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R H Derksen

Publications and source records attributed to R H Derksen.

At least 19 recordsLinked to original sources
PubMed2001

Complexes of anti-prothrombin antibodies and prothrombin cause lupus anticoagulant activity by competing with the binding of clotting factors for catalytic phospholipid surfaces.

We investigated the mechanism by which anti-prothrombin antibodies cause lupus anticoagulant (LAC) activity. Addition of affinity-purified anti-prothrombin antibodies from LAC-positive plasma samples (alpha-FII-LAC+) to normal plasma induced LAC activity. Upon increasing the phospholipid concentration, LAC activity was neutralized. Addition of purified alpha-FII-LAC+ to normal plasma strongly inhibited factor Xa formation. No inhibition was measured when alpha-FII-LAC+ were added to prothrombin-deficient plasma or when purified anti-prothrombin antibodies from LAC-negative plasma samples (alpha-FII-LAC-) were added. When a combination of prothrombin and alpha-FII-LAC+ was added to the purified clotting complex, a strong inhibition of factor Xa and IIa formation was seen. The alpha-FII-LAC+ alone or a combination of prothrombin and alpha-FII-LAC- did not show inhibition. Ellipsometry studies showed that, in the presence of alpha-FII-LAC+, the affinity of prothrombin for a phospholipid surface increased dramatically, whereas a much lower increase was observed with alpha-FII-LAC-. Our results show that complexes of prothrombin and anti-prothrombin antibodies with LAC activity inhibit both prothrombinase and tenase. The antibodies increase the affinity of prothrombin for the phospholipid surface, thereby competing with clotting factors for the available catalytic phospholipid surface, a mechanism similar to that of anti-beta2-glycoprotein I antibodies.

Antiphospholipid Syndrome↗
PubMed2001

Lupus anticoagulant and history of thrombosis are not associated with persistent endothelial cell activation in systemic lupus erythematosus.

Antiphospholipid antibodies (aPL), especially lupus anticoagulant (LAC), characterize systemic lupus erythematosus (SLE) patients at increased risk for arterial and venous thromboembolic complications. It has been reported that purified human anti-phospholipid antibodies cause endothelial cell activation in in vitro experiments. In order to investigate whether increased endothelial cell activation is associated with thromboembolic events in SLE patients with LAC, we measured plasma levels of thrombomodulin (TM), von Willebrand factor (vWf), sP-selectin, vascular cell adhesion molecule-1 (sVCAM-1) and ED1-fibronectin in a study of 76 patients with SLE. Patients were subdivided on the basis of: no history of thrombosis and LAC-negative (n = 22) or LAC-positive (n = 17); positive history of thrombosis and LAC-negative (n = 16) or LAC-positive (n = 21). The median SLE disease activity index (SLEDAI) was 4. Although concentrations of sTM, vWf, sP-selectin and sVCAM-1 were significantly elevated in SLE compared with values in healthy controls, they did not differ between the four groups, between patients with or without history of thrombosis, and between patients with or without LAC. Presence of anticardiolipin antibodies could not explain these negative findings. Adjustment of the concentrations for significantly associated variables, such as age, hypertension, smoking, immunosuppressive treatment and concentrations of creatinine, cholesterol and homocysteine, did not change the main results of the study. Only sTM was significantly lower in patients with both LAC and thrombosis than in patients without both these features after adjustment for serum creatinine concentrations. In conclusion, we did not find an association between endothelial cell activation and presence of LAC or history of thrombosis in SLE.

Adult↗
PubMed2000

Dimers of beta 2-glycoprotein I mimic the in vitro effects of beta 2-glycoprotein I-anti-beta 2-glycoprotein I antibody complexes.

