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Iron-sulfur (Fe-S) clusters are essential for mitochondrial metabolism, but their regulation in pulmonary hypertension (PH) remains enigmatic. We demonstrate that alterations of the miR-210-ISCU1/2 axis cause Fe-S deficiencies in vivo and promote PH. In pulmonary vascular cells and particularly endothelium, hypoxic induction of miR-210 and repression of the miR-210 targets ISCU1/2 down-regulated Fe-S levels. In mouse and human vascular and endothelial tissue affected by PH, miR-210 was elevated accompanied by decreased ISCU1/2 and Fe-S integrity. In mice, miR-210 repressed ISCU1/2 and promoted PH. Mice deficient in miR-210, via genetic/pharmacologic means or via an endothelial-specific manner, displayed increased ISCU1/2 and were resistant to Fe-S-dependent pathophenotypes and PH. Similar to hypoxia or miR-210 overexpression, ISCU1/2 knockdown also promoted PH. Finally, cardiopulmonary exercise testing of a woman with homozygous ISCU mutations revealed exercise-induced pulmonary vascular dysfunction. Thus, driven by acquired (hypoxia) or genetic causes, the miR-210-ISCU1/2 regulatory axis is a pathogenic lynchpin causing Fe-S deficiency and PH. These findings carry broad translational implications for defining the metabolic origins of PH and potentially other metabolic diseases sharing similar underpinnings.

ATP (extracellular messenger) is in much higher concentration in tumor microenvironment. It regulates cell functions through acting on purinergic receptors to activate a series of intracellular sig...

Just over 4 years ago we launched Pulmonary Circulation. Since then we have grown steadily as a journal, occupying an important niche and serving the clinical and research communities in our field. Our aim has been and continues to be to publish timely and novel research and provide in-depth reviews to the community of clinicians and researchers involved in the work of finding cures for deadly diseases such as pulmonary arterial hypertension. There exists a great need in the medical research community around the globe for up-to-date, relevant information on the latest research in the field of pulmonary vascular disease. Pulmonary vascular diseases, along with right heart failure, affect 3 million people per year worldwide. Idiopathic pulmonary arterial hypertension, although rare, remains an often fatal disease that predominantly affects women. So far there is no cure. Lung vascular diseases occur worldwide, with no respect for international borders; therefore, it is especially important for us to reach our colleagues in the developing world with this vital information. Already, clinicians around the world have grown to rely on Pulmonary Circulation as their source for critical research and scientific advancements that help them stay abreast of new discoveries in this field. Pulmonary Circulation is the only journal devoted exclusively to publishing cutting-edge research on the pulmonary circulation and pulmonary vascular diseases. Our mission is to encourage basic, translational, clinical, and population health research by investigators, physician-scientists, and clinicians in the hopes of increasing survival rates for pulmonary hypertension and other pulmonary vascular diseases worldwide and developing new therapeutic approaches for the diseases. The journal is a main communication medium that (1) connects clinicians and researchers interested in the pulmonary circulation, pulmonary vascular disease, and lung injury and (2) connects physicians/researchers in developing countries to their colleagues in developed countries. As Pulmonary Circulation matures, we are confident that the journal’s reach and impact on the medical and scientific communities will continue to grow. As the world becomes ever more interconnected through the internet, we are also changing with the times. Our goal for 2015 is to make our resources immediately available to you, our readers and contributors, whenever you need them—wherever you may be. A major step in our growth has been the switch to online publication. In today’s world, demand for digital content continues to rise, with an increasing number of doctors preferring to read medical journals online or on their mobile devices, such as tablets, e-readers, and smartphones. In order to continue to meet the demands of our readers, our plans in 2015 include increasing the functionality of our website, www.pulmonarycirculation.org, to offer not only access to the articles published in the journal but also an online newsletter and a blog. We have also moved into social media, as yet another way to connect with you. You can now find us on Facebook (www.facebook.com/PulmonaryCirculation) and Twitter (@PulmCirc). Over the past year, we have seen our readership increase dramatically. As 2014 drew to a close, our 312 published articles had been downloaded as PDFs more than 64,000 times, and our 35 most accessed articles published in the years 2013–2014 had been accessed through the University of Chicago Press website more than 23,300 times. Our PDF downloads alone more than doubled in the second half of 2014. Going forward, we want to continue to provide our readers across the globe with instant, free access to the information they need when they need it. In order to continue to do so, we have, with the advice of our publisher, made the decision to begin in 2015 to ask our authors to pay a publication fee. For Original Research and Guidelines articles, the publication fee is now $1,000. For a traditional Case Report (up to 1,000 words), the fee is $500, and for an Extended Case Report (up to 2,500 words), the fee is $750. These fees were instituted beginning January 1, 2015, for all new submissions received on or after that date. We will continue to expand our readership and be your much-needed connection in this time of rapidly advancing discoveries and ever-expanding global community of researchers and clinicians. We will continue to strive to bring you articles from well-respected names and scientists at the forefront of research. We will work hard to make these articles available more quickly after acceptance, so that you will have earlier access to the latest information in the field. We are still eagerly anticipating our impact factor. Thompson Reuters has received and is reviewing our application and in the meantime has been collecting citations for articles published in Pulmonary Circulation. To calculate the impact factor requires at least 3 years of data or a consistent and steady number of publications, both of which we have, so we are confident that our impact factor will be issued in the near future. Meanwhile, the editorial office is constantly making strides to increase the quality and diversity of the articles published in Pulmonary Circulation. We invite you to contribute to the journal’s reputation and quality by submitting your best work to the journal, by reading the articles published in Pulmonary Circulation and introducing them to your colleagues and students, and by citing the articles in Pulmonary Circulation that are relevant or related to your work. We encourage you to keep submitting your most novel and significant original-research articles in basic, translational, clinical, and population health research; your highly novel (and rare) case reports; and your rapid communications/research reports on novel findings. We also maintain our interest in considering your high-quality conference abstracts. We will continue to identify experts to contribute review articles for Pulmonary Circulation; if you are willing to write a comprehensive review, please send an outline or proposal to us. We would like to extend our thanks to those who have sustained the journal and seen us through our infancy—members of the Pulmonary Vascular Research Institute, members of our editorial board, reviewers, authors, and readers alike. We are excited to have you along for the next phase of our growth, and we respectfully ask that you continue the journey with us.

Pulmonary arterial hypertension (PAH) is a rare but progressive and deadly disease caused by functional and structural changes in the pulmonary vasculature, which lead to an increase in pulmonary vascular resistance. Regardless of the initial pathogenic trigger, the major causes of increased pulmonary vascular resistance in patients with PAH are sustained pulmonary vasoconstriction, pulmonary vascular remodeling, in situ thrombosis, and increased pulmonary vascular wall stiffness. Despite expanding research into the diagnosis and treatment of pulmonary hypertension, death rates from pulmonary hypertension have continued to increase 2.5% per year for women and 0.9% per year for men during the past decade.1 Patients with PAH, if untreated, die mainly because of progressive right heart failure, and the response of the right ventricle (RV) to the increased afterload is an important determinant of outcome in patients.2 During the development of pulmonary hypertension, an initial adaptive response of the RV to the increased afterload is to increase its wall thickness and contractility with varying degrees of RV hypertrophy.3 However, with disease progression, sustained long-term pressure overload of the RV can lead to progressive contractile dysfunction and eventually cause RV failure with further RV dilation. Little is known about the molecular and cellular mechanisms, which underlie the development of RV failure. The mechanism that determines the transition of RV function from compensated hypertrophy to decompensated failure is also uncertain. Article, see p 56 MicroRNAs (miRNAs), as crucial regulators of cardiovascular development and cardiac remodeling, have attracted increasing interest in recent years. Drake et al4 compared the gene expression patterns between RV hypertrophy in hypoxia-induced …

Chronic thromboembolic pulmonary hypertension or CTEPH is a serious complication of a venous embolism that fails to resolve. Its persistence leads to a complete blockade of the pulmonary artery and development of severe pulmonary hypertension. Mutations in fibrinogen that lead to a resistance to fibrinolysis are one explanation for the prolonged existence of the clot. It is thought that the fibrotic clot provides a unique micro-environmental niche that attracts stem and progenitor cells exacerbating the associated pulmonary vascular remodeling. This chapter focuses on what is currently known about the presence and role of such stem and progenitor cells in the pathogenesis of CTEPH.

