The antioxidant responsive element (ARE) mediates transcriptional regulation of phase II detoxification enzymes and antioxidant proteins such as NAD(P)H:quinone oxidoreductase (NQO1), glutathione S-transferases, and glutamate-cysteine ligase. In this study, we demonstrate that NF-E2-related factor-2 (Nrf2) plays a major role in transcriptional activation of ARE-driven genes and identify Nrf2-dependent genes by oligonucleotide microarray analysis using primary cortical astrocytes from Nrf2(+/+) and Nrf2(-/-) mice. Nrf2(-/-) astrocytes had decreased basal NQO1 activity and no induction by tert-butylhydroquinone compared with Nrf2(+/+) astrocytes. Similarly, both basal and induced levels of human NQO1-ARE-luciferase expression in Nrf2(-/-) astrocytes were significantly lower than in Nrf2(+/+) astrocytes. Furthermore, human NQO1-ARE-luciferase expression in Nrf2(-/-) astrocytes was restored by overexpression of Nrf2, whereas ARE activation in Nrf2(+/+) astrocytes was completely blocked by dominant-negative Nrf2. In addition, we observed that Nrf2-dependent genes protected primary astrocytes from H(2)O(2)- or platelet-activating factor-induced apoptosis. In support of these observations, we identified Nrf2-dependent genes encoding detoxification enzymes, glutathione-related proteins, antioxidant proteins, NADPH-producing enzymes, and anti-inflammatory genes using oligonucleotide microarrays. Proteins within these functional categories are vital to the maintenance and responsiveness of a cell defense system, suggesting that an orchestrated change in gene expression via Nrf2 and the ARE gives a synergistic protective effect against oxidative stress.