Antibody-specific behavioral effects: intracerebroventricular injection of antiphospholipid antibodies induces hyperactive behavior while anti-ribosomal-P antibodies induces depression and smell deficits in mice.

This study compares the effects of human antiphospholipid (aPL) and anti-P-ribosomal (anti-P) IgG and control IgG on the brain. Intracerebroventricular (ICV) injected aPL mice (exAPS) displayed specific hyperactivity compared to anti-P-injected (exSLE) and control mice. In contrast ICV injected anti-P-injected mice specifically displayed depression-like behavior and olfactory impairment compared to the other 2 groups. Both anti-P and aPL injected mice were impaired in the passive avoidance test compared to controls. The distinct cognitive effects of the 2 pathogenic antibodies argue for a specific and differential direct action of these autoantibodies on the brain in clinical disease.

Hyperactivity induced by antiphospholipid syndrome serum.

Antiphospholipid syndrome (APS) is a multisystem disorder characterized by arterial and venous thrombosis, pregnancy morbidity, and neuropsychiatric manifestations. Antiphospholipid IgG injected intracerebroventricularly (i.c.v.) cause behavioral hyperactivity in mice. In the present study we investigated the effects of APS whole-serum i.c.v. administration in female Balb/C mice. Control mice were injected with serum derived from healthy subjects or saline solution. Behavior was assessed by the staircase apparatus which combines locomotor (stair-climbing) exploratory activities and rearing as a measure of anxiety. Mice injected with serum from APS patients or serum from normal subjects showed a trend to an increase in the number of stairs climbed in the APS group. The results suggest a differential effect of specific IgG and other serum components in the CNS manifestations of APS.

Antiphospholipid antibodies induce vascular functional changes in mice: a mechanism of vascular lesions in antiphospholipid syndrome?

A premature atherosclerosis has been presumed in patients with antiphospholipid syndrome. The potential role of antiphospholipid antibodies in the development of atheroma is rather controversial. In this study, we tested the hypothesis that antiphospholipid antibodies could induce atherosclerosis via vascular functional changes. CD1 mice received one single injection of antiphospholipid monoclonal antibodies derived from male (BXSB x NZW) F1 mice with a lupus-like disease associated with an antiphospholipid syndrome and coronary artery disease. One week later, first-order mesenteric arteries (diameter 220-260 microm) were isolated and mounted on a small-vessel myograph for the measurement of the relaxation responses to acetylcholine or the NO donor nitroprusside after precontraction by phenylephrine. Five out of eight antiphospholipid monoclonal antibodies reduced the response to acetylcholine compared with control mice, and this effect was especially marked with one of them. No change in the response to nitroprusside was observed. The impairment was maintained after 3 weeks of treatment and appeared related to a moderate decrease in NO-mediated responses and a marked decrease in prostanoid-mediated relaxations. These vascular functional changes could be prevented by chronic treatment with statins or aspirin. These data could constitute additional elements supporting a direct pathogenic role of antiphospholipid antibodies. We suggest that a sub-population of these autoantibodies could be responsible for the endothelial dysfunction observed in antiphospholipid syndrome.

Antiphospholipid antibodies and pregnancy loss: a disorder of inflammation.

The antiphospholipid syndrome (APS) is a leading cause of miscarriage and maternal and fetal morbidity. APS is characterized by thrombosis and pregnancy loss that occur in the presence of antiphospholipid (aPL) antibodies. Using a mouse model of APS induced by passive transfer of human aPL antibodies, we have shown that complement activation plays an essential and causative role in pregnancy loss and fetal growth restriction, and that blocking activation of the complement cascade rescues pregnancies. Conventional treatment for APS patients is sub-anticoagulant doses of heparin throughout pregnancy. Could heparin prevent pregnancy loss by inhibiting complement? In our experimental model of APS, heparin inhibits activation of complement on trophoblasts in vivo and in vitro, and anticoagulation in and of itself is not sufficient to prevent pregnancy complications. These studies underscore the importance of inflammation in fetal injury associated with aPL antibodies and raise the importance of developing and testing targeted complement inhibitory therapy for patients with APS.

Activation of endothelial cells by antiphospholipid antibodies--a possible mechanism triggering thrombosis in patients with antiphospholipid syndrome.

Antiphospholipid syndrome (APS) is an antibody-mediated hypercoagulable state characterized by recurrent venous and arterial thromboembolic events. The presence of serum antibodies are collectively termed as antiphospholipid antibodies (aPL) and is the hallmark of the disease. Interest in the pathogenesis has mostly been focused on the blood coagulation factor. However, endothelial cells might play an important role. When stimulated, cell membrane would flip to expose negatively charged phospholipids and activation markers such as adhesive molecules may appear. We consider that these changes may play an important role in the initiation of the thrombotic process when endothelial cells encounter a PL. In this study, we incubated human umbilical vein endothelial cells (HUVECs) with IgG isolated from patients with APS and found that the HUVECs were activated by the expression of negatively charged phospholipids, as shown by high annexin V binding and negative propidium iodide staining and by an increase in the level of intracellular cell adhesion molecule-1 on the cell surface. The above findings indicate that endothelial cells can be activated on exposure to aPL and trigger the thrombotic event.

