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Functional interference between glycogen synthase kinase-3 beta and the transcription factor Nrf2 in protection
Ana I Rojo1, Patricia Rada, Javier Egea
1Instituto de Investigaciones Biomédicas "Alberto Sols" UAM-CSIC, Departamento de Bioquímica, and Centro de Investigación Biomédica en Red en Enfermedades Neurodegenerativas (CIBERNED), Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.
Abstract:
Excitotoxicity mediated by glutamate receptors may underlay the pathology of several neurologic diseases. Considering that oxidative stress is central to excitotoxic damage, in this study we sought to analyze if the transcription factor Nrf2, guardian of redox homeostasis, might be targeted to prevent kainate-induced neuron death. Hippocampal slices from Nrf2 knockout mice exhibited increased oxidative stress and cell death compared to those of control mice in response to kainate, as determined with the redox sensitive probes 2,7-dichlorodihydrofluorescein diacetate (H(2)DCFAC) and propidium iodide and lactate dehydrogenase release, respectively, therefore demonstrating a role of Nrf2 in antioxidant protection against excitotoxicity. In the hippocampus of mice intraperitoneally injected with kainate we observed a rapid activation of Akt, inhibition of GSK-3beta and translocation of Nrf2 to the nucleus, but after 4 h Akt was inactive, GSK-3beta was active and Nrf2 was mostly cytosolic, therefore extending our previous studies which indicate that GSK-3beta excludes Nrf2 from the nucleus. Lithium, a GSK-3beta inhibitor, promoted Nrf2 transcriptional activity towards an Antioxidant-Response-Element (ARE) luciferase reporter and cooperated with sulforaphane (SFN) to induce this reporter and to increase the protein levels of heme oxygenase-1 (HO-1), coded by a representative ARE-containing gene. Conversely, ARE activation by SFN was attenuated by over-expression of active GSK-3beta. Finally, combined treatment with SFN and lithium attenuated oxidative stress and cell death in kainate-treated hippocampal slices of wild type mice but not Nrf2 null littermates. Our findings identify the axis GSK-3beta/Nrf2 as a pharmacological target in prevention of excitotoxic neuronal death.
Insights
The study reveals that targeting the GSK-3beta/Nrf2 pathway can prevent excitotoxic neuron death. Inhibiting GSK-3beta enhances Nrf2
Area of Science:
- Neuroscience
- Cell Biology
- Pharmacology
Background:
- Excitotoxicity, mediated by glutamate receptors, contributes to neurological diseases.
- Oxidative stress is a key factor in excitotoxic neuronal damage.
- The transcription factor Nrf2 is crucial for maintaining redox homeostasis.
Purpose of the Study:
- To investigate the role of Nrf2 in preventing kainate-induced neuron death.
- To determine if the GSK-3beta/Nrf2 axis can be pharmacologically targeted for neuroprotection.
Main Methods:
- Utilized Nrf2 knockout mice and hippocampal slices.
- Assessed oxidative stress using H(2)DCFAC probes and cell death via propidium iodide and LDH release.
- Investigated the effects of lithium (GSK-3beta inhibitor) and sulforaphane (SFN) on Nrf2 activity and ARE-luciferase reporter assays.
Main Results:
- Nrf2 knockout mice showed increased oxidative stress and cell death after kainate exposure.
- Kainate induced transient Akt activation and GSK-3beta inhibition, followed by Akt inactivation and GSK-3beta activation, leading to Nrf2 cytosolic localization.
- Lithium and SFN treatment reduced oxidative stress and cell death in kainate-treated wild-type mice, an effect absent in Nrf2 null mice.
Conclusions:
- The GSK-3beta/Nrf2 signaling pathway plays a critical role in protecting neurons against excitotoxicity.
- Inhibition of GSK-3beta promotes Nrf2 nuclear translocation and transcriptional activity.
- The GSK-3beta/Nrf2 axis represents a promising therapeutic target for preventing excitotoxic neuronal death in neurological disorders.
