Plasma ADAMTS13 activity and von Willebrand factor antigen and activity in patients with subarachnoid haemorrhage

ADAMTS13 or Caplacizumab Reduces the Accumulation of Neutrophil Extracellular Traps and Thrombus in Whole Blood of COVID-19 Patients under Flow

BACKGROUND

 Neutrophil NETosis and neutrophil extracellular traps (NETs) play a critical role in pathogenesis of coronavirus disease 2019 (COVID-19)-associated thrombosis. However, the extents and reserve of NETosis, and potential of thrombus formation under shear in whole blood of patients with COVID-19 are not fully elucidated. Neither has the role of recombinant ADAMTS13 or caplacizumab on the accumulation of NETs and thrombus in COVID-19 patients' whole blood under shear been investigated.

METHODS

 Flow cytometry and microfluidic assay, as well as immunoassays, were employed for the study.

RESULTS

 We demonstrated that the percentage of H3Cit + MPO+ neutrophils, indicative of NETosis, was dramatically increased in patients with severe but not critical COVID-19 compared with that in asymptomatic or mild disease controls. Upon stimulation with poly [I:C], a double strain DNA mimicking viral infection, or bacterial shigatoxin-2, the percentage of H3Cit + MPO+ neutrophils was not significantly increased in the whole blood of severe and critical COVID-19 patients compared with that of asymptomatic controls, suggesting the reduction in NETosis reserve in these patients. Microfluidic assay demonstrated that the accumulation of NETs and thrombus was significantly enhanced in the whole blood of severe/critical COVID-19 patients compared with that of asymptomatic controls. Like DNase I, recombinant ADAMTS13 or caplacizumab dramatically reduced the NETs accumulation and thrombus formation under arterial shear.

CONCLUSION

 Significantly increased neutrophil NETosis, reduced NETosis reserve, and enhanced thrombus formation under arterial shear may play a crucial role in the pathogenesis of COVID-19-associated coagulopathy. Recombinant ADAMTS13 or caplacizumab may be explored for the treatment of COVID-19-associated thrombosis.

The Role of the von Willebrand Factor Collagen-Binding Assay (VWF:CB) in the Diagnosis and Treatment of von Willebrand Disease (VWD) and Way Beyond: A Comprehensive 36-Year History

The von Willebrand factor (VWF) collagen binding (VWF:CB) assay was first reported for use in von Willebrand diagnostics in 1986, by Brown and Bosak. Since then, the VWF:CB has continued to be used to help diagnose von Willebrand disease (VWD) (correctly) and also to help assign the correct subtype, as well as to assist in the monitoring of VWD therapy, especially desmopressin (DDAVP). However, it is important to recognize that the specific value of any VWF:CB is predicated on the use of an optimized VWF:CB, and that not all VWF:CB assays are so optimized. There are some good commercial assays available, but there are also some "not-so-good" commercial assays available, and these may continue to give the VWF:CB "a bad reputation." In addition to VWD diagnosis and management, the VWF:CB found purpose in a variety of other applications, from assessing ADAMTS13 activity, to investigation into acquired von Willebrand syndrome (especially as associated with use of mechanical circulatory support or cardiac assist devices), to assessment of VWF activity in disease states in where an excess of high-molecular-weight VWF may accumulate, and lead to increased (micro)thrombosis risk (e.g., coronavirus disease 2019, thrombotic thrombocytopenic purpura). The VWF:CB turns 37 in 2023. This review is a celebration of the utility of the VWF:CB over this nearly 40-year history.

Dynamic Assessment of Plasma von Willebrand Factor and ADAMTS13 Predicts Mortality in Hospitalized Patients with SARS-CoV-2 Infection

BACKGROUND

Plasma levels of von Willebrand factor (VWF) are significantly elevated in patients with coronavirus disease 2019 (COVID-19). However, dynamic changes and prognostic value of this biomarker in hospitalized patients with COVID-19 have not been determined.

