Differences in Endothelial Activation and Dysfunction Induced by Antiphospholipid Antibodies Among Groups of Patients With Thrombotic, Refractory, and Non-refractory Antiphospholipid Syndrome

Longitudinal assessment of cerebral infarcts and small vessel disease using magnetic resonance imaging in antiphospholipid syndrome: A single-centre retrospective study

Introduction

Stroke is the most frequent arterial thrombosis in antiphospholipid syndrome (APS) with high rates of recurrence.

Methods and patients

A retrospective, single-centre 10-year review of patients with APS having sequential cerebral magnetic resonance imaging (MRI) was performed to describe ischaemic features in APS and associated disease risk factors and progression over time.

Results

A total of 120 patients and 307 scans were included with 67% of patients receiving vitamin K antagonists (VKA). Note that 65% of patients had baseline ischaemic features with white matter hyperintensities (WMH), as a feature of small vessel disease (SVD), seen in 79% of abnormal scans. Fifteen percent of patients had progressive ischaemic changes with 83% demonstrating progressive WMH and 33% new infarcts (predominantly lacunar) on sequential scans. Progression-free survival for progressive ischaemia was 88% at 5 years. Multivariate analysis showed longer follow-up was a risk for developing progressive ischaemia (odds ratio [OR] 1.43, 95% confidence interval [CI] 1.13-1.86, p = 0.005). Hypertension (56% vs. 30%, p = 0.04) and ischaemic heart disease (22% vs. 6%, p = 0.04) were more prevalent with progressive ischaemia. There was no difference in progression or bleeding events according to VKA therapeutic intensity.

Discussion

These results show SVD is a common feature of APS using MRI with progressive changes despite anticoagulation. Traditional risk factors for cerebrovascular disease were associated with progression.

Can complement activation be the missing link in antiphospholipid syndrome?

APS is an autoimmune disorder with life-threatening complications that, despite therapeutic advantages, remains associated with thrombotic recurrences and treatment failure. The role of complement activation in APS pathogenesis is increasingly recognized, specifically in obstetric APS. However, its exact role in thrombotic APS and on the severity of the disease is not yet fully elucidated. Further mechanistic studies are needed to delineate the role of complement activation in the various APS clinical manifestations with aim to identify novel markers of disease severity, together with clinical trials to evaluate the efficacy of complement inhibition in APS. This could ultimately improve risk stratification in APS, patient-tailored targeted therapy with complement inhibition identified as an adjunctive treatment. This article reviews current findings and challenges about complement activation in APS, discusses the potential role of platelet-mediated complement activation in this setting and provides an overview of clinical implications and current therapeutics.

Parvovirus B19 Infection Is Associated with the Formation of Neutrophil Extracellular Traps and Thrombosis: A Possible Linkage of the VP1 Unique Region

Neutrophil extracellular traps (NETs) formation, namely NETosis, is implicated in antiphospholipid syndrome (APS)-related thrombosis in various autoimmune disorders such as systemic lupus erythematosus (SLE) and APS. Human parvovirus B19 (B19V) infection is closely associated with SLE and APS and causes various clinical manifestations such as blood disorders, joint pain, fever, pregnancy complications, and thrombosis. Additionally, B19V may trigger the production of autoantibodies, including those against nuclear and phospholipid components. Thus, exploring the connection between B19V, NETosis, and thrombosis is highly relevant. An in vitro NETosis model using differentiated HL-60 neutrophil-like cells (dHL-60) was employed to investigate the effect of B19V-VP1u IgG on NETs formation. A venous stenosis mouse model was used to test how B19V-VP1u IgG-mediated NETs affect thrombosis in vivo. The NETosis was observed in the dHL-60 cells treated with rabbit anti-B19V-VP1u IgG and was inhibited in the presence of either 8-Br-cAMP or CGS216800 but not GSK484. Significantly elevated reactive oxygen species (ROS), myeloperoxidase (MPO), and citrullinated histone (Cit-H3) levels were detected in the dHL60 treated with phorbol myristate acetate (PMA), human aPLs IgG and rabbit anti-B19V-VP1u IgG, respectively. Accordingly, a significantly larger thrombus was observed in a venous stenosis-induced thrombosis mouse model treated with PMA, human aPLs IgG, rabbit anti-B19V-VP1u IgG, and human anti-B19V-VP1u IgG, respectively, along with significantly increased amounts of Cit-H3-, MPO- and CRAMP-positive infiltrated neutrophils in the thrombin sections. This research highlights that anti-B19V-VP1u antibodies may enhance the formation of NETosis and thrombosis and implies that managing and treating B19V infection could lower the risk of thrombosis.

Single-cell transcriptome analyses reveal disturbed decidual homoeostasis in obstetric antiphospholipid syndrome

OBJECTIVES

Obstetric antiphospholipid syndrome (OAPS) is an autoimmune disease characterised by the presence of antiphospholipid antibodies in circulation and pathological pregnancy. However, the pathogenesis of OAPS remains unknown. We aimed to reveal cellular compositions and molecular features of decidual cells involved in the development of OAPS using single-cell RNA sequencing (scRNA-seq).

