Reactive Oxygen and Nitrogen Species in the Development of Pulmonary Hypertension

Pulmonary Hypertension and Hyperglycemia-Not a Sweet Combination

Hyperglycemia and pulmonary hypertension (PH) share common pathological pathways that lead to vascular dysfunction and resultant cardiovascular complications. These shared pathologic pathways involve endothelial dysfunction, inflammation, oxidative stress, and hormonal imbalances. Individuals with hyperglycemia or pulmonary hypertension also possess shared clinical factors that contribute to increased morbidity from both diseases. This review aims to explore the relationship between PH and hyperglycemia, highlighting the mechanisms underlying their association and discussing the clinical implications. Understanding these common pathologic and clinical factors will enable early detection for those at-risk for complications from both diseases, paving the way for improved research and targeted therapeutics.

Pulmonary Hypertension Induces Serotonin Hyperreactivity and Metabolic Reprogramming in Coronary Arteries via NOX1/4-TRPM2 Signaling Pathway

BACKGROUND

Clinical evidence revealed abnormal prevalence of coronary artery (CA) disease in patients with pulmonary hypertension (PH). The mechanistic connection between PH and CA disease is unclear. Serotonin (5-hydroxytryptamine), reactive oxygen species, and Ca2+ signaling have been implicated in both PH and CA disease. Our recent study indicates that NOXs (NADPH [nicotinamide adenine dinucleotide phosphate] oxidases) and TRPM2 (transient receptor potential cation channel subfamily M member 2) are key components of their interplay. We hypothesize that activation of the NOX-TRPM2 pathway facilitates the remodeling of CA in PH.

METHODS

Left and right CAs from chronic hypoxia and monocrotaline-induced PH rats were collected to study vascular reactivity, gene expression, metabolism, and mitochondrial function. Inhibitors or specific siRNA were used to examine the pathological functions of NOX1/4-TRPM2 in CA smooth muscle cells.

RESULTS

Significant CA remodeling and 5-hydroxytryptamine hyperreactivity in the right CA were observed in PH rats. NOX1/4-mediated reactive oxygen species production coupled with TRPM2-mediated Ca2+ influx contributed to 5-hydroxytryptamine hyperresponsiveness. CA smooth muscle cells from chronic hypoxia-PH rats exhibited increased proliferation, migration, apoptosis, and metabolic reprogramming in an NOX1/4-TRPM2-dependent manner. Furthermore, the NOX1/4-TRPM2 pathway participated in mitochondrial dysfunction, involving mitochondrial DNA damage, reactive oxygen species production, elevated mitochondrial membrane potential, mitochondrial Ca2+ accumulation, and mitochondrial fission. In vivo knockdown of NOX1/4 alleviated PH and suppressed CA remodeling in chronic hypoxia rats.

CONCLUSIONS

PH triggers an increase in 5-hydroxytryptamine reactivity in the right CA and provokes metabolic reprogramming and mitochondrial disruption in CA smooth muscle cells via NOX1/4-TRPM2 activation. This signaling pathway may play an important role in CA remodeling and CA disease in PH.

Rosmarinic acid ameliorates the complications of monocrotaline-induced right ventricular hypertrophy on the left ventricle: Investigating the signaling pathway of Wnt/β-catenin in the heart

Objectives

Right ventricular hypertrophy (RVH) often results in failure of the right ventricle or even the left ventricle. Rosmarinic acid (RA), a natural polyphenol, is commonly found in Boraginaceae species and some species of ferns and hornworts. This study looked at how RA affects oxidative stress and left ventricular hemodynamic functions as well as RVH in monocrotaline (MCT) induced RVH model rats.

Materials and Methods

To cause RVH, MCT (60 mg/kg) was intraperitoneally (IP) injected. Rats were given saline or RA (10, 15, and 30 mg/kg, gavage, over 21 days). In anesthetized rats, the lead II electrocardiogram was recorded. The hemodynamic functions of the isolated heart were measured using the Langendorff apparatus (at constant pressure). Investigations were made into the right ventricular hypertrophy index (RVHI), the activities of superoxide dismutase, catalase, glutathione, and Wnt and β-catenin gene expressions in the left ventricle. H&E staining was used.

Results

A significant decline in electrocardiogram parameters and anti-oxidant enzyme activities, an increase in QTc (Q-T corrected) intervals, MDA (Malondialdehyde), RVHI, and Wnt/β-catenin gene expression, and also significant changes in the hemodynamic parameters were demonstrated in the MCT group. RA improved the above-mentioned factors.

Conclusion

According to the findings, RA may act as a cardioprotective agent against cardiovascular complications brought on by RVH due to its capacity to boost the activity of cardiac anti-oxidant enzymes and decrease the expression of genes involved in vascular calcification.

Naked cuticle homolog 1 prevents mouse pulmonary arterial hypertension via inhibition of Wnt/β-catenin and oxidative stress

Pulmonary arterial hypertension (PAH) is a poorly prognostic cardiopulmonary disease characterized by abnormal contraction and remodeling of pulmonary artery (PA). Excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) are considered as the major etiology of PA remodeling. As a negative regulator of Wnt/β-catenin pathway, naked cuticle homolog 1 (NKD1) is originally involved in the tumor growth and metastasis via affecting the proliferation and migration of different types of cancer cells. However, the effect of NKD1 on PAH development has not been investigated. In the current study, downregulated NKD1 was identified in hypoxia-challenged PASMCs. NKD1 overexpression by adenovirus carrying vector encoding Nkd1 (Ad-Nkd1) repressed hypoxia-induced proliferation and migration of PASMCs. Mechanistically, upregulating NKD1 inhibited excessive reactive oxygen species (ROS) generation and β-catenin expression in PASMCs after hypoxia stimulus. Both inducing ROS and recovering β-catenin expression abolished NKD1-mediated suppression of proliferation and migration in PASMCs. In vivo, we also observed decreased expression of NKD1 in dissected PAs of monocrotaline (MCT)-induced PAH model. Upregulating NKD1 by Ad-Nkd1 transfection attenuated the increase in right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI), pulmonary vascular wall thickening, and vascular β-catenin expression after MCT treatment. After recovering β-catenin expression by SKL2001, the vascular protection of external expression of NKD1 was also abolished. Taken together, our data suggest that NKD1 inhibits the proliferation, migration of PASMC, and PAH via inhibition of β-catenin and oxidative stress. Thus, targeting NKD1 may provide novel insights into the prevention and treatment of PAH.

