title: Asymmetric dimethylarginine does not inhibit arginase activity and is pro-proliferative in pulmonary endothelial cells.
abstract: Asymmetric dimethylarginine (ADMA) is an endogenously produced nitric oxide synthase (NOS) inhibitor. L-Arginine can be metabolised by NOS and arginase, and arginase is the first step in polyamine production necessary for cellular proliferation. We tested the hypothesis that ADMA would inhibit NOS but not arginase activity and that this pattern of inhibition would result in greater L-arginine bioavailability to arginase, thereby increasing viable cell number. Bovine arginase was used in in vitro activity assays with various concentrations of substrate (L-arginine, ADMA, N(G) -monomethyl-L-arginine (L-NMMA) and N(G) -nitro-L-arginine methyl ester (L-NAME)). Only L-arginine resulted in measurable urea production (Km = 6.9 ± 0.8 mmol/L; Vmax = 6.6 ± 0.3 μmol/mg protein per min). We then incubated bovine arginase with increasing concentrations of ADMA, L-NMMA and L-NAME in the presence of 1 mmol/L l-arginine and found no effect of any of the tested compounds on arginase activity. Using bovine pulmonary arterial endothelial cells (bPAEC) we determined the effects of ADMA on nitric oxide (NO) and urea production and found significantly lower NO production and greater urea production (P < 0.003) with ADMA, without changes in arginase protein levels. In addition, ADMA treatment resulted in an approximately 30% greater number of viable cells after 48 h than in control bPAEC. These results demonstrate that ADMA is neither a substrate nor an inhibitor of arginase activity and that in bPAEC ADMA inhibits NO production and enhances urea production, leading to more viable cells. These results may have pathophysiological implications in disorders associated with higher ADMA levels, such as pulmonary hypertension.
authors.affiliation: Pulmonary Hypertension Group, Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University, Columbus, OH, USA.
authors.forename: Bernadette
authors.initials: B
authors.lastname: Chen
authors.forename: Krista
authors.initials: K
authors.lastname: Strauch
authors.forename: Yi
authors.initials: Y
authors.lastname: Jin
authors.forename: Hongmei
authors.initials: H
authors.lastname: Cui
authors.forename: Leif D
authors.initials: LD
authors.lastname: Nelin
authors.forename: Louis G
authors.initials: LG
authors.lastname: Chicoine
mesh_terms: D000818:Animals; D001119:Arginase / Q000037:antagonists & inhibitors*; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002417:Cattle; D049109:Cell Proliferation / Q000187:drug effects*; D042783:Endothelial Cells / Q000187:drug effects*; D008168:Lung / Q000166:cytology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D013379:Substrate Specificity; D014508:Urea / Q000378:metabolism; D019323:omega-N-Methylarginine / Q000494:pharmacology
chemical_list: D019323:omega-N-Methylarginine; D009569:Nitric Oxide; C018524:N,N-dimethylarginine; D014508:Urea; D001120:Arginine; D001119:Arginase; D019331:NG-Nitroarginine Methyl Ester
keywords: nitric oxide; nitric oxide synthase; pulmonary circulation; pulmonary hypertension