Exosomal miR-146a-5p derived from human umbilical cord mesenchymal stem cells can alleviate antiphospholipid antibody-induced trophoblast injury and placental dysfunction by regulating the TRAF6/NF-κB axis

Exosomes originating from human umbilical cord mesenchymal stem cells (hucMSC-exos) have become a novel strategy for treating various diseases owing to their ability to regulate intercellular signal communication. However, the potential of hucMSC-exos to improve placental injury in obstetric antiphospholipid syndrome and its underlying mechanism remain unclear. Our objective was to explore the potential application of hucMSC-exos in the treatment of obstetric antiphospholipid syndrome and elucidate its underlying mechanism. In our study, hucMSC-exos ameliorated the functional impairment of trophoblasts caused by antiphospholipid antibodies in vitro and attenuated placental dysfunction in mice with obstetric antiphospholipid syndrome by delivering miR-146a-5p. Exosomal miR-146a-5p suppressed the expression of tumor necrosis factor receptor-associated factor 6 (TRAF6) and inhibited the activation of NF-κB signaling, leading to the down-regulation of IL-1β and IL-18 to rescue inflammation and modulation of Cleaved-CASP3, BAX, and BCL2 to inhibit apoptosis in HTR8/SVneo cells and mice placenta. This study identified the potential molecular basis of how hucMSC-exos improved antiphospholipid antibody-induced placental injury and highlighted the functional importance of the miR-146a-5p/TRAF6 axis in the progression of obstetric antiphospholipid syndrome. More importantly, this study provided a fresh outlook on the promising use of hucMSC-exos as a novel and effective treatment approach in obstetric antiphospholipid syndrome.

Molecular Mechanisms of "Antiphospholipid Antibodies" and Their Paradoxical Role in the Pathogenesis of "Seronegative APS"

Antiphospholipid Syndrome (APS) is an autoimmune disease characterized by arterial and/or venous thrombosis and/or pregnancy morbidity, associated with circulating antiphospholipid antibodies (aPL). In some cases, patients with a clinical profile indicative of APS (thrombosis, recurrent miscarriages or fetal loss), who are persistently negative for conventional laboratory diagnostic criteria, are classified as "seronegative" APS patients (SN-APS). Several findings suggest that aPL, which target phospholipids and/or phospholipid binding proteins, mainly β-glycoprotein I (β-GPI), may contribute to thrombotic diathesis by interfering with hemostasis. Despite the strong association between aPL and thrombosis, the exact pathogenic mechanisms underlying thrombotic events and pregnancy morbidity in APS have not yet been fully elucidated and multiple mechanisms may be involved. Furthermore, in many SN-APS patients, it is possible to demonstrate the presence of unconventional aPL ("non-criteria" aPL) or to detect aPL with alternative laboratory methods. These findings allowed the scientists to study the pathogenic mechanism of SN-APS. This review is focused on the evidence showing that these antibodies may play a functional role in the signal transduction pathway(s) leading to thrombosis and pregnancy morbidity in SN-APS. A better comprehension of the molecular mechanisms triggered by aPL may drive development of potential therapeutic strategies in APS patients.

Amniotic fluid antiphospholipid antibodies: potential role in antiphospholipid syndrome-independent aberrant implantation process

BACKGROUND

The direct role of antiphospholipid antibodies (aPL) at maternal-fetal interface has not been fully investigated, especially whether they are involved in physiological and pathological implantation conditions, in an antiphospholipid syndrome (APS)-independent manner. In fact, trophoblast cells and placental endothelial cells at the implantation site express potential aPL targeted-phospholipid antigens (PL Ags); thus, the local production and presence of their specific antibodies, not related to APS (characterized by aPL presence in the peripheral blood), could be a potential marker of aberrant invasion, implantation and fetal-maternal immune tolerance processes.

METHODS

Anti-Beta₂glycoprotein I (anti-β₂GPI) and anticardiolipin (aCL Ab) antibodies (the most clinically relevant aPL) were detected by immunoenzymatic assay (ELISA), in the amniotic fluid (AF) of 167 women with physiological and complicated common pregnancy conditions, sharing an aberrant implantation process, such as recurrent pregnancy loss (RPL), autoimmune hypothyroidism (ahT) and smoking. All women included in the study were negative to peripheral blood aPL.

RESULTS

aCL and anti-β₂GPI antibodies were detectable in all the AF samples. RPL, ahT and smoking patients had higher level of anti-β₂GPI Abs (IgM) compared to women with physiological pregnancies (p < 0.0001). Since IgM cannot cross the placenta, their local production in response to maternal-fetal interface stimuli, could be hypothesized.

CONCLUSIONS

The presence of aPL in the AF (not related to APS) could reveal a potential clinical significance at maternal-fetal interface in selected pregnancy complications, in which an aberrant implantation process, and in turn an impaired fetal-maternal immune tolerance cross-talk, could occur.

The IgA Isotype of Anti-β2 Glycoprotein I Antibodies Recognizes Epitopes in Domains 3, 4, and 5 That Are Located in a Lateral Zone of the Molecule (L-Shaped)

Background: Antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with presence of anti-phospholipid antibodies (aPL). The APS classification criteria only consider the aPL of IgG/IgM isotype, however testing of aPL of IgA isotype is recommended when APS is suspected and consensus aPL are negative. IgA anti-βeta-2 glycoprotein-I (B2GP1) has been clearly related with occurrence of thrombotic events. Antibodies anti-B2GP1 of IgG/M isotypes recognize an epitope in Domain 1 (R39-G43), the epitopes that recognize IgA anti-B2GP1 antibodies are not well-identified. Aim: To determine the zones of B2GP1 recognized by antibodies of IgA isotype from patients with APS symptomatology and positive for IgA anti-B2GP1. Methods: IgA antibodies to Domain-1(D1) and Domain-4/5(D4/5) of B2GP1 (ELISA) and epitope mapping on oligopeptide arrays of B2GP1 were evaluated in sera from a group of 93 patients with at least one thrombotic and with isolated positivity for IgA anti-B2GP1 antibodies (negative for other aPL). Results: A total of 47 patients (50.5%) were positive for anti-D4/5 and 23(25%) were positive for anti-D1. When peptide arrays were analyzed, three zones of B2GP1 reactivity were identified for more than 50% of patients. The center of these zones corresponds to amino acids 140(D3), 204(D4), and 264(D5). The peptides recognized on D3 and D4 contain amino acid sequences sharing high homology with proteins of microorganism that were previously related with a possible APS infectious etiology. In the three-dimensional structure of B2GP1, the three peptides, as the R39-G43 epitope, are located on the right side of the molecule (L-shape). The left side (J-shape) does not bind the antibodies. Conclusions: Patients with thrombotic APS clinical-criteria, and isolated IgA anti-B2GP1 positivity appear to preferentially bind, not to the D1 or D4/5 domains of B2GP1, but rather to three sites in D3, D4, and D5. The sites on D3 and D4 were previously described as the target identified by human monoclonal antibodies derived from patients that were capable of inducing APS in animal models. The localization of these epitopes opens a new route to explore to increase understanding of the patholophysiology of the APS and to propose new alternatives and therapeutic targets.

Low molecular weight heparin and aspirin exacerbate human endometrial endothelial cell responses to antiphospholipid antibodies

PROBLEM

Women with antiphospholipid antibodies (aPL) are at risk for pregnancy complications despite treatment with low molecular weight heparin (LMWH) or aspirin (ASA). aPL recognizing beta2 glycoprotein I can target the uterine endothelium, however, little is known about its response to aPL. This study characterized the effect of aPL on human endometrial endothelial cells (HEECs), and the influence of LMWH and ASA.

METHOD OF STUDY

HEECs were exposed to aPL or control IgG, with or without low-dose LMWH and ASA, alone or in combination. Chemokine and angiogenic factor secretion were measured by ELISA. A tube formation assay was used to measure angiogenesis.

