Molecular mechanisms of thrombus formation in ischemic stroke: novel insights and targets for treatment

Targeting platelet receptors in thrombotic and thrombo-inflammatory disorders

Platelet activation at sites of vascular injury is critical for the formation of a hemostatic plug which limits excessive blood loss, but also represents a major pathomechanism of ischemic cardio- and cerebrovascular diseases. Although currently available antiplatelet therapies have proved beneficial in preventing the recurrence of vascular events, their adverse effects on primary hemostasis emphasize the necessity to identify and characterize novel pharmacological targets for platelet inhibition. Increasing experimental evidence has suggested that several major platelet surface receptors which regulate initial steps of platelet adhesion and activation may become promising new targets for anti-platelet drugs due to their involvement in thrombotic and thrombo-inflammatory signaling cascades.

This review summarizes recent developments in understanding the function of glycoprotein (GP)Ib, GPVI and the C-type lectin-like receptor 2 (CLEC-2) in hemostasis, arterial thrombosis and thrombo-inflammation and will discuss the suitability of the receptors as novel targets to treat these diseases in humans.

Bone morphogenetic protein 9 serves a protective role in response to ischemic‑reperfusion in the brain by promoting ERK activation

The aim of the present study was to investigate the expression and function mechanism of bone morphogenetic protein 9 (BMP9) in cerebral ischemia-reperfusion (I/R) injuries in vivo and in vitro. A total of 40 Sprague-Dawley rats were randomly divided into four groups (n=10): i) Normal control; ii) sham surgery group, the procedure without occlusion; iii) I/R group, right middle cerebral artery occlusion (MCAO) followed by reperfusion; and iv) adenoviral vector (Ad)-BMP9 + I/R group, Ad-BMP9 intracerebroventricular injection was performed 2 days prior to MCAO. Neurological deficit score and infarct volume were measured at 24 h following reperfusion. To further test the mechanism of BMP9, astrocytes were isolated and treated with Ad-BMP9, Ad-BMP9 + extracellular signal-regulated kinase (ERK) inhibitor PD098059, Ad-BMP9 + c-Jun N-terminal kinase inhibitor SP600125 and Ad-BMP9 + p38 inhibitor SB203580 for 24 h, followed by undergoing oxygen-glucose deprivation and reoxygenation (OGD/R) treatment. Cell viability and death were assessed by 3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxyphenyl)-(4-sulfophenyl)-2H-tetrazolium and lactate dehydrogenase release, respectively. Gene expression was determined by quantitative polymerase chain reaction and western blotting. BMP9 was identified to be upregulated at mRNA and protein levels in cerebral I/R animal and cell models. BMP9 pretreatment significantly reduced the neurological score and infarct volume compared with I/R rats. In astrocytes, overexpression of BMP9 significantly decreased cell death and improved cell viability, an effect which may be mediated by the ERK signaling pathway, as ERK was activated by BMP9 and the use of PD098059 partially reversed the protective effect of BMP9. Pretreatment with BMP-9 may be a promising treatment option for prevention of cerebral I/R injuries.

Platelets, inflammation and tissue regeneration

Blood platelets have long been recognised to bring about primary haemostasis with deficiencies in platelet production and function manifesting in bleeding while upregulated function favourises arterial thrombosis. Yet increasing evidence indicates that platelets fulfil a much wider role in health and disease. First, they store and release a wide range of biologically active substances including the panoply of growth factors, chemokines and cytokines released from α-granules. Membrane budding gives rise to microparticles (MPs), another active participant within the blood stream. Platelets are essential for the innate immune response and combat infection (viruses, bacteria, micro-organisms). They help maintain and modulate inflammation and are a major source of pro-inflammatory molecules (e.g. P-selectin, tissue factor, CD40L, metalloproteinases). As well as promoting coagulation, they are active in fibrinolysis; wound healing, angiogenesis and bone formation as well as in maternal tissue and foetal vascular remodelling. Activated platelets and MPs intervene in the propagation of major diseases. They are major players in atherosclerosis and related diseases, pathologies of the central nervous system (Alzheimers disease, multiple sclerosis), cancer and tumour growth. They participate in other tissue-related acquired pathologies such as skin diseases and allergy, rheumatoid arthritis, liver disease; while, paradoxically, autologous platelet-rich plasma and platelet releasate are being used as an aid to promote tissue repair and cellular growth. The above mentioned roles of platelets are now discussed.

Crosstalk between platelets and the complement system in immune protection and disease

Platelets have a central function in repairing vascular damage and stopping acute blood loss. They are equally central to thrombus formation in cardiovascular diseases such as myocardial infarction and ischaemic stroke. Beyond these classical prothrombotic diseases, immune mediated pathologies such as haemolytic uraemic syndrome (HUS) or paroxysmal nocturnal haemoglobinuria (PNH) also feature an increased tendency to form thrombi in various tissues. It has become increasingly clear that the complement system, part of the innate immune system, has an important role in the pathophysiology of these diseases. Not only does complement influence prothrombotic disease, it is equally involved in idiopathic thrombocytopenic purpura (ITP), an autoimmune disease characterised by thrombocytopenia. Thus, there are complex interrelationships between the haemostatic and immune systems, and platelets and complement in particular. Not only does complement influence platelet diseases such as ITP, HUS and PNH, it also mediates interaction between microbes and platelets during systemic infection, influencing the course of infection and development of protective immunity. This review aims to provide an integrative overview of the mechanisms underlying the interactions between complement and platelets in health and disease.

Focusing on plasma glycoprotein VI

New methods for analysing both platelet and plasma forms of the platelet-specific collagen receptor, glycoprotein VI (GPVI) in experimental models or human clinical samples, and the development of the first therapeutic compounds based on dimeric soluble GPVI-Fc or anti-GPVI antibody-based constructs, coincide with increased understanding of the potential pathophysiological role of GPVI ligand binding and shedding. Platelet GPVI not only mediates platelet activation at the site of vascular injury where collagen is exposed, but is also implicated in the pathogenesis of other diseases, such as atherosclerosis and coagulopathy, rheumatoid arthritis and tumour metastasis. Here, we describe some of the critical mechanisms for generating soluble GPVI from platelets, and future avenues for exploiting this unique platelet-specific receptor for diagnosis and/or disease prevention.

Inhibition of CD147 (Cluster of Differentiation 147) Ameliorates Acute Ischemic Stroke in Mice by Reducing Thromboinflammation

BACKGROUND AND PURPOSE

Inflammation and thrombosis currently are recognized as critical contributors to the pathogenesis of ischemic stroke. CD147 (cluster of differentiation 147), also known as extracellular matrix metalloproteinase inducer, can function as a key mediator of inflammatory and immune responses. CD147 expression is increased in the brain after cerebral ischemia, but its role in the pathogenesis of ischemic stroke remains unknown. In this study, we show that CD147 acts as a key player in ischemic stroke by driving thrombotic and inflammatory responses.

METHODS

Focal cerebral ischemia was induced in C57BL/6 mice by a 60-minute transient middle cerebral artery occlusion. Animals were treated with anti-CD147 function-blocking antibody (αCD147) or isotype control antibody. Blood-brain barrier permeability, thrombus formation, and microvascular patency were assessed 24 hours after ischemia. Infarct size, neurological deficits, and inflammatory cells invaded in the brain were assessed 72 hours after ischemia.

