title: Crosstalk between nitrite, myoglobin and reactive oxygen species to regulate vasodilation under hypoxia.
abstract: The systemic response to decreasing oxygen levels is hypoxic vasodilation. While this mechanism has been known for more than a century, the underlying cellular events have remained incompletely understood. Nitrite signaling is critically involved in vessel relaxation under hypoxia. This can be attributed to the presence of myoglobin in the vessel wall together with other potential nitrite reductases, which generate nitric oxide, one of the most potent vasodilatory signaling molecules. Questions remain relating to the precise concentration of nitrite and the exact dose-response relations between nitrite and myoglobin under hypoxia. It is furthermore unclear whether regulatory mechanisms exist which balance this interaction. Nitrite tissue levels were similar across all species investigated. We then investigated the exact fractional myoglobin desaturation in an ex vivo approach when gassing with 1% oxygen. Within a short time frame myoglobin desaturated to 58±12%. Given that myoglobin significantly contributes to nitrite reduction under hypoxia, dose-response experiments using physiological to pharmacological nitrite concentrations were conducted. Along all concentrations, abrogation of myoglobin in mice impaired vasodilation. As reactive oxygen species may counteract the vasodilatory response, we used superoxide dismutase and its mimic tempol as well as catalase and ebselen to reduce the levels of reactive oxygen species during hypoxic vasodilation. Incubation of tempol in conjunction with catalase alone and catalase/ebselen increased the vasodilatory response to nitrite. Our study shows that modest hypoxia leads to a significant nitrite-dependent vessel relaxation. This requires the presence of vascular myoglobin for both physiological and pharmacological nitrite levels. Reactive oxygen species, in turn, modulate this vasodilation response.
authors.affiliation: Department of Medicine, Division of Cardiology, Pulmonary Diseases and Vascular Medicine, Medical Faculty, University Hospital Düsseldorf, Düsseldorf, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Totzeck
authors.affiliation: Department of Medicine, Division of Cardiology, Pulmonary Diseases and Vascular Medicine, Medical Faculty, University Hospital Düsseldorf, Düsseldorf, Germany.
authors.forename: Ulrike B
authors.initials: UB
authors.lastname: Hendgen-Cotta
authors.affiliation: Department of Medicine, Division of Cardiology, Pulmonary Diseases and Vascular Medicine, Medical Faculty, University Hospital Düsseldorf, Düsseldorf, Germany.
authors.forename: Malte
authors.initials: M
authors.lastname: Kelm
authors.affiliation: Department of Medicine, Division of Cardiology, Pulmonary Diseases and Vascular Medicine, Medical Faculty, University Hospital Düsseldorf, Düsseldorf, Germany.
authors.forename: Tienush
authors.initials: T
authors.lastname: Rassaf
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009211:Myoglobin / Q000235:genetics / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D009211:Myoglobin; D009573:Nitrites; D017382:Reactive Oxygen Species; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse