Flow shear stress enhances intracellular Ca2+ signaling in pulmonary artery smooth muscle cells from patients with pulmonary arterial hypertension

Role of transient receptor potential channels in the regulation of vascular tone

Vascular tone is a major element in the control of hemodynamics. Transient receptor potential (TRP) channels conducting monovalent and/or divalent cations (e.g. Na+ and Ca2+) are expressed in the vasculature. Accumulating evidence suggests that TRP channels participate in regulating vascular tone by regulating intracellular Ca2+ signaling in both vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). Aberrant expression/function of TRP channels in the vasculature is associated with vascular dysfunction in systemic/pulmonary hypertension and metabolic syndromes. This review intends to summarize our current knowledge of TRP-mediated regulation of vascular tone in both physiological and pathophysiological conditions and to discuss potential therapeutic approaches to tackle abnormal vascular tone due to TRP dysfunction.

Up-regulated expression of two-pore domain K+ channels, KCNK1 and KCNK2, is involved in the proliferation and migration of pulmonary arterial smooth muscle cells in pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) is a severe and rare disease in the cardiopulmonary system. Its pathogenesis involves vascular remodeling of the pulmonary artery, which results in progressive increases in pulmonary arterial pressure. Chronically increased pulmonary arterial pressure causes right ventricular hypertrophy and subsequent right heart failure. Pulmonary vascular remodeling is attributed to the excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), which are induced by enhanced Ca2+ signaling following the up-/down-regulation of ion channel expression.

Objectives

In the present study, the functional expression of two-pore domain potassium KCNK channels was investigated in PASMCs from idiopathic PAH (IPAH) patients and experimental pulmonary hypertensive (PH) animals.

Results

In IPAH-PASMCs, the expression of KCNK1/TWIK1 and KCNK2/TREK1 channels was up-regulated, whereas that of KCNK3/TASK1 and KCNK6/TWIK2 channels was down-regulated. The similar up-regulated expression of KCNK1 and KCNK2 channels was observed in the pulmonary arterial smooth muscles of monocrotaline-induced PH rats, Sugen 5416/hypoxia-induced PH rats, and hypoxia-induced PH mice. The facilitated proliferation of IPAH-PASMCs was suppressed by the KCNK channel blockers, quinine and tetrapentylammonium. The migration of IPAH-PASMCs was also suppressed by these channel blockers. Furthermore, increases in the proliferation and migration were inhibited by the siRNA knockdown of KCNK1 or KCNK2 channels. The siRNA knockdown also caused membrane depolarization and subsequent decrease in cytosolic [Ca2+]. The phosphorylated level of c-Jun N-terminal kinase (JNK) was elevated in IPAH-PASMCs compared to normal-PASMCs. The increased phosphorylation was significantly reduced by the siRNA knockdown of KCNK1 or KCNK2 channels.

Conclusion

Collectively, these findings indicate that the up-regulated expression of KCNK1 and KCNK2 channels facilitates the proliferation and migration of PASMCs via enhanced Ca2+ signaling and JNK signaling pathway, which is associated with vascular remodeling in PAH.

Stretch response of the mechano-gated channel TMEM63A in membrane patches and single cells

The recently discovered ion channel TMEM63A has biophysical features distinctive for mechano-gated cation channels, activating at high pressures with slow kinetics while not inactivating. However, some biophysical properties are less clear, including no information on its function in whole cells. The aim of this study is to expand the TMEM63A biophysical characterization and examine the function in whole cells. Piezo1-knockout HEK293T cells were cotransfected with human TMEM63A and green fluorescent protein (GFP), and macroscopic currents in cell-attached patches were recorded by high-speed pressure clamp at holding voltages from -120 to -20 mV with 0-100 mmHg patch suction for 1 s. HEK293 cells cotransfected with TMEM63A and GCaMP5 were seeded onto polydimethylsiloxane (PDMS) membrane, and the response to 3-12 s of 1%-15% whole cell isotropic (equi-biaxial) stretch induced by an IsoStretcher was measured by the change in intracellular calcium ([Ca2+]i) and presented as (ΔF/F0 > 1). Increasing patch pressures activated TMEM63A currents with accelerating activation kinetics and current amplitudes that were pressure dependent but voltage independent. TMEM63A currents were plateaued within 2 s, recovered quickly, and were sensitive to Gd3+. In whole cells stretched on flexible membranes, radial stretch increased the [Ca2+]i responses in a larger proportion of cells cotransfected with TMEM63A and GCaMP5 than GCaMP5-only controls. TMEM63A currents are force activated and voltage insensitive, have a high threshold for pressure activation with slow activation and deactivation, and lack inactivation over 5 s. TMEM63A has the net polarity and kinetics that would depolarize plasma membranes and increase inward currents, contributing to a sustained [Ca2+]i increase in response to high stretch.NEW & NOTEWORTHY TMEM63A has biophysical features distinctive for mechano-gated cation channels, but some properties are less clear, including no functional information in whole cells. We report that pressure-dependent yet voltage-independent TMEM63A currents in cell membrane patches correlated with cell size. In addition, radial stretch of whole cells on flexible membranes increased the [Ca2+]i responses more in TMEM63A-transfected cells. Inward TMEM63A currents in response to high stretch can depolarize plasma membranes and contribute to a sustained [Ca2+]i increase.

Potential Roles of Metals in the Pathogenesis of Pulmonary and Systemic Hypertension

Pulmonary and systemic hypertension (PH, SH) are characterized by vasoconstriction and vascular remodeling resulting in increased vascular resistance and pulmonary/aortic artery pressures. The chronic stress leads to inflammation, oxidative stress, and infiltration by immune cells. Roles of metals in these diseases, particularly PH are largely unknown. This review first discusses the pathophysiology of PH including vascular oxidative stress, inflammation, and remodeling in PH; mitochondrial dysfunction and metabolic changes in PH; ion channel and its alterations in the pathogenesis of PH as well as PH-associated right ventricular (RV) remodeling and dysfunctions. This review then summarizes metal general features and essentiality for the cardiovascular system and effects of metals on systemic blood pressure. Lastly, this review explores non-essential and essential metals and potential roles of their dyshomeostasis in PH and RV dysfunction. Although it remains early to conclude the role of metals in the pathogenesis of PH, emerging direct and indirect evidence implicates the possible contributions of metal-mediated toxicities in the development of PH. Future research should focus on comprehensive clinical metallomics study in PH patients; mechanistic evaluations to elucidate roles of various metals in PH animal models; and novel therapy clinical trials targeting metals. These important discoveries will significantly advance our understandings of this rare yet fatal disease, PH.

Pathophysiology and pathogenic mechanisms of pulmonary hypertension: role of membrane receptors, ion channels, and Ca2+ signaling

The pulmonary circulation is a low-resistance, low-pressure, and high-compliance system that allows the lungs to receive the entire cardiac output. Pulmonary arterial pressure is a function of cardiac output and pulmonary vascular resistance, and pulmonary vascular resistance is inversely proportional to the fourth power of the intraluminal radius of the pulmonary artery. Therefore, a very small decrease of the pulmonary vascular lumen diameter results in a significant increase in pulmonary vascular resistance and pulmonary arterial pressure. Pulmonary arterial hypertension is a fatal and progressive disease with poor prognosis. Regardless of the initial pathogenic triggers, sustained pulmonary vasoconstriction, concentric vascular remodeling, occlusive intimal lesions, in situ thrombosis, and vascular wall stiffening are the major and direct causes for elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension and other forms of precapillary pulmonary hypertension. In this review, we aim to discuss the basic principles and physiological mechanisms involved in the regulation of lung vascular hemodynamics and pulmonary vascular function, the changes in the pulmonary vasculature that contribute to the increased vascular resistance and arterial pressure, and the pathogenic mechanisms involved in the development and progression of pulmonary hypertension. We focus on reviewing the pathogenic roles of membrane receptors, ion channels, and intracellular Ca2+ signaling in pulmonary vascular smooth muscle cells in the development and progression of pulmonary hypertension.

