Influence of cholesterol in the adhesion of Giardia intestinalis to cultured human enterocytes.

HUMEN, M.A.; LIÉVIN-LE MOAL V.; SERVIN, A. L.; PÉREZ P.F.

Congreso; XX Congreso Latinoamericano de Microbiología.; 2010

Giardia intestinalis is the protozoan associated to nonbacterial diarrhoeas more frequency diagnosed in the world. The adhesion of trophozoites to epithelial cells is the initial event in the colonization of the upper small intestine. Lipid rafts and the distribution of cholesterol and sphingolipids play an important role in the organization of cellular membrane, signal transduction and intercellular adhesion. Considering that the adhesion of the parasite to the enterocytes represents the first step in the pathogenesis of the disease, the aim of this work was to evaluate the influence of lipid rafts organization in the adhesion process, using an in vitro interaction model. Human enterocytes (lines Caco-2 clone TC7 and HT-29) were incubated with Giardia trophozoites (strains GS/H7, WB/C6 and WB/1267) in the presence and absence of metil-b-cyclodextrin (MbCD). Adhered trophozoites were counted in a hemocytometer. MbCD extracts the cholesterol of lipid rafts, leading to its disorganization. This strategy was used to evaluate the contribution of lipid rafts in the adhesion process. The adhesion assay carried out in the presence of MbCD showed a diminution in the adhesion capability of 2 to 4 logarithmic orders, with all the infection multiplicities evaluated. Enterocytes preincubated with MbCD (removed previously to the adhesion assay), did not show differences with respect to the non-pretreated controls. Trophozoites preincubated with MbCD (removed previously to the adhesion assay) reduced substantially its capacity to adhere. MbCD did not modify the viability of trophozoites. In addition, trophozoites of the 3 Giardia strains studied pretreated with MbCD, washed and then incubated in the Giardia proliferation media (TYI-S-33) until confluence (72 h), also reduced significantly its adhesion capacity. MbCD alters the structures implied in the adhesion of the parasite to human enterocytes. These are the first evidences of the possible existence of lipid raft in Giardia and the role of the parasite cholesterol organization in the adhesion process.