EFFECT OF CLOSTRIDIUM DIFFICILE TOXINS ON THE CAECAL EPITHELIAL BARRIER

The most striking effect of Clostridium difficile infection is its degrading of the intestinal barrier. The aim of this study was to characterize the effect of C. difficile toxins on the epithelial layer including cellular and paracellular constituents. Accordingly, the caecum of C3H/He mice was challenged under 3 experimental conditions with C. difficile strain VP1 10463 : 1) by in vivo inoculation of axenic mice, 2) by adding the toxins to ligated caeca in vivo, and 3) by adding them to the mucosal side of isolated caeca in Ussing chambers. Under all 3 conditionals, the epithelial barrier was tested in caeca mounted in these chambers. The transeptithelial potential difference (PD), electrical conductance (C), and intact and degraded Horseradish peroxidase (HRP) fluxes were used as indexes of permeability. Results : 1) In axenic mice, C. difficile caused severe infection, produced toxins A and B, reduced PD, and enhanced C and intact HRP fluxes without changing degraded HRP fluxes; 2) 4 hours after the toxins were added to ligated caeca in vivo, PD was relatively unaltered, but C intact and degraded HRP fluxes increased, and 3) when toxins were added to caeca during 2 hours in the Ussing chambers, the only modification observed was an increase in degraded-HRP fluxes. These results indicate that the C. difficile toxins gradually cause intestinal lesions. After an apparent resistance, they stimulate the endocytotic process, increase paracellular permeability and finally cause loss of cell viability.