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Published on: July 31, 2017
Erythropoietin-induced neuroprotection requires cystine glutamate exchanger activity
Brian Sims1, Melinda Clarke, Wilfred Njah
1Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA.
Insights
Erythropoietin (Epo) protects neonatal brain cells by boosting glutathione production via system Xc(-). This mechanism enhances cellular defense against excitotoxicity, revealing Epo
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Erythropoietin (Epo) is used to treat anemia in premature infants.
- Epo exhibits potential neuroprotective effects in neonates, but its mechanism is unclear.
- Cellular glutathione (GSH) is crucial for redox defense.
Purpose of the Study:
- To investigate the hypothesis that Epo confers neuroprotection by enhancing cellular glutathione (GSH) synthesis.
- To elucidate the role of system Xc(-) in Epo-mediated neuroprotection.
Main Methods:
- Used differentiated cortical neural stem cells and B104 cell line.
- Measured Epo's effect on system Xc(-) expression and activity.
- Assessed GSH levels and cell viability under excitotoxic conditions (kainate) with and without Epo.
- Utilized pharmacological inhibition (S4-CPG) and siRNA to block system Xc(-).
Main Results:
- Epo dose- and time-dependently increased system Xc(-) expression and activity, enhancing cystine uptake.
- Epo restored GSH levels and cell viability in kainate-induced excitotoxicity.
- Inhibition of system Xc(-) abolished Epo's neuroprotective effects, leading to cell death.
Conclusions:
- Epo confers neuroprotection by upregulating system Xc(-), thereby increasing GSH production.
- This Epo-induced enhancement of the cellular redox defense system is a key mechanism of its neuroprotective action.
Abstract:
Erythropoietin (Epo) has been used for many years in neonates for the treatment of anemia of prematurity. Epo has also been proposed for treatment of neonatal brain injury, as mounting evidence suggests neuroprotective properties for Epo. However, Epo's neuroprotective mechanism of action is poorly understood. In this study we hypothesized that Epo may confer neuroprotection by enhancing cellular redox defense brought about by cellular glutathione (GSH). This was examined in cultures of differentiated cortical neural stem cells and using the B104 cell line as model systems. Our data shows that Epo causes a time- and dose-dependent increase in expression and activity of system Xc(-), the transporter responsible for uptake of cystine for the production of glutathione. Cystine uptake increases 3-5 fold in differentiated neural stem cells and B104 cells treated with Epo. Exposure of cells to 100 microM kainate suppressed cellular GSH and caused excitotoxicity, but GSH levels and cell viability were completely restored by Epo in the continued presence of kainate. This rescue effect of Epo vanished if system Xc(-) was inhibited pharmacologically using S4-CPG in the presence of Epo leading to marked cell death of B104 cells and cultured mouse cortical neural stem cells. This could also be achieved using xCT siRNA to decrease xCT expression. This data suggests that system Xc(-) activity and protein expression are positively regulated by Epo directly explaining its neuroprotective effect.
