Cigarette smoke-induced pulmonary endothelial dysfunction is partially suppressed by sildenafil

Targeting IL-11 to reduce fibrocyte circulation and lung accumulation in animal models of pulmonary hypertension-associated lung fibrosis

BACKGROUND AND PURPOSE

IL-11 is a member of the IL-6 family of cytokine initially considered as haematopoietic and cytoprotective factor. Recent evidence indicates that IL-11 promotes lung fibrosis and pulmonary hypertension in animal models and is elevated in lung tissue of patients with pulmonary fibrosis and pulmonary hypertension. Fibrocytes are bone marrow-derived circulating cells that participate in lung fibrosis and pulmonary hypertension, but the role of IL-11 on fibrocytes is unknown. We investigated the role of IL-11 system on fibrocyte activation in different in vitro and in vivo models of lung fibrosis associated with pulmonary hypertension.

EXPERIMENTAL APPROACH

Human fibrocytes were isolated from peripheral blood of six healthy donors. Recombinant human (rh)-IL-11 and soluble rh-IL-11 receptor, α subunit (IL-11Rα) were used to stimulated fibrocytes in vitro to measure:- cell migration in a chemotactic migration chamber, fibrocyte to endothelial cell adhesion in a microscope-flow chamber and fibrocyte to myofibroblast transition. Mouse lung fibrosis and pulmonary hypertension was induced using either IL-11 (s.c.) or bleomycin (intra-tracheal), while in the rat monocrotaline (intra-tracheal) was used. In vivo siRNA-IL-11 was administered to suppress IL-11 in vivo.

KEY RESULTS

RhIL-11 and soluble rhIL-11Rα promote fibrocyte migration, endothelial cell adhesion and myofibroblast transition. Subcutaneous (s.c.) IL-11 infusion elevates blood, bronchoalveolar and lung tissue fibrocytes. SiRNA-IL-11 transfection in bleomycin and monocrotaline animal models reduces blood and lung tissue fibrocytes and reduces serum CXCL12 and CXCL12/CXCR4 lung expression.

CONCLUSION AND IMPLICATIONS

Targeting IL-11 reduces fibrocyte circulation and lung accumulation in animal models of pulmonary hypertension-associated lung fibrosis.

Targeting IL-11 system as a treatment of pulmonary arterial hypertension

IL-11 is linked to fibrotic diseases, but its role in pulmonary hypertension is unclear. We examined IL-11's involvement in idiopathic pulmonary arterial hypertension (iPAH). Using samples from control (n = 20) and iPAH (n = 6) subjects, we assessed IL-11 and IL-11Rα expression and localization through RT-qPCR, ELISA, immunohistochemistry, and immunofluorescence. A monocrotaline-induced PAH model helped evaluate the impact of siRNA-IL-11 on pulmonary artery remodeling and PH. The effects of recombinant human IL-11 and IL-11Rα on human pulmonary artery smooth muscle cell (HPASMC) proliferation, pulmonary artery endothelial cell (HPAEC) mesenchymal transition, monocyte interactions, endothelial tube formation, and precision cut lung slice (PCLS) pulmonary artery remodeling and contraction were evaluated. IL-11 and IL-11Rα were over-expressed in pulmonary arteries (3.2-fold and 75-fold respectively) and serum (1.5-fold and 2-fold respectively) of patients with iPAH. Therapeutic transient transfection with siRNA targeting IL-11 resulted in a significant reduction in pulmonary artery remodeling (by 98%), right heart hypertrophy (by 66%), and pulmonary hypertension (by 58%) in rats exposed to monocrotaline treatment. rhIL-11 and soluble rhIL-11Rα induce HPASMC proliferation and HPAEC to monocyte interactions, mesenchymal transition, and tube formation. Neutralizing monoclonal IL-11 and IL-11Rα antibodies inhibited TGFβ1 and EDN-1 induced HPAEC to mesenchymal transition and HPASMC proliferation. In 3D PCLS, rhIL-11 and soluble rhIL-11Rα do not promote pulmonary artery contraction but sensitize PCLS pulmonary artery contraction induced by EDN-1. In summary, IL-11 and IL-11Rα are more highly expressed in the pulmonary arteries of iPAH patients and contribute to pulmonary artery remodeling and the development of PH.

IL-11 system participates in pulmonary artery remodeling and hypertension in pulmonary fibrosis

Background

Pulmonary hypertension (PH) associated to idiopathic pulmonary fibrosis (IPF) portends a poor prognosis. IL-11 has been implicated in fibrotic diseases, but their role on pulmonary vessels is unknown. Here we analyzed the contribution of IL-11 to PH in patients with IPF and the potential mechanism implicated.

Methods

Pulmonary arteries, lung tissue and serum of control subjects (n = 20), IPF (n = 20) and PH associated to IPF (n = 20) were used to study the expression and localization of IL-11 and IL-11Rα. Two models of IL-11 and bleomycin-induced lung fibrosis associated to PH were used in Tie2-GFP transgenic mice to evaluate the contribution of IL-11 and endothelial cells to pulmonary artery remodeling. The effect of IL-11 and soluble IL-11Rα on human pulmonary artery endothelial cells and smooth muscle cell transformations and proliferation were analyzed.

