aCL Activity Research Articles

Abstract Mo026: ATP-dependent citrate lyase Drives Left Ventricular Dysfunction by Metabolic Remodeling of the Heart

Background: Metabolic remodeling is a hallmark of the failing heart. Oncometabolic stress during cancer increases the activity and abundance of the ATP-dependent citrate lyase (ACL, Acly ), which promotes histone acetylation and cardiac adaptation. ACL is critical for the de novo synthesis of lipids, but how these metabolic alterations contribute to cardiac structural and functional changes remains unclear. Methods: We utilized MyH6-Cas9 mice (male and female) and CRISPR/Cas9 gene editing to generate a cardiac-specific Acly knockdown (AclyKD) mouse model. To assess how the loss of Acly impacts cardiac energy substrate metabolism, we conducted positron emission tomography in vivo and ex vivo stable isotope tracer labelling using working heart preparation. We conducted a multi-omics analysis using RNA-sequencing and mass spectrometry-based metabolomics. Experimental data were integrated into computational modelling using the metabolic network CardioNet to identify significantly dysregulated metabolic processes at a systems level. Results: Loss of ACL expression causes a left-ventricular cardiomyopathy by histology and echocardiography. FDG-PET/CT imaging in male and female mice demonstrated an increased glucose uptake and utilization in AclyKD mice, suggesting a substrate switch from fatty acid oxidation towards glucose. These findings were corroborated by stable isotope tracing, demonstrating that AclyKD suppresses fatty acid oxidation while enhancing lipid remodelling. AclyKD also reduced the efflux of glucose-derived citrate from the mitochondria into the cytosol, confirming that citrate is required for reductive metabolism in the heart. Computational flux analysis and integrative multi-omics analysis indicate that ACL activity supports lipid biosynthesis in the heart. Blocking mitochondrial isocitrate dehydrogenase or alpha-ketoglutarate dehydrogenase sensitized cardiomyocytes to ACL inhibition, and overexpressing cytosolic isocitrate dehydrogenase was sufficient to prevent citrate accumulation. Conclusions: Our work demonstrates a previously undescribed function of ACL as a regulator of cardiac energy substrate metabolism and lipid modulation.

Clinical Predictors and Prediction Models for Frequency of Total and Joint Hemorrhage in Severe-Type Patients with Hemophilia a (PwHA) with/without Intermediate-Dose Prophylaxis Therapy with rFVIII

Introduction: It was well-known that severe-type patients with hemophilia A (PwHA) had great variability in bleeding phenotypes. Factors effecting bleeding patterns of PwHA include at least treatment modality and interindividual various procoagulant and anticoagulant levels. We aimed to investigate what clinical variables could predict bleeding frequency of severe PwHA and to develop models for predicting bleeding phenotypes among severe PwHA with/without FVIII prophylaxis therapy.Methods and materials: Totally 51 severe-type previously-treated PwHA from two Hemophilia Centers in Taiwan were enrolled, who received standard half life (SHL) rFVIII products with complete consecutive bleeding records at least more than 6 months, and their medical charts 2017－2018 were retrospectively viewed. The clinical data were collected for analysis, including age, body mass index (BMI), body weight (BW), ABO blood groups, hemoglobin (Hb), hematocrit (Hct), HCV infecton, HIV infection, treatment modality, baseline VWF levels, and genetic defects. Baseline VWF activity meant the data via VWF:ACL activity or VWF:RCo. Clinical variables for annualized bleeding rate (ABR) and annualized joint bleeding rate (AJBR) were evaluated by multivariate linear regression (MVLR) analysis.Results: The cohort of 51 severe-type PwHA included 8 boys and 43 adults, aged 8-64. For treatment modality, there were 19 patients receiving episodic treatment (ET) and 32 receiving prophylaxis therapy (PT) with intermediate-dose standard half life (SHL) rFVIII. The mean study period was 11.9 months, range 10－14.5 months. Among them, there were 31 with HCV infection and 4 with HIV infection. PwHA with non-O blood group were 31 and those with O blood group 20. The mean baseline VWF:Ag was 115.6±55.5%, range 50%－294.7%. The mean baseline VWF:activity was 105.4±52.1%, range 41.3%－307%. ABR of ET group and PT group were 46.1±29.2 and 6.8±7.1, respectively. (p<0.0001***) AJBR of ET group and PT group were 37.3±27.7 and 6.0±6.8, respectively. (p=0.0001***) By MVLR analysis, both treatment modality and baseline VWF:Ag were recognized as inverse predictors of ABR and AJBR, and HCV infection recognized a predictor for AJBR. Age, inhibitor histroy, BMI, BW, ABO blood groups, Hct, Hb, HIV infection, and missense mutation or not were eliminated as predictors. The predictive equations by MVLR were as the following two:(1) Predictive ABR = 56.5 - 37.8 * (Treatment model) - 11.8 * baseline VWF:Ag (IU/mL).(2) Predictive e AJBR = 41.9 - 28.6 * (Treatment model) - 12.0 * baseline VWF:Ag (IU/mL) + 10.0 * (HCV infection).(1 if Treatment model is PT, 0 if Treatment model is ET. 1 if HCV infection or anti-HCV antibody is positive, 0 if HCV infection or HCV antibody is negative.) Separate prediction models developed from MVLR analysis could explain 52.51% of the ABR variability and 50.56% of the AJBR variability. The correlation between predicted and observed bleeding frequency was significantly strong.(P-rank>0.7, p-value<0.0001***) Mean difference between predicted ABRs and observed ABRs was 1.75 and that between predicted AJBRs and observed AJBRs was 1.27. Predicted ABR deviated <21 (<2 per month) of observed ABR in 42/50 patients (84%). Predicted AJBR deviated < 24 (<2 per month) ofobserved AJBR in 44/50 patients (88%).Conclusion: Prophylaxis therapy and baseline VWF:Ag levels were the strongest two inverse predictors for ABR and AJBR. Positive HCV infection was another predictor for AJBR. The prediction models provided with an insight into personal bleeding quantified patterns and may identify PwHA with high bleeding risks based on individual characteristics of treatment modality, baseline VWF:Ag, and HCV infection. Our approach is of help for individualized treatment and refining of dosing strategies. DisclosuresNo relevant conflicts of interest to declare.

