BMPR2 Mutations Research Articles

Abstract 4134148: Reduced BMPR2 in Monocytes De-represses HERV-K and Sustains Inflammation in Pulmonary Arterial Hypertension

Background&Rationale: Human endogenous retroviral (HERV) elements are embedded in 8% of our genome. They remain quiescent but can be transiently activated by viral infection to induce an interferon (IFN) response. In pulmonary arterial hypertension (PAH), HERV-K expression is elevated in myeloid cells, and thus can promote inflammation observed in pulmonary arteries (PAs) with progressive obstructive remodeling. PAH is linked to a mutation or a decrease in BMPR2 expression which our laboratory has recently shown in monocytes (MONO). HERVs are silenced by SUMOylated (S) TRIM28 (KAP1, a methylase) and SPEN (a histone deacetylase) factors that are also sequestered by the lnc RNA XIST which is increased in females to inactivate the extra X-chromosome. When TRIM28 is phosphorylated (P) by DNA-PK, it loses methylase activity and can act as a transcription factor. Hypothesis: Reduced BMPR2 in MONO results in DNA-PK mediated P-TRIM28 causing demethylation of XIST targets (X-related genes) and HERV-K thus increasing their expression. Competitive SPEN binding to the increased XIST also de-represses HERV-K . Approach: We used THP-1 MONOs with BMPR2 shRNA and induced pluripotent stem cell (i) MONOs derived from BMPR2 mutant PAH patients and assessed HERV-K , XIST , IFNs and related our findings to DNA-PK–P-TRIM28 and sequestration of SPEN. Results: XIST and HERV-K mRNA were significantly elevated in THP-1 MONOs with shBMPR2 vs. shControl and in PAH-iMONO vs. control iMONO based on gender. Reduced BMPR2 also increased IFN genes. These findings were consistent with nuclear DNA-PK and P-TRIM28 shown to bind in affinity purification mass spectrometry analysis. Bisulfite conversion assay demonstrated decreased methylation of HERV-K in BMPR2 -deficient MONOs attributed to a reduction in the methylase S-TRIM28. RNA-IP in THP-1 MONOs with shBMPR2 vs. shControl indicated increased binding of XIST with TRIM28 and SPEN, suggesting a competitive reduction in binding to HERV-K. Conclusions: Loss of BMPR2 increases XIST and HERV-K in MONO related to DNA-PK induced P-TRIM28 and reduced methylase S-TRIM28. Increased HERV-K may also be a function of the increase in XIST sequestering its deacetylase SPEN. These molecular features underlie a chronic HERV-K -IFN inflammatory response in PAH. They may explain the female predisposition to PAH, because the increase in XIST in females heightens the propensity to activate HERV-K -IFN signaling and chronic inflammation in PAs infiltrated by MONO.

Deep phenotyping of unaffected carriers of pathogenic BMPR2 variants screened for pulmonary arterial hypertension.

Pathogenic variants in the gene encoding for BMPR2 are a major genetic risk factor for heritable pulmonary arterial hypertension. Owing to incomplete penetrance, deep phenotyping of unaffected carriers of a pathogenic BMPR2 variant through multimodality screening may aid in early diagnosis and identify susceptibility traits for future development of pulmonary arterial hypertension. 28 unaffected carriers (44±16 years, 57% female) and 21 healthy controls (44±18 years, 48% female) underwent annual screening, including cardiac magnetic resonance imaging, transthoracic echocardiography, cardiopulmonary exercise testing and right heart catheterisation. Right ventricular pressure-volume loops were constructed to assess load-independent contractility and compared with a healthy control group. A transgenic Bmpr2Δ71Ex1/+ rat model was employed to validate findings from humans. Unaffected carriers had lower indexed right ventricular end-diastolic (79.5±17.6 mL·m-2 versus 62.7±15.3 mL·m-2; p=0.001), end-systolic (34.2±10.5 mL·m-2 versus 27.1±8.3 mL·m-2; p=0.014) and left ventricular end-diastolic (68.9±14.1 mL·m-2 versus 58.5±10.7 mL·m-2; p=0.007) volumes than control subjects. Bmpr2Δ71Ex1/+ rats were also observed to have smaller cardiac volumes than wild-type rats. Pressure-volume loop analysis showed that unaffected carriers had significantly higher afterload (arterial elastance 0.15±0.06 versus 0.27±0.08 mmHg·mL-1; p<0.001) and end-systolic elastance (0.28±0.07 versus 0.35±0.10 mmHg·mL-1; p=0.047) in addition to lower right ventricular pulmonary artery coupling (end-systolic elastance/arterial elastance 2.24±1.03 versus 1.36±0.37; p=0.006). During the 4-year follow-up period, two unaffected carriers developed pulmonary arterial hypertension, with normal N-terminal pro-brain natriuretic peptide and transthoracic echocardiography indices at diagnosis. Unaffected BMPR2 mutation carriers have an altered cardiac phenotype mimicked in Bmpr2Δ71Ex1/+ transgenic rats. Future efforts to establish an effective screening protocol for individuals at risk for developing pulmonary arterial hypertension warrant longer follow-up periods.

