Mo2024 Remifentanil Preconditioning Protects Intestine Against Ischemia/Reperfusion Injury in Rats Through Inhibiting Intestinal Mucosal Epithelial Apoptosis via δ- and μ-Opioid Receptors

Objective: Intestinal ischemia/reperfusion (I/R) frequently occurs after major surgery, various types of shock and severe trauma, and it is associated with a high morbidity and mortality in the critical clinical settings. Intestinal I/R results in the injury of intestinal mucosal immunity and gut bacterial communities, however, little is known about the mechanisms and corresponding therapy for these damages. Immunoglobulin (Ig) A class switch recombination (CSR) plays a major role in gut IgA synthesis, and transforming growth factor (TGF)-β1 can potently induce other Ig isotypes CSR to IgA. Here, we aimed to investigate the effect of TGF-β1 on gut IgA generation and microbiota after intestinal I/R attack, and explore the underlying mechanisms. Methods: The 8-10 weeks Balb/c mice were randomly allocated into 5 groups. In the Sham group, the mice underwent laparotomy without occlusion of the superior mesenteric artery (SMA); whereas, the SMA was clamped for 1 hour in the Injury group; the mice of the TGF group received intravenous infusion of recombinant TGFβ1 before ischemia. In addition, SB-431542, a specific inhibitor of TGF-β receptor I/II, was administered alone (SB group) in intestinal ischemic mice or prior to TGF-β1 (TGF+SB group) to block its inductive effect on IgA CSR. The biomarkers of IgA CSR and IgA mRNA were detected by real-time PCR; the number of IgA+, IgM+ B cells and the percentage of bacteria coated with IgA were detected by flow cytometry; sIgA concentration was detected by ELISA; gut bacterial communities were detected by high-throughput 16S rRNA gene sequencing; and the mortality was analyzed by survival analysis. Results: Intestinal I/R disturbed the process of IgA CSR, and then caused severe disruptions of IgA production and microbiota in the gut. TGF-β1 significantly increased the activation biomarkers of IgA CSR (Fig. 1) and rectified the imbalance of IgA+ and IgM+ B cells in both the peyer's patches and lamina propria, and therefore enhanced gut IgA synthesis and bacteria-binding capacity (Fig. 2A-B). Meanwhile, induction of IgA CSR by TGF-β1 relieved the alterations of gut bacterial richness, diversity and compositions following intestinal I/R (Fig. 2C). Further, the mortality of mice was dramatically reduced. And SB-431542 diminished almost all the protective effects of TGF-β1 on I/R injury. Conclusions: The inhibition of IgA CSR was involved in the pathogenesis of intestinal I/R injury. TGF-β1 improved IgA dysfunction and enteric dysbacteriosis caused by intestinal I/R partly by increasing IgA generation and bacteriabinding capacity via inducing gut IgA CSR.