Lupus anticoagulant and history of thrombosis are not associated with persistent endothelial cell activation in systemic lupus erythematosus

Role of Platelets in Rheumatic Chronic Autoimmune Inflammatory Diseases

Platelets are essential in maintaining blood homeostasis and regulating several inflammatory processes. They constantly interact with immune cells, have immunoregulatory functions, and can affect, through immunologically active substances, endothelium, leukocytes, and other immune response components. In reverse, inflammatory and immune processes can activate platelets, which might be significant in autoimmune disease progression and arising complications. Thus, considering this interplay, targeting platelet activity may represent a new approach to treatment of autoimmune diseases. This review aims to highlight the role of platelets in the pathogenic mechanisms of the most frequent chronic autoimmune inflammatory diseases to identify gaps in current knowledge and to provide potential new targets for medical interventions.

Elevated circulating thrombomodulin levels in systemic lupus erythematosus: a systematic review and meta-analysis

OBJECTIVES

Thrombomodulin (TM) is closely related to the pathogenesis of autoimmune diseases, including systemic lupus erythematosus (SLE). However, current evidence on circulating TM levels in SLE patients is contradictory. We conducted this meta-analysis to more accurately assess circulating TM levels in patients with SLE and lupus nephritis (LN) and to analyze related influencing factors.

METHODS

Systematic search of relevant documents was conducted in PubMed, Embase, and The Cochrane Library databases (up to 28 February 2021). Studies on the comparison of circulating TM between SLE patients and controls were screened and evaluated for inclusion. Random-effects model analysis was applied to calculate the combined standardized mean difference (SMD) with a 95% confidence interval (CI). Heterogeneity was estimated by Q statistics and I2.

RESULTS

A total of 353 articles were identified, 14 provided adequate information for this study finally. The results illustrated that SLE patients had higher TM levels than healthy controls (SMD =0.38, 95% CI: 0.02 to 0.74, p=0.04). Circulating TM levels were increased in patients with active SLE compared to inactive SLE patients (SMD=1.12, 95% CI: 0.03 to 2.20, p=0.04). In addition, circulating TM levels of SLE patients with LN were higher than those without LN (SMD=4.55, 95% CI: 1.97 to 7.12, p=0.001).

CONCLUSIONS

The circulating TM levels in SLE patients are enhanced. In addition, circulating TM levels may be practical in reflecting the disease activity and nephritis involvement of SLE patients.

Serum of patients with antiphospholipid syndrome induces adhesion molecules in endothelial cells

OBJECTIVE

The antiphospholipid syndrome (APS) is a systemic auto-immune disease with an unclear pathophysiology. The aim of our study was to understand the development of APS on a cellular level. Therefore, we analyzed the influence of human serum of APS patients on endothelial expression of specific genes and proteins in comparison to a control group.

METHODS

In this study, we analyzed the expression of ICAM-1, VCAM-1, E-selectin and annexin V in primary cultures of human umbilical vein endothelial cells (HUVEC) in response to 10% (v/v) serum of control patients (n = 6), patients with systemic lupus erythematosus (SLE) and no APS (n = 4) or APS patients (n = 9) for 24 h. Total RNA was prepared from confluent endothelial cell layers and mRNA expression of ICAM-1, VCAM-1 and E-selectin was analyzed by reverse transcription polymerase-chain reaction (RT-PCR). The protein expression was determined by Western blot. Serum protein concentrations of soluble forms of adhesion molecules sICAM-1 and sVCAM-1 were quantified by ELISA. Gene expression data were correlated with clinical parameters.

RESULTS

The mRNA expression of ICAM-1 was increased in cells incubated with serum from APS patients (166 ± 22% of control; P = 0.023). Serum of patients with (SLE)/no APS caused a 1.4-fold higher ICAM-1 mRNA level. Western blot analysis showed an increase in protein expression of adhesion molecules ICAM-1 (260 ± 49%; P = 0.011) and VCAM-1 (357 ± 97%; P = 0.023) in cells that were incubated with serum from APS patients. Plasma analysis showed elevated levels of sVCAM-1 in APS patients (189 ± 34%; P = 0.045) compared to the levels measured in the control group. The sVCAM-1 plasma level was correlating with the frequency of abortions.

CONCLUSION

An augmented expression of endothelial adhesion molecules is involved in the pathophysiology of patients with antiphospholipid syndrome.

Hyperhomocysteinemia Relates to the Subtype of Antiphospholipid Antibodies in Non-SLE Patients

Abnormal increases of antiphospholipid antibody and plasma homocysteine levels are recently emerging as nonlipidic risk factors for cerebral atherogenesis and thrombosis. Both antiphospholipid antibody and homocysteine share many similar bioeffects in hemostasis, but their interaction is still inconsistent. In this study, we examined the relation between the plasma homocysteine level and lupus anticoagulant, anticardiolipin antibody, and anti-β2-glycoprotein I antibody in patients with noncardiac cerebral ischemia. Systemic lupus erythrematosus patients were excluded. The results showed a higher frequency of moderate hyperhomocysteinemia in patients with an abnormal increase of lupus anticoagulant only. Neither the serum folate and cobalamin levels nor methylenetetrahydrofolate reductase allele mutation contributes to this result. Accordingly, homocysteine interacts with lupus anticoagulant to promote cerebral atherosclerosis and ischemia. The role of vasculopathic or prothrombotic autoantibody generation in response to specific pathological change such as hyperhomocysteinemia warrants further investigation.

Primary Antiphospholipid Syndrome Associated with Pneumonia: A Case Report of a 16-Year-Old Male Patient

Antiphospholipid syndrome (APS) is an autoimmune disease characterised by arterial and/or venous thrombosis and/or recurrent pregnancy loss in the presence of antiphospholipid (APL) antibodies. It is evaluated as APS when it develops associated with other systemic autoimmune diseases or primary APS if there is no concomitant disorder. In this study, we present a case of a 16-year-old male patient with primary APS. The patient was admitted with presumptive diagnosis of pneumonia, but multiple pulmonary thromboembolism (PTE) was observed on computerized tomography (CT) pulmonary angiography. APL antibodies positivity and thrombocytopenia developed in our patient. The patient was evaluated as primary APS since another etiology that could explain PTE was not found. Primary APS is a rare disease in children along with adolescents, compared with APS associated with other systemic autoimmune diseases. We present here a young male patient with primary APS and PTE to contribute to the literature. The patient initially had pneumonia but later developed PTE and thrombocytopenia.

Pentraxin 3 as a biomarker of local inflammatory response to vascular injury in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder with organ injury related to vasculitis. Inflammation of blood vessels results from auto-immunological activation of endothelial cells. The pentraxin 3 (PTX3), might act as an indicator of vasculitides in many diseases. The aim of this study was to determine whether PTX3 might be useful as a marker of vascular injury in SLE. This study was carried out in a group of 56 SLE women, and in the 28 female volunteers control group. All participants' plasma and serum samples were collected to estimate concentrations (ELISA) of PTX3, soluble thrombomodulin, soluble E-selectin (sE-selectin), soluble P-selectin (sP-selectin), soluble form of vascular cell adhesion molecule 1 (sVCAM-1), soluble inter-cellular adhesion molecule-1 (sICAM-1), soluble platelet endothelial cell adhesion molecule 1, monocyte chemotactic protein-1 (MCP-1) and von Willebrand factor (vWF) activity. Anthropometric, demographic and lifestyle characteristics of SLE patients were also performed. The SLE patients had higher PTX3, vWF, MCP-1, sE-selectin and sVCAM-1 levels than the controls (1.82 ± 1.56 ng/mL, 237 ± 101%, 70.05 ± 18.31 ng/mL, 111.16 ± 49.15 ng/mL and 978.78 ± 462.35 ng/mL vs. 0.86 ± 0.40 ng/mL, 138 ± 43%, 58.56 ± 13.91 ng/mL, 66.04 ± 27.18 ng/mL and 499.07 ± 125.67 ng/mL, respectively). The independent factors affecting PTX3 expression included Systemic Lupus Erythematosus Disease Activity Index, prednisone dose and anemia severity. Moreover, the PTX3 areas under the curve-receiver operating characteristics curves 0.717 ± 0.056 with cut-off level of 1.96 ng/mL was comparable to vWF, MCP-1, sE-selectin, sP-selectin and sICAM-1. PTX3 and sVCAM-1 were the only factors related to SLE activity. Other vascular injury indicators associated with PTX3 were vWF and sVCAM-1. In conclusion, PTX3 concentrations in SLE patients might serve as a indicator of the activation/dysfunction of vascular endothelium.

Cell adhesion molecules as potential biomarkers of nephritis, damage and accelerated atherosclerosis in patients with SLE

Objectives

The aim of the current study was to compare levels of vascular cell adhesion molecule-1 (VCAM-1) and E-selectin in lupus patients and controls and to investigate their association with clinical phenotype, disease activity and damage.

Methods

We compared levels of serum VCAM-1 and E-selectin in 178 female lupus patients and 69 age-and sex-matched controls. Using linear regression we also examined the association between these markers and disease activity, damage, renal and skin involvement as well as clinical and subclinical cardiovascular disease.

Results

E-selectin was increased in patients compared to controls (median (IQR) 10.5 (6.85, 13.9) vs 7.86 (5.39, 10.4) ng/ml; p < 0.001). E-selectin was also associated with overall damage and carotid plaque (β (95% confidence interval): 0.27 (0.029, 0.511) and 0.26 (0.148, 0.507)). Whilst there was no significant difference in VCAM-1 levels between groups overall, we found a significant association between VCAM-1 and with active renal disease (β (95% confidence interval): 1.10 (0.69, 1.51)).

Conclusions

E-selectin may act as a marker of cardiovascular risk in SLE, whilst VCAM-1 may have a role as a non-invasive biomarker for lupus nephritis activity.

Patients with antiphospholipid syndrome display endothelial perturbation

BACKGROUND

There is strong evidence that antiphospholipid antibodies (aPL) perturb endothelium both in vitro and in experimental animal models. by inducing a vasculopathy and an endothelial pro-inflammatory/coagulant phenotype. However, few contrasting studies raised the issue about the possibility to detect a comparable endothelial perturbation in anti-phospholipid syndrome (APS) patients. The aim of this observational case-control study was to evaluate several parameters of endothelial perturbation in patients with APS and without any other atherosclerosis risk factor.

PATIENTS AND METHODS

We investigated plasma levels of soluble adhesion molecules (s-ICAM-1, s-VCAM-1, s-E-selectin), soluble thrombomodulin (sTM), von Willebrand factor (vWF) and tissue plasminogen activator (t-PA) by solid-phase assays in 40 selected APS patients and 40 age- and sex-matched healthy subjects. In addition, we evaluated circulating endothelial cells by flow cytometry and brachial artery flow-mediated vasodilation. Patients and controls were free of conditions known to affect both the biological and the functional endothelial parameters.

RESULTS

Plasma levels of sTM, s-E-selectin and s-VCAM-1 did not differ from controls, while a significant increase in s-ICAM-1 (P = 0.029), t-PA (P = 0.003) and vWF titres (P = 0.002) was found. Circulating mature endothelial cells were also significantly higher in patients than in controls (P = 0.05) and decreased during both vitamin K antagonists (P = 0.001) and antiplatelet (P = 0.032) treatments. Mean brachial artery flow-mediated vasodilation responses were significantly impaired compared to healthy subjects (P = 0.0001).

CONCLUSIONS

As a whole these findings indicate that APS patients display an endothelial perturbation in the absence of other detectable traditional risk factors for atherosclerosis.

