The antithrombotic effect of the aminoestrogen prolame (N-(3-hydroxy-1,3,5(10)-estratrien-17B-YL)-3-hydroxypropylamine) is linked to an increase in nitric oxide production by platelets and endothelial cells

Objective: Women under hormone replacement therapy carry an increased risk of venous thromboembolism (VTE), mostly during the first year. Despite great efforts devoted to hormone therapy research, VTE remains a major drawback of estrogenic therapy, and the search for new compounds continues. We have synthesized and evaluated prolame, an aminoestrogen with anticoagulant properties. The aim of our work was to elucidate the anticoagulant mechanism of prolame. Methods: We studied the effects of prolame on nitric oxide (NO) synthesis in cultured endothelial cells and platelets using flow cytometry, on NO metabolites using a modified Griess method, on NO formation in vivo using electron paramagnetic resonance spectroscopy, on participation of nuclear estrogen receptors using flow cytometry, and on endothelial NO synthase (eNOS) mRNA expression using RT-PCR. We also studied the impact of prolame-treated endothelial cells (EC) on ADP-induced platelet aggregation, as well as the ability to prevent occlusive thrombi in an in vivo mice thrombosis model. Results: (a) Prolame induces NO production in ECs, platelets, and in a mouse model in vivo. (b) The NO-elevating effect of prolame can only be partially attributed to the nuclear estrogen receptors (ERs) since endothelial nitric oxide synthase (e-NOS) is slightly induced (37%) in ECs treated with prolame. (c) Platelets become 60% less responsive to aggregation induced by 10 mu M ADP when in suspension with prolame-treated ECs. (d) Prolame reduces the formation of thrombi in an in vivo thrombosis model. Conclusions: Prolame could be a preferred alternative to other estrogens because of its reduced thromboembolic risk. (C) 2009 Elsevier Ireland Ltd. All rights reserved.