The principal pathways involved in the in vivo modulation of hypoxic pulmonary vasoconstriction, pulmonary arterial remodelling and pulmonary hypertension

Symposium review: high altitude travel with pulmonary vascular disease

Pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension are the main precapillary forms of pulmonary hypertension (PH) summarized as pulmonary vascular diseases (PVD). PVDs are characterized by exertional dyspnoea and oxygen desaturation, and reduced quality of life and survival. Medical therapies improve life expectancy and physical performance of PVD patients, of whom many wish to participate in professional work and recreational activities including traveling to high altitude. The exposure to the hypobaric hypoxic environment of mountain regions incurs the risk of high altitude adverse events (AEHA) due to severe hypoxaemia exacerbating symptoms and further increase in pulmonary artery pressure, which may lead to right heart decompensation. Recent prospective and randomized trials show that altitude-induced hypoxaemia, pulmonary haemodynamic changes and impairment of exercise performance in PVD patients are in the range found in healthy people. The vast majority of optimally treated stable PVD patients who do not require long-term oxygen therapy at low altitude can tolerate short-term exposure to moderate altitudes up to 2500 m. PVD patients that reveal persistent severe resting hypoxaemia (S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$  <80% for >30 min) at 2500 m respond well to supplemental oxygen therapy. Although there are no accurate predictors for AEHA, PVD patients with unfavourable risk profiles at low altitude, such as higher WHO functional class, lower exercise capacity with more pronounced exercise-induced desaturation and more severely impaired haemodynamics, are at increased risk of AEHA. Therefore, doctors with experience in PVD and high-altitude medicine should counsel PVD patients before any high-altitude sojourn. This review aims to summarize recent literature and clinical recommendations about PVD patients travelling to high altitude.

The Cavin-1/Caveolin-1 interaction attenuates BMP/Smad signaling in pulmonary hypertension by interfering with BMPR2/Caveolin-1 binding

Caveolin-1 (CAV1) and Cavin-1 are components of caveolae, both of which interact with and influence the composition and stabilization of caveolae. CAV1 is associated with pulmonary arterial hypertension (PAH). Bone morphogenetic protein (BMP) type 2 receptor (BMPR2) is localized in caveolae associated with CAV1 and is commonly mutated in PAH. Here, we show that BMP/Smad signaling is suppressed in pulmonary microvascular endothelial cells of CAV1 knockout mice. Moreover, hypoxia enhances the CAV1/Cavin-1 interaction but attenuates the CAV1/BMPR2 interaction and BMPR2 membrane localization in pulmonary artery endothelial cells (PAECs). Both Cavin-1 and BMPR2 are associated with the CAV1 scaffolding domain. Cavin-1 decreases BMPR2 membrane localization by inhibiting the interaction of BMPR2 with CAV1 and reduces Smad signal transduction in PAECs. Furthermore, Cavin-1 knockdown is resistant to CAV1-induced pulmonary hypertension in vivo. We demonstrate that the Cavin-1/Caveolin-1 interaction attenuates BMP/Smad signaling and is a promising target for the treatment of PAH.

Unmasking a Silent Threat: Improving Pulmonary Hypertension Screening Methods for Interstitial Lung Disease Patients

This article provides a comprehensive overview of the latest literature on the diagnostics and treatment of pulmonary hypertension (PH) associated with interstitial lung disease (ILD). Heightened suspicion for PH arises when the advancement of dyspnoea in ILD patients diverges from the expected pattern of decline in pulmonary function parameters. The complexity of PH associated with ILD (PH-ILD) diagnostics is emphasized by the limitations of transthoracic echocardiography in the ILD population, necessitating the exploration of alternative diagnostic approaches. Cardiac magnetic resonance imaging (MRI) emerges as a promising tool, offering insights into hemodynamic parameters and providing valuable prognostic information. The potential of biomarkers, alongside pulmonary function and cardiopulmonary exercise tests, is explored for enhanced diagnostic and prognostic precision. While specific treatments for PH-ILD remain limited, recent studies on inhaled treprostinil provide new hope for improved patient outcomes.

Medical Emergencies in Pulmonary Hypertension

The management of acute medical emergencies in patients with pulmonary hypertension (PH) can be challenging. Patients with preexisting PH can rapidly deteriorate due to right ventricular decompensation when faced with acute physiological challenges that would usually be considered low-risk scenarios. This review considers the assessment and management of acute medical emergencies in patients with PH, encompassing both pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH), acknowledging these comprise the more severe groups of PH. Management protocols are described in a systems-based approach. Respiratory emergencies include pulmonary embolism, airways disease, and pneumonia; cardiac emergencies including arrhythmia and chest pain with acute myocardial infarction are discussed, alongside PH-specific emergencies such as pulmonary artery dissection and extrinsic coronary artery compression by a dilated proximal pulmonary artery. Other emergencies including sepsis, severe gastroenteritis with dehydration, syncope, and liver failure are also considered. We propose management recommendations for medical emergencies based on available evidence, international guidelines, and expert consensus. We aim to provide advice to the specialist alongside the generalist, and emergency doctors, nurses, and acute physicians in nonspecialist centers. A multidisciplinary team approach is essential in the management of patients with PH, and communication with local and specialist PH centers is paramount. Close hemodynamic monitoring during medical emergencies in patients with preexisting PH is vital, with early referral to critical care recommended given the frequent deterioration and high mortality in this setting.

Role of KLF4/NDRG1/DRP1 axis in hypoxia-induced pulmonary hypertension

N-myc downstream regulated gene 1 (NDRG1) has recently drawn increasing attention because of its involvement in angiogenesis, cell proliferation, and differentiation. We used in vitro [human pulmonary artery smooth muscle cells (hPASMCs)] and in vivo (rat) models under hypoxic conditions and found a vital role of NDRG1 in reducing apoptosis and increasing proliferation and migration by overexpressing and knocking down NDRG1. We also proved that hypoxia induced the protein expression of dynamin-related protein 1 (DRP1) and stimulated The phosphatidylinositol-3-kinase (PI3K)/ Protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathways, and these effects were reversed by NDRG1 knockdown. The relationship between NDRG1 and DRP1 and the PI3K/Akt/mTOR pathway was further evaluated by adding mdivi-1 (DRP1 inhibitor) or LY294002 (PI3K inhibitor). NDRG1 was found to regulate the proliferation, apoptosis, and migration of hypoxia-treated hPASMCs via DRP1 and PI3K/Akt/mTOR signaling pathways. We explored the upstream regulators of NDRG1 using in vivo and in vitro hypoxia models. Hypoxia was found to upregulate and downregulate KLF transcription factor 4 (KLF4) protein expression in the cytoplasm and nucleus, respectively. Further, we showed that KLF4 regulated the proliferation and migration of hypoxia-treated hPASMCs via NDRG1. These results indicated a link between KLF4, NDRG1, and DRP1 for the first time, providing new ideas for treating hypoxic pulmonary hypertension.

Natural Products for the Treatment of Pulmonary Hypertension: Mechanism, Progress, and Future Opportunities

Pulmonary hypertension (PH) is a lethal disease due to the remodeling of pulmonary vessels. Its pathophysiological characteristics include increased pulmonary arterial pressure and pulmonary vascular resistance, leading to right heart failure and death. The pathological mechanism of PH is complex and includes inflammation, oxidative stress, vasoconstriction/diastolic imbalance, genetic factors, and ion channel abnormalities. Currently, many clinical drugs for the treatment of PH mainly play their role by relaxing pulmonary arteries, and the treatment effect is limited. Recent studies have shown that various natural products have unique therapeutic advantages for PH with complex pathological mechanisms owing to their multitarget characteristics and low toxicity. This review summarizes the main natural products and their pharmacological mechanisms in PH treatment to provide a useful reference for future research and development of new anti-PH drugs and their mechanisms.

Allgemeine Therapie der pulmonalarteriellen Hypertonie nach den neuen Leitlinien

In den neuen Leitlinien (LL) für pulmonalarterielle Hypertonie (PAH) sind die allgemeinen Maßnahmen ein integraler Bestandteil der Behandlung der Patienten. Auch die systemischen Auswirkungen der pulmonalen Hypertonie und Rechtsherzinsuffizienz sollten angemessen berücksichtigt und behandelt werden. Im folgenden Artikel werden die in den LL genannten Maßnahmen unter Berücksichtigung des bestehenden Empfehlungsgrads und der Evidenzen beschrieben. Leider sind die meisten Allgemeinmaßnahmen, wie die Gabe von Diuretika, Sauerstoff, psychosozialer Support und Impfungen, nicht oder unzureichend in randomisierten, kontrollierten Studien untersucht worden. So haben sie zwar einen hohen I-Empfehlungsgrad, aber einen niedrigen Evidenzgrad C. Nur bei dem spezialisierten körperlichen Training liegen bislang insgesamt 7 randomisierte, kontrollierte Studien und 5 Metaanalysen vor, die eine Verbesserung der Sauerstoffaufnahme, körperlichen Belastbarkeit, der Beschwerden (WHO-Funktionsklasse), Lebensqualität und Hämodynamik nachgewiesen haben (daher neu IA-Empfehlung). Auch weitere Maßnahmen wie die Antikoagulation, Eisensubstitution und andere werden im Folgenden besprochen.

Significance of Pulmonary Endothelial Injury and the Role of Cyclooxygenase-2 and Prostanoid Signaling

The endothelium plays a key role in the dynamic balance of hemodynamic, humoral and inflammatory processes in the human body. Its central importance and the resulting therapeutic concepts are the subject of ongoing research efforts and form the basis for the treatment of numerous diseases. The pulmonary endothelium is an essential component for the gas exchange in humans. Pulmonary endothelial dysfunction has serious consequences for the oxygenation and the gas exchange in humans with the potential of consecutive multiple organ failure. Therefore, in this review, the dysfunction of the pulmonary endothel due to viral, bacterial, and fungal infections, ventilator-related injury, and aspiration is presented in a medical context. Selected aspects of the interaction of endothelial cells with primarily alveolar macrophages are reviewed in more detail. Elucidation of underlying causes and mechanisms of damage and repair may lead to new therapeutic approaches. Specific emphasis is placed on the processes leading to the induction of cyclooxygenase-2 and downstream prostanoid-based signaling pathways associated with this enzyme.

Pipersentan: A De Novo Synthetic Endothelin Receptor Antagonist that Inhibits Monocrotaline- and Hypoxia-Induced Pulmonary Hypertension

Background: Although major advances have been made in the pathogenesis and management of pulmonary arterial hypertension (PAH), the endothelin system is still considered to play a vital role in the pathology of PAH due to its vasoconstrictive action. Endothelin receptor antagonists (ERAs), either as monotherapy or in combination with other drugs, have attracted much attention in the treatment of this lethal disease, and research is continuing.

Methods: A novel ERA, pipersentan 5-(1,3-Benzodioxol-5-yl)-6-[2-(5-bromopyrimidin-2-yl)oxyethoxy]-N-(2-methoxyethylsulfamoyl)pyrimidin-4-amine, was recently synthesized and the physicochemical characterizations and the pharmacology both in vitro and in vivo were studied.

Results: This orally administered ERA can both competitively and selectively inhibit the binding of endothelin-1 (ET-1) to its receptors with good physicochemical characteristics. Pipersentan efficaciously antagonized the effects of ET-1 on pulmonary artery smooth muscle cell proliferation, migration and calcium mobilization and effectively improved right ventricular hypertrophy and pulmonary arterial pressure in both monocrotaline- and hypoxia-induced pulmonary hypertension (PH) rat models.

Conclusions: This profile identifies pipersentan as a new agent for treating ET-1 system activation-related PH.

The mechanism of the imbalance between proliferation and ferroptosis in pulmonary artery smooth muscle cells based on the activation of SLC7A11

Pulmonary arterial hypertension (PAH) is a chronic, progressive pulmonary vascular disease. Pulmonary vascular remodelling (PVR) is one of the main pathological features of PAH. The main cause of PVR is cell death inhibition and excessive proliferation in pulmonary artery smooth muscle cells (PASMCs), which are also affected by oxidative stress. Ferroptosis is a newly identified form of cell death, which is associated with oxidative damage. It depends on the excessive accumulation of lipid peroxides and reactive oxygen species (ROS) in cells. Solute carrier family 7 member 11 (SLC7A11) is a subunit of the cystine/glutamate antiporter system Xc^-, which inhibits ferroptosis by eliminating ROS through the promotion of GSH synthesis in cancer cells. However, very few studies exist on the relationship between ferroptosis and SLC7A11 in PAH. In this study, SLC7A11 was up-regulated in Sugen5416/hypoxia-induced PAH rats and patients with PAH. Moreover, SLC7A11 inhibited ferroptosis and promoted proliferation by overexpressing SLC7A11 in PASMCs. Additionally, ubiquitin aldehyde binding 1 (OTUB1), the main regulator of SLC7A11 stability, was involved in the ferroptosis and proliferation of PASMCs. Furthermore, erastin induced ferroptosis by inhibiting SLC7A11 and glutathione peroxidase 4 (GPX4) expressions in vivo and in vitro, suggesting that the continuous proliferation in hypoxic PASMCs could be reversed by erastin. Therefore, this study identifies novel targets and new research directions regarding PAH pathogenesis and treatment.

Hypoxia and hemorheological properties in older individuals

Hypoxia is caused by insufficient oxygen availability for the organism leading to reduced oxygen delivery to tissues and cells. It has been regarded as a severe threat to human health and it is indeed implicated in pathophysiological mechanisms involved in the development and progression of many diseases. Nevertheless, the potential of controlled hypoxia interventions (i.e. hypoxia conditioning) for improving cardio-vascular health is gaining increased attention. However, blood rheology is often a forgotten factor for vascular health while aging and hypoxia exposure are both suspected to alter hemorheological properties. These changes in blood rheology may influence the benefits-risks balance of hypoxia exposure in older individuals. The benefits of hypoxia exposure for vascular health are mainly reported for healthy populations and the combined impact of aging and hypoxia on blood rheology could therefore be deleterious in older individuals. This review discusses evidence of hypoxia-related and aging-related changes in blood viscosity and its determinants. It draws upon an extensive literature search on the effects of hypoxia/altitude and aging on blood rheology. Aging increases blood viscosity mainly through a rise in plasma viscosity, red blood cell (RBC) aggregation and a decrease in RBC deformability. Hypoxia also causes an increase in RBC aggregation and plasma viscosity. In addition, hypoxia exposure may increase hematocrit and modulate RBC deformability, depending on the hypoxic dose, i.e, beneficial effect of intermittent hypoxia with moderate dose vs deleterious effect of chronic continuous or intermittent hypoxia or if the hypoxic dose is too high. Special attention is directed toward the risks vs. benefits of hemorheological changes during hypoxia exposure in older individuals, and its clinical relevance for vascular disorders.

Chronic obstructive pulmonary disease and atherosclerosis: common mechanisms and novel therapeutics

Chronic obstructive pulmonary disease (COPD) and atherosclerosis are chronic irreversible diseases, that share a number of common causative factors including cigarette smoking. Atherosclerosis drastically impairs blood flow and oxygen availability to tissues, leading to life-threatening outcomes including myocardial infarction (MI) and stroke. Patients with COPD are most likely to die as a result of a cardiovascular event, with 30% of all COPD-related deaths being attributed to cardiovascular disease (CVD). Both atherosclerosis and COPD involve significant local (i.e. lung, vasculature) and systemic inflammation and oxidative stress, of which current pharmacological treatments have limited efficacy, hence the urgency for the development of novel life-saving therapeutics. Currently these diseases must be treated individually, with no therapies available that can effectively reduce the likelihood of comorbid CVD other than cessation of cigarette smoking. In this review, the important mechanisms that drive atherosclerosis and CVD in people with COPD are explained and we propose that modulation of both the oxidative stress and the inflammatory burden will provide a novel therapeutic strategy to treat both the pulmonary and systemic manifestations related to these diseases.

