Thioredoxin-albumin fusion protein prevents urban aerosol-induced lung injury via suppressing oxidative stress-related neutrophil extracellular trap formation

Neutrophil extracellular traps and oxidative stress in systemic lupus erythematosus patients with and without renal involvement

OBJECTIVES

To investigate the levels of plasma neutrophil extracellular traps (NETs) and free thiols, the latter reflecting systemic oxidative stress (OS), and to explore the relationship between NETs and OS in quiescent systemic lupus erythematosus (SLE) patients with and without renal involvement.

METHODS

Plasma levels of NETs and free thiols were measured cross-sectionally in 100 SLE patients with low disease activity (SLEDAI < 5), of whom 73 patients had no renal involvement (non-LN) and 27 patients had lupus nephritis (LN). Additionally, 22 healthy controls (HCs) were included. NETs were measured using a myeloperoxidase-DNA complex ELISA and free thiols were measured using a thiol assay kit.

RESULTS

NETs levels were significantly higher in both non-LN and LN patients compared to HCs (p < 0.001, p = 0.013), with no difference between the two patient groups (p = 0.799). Free thiol levels were not significantly different between groups. Interestingly, NETs were negatively correlated with free thiols in all 100 SLE patients (rho = -0.32) and non-LN patients (rho = -0.38), but not in LN patients. Levels of free thiols were significantly lower in subgroups of patients with estimated glomerular filtration rate (eGFR) < 60, serum creatinine (sCr) ≥ 90, C reactive protein (CRP) levels ≥ 5 and body mass index (BMI) ≥ 30. In multivariable regression, disease duration, NETs levels, and eGFR were independently associated with free thiol levels.

CONCLUSIONS

Levels of NETs were increased in quiescent SLE patients. Although free thiol levels did not differ among the groups. The levels of NETs and free thiols were independently associated in SLE patients, suggesting a potential role of OS in NETs formation. Therefore, reducing OS might be an additional therapeutic target for SLE treatment.

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

Thioredoxin 1 and Thioredoxin Reductase 1 Redox System Is Dysregulated in Neutrophils of Subjects with Autism: In Vitro Effects of Environmental Toxicant, Methylmercury

Autism spectrum disorder (ASD) is a complex developmental disorder in children that results in abnormal communicative and verbal behaviors. Exposure to heavy metals plays a significant role in the pathogenesis or progression of ASD. Mercury compounds pose significant risk for the development of ASD as children are more exposed to environmental toxicants. Increased concentration of mercury compounds has been detected in different body fluids/tissues in ASD children, which suggests an association between mercury exposure and ASD. Thioredoxin1 (Trx1) and thioredoxin reductase1 (TrxR1) redox system plays a crucial role in detoxification of oxidants generated in different immune cells. However, the effect of methylmercury and the Nrf2 activator sulforaphane on the Trx1/TrxR1 antioxidant system in neutrophils of ASD subjects has not been studied previously. Therefore, this study examined the effect of methylmercury on Trx1/TrxR1 expression, TrxR activity, nitrotyrosine, and ROS in neutrophils of ASD and TDC subjects. Our study shows that Trx1/TrxR1 protein expression is dysregulated in ASD subjects as compared to the TDC group. Further, methylmercury treatment significantly inhibits the activity of TrxR in both ASD and TDC groups. Inhibition of TrxR by mercury is associated with upregulation of the Trx1 protein in TDC neutrophils but not in ASD neutrophils. Furthermore, ASD neutrophils have exaggerated ROS production after exposure to methylmercury, which is much greater in magnitude than TDC neutrophils. Sulforaphane reversed methylmercury-induced effects on neutrophils through Nrf2-mediated induction of the Trx1/TrxR1 system. These observations suggest that exposure to the environmental toxicant methylmercury may elevate systemic oxidative inflammation due to a dysregulated Trx1/TrxR1 redox system in the neutrophils of ASD subjects, which may play a role in the progression of ASD.

