Genistein, a phytoestrogen, attenuates monocrotaline-induced pulmonary hypertension

BACKGROUND: Pulmonary hypertension is characterized by high pulmonary blood pressure, vascular remodeling, and right ventricular hypertrophy. Although recent studies suggest that an imbalance between endothelial mediators on pulmonary vasculature may contribute to the development of pulmonary hypertension, the pathogenesis is not fully understood and the treatment of pulmonary hypertension is still unresolved. OBJECTIVE: The purpose of this study was to investigate whether genistein, a phytoestrogen derived from soybean, would prevent the development of monocrotaline (MCT)-induced pulmonary hypertension in rats. Hemodynamic parameters of catheterized rats and morphological feature of lungs were evaluated among MCT-treated rats receiving or not receiving genistein. Furthermore, examination of expression in endothelial nitric oxide synthase and endothelin-1 peptide level was performed. METHODS: Daily supplementation with either genistein (0.2 mg/kg) or vehicle was started 2 days prior to a single-dose injection of MCT (60 mg/kg). On day 28, rats underwent catheterization, and right ventricular hypertrophy and morphological features were assessed. Furthermore, endothelial nitric oxide synthase and endothelin-1 were examined by Western blot analysis and radioimmunoassay, respectively, in homogenated lungs. RESULTS: In rats that received daily supplementation of genistein, mean pulmonary arterial pressure was significantly reduced, whereas mean systemic arterial pressure and heart rate were unaltered compared with MCT control rats on day 28 after MCT injection. Right ventricular hypertrophy, medial wall thickness of pulmonary arteries corresponding to the terminal bronchioles, and the degree of neo-muscularization of more distal arteries were less severe in genistein-treated rats. Genistein supplementation improved MCT-induced downregulation of expression of endothelial nitric oxide synthase in the lungs. However, endothelin-1 peptide levels did not differ among all groups of lungs. CONCLUSIONS: We conclude that daily supplementation of genistein potently attenuates MCT-induced pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular remodeling in rats. The underlying mechanism responsible for this effect may be partly related to the restoration of a decreased expression of endothelial nitric oxide synthase.     

Myocardial and anti-inflammatory effects of chronic bosentan therapy in monocrotaline-induced pulmonary hypertension

Introduction and ObjectivesEndothelin-1 antagonists are increasingly used in the treatment of pulmonary hypertension despite the lack of knowledge of their myocardial and systemic effects. We assessed the right ventricular myocardial and systemic effects of endothelin-1 antagonists in monocrotaline-induced pulmonary hypertension.MethodsMale Wistar rats (180–200 g, n=57) randomly received 60 mg/kg monocrotaline or vehicle subcutaneously. Two days later, bosentan was randomly started (300 mg/kg/day) by oral route in a subgroup of monocrotaline-injected rats, while the other monocrotaline-injected and control rats received vehicle. At 25–30 days, invasive hemodynamic assessment was performed under anesthesia, arterial blood samples were collected for gas analysis and plasma was extracted for quantification of endothelin-1, cytokines, nitrates and 6-keto-prostaglandin F_1α. Right ventricular myocardium was collected for assessment of cyclooxygenase and nitric oxide synthase activity and gene expression.ResultsThe monocrotaline group developed pulmonary hypertension, low cardiac output, right ventricular hypertrophy and dilation, changes in gene expression and inflammatory activation that were attenuated in the group treated with bosentan. From a functional point of view, this group had improved right ventricular function and preserved ventriculo-vascular coupling, without deterioration in arterial gas parameters or systemic hypotension. In molecular terms, they showed reduced endothelin-1 and cytokine levels, decreased right ventricular inducible nitric oxide synthase and cyclooxygenase-2 activity and increased nitrate plasma levels compared with the non-treated group.ConclusionsIn this study we demonstrate that besides attenuating pulmonary hypertension, bosentan has beneficial hemodynamic, myocardial and anti-inflammatory effects.     

Simvastatin attenuates smooth muscle neointimal proliferation and pulmonary hypertension in rats

Hypertensive pulmonary vascular disease is characterized by abnormal proliferation of vascular endothelial and smooth muscle cells, leading to occlusion of pulmonary arterioles, pulmonary hypertension, right ventricular failure, and death. Compounds with antiproliferative effects on vascular endothelial and smooth muscle cells, such as 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, may prevent the development of experimental hypertensive pulmonary vascular disease. Pneumonectomized rats injected with monocrotaline at 7 days develop severe hypertensive pulmonary vascular disease with neointimal formation. Rats were randomized to receive either vehicle or treatment with the HMG-CoA reductase inhibitor simvastatin (2 mg/kg per day). By Day 35, rats that received vehicle had higher mean pulmonary arterial pressures (53 +/- 2 mm Hg) and right ventricular hypertrophy (right ventricle/[left ventricle plus septum] [RV/LV+S] = 0.78 +/- 0.09) than rats in Group PMS5-35 that received simvastatin from Day 5 to 35 (mean pulmonary arterial pressure = 27 +/- 3 mm Hg, RV/LV+S = 0.34 +/- 0.08; p < or = 0.001). Pulmonary vascular remodeling with neointimal formation consisting of vascular smooth muscle cells was more severe in vehicle-treated rats (vascular occlusion score, 1.98 +/- 0.02) than in Group PMS5-35 (vascular occlusion score, 0.59 +/- 0.46; p < 0.001). In addition, lung endothelial nitric oxide synthase gene expression was decreased in vehicle-treated animals but was restored toward normal levels in simvastatin-treated animals. Simvastatin attenuates monocrotaline-induced pulmonary vascular remodeling with neointimal formation, pulmonary arterial hypertension, and right ventricular hypertrophy in rats.     

Ghrelin ameliorates hypoxia-induced pulmonary hypertension via phospho-GSK3 β/β-catenin signaling in neonatal rats

Effective treatment and/or prevention strategies for neonatal persistent pulmonary hypertension of the newborn (PPHN) have been an important topic in neonatal medicine. However, mechanisms of impaired pulmonary vascular structure in hypoxia-induced PPHN are poorly understood and consequently limit the development of effective treatment. In this study, we aimed to explore the molecular signaling cascades in the lungs of a PPHN animal model and used primary cultured rat pulmonary microvascular endothelial cells to analyze the physiological benefits of ghrelin during the pathogenesis of PPHN. Randomly selected newborn rats were exposed to hypoxia (10-12%) or room air and received daily s.c. injections of ghrelin (150 μg/kg) or saline. After 2 weeks, pulmonary hemodynamics and morphometry were assessed in the rats. Compared with the control, hypoxia increased pulmonary arterial pressure, right ventricle (RV) hypertrophy, and arteriolar wall thickness. Ghrelin treatment reduced both the magnitude of PH and the RV/(left ventricle+septum (Sep)) weight ratio. Ghrelin protected neonatal rats from hypoxia-induced PH via the upregulation of phosphorylation of glycogen synthase kinase 3β (p-GSK3β)/β-catenin signaling and associated with β-catenin translocation to the nucleus in the presence of growth hormone secretagogue receptor-1a. Our findings suggest that s.c. administration of ghrelin improved PH and attenuated pulmonary vascular remodeling after PPHN. These beneficial effects may be mediated by the regulation of p-GSK3β/β-catenin expression. We propose ghrelin as a novel potential therapeutic agent for PPHN.     

Ghrelin reverses molecular, structural and hemodynamic alterations of the right ventricle in pulmonary hypertension.

Ghrelin is an endogenous peptide that has a dual effect by activating specific receptors and by stimulating release of growth hormone. There is increasing evidence that ghrelin has a potent vasodilator effect. Recently, we demonstrated that exogenous administration of ghrelin modulates its endogenous levels and attenuates the majority of alterations induced by monocrotaline (MCT). In the present study, we evaluate the effects of chronic administration of ghrelin on hemodynamic and morphometric parameters of the right ventricle, as well as on myocardial levels of SERCA2a and endothelin-1. Adult Wistar rats were injected with MCT (60 mg/kg, sc) or just the vehicle (day 0). One week later, the animals treated with MCT were randomly divided into two groups and treated with ghrelin (100 microg/kg, bid, sc) or with a similar volume of vehicle. Between days 21-25 the animals were instrumented to record right ventricular (RV) pressures and samples were collected for morphological and molecular analysis. Ghrelin treatment attenuated the effects of MCT, namely: RV myocyte fiber diameter, pulmonary vascular remodeling (evaluated by % medial wall thickness of peripheral arteries), RV peak systolic pressure, RV end-diastolic pressure, time constant tau, and SERCA2a and endothelin-1 mRNA levels. Chronic ghrelin administration attenuates MCT-induced pulmonary hypertension, vascular remodeling and RV hypertrophy. These results suggest a potential therapeutic role for the ghrelin-growth hormone axis in pulmonary hypertension.     

Effect of tryptophan hydroxylase 1 deficiency on the development of hypoxia-induced pulmonary hypertension

Tryptophan hydroxylase 1 catalyzes the rate-limiting step in the synthesis of serotonin in the periphery. Recently, it has been shown that expression of the tryptophan hydroxylase 1 gene is increased in lungs and pulmonary endothelial cells from patients with idiopathic pulmonary arterial hypertension. Here we investigated the effect of genetic deletion of tryptophan hydroxylase 1 on hypoxia-induced pulmonary arterial hypertension in mice by measuring pulmonary hemodynamics and pulmonary vascular remodeling before and after 2 weeks of hypoxia. In wild-type mice, hypoxia increased right ventricular pressure and pulmonary vascular remodeling. These effects of hypoxia were attenuated in the tryptophan hydroxylase 1-/-mice. Hypoxia increased right ventricular hypertrophy in both wild-type and tryptophan hydroxylase 1-/-mice suggesting that in vivo peripheral serotonin has a differential effect on the pulmonary vasculature and right ventricular hypertrophy. Contractile responses to serotonin were increased in pulmonary arteries from tryptophan hydroxylase 1-/-mice. Hypoxia increased serotonin-mediated contraction in vessels from the wild-type mice, but this was not further increased by hypoxia in the tryptophan hydroxylase 1-/-mice. In conclusion, these results indicate that tryptophan hydroxylase 1 and peripheral serotonin play an essential role in the development of hypoxia-induced elevations in pulmonary pressures and hypoxia-induced pulmonary vascular remodeling. In addition, the results suggest that, in mice, serotonin has differential effects on the pulmonary vasculature and right ventricular hypertrophy.     

Reduced hypoxic pulmonary vascular remodeling by nitric oxide from the endothelium

We examined whether overproduction of endogenous nitric oxide (NO) can prevent hypoxia-induced pulmonary hypertension and vascular remodeling by using endothelial NO-overexpressing (eNOS-Tg) mice. Male eNOS-Tg mice and their littermates (wild-type, WT) were maintained in normoxic or 10% hypoxic condition for 3 weeks. In normoxia, eNOS protein levels, Ca(2+)-dependent NOS activity, and cGMP levels in the lung of eNOS-Tg mice were higher than those of WT mice. Activity of eNOS and cGMP production in the lung did not change significantly by hypoxic exposure in either genotype. Chronic hypoxia did not induce iNOS expression nor increase its activity in either genotype. Plasma and lung endothelin-1 levels were increased by chronic hypoxia, but these levels were not significantly different between the 2 genotypes. In hemodynamic analysis, right ventricular systolic pressure (RVSP) in eNOS-Tg mice was similar to that in WT mice in normoxia. Chronic hypoxia increased RVSP and induced right ventricular hypertrophy in both genotypes; however, the degrees of these increases were significantly smaller in eNOS-Tg mice. Histological examination revealed that hypoxic mice showed medial wall thickening in pulmonary arteries. However, the increase of the wall thickening in small arteries (diameter <80 microm) by chronic hypoxia was inhibited in eNOS-Tg mice. Furthermore, muscularization of small arterioles was significantly attenuated in eNOS-Tg mice. Thus, we demonstrated directly that overproduction of eNOS-derived NO can inhibit not only the increase in RVSP associated with pulmonary hypertension but also remodeling of the pulmonary vasculature and right ventricular hypertrophy induced by chronic hypoxia.     

Attenuation of pulmonary vascular hypertension and cardiac hypertrophy with sitaxsentan sodium, an orally active ET(A) receptor antagonist