IS EARLY EXCELLENT ISOKINETIC AND FUNCTIONAL TESTING FOLLOWING ACL RECONSTRUCTION IN PATIENTS WITH OPEN-PHYSES PREDICTIVE OF SUBSEQUENT ACL DISRUPTION?

Introduction: It is unknown whether functional and isokinetic testing at 6 months following ACL reconstruction in patients with open-physes correlates with longer term outcomes. The purpose of this study was to compare subsequent ACL rupture risk, knee function, and activity level in patients with open-physes who had excellent 6-month testing to those who did not. Methods: Between the years of 2000 and 2015, 86 patients with open-physes underwent ACL reconstruction and had functional and isokinetic testing performed at 6-months post-operatively. Thirty-four (40%) tested in the excellent range in all categories of both functional and isokinetic testing and were labeled the excellent group. The remaining 52 (60%) patients were labeled the delayed testing group. Data regarding patient, injury, and surgical characteristics were retrospectively collected. The rate of second ACL injury as well as clinical outcome scores were collected postoperatively. Results: Graft rupture rate was 23.4% (n = 8) in the excellent group and 15.4% (n = 8) in the delayed group (p = 0.51). In the excellent group, 20.5% (n = 7) had a contralateral ACL tear versus 11.5% (n = 6) in the delayed group (p = 0.40). Five patients in the excellent group and 4 patients in the delayed group sustained both graft failure and contralateral ACL tear. The overall prevalence of second ACL injury was 29% in the excellent group and 23% in the delayed group. The delayed group returned to sport at an average of 8.8 months whereas the excellent group returned at an average of 6.6 months (p &lt; 0.01). At mean follow up of 3.59 years, the excellent group had a higher Tegner activity level (8.9 versus 8.3) than the delayed group (p &lt; 0.02). Conclusion: Pediatric patients with open-physes who had excellent isokinetic strength and functional testing 6-months postoperatively returned to sport sooner than those who did not. There was no statistical difference in either graft failure or contralateral ACL disruption between these groups. However, both groups had unacceptably high rates of second ACL injury (29% for the excellent group and 23% for the delayed group). Significance: Excellent 6 month return of strength and function was not protective of subsequent ACL disruption, the rate of which remains dismal within this pediatric population. Development of more sensitive functional measures for children could help to change these poor outcomes and guide clinicians when to allow return to sport.

