Autophagy mechanism of right ventricular remodeling in murine model of pulmonary artery constriction

Although right ventricular failure (RVF) is the hallmark of pulmonary arterial hypertension (PAH), the mechanism of RVF is unclear. Development of PAH-induced RVF is associated with an increased reactive oxygen species (ROS) production. Increases in oxidative stress lead to generation of nitro-tyrosine residues in tissue inhibitor of metalloproteinase (TIMPs) and liberate active matrix metalloproteinase (MMPs). To test the hypothesis that an imbalance in MMP-to-TIMP ratio leads to interstitial fibrosis and RVF and whether the treatment with folic acid (FA) alleviates ROS generation, maintains MMP/TIMP balance, and regresses interstitial fibrosis, we used a mouse model of pulmonary artery constriction (PAC). After surgery mice were given FA in their drinking water (0.03 g/l) for 4 wk. Production of ROS in the right ventricle (RV) was measured using oxidative fluorescent dye. The level of MMP-2, -9, and -13 and TIMP-4, autophagy marker (p62), mitophagy marker (LC3A/B), collagen interstitial fibrosis, and ROS in the RV wall was measured. RV function was measured by Millar catheter. Treatment with FA decreased the pressure to 35 mmHg from 50 mmHg in PAC mice. Similarly, RV volume in PAC mice was increased compared with the Sham group. A robust increase of ROS was observed in RV of PAC mice, which was decreased by treatment with FA. The protein level of MMP-2, -9, and -13 was increased in RV of PAC mice in comparison with that in the sham-operated mice, whereas supplementation with FA abolished this effect and mitigated MMPs levels. The protein level of TIMP-4 was decreased in RV of PAC mice compared with the Sham group. Treatment with FA helped PAC mice to improve the level of TIMP-4. To further support the claim of mitophagy occurrence during RVF, the levels of LC3A/B and p62 were measured by Western blot and immunohistochemistry. LC3A/B was increased in RV of PAC mice. Similarly, increased p62 protein level was observed in RV of PAC mice. Treatment with FA abolished this effect in PAC mice. These results suggest that FA treatment improves MMP/TIMP balance and ameliorates mitochondrial dysfunction that results in protection of RV failure during pulmonary hypertension.     

Synergistic effects of ANP and sildenafil on cGMP levels and amelioration of acute hypoxic pulmonary hypertension

We hypothesized that the phosphodiesterase 5 inhibitor, sildenafil, and the guanosine cyclase stimulator, atrial natriuretic peptide (ANP), would act synergistically to increase cGMP levels and blunt hypoxic pulmonary hypertension in rats, because these compounds act via different mechanisms to increase the intracellular second messenger. Acute hypoxia: Adult Sprague-Dawley rats were gavaged with sildenafil (1 mg/ kg) or vehicle and exposed to acute hypoxia with and without ANP (10(-8)-10(-5) M ). Sildenafil decreased systemic blood pressure (103 +/- 10 vs. 87 +/- 6 mm Hg, P < 0.001) and blunted the hypoxia-induced increase in right ventricular systolic pressure (RVSP; percent increase 73.7% +/- 9.4% in sildenafil-treated rats vs. 117.2% +/- 21.1% in vehicle-treated rats, P = 0.03). Also, ANP and sildenafil had synergistic effects on blunting the hypoxia-induced increase in RVSP (P < 0.001) and on rising plasma cGMP levels (P < 0.05). Chronic hypoxia: Other rats were exposed to prolonged hypoxia (3 weeks, 0.5 atm) after subcutaneous implantation of a sustained-release pellet containing lower (2.5 mg), or higher (25 mg) doses of sildenafil, or placebo. Higher-dose, but not lower-dose sildenafil blunted the chronic hypoxia-induced increase in RVSP (P = 0.006). RVSP and plasma sildenafil levels were inversely correlated in hypoxic rats (r(2) = 0.68, P = 0.044). Lung cGMP levels were increased by both chronic hypoxia and sildenafil, with the greatest increase achieved by the combination. Plasma and right ventricular (RV) cGMP levels were increased by hypoxia, but sildenafil had no effect. RV hypertrophy and pulmonary artery muscularization were also unaffected by sildenafil. In conclusion, sildenafil and ANP have synergistic effects on the blunting of hypoxia-induced pulmonary vasoconstriction. During chronic hypoxia, sildenafil normalizes RVSP, but in the doses used, sildenafil has no effect on RV hypertrophy or pulmonary vascular remodeling.     

