Fatty acid metabolism promotes TRPV4 activity in lung microvascular endothelial cells in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a morbid disease characterized by significant lung endothelial cell (EC) dysfunction. Prior work has shown that microvascular endothelial cells (MVECs) isolated from animals with experimental PAH and patients with PAH exhibit significant abnormalities in metabolism and calcium signaling. With regards to metabolism, we and others have shown evidence of increased aerobic glycolysis and evidence of increased utilization of alternate fuel sources (such as fatty acids) in PAH EC. In the realm of calcium signaling, our prior work linked increased activity of the transient receptor potential vanilloid-4 (TRPV4) channel to increased proliferation of MVECs isolated from the Sugen/Hypoxia rat model of PAH (SuHx-MVECs). However, the relationship between metabolic shifts and calcium abnormalities was not clear. Specifically, whether shifts in metabolism were responsible for increasing TRPV4 channel activity in SuHx-MVECs was not known. In this study, using human data, serum samples from SuHx rats, and SuHx-MVECs, we describe the consequences of increased MVEC fatty acid oxidation in PAH. In human samples, we observed an increase in long-chain fatty acid levels that was associated with PAH severity. Next, using SuHx rats and SuHx-MVECs, we observed increased intracellular levels of lipids. We also show that increasing intracellular lipid content increases TRPV4 activity, whereas inhibiting fatty acid oxidation normalizes basal calcium levels in SuHx-MVECs. By exploring the fate of fatty acid-derived carbons, we observed that the metabolite linking increased intracellular lipids to TRPV4 activity was ß-hydroxybutyrate (BOHB), a product of fatty acid oxidation. Finally, we show that BOHB supplementation alone is sufficient to sensitize the TRPV4 channel in rat and mouse MVECs. Returning to humans, we observe a transpulmonary BOHB gradient in human patients with PAH. Thus, we establish a link between fatty acid oxidation, BOHB production, and TRPV4 activity in MVECs in PAH. These data provide new insight into metabolic regulation of calcium signaling in lung MVECs in PAH.NEW & NOTEWORTHY In this paper, we explore the link between metabolism and intracellular calcium levels in microvascular endothelial cells (MVECs) in pulmonary arterial hypertension (PAH). We show that fatty acid oxidation promotes sensitivity of the transient receptor potential vanilloid-4 (TRPV4) calcium channel in MVECs isolated from a rodent model of PAH.

Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension due to septic emboli.

We present the case of a 28-year-old woman with a history of tricuspid valve endocarditis leading to chronic thromboembolic pulmonary hypertension (CTEPH) with multiple pulmonary artery chronic total occlusions (CTOs) due to septic emboli. Following a multidisciplinary care discussion, the patient was brought forward for balloon pulmonary angioplasty (BPA) with successful revascularization of all chronically occluded territories. This case highlights advances in pulmonary artery CTO interventions and demonstrates the feasibility of BPA for CTEPH patients with a history of septic emboli.

Premorbid weight in pulmonary arterial hypertension.

Relationships between obesity and outcomes in pulmonary arterial hypertension (PAH) are complex. Previous work suggested obesity, occurring alongside PAH, may be associated with better survival. In our work, we suggest obesity prior to PAH development is associated with worse survival. This may add a novel temporal element to the "obesity-paradox."

Regional Variation in Pulmonary Arterial Hypertension in the United States: The Pulmonary Hypertension Association Registry.

Rationale: Pulmonary arterial hypertension (PAH) is a heterogeneous disease within a complex diagnostic and treatment environment. Other complex heart and lung diseases have substantial regional variation in characteristics and outcomes; however, this has not been previously described in PAH. Objectives: To identify baseline differences between U.S. census regions in the characteristics and outcomes for participants in the Pulmonary Hypertension Association Registry (PHAR). Methods: Adults with PAH were divided into regional groups (Northeast, South, Midwest, and West), and baseline differences between census regions were presented. Kaplan-Meier survival analyses and Cox proportional hazards were used to estimate the association between region and mortality in unadjusted and adjusted models. Results: Substantial differences by census regions were seen in age, race, ethnicity, marital status, employment, insurance payor breakdown, active smoking, and current alcohol use. Differences were also seen in PAH etiology and baseline 6-minute walk distance test results. Treatment characteristics varied by census region, and mortality appeared to be lower in PHAR participants in the West (hazard ratio, 0.60; 95% confidence interval, 0.43-0.83, P = 0.005). This difference was not readily explained by differences in demographic characteristics, PAH etiology, baseline severity, baseline medication regimen, or disease prevalence. Conclusions: The present study suggests significant regional variation among participants at accredited pulmonary vascular disease centers in multiple baseline characteristics and mortality. This variation may have implications for clinical research planning and represent an important focus for further study to better understand whether there are remediable care aspects that can be addressed in the pursuit of providing equitable care in the United States.

