von Willebrand factor-cleaving protease ADAMTS13 reduces ischemic brain injury in experimental stroke. Blood. 2009;114:3329-3334. [PMID: 19687510 DOI: 10.1182/blood-2009-03-213264]

The Role of Thrombo-inflammation in Ischemic Stroke: Focus on the Manipulation and Clinical Application

Stroke leaves a great economic burden due to its high morbidity and mortality. Rapid revascularization of targeted vessel(s) is the effective treatment for ischemic stroke, but subsequent ischemia-reperfusion (I/R) injury is a common complication following revascularization, leading to microcirculation dysfunction and infarct volume increase. Thrombo-inflammation, the interaction between thrombosis and inflammation, plays a critical role in the pathophysiology of ischemic stroke. In the context of I/R injury, thrombo-inflammation consists of platelet activation, endothelial injury, and inflammatory cell infiltration. Numerous studies are devoted to exploring methods of regulating thrombo-inflammation to mitigate I/R injury post-stroke, including blocking activations of platelets and neutrophils. Drugs such as antiplatelet medications, anticoagulants, and glucocorticoids have been confirmed to have the potential to regulate thrombo-inflammation. Furthermore, several recently developed drugs have also shown promises in relieving I/R injury by manipulating thrombo-inflammation. However, the majority of these studies are still in the preclinical stage. Herein, in this review, we will address the mechanisms of thrombo-inflammation in ischemic stroke, related research advances, and particularly the clinical feasibility of thrombo-inflammation as a therapeutic strategy against I/R injury.

Identification of Disulfidptosis-Related Genes in Ischemic Stroke by Combining Single-Cell Sequencing, Machine Learning Algorithms, and In Vitro Experiments

BACKGROUND

Ischemic stroke (IS) is a severe neurological disorder with a pathogenesis that remains incompletely understood. Recently, a novel form of cell death known as disulfidptosis has garnered significant attention in the field of ischemic stroke research. This study aims to investigate the mechanistic roles of disulfidptosis-related genes (DRGs) in the context of IS and to examine their correlation with immunopathological features.

METHODS

To enhance our understanding of the mechanistic underpinnings of disulfidptosis in IS, we initially retrieved the expression profile of peripheral blood from human IS patients from the GEO database. We then utilized a suite of machine learning algorithms, including LASSO, random forest, and SVM-RFE, to identify and validate pivotal genes. Furthermore, we developed a predictive nomogram model, integrating multifactorial logistic regression analysis and calibration curves, to evaluate the risk of IS. For the analysis of single-cell sequencing data, we employed a range of analytical tools, such as "Monocle" and "CellChat," to assess the status of immune cell infiltration and to characterize intercellular communication networks. Additionally, we utilized an oxygen-glucose deprivation (OGD) model to investigate the effects of SLC7A11 overexpression on microglial polarization.

RESULTS

This study successfully identified key genes associated with disulfidptosis and developed a reliable nomogram model using machine learning algorithms to predict the risk of ischemic stroke. Examination of single-cell sequencing data showed a robust correlation between disulfidptosis levels and the infiltration of immune cells. Furthermore, "CellChat" analysis elucidated the intricate characteristics of intercellular communication networks. Notably, the TNF signaling pathway was found to be intimately linked with the disulfidptosis signature in ischemic stroke. In an intriguing finding, the OGD model demonstrated that SLC7A11 expression suppresses M1 polarization while promoting M2 polarization in microglia.

CONCLUSION

The significance of our findings lies in their potential to shed light on the pathogenesis of ischemic stroke, particularly by underscoring the pivotal role of disulfidptosis-related genes (DRGs). These insights could pave the way for novel therapeutic strategies targeting DRGs to mitigate the impact of ischemic stroke.

Improving our understanding on the clinical role of plasmin-mediated von Willebrand factor degradation

PURPOSE OF REVIEW

Von Willebrand factor (VWF) plays a pivotal role in primary hemostasis. A Disintegrin And Metalloproteinase with a ThromboSpondin type 1 motif, member 13 (ADAMTS13) is primarily responsible for cleaving ultra-large VWF multimers into smaller, less adhesive forms. However, plasmin has also been shown to cleave VWF multimers. This proteolytic cleavage of VWF results in a decreased multimer size and, hence, a lower VWF activity. This review aims to present a comprehensive overview of the involvement of plasmin-mediated VWF proteolysis in (micro)thrombosis.

RECENT FINDINGS

Plasmin-mediated VWF proteolysis has been suggested to play a role in various pathologies involving microthrombosis in combination with an imbalance in VWF antigen levels and ADAMTS13 activity, as well as activation of the fibrinolytic system, but quantitative assays to demonstrate this were lacking. Recently, a V H H-based bioassay was developed designed specifically to quantify plasmin-cleaved VWF (cVWF). The novel ELISA assay holds significant promise for gaining further insights into the clinical relevance of plasmin-mediated VWF proteolysis in several pathologies. Furthermore, local plasmin activation at the site of microthrombosis has been shown to be a promising treatment strategy by degrading VWF-rich microthrombi.

SUMMARY

Plasmin-mediated proteolysis of VWF is observed during microthrombosis; however, it remains unclear whether it impacts disease severity. A novel ELISA method to detect cVWF will improve our understanding of the clinical role of plasmin-mediated VWF degradation.

The effect of ADAMTS13 on graft-versus-host disease

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) can potentially cure malignant blood disorders and benign conditions such as haemoglobinopathies and immunologic diseases. However, allo-HSCT is associated with significant complications. The most common and debilitating among them is graft-versus-host disease (GVHD). In GVHD, donor-derived T cells mount an alloimmune response against the recipient. The alloimmune response involves several steps, including recognition of recipient antigens, activation and proliferation of T cells in secondary lymphoid organs, and homing into GVHD-targeted organs. Adhesion molecules on T cells and endothelial cells mediate homing of T cells into lymphoid and non-lymphoid tissues. In this study, we showed that Von Willebrand factor (VWF), an adhesion molecule secreted by activated endothelial cells, plays an important role in mouse models of GVHD. We investigated the effect of the VWF-cleaving protease ADAMTS13 on GVHD. We found that ADAMTS13 reduced the severity of GVHD after bone marrow transplantation from C57BL6 donor to BALB/C recipient mice. A recombinant VWF-A2 domain peptide also reduced GVHD in mice. We showed that ADAMTS13 and recombinant VWF-A2 reduced the binding of T cells to endothelial cells and VWF in vitro, and reduced the number of T cells in lymph nodes, Peyer's patches and GVHD-targeted organs in vivo. We identified LFA-1 (αLβ2) as the binding site of VWF on T cells. Our results showed that blocking T-cell homing by ADAMTS13 or VWF-A2 peptide reduced the severity of the GVHD after allo-HSCT, a potentially novel method for treating and preventing GVHD.

REVIEWING THE DYSREGULATION OF ADAMTS13 AND VWF IN SEPSIS

ABSTRACT

Sepsis is defined as a life-threatening organ dysfunction caused by excessive host response to infection, and represents the most common cause of in-hospital deaths. Sepsis accounts for 30% of all critically ill patients in the intensive care unit (ICU), and has a global mortality rate of 20%. Activation of blood coagulation during sepsis and septic shock can lead to disseminated intravascular coagulation, which is characterized by microvascular thrombosis. Von Willebrand factor (VWF) and ADAMTS13 are two important regulators of blood coagulation that may be important links between sepsis and mortality in the ICU. Herein we review our current understanding of VWF and ADAMTS13 in sepsis and other critical illnesses and discuss their contribution to disease pathophysiology, their use as markers of severe illness, and potential targets for new therapeutic development.

Immunothrombosis versus thrombo-inflammation: platelets in cerebrovascular complications

A State-of-the Art lecture titled "Thrombo-Neuroinflammatory Disease" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023. First, we would like to advocate for discrimination between immunothrombosis and thrombo-inflammation, as immunothrombosis describes an overshooting inflammatory reaction that results in detrimental thrombotic activity. In contrast, thrombo-inflammation describes the interplay of platelets and coagulation with the immunovascular system, resulting in the recruitment of immune cells and loss of barrier function (hence, hallmarks of inflammation). Both processes can be observed in the brain, with cerebral venous thrombosis being a prime example of immunothrombosis, while infarct progression in response to ischemic stroke is a paradigmatic example of thrombo-inflammation. Here, we review the pathomechanisms underlying cerebral venous thrombosis and ischemic stroke from a platelet-centric perspective and discuss translational implications. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress.

