Pulmonary vascular remodeling: a target for therapeutic intervention in pulmonary hypertension

Novel echocardiographic parameters in pulmonary hypertension assessment and the relationship between echocardiography and 6-minute walking test

Pulmonary artery stiffness (PAS) has been shown to be related to pulmonary artery pressure in patients with pulmonary artery hypertension (PAH). The aim of this study was to determine the correlation between functional capacity and echocardiographic indices of PAS in patients with PAH. This cross-sectional study was performed on patients with PAH who were confirmed by right heart catheterization and referred to Imam Reza PAH clinic for routine follow-up between November 2019 and January 2020. All patients underwent echocardiography and the maximum Doppler frequency shift, pulmonary acceleration time, peak velocity of the pulmonary flow, and velocity time integral, as well as PAS, were measured. All patients performed a 6-minute walk test. Fifty patients with a mean age of 41.90 ± 14.73 years old participated in this study. The majority of the patients were female (74%). The most common cause of PAH was idiopathic (74%). There was a significant correlation between PAS and pulmonary artery systolic pressure (r = 0.302, P = .041), second pulmonary valve pulse Doppler velocity (V2) (r = -0.461, P = .003), time from onset of pulmonary flow ejection to V2/first pulmonary valve pulse Doppler velocity (r = -0.311, P = .037) and Z3 ratio (r = -0.346, P = .023). There was no significant correlation between PAS and 6-minute walk test, pulmonary vascular resistance, and tricuspid annular plane systolic excursion (P > .05). There was a significant correlation between V2 and pulmonary vascular resistance (r = 0.359, P = .049). PAS and first pulmonary valve pulse Doppler velocity are simple, noninvasive, available tools for the evaluation of pulmonary vascular beds and diagnosis of presymptomatic clinical status in patients with PAH.

The association of SPARC with hypertension and its function in endothelial-dependent relaxation

BACKGROUND AND AIMS

Secreted protein acidic and rich in cysteine (SPARC) is involved in the pathological processes of many metabolic diseases. However, studies on the relevance of SPARC to hypertension and its involvement in endothelial function are scarce. In this study, we aim to explore the relevance of SPARC to hypertension and investigate its role in endothelium-dependent relaxation (EDR).

METHODS

110 patients who met the criteria were recruited as participants. Serum SPARC concentrations were determined by Luminex assay. The correlation between SPARC levels and hypertension was analyzed. After treatment with SPARC ex vivo or in vivo, endothelial-dependent relaxation (EDR) was measured by wire myography. Western blotting was performed to detect the expression of proteins relevant to endothelial function.

RESULTS

Our results showed that serum SPARC levels were significantly higher in the hypertensive group and were positively associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP). Functional results demonstrated that SPARC dramatically impaired EDR and induced the excess production of reactive oxygen species (ROS) in endothelial cells. Further experimental results confirmed that SPARC reduced angiotensin-converting enzyme 2 (ACE2) expression and ACE2 overexpression or activation completely abolished the impairing effect of SPARC on endothelial function.

CONCLUSIONS

The present study reveals the correlation between elevated SPARC and hypertension and confirms its adverse effect on endothelial function, helping establish a comprehensive understanding of hypertension-related endothelial dysfunction in a new scope.

Mitochondrial hyperfusion induces metabolic remodeling in lung endothelial cells by modifying the activities of electron transport chain complexes I and III

OBJECTIVE

Pulmonary hypertension (PH) is a progressive disease with vascular remodeling as a critical structural alteration. We have previously shown that metabolic reprogramming is an early initiating mechanism in animal models of PH. This metabolic dysregulation has been linked to remodeling the mitochondrial network to favor fission. However, whether the mitochondrial fission/fusion balance underlies the metabolic reprogramming found early in PH development is unknown.

METHODS

Utilizing a rat early model of PH, in conjunction with cultured pulmonary endothelial cells (PECs), we utilized metabolic flux assays, Seahorse Bioassays, measurements of electron transport chain (ETC) complex activity, fluorescent microscopy, and molecular approaches to investigate the link between the disruption of mitochondrial dynamics and the early metabolic changes that occur in PH.

RESULTS

We observed increased fusion mediators, including Mfn1, Mfn2, and Opa1, and unchanged fission mediators, including Drp1 and Fis1, in a two-week monocrotaline-induced PH animal model (early-stage PH). We were able to establish a connection between increases in fusion mediator Mfn1 and metabolic reprogramming. Using an adenoviral expression system to enhance Mfn1 levels in pulmonary endothelial cells and utilizing 13C-glucose labeled substrate, we found increased production of 13C lactate and decreased TCA cycle metabolites, revealing a Warburg phenotype. The use of a 13C5-glutamine substrate showed evidence that hyperfusion also induces oxidative carboxylation. The increase in glycolysis was linked to increased hypoxia-inducible factor 1α (HIF-1α) protein levels secondary to the disruption of cellular bioenergetics and higher levels of mitochondrial reactive oxygen species (mt-ROS). The elevation in mt-ROS correlated with attenuated ETC complexes I and III activities. Utilizing a mitochondrial-targeted antioxidant to suppress mt-ROS, limited HIF-1α protein levels, which reduced cellular glycolysis and reestablished mitochondrial membrane potential.

CONCLUSIONS

Our data connects mitochondrial fusion-mediated mt-ROS to the Warburg phenotype in early-stage PH development.

RGS5 as a Biomarker of Pericytes, Involvement in Vascular Remodeling and Pulmonary Arterial Hypertension

Introduction

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a sustained rise in mean pulmonary artery pressure. Pulmonary vascular remodeling serves an important role in PAH. Identifying a key driver gene to regulate vascular remodeling of the pulmonary microvasculature is critical for PAH management.

Methods

Differentially expressed genes were identified using the Gene Expression Omnibus (GEO) GSE117261, GSE48149, GSE113439, GSE53408 and GSE16947 datasets. A co-expression network was constructed using weighted gene co-expression network analysis. Novel and key signatures of PAH were screened using four algorithms, including weighted gene co-expression network analysis, GEO2R analysis, support vector machines recursive feature elimination and robust rank aggregation rank analysis. Regulator of G-protein signaling 5 (RGS5), a pro-apoptotic/anti-proliferative protein, which regulate arterial tone and blood pressure in vascular smooth muscle cells. The expression of RGS5 was determined using reverse transcription-quantitative PCR (RT-qPCR) in PAH and normal mice. The location of RGS5 and pericytes was detected using immunofluorescence.

Results

Compared with that in the normal group, RGS5 expression was upregulated in the PAH group based on GEO and RT-qPCR analyses. RGS5 expression in single cells was enriched in pericytes in single-cell RNA sequencing analysis. RGS5 co-localization with pericytes was detected in the pulmonary microvasculature of PAH.

Conclusion

RGS5 regulates vascular remodeling of the pulmonary microvasculature and the occurrence of PAH through pericytes, which has provided novel ideas and strategies regarding the occurrence and innovative treatment of PAH.

Downregulation of PDCD4 through STAT3/ATF6/autophagy mediates MIF-induced PASMCs proliferation/migration and vascular remodeling

To address the molecular mechanisms underlying macrophage migration inhibitory factor (MIF) induced pulmonary artery smooth muscle cells (PASMCs) proliferation, migration and vascular remodeling in pulmonary hypertension (PH), primary cultured rat PASMCs and monocrotaline (MCT)-induced rats with PH were applied in the present study. The results showed that MIF increased signal transducer and activator of transcription 3 (STAT3) phosphorylation, and then stimulated activating transcription factor 6 (ATF6) activation, subsequently triggered autophagy activation, which further led to programmed cell death factor 4 (PDCD4) lysosomal degradation, and eventually promoted PASMCs proliferation/migration. In lung tissues of MCT rats, MIF protein expression was elevated, phosphorylation of STAT3 and activation of ATF6 were increased, activation of autophagy was evident, and reduction of PDCD4 was observed. Intervention with MIF inhibitor 4-Iodo-6-phenylpyrimidine (4-IPP), ATF6 blocker melatonin or autophagy inhibitor chloroquine, confirmed the in vitro interaction among MIF, STAT3, ATF6, autophagy and PDCD4 in MCT induced rats with PH. Targeting MIF/STAT3/ATF6/autophagy/PDCD4 axis effectively prevented the development of PH by suppressing PASMCs proliferation and vascular remodeling. In conclusions, we demonstrate that MIF activates the STAT3/ATF6/autophagy cascade and then degrades PDCD4 leading to PASMCs proliferation/migration and pulmonary vascular remodeling, suggesting that intervention this axis might have potential value in management of PH.