This book covers the identification and role of endogenous lung stem cells in health and disease, particularly the most recent advances. In addition, it discusses the rapidly growing field of stem cells and cell therapy as it relates to lung biology and disease as well as ex vivo lung bioengineering. Such approaches may provide novel therapeutic approaches for lung diseases. Human pluripotent stem cell differentiation to model the pulmonary epithelium and vasculature is also discussed. World-recognized scientists who specialize in studying both the lung epithelium and pulmonary vasculature contribute the chapters. Topics covered include: stem cell niches in the lung, the role of progenitor cells in fibrosis and asthma, iPSC in modeling lung disease, vascular repair by endothelial progenitor cells and circulating fibrocytes in pulmonary vascular remodeling. This volume of the Stem Cell Biology and Regenerative Medicine series is essential reading for researchers and clinicians interested in stem cells, lung biology and regenerative medicine. It is also an invaluable resource for advanced students studying cell biology, regenerative medicine and lung physiology

Activity of voltage-gated K+(KV) channels in pulmonary artery smooth muscle cells (PASMC) plays an important role in control of apoptosis and proliferation in addition to regulating membrane potential and pulmonary vascular tone. Bone morphogenetic proteins (BMPs) inhibit proliferation and induce apoptosis in normal human PASMC, whereas dysfunctional BMP signaling and downregulated KVchannels are involved in pulmonary vascular medial hypertrophy associated with pulmonary hypertension. This study evaluated the effect of BMP-2 on KVchannel function and expression in normal human PASMC. BMP-2 (100 nM for 18–24 h) significantly (>2-fold) upregulated mRNA expression of KCNA5, KCNA7, KCNA10, KCNC3, KCNC4, KCNF1, KCNG3, KCNS1, and KCNS3 but downregulated (at least 2-fold) KCNAB1, KCNA2, KCNG2, and KCNV2. The most dramatic change was the >10-fold downregulation of KCNG2 and KCNV2, two electrically silent γ-subunits that form heterotetramers with functional KVchannel α-subunits (e.g., KCNB1–2). Furthermore, the amplitude and current density of whole cell KVcurrents were significantly increased in PASMC treated with BMP-2. It has been demonstrated that K+currents generated by KCNB1 and KCNG1 (or KCNG2) or KCNB1 and KCNV2 heterotetramers are smaller than those generated by KCNB1 homotetramers, indicating that KCNG2 and KCNV2 (2 subunits that were markedly downregulated by BMP-2) are inhibitors of functional KVchannels. These results suggest that BMP-2 divergently regulates mRNA expression of various KVchannel α-, β-, and γ-subunits and significantly increases whole cell KVcurrents in human PASMC. Finally, we present evidence that attenuation of c-Myc expression by BMP-2 may be involved in BMP-2-mediated increase in KVchannel activity and regulation of KVchannel expression. The increased KVchannel activity may be involved in the proapoptotic and/or antiproliferative effects of BMP-2 on PASMC.

Caveolae formation has raised the concept of energy efficiency to new heights. The ultimate purpose of caveolae formation is to colocalize signaling proteins with membrane microdomains in order to facilitate their interaction and improve signal transduction efficiency. Although we know that the main structural protein of caveolae is caveolin, how caveolin interacts with membrane proteins to facilitate their integration into lipid raft domains is unclear. A caveolin-scaffolding domain (CSD) on caveolin itself can associate with membrane proteins such as G proteins and endothelial nitric oxide synthase. In this issue, Kwiatek et al. (p. 1174) report that the TRPC1 channel protein contains a C-terminal CSD-consensus binding sequence that allows for its physical and functional interaction with caveolin-1 in the caveolae of human pulmonary artery endothelial cells (PAEC). Competitive interaction with a CSD-conjugated peptide attenuates thrombin- and thapsigargin-induced Ca2+ influx via store-operated TRPC1 channels. Their data suggest that caveolin-1 can directly regulate TRPC1 function, extending its already ascribed role as a structural protein.

An increase in cytosolic free Ca2+concentration ([Ca2+]cyt) results from Ca2+release from intracellular stores and extracellular Ca2+influx through Ca2+-permeable ion channels and is crucial for initiating intestinal epithelial restitution to reseal superficial wounds after mucosal injury. Capacitative Ca2+entry (CCE) induced by Ca2+store depletion represents a major Ca2+influx mechanism, but the exact molecular components constituting this process remain elusive. This study determined whether canonical transient receptor potential (TRPC)1 served as a candidate protein for Ca2+-permeable channels mediating CCE in intestinal epithelial cells and played an important role in early epithelial restitution. Normal intestinal epithelial cells (the IEC-6 cell line) expressed TRPC1 and TPRC5 and displayed typical records of whole cell store-operated Ca2+currents and CCE generated by Ca2+influx after depletion of intracellular stores. Induced TRPC1 expression by stable transfection with the TRPC1 gene increased CCE and enhanced cell migration during restitution. Differentiated IEC-Cdx2L1 cells induced by forced expression of the Cdx2 gene highly expressed endogenous TRPC1 and TRPC5 and exhibited increased CCE and cell migration. Inhibition of TRPC1 expression by small interfering RNA specially targeting TRPC1 not only reduced CCE but also inhibited cell migration after wounding. These findings strongly suggest that TRPC1 functions as store-operated Ca2+channels and plays a critical role in intestinal epithelial restitution by regulating CCE and intracellular [Ca2+]cyt.

Acute hypoxia causes pulmonary vasoconstriction in part by inhibiting voltage-gated K+ (Kv) channel activity in pulmonary artery smooth muscle cells (PASMC). The hypoxia-mediated decrease in Kv currents [ IK(V)] is selective to PASMC; hypoxia has little effect on IK(V) in mesenteric artery smooth muscle cells (MASMC). Functional Kv channels are homo- and/or heterotetramers of pore-forming α-subunits and regulatory β-subunits. KCNA5 is a Kv channel α-subunit that forms functional Kv channels in PASMC and regulates resting membrane potential. We have shown that acute hypoxia selectively inhibits IK(V) through KCNA5 channels in PASMC. Overexpression of the human KCNA5 gene increased IK(V) and caused membrane hyperpolarization in HEK-293, COS-7, and rat MASMC and PASMC. Acute hypoxia did not affect IK(V) in KCNA5-transfected HEK-293 and COS-7 cells. However, overexpression of KCNA5 in PASMC conferred its sensitivity to hypoxia. Reduction of Po2 from 145 to 35 mmHg reduced IK(V) by ∼40% in rat PASMC transfected with human KCNA5 but had no effect on IK(V) in KCNA5-transfected rat MASMC (or HEK and COS cells). These results indicate that KCNA5 is an important Kv channel that regulates resting membrane potential and that acute hypoxia selectively reduces KCNA5 channel activity in PASMC relative to MASMC and other cell types. Because Kv channels (including KCNA5) are ubiquitously expressed in PASMC and MASMC, the observation from this study indicates that a hypoxia-sensitive mechanism essential for inhibiting KCNA5 channel activity is exclusively present in PASMC. The divergent effect of hypoxia on IK(V) in PASMC and MASMC also may be due to different expression levels of KCNA5 channels.

