Simvastatin rescues rats from fatal pulmonary hypertension by inducing apoptosis of neointimal smooth muscle cells

Pharmacologic treatment for pulmonary arterial hypertension

PURPOSE OF REVIEW

Pulmonary arterial hypertension (PAH) has been a disease with limited treatment options and poor prognosis. This article reviews the recent advances that took place in the medical management of PAH.

RECENT FINDINGS

Sildenafil is a type 5 cGMP-specific phosphodiesterase inhibitor originally developed to treat erectile dysfunction. Multiple uncontrolled and randomized controlled trials have proven that it is useful in the treatment of PAH and it was approved by the US Food and Drug Administration. The switch from continuous intravenous infusion of epoprostenol to subcutaneous infusion of treprostinil has been proven feasible and safe. Bosentan has been shown effective as a monotherapy and it also improves survival in patients with functional classes III and IV. In smaller clinical trials bosentan has improved symptoms in different forms of PAH. Combinations of drugs of different classes such as prostanoids, endothelin receptor blockers and sildenafil are tested, and such a strategy improves both symptoms and survival. Animal models and anecdotal clinical experience suggest the possibility of using imatinib mesylate in PAH.

SUMMARY

With the approval of sildenafil, treatment options for this difficult disease have improved significantly. Combinations of drugs of different groups are promising and need further exploration.

Statins may ameliorate pulmonary hypertension via RhoA/Rho-kinase signaling pathway

Statins are the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors that function as potent inhibitors of cholesterol biosynthesis and have been used for many years for the treatment of hypercholesterolemia. However, accumulating experimental and clinical studies have revealed that the health benefits associated with statins treatment, particularly those conferred on the cardiovascular system, were the cholesterol-independent. Because statins inhibit an early step in the cholesterol biosynthetic pathway, they also inhibit the synthesis of isoprenoids such as farnesylpyrophosphate and geranylgeranylpyrophosphate, which are important postranslational lipid attachments for intracellular signaling molecules such as the Rho GTPases. The isoprenylation of Rho is a prerequisite for Rho activation, facilitating its interaction with the plasma membrane, undergoing GDP-GTP exchange and be activated. Inhibition of RhoA geranylgeranylation by statins decreases membrane GTP-bound active RhoA and subsequent Rho-kinase activity. Activated RhoA via its downstream effector Rho-kinase is involved in a wide range of cellular functions, such as cell migration, proliferation and apoptosis. Recently, rising evidences suggested that RhoA/Rho-kinase pathway was essentially involved in various models of pulmonary hypertension and statins effectively ameliorated pulmonary hypertension. Based on this findings, we hypothesis that statins attenuate pulmonary hypertension via RhoA/Rho-kinase signaling pathway in vivo.

Protective effects of atorvastatin in rat models of acute pulmonary embolism: Involvement of matrix metalloproteinase-9*

OBJECTIVE

Matrix metalloproteinases (MMPs) have been implicated in the pathophysiology of acute pulmonary embolism (APE)-induced pulmonary hypertension. Here, we evaluate the effects of atorvastatin pretreatment on APE-induced pulmonary hypertension, 24-hr mortality rate, and changes in plasma and lung MMP-2 and MMP-9 activities.

DESIGN

Controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Rats received atorvastatin (30 mg/kg/day orally) or tap water for 2 wks. In study 1, we examined whether atorvastatin affected APE-induced pulmonary hypertension by using a rat isolated lung perfusion model of APE. In study 2, we examined whether atorvastatin affects the survival rate after APE, which was induced by rapid intravenous injection of 14 mg/kg of a suspension of microspheres (or saline) into the tail vein.

MEASUREMENTS AND MAIN RESULTS

Plasma nitrite/nitrate concentrations were measured by chemiluminescence. Pretreatment with atorvastatin was associated with 49% higher nitrite/nitrate levels compared with controls (p < .05). In study 1, whereas APE increased mean pulmonary artery pressure (MPAP) by 13.0 +/- 1.6 mm Hg in perfused lungs isolated from rats pretreated with water, pretreatment with atorvastatin attenuated by 27% the increases in MPAP after APE. In study 2, pretreatment with atorvastatin was associated with a significant increase in 24-hr survival rate after APE, which was 48% in embolized rats pretreated with water and 64% in rats pretreated with atorvastatin (p < .05). Gelatin zymography of lung and plasma MMP-2 and MMP-9 was performed. Lungs and plasma from embolized rats showed higher levels of both pro- and activated forms of MMP-9 compared with those from nonembolized animals (all p < .05). However, pretreatment with atorvastatin attenuated by 32% the increases in lung-activated MMP-9 levels after APE (p < .05).

CONCLUSIONS

These results suggest that pretreatment with atorvastatin attenuates APE-induced pulmonary hypertension and increases 24-hr survival rate by mechanisms that result in attenuated increases in lung activated MMP-9 after APE.

