title: Erythropoietin increases bioavailability of tetrahydrobiopterin and protects cerebral microvasculature against oxidative stress induced by eNOS uncoupling.
abstract: This study was designed to determine whether treatment with erythropoietin (EPO) could protect cerebral microvasculature against the pathological consequences of endothelial nitric oxide (NO) synthase uncoupling. Wild-type and GTP cyclohydrolase I (GTPCH-I)-deficient hph1 mice were administered EPO (1000 U/kg/day, s.c., 3 days). Cerebral microvessels of hph1 mice demonstrated reduced tetrahydrobiopterin (BH4) bioavailability, increased production of superoxide anions and impaired endothelial NO signaling. Treatment of hph1 mice with EPO attenuated the levels of 7,8-dihydrobiopterin, the oxidized product of BH4, and significantly increased the ratio of BH4 to 7,8-dihydrobiopterin. Moreover, EPO decreased the levels of superoxide anions and increased NO bioavailability in cerebral microvessels of hph1 mice. Attenuated oxidation of BH4 and inhibition of endothelial NO synthase uncoupling were explained by the increased expression of antioxidant proteins, manganese superoxide dismutase, and catalase. The protective effects of EPO observed in cerebral microvessels of hph1 mice were also observed in GTPCH-I siRNA-treated human brain microvascular endothelial cells exposed to EPO (1 U/mL or 10 U/mL; 3 days). Our results suggest that EPO might protect the neurovascular unit against oxidative stress by restoring bioavailability of BH4 and endothelial NO in the cerebral microvascular endothelium. We demonstrate that treatment with erythropoietin (EPO) could protect cerebral microvasculature against the pathological consequences of endothelial nitric oxide (NO) synthase uncoupling. Our results suggest that EPO might protect the neurovascular unit against oxidative stress by restoring bioavailability of tetrahydrobiopterin (BH4) and endothelial nitric oxide.
authors.affiliation: Departments of Anesthesiology, and Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
authors.forename: Anantha Vijay R
authors.initials: AV
authors.lastname: Santhanam
authors.forename: Livius V
authors.initials: LV
authors.lastname: d'Uscio
authors.forename: Zvonimir S
authors.initials: ZS
authors.lastname: Katusic
mesh_terms: D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D004921:Erythropoietin / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D055806:Microvessels / Q000166:cytology / Q000187:drug effects*; D009154:Mutation / Q000235:genetics / Q000276:immunology; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects*; D063150:Polycomb Repressive Complex 1 / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism
chemical_list: C491239:PHC1 protein, human; D034741:RNA, Small Interfering; D004921:Erythropoietin; D001708:Biopterins; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D063150:Polycomb Repressive Complex 1; C003402:sapropterin
keywords: GTP cyclohydrolase I; brain; cerebral microvessels; hph1 mice; nitric oxide; superoxide