Different effects of oxidative stress on activation of transcription factors in primary cultured rat neuronal and glial cells

We compared the cytotoxic effects of oxidative stress on neuronal and glial cells in vitro by examining the cell viability and changes in DNA-binding activities of transcription factors, AP-1 and CREB, using Trypan blue exclusion and electrophoretic mobility shift assay (EMSA), respectively. Neurotoxin 6-hydroxydopamine (6-OHDA) and H₂O₂ reduced the viability of both types of cells in time- and concentration-dependent manner. Both neurotoxins dose-dependently decreased DNA-binding activities in neuronal cells. The results of cell viability assay suggested that these changes may reflect the reduction in neuronal cell viability. In contrast, both reagents increased DNA-binding activities in glial cells, although they decreased cell numbers. These results suggest that the effects of oxidative stress on transcription factors is different in neuronal and glial cells. We also examined the effect of brain-derived neurotrophic factor (BDNF) on 6-OHDA- or H₂O₂-induced changes in DNA-binding activities. In neuronal cells, pre-treatment with BDNF prevented the decrease in DNA-binding activities induced by 6-OHDA or H₂O₂. In glial cells, the effect of BDNF on oxidative stress-induced changes in DNA-binding activities in the 6-OHDA-treated group were opposite to those in H₂O₂-treated group. Our results suggest that 6-OHDA and H₂O₂ may exert their cytotoxic mechanisms through different signal transduction systems.