Cardiovascular disease in the antiphospholipid syndrome

Utilizing type I interferon expression in the identification of antiphospholipid syndrome subsets

INTRODUCTION

Antiphospholipid Syndrome (APS) is a systemic autoimmune disease with a complex multifactorial pathogenesis, combining genetic background, traditional cardiovascular risk factors, disease-specific features such as the presence of antiphospholipid antibodies (aPL), and an imbalance of various immune system functions. Recent data support the role of interferons (IFNs), especially type IIFN (IFN-I), in the onset and development of APS clinical manifestations, including thrombotic events and obstetric complications.

AREAS COVERED

In this review, the authors aimed to discuss the growing body of evidence on the relevance of IFN-I pathways in APS, both from a basic mechanistic perspective, focusing on its possible use in disease/patients stratification. The IFN-I signature has shown promising, although preliminary, results in segregating aPL-positive subjects by aPL profile, association with other autoimmune conditions, such as lupus, age at onset, and current treatment, among others.

EXPERT OPINION

To date, the scarce available data as well as methodological and technical heterogeneity among studies limit the comparability of the results, thus requiring further validation to translate these findings to routine clinical practice. Therefore, further research is required in pursuit of more nuanced patient profiling and the development of new immunomodulatory therapeutic strategies for APS beyond anti-coagulant and antiplatelet agents.

The Solitary Blue Toe: A Unique Presentation of Antiphospholipid Syndrome

Antiphospholipid syndrome is an autoimmune disease characterized by vascular thrombosis involving both the arterial and venous systems that can lead to tissue ischemia or end-organ damage. Much of the literature describes various symptoms at initial presentation, but isolated tissue ischemia manifesting as a solitary blue toe is unusual. We discuss a case of a 23-year-old man who presented to the emergency department with a solitary blue fourth digit with minimal erythema and edema, who was suffering from exquisite pain. Following an extensive workup, the patient was diagnosed with antiphospholipid syndrome with thrombi of the vasculature in their lower extremity. With therapeutic anticoagulation, the patient's symptoms subsided and amputation of the digit was prevented.

Pro‑atherogenic activation of A7r5 cells induced by the oxLDL/β2GPI/anti‑β2GPI complex

A previous study has revealed that oxidized low‑density lipoprotein (oxLDL)/β2‑glycoprotein I (β2GPI)/anti‑β2‑glycoprotein I (anti‑β2GPI), an immune complex, is able to activate the Toll‑like receptor 4 (TLR4)/nuclear factor κβ (NF‑κβ) inflammatory signaling pathway in macrophages, and consequently enhance foam cell formation and the secretion of prothrombin activators. However, the effects of the oxLDL/β2GPI/anti‑β2GPI complex on vascular smooth muscle cells have yet to be investigated. The present study investigated whether the oxLDL/β2GPI/anti‑β2GPI complex was able to reinforce the pro‑atherogenic activities of a rat thoracic aorta smooth muscle cell line (A7r5) and examined the underlying molecular mechanisms. The results revealed that the oxLDL/β2GPI/anti‑β2GPI complex treatment significantly (P<0.05 vs. the media, oxLDL, oxLDL/β2GPI and β2GPI/anti‑β2GPI groups) enhanced the pro‑atherogenic activation of A7r5 cells, including intracellular lipid loading, Acyl‑coenzyme A cholesterol acyltransferase mRNA expression, migration, matrix metalloproteinase‑9 and monocyte chemoattractant protein 1 secretion, all via TLR4. In addition, the expression of TLR4 and the phosphorylation of NF‑κβ p65, p38 and ERK1/2 were also upregulated in oxLDL/β2GPI/anti‑β2GPI complex‑treated A7r5 cells. Pre‑treatment with TAK‑242, a TLR4 inhibitor, was able to partly attenuate the oxLDL/β2GPI/anti‑β2GPI complex‑induced phosphorylation of NF‑κβ p65; however, it had no effect on the phosphorylation of extracellular regulated kinase 1/2 (ERK1/2) and p38. Meanwhile, the NF‑κβ p65 inhibitor ammonium pyrrolidinedithiocarbamate and the ERK1/2 inhibitor U0126, but not the p38 inhibitor SB203580, were able to block oxLDL/β2GPI/anti‑β2GPI complex‑induced foam cell formation and migration in A7r5 cells. Hence, it was demonstrated that the oxLDL/β2GPI/anti‑β2GPI complex is able to enhance the lipid uptake, migration and active molecule secretion of A7r5 cells via TLR4, and finally deteriorate atherosclerosis plaques. Additionally, it was demonstrated that oxLDL/β2GPI/anti‑β2GPI complex‑induced foam cell formation and migration may be partly mediated by the TLR4/NF‑κβ signaling pathway and that ERK1/2 may also participate in the process.

