NF-E2-related factor-2 mediates neuroprotection against mitochondrial complex I inhibitors and increased concentrations of intracellular calcium in primary cortical neurons

NF-E2-related factor-2 (Nrf2) regulates the gene expression of phase II detoxification enzymes and antioxidant proteins through an enhancer sequence referred to as the antioxidant-responsive element ( ARE). In this study, we demonstrate that Nrf2 protects neurons in mixed primary neuronal cultures containing both astrocytes (similar to 10%) and neurons (similar to 90%) through coordinate up-regulation of ARE- driven genes. Nrf2(-/-) neurons in this mixed culture system were more sensitive to mitochondrial toxin ( 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine or rotenone)-induced apoptosis compared with Nrf2(+/+) neurons. To understand the underlying mechanism of this observed differential sensitivity, we compared the gene expression profiles using oligonucleotide microarrays. Microarray data showed that Nrf2(+/+) neuronal cultures had higher expression levels of genes encoding detoxification enzymes, antioxidant proteins, calcium homeostasis proteins, growth factors, neuron-specific proteins, and signaling molecules compared with Nrf2(-/-) neuronal cultures. As predicted from the microarray data, Nrf2(-/-) neurons were indeed more vulnerable to the cytotoxic effects of ionomycin- and 2,5-di( t-butyl)-1,4-hydroquinone-induced increases in intracellular calcium. Finally, adenoviral vector-mediated overexpression of Nrf2 recovered ARE- driven gene expression in Nrf2(-/-) neuronal cultures and rescued Nrf2(+/+) neurons from rotenone- or ionomycin- induced cell death. Taken together, these findings suggest that Nrf2 plays an important role in protecting neurons from toxic insult.