Molecular and cellular basis of pulmonary vascular remodeling in pulmonary hypertension

BRCC3 Regulation of ALK2 in Vascular Smooth Muscle Cells: Implication in Pulmonary Hypertension

BACKGROUND

An imbalance of antiproliferative BMP (bone morphogenetic protein) signaling and proliferative TGF-β (transforming growth factor-β) signaling is implicated in the development of pulmonary arterial hypertension (PAH). The posttranslational modification (eg, phosphorylation and ubiquitination) of TGF-β family receptors, including BMPR2 (bone morphogenetic protein type 2 receptor)/ALK2 (activin receptor-like kinase-2) and TGF-βR2/R1, and receptor-regulated Smads significantly affects their activity and thus regulates the target cell fate. BRCC3 modifies the activity and stability of its substrate proteins through K63-dependent deubiquitination. By modulating the posttranslational modifications of the BMP/TGF-β-PPARγ pathway, BRCC3 may play a role in pulmonary vascular remodeling, hence the pathogenesis of PAH.

METHODS

Bioinformatic analyses were used to explore the mechanism by which BRCC3 deubiquitinates ALK2. Cultured pulmonary artery smooth muscle cells (PASMCs), mouse models, and specimens from patients with idiopathic PAH were used to investigate the rebalance between BMP and TGF-β signaling in regulating ALK2 phosphorylation and ubiquitination in the context of pulmonary hypertension.

RESULTS

BRCC3 was significantly downregulated in PASMCs from patients with PAH and animals with experimental pulmonary hypertension. BRCC3, by de-ubiquitinating ALK2 at Lys-472 and Lys-475, activated receptor-regulated Smad1/5/9, which resulted in transcriptional activation of BMP-regulated PPARγ, p53, and Id1. Overexpression of BRCC3 also attenuated TGF-β signaling by downregulating TGF-β expression and inhibiting phosphorylation of Smad3. Experiments in vitro indicated that overexpression of BRCC3 or the de-ubiquitin-mimetic ALK2-K472/475R attenuated PASMC proliferation and migration and enhanced PASMC apoptosis. In SM22α-BRCC3-Tg mice, pulmonary hypertension was ameliorated because of activation of the ALK2-Smad1/5-PPARγ axis in PASMCs. In contrast, Brcc3-/- mice showed increased susceptibility of experimental pulmonary hypertension because of inhibition of the ALK2-Smad1/5 signaling.

CONCLUSIONS

These results suggest a pivotal role of BRCC3 in sustaining pulmonary vascular homeostasis by maintaining the integrity of the BMP signaling (ie, the ALK2-Smad1/5-PPARγ axis) while suppressing TGF-β signaling in PASMCs. Such rebalance of BMP/TGF-β pathways is translationally important for PAH alleviation.

Impact of inhalation exposure to cigarette smoke on the pathogenesis of pulmonary hypertension primed by monocrotaline in rats

Extensive, long-term exposure to cigarette smoke (CS) was recently suggested to be a risk factor for pulmonary hypertension, although further validation is required. The vascular effects of CS share similarities with the etiology of pulmonary hypertension, including vascular inflammation and remodeling. Thus, we examined the influence of CS exposure on the pathogenesis of monocrotaline (MCT)-induced pulmonary hypertension, hypothesizing that smoking might accelerate the development of primed pulmonary hypertension. CS was generated from 3R4F reference cigarettes, and rats were exposed to CS by inhalation at total particulate matter concentrations of 100-300 μg/L for 4 h/day, 7 days/week for 4 weeks. Following 1 week of initial exposure, rats received 60 mg/kg MCT and were sacrificed and analyzed after an additional 3 weeks of exposure. MCT induced hypertrophy in pulmonary arterioles and increased the Fulton index, a measure of right ventricular hypertrophy. Additional CS exposure exacerbated arteriolar hypertrophy but did not further elevate the Fulton index. No significant alterations were observed in levels of endothelin-1 and vascular endothelial growth factor, or in hematological and serum biochemical parameters. Short-term inhalation exposure to CS exacerbated arteriolar hypertrophy in the lung, although this effect did not directly aggravate the overworked heart under the current experimental conditions.

Therapeutic potential and protective role of GRK6 overexpression in pulmonary arterial hypertension

Abnormal proliferation of pulmonary arterial smooth muscle cells (PASMCs) is a key mechanism in the development of pulmonary arterial hypertension (PAH). Signal transducer and activator of transcription 3 (STAT3) signalling plays a critical role in modulating PASMC proliferation, and G-protein-coupled receptor kinase 6 (GRK6) regulates the STAT3 pathway. However, the mechanism underlying the relationship between GRK6 and PAH remains unclear. In this study, we aimed to investigate the role of GRK6 in PAH and determine its potential as a therapeutic target. We utilised hypoxia- and SU5416-induced PAH mouse models and a monocrotaline-induced PAH rat model to analyse the involvement of GRK6. We conducted gain- and loss-of-function experiments using mouse PASMCs. Modulation of GRK6 expression was achieved via a lentiviral vector in vitro and an adeno-associated virus serotype 1 encoding GRK6 in vivo. GRK6 was significantly downregulated in the lung tissues of PAH mice and rats, predominantly in PASMCs. Knockout of GRK6 exacerbated PAH, while both therapeutic and prophylactic overexpression of GRK6 alleviated PAH, as evidenced by a reduction in right ventricular systolic pressure, right ventricular wall to left ventricular wall plus ventricular septum ratio, pulmonary vascular media thickness, and pulmonary vascular muscularisation. Mechanistically, GRK6 overexpression attenuated hypoxia-induced PASMC proliferation and STAT3 phosphorylation. Conversely, knockdown of GRK6 promoted hypoxia-induced proliferation, which was mitigated by a STAT3 inhibitor. Our findings highlight the potential protective and beneficial roles of GRK6 in PAH; we propose a lung-targeted GRK6 gene therapy utilizing adeno-associated virus serotype 1 as a potential treatment approach for patients with PAH.

Sinus venosus adaptation models prolonged cardiovascular disease and reveals insights into evolutionary transitions of the vertebrate heart

How two-chambered hearts in basal vertebrates have evolved from single-chamber hearts found in ancestral chordates remains unclear. Here, we show that the teleost sinus venosus (SV) is a chamber-like vessel comprised of an outer layer of smooth muscle cells. We find that in adult zebrafish nr2f1a mutants, which lack atria, the SV comes to physically resemble the thicker bulbus arteriosus (BA) at the arterial pole of the heart through an adaptive, hypertensive response involving smooth muscle proliferation due to aberrant hemodynamic flow. Single cell transcriptomics show that smooth muscle and endothelial cell populations within the adapting SV also take on arterial signatures. Bulk transcriptomics of the blood sinuses flanking the tunicate heart reinforce a model of greater equivalency in ancestral chordate BA and SV precursors. Our data simultaneously reveal that secondary complications from congenital heart defects can develop in adult zebrafish similar to those in humans and that the foundation of equivalency between flanking auxiliary vessels may remain latent within basal vertebrate hearts.

Sulforaphane alleviated vascular remodeling in hypoxic pulmonary hypertension via inhibiting inflammation and oxidative stress

Hypoxic pulmonary hypertension (HPH) is a cardiopulmonary disease featured by pulmonary vascular remodeling, which is due to abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) and dysfunction of endothelial cells (ECs). Sulforaphane (SFN) is a natural isothiocyanate extracted from cruciferous vegetables with promising anti-inflammatory and anti-oxidative activities. This study aimed to explore the effect and mechanism of SFN on HPH. Male mice were exposed to persistent chronic hypoxia for 4 weeks to induce HPH. The results demonstrated that SFN repressed the increased right ventricular systolic pressure (RVSP) and attenuated the right ventricular hypertrophy and pulmonary arteries remodeling in HPH mice. In particular, after SFN treatment, the CD68 positive cells in lung sections were reduced; TNF-α and IL-6 levels in lungs and serum declined; activation of NF-κB in PASMCs was inhibited in response to hypoxia. Besides, SFN enhanced the superoxide dismutase (SOD) activity in serum, SOD2 expression, total glutathione levels, and GSH/GSSG ratio in PASMCs, along with a decrease in malondialdehyde (MDA) contents in serum and ROS production in PASMCs after hypoxia exposure. Notably, SFN, as an Nrf2 activator, reversed the reduction in Nrf2 expression in hypoxic PASMCs. In vitro, SFN treatment inhibited hyperproliferation and promoted apoptosis of PASMCs under hypoxia conditions. SFN also prevented the apoptosis of pulmonary microvascular ECs caused by hypoxia. Therefore, these data suggested that SFN could significantly restrain the inflammation and oxidative stress, thereby inhibiting PASMCs proliferation, promoting PASMCs apoptosis, and reversing hypoxia injury in ECs to improve pulmonary vascular remodeling.

Circular RNAs Regulate Vascular Remodelling in Pulmonary Hypertension

Circular RNAs (circRNAs) are a newly identified type of noncoding RNA molecule with a unique closed-loop structure. circRNAs are widely expressed in different tissues and developmental stages of many species, participating in many important pathophysiological processes and playing an important role in the occurrence and development of diseases. This article reviews the discovery, characteristics, formation, and biological function of circRNAs. The relationship between circRNAs and vascular remodelling, as well as the current status of research and potential application value in pulmonary hypertension (PH), is discussed to promote a better understanding of the role of circRNAs in PH. circRNAs are closely related to the remodelling of vascular endothelial cells and vascular smooth muscle cells. circRNAs have potential application prospects for in-depth research on the possible pathogenesis and mechanism of PH. Future research on the role of circRNAs in the pathogenesis and mechanism of PH will provide new insights and promote screening, diagnosis, prevention, and treatment of this disease.

The Mechanism of Lung and Intestinal Injury in Acute Pancreatitis: A Review

Acute pancreatitis (AP), as a common cause of clinical acute abdomen, often leads to multi-organ damage. In the process of severe AP, the lungs and intestines are the most easily affected organs aside the pancreas. These organ damages occur in succession. Notably, lung and intestinal injuries are closely linked. Damage to ML, which transports immune cells, intestinal fluid, chyle, and toxic components (including toxins, trypsin, and activated cytokines to the systemic circulation in AP) may be connected to AP. This process can lead to the pathological changes of hyperosmotic edema of the lung, an increase in alveolar fluid level, destruction of the intestinal mucosal structure, and impairment of intestinal mucosal permeability. The underlying mechanisms of the correlation between lung and intestinal injuries are inflammatory response, oxidative stress, and endocrine hormone secretion disorders. The main signaling pathways of lung and intestinal injuries are TNF-α, HMGB1-mediated inflammation amplification effect of NF-κB signal pathway, Nrf2/ARE oxidative stress response signaling pathway, and IL-6-mediated JAK2/STAT3 signaling pathway. These pathways exert anti-inflammatory response and anti-oxidative stress, inhibit cell proliferation, and promote apoptosis. The interaction is consistent with the traditional Chinese medicine theory of the lung being connected with the large intestine (fei yu da chang xiang biao li in Chinese). This review sought to explore intersecting mechanisms of lung and intestinal injuries in AP to develop new treatment strategies.

Benefits of Curcumin in the Vasculature: A Therapeutic Candidate for Vascular Remodeling in Arterial Hypertension and Pulmonary Arterial Hypertension?

Growing evidence suggests that hypertension is one of the leading causes of cardiovascular morbidity and mortality since uncontrolled high blood pressure increases the risk of myocardial infarction, aortic dissection, hemorrhagic stroke, and chronic kidney disease. Impaired vascular homeostasis plays a critical role in the development of hypertension-induced vascular remodeling. Abnormal behaviors of vascular cells are not only a pathological hallmark of hypertensive vascular remodeling, but also an important pathological basis for maintaining reduced vascular compliance in hypertension. Targeting vascular remodeling represents a novel therapeutic approach in hypertension and its cardiovascular complications. Phytochemicals are emerging as candidates with therapeutic effects on numerous pathologies, including hypertension. An increasing number of studies have found that curcumin, a polyphenolic compound derived from dietary spice turmeric, holds a broad spectrum of pharmacological actions, such as antiplatelet, anticancer, anti-inflammatory, antioxidant, and antiangiogenic effects. Curcumin has been shown to prevent or treat vascular remodeling in hypertensive rodents by modulating various signaling pathways. In the present review, we attempt to focus on the current findings and molecular mechanisms of curcumin in the treatment of hypertensive vascular remodeling. In particular, adverse and inconsistent effects of curcumin, as well as some favorable pharmacokinetics or pharmacodynamics profiles in arterial hypertension will be discussed. Moreover, the recent progress in the preparation of nano-curcumins and their therapeutic potential in hypertension will be briefly recapped. The future research directions and challenges of curcumin in hypertension-related vascular remodeling are also proposed. It is foreseeable that curcumin is likely to be a therapeutic agent for hypertension and vascular remodeling going forwards.

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.

A literature review on pulmonary arterial hypertension (PAH)

Background:

PAH was first of all reported from German Doctor E. Romberg in 1891, It's usually found throughout the globe, but it is a burden in India and other developing countries. Pulmonary arterial hypertension (PAH) is characterized by a rise in pulmonary arterial pressure and the development of progressive symptoms like reduction in functional ability, shortness of breath and fatigue. The pulmonary arteries move blood from the right side of the heart over the lungs.

Introduction:

Increase pressure in pulmonary arteries known as pulmonary arterial pressure (PAH). The treatment of is require because without it, the right heart to work much harder due to high blood pressure in the lungs, and over time it became reason of heart failure. In this article, we have tried to provide brief information about the prevalence, pathology, classification and different therapies of PAH. Combining medicines from different categories is currently given as quality care and has been revealed to boost outcomes. A small part of the new treatment options has been included.

Lumican deficiency promotes pulmonary arterial remodeling

Pulmonary arterial hypertension (PAH) is caused by progressive extracellular matrix disorganization and increased pulmonary vascular cell proliferation. Lumican is a member of the small leucine-rich proteoglycan family that controls cell proliferation, and is a potential endogenous modulator of TGF-β signaling pathway. We show that the decreased lumican protein levels in pulmonary arterial smooth muscle cells (PASMCs) is related to the vascular remodeling and stiffening observed in PAH. The role of lumican in PASMC accumulation and activation in response to pulmonary vascular remodeling remains unclear and we hypothesized that the loss of lumican in PASMCs promotes the development of PAH. Our aim was to establish that lumican plays a pivotal role in modulating pathological vascular remodeling in humans using a rat model of monocrotaline-induced PAH and chronically hypoxic mice. We found that mice with a homozygous deletion of lumican (Lum-/-) showed severe pulmonary arterial remodeling and right ventricular hypertrophy in response to hypoxia, and these effects in mice with chronic hypoxia-induced pulmonary hypertension were successfully treated by the administration of a lumican C-terminal peptide (LumC13C-A, lumikine). We identified a mechanistic link by which lumican signaling prevents the activation of phosphorylated AKT, resulting in the suppression of PASMC proliferation. Lumican deficiency promotes pulmonary arterial remodeling. Administration of lumikine reverses the PAH pathogenesis caused by hypoxia-induced experimental PAH. Lumican is an antiproliferative target that functions to suppress pAKT activation during pathogenesis.

An evolutionary perspective on the interplays between hydrogen sulfide and oxygen in cellular functions

The physiological effects of the endogenously generated hydrogen sulfide (H2S) have been extensively studied in recent years. This review summarized the role of H2S in the origin of life and H2S metabolism in organisms from bacteria to vertebrates, examined the relationship between H2S and oxygen from an evolutionary perspective and emphasized the oxygen-dependent manner of H2S signaling in various physiological and pathological processes. H2S and oxygen are inextricably linked in various cellular functions. H2S is involved in aerobic respiration and stimulates oxidative phosphorylation and ATP production within the cell. Besides, H2S has protective effects on ischemia and reperfusion injury in several organs by acting as an oxygen sensor. Also, emerging evidence suggests the role of H2S is in an oxygen-dependent manner. All these findings indicate the subtle relationship between H2S and oxygen and further explain why H2S, a toxic molecule thriving in an anoxia environment several billion years ago, still affects homeostasis today despite the very low content in the body.

NAADP-induced intracellular calcium ion is mediated by the TPCs (two-pore channels) in hypoxia-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a form of obstructive vascular disease. Chronic hypoxic exposure leads to excessive proliferation of pulmonary arterial smooth muscle cells and pulmonary arterial endothelial cells. This condition can potentially be aggravated by [Ca²⁺] _i mobilization. In the present study, hypoxia exposure of rat's model was established. Two‐pore segment channels (TPCs) silencing was achieved in rats' models by injecting Lsh‐TPC1 or Lsh‐TPC2. The effects of TPC1/2 silencing on PAH were evaluated by H&E staining detecting pulmonary artery wall thickness and ELISA assay kit detecting NAADP concentrations in lung tissues. TPC1/2 silencing was achieved in PASMCs and PAECs, and cell proliferation was detected by MTT and BrdU incorporation assays. As the results shown, NAADP‐activated [Ca²⁺]_i shows to be mediated via two‐pore segment channels (TPCs) in PASMCs, with TPC1 being the dominant subtype. NAADP generation and TPC1/2 mRNA and protein levels were elevated in the hypoxia‐induced rat PAH model; NAADP was positively correlated with TPC1 and TPC2 expression, respectively. In vivo, Lsh‐TPC1 or Lsh‐TPC2 infection significantly improved the mean pulmonary artery pressure and PAH morphology. In vitro, TPC1 silencing inhibited NAADP‐AM‐induced PASMC proliferation and [Ca²⁺]_i in PASMCs, whereas TPC2 silencing had minor effects during this process; TPC2 silencing attenuated NAADP‐AM‐ induced [Ca²⁺]_i and ECM in endothelial cells, whereas TPC1 silencing barely ensued any physiological changes. In conclusion, TPC1/2 might provide a unifying mechanism within pulmonary arterial hypertension, which can potentially be regarded as a therapeutic target.

The newborn sheep translational model for pulmonary arterial hypertension of the neonate at high altitude

Chronic hypoxia during gestation induces greater occurrence of perinatal complications such as intrauterine growth restriction, fetal hypoxia, newborn asphyxia, and respiratory distress, among others. This condition may also cause a failure in the transition of the fetal to neonatal circulation, inducing pulmonary arterial hypertension of the neonate (PAHN), a syndrome that involves pulmonary vascular dysfunction, increased vasoconstrictor tone and pathological remodeling. As this syndrome has a relatively low prevalence in lowlands (~7 per 1000 live births) and very little is known about its prevalence and clinical evolution in highlands (above 2500 meters), our understanding is very limited. Therefore, studies on appropriate animal models have been crucial to comprehend the mechanisms underlying this pathology. Considering the strengths and weaknesses of any animal model of human disease is fundamental to achieve an effective and meaningful translation to clinical practice. The sheep model has been used to study the normal and abnormal cardiovascular development of the fetus and the neonate for almost a century. The aim of this review is to highlight the advances in our knowledge on the programming of cardiopulmonary function with the use of high-altitude newborn sheep as a translational model of PAHN.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

P2X7 receptor-mediated phenotype switching of pulmonary artery smooth muscle cells in hypoxia

P2X7R activation contributes to the pathogenesis of pulmonary hypertension. However, the molecular mechanism through which P2X7R participates in pulmonary vascular remodeling is largely unknown. The rats and pulmonary artery smooth muscle cells (PASMCs) were maintained under hypoxia. P2X7R expression was determined by real-time PCR and western blotting. The pathological changes of lung tissue were evaluated via HE staining after treatment with a P2X7R antagonist, A740003. After treatment with A740003 or silencing P2X7R, proliferating cell nuclear antigen (PCNA), phenotype markers and phospho-c-Jun N-terminal kinase (JNK)/JNK expression were tested by western blotting. P2X7R expression in hypoxia group was significantly higher than that in normoxia group in vivo and in vitro. The pathological changes of lung tissue induced by hypoxia were significantly relieved by treatment with a P2X7R antagonist, A740003. Hypoxia stimulated the proliferation and synthetic phenotype of PASMCs, which were aggravated by a P2X7R agonist treatment and alleviated by a P2X7R antagonist or silencing P2X7R mRNA treatment. Silencing P2X7R mRNA significantly decreased the hypoxia-induced upregulation of phospho-JNK/JNK in PASMCs. The phenotype switching of PASMCs in hypoxia was reversed by treatment with JNK inhibitor. The findings indicate that P2X7R may be involved in the hypoxia-induced proliferation and phenotype switching of PASMCs via JNK signaling pathway, which suggests a new therapeutic strategy targeting P2X7R in vascular remodeling of pulmonary arterial hypertension.

PDGF/MEK/ERK axis represses Ca2+ clearance via decreasing the abundance of plasma membrane Ca2+ pump PMCA4 in pulmonary arterial smooth muscle cells

Pulmonary arterial hypertension (PAH) is a rare and lethal disease characterized by vascular remodeling and vasoconstriction, which is associated with increased intracellular calcium ion concentration ([Ca2+]i). Platelet-derived growth factor-BB (PDGF-BB) is the most potent mitogen for pulmonary arterial smooth muscle cells (PASMCs) and is involved in vascular remodeling during PAH development. PDGF signaling has been proved to participate in maintaining Ca2+ homeostasis of PASMCs; however, the mechanism needs to be further elucidated. Here, we illuminate that the expression of plasma membrane calcium-transporting ATPase 4 (PMCA4) was downregulated in PASMCs after PDGF-BB stimulation, which could be abolished by restraining the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK). Functionally, suppression of PMCA4 attenuated the [Ca2+]i clearance in PASMCs after Ca2+ entry, promoting cell proliferation and elevating cell locomotion through mediating formation of focal adhesion. Additionally, the expression of PMCA4 was decreased in the pulmonary artery of monocrotaline (MCT)- or hypoxia-induced PAH rats. Moreover, knockdown of PMCA4 could increase the right ventricular systolic pressure (RVSP) and wall thickness (WT) of pulmonary artery in rats raised under normal conditions. Taken together, our findings demonstrate the importance of the PDGF/MEK/ERK/PMCA4 axis in intracellular Ca2+ homeostasis in PASMCs, indicating a functional role of PMCA4 in pulmonary arterial remodeling and PAH development.

