Contribution of oxidative stress to pulmonary arterial hypertension

Combined exercise hinders the progression of pulmonary and right heart harmful remodeling in monocrotaline-induced pulmonary arterial hypertension

The aim of this study was to test whether combined physical exercise training of moderate intensity executed during the development of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) hinders the progression of pulmonary and right heart harmful functional and structural remodeling in rats. Wistar rats were injected with MCT (60 mg/kg) and after 24 h were exposed to a combined exercise training program: aerobic exercise (treadmill running-60 min/day; 60% of maximum running speed); and resistance exercise (vertical ladder climbing-15 climbs; 60% of maximum carrying load), on alternate days, 5 days/wk, for ∼3 wk. After euthanasia, the lung and right ventricle (RV) were excised and processed for histological, single myocyte, and biochemical analyses. Combined exercise increased the tolerance to physical effort (time until fatigue and relative maximum load) and prevented increases in pulmonary artery resistance (acceleration time (TA)/ejection time (TE)] and reductions in RV function [tricuspid annular plane systolic excursion (TAPSE)]. Moreover, in myocytes isolated from the RV, combined exercise preserved contraction amplitude, as well as contraction and relaxation velocities, and inhibited reductions in the amplitude and maximum speeds to peak and to decay of the intracellular Ca2+ transient. Furthermore, combined exercise avoided RV (RV weight, cardiomyocyte, extracellular matrix, collagen, inflammatory infiltrate, and extracellular matrix) and lung (pulmonary alveoli and alveolar septum) harmful structural remodeling. In addition, combined exercise restricted RV [nitric oxide (NO) and carbonyl protein (CP)] and lung [catalase (CAT), glutathione S-transferase (GST), and NO] oxidative stress. In conclusion, the applied combined exercise regime hinders the progression of pulmonary and right heart functional and structural harmful remodeling in rats with MCT-induced PAH.NEW & NOTEWORTHY This study reveals that combined exercise improves tolerance to physical effort, prevents increases in pulmonary artery resistance, and conserves the right heart function during the progression of pulmonary arterial hypertension. Our analyses show that combined exercise hinders harmful right ventricular and lung structural remodeling and oxidative stress, which reflects in the maintenance of right ventricular myocytes' contractile function by preserving the intracellular calcium cycling. An attenuated progression of the disease impacts positively on its prognosis.

Inhalable Advanced Co-Spray Dried Microparticles/Nanoparticles of a Novel RhoA/Rho Kinase Inhibitor with Lung Surfactant Biomimetic Phospholipids for Targeted Lung Delivery

Co-spray dried inhalable powder formulations of fasudil monohydrochloride salt (FMCS) and inhalable lung surfactant-based nanocarriers composed of synthetic phospholipids, zwitterionic DPPC (1,2-palmitoyl-sn-glycero-3-phosphocholine) and anionic DPPG (1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-1-glycerol]) sodium salt, were designed and optimized using organic solution advanced spray drying. FMCS can potentially be used for the treatment of various complex pulmonary diseases with this current work focusing on pulmonary arterial hypertension. Comprehensive physicochemical characterization, electron and optical microscopy imaging, thermal analysis, molecular fingerprinting spectroscopy, in vitro aerosol dispersion performance with human dry powder inhaler (DPI) devices, in vitro membrane permeation and drug release, and in vitro human cellular studies were conducted. Well-defined, small, and smooth nanoparticles/microparticles in the solid state were engineered at different molar ratios of FMCS/DPPC/DPPG (25:75, 50:50, and 75:25) and successfully produced as inhalable powders having the properties necessary for targeted pulmonary delivery as dry powder inhalers. In vitro aerosol performance demonstrated excellent aerosol dispersion with different DPI devices. The phospholipid bilayer biophysical properties were confirmed and retained following cospray drying. Sustained release of fasudil drug and in vitro biocompatibility were demonstrated on human lung cells from different airway regions.

Current Overview of the Biology and Pharmacology in Sugen/Hypoxia-Induced Pulmonary Hypertension in Rats

The Sugen 5416/hypoxia (Su/Hx) rat model of pulmonary arterial hypertension (PAH) demonstrates most of the distinguishing features of PAH in humans, including increased wall thickness and obstruction of the small pulmonary arteries along with plexiform lesion formation. Recently, significant advancement has been made describing the epidemiology, genomics, biochemistry, physiology, and pharmacology in Su/Hx challenge in rats. For example, there are differences in the overall reactivity to Su/Hx challenge in different rat strains and only female rats respond to estrogen treatments. These conditions are also encountered in human subjects with PAH. Also, there is a good translation in both the biochemical and metabolic pathways in the pulmonary vasculature and right heart between Su/Hx rats and humans, particularly during the transition from the adaptive to the nonadaptive phase of right heart failure. Noninvasive techniques such as echocardiography and magnetic resonance imaging have recently been used to evaluate the progression of the pulmonary vascular and cardiac hemodynamics, which are important parameters to monitor the efficacy of drug treatment over time. From a pharmacological perspective, most of the compounds approved clinically for the treatment of PAH are efficacious in Su/Hx rats. Several compounds that show efficacy in Su/Hx rats have advanced into phase II/phase III studies in humans with positive results. Results from these drug trials, if successful, will provide additional treatment options for patients with PAH and will also further validate the excellent translation that currently exists between Su/Hx rats and the human PAH condition.

Pentacyclic triterpenes, potential novel therapeutic approaches for cardiovascular diseases

Cardiovascular diseases (CVDs) involve dysfunction of the heart and blood vessels and have become major health concerns worldwide. Multiple mechanisms may be involved in the occurrence and development of CVDs. Although therapies for CVDs are constantly being developed and applied, the incidence and mortality of CVDs remain high. The roles of natural compounds in CVD treatment are being explored, providing new approaches for the treatment of CVD. Pentacyclic triterpenes are natural compounds with a basic nucleus of 30 carbon atoms, and they have been widely studied for their potential applications in the treatment of CVDs, to which various pharmacological activities contribute, including anti-inflammatory, antioxidant, and antitumor effects. This review introduces the roles of triterpenoids in the prevention and treatment of CVDs, summarizes their potential underlying mechanisms, and provides a comprehensive overview of the therapeutic potential of triterpenoids in the management of CVDs.

Effect of free and nanoemulsified β-caryophyllene on monocrotaline-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary vascular resistance (PVR), right ventricular (RV) failure and premature death. Compounds with vasodilatory characteristics, such as β-caryophyllene, could be promising therapeutics for PAH. This study aimed to determine the effects of free and nanoemulsified β-caryophyllene in lung oxidative stress and heart function in PAH rats. Male Wistar rats (170 g, n = 6/group) were divided into four groups: control (CO), monocrotaline (MCT), monocrotaline + β-caryophyllene (MCT-Bcar) and monocrotaline + nanoemulsion with β-caryophyllene (MCT-Nano). PAH was induced by MCT (60 mg/kg i.p.), and 7 days later, treatment with β-caryophyllene, either free or in a nanoemulsion (by gavage, 176 mg/kg/day) or vehicle was given for 14 days. Echocardiographic and hemodynamic measurements were performed, and after, the RV was collected for morphometry and the lungs for evaluation of oxidative stress, antioxidant enzymes, total sulfhydryl compounds, nitric oxide synthase (NOS) activity and endothelin-1 receptor expression. RV hypertrophy, increased PVR and RV systolic and diastolic pressures (RVSP and RVEDP, respectively) and increased mean pulmonary arterial pressure (mPAP) were observed in the MCT group. Treatment with both free and nanoemulsified β-caryophyllene reduced RV hypertrophy, mPAP, RVSP and lipid peroxidation. The reduction in RVSP was more pronounced in the MCT-Nano group. Moreover, RVEDP decreased only in the MCT-Nano group. These treatments also increased superoxide dismutase, catalase and NOS activities and decreased endothelin-1 receptors expression. Both β-caryophyllene formulations improved mPAP, PVR and oxidative stress parameters. However, β-caryophyllene in a nanoemulsion was more effective in attenuating the effects of PAH.