Effects of sitaxsentan (TBC11251), an orally active, highly selective antagonist of endothelin A receptors, were examined on the development and maintenance of pulmonary hypertension, pulmonary vascular remodeling, and cardiac hypertrophy in the rat. The pulmonary vasoconstrictor response to acute hypoxia (10% O(2)for 90 min) was prevented with sitaxsentan (5 mg/kg infused iv 10 min prior to the onset of hypoxia) while BQ-788 (a specific endothelin B receptor antagonist) was without effect. The same dose of sitaxsentan delivered iv 50 min after the onset of hypoxia reversed the established pulmonary vasoconstriction. In a 2-week model of hypoxia using 10% O(2), treatment with sitaxsentan (15 mg/kg per day in drinking water) attenuated pulmonary hypertension and the associated right ventricular hypertrophy, and prevented the remodeling of small pulmonary arteries (50-100 microM) without affecting systemic arterial blood pressure or heart rate. Institution of sitaxsentan treatment (15 and 30 mg/kg per day in drinking water) for 4 weeks after 2 weeks of untreated hypoxia produced a significant, dose dependent reversal of the established pulmonary hypertension, right heart hypertrophy, and pulmonary vascular remodeling despite continued hypoxic exposure. Sitaxsentan blocked increased plasma endothelin levels in the prevention protocol but did not affect the established elevated levels in the intervention study. Sitaxsentan dose dependently (10 and 50 mg/kg per day in the drinking water) attenuated right ventricular systolic pressure, right heart hypertrophy, and pulmonary vascular remodeling observed 3 weeks after a single subcutaneous injection of monocrotaline. These findings support the hypothesis that endothelin-1 plays a significant role in the development of pulmonary hypertension, pulmonary vascular remodeling, and the associated cardiac hypertrophy, and further suggest that specific endothelin-A receptor blockade may be useful in the treatment of pulmonary hypertension of diverse etiologies.     

YM155, a selective survivin inhibitor,reverses chronic hypoxic pulmonary hypertension in rats via upregulating voltage-gated potassium channels

Abstract

To test the hypothesis that chronic hypoxic pulmonary hypertension (CH-PH) is associated with increased survivin and decreased voltage-gated potassium (K_V) channels expression in pulmonary arteries, rats were randomized as: normoxia (N); normoxia?+?YM155, survivin suppressor (NY); hypoxia (H); hypoxia?+?YM155 (HY). HY group had significantly reduced pulmonary arterial pressure, right ventricular weight and right ventricular hypertrophy compared with H group. Survivin mRNA and protein were detected in pulmonary arteries of rats with CH-PH, but not rats without CH-PH. YM155 downregulated survivin protein and mRNA. K_V channel expression and activity were upregulated after YM155 treatment. Survivin may play a role in the pathogenesis of CH-PH.     

Effects of monocrotaline on endothelial nitric oxide synthase expression and sulfhydryl levels in rat lungs

The nitric oxide-cyclic guanosine monophosphate signal-transduction mechanism plays a key role in the regulation of vascular tone and structure. Monocrotaline-induced pulmonary hypertension is associated with low bioavailability of nitric oxide. To characterize the mechanism(s) involved in this dysfunction, rats received a single subcutaneous injection of monocrotaline, normal saline (control), or monocrotaline plus daily L-arginine, a precursor of nitric oxide, in drinking water. Pulmonary artery pressure and right ventricular hypertrophy were assessed 2 weeks later. In addition, the authors evaluated the expression of endothelial nitric oxide synthase messenger RNA, endothelial nitric oxide synthase protein, cyclic guanosine monophosphate, and sulfhydryl levels in the lungs. Sulfhydryls are needed for the dynamic modulation of soluble guanylate cyclase by nitric oxide, which results in cyclic guanosine monophosphate formation. L-arginine treatment did not attenuate monocrotaline-induced pulmonary hypertension or right ventricular hypertrophy. Monocrotaline did not alter the expression of endothelial nitric oxide synthase messenger RNA or endothelial nitric oxide synthase protein in the lungs. Protein-bound sulfhydryls (28 +/- 5 vs. 75 +/- 16 pmol/microg protein) and cyclic guanosine monophosphate (0.63 +/- 0.05 vs. 1.06 +/- 0.017 pmol/microg protein) levels in the monocrotaline group were significantly low compared with controls. The low sulfhydryl levels, an indicator of oxidant stress, may account for the impaired availability of bioactive nitric oxide and low cyclic guanosine monophosphate levels. These results suggest that oxidative stress may, in part, contribute to the pathogenesis of pulmonary hypertension in the monocrotaline model.     

