TLR4 maintains Treg-mediated protection against adverse outcomes in a model of hepatic surgical stress

Surgical stress, such as hepatic ischemia-reperfusion (I/R) injury, induces excessive inflammation and adversely affects liver surgery outcomes. Regulatory T cells (Tregs) are crucial for immune homeostasis, yet their protective mechanisms against liver I/R injury remain unclear. In this study, we demonstrated that decreased hepatic Treg abundance correlates with increased liver injury in patients undergoing hepatic hemangioma resections. In murine models, Treg depletion worsened liver I/R injury. Bulk RNA-seq of hepatic Tregs showed enrichment of Toll-like receptor (TLR) signaling pathways, with flow cytometry identifying TLR4 as the most increased TLR after I/R. Treg-specific Tlr4 knockout mice (Treg-Tlr4-/- mice) exhibited exacerbated liver injury following I/R. Adoptive transfer of WT Tregs, but not Tlr4-deficient Tregs, alleviated liver injury in both Treg-depleted and Treg-Tlr4-/- mice. Transcriptomic analysis revealed that IL-10 production was impaired in Tlr4-deficient Tregs. Mechanistically, Tlr4-deficient Tregs showed reduced activation of the MyD88/ERK/CREB pathway, resulting in diminished IL-10 production. Myd88-/- and IL-10-/- Tregs failed to confer protection against liver I/R injury, whereas exogenous IL-10 administration rescued the hepatic dysfunction in Treg-Tlr4-/- mice. Our findings implicate the vital role of TLR4 in Tregs to mitigate liver I/R injury and offer a potential therapeutic option to reduce postoperative complications following liver surgery.