Pathophysiological Roles of the TRPV4 Channel in the Heart

The transient receptor potential vanilloid 4 (TRPV4) channel is a non-selective cation channel that is mostly permeable to calcium (Ca²⁺), which participates in intracellular Ca²⁺ handling in cardiac cells. It is widely expressed through the body and is activated by a large spectrum of physicochemical stimuli, conferring it a role in a variety of sensorial and physiological functions. Within the cardiovascular system, TRPV4 expression is reported in cardiomyocytes, endothelial cells (ECs) and smooth muscle cells (SMCs), where it modulates mitochondrial activity, Ca²⁺ homeostasis, cardiomyocytes electrical activity and contractility, cardiac embryonic development and fibroblast proliferation, as well as vascular permeability, dilatation and constriction. On the other hand, TRPV4 channels participate in several cardiac pathological processes such as the development of cardiac fibrosis, hypertrophy, ischemia-reperfusion injuries, heart failure, myocardial infarction and arrhythmia. In this manuscript, we provide an overview of TRPV4 channel implications in cardiac physiology and discuss the potential of the TRPV4 channel as a therapeutic target against cardiovascular diseases.

Effect of Static Pressure on Early Apoptosis of Condylar Chondrocytes by Activating Transient Receptor Potential Melastatin 7 (TRPM7) Channel

Background: This study is to detect the Ca2+ permeability of transient receptor potential melastatin 7 (TRPM7) channel under Static pressure, and to verify the effection of pressure on cell apoptosis through TRPM7 channel mediated Ca2+ influx. Materials and Methods: Rat condylar chondrocytes cells are divided into control group, pressure group and FTY720 group. TRPM7 protein content is detected by westernblot. Calcium current is detected by colorimetry, and flow cytometry is used to detect apoptotic cells. Results: The cell morphology is spindle or spindle shape with clear boundary. The nucleus is oval and located in the center of the cell. Compared with the control group, the protein content of TRPM7, the calcium concentration was significantly higher (P <0.05). apoptosis in the pressure group is significantly increased than that in the control group (P <0.05). Conclusion: Static pressure upregulates the expression of TRPM7 in chondrocytes, resulting in the increase of intracellular Ca2+ concentration, which leads to apoptosis through signal pathway.

No evidence of pulmonary hypertension revealed in an echographic evaluation of right-sided hemodynamics in hyperthyroid cats

OBJECTIVES

Hyperthyroidism is a common endocrinopathy affecting middle-aged to elderly cats, with multisystemic repercussions. Hyperthyroid humans show decreased lung compliance and increased cardiac output with subsequent left heart failure leading to pulmonary capillary congestion. Prognosis worsens with the development of increased pulmonary vascular pressures (ie, pulmonary hypertension [PH]) in hyperthyroid humans. The effect of excess thyroid hormone concentration on pulmonary arterial hemodynamics is unknown in cats. Assessing pulmonary vascular pressures in veterinary medicine relies heavily on echocardiographic measurements performed at the level of the heart and pulmonary trunk. This study investigated right-sided cardiac and pulmonary arterial hemodynamics in hyperthyroid cats using echocardiography.

METHODS

Echocardiographic examinations of hyperthyroid cats identified through a bi-institutional database search were reviewed for the determination of systolic pulmonary arterial pressure (PAP) and 20 other metrics. Values were compared with those of a healthy cat group using non-parametric statistical analyses.

RESULTS

Systolic PAP could not be determined in 23/26 hyperthyroid and 13/14 healthy cats owing to unmeasurable tricuspid regurgitation flow velocity. Hyperthyroid cats were roughly twice as old (P <0.001) and had 2-4-fold higher respiratory rates (P <0.001) than healthy cats. Hyperthyroid cats showed an increase in acceleration time-to-ejection time ratio of pulmonary flow (1.4-fold, P = 0.001), pulmonary artery velocity time integral (1.2-1.6-fold, P = 0.001), maximal pulmonary velocity (1.3-1.7-fold, P = 0.002), stroke volume (1.5-fold, P = 0.001) and cardiac output (1.6-fold, P <0.001) vs healthy cats. None of the other echocardiographic metrics reached statistical significance.

CONCLUSIONS AND RELEVANCE

Systolic PAP estimation proved unsuitable as a sole measurement for the assessment of PH in hyperthyroid cats owing to the frequent inability to interrogate tricuspid regurgitant flow velocity. Hyperthyroid cats have altered echocardiographic measures of pulmonary hemodynamics dissimilar to those reported in hyperthyroid humans. Differential effects of thyrotoxic cardiomyopathy on ventricular systolic function may underlie species differences.

Impact of achieving euthyroidism on pulmonary artery systolic pressures in hyperthyroidism-associated pulmonary hypertension - a systematic review

In this systematic review, we seek to clarify the impact of treatment of hyperthyroidism on pulmonary hypertension in patients with both these conditions. We included 39 of 709 articles retrieved, that studied patients with hyperthyroidism and pulmonary hypertension (PH). From these, those with a documented pre-treatment Pulmonary Artery Systolic Pressure (PASP) > 35 mmHg and complete follow up were analyzed, yielding 3 case series and 22 case reports with a total of 81 cases. A significant improvement in PASP was noted with achieving euthyroidism in the 3 case series. The case reports showed a significant reduction in mean PASP from 60.5 ± 13.2 mmHg to 37.5 ± 10.1 mmHg (p < 0.001) in patients with Grave's disease with achieving euthyroidism. No deaths were reported during the follow up period. Achievement of a euthyroid state in patients with hyperthyroidism is associated with statistically significant reductions in PASP.

Potential of the TRPM7 channel as a novel therapeutic target for pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an intractable vascular disease characterized by a progressive increase in pulmonary vascular resistance caused by pulmonary vascular remodeling, which ultimately leads to right-sided heart failure. PAH remains incurable, despite the development of PAH-targeted therapeutics centered on pulmonary artery relaxants. It is necessary to identify the target molecules that contribute to pulmonary artery remodeling. Transient receptor potential (TRP) channels have been suggested to modulate pulmonary artery remodeling. Our study focused on the transient receptor potential ion channel subfamily M, member 7, or the TRPM7 channel, which modulates endothelial-to-mesenchymal transition and smooth muscle proliferation in the pulmonary artery. In this review, we summarize the role and expression profile of TRPM7 channels in PAH progression and discuss TRPM7 channels as possible therapeutic targets. In addition, we discuss the therapeutic effect of a Chinese herbal medicine, Ophiocordyceps sinensis (OCS), on PAH progression, which partly involves TRPM7 inhibition.

Development of vascular disease models to explore disease causation and pathomechanisms of rare vascular diseases

As the field of medicine is striving forward heralded by a new era of next-generation sequencing (NGS) and integrated technologies such as bioprinting and biological material development, the utility of rare monogenetic vascular disease modeling in this landscape is starting to emerge. With their genetic simplicity and broader applicability, these patient-specific models are at the forefront of modern personalized medicine. As a collective, rare diseases are a significant burden on global healthcare systems, and rare vascular diseases make up a significant proportion of this. High costs are due to a lengthy diagnostic process, affecting all ages from infants to adults, as well as the severity and chronic nature of the disease. Their complex nature requires sophisticated disease models and integrated approaches involving multidisciplinary teams. Here, we review these emerging vascular disease models, how they contribute to our understanding of the pathomechanisms in rare vascular diseases and provide useful platforms for therapeutic discovery.

Mechanisms of Hypoxia-Induced Pulmonary Arterial Stiffening in Mice Revealed by a Functional Genetics Assay of Structural, Functional, and Transcriptomic Data

Hypoxia adversely affects the pulmonary circulation of mammals, including vasoconstriction leading to elevated pulmonary arterial pressures. The clinical importance of changes in the structure and function of the large, elastic pulmonary arteries is gaining increased attention, particularly regarding impact in multiple chronic cardiopulmonary conditions. We establish a multi-disciplinary workflow to understand better transcriptional, microstructural, and functional changes of the pulmonary artery in response to sustained hypoxia and how these changes inter-relate. We exposed adult male C57BL/6J mice to normoxic or hypoxic (FiO₂ 10%) conditions. Excised pulmonary arteries were profiled transcriptionally using single cell RNA sequencing, imaged with multiphoton microscopy to determine microstructural features under in vivo relevant multiaxial loading, and phenotyped biomechanically to quantify associated changes in material stiffness and vasoactive capacity. Pulmonary arteries of hypoxic mice exhibited an increased material stiffness that was likely due to collagen remodeling rather than excessive deposition (fibrosis), a change in smooth muscle cell phenotype reflected by decreased contractility and altered orientation aligning these cells in the same direction as the remodeled collagen fibers, endothelial proliferation likely representing endothelial-to-mesenchymal transitioning, and a network of cell-type specific transcriptomic changes that drove these changes. These many changes resulted in a system-level increase in pulmonary arterial pulse wave velocity, which may drive a positive feedback loop exacerbating all changes. These findings demonstrate the power of a multi-scale genetic-functional assay. They also highlight the need for systems-level analyses to determine which of the many changes are clinically significant and may be potential therapeutic targets.