Von Willebrand factor promotes radiation-induced intestinal injury (RIII) development and its cleavage enzyme rhADAMTS13 protects against RIII by reducing inflammation and oxidative stress

Patients with abdominopelvic cancer undergoing radiotherapy commonly develop radiation-induced intestinal injury (RIII); however, its underlying pathogenesis remains elusive. The von Willebrand factor (vWF)/a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) axis has been implicated in thrombosis, inflammation, and oxidative stress. However, its role in RIII remains unclear. In this study, the effect of radiation on vWF and ADAMTS13 expression was firstly evaluated in patients with cervical cancer undergoing radiotherapy and C57BL/6J mice exposed to different doses of total abdominal irradiation. Then, mice with the specific deletion of vWF in the platelets and endothelium were established to demonstrate the contribution of vWF to RIII. Additionally, the radioprotective effect of recombinant human (rh) ADAMTS13 against RIII was assessed. Results showed that both the patients with cervical cancer undergoing radiotherapy and RIII mouse model exhibited increased vWF levels and decreased ADAMTS13 levels. The knockout of platelet- and endothelium-derived vWF rectified the vWF/ADAMTS13 axis imbalance; improved intestinal structural damage; increased crypt epithelial cell proliferation; and reduced radiation-induced apoptosis, inflammation, and oxidative stress, thereby alleviating RIII. Administration of rhADAMTS13 could equally alleviate RIII. Our results demonstrated that abdominal irradiation affected the balance of the vWF/ADAMTS13 axis. vWF exerted a deleterious role and ADAMTS13 exhibited a protective role in RIII progression. rhADAMTS13 has the potential to be developed into a radioprotective agent.

To Gain Insights into the Pathophysiological Mechanisms of the Thrombo-Inflammatory Process in the Atherosclerotic Plaque

Thromboinflammation, the interplay between thrombosis and inflammation, is a significant pathway that drives cardiovascular and autoimmune diseases, as well as COVID-19. SARS-CoV-2 causes inflammation and blood clotting issues. Innate immune cells have emerged as key modulators of this process. Neutrophils, the most predominant white blood cells in humans, are strategically positioned to promote thromboinflammation. By releasing decondensed chromatin structures called neutrophil extracellular traps (NETs), neutrophils can initiate an organised cell death pathway. These structures are adorned with histones, cytoplasmic and granular proteins, and have cytotoxic, immunogenic, and prothrombotic effects that can hasten disease progression. Protein arginine deiminase 4 (PAD4) catalyses the citrullination of histones and is involved in the release of extracellular DNA (NETosis). The neutrophil inflammasome is also required for this process. Understanding the link between the immunological function of neutrophils and the procoagulant and proinflammatory activities of monocytes and platelets is important in understanding thromboinflammation. This text discusses how vascular blockages occur in thromboinflammation due to the interaction between neutrophil extracellular traps and ultra-large VWF (von Willebrand Factor). The activity of PAD4 is important for understanding the processes that drive thromboinflammation by linking the immunological function of neutrophils with the procoagulant and proinflammatory activities of monocytes and platelets. This article reviews how vaso-occlusive events in thrombo-inflammation occur through the interaction of neutrophil extracellular traps with von Willebrand factor. It highlights the relevance of PAD4 in neutrophil inflammasome assembly and neutrophil extracellular traps in thrombo-inflammatory diseases such as atherosclerosis and cardiovascular disease. Interaction between platelets, VWF, NETs and inflammasomes is critical for the progression of thromboinflammation in several diseases and was recently shown to be active in COVID-19.

Hemostasis without clot formation: how platelets guard the vasculature in inflammation, infection, and malignancy

Platelets are key vascular effectors in hemostasis, with activation signals leading to fast recruitment, aggregation, and clot formation. The canonical process of hemostasis is well-characterized and shares many similarities with pathological thrombus formation. However, platelets are also crucially involved in the maintenance of vascular integrity under both steady-state and inflammatory conditions by ensuring blood vessel homeostasis and preventing microbleeds. In these settings, platelets use distinct receptors, signaling pathways, and ensuing effector functions to carry out their deeds. Instead of simply forming clots, they mainly act as individual sentinels that swiftly adapt their behavior to the local microenvironment. In this review, we summarize previously recognized and more recent studies that have elucidated how anucleate, small platelets manage to maintain vascular integrity when faced with challenges of infection, sterile inflammation, and even malignancy. We dissect how platelets are recruited to the vascular wall, how they identify sites of injury, and how they prevent hemorrhage as single cells. Furthermore, we discuss mechanisms and consequences of platelets' interaction with leukocytes and endothelial cells, the relevance of adhesion as well as signaling receptors, in particular immunoreceptor tyrosine-based activation motif receptors, and cross talk with the coagulation system. Finally, we outline how recent insights into inflammatory hemostasis and vascular integrity may aid in the development of novel therapeutic strategies to prevent hemorrhagic events and vascular dysfunction in patients who are critically ill.

Short-term beneficial effects of human dental pulp stem cells and their secretome in a rat model of mild ischemic stroke

Although cell therapy has been applied in regenerative medicine for decades, recent years have seen greatly increased attention being given to the use of stem cell-based derivatives such as cell-free secretome. Dental pulp stem cells (DPSCs) are widely available, easily accessible, and have high neuroprotective and angiogenic properties. In addition, DPSC-derived secretome contains a rich mixture of trophic factors. The current investigation evaluated the short-term therapeutic effects of human DPSCs and their secretome in a rat model of mild ischemic stroke. Mild ischemic stroke was induced by 30 min middle cerebral artery occlusion, and hDPSCs or their secretome was administered intra-arterially and intranasally. Neurological function, infarct size, spatial working memory, and relative expression of seven target genes in two categories of neurotrophic and angiogenic factors were assessed three days after stroke. In the short-term, all treatments reduced the severity of neurological and histological deficits caused by ischemic stroke. Moreover, transient middle cerebral artery occlusion led to the striatal and cortical over-expression of BDNF, NT-3, and angiogenin, while NGF and VEGF expression was reduced. Almost all interventions were able to modulate the expression of target genes after stroke. The obtained data revealed that single intra-arterial administration of hDPSCs or their secretome, single intranasal transplantation of hDPSCs, or repeated intranasal administration of hDPSC-derived secretome was able to ameliorate the devastating effects of a mild stroke, at least in the short-term.

Impact of the von Willebrand factor-ADAMTS-13 axis on the risk of future venous thromboembolism

BACKGROUND

von Willebrand factor (VWF) and its cleaving protease, ADAMTS-13, form a pivotal axis that regulates hemostasis. However, the role of the VWF-ADAMTS-13 axis in the risk of future venous thromboembolism (VTE) is unknown.

OBJECTIVES

To investigate whether plasma ADAMTS-13 levels and an imbalance with VWF levels, assessed as the VWF/ADAMTS-13 ratio, are associated with the risk of future VTE.

PATIENTS/METHODS

A population-based nested case-control study, comprising 383 incident VTE cases and 780 age- and sex-matched controls, was derived from the Tromsø study cohort (1994-2007). Antigen levels of ADAMTS-13 and VWF were measured in plasma samples obtained at cohort baseline. Odds ratios (ORs) with 95% CIs were estimated according to quartile cutoffs of ADAMTS-13 and VWF/ADAMTS-13 ratio determined in controls.

RESULTS

In age- and sex-adjusted analysis, ADAMTS-13 levels were inversely associated with the VTE risk, with an OR of 1.40 (95% CI, 0.99-1.99) for the lowest vs highest quartiles. The VWF/ADAMTS-13 ratio was linearly associated with the VTE risk (P for trend = .001), with an OR of 1.70 (95% CI, 1.19-2.43) for the highest vs lowest quartiles, and the association was particularly pronounced for unprovoked VTE (OR, 2.81; 95% CI, 1.65-4.81). The ORs were only slightly attenuated after additional adjustments for body mass index and C-reactive protein.

CONCLUSIONS

Lowered ADAMTS-13 levels and an imbalance between ADAMTS-13 and VWF levels, reflected by an increased VWF/ADAMTS-13 ratio, were associated with an increased risk of future VTE. Our findings suggest that the VWF-ADAMTS-13 axis is involved in the pathogenesis of VTE.

NETs-Induced Thrombosis Impacts on Cardiovascular and Chronic Kidney Disease

Arterial and venous thrombosis constitute a major source of morbidity and mortality worldwide. Association between thrombotic complications and cardiovascular and other chronic inflammatory diseases are well described. Inflammation and subsequent initiation of thrombotic events, termed immunothrombosis, also receive growing attention but are still incompletely understood. Nevertheless, the clinical relevance of aberrant immunothrombosis, referred to as thromboinflammation, is evident by an increased risk of thrombosis and cardiovascular events in patients with inflammatory or infectious diseases. Proinflammatory mediators released from platelets, complement activation, and the formation of NETs (neutrophil extracellular traps) initiate and foster immunothrombosis. In this review, we highlight and discuss prominent and emerging interrelationships and functions between NETs and other mediators in immunothrombosis in cardiovascular disease. Also, with patients with chronic kidney disease suffering from increased cardiovascular and thrombotic risk, we summarize current knowledge on neutrophil phenotype, function, and NET formation in chronic kidney disease. In addition, we elaborate on therapeutic targeting of NETs-induced immunothrombosis. A better understanding of the functional relevance of antithrombotic mediators which do not increase bleeding risk may provide opportunities for successful therapeutic interventions to reduce thrombotic risk beyond current treatment options.

From the Discovery of ADAMTS13 to Current Understanding of Its Role in Health and Disease

ADAMTS13 (a disintegrin-like metalloprotease domain with thrombospondin type 1 motif, member 13) is a protease of crucial importance in the regulation of the size of von Willebrand factor multimers. Very low ADAMTS13 activity levels result in thrombotic thrombocytopenic purpura, a rare and life-threatening disease. The mechanisms involved can either be acquired (immune-mediated thrombotic thrombocytopenic purpura [iTTP]) or congenital (cTTP, Upshaw-Schulman syndrome) caused by the autosomal recessive inheritance of disease-causing variants (DCVs) located along the ADAMTS13 gene, which is located in chromosome 9q34. Apart from its role in TTP, and as a regulator of microthrombosis, ADAMTS13 has begun to be identified as a prognostic and/or diagnostic marker of other diseases, such as those related to inflammatory processes, liver damage, metastasis of malignancies, sepsis, and different disorders related to angiogenesis. Since its first description almost 100 years ago, the improvement of laboratory tests and the description of novel DCVs along the ADAMTS13 gene have contributed to a better and faster diagnosis of patients under critical conditions. The ability of ADAMTS13 to dissolve platelet aggregates in vitro and its antithrombotic properties makes recombinant human ADAMTS13 treatment a potential therapeutic approach targeting not only patients with cTTP but also other medical conditions.

Emerging Targets for Modulation of Immune Response and Inflammation in Stroke

The inflammatory and immunological responses play a significant role after stroke. The innate immune activation stimulated by microglia during stroke results in the migration of macrophages and lymphocytes into the brain and are responsible for tissue damage. The immune response and inflammation following stroke have no defined targets, and the intricacies of the immunological and inflammatory processes are only partially understood. Innate immune cells enter the brain and meninges during the acute phase, which can cause ischemia damage. Activation of systemic immunity is caused by danger signals sent into the bloodstream by injured brain cells, which is followed by a significant immunodepression that encourages life-threatening infections. Neuropsychiatric sequelae, a major source of post-stroke morbidity, may be induced by an adaptive immune response that is initiated by antigen presentation during the chronic period and is directed against the brain. Thus, the current review discusses the role of immune response and inflammation in stroke pathogenesis, their role in the progression of injury during the stroke, and the emerging targets for the modulation of the mechanism of immune response and inflammation that may have possible therapeutic benefits against stroke.

Spatiotemporal profile of neutrophil extracellular trap formation in a mouse model of ischemic stroke

Background

Thromboinflammatory processes modulate the complex pathophysiology of cerebral ischemia-reperfusion (I/R) injury in ischemic stroke, but the exact underlying mechanisms remain poorly understood. Emerging evidence indicates that neutrophil extracellular traps (NETs) might play an important role in the thromboinflammatory cascade. In addition, the link between von Willebrand factor (VWF) and neutrophil recruitment in the ischemic brain might promote thromboinflammation, possibly by the formation of NETs.

Objectives

To study NET formation in a murine model of cerebral I/R injury in ischemic stroke.

Methods

The filament-induced transient middle cerebral artery occlusion model was used to induce 60 minutes of focal cerebral ischemia after which reperfusion was allowed. At different time points postischemia, NETs were identified in the ischemic mouse brain using quantitative immunofluorescence microscopy.

Results

NETs could be identified in the ipsilateral brain hemisphere. Interestingly, NETs could already be detected at 6 hours poststroke. Their presence increased at 12 hours, was highest at 24 hours, and decreased again 48 hours postischemia. Remarkably, NETs were predominantly localized within the brain vasculature postischemia, suggesting that NETs play a role in secondary microthrombosis. Strikingly, NET formation was significantly decreased in VWF-deficient mice compared to littermate wild-type mice 24 hours postischemia, indicating a possible role for VWF in promoting NETosis in the ischemic brain.

Conclusion

This study identified the spatiotemporal profile of NET formation in a mouse model of cerebral I/R injury in ischemic stroke. NETs, potentially in combination with VWF, might be attractive targets for the development of novel therapeutic strategies in ischemic stroke treatment.

What is the role of Von Willebrand factor in chronic hepatitis B virus infection to hepatocellular carcinoma: a review article

Von Willebrand factor (VWF) is a glycoprotein synthesized and secreted by vascular endothelial cells and megakaryocytes, found on plasma surface, endothelial cells, and α-granule of platelets. VWF can be interacted with collagen and platelet membrane glycoproteins GPIb and GPIb-IIa and play an important role in platelet adhesion and aggregation. Growing research evidence suggests that VWF also mediates the prevention or protesting of hepatocellular carcinoma (HCC) in chronic hepatitis B (CHB) patients from several clinical studies. While the mechanism of VWF in HCC protection or protest is still unclear, further study is required. This article aims to rationalize the role of VWF in the development of HCC, and the functional domain of VWF in cancer as well as cross-talking with platelets and miRNAs. This article also looks forward to the future development and challenges of VWF research.

ADAMTS13 protease or lack of von Willebrand factor protects irradiation and melanoma-induced thrombotic microangiopathy in zebrafish

BACKGROUND

Severe deficiency of plasma ADAMTS13 activity may result in potentially fatal thrombotic thrombocytopenic purpura and relative deficiency of plasma ADAMTS13 activity may be associated with adverse outcomes of certain malignancies. Here, we report the role of ADAMTS13 or lack of von Willebrand factor (VWF) in reducing irradiation and melanoma-induced thrombotic microangiopathy (TMA) and mortality in zebrafish.

METHODS

Zebrafish melanoma cell line (ZMEL) was injected subcutaneously into wild-type (wt), adamts13-/- (a13-/- ), von Willebrand factor (vwf-/- ), and a13-/- vwf-/- zebrafish following total body irradiation; the tumor growth, its gene expression pattern, the resulting thrombocytopenia, and the mortality were determined.

RESULTS

Total body irradiation at 30 Gy alone resulted in a transient thrombocytopenia in both wt and a13-/- zebrafish. However, thrombocytopenia occurred earlier and more profound in a13-/- than in wt zebrafish, which was resolved 2 weeks following irradiation alone. An inoculation of ZMEL following the irradiation resulted in more severe and persistent thrombocytopenia, as well as earlier death in a13-/- than in wt zebrafish. The vwf-/- or a13-/- vwf-/- zebrafish were protected from developing severe thrombocytopenia following the same maneuvers. RNA-sequencing revealed significant differentially expressed genes associated with oxidation-reduction, metabolism, lipid, fatty acid and cholesterol metabolic processes, steroid synthesis, and phospholipid efflux in the melanoma explanted from a13-/- zebrafish compared with that from the wt controls.

CONCLUSIONS

Our results indicated that plasma ADAMTS13 or lack of VWF may offer a significant protection against the development of irradiation- and/or melanoma-induced TMA. Such a microenvironment may directly affect melanoma cell phenotypes via alternation in the oxidation-reduction and lipid metabolic pathways.

Association of Thrombin Generation With Leukocyte Inflammatory Profile in Patients With Acute Ischemic Stroke

BACKGROUND AND OBJECTIVES

Thrombosis is central to the pathogenesis of acute ischemic stroke, with higher thrombin generation being associated with increased stroke risk. The immune system may contribute to thrombin generation in stroke and thus may offer novel strategies for stroke prevention. This study addresses the research question regarding the relationship of thrombin generation to leukocyte gene expression in patients with acute ischemic stroke.

METHODS

We isolated RNA from whole blood and examined the relationship to thrombin generation capacity in patients with acute ischemic stroke. Due to its effects on thrombin generation, patients on anticoagulants were excluded from the study. The relationship of gene expression with peak thrombin was evaluated by analysis of covariance across peak thrombin quartiles adjusted for sex and age.

RESULTS

In 97 patients with acute ischemic stroke, peak thrombin was variable, ranging from 252.0 to 752.4 nM. Increased peak thrombin was associated with differences in thromboinflammatory leukocyte gene expression, including a decrease in ADAM metallopeptidase with thrombospondin type 1 motif 13 and an increase in nuclear factor κB (NF-κB)-activating protein, protein disulfide isomerase family A member 5, and tissue factor pathway inhibitor 2. Pathways associated with peak thrombin included interleukin 6 signaling, thrombin signaling, and NF-κB signaling. A linear discriminant analysis model summarizing the immune activation associated with peak thrombin in a first cohort of stroke could distinguish patients with low peak thrombin from high peak thrombin in a second cohort of 112 patients with acute ischemic stroke.

DISCUSSION

The identified genes and pathways support a role of the immune system contributing to thrombus formation in patients with stroke. These may have relevance to antithrombotic strategies for stroke prevention.

Thromboinflammation: From Atherosclerosis to COVID-19

The activating interplay of thrombosis and inflammation (thromboinflammation) has been established as a major underlying pathway, driving not only cardiovascular disease but also autoimmune disease and most recently, COVID-19. Throughout the years, innate immune cells have emerged as important modulators of this process. As the most abundant white blood cell in humans, neutrophils are well-positioned to propel thromboinflammation. This includes their ability to trigger an organized cell death pathway with the release of decondensed chromatin structures called neutrophil extracellular traps. Decorated with histones and cytoplasmic and granular proteins, neutrophil extracellular traps exert cytotoxic, immunogenic, and prothrombotic effects accelerating disease progression. Distinct steps leading to extracellular DNA release (NETosis) require the activities of PAD4 (protein arginine deiminase 4) catalyzing citrullination of histones and are supported by neutrophil inflammasome. By linking the immunologic function of neutrophils with the procoagulant and proinflammatory activities of monocytes and platelets, PAD4 activity holds important implications for understanding the processes that fuel thromboinflammation. We will also discuss mechanisms whereby vascular occlusion in thromboinflammation depends on the interaction of neutrophil extracellular traps with ultra-large VWF (von Willebrand Factor) and speculate on the importance of PAD4 in neutrophil inflammasome assembly and neutrophil extracellular traps in thromboinflammatory diseases including atherosclerosis and COVID-19.

Thromboinflammation in Brain Ischemia: Recent Updates and Future Perspectives

Despite decades of promising preclinical validation and clinical translation, ischemic stroke still remains as one of the leading causes of death and disability worldwide. Within its complex pathophysiological signatures, thrombosis and inflammation, that is, thromboinflammation, are highly interconnected processes leading to cerebral vessel occlusion, inflammatory responses, and severe neuronal damage following the ischemic event. Hence, we here review the most recent updates on thromboinflammatory-dependent mediators relevant after stroke focusing on recent discoveries on platelet modulation, a potential regulation of the innate and adaptive immune system in thromboinflammation, utterly providing a thorough up-to-date overview of all therapeutic approaches currently undergoing clinical trial.

Cerebral Infarction due to Severe ADAMTS-13 Deficiency with Normal Hematological Parameters: A Potentially Cause of Cryptogenic Stroke

OBJECTIVES

Thrombotic thrombocytopenic purpura (TTP) is a microangiopathy resulting from an inherited or acquired severe deficiency in a disintegrin and metalloproteinase called ADAMTS-13. Acquired or immune TTP is classically described as a pentad of microangiopathic hemolytic anemia (MAHA), thrombocytopenia, fever, renal insufficiency and neurological symptoms. Thrombotic thrombocytopenic purpura has been linked to stroke with the presence of hematologic abnormalities but whether or not severe ADAMTS-13 deficiency can cause stroke without hematological abnormalities is unknown.

MATERIALS AND METHODS

As part of routine clinical care, we identified four cases of recurrent stroke attributed to severe deficiency of ADAMTS-13. We also conducted a search of a centralized electronic health record database including all inpatients and outpatient charts at a single academic medical center over the last ten years in an attempt to identify additional cases.

RESULTS

Here we present four cases of stroke and severe ADAMTS-13 deficiency where stroke episodes occurred without microangiopathic hemolytic anemia or severe thrombocytopenia. These cases show the need to consider severe ADAMTS-13 deficiency in the setting of recurrent cryptogenic stroke in young patients.

CONCLUSIONS AND RELEVANCE

TTP directed therapies may be considered for patients with recurrent stroke who have extremely low ADAMTS-13 levels, even when platelet and hemoglobin values are normal.

Robust thrombolytic and anti-inflammatory action of a constitutively active ADAMTS13 variant in murine stroke models

Advances in our understanding of ADAMTS13 structure, and the conformation changes required for full activity, have rejuvenated the possibility of its use as a thrombolytic therapy. We have tested a novel Ala1144Val ADAMTS13 variant (constitutively active [ca] ADAMTS13) that exhibits constitutive activity, characterized using in vitro assays of ADAMTS13 activity, and greatly enhanced thrombolytic activity in 2 murine models of ischemic stroke, the distal FeCl3 middle cerebral artery occlusion (MCAo) model and transient middle cerebral artery occlusion (tMCAO) with systemic inflammation and ischemia/reperfusion injury. The primary measure of efficacy in both models was restoration of regional cerebral blood flow (rCBF) to the MCA territory, which was determined using laser speckle contrast imaging. The caADAMTS13 variant exhibited a constitutively active conformation and a fivefold enhanced activity against fluorescence resonance energy transfer substrate von Willebrand factor 73 (FRETS-VWF73) compared with wild-type (wt) ADAMTS13. Moreover, caADAMTS13 inhibited VWF-mediated platelet capture at subphysiological concentrations and enhanced t-PA/plasmin lysis of fibrin(ogen), neither of which were observed with wtADAMTS13. Significant restoration of rCBF and reduced lesion volume was observed in animals treated with caADAMTS13. When administered 1 hour after FeCl3 MCAo, the caADAMTS13 variant significantly reduced residual VWF and fibrin deposits in the MCA, platelet aggregate formation, and neutrophil recruitment. When administered 4 hours after reperfusion in the tMCAo model, the caADAMTS13 variant induced a significant dissolution of platelet aggregates and a reduction in the resulting tissue hypoperfusion. The caADAMTS13 variant represents a potentially viable therapeutic option for the treatment of acute ischemic stroke, among other thrombotic indications, due to its enhanced in vitro and in vivo activities that result from its constitutively active conformation.

Staphylococcus aureus and Neutrophil Extracellular Traps: The Master Manipulator Meets Its Match in Immunothrombosis

Over the past 10 years, neutrophil extracellular traps (NETs) have become widely accepted as an integral player in immunothrombosis, due to their complex interplay with both pathogens and components of the coagulation system. While the release of NETs is an attempt by neutrophils to trap pathogens and constrain infections, NETs can have bystander effects on the host by inducing uncontrolled thrombosis, inflammation, and tissue damage. From an evolutionary perspective, pathogens have adapted to bypass the host innate immune response. Staphylococcus aureus (S. aureus), in particular, proficiently overcomes NET formation using several virulence factors. Here we review mechanisms of NET formation and how these are intertwined with platelet activation, the release of endothelial von Willebrand factor, and the activation of the coagulation system. We discuss the unique ability of S. aureus to modulate NET formation and alter released NETs, which helps S. aureus to escape from the host's defense mechanisms. We then discuss how platelets and the coagulation system could play a role in NET formation in S. aureus-induced infective endocarditis, and we explain how targeting these complex cellular interactions could reveal novel therapies to treat this disease and other immunothrombotic disorders.

Biomarkers for Transient Ischemic Attack: A Brief Perspective of Current Reports and Future Horizons

Cerebrovascular disease is the leading cause of long-term disability in the world and the third-leading cause of death in the United States. The early diagnosis of transient ischemic attack (TIA) is of great importance for reducing the mortality and morbidity of cerebrovascular diseases. Patients with TIA have a high risk of early subsequent ischemic stroke and the development of permanent nervous system lesions. The diagnosis of TIA remains a clinical diagnosis that highly relies on the patient's medical history assessment. There is a growing list of biomarkers associated with different components of the ischemic cascade in the brain. In this review, we take a closer look at the biomarkers of TIA and their validity with a focus on the more clinically important ones using recent evidence of their reliability for practical usage.

Post-stroke treatment with K-134, a phosphodiesterase 3 inhibitor, improves stroke outcomes in the stroke-prone spontaneously hypertensive rat model-A comparative evaluation of antiplatelet drugs

Post-stroke antiplatelet therapy has been proved to reduce the risk of recurrent stroke; however, it may also increase the incidence of intracranial hemorrhage that could offset any benefits. Therefore, the balance between the benefits and risks of antiplatelet drugs is a critical issue to consider. In the present study, we have compared the effects of post-stroke administration of antiplatelet agents on functional outcomes in the stroke-prone spontaneously hypertensive rat (SHRSP), an established animal model that mimics human lacunar stroke and cerebral small vessel disease. We confirmed that a potent phosphodiesterase 3 (PDE3) inhibitor, K-134, significantly improved post-stroke survival rate and survival time, attenuated stroke-induced neurological deficits, and decreased the incidence of cerebral lesion caused by intracerebral hemorrhage and softening. Similarly, cilostazol showed beneficial effects, though to a lower extent with respect to the survival outcome and neurological symptoms. On the other hand, a P2Y12 inhibitor, clopidogrel significantly improved survival outcomes at the higher dose but caused massive bleeding in the brain at both low and high doses. In contrast, no hemorrhagic lesion was observed in K-134-treated SHRSPs despite its antiplatelet activity. Our findings indicate that K-134 may have a superior post-stroke therapeutic outcome in comparison to other antiplatelet drugs.

Involvement of platelet-derived VWF in metastatic growth of melanoma in the brain

Background

The prognosis of patients with brain metastases (BM) is poor despite advances in our understanding of the underlying pathophysiology. The high incidence of thrombotic complications defines tumor progression and the high mortality rate. We, therefore, postulated that von Willebrand factor (VWF) promotes BM via its ability to induce platelet aggregation and thrombosis.

Methods

We measured the abundance of VWF in the blood and intravascular platelet aggregates of patients with BM, and determined the specific contribution of endothelial and platelet-derived VWF using in vitro models and microfluidics. The relevance for the brain metastatic cascade in vivo was demonstrated in ret transgenic mice, which spontaneously develop BM, and by the intracardiac injection of melanoma cells.

Results

Higher levels of plasma VWF in patients with BM were associated with enhanced intraluminal VWF fiber formation and platelet aggregation in the metastatic tissue and peritumoral regions. Platelet activation triggered the formation of VWF multimers, promoting platelet aggregation and activation, in turn enhancing tumor invasiveness. The absence of VWF in platelets, or the blocking of platelet activation, abolished platelet aggregation, and reduced tumor cell transmigration. Anticoagulation and platelet inhibition consistently reduced the number of BM in preclinical animal models.

Conclusions

Our data indicate that platelet-derived VWF is involved in cerebral clot formation and in metastatic growth of melanoma in the brain. Targeting platelet activation with low-molecular-weight heparins represents a promising therapeutic approach to prevent melanoma BM.

ADAM and ADAMTS disintegrin and metalloproteinases as major factors and molecular targets in vascular malfunction and disease

A Disintegrin and Metalloproteinase (ADAM) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) are two closely related families of proteolytic enzymes. ADAMs are largely membrane-bound enzymes that act as molecular scissors or sheddases of membrane-bound proteins, growth factors, cytokines, receptors and ligands, whereas ADAMTS are mainly secreted enzymes. ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and transmembrane domain. Similarly, ADAMTS family members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but instead of a transmembrane domain they have thrombospondin motifs. Most ADAMs and ADAMTS are activated by pro-protein convertases, and can be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C. Activated ADAMs and ADAMTS participate in numerous vascular processes including angiogenesis, vascular smooth muscle cell proliferation and migration, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs and ADAMTS also play a role in vascular malfunction and cardiovascular diseases such as hypertension, atherosclerosis, coronary artery disease, myocardial infarction, heart failure, peripheral artery disease, and vascular aneurysm. Decreased ADAMTS13 is involved in thrombotic thrombocytopenic purpura and microangiopathies. The activity of ADAMs and ADAMTS can be regulated by endogenous tissue inhibitors of metalloproteinases and other synthetic small molecule inhibitors. ADAMs and ADAMTS can be used as diagnostic biomarkers and molecular targets in cardiovascular disease, and modulators of ADAMs and ADAMTS activity may provide potential new approaches for the management of cardiovascular disorders.

Neuroinflammation in Cerebral Ischemia and Ischemia/Reperfusion Injuries: From Pathophysiology to Therapeutic Strategies

Its increasing incidence has led stroke to be the second leading cause of death worldwide. Despite significant advances in recanalization strategies, patients are still at risk for ischemia/reperfusion injuries in this pathophysiology, in which neuroinflammation is significantly involved. Research has shown that in the acute phase, neuroinflammatory cascades lead to apoptosis, disruption of the blood-brain barrier, cerebral edema, and hemorrhagic transformation, while in later stages, these pathways support tissue repair and functional recovery. The present review discusses the various cell types and the mechanisms through which neuroinflammation contributes to parenchymal injury and tissue repair, as well as therapeutic attempts made in vitro, in animal experiments, and in clinical trials which target neuroinflammation, highlighting future therapeutic perspectives.

Transcriptomic Profiling Reveals the Antiapoptosis and Antioxidant Stress Effects of Fos in Ischemic Stroke

Arterial hypertension is considered the most prevalent risk factor for stroke. Both pathophysiologic and clinical data previously acquired suggest a strong correlation between the hemodynamic nature of arterial hypertension and an increase in the risk of ischemic insult to tissues. However, the knowledge of specific molecular interactions between hypertension and ischemic stroke (IS) is limited. In this study, we performed systematic bioinformatics analysis of stroke-prone spontaneous hypertensive brain tissue samples of rats (GSE41452), middle cerebral artery occlusion of brain tissue samples of rats (GSE97537), and peripheral blood array data of IS patients (GSE22255). We identified that Fos, an immediate-early gene (IEG) that responds to alterations in arterial blood pressure, has a strong correlation with the occurrence and prognosis of IS. To further evaluate the potential function of Fos, the oxygen–glucose deprivation model and RNA sequencing of HT22 neuronal cells were performed. Consistent with the sequencing results, real-time quantitative PCR and Western blot indicate that Fos was elevated at 3 h and returned to normal levels at 6 h after oxygen–glucose deprivation. Knock-down of Fos by lentivirus significantly increased the oxidative stress level, neuronal apoptosis, and inhibited the mitochondrial function. In conclusion, Fos acts as an important link between hypertension and IS. Furthermore, Fos can be used as a potential biomarker for target therapy in the prevention of stroke among hypertensive patients and also potential treatment targeting apoptosis and oxidative stress after its onset.

Novel Serum Biomarkers of Neurovascular Unit Associated with Cortical Amyloid Deposition

BACKGROUND

Whether blood biomarkers of neurovascular unit are associated with cortical amyloid deposition on positron emission tomography (PET) imaging remains unclear.

OBJECTIVE

To investigate the association between novel serum biomarkers of neurovascular unit, such as protein tyrosine phosphatase receptor type B (PTPRB), gap junction protein alpha-5 (GJA5), adenosine triphosphate-sensitive inward rectifier potassium channel-8 (KCNJ8), and von Willebrand factor (vWF), and cortical amyloid deposition.

METHODS

Between 2012 and 2018, 68 elderly individuals with amnestic mild cognitive impairment (32 men and 36 women; mean age 75.2 years) were enrolled. All participants underwent 11C-Pittsburgh compound-B (PiB)-PET, 18F-fluorodeoxyglucose-PET, and measurement of serum PTPRB, GJA5, KCNJ8, and vWF levels using commercially available human enzyme-linked immunosorbent assay kits. Based on the mean cortical standardized uptake value ratio, the participants were divided into two groups: PiB-negative group and PiB-positive group. Serum levels of PTPRB, GJA5, KCNJ8, and vWF were compared between the two groups. Multiple linear regression analysis was performed to investigate the relationship between serum PTPRB, GJA5, KCNJ8, and vWF levels and cortical amyloid deposition.

