Beneficial effects of a novel agonist of the adenosine A2A receptor on monocrotaline-induced pulmonary hypertension in rats

Purinergic regulation of pulmonary vascular tone

Purinergic signaling is a crucial determinant in the regulation of pulmonary vascular physiology and presents a promising avenue for addressing lung diseases. This intricate signaling system encompasses two primary receptor classes: P1 and P2 receptors. P1 receptors selectively bind adenosine, while P2 receptors exhibit an affinity for ATP, ADP, UTP, and UDP. Functionally, P1 receptors are associated with vasodilation, while P2 receptors mediate vasoconstriction, particularly in basally relaxed vessels, through modulation of intracellular Ca2+ levels. The P2X subtype receptors facilitate extracellular Ca2+ influx, while the P2Y subtype receptors are linked to endoplasmic reticulum Ca2+ release. Notably, the primary receptor responsible for ATP-induced vasoconstriction is P2X1, with α,β-meATP and UDP being identified as potent vasoconstrictor agonists. Interestingly, ATP has been shown to induce endothelium-dependent vasodilation in pre-constricted vessels, associated with nitric oxide (NO) release. In the context of P1 receptors, adenosine stimulation of pulmonary vessels has been unequivocally demonstrated to induce vasodilation, with a clear dependency on the A2B receptor, as evidenced in studies involving guinea pigs and rats. Importantly, evidence strongly suggests that this vasodilation occurs independently of endothelium-mediated mechanisms. Furthermore, studies have revealed variations in the expression of purinergic receptors across different vessel sizes, with reports indicating notably higher expression of P2Y1, P2Y2, and P2Y4 receptors in small pulmonary arteries. While the existing evidence in this area is still emerging, it underscores the urgent need for a comprehensive examination of the specific characteristics of purinergic signaling in the regulation of pulmonary vascular tone, particularly focusing on the disparities observed across different intrapulmonary vessel sizes. Consequently, this review aims to meticulously explore the current evidence regarding the role of purinergic signaling in pulmonary vascular tone regulation, with a specific emphasis on the variations observed in intrapulmonary vessel sizes. This endeavor is critical, as purinergic signaling holds substantial promise in the modulation of vascular tone and in the proactive prevention and treatment of pulmonary vascular diseases.

Low Thyroid Hormones Level Attenuates Mitochondrial Dysfunction and Right Ventricular Failure in Pulmonary Hypertensive Rats

PURPOSE

This study is to investigate the repercussions of hypothyroidism in the pathophysiological progression of pulmonary arterial hypertension (PAH).

METHODS

While the control (CTL, n = 5) male Wistar rats received vehicle, PAH was induced with monocrotaline (MCT group, n = 15). Hypothyroidism was induced in a subset of rats by methimazole 3 weeks prior to the MCT injection (MMZ + MCT group, n = 15). Plasma thyroid hormones were measured by radioimmunoassay. Electrocardiographic, echocardiographic, and hemodynamic analyses were performed to evaluate the progression of PAH. Gene expression of antioxidant enzymes and cardiac hypertrophy markers were assessed by qPCR. Mitochondrial respiration, ATP levels, and ROS production were measured in right ventricular (RV) samples.

RESULTS

Plasma T3 and T4 decreased in both MCT and MMZ + MCT groups (p < 0.05). Right ventricular systolic pressure (RVSP) increased, and RV - dP/dt, + dP/dt, and contractility index decreased in the MCT versus the CTL group and remained within control levels in the MMZ + MCT group (p < 0.05). Relative RV weight, RV wall thickness, RV diastolic area, and relative lung weight were augmented in the MCT versus the CTL group, whereas all parameters were improved to the CTL levels in the MMZ + MCT group (p < 0.05). Only the MCT group exhibited an increased duration of QTc interval compared to the baseline period (p < 0.05). ADP-induced mitochondrial respiration and ATP levels were decreased, and ROS production was increased in MCT versus the CTL group (p < 0.05), while the MMZ + MCT group exhibited increased mitochondrial respiration versus the MCT group (p < 0.05).

CONCLUSION

Hypothyroidism attenuated the RV mitochondrial dysfunction and the pathophysiological progression of MCT-induced PAH.

Protective role of baicalin in the dynamic progression of lung injury to idiopathic pulmonary fibrosis: A meta-analysis

BACKGROUND AND PURPOSE

The pathological progression of lung injury (LI) to idiopathic pulmonary fibrosis (IPF) is a common feature of the development of lung disease. At present, effective strategies for preventing this progression are unavailable. Baicalin has been reported to specifically inhibit the progression of LI to IPF. Therefore, this meta-analysis aimed to assess its clinical application and its potential as a therapeutic drug for lung disease based on integrative analysis.

METHODS

We systematically searched preclinical articles in eight databases and reviewed them subjectively. The CAMARADES scoring system was used to assess the degree of bias and quality of evidence, whereas the STATA software (version 16.0 software) was used for statistical analysis, including a 3D analysis of the effects of dosage frequency of baicalin in LI and IPF. The protocol of this meta-analysis is documented in the PROSPERO database (CRD42022356152).

RESULTS

A total of 23 studies and 412 rodents were included after several rounds of screening. Baicalin was found to reduce the levels of TNF-α, IL-1β, IL-6, HYP, TGF-β and MDA and the W/D ratio and increase the levels of SOD. Histopathological analysis of lung tissue validated the regulatory effects of baicalin, and the 3D analysis of dosage frequency revealed that the effective dose of baicalin is 10-200 mg/kg. Mechanistically, baicalin can prevent the progression of LI to IPF by modulating p-Akt, p-NF-κB-p65 and Bcl-2-Bax-caspase-3 signalling. Additionally, baicalin is involved in signalling pathways closely related to anti-apoptotic activity and regulation of lung tissue and immune cells.

CONCLUSION

Baicalin at the dose of 10-200 mg/kg exerts protective effects against the progression of LI to IPF through anti-inflammatory and anti-apoptotic pathways.

Purinoceptor: a novel target for hypertension

Hypertension is the leading cause of morbidity and mortality globally among all cardiovascular diseases. Purinergic signalling plays a crucial role in hypertension through the sympathetic nerve system, neurons in the brain stem, carotid body, endothelium, immune system, renin-angiotensin system, sodium excretion, epithelial sodium channel activity (ENaC), and renal autoregulation. Under hypertension, adenosine triphosphate (ATP) is released as a cotransmitter from the sympathetic nerve. It mediates vascular tone mainly through P2X1R activation on smooth muscle cells and activation of P2X4R and P2YR on endothelial cells and also via interaction with other purinoceptors, showing dual effects. P2Y1R is linked to neurogenic hypertension. P2X7R and P2Y11R are potential targets for immune-related hypertension. P2X3R located on the carotid body is the most promising novel therapeutic target for hypertension. A₁R, A_2AR, A_2BR, and P2X7R are all related to renal autoregulation, which contribute to both renal damage and hypertension. The main focus is on the evidence addressing the involvement of purinoceptors in hypertension and therapeutic interventions.