Computational simulation-derived hemodynamic and biomechanical properties of the pulmonary arterial tree early in the course of ventricular septal defects

Untreated ventricular septal defects (VSDs) can lead to pulmonary arterial hypertension (PAH) characterized by elevated pulmonary artery (PA) pressure and vascular remodeling, known as PAH associated with congenital heart disease (PAH-CHD). Though previous studies have investigated hemodynamic effects on vascular mechanobiology in late-stage PAH, hemodynamics leading to PAH-CHD initiation have not been fully quantified. We hypothesize that abnormal hemodynamics from left-to-right shunting in early stage VSDs affects PA biomechanical properties leading to PAH initiation. To model PA hemodynamics in healthy, small, moderate, and large VSD conditions prior to the onset of vascular remodeling, computational fluid dynamics simulations were performed using a 3D finite element model of a healthy 1-year-old's proximal PAs and a body-surface-area-scaled 0D distal PA tree. VSD conditions were modeled with increased pulmonary blood flow to represent degrees of left-to-right shunting. In the proximal PAs, pressure, flow, strain, and wall shear stress (WSS) increased with increasing VSD size; oscillatory shear index decreased with increasing VSD size in the larger PA vessels. WSS was higher in smaller diameter vessels and increased with VSD size, with the large VSD condition exhibiting WSS >100 dyn/cm[Formula: see text], well above values typically used to study dysfunctional mechanotransduction pathways in PAH. This study is the first to estimate hemodynamic and biomechanical metrics in the entire pediatric PA tree with VSD severity at the stage leading to PAH initiation and has implications for future studies assessing effects of abnormal mechanical stimuli on endothelial cells and vascular wall mechanics that occur during PAH-CHD initiation and progression.

Mechanosensitivity in Pulmonary Circulation: Pathophysiological Relevance of Stretch-Activated Channels in Pulmonary Hypertension

A variety of cell types in pulmonary arteries (endothelial cells, fibroblasts, and smooth muscle cells) are continuously exposed to mechanical stimulations such as shear stress and pulsatile blood pressure, which are altered under conditions of pulmonary hypertension (PH). Most functions of such vascular cells (e.g., contraction, migration, proliferation, production of extracellular matrix proteins, etc.) depend on a key event, i.e., the increase in intracellular calcium concentration ([Ca²⁺]_i) which results from an influx of extracellular Ca²⁺ and/or a release of intracellular stored Ca²⁺. Calcium entry from the extracellular space is a major step in the elevation of [Ca²⁺]_i, involving a variety of plasmalemmal Ca²⁺ channels including the superfamily of stretch-activated channels (SAC). A common characteristic of SAC is that their gating depends on membrane stretch. In general, SAC are non-selective Ca²⁺-permeable cation channels, including proteins of the TRP (Transient Receptor Potential) and Piezo channel superfamily. As membrane mechano-transducers, SAC convert physical forces into biological signals and hence into a cell response. Consequently, SAC play a major role in pulmonary arterial calcium homeostasis and, thus, appear as potential novel drug targets for a better management of PH.

Substantial involvement of TRPM7 inhibition in the therapeutic effect of Ophiocordyceps sinensis on pulmonary hypertension

Ophiocordyceps sinensis (OCS), an entomopathogenic fungus, is known to exert antiproliferative and antitissue remodeling effects. Vascular remodeling and vasoconstriction play critical roles in the development of pulmonary hypertension (PH). The therapeutic potential of OCS for PH was investigated using rodent PH models, and cultured pulmonary artery endothelial and smooth muscle cells (PAECs and PASMCs), with a focus on the involvement of TRPM7. OCS ameliorated the development of PH, right ventricular hypertrophy and dysfunction in the monocrotaline-induced PH rats. The genetic knockout of TRPM7 attenuated the development of PH in mice with monocrotaline pyrrole-induced PH. TRPM7 was associated with medial hypertrophy and the plexiform lesions in rats and humans with PH. OCS suppressed proliferation of PASMCs derived from the PH patients. Ethanol extracts of OCS inhibited TRPM7-like current, TGF-β2-induced endothelial-mesenchymal transition, IL-6-induced STAT3 phosphorylation, and PDGF-induced Akt phosphorylation in PAECs or PASMCs. These inhibitory effects were recapitulated by either siRNA-mediated TRPM7 knockdown or treatment with TRPM7 antagonist FTY-720. OCS and FTY-720 induced vasorelaxation in the isolated normal human pulmonary artery. As a result, the present study proposes the therapeutic potential of OCS for the treatment of PH. The inhibition of TRPM7 is suggested to underlie the therapeutic effect of OCS.

Caveolar peroxynitrite formation impairs endothelial TRPV4 channels and elevates pulmonary arterial pressure in pulmonary hypertension

Recent studies have focused on the contribution of capillary endothelial TRPV4 channels to pulmonary pathologies, including lung edema and lung injury. However, in pulmonary hypertension (PH), small pulmonary arteries are the focus of the pathology, and endothelial TRPV4 channels in this crucial anatomy remain unexplored in PH. Here, we provide evidence that TRPV4 channels in endothelial cell caveolae maintain a low pulmonary arterial pressure under normal conditions. Moreover, the activity of caveolar TRPV4 channels is impaired in pulmonary arteries from mouse models of PH and PH patients. In PH, up-regulation of iNOS and NOX1 enzymes at endothelial cell caveolae results in the formation of the oxidant molecule peroxynitrite. Peroxynitrite, in turn, targets the structural protein caveolin-1 to reduce the activity of TRPV4 channels. These results suggest that endothelial caveolin-1-TRPV4 channel signaling lowers pulmonary arterial pressure, and impairment of endothelial caveolin-1-TRPV4 channel signaling contributes to elevated pulmonary arterial pressure in PH. Thus, inhibiting NOX1 or iNOS activity, or lowering endothelial peroxynitrite levels, may represent strategies for restoring vasodilation and pulmonary arterial pressure in PH.

The Calcium Signaling Mechanisms in Arterial Smooth Muscle and Endothelial Cells

The contractile state of resistance arteries and arterioles is a crucial determinant of blood pressure and blood flow. Physiological regulation of arterial contractility requires constant communication between endothelial and smooth muscle cells. Various Ca²⁺ signals and Ca²⁺ -sensitive targets ensure dynamic control of intercellular communications in the vascular wall. The functional effect of a Ca²⁺ signal on arterial contractility depends on the type of Ca²⁺ -sensitive target engaged by that signal. Recent studies using advanced imaging methods have identified the spatiotemporal signatures of individual Ca²⁺ signals that control arterial and arteriolar contractility. Broadly speaking, intracellular Ca²⁺ is increased by ion channels and transporters on the plasma membrane and endoplasmic reticular membrane. Physiological roles for many vascular Ca²⁺ signals have already been confirmed, while further investigation is needed for other Ca²⁺ signals. This article focuses on endothelial and smooth muscle Ca²⁺ signaling mechanisms in resistance arteries and arterioles. We discuss the Ca²⁺ entry pathways at the plasma membrane, Ca²⁺ release signals from the intracellular stores, the functional and physiological relevance of Ca²⁺ signals, and their regulatory mechanisms. Finally, we describe the contribution of abnormal endothelial and smooth muscle Ca²⁺ signals to the pathogenesis of vascular disorders. © 2021 American Physiological Society. Compr Physiol 11:1831-1869, 2021.

