Colin Church

Nuclear IL-33 regulates soluble ST2 receptor and IL-6 expression in primary human arterial endothelial cells and is decreased in idiopathic pulmonary arterial hypertension.

Idiopathic pulmonary arterial hypertension (IPAH) is an incurable condition leading to right ventricular failure and death and inflammation is postulated to be associated with vascular remodelling. Interleukin (IL)-33, a member of the alarmin family can either act on the membrane ST2 receptor or as a nuclear repressor, to regulate inflammation. We show, using immunohistochemistry, that IL-33 expression is nuclear in the vessels of healthy subjects whereas nuclear IL-33 is markedly diminished in the vessels of IPAH patients. This correlates with reduced IL-33 mRNA expression in their lung. In contrast, serum levels of IL-33 are unchanged in IPAH. However, the expression of the soluble form of ST2, sST2, is enhanced in the serum of IPAH patients. Knock-down of IL-33 in human endothelial cells (ECs) using siRNA is associated with selective modulation of inflammatory genes involved in vascular remodelling including IL-6. Additionally, IL-33 knock-down significantly increased sST2 release from ECs. Chromatin immunoprecipitation demonstrated that IL-33 bound multiple putative homeodomain protein binding motifs in the proximal and distal promoters of ST2 genes. IL-33 formed a complex with the histone methyltransferase SUV39H1, a transcriptional repressor. In conclusion, IL-33 regulates the expression of IL-6 and sST2, an endogenous IL-33 inhibitor, in primary human ECs and may play an important role in the pathogenesis of PAH through recruitment of transcriptional repressor proteins.

Phenotypic Characterization of EIF2AK4 Mutation Carriers in a Large Cohort of Patients Diagnosed Clinically With Pulmonary Arterial Hypertension

Background: Pulmonary arterial hypertension (PAH) is a rare disease with an emerging genetic basis. Heterozygous mutations in the gene encoding the bone morphogenetic protein receptor type 2 (BMPR2) are the commonest genetic cause of PAH, whereas biallelic mutations in the eukaryotic translation initiation factor 2 alpha kinase 4 gene (EIF2AK4) are described in pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis. Here, we determine the frequency of these mutations and define the genotype-phenotype characteristics in a large cohort of patients diagnosed clinically with PAH. Methods: Whole-genome sequencing was performed on DNA from patients with idiopathic and heritable PAH and with pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis recruited to the National Institute of Health Research BioResource–Rare Diseases study. Heterozygous variants in BMPR2 and biallelic EIF2AK4 variants with a minor allele frequency of <1:10u2009000 in control data sets and predicted to be deleterious (by combined annotation-dependent depletion, PolyPhen-2, and sorting intolerant from tolerant predictions) were identified as potentially causal. Phenotype data from the time of diagnosis were also captured. Results: Eight hundred sixty-four patients with idiopathic or heritable PAH and 16 with pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis were recruited. Mutations in BMPR2 were identified in 130 patients (14.8%). Biallelic mutations in EIF2AK4 were identified in 5 patients with a clinical diagnosis of pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis. Furthermore, 9 patients with a clinical diagnosis of PAH carried biallelic EIF2AK4 mutations. These patients had a reduced transfer coefficient for carbon monoxide (KCO; 33% [interquartile range, 30%–35%] predicted) and younger age at diagnosis (29 years; interquartile range, 23–38 years) and more interlobular septal thickening and mediastinal lymphadenopathy on computed tomography of the chest compared with patients with PAH without EIF2AK4 mutations. However, radiological assessment alone could not accurately identify biallelic EIF2AK4 mutation carriers. Patients with PAH with biallelic EIF2AK4 mutations had a shorter survival. Conclusions: Biallelic EIF2AK4 mutations are found in patients classified clinically as having idiopathic and heritable PAH. These patients cannot be identified reliably by computed tomography, but a low KCO and a young age at diagnosis suggests the underlying molecular diagnosis. Genetic testing can identify these misclassified patients, allowing appropriate management and early referral for lung transplantation.

