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

Methyleugenol alleviates pulmonary vascular remodeling in rats with high-altitude pulmonary hypertension by improving pulmonary smooth muscle cell function

Pulmonary hypertension is divided into five groups, and chronic exposure to hypoxia causes pulmonary hypertension in the third group -- high altitude pulmonary hypertension, which is commonly seen in patients with chronic obstructive pulmonary disease, sleep-disordered breathing, and interstitial lung disease. Its clinicopathological features include right heart overload and right ventricular hypertrophy, with severe patients potentially experiencing right heart failure or even death. The pathogenesis of high altitude pulmonary hypertension is complex; it includes oxidative stress, mitochondrial dysfunction, apoptosis, and pyroptosis. Pharmacological therapy may alleviate the condition if immediate descent to lower altitudes or supplemental oxygen is not possible. Herein, we preliminarily investigated the effect of methyleugenol on high altitude pulmonary hypertension through in vitro and in vivo experiments. Methyleugenol alleviated pulmonary arteriole constriction by acting on potassium ion channels, and inhibited the proliferation of pulmonary artery smooth muscle cells(PASMCs) by decreasing and reactive oxygen species levels, as well as inhibiting the expression of HIF-1α. The cardiac systolic function improved and mitochondrial structure of pulmonary artery smooth muscle cells in rats with high altitude pulmonary hypertension was significantly improved after methyleugenol gavage intervention, and malondialdehyde levels in serum of rats were decreased while those of superoxide dismutase and glutathione increased, suggesting that the reduction of oxidative stress may be one of the mechanisms to improve mitochondrial function. Western blot experiments showed that methyleugenol regulated the oxidative stress level in rats by activating Nrf2/HO-1 signaling pathway, activate p27Kip1, inhibit CDK4/CCND1/ p-ERK1/2 and inhibited HIF-1α/RASSF1/Ras axis to inhibit cell proliferation, thereby improving the occurrence and development of high altitude pulmonary hypertension in rats. The results of this study reveal that methyl eugenol has the potential to alleviate pulmonary vasoconstriction and remodeling in rat models of high-altitude pulmonary hypertension, providing a scientific basis for the application of this compound in improving pulmonary vascular remodeling.

Mechanism of pulmonary arterial vascular cell dysfunction in pulmonary hypertension in broiler chickens

Broiler ascites syndrome is a common and complex disease in broiler farming, which severely impacts broiler growth performance and health and brings huge economic losses to the breeding industry. Hypoxia has been shown to be an important cause of this disease. Prolonged exposure of broiler chickens to a hypoxic environment induces pulmonary vasoconstriction, which leads to an increase in pulmonary artery pressure, triggering pulmonary artery remodelling and compensatory right ventricular hypertrophy, and ultimately ascites. Pulmonary artery remodelling is a process in which the vascular wall tissue structure and function undergo pathological changes after the pulmonary artery is stimulated by various injuries or hypoxia, including endothelial dysfunction, abnormal proliferation of pulmonary artery smooth muscle cells, vascular fibrosis, etc. When these cells are damaged or stimulated, they may undergo programmed cell death, an orderly and regulated mode of cell death that is important for maintaining the stability of the body's internal environment. It has been demonstrated that death modes such as apoptosis and autophagy are involved in the pathophysiologic process of pulmonary hypertension, but their specific molecular mechanisms are still unclear. In this review, we first describe the pathogenesis of broiler ascites, then describe the specific mechanism of dysfunction of pulmonary artery vascular cells in broiler ascites syndrome, and finally elaborate the progression of different programmed cell death in broiler pulmonary hypertension. This study aims to elucidate the specific mechanisms underlying the dysfunction of pulmonary artery vascular cells in broiler pulmonary hypertension, thereby enhancing our understanding of the pathogenesis of this syndrome.

Tissue remodeling during high-altitude pulmonary edema in rats: Biochemical and histomorphological analysis

High altitude characterized by the low partial pressure of the oxygen is a life-threatening condition that contributes to the development of acute pulmonary edema and hypoxic lung injury. In this study, we aimed to investigate the contribution of some inflammatory and oxidative stress markers along with antioxidant system enzymes in the pathogenesis of HAPE (high-altitude pulmonary edema) formation. We incorporated the study on 42 male rats to unravel the role of mast cells (MCs) and TNF-α in the lung after the effect of acute hypobaric hypoxia. The HAPE model was mimicked with a decompression chamber at the altitude of 7620 m for a duration of 24 h. The study reveals various histological changes in the rat's lung exposed to hypoxia that was accompanied by immense inflammatory cell infiltration, edema, hemorrhages, and fibrosis. Moreover, the wet weight of the lungs and the arginase level was also increased (p < 0.05). While the NO level was shown to be diminished (p < 0.01). Acute hypobaric hypoxia also caused MC degranulation and increased TNF-α-expression in the lung, which considerably promoted inflammation after hypoxic damage. However, the antioxidant system was weakened following the decreased activity of SOD and catalase. Moreover, the cell energy metabolism was also altered accompanied by an elevated level of LDH. Our findings suggest that the NO and arginase and antioxidant system enzymes along with TNF-α and MCs may play a role in HAPE pathogenesis and contribute to the alveolar-capillary barrier disruption that leads to edema formation. Uncovering the pathological mechanisms of this disease would provide valuable information about the molecular basis of pulmonary edema development and therefore used for further preventive tools to manage the risks posed by high altitude-induced lung damage.

The molecular determinants regulating redox signaling in diabetic endothelial cells

Oxidation and reduction are vital for keeping life through several prime mechanisms, including respiration, metabolism, and other energy supplies. Mitochondria are considered the cell's powerhouse and use nutrients to produce redox potential and generate ATP and H2O through the process of oxidative phosphorylation by operating electron transfer and proton pumping. Simultaneously, mitochondria also produce oxygen free radicals, called superoxide (O2 -), non-enzymatically, which interacts with other moieties and generate reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), peroxynitrite (ONOO-), and hydroxyl radical (OH-). These reactive oxygen species modify nucleic acids, proteins, and carbohydrates and ultimately cause damage to organs. The nutrient-sensing kinases, such as AMPK and mTOR, function as a key regulator of cellular ROS levels, as loss of AMPK or aberrant activation of mTOR signaling causes ROS production and compromises the cell's oxidant status, resulting in various cellular injuries. The increased ROS not only directly damages DNA, proteins, and lipids but also alters cellular signaling pathways, such as the activation of MAPK or PI3K, the accumulation of HIF-1α in the nucleus, and NFkB-mediated transcription of pro-inflammatory cytokines. These factors cause mesenchymal activation in renal endothelial cells. Here, we discuss the biology of redox signaling that underlies the pathophysiology of diabetic renal endothelial cells.

Super-Enhancer Target Gene CBP/p300-Interacting Transactivator With Glu/Asp-Rich C-Terminal Domain, 2 Cooperates With Transcription Factor Forkhead Box J3 to Inhibit Pulmonary Vascular Remodeling

The function of super-enhancers (SEs) in pulmonary hypertension (PH), especially in the proliferation of pulmonary artery smooth muscle cells (PASMCs), is currently unknown. We identified SEs-targeted genes in PASMCs with chromatin immunoprecipitation (ChIP)-sequence by H3K27ac antibody and proved that CBP/p300-interacting transactivator with Glu/Asp-rich C-terminal domain, 2 (CITED2) is an SEs-targeted gene through bioinformatics prediction, ChIP-PCR, dual-luciferase reporter gene assays and other experimental methods. We also found that the expression of CITED2 and the transcription factor Forkhead Box J3 (FOXJ3) was reduced in hypoxic mouse PASMCs. In addition, the expression of CITED2 and FOXJ3 also decreased in both the patients with idiopathic pulmonary arterial hypertension (iPAH) and the human PASMCs exposed to hypoxia. The decreased expression of CITED2 was reversed by co-transfection of FOXJ3 and SEs plasmids. Overexpressing of CITED2 attenuated the PASMCs proliferation induced by hypoxia. Lentiviral overexpression of CITED2 also reversed hypoxia-induced pulmonary hypertension mice model. Mechanically, the expression of CITED2 by affecting by FOXJ3, which binding with three SEs located in the about 2000 bp of TSS. In conclusion, we first identified that CITED2 is a kind of SEs-targeted gene, modulated by FOXJ3. The FOXJ3/SEs/CITED2 axis may become a new therapeutic target of PH.

