Key Role of Porcine Cytochrome P450 2A19 in the Bioactivation of Aflatoxin B1 in the Liver

The metabolic transformation of aflatoxin B₁ (AFB₁) 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 AFB₁ in porcine liver microsomes (PLMs) were AFB₁-8,9-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 AFB₁ 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 AFB₁-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 AFB₁ totally eliminated AFB₁-induced AFB₁-DNA adducts and γH2AX formations in CYP2A19 stable transfected HepLi cells. These results indicate that CYP2A19 mainly mediated AFB₁-induced cytotoxicity through metabolizing AFB₁ 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 AFB₁ bioactivation in pigs and provides a promising target to reduce porcine aflatoxicosis.