Endothelial function and markers of endothelial activation in relation to cardiovascular disease in systemic lupus erythematosus

OBJECTIVE

Cardiovascular disease (CVD) is common in patients with systemic lupus erythematosus (SLE) although it is not clear whether an increased risk of CVD is a general feature of SLE or whether it applies only to a subgroup of patients. Our objective was to evaluate endothelial function and markers of endothelial activation in relation to CVD in SLE.

METHODS

Twenty-six women with SLE and previous CVD (SLE/CVD cases, defined as objectively verified angina pectoris, myocardial infarction, cerebral infarction, or intermittent claudication; 52+/-8.2 years) were compared with age-matched SLE women without CVD (SLE controls) and population control women. Flow-mediated dilatation (FMD) of the brachial artery after reactive hyperaemia and nitroglycerin-mediated dilatation (NMD) after sublingual nitroglycerin administration were determined by ultrasound. Soluble thrombomodulin (sTM) and soluble vascular cellular adhesion molecule-1 (sVCAM-1) were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

FMD and NMD levels did not differ between SLE controls and population controls. In SLE cases FMD and NMD were not assessed because of interference with nitro-related medication. sVCAM-1 discriminated between SLE cases, SLE controls, and population controls (ng/mL; 814+/-221 vs. 545+/-214 vs. 401+/-189, p<0.01), whereas sTM (ng/mL; 5.2+/-2.8 vs. 4.2+/-1.9 vs. 3.0+/-0.5) differed between both SLE groups and controls (p<0.05).

CONCLUSION

In this study SLE women free of CVD had good endothelial function (FMD), a possible marker of protection from lupus-related CVD. In addition, high levels of sVCAM-1, associated with systemic tumour necrosis factor-alpha (TNFalpha) activity, were identified as a novel discriminator for SLE-related CVD. This supports our hypothesis that SLE patients with enhanced systemic TNFalpha activity are at high risk of developing CVD.

Antiphospholipid antibodies induce vascular functional changes in mice: a mechanism of vascular lesions in antiphospholipid syndrome?

Abstract

A premature atherosclerosis has been presumed in patients with antiphospholipid syndrome. The potential role of antiphospholipid antibodies in the development of atheroma is rather controversial. In this study, we tested the hypothesis that antiphospholipid antibodies could induce atherosclerosis via vascular functional changes. CD1 mice received one single injection of antiphospholipid monoclonal antibodies derived from male (BXSB × NZW) F1 mice with a lupus-like disease associated with an antiphospholipid syndrome and coronary artery disease. One week later, first-order mesenteric arteries (diameter 220–260 μm) were isolated and mounted on a small-vessel myograph for the measurement of the relaxation responses to acetylcholine or the NO donor nitroprusside after precontraction by phenylephrine. Five out of eight antiphospholipid monoclonal antibodies reduced the response to acetylcholine compared with control mice, and this effect was especially marked with one of them. No change in the response to nitroprusside was observed. The impairment was maintained after 3 weeks of treatment and appeared related to a moderate decrease in NO-mediated responses and a marked decrease in prostanoid-mediated relaxations. These vascular functional changes could be prevented by chronic treatment with statins or aspirin. These data could constitute additional elements supporting a direct pathogenic role of antiphospholipid antibodies. We suggest that a sub-population of these autoantibodies could be responsible for the endothelial dysfunction observed in antiphospholipid syndrome.

Role of anti-β2 glycoprotein I antibodies in antiphospholipid syndromeglycoprotein I antibodies in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by the presence of recurrent venous/ arterial thrombosis and fetal losses associated with a family of auto-antibodies directed against phospholipid (PL)-binding proteins. Among them, beta2 glycoprotein I (beta2GPI) is the most important. As a plasma cationic protein, beta2GPI binds to anionic PLs involved in several fluid-phase coagulation steps, and more importantly, it can be expressed on the surface of different cell types. Anti-beta2GPI antibodies recognize the molecule expressed on endothelial cells, platelets, monocytes, and trophoblast cells. Once bound, the antibodies trigger in vitro cell signaling that modulates biological responses potentially responsible for pathogenic mechanisms. Experimental animal models have supported the in vivo pathogenic role of anti-beta2GPI antibodies in both thrombosis and fetal loss models.