Neurologic manifestations of antiphospholipid syndrome

Neurological involvement in antiphospholipid antibody syndrome (APS) is common, and its occurrence increases morbidity and mortality. Patients may present variable neurological involvement, such as cerebrovascular disease, cognitive dysfunction, headache, seizures, movement disorders, multiple sclerosis-like syndrome, transverse myelitis and ocular symptoms. Most neurological manifestations are associated with thrombosis of the microcirculation or of large vessels; nonetheless, there is compelling evidence suggesting that, in some cases, symptoms are secondary to an immune-mediated pathogenesis, with direct binding of aPL on neurons and glia. Herein we describe clinical characteristics and management of neurological APS manifestations.

Antiphospholipid antibodies induce thrombosis by PP2A activation via apoER2-Dab2-SHC1 complex formation in endothelium

In the antiphospholipid syndrome (APS), antiphospholipid antibody (aPL) recognition of β2 glycoprotein I promotes thrombosis, and preclinical studies indicate that this is due to endothelial nitric oxide synthase (eNOS) antagonism via apolipoprotein E receptor 2 (apoER2)-dependent processes. How apoER2 molecularly links these events is unknown. Here, we show that, in endothelial cells, the apoER2 cytoplasmic tail serves as a scaffold for aPL-induced assembly and activation of the heterotrimeric protein phosphatase 2A (PP2A). Disabled-2 (Dab2) recruitment to the apoER2 NPXY motif promotes the activating L309 methylation of the PP2A catalytic subunit by leucine methyl transferase-1. Concurrently, Src homology domain-containing transforming protein 1 (SHC1) recruits the PP2A scaffolding subunit to the proline-rich apoER2 C terminus along with 2 distinct regulatory PP2A subunits that mediate inhibitory dephosphorylation of Akt and eNOS. In mice, the coupling of these processes in endothelium is demonstrated to underlie aPL-invoked thrombosis. By elucidating these intricacies in the pathogenesis of APS-related thrombosis, numerous potential new therapeutic targets have been identified.

New Insights in the Pathophysiology of Antiphospholipid Syndrome

The antiphospholipid syndrome (APS) is an autoimmune disorder characterized by an elevated risk for arterial and venous thrombosis and pregnancy-related morbidity. Since the discovery of the disease in 1980s, numerous studies in cell culture systems, in animal models, and in patient populations have been reported, leading to a deeper understanding of the pathogenesis of APS. These studies have determined that circulating autoantibodies, collectively called antiphospholipid antibodies (aPL), the majority of which recognize cell surface proteins attached to the plasma membrane phospholipids, play a causal role in the development of the disease. The binding of aPL to the cell surface antigens triggers interaction of the complex with transmembrane receptors to initiate intracellular signaling in critical cell types, including platelets, monocytes, endothelial cells, and trophoblasts. Subsequent alteration of various cell functions results in inflammation, thrombus formation, and pregnancy complications. Apolipoprotein E receptor 2 (apoER2), a lipoprotein receptor family member, has been implicated as a mediator for aPL actions in platelets and endothelial cells. Nitric oxide (NO) is a signaling molecule known to exert potent antithrombotic, anti-inflammatory, and anti-atherogenic effects. NO insufficiency and oxidative stress have been linked to APS pathogenesis. This review will focus on the recent findings on how apoER2 and dysregulation of NO production contribute to aPL-mediated pathologies in APS.

Endothelial progenitor dysfunction associates with a type I interferon signature in primary antiphospholipid syndrome

OBJECTIVES

Patients with antiphospholipid syndrome (APS) are at risk for subclinical endothelial injury, as well as accelerated atherosclerosis. In the related disease systemic lupus erythematosus, there is a well-established defect in circulating endothelial progenitors, which leads to an accrual of endothelial damage over time. This defect has been at least partially attributed to exaggerated expression of type I interferons (IFNs). We sought to determine whether these pathways are important in APS.

METHODS

We studied 68 patients with primary APS. Endothelial progenitors were assessed by flow cytometry and functional assay. Type I IFN activity was determined by a well-accepted bioassay, while peripheral blood mononuclear cells were scored for expression of IFN-responsive genes.

