The -1C>T mutation in the annexin A5 gene does not affect plasma levels of annexin A5

Annexin A5 haplotypes in familial hypercholesterolemia: lack of association with carotid intima-media thickness and cardiovascular disease risk

OBJECTIVE

Annexin A5 (ANXA5) has been suggested to possess antiatherogenic properties. We investigated whether ANXA5 genetic variations and plasma ANXA5 levels were associated with carotid atherosclerosis and contributed to cardiovascular disease (CVD) risk in patients with familial hypercholesterolemia (FH).

METHODS

We sequenced the promoter region and exon 2 of ANXA5 in 284 FH patients from the ASAP (Atorvastatin versus Simvastatin on Atherosclerosis Progression) trial. Common haplotypes (H) were constructed based on seven single nucleotide polymorphisms (SNPs). We studied whether plasma ANXA5 levels or ANXA5 haplotypes were associated with the extent of atherosclerosis (evaluated by carotid intima-media thickness (IMT). The association between ANXA5 haplotypes and the risk for CVD events was investigated in 1730 FH patients from the GIRaFH (Genetic Identification of Risk factors in Familial Hypercholesterolemia) study.

RESULTS

In ASAP, individuals carrying the ANXA5 haplotype H2 exhibited lower plasma ANXA5 levels, whereas H4 carriers had increased levels of circulating ANXA5 compared to non-carriers. Plasma ANXA5 levels were not associated with carotid IMT. None of the four ANXA5 haplotypes correlated with the age-related IMT progression (ASAP study) or contributed to CVD risk (GIRaFH cohort).

CONCLUSIONS

Both ANXA5 haplotypes and plasma ANXA5 levels were not associated with carotid IMT progression or CVD risk in FH patients.

Annexin V expression and anti-annexin V antibodies in type 1 diabetes

BACKGROUND

Annexin V (AnxV) has potent anticoagulant properties and regulatory functions for apoptosis and inflammation. Antibodies against annexin V (anti-AnxVs) may inhibit AnxV functions, leading to thrombosis during autoimmune diseases. Type 1 diabetes is an autoimmune disease and related with an ongoing autoimmune inflammation and thrombotic complications. There is no study evaluating anti-AnxVs/AnxV in a disease setting.

OBJECTIVE

The aim of this study was to evaluate the status of AnxV and anti-AnxVs in patients with type 1 diabetes.

METHODS

One hundred twenty-one patients with type 1 diabetes and 92 healthy controls were included in this study. Serum levels of AnxV and anti-AnxVs and expression of the AnxV gene and its common polymorphism in Kozak sequence (-1C>T) were studied. As a functional assay, the binding capacity of AnxV to platelets was evaluated.

RESULTS

As compared with controls, type 1 diabetic patients had significantly low serum AnxV levels and AnxV gene expression. The number of anti-AnxV positivity and their serum levels were significantly higher in type 1 diabetic patients than controls. AnxV binding to platelets were significantly decreased in the type 1 diabetic patients. The frequencies of the -1C>T polymorphism of AnxV gene did not differ between groups.

CONCLUSIONS

This study demonstrated the significant changes in AnxV levels and its function in type 1 diabetic patients. These results support the hypothesis that the defective AnxV system may have a role in ongoing autoimmune activity and the development of thrombotic complications in type 1 diabetes. Further studies are necessary to elucidate the clinical impact of anti-AnxVs and dysregulated AnxV function in type 1 diabetes.

Annexinopathies

Annexins comprise a conserved family of proteins characterised by their ability to bind and order charged phospholipids in membranes, often in response to elevated intracellular calcium. The family members (there are at least 12 in humans) have become specialised over evolutionary time and are involved in a diverse range of cellular functions both inside the cell and extracellularly Although a mutation in an annexin has never been categorically proven to be the cause of a disease state, they have been implicated in pathologies as diverse as autoimmunity, infection, heart disease, diabetes and cancer. 'Annexinopathies' were first described by Jacob H. Rand to describe the pathological sequelae in two disease states, the overexpression of annexin 2 in a patients with a haemorrhagic form of acute promyelocytic leukaemia, and the under-expression of annexin 5 on placental trophoblasts in the antiphospholipid syndrome. In this chapter we will outline some of the more recent observations in regard to these conditions, and describe the involvement of annexins in some other major causes of human morbidity.