Results

IL-11 and IL-11Rα were over-expressed in pulmonary arteries and serum of patients with PH associated to IPF vs IPF patients without PH. Recombinant mice (rm)IL-11 induced lung fibrosis and PH in Tie2-GFP mice, activating in vivo EnMT as a contributor of pulmonary artery remodeling and lung fibrosis. Transient transfection of siRNA-IL-11 reduced lung fibrosis and PH in Tie2-GFP bleomycin model. Human (h)rIL-11 and soluble hrIL-11Rα induced endothelial to mesenchymal transition (EnMT) and pulmonary artery smooth muscle cell to myofibroblast-like transformation, cell proliferation and senescence in vitro.

Conclusions

IL-11 and IL-11Rα are overexpressed in pulmonary arteries of PH associated to IPF patients, and contributes to pulmonary artery remodeling and PH.

Nitric Oxide System and Bronchial Epithelium: More Than a Barrier

Airway epithelium forms a physical barrier that protects the lung from the entrance of inhaled allergens, irritants, or microorganisms. This epithelial structure is maintained by tight junctions, adherens junctions and desmosomes that prevent the diffusion of soluble mediators or proteins between apical and basolateral cell surfaces. This apical junctional complex also participates in several signaling pathways involved in gene expression, cell proliferation and cell differentiation. In addition, the airway epithelium can produce chemokines and cytokines that trigger the activation of the immune response. Disruption of this complex by some inflammatory, profibrotic, and carcinogens agents can provoke epithelial barrier dysfunction that not only contributes to an increase of viral and bacterial infection, but also alters the normal function of epithelial cells provoking several lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) or lung cancer, among others. While nitric oxide (NO) molecular pathway has been linked with endothelial function, less is known about the role of the NO system on the bronchial epithelium and airway epithelial cells function in physiological and different pathologic scenarios. Several data indicate that the fraction of exhaled nitric oxide (FENO) is altered in lung diseases such as asthma, COPD, lung fibrosis, and cancer among others, and that reactive oxygen species mediate uncoupling NO to promote the increase of peroxynitrite levels, thus inducing bronchial epithelial barrier dysfunction. Furthermore, iNOS and the intracellular pathway sGC-cGMP-PKG are dysregulated in bronchial epithelial cells from patients with lung inflammation, fibrosis, and malignancies which represents an attractive drug molecular target. In this review we describe in detail current knowledge of the effect of NOS-NO-GC-cGMP-PKG pathway activation and disruption in bronchial epithelial cells barrier integrity and its contribution in different lung diseases, focusing on bronchial epithelial cell permeability, inflammation, transformation, migration, apoptosis/necrosis, and proliferation, as well as the specific NO molecular pathways involved.

Erectile dysfunction drugs altered the activities of antioxidant enzymes, oxidative stress and the protein expressions of some cytochrome P450 isozymes involved in the steroidogenesis of steroid hormones

OBJECTIVES

Infertility is a global health problem with about 15 percent of couples involved. About half of the cases of infertility are related to male-related factors. A major cause of infertility in men is oxidative stress, which refers to an imbalance between levels of reactive oxygen species (ROS) and antioxidants. Erectile dysfunction drugs (EDD), known as phosphodiesterase inhibitors (PDEIs), have been used for the treatment of ED. It has been shown that oxidative stress plays an important role in the progression of erectile dysfunction. Oxidative stress can be alleviated or decreased by non-antioxidants and antioxidant enzymes. The present study was undertaken to determine if these compounds could have a role in the incidence of infertility, especially after long-term use. Therefore, the present study aims to investigate the effect of EDD on the activities of antioxidant enzymes, free radical levels as well as the protein expression of different cytochrome P450 isozymes involved in the steroidogenesis of different hormones. In addition, the activity of both 17β-hydroxysteroid dehydrogenase and 17-ketosteroid reductase were assayed. The architectures of both livers and testes cells were investigated under the influence of EDD.

METHODS

A daily dose of Sildenafil (1.48 mg/kg), Tadalafil (0.285 mg/kg) and Vardenafil (0.285 mg/kg) were administered orally to male rabbits for 12 week. Western immunoblotting, ELISA, spectrophotometric and histopathological techniques were used in this study.

RESULTS

The present study showed that Sildenafil, Vardenafil, and Tadalafil treatments significantly decreased the levels of glutathione and free radicals in both livers and testes of rabbits. Also, Vardenafil and Sildenafil induced the activity of superoxide dismutase and catalase whereas, glutathione S-transferase, glutathione reductase, and glutathione peroxidase activities inhibited in livers of rabbits. The protein expression of cytochrome P450 isozymes (CYP 11A1, 21A2, and 19C) which are involved in the steroidogenesis was markedly changed in both livers and testes of rabbits after their treatments for 12 weeks. After the treatment of rabbits with these medication, the protein expression of CYP11A1 was slightly down-regulated in both livers and testes except Sildenafil up-regulated such protein expression. In addition, the protein expressions of CYP11A1 and CYP 19C in both livers and testes were down-regulated after treatment of rabbits with Sildenafil, Vardenafil, and Tadalafil for 12 weeks. Also, these drugs inhibited the activity of both 17β-hydroxysteroid dehydrogenase and 17-ketosteroid reductase in testes of rabbits. Moreover, Sildenafil, Vardenafil, and Tadalafil-treated rabbits showed a decrease in spermatocytes and the number of sperms in the testes.