METHODS

We performed unbiased scRNA-seq analysis on the first-trimester decidua from five OAPS patients and five healthy controls (HCs), followed by validations with flow cytometry, immunohistochemical staining and immunofluorescence in a larger cohort. Serum chemokines and cytokines were measured by using ELISA.

RESULTS

A higher ratio of macrophages but a lower ratio of decidual natural killer (dNK) cells was found in decidua from OAPS compared with HCs. Vascular endothelial cells shrinked in OAPS decidua while having upregulated chemokine expression and conspicuous responses to IFN-γ and TNF-α. Macrophages in OAPS had stronger phagocytosis function, complement activation signals and relied more on glycolysis. dNK cells were more activated in OAPS and had enhanced cytotoxicity and IFN-γ production. Downregulation of granules in OAPS dNK cells could be associated with suppressed glycolysis. Moreover, stromal cells had a prosenescent state with weakened immune surveillance for senescent cells in OAPS. In addition, the cellular interactions between decidual immune cells and those of immune cells with non-immune cells under disease state were altered, especially through chemokines, IFN-γ and TNF-α.

CONCLUSION

This study provided a comprehensive decidual cell landscape and identified aberrant decidual microenvironment in OAPS, providing some potential therapeutic targets for this disease.

Non-invasive imaging in antiphospholipid syndrome to assess subclinical coronary artery disease

Antiphospholipid antibody syndrome (usually named antiphospholipid syndrome, APS) is an autoimmune disorder seen mainly in young people. Clinically, APS is described by pregnancy complications and/or a hypercoagulable state, including the venous or arterial vasculature, and strongly related to antiphospholipid antibodies. Although several cardiac manifestations have been involved with APS, and accelerated atherosclerosis is present in this condition, little is known about cardiovascular (CV) risk and the relation between APS. Several studies have used imaging markers to associate them with the main clinical features of patients with APS and the probability of having subclinical atherosclerosis. However, it has not yet been established which markers are most related to the risk of developing CV diseases (CVD) in these patients. In this narrative review, we focus on non-invasive imaging markers that can predict CVD, including carotid intima-media thickness and carotid plaques assessed by carotid ultrasonography or coronary artery calcium score, which usually by computed tomography. We also examine the evidence about vascular function markers used in APS, such as arterial flow-mediated brachial dilation and artery stiffness measured by the velocity of the pulse wave. We present the current status of non-invasive imaging markers, which suggest the existence of subclinical atherosclerosis in patients with APS. However, new prospective research is required to identify the predictive value of these findings and their modification by current treatments for APS.

The effects of hydroxychloroquine and its promising use in refractory obstetric antiphospholipid syndrome

Hydroxychloroquine (HCQ) is obtained by hydroxylation of chloroquine (CQ) and the first indication was malaria. Nowadays, HCQ is commonly used in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) with favorable results. Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombosis and/or pregnancy morbidity and persistent positivity of antiphospholipid antibodies. Around 20-30% of pregnant women with APS develop adverse pregnancy outcomes despite conventional treatment with aspirin and heparin, called refractory obstetric APS. Interestingly, HCQ has shown positive effects on top of the standard of care in some refractory obstetric APS patients. HCQ mechanisms of action in APS comprise its ability to bind sialic acid present in cell membranes, its capacity to block the binding of antiphospholipid antibodies to the cell and the induced increase of pH in extracellular and intracellular compartments. However, the precise mechanisms of HCQ in the specific situation of refractory APS still need to be fully clarified. Therefore, this review summarizes the known modulating effects of HCQ and CQ, their side effects and use in APS and different pathologies to understand the benefit effects and the mechanism of action of HCQ in refractory obstetric APS.

Role of Lipid Rafts on LRP8 Signaling Triggered by Anti-β2-GPI Antibodies in Endothelial Cells

Antiphospholipid antibody syndrome is an autoimmune disease characterized by thrombosis and/or pregnancy morbidity in association with circulating antiphospholipid antibodies, mainly anti-β2 glycoprotein 1 antibodies (anti-β2-GPI antibodies). Previous studies demonstrated that the signaling pathway may involve lipid rafts, plasma membrane microdomains enriched in glycosphingolipid and cholesterol. In this study, we analyzed the signaling pathway of LRP8/ApoER2, a putative receptor of anti-β2-GPI antibodies, through lipid rafts in human endothelial cells. LRP8, Dab2 and endothelial nitric oxide synthase (e-NOS) phosphorylation were evaluated using Western blot, Nitric Oxide (NO) production with cytofluorimetric analysis, LRP8 enrichment in lipid rafts via sucrose gradient fractionation, and scanning confocal microscopy analysis of its association with ganglioside GM1 was also conducted. The analyses demonstrated that affinity-purified anti-β2-GPI antibodies induced LRP8 and Dab-2 phosphorylation, together with a significant decrease in e-NOS phosphorylation, with consequent decrease in NO intracellular production. These effects were almost completely prevented by Methyl-β-cyclodextrin (MβCD), indicating the involvement of lipid rafts. It was supported with the observation of LRP8 enrichment in lipid raft fractions and its association with ganglioside GM1, detected with scanning confocal microscopy. These findings demonstrate that LRP8 signaling triggered by anti-β2-GPI antibodies in endothelial cells occurs through lipid rafts. It represents a new task for valuable therapeutic approaches, such as raft-targeted therapy, including cyclodextrins and statins.