Combined effect of acute altitude exposure and vigorous exercise on platelet activation

Exposure to high altitudes and exercise alters body's physiology and may cause acute cardiovascular events. Platelet activation is one of the key players in these events. Therefore, we investigated the effect of vigorous exercise at higher altitude (2650 m) on platelet aggregation and serum markers of platelet activation. 14 healthy subjects performed a step incremental ergometer test until exhaustion at the Environmental Research Station (UFS, 2650 m) at Zugspitze. Platelet aggregation and serum levels of endothelin-1, soluble p-selectin, platelet factor 4 and Chromogranin A were measured. Platelet activation was significantly enhanced after exercise at high altitude compared to measures immediately prior exercise. We detected significantly enhanced serum levels of endothelin-1 and soluble p-selectin whereas chromogranin A and platelet factor 4 remained unchanged. This effect might be due to increased endothelin-1 levels causing pulmonary vasoconstriction, rheological changes and direct platelet activation. This might be of clinical relevance, especially in patients with pre-existing diseases.

MIR17HG polymorphisms contribute to high-altitude pulmonary edema susceptibility in the Chinese population

High-altitude pulmonary edema (HAPE) is a common acute altitude sickness. This study was designed to investigate the effect of MIR17HG polymorphisms on HAPE risk in the Chinese population. The Agena MassARRAY platform was used to genotype six single-nucleotide polymorphisms (SNPs) in the MIR17HG gene in 244 HAPE patients and 243 non-HAPE controls. The odds ratio (OR) and 95% confidence interval were used to evaluate the association between each MIR17HG polymorphisms and the risk of HAPE under a polygenetic model. Statistical analysis was performed using the χ² test. Multifactor dimensionality reduction (MDR) analysis was used to analyze the impacts of SNP–SNP interactions on the risk of HAPE. According to the allele model, the HAPE risk of people with the rs7318578 A allele of MIR17HG was lower than that of people with the C allele (OR 0.74, p = 0.036).Logistic regression analysis of four models for all selected MIR17HG SNPs showed significant differences in the frequencies of rs7318578 (OR 0.74, p = 0.037) and rs17735387 (OR 1.51, p = 0.036) between cases and controls. The results of the sex stratification analysis showed that among males, rs17735387 in the MIR17HG gene is associated with an increased risk of HAPE. MDR analysis showed that the best combination model was a three-locus model incorporating rs72640334, rs7318578, and rs7336610. This study revealed the correlations between rs7318578 and rs17735387 on the MIR17HG gene and the risk of HAPE in the Chinese population, providing a theoretical basis for the early screening, prevention, and diagnosis of HAPE in high-risk populations.

Pretreatment with the active fraction of Rhodiola tangutica (Maxim.) S.H. Fu rescues hypoxia-induced potassium channel inhibition in rat pulmonary artery smooth muscle cells

ETHNOPHARMACOLOGICAL RELEVANCE

Previous studies have shown that the active fraction of Rhodiola tangutica (Maxim.) S.H. Fu (ACRT) dilates pulmonary arteries and thwarts pulmonary artery remodelling. The dilatation effect of ACRT on pulmonary artery vascular rings could be reduced by potassium (K⁺) channel blockers. However the exact mechanisms of ACRT on ion channels are still unclear.

AIM OF THE STUDY

This study aimed to investigate whether the effect of ACRT on K⁺ channels inhibits cell proliferation after pulmonary artery smooth muscle cells (PASMCs) are exposed to hypoxia.

MATERIALS AND METHODS

The whole-cell patch-clamp method was used to clarify the effect of ACRT on the K⁺ current (I_K) of rat PASMCs exposed to hypoxia. The mRNA and protein expression levels were detected using real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting, respectively. The intracellular calcium (Ca²⁺) concentration ([Ca²⁺]_i) values in rat PASMCs were detected by laser scanning confocal microscopy. The cell cycle and cell proliferation were assessed using flow cytometry analysis and CCK-8 and EdU assays.

RESULTS

ACRT pretreatment alleviated the inhibition of I_K induced by hypoxia in rat PASMCs. Compared with hypoxia, ACRT upregulated voltage-dependent K⁺ channel (K_v) 1.5 and big-conductance calcium-activated K⁺ channel (BK_Ca) mRNA and protein expression and downregulated voltage-dependent Ca²⁺ channel (Ca_v) 1.2 mRNA and protein expression. ACRT decreased [Ca²⁺]_i, inhibited the promotion of cyclin D1 and proliferating cell nuclear antigen (PCNA) expression, and prevented the proliferation of rat PASMCs exposed to hypoxia.

CONCLUSION

In conclusion, the present study demonstrated that ACRT plays a key role in restoring ion channel function and then inhibiting the proliferation of PASMCs under hypoxia, ACRT has preventive and therapeutic potential in hypoxic pulmonary hypertension.

N7-methylguanosine modification of lncRNAs in a rat model of hypoxic pulmonary hypertension: a comprehensive analysis

Background

Long non-coding RNAs (lncRNAs) play a critical role in the pathogenesis of hypoxic pulmonary hypertension (HPH). The role of N7-methylguanosine (m7G) modification in lncRNAs has received increased attentions in recent years. However, the m7G-methylation of lncRNA in HPH has yet to be determined. We have therefore performed a transcriptome-wide analysis of m7G lncRNAs in HPH.

Results

Differentially-expressed m7Gs were detected in HPH, and m7G lncRNAs were significantly upregulated compared with non-m7G lncRNAs in HPH. Importantly, this was the first time that the upregulated m7G lncXR_591973 and m7G lncXR_592398 were identified in HPH.

Conclusion

This study provides the first m7G transcriptome-wide analysis of HPH. Importantly, two HPH-associated m7G lncRNAs were identified, although their clinical significance requires further validation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08188-8.

The hypoxic pulmonary vasoconstriction: From physiology to clinical application in thoracic surgery

More than 70 years after its original report, the hypoxic pulmonary vasoconstriction (HPV) response continues to spark scientific interest on its mechanisms and clinical implications, particularly for anesthesiologists involved in thoracic surgery. Selective airway intubation and one-lung ventilation (OLV) facilitates the surgical intervention on a collapsed lung while the HPV redirects blood flow from the "upper" non-ventilated hypoxic lung to the "dependent" ventilated lung. Therefore, by limiting intrapulmonary shunting and optimizing ventilation-to-perfusion (V/Q) ratio, the fall in arterial oxygen pressure (PaO₂) is attenuated during OLV. The HPV involves a biphasic response mobilizing calcium within pulmonary vascular smooth muscles, which is activated within seconds after exposure to low alveolar oxygen pressure and that gradually disappears upon re-oxygenation. Many factors including acid-base balance, the degree of lung expansion, circulatory volemia as well as lung diseases and patient age affect HPV. Anesthetic agents, analgesics and cardiovascular medications may also interfer with HPV during the perioperative period. Since HPV represents the homeostatic mechanism for regional ventilation-to-perfusion matching and in turn, for optimal pulmonary oxygen uptake, a clear understanding of HPV is clinically relevant for all anesthesiologists.

Systemic Sclerosis: Elevated Levels of Leukotrienes in Saliva and Plasma Are Associated with Vascular Manifestations and Nailfold Capillaroscopic Abnormalities

The role of leukotrienes (LTs) in the pathogenesis of systemic sclerosis (SSc) needs clarification. We analyzed the association of salivary (sa) and plasma (p) levels (pg/mL) of cysteinyl-leukotrienes (CysLT) and LTB4 with SSc vascular manifestations and nailfold capillaroscopy (NFC) in a cross-sectional study. Patients and healthy controls were evaluated for vascular manifestations and NFC. LTs were compared between groups as follows: SSc with or SSc without vascular features and controls, and by NFC parameters. Twenty SSc patients and 16 volunteers were recruited; Raynaud's phenomenon (RP) history (SSc: saCysLT 99.4 ± 21.8 vs. controls: 23.05 ± 23.7, p = 0.01), RP at examination (SSc: saCysLT 129.3 ± 24.6 vs. controls: 23.05 ± 22.46, p = 0.01; pCysLT SSc: 87.5 ± 11.2 vs. controls: 32.37 ± 10.75, p = 0.002), capillary loss (saCysLT 138.6 ± 26.7 vs. 23.05 ± 21.6, p = 0.0007; saLTB4 3380.9 ± 426.6 vs. 1216.33 ± 346.1, p = 0.0005), "late" scleroderma pattern vs. controls (saCysLT 205.6 ± 32 vs. 23 ± 19.6, p = 0.0002; saLTB4 4564.9 ± 503.6 vs. 1216.3 ± 308.3; p < 0.0001) were all significant. Late patterns had higher levels (saCysLT, p = 0.002; LTB4 p = 0.0006) compared to active and early patterns (LTB4, p = 0.0006), and giant capillaries (p = 0.01) showed higher levels of LTs. Levels of pCysLT were higher in patients with RP at examination vs. patients without RP; saCysLT and LTB4 were higher in SSc group with vs. without capillary loss. LTs could be involved in the pathophysiology of vascular abnormalities. Further research is required to determine if blocking LTs could be a therapeutic target for SSc vascular manifestations.