Anti-inflammatory Effects of Statins in Lung Vascular Pathology: From Basic Science to Clinical Trials

HMG-CoA reductase inhibitors (or statins) are cholesterol-lowering drugs and are among the most widely prescribed medications in the United States. Statins exhibit pleiotropic effects that extend beyond cholesterol reduction including anti-atherosclerotic, antiproliferative, anti-inflammatory, and antithrombotic effects. Over the last 20 years, statins have been studied and examined in pulmonary vascular disorders, including both chronic pulmonary vascular disease such as pulmonary hypertension, and acute pulmonary vascular endothelial injury such as acute lung injury. In both research and clinical settings, statins have demonstrated promising vascular protection through modulation of the endothelium, attenuation of vascular leak, and promotion of endothelial repair following lung inflammation. This chapter provides a summary of the rapidly changing literature, summarizes the anti-inflammatory mechanism of statins on pulmonary vascular disorders, and explores clinical evidence for statins as a potential therapeutic approach to modulation of the endothelium as well as a means to broaden our understanding of pulmonary vasculopathy pathophysiology.

MEIS1 regulated proliferation and migration of pulmonary artery smooth muscle cells in hypoxia-induced pulmonary hypertension

AIM

Proliferation and migration of pulmonary artery smooth muscle cells (PASMCs) are regarded as the primary factors resulting in pulmonary arterial remodeling in pulmonary hypertension (PH). Myeloid ecotropic viral integration site 1 (MEIS1) has been positioned as a negative cardiomyocyte cell cycle regulator and regulates proliferation of multiple kinds of cancer cells. Whether MESI1 is involved in the proliferation and migration of PASMCs deserves to be identified.

MAIN METHODS

Sprague Dawley rats were exposed to hypoxia condition (10% O₂) for 4 weeks to induce PH and primary rat PASMCs were cultured in hypoxia condition (3% O₂) for 48 h to induce proliferation and migration. Immunohistochemistry, immunofluorescence, reverse transcription PCR and Western blot analysis were performed to detect the expressions of target mRNAs and proteins. EDU, CCK8 and wound healing assays were conducted to measure the proliferation and migration of PASMCs.

KEY FINDINGS

Hypoxia down-regulated the expression of MEIS1 (both mRNA and protein) in pulmonary arteries and PASMCs. Over-expression of MEIS1 inhibited the proliferation and migration of PASMCs afforded by hypoxia. In contrast, knockdown of MEIS1 under normoxia condition like hypoxia induced the proliferation and migration of PASMCs. MEIS1 mediated hypoxia-induced the proliferation and migration of PASMCs via METTL14/MEIS1/p21 signaling.

SIGNIFICANCE

The present study revealed that MEIS1 regulated the proliferation and migration of PASMCs during hypoxia-induced PH. Thus, MEIS1 may be a potential target for PH therapy.

Homology modeling, molecular dynamics and virtual screening of endothelin-A receptor for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease of pulmonary arteries, causing serious shortness of breath and right ventricular failure with high mortality. Numerous studies have verified that the symptoms of PAH could be attenuated effectively with endothelin-A receptor (ETAR) antagonists. Unfortunately, the 3D structure of ETAR has not been released, making it difficult to understand the interactions between ETAR and its antagonists. In this study, computational methods including homology modeling, molecular docking and molecular dynamics simulations were performed to build the structure of ETAR and predict the binding patterns of ETAR with its two antagonists. Based on these results, virtual screening study was implemented against Traditional Chinese Medicine (TCM) database to identify novel natural ETAR antagonists. Six compounds with best binding energies were screened out and two of them were found to bind steadily with ETAR validated through molecular dynamics simulations and MM-GBSA calculation, indicating that they were potential antagonists of ETAR. In a word, our research provided a deep exploration into the interaction between ETAR and its antagonists, which could promote the development of novel therapy against PAH.[Formula: see text]Communicated by Ramaswamy H. Sarma.

Involvement of miR-200b-PKCα signalling in pulmonary hypertension in cor pulmonale model

The right ventricle (RV) enlargement and pulmonary fibrosis are involved in cor pulmonale. The role of miR-200b in cor pulmonale is less well understood. This study was designed to evaluate the regulatory roles of miR-200b in cor pulmonale. Cor pulmonary mouse model was built via monocrotaline injection of monocrotaline (MCT). The expression of miR-200b in the lungs, RV and left ventricle (LV) are using real-time polymerase chain reaction. The transthoracic echocardiography was employed to determine the effects of miR-200b mimics and Gö6976 injection on MCT mice. The protein levels of protein kinase C α (PKCα), collagen, and fibronectin in the lung, RV, and LV in the mice with and without miR-200b mimics and Gö6976 injection were evaluated using western blot. The expression of miR-200b decreased in MCT mice, while there was no difference in LV. Both the miR-200b mimics and Gö6976 injection reversed the muscularization in the pulmonary artery, reversed RV hypertrophy, reduced RV systolic pressure, wall thickness and pulmonary fibrosis. The injection of miR-200b can reduce the PKCα expression in the lung, RV, and LV. This study confirmed the down-regulation of miR-200b in cor pulmonale. The reverse effects of miR-200b in the present study may provide a potential tool for cor pulmonary treatment.

Metabolism and Redox in Pulmonary Vascular Physiology and Pathophysiology

Significance: This review considers how some systems controlling pulmonary vascular function are potentially regulated by redox processes to examine how and why conditions such as prolonged hypoxia, pathological mediators, and other factors promoting vascular remodeling contribute to the development of pulmonary hypertension (PH). Recent Advances and Critical Issues: Aspects of vascular remodeling induction mechanisms described are associated with shifts in glucose metabolism through the pentose phosphate pathway and increased cytosolic NADPH generation by glucose-6-phosphate dehydrogenase, increased glycolysis generation of cytosolic NADH and lactate, mitochondrial dysfunction associated with superoxide dismutase-2 depletion, changes in reactive oxygen species and iron metabolism, and redox signaling. Future Directions: The regulation and impact of hypoxia-inducible factor and the function of cGMP-dependent and redox regulation of protein kinase G are considered for their potential roles as key sensors and coordinators of redox and metabolic processes controlling the progression of vascular pathophysiology in PH, and how modulating aspects of metabolic and redox regulatory systems potentially function in beneficial therapeutic approaches.

Prevalence and Effect on Survival of Pulmonary Hypertension in Myelofibrosis

BACKGROUND

Myelofibrosis (MF), a rare disorder characterized by bone marrow fibrosis, has been implicated as a cause of pulmonary hypertension (PH). To date, studies examining this association have not looked at the impact of PH on survival in MF. We examined the relationship between MF and PH by echocardiogram (echo) using a retrospective patient database and examined the influence of PH on overall survival.

PATIENTS AND METHODS

In this single-center retrospective chart review, we identified 65 patients with biopsy-proven primary and secondary MF, 31 of whom underwent transthoracic echo. After accounting for chronic obstructive pulmonary disease and left-sided or valvular heart dysfunction, which excluded 6 patients, we identified 14 patients (56%) who had echo evidence of group 5 PH (ie, PH due to unclear or multifactorial mechanisms), 8 with primary MF and 6 with secondary MF. MF patients with PH trended toward being predominantly female, being older, and less often having constitutional symptoms compared to the non-PH cohort.

RESULTS

There was no effect of the presence of PH on overall survival in the entire MF cohort or in any subgroup analyzed, including primary MF versus secondary MF and primary MF intermediate risk patients.

CONCLUSION

Given the high prevalence of MF-associated PH, there may be a larger role for routine echo screening in MF patients. Further, the underlying association between PH and MF may signify an endothelial plasticity or increased telomerase activity as part of the pathogenesis of MF.

