Liraglutide prevents and reverses monocrotaline-induced pulmonary arterial hypertension by suppressing ET-1 and enhancing eNOS/sGC/PKG pathways. Sci Rep. 2016;6:31788. [PMID: 27581840 PMCID: PMC5007506 DOI: 10.1038/srep31788]

Effect of Benidipine Alone and in Combination With Bosentan and Sildenafil in Amelioration of Pulmonary Arterial Hypertension in Experimental Model in Rats

ABSTRACT

Pulmonary arterial hypertension (PAH) is a persistent condition affecting the pulmonary arteries' endothelium. Benidipine, a calcium channel blocker, possesses vasodilatory, anti-inflammatory activity, reduces oxidative stress, and inhibits the activity of Transforming growth factor-β (TGF-β) and α-smooth muscle actin (α-SMA). The present study was designed to investigate the effect of benidipine alone and in combination with bosentan and sildenafil on monocrotaline (MCT)-induced pulmonary hypertension in a rat model. PAH was induced by a single-dose administration of MCT in rats. Animals were randomized into different groups and treated with benidipine alone and in combination with bosentan or sildenafil. Various parameters such as hemodynamic parameters, Fulton's index and oxidative stress parameters were performed. Additionally, histopathology of lung and right ventricular of heart tissue, immunohistochemistry, expression of α-SMA, endothelial nitric oxide synthase (eNOS), TGF-β, and RT-PCR, and an in vitro study using human umbilical vein endothelial cells (HUVECs) was also carried out. Treatment of benidipine and its combination exhibited better prevention in the elevated right ventricular systolic pressure, right ventricular hypertrophy, rise in oxidative stress, and increase in expression of α-SMA and TGF-β receptor 1 compared with MCT control group rats. In HUVECs, the expression of α-SMA was increased, whereas that of eNOS decreased after TGF-β exposure and was substantially reversed after pretreatment with benidipine. We concluded that benidipine and its combination with bosentan and sildenafil exhibit beneficial effects in MCT-induced PAH through the eNOS/TGF-β/α-SMA signaling pathway.

Pulmonary hypertension and insulin resistance: a mechanistic overview

Pulmonary arterial hypertension (PAH) is a vascular remodeling disease, characterized by increased blood pressure levels in pulmonary circulation, leading to a restriction in the circulation flow and heart failure. Although the emergence of new PAH therapies has increased survival rates, this disease still has a high mortality and patients that receive diagnosis die within a few years. The pathogenesis of PAH involves multiple pathways, with a complex interaction of local and distant cytokines, hormones, growth factors, and transcription factors, leading to an inflammation that changes the vascular anatomy in PAH patients. These abnormalities involve more than just the lungs, but also other organs, and between these affected organs there are different metabolic dysfunctions implied. Recently, several publications demonstrated in PAH patients a disturbance in glucose metabolism, demonstrated by higher levels of glucose, insulin, and lipids in those patients. It is possible that a common molecular mechanism can have a significant role in this connection. In this regard, this narrative review intends to focus on the recent papers that mainly discuss the molecular determinants between insulin resistance (IR) associated PAH, which included obesity subclinical inflammation induced IR, PPAR gamma and Adiponectin, BMPR2, mitochondrial dysfunction and endoplasmic reticulum stress. Therefore, the following review will summarize some of the existing data for IR associated PAH, focusing on the better understanding of PAH molecular mechanisms, for the development of new translational therapies.

Rosmarinic acid ameliorates the complications of monocrotaline-induced right ventricular hypertrophy on the left ventricle: Investigating the signaling pathway of Wnt/β-catenin in the heart

Objectives

Right ventricular hypertrophy (RVH) often results in failure of the right ventricle or even the left ventricle. Rosmarinic acid (RA), a natural polyphenol, is commonly found in Boraginaceae species and some species of ferns and hornworts. This study looked at how RA affects oxidative stress and left ventricular hemodynamic functions as well as RVH in monocrotaline (MCT) induced RVH model rats.

Materials and Methods

To cause RVH, MCT (60 mg/kg) was intraperitoneally (IP) injected. Rats were given saline or RA (10, 15, and 30 mg/kg, gavage, over 21 days). In anesthetized rats, the lead II electrocardiogram was recorded. The hemodynamic functions of the isolated heart were measured using the Langendorff apparatus (at constant pressure). Investigations were made into the right ventricular hypertrophy index (RVHI), the activities of superoxide dismutase, catalase, glutathione, and Wnt and β-catenin gene expressions in the left ventricle. H&E staining was used.

Results

A significant decline in electrocardiogram parameters and anti-oxidant enzyme activities, an increase in QTc (Q-T corrected) intervals, MDA (Malondialdehyde), RVHI, and Wnt/β-catenin gene expression, and also significant changes in the hemodynamic parameters were demonstrated in the MCT group. RA improved the above-mentioned factors.

Conclusion

According to the findings, RA may act as a cardioprotective agent against cardiovascular complications brought on by RVH due to its capacity to boost the activity of cardiac anti-oxidant enzymes and decrease the expression of genes involved in vascular calcification.

The novel roles of YULINK in the migration, proliferation and glycolysis of pulmonary arterial smooth muscle cells: implications for pulmonary arterial hypertension

BACKGROUND

Abnormal remodeling of the pulmonary vasculature, characterized by the proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) along with dysregulated glycolysis, is a pathognomonic feature of pulmonary arterial hypertension (PAH). YULINK (MIOS, Entrez Gene: 54468), a newly identified gene, has been recently shown to possess pleiotropic physiologic functions. This study aims to determine novel roles of YULINK in the regulation of PAH-related pathogenesis, including PASMC migration, proliferation and glycolysis.

RESULTS

Our results utilized two PAH-related cell models: PASMCs treated with platelet-derived growth factor (PDGF) and PASMCs harvested from monocrotaline (MCT)-induced PAH rats (PAH-PASMCs). YULINK modulation, either by knockdown or overexpression, was found to influence PASMC migration and proliferation in both models. Additionally, YULINK was implicated in glycolytic processes, impacting glucose uptake, glucose transporter 1 (GLUT1) expression, hexokinase II (HK-2) expression, and pyruvate production in PASMCs. Notably, YULINK and GLUT1 were observed to colocalize on PASMC membranes under PAH-related pathogenic conditions. Indeed, increased YULINK expression was also detected in the pulmonary artery of human PAH specimen. Furthermore, YULINK inhibition led to the suppression of platelet-derived growth factor receptor (PDGFR) and the phosphorylation of focal adhesion kinase (FAK), phosphoinositide 3-kinase (PI3K), and protein kinase B (AKT) in both cell models. These findings suggest that the effects of YULINK are potentially mediated through the PI3K-AKT signaling pathway.

CONCLUSIONS

Our findings indicate that YULINK appears to play a crucial role in the migration, proliferation, and glycolysis in PASMCs and therefore positioning it as a novel promising therapeutic target for PAH.

