Lacticaseibacillus paracasei 36 attenuates D-GalN/LPS-induced acute liver injury in mice via suppressing the TLR4/NF-κB/MAPK pathway and NLRP3 inflammasome activation through modulating the intestinal microbiota

• L. paracasei 36 alleviates D-galactosamine (D-GalN) and lipopolysaccharide (LPS)-induced acute liver injury by modulating gut-liver axis. • L. paracasei 36 enhances Keap1/Nrf2/HO-1 signaling pathway and reduces oxidative stress damage. • L. paracasei 36 inhibits the Nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathway and suppresses the activation of NLRP3 • L. paracasei 36 restores gut microbiota balance and elevates beneficial metabolite levels. • This study suggests L. paracasei 36 as a probiotic candidate against acute liver injury. Introduction: Acute liver injury (ALI) is a severe clinical syndrome with high mortality, often triggered by toxins, viruses, or immune-mediated injury. The gut-liver axis serves as a key mediator in the progression of hepatic disorders, and probiotics are considered viable treatment options owing to their impact on modulating intestinal microbiota, reduce inflammation, and alleviate oxidative stress. Objectives: This study was designed to elucidate the hepatoprotective mechanisms of L. paracasei 36 against D-GalN/LPS-induced ALI in mice, with a specific focus on its roles in inflammation, oxidative stress, apoptosis, and intestinal microbiota regulation. Methods: The mice were pretreated with L. paracasei 36 for three weeks prior to the D-GalN/LPS challenge. Serum biomarker, oxidative damage indicators, inflammatory cytokines, and apoptosis-related genes were measured. Intestinal microbiota composition was analyzed via 16S rRNA sequencing, and hepatic transcriptomics and metabolomics were performed to identify key pathways and metabolites. Results: L. paracasei 36 pretreatment significantly reduced serum AST, ALT, and TBil levels, alleviated histopathological damage, and decreased oxidative stress and inflammatory cytokine production. It inhibited hepatocyte apoptosis by modulating Bcl-2/Bax expression and suppressed NLRP3 inflammasome activation. L. paracasei 36 restored intestinal microbiota balance, increasing beneficial genera ( Ligilactobacillus , Akkermansia ) and reducing harmful ones ( Alistipes , Parasutterella ). Multi-omics analysis revealed suppression of NF-κB/MAPK pathways along with an increase in hepatoprotective metabolites like berberine and flavin nucleotides. Conclusion: L. paracasei 36 exerts potent hepatoprotective effects against D-GalN/LPS-induced ALI by mitigating inflammation, oxidative damage, and apoptosis, and by restoring intestinal microbiota homeostasis. Collectively, these results suggest that L. paracasei 36 represents a potential therapeutic strategy for ALI.