Mechanisms Controlling the Behavior of Vascular Smooth Muscle Cells in Hypoxic Pulmonary Hypertension

Pulmonary hypertension is a complex and heterogeneous condition with five main subtypes (groups). This review focuses on pulmonary hypertension caused by chronic hypoxia (hypoxic pulmonary hypertension, HPH, group 3). It is based mainly on our own experimental work, especially our collaboration with the group of Professor Herget, whose fifth anniversary of death we commemorate. We have found that oxidation and degradation of the extracellular matrix (ECM) in vitro, in either the presence or the absence of pro-inflammatory cells, activate vascular smooth muscle cell (VSMC) proliferation. Significant changes in the ECM of pulmonary arteries also occurred in vivo in hypoxic rats, namely a decrease in collagen VI and an increase in matrix metalloproteinase 9 (MMP-9) in the tunica media, which may also contribute to the growth activation of VSMCs. The proliferation of VSMCs was also enhanced in their co-culture with macrophages, most likely due to the paracrine production of growth factors in these cells. However, hypoxia itself has a dual effect: on the one hand, it can activate VSMC proliferation and hyperplasia, but on the other hand, it can also induce VSMC hypertrophy and increased expression of contractile markers in these cells. The influence of hypoxia-inducible factors, microRNAs and galectin-3 in the initiation and development of HPH, and the role of cell types other than VSMCs (endothelial cells, adventitial fibroblasts) are also discussed. Keywords: Vasoconstriction, Remodeling, Oxidation, Degradation, Extracellular matrix, Collagen, Proteolytic enzymes, Metalloproteinases, Macrophages, Mast cells, Smooth muscle cells, Endothelial cells, Fibroblasts, Mesenchymal stem cells, Hypoxia-inducible factor, microRNA, Galectins, Hyperplasia, Hypertrophy, Therapy of hypoxic pulmonary hypertension.

Pre-treatment with notoginsenoside R1 from Panax notoginseng protects against high-altitude-induced pulmonary edema by inhibiting pyroptosis through the NLRP3/caspase-1/GSDMD pathway

High-altitude pulmonary edema (HAPE) is a potentially fatal condition that occurs when exposed to high-altitude hypoxia environments. Currently, there is no effective treatment for HAPE, and available interventions focus on providing relief. Notoginsenoside R1 (NGR1), a major active constituent of Panax notoginseng (Burkill) F.H.Chen (sānqī), has demonstrated heart and lung-protective effects under hypobaric hypoxia. However, there is a lack of clarity regarding the precise mechanisms that underlie the protective effects of NGR1 against inflammation. In this study, a rat model of HAPE was developed to assess the effect of NGR1 on this pathology. High-altitude hypoxia corresponding to 6000 m altitude was simulated with a hypobaric chamber. We found that NGR1 dose-dependently alleviated pulmonary oxidative stress damage and inflammatory response, and prevented acid-base balance disruption. In addition, NGR1 restored the expression levels of hypoxia-inducible factor-1 alpha, vascular endothelial growth factor, and aquaporin protein-5, correlated with the development of pulmonary edema induced by hypobaric hypoxia. Furthermore, NGR1 pre-treatment remarkably mitigated NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-induced pyroptosis, and this effect was partially counteracted by the use of an NLRP3 agonist. Thus, NGR1 may exert a lung-protective effect against HAPE by ameliorating hypoxia-induced lung edema, oxidative damage, and inflammation through inhibition of the NLRP3/Caspase-1/ GSDMD signaling pathway.

Evidence of Intraspecific Adaptive Variation in the American Pika (Ochotona princeps) on a Continental Scale Using a Target Enrichment and Mitochondrial Genome Skimming Approach

Montane landscapes present an array of abiotic challenges that drive adaptive evolution amongst organisms. These adaptations can promote habitat specialisation, which may heighten the risk of extirpation from environmental change. For example, higher metabolic rates in an endothermic species may contribute to heightened cold tolerance, whilst simultaneously limiting heat tolerance. Here, using the climate-sensitive American pika (Ochotona princeps), we test for evidence of intraspecific adaptive variation amongst environmental gradients across the Intermountain West of North America. We leveraged results from previous studies on pika adaptation to generate a custom nuclear target enrichment design to sequence several hundred candidate genes related to cold, hypoxia and dietary detoxification. We also applied a 'genome skimming' approach to sequence mitochondrial DNA. Using genotype-environment association tests, we identified rare genomic variants associated with elevation and temperature variation amongst populations. Amongst mitochondrial genes, we identified intraspecific variation in selective signals and significant changes to the amino acid property equilibrium constant, which may relate to electron transport chain efficiency. These results illustrate a complex dynamic of adaptive variation amongst O. princeps where lineages and populations have adapted to unique regional conditions. Some of the clearest signals of selection were in a genetic lineage that includes pikas of the Great Basin region, which is also where recent localised extirpations have taken place and highlights the risk of losing adaptive alleles during environmental change.

mTOR in the Development of Hypoxic Pulmonary Hypertension Associated with Cardiometabolic Risk Factors

The pathophysiology of pulmonary hypertension is complex and multifactorial. It is a disease characterized by increased pulmonary vascular resistance at the level due to sustained vasoconstriction and remodeling of the pulmonary arteries, which triggers an increase in the mean pulmonary artery pressure and subsequent right ventricular hypertrophy, which in some cases can cause right heart failure. Hypoxic pulmonary hypertension (HPH) is currently classified into Group 3 of the five different groups of pulmonary hypertensions, which are determined according to the cause of the disease. HPH mainly develops as a product of lung diseases, among the most prevalent causes of obstructive sleep apnea (OSA), chronic obstructive pulmonary disease (COPD), or hypobaric hypoxia due to exposure to high altitudes. Additionally, cardiometabolic risk factors converge on molecular mechanisms involving overactivation of the mammalian target of rapamycin (mTOR), which correspond to a central axis in the development of HPH. The aim of this review is to summarize the role of mTOR in the development of HPH associated with metabolic risk factors and its therapeutic alternatives, which will be discussed in this review.

CircLMBR1 inhibits phenotypic transformation of hypoxia-induced pulmonary artery smooth muscle via the splicing factor PUF60

Phenotypic transformation of pulmonary artery smooth muscle cells (PASMCs) contributes to vascular remodeling in hypoxic pulmonary hypertension (PH). Recent studies have suggested that circular RNAs (circRNAs) may play important roles in the vascular remodeling of hypoxia-induced PH. However, whether circRNAs cause pulmonary vascular remodeling by regulating the phenotypic transformation in PH has not been investigated. Microarray and RT-qPCR analysis identified that circLMBR1, a novel circRNA, decreased in mouse lung tissues of the hypoxia-SU5416 PH model, as well as in human PASMCs and mouse PASMCs exposed to hypoxia. Overexpression of circLMBR1 in the Semaxinib (SU5416) mouse model ameliorated hypoxia-induced PH and vascular remodeling in the lungs. Notably, circLMBR1 was mainly distributed in the nucleus and bound to the splicing factor PUF60. CircLMBR1 suppressed the phenotypic transformation of human PASMCs and vascular remodeling by inhibiting PUF60 expression. Furthermore, we identified U2AF65 as the downstream regulatory factor of PUF60. U2AF65 directly interacted with the pre-mRNA of the contractile phenotype marker smooth muscle protein 22-α (SM22α) and inhibited its splicing. Meanwhile, hypoxia exposure increased the formation of the PUF60-U2AF65 complex, thereby inhibiting SM22α production and inducing the transition of human PASMCs from a contractile phenotype to a synthetic phenotype. Overall, our results verified the important role of circLMBR1 in the pathological process of PH. We also proposed a new circLMBR1/PUF60-U2AF65/pre-SM22α pathway that could regulate the phenotypic transformation and proliferation of human PASMCs. This study may provide new perspectives for the diagnosis and treatment of PH.

Effect of the TGF-β/BMP Signaling Pathway on the Proliferation of Yak Pulmonary Artery Smooth Muscle Cells under Hypoxic Conditions

To survive in low-oxygen environments, yaks effectively avoid hypoxia-induced pulmonary arterial hypertension through vascular remodeling. The TGF-β/BMP signaling pathway plays a key role in maintaining the homeostasis of pulmonary artery smooth muscle cells (PASMCs). However, little is known about the molecular regulatory mechanisms by which the TGF-β/BMP signaling pathway contributes to the proliferation of yak PASMCs. In this study, yak PASMCs were cultured in vitro, and a hypoxia model was constructed to investigate the effect of TGFβ/BMP signaling on yak PASMC proliferation. Hypoxia treatment increased the proliferation of yak PASMCs significantly. As the duration of hypoxia increased, the expression levels of TGF-β1 and the phosphorylation levels of Smad2/3 were upregulated significantly. The BMP signaling pathway was transiently activated by hypoxia, with increases in BMPR2 expression and Smad1/5 phosphorylation, and these changes were gradually reversed with prolonged hypoxia exposure. In addition, exogenous TGF-β1 activated the TGF-β signaling pathway, increased the phosphorylation levels of the downstream proteins Smad2 and Smad3, and increased the proliferation and migration rates of yak PASMCs significantly. Finally, treatment with noggin (an inhibitor of BMP signaling) significantly reduced BMPR2 protein expression levels and Smad1/5 phosphorylation levels and increased yak PASMC proliferation and migration rates. In summary, these results revealed that under hypoxic conditions, the dynamic regulation of the TGF-β/BMP signaling pathway promotes the proliferation of yak PASMCs.

Cell Death in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe pulmonary vascular disease characterized by increased pulmonary vascular resistance because of vascular remodeling and vasoconstriction. Subsequently, PAH leads to right ventricular hypertrophy and heart failure. Cell death mechanisms play a significant role in development and tissue homeostasis, and regulate the balance between cell proliferation and differentiation. Several basic and clinical studies have demonstrated that multiple mechanisms of cell death, including pyroptosis, apoptosis, autophagy, ferroptosis, anoikis, parthanatos, and senescence, are closely linked with the pathogenesis of PAH. This review summarizes different cell death mechanisms involved in the death of pulmonary artery smooth muscle cells (PASMCs) and pulmonary artery endothelial cells (PAECs), the primary target cells in PAH. This review summarizes the role of these cell death mechanisms, associated signaling pathways, unique effector molecules, and various pro-survival or reprogramming mechanisms. The aim of this review is to summarize the currently known molecular mechanisms underlying PAH. Further investigations of the cell death mechanisms may unravel new avenues for the prevention and treatment of PAH.

Bawei Chenxiang Wan ameliorates right ventricular hypertrophy in rats with high altitude heart disease by SIRT3-HIF1α-PDK/PDH signaling pathway improving fatty acid and glucose metabolism

BACKGROUND

Bawei Chenxiang Wan (BCW) is among the most effective and widely used therapies for coronary heart disease and angina pectoris in Tibet. However, whether it confers protection through a right-ventricle (RV) myocardial metabolic mechanism is unknown.

METHODS

Male Sprague-Dawley rats were orally administrated with BCW, which was injected concurrently with a bolus of Sugen5416, and subjected to hypoxia exposure (SuHx; 5000 m altitude) for 4 weeks. Right ventricular hypertrophy (RVH) in high-altitude heart disease (HAHD) was assessed using Fulton's index (FI; ratio of RV to left ventricle + septum weights) and heart-weight-to-body-weight ratio (HW/BW). The effect of therapeutic administration of BCW on the RVH hemodynamics was assessed through catheterization (mean right ventricular pressure and mean pulmonary artery pressure (mRVP and mPAP, respectively)). Tissue samples were used to perform histological staining, and confirmatory analyses of mRNA and protein levels were conducted to detect alterations in the mechanisms of RVH in HAHD. The protective mechanism of BCW was further verified via cell culture.

RESULTS

BCW considerably reduced SuHx-associated RVH, as indicated by macro morphology, HW/BW ratio, FI, mPAP, mRVP, hypertrophy markers, heart function, pathological structure, and myocardial enzymes. Moreover, BCW can alleviate the disorder of glucose and fatty acid metabolism through upregulation of carnitine palmitoyltransferase1ɑ, citrate synthase, and acetyl-CoA and downregulation of glucose transport-4, phosphofructokinase, and pyruvate, which resulted in the reduced levels of free fatty acid and lactic acid and increased aerobic oxidation. This process may be mediated via the regulation of sirtuin 3 (SIRT3)-hypoxia-inducible factor 1α (HIF1α)-pyruvate dehydrogenase kinase (PDK)/pyruvate dehydrogenase (PDH) signaling pathway. Subsequently, the inhibition of SIRT3 expression by 3-TYP (a selective inhibitor of SIRT3) can reverse substantially the anti-RVH effect of BCW in HAHD, as indicated by hypertrophy marker and serum myocardial enzyme levels.

CONCLUSIONS

BCW prevented SuHx-induced RVH in HAHD via the SIRT3-HIF1ɑ-PDK/PDH signaling pathway to alleviate the disturbance in fatty acid and glucose metabolism. Therefore, BCW can be used as an alternative drug for the treatment of RVH in HAHD.

The role and mechanism of PDZ binding kinase in hypobaric and hypoxic acute lung injury

Background

Acute lung injury (ALI) caused by hypobaric hypoxia (HH) is frequently observed in high-altitude areas, and it is one of the leading causes of death in high-altitude-related diseases due to its rapid onset and progression. However, the pathogenesis of HH-related ALI (HHALI) remains unclear, and effective treatment approaches are currently lacking.

Methods

A new mouse model of HHALI developed by our laboratory was used as the study subject (Chinese patent No. ZL 2021 1 1517241 X). Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the messenger RNA (mRNA) expression levels of PDZ-binding kinase (PBK), sirtuin 1 (SIRT1), and PTEN-induced kinase 1 (PINK1) in mouse lung tissue. Hematoxylin and eosin staining was used to observe the main types of damage and damaged cells in lung tissue, and the lung injury score was used for quantification. The wet-dry (W/D) ratio was used to measure lung water content. Enzyme-linked immunosorbent assay was used to detect changes in inflammatory factors and oxidative stress markers in the lungs. Western blotting verified the expression of various mitochondrial autophagy-related proteins. The 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimi-dazoylcarbocyanine iodide (JC-1) method was used determined the health status of mitochondria based on changes in mitochondrial membrane potential. Transmission electron microscopy was used to directly observe the morphology of mitochondria. Multicolor immunofluorescence was used to observe the levels of mitochondrial autophagy markers. Other signaling pathways and molecular mechanisms that may play a role in epithelial cells were analyzed via through RNA sequencing.

