Short-chain fatty acids modulate regulatory T cells via NF-κB signaling pathway in a rat model of spinal cord injury

Objective To investigate the effects and mechanisms of short-chain fatty acids on regulatory T cells (Treg cells) in spinal cord injury (SCI) using cell and animal experiments. Methods A mixture of SCFAs (acetate, propionate, and butyrate) was used. In vitro, the optimal SCFAs concentration was determined by CCK-8 assay. The expression of IL-4, IL-10, and IL-13 was assessed by RT-qPCR and ELISA. IKKβ, P65, and p-P65 levels were analyzed by Western blot. In vivo, the modified Allen’s weight-drop method was used to establish a moderate contusion SCI model in SD rats. Animals were randomly divided into Sham, SCI, and SCFAs groups. Functional recovery was evaluated using BBB scoring, inclined plane test, and CatWalk analysis. Spinal cord pathology was examined by H&E and Nissl staining. Tissue cytokine levels and Treg cell numbers were measured by ELISA and flow cytometry. Statistical comparisons were performed using one-way or two-way ANOVA with appropriate post-hoc tests. Results In vitro, SCFAs at the working concentration (0.5 mM) did not compromise Treg cell viability ( P > 0.05), while promoting IL-4, IL-10, and IL-13 expression in SCI-derived Treg cells ( P < 0.05). SCFAs significantly decreased IKKβ and p-P65 levels in SCI-derived Treg cells ( P < 0.01). In vivo, SCFAs supplementation improved inclined plane test angles and BBB scores from day 7 onwards ( P < 0.01). CatWalk analysis revealed decreased hindlimb base of support ( P < 0.05) and increased regularity index ( P < 0.01). Histological examination showed reduced cavitation and improved neuronal morphology. SCFAs treatment elevated IL-4, IL-10, and IL-13 levels ( P < 0.05) and increased Treg cell numbers ( P < 0.01). Conclusions SCFAs enhanced anti-inflammatory cytokine production by Treg cells and promoted motor recovery after SCI in association with reduced NF-κB signaling activation, highlighting SCFAs as a potential therapeutic strategy for SCI.