Abstract
Oxidative stress is an important molecular mechanism of astrocyte injury and death following ischemia/reperfusion and may be an effective target of intervention. One therapeutic strategy for detoxifying the many different reactive oxygen and nitrogen species that are produced under these conditions is induction of the Phase II gene response by the use of chemicals or conditions that promote the translocation of the transcriptional activating factor NRF2 from the cytosol to the nucleus, where it binds to genomic antioxidant response elements. This study tested the hypothesis that pre- or post-treatment of cultured cortical astrocytes with sulforaphane, an alkylating agent known to activate the NRF2 pathway of gene expression protects against death of astrocytes caused by transient exposure to O(2) and glucose deprivation (OGD). Rat cortical astrocytes were exposed to 5 muM sulforaphane either 48 h prior to, or for 48 h after a 4-h period of OGD. Both pre- and post-treatments significantly reduced cell death at 48 h after OGD. Immunostaining for 8-hydroxy-2-deoxyguanosine, a marker of DNA/RNA oxidation, was reduced at 4 h reoxygenation with sulforaphane pretreatment. Sulforaphane exposure was followed by an increase in cellular and nuclear NRF2 immunoreactivity. Moreover, sulforaphane also increased the mRNA, protein level, and enzyme activity of NAD(P)H/Quinone Oxidoreductase1, a known target of NRF2 transcriptional activation. We conclude that sulforaphane stimulates the NRF2 pathway of antioxidant gene expression in astrocytes and protects them from cell death in an in vitro model of ischemia/reperfusion.