RESULTS

aPL increased HEEC secretion of pro-angiogenic VEGF and PlGF; increased anti-angiogenic sFlt-1; inhibited basal secretion of the chemokines MCP-1, G-CSF, and GRO-α; and impaired angiogenesis. LMWH and ASA, alone and in combination, exacerbated the aPL-induced changes in the HEEC angiogenic factor and chemokine profile. There was no reversal of the aPL inhibition of HEEC angiogenesis by either single or combination therapy.

CONCLUSION

By aPL inhibiting HEEC chemokine secretion and promoting sFlt-1 release, the uterine endothelium may contribute to impaired placentation and vascular transformation. LMWH and ASA may further contribute to endothelium dysfunction in women with obstetric APS.

Myocardial Ischaemia, Coronary Atherosclerosis and Pulmonary Pressure Elevation in Antiphospholipid Syndrome Patients

BACKGROUND

Thrombotic events in antiphospholipid syndrome (APS) involve venous and arterial circulation with the possible involvement of coronary or pulmonary microcirculation.

OBJECTIVES

To evaluate the influence of antiphospholipid antibodies (aPL) and on myocardial ischaemia assessed by single-photon emission computerized tomography (SPECT), coronary atherosclerosis assessed by multidetector computerized tomography (MDCT) and pulmonary pressure assessed by transthoracic echocardiography (TTE) in patients with primary antiphospholipid syndrome (PAPS).

MATERIAL AND METHODS

TTE, SPECT (Tc 99m sestamibi) and MDCT-based coronary calcium scoring were performed in 26 consecutive PAPS patients (20 females, 6 males, aged 20-61, mean 39.7) without any signs of other autoimmunological disease and without clinical symptoms of heart disease.

RESULTS

Out of 26 patients, TEE showed normal left and right ventricle function in 25 (96.2%) and elevated (≥ 30 mm Hg) right ventricle systolic pressure in 7 (26.9%) patients. SPECT revealed myocardial perfusion defects in 15 (57.7%) patients: exercise-induced in 6 (23.1%) and persistent in 11 (42.3%). MDCT revealed coronary calcifications in 4 (15.4%) patients. The number of plaques ranged from 1 to 11 (median 2), volume 3-201.7 mm³ (median 7), calcium scores 1.3-202.6 (median 5.7). In the group with perfusion defects or coronary calcifications (n = 15), all the patients showed elevated aCL IgG.

CONCLUSIONS

In most of the relatively young APS patients, without any symptoms of ischemic heart disease, SPECT showed myocardial perfusion defects, and coronary calcifications in 1/6 of them. Right ventricle systolic pressure was elevated in 1/4 of APS patients. These pathologies, well known as cardiovascular risk markers, were associated with elevated levels of the IgG class of both anti-cardiolipin and antiB2 GPI antibodies. Thus, in a high percentage of APS patients, clinically silent myocardial ischaemia, pulmonary pressure elevation and coronary atherosclerosis are present and related to the presence of antiphospholipid antibodies.

Peripheral vascular disease in systemic lupus erythematosus

With increasing longevity of lupus patients, peripheral vascular disease (PVD) has become an important cause of morbidity. With no systematic study of PVD in systemic lupus erythematosus (SLE), this study was undertaken to define the frequency and spectrum of PVD in SLE and factors affecting such an occurrence. All medium-sized peripheral arteries of bilateral upper and lower extremities were studied in 50 SLE patients using Doppler ultrasonography. PVD was defined clinically as one or more of intermittent claudication, absent/unequal pulses, gangrene or ischemic ulcers and sub-clinically as asymptomatic patients with Doppler abnormalities, with ≥50% reduction in diameter considered hemodynamically significant. Mean (SD) age of the patients was 31.6 (10.1) years. Forty-one percent were hypertensive. Dyslipidemia was found in 62%. Fifteen (30%) had Raynaud's phenomenon. Fourteen (28%) patients had PVD, of whom three had positive markers for antiphospholipid antibody (aPL) and six were asymptomatic. Ischemic ulcers were seen in eight (16%), gangrene in three (6%), femoral artery plaques in two (4%), stenosis in four (8%) and intermittent claudication in none. Dyslipidemia was found to independently affect occurrence of PVD (OR = 5.37, [95% CI 1.05—27.5], P = 0.05). The causes of PVD overlap significantly and further studies are needed to ascertain the relative contribution of each. Lupus (2007) 16, 720—723.

Endocrinologic Manifestations of the Antiphospholipid Syndrome

Our objective was to study the endocrinologic manifestations of the antiphospholipid syndrome (APS). We reviewed the medical literature from 1968 until 2005 using MEDLINE and the key words: APS, anticardiolipin antibodies, lupus anticoagulant, antiphospholipid antibodies, adrenal, thyroid, parathyroid, pituitary, diabetes, ovaries and testes. Adrenal insufficiency is the most common endocrinologic manifestation and can be the presenting symptom of APS. In patients with autoimmune thyroid disease circulating aPL have been detected. However, no clinical manifestations of APS have been described. A few cases of hypopituitarism have been reported, including a case of Sheehan’s syndrome. aPL has been detected in the sera of diabetic patients, probably associated with some macroangiopathic complications. Finally only very few cases of ovarian and testicular involvement have been reported. The adrenals are the most commonly involved glands in the APS. Clinicians should keep a high index of suspicion for adrenal insufficiency in patients with APS.

Cardiac involvement in the antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disease, associated with a hypercoagulable state and fetal loss and with other clinical manifestations including cardiac involvement. Cardiac manifestations of APS are valve abnormalities (valve thickening and vegetations), occlusive arterial disease (atherosclerosis and myocardial infarction), intracardiac emboli, ventricular dysfunction, and pulmonary hypertension. Antiphospholipid antibodies (aPLs) may have a role in the accelerated atherosclerotic arterial disease observed in APS, related to their ability to induce endothelial activation. aPLs have been incriminated in the pathogenesis of heart valve lesions in APS patients. Markers of endothelial cell activation are up-regulated with prominent deposition of aPL in heart valves, suggesting aPL deposition initiates an inflammatory process that recruits complement leading to the valve lesion. Autoantibody-mediated endothelial cell activation probably plays a role in sustaining a proadhesive, proinflammatory, and procoagulant phenotype. The heterogeneity of APS clinical manifestations is likely linked to the varied effects that aPL can induce on endothelial cells and to the different functions that endothelial cells display depending on the anatomic localization.

Ribophorin II is involved in the tissue factor expression mediated by phosphatidylserine-dependent antiprothrombin antibody on monocytes

OBJECTIVE

Phosphatidylserine-dependent, also called aPS-PT, recognizes the phosphatidylserine-prothrombin complex, which is associated with APS. We have previously reported that aPS-PT induces tissue factor (TF) expression on monocytes through the p38 mitogen-activated protein kinase pathway. However, the cell surface interaction between prothrombin and aPS-PT, which is involved in the activation of cell-signalling pathways, has remained unknown. The objective of this study was to identify membrane proteins involved in the binding of prothrombin and aPS-PT to monocyte surfaces as well as the induction of TF expression.

METHODS

RAW264.7 cells with FLAG-tagged prothrombin were incubated and separated using affinity chromatography with anti-FLAG antibody-conjugated Sepharose beads. Immunopurified proteins were then analysed by an online nano-liquid chromatography-tandem mass spectrometry. The binding between prothrombin and the identified protein, ribophorin II (RPN2), was analysed by ELISA and surface plasmon resonance. To elucidate the role of RPN2 in TF expression, the TF mRNA level in RAW264.7 cells treated with RPN2 small interfering RNA was determined by quantitative real-time PCR (qPCR).

RESULTS

RPN2 was identified as a candidate molecule involved in the binding of prothrombin to the cell surface. The binding between prothrombin and RPN2 was confirmed by ELISA and surface plasmon resonance. RAW264.7 cells treated with RPN2 small interfering RNA showed significant reduction of the TF expression mediated by prothrombin and a mouse monoclonal aPS-PT.

CONCLUSION

We identified that RPN2 is one of the prothrombin-binding proteins on monocyte surfaces, suggesting that RPN2 is involved in the pathophysiology of thrombosis in patients with APS.

Antiphospholipid antibodies bind syncytiotrophoblast mitochondria and alter the proteome of extruded syncytial nuclear aggregates

INTRODUCTION

Antiphospholipid antibodies (aPL) are autoantibodies that increase the risk of women developing the hypertensive disorder pre-eclampsia. aPL are internalised by the syncytiotrophoblast and increase extrusion of necrotic multinucleated syncytial nuclear aggregates (SNAs), which may trigger endothelial dysfunction in pre-eclampsia. The mechanisms by which aPL alter death processes in the syncytiotrophoblast leading to extrusion of SNAs are unknown.

METHODS

First trimester human placentae (n = 10) were dissected into explants and cultured either with aPL (50 μg/mL), isotype-matched control antibody (50 μg/mL), or media for 24 h. Harvested SNAs underwent iTRAQ proteomic analysis. Mitochondria in syncytiotrophoblast treated with aPL labelled with FluoroNanogold were visualised using transmission electron microscopy (TEM).

RESULTS

aPL altered the expression of 72 proteins in SNAs. Thirteen proteins were involved in mitochondrial function. TEM demonstrated that aPL bind to mitochondria in the syncytiotrophoblast and may cause mitochondrial swelling.

DISCUSSION

aPL disrupt mitochondria increasing the extrusion of SNAs with an altered proteome from the syncytiotrophoblast. These altered SNAs may trigger endothelial dysfunction and pre-eclampsia in these pregnancies.

A novel pathway of cellular activation mediated by antiphospholipid antibody-induced extracellular vesicles

BACKGROUND

Elevated levels of endothelial cell (EC)-derived extracellular vesicles (EVs) circulate in patients with antiphospholipid antibodies (APLAs), and APLAs, particularly those against β2 -glycoprotein I (β2 GPI), stimulate EV release from ECs. However, the effects of EC-derived EVs have not been characterized.

OBJECTIVE

To determine the mechanism by which EVs released from ECs by anti-β2 GPI antibodies activate unstimulated ECs.

PATIENTS/METHODS

We used interleukin (IL)-1 receptor inhibitors, small interfering RNA (siRNA) against Toll-like receptors (TLRs) and microRNA (miRNA) profiling to assess the mechanism(s) by which EVs released from ECs exposed to anti-β2 GPI antibodies activated unstimulated ECs.

RESULTS AND CONCLUSIONS

Anti-β2 GPI antibodies caused formation of an EC inflammasome and the release of EVs that were enriched in mature IL-1β, had a distinct miRNA profile, and caused endothelial activation. However, activation was not inhibited by an IL-1β antibody, an IL-1 receptor antagonist, or IL-1 receptor siRNA. EC activation by EVs required IL-1 receptor-associated kinase 4 phosphorylation, and was inhibited by pretreatment of cells with TLR7 siRNA or RNase A, which degrades ssRNA. Profiling of miRNA in EVs released from ECs incubated with β2 GPI and either control IgG or anti-β2 GPI antibodies revealed numerous differences in the content of specific miRNAs, including a significant decrease in mIR126. These observations demonstrate that, although anti-β2 GPI-derived endothelial EVs contain IL-1β, they activate unstimulated ECs through a TLR7-dependent and ssRNA-dependent pathway. Alterations in miRNA content may contribute to the ability of EVs derived from ECs exposed to anti-β2 GPI antibodies to activate unstimulated ECs in an autocrine or paracrine manner.

Treatment of Thrombotic Antiphospholipid Syndrome: The Rationale of Current Management-An Insight into Future Approaches

Vascular thrombosis and pregnancy morbidity represent the clinical manifestations of antiphospholipid syndrome (APS), which is serologically characterized by the persistent positivity of antiphospholipid antibodies (aPL). Antiplatelet and anticoagulant agents currently provide the mainstay of APS treatment. However, the debate is still open: controversies involve the intensity and the duration of anticoagulation and the treatment of stroke and refractory cases. Unfortunately, the literature cannot provide definite answers to these controversial issues as it is flawed by many limitations, mainly due to the recruitment of patients not fulfilling laboratory and clinical criteria for APS. The recommended therapeutic management of different aPL-related clinical manifestations is hereby presented, with a critical appraisal of the evidence supporting such approaches. Cutting edge therapeutic strategies are also discussed, presenting the pioneer reports about the efficacy of novel pharmacological agents in APS. Thanks to a better understanding of aPL pathogenic mechanisms, new therapeutic targets will soon be explored. Much work is still to be done to unravel the most controversial issues about APS management: future studies are warranted to define the optimal management according to aPL risk profile and to assess the impact of a strict control of cardiovascular risk factors on disease control.

Inhibition of the mTORC pathway in the antiphospholipid syndrome

BACKGROUND

Although thrombosis is considered the cardinal feature of the antiphospholipid syndrome, chronic vascular lesions are common, particularly in patients with life-threatening complications. In patients who require transplantation, vascular lesions often recur. The molecular pathways involved in the vasculopathy of the antiphospholipid syndrome are unknown, and adequate therapies are lacking.

METHODS

We used double immunostaining to evaluate pathway activation in the mammalian target of rapamycin complex (mTORC) and the nature of cell proliferation in the vessels of patients with primary or secondary antiphospholipid syndrome nephropathy. We also evaluated autopsy specimens from persons who had catastrophic antiphospholipid syndrome. The molecular pathways through which antiphospholipid antibodies modulate the mTORC pathway were evaluated in vitro, and potential pharmacologic inhibitors were also tested in vitro. Finally, we studied the effect of sirolimus in kidney-transplant recipients with the antiphospholipid syndrome.

RESULTS

The vascular endothelium of proliferating intrarenal vessels from patients with antiphospholipid syndrome nephropathy showed indications of activation of the mTORC pathway. In cultured vascular endothelial cells, IgG antibodies from patients with the antiphospholipid syndrome stimulated mTORC through the phosphatidylinositol 3-kinase (PI3K)-AKT pathway. Patients with antiphospholipid syndrome nephropathy who required transplantation and were receiving sirolimus had no recurrence of vascular lesions and had decreased vascular proliferation on biopsy as compared with patients with antiphospholipid antibodies who were not receiving sirolimus. Among 10 patients treated with sirolimus, 7 (70%) had a functioning renal allograft 144 months after transplantation versus 3 of 27 untreated patients (11%). Activation of mTORC was also found in the vessels of autopsy specimens from patients with catastrophic antiphospholipid syndrome.

CONCLUSIONS

Our results suggest that the mTORC pathway is involved in the vascular lesions associated with the antiphospholipid syndrome. (Funded by INSERM and others.).

Anti-phospholipid induced murine fetal loss: novel protective effect of a peptide targeting the β2 glycoprotein I phospholipid-binding site. Implications for human fetal loss

β2 glycoprotein I (β2GPI)-dependent anti-phospholipid antibodies (aPL) induce thrombosis and affect pregnancy. The CMV-derived synthetic peptide TIFI mimics the PL-binding site of β2GPI and inhibits β2GPI cell-binding in vitro and aPL-mediated thrombosis in vivo. Here we investigated the effect of TIFI on aPL-induced fetal loss in mice. TIFI inhibitory effect on in vitro aPL binding to human trophoblasts was evaluated by indirect immunofluorescence and ELISA. TIFI effect on aPL-induced fetal loss was investigated in pregnant C57BL/6 mice treated with aPL or normal IgG (NHS). Placenta/fetus weight and histology and RNA expression were analyzed. TIFI, but not the control peptide VITT, displayed a dose-dependent inhibition of aPL binding to trophoblasts in vitro. Injection of low doses of aPL at day 0 of pregnancy caused growth retardation and increased fetal loss rate, both significantly reduced by TIFI but not VITT. Consistent with observations in humans, histological analysis showed no evidence of inflammation in this model, as confirmed by the absence of an inflammatory signature in gene expression analysis, which in turn revealed a TIFI-dependent modulation of molecules involved in differentiation and development processes. These findings support the non-inflammatory pathogenic role of aPL and suggest innovative therapeutic approaches to aPL-dependent fetal loss.

