Pulmonary hypertension: therapeutic targets within the serotonin system

Pulmonary arterial hypertension (PAH) is characterized by a sustained and progressive elevation in pulmonary arterial pressure and pulmonary vascular remodelling leading to right heart failure and death. Prognosis is poor and novel therapeutic approaches are needed. The serotonin hypothesis of PAH originated in the 1960s after an outbreak of the disease was reported among patients taking the anorexigenic drugs aminorex and fenfluramine. These are indirect serotonergic agonists and serotonin transporter substrates. Since then many advances have been made in our understanding of the role of serotonin in the pathobiology of PAH. The rate-limiting enzyme in the synthesis of serotonin is tryptophan hydroxylase (Tph). Serotonin is synthesized, through Tph1, in the endothelial cells of the pulmonary artery and can then act on underlying pulmonary arterial smooth muscle cells and pulmonary arterial fibroblasts in a paracrine fashion causing constriction and remodelling. These effects of serotonin can be mediated through both the serotonin transporter and serotonin receptors. This review will discuss our current understanding of 'the serotonin hypothesis' of PAH and highlight possible therapeutic targets within the serotonin system.     

氟伐他汀对肺动脉高压大鼠5-羟色胺转载体表达的影响

目的观察氟伐他汀对野百合碱(MCT)所致的肺动脉高压大鼠肺组织5-羟色胺转载体(5-HTT)表达的影响。方法62只大鼠随机分为3组:①M+F组:大鼠首先给予MCT(40 mg/kg)皮下注射和氟伐他汀(1 mg/kg)灌胃,每日各1次,连续2周。第3~6周继续按氟伐他汀初始给药方案灌胃,不再进行MCT皮下注射。②MCT组:实验前2周给予MCT(40 mg/kg)1次/d皮下注射,第3~6周末给予同氟伐他汀等体积的0.9%盐水灌胃;③Saline组:分别于实验前2周及第3~6周给予等体积的盐水皮下注射和灌胃。分别于不同时间点,对大鼠的血流动力学及相关参数和5-HTT的表达情况进行测定。结果MCT组大鼠于实验第2周末即出现显著的肺动脉高压伴5-HTT蛋白水平异常增高,且在观察期间逐渐增高。M+F组大鼠第6周末出现肺动脉压异常增高,但未伴5-HTT表达增高。结论氟伐他汀能有效抑制5-HTT表达上调,该作用可能与其对大鼠肺动脉高压的抑制作用有关。     

Emerging therapies for pulmonary arterial hypertension

Pulmonary arterial hypertension is characterised by increased pulmonary vascular resistance due to increased vascular tone and structural remodelling of pulmonary vessels. The therapies that are in use so far have been developed to correct endothelial dysfunction and reduce vasomotor tone. These treatments have a limited effect on the remodelling process and, increasingly, the focus is turning to potent strategies for inhibiting vascular proliferation and promoting vascular apoptosis. Multiple novel targets have been uncovered over the last 5 years and several are now in early clinical trials. At present, it is clear that there is no single treatment for the condition. Although this is the case, studies are investigating the role of combining therapies that are already established.     

Advances in treatment of pulmonary arterial hypertension: patent review

Introduction: Current therapeutic approaches for pulmonary arterial hypertension (PAH) commonly include use of prostacyclins, endothelin pathway antagonists or NO (nitric oxide) pathway modulators. These agents are non-specific and suffer from several important shortcomings including short half-lives, invasive routes of administration, higher dose and frequency requirements, and several dose-related systemic side effects. Hence, discovery of novel agents with improved therapeutic efficacy with respect to survival benefits and the development of non-invasive routes of administration are in critical need. Current research aimed at developing more selective therapies for PAH are focused both on agents acting on novel molecular targets, as well as, novel compounds acting on conventional pathways with improved characteristics.

Area covered: The present review covers recently filed (issued/application) patents (2010–2016) describing novel agents acting on investigational targets as well as novel compounds with improved characteristics acting on established targets. Patents describing combinations of conventional and investigational compounds are also discussed.

Expert opinion: PAH has recently been considered as cancer-like disease with over-proliferation of pulmonary arterial smooth muscle cells and endothelial cells. New cellular and molecular biological advances have revealed novel target/pathways involved in the pathogenesis and progression of PAH. Thus, discovery of agents that act on these novel pathways provides a promising avenue of research for improving therapeutic approaches for PAH.     

