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

Abstract

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.

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

“…20 Thus, modulation of NF-B activity may provide an opportunity to reverse the pathologic vascular response in APS. The Krüppel-like factors (KLFs), 21 particularly KLF2 and KLF4, inhibit inflammatory cytokinemediated responses in endothelial cells, 22,23 at least in part through inhibition of NF-B activity.…”

The role of TLR4 in pathophysiology of antiphospholipid syndrome‐associated thrombosis and pregnancy morbidity

“…Activation of the MAPK pathway and NF-kB is an essential late step in TLR4 signal transduction pathways. Several research groups working independently have shown the integral role for p38MAPK and NF-jB in the transduction cascade of aPLinduced cell activation (Dunoyer-Geindre et al, 2002;Bohgaki et al, 2004;Simoncini et al, 2005;Sorice et al, 2007), while there is both in vitro and in vivo evidence that direct inhibitors of the two transcription factors interfere with aPL-induced pathogenesis (Montiel-Manzano et al, 2007;Vega-Ostertag et al, 2007). Therefore, inhibitors of NF-jB and p38MAPK may be a worthwhile approach in the APS setting.…”

Antiphospholipid Syndrome - An Evolving Story of a Multisystemic Disease

“…Pierangeli et al In summary, these animal models of thrombosis and endothelial cell activation have not only been useful in demonstrating the pathogenic effects of aPL antibodies and their causative role in inducing APS morbidity, but have also been instrumental in dissecting the intracellular mechanisms involved, in identifying cellular receptors activated by aPL antibodies in vivo and in testing potential new treatments for APS (discussed in detail in other sections of this chapter) [37,39,51,[93][94][95][96][97][98][99][100][101][102][103][104][105].…”

“…Most of these have been discussed in other sections of this chapter (Table 3). Clinical trials are needed to demonstrate whether any of those new therapies are safe and efficacious in APS patients [98,[100][101][102][103][163][164][165][166][167].…”