RESULTS

CD147 expression was rapidly increased in ischemic brain endothelium after transient middle cerebral artery occlusion. Inhibition of CD147 reduced infarct size and improved functional outcome on day 3 after transient middle cerebral artery occlusion. The neuroprotective effects were associated with (1) prevented blood-brain barrier damage, (2) decreased intravascular fibrin and platelet deposition, which in turn reduced thrombosis and increased cerebral perfusion, and (3) reduced brain inflammatory cell infiltration. The underlying mechanism may include reduced NF-κB (nuclear factor κB) activation, MMP-9 (matrix metalloproteinase-9) activity, and PAI-1 (plasminogen activator inhibitor-1) expression in brain microvascular endothelial cells.

CONCLUSIONS

Inhibition of CD147 ameliorates acute ischemic stroke by reducing thromboinflammation. CD147 might represent a novel and promising therapeutic target for ischemic stroke and possibly other thromboinflammatory disorders.

ROCK as a therapeutic target for ischemic stroke

INTRODUCTION

Stroke is a major cause of disability and the fifth leading cause of death. Currently, the only approved acute medical treatment of ischemic stroke is tissue plasminogen activator (tPA), but its effectiveness is greatly predicated upon early administration of the drug. There is, therefore, an urgent need to find new therapeutic options for acute stroke. Areas covered: In this review, we summarize the role of Rho-associated coiled-coil containing kinase (ROCK) and its potential as a therapeutic target in stroke pathophysiology. ROCK is a major regulator of cell contractility, motility, and proliferation. Many of these ROCK-mediated processes in endothelial cells, vascular smooth muscle cells, pericytes, astrocytes, glia, neurons, leukocytes, and platelets are important in stroke pathophysiology, and the inhibition of such processes could improve stroke outcome. Expert commentary: ROCK is a potential therapeutic target for cardiovascular disease and ROCK inhibitors have already been approved for human use in Japan and China for the treatment of acute stroke. Further studies are needed to determine the role of ROCK isoforms in the pathophysiology of cerebral ischemia and whether there are further therapeutic benefits with selective ROCK inhibitors.

GPVI‑Fc‑PEG improves cerebral infarct volume and cerebral thrombosis in mouse model with cerebral thrombosis

Cerebral thrombosis is one of the most common causes of cerebral infarction, and anticoagulation therapy is a routine treatment in patients with hemorrhagic cerebral venous thrombosis. The hemostatic function of platelets is important for the anticoagulation therapy of thrombosis. Glycoprotein VI (GPVI) is reported as the major signaling receptor for collagen and is exclusively expressed on platelets and megakaryocytes, initiating platelet recruitment at sites of vascular injury and demonstrating numerous beneficial effects for patients with cerebral thrombosis. In the present study, thrombus formation and platelet adhesion following endothelial injury was monitored in the jugular vein by intra‑vital fluorescence microscopy. The morphological and clinical observations of cerebral thrombosis were investigated and analyzed in a mouse model with cerebral thrombosis. In addition, the present study investigated the effect of fusion protein GPVI modified with Fc and PEG, which is specifically linked to the extracellular domain of GPVI (GPVI‑Fc‑PEG), on thrombus formation following vessel wall injury and on experimental mice with cerebral thrombosis. The maximum tolerated dose (MTD) was identified as 0.18 mg. GPVI‑Fc‑PEG competitively bound to and prevented von Willebrand Factor‑collagen interactions. The results of the present study demonstrated that cerebral thrombosis was greatly relieved and improved functional outcomes treatment with an MTD of GPVI‑Fc‑PEG following endothelial injury, compared with GPVI‑Fc‑treated mice. In addition, cerebral edema and infarct size was improved compared with GPVI‑Fc‑treated mice with ischemic stroke immediately prior to reperfusion. Furthermore, treatment of GPVI‑Fc‑PEG led to increased reperfusion and improved survival following cerebral thrombosis compared with treatment with either single agent alone. Taken together, GPVI‑Fc‑PEG relieved cerebral thrombosis following ischemic stroke and improved prognostic preclinical outcomes without intracranial bleeding, which suggested that GPVI‑Fc‑PEG may be a potential candidate for cerebral thrombosis therapy.

Multi-Targeting Andrographolide, a Novel NF-κB Inhibitor, as a Potential Therapeutic Agent for Stroke

A key focus in the field of drug discovery has been motivated by the neuroprotection of natural compounds. Cerebral ischemia is a multifaceted pathological process with a series of mechanisms, and a perspective for the development of neuroprotectants from traditional herbal medicine or natural products is a promising treatment for this disease. Natural compounds with the effects of anti-oxidation, anti-inflammation, anti-apoptosis, and neurofunctional regulation exhibit therapeutic effects on experimental ischemic brain injury. Conferring to the pharmacological mechanisms underlying neuroprotection, a study found that androgapholide, a diterpene lactone compound, exhibits varying degrees of neuroprotective activities in both in vitro and in vivo experimental models of stroke. The neuroprotective mechanisms of andrographolide are suggested as: (I) increasing nuclear factor E2-related factor 2-heme oxygenase (Nrf2-HO-1) expression through p38-mitogen activated protein kinase (MAPK) regulation, (II) inducing cerebral endothelial cells (CEC) apoptosis and caspase-3 activation, (III) down regulating Bax, inducible nitric oxide synthase (iNOS), and (IV) inhibiting hydroxyl radical (OH⁻) formation, and activating transcription factor NF-κB signaling pathways. Recently, several researchers have also been trying to unveil the principal mechanisms involved in the neuroprotective effects of andrographolide. Therefore, this review aims to summarize an overview on the neuroprotective effects of andrographolide and exemplifies the essential mechanisms involved. This paper can provide information that andrographolide drug discovery may be a promising strategy for the development of a novel class of neuroprotective drug.

The Myosin II Inhibitor, Blebbistatin, Ameliorates FeCl3-induced Arterial Thrombosis via the GSK3β-NF-κB Pathway

Arterial thrombosis and its related diseases are major healthcare problems worldwide. Blebbistatin is an inhibitor of myosin II, which plays an important role in thrombosis. The aim of our study is to explore the effect and potential mechanism of blebbistatin on arterial thrombosis. A ferric chloride (FeCl₃) solution at a concentration of 5% was used to induce carotid artery thrombosis in mice. Immunohistochemistry and immunofluorescence staining were used to detect the expression or activation of non-muscle myosin heavy chain IIA (NMMHC IIA), tissue factor (TF), GSK3β and NF-κB. Blebbistatin (1 mg/kg, i.p.) significantly reduced carotid artery thrombosis induced by FeCl₃ solution in mice, inhibited NMMHC IIA expression and impeded TF expression via the GSK3β-NF-κB signalling pathway in mouse arterial vascular tissues. The present study demonstrates that blebbistatin may impede TF expression partly via the Akt/GSK3β-NF-κB signalling pathways in the endothelium in a FeCl₃ model, shedding new insights into the pathogenesis of arterial thrombosis and providing new clues for the development of antithrombotic drugs.

