Abstract 10855: Murine Model of Phenylhydrazine-Induced Chronic Hemolytic Anemia Leads to Development of Early Pulmonary Hypertension

Abstract

Introduction: Pulmonary hypertension (PH) in sickle cell disease is associated with high morbidity and early mortality, yet the pathogenesis remains incompletely understood. In vitro data by our group implicates extracellular hemoglobin in the endothelial dysfunction that leads to precapillary vascular changes seen in PH and identifies endothelial to mesenchymal transition (EndoMT) as a likely mechanism. To support these findings, we hypothesize that a murine model of chronic hemolysis will show signs of EndoMT and early development of PH. Methods C57BL/6J mice were treated with 40 mg/kg of phenylhydrazine (PHZ), a toxin known to induce hemolysis, or saline, as control, twice a week for three weeks. Plasma cytokine concentrations and complete blood counts were measured. Non-invasive and invasive measures of PH were obtained by echocardiography (TTE), hemodynamic pressure assessments, and measures of right ventricular (RV) hypertrophy. Explanted lung tissue was homogenized and subjected to Western blot analysis to evaluate markers of EndoMT. Results PHZ administration causes anemia (9.1 g/dL vs 11.4 g/dL in control mice) without a significant drop in other hematopoietic cell lines. PHZ-treated mice have increased plasma cytokines CXCL1 and IL-6, which are known to be upregulated in PH. TTE shows significantly decreased pulmonary artery acceleration time (16.7 vs 19.5 msec, p < 0.05), and a trend toward decreased tricuspid annular plane systolic excursion in PHZ-treated mice (0.9 vs 1.2 mm). Invasive hemodynamics show a slight increase in right ventricular systolic pressure (25.6 vs 23.4 mm Hg) and analysis of RV hypertrophy shows increased Fulton index in PHZ-treated mice compared to control (0.28 vs 0.24). Western blot analysis of lung tissue shows upregulation of EndoMT transcription factor SNAI2 in PHZ-treated mice versus control. Conclusions PHZ-treated mice demonstrate early invasive and non-invasive signs of PH with upregulation of EndoMT transcription factor SNAI2, suggesting a relationship between hemolysis, EndoMT, and the development of PH. PHZ administration may be a novel murine model for PH due to chronic hemolysis, facilitating pathobiological and therapeutic discovery for this devastating complication of sickle cell disease.