An Update on the Role of Nrf2 in Respiratory Disease: Molecular Mechanisms and Therapeutic Approaches

Lead (Pb) Induces Osteotoxicity Through the Activation of Mutually Reinforced ER Stress and ROS in MC3T3-E1 Cells

Lead (Pb) is the most common contaminant of heavy metals and is widely present in the environment. Destruction of bone structure, malformation of bone development, and loss of bone mass are important pathological features of lead-exposed individuals. However, the exact molecular mechanisms associated with lead exposure and osteogenic injury are still not fully understood. MC3T3-E1 mouse embryonic osteoblast is a cell line widely used in osteoblast cytology. It can differentiate into mature osteoblasts and express bone-specific genes in cell culture. The doses of 1, 2, and 4 mM Pb were adopted to study the toxicity of Pb on MC3T3-E1 proliferation and differentiation. In this study, the results show that Pb increases the expression of apoptosis-related proteins, including PARP1, cleaved caspase-3, Bax, and cleaved caspase-9. More importantly, Pb activated endoplasmic reticulum stress and oxidative stress, as evident by elevated PERK/ATF4/CHOP and ROS/NRF2 signaling pathway. Pb induced ROS production in MC3T3-E1 cells through endoplasmic reticulum stress and produced a lethal effect. NAC mitigated these effects. Endoplasmic reticulum stress inhibitor 4-PBA can block the ER stress pathway, reduce ROS production, and enhance cell viability. In addition, studies have shown that ERO1 activation in the ER stress pathway is responsible for inducing ROS production. ROS produced by the mitochondrial pathway also aggravates ER stress. This study suggests that Pb induces MC3T3-E1 cell apoptosis by inducing PERK-mediated ER stress and NRF2-mediated oxidative stress via mutual enhancement, which may be an important mechanism leading to skeletal toxicity.

Selenomethionine alleviates Aeromonas hydrophila-induced oxidative stress and ferroptosis via the Nrf2/HO1/GPX4 pathway in grass carp

Aeromonas hydrophila infection is a severe, acute, and life-threatening disease affecting grass carp (Ctenopharyngodon idella) in aquaculture. Ferroptosis is a novel form of cell death characterized by the accumulation of free iron and harmful lipid peroxides within cells. While selenomethionine (Se-Met) is known to effectively inhibit ferroptosis and alleviate cell damage, its ability to counteract oxidative stress and ferroptosis induced by A. hydrophila remains unclear. The objective of this study is to reveal the possible mechanism behind the ferroptosis phenomenon during A. hydrophila infection. We established a macrophage model of A. hydrophila invasion to monitor the dynamic changes in iron metabolism markers to evaluate the correlation between ferroptotic stress and A. hydrophila infection. A. hydrophila infection induces cytotoxicity and mitochondrial membrane damage via ferroptosis. This damage is attributed to the accumulation of lipid peroxides due to intracellular ferrous ion overload and glutathione depletion. Supplementation of Se-Met reduced mitochondrial damage, enhanced antioxidant enzyme activity and reduced ferroptosis by activating the Nrf2/HO1/GPX4 axis. These findings provide new insights into the regulatory mechanisms of A. hydrophila-induced ferroptosis in teleosts and suggest that targeted inhibition of ferroptosis may offer a novel therapeutic strategy for managing A. hydrophila infections.

Influence and distinctions of particulate matter exposure across varying etiotypes in chronic obstructive pulmonary disease (COPD) mouse model

BACKGROUND

Air pollution, notably particulate matter (PM), significantly impacts chronic respiratory disease such chronic obstructive pulmonary disease (COPD). Although asthma-COPD overlap (ACO), considered one of the COPD etiotype, is associated with greater severity in both symptoms and outcomes, effects of PM exposure remain unclear. Thus, this study aimed to evaluate impact of PM on chronic airway disease animal models.

METHODS

We established two distinct COPD etiotypes, cigarette smoking-related COPD (COPD-C) and COPD with asthma (COPD-A), using porcine pancreatic elastase (PPE) for COPD-C and a combination of PPE with ovalbumin for COPD-A. To reflect smoking influence, cigarette smoking extract was administered to both disease models. To assess impact of PM exposure, bronchoalveolar lavage fluid (BALF), proinflammatory cytokines, lung histology, and cellular damage mechanisms were analyzed.

RESULTS

In the COPD-A model, cell counts and type 2 cytokines were elevated in BALF independent of PM exposure. All models exhibited increased lung inflammation and emphysema due to PM exposure. Expression levels of apoptosis-related protein B-cell lymphoma protein 2 (Bcl-2) associated X (Bax) showed an inclination to increase with PM exposure. In the COPD-A model, decreased expression of basal nuclear factor erythroid-derived 2-like 2 (Nrf-2) and increased production of reactive oxygen species (ROS) due to PM exposure were noted.

CONCLUSION

We developed two distinct models for the etiotypes of COPD and found increased vulnerability to cell damage in COPD-A after PM exposure. Moreover, the control group displayed escalated airway inflammation and emphysema due to PM exposure, substantiating the risk of respiratory diseases.

The role of Keap1-Nrf2 signaling pathway in the treatment of respiratory diseases and the research progress on targeted drugs

Lungs are exposed to external oxidants from the environment as in harmful particles and smog, causing oxidative stress in the lungs and consequently respiratory ailment. The NF-E2-related factor 2 (Nrf2) is the one with transcriptional regulatory function, while its related protein Kelch-like ECH-associated protein 1 (Keap1) inhibits Nrf2 activity. Together, they form the Keap1-Nrf2 pathway, which regulates the body's defense against oxidative stress. This pathway has been shown to maintain cellular homeostasis during oxidative stressing, inflammation, oncogenesis, and apoptosis by coordinating the expression of cytoprotective genes and making it a potential therapeutic target for respiratory diseases. This paper summarizes this point in detail in Chapter 2. In addition, this article summarizes the current drug development and clinical research progress related to the Keap1-Nrf2 signaling pathway, with a focus on the potential of Nrf2 agonists in treating respiratory diseases. Overall, the article reviews the regulatory mechanisms of the Keap1-Nrf2 signaling pathway in respiratory diseases and the progress of targeted drug research, aiming to provide new insights for treatment.

