title: Deoxycholate induces mitochondrial oxidative stress and activates NF-kappaB through multiple mechanisms in HCT-116 colon epithelial cells.
abstract: Nuclear factor kappa B (NF-kappaB) is a redox-associated transcription factor that is involved in the activation of survival pathways. We have previously shown that deoxycholate (DOC) activates NF-kappaB in hepatocytes and colon epithelial cells and that persistent exposure of HCT-116 cells to increasing concentrations of DOC results in the constitutive activation of NF-kappaB, which is associated with the development of apoptosis resistance. The mechanisms by which DOC activates NF-kappaB in colon epithelial cells, and whether natural antioxidants can reduce DOC-induced NF-kappaB activation, however, are not known. Also, it is not known if DOC can generate reactive oxygen species within mitochondria as a possible pathway of stress-related NF-kappaB activation. Since we have previously shown that DOC activates the NF-kappaB stress-response pathway in HCT-116 cells, we used this cell line to further explore the mechanisms of NF-kappaB activation. We found that DOC induces mitochondrial oxidative stress and activates NF-kappaB in HCT-116 cells through multiple mechanisms involving NAD(P)H oxidase, Na+/K+-ATPase, cytochrome P450, Ca++ and the terminal mitochondrial respiratory complex IV. DOC-induced NF-kappaB activation was significantly (P < 0.05) inhibited by pre-treatment of cells with CAPE, EGCG, TMS, DPI, NaN3, EGTA, Ouabain and RuR. The NF-kappaB-activating pathways, induced by the dietary-related endogenous detergent DOC, provide mechanisms for promotion of colon cancer and identify possible new targets for chemoprevention.
authors.affiliation: Department of Cell Biology & Anatomy, College of Medicine, University of Arizona, Tucson, AZ 85724-5044, USA. cpayne@email.arizona.edu
authors.forename: C M
authors.initials: CM
authors.lastname: Payne
authors.forename: C
authors.initials: C
authors.lastname: Weber
authors.forename: C
authors.initials: C
authors.lastname: Crowley-Skillicorn
authors.forename: K
authors.initials: K
authors.lastname: Dvorak
authors.forename: H
authors.initials: H
authors.lastname: Bernstein
authors.forename: C
authors.initials: C
authors.lastname: Bernstein
authors.forename: H
authors.initials: H
authors.lastname: Holubec
authors.forename: B
authors.initials: B
authors.lastname: Dvorakova
authors.forename: H
authors.initials: H
authors.lastname: Garewal
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003840:Deoxycholic Acid / Q000494:pharmacology*; D003902:Detergents / Q000494:pharmacology*; D003576:Electron Transport Complex IV / Q000378:metabolism; D045325:HCT116 Cells / Q000187:drug effects; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D019255:NADPH Oxidases / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D017382:Reactive Oxygen Species; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D003902:Detergents; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D003840:Deoxycholic Acid; D003577:Cytochrome P-450 Enzyme System; D019255:NADPH Oxidases; D003576:Electron Transport Complex IV; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium