Neutrophil activation by the tissue factor/Factor VIIa/PAR2 axis mediates fetal death in a mouse model of antiphospholipid syndrome
Patricia Redecha, Claus-Werner Franzke, Wolfram Ruf, Nigel Mackman, Guillermina Girardi
Patricia Redecha, Claus-Werner Franzke, Wolfram Ruf, Nigel Mackman, Guillermina Girardi
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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 4

Simvastatin prevents pregnancy loss in aPL-IgG–treated mice.

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Simvastatin prevents pregnancy loss in aPL-IgG–treated mice. (A and B) P...
(A and B) Pregnant C57BL/6 mice were given 10 mg aPL-IgG or NH-IgG i.p. on days 8 and 12, and some also received 20 μg simvastatin i.p. 18 h before administration of aPL-IgG (n = 5–11 mice per group). (A) Mice were killed on day 15 of pregnancy, uteri were dissected, and FRF was calculated. Treatment with simvastatin prevented fetal loss. †P < 0.01 versus aPL-IgG plus simvastatin. Data are mean ± SD. (B) Uteri from day 15 of pregnancy. There were 5 fetuses and 3 resorptions (asterisks) in the uterus of an aPL-IgG–treated mouse, while the uterus of a mouse that received aPL-IgG plus simvastatin contained 7 fetuses and no resorptions, similar to mice treated with NH-IgG (not shown). Data are representative of observations in 5–8 mice per group. (C) Mice were killed on day 8, 2 h after aPL-IgG or NH-IgG injection. Decidua sections were stained with an anti-C3 antibody as in Figure 3. In aPL-IgG–treated wild-type mice, there was extensive C3 staining (brown) in deciduae as well as embryo debris. In contrast, the decidual tissue from mice treated with aPL-IgG plus simvastatin showed minimal staining for C3 and intact embryo. (D) FACS analysis of DAF expression on trophoblast-like BeWo cells. There was no difference in DAF expression between untreated BeWo cells and BeWo cells incubated with 10 μg/ml simvastatin. Scale bars: 1 cm (B); 200 μm (C, left); 50 mm (C, right).