Consumption of vitamin B6 reduces colonic damage and protein expression of HSP70 and HO-1, the anti-tumor targets, in rats exposed to 1,2-dimethylhydrazine.

Mounting evidence indicates that vitamin B6 is a protective factor for colon cancer. Elevations in colonic damage, cell proliferation and heat shock proteins (HSPs, molecular chaperones) have been suggested to be associated with colon carcinogenesis. This study was performed to examine the effect of dietary levels of vitamin B6 (1, 7 or 35 mg pyridoxine HCl/kg diet) for 22 weeks on colon damage, epithelial cell proliferation and expression of HSPs in rats exposed to 1,2-dimethylhydrazine (DMH). Supplemental vitamin B6 with a low vitamin B6 diet (I mg pyridoxine HCl/kg diet) significantly reduced fecal activity of intestinal alkaline phosphatase (an index of intestinal damage) and the colonic epithelium PCNA labeling index (a marker of cell proliferation). Analysis using ELISA indicated that supplemental vitamin B6 significantly lowered protein levels of colonic HSP70 and heme oxygenase-1, HSP32 (HO-1). However, real-time RT-PCR analysis revealed that the mRNA levels of these HSPs were not decreased by supplemental vitamin B6, suggesting that the lowering effect of vitamin B6 on the colon protein expression of the HSPs is mediated by mechanisms not involving altered gene expression. This study provided evidence that dietary supplemental vitamin B6 suppresses colon damage, epithelial cell proliferation and protein expression of HSP70 and HO-1, the targets for anti-tumor agents, in rats exposed to DMH.