Gut Epithelial-derived CXCL9 Maintains Gut Homeostasis through Preventing Overgrown E. coli

Abstract

Abstract Background and Aims The increased E. coli in colon are related to the occurrence and development of multiple diseases. Chemokines are shown to possess potentially antimicrobial activity, including Gram positive and negative bacterial pathogens. We here investigated function(s) of chemokine CXCL9 expressed in the gut epithelial cells and mechanism(s) of CXCL9 to kill E. coli. Methods We generated CXCL9  fl/flpvillin-cre T mice (pvillin-cre positive mice) and their control CXCL9  fl/flpvillin-cre wmice (pvillin-cre negative mice), and then employed dextran sulfate sodium (DSS)-mediated colitis model to determine sensitivity of the CXCL9  fl/flpvillin-cre T mice. We analyzed composition of the gut microbiota by using 16S ribosomal RNA (V3-V4 variable region) sequencing and shotgun metagenomic analyses. We generated E. coli ∆FtsX (FtsX depleted E. coli) and E. coli ∆aceE (aceE depleted E. coli) by using bacterium red recombining system to investigate the mechanism(s) of CXCL9 to kill E. coli. Results CXCL9  fl/flpvillin-cre Tmice were more sensitive to chemically induced colitis than their control littermates CXCL9  fl/flpvillin-cre wmice. After DSS treatment, there were markedly increased gut E. coli (Escherichia-Shigella) in the colonic contents of CXCL9  fl/flpvillin-cre T mice as compared to control CXCL9  fl/flpvillin-cre w mice. The increased E. coli could promote colitis through NLRC4 and caspase 1/11-mediated IL-18, which was derived from gut epithelial cells. We finally demonstrated that CXCL9 expressed in gut epithelial cells could kill the overgrown E. coli. E. coli expressed Ftsx and PDHc subunits aceE. E.coli∆aceE but not E. coli∆FtsX were resistant to CXCL9-mediated killing. Conclusions Gut epithelial cells-derived CXCL9 can kill the expanded E. coli through aceE to remain gut homeostasis.