title: Cytochrome P450 2A13 enhances the sensitivity of human bronchial epithelial cells to aflatoxin B1-induced DNA damage.
abstract: Cytochrome P450 2A13 (CYP2A13) mainly expresses in human respiratory system and mediates the metabolic activation of aflatoxin B1 (AFB1). Our previous study suggested that CYP2A13 could increase the cytotoxic and apoptotic effects of AFB1 in immortalized human bronchial epithelial cells (BEAS-2B). However, the role of CYP2A13 in AFB1-induced DNA damage is unclear. Using BEAS-2B cells that stably express CYP2A13 (B-2A13), CYP1A2 (B-1A2), and CYP2A6 (B-2A6), we compared their effects in AFB1-induced DNA adducts, DNA damage, and cell cycle changes. BEAS-2B cells that were transfected with vector (B-vector) were used as a control. The results showed that AFB1 (5-80 nM) dose- and time-dependently induced DNA damage in B-2A13 cells. AFB1 at 10 and 80nM significantly augmented this effect in B-2A13 and B-1A2 cells, respectively. B-2A6 cells showed no obvious DNA damage, similar to B-vector cells and the vehicle control. Similarly, compared with B-vector, B-1A2 or B-2A6 cells, B-2A13 cells showed more sensitivity in AFB1-induced γH2AX expression, DNA adduct 8-hydroxy-deoxyguanosine formation, and S-phase cell-cycle arrest. Furthermore, AFB1 activated the proteins related to DNA damage responses, such as ATM, ATR, Chk2, p53, BRCA1, and H2AX, rather than the proteins related to DNA repair. These effects could be almost completely inhibited by 100 μM nicotine (a substrate of CYP2A13) or 1 μM 8-methoxypsoralen (8-MOP; an inhibitor of CYP enzyme). Collectively, these findings suggest that CYP2A13 plays an important role in low-concentration AFB1-induced DNA damage, possibly linking environmental airborne AFB1 to genetic injury in human respiratory system.
authors.affiliation: Key Lab of Modern Toxicology of Ministry of Education, School of Public Health, Nanjing Medical University, 818 East Tiangyuan Rd., Nanjing 211166, China.
authors.forename: Xuejiao
authors.initials: X
authors.lastname: Yang
authors.forename: Zhan
authors.initials: Z
authors.lastname: Zhang
authors.forename: Xichen
authors.initials: X
authors.lastname: Wang
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Zhang
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Lu
authors.forename: Shou-Lin
authors.initials: SL
authors.lastname: Wang
mesh_terms: D016604:Aflatoxin B1 / Q000378:metabolism / Q000633:toxicity*; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001980:Bronchi / Q000187:drug effects* / Q000201:enzymology; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D018736:DNA Adducts / Q000378:metabolism*; D004249:DNA Damage; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D015151:Immunoblotting; D008730:Methoxsalen / Q000494:pharmacology; D018613:Microscopy, Confocal; D009538:Nicotine / Q000494:pharmacology
chemical_list: D018736:DNA Adducts; C072611:aflatoxin B1-DNA adduct; D009538:Nicotine; D016604:Aflatoxin B1; D001189:Aryl Hydrocarbon Hydroxylases; C414206:CYP2A13 protein, human; D008730:Methoxsalen