Reactive oxygen species in pulmonary vascular remodeling

Overview of Methamphetamine-Associated Pulmonary Arterial Hypertension

TOPIC IMPORTANCE

The global surge in methamphetamine use is a critical public health concern, particularly due to its robust correlation with methamphetamine-associated pulmonary arterial hypertension (MA-PAH). This association raises urgent alarms about the potential escalation of MA-PAH incidence, posing a significant and imminent challenge to global public health.

REVIEW FINDINGS

This comprehensive review meticulously explores MA-PAH, offering insights into its epidemiology, pathophysiology, clinical presentation, diagnostic intricacies, and management strategies. The pathogenesis, yet to be fully described, involves complex molecular interactions, including alterations in serotonin signaling, reduced activity of carboxylesterase 1, oxidative stress, and dysregulation of pulmonary vasoconstrictors and vasodilators. These processes culminate in the structural remodeling of the pulmonary vasculature, resulting in pulmonary arterial hypertension. MA-PAH exhibits a more severe clinical profile in functional class and hemodynamics compared with idiopathic pulmonary arterial hypertension. Management involves a multifaceted approach, integrating pulmonary vasodilators, cessation of methamphetamine use, and implementing social and rehabilitation programs. These measures aim to enhance patient outcomes and detect potential relapses for timely intervention.

SUMMARY

This review consolidates our understanding of MA-PAH, pinpointing knowledge gaps for future studies. Addressing these gaps is crucial for advancing diagnostic accuracy, unraveling mechanisms, and optimizing treatment for MA-PAH, thereby addressing the evolving landscape of this complex health concern.

A peripheral system disease-Pulmonary hypertension

Pulmonary hypertension (PH) is a cardiovascular disorder characterized by substantial morbidity and mortality rates. It is a chronic condition characterized by intricate pathogenesis and uncontrollable factors. We summarized the pathological effects of estrogen, genetics, neuroinflammation, intestinal microbiota, metabolic reorganization, and histone modification on PH. PH is not only a pulmonary vascular disease, but also a systemic disease. The findings emphasize that the onset of PH is not exclusively confined to the pulmonary vasculature, consequently necessitating treatment approaches that extend beyond targeting pulmonary blood vessels. Hence, the research on the pathological mechanism of PH is not limited to target organs such as pulmonary vessels, but also focuses on exploring other fields (such as estrogen, genetics, neuroinflammation, intestinal microbiota, metabolic reorganization, and histone modification).

Repetitive sulfur dioxide exposure in mice models post-deployment respiratory syndrome

Soldiers deployed to Iraq and Afghanistan have a higher prevalence of respiratory symptoms than nondeployed military personnel and some have been shown to have a constellation of findings on lung biopsy termed post-deployment respiratory syndrome (PDRS). Since many of the subjects in this cohort reported exposure to sulfur dioxide (SO2), we developed a model of repetitive exposure to SO2 in mice that phenocopies many aspects of PDRS, including adaptive immune activation, airway wall remodeling, and pulmonary vascular (PV) disease. Although abnormalities in small airways were not sufficient to alter lung mechanics, PV remodeling resulted in the development of pulmonary hypertension and reduced exercise tolerance in SO2-exposed mice. SO2 exposure led to increased formation of isolevuglandins (isoLGs) adducts and superoxide dismutase 2 (SOD2) acetylation in endothelial cells, which were attenuated by treatment with the isoLG scavenger 2-hydroxybenzylamine acetate (2-HOBA). In addition, 2-HOBA treatment or Siruin-3 overexpression in a transgenic mouse model prevented vascular remodeling following SO2 exposure. In summary, our results indicate that repetitive SO2 exposure recapitulates many aspects of PDRS and that oxidative stress appears to mediate PV remodeling in this model. Together, these findings provide new insights regarding the critical mechanisms underlying PDRS.NEW & NOTEWORTHY We developed a mice model of "post-deployment respiratory syndrome" (PDRS), a condition in Veterans with unexplained exertional dyspnea. Our model successfully recapitulates many of the pathological and physiological features of the syndrome, revealing involvement of the ROS-isoLGs-Sirt3-SOD2 pathway in pulmonary vasculature pathology. Our study provides additional knowledge about effects and long-term consequences of sulfur dioxide exposure on the respiratory system, serving as a valuable tool for future PDRS research.

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.

Autophagy-modulating biomaterials: multifunctional weapons to promote tissue regeneration

Autophagy is a self-renewal mechanism that maintains homeostasis and can promote tissue regeneration by regulating inflammation, reducing oxidative stress and promoting cell differentiation. The interaction between biomaterials and tissue cells significantly affects biomaterial-tissue integration and tissue regeneration. In recent years, it has been found that biomaterials can affect various processes related to tissue regeneration by regulating autophagy. The utilization of biomaterials in a controlled environment has become a prominent approach for enhancing the tissue regeneration capabilities. This involves the regulation of autophagy in diverse cell types implicated in tissue regeneration, encompassing the modulation of inflammatory responses, oxidative stress, cell differentiation, proliferation, migration, apoptosis, and extracellular matrix formation. In addition, biomaterials possess the potential to serve as carriers for drug delivery, enabling the regulation of autophagy by either activating or inhibiting its processes. This review summarizes the relationship between autophagy and tissue regeneration and discusses the role of biomaterial-based autophagy in tissue regeneration. In addition, recent advanced technologies used to design autophagy-modulating biomaterials are summarized, and rational design of biomaterials for providing controlled autophagy regulation via modification of the chemistry and surface of biomaterials and incorporation of cells and molecules is discussed. A better understanding of biomaterial-based autophagy and tissue regeneration, as well as the underlying molecular mechanisms, may lead to new possibilities for promoting tissue regeneration. Video Abstract.

Role of Exercise in Pulmonary Hypertension: Evidence from Bench to Bedside

Background

Pulmonary hypertension (PH) is a debilitating condition characterized by elevated pulmonary arterial pressure and progressive vascular remodelling, leading to exercise intolerance. The progression of PAH is regulated at a cellular and molecular level which influences various physiological processes. Exercise plays an important role in improving function in PH. Although the signalling pathways that regulate cardio-protection through exercise have not been fully understood, the positive impact of exercise on the various physiological systems is well established.

Summary

Exercise has emerged as a potential adjunctive therapy for PH, with growing evidence supporting its beneficial effects on various aspects of the disease pathophysiology. This review highlights the contributions of cellular and molecular pathways and physiological processes to exercise intolerance. Preclinical studies have provided insight into the mechanisms underlying exercise-induced improvements in PH which are modulated through improvements in endothelial function, inflammation, oxidative stress, and mitochondrial function. Along with preclinical studies, various clinical studies have demonstrated that exercise training can lead to significant improvements in exercise capacity, haemodynamics, quality of life, and functional status. Moreover, exercise interventions have been shown to improve skeletal muscle function and enhance pulmonary vascular remodelling, contributing to overall disease management. Further research efforts aimed at better understanding the role of exercise in PH pathophysiology, and refining exercise interventions are warranted to realize its full potential in the management of this complex disease.