CTRP9抑制低氧环境下肺微血管内皮细胞IL-6和TNF-α表达的研究

目的 研究低氧环境下C1q肿瘤坏死因子相关蛋白9（C1q/TNF-related protein 9,CTRP9）对肺微血管内皮细胞（Pulmonary microvascular endothelial cell,PMVEC）中白介素（IL）-6、肿瘤坏死因子（TNF）-α表达的影响。 方法 将雄性SD大鼠随机分为常氧组、低氧组,采用低压低氧法建立大鼠低氧性肺动脉高压（Hypoxic pulmonary hypertension,HPH）模型,28 d后检测各组大鼠血流动力学、右心室肥厚指标和组织病理学改变;用RT-PCR检测HPH大鼠肺组织中IL-6、TNF-α mRNA表达水平;用ELISA法检测二者在血清中的变化。分离培养健康雄性SD大鼠的PMVEC,分别在常氧（210 ml/L O₂、50 ml/L CO₂）、低氧（50 ml/L O₂、50 ml/L CO₂）、或者低氧+CTRP9（5 μg/ml）环境中孵育48 h。 结果 与常氧组相比,低氧组大鼠右心室收缩压和右心室肥厚指标增加（P<0.05）,肺小动脉管壁增厚,显示造模成功;肺组织中IL-6、TNF-α mRNA水平上调（P<0.05）,两种炎症因子在血清中的含量增加（P<0.05）。与常氧组相比,低氧处理使两种炎症因子IL-6、TNF-α在PMVEC中mRNA水平及在细胞培养上清中的含量均增加（P<0.05）;在低氧的同时给予CTRP9孵育时,与单纯低氧组相比,两种炎症因子在PMVEC中mRNA水平及在细胞培养上清中的含量均降低（P<0.05）。 结论 大鼠发生HPH时,炎症因子IL-6、TNF-α表达升高。而CTRP9对低氧条件下PMVEC表达和分泌IL-6及TNF-α具有抑制作用,进而有望预防或延缓HPH的发生发展。     

舒肺颗粒对大鼠低氧性肺动脉高压的影响

目的观察舒肺颗粒对大鼠低氧性肺动脉高压的影响。方法将30只雄性Wistar大鼠分为常压对照组、低氧对照组和低氧/中药给药组。以常压低氧复制肺动脉高压模型。观察右心室肥厚指数、肺小动脉管壁厚度的变化。结果低氧/中药给药组应用舒肺颗粒后大鼠肺血管厚度、右心室肥厚指标显著低于低氧对照组(P<0.05),并可抑制低氧所致的大鼠右心室肥厚(P<0.05)。结论舒肺颗粒在防治低氧性肺动脉高压中具有一定的应用前景。     

Dehydroepiandrosterone sulphate reduces chronic hypoxic pulmonary hypertension in rats.

Pathogenesis of pulmonary hypertension includes vascular smooth muscle cell membrane depolarisation and consequent calcium influx. Usually, calcium-gated potassium channels are activated under such conditions and repolarise the membrane. However, in pulmonary hypertension they are downregulated. The authors hypothesised that pharmacological augmentation of these channels would reduce pulmonary hypertension. Dehydroepiandrosterone sulphate (DHEA-S, 0.1 mg x mL(-1)), a recently characterised activator of calcium-gated potassium channels, was given to rats in drinking water. Pulmonary arterial blood pressure, increased by 4 weeks of hypoxia (from 15 +/- 0.2 to 29.4 +/- 2.5 mmHg), was selectively attenuated in rats treated with DHEA-S for the whole duration of the hypoxic exposure (23.9 +/- 0.9 mmHg) and in rats given DHEA-S only after pulmonary hypertension had fully developed (last 2 weeks of hypoxia; 24.4 +/- 1.4 mmHg). Pulmonary vascular remodelling and right ventricular hypertrophy associated with pulmonary hypertension were also reduced by DHEA-S. Cardiac index and systemic arterial blood pressure did not differ among the groups. The authors conclude that treatment with an activator of calcium-gated potassium channels, dehydroepiandrosterone sulphate, known to be well tolerated by humans, reduces hypoxic pulmonary hypertension in rats.     