Targeting oxidative stress as a preventive and therapeutic approach for cardiovascular disease

Cardiovascular diseases (CVDs) continue to exert a significant impact on global mortality rates, encompassing conditions like pulmonary arterial hypertension (PAH), atherosclerosis (AS), and myocardial infarction (MI). Oxidative stress (OS) plays a crucial role in the pathogenesis and advancement of CVDs, highlighting its significance as a contributing factor. Maintaining an equilibrium between reactive oxygen species (ROS) and antioxidant systems not only aids in mitigating oxidative stress but also confers protective benefits on cardiac health. Herbal monomers can inhibit OS in CVDs by activating multiple signaling pathways, such as increasing the activity of endogenous antioxidant systems and decreasing the level of ROS expression. Given the actions of herbal monomers to significantly protect the normal function of the heart and reduce the damage caused by OS to the organism. Hence, it is imperative to recognize the significance of herbal monomers as prospective therapeutic interventions for mitigating oxidative damage in CVDs. This paper aims to comprehensively review the origins and mechanisms underlying OS, elucidate the intricate association between CVDs and OS, and explore the therapeutic potential of antioxidant treatment utilizing herbal monomers. Furthermore, particular emphasis will be placed on examining the cardioprotective effects of herbal monomers by evaluating their impact on cardiac signaling pathways subsequent to treatment.

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.

Specificity Protein 1-Mediated Promotion of CXCL12 Advances Endothelial Cell Metabolism and Proliferation in Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a rare yet devastating and incurable disease with few treatment options. The underlying mechanisms of PAH appear to involve substantial cellular proliferation and vascular remodeling, causing right ventricular overload and eventual heart failure. Recent evidence suggests a significant seminal role of the pulmonary endothelium in the initiation and promotion of PAH. Our previous work identified elevated reactive oxygen species (ROS)-producing enzyme NADPH oxidase 1 (NOX1) in human pulmonary artery endothelial cells (HPAECs) of PAH patients promoting endothelial cell proliferation in vitro. In this study, we interrogated chemokine CXCL12's (aka SDF-1) role in EC proliferation under the control of NOX1 and specificity protein 1 (Sp1). We report here that NOX1 can drive hypoxia-induced endothelial CXCL12 expression via the transcription factor Sp1 leading to HPAEC proliferation and migration. Indeed, NOX1 drove hypoxia-induced Sp1 activation, along with an increased capacity of Sp1 to bind cognate promoter regions in the CXCL12 promoter. Sp1 activation induced elevated expression of CXCL12 in hypoxic HPAECs, supporting downstream induction of expression at the CXCL12 promoter via NOX1 activity. Pathological levels of CXCL12 mimicking those reported in human PAH patient serum restored EC proliferation impeded by specific NOX1 inhibitor. The translational relevance of our findings is highlighted by elevated NOX1 activity, Sp1 activation, and CXCL12 expression in explanted lung samples from PAH patients compared to non-PAH controls. Analysis of phosphofructokinase, glucose-6-phosphate dehydrogenase, and glutaminase activity revealed that CXCL12 induces glutamine and glucose metabolism, which are foundational to EC cell proliferation. Indeed, in explanted human PAH lungs, demonstrably higher glutaminase activity was detected compared to healthy controls. Finally, infusion of recombinant CXCL12 into healthy mice amplified pulmonary arterial pressure, right ventricle remodeling, and elevated glucose and glutamine metabolism. Together these data suggest a central role for a novel NOX1-Sp1-CXCL12 pathway in mediating PAH phenotype in the lung endothelium.

Endothelial PHD2 deficiency induces nitrative stress via suppression of caveolin-1 in pulmonary hypertension

BACKGROUND

Nitrative stress is a characteristic feature of the pathology of human pulmonary arterial hypertension. However, the role of nitrative stress in the pathogenesis of obliterative vascular remodelling and severe pulmonary arterial hypertension remains largely unclear.

METHOD

Our recently identified novel mouse model (Egln1Tie2Cre, Egln1 encoding prolyl hydroxylase 2 (PHD2)) has obliterative vascular remodelling and right heart failure, making it an excellent model to use in this study to examine the role of nitrative stress in obliterative vascular remodelling.

RESULTS

Nitrative stress was markedly elevated whereas endothelial caveolin-1 (Cav1) expression was suppressed in the lungs of Egln1Tie2Cre mice. Treatment with a superoxide dismutase mimetic, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride or endothelial Nos3 knockdown using endothelial cell-targeted nanoparticle delivery of CRISPR-Cas9/guide RNA plasmid DNA inhibited obliterative pulmonary vascular remodelling and attenuated severe pulmonary hypertension in Egln1Tie2Cre mice. Genetic restoration of Cav1 expression in Egln1Tie2Cre mice normalised nitrative stress, reduced pulmonary hypertension and improved right heart function.

CONCLUSION

These data suggest that suppression of Cav1 expression secondary to PHD2 deficiency augments nitrative stress through endothelial nitric oxide synthase activation, which contributes to obliterative vascular remodelling and severe pulmonary hypertension. Thus, a reactive oxygen/nitrogen species scavenger might have therapeutic potential for the inhibition of obliterative vascular remodelling and severe pulmonary arterial hypertension.

Case Report: Vitamin C combined with multiple micronutrient deficiencies is associated with pulmonary arterial hypertension in children with autistic spectrum disorder

Children with developmental and behavioral problems including autistic spectrum disorders (ASDs) may have inappropriate feeding behaviors, which leads to an increased risk of multiple nutrient deficiencies. Vitamin C deficiency is one of the common nutrient deficiencies reported in children with inappropriate feeding. This case report illustrates two cases of ASD children with a clinical presentation of pulmonary arterial hypertension, a rare presentation of vitamin C deficiency. Vitamin C supplementation, pulmonary vasodilator, and supportive treatment were provided. Patients could recover from the illness and could be discharged from the hospital in a short time. In addition to vitamin C, the patients also had multiple micronutrient deficiencies. Nutrition counseling was given and micronutrient supplement was continued until follow-up. Regular nutrition assessment and counseling among children with ASD are needed to prevent nutrient deficiencies which may lead to life-threatening complications.

The Impact of Tobacco Cigarettes, Vaping Products and Tobacco Heating Products on Oxidative Stress

Cells constantly produce oxidizing species because of their metabolic activity, which is counteracted by the continuous production of antioxidant species to maintain the homeostasis of the redox balance. A deviation from the metabolic steady state leads to a condition of oxidative stress. The source of oxidative species can be endogenous or exogenous. A major exogenous source of these species is tobacco smoking. Oxidative damage can be induced in cells by chemical species contained in smoke through the generation of pro-inflammatory compounds and the modulation of intracellular pro-inflammatory pathways, resulting in a pathological condition. Cessation of smoking reduces the morbidity and mortality associated with cigarette use. Next-generation products (NGPs), as alternatives to combustible cigarettes, such as electronic cigarettes (e-cig) and tobacco heating products (THPs), have been proposed as a harm reduction strategy to reduce the deleterious impacts of cigarette smoking. In this review, we examine the impact of tobacco smoke and MRPs on oxidative stress in different pathologies, including respiratory and cardiovascular diseases and tumors. The impact of tobacco cigarette smoke on oxidative stress signaling in human health is well established, whereas the safety profile of MRPs seems to be higher than tobacco cigarettes, but further, well-conceived, studies are needed to better understand the oxidative effects of these products with long-term exposure.

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.

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.

