Unconjugated bilirubin inhibits proteolytic cleavage of von Willebrand factor by ADAMTS13 protease

Unconjugated bilirubin and its derivative ameliorate IMQ-induced psoriasis-like skin inflammation in mice by inhibiting MMP9 and MAPK pathway

Psoriasis is a chronic immune-mediated inflammatory skin disease that involves dysregulated proliferation of keratinocytes. Psoriatic skin lesions are characterized by redness, thickness, and scaling. The interleukin axis of IL-23/IL-17 is critically involved in the development of human psoriasis. Imiquimod (IMQ), an agonist of TLR7 is known to induce psoriatic-like skin inflammation in mice. The topical application of IMQ induces systemic inflammation with increased proinflammatory cytokines in serum and secondary lymphoid organs. Further, matrix metalloproteases (MMPs) have been implicated in the pathophysiology of psoriatic-like skin inflammation. The increased MMP9 activity and gene expression of proinflammatory cytokines in IMQ-induced psoriatic skin is mediated by the activation of the MAPK pathway. Moreover, the increased expression of neutrophil-specific chemokines confirmed the infiltration of neutrophils at the site of psoriatic skin inflammation. In contrast, expression of IL-10, an anti-inflammatory cytokine gene expression is reduced in IMQ-treated mice skin. Topical application of unconjugated bilirubin (UCB) and its derivative dimethyl ester of bilirubin (BD1) on IMQ-induced psoriatic mice skin significantly mitigated the symptoms of psoriasis by inhibiting the activity of MMP9. Further, UCB and BD1 reduced neutrophil infiltration as evidenced by decreased myeloperoxidase (MPO) activity and reduced gene expression of proinflammatory cytokines, and neutrophil-specific chemokines. Apart from these modulations UCB and BD1 reduced MAPK phosphorylation and upregulated anti-inflammatory cytokines. To conclude, UCB and BD1 immunomodulated the psoriatic skin inflammation induced by IMQ in mice by inhibiting neutrophil mediated MMP9, decreased proinflammatory cytokines gene expression and modulating the MAPK pathway.

ADAMTS13 Biomarkers in Management of Immune Thrombotic Thrombocytopenic Purpura

CONTEXT.—

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare but potentially fatal blood disorder resulting from acquired deficiency of plasma ADAMTS13, a metalloprotease that cleaves endothelium-derived ultralarge von Willebrand factor. Standard of care for iTTP including therapeutic plasma exchange, caplacizumab, and immunosuppressives, known as triple therapy, has led to a significant reduction in the disease-related mortality rate. The first International Society of Thrombosis and Haemostasis TTP guideline stresses the importance of having plasma ADAMTS13 activity testing in the algorithm for diagnosis and management of iTTP. However, the predictive role of assessing plasma ADAMTS13 activity and inhibitors or other ADAMTS13-related parameters in patients with acute iTTP and during remission has not been systematically evaluated.

OBJECTIVE.—

To review and assess the predictive values of testing plasma ADAMTS13 activity, antigen, and inhibitors or anti-ADAMTS13 immunoglobulin G at various stages of disease in outcomes of iTTP.

DATA SOURCES.—

Peer-reviewed publications and personal experience.

CONCLUSIONS.—

We conclude that assessing ADAMTS13 biomarkers is not only essential for establishing the initial diagnosis, but also crucial for risk stratification and the early detection of disease recurrence. This may guide therapeutic interventions during acute episodes and for long-term follow-up of iTTP patients.

Effect of hydroxyurea therapy on intravascular hemolysis and endothelial dysfunction markers in sickle cell anemia patients

