Nuclear factor E2-related factor 2 (Nrf2) is a transcription factor known to induce expression of a variety of cytoprotective and detoxification genes. Several of the genes commonly regulated by Nrf2 have been implicated in protection from neurodegenerative conditions. Work from several laboratories has uncovered the potential for Nrf2-mediated transcription to protect from neurodegeneration resulting from mechanisms involving oxidative stress. For this reason, Nrf2 may be considered a therapeutic target for conditions that are known to involve free radical damage. Because common mechanisms of neurodegeneration, such as mitochondrial dysfunction and build-up of reactive oxygen species, are currently being uncovered, targeting Nrf2 may be valuable in combating conditions with variable causes and etiologies. Most effectively to target this protein in neurodegenerative conditions, a description of the involvement of Nrf2 and potential for neuroprotection must come from laboratory models. Herein, we review the current literature that suggests that Nrf2 may be a valuable therapeutic target for neurodegenerative disease, as well as experiments that illustrate potential mechanisms of protection. Antioxid. Redox Signal. 11,[497][498][499][500][501][502][503][504][505][506][507][508]

Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by cell loss in the substantia nigra resulting in striatal dopamine depletion. Although the cause of sporadic PD is unknown, oxidative stress is thought to contribute to disease pathogenesis. One mechanism by which cells defend themselves against oxidative stress is through the transcriptional upregulation of cytoprotective genes. Under oxidative stress conditions, the transcription factor NF-E2-related factor (Nrf2) binds to the antioxidant response element (ARE) to induce antioxidant and phase II detoxification enzymes. Here we show that loss of Nrf2-mediated transcription exacerbates vulnerability to the neurotoxin 6-hydroxydopamine (6-OHDA) both in vitro and in vivo. We further demonstrate that activation of the Nrf2-ARE pathway by the known chemical inducer tert-butylhydroquinone can protect against 6-OHDA in vitro. Induction of this pathway by transplantation of astrocytes overexpressing Nrf2 can protect against 6-OHDA-induced damage in the living mouse. This suggests that the Nrf2-ARE pathway is a promising target for therapeutics aimed at reducing or preventing cell death in PD.

Systemic administration of cystamine is known to protect from both chemical and genetic models of neurotoxicity. Despite positive effects in laboratory models, cystamine has not been successfully translated to clinical application for neurodegenerative disease. Furthermore, the long held assumption that cystamine protects through tissue-transglutaminase inhibition has recently been challenged. The studies described here examine other potential mechanisms of cystamine-mediated protection in an attempt to reveal molecular targets for neurodegenerative therapy. Based on previously described effects of cystamine, we examined the potential for activation of NF-E2 related factor 2 (Nrf2) mediated signaling through the antioxidant response element (ARE). We found that cystamine activates Nrf2/ARE both in cell culture and in brain tissue and then probed the mechanism of activation in cell culture. In live animals, we show that neuroprotection from 3-nitropropionic acid (3NP) toxicity is Nrf2-dependent. Therefore, these findings provide strong evidence that Nrf2 signaling may be an effective target for prevention of neurodegeneration.

Transgenerational epigenetic inheritance requires transmission of environmentally-induced epigenetic changes and associated phenotypes to subsequent generations without continued exposure to the environmental factor that originated the change. Transgenerational epigenetic inheritance is well-established in plants and Caenorhabditis elegans; however, occurrence in mammals is debated and poorly understood. Here, we examined whether paternal diet from weaning to puberty induced changes in sperm DNA methylation that were transmitted to subsequent generations. Over 100 methylated cytosines, environmentally altered in the F0 generation, were inherited by the F1 and F2 generations. Furthermore, the F0 paternal diet was associated with growth and male fertility phenotypes in subsequent generations. Differentially methylated cytosines were correlated with gene expression. Our results demonstrate that some sperm methylation sites may escape DNA methylation erasure and are transmitted to subsequent generations despite the two waves of epigenetic programming: in primordial germ cells and in embryos after fertilization. These results advance our understanding of the complex relationships between nature and nurture.

Environmental effects on gene expression and offspring development can be mediated by epigenetic modifications. It is well established that maternal diet influences DNA methylation patterns and phenotypes in the offspring; however, the epigenetic effects of paternal diet on developing offspring warrants further investigation. Here, we examined how a prepubertal methionine-enriched paternal diet affected sperm DNA methylation and its subsequent effects on embryo gene expression. Three treatment and three control rams were bred to seven ewes, and blastocysts were flushed for RNA extraction. Semen was collected from all rams and submitted for reduced representation bisulfite sequencing (RRBS) analysis. In total, 166 differentially methylated cytosines (DMCs) were identified in the sperm from treatment versus control rams. Nine genes were found to be differentially expressed in embryos produced from treatment versus control rams, and seven DMCs in the sperm were found to be highly correlated with gene expression in the embryos. Our results demonstrate that sperm methylation differences induced by diet may influence fetal programming.