Matrix Metalloproteinase-9 Mediates the Deleterious Effects of α2-Antiplasmin on Blood–Brain Barrier Breakdown and Ischemic Brain Injury in Experimental Stroke

Satish Singh, Aiilyan K. Houng, Guy L. Reed

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

During acute brain ischemia, α2-antiplasmin markedly enhances brain injury, blood–brain barrier breakdown and matrix metalloproteinase-9 (MMP-9) expression. Although α2-antiplasmin inhibits fibrin thrombus-degradation, and MMP-9 is a collagen-degrading enzyme altering blood–brain barrier, both have similar deleterious effects on the ischemic brain. We examined the hypothesis that MMP-9 is an essential downstream mediator of α2-antiplasmin's deleterious effects during brain ischemia. Middle cerebral artery thromboembolic stroke was induced in a randomized, blinded fashion in mice with increased blood levels of α2-antiplasmin. There was a robust increase in MMP-9 expression (immunofluorescence) in the ischemic vs. the non-ischemic hemisphere of MMP-9+/+ but not MMP-9−/− mice, 24 h after stroke. Brain swelling and hemorrhage were significantly increased in the ischemic vs. the non-ischemic hemisphere of MMP-9+/+ mice. By comparison to MMP-9+/+ mice, the ischemic hemispheres of MMP-9−/− mice showed a ∼6-fold reduction in brain swelling (p < 0.001) and a ∼9-fold reduction in brain hemorrhage. Brain infarction (p < 0.0001) and TUNEL-positive cell death (p < 0.001) were significantly diminished in the ischemic hemisphere of MMP-9−/− mice vs. MMP-9+/+ mice. Ischemic breakdown of the blood–brain barrier and fibrin deposition were also significantly reduced in MMP-9−/− mice vs. MMP-9+/+ mice (p < 0.05), as measured by quantitative immunofluorescence. We conclude that MMP-9 deficiency ablates many of the deleterious effects of high α2-antiplasmin levels, significantly reducing blood–brain barrier breakdown, TUNEL-positive cell death, brain hemorrhage, swelling and infarction. This suggests that the two molecules may be in a shared pathway in which MMP-9 is essential downstream for the deleterious effects of α2-antiplasmin in ischemic stroke.

Original languageEnglish (US)
Pages (from-to)40-47
Number of pages8
JournalNeuroscience
Volume376
DOIs
StatePublished - Apr 15 2018
Externally publishedYes

Keywords

  • blood–brain barrier
  • fibrinogen
  • ischemic stroke
  • matrix metalloproteinase-9
  • α2-antiplasmin

ASJC Scopus subject areas

  • Neuroscience(all)

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