Importance of Serotonergic Mechanisms in the Thrombotic Complications in Hemodialyzed Patients Treated with Erythropoietin

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Abstract
So far it is not clear how erythropoietin affects the anticoagulant properties of vascular endothelium in uremia. Since serotonin is also thought to play a role in the pathogenesis of thrombosis, the aim of the study was to evaluate major components of extrinsic coagulation pathway, markers of endothelial cell injury, lipoprotein (a) and peripheral serotonergic mechanisms during rHuEPO therapy in hemodialyzed patients. The study was performed on chronically hemodialyzed patients divided into two groups: with rHuEPO treatment and without rHuEPO therapy in relation to the control group. In uremic patients, thrombomodulin and von Willebrand factor, activity of factor VII, tissue factor pathway inhibitor (TFPI) activity, TFPI and tissue factor (TF) concentrations, lipoprotein (a) level were significantly higher when compared to healthy volunteers. Treatment with rHuEPO resulted in a further significant rise in markers of endothelial cell injury: thrombomodulin and von Willebrand factor and TFPI concentration. Extrinsic coagulation factors: activities of factor VII and X, TFPI activity and TF activity and concentration, lipoprotein (a) and vitronectin remained unchanged during rHuEPO therapy. Platelet serotonin content and whole blood serotonin were significantly lower in uremic patients relative to healthy volunteers and during rHuEPO treatment they increased significantly. Whole blood serotonin reached normal values. Plasma serotonin, significantly elevated in uremia, did not change during rHuEPO therapy. Serotonin uptake by uremic platelets was significantly impaired and remained unaltered during rHuEPO administration. Serotonin release by uremic platelets was also significantly depressed but a significant improvement was observed in rHuEPO-treated patients. Our data suggest that endothelial injury, TF pathway components and peripheral serotonergic system disturbances may predispose to thromboembolic complications and play a role in the pathogenesis of atherosclerosis in uremic patients, particularly treated with rHuEPO. Increase in TFPI may compensate the increase in TF in these patients.