Diagnostic and therapeutic challenges in patients with coexistent chronic obstructive pulmonary disease and chronic heart failure

Chronic obstructive pulmonary disease (COPD) and heart failure (CHF) are common conditions. The prevalence of COPD ranges from 20% to 30% in patients with CHF. The diagnosis of CHF can remain unsuspected in patients with COPD, because shortness of breath is attributed to COPD. Measurement of plasma B-type natriuretic peptide (BNP) levels helps to uncover unsuspected CHF in patients with COPD and clinical deterioration. Noninvasive assessment of cardiac function may be preferable to BNP to uncover unsuspected left ventricular (LV) systolic dysfunction in patients with stable COPD. Patients with COPD or CHF develop skeletal muscle alterations that are strikingly similar. Functional intolerance correlates with severity of skeletal muscle alterations but not with severity of pulmonary or cardiac impairment in COPD and CHF, respectively. Improvement of pulmonary or cardiac function does not translate into relief of functional intolerance in patients with COPD or CHF unless skeletal muscle alterations concomitantly regress. The mechanisms responsible for skeletal muscle alterations are incompletely understood in COPD and in CHF. Disuse and low-level systemic inflammation leading to protein synthesis/degradation imbalance are likely to contribute. The presence of COPD impacts on the treatment of CHF, as COPD is still viewed as a contraindication to beta-blockade. Therefore, COPD often deprives patients with CHF due to LV systolic dysfunction of the most beneficial pharmacologic intervention. A large body of data indicates that patients with COPD tolerate well selective beta-blockade that should not be denied to CHF patients with concomitant COPD.

Malignant Natural History of Asymptomatic Severe Aortic Stenosis: Benefit of Aortic Valve Replacement

BACKGROUND

Patients with asymptomatic severe aortic stenosis (AS) are reported to have a benign prognosis and hence the American College of Cardiology/American Heart Association guidelines do not recommend aortic valve replacement (AVR) for patients with isolated asymptomatic severe AS. However, symptoms are subjective and would depend upon patient's life style. We examined the natural and unnatural history of initially asymptomatic patients with severe AS.

METHODS

A search of our echocardiographic database between 1993 and 2003 yielded 740 patients with severe AS defined as aortic valve area 0.8 cm2 or less. Thorough chart reviews were conducted to collect clinical and pharmacologic data. Of these, 338 patients were asymptomatic at the initial encounter forming the study cohort.

RESULTS

Patient characteristics were the following: age 71 +/- 15 years, males 51%, aortic valve area 0.72 +/- 0.17 cm2, left ventricular ejection fraction 0.59 +/- 0.17. Ninety-nine (29%) patients had AVR during a mean follow-up of 3.5 years. Survival at 1, 2, and 5 years in the nonoperated patients were 67%, 56%, and 38%, respectively, compared with 94%, 93%, and 90% in those who underwent AVR (p < 0.0001). The Cox regression model was used to adjust for the effect of 18 clinical, echocardiographic, and pharmacologic variables on survival. The adjusted hazard ratio for death with AVR was 0.17 (95% confidence interval [CI] 0.10 to 0.29). In the nonoperated group, renal insufficiency (risk ratio [RR] 3.1, 95% CI 1.5 to 6.6), beta blocker use (RR 0.52, 95% CI 0.31 to 0.88), statin use (RR 0.52, 95% CI 0.27 to 0.99), age (per year RR 1.03, 95% CI 1.02 to 1.05), and left ventricular ejection fraction (per % RR 0.99, 95% CI 0.98 to 1.00) were found to be the independent predictors of mortality. The benefit of AVR was further supported by sensitivity and propensity score analyses.

CONCLUSIONS

Our observational data indicate that the natural history of asymptomatic AS is not benign and that survival is dramatically improved by AVR. Survival of the asymptomatic unoperated or nonoperable patients may potentially be improved by the use of beta blockers and statins.

The protective effect of HMG-CoA reductase inhibitors against monocrotaline-induced pulmonary hypertension in the rat might not be a class effect: comparison of pravastatin and atorvastatin

Hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, so called statins, improve endothelial function and exert antiproliferative effects on vascular smooth muscle cells of systemic vessels. This study aimed at comparing the protective effects of two statins, pravastatin and atorvastatin, against monocrotaline (MC)-induced pulmonary hypertension in rats. Pravastatin or atorvastatin (PS or AS, 10 mg/kg per day) or vehicle were given orally for 28 days to Wistar male rats injected or not with MC (60 mg/kg intraperitoneally). At 4 weeks, MC-injected rats developed severe pulmonary hypertension, with an increase in right ventricular pressure (RVP) and right ventricle/left ventricle + septum weight ratio associated with a decrease in acetylcholine- or sodium-nitroprusside-induced pulmonary artery dilation observed in vitro. Hypertensive pulmonary arteries exhibited an increase in medial thickness and endothelial cell apoptosis and a decrease of endothelial nitric oxide synthase (eNOS) expression. MC-rat lungs showed a significant decrease of eNOS (P < 0.01) and increase of cleaved caspase-3 (P < 0.05) expression determined by Western blotting. PS (P = 0.02) but not AS (P = 0.30) significantly limited the development of pulmonary hypertension (RVP in mmHg: 30 +/- 3, 36 +/- 4 vs. 45 +/- 4 and 14 +/- 1 for MC + PS, MC + AS, MC, and control groups, respectively). Both statins significantly reduced MC-induced right ventricle hypertrophy [RV/left ventricular (LV) + S, in mg/g: 0.46 +/- 0.04, 0.39 +/- 0.03, 0.62 +/- 0.05 and 0.29 +/- 0.01 for MC + PS, MC + AS, MC, and control groups, respectively; P < 0.05),and reduced MC-induced thickening (61 +/- 6 microm, 82 +/- 5 microm, 154 +/- 4 microm, and 59 +/- 2 microm for MC + PS, MC + AS, MC, and control groups, respectively; P = 0.01) of small intrapulmonary artery medial wall, with MC + AS still being different from the control group. PS but not AS partially restored acetylcholine-induced pulmonary artery vasodilation in MC rats (E(max)=65 +/- 5%, 49 +/- 6%, 46 +/- 3%, and 76 +/- 4% for MC + PS, MC + AS, MC, and control groups, respectively; P < 0.05 for MC + PS vs. other groups). Both statins prevented apoptosis and restored eNOS expression of pulmonary artery endothelial cells as well as in the whole lung with a more pronounced effect with PS compared with AS. In conclusion, despite its effects on eNOS expression, apoptosis, and medial wall thickening, AS was unable to significantly reduce pulmonary hypertension and to restore endothelium-dependent relaxation, suggesting intermolecular differences between the two HMG-CoA reductase inhibitors in the protection against MC-induced hypertension.

