Role of Nrf2 regulating apoptosis in arsenite induced malignant transformation of HBE cells / 中华地方病学杂志

ABSTRACT

Objective:To observe the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in regulating apoptosis during malignant transformation of human bronchial epithelial cells (HBE cells) induced by sodium arsenite (NaAsO 2). Methods:HBE cells were treated with 0.0 and 1.0 μmol/L NaAsO 2, which were control group and arsenic exposed group respectively. HBE cells were treated with 1.0 μmol/L NaAsO 2 for 43 passages to establish a malignant transformation model. The dynamic changes of indexes in different passages (0, 1st, 8th, 15th, 22nd, 29th, 36th, and 43rd) after exposure to NaAsO 2 were monitored, including the apoptosis rate detected by flow cytometry and apoptosis-related proteins and Nrf2 protein detected by Western blotting. Nrf2 siRNA was transfected into malignant transformed HBE cells (T-HBE cells) to silence Nrf2. The silencing effect of Nrf2 protein was verified. And, the apoptosis rate and apoptosis-related proteins were detected. Results:With the increase of arsenic exposure, the apoptosis rates of HBE cells decreased (0, 1, 8, 15, 22, 29, 36 and 43 passages were 0.370 ± 0.029, 0.443 ± 0.069, 0.357 ± 0.046, 0.330 ± 0.016, 0.273 ± 0.050, 0.160 ± 0.024, 0.110 ± 0.022, 0.097 ± 0.012, respectively, Ftrend = 22.981, P < 0.05). Compared with the 0 passage cells, the apoptosis rates of the 22nd, 29th, 36th and 43rd passages in the arsenite group were lower. The differences between them were statistically significant ( P < 0.05). With the increase of arsenic exposure, the expressions of pro-apoptotic proteins caspase-3, cleaved-caspase-3, C/EBP-homologous protein (CHOP) and B-cell lymphoma-2 (Bcl-2) associated X protein (Bax) showed downward trends ( Ftrend = 22.356, 3.738, 6.130, 8.061, P < 0.05), while the anti-apoptotic proteins myeloid cell leukemia 1 protein (Mcl-1) and Bcl-2 showed upward trends ( Ftrend = 58.201, 7.691, P < 0.05). Compared with the 0 passage and the control group of the same passage, from the 22nd passage of caspase-3, cleaved-caspase-3, from the 15th passage of CHOP, Mcl-1, and Bcl-2, from the 29th passage of Bax in the arsenite group, the differences of protein were statistically significant ( P < 0.05). However, there were no significant differences in caspase-8, cleaved-caspase-8, caspase-12 and cleaved-caspase-12 protein expressions in the arsenic group ( P > 0.05). Compared with the 0 passage and the control group of the same passage, from the 8th passage of Nrf2 proteins in the arsenite group, the differences of expressions were statistically significant ( P < 0.05). Compared with T-HBE cells transfected with Con siRNA (control), the apoptosis rate of T-HBE cells transfected with Nrf2 siRNA was higher ( P < 0.05). Compared with T-HBE cells transfected with Con siRNA, the expression levels of Nrf2, Bcl-2 and Mcl-1 in T-HBE cells transfected with Nrf2 siRNA were lower ( P < 0.05), while the expression levels of cleaved-caspase-3/caspase-3, caspase-3, cleaved-caspase-3, CHOP, and Bax were higher ( P < 0.05). Conclusion:Nrf2 may regulate mitochondrial apoptotic pathway through Bcl-2, Mcl-1 and Bax, and endoplasmic reticulum apoptotic pathway through CHOP, so as to inhibit the apoptosis of HBE cells and participate in the process of malignant transformation of HBE cells induced by NaAsO 2.