Transient Receptor Potential Melastatin 7 Promotes Vascular Adventitial Fibroblasts Phenotypic Transformation and Inflammatory Reaction Induced by Mechanical Stretching Stress via p38 MAPK/JNK Pathway

Remodeling of the arteries is one of the pathological bases of hypertension. We have previously shown that transient receptor potential melastatin 7 (TRPM7) aggravates the vascular adventitial remodeling caused by pressure overload in the transverse aortic constriction (TAC) model. In this study, we sought to explore the functional expression and downstream signaling of TRPM7 in vascular adventitial fibroblasts (AFs) stimulated by mechanical stretching stress (MSS). The expression of TRPM7 was upregulated with a concomitant translocation to the cytoplasm in the AFs stimulated with 20% MSS. Meanwhile, the expression of α-smooth muscle actin (α-SMA), a marker of transformation from AFs to myofibroblasts (MFs) was also increased. Moreover, AF-conditioned medium caused a significant migration of macrophages after treatment with MSS and contained high levels of monocyte chemotactic protein-1 (MCP-1), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α). Pharmacological and RNA interference approaches using the TRPM7 inhibitor 2-aminoethoxydiphenyl borate (2-APB) and specific anti-TRPM7 small interfering RNA (si-RNA-TRPM7) abrogated these changes significantly. Further exploration uncloaked that inhibition of TRPM7 reduced the phosphorylation of p38 MAP kinase (p38MAPK) and c-Jun N-terminal kinase (JNK) in the AFs stimulated with MSS. Furthermore, inhibition of the phosphorylation of p38MAPK or JNK could also alleviate the MSS-induced expression of α-SMA and secretion of inflammatory factors. These observations indicate that activated TRPM7 participates in the phenotypic transformation and inflammatory action of AFs in response to MSS through the p38MAPK/JNK pathway and suggest that TRPM7 may be a potential therapeutic target for vascular remodeling caused by hemodynamic changes in hypertension.

The Rho kinase 2 (ROCK2)-specific inhibitor KD025 ameliorates the development of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease that is characterized by the irreversible remodeling of the pulmonary artery. Although several PAH drugs have been developed, additional drugs are needed. Rho kinases (ROCKs) are involved in the pathogenesis of PAH, and thus, their inhibitors may prevent the development of PAH. However, the therapeutic benefits of ROCK isoform-specific inhibitors for PAH remain largely unknown. The in vitro and in vivo effects of the ROCK2-specific inhibitor, KD025, were examined herein using pulmonary arterial smooth muscle cells (PASMCs) from idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline (MCT)-induced pulmonary hypertensive (PH) rats. The expression of ROCK1 was similar between normal- and IPAH-PASMCs, whereas that of ROCK2 was markedly higher in IPAH-PASMCs than in normal-PASMCs. KD025 inhibited the accelerated proliferation of IPAH-PASMCs in a concentration-dependent manner (IC50 = 289 nM). Accelerated proliferation was also reduced by the siRNA knockdown of ROCK2. In MCT-PH rats, the expression of ROCK2 was up-regulated in PASMCs. Elevated right ventricular systolic pressure in MCT-PH rats was attenuated by KD025 (1 mg/kg/day). These results strongly suggest that enhanced ROCK2 signaling is involved in the pathogenic mechanism underlying the development of PAH, including accelerated PASMC proliferation and vascular remodeling in patients with PAH. Therefore, ROCK2 may be a novel therapeutic target for the treatment of PAH.

TRPC and TRPV Channels' Role in Vascular Remodeling and Disease

Transient receptor potentials (TRPs) are non-selective cation channels that are widely expressed in vascular beds. They contribute to the Ca²⁺ influx evoked by a wide spectrum of chemical and physical stimuli, both in endothelial and vascular smooth muscle cells. Within the superfamily of TRP channels, different isoforms of TRPC (canonical) and TRPV (vanilloid) have emerged as important regulators of vascular tone and blood flow pressure. Additionally, several lines of evidence derived from animal models, and even from human subjects, highlighted the role of TRPC and TRPV in vascular remodeling and disease. Dysregulation in the function and/or expression of TRPC and TRPV isoforms likely regulates vascular smooth muscle cells switching from a contractile to a synthetic phenotype. This process contributes to the development and progression of vascular disorders, such as systemic and pulmonary arterial hypertension, atherosclerosis and restenosis. In this review, we provide an overview of the current knowledge on the implication of TRPC and TRPV in the physiological and pathological processes of some frequent vascular diseases.

[Pathophysiological roles of TRPC6 channels in pulmonary arterial hypertension]

Pulmonary arterial hypertension (PAH) is a progressive and lethal disease of the pulmonary artery. The pathogenesis of PAH is mainly sustained vasoconstriction and vascular remodeling of the pulmonary artery. These pathogeneses cause progressive elevations in pulmonary vascular resistance and pulmonary arterial pressure in PAH patients. Elevated pulmonary arterial pressure leads to right heart failure and finally death. The vascular remodeling is caused by the enhanced proliferation and reduced apoptosis of pulmonary arterial smooth muscle cells (PASMCs). Excitable abnormality in the pulmonary artery of PAH patients is mostly mediated by an elevated cytosolic Ca²⁺ concentration. PASMCs express several Ca²⁺-permeable channels including voltage-dependent Ca²⁺ channels, store-operated Ca²⁺ (SOC) channels, and receptor-operated Ca²⁺ (ROC) channels. The activation and upregulation of these Ca²⁺ channels have been reported in PASMCs from PAH patients. Here, we analyzed pathophysiological functions of enhanced Ca²⁺ signaling mediated by SOC and ROC channels using PASMCs from idiopathic PAH patients and animal PAH models. Notch signal enhanced transient receptor potential canonical 6 (TRPC6) "SOC" channels via direct (non-genomic and stimulatory) and indirect (genomic and upregulating) effects in PAH. On the other hand, the activation of Ca²⁺-sensing receptors evoked Ca²⁺ influx through TRPC6 "ROC" channels in PAH. In addition, TRPC6 channel blocker and TRPC6 gene deletion inhibited the development of PAH. Specifically, TRPC6 channels potentially form both ROC and SOC channels in PASMCs, which are involved in the pathophysiological events in PAH. Therefore, targeting TRPC6 channels in PASMCs may help develop novel therapeutic approach for PAH.

A Novel Mechanism of Sildenafil Improving the Excessive Proliferation and H2S Production in Pulmonary Arterial Smooth Muscle Cells

The dysregulation of pulmonary arterial vasoactive mediators or excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs) might result in contraction or remodeling of pulmonary blood vessels, leading to related lung diseases. Recent studies suggest that hydrogen sulfide (H2S), a gaseous vasodilator generated in the blood vessels by the enzymes cystathionine γ-lyase (CSE) and cystathionine-β-synthase (CBS), could induce the vasodilation, thus improving contraction or remodeling-induced lung diseases. In this study, we hypothesized that PASMCs could produce H2S and relax the pulmonary artery, and its mechanism is related to CSE, CBS, and TRPV4 channels by affecting both the excessive proliferation and pulmonary vasoconstriction in PASMCs. We found that the sildenafil treatment could remarkably promote H2S production and control the proliferation in PASMCs; meanwhile, the protein levels of CSE and CBS and the intracellular concentration of calcium could also be increased by sildenafil. Moreover, the effects of sildenafil could be reversed by a CBS inhibitor or a CSE inhibitor, indicating that sildenafil could affect CSE and CBS to modulate the production of H2S and the proliferation in rat PASMCs. Together, we demonstrated a new mechanism for sildenafil to modulate the synthesis of H2S and cell proliferation in PASMCs by affecting CSE and CBS. TRPV4-dependent Ca events and BMP4 may also be involved.

Notch enhances Ca2+ entry by activating calcium-sensing receptors and inhibiting voltage-gated K+ channels

The increase in cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt) and upregulation of calcium-sensing receptor (CaSR) and stromal interaction molecule 2 (STIM2) along with inhibition of voltage-gated K⁺ (K_V) channels in pulmonary arterial smooth muscle cells (PASMC) have been implicated in the development of pulmonary arterial hypertension; however, the precise upstream mechanisms remain elusive. Activation of CaSR, a G protein-coupled receptor (GPCR), results in Ca²⁺ release from the endoplasmic/sarcoplasmic reticulum (ER/SR) and Ca²⁺ influx through receptor-operated and store-operated Ca²⁺ channels (SOC). Upon Ca²⁺ depletion from the SR, STIM forms clusters to mediate store-operated Ca²⁺ entry. Activity of K_V channels, like KCNA5/K_V1.5 and KCNA2/K_V1.2, contributes to regulating membrane potential, and inhibition of K_V channels results in membrane depolarization that increases [Ca²⁺]_cyt by opening voltage-dependent Ca²⁺ channels. In this study, we show that activation of Notch by its ligand Jag-1 promotes the clustering of STIM2, and clustered STIM2 subsequently enhances the CaSR-induced Ca²⁺ influx through SOC channels. Extracellular Ca²⁺-mediated activation of CaSR increases [Ca²⁺]_cyt in CASR-transfected HEK293 cells. Treatment of CASR-transfected cells with Jag-1 further enhances CaSR-mediated increase in [Ca²⁺]_cyt. Moreover, CaSR-mediated increase in [Ca²⁺]_cyt was significantly augmented in cells co-transfected with CASR and STIM2. CaSR activation results in STIM2 clustering in CASR/STIM2-cotransfected cells. Notch activation also induces significant clustering of STIM2. Furthermore, activation of Notch attenuates whole cell K⁺ currents in KCNA5- and KCNA2-transfected cells. Together, these results suggest that Notch activation enhances CaSR-mediated increases in [Ca²⁺]_cyt by enhancing store-operated Ca²⁺ entry and inhibits KCNA5/K_V1.5 and KCNA2/K_V1.2, ultimately leading to voltage-activated Ca²⁺ entry.

