Bone morphogenetic protein 4 promotes pulmonary vascular remodeling in hypoxic pulmonary hypertension

We show that 1 of the type II bone morphogenetic protein (BMP) receptor ligands, BMP4, is widely expressed in the adult mouse lung and is upregulated in hypoxia-induced pulmonary hypertension (PH). Furthermore, heterozygous null Bmp4(lacZ/+) mice are protected from the development of hypoxia-induced PH, vascular smooth muscle cell proliferation, and vascular remodeling. This is associated with a reduction in hypoxia-induced Smad1/5/8 phosphorylation and Id1 expression in the pulmonary vasculature. In addition, pulmonary microvascular endothelial cells secrete BMP4 in response to hypoxia and promote proliferation and migration of vascular smooth muscle cells in a BMP4-dependent fashion. These findings indicate that BMP4 plays a dominant role in regulating BMP signaling in the hypoxic pulmonary vasculature and suggest that endothelium-derived BMP4 plays a direct, paracrine role in promoting smooth muscle proliferation and remodeling in hypoxic PH.     

氧化应激和肺动脉高压血管重构

氧化应激可通过促进肺动脉血管平滑肌细胞增殖、加重血管内皮功能损伤和促进血管外基质增生等多条途径参与肺动脉血管重构,加速肺动脉高压的发生发展进程。近来研究发现,针对氧化应激进行的抗氧化治疗可有效地抑制肺动脉血管重构及肺动脉高压的发生,进一步证明了氧化应激在肺动脉血管重构乃至肺动脉高压中的重要作用。阐明病理条件下氧化还原信号途径,寻找抗氧化治疗的特异性药物,是肺动脉高压抗氧化治疗的基础和研究方向。     

Bone marrow-derived cells contribute to pulmonary vascular remodeling in hypoxia-induced pulmonary hypertension

STUDY OBJECTIVE: In these days, it was reported that bone marrow (BM) cells might take part in the remodeling of some systemic vascular diseases; however, it remains unknown whether the BM cells were involved in the vascular remodeling of pulmonary arteries and the progression of pulmonary hypertension (PH). The purpose of this study was to investigate whether BM-derived cells contribute to pulmonary vascular remodeling in hypoxia-induced PH. MATERIALS AND METHODS: To investigate the role of BM-derived cells, we transplanted the whole BM of enhanced green fluorescent protein (GFP)-transgenic mice to the lethally irradiated syngeneic mice (n = 30). After 8 weeks, chimera mice were exposed to consistent hypoxia using a hypoxic chamber (10% O(2)) for up to 4 or 8 weeks (10 mice per group). After hemodynamics and the ratio of right ventricular (RV) weight to left ventricle (LV) weight, RV/(LV + septum [S]), were measured, histologic and immunofluorescent staining were performed. RESULTS: BM-transplanted mice showed a high chimerism (mean [+/- SEM], 91 +/- 2.3%). RV systolic pressure and the RV/(LV + S) ratio increased significantly with time in PH mice, indicating RV hypertrophy. Marked vascular remodeling including medial hypertrophy and adventitial proliferation was observed in the pulmonary arteries of PH mice. Strikingly, a number of GFP(+) cells were observed at the pulmonary arterial wall, including the adventitia, in hypoxia-induced PH mice, while very few cells were observed in the control mice. Metaspectrometer measurements using confocal laser scanning microscopy confirmed that this green fluorescence was produced by GFP, suggesting that these GFP(+) cells were mobilized from the BM. Most of them expressed alpha-smooth muscle actin, a smooth muscle cell, or myofibroblast phenotype, and contributed to the pulmonary vascular remodeling. A semiquantitative polymerase chain reaction of the GFP gene revealed that the BM-derived GFP-positive cells in the PH group were observed more than eightfold as often compared with the control mice. CONCLUSION: The BM-derived cells mobilize to the hypertensive pulmonary arteries and contribute to the pulmonary vascular remodeling in hypoxia-induced PH mice.     

