Endothelial cell activation by antiphospholipid antibodies is modulated by Krüppel-like transcription factors

Allen, Kristi L.; Hamik, Anne; Jain, Mukesh K.; McCrae, Keith R.

doi:10.1182/blood-2010-10-313072

Cited by 46 publications

(37 citation statements)

References 50 publications

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“…Furthermore, in vitro experiments established the ability of aPL antibodies to bind and activate endothelial cells in culture. [28][29][30][31][32][33][34][35][36][37][38] Our finding that the antib2GP1 autoantibody/b2GP1 complex does not bind to the endothelium but that the endothelium does become activated is consistent with prior experiments. This raises 2 questions: (1) Why does the antib2GP1 autoantibody/b2GP1 complex activate endothelial cells in Figure 7.…”

supporting

confidence: 89%

Platelets are required for enhanced activation of the endothelium and fibrinogen in a mouse thrombosis model of APS

Proulle

Furie

Merrill-Skoloff

et al. 2014

Blood

102

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• The anti-b2GP1 autoantibody/ b2GP1 complex binds to the platelet thrombus, amplifying platelet activation.• Platelets are required for enhanced activation of the endothelium and fibrin generation by the anti-b2GP1 autoantibody/b2GP1 complex.Antiphospholipid syndrome (APS) is defined by thrombosis, fetal loss, and the presence of antiphospholipid antibodies, including anti-b2-glycoprotein-1 autoantibodies (antib2GP1) that have a direct role in the pathogenesis of thrombosis in vivo. The cellular targets of the anti-b2GP1 autoantibody/b2GP1 complex in vivo were studied using a laserinduced thrombosis model of APS in a live mouse and human anti-b2GP1 autoantibodies affinity-purified from APS patients. Cell binding of fluorescently labeled b2GP1 and antib2GP1 autoantibodies revealed their colocalization on the platelet thrombus but not the endothelium. Anti-b2GP1 autoantibodies enhanced platelet activation, monitored by calcium mobilization, and endothelial activation, monitored by intercellular adhesion molecule-1 expression. When eptifibatide was infused to block platelet thrombus formation, enhanced fibrin generation and endothelial cell activation were eliminated. Thus, the anti-b2GP1 autoantibody/b2GP1 complex binds to the thrombus, enhancing platelet activation, and platelet secretion leads to enhanced endothelium activation and fibrin generation. These results lead to a paradigm shift away from the concept that binding of the anti-b2GP1 autoantibody/b2GP1 complex activates both endothelial cells and platelets toward one in which activation of platelets in response to anti-b2GP1 autoantibody/b2GP1 complex binding leads to subsequent enhanced endothelium activation and fibrin generation. (Blood. 2014;124(4):611-622) IntroductionAntiphospholipid syndrome (APS) is characterized by venous or arterial thrombosis and/or pregnancy morbidity and is associated with circulating antiphospholipid (aPL) autoantibodies.1-3 These antibodies, including anti-b2-glycoprotein-1 (anti-b2GP1) autoantibodies, recognize plasma proteins that bind to anionic phospholipids, among which b2GP1 is the major target. 4 Antibodies directed against b2GPI 5,6 are associated with thrombotic events in APS. Antib2GP1 autoantibodies from patients with APS and thrombosis enhance arterial thrombus formation after injury in a mouse model of APS, 7 with dramatic increases in platelet thrombus size and fibrin generation.The mechanisms leading to thrombosis in APS are unresolved. In vitro and in vivo studies using animal models demonstrated that aPL antibodies interact with endothelial cells and monocytes to increase tissue factor expression and complement activation and proinflammatory cytokines. 8,9 In vitro, platelet activation occurs after the binding of complexes of anti-b2GP1 antibodies and dimerized b2GP1 to GPIba and ApoER2. [10][11][12] Furthermore, APS patients exhibit markers of platelet activation. 13 The conventional understanding is that the antib2GP1/b2GP1 complex binds to receptors on both the endothelial cell and the platelet, lea...

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supporting

confidence: 89%

Platelets are required for enhanced activation of the endothelium and fibrinogen in a mouse thrombosis model of APS

Proulle

Furie

Merrill-Skoloff

et al. 2014

Blood

102

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“…11,22 Inhibiting the expression of these components also prevents increases in E-selectin, ICAM-1, VCAM-1, and TF mRNA, all of which encode proteins of importance in the pathogenesis of anti-␤ 2 GPI-mediated thrombosis. An intact multiprotein complex was also found to be essential for the activation of NF-B.…”