T18/S19 diphosphorylation of myosin regulatory light chain impairs pulmonary artery relaxation in monocrotaline-induced pulmonary hypertensive rats

Phosphorylation of Ser19 (S19-p) on the myosin regulatory light chain (MLC2) is critical for arterial contraction. It has been shown that elevated RhoA-dependent kinase (ROCK) activity or decreased MLC phosphatase (MLCP) activity leads to further phosphorylation of Thr18 (T18/S19-pp), which has been linked to vasospastic diseases. However, this phenomenon has not yet been studied in the context of pulmonary arterial hypertension (PAH). In the monocrotaline-induced PAH (PAH-MCT) rat model, we observed a significant delay in pulmonary artery (PA) relaxation following high potassium-induced contraction, which persisted even with the use of an L-type calcium channel blocker or in a calcium-free solution. Immunoblot analysis showed increased levels of both S19-p and T18/S19-pp in unstimulated PAs from PAH-MCT rats. Proteomics analysis revealed a reduction in soluble guanylate cyclase (sGC) and protein kinase G (PKG) levels, and immunoblotting confirmed decreased levels of MYPT1 (a component of MLCP) and increased ROCK in PAH-MCT. In the control PAs, the pharmacological inhibition of sGC with ODQ resulted in a prominent delay of relaxation and increased T18/S19-pp as in PAH-MCT. The delayed relaxation and the T18/S19-pp in PAH-MCT were reversed by ROCK inhibitor, Y27632, while not by membrane permeable 8-Br-cGMP. The delayed relaxation and T18/S19-diP in the ODQ-treated control PA were also reversed by Y27632. Taken together, the decreased sGC and MLCP, and increased ROCK increased T18/S19-pp, which leads to the decreased ability of PA to relax in PAH-MCT rats. PA specific inhibition of ROCK or activation of MLCP are expected to serve as potential drugs in the treatment of PAH.

Glucagon-like peptide-1 stimulates acute secretion of pro-atrial natriuretic peptide from the isolated, perfused pig lung exposed to warm ischemia

Glucagon-like peptide-1 (GLP-1) has proven to be protective in animal models of lung disease but the underlying mechanisms are unclear. Atrial natriuretic peptide (ANP) is mainly produced in the heart. As ANP possesses potent vaso- and bronchodilatory effects in pulmonary disease, we hypothesised that the protective functions of GLP-1 could involve potentiation of local ANP secretion from the lung. We examined whether the GLP-1 receptor agonist liraglutide was able to improve oxygenation in lungs exposed to 2 h of warm ischemia and if liraglutide stimulated ANP secretion from the lungs in the porcine ex vivo lung perfusion (EVLP) model. Pigs were given a bolus of 40 µg/kg liraglutide or saline 1 h prior to sacrifice. The lungs were then left in vivo for 2 h, removed en bloc and placed in the EVLP machinery. Lungs from the liraglutide treated group were further exposed to liraglutide in the perfusion buffer (1.125 mg). Main endpoints were oxygenation capacity, and plasma and perfusate concentrations of proANP and inflammatory markers. Lung oxygenation capacity, plasma concentrations of proANP or concentrations of inflammatory markers were not different between groups. ProANP secretion from the isolated perfused lungs were markedly higher in the liraglutide treated group (area under curve for the first 30 min in the liraglutide group: 635 ± 237 vs. 38 ± 38 pmol/L x min in the saline group) (p < 0.05). From these results, we concluded that liraglutide potentiated local ANP secretion from the lungs.

The Potential Application and Promising Role of Targeted Therapy in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare yet serious progressive disorder that is currently incurable. This female-predominant disease unfolds as a pan-vasculopathy that affects all layers of the vessel wall. Five classes of pharmacological agents currently exist to target the three major cellular signaling pathways identified in PAH but are incapable of effectively reversing the disease progression. While several targets have been identified for therapy, none of the current PAH specific therapies are curative and cost-effective as they fail to reverse vascular remodeling and do not address the cancer-like features of PAH. Our purpose is to review the current literature on the therapeutic management of PAH, as well as the molecular targets under consideration for therapy so as to shed light on the potential role and future promise of novel strategies in treating this high-mortality disease. This review study summarizes and discusses the potential therapeutic targets to be employed against PAH. In addition to the three major conventional pathways already used in PAH therapy, targeting PDGF/PDGFR signaling, regulators in glycolytic metabolism, PI3K/AKT pathways, mitochondrial heat shock protein 90 (HSP90), high-mobility group box-1 (HMGB1), and bromodomain and extra-terminal (BET) proteins by using their specific inhibitors, or a pharmacological induction of the p53 expression, could be attractive strategies for treating PAH.

Shufeiya Recipe Improves Monocrotaline-Induced Pulmonary Hypertension in Rats by Regulating SIRT3/FOXO3a and Its Downstream Signaling Pathways

Pulmonary hypertension (PH) is a chronic and progressive disease caused by obstructions and functional changes of small pulmonary arteries. Current treatment options of PH are costly with patients needing long-term taking medicine. The traditional Chinese medicine (TCM) compound "Shufeiya Recipe" was used to intervene in monocrotaline- (MCT-) induced pulmonary hypertension in rats. The rats were randomly divided into the control group, model group, positive drug (Sildenafil) group, and Shufeiya Recipe low-, moderate-, and high-dose groups. The improvement effect of the Shufeiya Recipe on the mean pulmonary artery pressure (mPAP) was assessed in PH rats, and pathological staining was used to observe the pathological changes of lung tissue. The impact of the Shufeiya Recipe on oxidative stress damage in rats with pulmonary hypertension and the regulation of SIRT3/FOXO3a and its downstream signaling pathways were determined. The results showed that Shufeiya Recipe could significantly downregulate mPAP and improve lung histopathological changes; downregulate serum levels of reactive oxygen species (ROS); upregulate the concentrations of COX-1 and COX-2 and the activity of Mn-SOD; inhibit oxidative response damage; promote the protein expression of SIRT3, FOXO3a, p-PI3K, p-AKT, and p-eNOS; increase the level of expression of NO, sGC, cGMP, and PKG; and downregulate the level of protein expression of Ras, p-MEK1/2, p-ERK1/2 and c-fos. These results indicate that Shufeiya Recipe can improve MCT-induced pulmonary hypertension in rats by regulating SIRT3/FOXO3a and its downstream PI3K/AKT/eNOS and Ras/ERK signaling pathways.

Future perspective in diabetic patients with pre- and post-capillary pulmonary hypertension

Pulmonary hypertension is a clinical syndrome that may include multiple clinical conditions and can complicate the majority of cardiovascular and respiratory diseases. Pulmonary hypertension secondary to left heart disease is the prevalent clinical condition and accounts for two-thirds of all cases. Type 2 diabetes mellitus, which affects about 422 million adults worldwide, has emerged as an independent risk factor for the development of pulmonary hypertension in patients with left heart failure. While a correct diagnosis of pulmonary hypertension secondary to left heart disease requires invasive hemodynamic evaluation through right heart catheterization, several scores integrating clinical and echocardiographic parameters have been proposed to discriminate pre- and post-capillary types of pulmonary hypertension. Despite new emerging evidence on the pathophysiological mechanisms behind the effects of diabetes in patients with pre- and/or post-capillary pulmonary hypertension, no specific drug has been yet approved for this group of patients. In the last few years, the attention has been focused on the role of antidiabetic drugs in patients with pulmonary hypertension secondary to left heart failure, both in animal models and in clinical trials. The aim of the present review is to highlight the links emerged in the recent years between diabetes and pre- and/or post-capillary pulmonary hypertension and new perspectives for antidiabetic drugs in this setting.

