title: Acute inhibition of guanosine triphosphate cyclohydrolase 1 uncouples endothelial nitric oxide synthase and elevates blood pressure.
abstract: GTP cyclohydrolase 1 (GTPCH1) is the rate-limiting enzyme in de novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for endothelial NO synthase (eNOS) dictating, at least partly, the balance of NO and superoxide produced by this enzyme. The aim of this study was to determine the effect of acute inhibition of GTPCH1 on BH4, eNOS function, and blood pressure (BP) in vivo. Exposure of bovine or mouse aortic endothelial cells to GTPCH1 inhibitors (2,4-diamino-6-hydroxypyrimidine or N-acetyl-serotonin) or GTPCH1 small-interference RNA (siRNA) significantly reduced BH4 and NO levels but increased superoxide levels. This increase was abolished by sepiapterin (BH4 precursor) or N(G)-nitro-L-arginine methyl ester (nonselective NOS inhibitor). Incubation of isolated murine aortas with 2,4-diamino-6-hydroxypyrimidine or N-acetyl-serotonin impaired acetylcholine-induced endothelium-dependent relaxation but not endothelium-independent relaxation. Aortas from GTPCH1 siRNA-injected mice, but not their control-siRNA injected counterparts, also exhibited impaired endothelium-dependent relaxation. BH4 reduction induced by GTPCH1 siRNA injection was associated with increased aortic levels of superoxide, 3-nitrotyrosine, and adhesion molecules (intercellular adhesion molecule 1 and vascular cell adhesion molecule 1), as well as a significantly elevated systolic, diastolic, and mean BP in C57BL6 mice. GTPCH1 siRNA was unable to elicit these effects in eNOS(-/-) mice. Sepiapterin supplementation, which had no effect on high BP in eNOS(-/-) mice, partially reversed GTPCH1 siRNA-induced elevation of BP in wild-type mice. In conclusion, GTPCH1 via BH4 maintains normal BP and endothelial function in vivo by preserving NO synthesis by eNOS.
authors.affiliation: Department of Medicine, Division of Endocrinology and Diabetes, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Shuangxi
authors.initials: S
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.forename: Ping
authors.initials: P
authors.lastname: Song
authors.forename: Yong
authors.initials: Y
authors.lastname: Wu
authors.forename: Junhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Hyoung
authors.initials: H
authors.lastname: Chul Choi
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zou
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D001708:Biopterins / Q000031:analogs & derivatives / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology*; D002417:Cattle; D042783:Endothelial Cells / Q000166:cytology / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006136:GTP Cyclohydrolase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism*; D007042:Hypoxanthines / Q000494:pharmacology; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D009924:Organ Culture Techniques; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D011622:Pterins / Q000494:pharmacology; D034741:RNA, Small Interfering; D012701:Serotonin / Q000031:analogs & derivatives / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D007042:Hypoxanthines; D011622:Pterins; D034741:RNA, Small Interfering; D013481:Superoxides; D001708:Biopterins; D009569:Nitric Oxide; D012701:Serotonin; C016727:sepiapterin; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D006136:GTP Cyclohydrolase; C017202:2,4-diaminohypoxanthine; C003402:sapropterin; C006389:N-acetylserotonin