Role of NRF2 on regulation of autophagy in arsenic-induced malignant transformation of HaCaT cells / 中华地方病学杂志

ABSTRACT

Objective:To explore the role of nuclear transcription factor erythrocyte line-2p45 (NF-E2) related factor-2 (NRF2) on autophagy during malignant transformation of immortalized human keratinocytes (HaCaT) induced by sodium arsenite (NaAsO 2). Methods:Using cell culture methods, long-term cultured HaCaT cells in DMEM high-glucose medium containing 0.0 (control group) and 1.0 μmol/L NaAsO 2 (arsenic-exposed group) to the 35th generation were used to construct a cell malignant transformation model, and 0, 1, 7, 14, 21, 28 and 35th generation cells of control group and arsenic-exposed group were collected during establishment of cell malignant transformation model. The NRF2 siRNA, phosphatidylinositol-3-hydroxykinase (PI3K) inhibitor LY294002 and mammalian target of rapamycin (mTOR) inhibitor Rapamycin were used to treat the 35th generation of malignant transformed HaCaT cells in arsenic-exposed group (T-HaCaT). The protein expressions of NRF2, PI3K-protein kinase B (Akt)-mTOR signaling pathway related indicators PI3K, Akt, mTOR, phosphorylated (p)-PI3K, p-Akt, p-mTOR, autophagy-related proteins p62, Beclin1, microtubule-associated protein-1 light chain (LC)3Ⅰ, and LC3Ⅱof different generations HaCaT cells in control group and arsenic-exposed group, and T-HaCaT cells of each treatment group were determined by Western blotting. Results:There were significant differences in the NRF2 protein and the ratios of p-PI3K/PI3K, p-Akt/Akt and p-mTOR/mTOR between different generations HaCaT cells in arsenic-exposed group ( F = 9.371, 16.035, 15.932, 27.739, P < 0.05), and they were higher than NRF2 protein and ratio of p-mTOR/ mTOR of the same generation in control group ( P < 0.05). Compared with HaCaT cells of the same generation, the expressions of NRF2, p-PI3K, p-Akt, p-mTOR and p62 proteins in T-HaCaT cells were significantly higher, Beclin1 protein expression and the ratio of LC3Ⅱ/LC3Ⅰ were significantly lower ( P < 0.05). The NRF2 silenced T-HaCaT cells had higher expression of Beclin1 and the ratio of LC3Ⅱ/LC3Ⅰ, and lower expressions of NRF2, p-mTOR and p62 than the corresponding control siRNA (Con siRNA) group ( P < 0.05). The T-HaCaT cells in LY294002 treatment group had higher expression of Beclin1 and the ratio of LC3Ⅱ/LC3Ⅰ, and lower expressions of NRF2, p-PI3K, p-Akt and p-mTOR proteins than the corresponding non-treatment group ( P < 0.05). The T-HaCaT cells in Rapamycin treatment group had higher expression of Beclin1 and the ratio of LC3Ⅱ/LC3Ⅰ, and lower expression of p-mTOR protein than the corresponding non-treatment group ( P < 0.05). Conclusions:During the arsenic-induced malignant transformation of HaCaT cells, NRF2 can act as a downstream factor of PI3K-Akt and an upstream factor of mTOR in PI3K-Akt-mTOR signaling pathway, an important regulatory mechanism of autophagy. This abnormal expression of autophagy may eventually lead to malignant transformation of cells.