Induction of Inflammatory Macrophages in the Gut and Extra-Gut Tissues by Colitis-Mediated Escherichia coli

Inflammatory macrophages play a critical role in gut and extra-gut inflammatory disorders, which may be promoted through the dysbiosis of gut microbiota. However, it is poorly understood how gut microbiota affect inflammatory macrophages. Here, we found that increased Escherichia coli (E. coli) in inflamed colon may induce inflammatory macrophages in gut and extra-gut tissues. These E. coli are different from other commensal and pathogenic E. coli in genomic components and also in ability to induce inflammatory responses. Dominant E. coli from colitic tissues induce gut inflammatory macrophages through a regulating network consisted of IL-18, IFN-γ, IL-12, and IL-22 in gut tissues. These E. coli also directly activate macrophages. Cytosolic inflammasome components PCKδ, NLRC4, caspase8, and caspase1/11 are involved in E. coli-mediated activation in both gut epithelial cells and macrophages. These disclose a novel mechanism for how dysbiosis of gut microbiota in colitis cause inflammatory macrophages related to multiple diseases.