METHODS

A total of 124 patients infected with SARS-CoV-2 were prospectively recruited for the study. Serial blood samples were obtained at the time of admission (D1), 3-4 days following standard-care treatments (D2), and 1-2 days prior to discharge or any time collected prior to death (D3). Plasma VWF antigen, ADAMTS13 antigen, and ADAMTS13 proteolytic activity, as well as the ratio of VWF/ADAMTS13 were determined, followed by various statistical analyses.

RESULTS

On admission, plasma levels of VWF in COVID-19 patients were significantly elevated compared with those in the healthy controls, but no statistical significance was detected among patients with different disease severity. Plasma ADAMTS13 activity but not its antigen levels were significantly lower in patients with severe or critical COVID-19 compared with that in other patient groups. Interestingly, the ratios of plasma VWF antigen to ADAMTS13 antigen were significantly higher in patients with severe or critical COVID-19 than in those with mild to moderate disease. More importantly, plasma levels of VWF and the ratios of VWF/ADAMTS13 were persistently elevated in patients with COVID-19 throughout hospitalization. Kaplan-Meier and Cox proportional hazard regression analyses demonstrated that an increased plasma level of VWF or ratio of VWF/ADAMTS13 at D2 and D3 was associated with an increased mortality rate.

CONCLUSIONS

Persistent endotheliopathy, marked by the elevated levels of plasma VWF or VWF/ADAMTS13 ratio, is present in all hospitalized patients following SARS-CoV-2 infection, which is strongly associated with mortality.

Immune thrombotic thrombocytopenic purpura: pathogenesis and novel therapies: a narrative review

Background and Objectives

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare, but potentially fatal blood disease, resulting from autoantibodies against A Disintegrin and Metalloprotease with ThromboSpondin Type 1 Repeats, 13 (ADAMTS13). While major progress has been made in past decades concerning early diagnosis and management of iTTP, the mechanisms underlying the formation and the mechanism of action of these autoantibodies against ADMATS13 are still unknown. This review will provide a narrative review of pathogenesis and novel therapeutics of iTTP.

Methods

We did PubMed literature search using a combination of thrombotic thrombocytopenic purpura and treatment or pathogenesis from 1955 to November 2022. A total of 4,767 articles with full text were found and only relevant articles in English were further reviewed and summarized.

Key Content and Findings

We found that the primary mechanism underlying severe ADAMTS13 deficiency in patients with iTTP is autoantibody-mediated inhibition and/or accelerated clearance of ADAMTS13 metalloprotease. Other factors including allosteric regulation and post-translational modifications (i.e., glycosylation and citrullination, and arginine methylation, etc.) may affect ADAMTS13 secretion and function and also contribute to the pathogenesis of iTTP. The standard of care for iTTP today consists of therapeutic plasma exchange, anti-von Willebrand factor (vWF) caplacizumab, and immunosuppressives (e.g., corticosteroids and rituximab), known as the triple therapy, which has significantly reduced exacerbation and mortality rates.

Conclusions

We hope that the information provided in the review article helps better understand the pathogenesis of iTTP, which may guide design novel and more effective therapeutics for this potentially fatal disorder.

Effects of convalescent plasma infusion on the ADAMTS13-von Willebrand factor axis and endothelial integrity in patients with severe and critical COVID-19

Background

Convalescent plasma infusion (CPI) was given to patients with COVID-19 during the early pandemic with mixed therapeutic efficacy. However, the impacts of CPI on the ADAMTS13-von Willebrand factor (VWF) axis and vascular endothelial functions are not known.

Objectives

To determine the impacts of CPI on the ADAMTS13-VWF axis and vascular endothelial functions.

Methods

Sixty hospitalized patients with COVID-19 were enrolled in the study; 46 received CPI and 14 received no CPI. Plasma ADAMTS13 activity, VWF antigen, endothelial syndecan-1, and soluble thrombomodulin (sTM) were assessed before and 24 hours after treatment.