Pulmonary Arterial Hypertension: Emerging Principles of Precision Medicine across Basic Science to Clinical Practice

Pulmonary arterial hypertension (PAH) is an enigmatic and deadly vascular disease with no known cure. Recent years have seen rapid advances in our understanding of the molecular underpinnings of PAH, with an expanding knowledge of the molecular, cellular, and systems-level drivers of disease that are being translated into novel therapeutic modalities. Simultaneous advances in clinical technology have led to a growing list of tools with potential application to diagnosis and phenotyping. Guided by fundamental biology, these developments hold the potential to usher in a new era of personalized medicine in PAH with broad implications for patient management and great promise for improved outcomes.

Prenatal hypoxia induced ETBR activation and abnormal ROS signalling in pulmonary artery cells of rat offspring

Pulmonary arterial hypertension is a progressive disorder characterized by remodeling and increased small pulmonary arteries resistance. Endothelin-1 (ET-1) was related to PAH and ET-1 receptors were up-regulated selectively in the lung when exposed to toxic factor hypoxia. However, the role of ET-1 signaling in the pathogenesis of prenatal hypoxia-induced pulmonary abnormalities remains to be elucidated. Pregnant rats were divided into prenatal hypoxia (10.5 % O2 from gestational day 4-21) and control group. Their three-month-old offspring male rats were tested for vascular functions and molecular analysis, DNA methylation was assessed for cellular hypoxia. Functional testing showed that ET-1-mediated vasoconstriction was enhanced, and the expressions of endothelin A receptor/B receptor (ETAR/ETBR), inositol 1,4,5-trisphosphate receptor, type 1, and the sensitivity of calcium channels were increased in the small pulmonary arteries following prenatal hypoxia. q-PCR and DHE staining showed that the expressions of NADPH oxidase 1/4 (Nox1/4) were up-regulated, along with the increased production of superoxide anion. Furthermore, superoxide anion promoted ET-1-mediated pulmonary artery contraction. In the pulmonary artery smooth muscle cell experiments, q-PCR, Western Blot, CCK8 and DHE staining showed that the expressions of ETBR, Nox1/4, and superoxide anion were increased by hypoxia, along with promoted cell proliferation. 2,2,6,6-Tetramethyl-1-piperidinyloxy reversed hypoxia-induced cell proliferation. ETBR antagonist BQ788 inhibited hypoxia-increased expressions of Nox1/4, superoxide anion production, and proliferation of cells. Moreover, methylation analysis indicated that hypoxia decreased the methylation levels of the ETBR promoter in the pulmonary artery smooth muscle cells. The results indicated that prenatal toxic factor hypoxia resulted in abnormal ETBR activation, which enhanced ET-1-mediated vasoconstriction of pulmonary arteries and pulmonary artery smooth muscle cell proliferation through ETBR/Nox1/4-derived ROS pathway.

The miR-182/Myadm axis regulates hypoxia-induced pulmonary hypertension by balancing the BMP- and TGF-β-signalling pathways in an SMC/EC-crosstalk-associated manner

We recently identified oncologic miR-182 as a new regulator of pulmonary artery hypertension (PAH) that targets myeloid-associated differentiation marker (Myadm), which is expressed in bone marrow stem cells and multipotent progenitors. Both miR-182 and Myadm are expressed in the cardiopulmonary system and correlated with the balance between the bone morphogenetic protein (BMP) and the transforming growth factor (TGF)-β signalling pathways, which are disturbed in PAH. We hypothesize that miR-182/Myadm are involved in BMP-TGF-β-signalling way in PAH. Hypoxia triggered pathological progression in cardiopulmonary PAH in vivo and in vitro; these changes were accompanied by strongly dowregulated BMP/SMAD1/5/8 expression and enhanced TGF-β/SMAD2/3 signalling pathway, favouring SMAD4/SMAD2 transcript formation and inhibiting the PAH negative regulator Id1 expression. miR-182 gain-of-function significantly inhibited the pathological progression in hypoxia-induced PAH (HPH) in vivo and in vitro, with a restoration of the balance in BMP-TGF-β signalling pathway. This recovery was abrogated by overexpression of Myadm. Conversely, loss-of-function of miR-182 increased the pathological progression of HPH followed by severe disturbance of BMP and TGF-β signal transduction and reduced Id1 expression, which was restored by Myadm knockdown. We also showed that the miR-182/Myadm relate BMP-TGF-β pathway is associated with NOS3/NO/cGMP via the crosstalk between endothelial cells and smooth muscle cells. Our findings further support the therapeutic significance of miR-182/Myadm in PAH via the balance of BMP- and TGF-β-associated mechanisms.

Oxidative Stress, GTPCH1, and Endothelial Nitric Oxide Synthase Uncoupling in Hypertension

Significance: Hypertension has major health consequences, which is associated with endothelial dysfunction. Endothelial nitric oxide synthase (eNOS)-produced nitric oxide (NO) signaling in the vasculature plays an important role in maintaining vascular homeostasis. Considering the importance of NO system, this review aims to provide a brief overview of the biochemistry of members of NO signaling, including GTPCH1 [guanosine 5'-triphosphate (GTP) cyclohydrolase 1], tetrahydrobiopterin (BH4), and eNOS. Recent Advances: Being NO signaling activators and regulators of eNOS signaling, BH4 treatment is getting widespread attention either as potential therapeutic agents or as preventive agents. Recent clinical trials also support that BH4 treatment could be considered a promising therapeutic in hypertension. Critical Issues: Under conditions of BH4 depletion, eNOS-generated superoxides trigger pathological events. Abnormalities in NO availability and BH4 deficiency lead to disturbed redox regulation causing pathological events. This disturbed signaling influences the development of systemic hypertension as well as pulmonary hypertension. Future Directions: Considering the importance of BH4 and NO to improve the translational significance, it is essential to continue research on this field to manipulate BH4 to increase the efficacy for treating hypertension. Thus, this review also examines the current state of knowledge on the effects of eNOS activators on preclinical models and humans to utilize this information for potential therapy.

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

AIMS

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

MAIN METHODS

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

KEY FINDINGS

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

SIGNIFICANCE

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

Empagliflozin, alone or in combination with liraglutide, limits cell death in vitro: role of oxidative stress and nitric oxide

BACKGROUND

Sodium-dependent glucose co-transporter 2 (SGLT2) inhibitor empagliflozin and glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide are characterized as having cardiovascular benefits in patients with type 2 diabetes (T2D). Little is known regarding the underlying mechanisms nor the potential interactions between cardiovascular benefits of these two drugs when combined. We sought to investigate: (1) whether combination of empagliflozin and liraglutide has additive effect against diabetes-induced cytotoxicity, and (2) potential mechanisms involved in cardioprotective effect of empagliflozin and liraglutide in diabetes.

METHODS

Capacity of empagliflozin and liraglutide alone and in combination to reduce cardiac injury in diabetes was evaluated. HL-1 cells, a cardiac muscle cell line, were exposed to hyperglycemia/hyperinsulinemia and treated with/without empagliflozin, liraglutide or empagliflozin + liraglutide for 24 h. At the end of treatments, cytotoxicity, oxidative stress, nitric oxide (NO) production, nitric oxide synthase (NOS) activity and phospho-eNOS (Thr⁴⁹⁵) expression were determined.