Targeting PDGF pathway in pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) encompasses a rare potentially lethal group of diseases characterized by vasoconstriction, in situ thrombosis and vascular remodeling. Most of the existing therapies including endothelin receptor antagonists, prostacyclin and derivatives, or phsophodiesterase-5 inhibitors tackle mainly the endothelial dysfunction, leaving the remodeling suboptimally inhibited. This explains the disease progression that occurs even with combined therapies and the need for other therapies able to adequately inhibit the vascular remodeling.

Areas covered: Platelet-derived growth factor (PDGF) signaling pathway was demonstrated to be involved in the vascular remodeling in PAH, and therefore, it might be a desirable therapeutic target in this setting. This review discusses the pathogenic role of this pathway in PAH and its potential inhibitory approaches, focusing on imatinib as well as on the existing preclinical data on this compound.

Expert opinion: Preclinical studies demonstrated that PDGF inhibition with receptor antagonists such as imatinib reduces vascular remodeling. Therefore, PDGF might represent a plausible therapeutic target in this disease. However, compounds able to block this pathway via different mechanisms might also become potential PAH therapies.     

Investigation on novel pharmacological target against pulmonary hypertension

Objective To investigation on novel pharmacological target against pulmonary hypertension.It was recognized in the recent years that pulmonary hypertension(PHT)compromised of four components,i.e.vasoconstriction,hyperplasia,micro thrombosis and inflammation of pulmonary vasculature.Pulmonary vascular hyperplasia is a hallmark pathologic feature of pulmonary hypertension.Hyperplasia of rat pulmonary artery smooth muscle cells(PASMCs)was significantly increased,and PASMCs from rats or human beings with PHT grow faster than those from control subjects when stimulated by serotonin or serum.Pulmonary hypertension(PHT)is the major cause of right ventricular hypertrophy and eventually right heart failure.5-hydroxytraptamine(5-HT)as mitogen for vascular smooth muscle cells plays an important role in the development of PHT.It is known that selective serotonin re-uptake inhibitors(SSRIs)restrain 5-HT internalization.Therefore,this study was aimed to investigate if SSRIs may have protective effect against monocrotaline(MCT)-induced right ventricular hypertrophy.Methods induced chronic pulmonary hypertension in Wistar rats was established;fluoxetine and sertraline(2,10 mg·kg-1·d-1 were administered by gavages.3 w after MCT injection,right ventricular index(RVI),pulmonary artery pressure(PAP),heart and lung morphology were measured or investigated.5-HT transporter(SERT)assayed by RT-PCR or Western blot.Results MCT-Results RVI was significantly increased in MCT group(P<0.01 vs control)and reduced to by fluoxetine(10 mg·kg-1·d-1)and 0.42±0.04 by Sertraline(10 mg·kg-1·d-1)(both P<0.05 vs MCT).PAP increased significantly by MCT(P<0.01 vs control).Fluoxetine(10 mg·kg-1·d-1),or sertraline(10 mg·kg-1·d-1)attenuated MCT-induced increase of PAP,respectively(both P<0.05 vs MCT).MCT raised significantly Pulmonary artery muscularization(P<0.01 vs control),and attenuated by fluoxetine or sertraline(P<0.01 vs MCT).MCT increased SERT mRNA and protein expression,and both were significantly attenuated by fluoxetine or sertraline,respectively.Conclusions SSRIs protect against MCT-induced right ventricular hypertrophy,RVI,PAP,Pulmonary artery muscularization,which may be relevant to inhibition of SERT and the results suggest that SERT may be a novel pharmacological target against pulmonary hypertension.     

Notch信号通路在肺动脉高压肺血管重构中的研究进展

肺动脉高压是一种以肺动脉压力和肺血管阻力持续升高为特征,引起肺血管重构发生的心血管性疾病。Notch信号通路是一种高度保守的信号路径,主要通过调控细胞的增殖、分化及凋亡等过程,参与心血管、神经、肿瘤等疾病的发生、发展。该文主要对Notch信号通路参与肺血管重构发生的分子机制进行综述,以期为肺动脉高压的治疗提供新的策略。     