Results

Patients with severe and critical COVID-19 exhibited significantly lower plasma ADAMTS13 activity than the healthy controls. Conversely, these patients showed a significantly increased VWF antigen. This resulted in markedly reduced ratios of ADAMTS13 to VWF in these patients. The levels of plasma ADAMTS13 activity in each patient remained relatively constant throughout hospitalization. Twenty-four hours following CPI, plasma ADAMTS13 activity increased by ∼12% from the baseline in all patients and ∼21% in those who survived. In contrast, plasma levels of VWF antigen varied significantly over time. Patients who died exhibited a significant reduction of plasma VWF antigen from the baseline 24 hours following CPI, whereas those who survived did not. Furthermore, patients with severe and critical COVID-19 showed significantly elevated plasma levels of syndecan-1 and sTM, similar to those found in patients with immune thrombotic thrombocytopenic purpura. Both syndecan-1 and sTM levels were significantly reduced 24 hours following CPI.

Conclusion

Our results demonstrate the relative deficiency of plasma ADAMTS13 activity and endothelial damage in patients with severe and critical COVID-19, which could be modestly improved following CPI therapy.

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.

rhADAMTS13 reduces oxidative stress by cleaving VWF in ischaemia/reperfusion-induced acute kidney injury

AIMS

Acute kidney injury (AKI), a major health burden, lacks effective therapy. Anti-inflammatory actions of a disintegrin and metalloproteinase with a thrombospondin type 1 motif member 13 (ADAMTS13) may provide a new treatment option for AKI. Along with inflammation, oxidative stress is critical for AKI development, yet the impact of ADAMTS13 on oxidative stress in AKI remains to be fully elucidated.

METHODS

We assess recombinant human ADAMTS13 (rhADAMTS13) actions on oxidative stress in a murine ischaemia/reperfusion (IR) model. Antioxidant stress-enzyme activities, renal morphology, kidney function markers and vascular function of isolated afferent arterioles are quantified.

RESULTS

rhADAMTS13 provided after IR, reduces blood urea nitrogen (BUN) by 33% and serum creatinine (Scr) by 73% in 24 hours post-IR. rhADAMTS13 reduces BUN (40.03 ± 20.34 mmol/L vs 72.35 ± 18.74 mmol/L, P < .01), Scr (75.67 ± 51.19 μmol/L vs 176.17 ± 55.38 μmol/L, P < .01) and proteinuria by 41% in 48 hours post-IR as well. Moreover, rhADAMTS13 administration decreases malondialdehyde (MDA) and increases the activity of antioxidant stress enzymes, and attenuates reactive oxygen species production. rhADAMTS13 also upregulates nuclear factor-erythroid-2-related factor 2/haem oxygenase-1, enhances antioxidant enzymes activity and alleviates endothelial dysfunction. Finally, treatment with rhADAMTS13 mitigates severe functional and morphological injury present in IR mice. Extracellular signal-regulated kinase (ERK) phosphorylation is limited by rhADAMTS13 and PPARγ expression is partly restored in ischaemic kidneys. Co-administration of von Willebrand factor (VWF) impairs rhADAMTS13's antioxidant capacity and its protective role in IR.

CONCLUSION

rhADAMTS13 alleviates renal IR injury through antioxidant effects by cleaving VWF.

Low ADAMTS-13 predicts adverse outcomes in hospitalized patients with suspected heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a life-threatening thrombotic complication after heparin exposure. However, the role of ADAMTS-13 and von Willebrand factor (VWF) in the disease process and outcomes of HIT is not known.

OBJECTIVE

To determine the potential role of ADAMTS-13 and VWF in hospitalized patients suspected with HIT.

METHODS

Associations of the HIT tests, ADAMTS-13 activity, and VWF antigen or activity with other clinical parameters and outcomes in the patients suspected with HIT were determined.

RESULTS

Of 261 patients, 87 (33.3%) were positive and 174 (66.7%) were negative for a HIT antibody determined by an enzyme immunoassay (EIA). Of these 87 EIA+ patients, 31 (35.6%) were also positive but 56 (64.4%) were negative for serotonin-releasing assay (SRA). There was no statistically significant difference among all three groups (i.e., EIA-, EIA+/SRA+, and EIA+/SRA-) as to their demographic features, reasons for admission to the hospital, type of procedures performed, and in-hospital mortality. Compared to those in the healthy controls, plasma ADAMTS-13 activity in patients suspected with HIT was significantly lower but plasma VWF antigen (VWFAg) and activity (VWFAc) in these patients were significantly higher. While there was no statistically significant difference among all three groups regarding plasma levels of ADAMTS-13 activity, VWFAg, and VWFAc, plasma levels of ADAMTS-13 activity <50% or the low ratios of ADAMTS-13 activity to VWFAg (or VWFAc) are highly predictive for a 90-day mortality rate, particularly in the EIA+SRA+ group.

