Abstract 14224: JAK2V617F Red Blood Cells Promote Atherosclerosis and Thrombosis

Abstract

Elevated hematocrit is associated with cardiovascular risk; however, the causality and mechanisms are unclear. The JAK2V617F (JAK2VF) mutation markedly increases cardiovascular risk both in myeloproliferative disorders with elevated blood cell counts and in the much more prevalent clonal hematopoiesis of indeterminate potential with normal blood cell counts. Jak2VF mouse models with elevated white blood cells (WBC), platelets and red blood cells (RBCs) display accelerated atherosclerosis. However, whether Jak2VF RBCs promote atherogenesis and thrombosis independently from increased WBC and platelets remains uncertain. We used Erythropoietin Receptor (EpoR) Cre recombinase to generate a conditional knock-in of murine Jak2VF (VFEpoR) in the RBC lineage. Hyperlipidemic VFEpoR mice without elevated blood cell counts showed accelerated arterial thrombosis and increased atherosclerotic plaque necrosis. Induction of erythrocytosis with low dose erythropoietin (EPO) without concomitant leukocytosis or thrombocytosis further worsened thrombosis and atherosclerosis. VFEpoR atherosclerotic lesions featured endothelial barrier breakdown, RBC infiltration, iron deposition, lipid peroxidation, macrophage erythrophagocytosis and macrophage ferroptosis. VFEpoR RBCs had reduced antioxidant defenses and contained increased ROS and lipid hydroperoxides. Phagocytosis of murine or human WT or Jak2 VF RBCs by WT macrophages induced lipid peroxidation and ferroptotic death that was prevented by the ferroptosis inhibitor Liproxstatin-1. Ferroptosis inhibition reversed increased atherosclerosis and necrotic core formation in VFEpoR mice but had no impact in controls. These studies demonstrate that both qualitative and quantitative defects in Jak2VF RBCs accelerate atherosclerosis and thrombosis. Phagocytosis of WT or Jak2VF RBCs by macrophages leads to ferroptotic cell death, suggesting ferroptosis as a new therapeutic target to reduce RBC-mediated cardiovascular risk.