REDISTRIBUTION AND DYSFUNCTION OF INTEGRINS IN CULTURED RENAL EPITHELIAL-CELLS EXPOSED TO OXIDATIVE STRESS

Tubular obstruction by detached renal tubular epithelial cells is a major cause of oliguria in acute renal failure. Viable renal tubular cells can be recovered from urine of patients with acute tubular necrosis, suggesting a possible defect in cell adhesion to the basement membrane. To study this process of epithelial cell desquamation in vitro, we investigated the effect of nonlethal oxidative stress on the integrin adhesion receptors of the primate kidney epithelial cell line BS-C-1. Morphological and functional studies of cell adhesion properties included the following: interference reflection microscopy, intravital confocal microscopy and immunocytochemistry, flow cytometric analysis of integrin receptor abundance, and cell-matrix attachment assay. High levels of the integrin subunits alpha3, alpha(v), and beta1 were detected on the cell surface by fluorescence-activated cell sorting (FACS) analysis, as well as lower levels of alpha1, alpha2, alpha4, alpha5, alpha6, and beta3. Exposure of BS-C-1 cells to nonlethal oxidative stress resulted in the disruption of focal contacts, disappearance of talin from the basal cell surface, and in the redistribution of integrin alpha3-subunits from predominantly basal location to the apical cell surface. As measured in a quantitative cell attachment assay, oxidative stress decreased BS-C-1 cell adhesion to type IV collagen, laminin, fibronectin, and vitronectin. Defective adhesion was not associated with a loss of alpha3-, alpha4-, or alpha(v)-integrin subunits from the cell surface. We conclude that nonlethal oxidative stress weakens epithelial cell attachment to the extracellular matrix by disrupting focal contacts, by altering physiological distribution of integrin receptors, and by impairing receptor function.