CONCLUSIONS

These results demonstrate that relative deficiency of plasma ADAMTS-13 activity in hospitalized patients suspected with HIT is common, which may contribute at least in part to the adverse outcomes in this patient population, particularly in those with true HIT.

Hemostasis and Fibrinolysis following Aneurysmal Subarachnoid Hemorrhage: A Systematic Review on Additional Knowledge from Dynamic Assays and Potential Treatment Targets

Mortality after aneurysmal subarachnoid hemorrhage (aSAH) is augmented by rebleeding and delayed cerebral ischemia (DCI). A range of assays evaluating the dynamic process of blood coagulation, from activation of clotting factors to fibrinolysis, has emerged and a comprehensive review of hemostasis and fibrinolysis following aSAH may reveal targets of treatment. We conducted a systematic review of existing literature assessing coagulation and fibrinolysis following aSAH, but prior to treatment. PubMed, Embase, and Web of Science were searched on November 18, 2020, without time boundaries. In total, 45 original studies were eventually incorporated into this systematic review, divided into studies presenting data only from conventional or quantitative assays (n = 22) and studies employing dynamic assays (n = 23). Data from conventional or quantitative assays indicated increased platelet activation, whereas dynamic assays detected platelet dysfunction possibly related to an increased risk of rebleeding. Secondary hemostasis was activated in conventional, quantitative, and dynamic assays and this was related to poor neurological outcome and mortality. Studies systematically investigating fibrinolysis were sparse. Measurements from conventional or quantitative assays, as well as dynamic fibrinolysis assays, revealed conflicting results with normal or increased lysis and changes were not associated with outcome. In conclusion, dynamic assays were able to detect reduced platelet function, not revealed by conventional or quantitative assays. Activation of secondary hemostasis was found in both dynamic and nondynamic assays, while changes in fibrinolysis were not convincingly demonstrable in either dynamic or conventional or quantitative assays. Hence, from a mechanistic point of view, desmopressin to prevent rebleeding and heparin to prevent DCI may hold potential as therapeutic options. As changes in fibrinolysis were not convincingly demonstrated and not related to outcome, the use of tranexamic acid prior to aneurysm closure is not supported by this review.

COVID-19 and Delayed Cerebral Ischemia-More in Common Than First Meets the Eye

Since the arrival of the global COVID-19 pandemic scientists around the world have been working to understand the pathological mechanisms resulting from infection. There has gradually been an understanding that COVID-19 triggers a widespread endotheliopathy and that this can result in a widespread thrombosis and in particular a microthrombosis. The mechanisms involved in the microthrombosis are not confined to infection and there is evidence that patients with aneurysmal sub-arachnoid haemorrhage (SAH) also suffer from an endotheliopathy and microthrombosis. In this article we attempt to shed light on similarities in the underlying processes involved in both diseases and suggest potential treatment options.

Relationships Among Circulating Levels of Hemostasis Inhibitors, Chemokines, Adhesion Molecules, and MRI Characteristics in Multiple Sclerosis

Background: Several studies suggested cross talk among components of hemostasis, inflammation, and immunity pathways in the pathogenesis, neurodegeneration, and occurrence of cerebral microbleeds (CMBs) in multiple sclerosis (MS).

Objectives: This study aimed to evaluate the combined contribution of the hemostasis inhibitor protein C (PC) and chemokine C-C motif ligand 18 (CCL18) levels to brain atrophy in MS and to identify disease-relevant correlations among circulating levels of hemostasis inhibitors, chemokines, and adhesion molecules, particularly in CMB occurrence in MS.

