Neuroprotection Against Ethanol Mediated Oxidative Stress and Apoptosis via Nrf2/ARE.

Abstract

This study characterizes a neuroprotective pathway responsible for coordinated enhancement of astrocyte glutathione (GSH)‐homeostatic machinery. Injuries in fetal rat cortical neurons associated with Fetal Alcohol Syndrome are correlated to ethanol (E) exposure leading to increased oxidative stress, GSH depletion, and ultimately neuroapoptosis. We hypothesize that neuroprotection is regulated by activation of the anti‐oxidant response elements (ARE) of cytoprotective genes, via the master transcription factor Nrf2. Primary cultured rat neonatal astrocytes were treated with 4mg/ml E at various time points. There was increased nuclear Nrf2 expression within 15 minutes after E treatment, and lasted up to 4 hours. Immunohistochemical studies corroborate cytoplasmic to nuclear translocation. Enhanced nuclear Nrf2 expression was further augmented by BSO pre‐treatment. In addition, the transcription factor Maf, which obligatorily dimerizes with Nrf2 to activate gene transcription, was increased by E or BSO. Known ARE inducers and oxidative stress mimicked the cytoplasmic to nuclear translocation seen in E treatment. Next, cells were pre‐incubated with Actinomycin D and subsequently treated with E. Nrf2 expression induced by E was abolished suggesting that E increases Nrf2 by stimulating gene transcription. Transfection of Nrf2 siRNA completely ablated Nrf2 expression, and furthermore blocks the tbHQ induced Nrf2, GGT, and Mrp1 expression. Taken together, this suggests that Nrf2 is required for activation of ARE. The role of E in Nrf2‐ARE control of astrocyte neuroprotection need to be further investigated. These points of regulation may allow for pharmacological augmentation of this crucial neuroprotective mechanism.