Biomechanics and Mechanobiology of Saphenous Vein Grafts

Within several weeks of use as coronary artery bypass grafts (CABG), saphenous veins (SV) exhibit significant intimal hyperplasia (IH). IH predisposes vessels to thrombosis and atherosclerosis, the two major modes of vein graft failure. The fact that SV do not develop significant IH in their native venous environment coupled with the rapidity with which they develop IH following grafting into the arterial circulation suggests that factors associated with the isolation and preparation of SV and/or differences between the venous and arterial environments contribute to disease progression. There is strong evidence suggesting that mechanical trauma associated with traditional techniques of SV preparation can significantly damage the vessel and might potentially reduce graft patency though modern surgical techniques reduces these injuries. In contrast, it seems possible that modern surgical technique, specifically endoscopic vein harvest, might introduce other mechanical trauma that could subtly injure the vein and perhaps contribute to the reduced patency observed in veins harvested using endoscopic techniques. Aspects of the arterial mechanical environment influence remodeling of SV grafted into the arterial circulation. Increased pressure likely leads to thickening of the medial wall but its role in IH is less clear. Changes in fluid flow, including increased average wall shear stress, may reduce IH while disturbed flow likely increase IH. Nonmechanical stimuli, such as exposure to arterial levels of oxygen, may also have a significant but not widely recognized role in IH. Several potentially promising approaches to alter the mechanical environment to improve graft patency are including extravascular supports or altered graft geometries are covered.

Soluble epoxide hydrolase inhibitor, TUPS, attenuates isoproterenol/angiotensin II-induced cardiac hypertrophy through mammalian target of rapamycin-mediated autophagy inhibition

OBJECTIVES

To investigate the potential role and mechanism of TUPS, a soluble epoxide hydrolase inhibitor, in cardiac hypertrophy.

METHODS

Rat and H9C2 cell models of cardiac hypertrophy were induced by isoproterenol and angiotensin II, respectively, followed by TUPS treatment. The expression of hypertrophic markers, ANP and BNP, was determined by quantitative real-time PCR. The abundance of Beclin-1, LC3, p-AMPK and phosphorylated-mammalian target of rapamycin (p-mTOR) proteins was analysed by Western blot and immunohistocytology. Cell morphology and viability were evaluated by F-actin staining and MTS. H9C2 cells were transfected with GFP-LC3 to evaluate autophagy flux.

KEY FINDINGS

TUPS significantly inhibited rat heart size, heart weight-to-body weight ratio, heart wall thickness, hypertrophic H9C2 cell swelling and viability suppression as well as the expression of ANP and BNP genes in hypertrophic models. In addition, autophagic markers Beclin-1 and LC3 were elevated in both cellular and animal models, which were suppressed by TUPS, with corresponding changes of autophagy flux. The abundance of p-AMPK was increased, while p-mTOR was decreased in hypertrophic cells, which were abolished by TUPS. Rapamycin decreased p-mTOR level, increased Beclin-1 and LC3 expression and induced cell size enlargement and cell viability inhibition in hypertrophic H9C2 cells treated with TUPS.

CONCLUSIONS

TUPS inhibits cardiac hypertrophy by regulating mTOR/autophagy axis.

DPP-4 inhibition: А novel therapeutic approach to the treatment of pulmonary hypertension?

Pulmonary hypertension (PH) is a progressive disorder characterized by alterations of the vascular structure and function in the lungs. Despite the success in its stabilisation by targeting pulmonary vascular tone and endothelial dysfunction, the prognosis remains poor and new therapeutic approaches via neglected macromolecular targets are needed. In the pathophysiology of PH the early stages of vascular remodelling are considered to be reversible, while endothelial to mesenchymal transition and proliferation/migration of fibroblasts play a critical role in staging the irreversible phase. Dipeptidyl peptidase-4 (DPP-4)/CD26 is present and active in the lungs and is expressed constitutively on lung fibroblasts, on which it exerts proliferative effects. Further, it is a marker of migrating fibroblasts and of their functional activation, including collagen synthesis and inflammatory cytokine secretion. Inhibiting DPP-4 improves the reversible phases of vascular dysfunction in PH, but is also highly likely to attenuate endothelial to mesenchymal transition and decrease the proliferation and migration of fibroblasts, preventing fibrosis and, consequently, should prolong or even inhibit entrance to the potentially irreversible phase of PH. Proposed mechanisms that support the multifaceted aspects of DPP-4 inhibition in terms of improving PH, involve pathways and mediators in pulmonary vascular and connective tissue remodelling. The latter are affected by the inhibition of this protease resulting in the synergistic beneficial antioxidative, anti-inflammatory and antifibrotic effects. We offer here an evidence-supported hypothesis that DPP-4 inhibitors are likely to be effective in the irreversible phase of remodelling in PH. Accordingly, we propose PH as a possible novel therapeutic indication for existing and new DPP-4 inhibitors.

Rab6A GTPase contributes to phenotypic modulation in pulmonary artery smooth muscle cells under hypoxia

Previous studies have demonstrated that hypoxia can induce phenotypic modulation of pulmonary smooth muscle cells; however, the mechanisms remain unclear. The present study aimed to investigate the effect of the GTPase Rab6A-mediated phenotypic modulation and other activities of rat pulmonary artery smooth muscle cells (RPASMCs). We revealed that Rab6A was induced by hypoxia (1% O₂ ) and was involved in a hypoxia-induced phenotypic switch and endoplasmic reticulum stress (ERS) in RPASMCs. After 48 hours of hypoxia, the expression of the phenotype marker protein smooth muscle actin was downregulated and vimentin (VIM) expression was upregulated. Rab6A was upregulated after 48 hours of hypoxia, and the level of glucose-regulated protein, 78 kDa (GRP78) after 12 hours of hypoxic stimulation was also increased. After transfection with a Rab6A short interfering RNA under hypoxic conditions, the expression levels of GRP78 and VIM in RPASMCs were downregulated. Overall, hypoxia-induced RPASMCs to undergo ERS followed by phenotypic transformation. Rab6A is involved in this hypoxia-induced phenotypic modulation and ERS in RPASMCs.

Preparation of Pulmonary Artery Myocytes and Rings to Study Vasoactive GPCRs

G protein-coupled receptors (GPCR) are crucial transducers of extracellular signals into changes in vascular tone. Vasoactive GPCR stimulation in the pulmonary circuit may be elicited by agonists released in acute tissue hypoxia or inflammation, as well as chronic disease. Acute responses involve activation of smooth muscle contraction or relaxation machinery causing changes in actomyosin interaction, thereby altering lumen diameter. Chronic responses may typically include activation of proliferation or fibrosis. Using pulmonary artery myocytes and pulmonary artery rings, we describe a general strategy for quantification of vasoconstrictor or vasodilator GPCR responses, and for comparison of signaling pathways in cultured cells and in contracted vessels using immunohistochemistry of contracting vessels.

Caspase-1 induces smooth muscle cell growth in hypoxia-induced pulmonary hypertension

Lung diseases with hypoxia are complicated by pulmonary hypertension, leading to heart failure and death. No pharmacological treatment exists. Increased proinflammatory cytokines are found in hypoxic patients, suggesting an inflammatory pathogenesis. Caspase-1, the effector of the inflammasome, mediates inflammation through activation of the proinflammatory cytokines interleukin (IL)-18 and IL-1β. Here, we investigate inflammasome-related mechanisms that can trigger hypoxia-induced pulmonary hypertension. Our aim was to examine whether caspase-1 induces development of hypoxia-related pulmonary hypertension and is a suitable target for therapy. Wild-type (WT) and caspase-1^-/- mice were exposed to 10% oxygen for 14 days. Hypoxic caspase-1^-/- mice showed lower pressure and reduced muscularization in pulmonary arteries, as well as reduced right ventricular remodeling compared with WT. Smooth muscle cell (SMC) proliferation was reduced in caspase-1-deficient pulmonary arteries and in WT arteries treated with a caspase-1 inhibitor. Impaired inflammation was shown in hypoxic caspase-1^-/- mice by abolished pulmonary influx of immune cells and lower levels of IL-18, IL-1β, and IL-6, which were also reduced in the medium surrounding caspase-1 abrogated pulmonary arteries. By adding IL-18 or IL-1β to caspase-1-deficient pulmonary arteries, SMC proliferation was retained. Furthermore, inhibition of both IL-6 and phosphorylated STAT3 reduced proliferation of SMC in vitro, indicating IL-18, IL-6, and STAT3 as downstream mediators of caspase-1-induced SMC proliferation in pulmonary arteries. Caspase-1 induces SMC proliferation in pulmonary arteries through the caspase-1/IL-18/IL-6/STAT3 pathway, leading to pulmonary hypertension in mice exposed to hypoxia. We propose that caspase-1 inhibition is a potential target for treatment of pulmonary hypertension.

