The multidrug resistance protein MRP1 mediates the release of glutathione disulfide from rat astrocytes during oxidative stress

The release of glutathione disulfide has been considered an important proce ss for the maintenance of a reduced thiol redox potential in cells during o xidative stress. In cultured rat astrocytes, permanent hydrogen peroxide-in duced oxidative stress caused a rapid increase in intracellular glutathione disulfide, which was followed by the appearance of glutathione disulfide i n the medium. Under these conditions, the viability of the cells was not co mpromised. In the presence of cyclosporin A and the quinoline-derivative MK 571, inhibitors of multidrug resistance proteins (MRP1 and MRP2), glutathio ne disulfide accumulated in cells and the release of glutathione disulfide from astrocytes during H2O2 stress was potently inhibited, suggesting a con tribution of MRP1 or MRP2 in the release of glutathione disulfide from astr ocytes. Using RT-PCR we amplified a cDNA from astroglial RNA with a high de gree of homology to MRP1 from humans and mouse. In contrast, no fragment wa s amplified by using primers specific for rat MRP2. In addition, the presen ce of MRP1 protein in astrocytes was demonstrated by its immunolocalization in cells expressing the astroglial marker protein glial fibrillary acidic protein. Our data identify rat astrocytes as a MRP1-expressing brain cell t ype and demonstrate that this transporter participates in the release of gl utathione disulfide from astrocytes during oxidative stress.