Neutrophil activation by the tissue factor/Factor VIIa/PAR2 axis mediates fetal death in a mouse model of antiphospholipid syndrome
Patricia Redecha, … , Nigel Mackman, Guillermina Girardi
Patricia Redecha, … , Nigel Mackman, Guillermina Girardi
Published September 18, 2008
Citation Information: J Clin Invest. 2008;118(10):3453-3461. https://doi.org/10.1172/JCI36089.
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Research Article

Neutrophil activation by the tissue factor/Factor VIIa/PAR2 axis mediates fetal death in a mouse model of antiphospholipid syndrome

Abstract

Women with antiphospholipid syndrome (APS), a condition characterized by the presence of antiphospholipid antibodies (aPL), often suffer pregnancy-related complications, including miscarriage. We have previously shown that C5a induction of tissue factor (TF) expression in neutrophils contributes to respiratory burst, trophoblast injury, and pregnancy loss in mice treated with aPL. Here we analyzed how TF contributes to neutrophil activation and trophoblast injury in this model. Neutrophils from aPL-treated mice expressed protease-activated receptor 2 (PAR2), and stimulation of this receptor led to neutrophil activation, trophoblast injury, and fetal death. An antibody specific for human TF that has little impact on coagulation, but potently inhibits TF/Factor VIIa (FVIIa) signaling through PAR2, inhibited aPL-induced neutrophil activation in mice that expressed human TF. Genetic deletion of the TF cytoplasmic domain, which allows interaction between TF and PAR2, reduced aPL-induced neutrophil activation in aPL-treated mice. Par2–/– mice treated with aPL exhibited reduced neutrophil activation and normal pregnancies, which indicates that PAR2 plays an important role in the pathogenesis of aPL-induced fetal injury. We also demonstrated that simvastatin and pravastatin decreased TF and PAR2 expression on neutrophils and prevented pregnancy loss. Our results suggest that TF/FVIIa/PAR2 signaling mediates neutrophil activation and fetal death in APS and that statins may be a good treatment for women with aPL-induced pregnancy complications.

Authors

Patricia Redecha, Claus-Werner Franzke, Wolfram Ruf, Nigel Mackman, Guillermina Girardi

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Figure 5

Statins inhibit TF and PAR2 synthesis and prevent neutrophil oxidative burst and oxidative damage in aPL-IgG–treated mouse placentas.

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Statins inhibit TF and PAR2 synthesis and prevent neutrophil oxidative b...
Pregnant C57BL/6 mice were given aPL-IgG or NH-IgG as in Figure 3; some also received 20 μg simvastatin or 5 μg pravastatin i.p. 18 h before aPL-IgG administration (n = 5–10 mice per group). (A) On day 8, 2 h after aPL-IgG or NH-IgG injection, a blood sample was drawn in order to determine ROS production and phagocytosis in neutrophils by FACS, measured as the number of DHR-positive cells. aPL-IgG increased ROS production, whereas simvastatin prevented neutrophil oxidative burst in aPL-IgG–treated mice. The number of DHR-positive neutrophils was similar between NH-IgG treated and aPL-IgG plus simvastatin–treated mice. (B and C) RT-PCR analysis was performed in isolated neutrophils to quantify TF and PAR2 gene expression. Neutrophils from aPL-IgG–treated mice showed a 28-fold increase in TF mRNA (B) and a 5-fold increase in Par2 mRNA (C). Simvastatin prevented aPL-IgG–induced increase in TF and PAR2 synthesis. (D) Mice were killed on day 8, and deciduae were removed to determine superoxide generation using DHE fluorescence. Increased free radical–mediated lipid peroxidation was observed in deciduae from aPL-IgG–treated mice. No oxidative damage was observed in NH-IgG and aPL-IgG plus simvastatin–treated mice. Scale bars: 50 μm. (E) Mice were killed on day 15 of pregnancy, uteri were dissected, and FRF was calculated. Similar to the effects of simvastatin, pravastatin treatment prevented fetal loss. ‡P < 0.05 versus aPL-IgG plus simvastatin or pravastatin as appropriate.