Neuroprotective Effects of the Triterpenoid, CDDO Methyl Amide, a Potent Inducer of Nrf2-Mediated Transcription

The NF-E2-related factor-2 (Nrf2)/antioxidant response element (ARE) signaling pathway regulates phase 2 detoxification genes, including a variety of antioxidative enzymes. We tested neuroprotective effects of the synthetic triterpenoid CDDO-MA, a potent activator of the Nrf2/ARE signaling. CDDO-MA treatment of neuroblastoma SH-SY5Y cells resulted in Nrf2 upregulation and translocation from cytosol to nucleus and subsequent activation of ARE pathway genes. CDDO-MA blocked t-butylhydroperoxide-induced production of reactive oxygen species (ROS) by activation of ARE genes only in wild type, but not Nrf2 knockout mouse embryonic fibroblasts. Oral administration of CDDO-MA resulted in significant protection against MPTP-induced nigrostriatal dopaminergic neurodegeneration, pathological alpha-synuclein accumulation and oxidative damage in mice. Additionally, CDDO-MA treatment in rats produced significant rescue against striatal lesions caused by the neurotoxin 3-NP, and associated increases in the oxidative damage markers malondialdehyde, F-2-Isoprostanes, 8-hydroxy-2-deoxyguanosine, 3-nitrotyrosine, and impaired glutathione homeostasis. Our results indicate that the CDDO-MA renders its neuroprotective effects through its potent activation of the Nrf2/ARE pathway, and suggest that triterpenoids may be beneficial for the treatment of neurodegenerative diseases like Parkinson's disease and Huntington's disease.