Key Role of Porcine Cytochrome P450 2A19 in the Bioactivation of Aflatoxin B in the Liver.

The metabolic transformation of aflatoxin B (AFB) in pigs remains understudied, presenting a gap in our toxicological understanding compared with extensive human-based research. Here, we found that the main products of AFB in porcine liver microsomes (PLMs) were AFB-8,9-epoxide (AFBO), the generation of which correlated strongly with the protein levels and activities of cytochrome P450 (CYP)3A and CYP2A. In addition, we found that porcine CYP2A19 can transform AFB into AFBO, and its metabolic activity was stronger than the other CYPs we have reported, including CYP1A2, CYP3A29, and CYP3A46. Furthermore, we stably transfected all identified CYPs in HepLi cells and found that CYP2A19 stable transfected HepLi cells showed more sensitivity in AFB-induced DNA adducts, DNA damage, and γH2AX formation than the other three stable cell lines. Moreover, the CYP2A19 N297A mutant that lost catalytic activity toward AFB totally eliminated AFB-induced AFB-DNA adducts and γH2AX formations in CYP2A19 stable transfected HepLi cells. These results indicate that CYP2A19 mainly mediated AFB-induced cytotoxicity through metabolizing AFB into a highly reactive AFBO, promoting DNA adduct formation and DNA damage, and lastly leading to cell death. This study advances the current understanding of AFB bioactivation in pigs and provides a promising target to reduce porcine aflatoxicosis.