Results

Low pressure and hypoxia caused pathological changes in mouse lung tissue, mainly ALI, leading to increased levels of inflammatory factors and intensified oxidative stress response in the lungs. Overexpression of PBK was found to alleviate HHALI, and activation of the p53 protein was shown to abrogate this therapeutic effect, while activation of SIRT1 protein reactivated this therapeutic effect. The therapeutic effect of PBK on HHALI is achieved via the activation of mitochondrial autophagy. Finally, RNA sequencing demonstrated that besides mitochondrial autophagy, PBK also exerts other functions in HHALI.

Conclusions

Overexpression of PBK inhibits the expression of p53 and activates SIRT1-PINK1 axis mediated mitochondrial autophagy to alleviate HHALI.

Activation of the p62-Keap1-Nrf2 pathway improves pulmonary arterial hypertension in MCT-induced rats by inhibiting autophagy

Autophagy is implicated in the pathogenesis of pulmonary arterial hypertension (PAH). We aimed to investigate whether the p62-Keap1-Nrf2 pathway affects the development of PAH by mediating autophagy. A PAH rat model was established using monocrotaline (MCT). Pulmonary artery smooth muscle cells (PASMCs) were extracted, and the changes in proliferation, migration, autophagy, and oxidative stress were analyzed following overexpression or knockdown of p62. The impact of p62 on the symptoms of PAH rats was assessed by the injection of an adenovirus overexpressing p62. We found that the knockdown of p62 increased the proliferation and migration of PASMCs, elevating the oxidative stress of PASMCs and upregulating gene expression of NADPH oxidases. Co-IP assay results demonstrated that p62 interacted with Keap1. p62 knockdown enhanced Keap1 protein stability and Nrf2 ubiquitination. LC3II/I and ATG5 were expressed more often when p62 was knocked down. Treating with an inhibitor of autophagy reversed the impact of p62 knockdown on PASMCs. Nrf2 inhibitor treatment reduced the expression of Nrf2 and p62, while increasing the expression of Keap1, LC3II/I, and ATG5 in PASMCs. However, overexpressing p62 diminished mRVP, SPAP, and Fulton index in PAH rats and attenuated pulmonary vascular wall thickening. Overexpression of p62 also decreased the expression of Keap1, LC3II/I, and ATG5 and increased the nuclear expression of Nrf2 in PAH rats. Importantly, overexpression of p62 reduced oxidative stress and the NADPH oxidase expression in PAH rats. Overall, activation of the p62-Keap1-Nrf2 positive feedback signaling axis reduces the proliferation and migration of PASMCs and alleviates PAH by inhibiting autophagy and oxidative stress.

Tsantan Sumtang, a traditional Tibetan medicine, protects pulmonary vascular endothelial function of hypoxia-induced pulmonary hypertension rats through AKT/eNOS signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Tsantan Sumtang (TS), originated from the Four Tantras, is an empirical Tibetan medicine prescription, which has been widely used for treating cardiovascular diseases in the clinic in Qinghai Province of China. Our previous studies found that TS alleviated hypoxia-induced pulmonary hypertension (HPH) in rats. However, the effect and bioactive fractions of TS on hypoxia-injured pulmonary vascular endothelium are unknown.

AIM OF THE STUDY

To investigate the effect, bioactive fractions and pharmacological mechanism of TS on hypoxia-injured pulmonary vascular endothelium in vivo and in vitro.

MATERIALS AND METHODS

In vivo studies, HPH animal model was established, and TS was administrated for four weeks. Then, hemodynamic indexes, ex vivo pulmonary artery perfusion experiment, morphological characteristics, nitric oxide (NO) production, and the protein expression of protein kinase B (AKT)/endothelial nitric oxide synthase (eNOS) and AMP-activated protein kinase (AMPK)/eNOS signaling were determined. In vitro studies, 1% O2-induced pulmonary artery endothelial cells (PAECs) injury model was applied for screening bioactive fractions of TS by cell proliferation assay and NO production measurement. The associated proteins of AKT/eNOS signaling were further measured to elucidate underlying mechanism of bioactive fraction of TS via using phosphatidylinositol-3 kinase (PI3K) inhibitor LY294002. Ultra-high performance liquid chromatography with hybrid quadrupole-orbitrap mass spectrometry (UHPLC-Q-Exactive Orbitrap-MS) was used to reveal the chemical profile of bioactive fraction of TS.

RESULTS

TS showed protective effect on the integrity of distal pulmonary arterial endothelium in HPH rats. Tsantan Sumtang dilated pulmonary arterial rings in HPH rats. TS enhanced NO bioavailability in lung tissue via regulating AKT/eNOS signaling. Furthermore, in the cellular level, cell viability as well as NO content of hypoxia-injured PAECs were elevated by fraction 17 of water extract of TS (WTS), through activating the AKT/eNOS signaling. Ellagic acid could be one of compositions in fraction 17 of WTS to produce NO in hypoxia-injured PAECs.

CONCLUSION

TS restored pulmonary arterial endothelial function in HPH rats. The bioactive fraction 17 was screened, which protected hypoxia-injured PAECs via upregulating AKT/eNOS signaling.

High altitude hypoxia and oxidative stress: The new hope brought by free radical scavengers

Various strategies can be employed to prevent and manage altitude illnesses, including habituation, oxygenation, nutritional support, and medication. Nevertheless, the utilization of drugs for the prevention and treatment of hypoxia is accompanied by certain adverse effects. Consequently, the quest for medications that exhibit minimal side effects while demonstrating high efficacy remains a prominent area of research. In this context, it is noteworthy that free radical scavengers exhibit remarkable anti-hypoxia activity. These scavengers effectively eliminate excessive free radicals and mitigate the production of reactive oxygen species (ROS), thereby safeguarding the body against oxidative damage induced by plateau hypoxia. In this review, we aim to elucidate the pathogenesis of plateau diseases that are triggered by hypoxia-induced oxidative stress at high altitudes. Additionally, we present a range of free radical scavengers as potential therapeutic and preventive approaches to mitigate the occurrence of common diseases associated with hypoxia at high altitudes.

Diabetic Cardiomyopathy: 2023 Update by the International Multidisciplinary Board of Experts

Diabetes mellitus (DM) is considered by many the pandemic of the 21st century and is associated with multiple organ damages. Among these, cardiovascular complications are responsible for an incredible burden of mortality and morbidity in Western Countries. The study of the pathological mechanisms responsible for the cardiovascular complications in DM patients is key for the development of new therapeutic strategies. The metabolic disorders caused by hyperglycemia, insulin resistance, and dyslipidemia, results in a cascade of pathomorphological changes favoring the atherosclerotic process and leading to myocardial remodeling. Parallel to this, oxidative stress, calcium overload, mitochondrial dysfunction, activation of protein kinase C signaling pathways, myocardial lipomatosis, and low-grade inflammation of the myocardium - are the main pathways responsible for the diabetic cardiomyopathy development. This review aims to appraise and discuss the pathogenetic mechanisms behind the diabetic cardiomyopathy development.

