Paeonol attenuates nonalcoholic steatohepatitis by regulating intestinal flora and AhR/NLRP3/Caspase-1 metabolic pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Non-alcoholic steatohepatitis (NASH) is a common metabolic liver injury disease that is closely associated with obesity and metabolic disorders. Paeonol, an active ingredient found in Moutan Cortex, a traditional Chinese medicine which exhibits significant therapeutic effect on liver protection, has shown promising effects in treating liver diseases, particularly NASH. However, the specific intervention mechanism of paeonol on NASH is still unknown.

AIM OF THE STUDY: Our objective is to elucidate the pharmacological mechanism of paeonol in intervening NASH at the in vivo level, focusing on the impact on intestinal flora, tryptophan-related targeted metabolome, and related Aryl hydrocarbon receptor (AhR) pathways.

MATERIALS AND METHODS: Here, we explored the intervention effect of paeonol on NASH by utilizing the NASH mouse model. The Illumina highthroughput sequencing technology was preformed to determine the differences of gut microbiota of model and paeonol treatment group. The concentration of Indoleacetic acid is determined by ELISA. The intervention effect of NASH mouse and AhR/NLRP3/Caspase-1 metabolic pathway is analyzed by HE staining, oil red O staining, Immunohistochemistry, Immunofluorescence, Western blot and qRT-PCR assays. Fecal microbiota transplantation experiment also was performed to verify the intervention effect of paeonol on NASH by affecting gut microbiota.

RESULTS: Firstly, we discovered that paeonol effectively reduced liver pathology and blood lipid levels in NASH mice, thereby intervening in the progression of NASH. Subsequently, through 16S meta-analysis, we identified that paeonol can effectively regulate the composition of intestinal flora in NASH mice, transforming it to resemble that of normal mice. Specifically, paeonol decreased the abundance of certain Gram-negative tryptophan-metabolizing bacteria. Moreover, we discovered that paeonol significantly increased the levels of metabolites Indoleacetic acid, subsequently enhancing the expression of AhR-related pathway proteins. This led to the inhibition of the NOD-like receptor protein 3 (NLRP3) inflammasome production and inflammation generation in NASH. Lastly, we verified the efficacy of paeonol in intervening NASH by conducting fecal microbiota transplantation experiments, which confirmed its role in promoting the AhR/NLRP3/cysteinyl aspartate specific proteinase (Caspase-1) pathway.

CONCLUSIONS: Our findings suggest that paeonol can increase the production of Indoleacetic acid by regulating the gut flora, and promote the AhR/NLRP3/Caspase-1 metabolic pathway to intervene NASH.