Pulmonary arterial hypertension and rheumatic diseases—from diagnosis to treatment

Survival rates in pulmonary arterial hypertension (PAH) associated with rheumatic diseases, in particular connective tissue diseases such as systemic sclerosis, are even lower than in idiopathic PAH. These low survival rates highlight the need for early diagnosis and treatment in these patients. Transthoracic Doppler-echocardiography is most often used for diagnostic screening of patients at risk. Other screening tests are serum pro-brain-natriuretic peptide (pro-BNP) and diffusion capacity for carbon monoxide (DLCO), which appear to be changed early in the course of the PAH associated with connective tissue diseases. The diagnosis needs to be confirmed by right heart catheterization, which is recommended in all patients with suspected PAH. Besides the conventional background therapy, a number of specific therapies have been evaluated in randomized controlled trials in the recent years. These therapies include prostacyclins and prostacyclin analogues, endothelin-receptor antagonists and phosphodiesterase-5 inhibitors. Response to treatment can be measured by exercise capacity (e.g. 6 min walk distance) and pro-BNP, although certain aspects of validation for these outcome measures are lacking in PAH associated with connective tissue diseases.

How valid are animal models to evaluate treatments for pulmonary hypertension?

Various animal models of pulmonary hypertension (PH) exist, among which injection of monocrotaline (MCT) and exposure to hypoxia are used most frequently. These animal models have not only been used to characterize the pathophysiology of PH and its sequelae such as right ventricular hypertrophy and failure, but also to test novel therapeutic strategies. This manuscript summarizes the available treatment studies in animal models of PH, and compares the findings to those obtained in patients with PH. The analysis shows that all approaches which have proven successful in patients, most notably prostacyclin and its analogs and endothelin receptor antagonists, are also effective in various animal models. However, the opposite it not always true. Therefore, promising results in animals have to be interpreted carefully until confirmed in clinical studies.

The HMG-CoA reductase inhibitor, pravastatin, prevents the development of monocrotaline-induced pulmonary hypertension in the rat through reduction of endothelial cell apoptosis and overexpression of eNOS

HMG-CoA reductase inhibitors improve endothelial function and exert antiproliferative effects on vascular smooth muscle cells of systemic vessels. This study was aimed to assess the protective effects of pravastatin (an HMG-CoA reductase inhibitor) against monocrotaline-induced pulmonary hypertension in rats. Pravastatin (PS, 10 mg/kg/day) or vehicle were given orally for 28 days to Wistar male rats injected or not with monocrotaline (MC, 60 mg/kg intraperitonealy) and treated or not by N(omega)-nitro-L-arginine methyl ester (L-NAME) 15 mg/kg/day. At 4 weeks, monocrotaline-injected rats developed severe pulmonary hypertension, with an increase in right ventricular pressure (RVP) and right ventricle/left ventricle+septum weight ratio (RV/LV+S), associated with a decrease in pulmonary artery dilation induced either by acetylcholine or sodium nitroprusside. Hypertensive pulmonary arteries exhibited an increase in medial thickness, medial wall area, endothelial cell apoptosis, and a decrease of endothelial nitric oxide synthase (eNOS) expression. Monocrotaline-rat lungs showed a significant decrease of eNOS expression (4080+/-27 vs 12189+/-761 arbitrary density units [ADU] for MC and control groups respectively, P<0.01) and a significant increase of cleaved caspase-3 expression by western blotting (Control=11628+/-2395 vs MC=2326+/-2243 ADU, P<0.05). A non-significant trend toward a reduced mortality was observed with pravastatin (relative risk of death = 0.33; 95% confidence interval [0.08-1.30], P= 0.12 for MC+PS vs MC groups). Pravastatine induced a protection against the development of the pulmonary hypertension (RVP in mmHg: 30+/-3 vs 45+/-4 and RV/LV+S: 0.46+/-0.04 vs 0.62+/-0.05 for MC+PS and MC groups respectively, P<0.05) and was associated with a significant reduction of MC-induced thickening (61+/-6 mum vs 81+/-3 mum for MC+PS and MC groups respectively, P= 0.01) of the medial wall of the small intrapulmonary arteries. Pravastatin partially restored acetylcholine-induced pulmonary artery vasodilation in MC rats (Emax=65+/-5% and 46+/-3% for MC+PS and MC group respectively, P<0.05) but had no effect on acetylcholine-induced pulmonary artery vasodilation in MC+L-NAME rats. It also prevented apoptosis and restored eNOS expression of pulmonary artery endothelial cells, as well as in the whole lung. Pravastatin reduces the development of monocrotaline-induced pulmonary hypertension and improves endothelium-dependent pulmonary artery relaxation, probably through a reduced apoptosis and a restored eNOS expression of endothelial cells.