Kaempferol and ginsenoside Rg1 ameliorate acute hypobaric hypoxia induced lung injury based on network pharmacology analysis

Acute hypobaric hypoxia at high altitude can cause fatal non-cardiogenic high altitude pulmonary edema. Anti-inflammatory and anti-oxidant treatments appear to be a prospective way to alleviate acute hypoxia lung injury. Kaempferol (KA) and ginsenoside Rg1 (GRg1) can be isolated and purified from ginseng with anti-inflammatory, antioxidant, anti-carcinogenic, neuroprotective, and antiaging effects. However, their effects and pharmacological mechanisms on lung injury remains unclear. Network pharmacology analyses were used to explore potential targets of KA and GRg1 against acute hypobaric hypoxia induced lung injury. Rat lung tissues were further used for animal experiment verification. Among the putative targets of KA and GRg1 for inhibition of acute hypobaric hypoxia induced lung injury, AKT1, PIK3R1, PTK2, STAT3, HSP90AA1 and AKT2 were recognized as higher interrelated targets. And PI3K-AKT signaling pathway is considered to be the most important and relevant pathway. The rat experimental results showed that KA and GRg1 significantly improved histopathological changes and decreased pulmonary edema in rats with lung injury caused by acute hypobaric hypoxia. The concentrations of IL-6, TNF-α, MDA, SOD and CAT in rats treated with KA and GRg1 were significantly ameliorated. Protein and mRNA levels of PI3K and AKTI were significantly inhibited after KA administration. KA and GRg1 can lower lung water content, improve lung tissue damage, reduce the production of pro-inflammatory cytokines and the oxidative stress level.

NLRC3 deficiency promotes hypoxia-induced pulmonary hypertension development via IKK/NF-κB p65/HIF-1α pathway

Hypoxia-induced pulmonary hypertension is a subgroup of type 3 pulmonary hypertension (PH) with the recommended treatment limited to oxygen therapy and lacks potential therapeutic targets. To investigate the role of NLRC3 in hypoxia-induced PH and its potential mechanism, we first collected lung tissues of high-altitude pulmonary hypertension (HAPH) patients. Immunohistochemistry and immunofluorescence showed that NLRC3 was downregulated and was mainly co-localized with the smooth muscle cells of the pulmonary vessels in HAPH patients. Besides, we found that NLRC3 was also expressed in endothelial cells in HAPH patients for the first time. Then, wild type (WT) and NLRC3 knockout (NLRC3-/-) mice were used to construct hypoxia models and primary pulmonary arterial smooth muscle cells (PASMCs) of rats and endothelial cells were cultured for verification. Right heart catheterization and echocardiography suggested that NLRC3 knockout promoted right ventricular systolic pressure (RVSP) up-regulation, right ventricular hypertrophy and fibrosis in hypoxia-induced mice. This study first demonstrated that NLRC3 deficiency promoted hypoxia-stimulated PASMCs proliferation, Human umbilical vein endothelial cells (HUVECs) apoptosis, migration and inflammation through IKK/NF-κB p65/HIF-1α pathway in vitro and in vivo, further promoted vascular remodeling and PH progression, which provided a new target for the treatment of hypoxia-induced PH.

Effects of Zinc on the Right Cardiovascular Circuit in Long-Term Hypobaric Hypoxia in Wistar Rats

Hypobaric hypoxia under chromic conditions triggers hypoxic pulmonary vasoconstriction (HPV) and right ventricular hypertrophy (RVH). The role of zinc (Zn) under hypoxia is controversial and remains unclear. We evaluated the effect of Zn supplementation in prolonged hypobaric hypoxia on HIF2α/MTF-1/MT/ZIP12/PKCε pathway in the lung and RVH. Wistar rats were exposed to hypobaric hypoxia for 30 days and randomly allocated into three groups: chronic hypoxia (CH); intermittent hypoxia (2 days hypoxia/2 days normoxia; CIH); and normoxia (sea level control; NX). Each group was subdivided (n = 8) to receive either 1% Zn sulfate solution (z) or saline (s) intraperitoneally. Body weight, hemoglobin, and RVH were measured. Zn levels were evaluated in plasma and lung tissue. Additionally, the lipid peroxidation levels, HIF2α/MTF-1/MT/ZIP12/PKCε protein expression and pulmonary artery remodeling were measured in the lung. The CIH and CH groups showed decreased plasma Zn and body weight and increased hemoglobin, RVH, and vascular remodeling; the CH group also showed increased lipid peroxidation. Zn administration under hypobaric hypoxia upregulated the HIF2α/MTF-1/MT/ZIP12/PKCε pathway and increased RVH in the intermittent zinc group. Under intermittent hypobaric hypoxia, Zn dysregulation could participate in RVH development through alterations in the pulmonary HIF2α/MTF1/MT/ZIP12/PKCε pathway.

Protective effects of the Terminalia bellirica tannin-induced Nrf2/HO-1 signaling pathway in rats with high-altitude pulmonary hypertension

BACKGROUND

Oxidative stress and endothelial cell dysfunction induced by high-altitude hypoxia have important roles in the pathological process of high-altitude pulmonary hypertension (HAPH). Tannins present in Terminalia bellirica (Gaertn.) Roxb. (TTR) have pharmacological activities that produce oxidation resistance and exert anti-inflammatory effects. Whether TTR exerts a protective effect on HAPH remains unknown.

METHODS

A rat model of HAPH was established. The mean pulmonary arterial pressure (mPAP) of the animals was measured, the serum levels of SOD, MDA, and GSH-Px were measured using ELISA, and the expression of Bax, Bcl-2, Nrf2, and HO-1 proteins in the lung tissue of each group of rats was measured using Western blotting. Pathological changes in the lung tissue were also observed. A model of damage to H₂O₂-induced pulmonary artery endothelial cells (PAECs) was generated, and cell proliferation was measured using CCK-8 assays. Flow cytometry was used to measure ROS levels in PAECs. Western blotting was used to detect the expression of Bax, Bcl-2, Nrf2, and HO-1 proteins in PAECs.

RESULTS

The hemodynamic and pathologic findings showed that the mPAP of HAPH rats increased markedly, and the vascular wall thickness increased (P < 0.05). TTR reduced mPAP, alleviated or slowed pulmonary arterial remodeling, increased GSH-Px and SOD activity, lowered the level of MDA (P < 0.05), and downregulated the expression of Bax in the lung tissues of HAPH rats, while the expression of Bcl-2, Nrf2, and HO-1 was upregulated (P < 0.05). The results of the cell experiments showed that TTR inhibited H₂O₂-induced PAEC apoptosis and ROS production (P < 0.05), downregulated the expression of Bax in PAECs, and upregulated the expression of Bcl-2, Nrf2, and HO-1 (P < 0.05).

CONCLUSION

The results suggest that TTR reduces pulmonary arterial pressure, decreases oxidative stress during HAPH, and exerts protective effects in rats with HAPH and that its mechanism of action is related to regulation of the Nrf2/HO-1 signaling pathway.

