SIRT1 Enhancement is Required for the Induction of Anti-Inflammatory Effect of Micheliolide in Carbon Tetrachloride Induced Liver Fibrosis in Mice

Purpose: Micheliolide (MCL), a guaianolide sesquiterpene lactone isolated from Michelia compressa and Michelia champaca, exhibits diverse pharmacological activities, with particularly potent hepatoprotective effects. However, research on its effects against liver fibrosis and underlying mechanisms remains limited. This study aimed to investigate the protective role of MCL in carbon tetrachloride (CCl₄)-induced liver fibrosis in mice and elucidate the potential mechanisms, with a focus on the regulation of Sirtuin 1 (SIRT1).

Methods: Liver fibrosis model was established in mice via intraperitoneal (i.p.) injections of 10% CCl₄. Serum biochemical indicators and liver fibrosis biomarkers were investigated. Liver Collagen deposition was assessed by Masson and Sirus red staining. Protein and inflammatory cytokine expression levels were assessed using qRT-PCR, Western blot, ELISA, Immunohistochemistry staining, and Tissue immunofluorescence assays.

Results: MCL attenuated CCl₄-induced liver injury and restored hepatic function in mice. Mechanistically, MCL reduced liver Collagen deposition, downregulated the protein expression of α-smooth muscle actin (α-SMA) and fibronectin in liver tissues, and decreased serological markers of liver fibrosis. Additionally, MCL suppressed the serum levels of pro-inflammatory cytokines interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein-1 (MCP-1) while increasing IL-10 levels. Notably, CCl₄ administration caused a significant reduction in SIRT1 protein and mRNA expression, which was markedly reversed by MCL treatment. The selective SIRT1 Inhibitor EX-527 abrogated both the anti-liver injury and anti-fibrotic effects of MCL. Moreover, EX-527 also attenuated MCL-mediated suppression of liver inflammation in CCl₄-induced fibrotic mice.

Conclusion: MCL mitigates CCl₄-induced liver injury and fibrosis by activating SIRT1 to suppress liver inflammation in mice. These findings uncover a novel molecular mechanism for the anti-liver fibrotic activity of MCL and highlight its potential as a therapeutic candidate for liver fibrosis.

SIRT1; carbon tetrachloride; inflammation; liver fibrosis; micheliolide.