title: Microvascular thrombosis, fibrinolysis, ischemic injury, and death after cerebral thromboembolism are affected by levels of circulating α2-antiplasmin.
abstract: OBJECTIVE
  Ischemic stroke is primarily attributable to thrombotic vascular occlusion. Elevated α2-antiplasmin (a2AP) levels correlate with increased stroke risk, but whether a2AP contributes to the pathogenesis of stroke is unknown. We examined how a2AP affects thrombosis, ischemic brain injury, and survival after experimental cerebral thromboembolism.
  
  
  RESULTS
  We evaluated the effects of a2AP on stroke outcomes in mice with increased, normal, or no circulating a2AP, as well as in mice given an a2AP-inactivating antibody. Higher a2AP levels were correlated with greater ischemic brain injury (rs=0.88, P<0.001), brain swelling (rs=0.82, P<0.001), and reduced middle cerebral artery thrombus dissolution (rs=-0.93, P<0.001). In contrast, a2AP deficiency enhanced thrombus dissolution, increased cerebral blood flow, reduced brain infarction, and decreased brain swelling. By comparison to tissue plasminogen activator (TPA), a2AP inactivation hours after thromboembolism still reduced brain infarction (P<0.001) and hemorrhage (P<0.05). Microvascular thrombosis, a process that enhances brain ischemia, was markedly reduced in a2AP-deficient or a2AP-inactivated mice compared with TPA-treated mice or mice with increased a2AP levels (all P<0.001). Matrix metalloproteinase-9 expression, which contributes to acute brain injury, was profoundly decreased in a2AP-deficient or a2AP-inactivated mice versus TPA-treated mice or mice with increased a2AP levels (all P<0.001). a2AP inactivation markedly reduced stroke mortality versus TPA (P<0.0001).
  
  
  CONCLUSIONS
  a2AP has profound, dose-related effects on ischemic brain injury, swelling, hemorrhage, and survival after cerebral thromboembolism. By comparison to TPA, the protective effects of a2AP deficiency or inactivation seem to be mediated through reductions in microvascular thrombosis and matrix metalloproteinase-9 expression.
authors.affiliation: From the Department of Medicine, University of Tennessee Health Sciences Center, Memphis. glreed@uthsc.edu.
authors.forename: Guy L
authors.initials: GL
authors.lastname: Reed
authors.affiliation: From the Department of Medicine, University of Tennessee Health Sciences Center, Memphis.
authors.forename: Aiilyan K
authors.initials: AK
authors.lastname: Houng
authors.affiliation: From the Department of Medicine, University of Tennessee Health Sciences Center, Memphis.
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology; D002560:Cerebrovascular Circulation; D004195:Disease Models, Animal; D005342:Fibrinolysis; D020244:Infarction, Middle Cerebral Artery / Q000097:blood* / Q000201:enzymology / Q000473:pathology*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D055806:Microvessels / Q000473:pathology; D000979:alpha-2-Antiplasmin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D000979:alpha-2-Antiplasmin; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse
keywords: brain ischemia; fibrinolysis; plasminogen activator; thromboembolism; tissue-type plasminogen activator