Pulmonary hypertension induced by right pulmonary artery occlusion: Hemodynamic consequences of BMPR2 mutation

Pulmonary hypertension induced by right pulmonary artery occlusion: Hemodynamic consequences of BMPR2 mutation

Pulmonary Hypertension Induced by Right Pulmonary Artery Occlusion: Hemodynamic Consequences of Bmpr2 Mutation.

The primary genetic risk factor for heritable pulmonary arterial hypertension is the presence of monoallelic mutations in the BMPR2 gene. The incomplete penetrance of BMPR2 mutations implies that additional triggers are necessary for pulmonary arterial hypertension occurrence. Pulmonary artery stenosis directly raises pulmonary artery pressure, and the redirection of blood flow to unobstructed arteries leads to endothelial dysfunction and vascular remodeling. We hypothesized that right pulmonary artery occlusion (RPAO) triggers pulmonary hypertension (PH) in rats with Bmpr2 mutations. Male and female rats with a 71 bp monoallelic deletion in exon 1 of Bmpr2 and their wild-type siblings underwent acute and chronic RPAO. They were subjected to full high-fidelity hemodynamic characterization. We also examined how chronic RPAO can mimic the pulmonary gene expression pattern associated with installed PH in unobstructed territories. RPAO induced precapillary PH in male and female rats, both acutely and chronically. Bmpr2 mutant and male rats manifested more severe PH compared with their counterparts. Although wild-type rats adapted to RPAO, Bmpr2 mutant rats experienced heightened mortality. RPAO induced a decline in cardiac contractility index, particularly pronounced in male Bmpr2 rats. Chronic RPAO resulted in elevated pulmonary IL-6 (interleukin-6) expression and decreased Gdf2 expression (corrected P value<0.05 and log2 fold change>1). In this context, male rats expressed higher pulmonary levels of endothelin-1 and IL-6 than females. Our novel 2-hit rat model presents a promising avenue to explore the adaptation of the right ventricle and pulmonary vasculature to PH, shedding light on pertinent sex- and gene-related effects.

Reversal of pulmonary veno-occlusive disease phenotypes by inhibition of the integrated stress response.

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary hypertension arising from EIF2AK4 gene mutations or mitomycin C (MMC) administration. The lack of effective PVOD therapies is compounded by a limited understanding of the mechanisms driving vascular remodeling in PVOD. Here we show that administration of MMC in rats mediates activation of protein kinase R (PKR) and the integrated stress response (ISR), which leads to the release of the endothelial adhesion molecule vascular endothelial (VE) cadherin (VE-Cad) in complex with RAD51 to the circulation, disruption of endothelial barrier and vascular remodeling. Pharmacological inhibition of PKR or ISR attenuates VE-Cad depletion, elevation of vascular permeability and vascular remodeling instigated by MMC, suggesting potential clinical intervention for PVOD. Finally, the severity of PVOD phenotypes was increased by a heterozygous BMPR2 mutation that truncates the carboxyl tail of the receptor BMPR2, underscoring the role of deregulated bone morphogenetic protein signaling in the development of PVOD.