Anti-beta(2)-glycoprotein I antibodies are thought to cause lupus anticoagulant activity by forming bivalent complexes with beta(2)-glycoprotein I (beta(2)GPI). To test this hypothesis, chimeric fusion proteins were constructed of the dimerization domain (apple 4) of factor XI and beta(2)GPI. Both a covalent (apple 4-beta(2)GPI) and a noncovalent (apple 4-C321S-beta(2)GPI) chimer were constructed. As controls, apple 2-beta(2)GPI and apple 4-C321S-beta(2)GPI-W316S, in which beta(2)GPI-W316S is not able to bind to phospholipids, were made. In a phospholipid binding assay, apple 4-beta(2)GPI and apple 4-C321S-beta(2)GPI were able to bind to phospholipids with an affinity 35 times higher than that of plasma-derived beta(2)GPI and apple 2-beta(2)GPI. Apple 4-C321S-beta(2)GPI-W316S did not bind at all. Only apple 4-beta(2)GPI and apple 4-C321S-beta(2)GPI were able to bind to adhered platelets as shown by immunofluorescence. Using the prothrombin time, which was the most responsive coagulation assay, the clotting time was approximately doubled when 200 microg/ml apple 4-beta(2)GPI or apple 4-C321S-beta(2)GPI was added. Addition of 200 microg/ml plasma-derived beta(2)GPI, apple 2-beta(2)GPI, or apple 4-C321S-beta(2)GPI-W316S did not affect clotting time. Clotting time could be corrected with the addition of extra phospholipids, which is indicative for lupus anticoagulant activity. An additional increase in clotting times for apple 4-beta(2)GPI or apple 4-C321S-beta(2)GPI was achieved by the addition of monoclonal antibodies against beta(2)GPI. In conclusion, dimerization of beta(2)GPI explains the in vitro observed effects of beta(2)GPI-anti-beta(2)GPI antibody complexes.

Animals↗
PubMed2000

Fcgamma receptor polymorphisms in systemic lupus erythematosus: association with disease and in vivo clearance of immune complexes.

OBJECTIVE: Fc receptors for IgG (FcgammaR) play a prominent role in the clearance of immune complexes in systemic lupus erythematosus (SLE). Polymorphisms of FcgammaR have been proposed as genetic factors that influence susceptibility to SLE. We analyzed 3 functional FcgammaR polymorphisms in a strictly Caucasian population of SLE patients, and determined the influence of these polymorphisms on the clearance of immune complexes in vivo. METHODS: Genomic DNA was isolated from 230 Caucasian patients with SLE and 154 controls. Amplification of FcgammaR-genomic regions in allotype-specific polymerase chain reactions was used to distinguish the genotypes. In addition, we analyzed the FcgammaR genotypes of 13 patients with SLE who participated in a study determining the half-life of IgG-coated erythrocytes in the blood. RESULTS: We found a strong trend toward skewing of FcgammaRIIa, with an enrichment of the homozygous FcgammaRIIa-R/R131 genotype in patients compared with controls. We did not find a correlation between this genotype and the development of lupus nephritis. However, we established that the half-life of IgG-coated erythrocytes in the blood was prolonged in patients expressing the FcgammaRIIa-R/R131 genotype. The homozygous FcgammaRIIIa-F/F158 genotype was found more frequently in patients with arthritis and/or serositis. CONCLUSION: In Caucasian populations, the R/H polymorphism of FcgammaRIIa is a minor determinant in susceptibility to SLE, whereas the V/F polymorphism of FcgammaRIIIa is associated with a set of disease manifestations. Notably, the R/H polymorphism of FcgammaRIIa affects the clearance of immune complexes in vivo, which may influence the course of a disease such as SLE.

Adolescent↗
PubMed2000

Structure-function studies on beta 2-glycoprotein I.

Human beta 2-glycoprotein I is a heavily glycosylated plasma protein which has been implicated in the binding of antiphospholipid antibodies to negatively charged phospholipids; a process considered as an important risk factor for the development of thrombosis. We have solved the crystal structure of beta 2-glycoprotein I. In this review we will discuss what the three-dimensional structure teaches us about the role of beta 2-glycoprotein I in the pathogenesis of the antiphospholipid syndrome.

Glycoproteins↗
PubMed2000

Do we know which patients with the antiphospholipid syndrome should receive long-term high dose anti-coagulation?