Nafamostat mesylate attenuates the pathophysiologic sequelae of neurovascular ischemia

Nafamostat mesylate, an apparent soi-disant panacea of sorts, is widely used to anticoagulate patients undergoing hemodialysis or cardiopulmonary bypass, mitigate the inflammatory response in patients diagnosed with acute pancreatitis, and reverse the coagulopathy of patients experiencing the commonly preterminal disseminated intravascular coagulation in the Far East. The serine protease inhibitor nafamostat mesylate exhibits significant neuroprotective effects in the setting of neurovascular ischemia. Nafamostat mesylate generates neuroprotective effects by attenuating the enzymatic activity of serine proteases, neuroinflammatory signaling cascades, and the endoplasmic reticulum stress responses, downregulating excitotoxic transient receptor membrane channel subfamily 7 cationic currents, modulating the activity of intracellular signal transduction pathways, and supporting neuronal survival (brain-derived neurotrophic factor/TrkB/ERK1/2/CREB, nuclear factor kappa B. The effects collectively reduce neuronal necrosis and apoptosis and prevent ischemia mediated disruption of blood-brain barrier microarchitecture. Investigational clinical applications of these compounds may mitigate ischemic reperfusion injury in patients undergoing cardiac, hepatic, renal, or intestinal transplant, preventing allograft rejection, and treating solid organ malignancies. Neuroprotective effects mediated by nafamostat mesylate support the wise conduct of randomized prospective controlled trials in Western countries to evaluate the clinical utility of this compound.

Medical Image-Based Hemodynamic Analyses in a Study of the Pulmonary Artery in Children With Pulmonary Hypertension Related to Congenital Heart Disease

Objective: Pulmonary hypertension related to congenital heart disease (PH-CHD) is a devastating disease caused by hemodynamic disorders. Previous hemodynamic research in PH-CHD mainly focused on wall shear stress (WSS). However, energy loss (EL) is a vital parameter in evaluation of hemodynamic status. We investigated if EL of the pulmonary artery (PA) is a potential biomechanical marker for comprehensive assessment of PH-CHD. Materials and Methods: Ten PH-CHD patients and 10 age-matched controls were enrolled. Subject-specific 3-D PA models were reconstructed based on computed tomography. Transient flow, WSS, and EL in the PA were calculated using non-invasive computational fluid dynamics. The relationship between body surface area (BSA)-normalized EL ( E . ) and PA morphology and PA flow were analyzed. Results: Morphologic analysis indicated that the BSA-normalized main PA (MPA) diameter (D_MPAnorm), MPA/aorta diameter ratio (D_MPA/D_AO), and MPA/(left PA + right PA) [D_MPA/D_(LPA+RPA)] diameter ratio were significantly larger in PH-CHD patients. Hemodynamic results showed that the velocity of the PA branches was higher in PH-CHD patients, in whom PA flow rate usually increased. WSS in the MPA was lower and E . was higher in PH-CHD patients. E . was positively correlated with D_MPAnorm, D_MPA/D_AO, and D_MPA/D_(LPA+RPA) ratios and the flow rate in the PA. E . was a sensitive index for the diagnosis of PH-CHD. Conclusion: E . is a potential biomechanical marker for PH-CHD assessment. This hemodynamic parameter may lead to new directions for revealing the potential pathophysiologic mechanism of PH-CHD.

Transgelin as a potential target in the reversibility of pulmonary arterial hypertension secondary to congenital heart disease

BACKGROUND

The reversibility of pulmonary arterial hypertension (PAH) in congenital heart disease (CHD) is of great importance for the operability of CHD. Proteomics analysis found that transgelin was significantly up-regulated in the lung tissue of CHD-PAH patients, especially in the irreversible group. However, how exactly it participated in CHD-PAH development is unknown.

METHODS

Immunohistochemical staining and Western blot were performed for further qualitative and quantitative analysis of transgelin in the lung tissues of CHD-PAH patients. The mechanism of transgelin in CHD-PAH development was explored in vitro. Primary human pulmonary arterial smooth muscle cells (hPASMCs) were cultured and infected with TAGLN siRNA or TAGLN lentiviral vector. Cell morphologic change (Coomassie Brilliant Blue staining), proliferation (cell count and EdU assay), apoptosis (terminal deoxyribonucleotidyl transferase mediated dUTP nick end labeling assay and Annexin-V flow cytometry) and migration (transwell) were evaluated following the cell treatment. The mRNA and protein expression levels were detected in real-time PCR and Western blot.

RESULTS

In line with the proteomic findings, transgelin was obviously expressed in PASMC of the middle pulmonary arterioles, especially in the irreversible PAH group. Also, transgelin expression showed positive relation with pathological grading. Experiment in vitro demonstrated that transgelin overexpression promoted PASMC proliferation and migration, strengthened cytoskeleton and was accompanied by increased expression of synthetic phenotype markers (osteopontin, proliferating cell nuclear antigen) and anti-apoptotic protein (bcl-2). On the other hand, suppression of transgelin expression activated PASMC apoptosis, reducing cell proliferation and migration.

CONCLUSIONS

Transgelin may be a potential target in the development of irreversible CHD-PAH through inducing PASMC phenotype change, proliferation, migration and reducing cell apoptosis.

Role of extracellular matrix in the pathogenesis of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by remodeling of the extracellular matrix (ECM) of the pulmonary arteries with increased collagen deposition, cross-linkage of collagen, and breakdown of elastic laminae. Extracellular matrix remodeling occurs due to an imbalance in the proteolytic enzymes, such as matrix metalloproteinases, elastases, and lysyl oxidases, and tissue inhibitor of matrix metalloproteinases, which, in turn, results from endothelial cell dysfunction, endothelial-to-mesenchymal transition, and inflammation. ECM remodeling and pulmonary vascular stiffness occur early in the disease process, before the onset of the increase in the intimal and medial thickness and pulmonary artery pressure, suggesting that the ECM is a cause rather than a consequence of distal pulmonary vascular remodeling. ECM remodeling and increased pulmonary arterial stiffness promote proliferation of pulmonary vascular cells (endothelial cells, smooth muscle cells, and adventitial fibroblasts) through mechanoactivation of various signaling pathways, including transcriptional cofactors YAP/TAZ, transforming growth factor-β, transient receptor potential channels, Toll-like receptor, and NF-κB. Inhibition of ECM remodeling and mechanotransduction prevents and reverses experimental pulmonary hypertension. These data support a central role for ECM remodeling in the pathogenesis of the PAH, making it an attractive novel therapeutic target.

Mechanobiological Feedback in Pulmonary Vascular Disease

Vascular stiffening in the pulmonary arterial bed is increasingly recognized as an early disease marker and contributor to right ventricular workload in pulmonary hypertension. Changes in pulmonary artery stiffness throughout the pulmonary vascular tree lead to physiologic alterations in pressure and flow characteristics that may contribute to disease progression. These findings have led to a greater focus on the potential contributions of extracellular matrix remodeling and mechanical signaling to pulmonary hypertension pathogenesis. Several recent studies have demonstrated that the cellular response to vascular stiffness includes upregulation of signaling pathways that precipitate further vascular remodeling, a process known as mechanobiological feedback. The extracellular matrix modifiers, mechanosensors, and mechanotransducers responsible for this process have become increasingly well-recognized. In this review, we discuss the impact of vascular stiffening on pulmonary hypertension morbidity and mortality, evidence in favor of mechanobiological feedback in pulmonary hypertension pathogenesis, and the major contributors to mechanical signaling in the pulmonary vasculature.