The Influence of Oxidative Stress Markers in Patients with Ischemic Stroke

Stroke is the second leading cause of death worldwide, and its incidence is rising rapidly. Acute ischemic stroke is a subtype of stroke that accounts for the majority of stroke cases and has a high mortality rate. An effective treatment for stroke is to minimize damage to the brain's neural tissue by restoring blood flow to decreased perfusion areas of the brain. Many reports have concluded that both oxidative stress and excitotoxicity are the main pathological processes associated with ischemic stroke. Current measures to protect the brain against serious damage caused by stroke are insufficient. For this reason, it is important to investigate oxidative and antioxidant strategies to reduce oxidative damage. This review focuses on studies assessing the concentration of oxidative stress biomarkers and the level of antioxidants (enzymatic and non-enzymatic) and their impact on the clinical prognosis of patients after stroke. Mechanisms related to the production of ROS/RNS and the role of oxidative stress in the pathogenesis of ischemic stroke are presented, as well as new therapeutic strategies aimed at reducing the effects of ischemia and reperfusion.

The role of Nrf2 signaling pathways in nerve damage repair

The protein, Nuclear factor-E2-related factor 2 (Nrf2), is a transitory protein that acts as a transcription factor and is involved in the regulation of many cytoprotective genes linked to xenobiotic metabolism and antioxidant responses. Based on the existing clinical and experimental data, it can be inferred that neurodegenerative diseases are characterized by an excessive presence of markers of oxidative stress (OS) and a reduced presence of antioxidant defense systems in both the brain and peripheral tissues. The presence of imbalances in the homeostasis between oxidants and antioxidants has been recognized as a substantial factor in the pathogenesis of neurodegenerative disorders. The dysregulations include several cellular processes such as mitochondrial failure, protein misfolding, and neuroinflammation. These dysregulations all contribute to the disruption of proteostasis in neuronal cells, leading to their eventual mortality. A noteworthy component of Nrf2, as shown by recent research undertaken over the last decade, is to its role in the development of resistance to OS. Nrf2 plays a pivotal role in regulating systems that defend against OS. Extant research offers substantiation for the protective and defensive roles of Nrf2 in the context of neurodegenerative diseases. The purpose of this study is to provide a comprehensive analysis of the influence of Nrf2 on OS and its function in regulating antioxidant defense systems within the realm of neurodegenerative diseases. Furthermore, we evaluate the most recent academic inquiries and empirical evidence about the beneficial and potential role of certain Nrf2 activator compounds within the realm of therapeutic interventions.

Copper homeostasis dysregulation in respiratory diseases: a review of current knowledge

Cu is an essential micronutrient for various physiological processes in almost all human cell types. Given the critical role of Cu in a wide range of cellular processes, the local concentrations of Cu and the cellular distribution of Cu transporter proteins in the lung are essential for maintaining a steady-state internal environment. Dysfunctional Cu metabolism or regulatory pathways can lead to an imbalance in Cu homeostasis in the lungs, affecting both acute and chronic pathological processes. Recent studies have identified a new form of Cu-dependent cell death called cuproptosis, which has generated renewed interest in the role of Cu homeostasis in diseases. Cuproptosis differs from other known cell death pathways. This occurs through the direct binding of Cu ions to lipoylated components of the tricarboxylic acid cycle during mitochondrial respiration, leading to the aggregation of lipoylated proteins and the subsequent downregulation of Fe-S cluster proteins, which causes toxic stress to the proteins and ultimately leads to cell death. Here, we discuss the impact of dysregulated Cu homeostasis on the pathogenesis of various respiratory diseases, including asthma, chronic obstructive pulmonary disease, idiopathic interstitial fibrosis, and lung cancer. We also discuss the therapeutic potential of targeting Cu. This study highlights the intricate interplay between copper, cellular processes, and respiratory health. Copper, while essential, must be carefully regulated to maintain the delicate balance between necessity and toxicity in living organisms. This review highlights the need to further investigate the precise mechanisms of copper interactions with infections and immune inflammation in the context of respiratory diseases and explore the potential of therapeutic strategies for copper, cuproptosis, and other related effects.

Evidence that a Novel Chalcone Derivative, Compound 27, Acts on the Epithelium Via the PI3K/AKT/Nrf2-Keap1 Signaling Pathway, to Mitigate LPS-Induced Acute Lung Injury in Mice

Acute lung injury (ALI) is a highly heterogeneous clinical syndrome and an important cause of mortality in critically ill patients, with limited treatment options currently available. Chalcone, an essential secondary metabolite found in edible or medicinal plants, exhibits good antioxidant activity and simple structure for easy synthesis. In our study, we synthesized a novel chalcone derivative, compound 27 (C27). We hypothesized that C27 could be a potential treatment for acute respiratory distress syndrome (ARDS). Therefore, the protective effects of C27 on lung epithelial cells during ALI and the underlying molecular mechanisms were investigated. In vivo, Intratracheal instillation of LPS (10 mg/kg) was used to induce acute lung injury in mice. In vitro, the bronchial epithelial cell line (Beas-2b) was treated with 30 μM tert-butyl hydroperoxide (t-BHP) to simulate oxidative stress. Our findings demonstrate that pretreatment with C27 reduces LPS-induced oxidative destruction and cellular apoptosis in lung tissues of mice. Furthermore, it significantly attenuates t-BHP-induced cellular reactive oxygen species (ROS) generation, mitochondrial damage, and apoptosis in vitro. Mechanistically, the signaling pathway involving Nrf2-Keap1 and the downstream antioxidative proteins were activated by C27 in vivo. Additionally, PI3K inhibitor LY294002 and Nrf2 inhibitor ML385 abolished the effect of C27 in vitro, indicating that the protective effect of C27 is mediated via the PI3K/AKT/Nrf2-Keap1 pathway. Our study provides evidence that C27 protects against LPS-induced ALI by mitigating oxidative stress via activation of the PI3K/AKT/Nrf2-Keap1 signaling pathway. Therefore, we hypothesize that C27 represents a viable alternative for ALI therapy.

