IRF-1 Intervention in the Classical ROS-Dependent Release of NETs during LPS-Induced Acute Lung Injury in Mice

Regulatory mechanism of TRIM21 in sepsis-induced acute lung injury by promoting IRF1 ubiquitination

Sepsis-induced acute lung injury (ALI) is characterized by inflammatory damage to pulmonary endothelial and epithelial cells. The aim of this study is to probe the significance and mechanism of tripartite motif-containing protein 21 (TRIM21) in sepsis-induced ALI. The sepsis-induced ALI mouse model was established by cecum ligation and puncture. The mice were infected with lentivirus and treated with proteasome inhibitor MG132. The lung respiratory damage, levels of interleukin-6 (IL-6), tumour necrosis factor α (TNF-α), IL-10 and pathological changes were observed. The expression levels of TRIM21, interferon regulatory factors 1 (IRF1) and triggering receptor expressed on myeloid cells 2 (TREM2) were measured and their interactions were analysed. The ubiquitination level of IRF1 was detected. TRIM21 and TREM2 were downregulated and IRF1 was upregulated in sepsis-induced ALI mice. TRIM21 overexpression eased inflammation and lung injury. TRIM21 promoted IRF1 degradation via ubiquitination modification. IRF1 bonded to the TREM2 promoter to inhibit its transcription. Overexpression of IRF1 or silencing TREM2 reversed the improvement of TRIM21 overexpression on lung injury in mice. In conclusion, TRIM21 reduced IRF1 expression by ubiquitination to improve TREM2 expression and ameliorate sepsis-induced ALI.

Loss of interferon regulatory factor-1 prevents lung fibrosis by upregulation of pon1 expression

BACKGROUND

Interferon regulatory factor-1 (IRF1) is a transcription factor that plays a significant role in various biological processes, including inflammatory injury, viral infection, cell death, and immune responses, and it has been extensively studied in the context of different lung diseases. However, the mechanism underlying its involvement in lung fibrosis remains largely unknown.

METHODS

Wild type (WT) mice, IRF1 global-null mice (Irf1-/-) were subjected to a bleomycin-induced lung fibrosis model to enable examination of the role of IRF1 in lung fibrosis. Proteomic analysis of lung tissue from WT and Irf1-/- mice treated with saline or bleomycin was performed to explore the mechanism of IRF1 in regulating lung fibrosis.

RESULTS

In the bleomycin-induced fibrosis mouse model, increased expression of IRF1 was observed. Irf1 knockout mice displayed decreased lung fibrosis relative to WT mice following treatment with bleomycin. The protein expression of fibronectin, as assessed by the Western blot analysis of lung tissues, was downregulated in Irf1-/- mice. We observed a similar reduction in collagen content using hydroxyproline detection. Histologically, there was less collagen deposition in the lungs of Irf1-/- mice compared with WT mice. Proteomics data revealed that IRF1 may be involved in lung fibrosis via the regulation of ferroptosis. We determined that paraoxonase 1(PON1), a poorly characterized protein in lung fibrosis, was upregulated in Irf1-/- mice following exposure to bleomycin. In vitro experiments revealed that IRF1 could regulate the level of GSH and MDA through PON1. We also determined that PON1 levels were lower in the plasma of IPF patients compared with healthy controls.

CONCLUSION

Our data highlight the importance of IRF1 in the fibrotic process, and PON1 may be a potential mediator of IRF1 in the progression of lung fibrosis.

The multiple roles of interferon regulatory factor family in health and disease

Interferon Regulatory Factors (IRFs), a family of transcription factors, profoundly influence the immune system, impacting both physiological and pathological processes. This review explores the diverse functions of nine mammalian IRF members, each featuring conserved domains essential for interactions with other transcription factors and cofactors. These interactions allow IRFs to modulate a broad spectrum of physiological processes, encompassing host defense, immune response, and cell development. Conversely, their pivotal role in immune regulation implicates them in the pathophysiology of various diseases, such as infectious diseases, autoimmune disorders, metabolic diseases, and cancers. In this context, IRFs display a dichotomous nature, functioning as both tumor suppressors and promoters, contingent upon the specific disease milieu. Post-translational modifications of IRFs, including phosphorylation and ubiquitination, play a crucial role in modulating their function, stability, and activation. As prospective biomarkers and therapeutic targets, IRFs present promising opportunities for disease intervention. Further research is needed to elucidate the precise mechanisms governing IRF regulation, potentially pioneering innovative therapeutic strategies, particularly in cancer treatment, where the equilibrium of IRF activities is of paramount importance.