Methods: Plasma levels of hemostasis inhibitors (ADAMTS13, PC, and PAI1), CCL18, and soluble adhesion molecules (sNCAM, sICAM1, sVCAM1, and sVAP1) were evaluated by multiplex in 138 MS patients [85 relapsing-remitting (RR-MS) and 53 progressive (P-MS)] and 42 healthy individuals (HI) who underwent 3-T MRI exams. Association of protein levels with MRI outcomes was performed by regression analysis. Correlations among protein levels were assessed by partial correlation and Pearson's correlation.

Results: In all patients, regression analysis showed that higher PC levels were associated with lower brain volumes, including the brain parenchyma (p = 0.002), gray matter (p < 0.001), cortex (p = 0.001), deep gray matter (p = 0.001), and thalamus (p = 0.001). These associations were detectable in RR-MS but not in P-MS patients. Higher CCL18 levels were associated with higher T2-lesion volumes in all MS patients (p = 0.03) and in the P-MS (p = 0.003). In the P-MS, higher CCL18 levels were also associated with lower volumes of the gray matter (p = 0.024), cortex (p = 0.043), deep gray matter (p = 0.029), and thalamus (p = 0.022). PC-CCL18 and CCL18-PAI1 levels were positively correlated in both MS and HI, PC–sVAP1 and PAI1–sVCAM1 only in MS, and PC–sICAM1 and PC–sNCAM only in HI. In MS patients with CMBs (n = 12), CCL18–PAI1 and PAI1–sVCAM1 levels were better correlated than those in MS patients without CMBs, and a novel ADAMTS13–sVAP1 level correlation (r = 0.78, p = 0.003) was observed.

Conclusions: Differences between clinical phenotype groups in association of PC and CCL18 circulating levels with MRI outcomes might be related to different aspects of neurodegeneration. Disease-related pathway dysregulation is supported by several protein level correlation differences between MS patients and HI. The integrated analysis of plasma proteins and MRI measures provide evidence for new relationships among hemostasis, inflammation, and immunity pathways, relevant for MS and for the occurrence of CMBs.

Microvascular platelet aggregation and thrombosis after subarachnoid hemorrhage: A review and synthesis

Delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) has been associated with numerous pathophysiological sequelae, including large artery vasospasm and microvascular thrombosis. The focus of this review is to provide an overview of experimental animal model studies and human autopsy studies that explore the temporal-spatial characterization and mechanism of microvascular platelet aggregation and thrombosis following SAH, as well as to critically assess experimental studies and clinical trials highlighting preventative therapeutic options against this highly morbid pathophysiological process. Upon review of the literature, we discovered that microvascular platelet aggregation and thrombosis occur after experimental SAH across multiple species and SAH induction techniques in a similar time frame to other components of DCI, occurring in the cerebral cortex and hippocampus across both hemispheres. We discuss the relationship of these findings to human autopsy studies. In the final section of this review, we highlight the important therapeutic options for targeting microvascular platelet aggregation and thrombosis, and emphasize why therapeutic targeting of this neurovascular pathology may improve patient care. We encourage ongoing research into the pathophysiology of SAH and DCI, especially in regard to microvascular platelet aggregation and thrombosis and the translation to randomized clinical trials.

Biospecimens and Molecular and Cellular Biomarkers in Aneurysmal Subarachnoid Hemorrhage Studies: Common Data Elements and Standard Reporting Recommendations

INTRODUCTION

Development of clinical biomarkers to guide therapy is an important unmet need in aneurysmal subarachnoid hemorrhage (SAH). A wide spectrum of plausible biomarkers has been reported for SAH, but none have been validated due to significant variabilities in study design, methodology, laboratory techniques, and outcome endpoints.

METHODS

A systematic review of SAH biomarkers was performed per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The panel's recommendations focused on harmonization of (1) target cellular and molecular biomarkers for future investigation in SAH, (2) standardization of best-practice procedures in biospecimen and biomarker studies, and (3) experimental method reporting requirements to facilitate meta-analyses and future validation of putative biomarkers.

RESULTS

No cellular or molecular biomarker has been validated for inclusion as "core" recommendation. Fifty-four studies met inclusion criteria and generated 33 supplemental and emerging biomarker targets. Core recommendations include best-practice protocols for biospecimen collection and handling as well as standardized reporting guidelines to capture the heterogeneity and variabilities in experimental methodologies and biomarker analyses platforms.

