Notoginsenoside R1 Alleviates Acetaminophen-Induced Liver Injury via MAPK/mTOR-Mediated Autophagy

Acetaminophen (APAP) overdose is a leading cause of acute liver injury (ALI), yet effective therapeutic options remain limited. Although notoginsenoside R1 (NGR1) is a major bioactive saponin isolated from Panax notoginseng with established anti-inflammatory and anti-oxidant properties, its hepatoprotective potential and underlying mechanisms in APAP-induced liver injury (AILI) have not been systematically investigated. In this study, we established an AILI mouse model and evaluated the protective effects of NGR1 through biochemical assays, histopathology, Western blotting, and immunofluorescence, complemented by integrative transcriptomic, metabolomic, and gut microbiota analyses. Mechanistic involvement of the MAPK/mTOR-autophagy pathway was further validated using L-leucine as a pharmacological activator of mTOR. NGR1 markedly attenuated AILI, as reflected by reduced serum ALT/AST levels, improved hepatic histology, and increased survival in acute liver failure. NGR1 suppressed inflammatory responses by decreasing IL-1[Formula: see text], IL-6, and TNF-[Formula: see text] levels and alleviated oxidative stress by restoring GSH and SOD while reducing MPO, ROS, and MDA accumulation. Multi-omics analysis revealed significant enrichment of MAPK/mTOR signaling, autophagy, ferroptosis, and glutathione metabolism pathways. Mechanistically, NGR1 promoted autophagic flux (increased LC3-II/I, ATG5, and ATG7 with decreased p62), inhibited ferroptosis (upregulation of GPX4 and SLC7A11 with downregulation of ACSL4), and suppressed APAP-induced activation of the MAPK/mTOR pathway. Pharmacological activation of mTOR by L-leucine partly abolished the protective effects of NGR1, reversing autophagy activation and restoring inflammatory and oxidative injury. These findings collectively demonstrate that NGR1 protects against AILI by inhibiting MAPK/mTOR signaling, restoring autophagy, and suppressing ferroptosis, highlighting NGR1 as a promising therapeutic candidate for APAP-induced hepatotoxicity.