Intravascular hemolysis (IH) contributes to the development of endothelial dysfunction (ED) in sickle cell anemia (SCA), and the effects of hydroxyurea (HU, the only approved drug that decreases the frequency and severity of vaso-oclussive crises) on IH and ED in SCA remain unclear. We evaluated and compared the markers of IH among steady-state adult Brazilians with SCA and HbAA individuals. Overall, this cross-sectional study enrolled 30 SCA patients not receiving HU therapy (HbSS), 25 SCA patients receiving HU therapy (HbSS_HU), and 32 HbAA volunteers (HbAA). The IH markers evaluated were serum Lactate Dehydrogenase (LDH), total heme, plasma hemoglobin (pHb), and soluble CD163 (sCD163). The ED markers analyzed were plasma von Willebrand factor (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo) levels, antigen of VWF-cleaving protease (ADAMTS13:Ag), thrombospondin-1, endothelin-1 levels, and ADAMTS13 Activity (ADAMTS13:Act). The levels of VWF:Ag, VWF:RCo, total heme, thrombospondin-1, and endothelin-1 were significantly higher in SCA patients (HbSS and HbSS_HU) compared to HbAA individuals. Also, pHb, LDH, and thrombospondin-1 levels were significantly higher in the HbSS group than in the HbSS_HU group. Contrarily, the levels of sCD163, ADAMTS13:Ag, and ADAMTS13:Act were significantly lower in both groups of SCA patients than HbAA controls, and ADAMTS13:Act levels were significantly lower in HbSS compared to HbSS_HU patients. The higher ADAMTS13 activity levels in those on HU therapy may be attributed to lower pHb and thrombospondin-1 levels as previously shown by in vitro studies that thrombospondin-1 and pHb are bound to VWF. Thus, VWF is restrained from ADAMTS13 activity and cleavage.

It takes two to thrombosis: Hemolysis and complement

Thromboembolic events represent the most common complication of hemolytic anemias characterized by complement-mediated hemolysis such as paroxysmal nocturnal hemoglobinuria and autoimmune hemolytic anemia. Similarly, atypical hemolytic uremic syndrome is characterized by hemolysis and thrombotic abnormalities. The main player in the development of thrombosis in hemolytic diseases is suggested to be the complement system. However, the release of extracellular hemoglobin and heme by hemolysis itself can also drive procoagulant responses. Both, complement activation and hemolysis promote the activation of neutrophils resulting in the formation of neutrophil extracellular traps and induce inflammation and vascular damage which all together might (synergistically) lead to hypercoagulability. In this review we aim to summarize the current knowledge on the role of complement activation and hemolysis in the onset of thrombosis in hemolytic diseases. This review will discuss the interplay between different biological systems and neutrophil activation contributing to the pathogenesis of thrombosis. Finally, we will combine this fundamental knowledge and address the pathophysiology of hemolysis in prototypical complement-driven diseases.

Current use of rivaroxaban in elderly patients with venous thromboembolism (VTE)

Venous thromboembolism (VTE), which is characterized by pulmonary embolism and deep vein thrombosis, has become a serious public concern. Notably, over half of the patients with VTE are over 70 years of age, but elderly patients are at high risk of anti-coagulation and bleeding, which increase with age. Moreover, risk factors and frailty also show a difference between elderly patients and ordinary patients diagnosed with VTE. Rivaroxaban is a direct inhibitor of activated factor Xa and has the advantage of predictable pharmacodynamics and pharmacokinetics, no coagulation monitoring, and few drug interactions. As a first-line therapy for VTE, this drug is more advantageous than traditional therapy and exhibits good efficacy and safety for ordinary patients. However, the effectiveness and safety of rivaroxaban in elderly patients have not been fully elucidated. This article reviewed the use of rivaroxaban in elderly patients, including drug interactions, monitoring, reversal agents of rivaroxaban, and the use of small dosages of rivaroxaban in elderly patients.

Diagnosis and follow-up of thrombotic thrombocytopenic purpura with an automated chemiluminescent ADAMTS13 activity immunoassay

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic microangiopathy (TMA) caused by a severe functional deficiency in ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type I repeats-13), the specific von Willebrand factor (VWF) cleaving protease. ADAMTS13 activity is essential to diagnose TTP but remains challenging to assess, as reference ADAMTS13 activity assays are manual and time consuming. Current techniques also lack robustness in low detectable ADAMTS13 activity range, which could prove problematic for therapy-driven monitoring.

OBJECTIVES

The HemosIL AcuStar ADAMTS13 activity assay is a fast, automated chemiluminescent assay, the performance of which remains to be evaluated prospectively on very large cohorts of patients with TMA and in real-life conditions.

PATIENTS AND METHODS

Our study was conducted over two successive sequences: a retrospective evaluation followed by a "real-life" prospective evaluation. Overall, we evaluated the HemosIL AcuStar ADAMTS13 activity assay on 539 citrated plasma samples. We extensively studied linearity, limit of detection, contamination, intra-assay and interassay precisions with a specific focus on levels < 25 IU/dL. Diagnostic performances for the detection of < 10 IU/dL ADAMTS13 activity and overall method comparison were conducted with the fluorescence resonance energy transfer (FRETS)-VWF73 assay as the reference method.