Key Messages

Despite the promising benefits of exercise in PH, several challenges remain, including the optimal intensity, duration, and type of exercise training, as well as patient selection criteria and long-term adherence. Additionally, the mechanisms underlying the observed improvements require further elucidation to optimize exercise protocols and personalize treatment strategies. Nonetheless, exercise represents a promising therapeutic approach that can complement existing pharmacological therapies and improve outcomes in PH patients.

Alleviation of Angiotensin II-Induced Vascular Endothelial Cell Injury Through Long Non-coding RNA TUG1 Inhibition

BACKGROUND

Hypertension damages endothelial cells, causing vascular remodelling. It is caused by Ang II-induced endothelial cell (EC) destruction. The long noncoding RNA (lncRNAs) are emerging regulators of endothelium homeostasis. Injured endothelium expresses lncRNA taurine-upregulated gene 1 (TUG1), which may mediate endothelial cell damage, proliferation, apoptosis, and autophagy and contribute to cardiovascular disease. However, uncertainty surrounds the function of lncRNA TUG1, on arterial endothelium cell damage.

OBJECTIVE

This research aimed to investigate the role and mechanism of lncRNA TUG1 in vascular endothelial cell injury.

METHOD

A microarray analysis of lncRNA human gene expression was used to identify differentially expressed lncRNAs in human umbilical vein endothelial cell (HUVEC) cultures. The viability, apoptosis, and migration of Ang II-treated HUVECs were then evaluated. In order to investigate the role of lncRNA TUG1 in hypertension, qRT-PCR, western blotting, and RNA-FISH were used to examine the expression of TUG1 in SHR mice.

RESULTS

Ang II-activated HUVECs and SHR rats' abdominal aortas highly express the lncRNA TUG1. LncRNA TUG1 knockdown in HUVECs could increase cell viability, reduce apoptosis, and produce inflammatory factors. In SHR rat abdominal aortas, lncRNA TUG1 knockdown promoted proliferation and inhibited apoptosis. HE spotting showed that lncRNA TUG1 knockdown improved SHR rats' abdominal aorta shape. lncRNA TUG1 knockdown promotes miR-9- 5p, which inhibits CXCR4 following transcription. The lncRNA TUG1/miR-9-5p/CXCR4 axis and vascular cell injury were also examined. MiR-9-5p silencing or CXCR4 overexpression lowered cell survival, apoptosis, and lncRNA TUG1-induced IL-6 and NO expression.

CONCLUSION

lncRNA TUG1 suppression could reduce Ang II-induced endothelial cell damage by regulating and targeting miR-9-5p to limit CXCR4 expression and open new vascular disease research pathways.

Sensing of H2O2-induced oxidative stress by the UPF factor complex is crucial for activation of catalase-3 expression in Neurospora

UPF-1-UPF-2-UPF-3 complex-orchestrated nonsense-mediated mRNA decay (NMD) is a well-characterized eukaryotic cellular surveillance mechanism that not only degrades aberrant transcripts to protect the integrity of the transcriptome but also eliminates normal transcripts to facilitate appropriate cellular responses to physiological and environmental changes. Here, we describe the multifaceted regulatory roles of the Neurospora crassa UPF complex in catalase-3 (cat-3) gene expression, which is essential for scavenging H2O2-induced oxidative stress. First, losing UPF proteins markedly slowed down the decay rate of cat-3 mRNA. Second, UPF proteins indirectly attenuated the transcriptional activity of cat-3 gene by boosting the decay of cpc-1 and ngf-1 mRNAs, which encode a well-studied transcription factor and a histone acetyltransferase, respectively. Further study showed that under oxidative stress condition, UPF proteins were degraded, followed by increased CPC-1 and NGF-1 activity, finally activating cat-3 expression to resist oxidative stress. Together, our data illustrate a sophisticated regulatory network of the cat-3 gene mediated by the UPF complex under physiological and H2O2-induced oxidative stress conditions.

Pathophysiology and pathogenic mechanisms of pulmonary hypertension: role of membrane receptors, ion channels, and Ca2+ signaling

The pulmonary circulation is a low-resistance, low-pressure, and high-compliance system that allows the lungs to receive the entire cardiac output. Pulmonary arterial pressure is a function of cardiac output and pulmonary vascular resistance, and pulmonary vascular resistance is inversely proportional to the fourth power of the intraluminal radius of the pulmonary artery. Therefore, a very small decrease of the pulmonary vascular lumen diameter results in a significant increase in pulmonary vascular resistance and pulmonary arterial pressure. Pulmonary arterial hypertension is a fatal and progressive disease with poor prognosis. Regardless of the initial pathogenic triggers, sustained pulmonary vasoconstriction, concentric vascular remodeling, occlusive intimal lesions, in situ thrombosis, and vascular wall stiffening are the major and direct causes for elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension and other forms of precapillary pulmonary hypertension. In this review, we aim to discuss the basic principles and physiological mechanisms involved in the regulation of lung vascular hemodynamics and pulmonary vascular function, the changes in the pulmonary vasculature that contribute to the increased vascular resistance and arterial pressure, and the pathogenic mechanisms involved in the development and progression of pulmonary hypertension. We focus on reviewing the pathogenic roles of membrane receptors, ion channels, and intracellular Ca2+ signaling in pulmonary vascular smooth muscle cells in the development and progression of pulmonary hypertension.

Inflammation and immunity in the pathogenesis of hypoxic pulmonary hypertension

Hypoxic pulmonary hypertension (HPH) is a complicated vascular disorder characterized by diverse mechanisms that lead to elevated blood pressure in pulmonary circulation. Recent evidence indicates that HPH is not simply a pathological syndrome but is instead a complex lesion of cellular metabolism, inflammation, and proliferation driven by the reprogramming of gene expression patterns. One of the key mechanisms underlying HPH is hypoxia, which drives immune/inflammation to mediate complex vascular homeostasis that collaboratively controls vascular remodeling in the lungs. This is caused by the prolonged infiltration of immune cells and an increase in several pro-inflammatory factors, which ultimately leads to immune dysregulation. Hypoxia has been associated with metabolic reprogramming, immunological dysregulation, and adverse pulmonary vascular remodeling in preclinical studies. Many animal models have been developed to mimic HPH; however, many of them do not accurately represent the human disease state and may not be suitable for testing new therapeutic strategies. The scientific understanding of HPH is rapidly evolving, and recent efforts have focused on understanding the complex interplay among hypoxia, inflammation, and cellular metabolism in the development of this disease. Through continued research and the development of more sophisticated animal models, it is hoped that we will be able to gain a deeper understanding of the underlying mechanisms of HPH and implement more effective therapies for this debilitating disease.

Beneficial effects of berberine against pulmonary complications of experimental pulmonary arterial hypertension in rats and some relevant mechanisms

Pulmonary arterial hypertension (PAH) is a severe disease that leads to pulmonary vascular remodeling characterized by a rise in pulmonary vascular resistance and pressure. We assessed the effects of an herbal compound, berberine (BB), and some related mechanisms on PAH in rats. Male Wistar rats were assigned to seven groups: control, monocrotaline (MCT), MCT+vehicle, and MCT+BB (with doses of 10, 20, 30, and 40 mg/kg) groups. Three weeks after induction of PAH by MCT, treatment groups received daily intraperitoneal injections of vehicle or BB for 3 weeks. On Day 43, the right ventricular systolic pressure (RVSP, as an index of pulmonary arterial pressure) and the ratio of RV to LV+septum weight (as RV hypertrophy index, right ventricle hypertrophy [RHVI]) were measured. Inflammatory and oxidative stress indices and histopathology of the lungs were also assessed. RVSP (89.4 ± 8.2 vs. 23 ± 3.3), RVHI (0.63 ± 0.08 vs. 0.26 ± 0.04), and lung inflammatory cytokines TNF-α (2.03 ± 0.25 vs. 1.21 ± 0.3) and IL-6 (8.8 ± 0.59 vs. 6.3 ± 0.95) significantly increased in the MCT group compared to the control group. MCT also raised the level of Malondialdehyde (0.11 ± 0.01 vs. 0.09 ± 0.01) and diminished total antioxidant capacity (6.5 ± 0.51 vs. 8.3 ± 0.62), the activity of superoxide dismutase (1.19 ± 0.22 vs. 1.93 ± 0.2), glutathione peroxidase (0.02 ± 0.002 vs. 0.03 ± 0.005), catalase (2.1 ± 0.29 vs. 2.8 ± 0.20) and Bax/Bcl-2 ratio (0.41 ± 0.07 vs. 0.61 ± 0.09) in the lungs. Treatment with BB significantly recovered all of these alterations. BB ameliorated pulmonary vascular remodeling by decreasing inflammation and fibrosis and increasing apoptosis and antioxidant/oxidant balance. Therefore, this herbal derivative may be considered a therapeutic goal against PAH.

Sulforaphane alleviated vascular remodeling in hypoxic pulmonary hypertension via inhibiting inflammation and oxidative stress

Hypoxic pulmonary hypertension (HPH) is a cardiopulmonary disease featured by pulmonary vascular remodeling, which is due to abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) and dysfunction of endothelial cells (ECs). Sulforaphane (SFN) is a natural isothiocyanate extracted from cruciferous vegetables with promising anti-inflammatory and anti-oxidative activities. This study aimed to explore the effect and mechanism of SFN on HPH. Male mice were exposed to persistent chronic hypoxia for 4 weeks to induce HPH. The results demonstrated that SFN repressed the increased right ventricular systolic pressure (RVSP) and attenuated the right ventricular hypertrophy and pulmonary arteries remodeling in HPH mice. In particular, after SFN treatment, the CD68 positive cells in lung sections were reduced; TNF-α and IL-6 levels in lungs and serum declined; activation of NF-κB in PASMCs was inhibited in response to hypoxia. Besides, SFN enhanced the superoxide dismutase (SOD) activity in serum, SOD2 expression, total glutathione levels, and GSH/GSSG ratio in PASMCs, along with a decrease in malondialdehyde (MDA) contents in serum and ROS production in PASMCs after hypoxia exposure. Notably, SFN, as an Nrf2 activator, reversed the reduction in Nrf2 expression in hypoxic PASMCs. In vitro, SFN treatment inhibited hyperproliferation and promoted apoptosis of PASMCs under hypoxia conditions. SFN also prevented the apoptosis of pulmonary microvascular ECs caused by hypoxia. Therefore, these data suggested that SFN could significantly restrain the inflammation and oxidative stress, thereby inhibiting PASMCs proliferation, promoting PASMCs apoptosis, and reversing hypoxia injury in ECs to improve pulmonary vascular remodeling.

Mitochondrial dysfunction in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by the increased pulmonary vascular resistance due to pulmonary vasoconstriction and vascular remodeling. PAH has high disability, high mortality and poor prognosis, which is becoming a more common global health issue. There is currently no drug that can permanently cure PAH patients. The pathogenesis of PAH is still not fully elucidated. However, the role of metabolic theory in the pathogenesis of PAH is becoming clearer, especially mitochondrial metabolism. With the deepening of mitochondrial researches in recent years, more and more studies have shown that the occurrence and development of PAH are closely related to mitochondrial dysfunction, including the tricarboxylic acid cycle, redox homeostasis, enhanced glycolysis, and increased reactive oxygen species production, calcium dysregulation, mitophagy, etc. This review will further elucidate the relationship between mitochondrial metabolism and pulmonary vasoconstriction and pulmonary vascular remodeling. It might be possible to explore more comprehensive and specific treatment strategies for PAH by understanding these mitochondrial metabolic mechanisms.

Taxifolin Reduces Blood Pressure in Elderly Hypertensive Male Wistar Rats

Male Wistar rats aged 10 months were assigned to groups according to the initial level of systolic BP: hypertensive (systolic BP >115 mm Hg) and normotensive (systolic BP <115 mm Hg). The animals were injected intraperitoneally with 100 μg/kg taxifolin daily for 7 days. Systolic BP and HR were measured on the next day after single taxifolin administration and on the next day after 7-day injection course. In the group of hypertensive animals, systolic BP markedly decreased on the next day after the first injection; this decrease became even more pronounced (to the level of normotensive animals) at the end of the taxifolin course. In the group of normotensive animals, systolic BP remained unchanged. Hence, we demonstrate the possibility of course administration of taxifolin for BP normalization in hypertensive patients.

Lycopene Ameliorates Hypoxic Pulmonary Hypertension via Suppression of Oxidative Stress

Hypoxic pulmonary hypertension (HPH) is a progressive cardiopulmonary system disease characterized by pulmonary vascular remodeling. Its occurrence and progression are closely related to oxidative stress. Lycopene, extracted from red vegetables and fruits, exhibits a particularly high antioxidant capacity that is beneficial for cardiovascular diseases. Nevertheless, the role and mechanism of lycopene in HPH remain unknown. Here, we found that lycopene reversed the elevated right ventricular systolic pressure (RVSP), right ventricular hypertrophy, and pulmonary vascular remodeling induced by hypoxia in rats. In vitro, lycopene caused lower proliferation and migration of PASMCs, with higher apoptosis. Consistent with the antiproliferative result of lycopene on hypoxic PASMCs, the hippo signaling pathway associated with cell growth was activated. Furthermore, lycopene reduced malondialdehyde (MDA) levels and enhanced superoxide dismutase (SOD) activity in the lungs and serum of rats under hypoxia conditions. The expression of NOX4 in the lungs was also significantly decreased. Hypoxic PASMCs subjected to lycopene showed decreased reactive oxygen species (ROS) production and NOX4 expression. Importantly, lycopene repressed HIF-1α expression both in the lungs and PASMCs in response to hypoxia in the absence of a significant change of HIF-1α mRNA. Compared with 2ME2 (a HIF-1α inhibitor) alone treatment, lycopene treatment did not significantly change PASMC proliferation, NOX4 expression, and ROS production after 2ME2 blocked HIF-1α, suggesting the inhibitory effect of lycopene on HIF-1α-NOX4-ROS axis and the targeted effect on HIF-1α. After CHX blocked protein synthesis, lycopene promoted the protein degradation of HIF-1α. MG-132, a proteasome inhibitor, notably reversed the decrease in HIF-1α protein level induced by lycopene in response to hypoxia. Therefore, lycopene suppressed hypoxia-induced oxidative stress through HIF-1α-NOX4-ROS axis, thereby alleviating HPH. Our findings will provide a new research direction for clinical HPH therapies.

Mechanosensitive cation currents through TRPC6 and Piezo1 channels in human pulmonary arterial endothelial cells

Mechanosensitive cation channels and Ca2+ influx through these channels play an important role in the regulation of endothelial cell functions. Transient receptor potential canonical channel 6 (TRPC6) is a diacylglycerol-sensitive nonselective cation channel that forms receptor-operated Ca2+ channels in a variety of cell types. Piezo1 is a mechanosensitive cation channel activated by membrane stretch and shear stress in lung endothelial cells. In this study, we report that TRPC6 and Piezo1 channels both contribute to membrane stretch-mediated cation currents and Ca2+ influx or increase in cytosolic-free Ca2+ concentration ([Ca2+]cyt) in human pulmonary arterial endothelial cells (PAECs). The membrane stretch-mediated cation currents and increase in [Ca2+]cyt in human PAECs were significantly decreased by GsMTX4, a blocker of Piezo1 channels, and by BI-749327, a selective blocker of TRPC6 channels. Extracellular application of 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane permeable analog of diacylglycerol, rapidly induced whole cell cation currents and increased [Ca2+]cyt in human PAECs and human embryonic kidney (HEK)-cells transiently transfected with the human TRPC6 gene. Furthermore, membrane stretch with hypo-osmotic or hypotonic solution enhances the cation currents in TRPC6-transfected HEK cells. In HEK cells transfected with the Piezo1 gene, however, OAG had little effect on the cation currents, but membrane stretch significantly enhanced the cation currents. These data indicate that, while both TRPC6 and Piezo1 are involved in generating mechanosensitive cation currents and increases in [Ca2+]cyt in human PAECs undergoing mechanical stimulation, only TRPC6 (but not Piezo1) is sensitive to the second messenger diacylglycerol. Selective blockers of these channels may help develop novel therapies for mechanotransduction-associated pulmonary vascular remodeling in patients with pulmonary arterial hypertension.

Novel and robust treatment of pulmonary hypertension with netrin-1 and netrin-1-derived small peptides

Limited medical therapies have been implemented for the treatment of the devastating cardiorespiratory disease of pulmonary hypertension (PH) while none of which is sufficiently effective to stop or regress development of PH. We have previously shown that netrin-1, an axon-guiding protein during development, protects against ischemia reperfusion injury induced myocardial infarction via modest and stable production of nitric oxide (NO) and attenuation of oxidative stress. Since NO deficiency and oxidative stress-mediated vascular remodeling play important roles in the pathogenesis of PH, our present study investigated therapeutic effects on PH of netrin-1 and its derived small peptides. Infused into mice for 3 weeks during exposure to hypoxia, netrin-1 and netrin-1 derived small peptides V1, V2 or V3 substantially alleviated pathophysiological and molecular features of PH, as indicated by abrogated increases in mean pulmonary artery pressure (mPAP) and right ventricular systolic pressure (RVSP), attenuated right ventricular hypertrophy, diminished vascular remodeling of medial thickening and upregulation in smooth muscle alpha-actin (SMA) and proliferative cell nuclear antigen (PCNA), and alleviated perivascular and peribronchial fibrosis reflected by collagen deposition. NO bioavailability was substantially improved by treatment with netrin-1 and netrin-1 derived small peptides, while hypoxia induced increases in total superoxide production and eNOS uncoupling activity were all attenuated. These dual mechanisms of increasing NO bioavailability and decreasing oxidative stress at the same time, underlie robust protective effects on PH of netrin-1 and its derived small peptides, which are different from existing medications that primarily target NO signaling alone. Our data for the first time demonstrate intriguing findings that netrin-1 and netrin-1 derived small peptides can be used as novel and robust therapeutics for the treatment of PH.

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.

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.

Pathogenesis of Congenital Malformations: Possible Role of Oxidative Stress

OBJECTIVE

Congenital anomalies are important causes of morbidity and mortality in children. Oxidative stress (OS) is involved in the physiopathology of pregnancy-related congenital malformations. This review summarizes the role of OS in the pathogenesis of congenital malformations; in particular, its purpose is to describe how OS influences the development of heart congenital malformations, oesophageal atresia, biliary atresia, diaphragmatic hernia, and autosomal dominant polycystic kidney disease.

STUDY DESIGN

Systematic review of previous studies about the role of OS in pregnancy and its possible effects in developing of congenital malformations. One electronic database (PubMed) was searched and reference lists were checked.

RESULTS

An imbalance between the production of reactive oxygen species (ROS) and antioxidant defense can occur early in pregnancy and continue in the postnatal life, producing OS. It may destroy the signaling pathways needed for a correct embryogenesis leading to birth defects. In fact, cell functions, especially during embryogenesis, needs specific signaling pathways to regulate the development. These pathways are sensitive to both endogenous and exogenous factors; therefore, they can produce structural alterations of the developing fetus.

CONCLUSION

Because OS plays a significant role in pathogenesis of congenital malformations, studies should be developed in order to better define their OS mechanisms and the beneficial effects of supplemental therapeutic strategies.

KEY POINTS

· Oxidative stress is involved in the pathogenesis of congenital malformations.. · Heart malformations, oesophageal atresia, biliary atresia, diaphragmatic hernia, and autosomal dominant polycystic kidney are analyzed.. · A knowledge of pathomechanism of OS-related congenital malformations could be useful to prevent them..

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.

