LYU Da, YANG Huinan, LIU Chuncheng, WANG Le, ZHAO Hongyu, CAI Lu. Responses of inflammatory factors and oxidative stress factors and expressions of key genes associated with pulmonary fibrosis in silica-exposed mice[J]. Journal of Environmental and Occupational Medicine, 2021, 38(10): 1150-1155. DOI: 10.13213/j.cnki.jeom.2021.21061
Citation: LYU Da, YANG Huinan, LIU Chuncheng, WANG Le, ZHAO Hongyu, CAI Lu. Responses of inflammatory factors and oxidative stress factors and expressions of key genes associated with pulmonary fibrosis in silica-exposed mice[J]. Journal of Environmental and Occupational Medicine, 2021, 38(10): 1150-1155. DOI: 10.13213/j.cnki.jeom.2021.21061

Responses of inflammatory factors and oxidative stress factors and expressions of key genes associated with pulmonary fibrosis in silica-exposed mice

  • Background It is well known that long-term deposition of silicon dioxide (SiO2) in lung tissues can induce inflammation and fibrosis and result in pneumoconiosis, but pathogenesis of pneumoconiosis remains elusive.
    Objective This experiment investigates the effect of SiO2 on pulmonary fibrosis in mice.
    Methods Thirty-five C57BL/6 mice were randomly divided into four groups: a blank control group (5 mice), a normal saline control group (10 mice), a 20 g·L-1 SiO2 group (10 mice), and a 60 g·L-1 SiO2 group (10 mice). The mice were exposed by intratracheal instillation of SiO2 suspension on day 0 and day 14, and the lung tissue and serum samples were collected on day 28 and day 56 after silica or saline instillation. HE sections of lung tissues were observed under optical microscope (10×magnification). ELISA was used to detect the levels of three inflammatory cytokines including fibroblast growth factor (FGF), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) in lung tissues, and three oxidative stress factors including superoxide dismutase (SOD), reactive oxygen species (ROS), and malondialdehyde (MDA) in serum. The distributions of collagen fibers in Masson-stained sections were observed under microscope (10×magnification). The level of hydroxyproline (HYP) in lung tissues was detected with a spectrophotometer. The expressions of Co/1a2 and α-SMA mRNA in lung tissues were measured by real-time PCR.
    Results The results of HE staining showed that there were obvious infiltration of inflammatory cells and some fibrous nodules in the two SiO2 groups compared with the normal saline control group. The detection results of inflammatory factors indicated that on day 56, the levels of TGF-β in lung tissues of the 20 g·L-1 SiO2 group and the 60 g·L-1 SiO2 group were 3.42 and 3.62 ng·g-1, the levels of FGF were 15.20 and 19.78 ng·g-1, the levels of TNF-α were 9.02 and 11.30 ng·g-1, respectively, all higher than those of the normal saline group (P < 0.01). The detection results of oxidative stress factors showed that the levels of MDA in serum of the 20 g·L-1 SiO2 group on day 28 and day 56 were 0.23 and 0.26 μmol·L-1, the levels of ROS were both 11 U·L-1, and the levels of SOD were 0.43 and 0.44 μg·L-1, respectively; in the 60g·L-1 SiO2 group on day 28 and day 56, the levels of MDA were 0.28 and 0.34μmol·L-1, the levels of ROS were 13 and 14U·L-1, and the levels of SOD were 0.38 and 0.36 μg·L-1, respectively. The serum levels of MDA and ROS were higher and the level of SOD was lower in the two SiO2 groups than in the normal saline control group (P < 0.01). The levels of HYP on day 28 and day 56 were 0.25 and 0.28 mg·g-1 in the 20 g·L-1 SiO2 group, and 0.32 and 0.43 mg·g-1 in the 60 g·L-1 SiO2 group, respectively, all higher than those in the normal saline control group (P < 0.01). Compared with the normal saline control group, the Masson staining sections demonstrated that the collagen areas in lung tissues of the mice exposed to SiO2 on day 28 and day 56 were obviously increased. The relative expression levels of Co/1a2 mRNA in the 60 g·L-1 SiO2 group on day 28 and day 56 were 1.62 and 3.08 times higher than those in the normal saline control group, respectively; the relative expression levels of α-SMA mRNA were 2.05 and 3.34 times higher, respectively (P < 0.01).
    Conclusion There exist combined effects of inflammation, oxidative stress, and collagen deposition in lung tissues during silica-induced pulmonary fibrosis in mice.
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