linoleic-acid-hydroperoxide and Colonic-Neoplasms

High consumption of dietary fat promotes colon carcinogenesis. While this effect is well known the underlying mechanism is not understood. Fatty acid hydroperoxides (LOOH) arise from unsaturated fatty acids in the presence of oxygen and elevated temperature during food processing. An approach was made starting from the assumption that LOOH are present in dietary fats as a result of boiling. LOOH undergoes homolytic cleavage in the presence of iron. We studied their effects on gene expression in colorectal tumour cells using linoleic acid hydroperoxide (LOOH) as model compound. Addition to the medium of LT97 adenoma and SW480 carcinoma cells enhanced the production of hydrogen peroxide. Both cell lines were observed to increase VEGF and COX-II expression based on mRNA. Expression of VEGF was inhibited by caroverine and ubiquinon.

Topics: Adenoma; Carcinoma; Colonic Neoplasms; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase Inhibitors; Dietary Fats; Gene Expression Regulation, Neoplastic; Humans; Linoleic Acids; Lipid Peroxides; Organic Chemicals; Pyrazoles; Quinoxalines; Sulfonamides; Tumor Cells, Cultured; Ubiquinone; Vascular Endothelial Growth Factor A

Prooxidant formation and resulting lipid peroxidation are supposed to be involved in the pathogenesis of various diseases including cancer. Cancer risk is possibly influenced by the composition of diet with high intake of fat and red meat being harmful and high consumption of fruits and vegetables being protective. Since dietary oils may contain potential prooxidants, the aim of the present study was to prove (i) whether oxidative stress in biomembranes may be induced by dietary oils and if, (ii) which impact it has on the viability and proliferation of cultured colon (carcinoma) cells. Lipid hydroperoxide content in dietary oils increased after heating. Linoleic acid hydroperoxide (LOOH) and/or oils with different hydroperoxide contents induced lipid peroxidation in liposomes, erythrocyte ghosts and colon cells. Upon incubation with liposomes, both LOOH and heated oil induced lipid peroxidation only in the presence of iron and ascorbate. LOOH was sufficient to start lipid peroxidation of erythrocyte ghosts. LOOH incorporates into the lipid bilayer decreasing membrane fluidity and initiating lipid peroxidation in the lipid phase. When cultured cells (IEC18 intestinal epithelial cells, SW480 and HT29/HI1 colon carcinoma cells) were exposed to LOOH, they responded by cell death both via apoptosis and necrosis. Cells with higher degree of membrane unsaturation were more susceptible and antioxidants (vitamin E and selenite) were protective indicating the involvement of oxidative stress. Thus, peroxidation of biomembranes can be initiated by lipid hydroperoxides from heated oils. Dietary consumption of heated oils may lead to oxidative damage and to cell death in the colon. This may contribute to the enhanced risk of colon cancer due to regenerative cell proliferation.

Topics: Animals; Antioxidants; Cell Division; Cell Line; Cell Survival; Colonic Neoplasms; Dietary Fats, Unsaturated; Electron Spin Resonance Spectroscopy; Erythrocyte Membrane; Fatty Acids; Hot Temperature; Humans; Iron; Linoleic Acids; Lipid Peroxidation; Lipid Peroxides; Liposomes; Membranes; Oxidants; Oxidative Stress; Oxygen Consumption; Rats; Tumor Cells, Cultured; Vitamin E

Effects of hydroperoxides, autoxidation products of linolic acid (HPO) and secondary oxidative products of HPO (SOP) (5% each in diet) were examined in female Sprague-Dawley rats. HPO and SOP administration was carried out during or subsequent to two injections of dimethylhydrazine (DMH) (40 mg/kg body wt s.c.), and a single i.g. dose of 7,12-dimethylbenz[a]anthracene (DMBA) (50 mg/kg body wt). No significant differences in the incidences of tumors in the mammary gland, colon, ear duct and hematopoietic system associated with HPO or SOP treatment were evident, during or after carcinogen exposure. The present results therefore indicate that the environmental contaminants, HPO and SOP, lack any potential for modification of mammary gland or colon carcinogenesis under the conditions of the investigation.

Topics: 1,2-Dimethylhydrazine; 9,10-Dimethyl-1,2-benzanthracene; Animals; Colonic Neoplasms; Dimethylhydrazines; Ear Neoplasms; Female; Leukemia, Experimental; Linoleic Acids; Lipid Peroxides; Mammary Neoplasms, Experimental; Oxidation-Reduction; Rats; Rats, Inbred Strains