Senescence Alterations in Pulmonary Hypertension

Cellular senescence is the arrest of normal cell division and is commonly associated with aging. The interest in the role of cellular senescence in lung diseases derives from the observation of markers of senescence in chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (IPF), and pulmonary hypertension (PH). Accumulation of senescent cells and the senescence-associated secretory phenotype in the lung of aged patients may lead to mild persistent inflammation, which results in tissue damage. Oxidative stress due to environmental exposures such as cigarette smoke also promotes cellular senescence, together with additional forms of cellular stress such as mitochondrial dysfunction and endoplasmic reticulum stress. Growing recent evidence indicate that senescent cell phenotypes are observed in pulmonary artery smooth muscle cells and endothelial cells of patients with PH, contributing to pulmonary artery remodeling and PH development. In this review, we analyze the role of different senescence cell phenotypes contributing to the pulmonary artery remodeling process in different PH clinical entities. Different molecular pathway activation and cellular functions derived from senescence activation will be analyzed and discussed as promising targets to develop future senotherapies as promising treatments to attenuate pulmonary artery remodeling in PH.

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.

Identification of ferroptosis-associated genes exhibiting altered expression in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening illness and ferroptosis is an iron-dependent form of regulated cell death, driven by the accumulation of lipid peroxides to levels that are sufficient to trigger cell death. However, only few studies have examined PAH-associated ferroptosis. In the present study, lung samples mRNA expression profiles (derived from 15 patients with PAH and 11 normal controls) were downloaded from a public database, and 514 differentially expressed genes (DEGs) were identified using the Wilcoxon rank-sum test and weighted gene correlation network analyses. These DEGs were screened for ferroptosis-associated genes using the FerrDb database: eight ferroptosis-associated genes were identified. Finally, the construction of gene-microRNA (miRNA) and gene-transcription factor (TF) networks, in conjunction with gene ontology and biological pathway enrichment analysis, were used to inform hypotheses regarding the molecular mechanisms underlying PAH-associated ferroptosis. Ferroptosis-associated genes were largely involved in oxidative stress responses and could be regulated by several identified miRNAs and TFs. This suggests the existence of modulatable pathways that are potentially involved in PAH-associated ferroptosis. Our findings provide novel directions for targeted therapy of PAH in regard to ferroptosis. These findings may ultimately help improve the therapeutic outcomes of PAH.

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.

Erythromycin inhibits cigarette smoke-induced inflammation through regulating the PPARγ/NF-κB signaling pathway in macrophages

Chronic obstructive pulmonary disease is characterized by chronic inflammation of the airway and lungs. Accumulating evidence has suggested that erythromycin (EM) plays a protective role against cigarette smoke-induced oxidative stress and the inflammatory response. However, the underlying mechanisms remain relatively unclear. The present study aimed to investigate the role of EM in inhibiting cigarette smoke-induced inflammation in human macrophages and its potential mechanism. A Cell Counting Kit-8 assay was used to determine the optimum concentration of EM and cigarette smoke extract (CSE) and it was found that 0.1 and 1% CSE and 0.1, 1.0 and 10 μg/ml EM exerted no significant effect on the cell proliferation activity, whereas 2 and 3% CSE exerted a significant inhibitory effect over the cell proliferation activity. We observed that 10 μmol/ml GW9662 (A PPARγ antagonist) and the presence of 1% CSE could promote the expression and activation of NF-κB p65. And this increased the expression of IL-6, IL-8 and reactive oxygen species (ROS). At the same time, 10 μmol/ml GW9662 and 1% CSE was found to inhibit the expression and activation of peroxisome proliferator activated receptors γ (PPARγ); However, 1 μg/ml EM was discovered to reverse these effects. Co-immunoprecipitation subsequently discovered an interaction between PPARγ and NF-κB p65. In conclusion, the present study suggested that EM may reduce the damage of PPARγ by inhibiting oxidative stress and reducing the expression of ROS and finally relieving cigarette smoke-induced inflammation through the PPARγ/NF-κB signaling pathway in macrophages.

The Role of JAK/STAT Molecular Pathway in Vascular Remodeling Associated with Pulmonary Hypertension

Pulmonary hypertension is defined as a group of diseases characterized by a progressive increase in pulmonary vascular resistance (PVR), which leads to right ventricular failure and premature death. There are multiple clinical manifestations that can be grouped into five different types. Pulmonary artery remodeling is a common feature in pulmonary hypertension (PH) characterized by endothelial dysfunction and smooth muscle pulmonary artery cell proliferation. The current treatments for PH are limited to vasodilatory agents that do not stop the progression of the disease. Therefore, there is a need for new agents that inhibit pulmonary artery remodeling targeting the main genetic, molecular, and cellular processes involved in PH. Chronic inflammation contributes to pulmonary artery remodeling and PH, among other vascular disorders, and many inflammatory mediators signal through the JAK/STAT pathway. Recent evidence indicates that the JAK/STAT pathway is overactivated in the pulmonary arteries of patients with PH of different types. In addition, different profibrotic cytokines such as IL-6, IL-13, and IL-11 and growth factors such as PDGF, VEGF, and TGFβ1 are activators of the JAK/STAT pathway and inducers of pulmonary remodeling, thus participating in the development of PH. The understanding of the participation and modulation of the JAK/STAT pathway in PH could be an attractive strategy for developing future treatments. There have been no studies to date focused on the JAK/STAT pathway and PH. In this review, we focus on the analysis of the expression and distribution of different JAK/STAT isoforms in the pulmonary arteries of patients with different types of PH. Furthermore, molecular canonical and noncanonical JAK/STAT pathway transactivation will be discussed in the context of vascular remodeling and PH. The consequences of JAK/STAT activation for endothelial cells and pulmonary artery smooth muscle cells’ proliferation, migration, senescence, and transformation into mesenchymal/myofibroblast cells will be described and discussed, together with different promising drugs targeting the JAK/STAT pathway in vitro and in vivo.

Alginate derived functional oligosaccharides: Recent developments, barriers, and future outlooks

Alginate is a biopolymer used extensively in the food, pharmaceutical, and chemical industries. Alginate oligosaccharides (AOS) derived from alginate exhibit superior biological activities and therapeutic potential. Alginate lyases with characteristic substrate specificity can facilitate the production of a broad array of AOS with precise structure and functionality. By adopting innovative analytical tools in conjunction with focused clinical studies, the structure-bioactivity relationship of a number of AOS has been brought to light. This review covers fundamental aspects and recent developments in AOS research. Enzymatic and microbial processes involved in AOS production from brown algae and sequential steps involved in AOS structure elucidation are outlined. Biological mechanisms underlying the health benefits of AOS and their potential industrial and therapeutic applications are elaborated. Withal, various challenges in AOS research are traced out, and future directions, specifically on recombinant systems for AOS preparation, are delineated to further widen the horizon of these exceptional oligosaccharides.

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.

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.

Ambient air pollution exposure and radiographic pulmonary vascular volumes

Supplemental Digital Content is available in the text.

Exposure to higher levels of ambient air pollution is a known risk factor for cardiovascular disease but long-term effects of pollution exposure on the pulmonary vessels are unknown.