Nrf-2 as a novel target in radiation induced lung injury

Radiation-induced lung injury (RILI) is a common and fatal complication of chest radiotherapy. The underlying mechanisms include radiation-induced oxidative stress caused by damage to the deoxyribonucleic acid (DNA) and production of reactive oxygen species (ROS), resulting in apoptosis of lung and endothelial cells and recruitment of inflammatory cells and myofibroblasts expressing NADPH oxidase to the site of injury, which in turn contribute to oxidative stress and cytokine production. Nuclear factor erythroid 2-related factor 2 (Nrf-2) is a vital transcription factor that regulates oxidative stress and inhibits inflammation. Studies have shown that Nrf-2 protects against radiation-induced lung inflammation and fibrosis. This review discusses the protective role of Nrf-2 in RILI and its possible mechanisms.

Nrf2/HO-1 signaling activation alleviates cigarette smoke-induced inflammation in chronic obstructive pulmonary disease by suppressing NLRP3-mediated pyroptosis

BACKGROUND

This study examined the effect of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway on chronic obstructive pulmonary disease (COPD) and the potential molecular mechanism.

METHODS

A COPD mouse model was established by cigarette smoke exposure and administered with either ML385 or dimethyl fumarate (DMF). Airway resistance of mice was detected. IL-1β and IL-6 levels in mice alveolar lavage fluid were examined by enzyme-linked immunosorbent assay. Hematoxylin and eosin staining and immunohistochemical of lung tissues were utilized to detect lung injury and NLRP3 expression. DMF was used to treat COPD cell model constructed by exposing normal human bronchial epithelial (NHBE) cells to cigarette smoke extract. NHBE cells were transfected by NLRP3-expression vectors. Expression of proteins was detected by Western blot.

RESULTS

COPD mice showed the enhanced airway resistance, the inactivated Nrf2/HO-1 pathway and the overexpressed NLRP3, Caspase-1 and GSDMD-N proteins in lung tissues, and the increased IL-1β and IL-6 levels in alveolar lavage fluid. ML385 treatment augmented these indicators and lung injury in COPD mice. However, DMF intervention attenuated these indicators and lung injury in COPD mice. Nrf2/HO-1 pathway inactivation and overexpression of NLRP3, Caspase-1 and GSDMD-N proteins were observed in COPD cells. DMF intervention activated Nrf2/HO-1 pathway and down-regulated NLRP3, Caspase-1 and GSDMD-N proteins in COPD cells. However, NLRP3 overexpression abolished the effect of DMF on COPD cells.

CONCLUSION

Nrf2/HO-1 pathway activation may alleviate inflammation in COPD by suppressing the NLRP3-related pyroptosis. Activating the Nrf2/HO-1 pathway may be an effective method to treat COPD.

Signaling pathways and potential therapeutic targets in acute respiratory distress syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a common condition associated with critically ill patients, characterized by bilateral chest radiographical opacities with refractory hypoxemia due to noncardiogenic pulmonary edema. Despite significant advances, the mortality of ARDS remains unacceptably high, and there are still no effective targeted pharmacotherapeutic agents. With the outbreak of coronavirus disease 19 worldwide, the mortality of ARDS has increased correspondingly. Comprehending the pathophysiology and the underlying molecular mechanisms of ARDS may thus be essential to developing effective therapeutic strategies and reducing mortality. To facilitate further understanding of its pathogenesis and exploring novel therapeutics, this review provides comprehensive information of ARDS from pathophysiology to molecular mechanisms and presents targeted therapeutics. We first describe the pathogenesis and pathophysiology of ARDS that involve dysregulated inflammation, alveolar-capillary barrier dysfunction, impaired alveolar fluid clearance and oxidative stress. Next, we summarize the molecular mechanisms and signaling pathways related to the above four aspects of ARDS pathophysiology, along with the latest research progress. Finally, we discuss the emerging therapeutic strategies that show exciting promise in ARDS, including several pharmacologic therapies, microRNA-based therapies and mesenchymal stromal cell therapies, highlighting the pathophysiological basis and the influences on signal transduction pathways for their use.

The Role of the NRF2 Pathway in the Pathogenesis of Viral Respiratory Infections

In humans, acute and chronic respiratory infections caused by viruses are associated with considerable morbidity and mortality. Respiratory viruses infect airway epithelial cells and induce oxidative stress, yet the exact pathogenesis remains unclear. Oxidative stress activates the transcription factor NRF2, which plays a key role in alleviating redox-induced cellular injury. The transcriptional activation of NRF2 has been reported to affect both viral replication and associated inflammation pathways. There is complex bidirectional crosstalk between virus replication and the NRF2 pathway because virus replication directly or indirectly regulates NRF2 expression, and NRF2 activation can reversely hamper viral replication and viral spread across cells and tissues. In this review, we discuss the complex role of the NRF2 pathway in the regulation of the pathogenesis of the main respiratory viruses, including coronaviruses, influenza viruses, respiratory syncytial virus (RSV), and rhinoviruses. We also summarize the scientific evidence regarding the effects of the known NRF2 agonists that can be utilized to alter the NRF2 pathway.

TRPA1: A promising target for pulmonary fibrosis?

Pulmonary fibrosis is a disease characterized by progressive scar formation and the ultimate manifestation of numerous lung diseases. It is known as "cancer that is not cancer" and has attracted widespread attention. However, its formation process is very complex, and the mechanism of occurrence has not been fully elucidated. Current research has found that TRPA1 may be a promising target in the pathogenesis of pulmonary fibrosis. The TRPA1 channel was first successfully isolated in human lung fibroblasts, and it was found to have a relatively concentrated distribution in the lungs and respiratory tract. It is also involved in various acute and chronic inflammatory processes of lung diseases and may even play a core role in the progression and/or prevention of pulmonary fibrosis. Natural ligands targeting TRPA1 could offer a promising alternative treatment for pulmonary diseases. Therefore, this review delves into the current understanding of pulmonary fibrogenesis, analyzes TRPA1 biological properties and regulation of lung disease with a focus on pulmonary fibrosis, summarizes the TRPA1 molecular structure and its biological function, and summarizes TRPA1 natural ligand sources, anti-pulmonary fibrosis activity and potential mechanisms. The aim is to decipher the exact role of TRPA1 channels in the pathophysiology of pulmonary fibrosis and to consider their potential in the development of new therapeutic strategies.

