title: Estrogen induces nitric oxide production via activation of constitutive nitric oxide synthases in human neuroblastoma cells.
abstract: Although it is becoming increasingly evident that nitric oxide (NO) mediates some of estrogen's actions in the brain, the effects of estrogen on NO production through NO synthases (NOS) in neuronal cells have not yet been identified. Here we assessed changes in NO production induced by 17beta-estradiol (E2) in cells of neuronal origin using human SK-N-SH neuroblastoma cells, which we show express all three isoforms of NOS. Involvement of NOS isoforms in E2-induced NO production was examined using isoform-specific NOS inhibitors. E2 (10(-10)-10(-6) m) induced rapid increases in NO release and changes in endothelial NOS (eNOS) expression, which were blocked by ICI 182,780, an antagonist of estrogen receptors. Increased levels of NO release and NOS activity induced by E2 were blocked by N5-(1-Imino-3-butenyl)-L-ornithine, a neuronal NOS inhibitor, and N(5)-(1-Iminoethyl)-L-ornithine, an eNOS inhibitor, but not by 1400W, an inducible NOS inhibitor. These results demonstrate that E2-stimulated NO production occurs via estrogen receptor-mediated activation of the constitutive NOSs, neuronal NOS and eNOS. The E2-induced NO increase was abolished when extracellular Ca2+ was removed from the medium or after the addition of nifedipine, an L-type channel blocker, and was partially inhibited using 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester, an intracellular Ca2+ chelator. However, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester itself also caused an increase in NO release that was blocked by 1400W, suggesting that inducible NOS mediates this response. Together these data reveal that constitutive NOS activities are responsible for E2-induced NO production in neuroblastoma cells and that differential activation of NOS isoforms in these cells occurs in response to different treatments.
authors.affiliation: Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
authors.forename: Yun
authors.initials: Y
authors.lastname: Xia
authors.forename: Teresa L
authors.initials: TL
authors.lastname: Krukoff
mesh_terms: D002118:Calcium / Q000502:physiology; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D000077267:Fulvestrant; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D009447:Neuroblastoma / Q000201:enzymology / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D002614:Chelating Agents; D004791:Enzyme Inhibitors; D004965:Estrogen Antagonists; D007527:Isoenzymes; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D000077267:Fulvestrant; D009569:Nitric Oxide; D004958:Estradiol; D004533:Egtazic Acid; D019001:Nitric Oxide Synthase; D002118:Calcium