Intracellular signaling triggered by antiphospholipid antibodies in platelets and endothelial cells: a pathway to targeted therapies

Does adding hydroxychloroquine to empiric treatment improve the live birth rate in refractory obstetrical antiphospholipid syndrome? A systematic review

PROBLEM

The current standard prevention of obstetric complications in patients with antiphospholipid antibody syndrome (APS) is the use of combination low-dose aspirin and low molecular weight heparin. However, 20-30% of women still experience refractory obstetrical APS. Hydroxychloroquine (HCQ) is an immunomodulatory agent that has been shown in laboratory studies to decrease thrombosis risk, support placentation, and minimize the destructive effects of antiphospholipid antibodies. The objective of this study was to evaluate the risk of pregnancy loss upon treatment with HCQ among women with refractory obstetrical APS.

METHOD OF STUDY

A systematic review was conducted according to PRISMA guidelines. Studies that evaluated the use of HCQ during pregnancy in women with primary APS were included. The primary outcomes of interest were live birth and pregnancy losses after treatment with HCQ.

RESULTS

Twelve studies met inclusion criteria. Three retrospective cohort studies demonstrated improved live birth rate, and four studies demonstrated a reduction in pregnancy loss rate. Two case reports also demonstrated a benefit in the use of HCQ compared to previous obstetrical outcomes.

CONCLUSIONS

Our findings suggest a significant benefit of HCQ in addition to aspirin and heparin for patients with APS to mitigate the risk of antiphospholipid antibody mediated obstetrical complications. Randomized controlled trials with standardized patient selection criteria need to be conducted to corroborate these findings.

Targeting thromboinflammation in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disease, where persistent presence of antiphospholipid antibodies (aPL) leads to thrombotic and obstetric complications. APS is a paradigmatic thromboinflammatory disease. Thromboinflammation is a pathophysiological mechanism coupling inflammation and thrombosis, which contributes to the pathophysiology of cardiovascular disease. APS can serve as a model to unravel mechanisms of thromboinflammation and the relationship between innate immune cells and thrombosis. Monocytes are activated by aPL into a proinflammatory and procoagulant phenotype, producing proinflammatory cytokines such as tumor necrosis factor α, interleukin 6, as well as tissue factor. Important cellular signaling pathways involved are the NF-κB-pathway, mammalian target of rapamycin (mTOR) signaling, and the NOD-, LRR-, and pyrin domain-containing protein 3 inflammasome. All of these may serve as future therapeutic targets. Neutrophils produce neutrophil extracellular traps in response to aPL, and this leads to thrombosis. Thrombosis in APS also stems from increased interaction of neutrophils with endothelial cells through P-selectin glycoprotein ligand-1. NETosis can be targeted not only with several experimental therapeutics, such as DNase, but also through the redirection of current therapies such as defibrotide and the antiplatelet agent dipyridamole. Activation of platelets by aPL leads to a procoagulant phenotype. Platelet-leukocyte interactions are increased, possibly mediated by increased levels of soluble P-selectin and soluble CD40-ligand. Platelet-directed future treatment options involve the inhibition of several platelet receptors activated by aPL, as well as mTOR inhibition. This review discusses mechanisms underlying thromboinflammation in APS that present targetable therapeutic options, some of which may be generalizable to other thromboinflammatory diseases.

Biologic Functions of Hydroxychloroquine in Disease: From COVID-19 to Cancer

Chloroquine (CQ) and Hydroxychloroquine (HCQ), initially utilized in the treatment of malaria, have now developed a long list of applications. Despite their clinical relevance, their mechanisms of action are not clearly defined. Major pathways by which these agents are proposed to function include alkalinization of lysosomes and endosomes, downregulation of C-X-C chemokine receptor type 4 (CXCR4) expression, high-mobility group box 1 protein (HMGB1) inhibition, alteration of intracellular calcium, and prevention of thrombus formation. However, there is conflicting data present in the literature. This is likely the result of the complex overlapping pathways between these mechanisms of action that have not previously been highlighted. In fact, prior research has focused on very specific portions of particular pathways without describing these in the context of the extensive CQ/HCQ literature. This review summarizes the detailed data regarding CQ/HCQ's mechanisms of action while also providing insight into the overarching themes. Furthermore, this review provides clinical context to the application of these diverse drugs including their role in malaria, autoimmune disorders, cardiovascular disease, thrombus formation, malignancies, and viral infections.

Efficacy of Hydroxychloroquine for Improving Pregnancy Outcomes in a Female with Systemic Lupus Erythematosus and Antiphospholipid Syndrome

The use of heparin and low-dose aspirin is the current conventional treatment for pregnant females with antiphospholipid syndrome (APS). However, there is no additional treatment recommended for cases where the standard treatment cannot prevent obstetric complications such as fetal loss and placental insufficiency. Recently, the addition of a novel antimalarial, hydroxychloroquine (HCQ), to the conventional treatment has shown the potential to prevent obstetric complications. Herein, we report a case in which the addition of HCQ improved adverse pregnancy outcomes in a pregnant female with systemic lupus erythematosus and aspirin-heparin-resistant APS.

Possible effects of chemokine-like factor-like MARVEL transmembrane domain-containing family on antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disease defined by thrombotic or obstetrical events and persistent antiphospholipid antibodies (aPLs). Chemokine-like factor-like MARVEL transmembrane domain-containing family (CMTM) is widely expressed in the immune system and may closely related to APS. This review aimed to systematically summarize the possible effects of CMTM on APS. Publications were collected from PubMed and Web of Science databases up to August 2020. CKLF, CKLFSF, CMTM, antiphospholipid syndrome, immune cells, and immune molecules were used as search criteria. Immune cells, including neutrophil, dendritic cells (DCs), T-cells, B-cells, and inflammatory cytokines, play an important role in the development of APS. Chemokine-like factor 1 (CKLF1) has a chemotactic effect on many cells and can affect the expression of inflammatory cytokines and adhesion molecules through the nuclear factor-kB (NF-kB) pathway or mitogen-activated protein kinase (MARK) pathway. CKLF1 can participate in the maturation of DCs, T lymphocyte activation, and the activation of neutrophils through the MAPK pathway. CMTM1 may act on Annexin A2 by regulating Ca²⁺ signaling. CMTM2 and CMTM6 are up-regulated in neutrophils of APS patients. Some CMTM family members influence the activation and accumulation of platelets. CMTM3 and CMTM7 are binding partners of B-cell linker protein (BLNK), thereby linking B cell receptor (BCR) and activating BLNK-mediated signal transduction in B cells. Moreover, CMTM3 and CMTM7 can act on DCs and B-1a cell development, respectively. CMTM may have potential effects on the development of APS by acting on immune cells and immune molecules. Thus, CMTM may act as a novel prognostic factor or immunomodulatory treatment option of APS.

COVID-19 and Its Implications for Thrombosis and Anticoagulation

Venous thromboembolism, occlusion of dialysis catheters, circuit thrombosis in extracorporeal membrane oxygenation (ECMO) devices, acute limb ischemia, and isolated strokes, all in the face of prophylactic and even therapeutic anticoagulation, are features of novel coronavirus disease 2019 (COVID-19) coagulopathy. It seems well established at this time that a COVID-19 patient deemed sick enough to be hospitalized, should receive at least prophylactic dose anticoagulation. However, should some hospitalized patients have dosage escalation to intermediate dose? Should some be considered for full-dose anticoagulation without a measurable thromboembolic event and how should that anticoagulation be monitored? Should patients receive postdischarge anticoagulation and with what medication and for how long? What thrombotic issues are related to the various medications being used to treat this coagulopathy? Is antiphospholipid antibody part of this syndrome? What is the significance of isolated ischemic stroke and limb ischemia in this disorder and how does this interface with the rest of the clinical and laboratory features of this disorder? The aims of this article are to explore these questions and interpret the available data based on the current evidence.

Methodological Issues and Controversies in COVID-19 Coagulopathy: A Tale of Two Storms

Venous thromboembolism, occlusion of dialysis catheters, circuit thrombosis in ECMO devices, all in the face of prophylactic and sometimes even therapeutic anti-coagulation, are frequent features of COVID-19 coagulopathy. The trials available to guide clinicians are methodologically limited. There are several unresolved controversies including 1) Should all hospitalized patients with COVID-19 receive prophylactic anti-coagulation? 2) Which patients should have their dosage escalated to intermediate dose? 3) Which patients should be considered for full-dose anti-coagulation even without a measurable thromboembolic event and how should that anti-coagulation be monitored? 4) Should patients receive post-discharge anti-coagulation? 5) What thrombotic issues are related to the various medications being used to treat this coagulopathy? 6) Is anti-phospholipid anti-body part of this syndrome? 7) How do the different treatments for this disease impact the coagulation issues? The aims of this article are to explore these questions and interpret the available data based on the current evidence.

Hydroxychloroquine may be beneficial in preeclampsia and recurrent miscarriage

Recurrent miscarriage (RM) and vasculoplacental disorders, such as preeclampsia (PE), affect women of childbearing age worldwide. Vascular endothelial dysfunction and immunological impairment are associated with both RM and PE. To date, there is no effective or optimal therapeutic approach for these conditions. Notably, aspirin use is only partially effective in the prevention of PE. Hydroxychloroquine (HCQ) has demonstrated beneficial effects on disease flares, pregnancy outcomes and cardiovascular impairment in systemic erythaematosus lupus (SLE) through its immunomodulatory, vasculoprotective and antithrombotic properties. Here, in the context of the underlying physiological dysregulation associated with PE and RM, the beneficial properties and potential therapeutic efficacy of HCQ are reviewed in anticipation of the results of current and future trials. Two related trials addressing RM in the absence of maternal autoimmune disease are ongoing. Other trials addressing pregnancy outcomes in the presence of maternal autoimmune disease are forthcoming. In this review, we hypothesise that the immunological and endothelial effects of HCQ may be beneficial in the context of PE and RM, regardless of the maternal autoimmune status.

Antiphospholipid Syndrome and the Neurologist: From Pathogenesis to Therapy

Antiphospholipid syndrome (APS) is an autoimmune antibody-mediated condition characterized by thrombotic events and/or pregnancy morbidity in association with persistent positivity to antiphospholipid antibodies (aPL). The nervous system is frequently affected, as intracranial vessels are the most frequent site of arterial pathology. Over the course of years, many other neurological conditions not included in the diagnostic criteria, have been associated with APS. The pathogenic mechanisms behind the syndrome are complex and not fully elucidated. aPL enhance thrombosis, interfering with different pathways. Nevertheless, ischemic injury is not always sufficient to explain clinical features of the syndrome and immune-mediated damage has been advocated. This may be particularly relevant in the context of neurological complications. The reason why only a subgroup of patients develop non-criteria nervous system disorders and what determines the clinical phenotype are questions that remain open. The double nature, thrombotic and immunologic, of APS is also reflected by therapeutic strategies. In this review we summarize known neurological manifestations of APS, revisiting pathogenesis and current treatment options.

Microthrombotic Renal Vascular Lesions Are Associated to Increased Renal Inflammatory Infiltration in Murine Lupus Nephritis

Background: Vascular microthrombotic lesions in lupus nephritis with or without antiphospholipid antibodies may relate to worse renal outcomes. Whether microthrombotic lesions are a consequence of renal inflammation or independently contribute to renal damage is unclear. Our aim was to investigate the relationship between microthrombotic renal vascular lesions and nephritis progression in MRL/lpr mice. Methods: MRL/lpr mice were analyzed for the presence of renal microvascular, glomerular and tubulointerstitial lesions and the effect of anti-aggregation (aspirin or clopidogrel) and dexamethasone on renal clinical and pathological manifestations was evaluated. Intravascular platelet aggregates (CD41), peri- (F4/80), and intraglomerular (Mac-2) macrophage infiltration, and C3 deposition were quantified by immunohistochemistry. Renal function was assessed by measuring proteinuria, and serum levels of creatinine and albumin. Anti-dsDNA and anti-cardiolipin antibodies, and thromboxane B2 levels were quantified by ELISA. Results: Frequency of microthrombotic renal lesions in MRL/lpr mice was high and was associated with immune-mediated renal damage. Proteinuria positively correlated with glomerular macrophage infiltration and was higher in mice with proliferative glomerular lesions. All mice had detectable anti-dsDNA and anti-cardiolipin IgG, regardless the presence of microthrombosis. Proteinuria and glomerular macrophage infiltration were significantly reduced in all treatment groups. Dexamethasone and platelet anti-aggregation similarly reduced glomerular damage and inflammation, but only platelet anti-aggregation significantly reduced anti-cardiolipin antibodies, renal complement deposition and thromboxane B2 levels. Conclusions: Platelet anti-aggregation reduced renal inflammatory damage, renal complement deposition, anti-cardiolipin antibodies, and thromboxane B2 levels and in MRL/lpr mice, suggesting that platelet activation has a pathogenic effect on immune-mediated nephritis. Our results point to MRL/lpr mice with lupus nephritis as an appropriate model to analyze the potential impact of anti-thrombotic intervention on renal inflammation.

Renal Involvement in Antiphospholipid Syndrome

Antiphospholipid syndrome is a complex autoimmune disease, characterized by the presence of vascular thrombosis, obstetric, hematologic, cutaneous, and cardiac manifestations. Renal disease in patients with antiphospholipid syndrome was not recognized in the first descriptions of the disease, but later on, the renal manifestations of the syndrome have been investigated widely. Renal manifestations of antiphospholipid syndrome conform a wide spectrum of diverse renal syndromes. Hypertension is one of the most frequent, but less commonly recognized renal alteration. It can be difficult to control as its origin is renovascular. Renal vascular thrombosis can be arterial or venous. Other alterations are renal infarction and vascular thrombosis in arterial territories. Venous thrombosis can be present in primary and secondary antiphospholipid syndrome; it presents with worsening of previous proteinuria or de novo nephrotic syndrome, hypertension and renal failure. Antiphospholipid syndrome nephropathy is a vascular disease that affects glomerular tuft, interstitial vessels, and peritubular vessels; histopathology characterizes the renal lesions as acute or chronic, the classic finding is thrombotic microangiopathy, that leads to fibrosis, tubule thyroidization, focal cortical atrophy, and glomerular sclerosis. Antiphospholipid syndrome nephropathy can also complicate patients with systemic lupus erythematosus, and there is vast information supporting the worse renal prognosis in this group of patients with the classic histopathologic lesions. Treatment consists of anticoagulation, as for other thrombotic manifestations of antiphospholipid syndrome. There is some evidence of glomerulonephritis as an isolated lesion in patients with antiphospholipid syndrome. The most frequently reported glomerulonephritis is membranous; with some reports suggesting that immunosuppressive treatment may be effective. Patients with end stage renal disease commonly are positive for antiphospholipid antibodies, but it is not clear what is the role of aPL in this setting. Patients with vascular access may have complications in the presence of antibodies so that anticoagulation is recommended. Patients ongoing renal transplant with persistent antiphospholipid antibody positivity may have early and late graft failure.

Antiphospholipid Syndrome: Role of Vascular Endothelial Cells and Implications for Risk Stratification and Targeted Therapeutics

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by venous thromboembolism, arterial thrombosis, and obstetric morbidities in the setting of persistently positive levels of antiphospholipid antibodies measured on 2 different occasions 12 weeks apart. Patients with APS are at increased risk for accelerated atherosclerosis, myocardial infarction, stroke, and valvular heart disease. Vascular endothelial cell dysfunction mediated by antiphospholipid antibodies and subsequent complement system activation play a cardinal role in APS pathogenesis. Improved understanding of their pathogenic function could help in the risk stratification of patients with APS and provide new molecular therapeutic targets.

Plasma Antiphospholipid Antibodies Effects on Activated Partial Thromboplastin Time Assays

BACKGROUND

Activated partial thromboplastin time (aPTT) assays can be affected by plasma antiphospholipid antibodies (aPLs), but the degree of the interference is not easy to predict. This study aimed to investigate the effects on aPTT assay results of different types and combinations of aPLs, including anti-β₂-glycoprotein I antibodies, anticardiolipin antibodies and lupus anticoagulant.

MATERIALS AND METHODS

We retrospectively collected clinical information and laboratory tests from aPL-positive patients. The potential influence of aPLs on aPTT assays was assessed.

RESULTS

The survey included 589 aPL-positive patients. No significant differences existed in basic characteristics such as sex, age, prothrombin time, fibrinogen and alanine aminotransferase among different cases with 1, 2 or 3 types of positive-aPL markers (P > 0.05). In 113 patients with abnormal aPTT values, multivariable linear regression analysis showed a significant correlation between an abnormal degree of aPTT values and dilute Russell viper venom time (dRVVT) or silica clotting time (SCT) with a correlation coefficient of 0.437 or 0.497 (P < 0.01), whereas age, anticardiolipin antibodies-immunoglobulin G, anticardiolipin antibodies-immunoglobulin M and anti-β₂-glycoprotein I antibodies were of no significance (P > 0.05). Among blood samples with 3 types of aPLs positivity, the rate of abnormal aPTT detection values was 55.3%, which was significantly higher than that observed in patients with negative, single-positive or double-positive aPL markers (P < 0.05). Patients with a moderate to strong dRVVT or SCT had a higher proportion of abnormal aPTT assays than did patients with a low dRVVT or SCT (P < 0.05).

CONCLUSIONS

When abnormal aPTT values are obtained, the influence of aPLs should be considered, especially in the presence of a moderate to strong dRVVT or SCT.

Emerging Therapies in Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a hypercoagulable state characterized by arterial and venous thromboses and pregnancy morbidity in the presence of antiphospholipid antibodies. Although warfarin remains the main therapeutic choice in APS, there is still concern about its efficacy, safety, and patient compliance. Patients with refractory APS to conventional therapy as well as patients with non-classical manifestations of APS may have alternative treatment approaches. APS pathogenesis has been further elucidated over the past years identifying new molecules as potential new treatment targets. This review summarizes available data from in vitro and animal models and clinical studies on the role of new potential treatment approaches including new oral anticoagulants and immunoregulatory agents: direct thrombin or factor Xa inhibitors, hydroxychloroquine, statins, B cell inhibition, complement inhibition, peptide therapy, nuclear factor κB and p38 mitogen-activated kinase inhibitors, defibrotide, abciximab, mTOR inhibitor, and other potential targets. Large multicenter prospective studies of well-characterized APS patients are needed to assess the efficacy and safety profile of these potential treatment alternatives.

Coagulation disorders and their cutaneous presentations: Pathophysiology

Hypercoagulable states are inherited or acquired predispositions to venous or arterial thromboses that are best understood in the context of the coagulation cascade. Dermatologists can play a critical role in diagnosing and treating patients with hypercoagulable states because cutaneous symptoms may be a presenting manifestation, thereby reducing morbidity and mortality related to these conditions. This review focuses on the epidemiology and pathophysiology of hypercoagulable states, while the accompanying article iterates the basic clinical features, diagnostic testing, and management of patients who have these conditions.

The efficacy of hydroxychloroquine in altering pregnancy outcome in women with antiphospholipid antibodies. Evidence and clinical judgment

The use of low-dose aspirin and heparinoids has improved the pregnancy outcome in obstetric antiphospholipid syndrome (APS). However, current treatment fails in 20-30% of APS pregnancies, raising the need to explore other treatments to improve obstetrical outcome. Hydroxychloroquine (HCQ) is widely used in patients with autoimmune diseases, mainly systemic lupus erythematous (SLE), due to its anti-inflammatory, anti-aggregant and immune-regulatory properties. Evidence from in vitro and animal models suggests a potential protective effect of HCQ in obstetric APS. Pending the availability of prospective trials, we aimed to systematically review the available evidence and to assess the clinical judgment of a panel of experts regarding the use of HCQ in improving pregnancy outcome in women with antiphospholipid antibodies (aPL). Clinical data on the ability of HCQ to improve pregnancy outcome in women with aPL are very limited in the available literature. Only one cohort study evaluating maternal and fetal outcome of pregnancy in patients with SLE who were exposed to HCQ was identified. Four of 14 (29%) treated with HCQ patients had pregnancy failure, compared with six of 24 (25%) of patients not treated with HCQ. However, the effect of HCQ was not adjusted for the use of other medications such as aspirin, heparins or steroids. Selected experts were contacted by e-mail and asked to review the summary of the evidence provided by the working group and to briefly answer each of the proposed questions. Overall, the panel of experts agreed that adding HCQ could be considered in selected cases or after failure of standard treatment with aspirin and a heparin agent. Specifically, the majority of experts considered adding HCQ in specific scenarios, such as women with previous thrombosis (either arterial and/or venous), and/or with previous ischaemic placenta-mediated complications. Prospective studies are necessary before the use of HCQ during pregnancy in women with aPL should be routinely recommended for clinical practice.

Immunotherapy in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a disorder characterized by the association of arterial or venous thrombosis and/or pregnancy morbidity with the presence of antiphospholipid antibodies (anticardiolipin antibodies, lupus anticoagulant antibodies, and/or anti-β2-glycoprotein I antibodies). Thrombosis is the major manifestation in patients with aPLs, but the spectrum of symptoms and signs associated with aPLs has broadened considerably, and other manifestations, such as thrombocytopenia, non-thrombotic neurological syndromes, psychiatric manifestations, livedo reticularis, skin ulcers, hemolytic anemia, pulmonary hypertension, cardiac valve abnormality, and atherosclerosis, have also been related to the presence of those antibodies. Several studies have contributed to uncovering the basis of antiphospholipid antibody pathogenicity, including the targeted cellular components, affected systems, involved receptors, intracellular pathways used, and the effector molecules that are altered in the process. Therapy for thrombosis traditionally has been based on long-term oral anticoagulation; however, bleeding complications and recurrence despite high-intensity anticoagulation can occur. The currently accepted first-line treatment for obstetric APS (OAPS) is low-dose aspirin plus prophylactic unfractionated or low-molecular-weight heparin (LMWH). However, in approximately 20% of OAPS cases, the final endpoint, i.e. a live birth, cannot be achieved. Based on all the data obtained in different research studies, new potential therapeutic approaches have been proposed, including the use of new oral anticoagulants, statins, hydroxychloroquine, coenzyme Q10, B-cell depletion, platelet and TF inhibitors, peptide therapy or complement inhibition among others. Current best practice in use of these treatments is discussed.

Identification of anti-moesin antibodies in the serums of patients with antiphospholipid syndrome

INTRODUCTION

The antiphospholipid syndrome (APS) is an acquired autoimmune disease characterized by recurrent vascular thrombosis and obstetric complications. However, the precise mechanisms by which the autoantibodies mediate disease remain to be elucidated. Moesin is an intracellular protein that links the cell membrane and cytoskeleton, mediating the formation of microtubules and cell adhesion sites as well as ruffling of the cell membrane, which is crucial for platelet activation.

MATERIALS AND METHODS

We screened the serums from patients with APS for the presence of anti-moesin antibodies (anti-moesin Abs) recognizing antigens derived from prokaryotic expression system, and investigated the effect of murine monoclonal anti-moesin Abs (anti-moesin mAbs) on platelet activation and aggregation by flow cytometry and platelet aggregation assay in vitro to study their potential pathogenic role in APS.

RESULTS

The presence of anti-amino (N)-terminal portion of moesin antibodies (anti-moesin-N Abs) was observed in 73% (73/100) patients with APS, which was significantly higher than anti-cardiolipin antibodies (aCL, 49%) and anti-β2 glycoprotein I antibodies (anti-β2GPI, 43%). Moreover, the elevated anti-moesin-N Abs levels significantly correlated with plasma levels of anti-β2GPI (rs=0.474, P<0.001) rather than aCL (P=0.203). The murine anti-moesin mAbs promote platelet activation and aggregation in vitro, which could be effectively neutralized by moesin-N.

CONCLUSIONS

In combination of the detection of aCL and anti-β2GPI, screening for the presence of anti-moesin-N Abs might has its value in facilitating the laboratory diagnosis of APS. The pathogenic role of anti-moesin-N Abs in the serums of APS patients needs to be further studied.

Antiphospholipid antibodies attenuate endothelial repair and promote neointima formation in mice

Background

Antiphospholipid syndrome patients have antiphospholipid antibodies (aPLs) that promote thrombosis, and they have increased cardiovascular disease risk. Although the basis for the thrombosis has been well delineated, it is not known why antiphospholipid syndrome patients also have an increased prevalence of nonthrombotic vascular occlusion. The aims of this work were to determine if aPLs directly promote medial hypertrophy or neointima formation in mice and to identify the underlying mechanisms.

Methods and Results

Medial hypertrophy and neointima formation invoked by carotid artery endothelial denudation were evaluated in mice administered normal human IgG or aPLs. While aPLs had no effect on medial hypertrophy, they caused exaggerated neointima development. This was related to an aPL‐induced impairment in reendothelialization post denudation, and scratch assays in cell culture revealed that there are direct effects of aPLs on endothelium that retard cell migration. Further experiments showed that aPL antagonism of endothelial migration and repair is mediated by antibody recognition of β2‐glycoprotein I, apolipoprotein E receptor 2, and a decline in bioavailable NO. Consistent with these mechanisms, the adverse impacts of aPLs on reendothelialization and neointima formation were fully prevented by the NO donor molsidomine.

Conclusions

APLs blunt endothelial repair, and there is related aPL‐induced exaggeration in neointima formation after endothelial injury in mice. The initiating process entails NO deficiency mediated by β2‐glycoprotein I recognition by aPLs and apolipoprotein E receptor 2. The modulation of endothelial apolipoprotein E receptor 2 function or NO bioavailability may represent new interventions to prevent the nonthrombotic vascular occlusion and resulting cardiovascular disorders that afflict antiphospholipid syndrome patients.

14th International Congress on Antiphospholipid Antibodies Task Force Report on Catastrophic Antiphospholipid Syndrome

The 'Task Force on Catastrophic Antiphospholipid Syndrome (CAPS)' was developed on the occasion of the 14th International Congress on Antiphospholipid Antibodies. The objectives of this Task Force were to assess the current knowledge on pathogenesis, clinical and laboratory features, diagnosis and classification, precipitating factors and treatment of this condition in order to address recommendations for future research. This article summarizes the studies analyzed by the Task Force, its recommendations and the future research agenda.

A non-complement-fixing antibody to β2 glycoprotein I as a novel therapy for antiphospholipid syndrome

A single-chain fragment variable (scFv) recognizing β2-glycoprotein 1 (β2GPI) from humans and other species was isolated from a human phage display library and engineered to contain an IgG1 hinge-CH2-CH3 domain. The scFv-Fc directed against β2GPI domain I-induced thrombosis and fetal loss, thus mimicking the effect of antibodies from patients with antiphospholipid syndrome (APS). Complement is involved in the biological effect of anti-β2GPI scFv-Fc, as demonstrated by its ability to promote in vitro and in vivo complement deposition and the failure to induce vascular thrombosis in C6-deficient rats and fetal loss in C5-depleted mice. A critical role for complement was also supported by the inability of the CH2-deleted scFv-Fc to cause vessel occlusion and pregnancy failure. This antibody prevented the pathological effects of anti-β2GPI antibodies from APS patients and displaced β2GPI-bound patient antibodies. The CH2-deleted antibody represents an innovative approach potentially useful to treat APS patients refractory to standard therapy.

Inhibition of nitric oxide and antiphospholipid antibody-mediated thrombosis

The antiphospholipid syndrome (APS) is characterized by recurrent vascular thrombosis, thrombocytopenia, and fetal loss occurring in the presence of antiphospholipid antibodies (aPL). Along with arterial and venous thrombosis and pregnancy complications, patients with APS have an increased risk of myocardial infarction, stroke, and coronary artery disease, resulting from vascular cell dysfunction induced by aPL. Accumulating evidence to date indicates that interactions between circulating aPL and cell surface molecules of target cells, primarily endothelial cells and platelets, underlie the vascular disease phenotypes of APS. However, the molecular basis of APS is poorly understood. Nitric oxide produced by endothelial cells is a key determinant of vascular health that regulates several physiologic processes, including thrombosis, endothelial-leukocyte interaction, vascular cell migration, and the modulation of vascular tone. This review will discuss recent findings that indicate a novel mechanism by which aPL antagonize endothelial cell production of nitric oxide and thereby promote thrombosis.

