Pulmonary arterial hypertension (PAH) is characterized by endothelial dysfunction, uncontrolled proliferation and migration of pulmonary arterial endothelial cells leading to increased pulmonary vascular resistance resulting in great morbidity and poor survival. Bone morphogenetic protein receptor II (BMPR2) plays an important role in the pathogenesis of PAH as the most common genetic mutation. Non-muscle myosin light chain kinase (nmMLCK) is an essential component of the cellular cytoskeleton and recent studies have shown that increased nmMLCK activity regulates biological processes in various pulmonary diseases such as asthma and acute lung injury. In this study, we aimed to discover the role of nmMLCK in the proliferation and migration of pulmonary arterial endothelial cells (HPAECs) in the pathogenesis of PAH. We used two cellular models relevant to the pathobiology of PAH including BMPR2 silenced and vascular endothelial growth factor (VEGF) stimulated HPAECs. Both models demonstrated an increase in nmMLCK activity along with a robust increase in cellular proliferation, inflammation, and cellular migration. The upregulated nmMLCK activity was also associated with increased ERK expression pointing towards a potential integral cytoplasmic interaction. Mechanistically, we confirmed that when nmMLCK is inhibited by MLCK selective inhibitor (ML-7), proliferation and migration are attenuated. In conclusion, our results demonstrate that nmMLCK upregulation in association with increased ERK expression may contribute to the pathogenesis of PAHby stimulating cellular proliferation and migration.

Introduction: Though the chronic, progressive disease Pulmonary Hypertension (PH) has no known cure, timely and appropriate treatment can improve outcomes. Social determinants of health (SDH) may influence treatment accessibility and outcomes. We hypothesized that Social Vulnerability Index (SVI) and Hardship Index (HDX, i.e., living in a zip code of higher hardship) are associated with measures of PH severity and quality of life (QoL). Methods: Patients at UI Health aged ≥18 years, diagnosed with PH from 2017-2021, and with EmPHasis-10 QoL scores and residence zip code data were included. SDH included Social Vulnerability Index (SVI) and Hardship Index (HDX). Income was retrieved from 2019 US Census data and most recent socio-behavioral data from the Chicago Health Atlas. Multivariate and logistic regression analysis were performed using SAS. Results: In 58 patients, mean age was 58 (SD 13.5), 47 (81.0%) were women, and 42 (72.4%) were non-Hispanic black. In this cohort, the uninsured rate showed a significant positive correlation with tricuspid regurgitant velocity on echocardiogram (p = 0.048) and, as SVI increased, there was a trend toward higher right atrial pressure (p = 0.07). Unexpectedly, there was a trend toward lower EmPHasis 10 scores (indicating better reported QoL) in subjects with worse SVI or HDX. When examining this further, a modified EmPHasis 10 QoL score focused on rest, exhaustion, and energy showed a significant inverse correlation of QoL with either SVI or HDX (p = .025 and p = .045, respectively). Conclusions: SDH appear to be associated with measures of PH severity. These findings suggest that SDH may negatively impact disease, which will need to be tested in a longitudinal study. The inverse correlation of SVI and HDX with QoL, particularly when focusing on personal experience, was unexpected. In theory, perceived norms and cultural context in high hardship, socially vulnerable communities may alter patient perception of disease impact on QoL. Future analysis should focus on further characterization of patient experiences in diverse populations with PH to ensure that we have accurate tools and are addressing the needs of our diverse community.

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.