Targeting Platelet GPVI Plus rt-PA Administration but Not α2β1-Mediated Collagen Binding Protects against Ischemic Brain Damage in Mice

• Main Authors: Michael K. Schuhmann, Peter Kraft, Michael Bieber, Alexander M. Kollikowski, Harald Schulze, Bernhard Nieswandt, Mirko Pham, David Stegner, Guido Stoll
• Format: Article
• Language: English
• Published: MDPI AG 2019-04-01
• Series: International Journal of Molecular Sciences
• Subjects: ischemic stroke; integrin α2; glycoprotein VI; recombinant tissue-type plasminogen activator; intracranial bleeding; transient middle cerebral artery occlusion
• Online Access: https://www.mdpi.com/1422-0067/20/8/2019

Platelet collagen interactions at sites of vascular injuries predominantly involve glycoprotein VI (GPVI) and the integrin &#945;2&#946;1. Both proteins are primarily expressed on platelets and megakaryocytes whereas GPVI expression is also shown on endothelial and integrin &#945;2&#946;1 expression on epithelial cells. We recently showed that depletion of GPVI improves stroke outcome without increasing the risk of cerebral hemorrhage. Genetic variants associated with higher platelet surface integrin &#945;2 (ITGA2) receptor levels have frequently been found to correlate with an increased risk of ischemic stroke in patients. However until now, no preclinical stroke study has addressed whether platelet integrin &#945;2&#946;1 contributes to the pathophysiology of ischemia/reperfusion (I/R) injury. Focal cerebral ischemia was induced in C57BL/6 and <i>Itga2^{&#8722;/&#8722;}</i> mice by a 60 min transient middle cerebral artery occlusion (tMCAO). Additionally, wild-type animals were pretreated with anti-GPVI antibody (JAQ1) or Fab fragments of a function blocking antibody against integrin &#945;2&#946;1 (LEN/B). In anti-GPVI treated animals, intravenous (IV) recombinant tissue plasminogen activator (rt-PA) treatment was applied immediately prior to reperfusion. Stroke outcome, including infarct size and neurological scoring was determined on day 1 after tMCAO. We demonstrate that targeting the integrin &#945;2&#946;1 (pharmacologic; genetic) did neither reduce stroke size nor improve functional outcome on day 1 after tMCAO. In contrast, depletion of platelet GPVI prior to stroke was safe and effective, even when combined with rt-PA treatment. Our results underscore that GPVI, but not ITGA2, is a promising and safe target in the setting of ischemic stroke.