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

Enhanced lung endothelial glycolysis is implicated in the development of severe pulmonary hypertension in type 2 diabetes

Metabolic abnormalities in pulmonary endothelial cells are implicated in pulmonary hypertension (PH) while increasing evidence shows the influence of diabetes on progressing PH. In this study, we examined the effect of type 2 diabetes on hypoxia-induced PH and investigated its molecular mechanisms using hypoxia-induced diabetic male mice. Chronic hypoxia led to a more severe PH in type 2 diabetic mice than in control mice. Next, we compared gene expression patterns in isolated pulmonary endothelial cells (MPECs) from control mice in normoxia (CN), diabetic mice in normoxia (DN), control mice exposed to hypoxia (CH), and diabetic mice exposed to hypoxia (DH). The results showed that expression levels of 27 mRNAs, out of 92 mRNAs, were significantly different among the four groups. Two glycolysis-related proteins, GAPDH and HK2, were increased in MPECs of DH mice compared with those in DN or CH mice. In addition, the levels of pyruvate and lactate (glycolysis end products) were significantly increased in MPECs of DH mice, but not in CH mice, compared with MPECs of CN mice. Augmentation of glycolysis by terazosin exacerbated hypoxia-induced PH in CH mice but not in DH mice. On the contrary, inhibiting GAPDH (a key enzyme of the glycolytic pathway) by koningic acid ameliorated hypoxia-induced PH in DH mice but had no effect in CH mice. These data suggest that enhanced glycolysis in diabetic mice is involved in severe hypoxia-induced PH, and glycolysis inhibition is a potential target to reduce the severe progression of PH in patients with diabetes.NEW & NOTEWORTHY Increasing evidence shows that diabetes exacerbates the progression of pulmonary hypertension; however, its molecular mechanisms are understudied. In this study, we revealed that augmented glycolysis in diabetic pulmonary endothelial cells is involved in the development of severe PH in diabetes. Inhibition of glycolysis could be a therapeutic strategy for treating pulmonary hypertension in patients with diabetes.

Beyond cancer: The potential application of CD47-based therapy in non-cancer diseases

CD47 is an immune checkpoint widely regarded as a 'don't eat me' signal. CD47-based anti-cancer therapy has received considerable attention, with a significant number of clinical trials conducted. While anti-cancer therapies based on CD47 remain a focal point of interest among researchers, it is noteworthy that an increasing number of studies have found that CD47-based therapy ameliorated the pathological status of non-cancer diseases. This review aims to provide an overview of the recent progress in comprehending the role of CD47-based therapy in non-cancer diseases, including diseases of the circulatory system, nervous system, digestive system, and so on. Furthermore, we sought to delineate the promising mechanisms of CD47-based therapy in treating non-cancer diseases. Our findings suggest that CD47-based agents may exert their effect by regulating phagocytosis, regulating T cells, dendritic cells, and neutrophils, and regulating the secretion of cytokines and chemokines. Additionally, we put forward the orientation of further research to bring to light the potential of CD47 and its binding partners as a target in non-cancer diseases.

Fatty acid metabolism promotes TRPV4 activity in lung microvascular endothelial cells in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a morbid disease characterized by significant lung endothelial cell (EC) dysfunction. Prior work has shown that microvascular endothelial cells (MVECs) isolated from animals with experimental PAH and patients with PAH exhibit significant abnormalities in metabolism and calcium signaling. With regards to metabolism, we and others have shown evidence of increased aerobic glycolysis and evidence of increased utilization of alternate fuel sources (such as fatty acids) in PAH EC. In the realm of calcium signaling, our prior work linked increased activity of the transient receptor potential vanilloid-4 (TRPV4) channel to increased proliferation of MVECs isolated from the Sugen/Hypoxia rat model of PAH (SuHx-MVECs). However, the relationship between metabolic shifts and calcium abnormalities was not clear. Specifically, whether shifts in metabolism were responsible for increasing TRPV4 channel activity in SuHx-MVECs was not known. In this study, using human data, serum samples from SuHx rats, and SuHx-MVECs, we describe the consequences of increased MVEC fatty acid oxidation in PAH. In human samples, we observed an increase in long-chain fatty acid levels that was associated with PAH severity. Next, using SuHx rats and SuHx-MVECs, we observed increased intracellular levels of lipids. We also show that increasing intracellular lipid content increases TRPV4 activity, whereas inhibiting fatty acid oxidation normalizes basal calcium levels in SuHx-MVECs. By exploring the fate of fatty acid-derived carbons, we observed that the metabolite linking increased intracellular lipids to TRPV4 activity was β-hydroxybutyrate (BOHB), a product of fatty acid oxidation. Finally, we show that BOHB supplementation alone is sufficient to sensitize the TRPV4 channel in rat and mouse MVECs. Returning to humans, we observe a transpulmonary BOHB gradient in human patients with PAH. Thus, we establish a link between fatty acid oxidation, BOHB production, and TRPV4 activity in MVECs in PAH. These data provide new insight into metabolic regulation of calcium signaling in lung MVECs in PAH.NEW & NOTEWORTHY In this paper, we explore the link between metabolism and intracellular calcium levels in microvascular endothelial cells (MVECs) in pulmonary arterial hypertension (PAH). We show that fatty acid oxidation promotes sensitivity of the transient receptor potential vanilloid-4 (TRPV4) calcium channel in MVECs isolated from a rodent model of PAH.