RESULTS

PTPRB and GJA5 levels were significantly lower and KCNJ8 and vWF levels were significantly higher in the PiB-positive group than in the PiB-negative group. PTPRB and GJA5 levels inversely correlated with mean PiB uptake, whereas KCNJ8 and vWF levels positively correlated with mean PiB uptake.

CONCLUSION

Serum levels of PTPRB, GJA5, KCNJ8, and vWF correlate with cortical amyloid deposition. These novel blood biomarkers of neurovascular unit are useful for identifying elderly individuals at risk of developing Alzheimer's disease.

Platelets as drivers of ischemia/reperfusion injury after stroke

Ischemic stroke is a leading cause of morbidity and mortality worldwide and, despite reperfusion either via thrombolysis or thrombectomy, stroke patients often suffer from lifelong disabilities. These persistent neurological deficits may be improved by treating the ischemia/reperfusion (I/R) injury that occurs following ischemic stroke. There are currently no approved therapies to treat I/R injury, and thus it is imperative to find new targets to decrease the burden of ischemic stroke and related diseases. Platelets, cell fragments from megakaryocytes, are primarily known for their role in hemostasis. More recently, investigators have studied the nonhemostatic role of platelets in inflammatory pathologies, such as I/R injury after ischemic stroke. In this review, we seek to provide an overview of how I/R can lead to platelet activation and how activated platelets, in turn, can exacerbate I/R injury after stroke. We will also discuss potential mechanisms by which platelets may ameliorate I/R injury.

Serum and cerebrospinal fluid host proteins indicate stroke in children with tuberculous meningitis

Introduction

Stroke is a common complication in children with tuberculous meningitis (TBM). Host proteins may give us insight into the mechanisms of stroke in TBM and serve as biomarkers for detection of stroke, however, they have not been widely explored. In this study, we compared the concentrations of cerebrospinal fluid (CSF) and serum proteins between children who had TBM-related stroke and children with TBM without stroke.

Methods

We collected CSF and serum from 47 children consecutively admitted to the Tygerberg Academic Hospital in Cape Town, South Africa between November 2016, and November 2017, on suspicion of having TBM. A multiplex platform was used to measure the concentrations of 69 host proteins in CSF and serum from all study participants.

Results

After classification of study participants, 23 (48.9%) out of the 47 study participants were diagnosed with TBM, of which 14 (60.9%) demonstrated radiological arterial ischemic infarction. The levels of lipocalin-2, sRAGE, IP-10/ CXCL10, sVCAM-1, MMP-1, and PDGF-AA in CSF samples and the levels of D-dimer, ADAMTS13, SAA, ferritin, MCP-1/ CCL2, GDF-15 and IL-13 in serum samples were statistically different between children who had TBM-related stroke and children with TBM without stroke. After correcting for multiple testing, only the levels of sVCAM-1, MMP-1, sRAGE, and IP-10/ CXCL10 in CSF were statistically different between the two groups. CSF and serum protein biosignatures indicated stroke in children diagnosed with TBM with up to 100% sensitivity and 88.9% specificity.

Conclusion

Serum and CSF proteins may serve as biomarkers for identifying individuals with stroke amongst children diagnosed with TBM at admission and may guide us to understand the biology of stroke in TBM. This was a pilot study, and thus further investigations in larger studies are needed.

Impaired adhesion of neutrophils expressing Slc44a2/HNA-3b to VWF protects against NETosis under venous shear rates

Genome-wide association studies linked expression of the human neutrophil antigen 3b (HNA-3b) epitope on the Slc44a2 protein with a 30% decreased risk of venous thrombosis (VT) in humans. Slc44a2 is a ubiquitous transmembrane protein identified as a receptor for von Willebrand factor (VWF). To explain the link between Slc44a2 and VT, we wanted to determine how Slc44a2 expressing either HNA-3a or HNA-3b on neutrophils could modulate their adhesion and activation on VWF under flow. Transfected HEK293T cells or neutrophils homozygous for the HNA-3a- or HNA-3b-coding allele were purified from healthy donors and perfused in flow chambers coated with VWF at venous shear rates (100 s-1). HNA-3a expression was required for Slc44a2-mediated neutrophil adhesion to VWF at 100 s-1. This adhesion could occur independently of β2 integrin and was enhanced when neutrophils were preactivated with lipopolysaccharide. Moreover, specific shear conditions with high neutrophil concentration could act as a "second hit," inducing the formation of neutrophil extracellular traps. Neutrophil mobilization was also measured by intravital microscopy in venules from SLC44A2-knockout and wild-type mice after histamine-induced endothelial degranulation. Mice lacking Slc44a2 showed a massive reduction in neutrophil recruitment in inflamed mesenteric venules. Our results show that Slc44a2/HNA-3a is important for the adhesion and activation of neutrophils in veins under inflammation and when submitted to specific shears. The fact that neutrophils expressing Slc44a2/HNA-3b have a different response on VWF in the conditions tested could thus explain the association between HNA-3b and a reduced risk for VT in humans.

Clinical significance of measuring ADAMTS-13, its inhibitor and von Willebrand factor in obstetric and gynecological practice

ADAMTS-13 is a crucial metalloproteinase involved in liberating fragments of von Willebrand factor (vWF) into the plasma as well as regulating its activity by cleaving "ultra-large" multimers into smaller and less active counterparts. Many pathological conditions, including those emerged during pregnancy are characterized by increased level of vWF and decreased ADAMTS-13 activity. In this regard, it is necessary to monitor the levels of vWF and ADAMTS-13 activity to prevent thrombotic thrombocytopenic purpura (Moschcowitz disease) as one of the most severe forms of thrombotic microangiopathy.

 

The von Willebrand Factor A1 domain mediates thromboinflammation, aggravating ischemic stroke outcome in mice

von Willebrand factor (VWF) plays an important role in ischemic stroke. However, the exact mechanism by which VWF mediates progression of ischemic stroke brain damage is not completely understood. Using flow cytometric analysis of single cell suspensions prepared from brain tissue and immunohistochemistry, we investigated the potential inflammatory mechanisms by which VWF contributes to ischemic stroke brain damage in a mouse model of cerebral ischemia/reperfusion injury. Twenty-four hours after stroke, flow cytometric analysis of brain tissue revealed that overall white blood cell recruitment in the ipsilesional brain hemisphere of VWF KO mice was 2 times lower than WT mice. More detailed analysis showed a specific reduction of proinflammatory monocytes, neutrophils and T-cells in the ischemic brain of VWF KO mice compared to WT mice. Interestingly, histological analysis revealed a substantial number of neutrophils and T-cells still within the microcirculation of the stroke brain, potentially contributing to the no-reflow phenomenon. Specific therapeutic targeting of the VWF A1 domain in WT mice resulted in reduced immune cell numbers in the affected brain and protected mice from ischemic stroke brain damage. More specifically, recruitment of proinflammatory monocytes was reduced two-fold, neutrophil recruitment was reduced five-fold and T-cell recruitment was reduced two-fold in mice treated with a VWF A1-targeting nanobody compared to mice receiving a control nanobody. In conclusion, our data identify a potential role for VWF in the recruitment of proinflammatory monocytes, neutrophils and T-cells to the ischemic brain via a mechanism that is mediated by its A1 domain.

ADAMTS proteases in cardiovascular physiology and disease

The a disintegrin-like and metalloproteinase with thrombospondin motif (ADAMTS) family comprises 19 proteases that regulate the structure and function of extracellular proteins in the extracellular matrix and blood. The best characterized cardiovascular role is that of ADAMTS-13 in blood. Moderately low ADAMTS-13 levels increase the risk of ischeamic stroke and very low levels (less than 10%) can cause thrombotic thrombocytopenic purpura (TTP). Recombinant ADAMTS-13 is currently in clinical trials for treatment of TTP. Recently, new cardiovascular roles for ADAMTS proteases have been discovered. Several ADAMTS family members are important in the development of blood vessels and the heart, especially the valves. A number of studies have also investigated the potential role of ADAMTS-1, -4 and -5 in cardiovascular disease. They cleave proteoglycans such as versican, which represent major structural components of the arteries. ADAMTS-7 and -8 are attracting considerable interest owing to their implication in atherosclerosis and pulmonary arterial hypertension, respectively. Mutations in the ADAMTS19 gene cause progressive heart valve disease and missense variants in ADAMTS6 are associated with cardiac conduction. In this review, we discuss in detail the evidence for these and other cardiovascular roles of ADAMTS family members, their proteolytic substrates and the potential molecular mechanisms involved.

