PDGFR-α inhibition preserves blood-brain barrier after intracerebral hemorrhage.

OBJECTIVE: Perihematomal edema results from disruption of the blood-brain barrier (BBB) by key mediators, such as thrombin, following intracerebral hemorrhage (ICH). Platelet-derived growth factor receptor alpha (PDGFR-α), a tyrosine kinase receptor, was found in previous studies to play a role in orchestrating BBB impairment. In the present study, we investigated the role of PDGFR-α following ICH-induced brain injury in mice, specifically investigating its effect on BBB disruption.
METHODS: Brain injury was induced by autologous arterial blood (30 μl) or thrombin (5 U) injection into mice brains. A PDGFR antagonist (Gleevec) or agonist (PDGF-AA) was administered following ICH. PDGF-AA was injected with a thrombin inhibitor, hirudin, in ICH mice. Thrombin-injected mice were given Gleevec or PDGF-AA neutralizing antibody. A p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, was delivered with PDGF-AA in naïve animals. Postassessment included neurological function tests, brain edema measurement, Evans blue extravasation, immunoprecipitation, western blot, and immunohistology assay.
RESULTS: PDGFR-α suppression prevented neurological deficits, brain edema, and Evans blue extravasation at 24 to 72 hours following ICH. PDGFR-α activation led to BBB impairment and this was reversed by SB203580 in naïve mice. Thrombin inhibition suppressed PDGFR-α activation and exogenous PDGF-AA increased PDGFR-α activation, regardless of thrombin inhibition. Animals receiving a PDGF-AA-neutralizing antibody or Gleevec showed minimized thrombin injection-induced BBB impairment.
INTERPRETATION: PDGFR-α signaling may contribute to BBB impairment via p38 MAPK-mediated matrix metalloproteinase (MMP) activation/expression following ICH, and thrombin may be the key upstream orchestrator. The therapeutic interventions targeting the PDGFR-α signaling may be a novel strategy to prevent thrombin-induced BBB impairment following ICH.