Effect of fecal microbiota transplantation on the TGF-β1/Smad signaling pathway in rats with TNBS-induced colitis

Background: Traditional treatments for inflammatory bowel disease (IBD) have adverse side effects, and patients who receive such treatments have high recurrence rates. Fecal microbiota transplantation (FMT) has become an increasingly popular therapeutic option for patients with IBD. However, the mechanism by which FMT alleviates this disease remains unclear. Methods: In this study, a rat model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis was established and used to explore whether the transforming growth factor-beta 1 (TGF-beta 1)/small mothers against decapentaplegic (Smad) signaling pathway plays a critical role in the FMT alleviation of IBD. Results: After the FMT intervention, the disease activity index and histologic scores were significantly decreased. In addition, the TGF-beta 1 expression level in the FMT group was significantly decreased by approximately 0.72-fold relative to the level in the TNBS colitis group, whereas the Smad3, Smad4, and Smad7 expression levels had increased by approximately 1.21, 1.40, and 1.18 folds, respectively. Similarly, SB431542 inhibited the expression of TGF-beta 1 and promoted the expression of Smad3, Smad4, and Smad7. Further, the serum levels of the inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) were significantly decreased, whereas that of the interferon-gamma (IFN-gamma) was not significantly changed after the FMT intervention. Conclusions: These results suggest that FMT inhibits the TGF-beta 1/Smad signaling pathway to attenuate inflammation.