Right ventricular dysfunction and pulmonary hypertension: a neglected presentation of thyrotoxicosis

Thyrotoxicosis is associated with cardiac dysfunction; more commonly, left ventricular dysfunction. However, in recent years, there have been more cases reported on right ventricular dysfunction, often associated with pulmonary hypertension in patients with thyrotoxicosis. Three cases of thyrotoxicosis associated with right ventricular dysfunction were presented. A total of 25 other cases of thyrotoxicosis associated with right ventricular dysfunction published from 1994 to 2017 were reviewed along with the present 3 cases. The mean age was 45 years. Most (82%) of the cases were newly diagnosed thyrotoxicosis. There was a preponderance of female gender (71%) and Graves' disease (86%) as the underlying aetiology. Common presenting features included dyspnoea, fatigue and ankle oedema. Atrial fibrillation was reported in 50% of the cases. The echocardiography for almost all cases revealed dilated right atrial and or ventricular chambers with elevated pulmonary artery pressure. The abnormal echocardiographic parameters were resolved in most cases after rendering the patients euthyroid. Right ventricular dysfunction and pulmonary hypertension are not well-recognized complications of thyrotoxicosis. They are life-threatening conditions that can be reversed with early recognition and treatment of thyrotoxicosis. Signs and symptoms of right ventricular dysfunction should be sought in all patients with newly diagnosed thyrotoxicosis, and prompt restoration of euthyroidism is warranted in affected patients before the development of overt right heart failure.

LEARNING POINTS

Thyrotoxicosis is associated with right ventricular dysfunction and pulmonary hypertension apart from left ventricular dysfunction described in typical thyrotoxic cardiomyopathy.Symptoms and signs of right ventricular dysfunction and pulmonary hypertension should be sought in all patients with newly diagnosed thyrotoxicosis.Thyrotoxicosis should be considered in all cases of right ventricular dysfunction or pulmonary hypertension not readily explained by other causes.Prompt restoration of euthyroidism is warranted in patients with thyrotoxicosis complicated by right ventricular dysfunction with or without pulmonary hypertension to allow timely resolution of the abnormal cardiac parameters before development of overt right heart failure.

The function of TRP channels in neutrophil granulocytes

Neutrophil granulocytes are exposed to widely varying microenvironmental conditions when pursuing their physiological or pathophysiological functions such as fighting invading bacteria or infiltrating cancer tissue. Examples for harsh environmental challenges include among others mechanical shear stress during the recruitment from the vasculature or the hypoxic and acidotic conditions within the tumor microenvironment. Chemokine gradients, reactive oxygen species, pressure, matrix elasticity, and temperature can be added to the list of potential challenges. Transient receptor potential (TRP) channels serve as cellular sensors since they respond to many of the abovementioned environmental stimuli. The present review investigates the role of TRP channels in neutrophil granulocytes and their role in regulating and adapting neutrophil function to microenvironmental cues. Following a brief description of neutrophil functions, we provide an overview of the electrophysiological characterization of neutrophilic ion channels. We then summarize the function of individual TRP channels in neutrophil granulocytes with a focus on TRPC6 and TRPM2 channels. We close the review by discussing the impact of the tumor microenvironment of pancreatic ductal adenocarcinoma (PDAC) on neutrophil granulocytes. Since neutrophil infiltration into PDAC tissue contributes to disease progression, we propose neutrophilic TRP channel blockade as a potential therapeutic option.

Endothelial Cell Reactive Oxygen Species and Ca2+ Signaling in Pulmonary Hypertension

Pulmonary hypertension (PH) refers to a disorder characterized by elevated pulmonary arterial pressure, leading to right ventricular overload and eventually right ventricular failure, which results in high morbidity and mortality. PH is associated with heterogeneous etiologies and distinct molecular mechanisms, including abnormal migration and proliferation of endothelial and smooth muscle cells. Although the exact details are not fully elucidated, reactive oxygen species (ROS) have been shown to play a key role in promoting abnormal function in pulmonary arterial smooth muscle and endothelial cells in PH. In endothelial cells, ROS can be generated from sources such as NADPH oxidase and mitochondria, which in turn can serve as signaling molecules in a wide variety of processes including posttranslational modification of proteins involved in Ca²⁺ homeostasis. In this chapter, we discuss the role of ROS in promoting abnormal vasoreactivity and endothelial migration and proliferation in various models of PH. Furthermore, we draw particular attention to the role of ROS-induced increases in intracellular Ca²⁺ concentration in the pathobiology of PH.

Acute Right Ventricular Heart Failure: An Uncommon Case of Thyrotoxicosis

Right ventricular failure can be secondary to right ventricular ischemia, pulmonary or tricuspid valvular disease, myocardial shunts, cardiomyopathy, acute and chronic pulmonary hypertension, myocarditis and pericardial disease and it generally carries a poor prognosis. Thyrotoxicosis is a clinical state resulting from high thyroid hormone action in tissues generally due to high thyroid hormone levels. The association between severe hyperthyroidism and high-output heart failure is well-known. Less widespread is the concept that hyperthyroid patients, irrespective of coexisting diseases and through mechanisms not fully elucidated, are at higher risk for pulmonary hypertension and right heart failure, both reversible with the achievement of euthyroidism and associated with a good prognosis. We describe the case of a 44-year-old woman with right ventricular failure and moderate pulmonary hypertension in the setting of thyrotoxicosis, which resolved rapidly after antithyroid treatment. The potential mechanisms underlying this condition will also be discussed.

STIM2 (Stromal Interaction Molecule 2)-Mediated Increase in Resting Cytosolic Free Ca2+ Concentration Stimulates PASMC Proliferation in Pulmonary Arterial Hypertension

An increase in cytosolic free Ca²⁺ concentration ([Ca²⁺]_cyt) in pulmonary artery smooth muscle cells (PASMCs) triggers pulmonary vasoconstriction and stimulates PASMC proliferation leading to vascular wall thickening. Here, we report that STIM2 (stromal interaction molecule 2), a Ca²⁺ sensor in the sarcoplasmic reticulum membrane, is required for raising the resting [Ca²⁺]_cyt in PASMCs from patients with pulmonary arterial hypertension (PAH) and activating signaling cascades that stimulate PASMC proliferation and inhibit PASMC apoptosis. Downregulation of STIM2 in PAH-PASMCs reduces the resting [Ca²⁺]_cyt, whereas overexpression of STIM2 in normal PASMCs increases the resting [Ca²⁺]_cyt The increased resting [Ca²⁺]_cyt in PAH-PASMCs is associated with enhanced phosphorylation (p) of CREB (cAMP response element-binding protein), STAT3 (signal transducer and activator of transcription 3), and AKT, increased NFAT (nuclear factor of activated T-cell) nuclear translocation, and elevated level of Ki67 (a marker of cell proliferation). Furthermore, the STIM2-associated increase in the resting [Ca²⁺]_cyt also upregulates the antiapoptotic protein Bcl-2 in PAH-PASMCs. Downregulation of STIM2 in PAH-PASMCs with siRNA (1) decreases the level of pCREB, pSTAT3, and pAKT and inhibits NFAT nuclear translocation, thereby attenuating proliferation, and (2) decreases Bcl-2, which leads to an increase of apoptosis. In summary, these data indicate that upregulated STIM2 in PAH-PASMCs, by raising the resting [Ca²⁺]_cyt, contributes to enhancing PASMC proliferation by activating the CREB, STAT3, AKT, and NFAT signaling pathways and stimulating PASMC proliferation. The STIM2-associated increase in the resting [Ca²⁺]_cyt is also involved in upregulating Bcl-2 that makes PAH-PASMCs resistant to apoptosis, and thus plays an important role in sustained pulmonary vasoconstriction and excessive pulmonary vascular remodeling in patients with PAH.

The transient receptor potential vanilloid-3 regulates hypoxia-mediated pulmonary artery smooth muscle cells proliferation via PI3K/AKT signaling pathway

OBJECTVES

Transient receptor potential vanilloid 3 (TRPV3) is a member of the TRP channels family of Ca²⁺ -permeant cation channels. In this study, we aim to investigate the role of TRPV3 in pulmonary vascular remodeling and PASMCs proliferation under hypoxia.

MATERIALS AND METHODS

The expression of TRPV3 was evaluated in patients with pulmonary arterial hypertension (PAH) and hypoxic rats, using hematoxylin and eosin (H&E) and immunohistochemistry. In vitro, MTT assay, flow cytometry, Western blotting and immunofluorescence were performed to investigate the effects of TRPV3 on proliferation of PASMCs.

