Abstract：
Aflatoxin B1 (AFB1) is the most toxic mycotoxin and a proven human carcinogen that requires metabolic activation, known by cytochrome P450 (CYP) 1A2 and 3A4. Previous evidence showed that AFB1 is activated by human recombinant CYP1A1 expressed in budding yeast. Yet, the toxicity, in particular the genotoxicity of the reactive metabolites formed from AFB1 remains unclear. Humans could be exposed to both AFB1 and benzo(a)pyrene (BaP) simultaneously, thus we were interested in their combined genotoxic effects subsequent to metabolic activation by CYP1A1. In this study, molecular docking of AFB1 to human CYP1A1 indicated that AFB1 is valid as a substrate. In the incubations with AFB1 in human CYP1A1-expressed microsomes, AFM1 as a marking metabolite of AFB1 was detected. Moreover, AFB1 induced micronucleus formation in a Chinese hamster V79-derived cell line and in a human lung epithelial BEAS-2B cell line, both expressing recombinant human CYP1A1, V79-hCYP1A1 and 2B-hCYP1A1 cells, respectively. Immunofluorescence of centromere protein B stained micronuclei was dominant in AFB1-treated BEAS-2B cells exposed to AFB1, suggesting an aneugenic effect. Moreover, AFB1 elevated the levels of ROS, 8-OHdG, AFB1-DNA adduct, and DNA breaks in 2B-hCYP1A1 cells, compared with those in the parental BEAS-2B cells. Meanwhile, AFB1 increased CYP1A1, RAD51, and γ-H2AX protein levels in 2B-hCYP1A1 cells, which were attenuated by the CYP1A1 inhibitor bergamottin. Co-exposure of AFB1 with BaP increased 8-OHdG, RAD51, and γ-H2AX levels (indicating DNA damage). In conclusion, AFB1 could be activated by human CYP1A1 for potent aneugenicity, which may be further enhanced by co-exposure to BaP.
摘要：
黄曲霉毒素B1（AFB1）是毒性最强的霉菌毒素，是一种经过证实的需要代谢激活的人类致癌物，已知细胞色素P450（CYP）1A2和3A4。先前的证据表明AFB1被在出芽酵母中表达的人重组CYP1A1激活。然而，毒性,特别是由AFB1形成的反应性代谢物的遗传毒性仍不清楚.人类可以同时暴露于AFB1和苯并（a）芘（BaP），因此,我们对CYP1A1代谢激活后它们的联合基因毒性作用感兴趣.在这项研究中,AFB1与人CYP1A1的分子对接表明AFB1是有效的底物。在人CYP1A1表达的微粒体中与AFB1孵育时，检测到AFB1的标记代谢物AFM1。此外，AFB1在中国仓鼠V79来源的细胞系和人肺上皮BEAS-2B细胞系中诱导微核形成，均表达重组人CYP1A1，V79-hCYP1A1和2B-hCYP1A1细胞，分别。着丝粒蛋白B染色的微核的免疫荧光在暴露于AFB1的AFB1处理的BEAS-2B细胞中占主导地位，表明有不良作用。此外，AFB1升高了ROS的水平，8-OHdG,AFB1-DNA加合物，2B-hCYP1A1细胞的DNA断裂,与亲本BEAS-2B细胞相比。同时,AFB1增加2B-hCYP1A1细胞中CYP1A1、RAD51和γ-H2AX蛋白水平,被CYP1A1抑制剂佛手蛋白减毒。AFB1与BaP的共同暴露增加了8-OHdG，RAD51和γ-H2AX水平(指示DNA损伤)。总之,AFB1可以被人CYP1A1激活，以获得有效的缺原性，通过共同暴露于BaP可以进一步增强。