Copaiba oil improves pulmonary nitric oxide bioavailability in monocrotaline-treated rats

Oxidative stress is involved in increased pulmonary vascular resistance (PVR) and right ventricular (RV) hypertrophy, characteristics of pulmonary arterial hypertension (PAH). Copaiba oil, an antioxidant compound, could attenuate PAH damage. This study's aim was to determine the effects of copaiba oil on lung oxidative stress, PVR, and mean pulmonary arterial pressure (mPAP) in the monocrotaline (MCT) model of PAH. Male Wistar rats (170 g, n = 7/group) were divided into four groups: control, MCT, copaiba oil, and MCT + copaiba oil (MCT-O). PAH was induced by MCT (60 mg/kg i.p.) and, after 1 week, the treatment with copaiba oil (400 mg/kg/day gavage) was started for 14 days. Echocardiographic and hemodynamic measurements were performed. RV was collected for morphometric evaluations and lungs and the pulmonary artery were used for biochemical analysis. Copaiba oil significantly reduced RV hypertrophy, PVR, mPAP, and antioxidant enzyme activities in the MCT-O group. Moreover, increased nitric oxide synthase and decreased NADPH oxidase activities were observed in the MCT-O group. In conclusion, copaiba oil was able to improve the balance between nitric oxide and reactive oxygen species in lungs and the pulmonary artery and to reduce PVR, which could explain a decrease in RV hypertrophy in this PAH model.

Oxidative Stress and Antioxidant Therapy in Pulmonary Hypertension

Pulmonary hypertension (PH) is a progressive disease characterized by elevated artery pressures and pulmonary vascular resistance. Underlying mechanisms comprise endothelial dysfunction, pulmonary artery remodeling and vasoconstriction. Several studies have shown evidence of the critical role of oxidative stress in PH pathophysiology. Alteration of redox homeostasis produces excessive generation of reactive oxygen species, inducing oxidative stress and the subsequent alteration of biological molecules. Exacerbations in oxidative stress production can lead to alterations in nitric oxide signaling pathways, contributing to the proliferation of pulmonary arterial endothelial cells and smooth muscle cells, inducing PH development. Recently, antioxidant therapy has been suggested as a novel therapeutic strategy for PH pathology. However, the favorable outcomes observed in preclinical studies have not been consistently reproduced in clinical practice. Therefore, targeting oxidative stress as a therapeutic intervention for PH is an area that is still being explored. This review summarizes the contribution of oxidative stress to the pathogenesis of the different types of PH and suggests antioxidant therapy as a promising strategy for PH treatment.

GATA6 coordinates cross-talk between BMP10 and oxidative stress axis in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by a progressive increase in pulmonary vascular resistance leading to right ventricular failure and often death. Here we report that deficiency of transcription factor GATA6 is a shared pathological feature of PA endothelial (PAEC) and smooth muscle cells (PASMC) in human PAH and experimental PH, which is responsible for maintenance of hyper-proliferative cellular phenotypes, pulmonary vascular remodeling and pulmonary hypertension. We further show that GATA6 acts as a transcription factor and direct positive regulator of anti-oxidant enzymes, and its deficiency in PAH/PH pulmonary vascular cells induces oxidative stress and mitochondrial dysfunction. We demonstrate that GATA6 is regulated by the BMP10/BMP receptors axis and its loss in PAECs and PASMC in PAH supports BMPR deficiency. In addition, we have established that GATA6-deficient PAEC, acting in a paracrine manner, increase proliferation and induce other pathological changes in PASMC, supporting the importance of GATA6 in pulmonary vascular cell communication. Treatment with dimethyl fumarate resolved oxidative stress and BMPR deficiency, reversed hemodynamic changes caused by endothelial Gata6 loss in mice, and inhibited proliferation and induced apoptosis in human PAH PASMC, strongly suggesting that targeting GATA6 deficiency may provide a therapeutic advance for patients with PAH.

Novel Oxidative Stress Biomarkers with Risk Prognosis Values in Heart Failure

Oxidative stress (OS) is mediated by reactive oxygen species (ROS), which in cardiovascular and other disease states, damage DNA, lipids, proteins, other cellular and extra-cellular components. OS is both initiated by, and triggers inflammation, cardiomyocyte apoptosis, matrix remodeling, myocardial fibrosis, and neurohumoral activation. These have been linked to the development of heart failure (HF). Circulating biomarkers generated by OS offer potential utility in patient management and therapeutic targeting. Novel OS-related biomarkers such as NADPH oxidases (sNox2-dp, Nrf2), advanced glycation end-products (AGE), and myeloperoxidase (MPO), are signaling molecules reflecting pathobiological changes in HF. This review aims to evaluate current OS-related biomarkers and their associations with clinical outcomes and to highlight those with greatest promise in diagnosis, risk stratification and therapeutic targeting in HF.

Mitochondrial Dysfunction in Pulmonary Hypertension

Pulmonary hypertension (PH) is a multi-etiological condition with a similar hemodynamic clinical sign and end result of right heart failure. Although its causes vary, a similar link across all the classifications is the presence of mitochondrial dysfunction. Mitochondria, as the powerhouse of the cells, hold a number of vital roles in maintaining normal cellular homeostasis, including the pulmonary vascular cells. As such, any disturbance in the normal functions of mitochondria could lead to major pathological consequences. The Warburg effect has been established as a major finding in PH conditions, but other mitochondria-related metabolic and oxidative stress factors have also been reported, making important contributions to the progression of pulmonary vascular remodeling that is commonly found in PH pathophysiology. In this review, we will discuss the role of the mitochondria in maintaining a normal vasculature, how it could be altered during pulmonary vascular remodeling, and the therapeutic options available that can treat its dysfunction.

Prognostic value of follow-up vasoreactivity test in pulmonary arterial hypertension

BACKGROUND

Acute vasoreactivity test with inhaled nitric oxide (NO) is performed during diagnostic right heart catheterization (RHC) to identify patients with pulmonary arterial hypertension (PAH) who respond to calcium channel blockers. Our purpose was to investigate the prognostic importance of follow-up vasoreactivity test after treatment.

METHODS

We retrospectively analyzed 36 PAH patients (mean age, 47 years; 61 % treatment-naïve), who underwent diagnostic and follow-up RHC and vasoreactivity tests at our center. The primary outcome was all-cause mortality.

RESULTS

The median time between baseline and follow-up RHC was 9.7 months. Absolute change in mean pulmonary arterial pressure (ΔmPAP) during NO challenge was less pronounced after treatment, but there was great variability among patients. Overall cohort was dichotomized into two groups: preserved vasoreactivity (ΔmPAP ≤ -1 mmHg) and less vasoreactivity (ΔmPAP ≥0 mmHg) at follow-up RHC. Less vasoreactivity group had higher usage rate of endothelin receptor antagonists and parenteral prostacyclin analogues. During a median observation period of 6.3 years after follow-up RHC, 7 patients died, of which 6 showed less vasoreactivity at follow-up. Absolute ΔmPAP ≥0 at follow-up RHC was associated with all-cause mortality in univariable Cox regression analysis (hazard ratio, 8.728; 95 % confidence interval, 1.045-72.887; p = 0.045), whereas other hemodynamic parameters were not. Absolute ΔmPAP ≥0 at follow-up RHC was associated with all-cause mortality in multivariable Cox analysis adjusted for age and known PAH prognostic factors (HR, 12.814; 95 % CI, 1.088-150.891; p = 0.043). Kaplan-Meier survival analysis revealed a significantly worse survival of less vasoreactivity group compared to preserved vasoreactivity group (log-rank test, p = 0.016).

CONCLUSIONS

Follow-up vasoreactivity test after treatment could contribute to the detection of high-risk subgroups who might need careful monitoring and referral for lung transplantation.

Ataxia telangiectasia mutated: The potential negative regulator in platelet-derived growth factor-BB promoted proliferation of pulmonary arterial smooth muscle cells

Objective

To study the role of ataxia telangiectasia mutated (ATM) in the platelet-derived growth factor (PDGF)-BB-induced proliferation of pulmonary arterial smooth muscle cells (PASMCs) through reactive oxygen species (ROS) formation.

Methods

Primary cultures of PASMCs were treated with different concentrations of PDGF-BB or exogenous hydrogen peroxide (H2O2). The activation level of ATM and the proliferation level of PASMCs were measured by immunofluorescence staining and Cell Counting Kit-8, respectively. Moreover, NADPH oxidase 2 (NOX2) and intracellular H2O2 were detected under the stimulation of different levels of PDGF-BB by Western blot and dihydroethidium staining.

Results

Both the control group and 50 ng/ml of the PDGF-BB group showed significantly higher levels of phosphorylation ATM compared to other groups (P < 0.05). With the ATM inhibitor, 50 ng/ml of the PDGF-BB group showed further increased proliferative level compared to the 10 ng/ml (P < 0.05). Both the levels of NOX2 and H2O2 showed dose-dependent manners under PDGF-BB stimulation (P < 0.05). ATM could be activated by H2O2 upon a dose-dependent way, except for the 500 μM H2O2 group. Under 200 μM H2O2 stimulation, proliferation level decreased significantly (P < 0.05), while no significant difference was shown with the addition of ATM inhibitor (P > 0.05).