Cigarette smoke extract stimulates human pulmonary artery smooth muscle cell proliferation: Role of inflammation and oxidative stress

Objectives

Cigarette smoke may play a direct role in proliferation of human pulmonary artery smooth muscle cells (HPASMCs). However, the mechanism involved and the effect of interventions remain unclear. We aimed to evaluate the effect of cigarette smoke extract (CSE) on HPASMCs, explore the role of inflammation and oxidative stress, and the effects of Tempol and PDTC in this process.

Materials and Methods

HPASMCs were subjected to normal control (NC), CSE, CSE+Tempol (CSE+T), and CSE+PDTC (CSE+P) groups. Proliferation of HPASMCs was measured by CCK-8 and Western blot. TNF-α, IL-6, MDA, and SOD levels were determined by ELISA and commercial kits. Nuclear translocation of NF-κB p65 was evaluated by western blot.

Results

1%, 2.5%, and 5% CSE all promoted proliferation of HPASMCs, and effect of 1% CSE was the most significant, however, 7.5% and 10% CSE inhibited viability of cells (all P<0.05). Compared with the NC group, TNF-α, IL-6, and MDA levels increased, SOD activity decreased (all P<0.05), and NF-κB p65 expression in nuclei increased (P=0.04) in the CSE group. Tempol and PDTC inhibited the proliferation of HPASMCs induced by CSE (all P<0.05). And compared with the CSE group, TNF-α, IL-6, and MDA levels in CSE+T and CSE+P groups decreased, while SOD activity increased (all P<0.05). Tempol reduced the expression of NF-κB p65 in nuclei but did not achieve a significant difference (P=0.08). PDTC inhibited the nuclear translocation of NF-κB p65 (P=0.03).

Conclusion

CSE stimulates HPASMCs proliferation in a certain concentration range. The CSE-induced proliferation of HPASMCs involved excessive inflammatory response and oxidative stress. Tempol and PDTC attenuate these effects of CSE on HPASMCs.

Novel Prognostic Predictor for Primary Pulmonary Hypertension: Focus on Blood Urea Nitrogen

Background: Primary pulmonary hypertension (PPH) is a life-threatening disease associated with increased mortality. The urea cycle pathway plays a major role in PPH severity and treatment response. Little is known about the association of the blood urea nitrogen (BUN) and PPH prognosis.

Methods: Clinical data were extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database. Adult patients (≥18 years) patients with primary pulmonary hypertension (PPH) in the database were enrolled. Spearman correlation was used to analyze the association of BUN with length of hospital and intensive care unit (ICU) stays. The chi-square test was used to analyze the association of BUN with mortality rate. Survival curves were estimated using the Kaplan-Meier method and compared by the log-rank test. Multivariable logistic regression was used to identify the BUN as an independent prognostic factor of mortality. Receiver operating characteristic (ROC) curves and the area under the curve (AUC) were used to analyze the sensitivity and specificity for mortality.

Results: In total, 263 patients who met the selection criteria were enrolled. BUN was significantly positively associated with length of hospital stay and ICU stay (hospital stay: ρ = 0.282, ICU stay: ρ = 0.276; all P < 0.001). Higher hospital, 90-day and 4-year mortality rates were observed in the higher BUN quartile of PPH patients (hospital: P = 0.002; 90-day: P = 0.025; 4-year: P < 0.001). The Kaplan-Meier survival curves showed that patients in higher BUN quartile tended to have lower 4-year survival (Q1:7.65%, Q2: 10.71%; Q3: 14.80%, Q4: 16.84%; P < 0.0001). Logistic regression analyses found a significant association of BUN and mortality (hospital: OR = 1.05, 95% CI = 1.02–1.08, P = 0.001; 90-day: OR = 1.02, 95% CI = 1.00–1.05, P = 0.027; 4-year: OR = 1.05, 95% CI = 1.02–1.08, P = 0.001). Results of ROC and AUC showed that the diagnostic performance of BUN for mortality was moderately good.

Conclusion: BUN was positively correlated with the length of hospital stay and ICU stay of PPH patients. Higher BUN was associated with higher hospital, 90-day and 4-year mortality and lower 4-year survival of PPH patients. These findings indicate that BUN can be a novel potential prognostic predictor for PPH.

Thioredoxin system activation is associated with the progression of experimental pulmonary arterial hypertension

In addition to being an antioxidant, thioredoxin (Trx) is known to stimulate signaling pathways involved in cell proliferation and to inhibit apoptosis. The aim of this study was to explore the role of Trx in some of these pathways along the progression of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). Male rats were first divided into two groups: monocrotaline (MCT - 60 mg/kg i.p.) and control (received saline), that were further divided into three groups: 1, 2, and 3 weeks. Animals were submitted to echocardiographic analysis. Right and left ventricles were used for the measurement of hypertrophy, through morphometric and histological analysis. The lung was prepared for biochemical and molecular analysis. One week after MCT injection, there was an increase in thioredoxin reductase (TrxR) activity, a reduction in glutathione reductase (GR) activity, and an increase in Trx-1 and vitamin D3 up-regulated protein-1 (VDUP-1) expression. Two weeks after MCT injection, there was an increase in VDUP-1, Akt and cleaved caspase-3 activation, and a decrease in Trx-1 and Nrf2 expression. PAH-induced by MCT promoted a reduction in Nrf2 and Trx-1 expression as well as an increase in Akt and VDUP-1 expression after three weeks. The increase in pulmonary vascular resistance was accompanied by increased TrxR activity, suggesting an association between the Trx system and functional changes in the progression of PAH. It seems that Trx-1 activation was an adaptive response to MCT administration to cope with pulmonary remodeling and disease progression, suggesting a potential new target for PAH therapeutics.

Nitric oxide — soluble guanylate cyclase — cyclic guanosine monophosphate signaling pathway in the pathogenesis of heart failure and search for novel therapeutic targets

Heart failure is a severe disease with an unfavorable prognosis, which requires intensification of therapy and the search for novel approaches to treatment. In this review, the physiological significance of soluble guanylate cyclase-related signaling pathway, reasons for decrease in its activity in heart failure and possible consequences are discussed. Pharmacological methods of stimulating the production of cyclic guanosine monophosphate using drugs with different mechanisms of action are considered. Data from clinical studies regarding their effectiveness and safety are presented. A promising approach is stimulation of soluble guanylate cyclase, which showed beneficial effects in preclinical studies, as well as in the recently completed phase III VICTORIA study.

