Mechanisms and pathology of monocrotaline pulmonary toxicity

Melatonin effects on oxidative stress and on TLR4/NF-kβ inflammatory pathway in the right ventricle of rats with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterised by an increase in mean pulmonary arterial pressure and a compromised the right ventricle (RV), together with progression to heart failure and premature death. Studies have evaluated the role of melatonin as a promising therapeutic strategy for PAH. The objective of this study was to evaluate melatonin's effects on oxidative stress and on the TLR4/NF-kβ inflammatory pathway in the RV of rats with PAH. Male Wistar rats were divided into the following groups: control, monocrotaline (MCT), and monocrotaline plus melatonin groups. These two last groups received one intraperitoneal injection of MCT (60 mg/kg) on the first day of experimental protocol. The monocrotaline plus melatonin group received 10 mg/kg/day of melatonin by gavage for 21 days. Echocardiographic analysis was performed, and the RV was collected for morphometric analysis oxidative stress and molecular evaluations. The main findings of the present study were that melatonin administration attenuated the reduction in RV function that was induced by monocrotaline, as assessed by TAPSE. In addition, melatonin prevented RV diastolic area reduction caused by PAH. Furthermore, animals treated with melatonin did not show an increase in ROS levels or in NF-kβ expression. In addition, the monocrotaline plus melatonin group showed a reduction in TLR4 expression when compared with control and monocrotaline groups. To our knowledge, this is the first study demonstrating a positive effect of melatonin on the TLR4/NF-kβ pathway in the RV of rats with PAH. In this sense, this study makes it possible to think of melatonin as a possible ally in mitigating RV alterations caused by PAH.

The Monocrotaline Rat Model of Right Heart Disease Induced by Pulmonary Artery Hypertension

Pulmonary artery hypertension (PAH) is characterised by increased pulmonary vascular resistance (PVR) resulting in elevated pressure in the pulmonary artery supplying the pulmonary circulation. Disease of the right ventricle (RV) often manifests as a result of PAH placing excessive pressure on the right side of the heart. Although a relatively rare disease in humans, the impact of sustained PAH is severe, with poor outcomes even in treated individuals. As PAH develops, the blood flow is restricted through the pulmonary arteries and the right ventricle hypertrophies due to the increased strain of pumping blood through the pulmonary circulation. With time, RV hypertrophy progresses to right heart failure, impacting the supply of blood to the left ventricle and systemic circulation. Although right heart failure can currently be treated, it cannot be cured. There is therefore a need for more research into the physiological changes that cause the heart to fail under pressure overload. This review aims to evaluate the monocrotaline (MCT) rat model of PAH as a means of studying the cellular mechanisms associated with the development of RV hypertrophy and right heart failure.

Early detection of pulmonary arterial hypertension through [18F] positron emission tomography imaging with a vascular endothelial receptor small molecule

The objective of this study is to provide a positron emission tomography (PET) imaging modality targeting vascular endothelial growth factor receptors (VEGFR) for the early noninvasive detection and assessment of pulmonary arterial hypertension (PAH) severity. To validate the effectiveness of the [18F]VEGFR PET tracer, we utilized a monocrotaline (MCT)-induced PAH rat model. Molecular optical imaging, using a Cy5.5-conjugated VEGFR targeting agent, was employed to demonstrate the uptake of the agent at pulmonary arterioles, correlating with the onset and progression of PAH. Histological examinations of the MCT-PAH rat lung revealed a significant correlation between VEGFR2 expression and the pathogenesis of PAH. Molecular optical imaging demonstrated heightened uptake of the Cy5.5-conjugated VEGFR targeting agent at pulmonary arterioles, corresponding with the onset and progression of PAH. [18F]VEGFR PET showed increased lung uptake detectable in early-stage PAH before increase in pulmonary artery pressures, and this uptake correlated with increased PAH severity. Moreover, when compared to [18F]FDG PET, [18F]VEGFR PET exhibited markedly lower background cardiac signal, enhancing imaging sensitivity for lung abnormalities. Our study provides a compelling evidence for the potential utility of the innovative [18F]VEGFR PET tracer, in non-invasively detecting early signs of PAH, and monitoring its progression. The observed correlations between VEGFR2 expression, molecular optical imaging results, and [18F]VEGFR PET findings support the use of this tracer for early detection, and assessment of PAH severity. The lower background cardiac signal observed with [18F]VEGFR PET further enhances its imaging sensitivity, emphasizing its potential clinical significance.

Extrapulmonary manifestations of pulmonary arterial hypertension

INTRODUCTION

Extrapulmonary manifestations of pulmonary arterial hypertension (PAH) may play a critical pathobiological role and a deeper understanding will advance insight into mechanisms and novel therapeutic targets. This manuscript reviews our understanding of extrapulmonary manifestations of PAH.

AREAS COVERED

A group of experts was assembled and a complimentary PubMed search performed (October 2023 - March 2024). Inflammation is observed throughout the central nervous system and attempts at manipulation are an encouraging step toward novel therapeutics. Retinal vascular imaging holds promise as a noninvasive method of detecting early disease and monitoring treatment responses. PAH patients have gut flora alterations and dysbiosis likely plays a role in systemic inflammation. Despite inconsistent observations, the roles of obesity, insulin resistance and dysregulated metabolism may be illuminated by deep phenotyping of body composition. Skeletal muscle dysfunction is perpetuated by metabolic dysfunction, inflammation, and hypoperfusion, but exercise training shows benefit. Renal, hepatic, and bone marrow abnormalities are observed in PAH and may represent both end-organ damage and disease modifiers.

EXPERT OPINION

Insights into systemic manifestations of PAH will illuminate disease mechanisms and novel therapeutic targets. Additional study is needed to understand whether extrapulmonary manifestations are a cause or effect of PAH and how manipulation may affect outcomes.

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

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

The siRNA-mediated knockdown of AP-1 restores the function of the pulmonary artery and the right ventricle by reducing perivascular and interstitial fibrosis and key molecular players in cardiopulmonary disease

BACKGROUND

Pulmonary hypertension (PH) is a complex multifactorial vascular pathology characterized by an increased pulmonary arterial pressure, vasoconstriction, remodelling of the pulmonary vasculature, thrombosis in situ and inflammation associated with right-side heart failure. Herein, we explored the potential beneficial effects of treatment with siRNA AP-1 on pulmonary arterial hypertension (PAH), right ventricular dysfunction along with perivascular and interstitial fibrosis in pulmonary artery-PA, right ventricle-RV and lung in an experimental animal model of monocrotaline (MCT)-induced PAH.

METHODS

Golden Syrian hamsters were divided into: (1) C group-healthy animals taken as control; (2) MCT group obtained by a single subcutaneous injection of 60 mg/kg MCT at the beginning of the experiment; (3) MCT-siRNA AP-1 group received a one-time subcutaneous dose of MCT and subcutaneous injections containing 100 nM siRNA AP-1, every two weeks. All animal groups received water and standard chow ad libitum for 12 weeks.

RESULTS

In comparison with the MCT group, siRNA AP-1 treatment had significant beneficial effects on investigated tissues contributing to: (1) a reduction in TGF-β1/ET-1/IL-1β/TNF-α plasma concentrations; (2) a reduced level of cytosolic ROS production in PA, RV and lung and notable improvements regarding the ultrastructure of these tissues; a decrease of inflammatory and fibrotic marker expressions in PA (COL1A/Fibronectin/Vimentin/α-SMA/CTGF/Calponin/MMP-9), RV and lung (COL1A/CTGF/Fibronectin/α-SMA/F-actin/OB-cadherin) and an increase of endothelial marker expressions (CD31/VE-cadherin) in PA; (4) structural and functional recoveries of the PA [reduced Vel, restored vascular reactivity (NA contraction, ACh relaxation)] and RV (enlarged internal cavity diameter in diastole, increased TAPSE and PRVOFs) associated with a decrease in systolic and diastolic blood pressure, and heart rate; (5) a reduced protein expression profile of AP-1S3/ pFAK/FAK/pERK/ERK and a significant decrease in the expression levels of miRNA-145, miRNA-210, miRNA-21, and miRNA-214 along with an increase of miRNA-124 and miRNA-204.

CONCLUSIONS

The siRNA AP-1-based therapy led to an improvement of pulmonary arterial and right ventricular function accompanied by a regression of perivascular and interstitial fibrosis in PA, RV and lung and a down-regulation of key inflammatory and fibrotic markers in MCT-treated hamsters.