Curcumin Mitigates Malathion-Induced Renal Injury: Suppression of Apoptosis and Modulation of NF-κβ/TNF-α and Nrf2, and HO-1 Signaling

Malathion is one of the most used organophosphorus pesticides that is used for many reasons such as agriculture and industry. Human exposure to malathion may occur through various means, such as eating food that has been treated with it. Malathion not only increases oxidative stress but also decreases the antioxidant capacity. Curcumin is a powerful antioxidant with many pharmacological actions. Curcumin can act as a free radical scavenger and inhibit the activation and nuclear translocation of NF-κB. Curcumin could combat the lipid peroxidation and antioxidant depletion that trigger the apoptotic pathways. This study aims to examine the antioxidant, anti-inflammatory, and antiapoptotic effects of curcumin. Twenty-four Sprague Dawley rats were divided into four groups (six rats each): control, curcumin, malathion, and malathion + curcumin groups. At the assigned time, blood samples were used for the assessment of serum creatinine, and the kidneys were excised and washed; parts of them were used for the assessment of total oxidant status (TOS), oxidative stress index (OSI), the oxidative stress marker malondialdehyde (MDA), total antioxidant capacity (TAC), and glutathione (GSH) activity, other parts were fixed in formalin for further staining. Histopathological evaluation was performed for the fixed specimens after staining with H&E, sirus red, and the immunohistochemical staining for NF-κβ, TNF-α, Caspase-3, Nrf2, and HO-1. Curcumin significantly decreases the serum creatinine after malathion exposure and significantly restores the oxidant/antioxidant balance by increasing TAC and GSH and decreasing TOS, OSI, and MDA. Curcumin exerts its reno-protective effect and restores the histological architecture of the kidney by downregulating the immune expression of NF-κβ, TNF-α, and Caspase-3 and upregulating the expression of Nrf2 and HO-1. This study concluded that curcumin protects against nephrotoxicity caused by malathion by exerting its antioxidant, anti-inflammatory, and anti-apoptotic capabilities.

Salidroside alleviates diet-induced obesity and insulin resistance by activating Nrf2/ARE pathway and enhancing the thermogenesis of adipose tissues

Recent reports suggest that salidroside protects cardiomyocytes from oxidative injury and stimulates glucose uptake by skeletal muscle cells. Despite these findings, the therapeutic potential of salidroside in the treatment of obesity and insulin resistance remains uncertain and requires further investigation. In the present study, the treatment effect of salidroside on the onset and development of the obese phenotype and insulin resistance as well as the underlying mechanisms was investigated using long-term high-fat diet-induced obese mice supplemented with salidroside. We used biochemical kits to determine serum biochemical parameters (including triacylglycerol, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, fasting glucose, and insulin). The results show that salidroside-supplemented animals showed better glucose tolerance and insulin sensitivity, decreased blood lipids, and weight gain (p < .05). Protein expression of p-Nrf2 and Nrf2 was analyzed by western blotting, and the mRNA levels of thermogenic-related genes (Ucp1, Pgc1a, Prdm16, and Cidea) were detected by quantitative RT-PCR. The results show an improvement in lipid peroxidation and Nrf2/ARE signaling, as well as an increased expression of the Ucp1, Pgc1a, Prdm16, and Cidea (p < .05). Our evidence suggests that salidroside alleviates diet-induced obesity and insulin resistance potentially by activating Nrf2/ARE pathway and enhancing the thermogenesis of adipose tissues. This induction represents a potential technique for the management of comorbidities related to obesity and its prevention.

Safflor Yellow A Protects Beas-2B Cells Against LPS-Induced Injury via Activating Nrf2

Acute lung injury and its severe form acute respiratory distress syndrome are lethal lung diseases. So far, effective therapy for the diseases is deficient and the prognosis is poor. Recently, it was found activating nuclear factor erythroid 2-related factor 2 could attenuate the injury including inflammation, oxidative stress, and apoptosis in those diseases. To discover novel therapy, we have evaluated safflor yellow A and explored the underlying mechanisms using Beas-2B cells injured by lipopolysaccharide. As a result, safflor yellow A could improve the viability of Beas-2B cells treated with lipopolysaccharide. Further investigations have revealed safflor yellow A suppressed oxidative stress induced by lipopolysaccharide via reducing reactive oxygen species and malondialdehyde, and elevating superoxide dismutase, catalase, and glutathione peroxidase. Meanwhile, the inflammation resulting from lipopolysaccharide was ameliorated through decreasing the pro-inflammatory cytokines including tumor necrosis factor-α, interleukin-1β, and interleukin-6. It was also found nuclear factor κB was inactivated by safflor yellow A. In addition, safflor yellow A downregulated cysteinyl aspartate specific proteinase-3 and Bcl-2-associated X protein and upregulated B-cell lymphoma-2 to inhibited apoptosis of Beas-2B cells induced by lipopolysaccharide. The activation of nuclear factor erythroid 2-related factor 2 was observed in Beas-2B cells, which was associated with the protective effects of safflor yellow A. And molecular docking elucidated safflor yellow A interacted with Kelch-like ECH-associated protein 1 to activate nuclear factor erythroid 2-related factor 2. These results can provide evidences for the discovery of novel therapy for further evaluation of safflor yellow A in the treatment of acute lung injury and acute respiratory distress syndrome.

Graphical Abstract

Sex-specific association of exposure to air pollutants and Nrf2 gene expression and inflammatory biomarkers in exhaled breath of healthy adolescents

Studies investigating the nuclear factor erythroid 2-related factor 2 (Nrf2) expression levels in the respiratory system of healthy subjects are scarce. Moreover, separate studies on the health-related outcomes of air pollution for each sex are limited. The current panel study investigated sex-specific Nrf2 expression levels and related oxidative stress and inflammatory responses among healthy adolescents exposed to PM2.5, PM10, O3, and PM2.5-bounded metals in a high traffic region. Forty-nine healthy nonsmoking subjects participated in the study for five consecutive months (Nov. 2019 to Feb. 2020). Each subject was asked to provide 1 mL of exhaled breath condensate (EBC). Data were analyzed using linear mixed-effects models. The results showed that PM10, PM2.5, O3, and PM2.5-bounded metals were negatively linked to Nrf2 expression level in EBC of females with -58.3% (95% CI: 79.5, -15.4), -32.1% (95% CI: -50.3, -7.1), -76.2% (95% CI: -92.6, -23.9), and -1.9 (95% CI: -3.4, -0.4), respectively. While our results presented no significant association between the studied pollutants and Nrf2 gene expression in males, significant associations were observed between the pollutants and total nitric oxide (NOx), interleukins 6 (IL-6), and tumor necrosis factor-alpha (TNF-α) in the EBC of females. In the case of males, only EBC cytokines showed a significant association with air pollutants. Overall, this study suggests that exposure to ambient air pollutants may affect the respiratory system with biologically different mechanisms in males and females. PM2.5 concentration had a positive correlation with exhaled TNF-α and IL6 values in females while positive correlation with TNF-α and negative correlation with IL6 values in males. O3 had a negative correlation with TNF-α in males.