CD39 in the development and progression of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a devastating progressive disease characterised by pulmonary arterial vasoconstriction and vascular remodelling. Endothelial dysfunction has emerged as a contributing factor in the development of PAH. However, despite progress in the understanding of the pathophysiology of this disease, current therapies fail to impact upon long-term outcomes which remain poor in most patients. Recent observations have suggested the disturbances in the balance between ATP and adenosine may be integral to the vascular remodelling seen in PAH. CD39 is an enzyme important in regulating these nucleos(t)ides which may also provide a novel pathway to target for future therapies. This review summarises the role of adenosine signalling in the development and progression of PAH and highlights the therapeutic potential of CD39 for treatment of PAH.

Computational modelling of multi-temporal ventricular-vascular interactions during the progression of pulmonary arterial hypertension

A computational framework is developed to consider the concurrent growth and remodelling (G&R) processes occurring in the large pulmonary artery (PA) and right ventricle (RV), as well as ventricular-vascular interactions during the progression of pulmonary arterial hypertension (PAH). This computational framework couples the RV and the proximal PA in a closed-loop circulatory system that operates in a short timescale of a cardiac cycle, and evolves over a long timescale due to G&R processes in the PA and RV. The framework predicts changes in haemodynamics (e.g. 68.2% increase in mean PA pressure), RV geometry (e.g. 38% increase in RV end-diastolic volume) and PA tissue microstructure (e.g. 90% increase in collagen mass) that are consistent with clinical and experimental measurements of PAH. The framework also predicts that a reduction in RV contractility is associated with long-term RV chamber dilation, a common biomarker observed in the late-stage PAH. Sensitivity analyses on the G&R rate constants show that large PA stiffening (both short and long term) is affected by RV remodelling more than the reverse. This framework can serve as a foundation for the future development of a more predictive and comprehensive cardiovascular G&R model with realistic heart and vascular geometries.

Novel p38 Mitogen-Activated Protein Kinase Inhibitor Reverses Hypoxia-Induced Pulmonary Arterial Hypertension in Rats

Mitogen-activated protein kinase (MAPK) signaling is strongly implicated in cardiovascular remodeling in pulmonary hypertension (PH) and right ventricle (RV) failure. The effects of a newly designed p38 inhibitor, LASSBio-1824, were investigated in experimentally induced PH. Male Wistar rats were exposed to hypoxia and SU5416 (SuHx), and normoxic rats were used as controls. Oral treatment was performed for 14 days with either vehicle or LASSBio-1824 (50 mg/kg). Pulmonary vascular resistance and RV structure and function were assessed by echocardiography and catheterization. Histological, immunohistochemical and Western blot analysis of lung and RV were performed to investigate cardiovascular remodeling and inflammation. Treatment with LASSBio-1824 normalized vascular resistance by attenuating vessel muscularization and endothelial dysfunction. In the heart, treatment decreased RV systolic pressure, hypertrophy and collagen content, improving cardiac function. Protein content of TNF-α, iNOS, phosphorylated p38 and caspase-3 were reduced both in lung vessels and RV tissues after treatment and a reduced activation of transcription factor c-fos was found in cardiomyocytes of treated SuHx rats. Therefore, LASSBio-1824 represents a potential candidate for remodeling-targeted treatment of PH.

Metabolite G-Protein Coupled Receptors in Cardio-Metabolic Diseases

G protein-coupled receptors (GPCRs) have originally been described as a family of receptors activated by hormones, neurotransmitters, and other mediators. However, in recent years GPCRs have shown to bind endogenous metabolites, which serve functions other than as signaling mediators. These receptors respond to fatty acids, mono- and disaccharides, amino acids, or various intermediates and products of metabolism, including ketone bodies, lactate, succinate, or bile acids. Given that many of these metabolic processes are dysregulated under pathological conditions, including diabetes, dyslipidemia, and obesity, receptors of endogenous metabolites have also been recognized as potential drug targets to prevent and/or treat metabolic and cardiovascular diseases. This review describes G protein-coupled receptors activated by endogenous metabolites and summarizes their physiological, pathophysiological, and potential pharmacological roles.

Pharmacological Tuning of Adenosine Signal Nuances Underlying Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) roughly represents half of the cardiac failure events in developed countries. The proposed 'systemic microvascular paradigm' has been used to explain HFpHF presentation heterogeneity. The lack of effective treatments with few evidence-based therapeutic recommendations makes HFpEF one of the greatest unmet clinical necessities worldwide. The endogenous levels of the purine nucleoside, adenosine, increase significantly following cardiovascular events. Adenosine exerts cardioprotective, neuromodulatory, and immunosuppressive effects by activating plasma membrane-bound P1 receptors that are widely expressed in the cardiovascular system. Its proven benefits have been demonstrated in preclinical animal tests. Here, we provide a comprehensive and up-to-date critical review about the main therapeutic advantages of tuning adenosine signalling pathways in HFpEF, without discounting their side effects and how these can be seized.

In situ Evidence of Collagen V and Interleukin-6/Interleukin-17 Activation in Vascular Remodeling of Experimental Pulmonary Hypertension

Several studies have reported the pathophysiologic and molecular mechanisms responsible for pulmonary arterial hypertension (PAH). However, the in situ evidence of collagen V (Col V) and interleukin-17 (IL-17)/interleukin-6 (IL-6) activation in PAH has not been fully elucidated. We analyzed the effects of collagen I (Col I), Col V, IL-6, and IL-17 on vascular remodeling and hemodynamics and its possible mechanisms of action in monocrotaline (MCT)-induced PAH. Twenty male Wistar rats were randomly divided into two groups. In the PAH group, animals received MCT 60 mg/kg intraperitoneally, whereas the control group (CTRL) received saline. On day 21, the pulmonary blood pressure (PAP) and right ventricular systolic pressure (RVSP) were determined. Lung histology (smooth muscle cell proliferation [α-smooth muscle actin; α-SMA] and periadventitial fibrosis), immunofluorescence (Col I, Col V, and α-SMA), immunohistochemistry (IL-6, IL-17, and transforming growth factor-beta [TGF-β]), and transmission electron microscopy to detect fibronexus were evaluated. The RVSP (40 ± 2 vs. 24 ± 1 mm Hg, respectively; p < 0.0001), right ventricle hypertrophy index (65 ± 9 and 25 ± 5%, respectively; p < 0.0001), vascular periadventitial Col I and Col V, smooth muscle cell α-SMA+, fibronexus, IL-6, IL-17, and TGF-β were higher in the MCT group than in the CTRL group. In conclusion, our findings indicate in situ evidence of Col V and IL-6/IL-17 activation in vascular remodeling and suggest that increase of Col V may yield potential therapeutic targets for treating patients with PAH.

