Astrocytes Prevent Ethanol Induced Apoptosis of Nrf2 Depleted Neurons by Maintaining GSH Homeostasis

Madhusudhanan Narasimhan, Marylatha Rathinam, Dhyanesh Patel, George Henderson, Lenin Mahimainathan

Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, USA.
South Plains Alcohol and Addiction Research Center, Texas Tech University Health Sciences Center, Lubbock, USA.

DOI: 10.4236/ojapo.2012.12002                

Abstract

Glutathione (GSH), a major cellular antioxidant protects cells against oxidative stress injury. Nuclear factor erythroid 2-related factor 2 (NFE2L2/Nrf2) is a redox sensitive master regulator of battery of antioxidant enzymes including those involved in GSH antioxidant machinery. Earlier we reported that ethanol (ETOH) elicits apoptotic death of pri-mary cortical neurons (PCNs) which in partly due to depletion of intracellular GSH levels. Further a recent report from our laboratory illustrated that ETOH exacerbated the dysregulation of GSH and caspase mediated cell death of pure cortical neurons that are compromised in Nrf2 machinery (Narasimhan et al., 2011). In various experimental models of neurodegeneration, neuronal antioxidant defenses mainly GSH has been shown to be supported by astrocytes. We therefore sought to determine whether astrocytes can render protection to neurons against ETOH toxicity, particularly when the function of Nrf2 is compromised in neurons. The experimental model consisted of co-culturing PCAs with Nrf2 downregulated PCNs that were exposed with and without 4 mg/mL ETOH for 24 h. Monochlorobimane (MCB) staining followed by FACS analysis showed that astrocytes blocked ETOH induced GSH decrement in Nrf2-silenced neurons as opposed to exaggerated GSH depletion in Nrf2 downregulated PCNs alone. Similarly, the heightened activa-tion of caspase 3/7 observed in Nrf2-compromised neurons was attenuated when co-cultured with astrocytes as meas-ured by luminescence based caspase Glo assay. Furthermore, annexin-V-FITC staining followed by FACS analysis re-vealed that Nrf2 depleted neurons showed resistance to ETOH induced neuronal apoptosis when co-cultured with as-trocytes. Thus, the current study identifies ETOH induced dysregulation of GSH and associated apoptotic events ob-served in Nrf2-depleted neurons can be blocked by astrocytes. Further our results suggest that this neuroprotective ef-fect of astrocyte despite dysfunctional Nrf2 system in neurons could be compensated by astrocytic GSH supply.

Keywords

Astrocyte-Neuron Co-Culture; Nrf2; Ethanol; Oxidative Stress; GSH

Conflicts of Interest

The authors declare no conflicts of interest.

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