Overexpression of endothelial nitric oxide synthase attenuates cardiac hypertrophy induced by chronic isoproterenol infusion.

Endogenous nitric oxide (NO) inhibits the contractile response to beta-adrenergic stimulation, but its effect on cardiac hypertrophy mediated by beta-adrenoceptors remains unclear. The present study was designed to determine whether overproduction of endothelial NO synthase (eNOS) could inhibit cardiac hypertrophy induced by chronic isoproterenol (ISO) infusion (30mg/kg per day) using eNOS overexpressing (eNOS-Tg) mice and wild-type (WT) mice. In a separate group, WT mice were treated with ISO and hydralazine to decrease blood pressure to the same levels in eNOS-Tg mice. The eNOS expression, NOS activity, and cGMP levels in the heart were remarkably higher in eNOS-Tg mice than in WT mice. ISO increased both heart weight and the heart/body weight ratio, which were significantly attenuated in eNOS-Tg mice compared with WT or hydralazine-treated WT mice. Histological examination revealed that the extent of fibrosis was not significantly different among the 3 groups, and that the increase in myocyte size was more than 10% lower in eNOS-Tg than in the other groups. In addition, up-regulated expression of atrial natriuretic peptide mRNA associated with cardiac hypertrophy was significantly inhibited in eNOS-Tg mice during ISO infusion. These results indicate that endogenous NO might act as a negative modulator for the hypertrophic response to beta-adrenergic stimulation.     

NOX4和eNOS在小鼠慢性缺氧肺血管重塑中的表达及意义

目的观察内皮型一氧化氮合酶（eNOS）和NOX4在小鼠慢性缺氧肺动脉高压形成过程中的改变。方法用HE染色法和免疫组织化学法观察C57BL／6J小鼠在常氧和慢性持续缺氧（10±0．5％O2）1、3、7、14d后肺血管的改变及非肌型小血管d．SMA和eNOS蛋白表达的改变。用Real TimePCR法检测各组小鼠肺组织中eNOS和NOX4mRNA的含量。结果C57BL／6J小鼠慢性缺氧后肺小动脉血管管壁增厚、肺泡内肺动脉d—SMA表达增加,肺组织eNOS和NOXdmRNA以及肺动脉内皮细胞eNOS蛋白的表达随缺氧时间延长进行性升高。结论eNOS和NOX4可能在慢性缺氧肺动脉高压的发病机制中发挥重要作用。     

Dissociation of pulmonary vascular remodeling and right ventricular pressure in tissue angiotensin-converting enzyme-deficient mice under conditions of chronic alveolar hypoxia

The present study was designed to characterize the role of tissue angiotensin-converting enzyme (ACE) on pulmonary vascular remodeling and its functional consequences in chronic hypoxia. On the basis of data obtained by pharmacological inhibition of ACE in rats we hypothesized that, under chronic hypoxic conditions, tissue ACE-deficient mice show less remodeling of pulmonary arterioles as compared with wild-type mice, but have equally increased right ventricular pressures. Wild-type and tissue ACE-deficient mice were exposed to chronic hypoxia for 4 wk. Absence of tissue ACE did not affect the increase in the mean right ventricular pressures (MRVP) and the extent of right ventricular hypertrophy under chronic hypoxic conditions. Chronic hypoxia induced significant remodeling of pulmonary arterioles in tissue ACE-deficient mice. The percentage of completely muscularized arterioles was, however, lower in tissue ACE-deficient mice compared with wild-type animals (29 +/- 12 versus 41 +/- 18%, p < 0.05), whereas the percentage of partially muscularized arterioles had increased (48 +/- 11 versus 39 +/- 11%, p < 0.05). No sex-based effects were found. We conclude that the absence of tissue ACE does not prevent the MRVP and right ventricular weight from increasing during chronic hypoxia in the mouse. Also, pulmonary vascular remodeling occurs in hypoxic tissue ACE-deficient mice, albeit to a lower level than in mice that do have an intact ACE gene.     