The placental bed in pregnancies complicated by primary antiphospholipid syndrome

Pregnancy in women with primary antiphospholipid syndrome (APS) is frequently associated with placental insufficiency leading to intrauterine growth restriction (IUGR)+/-fetal death, pre-eclampsia, placental abruption, premature delivery or thrombosis. The aim of this study was to investigate the placental bed in APS pregnancies for evidence of impaired trophoblast invasion, endothelial cell activation (ECA) and macrophage infiltration.

METHODS

Biopsies from the presumed site of the placental bed were obtained from 12 women with treated primary APS and 16 controls. Immunohistochemical methods were employed to investigate expression of cytokeratin (trophoblasts), alpha-actin (smooth muscle), CD68 (macrophages) and VCAM-1 (as marker of ECA). Fibrinoid and elastin distribution and expression were determined by periodic acid/Schiff and orcein stain, respectively.

RESULTS

Three APS pregnancies developed IUGR, one with concurrent pre-eclampsia. Eight of 12 APS biopsies were confirmed to be from the placental bed; one patient failed to meet APS criteria and was excluded from analysis; six included spiral arteries in the biopsy; 11 of 16 controls' biopsies were from the placental bed. APS biopsies had a higher concentration of inflammatory cells (p=0.0001), particularly macrophages (p=0.014). Three APS biopsies showed necrosis with hyperplastic vessels; one demonstrated arterial thromboses, but none had profound vasculopathy/atherosis or ECA.

CONCLUSION

Inflammatory mechanisms in the placental bed may contribute to APS pregnancy complications.

Innate immunity in the antiphospholipid syndrome: role of toll-like receptors in endothelial cell activation by antiphospholipid antibodies

Antiphospholipid antibodies are mainly directed against beta 2 glycoprotein I (beta2GPI), a plasma phospholipid-binding protein expressed on endothelial cells of different anatomical localizations. Anti-beta2GPI antibodies recognize the molecule on endothelial monolayers in vitro, and, once bound, might activate the cells both in vitro and in vivo experimental models inducing a proinflammatory and a procoagulant phenotype. Cell activation is associated with nuclear factor-kappaB (NF-kappaB) translocation and with a signaling cascade comparable to that triggered by the toll-like receptors (TLRs)-4. The cell membrane receptor(s) for beta2GPI adhesion is still under investigation. It has been suggested that beta2GPI might adhere through electrostatic interaction between its cationic phospholipid binding site and anionic structures on the cell membrane; however, binding to annexin II-the endothelial cell receptor for tissue plasminogen activator-plays also a role. Because annexin II does not display any transmembrane protein, it has been suggested that it requires a yet unknown "adaptor" protein to signal the cells. Because of the molecular mimicry between beta2GPI and viral/bacterial structures-the natural ligands for TLRs-antibodies might cross-link the molecule associated to annexin II and TLR-4 eventually triggering the signaling.

Inflammatory response and the endothelium

Antiphospholipid-mediated endothelium perturbation plays a role in antiphospholipid syndrome (APS)-associated vasculopathy. Antiphospholipid antibodies activate endothelium both in vitro and in vivo experimental models by inducing a pro-inflammatory/-coagulant phenotype; the antibodies recognize beta2 glycoprotein I (beta2GPI) on human endothelial cells (EC) from different parts of the vasculature. In spite of such large in vitro evidence, few studies have addressed the issue whether or not a comparable endothelial perturbation might be detectable in vivo. We investigated several indirect ex vivo parameters of endothelial dysfunction: plasma levels of soluble adhesion molecules (sADM), soluble thrombomodulin (sTM), von Willebrand factor (vWF) and tissue plasminogen activator (t-PA) by solid-phase assays. The study included: patients with primary antiphospholipid syndrome (n=32), with the syndrome secondary to non-active systemic lupus erythematosus (SLE, n=10), six patients with persistent antiphospholipid positivity at medium/high titre without any clinical manifestation of the syndrome. Fifty-two age and sex matched healthy subjects have been enrolled as controls. In addition, circulating endothelial cells identified by flow cytometry and the brachial artery flow-mediated vasodilation (FMV) were evaluated in 26 patients (20 primary and 6 lupus syndromes) and 30 healthy controls. Plasma levels of soluble adhesion molecules did not differ from controls, while a significant increase in von Willebrand factor titres (P<0.05) was found. No significant difference was found regarding the number of circulating endothelial cells and flow-mediated vasodilation. As a whole, these findings do suggest that antiphospholipid antibodies per se are not able to support a full-blown endothelial perturbation in vivo. As shown in antiphospholipid syndrome experimental animal models, a two-hit hypothesis is suggested.

The prevalence and clinical significance of autoantibodies to plasminogen activator inhibitor 1 in systemic lupus erythematosus

We have recently described the novel autoantigen plasminogen activator inhibitor (PAI-1) in systemic lupus erythematosus (SLE). The aim of this study was to determine the prevalence and clinical significance of anti-PAI-1 autoantibodies in patients with SLE. Autoantibodies to recombinant PAI-1 were measured in retrospective sera of 48 lupus patients by immunoassay in order to assess their clinical significance. This showed that 71% of sera from 48 lupus patients had significantly elevated anti-PAI-1 autoantibodies as compared with normal control subjects (P < 0.0001). There was a weak but significant (P < 0.043) correlation with anti-dsDNA autoantibodies. In longitudinal studies, autoantibodies against PAI-1 correlated with clinical parameters measured by the BILAG disease activity index including global clinical score. Our study demonstrates the high frequency of novel autoantibodies to PAI-1 in patients with lupus. The serial clinical correlations with anti-PAI-1 autoantibodies also support the hypothesis that these autoantibodies may play a pathogenic role in lupus.

Increased platelet deposition on extracellular matrix under flow conditions in patients with antiphospholipid syndrome who experience thrombotic events

OBJECTIVE

To assess platelet function under defined flow conditions in patients with antiphospholipid syndrome (APS) and to correlate the results with thrombotic complications and the presence of subsets of antiphospholipid antibodies (aPL), lupus anticoagulant (LAC), and/or anticardiolipin antibodies (aCL).

METHODS

We studied 88 randomized APS patients with or without a history of thrombosis. Seventeen patients with other thrombosis (no APS) and 26 healthy subjects served as controls. Platelet adhesion and aggregation on the extracellular matrix were measured with a cone-and-plate(let) analyzer (CPA) by examining the percentage of total area covered with platelets (surface coverage [SC]) and the mean size of surface-bound objects (average size [AS]) and were compared with platelet responses to different ADP concentrations by conventional aggregometry.

RESULTS

Under defined flow conditions, SC and AS were significantly higher for venous thrombosis and arterial thrombosis in APS patients compared with no thrombosis, other thrombosis, and healthy control groups. The increased platelet adhesion and aggregation in APS patients with thrombotic events was associated with higher levels of von Willebrand factor (vWF) antigen (mean +/- SD 230.6 +/- 51.2%) and ristocetin cofactor activity (181.0 +/- 36.0%). No change in CPA and vWF parameters was found in APS patients with positive results for aPL who did not undergo thrombotic events or in patients with other thrombosis. The CPA parameters were neither associated with the high response of platelets to ADP nor associated with the presence of LAC, aCL, or both. The CPA parameters were similarly increased irrespective of aspirin use. The results suggest that the increased adhesion properties of platelets in APS patients could be mediated by high levels and activity of vWF. This complements the known ability of APS antibodies to enhance platelet response to agonists in conventional aggregometry.