Purinergic Dysfunction in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a life‐threatening disease characterized by increased pulmonary arterial pressure and pulmonary vascular resistance, which result in an increase in afterload imposed onto the right ventricle, leading to right heart failure. Current therapies are incapable of reversing the disease progression. Thus, the identification of novel and potential therapeutic targets is urgently needed. An alteration of nucleotide‐ and nucleoside‐activated purinergic signaling has been proposed as a potential contributor in the pathogenesis of PAH. Adenosine‐mediated purinergic 1 receptor activation, particularly A_2AR activation, reduces pulmonary vascular resistance and attenuates pulmonary vascular remodeling and right ventricle hypertrophy, thereby exerting a protective effect. Conversely, A_2BR activation induces pulmonary vascular remodeling, and is therefore deleterious. ATP‐mediated P2X₇R activation and ADP‐mediated activation of P2Y₁R and P2Y₁₂R play a role in pulmonary vascular tone, vascular remodeling, and inflammation in PAH. Recent studies have revealed a role of ectonucleotidase nucleoside triphosphate diphosphohydrolase, that degrades ATP/ADP, in regulation of pulmonary vascular remodeling. Interestingly, existing evidence that adenosine activates erythrocyte A_2BR signaling, counteracting hypoxia‐induced pulmonary injury, and that ATP release is impaired in erythrocyte in PAH implies erythrocyte dysfunction as an important trigger to affect purinergic signaling for pathogenesis of PAH. The present review focuses on current knowledge on alteration of nucleot(s)ide‐mediated purinergic signaling as a potential disease mechanism underlying the development of PAH.

Cardioprotection Induced by Activation of GPER in Ovariectomized Rats With Pulmonary Hypertension

Pulmonary hypertension (PH) is a disease of women (female-to-male ratio 4:1), and is associated with cardiac and skeletal muscle dysfunction. Herein, the activation of a new estrogen receptor (GPER) by the agonist G1 was evaluated in oophorectomized rats with monocrotaline (MCT)-induced PH. Depletion of estrogen was induced by bilateral oophorectomy (OVX) in Wistar rats. Experimental groups included SHAM or OVX rats that received a single intraperitoneal injection of MCT (60 mg/kg) for PH induction. Animals received s.c. injection of either vehicle or G1, a GPER agonist, (400 µg/kg/day) for 14 days after the onset of disease. Rats with PH exhibited exercise intolerance and cardiopulmonary alterations, including reduced pulmonary artery flow, biventricular remodeling, and left ventricular systolic and diastolic dysfunction. The magnitude of these PH-induced changes was significantly greater in OVX versus SHAM rats. G1 treatment reversed both cardiac and skeletal muscle functional aberrations caused by PH in OVX rats. G1 reversed PH-related cardiopulmonary dysfunction and exercise intolerance in female rats, a finding that may have important implications for the ongoing clinical evaluation of new drugs for the treatment of the disease in females after the loss of endogenous estrogens.

Magnolol ameliorates pneumonectomy and monocrotaline-induced pulmonary arterial hypertension in rats through inhibition of angiotensin II and endothelin-1 expression

BACKGROUND

Magnolol, a major bioactive component extracted from Magnolia officinalis, exerts several beneficial effects, such as anti-inflammatory and anti-hypertensive activities.

PURPOSE

In this study, we investigated whether magnolol has a protective effect on pneumonectomy and monocrotaline-induced pulmonary arterial hypertension (PAH) in rats.

DESIGN/METHODS

The alterations of right ventricular (RV) hypertrophy, pulmonary vascular remodeling, histopathological parameters, and related gene expression and signaling pathways in lungs by magnolol treatment were studied in the PAH rats.

RESULTS

Administration of magnolol greatly ameliorated the characteristic features of PAH, including increased pulmonary arterial pressure, RV hypertrophy, and pulmonary vascular remodeling. Moreover, magnolol inhibited angiotensin-converting enzyme (ACE)/angiotensin II (Ang II)/Ang II type 1 receptor (AT-1R) cascade, whereas upregulates ACE2 in the lungs of PAH rats. The overexpression of endothelin-1 (ET-1) and ET_A receptor occurred in the PAH rats was significantly attenuated by magnolol through inhibition of Akt/ERK1/2/GSK3β/β-catenin pathway. Compared with that of untreated PAH rats, higher expression of endothelial nitric oxide synthase, and lower expression of inducible nitric oxide synthase and O₂^- production in lungs were observed in magnolol-treated PAH rats.

CONCLUSION

We demonstrated that treatment with magnolol reduces the development of PAH induced by pneumonectomy and monocrotaline in rats, and suppressing Ang II and ET-1-mediated processes may contribute to its protective effects. These findings suggest that magnolol may be a potential agent for PAH therapy.

A current view of G protein-coupled receptor - mediated signaling in pulmonary hypertension: finding opportunities for therapeutic intervention

Pathological vascular remodeling is observed in various cardiovascular diseases including pulmonary hypertension (PH), a disease of unknown etiology that has been characterized by pulmonary artery vasoconstriction, right ventricular hypertrophy, vascular inflammation, and abnormal angiogenesis in pulmonary circulation. G protein-coupled receptors (GPCRs) are the largest family in the genome and widely expressed in cardiovascular system. They regulate all aspects of PH pathophysiology and represent therapeutic targets. We overview GPCRs function in vasoconstriction, vasodilation, vascular inflammation-driven remodeling and describe signaling cross talk between GPCR, inflammatory cytokines, and growth factors. Overall, the goal of this review is to emphasize the importance of GPCRs as critical signal transducers and targets for drug development in PH.

GPCRs in pulmonary arterial hypertension: tipping the balance

Pulmonary arterial hypertension (PAH) is a progressive, fatal disease characterised by increased pulmonary vascular resistance and excessive proliferation of pulmonary artery smooth muscle cells (PASMC). GPCRs, which are attractive pharmacological targets, are important regulators of pulmonary vascular tone and PASMC phenotype. PAH is associated with the altered expression and function of a number of GPCRs in the pulmonary circulation, which leads to the vasoconstriction and proliferation of PASMC and thereby contributes to the imbalance of pulmonary vascular tone associated with PAH; drugs targeting GPCRs are currently used clinically to treat PAH and extensive preclinical work supports the utility of a number of additional GPCRs. Here we review how GPCR expression and function changes with PAH and discuss why GPCRs continue to be relevant drug targets for the disease.