Human immunodeficiency virus transgenic rats exhibit pulmonary hypertension

Human immunodeficiency virus (HIV)-associated pulmonary arterial hypertension (PAH) is a serious noninfectious disease involving an aberrant increase in pressure in the blood vessels of the lung, which leads to right ventricular (RV) heart failure and can eventually result in death. A lack of viable animal models of HIV-PAH has limited the identification of signaling pathways involved in HIV-mediated onset and progression of PAH. To determine whether the HIV-1 transgenic (HIV Tg) rat displays pathophysiological end points associated with PAH, we evaluated peak RV systolic pressure (RVSP), RV hypertrophy, pulmonary vessel remodeling, and alterations in gene expression by real-time PCR and microarray. RVSP was measured by RV catheterization via the right jugular vein in 3- and 9-mo-old HIV Tg and age-matched Fischer 344 (control) male rats while under 2% isoflurane anesthesia. RVSP was elevated in the HIV Tg rats (34.2 ± 2.5 mmHg) compared with the F344 controls (21.2 ± 2.5 mmHg), with more significant elevations in the 9-mo-old HIV Tg rats (42.5 ± 3.7 mmHg). We observed significant increases in RV wall thickness in HIV Tg rats compared with controls, both histologically and by echocardiograph measurement. HIV Tg rats also show increased thickening of the pulmonary artery and remodeling of small pulmonary arteries, as well as altered expression of gene pathways associated with PAH. These data represent the first analysis of PAH in HIV Tg rats and suggest that this model will be useful for investigating pathways and identifying potential therapies for HIV-PAH.     

Hemodynamics and right-ventricle functional characteristics of a swine carotid artery-jugular vein shunt model of pulmonary arterial hypertension: An 18-month experimental study

The continuous changes in pulmonary hemodynamic properties and right ventricular (RV) function in pulmonary arterial hypertension (PAH) have not been fully characterized in large animal model of PAH induced by a carotid artery–jugular vein shunt. A minipig model of PAH was induced by a surgical anastomosis between the left common carotid artery and the left jugular vein. The model was validated by catheter examination and pathologic analyses, and the hemodynamic features and right-ventricle functional characteristics of the model were continuously observed by Doppler echocardiography. Of the 45 minipigs who received the surgery, 27 survived and were validated as models of PAH, reflected by mean pulmonary artery pressure ≥25 mmHg, and typical pathologic changes of pulmonary arterial remodeling and RV fibrosis. Non-invasive indices of pulmonary hemodynamics (pulmonary artery accelerating time and its ratio to RV ventricular ejection time) were temporarily increased, then reduced later, similar to changes in tricuspid annular displacement. The Tei index of the RV was elevated, indicating a progressive impairment in RV function. Surgical anastomosis between carotid artery and jugular vein in a minipig is effective to establish PAH, and non-invasive hemodynamic and right-ventricle functional indices measured by Doppler echocardiography may be used as early indicators of PAH.     

Evolution of hemodynamic forces in the pulmonary tree with progressively worsening pulmonary arterial hypertension in pediatric patients

Biomechanics and Modeling in Mechanobiology - Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling resulting in right ventricular (RV) dysfunction and ultimately...     