Effectiveness of Albumin-Fused Thioredoxin against 6-Hydroxydopamine-Induced Neurotoxicity In Vitro

Parkinson's disease (PD) is a neurodegenerative disorder caused by oxidative stress-dependent loss of dopaminergic neurons in the substantia nigra and elevated microglial inflammatory responses. Recent studies show that cell loss also occurs in the hypothalamus in PD. However, effective treatments for the disorder are lacking. Thioredoxin is the major protein disulfide reductase in vivo. We previously synthesized an albumin-thioredoxin fusion protein (Alb-Trx), which has a longer plasma half-life than thioredoxin, and reported its effectiveness in the treatment of respiratory and renal diseases. Moreover, we reported that the fusion protein inhibits trace metal-dependent cell death in cerebrovascular dementia. Here, we investigated the effectiveness of Alb-Trx against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in vitro. Alb-Trx significantly inhibited 6-OHDA-induced neuronal cell death and the integrated stress response. Alb-Trx also markedly inhibited 6-OHDA-induced reactive oxygen species (ROS) production, at a concentration similar to that inhibiting cell death. Exposure to 6-OHDA perturbed the mitogen-activated protein kinase pathway, with increased phosphorylated Jun N-terminal kinase and decreased phosphorylated extracellular signal-regulated kinase levels. Alb-Trx pretreatment ameliorated these changes. Furthermore, Alb-Trx suppressed 6-OHDA-induced neuroinflammatory responses by inhibiting NF-κB activation. These findings suggest that Alb-Trx reduces neuronal cell death and neuroinflammatory responses by ameliorating ROS-mediated disruptions in intracellular signaling pathways. Thus, Alb-Trx may have potential as a novel therapeutic agent for PD.

The Importance of Thioredoxin-1 in Health and Disease

Thioredoxin-1 (Trx-1) is a multifunctional protein ubiquitously found in the human body. Trx-1 plays an important role in various cellular functions such as maintenance of redox homeostasis, proliferation, and DNA synthesis, but also modulation of transcription factors and control of cell death. Thus, Trx-1 is one of the most important proteins for proper cell and organ function. Therefore, modulation of Trx gene expression or modulation of Trx activity by various mechanisms, including post-translational modifications or protein-protein interactions, could cause a transition from the physiological state of cells and organs to various pathologies such as cancer, and neurodegenerative and cardiovascular diseases. In this review, we not only discuss the current knowledge of Trx in health and disease, but also highlight its potential function as a biomarker.

Triclocarban evoked neutrophil extracellular trap formation in common carp (Cyprinus carpio L.) by modulating SIRT3-mediated ROS crosstalk with ERK1/2/p38 signaling

Triclocarban (TCC), an antimicrobial ingredient in personal care products, is associated with immunosuppression and physiological dysfunctions of aquatic organisms. The aim of this study was to investigate whether TCC can induce common carp NETosis (neutrophil death by neutrophil extracellular trap (NET) release) and then to attempt to identify the potential molecular mechanisms. Herein, scanning electron microscopy and flow cytometric assays showed that revealed that TCC triggers DNA-containing web-like structures and increases extracellular DNA content. In the proteomic analysis, we observed that NET-related proteins, extracellular regulated protein kinase (Mapk1, Mapk14, Jak2) and apoptotic protein (caspase3) were significantly increased, and defender against cell death 1 (Dad1) was significantly decreased after TCC treatments. Meanwhile, we confirmed that TCC stress can trigger NETosis in common carp by activating the reactive oxygen species (ROS)/ERK1/2/p38 signaling. We think that the upregulated NDUFS1 expression is closely related to oxidative stress induced by TCC. Importantly, we discovered that SIRT3 expression was significantly decreased in the process of TCC-induced NETs. Importantly, pretreatment with the SIRT3 agonist honokiol (HKL) effectively suppressed TCC-induced NET release. In contrast, the SIRT3 antagonist 3-TYP escalated TCC-induced NET formation. Mechanistically, SIRT3 degradation serves as a potential mediator for regulating oxidative stress crosstalk between ERK1/2/p38 signals in the process of TCC-induced NET formation. These findings unveil new insights into the TCC-evoked health risk of fish and other aquatic organisms and suggest that SIRT3 is a potential pharmacological intervention target to alleviate TCC-induced common carp NETosis.

