[Effect of Maxing Kugan Decoction on intestinal flora in bleomycin-induced idiopathic pulmonary fibrosis rats].

Based on the "lung-gut axis" theory, this study explored the effects of Maxing Kugan Decoction(Mxd) on inflammation and intestinal barrier and flora in rats with bleomycin-induced idiopathic pulmonary fibrosis(IPF). A total of 24 male SD rats were randomly divided into four groups: a control group, a model group, a positive control group and an Mxd treatment group, with 6 rats in each group. After 5 days of quarantine and adaptive feeding, the IPF pathological model was induced by intratracheal instillation of bleomycin under laryngoscopic assistance in the model group, positive control group, and Mxd treatment group. Gastric gavage was initiated after successful modeling, and all SD rats were sacrificed on the 15th day post gavage. HE staining and Masson staining were used to observe histopathological changes of lung tissue, while HE staining was adopted to evaluate jejunal pathological changes. Enzyme-linked immunosorbent assay(ELISA) was performed to detect the serum levels of interleukin-1β(IL-1β), interleukin-6(IL-6), and tumor necrosis factor-α(TNF-α) in rats. AB-PAS staining was employed to determine the number of goblet cells in jejunal mucosal tissue. Immunofluorescence assay was used to detect the expression of zonula occludens-1(ZO-1) and occludin in rat jejunum, and 16S rDNA sequencing was conducted to analyze the intestinal microbiome of all rats. The results showed that the model group exhibited severe damage to jejunal mucosa and lung tissue accompanied by massive inflammatory cell infiltration, while the two treatment groups demonstrated partial structural defects with a small amount of inflammatory cell infiltration in the lungs and jejuna of rats. Compared with the control group, the model group showed significantly decreased body weight, number of goblet cells, and expression of ZO-1 and occludin proteins(P<0.01), while these indicators were notably increased after intervention in the two treatment groups(P<0.05 or P<0.01). According to 16S rDNA sequencing results, Mxd could regulate the richness and diversity of intestinal flora in rats. KEGG pathway analysis indicated that Mxd regulated pathways such as oxidative phosphorylation, amino sugar, and nucleotide sugar metabolism of intestinal flora in rats. In conclusion, the alteration of intestinal microbiome may be one of the potential mechanisms underlying the therapeutic effect of Mxd on IPF. Mxd can regulate the structure of intestinal microbiome, increase the abundance of beneficial bacteria, and reduce the number of harmful bacteria, as well as protect intestinal barrier and inhibit inflammatory response.