Abstract 20910: Alpha-Ketoglutarate Metabolism Regulates Oncometabolic Adaptation in the Heart

Introduction: The term “cancer and the heart” traditionally refers to the cardiotoxic effects of chemotherapeutic agents. However, independent of any cytostatic treatment cancer survivors have a five-fold higher risk for developing heart failure. Therefore, new therapeutic strategies must consider tumor biology when aiming at protecting the heart. In isocitrate dehydrogenase (IDH)1 and 2 mutant tumors, the elevated production of the oncometabolite D-2-hydroxyglutarate (D2-HG) is associated with systemic effects, including dilated cardiomyopathy. About 20% of acute myeloid leukemia cases harbor mutations of the IDH, which leads to reduced patient survival and causes metabolic dysfunction through production of the oncometabolite D2-HG. Recent findings have shown that D2-HG impairs oxidative decarboxylation of α-KG, which in turn increases ATP citrate lyase activity. Hypothesis: Based on these findings we are now proposing that modulation of ACL activity reverses D2-HG mediated metabolic changes. Methods: As models we used isolated working rat hearts; and combined C13-tracer studies with computational flux analysis. Results: Wild type rat hearts were perfused with the ACL inhibitor BMS303141 (0.5 μM; BMS) or D2-HG (1 mM). Cardiac power rapidly declined by 25% in the presence of BMS or D2-HG alone. Simultaneous perfusion with D2-HG and BMS, improved cardiac power, suggesting that modulation of ACL improves cardiac function only in presence of D2-HG. Further, α-KG dehydrogenase (α-KGDH) activity increased with ACL inhibition, reflecting an inverse relationship between these enzymes. Computational flux analysis using the metabolic genome-scale network CardioNet revealed that D2-HG-dependent inhibition by α-KGDH shifts cardiac metabolism towards increased reductive carboxylation of α-KG. Conclusions: Our findings suggest an “oncometabolic axis” in the heart and underscore the potential application of ACL inhibitors to protect the heart from failing in IDH-mutant tumors.

Proof-of-concept study demonstrating the pathogenicity of affinity-purified IgG antibodies directed to domain I of β2-glycoprotein I in a mouse model of anti-phospholipid antibody-induced thrombosis.

Objective. IgG aPL against domain I of β2-glycoprotein I (β2GPI) [anti-DI (aDI)] is associated with the pathogenesis of APS, an autoimmune disease defined by thrombosis and pregnancy morbidity. To date, however, no study has demonstrated direct pathogenicity of IgG aDI in vivo. In this proof-of-concept study, we designed a novel system to affinity purify polyclonal aDI aPL in order to assess its prothrombotic ability in a well-characterized mouse microcirculation model for APS.Methods. Two polyclonal IgG fractions were isolated from serum of a patient with APS, both with high aPL activity but differing in aDI activity (aDI-rich and aDI-poor). These IgG fractions were tested for their pathogenic ability in an in vivo mouse model of thrombosis. Male CD1 mice were injected intraperitoneally with either aDI-rich or aDI-poor IgG; as a control, IgG isolated from healthy serum was used. A pinch injury was applied to the right femoral vein and thrombus dynamics and tissue factor activity in isolated tissue were evaluated.Results. Both aDI-rich and aDI-poor IgG retained aCL and anti-β2GPI activity, while only aDI-rich IgG displayed high aDI activity, as defined by our in-house cut-offs for positivity in each assay. aDI-rich IgG induced significantly larger thrombi in vivo compared with aDI-poor IgG (P < 0.0001). Similarly, aDI-rich IgG significantly enhanced the procoagulant activity of carotid artery endothelium and peritoneal macrophages isolated from experimental animals (P < 0.01).Conclusion. These data directly demonstrate that the ability to cause thrombosis in vivo is concentrated in the aDI fraction of aPL.

Expression of anti-cardiolipin antibodies and inflammatory associated factors in patients with schizophrenia

Numerous studies have implicated a connection between schizophrenia and autoimmune disorders. However, the precise relationship and underlying mechanism are still obscure. To further identify the association between autoimmune disorders and schizophrenia, the mRNA expressions of various cytokines and Toll-like receptors (TLRs) in monocytes are examined by using RT-PCR. Additionally, ELISA and zymography were performed to determine the anti-cardiolipin antibody (aCL) and MMP9 activity in serum form schizophrenic patients. Notably, significantly increased interleukin (IL)-6 and IL-10 mRNA were observed in schizophrenic patients, whereas significant reductions of TLR-3 and TLR-5 mRNA were detected. Moreover, significantly increased levels of aCL antibody and a higher frequency of positive-MMP9 activity were detected in serum from patients with schizophrenia. Meanwhile, no significant association was found between each of the medications and aCL activity. These findings demonstrated autoimmune-related phenomena in schizophrenic patients and further suggested a connection between schizophrenia and autoimmune disorders.