Transient receptor potential (TRP) genes represent a novel class of genes that are generally believed to encode for nonselective cation channels. A subfamily of TRP channels, canonical TRP (TRPC), which are highly permeable to Ca2+ (and Na+), co-assembles with each other to form functional store- and receptor-operated Ca2+ channels. TRPC mRNA and protein have been identified in pulmonary arterial smooth muscle and endothelial cells. The currents generated by Ca2+ influx through store- and receptor-operated Ca2+ channels have also been extensively characterized in these cells. More recently, the attention has shifted to identify the TRP subunits that underlie the function of native channels in the pulmonary vasculature, with the understanding that TRP channels assemble as either homo-or heterotetramers in vivo. This work in progress has yielded exciting information regarding the involvement of TRP channels in the control of smooth muscle contraction, and cell proliferation and migration. In this review, the authors focus on describing the function and transcriptional regulation of TRP proteins, and the store- and receptor-operated Ca2+ channels for which they are responsible, in pulmonary artery smooth muscle cells (PASMC). They also identify some key TRP proteins whose role in the pulmonary vasculature has been established, as well as some more novel subunits whose role, although intriguing, can only be inferred from other vascular studies. Finally, they describe the involvement of TRP channels in regulating pulmonary vasoconstriction, PASMC proliferation, and pulmonary endothelial barrier function.

ANG-(1–7) improves the function of the remodeling heart. Although this peptide is generated directly within the myocardium, the effects of ANG-(1–7) on cardiac fibroblasts that play a critical role in cardiac remodeling are largely unknown. We tested the hypothesis that specific binding of ANG-(1–7) to cardiac fibroblasts regulates cellular functions that are involved in cardiac remodeling. 125I-labeled ANG-(1–7) binding assays identified specific binding sites of ANG-(1–7) on adult rat cardiac fibroblasts (ARCFs) with an affinity of 11.3 nM and a density of 131 fmol/mg protein. At nanomolar concentrations, ANG-(1–7) interacted with specific sites that were distinct from ANG II type 1 and type 2 receptors without increasing cytosolic Ca2+ concentration. At these concentrations, ANG-(1–7) had inhibitory effects on collagen synthesis as assessed by [3H]proline incorporation and decreased mRNA expression of growth factors in ARCFs. These effects of ANG-(1–7) contrasted with effects of ANG II. Pretreatment of ARCFs with ANG-(1–7) inhibited ANG II-induced increases in collagen synthesis and in mRNA expression of growth factors, including endothelin-1 and leukemia inhibitory factor. ANG-(1–7) pretreatment also inhibited the stimulatory effects of conditioned medium from ANG II-treated ARCFs on [3H]leucine incorporation and atrial natriuretic factor mRNA expression, markers of hypertrophy, in cardiomyocytes. Thus ANG-(1–7) interacted with specific receptors on ARCFs to exert potential antifibrotic and antitrophic effects that could reverse ANG II effects. These results suggest that ANG-(1–7) may play an important role in the heart in regulating cardiac remodeling.

Electrical excitability, which plays an important role in excitation-contraction coupling in the pulmonary vasculature, is regulated by transmembrane ion flux in pulmonary artery smooth muscle cells (PASMC). This study aimed to characterize the electrophysiological properties and molecular identities of voltage-gated Na(+) channels in cultured human PASMC. We recorded tetrodotoxin (TTX) sensitive and rapidly inactivating Na(+) currents with properties similar to those described in cardiac myocytes. Using RT-PCR, we detected transcripts of seven Na(+) channel alpha genes (SCN2A, 3A, 4A, 7A, 8A, 9A, and 11A), and two beta subunit genes (SCN1B and 2B). Our results demonstrate that human PASMC express TTX-sensitive voltage-gated Na(+) channels. Their physiological functions remain unresolved, although our data suggest that Na(+) channel activity does not directly influence membrane potential, intracellular Ca(2+) release, or proliferation in normal human PASMC. Whether their expression and/or activity are heightened in the pathological state is discussed.

Global alveolar hypoxia, as experienced at high-altitude living, has a serious impact on vascular physiology, particularly on the pulmonary vasculature. The effects of sustained hypoxia on pulmonary arteries include sustained vasoconstriction and enhanced medial hypertrophy. As the major component of the vascular media, pulmonary artery smooth muscle cells (PASMC) are the main effectors of the physiological response(s) induced during or following hypoxic exposure. Endothelial cells, on the other hand, can sense humoral and hemodynamic changes incurred by hypoxia, triggering their production of vasoactive and mitogenic factors that then alter PASMC function and growth. Transmembrane ion flux through channels in the plasma membrane not only modulates excitation- contraction coupling in PASMC, but also regulates cell volume, apoptosis, and proliferation. In this review, we examine the roles of K+ and Ca2+ channels in the pulmonary vasoconstriction and vascular remodeling observed during chronic hypoxia-induced pulmonary hypertension.

most membrane receptors in mammalian systems are seven-transmembrane domain G protein-coupled receptors. Proteinase (or protease)-activated receptors (PARs) are a novel family of G protein-coupled receptors. Unlike other G protein-coupled receptors that require ligand binding for activation, PARs

Bone morphogenetic proteins (BMPs) inhibit proliferation and induce apoptosis in pulmonary artery smooth muscle cells (PASMCs) from normal subjects. Dysfunction of BMP signaling due to mutations in and/or down-regulation of BMP receptors has been implicated in idiopathic pulmonary arterial hypertension (IPAH). The authors examined whether BMP differentially regulates gene expression in PASMCs from normal subjects and IPAH patients using the Affymetrix microarray analysis. BMP-2 treatment (200 nM for 24 hours) altered expression levels of 6206 genes in normal and IPAH PASMCs. Of these genes, 1063 were regulated oppositely by BMP-2: 523 genes were down-regulated by BMP-2 in normal PASMCs but up-regulated in IPAH PASMCs, whereas 540 genes were up-regulated by BMP-2 in normal PASMCs but down-regulated in IPAH PASMCs. The divergent effects of BMP-2 on gene expression profiles indicate that PASMCs may undergo significant phenotypic changes in IPAH patients during development of the disease. The transition of the antiproliferative effect of BMP-2 in normal PASMCs to its proliferative effect in IPAH patients is attributed potentially to its differential effect on expression patterns of various genes that are involved in cell proliferation and apoptosis. Among the 6206 BMP-2-sensitive genes, there are more than 1800 genes whose expression levels were negatively (correlation coefficient, r,-0.9) or positively (with r+ 0.9) correlated with the pulmonary arterial pressure. These results suggest that BMP-mediated gene regulation is significantly altered in PASMCs from IPAH patients and mRNA expression changes in BMP-regulated genes may be involved in the development of IPAH.