Transpulmonary amino acid metabolism in the sugen hypoxia model of pulmonary hypertension.

In pulmonary artery hypertension (PAH), emerging evidence suggests that metabolic abnormalities may be contributing to cellular dysfunction in PAH. Metabolic abnormalities such as glycolytic shift have been observed intracellularly in several cell types in PAH, including microvacular endothelial cells (MVECs). Concurrently, metabolomics of human PAH samples has also revealed a variety of metabolic abnormalities; however the relationship between the intracellular metabolic abnormalities and the serum metabolome in PAH remains under investigation. In this study, we utilize the sugen/hypoxia (SuHx) rodent model of PAH to examine the RV, LV and MVEC intracellular metabolome (using targeted metabolomics) in normoxic and SuHx rats. We additionally validate key findings from our metabolomics experiments with data obtained from cell culture of normoxic and SuHx MVECs, as well as metabolomics of human serum samples from two different PAH patient cohorts. Taken together, our data, spanning rat serum, human serum and primary isolated rat MVECs reveal that: (1) key classes of amino acids (specifically, branched chain amino acids-BCAA) are lower in the pre-capillary (i.e., RV) serum of SuHx rats (and humans); (2) intracellular amino acid levels (in particular BCAAs) are increased in SuHx-MVECs; (3) there may be secretion rather than utilization of amino acids across the pulmonary microvasculature in PAH and (4) an oxidized glutathione gradient is present across the pulmonary vasculature, suggesting a novel fate for increased glutamine uptake (i.e., as a source of glutathione). in MVECs in PAH. In summary, these data reveal new insight into the shifts in amino acid metabolism occurring across the pulmonary circulation in PAH.

Establishing a balloon pulmonary angioplasty program for chronic thromboembolic pulmonary hypertension: A United States single-center experience.

INTRODUCTION: Balloon pulmonary angioplasty (BPA) is a less invasive treatment alternative for patients with chronic thromboembolic pulmonary hypertension (CTEPH) who are unable to move forward with pulmonary thromboendarterectomy. This report describes a single-center experience with a nascent BPA program in the United States (US). METHODS: All patients who underwent BPA between August 2018-2021 were included in this retrospective, single-center observational cohort. Pre- and post-procedure clinical information was collected, along with procedural characteristics. RESULTS: Thirty patients began their BPA series during the study period. The majority of patients had segmental disease (n = 25, 83.3%). A total of 135 BPA procedures were performed on 417 segments. On average, patients completed 4.5 sessions and the majority of patients (n = 23, 76.7%) underwent more than 2. There were 24 episodes of hemoptysis and 20 procedural events that required treatment, typically with either heparin reversal or balloon tamponade. Of 26 participants with completed series, mean PA pressure (-6 mmHg, 95% CI -9 to -4 mmHg, p = 0.0001), PVR (-1.9 Wood units, 95% CI -2.9 to -1.0, p = 0.0002), and pulmonary compliance (-1.0 mL/mmHg, 95% CI -1.5 to -0.5, p = 0.0002) improved. Improvement was also seen in NYHA functional classification and walk distance (p = 0.01). Two deaths occurred, with one death peri-procedurally. CONCLUSION: This paper describes an early experience with BPA at a single US center. Improvement in non-invasive and invasive metrics were seen without adding a significant morbidity to an already high-risk patient population.

Metabolomic Signatures Associated With Pulmonary Arterial Hypertension Outcomes.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a complex disease characterized by progressive right ventricular (RV) failure leading to significant morbidity and mortality. Investigating metabolic features and pathways associated with RV dilation, mortality, and measures of disease severity can provide insight into molecular mechanisms, identify subphenotypes, and suggest potential therapeutic targets. METHODS: We collected data from a prospective cohort of PAH participants and performed untargeted metabolomic profiling on 1045 metabolites from circulating blood. Analyses were intended to identify metabolomic differences across a range of common metrics in PAH (eg, dilated versus nondilated RV). Partial least squares discriminant analysis was first applied to assess the distinguishability of relevant outcomes. Significantly altered metabolites were then identified using linear regression, and Cox regression models (as appropriate for the specific outcome) with adjustments for age, sex, body mass index, and PAH cause. Models exploring RV maladaptation were further adjusted for pulmonary vascular resistance. Pathway enrichment analysis was performed to identify significantly dysregulated processes. RESULTS: A total of 117 participants with PAH were included. Partial least squares discriminant analysis showed cluster differentiation between participants with dilated versus nondilated RVs, survivors versus nonsurvivors, and across a range of NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels, REVEAL 2.0 composite scores, and 6-minute-walk distances. Polyamine and histidine pathways were associated with differences in RV dilation, mortality, NT-proBNP, REVEAL score, and 6-minute walk distance. Acylcarnitine pathways were associated with NT-proBNP, REVEAL score, and 6-minute walk distance. Sphingomyelin pathways were associated with RV dilation and NT-proBNP after adjustment for pulmonary vascular resistance. CONCLUSIONS: Distinct plasma metabolomic profiles are associated with RV dilation, mortality, and measures of disease severity in PAH. Polyamine, histidine, and sphingomyelin metabolic pathways represent promising candidates for identifying patients at high risk for poor outcomes and investigation into their roles as markers or mediators of disease progression and RV adaptation.

