Piperine inhibits aflatoxin B1-induced cytotoxicity and genotoxicity in V79 Chinese hamster cells genetically engineered to express rat cytochrome P4502B1.

We have investigated the potential of piperine for inhibiting the activity of cytochrome P4502B1 and protecting against aflatoxin B1 (AFB1) in V79MZr2B1 (r2B1) cells, i.e. V79 Chinese hamster cells engineered for the expression of rat CYP4502B1. The cells were found to contain high activities of 7-methoxycoumarin demethylase (MOCD). Piperine inhibited MOCD in preparations of r2B1 cells with an IC50 of approximately 10 microM. The cells in culture dealkylated 7-methoxycoumarin (MOC) to 7-OH-coumarin linearly, at least for 12 h, where piperine produced concentration-dependent inhibition with IC50 < 30 microM. The time required for maximal inhibition was approximately 8 h with both 30 and 60 microM concentrations of piperine used. AFB1 at 0.1-20 microM caused a concentration dependent decrease in the amount of DNA and an increase in the formation of micronuclei (MN). The mycotoxin at 10 microM reduced DNA by approximately 30% and increased MN appearance by 20-fold against the background level of 7 MN per 500 nuclei. Piperine at 60 microM completely counteracted cytotoxicity and formation of MN by 10 microM AFB1 and reduced the toxic effects of 20 microM AFB1 by > 50%. The results suggest that: (i) Piperine is a potent inhibitor of rat CYP4502B1 activity; (ii) AFB1 is activated by r2B1 cells to cytotoxic and genotoxic metabolites; and (iii) piperine counteracts CYP4502B1 mediated toxicity of AFB1 in the cells and might, therefore, offer a potent chemopreventive effect against procarcinogens activated by CYP4502B1.