Anti-annexin A5 Antibodies in Reproductive Failures in Relation to Antiphospholipid Antibodies and Phosphatidylserine

Antiphosphatidylserine antibodies and reproductive failure

Some cases of reproductive failure with autoimmune background are characterized by the involvement of autoantibodies. This occurs mainly in patients having systemic lupus erythematosus or antiphospholipid syndrome. The autoantibodies associated with reproductive failure include: a) antibodies which directly bind phospholipid (e.g., cardiolipin, phosphatidylserine, phosphatidylethanolamine); b) antiphospholipid Abs which bind the phospholipid via phospholipid-binding glycoproteins such as b2glycoprotein-I, annexin V and prothrombin; c) autoantibodies directed to laminin-I, actin, thromboplastin, the corpus luteum, prolactin, poly (ADP-ribose), thyroglobulin and mitochondrial antibodies of the M5 type. This paper will focus on the association of antiphosphatidylserine autoantibodies and reproductive failure. Future studies are likely to help to identify peptides resembling the epitope specificities associated with the specific clinical manifestations.

Bouquet variety of antiphospholipid antibodies in recurrent pregnancy loss

Seventy-six female patients with two or more recurrent pregnancy losses (RPL) during the 1(st) trimester were studied. Based on the results of the aCL and aB2GPI antibodies testing, patients were divided in two groups: 22 patients with RPL and elevated immunoglobulin (Ig) G/IgM aCL and/or aB2GPI [RPL + antiphospholipid syndrome (APS)] and 54 patients with RPL alone (without high antibodies). Immunoglobulin G aPS and IgG a-AnV in patients with RPL + APS were higher than in controls and IgG aPS were higher in RPL + APS than in RPL alone. Additionally IgG a-AnV and IgM aPE are higher in RPL alone than in controls. In 18/22 (81%) patients with RPL + APS and 29/54 (54%) patients with RPL alone, there were one or more positive antibodies: aPS, aPT, a-AnV or aPE. These results raise a question whether or not these antiphospholipid antibodies should be routinely tested in women with RPL and especially in the context of the so-called "seronegative APS".

Association of annexin A5 polymorphisms with obesity

Annexin A5 (ANXA5), which is known as a protein with anticoagulative function, may play a role in triglyceride biosynthesis. Triglycerides are involved in lipid and energy metabolism, which are important in the elucidation of obesity. To investigate the association between single-nucleotide polymorphisms (SNPs) of ANXA5 and obesity in a Korean population, 372 participants (213 overweight/obese individuals and 159 control subjects) were enrolled from the Kyung Hee University Medical Center and Keimyung University Dongsan Medical Center. The genotypes of five SNPs (rs12510548, rs4240260, rs3756281, rs13136094 and rs6534313) were evaluated in ANXA5 using the multiple logistic regression analysis with the codominant 1, codominant 2, dominant, recessive and log-additive models. The genotype and allele frequencies of the five investigated SNPs exhibited significant differences between the control and the overweight/obese groups: rs12510548 (P=0.004 in the codominant 2 model, P=0.0019 in the recessive model, P=0.027 in the log-additive model and P=0.026 in allele frequencies); rs4240260 (P=0.002 and Fisher's exact P=0.0006 in the codominant 2 model, P=0.0007 and Fisher's exact P=0.0007 in the recessive model, P=0.020 and Fisher's exact P=0.0019 in the log-additive model and P=0.020 in allele frequencies); rs3756281 (P=0.016 in the codominant 2 model and P=0.0094 in the recessive model); rs13136094 (P=0.0030 and Fisher's exact P=0.0011 in the codominant 2 model, P=0.0012 and Fisher's exact P=0.0013 in the recessive model, P=0.034 and Fisher's exact P=0.0035 in the log-additive model and P=0.024 in allele frequencies); and rs6534313 (P=0.0010 and Fisher's exact P=0.0003 in the codominant 2 model, P=0.0003 and Fisher's exact P=0.0003 in the recessive model, P=0.0075 and Fisher's exact P=0.0010 in the log-additive model and P=0.005 in allele frequencies). Two haplotypes were weakly associated with obesity (GGATG, P=0.037 and CAGCC, P=0.020). Results of the present study suggested that ANXA5 may be associated with the development of obesity in a Korean population.

