Objective A mouse silicosis model was constructed by injecting silicon dioxide(SiO2)particles into the trachea to explore the effect and mechanism of Cordyceps cicadae polysaccharides(CCP)on ameliorating pulmonary fibrosis in silicosis mice.Methods In May 2023,CCP were extracted and isolated,the monosaccharide composition and functional group composition were analyzed by high performance liquid chromatography and Fourier transform infrared spectroscopy.C57BU6J mice were injected with 50 μl 50 mg/ml SiO2 suspension to construct silicosis mouse model,which were then randomly divided into model group,CCP intervention groups[low dose group(LCCP group),medium dose group(MCCP group)and high dose group(HCCP group)],the control group was administered by physiological saline,8 mice in each group.Mice in the CCP intervention groups received oral gavage administration once daily with CCP solution(100,200 and 400 mg/kg),while control group and model group received physiological saline,lasted for 30 days.The body weight of mice was recorded and the lung coefficient was calculated.The pathomorphological changes of mouse lung tissue were determined by HE and Masson staining.The contents of fibrosis indexes[hydroxyproline acid(HYP),connective tissue growth factor(CTGF)and matrix metallopeptidase 2(MMP-2)]of lung tissue and the pro-inflammatory factors[tumor necrosis factor-alpha(TNF-α),interleukin-1 beta(IL-1β)and interleukin-6(IL-6)]of lung tissue and alveolar lavage fluid were determined by ELISA.The expression level of Collagen Ⅰwas determined by immunohistochemistry.The relative protein expression levels of transforming growth factor-β1(TGF-β1),P-Smad2,α-smooth muscle actin(α-SMA),Toll-like receptor 4(TLR4),nuclear factor kappa-B p65(NF-κBp65)and myeloid differentiation primary response gene 88(MyD88)in lung tissue were determined by Western blot.Results The total sugar content of the CCP was 86.78％,composed of D-mannose,D-rhamnose,D-glucose and D-galactose,with a molar ratio of 12.71∶1.53∶1.00∶12.64.The infrared spectrum indicated the characteristic groups of its polysaccharides.Compared with the control group,the body weight of mice in the model group was decreased,lung coefficient was increased,the contents of HYP,CTGF and MMP-2 in lung tissue were increased,and the contents of TNF-α,IL-1β and IL-6 in lung tissue and alveolar lavage fluid were increased(P＜0.05).The mice lung showed massive inflammatory cell infiltration and collagen fiber deposition,and the silicosis fibrosis was severe.The expression of Collagen Ⅰ in lung tissue of model group was increased,and the proteins expression levels of TGF-β1,P-Smad2/Smad2,α-SMA,TLR4,NF-κBp65 and MyD88 were increased in mouse lung tissue(P＜0.05).Compared with the model group,the body weights of mice in the MCCP and HCCP groups were increased,the lung coefficients were decreased,the contents of HYP,CTGF and MMP-2 in lung tissue were decreased,and the contents of TNF-α,IL-1β and IL-6 in lung tissue and alveolar lavage fluid were decreased(P＜0.05).The inflammatory cell infiltration in the lung was reduced,and the degree of fibrosis was improved to varying degrees.The expression level of Collagen Ⅰ was down-regulated in the lung tissue of MCCP and HCCP groups,and the protein expression levels of TGF-β1,P-Smad2/Smad2,α-SMA,TLR4,NF-κBp65 and MyD88 were decreased in lung tissue(P＜0.05).Conclusion The CCP could reduce the levels of fibrosis-related indicators and pro-inflammatory factors in lung tissue,ameliorating mouse lung inflammation and silicosis fibrosis caused by SiO2 particles by inhibiting the activation of TGF-β1/Smad pathway and TLR4/nuclear factor kappa-B(NF-κB)pathway.
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