Intermittent short-duration reoxygenation relieves high-altitude pulmonary hypertension via NOX4/H2O2/PPAR-γ axis

High-altitude pulmonary hypertension (HAPH) is a severe and progressive disease that can lead to right heart failure. Intermittent short-duration reoxygenation at high altitude is effective in alleviating HAPH; however, the underlying mechanisms are unclear. In the present study, a simulated 5,000-m hypoxia rat model and hypoxic cultured pulmonary artery smooth muscle cells (PASMCs) were used to evaluate the effect and mechanisms of intermittent short-duration reoxygenation. The results showed that intermittent 3-h/per day reoxygenation (I3) effectively attenuated chronic hypoxia-induced pulmonary hypertension and reduced the content of H2O2 and the expression of NADPH oxidase 4 (NOX4) in lung tissues. In combination with I3, while the NOX inhibitor apocynin did not further alleviate HAPH, the mitochondrial antioxidant MitoQ did. Furthermore, in PASMCs, I3 attenuated hypoxia-induced PASMCs proliferation and reversed the activated HIF-1α/NOX4/PPAR-γ axis under hypoxia. Targeting this axis offset the protective effect of I3 on hypoxia-induced PASMCs proliferation. The present study is novel in revealing a new mechanism for preventing HAPH and provides insights into the optimization of intermittent short-duration reoxygenation.

Study of Transcriptomic Analysis of Yak (Bos grunniens) and Cattle (Bos taurus) Pulmonary Artery Smooth Muscle Cells under Oxygen Concentration Gradients and Differences in Their Lung Histology and Expression of Pyruvate Dehydrogenase Kinase 1-Related Factors

The aim of this study was to investigate the molecular mechanisms by which hypoxia affects the biological behavior of yak PASMCs, the changes in the histological structure of yak and cattle lungs, and the relationships and regulatory roles that exist regarding the differences in the distribution and expression of PDK1 and its hypoxia-associated factors screened for their role in the adaptation of yak lungs to the plateau hypoxic environment. The results showed that, at the level of transcriptome sequencing, the molecular regulatory mechanisms of the HIF-1 signaling pathway, glucose metabolism pathway, and related factors (HK2/PGK1/ENO1/ENO3/ALDOC/ALDOA) may be closely related to the adaptation of yaks to the hypoxic environment of the plateau; at the tissue level, the presence of filled alveoli and semi-filled alveoli, thicker alveolar septa and basement membranes, a large number of erythrocytes, capillary distribution, and collagen fibers accounted for all levels of fine bronchioles in the lungs of yaks as compared to cattle. A higher percentage of goblet cells was found in the fine bronchioles of yaks, and PDK1, HIF-1α, and VEGF were predominantly distributed and expressed in the monolayers of ciliated columnar epithelium in the branches of the terminal fine bronchioles of yak and cattle lungs, with a small amount of it distributed in the alveolar septa; at the molecular level, the differences in PDK1 mRNA relative expression in the lungs of adult yaks and cattle were not significant (p > 0.05), the differences in HIF-1α and VEGF mRNA relative expression were significant (p < 0.05), and the expression of PDK1 and HIF-1α proteins in adult yaks was stronger than that in adult cattle. PDK1 and HIF-1α proteins were more strongly expressed in adult yaks than in adult cattle, and the difference was highly significant (p < 0.01); the relative expression of VEGF proteins was not significantly different between adult yaks and cattle (p > 0.05). The possible regulatory relationship between the above results and the adaptation of yak lungs to the plateau hypoxic environment paves the way for the regulatory mechanisms of PDK1, HIF-1α, and VEGF, and provides basic information for studying the mechanism of hypoxic adaptation of yaks in the plateau. At the same time, it provides a reference for human hypoxia adaptation and a target for the prevention and treatment of plateau diseases in humans and plateau animals.

