Effects of cellular redox balance on induction of apoptosis by eicosapentaenoic acid in HT29 colorectal adenocarcinoma cells and rat colon in vivo.
OBJECTIVE
Epidemiological evidence suggests n-3 polyunsaturated lipids may protect against colorectal neoplasia. Consumption of fish oil modulates crypt cytokinetics in humans, and crypt apoptosis in animal models. To explore these effects, we investigated involvement of caspase enzymes and cellular redox balance in the induction of apoptosis by eicosapentaenoic acid (EPA) in HT29 cells, and in rat colon in vivo.


METHODS
Survival of HT29 cells grown with EPA in the presence of caspase inhibitors, antioxidants, or buthionine sulphoximine, an inhibitor of glutathione neosynthesis, was determined. The effects of EPA enriched fish oil and glutathione depletion on apoptosis in rat colon were assessed using microdissected crypts.


RESULTS
Treatment of HT29 cells with EPA reduced viable cell number and activated caspase 3, prior to cell detachment. Antioxidants and caspase inhibitors blocked HT29 cell death whereas glutathione depletion increased it. Rats fed fish oil had higher crypt cell apoptosis than those fed corn oil, and glutathione depletion enhanced this effect.


CONCLUSIONS
Incorporation of EPA into colonic epithelial cell lipids increases apoptosis. The results of this study, using both an animal and cell line model, support the hypothesis that this effect is mediated via cellular redox tone, and is sensitive to glutathione metabolism. The data suggest a mechanism whereby polyunsaturated fatty acids may influence the susceptibility of colorectal crypt cells to induction or progression of neoplasia.
Latham
P
P
Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK.
Lund
E K
EK
Brown
J C
JC
Johnson
I T
IT
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D061945:Caspase Inhibitors; D002470:Cell Survival; D003314:Corn Oil / Q000008:administration & dosage / Q000737:chemistry; D015118:Eicosapentaenoic Acid / Q000494:pharmacology*; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005395:Fish Oils / Q000008:administration & dosage / Q000737:chemistry; D019073:HT29 Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D014407:Tumor Cells, Cultured
D000975:Antioxidants; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D005395:Fish Oils; D019328:Buthionine Sulfoximine; D003314:Corn Oil; D015118:Eicosapentaenoic Acid