Reperfusion after an ischemic stroke event is known to produce ROS that can cause neurovascular injury, BBB disruption with secondary vasogenic edema, and hemorrhagic transformation of infarcted brain tissue. Thus, ROS can restrict the benefits of tissue reperfusion with thrombolytic agents or mechanical devices in stroke patients. We have demonstrated that cerebral ischemia and reperfusion increase superoxide radicals in brain mitochondria, which leads to metalloproteinase-9 (MMP-9) activation and BBB disruption that characterize neurovascular injury and cerebral infarction. We have recently discovered that signal transducer and activator of transcription 3 (STAT3) is a transcription activator of the promoter of manganese-superoxide dismutase (SOD2). During reperfusion, the level of phosphorylated (activated) STAT3 and its recruitment to the SOD2 promoter are significantly reduced prior to reduction in SOD2 activity in ischemic neurons. We have also demonstrated that reduced SOD2 activity and oxidative stress will cause cerebral infarction, damage to the BBB, and intracerebral hemorrhagic transformation. Novel strategies that activate the STAT3 signaling pathway and up-regulation of SOD2 activity may be of significant translational and/or therapeutic value in limiting neurovascular injury after ischemic reperfusion. We have also demonstrated that hyperglycemia, a known stroke risk factor, exacerbated reperfusion injury by enhancing MMP-9 activation, BBB damage, and neuronal death by an oxidative stress mechanism that may involve NADPH oxidase (NOX2), a major cytosolic superoxide radical-producing enzyme. We now hypothesize that ischemic reperfusion causes down-regulation of STAT3 signaling and reduced SOD2 transcription and expression in neurovasculature, which will cause neurovascular dysfunction. Pre-existing hyperglycemia will exacerbate oxidative stress-mediated reperfusion injury by down-regulation of STAT3/SOD2 signaling and/or by up-regulation of NOX2 activity in endothelia and neurons. It is our aim to test these hypotheses using animal models with transient focal cerebral ischemia and with cell cultures for an in-depth mechanistic investigation.
Our specific aims are: 1) To investigate the role of oxidative stress and STAT3 signaling in neurovascular injury following ischemia/reperfusion (I/R) 2) To investigate the role of oxidative stress via NOX2 and STAT3/SOD2 signaling in hyperglycemia- mediated neurovascular injury following I/R 3) To investigate the interleukin-6 receptor as an upstream signal of STAT3 activation and its role in neurovascular protection in mice following I/R We believe that these are novel, but high-risk studies that will provide insights into translational and therapeutic opportunities to minimize oxidative stress-mediated neurovascular damage in patients who suffer acute ischemic stroke and reperfusion injury.

Public Health Relevance

Nearly 80% of strokes are caused by occlusion of a cerebral artery, and early restoration of cerebral blood flow by reperfusion can salvage hyperfused brain tissue, thus limiting neurological dysfunction and enhancing behavioral recovery. However, reperfusion after cerebral ischemia produces reactive oxygen radicals that can damage the neurovasculature. Since the mechanism underlying this oxidative injury is not clear, with this application, we seek to elucidate this injurious mechanism and to provide therapeutic strategies to prevent or ameliorate brain injuries in stroke patients.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS025372-23
Application #
8277200
Study Section
Brain Injury and Neurovascular Pathologies Study Section (BINP)
Program Officer
Koenig, James I
Project Start
1988-02-01
Project End
2016-04-30
Budget Start
2012-05-01
Budget End
2013-04-30
Support Year
23
Fiscal Year
2012
Total Cost
$349,894
Indirect Cost
$131,144
Name
Stanford University
Department
Neurosurgery
Type
Schools of Medicine
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305
Wakai, Takuma; Sakata, Hiroyuki; Narasimhan, Purnima et al. (2014) Transplantation of neural stem cells that overexpress SOD1 enhances amelioration of intracerebral hemorrhage in mice. J Cereb Blood Flow Metab 34:441-9
Yoshioka, Hideyuki; Katsu, Masataka; Sakata, Hiroyuki et al. (2013) The role of PARL and HtrA2 in striatal neuronal injury after transient global cerebral ischemia. J Cereb Blood Flow Metab 33:1658-65
Okami, Nobuya; Narasimhan, Purnima; Yoshioka, Hideyuki et al. (2013) Prevention of JNK phosphorylation as a mechanism for rosiglitazone in neuroprotection after transient cerebral ischemia: activation of dual specificity phosphatase. J Cereb Blood Flow Metab 33:106-14
Yang, Jiwon; Ahn, Hye-Na; Chang, Minsun et al. (2013) Complement component 3 inhibition by an antioxidant is neuroprotective after cerebral ischemia and reperfusion in mice. J Neurochem 124:523-35
Kim, Gab Seok; Jung, Joo Eun; Narasimhan, Purnima et al. (2012) Release of mitochondrial apoptogenic factors and cell death are mediated by CK2 and NADPH oxidase. J Cereb Blood Flow Metab 32:720-30
Sakata, Hiroyuki; Niizuma, Kuniyasu; Yoshioka, Hideyuki et al. (2012) Minocycline-preconditioned neural stem cells enhance neuroprotection after ischemic stroke in rats. J Neurosci 32:3462-73
Kim, Gab Seok; Jung, Joo Eun; Narasimhan, Purnima et al. (2012) Induction of thioredoxin-interacting protein is mediated by oxidative stress, calcium, and glucose after brain injury in mice. Neurobiol Dis 46:440-9
Yoshioka, Hideyuki; Niizuma, Kuniyasu; Katsu, Masataka et al. (2011) NADPH oxidase mediates striatal neuronal injury after transient global cerebral ischemia. J Cereb Blood Flow Metab 31:868-80
Jung, Joo Eun; Kim, Gab Seok; Chan, Pak H (2011) Neuroprotection by interleukin-6 is mediated by signal transducer and activator of transcription 3 and antioxidative signaling in ischemic stroke. Stroke 42:3574-9
Chen, Hai; Yoshioka, Hideyuki; Kim, Gab Seok et al. (2011) Oxidative stress in ischemic brain damage: mechanisms of cell death and potential molecular targets for neuroprotection. Antioxid Redox Signal 14:1505-17

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