Pulmonary vascular mechanical consequences of ischemic heart failure and implications for right ventricular function

Left heart failure (LHF) is the most common cause of pulmonary hypertension, which confers an increase in morbidity and mortality in this context. Pulmonary vascular resistance has prognostic value in LHF, but otherwise the mechanical consequences of LHF for the pulmonary vasculature and right ventricle (RV) remain unknown. We sought to investigate mechanical mechanisms of pulmonary vascular and RV dysfunction in a rodent model of LHF to address the knowledge gaps in understanding disease pathophysiology. LHF was created using a left anterior descending artery ligation to cause myocardial infarction (MI) in mice. Sham animals underwent thoracotomy alone. Echocardiography demonstrated increased left ventricle (LV) volumes and decreased ejection fraction at 4 wk post-MI that did not normalize by 12 wk post-MI. Elevation of LV diastolic pressure and RV systolic pressure at 12 wk post-MI demonstrated pulmonary hypertension (PH) due to LHF. There was increased pulmonary arterial elastance and pulmonary vascular resistance associated with perivascular fibrosis without other remodeling. There was also RV contractile dysfunction with a 35% decrease in RV end-systolic elastance and 66% decrease in ventricular-vascular coupling. In this model of PH due to LHF with reduced ejection fraction, pulmonary fibrosis contributes to increased RV afterload, and loss of RV contractility contributes to RV dysfunction. These are key pathologic features of human PH secondary to LHF. In the future, novel therapeutic strategies aimed at preventing pulmonary vascular mechanical changes and RV dysfunction in the context of LHF can be tested using this model. NEW & NOTEWORTHY In this study, we investigate the mechanical consequences of left heart failure with reduced ejection fraction for the pulmonary vasculature and right ventricle. Using comprehensive functional analyses of the cardiopulmonary system in vivo and ex vivo, we demonstrate that pulmonary fibrosis contributes to increased RV afterload and loss of RV contractility contributes to RV dysfunction. Thus this model recapitulates key pathologic features of human pulmonary hypertension-left heart failure and offers a robust platform for future investigations.

Metabolic Alterations in Cardiopulmonary Vascular Dysfunction

Cardiovascular diseases (CVD) are the leading cause of death worldwide. CVD comprise a range of diseases affecting the functionality of the heart and blood vessels, including acute myocardial infarction (AMI) and pulmonary hypertension (PH). Despite their different causative mechanisms, both AMI and PH involve narrowed or blocked blood vessels, hypoxia, and tissue infarction. The endothelium plays a pivotal role in the development of CVD. Disruption of the normal homeostasis of endothelia, alterations in the blood vessel structure, and abnormal functionality are essential factors in the onset and progression of both AMI and PH. An emerging theory proposes that pathological blood vessel responses and endothelial dysfunction develop as a result of an abnormal endothelial metabolism. It has been suggested that, in CVD, endothelial cell metabolism switches to higher glycolysis, rather than oxidative phosphorylation, as the main source of ATP, a process designated as the Warburg effect. The evidence of these alterations suggests that understanding endothelial metabolism and mitochondrial function may be central to unveiling fundamental mechanisms underlying cardiovascular pathogenesis and to identifying novel critical metabolic biomarkers and therapeutic targets. Here, we review the role of the endothelium in the regulation of vascular homeostasis and we detail key aspects of endothelial cell metabolism. We also describe recent findings concerning metabolic endothelial cell alterations in acute myocardial infarction and pulmonary hypertension, their relationship with disease pathogenesis and we discuss the future potential of pharmacological modulation of cellular metabolism in the treatment of cardiopulmonary vascular dysfunction. Although targeting endothelial cell metabolism is still in its infancy, it is a promising strategy to restore normal endothelial functions and thus forestall or revert the development of CVD in personalized multi-hit interventions at the metabolic level.

Hypoxia/reperfusion predisposes to atherosclerosis

Surgical interventions on blood vessels bear a risk for intimal hyperplasia and atherosclerosis as a consequence of injury. A specific feature of intimal hyperplasia is the loss of vascular smooth muscle cell (VSMC) differentiation gene expression. We hypothesized that immediate responses following injury induce vascular remodeling. To differentiate injury due to trauma, reperfusion and pressure changes we analyzed vascular responses to carotid artery bypass grafting in mice compared to transient ligation. As a control, the carotid artery was surgically laid open only. In both, bypass or ligation models, the inflammatory responses were transient, peaking after 6h, whereas the loss of VSMC differentiation gene expression persisted. Extended time kinetics showed that transient carotid artery ligation was sufficient to induce a persistent VSMC phenotype change throughout 28 days. Transient arterial ligation in ApoE knockout mice resulted in atherosclerosis in the transiently ligated vascular segment but not on the not-ligated contralateral side. The VSMC phenotype change could not be prevented by anti-TNF antibodies, Sorafenib, Cytosporone B or N-acetylcysteine treatment. Surgical interventions involving hypoxia/reperfusion are sufficient to induce VSMC phenotype changes and vascular remodeling. In situations of a perturbed lipid metabolism this bears the risk to precipitate atherosclerosis.

JNK2 regulates vascular remodeling in pulmonary hypertension

Pulmonary arterial (PA) wall modifications are key pathological features of pulmonary hypertension (PH). Although such abnormalities correlate with heightened phosphorylation of c-Jun N-terminal kinases 1/2 (JNK1/2) in a rat model of PH, the contribution of specific JNK isoforms to the pathophysiology of PH is unknown. Hence, we hypothesized that activation of either one, or both JNK isoforms regulates PA remodeling in PH. We detected increased JNK1/2 phosphorylation in the thickened vessels of PH patients' lungs compared to that in lungs of healthy individuals. JNK1/2 phosphorylation paralleled a marked reduction in MAP kinase phosphatase 1 (JNK dephosphorylator) expression in patients' lungs. Association of JNK1/2 activation with vascular modification was confirmed in the calf model of severe hypoxia-induced PH. To ascertain the role of each JNK isoform in pathophysiology of PH, wild-type (WT), JNK1 null (JNK1-/-), and JNK2 null (JNK2-/-) mice were exposed to chronic hypoxia (10% O2 for six weeks) to develop PH. In hypoxic WT lungs, an increase in JNK1/2 phosphorylation was associated with PH-like pathology. Hallmarks of PH pathophysiology, i.e. excessive accumulation of extracellular matrix and vessel muscularization with medial wall thickening, was also detected in hypoxic JNK1-/- lungs, but not in hypoxia-exposed JNK2-/- lungs. However, hypoxia-induced increases in right ventricular systolic pressure (RVSP) and in right ventricular hypertrophy (RVH) were similar in all three genotypes. Our findings suggest that JNK2 participates in PA remodeling (but likely not in vasoconstriction) in murine hypoxic PH and that modulating JNK2 actions might quell vascular abnormalities and limit the course of PH.