Exogenous ghrelin attenuates the progression of chronic hypoxia-induced pulmonary hypertension in conscious rats

Chronic exposure to hypoxia, a common adverse consequence of most pulmonary disorders, can lead to a sustained increase in pulmonary arterial pressure (PAP), right ventricular hypertrophy, and is, therefore, closely associated with heart failure and increased mortality. Ghrelin, originally identified as an endogenous GH secretagogue, has recently been shown to possess potent vasodilator properties, likely involving modulation of the vascular endothelium and its associated vasoactive peptides. In this study we hypothesized that ghrelin would impede the pathogenesis of pulmonary arterial hypertension during chronic hypoxia (CH). PAP was continuously measured using radiotelemetry, in conscious male Sprague Dawley rats, in normoxia and during 2-wk CH (10% O(2)). During this hypoxic period, rats received a daily sc injection of either saline or ghrelin (150 microg/kg). Subsequently, heart and lung samples were collected for morphological, histological, and molecular analyses. CH significantly elevated PAP in saline-treated rats, increased wall thickness of peripheral pulmonary arteries, and, consequently, induced right ventricular hypertrophy. In these rats, CH also led to the overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA within the lung. Exogenous ghrelin administration attenuated the CH-induced overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA. Consequently, ghrelin significantly attenuated the development of pulmonary arterial hypertension, pulmonary vascular remodeling, and right ventricular hypertrophy. These results demonstrate the therapeutic benefits of ghrelin for impeding the pathogenesis of pulmonary hypertension and right ventricular hypertrophy, particularly in subjects prone to CH (e.g. pulmonary disorders).     

低氧诱导大鼠肺动脉中5-HT_(1B)受体的过度表达

目的:观察低氧对大鼠肺动脉中5-羟色胺1B(5-HT1B)受体表达的影响,初步探讨了5-HT1B受体在低氧性肺动脉高压形成中的变化。方法:40只健康雄性SD大鼠随机分为正常组、低氧3周组、低氧4周组和低氧6周组,每组10只。除正常组外,其余3组大鼠分别在低氧环境中饲养3周、4周和6周。测定各组大鼠的平均肺动脉压力(mPAP)、右心室收缩压(RVSP)和右心室肥厚度。应用免疫组化染色法检测大鼠肺动脉上5-HT1B的分布和表达;用Western blot法测定大鼠肺组织中5-HT1B受体蛋白的含量。结果:与正常组相比,低氧3周组大鼠的mPAP、RVSP和右心室肥厚度均显著升高(均P0.05),并且随着低氧时间的延长而持续升高(均P0.05)。免疫组化染色的结果显示,5-HT1B受体主要分布在正常大鼠肺动脉的内膜层,平滑肌肌层中仅有少量表达;与正常组相比,低氧3周组大鼠肺动脉平滑肌肌层中5-HT1B受体的表达显著增多(P0.05);随着低氧时间的延长,表达持续增多。Western blot的结果表明,大鼠肺组织中5-HT1B受体蛋白含量的变化与免疫组化染色法检测的结果相一致。结论:低氧可以诱导大鼠肺动脉中5-HT1B受体的过度表达,这可能是5-羟色胺系统参与低氧性肺动脉高压形成的机制之一。     

慢性低氧性肺动脉高压大鼠肺动脉内PTEN蛋白表达的变化

目的 通过观察慢性低氧性肺动脉高压大鼠肺动脉内人第10号染色体缺失的磷酸酶及张力蛋白同源的基因（PTEN）蛋白表达水平的变化,初步探讨PTEN在慢性低氧性肺动脉高压的发生、发展过程中所起的作用.方法 将6周龄健康雄性SD大鼠,随机分为正常对照组、低氧1d、3d、7d、14d和21d组,除对照组外,其他各组先建立慢性低氧肺动脉高压大鼠模型,然后检测各组大鼠右心室收缩压（right ventricle systolic pressure,RVSP）和右心室肥厚指数（right ventricle hypertrophy index,RVHI）,采用HE染色观察肺动脉病理学改变,采用Western blot技术检测肺动脉内PTEN蛋白的表达水平.结果 ①与正常对照组（23.76±0.82）mmHg相比,低氧暴露1d、3d、7d、14 d、21d后RVSP均明显上升（P＜0.05）;RVHI低氧3d、7d、14 d、21d组均较正常对照组（100％）明显上升（P＜0.05）;低氧暴露3d、7d和21d组肺动脉中膜明显增厚、管腔明显变小.②PTEN和p-PTEN在正常对照组和低氧各组均有表达.低氧各组肺动脉内PTEN蛋白的表达较对照组下降,但差异无统计学意义（P＞0.05）;而p-PTEN蛋白与PTEN总蛋白表达量的比值随低氧时间的延长有上升趋势,且在慢性低氧21d组（1.71±0.25）较正常对照组（1.00）明显增高（P＜0.05）.结论 PTEN蛋白表达的降低和p-PTEN蛋白表达的增高可能参与了大鼠慢性低氧性肺动脉高压的发生和发展过程.     

