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Proc Natl Acad Sci U S A. 2019 Apr 30;116(18):9115-9124. doi: 10.1073/pnas.1821979116. Epub 2019 Apr 17.

Protease-independent action of tissue plasminogen activator in brain plasticity and neurological recovery after ischemic stroke.

Pu H1,2, Shi Y1,2,3, Zhang L1,2,3, Lu Z1,2, Ye Q1,2,3, Leak RK4, Xu F1,2,3, Ma S1,2, Mu H1,2, Wei Z1,2, Xu N1,2, Xia Y1,2, Hu X1,2,3, Hitchens TK5, Bennett MVL6, Chen J7,2,3.

Author information

1
Pittsburgh Institute of Brain Disorders and Recovery, University of Pittsburgh, Pittsburgh, PA 15213.
2
Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213.
3
Geriatric Research, Education and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15261.
4
Graduate School of Pharmaceutical Sciences, School of Pharmacy, Duquesne University, Pittsburgh, PA 15282.
5
Animal Imaging Center, University of Pittsburgh, Pittsburgh, PA 15203.
6
Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461 michael.bennett@einstein.yu.edu chenj2@upmc.edu.
7
Pittsburgh Institute of Brain Disorders and Recovery, University of Pittsburgh, Pittsburgh, PA 15213; michael.bennett@einstein.yu.edu chenj2@upmc.edu.

Abstract

Emerging evidence suggests that tissue plasminogen activator (tPA), currently the only FDA-approved medication for ischemic stroke, exerts important biological actions on the CNS besides its well-known thrombolytic effect. In this study, we investigated the role of tPA on primary neurons in culture and on brain recovery and plasticity after ischemic stroke in mice. Treatment with recombinant tPA stimulated axonal growth in culture, an effect independent of its protease activity and achieved through epidermal growth factor receptor (EGFR) signaling. After permanent focal cerebral ischemia, tPA knockout mice developed more severe sensorimotor and cognitive deficits and greater axonal and myelin injury than wild-type mice, suggesting that endogenously expressed tPA promotes long-term neurological recovery after stroke. In tPA knockout mice, intranasal administration of recombinant tPA protein 6 hours poststroke and 7 more times at 2 d intervals mitigated white matter injury, improved axonal conduction, and enhanced neurological recovery. Consistent with the proaxonal growth effects observed in vitro, exogenous tPA delivery increased poststroke axonal sprouting of corticobulbar and corticospinal tracts, which might have contributed to restoration of neurological functions. Notably, recombinant mutant tPA-S478A lacking protease activity (but retaining the EGF-like domain) was as effective as wild-type tPA in rescuing neurological functions in tPA knockout stroke mice. These findings demonstrate that tPA improves long-term functional outcomes in a clinically relevant stroke model, likely by promoting brain plasticity through EGFR signaling. Therefore, treatment with the protease-dead recombinant tPA-S478A holds particular promise as a neurorestorative therapy, as the risk for triggering intracranial hemorrhage is eliminated and tPA-S478A can be delivered intranasally hours after stroke.

KEYWORDS:

axonal sprouting; diffusion tensor imaging; epidermal growth factor; oxygen–glucose deprivation; protease-inactive tPA

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