Phillygenin protects against lipopolysaccharide-induced acute lung injury by acting as a PXR agonist via NF-κB inhibition.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening conditions with substantial mortality and limited targeted therapies. The pregnane X receptor (PXR) has emerged as a promising therapeutic target for inflammatory diseases, though its role in ALI remains underexplored. This study characterizes phillygenin (PHI), a bioactive lignan isolated from Forsythia suspensa, as a PXR agonist, elucidating its protective mechanism in lipopolysaccharide (LPS)-induced ALI. PHI binding to PXR was characterized by ligand fishing using hollow fibers and luciferase reporter assays, revealing direct agonistic activity. In LPS-stimulated human bronchial epithelial cells, PHI-activated PXR competed with NF-κB p65 for RXRα, suppressing NF-κB p65 nuclear translocation and downstream inflammatory cascades. Concurrently, PHI upregulated antioxidant enzymes (GPX-2/GPX-7) and anti-apoptotic proteins (Bcl-2/Bcl-xL), while downregulating pro-inflammatory mediators (TNF-α, IL-6), in a PXR-dependent manner. PXR knockdown abolished these protective effects, confirming target specificity. In vivo, PHI dose-dependently attenuated lung histopathological injury, reduced inflammatory cytokine levels in bronchoalveolar lavage fluid, and mitigated alveolar epithelial apoptosis in LPS-challenged mice. These findings support PHI as a direct PXR agonist and the PHI-PXR-NF-κB axis as a mechanistic foundation for developing targeted interventions in acute inflammatory lung diseases.