Antiphospholipid antibodies promote leukocyte-endothelial cell adhesion and thrombosis in mice by antagonizing eNOS via β2GPI and apoER2.
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.
Division of Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Sangeetha
S
Ramesh
Craig N
CN
Morrell
Cristina
C
Tarango
Gail D
GD
Thomas
Ivan S
IS
Yuhanna
Guillermina
G
Girardi
Joachim
J
Herz
Rolf T
RT
Urbanus
Philip G
PG
de Groot
Philip E
PE
Thorpe
Jane E
JE
Salmon
Philip W
PW
Shaul
Chieko
C
Mineo
D000818:Animals; D017152:Antibodies, Antiphospholipid / Q000378:metabolism*; D002417:Cattle; D002448:Cell Adhesion / Q000276:immunology / Q000502:physiology; D019281:Dimerization; D042783:Endothelial Cells / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D026502:LDL-Receptor Related Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000276:immunology; D007962:Leukocytes / Q000276:immunology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008954:Models, Biological; D009569:Nitric Oxide / Q000502:physiology; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000276:immunology; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics; D013927:Thrombosis / Q000209:etiology / Q000276:immunology*; D053482:beta 2-Glycoprotein I / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000276:immunology
D017152:Antibodies, Antiphospholipid; D026502:LDL-Receptor Related Proteins; D034741:RNA, Small Interfering; D053482:beta 2-Glycoprotein I; C098773:low density lipoprotein receptor-related protein 8; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D054648:Protein Phosphatase 2