Impairment of hypoxic pulmonary vasoconstriction in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a serious complication of severe systemic or local pulmonary inflammation, such as caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. ARDS is characterised by diffuse alveolar damage that leads to protein-rich pulmonary oedema, local alveolar hypoventilation and atelectasis. Inadequate perfusion of these areas is the main cause of hypoxaemia in ARDS. High perfusion in relation to ventilation (V/Q<1) and shunting (V/Q=0) is not only caused by impaired hypoxic pulmonary vasoconstriction but also redistribution of perfusion from obstructed lung vessels. Rebalancing the pulmonary vascular tone is a therapeutic challenge. Previous clinical trials on inhaled vasodilators (nitric oxide and prostacyclin) to enhance perfusion to high V/Q areas showed beneficial effects on hypoxaemia but not on mortality. However, specific patient populations with pulmonary hypertension may profit from treatment with inhaled vasodilators. Novel treatment targets to decrease perfusion in low V/Q areas include epoxyeicosatrienoic acids and specific leukotriene receptors. Still, lung protective ventilation and prone positioning are the best available standard of care. This review focuses on disturbed perfusion in ARDS and aims to provide basic scientists and clinicians with an overview of the vascular alterations and mechanisms of V/Q mismatch, current therapeutic strategies, and experimental approaches.

The Role of Alveolar Edema in COVID-19

The coronavirus disease 2019 (COVID-19) has spread over the world for more than one year. COVID-19 often develops life-threatening hypoxemia. Endothelial injury caused by the viral infection leads to intravascular coagulation and ventilation-perfusion mismatch. However, besides above pathogenic mechanisms, the role of alveolar edema in the disease progression has not been discussed comprehensively. Since the exudation of pulmonary edema fluid was extremely serious in COVID-19 patients, we bring out a hypothesis that severity of alveolar edema may determine the size of poorly-ventilated area and the blood oxygen content. Treatments to pulmonary edema (conservative fluid management, exogenous surfactant replacements and ethanol–oxygen vapor therapy hypothetically) may be greatly helpful for reducing the occurrences of severe cases. Given that late mechanical ventilation may cause mucus (edema fluid) to be blown deep into the small airways, oxygen therapy should be given at the early stages. The optimal time and blood oxygen saturation (SpO₂) threshold for oxygen therapy are also discussed.

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.

Hsa_circ_0002062 Promotes the Proliferation of Pulmonary Artery Smooth Muscle Cells by Regulating the Hsa-miR-942-5p/CDK6 Signaling Pathway

Currently, new strategies for the diagnosis and treatment of hypoxia-induced pulmonary hypertension (HPH) are urgently required. The unique features of circRNAs have unveiled a novel perspective for understanding the biological mechanisms underlying HPH and the possibility for innovative strategies for treatment of HPH. CircRNAs function as competing endogenous RNAs (CeRNA) to sequester miRNAs and regulate the expression of target genes. This study aimed to explore the roles of hsa_circ_0002062 on the biological behaviors of pulmonary artery smooth muscle cells (PASMCs) in hypoxic conditions. A number of in vitro assays, such as RNA-binding protein immunoprecipitation (RIP), RNA pull-down, and dual-luciferase assays were performed to evaluate the interrelationship between hsa_circ_0002062, hsa-miR-942-5P, and CDK6. The potential physiological functions of hsa_circ_0002062, hsa-miR-942-5P, and CDK6 in hypoxic PASMCs were investigated through expression modulation. Our experiments demonstrated that hsa_circ_0002062 functions as a ceRNA, acts as a sponge for hsa-miR-942-5P, and consequently activates CDK6, which further promotes pulmonary vascular remodeling. Therefore, we speculate that hsa_circ_0002062 could serve as a candidate diagnostic biomarker and potential therapeutic target for HPH.

Oxygen sensing, mitochondrial biology and experimental therapeutics for pulmonary hypertension and cancer

The homeostatic oxygen sensing system (HOSS) optimizes systemic oxygen delivery. Specialized tissues utilize a conserved mitochondrial sensor, often involving NDUFS2 in complex I of the mitochondrial electron transport chain, as a site of pO₂-responsive production of reactive oxygen species (ROS). These ROS are converted to a diffusible signaling molecule, hydrogen peroxide (H₂O₂), by superoxide dismutase (SOD2). H₂O₂ exits the mitochondria and regulates ion channels and enzymes, altering plasma membrane potential, intracellular Ca²⁺ and Ca²⁺-sensitization and controlling acute, adaptive, responses to hypoxia that involve changes in ventilation, vascular tone and neurotransmitter release. Subversion of this O₂-sensing pathway creates a pseudohypoxic state that promotes disease progression in pulmonary arterial hypertension (PAH) and cancer. Pseudohypoxia is a state in which biochemical changes, normally associated with hypoxia, occur despite normal pO₂. Epigenetic silencing of SOD2 by DNA methylation alters H₂O₂ production, activating hypoxia-inducible factor 1α, thereby disrupting mitochondrial metabolism and dynamics, accelerating cell proliferation and inhibiting apoptosis. Other epigenetic mechanisms, including dysregulation of microRNAs (miR), increase pyruvate dehydrogenase kinase and pyruvate kinase muscle isoform 2 expression in both diseases, favoring uncoupled aerobic glycolysis. This Warburg metabolic shift also accelerates cell proliferation and impairs apoptosis. Disordered mitochondrial dynamics, usually increased mitotic fission and impaired fusion, promotes disease progression in PAH and cancer. Epigenetic upregulation of dynamin-related protein 1 (Drp1) and its binding partners, MiD49 and MiD51, contributes to the pathogenesis of PAH and cancer. Finally, dysregulation of intramitochondrial Ca²⁺, resulting from impaired mitochondrial calcium uniporter complex (MCUC) function, links abnormal mitochondrial metabolism and dynamics. MiR-mediated decreases in MCUC function reduce intramitochondrial Ca²⁺, promoting Warburg metabolism, whilst increasing cytosolic Ca²⁺, promoting fission. Epigenetically disordered mitochondrial O₂-sensing, metabolism, dynamics, and Ca²⁺ homeostasis offer new therapeutic targets for PAH and cancer. Promoting glucose oxidation, restoring the fission/fusion balance, and restoring mitochondrial calcium regulation are promising experimental therapeutic strategies.

ROCK Inhibition as Potential Target for Treatment of Pulmonary Hypertension

Pulmonary hypertension (PH) is a cardiovascular disease caused by extensive vascular remodeling in the lungs, which ultimately leads to death in consequence of right ventricle (RV) failure. While current drugs for PH therapy address the sustained vasoconstriction, no agent effectively targets vascular cell proliferation and tissue inflammation. Rho-associated protein kinases (ROCKs) emerged in the last few decades as promising targets for PH therapy, since ROCK inhibitors demonstrated significant anti-remodeling and anti-inflammatory effects. In this review, current aspects of ROCK inhibition therapy are discussed in relation to the treatment of PH and RV dysfunction, from cell biology to preclinical and clinical studies.