Antiphospholipid antibodies may impair factor XIIa–dependent activation of fibrinolysis in pregnancy: in vitro evidence with human endothelial cells in culture and monoclonal anticardiolipin antibodies

The purpose of this study was to analyze the in vitro activation of the contact complex with the use of human umbilical vein endothelial cells (HUVEC) in culture and monoclonal anticardiolipin antibodies (MaCL). Cultured HUVECs were incubated with pooled plasma from third-trimester pregnant women with the addition (20 mg/mL) of MaCL with anti-beta-2 glycoprotein I activity that was obtained from patients with antiphospholipid syndrome (APS), MaCL from an individual without APS, or from a control patient with immunoglobulin M without aCL activity. Supernatants were evaluated. Activated factors XII and VII, prothrombin-fragment 1 + 2, urokinase-type plasminogen activator (UPA), and differentiating 2 chain UPA were determined. In the cultured HUVEC supernatants, the addition of MaCL increased activated factor VII and prothrombin-fragment 1 + 2, did not modify UPA, and decreased activated factor XII and differentiating 2 chain UPA, in comparison with samples with control immunoglobulin M added. The MaCL without APS activity did not change any parameter that was evaluated. MaCL with anti-beta-2 activity that was obtained from patients with APS may interfere in the activation of the contact complex during pregnancy.

Inhibitor(s) of natural anti-cardiolipin autoantibodies.

IgG fractions were purified on Sepharose anti-human IgG column from eight sera of healthy donors, having no anti-cardiolipin (aCL) activity as measured by anti-cardiolipin ELISA assay (aCL-ELISA). All the IgG fractions, after elution with 4.9 M MgCl2, reacted with CL. The antigen-binding characteristics of the IgG fractions purified from normal human serum (NHS) were similar to those of IgG fractions purified from sera of four patients with the anti-phospholipid syndrome (APLS). Competition assay confirmed the specificity of the binding of the purified IgG fractions to CL. The same results have been achieved with IgG fractions purified on Sepharose Protein-A column. The binding to CL was completely inhibited by either whole NHS and sera from various animal species, or by beta 2-glycoprotein I (beta 2-GPI). Our results support the notion of the existence of both natural anti-CL antibodies and serum inhibitor(s) in sera of healthy individuals. It is conceivable that in part the pathogenesis of APLS entails defects in the natural inhibitors of aCL antibodies.

Some antiphospholipid antibodies recognize conformational epitopes shared by β2‐glycoprotein I and the homologous catalytic domains of several serine proteases

To test the hypothesis that some antiphospholipid antibodies (aPL) in patients with the antiphospholipid syndrome (APS) recognize a conformational epitope shared by beta2-glycoprotein I (beta2GPI; the major autoantigen for the antiphospholipid antibodies) and the homologous catalytic domains of several serine proteases (such as thrombin, activated protein C [APC], and plasmin) involved in hemostasis. We generated 4 new IgG monoclonal aPL (2 screened against beta2GPI, 1 against thrombin, and 1 against protein C) from 2 APS patients. The monoclonal antibodies (mAb) were analyzed for binding to beta2GPI, thrombin, APC, and plasmin, as well as for anticardiolipin antibody (aCL) activity. To demonstrate a shared epitope between beta2GPI and a serine protease, 1 mAb was studied by cross-inhibition analysis. Both of the IgG anti-beta2GPI mAb bound to thrombin, APC, and plasmin. On the other hand, the 1 anti-thrombin mAb and the 1 anti-protein C mAb also bound to beta2GPI. Moreover, the binding of 1 cross-reactive mAb to beta2GPI was inhibited by alpha-thrombin (which contains only the catalytic domain of thrombin). All 4 mAb displayed aCL activity. Taken together with the findings that some aCL bind to several serine proteases that participate in hemostasis and share homologous catalytic domains, these data demonstrate that some aCL in APS patients recognize one or more conformational epitopes shared by beta2GPI and the catalytic domains of disease-relevant serine proteases.