RESULTS

Technical performance proved excellent. Robustness in low detectable ADAMTS13 activity range was good, potentially qualifying this assay for therapy-driven monitoring. Comparison with the FRETS-VWF73 assay was satisfactory (r 2 = .83, P < .0001) as were the diagnostic performances for acute-phase TTP (specificity, 99.7%; positive predictive value, 99.2%).

CONCLUSION

The HemosIL AcuStar ADAMTS13 activity assay is a fast, reliable, automated technique well adapted as a first-line ADAMTS13 activity assay for TTP diagnosis and follow-up.

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.

Speed Modulation of the HeartWare HVAD to Assess In Vitro Hemocompatibility of Pulsatile and Continuous Flow Regimes in a Rotary Blood Pump

Although rotary blood pumps (RBPs) sustain life, blood exposure to continuous supra-physiological shear stress induces adverse effects (e.g., thromboembolism); thus, pulsatile flow in RBPs represents a potential solution. The present study introduced pulsatile flow to the HeartWare HVAD using a custom-built controller and compared hemocompatibility biomarkers (i.e., platelet aggregation, concentrations for ADAMTS13, von Willebrand factor (vWf), and free-hemoglobin in plasma (pfHb), red blood cell (RBC) deformability, and RBC-nitric oxide synthase (NOS) activity) between continuous and pulsatile flow in a blood circulation loop over 5 h. The HeartWare HVAD was operated using a custom-built controller, at continuous speed (3282 rev/min) or in a pulsatile mode (mean speed = 3273 rev/min, amplitude = 430 rev/min, frequency = 1 Hz) to generate a blood flow rate of 5.0 L/min, HVAD differential pressure of 90 mm Hg for continuous flow and 92 mm Hg for pulsatile flow, and systolic and diastolic pressures of 121/80 mm Hg. For both flow regimes, the current study found; (i) ADP- and collagen-induced platelet aggregation, and ADAMTS13 concentration significantly decreased after 5 h (P < 0.01; P < 0.05), (ii) ristocetin-induced platelet aggregation significantly increased after 45 min (P < 0.05), (iii) vWf concentration did not significantly differ at any time point, (iv) pfHb significantly increased after 5 h (P < 0.01), (v) RBC deformability improved during the continuous flow regime (P < 0.05) but not during pulsatile flow, and (vi) RBC-NOS activity significantly increased during continuous flow (15 min), and pulsatile flow (5 h; P < 0.05). The current study demonstrated: (i) speed modulation does not improve hemocompatibility of the HeartWare HVAD based on no observable differences being detected for routine biomarkers, and (ii) the time-course for increased RBC-NOS activity observed during continuous flow may have improved RBC deformability.

Conflicting effects of atazanavir therapy on atherosclerotic risk factors in stable HIV patients: A randomized trial of regimen switch to atazanavir

Bilirubin acts as a potent endogenous antioxidant, with higher concentrations associated with lower rates of CVD; the antiretroviral drug atazanavir (ATV) increases bilirubin levels but may also increase von Willebrand factor levels. We tested the hypothesis that increasing endogenous bilirubin using ATV would improve cardiometabolic risk factors and vascular function in older patients with HIV. Ninety participants were enrolled in two study protocols. In protocol 1, we evaluated markers of inflammation, thrombosis, and conduit artery endothelial function in subjects on non-ATV containing regimens. Participants were randomly assigned to continue baseline treatment or switch to an ATV-based regimen. Measurements were made at baseline and 28 days. In the protocol 2, we enrolled 30 subjects who received atazanavir for more than one year and were compared to the aim 1 protocol subjects at baseline. 60 subjects were enrolled in the first protocol (mean age 53, +/- 6 years), with 31 randomized to ATV and 29 continuing baseline treatment. Atazanavir significantly increased serum total bilirubin levels (p<0.001) and acutely but not chronically plasma total antioxidant capacity (p<0.001). An increase in von Willebrand Factor (p<0.001) and reduction in hs-CRP (p = 0.034) were noted. No changes were seen in either flow-mediated endothelium-dependent or vasodilation. In cross-sectional analysis (second protocol), similar findings were seen in the baseline attributes of non-atazanavir-based and long-term atazanavir users. Increasing serum bilirubin levels with atazanavir in subjects with HIV reduces hs-CRP, temporarily reduces oxidative stress, but increases von Willebrand Factor. Atazanavir does not improve endothelial function of conduit arteries.