Peroxisome proliferator-activated receptor gamma (PPARγ) activation: a potential treatment for ascites syndrome in broiler chickens

Ascites (serous fluid accumulation in the abdominal cavity) has been observed worldwide in fast growing broilers. Pulmonary vascular remodeling is an important pathological feature of broiler ascites syndrome. Peroxisome proliferators-activated receptor gamma (PPARγ) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) are expressed in pulmonary vascular endothelial cells and vascular smooth muscle cells (VSMC) where they participate in the regulation of normal pulmonary vascular function. The objective of the present study was to investigate the effects of omega-3 fatty acids (found in fish oil) and pioglitazone (PIO) as natural and synthetic PPARγ ligands supplementation on PPARγ and PGC-1α expression in the prevention of pulmonary arterial hypertension (PAH) syndrome in broiler chickens. The experiment was conducted with 4 treatment groups: 1) negative control, normal temperature conditions with basal diet; 2) positive control, low-temperature conditions with basal diet; 3) positive control + 10 mg PIO/kg of weight/d and 4) positive control + 1% FO. Each treatment had 5 replicates. Ascites heart index (RV/TV) was significantly (P < 0.05) reduced in chickens receiving FO (0.20) and PIO (0.21) compared to the positive control group (0.26). The addition of PIO in broilers under cold-induced ascites significantly increased the expression of PPARγ (9.44) and PGC-1α (5.81) genes in lung tissue compared to the negative control group (1.03, P < 0.05). Proliferative indexes of VSMC in pulmonary arteries such as PMT, PIT, and percentage wall thickness were significantly elevated in positive control group, indicating that pulmonary vascular remodeling occurred following VSMC proliferation in ascites. The vessel internal diameter was increased in FO and PIO groups. Based on these results, activation and expression of PPARγ and PGC-1α genes as a critical regulator of pulmonary artery smooth muscle cell using ligands, especially PIO, can be effective in reducing the incidence of PAH in broiler chickens.

Human pulmonary microvascular endothelial cell DDAH1-mediated nitric oxide production promotes pulmonary smooth muscle cell apoptosis in co-culture

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease in preterm infants, and pulmonary hypertension (PH) develops in 25%-40% of patients with BPD, increasing morbidity and mortality. BPD-PH is characterized by vasoconstriction and vascular remodeling. Nitric oxide (NO) is a pulmonary vasodilator and apoptotic mediator made in the pulmonary endothelium by NO synthase (eNOS). Asymmetric dimethylarginine (ADMA) is an endogenous eNOS inhibitor, primarily metabolized by dimethylarginine dimethylaminohydrolase-1 (DDAH1). Our hypothesis is that DDAH1 knockdown in human pulmonary microvascular endothelial cells (hPMVEC) will result in lower NO production, decreased apoptosis, and greater proliferation of human pulmonary arterial smooth muscle cells (hPASMC), whereas DDAH1 overexpression will have the opposite effect. hPMVECs were transfected with small interfering RNA targeting DDAH1 (siDDAH1)/scramble or adenoviral vector containing DDAH1 (AdDDAH1)/AdGFP for 24 h and co-cultured for 24 h with hPASMC. Analyses included Western blot for cleaved and total caspase-3, caspase-8, caspase-9, β-actin; trypan blue exclusion for viable cell numbers; terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL); and BrdU incorporation. Small interfering RNA targeting DDAH1 (siDDAH1) transfected into hPMVEC resulted in lower media nitrites, cleaved caspase-3 and caspase-8 protein expression, and TUNEL staining; and greater viable cell numbers and BrdU incorporation in co-cultured hPASMC. Adenoviral-mediated transfection of the DDAH1 gene (AdDDAH1) into hPMVEC resulted in greater cleaved caspase-3 and caspase-8 protein expression and lower viable cell numbers in co-cultured hPASMC. Partial recovery of hPASMC viable cell numbers after AdDDAH1-hPMVEC transfection was observed when media were treated with hemoglobin to sequester NO. In conclusion, hPMVEC-DDAH1-mediated NO production positively regulates hPASMC apoptosis, which may prevent/attenuate aberrant pulmonary vascular proliferation/remodeling in BPD-PH.NEW & NOTEWORTHY BPD-PH is characterized by vascular remodeling. NO is an apoptotic mediator made in the pulmonary endothelium by eNOS. ADMA is an endogenous eNOS inhibitor metabolized by DDAH1. EC-DDAH1 overexpression resulted in greater cleaved caspase-3 and caspase-8 protein expression and lower viable cell numbers in co-cultured SMC. After NO sequestration, SMC viable cell numbers partially recovered despite EC-DDAH1 overexpression. EC-DDAH1-mediated NO production positively regulates SMC apoptosis, which may prevent/attenuate aberrant pulmonary vascular proliferation/remodeling in BPD-PH.

Sirtuin3 confers protection against acute pulmonary embolism through anti-inflammation, and anti-oxidative stress, and anti-apoptosis properties: participation of the AMP-activated protein kinase/mammalian target of rapamycin pathway

An increasing number of studies have suggested that oxidative stress and inflammation play momentous roles in acute pulmonary embolism (APE). Honokiol, a bioactive biphenolic phytochemical substance, is known for its strong anti-oxidative and anti-inflammatory effects, and it served as an activator of sirtuin3 (SIRT3) in the present study. The purposes of the study were to explore the effects of honokiol on APE rats and investigate whether the function of honokiol is mediated by SIRT3 activation. In the study, the rats received a right femoral vein injection of dextran gel G-50 particles (12 mg/kg) to establish the APE model and were subsequently administered honokiol and/or a selective SIRT3 inhibitor 3-(1H-1,2,3-triazol-4-yl)pyridine (3-TYP; 5 mg/kg) intraperitoneally. The results showed that SIRT3 activation by honokiol attenuated the loss in lung function, ameliorated the inflammatory response and oxidative damage, and inhibited apoptosis in lung tissues of the rats with APE but that this was reversed by 3-TYP. In addition, we found that the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway might be activated by honokiol but restrained by 3-TYP. These results indicated that honokiol was capable of suppressing the adverse effects of APE and that this was diminished by SIRT3 suppression, implying that activation of SIRT3 might serve as a therapeutic method for APE.

Myeloid-derived suppressor cells and pulmonary hypertension

Pulmonary hypertension (PH) is a chronic pulmonary vascular disorder characterized by an increase in pulmonary vascular resistance and pulmonary arterial pressure. The detailed molecular mechanisms remain unclear. In recent decades, increasing evidence shows that altered immune microenvironment, comprised of immune cells, mesenchymal cells, extra-cellular matrix and signaling molecules, might induce the development of PH. Myeloid-derived suppressor cells (MDSCs) have been proposed over 30 years, and the functional importance of MDSCs in the immune system is appreciated recently. MDSCs are a heterogeneous group of cells that expand during cancer, chronic inflammation and infection, which have a remarkable ability to suppress T-cell responses and may exacerbate the development of diseases. Thus, targeting MDSCs has become a novel strategy to overcome immune evasion, especially in tumor immunotherapy. Nowadays, severe PH is accepted as a cancer-like disease, and MDSCs are closely related to the development and prognosis of PH. Here, we review the relationship between MDSCs and PH with respect to immune cells, cytokines, chemokines and metabolism, hoping that the key therapeutic targets of MDSCs can be identified in the treatment of PH, especially in severe PH.

Effects of Elexacaftor/Tezacaftor/Ivacaftor on Cardiorespiratory Polygraphy Parameters and Respiratory Muscle Strength in Cystic Fibrosis Patients with Severe Lung Disease

BACKGROUND

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators represent targeted therapies directly acting on the CFTR channel. The triple therapy Elexacaftor/Tezacaftor/Ivacaftor (ELX/TEZ/IVA) has been demonstrated to improve lung function and quality of life in cystic fibrosis (CF) patients. However, the effects of ELX/TEZ/IVA on sleep-disordered breathing (SDB) and respiratory muscle strength are poorly studied. The aim of this study was to assess the effects of ELX/TEZ/IVA in patients with CF and severe lung disease on cardiorespiratory polygraphy parameters, maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) measures.

METHODS

patients with CF aged ≥ 12 who started treatment in a compassionate use program were retrospectively studied through the evaluation of nocturnal cardiorespiratory polygraphy parameters, MIP and MEP; and six-minute walk test (6MWT) at baseline and at months 3, 6, and 12 of treatment.

RESULTS

Nine patients (mean age 30.3 ± 6.5 years) with severe CF (mean baseline ppFEV1 34.6 ± 5.1%) were evaluated. A significant improvement in nocturnal oxygenation measured by mean SpO2 (92.4 vs. 96.4%, p < 0.05), time spent with SpO2 ≤ 90% (-12.6, -14.6, -15.2 min from baseline at months 3, 6, and 12, respectively, p < 0.05), and respiratory rate (RR) was shown, at month 12 and across the time points compared with baseline, as well as in respiratory muscle strength, although only the change in MEP was significant.

CONCLUSIONS

We provide further evidence on the efficacy of the CFTR modulators ELX/TEZ/IVA, adding information about their effect on the respiratory muscles' performance and cardiorespiratory polygraphy parameters in CF patients with severe lung disease.

Apolipoprotein A5 ameliorates MCT induced pulmonary hypertension by inhibiting ER stress in a GRP78 dependent mechanism

Background

Pulmonary arterial hypertension (PAH) is a chronic, progressive lung vascular disease accompanied by elevated pulmonary vascular pressure and resistance, and it is characterized by increased pulmonary artery smooth muscle cell (PASMC) proliferation. Apolipoprotein A5 (ApoA5) improves monocrotaline (MCT)-induced PAH and right heart failure; however, the underlying mechanism remains unknown. Here we speculate that ApoA5 has a protective effect in pulmonary vessels and aim to evaluate the mechanism.