Regulatory B cells protect against chronic hypoxia-induced pulmonary hypertension by modulating the Tfh/Tfr immune balance

Hypoxia-induced pulmonary hypertension (HPH) is a progressive and lethal disease characterized by the uncontrolled proliferation of pulmonary artery smooth muscle cells (PASMCs) and obstructive vascular remodelling. Previous research demonstrated that Breg cells were involved in the pathogenesis of pulmonary hypertension. This work aimed to evaluate the regulatory function of Breg cells in HPH. HPH mice model were established and induced by exposing to chronic hypoxia for 21 days. Mice with HPH were treated with anti-CD22 or adoptive transferred of Breg cells. The coculture systems of Breg cells with CD4⁺ T cells and Breg cells with PASMCs in vitro were constructed. Lung pathology was evaluated by HE staining and immunofluorescence staining. The frequencies of Breg cells, Tfh cells and Tfr cells were analysed by flow cytometry. Serum IL-21 and IL-10 levels were determined by ELISA. Protein levels of Blimp-1, Bcl-6 and CTLA-4 were determined by western blot and RT-PCR. Proliferation rate of PASMCs was measured by EdU. Compared to the control group, mean PAP, RV/(LV + S) ratio, WA% and WT% were significantly increased in the model group. Anti-CD22 exacerbated abnormal hemodynamics, pulmonary vascular remodelling and right ventricle hypertrophy in HPH, which ameliorated by adoptive transfer of Breg cells into HPH mice. The proportion of Breg cells on day 7 induced by chronic hypoxia was significantly higher than control group, which significantly decreased on day 14 and day 21. The percentage of Tfh cells was significantly increased, while percentage of Tfr cells was significantly decreased in HPH than those of control group. Anti-CD22 treatment increased the percentage of Tfh cells and decreased the percentage of Tfr cells in HPH mice. However, Breg cells restrained the Tfh cells differentiation and expanded Tfr cells differentiation in vivo and in vitro. Additionally, Breg cells inhibited the proliferation of PASMCs under hypoxic condition in vitro. Collectively, these findings suggested that Breg cells may be a new therapeutic target for modulating the Tfh/Tfr immune balance in HPH.

Kaempferol ameliorates pulmonary vascular remodeling in chronic hypoxia-induced pulmonary hypertension rats via regulating Akt-GSK3β-cyclin axis

Excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) is considered a major contributor to elevated pulmonary vascular resistance and a key mechanism of vascular remodeling in hypoxia-induced pulmonary hypertension (HPH). Kaempferol is a natural flavonoid compound and can be derived from numerous common medicinal herbs and vegetables, which exhibit antiproliferative and proapoptotic properties, however, the effects of kaempferol on vascular remodeling in HPH remain unexplored. In this study, SD rats were placed in a hypobaric hypoxia chamber for four weeks to establish a pulmonary hypertension model and given either kaempferol or sildenafil (an inhibitor of PDE-5) during days 1-28, after which the hemodynamic parameter and pulmonary vascular morphometry were assessed. Furthermore, primary rat PASMCs were exposed to hypoxic conditions to generate a cell proliferation model, then incubated with either kaempferol or LY294002 (an inhibitor of PI3K). Immunoblotting and real-time quantitative PCR assessed the protein and mRNA expression levels in HPH rat lungs and PASMCs. We found that kaempferol reduced pulmonary artery pressure and pulmonary vascular remodeling, and alleviated right ventricular hypertrophy in HPH rats. The mechanistic analysis demonstrated that kaempferol reduced the protein levels of phosphorylation of Akt and GSK3β, leading to decreased expression of pro-proliferation (CDK2, CDK4, Cyclin D1, and PCNA) and anti-apoptotic related proteins (Bcl-2) and increased expression of pro-apoptosis proteins (Bax and cleaved caspase 3). These results collectively demonstrate that kaempferol ameliorates HPH in rats by inhibiting PASMC proliferation and pro-apoptosis via modulation of the Akt/GSK3β/CyclinD axis.

Tensions in Taxonomies: Current Understanding and Future Directions in the Pathobiologic Basis and Treatment of Group 1 and Group 3 Pulmonary Hypertension

In the over 100 years since the recognition of pulmonary hypertension (PH), immense progress and significant achievements have been made with regard to understanding the pathophysiology of the disease and its treatment. These advances have been mostly in idiopathic pulmonary arterial hypertension (IPAH), which was classified as Group 1 Pulmonary Hypertension (PH) at the Second World Symposia on PH in 1998. However, the pathobiology of PH due to chronic lung disease, classified as Group 3 PH, remains poorly understood and its treatments thus remain limited. We review the history of the classification of the five groups of PH and aim to provide a state-of-the-art review of the understanding of the pathogenesis of Group 1 PH and Group 3 PH including insights gained from novel high-throughput omics technologies that have revealed heterogeneities within these categories as well as similarities between them. Leveraging the substantial gains made in understanding the genomics, epigenomics, proteomics, and metabolomics of PAH to understand the full spectrum of the complex, heterogeneous disease of PH is needed. Multimodal omics data as well as supervised and unbiased machine learning approaches after careful consideration of the powerful advantages as well as of the limitations and pitfalls of these technologies could lead to earlier diagnosis, more precise risk stratification, better predictions of disease response, new sub-phenotype groupings within types of PH, and identification of shared pathways between PAH and other types of PH that could lead to new treatment targets. © 2023 American Physiological Society. Compr Physiol 13:4295-4319, 2023.

NOX Dependent ROS Generation and Cell Metabolism

Reactive oxygen species (ROS) represent a group of high reactive molecules with dualistic natures since they can induce cytotoxicity or regulate cellular physiology. Among the ROS, the superoxide anion radical (O2·-) is a key redox signaling molecule prominently generated by the NADPH oxidase (NOX) enzyme family and by the mitochondrial electron transport chain. Notably, altered redox balance and deregulated redox signaling are recognized hallmarks of cancer and are involved in malignant progression and resistance to drugs treatment. Since oxidative stress and metabolism of cancer cells are strictly intertwined, in this review, we focus on the emerging roles of NOX enzymes as important modulators of metabolic reprogramming in cancer. The NOX family includes seven isoforms with different activation mechanisms, widely expressed in several tissues. In particular, we dissect the contribute of NOX1, NOX2, and NOX4 enzymes in the modulation of cellular metabolism and highlight their potential role as a new therapeutic target for tumor metabolism rewiring.

Endogenous humoral determinants of vascular endothelial dysfunction as triggers of acute poisoning complications

The vascular endothelium is not only the semipermeable membrane that separates tissue from blood but also an organ that regulates inflammation, vascular tone, blood clotting, angiogenesis and synthesis of connective tissue proteins. It is susceptible to the direct cytotoxic action of numerous xenobiotics and to the acute hypoxia that accompanies acute poisoning. This damage is superimposed on the preformed state of the vascular endothelium, which, in turn, depends on many humoral factors. The probability that an exogenous toxicant will cause life-threatening dysfunction of the vascular endothelium, thereby complicating the course of acute poisoning, increases with an increase in the content of endogenous substances in the blood that disrupt endothelial function. These include ammonia, bacterial endotoxin, indoxyl sulfate, para-cresyl sulfate, trimethylamine N-oxide, asymmetric dimethylarginine, glucose, homocysteine, low-density and very-low-density lipoproteins, free fatty acids and products of intravascular haemolysis. Some other endogenous substances (albumin, haptoglobin, haemopexin, biliverdin, bilirubin, tetrahydrobiopterin) or food-derived compounds (ascorbic acid, rutin, omega-3 polyunsaturated fatty acids, etc.) reduce the risk of lethal vascular endothelial dysfunction. The individual variability of the content of these substances in the blood contributes to the stochasticity of the complications of acute poisoning and is a promising target for the risk reduction measures. Another feasible option may be the repositioning of drugs that affect the function of the vascular endothelium while being currently used for other indications.

Mechanism of Hypoxia-Mediated Smooth Muscle Cell Proliferation Leading to Vascular Remodeling

Vascular remodeling refers to changes in the size, contraction, distribution, and flow rate of blood vessels and even changes in vascular function. Vascular remodeling can cause cardiovascular and cerebrovascular diseases. It can also lead to other systemic diseases, such as pulmonary hypertension, pulmonary atherosclerosis, chronic obstructive pulmonary disease, stroke, and ascites of broilers. Hypoxia is one of the main causes of vascular remodeling. Prolonged hypoxia or intermittent hypoxia can lead to loss of lung ventilation, causing respiratory depression, irregular respiratory rhythms, and central respiratory failure. Animals that are unable to adapt to the highland environment are also prone to sustained constriction of the small pulmonary arteries, increased resistance to pulmonary circulation, and impaired blood circulation, leading to pulmonary hypertension and right heart failure if they live in a highland environment for long periods of time. However, limited studies have been found on the relationship between hypoxia and vascular remodeling. Therefore, this review will explore the relationship between hypoxia and vascular remodeling from the aspects of endoplasmic reticulum stress, mitochondrial dysfunction, abnormal calcium channel, disordered cellular metabolism, abnormal expression of miRNA, and other factors. This will help to understand the detailed mechanism of hypoxia-mediated smooth muscle cell proliferation and vascular remodeling for the better treatment and management of diseases due to 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.