人源性脐带间充质干细胞治疗实验性肺动脉高压所致右心衰竭的疗效观察

目的 拟通过建立MCT诱导的PAH大鼠模型,观察人脐带间充质干细胞（UC-MSCs）干预对大鼠PAH和右心衰竭的治疗效应。方法 实验动物分为3组（空白对照组、PAH组和UC-MSCs组）,在MCT腹腔注射1周后进行干预,UC-MSCs组舌下静脉注射UC-MSCs悬液,空白对照组和PAH组舌下静脉注射等量生理盐水。第4周大鼠行右心超声心动图、右心导管测压、右心肥厚指数以及肺组织病理等检测。结果 与对照组相比,PAH组大鼠右心室游离壁厚度(RVWT)和右心室内径(RVID)显著增大,肺动脉血流加速时间与射血时间比值（PAT/PET）显著下降,右心收缩压（RVSP）和右心肥厚指数(RVHI)显著增高,肺小动脉血管壁厚度（WT）明显增厚。与PAH组相比,UC-MSCs组RVWT和RVID显著减小,PAT/PET明显升高,RVSP和RVHI明显降低,WT明显变薄。结论 利用MCT腹腔注射成功制备PAH大鼠模型,经舌下静脉注射UC-MSCs可以显著降低肺动脉压力,改善右心功能,逆转肺血管重构。     

The effect of systemic beta-2 adrenergic agonist therapy on the pulmonary hypertensive response to chronic hypoxia in rats

Chronic hypoxia produces polycythemia, pulmonary hypertension, muscularization of peripheral pulmonary arteries, and right ventricular hypertrophy. The present study was designed to investigate the effects of systemic administration of a beta-2 adrenergic agonist on these responses. Male Wistar rats (9 or more in every group) were maintained in room air or 10% oxygen for 28 days. In the first experiment, they were treated with albuterol at various doses (0.05 mg/kg, 0.1 mg/kg, 0.5 mg/kg) twice during exposure to intermittent hypoxia (10 h/day). In the second experiment, rats were treated with albuterol 2.5 mg/kg subcutaneously twice daily during continuous hypoxia. Control animals in normoxia and hypoxia received 0.1 ml saline at equivalent times. All hypoxic groups developed polycythemia, significantly increased right ventricular systolic pressure, and right ventricular hypertrophy. At doses of albuterol that did not produce cardiac hypertrophy in normoxia, treatment had no effect on the development of right ventricular hypertrophy. With lower doses of albuterol in hypoxia, there was a trend towards an increase in hematocrit, but overall this did not reach significance. Treatment with high dose albuterol in continuous hypoxia significantly increased the hematocrit and enhanced the remodeling of the pulmonary vasculature (Hematocrit: saline-treated, 57.7 SEM 1.9; albuterol-treated, 63.4 SEM 1.7; p less than 0.05. Percentage of thick-walled peripheral vessels: saline-treated, 19.4 SEM 0.60; albuterol-treated, 22.7 SEM 0.85; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Chronic intermittent hypoxia increases haematocrit and causes right ventricular hypertrophy in the rat.

Chronic continuous hypoxia increases haematocrit and causes right ventricular hypertrophy and pulmonary hypertension. In obstructive sleep apnoea, the exposure to hypoxia is intermittent rather than continuous but the effects of chronic intermittent hypoxia on haematocrit and right ventricular mass are unclear. Wistar rats were exposed to alternating periods of hypoxia and normoxia twice per min for 8 h per day for 5 weeks in order to mimic the intermittent hypoxia of obstructive sleep apnoea in humans. Haematocrit was significantly raised at day 7, 14, 21, 28 and 35 of the treatment period. At the end of the treatment, there was a significant increase in right ventricular mass. Therefore, chronic intermittent hypoxia increases haematocrit and right heart mass. These results suggest that the raised haematocrit and pulmonary arterial pressure observed in some cases of obstructive sleep apnoea in humans may be caused by intermittent nocturnal hypoxaemia.     

