Vascular peroxidase 1 up regulation by angiotensin II attenuates nitric oxide production through increasing asymmetrical dimethylarginine in HUVECs

Asymmetric dimethylarginine (ADMA), the endogenous inhibitor of nitric oxide synthase, contributes to endothelial dysfunction and subsequent cardiovascular events including hypertension. Vascular peroxidase 1 (VPO1) is a novel heme-containing peroxidase that uses hydrogen peroxide (H2O2) generated from co-expressed nicotinamide adenine dinucleotide phosphate (NADPH) oxidase to catalyze peroxidative reactions. Our previous study revealed a clear connection between VPO1 gene expression and endothelial dysfunction in spontaneously hypertensive rats. In the present study, we explored whether VPO1 participates in endothelial dysfunction during hypertension by increasing ADMA production. Spontaneously hypertensive rats displayed impaired endothelium-dependent relaxation, decreased eNOS expression and nitric oxide production, significantly increased VPO1 expression in both plasma and aorta tissue, and an increased ADMA level in plasma. In cultured endothelial cells, angiotensin II increased the ADMA level by inhibiting dimethylarginine dimethylaminohydrolase activity, which was inhibited by knockdown of VPO1 using small hairpin RNA. Moreover, the NADPH oxidase inhibitor and the hydrogen peroxide scavenger attenuated angiotensin II-mediated up-regulation of VPO1 and generation of hypochlorous acid. Furthermore, VPO1-derived hypochlorous acid suppressed recombinant dimethylarginine dimethylaminohydrolase activity and increased ADMA production. VPO1 plays a critical role in ADMA production via H2O2-VPO1-hypochlorous acid pathways, which may contribute to endothelial dysfunction in hypertension.