Rho-kinase inhibition alleviates pulmonary hypertension in transgenic mice expressing a dominant-negative type II bone morphogenetic protein receptor gene

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a sustained elevation in the pulmonary artery pressure and subsequent right heart failure. The activation of Rho/Rho-kinase activity and the beneficial effect of Rho-kinase inhibition have been demonstrated in several experimental models of pulmonary hypertension. However, it remains unclear whether Rho-kinase inhibitors can also be used against pulmonary hypertension associated with mutations in the type II bone morphogenetic protein receptor (BMPRII) gene. Transgenic mice expressing a dominant-negative BMPRII gene (with an arginine to termination mutation at amino acid 899) in smooth muscle by a tetracycline-gene switch system (SM22-tet-BMPR2(R899X) mice) were examined. They developed an elevated right ventricular systolic pressure (RVSP), right ventricular (RV) hypertrophy, muscularization of small pulmonary arteries, and an associated disturbed blood flow in their lungs. The Rho/Rho-kinase activity and Smad activity were determined by a Western blot analysis by detecting GTP-RhoA and the phosphorylation of myosin phosphatase target subunit 1, Smad1, and Smad2. In the lungs of SM22-tet-BMPR2(R899X) mice, the Rho/Rho-kinase activity was elevated significantly, whereas the Smad activity was almost unchanged. Fasudil, a Rho-kinase inhibitor, significantly decreased RVSP, alleviated RV hypertrophy and muscularization of small pulmonary arteries, and improved blood flow in SM22-tet-BMPR2(R899X) mice, although it did not alter Smad signaling. Our study demonstrates that Rho/Rho-kinase signaling is activated via a Smad-independent pathway in an animal model of pulmonary hypertension with a BMPRII mutation in the cytoplasmic tail domain. Rho-kinase inhibition is therefore a possible therapeutic approach for the treatment of PAH associated with genetic mutation.     

The Soluble Guanylate Cyclase Stimulator Riociguat Ameliorates Pulmonary Hypertension Induced by Hypoxia and SU5416 in Rats

Background

The nitric oxide (NO)–soluble guanylate cyclase (sGC)–cyclic guanosine monophosphate (cGMP) signal-transduction pathway is impaired in many cardiovascular diseases, including pulmonary arterial hypertension (PAH). Riociguat (BAY 63–2521) is a stimulator of sGC that works both in synergy with and independently of NO to increase levels of cGMP. The aims of this study were to investigate the role of NO–sGC–cGMP signaling in a model of severe PAH and to evaluate the effects of sGC stimulation by riociguat and PDE5 inhibition by sildenafil on pulmonary hemodynamics and vascular remodeling in severe experimental PAH.

Methods and Results

Severe angioproliferative PAH was induced in rats by combined exposure to the vascular endothelial growth factor receptor antagonist SU5416 and hypoxia (SUHx). Twenty-one days thereafter rats were randomized to receive either riociguat (10 mg/kg/day), sildenafil (50 mg/kg/day) or vehicle by oral gavage, for 14 days until the day of the terminal hemodynamic measurements. Administration of riociguat or sildenafil significantly decreased right ventricular systolic pressure (RVSP). Riociguat significantly decreased RV hypertrophy (RVH) (0.55±0.02, p<0.05), increased cardiac output (60.8±.8 mL/minute, p<0.05) and decreased total pulmonary resistance (4.03±0.3 mmHg min⁻¹ ml⁻¹ 100 g BW, p<0.05), compared with sildenafil and vehicle. Both compounds significantly decreased the RV collagen content and improved RV function, but the effects of riociguat on tricuspid annular plane systolic excursion and RV myocardial performance were significantly better than those of sildenafil (p<0.05). The proportion of occluded arteries was significantly lower in animals receiving riociguat than in those receiving vehicle (p<0.05); furthermore, the neointima/media ratio was significantly lower in those receiving riociguat than in those receiving sildenafil or vehicle (p<0.05).

Conclusion

Riociguat and sildenafil significantly reduced RVSP and RVH, and improved RV function compared with vehicle. Riociguat had a greater effect on hemodynamics and RVH than sildenafil.     

Multiscale modelling of Potts shunt as a potential palliative treatment for suprasystemic idiopathic pulmonary artery hypertension: a paediatric case study

Biomechanics and Modeling in Mechanobiology - Potts shunt (PS) was suggested as palliation for patients with suprasystemic pulmonary arterial hypertension (PAH) and right ventricular (RV) failure....     