Section: Discussionmentioning

confidence: 99%

“…11,22 Confluent ECs in 96-well microplates were incubated for 3 hours in serum-free medium before incubation for 5 hours with 60nM human ␤ 2 GPI and 180nM anti-␤ 2 GPI IgG Abs. Cells were washed and then fixed by exposure to 2% paraformaldehyde for 15 minutes.…”

Section: Assessment Of Ec Activationmentioning

confidence: 99%

A novel pathway for human endothelial cell activation by antiphospholipid/anti-β2 glycoprotein I antibodies

Allen

Fonseca

Betapudi

et al. 2012

Blood

Self Cite

125

114

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Antiphospholipid Abs (APLAs) are associated with thrombosis and recurrent fetal loss. These Abs are primarily directed against phospholipid-binding proteins, particularly ␤ 2 GPI, and activate endothelial cells (ECs) in a ␤ 2 GPI-dependent manner after binding of ␤ 2 GPI to EC annexin A2. Because annexin A2 is not a transmembrane protein, the mechanisms of APLA/anti-␤ 2 GPI Ab-mediated EC activation are uncertain, although a role for a TLR4/myeloid differentiation factor 88-dependent pathway leading to activation of NF-B has been proposed. In the present study, we confirm a critical role for TLR4 in anti-␤ 2 GPI Ab-mediated EC activation and demonstrate that signaling through TLR4 is mediated through the assembly of a multiprotein signaling complex on the EC surface that includes annexin A2, TLR4, calreticulin, and nucleolin. An essential role for each of these proteins in cell activation is suggested by the fact that inhibiting the expression of each using specific siRNAs blocked EC activation mediated by APLAs/anti-␤ 2 GPI Abs. These results provide new evidence for novel proteinprotein interactions on ECs that may contribute to EC activation and the pathogenesis of APLA/anti-␤ 2 GPI-associated thrombosis and suggest potential new targets for therapeutic intervention in antiphospholipid syndrome. (Blood. 2012; 119(3):884-893) IntroductionAntiphospholipid syndrome (APS) is characterized by thrombosis and recurrent fetal loss in patients with circulating antiphospholipid Abs (APLAs) and is the most important cause of acquired thrombophilia. [1][2][3] Prospective studies have demonstrated that patients with APS experience significant morbidity and mortality despite recommendations for indefinite anticoagulation. 4 The term "antiphospholipid" is actually a misnomer, because the majority of APLAs are directed against phospholipid-binding proteins, of which ␤ 2 -glycoprotein I (␤ 2 GPI) is the most common. 5,6 The clinical importance of anti-␤ 2 GPI Abs has been demonstrated in several previous reports, 7 and recent studies have shown that affinity-purified human anti-␤ 2 GPI Abs induce thrombosis in mice. 8 Despite the clinical importance of APS, however, its pathogenesis has not been well defined. 1,3,9 One mechanism by which APLAs/anti-␤ 2 GPI Abs may promote thrombosis is through ␤ 2 GPI-dependent activation of endothelial cells (ECs). [10][11][12] ECs play a critical role in the maintenance of blood fluidity through expression of anticoagulant proteins on their luminal surface and the elaboration of antithrombotic substances. 13 However, EC activation leads to loss of these anticoagulant properties and transformation to a pro-adhesive, procoagulant phenotype. 13 APLAs/anti-␤ 2 GPI Abs induce EC activation in vitro and in vivo, as determined by their ability to increase the expression of adhesion molecules (E-selectin, ICAM-1, VCAM-1), and tissue factor (TF) and to enhance the expression, synthesis, and/or secretion of pro-inflammatory cytokines and chemokines. 3,[10][11][12] These effects may account for the ab...

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“…Mechanistically, a study has suggested that downregulation of endothelial NOS (eNOS) by antiphospholipid antibodies may be another important factor in increased leukocyte-endothelium interplay (17). Mechanistically, NF-κB, p38 MAPK, and Krüppel-like factors (KLFs) have all been implicated in antiphospholipid antibody-mediated activation of endothelial cells (18)(19)(20), demonstrating how antiphospholipid antibodies may co-opt pathways normally associated with more "authentic" inflammatory stimuli.…”

Section: Introductionmentioning

confidence: 99%

Activated signature of antiphospholipid syndrome neutrophils reveals potential therapeutic target

et al. 2017

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Endothelial cell activation by antiphospholipid antibodies is modulated by Krüppel-like transcription factors

Cited by 46 publications

References 50 publications

Platelets are required for enhanced activation of the endothelium and fibrinogen in a mouse thrombosis model of APS

Platelets are required for enhanced activation of the endothelium and fibrinogen in a mouse thrombosis model of APS

A novel pathway for human endothelial cell activation by antiphospholipid/anti-β2 glycoprotein I antibodies

Activated signature of antiphospholipid syndrome neutrophils reveals potential therapeutic target

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