Akt/eNOS and MAPK signaling pathways mediated the phenotypic switching of thoracic aorta vascular smooth muscle cells in aging/hypertensive rats

Considerable evidence demonstrates that phenotypic switching of vascular smooth muscle cells (VSMCs) is influenced by aging and hypertension. During phenotypic switching, VSMCs undergo a switch to a proliferative and migratory phenotype, with this switch being a common pathology in cardiovascular diseases. The aim of this study was to explore the joint influence of age and hypertension on thoracic aortic smooth muscle phenotypic switching and the balance of Akt and mitogen-activated protein kinase (MAPK) signaling during this switch. Different ages of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were used to establish hypertension and aging models. The phenotypic state was determined by detecting the marker proteins alpha-SM-actin, calponin, and osteopontin (OPN) via immunohistochemical staining and Western blot. Signaling proteins associated with the Akt and MAPK pathways were detected in rat thoracic aorta using Western blot. Both aging and hypertension caused a decrease in contractile (differentiated) phenotype markers (alpha-SM-actin and calponin), while the synthetic (proliferative or de-differentiated) phenotype maker was elevated (OPN). When combining hypertension and aging, this effect was enhanced, with Akt signaling decreased, while MAPK signaling was increased. These results suggested that VSMCs phenotype switching is modulated by a balance between Akt and MAPK signaling in the process of aging and hypertension.

Microrna-26b attenuates monocrotaline-induced pulmonary vascular remodeling via targeting connective tissue growth factor (CTGF) and cyclin D1 (CCND1)

MicroRNAs are involved in the control of cell growth, and deregulated pulmonary artery smooth muscle cell proliferation plays an essential role in the development of pulmonary hypertension. The objective of this study was to identify differentially expressed microRNA(s) and explore its therapeutic role in treatment of the disease. MicroRNA expression profile analysis showed microRNA-26b was differentially expressed in pulmonary artery smooth muscle cells harvested from monocrotaline-treated rats, and we validated microRNA-26b targets, in vitro and in vivo, CTGF and CCND1, both of which have been shown, in our previous work, to be involved in the pathogenesis of pulmonary hypertension. In vivo experiments demonstrated monocrotaline-induced pulmonary artery remodeling could be almost completely abolished by administration of microRNA-26b, while CTGF or CCND1 shRNA significantly, but only partially, attenuated the remodeling by silencing the designed target. Additionally, exogenous expression of the microRNA-26b substantially downregulated CTGF and CCND1 in human pulmonary artery smooth muscle cells. MicroRNA-26b might be a potent therapeutic tool to treat pulmonary hypertension.

Effect of miR-29b on the Proliferation and Apoptosis of Pulmonary Artery Smooth Muscle Cells by Targeting Mcl-1 and CCND2

The proliferation and apoptosis of pulmonary artery smooth muscle cells (PASMCs) are considered to be key steps in the progression of pulmonary arterial hypertension (PAH). MicroRNAs (e.g., miR-29b) have been identified in various diseases to be critical modulators of cell growth and apoptosis by targeting Mcl-1 and CCND2. However, the role of miR-29b in PAH remains unknown. So we try to investigate the effect of miR-29b on Mcl-1 and CCND2 protein in PASMCs, analyze the effect of miR-29b on the proliferation of PASMCs, and explore the significance of miR-29b in the proliferation, apoptosis, and gene therapy of PAH. It was observed that gene chip analysis showed miR-29b expression in pulmonary artery tissue. The expression of miR-29b was significantly reduced in PAH model mice. MiR-29b inhibited the proliferation of PASMCs and promoted the apoptosis of PASMCs. Mechanically, miR-29b could inhibit the expression of Mcl-1 and CCND2 protein and silenced Mcl-1 and CCND2 could abolish the change of proliferation and apoptosis of PASMCs. These results demonstrate that miR-29b suppressed cellular proliferation and promoted apoptosis of PASMCs, possibly through the inhibition of Mcl-1 and CCND2. Therefore, miR-29b may serve as a useful therapeutic tool to treat PAH.

Protection against monocrotaline-induced pulmonary arterial hypertension and caveolin-1 downregulation by fluvastatin in rats

Statins are Hydroxymethylglutaryl-coenzyme A reductase inhibitors, which are typically used to lower blood cholesterol. Additional beneficial effects, including improvement to pulmonary arterial hypertension (PAH), have also been confirmed. However, the mechanisms underlying this improvement have not yet been clarified. The present study was conducted to determine if fluvastatin was protective against experimental PAH development and to investigate the potential effects of fluvastatin on caveolin‑1 (cav‑1) expression. Rats were randomized to either receive a single subcutaneous injection of monocrotaline (MCT; 60 mg/kg; MCT group) or a single subcutaneous injection of MCT (60 mg/kg) followed by an oral gavage of fluvastatin (10 mg/kg) once daily until day 42 (M + F group). Rats in the MCT group received an equivalent volume of saline following the MCT injection. Six additional rats were given an equivalent volume of saline throughout as a control measure. PAH associated variables and cav‑1 protein expression were measured in each group at various times during the experimental period. Hemodynamic and morphometric analysis revealed that M + F rats developed moderate, delayed PAH. Cav‑1 western blot analysis demonstrated that cav‑1 expression was not significantly different in fluvastatin treated rats; however, MCT injured rats given saline had markedly reduced cav‑1 expression. It was concluded that fluvastatin may protect against PAH development and ameliorate MCT induced inhibition of cav‑1 expression in rats.

Hemodynamic and Pathologic Characterization of the TASK-1-/- Mouse Does Not Demonstrate Pulmonary Hypertension

Introduction

Pulmonary hypertension (PH) carries significant associated morbidity and mortality and the underlying molecular mechanisms of PH are not well understood. Loss-of-function mutations in TASK-1 potassium channels are associated with PH in humans. Although TASK-1 has been considered in the development of PH for over a decade, characterization of TASK-1 knockout mice has been limited to in vitro studies or in vivo studies in room air at isolated time points. The purpose of this study was twofold. First, we sought to determine if TASK^-/- male and female mice developed PH over the span of one year. Second, we sought to determine the effect of chronic hypoxia, a stimulus for PH, and its recovery on PH in TASK-1^-/- mice.

Methods

We measured right ventricular systolic pressure (RVSP) and vascular remodeling in male and female C57BL/6 WT and TASK-1^-/- mice at separate time points: 20-24 weeks and 1 year of age. Additionally, we measured RVSP and vascular remodeling in TASK-1^-/- and wild-type mice between 13 and 16 weeks of age exposed to 10% hypoxia for 3 weeks followed by recovery to room air conditions for an additional 6 weeks.

Results

RVSP was similar between WT and TASK^-/- mice. Male and female WT and TASK-1^-/- mice all demonstrated age-related increases in RVSP, which correlated to age-related vascular remodeling in male mice but not in female mice. Male TASK-1^-/- and WT mice exposed to chronic hypoxia demonstrated increased RVSP, which decreased following room air recovery. WT and TASK-1^-/- male mice demonstrated vascular remodeling upon exposure to hypoxia that persisted in room air recovery.

Conclusion

Female and male TASK-1^-/- mice do not develop hemodynamic or vascular evidence for PH, but RVSP rises in an age-dependent manner independent of genotype. TASK-1^-/- and WT male mice develop hypoxia-induced elevations in RVSP that decrease to baseline after recovery in room air. TASK-1^-/- and WT male mice demonstrate vascular remodeling after exposure to hypoxia that persists despite recovery to room air conditions and does not correlate with RVSP normalization.