CONCLUSION

Significant variabilities in study design, methodology, laboratory techniques, and outcome endpoints exist in SAH biomarker studies and present significant barriers toward validation and translation of putative biomarkers to clinical use. Adaptation of common data elements, recommended biospecimen protocols, and reporting guidelines will reduce heterogeneity and facilitate future meta-analyses and development of validated clinical biomarkers in SAH.

Apolipoprotein B100/Low-Density Lipoprotein Regulates Proteolysis and Functions of von Willebrand Factor under Arterial Shear

BACKGROUND

 Proteolytic cleavage of von Willebrand factor (VWF) by a plasma a disintegrin and metalloproteinase with a thrombospondin type 1 motifs, member 13 (ADAMTS13) is regulated by shear stress and binding of coagulation factor VIII, platelets or platelet glycoprotein 1b, and ristocetin to VWF.

OBJECTIVE

 Current study aims to identify novel VWF binding partners that may modulate VWF functions under physiological conditions.

METHODS

 A deoxyribonucleic acid aptamer-based affinity purification of VWF, followed by tandem mass spectrometry, functional, and binding assays was employed.

RESULTS

 Apolipoprotein B100/low-density lipoprotein (apoB100/LDL) was identified as a novel VWF-binding partner. Purified apoB100/LDL was able to accelerate the proteolytic cleavage of VWF by ADAMTS13 under shear in a concentration-dependent manner. This rate-enhancing activity was dramatically reduced when apoB100/LDL was oxidized. More interestingly, the oxidized apoB100/LDL appeared to compete with native apoB100/LDL for its enhancing activity on VWF proteolysis under shear. As a control, a purified apoA1/high-density lipoprotein (apoA1/HDL) or apoB48 exhibited a minimal or no activity enhancing VWF proteolysis by ADAMTS13 under the same conditions. Both VWF and ADAMTS13 were able to bind native or oxidized apoB100/LDL with high affinities. No binding interaction was detected between VWF (or ADAMTS13) and apoA1/HDL (or apoB48). Moreover, apoB100/LDL but not its oxidized products inhibited the adhesion of platelets to ultra large VWF released from endothelial cells under flow. Finally, significantly reduced ratios of high to low molecular weight of VWF multimers with increased levels of plasma VWF antigen were detected in LDLR-/- mice fed with high cholesterol diet.

CONCLUSION

 These results indicate that apoB100/LDL may be a novel physiological regulator for ADAMTS13-VWF functions.

Matrix metalloproteinases and ADAMs in stroke

Stroke is a leading cause of death and disability worldwide. However, after years of in-depth research, the pathophysiology of stroke is still not fully understood. Increasing evidence shows that matrix metalloproteinases (MMPs) and "a disintegrin and metalloproteinase" (ADAMs) participate in the neuro-inflammatory cascade that is triggered during stroke but also in recovery phases of the disease. This review covers the involvement of these proteins in brain injury following cerebral ischemia which has been widely studied in recent years, with efforts to modulate this group of proteins in neuroprotective therapies, together with their implication in neurorepair mechanisms. Moreover, the review also discusses the role of these proteins in specific forms of neurovascular disease, such as small vessel diseases and intracerebral hemorrhage. Finally, the potential use of MMPs and ADAMs as guiding biomarkers of brain injury and repair for decision-making in cases of stroke is also discussed.

Systemic inflammation in hemorrhagic strokes - A novel neurological sign and therapeutic target?