Mechanosensitivity in Pulmonary Circulation: Pathophysiological Relevance of Stretch-Activated Channels in Pulmonary Hypertension

A variety of cell types in pulmonary arteries (endothelial cells, fibroblasts, and smooth muscle cells) are continuously exposed to mechanical stimulations such as shear stress and pulsatile blood pressure, which are altered under conditions of pulmonary hypertension (PH). Most functions of such vascular cells (e.g., contraction, migration, proliferation, production of extracellular matrix proteins, etc.) depend on a key event, i.e., the increase in intracellular calcium concentration ([Ca²⁺]_i) which results from an influx of extracellular Ca²⁺ and/or a release of intracellular stored Ca²⁺. Calcium entry from the extracellular space is a major step in the elevation of [Ca²⁺]_i, involving a variety of plasmalemmal Ca²⁺ channels including the superfamily of stretch-activated channels (SAC). A common characteristic of SAC is that their gating depends on membrane stretch. In general, SAC are non-selective Ca²⁺-permeable cation channels, including proteins of the TRP (Transient Receptor Potential) and Piezo channel superfamily. As membrane mechano-transducers, SAC convert physical forces into biological signals and hence into a cell response. Consequently, SAC play a major role in pulmonary arterial calcium homeostasis and, thus, appear as potential novel drug targets for a better management of PH.

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.

Cinaciguat Prevents Postnatal Closure of Ductus Arteriosus by Vasodilation and Anti-remodeling in Neonatal Rats

Closure of the ductus arteriosus (DA) involves vasoconstriction and vascular remodeling. Cinaciguat, a soluble guanylyl cyclase (sGC) activator, was reported with vasodilatory and anti-remodeling effects on pulmonary hypertensive vessels. However, its effects on DA are not understood. Therefore, we investigated whether cinaciguat regulated DA patency and examined its underlying mechanisms. In vivo, we found that cinaciguat (10 mg/kg, i.p. at birth) prevented DA closure at 2 h after birth with luminal patency and attenuated intimal thickening. These anti-remodeling effects were associated with enhanced expression of cyclic guanosine monophosphate (cGMP) in DA. Ex vivo, cinaciguat dilated oxygen-induced DA constriction dose-dependently. Such vasodilatory effect was blunted by KT-5823, a PKG inhibitor. In DA smooth muscle cells (DASMCs), we further showed that cinaciguat inhibited angiotensin II (Ang II)-induced proliferation and migration of DASMCs. In addition, cinaciguat inhibited Ang II-induced mitochondrial reactive oxygen species (ROS) production. Finally, Ang II-activated MAPKs and Akt were also inhibited by cinaciguat. In conclusion, cinaciguat prevents postnatal DA closure by vasodilation and anti-remodeling through the cGMP/PKG pathway. The mechanisms underlying anti-remodeling effects include anti-proliferation and anti-migration, with attenuation of mitochondrial ROS production, MAPKs, and Akt signaling. Thus, this study implicates that sGC activation may be a promising novel strategy to regulate DA patency.

Hypoxia and the integrated stress response promote pulmonary hypertension and preeclampsia: Implications in drug development

Chronic hypoxia is a common cause of pulmonary hypertension, preeclampsia, and intrauterine growth restriction (IUGR). The molecular mechanisms underlying these diseases are not completely understood. Chronic hypoxia may induce the generation of reactive oxygen species (ROS) in mitochondria, promote endoplasmic reticulum (ER) stress, and result in the integrated stress response (ISR) in the pulmonary artery and uteroplacental tissues. Numerous studies have implicated hypoxia-inducible factors (HIFs), oxidative stress, and ER stress/unfolded protein response (UPR) in the development of pulmonary hypertension, preeclampsia and IUGR. This review highlights the roles of HIFs, mitochondria-derived ROS and UPR, as well as their interplay, in the pathogenesis of pulmonary hypertension and preeclampsia, and their implications in drug development.

Pleiotropic and Potentially Beneficial Effects of Reactive Oxygen Species on the Intracellular Signaling Pathways in Endothelial Cells

Endothelial cells (ECs) are exposed to molecular dioxygen and its derivative reactive oxygen species (ROS). ROS are now well established as important signaling messengers. Excessive production of ROS, however, results in oxidative stress, a significant contributor to the development of numerous diseases. Here, we analyze the experimental data and theoretical concepts concerning positive pro-survival effects of ROS on signaling pathways in endothelial cells (ECs). Our analysis of the available experimental data suggests possible positive roles of ROS in induction of pro-survival pathways, downstream of the G_i-protein-coupled receptors, which mimics insulin signaling and prevention or improvement of the endothelial dysfunction. It is, however, doubtful, whether ROS can contribute to the stabilization of the endothelial barrier.

Caveolar peroxynitrite formation impairs endothelial TRPV4 channels and elevates pulmonary arterial pressure in pulmonary hypertension

Recent studies have focused on the contribution of capillary endothelial TRPV4 channels to pulmonary pathologies, including lung edema and lung injury. However, in pulmonary hypertension (PH), small pulmonary arteries are the focus of the pathology, and endothelial TRPV4 channels in this crucial anatomy remain unexplored in PH. Here, we provide evidence that TRPV4 channels in endothelial cell caveolae maintain a low pulmonary arterial pressure under normal conditions. Moreover, the activity of caveolar TRPV4 channels is impaired in pulmonary arteries from mouse models of PH and PH patients. In PH, up-regulation of iNOS and NOX1 enzymes at endothelial cell caveolae results in the formation of the oxidant molecule peroxynitrite. Peroxynitrite, in turn, targets the structural protein caveolin-1 to reduce the activity of TRPV4 channels. These results suggest that endothelial caveolin-1-TRPV4 channel signaling lowers pulmonary arterial pressure, and impairment of endothelial caveolin-1-TRPV4 channel signaling contributes to elevated pulmonary arterial pressure in PH. Thus, inhibiting NOX1 or iNOS activity, or lowering endothelial peroxynitrite levels, may represent strategies for restoring vasodilation and pulmonary arterial pressure in PH.

Endothelial-to-Mesenchymal Transition in Pulmonary Arterial Hypertension

Endothelial-to-mesenchymal transition (EndMT) is a process that encompasses extensive transcriptional reprogramming of activated endothelial cells leading to a shift toward mesenchymal cellular phenotypes and functional responses. Initially observed in the context of embryonic development, in the last few decades EndMT is increasingly recognized as a process that contributes to a variety of pathologies in the adult organism. Within the settings of cardiovascular biology, EndMT plays a role in various diseases, including atherosclerosis, heart valvular disease, cardiac fibrosis, and myocardial infarction. EndMT is also being progressively implicated in development and progression of pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH). This review covers the current knowledge about EndMT in PH and PAH, and provides comprehensive overview of seminal discoveries. Topics covered include evidence linking EndMT to factors associated with PAH development, including hypoxia responses, inflammation, dysregulation of bone-morphogenetic protein receptor 2 (BMPR2), and redox signaling. This review amalgamates these discoveries into potential insights for the identification of underlying mechanisms driving EndMT in PH and PAH, and discusses future directions for EndMT-based therapeutic strategies in disease management.