Platelet secretion is crucial to prevent bleeding in the ischemic brain but not in the inflamed skin or lung in mice

Platelet granule content is dispensable for maintaining vascular integrity during skin and lung inflammation. In stark contrast, lack of platelet granule secretion causes increased mortality in experimental stroke due to intracranial hemorrhage.

Plasma kallikrein mediates brain hemorrhage and edema caused by tissue plasminogen activator therapy in mice after stroke

Thrombolytic therapy using tissue plasminogen activator (tPA) in acute stroke is associated with increased risks of cerebral hemorrhagic transformation and angioedema. Although plasma kallikrein (PKal) has been implicated in contributing to both hematoma expansion and thrombosis in stroke, its role in the complications associated with the therapeutic use of tPA in stroke is not yet available. We investigated the effects of tPA on plasma prekallikrein (PPK) activation and the role of PKal on cerebral outcomes in a murine thrombotic stroke model treated with tPA. We show that tPA increases PKal activity in vitro in both murine and human plasma, via a factor XII (FXII)-dependent mechanism. Intravenous administration of tPA increased circulating PKal activity in mice. In mice with thrombotic occlusion of the middle cerebral artery, tPA administration increased brain hemorrhage transformation, infarct volume, and edema. These adverse effects of tPA were ameliorated in PPK (Klkb1)-deficient and FXII-deficient mice and in wild-type (WT) mice pretreated with a PKal inhibitor prior to tPA. tPA-induced brain hemisphere reperfusion after photothrombolic middle cerebral artery occlusion was increased in Klkb1^-/- mice compared with WT mice. In addition, PKal inhibition reduced matrix metalloproteinase-9 activity in brain following stroke and tPA therapy. These data demonstrate that tPA activates PPK in plasma and PKal inhibition reduces cerebral complications associated with tPA-mediated thrombolysis in stroke.

Contraction of Blood Clots Is Impaired in Acute Ischemic Stroke

OBJECTIVE

Obstructive thrombi or thrombotic emboli are the pathogenic basis of ischemic stroke. In vitro blood clots and in vivo thrombi can undergo platelet-driven contraction (retraction), resulting in volume shrinkage. Clot contraction can potentially reduce vessel occlusion and improve blood flow past emboli or thrombi. The aim of this work was to examine a potential pathogenic role of clot contraction in ischemic stroke.

APPROACH AND RESULTS

We used a novel automated method that enabled us to quantify time of initiation and extent and rate of clot contraction in vitro. The main finding is that clot contraction from the blood of stroke patients was reduced compared with healthy subjects. Reduced clot contraction correlated with a lower platelet count and their dysfunction, higher levels of fibrinogen and hematocrit, leukocytosis, and other changes in blood composition that may affect platelet function and properties of blood clots. Platelets from stroke patents were spontaneously activated and displayed reduced responsiveness to additional stimulation. Clinical correlations with respect to severity and stroke pathogenesis suggest that the impaired clot contraction has the potential to be a pathogenic factor in ischemic stroke.

CONCLUSIONS

The changeable ability of clots and thrombi to shrink in volume may be a novel unappreciated mechanism that aggravates or alleviates the course and outcomes of ischemic stroke. The clinical importance of clot or thrombus transformations in vivo and the diagnostic and prognostic value of this blood test for clot contraction need further exploration.

Platelets and platelet adhesion molecules: novel mechanisms of thrombosis and anti-thrombotic therapies

Platelets are central mediators of thrombosis and hemostasis. At the site of vascular injury, platelet accumulation (i.e. adhesion and aggregation) constitutes the first wave of hemostasis. Blood coagulation, initiated by the coagulation cascades, is the second wave of thrombin generation and enhance phosphatidylserine exposure, can markedly potentiate cell-based thrombin generation and enhance blood coagulation. Recently, deposition of plasma fibronectin and other proteins onto the injured vessel wall has been identified as a new "protein wave of hemostasis" that occurs prior to platelet accumulation (i.e. the classical first wave of hemostasis). These three waves of hemostasis, in the event of atherosclerotic plaque rupture, may turn pathogenic, and cause uncontrolled vessel occlusion and thrombotic disorders (e.g. heart attack and stroke). Current anti-platelet therapies have significantly reduced cardiovascular mortality, however, on-treatment thrombotic events, thrombocytopenia, and bleeding complications are still major concerns that continue to motivate innovation and drive therapeutic advances. Emerging evidence has brought platelet adhesion molecules back into the spotlight as targets for the development of novel anti-thrombotic agents. These potential antiplatelet targets mainly include the platelet receptors glycoprotein (GP) Ib-IX-V complex, β3 integrins (αIIb subunit and PSI domain of β3 subunit) and GPVI. Numerous efforts have been made aiming to balance the efficacy of inhibiting thrombosis without compromising hemostasis. This mini-review will update the mechanisms of thrombosis and the current state of antiplatelet therapies, and will focus on platelet adhesion molecules and the novel anti-thrombotic therapies that target them.

Functional characterization of tissue factor in von Willebrand factor-dependent thrombus formation under whole blood flow conditions

Von Willebrand factor (VWF) plays an important role in mediating platelet adhesion and aggregation under high shear rate conditions. Such platelet aggregates are strengthened by fibrin-network formation triggered by tissue factor (TF). However, little is known about the role of TF in VWF-dependent thrombus formation under blood flow conditions. We evaluated TF in thrombus formation on immobilized VWF under whole blood flow conditions in an in vitro perfusion chamber system. Surface-immobilized TF amplified intra-thrombus fibrin generation significantly under both low and high shear flow conditions, while TF in sample blood showed no appreciable effects. Furthermore, immobilized TF enhanced VWF-dependent platelet adhesion and aggregation significantly under high shear rates. Neutrophil cathepsin G and elastase increased significantly intra-thrombus fibrin deposition on immobilized VWF-TF complex, suggesting the involvement of leukocyte inflammatory responses in VWF/TF-dependent mural thrombogenesis under these flow conditions. These results reveal a functional link between VWF and TF under whole blood flow conditions, in which surface-immobilized TF and VWF mutually contribute to mural thrombus formation, which is essential for normal hemostasis. By contrast, TF circulating in blood may be involved in systemic hypercoagulability, as seen in sepsis caused by severe microbial infection, in which neutrophil inflammatory responses may be active.

α2-Antiplasmin: New Insights and Opportunities for Ischemic Stroke

Thrombotic vascular occlusion is the leading cause of ischemic stroke. High blood levels of α₂-antiplasmin (a2AP), an ultrafast, covalent inhibitor of plasmin, have been linked in humans to increased risk of ischemic stroke and failure of tissue plasminogen activator (tPA) therapy. Consistent with these observations, a2AP neutralizes the therapeutic benefit of tPA therapy in experimental stroke. In addition, a2AP has deleterious, dose-related effects on ischemic brain injury in the absence of therapy. Experimental therapeutic inactivation of a2AP markedly reduces microvascular thrombosis, ischemic brain injury, brain swelling, brain hemorrhage, and death after thromboembolic stroke. These data provide new insights into the critical importance of a2AP in the pathogenesis of ischemic brain injury and suggest that transiently inactivating a2AP may have therapeutic value in ischemic stroke.