Atorvastatin combined with imipenem alleviates lung injury in sepsis by inhibiting neutrophil extracellular trap formation via the ERK/NOX2 signaling pathway

Sepsis is a systemic inflammatory response syndrome caused by the invasion of pathogenic microorganisms. Despite major advances in diagnosis and technology, morbidity and mortality remain high. The level of neutrophil extracellular traps (NETs) is closely associated with the progression and prognosis of sepsis, suggesting the regulation of NET formation as a new strategy in sepsis treatment. Owing to its pleiotropic effects, atorvastatin, a clinical lipid-lowering drug, affects various aspects of sepsis-related inflammation and immune responses. To align closely with clinical practice, we combined it with imipenem for the treatment of sepsis. In this study, we used a cecum ligation and puncture-induced lung injury mouse model and employed techniques including western blot, immunofluorescence, and enzyme-linked immunosorbent assay to measure the levels of NETs and other sepsis-related lung injury indicators. Our findings indicate that atorvastatin effectively inhibited the formation of NETs. When combined with imipenem, it significantly alleviated lung injury, reduced systemic inflammation, and improved the 7-day survival rate of septic mice. Additionally, we explored the inhibitory mechanism of atorvastatin on NET formation in vitro, revealing its potential action through the ERK/NOX2 pathway. Therefore, atorvastatin is a potential immunomodulatory agent that may offer new treatment strategies for patients with sepsis in clinical settings.

Analysis of neutrophil extracellular trap-related genes in Crohn's disease based on bioinformatics

Crohn's disease (CD) presents with diverse clinical phenotypes due to persistent inflammation of the gastrointestinal tract. Its global incidence is on the rise. Neutrophil extracellular traps (NETs) are networks released by neutrophils that capture microbicidal proteins and oxidases targeting pathogens. Research has shown that NETs are implicated in the pathogenesis of several immune-mediated diseases such as rheumatoid arthritis, systemic lupus erythematosus and inflammatory bowel disease. The goal of this study was to identify a panel of NET-related genes to construct a diagnostic and therapeutic model for CD. Through analysis of the GEO database, we identified 1950 differentially expressed genes (DEGs) associated with CD. Gene enrichment and immune cell infiltration analyses indicate that neutrophil infiltrates and chemokine-related pathways are predominantly involved in CD, with other immune cells such as CD4 and M1 macrophages also playing a role in disease progression. Utilizing weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) networks, we identified six hub genes (SPP1, SOCS3, TIMP1, IRF1, CXCL2 and CD274). To validate the accuracy of our model, we performed external validation with statistical differences(p < 0.05). Additionally, immunohistochemical experiments demonstrated higher protein expression of the hub genes in colonic tissues from CD patients compared to healthy subjects (p < 0.05). In summary, we identified six effective hub genes associated with NETs as potential diagnostic markers for CD. These markers not only offer targets for future research but also hold promise for the development of novel therapeutic interventions for CD.

Netrin-1 mitigates acute lung injury by preventing the activation of the Toll-like receptor 4/nuclear factor-κB (TLR4/NF-κB) signaling

Acute lung injury (ALI) is one of the most common high-risk diseases associated with a high mortality rate and is still a challenge to treat effectively. Netrin-1 (NT-1) is a novel peptide with a wide range of biological functions, however, its effects on ALI have not been reported before. In this study, an ALI model was constructed using lipopolysaccharide (LPS) and treated with NT-1. Pulmonary function and lung wet to dry weight ratio (W/D) were detected. The expressions of pro-inflammatory cytokines and chemokines interleukin-8 (IL-8), interleukin-1β (IL-1β), and chemokine (C-X-C motif) ligand 2 (CXCL2) were measured using real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). We found that the levels of NT-1 were reduced in the LPS-induced ALI mice model. Administration of NT-1 improved histopathological changes of lung tissues and lung function in LPS-challenged ALI mice. We also report that NT-1 decreased Myeloperoxidase (MPO) activity and ameliorated pulmonary edema. Additionally, treatment with NT-1 reduced the levels of pro-inflammatory cytokines and chemokines such as IL-8, IL-1β, and CXCL2 in lung tissues of LPS-challenged ALI mice. Importantly, NT-1 reduced cell count in BALF and mitigated oxidative stress (OS) by reducing the levels of MDA and increasing the levels of GSH. Mechanistically, it is shown that NT-1 reduced the levels of Toll-like receptor 4 (TLR4) and prevented nuclear translocation of nuclear factor-κB (NF-κB) p65. Our findings indicate that NT-1 is a promising agent for the treatment of ALI through inhibiting TLR4/NF-κB signaling.