Increased MAO-A Activity Promotes Progression of Pulmonary Arterial Hypertension

Monoamine oxidases (MAOs), a class of enzymes bound to the outer mitochondrial membrane, are important sources of reactive oxygen species. Increased MAO-A activity in endothelial cells and cardiomyocytes contributes to vascular dysfunction and progression of left heart failure. We hypothesized that inhibition of MAO-A can be used to treat pulmonary arterial hypertension (PAH) and right ventricular (RV) failure. MAO-A levels in lung and RV samples from patients with PAH were compared with levels in samples from donors without PAH. Experimental PAH was induced in male Sprague-Dawley rats by using Sugen 5416 and hypoxia (SuHx), and RV failure was induced in male Wistar rats by using pulmonary trunk banding (PTB). Animals were randomized to receive either saline or the MAO-A inhibitor clorgyline at 10 mg/kg. Echocardiography and RV catheterization were performed, and heart and lung tissues were collected for further analysis. We found increased MAO-A expression in the pulmonary vasculature of patients with PAH and in experimental experimental PAH induced by SuHx. Cardiac MAO-A expression and activity was increased in SuHx- and PTB-induced RV failure. Clorgyline treatment reduced RV afterload and pulmonary vascular remodeling in SuHx rats through reduced pulmonary vascular proliferation and oxidative stress. Moreover, clorgyline improved RV stiffness and relaxation and reversed RV hypertrophy in SuHx rats. In PTB rats, clorgyline had no direct clorgyline had no direct effect on the right ventricle effect. Our study reveals the role of MAO-A in the progression of PAH. Collectively, these findings indicated that MAO-A may be involved in pulmonary vascular remodeling and consecutive RV failure.

Novel Insights Regarding Nitric Oxide and Cardiovascular Diseases

Nitric oxide (NO) is a powerful mediator with biological activities such as vasodilation and prevention of vascular smooth muscle cell proliferation as well as functional regulation of cardiac cells. Thus, impaired production or reduced bioavailability of NO predisposes to the onset of different cardiovascular (CV) diseases. Alterations in the redox balance associated with excitation-contraction coupling have been identified in heart failure (HF), thus contributing to contractile abnormalities and arrhythmias. For its ability to influence cell proliferation and angiogenesis, NO may be considered a therapeutic option for the management of several CV diseases. Several clinical studies and trials investigated therapeutic NO strategies for systemic hypertension, atherosclerosis, and/or prevention of in stent restenosis, coronary heart disease (CHD), pulmonary arterial hypertension (PAH), and HF, although with mixed results in long-term treatment and effective dose administered in selected groups of patients. Tadalafil, sildenafil, and cinaguat were evaluated for the treatment of PAH, whereas vericiguat was investigated in the treatment of HF patients with reduced ejection fraction. Furthermore, supplementation with hydrogen sulfide, tetrahydrobiopterin, and nitrite/nitrate has shown beneficial effects at the vascular level.

The progression of pulmonary arterial hypertension induced by monocrotaline is characterized by lung nitrosative and oxidative stress, and impaired pulmonary artery reactivity

The time-course of pulmonary arterial hypertension in the monocrotaline (MCT) model was investigated. Male rats were divided into two groups: MCT (received a 60 mg/kg i.p. injection) and control (received saline). The MCT and control groups were further divided into three cohorts, based on the follow-up interval: 1, 2, and 3 weeks. Right ventricle (RV) catheterization was performed and RV hypertrophy (RVH) was estimated. The lungs were used for biochemical, histological, molecular, and immunohistochemical analysis, while pulmonary artery rings were used for vascular reactivity. MCT promoted lung perivascular edema, inflammatory cells exudation, greater neutrophils and lymphocytes profile, and arteriolar wall thickness, compared to CTR group. Increases in pulmonary artery pressure and in RVH were observed in the MCT 2- and 3-week groups. The first week was marked by the presence of nitrosative stress (50% moderate and 33% accentuated staining by nitrotyrosine). These alterations lead to an adaptation of NO production by NO synthase activity after 2 weeks. Oxidative stress was evident in the third week, probably by an imbalance between endothelin-1 receptors, resulting in extracellular matrix remodeling, endothelial dysfunction, and RVH. Also, it was found a reduced pulmonary arterial vasodilatory response to acetylcholine after 2 (55%) and 3 (45%) weeks in MCT groups. The relevance of this study is precisely to show that nitrosative and oxidative stress predominate in distinct time windows of the disease progression.

Redox Regulation, Oxidative Stress, and Inflammation in Group 3 Pulmonary Hypertension

Group 3 pulmonary hypertension (PH), which occurs secondary to hypoxia lung diseases, is one of the most common causes of PH worldwide and has a high unmet clinical need. A deeper understanding of the integrative pathological and adaptive molecular mechanisms within this group is required to inform the development of novel drug targets and effective treatments. The production of oxidants is increased in PH Group 3, and their pleiotropic roles include contributing to disease progression by promoting prolonged hypoxic pulmonary vasoconstriction and pathological pulmonary vascular remodeling, but also stimulating adaptation to pathological stress that limits the severity of this disease. Inflammation, which is increasingly being viewed as a key pathological feature of Group 3 PH, is subject to complex regulation by redox mechanisms and is exacerbated by, but also augments oxidative stress. In this review, we investigate aspects of this complex crosstalk between inflammation and oxidative stress in Group 3 PH, focusing on the redox-regulated transcription factor NF-κB and its upstream regulators toll-like receptor 4 and high mobility group box protein 1. Ultimately, we propose that the development of specific therapeutic interventions targeting redox-regulated signaling pathways related to inflammation could be explored as novel treatments for Group 3 PH.

Galectin-3 Promotes ROS, Inflammation, and Vascular Fibrosis in Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is a progressive vascular disease arising from the narrowing of pulmonary arteries (PA) resulting in high pulmonary arterial blood pressure and ultimately right ventricular (RV) failure. A defining characteristic of PAH is the excessive remodeling of PA that includes increased proliferation, inflammation, and fibrosis. There is no cure for PAH nor interventions that effectively impede or reverse PA remodeling, and research over the past several decades has sought to identify novel molecular mechanisms of therapeutic benefit. Galectin-3 (Gal-3; Mac-2) is a carbohydrate-binding lectin that is remarkable for its chimeric structure, comprised of an N-terminal oligomerization domain and a C-terminal carbohydrate-recognition domain. Gal-3 is a regulator of changes in cell behavior that contribute to aberrant PA remodeling including cell proliferation, inflammation, and fibrosis, but its role in PAH is poorly understood. Herein, we summarize the recent literature on the role of Gal-3 in the development of PAH and provide experimental evidence supporting the ability of Gal-3 to influence reactive oxygen species (ROS) production, NOX enzyme expression, inflammation, and fibrosis, which contributes to PA remodeling. Finally, we address the clinical significance of Gal-3 as a target in the development of therapeutic agents as a treatment for PAH.

A crucial role of endoplasmic reticulum stress in cellular responses during pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), a chronic and progressive disease of the lung vascular system, is characterized by vasculopathy in the pulmonary arterioles, especially in endothelial cells and pulmonary vascular smooth cells. Several mechanisms are involved in PAH occurrence and development, and all are characterized by excessive pulmonary vasoconstriction and abnormal vascular remodeling, which leads to a progressive resistance to blood flow and an increase in pulmonary artery pressure. Recent studies have shown that endoplasmic reticulum (ER) stress is implicated in the pathophysiology of PAH. In this review, we highlight the effect of ER stress on the proliferation and apoptosis of endothelial cells and pulmonary vascular smooth muscle cells, and discuss the feasibility of targeting unfolded protein response components as a strategy to reverse or alleviate the progression of PAH.

