Endothelium activation in the anti-phospholipid syndrome

Deficiency of Axl aggravates pulmonary arterial hypertension via BMPR2

Pulmonary arterial hypertension (PAH), is a fatal disease characterized by a pseudo-malignant phenotype. We investigated the expression and the role of the receptor tyrosine kinase Axl in experimental (i.e., monocrotaline and Su5416/hypoxia treated rats) and clinical PAH. In vitro Axl inhibition by R428 and Axl knock-down inhibited growth factor-driven proliferation and migration of non-PAH and PAH PASMCs. Conversely, Axl overexpression conferred a growth advantage. Axl declined in PAECs of PAH patients. Axl blockage inhibited BMP9 signaling and increased PAEC apoptosis, while BMP9 induced Axl phosphorylation. Gas6 induced SMAD1/5/8 phosphorylation and ID1/ID2 increase were blunted by BMP signaling obstruction. Axl association with BMPR2 was facilitated by Gas6/BMP9 stimulation and diminished by R428. In vivo R428 aggravated right ventricular hypertrophy and dysfunction, abrogated BMPR2 signaling, elevated pulmonary endothelial cell apoptosis and loss. Together, Axl is a key regulator of endothelial BMPR2 signaling and potential determinant of PAH.

Effects of antibodies against human parvovirus B19 on angiogenic signaling

Human parvovirus B19 (B19V) infection has symptoms similar to those of anti‑phospholipid syndrome (APS). Antibodies against B19V‑VP1 unique region (VP1u) exhibit activity similar to that of anti‑phospholipid antibodies (aPLs) by inducing vascular endothelial cell adhesion factors and APS‑like syndrome. Previous studies have identified an effect of aPLs on angiogenesis. However, little is understood regarding the effect of anti‑B19V‑VP1u antibodies on angiogenesis. The present study investigated the effects of anti‑B19V‑VP1u antibodies on the expression of adhesion molecules and angiogenic signaling using an aPL‑induced human umbilical vein endothelial cell (HUVEC) model, and trypan blue staining and western blotting. The effect of B19V‑VP1u antibodies on vascular endothelial growth factor (VEGF) expression in A549 cells, another well‑known model used to study angiogenesis, was also examined. Significantly higher intracellular adhesion molecule 1 expression was observed following treatments with 10% fetal calf serum (FCS), aPL immunoglobulin G (IgG), B19V‑VP1u IgG or B19V‑NS1 IgG, compared with in the normal human (NH) IgG‑treated cells. Conversely, significantly higher vascular cellular adhesion molecule 1 was only detected in HUVECs treated with B19V‑VP1u IgG. Significantly increased integrin β1 was detected in HUVECs treated with aPL IgG or B19V‑VP1u IgG, whereas no difference in integrin β1 was observed in those treated with 10% FCS, NH IgG or B19V‑NS1 IgG. No difference in AKT‑mTOR‑S6 ribosomal protein (S6RP) signaling was observed in HUVECs treated with B19‑VP1u IgG or B19V‑NS1 IgG, compared with NH IgG‑treated cells. Significantly higher human inducible factor‑1α was detected in HUVECs treated with 10% FCS, aPL IgG, B19V‑VP1u IgG or B19V‑NS1 IgG, compared with in NH IgG‑treated cells. However, there was no difference in the level of VEGF observed among HUVECs treated with NH IgG, B19V‑VP1u IgG or B19V‑NS1 IgG. Notably, no difference in VEGF level was observed in A549 cells treated with NH IgG, aPL IgG, B19V‑VP1u IgG or B19V‑NS1 IgG. These findings suggest that anti‑B19V‑VP1u antibodies may serve a role in activating adhesion molecules, but not in AKT‑mTOR‑S6RP signaling.

Hypertensive disorders of pregnancy associated with adverse pregnant outcomes in patients with systemic lupus erythematosus: a multicenter retrospective study

BACKGROUND

Hypertension disorders in pregnancy (HDP) were common complications in women with systemic lupus erythematosus (SLE). However, the impact of HDP and the measures to prevent HDP-related fetal adverse pregnancy outcomes (APOs) remained to be explored.

METHODS

A multicenter retrospective study of 342 pregnant women with SLE was performed. Variables related to SLE and APOs were recorded. Fetal development was evaluated by umbilical artery Doppler ultrasonography.