Methods

ApoA5 is overexpressed in an MCT-induced PAH animal model and platelet-derived growth factor (PDGF)-BB-induced proliferating PASMCs. Lung vasculature remodeling was measured by immunostaining, and PASMC proliferation was determined by cell counting kit‐8 and 5‐ethynyl‐2'‐deoxyuridine5‐ethynyl‐2'‐deoxyuridine incorporation assays. Coimmunoprecipitation-mass spectrometry was used to investigate the probable mechanism. Next, its role and mechanism were further verified by knockdown studies.

Results

ApoA5 level was decreased in MCT-induced PAH lung as well as PASMCs. Overexpression of ApoA5 could help to inhibit the remodeling of pulmonary artery smooth muscle. ApoA5 could inhibit PDGF-BB-induced PASMC proliferation and endoplasmic reticulum stress by increasing the expression of glucose-regulated protein 78 (GRP78). After knocking down GRP78, the protecting effects of ApoA5 have been blocked.

Conclusion

ApoA5 ameliorates MCT-induced PAH by inhibiting endoplasmic reticulum stress in a GRP78 dependent mechanism.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-022-01680-4.

SPARC, a Novel Regulator of Vascular Cell Function in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening disease, characterized by excessive pulmonary vascular remodeling, leading to elevated pulmonary arterial pressure and right heart hypertrophy. PH can be caused by chronic hypoxia, leading to hyper-proliferation of pulmonary arterial smooth muscle cells (PASMCs) and apoptosis-resistant pulmonary microvascular endothelial cells (PMVECs). On reexposure to normoxia, chronic hypoxia-induced PH in mice is reversible. In this study, the authors aim to identify novel candidate genes involved in pulmonary vascular remodeling specifically in the pulmonary vasculature.

METHODS

After microarray analysis, the authors assessed the role of SPARC (secreted protein acidic and rich in cysteine) in PH using lung tissue from idiopathic pulmonary arterial hypertension (IPAH) patients, as well as from chronically hypoxic mice. In vitro studies were conducted in primary human PASMCs and PMVECs. In vivo function of SPARC was proven in chronic hypoxia-induced PH in mice by using an adeno-associated virus-mediated Sparc knockdown approach.

RESULTS

C57BL/6J mice were exposed to normoxia, chronic hypoxia, or chronic hypoxia with subsequent reexposure to normoxia for different time points. Microarray analysis of the pulmonary vascular compartment after laser microdissection identified Sparc as one of the genes downregulated at all reoxygenation time points investigated. Intriguingly, SPARC was vice versa upregulated in lungs during development of hypoxia-induced PH in mice as well as in IPAH, although SPARC plasma levels were not elevated in PH. TGF-β1 (transforming growth factor β1) or HIF2A (hypoxia-inducible factor 2A) signaling pathways induced SPARC expression in human PASMCs. In loss of function studies, SPARC silencing enhanced apoptosis and reduced proliferation. In gain of function studies, elevated SPARC levels induced PASMCs, but not PMVECs, proliferation. Coculture and conditioned medium experiments revealed that PMVECs-secreted SPARC acts as a paracrine factor triggering PASMCs proliferation. Contrary to the authors' expectations, in vivo congenital Sparc knockout mice were not protected from hypoxia-induced PH, most probably because of counter-regulatory proproliferative signaling. However, adeno-associated virus-mediated Sparc knockdown in adult mice significantly improved hemodynamic and cardiac function in PH mice.

CONCLUSIONS

This study provides evidence for the involvement of SPARC in the pathogenesis of human PH and chronic hypoxia-induced PH in mice, most likely by affecting vascular cell function.

Research Progress on Pulmonary Arterial Hypertension and the Role of the Angiotensin Converting Enzyme 2-Angiotensin-(1-7)-Mas Axis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex aetiology and high mortality. Functional and structural changes in the small pulmonary arteries lead to elevated pulmonary arterial pressure, resulting in right heart failure. The pathobiology of PAH is not fully understood, and novel treatment targets in PAH are desperately needed. The renin-angiotensin system is critical for maintaining homeostasis of the cardiovascular system. The system consists of the angiotensin converting enzyme (ACE)-angiotensin (Ang) II-angiotensin type 1 receptor (AT₁R) axis and the ACE2-Ang-(1-7)-Mas receptor axis. The former, the ACE-Ang II-AT₁R axis, is involved in vasoconstrictive and hypertensive actions along with cardiac and vascular remodelling. The latter, the ACE2-Ang-(1-7)-Mas axis, generally mediates counterbalancing effects against those mediated by the ACE-Ang II-AT₁R axis. Based on established functions, the ACE2-Ang-(1-7)-Mas axis may represent a novel target for the treatment of PAH. This review focuses on recent advances in pulmonary circulation science and the role of the ACE2-Ang-(1-7)-Mas axis in PAH.

Effects of Sodium-Glucose Co-Transporter 2 Inhibitors on Vascular Cell Function and Arterial Remodeling

Cardiovascular disease is the leading cause of morbidity and mortality in diabetes. Recent clinical studies indicate that sodium-glucose co-transporter 2 (SGLT2) inhibitors improve cardiovascular outcomes in patients with diabetes. The mechanism underlying the beneficial effect of SGLT2 inhibitors is not completely clear but may involve direct actions on vascular cells. SGLT2 inhibitors increase the bioavailability of endothelium-derived nitric oxide and thereby restore endothelium-dependent vasodilation in diabetes. In addition, SGLT2 inhibitors favorably regulate the proliferation, migration, differentiation, survival, and senescence of endothelial cells (ECs). Moreover, they exert potent antioxidant and anti-inflammatory effects in ECs. SGLT2 inhibitors also inhibit the contraction of vascular smooth muscle cells and block the proliferation and migration of these cells. Furthermore, studies demonstrate that SGLT2 inhibitors prevent postangioplasty restenosis, maladaptive remodeling of the vasculature in pulmonary arterial hypertension, the formation of abdominal aortic aneurysms, and the acceleration of arterial stiffness in diabetes. However, the role of SGLT2 in mediating the vascular actions of these drugs remains to be established as important off-target effects of SGLT2 inhibitors have been identified. Future studies distinguishing drug- versus class-specific effects may optimize the selection of specific SGLT2 inhibitors in patients with distinct cardiovascular pathologies.

A 1H NMR spectroscopic metabolomic study of the protective effects of irbesartan in a rat model of chronic mountain sickness

Chronic mountain sickness (CMS) is a significant pathology in most high-altitude regions globally, affecting the cardiopulmonary system and its mechanism is largely unknown. A metabonomic approach using ¹H nuclear magnetic resonance spectroscopy allows for detecting differential metabolites, which provides a global view and mechanisms during CMS development. In this study, we simulated a high-altitude environment to establish a rat model of CMS. Irbesartan was administered to CMS rats at three doses (6.75, 13.5, and 27 mg/kg) once a day for 15 days. HE staining and transmission electron microscopy were used to evaluate the effect of changes on the lung. Based on ¹H NMR spectra obtained from serum samples, partial least squares-discriminant analysis (PLS-DA) and its variant orthogonal PLS-DA (OPLS-DA) models were applied to distinguish the different groups. Histopathological sections showed that the alveolar structure was abnormal, inflammatory infiltration occurred in CMS rats, and CMS induced notable metabolic disorder according to the ¹H NMR result. However, irbesartan reversed the imbalanced metabolites via energy metabolism, amino acid metabolism, and taurine metabolism pathways, and its effect was also confirmed by the general signs and morphology of the lung. The results revealed that irbesartan as an effective therapeutic agent to improve CMS is warranted.

Irbesartan ameliorates chronic mountain sickness in a rat model via the cholesterol metabolism: An iTRAQ -based proteomics analysis

OBJECTIVE

To study the effects of irbesartan on pulmonary artery lesions in a rat model with chronic mountain sickness (CMS) and identify the biomarkers involved.

METHODS

In this study, we used a rat model of CMS to evaluate the therapeutic effect of irbesartan by measuring pulmonary artery pressure and evaluating the histopathology of the pulmonary artery. We also used proteomics technology to identify differentially expressed proteins (DEPs) in the serum and performed bioinformatics analysis. Results were then verified by enzyme linked immunosorbent assay (ELISA) and immunohistochemistry (IHC).

RESULTS

Irbesartan treatment induced a significant decrease (P < 0.05) in the pulmonary artery pressure of CMS rats. Histopathological and electron microscope further confirmed that high altitude hypoxia induced changes in the structure of the pulmonary artery tissue and caused ultrastructural lesions. Proteomics analysis identified 40 DEPs; bioinformatics analysis further revealed that the cholesterol metabolism pathway plays a crucial role in the occurrence of CMS. ELISA and IHC verified that several DEPs (Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1) represent critical biological markers in pulmonary artery disease caused by CMS.