The standard treatment of thrombosis related to antiphospholipid antibodies is lifelong high-intensity oral anticoagulation. This standard is primarily based on retrospective evaluations of such patients. In this paper we give a summary of current treatment of deep leg vein thrombosis, pulmonary embolism, ischaemic stroke and transient ischaemic events in the general population and relate this to studies performed in patients with the anti-phospholipid syndrome (APS). It is concluded that many patients with APS can be treated with conventional doses of oral anticoagulants, and that anti-platelet drugs may have a role in the prevention of cerebral ischaemic events. Data from large scale prospective studies, which are underway, will ultimately identify the optimal treatment in individual patients.

Administration, Oral↗
PubMed2000

Lupus anticoagulant in cardiovascular diseases: the role of beta2-glycoprotein I.

The presence of antiphospholipid antibodies (aPL) in plasma is an important risk factor for the development of thrombosis. A major breakthrough came in 1990 with the finding that aPL do not react with phospholipids per se, but are directed towards beta2-glycoprotein I, a plasma protein with affinity for anionic phospholipids. Afterwards other plasma proteins with affinity for phospholipids have been identified as possible antigens for aPL. Human beta2-glycoprotein I is a heavily glycosylated plasma protein that has been implicated in the binding of aPL to negatively charged phospholipids. We recently solved the crystal structure of beta2-glycoprotein I. In this review we will discuss what the 3-dimensional structure teaches us about the role of beta2-glycoprotein I in the pathogenesis of the thrombotic complications characteristic of the antiphospholipid syndrome.

Animals↗
PubMed1999

Adhesion mechanism of human beta(2)-glycoprotein I to phospholipids based on its crystal structure.

Human beta(2)-glycoprotein I is a heavily glycosylated five-domain plasma membrane-adhesion protein, which has been implicated in blood coagulation and clearance of apoptotic bodies from the circulation. It is also the key antigen in the autoimmune disease anti-phospholipid syndrome. The crystal structure of beta(2)-glycoprotein I isolated from human plasma reveals an elongated fish-hook-like arrangement of the globular short consensus repeat domains. Half of the C-terminal fifth domain deviates strongly from the standard fold, as observed in domains one to four. This aberrant half forms a specific phospholipid-binding site. A large patch of 14 positively charged residues provides electrostatic interactions with anionic phospholipid headgroups and an exposed membrane-insertion loop yields specificity for lipid layers. The observed spatial arrangement of the five domains suggests a functional partitioning of protein adhesion and membrane adhesion over the N- and C-terminal domains, respectively, separated by glycosylated bridging domains. Coordinates are in the Protein Data Bank (accession No. 1QUB).

Antibodies, Antiphospholipid↗
PubMed1999

[Clinical thinking and decision-making in practice. A patient with arthritis, skin lesions and a perforated nasal septum].

A man aged 38 years had arthritis, skin lesions and a perforation of the nasal septum. He had slight deterioration of renal function and a few granular casts in the urine. Antineutrophil cytoplasmic antibody and other immune parameters were normal. A biopsy of the nasal septum did not show granulomatous lesions. The differential diagnosis on the available clinical grounds could be narrowed to Wegener's disease, Henoch-Schönlein vasculitis or microscopic polyangiitis. A biopsy of the skin showed leukocytoclastic vasculitis, with IgA and IgM depositions compatible with Henoch-Schönlein vasculitis. A renal biopsy showed small segmental necrotising lesions of the glomerular capillaries, with minimal extracapillary proliferation; immune fluorescence did not detect any significant depositions. The picture was compatible with Wegener's disease. A nasal septum defect together with glomerulonephritis, which could be suspected from only minimal abnormalities in the urine, is almost conclusive for the diagnosis.

Adult↗
PubMed1999

Beta2-glycoprotein I is proteolytically cleaved in vivo upon activation of fibrinolysis.