Some Plasmin-Induced Antibodies Bind to Cardiolipin, Display Lupus Anticoagulant Activity and Induce Fetal Loss in Mice

The combined presence of anti-phospholipid Ab (aPL), thrombosis, and/or fetal loss is recognized as the antiphospholipid syndrome (APS). aPL include anti-cardiolipin Ab (aCL) and/or lupus anticoagulants (LAC, detected as Ig that prolong certain in vitro phospholipid (PL)-restricted blood clotting tests); both aCL and LAC are the diagnostic Ab for APS. Studies show that aPL represent a heterogeneous group of Ab, which recognize various PL, PL-binding plasma proteins, and/or PL-protein complexes. Recently, we found that five of seven patient-derived IgG monoclonal aCL react with thrombin, activated protein C, and plasmin. All three proteins are trypsin-like serine proteases (SP), and are highly homologous in their catalytic domains. Importantly, among these SP autoantigens, the reactive aCL bind to plasmin with the highest affinity, suggesting that plasmin may serve as a major driving autoantigen for some aCL in approximately 30% of APS patients who are positive for IgG anti-plasmin Ab. To test this hypothesis, we immunized BALB/c mice with human plasmin and analyzed immune sera for aCL activity and reactivity with relevant SP. We found that some immune sera displayed aCL activity and/or bound to test SP. Subsequently, eight mAb were obtained and studied. The results revealed that one mAb displayed the aCL and the LAC activities and induced fetal loss when injected into pregnant mice. Immunohistological analyses of placentas revealed extensive deposits of activated C3 components. Combined, these data demonstrate that plasmin may serve as a driving Ag for some pathogenic aPL.

Enhanced oxidative status but not corresponding elevated antioxidative status by anticardiolipin antibody and disease activity in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is associated with premature atherosclerosis, and an increased susceptibility of plasma lipids and lipoproteins to oxidation could at least in part promote atherogenesis. The objective of this study was to identify the effects of anticardiolipin antibody (aCL) and disease activity on oxidative and antioxidative status in patients with SLE. In this study, patients in SLE/aCL+ group and in SLE disease activity index >3 group had significantly higher thiobarbituric acid reactive substance (TBARS) levels, titers of autoantibodies against oxidized low-density lipoprotein (ox-LDL), and glutathione peroxidase activity than that of healthy controls. However, only TBARS and titers of autoantibodies against ox-LDL but not antioxidant enzyme activities were significantly different between SLE subgroups. Thus, enhanced oxidative status but not corresponding elevated antioxidative status by the presence of aCL and active disease activity make potent antioxidant therapy valuable for these SLE patients in preventing oxidative damage.

Effects of beta2-glycoprotein I and monoclonal anticardiolipin antibodies in platelet interaction with subendothelium under flow conditions.

To evaluate whether the effect of human monoclonal anticardiolipin antibodies (aCL) on platelet interaction with the subendothelium under flow conditions is dependent on beta(2)-glycoprotein I (beta(2)GPI). Three monoclonal IgM aCL with anti-beta(2)GPI activity (TM1B3, GR1D5, and EY2C9) obtained from patients with antiphospholipid syndrome, a monoclonal aCL with lupus anticoagulant activity but without anti-beta(2)GPI activity (FRO) obtained from a patient with a splenic lymphoma, and a control monoclonal IgM without aCL activity were used. TM1B3, GR1D5, EY2C9, FRO, and control IgM (30 microg/ml) were added to reconstituted blood containing gel-filtered platelets (200 x 10(9)/liter), factor VIII (100 units/dl), and fibrinogen (1.5 gm/liter). Samples were perfused (wall-shear rate 800 seconds(-1)), with and without the addition of purified beta(2)GPI (20 microg/ml), through annular chambers containing collagen-rich denuded vascular segments, and the percentages of surface covered by platelets and by thrombi were evaluated. No differences in the percentages of surface covered by platelets and by thrombi were observed among samples with TM1B3, GR1D5, EY2C9, FRO, and control IgM added when reconstituted blood samples without beta(2)GPI were used. However, a significant increase in the percentage of surface covered by platelets was observed in the presence of TM1B3, GR1D5, and EY2C9 but not in the presence of FRO when samples containing beta(2)GPI were used. Increased thrombi formation was induced by TM1B3 and GR1D5 but not by EY2C9 or FRO in samples with added beta(2)GPI. Monoclonal aCL require anti-beta(2)GPI activity to promote platelet interaction with the subendothelium under flow conditions.

