The mechanism of astaxanthin in ameliorating primary sclerosing cholangitis-related liver-gut dysregulation in mice

Primary sclerosing cholangitis (PSC) is a chronic cholestatic disorder primarily resulting from various etiologies that impair bile acids production, secretion and excretion. This impairment leads to the accumulation of toxic bile acids in the liver, causing bile duct obstruction and ultimately resulting in liver fibrosis, cirrhosis, and eventually liver failure. Currently, ursodeoxycholic acid and obeticholic acid are used for PSC treatment approved by the Food and Drug Administration with side effects unfortunately. Astaxanthin (AX), a natural antioxidant, plays a crucial role in many diseases. Nevertheless, the therapeutic effects and underlying mechanisms of AX in PSC remain to be investigated. In this study, we initially employed bioinformatics to analyze common targets between AX and cholestasis, revealing a correlation between them. Subsequently, we aimed to explore the effects of AX on 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced PSC in mice. AX treatment substantially ameliorated liver injury in mice, including liver histological morphology, fibrosis and ductular reaction. Simultaneously, AX restored the homeostasis of bile acid metabolism while inhibited inflammation, oxidative stress and apoptosis in mice. In vitro studies also demonstrated that AX markedly alleviated taurocholic acid (TCA)-induced cellular damage and inflammation. 16S rRNA gene sequencing was used to further examine the gut microbiota composition of DDC group and AX group mice. AX reduced the relative abundance of potentially pathogenic bacteria and increased the relative abundance of probiotics. Furthermore, correlation analysis suggested that an increase in harmful gut bacteria corresponded with impaired liver function. Mechanistically, Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed significant involvement of these common targets of AX and cholestasis within the HIF-1 signaling pathway encompassing NF-kB/IL-6/STAT3/HIF-1a axis. Consistently, we determined that AX inhibited NF-kB/IL-6/STAT3/HIF-1a signaling pathway in DDC-fed mice and TCA-treated cells. Phorbol 12-myristate 13-acetate, an NF-kB agonist, reversed AX-suppressed cellular inflammation and NF-kB downstream signaling. Furthermore, AX can also ameliorate the disruption of the intestinal barrier caused by PSC, reducing intestinal permeability, thereby alleviating hepatocyte inflammation. In summary, our study demonstrated that AX synergistically ameliorated PSC through modulation of gut microbiota alongside targeting hepatic NF-kB/IL-6/STAT3/HIF-1a axis.