Baicalein Ameliorates Pulmonary Arterial Hypertension Caused by Monocrotaline through Downregulation of ET-1 and ETAR in Pneumonectomized Rats

Baicalein (BE) extracted from Scutellaria baicalensis Georgi is able to alleviate various cardiovascular and inflammatory diseases. However, the effects of BE on pulmonary arterial hypertension (PAH) remain unknown. Therefore, the present study aimed to examine whether BE ameliorates pneumonectomy and monocrotaline-induced PAH in rats and further investigate the underlying molecular mechanisms. Administration of BE greatly attenuated the development of PAH as evidenced by an improvement of its characteristic features, including elevation of right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary vascular remodeling. Moreover, the increased protein expression of endothelin-1 (ET-1) and ETA receptor (ETAR), superoxide overproduction, and activation of Akt/ERK1/2/GSK3[Formula: see text]/[Formula: see text]-catenin pathway that occurred in the lungs of PAH rats were markedly reversed by BE treatment. Compared with the untreated PAH rats, higher expression of endothelial nitric oxide synthase (eNOS), but lower levels of inducible nitric oxide synthase and vWF were observed in BE-treated PAH rats. Collectively, treatment with BE remarkably attenuates the pathogenesis of PAH, and the protection of BE may be associated with suppressing Akt/Erk1/2/GSK3[Formula: see text]/[Formula: see text]-catenin/ET-1/ETAR signaling and preventing endothelial dysfunction. These results suggest that BE is a potential agent for treatment of PAH.

Synergistic interaction between a PDE5 inhibitor (sildenafil) and a new adenosine A2A receptor agonist (LASSBio-1359) improves pulmonary hypertension in rats

Introduction

Pulmonary hypertension (PH) is characterized by enhanced pulmonary vascular resistance, which causes right ventricle (RV) pressure overload and results in right sided heart failure and death. This work investigated the effectiveness of a combined therapy with PDE5 inhibitor (PDE5i) and a new adenosine A2A receptor (A2AR) agonist in mitigating monocrotaline (MCT) induced PH in rats.

Methods

An in vitro isobolographic analysis was performed to identify possible synergistic relaxation effect between sildenafil and LASSBio 1359 in rat pulmonary arteries (PAs). In the in vivo experiments, PH was induced in male Wistar rats by a single intraperitoneal injection of 60 mg/kg MCT. Rats were divided into the following groups: control (saline injection only), MCT + vehicle, MCT + sildenafil, MCT + LASSBio 1359 and MCT + combination of sildenafil and LASSBio 1359. Fourteen days after the MCT injection, rats were treated daily with oral administration of the regimen therapies or vehicle for 14 days. Cardiopulmonary system function and structure were evaluated by echocardiography. RV systolic pressure and PA endothelial function were measured.

Results

Isobolographic analysis showed a synergistic interaction between sildenafil and LASSBio 1359 in rat PAs. Combined therapy with sildenafil and LASSBio 1359 but not monotreatment with low dosages of either sildenafil or LASSBio 1359 ameliorated all of PH related abnormalities in cardiopulmonary function and structure in MCT challenged rats.

Conclusions

The combination of sildenafil and LASSBio 1359 has a synergistic interaction, suggesting that combined use of these pharmacological targets may be an alternative to improve quality of life and outcomes for PH patients.

Adenosine A(2A) receptor activation reverses hypoxia‑induced rat pulmonary artery smooth muscle cell proliferation via cyclic AMP‑mediated inhibition of the SDF1‑CXC4 signaling pathway

The occurrence and the subsequent development of pulmonary arterial hypertension (PAH) involve complicated mechanisms. Of these, the proliferation of pulmonary artery smooth muscle cells (PASMCs) has been indicated to be closely associated with its progression. Therefore, therapeutic methods targeting PASMCs to inhibit proliferation is an effective method for alleviating PAH. The present study was designed to determine the role of the adenosine A(2A) receptor (A2A receptor) in hypoxia‑induced rat PASMC (RPASMC) proliferation. Primary RPASMCs were isolated from the pulmonary artery of adult male SD rats, cultured and used for the following experiments. The mRNA level and protein expression of CXCR4 were measured by reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. The cell proliferation of RPASMCs was measured using a cell proliferation assay kit. In the present study, it was demonstrated that the proliferation of RPASMCs was partially mediated by activation of the stromal cell‑derived factor 1 (SDF1)‑CXC chemokine receptor 4 (CXCR4) axis under hypoxic conditions. In addition, SDF1‑α alone upregulated the mRNA and protein expression levels of CXCR4, and stimulated the proliferation of RPASMCs. The protein expression of CXCR4 and the cell proliferation were markedly inhibited by application of A2A receptor agonist CGS21680 or cyclic adenosine monophosphate (cAMP) under hypoxic conditions or treatment with SDF1‑α and was reversed by the A2A receptor antagonist SCH58261 or 8‑bromoadenosine‑3',5'‑cyclic monophosphorothioate. These results demonstrated that the inhibition of SDF1‑CXC4 signaling by the activation of A2A receptor and subsequent increase in the level of cAMP may be a potential method to ameliorate PAH.

Adenosine Receptors As Drug Targets for Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a clinical condition characterized by pulmonary arterial remodeling and vasoconstriction, which promote chronic vessel obstruction and elevation of pulmonary vascular resistance. Long-term right ventricular (RV) overload leads to RV dysfunction and failure, which are the main determinants of life expectancy in PAH subjects. Therapeutic options for PAH remain limited, despite the introduction of prostacyclin analogs, endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and soluble guanylyl cyclase stimulators within the last 15 years. Through addressing the pulmonary endothelial and smooth muscle cell dysfunctions associated with PAH, these interventions delay disease progression but do not offer a cure. Emerging approaches to improve treatment efficacy have focused on beneficial actions to both the pulmonary vasculature and myocardium, and several new targets have been investigated and validated in experimental PAH models. Herein, we review the effects of adenosine and adenosine receptors (A₁, A_2A, A_2B, and A₃) on the cardiovascular system, focusing on the A_2A receptor as a pharmacological target. This receptor induces pulmonary vascular and heart protection in experimental models, specifically models of PAH. Targeting the A_2A receptor could potentially serve as a novel and efficient approach for treating PAH and concomitant RV failure. A_2A receptor activation induces pulmonary endothelial nitric oxide synthesis, smooth muscle cell hyperpolarization, and vasodilation, with important antiproliferative activities through the inhibition of collagen deposition and vessel wall remodeling in the pulmonary arterioles. The pleiotropic potential of A_2A receptor activation is highlighted by its additional expression in the heart tissue, where it participates in the regulation of intracellular calcium handling and maintenance of heart chamber structure and function. In this way, the activation of A_2A receptor could prevent the production of a hypertrophic and dysfunctional phenotype in animal models of cardiovascular diseases.

Mesenchymal stromal cell therapy reduces lung inflammation and vascular remodeling and improves hemodynamics in experimental pulmonary arterial hypertension

Background

Experimental research has reported beneficial effects of mesenchymal stromal cell (MSC) therapy in pulmonary arterial hypertension (PAH). However, these studies either were based on prophylactic protocols or assessed basic remodeling features without evaluating possible mechanisms. We analyzed the effects of MSC therapy on lung vascular remodeling and hemodynamics and its possible mechanisms of action in monocrotaline (MCT)-induced PAH.