RESULTS

HDP was diagnosed in 45 (13.2%) patients, including pre-eclampsia in 42 and gestational hypertension in 3. Patients with HDP had higher incidence of preterm birth (71.1% vs 20.9%, P < 0.001), intrauterine growth retardation (IUGR) (37.8% vs 11.8%, P < 0.001), low-birth-weight infants (62.2% vs 17.2%, P < 0.001), and very-low-birth-weight infants (37.8% vs 2.7%, P < 0.001), compared with lupus patients without HDP. A total of 35 (77.8%) HDP patients had disease activation during pregnancy. All the events occurred during the second and third trimesters, mainly presenting as moderate-to-high activity (65.7%). Active disease [odds ratios (OR) = 3.9, 95% confidential interval (CI) 1.5-9.7, P = 0.004] and positive anticardiolipin (aCL) antibody (OR = 7.6, 95% CI 2.7-18.6, P < 0.001) were independent risk factors for HDP in lupus patients. Doppler RI and S/D ratio predicted APOs in patients with HDP. The optimal cut-off values for RI and S/D ratio were 0.7 (sensitivity 48.1%, specificity 53.3%) and 3.4 (sensitivity 66.7%, specificity 100%), respectively.

CONCLUSIONS

HDP was a common pregnant complication and caused various fetal and maternal adverse outcomes in patients with SLE. Umbilical artery Doppler ultrasonography was effective in predicting fetal APOs in lupus patients with HDP.Key Points• HDP induced preterm birth, IUGR, low-birth-weight infants, and very-low-birth-weight infants in patients with SLE.• HDP led to lupus activation during the second and third trimesters.• Disease activation and aCL positivity were predictors for HDP.• RI and S/D ratio from umbilical artery Doppler predicted APOs in patients with HDP.

Arterial stenosis in antiphospholipid syndrome: Update on the unrevealed mechanisms of an endothelial disease

First described in 1983, antiphospholipid syndrome (APS) is an autoimmune condition characterized by the occurrence of recurrent arterial and/or venous thrombosis, and/or pregnancy morbidity, in the setting of persistent presence of antiphospholipid antibodies (aPL). While thrombosis is the most well-known pathogenic mechanism in this disorder, the relevance of some other mechanisms such as arterial stenosis is being increasingly recognized. Arterial stenosis has been first described in the renal arteries in patients with APS, however intracranial and coeliac arteries can also be involved with various and treatable clinical manifestations. The underlying pathophysiology of this stenotic arterial vasculopathy is not fully understood but some recent studies revealed new insights into the molecular mechanism behind this endothelial cell activation in APS. In this review, we discuss these newly discovered mechanisms and highlight the diagnostic and therapeutic modalities of the APS related arterial stenosis.

Circulating Immune Complexes of IgA Bound to Beta 2 Glycoprotein are Strongly Associated with the Occurrence of Acute Thrombotic Events

Aim: Antiphospholipid syndrome (APS) is characterized by recurrent thrombosis and/or gestational morbidity in patients with antiphospholipid autoantibodies (aPL). Over recent years, IgA anti-beta2-glycoprotein I (B2GPI) antibodies (IgA aB2GPI) have reached similar clinical relevance as IgG or IgM isotypes. We recently described the presence of immune complexes of IgA bounded to B2GPI (B2A-CIC) in the blood of patients with antecedents of APS symptomalology. However, B2A-CIC's clinical associations with thrombotic events (TEV) have not been described yet.

Methods: A total of 145 individuals who were isolate positive for IgA aB2GPI were studied: 50 controls without any APS antecedent, 22 patients with recent TEV (Group-1), and 73 patients with antecedents of old TEV (Group-2).

Results: Mean B2A-CIC levels and prevalence in Group-1 were 29.6 ± 4.1 AU and 81.8%, respectively, and were significantly higher than those of Group-2 and controls (p < 0.001). In a multivariable analysis, positivity of B2A-CIC was an independent variable for acute thrombosis with a 22.7 odd ratio (confidence interval 5.1 –101.6, 95%, p < 0.001). Levels of B2A-CIC dropped significantly two months after the TEV. B2A-CIC positive patients had lower platelet levels than B2A-CIC-negative patients (p < 0.001) and more prevalence of thrombocytopenia (p < 0.019). Group-1 had no significant differences in C3 and C4 levels compared with other groups.