Exploring the involvement of TASK-1 in the control of isolated rat right atrium function from healthy animals and an experimental model of monocrotaline-induced pulmonary hypertension

The TASK-1 channel belongs to the two-pore domain potassium channel family. It is expressed in several cells of the heart, including the right atrial (RA) cardiomyocytes and the sinus node, and TASK-1 channel has been implicated in the pathogenesis of atrial arrhythmias (AA). Thus, using the rat model of monocrotaline-induced pulmonary hypertension (MCT-PH), we explored the involvement of TASK-1 in AA. Four-week-old male Wistar rats were injected with 50 mg/kg of MCT to induce MCT-PH and isolated RA function was studied 14 days later. Additionally, isolated RA from six-week-old male Wistar rats were used to explore the ability of ML365, a selective blocker of TASK-1, to modulate RA function. The hearts developed right atrial and ventricular hypertrophy, inflammatory infiltrate and the surface ECG demonstrated increased P wave duration and QT interval, which are markers of MCT-PH. The isolated RA from the MCT animals showed enhanced chronotropism, faster contraction and relaxation kinetics, and a higher sensibility to extracellular acidification. However, the addition of ML365 to extracellular media was not able to restore the phenotype. Using a burst pacing protocol, the RA from MCT animals were more susceptible to develop AA, and simultaneous administration of carbachol and ML365 enhanced AA, suggesting the involvement of TASK-1 in AA induced by MCT. TASK-1 does not play a key role in the chronotropism and inotropism of healthy and diseased RA; however, it may play a role in AA in the MCT-PH model.

An Overview of Herbal Nutraceuticals, Their Extraction, Formulation, Therapeutic Effects and Potential Toxicity

Herbal nutraceuticals are foods derived from plants and/or their derivatives, such as oils, roots, seeds, berries, or flowers, that support wellness and combat acute and chronic ailments induced by unhealthful dietary habits. The current review enlists various traditional as well as unexplored herbs including angelica, burnet, caraway, laurel, parsley, yarrow, and zedoary, which are rich sources of bioactive components, such as aloesin, angelicin, trans-anethole, and cholesteric-7-en-3β-ol. The review further compares some of the extraction and purification techniques, namely, Soxhlet extraction, ultrasound assisted extraction, microwave assisted extraction, supercritical fluid extraction, accelerated solvent extraction, hydro-distillation extraction, ultra-high-pressure extraction, enzyme assisted extraction, pulsed electric field extraction, bio affinity chromatography, cell membrane chromatography, and ligand fishing. Herbal nutraceuticals can be purchased in varied formulations, such as capsules, pills, powders, liquids, and gels. Some of the formulations currently available on the market are discussed here. Further, the significance of herbal nutraceuticals in prevention and cure of diseases, such as diabetes, obesity, dementia, hypertension, and hypercholesterolemia; and as immunomodulators and antimicrobial agents has been discussed. Noteworthy, the inappropriate use of these herbal nutraceuticals can lead to hepatotoxicity, pulmonary toxicity, cytotoxicity, carcinogenicity, nephrotoxicity, hematotoxicity, and cardiac toxicity. Hence, this review concludes with a discussion of various regulatory aspects undertaken by the government agencies in order to minimize the adverse effects associated with herbal nutraceuticals.

Ranolazine exerts atrial antiarrhythmic effects in a rat model of monocrotaline-induced pulmonary hypertension

Atrial arrhythmias are a hallmark of heart diseases. The antiarrhythmic drug ranolazine with multichannel blocker properties is a promising agent to treat atrial arrhythmias. We therefore used the rat model of monocrotaline-induced pulmonary-hypertension to assess whether ranolazine can reduce the incidence of ex vivo atrial arrhythmias in isolated right atrium. Four-week-old Wistar rats were injected with 50 mg/kg of monocrotaline, and isolated right atrium function was studied 14 days later. The heart developed right atrium and right ventricular hypertrophy, and the ECG showed an increased P wave duration and QT interval, which are markers of the disease. Moreover, monocrotaline injection caused enhanced chronotropism and faster kinetics of contraction and relaxation in isolated right atrium. Additionally, in a concentration-dependent manner, ranolazine showed chronotropic and ionotropic effects upon isolated right atrium, with higher potency in the control when compared with experimental model. Using a burst pacing protocol, the isolated right atrium from the monocrotaline-treated animals was more susceptible to develop arrhythmias, and ranolazine was able to attenuate the phenotype. Thus, we concluded that the rat model of monocrotaline-induced pulmonary-hypertension develops right atrium remodelling, which increased the susceptibility to present ex vivo atrial arrhythmias, and the antiarrhythmic drug ranolazine ameliorated the phenotype.

Dapagliflozin reduces pulmonary vascular damage and susceptibility to atrial fibrillation in right heart disease

AIMS

Sodium-glucose cotransporter 2 inhibitors (SGLT2is) have made considerable progress in the field of heart failure, but their application in arrhythmia remains to be in-depth. Right heart disease (RHD) often leads to right heart dysfunction and is associated with atrial fibrillation (AF). Here, we explored the possible electrophysiologic effect of dapagliflozin (a type of SGLT2is) in the development of AF in rats with RHD.

METHODS AND RESULTS

Rats in the experimental group were intraperitoneally injected with a single dose of 60 mg/kg monocrotaline (MCT group, n = 32) on the first day of the experiment, whereas rats in the control group were injected with vehicle (CTL group, n = 32). Rats in the treatment subgroup were treated with dapagliflozin solution orally (MCT + DAPA and CTL + DAPA groups) for a total of 4 weeks, whereas rats in the rest of subgroups were given sterile drinking water. After 4 weeks, echocardiography demonstrated that MCT group rats developed obvious pulmonary arterial hypertension and right heart dysfunction. In addition, there were also obvious inflammatory infiltration, fibrosis, and muscularization in right atrial and pulmonary arteries. The P-wave duration (17.00 ± 0.53 ms, vs. 14.43 ± 0.57 ms in CTL; 14.00 ± 0.65 ms in CTL + DAPA; 14.57 ± 0.65 ms in MCT + DAPA; P < 0.05), RR interval (171.60 ± 1.48 ms, vs. 163.10 ± 1.10 ms in CTL; 163.30 ± 1.19 ms in CTL + DAPA; 163.10 ± 1.50 ms in MCT + DAPA; P < 0.05), Tpeak-Tend interval (65.93 ± 2.55 ms, vs. 49.55 ± 1.71 ms in CTL; 48.27 ± 3.08 ms in CTL + DAPA; P < 0.05), and corrected QT interval (200.90 ± 2.40 ms, vs. 160.00 ± 0.82 ms in CTL; 160.40 ± 1.36 ms in CTL + DAPA; 176.6 ± 1.57 ms in MCT + DAPA; P < 0.01) were significantly prolonged in the MCT group after 4 weeks, whereas P-wave amplitude (0.07 ± 0.0011 mV, vs. 0.14 ± 0.0009 mV in CTL; 0.14 ± 0.0011 mV in CTL + DAPA; 0.08 ± 0.0047 mV in MCT + DAPA; P < 0.05) and T-wave amplitude (0.04 ± 0.002 mV, vs. 0.13 ± 0.003 mV in CTL; 0.13 ± 0.003 mV in CTL + DAPA; P < 0.01) were decreased, and atrial 90% action potential duration (47.50 ± 0.93 ms, vs. 59.13 ± 2.1 ms in CTL; 59.75 ± 1.13 ms in CTL + DAPA; 60.63 ± 1.07 ms in MCT + DAPA; P < 0.01) and effective refractory periods (41.14 ± 0.88 ms, vs. 62.86 ± 0.99 ms in CTL; 63.14 ± 0.67 ms in CTL + DAPA; 54.86 ± 0.70 ms in MCT + DAPA; P < 0.01) were shortened. Importantly, the inducibility rate (80%, vs. 0% in CTL; 10% in CTL + DAPA; 40% in MCT + DAPA; P < 0.05) and duration of AF (30.85 ± 22.90 s, vs. 0 ± 0 s in CTL; 0.24 ± 0.76 s in CTL + DAPA; 5.08 ± 7.92 s in MCT + DAPA; P < 0.05) were significantly increased, whereas the expression levels of cardiac ion channels and calcium-handling proteins such as potassium/calcium channels and calmodulin were decreased. Mechanistically, 'NACHT, LRR, and PYD domain-containing protein 3' inflammasome-related pathway was significantly activated in the MCT group. Nevertheless, in the MCT + DAPA group, the above abnormalities were significantly improved.