Early changes in rat hearts with developing pulmonary arterial hypertension can be detected with three-dimensional electrocardiography

The study aim was to assess three-dimensional electrocardiogram (ECG) changes during development of pulmonary arterial hypertension (PAH). PAH was induced in male Wistar rats (n = 23) using monocrotaline (MCT; 40 mg/kg sc). Untreated healthy rats served as controls (n = 5). ECGs were recorded with an orthogonal three-lead system on days 0, 14, and 25 and analyzed with dedicated computer software. In addition, left ventricular (LV)-to-right ventricular (RV) fractional shortening ratio was determined using echocardiography. Invasively measured RV systolic pressure was 49 (SD 10) mmHg on day 14 and 64 (SD 10) mmHg on day 25 vs. 25 (SD 2) mmHg in controls (both P < 0.001). Baseline ECGs of controls and MCT rats were similar, and ECGs of controls did not change over time. In MCT rats, ECG changes were already present on day 14 but more explicit on day 25: increased RV electromotive forces decreased mean QRS-vector magnitude and changed QRS-axis orientation. Important changes in action potential duration distribution and repolarization sequence were reflected by a decreased spatial ventricular gradient magnitude and increased QRS-T spatial angle. On day 25, LV-to-RV fractional shortening ratio was increased, and RV hypertrophy was found, but not on day 14. In conclusion, developing PAH is characterized by early ECG changes preceding RV hypertrophy, whereas severe PAH is marked by profound ECG changes associated with anatomical and functional changes in the RV. Three-dimensional ECG analysis appears to be very sensitive to early changes in RV afterload.     

Role of extracellular superoxide dismutase in bleomycin-induced pulmonary fibrosis

Bleomycin administration results in well-described intracellular oxidative stress that can lead to pulmonary fibrosis. The role of alveolar interstitial antioxidants in this model is unknown. Extracellular superoxide dismutase (EC-SOD) is the primary endogenous extracellular antioxidant enzyme and is abundant in the lung. We hypothesized that EC-SOD plays an important role in attenuating bleomycin-induced lung injury. Two weeks after intratracheal bleomycin administration, we found that wild-type mice induced a 106 +/- 25% increase in lung EC-SOD. Immunohistochemical staining revealed that a large increase in EC-SOD occurred in injured lung. Using mice that overexpress EC-SOD specifically in the lung, we found a 53 +/- 14% reduction in bleomycin-induced lung injury assessed histologically and a 17 +/- 6% reduction in lung collagen content 2 wk after bleomycin administration. We conclude that EC-SOD plays an important role in reducing the magnitude of lung injury from extracellular free radicals after bleomycin administration.     

Characterization of right ventricular function after monocrotaline-induced pulmonary hypertension in the intact rat

We characterized hemodynamics and systolic and diastolic right ventricular (RV) function in relation to structural changes in the rat model of monocrotaline (MCT)-induced pulmonary hypertension. Rats were treated with MCT at 30 mg/kg body wt (MCT30, n = 15) and 80 mg/kg body wt (MCT80, n = 16) to induce compensated RV hypertrophy and RV failure, respectively. Saline-treated rats served as control (Cont, n = 13). After 4 wk, a pressure-conductance catheter was introduced into the RV to assess pressure-volume relations. Subsequently, rats were killed, hearts and lungs were rapidly dissected, and RV, left ventricle (LV), and interventricular septum (IVS) were weighed and analyzed histochemically. RV-to-(LV + IVS) weight ratio was 0.29 +/- 0.05 in Cont, 0.35 +/- 0.05 in MCT30, and 0.49 +/- 0.10 in MCT80 (P < 0.001 vs. Cont and MCT30) rats, confirming MCT-induced RV hypertrophy. RV ejection fraction was 49 +/- 6% in Cont, 40 +/- 12% in MCT30 (P < 0.05 vs. Cont), and 26 +/- 6% in MCT80 (P < 0.05 vs. Cont and MCT30) rats. In MCT30 rats, cardiac output was maintained, but RV volumes and filling pressures were significantly increased compared with Cont (all P < 0.05), indicating RV remodeling. In MCT80 rats, RV systolic pressure, volumes, and peak wall stress were further increased, and cardiac output was significantly decreased (all P < 0.05). However, RV end-systolic and end-diastolic stiffness were unchanged, consistent with the absence of interstitial fibrosis. MCT-induced pressure overload was associated with a dose-dependent development of RV hypertrophy. The most pronounced response to MCT was an overload-dependent increase of RV end-systolic and end-diastolic volumes, even under nonfailing conditions.     