A Narrative Review: The Role of NETs in Acute Respiratory Distress Syndrome/Acute Lung Injury

Nowadays, acute respiratory distress syndrome (ARDS) still has a high mortality rate, and the alleviation and treatment of ARDS remains a major research focus. There are various causes of ARDS, among which pneumonia and non-pulmonary sepsis are the most common. Trauma and blood transfusion can also cause ARDS. In ARDS, the aggregation and infiltration of neutrophils in the lungs have a great influence on the development of the disease. Neutrophils regulate inflammatory responses through various pathways, and the release of neutrophils through neutrophil extracellular traps (NETs) is considered to be one of the most important mechanisms. NETs are mainly composed of DNA, histones, and granuloproteins, all of which can mediate downstream signaling pathways that can activate inflammatory responses, generate immune clots, and cause damage to surrounding tissues. At the same time, the components of NETs can also promote the formation and release of NETs, thus forming a vicious cycle that continuously aggravates the progression of the disease. NETs are also associated with cytokine storms and immune balance. Since DNA is the main component of NETs, DNase I is considered a viable drug for removing NETs. Other therapeutic methods to inhibit the formation of NETs are also worthy of further exploration. This review discusses the formation and mechanism of NETs in ARDS. Understanding the association between NETs and ARDS may help to develop new perspectives on the treatment of ARDS.

Neutrophil extracellular traps and their implications in airway inflammatory diseases

Neutrophil extracellular traps (NETs) are essential for immune defense and have been increasingly recognized for their role in infection and inflammation. In the context of airway inflammatory diseases, there is growing evidence suggesting the involvement and significance of NETs. This review aims to provide an overview of the formation mechanisms and components of NETs and their impact on various airway inflammatory diseases, including acute lung injury/ARDS, asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis. By understanding the role of NETs in airway inflammation, we can gain valuable insights into the underlying pathogenesis of these diseases and identify potential targets for future therapeutic strategies that either target NETs formation or modulate their harmful effects. Further research is warranted to elucidate the complex interactions between NETs and airway inflammation and to develop targeted therapies that can effectively mitigate their detrimental effects while preserving their beneficial functions in host defense.

Rosavin inhibits neutrophil extracellular traps formation to ameliorate sepsis-induced lung injury by regulating the MAPK pathway

BACKGROUND

Sepsis is a systemic organ dysfunction caused by infection, and the most affected organ is the lungs. Rosavin, a traditional Tibetan medicine, exerts an impressive anti--inflammatory effect. However, its effects on sepsis-related lung damage have not been investigated.

PURPOSE

This study aimed to investigate the effects of Rosavin on cecal ligation and puncture (CLP)-induced lung injury.

METHODS

The sepsis mouse model was established by CLP, and the mice were pretreated with Rosavin to explore whether it contributed to the alleviation of lung injury. Hematoxylin-eosin (H&E) stain and lung injury score were used to assess the severity of lung injury. The bronchoalveolar lavage fluid (BALF) inflammatory mediators (tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6], IL-1β, and IL-17A) were detected by ELISA. The number of neutrophils in BALF was detected using flow cytometry. The immunofluorescence assay was used to detect histone and myeloperoxidase (MPO) in lung tissues. Then, the western blot was performed to detect the expression of mitogen-activated protein kinase (MAPK) pathways (extracellular regulated kinase [ERK], p-ERK, p38, p-p38, Jun N-terminal kinase 1/2 [JNK1/2], and p-JNK1/2) in lung tissues.

RESULTS

We found that Rosavin significantly attenuated sepsis-induced lung injury. Specifically, Rosavin significantly inhibited inflammation response by decreasing the secretion of inflammatory mediators. The level of neutrophil extracellular traps (NETs) and MPO activity in CLP were decreased after administration with Rosavin. Moreover, the western blot showed that Rosavin could suppress NETs formation by inhibiting the MAPK/ERK/p38/JNK signaling pathway.

CONCLUSION

These findings demonstrated that Rosavin inhibited NETs formation to attenuate sepsis-induced lung injury, and the inhibitory effect may be exerted via deregulation of the MAPK pathways.

Down-regulation of KLF9 ameliorates LPS-caused acute lung injury and inflammation in mice via reducing GSDMD expression

Acute lung injury (ALI) is considered as a severe respiratory disease with aggravated inflammatory responses. Krüppel-like factor 9 (KLF9), a member of KLF family, has been reported to be involved in inflammatory disorders. However, the effect of KLF9 in ALI has not been elucidated. Here the present study was to clarify the role of KLF9 and its mechanism in ALI. The ALI in vitro model was established with lipopolysaccharide (LPS)-treated RAW264.7 cells. Mice were injected with LPS to conduct an ALI in vivo model. The expression of KLF9 and gasdermin D (GSDMD) was examined using quantitative reverse transcription-PCR, haematoxylin-eosin/immunohistochemistry staining and western blot assays. Enzyme-linked immunosorbent assay was employed to detect the levels of inflammatory cytokines. JASPAR database was used to predict the recognition motif of KLF9, and the relationship between KLF9 and GSDMD was determined by luciferase reporter assay and chromatin immunoprecipitation analysis. The number of neutrophils in bronchoalveolar lavage fluid as well as the wet/dry weight ratio was caculated. The results showed that The expression of KLF9 in lung was significantly increased in LPS-stimulated mice. Moreover, KLF9 knockout relieved the lung injury in ALI mice. GSDMD is one of targets genes of the transcription factor KLF9. KLF9 knockout induced a decreased expression of GSDMD in LPS-treated mice. Furthermore, in RAW264.7 cells after LPS administration, KLF9 knockdown reduced the levels of inflammatory factors and suppressed the expression of GSDMD. In summarise, these findings exhibited that KLF9 knockout could mitigate the lung injury and inflammatory responses in ALI mice by directly regulating GSDMD.

