Accelerated atheroma, antiphospholipid antibodies, and the antiphospholipid syndrome

Innate immunity in the antiphospholipid syndrome: role of toll-like receptors in endothelial cell activation by antiphospholipid antibodies

Antiphospholipid antibodies are mainly directed against beta 2 glycoprotein I (beta2GPI), a plasma phospholipid-binding protein expressed on endothelial cells of different anatomical localizations. Anti-beta2GPI antibodies recognize the molecule on endothelial monolayers in vitro, and, once bound, might activate the cells both in vitro and in vivo experimental models inducing a proinflammatory and a procoagulant phenotype. Cell activation is associated with nuclear factor-kappaB (NF-kappaB) translocation and with a signaling cascade comparable to that triggered by the toll-like receptors (TLRs)-4. The cell membrane receptor(s) for beta2GPI adhesion is still under investigation. It has been suggested that beta2GPI might adhere through electrostatic interaction between its cationic phospholipid binding site and anionic structures on the cell membrane; however, binding to annexin II-the endothelial cell receptor for tissue plasminogen activator-plays also a role. Because annexin II does not display any transmembrane protein, it has been suggested that it requires a yet unknown "adaptor" protein to signal the cells. Because of the molecular mimicry between beta2GPI and viral/bacterial structures-the natural ligands for TLRs-antibodies might cross-link the molecule associated to annexin II and TLR-4 eventually triggering the signaling.

Impaired brachial endothelial function in patients with primary anti-phospholipid syndrome

Although the precise pathophysiology of thrombosis is unknown in primary anti-phospholipid syndrome (PAPS), it is assumed that autoantibodies developed against endothelial cells and platelets might be one of the primary mechanisms. However, whether interaction between autoantibodies and endothelium leads to an impaired vasodilator response has not been investigated yet. In this study, we aimed to investigate the endothelial functions in patients with PAPS. Thirty-one patients with PAPS (22 female, nine male, mean age: 34.6+/-8.9 years) and 27 age- and sex-matched, healthy controls were included in the study. Brachial artery responses to reactive hyperaemia (endothelium-dependent dilatation) [EDD] and sublingual nitroglycerine (endothelium-independent dilatation) [EID] were measured by using high-resolution vascular ultrasound both in patients with PAPS and in the controls. The results were expressed as percentage of change in baseline values. Regarding cardiovascular risk factors, there was no significant difference between the two groups. EDD in patients with PAPS was significantly lower than those of controls (6.9+/-4.9 vs. 14.8+/-4.1%; p<0.0001). EID measurements were not significantly different between the groups. In the PAPS group, EDD in patients with arterial involvement (17 patients) was significantly lower than those of patients with venous involvement (12 patients) (4.6+/-3.9 vs. 7.4+/-4.1%; p = 0.02). This study showed that endothelial functions determined by using brachial artery ultrasound were impaired in patients with PAPS, and this was more prominent in the subgroup of patients with arterial involvement compared to patients with venous involvement.

Endothelial cell activation by antiphospholipid antibodies

Antiphospholipid antibodies are mainly directed against beta 2 glycoprotein I, a phospholipid-binding protein expressed on endothelial cell membranes of different anatomical localizations and recognized by the specific autoantibodies. Antibody binding induces an endothelial activation both in in vitro and in vivo experimental models that might contribute to the prothrombotic state. Endothelial beta 2 glycoprotein I adhesion is mediated by the electrostatic interaction between its cationic phospholipid binding site and anionic structures on the cell membrane; however, binding to annexin II--the endothelial cell receptor for tissue plasminogen activator--plays also a role. Anti-beta-2 glycoprotein I antibodies up-regulate mRNA expression of pro-inflammatory mediators through NF-kappaB translocation and the signaling cascade triggered by Toll-like receptors. Because of the molecular mimicry between beta 2 glycoprotein I and viral/bacterial structures-the natural ligands for Toll-like receptors (TLR)-antibodies might cross-link the molecule associated to the receptors eventually triggering their signaling.

Increased carotid artery intima-media thickness may be associated with stroke in primary antiphospholipid syndrome

OBJECTIVE

To investigate the prevalence and clinical significance of carotid artery intima-media thickness (IMT) in patients with primary antiphospholipid syndrome (APS).

METHODS

28 patients with primary APS with at least a five year follow up, and 28 healthy subjects, matched by age and sex, were included in the study. Colour Doppler with high resolution B mode carotid ultrasonography and spectral analysis were performed in patients and controls. Information on cardiovascular risk factors and the clinical course were collected.

RESULTS

The mean (SD) age of patients and controls (12 male, 16 female in each group) was 40 (8.5) years; the mean (SD) disease duration 7.7 (3) years. Carotid artery IMT was found in 23/28 patients (2.6 (1.14) mm) and 7/28 controls (1.2 (0.44)) (p=0.0001). A decrease in the lumen diameter was also found in 11/28 patients with primary APS without carotid atherosclerotic plaque, and 2/28 controls (p=0.004). Hyperlipidaemia, diabetes, smoking, obesity, and hypertension were not associated with carotid artery IMT. Patients with carotid artery IMT had arterial vascular disease more often than patients without: 9/23 v 0/5 (p<0.009). These patients had stroke (seven patients), myocardial infarction (one), and mesenteric thrombosis (one). Subjects with IMT had a threefold higher risk for stroke than those without IMT (95% CI 0.78 to 14.3).

CONCLUSIONS

Patients with primary APS have a high prevalence of carotid artery IMT and a decreased lumen diameter. IMT in primary APS may be associated with stroke. Patients with primary APS with IMT must be considered as carriers of atherosclerosis.

Cardiac involvement in systemic autoimmune diseases

The heart and the vascular system are frequent and characteristic targets of several systemic autoimmune diseases, in particular Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA) and Systemic Sclerosis (SSc). In this chapter we review the classic cardiac abnormalities and the more recent data about cardiovascular involvement as part of a major disease complication determining a substantial morbidity and mortality. In addition to the classic cardiac abnormalities involving the heart structures, acute and chronic ischemic heart disease and cerebrovascular accidents are threatening clinical manifestations of SLE and RA associated to an early accelerated atherosclerosis. Immune-mediated inflammation is now recognized as an important factor involved in the pathogenesis of atherosclerosis. Ongoing clinical studies are being devised to find specific risk factors associated with systemic autoimmune diseases and/or treatment regimens. Hopefully, prophylactic measures should be available within the next few years.