Stroke in sickle cell anemia: alternative etiologies

Stroke is common in children with sickle cell anemia, but is rarely attributed to the traditional causes of stroke identified in other children. An 11-year-old girl with sickle cell anemia presented with severe headache and was found to have recurrent bilateral multifocal strokes in a cardioembolic pattern. Evaluation revealed the presence of a patent foramen ovale, antiphospholipid antibodies, and elevations in factor VIII and lipoprotein(a). Sickle cell anemia is itself a hypercoagulable state with potential for increased right heart pressures, both of which predispose to paradoxical embolization via right-to-left intracardiac shunting of emboli, thus causing stroke. The present case suggests that the more traditional etiologies for pediatric stroke may also cause stroke in children with sickle cell anemia.

Uncoupling of protein C and antithrombin III activity in cerebral ischemia patients associated with cutis marmorata

PURPOSE

Cutis marmorata is a cutaneous livedoid disorder which can be differentiated from livedo reticularis in both clinical and pathological presentations. Unlike Sneddon syndrome, a detailed immunocoagulation profile has not yet been delineated for cutis marmorata in patients with cerebral ischemia.

METHODS

To analyze the immunocoagulation profile in cutis marmorata patients associated with cerebral ischemia (CMCI) in a series of 135 cerebral ischemia patients.

RESULTS

A total of 32 patients were found to have cutis marmorata. The blood protein C activity, protein S activity, antithrombin III activity, platelet count, fibrinogen and frequency of abnormal antiphospholipid antibody level were similar among 32 CMCI patients, 103 cerebral ischemia patients without cutis marmorata, and 35 healthy subjects. However, uncoupling of protein C and anti-thrombin III was observed in CMCI patients. Serum antinuclear antibody and Venereal Disease Research Laboratory were not detected in these patients.

CONCLUSION

Cutis marmorata is not uncommon in our ischemic stroke patient population, and is characterized by uncoupling of protein C and antithrombin III with altered thrombin hemostasis. Our findings raise the need for a careful cutaneous examination in patients with ischemic stroke. Abnormal immunocoagulating profile should alert physicians to the risk for cerebral ischemia even in the absence of other cardiovascular risk factors.

Intracellular trafficking of beta2-glycoprotein I complexes with lipid vesicles in macrophages: implications on the development of antiphospholipid syndrome

Beta(2)-glycoprotein I (beta(2)GPI) is known as a major autoantigen for antiphospholipid antibodies. Our recent data show that binding of beta(2)GPI to oxidized low-density lipoprotein (oxLDL) or to liposomes containing anionic phospholipid(s) may facilitate the presentation of beta(2)GPI's epitope by macrophages/dendritic cells to autoreactive T cells. In the present study, we investigated intracellular trafficking of beta(2)GPI and its complexes with oxLDL or liposomes containing phosphatidylserine (PS-liposomes) in mouse macrophage-like J774 cells. A relatively small amount of non-complexed beta(2)GPI was taken up and stagnated in the late endosome after incubating for 16h. In contrast, beta(2)GPI complexes with oxLDL or PS-liposomes were transported into the lysosome. In the presence of the IgG anti-beta(2)GPI autoantibody, WB-CAL-1, beta(2)GPI/oxLDL complexes were rapidly incorporated into intracellular space and were finally localized in the lysosome. Interestingly, in vitro pulses by beta(2)GPI/oxLDL complexes together with WB-CAL-1 led to the expression of membranous CD36 as well as Fcgamma type I receptors (FcgammaRI). These observations suggest that IgG immune complexes of beta(2)GPI/oxLDL provide not only FcgammaRI- but also scavenger receptor-mediated uptake of beta(2)GPI/oxLDL complexes by macrophages. Thus, beta(2)GPI/oxLDL complexes as a major atherogenic autoantigen and IgG anti-beta(2)GPI autoantibodies may facilitate antigen presentation and foam cell formation in antiphospholipid syndrome.

In Vivo Effects of an Inhibitor of Nuclear Factor-Kappa B on Thrombogenic Properties of Antiphospholipid Antibodies

It has been shown that endothelial cell (EC) activation and tissue factor (TF) upregulation in EC and monocytes by antiphospholipid antibodies (aPL Abs) leads to a prothrombotic state and involves translocation of nuclear factor-kappa B (NF-kappaB). Here we examined the effects of an NF-kappaB inhibitor on aPL-induced thrombosis, TF activity, and EC in vivo. We treated CD1 mice with IgG from a patient with antiphospholipid syndrome (IgG-APS) or with control IgG (IgG-NHS). The adhesion of leukocytes (number of white blood cells) to EC in cremaster muscle (as an indication of EC activation) as well as the size of an induced thrombus in the femoral vein of the mice were examined. Some mice in each group were infused with 10 microM MG132 (an inhibitor of NF-kappaB). TF activity was determined using a chromogenic assay in homogenates of carotid arteries and in peritoneal cells of mice. In vivo, IgG-APS increased significantly the number of white blood cells adhering to ECs (4.7 +/- 2.2) when compared to control mice (1.5 +/- 0.8), and these effects were significantly reduced when mice were pretreated with MG132 (0.8 +/- 0.2). IgG-APS increased significantly the thrombus size and MG132 inhibited that effect (93%). Treatment of the mice with IgG-APS also induced significantly increased TF function in peritoneal cells and in homogenates of carotid arteries. Pretreatment of the mice with MG132 abrogated those effects significantly. Mice injected with IgG-APS or with IgM-APS with or without the inhibitor had medium-high titers of anticardiolipin antibodies in serum at the time of the surgical procedures. The data show that prothrombotic and proinflammatory properties of IgG-APS and IgM-APS are downregulated in vivo by an NF-kappaB inhibitor. These findings may be important in designing new modalities of targeted therapies to treat thrombosis in patients with APS.

Atherogenic Antiphospholipid Antibodies in Antiphospholipid Syndrome

Macrophage uptake of oxidized LDL (oxLDL) plays a critical role in early stages of atherosclerosis. We previously reported that oxLDL forms stable complexes with beta2-glycoprotein I (beta2GPI), and that these complexes were frequently present in the sera of patients with systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS). oxLDL/beta2GPI complexes were shown to be antigenic targets for autoantibodies present in APS. To understand the role of autoantibodies in accelerated atherosclerosis of SLE and APS, we investigated the binding characteristics of beta2GPI and oxLDL to mouse macrophages, and the effect of anti-beta2GPI and anti-oxLDL autoantibodies on this macrophage binding. IgM anti-oxLDL antibody (derived from Apoe -/- mouse) showed inhibitory effect on oxLDL binding to macrophages. Although beta2GPI partly inhibited oxLDL binding to macrophages, IgG anti-beta2GPI autoantibody (derived from APS model mouse) showed pro-atherogenic property by promoting the binding of oxLDL/beta2GPI to macrophages.

