Impact of Bradykinin Generation During Thrombolysis in Ischemic Stroke

Ischemic stroke is one of the leading causes of death and disability worldwide. Current medical management in the acute phase is based on the activation of the fibrinolytic cascade by intravenous injection of a plasminogen activator (such as tissue-type plasminogen activator, tPA) that promotes restauration of the cerebral blood flow and improves stroke outcome. Unfortunately, the use of tPA is associated with deleterious effects such as hemorrhagic transformation, symptomatic brain edema, and angioedema, which limit the efficacy of this therapeutic strategy. Preclinical and clinical evidence suggests that intravenous thrombolysis generates large amounts of bradykinin, a peptide with potent pro-inflammatory, and pro-edematous effects. This tPA-triggered generation of bradykinin could participate in the deleterious effects of thrombolysis and is a potential target to improve neurological outcome in tPA-treated patients. The present review aims at summarizing current evidence linking thrombolysis, bradykinin generation, and neurovascular damage

Matrix metalloproteinase-10 is upregulated by thrombin in endothelial cells and increased in patients with enhanced thrombin generation

OBJECTIVE: Thrombin is a multifunctional serine protease that promotes vascular proinflammatory responses whose effect on endothelial MMP-10 expression has not previously been evaluated. METHODS AND RESULTS: Thrombin induced endothelial MMP-10 mRNA and protein levels, through a protease-activated receptor-1 (PAR-1)-dependent mechanism, in a dose- and time-dependent manner. This effect was mimicked by a PAR-1 agonist peptide (TRAP-1) and antagonized by an anti-PAR-1 blocking antibody. MMP-10 induction was dependent on extracellular regulated kinase1/2 (ERK1/2) and c-jun N-terminal kinase (JNK) pathways. By serial deletion analysis, site-directed mutagenesis and electrophoretic mobility shift assay an AP-1 site in the proximal region of MMP-10 promoter was found to be critical for thrombin-induced MMP-10 transcriptional activity. Thrombin and TRAP-1 upregulated MMP-10 in murine endothelial cells in culture and in vivo in mouse aorta. This effect of thrombin was not observed in PAR-1-deficient mice. Interestingly, circulating MMP-10 levels (P<0.01) were augmented in patients with endothelial activation associated with high (disseminated intravascular coagulation) and moderate (previous acute myocardial infarction) systemic thrombin generation. CONCLUSIONS: Thrombin induces MMP-10 through a PAR-1-dependent mechanism mediated by ERK1/2, JNK, and AP-1 activation. Endothelial MMP-10 upregulation could be regarded as a new proinflammatory effect of thrombin whose pathological consequences in thrombin-related disorders and plaque stability deserve further investigation

Matrix metalloproteinase-10 effectively reduces infarct size in experimental stroke by enhancing fibrinolysis via a thrombin-activatable fibrinolysis inhibitor-mediated mechanism

BACKGROUND: The fibrinolytic and matrix metalloproteinase (MMP) systems cooperate in thrombus dissolution and extracellular matrix proteolysis. The plasminogen/plasmin system activates MMPs, and some MMPs have been involved in the dissolution of fibrin by targeting fibrin(ogen) directly or by collaborating with plasmin. MMP-10 has been implicated in inflammatory/thrombotic processes and vascular integrity, but whether MMP-10 could have a profibrinolytic effect and represent a promising thrombolytic agent is unknown. METHODS AND RESULTS: The effect of MMP-10 on fibrinolysis was studied in vitro and in vivo, in MMP-10-null mice (Mmp10(-/-)), with the use of 2 different murine models of arterial thrombosis: laser-induced carotid injury and ischemic stroke. In vitro, we showed that MMP-10 was capable of enhancing tissue plasminogen activator-induced fibrinolysis via a thrombin-activatable fibrinolysis inhibitor inactivation-mediated mechanism. In vivo, delayed fibrinolysis observed after photochemical carotid injury in Mmp10(-/-) mice was reversed by active recombinant human MMP-10. In a thrombin-induced stroke model, the reperfusion and the infarct size in sham or tissue plasminogen activator-treated animals were severely impaired in Mmp10(-/-) mice. In this model, administration of active MMP-10 to wild-type animals significantly reduced blood reperfusion time and infarct size to the same extent as tissue plasminogen activator and was associated with shorter bleeding time and no intracranial hemorrhage. This effect was not observed in thrombin-activatable fibrinolysis inhibitor-deficient mice, suggesting thrombin-activatable fibrinolysis inhibitor inactivation as one of the mechanisms involved in the MMP-10 profibrinolytic effect. CONCLUSIONS: A novel profibrinolytic role for MMP-10 in experimental ischemic stroke is described, opening new pathways for innovative fibrinolytic strategies in arterial thrombosis

Innovative thrombolytic strategy using a heterodimer diabody against TAFI and PAI-1 in mouse models of thrombosis and stroke