Differential expression of caveolin-1 during pathogenesis of combined pulmonary fibrosis and emphysema: Effect of phosphodiesterase-5 inhibitor

IntroductionCombined pulmonary fibrosis and emphysema (CPFE) is a relatively new entity within the spectrum of cigarette smoke induced lung disorders. Currently there is no consensus about its treatment. We hypothesized that caveolin-1 critically determines the parenchymal and vascular remodeling leading to the development of CPFE. We assessed the effect of therapeutic targeting of caveolin-1 in mesenchymal and endothelial cells by the phosphodiesterase-5 inhibitor, sildenafil.MethodsMale Wistar rats (n = 168) were exposed to; room air (control); bleomycin (7 U/kg), bleomycin+sildenafil (50 mg/kg/day P.O.), cigarette smoke (CS) (4 Gold Flake 69 mm/day), CS + sildenafil, CS + bleomycin, CS + bleomycin+sildenafil. Animals were euthanized at 8, 9, 11, 12 weeks and lung histopathological changes, collagen deposition, ROS, Xanthine oxidase, caveolin-1 determined.ResultsCigarette smoke causes progressive ROS accumulation, caveolin-1 up-regulation in alveolar epithelial cells, alveolar macrophages, peribronchiolar fibroblasts, endothelial and vascular smooth muscle cells, interstitial inflammation and emphysema. Sildenafil reduces oxidative stress, parenchymal caveolin-1 and attenuates emphysema caused by CS. Bleomycin increases lung ROS and downregulates caveolin-1 leading to fibroblast proliferation and fibrosis. Combined cigarette smoke and bleomycin exposure, results in differential caveolin-1 expression and heterogeneous parenchymal remodeling with alternating areas of emphysema and fibrosis. Increased caveolin-1 induces premature senescence of lung fibroblasts and emphysema. Decreased caveolin-1 is associated with propagation of EMT and fibrosis. Sildenafil attenuates the parenchymal remodeling however it is not effective in reducing VSMC hypertrophy in combined group.ConclusionCPFE is characterized by heterogenous parenchymal remodeling and differential caveolin-1 expression. Sildenafil therapy attenuates parenchymal pathologies in CPFE. Additional therapy is however needed for attenuating VSMC remodeling.     

Inhaled nitric oxide induced NOS inhibition and rebound pulmonary hypertension: a role for superoxide and peroxynitrite in the intact lamb

Previous in vivo studies indicate that inhaled nitric oxide (NO) decreases nitric oxide synthase (NOS) activity and that this decrease is associated with significant increases in pulmonary vascular resistance (PVR) upon the acute withdrawal of inhaled NO (rebound pulmonary hypertension). In vitro studies suggest that superoxide and peroxynitrite production during inhaled NO therapy may mediate these effects, but in vivo data are lacking. The objective of this study was to determine the role of superoxide in the decrease in NOS activity and rebound pulmonary hypertension associated with inhaled NO therapy in vivo. In control lambs, 24 h of inhaled NO (40 ppm) decreased NOS activity by 40% (P<0.05) and increased endothelin-1 levels by 64% (P<0.05). Withdrawal of NO resulted in an acute increase in PVR (60.7%, P<0.05). Associated with these changes, superoxide and peroxynitrite levels increased more than twofold (P<0.05) following 24 h of inhaled NO therapy. However, in lambs treated with polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) during inhaled NO therapy, there was no change in NOS activity, no increase in superoxide or peroxynitrite levels, and no increase in PVR upon the withdrawal of inhaled NO. In addition, endothelial NOS nitration was 18-fold higher (P<0.05) in control lambs than in PEG-SOD-treated lambs following 24 h of inhaled NO. These data suggest that superoxide and peroxynitrite participate in the decrease in NOS activity and rebound pulmonary hypertension associated with inhaled NO therapy. Reactive oxygen species scavenging may be a useful therapeutic strategy to ameliorate alterations in endogenous NO signaling during inhaled NO therapy.     