Circulating markers of inflammation and angiogenesis and clinical outcomes across subtypes of pulmonary arterial hypertension.

BACKGROUND: Subtypes of pulmonary arterial hypertension (PAH) differ in both fundamental disease features and clinical outcomes. Angiogenesis and inflammation represent disease features that may differ across subtypes and are of special interest in connective tissue disease-associated PAH (CTD-PAH). We compared inflammatory and angiogenic biomarker profiles across different etiologies of PAH and related them to clinical outcomes. METHODS: Participants with idiopathic PAH, CTD-PAH, toxin-associated PAH (tox-PAH), or congenital heart disease-associated PAH (CHD-PAH) were enrolled into a prospective observational cohort. Baseline serum concentrations of 33 biomarkers were related to 3-year mortality, echocardiogram, REVEAL score, and 6-minute walk distance (6MWD). Findings were validated using plasma proteomic data from the UK PAH Cohort Study. RESULTS: One hundred twelve patients were enrolled: 45 idiopathic, 27 CTD-PAH, 20 tox-PAH, and 20 CHD-PAH. Angiogenic and inflammatory biomarkers were distinctly elevated within the CTD-PAH cohort. Six biomarkers were associated with mortality within the entire PAH cohort: interleukin-6 (IL-6, HR:1.6, 95% CI:1.18-2.18), soluble fms-like tyrosine kinase 1 (sFlt-1, HR:1.35, 95% CI:1.02-1.80), placental growth factor (PlGF, HR:1.55, 95% CI:1.07-2.25), interferon gamma-induced protein 10 (IP-10, HR:1.44, 95% CI:1.04-1.99), tumor necrosis factor-beta (TNF-ß, HR:1.81, 95% CI:1.11-2.95), and NT-proBNP (HR:2.19, 95% CI:1.52-3.14). Only IL-6 and NT-proBNP remained significant after controlling for multiple comparisons. IL-6, IP-10, and sFlt-1 significantly associated with mortality in CTD-PAH, but not non-CTD-PAH subgroups. In the UK cohort, IP-10, PlGF, TNF-ß, and NT-proBNP significantly associated with 5-year survival. CONCLUSION: Levels of angiogenic and inflammatory biomarkers are elevated in CTD-PAH, compared with other etiologies of PAH, and may correlate with clinical outcomes including mortality.

A World of Maximalist Medicine: Physician Perspectives on Palliative Care and End-of-life for Patients With Pulmonary Arterial Hypertension.

CONTEXT: Physicians who specialize in pulmonary arterial hypertension (PAH) care for patients facing a serious, life-limiting illness. Palliative care is underutilized in patients with PAH, and little is known about how best to provide palliative care to this patient population. OBJECTIVES: Using a qualitative approach, assess physicians' perspectives on barriers and facilitators to the use of palliative care in PAH. METHODS: Participants were board-certified pulmonologists and cardiologists recruited from the Pulmonary Hypertension Association's list of physician specialists and academic center websites. We performed one-on-one semi-structured interviews that were recorded, transcribed, and analyzed using thematic analysis. RESULTS: Twelve physicians participated in the study, with a median age of 48.5 years and 20.5 years of clinical experience caring for patients with PAH. We identified the following themes and associated barriers and facilitators to effective implementation of palliative care for patients with PAH: a tailored approach to the individual patient; a PAH-specialist-led culture of care; effective collaboration with palliative care clinicians; and limitations imposed by health systems. CONCLUSION: PAH physicians are open to palliative care for their patients and are willing to partner with palliative care clinicians to implement this effectively and in the right setting. Areas for targeted improvement in enhancing palliative care for patients with PAH exist, especially enhancing collaboration between PAH physicians and palliative care specialists and navigating barriers in health systems.