CONCLUSIONS

Dapagliflozin reduces pulmonary vascular damage and right heart dysfunction, as well as the susceptibility to AF in RHD rats.

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.

Notopterol Attenuates Monocrotaline-Induced Pulmonary Arterial Hypertension in Rat

Introduction

Current targeted pulmonary arterial hypertension (PAH) therapies have improved lung hemodynamics, cardiac function, and quality of life; however, none of these have reversed the ongoing remodeling of blood vessels. Considering notopterol, a linear furocoumarin extracted from the root of traditional Chinese medicine Qiang-Huo (Notopterygium incisum), had shown the antiproliferative and anti-inflammatory properties in previous studies, we hypothesized that it could play a role in ameliorating PAH.

Methods

In vivo, we conducted monocrotaline (MCT) induced PAH rats and treated them with notopterol for 3 weeks. Then, the rats were examined by echocardiography and RV catheterization. The heart and lung specimens were harvested for the detection of gross examination, histological examination and expression of inflammatory molecules. In vitro, human pulmonary arterial smooth muscle cells (HPASMCs) were treated with notopterol after hypoxia; then, cell proliferation was assessed by cell counting kit-8 and Edu assay, and cell migration was detected by wound healing assays.

Results

We found that notopterol improved mortality rate and RV function while reducing right ventricular systolic pressure in MCT-induced PAH rats. Furthermore, notopterol reduced right ventricular hypertrophy and fibrosis, and it also eased pulmonary vascular remodeling and MCT-induced muscularization. In addition, notopterol attenuated the pro-inflammatory factor (IL-1β, IL-6) and PCNA in the lungs of PAH rats. For the cultured HPASMCs subjected to hypoxia, we found that notopterol can inhibit the proliferation and migration of HPASMCs.

Conclusion

Our studies show that notopterol exerts anti-inflammatory and anti-proliferative effects in the pulmonary arteries, which may contribute to prevention of PAH.

Implications of Hydrogen Sulfide in Development of Pulmonary Hypertension

The pathological mechanisms underlying pulmonary hypertension (PH), as well as its treatment strategy, are crucial issues in this field. This review aimed to summarize the pathological mechanisms by which the hydrogen sulfide (H2S) pathway contributes to PH development and its future implications. The data in this review were obtained from Medline and PubMed sources up to 2022 using the search terms "hydrogen sulfide" and "pulmonary hypertension". In the review, we discussed the significance of endogenous H2S pathway alteration in PH development and showed the advance of the role of H2S as the third gasotransmitter in the mechanisms for hypoxic PH, monocrotaline-induced PH, high blood flow-induced PH, and congenital heart disease-associated PH. Notably, H2S plays a crucial role in the development of PH via certain mechanisms, such as inhibiting the proliferation of pulmonary artery smooth muscle cells, suppressing the inflammation and oxidative stress of pulmonary artery endothelial cells, inducing pulmonary artery smooth muscle cell apoptosis, and interacting with other gaseous signaling pathways. Recently, a variety of H2S donors were developed, including naturally occurring donors and synthetic H2S donors. Therefore, understanding the role of H2S in PH development may help in further exploring novel potential therapeutic targets of PH.

Quantitative and qualitative analysis of pulmonary arterial hypertension fibrosis using wide-field second harmonic generation microscopy

We demonstrated that wide-field second harmonic generation (SHG) microscopy of lung tissue in combination with quantitative analysis of SHG images is a powerful tool for fast and label-free visualization of the fibrosis pathogenesis in pulmonary arterial hypertension (PAH). Statistical analysis of the SHG images revealed changes of the collagen content and morphology in the lung tissue during the monocrotaline-induced PAH progression in rats. First order statistics disclosed the dependence of the collagen overproduction on time, the second order statistics indicated tightening of collagen fiber network around blood vessels and their spreading into the alveolar region. Fourier analysis revealed that enhancement of the fiber orientation in the collagen network with PAH progression was followed with its subsequent reduction at the terminating phase of the disease. Proposed approach has potential for assessing pulmonary fibrosis in interstitial lung disease, after lung(s) transplantation, cancer, etc.

Xbp1s-Ddit3 promotes MCT-induced pulmonary hypertension

Pulmonary hypertension (PH) is a life-threatening disease characterized by vascular remodeling. Exploring new therapy target is urgent. The purpose of the present study is to investigate whether and how spliced x-box binding protein 1 (xbp1s), a key component of endoplasmic reticulum stress (ERS), contributes to the pathogenesis of PH. Forty male SD rats were randomly assigned to four groups: Control, Monocrotaline (MCT), MCT+AAV-CTL (control), and MCT+AAV-xbp1s. The xbp1s protein levels were found to be elevated in lung tissues of the MCT group. Intratracheal injection of adeno-associated virus serotype 1 carrying xbp1s shRNA (AAV-xbp1s) to knock down the expression of xbp1s effectively ameliorated the MCT-induced elevation of right ventricular systolic pressure (RVSP), total pulmonary resistance (TPR), right ventricular hypertrophy and medial wall thickness of muscularized distal pulmonary arterioles. The abnormally increased positive staining rates of proliferating cell nuclear antigen (PCNA) and Ki67 and decreased positive staining rates of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) in pulmonary arterioles were also reversed in the MCT+AAV-xbp1s group. For mechanistic exploration, bioinformatics prediction of the protein network was performed on the STRING database, and further verification was performed by qRT-PCR, Western blots and co-immunoprecipitation (Co-IP). DNA damage-inducible transcript 3 (Ddit3) was identified as a downstream protein that interacted with xbp1s. Overexpression of Ddit3 restored the decreased proliferation, migration and cell viability caused by silencing of xbp1s. The protein level of Ddit3 was also highly consistent with xbp1s in the animal model. Taken together, our study demonstrated that xbp1s-Ddit3 may be a potential target to interfere with vascular remodeling in PH.

Melatonin inhibits inflammasome-associated activation of endothelium and macrophages attenuating pulmonary arterial hypertension

AIMS

Pulmonary arterial hypertension (PAH) is a pathophysiological syndrome associated with pulmonary/systemic inflammation. Melatonin relieves PAH, but the molecular mode of action remains unclear. Here, we investigated the role of melatonin in normalizing vascular homeostasis.

METHODS AND RESULTS

Light-time mean serum melatonin concentration was lower in patients with PAH than in normal controls [11.06 ± 3.44 (7.13-15.6) vs. 14.55 ± 1.28 (8.0-19.4) pg/mL], which was negatively correlated with increased serum levels of interleukin-1β (IL-1β) in patients with PAH. We showed that inflammasomes were activated in the PAH mice model and that melatonin attenuated IL-1β secretion. On one hand, melatonin reduced the number of macrophages in lung by inhibiting the endothelial chemokines and adhesion factors. Moreover, use of Il1r-/- mice, Caspase1/11-/- mice, and melatonin-treated mice revealed that melatonin reduced hypoxia-induced vascular endothelial leakage in the lung. On the other hand, we verified that melatonin reduced the formation of inflammasome multiprotein complexes by modulating calcium ions in macrophages using a live cell station, and melatonin decreased inositol triphosphate and increased cAMP. Furthermore, knockdown of melatonin membrane receptors blocked melatonin function, and a melatonin membrane receptors agonist inactivated inflammasomes in macrophages.

CONCLUSION

Melatonin attenuated inflammasome-associated vascular disorders by directly improving endothelial leakage and decreasing the formation of inflammasome multiprotein complexes in macrophages. Taken together, our data provide a theoretical basis for applying melatonin clinically, and inflammasomes may be a possible target of PAH treatment.

Rodent models of hypertension

Elevated blood pressure (BP), or hypertension, is the main risk factor for cardiovascular disease. As a multifactorial and systemic disease that involves multiple organs and systems, hypertension remains a challenging disease to study. Models of hypertension are invaluable to support the discovery of the specific genetic, cellular and molecular mechanisms underlying essential hypertension, as well as to test new possible treatments to lower BP. Rodent models have proven to be an invaluable tool for advancing the field. In this review, we discuss the strengths and weaknesses of rodent models of hypertension through a systems approach. We highlight the ways how target organs and systems including the kidneys, vasculature, the sympathetic nervous system (SNS), immune system and the gut microbiota influence BP in each rodent model. We also discuss often overlooked hypertensive conditions such as pulmonary hypertension and hypertensive-pregnancy disorders, providing an important resource for researchers.