CONCLUSIONS

Irbesartan significantly improved pulmonary artery damage in a rat model of CMS possibly by impacting on the cholesterol metabolism pathway and by reducing damage to vascular endothelial cells. Irbesartan also inhibited the expression levels of IGF-1, Profilin1 and Col1a1 to relieve pulmonary artery pressure and improve lung function by inhibiting vascular remodeling. Several proteins were identified as potential biomarkers of CMS, including Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1.

S1P induces proliferation of pulmonary artery smooth muscle cells by promoting YAP-induced Notch3 expression and activation

Sphingosine-1-phosphate (S1P), a natural multifunctional phospholipid, is highly increased in plasma from patients with pulmonary arterial hypertension and mediates proliferation of pulmonary artery smooth muscle cells (PASMCs) by activating the Notch3 signaling pathway. However, the mechanisms underpinning S1P-mediated induction of PASMCs proliferation remain unclear. In this study, using biochemical and molecular biology approaches, RNA interference and gene expression analyses, 5'-ethynyl-2'-deoxyuridine incorporation assay, and 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay, we demonstrated that S1P promoted the activation of signal transducers and activators of transcription 3 (STAT3) through sphingosine-1-phosphate receptor 2 (S1PR2), and subsequently upregulated the expression of the microRNA miR-135b, which further reduced the expression of E3 ubiquitin ligase β-transduction repeat-containing protein and led to a reduction in yes-associated protein (YAP) ubiquitinated degradation in PASMCs. YAP is the core effector of the Hippo pathway and mediates the expression of particular genes. The accumulation of YAP further increased the expression and activation of Notch3 and ultimately promoted the proliferation of PASMCs. In addition, we showed that preblocking S1PR2, prior silencing of STAT3, miR-135b, or YAP, and prior inhibition of Notch3 all attenuated S1P-induced PASMCs proliferation. Taken together, our study indicates that S1P stimulates PASMCs proliferation by activation of the S1PR2/STAT3/miR-135b/β-transduction repeat-containing protein/YAP/Notch3 pathway, and our data suggest that targeting this cascade might have potential value in ameliorating PASMCs hyperproliferation and benefit pulmonary arterial hypertension.

The soluble guanylate cyclase stimulator, 1-nitro-2-phenylethane, reverses monocrotaline-induced pulmonary arterial hypertension in rats

AIMS

We examined the effects of treatment with 1-nitro-2-phenylethane (NP), a novel soluble guanylate cyclase stimulator, on monocrotaline (MCT)-induced PAH in rats.

MAIN METHODS

At day 0, male adult rats were injected with a single subcutaneous (s.c.) dose of monocrotaline (60 mg/kg). Control (CNT) rats received an equal volume of monocrotaline's vehicle only (s.c.). Four weeks later, MCT-treated rats were treated orally for 14 days with NP (50 mg/kg/day) (MCT-NP group) or its vehicle (Tween 2%) (MCT-V group). At the end of the treatment period and before invasive hemodynamic study, rats of all experimental groups were examined by echocardiography.

KEY FINDINGS

With respect to CNT rats, MCT-V rats showed significant; (1) increases in pulmonary artery (PA) diameter, RV free wall thickness and end-diastolic RV area, and increase of Fulton index; (2) decreases in maximum pulmonary flow velocity, PA acceleration time (PAAT), PAAT/time of ejection ratio, and velocity-time integral; (3) increases in estimated mean pulmonary arterial pressure; (4) reduction of maximal relaxation to acetylcholine in aortic rings, and (5) increases in wall thickness of pulmonary arterioles. All these measured parameters were significantly reduced or even abolished by oral treatment with NP.

SIGNIFICANCE

NP reversed endothelial dysfunction and pulmonary vascular remodeling, which in turn reduced ventricular hypertrophy. NP reduced pulmonary artery stiffness, normalized the pulmonary artery diameter and alleviated RV enlargement. Thus, NP may represent a new therapeutic or a complementary approach to treatment of PAH.

Discovery of Novel Pyrazolo[3,4-b] Pyridine Derivatives with Dual Activities of Vascular Remodeling Inhibition and Vasodilation for the Treatment of Pulmonary Arterial Hypertension

Current pulmonary arterial hypertension (PAH) therapeutic strategies mainly focus on vascular relaxation with less emphasis on vascular remodeling, which results in poor prognosis. Hence, dual pathway regulators with vasodilation effect via soluble guanylate cyclase (sGC) stimulation and vascular remodeling regulation effect by AMP-activated protein kinase (AMPK) inhibition provide more advantages and potentialities. Herein, we designed and synthesized a series of novel pyrazolo[3,4-b] pyridine derivatives based on sGC stimulator and AMPK inhibitor scaffolds. In vitro, 2 exhibited moderate vasodilation activity and higher proliferation and migration suppressive effects compared to riociguat. In vivo, 2 significantly decreased right ventricular systolic pressure (RVSP), attenuated pulmonary artery medial thickness (PAMT), and right ventricular hypertrophy (RVH) in hypoxia-induced PAH rat models (i.g.). Given the unique advantages of significant vascular remodeling inhibition and moderate vascular relaxation based on the dual pathway regulation, we proposed 2 as a promising lead for anti-PAH drug discovery.

Targeting Heme Oxygenase-1 in the Arterial Response to Injury and Disease

Heme oxygenase-1 (HO-1) catalyzes the degradation of heme into carbon monoxide (CO), iron, and biliverdin, which is rapidly metabolized to bilirubin. The activation of vascular smooth muscle cells (SMCs) plays a critical role in mediating the aberrant arterial response to injury and a number of vascular diseases. Pharmacological induction or gene transfer of HO-1 improves arterial remodeling in animal models of post-angioplasty restenosis, vascular access failure, atherosclerosis, transplant arteriosclerosis, vein grafting, and pulmonary arterial hypertension, whereas genetic loss of HO-1 exacerbates the remodeling response. The vasoprotection evoked by HO-1 is largely ascribed to the generation of CO and/or the bile pigments, biliverdin and bilirubin, which exert potent antioxidant and anti-inflammatory effects. In addition, these molecules inhibit vascular SMC proliferation, migration, apoptosis, and phenotypic switching. Several therapeutic strategies are currently being pursued that may allow for the targeting of HO-1 in arterial remodeling in various pathologies, including the use of gene delivery approaches, the development of novel inducers of the enzyme, and the administration of unique formulations of CO and bilirubin.

Novel insights on the pulmonary vascular consequences of COVID-19

In the last few months, the number of cases of a new coronavirus-related disease (COVID-19) rose exponentially, reaching the status of a pandemic. Interestingly, early imaging studies documented that pulmonary vascular thickening was specifically associated with COVID-19 pneumonia, implying a potential tropism of the virus for the pulmonary vasculature. Moreover, SARS-CoV-2 infection is associated with inflammation, hypoxia, oxidative stress, mitochondrial dysfunction, DNA damage, and lung coagulopathy promoting endothelial dysfunction and microthrombosis. These features are strikingly similar to what is seen in pulmonary vascular diseases. Although the consequences of COVID-19 on the pulmonary circulation remain to be explored, several viruses have been previously thought to be involved in the development of pulmonary vascular diseases. Patients with preexisting pulmonary vascular diseases also appear at increased risk of morbidity and mortality. The present article reviews the molecular factors shared by coronavirus infection and pulmonary vasculature defects, and the clinical relevance of pulmonary vascular alterations in the context of COVID-19.

Absence of the MFG-E8 gene prevents hypoxia-induced pulmonary hypertension in mice

Pulmonary hypertension (PH) is a chronic vascular disease characterized by elevated pulmonary arterial resistance and vascular remodeling, and chronic hypoxia plays an important role in PH. Milk fat globule‐EGF factor 8 (MFG‐E8) is a glycoprotein that regulates cell proliferation and apoptosis, but its role in hypoxia‐induced PH is unknown. The current study aimed to determine the function and fundamental mechanisms of MFG‐E8 in hypoxia‐induced PH. Herein, we exposed mice to hypoxia for 5 weeks, and MFG‐E8 was found to be elevated in mouse lung tissues, arteries, and plasma. Compared with wild‐type littermates, mice lacking MFG‐E8 showed a significant increase in the ratio of pulmonary artery acceleration time to ejection time (PAT/PET), while they showed decreases in right ventricular systolic pressure, the Fulton's Index, percent medial wall thickness (%WT), and vascular muscularization in pulmonary arteries. In addition, MFG‐E8 protein levels were also increased in the serum of patients with chronic PH. Similarly, we observed a higher expression of MFG‐E8 in human pulmonary artery smooth muscle cells (PASMCs) in the presence of hypoxic stimulation than MFG‐E8 in cells in normoxic conditions. Furthermore, MFG‐E8 silencing resulted in partial inhibition of proliferation, migration and cell cycle progression in human PASMCs, and the possible mechanisms might involve the interaction between MFG‐E8 and the p‐Akt/cyclin D1 pathway. Collectively, our study suggests that the absence of MFG‐E8 can attenuate the development of hypoxia‐induced PH and vascular remodeling. MFG‐E8 can be a potential therapeutic target or a biomarker for PH.

