Arginase II Regulates NO‐mediated Human Pulmonary Microvascular Endothelial Cell Migration
Authors: Nelin Leif D. , Jin Yi , Chen Bernadette , Liu Yusen 
Published: June 2021

Chronic hypoxia‐induced pulmonary hypertension (PH) is characterized by endothelial dysfunction and vascular remodeling of the pulmonary arterial bed, which causes exaggerated vasoconstriction and impairs responsiveness to vasodilators. Furthermore, chronic hypoxia‐induced PH results in loss of blood vessels in the vascular tree, so called vascular pruning. Endothelial cell adhesion and migration are critical to angiogenesis and vasculogenesis. Nitric oxide (NO) is an endogenous pulmonary vasodilator that is synthesized from L‐arginine by NO synthase (NOS). L‐arginine can also be metabolized by arginase in endothelial cells to produce urea and L‐ornithine. Endothelial cell produced NO has been shown to enhance the migration of endothelial cells. Since NOS and arginase compete for the same substrate, L‐arginine, we hypothesized that endothelial cell migration could be regulated by altering the expression of arginase in endothelial cells. To examine endothelial cell migration we used scratch assays. First to determine the effect of knocking down arginase II on endothelial cell migration, human pulmonary microvascular endothelial cells (hPMVECs) were seeded on the collagen I‐coated plates, transfected with scramble or arginase II siRNA, followed by overnight serum starvation and scratch migration test under normoxic (21% O2) and hypoxic (1% O2) conditions. hPMVECs transfected with arginase II siRNA displayed more cell migration under both conditions compared to the cells transfected with scramble siRNA. Second to determine the effect of over‐expressing arginase II on endothelial cell migration, hPMVECs were transfected with an adenoviral vector containing the gene for arginase II (AdArg2) or the gene for green fluorescent protein (AdGFP) as a control. hPMVEC transfected with AdArg2 showed less cell migration compared to the cells transfected with AdGFP in both normoxia and hypoxia. To determine the role of NO in the cell migration response to AdArg2, hPVMEC were transfected with AdArg2 and either vehicle or 0.5 μM DETA NONOnate was added to the media. hPMVEC transfected with AdArg2 + DETA NONOnate had greater cell migration than did cells transfected with AdArg2 + vehicle. To determine the role of NO in the cell migration response to siRNA against arginase II, hPMVEC were transfected with arginase II siRNA and either vehicle or 3 mM NG‐nitro‐L‐arginine methyl ester (L‐NAME, a NOS inhibitor) was added to the media. hPMVEC transfected with the arginase II siRNA + L‐NAME had significantly less cell migration than did hPMVEC transfected with arginase II siRNA + vehicle. These results demonstrate that alterations in arginase II expression result in altered endothelial cell migration, where arginase II knock‐down promotes cell migration, while arginase II over‐expression inhibits cell migration. The effects of arginase II on cell migration are likely mediated through alterations in endothelial cell NO production.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.