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.     

血管紧张素转化酶2激活预防肺动脉高压的实验研究

目的:探讨血管紧张素转化酶2(ACE2)激活,对肺叶切除联合野百合碱注射,诱导重度肺动脉高压(PAH)的预防作用。方法:左肺切除+野百合碱注射建立大鼠重度PAH模型。雄性SD大鼠50只,随机分为5组,A组为空白对照组、B组为Resorcinolnaphthalein(Res)对照组,C组为PAH组,D组为Res预防组,E组为Res+A-779干预组。测量平均肺动脉压力(mPAP)、右心室肥厚指数(RVHI);弹力纤维染色分析肺血管病变;ELISA、Western Blot分析肾素血管紧张素系统各主要成分的水平。结果:处理3 w后,C组大鼠mPAP、RVHI明显升高,出现了严重的肺动脉中膜肥厚、内膜增生(与A组比较,P<0.05),D组上述4项指标明显减轻(与C组比较,P<0.05);E组则比D组病变严重(P<0.05)。ACE、Ang-II及AT1R水平,D组明显低于C组(P<0.05),而ACE2、Ang-(1-7)及Mas水平D组明显高于C组(P<0.05)。结论:Res激活ACE2可以抑制重度肺动脉高压的形成,调节肾素血管紧张素系统的平衡,可能是其作用的主要机制之一。     

Murine Recombinant Angiotensin-Converting Enzyme 2: Effect on Angiotensin II-Dependent Hypertension and Distinctive Angiotensin-Converting Enzyme 2 Inhibitor Characteristics on Rodent and Human Angiotensin-Converting Enzyme 2

A newly produced murine recombinant angiotensin (Ang)-converting enzyme 2 (ACE2) was characterized in vivo and in vitro. The effects of available ACE2 inhibitors (MLN-4760 and 2 conformational variants of DX600, linear and cyclic) were also examined. When murine ACE2 was given to mice for 4 weeks, a marked increase in serum ACE2 activity was sustainable. In acute studies, mouse ACE2 (1 mg/kg) obliterated hypertension induced by Ang II infusion by rapidly decreasing plasma Ang II. These effects were blocked by MLN-4760 but not by either form of DX600. In vitro, conversion from Ang II to Ang-(1-7) by mouse ACE2 was blocked by MLN-4760 (10(-6) m) but not by either form of DX600 (10(-5) m). Quantitative analysis of multiple Ang peptides in plasma ex vivo revealed formation of Ang-(1-9) from Ang I by human but not by mouse ACE2. Both human and mouse ACE2 led to the dissipation of Ang II with formation of Ang (1-7). By contrast, mouse ACE2-driven Ang-(1-7) formation from Ang II was blocked by MLN-4760 but not by either linear or cyclic DX600. In conclusion, sustained elevations in serum ACE2 activity can be accomplished with murine ACE2 administration, thereby providing a strategy for ACE2 amplification in chronic studies using rodent models of hypertension and cardiovascular disease. Human but not mouse ACE2 degrades Ang I to form Ang-(1-9). There are also species differences regarding rodent and human ACE2 inhibition by known inhibitors such that MLN-4760 inhibits both human and mouse ACE2, whereas DX600 only blocks human ACE2 activity.     

ACE2 Activation Confers Endothelial Protection and Attenuates Neointimal Lesions in Prevention of Severe Pulmonary Arterial Hypertension in Rats

Background

Angiotensin-converting enzyme 2 (ACE2), an ACE homolog, hydrolyzes angiotensin II and opposes its actions, and plays a protective role in the pathogenesis of pulmonary arterial hypertension (PAH). However, the underlying mechanisms involved in the effect of ACE2 on PAH are still uncertain. In this study, we observed the effects of ACE2 activation on endothelial dysfunction and vascular remodeling in the development of severe PAH in rats.

Methods

Severe PAH was induced by monocrotaline injection 1 week following left pneumonectomy, and ACE2 was activated by continuous injection of resorcinolnaphthalein. The PAH-related hemodynamics, pathological changes, and endothelium-dependent vasorelaxation were examined to assess the effects of ACE2 activation. In addition, the changes of the main components of the renin-angiotensin system were identified by ELISA or Western blotting.

