Objective To investigate the protective effects of morusin on lipopolysaccharide (LPS)-induced acute liver injury in mice and its underlying mechanisms.
Methods Thirty-two male specific pathogen-free (SPF) C57BL/6J mice were randomly divided into four groups (n = 8 per group): control, LPS, low-dose morusin (morusin-L, 10 mg/kg), and high-dose morusin (morusin-H, 20 mg/kg) groups. The mice in each group were administered the corresponding drugs or normal saline via continuous gavage daily for 16 consecutive days. Except for control group, which received an equal volume of normal saline, other groups were intraperitoneally injected with LPS (5 mg/kg) 2 h after the last gavage to establish the acute liver injury model. Serum and liver tissues were collected for subsequent analysis 6 h after LPS injection. The activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum were detected with biochemical methods. The levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β in serum were measured by enzyme-linked immunosorbent assay (ELISA). Hepatic pathological changes were evaluated by hematoxylin-eosin (HE) staining. The 16S ribosomal RNA (16S rRNA) sequencing was performed to assess the composition of intestinal flora, linear discriminant analysis effect size (LEfSe) was applied for multi-level species discrimination, and Spearman’s correlation analysis was performed. The liver tissues of mice with acute liver injury were analyzed by RNA sequencing (RNA-seq) technology to identify differentially expressed genes (DEGs), and then enrichment analysis of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway was conducted. The expression levels of selected genes was validated by quantitative reverse transcription polymerase chain reaction (qRT-PCR), while immunohistochemistry (IHC) was performed to examine the expression levels of IL-6, myeloid differentiation primary response 88 (MYD88), and toll-like receptor 2 (TLR2).
Results Morusin significantly reduced the serum levels of ALT, AST, and inflammatory factors (TNF-α, IL-6, and IL-1β) (P < 0.05, P < 0.01, or P < 0.001), while alleviating the hepatic pathological damage in mice. Based on efficacy comparisons, morusin-H group was selected for subsequent microbiome and transcriptome analyses. Microbiome analysis revealed that morusin-H effectively mitigated LPS-induced gut dysbiosis and restored the Firmicutes/Bacteroidota balance (P < 0.01). At the genus level, morusin-H significantly reduced the abundances of norank_f_Muribaculaceae, Desulfovibrio, Parabacteroides, and Muribaculum (P < 0.05, P < 0.01, or P < 0.001). At the phylum, family, and genus levels, our findings indicated that morusin-H treatment caused a significant decrease in the abundance of Desulfobacterota, Desulfovibrionaceae, and Desulfovibrio (P < 0.01). Importantly, the abundance of Desulfovibrio was positively correlated with the levels of ALT, AST, TNF-α, IL-1β, and IL-6. Transcriptomic and molecular analyses showed that the therapeutic mechanism of morusin-H involved suppression of the IL-17/TNF signaling pathways and downregulating the mRNA levels of Tlr2, Tlr3, Myd88, Il6, and Cxcl10 (P < 0.05 or P < 0.001), as well as the protein levels of key inflammatory mediators (IL-6, MYD88, and TLR2) (P < 0.001).
Conclusion Morusin demonstrates protective effects against LPS-induced acute liver injury, likely through modulation of gut microbiota and suppression of pro-inflammatory factor expression. These findings indicate that morusin exerts its effects through the "microbiota-inflammation-liver" axis, providing a theoretical basis for its use as a multi-target plant-based drug in the treatment of metabolic inflammation-related liver diseases.
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