Sarrias Urruticoechea, Leyre
The intestinal mucosal barrier has the function to maintain a delicate balance between digestive function through the digestion and absorption of nutrients, the transport of water and electrolytes, and the secretion of water and protein into the intestinal lumen. In addition to providing a defensive function that prevents the passage of potentially harmful substances. This defense function is carried out by numerous elements of different nature and anatomical location and its purpose is to preserve intestinal integrity. Tight junctions critically determine barrier function, so understanding their regulation and how they modulate changes in epithelial cells is essential to understanding their contribution to the pathogenesis of gastrointestinal diseases associated with barrier dysfunction. An imbalance in homeostasis can lead to an inflammatory reaction associated with defects in the intestinal barrier elements and immune function as well as malabsorption of nutrients. This imbalance has been linked to multiple gastrointestinal (GI) disorders as diarrhea (AAD), ulcers, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and colon cancer.
It is therefore important to find ways of action, for example through diet, to prevent or at least reduce the nutritional and pathological consequences of intestinal inflammation, and to understand the mechanisms involved. Several studies using animal hosts suggest that Saccharomyces boulardii can be used as a biotherapeutic in humans and animals. Clinical trials indicate that it can alleviate symptoms from gastrointestinal tract infections to some extent, but further trials are needed to understand the full therapeutic potential of S. boulardii. Recent literature points to yeast cell wall and its components responsible for this protective effect but further experimentation is needed to confirm this theory.
The purpose of this project is to study how yeasts, and especially yeast cell walls, can activate and maintain the membrane integrity of epithelial cells.
The Caco-2 cell line (an immortal human cell line derived from a human colorectal adenocarcinoma which is regularly used in models of intestinal epithelium) will be used to evaluate, under various challenging conditions (inflammatory cocktail of cytokines, oxidative stress), the protective effects of whole yeasts or yeast cell wall extracts on the integrity of the intestinal barrier (measurements of transepithelial electrical resistance (TEER), immunofluorescence microscopy on tight junction proteins) and the differentiation status of the Caco-2 cells (Western botting of differentiation proteins Hes1 and NR3C1).
An inflammatory stimulus (cytokines mix + LPS) that weakened the epithelial barrier function was established for TEER measurements and immunofluorescence of occludin and ZO-1. S. boulardii L62 proliferation rate in Caco-2 cells culture medium and cytotoxicity towards the cell lane were established and deemed compatible for co-culture. Furthermore, a protective effect has been observed in some cases of treatment with both live and YCW forms of S. boulardii L62 through tight junction localization and TEER measurements. Due to lack of time and some technical problems the purpose of this study has not yet been achieved. However, this work has helped to lay a foundation to continue with further experimentation, towards characterizing the components responsible, and their mechanisms, of Saccharomyces boulardii, that provide a protective effect.