Induction of P53, P21Waf1, orinithine decorboxylase activity, and DNA damage leading to cell‐cycle arrest and apoptosis following topical application of repeated fish fried oil extract to mice

Repeated frying of food produces numerous carcinogens including polycyclic aromatic hydrocarbons (PAHs). Our prior studies have shown that repeated fish fried oil extract (RFFE) induces cytochrome P (CYP)-450 1A1/2 isozymes thereby causing increased generation of electrophilic reactive metabolites of PAHs and subsequent binding to DNA. In the present study, molecular events associated with DNA damage, apoptosis, and proliferation following topical exposure to RFFE have been investigated in mice. Single topical application of RFFE (500 microg) for 24-48 h caused significant DNA damage with Comet assay in terms of olive tail moment (OTM) (204-246%), tail DNA (253-293%), and tail length (172-195%). Overexpression of p53 and p21WAF1 proteins was observed in skin cells following single topical exposure of RFFE for 24-72 h, which was similar to that of benzo(a)pyrene (BP) exposure (24 h). Though RFFE and BP exposure separately, did not result in G(0)/G(1) arrest, but a significant increase in the proportion of cells in S-phase was observed. Apoptotic induction was noticed in skin cells, with maximum induction after 48 h of exposure to RFFE. Further, topical treatment of mice with RFFE (500 microg) for 6 h significantly increased orinithine decarboxylase (ODC) activity by 7.5-fold when compared to control. These results indicate that RFFE exposure caused ODC induction accompanied by increased levels of p53 and p21WAF1 proteins leading of apoptosis and delay of cells in S-phase thereby indicating the possible carcinogenic potential of RFFE.