Natural Targeting Potent ROS-Eliminating Tungsten-Based Polyoxometalate Nanodots for Efficient Treatment of Pulmonary Hypertension

Pulmonary hypertension (PH) is a disease of pulmonary artery stenosis and blockage caused by abnormal pulmonary artery smooth muscle cells (PASMCs), with high morbidity and mortality. High levels of reactive oxygen species (ROS) in pulmonary arteries play a crucial role in inducing phenotypic switch and abnormal proliferation of PASMCs. However, antioxidants are rarely approved for the treatment of PH because of a lack of targeting and low bioavailability. In this study, the presence of an enhanced permeability and retention effect (EPR)-like effect in the pulmonary arteries of PH is revealed by tissue transmission electron microscopy (TEM). Subsequently, for the first time, tungsten-based polyoxometalate nanodots (WNDs) are developed with potent elimination of multiple ROS for efficient treatment of PH thanks to the high proportion of reduced W5+ . WNDs are effectively enriched in the pulmonary artery by intravenous injection because of the EPR-like effect of PH, and significantly prevent the abnormal proliferation of PASMCs, greatly improve the remodeling of pulmonary arteries, and ultimately improve right heart function. In conclusion, this work provides a novel and effective solution to the dilemma of targeting ROS for the treatment of PH.

Myeloid-derived suppressor cells and pulmonary hypertension

Pulmonary hypertension (PH) is a chronic pulmonary vascular disorder characterized by an increase in pulmonary vascular resistance and pulmonary arterial pressure. The detailed molecular mechanisms remain unclear. In recent decades, increasing evidence shows that altered immune microenvironment, comprised of immune cells, mesenchymal cells, extra-cellular matrix and signaling molecules, might induce the development of PH. Myeloid-derived suppressor cells (MDSCs) have been proposed over 30 years, and the functional importance of MDSCs in the immune system is appreciated recently. MDSCs are a heterogeneous group of cells that expand during cancer, chronic inflammation and infection, which have a remarkable ability to suppress T-cell responses and may exacerbate the development of diseases. Thus, targeting MDSCs has become a novel strategy to overcome immune evasion, especially in tumor immunotherapy. Nowadays, severe PH is accepted as a cancer-like disease, and MDSCs are closely related to the development and prognosis of PH. Here, we review the relationship between MDSCs and PH with respect to immune cells, cytokines, chemokines and metabolism, hoping that the key therapeutic targets of MDSCs can be identified in the treatment of PH, especially in severe PH.

Role of cellular senescence in inflammatory lung diseases

Cellular senescence, a characteristic sign of aging, classically refers to permanent cell proliferation arrest and is a vital contributor to the pathogenesis of cancer and age-related illnesses. A lot of imperative scientific research has shown that senescent cell aggregation and the release of senescence-associated secretory phenotype (SASP) components can cause lung inflammatory diseases as well. In this study, the most recent scientific progress on cellular senescence and phenotypes was reviewed, including their impact on lung inflammation and the contributions of these findings to understanding the underlying mechanisms and clinical relevance of cell and developmental biology. Within a dozen pro-senescent stimuli, the irreparable DNA damage, oxidative stress, and telomere erosion are all crucial in the long-term accumulation of senescent cells, resulting in sustained inflammatory stress activation in the respiratory system. An emerging role for cellular senescence in inflammatory lung diseases was proposed in this review, followed by the identification of the main ambiguities, thus further understanding this event and the potential to control cellular senescence and pro-inflammatory response activation. In addition, novel therapeutic strategies for the modulation of cellular senescence that might help to attenuate inflammatory lung conditions and improve disease outcomes were also presented in this research.

Combined transcriptome and proteome analysis of yak PASMCs under hypoxic and normoxic conditions

Background

Yaks are animals that have lived in plateau environments for generations. Yaks can adapt to the hypoxic plateau environment and also pass this adaptability on to the next generation. The lungs are the most important respiratory organs for mammals to adapt to their environment. Pulmonary artery smooth muscle cells play an important role in vascular remodeling under hypoxia, but the genetic mechanism underpinning the yak's ability to adapt to challenging plateau conditions is still unknown.