Hereditary long QT syndrome is a fatal arrhythmia associated with gene mutations in potassium and sodium channels that are expressed in ventricle. By employing heterologous expression and making comparisons to cells expressing wild-type human-ether-a-go-go-related protein (HERG), a potassium channel that contributes to I(Kr) current in ventricular cardiomyocytes, we demonstrate activation of an elevated endoplasmic reticulum (ER) stress response by the mutant I593R HERG potassium channel implicated in long QT syndrome type 2. I593R HERG is trafficking-impaired and forms Triton-insoluble aggregates. Expression of I593R HERG activates the unfolded protein response pathway and, separately, NF-kappaB signaling. ATF6, the activating transcription factor of the unfolded protein response pathway, is processed into the active transcription factor in the cells expressing I593R HERG. Consistent with ATF6 activation, the ER chaperones/calcium-binding proteins Grp78, Grp94, and calreticulin are elevated in I593R HERG-expressing cells. Coexpression of I593R HERG with wild-type HERG also results in ER stress pathway activation. By eliciting downstream links in signal transduction pathways associated with ER stress, expression of mutant trafficking impaired ion channels may contribute to disease etiology mechanisms that augment those associated with attenuated ion flux.

KCNH2 encodes Kv11.1 and underlies the rapidly activating delayed rectifier K+ current (IKr) in the heart. Loss-of-function KCNH2 mutations cause the type 2 long QT syndrome (LQT2), and most LQT2-linked missense mutations inhibit the trafficking of Kv11.1 channels. Drugs that bind to Kv11.1 and block IKr (e.g., E-4031) can act as pharmacological chaperones to increase the trafficking and functional expression for most LQT2 channels (pharmacological correction). We previously showed that LQT2 channels are selectively stored in a microtubule-dependent compartment within the endoplasmic reticulum (ER). We tested the hypothesis that pharmacological correction promotes the trafficking of LQT2 channels stored in this compartment. Confocal analyses of cells expressing the trafficking-deficient LQT2 channel G601S showed that the microtubule-dependent ER compartment is the transitional ER. Experiments with E-4031 and the protein synthesis inhibitor cycloheximide suggested that pharmacological correction promotes the trafficking of G601S stored in this compartment. Treating cells in E-4031 or ranolazine (a drug that blocks IKr and has a short half-life) for 30 min was sufficient to cause pharmacological correction. Moreover, the increased functional expression of G601S persisted 4–5 h after drug washout. Coexpression studies with a dominant-negative form of Rab11B, a small GTPase that regulates Kv11.1 trafficking, prevented the pharmacological correction of G601S trafficking from the transitional ER. These data suggest that pharmacological correction quickly increases the trafficking of LQT2 channels stored in the transitional ER via a Rab11B-dependent pathway, and we conclude that the pharmacological chaperone activity of drugs like ranolazine might have therapeutic potential.

Genetic alterations in pulmonary arterial hypertension (PAH) have become increasingly recognized in both known familial or heritable and sporadic or idiopathic PAH (IPAH). Unrecognized genetic alterations have now been found in up to 40% of the IPAH in which no familial predisposition is apparent.1 Bone morphogenetic protein (BMP) receptor II (BMPR-II) is the most common gene implicated in this hereditary form of PAH; furthermore, it is implicated in the pathogenesis of nonhereditary forms of PAH with a significant reduction in the expression of BMPR-II in both IPAH and experimental animal models of pulmonary hypertension (PH).2 BMPs represent the largest group of cytokines in the transforming growth factor-β superfamily and regulate growth, differentiation, and apoptosis in multiple cell types, whereas BMPR-II has been shown to have unique roles in differing cells. Article, see p 1159 BMPR-II is constitutively active at the cell membrane, and ligand stimulation initiates cross-linking with BMPR-I to form a receptor complex that is necessary to activate intracellular signaling. BMPR-II is most highly expressed in endothelial cells in the pulmonary vasculature, and BMPR-II activation leads to the increased proliferation and decreased apoptosis through Smad signaling.3,4 This is in contrast to pulmonary arterial smooth muscle cells, where BMP activation leads to the inhibition of proliferation and increased apoptosis through Smad signaling in large vessels, although in small pulmonary arteries, a proliferative effect is seen through activation of extracellular signal–regulated kinase and mitogen-activated protein kinase, which inhibits Smad signaling.5,6 It is these unique yet complementary functions that make BMPR-II mutations particularly damaging in the pulmonary circulation, leading to development of PAH. A dysfunctional mutation of BMPR-II, as in heritable PAH, or downregulation of protein expression, as in IPAH and animal models, can lead to endothelial dysfunction hallmarked by abnormal barrier function through …

Transient receptor potential (TRP) cation channels are a critical pathway for Ca2+entry during pulmonary artery (PA) smooth muscle contraction. However, whether canonical TRP (TRPC) subunits and which TRP channel isoforms are involved in store depletion-induced pulmonary vasoconstriction in vivo remain unclear. This study was designed to test whether overexpression of the human TRPC1 gene ( hTRPC1) in rat PA enhances pulmonary vasoconstriction due to store depletion-mediated Ca2+influx. The hTRPC1 was infected into rat PA rings with an adenoviral vector. RT-PCR and Western blot analyses confirmed the mRNA and protein expression of hTRPC1 in the arterial rings. The amplitude of active tension induced by 40 mM K+(40K) in PA rings infected with an empty adenoviral vector (647 ± 88 mg/mg) was similar to that in PA rings infected with hTRPC1 (703 ± 123 mg/mg, P = 0.3). However, the active tension due to capacitative Ca2+entry (CCE) induced by cyclopiazonic acid was significantly enhanced in PA rings overexpressing hTRPC1 (91 ± 13% of 40K-induced contraction) compared with rings infected with an empty adenoviral vector (61 ± 14%, P < 0.001). Endothelial expression of hTRPC1 was not involved since the CCE-induced vasoconstriction was also enhanced in endothelium-denuded PA rings infected with the adenoviral vector carrying hTRPC1. These observations demonstrate that hTRPC1 is an important Ca2+-permeable channel that mediates pulmonary vasoconstriction when PA smooth muscle cell intracellular Ca2+stores are depleted.

Primary pulmonary hypertension (PPH) is a rare but often fatal condition characterized by pulmonary artery remodeling leading to chronic elevation of pulmonary artery pressure in the absence of causes. The pathophysiology of PPH is not completely understood, but a number of recent studies have elucidated many possible gentic, hormonal, and environmental factors. Current treatment options slow the progression of the disease but do not halt it. The study of molecular mechanisms that result from mutations in onmental and hormonal modifiers holds great promise for the development of novel therapies that may halt the progression of the disease.

Human ether-a-go-go-related gene (hERG) channels conduct delayed rectifier K(+) current. However, little information is available on physiological situations affecting hERG channel protein and function. In the present study we examined the effects of intermittent hypoxia (IH), which is a hallmark manifestation of sleep apnea, on hERG channel protein and function. Experiments were performed on SH-SY5Y neuroblastoma cells, which express hERG protein. Cells were exposed to IH consisting of alternating cycles of 30 s of hypoxia (1.5% O2) and 5 min of 20% O2. IH decreased hERG protein expression in a stimulus-dependent manner. A similar reduction in hERG protein was also seen in adrenal medullary chromaffin cells from IH-exposed neonatal rats. The decreased hERG protein was associated with attenuated hERG K(+) current. IH-evoked hERG protein degradation was not due to reduced transcription or increased proteosome/lysomal degradation. Rather it was mediated by calcium-activated calpain proteases. Both COOH- and NH2-terminal sequences of the hERG protein were the targets of calpain-dependent degradation. IH increased reactive oxygen species (ROS) levels, intracellular Ca(2+) concentration ([Ca(2+)]i), calpain enzyme activity, and hERG protein degradation, and all these effects were prevented by manganese-(111)-tetrakis-(1-methyl-4-pyridyl)-porphyrin pentachloride, a membrane-permeable ROS scavenger. These results demonstrate that activation of calpains by ROS-dependent elevation of [Ca(2+)]i mediates hERG protein degradation by IH.