Conclusion

Our study first established ROS-induced ATM activation in PDGF-BB-stimulated proliferation of PASMCs. Inhibition of ATM had promoted effects on the proliferation of PASMCs under the excessive levels of PDGF-BB and H2O2. Our study might provide a novel promising target for the treatment of pulmonary arterial hypertension (PAH).

Radiation-induced cardiac side-effects: The lung as target for interacting damage and intervention

Radiotherapy is part of the treatment for many thoracic cancers. During this treatment heart and lung tissue can often receive considerable doses of radiation. Doses to the heart can potentially lead to cardiac effects such as pericarditis and myocardial fibrosis. Common side effects after lung irradiation are pneumonitis and pulmonary fibrosis. It has also been shown that lung irradiation has effects on cardiac function. In a rat model lung irradiation caused remodeling of the pulmonary vasculature increasing resistance of the pulmonary vascular bed, leading to enhanced pulmonary artery pressure, right ventricle hypertrophy and reduced right ventricle performance. Even more pronounced effects are observed when both, lung and heart are irradiated.

The effects observed after lung irradiation show striking similarities with symptoms of pulmonary arterial hypertension. In particular, the vascular remodeling in lung tissue seems to have similar underlying features. Here, we discuss the similarities and differences of vascular remodeling observed after thoracic irradiation compared to those in pulmonary arterial hypertension patients and research models. We will also assess how this knowledge of similarities could potentially be translated into interventions which would be beneficial for patients treated for thoracic tumors, where dose to lung tissue is often unavoidable.

Surgical Treatment for Empyema Thoracis: Prognostic Role of Preoperative Transthoracic Echocardiography and Serum Calcium

Background: Empyema is a major cause of mortality and hospitalization. Symptoms include difficulty breathing and chest pain. Calcium plays an essential role in the physiology of the cardiovascular system. However, there is little evidence on the role of echocardiography and the serum calcium levels of patients undergoing video-assisted thoracoscopic surgery (VATS) for empyema. This study aimed to investigate the risk factors for postoperative mortality in patients with empyema who required surgery. Methods: This single-institution retrospective study compared the outcomes of VATS for thoracic empyema (in terms of survival and mortality) in 122 patients enrolled between July 2015 and June 2019. Results: This study examined patients with thoracic empyema. The majority of the patients were males (100/122, 81.9%). The in-hospital/30-day mortality rate was 10.6% (13 patients). The calcium levels were 7.82 ± 1.17 mg/dL in the survival group and 6.88 ± 1.88 mg/dL in the mortality group (p = 0.032). In the mortality group, the utilization of echocardiography and serum calcium levels independently contributed to the risk prediction more than clinical variables. Patients in our cohort exhibited elevated pulmonary artery systolic pressure (PASP) and hypocalcemia, which were associated with increased postoperative mortality. Conclusion: Elevated PASP and calcium levels at the low end of the normal range demonstrated significant prognostic value in predicting mortality in patients with thoracic empyema who required surgical intervention. Recognizing this potential is critical in order to obtain better outcomes.

Target Nuclear Factor Erythroid 2-Related Factor 2 in Pulmonary Hypertension: Molecular Insight into Application

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor involved in maintaining redox balance and activates the expression of downstream antioxidant enzymes. Nrf2 has received wide attention considering its crucial role in oxidative and electrophilic stress. Large amounts of studies have demonstrated the protective role of Nrf2 activation in various pulmonary hypertension (pH) models. Additionally, various kinds of natural phytochemicals acting as Nrf2 activators prevent the development of pH and provide a novel and promising therapeutic insight for the treatment of pH. In the current review, we give a brief introduction of Nrf2 and focus on the role and mechanism of Nrf2 in the pathophysiology of pH and then review the relevant research of Nrf2 agonists in pH in both experimental research and clinical trials.

Reviewing the suitability of mitochondrial transplantation as therapeutic approach for pulmonary hypertension in the era of personalised medicine

Pulmonary hypertension (PH) is a fatal disease, defined as a mean pulmonary artery pressure ≥ 25 mm Hg. It is caused, in part, by mitochondrial dysfunction. Among the various biological therapies proposed to rescue mitochondrial dysfunction, evidence going back as far as 2009, suggests that mitochondrial transplantation is an alternative. Although scant, recent PH findings and other literature supports a role for mitochondrial transplantation as a therapeutic approach in the context of PH. In experimental models of PH, it confers beneficial effects that include reduced pulmonary vasoconstriction, reduced pulmonary vascular remodelling, and improved right ventricular function. It also reduces the proliferation of pulmonary artery smooth muscle cells. However, first, we must understand that more research is needed before mitochondrial transplantation can be considered an effective therapy in the clinical setting, as many of the mechanisms or potential long-term risks are still unknown. Second, the current challenges of mitochondrial transplantation are surmountable and should not deter researchers from further investigating its effectiveness and trying to overcome these challenges in creative ways.

Tanreqing Injection Regulates Cell Function of Hypoxia-Induced Human Pulmonary Artery Smooth Muscle Cells (HPASMCs) through TRPC1/CX3CL1 Signaling Pathway

Hypoxia-induced pulmonary arterial hypertension (HPAH) is due to hypoxia caused by vascular endothelial cell remolding and damage. Previous studies have suggested that CX3CL1 plays an important role in HPAH which is affected by oxidative stress. Ca²⁺ channel activation correlated with increasing NF-κB levels induced by ROS. Tanreqing injection (TRQ) is a traditional Chinese medicine (TCM) for acute upper respiratory tract infection and acute pneumonia. In the present study, we explored the effect of TRQ on human pulmonary artery smooth muscle cells (HPASMCs) undergoing hypoxia and feasible molecular mechanisms involved in. Cell proliferation was assayed using CCK8 kits. Immunofluorescence and western blotting along with ELISA assay were performed to investigate the effect of TRQ on hypoxia-induced ROS, Ca²⁺, hydroxyl free radicals, and the expression of Ca²⁺ channel protein TRPC1, CX3CR1, HIF-1α, NF-κBp65, and p-NF-κBp65 in HPASMCs. Human CX3CL1 and the inhibitor of TRPC1 as SKF96365 were used for further investigation. TRQ inhibited hypoxia-induced increasing cell adhesion, ROS, Ca²⁺, hydroxyl free radicals, CX3CR1, HIF-1α, NF-κBp65 activation, and even on TRPC1 expression in HPASMC which tended to be attenuated even reversed by CX3CL1. Our results suggested that TRQ might help to attenuate remodeling of HPASMC through inhibiting the ROS and TRPC1/CX3CL1 signaling pathway.

Blueberry extract improves redox balance and functional parameters in the right ventricle from rats with pulmonary arterial hypertension

PURPOSE

Pulmonary arterial hypertension (PAH) is a disease characterized by increased pulmonary vascular resistance and right ventricle (RV) failure. In this context, oxidative stress is an essential element contributing to PAH's pathophysiology. Thus, blueberry (BB), which has a high antioxidant capacity, emerges as a natural therapeutic approach in PAH. This work evaluated the effect of BB extract on redox balance in RV in a PAH's animal model.

METHODS

Male Wistar rats (200 ± 20 g) (n = 72) were randomized into eight groups: control (CTR); monocrotaline (MCT); CTR and MCT treated at doses of 50, 100, and 200 mg/kg BB. PAH was induced by administration of MCT (60 mg/kg, intraperitoneal). Rats were treated with BB orally for 5 weeks (2 weeks before monocrotaline and 3 weeks after monocrotaline injection). On day 35, rats were submitted to echocardiography and catheterization, then euthanasia and RV harvesting for biochemical analyses.

RESULTS

RV hypertrophy, observed in the MCT groups, was reduced with BB treatment. MCT elevated RV systolic pressure and pressure/time derivatives, while the intervention with BB decreased these parameters. PAH decreased RV output and pulmonary artery outflow acceleration/ejection time ratio, while increased RV diameters, parameters restored by BB treatment. Animals from the MCT group showed elevated lipid peroxidation and NADPH oxidase activity, outcomes attenuated in animals treated with BB, which also led to increased catalase activity.

CONCLUSION

Treatment with BB partially mitigated PAH, which could be associated with improvement of RV redox state. Such findings constitute an advance in the investigation of the role of BB extract in chronic progressive cardiovascular diseases that involve the redox balance, such as PAH.

