Ischemic stroke produces rapid profound loss of microvascular integrity. Early following focal ischemia detectable disruption in the permeability barrier of cerebral microvessels occurs, with rapid loss of the endothelial cell ?1 integrin-matrix receptors. In amyloid angiopathy, microvessel alterations increase the risk of microhemorrhages. The hypotheses to be tested by this competing renewal Proposal state that i) the interaction of matrix receptors on microvessel endothelial cells (and astrocytes) with matri components of the basal lamina are a major determinant of the blood-brain barrier phenotype, ii) focal cerebral ischemia disrupts receptor-matrix interactions, and iii) interruptions of receptor-matrix interactions result in loss of the blood brain barrier phenotype. We have shown that adhesion of endothelial cells to the intact basal lamina matrix is central to the integrity of the barrier. The barrier phenotype (e.g. tight junctions (TJs)) and vascular matrix are generated by endothelial cells and astrocytes in concert, and are maintained by both cell compartments. The expression of ?1 integrins on endothelial cells and ??-dystroglycan on astrocytes in vivo, and their responses to focal ischemia, are mimicked by primary endothelial cells and astrocytes of murine origin in culture. These responses are matrix-dependent. Based upon successful completed work and preliminary data, we propose that ?1 integrins can determine TJ protein expression, and constitute the "vertical" component of the blood- brain and matrix barriers. The goal of this Project is to demonstrate that the actions of specific ?1 integrin family members are required for the integrity of the microvessel barrier, and those specific integrin inhibitors, geneic constructs and knockdowns, focal ischemia, and A?1 peptides disrupt the receptor-matrix interactions, producing barrier failure.
The Specific Aims are to demonstrate that: 1) the interactions of ?1 integrins on confluent endothelium with matrix proteins determine inter-endothelial cell cohesion by the TJ proteins, and these are modulated by astrocytes, 2) mechanisms of ?1 integrin signaling within endothelial cells mediate the matrix adhesion receptor-mediated changes in TJ expression (without or with astrocytes), 3) experimental ischemia significantly alters endothelial cell TJ expression by altering the endothelial cell ?1 integrin-matrix interactions, and 4) the exposure of endothelial cells (without or with astrocytes) to A?-peptides modulates TJ expression and the microvessel permeability barrier phenotype via ?1 integrin-dependent mechanisms. These novel studies provide a plausible explanation for the disruption of microvessel integrity immediately following focal ischemia and by amyloid angiopathy. The "vertical" component mediated by endothelial ?1 integrin-matrix adhesion suggests the premise that its disruption is responsible for loss of the blood-brain barrier. Understanding the mechanisms of the ?1 integrin-matrix adhesion is likely to lead to new testable approaches to preserve or selectively alter microvessel barrier function in other neurovascular disorders.

Public Health Relevance

Ischemic stroke is a devastating disorder that disrupts important bonds between the cells lining the small blood vessels of the brain (microvessel endothelial cells), that are thought to prevent leakage of fluid from inside the vessels, causing blood leakage and brain swelling. We have recently found that molecules (?1 integrins) that bind the endothelial cells to the scaffolding they sit on (matrix) within each microvessel are essential for maintaining the normal barrier to leakage, and that ischemic stroke quickly disrupts ?1 integrins, thereby causing leakage to occur. This continuing research work will define the exact mechanisms by which endothelial cell ?1 integrin-matrix binding maintains the barrier, and how its loss contributes to brain injury during ischemic stroke and other brain vascular disorders: fundamental studies needed for the development of new treatment strategies for stroke.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS053716-08
Application #
8468219
Study Section
Acute Neural Injury and Epilepsy Study Section (ANIE)
Program Officer
Bosetti, Francesca
Project Start
2005-12-16
Project End
2017-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
8
Fiscal Year
2013
Total Cost
$326,140
Indirect Cost
$115,046
Name
University of Washington
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
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Kalimo, Hannu; del Zoppo, Gregory J; Paetau, Anders et al. (2013) Polymorphonuclear neutrophil infiltration into ischemic infarctions: myth or truth? Acta Neuropathol 125:313-6
Del Zoppo, Gregory J (2013) Toward the neurovascular unit. A journey in clinical translation: 2012 Thomas Willis Lecture. Stroke 44:263-9
del Zoppo, Gregory J (2013) Plasminogen activators and ischemic stroke: conditions for acute delivery. Semin Thromb Hemost 39:406-25
Ciccone, Alfonso; Valvassori, Luca; Nichelatti, Michele et al. (2013) Endovascular treatment for acute ischemic stroke. N Engl J Med 368:904-13
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Hawkins, Brian T; Gu, Yu-Huan; Izawa, Yoshikane et al. (2013) Disruption of dystroglycan-laminin interactions modulates water uptake by astrocytes. Brain Res 1503:89-96
del Zoppo, Gregory J; Izawa, Yoshikane; Hawkins, Brian T (2013) Hemostasis and alterations of the central nervous system. Semin Thromb Hemost 39:856-75

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