瑞舒伐他汀干预野百合碱诱导大鼠肺动脉高压的实验研究

目的 探讨他汀类药物改善内皮细胞功能、抗增殖等降脂外作用在防治肺动脉高压中的作用及可能机制.方法 雄性SD大鼠,体重(255.7±12.5)g,皮下注射野百合碱诱导大鼠形成肺动脉高压,肺动脉高压形成前后分别接受瑞舒伐他汀预防和治疗.预防实验:32只SD大鼠随机分为4组,分别为瑞舒伐他汀低剂量(2 mg·kg-1·d-1)预防组(n=8)、瑞舒伐他汀高剂量(10 mg·kg-1·d-1)预防组(n=8)、肺动脉高压4周组(n=8)和正常对照4周组(n=8),野百合碱注射当日起预防组每日予瑞舒伐他汀灌胃至第4周末,正常对照组、肺动脉高压4周组仅予生理盐水灌胃.治疗实验:52只SD大鼠随机分为4组,分别为瑞舒伐他汀低剂量(2 mg·kg-1·d-1)治疗组(n=12)、瑞舒伐他汀高剂量(10 mg·kg-1·d-1)治疗组(n=12)、肺动脉高压8周组(n=20)和正常对照8周组(n=8),野百合碱注射4周后治疗组每日予瑞舒伐他汀灌胃至第8周末,正常对照组、肺动脉高压8周组仅予生理盐水灌胃.比较各组生存率、平均肺动脉压(mPAP)、肺小动脉管壁厚度、右心室肥厚程度,比较肺小动脉增殖细胞核抗原(PCNA)、内皮型一氧化氮合酶(eNOS)蛋白表达水平,比较肺组织Rho激酶1(ROCK-1)、eNOS mRNA表达水平.结果 预防实验大鼠均存活,肺动脉高压形成之后瑞舒伐他汀治疗能改善生存率(瑞舒伐他汀低剂量治疗组、瑞舒伐他汀高剂量治疗组与肺动脉高压8周组比较为58%、75%比30%,P均＜0.05);肺动脉高压形成之前和之后瑞舒伐他汀预防和治疗均能降低mPAP[预防实验:瑞舒伐他汀低剂量预防组、瑞舒伐他汀高剂量预防组与肺动脉高压4周组比较为(27.53±3.43)mm Hg(1 mm Hg=0.133 kPa)、(25.72±1.76)mm Hg比(36.05±2.45)mm Hg,P均＜0.01;治疗实验:瑞舒伐他汀低剂量治疗组、瑞舒伐他汀高剂量治疗组与肺动脉高压8周组比较为(30.39±3.17)mm Hg、(27.59±1.99)mmHg比(40.68±1.39)mm Hg,P均＜0.01],减轻肺小动脉管壁增厚、右心室肥厚程度(P均＜0.01),下调肺小动脉平滑肌细胞PCNA表达(P均＜0.01),上调内皮细胞eNOS表达(P均＜0.05),抑制ROCK-1基因表达(P均＜0.05),有一定的剂量依赖性(P均＜0.05).结论 瑞舒伐他汀防治肺动脉高压可能是通过抑制ROCK-1基因表达,抑制肺动脉平滑肌增殖和恢复内皮细胞功能等机制来实现的.

Abstract：

Objective To investigate the effects of rosuvastatin on monocrotaline (MCT)-induced pulmonary artery hypertension in rats. Methods Pulmonary arterial hypertension was induced by a single subcutaneous injection of monocrotaline (50 mg/kg) in rats. In the prevention protocol, 32 male SpragueDawley rats were randomly divided into four groups ( n = 8 each): low-dose rosuvastatin prevention group (2 mg · kg-1 · d-1 ), high-dose rosuvastatin prevention group ( 10 mg· kg-1 · d-1 ), pulmonary arterial hypertension group, normal control group. Beginning on the MCT injection day, rats were treated with rosuvastatin by daily gavage for 4 weeks. Normal control group and pulmonary arterial hypertension group received vehicle by garage. In the treatment protocol, 52 male Sprague-Dawley rats were randomly dividedinto four groups (n = 13 each): low-dose rosuvastatin treatment group (2 mg · kg-1 · d-1), high-dose rosuvastatin treatment group( 10 mg · kg-1 · d-1), pulmonary arterial hypertension group, normal control group. Four weeks after MCT injection, rats were treated with rnsuvastatin by daily gavage for 4 weeks.Normal control group and pulmonary arterial hypertension group received vehicle by gavage. At the end of study, survival rates, mean pulmonary arterial pressure (mPAP), wall thickness of small pulmonary artery and right ventricular hypertrophy among groups were compared. The expression levels of proliferating cell nuclear antigen (P CNA) and endothelial nitricoxide synthase (eNOS) protein in small pulmonary artery,the expression levels of Rho kinase 1 ( ROCK-1 ) and eNOS mRNA in lung tissue were also detected. Results All rats in the prevention protocol survived. Rosuvastatin treatment improved survival in the treatment protocol (58%, 75% vs. 30%, P ＜0. 05 ). Rosuvastatin therapy in both preventment or treatment protocols significantly lowered mPAP [prevention protocol: ( 27.53 ± 3.43 ), ( 25.72 ± 1.76 ) vs. ( 36. 05 ± 2. 45 )mm Hg(1 mm Hg =0. 133 kPa), P ＜0.01; treatment protocol: (30. 39 ±3. 17), (27.59 ±1.99) vs.(40. 68 ± 1.39) mm Hg, P ＜0. 01], reduced thickening of small pulmonary artery wall (P ＜0. 01 ) and right ventricular hypertrophy ( P ＜ 0. 01 ). Rosuvastatin also inhibited PCNA expression of SMC ( P ＜0. 01 ), restored eNOS expression of EC ( P ＜ 0. 05) and inhibited ROCK-1 mRNA expressions in lung tissue (P ＜ 0. 05 ). Conclusions Rosuvastatin therapy reduced mPAP in monocrotaline-induced pulmonary arterial hypertension rat model and this effect is linked with inhibition of ROCK-I expression, inhibition of smooth muscle cell proliferation and restoration of endothelial cell functions.     

