Carbamazepine (CBZ, an
antiepileptic) is metabolized by multiple CYP
enzymes to its
epoxide and
hydroxides; however, whether it is genotoxic remains unclear. In this study, molecular docking (CBZ to CYPs) and cytogenotoxic toxicity assays were employed to investigate the activation of CBZ for mutagenic effects, in various mammalian cell models. Docking results indicated that CBZ was valid as a substrate of human
CYP2B6 and 2E1, while not for
CYP1A1, 1A2, 1B1 or 3A4. In the Chinese hamster (V79) cell line and its derivatives genetically engineered for the expression of human
CYP1A1, 1A2, 1B1, 2E1 or 3A4 CBZ (2.5 ~ 40 μM) did not induce micronucleus, while in human CYP2B6-expressing cells CBZ significantly induced micronucleus formation. In a human
hepatoma C3A cell line, which endogenously expressed
CYP2B6 twofold higher than in HepG2 cells, CBZ induced micronucleus potently, which was blocked by
1-aminobenzotriazole (inhibitor of CYPs) and
ticlopidine (specific
CYP2B6 inhibitor). In HepG2 cells CBZ did not induce micronucleus; however, pretreatment of the cells with CICTO (
CYP2B6 inducer) led to micronucleus formation by CBZ, while
rifampicin (
CYP3A4 inducer) or
PCB126 (CYP1A inducer) did not change the negative results. Immunofluorescent assay showed that CBZ selectively induced centromere-free micronucleus. Moreover, CBZ induced double-strand DNA breaks (γ-H2AX elevation, by Western blot) and PIG-A gene mutations (by flowcytometry) in C3A (threshold being 5 μM, lower than its therapeutic serum concentrations, 17 ~ 51 μM), with no effects in HepG2 cells. Clearly, CBZ may induce clastogenesis and gene mutations at its therapeutic concentrations, human
CYP2B6 being a major activating
enzyme.