Saccharomyces boulardiiPreserves the Barrier Function and Modulates the Signal Transduction Pathway Induced in EnteropathogenicEscherichia coli-Infected T84 Cells

Abstract

Use of the nonpathogenic yeastSaccharomyces boulardii is a thermophilic, nonpathogenic yeast administered in Western Europe for the prevention and treatment of a variety of diarrheal diseases (17, 29). However, the mechanisms by which S. boulardii controls diarrhea remain elusive. The efficacy of this yeast has been attributed to several of its properties, such as its effect on the mucosa leading to an increase in dissaccharidase activity (8) or stimulation of the immune response (7). In animals, administration of S. boulardii provides protection against intestinal lesions caused by several diarrheal pathogens (10,33). In vitro studies have demonstrated that S. boulardii exerts antagonistic activity against various bacterial pathogens (6). Recent studies have reported the adhesion of the Salmonella enterica serovars Typhimurium and Enteritis and of enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli to S. boulardii (24,25).EPEC is a major cause of diarrhea in the developing world (31, 34). The pathogenesis of EPEC infections involves a three-stage process. (i) EPEC adheres initially to intestinal epithelial cells in a pattern described as localized adherence (36). This pattern of adherence, characterized by microcolonies of bacteria associated with the epithelial cells, is dependent on the expression of the bacterial type IV bundle-forming pilus (BFP) (3). (ii) Next, the bacteria induce signal transduction pathways in host cells, leading to an elevation in the intracellular levels of Ca 2ϩ and inositol triphosphate (16, 23) and the phosphorylation of cellular proteins (4, 35, 41). (iii) These signaling events culminate in the formation of attachingand-effacing lesions which are characterized by localized degeneration of the microvilli, intimate contact between the bacteria and the infected cell, and the assembly of highly organized cytoskeletal structures in the epithelial cells just beneath the attached bacteria, forming cuplike pedestals (22,27,30). EPEC is also able to induce its internalization by nonphagocytic epithelial cells (2, 15).The aim of our study was to investigate in vitro the effect of S. boulardii against EPEC infection using the T84 cell line derived from a colon carcinoma. This cell line has been extensively used to elucidate the mechanism of EPEC-induced diarrhea. EPEC infection results in a modification of the T84 barrier function, characterized by a drop in transepithelial resistance, an increase in permeability, and modification of the distribution of the tight junction-associated protein 37). Our study reveals that S. boulardii maintains the barrier function and the viability of EPEC-infected T84 cells. Although the yeast does not modify the number of cell-associated bacteria, it reduces the number of intracellular bacteria. The phosphorylation of several proteins induced by EPEC in T84 cells is diminished in the presence of S. boulardii. Finally, the yeast interferes with the ERK1/2 mitogen-activated protein (MAP) kinase pathway that, as demonstrated in this study, is ...

Enteropathogenic Escherichia coli , Shigella flexneri , and Listeria monocytogenes Recruit a Junctional Protein, Zonula Occludens-1, to Actin Tails and Pedestals

“…Upon infection by EPEC, the peripheral lining of ZO-1 began to disperse at 3 h postinfection and became discontinuous at 5 h or later. These changes are basically consistent with the observations made with T84 monolayers (10,37,43,48). In addition to these changes, we noticed the recruitment of ZO-1 to the sites of bacterial attachment (Fig.…”

Treatment of Diarrhea-Predominant Irritable Bowel Syndrome With Mesalazine and/or Saccharomyces Boulardii

“…During the intestinal transit, S. boulardii interacts with resident microflora and intestinal mucosa. Moreover, experimental studies suggest that S. boulardii is protective against enteric pathogens, modulating the host immune response, decreasing inflammation and hydro electrolytic secretions, inhibiting bacterial toxin and enhancing trophic factors such as brush border membrane enzymes and nutrient transporters (7,8,10,14,37,53,40,44,47) .…”

Enterocytes’ tight junctions: From molecules to diseases

“…Secondly, intestinal T� disrup- Table 5 Interaction between bacterial strains and tight junctional molecules Vibrio cholerae [87,88] It expresses zonula occludens toxin that reversibly increases paracellular permeability, triggering phospholipase C and protein kinase Ca dependent actin polymerization This process is primary or secondary related to TJ disruption Shigella flexneri [89] Secretes heat stable proteins that affect intestinal cells and lead to TJ disruption, even in the absence of living bacteria Clostridium perfringens [29,31,61,62] Its enterotoxin interacts with high affinity to claudin-4, therefore also known as CPE-R Lower affinity receptors are claudin-3 and occludin. CPE is proposed to be a multifunctional toxin that first induces cell damage at the level of the cell membrane, and thereby relates to TJ proteins, causing structural and functional alterations [61] Michl et al [31] have studied the effect of CPE on pancreatic cell cancers that expressed claudin 4 [31] , and they suggest that targeting of claudin-4 expressing tumors with CPE can represent a promising treatment method Clostridium difficile [90] This pathogenic microorganism, known etiologic factor of pseudomembranous colitis, secretes two toxins TcdA and TcdB that act through the Rho GTPase pathway to produce cell damage Study for their effect on epithelial TJ structure assumed that they lead to actin rearrangement, actin-ZO1 dissociation and dissociation of TJ components with changes of their cytoplasmic localization [90] EPEC [91][92][93] EPEC secretes through the type Ⅲ secretion mechanism [87] the EspF protein, that is dose-dependently related to TER and epithelial barrier disruption and cytoplasmic localization of occludin [91] These effects seem to relate primary with phosphorylation of 20 kDa myosin light chain and cytoskeletal contraction. Occludin appears dephosphorylated on serine/threonine residues [92] The pathogenic action of EPEC on the intestinal epithelium is reversed by Saccharomyces boulardii [93] CPE: Clostridium perfringens enterotoxin; CPE-R: Clostridium perfringens enterotoxin receptor; EPEC: Enteropathogenic Escherichia coli; TJ: Tight junction; ZO: Zonula occludens; GTPase: Guanosine triphosphatase.…”