Salvianolic Acid A Protects against Lipopolysaccharide-Induced Acute Lung Injury by Inhibiting Neutrophil NETosis

Salvianolic acid A (SAA) is one of bioactive polyphenol extracted from a Salvia miltiorrhiza (Danshen), which was widely used to treat cardiovascular disease in traditional Chinese medicine. SAA has been reported to be protective in cardiovascular disease and ischemia injury, with anti-inflammatory and antioxidative effect, but its role in acute lung injury (ALI) is still unknown. In this study, we sought to investigate the therapeutic effects of SAA in a murine model of lipopolysaccharide- (LPS-) induced ALI. The optimal dose of SAA was determined by comparing the attenuation of lung injury score after administration of SAA at three different doses (low, 5 mg/kg; medium, 10 mg/kg; and, high 15 mg/kg). Dexamethasone (DEX) was used as a positive control for SAA. Here, we showed that the therapeutic effect of SAA (10 mg/kg) against LPS-induced pathologic injury in the lungs was comparable to DEX. SAA and DEX attenuated the increased W/D ratio and the protein level, counts of total cells and neutrophils, and cytokine levels in the BALF of ALI mice similarly. The oxidative stress was also relieved by SAA and DEX according to the superoxide dismutase and malondialdehyde. NET level in the lungs was elevated in the injured lung while SAA and DEX reduced it significantly. LPS induced phosphorylation of Src, Raf, MEK, and ERK in the lungs, which was inhibited by SAA and DEX. NET level and phosphorylation level of Src/Raf/MEK/ERK pathway in the neutrophils from acute respiratory distress syndrome (ARDS) patients were also inhibited by SAA and DEX in vitro, but the YEEI peptide reversed the protective effect of SAA completely. The inhibition of NET release by SAA was also reversed by YEEI peptide in LPS-challenged neutrophils from healthy volunteers. Our data demonstrated that SAA ameliorated ALI via attenuating inflammation, oxidative stress, and neutrophil NETosis. The mechanism of such protective effect might involve the inhibition of Src activation.

Gut microbiota aggravate cardiac ischemia-reperfusion injury via regulating the formation of neutrophils extracellular traps

AIMS

Myocardial infarction (MI) is a leading cause of death worldwide for which there is no cure. Percutaneous coronary intervention (PCI) can restore blood supply in a timely manner, which greatly reduces the mortality of patients, but ischemia/reperfusion (I/R) injury is inevitable. A number of clinical studies have shown that gut microbiota play an essential role in cardiovascular diseases. This study aims to explore the mechanism of gut microbiota to limit I/R injury.

MATERIALS AND METHODS

This study adopted the myocardial I/R model using gut microbiota clearance mice, neutrophil clearance mice and double-scavenging mice, and explored the relationship between gut microbiota and NETs during I/R injury. Neutrophils were isolated in vitro to explore the effect of NETs on myocardial cell injury and its molecular mechanism.

KEY FINDINGS

Gut microbiota aggravate cardiac I/R injury via regulating the formation of NETs. The migration of gut microbiota to blood stimulated the formation of NETs after cardiac I/R. NETs, which can directly lead to apoptosis of myocardial cells and myocardial microvascular endothelial cells. The time point of NETs formation in tissue and blood after I/R were determined by experiments.

SIGNIFICANCE

It was confirmed that gut microbiota participates in cardiac I/R injury by regulating the formation of NETs, which reveals a new mechanism of I/R injury and provides a new potential target for the treatment of I/R injury.

The Modulation of Interferon Regulatory Factor-1 via Caspase-1-Mediated Alveolar Macrophage Pyroptosis in Ventilator-Induced Lung Injury

Background

To examine the role of interferon regulatory factor-1 (IRF-1) and to explore the potential molecular mechanism in ventilator-induced lung injury.