Inflammation in Pulmonary Hypertension and Edema Induced by Hypobaric Hypoxia Exposure

Exposure to high altitudes generates a decrease in the partial pressure of oxygen, triggering a hypobaric hypoxic condition. This condition produces pathophysiologic alterations in an organism. In the lung, one of the principal responses to hypoxia is the development of hypoxic pulmonary vasoconstriction (HPV), which improves gas exchange. However, when HPV is exacerbated, it induces high-altitude pulmonary hypertension (HAPH). Another important illness in hypobaric hypoxia is high-altitude pulmonary edema (HAPE), which occurs under acute exposure. Several studies have shown that inflammatory processes are activated in high-altitude illnesses, highlighting the importance of the crosstalk between hypoxia and inflammation. The aim of this review is to determine the inflammatory pathways involved in hypobaric hypoxia, to investigate the key role of inflammation in lung pathologies, such as HAPH and HAPE, and to summarize different anti-inflammatory treatment approaches for these high-altitude illnesses. In conclusion, both HAPE and HAPH show an increase in inflammatory cell infiltration (macrophages and neutrophils), cytokine levels (IL-6, TNF-α and IL-1β), chemokine levels (MCP-1), and cell adhesion molecule levels (ICAM-1 and VCAM-1), and anti-inflammatory treatments (decreasing all inflammatory components mentioned above) seem to be promising mitigation strategies for treating lung pathologies associated with high-altitude exposure.

Inflammation and Oxidative Stress Induce NGF Secretion by Pulmonary Arterial Cells through a TGF-β1-Dependent Mechanism

Expression of the nerve growth factor NGF is increased in pulmonary hypertension (PH). We have here studied whether oxidative stress and inflammation, two pathological conditions associated with transforming growth factor-β1 (TGF-β1) in PH, may trigger NGF secretion by pulmonary arterial (PA) cells. Effects of hydrogen peroxide (H2O2) and interleukin-1β (IL-1β) were investigated ex vivo on rat pulmonary arteries, as well as in vitro on human PA smooth muscle (hPASMC) or endothelial cells (hPAEC). TβRI expression was assessed by Western blotting. NGF PA secretion was assessed by ELISA after TGF-β1 blockade (anti-TGF-β1 siRNA, TGF-β1 blocking antibodies, TβRI kinase, p38 or Smad3 inhibitors). TβRI PA expression was evidenced by Western blotting both ex vivo and in vitro. H2O2 or IL-1β significantly increased NGF secretion by hPASMC and hPAEC, and this effect was significantly reduced when blocking TGF-β1 expression, binding to TβRI, TβRI activity, or signaling pathways. In conclusion, oxidative stress and inflammation may trigger TGF-β1 secretion by hPASMC and hPAEC. TGF-β1 may then act as an autocrine factor on these cells, increasing NGF secretion via TβRI activation. Since NGF and TGF-β1 are relevant growth factors involved in PA remodeling, such mechanisms may therefore be relevant to PH pathophysiology.

Vascular peroxidase 1 promotes phenotypic transformation of pulmonary artery smooth muscle cells via ERK pathway in hypoxia-induced pulmonary hypertensive rats

AIMS

Vascular peroxidase 1 (VPO1) plays an important role in mediation of vascular remodeling with pulmonary arterial hypertension (PAH). This study aims to determine whether VPO1 can promote phenotypic transformation of pulmonary artery smooth muscle cells (PASMCs) and the underlying mechanisms.

MAIN METHODS

Sprague-Dawley (SD) rats were exposed to 10 % O₂ for 21 days to establish the model of vascular remodeling in pulmonary arterial hypertension. PASMCs were incubated with 3 % O₂ for 48 h to induce phenotypic transformation. Western blot was performed to detect the expressions of target proteins. The 5-ethynyl-2'-deoxyuridine (EdU) assay was conducted to measure the proliferation of PASMCs.

KEY FINDINGS

In the rats exposed to hypoxia, there were increases in right ventricular systolic pressure, pulmonary vascular remodeling and phenotypic transformation of PASMCs (the down-regulated contractile proteins of α-smooth muscle actin, smooth muscle 22α while the up-regulated synthetic proteins of osteopontin, cyclinD1), accompanied by up-regulation of VPO1, increase of hypochlorous acid (HOCl) production and elevation of the phosphorylation of ERK. In the cultured PASMCs exposed to hypoxia, similar results were achieved but they were reversed by VPO1 small interfering RNA (VPO1 siRNA) or HOCl inhibitor. Replacement of hypoxia with NaOCl could induce PASMCs phenotypic transformation and activate the ERK signaling. Furthermore, ERK inhibitor (PD98059) could also attenuate hypoxia-induced PASMCs phenotypic transformation.

SIGNIFICANCE

VPO1 play a pivotal role in promotion of phenotypic transformation of PASMCs under hypoxic condition through activation of VPO1/HOCl/ERK pathway. It might serve as a potential target for prevention of pulmonary vascular remodeling.

Hypoxia in Aging and Aging-Related Diseases: Mechanism and Therapeutic Strategies

As the global aging process continues to lengthen, aging-related diseases (e.g., chronic obstructive pulmonary disease (COPD), heart failure) continue to plague the elderly population. Aging is a complex biological process involving multiple tissues and organs and is involved in the development and progression of multiple aging-related diseases. At the same time, some of these aging-related diseases are often accompanied by hypoxia, chronic inflammation, oxidative stress, and the increased secretion of the senescence-associated secretory phenotype (SASP). Hypoxia seems to play an important role in the process of inflammation and aging, but is often neglected in advanced clinical research studies. Therefore, we have attempted to elucidate the role played by different degrees and types of hypoxia in aging and aging-related diseases and their possible pathways, and propose rational treatment options based on such mechanisms for reference.

Impact of Zinc on Oxidative Signaling Pathways in the Development of Pulmonary Vasoconstriction Induced by Hypobaric Hypoxia

Hypobaric hypoxia is a condition that occurs at high altitudes (>2500 m) where the partial pressure of gases, particularly oxygen (PO2), decreases. This condition triggers several physiological and molecular responses. One of the principal responses is pulmonary vascular contraction, which seeks to optimize gas exchange under this condition, known as hypoxic pulmonary vasoconstriction (HPV); however, when this physiological response is exacerbated, it contributes to the development of high-altitude pulmonary hypertension (HAPH). Increased levels of zinc (Zn2+) and oxidative stress (known as the “ROS hypothesis”) have been demonstrated in the vasoconstriction process. Therefore, the aim of this review is to determine the relationship between molecular pathways associated with altered Zn2+ levels and oxidative stress in HPV in hypobaric hypoxic conditions. The results indicate an increased level of Zn2+, which is related to increasing mitochondrial ROS (mtROS), alterations in nitric oxide (NO), metallothionein (MT), zinc-regulated, iron-regulated transporter-like protein (ZIP), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-induced protein kinase C epsilon (PKCε) activation in the development of HPV. In conclusion, there is an association between elevated Zn2+ levels and oxidative stress in HPV under different models of hypoxia, which contribute to understanding the molecular mechanism involved in HPV to prevent the development of HAPH.

