Objective:To observe the effects of low expressed Angiotensin-converting enzyme 2 ( Ace2) gene on senescence related signals of alveolar type Ⅱ epithelial cells in silicotic mice. Methods:In March 2022, 20 8-12W SPF male wild-type C57BL/6 mice and 20 Ace2 gene knockdown mice (Ace2 +/-, C57BL/6 background) were randomly divided into wild-type control group, Ace2 low expression group, wild-type silicosis group, Ace2 low expression silicosis group, with 10 mice in each group. In vitro MLE-12 cells were divided into control group, MLN-4760 (ACE2 inhibitor) group, SiO 2 group and SiO 2+MLN-4760 group. The expression of ACE2, collagen I (Col I), fibronectin 1 (Fn1), α-smooth muscle actin (α-SMA), phosphorylation-ataxia telangiectasia-mutated serine/threonine kinase (p-ATM), phosphorylation-ATM Rad3-related kinase (p-ATR), p-p53, p21 and p16 in mice and MLE-12 cells were detected by Western blotting. The expression and location of β-galactosidase were detected by immunofluorescence, β-galactosidase (SA-β-Gal) staining were used to detect the senescence of MLE-12 cells. Results:HE and VG staining results showed that typical silicon nodules with collagen deposition were formed in the lung of wild-type silicotic mice and Ace2 low expression silicotic mice. Immunofluorescence staining results showed that β-galactosidase was mainly located in alveolar type Ⅱ epithelial cells. Western blot results showed that, compared with wild-type silicosis group, the expression of Col I, α-SMA, p-ATM, p-ATR, p-p53, p21 and p16 in Ace2 low expression silicosis group were significantly up-regulated by 540.71%、26.58%、336.84%、139.58%、152.78%、120.10% and 994.63% ( P<0.05). In MLE-12 cells, results of western blot showed that compared with SiO 2 group, the expression levels of p-ATM, p-ATR, p-p53, p21 and p16 in SiO 2+MLN-4760 group were significantly up-regulated by 168.71%、750.78%、149.51%、554.26% and 254.07% ( P<0.05). Immunofluorescence staining results showed that compared with SiO 2 group, β-galactosidase positive cells were strongly up-regulated in SiO 2+MLN-4760 group, and SA-β-Gal staining results showed that compared with SiO 2 group, the number of senescent cells in SiO 2+MLN-4760 group increased by 63.18% ( P<0.05) . Conclusion:Low expression of Ace2 gene activated senescence related signals of alveolar type Ⅱ epithelial cells and promoted the progression of silicotic fibrosis in mice.

Objective:To observe the effects of low expressed Angiotensin-converting enzyme 2 ( Ace2) gene on senescence related signals of alveolar type Ⅱ epithelial cells in silicotic mice. Methods:In March 2022, 20 8-12W SPF male wild-type C57BL/6 mice and 20 Ace2 gene knockdown mice (Ace2 +/-, C57BL/6 background) were randomly divided into wild-type control group, Ace2 low expression group, wild-type silicosis group, Ace2 low expression silicosis group, with 10 mice in each group. In vitro MLE-12 cells were divided into control group, MLN-4760 (ACE2 inhibitor) group, SiO 2 group and SiO 2+MLN-4760 group. The expression of ACE2, collagen I (Col I), fibronectin 1 (Fn1), α-smooth muscle actin (α-SMA), phosphorylation-ataxia telangiectasia-mutated serine/threonine kinase (p-ATM), phosphorylation-ATM Rad3-related kinase (p-ATR), p-p53, p21 and p16 in mice and MLE-12 cells were detected by Western blotting. The expression and location of β-galactosidase were detected by immunofluorescence, β-galactosidase (SA-β-Gal) staining were used to detect the senescence of MLE-12 cells. Results:HE and VG staining results showed that typical silicon nodules with collagen deposition were formed in the lung of wild-type silicotic mice and Ace2 low expression silicotic mice. Immunofluorescence staining results showed that β-galactosidase was mainly located in alveolar type Ⅱ epithelial cells. Western blot results showed that, compared with wild-type silicosis group, the expression of Col I, α-SMA, p-ATM, p-ATR, p-p53, p21 and p16 in Ace2 low expression silicosis group were significantly up-regulated by 540.71%、26.58%、336.84%、139.58%、152.78%、120.10% and 994.63% ( P<0.05). In MLE-12 cells, results of western blot showed that compared with SiO 2 group, the expression levels of p-ATM, p-ATR, p-p53, p21 and p16 in SiO 2+MLN-4760 group were significantly up-regulated by 168.71%、750.78%、149.51%、554.26% and 254.07% ( P<0.05). Immunofluorescence staining results showed that compared with SiO 2 group, β-galactosidase positive cells were strongly up-regulated in SiO 2+MLN-4760 group, and SA-β-Gal staining results showed that compared with SiO 2 group, the number of senescent cells in SiO 2+MLN-4760 group increased by 63.18% ( P<0.05) . Conclusion:Low expression of Ace2 gene activated senescence related signals of alveolar type Ⅱ epithelial cells and promoted the progression of silicotic fibrosis in mice.