Rationale We have previously shown that Nampt, which regulates intracellular NAD levels and cellular redox state, regulates histone deacetylases and inhibits apoptosis, is significantly upregulated in patients with pulmonary arterial hypertension (PAH). The aims of this study were to determine (1) whether Nampt+/− mice are protected from hypoxia-mediated pulmonary hypertension (HPH), (2) whether pharmacological inhibition of Nampt could attenuate monocrotaline (MCT)-induced pulmonary hypertension (PH) in rats. In addition, we hypothesized that Nampt secreted from pulmonary artery endothelial cells (PAECs) or overexpressing Nampt in pulmonary artery smooth muscle cells (PASMCs) may promote PASMC proliferation via upregulation of calcium signaling pathway, which plays a role in cell proliferation and vascular constriction. Methods Nampt+/− mice and their WT siblings (male, 7-wk old) were exposed to a hypoxia chamber with 10% O2 for four weeks. Male Sprague-Dawley rats (n=6 per group) received one dose of MCT (60 mg/kg), IP. They were administrated with FK866 (an inhibitor of Nampt enzymatic activity) (2.5 mg/kg, IP, twice daily for 2wks) two weeks after MCT. Right ventricular systolic pressure (RVSP) was determined with a pressure transducer catheter. The right ventricle: left ventricle+septum (RV/LV+S) ratio was calculated. In a cell culture model, hPASMCs were stimulated with recombinant Nampt (25 mg/ml) for 6 hrs and 48 hrs. [Ca2+]cyt was measured in PASMC loaded with flura-2/AM (4mM) in a fluorescence microscope and cyclepiazonic acid (CPA, a specific Ca2+-ATPase inhibitor) was used to induce store-operated calcium entry (SOCE). In addition, BrdU assays were conducted to examine rNampt or overexpressing Nampt can promote PASMC proliferation or Nampt secreted from PAECs isolated from PAH patients stimulates more PASMC proliferation than from healthy controls. Results Administration of FK866 reversed established PH (RVSP [mm Hg] 19.77±0.80 [control] vs 51.24±4.35 [MCT] vs 34.45±3.49 [MCT+FK866], p Conclusion Inhibition of Nampt attenuates hypoxia-mediated PH in mice or MCT-induced PH in rats. Nampt may play a role in vascular remodeling via regulation of calcium signaling pathway. These data suggest that Nampt inhibition could be a potential therapeutic target for PH.

Activating protein (AP)-1 transcription factors modulate expression of genes involved in cell proliferation and migration. Chronic hypoxia increases pulmonary artery smooth muscle cell proliferation by upregulating AP-1-responsive genes encoding for endothelium-derived vasoactive and mitogenic factors implicated in pulmonary hypertension development. The expression of AP-1 transcription factors is sensitive to changes in cytosolic free [Ca2+] ([Ca2+]cyt). Capacitative Ca2+entry (CCE) via store-operated Ca2+channels (SOC) is an important mechanism for raising [Ca2+]cytin pulmonary artery endothelial cells (PAEC). Using combined molecular biological, fluorescence microscopy, and biophysical approaches, we examined the effect of chronic hypoxia (3% O2, 72 h) on AP-1 DNA binding activity, CCE, and transient receptor potential (TRP) gene expression in human (h) PAEC. EMSA showed that AP-1 binding to hPAEC nuclear protein extracts was significantly enhanced by hypoxia, the increase being dependent on store-operated Ca2+influx and sensitive to La3+, an SOC inhibitor. Hypoxia also increased basal [Ca2+]cyt, the amount of CCE produced by store depletion with cyclopiazonic acid, and the amplitude of SOC-mediated currents ( ISOC). The increases of CCE amplitude and ISOCcurrent density by hypoxia were paralleled by enhanced TRPC4 mRNA and protein expression. Hypoxia-enhanced CCE and TRPC4 expression were also attenuated by La3+. These data suggest that hypoxia increases AP-1 binding activity by enhancing Ca2+influx via La3+-sensitive TRP-encoded SOC channels in hPAEC. The Ca2+-mediated increase in AP-1 binding may play an important role in upregulating AP-1-responsive gene expression, in stimulating pulmonary vascular cell proliferation and, ultimately, in pulmonary vascular remodeling in patients with hypoxia-mediated pulmonary hypertension.

Cell shrinkage is an early prerequisite in programmed cell death, and cytoplasmic K+ is a dominant cation that controls intracellular ion homeostasis and cell volume. Blockade of K+ channels inhibits apoptotic cell shrinkage and attenuates apoptosis. We examined whether apoptotic repressor with caspase recruitment domain (ARC), an antiapoptotic protein, inhibits cardiomyocyte apoptosis by reducing K+ efflux through voltage-gated K+ (Kv) channels. In heart-derived H9c2 cells, whole cell Kv currents ( I K(V)) were isolated by using Ca2+-free extracellular (bath) solution and including 5 mM ATP and 10 mM EGTA in the intracellular (pipette) solution. Extracellular application of 5 mM 4-aminopyridine (4-AP), a blocker of Kv channels, reversibly reduced I K(V)by 50–60% in H9c2 cells. The remaining currents during 4-AP treatment may be generated by K+ efflux through 4-AP-insensitive K+ channels. Overexpression of ARC in heart-derived H9c2 cells significantly decreased I K(V), whereas treatment with staurosporine, a potent apoptosis inducer, enhanced I K(V)in wild-type cells. The staurosporine-induced increase in I K(V) was significantly suppressed and the staurosporine-mediated apoptosis was markedly inhibited in cells overexpressing ARC compared with cells transfected with the control neomycin vector. These results suggest that the antiapoptotic effect of ARC is, in part, due to inhibition of Kv channels in cardiomyocytes.

Polyamines are required for the early phase of mucosal restitution that occurs as a consequence of epithelial cell migration. Our previous studies have shown that polyamines increase RhoA activity by elevating cytosolic free Ca2+ concentration ([Ca2+]cyt) through controlling voltage-gated K+ channel expression and membrane potential ( E m) during intestinal epithelial restitution. The current study went further to determine whether increased RhoA following elevated [Ca2+]cyt activates Rho-kinase (ROK/ROCK) resulting in myosin light chain (MLC) phosphorylation. Studies were conducted in stable Cdx2-transfected intestinal epithelial cells (IEC-Cdx2L1), which were associated with a highly differentiated phenotype. Reduced [Ca2+]cyt, by either polyamine depletion or exposure to the Ca2+-free medium, decreased RhoA protein expression, which was paralleled by significant decreases in GTP-bound RhoA, ROCK-1, and ROKα proteins, Rho-kinase activity, and MLC phosphorylation. The reduction of [Ca2+]cyt also inhibited cell migration after wounding. Elevation of [Ca2+]cyt induced by the Ca2+ ionophore ionomycin increased GTP-bound RhoA, ROCK-1, and ROKα proteins, Rho-kinase activity, and MLC phosphorylation. Inhibition of RhoA function by a dominant negative mutant RhoA decreased the Rho-kinase activity and resulted in cytoskeletal reorganization. Inhibition of ROK/ROCK activity by the specific inhibitor Y-27632 not only decreased MLC phosphorylation but also suppressed cell migration. These results indicate that increase in GTP-bound RhoA by polyamines via [Ca2+]cytcan interact with and activate Rho-kinase during intestinal epithelial restitution. Activation of Rho-kinase results in increased MLC phosphorylation, leading to the stimulation of myosin stress fiber formation and cell migration.

