Therapeutic Effects and Molecular Mechanism of Banxia Xiexin Decoction on Intestinal Mucosal Barrier Function in Sepsis

Aim: This study aims to investigate therapeutic effects and involved molecular mechanisms of Banxia Xiexin Decoction (BXD) in reducing gastrointestinal complications associated with sepsis. Background: Sepsis is a common critical illness that threatens patient survival and costs society a lot. This syndrome is a prominent cause of death in ICUs due to its high mortality rate, which exceeds 30% after 28 days and 35.5% after 90 days. Sepsis remains a major medical challenge despite a 20%–30% drop in fatality rates due to a better understanding of its physiological and pathological features and better therapeutic techniques. There is no pharmacological treatment for sepsis, highlighting the need for more study. Objective: We explored the protecting effects of BXD on intestinal functionality in sepsis by investigating its roles in the regulation of mitochondrial autophagy and mitochondrial functioning in small intestinal epithelial cells, primarily via the PINK1/Parkin signaling pathway. Method: We established a cell model of Human Intestinal Epithelial Cell (HIEC) injury induced by lipopolysaccharide (LPS) and a cecal ligation and perforation (CLP) sepsis model in Sprague Dawley (SD) rats. The cell model and animal model of sepsis were divided into control groups and different treatment groups that received different doses of BXD. We utilized HIECs with PINK1 knockdown to assess BXD';s protective effects on the sepsis intestinal barrier and its regulatory mechanism both on the PINK1/Parkin signaling pathway, exploring both its facilitative and inhibitory effects. ELISA method was used to measure inflammatory markers IL-6, IL-1β, and intestinal injury-related molecules IFABP and DAO. Pathological assessments were performed with H&E staining, and tight junction proteins ZO-1 and Occludin were detected using immunohistochemical staining. Mitochondrial membrane protein TOM20 was detected through immunofluorescence staining. Mitochondrial membrane potential and autophagy were assessed via flow cytometry. The expression levels of PINK1, Park, LC3, and p62 proteins and mRNA, integral to the PINK1/Parkin autophagy pathway, were evaluated using Western Blot and RT-PCR. result: BXD treatment significantly reduced serum DAO, IFABP, and DA levels, compared to the control group. The BXD treatment group exhibited a more substantial and sustained decrease in IL-6 and IL-1β levels than the control group. The BXD treatment alleviated damage to the intestinal mucosa indicated by reduced DAO and IFABP levels. Moreover, BXD improved the intestinal mucosal barrier function through restoration of tight junction proteins ZO-1 and Occludin. BXD treatment effectively reduced the serum levels of IL-6 and IL-1β, thus preventing further inflammation and lessening intestinal injury in septic rats. The BXD treatment increased the TOM20 level, which prevented the decrease of mitochondrial membrane potential, and exhibited a protective effect on the mitochondria of intestinal epithelial cells. BXD upregulated the PINK1 molecular level, leading to the upregulation of PINK1/Parkin mitochondrial autophagy pathway. Mitochondrial autophagy could clear damaged mitochondria, alleviate oxidative stress, maintain mitochondrial homeostasis, and promote the survival and functional realization of intestinal epithelial cells. Results: Compared to the control group, BXD therapy significantly lowered serum DAO, IFABP, and DA. The BXD therapy group showed a more significant and sustained drop in IL-6 and IL-1β levels than the control group. The BXD therapy reduced intestinal mucosa damage by lowering DAO and IFABP. BXD also restored tight junction proteins ZO-1 and Occludin, improving intestinal mucosal barrier function. In septic rats, BXD therapy lowered serum IL-6 and IL-1β levels, avoiding inflammation and reducing intestinal damage. BXD enhanced TOM20, which protected intestinal epithelial cell mitochondria against decreasing mitochondrial membrane potential. BXD increased the PINK1/Parkin mitochondrial autophagy pathway at the molecular level. Mitochondrial autophagy can repair mitochondria, reduce oxidative stress, maintain mitochondrial homeostasis, and help intestinal epithelial cells survive and function. Conclusion: BXD could improve intestinal mucosal damage and systemic inflammation caused by sepsis. BXD mainly promotes the PINK1/Parkin mitophagy pathway by upregulating PINK1 protein.