Methods

Wild-type C57BL/6 mice and IRF-1 gene knockout mice/caspase-1 knockout mice were mechanically ventilated with a high tidal volume to establish a ventilator-related lung injury model. The supernatant of the alveolar lavage solution and the lung tissues of these mice were collected. The degree of lung injury was examined by hematoxylin and eosin staining. The protein and mRNA expression levels of IRF-1, caspase-1 (p10), and interleukin (IL)-1β (p17) in lung tissues were measured by western blot and quantitative real-time polymerase chain reaction, respectively. Pyroptosis of alveolar macrophages was detected by flow cytometry and western blotting for active caspase-1 and cleaved GSDMD. An enzyme-linked immunosorbent assay was used to measure the levels of IL-1β, IL-18, IL-6, TNF-α, and high mobility group box protein 1 (HMGB-1) in alveolar lavage fluid.

Results

IRF-1 expression and caspase-1-dependent pyroptosis in lung tissues of wild-type mice were significantly upregulated after mechanical ventilation with a high tidal volume. The degree of ventilator-related lung injury in IRF-1 gene knockout mice and caspase-1 knockout mice was significantly improved compared to that in wild-type mice, and the levels of GSDMD, IL-1β, IL-18, IL-6, and HMGB-1 in alveolar lavage solution were significantly reduced (P < 0.05). The expression levels of caspase-1 (p10), cleaved GSDMD, and IL-1β (p17) proteins in lung tissues of IRF-1 knockout mice with ventilator-related lung injury were significantly lower than those of wild-type mice, and the level of pyroptosis of macrophages in alveolar lavage solution was significantly reduced.

Conclusions

IRF-1 may aggravate ventilator-induced lung injury by regulating the activation of caspase-1 and the focal death of alveolar macrophages.

Neutrophil Extracellular Traps Facilitate A549 Cell Invasion and Migration in a Macrophage-Maintained Inflammatory Microenvironment

Introduction

The biological functions of neutrophil extracellular traps (NETs) in tumorigenesis have drawn an increasing amount of attention. This study explored the relationship between NETs and the inflammatory microenvironment in lung cancer cell invasion and metastasis.

Methods

NETs were quantified using myeloperoxidase (MPO–DNA) and immunofluorescence staining. Cytokine levels were measured using ELISA kits. THP-1 and A549 cells were used for in vitro experiments. Transwell and Matrigel assays were used to assess the invasion and migration abilities of the cells.

Results

Neutrophil infiltration and NET formation were observed in the lung cancer tissues. Compared with healthy controls, the level of MPO–DNA complexes in lung cancer patients increased remarkably and was positively correlated with peripheral blood neutrophil counts, smoking status, and poor prognosis. Increased circulating NET levels were also positively correlated with the levels of inflammatory cytokines, including IL-1β, IL-6, IL-18, and TNF-α. Neutrophils isolated from patients with lung cancer are more prone to NET release. NETs can promote the invasion and migration ability of THP-1 and A549 cell in coculture systems, while pretreatment with NET inhibitors can effectively reduce NET-induced invasion and metastasis. The ability of NETs to promote invasion and metastasis is partly dependent on macrophages.

Conclusion

Taken together, our study demonstrated that NETs facilitate A549 cell invasion and migration in a macrophage-maintained inflammatory microenvironment.

The regulatory mechanism of neutrophil extracellular traps in cancer biological behavior

As the predominant host defense against pathogens, neutrophil extracellular traps (NETs) have attracted increasing attention due to their vital roles in infectious inflammation in the past few years. Interestingly, NETs also play important roles in noninfectious conditions, such as rheumatism and cancer. The process of NETs formation can be regulated and the form of cell death accompanied by the formation of NETs is regarded as "NETosis". A large amount of evidence has confirmed that many stimuli can facilitate the release of NETs from neutrophils. Furthermore, it has been illustrated that NETs promote tumor growth and progression via many molecular pathways. Meanwhile, NETs also can promote metastasis in many kinds of cancers based on multiple studies. In addition, some researchs have found that NETs can promote coagulation and cancer-associated thrombosis. In the present review, it will highlight how NETosis, which is stimulated by various stimuli and signaling pathways, affects cancer biological behaviors via NETs. Given their crucial roles in cancer, NETs will become possible therapeutic targets for inhibiting proliferation, metastasis and thrombosis in cancer patients.

Senkyunolide I protect against lung injury via inhibiting formation of neutrophil extracellular trap in a murine model of cecal ligation and puncture

BACKGROUND

Senkyunolide I (SEI), a component of a Chinese herb named Ligusticum Chuanxiong hort, which is included in the formulation of Xuebijing Injection, a medication used to treat sepsis in China. Our previous study showed that SEI was protective against sepsis-associated encephalopathy and the present study was performed to investigate the role of SEI in sepsis-induced lung injury in a murine model of cecal ligation and puncture (CLP).

