Low-molecular-weight heparin inhibits hypoxic pulmonary hypertension and vascular remodeling in guinea pigs

RATIONALE: We have shown previously that antiproliferative unfractionated heparins block hypoxia-induced pulmonary arterial hypertension (PAH) and vascular remodeling, and hypothesized that low-molecular-weight heparins (LMWHs) would too. OBJECTIVES: To determine the potential role and mechanisms of dalteparin and enoxaparin (two LMWHs) in inhibiting hypoxic PAH and vascular remodeling. METHODS: Male Hartley guinea pigs were exposed for 10 days to normobaric 10% oxygen with dalteparin (5 mg/kg), enoxaparin (5 mg/kg), or with an equivalent volume of normal saline solution. Normoxic control animals (n = 5) received room air for 10 days. Bovine pulmonary artery smooth-muscle cells (PASMCs) were grown in 10% fetal bovine serum without heparin, with dalteparin (1 microg/mL) or with enoxaparin (1 microg/mL). MEASUREMENTS: Pulmonary arterial pressure (PAP), cardiac index, right ventricular heart weight divided by left ventricular plus septum weight (RV/LV+S), hematocrit, percentage of wall thickness of intraacinar vessels (%WT-IA), percentage of wall thickness of terminal bronchiole vessels (%WT-TA), and the percentage of thick-walled vessels (%Thick) were determined. In PASMCs, expression of p27 and cell growth were compared because in mice whole heparin depends on p27 for its antiproliferative action. MAIN RESULTS: In hypoxic animals, hematocrit, PAP, total pulmonary vascular resistance index, RV/LV+S, %WT-IA, %WT-TA, and %Thick all rose significantly vs normoxic control animals (p < 0.05); cardiac index was unchanged. Dalteparin but not enoxaparin significantly reduced PAP, total pulmonary vascular resistance index, and RV/LV + S (p < 0.05 vs hypoxia alone); inhibited PASMC growth; and upregulated p27 expression. Enoxaparin moderately reduced vascular remodeling, which did not translate into less pulmonary hypertension. CONCLUSIONS: Not all LMWHs are the same. Dalteparin was more effective than enoxaparin in inhibiting pulmonary hypertension and vascular remodeling in hypoxic guinea pigs.     

肺血管重塑与低氧性肺动脉高压

肺血管重塑和肺动脉高压密切相关,慢性缺氧是肺血管重塑和肺动脉高压的一个常见原因.肺血管重塑以纤维母细胞、平滑肌细胞和内皮细胞增殖为最大特征,并导致管腔闭塞.了解肺血管重塑特征和机制对于预防或者逆转肺动脉高压具有重要的意义.     

安立生坦与波生坦对低氧性肺动脉高压大鼠肺血管重构的比较研究

目的:比较安立生坦和波生坦对低氧性肺动脉高压(hypoxic pulmonary hypertension,HPH)大鼠肺血管重构治疗效果的比较。方法:40只SD大鼠随机分成5组:对照组、模型组、波生坦组、安立生坦组和安慰剂组,每组8只。对照组于自然环境中饲养4周,其他组置于低压低氧舱中低氧(8 h/d)饲养4周。从低氧开始第3周起,安立生坦组、波生坦组和安慰剂组大鼠每天进舱前依次分别给予安立生坦(5 mg/kg)、波生坦组(125 mg/kg)和生理盐水(2 ml)灌胃,共两周。实验结束后,测定所有大鼠平均肺动脉压力(mPAP)、右心室收缩末压(RVSP)和右心室压力最大上升速率(dP/dtmax)。各组大鼠肺组织以HE染色后,观察中小动脉形态的变化。应用图像分析系统检测管壁厚度占外径的百分比[WT(%)]和管壁面积占总面积的百分比[WA(%)]。应用免疫组化染色法检测肺血管平滑肌肌动蛋白(α-SMA)的表达。结果:HE染色切片显示,模型组和安慰剂组大鼠的肺小动脉管壁增厚、管腔狭窄,安立生坦组和波生坦组可基本恢复至对照组状态。与对照组相比,模型组和安慰剂组mPAP、WT(%)、WA(%)和α-SMA蛋白的表达均显著升高(P<0.05),安立生坦组和波生坦组上述各项指标差异均无统计学意义。结论:安立生坦与波生坦均能显著降低HPH大鼠的肺动脉压力,逆转肺血管重构。安立生坦组与波生坦组的治疗效果无统计学差异。     

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.     