RESULTS

We found that empagliflozin treatment alone and combined treatment decreased in vitro HL-1 cell death caused by hyperglycemia. Liraglutide treatment alone improved NOS activity followed by increased NO production, while empagliflozin had little effect. Furthermore, the effects of empagliflozin + liraglutide to decrease diabetes-induced cytotoxicity and oxidative stress were synergistic.

CONCLUSION

While empagliflozin alone attenuated diabetes-induced cytotoxicity, combined treatment of liraglutide can synergistically ameliorates cell death and oxidative stress. This effect is potentially due to improved NOS activity and increased NO production induced by liraglutide.

Downregulation of Soluble Guanylate Cyclase and Protein Kinase G With Upregulated ROCK2 in the Pulmonary Artery Leads to Thromboxane A2 Sensitization in Monocrotaline-Induced Pulmonary Hypertensive Rats

Thromboxane A2 (TXA2) promotes various physiological responses including pulmonary artery (PA) contraction, and pathophysiological implications have been suggested in cardiovascular diseases including pulmonary hypertension. Here, we investigated the role of TXA2 receptor (TP)-mediated signaling in the pathophysiology of pulmonary arterial hypertension (PAH). The sensitivity of PA to the contractile agonist could be set by relaxing signals such as the nitric oxide (NO), soluble guanylate cyclase (sGC), and cGMP-dependent kinase (PKG) pathways. Changes in the TP agonist (U46619)-induced PA contraction and its modulation by NO/cGMP signaling were analyzed in a monocrotaline-induced PAH rat model (PAH-MCT). In the myograph study, PA from PAH-MCT showed higher responsiveness to U46619, that is decreased EC50. Immunoblot analysis revealed a lower expression of eNOS, sGC, and PKG, while there was a higher expression of RhoA-dependent kinase 2 (ROCK2) in the PA from PAH-MCT than in the control. In PAH-MCT, the higher sensitivity to U46619 was reversed by 8-Br-cGMP, a membrane-permeable cGMP analog, but not by the NO donor, sodium nitroprusside (SNP 30 μM). In contrast, in the control PA, inhibition of sGC by its inhibitor (1H- [1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), 10 μM) lowered the threshold of U46619-induced contraction. In the presence of ODQ, SNP treatment had no effect whereas the addition of 8-Br-cGMP lowered the sensitivity to U46619. The inhibition of ROCK by Y-27632 attenuated the sensitivity to U46619 in both control and PAH-MCT. The study suggests that the attenuation of NO/cGMP signaling and the upregulation of ROCK2 increase the sensitivity to TXA2 in the PAH animal, which might have pathophysiological implications in patients with PAH.

The Effects of Glucagon-Like Peptide-1 Receptor Agonists and Dipeptydilpeptidase-4 Inhibitors on Blood Pressure and Cardiovascular Complications in Diabetes

Glucagon-like peptide-1 receptor (GLP-1R) agonists are a class of newly introduced antidiabetic medications that potentially lower blood glucose by several molecular pathways. DPP-4 inhibitors are the other type of novel antidiabetic medications which act by preventing GLP-1 inactivation and thereby increasing the activity levels of GLP-1, leading to more glucose-induced insulin release from islet β-cells and suppression of glucagon release. Most patients with diabetes have concurrent hypertension and cardiovascular disorder. If antihyperglycemic agents can attenuate the risk of hypertension and cardiovascular disease, they will amplify their overall beneficial effects. There is conflicting evidence on the cardiovascular benefits of GLP-1R induction in laboratory studies and clinical trials. In this study, we have reviewed the main molecular mechanisms by which GLP-1R induction may modulate the cardiovascular function and the results of cardiovascular outcome clinical trials.

GLP-1 receptor agonist ameliorates experimental lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal lung disease. This disease is characterized by an excessive accumulation of extracellular matrix deposition that modify normal lung physiology. Up to date, there are not efficient therapeutic tools to fight IPF. Glucagon-like peptide-1 receptor (GLP-1R) activation plays an essential role in lung functions in normal and in pathological conditions. The aim of the present study was to study the possible beneficial effects of the administration of the GLP-1R agonist, liraglutide, in the pathogenesis of the fibrotic process in an animal model of pulmonary fibrosis induced by bleomycin. We observed that liraglutide decreased mRNA expression of collagen, hydroxyproline and key enzymes for the synthesis of collagen. In addition, GLP-1R activation restored the ACE2 mRNA levels modulating the activities of the RAS components, increased the production of surfactant proteins (SFTPa1, SFTPb, SFTPc) and promoted an improvement in pulmonary and cardiac functionality, including a partial restoration of lung alveolar structure. Liraglutide effects are shown at both the pro-inflammatory and fibrosis phases of the experimental disease. For these reasons, GLP-1 might be regarded as a promising drug for treating pulmonary fibrosis.

Glucagon-like peptide-1 receptor mediates the beneficial effect of liraglutide in an acute lung injury mouse model involving the thioredoxin-interacting protein

Repurposing clinically used drugs is among the important strategies in drug discovery. Glucagon-like peptide-1 (GLP-1) and its diabetes-based drugs, such as liraglutide, possess a spectrum of extra-pancreatic functions, while GLP-1 receptor (GLP-1R) is most abundantly expressed in the lung. Recent studies have suggested that GLP-1-based drugs exert beneficial effects in chronic, as well as acute, lung injury rodent models. Here, we show that liraglutide pretreatment reduced LPS induced acute lung injury in mice. It significantly reduced lung injury score, wet/dry lung weight ratio, bronchoalveolar lavage fluid immune cell count and protein concentration, and cell apoptosis in the lung, and it was associated with reduced lung inflammatory cytokine and chemokine gene expression. Importantly, these effects were virtually absent in GLP-1R^-/- mice. A well-known function of GLP-1 and GLP-based drugs in pancreatic β-cells is the attenuation of high-glucose stimulated expression of thioredoxin-interacting protein (TxNIP), a key component of inflammasome. LPS-challenged lungs showed elevated TxNIP mRNA and protein expression, which was attenuated by liraglutide treatment in a GLP-1R-dependent manner. Hence, our observations suggest that GLP-1R is essential in mediating beneficial effects of liraglutide in acute lung injury, with the inflammasome component TxNIP as a potential target.

Interstitial lung disease and diabetes

Diabetes mellitus (DM) is a chronic metabolic disease and its prevalence has been steadily increasing all over the world. DM and its associated micro and macrovascular complications result in significant morbidity and mortality. The microvascular complications are usually manifested as retinopathy, neuropathy, nephropathy and macrovascular complications generally affect the cardiovascular system. In addition to these complications, DM also affects the lungs because of its rich vascularity and abundance in connective tissue (collagen and elastin). DM has been found to cause microvascular complications and proliferation of extracellular connective tissue in the lungs, leading to decline in lung function in a restrictive pattern. Interstitial lung disease (ILD) includes a diverse group of disease conditions characterized by different degrees of inflammation and fibrosis in the pulmonary parenchyma. Idiopathic pulmonary fibrosis (IPF) is one of the common type of idiopathic interstitial pneumonia with a high mortality rate. IPF is characterized by chronic progressive fibrosis leading to progressive respiratory failure. In this review we focus on lung as the target organ in DM and the association of DM and ILD with special emphasis on IPF.