Apoptosis signal-regulating kinase 1 inhibition in in vivo and in vitro models of pulmonary hypertension

Pulmonary arterial hypertension, group 1 of the pulmonary hypertension disease family, involves pulmonary vascular remodelling, right ventricular dysfunction and cardiac failure. Oxidative stress, through activation of mitogen-activated protein kinases is implicated in these changes. Inhibition of apoptosis signal-regulating kinase 1, an apical mitogen-activated protein kinase, prevented pulmonary arterial hypertension developing in rodent models. Here, we investigate apoptosis signal-regulating kinase 1 in pulmonary arterial hypertension by examining the impact that its inhibition has on the molecular and cellular signalling in established disease. Apoptosis signal-regulating kinase 1 inhibition was investigated in in vivo pulmonary arterial hypertension and in vitro pulmonary hypertension models. In the in vivo model, male Sprague Dawley rats received a single subcutaneous injection of Sugen SU5416 (20 mg/kg) prior to two weeks of hypobaric hypoxia (380 mmHg) followed by three weeks normoxia (Sugen/hypoxic), then animals were either maintained for three weeks on control chow or one containing apoptosis signal-regulating kinase 1 inhibitor (100 mg/kg/day). Cardiovascular measurements were carried out. In the in vitro model, primary cultures of rat pulmonary artery fibroblasts and rat pulmonary artery smooth muscle cells were maintained in hypoxia (5% O₂) and investigated for proliferation, migration and molecular signalling in the presence or absence of apoptosis signal-regulating kinase 1 inhibitor. Sugen/hypoxic animals displayed significant pulmonary arterial hypertension compared to normoxic controls at eight weeks. Apoptosis signal-regulating kinase 1 inhibitor decreased right ventricular systolic pressure to control levels and reduced muscularised vessels in lung tissue. Apoptosis signal-regulating kinase 1 inhibition was found to prevent hypoxia-induced proliferation, migration and cytokine release in rat pulmonary artery fibroblasts and also prevented rat pulmonary artery fibroblast-induced rat pulmonary artery smooth muscle cell migration and proliferation. Apoptosis signal-regulating kinase 1 inhibition reversed pulmonary arterial hypertension in the Sugen/hypoxic rat model. These effects may be a result of intrinsic changes in the signalling of adventitial fibroblast.

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

AIMS

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

METHODS AND RESULTS

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

CONCLUSION

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

Association between cardiovascular risk factors and the diameter of the main pulmonary artery in asymptomatic population in the Appalachian region

Background

Pulmonary artery (PA) diameter may be altered in association with cardiovascular (CV) risk factors as noted in aorta in systemic hypertension. The flow of blood from the right ventricle to the PA and all the way to the capillary level depends on the pulmonary vascular resistance and to a lesser extent compliance and impedance of the PA, which are the fundamental conduit for maintenance of the right heart hemodynamics. Our objective is to determine the association between CV risk factors and the main pulmonary artery (MPA) diameter.

Methods

The study population are asymptomatic individuals with no known diagnosis of CV diseases in central Appalachia (n=1,282). Adults aged 18 years or older were eligible for the screening if they were referred by a physician. For self-referral, only males aged ≥45 years and females aged ≥55 years were eligible. Unadjusted and adjusted linear regression analyses were performed.

Results

The mean MPA diameter was significantly higher among males compared to females (27.19±4.20 vs. 24.99±3.91 mm, P<0.0001). Participants with diabetes also had wider MPA diameter (26.79±4.56 mm) compared to those without diabetes (25.93±4.11 mm) (P=0.015). Further, hypertensive (26.42±4.15 vs. 25.71±4.21 mm, P=0.002) and obese (27.25±4.11 vs. 25.28±4.07 mm, P<0.0001) participants had significantly wider MPA diameter compared to non-hypertensive and non-obese participants, respectively. Multivariable model showed that age, sex and body mass index (BMI) were significantly associated with MPA diameter. A 1-year increase in age increased MPA diameter by 0.046 mm (P<0.0001). The diameter of MPA was wider among males by 2.16 mm compared to females (P<0.0001). Finally, with one unit increase in BMI, the MPA diameter increased by 0.16 mm (P<0.0001).

Conclusions

MPA diameter was significantly associated with age, sex, and BMI. Further prospective studies are needed to correlate computed tomography (CT) measurement of MPA diameter with pulmonary pressure as assessed by echocardiogram to diagnose pulmonary hypertension (PH).

Indazole-Cl inhibits hypoxia-induced cyclooxygenase-2 expression in vascular smooth muscle cells

Atherosclerosis is the most common root cause of arterial disease, such as coronary artery disease and carotid artery disease. Hypoxia is associated with the formation of macrophages and increased inflammation and is known to be present in lesions of atherosclerotic. Vascular smooth muscle cells (VSMCs) are one of the major components of blood vessels, and hypoxic conditions affect VSMC inflammation, proliferation and migration, which contribute to vascular stenosis and play a major role in the atherosclerotic process. Estrogen receptor (ER)-β is thought to play an important role in preventing the inflammatory response in VSMCs. In this report, we studied the anti-inflammatory effect of indazole (In)-Cl, an ERβ-specific agonist, under conditions of hypoxia. Expression of cyclooxygenase-2 reduced by hypoxia was inhibited by In-Cl treatment in VSMCs, and this effect was antagonized by an anti-estrogen compound. Additionally, the production of reactive oxygen species induced under conditions of hypoxia was reduced by treatment with In-Cl. Increased cell migration and invasion by hypoxia were also dramatically decreased following treatment with In-Cl. The increase in cell proliferation following treatment with platelet-derived growth factor was attenuated by In-Cl in VSMCs. RNA sequencing analysis was performed to identify changes in inflammation-related genes following In-Cl treatment in the hypoxic state. Our results suggest that ERβ is a potential therapeutic target for the suppression of hypoxia-induced inflammation in VSMCs.

Effects of paclitaxel intervention on pulmonary vascular remodeling in rats with pulmonary hypertension

The aim of the present study was to investigate the effects of paclitaxel (PTX), at a non-cytotoxic concentration, on pulmonary vascular remodeling (PVR) in rats with pulmonary hypertension (PAH), and to explore the mechanisms underlying the PTX-mediated reversal of PVR in PAH. A total of 36 rats were divided into control group (n=12), model group (n=12) receiving a subcutaneous injection of monocrotaline (60 mg/kg) in the back on day 7 following left pneumonectomy and PTX group (n=12) with PTX (2 mg/kg) injection via the caudal vein 3 weeks following establishing the model. The degree of PVR among all groups, as well as the expression levels of Ki67, p27^Kip1 and cyclin B1, were compared. The mean pulmonary artery pressure, right ventricular hypertrophy index [right ventricle/(left ventricle + septum) ratio] and the thickness of the pulmonary arterial tunica media in the model group were 58.34±2.01 mmHg, 0.64±0.046 and 65.3±3.3%, respectively, which were significantly higher when compared with 23.30±1.14 mmHg, 0.32±0.028 and 16.2±1.3% in the control group, respectively (P<0.01). The mean pulmonary artery pressure, right ventricular hypertrophy index and thickness of the pulmonary arterial tunica media in the PTX group were 42.35±1.53 mmHg, 0.44±0.029 and 40.5±2.6%, respectively, which were significantly lower when compared with the model group (P<0.01). Compared with the control group, the expression levels of Ki67 and cyclin B1 in the model group were significantly increased (P<0.01), while p27^Kip1 expression was significantly reduced (P<0.01). Following PTX intervention, the expression levels of Ki67 and cyclin B1 were significantly reduced when compared with the model group (P<0.01), while p27^Kip1 expression was significantly increased (P<0.01). The results of the present study suggest that PTX, administered at a non-cytotoxic concentration, may reduce PAH in rats, and prevent the effects of PVR in PAH. These effects of PTX may be associated with increased expression of p27^Kip1 and decreased expression of cyclin B1.

Arctigenin prevents monocrotaline-induced pulmonary arterial hypertension in rats

The hallmark features of the development of pulmonary arterial hypertension (PAH) include the proliferation of pulmonary vascular smooth muscle cells, oxidative stress, inflammation, and pulmonary artery remodeling. Arctigenin is a bioactive component of Arctium lappa that exerts anti-inflammatory and antiproliferative effects in several diseases; however, its effects on pulmonary arteries are still unclear. This study aimed to investigate the efficacy of arctigenin to prevent PAH. Rats injected with monocrotaline (MCT) progressively developed PAH. Arctigenin treatment (50 mg per kg per day, intra-peritoneally) ameliorated right ventricular systolic pressure and pulmonary arterial remodeling, decreased the expression of inflammatory cytokines, and limited the proliferation of pulmonary vascular smooth muscle cells in lungs. Mechanistically, arctigenin effectively inhibited the MCT-induced elevation of NLRP3, caspase-1, and interleukin 1-beta expression in the lungs. These results indicate that arctigenin ameliorates MCT-induced PAH, at least in part, through exerting its anti-inflammatory, antioxidant, and antiproliferative effects, which inhibit the NLRP3 inflammasome signal pathway in rats.

