Proteomic analysis of lung tissues from patients with pulmonary arterial hypertension

Identification of MACC1 as a potential biomarker for pulmonary arterial hypertension based on bioinformatics and machine learning

BACKGROUND

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by abnormal early activation of pulmonary arterial smooth muscle cells (PASMCs), yet the underlying mechanisms remain to be elucidated.

METHODS

Normal and PAH gene expression profiles were obtained from the Gene Expression Omnibus (GEO) database and analyzed using gene set enrichment analysis (GSEA) to uncover the underlying mechanisms. Weighted gene co-expression network analysis (WGCNA) and machine learning methods were deployed to further filter hub genes. A number of immune infiltration analysis methods were applied to explore the immune landscape of PAH. Enzyme-linked immunosorbent assay (ELISA) was employed to compare MACC1 levels between PAH and normal subjects. The important role of MACC1 in the progression of PAH was verified through Western blot and real-time qPCR, among others.

RESULTS

39 up-regulated and 7 down-regulated genes were identified by 'limma' and 'RRA' packages. WGCNA and machine learning further narrowed down the list to 4 hub genes, with MACC1 showing strong diagnostic capacity. In vivo and in vitro experiments revealed that MACC1 was highsly associated with malignant features of PASMCs in PAH.

CONCLUSIONS

These findings suggest that targeting MACC1 may offer a promising therapeutic strategy for treating PAH, and further clinical studies are warranted to evaluate its efficacy.

[Research progress on bioinformatics in pulmonary arterial hypertension]

Pulmonary arterial hypertension (PAH) is a severe disease characterized by abnormal pulmonary vascular remodeling and increased right ventricular pressure load, posing a significant threat to patient health. While some pathological mechanisms of PAH have been revealed, the deeper mechanisms of pathogenesis remain to be elucidated. In recent years, bioinformatics has provided a powerful tool for a deeper understanding of the complex mechanisms of PAH through the integration of techniques such as multi-omics analysis, artificial intelligence, and Mendelian randomization. This review focuses on the bioinformatics methods and technologies used in PAH research, summarizing their current applications in the study of disease mechanisms, diagnosis, and prognosis assessment. Additionally, it analyzes the existing challenges faced by bioinformatics and its potential applications in the clinical and basic research fields of PAH in the future.

Proteomic and Phosphoproteomic Analysis of Right Ventricular Hypertrophy in the Pulmonary Hypertension Rat Model

Pulmonary arterial hypertension (PAH) is a progressive disease that affects both the lungs and heart. Right ventricle (RV) hypertrophy is a primary pathological feature of PAH; however, its underlying molecular mechanisms remain insufficiently studied. In this study, we employed tandem mass tag (TMT)-based quantitative proteomics for the integrative analysis of the proteome and phosphoproteome of the RV derived from monocrotaline-induced PAH model rats. Compared with control samples, 564 significantly upregulated proteins, 616 downregulated proteins, 622 downregulated phosphopeptides, and 683 upregulated phosphopeptides were identified (P < 0.05, abs (log2 (fold change)) > log2 1.2) in the MCT samples. The quantitative real-time polymerase chain reaction (qRT-PCR) validated the expression levels of top 20 significantly altered proteins, including Nppa (natriuretic peptides A), latent TGF-β binding protein 2 (Ltbp2), periostin, connective tissue growth factor 2 (Ccn2), Ncam1 (neural cell adhesion molecule), quinone reductase 2 (Nqo2), and tropomodulin 4 (Tmod4). Western blotting confirmed the upregulation of Ncam1 and downregulation of Nqo2 and Tmod4 in both MCT-induced and hypoxia-induced PH rat models. Pathway enrichment analyses indicated that the altered proteins are associated with pathways, such as vesicle-mediated transport, actin cytoskeleton organization, TCA cycle, and respiratory electron transport. These significantly changed phosphoproteins were enriched in pathways such as diabetic cardiomyopathy, hypertrophic cardiomyopathy, glycolysis/gluconeogenesis, and cardiac muscle contraction. In summary, this study provides an initial analysis of the RV proteome and phosphoproteome in the progression of PAH, highlighting several RV dysfunction-associated proteins and pathways.

Proteomic analysis of pulmonary arteries and lung tissues from dogs affected with pulmonary hypertension secondary to degenerative mitral valve disease

In dogs with degenerative mitral valve disease (DMVD), pulmonary hypertension (PH) is a common complication characterized by abnormally elevated pulmonary arterial pressure (PAP). Pulmonary arterial remodeling is the histopathological changes of pulmonary artery that has been recognized in PH. The underlying mechanisms that cause this arterial remodeling are poorly understood. This study aimed to perform shotgun proteomics to investigate changes in protein expression in pulmonary arteries and lung tissues of DMVD dogs with PH compared to normal control dogs and DMVD dogs without PH. Tissue samples were collected from the carcasses of 22 small-sized breed dogs and divided into three groups: control (n = 7), DMVD (n = 7) and DMVD+PH groups (n = 8). Differentially expressed proteins were identified, and top three upregulated and downregulated proteins in the pulmonary arteries of DMVD dogs with PH including SIK family kinase 3 (SIK3), Collagen type I alpha 1 chain (COL1A1), Transforming growth factor alpha (TGF-α), Apoptosis associated tyrosine kinase (AATYK), Hepatocyte growth factor activator (HGFA) and Tyrosine-protein phosphatase non-receptor type 13 (PTPN13) were chosen. Results showed that some of the identified proteins may play a role in the pathogenesis of pulmonary arterial remodeling. This study concluded shotgun proteomics has potential as a tool for exploring candidate proteins associated with the pathogenesis of PH secondary to DMVD in dogs.

Endothelial periostin regulates vascular remodeling by promoting endothelial dysfunction in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by vascular remodeling associated with extracellular matrix (ECM) deposition, vascular cell hyperproliferation, and neointima formation in the small pulmonary artery. Endothelial dysfunction is considered a key feature in the initiation of vascular remodeling. Although vasodilators have been used for the treatment of PAH, it remains a life-threatening disease. Therefore, it is necessary to identify novel therapeutic targets for PAH treatment. Periostin (POSTN) is a secretory ECM protein involved in physiological and pathological processes, such as tissue remodeling, cell adhesion, migration, and proliferation. Although POSTN has been proposed as a potential target for PAH treatment, its role in endothelial cells has not been fully elucidated. Here, we demonstrated that POSTN upregulation correlates with PAH by analyzing a public microarray conducted on the lung tissues of patients with PAH and biological experimental results from in vivo and in vitro models. Moreover, POSTN overexpression leads to ECM deposition and endothelial abnormalities such as migration. We found that PAH-associated endothelial dysfunction is mediated at least in part by the interaction between POSTN and integrin-linked protein kinase (ILK), followed by activation of nuclear factor-κB signaling. Silencing POSTN or ILK decreases PAH-related stimuli-induced ECM accumulation and attenuates endothelial abnormalities. In conclusion, our study suggests that POSTN serves as a critical regulator of PAH by regulating vascular remodeling, and targeting its role as a potential therapeutic strategy for PAH.

High-Soluble-Fiber Diet Attenuates Hypoxia-Induced Vascular Remodeling and the Development of Hypoxic Pulmonary Hypertension

BACKGROUND

Hypoxic pulmonary hypertension is a difficult disease to manage that is characterized by sustained elevation of pulmonary vascular resistance and pulmonary artery pressure due to vasoconstriction, perivascular inflammation, and vascular remodeling. Consumption of soluble-fiber is associated with lower systemic blood pressure, but little is known about its ability to affect the pulmonary circulation.

METHODS

Mice were fed either a low- or high-soluble-fiber diet (0% or 16.9% inulin) and then exposed to hypoxia (FiO2, 0.10) for 21 days to induce pulmonary hypertension. The impact of diet on right ventricular systolic pressure and pulmonary vascular resistance was determined in vivo or in ex vivo isolated lungs, respectively, and correlated with alterations in the composition of the gut microbiome, plasma metabolome, pulmonary inflammatory cell phenotype, and lung proteome.

RESULTS

High-soluble-fiber diet increased the abundance of short-chain fatty acid-producing bacteria, with parallel increases in plasma propionate levels, and reduced the abundance of disease-related bacterial genera such as Staphylococcus, Clostridioides, and Streptococcus in hypoxic mice with parallel decreases in plasma levels of p-cresol sulfate. High-soluble-fiber diet decreased hypoxia-induced elevations of right ventricular systolic pressure and pulmonary vascular resistance. These changes were associated with reduced proportions of interstitial macrophages, dendritic cells, and nonclassical monocytes. Whole-lung proteomics revealed proteins and molecular pathways that may explain the effect of soluble-fiber supplementation.

CONCLUSIONS

This study demonstrates for the first time that a high-soluble-fiber diet attenuates hypoxia-induced pulmonary vascular remodeling and the development of pulmonary hypertension in a mouse model of hypoxic pulmonary hypertension and highlights diet-derived metabolites that may have an immuno-modulatory role in the lung.

Hypoxia and panvascular diseases: exploring the role of hypoxia-inducible factors in vascular smooth muscle cells under panvascular pathologies

As an emerging discipline, panvascular diseases are a set of vascular diseases with atherosclerosis as the common pathogenic hallmark, which mostly affect vital organs like the heart, brain, kidney, and limbs. As the major responser to the most common stressor in the vasculature (hypoxia)-hypoxia-inducible factors (HIFs), and the primary regulator of pressure and oxygen delivery in the vasculature-vascular smooth muscle cells (VSMCs), their own multifaceted nature and their interactions with each other are fascinating. Abnormally active VSMCs (e.g., atherosclerosis, pulmonary hypertension) or abnormally dysfunctional VSMCs (e.g., aneurysms, vascular calcification) are associated with HIFs. These widespread systemic diseases also reflect the interdisciplinary nature of panvascular medicine. Moreover, given the comparable proliferative characteristics exhibited by VSMCs and cancer cells, and the delicate equilibrium between angiogenesis and cancer progression, there is a pressing need for more accurate modulation targets or combination approaches to bolster the effectiveness of HIF targeting therapies. Based on the aforementioned content, this review primarily focused on the significance of integrating the overall and local perspectives, as well as temporal and spatial balance, in the context of the HIF signaling pathway in VSMC-related panvascular diseases. Furthermore, the review discussed the implications of HIF-targeting drugs on panvascular disorders, while considering the trade-offs involved.

Risk Stratification in Pulmonary Arterial Hypertension, Update and Perspectives

Risk stratification in pulmonary arterial hypertension (PAH) is crucial in assessing patient prognosis. It serves a prominent role in everyday patient care and can be determined using several validated risk assessment scores worldwide. The recently published 2022 European Society of Cardiology (ESC)/European Respiratory Society (ERS) guidelines underline the importance of risk stratification not only at baseline but also during follow-up. Achieving a low-risk status has now become the therapeutic goal, emphasising the importance of personalised therapy. The application of these guidelines is also important in determining the timing for lung transplantation referral. In this review, we summarise the most relevant prognostic factors of PAH as well as the parameters used in PAH risk scores and their evolution in the guidelines over the last decade. Finally, we describe the central role that risk stratification plays in the current guidelines not only in European countries but also in Asian countries.

Quantitative Proteomic and Phosphoproteomic Profiling of Lung Tissues from Pulmonary Arterial Hypertension Rat Model

Pulmonary arterial hypertension (PAH) is a rare but fatal disease characterized by elevated pulmonary vascular resistance and increased pressure in the distal pulmonary arteries. Systematic analysis of the proteins and pathways involved in the progression of PAH is crucial for understanding the underlying molecular mechanism. In this study, we performed tandem mass tags (TMT)-based relative quantitative proteomic profiling of lung tissues from rats treated with monocrotaline (MCT) for 1, 2, 3 and 4 weeks. A total of 6759 proteins were quantified, among which 2660 proteins exhibited significant changes (p-value < 0.05, fold change < 0.83 or >1.2). Notably, these changes included several known PAH-related proteins, such as Retnla (resistin-like alpha) and arginase-1. Furthermore, the expression of potential PAH-related proteins, including Aurora kinase B and Cyclin-A2, was verified via Western blot analysis. In addition, we performed quantitative phosphoproteomic analysis on the lungs from MCT-induced PAH rats and identified 1412 upregulated phosphopeptides and 390 downregulated phosphopeptides. Pathway enrichment analysis revealed significant involvement of pathways such as complement and coagulation cascades and the signaling pathway of vascular smooth muscle contraction. Overall, this comprehensive analysis of proteins and phosphoproteins involved in the development and progression of PAH in lung tissues provides valuable insights for the development of potential diagnostic and treatment targets for PAH.

Multiomics Network Medicine Approaches to Precision Medicine and Therapeutics in Cardiovascular Diseases

Cardiovascular diseases (CVD) are the leading cause of death worldwide and display complex phenotypic heterogeneity caused by many convergent processes, including interactions between genetic variation and environmental factors. Despite the identification of a large number of associated genes and genetic loci, the precise mechanisms by which these genes systematically influence the phenotypic heterogeneity of CVD are not well understood. In addition to DNA sequence, understanding the molecular mechanisms of CVD requires data from other omics levels, including the epigenome, the transcriptome, the proteome, as well as the metabolome. Recent advances in multiomics technologies have opened new precision medicine opportunities beyond genomics that can guide precise diagnosis and personalized treatment. At the same time, network medicine has emerged as an interdisciplinary field that integrates systems biology and network science to focus on the interactions among biological components in health and disease, providing an unbiased framework through which to integrate systematically these multiomics data. In this review, we briefly present such multiomics technologies, including bulk omics and single-cell omics technologies, and discuss how they can contribute to precision medicine. We then highlight network medicine-based integration of multiomics data for precision medicine and therapeutics in CVD. We also include a discussion of current challenges, potential limitations, and future directions in the study of CVD using multiomics network medicine approaches.

Histologic and proteomic remodeling of the pulmonary veins and arteries in a porcine model of chronic pulmonary venous hypertension

AIMS

In heart failure (HF), pulmonary venous hypertension (PVH) produces pulmonary hypertension (PH) with remodeling of pulmonary veins (PV) and arteries (PA). In a porcine PVH model, we performed proteomic-based bioinformatics to investigate unique pathophysiologic mechanisms mediating PA and PV remodeling.

METHODS AND RESULTS

Large PV were banded (PVH, n = 10) or not (Sham, n = 9) in piglets. At sacrifice, PV and PA were perfusion labelled for vessel-specific histology and proteomics. The PA and PV were separately sampled with laser-capture micro-dissection for mass spectrometry. Pulmonary vascular resistance [Wood Units; 8.6 (95% confidence interval: 6.3, 12.3) vs. 2.0 (1.7, 2.3)] and PA [19.9 (standard error of mean, 1.1) vs. 10.3 (1.1)] and PV [14.2 (1.2) vs. 7.6 (1.1)] wall thickness/external diameter (%) were increased in PVH (P < 0.05 for all). Similar numbers of proteins were identified in PA (2093) and PV (2085) with 94% overlap, but biological processes differed. There were more differentially expressed proteins (287 vs. 161), altered canonical pathways (17 vs. 3), and predicted upstream regulators (PUSR; 22 vs. 6) in PV than PA. In PA and PV, bioinformatics indicated activation of the integrated stress response and mammalian target of rapamycin signalling with dysregulated growth. In PV, there was also activation of Rho/Rho-kinase signalling with decreased actin cytoskeletal signalling and altered tight and adherens junctions, ephrin B, and caveolae-mediated endocytosis signalling; all indicating disrupted endothelial barrier function. Indeed, protein biomarkers and the top PUSR in PV (transforming growth factor-beta) suggested endothelial to mesenchymal transition in PV. Findings were similar in human autopsy specimens.

CONCLUSION

These findings provide new therapeutic targets to oppose pulmonary vascular remodeling in HF-related PH.

Tensions in Taxonomies: Current Understanding and Future Directions in the Pathobiologic Basis and Treatment of Group 1 and Group 3 Pulmonary Hypertension

In the over 100 years since the recognition of pulmonary hypertension (PH), immense progress and significant achievements have been made with regard to understanding the pathophysiology of the disease and its treatment. These advances have been mostly in idiopathic pulmonary arterial hypertension (IPAH), which was classified as Group 1 Pulmonary Hypertension (PH) at the Second World Symposia on PH in 1998. However, the pathobiology of PH due to chronic lung disease, classified as Group 3 PH, remains poorly understood and its treatments thus remain limited. We review the history of the classification of the five groups of PH and aim to provide a state-of-the-art review of the understanding of the pathogenesis of Group 1 PH and Group 3 PH including insights gained from novel high-throughput omics technologies that have revealed heterogeneities within these categories as well as similarities between them. Leveraging the substantial gains made in understanding the genomics, epigenomics, proteomics, and metabolomics of PAH to understand the full spectrum of the complex, heterogeneous disease of PH is needed. Multimodal omics data as well as supervised and unbiased machine learning approaches after careful consideration of the powerful advantages as well as of the limitations and pitfalls of these technologies could lead to earlier diagnosis, more precise risk stratification, better predictions of disease response, new sub-phenotype groupings within types of PH, and identification of shared pathways between PAH and other types of PH that could lead to new treatment targets. © 2023 American Physiological Society. Compr Physiol 13:4295-4319, 2023.

Intracellular Chloride Channels Regulate Endothelial Metabolic Reprogramming in Pulmonary Arterial Hypertension

Mitochondrial fission and a metabolic switch from oxidative phosphorylation to glycolysis are key features of vascular pathology in pulmonary arterial hypertension (PAH) and are associated with exuberant endothelial proliferation and apoptosis. The underlying mechanisms are poorly understood. We describe the contribution of two intracellular chloride channel proteins, CLIC1 and CLIC4, both highly expressed in PAH and cancer, to mitochondrial dysfunction and energy metabolism in PAH endothelium. Pathological overexpression of CLIC proteins induces mitochondrial fragmentation, inhibits mitochondrial cristae formation, and induces metabolic shift toward glycolysis in human pulmonary artery endothelial cells, consistent with changes observed in patient-derived cells. Interactions of CLIC proteins with structural components of the inner mitochondrial membrane offer mechanistic insights. Endothelial CLIC4 excision and mitofusin 2 supplementation have protective effects in human PAH cells and preclinical PAH. This study is the first to demonstrate the key role of endothelial intracellular chloride channels in the regulation of mitochondrial structure, biogenesis, and metabolic reprogramming in expression of the PAH phenotype.

Periostin overexpression in scleroderma cardiac tissue and its utility as a marker for disease complications

OBJECTIVE

To evaluate the levels of periostin in patients with systemic sclerosis (SSc) and their association with features of systemic sclerosis.

METHODS

The levels of periostin were assessed in the serum of 106 SSc patients and 22 healthy controls and by immunofluorescence staining in cardiac tissue from 4 SSc patients and 4 controls. Serum periostin was measured via enzyme-linked immunosorbent assay. The results were analyzed using Mann-Whitney test or Kruskal-Wallis test followed by Dunn's multiple comparisons tests and Spearman's test for correlations. Cardiac tissue from SSc patients and controls was stained for periostin and co-stained for periostin and collagen type I using immunofluorescence.

RESULTS

Periostin levels were higher in patients with SSc compared to controls and directly correlated to modified Rodnan skin score and echocardiography parameters of left ventricular measurements. Immunofluorescence staining in SSc cardiac tissue showed patchy periostin expression in all SSc patients, but not in controls. Furthermore, there was extensive periostin expression even in areas without collagen deposition, while all established fibrotic areas showed colocalization of collagen and periostin. There was no association between periostin levels and interstitial lung disease, pulmonary hypertension or other vascular complications.

CONCLUSION

Periostin is elevated in SSc cardiac tissue in vivo and circulating levels of periostin are increased in SSc, correlating with the extent of disease duration, degree of skin fibrosis, and left ventricular structural assessments. Periostin may be a potential biomarker that can provide further pathogenic insight into cardiac fibrosis in SSc.

Metabolic reprogramming: A novel metabolic model for pulmonary hypertension

Pulmonary arterial hypertension, or PAH, is a condition that is characterized by pulmonary artery pressures above 20 mmHg (at rest). In the treatment of PAH, the pulmonary vascular system is regulated to ensure a diastolic and contraction balance; nevertheless, this treatment does not prevent or reverse pulmonary vascular remodeling and still causes pulmonary hypertension to progress. According to Warburg, the link between metabolism and proliferation in PAH is similar to that of cancer, with a common aerobic glycolytic phenotype. By activating HIF, aerobic glycolysis is enhanced and cell proliferation is triggered. Aside from glutamine metabolism, the Randle cycle is also present in PAH. Enhanced glutamine metabolism replenishes carbon intermediates used by glycolysis and provides energy to over-proliferating and anti-apoptotic pulmonary vascular cells. By activating the Randle cycle, aerobic oxidation is enhanced, ATP is increased, and myocardial injury is reduced. PAH is predisposed by epigenetic dysregulation of DNA methylation, histone acetylation, and microRNA. This article discusses the abnormal metabolism of PAH and how metabolic therapy can be used to combat remodeling.

Zn2+ triggered two-step mechanism of CLIC1 membrane insertion and activation into chloride channels

The chloride intracellular channel (CLIC) protein family displays the unique feature of altering its structure from a soluble form to a membrane-bound chloride channel. CLIC1, a member of this family, is found in the cytoplasm or in internal and plasma membranes, with membrane relocalisation linked to endothelial disfunction, tumour proliferation and metastasis. The molecular switch promoting CLIC1 activation remains under investigation. Here, cellular Cl⁻ efflux assays and immunofluorescence microscopy studies have identified intracellular Zn²⁺ release as the trigger for CLIC1 activation and membrane insertion. Biophysical assays confirmed specific binding to Zn²⁺, inducing membrane association and enhancing Cl⁻ efflux in a pH-dependent manner. Together, our results identify a two-step mechanism with Zn²⁺ binding as the molecular switch promoting CLIC1 membrane insertion, followed by pH-mediated activation of Cl⁻ efflux.

Summary: Identification of a two-step mechanism of CLIC1 membrane insertion based on Zn²⁺ binding and pH activation of Cl⁻ efflux.

Integrative Proteomic and Phosphoproteomic Analyses of Hypoxia-Treated Pulmonary Artery Smooth Muscle Cells

Abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) is one of the main causes of pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). Hypoxia is an important factor related to PAH and can induce the excessive proliferation of PASMCs and inhibit apoptosis. To explore the possible mechanism of hypoxia-related PAH, human PASMCs are exposed to hypoxia for 24 h and tandem mass tag (TMT)-based quantitative proteomic and phosphoproteomic analyses are performed. Proteomic analysis revealed 134 proteins are significantly changed (p < 0.05, |log2 (fold change)| > log2 [1.1]), of which 48 proteins are upregulated and 86 are downregulated. Some of the changed proteins are verified by using qRT-PCR and Western blotting. Phosphoproteomic analysis identified 404 significantly changed (p < 0.05, |log2 (fold change)| > log2 [1.1]) phosphopeptides. Among them, 146 peptides are upregulated while 258 ones are downregulated. The kinase-substrate enrichment analysis revealed kinases such as P21 protein-activated kinase 1/2/4 (PAK1/2/4), protein-kinase cGMP-dependent 1 and 2 (PRKG1/2), and mitogen-activated protein-kinase 4/6/7 (MAP2K4/6/7) are significantly enriched and activated. For all the significantly changed proteins or phosphoproteins, a comprehensive pathway analysis is performed. In general, this study furthers our understanding of the mechanism of hypoxia-induced PAH.

Harnessing Big Data to Advance Treatment and Understanding of Pulmonary Hypertension

Pulmonary hypertension is a complex disease with multiple causes, corresponding to phenotypic heterogeneity and variable therapeutic responses. Advancing understanding of pulmonary hypertension pathogenesis is likely to hinge on integrated methods that leverage data from health records, imaging, novel molecular -omics profiling, and other modalities. In this review, we summarize key data sets generated thus far in the field and describe analytical methods that hold promise for deciphering the molecular mechanisms that underpin pulmonary vascular remodeling, including machine learning, network medicine, and functional genetics. We also detail how genetic and subphenotyping approaches enable earlier diagnosis, refined prognostication, and optimized treatment prediction. We propose strategies that identify functionally important molecular pathways, bolstered by findings across multi-omics platforms, which are well-positioned to individualize drug therapy selection and advance precision medicine in this highly morbid disease.

The Glycobiology of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive pulmonary vascular disease of complex etiology. Cases of PAH that do not receive therapy after diagnosis have a low survival rate. Multiple reports have shown that idiopathic PAH, or IPAH, is associated with metabolic dysregulation including altered bioavailability of nitric oxide (NO) and dysregulated glucose metabolism. Multiple processes such as increased proliferation of pulmonary vascular cells, angiogenesis, apoptotic resistance, and vasoconstriction may be regulated by the metabolic changes demonstrated in PAH. Recent reports have underscored similarities between metabolic abnormalities in cancer and IPAH. In particular, increased glucose uptake and altered glucose utilization have been documented and have been linked to the aforementioned processes. We were the first to report a link between altered glucose metabolism and changes in glycosylation. Subsequent reports have highlighted similar findings, including a potential role for altered metabolism and aberrant glycosylation in IPAH pathogenesis. This review will detail research findings that demonstrate metabolic dysregulation in PAH with an emphasis on glycobiology. Furthermore, this report will illustrate the similarities in the pathobiology of PAH and cancer and highlight the novel findings that researchers have explored in the field.

Periostin-related progression of different types of experimental pulmonary hypertension: A role for M2 macrophage and FGF-2 signalling

Background and objective

Remodelling of pulmonary arteries (PA) contributes to the progression of pulmonary hypertension (PH). Periostin, a matricellular protein, has been reported to be involved in the development of PH. We examined the role of periostin in the pathogenesis of PH using different types of experimental PH.

Methods

PH was induced by vascular endothelial growth factor receptor antagonist (Sugen5416) plus hypoxic exposure (SuHx) and venous injection of monocrotaline‐pyrrole (MCT‐P) in wild‐type (WT) and periostin^−/− mice. Pulmonary haemodynamics, PA remodelling, expression of chemokines and fibroblast growth factor (FGF)‐2, accumulation of macrophages to small PA and the right ventricle (RV) were examined in PH‐induced WT and periostin^−/− mice. Additionally, the role of periostin in the migration of macrophages, human PA smooth muscle (HPASMCs) and endothelial cells (HPMVECs) was investigated.

Results

In PH induced by SuHx and MCT‐P, PH and accumulation of M2 macrophage to small PA were attenuated in periostin^−/− mice. PA remodelling post‐SuHx treatment was also mild in periostin^−/− mice compared to WT mice. Expression of macrophage‐associated chemokines and FGF‐2 in lung tissue, and accumulation of CD68‐positive cells in the RV were less in SuHx periostin^−/− than in SuHx WT mice. Periostin secretion in HPASMCs and HPMVECs was enhanced by transforming growth factor‐β. Periostin also augmented macrophage, HPASMCs and HPMVECs migration. Separately, serum periostin levels were significantly elevated in patients with PH compared to healthy controls.

Conclusion

Periostin is involved in the development of different types of experimental PH, and may also contribute to the pathogenesis of human PH.

Identifying Potential Mitochondrial Proteome Signatures Associated with the Pathogenesis of Pulmonary Arterial Hypertension in the Rat Model

Pulmonary arterial hypertension (PAH) is a severe and progressive disease that affects the heart and lungs and a global health concern that impacts individuals and society. Studies have reported that some proteins related to mitochondrial metabolic functions could play an essential role in the pathogenesis of PAH, and their specific expression and biological function are still unclear. We successfully constructed a monocrotaline- (MCT-) induced PAH rat model in the present research. Then, the label-free quantification proteomic technique was used to determine mitochondrial proteins between the PAH group (n = 6) and the normal group (n = 6). Besides, we identified 1346 mitochondrial differentially expressed proteins (DEPs) between these two groups. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyze the mainly mitochondrial DEPs' biological functions and the signal pathways. Based on the protein-protein interaction (PPI) network construction and functional enrichment, we screened 19 upregulated mitochondrial genes (Psmd1, Psmc4, Psmd13, Psmc2, etc.) and 123 downregulated mitochondrial genes (Uqcrfs1, Uqcrc1, Atp5c1, Atp5a1, Uqcrc2, etc.) in rats with PAH. Furthermore, in an independent cohort dataset and experiments with rat lung tissue using qPCR, validation results consistently showed that 6 upregulated mitochondrial genes (Psmd2, Psmc4, Psmc3, Psmc5, Psmd13, and Psmc2) and 3 downregulated mitochondrial genes (Lipe, Cat, and Prkce) were significantly differentially expressed in the lung tissue of PAH rats. Using the RNAInter database, we predict potential miRNA target hub mitochondrial genes at the transcriptome level. We also identified bortezomib and carfilzomib as the potential drugs for treatment in PAH. Finally, this study provides us with a new perspective on critical biomarkers and treatment strategies in PAH.

Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder associated with high morbidity and mortality despite currently available treatments. We compared the phosphoproteome of lung tissue from subjects with idiopathic PAH (iPAH) obtained at the time of lung transplant with control lung tissue. The mass spectrometry-based analysis found 60,428 phosphopeptide features from which 6622 proteins were identified. Within the subset of identified proteins there were 1234 phosphopeptides with q < 0.05, many of which are involved in immune regulation, angiogenesis, and cell proliferation. Most notably there was a marked relative increase in phosphorylated (S378) IKZF3 (Aiolos), a zinc finger transcription factor that plays a key role in lymphocyte regulation. In vitro phosphorylation assays indicated that GSK3 alpha and/or GSK3 beta could phosphorylate IKZF3 at S378. Western blot analysis demonstrated increased pIKZF3 in iPAH lungs compared to controls. Immunohistochemistry demonstrated phosphorylated IKZF3 in lymphocytes surrounding severely hypertrophied pulmonary arterioles. In situ hybrization showed gene expression in lymphocyte aggregates in PAH samples. A BCL2 reporter assay showed that IKZF3 increased BCL2 promoter activity and demonstrated the potential role of phosphorylation of IKZF3 in the regulation of BCL mediated transcription. Kinase network analysis demonstrated potentially important regulatory roles of casein kinase 2, cyclin-dependent kinase 1 (CDK1), mitogen-associated protein kinases (MAPKs), and protein kinases (PRKs) in iPAH. Bioinformatic analysis demonstrated enrichment of RhoGTPase signaling and the potential importance of cGMP-dependent protein kinase 1 (PRKG). In conclusion, this unbiased phosphoproteomic analysis demonstrated several novel targets regulated by kinase networks in iPAH, and reinforced the potential role of immune regulation in the pathogenesis of iPAH. The identified up- and down-regulated phosphoproteins have potential to serve as biomarkers for PAH and to provide new insights for therapeutic strategies.

Proteomic analysis of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare but fatal cardiovascular disorder with high morbidity and mortality. Diagnosis and treatment of this disease at an early stage would greatly improve outcomes. The molecular indicators of PAH are mostly nonspecific, and diagnostic and prognostic biomarkers are urgently needed. A more comprehensive understanding of the molecular mechanisms underlying this complex disease is crucial for the development of new and more effective therapeutics to improve patient outcomes. In this article, we review published literature on proteomic biomarkers and underlying molecular mechanisms in PAH and their value for disease management, aiming to deepen our understanding of the disease and, ultimately, pave the way for clinical application.

Soluble Receptor for Advanced Glycation End Products (sRAGE) Is a Sensitive Biomarker in Human Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive condition with an unmet need for early diagnosis, better monitoring, and risk stratification. The receptor for advanced glycation end products (RAGE) is activated in response to hypoxia and vascular injury, and is associated with inflammation, cell proliferation and migration in PAH. For the adult cohort, we recruited 120 patients with PAH, 83 with idiopathic PAH (IPAH) and 37 with connective tissue disease-associated PAH (CTD-PAH), and 48 controls, and determined potential plasma biomarkers by enzyme-linked immunoassay. The established heart failure marker NTproBNP and IL-6 plasma levels were several-fold higher in both adult IPAH and CTD-PAH patients versus controls. Plasma soluble RAGE (sRAGE) was elevated in IPAH patients (3044 ± 215.2 pg/mL) and was even higher in CTD-PAH patients (3332 ± 321.6 pg/mL) versus controls (1766 ± 121.9 pg/mL; p < 0.01). All three markers were increased in WHO functional class II+III PAH versus controls (p < 0.001). Receiver-operating characteristic analysis revealed that sRAGE has diagnostic accuracy comparable to prognostic NTproBNP, and even outperforms NTproBNP in the distinction of PAH FC I from controls. Lung tissue RAGE expression was increased in IPAH versus controls (mRNA) and was located predominantly in the PA intima, media, and inflammatory cells in the perivascular space (immunohistochemistry). In the pediatric cohort, plasma sRAGE concentrations were higher than in adults, but were similar in PH (n = 10) and non-PH controls (n = 10). Taken together, in the largest adult sRAGE PAH study to date, we identify plasma sRAGE as a sensitive and accurate PAH biomarker with better performance than NTproBNP in the distinction of mild PAH from controls.

Deficiency in ST2 signaling ameliorates RSV-associated pulmonary hypertension

Pulmonary hypertension (PH) observed during respiratory syncytial virus (RSV) bronchiolitis is associated with morbidity and mortality, especially in children with congenital heart disease. Yet, the pathophysiological mechanisms of RSV-associated PH remain unclear. Therefore, this study aimed to investigate the pathophysiological mechanism of RSV-associated PH. We used a translational mouse model of RSV-associated PH, in which wild-type (WT) and suppression of tumorigenicity 2 (ST2) knockout neonatal mice were infected with RSV at 5 days old and reinfected 4 wk later. The development of PH in WT mice following RSV reinfection was evidenced by elevated right ventricle systolic pressure, shortened pulmonary artery acceleration time (PAT), and decreased PAT/ejection time (ET) ratio. It coincided with the augmentation of periostin and IL-13 expression and increased arginase bioactivity by both arginase 1 and 2 as well as induction of nitric oxide synthase (NOS) uncoupling. Absence of ST2 signaling prevented RSV-reinfected mice from developing PH by suppressing NOS uncoupling. In summary, ST2 signaling was involved in the development of RSV-associated PH. ST2 signaling inhibition may be a novel therapeutic target for RSV-associated PH.NEW & NOTEWORTHY We report that the pathogenic role of ST2-mediated type 2 immunity and mechanisms contribute to RSV-associated pulmonary hypertension. Inhibiting ST2 signaling may be a novel therapeutic target for this condition.

Evolution of proteomics technologies for understanding respiratory syncytial virus pathogenesis

Introduction: Respiratory syncytial virus (RSV) is a major human pathogen associated with long term morbidity. RSV replication occurs primarily in the epithelium, producing a complex cellular response associated with acute inflammation and long-lived changes in pulmonary function and allergic disease. Proteomics approaches provide important insights into post-transcriptional regulatory processes including alterations in cellular complexes regulating the coordinated innate response and epigenome.Areas covered: Peer-reviewed proteomics studies of host responses to RSV infections and proteomics techniques were analyzed. Methodologies identified include 1)." bottom-up" discovery proteomics, 2). Organellar proteomics by LC-gel fractionation; 3). Dynamic changes in protein interaction networks by LC-MS; and 4). selective reaction monitoring MS. We introduce recent developments in single-cell proteomics, top-down mass spectrometry, and photo-cleavable surfactant chemistries that will have impact on understanding how RSV induces extracellular matrix (ECM) composition and airway remodeling.Expert opinion: RSV replication induces global changes in the cellular proteome, dynamic shifts in nuclear proteins, and remodeling of epigenetic regulatory complexes linked to the innate response. Pathways discovered by proteomics technologies have led to deeper mechanistic understanding of the roles of heat shock proteins, redox response, transcriptional elongation complex remodeling and ECM secretion remodeling in host responses to RSV infections and pathological sequelae.

Local Pressure Drives Low-Density Lipoprotein Accumulation and Coronary Atherosclerosis in Hypertensive Minipigs

BACKGROUND

The mechanisms by which hypertension accelerates coronary artery disease are poorly understood. Patients with hypertension often have confounding humoral changes, and to date, no experimental models have allowed analysis of the isolated effect of pressure on atherosclerosis in a setting that recapitulates the dimensions and biomechanics of human coronary arteries.

OBJECTIVES

This study sought to analyze the effect of pressure on coronary atherosclerosis and explore the underlying mechanisms.

METHODS

Using inflatable suprarenal aortic cuffs, we increased mean arterial pressure by >30 mm Hg in the cephalad body part of wild-type and hypercholesterolemic proprotein convertase subtilisin kexin type 9 (PCSK9)^D374Y Yucatan minipigs for >1 year. Caudal pressures remained normal.

RESULTS

Under hypercholesterolemic conditions in PCSK9^D374Y transgenic minipigs, cephalad hypertension accelerated coronary atherosclerosis to almost 5-fold with consistent development of fibroatheromas that were sufficiently large to cause stenosis on computed tomography angiography. This was caused by local pressure forces, because vascular beds shielded from hypertension, but exposed to the same humoral factors, showed no changes in lesion formation. The same experiment was conducted under normocholesterolemic conditions in wild-type minipigs to examine the underlying mechanisms. Hypertension produced clear changes in the arterial proteome with increased abundance of mechanical strength proteins and reduced levels of infiltrating plasma macromolecules. This was paralleled by increased smooth muscle cells and increased intimal accumulation of low-density lipoproteins in the coronary arteries.

CONCLUSIONS

Increased pressure per se facilitates coronary atherosclerosis. Our data indicate that restructuring of the artery to match increased tensile forces in hypertension alters the passage of macromolecules and leads to increased intimal accumulation of low-density lipoproteins.

Integrative Omics to Characterize and Classify Pulmonary Vascular Disease

Advances in high-throughput biotechnologies have facilitated omics profiling, a key component of precision phenotyping, in patients with pulmonary vascular disease. Omics provides comprehensive information pertaining to genes, transcripts, proteins, and metabolites. The resulting omics big datasets may be integrated for more robust results and are amenable to analysis using machine learning or newer analytical methodologies, such as network analysis. Results from fully integrated multi-omics datasets combined with clinical data are poised to provide novel insight into pulmonary vascular disease as well as diagnose the presence of disease and prognosticate outcomes.

Periostin

Rationale:

POSTN (Periostin) is an ECM (extracellular matrix) protein involved in tissue remodeling in response to injury and a contributing factor in tumorigenesis, suggesting that POSTN plays a role in the pathogenesis of pulmonary hypertension (PH).

Objective:

We aimed to gain insight into the mechanistic contribution of POSTN in experimental mouse models of PH and correlate these findings with PH in humans.

Methods and Results:

We used genetic epistasis approaches in human pulmonary artery endothelial cells (hPAECs), human pulmonary artery smooth muscle cells, and experimental mouse models of PH (Sugen 5416/hypoxia or chronic hypoxia) to discern the role of POSTN and its relationship to HIF (hypoxia-inducible factor)-1α signaling. We found that POSTN expression was correlated with the extent of PH in mouse models and in humans. Decreasing POSTN improved hemodynamic and cardiac responses in PH mice, blunted the release of growth factors and HIF-1α, and reversed the downregulated BMPR (bone morphogenetic protein receptor)-2 expression in hPAECs from patients with PH, whereas increasing POSTIN had the opposite effects and induced a hyperproliferative and promigratory phenotype in both hPAECs and human pulmonary artery smooth muscle cells. Overexpression of POSTN-induced activation of HIFs and increased the production of ET (endothelin)-1 and VEGF (vascular endothelial growth factor) in hPAECs. SiRNA-mediated knockdown of HIF-1α abolished the proangiogenic effect of POSTN. Blockade of TrkB (tyrosine kinase receptor B) attenuated the effect of POSTN on HIF-1α expression, while inhibition of HIF-1α reduced the expression of POSTN and TrkB. These results suggest that hPAECs produce POSTN via a HIF-1α-dependent mechanism.

Conclusions:

Our study reveals that POSTN expression is increased in human and animal models of PH and fosters PH development via a positive feedback loop between HIF-1α and POSTN during hypoxia. We propose that manipulating POSTIN expression may be an efficacious therapeutic target in the treatment of PH. Our results also suggest that POSTN may serve as a biomarker to estimate the severity of PH.

Endothelial Basement Membrane Components and Their Products, Matrikines: Active Drivers of Pulmonary Hypertension?

Pulmonary arterial hypertension (PAH) is a vascular disease that is characterized by elevated pulmonary arterial pressure (PAP) due to progressive vascular remodeling. Extracellular matrix (ECM) deposition in pulmonary arteries (PA) is one of the key features of vascular remodeling. Emerging evidence indicates that the basement membrane (BM), a specialized cluster of ECM proteins underlying the endothelium, may be actively involved in the progression of vascular remodeling. The BM and its steady turnover are pivotal for maintaining appropriate vascular functions. However, the pathologically elevated turnover of BM components leads to an increased release of biologically active short fragments, which are called matrikines. Both BM components and their matrikines can interfere with pivotal biological processes, such as survival, proliferation, adhesion, and migration and thus may actively contribute to endothelial dysfunction. Therefore, in this review, we summarize the emerging role of the BM and its matrikines on the vascular endothelium and further discuss its implications on lung vascular remodeling in pulmonary hypertension.

Research progress on the pathogenesis of CTEPH

Chronic thromboembolic pulmonary hypertension (CTEPH) is an established long-term complication of pulmonary thromboembolism (PTE). However, studies have shown that many patients with a definitive CTEPH diagnosis have no history of symptomatic PTE, suggesting that PTE is not the only cause of CTEPH. Despite extensive progress in research on pulmonary hypertension in recent years, due to a lack of relevant studies on the pathophysiology of CTEPH, implementing pulmonary endarterectomy (PEA) in patients has many challenges, and the prognosis of patients with CTEPH is still not optimistic. Therefore, revealing the pathogenesis of CTEPH would be of great significance for understanding the occurrence and development of CTEPH, developing relevant drug treatment studies and formulating intervention strategies, and may provide new preventive measures. This article summarizes the current research progress in CTEPH pathogenesis from the perspective of risk factors related to medical history, abnormal coagulation and fibrinolytic mechanisms, inflammatory mechanisms, genetic susceptibility factors, angiogenesis, in situ thrombosis, vascular remodeling, and other aspects.

The application of 'omics' to pulmonary arterial hypertension

Recent genome-wide analyses of rare and common sequence variations have brought greater clarity to the genetic architecture of pulmonary arterial hypertension and implicated novel genes in disease development. Transcriptional signatures have been reported in whole lung tissue, pulmonary vascular cells and peripheral circulating cells. High-throughput platforms for plasma proteomics and metabolomics have identified novel biomarkers associated with clinical outcomes and provided molecular instruments for risk assessment. There are methodological challenges to integrating these datasets, coupled to statistical power limitations inherent to the study of a rare disease, but the expectation is that this approach will reveal novel druggable targets and biomarkers that will open the way to personalized medicine. Here, we review the current state-of-the-art and future promise of 'omics' in the field of translational medicine in pulmonary arterial hypertension. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Therapeutic potential of KLF2-induced exosomal microRNAs in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a severe disorder of lung vasculature that causes right heart failure. Homoeostatic effects of flow-activated transcription factor Krüppel-like factor 2 (KLF2) are compromised in PAH. Here, we show that KLF2-induced exosomal microRNAs, miR-181a-5p and miR-324-5p act together to attenuate pulmonary vascular remodelling and that their actions are mediated by Notch4 and ETS1 and other key regulators of vascular homoeostasis. Expressions of KLF2, miR-181a-5p and miR-324-5p are reduced, while levels of their target genes are elevated in pre-clinical PAH, idiopathic PAH and heritable PAH with missense p.H288Y KLF2 mutation. Therapeutic supplementation of miR-181a-5p and miR-324-5p reduces proliferative and angiogenic responses in patient-derived cells and attenuates disease progression in PAH mice. This study shows that reduced KLF2 signalling is a common feature of human PAH and highlights the potential therapeutic role of KLF2-regulated exosomal miRNAs in PAH and other diseases associated with vascular remodelling.

Systems Analysis of the Human Pulmonary Arterial Hypertension Lung Transcriptome

Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary artery pressure and vascular resistance, typically leading to right heart failure and death. Current therapies improve quality of life of the patients but have a modest effect on long-term survival. A detailed transcriptomics and systems biology view of the PAH lung is expected to provide new testable hypotheses for exploring novel treatments. We completed transcriptomics analysis of PAH and control lung tissue to develop disease-specific and clinical data/tissue pathology gene expression classifiers from expression datasets. Gene expression data were integrated into pathway analyses. Gene expression microarray data were collected from 58 PAH and 25 control lung tissues. The strength of the dataset and its derived disease classifier was validated using multiple approaches. Pathways and upstream regulators analyses was completed with standard and novel graphical approaches. The PAH lung dataset identified expression patterns specific to PAH subtypes, clinical parameters, and lung pathology variables. Pathway analyses indicate the important global role of TNF and transforming growth factor signaling pathways. In addition, novel upstream regulators and insight into the cellular and innate immune responses driving PAH were identified. Finally, WNT-signaling pathways may be a major determinant underlying the observed sex differences in PAH. This study provides a transcriptional framework for the PAH-diseased lung, supported by previously reported findings, and will be a valuable resource to the PAH research community. Our investigation revealed novel potential targets and pathways amenable to further study in a variety of experimental systems.

FHL-1 is not involved in pressure overload-induced maladaptive right ventricular remodeling and dysfunction

AIMS

The cytoskeletal signaling protein four and-a-half LIM domains 1 (FHL-1) has recently been identified as a novel key player in pulmonary hypertension as well as in left heart diseases. In this regard, FHL-1 has been implicated in dysregulated hypertrophic signaling in pulmonary arterial smooth muscle cells leading to pulmonary hypertension. In mice, FHL-1-deficiency (FHL-1^-/-) led to an attenuated hypertrophic signaling associated with a blunted hypertrophic response of the pressure-overloaded left ventricle (LV). However, the role of FHL-1 in right heart hypertrophy has not yet been addressed.

METHODS AND RESULTS

We investigated FHL-1 expression in C57Bl/6 mice subjected to chronic biomechanical stress and found it to be enhanced in the right ventricle (RV). Next, we subjected FHL-1^-/- and corresponding wild-type mice to pressure overload of the RV by pulmonary arterial banding for various time points. However, in contrast to the previously published study in LV-pressure overload, which was confirmed here, RV hypertrophy and hypertrophic signaling was not diminished in FHL-1^-/- mice. In detail, right ventricular pressure overload led to hypertrophy, dilatation and fibrosis of the RV from both FHL-1^-/- and wild-type mice. RV remodeling was associated with impaired RV function as evidenced by reduced tricuspid annular plane systolic excursion. Additionally, PAB induced upregulation of natriuretic peptides and slight downregulation of phospholamban and ryanodine receptor 2 in the RV. However, there was no difference between genotypes in the degree of expression change.

CONCLUSION

FHL-1 pathway is not involved in the control of adverse remodeling in the pressure overloaded RV.

Integrative proteomics and phosphoproteomics in pulmonary arterial hypertension

Pulmonary arterial endothelial cells (PAEC) are mechanistically linked to origins of pulmonary arterial hypertension (PAH). Here, global proteomics and phosphoproteomics of PAEC from PAH (n = 4) and healthy lungs (n = 5) were performed using LC-MS/MS to confirm known pathways and identify new areas of investigation in PAH. Among PAH and control cells, 170 proteins and 240 phosphopeptides were differentially expressed; of these, 45 proteins and 18 phosphopeptides were located in the mitochondria. Pathologic pathways were identified with integrative bioinformatics and human protein-protein interactome network analyses, then confirmed with targeted proteomics in PAH PAEC and non-targeted metabolomics and targeted high-performance liquid chromatography of metabolites in plasma from PAH patients (n = 30) and healthy controls (n = 12). Dysregulated pathways in PAH include accelerated one carbon metabolism, abnormal tricarboxylic acid (TCA) cycle flux and glutamate metabolism, dysfunctional arginine and nitric oxide pathways, and increased oxidative stress. Functional studies in cells confirmed abnormalities in glucose metabolism, mitochondrial oxygen consumption, and production of reactive oxygen species in PAH. Altogether, the findings indicate that PAH is typified by changes in metabolic pathways that are primarily found in mitochondria.

CLIC4/Arf6 Pathway

RATIONALE

Increased expression of CLIC4 (chloride intracellular channel 4) is a feature of endothelial dysfunction in pulmonary arterial hypertension, but its role in disease pathology is not fully understood.

OBJECTIVE

To identify CLIC4 effectors and evaluate strategies targeting CLIC4 signaling in pulmonary hypertension.

METHODS AND RESULTS

Proteomic analysis of CLIC4-interacting proteins in human pulmonary artery endothelial cells identified regulators of endosomal trafficking, including Arf6 (ADP ribosylation factor 6) GTPase activating proteins and clathrin, while CLIC4 overexpression affected protein regulators of vesicular trafficking, lysosomal function, and inflammation. CLIC4 reduced BMPRII (bone morphogenetic protein receptor II) expression and signaling as a result of Arf6-mediated reduction in gyrating clathrin and increased lysosomal targeting of the receptor. BMPRII expression was restored by Arf6 siRNA, Arf inhibitor Sec7 inhibitor H3 (SecinH3), and inhibitors of clathrin-mediated endocytosis but was unaffected by chloride channel inhibitor, indanyloxyacetic acid 94 or Arf1 siRNA. The effects of CLIC4 on NF-κB (nuclear factor-kappa B), HIF (hypoxia-inducible factor), and angiogenic response were prevented by Arf6 siRNA and SecinH3. Sugen/hypoxia mice and monocrotaline rats showed elevated expression of CLIC4, activation of Arf6 and NF-κB, and reduced expression of BMPRII in the lung. These changes were established early during disease development. Lung endothelium-targeted delivery of CLIC4 siRNA or treatment with SecinH3 attenuated the disease, reduced CLIC4/Arf activation, and restored BMPRII expression in the lung. Endothelial colony-forming cells from idiopathic pulmonary hypertensive patients showed upregulation of CLIC4 expression and Arf6 activity, suggesting potential importance of this pathway in the human condition.

CONCLUSIONS

Arf6 is a novel effector of CLIC4 and a new therapeutic target in pulmonary hypertension.

Periostin-expressing cell-specific transforming growth factor-β inhibition in pulmonary artery prevents pulmonary arterial hypertension

Transforming growth factor beta (TGF-β) has been shown to play a critical role in pathogenesis of pulmonary arterial hypertension (PAH) although the precise role of TGF-β signaling remains uncertain. A recent report has shown that periostin (Pn) is one of the most upregulated proteins in human PAH lung compared with healthy lungs. We established type I TGF-β receptor knockout mice specifically with Pn expressing cell (Pn-Cre/Tgfb1fl/fl mice). Increases in PA pressure and pulmonary artery muscularization were induced by hypoxia of 10% oxygen for 4 weeks. Lung Pn expression was markedly induced by 4 week-hypoxia. Pn-Cre/Tgfb1fl/fl mice showed lower right ventricular pressure elevation, inhibition of PA medial thickening. Fluorescent co-immunostaining showed that Smad3 activation in Pn expressing cell is attenuated. These results suggest that TGF-β signaling in Pn expressing cell may have an important role in the pathogenesis of PAH by controlling medial thickening.

Revealing the pathogenic changes of PAH based on multiomics characteristics

BACKGROUND

Pulmonary artery hypertension (PAH), which is characterized by an increase in pulmonary circulation blood pressure, is a fatal disease, and its pathogenesis remains unclear.

METHODS

In this study, RNA sequencing (RNA-seq), tandem mass tags (TMT) and reduced representation bisulfite sequencing (RRBS) were performed to detect the levels of mRNA, protein, and DNA methylation in pulmonary arteries (PAs), respectively. To screen the possible pathways and proteins related to PAH, pathway enrichment analysis and protein-protein interaction (PPI) network analysis were performed. For selected genes, differential expression levels were confirmed at both the transcriptional and translational levels by real-time PCR and Western blot analyses, respectively.

RESULTS

A total of 362 differentially expressed genes (|Fold-change| > 1.5 and p < 0.05), 811 differentially expressed proteins (|Fold-change| > 1.2 and p < 0.05) and 76,562 differentially methylated regions (1000 bp slide windows, 500 bp overlap, p < 0.05, and |Fold-change| > 1.2) were identified when the PAH group (n = 15) was compared with the control group (n = 15). Through an integrated analysis of the characteristics of the three omic analyses, a multiomics table was constructed. Additionally, pathway enrichment analysis showed that the differentially expressed proteins were significantly enriched in five Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathways and ten Gene Ontology (GO) terms for the PAH group compared with the control group. Moreover, protein-protein interaction (PPI) networks were constructed to identify hub genes. Finally, according to the genes identified in the PPI and the protein expression fold-change, nine key genes and their associated proteins were verified by real-time PCR and Western blot analyses, including Col4a1, Itga5, Col2a1, Gstt1, Gstm3, Thbd, Mgst2, Kng1 and Fgg.

CONCLUSIONS

This study conducted multiomic characteristic profiling to identify genes that contribute to the hypoxia-induced PAH model, identifying new avenues for basic PAH research.

Increased plasma microfibrillar-associated protein 4 is associated with atrial fibrillation and more advanced left atrial remodelling

INTRODUCTION

This study aimed to evaluate the relationship of plasma microfibrillar-associated protein 4 (MFAP4) to atrial fibrillation (AF) and atrial structural remodelling.

MATERIAL AND METHODS

Plasma MFAP4 levels were measured in 92 patients with AF (61 paroxysmal AF (PAF) patients and 31 persistent AF (PersAF) patients) and 71 control subjects without AF. Linear and logistic multivariate regression analyses were performed to determine the potential value of MFAP4 for predicting the incidence of AF and left atrial size. Then, plasma and atrial protein levels of MFAP4 and its association with atrial fibrosis ratio were analysed in an atrial-specific fibrosis rat model.

RESULTS

There were significant differences in MFAP4 levels based on clinical group, with a gradient from control (1.71 ±0.53 ng/ml) to PAF (1.98 ±0.53 ng/ml) to PersAF (2.09 ±0.76 ng/ml) (p < 0.01). With multivariate analyses, plasma MFAP4 was found to be an independent determinant of left atrial diameter in AF patients. In atrial fibrosis rats, both plasma MFAP4 and atrial MFAP4 protein levels increased in atrial fibrosis rats and positively correlated with atrial fibrosis severity.

CONCLUSIONS

Plasma MFAP4 was increased in patients with AF and was highest in those with PersAF; both plasma MFAP4 and atrial MFAP4 protein expression were directly associated with the extent of LA structural remodelling.

AGE-RAGE Stress in the Pathophysiology of Pulmonary Hypertension and its Treatment

Pulmonary hypertension (PH) is a rare and fatal disease characterized by elevation of pulmonary artery pressure ≥ 25 mm Hg. There are five groups of PH: (1) pulmonary artery (PA) hypertension (PAH), (2) PH due to heart diseases, (3) PH associated with lung diseases/hypoxia, (4) PH associated with chronic obstruction of PA, and (5) PH due to unclear and/or multifactorial mechanisms. The pathophysiologic mechanisms of group 1 have been studied in detail; however, those for groups 2 to 5 are not that well known. PH pathology is characterized by smooth muscle cells (SMC) proliferation, muscularization of peripheral PA, accumulation of extracellular matrix (ECM), plexiform lesions, thromboembolism, and recanalization of thrombi. Advanced glycation end products (AGE) and its receptor (RAGE) and soluble RAGE (sRAGE) appear to be involved in the pathogenesis of PH. AGE and its interaction with RAGE induce vascular hypertrophy through proliferation of vascular SMC, accumulation of ECM, and suppression of apoptosis. Reactive oxygen species (ROS) generated by interaction of AGE and RAGE modulates SMC proliferation, attenuate apoptosis, and constricts PA. Increased stiffness in the artery due to vascular hypertrophy, and vasoconstriction due to ROS resulted in PH. The data also suggest that reduction in consumption and formation of AGE, suppression of RAGE expression, blockage of RAGE ligand binding, elevation of sRAGE levels, and antioxidants may be novel therapeutic targets for prevention, regression, and slowing of progression of PH. In conclusion, AGE-RAGE stress may be involved in the pathogenesis of PH and the therapeutic targets should be the AGE-RAGE axis.

G Protein α Subunit 14 Mediates Fibroblast Growth Factor 2-Induced Cellular Responses in Human Endothelial Cells

During pregnancy, a tremendous increase in fetoplacental angiogenesis is associated with elevated blood flow. Aberrant fetoplacental vascular function may lead to pregnancy complications including pre-eclampsia. Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) are crucial regulators of fetoplacental endothelial function. G protein α subunit 14 (GNA14), a member of Gαq/11 subfamily is involved in mediating hypertensive diseases and tumor vascularization. However, little is known about roles of GNA14 in mediating the FGF2- and VEGFA-induced fetoplacental endothelial function. Using human umbilical vein endothelial cells (HUVECs) cultured under physiological chronic low oxygen (3% O₂ ) as a cell model, we show that transfecting cells with adenovirus carrying GNA14 complementary DNA (cDNA; Ad-GNA14) increases (p < 0.05) protein expression of GNA14. GNA14 overexpression blocks (p < 0.05) FGF2-stimulated endothelial migration, whereas it enhances (p < 0.05) endothelial monolayer integrity (maximum increase of ~35% over the control at 24 hr) in response to FGF2. In contrast, GNA14 overexpression does not significantly alter VEGFA-stimulated cell migration, VEGFA-weakened cell monolayer integrity, and intracellular Ca⁺⁺ mobilization in response to adenosine triphosphate (ATP), FGF2, and VEGFA. GNA14 overexpression does not alter either FGF2- or VEGFA-induced phosphorylation of ERK1/2. However, GNA14 overexpression time-dependently elevates (p < 0.05) phosphorylation of phospholipase C-β3 (PLCβ3) at S1105 in response to FGF2, but not VEGFA. These data suggest that GNA14 distinctively mediates fetoplacental endothelial cell migration and permeability in response to FGF2 and VEGFA, possibly in part by altering activation of PLCβ3 under physiological chronic low oxygen.

RAGE-mediated extracellular matrix proteins accumulation exacerbates HySu-induced pulmonary hypertension

Aims

Extracellular matrix (ECM) proteins accumulation contributes to the progression of pulmonary arterial hypertension (PAH), a rare and fatal cardiovascular condition defined by high pulmonary arterial pressure, whether primary, idiopathic, or secondary to other causes. The receptor for advanced glycation end products (RAGE) is constitutively expressed in the lungs and plays an important role in ECM deposition. Nonetheless, the mechanisms by which RAGE mediates ECM deposition/formation in pulmonary arteries and its roles in PAH progression remain unclear.

Methods and results

Expression of RAGE and its activating ligands, S100/calgranulins and high mobility group box 1 (HMGB1), were increased in both human and mouse pulmonary arterial smooth muscle cells (PASMCs) under hypoxic conditions and were also strikingly upregulated in pulmonary arteries in hypoxia plus SU5416 (HySu)-induced PAH in mice. RAGE deletion alleviated pulmonary arterial pressure and restrained extracellular matrix accumulation in pulmonary arteries in HySu-induced PAH murine model. Moreover, blocking RAGE activity with a neutralizing antibody in human PASMCs, or RAGE deficiency in mouse PASMCs exposed to hypoxia, suppressed the expression of fibrotic proteins by reducing TGF-β1 expression. RAGE reconstitution in deficient mouse PASMCs restored hypoxia-stimulated TGF-β1 production via ERK1/2 and p38 MAPK pathway activation and subsequently increased ECM protein expression. Interestingly, HMGB1 acting on RAGE, not toll-like receptor 4 (TLR4), induced ECM deposition in PASMCs. Finally, in both idiopathic PAH patients and HySu-induced PAH mice, soluble RAGE (sRAGE) levels in serum were significantly elevated compared to those in controls.

Conclusions

Activation of RAGE facilitates the development of hypoxia-induced pulmonary hypertension by increase of ECM deposition in pulmonary arteries. Our results indicate that sRAGE may be a potential biomarker for PAH diagnosis and disease severity, and that RAGE may be a promising target for PAH treatment.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Development of a New Immunoassay for Human Cathepsin K-Generated Periostin Fragments as a Serum Biomarker for Cortical Bone

Periostin is a matricellular protein mainly expressed by periosteal cells and osteocytes in bone, but is also present in several other tissues. Available immunoassays use antibodies of unclear specificity. The aim of the study was to develop a bone-specific periostin ELISA based on the detection of fragments generated by the osteoclastic and osteocytic protease cathepsin K. In vitro digestion of human recombinant intact periostin by cathepsin K leads to the generation of multiple fragments. Using LS-MS/MS, it was found that the GSLQPIIK peptide was the most efficiently and abundantly generated periostin fragment. A rabbit polyclonal antibody directed against the synthetic GSLQPIIK sequence was produced. Immunohistochemistry experiments of the tibia showed that the GSLQPIIK fragments localized at the periosteal surface and within the osteocytes. Using the same antibody, we developed an ELISA for the measurement of GSLQPIIK in the serum. This ELISA demonstrated intra- and interassay variability below 14% with a sensitivity allowing accurate determinations in the serum of healthy individuals. Serum GSLQPIIK was measured in 160 healthy postmenopausal women (mean age 65 year) participating in the Geneva Retiree Cohort. Serum GSLQPIIK levels did not correlate with total periostin, hip BMD, and the bone markers PINP and CTX. However, GSLQPIIK was negatively correlated (p values ranging from 0.007 to 0.03) with Hr-pQCT measures of tibia and radius cortical bone, but not with trabecular parameters. We have developed the first assay for the detection of periostin fragments generated by cathepsin K. Because serum levels of this new marker significantly correlated with cortical bone measurements in postmenopausal women, it may prove to be useful for the clinical investigation of patients with osteoporosis.

Up-regulation of caveolin-1 by DJ-1 attenuates rat pulmonary arterial hypertension by inhibiting TGFβ/Smad signaling pathway

Pulmonary arterial hypertension (PAH), characterized by excessive proliferation and apoptosis resistance of pulmonary artery smooth muscle cells (PASMCs), is closely associated with the imbalance in vasoactive mediators and massive remodeling of pulmonary vasculature. DJ-1/park7, a multifunctional protein, plays a critical defense role in several cytobiological activity, such as transcriptional regulation, anti-oxidative stress and tumor formation. In this study, we investigated the effects of DJ-1 on hypoxia-induced PAH model rats and PASMCs, as well as its possible molecular mechanism. First, the low expressions of DJ-1 and caveolin-1 (Cav-1) were synchronously detected in lung tissue of PAH model rats and hypoxia-induced PASMCs by Western blot. Then, the DJ-1 wild type (WT) or Knock out (KO) rats were exposed to chronic hypoxia to mimic a hypoxic PAH condition. The protein level of Cav-1 was markedly decreased in the tissue of DJ-1 KO rats, and additionally lower in tissue of the hypoxia group than that in the normoxia group for DJ-1 WT and KO rats. In vivo, hemodynamic data showed that the pulmonary arterial pressure (mPAP), right ventricle systolic pressure (RVSP) and pulmonary arterial systolic pressure (PASP), as well as the weight of the right ventricle/left ventricle plus septum (RV/LV+S) ratio of PAH model rats were higher in the DJ-1 KO group than those in the DJ-1 WT group. Moreover, knockout of DJ-1 also results in the phenotype switch from contractile to synthetic PASMC, which is reflected by reduced calponin and SM22α expressions. In vitro, DJ-1 overexpression reversed hypoxia-induced elevation of PASMC cell proliferation, migration and Ca²⁺ concentration, which were not obviously observed in Cav-1 shRNA (sh-Cav-1) and DJ-1 co-transfected cells. Then the increased levels of calponin and SM22α were detected in the DJ-1 group; similarly those levels were not changed in the DJ-1+sh-Cav-1 group. Finally, the expression of TGFβ1, p-Smad2 and p-Smad3 were obviously decreased in the ad-DJ-1 group, however those were all elevated in the DJ-1 and sh-Cav-1 co-transfected groups. In conclusion, these results indicate that DJ-1 may alleviate hypoxia-induced PASMCs injury by Cav-1 through inhibiting the TGFβ/Smad signaling pathway.

Cerebrovascular gene expression in spontaneously hypertensive rats

Hypertension is a hemodynamic disorder and one of the most important and well-established risk factors for vascular diseases such as stroke. Blood vessels exposed to chronic shear stress develop structural changes and remodeling of the vascular wall through many complex mechanisms. However, the molecular mechanisms involved are not fully understood. Hypertension-susceptible genes may provide a novel insight into potential molecular mechanisms of hypertension and secondary complications associated with hypertension. The aim of this exploratory study was to identify gene expression differences in the middle cerebral arteries between 12-week-old male spontaneously hypertensive rats and their normotensive Wistar-Kyoto rats using an Affymetrix whole-transcriptome expression profiling. Quantitative PCR and western blotting were used to verify genes of interest. 169 genes were differentially expressed in the middle cerebral arteries from hypertensive compared to normotensive rats. The gene expression of 72 genes was decreased and the gene expression of 97 genes was increased. The following genes with a fold difference ≥1.40 were verified by quantitative PCR; Postn, Olr1, Fas, Vldlr, Mmp2, Timp1, Serpine1, Mmp11, Cd34, Ptgs1 and Ptgs2. The gene expression of Postn, Olr1, Fas, Vldlr, Mmp2, Timp1 and Serpine1 and the protein expression of LOX1 (also known as OLR1) were significantly increased in the middle cerebral arteries from spontaneously hypertensive rats compared to Wistar-Kyoto rats. In conclusion, the identified genes in the middle cerebral arteries from spontaneously hypertensive rats could be possible mediators of the vascular changes and secondary complications associated with hypertension. This study supports the selection of key genes to investigate in the future research of hypertension-induced end-organ damage.