Echocardiographic Right Ventricular Outflow Track Notch Formation and the Incidence of Acute Mountain Sickness

Yuan, Fangzhengyuan, Zhexue Qin, Chuan Liu, Shiyong Yu, Jie Yang, Jun Jin, Shizhu Bian, Xubin Gao, Jihang Zhang, Chen Zhang, Mingdong Hu, Jingbin Ke, Yuanqi Yang, Jingdu Tian, Chunyan He, Wenzhu Gu, Chun Li, Rongsheng Rao, and Lan Huang. Echocardiographic right ventricular outflow track notch formation and the incidence of acute mountain sickness. High Alt Med Biol. 00:000-000, 2021. Background: High-altitude exposure causes acute mountain sickness (AMS) and increases pulmonary arterial pressure (PAP). The notching of echocardiographic right ventricular outflow tract flow velocity envelope (right ventricular outflow tract [RVOT] notching), is related to increased PAP. We speculate that acute high-altitude exposure may trigger RVOT notching, which may be associated with AMS. Methods: All 130 subjects, ascended to 4,100 m from low altitude by bus within 7 days, underwent physiological and echocardiographic testing. The subjects with a total score of 3 or above and in the presence of a headache were diagnosed with AMS according to Lake Louise criteria. Results: After high-altitude exposure, the incidence of RVOT notching and AMS was 20% and 28.5%, respectively. The subjects with AMS had a higher incidence (37.8%) of RVOT notching than those without AMS (12.9%). Multivariate logistic regression analysis showed that RVOT notching was associated with systolic pulmonary artery pressure (SPAP) (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.05-1.17; p < 0.001) and the occurrence of AMS (OR, 5.48; 95% CI, 1.96-15.35; p = 0.001). Although linear regression analysis showed a weak correlation between SPAP and Lake Louise AMS score in the overall population (r = 0.20, p = 0.020), this correlation was more pronounced in the subpopulation with RVOT notching (r = 0.44, p = 0.023) and SPAP was not related to Lake Louise AMS score in the subpopulation without RVOT notching (r = 0.03, p = 0.698). Among AMS symptoms, the incidence of headache and fatigue were higher in subjects with RVOT notching than those in subjects without RVOT notching. Conclusions: We first observe that high-altitude exposure triggers RVOT notching formation, which is associated with AMS occurrence. Clinical Trial Registration No: ChiCTR-RCS-12002232.

Serotonin and chronic hypoxic pulmonary hypertension activate a NADPH oxidase 4 and TRPM2 dependent pathway for pulmonary arterial smooth muscle cell proliferation and migration

5-Hydroxytryptamine (5-HT)-dependent signaling mediated through its transporters and receptors plays important roles in chronic hypoxic pulmonary hypertension (CHPH), which is associated with aberrant reactive oxygen species (ROS) production. NADPH oxidase 4 (NOX4) is one of the major sources of ROS in pulmonary vasculature, and has been implicated in the development of PH. NOX4 generates H2O2, which can activate the transient receptor potential melastatin 2 (TRPM2) channels, providing Ca2+ signals for cell proliferation and migration. However, the connection between 5-HT, NOX4, ROS and TRPM2 in the context of PH has not been established. Here we examined the level of 5-HT and expression of NOX4 and TRPM2, and their roles in pulmonary arterial smooth muscle cells (PASMCs) proliferation and migration. NOX4 and TRPM2 were upregulated in pulmonary arteries of CHPH rats, which were associated with elevated levels of 5-HT and ROS, and enhanced proliferation and migration in PASMCs. The increase in ROS, and the enhanced proliferation and migration of PASMCs from CHPH rats were mimicked by treating normoxic PASMCs with 5-HT. 5-HT; and CH-induced ROS production were reversed by catalase, the NOX1/NOX4 inhibitor GKT137831, and Nox4 siRNA. 5-HT and H2O2 elicited Ca2+ responses were significantly augmented in CHPH PASMCs; and the augmented Ca2+ responses were obliterated by the 2-Aminoethoxydiphenyl borate (2-APB) and Trpm2-specific siRNA. Moreover, 5-HT and CH-induced proliferation and migration were suppressed by Nox4 or Trpm2 siRNA; and simultaneous transfection of both siRNA did not cause further inhibition. These results suggest that the 5-HT and CH-induced PASMC proliferation and migration were mediated, at least in part, by TRPM2 via activation of NOX4-dependent ROS production; and revealed a novel NOX4-ROS-TRPM2 signaling pathway for the pathogenesis of CHPH.

Roles of Genetic Predisposition in the Sex Bias of Pulmonary Pathophysiology, as a Function of Estrogens : Sex Matters in the Prevalence of Lung Diseases

In addition to studies focused on estrogen mediation of sex-different regulation of systemic circulations, there is now increasing clinical relevance and research interests in the pulmonary circulation, in terms of sex differences in the morbidity and mortality of lung diseases such as inherent-, allergic- and inflammatory-based events. Thus, female predisposition to pulmonary artery hypertension (PAH) is an inevitable topic. To better understand the nature of sexual differentiation in the pulmonary circulation, and how heritable factors, in vivo- and/or in vitro-altered estrogen circumstances and changes in the live environment work in concert to discern the sex bias, this chapter reviews pulmonary events characterized by sex-different features, concomitant with exploration of how alterations of genetic expression and estrogen metabolisms trigger the female-predominant pathological signaling. We address the following: PAH (Sect.7.2) is characterized as an estrogenic promotion of its incidence (Sect. 7.2.2), as a function of specific germline mutations, and as an estrogen-elicited protection of its prognosis (Sect.7.2.1). More detail is provided to introduce a less recognized gene of Ephx2 that encodes soluble epoxide hydrolase (sEH) to degrade epoxyeicosatrienic acids (EETs). As a susceptible target of estrogen, Ephx2/sEH expression is downregulated by an estrogen-dependent epigenetic mechanism. Increases in pulmonary EETs then evoke a potentiation of PAH generation, but mitigation of its progression, a phenomenon similar to the estrogen-paradox regulation of PAH. Additionally, the female susceptibility to chronic obstructive pulmonary diseases (Sect. 7.3) and asthma (Sect.7.4), but less preference to COVID-19 (Sect. 7.5), and roles of estrogen in their pathogeneses are briefly discussed.

Clinical guidelines for the treatment of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a birth defect of the diaphragm in which abdominal organs herniate through the defect into the thoracic cavity. The main pathophysiology is respiratory distress and persistent pulmonary hypertension because of pulmonary hypoplasia caused by compression of the elevated organs. Recent progress in prenatal diagnosis and postnatal care has led to an increase in the survival rate of patients with CDH. However, some survivors experience mid- and long-term disabilities and complications requiring treatment and follow-up. In recent years, the establishment of clinical practice guidelines has been promoted in various medical fields to offer optimal medical care, with the goal of improvement of the disease' outcomes, thereby reducing medical costs, etc. Thus, to provide adequate medical care through standardization of treatment and elimination of disparities in clinical management, and to improve the survival rate and mid- and long-term prognosis of patients with CDH, we present here the clinical practice guidelines for postnatal management of CDH. These are based on the principles of evidence-based medicine using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. The recommendations are based on evidence and were determined after considering the balance among benefits and harm, patient and society preferences, and medical resources available for postnatal CDH treatment.

Oxygen Enrichment Ameliorates Cardiorespiratory Alterations Induced by Chronic High-Altitude Hypoxia in Rats

Chronic high-altitude hypoxia (HAH) results in compensatory pathological adaptations, especially in the cardiorespiratory system. The oxygen enrichment technology can provide long-lasting oxygen supply and minimize oxygen toxicity, which has proven to be effective to increase oxygen saturation, decrease heart rate, and improve human exercise performance after ascending to high altitudes. Nevertheless, it remains unknown whether oxygen enrichment can resist chronic HAH-induced cardiorespiratory alterations. Thirty-six male rats were equally assigned to the normal control (NC), HAH, and HAH with oxygen enrichment (HAHO) groups. The HAH and HAHO rats were housed in a hypobaric hypoxia chamber equivalent to 5,000 m for 4 weeks. The HAHO rats were exposed to oxygen-enriched air for 8 h/day. We found that oxygen enrichment mitigated the augmented skin blood flow and improved the locomotor activity of HAH-exposed rats. Oxygen enrichment inhibited HAH-induced increase in the production of red blood cells (RBCs). The hemodynamic results showed that oxygen enrichment decreased right ventricular systolic pressure (RVSP) and mean pulmonary artery pressure (mPAP) in HAH-exposed rats. HAH-associated right ventricular hypertrophy and cardiomyocyte enlargement were ameliorated by oxygen enrichment. Oxygen enrichment inhibited HAH-induced excessive expression of cytokines associated with cardiac hypertrophy and myocardial fibrosis [angiotensin-converting enzyme (ACE)/angiotensin-converting enzyme 2 (ACE2), angiotensin II (Ang II), collagen type I alpha 1 (Col1α1), collagen type III alpha 1 (Col3α1), and hydroxyproline] in the right ventricle (RV). Oxygen enrichment inhibited medial thickening, stenosis and fibrosis of pulmonary arterioles, and cytokine expression related with fibrosis (Col1α1, Col3α1, and hydroxyproline) and pulmonary vasoconstriction [endothelin-1(ET-1)] in HAH-exposed rats. This study represents the first effort testing the efficacy of the oxygen enrichment technique on cardiopulmonary structure and function in chronic HAH animals, and we found oxygen enrichment has the capability of ameliorating chronic HAH-induced cardiopulmonary alterations.