Right Ventricular Heart Failure From Pulmonary Embolism: Key Distinctions From Chronic Pulmonary Hypertension

BackgroundThe right ventricle normally operates as a low pressure, high-flow pump connected to a high-capacitance pulmonary vascular circuit. Morbidity and mortality in humans with pulmonary hypertension (PH) from any cause is increased in the presence of right ventricular (RV) dysfunction, but the differences in pathology of RV dysfunction in chronic versus acute occlusive PH are not widely recognized.Methods and ResultsChronic PH that develops over weeks to months leads to RV concentric hypertrophy without inflammation that may progress slowly to RV failure. In contrast, pulmonary embolism (PE) results in an abrupt vascular occlusion leading to increased pulmonary artery pressure within minutes to hours that causes immediate deformation of the RV. RV injury is secondary to mechanical stretch, shear force, and ischemia that together provoke a cytokine and chemokine-mediated inflammatory phenotype that amplifies injury.ConclusionsThis review will briefly describe causes of pulmonary embolism and chronic PH, models of experimental study, and pulmonary vascular changes, and will focus on mechanisms of right ventricular dysfunction, contrasting mechanisms of RV adaptation and injury in these 2 settings.     

Pathophysiology of pulmonary hypertension due to lung disease

Pulmonary hypertension (PH) often complicates the course of patients with advanced lung disease, and it is associated with a worse prognosis. Per the recent classification of pulmonary hypertensive disorders, PH due to lung disease is considered as a separate category within a group of disorders that was previously referred to as "secondary" PH. Among the lung diseases associated with PH, the incidence and clinical course of PH is best known for patients with COPD. Per studies in patients with COPD and other lung disorders, it is evident that the pathophysiology and treatment of these disorders is generally distinct from that of pulmonary arterial hypertensive disorders. Changes in the pulmonary vasculature that accompany elevations in pulmonary vascular pressure are generally referred to as pulmonary vascular remodeling. Chronic hypoxia is well known to cause pulmonary vascular remodeling and PH, and it is the major mechanism implicated for the development of PH in patients with lung disease. Other mediators have also been implicated in the pathogenesis of PH in animal models and patients with PH, including patients with pulmonary diseases. General features of pulmonary vascular remodeling are discussed with particular emphasis on those changes that have been described in patients with lung diseases. Recent discoveries in these areas are also reviewed, and findings in pulmonary arterial hypertensive diseases are contrasted with those found in patients with PH due to lung diseases. Some of these discoveries have already led to new treatment strategies for patients with the most severe forms of PH. PH due to lung diseases shares some common pathophysiologic features with pulmonary arterial hypertension. Therefore, it is likely that these discoveries and new treatments will also be extended to benefit patients with PH due to lung disease.     

Discovery of a murine model of clinical PAH: Mission impossible?

Pulmonary arterial hypertension (PAH) is a lung vascular disease characterized with a progressive increase of pulmonary vascular resistance and obliterative pulmonary vascular remodeling resulting in right heart failure and premature death. In this brief review, we document the recent advances in identifying genetically modified murine models of PH, with a focus on the recent discovery of the mouse model of Tie2 Cre-mediated deletion of prolyl hydroxylase 2, which exhibits progressive obliterative vascular remodeling, severe PAH, and right heart failure, thus recapitulating many of the features of clinical PAH. We will also discuss the translational potential of recent findings arising from experimental studies of murine PH models.     

Right Ventricular Pulmonary Hypertension

In heart failure (HF) syndrome, the development of pulmonary hypertension (PH), right ventricular (RV) dysfunction and failure are ominous prognostic signs. Pathophysiology, clinical interest and targeted therapeutic approaches for left-sided PH and its consequences on RV function have been traditionally confined to advanced HF stages. Community- and population-based studies have clearly indicated that PH is frequent even in HF patients with preserved ejection fraction, and may carry important prognostic implications in normal ageing as well. HF guidelines are inconclusive on both preventive and curative strategies for left-sided PH and its consequences on RV function. The search for new therapeutic opportunities targeted on pulmonary vascular and right heart remodeling are an important challenge for the future.     