Platelet-derived growth factor (PDGF) signaling is implicated in a wide range of diseases, and PDGF drives the pathological responses in many vascular disorders and fibrotic diseases such as atherosclerosis, restenosis, pulmonary arterial hypertension, and pulmonary fibrosis. In vascular smooth muscle cells (VSMC), PDGF is a potent mitogen which promotes proliferation and migration and contributes to pathological vascular remodeling. Recent studies have demonstrated a role for PDGF in stromal interaction molecule 1 (STIM1)/Orai1-mediated Ca2+ influx in VSMC.1 Regulation of cytosolic Ca2+ concentration ([Ca2+]cyt) is critical for many cellular processes. A rise in [Ca2+]cyt is a major trigger for VSMC proliferation and contraction. One of the major routes of Ca2+ entry into cells is through store-operated Ca2+ (SOC) channels. On depletion of Ca2+ from the stores (sarcoplasmic or endoplasmic reticulum, SR/ER), a Ca2+ deficiency signal is transmitted to the SOC channels in the plasma membrane via STIM1. This causes the SOC to open, allowing Ca2+ to flow into the cytosol, a process referred to as store-operated Ca2+ entry (SOCE). The cytosolic Ca2+ is then sequestered into the stores by the sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA), thus replenishing the stores. Studies have demonstrated a role for Ca2+ release-activated Ca2+ (CRAC) channels in SOCE, with STIM1 and Orai1 as the major components.2 Article, see p 66 The majority of STIM1 is expressed in the SR/ER membrane, where it senses decreased Ca2+ concentration in the SR/ER when inositol 1,4,5-triphosphate (IP3)-mediated activation of IP3 receptor induces Ca2+ release. STIM1 then undergoes a conformational change allowing STIM1 to multimerize and translocate …

Pulmonary arterial hypertension (PAH) is a hemodynamic abnormality that ultimately results in mortality due to right heart failure. Although the clinical manifestations of primary and secondary PAH are diverse, medial hypertrophy and arterial vasoconstriction are key components in the vascular remodeling leading to PAH. Abnormalities in the homeostasis of intracellular Ca(2+), transmembrane flux of ions, and membrane potential may play significant roles in the processes leading to pulmonary vascular remodeling. Decreased activity of K(+) channels causes membrane depolarization, leading to Ca(2+) influx. The elevated cytoplasmic Ca(2+) is a major trigger for pulmonary vasoconstriction and an important stimulus for vascular smooth muscle proliferation. Dysfunctional K(+) channels have also been linked to inhibition of apoptosis and contribute further to the medial hypertrophy. This review focuses on the relative role of K(+) and Ca(2+) ions and channels in human pulmonary artery smooth muscle cells in the development of PAH.

Pulmonary vascular medial hypertrophy due to proliferation of pulmonary artery smooth muscle cells (PASMC) greatly contributes to the increased pulmonary vascular resistance in pulmonary hypertension patients. A rise in cytosolic free Ca2+concentration ([Ca2+]cyt) is an important stimulus for cell growth in PASMC. Resting [Ca2+]cyt, intracellularly stored [Ca2+], capacitative Ca2+entry (CCE), and store-operated Ca2+currents ( ISOC) are greater in proliferating human PASMC than in growth-arrested cells. Expression of TRP1, a transient receptor potential gene proposed to encode the channels responsible for CCE and ISOC, was also upregulated in proliferating PASMC. Our aim was to determine if inhibition of endogenous TRP1 gene expression affects ISOCand CCE and regulates cell proliferation in human PASMC. Cells were treated with an antisense oligonucleotide (AS, for 24 h) specifically designed to cleave TRP1 mRNA and then returned to normal growth medium for 40 h before the experiments. Then, mRNA and protein expression of TRP1 was downregulated, and amplitudes of ISOCand CCE elicited by passive depletion of Ca2+from the sarcoplasmic reticulum using cyclopiazonic acid were significantly reduced in the AS-treated PASMC compared with control. Furthermore, the rate of cell growth was decreased by 50% in AS-treated PASMC. These results indicate that TRP1 may encode a store-operated Ca2+channel that plays a critical role in PASMC proliferation by regulating CCE and intracellular [Ca2+]cyt.

Asthma is characterized by airway inflammation, bronchial hyperresponsiveness, and airway obstruction by bronchospasm and bronchial wall thickening due to smooth muscle hypertrophy. A rise in cytosolic free Ca2+concentration ([Ca2+]cyt) may serve as a shared signal transduction element that causes bronchial constriction and bronchial wall thickening in asthma. In this study, we examined whether capacitative Ca2+entry (CCE) induced by depletion of intracellular Ca2+stores was involved in agonist-mediated bronchial constriction and bronchial smooth muscle cell (BSMC) proliferation. In isolated bronchial rings, acetylcholine (ACh) induced a transient contraction in the absence of extracellular Ca2+because of Ca2+release from intracellular Ca2+stores. Restoration of extracellular Ca2+in the presence of atropine, an M-receptor blocker, induced a further contraction that was apparently caused by a rise in [Ca2+]cytdue to CCE. In single BSMC, amplitudes of the store depletion-activated currents ( ISOC) and CCE were both enhanced when the cells proliferate, whereas chelation of extracellular Ca2+with EGTA significantly inhibited the cell growth in the presence of serum. Furthermore, the mRNA expression of TRPC1, a transient receptor potential channel gene, was much greater in proliferating BSMC than in growth-arrested cells. Blockade of the store-operated Ca2+channels by Ni2+decreased ISOCand CCE and markedly attenuated BSMC proliferation. These results suggest that upregulated TRPC1 expression, increased ISOC, enhanced CCE, and elevated [Ca2+]cytmay play important roles in mediating bronchial constriction and BSMC proliferation.

Nitric oxide (NO) is an endogenous endothelium-derived relaxing factor that regulates vascular smooth muscle cell proliferation and apoptosis. This study investigated underlying mechanisms involved in NO-induced apoptosis in human and rat pulmonary artery smooth muscle cells (PASMC). Exposure of PASMC to NO, which was derived from the NO donor S-nitroso- N-acetyl-penicillamine, increased the percentage of cells undergoing apoptosis. Increasing extracellular K+concentration to 40 mM or blocking K+channels with 1 mM tetraethylammonia (TEA), 100 nM iberiotoxin (IBTX), and 5 mM 4-aminopyridine (4-AP) significantly inhibited the NO-induced apoptosis. In single PASMC, NO reversibly increased K+currents through the large-conductance Ca2+-activated K+(KCa) channels, whereas TEA and IBTX markedly decreased the KCacurrents. In the presence of TEA, NO also increased K+currents through voltage-gated K+(Kv) channels, whereas 4-AP significantly decreased the Kvcurrents. Opening of KCachannels with 0.3 mM dehydroepiandrosterone increased KCacurrents, induced apoptosis, and further enhanced the NO-mediated apoptosis. Furthermore, NO depolarized the mitochondrial membrane potential. These observations indicate that NO induces PASMC apoptosis by activating KCaand Kvchannels in the plasma membrane. The resulting increase in K+efflux leads to cytosolic K+loss and eventual apoptosis volume decrease and apoptosis. NO-induced apoptosis may also be related to mitochondrial membrane depolarization in PASMC.