Potential therapeutic role for statins in respiratory disease

Statins reduce cholesterol levels by inhibiting 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and have an established role in the treatment of atherosclerotic disease. Recent research has identified anti-inflammatory properties of statins. Statins appear to reduce the stability of lipid raft formation with subsequent effects on immune activation and regulation, and also prevent the prenylation of signalling molecules with subsequent downregulation of gene expression. Both these effects result in reduced cytokine, chemokine, and adhesion molecule expression, with effects on cell apoptosis or proliferation. This review considers the evidence for the anti-inflammatory properties of statins in the lung, and how these effects are being applied to research into the role of statins as a novel treatment of respiratory diseases.

Pulmonary arterial hypertension: new insights and new hope

Pulmonary arterial hypertension (PAH) is a devastating disorder characterized by abnormal increased vasoconstriction and vascular remodelling. In this review we discuss the pathophysiology, genetic basis and clinical features of this disorder. Current therapy of PAH is based on an understanding of its pathogenesis, and we review current treatment options based on the pathophysiology of the disease. We discuss three promising novel therapies studied in animal models and human tissue. All three therapies appear to prevent and reduce pulmonary arterial medial hyperplasia through their anti-proliferative and/or pro-apoptotic effects: serotonin transporter inhibitors by blocking serotonin uptake; dichloroacetate by activating voltage-gated potassium channels; and simvastatin by preventing activation of small GTPases.

2-Methoxyestradiol mediates the protective effects of estradiol in monocrotaline-induced pulmonary hypertension

When exposed to chronic hypoxia or toxin monocrotaline (MCT), female animals develop less severe pulmonary arterial hypertension (PH) compared to males; ovariectomy (OVX) exacerbates PH, and OVX animals treated with estradiol (E2) develop less severe disease. There is a line of evidence suggesting that cardiovascular protective effects of E2 are mediated by its major metabolite, 2-methoxyestradiol (2ME). Recently, we have shown that 2ME attenuates the development and retards the progression of MCT-induced pulmonary hypertension in male rats. We hypothesized that the protective effects of E2 in experimental PH are mediated by 2ME. Subsets of intact and OVX female rats were injected saline (Cont and OXV groups) or MCT (60 mg/kg; MCT and OVX-MCT groups) and some of OVX-MCT animals were treated with 2ME (10 microg/kg/h via osmotic minipumps; OVX-MCT+2ME). After 28 days, MCT caused PH, i.e., increased right ventricular peak systolic pressure (RVPSP) and right ventricle/left ventricle+septum (RV/LV+S) ratio, induced inflammatory response in the lungs and caused media hypertrophy (media thickness and % media index) and adventitia widening of small size pulmonary arteries. Ovariectomy exacerbated the disease, i.e., further increased RVPSP, and RV/LV+S ratio, and augmented vascular remodeling and inflammatory response. In diseased OVX rats, treatment with 2ME prevented the worsening of PH and attenuated the inflammatory response and vascular remodeling. No mortality was recorded in the OVX-MCT+2ME group vs. 10% and 36% mortality in the MCT and OVX-MCT group, respectively. This study suggests that 2-methoxyestradiol (a major non-estrogenic metabolite of E2) may mediate the protective effects of estradiol in MCT-induced PH, and warrants further evaluation of 2ME for treatment of PH.

Simvastatin causes endothelial cell apoptosis and attenuates severe pulmonary hypertension

Severe pulmonary hypertension (SPH) is characterized by precapillary arteriolar lumen obliteration, dramatic right ventricular hypertrophy, and pericardial effusion. Our recently published rat model of SPH recapitulates major components of the human disease. We used this model to develop new treatment strategies for SPH. SPH in rats was induced using VEGF receptor blockade in combination with chronic hypoxia. A large variety of drugs used in this study, including anticancer drugs (cyclophosphamide and paclitaxel), the angiotensin-converting enzyme inhibitor lisinopril, the antiangiogenic agent thalidomide, and the peroxisome proliferator-actived receptor-gamma agonist PGJ2, failed to decrease mean pulmonary artery pressure (PAP) or right ventricular hypertrophy. In contrast, treatment of rats with established SPH with simvastatin markedly reduced mean PAP and right ventricular hypertrophy, and this reduction was associated with caspase-3 activation and pulmonary microvascular endothelial cell apoptosis. Simvastatin partially restored caveolin-1, caveolin-2, and phospho-caveolin expression in vessel walls. In rat primary pulmonary microvascular endothelial cells, simvastatin induced caspase 3 activation and Rac 1 expression while suppressing Rho A and attenuated levels of Akt and ERK phosphorylation. We conclude that simvastatin is effective in inducing apoptosis in hyperproliferative pulmonary vascular lesions and could be considered as a potential drug for treatment of human SPH.

Mediators and modulators of pulmonary arterial hypertension

Pulmonary hypertension (PH), defined as a mean pulmonary arterial (PA) pressure of >25 mmHg at rest or >30 mmHg during exercise, is characterized by a progressive and sustained increase in pulmonary vascular resistance that eventually leads to right ventricular failure. Clinically, PH may result from a variety of underlying diseases (Table 1 and Refs. 50, 113, 124). Pulmonary arterial hypertension (PAH) may be familial (FPAH) or sporadic (idiopathic, IPAH), formerly known as primary pulmonary hypertension, i.e., for which there is no demonstrable cause. More often, PAH is due to a variety of identifiable diseases including scleroderma and other collagen disorders, liver disease, human immunodeficiency virus, and the intake of appetite-suppressant drugs such as phentermine and fenfluramine (72). Other, more common, causes of PAH include left ventricular failure (perhaps the most common cause), valvular lesions, chronic pulmonary diseases, sleep-disordered breathing, and prolonged residence at high altitude. This classification, now widely accepted, was first proposed at a meeting in Evian, France, in 1998, and modified in Venice, Italy, in 2003 (124).

