Role of Protein Kinase C in Increase of Transepithelial Permeability Induced by Oxidants in Opossum Kidney Cells

Abstract

This study was undertaken to determine if oxidants induce an increase in transepithelial permeability through protein kinase C (PKC) activation in opossum kidney (OK) cells. Exposure of cells to oxidants, t-butylhydroperoxide (t-BHP) and H₂O₂, resulted in a decrease in the transepithelial resistance and an increase in the transepithelial mannitol flux, indicating an increase of transepithelial permeability. These effects were not, however, prevented by staurosporine, a potent inhibitor of PKC enzyme. PKC activators, phorbol esters (PMA and PDBu), also increased the transepithelial permeability, but their effects were effectively prevented by staurosporine, unlike oxidants. Furthermore, phorbol esters induced a translocation of PKC enzyme from the cytosol to the plasma membrane, indicating PKC activation. Oxidants, however, did not induce a translocation of PKC, implying an involvement of other mechanisms. Effects of oxidants on the transepithelial permeability were associated with cell injury as evidenced by an increase in lactate dehydrogenase release. These results strongly suggest that oxidants induce an increase in the transepithelial permeability through cell damage rather than through PKC activation in OK cell monolayers.