A brief review on the mechanisms of aspirin resistance

Aspirin is the most widely prescribed drug for the primary and secondary prevention of cardiovascular and cerebrovascular diseases. However, a large number of patients continue to experience thromboembolic events despite aspirin therapy, a phenomenon referred to as aspirin resistance or treatment failure. Aspirin resistance is often observed along with a high incidence of unstable plaque, cardiovascular events and cerebrovascular accident. Studies have shown that aspirin reduces the production of TXA2, but not totally inhibits the activation of platelets. In this review, we analyze current and past research on aspirin resistance, presenting important summaries of results regarding the potential contributive roles of single nucleotide polymorphisms, inflammation, metabolic syndrome and miRNAs. The aim of this article is to provide a brief review on aspirin resistance and platelet function, which will provide important insights into the research of aspirin resistance.

Molecular mechanisms and cell signaling of 20-hydroxyeicosatetraenoic acid in vascular pathophysiology

Cytochrome P450s enzymes catalyze the metabolism of arachidonic acid to epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid and hydroxyeicosatetraeonic acid (HETEs). 20-HETE is a vasoconstrictor that depolarizes vascular smooth muscle cells by blocking K+ channels. EETs serve as endothelial derived hyperpolarizing factors. Inhibition of the formation of 20-HETE impairs the myogenic response and autoregulation of renal and cerebral blood flow. Changes in the formation of EETs and 20-HETE have been reported in hypertension and drugs that target these pathways alter blood pressure in animal models. Sequence variants in CYP4A11 and CYP4F2 that produce 20-HETE, UDP-glucuronosyl transferase involved in the biotransformation of 20-HETE and soluble epoxide hydrolase that inactivates EETs are associated with hypertension in human studies. 20-HETE contributes to the regulation of vascular hypertrophy, restenosis, angiogenesis and inflammation. It also promotes endothelial dysfunction and contributes to cerebral vasospasm and ischemia-reperfusion injury in the brain, kidney and heart. This review will focus on the role of 20-HETE in vascular dysfunction, inflammation, ischemic and hemorrhagic stroke and cardiac and renal ischemia reperfusion injury.

Protein methionine oxidation augments reperfusion injury in acute ischemic stroke

Reperfusion injury can exacerbate tissue damage in ischemic stroke, but little is known about the mechanisms linking ROS to stroke severity. Here, we tested the hypothesis that protein methionine oxidation potentiates NF-κB activation and contributes to cerebral ischemia/reperfusion injury. We found that overexpression of methionine sulfoxide reductase A (MsrA), an antioxidant enzyme that reverses protein methionine oxidation, attenuated ROS-augmented NF-κB activation in endothelial cells, in part, by protecting against the oxidation of methionine residues in the regulatory domain of calcium/calmodulin-dependent protein kinase II (CaMKII). In a murine model, MsrA deficiency resulted in increased NF-κB activation and neutrophil infiltration, larger infarct volumes, and more severe neurological impairment after transient cerebral ischemia/reperfusion injury. This phenotype was prevented by inhibition of NF-κB or CaMKII. MsrA-deficient mice also exhibited enhanced leukocyte rolling and upregulation of E-selectin, an endothelial NF-κB-dependent adhesion molecule known to contribute to neurovascular inflammation in ischemic stroke. Finally, bone marrow transplantation experiments demonstrated that the neuroprotective effect was mediated by MsrA expressed in nonhematopoietic cells. These findings suggest that protein methionine oxidation in nonmyeloid cells is a key mechanism of postischemic oxidative injury mediated by NF-κB activation, leading to neutrophil recruitment and neurovascular inflammation in acute ischemic stroke.

Thrombosis recanalization by paeoniflorin through the upregulation of urokinase‑type plasminogen activator via the MAPK signaling pathway

Paeoniflorin, the major component of Paeonia lactiflora pall, has previously been reported to prevent thrombosis. Plasminogen activator urokinase (uPA) is a serine protease that markedly facilitates normal thrombosis resolution. Paeoniflorin and uPA have been linked to the mitogen-activated protein kinase (MAPK) signaling pathway. In the current study, the influence of paeoniflorin on the expression of uPA was investigated and the underlying regulatory mechanism was preliminarily determined. The prothrombotic state of the model animals treated with paeoniflorin were assessed by enzyme-linked immunosorbent assay (ELISA). Additionally, the cytotoxicity of paeoniflorin on human umbilical vein endothelial cell (HUVEC) cultures was estimated using a methyl thiazolyl tetrazolium assay and the possible pathways involved in the interaction between paeoniflorin and uPA were evaluated using western blot analysis. The ELISA results demonstrated that the levels of 6-keto prostaglandin F_1a, fibronectin and uPA were significantly upregulated by treatment with paeoniflorin compared with control (P<0.05). By contrast, the expression of fibrinogen, D-dimer and thromboxane B₂ were inhibited. With an increase in the concentration of paeoniflorin the cell viability of HUVECs decreased gradually. The results of western blot analysis demonstrated that paeoniflorin increased the phosphorylation of MAPK 14 (p38) and MAPK 8 (JNK). The present study demonstrated that paeoniflorin has the potential to improve the prethrombotic state and recanalize thrombosis by increasing the expression of uPA, which may be mediated via regulation of the p38 and JNK MAPK signaling pathways. However, this treatment effect was dependent on the concentration of paeoniflorin used, an unsuitable concentration of the agent would result in a negative effect on the anti-thrombosis pathways.

Plasma L5 levels are elevated in ischemic stroke patients and enhance platelet aggregation

L5, the most electronegative and atherogenic subfraction of low-density lipoprotein (LDL), induces platelet activation. We hypothesized that plasma L5 levels are increased in acute ischemic stroke patients and examined whether lectin-like oxidized LDL receptor-1 (LOX-1), the receptor for L5 on endothelial cells and platelets, plays a critical role in stroke. Because amyloid β (Aβ) stimulates platelet aggregation, we studied whether L5 and Aβ function synergistically to induce prothrombotic pathways leading to stroke. Levels of plasma L5, serum Aβ, and platelet LOX-1 expression were significantly higher in acute ischemic stroke patients than in controls without metabolic syndrome (P < .01). In mice subjected to focal cerebral ischemia, L5 treatment resulted in larger infarction volumes than did phosphate-buffered saline treatment. Deficiency or neutralizing of LOX-1 reduced infarct volume up to threefold after focal cerebral ischemia in mice, illustrating the importance of LOX-1 in stroke injury. In human platelets, L5 but not L1 (the least electronegative LDL subfraction) induced Aβ release via IκB kinase 2 (IKK2). Furthermore, L5+Aβ synergistically induced glycoprotein IIb/IIIa receptor activation; phosphorylation of IKK2, IκBα, p65, and c-Jun N-terminal kinase 1; and platelet aggregation. These effects were blocked by inhibiting IKK2, LOX-1, or nuclear factor-κB (NF-κB). Injecting L5+Aβ shortened tail-bleeding time by 50% (n = 12; P < .05 vs L1-injected mice), which was prevented by the IKK2 inhibitor. Our findings suggest that, through LOX-1, atherogenic L5 potentiates Aβ-mediated platelet activation, platelet aggregation, and hemostasis via IKK2/NF-κB signaling. L5 elevation may be a risk factor for cerebral atherothrombosis, and downregulating LOX-1 and inhibiting IKK2 may be novel antithrombotic strategies.