CONCLUSIONS

It is concluded that ED drugs induced the activities of both SOD and catalase which consequently decreased MDA level. Decrement in MDA levels and oxidative stress could therefore sustain the erection for a long period of time. On the other hand, it is not advised to use these drugs for a long-term since the protein expressions of CYP isozymes involved in steroidogenesis as well as the numbers of spermatocytes in testes were decreased.

Periostin mediates cigarette smoke extract-induced proliferation and migration in pulmonary arterial smooth muscle cells

Cigarette smoking is an important risk factor for pulmonary arterial hypertension (PAH). Pulmonary arterial smooth muscle cells (PASMCs) play a critical role in the pathogenesis of PAH-associated arterial remodeling. This study was done to explore the expression and biological roles of periostin in PASMCs following exposure to cigarette smoke extract (CSE). PASMCs were exposed to different concentrations of CSE and tested for gene expression and reactive oxygen species (ROS) production. PASMCs were incubated with recombinant periostin protein or transfected with small interfering RNA targeting periostin before CSE exposure and then examined for cell proliferation and migration. Compared to control cells, exposure to CSE led to a significant upregulation of periostin. Pretreatment with 5mM N-acetyl-l-cysteine (an inhibitor of ROS formation) or 10μM U0126 (an inhibitor of ERK1/2) significantly prevented the induction of periostin in CSE-treated PASMCs. The addition of recombinant periostin protein significantly enhanced the proliferation and migration of PASMCs. In contrast, knockdown of endogenous periostin counteracted the proliferation and migration of PASMCs induced by CSE treatment. In conclusion, CSE induces the expression of periostin in PASMCs via promotion of ROS and activation of ERK1/2. Periostin mediates the effects of CSE on PASMC proliferation and migration. These findings warrant further exploration of the roles of periostin in cigarette smoking-associated pulmonary arterial remodeling.

Vascular effects of sildenafil in patients with pulmonary fibrosis and pulmonary hypertension: an ex vivo/in vitro study

Sildenafil improves the 6-min walking distance in patients with idiopathic pulmonary fibrosis (IPF) and right-sided ventricular systolic dysfunction.

We analysed the previously unexplored role of sildenafil on vasoconstriction and remodelling of pulmonary arteries from patients with IPF and pulmonary hypertension (PH) ex vivo. Pulmonary arteries from 18 donors without lung disease, nine IPF, eight PH+IPF and four PH patients were isolated to measure vasodilator and anti-contractile effects of sildenafil in isometric organ bath. Ventilation/perfusion was explored in an animal model of bleomycin lung fibrosis.

Sildenafil relaxed serotonin (5-HT) pre-contracted pulmonary arteries in healthy donors and IPF patients and, to a lesser extent, in PH+IPF and PH. Sildenafil inhibited 5-HT dose-response contraction curve mainly in PH+IPF and PH, but not in healthy donors. Sildenafil did not impair the ventilation/perfusion mismatching induced by bleomycin. Pulmonary arteries from PH+IPF patients showed a marked expression of phosphodiesterse-5 and extracellular matrix components. Sildenafil inhibited pulmonary artery endothelial and smooth muscle cell to mesenchymal transition by inhibition of extracellular regulated kinases 1 and 2 (ERK1/2) and SMAD3 phosphorylation.

These results suggest an absence of direct relaxant effect and a prominent anti-contractile and anti-remodelling role of sildenafil in PH+IPF pulmonary arteries that could explain the beneficial effects of sildenafil in IPF with PH phenotype.

Erectile dysfunction drugs and oxidative stress in the liver of male rats

Erectile dysfunction (ED) affected the lives of more than 300 million men worldwide. Erectile dysfunction drugs (EDD), known as phosphodiesterase inhibitors (PDEIs), have been used for treatment of ED. It has been shown that oxidative stress plays an important role in the progression of erectile dysfunction. Oxidative stress can be alleviated or decreased by antioxidant enzymes. Therefore, the present study aims at investigating the changes in the activity of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione reductase as well as protein expression of glutathione peroxidase and glutathione S-transferase after treatment of male rats with a daily dose of sildenafil (1.48 mg/kg), tadalafil (0.285 mg/kg) and vardenafil (0.285 mg/kg) for three weeks. In addition, levels of reduced glutathione and malondialdyhyde (MDA) were assayed. The present study showed that sildenafil, vardenafil, and tadalafil treatments significantly decreased the levels of glutathione, MDA and the activity of glutathione reductase. In addition, vardenafil and sildenafil increased the activity of superoxide dismutase and catalase. Interestingly, western immunoblotting data showed that vardenafil induced the activity of glutathione peroxidase (GPX) and its protein expression, whereas tadalafil and sildenafil inhibited such enzyme activity and its protein expression. In addition, the protein expression of GST π isozyme was markedly reduced after treatment of rats with sildenafil. It is concluded that ED drugs induced the activities of both SOD and catalase which consequently decreased MDA level. Therefore, decrement in MDA levels could increase nitric oxide-cGMP level which in turn promotes the erection mechanism.

