Objective: Erythropoietin (EPO) treatment has become the standard treatment of renal anemia. Though a link between hematopoiesis-stimulating drugs and thrombosis has not been proven, it is generally assumed that systemic application of EPO and its analogues increases the risk for thrombotic events.
Methods and results: Here we show in C57BL/6J mice that 4-week treatment with the long-lasting EPO analogue darbepoetin-alpha (DPO) at a dose of 10 microg/kg/week induces a reduction of platelet reactivity using flow cytometry and Western blot analysis of tyrosine-specific platelet phosphorylation. Additionally, immunohistochemistry of endothelial adhesion molecule expression and ELISA of circulating endothelial activation markers demonstrated a reduced endothelial activation. Immunohistochemistry and RT-PCR analysis revealed a significant (P<0.05) increase of eNOS expression. Further, DPO did not exert prothrombogenic effects in a murine intravital microscopic thrombosis model of the cremaster muscle. The role of eNOS in prevention of DPO-mediated microvascular thrombosis is further underlined by a significantly accelerated thrombus formation on DPO treatment in eNOS (-/-) mice.
Conclusion: Thus, DPO-related erythropoiesis with a raised hematocrit is not associated with an increased risk for thrombosis as long as endothelial NO production serves as compensatory mechanism.