Nuclear Factor Erythroid 2-Related Factor 2 Facilitates Neuronal Glutathione Synthesis by Upregulating Neuronal Excitatory Amino Acid Transporter 3 Expression

Abstract

Astrocytes support neuronal antioxidant capacity by releasing glutathione, which is cleaved to cysteine in brain extracellular space. Free cysteine is then taken up by neurons through excitatory amino acid transporter 3 [EAAT3; also termed Slc1a1 (solute carrier family 1 member 1)] to support de novo glutathione synthesis. Activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant responsive element (ARE) pathway by oxidative stress promotes astrocyte release of glutathione, but it remains unknown how this release is coupled to neuronal glutathione synthesis. Here we evaluated transcriptional regulation of the neuronal cysteine transporter EAAT3 by the Nrf2-ARE pathway. Nrf2 activators and Nrf2 overexpression both produced EAAT3 transcriptional activation in C6 cells. A conserved ARE-related sequence was found in the EAAT3 promoter of several mammalian species. This ARE-related sequence was bound by Nrf2 in mouse neurons in vivo as observed by chromatin immunoprecipitation. Chemical activation of the Nrf2-ARE pathway in mouse brain increased both neuronal EAAT3 levels and neuronal glutathione content, and these effects were abrogated in mice genetically deficient in either Nrf2 or EAAT3. Selective overexpression of Nrf2 in brain neurons by lentiviral gene transfer was sufficient to upregulate both neuronal EAAT3 protein and glutathione content. These findings identify a mechanism whereby Nrf2 activation can coordinate astrocyte glutathione release with neuronal glutathione synthesis through transcriptional upregulation of neuronal EAAT3 expression.

Fumarates Promote Cytoprotection of Central Nervous System Cells against Oxidative Stress via the Nuclear Factor (Erythroid-Derived 2)-Like 2 Pathway

“…Recent in vivo evidence also supports a role for activation of the Nrf2 pathway in increasing CNS GSH levels. These data suggested that enhanced astrocyte GSH biosynthesis and secretion led to increased extracellular cysteine as a product of GSH metabolism, which was then transported into neurons via up-regulation of the excitatory amino acid transporter 3, and ultimately drove increased neuronal GSH due to increased levels of biosynthetic substrate (Escartin et al, 2011). Elucidation of this pathway suggests a potential role for cell type-specific neuroprotective responses and is consistent with the astrocyte data presented here.…”

Gliopreventive effects of guanosine against glucose deprivation in vitro

“…In this study, under the deprivation of extracellular glucose, guanosine modulated the EAAC1 (EAAT3) levels. Although this transporter is responsible for the support of de novo GSH synthesis, it is also sensitive to oxidative stress [105]. Typically, the activation of PKC and PI3K pathways regulates the expression of EAAC1 [13,66].…”

Reactive Astrocytes Overexpress TSPO and Are Detected by TSPO Positron Emission Tomography Imaging

“…Striata were rapidly dissected out on ice and homogenized in 50 mM Tris-HCl, pH 7.4, 100 mM NaCl, and 1% SDS, with protease inhibitor cocktail (Roche). Western blots were performed using ECL detection as described previously (Escartin et al, 2011) using antibodies against actin (1:5000) and TSPO (1:500).…”