Conclusion: B2A-CIC is strongly associated with acute TEV. Patients who did not develop thrombosis and were B2A-CIC positive had lower platelet levels, which suggest a hypercoagulable state. This mechanism is unrelated to complement-fixing aPL. B2A-CIC could potentially select IgA aB2GPI-positive patients at risk of developing a thrombotic event.

Review on anti-lipoprotein lipase antibodies

Lipoprotein lipase (LPL) is a member of the lipase family, and LPL is known to hydrolyze triglyceride molecules found in lipoprotein particles. Understanding the pathogenesis of atherosclerosis in autoimmune diseases, particularly systemic lupus erythematosus (SLE), is vital to reduce morbidity and mortality of this disease. It is now recognized that SLE has a particular pattern of dyslipoproteinemia characterized by low HDL levels and increased triglycerides, which is aggravated by flare. Antilipoprotein lipase (anti-LPL) antibodies have been recently described in rheumatic diseases, mainly in SLE and systemic sclerosis (SSc). Several studies have reported a close link between antibodies, inflammation and lipoprotein levels and an increased risk of cardiovascular damage in this particular group of patients. These studies have emphasized the importance of rigorous clinical control of disease activity and prevention of cardiovascular risk factors. This review summarized the studies that have discussed the presence of anti-LPL in rheumatic diseases and other conditions and analyzed the importance of this antibody in the complex atherosclerotic process in autoimmune diseases.

The catastrophic antiphospholipid (Asherson's) syndrome

The catastrophic antiphospholipid syndrome (CAPS, Asherson's syndrome) develops rapidly following an identifiable triggering factor (eg infection, trauma, inadequate coagulation neoplasia, obstetric) in antiphospholipid antibody positive patients. It is most frequently encountered in patients with a primary antiphospholipid syndrome or systemic lupus erythematosus (SLE) or "lupus-like" disease (LLD). It manifests mainly with small vessel thromboses affecting organs (gastrointestinal tract, brain, heart), large vessel occlusions in one-third, manifestations of the systemic inflammatory response syndrome (SIRS), particularly the acute respiratory distress syndrome (ARDS). The mortality is high, although with early and effective therapies, including full parenteral anticoagulation, corticosteroids, plasma exchanges and IV globulins, an improvement in this high death rate has been noted recently.

Anti-lipoprotein lipase antibodies: A new player in the complex atherosclerotic process in systemic lupus erythematosus?

OBJECTIVE

The novel description of antibodies to lipoprotein lipase (anti-LPL) associated with dyslipoproteinemia prompted us to analyze the association of anti-LPL with clinical and serologic features in patients with systemic lupus erythematosus (SLE) and its link to markers of inflammation that are known to be involved in atherogenesis.

METHODS

Enzyme-linked immunosorbent assay was used to test for the presence of anti-LPL antibodies in 66 consecutive patients with SLE. Clinical and laboratory evaluation, including a fasting lipid profile, autoantibody screening, an assessment for markers of inflammation (C-reactive protein [CRP], erythrocyte sedimentation rate [ESR]), and the SLE Disease Activity Index (SLEDAI) were performed at the time of inclusion in the study. Exclusion criteria were any conditions that affect the lipid profile. SLE patients were categorized into 2 groups according to detection of these anti-LPL antibodies, as follows: anti-LPL+ and anti-LPL-.

