Role of mitochondrial complexes I and II, reactive oxygen species and arachidonic acid metabolism in deoxycholate-induced apoptosis.
Bile acids are promoters of colon cancer; however, the mechanism(s) of action of this tumor promoter are largely unknown. Bile acids induce apoptosis in colon epithelial cells and it is probable that the modulation of apoptosis contributes, in part, to colon carcinogenesis. We tested the hypothesis that damage to mitochondria is an upstream event in sodium deoxycholate (NaDOC)-induced apoptosis and that a pro-oxidant state of the cell favors survival. NaDOC-induced damage to mitochondria was assessed by a decrease in mitochondrial membrane potential using flow cytometry and an increase in megamitochondria formation using transmission electron microscopy. We found that inhibition of mitochondrial complexes I and II with rotenone and thenoyltrifluoroacetone, respectively, dramatically protected HT-29 cells against NaDOC-induced apoptosis. Antioxidants (e.g. lazaroids U-74389G and U-8389G), however, sensitized cells to NaDOC-induced apoptosis, in spite of a reduction in reactive oxygen/nitrogen species. Lazaroid pre-treatment caused a marked decrease in NaDOC-induced activation of the anti-apoptotic transcription factor, NF-kappaB, which may provide the basis for the sensitization to apoptosis caused by these antioxidants. Inhibitors of arachidonic acid metabolism (e.g. esculetin, sulindac sulfide, NS-398) also sensitized HT-29 cells to NaDOC-induced apoptosis. These results indicate that the life/death decision is the result of a shift in the balance between specific anti-apoptotic and pro-apoptotic factors, respectively, that may have significance to colon carcinogenesis.
Washo-Stultz
Delon
D
Department of Microbiology and Immunology, College of Medicine, University of Arizona, Tucson, AZ 85724, USA.
Crowley-Weber
Cara L
CL
Dvorakova
Katerina
K
Bernstein
Carol
C
Bernstein
Harris
H
Kunke
Kathleen
K
Waltmire
Caroline N
CN
Garewal
Harinder
H
Payne
Claire M
CM
D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D016718:Arachidonic Acid / Q000378:metabolism*; D002839:Chromans / Q000494:pharmacology; D003840:Deoxycholic Acid / Q000494:pharmacology*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D011281:Pregnatrienes / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013385:Succinate Dehydrogenase / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000975:Antioxidants; D002839:Chromans; D010879:Piperazines; D011281:Pregnatrienes; D017382:Reactive Oxygen Species; D003840:Deoxycholic Acid; C074965:U 74389F; C066382:U 78517F; D016718:Arachidonic Acid; D013385:Succinate Dehydrogenase; D009247:NADH, NADPH Oxidoreductases