Anti-β2-glycoprotein I antibodies

Anti-β(2)-glycoprotein I (anti-β(2)GPI) antibodies are the main antiphospholipid antibodies, along with anticardiolipin and lupus anticoagulant, that characterize the autoimmune disease antiphospholipid syndrome (APS). While the exact physiological functions of β(2)GPI are unknown, there is overwhelming evidence that anti-β(2)GPI antibodies are pathogenic, contributing to thrombosis, pregnancy morbidity, and accelerated atherosclerosis in APS and systemic lupus erythematosus patients. The revelation that these antibodies play a central role in the pathogenesis and pathophysiology of APS has driven research to characterize the physiology and structure of β(2)GPI as well as the pathogenic effects of anti-β(2)GPI antibodies. It has also resulted in the development of improved testing methodologies for detecting these antibodies. In this review we discuss the characteristics of β(2)GPI; the generation, pathogenic effects, and standardized testing of anti-β(2)GPI antibodies; and the potential use of therapies that target the β(2)GPI/anti-β(2)GPI interaction in the treatment of APS.

Síndrome antifosfolípide e trombocitopenia na infância

OBJETIVO: Relatar o caso de uma criança com diagnóstico de síndrome do anticorpo antifosfolípide associada à trombocitopenia grave e realizar uma revisão de literatura sobre o assunto. DESCRIÇÃO DO CASO: Criança de nove anos e oito meses de idade com trombocitopenia grave associada a anticorpo anticardiolipina positivo. Os dados foram coletados por meio de anamnese, exame físico e exames complementares da paciente. O diagnóstico foi determinado de acordo com os critérios estabelecidos para a síndrome antifosfolípide, associados às manifestações mais comuns na faixa etária pediátrica: livedo reticular e trombocitopenia. COMENTÁRIOS: A síndrome do anticorpo antifosfolípide é uma doença incomum na população pediátrica e suas manifestações clínicas, com a redução do número de plaquetas, devem ser consideradas.

Thrombosis in systemic lupus erythematosus: a review article

Thrombosis is a well-known clinical entity in systemic lupus erythematosus (SLE), and it is multifactorial. The most important risk factor is the presence of antiphospholipid antibodies (APLAs). However, approximately 40% of adults with SLE who are negative for APL A are diagnosed with thrombosis, indicating the importance of other risk factors. Thus, the thrombosis risk factors should be evaluated extensively and regularly and treated aggressively in every patient with systemic lupus erythematosus.

Secondary hypertrophic pachymeningitis in antiphospholipid syndrome

This report describes a rare case of hypertrophic pachymeningitis secondary to antiphospholipid syndrome in a 37-year-old woman. The patient had a history of antiphospholipid syndrome and developed hypertrophic pachymeningitis subsequently. Pathological examination of the dura mater showed not only fibrous thickening, the typical finding of hypertrophic pachymeningitis, but also thrombosis in the dural microvessels and T cell infiltration without B cell or plasma cell infiltration, suggesting cell-mediated immunity. The dural thickening spontaneously improved and did not deteriorate during corticosteroid therapy. The histological findings and spontaneous remission observed in this case might be characteristic of secondary hypertrophic pachymeningitis with antiphospholipid syndrome. Further investigations are necessary to elucidate the pathophysiology of this novel type of hypertrophic pachymeningitis.

Complement and the antiphospholipid syndrome

PURPOSE OF REVIEW

The antiphospholipid antibody syndrome (APS) is characterized by arterial or venous thrombosis or pregnancy morbidity in patients with persistent antiphospholipid antibodies (aPL). Experimental data supporting activation of the complement cascade has provided critical insight into the underlying pathophysiology of aPL-induced pregnancy loss and thrombosis.

RECENT FINDINGS

Although the mechanism by which pregnancy loss and thrombosis is incompletely elucidated, studies using mice deficient in complement components and specific inhibitors to complement have demonstrated that activation of complement contributes to fetal loss, growth restriction and thrombosis. Inhibition of complement activation can prevent these complications. Use of a specific complement inhibitor to C5 has been used successfully in a patient with catastrophic APS undergoing renal transplantation.

SUMMARY

Activation of complement plays an important role in the pathogenesis of aPL-induced pregnancy morbidity and thrombosis. This understanding has been advanced primarily using mouse models of APS and clinical studies in patients with APS are needed. Although there is currently no specific complement-targeted therapy approved for APS, developing and evaluating complement-targeted therapies in patients with APS are warranted. Complement inhibition may provide a novel upstream treatment option for patients with APS compared with the current standard treatment of anticoagulation.

Toll-like receptors play a crucial part in the pathophysiological activity of antiphospholipid antibodies

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis, recurrent fetal loss and the presence of a variety of antiphospholipid antibodies (aPL), directed to phospholipids like Cardiolipin and phospholipid binding proteins like β2-glycoprotein I. Till date, the pathophysiological processes underlying these thrombotic events were still not fully understood. Recent data support the idea that the aPL might act via enhanced cytokine release due to activation of certain Toll-like receptors. The investigation of some of those mechanisms in more detail enlightens the involvement of the intracellular receptors TLR7 and TLR8 in a central point. Using patients’ IgG fractions and/or monoclonal aPL, either generated from mouse or from human B-cells for the stimulation experiments of monocytes, endothelial cells or dendritic cells, all these stimuli induced an enhanced expression and secretion of cytokines, especially TNFα, caused by specific regulation or activation of Toll-like receptors. Using specific agonists or inhibitors could confirm the causal connection of these stimulatory effects. This review focuses on the recent developments connecting the binding of aPL with the activity of Toll-like receptors, especially in monocytes, endothelial cells and dendritic cells.