Background Pneumoconiosis is the most serious occupational disease in China, and silicosis accounts for about half of it. Any intervention effect of physical exercise as the key and core of lung rehabilitation training on silicosis is still unclear. Objective To explore potential intervention effect of physical exercise on silicotic mice. Methods Forty SPF C57BL/6 male mice were randomly divided into four groups, 10 in each group, including a control group, a physical exercise group, a silicosis model group, and a silicosis model + physical exercise intervention group. Silicotic mouse model was established by using 50 μL SiO₂ suspension (200 mg·mL⁻¹). A treadmill was used to prepare mice receiving physical exercise at 0° inclination, 12.3 m·min⁻¹, 60 min·d⁻¹, 5 d·week⁻¹ for 4 weeks. Pathological morphology of lung tissues was evaluated after hematoxylin-eosin (HE) staining; deposition of collagen in lung tissues was evaluated after Van Gieson (VG) staining; expression of p-protein kinase R-like endoplasmic reticulum kinase (PERK) was detected by immunofluorescence staining; expressions of cyclin dependent kinase inhibitors (p21) and p-p38 mitogen activated protein kinase (p38) were detected by immunohistochemistry. The protein expressions of endoplasmic reticulum stress signal factors [p-inositol-requiring enzyme-1α (p-IRE-1α), p-PERK, and p-eukaryotic initiation factor-2α (p-eIF-2α)], senescence signal factors (p-p53, p21, and p16), mitogen-activated protein kinase (MAPK) signal factors [p-p38, p-extracellular regulated protein kinases (p-ERK), and p-stress-activated protein kinase (p-JNK)] were detected by Western blotting. Results After designed acute SiO₂ exposure, the images of micro computed tomography (CT) showed high density shadows in lung tissues of the silicotic mice and less shadows in lung tissues of the physical exercise intervention mice. After HE staining, the proportions of silicotic nodule area in lung tissues was (18.67±3.89) % in the silicosis model group, and significantly decreased to (8.78±1.05) % in the silicosis model + physical exercise intervention group (P<0.05). After VG staining, the proportion of collagen fiber area of lung tissues was (10.37±2.18) % in the silicosis model group, and significantly decreased to (4.35±0.89) % in the silicosis model + physical exercise intervention group (P<0.05). The results of immunofluorescence staining showed that in the silicosis model group, the expression of p-PERK increased at the location of silicotic nodules, while in the silicotic model + physical exercise intervention group, the expression of p-PERK decreased. The immunohistochemical staining results showed that the expression of p21 and p-p38 increased in the lung tissues of the silicosis model group; the expression of p21 and p-p38 decreased in the lung tissues of the silicosis model + physical exercise intervention group. The results of Western blotting showed that compared with the control group, the expression levels of p-IRE-1α (0.11±0.03), p-PERK (0.95±0.40), p-eIF-2α (3.53±0.91), p-p53 (1.78±0.07), p21 (1.98±0.10), p16 (1.26±0.17), p-p38 (0.41±0.09), p-ERK (0.42±0.05), and p-JNK (3.20±1.23) of the silicosis model group were all upregulated (P<0.05). Compared with the silicosis model group, the expression levels of p-IRE-1α (0.03±0.01), p-PERK (0.31±0.12), p-eIF-2α (0.30±0.06), p-p53 (0.76±0.08), p21 (0.18±0.11), p16 (0.70±0.24), p-p38 (0.03±0.00), p-ERK (0.19±0.03), and p-JNK (0.46±0.21) of the silicosis model + physical exercise intervention group were downregulated (P<0.05). Conclusion Physical exercise may alleviate pulmonary fibrosis in silicotic mice, and inhibit abnormal expressions of endoplasmic reticulum stress signal, MAPK signal, and senescent signal.