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. Adhe rence to and contact dependent killing of host cells requires the gala ctose inhibitable lectin. To elucidate the mechanism whereby E. histol ytica influences host defence, the authors assessed the change of proi nflammatory cytokine genes expressed by colon epithelial cells in resp onse to coculture with E. histolytica trophozoites and carbohydrates, including galactose, N-acetyl-galactosamine or N-acetyl-lactosamine, w hich prevented E. histolytica from attaching to epithelial cells. Afte r HT-29 human colon epithelial cells were co-cultured with E. histolyt ica trophozoites in the presence or absence of carbohydrates (0.1-100 mM), RNA was extracted from the epithelial cells by an acid guanidiniu m thiocyanate-phenol-chloroform method. Cytokine gene expression was a ssessed by quantitative RT-PCR using a synthetic internal standard, an d proteins were determined by ELISA. IL-8 mRNA expressed by HT-29 cell s in response to E. histolytica trophozoites was downregulated in the presence of galactose, N-acetyl-galactosamine or N-acetyl-lactosamine (0.1-100 mM), and this was paralleled by decreased IL-8 protein secret ion. 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 pr eventing E. histolytica from attaching to the host's colon epithelial cells.