METHODS

SEI (36 mg/kg in 200 μl) or vehicle was administered immediately after CLP surgery. The lung injury was assessed 24 h later by histopathological tests, protein concentration in the bronchoalveolar lavage fluid (BALF), neutrophil recruitment in the lung tissue (myeloperoxidase fluorescence, MPO), pro-inflammatory cytokines and oxidative responses. Platelet activation was detected by CD42d/GP5 immunofluorescence and neutrophil extracellular trap (NET) were determined by immunofluorescence assays and enzyme linked immunosorbent assay (ELISA) of MPO-DNA. In vitro experiments were performed to detect the level of MPO-DNA complex released by SEI-treated neutrophils stimulated with phorbol 12-myristate 13-acetate (PMA) or co-cultured with platelets from CLP mice.

RESULTS

SEI administration relieved the injury degree in CLP mice according to the histopathological tests (P < 0.05 compared with DMSO + CLP group). Protein level in the BALF and neutrophil infiltration were remarkably reduced by SEI after CLP surgery (P < 0.05 compared with DMSO + CLP group). TNF-α, IL-1β and IL-6 were decreased in the plasma and lung tissues from CLP mice treated with SEI (P < 0.05 compared with DMSO + CLP group). The phosphorylation of JNK, ERK, p38 and p65 were all inhibited by SEI (P < 0.05 compared with DMSO + CLP group). Immunofluorescence of MPO showed that neutrophil number was significantly lower in SEI treated CLP mice than in vehicle treated CLP mice (P < 0.05). The CD42d/GP5 staining suggested that platelet activation was significantly reduced and the NET level in the lung tissue and plasma was greatly attenuated by SEI treatment (P < 0.05 compared with DMSO + CLP group). In vitro experiments showed that the MPO-DNA level stimulated by PMA was significantly reduced by SEI treatment (P < 0.05 compared with DMSO treatment). Co-culture neutrophils with platelets from CLP mice resulted in higher level of MPO-DNA complex, while SEI partly reversed such effects of platelet on NET formation.

CONCLUSIONS

SEI was protective against lung injury induced by CLP in mice. The NET formation was significantly reduced by SEI treatment, which might be involved in the mechanism of the protective effect.

Neutrophil Extracellular Traps Augmented Alveolar Macrophage Pyroptosis via AIM2 Inflammasome Activation in LPS-Induced ALI/ARDS

Background

Uncontrollable inflammation is a critical feature of gram-negative bacterial pneumonia-induced acute respiratory distress syndrome (ARDS). Both neutrophils and alveolar macrophages participate in inflammation, but how their interaction augments inflammation and triggers ARDS is unclear. The authors hypothesize that neutrophil extracellular traps (NETs), which are formed during neutrophil NETosis, partly cause alveolar macrophage pyroptosis and worsen the severity of ARDS.

Methods

The authors first analysed whether NETs and caspase-1 are involved in clinical cases of ARDS. Then, the authors employed a lipopolysaccharide (LPS)-induced ARDS model to investigate whether targeting NETs or alveolar macrophages is protective. The AIM2 sensor can bind to DNA to promote AIM2 inflammasome activation, so the authors studied whether degradation of NET DNA or silencing of the AIM2 gene could protect alveolar macrophages from pyroptosis in vitro.

Results

Analysis of aspirate supernatants from ARDS patients showed that NET and caspase-1 levels were correlated with the severity of ARDS and that the levels of NETs and caspase-1 were higher in nonsurvivors than in survivors. In vivo, the NET level and proportion of pyroptotic alveolar macrophages in bronchoalveolar lavage fluid (BALF) were obviously higher in LPS-challenged mice than in control mice 24 h after injury. Administration of DNase I (a NET DNA-degrading agent) and BB-Cl-amidine (a NET formation inhibitor) alleviated alveolar macrophage pyroptosis, and Ac-YVAD-cmk (a pyroptosis inhibitor) attenuated NET levels in BALF and neutrophil infiltration in alveoli. All treatments markedly attenuated the severity of ARDS. Notably, LPS causes NETs to induce alveolar macrophage pyroptosis, and degradation of NET DNA or silencing of the AIM2 gene protected against alveolar macrophage pyroptosis.

Conclusion

These findings shed light on the proinflammatory role of NETs in mediating the neutrophil-alveolar macrophage interaction, which influences the progression of ARDS.

Re-Du-Ning injection ameliorates LPS-induced lung injury through inhibiting neutrophil extracellular traps formation

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening diseases and could occur in severe COVID-19 patients. Re-Du-Ning injection (RDN) is a tradition Chinese medicine preparation which has been clinically used for treatment of respiratory diseases including COVID-19.

PURPOSE

To elucidate the potential mechanisms of RDN for the treatment of ALI.

