Endogenous oxidative damage to nuclear DNA, in the form of base damage, apurinic/apyrimidinic abasic sites (AP sites), and strand breaks, occurs rapidly following cerebral ischemia/reperfusion and is an important trigger of ischemic neuronal cell death. DNA base-excision-repair (BER) is the main repair mechanism for oxidative DNA damage in the brain. AP endonuclease (APE) is the rate-limiting enzyme in the BER pathway, which, when overexpressed, can boost BER activity. Recent studies in non-neuronal and neuronal cells have revealed that APE is an essential survival factor under oxidative stress or DNA-damaging insults. The expression and activity of APE are markedly upregulated in the brain after sublethal ischemia, which has been considered to be a contributing mechanism in neuroprotection induced by ischemic preconditioning. APE activity and the APE-dependent overall BER activity instead rapidly decline following lethal ischemic injury, and lead to the accumulation of cytotoxic oxidative DNA lesions. Despite recent evidence for neuroprotection of cultured neurons, the role of APE in ischemic brain injury is currently poorly understood. Using animal models of cerebral ischemia, we have now obtained the first evidence that overexpression of APE protects against ischemic brain injury in vivo, whereas deletion of APE in the brain remarkably exacerbates ischemic injury. Furthermore, we have identified PKCzeta, the atypical isoform of protein kinase C, as a potent endogenous inhibitor of APE. Based on these novel findings, we hypothesize that augmentation of APE activity by gene delivery or inhibiting PKCzeta protects against ischemic brain injury via preventing accumulation of oxidative DNA damage. We propose three specific aims:
Aim 1. Test the hypothesis that transgenic overexpression of APE prevents hippocampal cell death induced by transient global ischemia in rats.
Aim 2. Test the hypothesis that aberrant activation of PKCzeta mediates ischemic neuronal injury by functionally disabling APE.
Aim 3. Test the hypothesis that enhanced DNA repair via PKCzeta inhibition or intracerebral delivery of biologically active APE prevents hippocampal cell death induced by transient global ischemia. Successful completion of this proposed project would yield important information valuable for future development of new therapeutic strategies for stroke.Oxidative damage to genomic DNA is an important mechanism initiating neuron death in the brain after ischemic stroke. The objective of this proposal is to investigate whether molecular or pharmacological manipulations that enhance DNA repair capacity can ameliorate brain injury in animal models of cerebral ischemia. This information will be valuable for future development of new therapeutic strategies for the treatment of stroke.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS036736-13
Application #
8018544
Study Section
Brain Injury and Neurovascular Pathologies Study Section (BINP)
Program Officer
Bosetti, Francesca
Project Start
1997-06-16
Project End
2012-11-30
Budget Start
2011-02-01
Budget End
2012-01-31
Support Year
13
Fiscal Year
2011
Total Cost
$292,301
Indirect Cost
Name
University of Pittsburgh
Department
Neurology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
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Li, Peiying; Stetler, R Anne; Leak, Rehana K et al. (2017) Oxidative stress and DNA damage after cerebral ischemia: Potential therapeutic targets to repair the genome and improve stroke recovery. Neuropharmacology :
Cai, Wei; Zhang, Kai; Li, Peiying et al. (2017) Dysfunction of the neurovascular unit in ischemic stroke and neurodegenerative diseases: An aging effect. Ageing Res Rev 34:77-87
Shi, Yejie; Jiang, Xiaoyan; Zhang, Lili et al. (2017) Endothelium-targeted overexpression of heat shock protein 27 ameliorates blood-brain barrier disruption after ischemic brain injury. Proc Natl Acad Sci U S A 114:E1243-E1252
Jiang, Xiaoyan; Pu, Hongjian; Hu, Xiaoming et al. (2016) A Post-stroke Therapeutic Regimen with Omega-3 Polyunsaturated Fatty Acids that Promotes White Matter Integrity and Beneficial Microglial Responses after Cerebral Ischemia. Transl Stroke Res 7:548-561
Zhang, Wenting; Zhang, Hui; Mu, Hongfeng et al. (2016) Omega-3 polyunsaturated fatty acids mitigate blood-brain barrier disruption after hypoxic-ischemic brain injury. Neurobiol Dis 91:37-46
Stetler, R Anne; Gao, Yanqin; Leak, Rehana K et al. (2016) APE1/Ref-1 facilitates recovery of gray and white matter and neurological function after mild stroke injury. Proc Natl Acad Sci U S A 113:E3558-67
Zhang, Wenting; Wang, Hailian; Zhang, Hui et al. (2015) Dietary supplementation with omega-3 polyunsaturated fatty acids robustly promotes neurovascular restorative dynamics and improves neurological functions after stroke. Exp Neurol 272:170-80
Shi, Hong; Hu, Xiaoming; Leak, Rehana K et al. (2015) Demyelination as a rational therapeutic target for ischemic or traumatic brain injury. Exp Neurol 272:17-25
Hu, Xiaoming; Leak, Rehana K; Shi, Yejie et al. (2015) Microglial and macrophage polarization—new prospects for brain repair. Nat Rev Neurol 11:56-64

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