The mitochondrial redistribution of eNOS is involved in lipopolysaccharide induced inflammasome activation during acute lung injury

Acute lung injury (ALI) is a devastating clinical syndrome with no effective therapies. Inflammasome activation has been reported to play a critical role in the initiation and progression of ALI. The molecular mechanisms involved in regulating the activation of inflammasome in ALI remains unresolved, although increases in mitochondrial derived reactive oxygen species (mito-ROS) are involved. Our previous work has shown that the mitochondrial redistribution of uncoupled eNOS impairs mitochondrial bioenergetics and increases mito-ROS generation. Thus, the focus of our study was to determine if lipopolysaccharide (LPS)-mediated inflammasome activation involves the mitochondrial redistribution of uncoupled eNOS. Our data show that the increase in mito-ROS involved in LPS-mediated inflammasome activation is associated with the disruption of mitochondrial bioenergetics in human lung microvascular endothelial cells (HLMVEC) and the mitochondrial redistribution of eNOS. These effects are dependent on RhoA-ROCK signaling and are mediated via increased phosphorylation of eNOS at Threonine (T)-495. A derivative of the mitochondrial targeted Szeto-Schiller peptide (SSP) attached to the antioxidant Tiron (T-SSP), significantly attenuated LPS-mediated mito-ROS generation and inflammasome activation in HLMVEC. Further, T-SSP attenuated mitochondrial superoxide production in a mouse model of sepsis induced ALI. This in turn significantly reduced the inflammatory response and attenuated lung injury. Thus, our findings show that the mitochondrial redistribution of uncoupled eNOS is intimately involved in the activation of the inflammatory response in ALI and implicate attenuating mito-ROS as a therapeutic strategy in humans.

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.

Cellular and Molecular Processes in Pulmonary Hypertension

Pulmonary hypertension (PH) is a progressive lung disease characterized by persistent pulmonary vasoconstriction. Another well-recognized characteristic of PH is the muscularization of peripheral pulmonary arteries. This pulmonary vasoremodeling manifests in medial hypertrophy/hyperplasia of smooth muscle cells (SMCs) with possible neointimal formation. The underlying molecular processes for these two major vascular responses remain not fully understood. On the other hand, a series of very recent studies have shown that the increased reactive oxygen species (ROS) seems to be an important player in mediating pulmonary vasoconstriction and vasoremodeling, thereby leading to PH. Mitochondria are a primary site for ROS production in pulmonary artery (PA) SMCs, which subsequently activate NADPH oxidase to induce further ROS generation, i.e., ROS-induced ROS generation. ROS control the activity of multiple ion channels to induce intracellular Ca²⁺ release and extracellular Ca²⁺ influx (ROS-induced Ca²⁺ release and influx) to cause PH. ROS and Ca²⁺ signaling may synergistically trigger an inflammatory cascade to implicate in PH. Accordingly, this paper explores the important roles of ROS, Ca²⁺, and inflammatory signaling in the development of PH, including their reciprocal interactions, key molecules, and possible therapeutic targets.

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.

Intermittent short-duration reoxygenation protects against simulated high altitude-induced pulmonary hypertension in rats

High-altitude pulmonary hypertension (HAPH) is a severe and progressive disease caused by chronic hypoxia and subsequent pulmonary vascular remodeling. No cure is currently available owing to an incomplete understanding about vascular remodeling. It is believed that hypoxia-induced diseases can be prevented by treating hypoxia. Thus, this study aimed to determine whether daily short-duration reoxygenation at sea level attenuates pulmonary hypertension under high-altitude hypoxia. To this end, a simulated 5000-m hypoxia rat model and hypoxic cultured human pulmonary artery smooth muscle cells were used to evaluate the effect of short-duration reoxygenation. Results show that intermittent, not continuous, short-duration reoxygenation effectively attenuates hypoxia-induced pulmonary hypertension. The mechanisms underlining the protective effects involved that intermittent, short-duration reoxygenation prevented functional and structural remodeling of pulmonary arteries and proliferation, migration, and phenotypic conversion of pulmonary artery smooth muscle cells under hypoxia. The specific genes or potential molecular pathways responsible for mediating the protective effects were also characterised by RNA sequencing. Further, the frequency and the total time of intermittent reoxygenation affected its preventive effect of HAPH, which was likely attributable to augmented oxidative stress. Hence, daily intermittent, not continuous, short-duration reoxygenation partially prevented pulmonary hypertension induced by 5000-m hypoxia in rats. This study is novel in revealing a new potential method in preventing HAPH. It gives insights into the selection and optimisation of oxygen supply schemes in high-altitude areas.

NC2 complex is a key factor for the activation of catalase-3 transcription by regulating H2A.Z deposition

Negative cofactor 2 (NC2), including two subunits NC2α and NC2β, is a conserved positive/negative regulator of class II gene transcription in eukaryotes. It is known that NC2 functions by regulating the assembly of the transcription preinitiation complex. However, the exact role of NC2 in transcriptional regulation is still unclear. Here, we reveal that, in Neurospora crassa, NC2 activates catalase-3 (cat-3) gene transcription in the form of heterodimer mediated by histone fold (HF) domains of two subunits. Deletion of HF domain in either of two subunits disrupts the NC2α–NC2β interaction and the binding of intact NC2 heterodimer to cat-3 locus. Loss of NC2 dramatically increases histone variant H2A.Z deposition at cat-3 locus. Further studies show that NC2 recruits chromatin remodeling complex INO80C to remove H2A.Z from the nucleosomes around cat-3 locus, resulting in transcriptional activation of cat-3. Besides HF domains of two subunits, interestingly, C-terminal repression domain of NC2β is required not only for NC2 binding to cat-3 locus, but also for the recruitment of INO80C to cat-3 locus and removal of H2A.Z from the nucleosomes. Collectively, our findings reveal a novel mechanism of NC2 in transcription activation through recruiting INO80C to remove H2A.Z from special H2A.Z-containing nucleosomes.

