Erythrocyte-derived microvesicles induce arterial spasms in [JAK2.sup.V617F] myeloproliferative neoplasm

Arterial cardiovascular events are the leading cause of death in patients with [JAK2.sup.V617F] myeloproliferative neoplasms (MPNs). However, their mechanisms are poorly understood. The high prevalence of myocardial infarction without significant coronary stenosis or atherosclerosis in patients with MPNs suggests that vascular function is altered. The consequences of [JAK2.sup.V617F] mutation on vascular reactivity are unknown. We observe here increased responses to vasoconstrictors in arteries from [Jak2.sup.V617F] mice resulting from a disturbed endothelial NO pathway and increased endothelial oxidative stress. This response was reproduced in WT mice by circulating microvesicles isolated from patients carrying [JAK2.sup.V617F] and by erythrocyte-derived microvesicles from transgenic mice. Microvesicles of other cellular origins had no effect. This effect was observed ex vivo on isolated aortas, but also in vivo on femoral arteries. Proteomic analysis of microvesicles derived from [JAK2.sup.V617F] erythrocytes identified increased expression of myeloperoxidase as the likely mechanism accounting for their effect. Myeloperoxidase inhibition in microvesicles derived from [JAK2.sup.V617F] erythrocytes suppressed their effect on oxidative stress. Antioxidants such as simvastatin and W-acetyl cysteine improved arterial dysfunction in [Jak2.sup.V617F] mice. In conclusion, [JAK2.sup.V617F] MPNs are characterized by exacerbated vasoconstrictor responses resulting from increased endothelial oxidative stress caused by circulating erythrocyte-derived microvesicles. Simvastatin appears to be a promising therapeutic strategy in this setting.
Introduction Bcr/Abl-negative myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders characterized by the proliferation of particular hematopoietic lineages without blockage in cell maturation. They include polycythemia vera, essential thrombocythemia, [...]