Inhaled iloprost reverses vascular remodeling in chronic experimental pulmonary hypertension

RATIONALE: Inhaled iloprost is an effective therapy for pulmonary arterial hypertension (PAH). However, no study to date has addressed the effects of inhaled iloprost on changes to pulmonary vascular structure that occur in PAH. OBJECTIVES: The present study was designed to investigate chronic antiremodeling effects of inhaled iloprost in monocrotaline (MCT)-induced PAH in rats. Methods: Four weeks after a single injection of MCT, after full establishment of PAH, rats were nebulized with iloprost at a dose of 6 microg . kg(-1) . day(-1), or underwent sham nebulization with saline. RESULTS: After 2 weeks of inhalation therapy, right ventricular pressure and pulmonary vascular resistance were reversed in rats treated with iloprost, but not in sham-treated control animals. Systemic arterial pressure was unaffected. In addition, right heart hypertrophy, the degree of pulmonary artery muscularization, and the medial wall thickness of intraacinar pulmonary arteries regressed in response to iloprost. Furthermore, the MCT-induced increase in matrix metalloproteinase-2 and -9 activities and tenascin-C expression was suppressed. CONCLUSIONS: We conclude that the inhalation of iloprost reverses PAH and vascular structural remodeling in MCT-treated rats. This regimen suggests the possibility of an antiremodeling therapy in PAH.     

Impairment of hypoxic pulmonary artery remodeling by heparin in mice

Chronic hypoxia produces pulmonary artery hypertension and remodeling of pulmonary arteries with hypertrophy of smooth muscle in the media and extension of smooth muscle into more distal small precapillary arteries. The present study investigated the influence of heparin, an inhibitor of platelet-derived growth factor, and of the clotting cascade on this remodeling. Mice maintained in room air or 10% O2 for 26 days were treated with low-dose heparin at 75 units/kg or high dose heparin at 300 units/kg. Pulmonary hypertension and right ventricular hypertrophy developed in the hypoxic mice compared with the room air mice as evidenced by the greater (p less than 0.05) right ventricular systolic pressure (36 +/- 4 SEM versus 21 +/- 1 mmHg) and the increase (p less than 0.05) in right heart weight/left ventricular plus septal weight (35 +/- 1.6 SEM versus 25.2 +/- 1.3). Hypoxia also induced smooth muscle hypertrophy in small pulmonary arteries, with an increase (p less than 0.05) in the percent media thickness/vascular diameter from 5.7 +/- 1 SEM to 13.3 +/- 3 and an apparent decrease (p less than 0.05) in distal small pulmonary arteries from 4.4 +/- 0.2 SEM to 2.05 +/- 0.1 per 100 alveoli. High-dose heparin partially but significantly (p less than 0.05) prevented the pulmonary artery hypertension (right ventricular systolic pressure of 28 +/- 2 mmHg), the right ventricular hypertrophy (right ventricular weight/left ventricular plus septal weight of 30.1 +/- 1) and remodeling of distal small pulmonary arteries (media thickness/vascular diameter of 8.4 +/- 1%, small pulmonary artery/100 alveoli of 3.63 +/- 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulmonary vascular remodeling in pulmonary hypertension due to chronic heart failure

Pulmonary hypertension (PHT) associated with chronic heart failure (CHF) is a risk factor of right ventricular failure after heart transplantation (HT). Our aim was to study pulmonary vascular changes in patients with CHF and to assess any correlation with haemodynamic data. METHODS: We studied 17 HT recipients with preoperative CHF who died shortly after HT. Preoperative haemodynamic information was obtained immediately before HT. Vascular lesions in muscular arteries were assessed by linear morphometry. Haemodynamic data were correlated with the morphologic changes. RESULTS: Mean transpulmonary gradient (TPG) was 8.9+/-4.5 mm Hg and pulmonary vascular resistance (PVR) was 2.25+/-1.34 Wu. According to the threshold for at-risk PHT (TPG>12 mm Hg or PVR>2.5 Wu), six patients had at-risk PHT. Medial thickness was 23.82+/-7.23% in patients with at-risk PHT and 17.16+/-3.24% in patients without at-risk PHT (p=0.018). CONCLUSIONS: Medial hypertrophy of muscular pulmonary arteries is more common and severe than expected in patients with CHF, even in patients without at-risk PHT. This structural change could explain why PHT, even in range of values not excluding HT, is a risk factor for right ventricular failure after HT and influences post-HT haemodynamic behaviour.     