Vascular endothelial growth factor-B-deficient mice show impaired development of hypoxic pulmonary hypertension

OBJECTIVE: To test the hypothesis that Vegf-B contributes to the pulmonary vascular remodelling, and the associated pulmonary hypertension, induced by exposure of mice to chronic hypoxia. METHODS: Right ventricular systolic pressure, the ratio of right ventricle/[left ventricle+septum] (RV/[LV+S]) and the thickness of the media (relative to vessel diameter) of intralobar pulmonary arteries (o.d. 50-150 and 151-420 microm) were determined in Vegfb knockout mice (Vegfb(-/-); n=17) and corresponding wild-type mice (Vegfb(+/+); n=17) exposed to chronic hypoxia (10% oxygen) or housed in room air (normoxia) for 4 weeks. RESULTS: In Vegfb(+/+) mice hypoxia caused (i) pulmonary hypertension (a 70% increase in right ventricular systolic pressure compared with normoxic Vegfb(+/+) mice; P<0.001), (ii) right ventricular hypertrophy (a 66% increase in RV/[LV+S]; P<0.001) and (iii) pulmonary vascular remodelling (a 27-36% increase in pulmonary arterial medial thickness; P<0.05). In contrast, in Vegfb(-/-) mice hypoxia did not cause any increase in either right ventricular systolic pressure or pulmonary arterial medial thickness; also right ventricular hypertrophy (41% increase in RV/[LV+S]; P<0.001) was less pronounced (P<0.05) than in Vegfb(+/+) mice. CONCLUSION: Vegf-B may have a role in the development of chronic hypoxic pulmonary hypertension in mice by contributing to pulmonary vascular remodelling. If so, the effect of Vegf-B appears to be different from that of Vegf-A which is reported to protect against, rather than contribute to, hypoxia-induced pulmonary vascular remodelling.     

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。     

Regression of Chronic Hypoxia-Induced Pulmonary Hypertension, Right Ventricular Hypertrophy, and Fibrosis: Effect of Enalapril

Chronic hypoxia induces pulmonary hypertension and right ventricular hypertrophy. These changes are completely reversible, except for persistent myocardial fibrosis. The aim of the present study was to determine whether treatment with the angiotensin-converting enzyme (ACE) inhibitor enalapril can reduce the ventricular collagen content in animals recovering from chronic hypoxia. Adult male Wistar rats were exposed to intermittent high-altitude hypoxia simulated in a barochamber (7000 m, 8 hr/day, 5 days a week, 24 exposures), then transferred to normoxia and divided into two groups: (a) treated with enalapril (0.1 g/kg/day for 60 days) and (b) without treatment. The corresponding control groups were kept under normoxic conditions. Enalapril significantly decreased the heart rate, systemic arterial pressure, and absolute left and right ventricular weights in both hypoxic and control rats; on the other hand, the pulmonary blood pressure was unchanged. The content and concentration of collagen was reduced in both ventricles of enalapril-treated hypoxic and control animals by 10–26% compared with the corresponding untreated groups. These data suggest that the partial regression of cardiac fibrosis due to enalapril may be independent of the pressure load.     

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.     

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.     

Mitochondrial complex II participates in normoxic and hypoxic regulation of α-keto acids in the murine heart

α-Keto acids (α-KAs) are not just metabolic intermediates but are also powerful modulators of different cellular pathways. Here, we tested the hypothesis that α-KA concentrations are regulated by complex II (succinate dehydrogenase=SDH), which represents an intersection between the mitochondrial respiratory chain for which an important function in cardiopulmonary oxygen sensing has been demonstrated, and the Krebs cycle, a central element of α-KA metabolism. SDH subunit D heterozygous (SDHD(+/-)) and wild-type (WT) mice were housed at normoxia or hypoxia (10% O(2)) for 4 days or 3 weeks, and right ventricular pressure, right ventricle/(left ventricle+septum) ratio, cardiomyocyte ultrastructure, pulmonary vascular remodelling, ventricular complex II subunit expression, SDH activity and α-KA concentrations were analysed. In both strains, hypoxia induced increases in right ventricular pressure and enhanced muscularization of distal pulmonary arteries. Right ventricular hypertrophy was less severe in SDHD(+/-) mice although the cardiomyocyte ultrastructure and mitochondrial morphometric parameters were unchanged. Protein amounts of SDHA, SDHB and SDHC, and SDH activity were distinctly reduced in SDHD(+/-) mice. In normoxic SDHD(+/-) mice, α-ketoisocaproate concentration was lowered to 50% as compared to WT animals. Right/left ventricular concentration differences and the hypoxia-induced decline in individual α-KAs were less pronounced in SDHD(+/-) animals indicating that mitochondrial complex II participates in the adjustment of cardiac α-KA concentrations both under normoxic and hypoxic conditions. These characteristics are not related to the hemodynamic consequences of hypoxia-induced pulmonary vascular remodelling, since its extent and right ventricular pressure were not affected in SDHD(+/-) mice albeit right ventricular hypertrophy was attenuated.     

