The antiphospholipid syndrome

Interaction of antiphospholipid antibodies with endothelial cells in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease with arteriovenous thrombosis and recurrent miscarriages as the main clinical manifestations. Due to the complexity of its mechanisms and the diversity of its manifestations, its diagnosis and treatment remain challenging issues. Antiphospholipid antibodies (aPL) not only serve as crucial "biomarkers" in diagnosing APS but also act as the "culprits" of the disease. Endothelial cells (ECs), as one of the core target cells of aPL, bridge the gap between the molecular level of these antibodies and the tissue and organ level of pathological changes. A more in-depth exploration of the relationship between ECs and the pathogenesis of APS holds the potential for significant advancements in the precise diagnosis, classification, and therapy of APS. Many researchers have highlighted the vital involvement of ECs in APS and the underlying mechanisms governing their functionality. Through extensive in vitro and in vivo experiments, they have identified multiple aPL receptors on the EC membrane and various intracellular pathways. This article furnishes a comprehensive overview and summary of these receptors and signaling pathways, offering prospective targets for APS therapy.

Mechanisms of YAP1-mediated trophoblast ferroptosis in recurrent pregnancy loss

PURPOSE

The purpose of our study is to investigate the function of YAP1 in the trophoblast ferroptosis and maternal-fetal interface communication of RPL.

METHODS

We collected 25 villous tissues and detected the expression of YAP1. Cell counting kit-8 assay, scratch wound-healing assay, and Matrigel invasion assay were performed to observe the proliferation, migration, and invasion of HTR-8/SVneo and JAR cells. Subsequently, measured the levels of reactive oxygen species (ROS), malondialdehyde (MDA), reduced glutathione (GSH), SLC7A11, SOD2, and GPX4. Ultimately, the use of ferroptosis activator (erastin) and inhibitor (Ferrostatin-1, fer-1) further confirmed the regulation by YAP1. In addition, established an in vitro-induced cell model to study the effect of YAP1 on the decidualization process. Finally, animal models were implemented for further confirmation.

RESULTS

We found that YAP1 was downregulated in RPL patients. Overexpression of YAP1 could significantly enhance the proliferation, migration, and invasion of trophoblasts, and inhibit ferroptosis. Knocking down YAP1 exhibited the opposite effect. Rescue experiments have shown that YAP1 could upregulate the expression of SLC7A11 and GPX4, which are key molecules in the classic pathway of ferroptosis. In addition, the decidualization was impaired when hESCs were treated with conditioned medium of YAP1 knockdown trophoblasts. Moreover, we found that Yap1, Slc7a11, and Gpx4 were downregulated in the RPL mice, along with increased MDA and decreased GSH.

CONCLUSION

Downregulation of YAP1 induces ferroptosis, thereby damaging the trophoblast invasion processes, which also disturbs the communication at the maternal-fetal interface. Our study identified YAP1 as a potential key molecule in the pathogenesis of RPL.

Clinical and Laboratory Diagnosis of Antiphospholipid Syndrome: A Review

The antiphospholipid syndrome (APS) manifests through venous or arterial thrombosis, with or without pregnancy complication alongside the continuous presence of antiphospholipid antibodies (aPL). APS classification relies on three aPL subtypes: anticardiolipin (aCL), anti-β2-glycoprotein I antibodies (anti-β2GPI), and lupus anticoagulants (LA) antibodies. Given that thrombosis and pregnancy issues are not unique to APS, the precise and reliable identification of aPL forms the basis for diagnosis. Semi-quantitative solid-phase assays identify two antibodies, aCL and anti-β2GPI, while LA detection occurs through various phospholipid-dependent coagulation assays that are based on antibody behaviour. LA, specifically, is conclusively associated with thrombosis, prompting discussions around the serological criteria for APS. Despite advancements in LA detection, the standardisation of all aPL detection assays remains imperative. The combined presence of aCL and anti-β2GPI with thrombosis inconsistently triggers concern. Initial presentations by APS patients commonly exhibit a heightened risk of stroke, miscarriages in the later stages of pregnancy, positive results of LA tests, and widespread thrombosis across multiple organs, often leading to adverse outcomes. Correctly diagnosing this condition is pivotal to avoid unnecessary long-term secondary thromboprophylaxis.

Molecular mapping of α-thrombin (αT)/β2-glycoprotein I (β2GpI) interaction reveals how β2GpI affects αT functions

β2-Glycoprotein I (β2GpI) is the major autoantigen in the antiphospholipid syndrome, a thrombotic autoimmune disease. Nonetheless, the physiological role of β2GpI is still unclear. In a recent work, we have shown that β2GpI selectively inhibits the procoagulant functions of human α-thrombin (αT; i.e. prolongs fibrin clotting time, t_c, and inhibits αT-induced platelet aggregation) without affecting the unique anticoagulant activity of the protease, i.e. the proteolytic generation of the anticoagulant protein C (PC) from the PC zymogen, which interacts with αT exclusively at the protease catalytic site. Here, we used several different biochemical/biophysical techniques and molecular probes for mapping the binding sites in the αT-β2GpI complex. Our results indicate that αT exploits the highly electropositive exosite-II, which is also responsible for anchoring αT on the platelet GpIbα (platelet receptor glycoprotein Ibα) receptor, for binding to a continuous negative region on β2GpI structure, spanning domain IV and (part of) domain V, whereas the protease active site and exosite-I (i.e. the fibrinogen-binding site) remain accessible for substrate/ligand binding. Furthermore, we provided evidence that the apparent increase in t_c, previously observed with β2GpI, is more likely caused by alteration in the ensuing fibrin structure rather than by the inhibition of fibrinogen hydrolysis. Finally, we produced a theoretical docking model of αT-β2GpI interaction, which was in agreement with the experimental results. Altogether, these findings help to understand how β2GpI affects αT interactions and suggest that β2GpI may function as a scavenger of αT for binding to the GpIbα receptor, thus impairing platelet aggregation while enabling normal cleavage of fibrinogen and PC.

The environment and antiphospholipid syndrome

The etiology of autoimmune diseases is multifactorial. The degree to which genetic and environmental factors influence susceptibility to autoimmune diseases is poorly defined. It is believed that versatile clinical presentations of autoimmune diseases stem from various combinations of the genetic and environmental factors. One of the newly diagnosed autoimmune diseases is the antiphospholipid syndrome (APS). APS is characterized by vascular thrombosis, and/or pregnancy morbidity associated with anticardiolipin (aCL), anti-β2-glycoprotein-I (anti-β2GPI) and lupus anticoagulant (LAC).

Cytokines in recurrent miscarriage

Cytokines act at all stages of pregnancy from implantation to parturition. This review examines their relevance in recurrent miscarriage. However, recurrent miscarriage may be due to an inherently abnormal embryo (e.g., chromosomal abberations) or maternal factors (e.g., uterine anomalies or antiphospholipid antibodies). In the former, cytokines are not causitive, but may be part of the mechanism of abortion. In the antiphospholipid syndrome, cytokines such as TNFa and IL-6 may be responsible for the associated thrombosis. Hence, an appropriate cytokine milieu could be responsible for whether the antibodies are pathogenic or merely an epiphenomenon. Natural killer cells seem to have a key role in immunosurveillance of the invading trophoblast. However, if activated by TNFa, natural killer cells may induce apoptosis in the trophoblast possibly leading to miscarriage. This action is inhibited by TGFb. Early ultrasound scanning and embryoscopy have revealed structural anomalies in karyotypically normal embryos which have terminated in first trimester missed abortion. Teratogens such as cyclophosphamide cause fetal demise by excessive apoptosis. Excessive apoptosis may be mediated by TNFa, TGFb and other cytokines. GM-CSF has been reported to prevent teratogenesis in laboratory animals. Both immunomodulation and hormonal support (progesterone or hCG supplements) have been used to improve the live birth rate in recurrently aborting women. Each may modulate the balance between various cytokines. Although neither hormonal support or immunopotentiation have been proven to be beneficial, the results and the role of cytokines themselves can only be assessed in trials of karyotypically normal embryos.

Recurrent pregnancy loss: evaluation and treatment

Recurrent pregnancy loss (RPL) is a multifactorial condition. Approximately half of patients with RPL will have no explanation for their miscarriages. De novo chromosome abnormalities are common in sporadic and recurrent pregnancy loss. Testing for embryonic abnormalities can provide an explanation for the miscarriage in many cases and prognostic information. Regardless of the cause of RPL, patients should be reassured that the prognosis for live birth with an evidence-based approach is excellent for most patients. The authors review current evidence for the evaluation and treatment of RPL and explore the proposed use of newer technology for patients with RPL.

The role of the gut microbiota in the pathogenesis of antiphospholipid syndrome

Infectious triggers are associated with the induction of transient antiphospholipid antibodies. One therefore wonders if microbes that permanently colonize us play a role in the pathogenesis of antiphospholipid syndrome (APS). The microbiota represents the collection of all microorganisms colonizing humans and is necessary for normal host physiology. The microbiota, however, is a constant stress on the immune system, which is tasked with recognizing and eliminating pathogenic microbes while tolerating commensal populations. A growing body of literature supports a critical role for the commensal-immune axis in the development of autoimmunity against colonized barriers (e.g., gut or skin) and sterile organs (e.g., pancreas or joints). Whether these interactions affect the development and sustainment of autoreactive CD4(+) T cells and pathogenic autoantibodies in APS is unknown. This review provides an overview of the current understanding of the commensal-immune axis in autoimmunity with a focus on the potential relevance to APS. Additionally, we discuss emerging findings supporting the involvement of the gut microbiota in a spontaneous model of APS, the (NZW × BXSB)F1 hybrid, and formalize hypotheses to explain how interactions between the immune system and the microbiota may influence human APS etiopathogenesis.

Synthesis of Phospholipid-Protein Conjugates as New Antigens for Autoimmune Antibodies

Copper(I)-catalyzed azide-alkyne cycloaddition, or CuAAC click chemistry, is an efficient method for bioconjugation aiming at chemical and biological applications. Herein, we demonstrate how the CuAAC method can provide novel phospholipid-protein conjugates with a high potential for the diagnostics and therapy of autoimmune conditions. In doing this, we, for the first time, covalently bind via 1,2,3-triazole linker biologically complementary molecules, namely phosphoethanol amine with human β2-glycoprotein I and prothrombin. The resulting phospholipid-protein conjugates show high binding affinity and specificity for the autoimmune antibodies against autoimmune complexes. Thus, the development of this work might become a milestone in further diagnostics and therapy of autoimmune diseases that involve the production of autoantibodies against the aforementioned phospholipids and proteins, such as antiphospholipid syndrome and systemic lupus erythematosus.

Circulating microparticles in patients with antiphospholipid antibodies: characterization and associations

The antiphospholipid syndrome is characterized by venous or arterial thrombosis and/or recurrent fetal loss in the presence of circulating antiphospholipid antibodies. These antibodies cause activation of endothelial and other cell types leading to the release of microparticles with procoagulant and pro-inflammatory properties. The aims of this study were to characterize the levels of endothelial cell, monocyte or platelet derived, and tissue factor-bearing microparticles in patients with antiphospholipid antibodies, to determine the association of circulating microparticles with anticardiolipin and anti-β2-glycoprotein antibodies, and to define the cellular origin of microparticles that express tissue factor. Microparticle content within citrated blood from 47 patients with antiphospholipid antibodies and 144 healthy controls was analyzed within 2hours of venipuncture. Levels of Annexin-V, CD105 and CD144 (endothelial derived), CD41 (platelet derived) and tissue factor positive microparticles were significantly higher in patients than controls. Though levels of CD14 (monocyte-derived) microparticles in patient plasma were not significantly increased, increased levels of CD14 and tissue factor positive microparticles were observed in patients. Levels of microparticles that stained for CD105 and CD144 showed a positive correlation with IgG (R=0.60, p=0.006) and IgM anti-beta2-glycoprotein I antibodies (R=0.58, p=0.006). The elevation of endothelial and platelet derived microparticles in patients with antiphospholipid antibodies and their correlation with anti-β2-glycoprotein I antibodies suggests a chronic state of vascular cell activation in these individuals and an important role for β2-glycoprotein I in development of the pro-thrombotic state associated with antiphospholipid antibodies.

Classic and cutting-edge strategies for the management of early pregnancy loss

There are few conditions in medicine associated with more heartache to patients than recurrent pregnancy loss (RPL). The management of early RPL is a formidable clinical challenge for physicians. Great strides have been made in characterizing the incidence and diversity of this heterogeneous disorder, and a definite cause of pregnancy loss can be established in more than half of couples after a thorough evaluation. In this review, current data are evaluated and a clear roadmap is provided for the evaluation and treatment of RPL.

Study on antiphospholipid/anticardioliplin antibodies in women with recurrent abortion

Background

Antiphospholipid antibodies are associated with recurrent abortion but correlation between level of antibodies and gestational age of abortion and duration post abortion is not clear.

Objectives

Aim of this study was study on relation between antiphospholipid antibodies in women with recurrent abortion and their gestational age and duration post abortion.

Patients and Methods

We performed a case-control study on 197 pregnant women who had history of spontaneous recurrent abortion as case group and 50 pregnant healthy women as control group. Demographic characteristic of all participants filled in questionnaire forms. Antipospholipid and anticardiolipin antibodies were measured in their serum by Enzyme linked Immunoassay with orgenec kits. Data analyzed by SPSS software (version 13) and T statistical test. P value less than 0.05 was considered significant.

Results

Mean age of participants was 24-39 years old. The average rate of antiphospolipid antibodies in patients with normal anticardiolipin was greater than those with abnormal anticardiolipin and T-test showed significant difference between two groups.(P = 0.000) In case group the number of abortions was more, mean of antiphosopolipid antibody levels were also higher. Mean anticardiolipin and antiphospholipid antibodies rate was greater with increasing gestational age at time of first abortion. Almost mean antipospholipid and anticardiolipin antibodies in all patients remained in high level just in first 5 years with any number of abortions and five years later, antibodies began to fall.

Conclusions

Antipospholipid antibodies based on number of abortions and gestational age of abortions were increased. Mean antipospholipid and anticardiolipin antibodies in all patients remained in high level just in first 5 years post abortion and then began to fall.

Viewing dynamic interactions of proteins and a model lipid membrane with atomic force microscopy

The information covered in this chapter will present a model homogenous membrane preparation technique and dynamic imaging procedure that can be successfully applied to more than one type of lipid study and atomic force microscope (AFM) instrument setup. The basic procedural steps have been used with an Asylum Research MFP-3D BIO and the Bruker (formerly, Veeco) BioScope. The AFM imaging protocol has been supplemented by procedures (not to be presented in this chapter) of ellipsometry, standardized western blotting, and dot-blots to verify appropriate purity and activity of all experimental molecular components; excellent purity and activity level of the lipids, proteins, and drug(s) greatly influence the success of imaging experiments in the scanning probe microscopy field. The major goal of the chapter is to provide detailed procedures for sample preparation and operation of the Asylum Research MFP-3D BIO AFM. In addition, one should be cognizant that our comprehensive description in the use of the MFP-3D BIO's functions for successful image acquisitions and analyses is greatly enhanced by Asylum Research's (AR's) accompanying extensive manual(s), technical notes, and AR's users forum. Ultimately, the stepwise protocol and information will allow novice personnel to begin acquiring quality images for processing and analysis with minimal supervision.

Evaluation and treatment of recurrent pregnancy loss: a committee opinion

The majority of miscarriages are sporadic and most result from genetic causes that are greatly influenced by maternal age. Recurrent pregnancy loss (RPL) is defined by two or more failed clinical pregnancies, and up to 50% of cases of RPL will not have a clearly defined etiology.

A novel pathway for human endothelial cell activation by antiphospholipid/anti-β2 glycoprotein I antibodies

Antiphospholipid Abs (APLAs) are associated with thrombosis and recurrent fetal loss. These Abs are primarily directed against phospholipid-binding proteins, particularly β(2)GPI, and activate endothelial cells (ECs) in a β(2)GPI-dependent manner after binding of β(2)GPI to EC annexin A2. Because annexin A2 is not a transmembrane protein, the mechanisms of APLA/anti-β(2)GPI Ab-mediated EC activation are uncertain, although a role for a TLR4/myeloid differentiation factor 88-dependent pathway leading to activation of NF-κB has been proposed. In the present study, we confirm a critical role for TLR4 in anti-β(2)GPI Ab-mediated EC activation and demonstrate that signaling through TLR4 is mediated through the assembly of a multiprotein signaling complex on the EC surface that includes annexin A2, TLR4, calreticulin, and nucleolin. An essential role for each of these proteins in cell activation is suggested by the fact that inhibiting the expression of each using specific siRNAs blocked EC activation mediated by APLAs/anti-β(2)GPI Abs. These results provide new evidence for novel protein-protein interactions on ECs that may contribute to EC activation and the pathogenesis of APLA/anti-β(2)GPI-associated thrombosis and suggest potential new targets for therapeutic intervention in antiphospholipid syndrome.

Effects of antiphospholipid antibodies on in vitro platelet aggregation

Antiphospholipid antibodies contribute to the development of thrombosis, although precise mechanisms remain to be elucidated. We determined the effects of affinity-purified anti-beta(2)-glycoprotein 1 (anti-β(2)GP1) and anti-prothrombin (anti-PT) antibodies on in vitro platelet aggregation. Adenosine diphosphate (ADP) and collagen-induced platelet aggregation were performed using platelet-rich plasma ([PRP] 250 × 10(9)/L). Antiphospholipid antibodies (1.25-10 μg/mL) were preincubated with PRP for 10 minutes at 37°C prior to the addition of agonist. Anti-β(2)GP1 antibodies significantly reduced platelet aggregation (percentage area under the curve; %AUC) in a concentration-dependent manner using both 5 μmol/L (P < .001) and 2.5 μmol/L (P = .038) ADP but did not significantly affect the rate of aggregation. Anti-PT antibodies significantly enhanced 5 µg/mL collagen-induced platelet aggregation (%AUC; P = .034) but did not affect ADP-induced platelet aggregation. These results suggest (1) interactions and effects of antiphospholipid antibodies on platelets are agonist and concentration dependent and (2) anti-β(2)GP1 antibodies may inhibit dense granule release and/or inhibition of the arachidonic acid pathway.

Endothelial cell activation by antiphospholipid antibodies is modulated by Kruppel-like transcription factors

Antiphospholipid syndrome is characterized by thrombosis and/or recurrent pregnancy loss in the presence of antiphospholipid antibodies (APLAs). The majority of APLAs are directed against phospholipid-binding proteins, particularly β₂-glycoprotein I (β₂GPI). Anti-β₂GPI antibodies activate endothelial cells in a β₂GPI-dependent manner through a pathway that involves NF-κB. Krüppel-like factors (KLFs) play a critical role in regulating the endothelial response to inflammatory stimuli. We hypothesized that activation of endothelial cells by APLA/anti-β₂GPI antibodies might be associated with decreased expression of KLFs, which in turn might facilitate cellular activation mediated through NF-κB. Our experimental results confirmed this hypothesis, demonstrating markedly decreased expression of KLF2 and KLF4 after incubation of cells with APLA/anti-β₂GPI antibodies. Restoration of KLF2 or KLF4 levels inhibited NF-κB transcriptional activity and blocked APLA/anti-β₂GPI-mediated endothelial activation despite NF-κB p65 phosphorylation. Chromatin immunoprecipitation analysis demonstrated that inhibition of NF-κB transcriptional activity by KLFs reflects sequestration of the cotranscriptional activator CBP/p300, making this cofactor unavailable to NF-κB. These findings suggest that the endothelial response to APLA/anti-β₂GPI antibodies reflects competition between KLFs and NF-κB for their common cofactor, CBP/p300. Taken together, these observations are the first to implicate the KLFs as novel participants in the endothelial proinflammatory response to APLA/anti-β₂GPI antibodies.

The association of antibodies to cardiolipin,β2‐glycoprotein I, prothrombin, and oxidized low‐density lipoprotein with thrombosis in 292 patients with familial and sporadic systemic lupus erythematosus

OBJECTIVE

To determine the prevalence of antibodies to phospholipid-binding plasma proteins (aPL) and to oxidized low-density lipoprotein (OX-LDL), and to study the association of these antibodies with thrombosis and coronary heart disease (CHD) in patients with systemic lupus erythematosus (SLE).

METHODS

Clinical data and sera from 89 Finnish patients with familial and 203 with sporadic SLE were available for the study. Enzyme-linked immunosorbent assays (ELISA) were used for antibody determination.

RESULTS

The occurrence of thrombosis in our SLE patients was 13.7% (40/292) and of clinically diagnosed CHD was 1.4% (4/292). All antibody assays, except IgM-aCL, were significantly associated with thrombosis. IgG-aCL alone or in combination with anti beta 2-GPI or with anti OX-LDL were reasonably sensitive (38%, 48%, and 58%, respectively) and specific (87%, 80% and 72%, respectively) for a history of thrombosis. A high risk of arterial thrombosis (TIA or stroke) was associated with positivity of IgG-aCL, anti beta 2-GPI, and anti-prothrombin. Venous thrombosis was significantly associated with all other assays except IgM-aCL and anti-prothrombin. No test correlated with CHD, but the number of affected patients was small. There were three multiplex SLE families with two patients having a history of thrombosis: no consistent pattern of aPL or anti OX-LDL was found in these patients.

CONCLUSION

IgG-aCL alone or in combination with anti beta 2-GPI or anti OX-LDL are sensitive and specific tests for detecting SLE patients at increased risk of thrombosis. The aetiopathogenesis of thrombosis in familial SLE appears to be multifactorial.

Chorea associated with antiphospholipid antibodies in a patient with Kabuki syndrome

Kabuki syndrome, OMIM 147920 (KS) is a disorder characterized by multi-system abnormalities. These include physical, neurological, endocrine, and autoimmune abnormalities. Multiple autoimmune abnormalities are described in KS such as immune thrombocytopenic purpura (ITP), vitiligo, thyroiditis, hemolytic anemia, and hypogammaglobulinemia. In this report, we describe a patient with KS with sudden onset chorea associated with the presence of anti-phospholipid antibodies (aPLs) in the serum. Chorea in the presence of aPLs has been well described in the literature both in the presence and absence of antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). This report of APL in a patient with KS adds to the list of autoimmune disorders seen in patients with KS and also strengthens the hypothesis that patients with this syndrome have an increased incidence of immune dysregulation.

[Coagulopathy resulting from lupus anticoagulant antibodies as a paraneoplastic phenomenon in renal cell carcinoma relapse]

Lupus anticoagulant syndrome (LAS) is a form of coagulopathy with protracted PTT and an elevated risk of thromboembolic events, which occasionally occurs as a paraneoplastic phenomen in the presence of tumors. It is diagnosed by specific coagulation tests that identify lupus anticoagulant antibodies. We present the case of a 57-year-old woman with a coagulopathy caused by lupus anticoagulant antibodies as a paraneoplastic phenomenon in the course of a relapse of clear cell renal cell carcinoma in the area of the ipsilateral adrenal gland 18 months after tumor nephrectomy. After adrenalectomy with concomitant administration of low-molecular-weight heparin the PTT became normal and the diagnostic tests for lupus anticoagulant antibodies became negative.

The role of TLR2 in the inflammatory activation of mouse fibroblasts by human antiphospholipid antibodies

Antiphospholipid antibodies (APLAs) promote inflammatory and procoagulant responses in endothelial cells and monocytes. Previous studies have shown that MyD88, TRAF6, and NF-kappaB mediate cell activation by APLAs. These intermediates are also used by toll-like receptors (TLRs). We investigated the role of TLRs in the cellular response to APLAs. IgGs were isolated from the plasma of 5 patients with antiphospholipid syndrome along with immunopurified anti-beta2-glycoprotein 1 IgG from a sixth patient. Control IgG was obtained from a pool of healthy donor plasmas negative for APLAs. Wild-type mouse embryonic fibroblasts (EFs) and EFs deficient in TLR1, TLR2, TLR4, or TLR6 were incubated with APLAs, anti-beta2-glycoprotein 1 IgG, or control IgG. On incubation with the patient IgG, but not control IgG, a significant increase in mRNA levels of the inflammatory marker proteins MCP-1, ICAM-1, and IL-6 as well as IL-6 secretion was observed in wild-type EFs, whereas TLR2-deficient EFs did not respond. Responses in TLR1- and TLR6-deficient EFs were decreased and those in TLR4-deficient EFs comparable to those in wild-type EFs. Overexpression of human TLR2 in the TLR2-deficient EFs restituted the response to patient IgG. Our results imply that TLR2 plays a role in mouse fibroblast activation by APLAs.

Placental thrombosis and spontaneous fetal death in mice deficient in ethanolamine kinase 2

Ethanolamine kinase catalyzes the first step in the CDP-ethanolamine pathway for the formation of the major membrane phospholipid phosphatidylethanolamine (PtdEtn). In this work, the predicted Etnk2 cDNA was established as a soluble protein with ethanolamine-specific kinase activity that was most highly expressed in liver. Mice with an inactivated Etnk2 gene were derived, and its absence reduced the rate of PtdEtn synthesis from exogenous ethanolamine in hepatocytes. PtdEtn is a major precursor to phosphatidylcholine in liver; however, Etnk2(-/-) mice did not have reduced amounts of either PtdEtn or phosphatidylcholine or an altered phospholipid molecular species distribution. The knock-out animals were able to adapt to a choline-deficient diet. The Etnk2(-/-) mice exhibited a maternal-specific intrauterine growth retardation phenotype that resulted in a 33% reduction in litter size and frequent perinatal death. Histological analysis of pregnant Etnk2(-/-) females showed that fetal development failed at the late stage of pregnancy in a significant percentage of embryos because of the appearance of extensive placental thrombosis. These results illustrate a non-redundant role for EtnK2 expression in regulating placental hemostasis.

Thrombophilia and Recurrent Pregnancy Loss

Many unanswered questions regarding thrombophilia and recurrent pregnancy loss exist. For example, does a true association exist? Are thrombotic mechanisms relevant? Is a second messenger necessary to cause the manifestation of thrombosis? At present it seems that thrombophilia are associated with and may even cause some cases of pregnancy loss. The role of treatment remains to be determined. Although the aim of physicians working in this field is entirely laudable, to allow childless couples to have children, it is necessary to have good evidence of effect before treatment is given to all patients. A serious ethical dilemma remains, however, namely should treatment that may be effective be denied to patients who have prior pregnancy losses? Denial of treatment is extremely distressing for the patient and the physician. The author's own practice is to offer treatment after a full explanation, particularly because treatment is generally prescribed in the antiphospholipid syndrome and justified in hereditary thrombophilias according to the report of Carp and colleagues, showing a 25% improvement in live birth rates in treated patients. When treatment fails, however, the embryo should be karyotyped to exclude chromosomal aberrations.

Purpura fulminans in an adult patient with Haemophilus influenzae sepsis: case report and review of the literature

Purpura fulminans is a rare complication of a coagulopathy or an infection. Haemophilus influenzae infection, which has decreased since the haemophilus influenzae type B vaccine was initiated, is an unusual initiating cause of purpura fulminans. This case is the first reported in the literature of an adult who developed purpura fulminans after Haemophilus influenzae sepsis. Her elevated beta2 glycoprotein 1 ratio may have contributed to the severity of her disease. Although rare, Haemophilus influenzae may precipitate purpura fulminans. Current therapy is directed at control of precipitating factors, removal of nonviable tissue, treatment of secondary infections, and physiologic support. There also is evidence that patients respond well to hyperbaric oxygen therapy, with decreasing limb and tissue loss.

Mucous Membrane Pemphigoid With Fatal Bronchial Involvement in a Seventeen-Year-Old Girl

PURPOSE

This study was designed to report a case of biopsy-proven mucous membrane pemphigoid with severe bronchial involvement in a young woman.

METHODS

Case report of a 17-year-old girl who presented with worsening dyspnea, skin rash, and bilateral ocular injection, symblepharon, and fornix foreshortening. Conjunctival, skin, and bronchial biopsies were performed along with imaging and serological tests in an effort to establish a diagnosis for this unusual constellation of findings. The surprising occurrence of a cerebrovascular accident during her hospitalization also prompted a search for a concurrent coagulation disorder.

RESULTS

Immunofluorescence studies of conjunctival, skin, and bronchial tissue specimens revealed deposition of multiple antibody classes at the basement membrane zone. The patient also possessed circulating basement membrane zone antibodies in her serum and a significant titer of antiphospholipid antibodies. She underwent dilation and stent placement for subglottic tracheal and left bronchial stenosis and was treated with immunosuppressive agents. After a favorable initial response, the patient experienced progressive bronchial stenosis and respiratory compromise, culminating in her death from bronchospasm and cardiopulmonary arrest.

CONCLUSION

To our knowledge, this is the first report of mucous membrane pemphigoid involving the lower airways that was confirmed by immunofluorescence analysis. It highlights the potentially lethal, systemic nature of mucous membrane pemphigoid and underscores the need to question patients about symptoms of respiratory dysfunction.