A peptide that mimics the Vth region of beta-2-glycoprotein I reverses antiphospholipid-mediated thrombosis in mice.

Antiphospholipid (aPL) antibodies bind to beta2glycoprotein I (beta2GPI) and cause endothelial cell (EC) activation and thrombosis in mice. beta2GPI binds to EC through its Vth domain and induces their activation. TIFI is a 20 amino acid synthetic peptide that shares similarity with the Vth domain of beta2GPI. Our objectives were to examine the ability of TIFI to affect aPL-mediated thrombosis in mice and the interactions of TIFI, beta2GPI with phospholipid surfaces and target cells. CD1 mice were injected with IgG from a patient with antiphospholipid syndrome (IgG-APS) or with control IgG-NHS and with either TIFI or with control peptide (VITT). Size of induced thrombi was determined. Inhibition and competition studies were done using aPL antibodies, cardiolipin (CL) liposomes in the presence of varying amounts of TIFI and beta2GPI. Binding of fluorescinated beta2GPI to human ECs and to murine macrophages in the presence or absence of TIFI, was also examined. TIFI significantly decreased thrombus size in mice injected with IgG-APS. TIFI reverted the beta2GPI-dependent binding of aPL antibodies to CL liposomes in a dose-dependent fashion. This effect was abrogated by addition of beta2GPI, suggesting that TIFI displaces the binding of beta2GPI to phospholipids. TIFI inhibited the binding of fluorescinated beta2GPI to human EC and to murine macrophages. The data indicate that TIFI abrogates thrombogenic properties of aPL in mice by competing with beta2GPI and preventing its binding to target cells. This may be important in designing new modalities for the treatment of thrombosis in APS.

Human decidua-associated protein 200 neutralizes the detrimental effect of serum containing antiphospholipid antibodies on fetal survival in the rat.

PROBLEM: We wanted to examine whether the detrimental effect of serum containing antiphospholipid (APL) antibodies on rat pregnancy outcome can be neutralized by addition of human decidua-associated protein (hDP) 200, a kind of rheumatoid factor, extracted from decidual tissue. METHODS: Fifty microliters of pooled serum, obtained from women having anticardiolipin antibody and lupus anticoagulant and presenting with APL antibody syndrome, added with 100 microL of immunoaffinity purified hDP200 was injected into unilateral uterine horn of each rat on day L5 of rat pregnancy. The contralateral uterine horn was used for injection of 50 microL APL positive serum added with physiologic saline as a control. The rats were killed on day L14, and the uterus of each rat was inspected for the presence of live and resorbed fetuses. RESULTS: The addition of hDP200 to APL positive serum before the intrauterine injection neutralized the detrimental effect of APL serum on fetal resorption rate. Although the neutralizing effect was demonstrated following the addition of hDP200 and immediate intrauterine injection (a decrease in fetal resorption rate, P = 0.004), still the effect was more impressive following the addition of hDP200 and incubation period of 24 hr before the injection, thus causing a significant increase in the number of normal embryos and a significant decrease in fetal resorption rate (P < 0.001). CONCLUSION: Human decidua-associated protein 200, extracted from human decidual tissue neutralizes the detrimental effect of serum containing APL antibodies in an experimental rat model. Further studies are needed to prove this finding.

Pathogenic antiphospholipid antibody: an antigen-selected needle in a haystack.

Antiphospholipid antibodies represent a heterogeneous group of autoantibodies directed against anionic phospholipids (PLs) usually linked to protein cofactors. Their presence during the antiphospholipid syndrome is associated with risks of thrombosis and fetal losses. Among 5 randomly selected monoclonal antiphospholipid antibodies, all originating from a single patient suffering from this autoimmune disease, only 1 induced fetal losses when passively injected into pregnant mice. Its antiphospholipid activity was dependent on annexin A5, and its variable regions contained mainly 3 replacement mutations. To clarify the role of these mutations in the pathogenicity of the antibody, they were in vitro reverted to the germ line configuration. The resulting "germ line" antibody reacted with multiple self-antigens and only partially lost its reactivity against PLs, but it was no more dependent on annexin A5 and, more importantly, was no more pathogenic. This study illustrates that the in vivo antigen-driven maturation process of natural autoreactive B cells can be responsible for pathogenicity.