The Severity of Oxidative Stress in Comorbid Chronic Obstructive Pulmonary Disease (COPD) and Hypertension: Does it Depend On ACE and AGT Gene Polymorphisms?

There is an increasing number of studies suggesting the role of genetic factors in the development and progression of chronic obstructive pulmonary disease and hypertension. Therefore, our study aimed to establish the role of ACE and AGT gene polymorphisms in the mechanisms behind the development of oxidative stress in patients with concomitant chronic obstructive pulmonary disease and hypertension. The study group consisted of 96 patients: Group 1 (individuals with a chronic obstructive pulmonary disease), Group 2 (individuals with arterial hypertension), Group 3 (individuals with a chronic obstructive pulmonary disease and arterial hypertension). The control group consisted of 20 healthy subjects. ACE and AGT gene polymorphisms were determined by polymerase chain reaction amplification. Detection of intracellular reactive oxygen species levels was performed by EPICS XL cytometer (Beckman Coulter, USA) with dichlorodihydrofluorescein diacetate and dihydroethidium. Serum levels of 8-isoprostane were assayed with ELISA, Cayman Chemicals (USA). No significant correlations between ACE and AGT gene polymorphisms and parameters of oxidative stress in a setting of comorbid chronic obstructive pulmonary disease and hypertension were observed. However, the increase in oxidative stress parameters was observed to be the most significant in patients with chronic obstructive pulmonary disease + hypertension and with I/I genotype of the ACE gene, which was due to their lowest values in virtually healthy individuals. This suggests that I/I genotype may be associated with lower levels of reactive oxygen species production compared with other genotypes.

Current and future treatments of pulmonary arterial hypertension

Therapeutic options for pulmonary arterial hypertension (PAH) have increased over the last decades. The advent of pharmacological therapies targeting the prostacyclin, endothelin, and NO pathways has significantly improved outcomes. However, for the vast majority of patients, PAH remains a life-limiting illness with no prospect of cure. PAH is characterised by pulmonary vascular remodelling. Current research focusses on targeting the underlying pathways of aberrant proliferation, migration, and apoptosis. Despite success in preclinical models, using a plethora of novel approaches targeting cellular GPCRs, ion channels, metabolism, epigenetics, growth factor receptors, transcription factors, and inflammation, successful transfer to human disease with positive outcomes in clinical trials is limited. This review provides an overview of novel targets addressed by clinical trials and gives an outlook on novel preclinical perspectives in PAH. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Proinflammation, profibrosis, and arterial aging

Aging is a major risk factor for quintessential cardiovascular diseases, which are closely related to arterial proinflammation. The age-related alterations of the amount, distribution, and properties of the collagen fibers, such as cross-links and degradation in the arterial wall, are the major sequelae of proinflammation. In the aging arterial wall, collagen types I, II, and III are predominant,  and are mainly produced by stiffened vascular smooth muscle cells (VSMCs) governed by proinflammatory signaling, leading to profibrosis. Profibrosis is regulated by an increase in the proinflammatory molecules angiotensin II, milk fat globule-EGF-VIII, and transforming growth factor-beta 1 (TGF-β1) signaling and a decrease in the vasorin signaling cascade. The release of these proinflammatory factors triggers the activation of matrix metalloproteinase type II (MMP-2) and activates profibrogenic TGF-β1 signaling, contributing to profibrosis. The age-associated increase in activated MMP-2 cleaves latent TGF-β and subsequently increases TGF-β1 activity leading to collagen deposition in the arterial wall. Furthermore, a blockade of the proinflammatory signaling pathway alleviates the fibrogenic signaling, reduces profibrosis, and prevents arterial stiffening with aging. Thus, age-associated proinflammatory-profibrosis coupling is the underlying molecular mechanism of arterial stiffening with advancing age.

Mechanisms of the protective effects of nitrate and nitrite in cardiovascular and metabolic diseases

Within the body, NO is produced by nitric oxide synthases via converting _l-arginine to citrulline. Additionally, NO is also produced via the NOS-independent nitrate-nitrite-NO pathway. Unlike the classical pathway, the nitrate-nitrite-NO pathway is oxygen independent and viewed as a back-up function to ensure NO generation during ischaemia/hypoxia. Dietary nitrate and nitrite have emerged as substrates for endogenous NO generation and other bioactive nitrogen oxides with promising protective effects on cardiovascular and metabolic function. In brief, inorganic nitrate and nitrite can decrease blood pressure, protect against ischaemia-reperfusion injury, enhance endothelial function, inhibit platelet aggregation, modulate mitochondrial function and improve features of the metabolic syndrome. However, many questions regarding the specific mechanisms of these protective effects on cardiovascular and metabolic diseases remain unclear. In this review, we focus on nitrate/nitrite bioactivation, as well as the potential mechanisms for nitrate/nitrite-mediated effects on cardiovascular and metabolic diseases. Understanding how dietary nitrate and nitrite induce beneficial effect on cardiovascular and metabolic diseases could open up novel therapeutic opportunities in clinical practice.

Galectin-3: A Harbinger of Reactive Oxygen Species, Fibrosis, and Inflammation in Pulmonary Arterial Hypertension

Significance: Pulmonary arterial hypertension (PAH) is a progressive disease arising from the narrowing of pulmonary arteries (PAs) resulting in high pulmonary arterial blood pressure and ultimately right ventricle (RV) failure. A defining characteristic of PAH is the excessive and unrelenting inward remodeling of PAs that includes increased proliferation, inflammation, and fibrosis. Critical Issues: There is no cure for PAH nor interventions that effectively arrest or reverse PA remodeling, and intensive research over the past several decades has sought to identify novel molecular mechanisms of therapeutic value. Recent Advances: Galectin-3 (Gal-3) is a carbohydrate-binding lectin remarkable for its chimeric structure, composed of an N-terminal oligomerization domain and a C-terminal carbohydrate-recognition domain. Gal-3 has been identified as a regulator of numerous changes in cell behavior that contributes to aberrant PA remodeling, including cell proliferation, inflammation, and fibrosis, but its role in PAH has remained poorly understood until recently. In contrast, pathological roles for Gal-3 have been proposed in cancer and inflammatory and fibroproliferative disorders, such as pulmonary vascular and cardiac fibrosis. Herein, we summarize the recent literature on the role of Gal-3 in the development of PAH. We provide experimental evidence supporting the ability of Gal-3 to influence reactive oxygen species production, NADPH oxidase enzyme expression, and redox signaling, which have been shown to contribute to both vascular remodeling and increased pulmonary arterial pressure. Future Directions: While several preclinical studies suggest that Gal-3 promotes hypertensive pulmonary vascular remodeling, the clinical significance of Gal-3 in human PAH remains to be established. Antioxid. Redox Signal. 00, 000-000.