Methods

Twenty-eight Wistar rats were randomly divided into two groups. In the PAH group, animals received MCT 60 mg/kg intraperitoneally, while a control group received saline (SAL) instead. On day 14, both groups were further randomized to receive 10⁵ adipose-derived MSCs or SAL intravenously (n = 7/group). On day 28, right ventricular systolic pressure (RVSP) and the gene expression of mediators associated with apoptosis, inflammation, fibrosis, Smad-1 levels, cell proliferation, and endothelial–mesenchymal transition were determined. In addition, lung histology (smooth muscle cell proliferation and plexiform-like injuries), CD68⁺ and CD163⁺ macrophages, and plasma levels of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) were evaluated.

Results

In the PAH group, adipose-derived MSCs, compared to SAL, reduced mean RVSP (29 ± 1 vs 39 ± 2 mmHg, p < 0.001), lung tissue collagen fiber content, smooth muscle cell proliferation, CD68⁺ macrophages, interleukin-6 expression, and the antiapoptotic mediators Bcl-2 and survivin. Conversely, expression of the proapoptotic mediator procaspase-3 and plasma VEGF increased, with no changes in PDGF. In the pulmonary artery, MSCs dampened the endothelial–mesenchymal transition.

Conclusion

In MCT-induced PAH, MSC therapy reduced lung vascular remodeling, thus improving hemodynamics. These beneficial effects were associated with increased levels of proapoptotic markers, mesenchymal-to-endothelial transition, reduced cell proliferation markers, and inflammation due to a shift away from the M1 phenotype.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0669-0) contains supplementary material, which is available to authorized users.

Role of P2X7R in the development and progression of pulmonary hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a devastating disease that lacks sufficient treatment. Studies have shown that the Nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome contributes to PAH pathogenesis, but the role of the upstream molecular P2X₇ receptor (P2X₇R) has remained unexplored. We investigated the role of P2X7R in the pathogenesis of PAH.

METHODS AND RESULTS

PH was induced by a single subcutaneous injection of monocrotaline (MCT) (60 mg/kg) on left pneumonectomised Sprague-Dawley rats, as validated by significant increases in pulmonary artery pressure and vessel wall thickness. Marked P2X₇R was detected by predominant PA immunostaining in lungs from PH rats. Western blot revealed a significant increase in the protein levels of P2X₇R as well as NLRP3 and caspase-1 in the diseased lung tissue compared with normal tissue. The rats received A-740003 (a selective P2X₇ receptor antagonist, 30 mg/kg) daily starting from 1 week before or 2 weeks after MCT injection. Consequently, A-740003 reversed the NLRP3 inflammasome upregulation, significantly decreased the mean right ventricular (RV) pressure and RV hypertrophy, and reversed pulmonary arterial remodelling 4 weeks after MCT injection, as both a pretreatment and rescue intervention. Notably, A-740003 significantly reduced macrophage and pro-inflammatory cytokine levels, as measured via bronchoalveolar lavage. The recruitment of macrophages as well as collagen fibre deposition in the perivascular areas were also reduced, as confirmed by histological staining.

CONCLUSIONS

P2X₇R contributes to the pathogenesis of PH, probably in association with activation of the NLRP3 inflammasome. Blockade of P2X7R might be applied as a novel therapeutic approach for the treatment of PAH.

The Adenosinergic System as a Therapeutic Target in the Vasculature: New Ligands and Challenges

Adenosine is an adenine base purine with actions as a modulator of neurotransmission, smooth muscle contraction, and immune response in several systems of the human body, including the cardiovascular system. In the vasculature, four P1-receptors or adenosine receptors—A₁, A_2A, A_2B and A₃—have been identified. Adenosine receptors are membrane G-protein receptors that trigger their actions through several signaling pathways and present differential affinity requirements. Adenosine is an endogenous ligand whose extracellular levels can reach concentrations high enough to activate the adenosine receptors. This nucleoside is a product of enzymatic breakdown of extra and intracellular adenine nucleotides and also of S-adenosylhomocysteine. Adenosine availability is also dependent on the activity of nucleoside transporters (NTs). The interplay between NTs and adenosine receptors’ activities are debated and a particular attention is given to the paramount importance of the disruption of this interplay in vascular pathophysiology, namely in hypertension., The integration of important functional aspects of individual adenosine receptor pharmacology (such as in vasoconstriction/vasodilation) and morphological features (within the three vascular layers) in vessels will be discussed, hopefully clarifying the importance of adenosine receptors/NTs for modulating peripheral mesenteric vascular resistance. In recent years, an increase interest in purine physiology/pharmacology has led to the development of new ligands for adenosine receptors. Some of them have been patented as having promising therapeutic activities and some have been chosen to undergo on clinical trials. Increased levels of endogenous adenosine near a specific subtype can lead to its activation, constituting an indirect receptor targeting approach either by inhibition of NT or, alternatively, by increasing the activity of enzymes responsible for ATP breakdown. These findings highlight the putative role of adenosinergic players as attractive therapeutic targets for cardiovascular pathologies, namely hypertension, heart failure or stroke. Nevertheless, several aspects are still to be explored, creating new challenges to be addressed in future studies, particularly the development of strategies able to circumvent the predicted side effects of these therapies.

Adenosine A2A receptor agonist prevents cardiac remodeling and dysfunction in spontaneously hypertensive male rats after myocardial infarction

Background

This work evaluated the hypothesis that 3,4-methylenedioxybenzoyl-2-thienylhydrazone (LASSBio-294), an agonist of adenosine A_2A receptor, could be beneficial for preventing cardiac dysfunction due to hypertension associated with myocardial infarction (MI).

Methods

Male spontaneously hypertensive rats (SHR) were randomly divided into four groups (six animals per group): sham-operation (SHR-Sham), and myocardial infarction rats (SHR-MI) were treated orally either with vehicle or LASSBio-294 (10 and 20 mg.kg⁻¹.d⁻¹) for 4 weeks. Echocardiography and in vivo hemodynamic parameters measured left ventricle (LV) structure and function. Exercise tolerance was evaluated using a treadmill test. Cardiac remodeling was accessed by LV collagen deposition and tumor necrosis factor α expression.

Results

Early mitral inflow velocity was significantly reduced in the SHR-MI group, and there was significant recovery in a dose-dependent manner after treatment with LASSBio-294. Exercise intolerance observed in the SHR-MI group was prevented by 10 mg.kg⁻¹.d⁻¹ of LASS-Bio-294, and exercise tolerance exceeded that of the SHR-Sham group at 20 mg.kg⁻¹.d⁻¹. LV end-diastolic pressure increased after MI, and this was prevented by 10 and 20 mg.kg⁻¹.d⁻¹ of LASSBio-294. Sarcoplasmic reticulum Ca²⁺ ATPase levels were restored in a dose-dependent manner after treatment with LASSBio-294. Fibrosis and inflammatory processes were also counteracted by LASSBio-294, with reductions in LV collagen deposition and tumor necrosis factor α expression.

