Effect of silicon dioxide exposure on airway surface microenvironment and NEK7/NLPR3 inflammasome in rats
HANG Wenlu1,2, WU Qi3, LI Wanjun3, BO Yun3, ZHOU Xianmei2,4
1. Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu 221000, China; 2. Nanjing University of Traditional Chinese Medicine, Nanjing, Jiangsu 210023, China; 3. Xuzhou Medical University, Xuzhou, Jiangsu 221000, China; 4. Jiangsu Province Hospital of Chinese Medicine, Affiliated Hospital of Nanjing University of Traditional Chinese Medicine, Nanjing, Jiangsu 210023, China
Abstract：Objective To examine the effect of SiO2 exposure on the airway surface microenvironment and NIMA-related kinase 7 (NEK7)/nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome in rats. Methods Twenty-four specific pathogen-free male rats of the SD strain were randomly divided into the control group and the model group, of 12 rats in each group. Rats in the model group were given SiO2 suspensions through disposable tracheal intubation perfusion to model silicosis in rats, while rats in the control group was perfused with the same amount of physiological saline. The pH value and glucose level were measured in the rat bronchoalveolar lavage fluid (BALF) 14 and 28 days after modeling. Lung tissues were stained with HE and Masson and the distribution of inflammatory cells and the deposition of pulmonary interstitial collagens were observed in lung tissues under a light microscope. The expression of transforming growth factor β1 (TGF-β1), collagen type Ⅰ(ColⅠ), collagen type Ⅲ (Col Ⅲ), interleukin-1β (IL-1β), NLRP3, N-terminal domain of Gasdermin D (GSDMD-NT), caspase-1, and NEK7 was quantified in lung specimens using immunohistochemistry. Results Lower pH values were measured in rat BALF in the model group than in the control group 14 [(6.38±0.05) vs. (6.68±0.08), P<0.05] and 28 days after modeling [(6.63±0.14) vs. (6.86±0.05), P<0.05], while higher glucose levels were seen in the model group than in the control group 14 [(0.39±0.06) vs. (0.31±0.04) mg/dL, P<0.05] and 28 days after modeling [(0.39±0.08) vs. (0.31±0.06) mg/dL, P<0.05]. HE and Masson staining showed mild to moderate alveolitis and pulmonary fibrosis in rats 14 days post-exposure to SiO2, and showed moderate to severe alveolitis and pulmonary fibrosis 28 days post-exposure. Immunohistochemistry detected higher TGF-β1, ColⅠ, Col Ⅲ, IL-1β, NLRP3, GSDMD-NT, caspase-1 and NEK7 expression in rat lung tissues in the model group than in the control group (all P<0.05). Conclusions SiO2 exposure may cause changes in rat airway surface microenvironment, including BALF acidification and elevated glucose. Pyroptosis induced by activation of NEK7-associated NLRP3 inflammasome may be an important mechanism of pulmonary fibrosis caused by silicosis.
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