CONCLUSION

The CPA test was found to be valuable in differentiating APS patients with and without thrombotic complications.

Antiphospholipid antibodies bind to activated but not resting endothelial cells: is an independent triggering event required to induce antiphospholipid antibody-mediated disease?

INTRODUCTION

Antiphospholipid antibodies (aPL) cause thrombotic disease and recurrent pregnancy loss. Despite their name it is now clear that the antigen for most antiphospholipid antibodies is the phospholipid-binding protein beta(2) glycoprotein I (beta(2)GPI). However, beta(2) glycoprotein I is only antigenic for antiphospholipid antibodies when the protein is immobilised on a suitable surface such as phosphatidyl serine. It has been suggested that antiphospholipid antibodies bind to beta(2) glycoprotein I on the surface of resting endothelial cells and this in turn leads to endothelial activation and the initiation of thrombosis. However, as phosphatidyl serine is absent from resting endothelial cell membranes, we questioned this hypothesis.

MATERIALS AND METHODS

The ability of human antiphospholipid antibody-containing sera and monoclonal antiphospholipid antibodies to interact with endothelial cells was examined using cell-based ELISAs employing human umbilical vein endothelial cells (HUVECs) as the antigen. The expression of adhesion molecules in response to treatment with antiphospholipid antibodies was also measured by a cell-based ELISA. Activation of NF kappa beta was examined using electrophoretic mobility shift assays (EMSAs).

RESULTS

Neither monoclonal antiphospholipid antibodies nor human sera containing antiphospholipid antibodies bound to resting endothelial cells. In contrast, one monoclonal antiphospholipid antibody did bind to both activated and apoptotic endothelial cells.

CONCLUSIONS

Antiphospholipid antibodies do not bind to resting endothelial cells nor do antiphospholipid antibodies activate resting endothelial cells. Rather, an independent triggering event is required to activate endothelial cells and subsequently some antiphospholipid antibodies may then bind to the activated endothelial cells and initiate a thrombogenic process.

Antiphospholipid syndrome: pathogenic mechanisms

Despite the strong association between antiphospholipid antibodies (aPL) and thrombosis, the pathogenic role of aPL in the development of thrombosis has not been fully elucidated. Proposed pathophysiological mechanisms may be categorized into two types. First, aPL may act in vivo by disrupting the kinetics of the normal procoagulant and anticoagulant reactions occurring on cell membranes. Second, aPL may stimulate certain cells thereby altering the expression and secretion of various molecules. In this article, we review the mechanisms by which aPL may develop thrombotic events.

Longitudinal evaluation of markers of endothelial cell dysfunction and hemostasis in treated antiphospholipid syndrome and in healthy pregnancy

OBJECTIVE

The purpose of this study was to determine whether primary antiphospholipid syndrome pregnancies are associated with endothelial cell activation in the maternal circulation.

STUDY DESIGN

Markers of endothelial cell activation were measured every 4 weeks during pregnancy in the blood of 23 women with primary antiphospholipid syndrome and 19 control subjects. All women with antiphospholipid syndrome received anticoagulant treatment. Plasma concentrations of plasminogen activator inhibitor type 1, tissue plasminogen activator, soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, and soluble thrombomodulin were determined by enzyme-linked immunoassay. Concentrations of prothrombin fragments 1+2 and D-dimers were also determined.

RESULTS

Three antiphospholipid syndrome pregnancies (13%) were complicated by intrauterine growth restriction and preeclampsia; one antiphospholipid syndrome pregnancy (4%) was complicated by preterm rupture of membranes. Six women with antiphospholipid syndrome (26%) had thrombotic events. Differences in concentrations of endothelial cell activation markers between antiphospholipid syndrome and control pregnancies were not significant.

CONCLUSION

Despite poorer pregnancy outcome, there was no evidence of greater endothelial cell activation in antiphospholipid syndrome pregnancies that were treated.