J Orbe1, N Alexandru2, C Roncal3, M Belzunce3, P Bibiot3, J A Rodriguez3, J C M Meijers4, A Georgescu2, J A Paramo3. 1. Laboratory of Atherothrombosis, Program of Cardiovascular Diseases, CIMA-University of Navarra, Navarra Institute for Health Research (IdiSNA), Pamplona, Spain. Electronic address: josuneor@unav.es. 2. Pathophysiology and Pharmacology Department, Institute of Cellular Biology and Pathology 'Nicolae Simionescu' of Romanian Academy, Bucharest, Romania. 3. Laboratory of Atherothrombosis, Program of Cardiovascular Diseases, CIMA-University of Navarra, Navarra Institute for Health Research (IdiSNA), Pamplona, Spain. 4. Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, the Netherlands; Department of Plasma Proteins, Sanquin Research, Amsterdam, the Netherlands.
Abstract
BACKGROUND: Thrombin-activatable fibrinolysis inhibitor (TAFI) plays an important role in coagulation and fibrinolysis. Whereas TAFI deficiency may lead to a haemorrhagic tendency, data from TAFI knockout mice (TAFI-/-) are controversial and no differences have been reported in these animals after ischemic stroke. There are also no data regarding the role of circulating microparticles (MPs) in TAFI-/-. OBJECTIVES: to examine the effect of tPA on the rate of intracranial haemorrhage (ICH) and on MPs generated in a model of ischemic stroke in TAFI-/- mice. METHODS: Thrombin was injected into the middle cerebral artery (MCA) to analyse the effect of tPA (10mg/Kg) on the infarct size and haemorrhage in the absence of TAFI. Immunofluorescence for Fluoro-Jade C was performed on frozen brain slides to analyse neuronal degeneration after ischemia. MPs were isolated from mouse blood and their concentrations calculated by flow cytometry. RESULTS: Compared with saline, tPA significantly increased the infarct size in TAFI-/- mice (p<0.05). Although plasma fibrinolytic activity (fibrin plate assay) was higher in these animals, no macroscopic or microscopic ICH was detected. A positive signal for apoptosis and degenerating neurons was observed in the infarct area, being significantly higher in tPA treated TAFI-/- mice (p<0.05). Interestingly, higher numbers of MPs were found in TAFI-/- plasma as compared to wild type, after stroke (p<0.05). CONCLUSIONS: TAFI deficiency results in increased brain damage in a model of thrombolysis after ischemic stroke, which was not associated with bleeding but with neuronal degeneration and MP production.
BACKGROUND:Thrombin-activatable fibrinolysis inhibitor (TAFI) plays an important role in coagulation and fibrinolysis. Whereas TAFI deficiency may lead to a haemorrhagic tendency, data from TAFI knockout mice (TAFI-/-) are controversial and no differences have been reported in these animals after ischemic stroke. There are also no data regarding the role of circulating microparticles (MPs) in TAFI-/-. OBJECTIVES: to examine the effect of tPA on the rate of intracranial haemorrhage (ICH) and on MPs generated in a model of ischemic stroke in TAFI-/- mice. METHODS:Thrombin was injected into the middle cerebral artery (MCA) to analyse the effect of tPA (10mg/Kg) on the infarct size and haemorrhage in the absence of TAFI. Immunofluorescence for Fluoro-Jade C was performed on frozen brain slides to analyse neuronal degeneration after ischemia. MPs were isolated from mouse blood and their concentrations calculated by flow cytometry. RESULTS: Compared with saline, tPA significantly increased the infarct size in TAFI-/- mice (p<0.05). Although plasma fibrinolytic activity (fibrin plate assay) was higher in these animals, no macroscopic or microscopic ICH was detected. A positive signal for apoptosis and degenerating neurons was observed in the infarct area, being significantly higher in tPA treated TAFI-/- mice (p<0.05). Interestingly, higher numbers of MPs were found in TAFI-/- plasma as compared to wild type, after stroke (p<0.05). CONCLUSIONS:TAFI deficiency results in increased brain damage in a model of thrombolysis after ischemic stroke, which was not associated with bleeding but with neuronal degeneration and MP production.