Beta2-glycoprotein I (beta2GPI) is a plasma glycoprotein with unknown physiological function(s). In in vitro experiments it has been demonstrated that beta2GPI has both anticoagulant properties, such as the inhibition of factor X and prothrombin activation and procoagulant properties, such as the inhibition of the anticoagulant activity of activated protein C. Besides this, beta2GPI bound to cardiolipin is recognized by antiphospholipid antibodies (aPL). In this study we demonstrate that beta2GPI is very sensitive for cleavage between Lys317 and Thr318 by plasmin, resulting in two immunologically different cleaved forms. In vitro experiments show that these plasmin cleaved forms of beta2GPI bind to negatively charged phospholipids with much lower affinity compared to intact beta2GPI. Similar to plasmin, trypsin and elastase can also induce this proteolytical cleavage in beta2GPI, whereas thrombin and factor Xa do not cleave beta2GPI. The in vivo occurrence of the proteolytical cleavage was demonstrated by the finding that in plasmas of patients with disseminated intravascular coagulation (DIC) and in plasmas of patients treated with streptokinase, significant amounts of cleaved beta2GPI (up to 12 microg/ml) are present. During the development of DIC, the increase in levels of cleaved beta2GPI is accompanied by a 70% decrease in the levels of intact beta2GPI, whereas in streptokinase treated patients levels of intact beta2GPI stay within the normal range. This study demonstrates for the first time that during in vivo activation of fibrinolysis beta2GPI is cleaved. which results in the formation of a form of beta2GPI with much lower affinity for negatively charged phospholipids. Plasmin is most likely responsible for this modification.

Adult↗
PubMed1998

Dehydroepiandrosterone (DHEA) and systemic lupus erythematosus.

OBJECTIVE: This study was performed to evaluate in vivo and in vitro data on the effects of the adrenal steroid dehydroepiandrosterone (DHEA) with emphasis on its potential use in the treatment of systemic lupus erythematosus (SLE). METHODS: The literature dealing with DHEA was reviewed. RESULTS: Initially, research on DHEA focused on effects of DHEA in relation to obesity. Over the past decade, research stimulated by associations between the physiological decline in DHEA and aging, cardiovascular disease, changes in metabolism, brain function, and immune senescence have generated insight into the many effects that DHEA or its metabolites may have. In SLE a role for sex hormones in both the etiopathogenesis and disease activity is recognized. In SLE, as in aging, low DHEA levels are frequently found, especially with corticosteroid treatment. CONCLUSIONS: Research data in the elderly, on both hormonal and immunologic effects, suggest that DHEA may become an adjunctive treatment for SLE patients.

Aged↗
PubMed1998

Deforming arthropathy or lupus and rhupus hands in systemic lupus erythematosus.

OBJECTIVE: Although deforming arthropathy in systemic lupus erythematosus (SLE) is characterised by a number of manifestations, definitive criteria for the different forms have not yet been established. To define deforming arthropathy and its different types a study was undertaken of 176 SLE patients. METHODS: Using as criterion any deviation from any of the metacarpus finger axes 17 patients (16 women, one man) were identified with clinical deforming arthropathy. These patients were evaluated according to a standardised protocol that covered all known characteristics of deforming arthropathy. By means of "Jaccoud's arthropathy index" three different forms were identified. RESULTS: Three patients had an erosive form of deforming arthropathy (or rhupus hand) such as those seen in frank rheumatoid arthritis (RA), eight patients were identified as having Jaccoud's arthropathy (or lupus hand), and the remaining six patients had mild deforming arthropathy. Jaccoud's arthropathy is characterised by severe deformation of the hands (ulnar deviation, swan neck deformities, and Z deformity of the thumb) and feet with multiple non-erosive subluxations, mild aching and little or no evidence of synovitis. All patients, but one, fulfilled just four criteria of the ACR classification and joint symptoms were always found to precede the diagnosis of SLE. Furthermore a remarkable association of Jaccoud's arthropathy with fetal loss, thrombosis--both venous and arterial--and the presence of antiphospholipid antibodies was found. CONCLUSIONS: These data suggest that Jaccoud's arthropathy represents a subset of SLE. Subdivision of deforming arthropathy into several clinical forms can facilitate the clinical management of this disorder.

Adolescent↗
PubMed1998

Anti-prothrombin antibodies and their relation with thrombosis and lupus anticoagulant.

