Paeoniflorin attenuates sepsis-induced liver injury by reprogramming macrophage polarization via the TLR4/NF-κB pathway.

BACKGROUND: Sepsis-associated liver injury (SALI) increases mortality in critically ill patients but lacks targeted treatments. Although the natural compound Paeoniflorin shows anti-inflammatory and immunomodulatory potential, its specific function and mechanism in SALI remain unclear. METHODS: A murine model of polymicrobial sepsis was established using cecal ligation and puncture (CLP). Male C57BL/6 mice were randomly allocated to Sham, CLP, CLP+Paeoniflorin (30, 60, 120 mg/kg), CLP+Paeoniflorin+TLR4 agonist (RS09 TFA), and Paeoniflorin-only control groups. Liver injury was assessed through serum ALT/AST measurements, histopathological evaluation, and TUNEL apoptosis assay. Hepatic inflammatory cytokine expression was quantified by qPCR. Macrophage polarization was analyzed via immunohistochemistry for F4/80, CD86 (M1), and CD206 (M2) markers. TLR4/NF-κB pathway activity was examined using Western blotting and immunohistochemistry. Transcriptomic profiling was performed through RNA sequencing and KEGG pathway analysis. RESULTS: Paeoniflorin administration significantly attenuated CLP-induced elevations in serum ALT and AST levels in a dose-dependent manner, ameliorated histopathological liver damage, and reduced hepatocyte apoptosis. Treatment with Paeoniflorin substantially downregulated hepatic mRNA expression of pro-inflammatory cytokines (IL-6, TNF-α, IL-1β). Immunohistochemical analysis revealed that Paeoniflorin treatment was associated with a shift in macrophage marker expression, characterized by a reduction in cells co-staining for F4/80 and the classic M1 marker CD86, and an increase in cells co-staining for F4/80 and the classic M2 marker CD206. This suggests a potential modulation of macrophage polarization balance towards an anti-inflammatory phenotype. Both transcriptomic and protein analyses confirmed that Paeoniflorin suppressed activation of the TLR4/NF-κB signaling pathway. The protective effects of Paeoniflorin were completely abolished by co-administration of the TLR4 agonist RS09 TFA. CONCLUSION: Paeoniflorin confers protection against sepsis-induced liver injury by modulating macrophage polarization from the pro-inflammatory M1 phenotype toward the anti-inflammatory M2 phenotype through inhibition of the TLR4/NF-κB signaling pathway. These findings identify Paeoniflorin as a promising candidate for further development as an immunomodulatory therapy for SALI.