Traditional medicine Xianglian pill suppresses high-fat diet-related colorectal cancer via inactivating TLR4/MyD88 by remodeling gut microbiota composition and bile acid metabolism

Abstract

Ethnopharmacological relevance: Previous studies have revealed that a high-fat diet (HFD) promotes the progression of colorectal cancer (CRC) in close association with disturbances in the intestinal flora and metabolic disorders. Xianglian pill (XLP) is a well-established traditional prescription with unique advantages in controlling intestinal flora imbalance and inflammation. However, its therapeutic effects on HFD-related CRC remain largely unknown.

Aim of the study: The primary objective of this research was to investigate the anticancer mechanism of XLP in countering HFD-related CRC.

Materials and methods: The protective effect of XLP was evaluated using azoxymethane (AOM) and dextran sulfate sodium (DSS)-induced CRC model of mice exposed to a HFD. The degree of colorectal carcinogenesis, including body weight, colon length, and histopathology, was measured in mice treated with XLP and untreated mice. The effect of XLP on gut microbiota and its metabolites was detected using 16S rDNA and liquid chromatography/mass spectrometry analysis. Furthermore, a "pseudo-sterile" mouse model was constructed using antibiotics (Abx) to verify whether the gut microbiota and metabolites play a role in the pathogenesis of CRC.

Results: XLP inhibited colorectal tumorigenesis in a dose-dependent fashion. Our findings also highlighted that XLP protected the integrity of the intestinal barrier by reducing the expression of pro-inflammatory cytokines, such as IL-6 and TNF-α, as well as the infiltration of pro-inflammatory macrophages. Mechanistically, XLP inhibited the TLR4/MyD88 pathway. Notably, the XLP treatment increased the proportion of probiotics (particularly Akkermansia) and significantly reduced fecal deoxycholic acid (DCA), a microbiota-derived metabolite of bile acids (BA) closely related to Muribaculaceae. Furthermore, after Abx treatment, XLP showed no clear antitumor effects on CRC. Simultaneously, DCA-supplemented feedings promoted colorectal tumorigenesis and provoked obvious colonic inflammation, M1 macrophage infiltration, and colonic injury. In vitro, the results of RAW-264.7 macrophages and normal intestinal epithelial cells treated with DCA corroborated our in vivo findings, demonstrating consistent patterns in inflammatory responses and intestinal barrier protein expression.

Conclusion: Our findings suggest that XLP inhibits colorectal cancer associated with HFD via inactivating TLR4/MyD88 by remodeling gut microbiota composition and BA metabolism.

Keywords: Bile acid metabolism; Colorectal cancer; Gut microbiota; High-fat diet; TLR4 pathway; Xianglian pill.