Growing evidences suggest that stroke is a systemic disease affecting many organ systems beyond the brain. Stroke-related systemic inflammatory response and immune dysregulations may play an important role in brain injury, recovery, and stroke outcome. The two main phenomena in stroke-related peripheral immune dysregulations are systemic inflammation and post-stroke immunosuppression. There is emerging evidence suggesting that the spleen contracts following ischemic stroke, activates peripheral immune response and this may further potentiate brain injury. Whether similar brain-immune crosstalk occurs in hemorrhagic strokes such as intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) is not established. In this review, we systematically examined animal and human evidence to date on peripheral immune responses associated with hemorrhagic strokes. Specifically, we reviewed the impact of clinical systemic inflammatory response syndrome (SIRS), inflammation- and immune-associated biomarkers, the brain-spleen interaction, and cellular mediators of peripheral immune responses to ICH and SAH including regulatory T cells (Tregs). While there is growing data suggesting that peripheral immune dysregulation following hemorrhagic strokes may be important in brain injury pathogenesis and outcome, details of this brain-immune system cross-talk remain insufficiently understood. This is an important unmet scientific need that may lead to novel therapeutic strategies in this highly morbid condition.

Clinical factors and biomarkers predict outcome in patients with immune-mediated thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura is characterized by severe thrombocytopenia and microangiopathic hemolytic anemia. It is primarily caused by immunoglobin G type autoantibodies against ADAMTS13, a plasma metalloprotease that cleaves von Willebrand factor. However, reliable markers predictive of patient outcomes are yet to be identified. Seventy-three unique patients with a confirmed diagnosis of immune-mediated thrombotic thrombocytopenic purpura between April 2006 and December 2017 were enrolled from the Univeristy of Alabama at Birmingham Medical Center. Clinical information, laboratory values, and a panel of special biomarkers were collected and/or determined. The results demonstrated that the biomarkers associated with endothelial injury (e.g., von Willebrand factor antigen and collagen-binding activity), acute inflammation (e.g., human neutrophil peptides 1-3 and histone/deoxyribonucleic acid complexes), and activation of the complement alternative pathway (e.g., factors Bb and iC3b) were all significantly increased in patients with acute immune-mediated thrombotic thrombocytopenic purpura compared to those in the healthy controls. Moreover, failure to normalize platelet counts within 7 days or failure to markedly reduce serum lactate dehydrogenase by day 5, low total serum protein or albumin, and high serum troponin levels were also predictive of mortality, as were the prolonged activated partial thromboplastin time, high fibrinogen, and elevated serum lactate dehydrogenase, Bb, and sC5b-9 on admission. These results may help to stratify patients for more intensive management. The findings may also provide a framework for future multicenter studies to identify valuable prognostic markers for immune-mediated thrombotic thrombocytopenic purpura.

Relative Deficiency of Plasma A Disintegrin and Metalloprotease with Thrombospondin Type 1 Repeats 13 Activity and Elevation of Human Neutrophil Peptides in Patients with Traumatic Brain Injury

Traumatic microvascular injury (tMVI) is a universal endophenotype of traumatic brain injury (TBI) that is responsible for significant neurological morbidity and mortality. The mechanism underlying tMVI is not fully understood. The present study aims to determine plasma levels of von Willebrand factor (VWF), a disintegrin and metalloprotease with thrombospondin type 1 repeats (ADAMTS) 13 activity, and human neutrophil peptides (HNP) 1-3 and to correlate these biomarkers with functional outcomes after moderate-severe TBI. Thirty-one consecutive TBI patients (Glasgow Coma Scale [GCS] range, 3-12) were enrolled into the study between February 2010 and November 2014. Blood samples were collected on 0, 1, 2, 3, and 5 days after admission and analyzed for plasma levels of VWF antigen (VWFAg), collagen-binding activity (VWFAc), ADAMTS13 activity, and HNP1-3 proteins. Mean values of plasma VWFAg, VWFAc, and HNP1-3 were significantly increased in TBI patients compared to those in healthy controls (n = 30). Conversely, mean plasma values of ADAMTS13 activity in TBI patients were significantly decreased during the first 2 days after admission. This resulted in a dramatic reduction in the ratio of ADAMTS13 activity to VWFAg or ADAMTS13 to VWFAc in all 5 post-TBI days. Cluster analysis demonstrated that high median plasma levels of VWFAg and HNP1-3 were observed in the cluster with a high mortality rate. These results demonstrate that a relative deficiency of plasma ADAMTS13 activity, resulting from activation of neutrophils and endothelium, may contribute to the formation of microvascular thrombosis and mortality after moderate-severe TBI.