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。     

Prevention and reversal of hypoxic pulmonary hypertension by calcium antagonists

There exists no agreement as to the best vasodilator drug for treatment of hypoxic pulmonary hypertension. We wondered which of 3 commonly used vasodilators - verapamil, nifedipine, or hydralazine - would be the most effective in reducing and reversing the development of hypoxic pulmonary hypertension in the conscious rat. Hemodynamic studies showed that all 3 drugs inhibited the pressor response to acute hypoxia. Given for 1 month to conscious rats during exposure to intermittent hypoxia, verapamil and nifedipine reduced pulmonary hypertension when compared with hypoxic control animals, as indicated by right ventricular hypertrophy, total pulmonary resistance, and medial thickening. Hydralazine caused similar, but smaller, changes. Nifedipine, when used to reverse established hypoxic pulmonary hypertension, reduced right ventricular hypertrophy and medial thickening. Cardiac and systemic effects were negligible. These results demonstrate that the calcium channel blockers reduce the development of hypoxic pulmonary hypertension and that nifedipine partially reverses established hypertension.     

Normal and high eNOS levels are detrimental in both mild and severe cardiac pressure-overload

Nitric oxide (NO) produced by endothelial NO synthase (eNOS) exerts beneficial effects in a variety of cardiovascular disease states. Studies on the benefit of eNOS activity in pressure-overload cardiac hypertrophy and dysfunction produced by aortic stenosis are equivocal, which may be due to different expression levels of eNOS or different severities of pressure-overload. Consequently, we investigated the effects of eNOS-expression level on cardiac hypertrophy and dysfunction produced by mild or severe pressure-overload. To unravel the impact of eNOS on pressure-overload cardiac dysfunction we subjected eNOS deficient, wildtype and eNOS overexpressing transgenic (eNOS-Tg) mice to 8 weeks of mild or severe transverse aortic constriction (TAC) and studied cardiac geometry and function at the whole organ and tissue level. In both mild and severe TAC, lack of eNOS ameliorated, whereas eNOS overexpression aggravated, TAC-induced cardiac remodeling and dysfunction. Moreover, the detrimental effects of eNOS in severe TAC were associated with aggravation of TAC-induced NOS-dependent oxidative stress and by further elevation of eNOS monomer levels, consistent with enhanced eNOS uncoupling. In the presence of TAC, scavenging of reactive oxygen species with N-acetylcysteine reduced eNOS S-glutathionylation, eNOS monomer and NOS-dependent superoxide levels in eNOS-Tg mice to wildtype levels. Accordingly, N-acetylcysteine improved cardiac function in eNOS-Tg but not in wildtype mice with TAC. In conclusion, independent of the severity of TAC, eNOS aggravates cardiac remodeling and dysfunction, which appears due to TAC-induced eNOS uncoupling and superoxide production.     

安立生坦与波生坦对低氧性肺动脉高压大鼠右心室重构影响的比较研究

目的:比较安立生坦(ambrisentan)与波生坦(bosentan)对低氧性肺动脉高压大鼠(HPH)右心室重构的影响。方法:40只SD大鼠随机分成5组:正常对照组、模型组、安立生坦组、波生坦组、安慰剂组,每组8只。正常对照组于自然环境中饲养4周,其他组置于低压低氧舱中(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(125 mg/kg)及生理盐水(2 ml)灌胃,共两周。实验结束后,测定平均肺动脉压(mPAP)和右心室收缩压(RVSP);计算右心室肥厚指数[RV/(LV+S)]及右心室质量/体质量(RW/BW)。右心室心肌以HE染色后,观察其形态学变化,以Masson染色后观察心肌胶原纤维容积分数(CVF)的变化。结果:与模型组和安慰剂组相比,安立生坦组和波生坦组的mPAP、RVSP、RV/(LV+S)、RW/BW、CVF值明显降低(P<0.05),安立生坦组和波生坦组相比,上述指标的差异无明显的统计学意义。HE染色切片显示,模型组和安慰剂组大鼠心肌细胞肥大,安立生坦组和波生坦组可基本恢复至正常组状态。结论:安立生坦与波生坦能显著降低HPH大鼠的肺动脉压力,抑制右心室肥厚及纤维化。安立生坦与波生坦相比,对HPH大鼠右心室重构的影响无明显差别。