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Journal of Pharmacology And Experimental Therapeutics Fast Forward
First published on December 15, 2005; DOI: 10.1124/jpet.105.094391

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Received for publication August 19, 2005.
Revised December 14, 2005.
Accepted for publication December 14, 2005.

Cell Death Mechanism and Protective Effect of Erythropoietin after Focal Ischemia in the Whisker-barrel Cortex of Neonatal Rats

Ling Wei 1, Byung H Han 2, Ying Li 1, Christine Keogh 1, David M Holtzman 2, Shan P Yu 1*

1 Medical University of South Carolina 2 Washington University

* Address correspondence to: E-mail: yusp{at}musc.edu

Abstract

Cell death induced by the combined insult of hypoxia-ischemia in neonatal rodents has been extensively investigated. Ischemia-only-induced cell death, however, has been much less characterized. Based on the notion that 1) ischemic stroke is a relatively common disorder in human neonates, and 2) developing cells are more susceptible to apoptosis, the present study examined whether typical apoptosis was induced by cerebral ischemia in a new neonatal rat model. Erythropoietin (EPO, Epoetin) was tested for its protective effect against ischemia-induced cell death. Postnatal day-7 (P7) rats were subjected to permanent occlusion of the middle cerebral artery (MCA) branch supplying the right whisker-barrel cortex. TUNEL positive cells in the ischemic region were detectable 4 hrs after ischemia and reached a peak level 16 hrs later. The cell death was preceded by caspase activation and cytochrome c release. Cell body shrinkage was evident among damaged cells. Agarose gel electrophoresis showed DNA damage with a smear pattern as well as DNA laddering. Electron microscopy demonstrated apoptotic features such as cell shrinkage, chromatin condensation and fragmentation; meanwhile, necrotic alterations coexisted in the cytoplasm. EPO treatment increased STAT-5 and Bcl-2 levels, markedly attenuated apoptotic cell death and reduced ischemic infarct in the cortex. It is suggested that focal ischemia in the developing brain causes cell death with prominent apoptotic features coexisting with some characteristics of necrosis. This is consistent with the concept of hybrid death previously described in cultures and adult or developing brain. EPO may be explored as a potential therapy for neonatal ischemic stroke.


Key words: Apoptosis, Erythropoietin, Hybrid death, Neonatal Ischemic stroke, Small strokes, Whisker-barrel cortex


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C. L. Keogh, S. P. Yu, and L. Wei
The Effect of Recombinant Human Erythropoietin on Neurovasculature Repair after Focal Ischemic Stroke in Neonatal Rats
J. Pharmacol. Exp. Ther., August 1, 2007; 322(2): 521 - 528.
[Abstract] [Full Text] [PDF]


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