Treatment of the antiphospholipid syndrome

Interaction of beta2-glycoprotein I with members of the low density lipoprotein receptor family

The antiphospholipid syndrome (APS) is a non-inflammatory autoimmune disease characterized by arterial and/or venous thrombosis and/or pregnancy morbidity in the presence of autoantibodies that recognize beta2-glycoprotein I (beta2GPI) bound to phospholipids. We have previously demonstrated that dimerization of beta2GPI by autoantibodies induces platelet activation, involving the platelet receptor apolipoprotein E receptor 2' (apoER2') a receptor belonging to the low-density lipoprotein receptor (LDL-R) family. Here, we show that dimeric beta2GPI, but not monomeric beta2GPI, interacts with four other LDL-R family members: the LDL-R related protein (LRP), megalin, the LDL-R and the very-low density lipoprotein receptor (VLDL-R). Interaction between dimeric beta2GPI and LDL-R, apoER2' and VLDL-R was best described with a one-site binding model (half-maximal binding; approximately 20 nm for apoER2' and VLDL-R and approximately 300 nm for LDL-R), whereas the interaction between dimeric beta2GPI and LRP or megalin was best described with a two-site binding model, representing a high- (approximately 3 nm) and a low-affinity site (approximately 0.2 microm). Binding to all receptors tested was unaffected by a tryptophane to serine (W316S) substitution in domain V of beta2GPI, which is known to disrupt the phospholipid binding site of beta2GPI. Also deletion of domain I or II left the interaction with the receptors unaffected. Deletion of domain V, however, significantly decreased the affinity for the receptors. In conclusion, our data show that dimeric beta2GPI can interact with different LDL-R family members. This interaction is dependent on a binding site within domain V of beta2GPI, which does not overlap with the phospholipid-binding site within domain V.

Antiphospholipid antibodies as a cause of pulmonary capillaritis and diffuse alveolar hemorrhage: a case series and literature review

OBJECTIVES

To discuss the clinical manifestations and possible pathogenic mechanisms of the unusual syndrome of diffuse alveolar hemorrhage (DAH) and pulmonary capillaritis without thrombosis in the setting of the primary antiphospholipid antibody syndrome (PAPS).

METHODS

Four men with DAH and capillaritis in the setting of PAPS are identified. Their clinical presentations, laboratory, radiographic, and pathologic findings are reviewed as is their clinical course and response to therapy. In addition, the literature regarding DAH and pulmonary capillaritis in the setting of PAPS is reviewed.

RESULTS

The patients presented with dyspnea, hemoptysis, fever, hypoxia, and diffuse alveolar infiltrates; none had evidence of acute thromboembolic disease. All secondary causes of DAH were ruled out. All patients had positive testing for the lupus anticoagulant and high-titer anticardiolipin antibodies, including antibodies against the beta-2-glycoprotein I antigen. Three cases had lung biopsies that revealed pulmonary capillaritis and DAH with no evidence of thrombosis. All patients improved with high-dose corticosteroids. Recurrent disease in the setting of aggressive immunosuppression responded to intravenous immunoglobulin. Antiphospholipid antibody-mediated endothelial cell activation in the absence of thrombosis may induce capillaritis as seen in these cases.

CONCLUSIONS

The syndrome of DAH and pulmonary capillaritis is further defined. Evidence supports a causative relationship between PAPS, pulmonary capillaritis, and DAH in the absence of thromboembolic disease. Further elucidation of a possible nonthrombotic mechanism of antiphospholipid antibody-mediated pathology is needed to guide future therapies for this unusual manifestation of PAPS.

Hematologic ramifications of patent foramen ovale--role of hypercoagulable state

This article discusses the ramifications of a hypercoagulable state in patients with a patent foramen ovale.

Intestinal ischemia as the first manifestation of vasculitis

OBJECTIVE

To summarize current knowledge regarding the diagnosis and management of gastrointestinal vasculitis.

METHODS

Three cases of gastrointestinal vasculitis with acute abdominal ischemia as their first manifestation are presented. Underlying diseases were microscopic polyangiitis, systemic lupus erythematosus (SLE), and polyarteritis nodosa (PAN). Relevant English-language articles collected from the PubMed database were reviewed.