Focus on Early Events: Pathogenesis of Pulmonary Arterial Hypertension Development

Significance: Pulmonary arterial hypertension (PAH) is a progressive disease of the lung vasculature characterized by the proliferation of all vascular wall cell types, including endothelial, smooth muscle, and fibroblasts. The disease rapidly advances into a form with extensive pulmonary vascular remodeling, leading to a rapid increase in pulmonary vascular resistance, which results in right heart failure. Recent Advances: Most current research in the PAH field has been focused on the late stage of the disease, largely due to an urgent need for patient treatment options in clinics. Further, the pathobiology of PAH is multifaceted in the advanced disease, and there has been promising recent progress in identifying various pathological pathways related to the late clinical picture. Critical Issues: Early stage PAH still requires additional attention from the scientific community, and although the survival of patients with early diagnosis is comparatively higher, the disease develops in patients asymptomatically, making it difficult to identify and treat early. Future Directions: There are several reasons to focus on the early stage of PAH. First, the complexity of late stage disease, owing to multiple pathways being activated in a complex system with intra- and intercellular signaling, leads to an unclear picture of the key contributors to the pathobiology. Second, an understanding of early pathophysiological events can increase the ability to identify PAH patients earlier than what is currently possible. Third, the prompt diagnosis of PAH would allow for the therapy to start earlier, which has proved to be a more successful strategy, and it ensures better survival in PAH patients.

rBMSC/Cav-1F92A Mediates Oxidative Stress in PAH Rat by Regulating SelW/14-3-3η and CA1/Kininogen Signal Transduction

Background/Objectives

Carbonic anhydrase 1 (CA1)/kininogen and selenoprotein W (SelW)/14-3-3η signal transduction orchestrate oxidative stress, which can also be regulated by nitric oxide (NO). The mutated caveolin-1 (Cav-1^F92A) gene may enhance NO production. This study explored the effect of Cav-1^F92A-modified rat bone marrow mesenchymal stem cells (rBMSC/Cav-1^F92A) on oxidative stress regulation through CA1/kininogen and SelW/14-3-3η signal transduction in a rat model of monocrotaline- (MCT-) induced pulmonary arterial hypertension (PAH).

Method

PAH was induced in rats through the subcutaneous injection of MCT. Next, rBMSC/Vector (negative control), rBMSC/Cav-1, rBMSC/Cav-1^F92A, or rBMSC/Cav-1^F92A+L-NAME were administered to the rats. Changes in pulmonary hemodynamic and vascular morphometry and oxidative stress levels were evaluated. CA1/kininogen and SelW/14-3-3η signal transduction, endothelial nitric oxide synthase (eNOS) dimerization, and eNOS/NO/sGC/cGMP pathway changes were determined through real-time polymerase chain reaction, Western blot, or immunohistochemical analyses.

Results

In MCT-induced PAH rats, rBMSC/Cav-1^F92A treatment reduced right ventricular systolic pressure, vascular stenosis, and oxidative stress; downregulated CA1/kininogen signal transduction; upregulated SelW/14-3-3η signal transduction; and reactivated the NO pathway.

Conclusions

In a rat model of MCT-induced PAH, rBMSC/Cav-1^F92A reduced oxidative stress by regulating CA1/kininogen and SelW/14-3-3η signal transduction.

Mitochondrial Dysfunction: Metabolic Drivers of Pulmonary Hypertension

Significance: Pulmonary hypertension (PH) is a progressive disease characterized by pulmonary vascular remodeling and lung vasculopathy. The disease displays progressive dyspnea, pulmonary artery uncoupling and right ventricular (RV) dysfunction. The overall survival rate is ranging from 28-72%. Recent Advances: The molecular events that promote the development of PH are complex and incompletely understood. Metabolic impairment has been proposed to contribute to the pathophysiology of PH with evidence for mitochondrial dysfunction involving the electron transport chain proteins, antioxidant enzymes, apoptosis regulators, and mitochondrial quality control. Critical Issues: It is vital to characterize the mechanisms by which mitochondrial dysfunction contribute to PH pathogenesis. This review focuses on the currently available publications that supports mitochondrial mechanisms in PH pathophysiology. Future Directions: Further studies of these metabolic mitochondrial alterations in PH could be viable targets of diagnostic and therapeutic intervention.

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.

Novel Regulators and Targets of Redox Signaling in Pulmonary Vasculature

Dysregulated redox signaling in pulmonary vasculature is central to the development of pulmonary arterial hypertension (PAH) and lung injury. Modulators of reactive oxygen species (ROS) production and downstream signaling targets are critical for mediating the physiological or pathological effects of ROS. Understanding the complex interactions between the modulators and signaling targets of ROS is essential for developing novel strategies to prevent or attenuate lung pathologies. In this review, we discuss recent studies on the modulators and targets of ROS in pulmonary endothelial and smooth muscle cells, their cellular effects, and the disease conditions associated with dysregulated redox signaling.

Mitochondrial electron transport chain, ROS generation and uncoupling (Review)

The mammalian mitochondrial electron transport chain (ETC) includes complexes I-IV, as well as the electron transporters ubiquinone and cytochrome c. There are two electron transport pathways in the ETC: Complex I/III/IV, with NADH as the substrate and complex II/III/IV, with succinic acid as the substrate. The electron flow is coupled with the generation of a proton gradient across the inner membrane and the energy accumulated in the proton gradient is used by complex V (ATP synthase) to produce ATP. The first part of this review briefly introduces the structure and function of complexes I-IV and ATP synthase, including the specific electron transfer process in each complex. Some electrons are directly transferred to O₂ to generate reactive oxygen species (ROS) in the ETC. The second part of this review discusses the sites of ROS generation in each ETC complex, including sites I_F and I_Q in complex I, site II_F in complex II and site III_Qo in complex III, and the physiological and pathological regulation of ROS. As signaling molecules, ROS play an important role in cell proliferation, hypoxia adaptation and cell fate determination, but excessive ROS can cause irreversible cell damage and even cell death. The occurrence and development of a number of diseases are closely related to ROS overproduction. Finally, proton leak and uncoupling proteins (UCP_S) are discussed. Proton leak consists of basal proton leak and induced proton leak. Induced proton leak is precisely regulated and induced by UCPs. A total of five UCPs (UCP1-5) have been identified in mammalian cells. UCP1 mainly plays a role in the maintenance of body temperature in a cold environment through non-shivering thermogenesis. The core role of UCP2-5 is to reduce oxidative stress under certain conditions, therefore exerting cytoprotective effects. All diseases involving oxidative stress are associated with UCPs.

Regulation of Smooth Muscle Cell Proliferation by NADPH Oxidases in Pulmonary Hypertension

Hyperproliferation of pulmonary arterial smooth muscle cells is a key component of vascular remodeling in the setting of pulmonary hypertension (PH). Numerous studies have explored factors governing the changes in smooth muscle cell phenotype that lead to the increased wall thickness, and have identified various potential candidates. A role for reactive oxygen species (ROS) has been well documented in PH. ROS can be generated from a variety of sources, including mitochondria, uncoupled nitric oxide synthase, xanthine oxidase, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In this article, we will review recent data supporting a role for ROS generated from NADPH oxidases in promoting pulmonary arterial smooth muscle cell proliferation during PH.