Effects of tadalafil administration on plasma markers of exercise-induced muscle damage, IL6 and antioxidant status capacity

INTRODUCTION

Physical exercise is associated with enhanced production of reactive oxygen species, which if uncontrolled can result in tissue injury. Phosphodiesterase type 5 inhibitors (PDE5i) exhibit protective effect against oxidative stress, both in animals and healthy/unhealthy humans. However, the effect of a chronic administration of PDE5i, particularly combined with physical exercise, has never been investigated.

PURPOSE

The present study was designed to evaluate the effect of the long-acting PDE5i tadalafil on oxidative status and muscle damage after exhaustive exercise in healthy males included in a double-blind crossover trial.

HYPOTHESIS

Tadalafil, having a putative antioxidant activity, may reduce oxidative damage after strenuous exercise.

METHODS

Each volunteer randomly received two tablets of placebo or tadalafil (20 mg/day) with 36 h of interval before performing exhaustive exercise. After 2 weeks of washout, the volunteers were crossed over. Blood samples were collected immediately before exercise, immediately after, and during recovery (15, 30, 60 min). Plasma total antioxidant status, glutathione homeostasis (GSH/GSSG), malondialdehyde (MDA), protein carbonyls, creatine kinase (CK), lactate dehydrogenase (LDH) and the inflammatory cytokine interleukin 6 were assessed.

RESULTS

Tadalafil administration per se affected redox homeostasis (GSH/GSSG -36%; p < 0.05), cellular (CK +75% and LDH +36%; p < 0.05) and oxidative damage (MDA +41% and protein carbonyls +50%; p < 0.05) markers. The exhaustive exercise increased all the above-reported biochemical parameters, with subjects from the tadalafil group showing significantly higher values with respect to the placebo group.

CONCLUSIONS

A prolonged exposure to tadalafil decreases antioxidant capacity at resting condition, therefore making subjects more susceptible to the oxidative stress induced by an exhaustive bout of exercise.

Cavernous antioxidant effect of green tea, epigallocatechin-3-gallate with/without sildenafil citrate intake in aged diabetic rats

This study aimed to assess the cavernous antioxidant effect of green tea (GT), epigallocatechin-3-gallate (EGCG) with/without sildenafil citrate intake in aged diabetic rats. One hundred and four aged male white albino rat were divided into controls that received ordinary chow, streptozotocin (STZ)-induced aged diabetic rats, STZ-induced diabetic rats on infused green tea, induced diabetic rats on epigallocatechin-3-gallate and STZ-induced diabetic rats on sildenafil citrate added to EGCG. After 8 weeks, dissected cavernous tissues were assessed for gene expression of eNOS, cavernous malondialdehyde (MDA), glutathione peroxidase (GPx), cyclic guanosine monophosphate (cGMP), and serum testosterone (T). STZ-induced diabetic rats on GT demonstrated significant increase in cavernous eNOS, cGMP, GPx and significant decrease in cavernous MDA compared with diabetic rats. Diabetic rats on EGCG demonstrated significant increase in cavernous eNOS, cGMP, GPx and significant decrease in cavernous MDA compared with diabetic rats or diabetic rats on GT. Diabetic rats on EGCG added to sildenafil showed significant increase in cavernous eNOS, cGMP and significant decrease in cavernous MDA compared with other groups. Serum T demonstrated nonsignificant difference between the investigated groups. It is concluded that GT and EGCG have significant cavernous antioxidant effects that are increased if sildenafil is added.

Pulmonary hypertension in chronic obstructive and interstitial lung diseases

The purpose of the present review is to summarize the current knowledge on PH in relation to COPD and ILD from a clinical perspective with emphasis on diagnosis, biomarkers, prevalence, impact, treatment, and practical implications. PH in COPD and ILD is associated with a poor prognosis, and is considered one of the most frequent types of PH. However, the prevalence of PH among patients with COPD and ILD is not clear. The diagnosis of PH in chronic lung disease is often established by echocardiographic screening, but definitive diagnosis requires right heart catheterization, which is not systematically performed in clinical practice. Given the large number of patients with chronic lung disease, biomarkers to preclude or increase suspicion of PH are needed. NT-proBNP may be used as a rule-out test, but biomarkers with a high specificity for PH are still required. It is not known whether specific treatment with existent drugs effective in pulmonary arterial hypertension (PAH) is beneficial in lung disease related PH. Studies investigating existing PAH drugs in animal models of lung disease related PH have indicated a positive effect, and so have case reports and open label studies. However, treatment with systemically administered pulmonary vasodilators implies the risk of worsening the ventilation-perfusion mismatch in patients with lung disease. Inhaled vasodilators may be better suited for PH in lung disease, but new treatment modalities are also required.