Emerging Mechanisms of Pulmonary Vasoconstriction in SARS-CoV-2-Induced Acute Respiratory Distress Syndrome (ARDS) and Potential Therapeutic Targets

The 1918 influenza killed approximately 50 million people in a few short years, and now, the world is facing another pandemic. In December 2019, a novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused an international outbreak of a respiratory illness termed coronavirus disease 2019 (COVID-19) and rapidly spread to cause the worst pandemic since 1918. Recent clinical reports highlight an atypical presentation of acute respiratory distress syndrome (ARDS) in COVID-19 patients characterized by severe hypoxemia, an imbalance of the renin-angiotensin system, an increase in thrombogenic processes, and a cytokine release storm. These processes not only exacerbate lung injury but can also promote pulmonary vascular remodeling and vasoconstriction, which are hallmarks of pulmonary hypertension (PH). PH is a complication of ARDS that has received little attention; thus, we hypothesize that PH in COVID-19-induced ARDS represents an important target for disease amelioration. The mechanisms that can promote PH following SARS-CoV-2 infection are described. In this review article, we outline emerging mechanisms of pulmonary vascular dysfunction and outline potential treatment options that have been clinically tested.

Long-term chronic intermittent hypoxia: a particular form of chronic high-altitude pulmonary hypertension

In some subjects, high-altitude hypobaric hypoxia leads to high-altitude pulmonary hypertension. The threshold for the diagnosis of high-altitude pulmonary hypertension is a mean pulmonary artery pressure of 30 mmHg, even though for general pulmonary hypertension is ≥25 mmHg. High-altitude pulmonary hypertension has been associated with high hematocrit findings (chronic mountain sickness), and although these are two separate entities, they have a synergistic effect that should be considered. In recent years, a new condition associated with high altitude was described in South America named long-term chronic intermittent hypoxia and has appeared in individuals who commute to work at high altitude but live and rest at sea level. In this review, we discuss the initial epidemiological pattern from the early studies done in Chile, the clinical presentation and possible molecular mechanism and a discussion of the potential management of this condition.

Residence at moderately high altitude and its relationship with WHO Group 1 pulmonary arterial hypertension symptom severity and clinical characteristics: the Pulmonary Hypertension Association Registry

BACKGROUND

WHO Group 1 pulmonary arterial hypertension is a progressive and potentially fatal disease. Individuals living at higher altitude are exposed to lower barometric pressure and hypobaric hypoxemia. This may result in pulmonary vasoconstriction and contribute to disease progression. We sought to examine the relationship between living at moderately high altitude and pulmonary arterial hypertension characteristics.

METHODS

Forty-two US centers participating in the Pulmonary Hypertension Association Registry enrolled patients who met the definition of WHO Group 1 pulmonary arterial hypertension. We utilized baseline data and patient questionnaire responses. Patients were divided into two groups: moderately high altitude residence (home ≥4000 ft) and low altitude residence (home <4000 ft) based on zip-code. Clinical characteristics, hemodynamic data, patient demographics, and patient reported quality of life metrics were compared.

RESULTS

Controlling for potential confounders (age, sex at birth, body mass index, supplemental oxygen use, race, 100-day cigarette use, alcohol use, and pulmonary arterial hypertension medication use), subjects residing at moderately high altitude had a 6-min walk distance 32 m greater than those at low altitude, despite having a pulmonary vascular resistance that was 2.2 Wood units higher. Additionally, those residing at moderately high altitude had 3.7 times greater odds of using supplemental oxygen.

CONCLUSION

Patients with pulmonary arterial hypertension who live at moderately high altitude have a higher pulmonary vascular resistance and are more likely to need supplemental oxygen. Despite these findings, moderately high altitude Pulmonary Hypertension Association Registry patients have better functional tolerance as measured by 6-min walk distance. It is possible that a "high-altitude phenotype" of pulmonary arterial hypertension may exist. These findings warrant further study.

hsa_circNFXL1_009 modulates apoptosis, proliferation, migration, and potassium channel activation in pulmonary hypertension

In this study, we explored the circular RNA (circRNA) profile in pulmonary arterial hypertension (PAH) patients caused by chronic obstructive pulmonary disease (COPD) and the effects of hsa_circNFXL1_009 on abnormal proliferation, apoptosis, and migration of human pulmonary arterial smooth muscle cells (hPASMCs) driven by hypoxia. Using microarrays, we screened the circRNA profile in whole-blood samples from three pairs of subjects and found 158 dysregulated circRNAs in patients with PAH-COPD. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis further validated that hsa_circNFXL1_009 was dramatically downregulated with the highest area under a receiver operating characteristic curve (ROC) in 21 pairs of subjects. Consistently, exposure to hypoxia markedly reduced the hsa_circNFXL1_009 level in cultured hPASMCs. Delivery of exogenous hsa_circNFXL1_009 attenuated hypoxia-induced proliferation, apoptotic resistance, and migration of hPASMCs, as evidenced by immunocytochemistry, 5-ethynyl-2′-deoxyuridine incorporation, wound healing, and a TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling) assay. A luciferase assay showed that hsa_circNFXL1_009 directly sponged hsa-miR-29b-2-5p (miR-29b) and positively regulated the expression of voltage-gated potassium (K⁺) channel subfamily B member 1 (KCNB1) at the mRNA level. Using patch-clamp electrophysiology, we proved that overexpression of hsa_circNFXL1_009 promoted a whole-cell K⁺ current in hPASMCs. Taken together, these studies identify hsa_circNFXL1_009 as a key regulator of PAH, and it may be used as a potential therapeutic target for the treatment of PAH.

Role of 20-hydroxyeicosatetraenoic acid in pulmonary hypertension and proliferation of pulmonary arterial smooth muscle cells

OBJECTIVE

To investigate the level of 20-Hydroxyeicosatetraenoic acid (20-HETE) in model of pulmonary hypertension (PH) and its effect on the proliferation of pulmonary arterial smooth muscle cells (PASMCs).

METHODS

Twenty male Sprague-Dawley rats were randomly divided into two groups, including control group and PH group. PH was induced by intra-peritoneal injection of 20 mg/kg monocrotaline (MCT) twice in a week in 10 rats, and control rats were given equal amount of saline. Mean pulmonary arterial pressure (mPAP), right ventricular hypertrophy index (RVHI) and pulmonary vascular remodeling index (WA%, WT%) were assessed at the week 4. The levels of 20-HETE were analysed by liquid chromatography tandem-mass spectrometry (LC-MS/MS). EdU test was used to determine the proliferation of PASMCs. Intracellular levels of reactive oxygen species (ROS) were detected using DCFH-DA dye.

