title: Hypoxia induces a functionally significant and translationally efficient neuronal NO synthase mRNA variant.
abstract: We tested the hypothesis that induction of neuronal NO synthase (nNOS) impairs vascular smooth muscle contractility after hypoxia. nNOS protein was increased in aorta, mesenteric arterioles, pulmonary arteries, brain, and diaphragm from rats exposed to 8% O2 for 48 hours and in human aortic SMCs after hypoxic incubation (1% O2). Ca-dependent NO synthase activity was increased in endothelium-denuded aortic segments from hypoxia-exposed rats. N-nitro-L-arginine methyl ester enhanced the contractile responses of endothelium-denuded aortic rings and mesenteric arterioles from hypoxia-exposed but not normoxic rats (P < 0.05). The hypoxia-inducible mRNA transcript expressed by human cells was found to contain a novel 5'-untranslated region, consistent with activation of transcription in the genomic region contiguous with exon 2. Translational efficiency of this transcript is markedly increased compared with previously described human nNOS mRNAs. Transgenic mice possessing a lacZ reporter construct under control of these genomic sequences demonstrated expression of the construct after exposure to hypoxia (8% O2, 48 hours) in the aorta, mesenteric arterioles, renal papilla, and brain. These results reveal a novel human nNOS promoter that confers the ability to rapidly upregulate nNOS expression in response to hypoxia with a functionally significant effect on vascular smooth muscle contraction.
authors.affiliation: Division of Respirology, University of Toronto, Toronto, Ontario, Canada. wardm@smh.toronto.on.ca
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ward
authors.forename: Mourad
authors.initials: M
authors.lastname: Toporsian
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Scott
authors.forename: Hwee
authors.initials: H
authors.lastname: Teoh
authors.forename: Vasanthi
authors.initials: V
authors.lastname: Govindaraju
authors.forename: Adrian
authors.initials: A
authors.lastname: Quan
authors.forename: Avraham D
authors.initials: AD
authors.lastname: Wener
authors.forename: Guilin
authors.initials: G
authors.lastname: Wang
authors.forename: Siân C
authors.initials: SC
authors.lastname: Bevan
authors.forename: Derek C
authors.initials: DC
authors.lastname: Newton
authors.forename: Philip A
authors.initials: PA
authors.lastname: Marsden
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism; D015153:Blotting, Western; D017930:Genes, Reporter; D014644:Genetic Variation; D006801:Humans; D000860:Hypoxia / Q000201:enzymology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D052248:Nitric Oxide Synthase Type I / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D012333:RNA, Messenger; D052248:Nitric Oxide Synthase Type I