Role of von Willebrand factor and ADAMTS-13 in early brain injury after experimental subarachnoid hemorrhage

Essentials von Willebrand Factor (VWF) and ADAMTS13 may affect early injury after subarachnoid hemorrhage (SAH). Early brain injury was assessed in VWF-/- , ADAMTS13-/- and recombinant (r) ADAMTS13 treated mice. VWF-/- and rADAMTS13 treated mice had less brain injury than ADAMTS13-/- and wild-type mice. Early administration of rADAMTS13 may improve outcome after SAH by reducing early brain injury.

SUMMARY

Background Early brain injury is an important determinant of poor functional outcome and case fatality after aneurysmal subarachnoid hemorrhage (SAH), and is associated with early platelet aggregation. No treatment exists for early brain injury after SAH. We investigated whether von Willebrand factor (VWF) is involved in the pathogenesis of early brain injury, and whether ultra-early treatment with recombinant ADAMTS-13 (rADAMTS-13) reduces early brain injury after experimental SAH. Methods Experimental SAH in mice was induced by prechiasmatic injection of non-anticoagulated blood from a littermate. The following experimental SAH groups were investigated: C57BL/6J control (n = 21), VWF-/- (n = 25), ADAMTS-13-/- (n = 23), and C57BL/6J treated with rADAMTS-13 (n = 26). Mice were killed at 2 h after SAH. Primary outcome measures were microglial activation (IBA-1 surface area) and neuronal injury (number of cleaved caspase-3-positive neurons). Results As compared with controls, microglial activation was decreased in VWF-/- mice (mean difference of - 20.0%, 95% confidence interval [CI] - 4.0% to - 38.6%), increased in ADAMTS-13-/- mice (mean difference of + 34.0%, 95% CI 16.2-51.7%), and decreased in rADAMTS-13-treated mice (mean difference of - 22.1%, 95% CI - 3.4% to - 39.1%). As compared with controls (185 neurons, interquartile range [IQR] 133-353), neuronal injury in the cerebral cortex was decreased in VWF-/- mice (63 neurons, IQR 25-78), not changed in ADAMTS-13-/- mice (53 neurons, IQR 26-221), and reduced in rADAMTS-13-treated mice (45 neurons, IQR 9-115). Conclusions Our findings suggest that VWF is involved in the pathogenesis of early brain injury, and support the further study of rADAMTS-13 as a treatment option for early brain injury after SAH.

Low Plasma ADAMTS13 Activity Is Associated with Coagulopathy, Endothelial Cell Damage and Mortality after Severe Paediatric Trauma

Decrease of plasma activity of ADAMTS13, a metalloenzyme that cleaves von Willebrand factor (VWF) and prevents adhesion and aggregation of platelets, has been reported early after onset of systemic inflammation resulting from infections and after severe trauma. Here, we determined whether trauma-induced systemic (sterile) inflammation would be associated with a reduction of plasma ADAMTS13 activity in paediatric patients and its association with disease severity and outcome. Paediatric patients (n = 106) with severe trauma at a level 1 paediatric trauma centre between 2014 and 2016 were prospectively enrolled. Blood samples were collected upon arrival and at 24 hours and analysed for plasma levels of ADAMTS13 activity, VWF antigen, collagen binding activity, human neutrophil peptides (HNP) 1-3, coagulation abnormalities, endothelial glycocalyx damage and clinical outcome. Plasma samples were also collected for similar measurements from 52 healthy paediatric controls who underwent elective minor surgery. The median age of patients was 9 years with 81% sustaining blunt trauma. The median injury severity score was 22 and the mortality rate was 11%. Plasma levels of ADAMTS13 activity were significantly lower and plasma levels of VWF antigen and HNP 1-3 proteins were significantly higher for paediatric trauma patients on admission and at 24 hours when compared with controls. Finally, the lowest plasma ADAMTS13 activity was found in patients who died from their injuries. We conclude that relative plasma deficiency of ADAMTS13 activity may be associated with more severe traumatic injury, significant endothelial glycocalyx damage, coagulation abnormalities and mortality after severe trauma in paediatric patients.