Pathogenic role of anti- 2-glycoprotein I antibodies in antiphospholipid associated fetal loss: characterisation of  2-glycoprotein I binding to trophoblast cells and functional effects of anti- 2-glycoprotein I antibodies in vitro

ABSTRACT Because Staphylococcus aureus strains contain multiple virulence factors, studying their pathogenic role by single-gene inactivation generated equivocal results. To circumvent this problem, we have expressed specific S. aureus genes in the less virulent organism Streptococcus gordonii and tested the recombinants for a gain of function both in vitro and in vivo. Clumping factor A (ClfA) and coagulase were investigated. Both gene products were expressed functionally and with similar kinetics during growth by streptococci and staphylococci. ClfA-positive S. gordoniiwas more adherent to platelet-fibrin clots mimicking cardiac vegetations in vitro and more infective in rats with experimental endocarditis (P < 0.05). Moreover, deletingclfA from clfA-positive streptococcal transformants restored both the low in vitro adherence and the low in vivo infectivity of the parent. Coagulase-positive transformants, on the other hand, were neither more adherent nor more infective than the parent. Furthermore, coagulase did not increase the pathogenicity ofclfA-positive streptococci when both clfA andcoa genes were simultaneously expressed in an artificial minioperon in streptococci. These results definitively attribute a role for ClfA, but not coagulase, in S. aureus endovascular infections. This gain-of-function strategy might help solve the role of individual factors in the complex the S. aureus-host relationship.

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Deficiency of C3a receptor attenuates the development of diabetic nephropathy

BMJ Open Diabetes Research & Care ◽

10.1136/bmjdrc-2019-000817 ◽

2019 ◽

Vol 7 (1) ◽

pp. e000817 ◽

Cited By ~ 2

Author(s):

Xiao-Qian Li ◽

Dong-Yuan Chang ◽

Min Chen ◽

Ming-Hui Zhao

Keyword(s):

Diabetic Nephropathy ◽

T Cell ◽

Adaptive Immunity ◽

Renal Damage ◽

Inflammatory Responses ◽

Gene Knockout ◽

Diabetic Mice ◽

Pathogenic Role

ObjectiveDiabetic nephropathy (DN) is the leading cause of chronic kidney disease and end-stage renal disease. Emerging evidence suggests that complement activation is involved in the pathogenesis of DN. The aim of this study was to investigate the pathogenic role of C3a and C3a receptor (C3aR) in DN.Research design and methodsThe expression of C3aR was examined in the renal specimen of patients with DN. Using a C3aR gene knockout mice (C3aR−/−), we evaluated kidney injury in diabetic mice. The mouse gene expression microarray was performed to further explore the pathogenic role of C3aR. Then the underlying mechanism was investigated in vitro with macrophage treated with C3a.ResultsCompared with normal controls, the renal expression of C3aR was significantly increased in patients with DN. C3aR−/− diabetic mice developed less severe diabetic renal damage compared with wild-type (WT) diabetic mice, exhibiting significantly lower level of albuminuria and milder renal pathological injury. Microarray profiling uncovered significantly suppressed inflammatory responses and T-cell adaptive immunity in C3aR−/− diabetic mice compared with WT diabetic mice, and this result was further verified by immunohistochemical staining of renal CD4+, CD8+ T cells and macrophage infiltration. In vitro study demonstrated C3a can enhance macrophage-secreted cytokines which could induce inflammatory responses and differentiation of T-cell lineage.ConclusionsC3aR deficiency could attenuate diabetic renal damage through suppressing inflammatory responses and T-cell adaptive immunity, possibly by influencing macrophage-secreted cytokines. Thus, C3aR may be a promising therapeutic target for DN.

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Mechanism of action of β2-glycoprotein I-dependent lupus anticoagulants

Lupus ◽

10.1177/096120339800700206 ◽

1998 ◽

Vol 7 (2_suppl) ◽

pp. 23-28 ◽

Cited By ~ 15

Author(s):

J Amout ◽

J Vermylen

Keyword(s):

Mechanism Of Action ◽

Molecular Basis ◽

Current Knowledge ◽

Indirect Evidence ◽

Integrated Model ◽

Anticardiolipin Antibodies ◽

Pathogenic Role ◽

Lupus Anticoagulants ◽

Glycoprotein I

There is accumulating evidence showing that lupus anticoagulants (LA) are more strongly associated with thrombosis than anticardiolipin antibodies. In addition, indirect evidence has been presented indicating that β2GPI-dependent LA are more strongly associated with thrombosis than prothrombin-dependent LA. From this, one may assume that anti-β2GPl antibodies with LA activity are more pathogenic than anti-β2GPI antibodies without LA activity. Therefore, it is of the utmost importance to understand the molecular basis on which some anti-β2GPI antibodies behave as LA. In this presentation, the current knowledge on the interaction of β2GPI with phospholipids and with anti-β2GPI antibodies is reviewed and an integrated model for the anti-β2GPI - dependent LA activity is proposed with implications for a pathogenic role of these particular antibodies.

