C. difficile toxin A increases intestinal permeability and induces Cl- secretion.

Mucosal sheets of guinea pig ileum mounted in Ussing chambers were used to determine effects of highly purified Clostridium difficile toxin A on intestinal structure and barrier function in the absence of recruited neutrophils and blood flow. With the use of standard electrophysiological and morphological techniques, our results indicate that 5 micrograms/ml mucosal toxin A induces substantial alteration in epithelial permeability and in structure of absorptive cells. Transepithelial fluxes of mannitol (3.6 A) and inulin (11.5 A) increased 20-80 min after toxin A exposure (63 +/- 13 vs. 149 +/- 14 and 2.33 +/- 0.43 vs. 7.03 +/- 1.0 nmol.cm-2.h-1 for mannitol and inulin; controls vs. toxin exposed, respectively, both P less than 0.01). Toxin A exposure diminished short-circuit current (153 +/- 8 vs. 77 +/- 6 microA/cm2 for control and toxin exposed, respectively, P less than 0.001), decreased transepithelial electrical resistance (61.6 +/- 3 vs. 50.1 +/- 3.9 omega.cm2 for control and toxin exposed, respectively, P less than 0.05), increased passive permeation of Na+ (19.1 +/- 0.9 vs. 27.4 +/- 0.9 mumol.cm-2.h-1 for control and toxin exposed, respectively), and induced a Cl- secretory response (net flux 3.65 +/- 3.0 vs. -4.62 +/- 2.6 mumol.cm-2.h-1, for control and toxin exposed, respectively, P less than 0.05) over the 2-h experimental time course. Toxin A-induced structural alterations of villus tip absorptive cells were strikingly similar to those induced by the actin-binding agent cytochalasin D. Specifically, cells displayed constricted subjunctional zones, flared microvillus brush borders, condensation of microfilaments in the zone of the perijunctional actomyosin ring, and breakdown of intercellular tight junctions.(ABSTRACT TRUNCATED AT 250 WORDS)