title: The Staphylococcus aureus alpha-toxin perturbs the barrier function in Caco-2 epithelial cell monolayers by altering junctional integrity.
abstract: Increased microvascular permeability is a hallmark of sepsis and septic shock. Intestinal mucosal dysfunction may allow translocation of bacteria and their products, thereby promoting sepsis and inflammation. Although Staphylococcus aureus alpha-toxin significantly contributes to sepsis and perturbs the endothelial barrier function, little is known about possible effects of S. aureus alpha-toxin on human epithelial barrier functions. We hypothesize that S. aureus alpha-toxin in the blood can impair the intestinal epithelial barrier and thereby facilitate the translocation of luminal bacteria into the blood, which may in turn aggravate a septic condition. Here, we showed that staphylococcal alpha-toxin disrupts the barrier integrity of human intestinal epithelial Caco-2 cells as evidenced by decreased transepithelial electrical resistance (TER) and reduced cellular levels of junctional proteins, such as ZO-1, ZO-3, and E-cadherin. The Caco-2 cells also responded to alpha-toxin with an elevated cytosolic calcium ion concentration ([Ca(2+)](i)), elicited primarily by calcium influx from the extracellular environment, as well as with a significant reduction in TER, which was modulated by intracellular calcium chelation. Moreover, a significantly larger reduction in TER and amounts of the junctional proteins, viz., ZO-3 and occludin, was achieved by basolateral than by apical application of the alpha-toxin. These experimental findings thus support the hypothesis that free staphylococcal alpha-toxin in the bloodstream may cause intestinal epithelial barrier dysfunction and further aggravate the septic condition by promoting the release of intestinal bacteria into the underlying tissues and the blood.
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Young-Keun
authors.initials: YK
authors.lastname: Kwak
authors.forename: Elena
authors.initials: E
authors.lastname: Vikström
authors.forename: Karl-Eric
authors.initials: KE
authors.lastname: Magnusson
authors.forename: Beatrix
authors.initials: B
authors.lastname: Vécsey-Semjén
authors.forename: Patricia
authors.initials: P
authors.lastname: Colque-Navarro
authors.forename: Roland
authors.initials: R
authors.lastname: Möllby
mesh_terms: D001427:Bacterial Toxins / Q000633:toxicity*; D018938:Caco-2 Cells; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D006460:Hemolysin Proteins / Q000633:toxicity*; D006801:Humans; D007365:Intercellular Junctions / Q000187:drug effects*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D062793:Occludin; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013211:Staphylococcus aureus / Q000378:metabolism*; D013997:Time Factors; D062825:Zonula Occludens Proteins; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D015820:Cadherins; D002352:Carrier Proteins; D006460:Hemolysin Proteins; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; D012333:RNA, Messenger; C569042:TJP1 protein, human; C111873:TJP3 protein, human; D062825:Zonula Occludens Proteins; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; C021091:staphylococcal alpha-toxin; D002118:Calcium