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SMAD1/5 Signaling in the Early Equine Placenta Regulates Trophoblast Differentiation and Chorionic Gonadotropin Secretion

Endocrinology ◽

10.1210/en.2013-2116 ◽

2014 ◽

Vol 155 (8) ◽

pp. 3054-3064 ◽

Cited By ~ 11

Author(s):

Victoria Cabrera-Sharp ◽

Jordan E. Read ◽

Stephanie Richardson ◽

Alycia A. Kowalski ◽

Douglas F. Antczak ◽

...

Keyword(s):

Chorionic Gonadotropin ◽

Trophoblast Cells ◽

Rt Pcr ◽

Trophoblast Differentiation ◽

Gonadotropin Secretion ◽

Morphogenetic Protein ◽

Dose Dependent

TGFβ superfamily proteins, acting via SMAD (Sma- and Mad-related protein)2/3 pathways, regulate placental function; however, the role of SMAD1/5/8 pathway in the placenta is unknown. This study investigated the functional role of bone morphogenetic protein (BMP)4 signaling through SMAD1/5 in terminal differentiation of primary chorionic gonadotropin (CG)-secreting trophoblast. Primary equine trophoblast cells or placental tissues were isolated from day 27–34 equine conceptuses. Detected by microarray, RT-PCR, and quantitative RT-PCR, equine chorionic girdle trophoblast showed increased gene expression of receptors that bind BMP4. BMP4 mRNA expression was 20- to 60-fold higher in placental tissues adjacent to the chorionic girdle compared with chorionic girdle itself, suggesting BMP4 acts primarily in a paracrine manner on the chorionic girdle. Stimulation of chorionic girdle-trophoblast cells with BMP4 resulted in a dose-dependent and developmental stage-dependent increase in total number and proportion of terminally differentiated binucleate cells. Furthermore, BMP4 treatment induced non-CG-secreting day 31 chorionic girdle trophoblast cells to secrete CG, confirming a specific functional response to BMP4 stimulation. Inhibition of SMAD2/3 signaling combined with BMP4 treatment further enhanced differentiation of trophoblast cells. Phospho-SMAD1/5, but not phospho-SMAD2, expression as determined by Western blotting was tightly regulated during chorionic girdle trophoblast differentiation in vivo, with peak expression of phospho-SMAD1/5 in vivo noted at day 31 corresponding to maximal differentiation response of trophoblast in vitro. Collectively, these experiments demonstrate the involvement of BMP4-dependent pathways in the regulation of equine trophoblast differentiation in vivo and primary trophoblast differentiation in vitro via activation of SMAD1/5 pathway, a previously unreported mechanism of TGFβ signaling in the mammalian placenta.

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The Role of β2-Glycoprotein I in the Clearance of Platelet Microvesicles.

Blood ◽

10.1182/blood.v114.22.145.145 ◽

2009 ◽

Vol 114 (22) ◽

pp. 145-145

Author(s):

Hanan Abdel-Monem ◽

Swapan Kumar Dasgupta ◽

Anhquyen Le ◽

Anthony Prakasam ◽

Perumal Thiagarajan

Keyword(s):