Inhibition of lincRNA-Cox2 alleviates apoptosis and inflammatory injury of lipopolysaccharide-stimulated human bronchial epithelial cells via the Nrf2/HO-1 axis

This study mainly explored the role and mechanism of lincRNA-Cox2 in inflammatory injury of human bronchial epithelial cells. BEAS-2B cells were stimulated with lipopolysaccharide to establish an in vitro inflammatory injury model. Real-time polymerase chain reaction was used to detect lincRNA-Cox2 expression in LPS-stimulated BEAS-2B. Cell viability and apoptosis of cells were assessed using CCK-8 and Annexin V-PI double staining. The contents of inflammatory factors were determined by enzyme-linked immunosorbent assay kits. The protein levels of nuclear factor erythrocyte 2-related factor 2 and haem oxygenase 1 protein levels were measured by Western blot. The results showed that lincRNA-Cox2 was upregulated in LPS-stimulated BEAS-2B cells. lincRNA-Cox2 knockdown inhibited apoptosis and the release of tumour necrosis factor alpha, interleukin 1beta (IL-1β), IL-4, IL-5, and IL-13 in BEAS-2B cells. lincRNA-Cox2 overexpression had the opposite effect. lincRNA-Cox2 knockdown also inhibited LPS-induced oxidative damage in BEAS-2B cells. Further mechanistic studies showed that inhibition of lincRNA-Cox2 upregulated the levels of Nrf2 and HO-1, and si-Nrf2 reversed the effects of si-lincRNA-Cox2. In conclusion, lincRNA-Cox2 knockdown inhibited BEAS-2B apoptosis and the level of inflammatory factors by activating the Nrf2/HO-1 pathway.

Conventional, Complementary and Alternative Medicines: Mechanistic Insights into Therapeutic Landscape of Chronic Obstructive Pulmonary Disease

COPD (chronic obstructive pulmonary disease) is a major public health concern associated with significant morbidity and mortality worldwide. Current therapeutic guidelines for this disease recommend starting with an inhaled bronchodilator, stepping up to combination therapy as necessary, and/or adding inhaled corticosteroids as symptoms and airflow obstruction progress. However, no drug therapy exists to stop disease progression. The mechanistic definition underlying COPD pathogenesis remains poorly understood, it is generally accepted that oxidative stress and the altered immune response of low-grade airway inflammation are major factors contributing to COPD development. There are several potential therapeutic targets that are currently under investigation, including immune regulatory pathways in inflammation and lung-associated steroid resistance induced by oxidative stress signaling cascades. Patients with COPD have increased levels of inflammatory mediators, including lipid and peptide mediators, as well as a network of cytokines and chemokines that maintain inflammatory immune response and recruit circulating cells into the lungs. Many of these pro-inflammatory mediators are regulated by nuclear factor-kappaB (NF-κB) and mitogen-activated protein kinases (MAPKs), such as p38 MAPK. Increased oxidative stress is a key driving mechanism in perpetuating inflammation and lung injury. Furthermore, many proteases that degrade elastin fibres are secreted by airway resident infiltrating immune cells in COPD patients. In this perspective, we discuss novel aspects of signaling pathway activation in the context of inflammation and oxidative stress, and the broad view of potential effective pharmacotherapies that target the underlying mechanistic disease process in COPD.

Skeletal Muscle Mitochondrial Dysfunction in Chronic Obstructive Pulmonary Disease: Underlying Mechanisms and Physical Therapy Perspectives

Skeletal muscle dysfunction (SMD) is a prevalent extrapulmonary complication and a significant independent prognostic factor in patients with chronic obstructive pulmonary disease (COPD). Mitochondrial dysfunction is one of the core factors that damage structure and function in COPD skeletal muscle and is closely related to smoke exposure, hypoxia, and insufficient physical activity. The currently known phenotypes of mitochondrial dysfunction are reduced mitochondrial content and biogenesis, impaired activity of mitochondrial respiratory chain complexes, and increased mitochondrial reactive oxygen species production. Significant progress has been made in research on physical therapy (PT), which has broad prospects for treating the abovementioned potential mitochondrial-function changes in COPD skeletal muscle. In terms of specific types of PT, exercise therapy can directly act on mitochondria and improve COPD SMD by increasing mitochondrial density, regulating mitochondrial biogenesis, upregulating mitochondrial respiratory function, and reducing oxidative stress. However, improvements in mitochondrial-dysfunction phenotype in COPD skeletal muscle due to different exercise strategies are not entirely consistent. Therefore, based on the elucidation of this phenotype, in this study, we analyzed the effect of exercise on mitochondrial dysfunction in COPD skeletal muscle and the regulatory mechanism thereof. We also provided a theoretical basis for exercise programs to rehabilitate this condition.

Antioxidant Defense in Primary Murine Lung Cells following Short- and Long-Term Exposure to Plastic Particles

Polystyrene nano- and micro-sized plastic particles (NMP) are one of the common plastic materials produced that dramatically pollute the environment, water, and oceanic habitats worldwide. NMP are continuously absorbed by the body through a number of routes, especially via intestinal ingestion, dermal uptake, and inhalation into the lung. Several studies provided evidence of NMP provoking oxidative stress and affecting cellular responses. Yet, the NMP effects on primary lung cells have not been studied. To this end, we isolated and cultured murine lung cells and exposed them short-term or long-term to polystyrene 0.2-6.0 µm-sized NMP. We studied cellular consequences regarding oxidative stress, morphology, and secretion profiling. Visualization, distribution, and expression analyses confirmed lung cells accumulating NMP and showed several significant correlations with particle size. Moreover, we found substantial evidence of biological consequences of small-scale NMP uptake in lung cells. Besides alterations of cytokine secretion profiles resulting in inflammatory responses, indicators of oxidative stress were identified that were accompanied by Nrf2 and β-catenin signaling changes. Our results serve as an important basis to point out the potential hazards of plastic contaminations and uptake in lung cells.