Hydroxymethylglutaryl-coenzyme A reductase inhibitors induce apoptosis in human cardiac myocytes in vitro

Recent findings have implicated hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors or statins, an established class of drugs for the treatment of hypercholesterolemia, in tissue remodeling in the heart. Statins induce apoptosis in different cell culture systems including rat neonatal cardiomyocytes. We investigated possible effects of different statins in vitro in human adult cardiac myocytes on the expression of proteins thought to be involved in the regulation of apoptosis such as Mcl-1, an inhibitor of apoptosis, Bax, an inducer of apoptosis, as well as on cytoplasmic histone-associated-DNA-fragments. Human adult cardiac myocytes (HACM) were treated with different statins at concentrations from 0.01 to 5 microM for up to 96 h. Whereas the lipophilic statin simvastatin at a concentration of 5 microM downregulated Mcl-1 mRNA by 49%, the hydrophilic pravastatin had no effect. Bax mRNA levels were not affected by neither of the statins. Simvastatin but not pravastatin reduced Mcl-1 protein expression whereas Bax protein was not detectable in HACM as determined by Western blotting. Simvastatin, atorvastatin and fluvastatin induced an up to seven-fold increase in histone-associated-DNA-fragments whereas pravastatin did not. Simvastatin up regulated histone-associated-DNA-fragments dose-dependently, and mevalonate and geranylgeranyl pyrophosphate reversed this effect to control levels. Our results show that lipophilic statins can induce a pro-apoptotic state in human adult cardiac myocytes in vitro. We speculate that, similar to findings in animal models, statins might be involved in the attenuation of cardiac hypertrophy and remodeling in humans by modulating the balance between cell survival and apoptosis.

A novel peptide CXCR ligand derived from extracellular matrix degradation during airway inflammation

We describe the tripeptide neutrophil chemoattractant N-acetyl Pro-Gly-Pro (PGP), derived from the breakdown of extracellular matrix (ECM), which shares sequence and structural homology with an important domain on alpha chemokines. PGP caused chemotaxis and production of superoxide through CXC receptors, and administration of peptide caused recruitment of neutrophils (PMNs) into lungs of control, but not CXCR2-deficient mice. PGP was generated in mouse lung after exposure to lipopolysaccharide, and in vivo and in vitro blockade of PGP with monoclonal antibody suppressed PMN responses as much as chemokine-specific monoclonal antibody. Extended PGP treatment caused alveolar enlargement and right ventricular hypertrophy in mice. PGP was detectable in substantial concentrations in a majority of bronchoalveolar lavage samples from individuals with chronic obstructive pulmonary disease, but not control individuals. Thus, PGP's activity links degradation of ECM with neutrophil recruitment in airway inflammation, and PGP may be a biomarker and therapeutic target for neutrophilic inflammatory diseases.

Simvastatin enhances bone morphogenetic protein receptor type II expression

Statins confer therapeutic benefits in systemic and pulmonary vascular diseases. Bone morphogenetic protein (BMP) receptors serve essential signaling functions in cardiovascular development and skeletal morphogenesis. Mutations in BMP receptor type II (BMPR2) are associated with human familial and idiopathic pulmonary arterial hypertension, and pathologic neointimal proliferation of vascular endothelial and smooth muscle cells within small pulmonary arteries. In severe experimental pulmonary hypertension, simvastatin reversed disease and conferred a 100% survival advantage. Here, modulation of BMPR2 gene expression by simvastatin is characterized in human embryonic kidney (HEK) 293T, pulmonary artery smooth muscle, and lung microvascular endothelial cells (HLMVECs). A 1.4kb BMPR2 promoter containing Egr-1 binding sites confers reporter gene activation in 293T cells which is partially inhibited by simvastatin. Simvastatin enhances steady-state BMPR2 mRNA and protein expression in HLMVEC, through posttranscriptional mRNA stabilization. Simvastatin induction of BMPR2 expression may improve BMP-BMPR2 signaling thereby enhancing endothelial differentiation and function.

Inhibition of RhoA/Rho kinase pathway is involved in the beneficial effect of sildenafil on pulmonary hypertension

Inhibition of the type 5 phosphodiesterase and inhibition of Rho kinase are both effective in reducing pulmonary hypertension (PH). Here we investigate whether Rho kinase inhibition is involved in the beneficial effect of the type 5 phosphodiesterase inhibitor sildenafil on PH. Chronic hypoxia-induced PH in rats is associated with an increase in RhoA activity in pulmonary artery that was maximal after 2 days (10.7+/-0.9-fold increase, n=6, P<0.001). The activity of Rho kinase assessed by measuring the level of myosin phosphatase target subunit 1 (MYPT1) phosphorylation was also increased (5.7+/-0.8-fold over control, n=8). Chronic fasudil (30 mg kg(-1) day(-1); 14 days) and sildenafil (25 mg kg(-1) day(-1); 14 days) treatments reduced PH and pulmonary cardiovascular remodelling, and inhibited the MYPT1 phosphorylation in pulmonary artery from hypoxic rats by 82.3+/-3% (n=4) and by 76.6+/-2% (n=4), respectively. The inhibitory effect of sildenafil (10 microM) on MYPT1 phosphorylation was demonstrated by the loss of actin stress fibres in vascular smooth muscle cells. However, in vitro kinase assays indicated that sildenafil had no direct inhibitory action on Rho kinase activity. Sildenafil treatment induced increased RhoA phosphorylation and association to its cytosolic inhibitory protein, guanine dissociation inhibitor (GDI) in pulmonary artery.We propose that sildenafil inhibits RhoA/Rho kinase-dependent functions in pulmonary artery through enhanced RhoA phosphorylation and cytosolic sequestration by GDI. The inhibition of intracellular events downstream of RhoA thus participates in the beneficial effect of sildenafil on PH.