Plasma Proteins ◽

Plasma Concentrations ◽

Major Protein ◽

Maximal Effect ◽

Dependent Manner ◽

Anionic Phospholipid ◽

Concentration Dependent Manner ◽

Glycoprotein I

Abstract Abstract 145 The physiological function of β2-glycoprotein I is unclear and several studies suggest a role in the clearance of anionic phospholipid containing membranes. Anionic phospholipid containing liposomes are cleared rapidly from the circulation by the reticuloendothelial cells. In rats, uptake of liposomes by Kupffer cells requires that the liposomes bind to plasma proteins. In mice, the clearance of liposomes from the circulation is related to their ability to interact with plasma proteins. β2-glycoprotein I was identified as a major protein associated with rapid clearance of liposomes and pretreating the mice with antiβ2- glycoprotein I antibodies was found to significantly increase the half-life of the liposome. In vitro, β2-glycoprotein I was also shown to promote the phagocytosis of phosphatidylserine containing liposomes and apoptotic tumor cells. In conditions associated with increased microvesicles generation such as disseminated intravascular coagulation, plasma levels of β;2-glycoprotein I was reduced presumably due to its consumption. Antibodies to β2 glycoprotein I are frequently seen in patients with systemic lupus erythematosus and at times, in otherwise normal individuals. A subset of these antibodies prevents the assembly of the prothrombinase and the tenase complexes on phospholipid membrane, leading to the lupus anticoagulant effect. The presence of these antibodies is clinically very significant, as individuals harboring these antibodies are at risk for thromboembolic manifestations. We studied the role of β-glycoprotein I in the clearance of procoagulant platelet microvesicles and the effect of the auto antibodies in the phagocytosis of platelet microvesicles. We labeled β2-glycoprotein I with BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)-hydrazide and β2-glycoprotein I incorporated 1.8 mole of BODIPY /mole. Labeling of β2-glycoprotein I with BODIPY did not change the binding efficacy of β2-glycoprotein I to cardiolipin as determined by Elisa assay. Binding of BODIPY-β2-glycoprotein I to platelet microvesicles was analyzed by flow cytometry. BODIPY- β2-glycoprotein I bound to phosphatidylserine-expressing platelet microvesicles in a concentration-dependent manner. Binding was inhibited by 50 fold molar excess of unlabeled β2-glycoprotein I, annexin A5 and the phosphatidylserine-binding C1C2 fragment of lactadherin. β2-glycoprotein I also promoted the phagocytosis of platelet microvesicles by THP-1 derived macrophages in vitro at physiological plasma concentrations with a half maximal effect at ∼10 ug/ml. β2-glycoprotein I-mediated phagocytosis was inhibited by annexin V and the C1C2 fragment of lactadherin. Furthermore, immunoaffinity purified β2-glycoprotein I-dependent antiphospholipid antibodies from 5 patients inhibited the phagocytosis in a concentration dependent manner. These studies suggest β2-glycoprotein I binding to phosphatidylserine-expressing procoagulant platelet microvesicles promotes their clearance by macrophages and autoantibodies to β2-glycoprotein I inhibit the process. The predictive value of antiβ-2 glycoprotein I for thrombosis is highly variable but the correlation is stronger in patients with lupus. In lupus, there is impaired clearance of procoagulant apoptotic cells. β2-glycoprotein I may have a significant role in their clearance and antibodies to β2-glycoprotein I may causally related to the thrombosis in these patients by inhibiting the clearance. Disclosures: No relevant conflicts of interest to declare.

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Pathogenic role of anti-β2-glycoprotein I antibodies on human placenta: functional effects related to implantation and roles of heparin

Human Reproduction Update ◽

10.1093/humupd/dml051 ◽

2006 ◽

Vol 13 (2) ◽

pp. 189-196 ◽

Cited By ~ 38

Author(s):

N. Di Simone ◽

P.L. Meroni ◽

M. D’Asta ◽

F. Di Nicuolo ◽

M.C. D’Alessio ◽

...

Keyword(s):

Human Placenta ◽

Pathogenic Role ◽

Glycoprotein I

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Role of beta 2-glycoprotein I and anti-phospholipid antibodies in activation of protein C in vitro.

Journal of Clinical Pathology ◽

10.1136/jcp.46.10.908 ◽

1993 ◽

Vol 46 (10) ◽

pp. 908-911 ◽

Cited By ~ 30

Author(s):

D M Keeling ◽

A J Wilson ◽

I J Mackie ◽

D A Isenberg ◽

S J Machin

Keyword(s):

Protein C ◽

Glycoprotein I ◽

Beta 2

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Maternal Par4 and platelets contribute to defective placenta formation in mouse embryos lacking thrombomodulin

Blood ◽

10.1182/blood-2007-09-111302 ◽

2008 ◽

Vol 112 (3) ◽

pp. 585-591 ◽

Cited By ~ 26

Author(s):

Rashmi Sood ◽

Lynette Sholl ◽

Berend Isermann ◽

Mark Zogg ◽

Shaun R. Coughlin ◽

...