Endoplasmic reticulum Ca2+ release causes Rieske iron-sulfur protein-mediated mitochondrial ROS generation in pulmonary artery smooth muscle cells

Mitochondrial reactive oxygen species (ROS) cause Ca²⁺ release from the endoplasmic reticulum (ER) via ryanodine receptors (RyRs) in pulmonary artery smooth muscle cells (PASMCs), playing an essential role in hypoxic pulmonary vasoconstriction (HPV). Here we tested a novel hypothesis that hypoxia-induced RyR-mediated Ca²⁺ release may, in turn, promote mitochondrial ROS generation contributing to hypoxic cellular responses in PASMCs. Our data reveal that application of caffeine to elevate intracellular Ca²⁺ concentration ([Ca²⁺]_i) by activating RyRs results in a significant increase in ROS production in cytosol and mitochondria of PASMCs. Norepinephrine to increase [Ca²⁺]_i due to the opening of inositol 1,4,5-triphosphate receptors (IP3Rs) produces similar effects. Exogenous Ca²⁺ significantly increases mitochondrial-derived ROS generation as well. Ru360 also inhibits the hypoxic ROS production. The RyR antagonist tetracaine or RyR2 gene knockout (KO) suppresses hypoxia-induced responses as well. Inhibition of mitochondrial Ca²⁺ uptake with Ru360 eliminates N- and Ca²⁺-induced responses. RISP KD abolishes the hypoxia-induced ROS production in mitochondria of PASMCs. Rieske iron–sulfur protein (RISP) gene knockdown (KD) blocks caffeine- or NE-induced ROS production. Taken together, these findings have further demonstrated that ER Ca²⁺ release causes mitochondrial Ca²⁺ uptake and RISP-mediated ROS production; this novel local ER/mitochondrion communication-elicited, Ca²⁺-mediated, RISP-dependent ROS production may play a significant role in hypoxic cellular responses in PASMCs.

Complex interplay between autophagy and oxidative stress in the development of pulmonary disease

The autophagic pathway involves the encapsulation of substrates in double-membraned vesicles, which are subsequently delivered to the lysosome for enzymatic degradation and recycling of metabolic precursors. Autophagy is a major cellular defense against oxidative stress, or related conditions that cause accumulation of damaged proteins or organelles. Selective forms of autophagy can maintain organelle populations or remove aggregated proteins. Dysregulation of redox homeostasis under pathological conditions results in excessive generation of reactive oxygen species (ROS), leading to oxidative stress and the associated oxidative damage of cellular components. Accumulating evidence indicates that autophagy is necessary to maintain redox homeostasis. ROS activates autophagy, which facilitates cellular adaptation and diminishes oxidative damage by degrading and recycling intracellular damaged macromolecules and dysfunctional organelles. The cellular responses triggered by oxidative stress include the altered regulation of signaling pathways that culminate in the regulation of autophagy. Current research suggests a central role for autophagy as a mammalian oxidative stress response and its interrelationship to other stress defense systems. Altered autophagy phenotypes have been observed in lung diseases such as chronic obstructive lung disease, acute lung injury, cystic fibrosis, idiopathic pulmonary fibrosis, and pulmonary arterial hypertension, and asthma. Understanding the mechanisms by which ROS regulate autophagy will provide novel therapeutic targets for lung diseases. This review highlights our current understanding on the interplay between ROS and autophagy in the development of pulmonary disease.

Obesity, estrogens and adipose tissue dysfunction - implications for pulmonary arterial hypertension

Obesity is a prevalent global public health issue characterized by excess body fat. Adipose tissue is now recognized as an important endocrine organ releasing an abundance of bioactive adipokines including, but not limited to, leptin, adiponectin and resistin. Obesity is a common comorbidity amongst pulmonary arterial hypertension patients, with 30% to 40% reported as obese, independent of other comorbidities associated with pulmonary arterial hypertension (e.g. obstructive sleep apnoea). An 'obesity paradox' has been observed, where obesity has been associated with subclinical right ventricular dysfunction but paradoxically may confer a protective effect on right ventricular function once pulmonary hypertension develops. Obesity and pulmonary arterial hypertension share multiple pathophysiological mechanisms including inflammation, oxidative stress, elevated leptin (proinflammatory) and reduced adiponectin (anti-inflammatory). The female prevalence of pulmonary arterial hypertension has instigated the hypothesis that estrogens may play a causative role in its development. Adipose tissue, a major site for storage and metabolism of sex steroids, is the primary source of estrogens and circulating estrogens levels which are elevated in postmenopausal women and men with pulmonary arterial hypertension. This review discusses the functions of adipose tissue in both health and obesity and the links between obesity and pulmonary arterial hypertension. Shared pathophysiological mechanisms and the contribution of specific fat depots, metabolic and sex-dependent differences are discussed.

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.

Obesity, Systemic Hypertension, and Pulmonary Hypertension: A Tale of Three Diseases

Cardiovascular disease (CVD), especially ischemic heart disease and stroke, is the major cause of death worldwide, accounting for more than one-third of all deaths annually. Hypertension is the most prevalent and modifiable risk factor of CVD-related deaths. The same is true for obesity, which is currently being recognized as a major global epidemic. The prevalence of obesity in the United States has increased dramatically, from 13.4% in 1960 to 36.5% in 2014, with as much as 70.7% of the American adult population being overweight or obese (CDC). Epidemiological studies have shown that obesity predisposes to hypertension and CVD - with the relationship between markers of obesity and blood pressure being almost linear across different populations. In this review, we discuss systemic and pulmonary hypertension in the context of obesity.

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.

Important Role of Sarcoplasmic Reticulum Ca2+ Release via Ryanodine Receptor-2 Channel in Hypoxia-Induced Rieske Iron-Sulfur Protein-Mediated Mitochondrial Reactive Oxygen Species Generation in Pulmonary Artery Smooth Muscle Cells

Aims: It is known that mitochondrial reactive oxygen species generation ([ROS]_m) causes the release of Ca²⁺via ryanodine receptor-2 (RyR2) on the sarcoplasmic reticulum (SR) in pulmonary artery smooth muscle cells (PASMCs), playing an essential role in hypoxic pulmonary vasoconstriction (HPV). In this study, we sought to determine whether hypoxia-induced RyR2-mediated Ca²⁺ release may in turn promote [ROS]_m in PASMCs and the underlying signaling mechanism. Results: Our data reveal that application of caffeine or norepinephrine to induce Ca²⁺ release increased [ROS]_m in PASMCs. Likewise, exogenous Ca²⁺ augmented ROS generation in isolated mitochondria and at complex III from PASMCs. Inhibition of mitochondrial Ca²⁺ uniporter (MCU) with Ru360 attenuated agonist-induced [ROS]_m. Ru360 produced a similar inhibitory effect on hypoxia-induced [ROS]_m. Rieske iron-sulfur protein (RISP) gene knockdown inhibited Ca²⁺- and caffeine-induced [ROS]_m. Inhibition of RyR2 by tetracaine or RyR2 gene knockout suppressed hypoxia-induced [ROS]_m as well. Innovation: In this article, we present convincing evidence that Ca²⁺ release following hypoxia or RyR simulation causes a significant increase in MCU, and the increased MCU subsequently RISP-dependent [ROS]_m, which provides a positive feedback mechanism to enhance hypoxia-initiated [ROS]_m in PASMCs. Conclusion: Our findings demonstrate that hypoxia-induced mitochondrial ROS-dependent SR RyR2-mediated Ca²⁺ release increases MCU and then RISP-dependent [ROS]_m in PASMCs, which may make significant contributions to HPV and associated pulmonary hypertension.

