Role of nitric oxide and peroxynitrite in bile salt-induced apoptosis: relevance to colon carcinogenesis.
Previous work from our laboratory indicated that the bile salt sodium deoxycholate (NaDOC) induced apoptosis in cultured cells and in normal goblet cells of the colonic mucosa. We also reported that the normal-appearing flat mucosa of patients with colon cancer exhibited apoptosis resistance. Using immunofluorescence in conjunction with confocal microscopy, we now report that high physiological concentrations (0.5 mM) of NaDOC result in the formation of nitrotyrosine residues, a footprint for the formation of reactive nitrogen species, including peroxynitrite, in plasma membrane-associated proteins of HT-29 cells. Because peroxynitrite is formed from the reaction between nitric oxide and superoxide anion, we specifically looked at the role of nitric oxide and superoxide anion in NaDOC-induced apoptosis. Pretreatment of cells with the inhibitor/antioxidants, N-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, copper (II) 3,5-diisopropyl salicylate hydrate, a superoxide dismutase mimetic compound, and Trolox, a water-soluble analog of alpha-tocopherol, alone or in combination, sensitized cells to apoptosis induced by 0.5 mM NaDOC. These results suggest that nitric oxide may be part of a signaling pathway that is responsible for apoptosis resistance. The results also indicate that nitric oxide does not appear to protect cells against NaDOC-induced apoptosis by scavenging superoxide anion.
Washo-Stultz
D
D
Department of Microbiology and Immunology, College of Medicine, University of Arizona, Tucson 85724, USA.
Hoglen
N
N
Bernstein
H
H
Bernstein
C
C
Payne
C M
CM
D017209:Apoptosis / Q000187:drug effects*; D001647:Bile Acids and Salts / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000209:etiology*; D003840:Deoxycholic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D016166:Free Radical Scavengers; D006801:Humans; D018613:Microscopy, Confocal; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D018384:Oxidative Stress; D012459:Salicylates / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D001647:Bile Acids and Salts; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D009566:Nitrates; D012459:Salicylates; D003840:Deoxycholic Acid; D013481:Superoxides; C030865:copper bis(3,5-diisopropylsalicylate); C039642:peroxynitric acid; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester