Impaired transforming growth factor-beta signaling in idiopathic pulmonary arterial hypertension

Intrapulmonary T Cells Are Sufficient for Schistosoma-Induced Pulmonary Hypertension

BACKGROUND

Schistosomiasis is a parasitic infection that can cause pulmonary hypertension (PH). Th2 CD4 T cells are necessary for experimental Schistosoma-PH. However, if T cells migrate to the lung to initiate, the localized inflammation that drives vascular remodeling and PH is unknown.

METHODS

Mice were sensitized to Schistosoma mansoni eggs intraperitoneally and then challenged using tail vein injection. FTY720 was administered, which blocks lymphocyte egress from lymph nodes. T cells were quantified using flow cytometry, PH severity via heart catheterization, and cytokine concentration through ELISA.

RESULTS

FTY720 decreased T cells in the peripheral blood, and increased T cells in the mediastinal lymph nodes. However, FTY720 treatment resulted in no change in PH or type 2 inflammation severity in mice sensitized and challenged with S. mansoni eggs, and the number of memory and effector CD4 T cells in the lung parenchyma was also unchanged. Notably, intraperitoneal Schistosoma egg sensitization alone resulted in a significant increase in intravascular lymphocytes and T cells, including memory T cells, although there was no significant change in parenchymal cell density, IL-4 or IL-13 expression, or PH.

CONCLUSION

Blocking T cell migration did not suppress PH following Schistosoma egg challenge. Memory CD4 T cells, located in the lung intravascular space following egg sensitization, appear sufficient to cause type 2 inflammation and PH.

Digital Spatial Profiling Identifies Distinct Molecular Signatures of Vascular Lesions in Pulmonary Arterial Hypertension

Rationale: Idiopathic pulmonary arterial hypertension (IPAH) is characterized by extensive pulmonary vascular remodeling caused by plexiform and obliterative lesions, media hypertrophy, inflammatory cell infiltration, and alterations of the adventitia. Objective: We sought to test the hypothesis that microscopic IPAH vascular lesions express unique molecular profiles, which collectively are different from control pulmonary arteries. Methods: We used digital spatial transcriptomics to profile the genomewide differential transcriptomic signature of key pathological lesions (plexiform, obliterative, intima+media hypertrophy, and adventitia) in IPAH lungs (n = 11) and compared these data with the intima+media hypertrophy and adventitia of control pulmonary artery (n = 5). Measurements and Main Results: We detected 8,273 transcripts in the IPAH lesions and control lung pulmonary arteries. Plexiform lesions and IPAH adventitia exhibited the greatest number of differentially expressed genes when compared with intima+media hypertrophy and obliterative lesions. Plexiform lesions in IPAH showed enrichment for 1) genes associated with transforming growth factor β signaling and 2) mutated genes affecting the extracellular matrix and endothelial-mesenchymal transformation. Plexiform lesions and IPAH adventitia showed upregulation of genes involved in immune and IFN signaling, coagulation, and complement pathways. Cellular deconvolution indicated variability in the number of vascular and inflammatory cells between IPAH lesions, which underlies the differential transcript profiling. Conclusions: IPAH lesions express unique molecular transcript profiles enriched for pathways involving pathogenetic pathways, including genetic disease drivers, innate and acquired immunity, hypoxia sensing, and angiogenesis signaling. These data provide a rich molecular-structural framework in IPAH vascular lesions that inform novel biomarkers and therapeutic targets in this highly morbid disease.

Imaging the TGFβ type I receptor in pulmonary arterial hypertension

Transforming growth factor β (TGFβ) activity is perturbed in remodelled pulmonary vasculature of patients with pulmonary arterial hypertension (PAH), cancer, vascular diseases and developmental disorders. Inhibition of TGFβ, which signals via activin receptor-like kinase 5 (ALK5), prevents progression and development of experimental PAH. The purpose of this study was to assess two ALK5 targeting positron emission tomography (PET) tracers ([¹¹C]LR111 and [¹⁸F]EW-7197) for imaging ALK5 in monocrotaline (MCT)- and Sugen/hypoxia (SuHx)-induced PAH. Both tracers were subjected to extensive in vitro and in vivo studies. [¹¹C]LR111 showed the highest metabolic stability, as 46 ± 2% of intact tracer was still present in rat blood plasma after 60 min. In autoradiography experiments, [¹¹C]LR111 showed high ALK5 binding in vitro compared with controls, 3.2 and 1.5 times higher in SuHx and MCT, respectively. In addition, its binding could be blocked by SB431542, an adenosine triphosphate competitive ALK5 kinase inhibitor. However, [¹⁸F]EW-7197 showed the best in vivo results. 15 min after injection, uptake was 2.5 and 1.4 times higher in the SuHx and MCT lungs, compared with controls. Therefore, [¹⁸F]EW-7197 is a promising PET tracer for ALK5 imaging in PAH.

Transcription factors in the pathogenesis of pulmonary arterial hypertension-Current knowledge and therapeutic potential

Pulmonary arterial hypertension (PAH) is a disease characterized by elevated pulmonary vascular resistance and pulmonary artery pressure. Mortality remains high in severe cases despite significant advances in management and pharmacotherapy. Since currently approved PAH therapies are unable to significantly reverse pathological vessel remodeling, novel disease-modifying, targeted therapeutics are needed. Pathogenetically, PAH is characterized by vessel wall cell dysfunction with consecutive remodeling of the pulmonary vasculature and the right heart. Transcription factors (TFs) regulate the process of transcribing DNA into RNA and, in the pulmonary circulation, control the response of pulmonary vascular cells to macro- and microenvironmental stimuli. Often, TFs form complex protein interaction networks with other TFs or co-factors to allow for fine-tuning of gene expression. Therefore, identification of the underlying molecular mechanisms of TF (dys-)function is essential to develop tailored modulation strategies in PAH. This current review provides a compendium-style overview of TFs and TF complexes associated with PAH pathogenesis and highlights their potential as targets for vasculoregenerative or reverse remodeling therapies.

MED1 Regulates BMP/TGF-β in Endothelium: Implication for Pulmonary Hypertension

BACKGROUND

Dysregulated BMP (bone morphogenetic protein) or TGF-β (transforming growth factor beta) signaling pathways are imperative in idiopathic and familial pulmonary arterial hypertension (PAH) as well as experimental pulmonary hypertension (PH) in rodent models. MED1 (mediator complex subunit 1) is a key transcriptional co-activator and KLF4 (Krüppel-like factor 4) is a master transcription factor in endothelium. However, MED1 and KLF4 epigenetic and transcriptional regulations of the BMP/TGF-β axes in pulmonary endothelium and their dysregulations leading to PAH remain elusive. We investigate the MED1/KLF4 co-regulation of the BMP/TGF-β axes in endothelium by studying the epigenetic regulation of BMPR2 (BMP receptor type II), ETS-related gene (ERG), and TGFBR2 (TGF-β receptor 2) and their involvement in the PH.

METHODS

High-throughput screening involving data from RNA-seq, MED1 ChIP-seq, H3K27ac ChIP-seq, ATAC-seq, and high-throughput chromosome conformation capture together with in silico computations were used to explore the epigenetic and transcriptional regulation of BMPR2, ERG, and TGFBR2 by MED1 and KLF4. In vitro experiments with cultured pulmonary arterial endothelial cells (ECs) and bulk assays were used to validate results from these in silico analyses. Lung tissue from patients with idiopathic PAH, animals with experimental PH, and mice with endothelial ablation of MED1 (EC-MED1^-/-) were used to study the PH-protective effect of MED1.

RESULTS

Levels of MED1 were decreased in lung tissue or pulmonary arterial endothelial cells from idiopathic PAH patients and rodent PH models. Mechanistically, MED1 acted synergistically with KLF4 to transactivate BMPR2, ERG, and TGFBR2 via chromatin remodeling and enhancer-promoter interactions. EC-MED1^-/- mice showed PH susceptibility. In contrast, MED1 overexpression mitigated the PH phenotype in rodents.

CONCLUSIONS

A homeostatic regulation of BMPR2, ERG, and TGFBR2 in ECs by MED1 synergistic with KLF4 is essential for the normal function of the pulmonary endothelium. Dysregulation of MED1 and the resulting impairment of the BMP/TGF-β signaling is implicated in the disease progression of PAH in humans and PH in rodent models.

Contribution of fatty acid oxidation to the pathogenesis of pulmonary hypertension

Dysregulated metabolism characterizes both animal and human forms of pulmonary hypertension (PH). Enzymes involved in fatty acid metabolism have previously not been assessed in human pulmonary arteries affected by pulmonary arterial hypertension (PAH), and how inhibition of fatty acid oxidation (FAO) may attenuate PH remains unclear. Fatty acid metabolism gene transcription was quantified in laser-dissected pulmonary arteries from 10 explanted lungs with advanced PAH (5 idiopathic, 5 associated with systemic sclerosis), and 5 donors without lung diseases. Effects of oxfenicine, a FAO inhibitor, on female Sugen 5416-chronic hypoxia (SuHx) rats were studied in vivo using right heart catheterization, and ex vivo using perfused lungs and pulmonary artery ring segments. The impact of pharmacologic (oxfenicine) and genetic (carnitine palmitoyltransferase 1a heterozygosity) FAO suppression was additionally probed in mouse models of Schistosoma and hypoxia-induced PH. Potential mechanisms underlying FAO-induced PH pathogenesis were examined by quantifying ATP and mitochondrial mass in oxfenicine-treated SuHx pulmonary arterial cells, and by assessing pulmonary arterial macrophage infiltration with immunohistochemistry. We found upregulated pulmonary arterial transcription of 26 and 13 FAO genes in idiopathic and systemic sclerosis-associated PAH, respectively. In addition to promoting de-remodeling of pulmonary arteries in SuHx rats, oxfenicine attenuated endothelin-1-induced vasoconstriction. FAO inhibition also conferred modest benefit in the two mouse models of PH. Oxfenicine increased mitochondrial mass in cultured rat pulmonary arterial cells, and decreased the density of perivascular macrophage infiltration in pulmonary arteries of treated SuHx rats. In summary, FAO inhibition attenuated experimental PH, and may be beneficial in human PAH.

[Morphological assessment of pulmonary vessels in pulmonary arterial hypertension associated with congenital heart disease]

Pulmonary vascular remodeling is the key structural alteration in pulmonary arterial hypertension associated with congenital heart disease (CHD). Changes in the pulmonary vessels in CHD generally occur in the inner and middle coats. This review considers the pathology of these changes and highlights some issues of a stereological approach to the morphometry of pulmonary vasculature. It also touches upon the issues of the morphology of pulmonary vessels in post-capillary and segmental pulmonary hypertension.

Persistent, Progressive Pulmonary Fibrosis and Epithelial Remodeling in Mice

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic interstitial lung disease with underlying mechanisms that have been primarily investigated in mice after intratracheal instillation of a single dose of bleomycin. However, the model has significant limitations, including transient fibrosis that spontaneously resolves and its failure to fully recapitulate the epithelial remodeling in the lungs of patients with IPF. Thus, there remains an unmet need for a preclinical model with features that more closely resemble the human disease. Repetitive intratracheal instillation of bleomycin has previously been shown to recapitulate some of these features, but the instillation procedure is complex, and the long-term consequences on epithelial remodeling and fibrosis persistence and progression remain poorly understood. Here, we developed a simplified repetitive bleomycin instillation strategy consisting of three bi-weekly instillations that leads to persistent and progressive pulmonary fibrosis. Lung histology demonstrates increased collagen deposition, fibroblast accumulation, loss of type I and type II alveolar epithelial cells within fibrotic areas, bronchiolization of the lung parenchyma with CCSP+ cells, remodeling of the distal lung into cysts reminiscent of simple honeycombing, and accumulation of hyperplastic transitional KRT8+ epithelial cells. Micro-computed tomographic imaging demonstrated significant traction bronchiectasis and subpleural fibrosis. Thus, the simplified repetitive bleomycin instillation strategy leads to progressive fibrosis and recapitulates the histological and radiographic characteristics of IPF. Compared with the single bleomycin instillation model, we suggest that the simplified repetitive instillation model may be better suited to address mechanistic questions about IPF pathogenesis and preclinical studies of antifibrotic drug candidates.

Targeting transforming growth factor-β receptors in pulmonary hypertension

The transforming growth factor-β (TGF-β) superfamily includes several groups of multifunctional proteins that form two major branches, namely the TGF-β-activin-nodal branch and the bone morphogenetic protein (BMP)-growth differentiation factor (GDF) branch. The response to the activation of these two branches, acting through canonical (small mothers against decapentaplegic (Smad) 2/3 and Smad 1/5/8, respectively) and noncanonical signalling pathways, are diverse and vary for different environmental conditions and cell types. An extensive body of data gathered in recent years has demonstrated a central role for the cross-talk between these two branches in a number of cellular processes, which include the regulation of cell proliferation and differentiation, as well as the transduction of signalling cascades for the development and maintenance of different tissues and organs. Importantly, alterations in these pathways, which include heterozygous germline mutations and/or alterations in the expression of several constitutive members, have been identified in patients with familial/heritable pulmonary arterial hypertension (PAH) or idiopathic PAH (IPAH). Consequently, loss or dysfunction in the delicate, finely-tuned balance between the TGF-β-activin-nodal branch and the BMP-GDF branch are currently viewed as the major molecular defect playing a critical role in PAH predisposition and disease progression. Here we review the role of the TGF-β-activin-nodal branch in PAH and illustrate how this knowledge has not only provided insight into understanding its pathogenesis, but has also paved the way for possible novel therapeutic approaches.

Altered TGFβ/SMAD Signaling in Human and Rat Models of Pulmonary Hypertension: An Old Target Needs Attention

Recent translational studies highlighted the inhibition of transforming growth factor (TGF)-β signaling as a promising target to treat pulmonary arterial hypertension (PAH). However, it remains unclear whether alterations in TGF-β signaling are consistent between PAH patients and animal models. Therefore, we compared TGF-β signaling in the lungs of PAH patients and rats with experimental PAH induced by monocrotaline (MCT) or SU5416+hypoxia (SuHx). In hereditary PAH (hPAH) patients, there was a moderate increase in both TGFβR2 and pSMAD2/3 protein levels, while these were unaltered in idiopathic PAH (iPAH) patients. Protein levels of TGFβR2 and pSMAD2/3 were locally increased in the pulmonary vasculature of PAH rats under both experimental conditions. Conversely, the protein levels of TGFβR2 and pSMAD2/3 were reduced in SuHx while slightly increased in MCT. mRNA levels of plasminogen activator inhibitor (PAI)-1 were increased only in MCT animals and such an increase was not observed in SuHx rats or in iPAH and hPAH patients. In conclusion, our data demonstrate considerable discrepancies in TGFβ-SMAD signaling between iPAH and hPAH patients, as well as between patients and rats with experimental PAH.

Approaches to treat pulmonary arterial hypertension by targeting bmpr2 - from cell membrane to nucleus

Pulmonary arterial hypertension (PAH) is estimated to affect between 10-50 people per million worldwide. The lack of cure and devastating nature of the disease means that treatment is crucial to arrest rapid clinical worsening. Current therapies are limited by their focus on inhibiting residual vasoconstriction rather than targeting key regulators of the cellular pathology. Potential disease-modifying therapies may come from research directed towards causal pathways involved in the cellular and molecular mechanisms of disease. It is widely acknowledged, that targeting reduced expression of the critical bone morphogenetic protein type-2 receptor (BMPR2) and its associated signalling pathways is a compelling therapeutic avenue to explore. In this review we highlight the advances that have been made in understanding this pathway and the therapeutics that are being tested in clinical trials and the clinic to treat PAH.

Eicosapentaenoic acid ameliorates pulmonary hypertension via inhibition of tyrosine kinase Fyn

Pulmonary arterial hypertension (PAH) is a multifactorial disease characterized by pulmonary arterial vasoconstriction and remodeling. Src family tyrosine kinases, including Fyn, play critical roles in vascular remodeling via the inhibition of STAT3 signaling. EPA is known to inhibit Fyn kinase activity. This study investigated the therapeutic potential and underlying mechanisms of EPA and its metabolite, resolvin E1 (RvE1), to treat PAH using monocrotaline-induced PAH model rats (MCT-PAH), human pulmonary artery endothelial cells (HPAECs), and human pulmonary artery smooth muscle cells (HPASMCs). Administration of EPA 1 and 2 weeks after MCT injection both ameliorated right ventricular hypertrophy, remodeling and dysfunction, and medial wall thickening of the pulmonary arteries and prolonged survival in MCT-PAH rats. EPA attenuated the enhanced contractile response to 5-hydroxytryptamine in isolated pulmonary arteries of MCT-PAH rats. Mechanistically, the treatment with EPA and RvE1 or the introduction of dominant-negative Fyn prevented TGF-β2-induced endothelial-to-mesenchymal transition and IL-6-induced phosphorylation of STAT3 in cultured HPAECs. EPA and RvE1 suppressed Src family kinases' activity as evaluated by their phosphorylation status in cultured HPAECs and HPASMCs. EPA and RvE1 suppressed vasocontraction of rat and human PA. Furthermore, EPA and RvE1 inhibited the enhanced proliferation and activity of Src family kinases in HPASMCs derived from patients with idiopathic PAH. EPA ameliorated PAH's pathophysiology by mitigating vascular remodeling and vasoconstriction, probably inhibiting Src family kinases, especially Fyn. Thus, EPA is considered a potent therapeutic agent for the treatment of PAH.

Vital Roles of Gremlin-1 in Pulmonary Arterial Hypertension Induced by Systemic-to-Pulmonary Shunts

Background Heterozygous mutation in BMP (bone morphogenetic protein) receptor 2 is rare, but BMP cascade suppression is common in congenital heart disease-associated pulmonary arterial hypertension (CHD-PAH); however, the underling mechanism of BMP cascade suppression independent of BMP receptor 2 mutation is unknown. Methods and Results Pulmonary hypertensive status observed in CHD-PAH was surgically reproduced in rats. Gremlin-1 expression was increased, but BMP cascade was suppressed, in lungs from CHD-PAH patients and shunted rats, whereas shunt correction retarded these trends in rats. Immunostaining demonstrated increased gremlin-1 was mainly in the endothelium and media of remodeled pulmonary arteries. However, mechanical stretch time- and amplitude-dependently stimulated gremlin-1 secretion and suppressed BMP cascade in distal pulmonary arterial smooth muscle cells from healthy rats. Under static condition, gremlin-1 significantly promoted the proliferation and inhibited the apoptosis of distal pulmonary arterial smooth muscle cells from healthy rats via BMP cascade. Furthermore, plasma gremlin-1 closely correlated with hemodynamic parameters in CHD-PAH patients and shunted rats. Conclusions Serving as an endogenous antagonist of BMP cascade, the increase of gremlin-1 in CHD-PAH may present a reasonable mechanism explanation for BMP cascade suppression independent of BMP receptor 2 mutation.

Growth factors in pulmonary arterial hypertension: Focus on preserving right ventricular function

Pulmonary arterial hypertension (PAH) is a rare and progressive disease, characterized by increased vascular resistance leading to right ventricle (RV) failure. The extent of right ventricular dysfunction crucially influences disease prognosis; however, currently no therapies have specific cardioprotective effects. Besides discussing the pathophysiology of right ventricular adaptation in PAH, this review focuses on the roles of growth factors (GFs) in disease pathomechanism. We also summarize the involvement of GFs in the preservation of cardiomyocyte function, to evaluate their potential as cardioprotective biomarkers and novel therapeutic targets in PAH.

Implications of immune-inflammatory responses in smooth muscle dysfunction and disease

In the past few decades, solid evidence has been accumulated for the pivotal significance of immunoinflammatory processes in the initiation, progression, and exacerbation of many diseases and disorders. This groundbreaking view came from original works by Ross who first described that excessive inflammatory-fibroproliferative response to various forms of insult to the endothelium and smooth muscle of the artery wall is essential for the pathogenesis of atherosclerosis (Ross, Nature 1993; 362(6423): 801–9). It is now widely recognized that both innate and adaptive immune reactions are avidly involved in the inflammation-related remodeling of many tissues and organs. When this state persists, irreversible fibrogenic changes would occur often culminating in fatal insufficiencies of many vital parenchymal organs such as liver, lung, heart, kidney and intestines. Thus, inflammatory diseases are becoming the common life-threatening risk for and urgent concern about the public health in developed countries (Wynn et al., Nature Medicine 2012; 18(7): 1028–40). Considering this timeliness, we organized a special symposium entitled “Implications of immune/inflammatory responses in smooth muscle dysfunction and disease” in the 58th annual meeting of the Japan Society of Smooth Muscle Research. This symposium report will provide detailed synopses of topics presented in this symposium; (1) the role of inflammasome in atherosclerosis and abdominal aortic aneurysms by Fumitake Usui-Kawanishi and Masafumi Takahashi; (2) Mechanisms underlying the pathogenesis of hyper-contractility of bronchial smooth muscle in allergic asthma by Hiroyasu Sakai, Wataru Suto, Yuki Kai and Yoshihiko Chiba; (3) Vascular remodeling in pulmonary arterial hypertension by Keizo Hiraishi, Lin Hai Kurahara and Ryuji Inoue.

The BMP Receptor 2 in Pulmonary Arterial Hypertension: When and Where the Animal Model Matches the Patient

Background: Mutations in bone morphogenetic protein receptor type II (BMPR2) are leading to the development of hereditary pulmonary arterial hypertension (PAH). In non-hereditary forms of PAH, perturbations in the transforming growth factor-β (TGF-β)/BMP-axis are believed to cause deficient BMPR2 signaling by changes in receptor expression, the activity of the receptor and/or downstream signaling. To date, BMPR2 expression and its activity in the lungs of patients with non-hereditary PAH is poorly characterized. In recent decades, different animal models have been used to understand the role of BMPR2 signaling in PAH pathophysiology. Specifically, the monocrotaline (MCT) and Sugen-Hypoxia (SuHx) models are extensively used in interventional studies to examine if restoring BMPR2 signaling results in PAH disease reversal. While PAH is assumed to develop in patients over months or years, pulmonary hypertension in experimental animal models develops in days or weeks. It is therefore likely that modifications in BMP and TGF-β signaling in these models do not fully recapitulate those in patients. In order to determine the translational potential of the MCT and SuHx models, we analyzed the BMPR2 expression and activity in the lungs of rats with experimentally induced PAH and compared this to the BMPR2 expression and activity in the lungs of PAH patients. Methods: the BMPR2 expression was analyzed by Western blot analysis and immunofluorescence (IF) microscopy to determine the quantity and localization of the receptor in the lung tissue from normal control subjects and patients with hereditary or idiopathic PAH, as well as in the lungs of control rats and rats with MCT or SuHx-induced PAH. The activation of the BMP pathway was analyzed by determining the level and localization of phosphorylated Smad1/5/8 (pSmad 1/5/8), a downstream mediator of canonical BMPR2 signaling. Results: While BMPR2 and pSmad 1/5/8 expression levels were unaltered in whole lung lysates/homogenates from patients with hereditary and idiopathic PAH, IF analysis showed that BMPR2 and pSmad 1/5/8 levels were markedly decreased in the pulmonary vessels of both PAH patient groups. Whole lung BMPR2 expression was variable in the two PAH rat models, while in both experimental models the expression of BMPR2 in the lung vasculature was increased. However, in the human PAH lungs, the expression of pSmad 1/5/8 was downregulated in the lung vasculature of both experimental models. Conclusion: BMPR2 receptor expression and downstream signaling is reduced in the lung vasculature of patients with idiopathic and hereditary PAH, which cannot be appreciated when using human whole lung lysates. Despite increased BMPR2 expression in the lung vasculature, the MCT and SuHx rat models did develop PAH and impaired downstream BMPR2-Smad signaling similar to our findings in the human lung.

Transcriptomic analysis of pulmonary artery smooth muscle cells identifies new potential therapeutic targets for idiopathic pulmonary arterial hypertension

BACKGROUND AND PURPOSE

Pulmonary arterial hypertension (PAH, type 1 pulmonary hypertension) has a 3-year survival of ~50% and is in need of new, effective therapies. In PAH, remodelling of the pulmonary artery (PA) increases pulmonary vascular resistance and can result in right heart dysfunction and failure. Genetic mutations can cause PAH but it can also be idiopathic (IPAH). Enhanced contractility and proliferation of PA smooth muscle cells (PASMCs) are key contributors to the pathophysiology of PAH, but the underlying mechanisms are not well understood.

EXPERIMENTAL APPROACH

We utilized RNA-sequencing (RNA-seq) of IPAH and control patient-derived PASMCs as an unbiased approach to define differentially expressed (DE) genes that may identify new biology and potential therapeutic targets.

KEY RESULTS

Analysis of DE genes for shared gene pathways revealed increases in genes involved in cell proliferation and mitosis and decreases in a variety of gene sets, including response to cytokine signalling. ADGRG6/GPR126, an adhesion G protein-coupled receptor (GPCR), was increased in IPAH-PASMCs compared to control-PASMCs. Increased expression of this GPCR in control-PASMCs decreased their proliferation; siRNA knockdown of ADGRG6/GPR126 in IPAH-PASMCs tended to increase proliferation.

CONCLUSION AND IMPLICATIONS

These data provide insights regarding the expression of current and experimental PAH drug targets, GPCRs and GPCR-related genes as potentially new therapeutic targets in PAH-PASMCs. Overall, the findings identify genes and pathways that may contribute to IPAH-PASMC function and suggest that ADGRG6/GPR126 is a novel therapeutic target for IPAH.

Medicinal Plants and Phytochemicals for the Treatment of Pulmonary Hypertension

Background

Pulmonary hypertension (PH) is a progressive disease that is associated with pulmonary arteries remodeling, right ventricle hypertrophy, right ventricular failure and finally death. The present study aims to review the medicinal plants and phytochemicals used for PH treatment in the period of 1994 – 2019.

Methods

PubMed, Cochrane and Scopus were searched based on pulmonary hypertension, plant and phytochemical keywords from August 23, 2019. All articles that matched the study based on title and abstract were collected, non-English, repetitive and review studies were excluded.

Results

Finally 41 studies remained from a total of 1290. The results show that many chemical treatments considered to this disease are ineffective in the long period because they have a controlling role, not a therapeutic one. On the other hand, plants and phytochemicals could be more effective due to their action on many mechanisms that cause the progression of PH.

Conclusion

Studies have shown that herbs and phytochemicals used to treat PH do their effects from six mechanisms. These mechanisms include antiproliferative, antioxidant, antivascular remodeling, anti-inflammatory, vasodilatory and apoptosis inducing actions. According to the present study, many of these medicinal plants and phytochemicals can have effects that are more therapeutic than chemical drugs if used appropriately.

Metabolic syndrome, neurohumoral modulation, and pulmonary arterial hypertension

Pulmonary vascular disease, including pulmonary arterial hypertension (PAH), is increasingly recognized to be affected by systemic alterations including up-regulation of the renin-angiotensin-aldosterone system and perturbations to metabolic pathways, particularly glucose and fat metabolism. There is increasing preclinical and clinical data that each of these pathways can promote pulmonary vascular disease and right heart failure and are not simply disease markers. More recently, trials of therapeutics aimed at neurohormonal activation or metabolic dysfunction are beginning to shed light on how interventions in these pathways may affect patients with PAH. This review will focus on underlying mechanistic data that supports neurohormonal activation and metabolic dysfunction in the pathogenesis of PAH and right heart failure as well as discussing early translational data in patients with PAH.

Schistosomiasis-associated pulmonary arterial hypertension: a systematic review

Schistosomiasis-associated pulmonary arterial hypertension (Sch-PAH) is a life-threatening complication of chronic hepatosplenic schistosomiasis. It is suggested to be the leading cause of pulmonary arterial hypertension (PAH) worldwide. However, pathophysiological data on Sch-PAH are scarce. We examined the hypothesis that there are pronounced similarities in pathophysiology, haemodynamics, and survival of Sch-PAH and idiopathic PAH (iPAH).

This systematic review and meta-analysis was registered in the PROSPERO database (identifier CRD42018104066). A systematic search and review of the literature was performed according to PRISMA guidelines for studies published between 01 January 1990 and 29 June 2018.

For Sch-PAH, 18 studies evaluating pathophysiological mechanisms, eight studies on haemodynamics (n=277), and three studies on survival (n=191) were identified. 16 clinical registries reporting data on haemodynamics and survival including a total of 5792 patients with iPAH were included for comparison. Proinflammatory molecular pathways are involved in both Sch-PAH and iPAH. The transforming growth factor (TGF)-β signalling pathway is upregulated in Sch-PAH and iPAH. While there was no difference in mean pulmonary artery pressure (54±17 mmHg versus 55±15 mmHg, p=0.29), cardiac output (4.4±1.3 L·min−1versus 4.1±1.4 L·min−1, p=0.046), and cardiac index (2.6±0.7 L·min−1·m−2versus 2.3±0.8 L·min−1·m−2, p<0.001) were significantly higher in Sch-PAH compared to iPAH, resulting in a lower pulmonary vascular resistance in Sch-PAH (10±6 Woods units versus 13±7 Woods units, p<0.001). 1- and 3-year survival were significantly better in the Sch-PAH group (p<0.001).

Sch-PAH and iPAH share common pathophysiological mechanisms related to inflammation and the TGF-β signalling pathway. Patients with Sch-PAH show a significantly better haemodynamic profile and survival than patients with iPAH.

Loss of SMAD3 Promotes Vascular Remodeling in Pulmonary Arterial Hypertension via MRTF Disinhibition

RATIONALE

Vascular remodeling in pulmonary arterial hypertension (PAH) results from smooth muscle cell hypertrophy and proliferation of vascular cells. Loss of BMPR-II (bone morphogenetic protein receptor 2) signaling and increased signaling via TGF-β (transforming growth factor β) and its downstream mediators SMAD (small body size [a C. elegans protein] mothers against decapentaplegic [a Drosophila protein family])-2/3 has been proposed to drive lung vascular remodeling; yet, proteomic analyses indicate a loss of SMAD3 in PAH.

OBJECTIVES

We proposed that SMAD3 may be dysregulated in PAH and that loss of SMAD3 may present a pathophysiological master switch by disinhibiting its interaction partner, MRTF (myocardin-related transcription factor), which drives muscle protein expression.

METHODS

SMAD3 levels were measured in lungs from PAH patients, rats treated either with Sugen/hypoxia or monocrotaline (MCT), and in mice carrying a BMPR2 mutation. In vitro, effects of SMAD3 or BMPR2 silencing or SMAD3 overexpression on cell proliferation or smooth muscle hypertrophy were assessed. In vivo, the therapeutic and prophylactic potential of CCG1423, an inhibitor of MRTF, was investigated in Sugen/hypoxia rats.

MEASUREMENTS AND MAIN RESULTS

SMAD3 was downregulated in lungs of patients with PAH and in pulmonary arteries of three independent PAH animal models. TGF-β treatment replicated the loss of SMAD3 in human pulmonary artery smooth muscle cells (huPASMCs) and human pulmonary artery endothelial cells. SMAD3 silencing increased proliferation and migration in huPASMCs and human pulmonary artery endothelial cells. Coimmunoprecipitation revealed reduced interaction of MRTF with SMAD3 in TGF-β-treated huPASMCs and pulmonary arteries of PAH animal models. In huPASMCs, loss of SMAD3 or BMPR-II increased smooth muscle actin expression, which was attenuated by MRTF inhibition. Conversely, SMAD3 overexpression prevented TGF-β-induced activation of an MRTF reporter and reduced actin stress fibers in BMPR2-silenced huPASMCs. MRTF inhibition attenuated PAH and lung vascular remodeling in Sugen/hypoxia rats.

CONCLUSIONS

Loss of SMAD3 presents a novel pathomechanism in PAH that promotes vascular cell proliferation and-via MRTF disinhibition-hypertrophy of huPASMCs, thereby reconciling the parallel induction of a synthetic and contractile huPASMC phenotype.

Schistosome infection and its effect on pulmonary circulation

Schistosomiasis is the most common parasitic disease associated with pulmonary hypertension. It induces remodelling via complex inflammatory processes, which eventually produce the clinical manifestation of pulmonary hypertension. The pulmonary hypertension shows clinical signs and symptoms that are not distinguishable from other forms of pulmonary arterial hypertension.

Elucidating the contributory role of microRNA to cardiovascular diseases (a review)

Cardiovascular diseases encompassing atherosclerosis, aortic aneurysms, restenosis, and pulmonary arterial hypertension, remain the leading cause of morbidity and mortality worldwide. In response to a range of stimuli, the dynamic interplay between biochemical and biomechanical mechanisms affect the behaviour and function of multiple cell types, driving the development and progression of cardiovascular diseases. Accumulating evidence has highlighted microRNAs (miRs) as significant regulators and micro-managers of key cellular and molecular pathophysiological processes involved in predominant cardiovascular diseases, including cell mitosis, motility and viability, lipid metabolism, generation of inflammatory mediators, and dysregulated proteolysis. Human pathological and clinical studies have aimed to identify select microRNA which may serve as biomarkers of disease and their progression, which are discussed within this review. In addition, I provide comprehensive coverage of in vivo investigations elucidating the modulation of distinct microRNA on the pathophysiology of atherosclerosis, abdominal aortic aneurysms, restenosis, and pulmonary arterial hypertension. Collectively, clinical and animal studies have begun to unravel the complex and often diverse effects microRNAs and their targets impart during the development of cardiovascular diseases and revealed promising therapeutic strategies through which modulation of microRNA function may be applied clinically.

TGF-β and BMPR2 Signaling in PAH: Two Black Sheep in One Family

Knowledge pertaining to the involvement of transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP) signaling in pulmonary arterial hypertension (PAH) is continuously increasing. There is a growing understanding of the function of individual components involved in the pathway, but a clear synthesis of how these interact in PAH is currently lacking. Most of the focus has been on signaling downstream of BMPR2, but it is imperative to include the role of TGF-β signaling in PAH. This review gives a state of the art overview of disturbed signaling through the receptors of the TGF-β family with respect to vascular remodeling and cardiac effects as observed in PAH. Recent (pre)-clinical studies in which these two pathways were targeted will be discussed with an extended view on cardiovascular research fields outside of PAH, indicating novel future perspectives.

Consequences of BMPR2 Deficiency in the Pulmonary Vasculature and Beyond: Contributions to Pulmonary Arterial Hypertension

Since its association with familial pulmonary arterial hypertension (PAH) in 2000, Bone Morphogenetic Protein Receptor II (BMPR2) and its related signaling pathway have become recognized as a key regulator of pulmonary vascular homeostasis. Herein, we define BMPR2 deficiency as either an inactivation of the receptor, decreased receptor expression, or an impairment of the receptor’s downstream signaling pathway. Although traditionally the phenotypic consequences of BMPR2 deficiency in PAH have been thought to be limited to the pulmonary vasculature, there is evidence that abnormalities in BMPR2 signaling may have consequences in many other organ systems and cellular compartments. Revisiting how BMPR2 functions throughout health and disease in cells and organs beyond the lung vasculature may provide insight into the contribution of these organ systems to PAH pathogenesis as well as the potential systemic manifestation of PAH. Here we review our knowledge of the consequences of BMPR2 deficiency across multiple organ systems.

An upregulation of CD8+CD25+Foxp3+ T cells with suppressive function through interleukin 2 pathway in pulmonary arterial hypertension

Accumulating evidence suggests that abnormal inflammation plays a critical role in the pathogenesis of pulmonary arterial hypertension (PAH). CD8⁺CD25⁺Foxp3⁺ T cell is a novel cell subtype, and its role in PAH is not yet investigated. Here, we observed that PAH patients presented a significant upregulation of CD8⁺CD25⁺Foxp3⁺ T cells and a downregulation of CD4⁺CD25⁺Foxp3⁺ T cells compared to healthy controls. Regardless, the total number of CD25⁺Foxp3⁺ T cells in PAH patients was still smaller than that in healthy controls. Compared to CD8⁺CD25^- T cells, CD8⁺CD25⁺ T cells presented higher Foxp3 expression, lower interferon (IFN)-γ expression and higher transforming growth factor (TGF)-β expression, in both healthy and PAH individuals. The CD8⁺CD25⁺ T cells in PAH patients also demonstrated regulatory function by suppressing the proliferation of CD4⁺CD25^- and CD8⁺CD25^- effector T cells, albeit at lower efficiency than CD4⁺CD25⁺ T cells from PAH patients and healthy volunteers. CD8⁺CD25⁺ T cells from PAH responded to interleukin (IL)-2 supplement by expansion and upregulating Foxp3 expression. In PAH patients, IL-2-treated CD8⁺CD25⁺ T cells were more potent at inhibiting CD4⁺CD25^- effector T cell proliferation than IL-2-untreated CD8⁺CD25⁺ T cells. Together, we found an upregulation of CD8⁺CD25⁺Foxp3⁺ T cells in PAH patients, and this T cell population presented suppressive activity that could be enhanced by IL-2 treatment.

TGF-β activation by bone marrow-derived thrombospondin-1 causes Schistosoma- and hypoxia-induced pulmonary hypertension

Pulmonary arterial hypertension (PAH) is an obstructive disease of the precapillary pulmonary arteries. Schistosomiasis-associated PAH shares altered vascular TGF-β signalling with idiopathic, heritable and autoimmune-associated etiologies; moreover, TGF-β blockade can prevent experimental pulmonary hypertension (PH) in pre-clinical models. TGF-β is regulated at the level of activation, but how TGF-β is activated in this disease is unknown. Here we show TGF-β activation by thrombospondin-1 (TSP-1) is both required and sufficient for the development of PH in Schistosoma-exposed mice. Following Schistosoma exposure, TSP-1 levels in the lung increase, via recruitment of circulating monocytes, while TSP-1 inhibition or knockout bone marrow prevents TGF-β activation and protects against PH development. TSP-1 blockade also prevents the PH in a second model, chronic hypoxia. Lastly, the plasma concentration of TSP-1 is significantly increased in subjects with scleroderma following PAH development. Targeting TSP-1-dependent activation of TGF-β could thus be a therapeutic approach in TGF-β-dependent vascular diseases.

Thrombospondin-1 (TSP-1) activates latent TGF-β in the extracellular matrix. Here the authors show that inappropriate activation of latent TGF-β in murine, bovine and human lung by monocyte-produced TSP-1 causes pulmonary hypertension, and that interference with the activation process prevents disease development.

Kidney dysfunction in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PH) and chronic kidney disease (CKD) both profoundly impact patient outcomes, whether as primary disease states or as co-morbid conditions. PH is a common co-morbidity in CKD and vice versa. A growing body of literature describes the epidemiology of PH secondary to chronic kidney disease and end-stage renal disease (ESRD) (WHO group 5 PH). But, there are only limited data on the epidemiology of kidney disease in group 1 PH (pulmonary arterial hypertension [PAH]). The purpose of this review is to summarize the current data on epidemiology and discuss potential disease mechanisms and management implications of kidney dysfunction in PAH. Kidney dysfunction, determined by serum creatinine or estimated glomerular filtration rate, is a frequent co-morbidity in PAH and impaired kidney function is a strong and independent predictor of mortality. Potential mechanisms of PAH affecting the kidneys are increased venous congestion, decreased cardiac output, and neurohormonal activation. On a molecular level, increased TGF-β signaling and increased levels of circulating cytokines could have the potential to worsen kidney function. Nephrotoxicity does not seem to be a common side effect of PAH-targeted therapy. Treatment implications for kidney disease in PAH include glycemic control, lifestyle modification, and potentially Renin-Angiotensin-Aldosterone System (RAAS) blockade.

BMP4 inhibits PDGF-induced proliferation and collagen synthesis via PKA-mediated inhibition of calpain-2 in pulmonary artery smooth muscle cells

In the present study, we investigated the effect of bone morphogenetic protein 4 (BMP4) on PDGF-induced cell proliferation and collagen synthesis in pulmonary artery smooth muscle cells (PASMCs). Normal human PASMCs were incubated with and without PDGF-BB in the absence and presence of BMP4 for 0.5 to 24 h. The protein levels of collagen-I, p-Smad2/3, p-Smad1/5, and intracellular active TGF-β1, calpain activity, and cell proliferation were then measured. The results showed that BMP4 induced an increase in p-Smad1/5 but had no effect on the protein levels of collagen-I, p-Smad2/3, and intracellular active TGF-β1 and calpain activity in control PASMCs. Nevertheless, BMP4 attenuated increases in cell proliferation and protein levels of collagen-I, p-Smad2/3, and intracellular active TGF-β1 and calpain activity in PASMCs exposed to PDGF-BB. Moreover, BMP4 increased PKA activity and inhibition of PKA prevented the inhibitory effects of BMP4 on PDGF-BB-induced calpain activation in normal PASMCs. The PKA activator forskolin recapitulated the suppressive effect of BMP4 on PDGF-induced calpain activation. Furthermore, BMP4 prevented a PDGF-induced decrease in calpain-2 phosphorylation at serine-369 in normal PASMCs. Finally, BMP4 did not attenuate PDGF-induced increases in cell proliferation, collagen-I protein levels, and calpain activation and did not induce PKA activation and did not prevent a PDGF-induced decrease in calpain-2 phosphorylation at serine-369 in PASMCs from idiopathic pulmonary arterial hypertension (PAH) patients. These data demonstrate that BMP4 inhibits PDGF-induced cell proliferation and collagen synthesis via PKA-mediated inhibition of calpain-2 in normal PASMCs. The inhibitory effects of BMP4 on PDGF-induced cell proliferation, collagen synthesis, and calpain-2 activation are impaired in PASMCs from PAH patients, which may contribute to pulmonary vascular remodeling in PAH.

Sulfur Dioxide Protects Against Collagen Accumulation in Pulmonary Artery in Association With Downregulation of the Transforming Growth Factor β1/Smad Pathway in Pulmonary Hypertensive Rats

BACKGROUND

We aimed to explore the role of endogenous sulfur dioxide (SO2) in pulmonary vascular collagen remodeling induced by monocrotaline and its mechanisms.

METHODS AND RESULTS

A rat model of monocrotaline-induced pulmonary vascular collagen remodeling was developed and administered with l-aspartate-β-hydroxamate or SO2 donor. The morphology of small pulmonary arteries and collagen metabolism were examined. Cultured pulmonary arterial fibroblasts stimulated by transforming growth factor β1 (TGF-β1) were used to explore the mechanism. The results showed that in monocrotaline-treated rats, mean pulmonary artery pressure increased markedly, small pulmonary arterial remodeling developed, and collagen deposition in lung tissue and pulmonary arteries increased significantly in association with elevated SO2 content, aspartate aminotransferase (AAT) activity, and expression of AAT1 compared with control rats. Interestingly, l-aspartate-β-hydroxamate, an inhibitor of SO2 generation, further aggravated pulmonary vascular collagen remodeling in monocrotaline-treated rats, and inhibition of SO2 in pulmonary artery smooth muscle cells activated collagen accumulation in pulmonary arterial fibroblasts. SO2 donor, however, alleviated pulmonary vascular collagen remodeling with inhibited collagen synthesis, augmented collagen degradation, and decreased TGF-β1 expression of pulmonary arteries. Mechanistically, overexpression of AAT1, a key enzyme of SO2 production, prevented the activation of the TGF-β/type I TGF-β receptor/Smad2/3 signaling pathway and abnormal collagen synthesis in pulmonary arterial fibroblasts. In contrast, knockdown of AAT1 exacerbated Smad2/3 phosphorylation and deposition of collagen types I and III in TGF-β1-treated pulmonary arterial fibroblasts.

CONCLUSIONS

Endogenous SO2 plays a protective role in pulmonary artery collagen accumulation induced by monocrotaline via inhibition of the TGF-β/type I TGF-β receptor/Smad2/3 pathway.

Gene expression profile of angiogenic factors in pulmonary arteries in COPD: relationship with vascular remodeling

Pulmonary vessel remodeling in chronic obstructive pulmonary disease (COPD) involves changes in smooth muscle cell proliferation, which are highly dependent on the coordinated interaction of angiogenic-related growth factors. The purpose of the study was to investigate, in isolated pulmonary arteries (PA) from patients with COPD, the gene expression of 46 genes known to be modulators of the angiogenic process and/or involved in smooth muscle cell proliferation and to relate it to vascular remodeling. PA segments were isolated from 29 patients and classified into tertiles, according to intimal thickness. After RNA extraction, the gene expression was assessed by RT-PCR using TaqMan low-density arrays. The univariate analysis only showed upregulation of angiopoietin-2 (ANGPT-2) in remodeled PA (P < 0.05). The immunohistochemical expression of ANGPT-2 correlated with intimal enlargement (r = 0.42, P < 0.05). However, a combination of 10 factors in a multivariate discriminant analysis model explained up to 96% of the classification of the arteries. A network analysis of 46 genes showed major decentralization. In this network, the metalloproteinase-2 (MMP-2) was shown to be the bridge between intimal enlargement and fibrogenic factors. In COPD patients, plasma levels of ANGPT-2 were higher in current smokers or those with pulmonary hypertension. We conclude that an imbalance in ANGPT-2, combined with related factors such as VEGF, β-catenin, and MMP-2, may partially explain the structural derangements of the arterial wall. MMP-2 may act as a bridge channeling actions from the main fibrogenic factors.

Transforming growth factor-β superfamily in obstructive lung diseases. more suspects than TGF-β alone

Asthma and chronic obstructive pulmonary disease are respiratory disorders and a major global health problem with increasing incidence and severity. Genes originally associated with lung development could be relevant in the pathogenesis of chronic obstructive pulmonary disease/asthma, owing to either an early-life origin of adult complex diseases or their dysregulation in adulthood upon exposure to environmental stressors (e.g., smoking). The transforming growth factor (TGF)-β superfamily is conserved through evolution and is involved in a range of biological processes, both during development and in adult tissue homeostasis. TGF-β1 has emerged as an important regulator of lung and immune system development. However, considerable evidence has been presented for a role of many of the other ligands of the TGF-β superfamily in lung pathology, including activins, bone morphogenetic proteins, and growth differentiation factors. In this review, we summarize the current knowledge on the mechanisms by which activin, bone morphogenetic protein, and growth differentiation factor signaling contribute to the pathogenesis of obstructive airway diseases.

Schistosomiasis-associated pulmonary hypertension

Schistosomiasis, a parasite-borne disease, is highly prevalent in Africa and Asia; it is estimated that close to 20 million people worldwide have a severe form of the disease. The chronic form can affect the gastrointestinal system and lead to hepatosplenic disease, and it may cause cardiopulmonary complications, including pulmonary hypertension. The exact pathogenesis of schistosomiasis-associated pulmonary hypertension (Sch-PH) remains unclear, although several mechanisms, including parasitic arterial embolization, pulmonary arteriopathy, and portopulmonary hypertension-like pathophysiology, have been suggested. The immunopathology of the disease is also unclear, although there are similarities with the immunology of idiopathic pulmonary arterial hypertension (PAH). Finally, the treatment of Sch-PH has not been well studied. There is some evidence on treating the underlying infection, with unclear effect on Sch-PH, and advanced PAH therapies are now being suggested, but more studies are needed to confirm their efficacy.

Heterozygous null bone morphogenetic protein receptor type 2 mutations promote SRC kinase-dependent caveolar trafficking defects and endothelial dysfunction in pulmonary arterial hypertension

Hereditary pulmonary arterial hypertension (HPAH) is a rare, fatal disease of the pulmonary vasculature. The majority of HPAH patients inherit mutations in the bone morphogenetic protein type 2 receptor gene (BMPR2), but how these promote pulmonary vascular disease is unclear. HPAH patients have features of pulmonary endothelial cell (PEC) dysfunction including increased vascular permeability and perivascular inflammation associated with decreased PEC barrier function. Recently, frameshift mutations in the caveolar structural protein gene Caveolin-1 (CAV-1) were identified in two patients with non-BMPR2-associated HPAH. Because caveolae regulate endothelial function and vascular permeability, we hypothesized that defects in caveolar function might be a common mechanism by which BMPR2 mutations promote pulmonary vascular disease. To explore this, we isolated PECs from mice carrying heterozygous null Bmpr2 mutations (Bmpr2(+/-)) similar to those found in the majority of HPAH patients. We show that Bmpr2(+/-) PECs have increased numbers and intracellular localization of caveolae and caveolar structural proteins CAV-1 and Cavin-1 and that these defects are reversed after blocking endocytosis with dynasore. SRC kinase is also constitutively activated in Bmpr2(+/-) PECs, and localization of CAV-1 to the plasma membrane is restored after treating Bmpr2(+/-) PECs with the SRC kinase inhibitor 3-(4-chlorophenyl)-1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine (PP2). Late outgrowth endothelial progenitor cells isolated from HPAH patients show similar increased activation of SRC kinase. Moreover, Bmpr2(+/-) PECs have impaired endothelial barrier function, and barrier function is restored after treatment with PP2. These data suggest that heterozygous null BMPR2 mutations promote SRC-dependent caveolar trafficking defects in PECs and that this may contribute to pulmonary endothelial barrier dysfunction in HPAH patients.

Targeted delivery of genes to endothelial cells and cell- and gene-based therapy in pulmonary vascular diseases

Pulmonary arterial hypertension (PAH) is a devastating disease that, despite significant advances in medical therapies over the last several decades, continues to have an extremely poor prognosis. Gene therapy is a method to deliver therapeutic genes to replace defective or mutant genes or supplement existing cellular processes to modify disease. Over the last few decades, several viral and nonviral methods of gene therapy have been developed for preclinical PAH studies with varying degrees of efficacy. However, these gene delivery methods face challenges of immunogenicity, low transduction rates, and nonspecific targeting which have limited their translation to clinical studies. More recently, the emergence of regenerative approaches using stem and progenitor cells such as endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) have offered a new approach to gene therapy. Cell-based gene therapy is an approach that augments the therapeutic potential of EPCs and MSCs and may deliver on the promise of reversal of established PAH. These new regenerative approaches have shown tremendous potential in preclinical studies; however, large, rigorously designed clinical studies will be necessary to evaluate clinical efficacy and safety.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Schistosomiasis and pulmonary arterial hypertension

Schistosomiasis is caused by infection with the parasite Schistosoma, which is a flat-worm or fluke. The dominant species are Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium. Schistosomiasis is the third most common parasitic disease in the world after malaria and amoebiasis. It is endemic in more than 70 countries affecting about 200 million people worldwide, of whom 80% are in sub-Saharan Africa. There are pockets of infection in north-eastern Brazil, near the Yangtze River in China, and some pockets in south East Asia. In the East Mediterranean regions, the Schistosoma have been reported in Iraq and Egypt as well as in Sudan. The latter has the highest infection rate nowadays, particularly in the Al Jazeera area, due to the poor Schistosoma control program. In the Arabian peninsula, schistosomiasis has been reported in southwest part of Saudi Arabia, mainly in the Asir province and Jizan province, which lay in the southwest corner of Saudi Arabia and directly north of the border with Yemen. The efforts to control schistosomiasis have been very successful in Saudi Arabia due to the irrigation system control. However, the infection is prone in Yemen, where the schistosomiasis control is much less strict. Thus as a result, the problem still exists due to transmigration of the populations from both countries.

As a cause of pulmonary arterial hypertension (PAH), schistosomiasis is still under diagnosed and undertreated. This article with give a highlight about the pathophysiology of the disease and both diagnostic and therapeutic strategies.

Chronic hypoxia promotes pulmonary artery endothelial cell proliferation through H2O2-induced 5-lipoxygenase

Pulmonary Hypertension (PH) is a progressive disorder characterized by endothelial dysfunction and proliferation. Hypoxia induces PH by increasing vascular remodeling. A potential mediator in hypoxia-induced PH development is arachidonate 5-Lipoxygenase (ALOX5). While ALOX5 metabolites have been shown to promote pulmonary vasoconstriction and endothelial cell proliferation, the contribution of ALOX5 to hypoxia-induced proliferation remains unknown. We hypothesize that hypoxia exposure stimulates HPAEC proliferation by increasing ALOX5 expression and activity. To test this, human pulmonary artery endothelial cells (HPAEC) were cultured under normoxic (21% O2) or hypoxic (1% O2) conditions for 24-, 48-, or 72 hours. In a subset of cells, the ALOX5 inhibitor, zileuton, or the 5-lipoxygenase activating protein inhibitor, MK-886, was administered during hypoxia exposure. ALOX5 expression was measured by qRT-PCR and western blot and HPAEC proliferation was assessed. Our results demonstrate that 24 and 48 hours of hypoxia exposure have no effect on HPAEC proliferation or ALOX5 expression. Seventy two hours of hypoxia significantly increases HPAEC ALOX5 expression, hydrogen peroxide (H2O2) release, and HPAEC proliferation. We also demonstrate that targeted ALOX5 gene silencing or inhibition of the ALOX5 pathway by pharmacological blockade attenuates hypoxia-induced HPAEC proliferation. Furthermore, our findings indicate that hypoxia-induced increases in cell proliferation and ALOX5 expression are dependent on H2O2 production, as administration of the antioxidant PEG-catalase blocks these effects and addition of H2O2 to HPAEC promotes proliferation. Overall, these studies indicate that hypoxia exposure induces HPAEC proliferation by activating the ALOX5 pathway via the generation of H2O2.

How do we measure pathology in PAH (lung and RV) and what does it tell us about the disease

The current understanding of the pathology that underlies pulmonary vascular and right ventricular remodeling in pulmonary hypertension is discussed. Although recent studies underscored the importance of intima and media remodeling and, for the first time, the relevance of perivascular inflammation, much is needed to move the field forward. Reassessment of distribution and extension of the different vascular lesions requires state-of-the-art stereological tools, allied to three-dimensional casting and integration with data concerning cellular and molecular pathobiological processes. This integrated approach is ever more pressing in the right ventricle, because our understanding of key structural alterations of the failing right ventricle in pulmonary hypertension is lacking. This enterprise will enable better translation of pathogenetic processes to the human disease and provide key data to guide diagnostic and prognostic imaging approaches.

The current approach into signaling pathways in pulmonary arterial hypertension and their implication in novel therapeutic strategies

Many mediators and signaling pathways, with their downstream effectors, have been implicated in the pathogenesis of pulmonary hypertension. Currently approved drugs, representing an option of specific therapy, target NO, prostacyclin or ET-1 pathways and provide a significant improvement in the symptomatic status of patients and a slower rate of clinical deterioration. However, despite such improvements in the treatment, PAH remains a chronic disease without a cure, the mortality associated with PAH remains high and effective therapeutic regimens are still required. Knowledge about the role of the pathways involved in PAH and their interactions provides a better understanding of the pathogenesis of the disease and may highlight directions for novel therapeutic strategies for PAH. This paper reviews some novel, promising PAH-associated signaling pathways, such as RAAS, RhoA/ROCK, PDGF, PPAR, and TGF, focusing also on their possible interactions with well-established ones such as NO, ET-1 and prostacyclin pathways.

Physiological and pathological angiogenesis in the adult pulmonary circulation

Angiogenesis occurs during growth and physiological adaptation in many systemic organs, for example, exercise-induced skeletal and cardiac muscle hypertrophy, ovulation, and tissue repair. Disordered angiogenesis contributes to chronic inflammatory disease processes and to tumor growth and metastasis. Although it was previously thought that the adult pulmonary circulation was incapable of supporting new vessel growth, over that past 10 years new data have shown that angiogenesis within this circulation occurs both during physiological adaptive processes and as part of the pathogenic mechanisms of lung diseases. Here we review the expression of vascular growth factors in the adult lung, their essential role in pulmonary vascular homeostasis and the changes in their expression that occur in response to physiological challenges and in disease. We consider the evidence for adaptive neovascularization in the pulmonary circulation in response to alveolar hypoxia and during lung growth following pneumonectomy in the adult lung. In addition, we review the role of disordered angiogenesis in specific lung diseases including idiopathic pulmonary fibrosis, acute adult distress syndrome and both primary and metastatic tumors of the lung. Finally, we examine recent experimental data showing that therapeutic enhancement of pulmonary angiogenesis has the potential to treat lung diseases characterized by vessel loss.

Over, and underexpression of endothelin 1 and TGF-beta family ligands and receptors in lung tissue of broilers with pulmonary hypertension

Transforming growth factor beta (TGF β ) is a family of genes that play a key role in mediating tissue remodeling in various forms of acute and chronic lung disease. In order to assess their role on pulmonary hypertension in broilers, we determined mRNA expression of genes of the TGF β family and endothelin 1 in lung samples from 4-week-old chickens raised either under normal or cold temperature conditions. Both in control and cold-treated groups of broilers, endothelin 1 mRNA expression levels in lungs from ascitic chickens were higher than levels from healthy birds (P < 0.05), whereas levels in animals with cardiac failure were intermediate. Conversely, TGF β 2 and TGF β 3 gene expression in lungs were higher in healthy animals than in ascitic animals in both groups (P < 0.05). TGF β 1, T β RI, and T β RII mRNA gene expression among healthy, ascitic, and chickens with cardiac failure showed no differences (P > 0.05). BAMBI mRNA gene expression was lowest in birds with ascites only in the control group as compared with the values from healthy birds (P < 0.05).

Downregulation of bone morphogenetic protein receptor axis during HIV-1 and cocaine-mediated pulmonary smooth muscle hyperplasia: implications for HIV-related pulmonary arterial hypertension

OBJECTIVE

Our previous findings support an additive effect of cocaine to HIV infection in the development of pulmonary arteriopathy through enhanced proliferation of human pulmonary smooth muscle cells. We now examined the role of antiproliferative bone morphogenetic protein receptor (BMPR) axis in HIV protein and cocaine-mediated pulmonary smooth muscle hyperplasia.

APPROACH AND RESULTS

Stimulation of BMPR axis resulted in attenuation of synergistic increase in the proliferation of human pulmonary arterial smooth muscle cells in response to cocaine and HIV protein, transactivator of transcription (Tat). Interestingly, an increase in mRNA but decrease in protein levels of BMPR with correlated decrease in the activation of Sma- and MAD-related family protein 1/5/8 and Id1 gene expression was observed on combined treatment with cocaine and Tat when compared with the untreated cells at all time points tested. Although longer exposure to either cocaine or Tat alone also resulted in a significant decrease in the BMPR protein expression, the abrogation on combined treatment was still significantly more when compared with that of the monotreatments. Significant increase in mRNA but downmodulation of BMPR protein expression was also observed in the lung extracts from HIV-infected intravenous drug users (HIV+IVDU) when compared with that from HIV-infected non-IVDUs (HIV) or uninfected IVDUs (IVDU). Furthermore, significant decrease in BMPR protein expression was also observed in HIV or IVDUs when compared with normal controls that correlated with in vitro findings on chronic exposure to cocaine or HIV protein alone.

CONCLUSIONS

Simultaneous exposure of pulmonary smooth muscle cells to viral protein(s) and cocaine exacerbates downregulation of BMPR axis that may result in enhanced pulmonary vasculature aberrations in HIV+IVDUs.