MicroRNA-199a-3p and MicroRNA-199a-5p Take Part to a Redundant Network of Regulation of the NOS (NO Synthase)/NO Pathway in the Endothelium.

Objective- Members of the microRNA (miR)-199a family, namely miR-199a-5p and miR-199a-3p, have been recently identified as potential regulators of cardiac homeostasis. Also, upregulation of miR-199a expression in cardiomyocytes was reported to influence endothelial cells. Whether miR-199a is expressed by endothelial cells and, if so, whether it directly regulates endothelial function remains unknown. We investigate the implication of miR-199a products on endothelial function by focusing on the NOS (nitric oxide synthase)/NO pathway. Approach and Results- Bovine aortic endothelial cells were transfected with specific miRNA inhibitors (locked-nucleic acids), and potential molecular targets identified with prediction algorithms were evaluated by Western blot or immunofluorescence. Ex vivo experiments were performed with mice treated with antagomiRs targeting miR-199a-3p or -5p. Isolated vessels and blood were used for electron paramagnetic resonance or myograph experiments. eNOS (endothelial NO synthase) activity (through phosphorylations Ser1177/Thr495) is increased by miR-199a-3p/-5p inhibition through an upregulation of the PI3K (phosphoinositide 3-kinase)/Akt (protein kinase B) and calcineurin pathways. SOD1 (superoxide dismutase 1) and PRDX1 (peroxiredoxin 1) upregulation was also observed in locked-nucleic acid-treated cells. Moreover, miR-199a-5p controls angiogenesis and VEGFA (vascular endothelial growth factor A) production and upregulation of NO-dependent relaxation were observed in vessels from antagomiR-treated mice. This was correlated with increased circulated hemoglobin-NO levels and decreased superoxide production. Angiotensin infusion for 2 weeks also revealed an upregulation of miR-199a-3p/-5p in vascular tissues. Conclusions- Our study reveals that miR-199a-3p and miR-199a-5p participate in a redundant network of regulation of the NOS/NO pathway in the endothelium. We highlighted that inhibition of miR-199a-3p and -5p independently increases NO bioavailability by promoting eNOS activity and reducing its degradation, thereby supporting VEGF-induced endothelial tubulogenesis and modulating vessel contractile tone.