Improvement of pulmonary arterial hypertension,inflammatory response,and epithelium injury by dual activation of cAMP/cGMP pathway in a rat model of monocrotaline-induced pulmonary hypertension

Pulmonary hypertension (PH) is a life-threatening lung disease. PH with concomitant lung diseases, e.g., idiopathic pulmonary fibrosis, is associated with poor prognosis. Development of novel therapeutic vasodilators for treatment of these patients is a key imperative. We evaluated the efficacy of dual activation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) using an active, small-molecule phosphodiesterase (PDE4)/PDE5 dual inhibitor (Compound A). Compound A increased both cAMP and cGMP levels in WI-38 lung fibroblasts and suppressed the expressions of type-1 collagen α1 chain and fibronectin. Additionally, compound A reduced right ventricular weight/left ventricular weight+septal weight ratio, brain natriuretic peptide expression levels in right ventricle, C─C motif chemokine ligand 2 expression levels in lung, and plasma surfactant protein D. Our data indicate that dual activation of cAMP/cGMP pathways may be a novel treatment strategy for PH.     

实验性肺纤维化大鼠发病过程中肺组织FIZZ1蛋白和mRNA表达的动态变化

为了探讨FIZZ1（found in inflammatory zone 1）在肺纤维化发病中的作用,应用博莱霉素（5mg／kg体重）气管内注入复制实聆性人鼠肺纤维化模犁,采用HE染色、Masson三联染色、羟脯氨酸含量测定、免疫组织化学染色、原位杂交等方法,观察实验性人鼠肺纤维化的发病过程及其肺组织中FIZZ1蛋白、mRNA表达水平的动态变化。结果显示：（1）实验性人鼠肺纤维化发病过程中,呈现舆型的肺泡炎（7d）、纤维组织增生（14～2ld）及稳定的肺纤维化（28d）等表现;（2）FIZZ1蛋白在正常肺组织表达较弱,存肺纤维化组7d时表达明显增强,14d时较7d时有所减弱,21及28d明显减弱;（3）FIZZ1 mRNA在正常肺组织巾表达较弱,在肺纤维化组7d时表达明显增强,14d时开始减弱,2l及28d明显减弱,但仍强于正常组。上述结果提示,FIZZ1蛋白和mRNA在实验性大鼠肺纤维化发病过程中呈现明显的动态变化,并可能参与了肺纤维化的发生。     

Enalapril protects mice from pulmonary hypertension by inhibiting TNF-mediated activation of NF-kappaB and AP-1

The present study was undertaken to investigate the effects of treatment with the angiotensin-converting enzyme (ACE) inhibitor enalapril in a mouse model of pulmonary hypertension induced by bleomycin. Bleomycin-induced lung injury in mice is mediated by enhanced tumor necrosis factor-alpha (TNF) expression in the lung, which determines the murine strain sensitivity to bleomycin, and murine strains are sensitive (C57BL/6) or resistant (BALB/c). Bleomycin induced significant pulmonary hypertension in C57BL/6, but not in BALB/c, mice; average pulmonary arterial pressure (PAP) was 26.4 +/- 2.5 mmHg (P < 0.05) vs. 15.2 +/- 3 mmHg, respectively. Bleomycin treatment induced activation of nuclear factor (NF)-kappaB and activator protein (AP)-1 and enhanced collagen and TNF mRNA expression in the lung of C57BL/6 but not in BALB/c mice. Double TNF receptor-deficient mice (in a C57BL/6 background) that do not activate NF-kappaB or AP-1 in response to bleomycin did not develop bleomycin-induced pulmonary hypertension (PAP 14 +/- 3 mmHg). Treatment of C57BL/6 mice with enalapril significantly (P < 0.05) inhibited the development of pulmonary hypertension after bleomycin exposure. Enalapril treatment inhibited NF-kappaB and AP-1 activation, the enhanced TNF and collagen mRNA expression, and the deposition of collagen in bleomycin-exposed C57BL/6 mice. These results suggest that ACE inhibitor treatment decreases lung injury and the development of pulmonary hypertension in bleomycin-treated mice.     

