ABSTRACT
A cell-based assay system was developed to evaluate the potential antioxidant and pro-oxidant effects of various dietary polyphenolic compounds based on the induction of p53 activity by hydrogen peroxide. A p53-luciferase reporter vector was stably transfected into NIH3T3 cells. Individual clones were isolated, and one clone (number 33) was selected that showed the highest induction levels with different generators of free radicals. Clone 33 was preincubated for 1 hour with 0, 0.1, 1.0, 10, 50, and 100 microM genistein, resveratrol, naringenin, quercetin, epicatechin gallate, and epigallocatechin-3-gallate and then treated with 40 microM hydrogen peroxide or left untreated for 4 hours. Cell lysates were prepared and assayed for luciferase activity. Results show that the effects on p53 activity by the different polyphenolics varied depending on the compound and concentration. Quercetin and genistein reduced p53 activity at 1.0 microM, whereas the other four compounds did not attenuate p53 activity. With the exception of naringenin, the other compounds increased p53 at the higher (50 microM or 100 microM) amounts, without added hydrogen peroxide, suggesting that these compounds can act as pro-oxidants or possibly stimulate p53 activity by another mechanism.