Role of Ferroptosis in Regulating the Epithelial-Mesenchymal Transition in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a chronic interstitial lung disease whose pathogenesis involves a complex interaction of cell types and signaling pathways. Lung epithelial cells responding to repeated injury experience persistent inflammation and sustained epithelial-mesenchymal transition (EMT). The persistence of EMT-induced signals generates extracellular matrix accumulation, thereby causing fibrosis. Ferroptosis is a newly characterized iron-dependent non-apoptotic regulated cell death. Increased iron accumulation can increase iron-induced oxidant damage in alveolar epithelial cells. Studies have demonstrated that iron steady states and oxidation steady states play an important role in the iron death regulation of EMT. This review summarizes the role of ferroptosis in regulating EMT in pulmonary fibrosis, aiming to provide a new idea for the prevention and treatment of this disease.

Overview of the Mechanisms of Oxidative Stress: Impact in Inflammation of the Airway Diseases

Inflammation of the human lung is mediated in response to different stimuli (e.g., physical, radioactive, infective, pro-allergenic or toxic) such as cigarette smoke and environmental pollutants. They often promote an increase in inflammatory activities in the airways that manifest themselves as chronic diseases (e.g., allergic airway diseases, asthma, chronic bronchitis/chronic obstructive pulmonary disease (COPD) or even lung cancer). Increased levels of oxidative stress (OS) reduce the antioxidant defenses, affect the autophagy/mitophagy processes, and the regulatory mechanisms of cell survival, promoting inflammation in the lung. In fact, OS potentiate the inflammatory activities in the lung, favoring the progression of chronic airway diseases. OS increases the production of reactive oxygen species (ROS), including superoxide anions (O₂^-), hydroxyl radicals (OH) and hydrogen peroxide (H₂O₂), by the transformation of oxygen through enzymatic and non-enzymatic reactions. In this manner, OS reduces endogenous antioxidant defenses in both nucleated and non-nucleated cells. The production of ROS in the lung can derive from both exogenous insults (cigarette smoke or environmental pollution) and endogenous sources such as cell injury and/or activated inflammatory and structural cells. In this review, we describe the most relevant knowledge concerning the functional interrelation between the mechanisms of OS and inflammation in airway diseases.

Endoplasmic Reticulum Stress in Chronic Obstructive Pulmonary Disease: Mechanisms and Future Perspectives

The endoplasmic reticulum (ER) is an integral organelle for maintaining protein homeostasis. Multiple factors can disrupt protein folding in the lumen of the ER, triggering ER stress and activating the unfolded protein response (UPR), which interrelates with various damage mechanisms, such as inflammation, apoptosis, and autophagy. Numerous studies have linked ER stress and UPR to the progression of chronic obstructive pulmonary disease (COPD). This review focuses on the mechanisms of other cellular processes triggered by UPR and summarizes drug intervention strategies targeting the UPR pathway in COPD to explore new therapeutic approaches and preventive measures for COPD.

Antioxidant, Anti-inflammatory, and Immunomodulatory Roles of Nonvitamin Antioxidants in Anti-SARS-CoV-2 Therapy

Viral pathologies encompass activation of pro-oxidative pathways and inflammatory burst. Alleviating overproduction of reactive oxygen species and cytokine storm in COVID-19 is essential to counteract the immunogenic damage in endothelium and alveolar membranes. Antioxidants alleviate oxidative stress, cytokine storm, hyperinflammation, and diminish the risk of organ failure. Direct antiviral roles imply: impact on viral spike protein, interference with the ACE2 receptor, inhibition of dipeptidyl peptidase 4, transmembrane protease serine 2 or furin, and impact on of helicase, papain-like protease, 3-chyomotrypsin like protease, and RNA-dependent RNA polymerase. Prooxidative environment favors conformational changes in the receptor binding domain, promoting the affinity of the spike protein for the host receptor. Viral pathologies imply a vicious cycle, oxidative stress promoting inflammatory responses, and vice versa. The same was noticed with respect to the relationship antioxidant impairment-viral replication. Timing, dosage, pro-oxidative activities, mutual influences, and interference with other antioxidants should be carefully regarded. Deficiency is linked to illness severity.

Loranthus tanakae Franch. & Sav. Suppresses Inflammatory Response in Cigarette Smoke Condensate Exposed Bronchial Epithelial Cells and Mice

Loranthus tanakae Franch. & Sav. found in China, Japan, and Korea is traditionally used for managing arthritis and respiratory diseases. In this study, we analyzed the components of L. tanakae 70% ethanol extract (LTE) and investigated the therapeutic effects of LTE on pulmonary inflammation using cells exposed to cigarette smoke condensate (CSC) and lipopolysaccharide (LPS) in vitro and in vivo in mice and performed a network analysis between components and genes based on a public database. We detected quercitrin, afzelin, rhamnetin 3-rhamnoside, and rhamnocitrin 3-rhamnoside in LTE, which induced a significant reduction in inflammatory mediators including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and inflammatory cells in CSC exposed H292 cells and in mice, accompanied by a reduction in inflammatory cell infiltration into lung tissue. In addition, LTE increased translocation into the nuclei of nuclear factor erythroid-2-related factor 2 (Nrf2). By contrast, the activation of nuclear factor (NF)-κB, induced by CSC exposure, decreased after LTE application. These results were consistent with the network pharmacological analysis. In conclusion, LTE effectively attenuated pulmonary inflammation caused by CSC+LPS exposure, which was closely involved in the enhancement of Nrf2 expression and suppression of NF-κB activation. Therefore, LTE may be a potential treatment option for pulmonary inflammatory diseases including chronic obstructive pulmonary disease (COPD).

