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BACKGROUND: Tetrahydrobiopterin (BH4) is an essential cofactor of endothelial nitric oxide synthase (eNOS). When BH4 levels are decreased, eNOS becomes uncoupled to produce superoxide anion (O2(-)) instead of NO, which contributes to endothelial dysfunction. Deoxycorticosterone acetate (DOCA)-salt hypertension is characterized by a suppressed plasma renin level due to sodium retention but manifests in eNOS uncoupling; however, how endogenous BH4 regulates blood pressure is unknown. GTP cyclohydrolase I (GTPCH I) is the rate-limiting enzyme for de novo BH4 synthesis. This study tested the hypothesis that endothelium-specific GTPCH I overexpression retards the progression of hypertension through preservation of the structure and function of resistance mesenteric arteries. METHODS AND RESULTS: During 3 weeks of DOCA-salt treatment, arterial blood pressure was increased significantly in wild-type mice, as determined by radiotelemetry, but this increase was attenuated in transgenic mice with endothelium-specific GTPCH I overexpression (Tg-GCH). Arterial GTPCH I activity and BH4 levels were decreased significantly in wild-type DOCA-salt mice, but both were preserved in Tg-GCH mice despite DOCA-salt treatment. Significant remodeling of resistance mesenteric arteries (approximately 100-microm outside diameter) in wild-type DOCA-salt mice exists, evidenced by increased medial cross-sectional area, media thickness, and media-lumen ratio and overexpression of tenascin C, an extracellular matrix glycoprotein that contributes to hypertrophic remodeling; all of these effects were prevented in DOCA-salt-treated Tg-GCH mice. Furthermore, NO-mediated relaxation in mesenteric arteries was significantly improved in DOCA-salt-treated Tg-GCH mice, in parallel with reduced O2(-) levels. Finally, phosphorylation of eNOS at serine residue 1177 (eNOS-S1177), but not its dimer-monomer ratio, was decreased significantly in wild-type DOCA-salt mice compared with sham controls but was preserved in DOCA-salt-treated Tg-GCH mice. CONCLUSIONS: These results demonstrate that endothelium-specific GTPCH I overexpression abrogates O2(-) production and preserves eNOS phosphorylation, which results in preserved structural and functional integrity of resistance mesenteric arteries and lowered blood pressure in low-renin hypertension.

Original publication

DOI

10.1161/CIRCULATIONAHA.107.748236

Type

Journal article

Journal

Circulation

Publication Date

26/02/2008

Volume

117

Pages

1045 - 1054

Keywords

Animals, Biopterin, Blood Pressure, Body Weight, Coronary Vessels, Desoxycorticosterone, Endothelium, Vascular, GTP Cyclohydrolase, Gene Expression Regulation, Enzymologic, Hypertension, Male, Mesenteric Arteries, Mice, Mice, Inbred C57BL, Mice, Transgenic, Mineralocorticoids, Nitric Oxide, Nitric Oxide Synthase Type II, Nitric Oxide Synthase Type III, Reactive Oxygen Species, Renin, Sodium Chloride, Tenascin, Vascular Resistance, Vasodilation