Recovery from Oxidative Stress: Effects on the Tight Junction in Epithelial Cells.

Abstract

Loss of barrier function in kidney epithelial cells due to alterations in the tight junction (TJ) may be a contributory mechanism of ischemia‐reperfusion injury. The objective of this study was to demonstrate the changes in TJ function and protein composition during recovery after exposure to oxidative stress. Oxidative stress was induced in MDCK Type II cells by exposure to H2O2, and cells were subsequently recovered for 24 hours. Transepithelial electrical resistance (TER) and solute flux were used as measures of barrier function. Protein expression and localization was determined for TJ proteins during the recovery period. Moderate doses of H2O2 perturbed TJ function without exhibiting a significant cytotoxic effect. ERK‐1/2, an enzyme of the mitogen activated protein kinase (MAPK) pathway, was activated within minutes of exposure to H2O2. Exposure to H2O2 with subsequent recovery resulted in initially decreased TER followed by recovery of function and was accompanied by changes in expression and localization of the TJ proteins occludin and claudin‐1. Inhibition of ERK activation significantly attenuated recovery changes in TER and TJ protein composition induced by H2O2. Our findings suggest that the TJ in kidney epithelial cells is altered by H2O2 exposure and recovery. These changes appear to be mediated by activation of the MAPK pathway. This work was supported by NIH Grant DK065652 and the HHMI Foundation.