von Willebrand factor independently predicts long-term survival in patients with pulmonary arterial hypertension

OBJECTIVES

We hypothesized that higher plasma levels of von Willebrand factor (vWF) and reduced ristocetin cofactor activity (RCA)/vWF ratios at baseline and follow-up would be associated with an increased risk of death in patients with pulmonary arterial hypertension (PAH).

BACKGROUND

Endothelial injury and dysfunction cause increased vWF levels in patients with cardiovascular disease. Increased vWF is associated with a higher risk of death in patients with coronary artery disease, congestive heart failure, and ARDS. In PAH, vWF is elevated and functions abnormally, resulting in reduced platelet binding. The ability of vWF to bind platelets is reflected by RCA.

METHODS

We performed a retrospective cohort study of 66 PAH patients who underwent initial evaluation at our center from January 1994 to June 2002. The primary outcome was death or lung transplantation.

RESULTS

vWF level was directly associated with Factor VIII activity, RCA, fibrinogen, and prothrombin time (p < or = 0.01). vWF levels at baseline and follow-up were associated with the risk of death (hazard ratio [HR] per 50% increase, 1.4; 95% confidence interval [CI], 1.1 to 1.8 [p = 0.02]; and HR per 50% increase, 1.5; 95% CI, 1.1 to 2.0 [p = 0.011]; n = 48, respectively). RCA/vWF ratios were not associated with outcome. These results were unaffected by adjustment for demographics, baseline hemodynamics, laboratory results, or PAH therapy in multivariate analyses.

CONCLUSIONS

Increased vWF levels at baseline and follow-up are associated with worse survival in patients with PAH; however, RCA/vWF ratios are not. The hemostatic effects of vWF do not account for these findings. This suggests that endothelial injury and dysfunction may persist despite treatment and may impact on disease course. Therapies that target endothelial injury may therefore improve outcomes for patients with PAH.

Traitement de l’hypertension artérielle pulmonaire

Pulmonary arterial hypertension (PAH) is characterized by vasoconstriction, in situ thrombosis, and vascular remodeling of small pulmonary arteries. It induces a fixed pulmonary arterial obstruction, persistent elevation of pulmonary arterial resistance, and eventually right heart failure. Conventional therapy is based on simple measures (exercise limitation) and nonspecific treatments (warfarin, diuretics, and oxygen). Pure vasodilators, such as calcium channel blockers, are effective only in a minority of patients who have an acute response to vasodilator testing. Intravenous prostacyclin (epoprostenol) and endothelin receptor blockers have vasodilator and antiproliferative properties. Epoprostenol therapy has significantly improved PAH prognosis and remains the first-line treatment for patients with the most severe disease. Bosentan is an interesting first-line treatment for NYHA functional class III patients. Availability of novel specific drugs (endothelin receptor type A antagonists, prostacyclin analogues, type 5 phosphodiesterase inhibitors) is opening new perspectives in PAH treatment. The long-term benefit of these drugs remains to be evaluated and their respective place in treatment of these patients is still uncertain. The evolution of therapy from vasodilators to antiproliferative agents reflects the advancement in our understanding of the mechanisms mediating pulmonary arterial hypertension.

Effects of Nicorandil on Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats

We investigated whether nicorandil might prevent and reverse monocrotaline (MCT)-induced pulmonary arterial hypertension. Rats were injected with 50 mg/kg of MCT subcutaneously and randomized to either 7.5 mg/kg/d of nicorandil in drinking water or placebo for 3 weeks. Animals that were treated with MCT and survived for 3 weeks were assigned to either nicorandil or placebo. Nicorandil markedly attenuated pulmonary arterial hypertension with severe structural remodeling of the pulmonary vessels. The survival rate at 3 weeks after treatment was significantly increased in the nicorandil group compared with the placebo group (73% versus 39%, P<0.05). In the placebo group, endothelial nitric oxide synthase (eNOS) protein was significantly decreased, the numbers of the CD45-positive cells and those of the proliferating cell nuclear antigen-positive cells were increased in the lung tissue, and P-selectin was intensely expressed on the endothelium of the pulmonary arteries. These features were prevented by nicorandil. Late treatment with nicorandil did not palliate established pulmonary arterial hypertension nor improved survival. Thus, nicorandil inhibited development of MCT-induced pulmonary arterial hypertension but failed to reverse it. These effects were associated with marked up-regulation of diminished lung eNOS protein along with improvement of pulmonary vascular endothelial activation and anti-inflammatory and anti-proliferative effects in the lung tissue.