Conclusion

In summary, oral administration of LASSBio-294 after MI in a dose-dependent manner prevented the development of cardiac dysfunction, demonstrating this compound’s potential as an alternative treatment for heart failure in the setting of ischemic heart disease with superimposed chronic hypertension.

Bucindolol improves right ventricle function in rats with pulmonary arterial hypertension through the reversal of autonomic imbalance

Pulmonary arterial hypertension (PAH) is characterised by an elevation in afterload imposed on the right ventricle (RV), leading to hypertrophy and failure. The autonomic nervous system (ANS) plays a key role in the progression to heart failure, and the use of beta-blockers attenuates this process. The aim of this study was to verify the role of bucindolol, aβ1-, β2- and α1-blocker, on the ANS, and its association with RV function in rats with PAH. Male Wistar rats were divided into four groups: control, monocrotaline, control+bucindolol, and monocrotaline+bucindolol. PAH was induced by a single intraperitoneal injection of monocrotaline (60mg/kg). After two weeks, animals were treated for seven days with bucindolol (2mg/kg/day i.p.) or vehicle. At the end of the treatment, animals underwent echocardiographic assessment, catheterisation of the femoral artery and RV, and tissue collection for morphometric and histological evaluation. In the monocrotaline+bucindolol group, there was a decrease in mean pulmonary artery pressure (33%) and pulmonary congestion (21%), when compared to the monocrotaline. Bucindolol treatment also reduced RV pleomorphism, necrosis, fibrosis and infiltration of inflammatory cells. An improvement in RV systolic function was also observed in the monocrotaline+bucindolol group compared to the monocrotaline. In addition, bucindolol promoted a decrease in the cardiac sympathovagal balance (93%) by reducing sympathetic drive (70%) and increasing parasympathetic drive (142%). Bucindolol also reduced blood pressure variability (75%). Our results show that the beneficial effects from bucindolol treatment appeared to be a consequence of the reversal of monocrotaline-induced autonomic imbalance.

Activation of GPER ameliorates experimental pulmonary hypertension in male rats

RATIONALE

Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling that leads to pulmonary congestion, uncompensated right-ventricle (RV) failure, and premature death. Preclinical studies have demonstrated that the G protein-coupled estrogen receptor (GPER) is cardioprotective in male rats and that its activation elicits vascular relaxation in rats of either sex.

OBJECTIVES

To study the effects of GPER on the cardiopulmonary system by the administration of its selective agonist G1 in male rats with monocrotaline (MCT)-induced PH.

METHODS

Rats received a single intraperitoneal injection of MCT (60mg/kg) for PH induction. Experimental groups were as follows: control, MCT+vehicle, and MCT+G1 (400μg/kg/daysubcutaneous). Animals (n=5pergroup) were treated with vehicle or G1 for 14days after disease onset.

MEASUREMENTS AND MAIN RESULTS

Activation of GPER attenuated exercise intolerance and reduced RV overload in PH rats. Rats with PH exhibited echocardiographic alterations, such as reduced pulmonary flow, RV hypertrophy, and left-ventricle dysfunction, by the end of protocol. G1 treatment reversed these PH-related abnormalities of cardiopulmonary function and structure, in part by promoting pulmonary endothelial nitric oxide synthesis, Ca²⁺ handling regulation and reduction of inflammation in cardiomyocytes, and a decrease of collagen deposition by acting in pulmonary and cardiac fibroblasts.

CONCLUSIONS

G1 was effective to reverse PH-induced RV dysfunction and exercise intolerance in male rats, a finding that have important implications for ongoing clinical evaluation of new cardioprotective and vasodilator drugs for the treatment of the disease.

Baicalin attenuates bleomycin-induced pulmonary fibrosis via adenosine A2a receptor related TGF-β1-induced ERK1/2 signaling pathway

BACKGROUND

Baicalin has been reported to have anti-fibrosis effect; however, its mechanism still remains to be elucidated. Adenosine A2a receptor (A2aR) is a novel inflammation regulator, and transforming growth factor-β1 (TGF-β1)-induced extracellular signal regulated kinase1/2 (ERK1/2) signaling pathway plays an important role in idiopathic pulmonary fibrosis (IPF). This study was to explore the relationship of A2aR and TGF-β1-induced ERK1/2 in bleomycin (BLM)-induced pulmonary fibrosis in mice, and to investigate whether A2aR mediate the anti-fibrosis effect of Baicalin on BLM-induced pulmonary fibrosis.

METHODS

The A2aR-/- and A2aR+/+ mice were respectively divided into three groups: control group, model group, baicalin group. Pulmonary fibrosis was induced in mice of model groups by intratracheal instillation of bleomycin, and baicalin was administered in mice of baicalin groups daily for 28 days. Histopathological and ultrastructural changes of lung tissues were evaluated. Lung coefficient and the levels of hydroxyproline (HYP) in lung tissues were measured at the same time. The levels of serum TGF-β1 were measured by ELISA. The expression of TGF-β1, ERK1/2, p-ERK1/2 and A2aR were detected by western blot and immunohistochemical staining techniques.

RESULTS

Severe lung fibrosis was observed in the bleomycin-treated mice on day 28. The histopathological findings and collagen content of lung tissues were much severer/higher in A2aR-/- mice than in A2aR+/+ mice. We also showed that TGF-β1 and p-ERK1/2 were upregulated in bleomycin-treated mice and expressed higher in A2aR-/- mice compared to A2aR+/+ mice. Besides, bleomycin-treated A2aR+/+ mice had increased A2aR level in lungs. However, long-term treatment with baicalin in A2aR-/- and A2aR+/+ mice significantly ameliorated the histopathological changes in lungs. Moreover, Increased TGF-β1 and p-ERK1/2 expressions in bleomycin-treated A2aR-/- and A2aR+/+ mice were obviously diminished by baicalin. The baicalin-treated A2aR-/- mice had severer lung fibrosis and higher expressions of TGF-β1 and p-ERK1/2 than A2aR+/+ mice. Baicalin has also upregulated the expression of A2aR in A2aR+/+ mice.

CONCLUSIONS

Genetic inactivation of A2aR exacerbated the pathological processes of bleomycin-induced pulmonary fibrosis. Together, baicalin could inhibit BLM-induced pulmonary fibrosis by upregulating A2aR, suggesting A2aR as a therapeutic target of baicalin for the treatment of pulmonary fibrosis.

Lung-specific RNA interference of coupling factor 6, a novel peptide, attenuates pulmonary arterial hypertension in rats

Background

Pulmonary arterial hypertension (PAH) is a progressive and life-threatening disease associated with high morbidity and mortality rates. However, the exact regulatory mechanism of PAH is unknown. Although coupling factor 6 (CF6) is known to function as a repressor, its role in PAH has not been explored. Here, we investigated the involvement of endogenous CF6 in the development of PAH.