C5a Receptor-Deficient Mice Are Protected from Thrombophilia and Endothelial Cell Activation Induced by Some Antiphospholipid Antibodies

Recent findings indicate that complement activation--involving specifically C3 and C5--contributes to antiphospholipid (aPL)-mediated thrombosis. Two complement effector pathways are initiated by the cleavage of C5, C5a and C5b, which leads to the formation of the C5b-9 membrane attack complex. To delineate and distinguish the role of C5a from the C5b-9 membrane attack complex seeded by C5b, we examined the in vivo effects (thrombosis) of aPL on C5a receptor-deficient (C5aR-/-) mice. C5aR-/- and C5aR+/+ mice were injected with IgM or with IgG from two different patients with APS (IgM-APS or IgG-APS) or with control IgM or IgG (IgM-NHS or IgG-NHS) twice. Complement fixing activity of the Ig fractions and anticardiolipin activity in the sera of the mice were determined by enzyme-linked immunosorbent assay. Surgical procedures to study thrombus dynamics were performed. IgM-APS but not IgG-APS fixed C1q to cardiolipin-coated plates. IgM-APS significantly enhanced thrombus size in C5aR+/+ mice compared to C5aR+/+ mice treated with IgM-NHS (3198 +/- 2361 microm2 versus 585 +/- 460 microm2). C5aR-/- mice treated with IgM-APS showed a significant reduction in thrombi size as compared with C5aR+/+ mice (676 +/- 690 microm2 versus 3198 +/- 2361 microm2; P = 0.001). IgG-APS enhanced thrombus formation significantly in C5aR+/+ when compared to IgG-NHS-treated mice (3507 +/- 965 microm2 versus 1321 +/- 798 microm2), and these effects were not altered in C5aR-/- mice (3400 +/- 1681 microm2). The data indicate that C5aR-/- mice are protected from the thrombogenic effects of some aPL antibodies.

Induction of antiphospholipid antibodies and antiphospholipid syndrome-like autoimmunity in naive mice with antibody against human parvovirus B19 VP1 unique region protein

BACKGROUND

Previous studies have postulated a connection between human parvovirus B19 (B19) infection and anti-phospholipid antibodies (APhL). B19 infection and anti-phospholipid syndrome (APS) exhibit congruent symptoms. Recently, phospholipase A2 (PLA2)-like activity has been linked to the VP1 unique region (VP1u) of B19. However, the precise role of B19-VP1u in pathogenesis of autoimmunity is still obscure.

METHODS

To elucidate the roles of VP1u in B19 infection and autoimmunity, the reactivity of B19-VP1u proteins with various autoantibodies were evaluated by ELISA and immunoblotting. Rabbits were immunized with purified recombinant B19-VP1u protein to generate anti-sera. Absorption experiments were conducted to determine the binding specificity of rabbit anti-sera against B19-VP1u, cardiolipin (CL) and beta-2-glycoprotein I (beta2GPI). Moreover, the effects of passive transfer of polyclonal rabbit anti-B19-VP1u IgG antibodies on platelets, activated partial thromboplastin time (aPTT), and autoantibodies were assessed.

RESULTS

Autoantibodies against CL, beta2GPI, and phospholipid (PhL) in sera from patients with B19 infection, were cross-reactive with B19-VP1u. Consistently, sera from rabbits immunized with recombinant B19-VP1u protein displayed raised detectable immunoglobulins against B19-VP1u, CL, beta2GPI and PhL. Additionally, the mice immunized with anti-B19-VP1u IgG developed thrombocytopenia, prolongation of aPTT, and autoantibody against beta2GPI and PhL.

CONCLUSIONS

These experimental results suggested the association between B19-VP1u and production of anti-beta2GPI antibodies, APhL, and APS-like autoimmunity. Altogether, it may provide a clue in understanding the role of B19-VP1u in inducing autoantibodies and B19-associated APS manifestations.

Antiphospholipid reactivity against cardiolipin metabolites occurring during endothelial cell apoptosis

We have recently shown that cardiolipin (CL) and its metabolites move from mitochondria to other cellular membranes during death receptor-mediated apoptosis. In this study, we investigate the immunoreactivity to CL derivatives occurring during endothelial apoptosis in patients with antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). We compared the serum immunoreactivity to CL with that of its derivatives monolysocardiolipin (MCL), dilysocardiolipin (DCL), and hydrocardiolipin (HCL) by means of both enzyme-linked immunosorbent assay and thin-layer chromatography (TLC) immunostaining. In addition, we investigated the composition of phospholipid extracts from the plasma membrane of apoptotic endothelial cells and the binding of patients' sera to the surface of the same cells by using high-performance TLC and immunofluorescence analysis. The average reactivity to MCL was comparable with that of CL and significantly higher than that for DCL and HCL in patients studied, both in the presence or in the absence of beta₂-glycoprotein I. Of relevance for the pathogenic role of these autoantibodies, immunoglobulin G from patients' sera showed an increased focal reactivity with the plasma membrane of endothelial cells undergoing apoptosis. Interestingly, the phospholipid analysis of these light membrane fractions showed an accumulation of both CL and MCL. Our results demonstrated that a critical number of acyl chains in CL derivatives is important for the binding of antiphospholipid antibodies and that MCL is an antigenic target with immunoreactivity comparable with CL in APS and SLE. Our finding also suggests a link between apoptotic perturbation of CL metabolism and the production of these antibodies.

Binding of antiphospholipid antibodies to discontinuous epitopes on domain I of human beta(2)-glycoprotein I: mutation studies including residues R39 to R43

OBJECTIVE

Pathogenic antiphospholipid antibodies (aPL) bind the self antigen N-terminal domain (domain I) of beta(2)-glycoprotein I (beta(2)GPI), with residues G40-R43 being important. However, peptides homologous to other regions of domain I have also been shown to bind aPL. Furthermore, there are no published reports of the effects of altering R39, which has greater surface exposure than the G40-R43 residues.

METHODS

We used a novel, efficient method of production and purification of human domain I by Escherichia coli to create multiple mutants of domain I. These domain I mutants were then screened for binding to a range of polyclonal IgG purified from patients with antiphospholipid syndrome, using both solid-phase and fluid-phase assays.

RESULTS

E coli-expressed purified domain I selectively bound IgG derived from patients with antiphospholipid syndrome. In region R39-R43, the R39S mutation had the greatest effect in terms of reducing binding to a panel of aPL in the fluid phase (mean +/- SD inhibition 14 +/- 18.5% versus 44.1 +/- 31.7% for G40E and 62.9 +/- 25.7% for wild-type domain I). Conversely, altering both D8 and D9 to S8 and G9, respectively, had the effect of enhancing binding to aPL in the fluid phase. Adding the remainder of the domain I-II interlinker resulted in enhanced binding over wild-type in the solid phase but not the fluid phase.

CONCLUSION

The binding of aPL to beta(2)GPI domain I is complex and likely to involve discontinuous epitopes that include R39 in addition to G40-R43, the domain I-II interlinker, and possibly D8 and D9. Domain I variants with enhanced binding to aPL compared with wild-type domain I may aid in the development of novel therapies.

Laboratory evaluation of the antiphospholipid syndrome

The antiphospholipid syndrome (APS) was first described in 1986. The original association of this hypercoagulable state with anticardiolipin antibodies (aCL) resulted from the synthesis of evidence stemming from laboratory findings in systemic lupus erythematosus (SLE), ie, the frequent occurrence of false-positive VDRL tests and the paradoxical observation of the so-called "lupus anticoagulant" (LA), an increase in phospholipid (PL)-dependent clotting times. By the early 1990s, it was clear that a co-factor was involved in the reaction of antibodies to PL (aPL) in SLE patients with secondary APS and that this was a hitherto-obscure protein, beta-2 glycoprotein I (beta2GPI). In the intervening years, it has been established that beta2GPI and other PL-binding proteins such as prothrombin (PT) are relevant antigens in APS and assays for these antigens have been developed, standardized, and applied to subjects with both primary and secondary APS. Measurement and confirmation of LA activity is based on a stepwise approach and should follow the recommendations of the International Society of Thrombosis and Haemostasis. Although antibodies to various PL-binding proteins have been suggested as diagnostic targets for APS, the current (2006) consensus guidelines recognize only LA, aCL, and anti-beta2GPI for the classification of APS.