Results

Severe PAH was established at 3 weeks and was characterized by high pulmonary arterial pressure (45 mmHg), significant right ventricular hypertrophy, neointimal occlusive lesions, and impaired endothelium-dependent relaxation in pulmonary arteries. Coadministration of resorcinolnaphthalein reduced pulmonary arterial pressure, right ventricular hypertrophy, and neointimal formation and shifted the endothelial-dependent responses toward values measured in normal rats. Theses changes were associated with an increase in ACE2 and angiotensin-(1–7) levels and a decrease in ACE and angiotensin II levels, in addition to a decrease in the ACE/ACE2 ratio and the angiotensin II/angiotensin-(1–7) ratio. The beneficial effects of resorcinolnaphthalein were abolished by A-779.

Conclusions

These findings suggested that ACE2 activation by resorcinolnaphthalein improved endothelial function and suppressed neointimal formation in the prevention of severe PAH by the mechanism of mediating the levels of the components of the renin-angiotensin system.     

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.     

Ion channels in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a hemodynamic abnormality that ultimately results in mortality due to right heart failure. Although the clinical manifestations of primary and secondary PAH are diverse, medial hypertrophy and arterial vasoconstriction are key components in the vascular remodeling leading to PAH. Abnormalities in the homeostasis of intracellular Ca(2+), transmembrane flux of ions, and membrane potential may play significant roles in the processes leading to pulmonary vascular remodeling. Decreased activity of K(+) channels causes membrane depolarization, leading to Ca(2+) influx. The elevated cytoplasmic Ca(2+) is a major trigger for pulmonary vasoconstriction and an important stimulus for vascular smooth muscle proliferation. Dysfunctional K(+) channels have also been linked to inhibition of apoptosis and contribute further to the medial hypertrophy. This review focuses on the relative role of K(+) and Ca(2+) ions and channels in human pulmonary artery smooth muscle cells in the development of PAH.     

Notch3 signaling activation in smooth muscle cells promotes extrauterine growth restriction-induced pulmonary hypertension

Background and aimsEarly postnatal life is a critical developmental period that affects health of the whole life. Extrauterine growth restriction (EUGR) causes cardiovascular development problems and diseases, including pulmonary arterial hypertension (PAH). PAH is characterized by proliferation, migration, and anti-apoptosis of pulmonary artery smooth muscle cells (PASMCs). However, the role of PASMCs in EUGR has not been studied. Thus, we hypothesized that PASMCs dysfunction played a role in EUGR-induced pulmonary hypertension.Methods and resultsHere we identified that postnatal nutritional restriction-induced EUGR rats exhibited an elevated mean pulmonary arterial pressure and vascular remodeling at 12 weeks old. PASMCs of EUGR rats showed increased cell proliferation and migration features. In EUGR-induced PAH rats, Notch3 signaling was activated. Relative mRNA and protein expression levels of Notch3 intracellular domain (Notch3 ICD), and Notch target gene Hey1 in PASMCs were upregulated. We further demonstrated that pharmacological inhibition of Notch3 activity by using a γ-secretase inhibitor DAPT, which blocked the cleavage of Notch proteins to ICD peptides, could effectively inhibit PASMC proliferation. Specifically knocked down of Notch3 in rat PASMCs by shRNA restored the abnormal PASMC phenotype in vitro. We found that administration of Notch signaling inhibitor DAPT could successfully reduce mean pulmonary arterial pressure in EUGR rats.ConclusionsThe present study demonstrated that upregulation of Notch3 signaling in PASMCs was crucial for the development of EUGR-induced PAH. Blocking Notch3-Hey1 signaling pathway in PASMCs provides a potential therapeutic target for PAH.     

