抄録
Azo dye precursors and some aromatic amine metabolites such as 3,3'-Dichlorobenzidine (DCB) produced through biotransformation of azo dye compounds have been shown to be carcinogenic, especially bladder cancer and lymphohematopoietic cancer. Epidemiological studies have suggested a relationship between workers long term exposed to DCB-based dyes in the dyeing industry and increased the risks of cancer development. In this study, the signaling pathways of DCB-induced cytotoxicity in HepG2 cells were investigated. We found that DCB could increase the expression level of γ-H2AX, a sensitive molecular marker of DNA double-strand breaks, in a dose-dependent manner and reach a maximum effect in cell treated with 10 μM of DCB. DCB at concentration ranges of 25-100 μM showed a 20~40% inhibition of HepG2 cell viability. Cell cycle analysis revealed G2/M phase arrest and accumulation of sub-G1 phase in HepG2 cells following 24 h exposure to DCB. We found Bcl-2/Bax ratio and mitochondrial membrane potential were decreased in cell treated with DCB. In addition, DCB also could enhance caspase-3 and caspase-9 activities in a dose-dependent manner. These results indicated that DCB could induce HepG2 cell apoptosis through a mitochondria/caspases pathway. To determine the signaling pathways of DCB-induced cytotoxicity in HepG2 cells, we found that DCB significantly increased the phosphorylation levels of JNK and ERK but not p38 in a time- and dose-dependent manner. To further determine whether ERK and JNK activation were required for DCB-induced apoptosis, the pharmacological inhibitors were used. We found JNK inhibitor, SP600125, could attenuate DCB-induced caspase-3 activity. Taken together, DCB could induce cell apoptosis in HepG2 cells via MAPK (JNK) and mitochondria/caspases pathways.
