Prothrombotic State, Platelet Activation and Netosis in Systemic Lupus Erythematosus

Introduction: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown origin characterized by a hypercoagulable state and a high mortality rate. Mechanisms that cause the accelerated deterioration of cardiovascular health in SLE are unknown. Objectives: to characterize the prothrombotic state in SLE patients by global coagulation assays and the contribution of platelets, endothelial damage, microparticles and neutrophil extracellular traps (NETs) in their prothombotic profile. Material and methods: 72 patients and 90 healthy controls were recruited. Patients were classified according to clinical characteristics in: 32 with lupus (SLE group), 29 with SLE and antiphospholipid antibodies (aFL, SLE+aFL group) and 12 who met the criteria for SLE and antiphospholipid syndrome (APS, SLE+APS group). Experimental protocol was approved by La Paz University Hospital Ethics Committee. Venous blood collected in BD sodium citrate tubes (3.2%) was centrifuged at 150 g for 20 min at 23oC to obtain platelet-rich plasma (PRP). PPP was obtained by centrifugation at 1500 g for 15 min at 23oC. To obtain neutrophils, whole blood was centrifuged to 1600 rpm 25 min using a Ficoll gradient and red cells were lysed. Rotational thromboelastometry (ROTEM®) was performed in naTEM condition. Clotting time (CT, time from start of measurement until initiation of clotting [in seconds]); alpha angle (tangent to the curve at 2-mm amplitude [in degrees]), Ax (clot firmness at time x, [in mm]) and maximum clot firmness (MCF, [in mm]) were recorded. Procoagulant activity associated to microparticle's content of tissue factor was determined in PPP by Calibrated Automated Thrombogram (CAT) using MP-reagent (4 mM phospholipids, Diagnostica Stago, Spain). We evaluated the endogenous thrombin potential (ETP, the total amount of thrombin generated over time); the lag time (the time to the beginning of the explosive burst of thrombin generation); the peak height of the curve (the maximum thrombin concentration produced) and the time to the peak. Thrombin generation associated to NETs was also measured by CAT. Neutrophils from healthy controls or from LES patients were stimulated with 100 nM PMA in RPMI medium during 45 min at 37o and then cocultivated with PRP adjusted to 105 platelets/µL. NETs formation was verified by fluorescent microscopy performed with DAPI and an anti-myeloperoxidase antibody. Plasma levels of LDL-ox, E-Selectin and PAI-1 were determined by Elisa (RD CSL Behring: Consultancy, Speakers Bureau; Roche: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Bayer: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Takeda: Research Funding; NovoNordisk: Consultancy, Speakers Bureau. Canales: Celgene: Honoraria; Gilead: Honoraria; Novartis: Honoraria; Janssen: Honoraria, Speakers Bureau; Sandoz: Honoraria; iQone: Honoraria; Takeda: Speakers Bureau; SOBI: Research Funding; Karyopharm: Honoraria; F. Hoffmann-La Roche Ltd: Honoraria, Speakers Bureau. Jimenez-Yuste: Bayer, CSL Behring, Grifols, Novo Nordisk, Octapharma, Pfizer, Roche, Sobi, Shire: Consultancy, Honoraria, Other: reimbursement for attending symposia/congresses , Research Funding, Speakers Bureau. Butta: Novartis: Consultancy; Roche, Pfizer: Speakers Bureau.