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.

Pulmonary arterial hypertension and the potential roles of metallothioneins: A focused review

The pathophysiology of pulmonary arterial hypertension (PAH) is underlined by cell proliferation and vasoconstriction of pulmonary arterioles this involves multiple molecular factors or proteins, but it is not clear what the exact roles of these factors/proteins are. In addition, there may be other factors/proteins that have not been identified that contribute to PAH pathophysiology. Therefore, research has focused on investigating novel role players, in order to facilitate a better understanding of how PAH develop. Evidence suggest that mitochondrial regulators are key role players in PAH pathophysiology, but regulators that have not received sufficient attention in PAH are metallothioneins (MTs). In PAH patients, MT expression is elevated compared to healthy individuals, suggesting that MTs may be possible biomarkers. In other disease-models, MTs have been shown to regulate cell proliferation and vasoconstriction, processes that are instrumental in PAH pathophysiology. Due to the involvement of these processes in PAH pathophysiology and the ability of MTs to modulate them, this paper propose that cellular MTs may also play a role in PAH development. This paper suggests that PAH-research should perhaps begin to investigate the involvement of cellular MTs in the development of PAH.

Change of voltage-gated potassium channel 1.7 expressions in monocrotaline-induced pulmonary arterial hypertension rat model

Purpose

Abnormal potassium channels expression affects vessel function, including vascular tone and proliferation rate. Diverse potassium channels, including voltage-gated potassium (Kv) channels, are involved in pathological changes of pulmonary arterial hypertension (PAH). Since the role of the Kv1.7 channel in PAH has not been previously studied, we investigated whether Kv1.7 channel expression changes in the lung tissue of a monocrotaline (MCT)-induced PAH rat model and whether this change is influenced by the endothelin (ET)-1 and reactive oxygen species (ROS) pathways.

Methods

Rats were separated into 2 groups: the control (C) group and the MCT (M) group (60 mg/kg MCT). A hemodynamic study was performed by catheterization into the external jugular vein to estimate the right ventricular pressure (RVP), and pathological changes in the lung tissue were investigated. Changes in protein and mRNA levels were confirmed by western blot and polymerase chain reaction analysis, respectively.

Results

MCT caused increased RVP, medial wall thickening of the pulmonary arterioles, and increased expression level of ET-1, ET receptor A, and NADPH oxidase (NOX) 4 proteins. Decreased Kv1.7 channel expression was detected in the lung tissue. Inward-rectifier channel 6.1 expression in the lung tissue also increased. We confirmed that ET-1 increased NOX4 level and decreased glutathione peroxidase-1 level in pulmonary artery smooth muscle cells (PASMCs). ET-1 increased ROS level in PASMCs.

Conclusion

Decreased Kv1.7 channel expression might be caused by the ET-1 and ROS pathways and contributes to MCT-induced PAH.

Oxidative stress and bronchopulmonary dysplasia

With the progress of modern medicine, oxygen therapy has become a crucial measure for the treatment of premature infants. As an environmental stimulus, in the normal development of lungs, oxygen plays a very important regulatory role. However, the problem is that long-term exposure to hyperoxia can interfere with the development of lungs, leading to irreversible developmental abnormalities. Now, the incidence of bronchopulmonary dysplasia (BPD) is increasing year by year. The existing related research shows that although BPD is a multi-factor triggered disease, its main risk factors are the premature exposure to hyperoxia and the role of reactive oxygen species (ROS). As for premature infants, especially very premature babies and those with very low birth weight, prolonged exposure to high oxygen can affect and alter the normal developmental trajectories of lung tissue and vascular beds, triggering developmental disorders, such as BPD. In the relevant studies about human BPD, a large number of them support that ROS is associated with impaired lung development. Neonates, due to the damage in the development of alveolar, are specific to hyperoxia-induced inflammatory damage. This review while focusing on the role of oxidative stress in the pathogenesis of BPD, suggests that antioxidant measures may be effective to guard against BPD of preterm infants.

Association between MDR1 gene polymorphism and clinical course of pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex pathogenesis. The polymorphism of the gene of multidrug resistance-1 (MDR1) has been associated with many diseases including PAH.

Objective. In this study we aimed to investigate the relevance of the MDR1 polymorphism to pediatric PAH clinical course.

Methods. A total of 40 pediatric patients with PAH (secondary to congenital heart defects or idiopathic) and 40 control subjects were enrolled. Patients with PAH were divided into 2 groups, according to their evolution: 28 patients who remained clinically stable at 12-months (non-worsening group) and 12 patients who presented clinical worsening at 12-months (worsening group). Genomic DNA was genotyped for MDR1 gene polymorphisms as follows: C1236T, G2677T and C3435T.

Results. There were no significant differences between PAH children groups (clinical worsening and non-worsening) nor between PAH children and controls in terms of frequency distribution of the three studied genotypes or alleles.

Conclusions. The MDR1 polymorphism could not be correlated with the clinical evolution of pediatric PAH patients in our study.

NOX4 expression and distal arteriolar remodeling correlate with pulmonary hypertension in COPD

Background

Pulmonary hypertension (PH) in chronic obstructive pulmonary disease (COPD) is suggested as the consequence of emphysematous destruction of vascular bed and hypoxia of pulmonary microenvironment, mechanisms underpinning its pathogenesis however remain elusive. The dysregulated expression of nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases and superoxide generation by pulmonary vasculatures have significant implications in the hypoxia-induced PH.

Methods

In this study, the involvement of NADPH oxidase subunit 4 (NOX4) in pulmonary arteriolar remodeling of PH in COPD was investigated by ascertaining the morphological alteration of pulmonary arteries and pulmonary blood flow using cardiac magnetic resonance imaging (cMRI), and the expression and correlation of NOX4 with pulmonary vascular remodeling and pulmonary functions in COPD lungs.

Results

Results demonstrated that an augmented expression of NOX4 was correlated with the increased volume of pulmonary vascular wall in COPD lung. While the volume of distal pulmonary arteries was inversely correlated with pulmonary functions, despite it was positively associated with the main pulmonary artery distensibility, right ventricular myocardial mass end-systolic and right ventricular myocardial mass end-diastolic in COPD. In addition, an increased malondialdehyde and a decreased superoxide dismutase were observed in sera of COPD patients. Mechanistically, the abundance of NOX4 and production of reactive oxygen species (ROS) in pulmonary artery smooth muscle cells could be dynamically induced by transforming growth factor-beta (TGF-β), which in turn led pulmonary arteriolar remodeling in COPD lungs.

Conclusion

These results suggest that the NOX4-derived ROS production may play a key role in the development of PH in COPD by promoting distal pulmonary vascular remodeling.