Grape seed procyanidin suppresses inflammation in cigarette smoke-exposed pulmonary arterial hypertension rats by the PPAR-γ/COX-2 pathway

Background and aimPulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling, which is mainly caused by inflammation. Inhibiting inflammation can relieve PAH. Grape seed procyanidin (GSP) possesses remarkable anti-inflammatory property and vascular protective function. In this experiment, we verified the anti-inflammatory property of GSP in cigarette smoke-exposed PAH rats and revealed its molecular mechanism.Methods and resultsIn vivo, 45 Sprague Dawley (SD) rats were divided into 5 groups randomly, treated with normoxia/cigarette smoke (CS)/GSP + CS/CS + solvent/GSP. After GSP + CS administration, a decrease in mPAP, PVR, RVHI, WT%, and WA% was detected in the rats as compared to those treated with CS. In vitro, the proliferation of pulmonary arterial smooth muscle cells (PASMCs) caused by cigarette smoke extract (CSE) was effectively attenuated with GSP + CSE administration. Furthermore, GSP significantly increased the expression of peroxisome proliferator-activated receptor γ (PPAR-γ) together with the lowered expression level of cyclooxygenase 2 (COX-2) in PASMCs co-incubated with CSE.ConclusionThese findings indicate that GSP ameliorates inflammation by the PPAR-γ/COX-2 pathway and finally inhibits the proliferation of PASMCs, which leads to pulmonary vascular remodeling.     

Salidroside attenuates chronic hypoxia-induced pulmonary hypertension via adenosine A2a receptor related mitochondria-dependent apoptosis pathway

Pulmonary arterial hypertension (PAH) is characterized by pulmonary arterial remodeling mainly due to excess cellular proliferation and apoptosis resistance of pulmonary arterial smooth muscle cells (PASMCs). Salidroside, an active ingredient isolated from Rhodiola rosea is proposed to exert protective effects against PAH. However, the function of salidroside in PAH has not been investigated systematically and the underlying mechanisms are not clear. To investigate the effects of salidroside on PAH, the mice in chronic hypoxia model of PAH were given by an increasing concentration of salidroside (0, 16 mg/kg, 32 mg/kg, and 64 mg/kg). After salidroside treatment, the chronic hypoxia-induced right ventricular hypertrophy and pulmonary arterial remodeling were attenuated, suggesting a protective role played by salidroside in PAH. To explore the potential mechanisms, the apoptosis of PASMCs after salidroside treatment under hypoxia conditions were determined in vivo and in vitro, and also the mitochondria-dependent apoptosis factors, Bax, Bcl-2, cytochrome C, and caspase 9 were examined. The results revealed that salidroside reversed hypoxia-induced cell apoptosis resistance at least partially via a mitochondria-dependent pathway. In addition, salidroside upregulated the expression of adenosine A_2a receptor (A_2aR) in lung tissues of mice and in PASMCs in vitro after hypoxia exposure. Combined the evidence above, we conclude that salidroside can attenuate chronic hypoxia-induced PAH by promoting PASMCs apoptosis via an A_2aR related mitochondria dependent pathway.     

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.     

肺动脉平滑肌细胞:肺动脉高压的关键治疗靶点

肺动脉高压(PAH)是一种进展快、预后欠佳、死亡率高的心血管疾病。研究表明,肺血管重构是PAH发生发展的重要病理基础,而肺动脉平滑肌细胞的增殖和肥大是PAH肺血管重构的主要病理改变。在PAH时,肺血管平滑肌细胞由收缩表型向增殖状态的合成表型转化,主要表现为肺血管平滑肌细胞的增殖和肥大。上述病理改变最终导致肺血管管腔狭窄,管壁僵硬,进而促进PAH的发生发展。本文对肺动脉平滑肌细胞在PAH中的关键作用及作用机制进行阐述,为临床防治PAH提供新靶点和新策略。     

The synergistic therapeutic effect of hepatocyte growth factor and granulocyte colony-stimulating factor on pulmonary hypertension in rats

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary arterial pressure and vascular resistance. Despite advances in therapy for PAH, its treatment and prognosis remain poor. We aimed to investigate whether the transplantation of bone marrow mesenchymal stem cells (MSCs) overexpressing hepatocyte growth factor (HGF), alone or in combination with granulocyte colony-stimulating factor (G-CSF), attenuates the development of experimental monocrotaline (MCT)-induced PAH. Three weeks after MCT administration, rats were divided into the following groups: (1) untreated (PAH); (2) HGF treated; (3) MSCs administered; (4) HGF-MSCs treated; and (5) HGF-MSCs plus G-CSF treated. After 3 weeks, hemodynamic changes, histomorphology, and angiogenesis were evaluated. To elucidate the molecular mechanisms of vascular remodeling and angiogenesis, serum levels of transforming growth factor (TGF)-β and endothelin-1 (ET-1) were measured, and the gene and protein expression levels of vascular cell adhesion molecule-1 (VCAM-1) and matrix metalloproteinase-9 (MMP-9) were determined. Compared with the PAH, MSC, and G-CSF groups, the HGF and HGF+G-CSF groups exhibited significantly reduced right ventricular hypertrophy and mean pulmonary arterial pressure (P < 0.05). Histologically, vessel muscularization or thickening and collagen deposition were also significantly decreased (P < 0.05). The number of vessels in the HGF+G-CSF group was higher than that in the other groups (P < 0.05). The TGF-β and ET-1 concentrations in the plasma of pulmonary hypertensive rats were markedly lower in the HGF and HGF+G-CSF groups (P < 0.05). Furthermore, HGF induced the expression of VCAM-1, and HGF treatment together with G-CSF synergistically stimulated MMP-9 expression. Transplanted HGF-MSCs combined with G-CSF potentially offer synergistic therapeutic benefit for the treatment of PAH.     

Current Therapy of Pulmonary Hypertension

Abstract Pulmonary arterial hypertension (PAH) affects vascular proliferation and remodeling in small pulmonary arteries and results in right ventricular failure and death due to a progressive increase in pulmonary vascular resistance. Recent advances in understanding of the molecular mechanisms involved in PAH suggest that endothelial dysfunction plays a major role. Impaired production of vasoactive mediators, such as prostacyclin and nitric oxide, accompanied with prolonged overexpression of vasoconstrictors such as endothelin-1, affects vascular tone and reinforces vascular remodeling. As the latter substances represent logical pharmacological targets, new drugs affecting these mechanisms have evolved during the past 2 decades and led to umpteen placebo-controlled trials in bygone years. Prognosis and quality of life of patients suffering from PAH seem to improve due to these new treatment strategies resulting in a reduction of mortality and morbidity, but there is still a substantial need for further long-term and head-to-head trials.     

Significance of BMPR2 mutations in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a debilitating disease that results from progressive remodeling and inflammation of pulmonary arteries. PAH develops gradually, is difficult to diagnose, and has a high mortality rate. Although mutation in the bone morphogenetic protein receptor 2 (BMPR2) gene has been identified as the main genetic cause of PAH, the underlying pathways involving the pathophysiology of PAH are complex and still not fully understood. Endothelial dysfunction has been observed in PAH development that results in a multitude of disturbances in the cellular processes in pulmonary vessels. Changes in the pulmonary vasculature caused by the disruption of BMPR2 signaling are observed in three main vascular components; endothelial cells, smooth muscle cells, and fibroblasts. BMPR2 also has a prominent role in maintenance of the immune system. The disruption of BMPR2 signaling pathway causes an increased degree of inflammation and decreases the ability of the immune system to resolve it. Inflammatory processes and changes in pulmonary vasculature interact with one another, resulting in the progression of chronic PAH. In this review, we highlight the various components of vascular remodeling and immune response that are caused by disruption of BMPR2 signaling, including the clinical evidence and the prospects of these components as a potential target for PAH therapy. Indeed, development of drugs to target the pathogenic pathways involved in PAH may complement existing treatment regimens and improve patient prognosis.     

电压依赖性钾离子通道在肺动脉高压发病过程中的作用

肺动脉高压是一种肺血流受限引起肺血管阻力和压力持续性增高,最终导致右心衰竭甚至死亡的综合征.病理生理学改变主要为肺血管收缩、重塑及原位血栓形成.研究表明,钾离子通道尤其电压依赖性钾离子通道功能与表达水平的降低是引起肺血管平滑肌细胞增殖和凋亡异常、肺血管重塑的关键因素.本文着重论述近年来有关电压依赖性钾离子通道与肺动脉高...     