Long-term exposure to cigarette smoke extract induces hypomethylation at the RUNX3 and IGF2-H19 loci in immortalized human urothelial cells

Cigarette smoking is the single most important epidemiological risk factor for bladder cancer but it is not known whether exposure of urothelial cells to the systemic soluble contents of cigarette smoke is directly causative to bladder cancer and the associated epigenetic changes such as tumor suppressor gene hypermethylation. We undertook this study to investigate if long-term treatment of human urothelial cells with cigarette smoke extract (CSE) results in tumor suppressor gene hypermethylation, a phenotype that was previously associated with long-term constant CSE treatment of airway epithelial cells. We chronically treated an immortalized human urothelial cell line UROtsa with CSE using a cyclic daily regimen but the cells were cultured in CSE-free medium between daily treatments. Bisulfite sequencing and real-time PCR array-based methylation profiling were employed to evaluate methylation changes at tumor suppressor gene loci in the chronically CSE-treated cells versus the passage-matched untreated control cells. The RUNX3 tumor suppressor gene promoter was hypomethylated with a significant increase in proportion of the completely unmethylated haplotype after the long-term CSE treatment; whereas RUNX3 promoter hypermethylation was previously reported for bladder cancers of smokers. Hypomethylation induced by the long-term CSE treatment was also observed for the IGF2-H19 locus. The methylation status at the PRSS8/prostasin and 16 additional loci however, was unaffected by the chronic CSE treatment. Transient CSE treatment over 1 daily regimen resulted in transcriptional down-regulation of RUNX3 and H19, but only the H19 transcription was down-regulated in the chronically CSE-treated urothelial cells. Transcription of a key enzyme in one-carbon metabolism, dihydrofolate reductase (DHFR) was greatly reduced by the long-term CSE treatment, potentially serving as a mechanism for the hypomethylation phenotype via a reduced supply of methyl donor. In conclusion, chronic cyclic CSE treatment of urothelial cells induced hypomethylation rather than hypermethylation at specific loci.

Phosphodiesterase-4 inhibition improves corticosteroid insensitivity in pulmonary endothelial cells under oxidative stress

BACKGROUND

Several clinical studies have shown that smoking in asthmatics and chronic obstructive pulmonary disease patients is closely associated with corticosteroid refractoriness. In this work, we have analyzed glucocorticoid insensitivity in human pulmonary artery endothelial cells (HPAECs) under cigarette smoke extract (CSE) exposure as well as the possible additive effects of the combination therapy with a phosphodiesterase (PDE)-4 inhibitor.

METHODS

Interleukin (IL)-8 was measured in cell supernatants by ELISA. Histone deacetylase (HDAC), histone acetylase (HAT), and intracellular cAMP levels were measured by colorimetric assays and enzyme immunoassay, respectively. PDE4 isotypes and glucocorticoid receptor (GR)-α and β expression were measured by real-time RT-PCR.

RESULTS

The PDE4 inhibitor rolipram dose dependently inhibited the IL-8 secretion induced by CSE 5%. In contrast, dexamethasone 1 μM did not show inhibitory effect on IL-8 secretion. Combination of subeffective rolipram concentrations at 10 nM increased the inhibitory effect of dexamethasone to ~45% of inhibition. Cigarette smoke extract 5% inhibited HDAC activity and increased HAT activity generating glucocorticoid insensitivity. Rolipram did not modify the HDAC activity, however partially inhibited the increase in HAT activity at 1 μM. PDE4 isotypes were up-regulated by CSE 5% with the consequent cAMP down-regulation. Dexamethasone reduced all PDE4 isotypes expression and showed additive effects with rolipram enhancing cAMP levels. Furthermore, rolipram enhanced GR-α expression and inhibited the increase in GR-β induced by CSE.

CONCLUSIONS

Combination of rolipram and dexamethasone shows additive properties in HPAECs under glucocorticoid insensitive conditions. These results may be of potential value in future anti-inflammatory therapies using combination of PDE4 inhibitors and glucocorticoids.

PGC-1α induction in pulmonary arterial hypertension

Idiopathic Pulmonary arterial hypertension (IPAH) is characterized by the obstructive remodelling of pulmonary arteries, and a progressive elevation in pulmonary arterial pressure (PAP) with subsequent right-sided heart failure and dead. Hypoxia induces the expression of peroxisome proliferator activated receptor γ coactivator-1α (PGC-1α) which regulates oxidative metabolism and mitochondrial biogenesis. We have analysed the expression of PGC-1α, cytochrome C (CYTC), superoxide dismutase (SOD), the total antioxidant status (TAS) and the activity of glutathione peroxidase (GPX) in blood samples of IPAH patients. Expression of PGC-1α was detected in IPAH patients but not in healthy volunteers. The mRNA levels of SOD were lower in IPAH patients compared to controls (3.93 ± 0.89 fold change). TAS and GPX activity were lower too in patients compared to healthy donors, (0.13 ± 0.027 versus 0.484 ± 0.048 mM and 56.034 ± 10.37 versus 165.46 ± 11.38 nmol/min/mL, resp.). We found a negative correlation between expression levels of PGC-1α and age, PAP and PVR, as well as a positive correlation with CI, PaO₂, mRNA levels of CYTC and SOD, TAS and GPX activity. These results taken together are indicative of the possible role of PGC-1α as a potential biomarker of the progression of IPAH.

