Effect of the Oral Administration of Fungal Ligands in a Murine Model of DSS-Induced Colitis

Background: The molecular interaction between ligands of commensal microbiota and host receptors, such as Toll-like receptors (TLRs), at the surface of the epithelial cells of the gastrointestinal (GI) tract plays a critical role in its homeostasis and protection. The aim of this work was to determine the usefulness of the oral administration of yeast cells or soluble yeast-derived ligands for TLRs in the protection and modulation of the inflammatory response of the GI tract in a murine model of experimentally induced colitis. Materials and Methods: C57BL/6 mice were given 3% dextran sulphate sodium salt (DSS) to induce experimental colitis. Protection assays were performed by oral administration of viable Saccharomyces spp. yeasts cells, soluble yeast mannan or PBS (control), starting either after or during the DSS treatment. The in vitro production of cytokines was measured in colon segments of selected mice, either in the presence or absence of heat-inactivated yeasts or mannan. Results: In mice with experimental acute or sublethal colitis, no statistically significant differences were found between yeast/mannan treated mice and controls, both for mortality and loss of weight. The in vitro production of cytokines was not altered by the addition of mannan or yeasts to the culture, in both healthy mice and mice with induced colitis. Conclusions: Direct oral administration of viable yeasts or soluble yeast mannan does not show any protective effect during disease in a model of experimentally induced colitis in immunocompetent mice.