中国肺动脉高压诊断与治疗指南

白细胞介素-6 (interleukin-6,IL-6)是一种多效性细胞因子,在炎症反应中起重要作用。越来越多的证据表明,IL-6在肺动脉高压的发生发展中也起到了十分重要的作用,肺动脉高压患者和动物模型的循环中IL-6水平明显升高,小鼠体内过表达IL-6可以诱导重度肺动脉高压,针对IL-6的治疗可以改善肺动脉高压。本文主要从分子水平对IL-6在肺动脉高压中的作用及其机制的研究进展进行综述,并对目前以IL-6为靶点治疗肺动脉高压的候选方案进行介绍,以期为肺动脉高压的临床药物研究开发提供参考。

     

Treatment of obesity and pulmonary arterial hypertension with inhibitors of the prostaglandin transporter: evaluation of patent WO2014/204895A1

Prostaglandins display a wide array of pharmacological effects and prostaglandin analogs are already used in the treatment of pulmonary arterial hypertension (PAH). After synthesis and release from cells, prostaglandins undergo reuptake by the prostaglandin transporter (PGT). WO2014/204895 claims the use of a series of trisubstituted triazine derivatives for the treatment of obesity and PAH. Composition of matter of these triazines has been claimed in WO2011/037610 and the compounds are described as potent inhibitors of the PGT. One compound (nr 146) was shown to improve high fat diet-induced glucose tolerance in a mouse model. In addition, this compound has been explored in the rat monocrotaline model of PAH and reduced characteristic features of the pathology. This class of compounds presents a potential new treatment paradigm in the treatment of obesity-related disorders and PAH.     

5型磷酸二酯酶抑制剂在肺动脉高压中的应用

肺动脉高压（PAH）是一类以小肺动脉血管重构为特征的恶性心肺血管疾病。5型磷酸二酯酶（PDE-5）抑制剂可减少环鸟苷酸的降解而舒张肺血管平滑肌,有效降低肺血管阻力。本文综述PDE-5抑制剂的作用机制、药动学及临床应用研究进展。     

Sildenafil for pulmonary arterial hypertension: when blue turns into white

Pulmonary arterial hypertension is a life-threatening, rare disease characterised by vasoconstriction and vascular remodelling of pulmonary artery vessels. Pulmonary arterial hypertension can occur without an obvious cause or can be secondary. Until several years ago, therapeutic approaches were represented mainly by ‘conventional therapy’ (anticoagulants, calcium channel blockers, diuretics and digoxin, and oxygen therapy). But recently ‘specific therapies’ (i.e., therapies targeting specific pathogenic pathways) have become available; these are therapies represented by prostacyclin and its derivatives, endothelin receptor antagonists or phosphodiesterase-5 inhibitors. Sildenafil citrate is a phosphodiesterase-5 inhibitor and is the second oral pharmacological agent recently approved for the treament of pulmonary arterial hypertension. Sildenafil has demonstrated short- and long-term clincal efficacy in the treatment of various forms of pulmonary arterial hypertension, either alone or in combination with other agents, but its safety profile needs further assessment.     

野百合碱诱导的肺动脉高压大鼠肺血管5-HT转载体表达增强

目的　研究野百合碱诱导的大鼠肺动脉高压与5 HT转载体基因表达的关系。方法　应用MCT诱导的慢性肺动脉高压大鼠模型,建立离体动脉环5 HT浓度反应曲线;HE染色观察肺动脉构型重建,应用RT PCR检测大鼠肺动脉5 HT转载体mRNA表达。结果　MCT大鼠肺血管对5 HT收缩反应增强,肺肌型小动脉中膜增厚,MCT诱导的肺动脉高压大鼠肺血管5 HT转载体mRNA表达明显增多。5 HT转载体基因表达与肺肌型小动脉中膜增厚有明显相关性。结论　MCT诱导的肺动脉高压大鼠肺血管构型重建及5 HT引起收缩反应增强,伴有5 HT转载体mRNA表达增多;同时5 HT转载体mRNA表达与肺肌型小动脉中膜增厚有明显相关性,提示5 HT转载体可能在肺动脉高压中起重要作用。     

