Transcriptional upregulation of inflammatory cytokines in human intestinal epithelial cells following Vibrio cholerae infection

Abstract

Coordinated expression and upregulation of interleukin-1alpha, interleukin-1beta, tumor necrosis factor-alpha, interleukin-6, granulocyte-macrophage colony-stimulating factor, interleukin-8, monocyte chemotactic protein-1 (MCP-1) and epithelial cell derived neutrophil activator-78, with chemoattractant and proinflammatory properties of various cytokine families, were obtained in the intestinal epithelial cell line Int407 upon Vibrio cholerae infection. These proinflammatory cytokines also showed increased expression in T84 cells, except for interleukin-6, whereas a striking dissimilarity in cytokine expression was observed in Caco-2 cells. Gene expression studies of MCP-1, granulocyte-macrophage colony-stimulating factor, interleukin-1alpha, interleukin-6 and the anti-inflammatory cytokine transforming growth factor-beta in Int407 cells with V. cholerae culture supernatant, cholera toxin, lipopolysaccharide and ctxA mutant demonstrated that, apart from cholera toxin and lipopolysaccharide, V. cholerae culture supernatant harbors strong inducer(s) of interleukin-6 and MCP-1 and moderate inducer(s) of interleukin-1alpha and granulocyte-macrophage colony-stimulating factor. Cholera toxin- or lipopolysaccharide-induced cytokine expression is facilitated by activation of nuclear factor-kappaB (p65 and p50) and cAMP response element-binding protein in Int407 cells. Studies with ctxA mutants of V. cholerae revealed that the mutant activates the p65 subunit of nuclear factor-kappaB and cAMP response element-binding protein, and as such the activation is mediated by cholera toxin-independent factors as well. We conclude that V. cholerae elicits a proinflammatory response in Int407 cells that is mediated by activation of nuclear factor-kappaB and cAMP response element-binding protein by cholera toxin, lipopolysaccharide and/or other secreted products of V. cholerae.