成纤维细胞活化在低氧性肺血管重构中的作用

以往在低氧性肺血管重构机制的研究中,外膜的作用往往被忽略。新近的研究表明,血管外膜特别是其中的成纤维细胞在调节血管功能中发挥着重要的作用。外膜中的成纤维细胞是低氧刺激的首要“损伤感受细胞”,低氧可以激活血管外膜成纤维细胞,活化的成纤维细胞既可以合成分泌细胞生长因子、炎症因子,进而促进中膜血管平滑肌细胞增殖,又可以转分化为平滑肌样细胞（肌纤维母细胞）、分泌胶原蛋白,导致血管重构。因此,低氧导致的成纤维细胞活化及表型转换在肺血管重构中起重要作用,贯穿着低氧性肺血管重构的整个病理过程。     

Key role of 15-lipoxygenase/15-hydroxyeicosatetraenoic acid in pulmonary vascular remodeling and vascular angiogenesis associated with hypoxic pulmonary hypertension

We have found that 15-hydroxyeicosatetraenoic acid (15-HETE) induced by hypoxia was an important mediator in the regulation of hypoxic pulmonary hypertension, including the pulmonary vasoconstriction and remodeling. However, the underlying mechanisms of the remodeling induced by 15-HETE are poorly understood. In this study, we performed immunohistochemistry, pulmonary artery endothelial cells migration and tube formation, pulmonary artery smooth muscle cells bromodeoxyuridine incorporation, and cell cycle analysis to determine the role of 15-HETE in hypoxia-induced pulmonary vascular remodeling. We found that hypoxia induced pulmonary vascular medial hypertrophy and intimal endothelial cells migration and angiogenesis, which were mediated by 15-HETE. Moreover, 15-HETE regulated the cell cycle progression and made more smooth muscle cells from the G(0)/G(1) phase to the G(2)/M+S phase and enhanced the microtubule formation in cell nucleus. In addition, we found that the Rho-kinase pathway was involved in 15-HETE-induced endothelial cells tube formation and migration and smooth muscle cell proliferation. Together, these results show that 15-HETE mediates hypoxia-induced pulmonary vascular remodeling and stimulates angiogenesis via the Rho-kinase pathway.     

Pulmonary vascular remodeling is prior to the increase in pulmonary hypertension of chronic obstructive pulmonary disease

正Objective To explore the remodeling of pulmonary arterioles in chronic obstructive pulmonary disease(COPD), and its effect on hemorheology of proximal pulmonary arteries, right ventricular structure and function, and the potential mechanisms.Methods A total of34 patients undergoing surgical treatment for lung tumors     

Partial reversal of hypoxic pulmonary hypertension by heparin.

Chronic hypoxia produces pulmonary hypertension and an increase in medial thickness of pulmonary arteries that reach maximal values after 10 days of hypoxia. We previously showed that heparin given during the first 10 days of hypoxia reduced the development of both pulmonary hypertension and vascular remodeling in the guinea pig. To determine if heparin could reverse established hypoxic pulmonary hypertension and vascular remodeling, we administered heparin by continuous subcutaneous infusion (20 U/kg/h) for the last 7 days of a 21-day exposure to hypoxia (10% O2, balance N2) and compared these animals with normal saline-infused hypoxic control and room air-exposed animals. Hypoxia increased pulmonary artery pressure from 11 +/- 1 mm Hg (mean +/- SEM) in room air animals to 20 +/- 2 mm Hg (p less than 0.05) in saline-treated hypoxic control animals. Heparin reduced pulmonary artery pressure to 16 +/- 1 mm Hg (p less than 0.05 versus hypoxic control and room air control animals). Total pulmonary resistance (TPR) increased with hypoxia from 0.043 +/- 0.003 mm Hg x min x kg-1 x ml-1 in room air to 0.090 +/- 0.004 in hypoxia (p less than 0.05), and in the rise in TPR was also partially reversed by heparin to 0.068 +/- 0.0003 (p less than 0.05). The percentage of medial thickness of alveolar duct arteries increased from 5.8 +/- 0.6% in room air to 9.5 +/- 0.1% (p less than 0.05) after 3 wk of hypoxia, and heparin therapy partially reversed the increase in medial thickness to 7.2 +/- 0.7% (p less than 0.05 versus both hypoxia control and room air).(ABSTRACT TRUNCATED AT 250 WORDS)     