Stable Gastric Pentadecapeptide BPC 157 Therapy for Monocrotaline-Induced Pulmonary Hypertension in Rats Leads to Prevention and Reversal

Background. Monocrotaline selectively injures the lung's vascular endothelium and induces pulmonary arterial hypertension. The stable gastric pentadecapeptide BPC 157 acts as a prototype cytoprotective agent that maintains endothelium, and its application may be a novel therapy. Besides, BPC 157 prevents and reverses thrombosis formation, maintains platelet function, alleviates peripheral vascular occlusion disturbances, and has anti-arrhythmic and anti-inflammatory effects. Monocrotaline-induced pulmonary arterial hypertension in rats (wall thickness, total vessel area, heart frequency, QRS axis deviation, QT interval prolongation, increase in right ventricle systolic pressure and bodyweight loss) can be counteracted with early or delayed BPC 157 therapy. Methods and Results. After monocrotaline (80 mg/kg subcutaneously), BPC 157 (10 μg/kg or 10 ng/kg, days 1-14 or days 1-30 (early regimens), or days 14-30 (delayed regimen)) was given once daily intraperitoneally (last application 24 h before sacrifice) or continuously in drinking water until sacrifice (day 14 or 30). Without therapy, the outcome was the full monocrotaline syndrome, marked by right-side heart hypertrophy and massive thickening of the precapillary artery's smooth muscle layer, clinical deterioration, and sometimes death due to pulmonary hypertension and right-heart failure during the 4th week after monocrotaline injection. With all BPC 157 regimens, monocrotaline-induced pulmonary arterial hypertension (including all disturbed parameters) was counteracted, and consistent beneficial effects were documented during the whole course of the disease. Pulmonary hypertension was not even developed (early regimens) as quickly as the advanced pulmonary hypertension was rapidly attenuated and then completely eliminated (delayed regimen). Conclusions. Thus, pentadecapeptide BPC 157 prevents and counteracts monocrotaline-induced pulmonary arterial hypertension and cor pulmonale in rats.

Luteolin Ameliorates Experimental Pulmonary Arterial Hypertension via Suppressing Hippo-YAP/PI3K/AKT Signaling Pathway

Luteolin is a flavonoid compound with a variety of pharmacological effects. In this study, we explored the effects of luteolin on monocrotaline (MCT) induced rat pulmonary arterial hypertension (PAH) and underlying mechanisms. A rat PAH model was generated through MCT injection. In this model, luteolin improved pulmonary vascular remodeling and right ventricular hypertrophy, meanwhile, luteolin could inhibit the proliferation and migration of pulmonary artery smooth muscle cells induced by platelet-derived growth factor-BB (PDGF-BB) in a dose-dependent manner. Moreover, our results showed that luteolin could downregulate the expression of LATS1 and YAP, decrease YAP nuclear localization, reduce the expression of PI3K, and thereby restrain the phosphorylation of AKT induced by PDGF-BB. In conclusion, luteolin ameliorated experimental PAH, which was at least partly mediated through suppressing HIPPO-YAP/PI3K/AKT signaling pathway. Therefore, luteolin might become a promising candidate for treatment of PAH.

Deficiency of cold-inducible RNA-binding protein exacerbated monocrotaline-induced pulmonary artery hypertension through Caveolin1 and CAVIN1

Cold‐inducible RNA‐binding protein (CIRP) was a crucial regulator in multiple diseases. However, its role in pulmonary artery hypertension (PAH) is still unknown. Here, we first established monocrotaline (MCT)‐induced rat PAH model and discovered that CIRP was down‐regulated predominantly in the endothelium of pulmonary artery after MCT injection. We then generated Cirp‐knockout (Cirp‐KO) rats, which manifested severer PAH with exacerbated endothelium damage in response to MCT. Subsequently, Caveolin1 (Cav1) and Cavin1 were identified as downstream targets of CIRP in MCT‐induced PAH, and the decreased expression of these two genes aggravated the injury and apoptosis of pulmonary artery endothelium. Moreover, CIRP deficiency intensified monocrotaline pyrrole (MCTP)‐induced rat pulmonary artery endothelial cells (rPAECs) injuries both in vivo and in vitro, which was counteracted by Cav1 or Cavin1 overexpression. In addition, CIRP regulated the proliferative effect of conditioned media from MCTP‐treated rPAECs on rat pulmonary artery smooth muscle cells, which partially explained the exceedingly thickened pulmonary artery intimal media in Cirp‐KO rats after MCT treatment. These results demonstrated that CIRP acts as a critical protective factor in MCT‐induced rat PAH by directly regulating CAV1 and CAVIN1 expression, which may facilitate the development of new therapeutic targets for the intervention of PAH.

Animal models of pulmonary hypertension: Getting to the heart of the problem

Despite recent therapeutic advances, pulmonary hypertension (PH) remains a fatal disease due to the development of right ventricular (RV) failure. At present, no treatments targeted at the right ventricle are available, and RV function is not widely considered in the preclinical assessment of new therapeutics. Several small animal models are used in the study of PH, including the classic models of exposure to either hypoxia or monocrotaline, newer combinational and genetic models, and pulmonary artery banding, a surgical model of pure RV pressure overload. These models reproduce selected features of the structural remodelling and functional decline seen in patients and have provided valuable insight into the pathophysiology of RV failure. However, significant reversal of remodelling and improvement in RV function remains a therapeutic obstacle. Emerging animal models will provide a deeper understanding of the mechanisms governing the transition from adaptive remodelling to a failing right ventricle, aiding the hunt for druggable molecular targets.

Metabolic Pattern of Hepatotoxic Pyrrolizidine Alkaloids in Liver Cells

Contamination with 1,2-unsaturated pyrrolizidine alkaloids (PAs) is a serious problem for certain phytomedicines, foods, and animal feeds. Several of these PAs are genotoxic and carcinogenic, primarily in the liver, upon cytochrome P450 (CYP)-catalyzed activation into reactive (pyrrolic and pyrrole-like) metabolites. Here we investigated the metabolism of selected PAs (echimidine, europine, lasiocarpine, lycopsamine, retrorsine, and senecionine) in rat hepatocytes in primary culture and in human CYP3A4-transfected HepG2 cells. The open-chained diesters echimidine and lasiocarpine and the cyclic diester senecionine were extensively metabolized in rat hepatocytes into a broad spectrum of products released into the medium. A large portion of unidentified, possibly irreversibly bound, products remained in the cells while detectable amounts of reactive and other metabolites were found in the incubation media. In HepG2-CYP3A4 cells, lasiocarpine was more extensively metabolized than echimidine and senecionine which also gave rise to the release of pyrrolic metabolites. In human cells, no pyrrolic metabolites were detected in retrorsine or lycopsamine incubations, while no such metabolites were detected from europine in both cell types. Other types of metabolic changes comprised modifications such as side chain demethylation or oxygenation reactions like the formation of N-oxides. The latter, considered as a detoxification step, was a major pathway with cyclic diesters, was less distinctive for echimidine and lycopsamine and almost negligible for lasiocarpine and europine. Our data are in agreement with previously published cyto- and genotoxicity findings and suggests that the metabolic pattern may contribute substantially to the specific toxic potency of a certain congener. In addition, marked differences were found for certain congeners between rat hepatocytes and transfected human HepG2 cells, whereby a high level of bioactivation was found for lasiocarpine, whereas a very low level of bioactivation was observed for monoesters, in particular in human cells.

The G Protein Biased Small Molecule Apelin Agonist CMF-019 is Disease Modifying in Endothelial Cell Apoptosis In Vitro and Induces Vasodilatation Without Desensitisation In Vivo

Signaling through the apelin receptor is beneficial for a number of diseases including pulmonary arterial hypertension. The endogenous small peptides, apelin and elabela/toddler, are downregulated in pulmonary arterial hypertension but are not suitable for exogenous administration owing to a lack of bioavailability, proteolytic instability and susceptibility to renal clearance. CMF-019, a small molecule apelin agonist that displays strong bias towards G protein signaling over β-arrestin (∼400 fold), may be more suitable. This study demonstrates that in addition to being a positive inotrope, CMF-019 caused dose-dependent vasodilatation in vivo (50 nmol 4.16 ± 1.18 mmHg, **p < 0.01; 500 nmol 6.62 ± 1.85 mmHg, **p < 0.01), without receptor desensitization. Furthermore, CMF-019 rescues human pulmonary artery endothelial cells from apoptosis induced by tumor necrosis factor α and cycloheximide (5.66 ± 0.97%, **p < 0.01) by approximately 50% of that observable with rhVEGF (11.59 ± 1.85%, **p < 0.01), suggesting it has disease-modifying potential in vitro. CMF-019 displays remarkable bias at the apelin receptor for a small molecule and importantly recapitulates all aspects of the cardiovascular responses to the endogenous ligand, [Pyr¹]apelin-13, in vivo. Additionally, it is able to protect human pulmonary artery endothelial cells from apoptosis, suggesting that the beneficial effects observed with apelin agonists extend beyond hemodynamic alleviation and address disease etiology itself. These findings support CMF-019 as a G protein biased small molecule apelin agonist in vitro and in vivo that could form the basis for the design of novel therapeutic agents in chronic diseases, such as, pulmonary arterial hypertension.

