title: Overexpression of cationic amino acid transporter-1 increases nitric oxide production in hypoxic human pulmonary microvascular endothelial cells.
abstract: 1. The endogenous production of and/or the bioavailability of nitric oxide (NO) is decreased in pulmonary hypertensive diseases. L-arginine (L-arg) is the substrate for NO synthase (NOS). L-arg is transported into cells via the cationic amino acid transporters (CAT), of which there are two isoforms in endothelial cells, CAT-1 and CAT-2. 2. To test the hypothesis that hypoxia will decrease CAT expression and L-arg uptake resulting in decreased NO production in human pulmonary microvascular endothelial cells (hPMVEC), cells were incubated in either normoxia (21% O(2), 5% CO(2), balance N(2)) or hypoxia (1% O(2), 5% CO(2), balance N(2)). 3. The hPMVEC incubated in hypoxia had 80% less NO production than cells incubated in normoxia (P < 0.01). The hPMVEC incubated in hypoxia had significantly lower CAT-2 mRNA levels than normoxic hPMVEC (P < 0.005), and the transport of L-arg was 40% lower in hypoxic than in normoxic hPMVEC (P < 0.01). In hypoxic cells, overexpression of CAT-1 resulted in significantly greater L-arg transport and NO production (P < 0.05). 4. These results demonstrate that in hPMVEC, hypoxia decreased CAT-2 expression, L-arg uptake and NO production. Furthermore, the hypoxia-induced decrease in NO production in hPMVEC can be attenuated by overexpressing CAT in these cells. We speculate that the CAT may represent a novel therapeutic target for treating pulmonary hypertensive disorders.
authors.affiliation: Pulmonary Hypertension Group, Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, The Ohio State University, Columbus, OH, USA.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Cui
authors.forename: Bernadette
authors.initials: B
authors.lastname: Chen
authors.forename: Louis G
authors.initials: LG
authors.lastname: Chicoine
authors.forename: Leif D
authors.initials: LD
authors.lastname: Nelin
mesh_terms: D026923:Amino Acid Transport Systems, Basic / Q000096:biosynthesis; D001120:Arginine / Q000378:metabolism; D027201:Cationic Amino Acid Transporter 1 / Q000096:biosynthesis*; D002460:Cell Line; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D008168:Lung / Q000098:blood supply*; D055806:Microvessels / Q000166:cytology / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*
chemical_list: D026923:Amino Acid Transport Systems, Basic; D027201:Cationic Amino Acid Transporter 1; C420825:SLC7A1 protein, human; C414177:SLC7A2 protein, human; D009569:Nitric Oxide; D001120:Arginine