Methods

A tandem mass tag (TMT) proteomics study together with an RNA-seq transcriptome analysis were carried out on pulmonary artery smooth muscle cells (PASMCs) that had been grown for 72 hours in both normoxic (20% O2) and hypoxic (1% O2) environments. RNA and TP (total protein) were collected from the hypoxic and normoxic groups for RNA-seq transcriptome sequencing and TMT marker protein quantification, and RT-qPCR validation was performed.

Results

A total of 17,711 genes and 6,859 proteins were identified. Further, 5,969 differentially expressed genes (DEGs) and 531 differentially expressed proteins (DEPs) were identified in the comparison group, including 2,924 and 186 upregulated genes and proteins and 3,045 and 345 down-regulated genes and proteins, respectively. The transcriptomic and proteomic analyses revealed that 109 DEGs and DEPs were highly positively correlated, with 77 genes showing the same expression trend. Nine overlapping genes were identified in the HIF-1 signaling pathway, glycolysis / gluconeogenesis, central carbon metabolism in cancer, PPAR signaling pathway, AMPK signaling pathway, and cholesterol metabolism (PGAM1, PGK1, TPI1, HMOX1, IGF1R, OLR1, SCD, FABP4 and LDLR), suggesting that these differentially expressed genes and protein functional classifications are related to the hypoxia-adaptive pathways. Overall, our study offers abundant data for further analysis of the molecular mechanisms in yak PASMCs and their adaptability to different oxygen concentrations.

Aldehyde Dehydrogenase 2 (ALDH2) Elicits Protection against Pulmonary Hypertension via Inhibition of ERK1/2-Mediated Autophagy

Pulmonary hypertension (PH) is caused by chronic hypoxia that induces the migration and proliferation of pulmonary arterial smooth muscle cells (PASMCs), eventually resulting in right heart failure. PH has been related to aberrant autophagy; however, the hidden mechanisms are still unclear. Approximately 40% East Asians, equivalent to 8% of the universal population, carry a mutation in Aldehyde dehydrogenase 2 (ALDH2), which leads to the aggregation of noxious reactive aldehydes and increases the propensity of several diseases. Therefore, we explored the potential aspect of ALDH2 in autophagy associated with PH. In vitro mechanistic studies were conducted in human PASMCs (HPASMCs) after lentiviral ALDH2 knockdown and treatment with platelet-derived growth factor-BB (PDGF-BB). PH was induced in wild-type (WT) and ALDH2-knockout (ALDH2^−/−) mice using vascular endothelial growth factor receptor inhibitor SU5416 under hypoxic conditions (HySU). Right ventricular function was assessed using echocardiography and invasive hemodynamic monitoring. Histological and immunohistochemical analyses were performed to evaluate pulmonary vascular remodeling. EdU, transwell, and wound healing assays were used to evaluate HPASMC migration and proliferation, and electron microscopy and immunohistochemical and immunoblot assays were performed to assess autophagy. The findings demonstrated that ALDH2 deficiency exacerbated right ventricular pressure, hypertrophy, fibrosis, and right heart failure resulting from HySU-induced PH. ALDH2^−/− mice exhibited increased pulmonary artery muscularization and 4-hydroxynonenal (4-HNE) levels in lung tissues. ALDH2 knockdown increased PDGF-BB-induced PASMC migration and proliferation and 4-HNE accumulation in vitro. Additionally, ALDH2 deficiency increased the number of autophagosomes and autophagic lysosomes together with autophagic flux and ERK1/2-Beclin-1 activity in lung tissues and PASMCs, indicating enhanced autophagy. In conclusion, the study shows that ALDH2 has a protective role against the migration and proliferation of PASMCs and PH, possibly by regulating autophagy through the ERK1/2-Beclin-1 pathway.

Hypoxic pulmonary endothelial cells release epidermal growth factor leading to vascular smooth muscle cell arginase-2 expression and proliferation