HIF1α stabilization in hypoxia is not oxidant-initiated

Hypoxic adaptation mediated by HIF transcription factors requires mitochondria, which have been implicated in regulating HIF1α stability in hypoxia by distinct models that involve consuming oxygen or alternatively converting oxygen into the second messenger peroxide. Here, we use a ratiometric, peroxide reporter, HyPer to evaluate the role of peroxide in regulating HIF1α stability. We show that antioxidant enzymes are neither homeostatically induced nor are peroxide levels increased in hypoxia. Additionally, forced expression of diverse antioxidant enzymes, all of which diminish peroxide, had disparate effects on HIF1α protein stability. Moreover, decrease in lipid peroxides by glutathione peroxidase-4 or superoxide by mitochondrial SOD, failed to influence HIF1α protein stability. These data show that mitochondrial, cytosolic or lipid ROS were not necessary for HIF1α stability, and favor a model where mitochondria contribute to hypoxic adaptation as oxygen consumers.

Oxidative Stress, Kinase Activation, and Inflammatory Pathways Involved in Effects on Smooth Muscle Cells During Pulmonary Artery Hypertension Under Hypobaric Hypoxia Exposure

High-altitude exposure results in hypobaric hypoxia, which affects organisms by activating several mechanisms at the physiological, cellular, and molecular levels and triggering the development of several pathologies. One such pathology is high-altitude pulmonary hypertension (HAPH), which is initiated through hypoxic pulmonary vasoconstriction to distribute blood to more adequately ventilated areas of the lungs. Importantly, all layers of the pulmonary artery (adventitia, smooth muscle, and endothelium) contribute to or are involved in the development of HAPH. However, the principal action sites of HAPH are pulmonary artery smooth muscle cells (PASMCs), which interact with several extracellular and intracellular molecules and participate in mechanisms leading to proliferation, apoptosis, and fibrosis. This review summarizes the alterations in molecular pathways related to oxidative stress, inflammation, kinase activation, and other processes that occur in PASMCs during pulmonary hypertension under hypobaric hypoxia and proposes updates to pharmacological treatments to mitigate the pathological changes in PASMCs under such conditions. In general, PASMCs exposed to hypobaric hypoxia undergo oxidative stress mediated by Nox4, inflammation mediated by increases in interleukin-6 levels and inflammatory cell infiltration, and activation of the protein kinase ERK1/2, which lead to the proliferation of PASMCs and contribute to the development of hypobaric hypoxia-induced pulmonary hypertension.

Novel Experimental Therapies for Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive and devastating disease characterized by pulmonary artery vasoconstriction and vascular remodeling leading to vascular rarefaction with elevation of pulmonary arterial pressures and pulmonary vascular resistance. Often PAH will cause death from right heart failure. Current PAH-targeted therapies improve functional capacity, pulmonary hemodynamics and reduce hospitalization. Nevertheless, today PAH still remains incurable and is often refractory to medical therapy, underscoring the need for further research. Over the last three decades, PAH has evolved from a disease of unknown pathogenesis devoid of effective therapy to a condition whose cellular, genetic and molecular underpinnings are unfolding. This article provides an update on current knowledge and summarizes the progression in recent advances in pharmacological therapy in PAH.

Pulmonary arterial hypertension and flavonoids: A role in treatment

Pulmonary arterial hypertension (PAH) is a high mortality progressive pulmonary vascular disease that can lead to right heart failure. The use of clinical drugs for the treatment of PAH is limited to a great extent because of its single target and high price. Flavonoids are widely distributed in nature, and have been found in fruits, vegetables, and traditional Chinese medicine. They have diverse biological activities and various pharmacological effects such as antitumor, antioxidation, and anti-inflammatory. This review summarizes the progress in pharmacodynamics and mechanism of flavonoids in the treatment of PAH in recent years, in order to provide some theoretical references for relevant researchers.

Sex Dimorphism in Pulmonary Hypertension: The Role of the Sex Chromosomes

Pulmonary hypertension (PH) is a condition characterised by an abnormal elevation of pulmonary artery pressure caused by an increased pulmonary vascular resistance, frequently leading to right ventricular failure and reduced survival. Marked sexual dimorphism is observed in patients with pulmonary arterial hypertension, a form of pulmonary hypertension with a particularly severe clinical course. The incidence in females is 2-4 times greater than in males, although the disease is less severe in females. We review the contribution of the sex chromosomes to this sex dimorphism highlighting the impact of proteins, microRNAs and long non-coding RNAs encoded on the X and Y chromosomes. These genes are centrally involved in the cellular pathways that cause increased pulmonary vascular resistance including the production of reactive oxygen species, altered metabolism, apoptosis, inflammation, vasoconstriction and vascular remodelling. The interaction with genetic mutations on autosomal genes that cause heritable pulmonary arterial hypertension such as bone morphogenetic protein 2 (BMPR2) are examined. The mechanisms that can lead to differences in the expression of genes located on the X chromosomes between females and males are also reviewed. A better understanding of the mechanisms of sex dimorphism in this disease will contribute to the development of more effective therapies for both women and men.

Perillyl alcohol suppresses monocrotaline-induced pulmonary arterial hypertension in rats via anti-remodeling, anti-oxidant, and anti-inflammatory effects

Background: Pulmonary arterial hypertension (PAH) is a disastrous disease that current treatments cannot prevent its progression. The present study investigated the effects of perillyl alcohol (PA), a natural monoterpene, on the experimental PAH in male Wistar rats. Methods: Rats divided into eight groups of control, Monocrotaline (MCT), MCT+vehicle, and MCT+PA with doses of 20, 30, 40, 50, and 60 mg/kg. PAH was induced by a single injection of monocrotaline (60 mg/kg) on day 0. The animals in the groups of MCT+vehicle and MCT+PA received the vehicle or PA from day 22 to 42 once a day. On day 43, under general anesthesia, right ventricular systolic pressure (RVSP), as an index of pulmonary artery systolic pressure, and the ratio of the right ventricle to the left ventricle plus septum weight, as the right ventricular hypertrophy index (RVHI), were measured. Also, some histological and biochemical indices were assessed in the lung tissue. Results: MCT significantly (p < .001) enhanced the RVSP and RVHI compared to the control group (89.4 ± 8.2 vs 23 ± 3.3 mmHg & 0.63 ± 0.08 vs 0.26 ± 0.04 respectively). It also increased oxidative stress and inflammatory cytokines and reduced Bax/Bcl2 ratio. Treatment with PA significantly recovered RVSP and hypertrophy index and suppressed vascular cell proliferation, oxidant production, and inflammatory processes. Conclusion: PA exerted noticeable protective and curative effects against MCT-induced PAH and pulmonary vascular remodeling through inhibiting cellular proliferation, oxidative stress, and inflammation. Therefore, PA can be considered as a new therapeutic goal for the treatment of PAH.

Effects of chronic moderate alcohol consumption on right ventricle and pulmonary remodelling

NEW FINDINGS

What is the central question of this study? Does the consumption of a moderate amount of alcohol differentially impact the heart ventricles and pulmonary vasculature. What is the main finding and its importance? Moderate alcohol consumption for a short period of time impaired pulmonary vascular cellular renewal through an apoptosis resistance pattern that ultimately affected the right ventricular function and structure. These findings support the need for a deeper understanding of effects of moderate alcohol consumption on the overall cardiovascular and pulmonary systems.

ABSTRACT

Over the past decades, observational studies have supported an association between moderate alcohol consumption and a lower risk of cardiovascular disease and mortality. However, recent and more robust meta-analyses have raised concerns around the robustness of the evidence for the cardioprotective effects of alcohol. Also, studies of the functional, structural and molecular changes promoted by alcohol have focused primarily on the left ventricle, ignoring the fact that the right ventricle could adapt differently. The aim of this study was to evaluate the bi-ventricular impact of daily moderate alcohol intake, during a 4-week period, in a rodent model. Male Wistar rats were allowed to drink water (Control) or a 5.2% ethanol mixture (ETOH) for 4 weeks. At the end of the protocol bi-ventricular haemodynamic recordings were performed and samples collected for further histological and molecular analysis. ETOH ingestion did not impact cardiac function. However, it caused right ventricle hypertrophy, paralleled by an activation of molecular pathways responsible for cell growth (ERK1/2, AKT), proteolysis (MURF-1) and oxidative stress (NOX4, SOD2). Furthermore, ETOH animals also presented remodelling of the pulmonary vasculature with an increase in pulmonary arteries' medial thickness, which was characterized by increased expression of apoptosis-related proteins expression (BCL-XL, BAX and caspases). Moderate alcohol consumption for a short period of time impaired the lungs and the right ventricle early, before any change could be detected on the left ventricle. Right ventricular changes might be secondary to alcohol-induced pulmonary vasculature remodelling.

Comparison of l-Carnitine and l-Carnitine HCL salt for targeted lung treatment of pulmonary hypertension (PH) as inhalation aerosols: Design, comprehensive characterization, in vitro 2D/3D cell cultures, and in vivo MCT-Rat model of PH

Disrupted l-Carnitine (L-Car) homeostasis has been implicated in the development of pulmonary hypertension (PH). L-Car has been administered orally and intravenously causing systemic side effects. To the authors' knowledge, there are no reports using L-Car or L-Car HCl as an inhaled aerosol through the respiratory route in a targeted manner either from dry powder inhaler (DPI) or liquid delivery system. The purpose of the comprehensive and systematic comparative study between L-Car and L-Car HCl salt was to design and develop dry powder inhalers (DPIs) of each. This was followed by comprehensive physicochemical characterization, in vitro cell viability as a function of dose on 2D human pulmonary cell lines from different lung regions and in vitro cell viability on 3D small airway epithelia human primary cells at the air-liquid interface (ALI). In addition in vitro transepithelial electrical resistance (TEER) in air-interface culture (AIC) conditions on 2D human pulmonary cell line and 3D small airway epithelia human primary cells was carried out. In vitro aerosol dispersion performance using three FDA-approved human DPI devices with different device properties was also examined. Following advanced spray drying under various conditions, two spray drying pump rates (low and medium) were found to successfully produce spray-dried L-Car powders while four spray drying pump rates (low, medium, medium-high, and high) all resulted in the production of spray-dried L-Car HCl powders. Raw L-Car and L-Car HCl were found to be crystalline. All SD powders retained crystallinity following spray drying and polymorphic interconversion in the solid-state was identified as the mechanism for retaining crystallinity after the advanced spray drying process. All SD powders aerosolized readily with all three human DPI devices. However, the in vitro dispersion parameters for the SD powders was not conducive for in vivo administration to rats in DPIs due to hygroscopicity and nanoaggreation. In vivo rat studies were successfully accomplished using inhaled liquid aerosols. Safety was successfully demonstrated in vivo in healthy Sprague Dawley rats. Furthermore, therapeutic efficacy was successfully demonstrated in vivo in the monocrotaline (MCT)-rat model of PH after two weeks of daily L-Car inhalation aerosol treatment.

Single Mutation in the NFU1 Gene Metabolically Reprograms Pulmonary Artery Smooth Muscle Cells

OBJECTIVE

NFU1 is a mitochondrial iron-sulfur scaffold protein, involved in iron-sulfur assembly and transfer to complex II and LAS (lipoic acid synthase). Patients with the point mutation NFU1G208C and CRISPR/CAS9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9)-generated rats develop mitochondrial dysfunction leading to pulmonary arterial hypertension. However, the mechanistic understanding of pulmonary vascular proliferation due to a single mutation in NFU1 remains unresolved. Approach and Results: Quantitative proteomics of isolated mitochondria showed the entire phenotypic transformation of NFU1G206C rats with a disturbed mitochondrial proteomic landscape, involving significant changes in the expression of 208 mitochondrial proteins. The NFU1 mutation deranged the expression pattern of electron transport proteins, resulting in a significant decrease in mitochondrial respiration. Reduced reliance on mitochondrial respiration amplified glycolysis in pulmonary artery smooth muscle cell (PASMC) and activated GPD (glycerol-3-phosphate dehydrogenase), linking glycolysis to oxidative phosphorylation and lipid metabolism. Decreased PDH (pyruvate dehydrogenase) activity due to the lipoic acid shortage is compensated by increased fatty acid metabolism and oxidation. PASMC became dependent on extracellular fatty acid sources due to upregulated transporters such as CD36 (cluster of differentiation 36) and CPT (carnitine palmitoyltransferase)-1. Finally, the NFU1 mutation produced a dysregulated antioxidant system in the mitochondria, leading to increased reactive oxygen species levels. PASMC from NFU1 rats showed apoptosis resistance, increased anaplerosis, and attained a highly proliferative phenotype. Attenuation of mitochondrial reactive oxygen species by mitochondrial-targeted antioxidant significantly decreased PASMC proliferation.

CONCLUSIONS

The alteration in iron-sulfur metabolism completely transforms the proteomic landscape of the mitochondria, leading toward metabolic plasticity and redistribution of energy sources to the acquisition of a proliferative phenotype by the PASMC.

DNA Damage and Repair in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex multifactorial disease with both genetic and environmental dynamics contributing to disease progression. Over the last decade, several studies have demonstrated the presence of genomic instability and increased levels of DNA damage in PAH lung vascular cells, which contribute to their pathogenic apoptosis-resistant and proliferating characteristics. In addition, the dysregulated DNA damage response pathways have been indicated as causal factors for the presence of persistent DNA damage. To understand the significant implications of DNA damage and repair in PAH pathogenesis, the current review summarizes the recent advances made in this field. This includes an overview of the observed DNA damage in the nuclear and mitochondrial genome of PAH patients. Next, the irregularities observed in various DNA damage response pathways and their role in accumulating DNA damage, escaping apoptosis, and proliferation under a DNA damaging environment are discussed. Although the current literature establishes the pertinence of DNA damage in PAH, additional studies are required to understand the temporal sequence of the above-mentioned events. Further, an exploration of different types of DNA damage in conjunction with associated impaired DNA damage response in PAH will potentially stimulate early diagnosis of the disease and development of novel therapeutic strategies.

SIRT1 promotes pulmonary artery endothelial cell proliferation by targeting the Akt signaling pathway

Pulmonary arterial hypertension (PAH) is a disease characterized by a progressive increase in pulmonary vascular resistance and obliterative pulmonary vascular remodeling; however, the pathogenesis of the disease is not completely understood. Sirtuin 1 (SIRT1) is a histone deacetylase involved in cell survival and metabolism. The present study explored the potential role of SIRT1 in human pulmonary arterial endothelial cells (HPAECs) under hypoxic conditions. In vitro HPAECs were cultured and exposed to hypoxic conditions. Subsequently, SIRT1 expression levels were measured via western blotting, the generation of reactive oxygen species (ROS) was evaluated, and the interaction between SIRT1 and Akt was assessed via reverse transcription-quantitative PCR and western blotting. In addition, the effects of SIRT1 on cell proliferation and apoptosis were also investigated. The results indicated that hypoxia induced SIRT1 expression in pulmonary arterial endothelial cells, which may be associated with ROS generation. SIRT1 expression activated the Akt signaling pathway, which increased the expression levels of Bcl-2 and hypoxia-inducible factor-1 in HPAECs. Moreover, SIRT1 promoted HPAEC proliferation and inhibited HPAEC apoptosis. ROS generation enhanced the SIRT1/Akt axis, which was essential for epithelial cell injury under hypoxic conditions. Therefore, blocking SIRT1 may reduce hypoxia-induced pathological damage in HPAECs.

Inflammation as the Common Biological Link Between Depression and Cardiovascular Diseases: Can Carnosine Exert a Protective Role?

Several epidemiological studies have clearly shown the high co-morbidity between depression and Cardiovascular Diseases (CVD). Different studies have been conducted to identify the common pathophysiological events of these diseases such as the overactivation of the hypothalamic- pituitary-adrenal axis and, most importantly, the dysregulation of immune system which causes a chronic pro-inflammatory status. The biological link between depression, inflammation, and CVD can be related to high levels of pro-inflammatory cytokines, such as IL-1β, TNF-α, and IL-6, released by macrophages which play a central role in the pathophysiology of both depression and CVD. Pro-inflammatory cytokines interfere with many of the pathophysiological mechanisms relevant to depression by upregulating the rate-limiting enzymes in the metabolic pathway of tryptophan and altering serotonin metabolism. These cytokines also increase the risk to develop CVD, because activation of macrophages under this pro-inflammatory status is closely associated with endothelial dysfunction and oxidative stress, a preamble to atherosclerosis and atherothrombosis. Carnosine (β-alanyl-L-histidine) is an endogenous dipeptide which exerts a strong antiinflammatory activity on macrophages by suppressing reactive species and pro-inflammatory cytokines production and altering pro-inflammatory/anti-inflammatory macrophage polarization. This dipeptide exhibits antioxidant properties scavenging reactive species and preventing oxidative stress-induced pathologies such as CVD. In the present review we will discuss the role of oxidative stress and chronic inflammation as common pathophysiological events both in depression and CVD and the preclinical and clinical evidence on the protective effect of carnosine in both diseases as well as the therapeutic potential of this dipeptide in depressed patients with a high co-morbidity of cardiovascular diseases.

Apoptosis signal-regulating kinase 1 inhibition in in vivo and in vitro models of pulmonary hypertension

Pulmonary arterial hypertension, group 1 of the pulmonary hypertension disease family, involves pulmonary vascular remodelling, right ventricular dysfunction and cardiac failure. Oxidative stress, through activation of mitogen-activated protein kinases is implicated in these changes. Inhibition of apoptosis signal-regulating kinase 1, an apical mitogen-activated protein kinase, prevented pulmonary arterial hypertension developing in rodent models. Here, we investigate apoptosis signal-regulating kinase 1 in pulmonary arterial hypertension by examining the impact that its inhibition has on the molecular and cellular signalling in established disease. Apoptosis signal-regulating kinase 1 inhibition was investigated in in vivo pulmonary arterial hypertension and in vitro pulmonary hypertension models. In the in vivo model, male Sprague Dawley rats received a single subcutaneous injection of Sugen SU5416 (20 mg/kg) prior to two weeks of hypobaric hypoxia (380 mmHg) followed by three weeks normoxia (Sugen/hypoxic), then animals were either maintained for three weeks on control chow or one containing apoptosis signal-regulating kinase 1 inhibitor (100 mg/kg/day). Cardiovascular measurements were carried out. In the in vitro model, primary cultures of rat pulmonary artery fibroblasts and rat pulmonary artery smooth muscle cells were maintained in hypoxia (5% O₂) and investigated for proliferation, migration and molecular signalling in the presence or absence of apoptosis signal-regulating kinase 1 inhibitor. Sugen/hypoxic animals displayed significant pulmonary arterial hypertension compared to normoxic controls at eight weeks. Apoptosis signal-regulating kinase 1 inhibitor decreased right ventricular systolic pressure to control levels and reduced muscularised vessels in lung tissue. Apoptosis signal-regulating kinase 1 inhibition was found to prevent hypoxia-induced proliferation, migration and cytokine release in rat pulmonary artery fibroblasts and also prevented rat pulmonary artery fibroblast-induced rat pulmonary artery smooth muscle cell migration and proliferation. Apoptosis signal-regulating kinase 1 inhibition reversed pulmonary arterial hypertension in the Sugen/hypoxic rat model. These effects may be a result of intrinsic changes in the signalling of adventitial fibroblast.

New Insights into the Implication of Mitochondrial Dysfunction in Tissue, Peripheral Blood Mononuclear Cells, and Platelets during Lung Diseases

Lung diseases such as chronic obstructive pulmonary disease, asthma, pulmonary arterial hypertension, or idiopathic pulmonary fibrosis are major causes of morbidity and mortality. Complex, their physiopathology is multifactorial and includes lung mitochondrial dysfunction and enhanced reactive oxygen species (ROS) release, which deserves increased attention. Further, and importantly, circulating blood cells (peripheral blood mononuclear cells-(PBMCs) and platelets) likely participate in these systemic diseases. This review presents the data published so far and shows that circulating blood cells mitochondrial oxidative capacity are likely to be reduced in chronic obstructive pulmonary disease (COPD), but enhanced in asthma and pulmonary arterial hypertension in a context of increased oxidative stress. Besides such PBMCs or platelets bioenergetics modifications, mitochondrial DNA (mtDNA) changes have also been observed in patients. These new insights open exciting challenges to determine their role as biomarkers or potential guide to a new therapeutic approach in lung diseases.

β3 adrenergic receptor antagonist SR59230A exerts beneficial effects on right ventricular performance in monocrotaline-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a high mortality rate. Previous studies have revealed the important function of the β3 adrenergic receptor (β3-AR) in cardiovascular diseases, and the potential beneficial effects of numerous β3-AR agonists on pulmonary vasodilation. Conversely, a number of studies have proposed that the antagonism of β3-AR may prevent heart failure. The present study aimed to investigate the functional involvement of β3-AR and the effects of the β3-AR antagonist, SR59230A, in PAH and subsequent heart failure. A rat PAH model was established by the subcutaneous injection of monocrotaline (MCT), and the rats were randomly assigned to groups receiving four weeks of SR59230A treatment or the vehicle control. SR59230A treatment significantly improved right ventricular function in PAH in vivo compared with the vehicle control (P<0.001). Additionally, the expression level of β3-AR was significantly upregulated in the lung and heart tissues of PAH rats compared with the sham group (P<0.01), and SR59230A treatment inhibited this increase in the lung (P<0.05), but not the heart. Specifically, SR59230A suppressed the elevated expression of endothelial nitric oxide and alleviated inflammatory infiltration to the lung under PAH conditions. These results are, to the best of our knowledge, the first to reveal that SR59230A exerts beneficial effects on right ventricular performance in rats with MCT-induced PAH. Furthermore, blocking β3-AR with SR59230A may alleviate the structural changes and inflammatory infiltration to the lung as a result of reduced oxidative stress.

Nitric Oxide Synthase 2 Induction Promotes Right Ventricular Fibrosis

The ability of the right ventricle to compensate pressure overload determines survival in pulmonary arterial hypertension (PAH). Nitric oxide (NO) reduces the right ventricular afterload through pulmonary vasodilation, but excessive NO amounts cause oxidative stress. Oxidative stress drives remodeling of pulmonary arteries and the right ventricle. In the present study, we hypothesized that nitric oxide synthase 2 (NOS2) induction leads to excessive NO amounts that contribute to oxidative stress and impair right ventricular adaptation to PAH. We used a surgical pulmonary artery banding (PAB) mouse model in which right ventricular dysfunction and remodeling occur independently of changes in the pulmonary vasculature. Three weeks after PAB, NOS2 expression was increased twofold in the hypertrophied right ventricle on transcript and protein levels together with increased NO production. Histomorphology localized NOS2 in interstitial and perivascular cardiac fibroblasts after PAB, which was confirmed by cell isolation experiments. In the hypertrophied right ventricle, NOS2 induction was accompanied by an increased formation of reactive oxidants blocked by ex vivo NOS inhibition. We show that reactive oxidant formation in the hypertrophied right ventricle is in part NOS2 dependent (in NOS2-deficient mice [NOS2^-/-]). Lack of NOS2 induction prevented superoxide scavenging and decreased reactive oxidant formation. Functional measures of cardiac function by noninvasive echocardiography together with intracardiac catheterization revealed no differences in heart function between both genotypes after PAB. However, reduced NO and reactive oxidant formation in the hypertrophied right ventricle of NOS2^-/- mice was linked to reduced collagen accumulation through reduced collagen deposition from the cardiac fibroblast. Together, our data demonstrate a profibrotic role for NOS2 induction in the hypertrophied right ventricle.

Oxidative Stress and Its Implications in the Right Ventricular Remodeling Secondary to Pulmonary Hypertension

Pulmonary hypertension (PH) is a pulmonary vascular disease characterized by increased pulmonary artery pressures. Long standing pulmonary arterial pressure overload leads to right ventricular (RV) hypertrophy, RV failure, and death. RV failure is a major determinant of survival in PH. Oxidative stress has been associated with the development of RV failure secondary to PH. Here we summarize the structural and functional changes in the RV in response to sustained pulmonary arterial pressure overload. Furthermore, we review the pre-clinical and clinical studies highlighting the association of oxidative stress with pulmonary vasculature and RV remodeling in chronic PH. Targeting oxidative stress promises to be an effective therapeutic strategy for the treatment of RV failure.

Role of Gender in Regulation of Redox Homeostasis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is one of the diseases with a well-established gender dimorphism. The prevalence of PAH is increased in females with a ratio of 4:1, while poor survival prognosis is associated with the male gender. Nevertheless, the specific contribution of gender in disease development and progression is unclear due to the complex nature of the PAH. Oxidative and nitrosative stresses are important contributors in PAH pathogenesis; however, the role of gender in redox homeostasis has been understudied. This review is aimed to overview the possible sex-specific mechanisms responsible for the regulation of the balance between oxidants and antioxidants in relation to PAH pathobiology.

Effect of a phosphodiesterase-5A (PDE5A) gene polymorphism on response to sildenafil therapy in canine pulmonary hypertension

Pulmonary hypertension (PH) is a common clinical condition associated with morbidity and mortality in both humans and dogs. Sildenafil, a phosphodiesterase-5 (PDE5) inhibitor causing accumulation of cGMP, is frequently used for treatment of PH. The authors previously reported a PDE5A:E90K polymorphism in dogs that results in lower basal cyclic guanosine monophosphate (cGMP) concentrations than in wild-type dogs, which could contribute to variability in the efficacy of sildenafil. In this study, response to sildenafil therapy was evaluated in dogs with PH by comparing echocardiographic parameters, quality-of-life (QOL) score, and plasma cGMP concentrations before and after sildenafil therapy. Overall, tricuspid regurgitation estimated systolic pressure gradient (PG) and QOL score were significantly improved after sildenafil therapy, and the plasma cGMP concentration was significantly decreased. Dogs that had a heterozygous PDE5A status had a significantly worse QOL score when compared to the wildtype group after sildenafil treatment. The simple and multiple regression analyses revealed a significant but weak prediction for the percent reduction in QOL score with sildenafil treatment by plasma cGMP level and by the PDE5A:E90K polymorphic status. This study showed that sildenafil treatment improved PH in dogs, and the PDE5A:E90K polymorphism blunted the efficacy of sildenafil in terms of QOL improvement.

ASK1 Inhibition Halts Disease Progression in Preclinical Models of Pulmonary Arterial Hypertension

RATIONALE

Progression of pulmonary arterial hypertension (PAH) is associated with pathological remodeling of the pulmonary vasculature and the right ventricle (RV). Oxidative stress drives the remodeling process through activation of MAPKs (mitogen-activated protein kinases), which stimulate apoptosis, inflammation, and fibrosis.

OBJECTIVES

We investigated whether pharmacological inhibition of the redox-sensitive apical MAPK, ASK1 (apoptosis signal-regulating kinase 1), can halt the progression of pulmonary vascular and RV remodeling.

METHODS

A selective, orally available ASK1 inhibitor, GS-444217, was administered to two preclinical rat models of PAH (monocrotaline and Sugen/hypoxia), a murine model of RV pressure overload induced by pulmonary artery banding, and cellular models.

MEASUREMENTS AND MAIN RESULTS

Oral administration of GS-444217 dose dependently reduced pulmonary arterial pressure and reduced RV hypertrophy in PAH models. The therapeutic efficacy of GS-444217 was associated with reduced ASK1 phosphorylation, reduced muscularization of the pulmonary arteries, and reduced fibrotic gene expression in the RV. Importantly, efficacy was observed when GS-444217 was administered to animals with established disease and also directly reduced cardiac fibrosis and improved cardiac function in a model of isolated RV pressure overload. In cellular models, GS-444217 reduced phosphorylation of p38 and JNK (c-Jun N-terminal kinase) induced by adenoviral overexpression of ASK1 in rat cardiomyocytes and reduced activation/migration of primary mouse cardiac fibroblasts and human pulmonary adventitial fibroblasts derived from patients with PAH.

CONCLUSIONS

ASK1 inhibition reduced pathological remodeling of the pulmonary vasculature and the right ventricle and halted progression of pulmonary hypertension in rodent models. These preclinical data inform the first description of a causal role of ASK1 in PAH disease pathogenesis.

Protective Effects of 18β-Glycyrrhetinic Acid on Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats

Pulmonary arterial hypertension (PAH) is a destructive and rare disorder characterized by a progressive increase in pulmonary artery pressure and vasoconstriction, ultimately leading to right ventricular failure and death. 18β-Glycyrrhetinic acid (18β-GA) is an active ingredient in the commonly used Chinese herbal medicine radix glycyrrhizae, and it possesses antioxidant, anti-inflammatory, anti-tumor, and other pharmacological properties. This study aimed to determine whether 18β-GA has protective effects against monocrotaline (MCT)-induced PAH and whether it is associated with oxidative stress. The PAH of rats was induced by MCT (60 mg/kg) and oral administration of 18β-GA (100, 50, or 25 mg/kg/day), sildenafil (30 mg/kg), or saline for 21 consecutive days. The development of PAH was evaluated by hemodynamic parameters and right ventricular hypertrophy index. Hematoxylin and eosin staining, Masson trichrome staining, and electron microscopy were used to determine the degree of vascular remodeling and proliferation in lung tissue. Moreover, the antioxidant capacity and malondialdehyde levels in the lungs were measured according to the instructions provided by the test kits, and the expression levels of nicotinamide adenine dinucleotide phosphate oxidase-2 (Nox2) and Nox4 were detected through Western blot analysis. Results of our study indicated that 18β-GA treatment significantly improved the hemodynamic and pathomorphological data of the rats, reduced the changes in oxidative stress biomarkers, and inhibited Nox2 and Nox4 expression. Our research indicated that 18β-GA has a protective effect against MCT-induced PAH by inhibiting oxidative stress in rats.

Stabilization of p22phox by Hypoxia Promotes Pulmonary Hypertension

AIMS

Hypoxia and reactive oxygen species (ROS) have been shown to play a role in the pathogenesis of pulmonary hypertension (PH), a potentially fatal disorder characterized by pulmonary vascular remodeling, elevated pulmonary arterial pressure, and right ventricular hypertrophy. However, how they are linked in the context of PH is not completely understood. We, therefore, investigated the role of the NADPH oxidase subunit p22phox in the response to hypoxia both in vitro and in vivo.

RESULTS

We found that hypoxia decreased ubiquitinylation and proteasomal degradation of p22phox dependent on prolyl hydroxylases (PHDs) and the E3 ubiquitin ligase protein von Hippel Lindau (pVHL), which resulted in p22phox stabilization and accumulation. p22phox promoted vascular proliferation, migration, and angiogenesis under normoxia and hypoxia. Increased levels of p22phox were also detected in lungs and hearts from mice with hypoxia-induced PH. Mice harboring a point mutation (Y121H) in the p22phox gene, which resulted in decreased p22phox stability and subsequent loss of this protein, were protected against hypoxia-induced PH. Mechanistically, p22phox contributed to ROS generation under normoxia, hypoxia, and hypoxia/reoxygenation. p22phox increased the levels and activity of HIF1α, the major cellular regulator of hypoxia adaptation, under normoxia and hypoxia, possibly by decreasing the levels of the PHD cofactors ascorbate and iron(II), and it contributed to the downregulation of the tumor suppressor miR-140 by hypoxia.

INNOVATION

These data identify p22phox as an important regulator of the hypoxia response both in vitro and in vivo.

CONCLUSION

p22phox-dependent NADPH oxidases contribute to the pathophysiology of PH induced by hypoxia.

Umbilical cord blood metabolomics reveal distinct signatures of dyslipidemia prior to bronchopulmonary dysplasia and pulmonary hypertension

Pulmonary hypertension (PH) is a common consequence of bronchopulmonary dysplasia (BPD) and remains a primary contributor to increased morbidity and mortality among preterm infants. Unfortunately, at the present time, there are no reliable early predictive markers for BPD-associated PH. Considering its health consequences, understanding in utero perturbations that lead to the development of BPD and BPD-associated PH and identifying early predictive markers is of utmost importance. As part of the discovery phase, we applied a multiplatform metabolomics approach consisting of untargeted and targeted methodologies to screen for metabolic perturbations in umbilical cord blood (UCB) plasma from preterm infants that did ( n = 21; cases) or did not ( n = 21; controls) develop subsequent PH. A total of 1,656 features were detected, of which 407 were annotated by metabolite structures. PH-associated metabolic perturbations were characterized by reductions in major choline-containing phospholipids, such as phosphatidylcholines and sphingomyelins, indicating altered lipid metabolism. The reduction in UCB abundances of major choline-containing phospholipids was confirmed in an independent validation cohort consisting of UCB plasmas from 10 cases and 10 controls matched for gestational age and BPD status. Subanalyses in the discovery cohort indicated that elevations in the oxylipins PGE1, PGE2, PGF2a, 9- and 13-HOTE, 9- and 13-HODE, and 9- and 13-KODE were positively associated with BPD presence and severity. This expansive evaluation of cord blood plasma identifies compounds reflecting dyslipidemia and suggests altered metabolite provision associated with metabolic immaturity that differentiate subjects, both by BPD severity and PH development.