P-522 Impact of TGFß/BMP/SMAD Pathway on Premature Ovarian Insuffiency (POI)

Abstract Study question Is TGFß/BMP/SMAD pathway altered in women with POI and can results be detected from peripheral blood samples? Summary answer The TGFß/BMP/SMAD pathway mRNA-expression-alterations are detectable in leukocytes of women with Premature Ovarian Insufficiency (POI) paving the way to use it as predictive tool. What is known already A proper ovarian function relies on a complex system of signalling molecules including several BMP/TGFß-superfamily-members expressed in the ovary at different stages of folliculogenesis acting via two types of Serine/Threonine Kinase receptors. The downstream located SMAD proteins are classified into three subclasses according to their function as activated R-SMADs1,2,3,4,9, common-partner SMAD4 or inhibitory SMADs6,7. Mutations in BMPR2 and its ligands have been shown to be related to POI. Recently neurologic studies demonstrated that FMRP(Fragile-X-Mental-Retardation-1-Protein) represses BMPR2 and its gene FMR1(Fragile X Mental-Retardation-1) is one major regulator of follicular development and the most frequent genetic cause of POI if premutated. Study design, size, duration RT-q-PCR was performed to measure the mRNA-levels of SMAD 1,3,4,5, BMPR2 and FMR1. cDNA was synthesized using RNA obtained from leucocytes of patients with POI and of the control group with a normal ovarian reserve. 163 patients diagnosed with POI and 51 women in the control group were recruited between 2008 and 2022 at Heidelberg University’s Women’s Hospital. Participants/materials, setting, methods Blood samples were drawn from every participant to extract leucocyte-RNA and synthesize non-specific cDNA. RT-q-PCR was performed with TaqMan reagents to quantify relative mRNA-expression levels of SMAD 1,3,4, 5, BMPR2 and FMR1. Statistical analysis was performed with Microsoft Excel and GraphPad Prism 10 using the 2–ΔΔCt method and Mann-Whitney-Test. Statistical significance was set to p = 0.05. Main results and the role of chance In our investigation, we observed a consistent and statistically significant decrease in the expression levels of all tested SMADs—SMAD1, SMAD3, SMAD4, and SMAD5—in leukocytes of women diagnosed with POI compared to unaffected controls. The p-values amounted to p &amp;lt; 0.0001 for SMAD1, p = 0.0340 for SMAD3, p &amp;lt; 0.0001 for SMAD4, and p = 0.0076 for SMAD5. However, we did not identify notable differences in the expression levels of FMR1 and BMPR2 between the two groups. These results suggest an alteration in the regulation of the activated downstream elements SMAD 1, 3, and 5 and their common partner SMAD4 in women with POI, emphasizing its potential role as a contributing factor to diminished ovarian function. These effects seem to be independent of BMPR2 and FMR1 and regulated by other receptors and or ligands. Limitations, reasons for caution Our data are limited to mRNA-levels. So further experiments including protein-level and their phosphorylation-status are needed to receive an overall assessment of its impact on ovarian damage. It’s worth noting that the study is concentrated on leukocytes as potential diagnostic tool and results should be cross-checked in ovarian-tissue and cells. Wider implications of the findings The identified alteration in TGFß/BMP/SMAD pathway gene expression in women with POI suggest a role in ovarian damage. Lower expression levels in the aforementioned mRNAs could serve as a potential predictive biomarker for POI risks and putatively used in consultations of women prior to fertility treatment and/or preservation. Trial registration number not applicable

(76) - Case Report: A Pulmonary and Peripheral Arteriovenous Malformation in a Pulmonary Hypertension Patient with an Underlying BMPR2 Mutation

(76) - Case Report: A Pulmonary and Peripheral Arteriovenous Malformation in a Pulmonary Hypertension Patient with an Underlying BMPR2 Mutation

A multimodal approach identifies lactate as a central feature of right ventricular failure that is detectable in human plasma.

In PAH metabolic abnormalities in multiple pathways are well-recognized features of right ventricular dysfunction, however, prior work has focused mainly on the use of a single "omic" modality to describe a single deranged pathway. We integrated metabolomic and epigenomic data using transcriptomics in failing and non-failing RVs from a rodent model to provide novel mechanistic insight and translated these findings to accessible human specimens by correlation with plasma from PAH patients. Study was conducted in a doxycycline-inducible BMPR2 mutant mouse model of RV failure. Plasma was collected from controls and PAH patients. Transcriptomic and metabolomic analyses were done on mouse RV tissue and human plasma. For mouse RV, we layered metabolomic and transcriptomic data for multiple metabolic pathways and compared our findings with metabolomic and transcriptomic data obtained for human plasma. We confirmed our key findings in cultured cardiomyocyte cells with BMPR2 mutation. In failing mouse RVs, (1) in the glycolysis pathway, glucose is converted to lactate via aerobic glycolysis, but may also be utilized for glycogen, fatty acid, and nucleic acid synthesis, (2) in the fatty acid pathway, FAs are accumulated in the cytoplasm because the transfer of FAs to mitochondria is reduced, however, the ß-oxidation pathway is likely to be functional. (3) the TCA cycle is altered at multiple checkpoints and accumulates citrate, and the glutaminolysis pathway is not activated. In PAH patients, plasma metabolic and transcriptomic data indicated that unlike in the failing BMPR2 mutant RV, expression of genes and metabolites measured for the glycolysis pathway, FA pathway, TCA cycle, and glutaminolysis pathway were increased. Lactate was the only metabolite that was increased both in RV and circulation. We confirmed using a stable isotope of lactate that cultured cardiomyocytes with mutant BMPR2 show a modest increase in endogenous lactate, suggesting a possibility of an increase in lactate production by cardiomyocytes in failing BMPR2 mutant RV. In the failing RV with mutant BMPR2, lactate is produced by RV cardiomyocytes and may be secreted out, thereby increasing lactate in circulation. Lactate can potentially serve as a marker of RV dysfunction in PAH, which warrants investigation.

