Epidermal growth factor (eof) suppresses oxidant-induced protein tyrosine phosphorylation (ftp) in caco-2 cell monolayers

Oxidative stress is known to cause an increase in cellular PTP. Hydrogen peroxide (H.Q:) has been shown to increase tyrosine phosphorylation of a number of cellular proteins that may play a role in the oxidant-induced cell injury. In the present study, we analyzed the effect of H;O: on intestinal epithelial integrity and PTP using Caco-2 (colon adenocarcinoma) cells grown to umflucncy as monolaycrs on polycarbonate membranes (form a tight monolayer of epithelium). Additionally, we evaluated the effect of EOF on H 0.-induced PTP in these cells. PTP was analyzed by Western blot technique using anu-phosphotyrosine antibody, Exposure of Caco-2 cell monolaycrs to HO 110 mM) resulted in a decrease in transepithelial electrical resistance (TER), while pretreatment of monolayers with apical or basal EGF (30 nM) prevented this H-O-induccd decrease in TER. Exposure to FJ 0 increased tyrosine phosphorylation of a number of proteins (especially those with the M W range of 150-200. 110-130, 60-90. 54 & 44 kDa) in a dose- and timedependent manner. Pretreatment of monolayers with apical or basal EGF (1-30 nM) suppressed H;O -induced phosphorylation of these proteins in a dosedependent manner. We speculate that H:O; increases epithelial permeability by increasing PTP in Caco-2 cells, and that EGF protects epithelium from oxidantmiurv. which involves suppression of uxidant-induccd PTP.