血管重构在动脉型肺动脉高压中的研究进展

动脉型肺动脉高压（PAH）是以肺动脉压力持续升高、肺小动脉结构持续改变为特征的致命性疾病,肺动脉重构是其主要的病理学特点。许多研究发现PAH中血管重构的病理机制主要包括各种细胞的病理学改变和多种分子信号通路的参与,最新的研究指出表观遗传学也参与血管重构,从而导致疾病的发生发展。目前针对PAH发病机制的各种新型药物及新疗法正在被开发,其副作用更小、疗效更佳。本文重点阐述PAH中血管重构的病理机制包括病理学改变、新分子信号通路及表观遗传学内容,以及治疗的新进展。     

Molecular and cellular basis of pulmonary vascular remodeling in pulmonary hypertension

Clinical pulmonary hypertension is characterized by a sustained elevation in pulmonary arterial pressure. Pulmonary vascular remodeling involves structural changes in the normal architecture of the walls of pulmonary arteries. The process of vascular remodeling can occur as a primary response to injury, or stimulus such as hypoxia, within the resistance vessels of the lung. Alternatively, the changes seen in more proximal vessels may arise secondary to a sustained increase in intravascular pressure. To withstand the chronic increase in intraluminal pressure, the vessel wall becomes thickened and stronger. This "armouring" of the vessel wall with extra-smooth muscle and extracellular matrix leads to a decrease in lumen diameter and reduced capacity for vasodilatation. This maladaptive response results in increased pulmonary vascular resistance and consequently, sustained pulmonary hypertension. The process of pulmonary vascular remodeling involves all layers of the vessel wall and is complicated by the finding that cellular heterogeneity exists within the traditional compartments of the vascular wall: intima, media, and adventitia. In addition, the developmental stage of the organism greatly modifies the response of the pulmonary circulation to injury. This review focuses on the latest advances in our knowledge of these processes as they relate to specific forms of pulmonary hypertension and particularly in the light of recent genetic studies that have identified specific pathways involved in the pathogenesis of severe pulmonary hypertension.     

Alteration of pulmonary vascular resistance and pulmonary cyclic nucleotide metabolism in the hypoxic pig

Summary Hypoxia leads to an elevation of the pulmonary vascular resistance (pvR) in pigs. This alteration of the hemodynamic was accompanied by a slight increase of intraparenchymatous concentrations of cyclic GMP (cGMP) while cycle AMP (cAMP) levels were not different from values, measured during normoxia. -adrenergic agents are potent inhibitors of the hypoxia induced vasoconstriction. This effect was associated with an increase of intraparenchymatous cAMP-concentrations and a decrease of cGMP-levels. The regression analysis between pvR versus the ratio cGMP/cAMP revealed a significant linears correlation. These data may indicate, that cAMP and cGMP are involved in hypoxia induced vasoconstriction and its pharmacological inhibition.

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Veränderungen des pulmonal-vaskulären Widerstandes und Metabolismus der cyclischen Nukleotide beim hypoxischen Schwein

Zusammenfassung Hypoxie führt beim Schwein zur Erhöhung des pulmonal-vaskulären Widerstandes (pvR). Diese hämodynamische Veränderung ist von einem Anstieg des intraparenchymatösen Spiegels von cyclischem GMP (cGMP) begleitet, während die Konzentrationen des cyclischen AMP (cAMP) im Vergleich zu Werten unter Normoxie unverändert sind. -Sympathikomimetika sind potente Inhibitoren dieser hypoxie-induzierten Vasokonstriktion. Dieser Effekt ist mit einem Anstieg des intraparenchymatösen Spiegels von cAMP und einem Abfall des cGMP-Spiegels assoziiert. Die Regressionsanalyse zwischen dem pvR und dem Quotienten cGMP/cAMP erbrachte eine signifikante lineare Korrelation. Dieses läßt vermuten, daß cAMP und cGMP bei der hypoxie-induzierten pulmonalen Visokonstriktion und deren Aufhebung durch -Sympathikomimetika kausal beteiligt sind.