Longitudinal in vivo SPECT/CT imaging reveals morphological changes and cardiopulmonary apoptosis in a rodent model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) has a complex pathogenesis involving both heart and lungs. Animal models can reflect aspects of the human pathology and provide insights into the development and underlying mechanisms of disease. Because of the variability of most animal models of PAH, serial in vivo measurements of cardiopulmonary function, morphology, and markers of pathology can enhance the value of such studies. Therefore, quantitative in vivo SPECT/CT imaging was performed to assess cardiac function, morphology and cardiac perfusion utilizing ²⁰¹Thallium (²⁰¹Tl) in control and monocrotaline-treated rats. In addition, lung and heart apoptosis was examined with ^99mTc-Annexin V (^99mTc-Annexin) in these cohorts. Following baseline imaging, rats were injected with saline or monocrotaline (50 mg/kg, i.p.) and imaged weekly for 6 weeks. To assess a therapeutic response in an established pulmonary hypertensive state, a cohort of rats received resveratrol in drinking water (3 mg/kg/day) on days 28–42 post-monocrotaline injection to monitor regression of cardiopulmonary apoptosis. PAH in monocrotaline-treated rats was verified by conventional hemodynamic techniques on day 42 (right ventricular systolic pressure (RSVP) = 66.2 mmHg in monocrotaline vs 28.8 mmHg in controls) and in terms of right ventricular hypertrophy (RV/LVS = 0.70 in monocrotaline vs 0.32 in controls). Resveratrol partially reversed both RVSP (41.4 mmHg) and RV/LVS (0.46), as well as lung edema and RV contractility +dP/dt_max. Serial ^99mTc-Annexin V imaging showed clear increases in pulmonary and cardiac apoptosis when compared to baseline, which regressed following resveratrol treatment. Monocrotaline induced modest changes in whole-heart perfusion as assessed by ²⁰¹TI imaging and cardiac morphological changes consistent with septal deviation and enlarged RV. This study demonstrates the utility of functional in vivo SPECT/CT imaging in rodent models of PAH and further confirms the efficacy of resveratrol in reversing established monocrotaline-induced PAH presumably by attenuation of cardiopulmonary apoptosis.     

Effects of sildenafil on hypoxic pulmonary vascular function in dogs.

Sildenafil has been shown to be an effective treatment of pulmonary arterial hypertension and is believed to present with pulmonary selectivity. This study was designed to determine the site of action of sildenafil compared with inhaled nitric oxide (NO) and intravenous sodium nitroprusside (SNP), known as selective and nonselective pulmonary vasodilators, respectively. Inhaled NO (40 ppm), and maximum tolerated doses of intravenous SNP and sildenafil, (5 microg x kg(-1) x min(-1) and 0.1 mg x kg(-1) x h(-1)), respectively, were administered to eight dogs ventilated in hypoxia. Pulmonary vascular resistance (PVR) was evaluated by pulmonary arterial pressure (Ppa) minus left atrial pressure (Pla) vs. flow curves, and partitioned into arterial and venous segments by the occlusion method. Right ventricular hydraulic load was defined by pulmonary arterial characteristic impedance (Zc) and elastance (Ea) calculations. Right ventricular arterial coupling was estimated by the ratio of end-systolic elastance (Ees) to Ea. Decreasing the inspired oxygen fraction from 0.4 to 0.1 increased Ppa - Pla at a standardized flow of 3 l x min(-1) x m(-2) from 6 +/- 1 to 18 +/- 1 mmHg (mean +/- SE). Ppa - Pla was decreased to 9 +/- 1 by inhaled NO, 14 +/- 1 by SNP, and 14 +/- 1 mmHg by sildenafil. The partition of PVR, Zc, Ea, and Ees/Ea was not affected by the three interventions. Inhaled NO did not affect systemic arterial pressure, which was similarly decreased by sildenafil and SNP, from 115 +/- 4 to 101 +/- 4 and 98 +/- 5 mmHg, respectively. We conclude that inhaled NO inhibits hypoxic pulmonary vasoconstriction more effectively than sildenafil or SNP, and sildenafil shows no more selectivity for the pulmonary circulation than SNP.     