Preventive Effect of Epigallocatechin Gallate, the Main Component of Green Tea, on Acute Lung Injury Caused by Air Pollutants

Reducing the health hazards caused by air pollution is a global challenge and is included in the Sustainable Development Goals. Air pollutants, such as PM_2.5, induce respiratory and cardiovascular disorders by causing various inflammatory responses via oxidative stress. Catechins and polyphenols, which are components of green tea, have various protective effects, owing to their antioxidant ability. The main catechin in green tea, epigallocatechin gallate (EGCG), is potentially effective against respiratory diseases, such as idiopathic pulmonary fibrosis and asthma, but its effectiveness against air-pollution-dependent lung injury has not yet been investigated. In this study, we examined the effect of EGCG on urban aerosol-induced acute lung injury in mice. Urban aerosol treatment caused increases in inflammatory cell counts, protein levels, and inflammatory cytokine expression in the lungs of ICR mice, but pretreatment with EGCG markedly suppressed these responses. Analyses of oxidative stress revealed that urban aerosol exposure enhanced reactive oxygen species (ROS) production and the formation of ROS-activated neutrophil extracellular traps (NETs) in the lungs of mice. However, ROS production and NETs formation were markedly suppressed by pretreating the mice with EGCG. Gallocatechin gallate (GCG), a heat-epimerized form of EGCG, also markedly suppressed urban aerosol-dependent inflammatory responses and ROS production in vivo and in vitro. These findings suggest that EGCG and GCG prevent acute lung injury caused by urban aerosols through their inhibitory effects on ROS production. Thus, we believe that foods and medications containing EGCG or GCG may be candidates to prevent the onset and progression of acute lung injury caused by air pollutants.

Changing Perspectives from Oxidative Stress to Redox Signaling-Extracellular Redox Control in Translational Medicine

Extensive research has changed the understanding of oxidative stress that has been linked to every major disease. Today we distinguish oxidative eu- and distress, acknowledging that redox modifications are crucial for signal transduction in the form of specific thiol switches. Long underestimated, reactive species and redox proteins of the Thioredoxin (Trx) family are indeed essential for physiological processes. Moreover, extracellular redox proteins, low molecular weight thiols and thiol switches affect signal transduction and cell–cell communication. Here, we highlight the impact of extracellular redox regulation for health, intermediate pathophenotypes and disease. Of note, recent advances allow the analysis of redox changes in body fluids without using invasive and expensive techniques. With this new knowledge in redox biochemistry, translational strategies can lead to innovative new preventive and diagnostic tools and treatments in life sciences and medicine.

Exacerbation of Elastase-Induced Emphysema via Increased Oxidative Stress in Metallothionein-Knockout Mice

Although the pathogenesis of chronic obstructive pulmonary disease (COPD) is not yet fully understood, recent studies suggest that the disruption of the intracellular balance of oxidative (such as reactive oxygen species (ROS)) and antioxidant molecules plays an important role in COPD development and progression. Metallothionein is an endogenous metal-binding protein with reported ROS scavenging activity. Although there have been many publications on the protective effects of metallothionein in the kidney and liver, its role in COPD models such as elastase- or cigarette smoke (CS)-induced lung injury is unknown. Thus, in the present study, we analyzed the elastase-induced lung injury model using metallothionein-knockout (MT-KO; MT-1 and -2 gene deletion) mice. The expression of MT-1 and MT-2 in the lungs of MT-KO mice was markedly lower compared with that in the lungs of wildtype (WT) mice. Porcine pancreatic elastase (PPE)-induced lung injury (alveolar enlargement and respiratory impairment) was significantly exacerbated in MT-KO mice compared with WT mice. Additionally, PPE-induced increases in the number of inflammatory cells, inflammatory cytokines, and cell death in lung tissue were significantly more pronounced in MT-KO mice compared with WT mice. Finally, using an in vivo imaging system, we also found that PPE-induced ROS production in the lungs was enhanced in MT-KO mice compared with WT mice. These results suggest that metallothionein may act as an inhibitor against elastase-induced lung injury by suppressing ROS production. These results suggest that metallothionein protein, or compounds that can induce metallothionein, could be useful in the treatment of COPD.

N-acetylcysteine alleviates pulmonary inflammatory response during benzo[a]pyrene-evoked acute lung injury

Benzo[a]pyrene (BaP), a representative polycyclic aromatic hydrocarbon, exists widely in automobile emissions and polluted atmosphere. The current study aimed to describe pulmonary inflammation during BaP-induced acute lung injury (ALI). All mice except controls were intratracheally instilled with a single dose of BaP (90 μg per mouse). The alveolar structure was damaged, accompanied by numerous inflammatory cell infiltration around pulmonary interstitium and small airway. Airway wall area and mean linear intercept were reduced in BaP-exposed mouse lungs. By contrast, airway wall thickness and destructive index were elevated in BaP-exposed mouse lungs. Several inflammatory genes, such as Tnf-α, Il-1β, Il-6, Mip-2, Kc, and Mcp-1, were upregulated in mouse lungs. Phosphorylated IκBα was elevated in BaP-exposed mouse lungs. Nuclear translocation of NF-κB p65 and p50 was accordingly observed in BaP-exposed mouse lungs. Several molecules of the MAPK pathway, including JNK, ERK1/2, and p38, were activated in mouse lungs. Of interest, pretreatment with N-acetylcysteine (NAC), an antioxidant, alleviated BaP-induced ALI. Moreover, NAC attenuated BaP-induced inflammatory cell infiltration in mouse lungs and inflammatory gene upregulation in A549 cells. In addition, NAC attenuated BaP-induced NF-κB activation in A549 cells and mouse lungs. These results suggest that NAC alleviates pulmonary inflammatory response during BaP-evoked ALI.

