Protective effect of human HDL against Cu(2+)-induced oxidation of astrocytes

Several studies support the role of copper-mediated oxidative injury in the development of neurodegenerative diseases. In this study we demonstrated that copper exerts an oxidant effect on cultured astrocytes as shown by the significant increase in the levels of hydroperoxides in astrocytes oxidized with 10 micromol/L Cu2+ for 4 h with respect to control cells. Using the fluorescent probe 2,7-dichloro-dihydrofluorescein diacetate (H2DCFDA) that represents an useful approach for measuring the production of reactive oxygen species (ROS), a significant increase in fluorescence intensity was observed in Cu(2+)-oxidized cells. The increase in the levels of lipid peroxidation products was associated with a significant decrease in cell viability in Cu(2+)-treated cells with respect to untreated cells. Many evidences suggest that human high-density lipoproteins (HDL) play a key role against lipid peroxidation of plasma low-density lipoproteins (LDL) and peripheral cells. We investigated whether HDL isolated from human plasma exert a protective role against copper-induced lipid peroxidation on astrocytes in culture. The increase in the levels of hydroperoxides and in the fluorescent intensity of H2DCFDA was significantly lower in astrocytes oxidized after preincubation for 20 h in the presence of HDL (50-200 microg/mL) with respect to cells preincubated without HDL. The decrease in viability in Cu(2+)-treated astrocytes preincubated with HDL was significantly lower with respect to cells preincubated without. These results demonstrate that preincubation of astrocytes with HDL for 20 h makes cells more resistant to the Cu2+ oxidant effect. The protective effect exerted by HDL against copper-induced oxidative damage on astrocytes was concentration dependent. These data suggest that copper, at concentrations similar to those observed in cerebro-spinal fluid of patients affected by neurodegenerative diseases, induces oxidative damage to astrocytes and confirm that HDL exert a protective effect against oxidative damage induced by copper ions.