Augmented oxidative stress, accumulation of DNA damage and impaired DNA repair mechanisms in thrombotic primary antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a rare autoimmune disorder with complex pathogenesis. Studies have shown that oxidative stress may contribute to APS pathophysiology. In peripheral blood mononuclear cells (PBMCs) from thrombotic Primary APS (thrPAPS) patients and age/sex-matched healthy controls (HC), as well as a control group of asymptomatic antiphospholipid antibody (aPL) positive individuals without APS (aPL+/non-APS), we examined oxidative stress, abasic (apurinic/apyrimidinic) sites, and DNA damage response (DDR)-associated parameters, including endogenous DNA damage (single- and double-strand breaks) and DNA repair mechanisms, namely nucleotide excision repair (NER) and double-strand breaks repair (DSB/R). We found that thrPAPS patients exhibited significantly higher levels of endogenous DNA damage, increased oxidative stress and abasic sites, as well as lower NER and DSB/R capacities versus HC (all P < 0.001) and versus aPL+/non-APS subjects (all P < 0.05). Our findings demonstrate that oxidative stress and decreased DNA repair mechanisms contribute to the accumulation of endogenous DNA damage in PBMCs from thrPAPS patients and, if further validated, may be exploited as therapeutic targets and potential biomarkers.

In Vitro Assessment of Poly-N-Vinylpyrrolidone/Acrylic Acid Nanoparticles Biocompatibility in a Microvascular Endothelium Model

An amphiphilic copolymer of N-vinyl-2-pyrrolidone and acrylic acid-namely, p(VP-AA)-OD6000 (p(VP-AA))-was synthesized to prepare p(VP-AA) nanoparticles (NPs). Furthermore, the copolymer was linked with CFSE, and the so-prepared nanoparticles were loaded with the DiI dye to form D nanoparticles (DNPs). In this study, as demonstrated by immunofluorescence microscopy, immunofluorescence, and confocal microscopy, DNPs were readily taken up by human microvascular endothelial cells (HMEC-1) cells in a concentration-dependent manner. Upon uptake, both the CFSE dye (green stain) and the DiI dye (red stain) were localized to the cytoplasm of treated cells. Treatment with p(VP-AA) did not affect the viability of normal and challenged with LPS, HMEC-1 cells at 0.010 mg/mL and induced a dose-dependent decrease of these cells' viability at the higher concentrations of 0.033 and 0.066 mg/mL (p ≤ 0.01; p ≤ 0.001, respectively). Furthermore, we focused on the potential immunological activation of HMEC-1 endothelial cells upon p(VP-AA) NPs treatment by assessing the expression of adhesion molecules (E-Selectin, ICAM-1, and V-CAM). NPs treatments at concentrations utilized (p = NS) did not affect individual adhesion molecules' expression. p(VP-AA) NPs do not activate the endothelium and do not affect its viability at pharmacologically relevant concentrations.

Asymmetric Dimethylarginine Is a Marker of Endothelial Dysfunction in Thrombotic Antiphospholipid Syndrome Patients

Objective: The potential contribution of asymmetric dimethylarginine (ADMA) and high-sensitivity C reactive protein (hsCRP) to endothelial dysfunction in APS patients has not been studied in detail, until now. The study involved 105 APS patients (59 diagnosed with primary APS (PAPS) and 46 APS associated with systemic lupus erythematosus (SAPS)) who were compared to 40 controls. Endothelial dysfunction was assessed by measurement of flow-mediated dilatation (FMD) and glyceryl trinitrate dilatation (NMD) of the brachial artery. ADMA (micromol/L) was analyzed by ELISA. Results: FMD in patients with APS was significantly lower than that of the controls (p < 0.001), with no difference between the PAPS and the SAPS groups. ADMA and hsCRP concentrations were significantly higher in the patient cohort than in the control group (p < 0.001, p = 0.006, respectively), as was the case with the SAPS group as compared to the PAPS group (p < 0.001, p = 0.022, respectively). FMD impairment correlated to ADMA (ρ 0.472, p < 0.001) and to hsCRP (ρ 0.181, p = 0.033). In the regression model, the ADMA concentration confirmed the strength of its association (B 0.518, SE 0.183, Wald 8.041, p = 0.005, Exp(B) 1.679, 95% CI 1.174−2.402) to FMD impairment. The synergistic probability model of ADMA and hsCRP caused FMD impairment when the positivity of β2GPIIgG was added. ADMA may be used as a simple and low-cost tool for verifying the presence of endothelial dysfunction in APS patients. According to the results of the study, we could presume that hsCRP, together with aPL, has a preparatory effect on the endothelium in causing endothelial dysfunction.