Yangqing Chenfei formula(养清尘肺方)alleviates crystalline silica induced pulmonary inflammation and fibrosis by suppressing macrophage polarization

OBJECTIVE:To explore the underlying mechanisms of the effects of Yangqing Chenfei formula(养清尘肺方,YCF) on inflammation and fibrosis in silicosis via inhibition of macrophage polarization.METHODS:A silicotic rat model was established via a single intratracheal instillation of silica particles on the first day of week 0.Subsequently,YCF was administered intragastrically to silicotic rats during weeks 0-2 and 5-8 twice daily.The mouse-derived alveolar macrophage cell line was used to investigate the mechanisms of YCF in M1/M2 polarization.RESULTS:YCF treatment effectively inhibited lung pathological changes,including inflammatory cell infiltration and tissue damage,and increased the forced expiratory volume in the first 0.3 s,functional residual capacity,and maximal mid-expiratory flow in weeks 2 and 8.Furthermore,the treatment improved lung functions by upregulating tidal volume,pause increase,and expiratory flow at 50% tidal volume from weeks 5 to 8.Moreover,YCF could significantly suppressed the progression of inflammation and fibrosis,by reducing the levels of inflammatory cytokines,as well as collagen-Ⅰ and Ⅲ.YCF treatment also decreased the numbers of macrophages and M1/M2 macrophages and the level of transforming growth factor-β(TGF-β).Additionally,YCF5,the effective substance in YCF,decreased lipopolysaccharide and interferon-γ-induced M1 macrophage polarization in a concentration-dependent manner.The mechanism of anti-M1 polarization might be related to a decrease in extracellular signal-regulated kinase,c-JUN N-terminal kinase,P38,and P65 phosphorylation.Furthermore,YCF5 inhibited interleukin-4-induced M2 macrophages by decreasing the protein and m RNA expressions of arginase-1 and CD206 as well as the levels of profibrotic factors,such as TGF-β and connective tissue growth factor.The mechanisms underlying the anti-M2 polarization of YCF5 were primarily associated with the inhibition of the nuclear translocation of phosphorylated signal transducer and activator of transcription 6(pSTAT6).CONCLUSION:YCF significantly inhibits inflammation and fibrosis in silicotic rats probably via the suppression of M1/M2 macrophage polarization mediated by the inhibition of mitogen-activated protein kinase and nuclear factor kappa B signaling pathways and Janus kinase/STAT6 pathways.