Methods

PAH was induced with monocrotaline (MCT), as demonstrated by significant increases in pulmonary artery pressure and vessel wall thickness. The adeno-associated virus (AAV) carrying CF6 short hairpin RNA (shRNA) or control vector (2×10¹⁰ gp) was intratracheally transfected into the lungs of rats 2 weeks before or after MCT injection.

Results

A 2-6-fold increase in CF6 was observed in the lungs and circulation of the MCT-injected rats as confirmed by qRT-PCR and ELISA. Immunohistochemistry analysis revealed a small quantity of CF6 localized to endothelial cells (ECs) under physiological conditions spread to surrounding tissues in a paracrine manner in PAH lungs. Notably, CF6 shRNA effectively inhibited CF6 expression, abolished lung macrophage infiltration, reversed endothelial dysfunction and vascular remodeling, and ameliorated the severity of pulmonary hypertension and right ventricular dysfunction at 4 weeks both as a pretreatment and rescue intervention. In addition, the circulating and lung levels of 6-keto-PGF1a, a stable metabolite of prostacyclin, were reversed by CF6 inhibition, suggesting that the effect of CF6 inhibition may partly be mediated through prostacyclin.

Conclusions

CF6 contributes to the pathogenesis of PAH, probably in association with downregulation of prostacyclin. The blockage of CF6 might be applied as a novel therapeutic approach for PAH and PA remodeling.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0409-5) contains supplementary material, which is available to authorized users.

Treatment with Adenosine Receptor Agonist Ameliorates Pain Induced by Acute and Chronic Inflammation

Rheumatoid arthritis is an inflammatory autoimmune condition, and tumor necrosis factor-α (TNF-α) plays an important role in its pathophysiology. In vitro, (E)-N'-(3,4-dimethoxybenzylidene)-N-methylbenzohydrazide (LASSBio-1359) has exhibited anti-TNF-α properties, and in vivo these effects are mediated via activation of adenosine receptor. This work investigates the antinociceptive action of LASSBio-1359 in murine models of acute and chronic inflammatory pain. Male mice received an intraperitoneal injection of LASSBio-1359 and then were evaluated in formalin- and carrageenan-induced paw edema assays. Complete Freund's adjuvant (CFA) was used to induce a mouse model of monoarthritis. These mice were treated with LASSBio-1359 by oral gavage to evaluate thermal and mechanical hyperalgesia. TNF-α and inducible nitric oxide synthase (iNOS) expression as well as histologic features were analyzed. The time of reactivity to formalin in the neurogenic phase was reduced from 56.3 ± 6.0 seconds to 32.7 ± 2.2 seconds and 23.8 ± 2.6 seconds after treatment with LASSBio-1359 at doses of 10 mg/kg and 20 mg/kg, respectively. A reversal of the antinociceptive action of LASSBio-1359 was observed in the inflammatory phase after treatment with ZM 241385 [4-(2-[7-amino-2-(2-furly)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol], an adenosine A2A antagonist. Carrageenan-induced thermal and mechanical hyperalgesia were reduced after treatment with LASSBio-1359. Similarly, CFA-induced thermal and mechanical hyperalgesia were reduced after treatment with LASSBio-1359 (25 and 50 mg/kg). Levels of TNF-α and iNOS expression increased in the monoarthritis model and were normalized in animals treated with LASSBio-1359, which was also associated with beneficial effects in the histologic analysis. These results suggest that LASSBio-1359 represents an alternative treatment of monoarthritis.

Purinergic dysregulation in pulmonary hypertension

Despite the fact that nucleotides and adenosine help regulate vascular tone through purinergic signaling pathways, little is known regarding their contributions to the pathobiology of pulmonary arterial hypertension, a condition characterized by elevated pulmonary vascular resistance and remodeling. Even less is known about the potential role that alterations in CD39 (ENTPD1), the ectonucleotidase responsible for the conversion of the nucleotides ATP and ADP to AMP, may play in pulmonary arterial hypertension. In this study we identified decreased CD39 expression on the pulmonary endothelium of patients with idiopathic pulmonary arterial hypertension. We next determined the effects of CD39 gene deletion in mice exposed to normoxia or normobaric hypoxia (10% oxygen). Compared with controls, hypoxic CD39(-/-) mice were found to have a markedly elevated ATP-to-adenosine ratio, higher pulmonary arterial pressures, more right ventricular hypertrophy, more arterial medial hypertrophy, and a pro-thrombotic phenotype. In addition, hypoxic CD39(-/-) mice exhibited a marked increase in lung P2X1 receptors. Systemic reconstitution of ATPase and ADPase enzymatic activities through continuous administration of apyrase decreased pulmonary arterial pressures in hypoxic CD39(-/-) mice to levels found in hypoxic CD39(+/+) controls. Treatment with NF279, a potent and selective P2X1 receptor antagonist, lowered pulmonary arterial pressures even further. Our study is the first to implicate decreased CD39 and resultant alterations in circulating purinergic signaling ligands and cognate receptors in the pathobiology of pulmonary arterial hypertension. Reconstitution and receptor blocking experiments suggest that phosphohydrolysis of purinergic nucleotide tri- and diphosphates, or blocking of the P2X1 receptor could serve as treatment for pulmonary arterial hypertension.

Beneficial and detrimental role of adenosine signaling in diseases and therapy

Adenosine is a major signaling nucleoside that orchestrates cellular and tissue adaptation under energy depletion and ischemic/hypoxic conditions by activation of four G protein-coupled receptors (GPCR). The regulation and generation of extracellular adenosine in response to stress are critical in tissue protection. Both mouse and human studies reported that extracellular adenosine signaling plays a beneficial role during acute states. However, prolonged excess extracellular adenosine is detrimental and contributes to the development and progression of various chronic diseases. In recent years, substantial progress has been made to understand the role of adenosine signaling in different conditions and to clarify its significance during the course of disease progression in various organs. These efforts have and will identify potential therapeutic possibilities for protection of tissue injury at acute stage by upregulation of adenosine signaling or attenuation of chronic disease progression by downregulation of adenosine signaling. This review is to summarize current progress and the importance of adenosine signaling in different disease stages and its potential therapeutic effects.

Novel agonist of adenosine receptor induces relaxation of corpus cavernosum in guinea pigs: an in vitro and in vivo study

OBJECTIVE

To test the relaxation effect of a new adenosine receptor agonist N-acylhydrazone derivative, 3,4-dimethoxyphenyl-N-methyl-benzoylhydrazide (LASSBio-1359), on in vitro and in vivo preparation of corpus cavernosum (CC), and its interaction with type-5 phosphodiesterase enzyme inhibitor, sildenafil.