RESULTS

Among the angiitides, PAN, SLE, and Henoch-Schönlein are those most commonly accompanied by gastrointestinal complications. Intestinal vasculitis usually occurs when there is evidence of generalized disease activity. Abdominal computerized tomography is a valuable tool for diagnosing intestinal ischemia and suspected vasculitis.

CONCLUSIONS

In young patients presenting with intestinal ischemia, it is essential to assess the possibility of an underlying systemic disease. With prompt initiation of immunosuppressive treatment, surgery may be avoided. Prognosis is improved when there is minimal delay in surgical intervention.

β2-Glycoprotein I, the playmaker of the antiphospholipid syndrome

From its discovery in the early 60s till the beginning of the 90s, there was not much interest in plasma protein beta2-glycoprotein I (beta2-GPI). The finding that beta2-GPI acts as an essential cofactor for the detection of antiphospholipid antibodies (aPL) tremendously increased the interest in beta2-GPI [Lancet 335 (1990) 1544; Lancet 336 (1990) 177; Proc. Natl. Acad. Sci. U. S. A. 87 (1990) 4120]. It is now generally accepted that autoantibodies directed towards beta2-GPI are not only a serological marker but that they are involved in the pathology of the antiphospholipid syndrome (APS). In this review, we will first discuss the biochemistry of the protein beta2-GPI and the influence that the antibodies have on the function of beta2-GPI. Next, we will discuss the problems that are faced when assays to detect the presence of the autoantibodies are performed, emphasizing the urgent need for standardization of the anti-beta2-GPI-ELISA. Finally, we will discuss our latest insights into beta2-GPI and its role in the pathology of APS. Thereby, we will focus on the role of dimerized beta2-GPI on platelet and endothelial cell function.

Regulation of Interleukin-6 Fetoplacental Levels could be Involved in the Protective Effect of Low-molecular Weight Heparin Treatment on Murine Spontaneous Abortion

PROBLEM

CBA/J x DBA/2 abortion rate could be the consequence of a deficient local production of T helper (Th2) cytokines, which cause fetal wastage via fgl2 prothrombinase. Heparin reduces significantly the abortion rate in mice and recurrent spontaneous abortion (RSA) patients. We proposed to determine the effect of enoxaparin on the levels of local interleukin (IL)-6 during murine pregnancy.

METHOD OF STUDY

Recombinant human IL-6 (rhIL-6) or enoxaparin were inoculated in CBA/J x DBA/2 pregnant mice on days 6.5-12.5. IL-6 levels in sera as well as in culture supernatants of day 9.5 fetoplacental units of CBA/J x BALB/c control mice or CBA/J x DBA/2 abortion combination were determined by enzyme-linked immunosorbent assay (ELISA) test.

RESULTS

CBA/J x DBA/2 fetoplacental units secreted significantly lower levels of IL-6 with regard to CBA/J x BALB/c normal units. rhIL-6h and enoxaparin treatments decreased the resorption rate and regulated IL-6 fetoplacental levels.

CONCLUSION

This study suggests that regulation of IL-6 fetoplacental levels could be involved in heparin-mediated anticoagulation protection against abortion.

Acquired thrombophilias and pregnancy

Acquired thrombophilias are hypercoagulable states secondary to various aetiologies. In particular, during pregnancy the risks are exaggerated due to the underlying physiological changes. The commonest cause of acquired thrombophilia in pregnancy is antiphospholipid syndrome. Antiphospholipid syndrome (APS) is a complex multisystem disorder that has been associated with varied medical and obstetric complications. The pathogenesis of APS has been further elucidated in recent studies. The two most clinically significant antiphospholipid antibodies that are associated with recurrent pregnancy loss and thromboembolism are anticardiolipin antibodies (aCL) and lupus anticoagulant (LA). The laboratory diagnosis is based on the presence of moderate to high positive aCL and/or LA antibodies. It is crucial that APS is not inappropriately diagnosed as this has implications for counselling and management with thromboprophylaxis during pregnancy. Over the last decade there have been significant changes in the laboratory and clinical criteria for the diagnosis of APS. National and international collaborations have made efforts to standardize the laboratory methods. There have been very few randomized placebo-controlled trials of drug therapy and so not all drug treatment strategies have a strong evidence base. With current management strategies, using low-molecular-weight heparin and aspirin, a greater than 70% live birth rate may be achieved in affected pregnancies. A multidisciplinary approach in the management of these women is vital.