Antiphospholipid antibodies promote leukocyte–endothelial cell adhesion and thrombosis in mice by antagonizing eNOS via β2GPI and apoER2
Sangeetha Ramesh, … , Philip W. Shaul, Chieko Mineo
Sangeetha Ramesh, … , Philip W. Shaul, Chieko Mineo
Published December 1, 2010
Citation Information: J Clin Invest. 2011;121(1):120-131. https://doi.org/10.1172/JCI39828.
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Research Article Hematology

Antiphospholipid antibodies promote leukocyte–endothelial cell adhesion and thrombosis in mice by antagonizing eNOS via β2GPI and apoER2

Abstract

In antiphospholipid syndrome (APS), antiphospholipid antibodies (aPL) binding to β2 glycoprotein I (β2GPI) induce endothelial cell–leukocyte adhesion and thrombus formation via unknown mechanisms. Here we show that in mice both of these processes are caused by the inhibition of eNOS. In studies of cultured human, bovine, and mouse endothelial cells, the promotion of monocyte adhesion by aPL entailed decreased bioavailable NO, and aPL fully antagonized eNOS activation by diverse agonists. Similarly, NO-dependent, acetylcholine-induced increases in carotid vascular conductance were impaired in aPL-treated mice. The inhibition of eNOS was caused by antibody recognition of domain I of β2GPI and β2GPI dimerization, and it was due to attenuated eNOS S1179 phosphorylation mediated by protein phosphatase 2A (PP2A). Furthermore, LDL receptor family member antagonism with receptor-associated protein (RAP) prevented aPL inhibition of eNOS in cell culture, and ApoER2–/– mice were protected from aPL inhibition of eNOS in vivo. Moreover, both aPL-induced increases in leukocyte–endothelial cell adhesion and thrombus formation were absent in eNOS–/– and in ApoER2–/– mice. Thus, aPL-induced leukocyte–endothelial cell adhesion and thrombosis are caused by eNOS antagonism, which is due to impaired S1179 phosphorylation mediated by β2GPI, apoER2, and PP2A. Our results suggest that novel therapies for APS can now be developed targeting these mechanisms.

Authors

Sangeetha Ramesh, Craig N. Morrell, Cristina Tarango, Gail D. Thomas, Ivan S. Yuhanna, Guillermina Girardi, Joachim Herz, Rolf T. Urbanus, Philip G. de Groot, Philip E. Thorpe, Jane E. Salmon, Philip W. Shaul, Chieko Mineo

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Figure 7

aPL-induced thrombosis in mice is mediated by eNOS and apoER2.

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aPL-induced thrombosis in mice is mediated by eNOS and apoER2. eNOS+/+ (...
eNOS+/+ (A) and eNOS–/– (B) mice were i.p. injected with NHIgG or aPL (100 μg) and 24 hours later prepared for intravital microscopy. Platelets were fluorescence-labeled by injection of anti–mouse GPIbβ antibody, and the mesentery was exposed for the observation and recording of images of thrombi. Representative still images at 300 seconds are shown. (C) Time required for complete vessel occlusion in eNOS+/+ and eNOS–/– mice. Parallel experiments were performed in ApoER2+/+ (D) and ApoER2–/– (E) mice, and representative still images at 300 seconds are shown. (F) Time required for complete vessel occlusion in ApoER2+/+ and ApoER2–/– mice. In C and F, values are mean ± SEM. n = 5–7/group; *P < 0.05 versus NHIgG, †P < 0.05 versus eNOS+/+, ‡P < 0.05 versus ApoER2+/+.