芍药苷对大鼠低氧性肺动脉高压的防治作用及其抗氧化机制研究

目的 研究芍药苷对低氧诱导的肺动脉高压大鼠模型的作用并初步探讨其作用机制。方法 60只SD大鼠随机分为6组,每组10只,分别为：对照组（等体积生理盐水,ig）、模型组（等体积生理盐水,ig）、阳性对照组（西地那非25 mg/kg,ig）、芍药苷低、中、高剂量组（20、40、80 mg/kg,ig）。对照组大鼠置于正常环境中饲养,其余各组均于给药0.5 h后置于全自动低压低氧舱内（大气压50 kPa,氧浓度10%）,每天8 h,持续21 d。在实验终点时检测各组大鼠平均肺动脉压（mPAP）、平均颈动脉压（mCAP）、右心室肥厚指数（RVHI）及观察肺动脉病理变化;检测血浆内皮素（ET-1）、血清一氧化氮（NO）水平;检测肺组织匀浆超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GSH-Px）活性、丙二醛（MDA）含量。结果 与对照组比较,模型组大鼠mPAP、RVHI、血浆ET-1水平、肺组织中MDA含量显著升高（P＜0.01）,血清中NO水平、肺组织中SOD、CAT、GSH-Px活性显著降低（P＜0.01）,HE染色显示大鼠肺小动脉管壁明显增厚,管腔狭窄。与模型组比较,芍药苷中、高剂量组大鼠mPAP、RVHI、血浆ET-1水平、肺组织中MDA含量显著降低（P＜0.05或P＜0.01）,血清中NO水平、肺组织中SOD、CAT、GSH-Px活性显著升高（P＜0.05或P＜0.01）;HE染色显示不同剂量芍药苷干预后,大鼠肺小动脉管壁增厚和管腔狭窄均不同程度减轻。结论 芍药苷可降低低氧诱导的大鼠肺动脉高压与右心室肥厚程度,减轻肺小动脉血管重塑,其机制可能与降低大鼠血浆ET-1水平、升高血清NO水平,改善血管内皮舒缩因子失衡,提高大鼠肺组织匀浆中SOD、CAT、GSH-Px活性、降低MDA含量,减轻大鼠肺组织氧化应激损伤有关。     

Oral treprostinil in the treatment of pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a rare disease resulting in progressive remodeling of the pulmonary vasculature and eventual right ventricular failure. Despite the development of 13 therapies for PAH since 2000, the use of continuously infused prostanoids retains a special role. Infused medications present unique challenges, and the search for an efficacious oral prostanoid culminated in the FDA approval of oral treprostinil – a first in class oral prostanoid medication approved to treat pulmonary arterial hypertension (PAH).

Areas covered: In this discussion, we review the pharmacologic properties of oral treprostinil, and discuss three original major registration studies that resulted in the approval and widespread use of the drug. We also review several post-approval analyses and transitional studies. We discuss administration issues including side effects, transitioning, cost, and comparative analysis with selexipag.

Expert opinion: Though the prospects of harnessing the benefits of continuously infused prostanoid therapy in a pill form are tantalizing, the gap in efficacy between oral and infused treatment is substantial. Major side effects and exorbitant cost are further barriers to broad uptake. Competition from oral prostaglandin receptor agonist selexipag challenges the commercial success of oral treprostinil. The long-term viability of oral treprostinil rests largely on the outcome of the long-term event-driven study of the molecule added to background approved ERA or PDE5 inhibitor monotherapy.     

Macitentan for the treatment of pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a serious disease characterized by elevation of pulmonary artery pressures and right ventricular failure. It is a progressive disease with a poor 5-year survival despite recent advances in treatment. Endothelin plays an important role in the development and progression of the disease. Endothelin receptor blockers have been used to treat PAH since 2001. More recently, macitentan was approved for treatment of PAH.

Area covered: This review covers the preclinical and clinical data on macitentan.

Expert opinion: Macitentan is a more potent ERA and has been shown to delay progression of the disease. It does not appear to have any significant hepatotoxicity and has a convenient once-a-day dosing. In the large event driven trial, macitentan significantly reduced morbidity in patients with PAH. It was safe and well tolerated and the benefit was seen in treatment-naïve patients and those already receiving PAH therapy.     

Bosentan预防大鼠低氧性肺动脉高压形成的作用

目的研究Bosentan预防低氧诱导的肺动脉高压发生的药效作用,探讨内皮素-1(ET-1)在慢性高原病发病中的作用。方法30只Wistar大鼠随机均分为常氧对照组、低氧对照组和Bosentan组,将低氧对照组和Bosentan组放入模拟海拔为5.5 km的低氧、低压环境中。常氧对照组和低氧对照组ig 0.9%生理盐水,Bosentan组ig 100 mg.ml-1Bosentan水剂,每天2次。饲养15 d后,测量大鼠平均肺动脉高压(PAP)、左右心室比重[RV/(LV S)]比值。结果Bosentan组大鼠血红蛋白(Hb)、红细胞压积(Hct),ET-1与低氧对照组相比无差异,而PAP、RV/(LV S)均显著低于低氧对照组(P<0.01)。结论Bosentan可显著预防低氧性肺动脉压的升高,缓解低氧对心肌细胞和血管平滑肌细胞的损伤,但不能抑制红细胞的过度增生。     