Current and future treatments of pulmonary arterial hypertension

Therapeutic options for pulmonary arterial hypertension (PAH) have increased over the last decades. The advent of pharmacological therapies targeting the prostacyclin, endothelin, and NO pathways has significantly improved outcomes. However, for the vast majority of patients, PAH remains a life-limiting illness with no prospect of cure. PAH is characterised by pulmonary vascular remodelling. Current research focusses on targeting the underlying pathways of aberrant proliferation, migration, and apoptosis. Despite success in preclinical models, using a plethora of novel approaches targeting cellular GPCRs, ion channels, metabolism, epigenetics, growth factor receptors, transcription factors, and inflammation, successful transfer to human disease with positive outcomes in clinical trials is limited. This review provides an overview of novel targets addressed by clinical trials and gives an outlook on novel preclinical perspectives in PAH. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Autophagy in chronic lung disease

The development of chronic lung disease occurs as a consequence of multiple cellular events that involve an initial insult which often leads to the development of chronic inflammation, and the dysregulation of cellular proliferation and cell death mechanisms. Multiple cell types in the lung are key to the respiratory and protective/barrier functions necessary to manage the chronic exposures to environmental, mechanical, and oxidative stressors. Autophagy is essential to lung development and homeostasis, as well as the prevention and development of disease. The cellular process involves the collection and removal of unwanted organelles and proteins through lysosomal degradation. In recent years, investigations have addressed the roles of autophagy and selective autophagy in numerous chronic lung diseases. Here, we highlight recent advances on the role of autophagy in the pathogenesis of asthma, chronic obstructive pulmonary disease and emphysema, pulmonary arterial hypertension, and idiopathic pulmonary fibrosis.

The SGLT2 inhibitor empagliflozin reduces mortality and prevents progression in experimental pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a rare, but progressive and devastating vascular disease with few treatment options to prevent the advancement to right ventricular dysfunction hypertrophy and failure. Empagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, enhances urinary glucose excretion as well as reduces cardiovascular events and mortality in individuals with type 2 diabetes. While empagliflozin has been reported to lower systemic hypertension due to increased diuresis, the effect of empagliflozin on PAH is unknown. We used monocrotaline (MCT)-treated Sprague-Dawley rats to determine if empagliflozin alters PAH-associated outcomes. Compared to vehicle control, daily empagliflozin administration significantly improved survival in rats with severe MCT-induced PAH. Hemodynamic assessments showed that empagliflozin treatment significantly reduced mean pulmonary artery pressure, right ventricular systolic pressure, and increased pulmonary acceleration time. Empagliflozin treatment resulted in reduced right ventricular hypertrophy and fibrosis. Histological and molecular assessments of lung vasculature revealed significantly reduced medial wall thickening and decreased muscularization of pulmonary arterioles after empagliflozin treatment compared to vehicle-treated rats. In summary, SGLT2 inhibition with empagliflozin lowered mortality, reduced right ventricle systolic pressure, and attenuated maladaptive pulmonary remodeling in MCT-induced PAH. Clinical studies evaluating the efficacy of SGLT-2 inhibition should be considered for patients with PAH.

Glucagon-Like Peptide 1 and Atrial Natriuretic Peptide in a Female Mouse Model of Obstructive Pulmonary Disease

Glucagon-like peptide-1 (GLP-1) is protective in lung disease models but the underlying mechanisms remain elusive. Because the hormone atrial natriuretic peptide (ANP) also has beneficial effects in lung disease, we hypothesized that GLP-1 effects may be mediated by ANP expression. To study this putative link, we used a mouse model of chronic obstructive pulmonary disease (COPD) and assessed lung function by unrestrained whole-body plethysmography. In 1 study, we investigated the role of endogenous GLP-1 by genetic GLP-1 receptor (GLP-1R) knockout (KO) and pharmaceutical blockade of the GLP-1R with the antagonist exendin-9 to -39 (EX-9). In another study the effects of exogenous GLP-1 were assessed. Lastly, we investigated the bronchodilatory properties of ANP and a GLP-1R agonist on isolated bronchial sections from healthy and COPD mice.

Lung function did not differ between mice receiving phosphate-buffered saline (PBS) and EX-9 or between GLP-1R KO mice and their wild-type littermates. The COPD mice receiving GLP-1R agonist improved pulmonary function (P < .01) with less inflammation, but no less emphysema compared to PBS-treated mice. Compared with the PBS-treated mice, treatment with GLP-1 agonist increased ANP (nppa) gene expression by 10-fold (P < .01) and decreased endothelin-1 (P < .01), a peptide associated with bronchoconstriction. ANP had moderate bronchodilatory effects in isolated bronchial sections and GLP-1R agonist also showed bronchodilatory properties but less than ANP. Responses to both peptides were significantly increased in COPD mice (P < .05, P < .01).

Taken together, our study suggests a link between GLP-1 and ANP in COPD.

Glucagon-Like Peptide-1 Receptor Agonist Attenuates Autophagy to Ameliorate Pulmonary Arterial Hypertension through Drp1/NOX- and Atg-5/Atg-7/Beclin-1/LC3β Pathways

Mitochondrial dysfunction is associated with cardiovascular diseases and diabetes. Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling, and the abnormal proliferation, apoptosis and migration of pulmonary arterial smooth muscle cells (PASMCs). The glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide, has been shown to prevent pulmonary hypertension in monocrotaline-exposed rats. The aim of this study was to investigate the effect of liraglutide on autophagy, mitochondrial stress and apoptosis induced by platelet-derived growth factor BB (PDGF-BB). PASMCs were exposed to PDGF-BB, and changes in mitochondrial morphology, fusion-associated protein markers, and reactive oxygen species (ROS) production were examined. Autophagy was assessed according to the expressions of microtubule-associated protein light chain 3 (LC3)-II, LC3 puncta and Beclin-1. Western blot analysis was used to assess apoptosis, mitochondrial stress and autophagy markers. Liraglutide significantly inhibited PDGF-BB proliferation, migration and motility in PASMCs. PDGF-BB-induced ROS production was mitigated by liraglutide. Liraglutide increased the expression of α-smooth muscle actin (α-SMA) and decreased the expression of p-Yes-associated protein (p-YAP), inhibited autophagy-related protein (Atg)-5, Atg-7, Beclin-1 and the formation of LC3-β and mitochondrial fusion protein dynamin-related (Drp)1. Therefore, liraglutide can mitigate the proliferation of PASMCs via inhibiting cellular Drp1/nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) pathways and Atg-5/Atg-7/Beclin-1/LC3β-dependent pathways of autophagy in PAH.

Effects of vasopressin during a pulmonary hypertensive crisis induced by acute hypoxia in a rat model of pulmonary hypertension

BACKGROUND

A pulmonary hypertensive crisis (PHC) can be a life-threatening condition. We established a PHC model by exposing rats with monocrotaline (MCT)-induced pulmonary hypertension to acute hypoxia, and investigated the effects of vasopressin, phenylephrine, and norepinephrine on the PHC.