RESULTS

(1) Prominent right ventricular hypertrophy and pulmonary vascular remodeling were verified in PH rats; (2) 20-HETE levels in lung tissue and serum were significantly lifted in PH rats; (3) Increased 20-HETE levels in cell culture supernatants were significantly noted in hypoxia condition; (4) Proliferation of PASMCs was induced by 20-HETE and hypoxia, and was inhibited by HET0016; (5) Production of ROS was elevated by 20-HETE and hypoxia, and was reduced by HET0016; CONCLUSION: Vascular remodeling was demonstrated in PH rats. 20-HETE levels were significantly increased in PH rats and under hypoxia condition. PASMCs proliferation and ROS production were elevated by 20-HETE and could be inhibited by HET0016, a specific inhibitor of 20-HETE. Taken together, changes in the level of 20-HETE may be related to the excessive proliferation of PASMCs in PH rats.

Evolution of blood rheology and its relationship to pulmonary hemodynamic during the first days of exposure to moderate altitude

Blood rheology and hemodynamic parameters have never been explored together during acclimatization to altitude. This study aimed to investigate changes in blood rheology parameters and pulmonary hemodynamics during the first days of real moderate altitude exposure.Seventeen athletes were tested at sea-level, 20 hours after their arrival at 2,400 meters of altitude (H1) and five days later (H2). Blood was sampled to analyze red blood cell (RBC) aggregation, blood viscosity and hematocrit. Pulmonary arterial pressure (PAP), pulmonary capillary pressure (Pcap) and pulmonary vascular resistance (PVR) were assessed by echocardiography.We observed a rise in hematocrit, blood viscosity, RBC aggregation, PAP, Pcap and PVR between sea-level and H1. In H2, RBC aggregation, hematocrit, PAP, Pcap and PVR remained different compared to sea-level and no difference was observed between H1 and H2. Blood viscosity decreased in H2 and returned to sea-level values.Our results suggest that hemoconcentration occurring within the first hours of altitude exposure increased blood viscosity, which contributed to the changes in pulmonary hemodynamic. When blood viscosity decreased in H2, no change occurred in pulmonary hemodynamic parameters suggesting that hypoxic pulmonary vasoconstriction was still present. The elevated RBC aggregation observed after in H2 could participate in the increase of Pcap.

Epoxy Fatty Acids: From Salt Regulation to Kidney and Cardiovascular Therapeutics: 2019 Lewis K. Dahl Memorial Lecture

Epoxyeicosatrienoic acids (EETs) are epoxy fatty acids that have biological actions that are essential for maintaining water and electrolyte homeostasis. An inability to increase EETs in response to a high-salt diet results in salt-sensitive hypertension. Vasodilation, inhibition of epithelial sodium channel, and inhibition of inflammation are the major EET actions that are beneficial to the heart, resistance arteries, and kidneys. Genetic and pharmacological means to elevate EETs demonstrated antihypertensive, anti-inflammatory, and organ protective actions. Therapeutic approaches to increase EETs were then developed for cardiovascular diseases. sEH (soluble epoxide hydrolase) inhibitors were developed and progressed to clinical trials for hypertension, diabetes mellitus, and other diseases. EET analogs were another therapeutic approach taken and these drugs are entering the early phases of clinical development. Even with the promise for these therapeutic approaches, there are still several challenges, unexplored areas, and opportunities for epoxy fatty acids.

Alterations to cardiac morphology and function among high-altitude workers: a retrospective cohort study

OBJECTIVES

Exposure to high altitude can affect human health, including the development of adverse cardiovascular effects. This study aimed to investigate alterations in cardiac morphology and function in high-altitude workers and to identify risk factors associated with cardiac abnormalities.

METHODS

A retrospective cohort study was conducted with 286 Qinghai-Tibetan Railroad maintenance workers. Participant data were collected from company personnel records. Data on echocardiography and diagnosis of cardiac abnormalities were extracted from participants' medical records. Time-to-event analysis was used to investigate the risk of cardiac abnormalities among participants with different baseline characteristics and identify risk factors associated with cardiac abnormalities that developed as a result of working at high altitude.

RESULTS

A total of 173 participants had developed cardiac abnormalities during the follow-up period. The most common cardiac abnormality was right atrial enlargement, followed by left ventricular diastolic dysfunction and tricuspid regurgitation. Among participants with cardiac abnormalities, the median follow-up time was 17 months. Compared with participants who were younger than 20 years and working at altitude <4000 m, participants older at employment and working at extremely high altitude were more likely to develop cardiac abnormalities. Nearly 40% of the participants who worked at altitude <4000 m remained without cardiac abnormalities during the follow-up period.

CONCLUSIONS

Over 60% of participants developed cardiac abnormalities after working at high altitude, predominantly right heart enlargement and left ventricular diastolic dysfunction. Age at employment and workplace altitude were significant risk factors for cardiac abnormalities. Enhanced regular physical examinations are recommended for high-altitude workers.

Systems Analysis of the Human Pulmonary Arterial Hypertension Lung Transcriptome

Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary artery pressure and vascular resistance, typically leading to right heart failure and death. Current therapies improve quality of life of the patients but have a modest effect on long-term survival. A detailed transcriptomics and systems biology view of the PAH lung is expected to provide new testable hypotheses for exploring novel treatments. We completed transcriptomics analysis of PAH and control lung tissue to develop disease-specific and clinical data/tissue pathology gene expression classifiers from expression datasets. Gene expression data were integrated into pathway analyses. Gene expression microarray data were collected from 58 PAH and 25 control lung tissues. The strength of the dataset and its derived disease classifier was validated using multiple approaches. Pathways and upstream regulators analyses was completed with standard and novel graphical approaches. The PAH lung dataset identified expression patterns specific to PAH subtypes, clinical parameters, and lung pathology variables. Pathway analyses indicate the important global role of TNF and transforming growth factor signaling pathways. In addition, novel upstream regulators and insight into the cellular and innate immune responses driving PAH were identified. Finally, WNT-signaling pathways may be a major determinant underlying the observed sex differences in PAH. This study provides a transcriptional framework for the PAH-diseased lung, supported by previously reported findings, and will be a valuable resource to the PAH research community. Our investigation revealed novel potential targets and pathways amenable to further study in a variety of experimental systems.

Grape seed procyanidin suppresses inflammation in cigarette smoke-exposed pulmonary arterial hypertension rats by the PPAR-γ/COX-2 pathway

BACKGROUND AND AIM

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling, which is mainly caused by inflammation. Inhibiting inflammation can relieve PAH. Grape seed procyanidin (GSP) possesses remarkable anti-inflammatory property and vascular protective function. In this experiment, we verified the anti-inflammatory property of GSP in cigarette smoke-exposed PAH rats and revealed its molecular mechanism.

METHODS AND RESULTS

In vivo, 45 Sprague Dawley (SD) rats were divided into 5 groups randomly, treated with normoxia/cigarette smoke (CS)/GSP + CS/CS + solvent/GSP. After GSP + CS administration, a decrease in mPAP, PVR, RVHI, WT%, and WA% was detected in the rats as compared to those treated with CS. In vitro, the proliferation of pulmonary arterial smooth muscle cells (PASMCs) caused by cigarette smoke extract (CSE) was effectively attenuated with GSP + CSE administration. Furthermore, GSP significantly increased the expression of peroxisome proliferator-activated receptor γ (PPAR-γ) together with the lowered expression level of cyclooxygenase 2 (COX-2) in PASMCs co-incubated with CSE.

CONCLUSION

These findings indicate that GSP ameliorates inflammation by the PPAR-γ/COX-2 pathway and finally inhibits the proliferation of PASMCs, which leads to pulmonary vascular remodeling.

Effect of Acute Altitude Exposure on Serum Markers of Platelet Activation

Background: Platelets are the key factor in primary hemostasis. It has been shown that chronic altitude exposure increases platelets' aggregability. Nevertheless, data about acute effects and the underlying mechanisms are sparse. Methods: Sixteen healthy volunteers were examined in our hospital (519 m alt.) and 30 minutes after arrival in the environmental research station on the Zugspitze Mountain (2656 m alt.). Serum levels of soluble p-selectin were examined to elucidate platelet activation. In addition, serum levels of chromogranin A (CGA) as a measure of adrenergic activation, endothelin 1 (ET-1) representing pulmonary vascular tone and monocyte chemoattractant protein-1 (MCP-1) as a measure of inflammatory response were examined. Results: Acute altitude exposure induced a significant increase of p-selectin (116 ± 4.8 pg/mL vs. 132 ± 6.2 pg/mL; p < 0.01). Whereas MCP-1 was significantly lowered (538 ± 50.6 pg/mL to 470 ± 41.1 pg/mL; p = 0.02) and CGA was not altered significantly (88 ± 47.4 ng/mL vs. 79 ± 44 ng/mL; p = 0.22), ET1 was increased significantly from 0.8 ± 0.07 pg/mL to 1.15 ± 0.09 pg/mL (p < 0.01). Conclusion: Our study could demonstrate relevant platelet activation that was accompanied by a 44% increase of ET-1. This activation might obtain clinical relevance in patients with pre-existing cardiovascular disease as a trigger for acute events.