Targeting LOX-1 in atherosclerosis and vasculopathy: current knowledge and future perspectives

LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1; also known as OLR1) is the dominant receptor that recognizes and internalizes oxidized low-density lipoproteins (ox-LDLs) in endothelial cells. Several genetic variants of LOX-1 are associated with the risk and severity of coronary artery disease. The LOX-1-ox-LDL interaction induces endothelial dysfunction, leukocyte adhesion, macrophage-derived foam cell formation, smooth muscle cell proliferation and migration, and platelet activation. LOX-1 activation eventually leads to the rupture of atherosclerotic plaques and acute cardiovascular events. In addition, LOX-1 can be cleaved to generate soluble LOX-1 (sLOX-1), which is a useful diagnostic and prognostic marker for atherosclerosis-related diseases in human patients. Of therapeutic relevance, several natural products and clinically used drugs have emerged as LOX-1 inhibitors that have antiatherosclerotic actions. We hereby provide an updated overview of role of LOX-1 in atherosclerosis and associated vascular diseases, with an aim to highlighting the potential of LOX-1 as a novel theranostic tool for cardiovascular disease prevention and treatment.

Insights on the epigenetic mechanisms underlying pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), characterized by localized increased arterial blood pressure in the lungs, is a slow developing long-term disease that can be fatal. PAH is characterized by inflammation, vascular tone imbalance, pathological pulmonary vascular remodeling, and right-sided heart failure. Current treatments for PAH are palliative and development of new therapies is necessary. Recent and relevant studies have demonstrated that epigenetic processes may exert key influences on the pathogenesis of PAH and may be promising therapeutic targets in the prevention and/or cure of this condition. The aim of the present mini-review is to summarize the occurrence of epigenetic-based mechanisms in the context of PAH physiopathology, focusing on the roles of DNA methylation, histone post-translational modifications and non-coding RNAs. We also discuss the potential of epigenetic-based therapies for PAH.

Beneficial Effect of Ocimum sanctum (Linn) against Monocrotaline-Induced Pulmonary Hypertension in Rats

Background: The study was designed to explore any beneficial effect of Ocimum sanctum (Linn) (OS) in experimental pulmonary hypertension (PH) in rats. OS is commonly known as “holy basil” and “Tulsi” and is used in the Indian System of Medicine as antidiabetic, antioxidant, hepatoprotective, adaptogenic, and cardioprotective. Methods: Monocrotaline (MCT) administration caused development of PH in rats after 28 days and rats were observed for 42 days. Treatments (sildenafil; 175 µg/kg, OS; 200 mg/kg) were started from day 29 after the development of PH and continued for 14 days. Parameters to assess the disease development and effectiveness of interventions were echocardiography, right and left ventricular systolic pressures, and right ventricular end diastolic pressure, percentage medial wall thickness (%MWT) of pulmonary artery, oxidative stress markers in lung tissue, NADPH oxidase (Nox-1) protein expression in lung, and mRNA expression of Bcl2 and Bax in right ventricular tissue. Results: OS (200 mg/kg) treatment ameliorated increased lung weight to body weight ratio, right ventricular hypertrophy, increased RVSP, and RVoTD/AoD ratio. Moreover, OS treatment decreases Nox-1 expression and increases expression of Bcl2/Bax ratio caused by MCT. Conclusion: The present study demonstrates that OS has therapeutic ability against MCT-induced PH in rat which are attributed to its antioxidant effect. The effect of OS was comparable with sildenafil.

Natural Antioxidants as Potential Therapy, and a Promising Role for Melatonin Against Pulmonary Hypertension

Plasma and serum samples, and lung/heart tissue of pulmonary hypertension (PH) patients and animal models of PH display elevated oxidative stress. Moreover, the severity of PH and levels of oxidative stress increase concurrently, which suggests that oxidative stress could be utilized as a biomarker for PH progression. Accumulating evidence has well established that oxidative stress is also key role player in the development of PH. Preclinical studies have demonstrated that natural antioxidants improved PH condition, and, therefore, antioxidant therapy has been proposed as a potential therapeutic strategy against PH. These natural antioxidants include medicinal plant extracts and compounds such as resveratrol and melatonin. Recent studies suggest that melatonin provides health benefit against PH, by enhancing antioxidant capacity, increasing vasodilation, counteracting lung and cardiac fibrosis, and stunting right ventricular (RV) hypertrophy/failure. This chapter comprehensively reviews and discusses a variety of natural antioxidants and their efficacy in modulating experimental PH. This chapter also demonstrates that antioxidant therapy remains a therapeutic strategy for PH, and particularly identifies melatonin as a safe, cost-effective, and promising antioxidant therapy.

Tetrandrine prevents monocrotaline-induced pulmonary arterial hypertension in rats through regulation of the protein expression of inducible nitric oxide synthase and cyclic guanosine monophosphate-dependent protein kinase type 1

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by a persistent elevation of pulmonary artery pressure and ventricular hypertrophy. Tetrandrine is a bisbenzylisoquinoline alkaloid that can decrease blood pressure, inhibit the proliferation of vascular smooth muscle cells, and block cardiac hypertrophy, but whether it has a therapeutic effect on PAH remains poorly defined. This study was undertaken to investigate the efficacy of tetrandrine on PAH.

METHODS

Forty-eight male Sprague-Dawley rats were randomly and equally divided into four groups. The control group was injected with normal saline; the others were injected with monocrotaline (MCT) to induce PAH, then treated with saline, tetrandrine, and vardenafil, respectively, from day 21 to day 42. On day 43, we measured the mean pulmonary artery pressure under general anesthesia, dissected the rat, and calculated the right ventricular hypertrophy index [right ventricle/(left ventricle plus septum)]. Later we observed the changes in the pulmonary vascular wall; measured the expression of cyclic guanosine monophosphate-dependent protein kinase type 1 and inducible nitric oxide synthase; measured the levels of superoxide dismutase, glutathione, malondialdehyde, and catalase; and then compared the results among groups.

RESULTS

Compared with the MCT group, rats treated with tetrandrine had attenuated mean pulmonary artery pressure (20.48 ± 1.49 vs 30.07 ± 1.51; P < .01) and right ventricular hypertrophy index (49.19 ± 2.45 vs 68.50 ± 1.95; P < .01), inhibited proliferation of pulmonary artery smooth muscle cells, and improved endothelial function. Tetrandrine also upregulated the expression of protein kinase type 1 (90.86 ± 1.95 vs 67.34 ± 1.50; P < .01); downregulated the expression of inducible nitric oxide synthase (74.76 ± 1.48 vs 80.19 ± 0.28; P < .01); increased levels of superoxide dismutase (245.54 ± 12.98 vs 166.16 ± 21.42; P < .01), glutathione (0.699 ± 0.032 vs 0.514 ± 0.056; P < .01), and catalase (32.13 ± 2.33 vs 27.19 ± 2.72; P < .01); and decreased malondialdehyde (1.027 ± 0.039 vs 1.462 ± 0.055; P < .01).

CONCLUSIONS

Tetrandrine alleviated MCT-induced PAH through regulation of nitric oxide signaling pathway and antioxidant and antiproliferation effects.

Extracellular Cyclophilin A, Especially Acetylated, Causes Pulmonary Hypertension by Stimulating Endothelial Apoptosis, Redox Stress, and Inflammation

OBJECTIVE

Oxidative stress and inflammation play key roles in the development of pulmonary arterial hypertension (PAH). Cyclophilin A (CypA) is secreted in response to oxidative stress and promotes inflammation and cardiovascular disease. Endothelial cell (EC) dysfunction is an early event in the pathogenesis of PAH. We evaluated the role of extracellular CypA in PAH and compared the effects of acetylated CypA (AcK-CypA, increased by oxidative stress) and CypA on EC dysfunction.

APPROACH AND RESULTS

In transgenic mice that express high levels of CypA in EC specifically, a PAH phenotype was observed at 3 months including increased right ventricular systolic pressure, α-smooth muscle actin expression in small arterioles, and CD45-positive cells in the lungs. Mechanistic analysis using cultured mouse pulmonary microvascular EC and human pulmonary microvascular EC showed that extracellular CypA and AcK-CypA stimulated EC inflammatory signals: increased VCAM1 (vascular cell adhesion molecule 1) and ICAM1 (intercellular adhesion molecule 1), phosphorylation of p65, and degradation of IkB. Extracellular CypA and AcK-CypA increased EC apoptosis measured by TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) staining, Apo-ONE assay, and caspase 3 cleavage. Oxidative stress stimulated CypA and AcK-CypA secretion, which further promoted EC oxidative stress. AcK-CypA, compared with CypA, stimulated greater increases in apoptosis, inflammation, and oxidative stress. MM284, a specific inhibitor of extracellular CypA, attenuated EC apoptosis induced by CypA and AcK-CypA.

CONCLUSIONS

EC-derived CypA (especially AcK-CypA) causes PAH by a presumptive mechanism involving increased EC apoptosis, inflammation, and oxidative stress. Our results suggest that inhibiting secreted extracellular CypA is a novel therapeutic approach for PAH.