Silvia Resta-Lenert

Modulation of Intestinal Barrier Properties by Probiotics: Role in Reversing Colitis

Probiotic bacteria, commensals selected for their presumed therapeutic properties when ingested orally, have attracted increasing attention for their possible efficacy in a range of gastrointestinal disorders, including the inflammatory bowel diseases of Crohns disease and ulcerative colitis. Since the barrier properties of the intestinal epithelium are believed to be compromised as a consequence (or perhaps as a cause) of intestinal inflammation, we hypothesized that probiotics might ameliorate such epithelial dysfunction as part of their spectrum of beneficial effects. We have used both cell line and animal models to test this hypothesis and show that two probiotics have significant effects on epithelial barrier properties, both at baseline and when deranged by inflammatory cytokines or in the setting of inflammation in a mouse model of colitis. Moreover, the probiotics also normalize epithelial ion transport function, which could also contribute to clinical efficacy. Overall, our studies extend the spectrum of functional effects attributable to probiotics, and may provide a rationale for their use in a range of gastrointestinal disorders associated with epithelial dysfunction.

Muc17 protects intestinal epithelial cells from enteroinvasive E. coli infection by promoting epithelial barrier integrity

The membrane-bound mucin MUC17 (mouse homolog Muc3) is highly expressed on the apical surface of intestinal epithelia and is thought to play a role in epithelial restitution and protection. Therefore, we hypothesized that MUC17 has a role in protection of the intestinal mucosa against luminal pathogens. Human intestinal cell lines were transfected by electroporation (Caco-2 and HT 29/19A) and by retroviral expression vector (LS174T, a cell line with high levels of MUC17 expression) using MUC17 siRNA. Transepithelial electrical resistance, permeability, tight-junction protein expression, adhesion, and invasion in response to enteroinvasive Escherichia coli (EIEC) were measured in all cell lines. In some experiments, the effect of the addition of exogenous purified crude mucin or recombinant Muc3 cysteine-rich domain protein (Muc3 CRD1-L-CRD2) as preventative or protective treatment was tested. Reduction of endogenous MUC17 is associated with increased permeability, inducible nitric oxide synthase and cyclooxygenase 2 induction, and enhanced bacterial invasion in response to EIEC exposure. Bacterial adhesion is not affected. Exogenous mucin (Muc3) and recombinant Muc3CRD treatment had a small but significant effect in attenuating the effects of EIEC infection. In conclusion, these data suggest that both native and exogenous MUC17 play a role in attachment and invasion of EIEC in colonic cell lines and in maintaining epithelial barrier function.

Natural history of colitis and associated epithelial dysfunction in conventionally housed Mdrla-/-mice

ism and host cells Using a T84 cell culture model, we have analyzed the elti:cts of EcN on the epithelial transcriptom, especially on the expre~ion of genes directly affecting an immediate cellular reacnon utilizmg the NF-kB signaling pathway and its control on the transcription of inBammatory cytokines, Selected from 300 differentially regulated genes we are currently investigating five upregulated and three downregulared genes in further detail by Real-Time PCR. In addition, we could show that exposute of T84 ceils to EcN also affected genes revolved in the regulation of the barrier flmction of the intestinal epithelium. Further studies are in progress to increase our knowledge about expression profiles in epithelial cells depending on probiotic colonization. This will not only lead to a better understanding of the mode of action of probiotic strains, such as EcN, but also to the development of new strategies in the treatment of ini?ctions and inflammatory bowel diseases