Identification of rare sequence variation underlying heritable pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder with a poor prognosis. Deleterious variation within components of the transforming growth factor-β pathway, particularly the bone morphogenetic protein type 2 receptor (BMPR2), underlies most heritable forms of PAH. To identify the missing heritability we perform whole-genome sequencing in 1038 PAH index cases and 6385 PAH-negative control subjects. Case-control analyses reveal significant overrepresentation of rare variants in ATP13A3, AQP1 and SOX17, and provide independent validation of a critical role for GDF2 in PAH. We demonstrate familial segregation of mutations in SOX17 and AQP1 with PAH. Mutations in GDF2, encoding a BMPR2 ligand, lead to reduced secretion from transfected cells. In addition, we identify pathogenic mutations in the majority of previously reported PAH genes, and provide evidence for further putative genes. Taken together these findings contribute new insights into the molecular basis of PAH and indicate unexplored pathways for therapeutic intervention.Pulmonary arterial hypertension (PAH) is a rare lung disorder characterised by narrowing and obliteration of small pulmonary arteries ultimately leading to right heart failure. Here, the authors sequence whole genomes of over 1000 PAH patients and identify likely causal variants in GDF2, ATP13A3, AQP1 and SOX17.

Isolated large vessel pulmonary vasculitis as a cause of chronic obstruction of the pulmonary arteries

Isolated pulmonary artery involvement by large vessel vasculitis is rare. This case report describes two patients with large vessel pulmonary vasculitis initially thought to have chronic thromboembolic pulmonary hypertension who had their diagnosis revised following pulmonary endarterectomy surgery. Advances in imaging techniques such as positron emission tomography and magnetic resonance imaging have permitted complementary radiological methods of diagnosis and follow up of large vessel disease and these are discussed in conjunction with the immunosuppressive and operative management of these patients.

Clinical trial protocol for TRANSFORM-UK: A therapeutic open-label study of tocilizumab in the treatment of pulmonary arterial hypertension:

Our aim is to assess the safety and potential efficacy of a novel treatment paradigm in pulmonary arterial hypertension (PAH), immunomodulation by blocking interleukin-6 (IL6) signaling with the IL6 receptor antagonist, tocilizumab. Inflammation and autoimmunity are established as important in PAH pathophysiology. One of the most robust observations across multiple cohorts in PAH has been an increase in IL6, both in the lung and systemically. Tocilizumab is an IL-6 receptor antagonist established as safe and effective, primarily in rheumatoid arthritis, and has shown promise in scleroderma. In case reports where the underlying cause of PAH is an inflammatory process such as systemic lupus erythematosus, mixed connective tissue disease (MCTD), and Castleman’s disease, there have been case reports of regression of PAH with tocilizumab. TRANSFORM-UK is an open-label study of intravenous (IV) tocilizumab in patients with group 1 PAH. The co-primary outcome measures will be safety and the change in resting pulmonary vascular resistance (PVR). Clinically relevant secondary outcome measurements include 6-minute walk distance, WHO functional class, quality of life score, and N-terminal pro-brain natriuretic peptide (NT-proBNP). If the data support a potentially useful therapeutic effect with an acceptable risk profile, the study will be used to power a Phase III study to properly address efficacy.

Ambrisentan use for pulmonary arterial hypertension in a post-authorization drug registry: The VOLibris Tracking Study

BACKGROUNDnThe VOLibris Tracking (VOLT) Study was an open-label, prospective, observational, multicenter, post-marketing registry program designed to more fully characterize the safety profile of ambrisentan for the treatment of pulmonary arterial hypertension (PAH). The key outcome was the incidence of aminotransferase elevations >3× the upper limit of normal (ULN).nnnMETHODSnIn total, 999 patients from 115 centers in 15 countries, who were prescribed ambrisentan for the treatment of PAH (Functional Class II and III) between 30 June 2008 and 13 May 2011, were enrolled. Of these, 238 had PAH associated with connective tissue disease (PAH-CTD) and 220 had no prior PAH-specific therapy. Routine clinical monitoring data were collected by physicians.nnnRESULTSnThe incidence of both alanine and aspartate aminotransferase events (>3× ULN) was 0.02 per patient-year (95% confidence interval 0.015 to 0.027). Similar results were reported for the PAH-CTD and PAH-specific-therapy-naive subgroups. Overall, 514 (52%) patients reported treatment-emergent adverse events of special interest, most commonly edema/fluid retention (249, or 25%) and anemia (143, or 14%).nnnCONCLUSIONSnData from the VOLT study indicate no new ambrisentan-related safety signals. Ambrisentan was not associated with increases in liver function test abnormalities above the assumed background incidence of 1.5% per year, and the observed safety profile of ambrisentan was consistent with previously published data.

Social deprivation and prognosis in Scottish patients with pulmonary arterial hypertension

Several demographic and clinical factors have prognostic significance in idiopathic pulmonary arterial hypertension (IPAH). Studies in China and the USA have suggested an association between low socioeconomic status and reduced survival. The impact of social deprivation on IPAH survival in the UK is not known. 280 patients with IPAH and hereditary PAH (HPAH) attending the Scottish Pulmonary Vascular Unit (Glasgow, UK) were assigned to social deprivation quintiles using the Scottish Index of Multiple Deprivation database. The association between survival and social deprivation quintile was assessed using Cox proportional hazards regression analysis. The distribution of IPAH/HPAH patients was more socially deprived than would be expected based on Scottish citizenry as a whole (Chi-squared 16.16, p=0.003), suggesting referral and access to care is not impeded by socioeconomic status. Univariate analysis demonstrated no significant association between social deprivation and survival (p=0.81), and this association failed to reach significance with inclusion of time, sex and age as covariates in the model (p=0.23). There were no statistically significant correlations between social deprivation and baseline clinical variables of prognostic importance except for age, sex and quality of life. Social deprivation is not a significant referral barrier or prognostic factor for IPAH and HPAH in Scotland. Social deprivation is not a significant referral barrier or prognostic factor for IPAH and HPAH in Scotland http://ow.ly/N7aL30gE4ui

Novel causative genes for heritable pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder with a poor prognosis. Deleterious variation within components of the transforming growth factor-β pathway, particularly the bone morphogenetic protein type 2 receptor (BMPR2), underlie most heritable forms of PAH. Since the missing heritability likely involves genetic variation confined to small numbers of cases, we performed whole genome sequencing in 1038 PAH index cases and 6385 PAH-negative control subjects. Case-control analyses revealed significant overrepresentation of rare variants in novel genes, namely ATP13A3, AQP1 and SOX17, and provided independent validation of a critical role for GDF2 in PAH. We provide evidence for familial segregation of mutations in SOX17 and AQP1 with PAH. Mutations in GDF2, encoding a BMPR2 ligand, led to reduced secretion from transfected cells. In addition, we identified pathogenic mutations in the majority of previously reported PAH genes, and provide evidence for further putative genes. Taken together these findings provide new insights into the molecular basis of PAH and indicate unexplored pathways for therapeutic intervention.Pulmonary arterial hypertension (PAH) is a rare disorder with a poor prognosis. Deleterious variation within genes encoding components of the transforming growth factor-ß pathway, particularly the bone morphogenetic protein type 2 receptor (BMPR2), underlie the majority of heritable forms of PAH. Since the missing genetic contribution likely involves mutations in genes confined to small numbers of cases, we performed whole genome sequencing in 1038 PAH index cases and 6385 subjects with other rare diseases. Case-control analyses revealed significant overrepresentation of rare variants in novel genes, namely ATP13A3, AQP1 and SOX17, and provided independent validation of a critical role for GDF2 in PAH. Mutations in GDF2, encoding a ligand for BMPR2, led to reduced secretion from transfected cells. In addition, we confirmed the presence of mutations in most, but not all, previously reported PAH genes, and provide evidence for further putative genes. Taken together these findings provide new insights into the molecular basis of PAH and indicate unexplored pathways for therapeutic intervention.

Current management of pulmonary arterial hypertension

The management of pulmonary arterial hypertension has been transformed by the introduction of disease‐targeted therapies. This article examines the diagnosis of pulmonary arterial hypertension, the efficacy of current treatments, and the role of the GP in management.

Right Ventricular free wall myocardial tissue characterisation by systolic Cardiac Magnetic Resonance T1 mapping in pulmonary hypertension

Background Pulmonary hypertension is a rare progressive disorder characterised by elevated pulmonary artery pressure leading to right ventricular (RV) failure and death. Cardiac MR (CMR) derived right and left ventricular functional variables have shown to be prognostic in pulmonary hypertension. Native T1 mapping is a CMR technique of myocardial tissue characterisation without the need for a reference area or contrast administration. T1 mapping of the RV free wall has shown to have poor inter-observer reproducibility due to the relatively thin RV myocardium. An alternative is to acquire T1 maps in systole when the RV myocardium is thicker. We investigated whether native T1 values in systole relate to invasive pressure measurements and markers of RV dysfunction in patients with pre-capillary pulmonary hypertension (PH).