title: Ascorbate inhibits iNOS expression and preserves vasoconstrictor responsiveness in skeletal muscle of septic mice.
abstract: Inducible nitric oxide synthase (iNOS) expression in blood vessels contributes to the vascular hyporeactivity characteristic of sepsis. Our previous work demonstrated in vitro that ascorbate inhibits iNOS expression in lipopolysaccharide- and interferon-gamma-stimulated skeletal muscle endothelial cells (ECs) through an antioxidant mechanism. The present study evaluated in vivo the hypothesis that administration of ascorbate decreases oxidative stress, prevents endothelial iNOS expression, and improves vascular reactivity in septic skeletal muscle. Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). Plasma nitrite and nitrate (NOx) levels were elevated by 6 h after CLP. Prior ascorbate bolus injection (200 mg/kg body wt iv) blocked the elevation of plasma NOx and abolished the expression of iNOS protein and activity in the septic skeletal muscle. We also demonstrated that iNOS mRNA determined by RT-PCR was induced in the microvascular ECs of the muscle at 3 h after CLP. This induction was attenuated by prior ascorbate administration. Ascorbate inhibition of iNOS expression was associated with decreased oxidant levels in the septic muscle. Moreover, ascorbate administration restored partially the baseline arterial pressure and preserved completely the microvascular constriction and arterial pressure responses to norepinephrine in CLP mice. These results suggest that early administration of ascorbate may be a valuable adjunct treatment of sepsis.
authors.affiliation: Dept. of Medical Biophysics, University of Western Ontario, London, ON, Canada N6C 5C1.
authors.forename: Feng
authors.initials: F
authors.lastname: Wu
authors.forename: John X
authors.initials: JX
authors.lastname: Wilson
authors.forename: Karel
authors.initials: K
authors.lastname: Tyml
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D001794:Blood Pressure; D002432:Cecum; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D008026:Ligation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation / Q000187:drug effects; D018482:Muscle, Skeletal / Q000098:blood supply*; D019001:Nitric Oxide Synthase / Q000235:genetics* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009638:Norepinephrine / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D018805:Sepsis / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D012333:RNA, Messenger; D014662:Vasoconstrictor Agents; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D001205:Ascorbic Acid; D009638:Norepinephrine