Western diet induces Gsdme-mediated epithelial pyroptosis through the DCA-S1PR2 pathway to disrupt the intestinal epithelial barrier

This study is led by Professor Fachao Zhi's research team from Nanfang Hospital, Southern Medical University. This study utilizes Western diet-fed mice to determine the role that the Western Diet plays in IBD’s onset and explore its potential mechanism. The study shows that the Western Diet could increase the sensitivity of IBD onset through DCA-induced Gsdme-mediated pyroptosis via the DCA-S1PR2 pathway, leading to disruption of the IEC barrier.

Compared to a regular diet (RD), a high sugar-diet (HSD), and a high-fat diet (HFD), only mice fed with the Western Diet (WD) exhibited increased colon shortening, epithelium damage, and higher histology scores in the colon. This suggests that the WD induces colitis in wild-type (WT) mice. Additionally, the mucin layer of the colons in HSD- and WD-fed mice was thinner than that in RD-fed mice. Further immunofluorescence staining revealed that the intestinal epithelial cell (IEC) barrier was disrupted, suggesting that WD initiates colitis by disrupting the mucus and IEC barrier. Single-cell RNA sequencing (scRNA-seq) analysis of colorectal tissues from mice fed with WD and RD showed an enrichment of apoptosis and pyroptosis-related inflammation in WD-fed mice. Moreover, WD-fed mice exhibited a significantly increased expression of Gsdme and the pyroptosis-inducing fragment Gsdme-NT in IECs. These findings suggest that Gsdme-mediated cell death plays a role in WD-induced colitis and disruption of IECs.

The microbial and metabolite compositions of fecal samples show that Lactobacillus is one of the most abundant bacteria in WD-fed mice, and deoxycholic acid (DCA) is positively correlated with Lactobacillus. In vivo, mice treated with glucose plus DCA developed significant colitis and exhibited a significant increase in the pyroptosis-inducing fragment Gsdme N-terminal in the IECs. In vitro, a high concentration of DCA induced noticeable pyroptotic bubbles in the human intestinal epithelial cell line NCM460 and activated GSDME. Furthermore, murine colon crypts were isolated and co-cultured with a high concentration of DCA, suggesting that a high concentration of DCA inhibited the formation, maturation, and survival of colon organoids. These results suggest that WD disrupts the epithelial barrier by altering gut bacteria to produce a high concentration of DCA, which induces Gsdme-mediated pyroptosis and disrupts the intestinal mucus layer.

RNA-seq shows that genes associated with inflammatory cytokines and chemokines are upregulated in DCA-treated NCM460 cells. Enrichment analysis shows that these genes are associated with Lysosome, Mitochondrial, and MAPK pathways, and DCA significantly increased the levels of Cathepsin B, Cyt c, and ERK phosphorylation. Further JC-1 and AO staining experiments showed that the stability of mitochondrial and lysosome membranes was compromised after DCA stimulation. DCA could exert its effects through the receptor S1PR2, which is highly expressed in NCM460 cells treated with a high dose of DCA. S1PR2-knockout NCM460 cells prevented the mitochondrial and lysosome membranes from being damaged by DCA. Moreover, inhibitors of ERK and Cathepsin B, SCH772984 and CA074, could also prevent the mitochondrial and lysosome membranes from DCA damage. Taken together, these results indicate that DCA induces GSDME-mediated IEC pyroptosis via the S1PR2/ERK/Cathepsin B pathway.

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Western diet induces Gsdme-mediated epithelial pyroptosis through the DCA-S1PR2 pathway to disrupt the intestinal epithelial barrier.