The Nrf2-ARE pathway: A potential therapeutic target for neurodegenerative diseases

Maneb causes pro-oxidant effects in the hippocampus of Nrf2 knockout mice

The effects of maneb were investigated in C57BL/6 Nrf2 wildtype and knockout mice. Treated KO mice showed significant weight loss as compared to WT counterparts. ICPAAS analysis demonstrated a significant increase in manganese concentration in the tissues of treated KO mice as compared to WT. Biochemical analysis revealed significant decreases of antioxidants including glutathione, glutathione reductase and heme oxygenase-1. Levels of TBARS were significantly increased in hippocampal tissue in Nrf2 KO mice at the 30 and 60mg doses. qPCR demonstrated that the only gene mediated by the Nrf2 transcription pathway that was significantly modulated by at least 1.5 fold was glutathione peroxidase 4. GPX4 was significantly upregulated in Nrf2 WT mice treated with 30mg/kg maneb and significantly downregulated in Nrf2 KO mice treated with the same dose. Microscopy revealed neuronal pyknosis and eosinophilia of the cytoplasm in the hippocampi of both WT and KO animals treated with 60mg/kg maneb.

Protective effect of combination of sulforaphane and riluzole on glutamate-mediated excitotoxicity

Threohydroxyaspartate (THA) causes glutamate excitotoxicity in motor neurons in organotypic culture of rat spinal cord. Some drugs, including sulforaphane (SF) and riluzole, can protect motor neuron against excitotoxicity. It has been demonstrated that SF is a potent inducer of Phase II enzymes, while riluzole is a classic anti-glutamate agent. The objective of the current study is to investigate whether the combination of SF and riluzole is superior to either one used alone. In our study, the combination of SF with riluzole not only stimulates the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), reduced nicotinamide adenine dinucleotide phosphate (NADPH): quinone oxidoreductase 1 (NQO1) and heme oxygenase 1 (HO-1), but also reduces the extracellular accumulation of glutamate. When used at optimal doses, SF (10 microM) and riluzole (5 microM), either alone or in combination, all exert significant and similar neuroprotection, as measured by the number of motor neuron, medium malondialdehyde (MDA) level and lactate dehydrogenase (LDH) level. When used at low doses, the combination is better than each agent used alone. In conclusion, these results suggest the potential utility of combination use of SF and riluzole for protection of motor neuron against excitotoxicity.

The Nrf2/ARE pathway as a potential therapeutic target in neurodegenerative disease

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.