Ehlers-Danlos syndrome type IV in a young man

We describe a 19-year-old male, with a family history of both systemic lupus erythematosus and Marfan syndrome, who had a history of bruising easily and skin lesions since childhood. He had a spontaneous colonic perforation at the age of 16 years, followed 3 years later by sudden development of bilateral renal infarctions and hypertension, which on angiography were found to be due to dissection of both renal arteries. Transient elevations of 3 types of antiphospholipid antibodies (aPL) were detected. Skin biopsy showed typical elastosis perforans serpiginosa. The history together with the generalized connective tissue phenotype, histology, and angiographic features combined to establish a diagnosis of vascular Ehlers-Danlos syndrome, type IV; the body habitus resembled the phenotypically-related condition of Marfan syndrome. The coincidental finding of transient aPL elevations combined to make this a difficult diagnostic and clinical management problem.

Arginine residues are important in determining the binding of human monoclonal antiphospholipid antibodies to clinically relevant antigens

In the antiphospholipid syndrome (APS), antiphospholipid Abs (aPL) bind to anionic phospholipids (PL) and various associated proteins, especially beta(2)-glycoprotein I (beta2GPI) and prothrombin. In the present study, we show that altering specific Arg residues in the H chain of a human pathogenic beta2GPI-dependent aPL, IS4, has major effects on its ability to bind these clinically important Ags. We expressed whole human IgG in vitro by stable transfection of Chinese hamster ovary cells with expression plasmids containing different V(H) and V(L) sequences. V(H) sequences were derived from IS4 by altering the number of Arg residues in CDR3. V(L) sequences were those of IS4, B3 (anti-nucleosome Ab), and UK4 (beta2GPI-independent aPL). Binding of the expressed H/L chain combinations to a range of anionic, neutral, and zwitterionic PL, as well as prothrombin, beta2GPI, dsDNA, and chicken OVA, was determined by ELISA. Of four Arg residues in IS4VH CDR3 substituted to Ser, two at positions 100 and 100g, reduced binding to all Ags, while two at positions 96 and 97 reduced binding to beta2GPI but increased or decreased binding to different PL. Eleven of 14 H/L chain combinations displayed weak binding to OVA with Arg to Ser replacements of all four Arg residues enhancing binding to this Ag. Only one H/L chain combination bound neutral PL and none bound dsDNA; hence, these effects are particularly relevant to Ags important in antiphospholipid syndrome. We hypothesize that these four Arg residues have developed as a result of somatic mutations driven by an Ag containing both PL and beta2GPI.

Evidence-based guidelines for the investigation and medical treatment of recurrent miscarriage

Recurrent miscarriage (RM; > or =3 consecutive early pregnancy losses) affects around 1% of fertile couples. Parental chromosomal anomalies, maternal thrombophilic disorders and structural uterine anomalies have been directly associated with recurrent miscarriage; however, in the vast majority of cases the pathophysiology remains unknown. We have updated the ESHRE Special Interest Group for Early Pregnancy (SIGEP) protocol for the investigation and medical management of RM. Based on the data of recently published large randomized controlled trials (RCTs) and meta-analyses, we recommend that basic investigations of a couple presenting with recurrent miscarriage should include obstetric and family history, age, BMI and exposure to toxins, full blood count, antiphospholipid antibodies (lupus anticoagulant and anticardiolipin antibodies), parental karyotype, pelvic ultrasound and/or hysterosalpingogram. Other investigations should be limited to particular cases and/or used within research programmes. Tender loving care and health advice are the only interventions that do not require more RCTs. All other proposed therapies, which require more investigations, are of no proven benefit or are associated with more harm than good.

IgG-antiphospholipid antibodies in follicular fluid of IVF-ET patients are related to low fertilization rate of their oocytes

PROBLEM

Patients undergoing in vitro fertilization and embryo transfer (IVF-ET) failures show an increased incidence of antiphospholipid antibodies (aPL) in their blood. The physiological manifestations of aPL in this patient group are nonetheless controversial. Pathological effects of aPL on embryos in vitro have been documented. We questioned whether aPL if found in follicular fluids (FFs) could result in embryonic damage.

METHOD OF STUDY

Blood from 44 patients with three or more IVF-ET failures were tested by enzyme-linked immunosorbent assays (ELISA) for the presence of immunoglobulin (Ig)G, IgM and IgA aPL. Both the 29 aPL-positive and 15 aPL-negative patients gave permission for FF collection during their next IVF-ET attempt for additional aPL determinations.

RESULTS

Patients with no aPL in their blood, had no aPL in their FFs. Patients with IgG and/or IgM aPL in their blood had IgG but not IgM in their respective FFs.

CONCLUSIONS

The presence of IgG aPL in FFs and increased infertility length were significantly related to lower fertilization rates, independently. Follicular fluid IgG aPL appears as a risk factor in association with successful IVF-ET outcomes.

Human decidua-associated protein 200 neutralizes the detrimental effect of serum containing antiphospholipid antibodies on fetal survival in the rat

PROBLEM

We wanted to examine whether the detrimental effect of serum containing antiphospholipid (APL) antibodies on rat pregnancy outcome can be neutralized by addition of human decidua-associated protein (hDP) 200, a kind of rheumatoid factor, extracted from decidual tissue.

METHODS

Fifty microliters of pooled serum, obtained from women having anticardiolipin antibody and lupus anticoagulant and presenting with APL antibody syndrome, added with 100 microL of immunoaffinity purified hDP200 was injected into unilateral uterine horn of each rat on day L5 of rat pregnancy. The contralateral uterine horn was used for injection of 50 microL APL positive serum added with physiologic saline as a control. The rats were killed on day L14, and the uterus of each rat was inspected for the presence of live and resorbed fetuses.

RESULTS

The addition of hDP200 to APL positive serum before the intrauterine injection neutralized the detrimental effect of APL serum on fetal resorption rate. Although the neutralizing effect was demonstrated following the addition of hDP200 and immediate intrauterine injection (a decrease in fetal resorption rate, P = 0.004), still the effect was more impressive following the addition of hDP200 and incubation period of 24 hr before the injection, thus causing a significant increase in the number of normal embryos and a significant decrease in fetal resorption rate (P < 0.001).

CONCLUSION

Human decidua-associated protein 200, extracted from human decidual tissue neutralizes the detrimental effect of serum containing APL antibodies in an experimental rat model. Further studies are needed to prove this finding.

Antiphospholipid antibodies bind ATP: a putative mechanism for the pathogenesis of neuronal dysfunction

Antiphospholipid antibodies (aPL) generated in experimental animals cross-react with ATP. We therefore examined the possibility that aPL IgG from human subjects bind to ATP by affinity column and an enzyme linked immunosorbent assay (ELISA). Sera with high levels of aPL IgG were collected from 12 patients with the antiphospholipid syndrome (APS). IgG fractions from 10 of 12 APS patients contained aPL that could be affinity-bound to an ATP column and completely eluted with NaCl 0.5 M. A significant (>50%) inhibition of aPL IgG binding by ATP 5 mM was found in the majority. Similar inhibition was obtained with ADP but not with AMP or cAMP. All the affinity purified anti-ATP antibodies also bound β₂-glycoprotein-I (β₂-GPI, also known as apolipoprotein H) suggesting that, similar to most pathogenic aPL, their binding depends on this serum cofactor. We further investigated this possibility and found that the binding of β₂-GPI to the ATP column was similar to that of aPL IgG in that most was reversed by NaCl 0.5 M. Furthermore, addition of β₂-GPI to aPL IgG significantly increased the amount of aPL binding to an ATP column. We conclude that aPL IgG bind ATP, probably through β₂-GPI. This binding could interfere with the normal extracellular function of ATP and similar neurotransmitters.