The annexin A5-mediated pathogenic mechanism in the antiphospholipid syndrome: role in pregnancy losses and thrombosis

Annexin A5 (AnxA5) binds to phospholipid bilayers, forming two-dimensional crystals that block the phospholipids from availability for coagulation enzyme reactions. Antiphospholipid (aPL) antibodies cause gaps in the ordered crystallization of AnxA5 which expose phospholipids and thereby accelerate blood coagulation reactions. The aPL antibody-mediated disruption of AnxA5 crystallization has been confirmed on artificial phospholipid bilayers and on cell membranes including endothelial cells, placental trophoblasts and platelets. Recently, we reported that hydroxychloroquine, a synthetic antimalarial drug, can reverse this antibody-mediated process through two mechanisms: (1) by inhibiting the formation of aPL IgG-β2glycoprotein I complexes; and (2) by promoting the formation of a second layer of AnxA5 crystal ‘patches’ over areas where the immune complexes had disrupted AnxA5 crystallization. In another translational application, we have developed a mechanistic assay that reports resistance to AnxA5 anticoagulant activity in plasmas of patients with aPL antibodies. AnxA5 resistance may identify a subset of aPL syndrome patients for whom this is a mechanism for pregnancy losses and thrombosis. The elucidation of aPL-mediated mechanisms for thrombosis and pregnancy complications may open new paths towards addressing this disorder with targeted treatments and mechanistic assays.

Autoantibodies and coagulation in reproductive medicine

Management of recurrent pregnancy loss (RPL) is considered to be difficult, in part because of cunfusion between autoantibodies and coagulation disorders. Autoantibodies and coagulation are related; two groups of multicenter studies concerning autoantibodies and coagulation reported that factor XII deficiency, hypofibrinolysis, anti-phosphatidylethanolamine (aPE), anti-beta2-glycoprotein I, anti-annexin A5, and lupus anticoagulant (LA) were found to be frequent risk factors in RPL women. Therefore, discrimination of autoantibodies and coagulation is important in understanding RPL well. We propose three types of pathways regarding reproduction, which are different and independent: (1) Negatively charged-phospholipid related antibodies (anti-phosphatidylserine; aPS, anti-cardiolipin; aCL, lupus anticoagulant; LA, anti-annexin A5; aANX), (2) factor XII-aPE-fibrinolysis: suppression of fibrinolysis, (3) protein C-protein S-factor V: loss of inactivation against activated factor V. Women with RPL and infertility showed similar findings in terms of the above clinical tests. Available data, however, is not enough to conclude whether these are pathogenic to infertile women.

Resistance to annexin A5 anticoagulant activity: a thrombogenic mechanism for the antiphospholipid syndrome

The phospholipid binding protein, annexin A5 (AnxA5), has potent anticoagulant properties that result from its forming 2-dimensional crystals over phospholipids, blocking the availability of the phospholipids for critical coagulation enzyme reactions. This article reviews the evidence that antiphospholipid antibodies can disrupt this anticoagulant shield and unmask thrombogenic anionic phospholipids, which may thereby contribute to thrombosis in patients with the antiphospholipid syndrome (APS). This mechanism for thrombosis in APS can be monitored with coagulation assays for resistance to anticoagulant activity of AnxA5.

Antiphospholipid antibodies: effects on trophoblast and endothelial cells

PROBLEM

Antiphospholipid syndrome (APS) may affect placental functions through several possible mechanisms. Interaction of antiphospholipid antibodies (aPL) with cells involved in the coagulation cascade is thought to produce a procoagulant state. Thrombotic placental pathology is however not specific for the APS.

METHOD OF STUDY

An analysis of published data.

RESULTS

It is now generally accepted that the clinically relevant aPL bind to proteins with affinity for phospholipids (PL), such as beta2-glycoprotein I (beta2-GPI). Following the attachment of beta2-GPI to trophoblast anionic PL, both molecules undergo conformational changes resulting in the exposure of cryptic epitopes within the structure of beta2-GPI. This may allow the subsequent binding of antibodies hence affecting trophoblast functions directly. Moreover anti-beta2-GPI antibodies induce the activation of endothelial cells (ECs), resulting in a proinflammatory state which favours the prothrombotic diathesis of the syndrome.

CONCLUSION

Numerous ameliorations in the APS knowledge have been introduced in the last few years. To have clarified the mechanism of antibody mediated damage on trophoblast and ECs represents an important step to explain the cellular events leading to pregnancy complications.

Physiopathologie du syndrome des antiphospholipides

The antiphospholipid syndrome is characterized by the association of clinical events (thrombosis and/or obstetrical complications) and heterogeneous autoantibodies reacting with complexes of proteins and anionic phospholipids. Most of these recognized proteins can bind to anionic phospholipids and play a role in natural regulation of coagulation. Inhibition by these autoantibodies of the natural regulators of excessive coagulation is probably responsible for the prothrombotic state that characterizes this disease. Animal models have helped explain the mechanisms of obstetrical complications. Human antiphospholipid antibodies passively transferred to pregnant mice directly cause fetal resorption. This effect is mediated by complement fractions and neutrophil activation and is inhibited by heparin. The origin of these autoantibodies is still debated. Physiologically, the cause may be associated with exposure to anionic phospholipids on the surface of apoptotic cells. The affinity maturation process, which leads to the acquisition of somatic mutations, can then generate highly pathogenic antiphospholipid antibodies.