Diverse activities of von Willebrand factor in traumatic brain injury and associated coagulopathy

Traumatic brain injury (TBI) is a leading cause of death and disability. Patients with isolated TBI lose a limited amount of blood to primary injury, but they often develop secondary coagulopathy, resulting in delayed or recurrent intracranial and intracerebral hematoma. TBI-induced coagulopathy is closely associated with poor outcomes for these patients, including death. This secondary coagulopathy is consumptive in nature, involving not only brain-derived molecules, coagulation factors, and platelets, but also endothelial cells in a complex process now called blood failture. A key question is how a localized injury to the brain is rapidly disseminated to affect systemic hemostasis that is not directly affected the way it is in trauma to the body and limbs, especially with hemorrhagic shock. Increasing evidence suggests that the adhesive ligand von Willebrand factor (VWF), which is synthesized in and released from endothelial cells, plays a paradoxical role in both facilitating local hemostasis at the site of injury and also propagating TBI-induced endotheliopathy and coagulopathy systemically. This review discusses recent progress in understanding these diverse activities of VWF and the knowledge gaps in defining their roles in TBI and associated coagulopathy.

Designing Enzyme-responsive Biomaterials

Enzymes are a class of protein that catalyze a wide range of chemical reactions, including the cleavage of specific peptide bonds. They are expressed in all cell types, play vital roles in tissue development and homeostasis, and in many diseases, such as cancer. Enzymatic activity is tightly controlled through the use of inactive pro-enzymes, endogenous inhibitors and spatial localization. Since the presence of specific enzymes is often correlated with biological processes, and these proteins can directly modify biomolecules, they are an ideal biological input for cell-responsive biomaterials. These materials include both natural and synthetic polymers, cross-linked hydrogels and self-assembled peptide nanostructures. Within these systems enzymatic activity has been used to induce biodegradation, release therapeutic agents and for disease diagnosis. As technological advancements increase our ability to quantify the expression and nanoscale organization of proteins in cells and tissues, as well as the synthesis of increasingly complex and well-defined biomaterials, enzyme-responsive biomaterials are poised to play vital roles in the future of biomedicine.

Role of the Platelets and Nitric Oxide Biotransformation in Ischemic Stroke: A Translative Review from Bench to Bedside

Ischemic stroke remains the fifth cause of death, as reported worldwide annually. Endothelial dysfunction (ED) manifesting with lower nitric oxide (NO) bioavailability leads to increased vascular tone, inflammation, and platelet activation and remains among the major contributors to cardiovascular diseases (CVD). Moreover, temporal fluctuations in the NO bioavailability during ischemic stroke point to its key role in the cerebral blood flow (CBF) regulation, and some data suggest that they may be responsible for the maintenance of CBF within the ischemic penumbra in order to reduce infarct size. Several years ago, the inhibitory role of the platelet NO production on a thrombus formation has been discovered, which initiated the era of extensive studies on the platelet-derived nitric oxide (PDNO) as a platelet negative feedback regulator. Very recently, Radziwon-Balicka et al. discovered two subpopulations of human platelets, based on the expression of the endothelial nitric oxide synthase (eNOS-positive or eNOS-negative platelets, respectively). The e-NOS-negative ones fail to produce NO, which attenuates their cyclic guanosine monophosphate (cGMP) signaling pathway and-as result-promotes adhesion and aggregation while the e-NOS-positive ones limit thrombus formation. Asymmetric dimethylarginine (ADMA), a competitive NOS inhibitor, is an independent cardiovascular risk factor, and its expression alongside with the enzymes responsible for its synthesis and degradation was recently shown also in platelets. Overproduction of ADMA in this compartment may increase platelet activation and cause endothelial damage, additionally to that induced by its plasma pool. All the recent discoveries of diverse eNOS expression in platelets and its role in regulation of thrombus formation together with studies on the NOS inhibitors have opened a new chapter in translational medicine investigating the onset of acute cardiovascular events of ischemic origin. This translative review briefly summarizes the role of platelets and NO biotransformation in the pathogenesis and clinical course of ischemic stroke.

The Value of ADAMTS13 in Predicting Clinical Outcomes in Patients With Acute Ischemic Stroke Receiving Thrombolysis

Objective: To determine the association between baseline ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) antigen level and 90-days clinical outcome in patients with acute ischemic stroke (AIS) receiving recombinant tissue plasminogen activator (rt-PA) thrombolysis.

Methods: AIS patients receiving rt-PA thrombolytic therapy from Huashan Hospital and Fifth People's Hospital of Shanghai, China in 2014–2017 were consecutively enrolled. Blood samples for ADAMTS13 tests were drawn before intravenous rt-PA administration. The primary outcome was defined as the poor functional outcome of modified Rankin Scale (mRS) >2 at 90-days follow-up. Secondary outcome was hemorrhagic transformation after rt-PA therapy. Moreover, for AIS patients with large vessel occlusion from Huashan Hospital, the association between baseline ADAMTS13 level and cerebral collateral flow was also assessed.

Results: A total of 163 AIS patients (median age 66.2 years, 63.8% male) were included. Baseline ADAMTS13 level was marginally decreased in patients with 90-days mRS >2 than in those with mRS ≤ 2 (mean ± SD, 1458.4 ± 323.3 vs. 1578.3 ± 395.4 ng/mL, p = 0.046). However, no difference of ADAMTS13 level was found after adjusting for age, history of atrial fibrillation, glycemia, baseline NIHSS score and TOAST classification (p = 0.43). We found no difference in ADAMTS13 level between patients with parenchymal hemorrhage after rt-PA therapy and those without (p = 0.44). Among 66 patients with large vessel occlusion, there was also no association between ADAMTS13 level and cerebral collateral flow in multivariable analyses.

Conclusion: In our cohort, blood ADAMTS13 antigen level before rt-PA therapy could not be used as an independent biomarker in predicting clinical outcomes of AIS patients at 90 days.

Protective Effects of Polyphenols against Ischemia/Reperfusion Injury

Myocardial infarction (MI) is a leading cause of morbidity and mortality across the world. It manifests as an imbalance between blood demand and blood delivery in the myocardium, which leads to cardiac ischemia and myocardial necrosis. While it is not easy to identify the first pathogenic cause of MI, the consequences are characterized by ischemia, chronic inflammation, and tissue degeneration. A poor MI prognosis is associated with extensive cardiac remodeling. A loss of viable cardiomyocytes is replaced with fibrosis, which reduces heart contractility and heart function. Recent advances have given rise to the concept of natural polyphenols. These bioactive compounds have been studied for their pharmacological properties and have proven successful in the treatment of cardiovascular diseases. Studies have focused on their various bioactivities, such as their antioxidant and anti-inflammatory effects and free radical scavenging. In this review, we summarized the effects and benefits of polyphenols on the cardiovascular injury, particularly on the treatment of myocardial infarction in animal and human studies.

Role of HMGB1 in the Interplay between NETosis and Thrombosis in Ischemic Stroke: A Review

Neutrophil extracellular traps (NETs) comprise decondensed chromatin, histones and neutrophil granular proteins and are involved in the response to infectious as well as non-infectious diseases. The prothrombotic activity of NETs has been reported in various thrombus-related diseases; this activity can be attributed to the fact that the NETs serve as a scaffold for cells and numerous coagulation factors and stimulate fibrin deposition. A crosstalk between NETs and thrombosis has been indicated to play a role in numerous thrombosis-related conditions including stroke. In cerebral ischemia, neutrophils are the first group of cells to infiltrate the damaged brain tissue, where they produce NETs in the brain parenchyma and within blood vessels, thereby aggravating inflammation. Increasing evidences suggest the connection between NETosis and thrombosis as a possible cause of “tPA resistance”, a problem encountered during the treatment of stroke patients. Several damage-associated molecular pattern molecules have been proven to induce NETosis and thrombosis, with high mobility group box 1 (HMGB1) playing a critical role. This review discusses NETosis and thrombosis and their crosstalk in various thrombosis-related diseases, focusing on the role of HMGB1 as a mediator in stroke. We also addresses the function of peptidylarginine deiminase 4 with respect to the interplay with HMGB1 in NET-induced thrombosis.

von Willebrand factor/ADAMTS13 ratio at presentation of acute ischemic brain injury is predictive of outcome