The hallmark of pulmonary hypertension (PH) is vascular remodeling. We have previously shown that human pulmonary microvascular endothelial cells (hPMVEC) respond to hypoxia with epidermal growth factor (EGF) mediated activation of the receptor tyrosine kinase, EGF receptor (EGFR), resulting in arginase-2 (Arg2)-dependent proliferation. We hypothesized that the release of EGF by hPMVEC could result in the proliferation of human pulmonary arterial smooth muscle cells (hPASMC) via activation of EGFR on the hPASMC leading to Arg2 up-regulation. To test this hypothesis, we used conditioned media (CM) from hPMVEC grown either in normoxia (NCM) or hypoxia (HCM). Human PASMC were incubated in normoxia with either HCM or NCM, and HCM caused significant induction of Arg2 and viable cell numbers. When HCM was generated with either an EGF-neutralizing antibody or an EGFR blocking antibody the resulting HCM did not induce Arg2 or increase viable cell numbers in hPASMC. Adding an EGFR blocking antibody to HCM, prevented the HCM-induced increase in Arg2 and viable cell numbers. HCM induced robust phosphorylation of hPASMC EGFR. When hPASMC were transfected with siRNA against EGFR the HCM-induced increase in viable cell numbers was prevented. When hPASMC were treated with the arginase antagonist nor-NOHA, the HCM-induced increase in viable cell numbers was prevented. These data suggest that hypoxic hPMVEC releases EGF, which activates hPASMC EGFR leading to Arg2 protein expression and an increase in viable cell numbers. We speculate that EGF neutralizing antibodies or EGFR blocking antibodies represent potential therapeutics to prevent and/or attenuate vascular remodeling in PH associated with hypoxia.

Important Functions and Molecular Mechanisms of Mitochondrial Redox Signaling in Pulmonary Hypertension

Mitochondria are important organelles that act as a primary site to produce reactive oxygen species (ROS). Additionally, mitochondria play a pivotal role in the regulation of Ca²⁺ signaling, fatty acid oxidation, and ketone synthesis. Dysfunction of these signaling molecules leads to the development of pulmonary hypertension (PH), atherosclerosis, and other vascular diseases. Features of PH include vasoconstriction and pulmonary artery (PA) remodeling, which can result from abnormal proliferation, apoptosis, and migration of PA smooth muscle cells (PASMCs). These responses are mediated by increased Rieske iron–sulfur protein (RISP)-dependent mitochondrial ROS production and increased mitochondrial Ca²⁺ levels. Mitochondrial ROS and Ca²⁺ can both synergistically activate nuclear factor κB (NF-κB) to trigger inflammatory responses leading to PH, right ventricular failure, and death. Evidence suggests that increased mitochondrial ROS and Ca²⁺ signaling leads to abnormal synthesis of ketones, which play a critical role in the development of PH. In this review, we discuss some of the recent findings on the important interactive role and molecular mechanisms of mitochondrial ROS and Ca²⁺ in the development and progression of PH. We also address the contributions of NF-κB-dependent inflammatory responses and ketone-mediated oxidative stress due to abnormal regulation of mitochondrial ROS and Ca²⁺ signaling in PH.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Targeting Oxidative Stress as a Therapeutic Approach for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease characterized by an abnormal reepithelialisation, an excessive tissue remodelling and a progressive fibrosis within the alveolar wall that are not due to infection or cancer. Oxidative stress has been proposed as a key molecular process in pulmonary fibrosis development and different components of the redox system are altered in the cellular actors participating in lung fibrosis. To this respect, several activators of the antioxidant machinery and inhibitors of the oxidant species and pathways have been assayed in preclinical in vitro and in vivo models and in different clinical trials. This review discusses the role of oxidative stress in the development and progression of IPF and its underlying mechanisms as well as the evidence of oxidative stress in human IPF. Finally, we analyze the mechanism of action, the efficacy and the current status of different drugs developed to inhibit the oxidative stress as anti-fibrotic therapy in IPF.

miR-31-5p Promotes Oxidative Stress and Vascular Smooth Muscle Cell Migration in Spontaneously Hypertensive Rats via Inhibiting FNDC5 Expression

Oxidative stress and the migration of vascular smooth muscle cells (VSMCs) are important for vascular remodeling in a variety of vascular diseases. miR-31-5p promotes cell migration in colorectal cancer cells but inhibits cell migration in renal cell carcinoma. However, whether miR-31-5p is involved in oxidative stress and VSMC migration remains unknown. This study shows the crucial roles of miR-31-5p in oxidative stress and VSMC migration, as well as underlying mechanisms. Experiments were carried out in primary VSMCs from aortic media of Wistar–Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), as well as the A7r5 cell line. Oxidative stress was assessed by NADPH oxidase (NOX) expression, NOX activity, and reactive oxygen species (ROS) production. Cell migration was evaluated with a Boyden chamber assay and a wound healing assay. The miR-31-5p mimic and inhibitor promoted and attenuated oxidative stress and cell migration in the VSMCs of SHR, respectively. A dual-luciferase reporter assay indicated that miR-31-5p targeted the 3’UTR domain of FNDC5. The miR-31-5p level was raised and FNDC5 expression was reduced in the VSMCs of SHR compared with those of WKY. The miR-31-5p mimic reduced FNDC5 expression in the A7r5 cells and the VSMCs of both WKY and SHR, while the miR-31-5p inhibitor only increased FNDC5 expression in the VSMCs of SHR. Exogenous FNDC5 attenuated not only the oxidative stress and VSMC migration in SHR but also the roles of the miR-31-5p mimic in inducing oxidative stress and VSMC migration. These results indicate that miR-31-5p promotes oxidative stress and VSMC migration in SHR via inhibiting FNDC5 expression. The increased miR-31-5p and reduced FNDC5 in the VSMCs of SHR contribute to enhanced oxidative stress and cell migration.

