Plasma receptor tyrosine kinase RET in pulmonary arterial hypertension diagnosis and differentiation

ErbB3 Governs Endothelial Dysfunction in Hypoxia-Induced Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension, characterized by vascular remodeling, currently lacks curative therapeutic options. The dysfunction of pulmonary artery endothelial cells plays a pivotal role in the initiation and progression of pulmonary hypertension (PH). ErbB3 (human epidermal growth factor receptor 3), also recognized as HER3, is a member of the ErbB family of receptor tyrosine kinases.

METHODS

Microarray, immunofluorescence, and Western blotting analyses were conducted to investigate the pathological role of ErbB3. Blood samples were collected for biomarker examination from healthy donors or patients with hypoxic PH. The pathological functions of ErbB3 were further validated in rodents subjected to chronic hypoxia- and Sugen-induced PH, with or without adeno-associated virus-mediated ErbB3 overexpression, systemic deletion, or endothelial cell-specific ErbB3 knockdown. Primary human pulmonary artery endothelial cells and pulmonary artery smooth muscle cells were used to elucidate the underlying mechanisms.

RESULTS

ErbB3 exhibited significant upregulation in the serum, lungs, distal pulmonary arteries, and pulmonary artery endothelial cells isolated from patients with PH compared with those from healthy donors. ErbB3 overexpression stimulated hypoxia-induced endothelial cell proliferation, exacerbated pulmonary artery remodeling, elevated systolic pressure in the right ventricle, and promoted right ventricular hypertrophy in murine models of PH. Conversely, systemic deletion or endothelial cell-specific knockout of ErbB3 yielded opposite effects. Coimmunoprecipitation and proteomic analysis identified YB-1 (Y-box binding protein 1) as a downstream target of ErbB3. ErbB3 induced nuclear translocation of YB-1 and subsequently promoted hypoxia-inducible factor 1/2α transcription. A positive loop involving ErbB3-periostin-hypoxia-inducible factor 1/2α was identified to mediate the progressive development of this disease. MM-121, a human anti-ErbB3 monoclonal antibody, exhibited both preventive and therapeutic effects against hypoxia-induced PH.

CONCLUSIONS

Our study reveals, for the first time, that ErbB3 serves as a novel biomarker and a promising target for the treatment of PH.

Circulating biomarkers in pulmonary arterial hypertension: State-of-the-art review and future directions

Pulmonary arterial hypertension is a complex and heterogeneous condition, associated with a considerable diagnostic delay, diminished exercise capacity, and poor outcomes. In pulmonary arterial hypertension, biomarker research has become a subject of intense inquiry, and novel circulating biomarkers acknowledged in a multitude of mechanistic pathways are emerging. Beyond the widely used natriuretic peptides, novel biomarkers may provide deeper pathophysiological understanding, support clinical decision-making, and prompt the incorporation of precision medicine by enabling a more precise individual phenotyping. In this state-of-the-art review, the recent advances in circulating biomarkers in pulmonary arterial hypertension from a clinical perspective are discussed, with particular emphasis on the current state of knowledge, gaps in evidence, and future perspectives.

Plasma Proteomics Identifies B2M as a Regulator of Pulmonary Hypertension in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Pulmonary hypertension (PH) represents an important phenotype in heart failure with preserved ejection fraction (HFpEF). However, management of PH-HFpEF is challenging because mechanisms involved in the regulation of PH-HFpEF remain unclear.

METHODS

We used a mass spectrometry-based comparative plasma proteomics approach as a sensitive and comprehensive hypothesis-generating discovery technique to profile proteins in patients with PH-HFpEF and control subjects. We then validated and investigated the role of one of the identified proteins using in vitro cell cultures, in vivo animal models, and independent cohort of human samples.

RESULTS

Plasma proteomics identified high protein abundance levels of B2M (β2-microglobulin) in patients with PH-HFpEF. Interestingly, both circulating and skeletal muscle levels of B2M were increased in mice with skeletal muscle SIRT3 (sirtuin-3) deficiency or high-fat diet-induced PH-HFpEF. Plasma and muscle biopsies from a validation cohort of PH-HFpEF patients were found to have increased B2M levels, which positively correlated with disease severity, especially pulmonary capillary wedge pressure and right atrial pressure at rest. Not only did the administration of exogenous B2M promote migration/proliferation in pulmonary arterial vascular endothelial cells but it also increased PCNA (proliferating cell nuclear antigen) expression and cell proliferation in pulmonary arterial vascular smooth muscle cells. Finally, B2m deletion improved glucose intolerance, reduced pulmonary vascular remodeling, lowered PH, and attenuated RV hypertrophy in mice with high-fat diet-induced PH-HFpEF.

CONCLUSIONS

Patients with PH-HFpEF display higher circulating and skeletal muscle expression levels of B2M, the magnitude of which correlates with disease severity. Our findings also reveal a previously unknown pathogenic role of B2M in the regulation of pulmonary vascular proliferative remodeling and PH-HFpEF. These data suggest that circulating and skeletal muscle B2M can be promising targets for the management of PH-HFpEF.

Early detection of pulmonary arterial hypertension through [18F] positron emission tomography imaging with a vascular endothelial receptor small molecule

The objective of this study is to provide a positron emission tomography (PET) imaging modality targeting vascular endothelial growth factor receptors (VEGFR) for the early noninvasive detection and assessment of pulmonary arterial hypertension (PAH) severity. To validate the effectiveness of the [18F]VEGFR PET tracer, we utilized a monocrotaline (MCT)-induced PAH rat model. Molecular optical imaging, using a Cy5.5-conjugated VEGFR targeting agent, was employed to demonstrate the uptake of the agent at pulmonary arterioles, correlating with the onset and progression of PAH. Histological examinations of the MCT-PAH rat lung revealed a significant correlation between VEGFR2 expression and the pathogenesis of PAH. Molecular optical imaging demonstrated heightened uptake of the Cy5.5-conjugated VEGFR targeting agent at pulmonary arterioles, corresponding with the onset and progression of PAH. [18F]VEGFR PET showed increased lung uptake detectable in early-stage PAH before increase in pulmonary artery pressures, and this uptake correlated with increased PAH severity. Moreover, when compared to [18F]FDG PET, [18F]VEGFR PET exhibited markedly lower background cardiac signal, enhancing imaging sensitivity for lung abnormalities. Our study provides a compelling evidence for the potential utility of the innovative [18F]VEGFR PET tracer, in non-invasively detecting early signs of PAH, and monitoring its progression. The observed correlations between VEGFR2 expression, molecular optical imaging results, and [18F]VEGFR PET findings support the use of this tracer for early detection, and assessment of PAH severity. The lower background cardiac signal observed with [18F]VEGFR PET further enhances its imaging sensitivity, emphasizing its potential clinical significance.

Idiopathic and connective tissue disease-associated pulmonary arterial hypertension (PAH): Similarities, differences and the role of autoimmunity

Pre-capillary pulmonary arterial hypertension (PAH) is hemodynamically characterized by a mean pulmonary arterial pressure (mPAP) ≥ 20 mmHg, pulmonary capillary wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) > 2. PAH is classified in six clinical subgroups, including idiopathic PAH (IPAH) and PAH associated to connective tissue diseases (CTD-PAH), that will be the main object of this review. The aim is to compare these two PAH subgroups in terms of epidemiology, histological and pathogenic findings in an attempt to define disease-specific features, including autoimmunity, that may explain the heterogeneity of response to therapy between IPAH and CTD-PAH.

Plasma VEGF-D and sFLT-1 are potential biomarkers of hemodynamics and congestion in heart failure and following heart transplantation

Background

Inflammation and tyrosine-kinases are known mediators in the pathobiology of cardiovascular disease. Plasma biomarkers reflecting these systems may provide a noninvasive complement reflecting hemodynamics, aiding in clinical decision-making. We therefore aimed to investigate the plasma levels of vascular and inflammatory proteins, and their associations with invasive hemodynamics in advanced heart failure (HF) before, and at multiple follow-ups after heart transplantation (HT).

Methods

Using multiplex sandwich immunoassays, absolute plasma concentrations of 9 vascular and inflammatory proteins were assessed in 26 patients with advanced HF, before HT, and at 4 weeks, 6 months, and 1year after HT. Right heart catheterization hemodynamics were assessed at the time of blood sampling. Repeated measures correlations were performed to evaluate the overall intra-individual development of plasma protein levels in relation to hemodynamics' development over time.

Results

Out of 9 proteins included initially, in advanced HF, elevated plasma levels of vascular endothelial growth factor D (VEGF-D) and soluble fms-like tyrosine kinase-1 (sFlt-1) decreased most markedly at 4 weeks (p < 0.0001), and decreased further at 6 months (p < 0.05) and at the 1 year follow-ups after-HT (p < 0.05). Over time, plasma VEGF-D correlated strongest with hemodynamic parameters including pulmonary arterial wedge pressure (PAWP) (r mr = 0.75, 95% bootstrapped confidence interval (CI) 0.61-0.84, p < 0.0001), followed by mean right atrial pressure (MRAP) (r mr = 0.74, 95% CI 0.61-0.82, p < 0.0001), and mean pulmonary arterial pressure (mPAP) (r mr = 0.74, 95% CI 0.58-0.82, p < 0.0001). Plasma sFlt-1 correlated also with multiple hemodynamic parameters including PAWP (r mr = 0.66, 95% CI 0.58-0.79, p < 0.0001), MRAP (r mr = 0.64, 95% CI 0.58-0.81, p < 0.0001), and mPAP (r mr = 0.61, 95% CI 0.51-0.76, p < 0.0001).

Conclusions

In advanced HF, elevated plasma VEGF-D and sFlt-1 levels decrease early, already within 4 weeks after HT, and further throughout the first year postoperatively. Our findings support that high plasma VEGF-D and sFlt-1 concentrations before HT are related to congestion and overall hemodynamic improvement. Plasma VEGF-D and sFlt-1 may consequently be potential noninvasive biomarkers for monitoring hemodynamic deterioration and congestion in HF, and surveillance after HT.

Vascular endothelial growth factor-D plasma levels and VEGFD genetic variants are independently associated with outcomes in patients with cardiovascular disease

AIMS

The vascular endothelial growth factor (VEGF) family is involved in pathophysiological mechanisms underlying cardiovascular (CV) diseases. The aim of this study was to investigate the associations between circulating VEGF ligands and/or soluble receptors and CV outcome in patients with acute coronary syndrome (ACS) and chronic coronary syndrome (CCS).

METHODS AND RESULTS

Levels of VEGF biomarkers, including bFGF, Flt-1, KDR (VEGFR2), PlGF, Tie-2, VEGF-A, VEGF-C, and VEGF-D, were measured in the PLATO ACS cohort (n = 2091, discovery cohort). Subsequently, VEGF-D was also measured in the STABILITY CCS cohort (n = 4015, confirmation cohort) to verify associations with CV outcomes. Associations between plasma VEGF-D and outcomes were analysed by multiple Cox regression models with hazard ratios (HR [95% CI]) comparing the upper vs. the lower quartile of VEGF-D. Genome-wide association study (GWAS) of VEGF-D in PLATO identified SNPs that were used as genetic instruments in Mendelian randomization (MR) meta-analyses vs. clinical endpoints. GWAS and MR were performed in patients with ACS from PLATO (n = 10 013) and FRISC-II (n = 2952), and with CCS from the STABILITY trial (n = 10 786). VEGF-D, KDR, Flt-1, and PlGF showed significant association with CV outcomes. VEGF-D was most strongly associated with CV death (P = 3.73e-05, HR 1.892 [1.419, 2.522]). Genome-wide significant associations with VEGF-D levels were identified at the VEGFD locus on chromosome Xp22. MR analyses of the combined top ranked SNPs (GWAS P-values; rs192812042, P = 5.82e-20; rs234500, P = 1.97e-14) demonstrated a significant effect on CV mortality [P = 0.0257, HR 1.81 (1.07, 3.04) per increase of one unit in log VEGF-D].

CONCLUSION

This is the first large-scale cohort study to demonstrate that both VEGF-D plasma levels and VEGFD genetic variants are independently associated with CV outcomes in patients with ACS and CCS. Measurements of VEGF-D levels and/or VEGFD genetic variants may provide incremental prognostic information in patients with ACS and CCS.

An Overview of Circulating Pulmonary Arterial Hypertension Biomarkers

Pulmonary arterial hypertension (PAH), also known as Group 1 Pulmonary Hypertension (PH), is a PH subset characterized by pulmonary vascular remodeling and pulmonary arterial obstruction. PAH has an estimated incidence of 15-50 people per million in the United States and Europe, and is associated with high mortality and morbidity, with patients' survival time after diagnosis being only 2.8 years. According to current guidelines, right heart catheterization is the gold standard for diagnostic and prognostic evaluation of PAH patients. However, this technique is highly invasive, so it is not used in routine clinical practice or patient follow-up. Thereby, it is essential to find new non-invasive strategies for evaluating disease progression. Biomarkers can be an effective solution for determining PAH patient prognosis and response to therapy, and aiding in diagnostic efforts, so long as their detection is non-invasive, easy, and objective. This review aims to clarify and describe some of the potential new candidates as circulating biomarkers of PAH.

Understanding the Pathobiology of Pulmonary Hypertension Due to Left Heart Disease

The development of pulmonary hypertension (PH) is common and has adverse prognostic implications in patients with heart failure due to left heart disease (LHD), and thus far, there are no known treatments specifically for PH-LHD, also known as group 2 PH. Diagnostic thresholds for PH-LHD, and clinical classification of PH-LHD phenotypes, continue to evolve and, therefore, present a challenge for basic and translational scientists actively investigating PH-LHD in the preclinical setting. Furthermore, the pathobiology of PH-LHD is not well understood, although pulmonary vascular remodeling is thought to result from (1) increased wall stress due to increased left atrial pressures; (2) hemodynamic congestion-induced decreased shear stress in the pulmonary vascular bed; (3) comorbidity-induced endothelial dysfunction with direct injury to the pulmonary microvasculature; and (4) superimposed pulmonary arterial hypertension risk factors. To ultimately be able to modify disease, either by prevention or treatment, a better understanding of the various drivers of PH-LHD, including endothelial dysfunction, abnormalities in vascular tone, platelet aggregation, inflammation, adipocytokines, and systemic complications (including splanchnic congestion and lymphatic dysfunction) must be further investigated. Here, we review the diagnostic criteria and various hemodynamic phenotypes of PH-LHD, the potential biological mechanisms underlying this disorder, and pressing questions yet to be answered about the pathobiology of PH-LHD.

Plasma tumour and metabolism related biomarkers AMBP, LPL and Glyoxalase I differentiate heart failure with preserved ejection fraction with pulmonary hypertension from pulmonary arterial hypertension

BACKGROUND

Discrimination of heart failure with preserved ejection fraction with pulmonary hypertension (HFpEF-PH) from pulmonary arterial hypertension (PAH) is crucial for clinical management but may be challenging due to similarities in clinical and comorbid characteristics. We aimed to investigate tumour and metabolism related proteins in differentiating HFpEF-PH from PAH.

METHODS

Sixty-nine tumour and metabolism plasma proteins were analysed with proximity extension assay in heathy controls (n = 20), patients with PAH (n = 48) and LHF-PH (n = 67) [HFpEF-PH (n = 31) and HF reduced EF-PH (n = 36)]. Haemodynamics were assessed with right heart catheterization.

RESULTS

The plasma levels of alpha-1-microglobulin/bikunin precursor (AMBP) and lipoprotein lipase (LPL), were higher in HFpEF-PH compared to healthy controls (p < 0.01), HFrEF-PH (p < 0.05), and PAH (p < 0.001). Glyoxalase I levels were higher in HFpEF-PH and HFrEF-PH compared to controls (p < 0.001) and PAH (p < 0.001). Each of plasma AMBP, LPL, and glyoxalase I, adjusted for age and sex in multivariable logistic regression models, could differentiate HFpEF-PH from PAH, with areas under the receiver operating characteristic curve (AUC) of 0.81, 0.84 and 0.79, respectively. The combination of AMBP, LPL and glyoxalse I yielded the largest AUC of 0.87 [95% confidence interval (0.79-0.95)] in discriminating HFpEF-PH from PAH, with a sensitivity of 87.1% and a specificity of 85.4%. In HFpEF-PH, the plasma levels of AMBP correlated with pulmonary arterial wedge pressure (r_s = -0.42, p = 0.018).

CONCLUSIONS

Plasma AMBP, LPL and glyoxalase I may facilitate the distinction of HFpEF-PH from PAH. Larger clinical studies are encouraged to confirm and validate our findings.

Plasma ADAMTS13 and von Willebrand factor in diagnosis and prediction of prognosis in pulmonary arterial hypertension

To improve outcome in pulmonary arterial hypertension, earlier diagnosis and better prognostic assessments are required. We aimed to investigate the diagnostic and prognostic potential of plasma proteins related to pathways recognized in pulmonary arterial hypertension including coagulation, inflammation, and metabolism. Forty-two proteins were analysed with proximity extension assay from plasma of 20 healthy controls and 150 patients, including (pulmonary arterial hypertension, n = 48, whereof 33 also during early treatment follow-ups); chronic thromboembolic pulmonary hypertension (CTEPH, n = 20); pulmonary hypertension (PH) due to heart failure (HF) with preserved ejection fraction (HFpEF-PH, n = 31); PH due to HF with reduced ejection fraction (HFrEF-PH, n = 36); and HF without PH (Dyspnoea/HF-non-PH, n = 15). Patients' haemodynamics were assessed by right heart catheterization. Plasma ADAMTS13 in incident pulmonary arterial hypertension was lower compared to the healthy controls (p = 0.055), as well as CTEPH (p < 0.0001), HFrEF-PH (p < 0.0001), HFrEF-PH (p < 0.0001), and Dyspnoea/HF-non-PH (p < 0.0001). Adjusted for age and sex, ADAMTS13 discriminated pulmonary arterial hypertension from the other disease groups with an AUC of 0.91 (sensitivity = 87.5%, and specificity = 78.4%). Higher plasma von Willebrand factor was associated with worse survival (log-rank p = 0.0029), and a higher mortality rate (adjusted hazard ratio 1.002, 95% confidence interval 1-1.004; p = 0.041). Adjusted for age, sex, and combined with the ESC/ERS risk score, von Willebrand factor predicted mortality (median follow-up 3.6 years) in pulmonary arterial hypertension with an AUC of 0.94 (sensitivity = 81.3%, and specificity=93.8%). ADAMTS13 may be a promising biomarker for early detection of PAH and von Willebrand factor as a candidate prognostic biomarker. The putative additional value of von Willebrand factor to the European multiparametric risk assessment strategy remains to be elucidated.

Endothelial Dysfunction in Pulmonary Hypertension: Cause or Consequence?

Pulmonary arterial hypertension (PAH) is a rare, complex, and progressive disease that is characterized by the abnormal remodeling of the pulmonary arteries that leads to right ventricular failure and death. Although our understanding of the causes for abnormal vascular remodeling in PAH is limited, accumulating evidence indicates that endothelial cell (EC) dysfunction is one of the first triggers initiating this process. EC dysfunction leads to the activation of several cellular signalling pathways in the endothelium, resulting in the uncontrolled proliferation of ECs, pulmonary artery smooth muscle cells, and fibroblasts, and eventually leads to vascular remodelling and the occlusion of the pulmonary blood vessels. Other factors that are related to EC dysfunction in PAH are an increase in endothelial to mesenchymal transition, inflammation, apoptosis, and thrombus formation. In this review, we outline the latest advances on the role of EC dysfunction in PAH and other forms of pulmonary hypertension. We also elaborate on the molecular signals that orchestrate EC dysfunction in PAH. Understanding the role and mechanisms of EC dysfunction will unravel the therapeutic potential of targeting this process in PAH.

Role of biomarkers in evaluation, treatment and clinical studies of pulmonary arterial hypertension

Pulmonary arterial hypertension is a complex disease resulting from the interplay of myriad biological and environmental processes that lead to remodeling of the pulmonary vasculature with consequent pulmonary hypertension. Despite currently available therapies, there remains significant morbidity and mortality in this disease. There is great interest in identifying and applying biomarkers to help diagnose patients with pulmonary arterial hypertension, inform prognosis, guide therapy, and serve as surrogate endpoints. An extensive literature on potential biomarker candidates is available, but barriers to the implementation of biomarkers for clinical use in pulmonary arterial hypertension are substantial. Various omic strategies have been undertaken to identify key pathways regulated in pulmonary arterial hypertension that could serve as biomarkers including genomic, transcriptomic, proteomic, and metabolomic approaches. Other biologically relevant components such as circulating cells, microRNAs, exosomes, and cell-free DNA have recently been gaining attention. Because of the size of the datasets generated by these omic approaches and their complexity, artificial intelligence methods are being increasingly applied to decipher their meaning. There is growing interest in imaging the lung with various modalities to understand and visualize processes in the lung that lead to pulmonary vascular remodeling including high resolution computed tomography, Xenon magnetic resonance imaging, and positron emission tomography. Such imaging modalities have the potential to demonstrate disease modification resulting from therapeutic interventions. Because right ventricular function is a major determinant of prognosis, imaging of the right ventricle with echocardiography or cardiac magnetic resonance imaging plays an important role in the evaluation of patients and may also be useful in clinical studies of pulmonary arterial hypertension.

Current Understanding of Circulating Biomarkers in Pulmonary Hypertension Due to Left Heart Disease

Pulmonary hypertension due to left heart disease (PH-LHD; Group 2), especially in the setting of heart failure with preserved ejection fraction (HFpEF), is the most frequent cause of PH. Despite its prevalence, no effective therapies for PH-LHD are available at present. This is largely due to the lack of a concise definition for hemodynamic phenotyping, existence of significant gaps in the understanding of the underlying pathology and the impact of associated comorbidities, as well as the absence of specific biomarkers that can aid in the early diagnosis and management of this challenging syndrome. Currently, B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are guideline-recommended biomarkers for the diagnosis and prognosis of heart failure (HF) and PH. Endothelin-1 (ET-1), vascular endothelial growth factor-D (VEGF-D), and microRNA-206 have also been recently identified as new potential circulating biomarkers for patients with PH-LHD. In this review, we aim to present the current state of knowledge of circulating biomarkers that can be used to guide future research toward diagnosis, refine specific patient phenotype, and develop therapeutic approaches for PH-LHD, with a particular focus on PH-HFpEF. Potential circulating biomarkers identified in pre-clinical models of PH-LHD are also summarized here.

Plasma adrenomedullin peptides and precursor levels in pulmonary arterial hypertension disease severity and risk stratification

Adrenomedullin is a potent vasodilatory peptide, linked to pulmonary arterial hypertension pathology. Proximity extension assays were utilized to study plasma biomarkers related to vasoregulation, with focus on adrenomedullin peptides and precursor levels, collectively referred to as ADM. ADM was measured in 48 treatment-naïve pulmonary arterial hypertension patients at diagnosis, and in 31 of them at an early treatment follow-up. Plasma ADM was additionally assessed in patients with chronic thromboembolic pulmonary hypertension (n = 20) and pulmonary hypertension due to heart failure with preserved (HFpEF_(PH)) (n = 33) or reduced (HFrEF_(PH)) (n = 36) ejection fraction, as well as healthy controls (n = 16). ADM was studied in relation to pulmonary arterial hypertension hemodynamics, risk assessment, prognosis, treatment response, and differentiation. Plasma ADM levels in pulmonary arterial hypertension patients at diagnosis were higher than in healthy controls (p < 0.001), similar as in chronic thromboembolic pulmonary hypertension patients (p = ns), but lower compared to HFpEF_(PH) (p < 0.03) and HFrEF_(PH) (p < 0.001). In pulmonary arterial hypertension, specifically, plasma ADM at diagnosis correlated mainly to mean right atrial pressure (r = 0.73, p < 0.001), N-terminal prohormone of brain natriuretic peptide (r = 0.75, p < 0.001), six-minute walking distance (r = -0.57, p < 0.001), and venous oxygen saturation (r = -0.57, p < 0.001). ADM also correlated to the ECS/ERS- (r = 0.74, p < 0.001) and REVEAL risk scores (r = 0.54, p < 0.001) at pulmonary arterial hypertension diagnosis. Plasma ADM in pulmonary arterial hypertension patients was unaltered at early treatment follow-up compared to baseline (p = ns). Pulmonary arterial hypertension patients with supra-median ADM at diagnosis showed worse overall survival than those with infra-median levels (median survival 34 versus 66 months, p = 0.0077). In conclusion, the present results suggest that baseline plasma ADM levels mirror disease severity, correlating to both ECS/ERS- and the REVEAL risk scores.

Elevated plasma tyrosine kinases VEGF-D and HER4 in heart failure patients decrease after heart transplantation in association with improved haemodynamics

Receptor tyrosine kinases (RTKs) are implicated in cardiovascular growth and remodelling. We aimed to identify the plasma levels of RTKs and related proteins and their association with haemodynamic alterations in heart failure (HF) and related pulmonary hypertension (PH) following heart transplantation (HT). Using proximity extension assay, 28 RTKs and related proteins were analysed in plasma from 20 healthy controls and 26 HF patients before and 1-year after HT. In end-stage HF, out of 28 RTKs, plasma vascular endothelial growth factor-D (VEGF-D) and human epidermal growth factor-4 (HER4) were elevated compared to controls (p < 0.001), but decreased (p < 0.0001) and normalised after HT. Following HT, plasma changes (Δ) of VEGF-D correlated with Δmean pulmonary artery pressure (rs = 0.65, p = 0.00049), Δpulmonary artery wedge pressure (rs = 0.72, p < 0.0001), Δpulmonary arterial compliance (PAC) (rs = - 0.52, p = 0.0083) and Δpulmonary vascular resistance (PVR) (rs = 0.58, p = 0.0032). ΔHER4 correlated with Δmean right atrial pressure (rs = 0.51, p = 0.012), ΔNT-proBNP (rs = 0.48, p = 0.016) and Δcardiac index (rs = - 0.56, p = 0.0044). In HF patients following HT, normalisation of VEGF-D reflected reversal of passive pulmonary congestion and restored PAC and PVR; whereas the normalisation of HER4 reflected decreased volume overload and improved cardiac function. The precise function of these proteins, their potential clinical use and pathophysiological relation in HF and related PH remain to be elucidated.

Pulmonary hypertension: Proteins in the blood

The plasma proteome is rich in information. It comprises proteins that are secreted or lost from cells as they respond to their local environment. Changes in the constitution of the plasma proteome offer a relatively non-invasive report on the health of tissues. This is particularly true of the lung in pulmonary hypertension, given the large surface area of the pulmonary vasculature in direct communication with blood. So far, this is relatively untapped; we have relied on proteins released from the heart, specifically brain natriuretic peptide and troponin, to inform clinical management. New technology allows the measurement of a larger number of proteins that cover a broad range of molecular pathways in a single small aliquot. The emerging data will yield more than just new biomarkers of pulmonary hypertension for clinical use. Integrated with genomics and with the help of new bioinformatic tools, the plasma proteome can provide insight into the causative drivers of pulmonary vascular disease and guide drug development.