Intersectin-1s deficiency in pulmonary pathogenesis

Intersectin-1s (ITSN-1s), a multidomain adaptor protein, plays a vital role in endocytosis, cytoskeleton rearrangement and cell signaling. Recent studies have demonstrated that deficiency of ITSN-1s is a crucial early event in pulmonary pathogenesis. In lung cancer, ITSN-1s deficiency impairs Eps8 ubiquitination and favors Eps8-mSos1 interaction which activates Rac1 leading to enhanced lung cancer cell proliferation, migration and metastasis. Restoring ITSN-1s deficiency in lung cancer cells facilitates cytoskeleton changes favoring mesenchymal to epithelial transformation and impairs lung cancer progression. ITSN-1s deficiency in acute lung injury leads to impaired endocytosis which leads to ubiquitination and degradation of growth factor receptors such as Alk5. This deficiency is counterbalanced by microparticles which, via paracrine effects, transfer Alk5/TGFβRII complex to non-apoptotic cells. In the presence of ITSN-1s deficiency, Alk5-restored cells signal via Erk1/2 MAPK pathway leading to restoration and repair of lung architecture. In inflammatory conditions such as pulmonary artery hypertension, ITSN-1s full length protein is cleaved by granzyme B into EH_ITSN and SH3A-E_ITSN fragments. The EH_ITSN fragment leads to pulmonary cell proliferation via activation of p38 MAPK and Elk-1/c-Fos signaling. In vivo, ITSN-1s deficient mice transduced with EH_ITSN plasmid develop pulmonary vascular obliteration and plexiform lesions consistent with pathological findings seen in severe pulmonary arterial hypertension. These novel findings have significantly contributed to understanding the mechanisms and pathogenesis involved in pulmonary pathology. As demonstrated in these studies, genetically modified ITSN-1s expression mouse models will be a valuable tool to further advance our understanding of pulmonary pathology and lead to novel targets for treating these conditions.

Pulmonary hypertensive vasculopathy in parenchymal lung diseases and/or hypoxia: Number 1 in the Series "Pathology for the clinician" Edited by Peter Dorfmüller and Alberto Cavazza

Pulmonary hypertension (PH) with complicating chronic lung diseases and/or hypoxia falls into group 3 of the updated classification of PH. Patients with chronic obstructive lung disease (COPD), diffuse lung disease (such as idiopathic pulmonary fibrosis (IPF)) and with sleep disordered breathing are particularly exposed to the risk of developing PH. Although PH in such a context is usually mild, a minority of patients exhibit severe haemodynamic impairment, defined by a mean pulmonary arterial pressure (mPAP) of ≥35 mmHg or mPAP values ranging between 25 mmHg and 35 mmHg with a low cardiac index (<2 L·min^-1·m^-2). The overlap between lung parenchymal disease and PH heavily affects life expectancy in such a patient population and complicates their therapeutic management. In this review we illustrate the pathological features and the underlying pathophysiological mechanisms of pulmonary circulation in chronic lung diseases, with an emphasis on COPD, IPF and obstructive sleep apnoea syndrome.

Chemical and biological assessment of metal organic frameworks (MOFs) in pulmonary cells and in an acute in vivo model: relevance to pulmonary arterial hypertension therapy

Pulmonary arterial hypertension (PAH) is a progressive and debilitating condition. Despite promoting vasodilation, current drugs have a therapeutic window within which they are limited by systemic side effects. Nanomedicine uses nanoparticles to improve drug delivery and/or reduce side effects. We hypothesize that this approach could be used to deliver PAH drugs avoiding the systemic circulation. Here we report the use of iron metal organic framework (MOF) MIL-89 and PEGylated MIL-89 (MIL-89 PEG) as suitable carriers for PAH drugs. We assessed their effects on viability and inflammatory responses in a wide range of lung cells including endothelial cells grown from blood of donors with/without PAH. Both MOFs conformed to the predicted structures with MIL-89 PEG being more stable at room temperature. At concentrations up to 10 or 30 µg/mL, toxicity was only seen in pulmonary artery smooth muscle cells where both MOFs reduced cell viability and CXCL8 release. In endothelial cells from both control donors and PAH patients, both preparations inhibited the release of CXCL8 and endothelin-1 and in macrophages inhibited inducible nitric oxide synthase activity. Finally, MIL-89 was well-tolerated and accumulated in the rat lungs when given in vivo. Thus, the prototypes MIL-89 and MIL-89 PEG with core capacity suitable to accommodate PAH drugs are relatively non-toxic and may have the added advantage of being anti-inflammatory and reducing the release of endothelin-1. These data are consistent with the idea that these materials may not only be useful as drug carriers in PAH but also offer some therapeutic benefit in their own right.

T-type Ca2+ channels elicit pro-proliferative and anti-apoptotic responses through impaired PP2A/Akt1 signaling in PASMCs from patients with pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension (iPAH) is characterized by obstructive hyperproliferation and apoptosis resistance of distal pulmonary artery smooth muscle cells (PASMCs). T-type Ca²⁺ channel blockers have been shown to reduce experimental pulmonary hypertension, although the impact of T-type channel inhibition remains unexplored in PASMCs from iPAH patients. Here we show that T-type channels Cav3.1 and Cav3.2 are present in the lung and PASMCs from iPAH patients and control subjects. The blockade of T-type channels by the specific blocker, TTA-A2, prevents cell cycle progression and PASMCs growth. In iPAH cells, T-type channel signaling fails to activate phosphatase PP2A, leading to an increase in ERK1/2, P38 activation. Moreover, T-type channel signaling is redirected towards the activation of the kinase Akt1, leading to increased expression of the anti-apoptotic protein survivin, and a decrease in the pro-apoptotic mediator FoxO3A. Finally, in iPAH cells, Akt1 is no longer able to regulate caspase 9 activation, whereas T-type channel overexpression reverses PP2A defect in iPAH cells but reinforces the deleterious effects of Akt1 activation. Altogether, these data highlight T-type channel signaling as a strong trigger of the pathological phenotype of PASMCs from iPAH patients (hyper-proliferation/cells survival and apoptosis resistance), suggesting that both T-type channels and PP2A may be promising therapeutic targets for pulmonary hypertension.

Reoxygenation Reverses Hypoxic Pulmonary Arterial Remodeling by Inducing Smooth Muscle Cell Apoptosis via Reactive Oxygen Species-Mediated Mitochondrial Dysfunction

Background

Pulmonary arterial remodeling, a main characteristic of hypoxic pulmonary hypertension, can gradually reverse once oxygen has been restored. Previous studies documented that apoptosis increased markedly during the reversal of remodeled pulmonary arteries, but the types of cells and mechanisms related to the apoptosis have remained elusive. This study aimed to determine whether pulmonary artery smooth muscle cell (PASMC)‐specific apoptosis was involved in the reoxygenation‐induced reversal of hypoxic pulmonary arterial remodeling and elucidate the underlying mechanism.

Methods and Results

Hypoxic pulmonary hypertension was induced in adult male Sprague‐Dawley rats (n=6/group) by chronic hypobaric hypoxia. and the hypoxic pulmonary hypertension rats were then transferred to a normoxia condition. During reoxygenation, hypoxia‐induced pulmonary arterial remodeling gradually reversed. The reversal of remodeled pulmonary arteries was associated with increased H₂O₂ and with changes in lung expression of cleaved caspase3/PARP, Bax, and Bcl‐2, consistent with increased apoptosis. The PASMC apoptosis, in particular, increased remarkably during this reversal. In vitro, reoxygenation induced the apoptosis of cultured rat primary PASMCs accompanied by increased mitochondrial reactive oxygen species, mitochondrial dysfunction, and the release of cytochrome C from mitochondria to cytoplasm. Clearance of reactive oxygen species alleviated mitochondrial dysfunction as well as the release of cytochrome C and, finally, decreased PASMC apoptosis.

Conclusions

Reoxygenation‐induced apoptosis of PASMCs is implicated in the reversal of hypoxic pulmonary arterial remodeling, which may be attributed to the mitochondrial reactive oxygen species–mediated mitochondrial dysfunction.