Bacterial interference with host epithelial junctional complexes: Probiotic bacteria vs. A/E lesion-forming Escherichia coli

During colonization, enteropathogenic (EPEC) and enterohaemorrhagic (EHEC) Escherichia coli are capable to manipulate host cytoskeleton and colonize gut epithelia by a specific mode of attachment known as the attaching and effacing lesion (A/E lesion). While actin rearrangements during A/E lesion formation have been extensively investigated, the possible alterations of other cytoskeletal elements like those comprising the intercellular junctional complexes (JC) of polarized cells during infection have only lately attracted attention. The present mini-review addresses the opposite effects of two groups of bacteria, A/E lesion-forming pathogenic E. coli and probiotic bacterial strains, on JC. JC are important in maintaining gut barrier functions. EPEC and EHEC can disrupt JC which as a consequence leads to reduction in the transepitelial electrical resistance (TER) and an increase of the permeability to macromolecules. Probiotic bacteria on the other hand stabilize JC thus increasing TER and reducing permeability to macromolecular markers. Probiotic strains can protect JC integrity of polarized cells from the damage caused by EPEC or EHEC. Together with the promise of these results, of concern is the fact that the outcome of the studies can differ dependent on experimental protocols. Studies with living bacteria and different strain combinations have also put forward strain specific effects. Therefore, an important practical item for future studies is the identification of the molecules synthesized by probiotic bacteria that may be active on JC stability.