Keyword(s):

Cell Function ◽

Immune Cell ◽

Fetal Loss ◽

Trophoblast Cells ◽

Protease Activated Receptors ◽

Genetic Ablation ◽

Coagulation Inhibitor ◽

Placental Failure ◽

New Evidence

Abstract Absence of the blood coagulation inhibitor thrombomodulin (Thbd) from trophoblast cells of the mouse placenta causes a fatal arrest of placental morphogenesis. The pathogenesis of placental failure requires tissue factor, yet is not associated with increased thrombosis and persists in the absence of fibrinogen. Here, we examine the role of alternative targets of coagulation that might contribute to the placental failure and death of Thbd−/− embryos. We demonstrate that genetic deficiency of the protease-activated receptors, Par1 or Par2, in the embryo and trophoblast cells does not prevent the death of Thbd−/− embryos. Similarly, genetic ablation of the complement pathway or of maternal immune cell function does not decrease fetal loss. In contrast, Par4 deficiency of the mother, or the absence of maternal platelets, restores normal development in one-third of Thbd-null embryos. This finding generates new evidence implicating increased procoagulant activity and thrombin generation in the demise of thrombomodulin-null embryos, and suggests that platelets play a more prominent role in placental malfunction associated with the absence of thrombomodulin than fibrin formation. Our findings demonstrate that fetal prothrombotic mutations can cause localized activation of maternal platelets at the feto-maternal interface in a mother with normal hemostatic function.

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MicroRNA-709 Mediates Acute Tubular Injury through Effects on Mitochondrial Function

Journal of the American Society of Nephrology ◽

10.1681/asn.2017040381 ◽

2017 ◽

Vol 29 (2) ◽

pp. 449-461 ◽

Cited By ~ 27

Author(s):

Yan Guo ◽

Jiajia Ni ◽

Shuang Chen ◽

Mi Bai ◽

Jiajuan Lin ◽

...

Keyword(s):

Mitochondrial Dysfunction ◽

Mitochondrial Function ◽

Cell Injury ◽

Kidney Tissue ◽

Kidney Injury ◽

Tubular Injury ◽

Pathogenic Role ◽

Novel Target

Mitochondrial dysfunction has important roles in the pathogenesis of AKI, yet therapeutic approaches to improve mitochondrial function remain limited. In this study, we investigated the pathogenic role of microRNA-709 (miR-709) in mediating mitochondrial impairment and tubular cell death in AKI. In a cisplatin-induced AKI mouse model and in biopsy samples of human AKI kidney tissue, miR-709 was significantly upregulated in the proximal tubular cells (PTCs). The expression of miR-709 in the renal PTCs of patients with AKI correlated with the severity of kidney injury. In cultured mouse PTCs, overexpression of miR-709 markedly induced mitochondrial dysfunction and cell apoptosis, and inhibition of miR-709 ameliorated cisplatin-induced mitochondrial dysfunction and cell injury. Further analyses showed that mitochondrial transcriptional factor A (TFAM) is a target gene of miR-709, and genetic restoration of TFAM attenuated mitochondrial dysfunction and cell injury induced by cisplatin or miR-709 overexpression in vitro. Moreover, antagonizing miR-709 with an miR-709 antagomir dramatically attenuated cisplatin-induced kidney injury and mitochondrial dysfunction in mice. Collectively, our results suggest that miR-709 has an important role in mediating cisplatin-induced AKI via negative regulation of TFAM and subsequent mitochondrial dysfunction. These findings reveal a pathogenic role of miR-709 in acute tubular injury and suggest a novel target for the treatment of AKI.

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Mechanism of action of Lupus anticoagulants

Hämostaseologie ◽

10.1055/s-0037-1619504 ◽

2001 ◽

Vol 21 (02) ◽

pp. 44-49 ◽

Cited By ~ 1

Author(s):

J. Arnout

Keyword(s):

Binding Proteins ◽

Fetal Loss ◽

Coagulation Factors ◽

Anticardiolipin Antibodies ◽

Heparin Induced Thrombocytopenia ◽

Glycoprotein I ◽

Direct Binding ◽

Initial Activation ◽

The Complement System

SummaryThe antiphospholipid syndrome (APS) is defined as the association of antiphospholipid antibodies (aPL) with thrombosis, fetal loss or thrombocytopenia. Some aPL can be detected via coagulation assays where they present as an aspecific inhibitor termed the lupus anticoagulant (LA). Others can be measured via direct binding to cardiolipin and are termed anticardiolipin antibodies. aPL found in APS patients bind to a variety of PL-binding proteins such as beta-2-glycoprotein I (β2GPI) and prothrombin bound to PL surfaces. LA retard coagulation reactions in vitro by forming stable bivalent immune complexes on coagulation active phospholipids. These complexes have increased affinity for PL and compete with coagulation factors for the same catalytic surface. Animal experimental work has provided evidence that aPL are pathogenic. Based on similarities with heparin induced thrombocytopenia, another thrombotic syndrome, the following mechanism might be proposed. As a consequence of an initial activation, anionic PL exposed on bloodcells, endothelium or trophoblasts may promote the formation of bivalent complexes of aPL and PL-binding proteins. In this way, aPL concentrate on the cell surface, activate cellular FcγRII receptors or the complement system and induce thrombosis.

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