The progression of pulmonary arterial hypertension induced by monocrotaline is characterized by lung nitrosative and oxidative stress, and impaired pulmonary artery reactivity

The time-course of pulmonary arterial hypertension in the monocrotaline (MCT) model was investigated. Male rats were divided into two groups: MCT (received a 60 mg/kg i.p. injection) and control (received saline). The MCT and control groups were further divided into three cohorts, based on the follow-up interval: 1, 2, and 3 weeks. Right ventricle (RV) catheterization was performed and RV hypertrophy (RVH) was estimated. The lungs were used for biochemical, histological, molecular, and immunohistochemical analysis, while pulmonary artery rings were used for vascular reactivity. MCT promoted lung perivascular edema, inflammatory cells exudation, greater neutrophils and lymphocytes profile, and arteriolar wall thickness, compared to CTR group. Increases in pulmonary artery pressure and in RVH were observed in the MCT 2- and 3-week groups. The first week was marked by the presence of nitrosative stress (50% moderate and 33% accentuated staining by nitrotyrosine). These alterations lead to an adaptation of NO production by NO synthase activity after 2 weeks. Oxidative stress was evident in the third week, probably by an imbalance between endothelin-1 receptors, resulting in extracellular matrix remodeling, endothelial dysfunction, and RVH. Also, it was found a reduced pulmonary arterial vasodilatory response to acetylcholine after 2 (55%) and 3 (45%) weeks in MCT groups. The relevance of this study is precisely to show that nitrosative and oxidative stress predominate in distinct time windows of the disease progression.

Galectin-3 Promotes ROS, Inflammation, and Vascular Fibrosis in Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is a progressive vascular disease arising from the narrowing of pulmonary arteries (PA) resulting in high pulmonary arterial blood pressure and ultimately right ventricular (RV) failure. A defining characteristic of PAH is the excessive remodeling of PA that includes increased proliferation, inflammation, and fibrosis. There is no cure for PAH nor interventions that effectively impede or reverse PA remodeling, and research over the past several decades has sought to identify novel molecular mechanisms of therapeutic benefit. Galectin-3 (Gal-3; Mac-2) is a carbohydrate-binding lectin that is remarkable for its chimeric structure, comprised of an N-terminal oligomerization domain and a C-terminal carbohydrate-recognition domain. Gal-3 is a regulator of changes in cell behavior that contribute to aberrant PA remodeling including cell proliferation, inflammation, and fibrosis, but its role in PAH is poorly understood. Herein, we summarize the recent literature on the role of Gal-3 in the development of PAH and provide experimental evidence supporting the ability of Gal-3 to influence reactive oxygen species (ROS) production, NOX enzyme expression, inflammation, and fibrosis, which contributes to PA remodeling. Finally, we address the clinical significance of Gal-3 as a target in the development of therapeutic agents as a treatment for PAH.

Animal models of right heart failure

Right heart failure may be the ultimate cause of death in patients with acute or chronic pulmonary hypertension (PH). As PH is often secondary to other cardiovascular diseases, the treatment goal is to target the underlying disease. We do however know, that right heart failure is an independent risk factor, and therefore, treatments that improve right heart function may improve morbidity and mortality in patients with PH. There are no therapies that directly target and support the failing right heart and translation from therapies that improve left heart failure have been unsuccessful, with the exception of mineralocorticoid receptor antagonists. To understand the underlying pathophysiology of right heart failure and to aid in the development of new treatments we need solid animal models that mimic the pathophysiology of human disease. There are several available animal models of acute and chronic PH. They range from flow induced to pressure overload induced right heart failure and have been introduced in both small and large animals. When initiating new pre-clinical or basic research studies it is key to choose the right animal model to ensure successful translation to the clinical setting. Selecting the right animal model for the right study is hence important, but may be difficult due to the plethora of different models and local availability. In this review we provide an overview of the available animal models of acute and chronic right heart failure and discuss the strengths and limitations of the different models.

Plexiform Lesions in an Experimental Model of Monocrotalin-Induced Pulmonary Arterial Hypertension

BACKGROUND

The monocrotaline (MCT)-induced pulmonary arterial hypertension model is one of the most reproduced today, presenting as a limitation the absence of plexiform lesions, typical manifestations of the severe disease in humans.

OBJECTIVE

To evaluate the severity of MCT-induced pulmonary arteriopathy by pathological findings of lung and heart tissue samples, clinical course and 37-day survival.

METHODS

Fifty male Wistar rats were divided into one of the four groups - control (CG) (n = 10) and three intervention (MCT) groups. The MCT groups received intraperitoneal injection (60 mg/kg) of MCT and remained exposed to the substance for 15 days (G15, n = 10), 30 days (G30, n = 10) and 37 days (G37, n = 20). At the end of each period, the animals were sacrificed, and pulmonary and cardiac tissues were collected for anatomopathological and morphometric analysis. The Kruskal-Wallis test was used, considering a level of significance of 5%.

RESULTS

In the lungs of MCT animals, lesions related to pulmonary arteriopathy were found, including muscularization of the arterioles, hypertrophy of the middle layer and concentric neointimal lesions. Complex lesions were observed in MCT groups, described as plexiform and plexiform-like lesions. Right ventricular hypertrophy was evidenced by increased thickness and diameter of the cardiomyocytes and a significant increase in the right ventricular wall thickness (p <0.0000).

CONCLUSION

The MCT model was able to generate moderate-severe pulmonary arteriopathy associated with secondary right ventricular hypertrophy. The 37-day survival rate was 50%. To our knowledge, this study was the first to note the presence of complex vascular lesions, similar to those observed in patients with severe pulmonary arterial hypertension, in an isolated MCT model. (Arq Bras Cardiol. 2020; 115(3):480-490).

Small animal models of heart failure

Heart disease is a major cause of death worldwide with increasing prevalence, which urges the development of new therapeutic strategies. Over the last few decades, numerous small animal models have been generated to mimic various pathomechanisms contributing to heart failure (HF). Despite some limitations, these animal models have greatly advanced our understanding of the pathogenesis of the different aetiologies of HF and paved the way to understanding the underlying mechanisms and development of successful treatments. These models utilize surgical techniques, genetic modifications, and pharmacological approaches. The present review discusses the strengths and limitations of commonly used small animal HF models, which continue to provide crucial insight and facilitate the development of new treatment strategies for patients with HF.

A novel rat model of pulmonary hypertension induced by mono treatment with SU5416

Pulmonary hypertension (PH) is responsible for premature death caused by progressive and severe heart failure. A simple, feasible, and reproducible animal model of PH is essential for the investigation of the pathogenesis and treatment of this condition. Previous studies have demonstrated that the vascular endothelial growth factor receptor 2 (VEGFR-2) inhibitor SU5416 combined with hypoxia could establish an animal model of PH. Here, we investigated whether SU5416 itself could induce PH in rats. The effects of SU5416 treatment followed by 5 weeks of normoxia were examined. Hemodynamic measurements and histological assessments of the pulmonary vasculature and the heart were conducted to evaluate the physiological and pathophysiological characteristics of PH. Compared with the control rats, the SU5416-treated rats showed significantly increased right ventricle systolic pressure, right ventricle mass, total pulmonary vascular resistance, and total pulmonary vascular resistance index, while the cardiac output and cardiac index were substantially decreased. Moreover, the degree of occlusion and the muscularization levels of the distal small pulmonary vessels and the medial wall thickness of larger vessels (OD > 50 μm) simultaneously increased. SU5416 inhibited pulmonary vascular endothelial cell apoptosis in rats, as shown by immunostaining of cleaved caspase-3. Furthermore, changes in the right ventricle, myocardial hypertrophy, myocardial edema, myocardial necrosis, striated muscle cell atrophy, vessel muscularization, neointimal occlusion, and increased collagen deposition were observed in the SU5416 group compared with the control group. Thus, treatment with SU5416 alone plus 5 weeks of normoxia could be sufficient to induce PH in rats, which may provide a good and convenient model for future investigation of PH.

