Copper treatment alters the permeability of tight junctions in cultured human intestinal Caco-2 cells

The effects of copper on tight-junction permeability were investigated in h uman intestinal Caco-2 cells, monitoring transepithelial electrical resista nce and transepithelial passage of mannitol. Apical treatment of Caco-2 cel ls with 10-100 mu M CuCl2 (up to 3 h) produced a time- and concentration-de pendent increase in tight-junction permeability, reversible after 24 h in c omplete medium in the absence of added copper. These effects were not obser ved in cells treated with copper complexed to L-histidine [Cu(His)(2)]. The copper-induced increase in tight-junction permeability was affected by the pH of the apical medium, as was the apical uptake of (CuCl2)-Cu-64, both e xhibiting a maximum at pH 6.0. Treatment with CuCl2 produced a concentratio n-dependent reduction in the staining of F actin but not of the junctional proteins zonula occludens-l, occludin, and E-cadherin and produced ultrastr uctural alterations to microvilli and tight junctions that, were not observ ed after treatment with up to 200 mu M Cu(His)(2) for 3 h. Overall, these d ata point to an intracellular effect of copper on tight junctions, mediated by perturbations of the F actin cytoskeleton.