Pharmacological characterization of a novel peptide inhibitor of the Keap1-Nrf2 protein-protein interaction

LAS200813 is a novel bicyclic lipopeptide that activates Nrf2 by binding to Keap1, thereby antagonising the Keap1-Nrf2 protein-protein interaction. In this work we report the pharmacological characterization of LAS200813 in Nrf2-dependent translational preclinical models. LAS200813 binds to Keap1 with high affinity (IC₅₀: 0.73 nM) and is able to induce the translocation of Nrf2 to the nucleus. Furthermore, LAS200813 increases the expression of Nrf2 target genes in human bronchial epithelial cells (EC₅₀ of 96 and 70 nM for srxn1 and nqo1, respectively). Similarly, the intratracheal administration of LAS200813 to rats increases the expression of Nrf2-dependent genes in lung tissue, an effect that lasts for a few hours. Moreover, in cells exposed to cigarette smoke, LAS200813 shows an antioxidant effect by increasing the production of glutathione and prevents cellular apoptosis. In conclusion, the results described herein demonstrate that LAS200813 is a potent non-electrophilic Nrf2-activating peptide designed to be administered by inhaled route which may be a potential therapeutic strategy for respiratory diseases driven by oxidative stress.

Antioxidant Effects of Dietary Supplements on Adult COVID-19 Patients: Why Do We Not Also Use Them in Children?

Respiratory tract infections (RTIs) are very common in children, especially in the first five years of life, and several viruses, such as the influenza virus, Respiratory Syncytial Virus, and Rhinovirus, are triggers for symptoms that usually affect the upper airways. It has been known that during respiratory viral infections, a condition of oxidative stress (OS) occurs, and many studies have suggested the potential use of antioxidants as complementary components in prophylaxis and/or therapy of respiratory viral infections. Preliminary data have demonstrated that antioxidants may also interfere with the new coronavirus 2’s entry and replication in human cells, and that they have a role in the downregulation of several pathogenetic mechanisms involved in disease severity. Starting from preclinical data, the aim of this narrative review is to evaluate the current evidence about the main antioxidants that are potentially useful for preventing and treating Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection in adults and to speculate on their possible use in children by exploring the most relevant issues affecting their use in clinical practice, as well as the associated evidence gaps and research limitations.

Green Tea Polyphenol (-)-Epigallocatechin-3-Gallate (EGCG): A Time for a New Player in the Treatment of Respiratory Diseases?

(-)-Epigallocatechin-3-gallate (EGCG) is a major polyphenol of green tea that possesses a wide variety of actions. EGCG acts as a strong antioxidant which effectively scavenges reactive oxygen species (ROS), inhibits pro-oxidant enzymes including NADPH oxidase, activates antioxidant systems including superoxide dismutase, catalase, or glutathione, and reduces abundant production of nitric oxide metabolites by inducible nitric oxide synthase. ECGC also exerts potent anti-inflammatory, anti-fibrotic, pro-apoptotic, anti-tumorous, and metabolic effects via modulation of a variety of intracellular signaling cascades. Based on this knowledge, the use of EGCG could be of benefit in respiratory diseases with acute or chronic inflammatory, oxidative, and fibrotizing processes in their pathogenesis. This article reviews current information on the biological effects of EGCG in those respiratory diseases or animal models in which EGCG has been administered, i.e., acute respiratory distress syndrome, respiratory infections, COVID-19, bronchial asthma, chronic obstructive pulmonary disease, lung fibrosis, silicosis, lung cancer, pulmonary hypertension, and lung embolism, and critically discusses effectiveness of EGCG administration in these respiratory disorders. For this review, articles in English language from the PubMed database were used.

Roles of NRF2 in Fibrotic Diseases: From Mechanisms to Therapeutic Approaches

Fibrosis is a persistent inflammatory response that causes scarring and tissue sclerosis by stimulating myofibroblasts to create significant quantities of extracellular matrix protein deposits in the tissue. Oxidative stress has also been linked to the development of fibrosis in several studies. The nuclear erythroid 2-related factor 2 (NRF2) transcription factor controls the expression of several detoxification and antioxidant genes. By binding to antioxidant response elements, NRF2 is activated by oxidative or electrophilic stress and promotes its target genes, resulting in a protective effect on cells. NRF2 is essential for cell survival under oxidative stress conditions. This review describes Kelch-like epichlorohydrin-associated protein 1 (KEAP1)/NRF2 signaling mechanisms and presents recent research advances regarding NRF2 and its involvement in primary fibrotic lesions such as pulmonary fibrosis, hepatic fibrosis, myocardial fibrosis, and renal fibrosis. The related antioxidant substances and drugs are described, along with the mechanisms by which KEAP1/NRF2 regulation positively affects the therapeutic response. Finally, the therapeutic prospects and potential value of NRF2 in fibrosis are summarized. Further studies on NRF2 may provide novel therapeutic approaches for fibrosis.

Oxidative Stress in Chronic Obstructive Pulmonary Disease

There is a marked increase in oxidative stress in the lungs of patients with COPD, as measured by increased exhaled 8-isoprostane, ethane, and hydrogen peroxide in the breath. The lung may be exposed to exogenous oxidative stress from cigarette smoking and indoor or outdoor air pollution and to endogenous oxidative stress from reactive oxygen species released from activated inflammatory cells, particularly neutrophils and macrophages, in the lungs. Oxidative stress in COPD may be amplified by a reduction in endogenous antioxidants and poor intake of dietary antioxidants. Oxidative stress is a major driving mechanism of COPD through the induction of chronic inflammation, induction of cellular senescence and impaired autophagy, reduced DNA repair, increased autoimmunity, increased mucus secretion, and impaired anti-inflammatory response to corticosteroids. Oxidative stress, therefore, drives the pathology of COPD and may increase disease progression, amplify exacerbations, and increase comorbidities through systemic oxidative stress. This suggests that antioxidants may be effective as disease-modifying treatments. Unfortunately, thiol-based antioxidants, such as N-acetylcysteine, have been poorly effective, as they are inactivated by oxidative stress in the lungs, so there is a search for more effective and safer antioxidants. New antioxidants in development include mitochondria-targeted antioxidants, NOX inhibitors, and activators of the transcription factor Nrf2, which regulates several antioxidant genes.