Current animal models for the study of congestion in heart failure: an overview

Congestion (i.e., backward failure) is an important culprit mechanism driving disease progression in heart failure. Nevertheless, congestion remains often underappreciated and clinicians underestimate the importance of congestion on the pathophysiology of decompensation in heart failure. In patients, it is however difficult to study how isolated congestion contributes to organ dysfunction, since heart failure and chronic kidney disease very often coexist in the so-called cardiorenal syndrome. Here, we review the existing relevant and suitable backward heart failure animal models to induce congestion, induced in the left- (i.e., myocardial infarction, rapid ventricular pacing) or right-sided heart (i.e., aorta-caval shunt, mitral valve regurgitation, and monocrotaline), and more specific animal models of congestion, induced by saline infusion or inferior vena cava constriction. Next, we examine critically how representative they are for the clinical situation. After all, a relevant animal model of isolated congestion offers the unique possibility of studying the effects of congestion in heart failure and the cardiorenal syndrome, separately from forward failure (i.e., impaired cardiac output). In this respect, new treatment options can be discovered.

Morphological and Functional Characteristics of Animal Models of Myocardial Fibrosis Induced by Pressure Overload

Myocardial fibrosis is characterized by excessive deposition of myocardial interstitial collagen, abnormal distribution, and excessive proliferation of fibroblasts. According to the researches in recent years, myocardial fibrosis, as the pathological basis of various cardiovascular diseases, has been proven to be a core determinant in ventricular remodeling. Pressure load is one of the causes of myocardial fibrosis. In experimental models of pressure-overload-induced myocardial fibrosis, significant increase in left ventricular parameters such as interventricular septal thickness and left ventricular posterior wall thickness and the decrease of ejection fraction are some of the manifestations of cardiac damage. These morphological and functional changes have a serious impact on the maintenance of physiological functions. Therefore, establishing a suitable myocardial fibrosis model is the basis of its pathogenesis research. This paper will discuss the methods of establishing myocardial fibrosis model and compare the advantages and disadvantages of the models in order to provide a strong basis for establishing a myocardial fibrosis model.

Blockade of JAK2 protects mice against hypoxia-induced pulmonary arterial hypertension by repressing pulmonary arterial smooth muscle cell proliferation

Objectives

Hypoxia is an important risk factor for pulmonary arterial remodelling in pulmonary arterial hypertension (PAH), and the Janus kinase 2 (JAK2) is believed to be involved in this process. In the present report, we aimed to investigate the role of JAK2 in vascular smooth muscle cells during the course of PAH.

Methods

Smooth muscle cell (SMC)‐specific Jak2 deficient mice and their littermate controls were subjected to normobaric normoxic or hypoxic (10% O₂) challenges for 28 days to monitor the development of PAH, respectively. To further elucidate the potential mechanisms whereby JAK2 influences pulmonary vascular remodelling, a selective JAK2 inhibitor was applied to pre‐treat human pulmonary arterial smooth muscle cells (HPASMCs) for 1 hour followed by 24‐hour hypoxic exposure.

Results

Mice with hypoxia‐induced PAH were characterized by the altered JAK2/STAT3 activity in pulmonary artery smooth muscle cells. Therefore, induction of Jak2 deficiency in SMCs protected mice from hypoxia‐induced increase of right ventricular systolic pressure (RVSP), right ventricular hypertrophy and pulmonary vascular remodelling. Particularly, loss of Jak2 significantly attenuated chronic hypoxia‐induced PASMC proliferation in the lungs. Similarly, blockade of JAK2 by its inhibitor, TG‐101348, suppressed hypoxia‐induced human PASMC proliferation. Upon hypoxia‐induced activation, JAK2 phosphorylated signal transducer and activator of transcription 3 (STAT3), which then bound to the CCNA2 promoter to transcribe cyclin A2 expression, thereby promoting PASMC proliferation.

Conclusions

Our studies support that JAK2 could be a culprit contributing to the pulmonary vascular remodelling, and therefore, it could be a viable target for prevention and treatment of PAH in clinical settings.

Aquaporin-2 expression in the kidney and urine is elevated in rats with monocrotaline-induced pulmonary heart disease

Objective

Little is known about how renal aquaporin-2 (AQP2) expression is affected by right heart failure caused by pulmonary heart disease (PHD). Therefore, we examined the expression of AQP2 in a rat model of PHD induced by monocrotaline (MCT).

Methods

After 4 weeks of treatment, urine and blood samples were collected from sham-treated and MCT-treated rats. Plasma arginine vasopressin (AVP) levels were measured by radioimmunoassay, and kidney Aqp2 mRNA expression was detected by reverse transcription (RT)-PCR. Kidney AQP2 protein expression was quantified by immunohistochemistry and western blotting assays. The concentration of urine AQP2 was determined by indirect enzyme-linked immunosorbent assay.

Results

We successfully established an animal model of MCT-induced PHD in rats. MCT-treated rats had significantly higher mRNA and protein levels of AQP2 in their kidney tissue. Following MCT treatment, rats also had markedly increased concentrations of both urine AQP2 and plasma AVP.

Conclusions

AQP2 expression was significantly increased in the kidney tissues and urine of rats with PHD induced by MCT. Our findings suggest that the evaluation of AQP2 expression contributes to an early diagnosis of PHD, and may also be an important reference to improve PHD therapeutics.

Galectin-3: A Harbinger of Reactive Oxygen Species, Fibrosis, and Inflammation in Pulmonary Arterial Hypertension

Significance: Pulmonary arterial hypertension (PAH) is a progressive disease arising from the narrowing of pulmonary arteries (PAs) resulting in high pulmonary arterial blood pressure and ultimately right ventricle (RV) failure. A defining characteristic of PAH is the excessive and unrelenting inward remodeling of PAs that includes increased proliferation, inflammation, and fibrosis. Critical Issues: There is no cure for PAH nor interventions that effectively arrest or reverse PA remodeling, and intensive research over the past several decades has sought to identify novel molecular mechanisms of therapeutic value. Recent Advances: Galectin-3 (Gal-3) is a carbohydrate-binding lectin remarkable for its chimeric structure, composed of an N-terminal oligomerization domain and a C-terminal carbohydrate-recognition domain. Gal-3 has been identified as a regulator of numerous changes in cell behavior that contributes to aberrant PA remodeling, including cell proliferation, inflammation, and fibrosis, but its role in PAH has remained poorly understood until recently. In contrast, pathological roles for Gal-3 have been proposed in cancer and inflammatory and fibroproliferative disorders, such as pulmonary vascular and cardiac fibrosis. Herein, we summarize the recent literature on the role of Gal-3 in the development of PAH. We provide experimental evidence supporting the ability of Gal-3 to influence reactive oxygen species production, NADPH oxidase enzyme expression, and redox signaling, which have been shown to contribute to both vascular remodeling and increased pulmonary arterial pressure. Future Directions: While several preclinical studies suggest that Gal-3 promotes hypertensive pulmonary vascular remodeling, the clinical significance of Gal-3 in human PAH remains to be established. Antioxid. Redox Signal. 00, 000-000.

Preincubation format for a sensitive immunochromatographic assay for monocrotaline, a toxic pyrrolizidine alkaloid

INTRODUCTION

Monocrotaline (MCT), which is classified as a 1,2-dehydropyrrolizidine alkaloid (DHPA), is a toxic compound that is mainly produced by Crotalaria spp. MCT contamination in cereals and herbs leads to hepatitis, gastroenteritis, pulmonary vasculitis and hypertension, and different types of cancer. The current analytical methods for MCT are complicated and expensive using liquid chromatography equipped with mass spectrometry detection.

OBJECTIVE

The aim of this study was to develop a simple and sensitive preincubation format for an immunochromatographic assay (PI-ICA) for MCT detection.

METHODOLOGY

We conducted the PI-ICA via incubation of an MCT-containing sample with an anti-MCT monoclonal antibody conjugated with colloidal gold before strip dipping. We compared the PI-ICA detection sensitivity with that of the conventional ICA (Conv-ICA) format.

RESULTS

The PI-ICA was sensitive with a limit of detection (LOD) of 0.61 ng/mL, which is a 16-fold improvement over the Conv-ICA format. These results indicated that the PI-ICA method exhibits high binding specificity for MCT and low cross-reactivity towards retronecine, retrorsine, senecionine and heliotrine. Sample solutions from plants containing MCT and related DHPAs produced positive results via PI-ICA analysis.