Antiphospholipid antibodies are a heterogeneous group of antibodies, comprising antibodies with different antigen specificity. Prothrombin is one of the antigens which can be detected by antiphospholipid antibodies and therefore anti-prothrombin antibodies belong to the antiphospholipid antibody family. The presence of antiphospholipid antibodies correlates strongly with thromboembolic complications; however a mechanism by which these autoantibodies induce a thrombotic complication in vivo is not understood. The classic assays for the detection of antiphospholipid antibodies (LAC and anticardiolipin ELISAs) aim to measure all the antiphospholipid antibodies present in the samples without making a distinction between the different subspecificities of the antibodies present in one single sample. Moreover, most of the in-vitro studies performed were carried out with total IgGs, which contain a mixture of antibodies. The absence of an accurate characterization of the plasma samples and the lack of specificity of the IgGs used in in-vitro tests makes it difficult to determine the contribution of antiprothrombin antibodies to the thrombotic complications. Here we review and critically analyse the literature regarding the clinical relevance of the presence of antiprothrombin antibodies and the possible participation of these antibodies in the pathogenesis of the thrombotic complications.

Animals↗
PubMed1998

Transient monocular blindness and antiphospholipid antibodies in systemic lupus erythematosus.

BACKGROUND AND OBJECTIVE: Among patients with systemic lupus erythematosus (SLE), the presence of antiphospholipid antibodies (APA), notably the lupus anticoagulant, and anticardiolipin antibodies (aCL) characterizes a subset of patients with a thrombotic tendency. During the regular follow-up care of patients with SLE, we noticed that many described transient visual disturbances. Because a hypercoagulable state may cause transient monocular blindness (TMB), we determined the frequency of TMB and studied its relation to the presence of APA in patients with SLE. METHODS: We asked 175 unselected patients with SLE whether they had transient visual disturbances and reviewed their medical charts. All patients were examined with specific attention to the presence of livedo reticularis. Blood was examined for APA. RESULTS: Visual disturbances were recorded for 136 (78%) patients. According to predefined criteria, the symptoms were diagnosed as TMB for 10 (6%) patients and as visual disturbances associated with migraine for 18 (10%) patients. Five of the 10 patients with TMB had attacks in either eye. The 175 patients with SLE accrued a maximum total of 6,349 patient years in their lifetime. From this, the incidence of TMB can be calculated to be at least 158 per 100,000 per year. Lupus anticoagulant was detected in 3 of 10 patients with TMB and 41 of 165 patients without TMB (odds ratio, 1.3; 95% CI, 0.2 to 6.0). aCLs were found in 5 of 10 patients with TMB and 91 of 165 patients without TMB (odds ratio, 0.8; 95% CI, 0.2 to 3.7). CONCLUSIONS: The frequency of TMB among patients with SLE is at least 158 per 100,000 compared with the normal population (14 per 100,000 per year). However, among patients with SLE, no significant relation could be shown between TMB and the presence of APA or livedo reticularis.

Acute Disease↗
PubMed1998

The contribution of anti-prothrombin-antibodies to lupus anticoagulant activity--discrimination between functional and non-functional anti-prothrombin-antibodies.

The presence of lupus anticoagulant (LAC) is strongly correlated with a history of thrombosis in patients with SLE. LAC activity can be caused by anti-prothrombin (FII)- and/or anti-beta2glycoprotein I (beta2GPI)-antibodies. In the present study, the contribution of anti-FII-antibodies to LAC activity was measured in 28 LAC positive plasmas. Plasmas were incubated with prothrombin or BSA, immobilized on CNBr-activated Sepharose, to absorb all anti-FII-antibodies. In 4 out of the 28 plasmas LAC activity was completely dependent on anti-FII-antibodies. In 7 out of the 28 plasmas, anti-FII-antibodies did not contribute to LAC activity. These anti-FII-antibodies can be regarded as non-functional antibodies. In the majority (17/28) of the samples, LAC activity within a single plasma was caused by a combination of antibodies with different specificities. Both dRVVT and KCT showed comparable sensitivity for the detection of functional anti-FII-antibodies. In conclusion, in most samples LAC activity is not caused by anti-FII-antibodies alone but by a combination of different types of antibodies. The presence of LAC activity and anti-FII-antibodies in one plasma does not automatically implicate that these antibodies are responsible for the LAC activity.