Treprostinil Effectiveness in Higher-Risk Pediatric Patients With Idiopathic and Heritable Pulmonary Arterial Hypertension

BackgroundLittle is known about the effectiveness of treprostinil in higher-risk paediatric patients with various pulmonary arterial hypertension genotypes. This study was designed to investigate the prognosis of higher-risk paediatric patients with idiopathic or heritable pulmonary arterial hypertension (IPAH/HPAH) after treprostinil therapy. MethodsChildren with IPAH/HPAH who were stratified as higher risk and treated with treprostinil in our centre were included as the study cohort. Those who received only oral medications were included as the reference cohort. All patients in the study cohort received PAH-related genotyping. Survival was defined as no death. Event-free survival was defined as no death, Potts shunt, or atrial septostomy. ResultsForty-nine children (median age 7.7 years [interquartile range (IQR) 4.2-11.5 years], 65% female) were included in the study cohort and 48 children were included in the reference cohort; 84% of the study cohort had genetic disorders after genetic testing with a dominance of BMPR2 and ACVRL1 mutations. After a median therapy duration of 5.56 months (IQR 2.66-11.12 months), all patients were alive with significant improvements in clinical characteristics. One-, 2-, and 3-year survival rates were 91%, 84%, and 69%, respectively with a median follow-up duration of 19.17 months (IQR 9.7-29.79 months), which was significantly superior to the reference cohort (P = 0.038). Multivariate Cox regression analysis identified World Health Organisation functional class after therapy as a predictor for survival. There was no significant difference in survival among patients with different genotypes. ConclusionsTreprostinil can significantly improve the prognosis in children with IPAH/HPAH who are at higher risk, despite genetic backgrounds.

A potential adverse role for leptin and cardiac leptin receptor in the right ventricle in pulmonary arterial hypertension: effect of metformin is BMPR2 mutation-specific.

Pulmonary arterial hypertension is a fatal cardiopulmonary disease. Leptin, a neuroendocrine hormone released by adipose tissue, has a complex relationship with cardiovascular diseases, including PAH. Leptin is thought to be an important factor linking metabolic syndrome and cardiovascular disorders. Given the published association between metabolic syndrome and RV dysfunction in PAH, we sought to determine the association between leptin and RV dysfunction. We hypothesized that in PAH-RV, leptin influences metabolic changes via leptin receptors, which can be manipulated by metformin. Plasma leptin was measured in PAH patients and healthy controls from a published trial of metformin in PAH. Leptin receptor localization was detected in RV from PAH patients, healthy controls, animal models of PH with RV dysfunction before and after metformin treatment, and cultured cardiomyocytes with two different BMPR2 mutants by performing immunohistochemical and cell fractionation studies. Functional studies were conducted in cultured cardiomyocytes to examine the role of leptin and metformin in lipid-driven mitochondrial respiration. In human studies, we found that plasma leptin levels were higher in PAH patients and moderately correlated with higher BMI, but not in healthy controls. Circulating leptin levels were reduced by metformin treatment, and these findings were confirmed in an animal model of RV dysfunction. Leptin receptor expression was increased in PAH-RV cardiomyocytes. In animal models of RV dysfunction and cultured cardiomyocytes with BMPR2 mutation, we found increased expression and membrane localization of the leptin receptor. In cultured cardiomyocytes with BMPR2 mutation, leptin moderately influences palmitate uptake, possibly via CD36, in a mutation-specific manner. Furthermore, in cultured cardiomyocytes, the Seahorse XFe96 Extracellular Flux Analyzer and gene expression data indicate that leptin may not directly influence lipid-driven mitochondrial respiration in BMPR2 mutant cardiomyocytes. However, metformin alone or when supplemented with leptin can improve lipid-driven mitochondrial respiration in BMPR2 mutant cardiomyocytes. The effect of metformin on lipid-driven mitochondrial respiration in cardiomyocytes is BMPR2 mutation-specific. In PAH, increased circulating leptin can influence metabolic signaling in RV cardiomyocytes via the leptin receptor; in particular, it may alter lipid-dependent RV metabolism in combination with metformin in a mutation-specific manner and warrants further investigation.