Ventilator-induced lung injury (VILI) is an acute lung injury that develops during mechanical ventilation with high tidal volume in patients in the intensive care unit (ICU). VILI is a common entity with an unacceptable mortality rate (~20%). As no current therapies exist for VILI, novel therapeutic targets for VILI and mechanical stress-induced tissue injury are needed. In this study, we defined Nrf2 signaling in VILI and mechanical stress-induced endothelial cell pathobiology. Nrf2 is a transcription factor that alters ROS balance and is a novel therapeutic target for VILI. First, we defined Nrf2 as a sensory marker for mechanical stress-induced endothelial cell injury. Antioxidant response element (ARE) luciferase plasmids were transfected to both endothelial cells and murine lung tissues. EC exposed to 18% cyclic stretch (18% CS) or mice exposed to excessive tidal volume ventilation (40 ml/kg) resulted in ARE activation, site of Nrf2 binding. We next confirmed Nrf2 signaling is essential for gene expression dysregulation by 18% CS via Nrf2 knockdown that significantly ameliorates 18% CS-induced gene expression pattern, including signaling pathways regulating endothelial barrier function including MYLK. Finally, we validated that Nrf2 is a novel and effective therapeutic target for VILI in pre-clinical models of VILI. Nrf2 activator sulforaphane (SF, 11.5 mg/kg) significantly attenuated VILI (40 ml/kg, 4 hrs)-induced lung inflammation, including BAL protein leakage and white blood cell infiltration. These novel findings characterized Nrf2 as a sensor for mechanical stress, a central mediator of mechanical stress induced gene expression dysregulation, and a novel therapeutic target for VILI.

Sphingosine kinases (SphKs) 1 and 2 regulate the synthesis of the bioactive sphingolipid sphingosine-1-phosphate (S1P), an important lipid mediator that promotes cell proliferation, migration, and angiogenesis.We aimed to examine whether SphKs and their product, S1P, play a role in the development of pulmonary arterial hypertension (PAH).SphK1(-/-), SphK2(-/-), and S1P lyase heterozygous (Sgpl1(+/-)) mice, a pharmacologic SphK inhibitor (SKI2), and a S1P receptor 2 (S1PR2) antagonist (JTE013) were used in rodent models of hypoxia-mediated pulmonary hypertension (HPH). S1P levels in lung tissues from patients with PAH and pulmonary arteries (PAs) from rodent models of HPH were measured.mRNA and protein levels of SphK1, but not SphK2, were significantly increased in the lungs and isolated PA smooth muscle cells (PASMCs) from patients with PAH, and in lungs of experimental rodent models of HPH. S1P levels were increased in lungs of patients with PAH and PAs from rodent models of HPH. Unlike SphK2(-/-) mice, SphK1(-/-) mice were protected against HPH, whereas Sgpl1(+/-) mice were more susceptible to HPH. Pharmacologic SphK1 and S1PR2 inhibition prevented the development of HPH in rodent models of HPH. Overexpression of SphK1 and stimulation with S1P potentially via ligation of S1PR2 promoted PASMC proliferation in vitro, whereas SphK1 deficiency inhibited PASMC proliferation.The SphK1/S1P axis is a novel pathway in PAH that promotes PASMC proliferation, a major contributor to pulmonary vascular remodeling. Our results suggest that this pathway is a potential therapeutic target in PAH.

Background— Pulmonary veno-occlusive disease is caused by excessive cell proliferation and fibrosis, which obliterate the lumen of pulmonary venules, leading to pulmonary hypertension, right ventricular failure, and death. This condition has no effective treatment and a 5-year survival of Methods and Results— We show that mice with homozygous deletion of the Ets transcription factor Erg die between embryonic day 16.5 and 3 months of age as a result of pulmonary veno-occlusive disease, capillary hemorrhage, and pancytopenia. We demonstrate that Erg binds to and serves as a transcriptional activator of the G-protein–coupled receptor gene Aplnr , the expression of which is uniquely specific for venous endothelium and that knockout of either Erg or Aplnr results in pulmonary venule–specific endothelial proliferation in vitro. We show that mice with either homozygous-global or endothelium-directed deletion of Aplnr manifest pulmonary veno-occlusive disease and right heart failure, detectable at 8 months of age. Levels of pulmonary ERG and APLNR in patients with pulmonary veno-occlusive disease undergoing lung transplantation were significantly lower than those of control subjects. Conclusions— Our results suggest that ERG and APLNR are essential for endothelial homeostasis in venules in the lung and that perturbation in ERG-APLNR signaling is crucial for the development of pulmonary veno-occlusive disease. We identify this pathway as a potential therapeutic target for the treatment of this incurable disease.

To explore the effects of gender on pathology and pulmonary vascular reactivity in chronic hypoxic pulmonary hypertension (HPH) in mice.HPH was induced by a 4-week exposure of male and female mice (8 weeks old C57BL/6, n = 15 each) to chronic hypoxia (10%O2). Normoxic controls were established both in male and female groups (n = 15 each). Right ventricular systolic pressure (RVSP) and Fulton index were detected.Isolated pulmonary artery ring contraction induced by high potassium (K(+)) and U-46619 was recorded and compared between two groups.Chronic hypoxia induced pulmonary hypertension after 4 weeks.RVSP significantly increased both in hypoxic female and male groups (normoxic vs hypoxic: (23.40 ± 0.16) vs (31.46 ± 2.33) and (24.71 ± 0.44) vs (33.66 ± 1.38) mmHg (1 mmHg = 0.133 kPa), P = 0.029 and P0.001).However, there were no inter-group differences (P = 0.447). The Fulton index of hypoxic female and male mice was higher than normoxic counterparts (P = 0.001, P0.001). But there were no gender differences (P = 0.471). Contraction of high K(+) and U-46619 was calcium ion (Ca(2+))-dependent and decreased markedly without calcium (P0.001, P = 0.007). High K(+) and U-46619-induced contraction of pulmonary artery was concentration dependent and greater in chronic hypoxic female (P = 0.002, P0.001) and male mice (both P0.001). But no differences existed between male and female mice in high K(+) (P = 0.657) or U-46619 (P = 0.751)-induced contraction.No significant correlation exists between gender and occurrence and severity of pulmonary hypertension or pulmonary artery vascular reactivity in HPH mice.