SOD1 nanozyme salvages ischemic brain by locally protecting cerebral vasculature

Copper/zinc superoxide dismutase (CuZnSOD; SOD1) is widely considered as a potential therapeutic candidate for pathologies involving oxidative stress, but its application has been greatly hindered by delivery issues. In our previous study, nanoformulated SOD1 (cl-nanozyme) was shown to decrease infarct volume and improve sensorimotor functions after a single intravenous (IV) injection in a rat middle cerebral artery occlusion (MCAO) model of ischemia/reperfusion (I/R) injury (stroke). However, it remained unclear how cl-nanozyme was able to deliver SOD1 to the brain and exert therapeutic efficacy. The present study aims to answer this question by exploring micro-distribution pattern of cl-nanozyme in the rat brain after stroke. Immunohistochemistry studies demonstrated cl-nanozyme co-localization with fibrin along damaged arteries and capillaries in the ischemic hemisphere. We further found that cl-nanozyme can be cross-linked into thrombi formed after I/R injury in the brain, and this effect is independent of animal species (rat/mouse) used for modeling I/R injury. This work is also the first report reinforcing therapeutic potential of cl-nanozyme in a well-characterized mouse MCAO model of I/R injury.

A novel snake venom-derived GPIb antagonist, anfibatide, protects mice from acute experimental ischaemic stroke and reperfusion injury

BACKGROUND AND PURPOSE

Ischaemic stroke is a serious disease with limited therapy options. Glycoprotein (GP)Ib binding to von Willebrand factor (vWF) exposed at vascular injury initiates platelet adhesion and contributes to platelet aggregation. GPIb has been suggested as an effective target for antithrombotic therapy in stroke. Anfibatide is a GPIb antagonist derived from snake venom and we investigated its protective effect on experimental brain ischaemia in mice.

EXPERIMENTAL APPROACH

Focal cerebral ischaemia was induced by 90 min of transient middle cerebral artery occlusion (MCAO). These mice were then treated with anfibatide (4, 2, 1 μg·kg(-1) ), injected i.v., after 90 min of MCAO, followed by 1 h of reperfusion. Tirofiban, a GPIIb/IIIα antagonist, was used as a positive control.

KEY RESULTS

Twenty-four hours after MCAO, anfibatide-treated mice showed significantly improved ischaemic lesions in a dose-dependent manner. The mice had smaller infarct volumes, less severe neurological deficits and histopathology of cerebrum tissues compared with the untreated MCAO mice. Moreover, anfibatide decreased the amount of GPIbα, vWF and accumulation of fibrin(ogen) in the vasculature of the ischaemic hemisphere. Tirofiban had similar effects on infarct size and fibrin(ogen) deposition compared with the MCAO group. Importantly, the anfibatide-treated mice showed a lower incidence of intracerebral haemorrhage and shorter tail bleeding time compared with the tirofiban-treated mice.

CONCLUSIONS AND IMPLICATIONS

Our data indicate anfibatide is a safe GPIb antagonist that exerts a protective effect on cerebral ischaemia and reperfusion injury. Anfibatide is a promising candidate that could be beneficial for the treatment of ischaemic stroke.

Protective effects of Echium amoenum Fisch. and C.A. Mey. against cerebral ischemia in the rats

Background:

This study was designed to evaluate the protective effect of Echium amoenum total anthocyanin extract (ETAE) on partial/transient cerebral ischemia in the rats.

Materials and Methods:

Rats received ETAE (50, 100 and 200 mg/kg, i.p.) 30 min before the induction of cerebral ischemia. Cerebral ischemia was induced by bilateral common carotid arteries occlusion (BCCAO) for 30 min, followed by 72 h reperfusion. The neurological deficit, brain performance, and sensory motor function were assessed 48 h and 72 h after surgery. After sacrification, the brains were evaluated for myeloperoxidase (MPO) activity and histopathological changes.

Results:

Our results showed that motor function significantly decreased in ischemia/reperfusion (I/R) group as compared to the sham group. Histopathological analysis exhibited the shrinkage and atrophy of the neurons in I/R group. ETAE at the dose of 200 mg/kg improved spontaneous activity and memory induced by cerebral ischemia compared to the control group and also decreased brain MPO activity following cerebral ischemia. However, it could not affect the ability to climbing, body proprioception, vibrissae touch and brain water content. In addition, pretreatment with ETAE at higher doses significantly reduced ischemia-induced neuronal loss of the brain.

Conclusion:

The anthocyanin rich fraction from E. amoenum was found to have protective effects against some brain damages postischemic reperfusion. However, further researches are required for investigating the exact mechanisms of the effect of this plant in the prevention of cerebral ischemia in human.

Platelets and vascular inflammation of the brain

There is emerging evidence that platelets have an important role in inflammation beyond their involvement in hemostasis. Platelets can contribute to inflammatory reactions via crosstalk both with immune cells and endothelial cells. Inflamed vessels are characterized by the presence of activated endothelial cells. These activated endothelial cells upregulate receptors necessary for leukocyte recruitment, but also for the adhesion of platelets. Subsequently, immune cells can bind to platelets through adhesion receptors presented on the platelet surface, thus supporting leukocyte recruitment to the vessel wall. There are several neurological diseases associated with vascular inflammation including multiple sclerosis (MS) and stroke. Increased markers of platelet activation could be demonstrated in patients suffering from MS compared to healthy individuals. Reports from murine models indicate that platelets may be of importance for disease progression and severity by mediating leukocyte recruitment as one potential underlying mechanism. Blocking platelet function disease severity was considerably ameliorated. Moreover, processes of tissue remodelling may be influenced by platelet derived mediators. Whether a role of platelets for vascular inflammation can be extrapolated to further neurological diseases will have to be investigated in further in depth experimental and clinical trials.

CONCLUSION

Platelets and platelet associated mechanisms may offer novel starting points to understand neurovascular diseases from a different point of view and to develop novel approaches to access the disease.

Natural Products for Antithrombosis

Thrombosis is considered to be closely related to several diseases such as atherosclerosis, ischemic heart disease and stroke, as well as rheumatoid arthritis, hyperuricemia, and various inflammatory conditions. More and more studies have been focused on understanding the mechanism of molecular and cellular basis of thrombus formation as well as preventing thrombosis for the treatment of thrombotic diseases. In reality, there is considerable interest in the role of natural products and their bioactive components in the prevention and treatment of thrombosis related disorders. This paper briefly describes the mechanisms of thrombus formation on three aspects, including coagulation system, platelet activation, and aggregation, and change of blood flow conditions. Furthermore, the natural products for antithrombosis by anticoagulation, antiplatelet aggregation, and fibrinolysis were summarized, respectively.

Blocking of plasma kallikrein ameliorates stroke by reducing thromboinflammation

OBJECTIVE

Recent evidence suggests that ischemic stroke is a thromboinflammatory disease. Plasma kallikrein (PK) cleaves high-molecular-weight kininogen to release bradykinin (BK) and is a key constituent of the proinflammatory contact-kinin system. In addition, PK can activate coagulation factor XII, the origin of the intrinsic coagulation cascade. Thus, PK triggers 2 important pathological pathways of stroke formation, thrombosis and inflammation.

