Curcumin improves spinal cord injury by regulating the Treg/Th17 balance via modulation of the gut microbiota

Abstract Spinal cord injury (SCI) is a severe traumatic disorder of the central nervous system, for which effective therapeutic strategies remain limited. The balance between regulatory T (Treg) cells and T helper 17 (Th17) cells plays a crucial role in immune regulation and the inflammatory response following SCI. As a vital component of the host microecosystem, the gut microbiota is closely associated with immune regulation. Our previous experimental findings demonstrated that curcumin alters the composition and richness of the gut microbiota. However, the relationship between the curcumin-modulated gut microbiota, Treg/Th17 cell balance, and SCI has not been clearly elucidated. This study aims to investigate the role and underlying mechanisms of the gut microbiota, following curcumin intervention, in improving SCI outcomes. Our results show that the gut microbiota modified by curcumin effectively regulates the Treg/Th17 cell balance, promoting the proliferation of Treg cells and suppressing the activation of Th17 cells. It reduces the release of pro-inflammatory cytokines interleukin-17A (IL-17A) and interleukin-6 (IL-6), as well as the expression of the transcription factor retinoic acid-related orphan receptor γt (RORγt), while increasing the secretion of anti-inflammatory cytokines interleukin-10 (IL-10) and transforming growth factor-β1 (TGF-β1), along with the transcription factor forkhead box P3 (FOXP3). These findings suggest that the gut microbiota altered by curcumin alleviates inflammation and promotes spinal cord repair by modulating the Treg/Th17 cell balance. This study provides a novel potential strategy and theoretical foundation for the treatment of SCI.