New Insights into the Molecular Basis of the Antiphospholipid Syndrome

Antiphospholipid syndrome is an autoimmune disease characterized by the presence of circulating antiphospholipid antibodies (aPL) that promote thrombosis, pregnancy complications and cardiovascular diseases. Alterations in the function of vascular cells induced by aPL underlie these outcomes. This review will discuss recent findings that indicate a novel mechanism by which aPL antagonize endothelial cell production of nitric oxide and thereby promote thrombosis.

Pathophysiological mechanisms in antiphospholipid syndrome

Antiphospholipid syndrome is a systemic autoimmune disease associated with thrombosis and recurrent fetal loss in the setting of detectable antiphospholipid (aPL) antibodies. The major antigenic target has been identifed as β₂-glycoprotein I (β₂GPI), which mediates binding of aPL antibodies to target cells including endothelial cells, monocytes, platelets and trophoblasts, leading to prothrombotic and proinfammatory changes that ultimately result in thrombosis and fetal loss. This article summarizes recent insights into the role of β₂GPI in normal hemostasis, interactions between aPL antibodies, β₂GPI and cell-surface molecules, molecular prothrombotic and proinfammatory changes induced by aPL antibodies and pathogenic changes leading to fetal loss in antiphospholipid syndrome. New directions in therapy using these insights are examined.

Pathophysiology of the antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) are associated with the recurrent pregnancy loss and thrombosis that characterizes the antiphospholipid antibody syndrome (APS). Although the ontogeny of these pathogenic antibodies has not been fully elucidated, there is evidence that indicates the involvement of both genetic and environmental factors. The ability of aPL to induce a procoagulant phenotype in APS patients plays a central role in the development of arterial and venous thrombotic manifestations typical of the disease. Inflammation serves as a necessary link between this procoagulant phenotype and actual thrombus development and is an important mediator of the placental injury seen in APS patients with obstetric complications. Recent evidence has indicated a role for abnormal cellular proliferation and differentiation in the pathophysiology of APS, especially in those patients with pregnancy morbidity and other more atypical manifestations that have no identifiable thrombotic cause. The interplay of genetic and environmental factors responsible for aPL development and the mechanisms by which these antibodies produce disease in APS patients is the focus of this review.

A novel dimeric inhibitor targeting Beta2GPI in Beta2GPI/antibody complexes implicated in antiphospholipid syndrome

BACKGROUND

β2GPI is a major antigen for autoantibodies associated with antiphospholipid syndrome (APS), an autoimmune disease characterized by thrombosis and recurrent pregnancy loss. Only the dimeric form of β2GPI generated by anti-β2GPI antibodies is pathologically important, in contrast to monomeric β2GPI which is abundant in plasma.

PRINCIPAL FINDINGS

We created a dimeric inhibitor, A1-A1, to selectively target β2GPI in β2GPI/antibody complexes. To make this inhibitor, we isolated the first ligand-binding module from ApoER2 (A1) and connected two A1 modules with a flexible linker. A1-A1 interferes with two pathologically important interactions in APS, the binding of β2GPI/antibody complexes with anionic phospholipids and ApoER2. We compared the efficiency of A1-A1 to monomeric A1 for inhibition of the binding of β2GPI/antibody complexes to anionic phospholipids. We tested the inhibition of β2GPI present in human serum, β2GPI purified from human plasma and the individual domain V of β2GPI. We demonstrated that when β2GPI/antibody complexes are formed, A1-A1 is much more effective than A1 in inhibition of the binding of β2GPI to cardiolipin, regardless of the source of β2GPI. Similarly, A1-A1 strongly inhibits the binding of dimerized domain V of β2GPI to cardiolipin compared to the monomeric A1 inhibitor. In the absence of anti-β2GPI antibodies, both A1-A1 and A1 only weakly inhibit the binding of pathologically inactive monomeric β2GPI to cardiolipin.

CONCLUSIONS

Our results suggest that the approach of using a dimeric inhibitor to block β2GPI in the pathological multivalent β2GPI/antibody complexes holds significant promise. The novel inhibitor A1-A1 may be a starting point in the development of an effective therapeutic for antiphospholipid syndrome.

New therapeutic targets for the antiphospholipid syndrome

IMPORTANCE OF THE FIELD

The antiphospholipid syndrome (APS) is an autoimmune condition whereby pathogenic antiphospholipid antibodies (aPL) cause vascular thrombosis and/or recurrent miscarriage, and carries a high burden of morbidity and mortality. Currently the only proven treatment is long-term anticoagulation, which is not effective in all patients and carries risk of haemorrhage.

AREAS COVERED IN THIS REVIEW

Novel therapeutic targets that are currently being explored for APS in order to address the unmet needs of better, safer and ideally targeted therapy. These include B cell depletion, new-generation anticoagulants, interfering with aPL cell-mediated activation of endothelial cells and platelets both at the cell surface level and intracellularly, targeting components of the complement system and the novel concept of using decoy peptides to target only the pathogenic sub-population of aPL.

WHAT THE READER WILL GAIN

An overview of the potential targets and rationale underpinning them.

TAKE HOME MESSAGE

Though current options remain limited for the treatment of APS, the future holds much promise with the identification of multiple targets, many of which are currently being explored. The challenge will be to undertake carefully designed prospective multi-centre trials to generate the evidence necessary to support integration of such candidates into clinical practice.

Antiphospholipid syndrome treatment beyond anticoagulation: are we there yet?

