Study of the Efficiency of Hydroxychloroquine on the Endothelial Dysfunction and Its Vascular Consequences During the Antiphospholipid Syndrome

Antiphospholipid Syndrome (APS)

This study evaluates the benefits of hydroxychloroquine on arterial function in antiphospholipid syndrome. Briefly, the patients will be randomized in two groups, one will receive hydroxychloroquine and standard treatment, the other will receive placebo in addition of standard treatment.

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by recurrent thrombotic events and miscarriages, with persistently positive antiphospholipid antibodies (aPL). APS may be isolated (primary APS) or associated to a connective tissue disease, most often systemic lupus erythematous (SLE). Pathogenic effects of aPL were first described by the demonstration that in vitro incubation of endothelial cells or monocytes with aPL induce an endothelial dysfunction characterized by pro-coagulant (overexpression of tissue factor and modulation of protein C and S), pro-inflammatory (increased level of IL-6(interleukin 6) , IL-1β and TNFα) and pro-adhesive (increased levels of ICAM-1(intercellular adhesion molecule ), VCAM-1 (vascular endothelial cell adhesion molecule) and E-selectin) phenotypes. In parallel the investigators and others reported that endothelial function, assessed by flow mediated dilatation, is altered in patients with primary and secondary forms of APS. Although a role for TLR (toll-like receptor )-mediated NFkB translocation has been advanced, the pathogenic mechanisms that lead to in vivo endothelial injury in APS are incompletely understood. In an experimental model, the investigators demonstrated that passive transfer of human aPL to mice induced a marked endothelial dysfunction assessed ex vivo in small resistance arteries, and an increase in TNFα levels. Moreover, the investigators group have demonstrated that patients with primary arterial APS display endothelial dysfunction and structural arterial changes, associated with a pro-oxidative and pro-coagulant state and with activation of the TLR2 and TLR4 signalling pathways. Recently, in a preliminary study the investigators have found that endothelial glycocalyx which is an important part of the vascular barrier and which is intimately linked to the homeostatic functions of the endothelium was altered in APL patients. Hydroxychloroquine (HCQ) is an antimalarial drug, also used to treat rheumatic diseases such as SLE. There is experimental evidence to suggest a direct role of hydroxychloroquine on the pathophysiology of APS: it directly reduces the binding of antibodies on the phospholipid bilayers, protects the annexin A5 anticoagulant shield and it reverses platelet adhesion induced by aPL. Furthermore it is known to decrease the expression of lysosomal TLRs, but also extra lysosomal TLR2 and TLR4. The aim of this study is to investigate whether treatment with hydroxychloroquine modulates vascular endothelial function in patients.

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