Copper treatment alters the barrier functions of human intestinal Caco-2 cells: involving tight junctions and P-glycoprotein

This study investigated the effects of copper on paracellular permeability and P-glycoprotein (P-gp) in Caco-2 cells. Apical treatment with 100 - 300 mM CuSO4 in Hanks' balanced salt solution (HBSS, up to 3 hours) induced a time- and concentration-dependent increase in permeability of Caco-2 cell monolayers monitored by transepithelial electrical resistance ( TEER). Copper treatment also induced a concentration-dependent reduction of F-actin stain, but not of tight junctional protein ZO-1. In addition, without any adverse effects on TEER, apical treatment with 300 mM CuSO4 in complete medium ( for 24 hours) could reduce basolateral-to-apical transport, and increase apical-to-basolateral transport of rhodamine-123 (Rho-123) and accumulation of Rho-123 in Caco-2 cells. Treatment with 10 - 100 muM CuSO4 in HBSS ( up to 3 hours) also induced a time- and concentration-dependent increase in accumulation of Rho-123 in Caco-2 cells. The results indicated that copper treatment increased the paracellular permeability probably by perturbing F-actin skeleton, and inhibited P-gp, thus altering the barrier functions of Caco-2 cells.