RESULTS

Endothelial progenitors from patients with APS demonstrated a marked defect in the ability to differentiate into endothelial cells, a phenotype which could be mimicked by treating control progenitors with APS sera. Elevated type I IFN activity was detected in the circulation of patients with APS (a finding that was then replicated in an independent cohort). While IgG depletion from APS sera did not rescue endothelial progenitor function, the dysfunction was successfully reversed by a type I IFN receptor-neutralising antibody.

CONCLUSIONS

We describe, for the first time to our knowledge, an IFN signature in primary APS and show that this promotes impaired endothelial progenitor function. This work opens the door to novel approaches that may mitigate vascular damage in APS, such as anti-IFN drugs.

Maternal-placental syndrome and future risk of accelerated cardiovascular events in Parous Swedish women with systemic lupus erythematosus - a population-based retrospective cohort study with time-to-event analysis

OBJECTIVES

Women with SLE are at increased risk of cardiovascular events (CVEs), but a relationship with traditional cardiovascular and SLE-specific risk factors has not been established. In unselected populations, adverse pregnancy outcomes linked to maternal-placental syndrome (MPS) are associated with an increased risk of CVEs. However, the effect of MPS on CVEs is unknown in women with SLE. The aim of this study was to determine if MPS increased the risk and accelerated the development of CVEs in women with SLE.

METHODS

Utilizing Swedish population registries, parous women with SLE were identified. Exposures were the following: MPS defined as hypertensive disorders of pregnancy; small-for-gestational-age; placental abruption and stillbirth; and preterm delivery <34 weeks. Outcomes were CVE encompassing cardiovascular morbidity and mortality. Risk of an event was modelled using Cox proportional hazards adjusted for year of delivery, age at CVE, severity of SLE and cardiovascular risk factors. Time-to-CVE was estimated using Kaplan-Meier methods.

RESULTS

Over the 38-year study period, there were 3977 women with 7410 pregnancies, of whom 413 (10.2%) suffered a CVE. Hazard of CVE was higher in those with MPS, particularly when MPS (adjusted HR = 1.64; 95% CI: 1.31, 2.05) was combined with preterm delivery < 34 weeks' gestation (adjusted HR 1.99; 95% CI 1.39, 2.84). There was accelerated development of CVEs in women with MPS of 10.5% (vs 7.3% in uncomplicated pregnancies) over the 38-year interval (P < 0.05).

CONCLUSION

Pregnancy complicated by MPS and preterm delivery exerts an independent effect to increase the risk and accelerate the development of CVEs in parous women with SLE.

Association between serum total antioxidant status and flow-mediated dilation in patients with systemic lupus erythematosus: an observational study

Objective:

Endothelial dysfunction (ED) is a condition that involves increased oxidative stress and decreased total antioxidant status (TAS) levels. Systemic lupus erythematosus (SLE) is also associated with ED. We aimed to determine the association between serum TAS and ED as assessed by flow-mediated dilation (FMD) in patients with SLE.

Methods:

Thirty-four patients with stable SLE who were not undergoing any treatment and 39 healthy volunteers without any overt cardiovascular disease were included in this cross-sectional study. Doppler ultrasound was used to measure FMD to assess ED in the study groups. Serum TAS levels were measured using a TAS kit. High-sensitivity C-reactive protein (hs-CRP) and anticardiolipin antibody (aCLA) levels were also measured to assess the inflammatory state. The SLE group further was divided into 2 groups according to presence or absence of aCLA. SLE disease activity was assessed using the SLE disease activity index (SLEDAI). Regression analysis was used to define independent predictors.

Results:

The mean TAS levels were significantly lower in patients with SLE than in controls (1.60±0.11 versus 1.73±0.15 mmol/L, p<0.001). hs-CRP levels were significantly higher in patients with SLE than in controls (8.2±6.0 vs. 2.9±4.0 mg/L; p<0.001), particularly in SLE patients with positive aCLA when compared with SLE patients with negative aCLA (13.8±4.3 vs. 5.6±4.8 mg/L, p<0.001). The FMD percent was significantly lower in patients with SLE than in controls (8.1±4.9 vs. 10.6±4.7, p=0.04). There was a significant positive correlation between FMD and TAS in the SLE group (r=0.448, p=0.008) and the control group (r=0.367, p=0.03) and a significant negative correlation between FMD and serum hs-CRP (r=-0.368, p=0.04) in only the SLE group. In multiple linear regression analysis, TAS, hs-CRP and SLEDAI were independently correlated with FMD (ß=0.50, p=0.003; ß=-0.33, p=0.03; and ß=-0.36, p=0.03; respectively).

Conclusion:

Patients with SLE who have no overt cardiovascular disease are at increased risk for ED and this may be associated with underlying inflammation and impairment of TAS.