Role of p38 mitogen-activated protein kinase in antiphospholipid antibody-mediated thrombosis and endothelial cell activation.

BACKGROUND: The purpose of this study was to examine whether SB 203580, a p38 mitogen-activated protein kinase (MAPK) inhibitor, is effective in reversing the pathogenic effects of antiphospholipid antibodies. METHODS: The adhesion of THP-1 monocytes to cultured endothelial cells (EC) treated with immunoglobulin G (IgG) from a patient with antiphospholipid syndrome (IgG-APS) or control IgG (IgG-NHS) in the presence and absence of SB 203580 was examined. The size of an induced thrombus in the femoral vein, the adhesion of leukocytes to EC of cremaster muscle, tissue factor (TF) activity in carotid artery and in peritoneal macrophages, the ex vivo expression of vascular cell adhesion molecule-1 (VCAM-1) in aorta preparations and platelet aggregation were studied in mice injected with IgG-APS or control IgG-NHS and with or without SB 203580. RESULTS: SB 203580 significantly reduced the increased adhesion of THP-1 to EC in vitro, the number of leukocytes adhering to EC, the thrombus size, the TF activity in carotid arteries and in peritoneal mononuclear cells, and the expression of VCAM-1 in aorta of mice, and completely abrogated platelet aggregation induced by IgG-APS. CONCLUSION: These data suggest that targeting the p38 MAPK pathway may be valuable in designing new therapy modalities for treating thrombosis in patients with APS.

Fluvastatin inhibits up-regulation of tissue factor expression by antiphospholipid antibodies on endothelial cells.

BACKGROUND: Mechanisms of thrombosis induced by antiphospholipid (aPL) antibodies include up-regulation of tissue factor (TF) expression on endothelial cells (ECs). Statins have been shown to reduce levels of TF induced by tumor necrosis factor (TNF-alpha) and lipopolysaccharide (LPS) on ECs. In a recent study, fluvastatin inhibited thrombogenic and proinflammatory properties of aPL antibodies in in vivo models. The aim of this study was to determine whether fluvastatin has an effect on aPL-induced expression of TF on ECs. METHODS: IgGs were purified from four patients with APS (IgG-APS) and from control sera (IgG-NHS). Cultured human umbilical vein endothelial cells (HUVEC) were treated with IgG-APS or IgG-NHS or with medium alone or with phorbol myristate acetate (PMA), as a positive control. In some experiments, cells were pretreated with fluvastatin (2.5, 5 or 10 micro m) with and without mevalonate (100 micro m). TF expression on HUVECs was measured by ELISA. RESULTS: PMA and the four IgG-APS preparations increased the expression of TF on EC significantly (4.9-, 2.4-, 4.2-, 3.5- and 3.1-fold, respectively), in a dose-dependent fashion. Fluvastatin (10 micro m) inhibited the effects of PMA and the four IgG-APS on TF expression by 70, 47, 65, 22 and 68%, respectively, and this effect was dose-dependent. Mevalonate (100 micro m) completely abrogated the inhibitory effects of fluvastatin on TF expression induced by aPL. CONCLUSION: Because of the suggested pathogenic role of aPL on induction of TF on ECs, our data provide a rationale for using statins as a therapeutic tool in treatment of thrombosis in APS.