Antibodies to β2-glycoprotein I and annexin V in women with early and late idiopathic recurrent spontaneous abortions

Anti-phospholipid antibodies (APA) are heterogeneous group of autoantibodies that target phospholipid or phospholipid-binding proteins. APAs were previously shown to induce several thrombotic states, including idiopathic recurrent spontaneous abortion (RSA). Unlike the contribution of the classical lupus anticoagulant (LAC) and anticardiolipin antibodies (ACA), the contribution of anti-beta2 glycoprotein 1 (beta2GPI) and anti-annexin V antibodies to RSA risk remain poorly understood. We assessed anti-beta2GPI and anti-annexin V IgM and IgG antibodies as RSA risk factors for RSA in 172 Tunisian women with >3 consecutive idiopathic pregnancy losses, together with 173 matched control women. The prevalence of anti-beta2GPI IgG (P=0.41, OR=1.64) and IgM (P=0.50, OR=1.70) were comparable between cases and controls. Higher anti-annexin V IgG (P=0.02, OR=5.28), but not IgM (P=0.25, OR=1.78), levels were seen in cases. Regression analysis showed that anti-beta2GPI IgM (OR=8.90; 95% CI=1.23-64.63) was associated with early RSA, while anti-annexin V IgG (OR=9.35, 95% CI=1.44-60.86) was associated with late RSA. For combined early + late RSA, the only variable selected was BMI (OR=0.93; 95% CI=0.87-0.99), and neither anti-annexin V nor anti-beta2GPI IgM and IgG were associated with early + late RSA. Anti-annexin V and anti-beta2GPI appear to be independent risk markers of RSA.

A case-control study on the association of idiopathic recurrent pregnancy loss with autoantibodies against β2-glycoprotein I and annexin V

Whereas antiphospholipid antibodies (aPL) are associated with thrombotic events and recurrent spontaneous abortion (RSA), the contribution of anti-β2 glycoprotein 1 (β2GP1) and anti-annexin V antibodies as risk factors for RSA remain poorly understood. We investigated anti-β2-GPI and anti-annexin V IgM and IgG antibodies as potential risk factors for RSA in 200 women with more than three consecutive idiopathic RSA, and 200 age-matched, healthy, parous women. Pearson’s chi squared test analysis showed that while anti-β2-GPI IgG (P= 0.416) and IgM (P= 0.72) were comparable between patients and controls, elevated anti-annexin V IgG (P= 0.006), but not IgM (P= 0.084), was more pronounced in patients. Higher frequencies of elevated IgG-only (P= 0.005), but not IgM-only (P= 1.000; OR = 6.66), anti-annexin V antibodies were noted among patients. Multinomial regression analysis showed that body-mass index (overweight and obesity;P= 0.008), education status (P< 0.001) and anti-β2-GPI IgM (P= 0.033), but not IgG (P= 0.723), were associated with early abortion, while anti-β2-GPI IgG (P= 0.030) and anti-annexin V IgG (P= 0.004) were associated with late RSA. For combined early-late RSA, the only variable selected was education status (P< 0.001), and neither anti-annexin V nor anti-β2-GPI IgM and IgG was associated with early-late RSA. Accordingly, anti-annexin V and anti-β2-GPI should be regarded as independent risk markers of RSA.

Reduction of circulating annexin A5 levels and resistance to annexin A5 anticoagulant activity in women with recurrent spontaneous pregnancy losses

OBJECTIVE

We investigated whether levels of annexin A5, evidence for resistance to annexin A5 activity, and levels anti-annexin A5 antibodies might be altered in women with a history of recurrent spontaneous pregnancy losses.

STUDY DESIGN

These annexin A5 parameters were assayed in 70 nonpregnant women with a history of > or = 3 recurrent spontaneous pregnancy losses (cases) and 50 women without adverse pregnancy history (control subjects).

RESULTS

Cases had significantly lower plasma annexin A5 levels than control subjects (median, 4.7 ng/mL [range, 0.3-40.4 ng/mL] vs 6.7 ng/mL [range, 0.7-56.0]; P = .01), significantly reduced anticoagulant ratios (188% [range, 119%-279%] vs 238% [range, 159%-286%]; P < .0001), and reduced binding of annexin A5 to phospholipid (6.3 ng/aliquot phospholipid [range, 1.5-16.4 ng/aliquot phospholipid] vs 9.7 ng/aliquot phospholipid (range, 3.5-17.0 ng/aliquot phospholipid]; P = .0002). There were no significant differences in anti-annexin A5 antibody levels.