Gene therapy targeting survivin selectively induces pulmonary vascular apoptosis and reverses pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by genetic and acquired abnormalities that suppress apoptosis and enhance cell proliferation in the vascular wall, including downregulation of the bone morphogenetic protein axis and voltage-gated K+ (Kv) channels. Survivin is an "inhibitor of apoptosis" protein, previously thought to be expressed primarily in cancer cells. We found that survivin was expressed in the pulmonary arteries (PAs) of 6 patients with PAH and rats with monocrotaline-induced PAH, but not in the PAs of 3 patients and rats without PAH. Gene therapy with inhalation of an adenovirus carrying a phosphorylation-deficient survivin mutant with dominant-negative properties reversed established monocrotaline-induced PAH and prolonged survival by 25%. The survivin mutant lowered pulmonary vascular resistance, RV hypertrophy, and PA medial hypertrophy. Both in vitro and in vivo, inhibition of survivin induced PA smooth muscle cell apoptosis, decreased proliferation, depolarized mitochondria, caused efflux of cytochrome c in the cytoplasm and translocation of apoptosis-inducing factor into the nucleus, and increased Kv channel current; the opposite effects were observed with gene transfer of WT survivin, both in vivo and in vitro. Inhibition of the inappropriate expression of survivin that accompanies human and experimental PAH is a novel therapeutic strategy that acts by inducing vascular mitochondria-dependent apoptosis.

Simvastatin inhibits cigarette smoking-induced emphysema and pulmonary hypertension in rat lungs

RATIONALE

In cigarette smoking-induced chronic obstructive pulmonary disease, structural and functional derangements are characterized by parenchymal destruction and pulmonary hypertension. Statins are 3-hydroxy-3-methyl-glutaryl-coenzyme-A reductase inhibitors that have been used as lipid-lowering agents. These drugs also have additional pharmacologic properties, including antiinflammation, scavenging reactive oxygen species, restoring endothelial function, and antithrombogenesis, all of which can counteract the harmful effects of cigarette smoking.

OBJECTIVE

We performed assays to determine whether simvastatin could attenuate lung damage induced by chronic cigarette smoking in rats.

METHODS

In Sprague-Dawley rats exposed to cigarette smoke for 16 weeks, morphologic changes in the lungs and pulmonary arterial pressure were examined.

MAIN RESULTS

Simvastatin inhibited lung parenchymal destruction and development of pulmonary hypertension, and also inhibited peribronchial and perivascular infiltration of inflammatory cells and induction of matrix metalloproteinase-9 activity in lung tissue. Simvastatin additionally prevented pulmonary vascular remodeling and the changes in endothelial nitric oxide synthase expression induced by smoking. In human lung microvascular endothelial cells, simvastatin increased expression of endothelial nitric oxide synthase mRNA.

CONCLUSIONS

Simvastatin ameliorated the structural and functional derangements of the lungs caused by cigarette smoking, partly by suppressing inflammation and matrix metalloproteinase-9 induction and preventing pulmonary vascular abnormality. These findings indicate that statins may play a role in the treatment of cigarette smoking-induced chronic obstructive pulmonary disease.

The statins--therapeutic diversity in renal disease?

PURPOSE OF REVIEW

Statins significantly reduce cholesterol synthesis and reduce cardiovascular morbidity and mortality. In addition, they appear to have beneficial effects independent of their ability to lower cholesterol. Recent publications suggesting a potential role for statin therapy in chronic renal insufficiency, hypertension and following organ transplantation are reviewed.

RECENT FINDINGS

Pharmacokinetic studies have shown statins to be well-tolerated and effective in patients on long-term haemodialysis, providing equivalent control of lipid levels to that seen in matched controls. Preliminary clinical trials suggest that statins may have beneficial disease-modifying effects in chronic inflammatory disease. Furthermore, immunosuppressive and immunomodulatory actions may confer benefit following cardiac transplantation, but this remains to be demonstrated definitively in renal transplant patients. Data to date suggest that, in addition to reduction of cardiovascular risk, statins may help slow the progress of chronic renal insufficiency, particularly in patients with proteinuria. Addition of statin therapy may also contribute to the control of systemic and pulmonary hypertension.

SUMMARY

Encouraging data in support of a wider spectrum of use for statins are emerging. In addition to reduction of cardiovascular risk through lipid lowering, they may represent an important adjunctive therapy in patients with chronic kidney diseases and post-transplantation. However, further large, well-designed clinical trials are required before their widespread use can be recommended in this setting.

Regulation of therapeutic apoptosis: a potential target in controlling hypertensive organ damage

Cell growth and survival are potential therapeutic targets for the control of complications associated with hypertension. In most cardiovascular disorders, cardiac fibroblasts and large-vessel smooth muscle cells can replicate and thus contribute to the disease. We propose that cardiovascular hyperplasia may be reversed via therapeutic apoptosis induction with drugs that are safe and already used in the clinic. We first reported that, irrespective of the drug class, those drugs that are able to induce regression of cardiovascular hypertrophy are also able to reverse cardiovascular hyperplasia via apoptosis. Drugs active in this regard include inhibitors of the renin-angiotensin system, calcium channel blockers, and beta-blockers. Moreover, the effects of these drugs on cell survival is not merely secondary to blood pressure reduction. Therapeutic apoptosis in the cardiovascular system of the spontaneously hypertensive rat is characterized by a rapid and transient onset following initiation of antihypertensive treatment. Herein, the induction and termination of therapeutic apoptosis during drug treatment of hypertension will be briefly reviewed and supported by novel data suggesting that reversal of cardiovascular hyperplasia is associated with reduced cell growth and a resistance to further induction of therapeutic apoptosis, as shown in spontaneously hypertensive rats receiving an intermittent regime of nifedipine therapy. We propose that the presence of a cell subpopulation with defective cell cycle regulation may determine organ susceptibility to undergo therapeutic apoptosis.Key words: apoptosis, hypertension, hyperplasia, growth, nifedipine.