Nitric oxide in the pulmonary vasculature

Homeostasis in the pulmonary vasculature is maintained by the actions of vasoactive compounds, including nitric oxide (NO). NO is critical for normal development of the pulmonary vasculature and continues to mediate normal vasoregulation in adulthood. Loss of NO bioavailability is one component of the endothelial dysfunction and vascular pathology found in pulmonary hypertension (PH). A broad research effort continues to expand our understanding of the control of NO production and NO signaling and has generated novel theories on the importance of pulmonary NO production in the control of the systemic vasculature. This understanding has led to exciting developments in our ability to treat PH, including inhaled NO and phosphodiesterase inhibitors, and to several promising directions for future therapies using nitric oxide-donor compounds, stimulators of soluble guanylate cyclase, progenitor cells expressing NO synthase (NOS), and NOS gene manipulation.     

Inhibition of Rho-kinase attenuates hypoxia-induced angiogenesis in the pulmonary circulation

Pulmonary hypertension (PH) is a common complication of chronic hypoxic lung diseases, which increase morbidity and mortality. Hypoxic PH has previously been attributed to structural changes in the pulmonary vasculature including narrowing of the vascular lumen and loss of vessels, which produce a fixed increase in resistance. Using quantitative stereology, we now show that chronic hypoxia caused PH and remodeling of the blood vessel walls in rats but that this remodeling did not lead to structural narrowing of the vascular lumen. Sustained inhibition of the RhoA/Rho-kinase pathway throughout the period of hypoxic exposure attenuated PH and prevented remodeling in intra-acinar vessels without enlarging the structurally determined lumen diameter. In chronically hypoxic lungs, acute Rho kinase inhibition markedly decreased PVR but did not alter the alveolar to arterial oxygen gap. In addition to increased vascular resistance, chronic hypoxia induced Rho kinase-dependent capillary angiogenesis. Thus, hypoxic PH was not caused by fixed structural changes in the vasculature but by sustained vasoconstriction, which was largely Rho kinase dependent. Importantly, this vasoconstriction had no role in ventilation-perfusion matching and optimization of gas exchange. Rho kinase also mediated hypoxia-induced capillary angiogenesis, a previously unrecognized but potentially important adaptive response.     

Swine Model of Chronic Postcapillary Pulmonary Hypertension with Right Ventricular Remodeling: Long-Term Characterization by Cardiac Catheterization,Magnetic Resonance,and Pathology

Pulmonary hypertension (PH) is prevalent and carries high morbidity and mortality, mostly due to right ventricular (RV) dysfunction. Postcapillary PH is the most frequent form but there are no large-animal models available. We developed and characterized a porcine model of postcapillary PH by non-restrictive banding of the confluent of both inferior pulmonary veins (n?=?10; sham controls n?=?3). Right heart catheterization and magnetic resonance were performed before the procedure and monthly during 4 months. All banded animals developed PH. Compared to controls, banded animals presented higher mean pulmonary artery pressure [median (first to third quartile) 30 mmHg (25–37) vs. 20 mmHg (18–23); p?=?0.018] and higher pulmonary vascular resistance [5.2 WU (3.8–7.1) vs. 2.3 WU (2.1–3.5); p?=?0.028] after 2 months. Differences in indexed RV end-systolic volume [42 mL/m² (36–53) vs. 24 mL/m² (24–33); p?=?0.028] and RV ejection fraction [59 % (54–63) vs. 66 % (64–68); p?=?0.028] were also significant after 2 months. Differences remained significant throughout the study. Histopathology revealed increased lung weight and fibrosis but no increase in average water content. Also, remodeling on pulmonary arteries including increased medial and intimal thickness and fibrosis and RV myocardial disarray and fibrosis was demonstrated. Lung remodeling findings were similar in all pulmonary lobes.     