Hypoxia-induced pulmonary hypertension: different impact of iloprost, sildenafil, and nitric oxide

OBJECTIVES: Chronic alveolar hypoxia induces pulmonary hypertension, evident from elevated pulmonary artery pressure (PAP), pulmonary vascular resistance, right ventricular hypertrophy (RVH), and increased muscularization of the pulmonary vasculature. Additionally, the vasoconstrictor response to acute hypoxia (HPV) may be reduced in the remodeled vasculature. However, no direct comparison of different treatments on the various parameters characterizing pulmonary hypertension has been performed yet. Against this background, we compared the effects of inhaled NO, infused iloprost, a stable prostacyclin analogue, and oral sildenafil, a phosphodiesterase 5 inhibitor, on hypoxia-induced pulmonary hypertension. METHODS: Exposure of rabbits to chronic hypoxia (FiO(2)=0.10) for 42 days. Treatment with infused iloprost, oral sildenafil, and inhaled nitric oxide. RESULTS: We quantified PAP, pulmonary vascular resistance, RVH, vascular remodeling, vasoreactivity, and the strength of HPV. Chronic hypoxia resulted in an increase in (a) the right ventricle/(left ventricle+septum) ratio from 0.26+/-0.01 to 0.44+/-0.01, (b) PAP, and (c) the degree of muscularization from 14.0+/-4.0% to 43.5+/-5.3%. Treatment with iloprost and sildenafil, but not with NO, prevented the increase in muscularization. In contrast, RVH was strongly inhibited by sildenafil, whereas NO had some minor, and iloprost had no effect. Only iloprost reduced PAP compared to NO and sildenafil. The downregulation of HPV was abrogated only by NO. CONCLUSION: We demonstrated (a) that the parameters characterizing hypoxia-induced pulmonary hypertension are not functionally linked, (b) that the downregulation of HPV under chronic hypoxia can be prevented by inhaled NO but not by sildenafil and iloprost, and (c) that iloprost is particularly effective in preventing vascular remodeling and sildenafil in preventing RVH.     