Antiphospholipid antibodies induce monocyte chemoattractant protein-1 in endothelial cells.

The presence of antiphospholipid Ab is associated with increased risk of thrombosis. The monocyte-endothelial cell interaction has been suggested to play a key role at the site of vascular injury during thrombosis. Therefore, we tested the effect of anticardiolipin Abs (aCL) on the production of monocyte chemoattractant protein-1 (MCP-1) in HUVEC. We found that monoclonal aCL as well as IgG fractions from patients with antiphospholipid syndrome (APS-IgG) could induce the production of MCP-1 in HUVEC. The ability of IgG aCL to induce MCP-1 production could be abrogated by preabsorption with cardiolipin liposomes. Simultaneous addition of either monoclonal aCL or APS-IgG with IL-1beta resulted in synergistic increase in MCP-1 production, whereas the addition of control IgG lacking aCL activity did not alter IL-1beta-induced levels of MCP-1. MCP-1 mRNA expression was also up-regulated when HUVEC were incubated with either APS-IgG or monoclonal aCL, and down-regulated by the treatment of dexamethasone. In addition, we found that serum levels of MCP-1 in 76 systemic lupus erythematosus patients correlated well with the titers of IgG aCL. Collectively, these results indicate that aCL could promote endothelial cell-monocyte cross-talk by enhancing the endothelial production of MCP-1, thereby shifting the hemostatic balance toward the prothrombotic state of APS.

A chimeric antibody with the human gamma1 constant region as a putative standard for assays to detect IgG beta2-glycoprotein I-dependent anticardiolipin and anti-beta2-glycoprotein I antibodies.

Thromboembolic manifestations or thrombocytopenia in association with anticardiolipin antibodies (aCL) or lupus anticoagulant are known as the antiphospholipid syndrome (APS). Efforts have been made to elucidate precise clinical features and adequate therapeutic options for treating patients with APS. However, the lack of a proper international standard for measurement of aCL makes it difficult to compare data derived from different laboratories. We attempted to design a chimeric antibody with human gamma constant regions and variable regions of WBCAL-1, a monoclonal antibody established from an APS-prone mouse which has a specificity similar to that of aCL in sera from humans with APS. Variable-region genes of WBCAL-1, which were cloned using reverse transcription-polymerase chain reaction, were inserted into plasmids containing human gamma1 and kappa constant-region genes. The construct was transfected to a mouse myeloma cell line. Stable transfectants that secreted a chimeric antibody, HCAL, into the culture supernatant were obtained. The reactivity of HCAL to cardiolipin and to beta2-glycoprotein I (beta2GPI) was studied using a solid-phase enzyme immunoassay. The binding of HCAL was compared with the binding of standards for IgG aCL and anti-beta2GPI antibody assays done in 18 independent laboratories. In the presence of beta2GPI, HCAL bound to the wells of cardiolipin-coated microtiter plates in a dose-dependent manner and reacted with beta2GPI on oxygenated polystyrene plates. The aCL activity of HCAL can be converted into GPL units (IgG phospholipid units), which is widely used to quantify IgG aCL activity, using the following formula: 1 GPL unit = 32.9 x (concentration of HCAL [in microg/ml])(0.503). The reactivity of HCAL to cardiolipin or beta2GPI was similar to the reactivity of standards for IgG aCL or anti-beta2GPI antibody assays done in collaborative laboratories. Because the reactivity of HCAL is similar to that of aCL in sera from humans with APS, HCAL will be useful as a standard for human IgG aCL and anti-beta2GPI antibody assays.

Thrombogenic properties of antiphospholipid antibodies do not depend on their binding to beta2 glycoprotein 1 (beta2GP1) alone.

Immunization of mice with beta2glycoprotein 1 (beta2GP1) induces production of antiphospholipid (aPL) antibodies, which were shown to have thrombus enhancing properties in an experimental mouse model, indicating that these antibodies are thrombogenic in vivo. To determine whether the thrombogenic effect of murine antiphospholipid antibodies is due to their aPL or their anti-beta2GP1 activity, we injected mice with murine monoclonal anticardiolipin (aCL) and anti-beta2GP1 antibodies. Effects of these antibodies on thrombus formation, was evaluated utilizing a mouse model which enables kinetics of thrombus formation to be studied. The results of this study showed that the size of the thrombus in animals injected with murine aCL antibodies was larger than that in control groups. There was no difference in thrombus kinetics between anti-beta2GP1 injected mice and controls, suggesting that the thrombogenic effect of aPL antibodies is not related to their anti-beta2GP1 activity alone. Mice receiving monoclonal antibodies with both aCL and anti-beta2GP1 activity, also increase thrombus size when compared with controls. These data indicate that murine aCL, but not anti-beta2GP1, antibodies are thrombogenic in vivo.