METHODS

Four weeks after MCT 60 mg kg^-1 administration i.v., right ventricular systolic pressure (RVSP), systolic BP (SBP), mean BP (MBP), cardiac index (CI), and pulmonary vascular resistance index (PVRI) were measured. PHC defined as an RVSP exceeding or equal to SBP was induced by changing the fraction of inspiratory oxygen to 0.1. Rats were subsequently treated by vasopressin, phenylephrine, or norepinephrine, followed by assessment of systemic haemodynamics, isometric tension of femoral and pulmonary arteries, cardiac function, blood gas composition, and survival.

RESULTS

PHC was associated with increased RV dilatation and paradoxical septal motion. Vasopressin increased MBP [mean (standard error)] from 52.6 (3.8) to 125.0 (8.9) mm Hg and CI from 25.4 (2.3) to 40.6 (1.8) ml min^-1 100 g^-1 while decreasing PVRI. Vasopressin also improved RV dilatation, oxygenation, and survival in PHC. In contrast, phenylephrine increased MBP from 54.8 (2.3) to 96.8 (3.2) mm Hg without improving cardiac pump function. Norepinephrine did not alter MBP. Vasopressin contracted femoral but not pulmonary arteries, whereas phenylephrine contracted both arterial beds. Hence, improvements with vasopressin in PHC might be associated with decreased PVRI and selective systemic vasoconstriction.

CONCLUSIONS

In this rat model of a PHC, vasopressin, but not phenylephrine or norepinephrine, resulted in better haemodynamic and vascular recovery.

Glucagon-like peptide-1 (GLP-1) mediates the protective effects of dipeptidyl peptidase IV inhibition on pulmonary hypertension

Background

Pulmonary hypertension (PH) is a progressive disease leading to death ultimately. Our recently published data demonstrated that inhibiting dipeptidyl peptidase IV (DPP-4) alleviated pulmonary vascular remodeling in experimental PH. However, whether glucagon-like peptide-1 (GLP-1) mediated the protective effect of DPP-4 inhibition (DPP-4i) on PH is unclear.

Results

In the present study, GLP-1 receptor antagonist (exendin-3) abolished the protective effects of DPP-4 inhibitor (sitagliptin) on right ventricular systolic pressure (RVSP) and pulmonary vascular remodeling (PVR) in monocrotaline (MCT, 60 mg/kg)-induced PH in rat. Notably, activation of GLP-1 receptor by GLP-1 analogue liraglutide directly attenuated RVSP and PVR in MCT-induced PH, as well as bleomycin- and chronic hypoxia-induced PH. Moreover, liraglutide potently inhibited MCT-induced inflammation and suppressed MCT-induced down-regulation of vascular endothelial marker (VE-cadherin and vWF) in lung. In vitro studies showed liraglutide reversed TGF-β1 (5 ng/ml) combining IL-1β (5 ng/ml) induced endothelial-mesenchymal transition (EndMT) in human umbilical vein endothelial cells (HUVECs), which could be abolished by GLP-1 receptor antagonist (exendin-3). Furtermore, liraglutide suppressed TGF-β1-IL-1β-induced phosphorylation of both Smad3 and ERK1/2.

Conclusions

Our data suggest that GLP-1 mediated the protective effects of DPP-4i on pulmonary vascular and RV remodeling in experimental PH, which may be attributed to the inhibitory effect on EndMT.

Increased endothelin-1-mediated vasoconstrictor tone in human obesity: effects of gut hormones

The heavy impact of obesity on the development and progression of cardiovascular disease has sparked sustained efforts to uncover the mechanisms linking excess adiposity to vascular dysfunction. Impaired vasodilator reactivity has been recognized as an early hemodynamic abnormality in obese patients, but also increased vasoconstrictor tone importantly contributes to their vascular damage. In particular, upregulation of the endothelin (ET)-1 system, consistently reported in these patients, might accelerate atherosclerosis and its complication, given the pro-inflammatory and mitogenic properties of ET-1. In recent years, a number of gut hormones, in addition to their role as modulators of food intake, energy balance, glucose and lipid metabolism, and insulin secretion and action, have demonstrated favorable vascular actions. They increase the bioavailability of vasodilator mediators like nitric oxide, but they have also been shown to inhibit the ET-1 system. These features make gut hormones promising tools for targeting both the metabolic and cardiovascular complications of obesity, a view supported by recent large-scale clinical trials indicating that novel drugs for type 2 diabetes with cardiovascular potential may translate into clinically significant advantages. Therefore, there is real hope that better understanding of the properties of gut-derived substances might provide more effective therapies for the obesity-related cardiometabolic syndrome.

Platelet and coagulation disorders in newly diagnosed patients with pulmonary arterial hypertension

There is a complex and not fully elucidated association between pulmonary arterial hypertension (PAH) and coagulation disorders. The goal of this study was to evaluate platelet function, coagulation and fibrinolysis in PAH patients at diagnosis, before PAH-specific treatment initiation. We enrolled 20 healthy controls and 30 PAH patients (20 with connective tissue disease (CTD-PAH) and 10 idiopathic (iPAH)). None of the participants was on any antiplatelet or anticoagulation therapy. Blood samples from PAH patients were collected during the initial right heart catheterization. All subjects were assessed with platelet function analyzer-100 (PFA-100), epinephrine (Epi) and ADP-induced light transmission aggregometry (LTA), thromboelastometry (ROTEM) and endogenous thrombin potential (ETP). Our results showed that Epi and ADP-LTA values were significantly lower in newly diagnosed PAH patients compared to controls. Disaggregation was present in 73% of patients, a characteristic not seen in healthy individuals. In ROTEM assay, CT and CFT measurements were significantly higher and a angle lower compared to controls. ETP testing revealed significantly reduced outcomes in AUC, Cmax and Tmax. When CTD-PAH and iPAH patient groups were compared, iPAH ADP-LTA values were significantly decreased compared to CTD-PAH. In conclusion, newly diagnosed PAH patients presented with decreased platelet aggregation, clot propagation and thrombin generation, along with delayed initiation of the coagulation process. These hemostatic deficits could indicate an "exhaustion" of the coagulation process that could be caused by endothelial dysfunction and chronic activation of the procoagulant pathways. Further studies are warranted to confirm these laboratory findings and assess their potential clinical significance.

Recent advances in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare disorder with a high mortality rate. Treatment options have improved in the last 20 years, but patients still die prematurely of right heart failure. Though rare, it is heterogeneous at the genetic and molecular level, and understanding and exploiting this is key to the development of more effective treatments. BMPR2, encoding bone morphogenetic receptor type 2, is the most commonly affected gene in both familial and non-familial PAH, but rare mutations have been identified in other genes. Transcriptomic, proteomic, and metabolomic studies looking for endophenotypes are under way. There is no shortage of candidate new drug targets for PAH, but the selection and prioritisation of these are challenges for the research community.

