Cytochrome P450 2A13 mediates aflatoxin B1-induced cytotoxicity and apoptosis in human bronchial epithelial cells

Cytochrome P450 (CYP) 2A13 is mainly expressed in the respiratory system and has the ability to metabolize aflatoxin B1 (AFB1). However, the role of CYP2A13-mediated AFB1 metabolism and its consequences in human lung epithelial cell is not clear. Therefore, the objectives of this study were to investigate the significance of CYP2A13 in AFB1-induced cytotoxicity, DNA adducts, and apoptosis. To achieve these objectives, CYP2A13 was stably over-expressed in immortalized human bronchial epithelial BEAS-2B cells (B-2A13) and its significance in AFB1-induced cytotoxicity, DNA adducts, and apoptosis was compared to cells with stably expression of CYP1A2 (B-1A2), the predominant AFB1 metabolizing enzyme in liver, as well as CYP2A6 (B-2A6) as controls. AFB1 induced B-2A13 cytotoxicity and apoptosis in a dose- and time-dependent manner. The cytotoxic and apoptotic effects of AFB1 were significantly remarkable in B-2A13 cells than those of B-1A2 and B-2A6 cells. The increased expression of pro-apoptotic proteins, such as C-PARP, C-caspase-3, and Bax, and decreased expression of anti-apoptotic proteins, such as caspase-3, Bcl-2, and p-Bad further confirmed the data of AFB1-induced cytotoxicity and apoptosis. Furthermore, increased DNA adduct was observed in B-2A13 after AFB1 treatment as compared to B-1A2 cells and B-2A6 cells. Finally, treatment with nicotine, a competitor of AFB1, and 8-methoxypsoralen (8-MOP), an inhibitor of CYP enzyme, further confirm the critical role of CYP2A13 in AFB1-induced cytotoxicity and apoptosis. Collectively, these findings suggest adverse effects of AFB1 in respiratory diseases mediated by CYP2A13.