Arctigenin ameliorates monocrotaline-induced pulmonary arterial hypertension, at least in part, through exerting its anti-inflammatory, antioxidant, and antiproliferative effects, which inhibit the NLRP3 inflammasome signal pathway in rats.

Protective effects of astragaloside IV against hypoxic pulmonary hypertension

The present study aimed to evaluate the protective effects of astragaloside IV (As-IV) against hypoxic pulmonary hypertension (HPH) and its mechanisms of action. Sprague-Dawley rats were used in a model of HPH induced by chronic hypoxia. After hypoxia, the mean pulmonary arterial pressure (mPAP), right ventricular pressure (RVP), and right ventricular hypertrophy index (RVHI) were monitored. Relaxation of the pulmonary artery in response to As-IV was measured. The levels of endothelin-1 (ET-1), angiotensin II (Ang II), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in serum were assessed. Cell proliferation was detected by the cell counting kit-8 (CCK-8) assay. Treatment with As-IV significantly decreased mPAP, RVP and RV/(LV + S) and attenuated the development of HPH. Moreover, As-IV time-dependently relaxed the pulmonary arteries from HPH rats. In addition, As-IV decreased the levels of ET-1, Ang II, TNF-α, and IL-6 in serum of HPH rats. In vitro experiments demonstrated that As-IV also significantly inhibited the proliferation of pulmonary artery smooth muscle cells (PASMCs) subjected to hypoxia. Our findings suggested the therapeutic potential of As-IV in the treatment of pulmonary hypertension.

Biomimetic soft fibrous hydrogels for contractile and pharmacologically responsive smooth muscle

The ability to assess changes in smooth muscle contractility and pharmacological responsiveness in normal or pathological-relevant vascular tissue environments is critical to enable vascular drug discovery. However, major challenges remain in both capturing the complexity of in vivo vascular remodeling and evaluating cell contractility in complex, tissue-like environments. Herein, we developed a biomimetic fibrous hydrogel with tunable structure, stiffness, and composition to resemble the native vascular tissue environment. This hydrogel platform was further combined with the combinatory protein array technology as well as advanced approaches to measure cell mechanics and contractility, thus permitting evaluation of smooth muscle functions in a variety of tissue-like microenvironments. Our results demonstrated that biomimetic fibrous structure played a dominant role in smooth muscle function, while the presentation of adhesion proteins co-regulated it to various degrees. Specifically, fibre networks enabled cell infiltration and upregulated expression of actomyosin proteins in contrast to flat hydrogels. Remarkably, fibrous structure and physiologically relevant stiffness of hydrogels cooperatively enhanced smooth muscle contractility and pharmacological responses to vasoactive drugs at both the single cell and intact tissue levels. Together, this study is the first to demonstrate alterations of human vascular smooth muscle contractility and pharmacological responsiveness in biomimetic soft, fibrous environments with a cellular array platform. The integrated platform produced here could enable investigations for pathobiology and pharmacological interventions by developing a broad range of patho-physiologically relevant in vitro tissue models.

STATEMENT OF SIGNIFICANCE

Engineering functional smooth muscle in vitro holds the great potential for diseased tissue replacement and drug testing. A central challenge is recapitulating the smooth muscle contractility and pharmacological responses given its significant phenotypic plasticity in response to changes in environment. We present a biomimetic fibrous hydrogel with tunable structure, stiffness, and composition that enables the creation of functional smooth muscle tissues in the native-like vascular tissue microenvironment. Such fibrous hydrogel is further combined with the combinatory protein array technology to construct a cellular array for evaluation of smooth muscle phenotype, contraction, and cell mechanics. The integrated platform produced here could be promising for developing a broad range of normal or diseased in vitro tissue models.

Inflammasomes: a novel therapeutic target in pulmonary hypertension?

Pulmonary hypertension (PH) is a rare, progressive pulmonary vasculopathy characterized by increased mean pulmonary arterial pressure, pulmonary vascular remodelling and right ventricular failure. Current treatments are not curative, and new therapeutic strategies are urgently required. Clinical and preclinical evidence has established that inflammation plays a key role in PH pathogenesis, and recently, inflammasomes have been suggested to be central to this process. Inflammasomes are important regulators of inflammation, releasing the pro-inflammatory cytokines IL-1β and IL-18 in response to exogenous pathogen- and endogenous damage-associated molecular patterns. These cytokines are elevated in PH patients, but whether this is a consequence of inflammasome activation remains to be determined. This review will briefly summarize current PH therapies and their pitfalls, introduce inflammasomes and the mechanisms by which they promote inflammation and, finally, highlight the preclinical and clinical evidence for the potential involvement of inflammasomes in PH pathobiology and how they may be targeted therapeutically. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Beneficial Effect of Ocimum sanctum (Linn) against Monocrotaline-Induced Pulmonary Hypertension in Rats

Background: The study was designed to explore any beneficial effect of Ocimum sanctum (Linn) (OS) in experimental pulmonary hypertension (PH) in rats. OS is commonly known as “holy basil” and “Tulsi” and is used in the Indian System of Medicine as antidiabetic, antioxidant, hepatoprotective, adaptogenic, and cardioprotective. Methods: Monocrotaline (MCT) administration caused development of PH in rats after 28 days and rats were observed for 42 days. Treatments (sildenafil; 175 µg/kg, OS; 200 mg/kg) were started from day 29 after the development of PH and continued for 14 days. Parameters to assess the disease development and effectiveness of interventions were echocardiography, right and left ventricular systolic pressures, and right ventricular end diastolic pressure, percentage medial wall thickness (%MWT) of pulmonary artery, oxidative stress markers in lung tissue, NADPH oxidase (Nox-1) protein expression in lung, and mRNA expression of Bcl2 and Bax in right ventricular tissue. Results: OS (200 mg/kg) treatment ameliorated increased lung weight to body weight ratio, right ventricular hypertrophy, increased RVSP, and RVoTD/AoD ratio. Moreover, OS treatment decreases Nox-1 expression and increases expression of Bcl2/Bax ratio caused by MCT. Conclusion: The present study demonstrates that OS has therapeutic ability against MCT-induced PH in rat which are attributed to its antioxidant effect. The effect of OS was comparable with sildenafil.

Relationship between Pulmonary Artery Stiffness and Functional Capacity in Patients with Heart Failure with Reduced Ejection Fraction

BACKGROUND AND OBJECTIVES

Functional capacity varies significantly among patients with heart failure with reduced ejection fraction (HFrEF), and it remains unclear why functional capacity is severely compromised in some patients with HFrEF while it is preserved in others. In this study, we aimed to evaluate the role of pulmonary artery stiffness (PAS) in the functional status of patients with HFrEF.

METHODS

A total of 46 heart failure (HF) patients without overt pulmonary hypertension or right HF and 52 controls were enrolled in the study. PAS was assessed on parasternal short-axis view using pulsed-wave Doppler recording of pulmonary flow one centimeter distal to the pulmonic valve annulus at a speed of 100 mm/sec. PAS was calculated according to the following formula: the ratio of maximum flow velocity shift of pulmonary flow to pulmonary acceleration time.

RESULTS

PAS was significantly increased in the HFrEF group compared to the control group (10.53±2.40 vs. 7.41±1.32, p<0.001). In sub-group analysis of patients with HFrEF, PAS was significantly associated with the functional class of the patients. HFrEF patients with poor New York Heart Association (NYHA) functional capacity had higher PAS compared those with good functional capacity. In multivariate regression analysis, NYHA class was independently correlated with PAS.

CONCLUSION

PAS is associated with functional status and should be taken into consideration as an underlying pathophysiological mechanism of dyspnea in patients with HFrEF.

Angiotensin-converting enzyme 2 activation ameliorates pulmonary endothelial dysfunction in rats with pulmonary arterial hypertension through mediating phosphorylation of endothelial nitric oxide synthase