Alginate Oligosaccharide Alleviates Monocrotaline-Induced Pulmonary Hypertension via Anti-Oxidant and Anti-Inflammation Pathways in Rats

Pulmonary arterial hypertension (PAH) is a serious and fatal cardiovascular disorder characterized by increased pulmonary vascular resistance and progressive pulmonary vascular remodeling. The underlying pathological mechanisms of PAH are multi-factorial and multi-cellular. Alginate oligosaccharide (AOS), which is produced by depolymerizing alginate, shows better pharmacological activities and beneficial effects. The present study was undertaken to investigate the effects and potential mechanisms of AOS-mediated alleviation of pulmonary hypertension. Pulmonary hypertension was induced in Sprague-Dawley rats by a single intraperitoneal injection of monocrotaline (MCT; 60 mg/kg). Five weeks after the injection of MCT, AOS (5, 10, and 20 mg·kg^-1·d^-1) was injected intraperitoneally for another three weeks. The results showed that AOS prevented the development of MCT-induced pulmonary hypertension and right ventricular hypertrophy in a dose-dependent manner. AOS treatment also prevented MCT-induced pulmonary vascular remodeling via inhibition of the TGF-β1/p-Smad2 signaling pathway. Furthermore, AOS treatment downregulated the expression of malondialdehyde, nicotinamide adenine dinucleotide phosphate oxidase, and pro-inflammatory cytokines, decreased macrophage infiltration, and upregulated the expression of anti-inflammatory cytokines. These findings indicate that AOS exerts anti-oxidative and anti-inflammatory effects in pulmonary arteries, which may contribute to the alleviation of pulmonary hypertension and pulmonary vascular remodeling.

NADPH oxidase in the vasculature: Expression, regulation and signalling pathways; role in normal cardiovascular physiology and its dysregulation in hypertension

The last 20-25 years have seen an explosion of interest in the role of NADPH oxidase (NOX) in cardiovascular function and disease. In vascular smooth muscle and endothelium, NOX generates reactive oxygen species (ROS) that act as second messengers, contributing to the control of normal vascular function. NOX activity is altered in response to a variety of stimuli, including G-protein coupled receptor agonists, growth-factors, perfusion pressure, flow and hypoxia. NOX-derived ROS are involved in smooth muscle constriction, endothelium-dependent relaxation and smooth muscle growth, proliferation and migration, thus contributing to the fine-tuning of blood flow, arterial wall thickness and vascular resistance. Through reversible oxidative modification of target proteins, ROS regulate the activity of protein tyrosine phosphatases, kinases, G proteins, ion channels, cytoskeletal proteins and transcription factors. There is now considerable, but somewhat contradictory evidence that NOX contributes to the pathogenesis of hypertension through oxidative stress. Specific NOX isoforms have been implicated in endothelial dysfunction, hyper-contractility and vascular remodelling in various animal models of hypertension, pulmonary hypertension and pulmonary arterial hypertension, but also have potential protective effects, particularly NOX4. This review explores the multiplicity of NOX function in the healthy vasculature and the evidence for and against targeting NOX for antihypertensive therapy.

The Biological Bases of Group 2 Pulmonary Hypertension

Pulmonary hypertension (PH) is a potentially fatal condition with a prevalence of around 1% in the world population and most commonly caused by left heart disease (PH-LHD). Usually, in PH-LHD, the increase of pulmonary pressure is only conditioned by the retrograde transmission of the left atrial pressure. However, in some cases, the long-term retrograde pressure overload may trigger complex and irreversible biomechanical and biological changes in the pulmonary vasculature. This latter clinical entity, designated as combined pre- and post-capillary PH, is associated with very poor outcomes. The underlying mechanisms of this progression are poorly understood, and most of the current knowledge comes from the field of Group 1-PAH. Treatment is also an unsolved issue in patients with PH-LHD. Targeting the molecular pathways that regulate pulmonary hemodynamics and vascular remodeling has provided excellent results in other forms of PH but has a neutral or detrimental result in patients with PH-LHD. Therefore, a deep and comprehensive biological characterization of PH-LHD is essential to improve the diagnostic and prognostic evaluation of patients and, eventually, identify new therapeutic targets. Ongoing research is aimed at identify candidate genes, variants, non-coding RNAs, and other biomarkers with potential diagnostic and therapeutic implications. In this review, we discuss the state-of-the-art cellular, molecular, genetic, and epigenetic mechanisms potentially involved in PH-LHD. Signaling and effective pathways are particularly emphasized, as well as the current knowledge on -omic biomarkers. Our final aim is to provide readers with the biological foundations on which to ground both clinical and pre-clinical research in the field of PH-LHD.

Regulation of mitochondrial fragmentation in microvascular endothelial cells isolated from the SU5416/hypoxia model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a morbid disease characterized by progressive right ventricle (RV) failure due to elevated pulmonary artery pressures (PAP). In PAH, histologically complex vaso-occlusive lesions in the pulmonary vasculature contribute to elevated PAP. However, the mechanisms underlying dysfunction of the microvascular endothelial cells (MVECs) that comprise a significant portion of these lesions are not well understood. We recently showed that MVECs isolated from the Sugen/hypoxia (SuHx) rat experimental model of PAH (SuHx-MVECs) exhibit increases in migration/proliferation, mitochondrial reactive oxygen species (ROS; mtROS) production, intracellular calcium levels ([Ca2+]i), and mitochondrial fragmentation. Furthermore, quenching mtROS with the targeted antioxidant MitoQ attenuated basal [Ca2+]i, migration and proliferation; however, whether increased mtROS-induced [Ca2+]i entry affected mitochondrial morphology was not clear. In this study, we sought to better understand the relationship between increased ROS, [Ca2+]i, and mitochondrial morphology in SuHx-MVECs. We measured changes in mitochondrial morphology at baseline and following inhibition of mtROS, with the targeted antioxidant MitoQ, or transient receptor potential vanilloid-4 (TRPV4) channels, which we previously showed were responsible for mtROS-induced increases in [Ca2+]i in SuHx-MVECs. Quenching mtROS or inhibiting TRPV4 attenuated fragmentation in SuHx-MVECs. Conversely, inducing mtROS production in MVECs from normoxic rats (N-MVECs) increased fragmentation. Ca2+ entry induced by the TRPV4 agonist GSK1017920A was significantly increased in SuHx-MVECs and was attenuated with MitoQ treatment, indicating that mtROS contributes to increased TRPV4 activity in SuHx-MVECs. Basal and maximal respiration were depressed in SuHx-MVECs, and inhibiting mtROS, but not TRPV4, improved respiration in these cells. Collectively, our data show that, in SuHx-MVECs, mtROS production promotes TRPV4-mediated increases in [Ca2+]i, mitochondrial fission, and decreased mitochondrial respiration. These results suggest an important role for mtROS in driving MVEC dysfunction in PAH.