OXIDANT-INDUCED DISRUPTION OF INTESTINAL EPITHELIAL BARRIER FUNCTION - ROLE OF PROTEIN-TYROSINE PHOSPHORYLATION

The effect of hydrogen peroxide (H2O2) on intestinal epithelial barrie r function was examined in Caco-2 and T84 cell monolayers. H2O2 reduce d transepithelial electrical resistance (TER) of Caco-2 and T84 cell m onolayers. This decrease in TER was associated with a decrease in dilu tion potential and an increase in [H-3]mannitol permeability, suggesti ng an H2O2-induced disruption of the paracellular junctional complexes . H2O2 administration also induced tyrosine phosphorylation of several proteins (at the molecular mass ranges of 50-90, 100-130, and 150-180 kDa) in Caco-2 cell monolayers. Phenylarsine oxide and sodium orthova nadate, inhibitors of protein tyrosine phosphatase, decreased TER and increased mannitol permeability and protein tyrosine phosphorylation ( PTP). A low concentration of sodium orthovanadate also potentiated the effect of H2O2 on TER, dilution potential, mannitol permeability, and PTP. Pretreatment with genistein (30-300 mu M) and tyrphostin (100 mu M) inhibited the effect of H2O2 on TER, dilution potential, mannitol permeability, and PTP. These studies show that H2O2 increases the epit helial permeability by disrupting paracellular junctional complexes, m ost likely by a PTP-dependent mechanism.