Urantide alleviates monocrotaline induced pulmonary arterial hypertension in Wistar rats

Pulmonary arterial hypertension (PAH) is a serious disorder with poor prognosis. Urotensin II (UII) has been confirmed to be powerful vasoconstrictor than endothelin-1, which may play an important role in PAH development. The aim of this study is to observe the effects of urantide, a UII receptor antagonist, on monocrotaline (MCT) induced PAH in rats. 60 male Wistar rats were divided into six groups. For early treatment experiment, rats were divided into normal control group, MCT(4w) model group (MCT + saline × 3 wks from the 8th day of MCT injection) and urantide early treatment group (MCT + urantide 10 μg/kg/d × 3 wks, 1 week after MCT injection once). For late treatment experiment, rats were divided as controls, MCT(6w) model group (MCT + saline × 2 wks, 4 weeks after MCT injection once) and urantide late treatment group (MCT + urantide 10 μg/kg/d × 2 wks, 4 weeks after MCT injection once). At the end of experiments, mean pulmonary arterial pressures (mPAP) and mean blood pressure (MBP) of rats in each group were measured by catheterization. Right ventricular weight ratio was also weighed. Relaxation effects of urantide on intralobar pulmonary arterial rings of normal control and MCT(4w) model rats were investigated. Pulmonary artery remodeling was detected by hematoxylin and eosin (HE) staining and immunohistochemistry analysis. Serum nitric oxide (NO) levels in all six groups were assayed by ELISA kits. Urantide markedly reduced the mPAP levels of MCT induced PAH in both early and late treatment groups. It didn't change the MBP. Urantide dose-dependently relaxed the pulmonary arterial rings of normal control and MCT(4w) model rats. Moreover, N(G)-Nitro-l-arginine Methyl Ester (l-NAME) blocked the dilation response induced by urantide. In addition, urantide inhibited the pulmonary vascular remodeling remarkably. Serum NO level elevated in both early and late treatment rats with urantide infusion. These results suggest that urantide effectively alleviated MCT induced rats PAH may through relaxing pulmonary arteries and inhibiting pulmonary vascular remodeling. NO pathway might be one of the mechanisms in urantide induced pulmonary artery dilation. Thus, it is expected that urantide may be a novel therapy for PAH.     

Inhibition of the RhoA/Rho-associated,coiled-coil-containing protein kinase-1 pathway is involved in the therapeutic effects of simvastatin on pulmonary arterial hypertension

Background: Recent research has shown that statins improve pulmonary arterial hypertension (PAH), but their mechanisms of action are not fully understood. This study aimed to investigate the role of RhoA/ROCK1 regulation in the therapeutic effects of simvastatin on PAH. Methods: For in vivo experiments, rats (N = 40) were randomly assigned to four groups: control, simvastatin, monocrotaline (MCT), and MCT + simvastatin. The MCT group and MCT + simvastatin groups received proline dithiocarbamate (50 mg/kg, i.p.) on the first day of the study. The MCT + simvastatin group received simvastatin (2 mg/kg) daily for 4 weeks, after which pulmonary arterial pressure was measured by right heart catheterization. The protein and mRNA levels of Rho and ROCK1 were measured by immunohistochemistry, Western blot, and PCR. For in vitro experiments, human pulmonary endothelial cells were divided into seven groups: control, simvastatin, monocrotaline pyrrole (MCTP), MCTP + simvastatin, MCTP + simvastatin + mevalonate, MCTP + simvastatin + farnesyl pyrophosphate (FPP), and MCTP + simvastatin + FPP + geranylgeranyl pyrophosphate (GGPP). After 72 h exposed to the drugs, the protein and mRNA levels of RhoA and ROCK1 were measured by Western blot and PCR. Results: The MCT group showed increased mean pulmonary arterial pressure, marked vascular remodeling, and increased protein and mRNA levels of RhoA and ROCK1 compared to the other groups (P < 0.05). In vitro, the MCTP group showed a marked proliferation of vascular endothelial cells, as well as increased protein and mRNA levels of RhoA and ROCK1 compared to the MCTP + simvastatin group. The MCTP + simvastatin + mevalonate group, MCTP + simvastatin+ FPP group, and MCTP + simvastatin + FPP + GGPP group showed increased mRNA levels of RhoA and ROCK1, as well as increased protein levels of RhoA, compared to the MCTP + simvastatin group. Conclusions: Simvastatin improved vascular remodeling and inhibited the development of PAH. The effects of simvastatin were mediated by inhibition of RhoA/ROCK1. Simvastatin decreased RhoA/ROCK1 overexpression by inhibition of mevalonate, FPP, and GGPP synthesis.