Research around beta 2-glycoprotein I: a major target for antiphospholipid antibodies

Beta2-glycoprotein I (beta2GPI), a phospholipid-binding protein, is one of the major target antigens for antiphospholipid antibodies (aPL) found in patients with antiphospholipid syndrome (APS). Thrombophilic disorders in APS patients are strongly associated with aPL, and their pathogenic properties depend on the presence of beta2GPI. Procoagulant cell stimulation by aPL, via beta2GPI, is one of the most plausible mechanisms of thrombosis in APS, and p38 mitogen activated protein kinase (MAPK) pathway plays a crucial role in such activation. beta2GPI is proteolytically cleaved in domain V by activated factor X or plasmin, leading to the generation of the nicked form of beta2GPI. Recently, increasing attention is focused on the role of nicked-beta2GPI as a regulator of extrinsic fibrinolysis pathway.

New Facet of Antiphospholipid Antibodies

Since the aCL test was first described, several reports have described the heterogeneity of aPL, which binds to different anionic phospholipids, proteins, or to a phospholipid-protein complex. It has been recently reported that antiphospholipids (aPLs) from the sera of patients with the antiphospholipid syndrome (APS) are able to bind some newly identified antigens, the lyso(bis)phosphatidic acid (LBPA), lipid restricted to the late endosomes, and the sulfatides, acidic glycosphingolipids involved in the hemostatic process. Of interest, aLBPAs are present in the sera of a large number of patients with APS showing similar sensitivity and specificity compared to anti-beta(2) glycoprotein I antibodies (abeta(2)-GPIs) and close association with lupus anticoagulant. Moreover, beta(2)-GPI binds to sulfatides and the majority of the aPL reacting with cardiolipin-beta(2)-GPI complex also react with the sulfatide-beta(2)-GPI complex. Different mechanisms involved in the production of autoantibodies in autoimmune diseases have been proposed and, among them, apoptosis or programmed cell death seems to play a leading role. The relocation of CL and its metabolites during apoptosis may represent an in vivo trigger for the generation of aCL, and the higher reactivity of sera from APS patients to monolysocardiolipin, the immediate degradation product of mitochondrial CL validates this hypothesis. Finally, increasing evidence suggests that oxidative stress could be a pathogenic link between aPL and thrombosis, and antioxidant treatment may have some efficacy in preventing the clinical manifestations of this syndrome.

Lupus headaches in childhood-onset systemic lupus erythematosus: relationship to disease activity as measured by the systemic lupus erythematosus disease activity index (SLEDAI) and disease damage

The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) is the most commonly used measure of disease activity for children with systemic lupus erythematosus (SLE). For headaches to be scored in the SLEDAI as a symptom of active disease, they have to be nonresponsive to narcotic analgesia. This may affect the overall estimation of disease activity, especially because headaches are common among children with SLE and narcotic analgesia is rarely used for headache therapy in paediatrics. Moreover, the importance of headaches for the development of damage and their relation to other clinical parameters and outcomes has not been well described for children with SLE. We reviewed the medical charts of an inception cohort of children (n = 63) who were newly diagnosed with SLE. Information on headaches and other disease parameters was obtained. Disease activity and damage were measured using the SLEDAI and the Systemic Lupus International Collaboration Clinics/American College of Rheumatology Damage Index (SDI), respectively. It has been shown that the accumulated burden of active disease as measured by serial SLEDAI scores over time is one of the best predictors of eventual damage to children with SLE. New-onset or significant increase of severe and/or persistent headaches (LHA) were reported in 43% of the patients during a mean follow-up of 3.6 years. LHA occurred preferentially among patients with elevated levels of antiphospholipid antibodies (aPL) (P < 0.02) and only 6% of all LHA episodes were treated with narcotics and thus considered for the measurement of disease activity in the SLEDAI. LHA were unrelated to proxy-measures of disease activity, such as the need to intensify therapies. When used in children, the insensitivity of the SLEDAI to capture LHA did not seem to decrease the responsiveness of the SLEDAI to detect clinically important worsening of disease, or negatively impact on its ability to predict damage.

Anti-phospholipid antibodies restore mesenteric ischemia/reperfusion-induced injury in complement receptor 2/complement receptor 1-deficient mice

Complement receptor 2-deficient (Cr2(-/-)) mice are resistant to mesenteric ischemia/reperfusion (I/R) injury because they lack a component of the natural Ab repertoire. Neither the nature of the Abs that are involved in I/R injury nor the composition of the target Ag, to which recognition is lacking in Cr2(-/-) mice, is known. Because anti-phospholipid Abs have been shown to mediate fetal growth retardation and loss when injected into pregnant mice, we performed experiments to determine whether anti-phospholipid Abs can also reconstitute I/R injury and, therefore, represent members of the injury-inducing repertoire that is missing in Cr2(-/-) mice. We demonstrate that both murine and human monoclonal and polyclonal Abs against negatively charged phospholipids can reconstitute mesenteric I/R-induced intestinal and lung tissue damage in Cr2(-/-) mice. In addition, Abs against beta2 glycoprotein I restore local and remote tissue damage in the Cr2(-/-) mice. Unlike Cr2(-/-) mice, reconstitution of I/R tissue damage in the injury-resistant Rag-1(-/-) mouse required the infusion of both anti-beta2-glycoprotein I and anti-phospholipid Ab. We conclude that anti-phospholipid Abs can bind to tissues subjected to I/R insult and mediate tissue damage.

Autoantibodies, lupus and the science of sabotage

Anti-double-stranded DNA antibodies (anti-dsDNA) and antiphospholipid antibodies (APL) are important in the pathogenesis of systemic lupus erythematosus (SLE) and the antiphospholipid syndrome (APS) respectively. Not all anti-dsDNA or APL antibodies can cause clinical effects. Those that are particularly likely to cause tissue damage tend to be of IgG isotype and to possess particular binding properties. Rigorous statistical analysis of published sequences of human monoclonal anti-DNA and APL antibodies showed that IgG antibodies with binding properties characteristic of pathogenicity tend to have multiple somatic mutations in their variable regions. The distribution of these mutations suggests that they have been selected by antigen. This leads to accumulation of certain residues at the antigen-binding sites of these antibodies. Arginine residues are especially important. A computer-generated model of the pathogenic human monoclonal anti-DNA antibody B3 predicted that arginines in the heavy and light chain complementarity-determining regions (CDRs) would interact with dsDNA. We expressed cloned sequences encoding the B3 heavy and light chains in vitro to produce whole IgG. The cloned sequences of the heavy and light chains were manipulated to express a range of variant IgG antibodies. Binding assays on the expressed antibodies showed that altering specific arginine residues reduced binding to dsDNA in a way consistent with computer generated structural models. Changing the pattern of somatic mutations in the light chain altered binding to both dsDNA and histones, but in different ways. A single arginine-to-serine mutation in light-chain CDR1 of B3 reduced binding to both those antigens and may also have reduced the pathogenicity of the expressed antibodies in severe combined immunodeficiency (SCID) mice. Monoclonal human APL were expressed using the same system. Nineteen different heavy-light combinations were expressed. The ability to bind cardiolipin correlated well with the presence of exposed arginine residues in the heavy- and light-chain CDRs. The heavy chain of the pathogenic APL antibody IS4 contains four exposed arginines in CDR3. The results of mutagenesis studies suggested that two of these promote binding to cardiolipin whereas the other two have no such effect.

Endothelial cell activation by antiphospholipid antibodies

Antiphospholipid antibodies are mainly directed against beta 2 glycoprotein I, a phospholipid-binding protein expressed on endothelial cell membranes of different anatomical localizations and recognized by the specific autoantibodies. Antibody binding induces an endothelial activation both in in vitro and in vivo experimental models that might contribute to the prothrombotic state. Endothelial beta 2 glycoprotein I adhesion is mediated by the electrostatic interaction between its cationic phospholipid binding site and anionic structures on the cell membrane; however, binding to annexin II--the endothelial cell receptor for tissue plasminogen activator--plays also a role. Anti-beta-2 glycoprotein I antibodies up-regulate mRNA expression of pro-inflammatory mediators through NF-kappaB translocation and the signaling cascade triggered by Toll-like receptors. Because of the molecular mimicry between beta 2 glycoprotein I and viral/bacterial structures-the natural ligands for Toll-like receptors (TLR)-antibodies might cross-link the molecule associated to the receptors eventually triggering their signaling.