Gene-expression patterns predict phenotypes of immune-mediated thrombosis

Antiphospholipid antibody syndrome (APS) is a complex autoimmune thrombotic disorder with defined clinical phenotypes. Although not all patients with elevated antiphospholipid antibody (aPLA) levels develop complications, the severity of these potential events mandates aggressive and extended lifelong anti-thrombotic therapy. One hundred twenty-nine patients (57 patients with APS and venous thromboembolism [VTE], 32 patients with VTE without aPLA, 32 patients with aPLA only, and 8 healthy patients) were enrolled. RNA from peripheral-blood collection was used for DNA microarray analysis. Patterns of gene expression that characterize APS as well as thrombosis in the presence of aPLA were identified by hierarchical clustering and binary regression methods. Gene-expression profiles identify and predict individuals with APS from patients with VTE without aPLA. Importantly, similar methods identified expression profiles that accurately predicted those patients with aPLA at high risk for thrombotic events. All profiles were validated in independent cohorts of patients. The ability to predict APS, but more importantly, those patients at risk for venous thrombosis, represents a paradigm for a genomic approach that can be applied to other populations of patients with venous thrombosis, providing for more effective clinical management of disease, while also reflecting the possible underlying biologic processes.

Thrombosis in infants and children

During the last decade much progress has been made toward better understanding of the underlying reasons causing thromboembolism in children. A considerable number of acquired and hereditary thrombotic risk factors have been identified which may also have an impact on therapeutic decisions and prognosis concerning outcome and the risk of a second event. However, indications for therapeutic interventions, such as thrombolysis and prophylactic anticoagulation with respect to the different clinical conditions and their combination with other risk factors, are not yet well defined. The following article describes the causes, clinical presentation and management of thrombosis in neonates, infants and older children, focusing on the clinically most relevant conditions.

Adenosine receptors and the control of endothelial cell function in inflammatory disease

The nucleoside adenosine accumulates in many tissues following the onset of ischaemia and inflammation. This initiates a series of protective mechanisms in target cells upon binding and activation of a family of four G-protein-coupled cell surface adenosine receptor (AR) proteins. The magnitude and duration of adenosine's effects are dictated by the identity and expression levels of each receptor subtype on individual cell types within the hypoxic microenvironment. Given the key role of endothelial cells (ECs) in the development of inflammatory diseases, such as sepsis, rheumatoid arthritis (RA) and atherosclerosis, ARs represent attractive targets for therapeutic intervention in these conditions. In this review, we examine several critical aspects of endothelial function in vivo, assess the role of individual AR subtypes in these events and, where known, discuss the molecular mechanisms by which specific ARs exert their effects.

Annexin A2 mediates endothelial cell activation by antiphospholipid/anti-β2 glycoprotein I antibodies

Patients with antiphospholipid antibodies (APLAs) are at increased risk for arterial and venous thrombosis. Many APLAs associated with these events react with β2 glycoprotein I (β2GPI), and endothelial cell reactive antibodies that activate endothelial cells in a β2GPI-dependent manner occur commonly in these patients. We previously reported that β2GPI binds with high affinity to annexin A2 on the endothelial surface, though the relevance of this interaction to APLA/anti-β2GPI antibody–induced endothelial activation has not been determined. In this report, we confirm that anti-β2GPI antibodies activate endothelial cells in the presence of β2GPI, and demonstrate that anti–annexin A2 antibodies directly cause endothelial cell activation of a similar magnitude and with a similar time course. Moreover, bivalent anti–annexin A2 F(ab′)2 fragments also caused endothelial cell activation, whereas monomeric Fab fragments not only did not cause activation, but blocked activation induced by anti–annexin A2 antibodies and F(ab′)2 fragments, as well as that caused by anti-β2GPI antibodies in the presence of β2GPI. These observations suggest a novel pathway for endothelial activation induced by APLA/anti-β2GPI antibodies that is initiated by cross-linking or clustering of annexin A2 on the endothelial surface.

Antiphospholipid antibodies in patients with sensorineural hearing loss

Sensorineural hearing loss can be associated with autoimmune diseases and the presence of antiphospholipid antibodies. Sixty patients (mean age 47 years, range 18-76 years) with sudden sensorineural hearing loss were studied with audiograms, stapedial thresholds, otoacoustic emissions, positional and caloric testing. The serologic testing included antibodies against phosphatidylserine and beta(2)-glycoprotein. Additionally, a group of 34 patients (mean age 65 years, range 31-81 years) with normal tension glaucoma was examined because in a previous study these patients were reported to have elevated concentrations of antiphospholipid antibodies with a coincidence of progressive sensorineural hearing loss. The baseline for antiphospholipid antibody levels was established in a control group of 40 healthy blood donors. In 12 of the 60 patients with sudden sensorineural hearing loss, levels of antiphospholipid antibodies were elevated. Antiphosphatidylserine IgM antibodies were significantly lower compared to controls and patients with the combination of hearing loss and normal tension glaucoma (Fisher's exact two-sided test, P < 0.01). Our data suggest that antibodies against beta2-glycoprotein seem to coincidence with an acute event, such as sudden sensorineural hearing loss, whereas antibodies against phosphatidylserine IgG are detectable in the prolonged sequel, such as in patients with progressive sensorineural hearing loss and normal tension glaucoma.

Thrombosis and the Antiphospholipid Syndrome

The antiphospholipid syndrome is an antibody-mediated hypercoagulable state characterized by recurrent venous and arterial thromboembolic events. Several studies have determined that the frequency of antiphospholipid syndrome in patients presenting with a venous thromboembolic event is between 4% and 14%. Because of the high risk for recurrent thromboembolism in these patients, current recommendations suggest a longer, potentially lifelong, course of antithrombotic therapy following an initial event. Although most authorities agree on an extended course of therapy, considerable controversy surrounds the optimal target therapeutic INR for patients with antiphospholipid syndrome. For an initial venous thromboembolic event, a target INR of 2.0 to 3.0 is supported by two prospective, randomized clinical trials. In contrast, relatively limited data exist for an initial arterial thromboembolic event in patients who have the antiphospholipid syndrome, and therapeutic recommendations range from aspirin to warfarin with a high target INR. Recurrent thromboembolic events can be extremely difficult to treat, and some patients may benefit from the addition of immunosuppressive therapies. Importantly, as many as 50% of the initial thromboembolic events sustained by patients with antiphospholipid antibodies occur in the setting of additional, coincident prothrombotic risk factors, indicating the importance of addressing any additional risk factors, such as hypercholesterolemia, in these patients. Prospective studies are needed to address the role of thromboprophylactic strategies in asymptomatic individuals with antiphospholipid antibodies in the absence of additional risk factors.

Identification and Characterization of a Gene Encoding Human LPGAT1, an Endoplasmic Reticulum-associated Lysophosphatidylglycerol Acyltransferase

Phosphatidylglycerol (PG) is an important membrane polyglycerolphospholipid required for the activity of a variety of enzymes and is a precursor for synthesis of cardiolipin and bis(monoacylglycerol) phosphate. PG is subjected to remodeling subsequent to its de novo biosynthesis to incorporate appropriate acyl content for its biological functions and to prevent the harmful effect of lysophosphatidylglycerol (LPG) accumulation. The enzymes involved in the remodeling process have not yet been identified. We report here the identification and characterization of a human gene encoding an acyl-CoA: lysophosphatidylglycerol acyltransferase (LPGAT1). Expression of the LPGAT1 cDNA in Sf9 insect and COS-7 cells led to a significant increase in LPG acyltransferase activity. In contrast, no significant acyltransferase activities were detected against glycerol 3-phosphate or a variety of lysophospholipids, including lysophosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylinositol, and lysophosphatidylserine. The recombinant human LPGAT1 enzyme recognized various acyl-CoAs and LPGs as substrates but demonstrated clear preference to long chain saturated fatty acyl-CoAs and oleoyl-CoA as acyl donors, which is consistent with the lipid composition of endogenous PGs identified from different tissues. Kinetic analyses of LPGAT1 expressed in COS-7 cells showed that oleoyl-LPG was preferred over palmitoyl-LPG as an acyl receptor, whereas oleoyl-CoA was preferred over lauroyl-CoA as an acyl donor. Consistent with its proposed microsomal origin, LPGAT1 was localized to the endoplasmic reticulum by subcellular fractionation and immunohistochemical analyses. Northern blot analysis indicated that the human LPGAT1 was widely distributed, suggesting a dynamic functional role of the enzyme in different tissues.

Apoptosis, subcellular particles, and autoimmunity

Firm evidence links the process of apoptosis to the induction of autoimmune disease. However, questions remain regarding the precise interactions of dying cells with the immune system. Genetic analyses indicate that deficiencies in serum proteins or receptors that mediate clearance of apoptotic cells increase the risk of autoimmunity. Moreover, administration of apoptotic cells to naive animals elicits transient autoimmune responses. Because known autoantigens are covalently modified and redistributed to cell surface blebs during the execution stage of apoptosis, increasing attention is being directed at this stage of programmed cell death, and researchers have identified a variety of autoantigens that are sequestered within blebs. However, blebs are merely a transition stage toward the complete cellular fragmentation, as blebs quickly convert into apoptotic bodies, subcellular particles (SCPs) of heterogeneous size, surface composition, and cargo. Because certain types of subcellular particles represent packets of highly enriched autoantigens, we propose that they are relevant to our understanding of autoimmunity.

Unusually high concentrations of cTnI and cTnT in a patient with catastrophic antiphospholipid antibody syndrome

BACKGROUND

We present a case of a patient with catastrophic antiphospholipid antibody syndrome with unusually high concentrations of cardiac Troponin I (cTnI) and cardiac Troponin T (cTnT). Troponins are sensitive and specific markers of myocardial injury. The degree of their elevation, in the context of the chronic autoimmune condition of the patient, elicited a thorough investigation for the presence of interfering antibodies.

METHODS

Cardiac markers, including total CK, CK-MB, cTnI, and cTnT, were measured in this patient over a period of 14 days after the onset of symptoms. In order to rule out a possible interference, serum samples were subjected to serial dilutions and were incubated with a blocking reagent (HBR) prior to analysis.

RESULTS

The time release of the cardiac markers into the systemic circulation of this patient followed the typical pattern after a myocardial infraction. Serial dilutions of the samples, and incubation with the blocking reagent revealed no indication of the presence of interfering antibodies.

CONCLUSIONS

The results strongly suggest that the extremely high concentrations of cTnT and cTnI in this patient were real and indicative of a massive myocardial infarction (MI). These may be the highest concentrations of cTnI and cTnT reported in the systemic circulation of a single patient.

Requirement of dying cells and environmental adjuvants for the induction of autoimmunity

OBJECTIVE

Cells commonly die without eliciting autoimmunity. However, dying cells are a potential initiating stimulus for systemic lupus erythematosus (SLE). Our goal was to verify whether immune adjuvants influence the autoimmunity induction that ensues following in vivo injection of dying cells.

METHODS

Mice were immunized with apoptotic thymocytes in the presence of artificial moieties, such as Freund's incomplete adjuvant (IFA), or natural adjuvants, such as dendritic cells (DCs). Renal involvement and the development of autoantibodies were monitored.

RESULTS

Apoptotic cells failed to induce clinical disease or to sustain production of autoantibodies in (NZB x NZW)F(1) mice. In contrast, autoimmunity developed in the presence of IFA or DCs. The characteristics of the adjuvant influenced the array of autoantibodies, the kinetics of their development, and the severity of the disease. DCs were required for induction of anti-beta(2)-glycoprotein I IgG. Adjuvants alone did not elicit disease.

CONCLUSION

A "two-hit" signal composed of autoantigens and adjuvants initiates systemic autoimmunity. Moreover, environmental signals at the site of clearance of dead cells shape the features and the severity of the autoimmune disease. Strategies aimed at preventing the accumulation of dying cells and at modulating endogenous adjuvants may be beneficial for the treatment of SLE.