Antibody Specificity↗
PubMed1998

Homocysteine, methylenetetrahydrofolate reductase polymorphism, antiphospholipid antibodies, and thromboembolic events in systemic lupus erythematosus: a retrospective cohort study.

OBJECTIVE: To examine the relationship between plasma homocysteine, 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphism, and the risk of arterial and/or venous thrombosis in systemic lupus erythematosus (SLE). METHODS: Plasma homocysteine and MTHFR polymorphism were determined in a retrospective cohort of 175 patients with SLE. Associations between homocysteine levels and antiphospholipid antibodies, renal function, and drug therapy were analyzed. RESULTS: Patients with arterial thrombosis had higher homocysteine concentration than nonthrombotic patients (20.6+/-10.2 vs 13.2+/-6.8 micromol/l; p < 0.001). The crude odds ratio for arterial thrombosis for the highest versus lowest quartile of homocysteine was 4.4 (95% CI 1.3-14.9). After adjustment for other risk factors the odds ratio remained significant (3.7; 95% CI 1.2-13.0). Increased plasma homocysteine was not associated with venous thrombosis. A significant correlation was found between homocysteine and creatinine (r=0.57, p < 0.0001) or the use of methotrexate. Homocysteine levels were higher in patients using corticosteroids and lower in patients using oral contraceptive drugs. This finding may be biased by impaired renal function in patients using corticosteroids and the advice to stop estrogen-containing contraceptives in female patients upon an episode of thrombosis. The distribution of MTHFR genotypes was 50% for homozygous wild type, 42% for heterozygous, and 8% for homozygous mutant, with a similar distribution among patients with or without a history of thrombosis. CONCLUSION: Raised levels of homocysteine are associated with arterial thrombosis in patients with SLE. Mutation in the MTHFR gene does not explain the raised levels, and renal failure is by far the most frequent cause.

Adolescent↗
PubMed1998

The prevalence of a non-phospholipid-binding form of beta2-glycoprotein I in human plasma--consequences for the development of anti-beta2-glycoprotein I antibodies.

The presence of antiphospholipid antibodies (aPL) is strongly correlated with venous and arterial thrombosis, fetal loss and thrombocytopenia. This relation is called the antiphospholipid syndrome (APS). It is well recognized that thrombosis related aPL are not directed against phospholipids alone, but to phospholipid bound plasma proteins like beta2-glycoprotein I (beta2GPI). aPL that need beta2GPI for the binding to negatively charged phospholipids are called anti-beta2GPI-antibodies. Recently, a mutation in the gene encoding beta2GPI has been described, which results in an amino acid substitution Trp316 into Ser316. This Ser316-beta2GPI did not bind to negatively charged phospholipids. Because only phospholipid bound beta2GPI is recognized by human anti-beta2GPI-antibodies, it might be argued that individuals carrying the Trp316Ser mutation are protected against the development of anti-beta2GPI-antibodies. To investigate this hypothesis, the prevalence of the Trp316Ser mutation was measured in 170 systemic lupus erythematosus (SLE) patients and in 18 patients with the primary antiphospholipid syndrome (PAPS) and the mutation was correlated with the presence of anti-beta2GPI-antibodies. In the total patient group 1 homozygous patient and 21 heterozygous patients were found. The allele frequency of the mutation in SLE patients with anti-beta2GPI-antibodies (0.063) was comparable to that found in SLE patients without anti-beta2GPI-antibodies (0.062). These results indicate that the heterozygous presence of Trp316Ser mutation does not prevent an individual from developing anti-beta2GPI-antibodies. We showed that this can be explained by the concentration of Trp316-beta2GPI in heterozygous patients, which is far above the minimal beta2GPI level necessary for optimal phospholipid binding. In our single patient homozygous for the Trp316Ser mutation no binding beta2GPI to the phospholipid surface was detected and no anti-beta2GPI-antibodies were present in the plasma of this patient. In conclusion, heterozygous Trp316Ser beta2GPI persons are not protected against the development of anti-beta2GPI-antibodies. To confirm that homozygotes do not develop anti-beta2GPI-antibodies a very large population is needed, due to the relatively low prevalence of the mutation.

Adolescent↗