Imaging Features in BMPR2 Mutation-associated Pulmonary Arterial Hypertension.

Background Germline mutation in the BMPR2 gene is common in patients with pulmonary arterial hypertension (PAH). However, its association with imaging findings in these patients is, to the knowledge of the authors, unknown. Purpose To characterize distinctive pulmonary vascular abnormalities at CT and pulmonary artery angiography in patients with and without BMPR2 mutation. Materials and Methods In this retrospective study, chest CT scans, pulmonary artery angiograms, and genetic test data were acquired for patients diagnosed with idiopathic PAH (IPAH) or heritable PAH (HPAH) between January 2010 and December 2021. Perivascular halo, neovascularity, centrilobular ground-glass opacity (GGO), and panlobular GGO were evaluated at CT and graded on a four-point severity scale by four independent readers. Clinical characteristics and imaging features between patients with BMPR2 mutation and noncarriers were analyzed using the Kendall rank-order coefficient and the Kruskal-Wallis test. Results This study included 82 patients with BMPR2 mutation (mean age, 38 years ± 15 [SD]; 34 men; 72 patients with IPAH and 10 patients with HPAH) and 193 patients without the mutation, all with IPAH (mean age, 41 years ± 15; 53 men). A total of 115 patients (42%; 115 of 275) had neovascularity, and 56 patients (20%; 56 of 275) had perivascular halo at CT, and so-called frost crystals were observed on pulmonary artery angiograms in 14 of 53 (26%) patients. Compared with patients without BMPR2 mutation, patients with BMPR2 mutation more frequently showed two distinctive radiographic manifestations, perivascular halo and neovascularity (38% [31 of 82] vs 13% [25 of 193] in perivascular halo [P < .001] and 60% [49 of 82] vs 34% [66 of 193] in neovascularity [P < .001], respectively). "Frost crystals" were more frequent in patients with BMPR2 mutation compared with noncarriers (53% [10 of 19] vs 12% [four of 34]; P < .01). Severe perivascular halo frequently coexisted with severe neovascularity in patients with BMPR2 mutation. Conclusion Patients with PAH with BMPR2 mutation showed distinctive features at CT, specifically perivascular halo and neovascularity. This suggested a link between the genetic, pulmonary, and systemic manifestations that underly the pathogenesis of PAH. © RSNA, 2023 Supplemental material is available for this article.

Is iron deficiency caused by BMPR2 mutations or dysfunction in pulmonary arterial hypertension patients?

Iron deficiency is common in idiopathic and heritable pulmonary arterial hypertension patients (I/HPAH). A previous report suggested a dysregulation of the iron hormone hepcidin, which is controlled by BMP/SMAD signaling involving the bone morphogenetic protein receptor 2 (BMPR-II). Pathogenic variants in the BMPR2 gene are the most common cause of HPAH. Their effect on patients'hepcidin levels has not been investigated. The aim of this study was to assess whether iron metabolism and regulation of the iron regulatory hormone hepcidin was disturbed in I/HPAH patients with and without a pathogenic variant in the gene BMPR2 compared to healthy controls. In this explorative, cross-sectional study hepcidin serum levels were quantified by enzyme-linked immunosorbent assay. We measured iron status, inflammatory parameters and hepcidin modifying proteins such as IL6, erythropoietin, and BMP2, BMP6 in addition to BMPR-II protein and mRNA levels. Clinical routine parameters were correlated with hepcidin levels. In total 109 I/HPAH patients and controls, separated into three groups, 23 BMPR2 variant-carriers, 56 BMPR2 noncarriers and 30 healthy controls were enrolled. Of these, 84% had iron deficiency requiring iron supplementation. Hepcidin levels were not different between groups and corresponded to the degree of iron deficiency. The levels of IL6, erythropoietin, BMP2, or BMP6 showed no correlation with hepcidin expression. Hence, iron homeostasis and hepcidin regulation was largely independent from these parameters. I/HPAH patients had a physiologically normal iron regulation and no false elevation of hepcidin levels. Iron deficiency was prevalent albeit independent of pathogenic variants in the BMPR2 gene.

