Betulinic acid alleviates lipopolysaccharide-induced spleen injury by inhibiting the IL-17 signaling pathway in broilers.

Betulinic acid (BA), a naturally occurring pentacyclic triterpenoid compound widely distributed in various natural plant species, has immunomodulatory, anti-inflammatory, and antioxidant effects. Spleen injury triggers an immune stress response, leading to compromised systemic immunity and diminished production performance in broilers. However, the protective effects of BA against splenic injury in broilers and the underlying mechanisms remain unclear. This study aimed to investigate the protective effects and underlying mechanisms of dietary supplementation with BA against lipopolysaccharide (LPS)-induced spleen injury in broilers. After establishing a LPS-induced spleen injury model in broilers via intraperitoneal injection, we assessed BA's protective effects by analyzing splenic histomorphology, serum immunoglobulins, inflammatory cytokines, and redox status. Network pharmacology, transcriptomics, and molecular docking predicted the underlying mechanisms, which were further validated in vivo through RT-qPCR and Western blotting. Our results revealed that BA pretreatment significantly ameliorated splenic histopathological damage, increased serum concentrations of immunoglobulin, reduced the expression of inflammatory cytokines and enhanced antioxidant capacity in the spleen. Transcriptomic and network pharmacology analyses revealed that the IL-17 signaling pathway played a pivotal role in mediating BA's protective properties. Further molecular docking, molecular dynamics simulations, and in vivo experimental results indicated that BA bound stably to IL-17, inhibited the release of downstream inflammatory cytokines, maintained redox homeostasis and ultimately attenuated LPS-induced spleen injury in broilers. This study demonstrated that BA pretreatment ameliorated LPS-induced spleen injury by inhibiting the IL-17 signaling pathway.