Antiphospholipid syndrome in pregnancy

PURPOSE OF REVIEW

Antiphospholipid syndrome is widely recognized as a risk factor for numerous obstetric complications including miscarriage, intrauterine growth restriction, preeclampsia, fetal death and preterm labour. The many recent changes in concept regarding this syndrome, the role of the relevant antibodies, mechanism of action, diagnosis and treatment are assessed in this review.

RECENT FINDINGS

In recent years, our understanding of antiphospholipid syndrome has grown. The antigen has become better defined and is now thought to be beta2 glycoprotein 1. The 'classical' antibodies, lupus anticoagulant and anticardiolipin antibody are known to be pathogenic even when passively transferred to animal hosts. It seems, however, that the pathogenic antibodies are those directed towards beta2 glycoprotein 1, and that those which are directed to phospholipids without binding to beta2 glycoprotein 1 may not be pathogenic, but merely epiphenomena. The treatment of this condition has also been changed due to the influence of randomized trials in which heparin or low molecular weight heparin has replaced the use of steroids.

SUMMARY

There are numerous pitfalls in managing this condition. As beta2 glycoprotein 1 antibodies are not usually tested, the condition may be over diagnosed or misdiagnosed. Similarly, the results of treatment are not usually corrected for confounding factors such as fetal chromosomal aberrations. In the absence of other confounding factors low molecular weight heparins are probably the treatment of choice.

Antiphospholipid syndrome

Antiphospholipid syndrome has received considerable attention from the medical community because of its association with a number of serious clinical disorders, including arterial and venous thromboembolism, acute ischemic encephalopathy, recurrent pregnancy loss, thrombocytopenia, and livido reticularis. It can occur within the context of several diseases, mainly autoimmune disorders, and is then called secondary antiphospholipid syndrome. However, it may be also be present without any recognizable disease, or so-called primary antiphospholipid syndrome. There is no defined racial predominance for primary antiphospholipid syndrome, although a higher prevalence of systemic lupus erythematosus (SLE) occurs in African Americans and the Hispanic population. Multiple terms exist for this syndrome, some of which can be confusing. Lupus anticoagulant syndrome, for example, is a misleading term, because patients may not necessarily have SLE, and it is associated with thrombotic rather than hemorrhagic complications. To avoid further confusion, antiphospholipid syndrome is currently the preferred term for this clinical syndrome. Antiphospholipid antibodies are found in 1% to 5% of young healthy control subjects; however, the incidence increases with age and coexistent chronic disease. The syndrome occurs most commonly in young to middle-aged adults; however, it also can occur in children and the elderly. Among patients with SLE, the prevalence of antiphospholipid antibodies is high, ranging from 12% to 30% for anticardiolipin antibodies, and 15% to 34% for lupus anticoagulant antibodies. In general, anticardiolipin antibodies occur approximately five times more often then lupus anticoagulant in patients with antiphospholipid syndrome. This syndrome is the most common cause of acquired thrombophilia, associated with either venous or arterial thrombosis or both. It is characterized by the presence of antiphospholipid antibodies, recurrent arterial and venous thrombosis, and spontaneous abortion. Rarely, patients with antiphospholipid syndrome may have fulminate multiple organ failure, or catastrophic antiphospholipid syndrome. This is caused by widespread microthrombi in multiple vascular beds, and can be devastating. Patients with catastrophic antiphospholipid syndrome may have massive venous thromboembolism, along with respiratory failure, stroke, abnormal liver enzyme concentrations, renal impairment, adrenal insufficiency, and areas of cutaneous infarction. According to the international consensus statement, at least one clinical criterion (vascular thrombosis, pregnancy complications) and one laboratory criterion (lupus anticoagulant, antipcardiolipin antibodies) should be present for a diagnosis of antiphospholipid syndrome. The hallmark result from laboratory tests that defines antiphospholipid syndrome is the presence of antibodies or abnormalities in phospholipid-dependent tests of coagulation, such as dilute Russell viper venom time. There is no consensus for treatment among physicians. Overall, there is general agreement that patients with recurrent thrombotic episodes require life-long anticoagulation therapy and that those with recurrent spontaneous abortion require anticoagulation therapy and low- dose aspirin therapy during most of gestation. Prophylactic anticoagulation therapy is not justified in patients with high titer anticardiolipin antibodies with no history of thrombosis. However, if a history of recurrent deep vein thrombosis or pulmonary embolism is established, long-term anticoagulant therapy with international normalized ratio (INR) of approximately 3 is needed.

Human monoclonal antiphospholipid antibodies disrupt the annexin A5 anticoagulant crystal shield on phospholipid bilayers: evidence from atomic force microscopy and functional assay

The antiphospholipid (aPL) syndrome is an autoimmune condition that is marked by recurrent pregnancy losses and/or systemic vascular thrombosis in patients who have antibodies against phospholipid/co-factor complexes. The mechanism(s) for pregnancy losses and thrombosis in this condition is (are) not known. Annexin A5 is a potent anticoagulant protein, expressed by placental trophoblasts and endothelial cells, that crystallizes over anionic phospholipids, shielding them from availability for coagulation reactions. We previously presented data supporting the hypothesis that aPL antibody-mediated disruption of the anticoagulant annexin A5 shield could be a thrombogenic mechanism in the aPL syndrome. However, this has remained a subject of controversy. We therefore used atomic force microscopy, a method previously used to study the crystallization of annexin A5, to image the effects of monoclonal human aPL antibodies on the crystal structure of the protein over phospholipid bilayers. In the presence of the aPL monoclonal antibodies (mAbs) and beta(2)-GPI, the major aPL co-factor, structures presumed to be aPL mAb-antigen complexes were associated with varying degrees of disruption to the annexin A5 crystallization pattern over the bilayer. In addition, measurements of prothrombinase activity on the phospholipid bilayers showed that the aPL mAbs reduced the anti-coagulant effect of annexin A5 and promoted thrombin generation. These data provide morphological evidence that support the hypothesis that aPL antibodies can disrupt annexin A5 binding to phospholipid membranes and permit increased generation of thrombin. The aPL antibody-mediated disruption of the annexin A5 anticoagulant shield may be an important prothrombotic mechanism in the aPL syndrome.