METHODS

Female C57BL/6J mice were used to establish ALI model by intraperitoneal injection 10 mg/kg LPS, and RDN injection was intraperitoneally administered with the dose of 5 and 10 ml/kg. The cytokines were measured by ELISA and qPCR. The data related to NETs were analyzed by ELISA, immunofluorescence, Western blotting and network pharmacological approach.

RESULTS

RDN robustly alleviated LPS-induced ALI. Meanwhile, RDN downregulated the expression of pro-inflammatory cytokines, such as IL-1β, IL-6 and TNF-α. Specifically, RDN treatment inhibited the formation of neutrophil extracellular traps (NETs) and remarkably suppressed the protein of PAD4. The active compound from RDN decreased the phosphorylation of ERK1/2.

CONCLUSION

These findings demonstrate that RDN ameliorates LPS-induced ALI through suppressing MAPK pathway to inhibit the formation of NETs.

Identification of significant alteration genes, pathways and TFs induced by LPS in ARDS via bioinformatical analysis

Background and aims

Acute respiratory distress syndrome (ARDS) or acute lung injury (ALI) is one of the most common acute thoracopathy with complicated pathogenesis in ICU. The study is to explore the differentially expressed genes (DEGs) in the lung tissue and underlying altering mechanisms in ARDS.

Methods

Gene expression profiles of GSE2411 and GSE130936 were available from GEO database, both of them included in GPL339. Then, an integrated analysis of these genes was performed, including gene ontology (GO) and KEGG pathway enrichment analysis in DAVID database, protein–protein interaction (PPI) network construction evaluated by the online database STRING, Transcription Factors (TFs) forecasting based on the Cytoscape plugin iRegulon, and their expression in varied organs in The Human Protein Atlas.

Results

A total of 39 differential expressed genes were screened from the two datasets, including 39 up-regulated genes and 0 down-regulated genes. The up-regulated genes were mainly enriched in the biological process, such as immune system process, innate immune response, inflammatory response, and also involved in some signal pathways, including cytokine–cytokine receptor interaction, Salmonella infection, Legionellosis, Chemokine, and Toll-like receptor signal pathway with an integrated analysis. GBP2, IFIT2 and IFIT3 were identified as hub genes in the lung by PPI network analysis with MCODE plug-in, as well as GO and KEGG re-enrichment. All of the three hub genes were regulated by the predictive common TFs, including STAT1, E2F1, IRF1, IRF2, and IRF9.

Conclusions

This study implied that hub gene GBP2, IFIT2 and IFIT3, which might be regulated by STAT1, E2F1, IRF1, IRF2, or IRF9, played significant roles in ARDS. They could be potential diagnostic or therapeutic targets for ARDS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06578-7.

hucMSC Conditioned Medium Ameliorate Lipopolysaccharide-Induced Acute Lung Injury by Suppressing Oxidative Stress and Inflammation via Nrf2/NF-κB Signaling Pathway

Acute lung injury (ALI) is a common clinical syndrome in the cardiac intensive care unit with a high mortality rate. Inflammation and oxidative stress have been reported to play a crucial role in the development of ALI. Previous studies have shown that human umbilical cord mesenchymal stem cells (hucMSCs) have anti-inflammatory and antioxidative effects in various diseases. However, the anti-inflammatory and antioxidative effects of the hucMSC conditioned medium (CM) on LPS-induced ALI remain unclear. Therefore, in this study, we assessed whether the hucMSC conditioned medium could attenuate LPS-induced ALI and the underlying mechanisms. Mice were randomly divided into four groups: the control group, PBS group, LPS+PBS group, and LPS+CM group. The lung histopathology and bronchoalveolar lavage fluid (BALF) were analyzed after intervention. The Nrf2/NF-κB signaling pathway and its downstream target genes were tested, and the cytokines and growth factors in CM were also measured. The results showed that CM significantly attenuated the histological alterations; decreased the wet/dry weight ratio; reduced the levels of MPO, MDA and ROS; increased SOD and GSH activity; and downregulated the level of proinflammatory cytokines such as IL-1β, IL-6, and TNF-α. Furthermore, CM promoted the expression of Nrf2 and its target genes NQ01, HO-1, and GCLC and inhibited the expression of NF-κB and its target genes IL-6, IL-1β, and TNF-α. These effects may be closely related to the large amounts of cytokines and growth factors in the CM. In conclusion, our results demonstrated that CM could attenuate LPS-induced ALI, probably due to inhibition of inflammation and oxidative stress via the Nrf2/NF-κB signaling pathway.

