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.