Arterial disease and thrombosis in the antiphospholipid syndrome: a pathogenic role for endothelin 1.

To explore a possible correlation between endothelin 1 (ET-1), the most potent endothelium-derived contracting factor that modulates vascular smooth muscle tone, and arterial disease in patients with the antiphospholipid syndrome (APS). Plasma levels of ET-1 were measured in APS patients with (n = 16) and without (n = 11) arterial thrombosis and in non-APS patients with arterial thrombosis (n = 9). In addition, steady-state prepro-ET-1 messenger RNA (mRNA) levels were determined in endothelial cells treated with a range of human monoclonal anticardiolipin antibodies (aCL) (as anti-beta2-glycoprotein I antibodies) by semiquantitative 32P-dCTP-labeled reverse transcription-polymerase chain reaction. Compared with healthy controls, markedly increased plasma levels of ET-1 were found in APS patients with arterial thrombosis (2.00 +/- 0.87 versus 0.96 +/- 0.37 pg/ml; P = 0.0001) but not in other groups. Three human monoclonal aCL induced prepro-ET-1 mRNA levels significantly more than did control monoclonal antibody lacking aCL activity. Plasma ET-1 levels correlated significantly with a history of arterial thrombosis in patients with APS. Prepro-ET-1 mRNA was induced by human monoclonal aCL in the in vitro experimental system. The induction of ET-1 by antiphospholipid antibodies might contribute to increased arterial tone, leading to vasospasm and, ultimately, to arterial occlusion.

High prevalence of thrombocytopenia in SLE patients with a high level of anticardiolipin antibodies combined with lupus anticoagulant

The relationship between thrombocytopenia and the level of anticardiolipin antibodies (aCL) and/or the existence of lupus anticoagulant (LA) ware studied in 146 patients with systemic lupus erythematosus (SLE). These patients were divided into six groups: A, those LA positive with a high level of aCL (>10 U/ml) (10 cases); B, those LA positive with a low level of aCL (3–10 U/ml) (15 cases); C, those LA positive but aCL negative (<3 U/ml) (12 cases); D, LA negatives with a high level of aCL (12 cases); E, LA negatives with a low level of aCL (16 cases); and F, aCL and LA double negatives (81 cases). The prevalence of thrombocytopenia (platelet count ≦ 100 × 109/L) was by far the highest in group A (9/10 cases, 90.0%, P < 0.005, Fisher's exact probability test) as compared with group B (4/15 cases, 26.7%), group C (4/12 cases, 33.3%), group D (1/12 cases, 8.3%), group E (4/16 cases, 25.5%), and group F (9/81 cases, 11.1%). When the relationship between moderate thrombocytopenia and arterial or venous thrombosis was studied in these patients with SLE, thrombocytopenia was detected in 10 (83.3%, P < 0.005, Fisher's exact probability test) of 12 patients with arterial thrombosis; however, it was present in only 4 (23.5%) of 17 patients with venous thrombosis and in 14 (12.3%) of 114 patients without thrombosis. These findings suggest that a high aCL activity combined with LA positively reflects a high risk for both thrombocytopenia and arterial thrombosis. Am. J. Hematol 58:55–60, 1998. © 1998 Wiley-Liss, Inc.

High prevalence of thrombocytopenia in SLE patients with a high level of anticardiolipin antibodies combined with lupus anticoagulant.