Stress-triggered hematopoietic stem cell proliferation relies on PrimPol-mediated repriming.

Stem cell division is linked to tumorigenesis by yet-elusive mechanisms. The hematopoietic system reacts to stress by triggering hematopoietic stem and progenitor cell (HSPC) proliferation, which can be accompanied by chromosomal breakage in activated hematopoietic stem cells (HSCs). However, whether these lesions persist in their downstream progeny and induce a canonical DNA damage response (DDR) remains unclear. Inducing HSPC proliferation by simulated viral infection, we report that the associated DNA damage is restricted to HSCs and that proliferating HSCs rewire their DDR upon endogenous and clastogen-induced damage. Combining transcriptomics, single-cell and single-molecule assays on murine bone marrow cells, we found accelerated fork progression in stimulated HSPCs, reflecting engagement of PrimPol-dependent repriming, at the expense of replication fork reversal. Ultimately, competitive bone marrow transplantation revealed the requirement of PrimPol for efficient HSC amplification and bone marrow reconstitution. Hence, fine-tuning replication fork plasticity is essential to support stem cell functionality upon proliferation stimuli.

Thyroid-stimulating hormone and mortality in pulmonary arterial hypertension.

INTRODUCTION: Pulmonary arterial hypertension (PAH) remains a serious and life-threatening illness. Thyroid dysfunction is relatively understudied in individuals with PAH but is known to affect cardiac function and vascular tone in other diseases. The aim of this observational study was to evaluate the association between thyroid-stimulating hormone (TSH), mortal and non-mortal outcomes in individuals with PAH. METHODS: The Seattle Right Ventricle Translational Science (Servetus) Study is an observational cohort that enrolled participants with PAH between 2014 and 2016 and then followed them for 3 years. TSH was measured irrespective of a clinical suspicion of thyroid disease for all participants in the cohort. Linear regression was used to estimate the relationships between TSH and right ventricular basal diameter, tricuspid annular plane systolic excursion and 6-minute walk distance. Logistic regression was used to estimate the relationship with New York Heart Association Functional Class, and Cox proportional hazards were used to estimate the relationship with mortality. Staged models included unadjusted models and models accounting for age, sex at birth and aetiology of pulmonary hypertension with or without further adjustment for N-terminal-pro hormone brain natriuretic peptide. RESULTS: Among 112 participants with PAH, TSH was strongly associated with mortality irrespective of adjustment. There was no clear consistent association between TSH and other markers of severity in a cohort with PAH. DISCUSSION: This report reinforces the important observation that TSH is associated with survival in patients with PAH, and future study of thyroid dysfunction as a potential remediable contributor to mortality in PAH is warranted.

Prevalence, incidence, and survival of pulmonary arterial hypertension: A systematic review for the global burden of disease 2020 study.

Pulmonary arterial hypertension (PAH) is characterized by increased resistance in the pulmonary arterioles as a result of remodeled blood vessels. We sought all available epidemiologic data on population-based prevalence, incidence, and 1-year survival of PAH as part of the Global Burden of Disease Study. We performed a systematic review searching Global Index Medicus (GIM) for keywords related to PAH between 1980 and 2021 and identified population-representative sources of prevalence, incidence, and mortality for clinically diagnosed PAH. Of 6772 articles identified we found 65 with population-level data: 17 for prevalence, 17 for incidence, and 58 reporting case fatality. Reported prevalence ranged from 0.37 cases/100,000 persons in a referral center of French children to 15 cases/100,000 persons in an Australian study. Reported incidence ranged from 0.008 cases/100,000 person-years in Finland, to 1.4 cases/100,000 person-years in a retrospective chart review at a clinic in Utah, United States. Reported 1-year survival ranged from 67% to 99%. All studies with sex-specific estimates of prevalence or incidence reported higher levels in females than males. Studies varied in their size, study design, diagnostic criteria, and sampling procedures. Reported PAH prevalence, incidence, and mortality varied by location and study. Prevalence ranged from 0.4 to 1.4 per 100,000 persons. Harmonization of methods for PAH registries would improve efforts at disease surveillance. Results of this search contribute to ongoing efforts to quantify the global burden of PAH.

Endothelial-derived von Willebrand factor accelerates fibrin clotting within engineered microvessels.