CONCLUSIONS

The proposed PI-ICA system provides a highly sensitive method compared to Conv-ICA. In addition, the developed PI-ICA method is simple and highly effective for detecting MCT contamination.

Therapeutic efficacy of mesenchymal stromal cells and secretome in pulmonary arterial hypertension: A systematic review and meta-analysis

Mesenchymal stromal cells (MSCs) and secretome are promising therapies for pulmonary arterial hypertension (PAH). This meta-analysis aimed to provide a precise estimate and compare the therapeutic efficacy of MSC and secretome in PAH. We searched six databases (CINAHL, Cochrane, Ovid Medline, PubMed, Science Direct and Scopus) until December 2018 using search terms related to MSCs, secretome and PAH. Twenty-three studies were included for the meta-analysis. The effect size of pulmonary hemodynamics and right ventricular hypertrophy markers was estimated using random effects model. MSCs and secretome significantly improved pulmonary hemodynamics and right ventricular hypertrophy compared to control. Comparison between MSCs and secretome indicate no significant difference in reducing right ventricular systolic pressure (RVSP) and medial wall thickening (MWT). However, treatment of PAH with secretome significantly improved mean pulmonary arterial pressure (mPAP) (p = 0.018) and right ventricular/left ventricular + septum (RV/LV+S) (p = 0.017) better than MSCs. Meta-regression shows that cell type (p = 0.034) is a predictor of MSCs to reduce RVSP in PAH. Similarly, the effect of secretome on MWT was significantly (p = 0.011) better at 4 weeks compared to 2 weeks of intervention. The overall risk of bias ranges from low to moderate; however, some of the essential elements required in reports of animal trials were not reported. There was evidence of publication bias for RV/LV+S and MWT, but not RVSP. This meta-analysis provides evidence of the therapeutic benefits of MSCs and secretome in PAH and the effect of secretome was similar or superior to MSCs.

Monocrotaline pyrrole enhanced bone morphogenetic protein 7 signaling transduced by alternative activin A receptor type 2A in pulmonary arterial smooth muscle cells

BACKGROUND

Increased expression levels of bone morphogenetic protein 7 (BMP7) are associated with poor prognosis in pulmonary hypertension patients. However, whether BMP7 signaling conspire to involve in the proliferation of pulmonary artery smooth muscle cells (PASMC) underlying monocrotaline (MCT) induced pulmonary arterial hypertension (PAH) remain unclear.

METHODS AND RESULTS

Western blot experiments found BMP7 was increased in pulmonary arteries isolated from MCT-PAH rat. In addition, monocrotaline pyrrole (MCTP), the putative toxic metabolite of the MCT, increases the expression of BMP7, proliferating cell nuclear antigen (PCNA) and activin A receptor type 2A, but decreases bone morphogenetic protein receptor type 2 in cultured pulmonary artery smooth muscle cells (PASMC). In PASMCs, exogenous BMP7 leads to the decreasing expression of activin A receptor type 2, increasing phosphorylation of p38MAPK and elevation of P21. However, BMP7 treatment results in the increasing expression of activin A receptor type 2A, p38MAPK, and PCNA in bone morphogenetic protein receptor type 2 knockdown PASMCs. Knockdown of activin A receptor type 2A abrogated the MCTP-induced PCNA and cell cycle progression.

CONCLUSIONS

MCTP treatment lead to the expression of BMP7, suppression of bone morphogenetic protein receptor type 2 but increasing expression of activin A receptor type 2A, the BMP7 mediated PASMC proliferation via preferential activation of an activin A receptor type 2A signaling axis.

Safety and tolerability of macitentan in the management of pulmonary arterial hypertension: an update

Macitentan is a medication in the endothelin receptor antagonist class, approved for treatment of pulmonary arterial hypertension in 2013 based on the results of the pivotal SERAPHIN Trial (Study with an Endothelin Receptor Antagonist in Pulmonary arterial Hypertension to Improve cliNical outcome). Macitentan was shown in initial trials to reduce the likelihood of a morbidity/mortality event. Real-world use of this medication additionally reveals a reduced risk of hospitalizations related to pulmonary arterial hypertension, improved health-related quality of life scores, potential clinical utility in other conditions (such as chronic thromboembolic pulmonary hypertension and pulmonary hypertension related to congenital heart disease), and has a similar safety profile as demonstrated in initial trials.

A novel cyclic biased agonist of the apelin receptor, MM07, is disease modifying in the rat monocrotaline model of pulmonary arterial hypertension

BACKGROUND AND PURPOSE

Apelin is an endogenous vasodilatory and inotropic peptide that is down-regulated in human pulmonary arterial hypertension, although the density of the apelin receptor is not significantly attenuated. We hypothesised that a G protein-biased apelin analogue MM07, which is more stable than the endogenous apelin peptide, may be beneficial in this condition with the advantage of reduced β-arrestin-mediated receptor internalisation with chronic use.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats received either monocrotaline to induce pulmonary arterial hypertension or saline and then daily i.p. injections of either MM07 or saline for 21 days. The extent of disease was assessed by right ventricular catheterisation, cardiac MRI, and histological analysis of the pulmonary vasculature. The effect of MM07 on signalling, proliferation, and apoptosis of human pulmonary artery endothelial cells was investigated.

KEY RESULTS

MM07 significantly reduced the elevation of right ventricular systolic pressure and hypertrophy induced by monocrotaline. Monocrotaline-induced changes in cardiac structure and function, including right ventricular end-systolic and end-diastolic volumes, ejection fraction, and left ventricular end-diastolic volume, were attenuated by MM07. MM07 also significantly reduced monocrotaline-induced muscularisation of small pulmonary blood vessels. MM07 stimulated endothelial NOS phosphorylation and expression, promoted proliferation, and attenuated apoptosis of human pulmonary arterial endothelial cells in vitro.

CONCLUSION AND IMPLICATIONS

Our findings suggest that chronic treatment with MM07 is beneficial in this animal model of pulmonary arterial hypertension by addressing disease aetiology. These data support the development of G protein-biased apelin receptor agonists with improved pharmacokinetic profiles for use in human disease.

Evidence of Amniotic Epithelial Cell Differentiation toward Hepatic Sinusoidal Endothelial Cells

Amniotic epithelial cells (AECs) represent a useful and noncontroversial source for liver-based regenerative medicine, as they can differentiate into hepatocytes upon transplantation into the liver. However, the possibility that AECs can differentiate into other liver cell types, such as hepatic sinusoidal endothelial cells (HSECs), has never been assessed. In order to test this hypothesis, rat- and human-derived AECs (rAECs and hAECs, respectively) were subjected to endothelial cell tube formation assay in vitro. Moreover, to evaluate differentiation in vivo, the retrorsine (RS) model of liver repopulation was used. Pyrrolizidine alkaloids (including RS) are known to target both hepatocytes and endothelial cells, inducing cell enlargement and inhibition of cell cycle progression. rAECs and hAECs were able to form capillary-like structures when cultured under proangiogenic conditions. For in vivo experiments, rAECs were obtained from dipeptidyl peptidase type IV (DPP-IV, CD26) donors and were transplanted into the liver of recipient CD26 negative animals pretreated with RS. rAEC-derived cells were engrafted in between hepatocytes and resembled HSECs as assessed by morphological analysis and the pattern of expression of CD26. Donor-derived CD26⁺ cells coexpressed HSEC markers RECA-1 and SE-1, while they lacked expression of typical hepatocyte markers (i.e., cytochrome P450, hepatocyte nuclear factor 4α). As such, these results provide the first evidence that AECs can respond to proangiogenic signals in vitro and differentiate into HSECs in vivo. Furthermore, they support the conclusion that AECs possesses great plasticity and represents a promising tool in the field of regenerative medicine both in the liver and in other organs.

Hepatocyte growth factor plays a particular role in progression of overall cardiac damage in experimental pulmonary hypertension

Background: HGF/MET pathway may have a role in pulmonary hypertension (PH). However, the link between the pathway and development of target organ damage in PH remains elusive. We aimed to demonstrate the relation between plasma HGF and HGF/MET tissue expressions in affected organs during PH progression. Methods: 12 weeks old male Wistar rats were injected with monocrotaline (MCT, 60 mg/kg, s.c.) to induce PH and sacrificed after 1, 2 and 4 weeks. Controls received saline. mRNA levels of HGF regulatory complex (Hgf, Met, Hgfa, Hai-1, Hai-2) were determined in right and left ventricles (RV, LV), lungs, pulmonary artery and liver by RT-qPCR. HGF protein levels in plasma were analysed by ELISA. Results: PH development was associated with a progressive elevation of HGF plasma levels that correlated with relative RV mass. Furthermore, Hgf mRNA expressions at week 4 were upregulated solely in the cardiac ventricles while being downregulated in a. pulmonalis, lungs and liver. Met and Hai-1/Hai-2 followed a similar pattern and were upregulated in cardiac ventricles, where Hgfa remained unchanged, but downregulated in lungs. Conclusion: We suggest that cardiac overexpression of Hgf might contribute to increased plasma HGF in MCT-induced PH. HGF could be exploited as a cardiospecific biomarker and HGF/MET pathway as a target in drug discovery for PH.

