Human epithelial cell response to bacterial signal indole

Indole is a bacterial signal secreted by pathogenic and commensal Escherichia coli in the stationary phase at high concentrations (~600 µM). Prior work from our lab has shown that indole decreases E. coli O157:H7 (EHEC) chemotaxis, motility, attachment to epithelial cells and biofilm formation. However, its effect on epithelial cells is not known. We hypothesized that indole induces gene expression changes in epithelial cells that lead to decreased pathogen colonization and infection. Changes in gene expression with the human enterocyte cell line HCT-8 exposed to indole suggested down-regulation of Toll-like receptor signaling and coordinated changes in Jak-STAT and p38 MAPK pathways. Corresponding changes in the expression of cytokines, chemokines, and their receptors also suggested that indole functions as a modulator of inflammation in intestinal epithelial cells. In addition, the expression of genes involved in tight junction organization (claudins, and tight junction proteins) and mucin production were also up-regulated by indole. Keywords: Inter-kingdom signaling interactions between human cells and bacterial signal indole