Abstract:

Objective To investigate the mechanism by which Xiebai San regulates respiratory tract and intestinal mucosal immunity in rats with allergic asthma. Methods Forty male SD rats were randomly divided into four groups based on body weight: control group, model group, positive control group, and Xiebai San group. The model group, positive control group, and Xiebai San group were sensitized with ovalbumin to establish a rat model of allergic asthma. From day 21 (the aerosol challenge phase), each group received daily gavage interventions simultaneously: the positive control group was administered dexamethasone (0.068 mg/kg), the Xiebai San group received Xiebai San solution (2 g/mL, 11.3 mL/kg), while the control and model groups were given an equal volume of normal saline, once daily for 14 consecutive days. After euthanasia, lung and intestinal tissues were collected. Hematoxylin and eosin staining was used to observe histopathological changes. Transmission electron microscopy was employed to examine tissue ultrastructure. Immunohistochemistry was applied to detect the positive reaction areas of phosphatidyl-inositol 3-kinase (PI3K) and protein kinase B (Akt) proteins. Total protein and total RNA were extracted from lung and intestinal tissues, then the protein and mRNA expression levels of PI3K and Akt genes were detected by Western blotting and real-time quantitative PCR, respectively. Results Histopathological results showed alveolar emphysema accompanied by inflammatory cell infiltration, and intestinal mucosal injury with inflammatory cell infiltration in the model group as compared with the control group; the cellular structure of lung tissues was disrupted in the model group, with reduced organelles, while the ultrastructural lesions in the intestine were relatively mild. Compared with the model group, Xiebai San group exhibited milder pathological changes in lung tissues, with occasional alveolar wall damage and a small amount of inflammatory cell infiltration; the intestinal mucosal structure was improved, glands were arranged regularly, and pathological changes such as tissue loosening and inflammatory infiltration were alleviated; the cellular structure of lung tissues was relatively intact with reduced severity of lesions, and no ultrastructural pathological changes were observed in intestinal tissues. Immunohistochemistry and Western blotting results showed that compared with the control group, the specific positive reaction areas of PI3K and Akt in lung and intestinal tissues were significantly increased in the model group (all P<0.001); meanwhile, the protein expression levels of PI3K and Akt were significantly upregulated (all P<0.05). Compared with the model group, the positive area of Akt protein in lung tissue was significantly reduced in the Xiebai San group (P<0.001), and the positive area of PI3K in intestinal tissue was also significantly decreased (P<0.000 1). Additionally, the protein expression levels of PI3K and Akt in lung and intestinal tissues were significantly downregulated (all P<0.01). Real-time quantitative PCR results showed that compared with the control group, the mRNA expression levels of PI3K and Akt genes in lung and intestinal tissues were significantly elevated in the model group (all P<0.05). Compared with the model group, the mRNA expression levels of PI3K and Akt genes in lung and intestinal tissues were significantly reduced in the Xiebai San group (all P<0.05). Conclusion Xiebai San exerts protective effects on rats with allergic asthma by inhibiting the expression of key nucleic acids and proteins in the PI3K-Akt signaling pathway in lung and intestinal tissues, improving the morphological structure of lung tissue, and maintaining intestinal mucosal integrity, and regulating intestinal mucosal immune function.