Paeoniae Decoction restores intestinal barrier dysfunction by promoting the interaction between ILC3 and gut flora

Background: Intestinal barrier dysfunction is a significant contributor to the recurrence and refractory of ulcerative colitis (UC). Promoting the interaction between group 3 innate lymphoid cells (ILC3s) and gut flora is a valuable strategy for mucosal repair. Paeoniae decoction (PD) is a compound commonly used in clinical treatment of UC, but its exact mechanism remains unclear. Purpose: We aimed to investigate the protective effect of PD on intestinal mucosal injury induced by dextran sulfate sodium (DSS) in chronic colitis, as well as to elucidate its potential mechanism. Methods: C57BL/6 mice were induced with chronic colitis by 2 % DSS and divided into four groups: control group, model group, PD low dose (4 g/kg), and high dose (8 g/kg) group. The effectiveness of PD in treating chronic colitis mice was evaluated based on changes in body weight, colon length, colon pathological tissue scores, and the mRNA levels of inflammatory factors IL-6 and IL-1 beta. The expressions of intestinal epithelial tight junction proteins (ZO-1 and Occludin), IL-22, and MUC2 were observed using immunofluorescence and RT-PCR. Additionally, the proportion of ILC3 and natural cytotoxicity receptor (NCR) + ILC3 in the colon were detected using flow cytometry. Furthermore, UHPLC-QE-MS was utilized to identify chemical components of PD and network pharmacology was employed to predict potential pathways for PD intervention in UC. Subsequently, MNK-3 cells (ILC3 in vitro cell line) and NCM460 cells were used to verify the network pharmacology results. Finally, the effects of PD on UC gut flora have been explored using in vitro fermentation and 16S rDNA techniques. Results: The results showed that PD significantly restored body weight and colon length in mice with chronic colitis, while also reducing colon inflammatory cell infiltration and the expression of IL-6 and IL-1 beta. Additionally, PD notably promoted the expression of MUC2, ZO-1, Occludin, and IL-22, as well as increasing the ratio of ILC3 and NCR + ILC3. UHPLC-QE-MS analysis identified 443 components of PD, and network pharmacology suggested that PD could target the aryl hydrocarbon receptor (AHR) signaling pathway, which was confirmed by MNK-3 cells and in vitro fermentation experiments. Furthermore, MNK-3-conditioned medium (CM) increased the expression of ZO-1 and Occludin in NCM460 cells. In addition, 16S rDNA results indicated that PD promoted the abundance of Lactobacillales , thus contributing to mucosal damage repair by activating the AHR signal in ILC3s. Conclusion: In summary, our study demonstrates that PD repairs intestinal mucosal damage in chronic colitis by regulating the interaction of gut flora with ILC3, and the specific mechanism is related to the activation of AHR