Persistently positive antiphospholipid antibodies in association with thromboses and/or pregnancy morbidity is the hallmark of the antiphospholipid syndrome. The management of antiphospholipid antibody-positive patients has been focused on utilizing anti-thrombotic medications such as heparin or warfarin. Given that our understanding of the molecular mechanisms of antiphospholipid antibody-mediated thrombosis has been growing, it is highly likely that the current ‘anti-thrombotic’ approach to these patients will be replaced by an ‘immunomodulatory’ approach in the near future. This review article will address the experimental and/or clinical evidence behind some of these potential ‘immunomodulatory’ approaches (tissue factor inhibition, P38 mitogen-activated protein kinase inhibition, nuclear factor-κB inhibition, platelet glycoprotein receptor inhibition, hydroxychloroquine, statins, inhibition of β2GPI and/or anti-β2GPI binding to target cells, complement inhibition, and B cell inhibition) in antiphospholipid syndrome.

Neurologic manifestations of the antiphospholipid syndrome

Antiphospholipid syndrome is an important cause of neurologic morbidity. The clinical criteria for antiphospholipid syndrome include only cerebrovascular arterial and venous thrombosis, but many other neurologic manifestations have been associated with antiphospholipid antibodies (aPL). This review discusses the role of aPL in cerebrovascular manifestations and in some of the other neurologic manifestations commonly associated with these antibodies, as well as data pertaining to the pathophysiology of aPL-associated neurologic manifestations and treatment issues.

Role of complement in antiphospholipid antibody-mediated thrombosis

The mechanisms by which an antibody that reacts with phospholipids (universal components of mammalian membranes) causes thrombosis are not immediately obvious. The development of an animal model of antiphospholipid antibody syndrome has moved the field forward in dissecting the pathogenesis of antiphospholipid antibody syndrome and has implicated the complement system in the mechanism of disease. Understanding complement's role in promoting thrombosis will be important in designing safer, more effective approaches to the treatment of patients with antiphospholipid antibodies, and may shed light on which patients are at greatest risk for thrombosis, perhaps permitting primary prophylaxis before irreversible tissue and organ damage occur.

Endothelial dysfunction in patients with antiphospholipid syndrome assessed with positron emission tomography

BACKGROUND

There is limited knowledge about endothelial dysfunction in patients with primary antiphospholipid syndrome (PAPS). The purpose of this study was to evaluate endothelial function in patients with PAPS assessed by positron emission tomography.

METHODS AND RESULTS

A 3-phase protocol--rest, cold pressor test (CPT), and adenosine positron emission tomography with nitrogen 13 ammonia--was used in 18 patients with PAPS and 18 healthy volunteers (HVs). Myocardial blood flow (MBF) was measured in each phase, with calculation of the endothelial-dependent vasodilation index, the increase in the MBF in response to CPT, and the myocardial flow reserve. An important trend was found in the myocardial flow reserve (2.76 +/- 1.04 in PAPS group vs 3.27 +/- 0.72 in HV group, P > .05), in the endothelial-dependent vasodilation index (1.19 +/- 0.31 in PAPS group vs 1.55 +/- 0.37 in HV group, P < .05), and in the percent change in the MBF in response to CPT (from rest) (19% +/- 31% in PAPS group vs 55% +/- 37% in HV group, P < .05).

CONCLUSION

The CPT results obtained in this study showed that the PAPS patients studied have endothelial dysfunction.

Mulberry leaf aqueous fractions inhibit TNF-α-induced nuclear factor κB (NF-κB) activation and lectin-like oxidized LDL receptor-1 (LOX-1) expression in vascular endothelial cells

Mulberry (Morus Alba L., family Moraceae) leaf extracts have various biological effects including inhibition of oxidative modification of low-density lipoprotein (LDL), which is the major cause of atherosclerosis. Endothelial dysfunction elicited by oxidized LDL (Ox-LDL) has been implicated in atherogenesis. Lectin-like Ox-LDL receptor-1 (LOX-1), a cell-surface receptor for atherogenic Ox-LDL, appears to mediate Ox-LDL-induced inflammation, which may be crucial in atherogenesis. Previous studies revealed that expression of LOX-1 is highly inducible by proinflammatory stimuli, including tumor necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS), and transforming growth factor-beta (TGF-beta). Therefore, we examined whether mulberry leaf aqueous fractions inhibit LOX-1 expression induced by proinflammatory stimuli. Pretreatment of cultured bovine aortic endothelial cells (BAECs) with mulberry leaf aqueous fractions inhibited TNF-alpha- and LPS-induced expression of LOX-1 at both protein and mRNA levels in a time- and concentration-dependent manner. In contrast, mulberry leaf aqueous fractions did not affect TGF-beta-induced LOX-1 expression. Furthermore, mulberry leaf aqueous fractions inhibited TNF-alpha-induced activation of nuclear factor-kappaB (NF-kappaB) and phosphorylation of inhibitory factor of NF-kappaB-alpha (IkappaB-alpha) in a time- and concentration-dependent fashion. Thus, mulberry leaf aqueous fractions suppress TNF-alpha- and LPS-induced LOX-1 gene expression, by inhibiting NF-kappaB activation.

Antiphospholipid antibodies: lessons from the bench

Antiphospholipid antibodies (aPL) are an heterogeneous group of circulating immunoglobulins arising in a wide range of infectious and autoimmune diseases. Since the early 80s, the interest on anticardiolipin antibodies (aCL) has exponentially increased due to their association with thrombosis. The antiphospholipid syndrome (APS) was defined as a clinical disorder characterized by thrombosis and pregnancy morbidity associated to the persistent presence of aCL and/or lupus anticoagulant (LA). Thrombosis is the major manifestation in patients with aPL, but the spectrum of symptoms and signs associated with aPL has considerably broadened, and other manifestations such as thrombocytopenia, non-thrombotic neurological syndromes, psychiatric manifestations, livedo reticularis, skin ulcers, haemolytic anemia, pulmonary hypertension, cardiac valve abnormality and atherosclerosis have also been related to the presence of those antibodies. Numerous mechanisms have been proposed to explain the thrombotic tendency of patients with aPL, but the pathogenesis seems to be multifactorial.