Oxidant-induced disruption of intestinal epithelial barrier function: Role of protein tyrosine phosphorylation

The effect of hydrogen peroxide (H₂O₂) on intestinal epithelial barrier function was examined in Caco-2 and T84 cell monolayers. H₂O₂ reduced transepithelial electrical resistance (TER) of Caco-2 and T84 cell monolayers. This decrease in TEE was associated with a decrease in dilution potential and an increase in [³H]mannitol permeability, suggesting 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 orthovanadate, 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 μM) and tyrphostin (100 μM) inhibited the effect of H₂O₂ on TER, dilution potential, mannitol permeability, and PTP. These studies show that H₂O₂ increases the epithelial permeability by disrupting paracellular junctional complexes, most likely by a PTP-dependent mechanism.