RESULTS

We found that, in vivo, the expression of TRPV3 was increased in patients with PAH and hypoxic rats. Right ventricular hypertrophy measurements and pulmonary pathomorphology data show that the ratio of the heart weight/tibia length (HW/TL), the right ventricle/left ventricle plus septum (RV/LV+S) and the medial width of the pulmonary artery were increased in chronic hypoxic rats. Moreover, the expression of proliferating cell nuclear antigen (PCNA), Cyclin D, Cyclin E and Cyclin A, phospho-CaMKII (p-CaMKII) were induced by hypoxia. In vitro, we revealed that hypoxia promoted PASMCs viability, increased the expression of PCNA, Cyclin D, Cyclin E, Cyclin A p-CaMKII, made more cells from G₀ /G₁ phase to G₂ /M + S phase, enhanced the microtubule formation, and increased [Ca²⁺ ]_i , which could be suppressed by Ruthenium Red, an inhibitor of TRPV3, and TRPV3 silencing has similar effects. Furthermore, the up-regulated expression of PCNA, Cyclin D, Cyclin E and Cyclin A, the increased number of cells in G₂ /M and S phase, and the enhanced activation and expression of PI3K and AKT proteins induced by hypoxia and in presence of carvacrol (an agonist of TRPV3), was significantly attenuated by incubation of LY 294002, a specific inhibitor for PI3K/AKT.

CONCLUSIONS

These findings suggest that TRPV3 is involved in hypoxia-induced pulmonary vascular remodeling and promotes proliferation of PASMCs and the effect is, at least in part, mediated via the PI3K/AKT pathway.

The Role of Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Lung Architecture Remodeling

Chronic lung disorders, such as pulmonary artery hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma and neonatal bronchopulmonary dysplasia (BPD), are characterized by airway and/or vascular remodeling. Despite differences in the pathology, reactive oxygen species (ROS) have been highlighted as a critical contributor to the initiation and development of airway and vascular remodeling. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox) appear to play a pivotal role in lung signaling, leading to marked changes in pulmonary airway and vascular cell phenotypes, including proliferation, hypertrophy and apoptosis. In this review, we summarized the current literature regarding the role of Nox in the airway and vascular remodeling.

TRPV4: Molecular Conductor of a Diverse Orchestra

Transient receptor potential vanilloid type 4 (TRPV4) is a calcium-permeable nonselective cation channel, originally described in 2000 by research teams led by Schultz (Nat Cell Biol 2: 695-702, 2000) and Liedtke (Cell 103: 525-535, 2000). TRPV4 is now recognized as being a polymodal ionotropic receptor that is activated by a disparate array of stimuli, ranging from hypotonicity to heat and acidic pH. Importantly, this ion channel is constitutively expressed and capable of spontaneous activity in the absence of agonist stimulation, which suggests that it serves important physiological functions, as does its widespread dissemination throughout the body and its capacity to interact with other proteins. Not surprisingly, therefore, it has emerged more recently that TRPV4 fulfills a great number of important physiological roles and that various disease states are attributable to the absence, or abnormal functioning, of this ion channel. Here, we review the known characteristics of this ion channel's structure, localization and function, including its activators, and examine its functional importance in health and disease.

A pilot observational study on magnesium and calcium imbalance in elderly patients with acute aortic dissection

Background

Magnesium (Mg) and calcium (Ca) are the principal essential elements involved in endothelial cell homeostasis. Extracellular changes in the levels of either alter endothelial contraction and dilatation. Consequently Mg and Ca imbalance is associated with a high risk of endothelial dysfunction, the main process observed during acute aortic dissection (AAD); in this clinical condition, which mainly affects elderly men, smooth muscle cell alterations lead to intimal tears, creating a false new lumen in the media of the aorta. AAD patients have a high risk of mortality as a result of late diagnosis because often it is not distinguished from other cardiovascular diseases.

We investigated Mg and Ca total circulating levels and the associated pro-inflammatory mediators in elderly AAD patients, to gain further information on the pathophysiology of this disorder, with a view to suggesting newer and earlier potential biomarkers of AAD.

Results

Total circulating Mg and Ca levels were both lower in AAD patients than controls (p < 0.0001). Using Ca as cut-off, 90% of AAD patients with low Ca (<8.4 mg/dL) came into the type A classification of AAD. Stratifying AAD according to this cut-off, Mg was lower in patients with lower total Ca.

Compared to controls, both type A and B AAD patients had higher levels of all the pro-coagulant and pro-inflammatory mediators analyzed, including sP-sel, D-dimer, TNF-α, IL-6, and CRP (p < 0.05). Dividing types A and B using the Stanford classification, no significant differences were found (p > 0.05) The levels of both ICAM-1 and EN-1 were lower in AAD than in a control group (p < 0.0001 and p < 0.05 respectively).

Conclusions

These findings suggest that low Mg and Ca in AAD elderly patients may contribute to altering normal endothelial physiology and also concur in changing the normal concentrations of different mediators involved in vasodilatation and constriction, associated with AAD onset and severity.

Capsaicin-induced Ca2+ signaling is enhanced via upregulated TRPV1 channels in pulmonary artery smooth muscle cells from patients with idiopathic PAH

Capsaicin is an active component of chili pepper and a pain relief drug. Capsaicin can activate transient receptor potential vanilloid 1 (TRPV1) channels to increase cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt). A rise in [Ca²⁺]_cyt in pulmonary artery smooth muscle cells (PASMCs) is an important stimulus for pulmonary vasoconstriction and vascular remodeling. In this study, we observed that a capsaicin-induced increase in [Ca²⁺]_cyt was significantly enhanced in PASMCs from patients with idiopathic pulmonary arterial hypertension (IPAH) compared with normal PASMCs from healthy donors. In addition, the protein expression level of TRPV1 in IPAH PASMCs was greater than in normal PASMCs. Increasing the temperature from 23 to 43°C, or decreasing the extracellular pH value from 7.4 to 5.9 enhanced capsaicin-induced increases in [Ca²⁺]_cyt; the acidity (pH 5.9)- and heat (43°C)-mediated enhancement of capsaicin-induced [Ca²⁺]_cyt increases were greater in IPAH PASMCs than in normal PASMCs. Decreasing the extracellular osmotic pressure from 310 to 200 mOsmol/l also increased [Ca²⁺]_cyt, and the hypo-osmolarity-induced rise in [Ca²⁺]_cyt was greater in IPAH PASMCs than in healthy PASMCs. Inhibition of TRPV1 (with 5'-IRTX or capsazepine) or knockdown of TRPV1 (with short hairpin RNA) attenuated capsaicin-, acidity-, and osmotic stretch-mediated [Ca²⁺]_cyt increases in IPAH PASMCs. Capsaicin induced phosphorylation of CREB by raising [Ca²⁺]_cyt, and capsaicin-induced CREB phosphorylation were significantly enhanced in IPAH PASMCs compared with normal PASMCs. Pharmacological inhibition and knockdown of TRPV1 attenuated IPAH PASMC proliferation. Taken together, the capsaicin-mediated [Ca²⁺]_cyt increase due to upregulated TRPV1 may be a critical pathogenic mechanism that contributes to augmented Ca²⁺ influx and excessive PASMC proliferation in patients with IPAH.

Pulmonary hypertension in thyroid diseases

The influence of thyroid hormones on cardiovascular system is well established. Thyroid diseases can effectively enhance the alteration on cardiovascular system by influencing chronotropic and inotropic actions of the heart; altering the strength and the speed of contraction, the speed of relaxation, the duration of the potential of action, and the duration of the refractory period and atrio-ventricular conduction time; modulating circulation and peripheral vascular beds. One of the more intriguing insights in the connection between thyroid diseases and cardiovascular alterations is related to the evaluation of the influence of thyroid hormones on pulmonary vascular beds. Literature reported several studies regarding the association between both hypothyroidism and hyperthyroidism and the occurrence of increased vascular pulmonary arterial pressure. Nevertheless, the pathogenetic mechanisms able to explain such relationship are not fully understood. Many doubts still persist in the comprehension of the mechanisms of pulmonary hypertension in thyroid diseases. The aim of this review was to provide possible explanation about the possible interaction between pulmonary vascular beds and thyroid function in order to evaluate the possibility of novel perspectives in the general management of patients suffering from thyroid and cardiovascular diseases.

Is CHA2DS2-VASc appropriate for hyperthyroid patients with atrial fibrillation? Implications of adding a transesophageal echocardiography evaluation

BACKGROUND

Anticoagulation remains a controversial issue among hyperthyroid patients with atrial fibrillation (AF). We aimed to evaluate the prevalence of the thrombogenic milieu (TM), detected using transesophageal echocardiography (TEE), among patients with AF related to hyperthyroidism, and to correlate these findings with the clinical embolic risk classification (CHA₂DS₂-VASc).

