MicroRNA miR-378-3p is a novel regulator of endothelial autophagy and function

Autophagy 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 various cellular processes including autophagy and endothelial function. Accordingly, we hypothesize that miRNA, miR-378-3p, is an essential regulator of endothelial autophagy and endothelial function. MiR-378-3p expression was measured following inhibition and activation of autophagy in endothelial cells. A gain- or loss-of function approach was employed to either overexpress or inhibit the expression of miR-378-3p, respectively, in cultured endothelial cells, and markers of autophagy and indices of endothelial function, such as proliferation, migration and tube forming potential were measured. Inhibition and activation of autophagy up- and down-regulated the expression of miR-378-3p, respectively. Furthermore, miR-378a-3p overexpression was associated with impaired autophagy indicated by a reduced LC3-II/LC3-I ratio, and endothelial function indicated by increased proliferation associated with reduced p21 expression, reduced angiogenic potential and increased migration, which were associated with reduced expression of endothelial nitric oxide synthase (eNOS), an essential regulator of endothelial function. Accordingly, miR-378a-3p inhibition was associated with reduced cell proliferation, migration and increased eNOS in endothelial cells. Apoptosis was not affected in cells transfected with antagomir. Using in silico approach, Protein Disulfide Isomerase Family A Member 4 (PDIA-4) was identified and confirmed as a target of miR-378-3p. PDIA-4 expression was significantly reduced or enhanced in miR-378-3p-overexpressing or -silenced endothelial cells, respectively. Our findings show an inverse relationship between miR-378-3p and endothelial autophagy and function, providing a novel insight about the epigenetic regulation of these processes.