Studio delle alterazioni post-traduzionali e funzionali del fibrinogeno in pazienti con lupus eritematoso sistemico

Fibrinogen is a plasma glycoprotein with an average concentration of 200-400 mg/dl and a central role in coagulation, being crucial in fibrin clot assembly. Many studies in literature revealed that oxidative modifications of fibrinogen are significantly associated with altered protein function and structure in several haemostatic system disorders. However, a higher risk of thrombotic events has been also observed in autoimmunity, suggesting the emerging relation between inflammation and thrombosis. Among autoimmune disorders, Systemic Lupus Erythematosus (SLE) is an autoimmune disease with multi-systemic clinical manifestations and unpredictable course. The majority of clinical signs are due to vascular system affections; accordingly, the main cause of mortality in SLE patients with a long standing disease is represented by cardiovascular events. However, the pathophysiological mechanisms of cardiovascular risk in SLE are still under debate. Based on this background, the aim of the project was to evaluate systemic oxidative stress effects on functional and structural properties of fibrinogen purified from SLE patients. In 144 SLE patients and 190 sex- and age-matched healthy subjects, blood leukocyte intracellular ROS (Reactive Oxygen Species) levels were detected by FACS analysis. Plasma oxidative stress markers- Thiobarbituric Acid-Reactive Substances (TBARS) as an index of lipid peroxidation and Oxygen Radical Absorbance Capacity (ORAC) for the assessment of total antioxidant capacity- and fibrinogen di-tyrosine content, an indicator of protein oxidation, were measured using fluorometric assays. Furthermore, thrombin-catalyzed fibrin polymerization and plasmin-induced fibrinolysis were investigated in patients and controls. Finally, fibrinogen secondary structure and conformational properties were also explored by Circular Dichroism Spectroscopy (CD) and Intrinsic Fluorescence (FI) respectively. Our results described an altered redox status in SLE patients and a significant association of fibrinogen oxidative modification with changes in its structural and functional properties, leading to a pro-thrombotic phenotype. This evidence suggests a crucial role of oxidative stress and fibrinogen oxidation in the increased cardiovascular risk in SLE patients. Further investigations are needed in order to evaluate the effects of therapeutic supplementations with antioxidants on redox status and fibrinogen features in SLE.