Betaine Attenuates Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats via Inhibiting Inflammatory Response

Background: Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary vascular resistance, leading to right ventricular failure and death. Recent studies have suggested that chronic inflammatory processes are involved in the pathogenesis of PAH. Several studies have demonstrated that betaine possesses outstanding anti-inflammatory effects. However, whether betaine exerts protective effects on PAH by inhibiting inflammatory responses in the lungs needs to be explored. To test our hypothesis, we aimed to investigate the effects of betaine on monocrotaline-induced PAH in rats and attempted to further clarify the possible mechanisms. Methods: PAH was induced by monocrotaline (50 mg/kg) and oral administration of betaine (100, 200, and 400 mg/kg/day). The mean pulmonary arterial pressure, right ventricular systolic pressure, and right ventricle hypertrophy index were used to evaluate the development of PAH. Hematoxylin and eosin staining and Masson staining were performed to measure the extents of vascular remodeling and proliferation in fibrous tissue. Monocyte chemoattractant protein-1 (MCP-1) and endothelin-1 (ET-1) were also detected by immunohistochemical staining. Nuclear factor-κB (NF-κB), tumor necrosis factor alpha (TNF-α), and interleukin-1β (IL-1β) were assessed by Western blot. Results: This study showed that betaine improved the abnormalities in right ventricular systolic pressure, mean pulmonary arterial pressure, right ventricle hypertrophy index, and pulmonary arterial remodeling induced by monocrotaline compared with the PAH group. The levels of MCP-1 and ET-1 also decreased. Western blot indicated that the protein expression levels of NF-κB, TNF-α, and IL-1β significantly decreased (p < 0.01). Conclusion: Our study demonstrated that betaine attenuated PAH through its anti-inflammatory effects. Hence, the present data may offer novel targets and promising pharmacological perspectives for treating monocrotaline-induced PAH.

3,7-Bis(2-hydroxyethyl)icaritin, a potent inhibitor of phosphodiesterase-5, prevents monocrotaline-induced pulmonary arterial hypertension via NO/cGMP activation in rats

Pulmonary arterial hypertension (PAH) is a chronic progressive disease which leads to elevated pulmonary arterial pressure and right heart failure. 3,7-Bis(2-hydroxyethyl)icaritin (ICT), an icariin derivatives, was reported to have potent inhibitory activity on phosphodiesterase type 5 (PDE5) which plays a crucial role in the pathogenesis of PAH. The present study was designed to investigate the effects of ICT on monocrotaline (MCT)-induced PAH rat model and reveal the underlying mechanism. MCT-induced PAH rat models were established with intragastric administration of ICT (10, 20, 40 mg/kg/d), Icariin (ICA) (40 mg/kg/d) and Sildenafil (25 mg/kg/d). The mean pulmonary arterial pressure (mPAP) and right ventricle hypertrophy index (RVHI) were measured. Pulmonary artery remodeling was assessed by H&E staining. Blood and lung tissue were collected to evaluate the level of endothelin 1 (ET-1), nitric oxide (NO), and cyclic guanosine monophosphate (cGMP). The expressions endothelial nitric oxide synthase (eNOS) and PDE5A in lung tissues were determined by Western blot analysis. The results showed that ICT reduced RVHI and mPAP, and reversed lung vascular remodeling in rats with MCT-induced PAH. ICT also reversed MCT-induced ET-1 elevation, NO and cGMP reduction in serum or lung tissue. Moreover, ICT administration significantly induced eNOS activation and PDE5A inhibition. ICT with lower dose had better effects than ICA. In summary, ICT is more effective in preventing MCT-induced PAH in rats via NO/cGMP activation compared with ICA. These findings demonstrate a novel mechanism of the action of ICT that may have value in prevention of PAH.

Endothelial nitric oxide synthase overexpressing human early outgrowth cells inhibit coronary artery smooth muscle cell migration through paracrine functions

Cells mobilized from the bone marrow can contribute to endothelial regeneration and repair. Nevertheless, cardiovascular diseases are associated with diminished numbers and function of these cells, attenuating their healing potential. Gene transfer of endothelial nitric oxide synthase (eNOS) can restore the activity of circulating cells. Furthermore, estrogen accelerates the reendothelialization capacity of early outgrowth cells (EOCs). We hypothesized that overexpressing eNOS alone or in combination with estrogen stimulation in EOCs would potentiate the beneficial effects of these cells in regulating smooth muscle cell (SMC) function. Native human EOCs did not have any effect on human coronary artery SMC (hCASMC) proliferation or migration. Transfecting EOCs with a human eNOS plasmid and/or stimulating with 17β-estradiol (E₂) increased NO production 3-fold and enhanced EOC survival. Moreover, in co-culture studies, eNOS overexpressing or E2-stimulated EOCs reduced hCASMC migration (by 23% and 56% respectively), vs. control EOCs. These effects do not implicate ERK1/2 or focal adhesion kinases. Nevertheless, NOS-EOCs had no effect on hCASMC proliferation. These results suggest that overexpressing or activating eNOS in EOCs increases their survival and enhances their capacity to regulate SMC migration through paracrine effects. These data elucidate how eNOS overexpression or activation in EOCs can prevent vascular remodeling.

The role of endothelial nitric oxide in the anti-restenotic effects of liraglutide in a mouse model of restenosis

Background

Previous animal studies have shown that glucagon-like peptide-1 receptor agonists (GLP-1RAs) suppress arterial restenosis, a major complication of angioplasty, presumably through their direct action on vascular smooth muscle cells. However, the contribution of vascular endothelial cells (VECs) to this process remains unknown. In addition, the potential interference caused by severe hyperglycemia and optimal treatment regimen remain to be determined.

Methods

Nine-week-old male C57BL6 (wild-type) and diabetic db/db mice were randomly divided into vehicle or liraglutide treatment groups (Day 1), and subject to femoral artery wire injuries (Day 3). The injured arteries were collected on Day 29 for morphometric analysis. Human umbilical vein endothelial cells (HUVECs) were used for in vitro experiments. One-way ANOVA, followed by Tukey’s test, was used for comparisons.

Results

In wild-type mice, liraglutide treatment (5.7, 17, or 107 nmol/kg/day) dose-dependently reduced the neointimal area (20, 50, and 65%) without inducing systemic effects, and caused an associated decrease in the percentage of vascular proliferating cells. However, these effects were completely abolished by the nitric oxide synthase (NOS) inhibitor N-omega-nitro-l-arginine methyl ester. Next, we investigated the optimal treatment regimen. Early treatment (Days 1–14) was as effective in reducing the neointimal area and vascular cell proliferation as full treatment (Days 1–29), whereas delayed treatment (Days 15–29) was ineffective. In HUVECs, liraglutide treatment dose-dependently stimulated NO production, which was dependent on GLP-1R, cAMP, cAMP-dependent protein kinase, AMP-activated protein kinase (AMPK), and NOS. Subsequently, we investigated the role of liver kinase B (LKB)-1 in this process. Liraglutide increased the phosphorylation of LKB-1, and siRNA-induced LKB-1 knockdown abolished liraglutide-stimulated NO production. In severe hyperglycemic db/db mice, liraglutide treatment also suppressed neointimal hyperplasia, which was accompanied by reductions in vascular cell proliferation and density. Furthermore, liraglutide treatment suppressed hyperglycemia-enhanced vascular inflammation 7 days after arterial injury.

Conclusions

We demonstrate that endothelial cells are targets of liraglutide, and suppress restenosis via endothelial NO. Furthermore, the protective effects are maintained in severe hyperglycemia. Our findings provide an evidence base for a future clinical trial to determine whether treatment with GLP-1RAs represents potentially effective pharmacological therapy following angioplasty in patients with diabetes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0603-x) contains supplementary material, which is available to authorized users.