METHODS

We investigated the consequences of PK inhibition in transient and permanent models of ischemic stroke.

RESULTS

PK-deficient mice of either sex challenged with transient middle cerebral artery occlusion developed significantly smaller brain infarctions and less severe neurological deficits compared with controls without an increase in infarct-associated hemorrhage. This protective effect was preserved at later stages of infarctions as well as after permanent stroke. Reduced intracerebral thrombosis and improved cerebral blood flow could be identified as underlying mechanisms. Moreover, blood-brain barrier function was maintained in mice lacking PK, and the local inflammatory response was reduced. PK-deficient mice reconstituted with PK or BK again developed brain infarctions similar to wild-type mice. Important from a translational perspective, inhibition of PK in wild-type mice using a PK-specific antibody was likewise effective even when performed in a therapeutic setting up to 3 hours poststroke.

INTERPRETATION

PK drives thrombus formation and inflammation via activation of the intrinsic coagulation cascade and the release of BK but appears to be dispensable for hemostasis. Hence, PK inhibition may offer a safe strategy to combat thromboembolic disorders including ischemic stroke.

Case-control study of platelet glycoprotein receptor Ib and IIb/IIIa expression in patients with acute and chronic cerebrovascular disease

Background

Animal models have been instrumental in defining thrombus formation, including the role of platelet surface glycoprotein (GP) receptors, in acute ischemic stroke (AIS). However, the involvement of GP receptors in human ischemic stroke pathophysiology and their utility as biomarkers for ischemic stroke risk and severity requires elucidation.

Aims

To determine whether platelet GPIb and GPIIb/IIIa receptors are differentially expressed in patients with AIS and chronic cerebrovascular disease (CCD) compared with healthy volunteers (HV) and to identify predictors of GPIb and GPIIb/IIIa expression.

Methods

This was a case—control study of 116 patients with AIS or transient ischemic attack (TIA), 117 patients with CCD, and 104 HV who were enrolled at our University hospital from 2010 to 2013. Blood sampling was performed once in the CCD and HV groups, and at several time points in patients with AIS or TIA. Linear regression and analysis of variance were used to analyze correlations between platelet GPIb and GPIIb/IIIa receptor numbers and demographic and clinical parameters.

Results

GPIb and GPIIb/IIIa receptor numbers did not significantly differ between the AIS, CCD, and HV groups. GPIb receptor expression level correlated significantly with the magnitude of GPIIb/IIIa receptor expression and the neutrophil count. In contrast, GPIIb/IIIa receptor numbers were not associated with peripheral immune-cell sub-population counts. C-reactive protein was an independent predictor of GPIIb/IIIa (not GPIb) receptor numbers.

Conclusions

Platelet GPIb and GPIIb/IIIa receptor numbers did not distinguish between patient or control groups in this study, negating their potential use as a biomarker for predicting stroke risk.

Platelet-neutrophil interactions under thromboinflammatory conditions

Platelets primarily mediate hemostasis and thrombosis, whereas leukocytes are responsible for immune responses. Since platelets interact with leukocytes at the site of vascular injury, thrombosis and vascular inflammation are closely intertwined and occur consecutively. Recent studies using real-time imaging technology demonstrated that platelet-neutrophil interactions on the activated endothelium are an important determinant of microvascular occlusion during thromboinflammatory disease in which inflammation is coupled to thrombosis. Although the major receptors and counter receptors have been identified, it remains poorly understood how heterotypic platelet-neutrophil interactions are regulated under disease conditions. This review discusses our current understanding of the regulatory mechanisms of platelet-neutrophil interactions in thromboinflammatory disease.

Microvascular thrombosis, fibrinolysis, ischemic injury, and death after cerebral thromboembolism are affected by levels of circulating α2-antiplasmin

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.

APPROACH AND 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.

Purinergic control of inflammation and thrombosis: Role of P2X1 receptors

Inflammation shifts the hemostatic mechanisms in favor of thrombosis. Upon tissue damage or infection, a sudden increase of extracellular ATP occurs, that might contribute to the crosstalk between inflammation and thrombosis. On platelets, P2X1 receptors act to amplify platelet activation and aggregation induced by other platelet agonists. These receptors critically contribute to thrombus stability in small arteries. Besides platelets, studies by our group indicate that these receptors are expressed by neutrophils. They promote neutrophil chemotaxis, both in vitro and in vivo. In a laser-induced injury mouse model of thrombosis, it appears that neutrophils are required to initiate thrombus formation and coagulation activation on inflamed arteriolar endothelia. In this model, by using P2X1−/ − mice, we recently showed that P2X1 receptors, expressed on platelets and neutrophils, play a key role in thrombus growth and fibrin generation. Intriguingly, in a model of endotoxemia, P2X1−/ − mice exhibited aggravated oxidative tissue damage, along with exacerbated thrombocytopenia and increased activation of coagulation, which translated into higher susceptibility to septic shock. Thus, besides its ability to recruit neutrophils and platelets on inflamed endothelia, the P2X1 receptor also contributes to limit the activation of circulating neutrophils under systemic inflammatory conditions. Taken together, these data suggest that P2X1 receptors are involved in the interplay between platelets, neutrophils and thrombosis. We propose that activation of these receptors by ATP on neutrophils and platelets represents a new mechanism that regulates thrombo-inflammation.

Another "string to the bow" of PJ34, a potent poly(ADP-Ribose)polymerase inhibitor: an antiplatelet effect through P2Y12 antagonism?

Background

Neuro- and vasoprotective effects of poly(ADP-ribose)polymerase (PARP) inhibition have been largely documented in models of cerebral ischemia, particularly with the potent PARP inhibitor PJ34. Furthermore, after ischemic stroke, physicians are faced with incomplete tissue reperfusion and reocclusion, in which platelet activation/aggregation plays a key role. Data suggest that certain PARP inhibitors could act as antiplatelet agents. In that context, the present in vitro study investigated on human blood the potential antiplatelet effect of PJ34 and two structurally different PARP inhibitors, DPQ and INO-1001.

Methods and results

ADP concentrations were chosen to induce a biphasic aggregation curve resulting from the successive activation of both its receptors P2Y₁ and P2Y₁₂. In these experimental conditions, PJ34 inhibited the second phase of aggregation; this effect was reduced by incremental ADP concentrations. In addition, in line with a P2Y₁₂ pathway inhibitory effect, PJ34 inhibited the dephosphorylation of the vasodilator stimulated phosphoprotein (VASP) in a concentration-dependent manner. Besides, PJ34 had no effect on platelet aggregation induced by collagen or PAR1 activating peptide, used at concentrations inducing a strong activation independent on secreted ADP. By contrast, DPQ and INO-1001 were devoid of any effect whatever the platelet agonist used.

Conclusions

We showed that, in addition to its already demonstrated beneficial effects in in vivo models of cerebral ischemia, the potent PARP inhibitor PJ34 exerts in vitro an antiplatelet effect. Moreover, this is the first study to report that PJ34 could act via a competitive P2Y₁₂ antagonism. Thus, this antiplatelet effect could improve post-stroke reperfusion and/or prevent reocclusion, which reinforces the interest of this drug for stroke treatment.