Cannabidiol Improves Antioxidant Capacity and Reduces Inflammation in the Lungs of Rats with Monocrotaline-Induced Pulmonary Hypertension

Cannabidiol (CBD) is a plant-derived compound with antioxidant and anti-inflammatory properties. Pulmonary hypertension (PH) is still an incurable disease. CBD has been suggested to ameliorate monocrotaline (MCT)-induced PH, including reduction in right ventricular systolic pressure (RVSP), a vasorelaxant effect on pulmonary arteries and a decrease in the white blood cell count. The aim of our study was to investigate the effect of chronic administration of CBD (10 mg/kg daily for 21 days) on the parameters of oxidative stress and inflammation in the lungs of rats with MCT-induced PH. In MCT-induced PH, we found a decrease in total antioxidant capacity (TAC) and glutathione level (GSH), an increase in inflammatory parameters, e.g., tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), nuclear factor kappa B (NF-κB), monocyte chemoattractant protein-1 (MCP-1), and cluster of differentiation 68 (CD68), and the overexpression of cannabinoid receptors type 1 and 2 (CB₁-Rs, CB₂-Rs). Administration of CBD increased TAC and GSH concentrations, glutathione reductase (GSR) activity, and decreased CB₁-Rs expression and levels of inflammatory mediators such as TNF-α, IL -1β, NF-κB, MCP-1 and CD68. In conclusion, CBD has antioxidant and anti-inflammatory effects in MCT-induced PH. CBD may act as an adjuvant therapy for PH, but further detailed preclinical and clinical studies are recommended to confirm our promising results.

Integrated Bioinformatic Analysis Reveals TXNRD1 as a Novel Biomarker and Potential Therapeutic Target in Idiopathic Pulmonary Arterial Hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is a life-threatening cardiopulmonary disease lacking specific diagnostic markers and targeted therapy, and its mechanism of development remains to be elucidated. The present study aimed to explore novel diagnostic biomarkers and therapeutic targets in IPAH by integrated bioinformatics analysis. Four eligible datasets (GSE117261, GSE15197, GSE53408, GSE48149) was firstly downloaded from GEO database and subsequently integrated by Robust rank aggregation (RRA) method to screen robust differentially expressed genes (DEGs). Then functional annotation of robust DEGs was performed by GO and KEGG enrichment analysis. The protein-protein interaction (PPI) network was constructed followed by using MCODE and CytoHubba plug-in to identify hub genes. Finally, 10 hub genes were screened including ENO1, TALDO1, TXNRD1, SHMT2, IDH1, TKT, PGD, CXCL10, CXCL9, and CCL5. The GSE113439 dataset was used as a validation cohort to appraise these hub genes and TXNRD1 was selected for verification at the protein level. The experiment results confirmed that serum TXNRD1 concentration was lower in IPAH patients and the level of TXNRD1 had great predictive efficiency (AUC:0.795) as well as presents negative correlation with mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR). Consistently, the expression of TXNRD1 was proved to be inhibited in animal and cellular model of PAH. In addition, GSEA analysis was performed to explore the functions of TXNRD1 and the results revealed that TXNRD1 was closely correlated with mTOR signaling pathway, MYC targets, and unfolded protein response. Finally, knockdown of TXNRD1 was shown to exacerbate proliferative disorder, migration and apoptosis resistance in PASMCs. In conclusion, our study demonstrates that TXNRD1 is a promising candidate biomarker for diagnosis of IPAH and plays an important role in PAH pathogenesis, although further research is necessary.

Therapeutic potential of carbon monoxide in hypertension-induced vascular smooth muscle cell damage revisited: from physiology and pharmacology

As a chronic and progressive disorder, hypertension remains to be a serious public health problem around the world. Among the different types of hypertension, pulmonary arterial hypertension (PAH) is a devastating disease associated with pulmonary arteriole remodeling, right ventricular failure and death. The contemporary management of systemic hypertension and PAH has substantially grown since more therapeutic targets and/or agents have been developed. Evolving treatment strategies targeting the vascular remodeling lead to improving outcomes in patients with hypertension, nevertheless, significant advancement opportunities for developing better antihypertensive drugs remain. Carbon monoxide (CO), an active endogenous gasotransmitter along with hydrogen sulfide (H₂S) and nitric oxide (NO), is primarily generated by heme oxygenase (HO). Cumulative evidence suggests that CO is considered as an important signaling molecule under both physiological and pathological conditions. Studies have shown that CO confers a number of biological and pharmacological properties, especially its involvement in the pathological process and treatment of hypertension-related vascular remodeling. This review will critically outline the roles of CO in hypertension-associated vascular remodeling and discuss the underlying mechanisms for the protective effects of CO against hypertension and vascular remodeling. In addition, we will propose the challenges and perspectives of CO in hypertensive vascular remodeling. It is expected that a comprehensive understanding of CO in the vasculature might be essential to translate CO to be a novel pharmacological agent for hypertension-induced vascular remodeling.

Oxidative Stress and Diseases Associated with High-Altitude Exposure

Several diseases associated with high-altitude exposure affect unacclimated individuals. These diseases include acute mountain sickness (AMS), high-altitude cerebral edema (HACE), high-altitude pulmonary edema (HAPE), chronic mountain sickness (CMS), and, notably, high-altitude pulmonary hypertension (HAPH), which can eventually lead to right ventricle hypertrophy and heart failure. The development of these pathologies involves different molecules and molecular pathways that might be related to oxidative stress. Studies have shown that acute, intermittent, and chronic exposure to hypobaric hypoxia induce oxidative stress, causing alterations to molecular pathways and cellular components (lipids, proteins, and DNA). Therefore, the aim of this review is to discuss the oxidative molecules and pathways involved in the development of high-altitude diseases. In summary, all high-altitude pathologies are related to oxidative stress, as indicated by increases in the malondialdehyde (MDA) biomarker and decreases in superoxide dismutase (SOD) and glutathione peroxidase (GPx) antioxidant activity. In addition, in CMS, the levels of 8-iso-PGF2α and H₂O₂ are increased, and evidence strongly indicates an increase in Nox4 activity in HAPH. Therefore, antioxidant treatments seem to be a promising approach to mitigating high-altitude pathologies.

Single-Cell RNA Sequencing Reveals Novel Genes Regulated by Hypoxia in the Lung Vasculature

Pulmonary arterial hypertension (PAH) is a chronic progressive disease with significant morbidity and mortality. The disease is characterized by vascular remodeling that includes increased muscularization of distal blood vessels and vessel stiffening associated with changes in extracellular matrix deposition. In humans, chronic hypoxia causes PAH, and hypoxia-induced rodent models of PAH have been used for years to study the disease. With the development of single-cell RNA sequencing technology, it is now possible to examine hypoxia-dependent transcriptional changes in vivo at a cell-specific level. In this study, we used single-cell RNA sequencing to compare lungs from wild-type (Wt) mice exposed to hypoxia for 28 days to normoxia-treated control mice. We additionally examined mice deficient for Notch3, a smooth muscle-enriched gene linked to PAH. Data analysis revealed that hypoxia promoted cell number changes in immune and endothelial cell types in the lung, activated the innate immunity pathway, and resulted in specific changes in gene expression in vascular cells. Surprisingly, we found limited differences in lungs from mice deficient for Notch3 compared to Wt controls. These findings provide novel insight into the effects of chronic hypoxia exposure on gene expression and cell phenotypes in vivo and identify unique changes to cells of the vasculature.