Melatonin attenuates LPS-induced pyroptosis in acute lung injury by inhibiting NLRP3-GSDMD pathway via activating Nrf2/HO-1 signaling axis

Acute lung injury (ALI)/ acute respiratory distress syndrome (ARDS) is featured by intensive inflammatory responses and oxidative stress, which lead to cytokine storms and pyroptosis. Here, we aimed to investigate whether melatonin was capable of alleviating LPS-induced ALI via activating the nuclear factor erythroid 2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signaling axis and inhibiting pyroptosis. Mice were injected with melatonin (30 mg/kg) intraperitoneally for consecutive five days before LPS instillation intratracheally, and human alveolar epithelial cell (AECⅡ) A549 cell lines and murine macrophages Raw264.7 cell lines were pretreated with melatonin (400 μM) before LPS (10 μg/ml) stimulation. The result demonstrated that LPS induced obvious lung injury characterized by alveolar damage, neutrophil infiltration and lung edema as well as the reduction of the survival rate of mice, which were totally reversed by melatonin pretreatment. Mechanistically, melatonin pretreatment activated nuclear factor erythroid2-related factor (Nrf) 2 signaling, subsequently, drove antioxidant pathways including significant increases in the expression of Nrf2, HO-1, NQO1, Mn-SOD and Catalase in vivo and in vitro. Simultaneously, melatonin inhibited ROS and MDA overproduction, iNOS expression as well as TNF-α and IL-1β expression and release. Furthermore, melatonin inhibited LPS-induced pyroptosis by reversing the overexpression of NLRP3, Caspase-1, IL-1β, IL-18 and GSDMD-N, as well as LDH release and TUNEL-positive cells in A549 cells and Raw264.7 cells. Overall, the current study suggests that melatonin exerts protective roles on LPS-induced ALI and pyroptosis by inhibiting NLRP3-GSDMD pathway via activating Nrf2/HO-1 signaling axis.

Obacunone alleviates ferroptosis during lipopolysaccharide-induced acute lung injury by upregulating Nrf2-dependent antioxidant responses

BACKGROUND

Acute lung injury (ALI) has received considerable attention in the field of intensive care as it is associated with a high mortality rate. Obacunone (OB), widely found in citrus fruits, is a natural bioactive compound with anti-inflammatory and antioxidant activities. However, it is not clear whether OB protects against lipopolysaccharide (LPS)-induced ALI. Therefore, in this study, we aimed to evaluate the protective effects of OB and the potential mechanisms against LPS-induced ALI and BEAS-2B cell injury.

METHODS

We established a model of BEAS-2B cell injury and a mouse model of ALI by treating with LPS. Samples of in vitro model were subjected to cell death, Cell Counting Kit-8, and lactate dehydrogenase (LDH) release assays. The total number of cells and neutrophils, protein content, and levels of IL-6, TNF-α, and IL-1β were determined in bronchoalveolar lavage fluid (BALF). Glutathione, reactive oxygen species, and malondialdehyde levels were determined in lung tissue. Additionally, immunohistochemical analysis, immunofluorescence, western blot, quantitative real-time PCR, and enzyme-linked immunosorbent assay were conducted to examine the effects of OB. Furthermore, mice were treated with an Nrf2 inhibitor (ML385) to verify its role in ferroptosis. Data were analyzed using one-way analysis of variance or paired t-tests.

RESULTS

Compared with the LPS group, OB effectively alleviated LPS-induced ALI by decreasing lung wet/dry weight ratio, reactive oxygen species and malondialdehyde production, and superoxide dismutase and glutathione consumption in vivo. In addition, OB significantly alleviated lung histopathological injury, reduced inflammatory cytokine secretion and Fe²⁺ and 4-HNE levels, and upregulated GPX4, SLC7A11, and Nrf2 expression. Mechanistically, OB activated Nrf2 by inhibiting Nrf2 ubiquitinated proteasome degradation. ML385 reversed the protective effects of OB against LPS-induced ALI.

CONCLUSION

Overall, OB alleviates LPS-induced ALI, making it a potential novel protective agent against LPS-induced ALI.

Molecular hydrogen is a potential protective agent in the management of acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome, which is a more severe form of ALI, are life-threatening clinical syndromes observed in critically ill patients. Treatment methods to alleviate the pathogenesis of ALI have improved to a great extent at present. Although the efficacy of these therapies is limited, their relevance has increased remarkably with the ongoing pandemic caused by the novel coronavirus disease 2019 (COVID-19), which causes severe respiratory distress syndrome. Several studies have demonstrated the preventive and therapeutic effects of molecular hydrogen in the various diseases. The biological effects of molecular hydrogen mainly involve anti-inflammation, antioxidation, and autophagy and cell death modulation. This review focuses on the potential therapeutic effects of molecular hydrogen on ALI and its underlying mechanisms and aims to provide a theoretical basis for the clinical treatment of ALI and COVID-19.

Oxidative Stress and Assisted Reproduction: A Comprehensive Review of Its Pathophysiological Role and Strategies for Optimizing Embryo Culture Environment

Oxidative stress (OS) due to an imbalance between reactive oxygen species (ROS) and antioxidants has been established as an important factor that can negatively affect the outcomes of assisted reproductive techniques (ARTs). Excess ROS exert their pathological effects through damage to cellular lipids, organelles, and DNA, alteration of enzymatic function, and apoptosis. ROS can be produced intracellularly, from immature sperm, oocytes, and embryos. Additionally, several external factors may induce high ROS production in the ART setup, including atmospheric oxygen, CO2 incubators, consumables, visible light, temperature, humidity, volatile organic compounds, and culture media additives. Pathological amounts of ROS can also be generated during the cryopreservation-thawing process of gametes or embryos. Generally, these factors can act at any stage during ART, from gamete preparation to embryo development, till the blastocyst stage. In this review, we discuss the in vitro conditions and environmental factors responsible for the induction of OS in an ART setting. In addition, we describe the effects of OS on gametes and embryos. Furthermore, we highlight strategies to ameliorate the impact of OS during the whole human embryo culture period, from gametes to blastocyst stage.

Antioxidants as Therapeutic Agents in Acute Respiratory Distress Syndrome (ARDS) Treatment-From Mice to Men

Acute respiratory distress syndrome (ARDS) is a major cause of patient mortality in intensive care units (ICUs) worldwide. Considering that no causative treatment but only symptomatic care is available, it is obvious that there is a high unmet medical need for a new therapeutic concept. One reason for a missing etiologic therapy strategy is the multifactorial origin of ARDS, which leads to a large heterogeneity of patients. This review summarizes the various kinds of ARDS onset with a special focus on the role of reactive oxygen species (ROS), which are generally linked to ARDS development and progression. Taking a closer look at the data which already have been established in mouse models, this review finally proposes the translation of these results on successful antioxidant use in a personalized approach to the ICU patient as a potential adjuvant to standard ARDS treatment.