Chronic hypoxia induces right heart failure in caveolin-1-/- mice

Caveolin-1 (Cav-1)-/- mice develop mild pulmonary hypertension as they age. In this study, we sought to determine the effect of chronic hypoxia, an established model of pulmonary hypertension, on young Cav-1-/- mice with no measurable signs of pulmonary hypertension. Exposure of Cav-1-/- mice to chronic hypoxia resulted in an initial rise in right ventricular (RV) systolic pressure (RVSP) similar to wild-type (WT) mice. By three weeks RVSP decreased in the Cav-1-/- mice, whereas it was maintained in WT mice. The drop in RVSP in Cav-1-/- mice was accompanied by decreased cardiac output, increased RV hypertrophy, RV interstitial fibrosis, decreased RV sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a mRNA and decreased RV function compared with WT mice. Importantly, minimal differences were noted in pulmonary vascular remodeling between WT and Cav-1-/- mice, and left ventricular function was normal in hypoxic Cav-1-/- mice. Mechanistically, increased endothelial nitric oxide synthase uncoupling and increased tyrosine nitration of protein kinase G were detected in the RV of Cav-1-/- mice. These hemodynamic, histological, and molecular changes were prevented in Cav-1-/- mice expressing an endothelial-specific Cav-1 transgene or by nitric oxide synthase inhibition. These data suggest that, in Cav-1-/- mice, increased oxidative/nitrosative stress due to endothelial nitric oxide synthase uncoupling modifies the response of the RV to pressure overload, accelerating the deterioration of RV function.     

Diallyl sulfide attenuates bleomycin-induced pulmonary fibrosis: critical role of iNOS, NF-kappaB, TNF-alpha and IL-1beta

Diallylsulfide (DAS), an antioxidant and anti-inflammatory agent was evaluated for its ability to repress lung fibrosis induced by bleomycin in Wistar rats. A single intra tracheal administration of bleomycin (6.5 U/kg BW) was administered to pulmonary fibrosis group, while DAS (120 mg/kg BW) was administered intraperitoneally throughout the experimental period. Fibrotic changes in the lungs were estimated by measuring lung hydroxyproline content. Bleomycin administration significantly (P<0.05) reduced the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in the lung tissues. Bleomycin caused a significant decrease in the level of reduced glutathione (GSH), which was accompanied with significant increase in lipid peroxidation (LPO) level, and myeloperoxidase (MPO) activity, in the lung tissues. An increase in the level of cell counts in bronchoalveolar lavage fluid (BALF) was observed in bleomycin induced group. DAS administration altered the levels of enzymic antioxidants, TBARS, MPO and GSH towards normal values. Histopathological analysis and picrosirius red staining showed an increased collagen deposition in rats receiving bleomycin alone that was decreased upon DAS treatment. Immunohistochemical studies revealed that DAS reduced the bleomycin-induced activation of inducible nitric oxide synthase (iNOS) and nuclear factor kappa-B (NF-kappaB) and decreased the augmented levels of the early inflammatory cytokines, tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta), in the lung tissues. The present study provides evidence that DAS might serve as a novel target for the therapeutic treatment of lung fibrosis.