The relationship between thrombocytopenia and the level of anticardiolipin antibodies (aCL) and/or the existence of lupus anticoagulant (LA) ware studied in 146 patients with systemic lupus erythematosus (SLE). These patients were divided into six groups: A, those LA positive with a high level of aCL (>10 U/ml) (10 cases); B, those LA positive with a low level of aCL (3-10 U/ml) (15 cases); C, those LA positive but aCL negative (<3 U/ml) (12 cases); D, LA negatives with a high level of aCL (12 cases); E, LA negatives with a low level of aCL (16 cases); and F, aCL and LA double negatives (81 cases). The prevalence of thrombocytopenia (platelet count < or = 100 x 10(9)L) was by far the highest in group A (9/10 cases, 90.0%, P < 0.005, Fisher's exact probability test) as compared with group B (4/15 cases, 26.7%), group C (4/12 cases, 33.3%), group D (1/12 cases, 8.3%), group E (4/16 cases, 25.5%), and group F (9/81 cases, 11.1%). When the relationship between moderate thrombocytopenia and arterial or venous thrombosis was studied in these patients with SLE, thrombocytopenia was detected in 10 (83.3%, P < 0.005, Fisher's exact probability test) of 12 patients with arterial thrombosis; however, it was present in only 4 (23.5%) of 17 patients with venous thrombosis and in 14 (12.3%) of 114 patients without thrombosis. These findings suggest that a high aCL activity combined with LA positively reflects a high risk for both thrombocytopenia and arterial thrombosis.

Anticardiolipin IgG subclasses association of IgG2 with arterial and/or venous thrombosis

To determine whether the presence of anticardiolipin antibodies (aCL) of a specific IgG subclass is associated with clinical complications of the antiphospholipid antibody syndrome (APS) and whether polymorphisms of Fc receptors for IgG (FcgammaR) with differential binding preferences contribute to an increased risk of thrombotic complications. In 60 patients with IgG aCL, we assessed clinical complications of the APS, measured the level of antibody activity, and determined the IgG subclass distribution of aCL by a modified enzyme-linked immunosorbent assay (ELISA) with murine anti-human IgG subclass monoclonal antibodies. Selective IgG subclass adsorption studies were performed to determine the relative contribution of specific IgG subclasses to overall aCL activity. Fcgamma receptor IIA (FcgammaRIIA) genotypes of aCL patients with thrombosis and of non-systemic lupus erythematosus controls were determined by polymerase chain reaction amplification of genomic DNA and allele-specific probes. IgG2 aCL, detected in 75% of the patients, was the major subclass of aCL. Selective adsorption studies demonstrated that IgG2, in contrast to IgG1, was the predominant subclass responsible for aCL reactivity. IgG2 aCL was the only subclass associated with clinical complications, specifically, arterial and/or venous thrombosis (P < 0.04). The presence of FcgammaRIIA-H131, a receptor expressed on platelets, monocytes, and endothelial cells and the only human FcgammaR which efficiently recognizes IgG2, was associated with thrombosis in aCL patients. Among 45 high-titer (>40 GPL [IgG phospholipid] units) aCL patients with thrombosis, 40% were homozygous for FcgammaRIIA-H131, compared with 25% of disease-free controls (P = 0.042). While all 4 IgG subclasses are found in autoimmune aCL, only the presence of IgG2 is significantly associated with thrombotic complications. Reactivity in aCL ELISA is largely due to the presence of IgG2 in high-titer patients. The presence of IgG2 aCL, particularly in association with FcgammaRIIA-H131, may be a useful clinical predictor of increased thrombotic risk in patients with autoimmune IgG aCL. Allelic variants of FcgammaRIIA with distinct capacities to interact with IgG subclasses provide a mechanism for genetic susceptibility to an autoantibody-induced prothrombotic state.

Autoimmune aberration in sudden sensorineural hearing loss: association with anti-cardiolipin antibodies.

In view of the presence of autoantibodies against inner ear antigens, the pathogenesis of sudden deafness (SD) and progressive sensorineural hearing loss (PSNHL) is suggested to be of an autoimmune nature. However, microthrombosis of the inner ear may result from pathogenic anti-cardiolipin antibody (aCL) activity. We studied 30 patients (17 females and 13 males, age range 20-52 y), of whom 11 suffered from SD and 19 from PSNHL. All were clinically and serologically evaluated for association with autoimmune disorders (serological examination included: aCL, ANA, ENA, ANCA, proteinelectrophoresis, and complement levels). Twenty healthy matched subjects served as controls. None of the control group were aCL positive, whereas 8 out of 30 (27%) patients demonstrated low-moderate titers (P < 0.02), of whom 5 out of 8 suffered from SD. In addition, 2 aCL negative patients with PSNHL demonstrated hypergammaglubolinemia accompanied by hypocomplementemia, whereas none with SD had such abnormalities. Our data suggests that aCL is detected in patients with sudden sensorineural hearing loss and therefore may play an important role in the pathogenesis of this disability. If sustained by additional studies, these findings would warrant the consideration of anticoagulant therapy.