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Mit 3 figures and 2 tables     

Tissue remodeling of rat pulmonary arteries in recovery from hypoxic hypertension

The reversibility of tissue remodeling is of general interest to medicine. Pulmonary arterial tissue remodeling during hypertension induced by hypoxic breathing is well known, but little has been said about the recovery of the arterial wall when the blood pressure is lowered again. We hypothesize that tissue recovery is a function of the oxygen concentration, blood pressure, location on the vascular tree, and time. We measured the changes of blood pressure, vessel lumen, vessel wall thicknesses, and opening angle of each segment of the blood vessel at its zero-stress state after step changes of the oxygen concentration in the breathing gas. The zero-stress state of each vessel is emphasized because it is important to the analysis of stress and strain and in morphometry. Experimental results are presented as histories of tissue parameters after step changes of the oxygen level. Tissue characteristics are examined under the hypothesis that they are linearly related to changes in the local blood pressure. Under this linearity hypothesis, each aspect of the tissue change can be expressed as a convolution integral of the blood pressure history with a kernel called the indicial response function. It is shown the indicial response function for rising blood pressure is different from that for falling blood pressure. This difference represents a major nonlinearity of the tissue remodeling process of the blood vessels.     

大鼠慢性栓塞性肺动脉高压模型的建立和肺血管重构的研究

目的探讨妥善建立大鼠栓塞性肺动脉高压模型的方法,研究肺血管重构和右心室的改变。方法雄性Wistar大鼠141只,随机分为12组,采血加入凝血酶200 U/ml,体外制备栓子,经颈静脉注入栓子,制备肺栓塞模型,2周后同法进行二次栓塞,全程腹腔注射纤溶抑制剂氨甲环酸,达目标时间后用右心导管法测平均肺动脉压（mPAP）;开胸取肺组织,HE染色及弹力纤维染色,观察肺组织和肺血管结构的变化;用病理图像分析软件测定肺动脉相对中膜厚度（PAMT）和管壁面积/管总面积（WA/TA）;取心脏组织测定右心室游离壁（RV）和左心室加室间隔（LV＋S）的重量比即右心室肥大指数（RVHI）。结果①动物模型成功率85.1%（120/141）;②4周组至12周组肺动脉压明显升高（P均〈0.01）,8周后RVHI较对照组明显增高（8周组P〈0.05;12周组P〈0.01）;③8周和12周组肺小动脉结构出现明显变化：中膜平滑肌细胞明显增生,PAMT和WA/TA值明显增大（P均〈0.01）,管壁增厚,管腔狭窄,肺动脉有显著重构;④mPAP、RVHI与PAMT有明显相关性（r分别为0.681和0.690,P均〈0.01）;mPAP、RVHI与WA/TA有明显相关性（r分别为0.677和0.794,P均〈0.01）。结论用二次栓塞并应用氨甲环酸抑制纤溶,成功制备了大鼠栓塞性肺动脉高压模型;模型组大鼠出现明显肺动脉重构,继之出现右心室重构;栓塞时间越长肺动脉高压越明显;肺动脉重构与肺动脉高压之间有显著相关关系。     

Capsaicin pretreatment attenuates chronic hypoxic pulmonary hypertension

Capsaicin pretreatment was used to deplete tachykinins in order to study the role of tachykinins in chronic hypoxia-induced pulmonary hypertension. Forty three young Wistar rats weighing 235 ± 4 g were randomly divided into four groups: control (n = 10); capsaicin pretreatment (n = 10); intermittent chronic hypoxia (n = 10); and capsaicin pretreatment + intermittent chronic hypoxia (n = 13). Control animals breathed room air. Rats in the capsaicin pretreatment groups were given capsaicin via subcutaneous injection over a three-day period. Hypobaric hypoxia was intermittently applied by placing animals into a hypobaric chamber with a barometric pressure of 380 Torr for two weeks. In the capsaicin pretreatment + intermittent chronic hypoxia group, rats were exposed to intermittent hypoxia for two weeks immediately after the last dose of capsaicin. Subsequently, pulmonary vascular function, as well as substance P (a tachykinin) level and neutral endopeptidase (NEP, the major degradation enzyme for tachykinins) activity in the lungs were measured. Chronic hypoxia caused significant increases in pulmonary artery pressure, right ventricle/(left ventricle + septum) weight ratio, hematocrit, and lung substance P level, as well as a significant decrease in lung NEP activity. All these chronic hypoxia-induced changes were significantly lessened by capsaicin pretreatment. Capsaicin pretreatment alone did not induce any significant alteration in vascular function. These results suggest that the chronic hypoxia causes an increase in lung tachykinin levels which, in turn, enhance the development of pulmonary hypertension.