Abstract WP342: Activate the Pentose Phosphate Pathway to Reduce the Cerebral Ischemia/Reperfusion Injury: The Impact of Heat Shock Protein 27 Phosphorylation

Abstract

Introduction: Based on metabolomics with gas chromatography-mass spectrometry, we showed that pentose phosphate pathway (PPP) is activated during cerebral ischemia and reperfusion in rat cerebral cortex. Especially, heat shock protein 27 (HSP27) phosphorylation seems to play an important role in activating glucose 6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in PPP. To confirm the hypothesis that HSP27 phosphorylation can be a potential target for the treatment of ischemic stroke, we used KU55933 and geranylgeranylacetone (GGA). KU55933 is the inhibitor of ataxia telangiectasia mutated kinase (ATMK), inhibiting the phosphorylation of HSP27. GGA can induce the expression of HSP families in various organs. Methods: First, 10 μl of KU55933 or DMSO was injected into the lateral ventricle of male Wistar rats (n=5 each). One hour after the injection, 1.5-h middle cerebral artery occlusion (MCAO) and following 24-h reperfusion were performed to evaluate the effect. Next, intracerebroventricular (ICV) injection of 10 μl of GGA or DMSO was performed 3-h prior to 1-h MCAO/24-h reperfusion. Infarct size, immunoblotting, G6PD activity, and protein carbonyl indicating protein oxidation, were examined. Results: ICV injection of KU-55933 significantly reduced the phosphorylated HSP27 (pHSP27) and G6PD activity (Fig. 1A and B). In addition, it increased the infarct size and the protein carbonyl (Fig. 1 C and D). In contrast, ICV injection of GGA increased both HSP27 and pHSP27, which resulted in significant reduction of the infarct size (19.9% vs 31.3%, p<0.01) (Fig. 1 E and F). Conclusions: ATMK contribute the antioxidative effect with phosphorylation of HSP27 during cerebral ischemia/reperfusion. GGA may be a potential therapeutic drug for ischemic stroke. Further studies are required prior to clinical application, including investigation that use more convenient route of administration; and that evaluate the effect of GGA administration after MCAO.