Hereditary pulmonary arterial hypertension burden in pediatrics: A single referral center experience.

Hereditary pulmonary arterial hypertension (HPAH) is a rare yet serious type of pulmonary arterial hypertension (PAH). The burden in the pediatric population remains high yet underreported. The objective of this study is to describe the distribution of mutations found on targeted PAH panel testing at a large pediatric referral center. Children with PAH panel administered by the John Welsh Cardiovascular Diagnostic Laboratory at Texas Children's Hospital and Baylor College of Medicine in Houston, Texas between October 2012 to August 2021 were included into this study. Medical records were retrospectively reviewed for clinical correlation. Sixty-six children with PAH underwent PAH genetic testing. Among those, 9 (14%) children were found to have pathogenic mutations, 16 (24%) children with variant of unknown significance and 41 (62%) children with polymorphism (classified as likely benign and benign). BMPR2 mutation was the most common pathogenic mutation, seen in 6 of the 9 children with detected mutations. Hemodynamic studies showed higher pulmonary vascular resistance among those with pathogenic mutations than those without (17.4 vs. 4.6 Wood units). All children with pathogenic mutations had severe PAH requiring triple therapy. There were tendencies for higher lung transplantation rate but lower mortality among those with pathogenic mutations. Abnormalities on genetic testing are not uncommon among children with PAH, although majority are of unclear significance. However, children with pathogenic mutations tended to present with more severe PAH requiring aggressive medical and surgical therapies. Genetic testing should be routinely considered due to consequences for treatment and prognostic implications. Larger scale population studies and registries are warranted to characterize the burden of HPAH in the pediatric population specifically.

In this Issue.

HomeCirculation ResearchVol. 132, No. 5In this Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn this Issue Originally published2 Mar 2023https://doi.org/10.1161/RES.0000000000000600Circulation Research. 2023;132:541is related toInfarcted Myocardium Calls for T-Cell Help to Regulate RepairDysregulated Smooth Muscle Cell BMPR2 – ARRB2 Axis Causes Pulmonary Hypertension (p 545)Download figureDownload PowerPointβ-arrestin2 may be a novel target for treating pulmonary arterial hypertension, say Wang et al.Pulmonary arterial hypertension (PAH) is a chronic condition in which the blood vessels of the lungs progressively narrow due in part to excess proliferation of pulmonary artery smooth muscle cells (PASMCs). This narrowing leads to increased blood pressure and ultimately heart failure. Lack of a signaling protein called BMPR2 is common in PAH patients, so to better understand the effect of this deficiency, Wang and colleagues studied PASMCs in which BMPR2 had been experimentally suppressed, as well as PASMCs from PAH patients with a BMPR2 mutation. In both cases, the cells exhibited excessive proliferation and decreased contractility compared with controls. PASMC cells from mice with a PASMC-specific BMPR2 deletion had similar phenotypes, and the animals themselves, unlike control mice, experienced persistent pulmonary hypertension after hypoxia exposure. Molecular investigations revealed cells lacking BMPR2 had elevated levels of the signal transduction factor β-arrestin2, suppression of which prevented the proliferation and contractility problems. This result, together with the finding that β-arrestin2 suppression prevented persistent hypertension in the BMPR2-lacking mice, suggests β-arrestin2 inhibition could be an approach for tackling PAH.The Myocardial Milieu Favors Local Differentiation of Regulatory T Cells (p 565)Download figureDownload PowerPointThe damaged heart promotes anti-inflammatory T cell differentiation, say Delgobo et al.After a myocardial infarction, the release of autoantigens from the damaged heart cells activates local and infiltrating immune cells such as T cells. Studies in mice have shown that, of these autoantigens, fragments of the muscle protein myosin are the dominant drivers of the T cell response. But how do these myosin-specific T cells behave in the damaged heart to drive inflammation and repair? To find out, Delgobo and colleagues have studied endogenous myosin-specific T cells as well as those transferred to recipient mice. They found that, whether exogenously supplied or endogenous, the myosin-specific T cells that accumulated in the animals’ infarcted hearts tended to adopt an immunosuppressive T regulatory (T reg) phenotype. Strikingly, even if the exogenous cells were differentiated into inflammatory Th17 cells prior to transfer, a significant proportion of them were still reprogrammed into T regs within the heart. Although cells pre-differentiated to an inflammatory Th1 phenotype were less inclined to change after transfer, the results nevertheless indicate that, by and large, the infarcted heart promotes T cell reprograming to quell inflammation and drive repair. Exactly how the heart does this is a question for future studies, say the team.Inhibition of Fibroblast 1 Activation Protein Promotes Cardiac Repair by Stabilizing Brain Natriuretic Peptide After Myocardial Infarction (p 586)Download figureDownload PowerPointInhibiting a key fibrosis factor promotes angiogenesis and saves tissue function in the infarcted heart, say Sun et al.After a myocardial infarction (MI), there is a balance of recovery processes to protect the tissue. Fibrosis, for example, acts like an immediate band-aid to hold the damaged muscle together but can limit contractile function. Angiogenesis, on the other hand, promotes survival of cardiomyocytes within the ischemic tissue and protects heart function. To better understand this balance, Sun and colleagues have examined the actions of the fibrosis factor, fibroblast activation protein (FAP), which is dramatically upregulated in damaged hearts, and brain natriuretic peptide (BNP), which promotes angiogenesis in the heart. The team now show that genetic deletion or pharmacological inhibition of FAP in mice reduces cardiac fibrosis and improves angiogenesis and heart function after MI. Such benefits are not seen, however, if BNP, or its receptor Npr1, is also lacking. Indeed, in vitro experiments revealed that FAP’s protease activity degrades BNP, thus inhibiting the latter’s angiogenic activity. Interestingly, while FAP is upregulated in the heart, its levels drop in the blood, showing the BNP inhibition is localized. Together the results suggest blocking FAP activity in the heart after MI could be a possible strategy for protecting the muscle’s function. Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesInfarcted Myocardium Calls for T-Cell Help to Regulate RepairXudong Li, et al. Circulation Research. 2023;132:583-585 March 3, 2023Vol 132, Issue 5 Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000600PMID: 36862811 Originally publishedMarch 2, 2023 PDF download Advertisement

Lipidomic Profile Analysis of Lung Tissues Revealed Lipointoxication in Pulmonary Veno-Occlusive Disease.

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary arterial hypertension (PAH) occurring in a heritable form (hPVOD) due to biallelic inactivating mutations of EIF2AK4 (encoding GCN2, general control nonderepressible 2) or in a sporadic form in older age (sPVOD), following exposure to chemotherapy or organic solvents. In contrast to PAH, PVOD is characterized by a particular remodeling of the pulmonary venous system and the obliteration of small pulmonary veins by fibrous intimal thickening and patchy capillary proliferation. The pathobiological knowledge of PVOD is poor, explaining the absence of medical therapy for PVOD. Lung transplantation remains the only therapy for eligible PVOD patients. As we recently demonstrated, respiratory diseases, chronic obstructive pulmonary disease, or cystic fibrosis exhibit lipointoxication signatures characterized by excessive levels of saturated phospholipids contributing to the pathological features of these diseases, including endoplasmic reticulum stress, pro-inflammatory cytokines production, and bronchoconstriction. In this study, we investigated and compared the clinical data and lung lipid signature of control (10 patients), idiopathic PAH (7 patients), heritable PAH (9 BMPR2 mutations carriers), hPVOD (10 EIF2AK4 mutation carriers), and sPVOD (6 non-carriers) subjects. Mass spectrometry analyses demonstrated lung lipointoxication only in hPVOD patients, characterized by an increased abundance of saturated phosphatidylcholine (PC) at the expense of the polyunsaturated species in the lungs of hPVOD patients. The present data suggest that lipointoxication could be a potential player in the etiology of PVOD.

Abstract 15374: Somatic Mutations of Dnmt3a Contribute to Pulmonary Vascular Remodeling and Right Ventricular Dysfunction in PAH

Background: Pulmonary Arterial Hypertension (PAH) is an obliterative pulmonary vasculopathy in which structural changes are driven by inflammation, fibrosis, mitochondrial dysfunction, and pathological angiogenesis. While ~10% of cases of PAH have germline BMPR2 mutations (or one of 16 other recognized or putative PAH genes), the genetic basis for the majority of PAH patients remains unexplained. Somatic mutations in hematopoietic stem cells (HSC) are related to the disorders of clonal hematopoiesis of indeterminate potential (CHIP). Tet methylcytosine dioxygenase 2 (TET2) and DNA methyltransferase 3a (DNMT3A) are among the primary genes involved in CHIP. We found in a PAH-Biobank that 0.39% of PAH patients had somatic or germline TET2 mutations. Also, TET2-knockout mice can develop PAH spontaneously. Thus TET2 is a new PAH gene. We now hypothesize that CHIP driven by mutations of DNMT3A can also cause pulmonary vascular remodeling and right ventricular failure (RVF), contributing to PAH. Methods: Studies were performed on 9 month old DNMT3A knockout (-/-) mice and their relative controls (f/f) (N=5/group). The right ventricular (RV) function was assessed via cardiac ultrasound. Pulmonary artery medial wall thickness (PAMWT) and radial alveolar count (RAC) were assessed in lung tissue sections using light microscopy. Results: In DNMT3A -/- mice, there was a reduction in pulmonary artery acceleration time (PAAT) compared to controls ( p= 0.0268). There was also a significant reduction in percent RV free wall thickening (RVFWT %) compared to controls (57.44±9.97 DNMT3A-/-, 118.5±14.98 f/f; p= 0.017). Both Tricuspid annular plane systolic excursion (TAPSE) and cardiac output (CO) were also significantly reduced in DNMT3A -/- mice ( p &lt; 0.0001, p = 0.0135). The medial thickness of small pulmonary arteries was significantly higher in DNMT3A -/- mice compared to controls (56.51% ±1.19 DNMT3A-/-, 39.79% ±2.07 f/f; p= 0.002). RAC was significantly reduced in the DNMT3A -/- mice when compared to controls ( p= 0.018). Conclusions: DNMT3A mutations may contribute to the development of pulmonary vascular disease and RVF in PAH.

Impaired Interleukin-15 Signaling via BMPR2 Loss Drives Natural Killer Cell Deficiency and Pulmonary Hypertension.

Natural killer (NK) cell impairment is a feature of pulmonary arterial hypertension (PAH) and contributes to vascular remodeling in animal models of disease. Although mutations in BMPR2, the gene encoding the BMP (bone morphogenetic protein) type-II receptor, are strongly associated with PAH, the contribution of BMPR2 loss to NK cell impairment remains unknown. We explored the impairment of IL (interleukin)-15 signaling, a central mediator of NK cell homeostasis, as both a downstream target of BMPR2 loss and a contributor to the pathogenesis of PAH. The expression, trafficking, and secretion of IL-15 and IL-15Rα (interleukin 15 α-type receptor) were assessed in human pulmonary artery endothelial cells, with or without BMPR2 silencing. NK cell development and IL-15/IL-15Rα levels were quantified in mice bearing a heterozygous knock-in of the R899X-BMPR2 mutation (bmpr2+/R899X). NK-deficient Il15-/- rats were exposed to the Sugen/hypoxia and monocrotaline models of PAH to assess the impact of impaired IL-15 signaling on disease severity. BMPR2 loss reduced IL-15Rα surface presentation and secretion in human pulmonary artery endothelial cells via impaired trafficking through the trans-Golgi network. bmpr2+/R899X mice exhibited a decrease in NK cells, which was not attributable to impaired hematopoietic development but was instead associated with reduced IL-15/IL-15Rα levels in these animals. Il15-/- rats of both sexes exhibited enhanced disease severity in the Sugen/hypoxia model, with only male Il15-/- rats developing more severe PAH in response to monocrotaline. This work identifies the loss of IL-15 signaling as a novel BMPR2-dependent contributor to NK cell impairment and pulmonary vascular disease.

Bmpr2 mutant mice are an inadequate model for studying iron deficiency in pulmonary hypertension.

As bone morphogenetic protein receptor type II (Bmpr2) mutations are the most common genetic cause of pulmonary arterial hypertension (PAH), and iron deficiency(ID) is associated with worse clinical outcomes in PAH patients, we proposed to use Bmpr2 ± mice to induce a model of ID in pulmonary vascular disease. Our study shows that these transgenic mice are not a good model for this clinical phenomenon.

AVOIDING THYROID TESTING FATIGUE: PULMONARY ARTERIAL HYPERTENSION (PAH) IN A PATIENT WITH HASHIMOTO DISEASE

AVOIDING THYROID TESTING FATIGUE: PULMONARY ARTERIAL HYPERTENSION (PAH) IN A PATIENT WITH HASHIMOTO DISEASE

2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension.

2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension.