The Glutathione System of Peroxide Detoxification Is Less Efficient in Neurons than in Astroglial Cells

The ability of neurons to detoxify exogenously applied peroxides was analyzed using neuron-rich primary cultures derived from embryonic rat brain. Incubation of neurons with H 2 O 2 at an initial concentration of 100 μM (300 nmol/3 ml) led to a decrease in the concentration of the peroxide, which depended strongly on the seeding density of the neurons. When 3 x 10 6 viable cells were seeded -per dish, the half-time for the clearance by neurons of H 2 O 2 from the incubation buffer was 15, min. Immediately after application of 100 μM H 2 O 2 to neurons, glutathione was quickly oxidized. After incubation for 2.5 min, GSSG accounted- for 48% of the total glutathione. Subsequent removal of H 2 O 2 caused an almost complete regeneration of the original ratio of GSH to GSSG within 2.5 min. Compared with confluent astroglial cultures, neuron-rich cultures cleared H 2 O 2 more slowly from the incubation buffer, However, if the differences in protein content were taken into consideration, the ability of the cells to dispose of H 2 O 2 was identical in the two culture types. The clearance rate by neurons for H 2 O 2 was strongly reduced in the presence of the catalase inhibitor 3-aminotriazol, a situation contrasting with that in astroglial cultures. This indicates that for the rapid clearance of H 2 O 2 by neurons, both glutathione peroxidase and catalase are essential and that the glutathione system cannot functionally compensate for the loss of the catalase reaction. In addition, the protein-normalized ability of neuronal cultures to detoxify exogenous cumene hydroperoxide, an alkyl hydroperoxide that is reduced exclusively via the glutathione system, was lower than that of astroglial cells by a factor of 3. These results demonstrate that the glutathione system of peroxide detoxification in neurons is less efficient than that of astroglial cells.