Brief hyperoxia increases mitochondrial oxidation and increases phosphodiesterase 5 activity in fetal pulmonary artery smooth muscle cells

AIMS

Oxygen is a pulmonary vasodilator, but data suggest high O(2) concentrations impede that response. We previously reported 24 h of 100% O(2) increased phosphodiesterase 5 (PDE5) activity in fetal pulmonary artery smooth muscle cells (FPASMC) and in ventilated neonatal lambs. PDE5 degrades cyclic GMP (cGMP) and inhibits nitric oxide (NO)-mediated cGMP-dependent vasorelaxation. We sought to determine the mechanism by which hyperoxia initiates reactive oxygen species (ROS) production and regulates PDE5.

RESULTS

Thirty minutes of hyperoxia increased mitochondrial ROS versus normoxia (30.3±1.7% vs. 21.1±2.8%), but had no effect on cytosolic ROS, measured by roGFP, a ratiometric protein thiol redox sensor. Hyperoxia increased PDE5 activity (220±39%) and decreased cGMP responsiveness to NO (37±17%). Mitochondrial catalase overexpression attenuated hyperoxia-induced mitochondrial roGFP oxidation, compared to FPASMC infected with empty adenoviral vector (50±3% of control) or mitochondrial superoxide dismutase. MitoTEMPO, mitochondrial catalase, and DT-3, a cGMP-dependent protein kinase I alpha inhibitor, decreased PDE5 activity (32±13%, 26±21%, and 63±10% of control, respectively), and restored cGMP responsiveness to NO (147±16%,172±29%, and 189±43% of control, respectively). C57Bl6 mice exposed to 90%-100% O(2) for 45 min±mechanical ventilation had increased PA PDE5 activity (206±39% and 235±75%, respectively).

INNOVATION

This is the first description that hyperoxia induces ROS in the mitochondrial matrix prior to the cytosol. Our results indicate that short hyperoxia exposures can produce significant changes in critical cellular signaling pathways.

CONCLUSIONS

These results indicate that mitochondrial matrix oxidant signals generated during hyperoxia, specifically H(2)O(2), activate PDE5 in a cGMP-dependent protein kinase-dependent manner in pulmonary vascular smooth muscle cells.

The effects of long-term administration of tadalafil on STZ-induced diabetic rats with erectile dysfunction via a local antioxidative mechanism

Type 5 phosphodiesterase inhibitors (PDE5Is) are well known being effective via the nitric oxide and cyclic guanosine monophosphate (NO-cGMP) pathway and are widely used in the treatment of diabetic erectile dysfunction (ED). However, it is unclear whether other pathways may be involved in the treatment of diabetic ED with PDE5Is. The purpose of this study was to clarify the role of antioxidants in diabetic ED treatment through the long-term administration of PDE5Is. Three groups of Sprague-Dawley rats were utilized: Group N, the normal control; Group D, streptozotocin (STZ)-induced diabetic rats as a control; and Group D+T, STZ-induced diabetic rats who received oral administration of tadalafil for 8 weeks. Erectile function was assessed by intracavernous pressure (ICP) and mean arterial pressure (MAP) during electrical stimulation of the cavernous nerve before euthanasia. The levels of malondialdehyde (MDA), superoxide dismutase (SOD) and mitochondrial membrane potential (MMP) of cavernous tissue were assessed by biochemical analysis. The morphology of mitochondria was observed by electron microscopy. The ICP/MAP ratio was higher in Group D+T than in Group D (P<0.05). The levels of MDA decreased and the activities of SOD increased in Group D+T in comparison with Group D (P<0.05). The mitochondrial membrane potential level of cavernous tissue in diabetic rats was partially recovered by tadalafil treatment for 8 weeks. The morphology changes of mitochondria were also remarkably ameliorated in Group D+T. Collectively, the long-term administration of tadalafil in diabetic rats partially reduced oxidative stress lesions of the penis via a local antioxidative stress pathway. Long-term dosages of tadalafil given once daily beginning soon after the onset of diabetes may aid in preventing rats from developing diabetic ED.

Combination effects of cigarette smoke extract and ambient ultrafine particles on endothelial cells