Tadalafil for the treatment of pulmonary arterial hypertension

Background: Tadalafil, a long-acting phosphodiesterase-5 inhibitor (PDE-5) is the most recent oral agent to receive FDA approval for the treatment of pulmonary arterial hypertension (PAH). Objective: With several new agents emerging for the treatment of PAH, this article reviews tadalafil, the compound and its properties, clinical evidence supporting its use, and the role of tadalafil in the current treatment approach for patients with PAH. Methods: A broad PubMed literature search was performed to identify the most current data on the use of tadalafil for PAH. Results: Tadalafil received FDA approval in 2009 following the recently published pivotal trial that demonstrated that the use of tadalafil 40 mg once daily was well tolerated, improved exercise capacity and quality of life measures and reduced time to clinical worsening in PAH patients. As the second PDE-5 inhibitor to gain approval for PAH, clinical properties such as its long half-life leading to once-daily dosing and possibly improved compliance, as well as potential cost benefit, may distinguish tadalafil from sildenafil in the widespread treatment of PAH.     

Downregulation of osteopontin is associated with fluoxetine amelioration of monocrotaline-induced pulmonary inflammation and vascular remodelling

1. Osteopontin (OPN) has emerged as a key factor in inflammatory activation and cardiovascular remodelling. The aim of the present study was to investigate the involvement of OPN in fluoxetine amelioration of monocrotaline (MCT)-induced pulmonary inflammation and vascular remodelling in rats. 2. Wistar rats were divided into control, MCT and two fluoxetine-treated groups. Pulmonary arterial hypertension (PAH) was induced by a single injection of MCT (60 mg/kg, i.p.). Fluoxetine (2 and 10 mg/kg) was administered via the intragastric route once a day for 21 days. On Day 22, pulmonary haemodynamic measurements were undertaken, followed by ELISA, western blotting and immunohistochemistry. 3. Monocrotaline caused pulmonary inflammation and vascular remodelling and significantly enhanced OPN expression in the plasma, lungs and pulmonary arteries. Fluoxetine decreased pulmonary arterial pressure and ameliorated pulmonary inflammation and pulmonary vascular remodelling. At 10 mg/kg, fluoxetine significantly inhibited MCT-induced increases in the expression of serotonin transporter (SERT) and phosphorylated extracellular signal-regulated kinase 1/2 and downregulated the expression of OPN, macrophage inflammatory protein-1β and matrix metalloproteinase 2/tissue inhibitor of metalloproteinase 2. Although 2 mg/kg fluoxetine tended to ameliorate some MCT-induced changes in the lung, the differences did not always reach statistical significance. Linear regression analysis showed that there was a positive correlation between plasma OPN concentrations and mean pulmonary arterial pressure, as well as percentage medial wall thickness and percentage wall area in the pulmonary artery. 4. In conclusion, the amelioration by fluoxetine of MCT-induced pulmonary inflammation and vascular remodelling is associated with downregulation of OPN expression in rats.     

Pulmonary arterial hypertension: basis of sex differences in incidence and treatment response

Pulmonary arterial hypertension (PAH) is a complex disease characterized by elevated pulmonary arterial pressure, pulmonary vascular remodelling and occlusive pulmonary vascular lesions, leading to right heart failure. Evidence from recent epidemiological studies suggests the influence of gender on the development of PAH with an approximate female to male ratio of 4:1, depending on the underlying disease pathology. Overall, the therapeutic strategy for PAH remains suboptimal with poor survival rates observed in both genders. Endogenous sex hormones, in particular 17β oestradiol and its metabolites, have been implicated in the development of the disease; however, the influence of sex hormones on the underlying pathobiology remains controversial. Further understanding of the influence of sex hormones on the normal and diseased pulmonary circulation will be critical to our understanding the pathology of PAH and future therapeutic strategies. In this review, we will discuss the influence of sex hormones on the development of PAH and address recent controversies.

Linked Articles

This article is part of a themed section on Biological Sex and Cardiovascular Pharmacology. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-3