When Pulmonary Circulation was first launched in 2011, no one knew what to expect. A journal focused exclusively on research around the pulmonary circulation and pulmonary vascular disease? Are there enough people interested to sustain the journal’s readership? Who will submit to yet another new, unknown medical journal? And how will we establish and differentiate ourselves from the other journals in the field? After three years, and after more than 350 submissions, more than 200 published articles, and more than 57,000 PDF article downloads, Pulmonary Circulation has proven its ability to capture some of the best original research articles and comprehensive reviews in the field. The voice of the journal is made up of a diverse group of both new and established board members ranging from clinicians to physician scientists to investigators; it is heard in the authors from more than 35 different countries across the globe; and it is seen in the various types of articles we publish. Our goal was that Pulmonary Circulation would become the valued journal in the field. We believe that we are well on the way to achieving this. In order to maintain and exceed this goal, we recently had to make several changes to the production of the journal. Our biggest, and most valued, change is our new publisher. We are very excited to formally introduce our readers to the University of Chicago Press (UCP). With this change in publisher, we expect to see enhanced visibility for the journal, improved visual quality of articles published, and most importantly, a heightened efficiency of publication. UCP has been around for more than 100 years and publishes around 50 journals every year. They have recently established a medical journals division within the Press, which we are honored to join. The Press offers many new features to both its readers and its authors, including prompt ahead-of-print publication and a just-accepted link where new articles will be posted online, unedited, within 3 days of acceptance. Next, we have decided to go digital. We have seen over the past few years that, overwhelmingly, readers were accessing our articles online and not in print. In an effort to increase efficiency, we decided to make the journal available online only, with the option for readers to request any print-on-demand issue they may be interested in receiving. In addition, UCP offers an e-book format of the journal, which can be downloaded to all versions of e-readers and iPads, smart phones, and iPhones. Again, we look to you, our readers and contributors, to help sustain the journal and take us to the next level. We eagerly await the announcement of our impact factor, which will be another major step for us. Please submit to us your most novel and significant original research articles in basic, translational, clinical, and population health research; your most comprehensive review articles on scientifically impactful and clinically relevant topics related to the pulmonary circulation and pulmonary vascular disease; your highly novel (and rare) case reports; and your rapid communications/research reports on novel findings. We also continue to be interested in considering the publication of high-quality conference abstracts of selected scientific conferences in the pulmonary circulation field. We are grateful to all who support the journal—members of the Pulmonary Vascular Research Institute, editorial board members, authors, reviewers, and readers—for helping establish our unique voice within the world of medical publishing.

Pulmonary arterial hypertension (PAH) is a progressive disease that, if left untreated, eventually leads to right heart failure and death. Elevated pulmonary arterial pressure (PAP) in patients with PAH is mainly caused by an increase in pulmonary vascular resistance (PVR). Sustained vasoconstriction and excessive pulmonary vascular remodeling are two major causes for elevated PVR in patients with PAH. Excessive pulmonary vascular remodeling is mediated by increased proliferation of pulmonary arterial smooth muscle cells (PASMC) due to PASMC dedifferentiation from a contractile or quiescent phenotype to a proliferative or synthetic phenotype. Increased cytosolic Ca2+concentration ([Ca2+]cyt) in PASMC is a key stimulus for cell proliferation and this phenotypic transition. Voltage-dependent Ca2+entry (VDCE) and store-operated Ca2+entry (SOCE) are important mechanisms for controlling [Ca2+]cyt. Stromal interacting molecule proteins (e.g., STIM2) and Orai2 both contribute to SOCE and we have previously shown that STIM2 and Orai2, specifically, are upregulated in PASMC from patients with idiopathic PAH and from animals with experimental pulmonary hypertension in comparison to normal controls. In this study, we show that STIM2 and Orai2 are upregulated in proliferating PASMC compared with contractile phenotype of PASMC. Additionally, a switch in Ca2+regulation is observed in correlation with a phenotypic transition from contractile PASMC to proliferative PASMC. PASMC in a contractile phenotype or state have increased VDCE, while in the proliferative phenotype or state PASMC have increased SOCE. The data from this study indicate that upregulation of STIM2 and Orai2 is involved in the phenotypic transition of PASMC from a contractile state to a proliferative state; the enhanced SOCE due to upregulation of STIM2 and Orai2 plays an important role in PASMC proliferation.

Introduction: Recent studies suggest that microRNAs (miRNAs) play important roles in development and pathogenesis of human diseases. We sought to identify novel miRNAs that may be involved in the pathogenesis of pulmonary arterial hypertension (PAH) and to investigate underlying mechanisms. Methods and Results: We performed miRNA qPCR array using pulmonary arterial smooth muscle cells (PASMC) isolated from lungs of normal donor and PAH patients. We found that all of the six members of the miR-17~92 cluster were down-regulated in PAH PASMCs. In hypoxia-induced PAH mouse model and cultured human PASMCs, we found that short term hypoxia induced miR-17~92 whereas prolonged hypoxia suppressed miR-17~92. We generated a strain of SMC-specific miR-17~92 knockout (sm-17~92-/-) mouse by crossbreeding miR-17~92 fl/fl mice with sm22α-Cre mice and subsequent backcrossing. We exposed 8-10 week old sm-17~92-/- mice along with their wild type littermates to hypoxia (10% O2) or normoxia for five weeks. We showed that knoc...

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new class of oral drugs for the treatment of type 2 diabetes and they reduce plasma blood glucose levels by inhibiting renal glucose reabsorp...

Idiopathic pulmonary arterial hypertension (IPAH) is a fatal and progressive disease which is attributed to elevated pulmonary arterial pressure and pulmonary vascular resistance due in part to sustained pulmonary vasoconstriction and vascular remodeling. Pulmonary arterial smooth muscle cells (PASMC) are normally shielded from exposure to shear stress and sense small flow shear through transmural interstitial flow driven by transvascular pressure differential. However, in the context of endothelial injury or enhanced vascular permeability caused by increased pulmonary arterial pressure, PASMC are exposed to shear stress or to enhanced transmural interstitial flow. Shear stress can increase cytosolic Ca2+ concentration ([Ca2+]cyt). An increase in [Ca2+]cyt in PASMC is a major trigger for vasoconstriction and a key stimulus for cell proliferation, which contribute to vascular remodeling. We show here that shear stress induced increased [Ca2+]cyt in PASMC from patients with IPAH compared with control. Fluid...

Rationale: An increase in cytosolic free Ca2+ in pulmonary arterial smooth muscle cells (PASMC) is not only a major trigger for pulmonary vasoconstriction but also an important stimulus for PASMC p...

hypoxic pulmonary vasoconstriction(HPV) serves as an important regulatory mechanism to match perfusion to ventilation by directing blood flow away from poorly ventilated regions of the lung to ensure maximal oxygenation of the venous blood. Persistent HPV, however, causes pulmonary hypertension that

The balance between apoptosis and proliferation in pulmonary artery smooth muscle cells (PASMCs) is important in maintaining normal pulmonary vascular structure. Activity of voltage-gated K+(KV) channels has been demonstrated to regulate cell apoptosis and proliferation. Treatment of PASMCs with staurosporine (ST) induced apoptosis in PASMCs, augmented KVcurrent [ IK(V)], and induced mitochondrial membrane depolarization. High K+(40 mM) negligibly affected the ST-induced mitochondrial membrane depolarization but inhibited the ST-induced IK(V)increase and apoptosis. Blockade of KVchannels with 4-aminopyridine diminished IK(V)and markedly decreased the ST-mediated apoptosis. Furthermore, the ST-induced apoptosis was preceded by the increase in IK(V). These results indicate that ST induces PASMC apoptosis by activation of plasmalemmal KVchannels and mitochondrial membrane depolarization. The increased IK(V)would result in an apoptotic volume decrease due to a loss of cytosolic K+and induce apoptosis. The mitochondrial membrane depolarization would cause cytochrome c release, activate the cytosolic caspases, and induce apoptosis. Inhibition of KVchannels would thus attenuate PASMC apoptosis.