Trial registration: ClinicalTrials.gov NCT03019783.

ADAMTS13 test and/or PLASMIC clinical score in management of acquired thrombotic thrombocytopenic purpura: a cost-effective analysis

BACKGROUND

The ADAMTS13 test distinguishes thrombotic thrombocytopenic purpura (TTP) from other thrombotic microangiopathies (TMAs). The PLASMIC score helps determine the pretest probability of ADAMTS13 deficiency. Due to inherent limitations of both tests, and potential adverse effects and cost of unnecessary treatments, we performed a cost-effectiveness analysis (CEA) investigating the benefits of incorporating an in-hospital ADAMTS13 test and/or PLASMIC score into our clinical practice.

STUDY DESIGN AND METHODS

A CEA model was created to compare four scenarios for patients with TMAs, utilizing either an in-house or a send-out ADAMTS13 assay with or without prior risk stratification using PLASMIC scoring. Model variables, including probabilities and costs, were gathered from the medical literature, except for the ADAMTS13 send-out and in-house tests, which were obtained from our institutional data.

RESULTS

If only the cost is considered, in-house ADAMTS13 test for patients with intermediate- to high-risk PLASMIC score is the least expensive option ($4,732/patient). If effectiveness is assessed as measured by the number of averted deaths, send-out ADAMTS13 test is the most effective. Considering the cost/effectiveness ratio, the in-house ADAMTS13 test in patients with intermediate- to high-risk PLASMIC score is the best option, followed by the in-house ADAMTS13 test without the PLASMIC score.

CONCLUSIONS

In patients with clinical presentations of TMAs, having an in-hospital ADAMTS13 test to promptly establish the diagnosis of TTP appears to be cost-effective. Utilizing the PLASMIC score further increases the cost-effectiveness of the in-house ADAMTS13 test. Our findings indicate the benefit of having a rapid and reliable in-house ADAMTS13 test, especially in the tertiary medical center.

Severe Hemolysis and Pulmonary Hypertension in a Neonate With Upshaw-Schulman Syndrome

Pulmonary involvement is extremely rare in thrombotic thrombocytopenic purpura. In this report, we present a girl patient with congenital thrombotic thrombocytopenic purpura, known as Upshaw-Schulman syndrome (USS), complicated with severe hemolysis and pulmonary hypertension (PH). The assay results of a disintegrin-like and metalloprotease with thrombospondin type 1 motifs 13 (ADAMTS13) activity measured by FRETS-VWF73 and ADAMTS13-act-ELISA were different. Hyperbilirubinemia (total bilirubin, 25.3 mg/dL) interfered strongly with the FRETS-VWF73 assay. Plasma levels of ADAMTS13 activity by act-ELISA were <0.5% of normal. The diagnosis of USS was confirmed by ADAMTS13 gene analysis, which showed compound heterozygous mutations of p.G139Vfs*17 and p.I673F. The p.G139Vfs*17 mutation was previously unreported, and its effect in splicing was confirmed by reverse transcription polymerase chain reaction. The patient received oxygen therapy for PH and exchange blood transfusion for severe hemolysis. The PH resolved without specific treatment. Based on these findings, the PH may have been caused by free hemoglobin that scavenged nitrogen oxide or platelet thrombi in the lungs caused by ADAMTS13 deficiency. Thus, severe PH can occur in neonatal patients with USS, and severe hemolysis might result in overestimation of ADAMTS 13 activity. Both possibilities are important for the diagnosis and management of USS.

Human neutrophil peptides inhibit cleavage of von Willebrand factor by ADAMTS13: a potential link of inflammation to TTP