Dichloroacetate prevents and reverses pulmonary hypertension by inducing pulmonary artery smooth muscle cell apoptosis

The pulmonary arteries (PA) in pulmonary arterial hypertension (PAH) are constricted and remodeled;. They have suppressed apoptosis, partly attributable to suppression of the bone morphogenetic protein axis and selective downregulation of PA smooth muscle cell (PASMC) voltage-gated K+ channels, including Kv1.5. The Kv downregulation-induced increase in [K+]i, tonically inhibits caspases, further suppressing apoptosis. Mitochondria control apoptosis and produce activated oxygen species like H2O2, which regulate vascular tone by activating K+ channels, but their role in PAH is unknown. We show that dichloroacetate (DCA), a metabolic modulator that increases mitochondrial oxidative phosphorylation, prevents and reverses established monocrotaline-induced PAH (MCT-PAH), significantly improving mortality. Compared with MCT-PAH, DCA-treated rats (80 mg/kg per day in drinking water on day 14 after MCT, studied on day 21) have decreased pulmonary, but not systemic, vascular resistance (63% decrease, P<0.002), PA medial thickness (28% decrease, P<0.0001), and right ventricular hypertrophy (34% decrease, P<0.001). DCA is similarly effective when given at day 1 or day 21 after MCT (studied day 28) but has no effect on normal rats. DCA depolarizes MCT-PAH PASMC mitochondria and causes release of H2O2 and cytochrome c, inducing a 10-fold increase in apoptosis within the PA media (TUNEL and caspase 3 activity) and decreasing proliferation (proliferating-cell nuclear antigen and BrdU assays). Immunoblots, immunohistochemistry, laser-captured microdissection-quantitative reverse-transcription polymerase chain reaction and patch-clamping show that DCA reverses the Kv1.5 downregulation in resistance PAs. In summary, DCA reverses PA remodeling by increasing the mitochondria-dependent apoptosis/proliferation ratio and upregulating Kv1.5 in the media. We identify mitochondria-dependent apoptosis as a potential target for therapy and DCA as an effective and selective treatment for PAH.

Pulmonary arterial hypertension: a look to the future

The Third World Symposium on Pulmonary Arterial Hypertension served not only as a forum for the presentation of state-of-the art overviews of the pathobiologic and clinical aspects of pulmonary arterial hypertension (PAH), but also afforded an opportunity to the international scientific community to explore future directions of research and collaboration. This summary provides a brief overview of future directions in the field.

Longitudinal transcriptional analysis of developing neointimal vascular occlusion and pulmonary hypertension in rats

Pneumonectomized rats injected with the alkaloid toxin, monocrotaline, develop progressive neointimal pulmonary vascular obliteration and pulmonary hypertension resulting in right ventricular failure and death. The antiproliferative immunosuppressant, triptolide, attenuates neointimal formation and pulmonary hypertension in this disease model (Faul JL, Nishimura T, Berry GJ, Benson GV, Pearl RG, and Kao PN. Am J Respir Crit Care Med 162: 2252–2258, 2000). Pneumonectomized rats, injected with monocrotaline on day 7, were killed at days 14, 21, 28, and 35 for measurements of physiology and gene expression patterns. These data were compared with pneumonectomized, monocrotaline-injected animals that received triptolide from day 5 to day 35. The hypothesis was tested that a group of functionally related genes would be significantly coexpressed during the development of disease and downregulated in response to treatment. Transcriptional analysis using total lung RNA was performed on replicate animals for each experimental time point with exploratory data analysis followed by statistical significance analysis. Marked, statistically significant increases in proteases (particularly derived from mast cells) were noted that parallel the development of vascular obliteration and pulmonary hypertension. Mast-cell-derived proteases may play a role in regulating the development of neointimal pulmonary vascular occlusion and pulmonary hypertension in response to injury.

Long-Term Treatment With a Rho-Kinase Inhibitor Improves Monocrotaline-Induced Fatal Pulmonary Hypertension in Rats

Primary pulmonary hypertension is a fatal disease characterized by endothelial dysfunction, hypercontraction and proliferation of vascular smooth muscle cells (VSMCs), and migration of inflammatory cells, for which no satisfactory treatment has yet been developed. We have recently demonstrated that intracellular signaling pathway mediated by Rho-kinase, an effector of the small GTPase Rho, is involved in the pathogenesis of arteriosclerosis. In the present study, we examined whether the Rho-kinase–mediated pathway is also involved in the pathogenesis of fatal pulmonary hypertension in rats. Animals received a subcutaneous injection of monocrotaline, which resulted in the development of severe pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular lesions in 3 weeks associated with subsequent high mortality rate. The long-term blockade of Rho-kinase with fasudil, which is metabolized to a specific Rho-kinase inhibitor hydroxyfasudil after oral administration, markedly improved survival when started concomitantly with monocrotaline and even when started after development of pulmonary hypertension. The fasudil treatment improved pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular lesions with suppression of VSMC proliferation and macrophage infiltration, enhanced VSMC apoptosis, and amelioration of endothelial dysfunction and VSMC hypercontraction. These results indicate that Rho-kinase–mediated pathway is substantially involved in the pathogenesis of pulmonary hypertension, suggesting that the molecule could be a novel therapeutic target for the fatal disorder.