The Keap1-Nrf2 pathway is the major regulator of cytoprotective responses to oxidative and electrophilic stress. Although cell signaling pathways triggered by the transcription factor Nrf2 prevent cancer initiation and progression in normal and premalignant tissues, in fully malignant cells Nrf2 activity provides growth advantage by increasing cancer chemoresistance and enhancing tumor cell growth. In this graphical review, we provide an overview of the Keap1-Nrf2 pathway and its dysregulation in cancer cells. We also briefly summarize the consequences of constitutive Nrf2 activation in cancer cells and how this can be exploited in cancer gene therapy.

The amyloid hypothesis of Alzheimer's disease (AD) postulates that amyloid-␤ (A␤) deposition and neurotoxicity play a causative role in AD; oxidative injury is thought to be central in the pathogenesis. An endogenous defense system against oxidative stress is induced by binding of the transcription factor nuclear factor E2-related factor 2 (Nrf2) to the antioxidant response element (ARE) enhancer sequence. The Nrf2-ARE pathway is activated in response to reactive oxygen species to trigger the simultaneous expression of numerous protective enzymes and scavengers. To exploit the Nrf2-ARE pathway therapeutically, we delivered Nrf2 bilaterally into the hippocampus of 9-month-old transgenic AD mice (APP/PS1 mice) using a lentiviral vector encoding human Nrf2. The data indicate that significant reductions in spatial learning deficits of aged APP/PS1 mice in a Morris Water Maze can be achieved by modulating levels of Nrf2 in the brain. Memory improvement in APP/PS1 mice after Nrf2 transduction shifts the balance between soluble and insoluble A␤ toward an insoluble A␤ pool without concomitant change in total brain A␤ burden. Nrf2 gene transfer is associated with a robust reduction in astrocytic but not microglial activation and induction of Nrf2 target gene heme oxygenase 1, indicating overall activation of the Nrf2-ARE pathway in hippocampal neurons 6 months after injection. Results warrant further exploration of the Nrf2-ARE pathway for treatment of AD and suggest that the Nrf2-ARE pathway may represent a potential therapeutic strategy to pursue in AD in humans, particularly in view of the multiple mechanisms by which Nrf2 can exert its protective effects.amyloid-beta ͉ astrocyte ͉ heme oxygenase-1 ͉ microglia ͉ oxidative stress

Nitro-fatty acids (NOIn this study, we investigate the molecular mechanisms by which 9-and 10-nitro-octadec-9-enoic acid (OA-NO 2 ) activate the transcription factor Nrf2, focusing on the post-translational modifications of cysteines in the Nrf2 inhibitor Keap1 by nitroalkylation and its downstream responses. Of the two regioisomers, 9-nitrooctadec-9-enoic acid was a more potent ARE inducer than 10-nitro-octadec-9-enoic acid. (2), the enzyme xanthine oxidoreductase (3), and the transcription factor peroxisome proliferator-activated receptor ␥ (PPAR␥) (4). Moreover, NO 2 -FAs activate heat shock (5) and antioxidant response pathways (5, 6) via mechanisms that remain to be defined. Antioxidant response element (ARE)-regulated genes play an essential role in the protection against endogenous and exogenous stresses (7). The transcription factor nuclear factor E2-related factor-2 (Nrf2) can activate these genes via binding to AREs as a heterodimer with small Maf proteins (7). Under basal conditions, Nrf2 is bound to its inhibitor Kelch-like ECHassociated protein 1 (Keap1), which functions as an adaptor molecule in the Cul3-based E3 ligase complex. Nrf2 is then rapidly ubiquitinated and degraded (8, 9). During periods when cellular concentrations of oxidative or electrophilic species are elevated, the interaction of Nrf2 with the ubiquitin ligase complex is disrupted, enabling the escape of Nrf2 from degradation, its nuclear translocation, and transactivation of target genes.Keap1 is a Cys-rich protein with 27 Cys residues in the human and 25 Cys residues in the murine protein. Keap1 has four functional domains: the Bric-a-Brac, tramtrack, broad complex (BTB) domain, the intervening region (IVR), the Kelch domain (also known as the double glycine repeat), and the C-terminal region. Alkylation or oxidation of Keap1 Cys residues, predominantly within the IVR, leads to the inactivation of Keap1 and is the central mechanism for the activation of Nrf2 (10 -12). A number of studies utilizing mass spectrometry (MS) analysis show that electrophilic inducers of Nrf2 modify several different Cys residues in recombinant Keap1. These data indi-* This work was supported, in whole or in part, by National Institutes of Health BTB, Bric-a-Brac, tramtrack, broad complex; IVR, intervening region; 15d-PGJ 2 , 15-deoxy-⌬12,14-prostaglandin J 2 ; HEK, human embryonic kidney; ␤-ME, ␤-mercaptoethanol; OA-NO 2 , 9-and 10-nitro-octadec-9-enoic acid; 9-OA-NO 2 , 9-nitro-octadec-9-enoic acid; 10-OA-NO 2 , 10-nitro-octadec-9-enoic acid; LNO 2 , 9-, 10-, 12-, or 13-nitro-octadeca-9,12-dienoic acid.

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. Moreover, gene set enrichment analysis revealed that the heat shock response is the major pathway activated by OA-NO 2 , with robust induction of a number of heat shock genes regulated by the heat shock transcription factor. Inasmuch as the heat shock response mediates anti-inflammatory and cytoprotective actions, this mechanism is proposed to contribute to the protective cell signaling functions of nitro-fatty acids and other electrophilic fatty acid derivatives.