Pre-clinical assessment of a water-in-fluorocarbon emulsion for the treatment of pulmonary vascular diseases

Hypoxic pulmonary vasoconstriction (HPV) is a well-characterized vascular response to low oxygen pressures and is involved in life-threatening conditions such as high-altitude pulmonary edema (HAPE) and pulmonary arterial hypertension (PAH). While the efficacy of oral therapies can be affected by drug metabolism, or dose-limiting systemic toxicity, inhaled treatment via pressured metered dose inhalers (pMDI) may be an effective, nontoxic, practical alternative. We hypothesized that a stable water-in-perfluorooctyl bromide (PFOB) emulsion that provides solubility in common pMDI propellants, engineered for intrapulmonary delivery of pulmonary vasodilators, reverses HPV during acute hypoxia (HX). Male Sprague Dawley rats received two 10-min bouts of HX (13% O₂) with 20 min of room air and drug application between exposures. Treatment groups: intrapulmonary delivery (PUL) of (1) saline; (2) ambrisentan in saline (0.1 mg/kg); (3) empty emulsion; (4) emulsion encapsulating ambrisentan or sodium nitrite (NaNO₂) (0.1 and 0.5 mg/kg each); and intravenous (5) ambrisentan (0.1 mg/kg) or (6) NaNO₂ (0.5 mg/kg). Neither PUL of saline or empty emulsion, nor infusions of drugs prevented pulmonary artery pressure (PAP) elevation (32.6 ± 3.2, 31.5 ± 1.2, 29.3 ± 1.8, and 30.2 ± 2.5 mmHg, respectively). In contrast, PUL of aqueous ambrisentan and both drug emulsions reduced PAP by 20–30% during HX, compared to controls. IL6 expression in bronchoalveolar lavage fluid and whole lung 24 h post-PUL did not differ among cohorts. We demonstrate proof-of-concept for delivering pulmonary vasodilators via aerosolized water-in-PFOB emulsion. This concept opens a potentially feasible and effective route of treating pulmonary vascular pathologies via pMDI.

Asymmetric Dimethylarginine at Sea Level Is a Predictive Marker of Hypoxic Pulmonary Arterial Hypertension at High Altitude

Background: Prolonged exposure to altitude-associated chronic hypoxia (CH) may cause high-altitude pulmonary hypertension (HAPH). Chronic intermittent hypobaric hypoxia (CIH) occurs in individuals who commute between sea level and high altitude. CIH is associated with repetitive acute hypoxic acclimatization and conveys the long-term risk of HAPH. As nitric oxide (NO) regulates pulmonary vascular tone and asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis, we investigated whether ADMA concentration at sea level predicts HAPH among Chilean frontiers personnel exposed to 6 months of CIH.

Methods: In this prospective study, 123 healthy army draftees were subjected to CIH (5 days at 3,550 m, 2 days at sea level) for 6 months. In 100 study participants with complete data, ADMA, symmetric dimethylarginine (SDMA), L-arginine, arterial oxygen saturation (SaO₂), systemic blood pressure, and hematocrit were assessed at months 0 (sea level), 1, 4, and 6. Acclimatization to altitude was determined using the Lake Louise Score (LLS) and the presence of acute mountain sickness (AMS). Echocardiography was performed after 6 months of CIH in 43 individuals with either good (n = 23) or poor (n = 20) acclimatization.

Results: SaO₂ acutely decreased at altitude and plateaued at 90% thereafter. ADMA increased and SDMA decreased during the study course. The incidence of AMS and the LLS was high after the first ascent (53 and 3.1 ± 2.4) and at 1 month of CIH (47 and 3.0 ± 2.6), but decreased to 20 and 1.4 ± 2.0 at month 6 (both p < 0.001). Eighteen participants (42%) showed a mean pulmonary arterial pressure (mPAP) >25 mm Hg, out of which 9 (21%) were classified as HAPH (mPAP ≥ 30 mm Hg). ADMA at sea level was significantly associated with mPAP at high altitude in month 6 (R = 0.413; p = 0.007). In ROC analysis, a cutoff for baseline ADMA of 0.665 μmol/L was determined to predict HAPH (mPAP > 30 mm Hg) with a sensitivity of 100% and a specificity of 63.6%.

Conclusions: ADMA concentration increases during CIH. ADMA at sea level is an independent predictive biomarker of HAPH. SDMA concentration decreases during CIH and shows no association with HAPH. Our data support a role of impaired NO-mediated pulmonary vasodilation in the pathogenesis of HAPH.

The role of nitric oxide signaling in pulmonary circulation of high- and low-altitude newborn sheep under basal and acute hypoxic conditions

Nitric oxide (NO) is the main vasodilator agent that drives the rapid decrease of pulmonary vascular resistance for the respiratory onset during the fetal to neonatal transition. Nevertheless, the enhanced NO generation by the neonatal pulmonary arterial endothelium does not prevent development of hypoxic pulmonary hypertension in species without an evolutionary story at high altitude. Therefore, this study aims to describe the limits of the NO function at high-altitude during neonatal life in the sheep as an animal model without tolerance to perinatal hypoxia. We studied the effect of blockade of NO synthesis with l-NAME in the cardiopulmonary response of lowland (580 m) and highland (3600 m) newborn lambs basally and under an episode of acute hypoxia. We also determined the pulmonary expression of proteins that mediate the actions of the NO vasodilator pathway in the pulmonary vasoactive tone and remodeling. We observed an enhanced nitrergic function in highland lambs under basal conditions, evidenced as a markedly greater increase in basal mean pulmonary arterial pressure (mPAP) and resistance (PVR) under blockade of NO synthesis. Further, acute hypoxic challenge in lowland lambs infused with l-NAME markedly increased their mPAP and PVR to values greater than baseline, whilst in highland animals under NO synthesis blockade, these variables did not show additional increase in response to low PO₂. Highland animals showed increased pulmonary RhoA expression, decreased PSer188-RhoA fraction, increased PSer311-p65-NFқβ fraction and up-regulated smooth muscle α-actin, relative to lowland controls. Taken together our data suggest that NO-mediated vasodilation is important to keep a low pulmonary vascular resistance under basal conditions and acute hypoxia at low-altitude. At high-altitude, the enhanced nitrergic signaling partially prevents excessive pulmonary hypertension but does not protect against acute hypoxia. The decreased vasodilator efficacy of nitrergic tone in high altitude lambs could be in part due to increased RhoA signaling that opposes to NO action in the hypoxic pulmonary circulation.

Body Composition and Endocrine Adaptations to High-Altitude Trekking in the Himalayas

Long-term exposure to high altitude causes adaptive changes in several blood biochemical markers along with a marked body mass reduction involving both the lean and fat components. The aim of this study was to evaluate the impact of extended physical strain, due to extensive trekking at high altitude, on body composition, selected biomarkers in the blood, and the protective role of a high-protein diet in muscle dysfunction. We found that physical strain at high altitude caused a significant reduction in body mass and body fat, with a concomitant increase in the cross-sectional area of thigh muscles and an unchanged total lean body mass. Further, we found reductions in plasma leptin and homocysteine, while myoglobin, insulin, and C-reactive protein significantly increased. Creatine kinase, lactate dehydrogenase, and leptin normalized per body fat were unchanged. These findings demonstrate that high-altitude hypoxia, involving extended physical effort, has an impact on muscle function and body composition, facilitating sarcopenia and affecting body mass and fat distribution. It also activates pro-inflammatory metabolic pathways in response to muscular distress. These changes can be mitigated by a provision of a high-protein diet.