Subcutaneous Granuloma pyogenicum in Patients with Antiphospholipid Antibodies

We describe 2 cases of subcutaneous granuloma pyogenicum occurring in patients with antiphospholipid antibodies. The 2 patients had asymptomatic nodules with histopathological findings of a typical subcutaneous granuloma pyogenicum. In addition, case 1 was diagnosed as primary antiphospholipid syndrome with livedo reticularis, superficial thrombophlebitis, thrombocytopenia, cerebral and pulmonary infarcts and renal involvement. Case 2 had no clinical manifestations of vascular occlusive diseases, although anticardiolipin antibody levels were highly positive. To our knowledge, these are the first reported cases of subcutaneous granuloma pyogenicum associated with antiphospholipid antibodies. Antiphospholipid-antibody-mediated thrombosis or immunological mechanisms may be involved in subcutaneous granuloma pyogenicum in our cases.

[Paraneoplastic syndrome associated with antiphospholipid antibodies]

In patients with malignant tumour signs and symptoms develop that cannot be explained on the basis of the mass effect produced by either primary tumour or its metastases, production of a hormone associated with tissue type giving rise to the malignant tumour, or patients' immune status. These symptom complexes are known as paraneoplastic syndrome. It is known that the patients with malignant tumours are prone to develop venous thromboembolism in any stage of their disease. It is suggested that thromboembolic manifestations in cancer patients may be part of the secondary antiphospholipid syndrome (APS) and an example of the paraneoplastic autoimmunity, eg., paraneoplastic syndrome. Antiphospholipid antibodies (APA), e.g., anticardiolipin antibodies (ACA) and circulating lupus anticoagulant (LAC) are known to predispose to venous and arterial thromboses. The growing number of clinical reports on the association of APA and malignant tumours suggests that APA may be one of contributory factors in the paraneoplastic thromboembolism occurring in malignancy.

Effect of 2-glycoprotein I null mutation on reproductive outcome and antiphospholipid antibody-mediated pregnancy pathology in mice

beta(2)-Glycoprotein I (beta(2)GPI) is a principal target antigen for antiphospholipid antibodies associated with recurrent pregnancy loss and fetal growth restriction in women. The significance of disrupted beta(2)GPI activity in contributing to pregnancy pathology in antiphospholipid syndrome (APS) is not clear. In this study the physiological requirement for functional beta(2)GPI in pregnancy was investigated by evaluating reproductive outcomes in beta(2)GPI null mutant (beta(2)GPI-/-) mice. beta(2)GPI-/- mice were fertile and carried viable fetuses to term. However, there was an 18% reduction in the number of viable implantation sites in beta(2)GPI-/- mice and reduced fetal weight and fetal:placental weight ratio in late gestation, suggesting compromised placental function. Placental architecture was altered in beta(2)GPI-/- implantation sites with a 24% increase in the junctional zone: labyrinthine ratio, but placentae showed no evidence of increased thrombosis in the absence of beta(2)GPI. The effect of beta(2)GPI genotype on pregnancy success after passive transfer of human and mouse antibodies reactive with beta(2)GPI was also explored. Two of five anti-beta(2)GPI antibodies induced pregnancy loss in beta(2)GPI+/+ mice but beta(2)GPI-/- mice were refractory to antibody-induced pregnancy failure. We conclude that functional beta(2)GPI is not essential for successful pregnancy in mice, but optimal placental development and fetal growth require this molecule. Together these data are consistent with pathogenic mechanisms in antiphospholipid syndrome involving both neutralization of beta(2)GPI function and beta(2)GPI-immunoglobulin complex formation.

Are phospholipid-binding antibodies implicated in the pathogenesis of diabetic microangiopathy?

Diabetic retinopathy (DR) is a major cause of blindness in the working population of the Western world and there is no doubt that its prevalence is strongly related to the duration of diabetes and the glycemic control. However, although intensive diabetes management, with the goal of achieving near-normal glycemia, has been shown to prevent and/or delay the onset of DR, there is now ample of evidence that the development of this microangiopathy is a multifactorial process in which genetic, metabolic, haemostatic and growth factors play an important role. Moreover, given the suggestions that immunological mechanisms might have a role in the pathogenesis of diabetic microangiopathy via immune complex deposition, it has been hypothesized that antiphospholipid antibodies (A-Ab) directed against endothelial antigens could be responsible for initiating vascular injury. In particular, not only A-Ab production was found to be increased in patients with overt nephropathy or macroangiopathy but also Lupus Anticoagulant positivity, representing an intersection point between immune and haemostatic alterations, has been highlighted as a potential and additional risk factor in the pathogenesis of microangiopathy in type 1 diabetics. Moreover, given the high levels of activated protein C, endothelin-1 and thrombo-modulin that have been observed in normo-albuminuric and uncomplicated patients, it has been concluded that the vascular endothelium shifts pathologically from an antithrombotic to a prothrombotic state even in the early phases of the disease. This condition was found to be more pronounced in subjects with anticardiolipin positivity and/or high circulating immune complexes concentrations, since they possess the ability not only to induce platelet activation and aggregation but also to activate the complement system via the classical pathway. Therefore, a potential synergism between generation of autoantibodies, haemostatic alterations and endothelial stress has been suggested, a stimulating hypothesis that needs further studies to be clarified in its complexity.

Hypercoagulability in renal transplant recipients. Identifying patients at risk of renal allograft thrombosis and evaluating strategies for prevention

Renal transplantation improves survival and quality of life for patients with end-stage renal disease (ESRD). Improvements in immunosuppressive therapy have reduced early allograft loss due to acute rejection to very low levels. Early allograft loss, due to acute thrombotic complications, remains a constant and proportionally increasing complication of renal transplantation. Identifying risk factor(s) for thrombosis amenable to preventive strategies has been elusive. Epidemiological studies have attempted to define risk in terms of modifiable (drugs, dialysis modality, surgical procedure) and non-modifiable (age, diabetes mellitus, vascular anomalies) factors, or identify changes in coagulation or fibrinolysis promoting a more thrombotic state. Most recently the evolution of thrombophilia research has established the potential for inherited hypercoagulability to predispose to acute allograft thrombosis. Inheritance of the factor V Leiden (FVL), prothrombin G20210A mutation, or the presence of antiphospholipid antibodies (APA) may increase the risk of renal allograft thrombosis approximately 3-fold in selected patients. Patients with ESRD due to systemic lupus erythematosus (SLE) appear at particularly high risk of thrombosis, especially if they have either APA or detectable beta(2)-glycoprotein-1. Data for other hypercoagulable states such as hyperhomocystinemia or the C677T polymorphism of the methylenetetrahydrofolate reductase gene are deficient. Patients with APA, FVL, or prothrombin G20210A mutation also appear to have greater graft loss due to vascular rejection, possibly reflecting immunological injury upon the vascular wall exacerbated or induced by the prothrombotic state. While substantial in vitro data suggest cyclosporine is prothrombotic, an independent clinical association with allograft thrombosis is unproven. Interventions to reduce thrombotic risk including heparin, warfarin, and aspirin have been evaluated in both selected high-risk groups (heparin and warfarin) and unselected populations (heparin and aspirin). In unselected patients at low clinical risk, aspirin (75-150 mg/day) with or without a short period of unfractionated heparin (5000U twice a day for 5 days) appears to reduce the risk of renal allograft thrombosis significantly with a low risk of bleeding, especially when compared with low molecular weight heparins which risk accumulation in renal failure. In high-risk groups (identified thrombophilic risk factor, previous thrombosis, or SLE) longer period of heparin, with or without aspirin and maintenance with warfarin, should be considered. Re-transplantation following graft loss due to vascular thrombosis can be undertaken with a low risk of recurrence. Further prospective studies evaluating both putative risk factors and intervention strategies are required to determine whether routine clinical screening for thrombophilic factors is justified.