Protein-protein interaction network and mechanism analysis in ischemic stroke

Ischemic stroke is a leading cause of mortality and permanent disability, with enormous financial repercussions on health systems worldwide. Ischemic brain injury results from a complex sequence of pathophysiological events that evolve over time. In order to examine the molecular mechanisms underlying middle cerebral artery occlusion (MCAO)-induced ischemic stroke, the GSE35338 affymetrix microarray data was obtained from the Gene Expression Omnibus database and the differentially expressed genes (DEGs) between samples from patients with MCAO-induced ischemic stroke and sham controls at various time points were identified. Furthermore, protein-protein interaction (PPI) networks were constructed by mapping the DEGs into PPI data to identify the pathways that these DEGS are involved in. The results revealed that the expression of 438 DEGs, which are mainly involved in cell death, oxidant reduction, cell cycle and cell-cell signaling, were altered in MCAO samples. The nodes of CXC motif chemokine 10 (CXCL10) and interleukin-6 (IL-6) were large, with degrees of >20. In conclusion, the results suggest that CXCL10 and IL-6 have important roles in the occurrence and progression of MCAO-induced ischemic stroke.

SLAP/SLAP2 prevent excessive platelet (hem)ITAM signaling in thrombosis and ischemic stroke in mice

Glycoprotein VI and C-type lectin-like receptor 2 are essential platelet activating receptors in hemostasis and thrombo-inflammatory disease, which signal through a (hem)immunoreceptor tyrosine-based activation motif (ITAM)-dependent pathway. The adapter molecules Src-like adapter proteins (SLAP and SLAP2) are involved in the regulation of immune cell surface expression and signaling, but their function in platelets is unknown. In this study, we show that platelets expressed both SLAP isoforms and that overexpression of either protein in a heterologous cell line almost completely inhibited glycoprotein VI and C-type lectin-like receptor 2 signaling. In mice, single deficiency of SLAP or SLAP2 had only moderate effects on platelet function, whereas double deficiency of both adapters resulted in markedly increased signal transduction, integrin activation, granule release, aggregation, procoagulant activity, and thrombin generation in response to (hem)ITAM-coupled, but not G protein-coupled, receptor activation. In vivo, constitutive SLAP/SLAP2 knockout mice displayed accelerated occlusive arterial thrombus formation and a dramatically worsened outcome after focal cerebral ischemia. This was attributed to the absence of both adapter proteins in platelets, as demonstrated by adoptive transfer of Slap(-/-)/Slap2(-/-) platelets into wild-type mice. Our results establish SLAP and SLAP2 as critical inhibitors of platelet (hem)ITAM signaling in the setting of arterial thrombosis and ischemic stroke.

Syntaxin-binding protein STXBP5 inhibits endothelial exocytosis and promotes platelet secretion

In humans, vWF levels predict the risk of myocardial infarction and thrombosis; however, the factors that influence vWF levels are not completely understood. Recent genome-wide association studies (GWAS) have identified syntaxin-binding protein 5 (STXBP5) as a candidate gene linked to changes in vWF plasma levels, though the functional relationship between STXBP5 and vWF is unknown. We hypothesized that STXBP5 inhibits endothelial cell exocytosis. We found that STXBP5 is expressed in human endothelial cells and colocalizes with and interacts with syntaxin 4. In human endothelial cells reduction of STXBP5 increased exocytosis of vWF and P-selectin. Mice lacking Stxbp5 had higher levels of vWF in the plasma, increased P-selectin translocation, and more platelet-endothelial interactions, which suggests that STXBP5 inhibits endothelial exocytosis. However, Stxbp5 KO mice also displayed hemostasis defects, including prolonged tail bleeding times and impaired mesenteric arteriole and carotid artery thrombosis. Furthermore, platelets from Stxbp5 KO mice had defects in platelet secretion and activation; thus, STXBP5 inhibits endothelial exocytosis but promotes platelet secretion. Our study reveals a vascular function for STXBP5, validates the functional relevance of a candidate gene identified by GWAS, and suggests that variation within STXBP5 is a genetic risk for venous thromboembolic disease.

Discovery of novel GPVI receptor antagonists by structure-based repurposing

Inappropriate platelet aggregation creates a cardiovascular risk that is largely managed with thienopyridines and aspirin. Although effective, these drugs carry risks of increased bleeding and drug ‘resistance’, underpinning a drive for new antiplatelet agents. To discover such drugs, one strategy is to identify a suitable druggable target and then find small molecules that modulate it. A good and unexploited target is the platelet collagen receptor, GPVI, which promotes thrombus formation. To identify inhibitors of GPVI that are safe and bioavailable, we docked a FDA-approved drug library into the GPVI collagen-binding site in silico. We now report that losartan and cinanserin inhibit GPVI-mediated platelet activation in a selective, competitive and dose-dependent manner. This mechanism of action likely underpins the cardioprotective effects of losartan that could not be ascribed to its antihypertensive effects. We have, therefore, identified small molecule inhibitors of GPVI-mediated platelet activation, and also demonstrated the utility of structure-based repurposing.

Von Willebrand factor regulation in patients with acute and chronic cerebrovascular disease: a pilot, case-control study

BACKGROUND AND PURPOSE

In animal models, von Willebrand factor (VWF) is involved in thrombus formation and propagation of ischemic stroke. However, the pathophysiological relevance of this molecule in humans, and its potential use as a biomarker for the risk and severity of ischemic stroke remains unclear. This study had two aims: to identify predictors of altered VWF levels and to examine whether VWF levels differ between acute cerebrovascular events and chronic cerebrovascular disease (CCD).

METHODS

A case-control study was undertaken between 2010 and 2013 at our University clinic. In total, 116 patients with acute ischemic stroke (AIS) or transitory ischemic attack (TIA), 117 patients with CCD, and 104 healthy volunteers (HV) were included. Blood was taken at days 0, 1, and 3 in patients with AIS or TIA, and once in CCD patients and HV. VWF serum levels were measured and correlated with demographic and clinical parameters by multivariate linear regression and ANOVA.

RESULTS

Patients with CCD (158 ± 46%) had significantly higher VWF levels than HV (113 ± 36%, P<0.001), but lower levels than AIS/TIA patients (200 ± 95%, P<0.001). Age, sex, and stroke severity influenced VWF levels (P<0.05).

CONCLUSIONS

VWF levels differed across disease subtypes and patient characteristics. Our study confirms increased VWF levels as a risk factor for cerebrovascular disease and, moreover, suggests that it may represent a potential biomarker for stroke severity, warranting further investigation.

Effects of Cydonia oblonga Miller extracts on blood hemostasis, coagulation and fibrinolysis in mice, and experimental thrombosis in rats

INTRODUCTION

Cydonia oblonga Miller (COM) is traditionally used in Uyghur medicine for the prevention of cardiovascular disease. The present study is designed to explore the effects of COM extracts on models and markers of thrombosis and related biomarkers.

MATERIALS AND METHODS

20, 40, 80 mg/kg/day COM aqueous extracts and 5mg/kg/day aspirin, orally for 14 days were compared to untreated controls in mice on bleeding and clotting times, using the tail cutting and glass slide methods and for death rates in collagen-epinephrine pulmonary thrombosis, thrombolysis in vitro and euglobulin lysis time (ELT). In rats, common carotid artery FeCl3-induced thrombus and inferior vena cava thrombosis occlusion time, plasma concentrations of thromboxane B2 (TXB2) and 6-keto-prostaglandine F1α (6-keto-PGF1α) were measured.