This study aims to investigate the effect of angiotensin-converting enzyme 2 (ACE2) activation on pulmonary endothelial function in the process of preventing pulmonary arterial hypertension (PAH) in rat models and to explore the underlying mechanisms. Specific pathogen free rats were randomly divided into five groups including control group, PAH group, PAH + Resorcinolnaphthalein (Res) group (ACE2 activation), PAH + Res + MLN4760 group (ACE2 inhibition), and PAH + Res + L-NAME group (endothelial nitric oxide synthase [eNOS] inhibition). Rat PAH model was constructed using combined left pneumonectomy with a single dose of monocrotaline injection 1 week after the surgery, and the rats were then given corresponding reagents. Hemodynamics, endothelial function, and pathologic changes were evaluated 3 weeks after monocrotaline injection. The concentration of nitric oxide (NO), expression of eNOS, and phosphorylation of eNOS at Ser1177 and Thr495 in the lung tissues from rats were also investigated.The Res-induced activation of ACE2 led to decreased mean pulmonary arterial pressure (mPAP) and pulmonary artery remodeling in the PAH + Res group comparing with the PAH rats (P < .05). In addition, the reduction in mPAP induced by acetylcholine (Ach) was augmented in PAH + Res group (P < .05), but this was not observed under the treatment with sodium nitroprusside (SNP) (P > .05). The ratio of decrease in mPAP caused by Ach to that caused by SNP (Ach/SNP) was also increased (P < .05) in ACE2-activated rats. However, the protective effects of ACE2 activation on PAH were counteracted by co-administration of MLN4760, an ACE2 antagonist (all P > .05). The mechanistic study showed that the concentration of NO in the lung tissues was downregulated in the PAH group but upregulated in the PAH + Res group (P < .05), whereas the NO concentration in the PAH + Res + MLN4760 group was not obviously different from that in the PAH group (P > .05). Regarding the factors regulating NO release, we found that the eNOS was upregulated in the PAH group, and Res did not affect the expression of eNOS. The phosphorylation of eNOS at Ser1177 was increased but at Thr495 was reduced after Res injection, when compared with the PAH group (P < .05). As expected, co-injection of MLN4760 eliminated these differences (P > .05). The reduction in mPAP induced by Ach was attenuated in the PAH + Res + L-NAME group compared with the PAH + Res group (P < .05), but this was not observed in rats treated with SNP (P > .05). The Ach/SNP ratio of decline in mPAP was also decreased in the PAH + Res + L-NAME group (P < .05). Activation of ACE2 had a protective role in the development of PAH via improving the function of pulmonary arterial endothelium. This effect was potentially mediated by promoted NO release as a consequence of increased phosphorylation of eNOS at Ser1177 and dephosphorylation of eNOS at Thr495.

Hypoxia and Redox Signaling on Extracellular Matrix Remodeling: From Mechanisms to Pathological Implications

SIGNIFICANCE

The extracellular matrix (ECM) is an essential modulator of cell behavior that influences tissue organization. It has a strong relevance in homeostasis and translational implications for human disease. In addition to ECM structural proteins, matricellular proteins are important regulators of the ECM that are involved in a myriad of different pathologies. Recent Advances: Biochemical studies, animal models, and study of human diseases have contributed to the knowledge of molecular mechanisms involved in remodeling of the ECM, both in homeostasis and disease. Some of them might help in the development of new therapeutic strategies. This review aims to review what is known about some of the most studied matricellular proteins and their regulation by hypoxia and redox signaling, as well as the pathological implications of such regulation.

CRITICAL ISSUES

Matricellular proteins have complex regulatory functions and are modulated by hypoxia and redox signaling through diverse mechanisms, in some cases with controversial effects that can be cell or tissue specific and context dependent. Therefore, a better understanding of these regulatory processes would be of great benefit and will open new avenues of considerable therapeutic potential.

FUTURE DIRECTIONS

Characterizing the specific molecular mechanisms that modulate matricellular proteins in pathological processes that involve hypoxia and redox signaling warrants additional consideration to harness the potential therapeutic value of these regulatory proteins. Antioxid. Redox Signal. 27, 802-822.

Wnt/β-catenin signaling links embryonic lung development and asthmatic airway remodeling

Embryonic lung development requires reciprocal endodermal-mesodermal interactions; mediated by various signaling proteins. Wnt/β-catenin is a signaling protein that exhibits the pivotal role in lung development, injury and repair while aberrant expression of Wnt/β-catenin signaling leads to asthmatic airway remodeling: characterized by hyperplasia and hypertrophy of airway smooth muscle cells, alveolar and vascular damage goblet cells metaplasia, and deposition of extracellular matrix; resulting in decreased lung compliance and increased airway resistance. The substantial evidence suggests that Wnt/β-catenin signaling links embryonic lung development and asthmatic airway remodeling. Here, we summarized the recent advances related to the mechanistic role of Wnt/β-catenin signaling in lung development, consequences of aberrant expression or deletion of Wnt/β-catenin signaling in expansion and progression of asthmatic airway remodeling, and linking early-impaired pulmonary development and airway remodeling later in life. Finally, we emphasized all possible recent potential therapeutic significance and future prospectives, that are adaptable for therapeutic intervention to treat asthmatic airway remodeling.

Plasma l-citrulline concentrations in l-arginine-supplemented healthy dogs

INTRODUCTION

To determine whether oral l-arginine increases plasma [l-citrulline] in dogs.

ANIMALS

Eleven healthy staff-owned dogs were used in this study.

MATERIALS AND METHODS

Dogs (n = 3) were given l-arginine (50mg/kg PO q8h) for 7 days, and plasma [l-arginine] and [l-citrulline] were analyzed by high performance liquid chromatography at baseline (BL), steady state trough, and 0.5, 1, 1.5, 2, 4, 6, and 8 h after final dosing on day 7. Eleven dogs were then treated with 100mg/kg l-arginine PO q8h for 7 days, and [l-arginine] and [l-citrulline] were measured at BL, steady state trough, and at peak 4 hrs after dosing (T4 hrs).

RESULTS

- Plasma [l-arginine] and [l-citrulline] peaked at T4 hrs on the 50mg/kg dosage. Target outcome, modeled after human study results, of a doubling of [l-arginine] and a 25-30% increase in [l-citrulline] from BL were not reached. After the 100mg/kg dosage, plasma [l-arginine] increased from a BL median of 160.1 μM (range, 100.2-231.4 μM) to a peak of 417.4 μM (206.5-807.3 μM) at T4 hrs, and plasma [l-citrulline] increased from a BL median of 87.8 μM (59.1-117.1 μM) to peak of 102.2 μM (47.4-192.6 μM) at T4 hrs. Ten of eleven dogs showed a doubling of plasma [l-arginine] and 4/11 dogs achieved 25-30% or greater increases in plasma [l-citrulline]. No adverse effects on heart rate or blood pressure were noted.

CONCLUSIONS

- Oral l-arginine dosage of 100mg/kg q8h doubles plasma [l-arginine] in healthy dogs, but conversion to l-citrulline is quite variable. Further evaluation of this dosage regimen in dogs with pulmonary hypertension is warranted.

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

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

Pinocembrin ex vivo preconditioning improves the therapeutic efficacy of endothelial progenitor cells in monocrotaline-induced pulmonary hypertension in rats

Pulmonary hypertension is still not curable and the available current therapies can only alleviate symptoms without hindering the progression of disease. The present study was directed to investigate the possible modulatory effect of pinocembrin on endothelial progenitor cells transplanted in monocrotaline-induced pulmonary hypertension in rats. Pulmonary hypertension was induced by a single subcutaneous injection of monocrotaline (60mg/kg). Endothelial progenitor cells were in vitro preconditioned with pinocembrin (25mg/L) for 30min before being i.v. injected into rats 2weeks after monocrotaline administration. Four weeks after monocrotaline administration, blood pressure, electrocardiography and right ventricular systolic pressure were recorded. Rats were sacrificed and serum was separated for determination of endothelin-1 and asymmetric dimethylarginine levels. Right ventricles and lungs were isolated for estimation of tumor necrosis factor-alpha and transforming growth factor-beta contents as well as caspase-3 activity. Moreover, protein expression of matrix metalloproteinase-9 and endothelial nitric oxide synthase in addition to myocardial connexin-43 was assessed. Finally, histological analysis of pulmonary arteries, cardiomyocyte cross-sectional area and right ventricular hypertrophy was performed and cryosections were done for estimation of cell homing. Preconditioning with pinocembrin provided a significant improvement in endothelial progenitor cells' effect towards reducing monocrotaline-induced elevation of inflammatory, fibrogenic and apoptotic markers. Furthermore, preconditioned cells induced a significant amelioration of endothelial markers and cell homing and prevented monocrotaline-induced changes in right ventricular function and histological analysis compared with native cells alone. In conclusion, pinocembrin significantly improves the therapeutic efficacy of endothelial progenitor cells in monocrotaline-induced pulmonary hypertension in rats.

TASK-1 potassium channel is not critically involved in mediating hypoxic pulmonary vasoconstriction of murine intra-pulmonary arteries

The two-pore domain potassium channel KCNK3 (TASK-1) is expressed in rat and human pulmonary artery smooth muscle cells. There, it is associated with hypoxia-induced signalling, and its dysfunction is linked to pathogenesis of human pulmonary hypertension. We here aimed to determine its role in hypoxic pulmonary vasoconstriction (HPV) in the mouse, and hence the suitability of this model for further mechanistic investigations, using appropriate inhibitors and TASK-1 knockout (KO) mice. RT-PCR revealed expression of TASK-1 mRNA in murine lungs and pre-acinar pulmonary arteries. Protein localization by immunohistochemistry and western blot was unreliable since all antibodies produced labelling also in TASK-1 KO organs/tissues. HPV was investigated by videomorphometric analysis of intra- (inner diameter: 25–40 μm) and pre-acinar pulmonary arteries (inner diameter: 41–60 μm). HPV persisted in TASK-1 KO intra-acinar arteries. Pre-acinar arteries developed initial HPV, but the response faded earlier (after 30 min) in KO vessels. This HPV pattern was grossly mimicked by the TASK-1 inhibitor anandamide in wild-type vessels. Hypoxia-provoked rise in pulmonary arterial pressure (PAP) in isolated ventilated lungs was affected neither by TASK-1 gene deficiency nor by the TASK-1 inhibitor A293. TASK-1 is dispensable for initiating HPV of murine intra-pulmonary arteries, but participates in sustained HPV specifically in pre-acinar arteries. This does not translate into abnormal rise in PAP. While there is compelling evidence that TASK-1 is involved in the pathogenesis of pulmonary arterial hypertension in humans, the mouse does not appear to serve as a suitable model to study the underlying molecular mechanisms.

