HELICOBACTER-PYLORI DISRUPTS EPITHELIAL BARRIER FUNCTION IN A PROCESSINHIBITED BY PROTEIN-KINASE-C ACTIVATORS

Helicobacter pylori colonizes the gastric mucosa, and the infection is related to the development of diverse gastric pathologies, possibly b y directly or indirectly affecting epithelial-cell function. We analyz ed the influence of the bacteria on transepithelial electrical resista nce (TER) on a model tight epithelium, T84, grown to confluence in per meable filters. H. pylori sonicates produced a dramatic decrease in TE R after 1 to 2 h of exposure, while sonicates from other bacteria did not induce a significant reduction of TER. The effect induced by sonic ates was mimicked by a water-soluble fraction from the bacterial surfa ce, was not reproducible with isolated lipopolysaccharide, and was con comitant with a significant increase in the paracellular permeability of the marker molecule [C-14]mannitol. Furthermore, H. pylori sonicate s also provoked a significant increase in permeability to [C-14]mannit ol across rat gastric mucosa in vitro. The sonicate-induced decrease i n TER in T84 monolayers was inhibited by the protein kinase C (PKC) ac tivator phorbol myristate acetate. As PKC is directly involved in tigh t junction regulation, we suggest that H. pylori may induce intracellu lar signalling events counteracting PKC effects. Following long-term H . pylori stimulation, epithelial monolayers regained baseline resistan ce values slowly after 24 h. The resistance recovery process was inhib ited by cycloheximide, indicating its dependency upon protein synthesi s. No association between resistance variation and E-cadherin protein levels was observed. These results indicate that H. pylori alters in v itro the barrier properties of the epithelium, probably by generating cell signalling events counteracting the normal function of PKC. This increased permeability may provide a potential mechanism by which H. p ylori antigens can reach the gastric lamina propria, thereby activatin g the mucosal immune system.