Notch信号通路与肺动脉高压

肺动脉高压( pulmonary hypertension,PH)时,参与肺血管重塑的内皮细胞、平滑肌细胞等存在不同程度的Notch家族基因表达上调.Notch信号转导通路在肺血管形成,血管平滑肌细胞及内皮细胞等增殖、分化、凋亡方面起重要调控作用.Notch信号转导通路参与PH形成和发展.这为PH的治疗提供了前景广阔的...     

Quantitative assessment of right ventricular geometric remodeling in pulmonary hypertension secondary to left-sided heart disease using real-time three-dimensional echocardiography

We assessed right ventricular (RV) geometric remodeling quantitatively in patients with chronic pulmonary hypertension (PH) secondary to left-sided heart disease using real-time 3-dimensional echocardiography by comparing segmental and total volumes to that in normal subjects. The comparison result revealed that RV geometric remodeling in the PH group mainly occurred at the basal, mid-basal, and mid-segments. Total RV end-diastolic and end-systolic volumes in the PH group were significantly larger than that in normal subjects.     

重叠综合征相关性肺动脉高压研究进展

阻塞性睡眠呼吸暂停综合征(obstructive sleep apnea syndrome,OSAS)和 COPD 是常见的呼吸系统疾病,二者并存率很高,称为重叠综合征(overlap syndrome, OS),肺动脉高压(pulmonary hypertension,PH)是两者的常见并发症。COPD 患者伴口咽部为主的上呼吸道阻塞可导致 OSAS 的发生,COPD 相关的 PH 多为香烟烟雾、炎症产物引起内皮损害,致内皮功能失调,慢性低氧导致血管收缩,肺血管重塑导致管腔变小,血管阻力增加,重度肺气肿时肺毛细血管的丧失都与COPD 时的 PH 相关。而 OSAS 主要为间歇性低氧(intermittent hypoxia,IH)状态导致 PH,很多研究显示持续性低氧与 IH 状态可导致 PH,而 OS 与单纯 COPD 或 OSAS 相比,其夜间低氧及高碳酸血症更严重,更易发生 PH,增加病死率。本文将就 OS 导致 PH 的可能发病机制作一综述。     

Right ventricular remodeling in pulmonary hypertension

The right ventricle (RV) is in charge of pumping blood to the lungs for oxygenation. Pulmonary arterial hypertension (PAH) is characterized by high pulmonary vascular resistance and vascular remodeling, which results in a striking increase in RV afterload and subsequent failure. There is still unexploited potential for therapies that directly target the RV with the aim of supporting and protecting the right side of the heart, striving to prolong survival in patients with PAH.     

Hematological disorders and pulmonary hypertension

Pulmonary hypertension(PH),a serious disorder with a high morbidity and mortality rate,is known to occur in a number of unrelated systemic diseases.Several hematological disorders such as sickle cell disease,thalassemia and myeloproliferative diseases develop PH which worsens the prognosis.Associated oxidant injury and vascular inflammation cause endothelial damage and dysfunction.Pulmonary vascular endothelial damage/dysfunction is an early event in PH resulting in the loss of vascular reactivity,activation of proliferative and antiapoptotic pathways leading to vascular remodeling,elevated pulmonary artery pressure,right ventricular hypertrophy and premature death.Hemolysis observed in hematological disorders leads to free hemoglobin which rapidly scavenges nitric oxide(NO),limiting its bioavailability,and leading to endothelial dysfunction.In addition,hemolysis releases arginase into the circulation which converts L-arginine to ornithine,thus bypassing NO production.Furthermore,treatments for hematological disorders such as immunosuppressive therapy,splenectomy,bone marrow transplantation,and radiation have been shown to contribute to the development of PH.Recent studies have shown deregulated iron homeostasis in patients with cardiopulmonary diseases including pulmonary arterial hypertension(PAH).Several studies have reported low iron levels in patients with idiopathic PAH,and iron deficiency is an important risk factor.This article reviews PH associated with hematological disorders and its mechanism:and iron homeostasis and its relevance to PH.     