RESULTS AND CONCLUSION

Compared to controls, COM extracts dose-dependently prolonged bleeding by 2.17, 2.78 and 3.63 times, vs. aspirin 2.58, and the clotting time by 1.44, 2.47 and 2.48 times, vs. aspirin 1.91. COM reduced pulmonary embolus mortality by 27, 40 and 53%, vs. 47% for aspirin. COM dose-dependently increased thrombolysis by 45, 55 and 63%, vs. 56% for aspirin, and shortened ELT to 71, 61 and 43%, vs. 43% for aspirin. In rats, venous occlusion time was prolonged. Arterial and venous thrombus weights were dose-dependently reduced in COM groups. TXB2 decreased and 6-keto-PGF1α increased with COM and aspirin, with an association between 6-keto-PGF1α/TXB2 and arterial or venous thrombus weight for all products, and for occlusion time with COM but not for aspirin.

CONCLUSION

We confirm the experimental effects of COM on hemostasis and thrombosis. Further exploration of putative clinical effects appear justified.

Mannose-binding lectin promotes local microvascular thrombosis after transient brain ischemia in mice

BACKGROUND AND PURPOSE

Several lines of evidence support the involvement of mannose-binding lectin (MBL) in stroke brain damage. The lectin pathway of the complement system facilitates thrombin activation and clot formation under certain experimental conditions. In the present study, we examine whether MBL promotes thrombosis after ischemia/reperfusion and influences the course and prognosis of ischemic stroke.

METHODS

Middle cerebral artery occlusion/reperfusion was performed in MBL-deficient (n=85) and wild-type (WT; n=83) mice, and the brain lesion was assessed by MRI at days 1 and 7. Relative cerebral blood flow was monitored up to 6 hours after middle cerebral artery occlusion with laser speckle contrast imaging. Fibrin(ogen) was analyzed in the brain vasculature and plasma, and the effects of thrombin inhibitor argatroban were evaluated to assess the role of MBL in thrombin activation.

RESULTS

Infarct volumes and neurological deficits were smaller in MBL knockout mice than in WT mice. Relative cerebral blood flow values during middle cerebral artery occlusion and at reperfusion were similar in both groups, but decreased during the next 6 hours in the WT group only. Also, the WT mice showed more fibrin(ogen) in brain vessels and a better outcome after argatroban treatment. In contrast, argatroban did not improve the outcome in MBL knockout mice.

CONCLUSIONS

MBL promotes brain damage and functional impairment after brain ischemia/reperfusion in mice. These effects are secondary to intravascular thrombosis and impaired relative cerebral blood flow during reperfusion. Argatroban protects WT mice, but not MBL knockout mice, emphasizing a role of MBL in local thrombus formation in acute ischemia/reperfusion.

PET Demonstrates Functional Recovery after Treatment by Danhong Injection in a Rat Model of Cerebral Ischemic-Reperfusion Injury

This study aimed to investigate neuroprotection of Danhong injection (DHI) in a rat model of cerebral ischemia using ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET). Method. Rats were divided into 5 groups: sham group, ischemia-reperfusion untreated (IRU) group, DHI-1 group (DHI 1 mL/kg/d), DHI-2 group (DHI 2 mL/kg/d), and DHI-4 group (DHI 4 mL/kg/d). AII the treated groups were intraperitoneally injected with DHI daily for 14 days. The therapeutic effects in terms of cerebral infarct volume, neurological function, and cerebral glucose metabolism were evaluated. Expression of TNF-α and IL-1β was detected with enzyme-linked immunosorbent assay (ELISA). Levels of mature neuronal marker (NeuN), glial marker (GFAP), vascular density factor (vWF), and glucose transporter 1 (GLUT1) were assessed by immunohistochemistry. Results. Compared with the IRU group, rats treated with DHI showed dose dependent reductions in cerebral infarct volume and levels of proinflammatory cytokines, improvement of neurological function, and recovery of cerebral glucose metabolism. Meanwhile, the significantly increased numbers of neurons, gliocytes, and vessels and the recovery of glucose utilization were found in the peri-infarct region after DHI treatment using immunohistochemical analysis. Conclusion. This study demonstrated the metabolic recovery after DHI treatment by micro-PET imaging with ¹⁸F-FDG and the neuroprotective effects of DHI in a rat model of cerebral ischemic-reperfusion injury.

Involvement of neutrophils in thrombus formation in living mice

Thrombosis is one of the major causes of human death worldwide. Identification of the cellular and molecular mechanisms leading to thrombus formation is thus crucial for the understanding of the thrombotic process. To examine thrombus formation in a living mouse, new technologies have been developed. Digital intravital microscopy allows to visualize the development of thrombosis and generation of fibrin in real-time within living animal in a physiological context. This specific system allowed the identification of new cellular partners involved in platelet adhesion and activation. Furthermore, it improved, especially, the knowledge of the early phase of thrombus formation and fibrin generation in vivo. Until now, platelets used to be considered the sole central player in thrombus generation. However, recently, it has been demonstrated that leukocytes, particularly neutrophils, play a crucial role in the activation of the blood coagulation cascade leading to thrombosis. In this review, we summarized the mechanisms leading to thrombus formation in the microcirculation according to the method of injury in mice with a special focus on the new identified roles of neutrophils in this process.

Contribution of blood platelets to vascular pathology in Alzheimer's disease

Cerebral amyloid angiopathy (CAA) is a critical factor in the pathogenesis of Alzheimer’s disease (AD). In the clinical setting, nearly 98% AD patients have CAA, and 75% of these patients are rated as severe CAA. It is characterized by the deposition of the β-amyloid peptide (mainly Aβ40) in the walls of cerebral vessels, which induces the degeneration of vessel wall components, reduces cerebral blood flow, and aggravates cognitive decline. Platelets are anuclear cell fragments from bone marrow megakaryocytes and their function in hemostasis and thrombosis has long been recognized. Recently, increasing evidence suggests that platelet activation can also mediate the onset and development of CAA. First, platelet activation and adhesion to a vessel wall is the initial step of vascular injury. Activated platelets contribute to more than 90% circulating Aβ (mainly Aβ1-40), which in turn activates platelets and results in the vicious cycle of Aβ overproduction in damaged vessel. Second, the uncontrolled activation of platelets leads to a chronic inflammatory reaction by secretion of chemokines (eg, platelet factor 4 [PF4], regulated upon activation normal T-cell expressed and presumably secreted [RANTES], and macrophage inflammatory protein [MIP-1α]), interleukins (IL-1β, IL-7, and IL-8), prostaglandins, and CD40 ligand (CD40L). The interaction of these biological response modulators with platelets, endothelial cells, and leukocytes establishes a localized inflammatory response that contributes to CAA formation. Finally, activated platelets are the upholder of fibrin clots, which are structurally abnormal and resistant to degradation in the presence of Aβ42. Thus, opinion has emerged that targeting blood platelets may provide a new avenue for anti-AD therapy.