Protective activity of butyrate on hydrogen peroxide-induced DNA damage inisolated human colonocytes and HT29 tumour cells

Epidemiological studies support the involvement of short-chain fatty acids (SCFA) in colon physiology and the protective role of butyrate on colon car cinogenesis. Among the possible mechanisms by which butyrate may exert its anti-carcinogenicity an antioxidant activity has been recently suggested. W e investigated the effects of butyrate and mixtures of SCFA (butyrate, prop ionate and acetate) on DNA damage induced by H2O2 in isolated human colonoc ytes and in two human colon tumour cell lines (HT29 and HT29 19A). Human co lonocytes were isolated from endoscopically obtained samples and the DNA da mage was assessed by the comet assay. H2O2 induced DNA damage in normal col onocytes in a dose-dependent manner which was statistically significant at concentrations over 10 muM. At 15 muM H2O2 DNA damage in HT29 and HT29 19A cells was significantly lower than that observed in normal colonocytes (P < 0.01). Pre-incubation of the cells with physiological concentrations of bu tyrate (6.25 and 12.5 mM) reduced H2O2 (15 muM) induced damage by 33 and 51 % in human colonocytes, 45 and 75% in HT29 and 30 and 80% in HT29 19A, resp ectively. Treatment of cells with a mixture of 25 mM acetate + 10.4 mM prop ionate + 6.25 mM butyrate did not induce DNA damage, while a mixture of 50 mM acetate + 20.8 mM propionate + 12.5 mM butyrate was weakly genotoxic onl y towards normal colonocytes. However, both mixtures were able to reduce th e H2O2-induced DNA damage by about 50% in all cell types. The reported prot ective effect of butyrate might be important in pathogenetic mechanisms med iated by reactive oxygen species, and aids understanding of the apparent pr otection toward colorectal cancer exerted by dietary fibres, which enhance the butyrate bioavailability in the colonic mucosa.