Serotonin 5-HT2B receptors are required for bone-marrow contribution to pulmonary arterial hypertension

Abstract

Abstract Pulmonary arterial hypertension (PAH) is a progressive disease characterized by lung endothelial dysfunction and vascular remodeling. Recently, bone marrow progenitor cells have been localized to PAH lungs, raising the question of their role in disease progression. Independently, serotonin (5-HT) and its receptors have been identified as contributors to the PAH pathogenesis. We hypothesized that 1 of these receptors, 5-HT2B, is involved in bone marrow stem cell mobilization that participates in the development of PAH and pulmonary vascular remodeling. A first study revealed expression of 5-HT2B receptors by circulating c-kit+ precursor cells, whereas mice lacking 5-HT2B receptors showed alterations in platelets and monocyte-macrophage numbers, and in myeloid lineages of bone marrow. Strikingly, mice with restricted expression of 5-HT2B receptors in bone marrow cells developed hypoxia or monocrotaline-induced increase in pulmonary pressure and vascular remodeling, whereas restricted elimination of 5-HT2B receptors on bone marrow cells confers a complete resistance. Moreover, ex vivo culture of human CD34+ or mice c-kit+ progenitor cells in the presence of a 5-HT2B receptor antagonist resulted in altered myeloid differentiation potential. Thus, we demonstrate that activation of 5-HT2B receptors on bone marrow lineage progenitors is critical for the development of PAH.