Infection or inflammation may precede and trigger formation of microvascular thrombosis in patients with acquired thrombotic thrombocytopenic purpura (TTP). However, the mechanism underlying this clinical observation is not fully understood. Here, we show that human neutrophil peptides (HNPs) released from activated and degranulated neutrophils inhibit proteolytic cleavage of von Willebrand factor (VWF) by ADAMTS13 in a concentration-dependent manner. Half-maximal inhibitory concentrations of native HNPs toward ADAMTS13-mediated proteolysis of peptidyl VWF73 and multimeric VWF are 3.5 μM and 45 μM, respectively. Inhibitory activity of HNPs depends on the RRY motif that is shared by the spacer domain of ADAMTS13. Native HNPs bind to VWF73 (KD = 0.72 μM), soluble VWF (KD = 0.58 μM), and ultra-large VWF on endothelial cells. Enzyme-linked immunosorbent assay (ELISA) demonstrates markedly increased plasma HNPs1-3 in most patients with acquired autoimmune TTP at presentation (median, ∼170 ng/mL; range, 58-3570; n = 19) compared with healthy controls (median, ∼23 ng/mL; range, 6-44; n = 18) (P < .0001). Liquid chromatography plus tandem mass spectrometry (LC-MS/MS) reveals statistically significant increases of HNP1, HNP2, and HNP3 in patient samples (all P values <.001). There is a good correlation between measurement of HNPs1-3 by ELISA and by LC-MS/MS (Spearman ρ = 0.7932, P < .0001). Together, these results demonstrate that HNPs1-3 may be potent inhibitors of ADAMTS13 activity, likely by binding to the central A2 domain of VWF and physically blocking ADAMTS13 binding. Our findings may provide a novel link between inflammation/infection and the onset of microvascular thrombosis in acquired TTP and potentially other immune thrombotic disorders.

Heme: Modulator of Plasma Systems in Hemolytic Diseases

Hemolytic diseases such as sickle-cell disease, β-thalassemia, malaria, and autoimmune hemolytic anemia continue to present serious clinical hurdles. In these diseases, lysis of erythrocytes causes the release of hemoglobin and heme into plasma. Extracellular heme has strong proinflammatory potential and activates immune cells and endothelium, thus contributing to disease pathogenesis. Recent studies have revealed that heme can interfere with the function of plasma effector systems such as the coagulation and complement cascades, in addition to the activity of immunoglobulins. Any perturbation in such functions may have severe pathological consequences. In this review we analyze heme interactions with coagulation, complement, and immunoglobulins. Deciphering such interactions to better understand the complex pathogenesis of hemolytic diseases is pivotal.

Pulmonary platelet thrombi and vascular pathology in acute chest syndrome in patients with sickle cell disease

A growing body of evidence suggests a role for platelets in sickle cell disease (SCD). Despite the proinflammatory, occlusive nature of platelets, a role for platelets in acute chest syndrome (ACS), however, remains understudied. To provide evidence and potentially describe contributory factors for a putative link between ACS and platelets, we performed an autopsy study of 20 SCD cases—10 of whom died from ACS and 10 whose deaths were not ACS‐related. Pulmonary histopathology and case history were collected. We discovered that disseminated pulmonary platelet thrombi were present in 3 out of 10 of cases with ACS, but none of the matched cases without ACS. Those cases with detected thrombi were associated with significant deposition of endothelial vWF and detection of large vWF aggregates adhered to endothelium. Potential clinical risk factors were younger age and higher platelet count at presentation. However, we also noted a sharp and significant decline in platelet count prior to death in each case with platelet thrombi in the lungs. In this study, neither hydroxyurea use nor perimortem transfusion was associated with platelet thrombi. Surprisingly, in all cases, there was profound pulmonary artery remodeling with both thrombotic and proliferative pulmonary plexiform lesions. The severity of remodeling was not associated with a severe history of ACS, or hydroxyurea use, but was inversely correlated with age. We thus provide evidence of undocumented presence of platelet thrombi in cases of fatal ACS and describe clinical correlates. We also provide novel correlates of pulmonary remodeling in SCD. Am. J. Hematol. 91:173–178, 2016. © 2015 The Authors. American Journal of Hematology Published by Wiley Periodicals, Inc.

What's new in the diagnosis and pathophysiology of thrombotic thrombocytopenic purpura

Severe ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency causes thrombotic thrombocytopenic purpura (TTP), which is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and the absence of oliguric or anuric renal failure. However, some patients with this constellation of findings do not have ADAMTS13 deficiency, and some patients with ADAMTS13 deficiency have renal failure or relatively normal blood counts. Consequently, many investigators and clinicians have incorporated severe ADAMTS13 deficiency into the case definition of TTP. This change has facilitated the timely initiation of treatment for patients with atypical clinical features who otherwise would not be recognized as having TTP. Conversely, excluding severe ADAMTS13 deficiency focuses attention on the diagnosis and treatment of other causes of thrombotic microangiopathy that require different treatment. The rapid return of ADAMTS13 data is important to make the best use of this information.