Abstract 2131: Bone Marrow-derived Macrophages May Contribute To Elevation Of Et-1 And Pulmonary Hypertension In Female Bmpr2 +/r899x Mutant Mice

Introduction: Mutation that causes loss of function of bone morphogenetic protein receptor 2 (BMPR2) has been implicated in the pathogenesis of Pulmonary Arterial Hypertension (PAH), a disease that currently has no cure and is characterized by elevated right ventricular systolic pressure and right ventricle hypertrophy. Females experience thrice more incidence of PAH. Elevation in the expression of ET-1, Endothelin-1, has been linked to the development of PAH. It is unclear what is contributing to the elevation of ET-1 observed in female mutants. Hypothesis: Macrophage activation in the microvasculature contributes to ET-1 elevation and PH pathogenesis in female BMPR2 +/R899X mice. Materials/Methods: Lung samples from 12-month-old male and female wild-type and BMPR2 +/R899X mutants were used for analysis of the ET-1 expression via Western Blot (WB). Accumulation of CD45+ET-1+ cells in the lungs was evaluated by immunohistochemistry (IHC). Finally, bone marrow-derived macrophages (BMDM) isolated from male and female mutant mice underwent a 24-hour treatment with 100 ng/mL Lipopolysaccharide (LPS) and vehicle (control) and ET-1 expression was measured in the cell lysate by WB. Results/Discussion: In exploring the source of ET-1, our initial findings indicated an accumulation in inflammatory perivascular cells. A double-blind analysis of the CD45 pan-leukocyte marker revealed a substantial increase in CD45+ cells in female mutants (4.09 +/- 0.68 and 10.46 +/- 1.15 CD45+ cells/microvessel, male and female, respectively; 8 micrographs/animal; 3 mice/group). Colocalization between CD45+ cells and ET-1 suggests these cells may be a source or contribute to ET-1 clearance in the lungs of female mutants. While the identity of CD45+ cells remain unclear, their morphology suggests they are likely macrophages. Indeed, preliminary results indicate a significant rise in ET-1 expression in BMDM from female mutants at baseline and upon LPS exposure. Conclusion: Accumulation of CD45+ cells in female mutant lungs, along with colocalization with ET-1, may contribute to PAH development. Additionally, increased ET-1 expression in macrophages from female mutant mice suggests macrophage activation as a potential factor in ET-1 elevation in female mutant lungs.