METHODS

For in vitro study, an increasing concentration of LASSBio-1359 was added in the solution at the plateau isometric tension recording of isolated guinea pig CC induced by phenylephrine (30 μM). Concentration-response curve was repeated in the presence of A2A receptor antagonist, ZM 241385 (10 μM). Sildenafil-induced CC relaxing effect was compared with that of LASSBio-1359. Isobolographic analysis was performed to identify possible synergistic interaction between LASSBio-1359 and sildenafil. For in vivo study, blood pressure response in the CC of guinea pig was measured after administration of LASSBio-1359 (10 mg/kg intravenously) or sildenafil (10 mg/kg intravenously).

RESULTS

LASSBio-1359 caused relaxation of phenylephrine-induced contraction of isolated CC in a concentration-dependent manner (IC50 = 10.1 ± 1.8 μM), which was shifted to the right in the presence of ZM 241385 (IC50 = 27.1 ± 1.4 μM; P <.05). Isobolographic analysis showed synergistic interaction between LASSBio-1359 and sildenafil. As sildenafil, LASSBio-1359 increased blood pressure oscillation in the CC confirming its systemic efficacy.

CONCLUSION

CC relaxing effects induced by the adenosine A2A receptor agonist, LASSBio-1359, demonstrated in vitro and in vivo experimental protocols, represent a promise therapeutic option for the treatment of erectile dysfunction. Synergistic interaction of LASSBio-1359 with sildenafil suggests a combined use to reach a higher population of patients with erectile dysfunction.

The role of ecto-5'-nucleotidase in endothelial dysfunction and vascular pathologies

Ecto-5'-nucleotidase (e5NT, CD73) is an enzyme that is highly expressed in endothelium and is involved in the extracellular nucleotide catabolism. CD73 converts AMP to adenosine that via specific subtypes of P1 receptor mediates cytoprotection involving diverse mechanisms such as vasodilatation, suppression of inflammation, inhibition of thrombosis and anti-adrenergic effect. Physiological intravascular concentration of adenosine is in nanomolar range, but could become micromolar in response to various forms of stress. Endothelium is a major site for both CD73 mediated production of adenosine and its cytoprotective effect. Nucleotides (predominantly ATP or ADP) that could be released from different cells via controlled specific of unspecific mechanisms constitute a major source of substrate for adenosine production via CD73. Direct effects of extracellular nucleotides (mediated by P2 receptors) are typically opposite to adenosine P1 mediated activities. Retention of nucleotides and decreased adenosine production due to loss of CD73 function may have negative implications and could be important cause of various pathologies. Protective role of CD73 was indicated in ectopic calcification, atherosclerosis, rejection after xenotransplantation and thrombosis. Reduced activity of CD73 due to lymphocyte contact with endothelium increases its permeability that leads to enhanced leukocyte transmigration. Upregulation of endothelial CD73 may therefore be protective in a number of cardiovascular pathologies. Such effect has been confirmed for some common drugs such as statins and it could be part of its pleiotropic portfolio. Activation of CD73 could be a new target for specific treatment strategy that in particular will enhance endothelial protection.

Combined hypoxia inducible factor-1α and homogeneous endothelial progenitor cell therapy attenuates shunt flow-induced pulmonary arterial hypertension in rabbits

BACKGROUND

Hyperkinetic pulmonary arterial hypertension (PAH) is a common complication in congenital heart disease, and affects operations, indications, and prognoses for patients. Gene-based stem cell transplantation is an alternative treatment that can attenuate PAH.

METHODS

Hyperkinetic PAH rabbit models were successfully established, using common carotid artery and jugular vein anastomosis. Endothelial progenitor cells (EPCs) were isolated from the bone marrow, cultured, and transfected with human hypoxia inducible factor-1 alpha (hHIF-1α), using lentiviruses. Two weeks after the transfected EPCs were transplanted into the rabbits, catheterization was applied to collect hemodynamic data. The hypertrophy of the right ventricle and pulmonary vascular remodeling were evaluated by measuring the right ventricle hypertrophy index, the medial wall thickness, and the medial wall area. Western blot and immunohistochemistry analyses were used to detect the expression of hHIF-1α in the pulmonary small arteries.

RESULTS

Two weeks after transplantation, systolic pulmonary arterial pressure and mean pulmonary arterial pressure were both attenuated. The hypertrophy of the right ventricle, and pulmonary vascular remodeling were reversed. Expression of hHIF-1α in the hHIF-1α-transfected EPCs that had been transplanted was high, and the number of pulmonary small arteries had increased. In addition, combined HIF-1α and homogeneous EPC therapy was more effective at attenuating PAH and increasing the density of pulmonary small arteries, compared with EPC transplantation alone.

CONCLUSIONS

Both the therapy with HIF-1α-transfected EPCs, and EPC transplantation, attenuated shunt flow-induced PAH, by means of an angiogenic effect. The former therapeutic method was more effective.

N-acylhydrazone derivative ameliorates monocrotaline-induced pulmonary hypertension through the modulation of adenosine AA2R activity

BACKGROUND

Pulmonary arterial hypertension (PAH) is a disease that results in right ventricular (RV) dysfunction. While pulmonary vascular disease is the primary pathological focus, RV hypertrophy and RV dysfunction are the major determinants of prognosis in PAH. The aim of this study was to investigate the effects of (E)-N'-(3,4-dimethoxybenzylidene)-4-methoxybenzohydrazide (LASSBio-1386), an N-acylhydrazone derivative, on the lung vasculature and RV dysfunction induced by experimental PAH.

METHODS

Male Wistar rats were injected with a single dose (60mg/kg, i.p.) of monocrotaline (MCT) and given LASSBio-1386 (50mg/kg, p.o.) or vehicle for 14 days. The hemodynamic, exercise capacity (EC), endothelial nitric oxide synthase (eNOS), adenosine A2A receptor (A2AR), sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a), phospholamban (PLB) expression, Ca(2+)-ATPase activity and vascular activity of LASSBio-1386 were evaluated.

RESULTS AND CONCLUSIONS

The RV systolic pressure was elevated in the PAH model and reduced from 49.6 ± 5.0 mm Hg (MCT group) to 27.2 ± 2.1 mm Hg (MCT+LASSBio-1386 group; P<0.05). MCT administration also impaired the EC, increased the RV and pulmonary arteriole size, and promoted endothelial dysfunction of the pulmonary artery rings. In the PAH group, the eNOS, A2AR, SERCA2a, and PLB levels were changed compared with the control; in addition, the Ca(2+)-ATPase activity was reduced. These alterations were related with MCT-injected rats, and LASSBio-1386 had favorable effects that prevented the development of PAH. LASSBio-1386 is effective at preventing endothelial and RV dysfunction in PAH, a finding that may have important implications for ongoing clinical evaluation of A2AR agonists for the treatment of PAH.