The aging lung: Physiology, disease, and immunity

The population is aging at a rate never seen before in human history. As the number of elderly adults grows, it is imperative we expand our understanding of the underpinnings of aging biology. Human lungs are composed of a unique panoply of cell types that face ongoing chemical, mechanical, biological, immunological, and xenobiotic stress over a lifetime. Yet, we do not fully appreciate the mechanistic drivers of lung aging and why age increases the risk of parenchymal lung disease, fatal respiratory infection, and primary lung cancer. Here, we review the molecular and cellular aspects of lung aging, local stress response pathways, and how the aging process predisposes to the pathogenesis of pulmonary disease. We place these insights into context of the COVID-19 pandemic and discuss how innate and adaptive immunity within the lung is altered with age.

NADPH oxidases: Pathophysiology and therapeutic potential in age-associated pulmonary fibrosis

Oxidative stress has been associated with a number of human fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). Although oxidative stress is associated with both fibrosis and aging, the precise cellular sources(s) of reactive oxygen species (ROS) that contribute to the disease pathogenesis remain poorly understood. NADPH oxidase (Nox) enzymes are an evolutionarily conserved family, where their only known function is the production of ROS. A growing body of evidence supports a link between excessive Nox-derived ROS and numerous chronic diseases (including fibrotic disease), which is most prevalent among the elderly population. In this review, we examine the evidence for Nox isoforms in the pathogenesis of IPF, and the potential to target this enzyme family for the treatment of IPF and related fibrotic disorders. A better understanding of the Nox-mediated redox imbalance in aging may be critical to the development of more effective therapeutic strategies for age-associated fibrotic disorders. Strategies aimed at specifically blocking the source(s) of ROS through Nox inhibition may prove to be more effective as anti-fibrotic therapies, as compared to antioxidant approaches. This review also discusses the potential of Nox-targeting therapeutics currently in development.

MiR155-5p Inhibits Cell Migration and Oxidative Stress in Vascular Smooth Muscle Cells of Spontaneously Hypertensive Rats

Migration of vascular smooth muscle cells (VSMCs) is essential for vascular reconstruction in hypertension and several vascular diseases. Our recent study showed that extracellular vesicles derived from vascular adventitial fibroblasts of normal rats inhibited VSMC proliferation by delivering miR155-5p to VSMCs. It is unknown whether miR155-5p inhibits cell migration and oxidative stress in VSMCs of spontaneously hypertensive rats (SHR) and in angiotensin II (Ang II)-treated VSMCs. The purpose of this study was to determine the role of miR155-5p in VSMC migration and its underlying mechanisms. Primary VSMCs were isolated from the aortic media of Wistar-Kyoto rats (WKY) and SHR. Wound healing assay and Boyden chamber assay were used to evaluate VSMC migration. A miR155-5p mimic inhibited, and a miR155-5p inhibitor promoted the migration of VSMC of SHR but had no significant effect on the migration of VSMC of WKY. The miR155-5p mimic inhibited angiotensin-converting enzyme (ACE) mRNA and protein expression in VSMCs. It also reduced superoxide anion production, NAD(P)H oxidase (NOX) activity, as well as NOX2, interleukin-1β (IL-1β), and tumor necrosis factor α (TNF-α) expression levels in VSMCs of SHR but not in VSMCs of WKY rats. Overexpression of miR155-5p inhibited VSMC migration and superoxide anion and IL-1β production in VSMCs of SHR but had no impact on exogenous Ang II-induced VSMC migration and on superoxide anion and IL-1β production in WKY rats and SHR. These results indicate that miR155-5p inhibits VSMC migration in SHR by suppressing ACE expression and its downstream production of Ang II, superoxide anion, and inflammatory factors. However, miR155-5p had no effects on exogenous Ang II-induced VSMC migration.

Novel Regulators and Targets of Redox Signaling in Pulmonary Vasculature

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