[Effects of Qingzao Jiufei Decoction on bleomycin-induced pulmonary fibrosis via JAK1/STAT6 signaling pathway-mediated polarization of M2 macrophages].

This study investigated the effects of Qingzao Jiufei Decoction on M2 macrophage polarization in bleomycin(BLM)-induced pulmonary fibrosis(PF) mice via the janus kinase 1(JAK1)/signal transducer and activator of transcription 6(STAT6) signaling pathway. Sixty C57BL/BJ mice were randomly divided into normal group, model group, pirfenidone group(200 mg·kg~(-1)), and low-, medium-, and high-dose Qingzao Jiufei Decoction groups(4.9, 9.8, and 19.6 g·kg~(-1)). The PF model was established in the model and treatment groups by intratracheal instillation of BLM(5 mg·kg~(-1)). Mice in each group were administered the same volume of normal saline or the corresponding dose of Qingzao Jiufei Decoction by gavage for 21 consecutive days. After 21 days, blood gas analysis was performed. ELISA was used to detect the levels of interleukin-4(IL-4), interleukin-13(IL-13), arginase-1(Arg-1), transforming growth factor-β(TGF-β), and interleukin-10(IL-10) in bronchoalveolar lavage fluid(BALF). HE and Masson staining were performed to observe pathological changes in lung tissue and for histopathological scoring. Immunofluorescence staining was used to detect the expression of α-smooth muscle actin(α-SMA), type Ⅰ collagen(COL-1), the macrophage marker CD11b, and the M2 macrophage marker CD206. Western blot and RT-qPCR were used to detect the expression of JAK1/STAT6 signaling pathway-related proteins and mRNA, as well as M2 macrophage-related proteins and mRNA, in lung tissue. The results showed that, compared with the normal group, the levels of IL-4, IL-13, Arg-1, TGF-β, and IL-10 in BALF were significantly increased in the model group(P<0.01). Histopathological staining revealed extensive inflammatory cell infiltration and increased collagen fiber deposition in the alveolar septa, accompanied by significantly increased Szapiel alveolitis scores and Ashcroft fibrosis scores(P<0.01). Immunofluorescence staining showed significantly increased fluorescence intensity of α-SMA, COL-1, CD11b, and CD206. The mRNA expression levels of JAK1, STAT6, CD206, and Arg-1, as well as the protein expression levels of phosphorylated(p)-JAK1, p-STAT6, CD206, and Arg-1 in lung tissue, were significantly increased(P<0.01). Compared with the model group, treatment with Qingzao Jiufei Decoction significantly reduced the levels of IL-4, IL-13, Arg-1, TGF-β, and IL-10 in BALF(P<0.05, P<0.01), markedly improved pathological changes in lung tissue, and downregulated the expression of α-SMA, COL-1, CD11b, and CD206 detected by immunofluorescence staining. In addition, Qingzao Jiufei Decoction significantly downregulated the mRNA expression of JAK1, STAT6, CD206, and Arg-1, as well as the protein expression of p-JAK1, p-STAT6, CD206, and Arg-1 in lung tissue(P<0.05, P<0.01). In conclusion, Qingzao Jiufei Decoction exerts a protective effect against BLM-induced PF in mice, and its mechanism may be related to inhibition of M2 macrophage polarization through regulation of the JAK1/STAT6 signaling pathway.