METHODS

CHA₂DS₂-VASc score, thyroid hormonal status, time since hyperthyroidism diagnosis, transthoracic echocardiography (TTE) and TEE were assessed in 47 consecutive patients aged between 18 and 65years with AF related to hyperthyroidism. The following TEE parameters defined TM: dense spontaneous echo contrast, thrombi, or left atrial appendage (LAA) blood flow velocities <0.20m/s. Non-classic TM was defined as non-dense SEC plus LAA flow velocity 0.20-0.40m/s.

RESULTS

Pulmonary hypertension was present in 39/47 (81.4%) and TM in 22/47 (46.8%) patients. Despite a low CHA₂DS₂-VASc score of 0/1, 10 of 19 (52.6%) patients had a TM, whereas 16 of 28 (57.1%) patients with score ≥2 had none. The probability of having a TM did not correlate with CHA₂DS₂-VASc scores. On regression binary analysis, hyperthyroidism diagnosed more than 12months previous was independently associated with non-classic TM (p=0.031).

CONCLUSION

Among patients younger than 65years of age with AF related to hyperthyroidism, pulmonary hypertension and TM on TEE were highly prevalent. There was no association between CHA₂DS₂-VASc with TEE markers of TM. Thyroid status, especially longer duration of hyperthyroidism might influence thrombogenic abnormalities. TEE adds useful information that may change antithrombotic therapy if otherwise guided solely by clinical risk classification.

The Critical Role of Pulmonary Arterial Compliance in Pulmonary Hypertension

The normal pulmonary circulation is a low-pressure, high-compliance system. Pulmonary arterial compliance decreases in the presence of pulmonary hypertension because of increased extracellular matrix/collagen deposition in the pulmonary arteries. Loss of pulmonary arterial compliance has been consistently shown to be a predictor of increased mortality in patients with pulmonary hypertension, even more so than pulmonary vascular resistance in some studies. Decreased pulmonary arterial compliance causes premature reflection of waves from the distal pulmonary vasculature, leading to increased pulsatile right ventricular afterload and eventually right ventricular failure. Evidence suggests that decreased pulmonary arterial compliance is a cause rather than a consequence of distal small vessel proliferative vasculopathy. Pulmonary arterial compliance decreases early in the disease process even when pulmonary artery pressure and pulmonary vascular resistance are normal, potentially enabling early diagnosis of pulmonary vascular disease, especially in high-risk populations. With the recognition of the prognostic importance of pulmonary arterial compliance, its impact on right ventricular function, and its contributory role in the development and progression of distal small-vessel proliferative vasculopathy, pulmonary arterial compliance is an attractive target for the treatment of pulmonary hypertension.

Pathogenic role of calcium-sensing receptors in the development and progression of pulmonary hypertension

An increase in cytosolic free Ca(2+) concentration ([Ca(2+)]cyt) in pulmonary arterial smooth muscle cells (PASMC) is a major trigger for pulmonary vasoconstriction and a critical stimulation for PASMC proliferation and migration. Previously, we demonstrated that expression and function of calcium sensing receptors (CaSR) in PASMC from patients with idiopathic pulmonary arterial hypertension (IPAH) and animals with experimental pulmonary hypertension (PH) were greater than in PASMC from normal subjects and control animals. However, the mechanisms by which CaSR triggers Ca(2+) influx in PASMC and the implication of CaSR in the development of PH remain elusive. Here, we report that CaSR functionally interacts with TRPC6 to regulate [Ca(2+)]cyt in PASMC. Downregulation of CaSR or TRPC6 with siRNA inhibited Ca(2+)-induced [Ca(2+)]cyt increase in IPAH-PASMC (in which CaSR is upregulated), whereas overexpression of CaSR or TRPC6 enhanced Ca(2+)-induced [Ca(2+)]cyt increase in normal PASMC (in which CaSR expression level is low). The upregulated CaSR in IPAH-PASMC was also associated with enhanced Akt phosphorylation, whereas blockade of CaSR in IPAH-PASMC attenuated cell proliferation. In in vivo experiments, deletion of the CaSR gene in mice (casr(-/-)) significantly inhibited the development and progression of experimental PH and markedly attenuated acute hypoxia-induced pulmonary vasoconstriction. These data indicate that functional interaction of upregulated CaSR and upregulated TRPC6 in PASMC from IPAH patients and animals with experimental PH may play an important role in the development and progression of sustained pulmonary vasoconstriction and pulmonary vascular remodeling. Blockade or downregulation of CaSR and/or TRPC6 with siRNA or miRNA may be a novel therapeutic strategy to develop new drugs for patients with pulmonary arterial hypertension.

Effect of hypoxia on TRPV1 and TRPV4 channels in rat pulmonary arterial smooth muscle cells

Transient receptor potential (TRP) channels of the vanilloid subfamily, mainly TRPV1 and TRPV4, are expressed in pulmonary artery smooth muscle cells (PASMC) and implicated in the remodeling of pulmonary artery, a landmark of pulmonary hypertension (PH). Among a variety of PH subtypes, PH of group 3 are mostly related to a prolonged hypoxia exposure occurring in a variety of chronic lung diseases. In the present study, we thus investigated the role of hypoxia on TRPV1 and TRPV4 channels independently of the increased pulmonary arterial pressure that occurs during PH. We isolated PASMC from normoxic rat and cultured these cells under in vitro hypoxia. Using microspectrofluorimetry and the patch-clamp technique, we showed that hypoxia (1 % O2 for 48 h) significantly increased stretch- and TRPV4-induced calcium responses. qRT-PCR, Western blotting, and immunostaining experiments revealed that the expression of TRPV1 and TRPV4 was not enhanced under hypoxic conditions, but we observed a membrane translocation of TRPV1. Furthermore, hypoxia induced a reorganization of the F-actin cytoskeleton, the tubulin, and intermediate filament networks (immunostaining experiments), associated with an enhanced TRPV1- and TRPV4-induced migratory response (wound-healing assay). Finally, as assessed by immunostaining, exposure to in vitro hypoxia elicited a significant increase in NFATc4 nuclear localization. Cyclosporin A and BAPTA-AM inhibited NFATc4 translocation, indicating the activation of the Ca(2+)/calcineurin/NFAT pathway. In conclusion, these data point out the effect of hypoxia on TRPV1 and TRPV4 channels in rat PASMC, suggesting that these channels can act as direct signal transducers in the pathophysiology of PH.

Hemodynamic shear stress via ROS modulates PCSK9 expression in human vascular endothelial and smooth muscle cells and along the mouse aorta

AIMS

To investigate a possible link between hemodynamic shear stress, reactive oxygen species (ROS) generation, and proprotein convertase subtilisin/kexin type 9 (PCSK9) expression.

RESULTS

Using a parallel-plate flow chamber, we observed that PCSK9 expression in vascular smooth muscle cells (SMCs) and endothelial cells (ECs) reached maximal value at low shear stress (3-6 dynes/cm(2)), and then began to decline with an increase in shear stress. PCSK9 expression increased when cells were treated with lipopolysaccharide. PCSK9 expression was always greater in SMCs than in ECs. ROS generation followed the same pattern as PCSK9 expression. Aortic branching and aorta-iliac bifurcation regions of mouse aorta that express low shear stress were also found to have greater PCSK9 expression (vs. other regions). To determine a relationship between ROS and PCSK9 expression, ECs and SMCs were treated with ROS inhibitors diphenylene-iodonium chloride and apocynin, and both markedly reduced PCSK9 expression. Relationship between PCSK9 and ROS was further studied in p47(phox) and gp91(phox) knockout mice; both mice strains revealed low PCSK9 levels in serum and mRNA levels in aorta-iliac bifurcation regions (vs. wild-type mice). Other studies showed that ROS and NF-κB activation plays a bridging role in PCSK9 expression via lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1).

INNOVATION

Low shear stress induces PCSK9 expression, which is mediated by NADPH oxidase-dependent ROS production.

CONCLUSIONS

This study provides evidence that low shear stress enhances PCSK9 expression in concert with ROS generation in vascular ECs and SMCs. ROS seem to regulate PCSK9 expression. We propose that PCSK9-ROS interaction may be important in the development of atherosclerosis in arterial channels with low shear stress.