Histone deacetylase inhibitors promote eNOS expression in vascular smooth muscle cells and suppress hypoxia-induced cell growth

Hypoxia stimulates excessive growth of vascular smooth muscle cells (VSMCs) contributing to vascular remodelling. Recent studies have shown that histone deacetylase inhibitors (HDIs) suppress VSMC proliferation and activate eNOS expression. However, the effects of HDI on hypoxia-induced VSMC growth and the role of activated eNOS in VSMCs are unclear. Using an EdU incorporation assay and flow cytometry analysis, we found that the HDIs, butyrate (Bur) and suberoylanilide hydroxamic acid (SAHA) significantly suppressed the proliferation of hypoxic VSMC lines and induced apoptosis. Remarkable induction of cleaved caspase 3, p21 expression and reduction of PCNA expression were also observed. Increased eNOS expression and enhanced NO secretion by hypoxic VSMC lines were detected using Bur or SAHA treatment. Knockdown of eNOS by siRNA transfection or exposure of hypoxic VSMCs to NO scavengers weakened the effects of Bur and SAHA on the growth of hypoxic VSMCs. In animal experiments, administration of Bur to Wistar rats exposed to hypobaric hypoxia for 28 days ameliorated the thickness and collagen deposition in pulmonary artery walls. Although the mean pulmonary arterial pressure (mPAP) was not obviously decreased with Bur in hypoxic rats, right ventricle hypertrophy index (RVHI) was decreased and the oxygen partial pressure of arterial blood was elevated. Furthermore, cell viability was decreased and eNOS and cleaved caspase 3 were induced in HDI-treated rat pulmonary arterial SMCs. These findings imply that HDIs prevent hypoxia-induced VSMC growth, in correlation with activated eNOS expression and activity in hypoxic VSMCs.

Beneficial effects of aqueous extract of stem bark of Terminalia arjuna (Roxb.), An ayurvedic drug in experimental pulmonary hypertension

ETHNOPHARMACOLOGICAL RELEVANCE

The stem bark of Terminalia arjuna (Roxb.) is widely used in Ayurveda in various cardiovascular diseases. Many animal and clinical studies have validated its anti-ischemic, antihypertensive, antihypertrophic and antioxidant effects. Pulmonary hypertension (PH) is a fatal disease which causes right ventricular hypertrophy and right heart failure. Pulmonary vascular smooth muscle hypertrophy and increased oxidative stress are major pathological features of PH. As available limited therapeutic options fail to reduce the mortality associated with PH, alternative areas of therapy are worth exploring for potential drugs, which might be beneficial in PH.

AIM OF THE STUDY

The effect of a standardised aqueous extract of the stem bark of Terminalia arjuna (Roxb.) in preventing monocrotaline (MCT)-induced PH in rat was investigated.

MATERIALS AND METHODS

The study was approved by Institutional Animal Ethics Committe. Male Wistar rats (150-200g) were randomly distributed into five groups; Control, MCT (50mg/kg subcutaneously once), sildenafil (175µg/kg/day three days after MCT for 25 days), and Arjuna extract (TA125 and TA250 mg/kg/day orally after MCT for 25 days). PH was confirmed by right ventricular weight to left ventricular plus septum weight (Fulton index), right ventricular systolic pressure (RVSP), echocardiography, percentage medial wall thickness of pulmonary arteries (%MWT). Oxidative stress in lung was assessed by super oxide dismutase (SOD), catalase, reduced glutathione (GSH) and thiobarbituric acid reactive substance (TBARS). The protein expressions of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX-1) in lung and gene expression of Bcl2 and Bax in heart were analyzed by Western blot and RT PCR respectively.

RESULTS

MCT caused right ventricular hypertrophy (0.58±0.05 vs 0.31±0.05; P<0.001 vs. control) and increase in RVSP (33.5±1.5 vs 22.3±4.7mm of Hg; P<0.001). Both sildenafil and Arjuna prevented hypertrophy and RVSP. Pulmonary artery acceleration time to ejection time ratio in echocardiography was decreased in PH rats (0.49±0.05 vs 0.32±0.06; P<0.001) which was prevented by sildenafil (0.44±0.06; P<0.01) and TA250 (0.45±0.06; P<0.01). % MWT of pulmonary arteries was increased in PH and was prevented by TA250. Increase in TBARS (132.7±18.4 vs 18.8±1.6nmol/mg protein; P<0.001) and decrease in SOD (58.4±14.1 vs 117.4±26.9U/mg protein; P<0.001) and catalase (0.30±0.05 vs 0.75±0.31U/mg protein; P<0.001) were observed in lung tissue of PH rats, which were prevented by sildenafil and both the doses of Arjuna extract. Protein expression of NOX1 was significantly increased in lung and gene expression of Bcl2/Bax ratio was significantly decreased in right ventricle in MCT-induced PH, both were significantly prevented by Arjuna and sildenafil.

CONCLUSIONS

Aqueous extract of Terminalia arjuna prevented MCT-induced pulmonary hypertension which may be attributed to its antioxidant as well as its effects on pulmonary arteriolar wall thickening.

Pulmonary hypertension as estimated by Doppler echocardiography in adolescent and adult patients with cystic fibrosis and their relationship with clinical, lung function and sleep findings

BACKGROUND

In cystic fibrosis (CF) patients, end stage of pulmonary disease is characterized by pulmonary hypertension (PH), hypoxemia, decrease in exercise tolerance, and sleep quality.

OBJECTIVE

To evaluate the association between clinical, lung function, sleep quality, and polysomnographic variables with PH in CF patients aged 16 years or older.

METHODS

In a cross-sectional study, 51 clinically stable CF patients underwent a clinical evaluation, an overnight polysomnography and answered sleep questionnaires (Pittsburgh Sleep Quality Index and Epworth sleepiness scale). Also, CF patients had their pulmonary function, 6-minute walk test (6MWT) and echocardiography assessed.

RESULTS

Fifty-one CF patients participated in the study; 47% were female. The mean age was 25.1 ± 8.8 years. Pulmonary artery systolic pressure (PASP) was greater than 35 mm Hg in 11 (27.5%) patients. Variables associated with PASP>35 mm Hg in univariate analysis were Shwachman-Kulczycki clinical score, forced expiratory volume in 1 second % of predicted, Pseudomonas aeruginosa in sputum culture, at-rest peripheral capillary oxygen saturation (SpO₂ ), SpO₂ at end of 6MWT and time of oxygen desaturation <90% during sleep. These variables were included in the binary logistic regression. The independent variable associated with the PASP > 35 mm Hg was at-rest SpO₂ (OR = 10.8, CI 95% 1.7-67.3, P = .011). The cuttoff SpO₂ < 94% had the sensitivity = 7/11 = 64%, specificity = 40/40 = 100%, positive predicted values = 7/7 = 100% and negative predicted values = 40/44 = 91% to the diagnosis of PH.

CONCLUSION

the present study showed a high rate of PH in adolescent and adult CF patients. At-rest SpO₂ was associated with PH.

Pulmonary artery denervation improves pulmonary arterial hypertension induced right ventricular dysfunction by modulating the local renin-angiotensin-aldosterone system

Background

Pulmonary arterial hypertension (PAH) is commonly accompanied with the activation of the renin-angiotensin-aldosterone system (RAAS). Renal sympathetic denervation (RSD) reduces PAH partly through the inhibition of RAAS. Analogically, we hypothesized that pulmonary artery denervation (PADN) could reverse PAH and PAH-induced right ventricular (RV) dysfunction by downregulating the local RAAS activity.

Methods

Twenty-five beagle dogs were randomized into two groups: control group (intra-atrial injection of N-dimethylacetamide, 3 mg/kg, n = 6) and test group (intra-atrial injection of dehydrogenized-monocrotaline, 3 mg/kg, n = 19). Eight weeks later, dogs in the test group with mean pulmonary arterial pressure (mPAP) ≥25 mmHg (n = 16) were reassigned into the sham (n = 8) and PADN groups (n = 8) by chance. After another 6 weeks, the hemodynamics, pulmonary tissue morphology and the local RAAS expression in lung and right heart tissue were measured.

Results

PADN reduced the mPAP (25.94 ± 3.67 mmHg vs 33.72 ± 5.76 mmHg, P < 0.05) and the percentage of medial wall thickness (%MWT) (31.0 ± 2.6 % vs 37.9 ± 2.8 %, P < 0.05) compared with the sham group. PADN attenuated RV dysfunction, marked with reduced atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and ratio of right ventricular to left ventricular plus septum weight [RV/(LV + S)]. Moreover, the local RAAS expression was activated in PAH dogs while inhibited after PADN.

Conclusions

PADN improves hemodynamics and relieves RV dysfunction in dogs with PAH, which can be associated with the downregulating RAAS activity in local tissue.