| Objectives This research focused on the role of Nrf2/ARE signaling pathway on nm-Si O2’s toxicity and its influence. To provide data for the exposure risk assessment of population and investigate the toxicity of nm-Si O2, the oxidative damage induced by nm-Si O2 and the defense mechanism of Nrf2/ARE signaling pathway against the toxicity of nm-Si O2 were studied at either the cell or animal level.Methods nm-Si O2(10-20nm) and μm-Si O2(1-5μm) were characterized first, and then ①A549 cells were treated with different concentrations of nm-Si O2 or μm-Si O2, and cell viability and IC50 of Si O2 on A549 cells were determined; A549 cells were then treated with 15μg/ml nm-Si O2 orμm-Si O2, and morphological changes, apoptosis, cell cycle, membrane potential, SOD activity, ROS content and the expression of Nrf2/ARE signaling pathway related proteins were detected. ② A549-sh Nrf2 cell model were constructed and treated with 15μg/ml nm-Si O2, and cell viability, SOD activity, ROS contents,T-AOC, and the expression of Nrf2/ARE signal pathway related proteins were detected. ③ ICR mice and Nrf2-/- ICR mice were exposed with 10mg/kg nm-Si O2 for 14 days,and the body weight changes, the lung, liver and kidney coefficients were measured; the subcellular localization of nm-Si O2 in mouse lung and lung pathological changes were observed; the content of ROS, T-AOC, the content of 8-OHd G and the expression of Nrf2/ARE signalpathway-related proteins were also detected.Results Characterization of Si O2 showed that both nm-Si O2 and μm-Si O2 were qualified and finely disseminated, with no heavy metal impurities and reunion. ①A549 cells showed significant cytotoxic effect after nm-Si O2 exposure, with IC50 value of 25.063 g/ml; nm-Si O2(15 g/ml)increased the rate of apoptosis of A549, but not that of cell cycle arrest;intracellular ROS, SOD activity were increased, Nrf2/ARE signaling pathway was actived, while membrane potential was declined; μm-Si O2 showed no significant change in density, apoptosis rate, cell cycle arrest,SOD activity, membrane potential and Nrf2/ARE pathway, but increased intracellular ROS. ② After expose to the same concentration of nm-Si O2, A549-sh Nrf2 showed decreased cell viability, SOD activity and T-AOC, and increased ROS compared to normal A549 cells; Nrf2/ARE signaling pathway activation was blocked leading to decreased HO-1protein and upregulation of PERK protein. ③ After expose to 10mg/kg of nm-Si O2 with 14 days, The control group showed no lung deposition of nm-Si O2 compared to the exposed group; Nrf2-/- mice showed dreased body weight, Lung, liver coefficient, damaged lobe, increased ROS, 8-OHd G level, and decreased T-AOC; Nrf2-/- mice also showed Nrf2/ARE signaling pathway activation disruption, leading inhibition of HO-1 and upregulation of PERK.Conclusions The toxicity of nm-SiO2(10-20nm) is greater than μm-SiO2(1-5μm), which includes oxidative damage. While Nrf2/ARE signaling pathway activation may resist nm-Si O2 induced oxidative damage. Thus the activation of Nrf2/ARE pathway related protein may have potential for biomarker of nm-Si O2 exposure. |