A Novel Therapeutic Approach in the Treatment of Pulmonary Arterial Hypertension: Allium ursinum Liophylisate Alleviates Symptoms Comparably to Sildenafil

Right-sided heart failure—often caused by elevated pulmonary arterial pressure—is a chronic and progressive condition with particularly high mortality rates. Recent studies and our current findings suggest that components of Wild garlic (Allium ursinum, AU) may play a role in reducing blood pressure, inhibiting angiotensin-converting enzyme (ACE), as well as improving right ventricle function in rabbit models with heart failure. We hypothesize that AU may mitigate cardiovascular damage caused by pulmonary arterial hypertension (PAH) and has value in the supplementary treatment of the complications of the disease. In this present investigation, PAH was induced by a single dose of monocrotaline (MCT) injection in Sprague-Dawley rats, and animals were divided into 4 treatment groups as follows: I. healthy control animals (Control group); II. pulmonary hypertensive rats (PAH group); III. pulmonary hypertensive rats + daily sildenafil treatment (Sildenafil group); and IV. pulmonary hypertensive rats + Wild garlic liophylisate-enriched chow (WGLL group), for 8 weeks. Echocardiographic measurements were obtained on the 0 and 8 weeks with fundamental and Doppler imaging. Isolated working heart method was used to determinate cardiac functions ex vivo after thoracotomy on the 8th week. Histological analyses were carried out on excised lung samples, and Western blot technique was used to determine Phosphodiesterase type 5 enzyme (PDE5) expression in both myocardial and pulmonary tissues. Our data demonstrate that right ventricle function measured by echocardiography was deteriorated in PAH animals compared to controls, which was counteracted by AU treatment. Isolated working heart measurements showed elevated aortic flow in WGLL group compared to PAH animals. Histological analysis revealed dramatic increase in medial wall thickness of pulmonary arteries harvested from PAH animals, but arteries of animals in sildenafil- and WGLL-treated groups showed physiological status. Our results suggest that bioactive compounds in Allium ursinum could have beneficial effects in pulmonary hypertension.

Exendin-4 inhibits structural remodeling and improves Ca2+ homeostasis in rats with heart failure via the GLP-1 receptor through the eNOS/cGMP/PKG pathway

The glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4 is a long-acting analog of GLP-1, which stimulates insulin secretion and is clinically used in the treatment of type 2 diabetes. Previous studies have demonstrated that GLP-1 agonists and analogs serve as cardioprotective factors in various conditions. Disturbances in calcium cycling are characteristic of heart failure (HF); therefore, the aim of this study was to investigate the effect of exendin-4 (a GLP-1 mimetic) on the regulation of calcium handling and to identify the underlying mechanisms in an HF rat model after myocardial infarction (MI). Rats underwent surgical ligation of the left anterior descending coronary artery or sham surgery prior to infusion with vehicle, exendin-4, or exendin-4 and exendin9-39 for 4 weeks. Exendin-4 treatment decreased MI size, suppressed chamber dilation, myocyte hypertrophy, and fibrosis and improved in vivo heart function in the rats subjected to MI. Exendin-4 resulted in an increase in circulating GLP-1 and GLP-1R in ventricular tissues. Additionally, exendin-4 activated the eNOS/cGMP/PKG signaling pathway and inhibited the Ca²⁺/calmodulin-dependent kinase II (CaMKII) pathways. Myocytes isolated from exendin-4-treated hearts displayed higher Ca²⁺ transients, higher sarcoplasmic reticulum Ca²⁺ content, and higher l-type Ca²⁺ current densities than MI hearts. Exendin-4 treatment restored the protein expression of sarcoplasmic reticulum Ca²⁺ uptake ATPase (SERCA2a), phosphorylated phospholamban (PLB) and Cav1.2 and decreased the levels of phosphorylated ryanodine receptor (RyR). Moreover, the favorable effects of exendin-4 were significantly inhibited by exendin9-39 (a GLP-1 receptor antagonist). Exendin-4 treatment of an HF rat model after MI inhibited cardiac and cardiomyocytes progressive remodeling. In addition, Ca²⁺ handling and its molecular modulation were also improved by exendin-4 treatment. The beneficial effects of exendin-4 on cardiac remodeling may be mediated through activation of the eNOS/cGMP/PKG pathway.

Vascular Biology of Glucagon Receptor Superfamily Peptides: Mechanistic and Clinical Relevance

Regulatory peptides produced in islet and gut endocrine cells, including glucagon, glucagon-like peptide-1 (GLP-1), GLP-2, and glucose-dependent insulinotropic polypeptide, exert actions with considerable metabolic importance and translational relevance. Although the clinical development of GLP-1 receptor agonists and dipeptidyl peptidase-4 inhibitors has fostered research into how these hormones act on the normal and diseased heart, less is known about the actions of these peptides on blood vessels. Here we review the effects of these peptide hormones on normal blood vessels and highlight their vascular actions in the setting of experimental and clinical vascular injury. The cellular localization and signal transduction properties of the receptors for glucagon, GLP-1, GLP-2, and glucose-dependent insulinotropic polypeptide are discussed, with emphasis on endothelial cells and vascular smooth muscle cells. The actions of these peptides on the control of blood flow, blood pressure, angiogenesis, atherosclerosis, and vascular inflammation are reviewed with a focus on elucidating direct and indirect mechanisms of action. How these peptides traverse the blood-brain barrier is highlighted, with relevance to the use of GLP-1 receptor agonists to treat obesity and neurodegenerative disorders. Wherever possible, we compare actions identified in cell lines and primary cell culture with data from preclinical studies and, when available, results of human investigation, including studies in subjects with diabetes, obesity, and cardiovascular disease. Throughout the review, we discuss pitfalls, limitations, and challenges of the existing literature and highlight areas of controversy and uncertainty. The increasing use of peptide-based therapies for the treatment of diabetes and obesity underscores the importance of understanding the vascular biology of peptide hormone action.

Functional Improvement and Regression of Medial Hypertrophy in the Remodeled Pulmonary Artery after Correction of Systemic Left-to-Right Shunt

The presence of systemic left-to-right shunt and increased pulmonary blood flow can result in right heart failure and pulmonary arteriopathy. Correction of left-to-right shunt has been shown to improve cardiac function and physical performance. However, the cardiopulmonary remodeling processes following cessation of left-to-right shunt have yet to be reported. In this experimental study, excessive pulmonary flow was restored through ligation of the aortocaval fistula in rats with flow-induced pulmonary hypertension. The cardiopulmonary morphometric functions were assessed, and phenotypic switching of pulmonary vascular smooth muscle cells (VSMC) was determined. Ligation of aortocaval fistula significantly attenuated pulmonary blood flow and right ventricular mass, and potentiated the isometric contraction of pulmonary artery. Inflammatory cytokines IL-1β and IL-6 were reduced in the lung after ligation. Reduction of pulmonary blood flow restored the expressions of smooth muscle myosin heavy chain and α-smooth muscle actin in pulmonary artery, indicating the switching of VSMCs to the contractile phenotype. Our study demonstrated that normalization of pulmonary blood flow in flow-induced pulmonary hypertension reverses the remodeling in the right ventricle and pulmonary artery. The remodeling process of flow-induced pulmonary hypertension is functionally and morphometrically reversible by inducing transdifferentiation of pulmonary VSMC to contractile phenotypes and modulation of tissue inflammatory cytokines.