Pyruvate Protects the Brain Against Ischemia–Reperfusion Injury by Activating the Erythropoietin Signaling Pathway

Abstract

Background and Purpose Pyruvate is known to be cytoprotective through antioxidant and anti-inflammatory mechanisms. We tested the hypothesis that pyruvate protects brain against ischemia-reperfusion injury by inducing endogenous erythropoietin (EPO) expression. Methods Pyruvate’s protective effect was evaluated in C6 glioma cells and HT22 neuronal cells subjected to transient oxygen glucose deprivation (OGD). Cell viability (calcein AM assay) and expression of HIF-1α, EPO, Akt and Erk (immunoblot) and EPO receptor (RT-PCR) were analyzed. Transient focal cerebral ischemia in rats was induced by 2h middle cerebral artery occlusion followed by 24h reperfusion. Pyruvate or saline was infused from 60 min occlusion until 30 min reperfusion. Lesion volume and DNA fragmentation were assessed by 2,3,5-triphenyltetrazolium staining and TUNEL assay, respectively. Immunoblots were conducted to determine cerebral EPO contents. Results Pyruvate increased cell viability, HIF-1α, EPO, and Akt phosphorylation. siRNA suppression of HIF-1α and EPO abolished pyruvate-induced cytoprotection. In the rat stroke model, pyruvate reduced lesion volume by 84% and DNA fragmentation by 77% vs. controls; increased EPO content paralleled these cerebroprotective actions of pyruvate. Conclusions Pyruvate activation of the HIF-1α-EPO signaling cascade in neurons and glia could protect brain from ischemia-reperfusion injury.

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