Azilsartan attenuates lipopolysaccharide-induced acute lung injury via the Nrf2/HO-1 signaling pathway

Acute lung injury (ALI) is a severe complication of sepsis and hemorrhagic shock with high morbidity. In the present study, the protective effect of Azilsartan on lipopolysaccharide (LPS)-induced ALI in mice was investigated to explore the potential therapeutic property of Azilsartan for the treatment of ALI. LPS was used to induce an ALI model in mice. Hematoxylin-eosin (HE) staining sections were then evaluated for the pathological state of lung tissues. Bronchoalveolar lavage fluid (BALF) protein concentration, wet/dry weight ratios of lung tissues, and pulmonary myeloperoxidase (MPO) activity were detected to determine the degree of pulmonary injury. The number of total cells, macrophages, and neutrophils in BALF were counted using a hemocytometer to illustrate the inflammatory cell infiltration. The lung function was monitored using a spirometer. The concentrations of interleukin-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1), and interleukin-8 (IL-8) were determined using enzyme-linked immunosorbent assay (ELISA). Oxidative stress was evaluated by the superoxide dismutase (SOD) activity, glutathione (GSH), and malondialdehyde (MDA) concentrations in the lung tissue. The expressions of nuclear erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were determined using Western blot analysis. Azilsartan therapy alleviated LPS-induced lung tissue damage, increased BALF protein concentration, lung wet to dry weight ratio, MPO activity, and macrophage and neutrophils infiltration. Also, Azilsartan ameliorated the production of inflammatory factors (IL-1β, MCP-1, and IL-8). Azilsartan ameliorated LPS-impaired lung SOD activity, the GSH concentration, and the MDA concentration. Mechanistically, Azilsartan activated the LPS-impaired Nrf2/HO-1 signaling pathway. Azilsartan therapy attenuates LPS-induced ALI via the Nrf2/HO-1 signaling pathway.

PM2.5-induced lung injury is attenuated in macrophage-specific NLRP3 deficient mice

Fine particulate matter (PM2.5) is one of the most important components of environmental pollutants and is associated with lung injury. Pyroptosis, a form of programmed cell death mainly mediated by the NLRP3 inflammasome, has been reported to be involved in sepsis-induced or ischemia/reperfusion-induced lung injury. However, the specific mechanisms of pyroptosis in PM2.5-induced lung injury are not yet clear. We constructed macrophage-specific NLRP3 knockout mice to explore the mechanism of PM2.5-induced lung injury in terms of inflammatory response, oxidative stress, and apoptosis levels, including the relationship between these effects and pyroptosis. The results disclosed that PM2.5 exposure increased the infiltration of macrophages and leukocytes and the secretion of inflammatory cytokines, including TNF-α and IL-6, in lung tissue. The activity of antioxidant enzymes, including SOD, GSH-PX, and CAT, significantly decreased, while MDA, the end product of lipid oxidation, remarkably increased. The level of apoptosis in lung tissue, measured by the TUNEL assay and apoptosis-related proteins (BAX and BCL-2), was significantly increased. Macrophage-specific NLRP3 knockout could offset these effects. We further observed that PM2.5 treatment activated the NLRP3 inflammasome and subsequently induced pyroptosis, as evidenced by the increased production of IL-1β and IL-18 and the increase of the protein levels of NLRP3, ASC, caspase-1, and GSDMD, which were inhibited when NLRP3 was knocked out in macrophages. Taken together, these results revealed that NLRP3-mediated macrophage pyroptosis promoted PM2.5-induced lung injury through aggravating inflammation, oxidative stress, and apoptosis. Targeting the inhibition of NLRP3-mediated macrophage pyroptosis provides a new way to study lung injury induced by the exposure to PM2.5.