Oxymatrine prevents the development of monocrotaline-induced pulmonary hypertension via regulation of the NG, NG-dimethyl-L-arginine metabolism pathways in rats

The purpose of this study was to investigate the potential effect of oxymatrine in monocrotaline-induced pulmonary hypertension and its possible influence on the N^G,N^G-dimethyl-L-arginine (ADMA) metabolism pathway. Pulmonary hypertension was induced in rats by a single-dose injection of monocrotaline (60 mg/kg). Daily oral administration of oxymatrine (25, 50 and 100 mg/kg) was started on the day following the monocrotaline injection for 28 days. Oxymatrine (50 and 100 mg/kg) significantly attenuated monocrotaline-induced lung and right ventricular hypertrophy, right ventricular systolic pressure elevation, and right ventricular dysfunction. Oxymatrine also reduced the thickening of monocrotaline-induced pulmonary arterial medial wall. Meanwhile, oxymatrine normalized the level of pulmonary asymmetric ADMA and attenuated the upregulated expression of protein arginine methyltransferase 1 (PRMT1). Oxymatrine had no effect on the expression of protein arginine methyltransferase 2 (PRMT2) and N^G,N^G-Dimethylarginine dimethylaminohydrolase 1 (DDAH1), which were upregulated in monocrotaline-induced pulmonary arterial hypertensive rats. However, the expression of the protein N^G,N^G-Dimethylarginine dimethylaminohydrolase 2 (DDAH2) did not differ among all groups (all P﹥0.05). These results suggest that oxymatrine may offer protective effects on the development of pulmonary hypertension by ameliorating pulmonary remodeling and modulating the ADMA metabolism pathway.

Primary and secondary pyrrolic metabolites of pyrrolizidine alkaloids form DNA adducts in human A549 cells

Humans and animals can be exposed to carcinogenic pyrrolizidine alkaloids (PAs) through consumption of plants commonly found in many parts of the world. Although the liver is the primary target organ for carcinogenic PAs, they have also induced lung tumors in rodents. Hepatic cytochrome P450 activity converts PAs into dehydro-PAs that can be hydrolyzed to dehydropyrrolizidine (DHP); these reactive pyrrolic metabolites can produce four characteristic DNA adducts associated with PA-induced liver tumor initiation in laboratory animals. We reported recently that these four DNA adducts are also formed when 7-glutathione-DHP (7-GS-DHP) or 7-cysteine-DHP is incubated with calf thymus DNA. Here we showed that the four characteristic DNA adducts were formed when human A549 brochoalveolar carcinoma cells were treated with three dehydro-PAs (dehydroriddelliine, dehydromonocrotaline, or dehydroretronecine) or with 7-GS-DHP or 7-cysteine-DHP. For comparison, two parent PAs (riddelliine and monocrotaline) and 7,9-di-glutathionine-DHP were studied. No DHP-DNA adducts were detected with these incubations, confirming that A549 lung carcinoma cells do not express cytochrome P450 enzymes required for metabolic activation of PAs. Our results show that primary and secondary pyrrolic metabolites of carcinogenic PAs produce characteristic DHP-containing DNA adducts in A549 lung cancer cells, suggesting that they are DNA reactive metabolites.

Role of cardiac inflammation in right ventricular failure

Right ventricular failure (RVF) is the main determinant of mortality in patients with pulmonary arterial hypertension (PAH). Although the exact pathophysiology underlying RVF remains unclear, inflammation may play an important role, as it does in left heart failure. Perivascular pulmonary artery and systemic inflammation is relatively well studied and known to contribute to the initiation and maintenance of the pulmonary vascular insult in PAH. However, less attention has been paid to the role of cardiac inflammation in RVF and PAH. Consistent with many other types of heart failure, cardiac inflammation, triggered by systemic and local stressors, has been shown in RVF patients as well as in RVF animal models. RV inflammation likely contributes to impaired RV contractility, maladaptive remodelling and a vicious circle between RV and pulmonary vascular injury. Although the potential to improve RV function through anti-inflammatory therapy has not been tested, this approach has been applied clinically in left ventricular failure patients, with variable success. Because inflammation plays a dual role in the development of both pulmonary vascular pathology and RVF, anti-inflammatory therapies may have a potential double benefit in patients with PAH and associated RVF.

Molecular pathogenesis and current pathology of pulmonary hypertension

Following its initial description over a century ago, pulmonary arterial hypertension (PAH) continues to challenge researchers committed to understanding its pathobiology and finding a cure. The last two decades have seen major developments in our understanding of the genetics and molecular basis of PAH that drive cells within the pulmonary vascular wall to produce obstructive vascular lesions; presently, the field of PAH research has taken numerous approaches to dissect the complex amalgam of genetic, molecular and inflammatory pathways that interact to initiate and drive disease progression. In this review, we discuss the current understanding of PAH pathology and the role that genetic factors and environmental influences share in the development of vascular lesions and abnormal cell function. We also discuss how animal models can assist in elucidating gene function and the study of novel therapeutics, while at the same time addressing the limitations of the most commonly used rodent models. Novel experimental approaches based on application of next generation sequencing, bioinformatics and epigenetics research are also discussed as these are now being actively used to facilitate the discovery of novel gene mutations and mechanisms that regulate gene expression in PAH. Finally, we touch on recent discoveries concerning the role of inflammation and immunity in PAH pathobiology and how they are being targeted with immunomodulatory agents. We conclude that the field of PAH research is actively expanding and the major challenge in the coming years is to develop a unified theory that incorporates genetic and mechanistic data to address viable areas for disease modifying drugs that can target key processes that regulate the evolution of vascular pathology of PAH.

Pulmonary Artery Hypertension Model in Rats by Monocrotaline Administration

Pulmonary arterial hypertension (PAH) is a syndrome characterized by pulmonary vascular remodeling and vasoconstriction, leading to increased pulmonary vascular resistance, right ventricular pressure overload and, eventually, to right ventricular failure and premature death. Animal models have been an essential tool for understanding pulmonary hypertension pathophysiology and for the discovery and development of novel therapies.MCT-induced PAH in rats leads to a significant increase in RV pressure and pulmonary vascular remodeling, as well as greater RV hypertrophy. In this chapter, we describe protocols for inducing and assessing the monocrotaline (MCT) rat model, the most classical and widely used in vivo model of PAH. Using this protocol, rats reproducibly develop pulmonary hypertension with a mean pulmonary pressure of ~40 mmHg approximately 4 weeks after single MCT administration.

Immune regulation of systemic hypertension, pulmonary arterial hypertension, and preeclampsia: shared disease mechanisms and translational opportunities

Systemic hypertension, preeclampsia, and pulmonary arterial hypertension (PAH) are diseases of high blood pressure in the systemic or pulmonary circulation. Beyond the well-defined contribution of more traditional pathophysiological mechanisms, such as changes in the renin-angiotensin-aldosterone system, to the development of these hypertensive disorders, there is substantial clinical evidence supporting an important role for inflammation and immunity in the pathogenesis of each of these three conditions. Over the last decade, work in small animal models, bearing targeted deficiencies in specific cytokines or immune cell subsets, has begun to clarify the immune-mediated mechanisms that drive changes in vascular structure and tone in hypertensive disease. By summarizing the clinical and experimental evidence supporting a contribution of the immune system to systemic hypertension, preeclampsia, and PAH, the current review highlights the cellular and molecular pathways that are common to all three hypertensive disorders. These mechanisms are centered on an imbalance in CD4⁺ helper T cell populations, defined by excessive Th17 responses and impaired T_reg activity, as well as the excessive activation or impairment of additional immune cell types, including macrophages, dendritic cells, CD8⁺ T cells, B cells, and natural killer cells. The identification of common immune mechanisms in systemic hypertension, preeclampsia, and PAH raises the possibility of new therapeutic strategies that target the immune component of hypertension across multiple disorders.