Intestinal barrier dysfunction triggered by invasive bacteria.

The ability to control uptake across the mucosa and to protect the gut from harmful substances present in the lumen is defined as intestinal barrier function. Two routes are usually distinguished for transepithelial transport. The paracellular route allows the passage of ions and small molecules and is mainly regulated by tight junctions (TJ). The transcellular route concerns large molecules or small particles (including bacteria) and is mediated by cell endocytosis and intracellular vesicular traffic. Enteropathogenic bacteria increase the transcellular permeability, especially in the follicle-associated epithelium. They also modulate TJ opening via the redistribution of TJ proteins and the activation of the myosin light chain kinase (MLCK). This review focuses on the molecular mechanisms involved in the bacteria-induced barrier defect and briefly discusses their consequences in human diseases.