Previous studies have shown that ambient ultrafine particles with diameters less than 100nm (UFPs) can pass from the lungs to the circulation because of their very small diameter, and induce lung oxidative stress with a resultant dysfunction of lung endothelial cells. However, no studies have addressed the potential combined effects of UFPs and cigarette smoke on vascular endothelial cells. We hypothesized that co-exposure to UFPs and cigarette smoke extract (CSE) may cause combined effects on activation of endothelial cells and dysfunction of endothelium by oxidative stress through activation of NADPH oxidase. We determined the effects of UFPs with or without CSE on mouse pulmonary microvascular endothelial cells (MPMVEC) obtained from C57BL/6J (wild-type) and gp91(phox) knock-out mice (gp91(phox) is one of the key components of NADPH oxidase, one of ROS generators). Our results showed that exposure of MPMVEC from wild-type mice to UFPs or CSE, at a non-toxic dose, induced reactive oxygen species (ROS) generation, increased phosphorylation of p38 and Erk1/2, and up-regulated early growth response -1 (Egr-1) and IL-6 genes. These effects were significantly enhanced when cells were co-exposed to both UFPs and CSE. However, exposure of MPMVEC from gp91(phox) knock-out mice did not induce the above effects. Furthermore, UFPs- and/or CSE-induced Egr-1 mRNA upregulation was attenuated significantly when cells were pre-treated with p38 specific inhibitor, SB 203580, or MEK1/2 inhibitor, PD98059, and Egr-1 siRNA treatment abolished UFPs- and/or CSE-induced overexpression of IL-6. Our results suggest that UFPs and/or CSE caused activation of NADPH oxidase, resulting in ROS generation that led to activation of MAPKs through induced phosphorylation of p38 and ERK1/2 MAPKs and upregulation of Egr-1. Those effects may further result in endothelial dysfunction through production of cytokines such as IL-6. Our results suggest that co-exposure to UFPs and CSE causes enhanced injury to endothelial cells.

Long-term methylglyoxal treatment impairs smooth muscle contractility in organ-cultured rat mesenteric artery

Methylglyoxal (MGO), a metabolite of glucose accumulates in vascular tissues of hypertensive rats. We recently showed that short-term (30min) treatment with MGO inhibits noradrenaline (NA)-induced smooth muscle contraction in rat aorta and mesenteric artery. In the present study, long-term effect of MGO was examined using organ culture method. The contractility, morphology, and protein expression of rat mesenteric artery after organ culture with MGO for 3 days were examined. MGO (4 and 42μM) inhibited NA (0.1nM to 3μM) or KCl (72.7mM)-induced contraction. The inhibitory effect was higher in endothelium-denuded than endothelium-intact artery. An anti-oxidant drug, N-acetyl-l-cysteine (NAC; 1mM) or an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX), gp91ds-tat (0.1μM) prevented the inhibitory effect of MGO. MGO increased superoxide production as detected by lucigenin assay. In the medial layer of the arteries cultured with MGO, apoptotic morphological change was observed, and NAC or gp91ds-tat prevented it. MGO significantly increased expression of a homolog of gp91(phox), NOX1 but not gp91(phox) as determined by Western blotting. An NF-κB inhibitor, pyrrolidine dithiocarbamate prevented the MGO-induced NOX1 expression. MGO had no effect on protein expression of p22(phox), p67(phox), p47(phox), as well as superoxide dismutase (SOD)-1, SOD-2 and SOD-3. Present results indicate that long-term MGO treatment has an inhibitory effect on contractility of isolated blood vessel, which is likely mediated via increased NOX1-derived superoxide production and subsequent apoptosis.

COPD/emphysema: The vascular story

In this perspective, we review published data which support the concept that many or most chronic and progressive lung diseases also involve the lung vessels and that microvascular abnormalities and endothelial cell death contribute to the pathobiology of emphysema. Lung vessel maintenance depends on Vascular Endothelial Growth Factor signaling and both are compromised in the emphysematous lung tissue. Although hypoxic pulmonary vasoconstriction has been considered as an important factor contributing to the vascular remodeling in chronic obstructive pulmonary disease (COPD) (COPD/emphysema, it is now clear that inhaled cigarette smoke can damage the lung vessels independent of the lung vascular tone. We propose that a "sick lung circulation" rather than the right heart afterload may better explain the cardiac abnormalities in COPD patients which are usually summarized with the term "cor pulmonale." The mechanisms and causes of pulmonary hypertension are likely complex and include vessel loss, in situ thrombosis, and endothelial cell dysfunction. Assessment of the functional importance of pulmonary hypertension in COPD requires hemodynamic measurements during exercise.

Oxidative stress-induced glucocorticoid resistance is prevented by dual PDE3/PDE4 inhibition in human alveolar macrophages

BACKGROUND

Oxidative stress is present in airway diseases such as severe asthma or Chronic Obstructive Pulmonary Disease and contributes to the low response to glucocorticoids through the down-regulation of histone deacetylase (HDAC) activity.

OBJECTIVE

To study the effects of the phosphodiesterase (PDE)-3 and 4 inhibitors and their combination vs. glucocorticoids in a model of lipopolysaccharide (LPS)-induced cytokine release in alveolar macrophages under oxidative stress conditions.

METHODS

Differentiated U937 or human alveolar macrophages were stimulated with H(2) O(2) (10-1000 μM) or cigarette smoke extract (CSE, 0-15%) for 4 h before LPS (0.5 μg/mL, 24 h) addition. In other experiments, cells were pre-treated with dexamethasone or budesonide (10(-9) -10(-6) M), with the PDE4 inhibitor rolipram (10(-9) -10(-5) M), PDE3 inhibitor motapizone (10 μM), 3',5'-cyclic monophosphate enhancer PGE(2) (10 nM), or with the combination of rolipram (10(-6) M)+PGE(2) (10 nM)+motapizone (10 μM) 15 min before oxidants. IL-8 and TNF-α were measured by ELISA and HDAC activity by a colorimetric assay.