Circulating thrombin-activatable fibrinolysis inhibitor (TAFI) and plasminogen activator inhibitor-1 (PAI-1) are causal factors for thrombolytic failure. Therefore, we evaluated an antibody-engineered bispecific inhibitor against TAFI and PAI-1 (heterodimer diabody, Db-TCK26D6x33H1F7) in several mouse models of thrombosis and stroke. Prophylactic administration of the diabody (0.8mg/kg) in a thromboplastin-induced model of thromboembolism led to decreased lung fibrin deposition. In a model of cerebral ischemia/reperfusion, diabody administration (0.8mg/kg, 1h post occlusion) led to a mitigated cerebral injury with a 2.3-fold reduced lesion and improved functional outcomes. In a mouse model of thrombin-induced middle cerebral artery occlusion (MCAo), the efficacy of the diabody was compared to the standard thrombolytic treatment with recombinant tissue-type plasminogen activator (tPA). Early administration of diabody (0.8mg/kg, 20min post occlusion) caused a 2-fold decrease in brain lesion size, whereas that of tPA (10mg/kg) had a much smaller effect. Delayed administration of diabody or tPA (90min post occlusion) had no effect on lesion size, whereas the combined administration of diabody with tPA caused a 1.7-fold decrease in lesion size. In contrast to tPA, the diabody did not increase accumulative bleeding. In conclusion, administration of a bispecific inhibitor against TAFI and PAI-1 results in a prominent profibrinolytic effect in mice without increased bleeding.status: publishe

Molecular magnetic resonance imaging discloses endothelial activation after transient ischaemic attack

International audienceAbout 20% of patients with ischaemic stroke have a preceding transient ischaemic attack, which is clinically defined as focal neurological symptoms of ischaemic origin resolving spontaneously. Failure to diagnose transient ischaemic attack is a wasted opportunity to prevent recurrent disabling stroke. Unfortunately, diagnosis can be difficult, due to numerous mimics, and to the absence of a specific test. New diagnostic tools are thus needed, in particular for radiologically silent cases, which correspond to the recommended tissue-based definition of transient ischaemic attack. As endothelial activation is a hallmark of cerebrovascular events, we postulated that this may also be true for transient ischaemic attack, and that it would be clinically relevant to develop non-invasive in vivo imaging to detect this endothelial activation. Using transcriptional and immunohistological analyses for adhesion molecules in a mouse model, we identified brain endothelial P-selectin as a potential biomarker for transient ischaemic attack. We thus developed ultra-sensitive molecular magnetic resonance imaging using antibody-based microparticles of iron oxide targeting P-selectin. This highly sensitive imaging strategy unmasked activated endothelial cells after experimental transient ischae-mic attack and allowed discriminating transient ischaemic attack from epilepsy and migraine, two important transient ischaemic attack mimics. We provide preclinical evidence that combining conventional magnetic resonance imaging with molecular magnetic resonance imaging targeting P-selectin might aid in the diagnosis of transient ischaemic attack

Increased thrombin generation after acute versus chronic coronary disease as assessed by the thrombin generation test

Atherosclerosis is the most common pathophysiologic substrate of coronary artery disease (CAD). Whereas plaque progression and arterial remodeling are critical components in chronic CAD, intracoronary thrombosis over plaque disruption is causally related to acute CAD. It was the objective of this study to investigate the differences between prior acute CAD and chronic CAD by a simple global coagulation assay measuring thrombin generation. A cross-sectional study involving 15 healthy controls, 35 patients with chronic stable CAD, and 60 patients after an episode of acute myocardial infarction (AMI) was performed. Thrombin generation was measured between three and 11 months after the initial diagnosis (mean 6 months) by a commercially available fluorogenic assay (Technothrombin TGA). In each patient the lag phase, velocity index and peak thrombin were obtained from the thrombogram profile. Traditional cardiovascular risk factors were recorded, and the inflammatory markers, fibrinogen and hs-C-reactive protein were determined. Compared with stable CAD patients, showing normal thrombograms, those with previous AMI showed earlier lag phase (p < 0.05) and significant increase of both the velocity index (p < 0.001) and peak thrombin (p < 0.05), indicating faster and higher thrombin generation in the AMI group. Differences in thrombin generation between stable and acute CAD patients remained significant (p < 0.001) after adjusting for conventional CAD risk factors (age, gender, diabetes, hypertension, smoking, and hypercholesterolemia). In conclusion, patients with a previous history of acute CAD showed earlier, faster and higher thrombin generation than stable chronic CAD patients. The thrombin generation test may be of clinical value to monitor hypercoagulable/vulnerable blood and/or guide therapy in CAD

Increased thrombin generation after acute versus chronic coronary disease as assessed by the thrombin generation test

Atherosclerosis is the most common pathophysiologic substrate of coronary artery disease (CAD). Whereas plaque progression and arterial remodeling are critical components in chronic CAD, intracoronary thrombosis over plaque disruption is causally related to acute CAD. It was the objective of this study to investigate the differences between prior acute CAD and chronic CAD by a simple global coagulation assay measuring thrombin generation. A cross-sectional study involving 15 healthy controls, 35 patients with chronic stable CAD, and 60 patients after an episode of acute myocardial infarction (AMI) was performed. Thrombin generation was measured between three and 11 months after the initial diagnosis (mean 6 months) by a commercially available fluorogenic assay (Technothrombin TGA). In each patient the lag phase, velocity index and peak thrombin were obtained from the thrombogram profile. Traditional cardiovascular risk factors were recorded, and the inflammatory markers, fibrinogen and hs-C-reactive protein were determined. Compared with stable CAD patients, showing normal thrombograms, those with previous AMI showed earlier lag phase (p < 0.05) and significant increase of both the velocity index (p < 0.001) and peak thrombin (p < 0.05), indicating faster and higher thrombin generation in the AMI group. Differences in thrombin generation between stable and acute CAD patients remained significant (p < 0.001) after adjusting for conventional CAD risk factors (age, gender, diabetes, hypertension, smoking, and hypercholesterolemia). In conclusion, patients with a previous history of acute CAD showed earlier, faster and higher thrombin generation than stable chronic CAD patients. The thrombin generation test may be of clinical value to monitor hypercoagulable/vulnerable blood and/or guide therapy in CAD