A common haplotype of the annexin A5 (ANXA5) gene promoter is associated with recurrent pregnancy loss

We sought to verify whether variation in the promoter of the gene encoding placental anticoagulant protein annexin A5 (ANXA5) represents a risk factor for recurrent pregnancy loss (RPL). Sequence analysis of 70 German RPL patients, all known to carry neither factor V Leiden nor a prothrombin mutation, revealed four consecutive nucleotide substitutions in the ANXA5 promoter, which were transmitted as a joint haplotype (M2). Reporter gene assays revealed that M2 reduces the in vitro activity of the ANXA5 promoter to 37-42% of the normal level. The possible relationship between M2 and RPL was evaluated by comparing RPL patients with two independent control groups recruited from the registry of the Institut für Humangenetik in Münster and the PopGen biobank in Kiel, respectively. Carriers of M2 were found to exhibit a > 2-fold higher RPL risk than non-carriers (odds ratio, 2.42; 95% confidence interval, 1.27-4.58) when using unselected controls (PopGen) and an almost 4-fold higher risk when using the Münster 'super-controls', i.e. women with successful pregnancies and no previous history of pregnancy losses (odds ratio, 3.88; 95% confidence interval, 1.98-7.54). This statistically significant association should facilitate the development of improved prognostic algorithms for RPL, involving a more precise assessment of individual disease risks, and provide a guide to offering adequate therapies where relevant.

Annexin A5 polymorphism (-1C-->T) and the presence of anti-annexin A5 antibodies in the antiphospholipid syndrome

BACKGROUND

Annexin A5 is thought to have a role in the pathophysiology of the antiphospholipid syndrome (APS)-a syndrome characterised by recurrent thrombosis and pregnancy morbidity.

OBJECTIVE

To investigate whether anti-annexin A5 immunoglobulin (Ig)M or IgG antibodies, or the -1C-->T polymorphism of annexin A5, is a risk factor for thrombosis or miscarriage, and whether the -1C-->T polymorphism is correlated with APS.

METHODS

A cohort study was carried out with a population of 198 patients with primary APS, systemic lupus erythematosus or lupus-like disease. For the detection of anti-annexin A5 antibodies and the measurement of annexin A5 plasma levels, ELISA-type methods were used. The annexin A5 -1C-->T mutation was detected by restriction fragment length polymorphism.

RESULTS

71 patients were positive for annexin A5 IgM or IgG antibodies, of whom 53 patients were positive for anti-annexin A5 IgG antibodies and 27 of 198 patients were positive for anti-annexin A5 IgM antibodies. The prevalence of IgM or IgG anti-annexin A5 antibodies was not significantly associated with thrombosis or miscarriage on multivariate analysis. The prevalence of the -1C-->T mutation in the annexin A5 gene (46/198 patients) was significantly associated with miscarriage (odds ratio 2.7, 95% confidence interval 1.1 to 6.7, independent risk factor).

CONCLUSION

The detection of anti-annexin A5 antibodies does not seem relevant for estimating the risk for thrombosis or miscarriage in APS. The -1C-->T mutation was an independent risk factor for miscarriage, which is independent of APS.

Annexin A5 in cardiovascular disease and systemic lupus erythematosus

Atherosclerosis, a major cause of disease and death from cardiovascular disease (CVD), is an inflammatory disease characterized by T cell and monocyte/macrophage infiltration in the intima of large arteries. During recent years and with improved treatment of acute disease manifestations, it has become clear that the risk of CVD is very high in systemic lupus erythematosus (SLE), often considered a prototypic autoimmune disease. A combination of traditional and non-traditional risk factors, including dyslipidemia, inflammation, antiphospholipid antibodies (aPL) and lipid oxidation are related to CVD in SLE. aPL are highly thrombogenic, and possible mechanisms include direct effects of aPL on endothelial and other cells, and interference with coagulation reactions. More than a thousand proteins of the annexin-superfamily are expressed in eukaryotes. Annexins are ubiquitous, highly conserved, predominantly intracellular proteins, widely distributed in tissues. Annexin A5 (ANXA5) is an important member of the annexin family due to its antithrombotic properties. These are believed to be caused by it forming a two-dimensional protective shield, covering exposed potentially thrombogenic cell surfaces. Recently, ANXA5 has been implicated in SLE since aPL interfere with ANXA5 binding to placental trophoblasts, causing microthrombosis and miscarriage, a rather common complication in SLE. We recently demonstrated that ANXA5 may play a role in CVD and is abundant in late-stage atherosclerotic lesions. Sera from SLE-patients with a history of CVD inhibited ANXA5 binding to endothelium, caused by IgG antibodies, to a significant degree aPL. This review will focus on potential involvement of ANXA5 in pathogenesis of CVD, particularly caused by underlying atherosclerosis and atherothrombosis.