RESULTS

Budesonide and dexamethasone produced a concentration-dependent inhibition of the LPS-induced IL-8 and TNF-α secretion with an E(max) about 90% of inhibition, which was reduced by approximately 30% in the presence of H(2)O(2) or CSE. Pre-treatment with rolipram, motapizone or PGE2 only reached about 20% of inhibition but was not affected by oxidative stress. In contrast, PDE4/PDE3 combination in presence of PGE2 effectively inhibited the LPS-induced cytokine secretion by about 90% and was not affected by oxidative stress. Combined PDE4 and PDE3 inhibition reversed glucocorticoid resistance under oxidative stress conditions. HDAC activity was reduced in the presence of oxidative stress, and in contrast to glucocorticoids, pre-treatment with PDE4/PDE3 combination was able to prevent HDAC inactivity.

CONCLUSIONS & CLINICAL RELEVANCE

This study shows that the combination of the PDE3/PDE4 inhibitors prevents alveolar macrophage activation in those situations of glucocorticoid resistance, which may be of potential interest to develop new effective anti-inflammatory drugs in airway diseases.

Sildenafil reduces insulin-resistance in human endothelial cells

BACKGROUND

The efficacy of Phosphodiesterase 5 (PDE5) inhibitors to re-establish endothelial function is reduced in diabetic patients. Recent evidences suggest that therapy with PDE5 inhibitors, i.e. sildenafil, may increase the expression of nitric oxide synthase (NOS) proteins in the heart and cardiomyocytes. In this study we analyzed the effect of sildenafil on endothelial cells in insulin resistance conditions in vitro.

METHODOLOGY/PRINCIPAL FINDINGS

Human umbilical vein endothelial cells (HUVECs) were treated with insulin in presence of glucose 30 mM (HG) and glucosamine 10 mM (Gluc-N) with or without sildenafil. Insulin increased the expression of PDE5 and eNOS mRNA assayed by Real time-PCR. Cytofluorimetric analysis showed that sildenafil significantly increased NO production in basal condition. This effect was partially inhibited by the PI3K inhibitor LY 294002 and completely inhibited by the NOS inhibitor L-NAME. Akt-1 and eNOS activation was reduced in conditions mimicking insulin resistance and completely restored by sildenafil treatment. Conversely sildenafil treatment can counteract this noxious effect by increasing NO production through eNOS activation and reducing oxidative stress induced by hyperglycaemia and glucosamine.

CONCLUSIONS/SIGNIFICANCE

These data indicate that sildenafil might improve NOS activity of endothelial cells in insulin resistance conditions and suggest the potential therapeutic use of sildenafil for improving vascular function in diabetic patients.

Cigarette smoke exposure up-regulates endothelin receptor B in human pulmonary artery endothelial cells: molecular and functional consequences

BACKGROUND AND PURPOSE

Pulmonary arteries from smokers and chronic obstructive pulmonary disease patients show abnormal endothelium-dependent vascular reactivity. We studied the effect of cigarette smoke extract (CSE) on endothelin receptor B (ET(B) ) expression in human pulmonary artery endothelial cells (HPAECs) and its role in endothelial dysfunction.

EXPERIMENTAL APPROACH

ET(B) receptor expression was measured by real time RT-PCR, Western blot and immunofluorescence. Cell contraction, intracellular Ca(2+) , F/G-actin, RhoA activity, myosin light chain phosphorylation, ET, NO, thromboxane (Tx)A(2) and reactive oxygen species (ROS) were measured by traction microscopy, fluorescence microscopy, phalloidin fluorescence, colorimetric assay, Western blot, elisa and DCFDA fluorescence respectively.

KEY RESULTS

Cigarette smoke extract dose-dependently increased ET(B) receptor expression in HPAECs after 24h incubation. CSE-induced ET(B) expression was attenuated by bosentan, the ET(B) receptor antagonist BQ788, the Rho kinase antagonist Y27632 and the antioxidant N-acetylcysteine. A monoclonal antibody to ET-1 prevented CSE-induced ET(B) receptor overexpression. Twenty-four hour exposure to ET-1 dose-dependently increased ET(B) receptor expression, mimicking the effect of CSE. CSE-induced ET(B) receptor overexpression caused greater cell contraction; increased intracellular Ca(2+) ; increased F/G-actin and RhoA activity; increased myosin light chain phosphorylation; augmented TxA(2) and ROS production; and decreased NO after acute ET-1 (10nM). These effects were attenuated by bosentan, BQ788, Y27632 and N-acetylcysteine.

CONCLUSIONS AND IMPLICATION

Cigarette smoke extract induced ET(B) receptor overexpression by a feed forward mechanism mediated partly by ET release, promoting HPAEC dysfunction and attenuated by ET(B) receptor blockade, Rho kinase and ROS inhibition. These results provide support for the use of bosentan in CS-related endothelial dysfunction.