RESULTS

Anti-LPL antibody IgG was detected in 25 SLE patients (37.8%). Triglyceride levels were significantly higher in the anti-LPL+ group (112.4 +/- 50.2 versus 89.9 +/- 54.5 mg/dl in the anti-LPL- group; P = 0.033), but no significant differences between the 2 groups were detected for total, high-density lipoprotein, and low-density lipoprotein cholesterol levels. A higher frequency of elevated CRP levels and ESRs was observed in the anti-LPL+ group compared with the anti-LPL- group (44% and 17.1%, respectively [P = 0.023] and 52% and 19.5%, respectively [P = 0.013]). Moreover, SLE patients with anti-LPL antibodies also had significantly higher levels of CRP (11.1 +/- 16.4 versus 2.4 +/- 2.6 mug/ml; P = 0.036) and higher ESRs (33.4 +/- 29.8 versus 16.5 +/- 11.8 mm/hour; P = 0.020). Anti-LPL titers had a significant positive correlation with the CRP level (r = 0.56, P < 0.001), the ESR (r = 0.55, P < 0.001), the SLEDAI score (r = 0.45, P < 0.001), anti-double-stranded DNA (anti-dsDNA; r = 0.52, P < 0.001), and anticardiolipin IgG antibodies (r = 0.25, P = 0.04), and a significant negative correlation was detected with total hemolytic complement activity (CH100) (r = -0.34, P = 0.005). Reinforcing these findings, multiple regression analysis also revealed a significant association of anti-LPL with the CRP level (P = 0.025) and anti-dsDNA (P < 0.001). Importantly, a comparison of positive and negative anti-dsDNA sera revealed similar mean CRP levels (P = 0.56) and ESRs (P = 0.102), contrasting with the SLEDAI score (P = 0.004) and CH100 (P = 0.008).

CONCLUSION

These data support the link between inflammation, immune response, and dyslipoproteinemia in SLE, introducing anti-LPL as a possible new player that may ultimately help in understanding the complex events of atherogenesis in this disease.

Clinical Significance of Anticardiolipin and Anti-β2-Glycoprotein I Antibodies

BACKGROUND

Anticardiolipin (aCl) and anti-beta2-glycoprotein I (anti-beta2-gpI) antibodies are autoantibodies associated with the antiphospholipid syndrome (APS), which is characterized by both arterial and venous thrombosis and miscarriages. The scope of this study was to explore the clinical characteristics of patients with aCl and anti-beta2-gpI antibodies.

METHODS

ACl were tested in 3,600 consecutive sera in our laboratory between January 1999 and June 2001. The clinical diagnosis and prevalence of thrombosis and pregnancy morbidity were retrospectively reviewed in aCl-positive patients. Furthermore, the frequency of anti-beta2-gpI antibodies, lupus anticoagulant (LA), prolonged activated partial thromboplastin time (aPTT), and thrombocytopenia were investigated in aCl-positive patients.

RESULTS

147 aCl-positive patients, 110 women and 37 men with a mean age of 41 years (range 7.8-82.5), were identified. 42 (28.6%) aCl-positive patients fulfilled the criteria for APS which was secondary to a connective tissue disorder in 8 patients. The frequency of anti-beta2-gpI antibodies and LA, prolonged aPTT, and thrombocytopenia in aCl-positive patients was 23.8, 27.2, 25.7 and 9.2%, respectively. The presence of both aCl and anti-beta2-gpI antibodies was strongly associated with clinical symptoms of APS (p = 0.007) compared to p = 0.008 for LA.

CONCLUSION

Our data suggest that assessment of anti-beta2-gpI antibodies in addition to aCl is a valuable diagnostic tool in the workup of patients with APS.

An adapted ELISA method for differentiating pathogenic from nonpathogenic aPL by a beta 2 glycoprotein I dependency anticardiolipin assay

With the currently available commercial kits, as well as homemade assays for detecting anticardiolipin antibodies (aCL), it is not possible to discriminate nonpathogenic, beta 2 glycoprotein (GPI)-independent, infection-related antibodies from those of patients with the true autoimmune thrombotic syndrome, known as antiphospholipid syndrome (APS). We devised an assay that is able to differentiate these two types of antibodies by determining the beta 2 GPI requirements to bind in a cardiolipin ELISA. Beta 2 GPI was purified by perchloric acid precipitation, and fixed amounts were used in the dilution solutions of the tested samples that were also tested with no source of beta 2 GPI. The ELISA plates were coated with cardiolipin, as usual, and blocked with a chicken ovalbumin solution. The serum samples had to be highly diluted in order not to have beta 2 GPI from the patient serum. The reaction was detected with alkaline phosphate tablets and developed with pNp in diethanolamine buffer. The adapted ELISA aCL assay described here was able to discriminate infectious [syphilis, hepatitis C virus (HCV), dengue fever, human immunodeficiency virus (HIV) and leprosy] and autoimmune [primary APS and systemic lupus erythematosus (SLE) related APS]. Further testing should be performed to demonstrate that this method consistently differentiates pathogenic antibodies that bind in an aCL ELISA only in the presence of beta 2 GPI.