Cytokine genes are down-regulated when attachment of Entamoeba histolytica to HT-29 colon epithelial cells is prevented.

Entamoeba histolytica can cause invasive disease by disruption of the intestinal barriers and subsequent lysis of the intestinal cells. Adherence to and contact dependent killing of host cells requires the galactose inhibitable lectin. To elucidate the mechanism whereby E. histolytica influences host defence, the authors assessed the change of proinflammatory cytokine genes expressed by colon epithelial cells in response to co-culture with E. histolytica trophozoites and carbohydrates, including galactose, N-acetyl-galactosamine or N-acetyl-lactosamine, which prevented E. histolytica from attaching to epithelial cells. After HT-29 human colon epithelial cells were co-cultured with E. histolytica trophozoites in the presence or absence of carbohydrates (0.1-100 mM), RNA was extracted from the epithelial cells by an acid guanidinium thiocyanate-phenol-chloroform method. Cytokine gene expression was assessed by quantitative RT-PCR using a synthetic internal standard, and proteins were determined by ELISA. IL-8 mRNA expressed by HT-29 cells in response to E. histolytica trophozoites was downregulated in the presence of galactose, N-acetylgalactosamine or N-acetyl-lactosamine (0.1-100 mM), and this was paralleled by decreased IL-8 protein secretion. GM-CSF and IL-1 alpha/beta mRNAs were also downregulated in those cells in the presence of these agents. These results suggest that the expression of proinflammatory cytokine genes could be inhibited by preventing E. histolytica from attaching to the host's colon epithelial cells.