Intermedin modulates hypoxic pulmonary vascular remodeling by inhibiting pulmonary artery smooth muscle cell proliferation

BackgroundHypoxic pulmonary arterial hypertension (PAH) is a disabling disease with limited treatment options. Hypoxic pulmonary vascular remodeling is a major cause of hypoxic PAH. Pharmacological agents that can inhibit the remodeling process may have great therapeutic value.ObjectiveTo examine the effect of intermedin (IMD), a new calcitonin gene-related peptide family of peptide, on hypoxic pulmonary vascular remodeling.MethodsRats were exposed to normoxia or hypoxia (∼10% O₂), or exposed to hypoxia and treated with IMD, administered by an implanted mini-osmotic pump (6.5 μg/rat/day), for 4 weeks. The effects of IMD infusion on the development of hypoxic PAH and right ventricle (RV) hypertrophy, on pulmonary vascular remodeling, on pulmonary artery smooth muscle cell (PASMC) proliferation and apoptosis, and on the activations of l-arginine nitric oxide (NO) pathway and endoplasmic reticulum stress apoptotic pathway were examined.ResultsRats exposed to hypoxia developed PAH and RV hypertrophy. IMD treatment alleviated PAH and prevented RV hypertrophy. IMD inhibited hypoxic pulmonary vascular remodeling as indicated by reduced wall thickness and increased lumen diameter of pulmonary arterioles, and decreased muscularization of distal pulmonary vasculature in hypoxia-exposed rats. IMD treatment inhibited PASMC proliferation and promoted PASMC apoptosis. IMD treatment increased tissue level of constitutive NO synthase activity and tissue NO content in lungs, and enhanced l-arginine uptake into pulmonary vascular tissues. IMD treatment increased cellular levels of glucose-regulated protein (GRP) 78 and GRP94, two major markers of endoplasmic reticulum (ER) stress, and increased caspase-12 expression, the ER stress-specific caspase, in lungs and cultured PASMCs.ConclusionsThese results demonstrate that IMD treatment attenuates hypoxic pulmonary vascular remodeling, and thereby hypoxic PAH mainly by inhibiting PASMC proliferation. Promotion of PASMC apoptosis may also contribute to the inhibitory effect of IMD. Activations l-arginine–NO pathway and of ER stress-specific apoptosis pathway could be the mechanisms mediating the anti-proliferative and pro-apoptotic effects of IMD.     

慢性阻塞性肺疾病合并肺动脉高压的发病机制研究进展

肺动脉高压(pulmonary hypertension,PH)是慢性阻塞性肺疾病(chronic obstructivepulmonary disease,COPD)的一个重要合并症.COPD合并PH是逐渐发生和进展的,最初于运动或睡眠时出现,逐渐发展为休息时即存在PH,运动、睡眠或病情恶化时进一步升高.COPD相关的PH多为轻到中度,但某些COPD患者可表现为"不成比例"的PH.香烟烟雾、炎症产物引起内皮损害,造成内皮功能失调;慢性低氧引起肺血管收缩;肺血管重构导致管腔变小,血管膨胀性降低,阻力增加;重度肺气肿时肺毛细血管的丧失等均与COPD时的PH相关.     

Long-term effects of epoprostenol on the pulmonary vasculature in idiopathic pulmonary arterial hypertension

The current treatment of pulmonary arterial hypertension (PAH) uses vasodilator drugs. Although they improve symptoms associated with PAH, their chronic effects on the pulmonary vasculature and the right ventricle (RV) in humans remain unknown. We report the autopsy findings from a patient with idiopathic PAH treated with epoprostenol successfully for 18 years. The patient died of colon cancer. The pulmonary vasculature surprisingly showed extensive changes of a proliferative vasculopathy. Immunohistochemical studies confirmed ongoing cellular proliferation. Studies of the RV demonstrated concentric hypertrophy with seemingly preserved contractility. The myocardium shifted to glycolytic metabolism. Although the long-term use of epoprostenol contributed to the patient's increased survival, it did not prevent progression of the underlying vascular disease. Remarkably, the RV was able to sustain a normal cardiac output in the face of advanced vascular pathology. The mechanisms by which the RV adapts to chronic PAH need further study.