CONCLUSION

Reduction of annexin A5 and interference with its anticoagulant and binding activities are associated significantly with a history of recurrent spontaneous pregnancy losses. These data support the concept of a significant role for annexin A5 in the maintenance of pregnancy.

Antibodies and clinical features of the antiphospholipid syndrome as criteria for systemic lupus erythematosus

The antiphospholipid syndrome (APS) can occur as a primary diagnosis or as a prominent feature of other diseases, predominantly systemic lupus erythematosus (SLE). The 1982 revised criteria for SLE were published prior to many of the studies which have illuminated current understanding of the antiphospholipid syndrome and several current clinical criteria for SLE, when arising from thrombotic damage to different organ systems, could be attributed to APS, leading to some confusion about where the diagnoses of these two disorders should begin and end. Additionally, APS is a significant generalized risk factor for irreversible organ damage and overall mortality in SLE patients and genetic linkages to HLA in APS hold up whether the disorder is primary or linked to SLE. It is increasingly recognized that APS itself is a complex, heterogenous disorder, involving a spectrum of autoantibodies to phospholipid-binding proteins, many of which have known coagulation-regulating functions. Although the combination of more than one antiphospholipid-related antibody might indicate a more severe phenotype, it is not suggested here that additive criteria for the diagnosis of SLE be accumulated with more than one of these pathologically related autoantibodies. Patients with multiple criteria for APS should be considered to have severe APS but it would be recommended to restrict APS-attributed criteria for SLE to a maximal of two: one immunologic and one clinical. Thus people meeting the Sapporo criteria for APS could gain only a maximum of two criteria for SLE, regardless of how many autoantibodies were detected or how severe the clinical syndrome might be. This would allow manifestations of fullblown APS an appropriate impact towards the diagnosis of SLE without leading to a premature diagnosis of SLE for people who might better be considered to have moderate to severe primary APS.

Diagnosis of the antiphospholipid syndrome: How far to go?

The past decade has seen an evolution in the way that thrombophilic conditions are diagnosed and understood. This has largely evolved through the detection of single nucleotide polymorphisms in critical regulating proteins that are thought to confer significant structural-functional changes at key points in the coagulation cascade. The antiphospholipid syndrome (APS) is a complex hypercoagulable disorder that as yet defies the possibility of simple, predictive testing.

Apoptosis-detecting radioligands: current state of the art and future perspectives

This review provides a critical and thorough overview of the radiopharmaceutical development and in vivo evaluation of all apoptosis-detecting radioligands that have emerged so far, along with their possible applications in nuclear medicine. The following SPECT and PET radioligands are discussed: all forms of halogenated Annexin V (i.e. (123)I-labelled, (124)I-labelled, (125)I-labelled, (18)F-labelled), (99m)Tc/(94m)Tc-labelled Annexin V derivatives using different chelators and co-ligands (i.e. BTAP, Hynic, iminothiolane, MAG(3), EDDA, EC, tricarbonyl, SDH) or direct (99m)Tc-labelling, (99m)Tc-labelled Annexin V mutants and (99m)Tc/(18)F-radiopeptide constructs (i.e. AFIM molecules), (111)In-DTPA-PEG-Annexin V, (11)C-Annexin V and (64)Cu-, (67)Ga- and (68)Ga-DOTA-Annexin V. In addition, the potential role and clinical relevance of anti-PS monoclonal antibodies and other alternative apoptosis markers are reviewed, including: anti-Annexin V monoclonal antibodies, radiolabelled caspase inhibitors and substrates and mitochondrial membrane permeability targeting radioligands. Nevertheless, major emphasis is placed on the group of Annexin V-based radioligands, in particular (99m)Tc-Hynic-Annexin V, since this molecule is by far the most extensively investigated and best-characterised apoptosis marker at present. Furthermore, the newly emerging imaging modalities for in vivo detection of programmed cell death, such as MRI, MRS, optical, bioluminescent and ultrasound imaging, are briefly described. Finally, some future perspectives are presented with the aim of promoting the development of potential new strategies in pursuit of the ideal cell death-detecting radioligand.

Antibody-mediated interference with annexins in the antiphospholipid syndrome

Targeting of the annexin A5 anticoagulant shield may be a significant mechanism for thrombosis and pregnancy losses in APS. This may occur via high affinity antibodies that recognize phospholipid-binding proteins that are capable of interfering with the assembly of the annexin A5 shield on phospholipid surfaces or via direct recognition of annexin A5 by autoantibodies. In addition, antibodies against other members of the annexin family of proteins may also have pathogenic roles in APS. It is anticipated that further research will elucidate the biologic functions of these proteins and their roles in the aPL disease processes.