Acute ischemic stroke (IS) and transient ischemic attack (TIA) are associated with raised von Willebrand factor (VWF) and decreased ADAMTS13 activity (ADAMTS13Ac). Their impact on mortality and morbidity is unclear. We conducted a prospective investigation of the VWF-ADAMTS13 axis in 292 adults (acute IS, n = 103; TIA, n = 80; controls, n = 109) serially from presentation until >6 weeks. The National Institutes of Health Stroke Score (NIHSS) and modified Rankin scale (mRS) were used to assess stroke severity. Presenting median VWF antigen (VWF:Ag)/ADAMTS13Ac ratios were: IS, 2.42 (range, 0.78-9.53); TIA, 1.89 (range, 0.41-8.14); and controls, 1.69 (range, 0.25-15.63). Longitudinally, the median VWF:Ag/ADAMTS13Ac ratio decreased (IS, 2.42 to 1.66; P = .0008; TIA, 1.89 to 0.65; P < .0001). The VWF:Ag/ADAMTS13Ac ratio was higher at presentation in IS patients who died (3.683 vs 2.014; P < .0001). A presenting VWF:Ag/ADAMTS13Ac ratio >2.6 predicted mortality (odds ratio, 6.33; range, 2.22-18.1). Those with a VWF:Ag/ADAMTS13Ac ratio in the highest quartile (>3.091) had 31% increased risk mortality. VWF:Ag/ADAMTS13Ac ratio at presentation of ischemic brain injury was associated with higher mRS (P = .021) and NIHSS scores (P = .029) at follow-up. Thrombolysis resulted in prompt reduction of the VWF:Ag/ADAMTS13Ac ratio and significant improvement in mRS on follow-up. A raised VWF:Ag/ADAMTS13Ac ratio at presentation of acute IS or TIA is associated with increased mortality and poorer functional outcome. A ratio of 2.6 seems to differentiate outcome. Prompt reduction in the ratio in thrombolysed patients was associated with decreased mortality and morbidity. The VWF:Ag/ADAMTS13Ac ratio is a biomarker for the acute impact of an ischemic event and longer-term outcome.

Biomechanical thrombosis: the dark side of force and dawn of mechano-medicine

Arterial thrombosis is in part contributed by excessive platelet aggregation, which can lead to blood clotting and subsequent heart attack and stroke. Platelets are sensitive to the haemodynamic environment. Rapid haemodynamcis and disturbed blood flow, which occur in vessels with growing thrombi and atherosclerotic plaques or is caused by medical device implantation and intervention, promotes platelet aggregation and thrombus formation. In such situations, conventional antiplatelet drugs often have suboptimal efficacy and a serious side effect of excessive bleeding. Investigating the mechanisms of platelet biomechanical activation provides insights distinct from the classic views of agonist-stimulated platelet thrombus formation. In this work, we review the recent discoveries underlying haemodynamic force-reinforced platelet binding and mechanosensing primarily mediated by three platelet receptors: glycoprotein Ib (GPIb), glycoprotein IIb/IIIa (GPIIb/IIIa) and glycoprotein VI (GPVI), and their implications for development of antithrombotic 'mechano-medicine' .

Role of ADAMTS-13 and nNOS expression in neuropathogenesis of listeric encephalitis of small ruminants

We investigated the expression of A disintegrin and metalloprotease with thrombospondin type I repeats-13 (ADAMTS-13) in the central nervous system (CNS), because it is related to blood-brain barrier (BBB) permeability. We also investigated 8-OHdG, caspase-3 and neuronal nitric oxide synthase (nNOS) expression for the cytotoxic effects of oxidative stress (OS) and nNOS, and their relation to apoptosis. We also investigated the neuroimmunopathology caused by L. monocytogenes. Brain tissues were obtained from 10 lambs and 10 kids with listeric meningoencephalitis, and healthy brain tissue from six lambs and six kids. Serial sections of brain were stained by hematoxylin and eosin (H & E), and using immunohistochemistry (IHC) for L. monocytogenes antigen, ADAMTS-13, 8-hydroxy-2'-deoxyguanosine (8-OHdG), nNOS and caspase-3. We found that ADAMTS-13, 8-OHdG, nNOS and caspase-3 expression in the brain was increased in L. Monocytogenes infected animals compared to uninfected controls. Intense staining for 8-OHdG was observed only in neurons and glia that were exposed to OS. ADAMTS-13 was increased significantly, which may play a role in regulating and protecting BBB integrity and cells of the CNS in cases of listeric encephalitis. Increased expression of ADAMTS-13 may be critical for supporting the survival of neurons and glia. We found that L. monocytogenes-related increases in OS and nNOS, and that the associated apoptosis, may participate in neurodegeneration and neuropathology in listeric encephalitis.

Von Willebrand factor and ADAMTS13 impact on the outcome of Staphylococcus aureus sepsis

BACKGROUND

Previous clinical evidence correlates levels of von Willebrand factor (VWF) and its cleaving protease ADAMTS13 with outcome in septic patients. No previous studies addressed if VWF and ADAMTS13 affected the outcome of Staphylococcus aureus sepsis.

OBJECTIVES

We studied the role of VWF and ADAMTS13 in S. aureus sepsis both in patients and in mice.

METHODS

VWF levels and ADAMTS13 activity levels were measured in plasma samples from 89 S. aureus bacteremia patients by chemiluminescent assays and were correlated with clinical sepsis outcome parameters. In wild-type mice and mice deficient in VWF and ADAMTS13, we investigated the outcome of S. aureus sepsis and quantified bacterial clearance and organ microthrombi.

RESULTS

In patients with S. aureus bloodstream infections, high VWF levels and low ADAMTS13 activity levels correlated with disease severity and with parameters of inflammation and disseminated intravascular coagulation. In septic mice, VWF deficiency attenuated mortality, whereas ADAMTS13 deficiency increased mortality. Bacterial clearance was enhanced in VWF-deficient mice. The differences in mortality for the studied genotypes were associated with differential loads of organ microthrombi in both liver and kidneys.

CONCLUSIONS

In conclusion, this study reports the consistent relation of VWF, ADAMTS13 and their ratio to disease severity in patients and mice with S. aureus sepsis. Targeting VWF multimers and/or the relative ADAMTS13 deficiency that occurs in sepsis should be explored as a potential new therapeutic target in S. aureus endovascular infections.

ADAMTS13 ameliorates inflammatory responses in experimental autoimmune encephalomyelitis

BACKGROUND

ADAMTS13 (a disintegrin and metalloprotease with a thrombospondin type 1 motif, member 13) plays a vital role in preventing microvascular thrombosis and inflammation. Reduced ADAMTS13 levels in plasma have been detected in multiple sclerosis (MS) patients. In the present study, we have determined the role of ADAMTS13 in the disease progression of MS using a mouse model of experimental autoimmune encephalomyelitis (EAE).

METHODS

Female C57BL/6 mice were immunized with MOG_35-55 peptide and then treated with ADAMTS13 or vehicle in preventive and therapeutic settings. Mice were analyzed for clinical deficit, white matter demyelination and inflammatory cell infiltration. To explore the underlying mechanism, VWF expression and blood-spinal cord barriers (BSCB) were determined.

RESULTS

Plasma ADAMTS13 activity was suppressed in EAE mice. ADAMTS13-treated EAE mice exhibited an ameliorated disease course, reduced demyelination, and decreased T lymphocyte, neutrophil and monocyte infiltration into the spinal cord. Consistently, ADAMTS13 treatment reduced VWF levels and inhibited BSCB breakdown in the spinal cords of EAE mice. However, leukocytes in the blood and spleen of EAE mice remained unaffected by ADAMTS13 administration.

CONCLUSION

Our results demonstrate that ADAMTS13 treatment ameliorates inflammatory responses, demyelination and disease course in EAE mice. Therefore, our study suggests that ADAMTS13 may represent a potential therapeutic strategy for MS patients.

von Willebrand Factor and Platelet Glycoprotein Ib: A Thromboinflammatory Axis in Stroke

von Willebrand factor (VWF) and platelets are key mediators of normal hemostasis. At sites of vascular injury, VWF recruits platelets via binding to the platelet receptor glycoprotein Ibα (GPIbα). Over the past decades, it has become clear that many hemostatic factors, including VWF and platelets, are also involved in inflammatory processes, forming intriguing links between hemostasis, thrombosis, and inflammation. The so-called “thrombo-inflammatory” nature of the VWF-platelet axis becomes increasingly recognized in different cardiovascular pathologies, making it a potential therapeutic target to interfere with both thrombosis and inflammation. In this review, we discuss the current evidence for the thrombo-inflammatory activity of VWF with a focus on the VWF-GPIbα axis and discuss its implications in the setting of ischemic stroke.