BACKGROUND: Von Willebrand factor (VWF) is classically associated with primary hemostasis and platelet-rich arterial thromboses, but recently has also been implicated in fibrin clotting and venous thrombosis. Direct interaction between fibrin and VWF may mediate these processes, although prior reports are conflicting. OBJECTIVES: We combined two complementary platforms to characterize VWF-fibrin(ogen) interactions and identify their potential physiologic significance. METHODS: Engineered microvessels were lined with human endothelial cells, cultured under flow, and activated to release VWF and form transluminal VWF fibers. Fibrinogen, fibrin monomers, or polymerizing fibrin were then perfused, and interactions with VWF evaluated. Thrombin and fibrinogen were perfused into living versus paraformeldahyde-fixed microvessels and the pressure drop across microvessels monitored. Separately, protein binding to tethered VWF was assessed on a single-molecule level using total internal reflection fluorescence (TIRF) microscopy. RESULTS: Within microvessels, VWF fibers colocalized with polymerizing fibrin, but not fibrinogen. TIRF microscopy showed no colocalization between VWF and fibrinogen or fibrin monomers in a microfluidic flow chamber across a range of shear rates and protein concentrations. Thrombin-mediated fibrin polymerization within living microvessels triggered endothelial VWF release, increasing the rate and amount of microvessel obstruction compared to fixed vessels with an inert endothelium. CONCLUSIONS: We did not identify specific binding between fibrin(ogen) and VWF at a single-molecule level. Despite this, our results suggest that rapid release of endothelial VWF during clotting may provide a physical support for fibrin polymerization and accelerate thrombosis. This interaction may be of fundamental importance for the understanding and treatment of human thrombotic disease.

Association of soluble Flt-1 with heart failure and cardiac morphology: The MESA angiogenesis study.

BACKGROUND: Soluble Fms-like tyrosine kinase 1 (sFlt-1) may inhibit angiogenesis. Higher levels of sFlt-1 are associated with worse prognosis in prevalent heart failure patients. The aim of this study was to better understand the role of sFlt-1 in heart failure pathogenesis by characterizing relationships between sFlt-1, cardiac morphology, and the composite outcome of incident heart failure or cardiovascular (CV) death in in a multiethnic cohort free of CV disease at baseline. METHODS: sFlt-1 was measured in 1,381 participants in the Multi-Ethnic Study of Atherosclerosis Angiogenesis sub-study. Linear regression was used to estimate the association between sFlt-1 and cardiac morphology and Cox proportional hazard regression was used to estimate associations with incident heart failure or CV mortality. RESULTS: Over a median follow-up of 13.1 years, higher sFlt-1 levels were associated with incident heart failure or CV mortality independent from CV risk factors or NT-proBNP levels (HR 1.17, 95% CI 1.10-1.26, p < 0.001). Higher sFlt-1 levels were also associated with greater baseline left ventricular (LV) mass by cardiac MRI and increased loss of LV mass over the 10 years following the baseline exam (p-value 0.02 for each), but this association was no longer statistically significant after adjustment for baseline NT-proBNP (p = 0.11 and 0.10 respectively). CONCLUSIONS: Baseline sFlt-1 levels are associated with incident heart failure and cardiovascular mortality independent of traditional CV risk factors or NT-proBNP. An association was also found with cardiac mass but was no longer significant after adjustment for NT-proBNP.

Histamine H2 Receptor Antagonists and Heart Failure Risk in Postmenopausal Women: The Women's Health Initiative.

Background Prior studies suggested lower risk of heart failure (HF) in individuals taking H2 receptor antagonists (H2RA) compared with H2RA nonusers in relatively small studies. We evaluated the association of H2RA use and incident HF in postmenopausal women in the large-scale WHI (Women's Health Initiative) study. Methods and Results This study included postmenopausal women from the WHI without a history of HF at baseline. HF was defined as first incident hospitalization for HF and physician adjudicated. Multivariable Cox proportional hazards regression models evaluated the association of H2RA use as a time-varying exposure with HF risk, after adjustment for demographic, lifestyle, and medical history variables. Sensitivity analyses examined (1) risk of HF stratified by the ARIC (Atherosclerosis Risk in Communities) score, (2) propensity score matching on H2RA use, (3) use of proton pump inhibitors rather than H2RA nonuse as the referent, and (4) exclusion of those taking diuretics at baseline. The primary analysis included 158 854 women after exclusion criteria, of whom 9757 (6.1%) were H2RA users. During median 8.2 years of follow-up, 376 H2RA users (4.9 events/1000 person-years) and 3206 nonusers (2.7 events/1000 person-years) developed incident HF. After multivariable adjustment, there was no association between H2RA use and HF in the primary analysis (hazard ratio, 1.07; 95% CI, 0.94-1.22; P=0.31) or in any of the sensitivity analyses. Conclusions Clinical H2RA use was not associated with incident HF among postmenopausal women. Future studies are needed to evaluate potential effect modification by sex, HF severity, or patterns of use on H2RA exposure and HF risk. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT00000611.