YC-1 attenuates hypoxia-induced pulmonary arterial hypertension in mice

BackgroundPulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary vascular resistance and elevation of pulmonary arterial pressure, leading to right ventricular failure and eventual death. Currently, no curative therapy for PAH is available, and the overall prognosis is very poor. Recently, direct activators of soluble guanylyl cyclase (sGC) have been tested as a novel therapeutic modality in experimental models of pulmonary arterial hypertension (PAH).ObjectiveIn this study, we used in vitro and in vivo models to evaluate the therapeutic potential of 3-(5′-hydroxymethyl-2′-furyl)-1-benzylindazole (YC-1), a dual functioning chemical, as a direct activator of guanylyl cyclase and an inhibitor of hypoxia-inducible factor-1.MethodsWe analyzed the effects of YC-1 on cell proliferation and the levels of p21 and p53 in human pulmonary artery smooth muscle cells (HPASMCs) under hypoxia. We also determined the effects of YC-1 on expression of endothelin-1 (ET-1) and phosphorylation status of endothelial nitric oxide synthase (eNOS) at Ser¹¹⁷⁹ in human pulmonary artery endothelial cells (HPAECs) under hypoxia. In mice, hypoxic PAH was induced by exposure to normobaric hypoxic conditions for 28 days. To assess preventive or therapeutic effects, randomized mice were subjected to once daily i.p. injections of YC-1 for the entire hypoxic period (5 mg/kg) or for the last seven days of a 28-day hypoxic period (5 and 10 mg/kg). On day 28, we measured the right ventricular systolic pressure (RVSP) and determined the degrees of right ventricular hypertrophy (RVH) and vascular remodeling.ResultsIn HPASMCs, YC-1 inhibited hypoxia-induced proliferation and induction of p53 and p21 in a concentration-dependent manner. Also, YC-1 suppressed the hypoxia-induced expression of ET-1 mRNA and dephosphorylation of eNOS at Ser¹¹⁷⁹ in HPAECs. In the preventive in vivo model, a daily dose of 5 mg/kg YC-1 significantly prevented the elevation of RVSP, development of RVH, and pulmonary vascular remodeling, which were caused by hypoxic exposure. In the therapeutic model, YC-1 at daily doses of 5 and 10 mg/kg alleviated RVH and pulmonary vascular remodeling but did not prevent the elevation of RVSP.ConclusionsOur results indicate that YC-1 prevents the development of hypoxia-induced PAH in a preventive model and alleviates RVH and pulmonary vascular remodeling in a therapeutic model. Therefore, these data imply that YC-1 has therapeutic potential for use in a single or combination therapy for PAH.     

Nitric oxide formation and plasma L-arginine levels in pulmonary hypertensive rats

The elevation of plasma L-arginine levels stimulates nitric oxide (NO) synthesis, but the underlying mechanisms are not yet understood. We examined the role of physiological changes in pulmonary arteries on endogenous NO production. Male Wistar rats were divided into following groups: (1) control rats receiving normal water orally, (2) ARG rats receiving L-arginine water orally, (3) MCT rats injected with monocrotaline (MCT) on day 0 and receiving normal water orally, and (4) MCT+ARG rats injected with MCT on day 0 and receiving L-arginine water orally. The rats were studied after 23 days of dietary intervention. In MCT+ARG rats, supplemental L-arginine exhibited a significant pulmonary vasodilatory effect, as shown by a decreased pulmonary arterial pressure (PAP) (P<0.001), decreased right ventricular hypertrophy (P<0.01), and improved endothelium-dependent relaxation (P<0.01). Also L-arginine inhibited the elevation of plasma endothelin-1 (P<0.01). Oral L-arginine administration increased plasma L-arginine levels about twofold, but in only MCT+ARG rats (i.e., not in ARG rats) did the urinary nitrate excretion significantly increase (P<0.05), which is an indicator of endogenous NO formation. Oral administration of L-arginine is effective against pulmonary vascular remodeling. The data also suggest that the initial elevation of PAP is important for the induction of endogenous NO synthesis.     

Intermittent high altitude hypoxia

The effect of intermittent high altitude (IHA) hypoxia on the myocardium and lesser circulation was investigated in adult male Wistar rats. IHA can induce intermittent pulmonary hypertension and right ventricular hypertrophy in a relatively short time. Even marked pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular changes can be normalized when rats are removed from the hypoxic atmosphere. At the beginning of the exposure to IHA acute myocardial necrotic changes were found; prolongation of IHA did not lead to further acute lesions. Experimentally induced CO polycythemia leads to mild pulmonary hypertension; IHA-induced pulmonary hypertension may, thus, be partly due to polycythemia. Beta blocking agents are able to decrease chronic hypoxic pulmonary hypertension, hypertensive changes in the pulmonary circulation, the degree of right ventricular hypertrophy, and necrotic myocardial changes.     

A model of isobaric hypoxic pulmonary hypertension in rats

Male Wistar rats were kept in isobaric hypoxic chamber (O2 = 10%) with intermittent hypoxia for 1, 2, 4 weeks (6 hrs/day, 6 days/wk). The pulmonary arterial blood pressures increased significantly after 1 week of hypoxia, reached the maximum at 2 weeks of hypoxia and thereafter plateaued in 4 weeks of hypoxia. The elevated Pap were paralleled by increase in the right ventricular blood pressure. The prolonged exposure to hypoxia also led to the right ventricular hypertrophy, which were presented in the increase in both the weight ratio of right ventricle to the left ventricle plus septum and to the body weight. There were no significant hemodynamic changes in the pulmonary circulation by the 24 hours hypoxia. The result suggested that the intermittent hypoxia can lead to the pulmonary hypertension in the model.