which resulted in the upregulation of miRNA miR‐378a‐3p. We also measured miR‐378a‐3p expression following autophagy activation (via starvation) and observed a significant down‐regulation of miR‐378‐3p expression. Next, we over‐expressed miR‐378a‐3p (by mimic) in HUVECs and measured autophagy and endothelial function in the form of endothelial cell proliferation and migration. MiR‐378a‐3p over‐expression was associated with impaired autophagy indicated by reduced LC3‐II/LC‐3‐I ratio, reduced proliferation and migration in HUVECs. At the molecular level, miR‐378a‐3p over‐expression was associated with increased mTOR (mammalian target of rapamycin; an autophagy regulator) expression at the transcript and the protein levels in HUVECs. Conclusion Our preliminary findings indicate an essential role of miR‐378a‐3p in the regulation of endothelial autophagy and endothelial function. We demonstrate an inverse relationship between miR‐378a‐3p expression and endothelial autophagy and function, warranting future investigations.