Objective To investigate the oxidative damage of nuclear factor E2-related factor 2 (Nrf-2) gene silenced human immortalized epidermal cells induced by silica nanoparticles (nano-SiO2).
Methods RNA interference technology was used to construct a Nrf-2 gene silenced cell model of human immortalized epidermal cells (HaCaT) (HaCaT-SiRNA-Nrf2). Then the HaCaT and HaCaT-SiRNA-Nrf2 cells were exposed to different final concentrations (2.5, 5.0, and 10.0 mg/L) of nano-SiO2 (15 nm) for 24 h. Cellular reactive oxygen species (ROS), 8-hydroxy-2-deoxyguanosine (8-oHdG), malondialdehyde (MDA), total superoxide dismutase (T-SOD), and glutathione peroxidase (GSH-Px) were detected for each group. Western blot was used to detect total protein and nuclear protein expression levels of Nrf-2.
Results The cell viability of HaCaT cells decreased significantly in the 5.0 and 10.0 mg/L nano-SiO2 groups (P < 0.05), but 2.5, 5.0, and 10.0 mg/L nano-SiO2 decreased the viability of HaCaT-SiRNA-Nrf2 cells in a dose-dependent manner (r=-0.914, P < 0.05), and the viabilities of HaCaT-SiRNA-Nrf2 cells were significantly lower in all dose groups compare with those of HaCaT cells (P < 0.05). The cellular ROS, 8-oHdG, and MDA levels significantly increased (P < 0.05), while the T-SOD and GSH-Px levels decreased (P < 0.05) in a dose-independent manner for both HaCaT and HaCaT-SiRNA-Nrf2 cells. The variances of related indicators for HaCaTSiRNA-Nrf2 cells were statistically higher than the variances for HaCaT cells in the same concentration group (P < 0.05). The expression levels of total Nrf-2 protein in low-dose group and the expression levels of nuclear Nrf-2 protein in low- & medium-dose groups were significantly increased in normal HaCaT cells (P < 0.05), then decreased with the increase of exposure concentrations. Total Nrf-2 protein expression levels in HaCaT-SiRNA-Nrf2 cells also showed a similar trend described above, but there was no significant difference in nuclear Nrf-2 protein expression levels compare with the HaCaT control group (P > 0.05).
Conclusion Nano-SiO2 could induce oxidative damage in HaCaT cells at 5.0 mg/L. Nrf-2 gene silencing would increase the sensitivity of HaCaT cells exposed to nano-SiO2 by changing antioxidant defense capability.
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