Polydatin alleviates severe traumatic brain injury induced acute lung injury by inhibiting S100B mediated NETs formation

Severe traumatic brain injury (sTBI)-induced acute lung injury (sTBI-ALI) is regarded as the most common complication of sTBI that is an independent predictor of poor outcomes in patients with sTBI and strongly increases sTBI mortality. Polydatin (PD) has been shown to have a potential therapeutic effect on sTBI-induced neurons injury and sepsis-induced acute lung injury (ALI), therefore, it is reasonable to believe that PD has a protective effect on sTBI-ALI. Here, to clarify the PD protective effect following sTBI-ALI, a rat brain injury model of lateral fluid percussion was established to mimic sTBI. As a result, sTBI induced ALI, and caused an increasing of wet/dry weight ratio and lung vascular permeability, as well as sTBI promoted oxidative stress response in the lung; sTBI caused inflammatory cytokines release, such as IL-6, IL-1β, TNF-α and MCP-1; and sTBI promoted NETs formation, mainly including an increasing expression of MPO, NE and CitH3. Simultaneously, sTBI induced a significant increase in the level of S100B; however, when inhibition of S100B, the expression of MPO, NE and CITH3 were significantly inhibited following sTBI. Inhibition of S100B also promoted lung vascular permeability recovery and alleviated oxidative stress response. Furthermore, PD treatmentreduced the pathological lung damage, promoted lung vascular permeability recovery, alleviated oxidative stress response and inflammatory cytokines release; more importantly, PD inhibited the expression of S100B, and NETs formation in the lung following sTBI. These results indicate that PD alleviates sTBI-ALI by inhibiting S100B mediated NETs formation. Thus, PD may be valuable in sTBI-ALI treatment.

Effect and Mechanism Study of Sodium Houttuyfonate on Ventilator-Induced Lung Injury by Inhibiting ROS and Inflammation

PURPOSE

Ventilator-induced lung injury (VILI) is a serious complication of mechanical ventilation (MV) that increases morbidity and mortality of patients receiving ventilator treatment. This study aimed to reveal the molecular mechanism of sodium houttuyfonate (SH) on VILI.

MATERIALS AND METHODS

The male mice VILI model was established by high tidal volume ventilation. The cell model was established by performing cell stretch (CS) experiments on murine respiratory epithelial cells MLE-15. In addition, the JNK activator Anisomycin and JNK inhibitor SP600125 were used on VILI mice and CS-treated cells.

RESULTS

VILI modeling damaged the structural integrity, increased apoptosis and wet-to-dry (W/D) ratio, enhanced the levels of inflammatory factors, reactive oxygen species (ROS) and malonaldehyde (MDA), and activated JNK pathway in lung tissues. SH gavage alleviated lung injury, decreased apoptosis and W/D ratio, and reduced levels of inflammatory factors, ROS and MDA, and p-JNK/JNK expression of lung tissues in VILI mice. However, activation of JNK wiped the protective effect of SH on VILI. Contrary results were found in experiments with JNK inhibitor SP600125.

CONCLUSION

SH relieved VILI by inhibiting the ROS-mediated JNK pathway.

Hemozoin Promotes Lung Inflammation via Host Epithelial Activation

Respiratory distress (RD) is a complication of severe malaria associated with a particularly high risk for death in African children infected with the parasite Plasmodium falciparum. The pathophysiology underlying RD remains poorly understood, and the condition is managed supportively.

Respiratory distress in severe malaria is associated with high mortality, but its pathogenesis remains unclear. The malaria pigment hemozoin (HZ) is abundant in target organs of severe malaria, including the lungs, and is known to be a potent innate immune activator of phagocytes. We hypothesized that HZ might also stimulate lung epithelial activation and thereby potentiate lung inflammation. We show here that airway epithelium stimulated with HZ undergoes global transcriptional reprogramming and changes in cell surface protein expression that comprise an epithelial activation phenotype. Proinflammatory signaling is induced, and key cytoadherence molecules are upregulated, including several associated with severe malaria, such as CD36 and ICAM1. Epithelial and extracellular matrix remodeling pathways are transformed, including induction of key metalloproteases and modulation of epithelial junctions. The overall program induced by HZ serves to promote inflammation and neutrophil transmigration, and is recapitulated in a murine model of HZ-induced acute pneumonitis. Together, our data demonstrate a direct role for hemozoin in stimulating epithelial activation that could potentiate lung inflammation in malaria.

Tissue-level inflammation and ventricular remodeling in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a common cardiac condition caused primarily by sarcomeric protein mutations with several distinct phenotypes, ranging from asymmetric septal hypertrophy, either with or without left ventricular outflow tract obstruction, to moderate left ventricular dilation with or without apical aneurysm formation and marked, end-stage dilation with refractory heart failure. Sudden cardiac death can occur at any stage. The phenotypic variability observed in HCM is the end-result of many factors, including pre-load, after-load, wall stress and myocardial ischemia stemming from microvascular dysfunction and thrombosis; however, tissue level inflammation to include leukocyte-derived extracellular traps consisting of chromatin and histones, apoptosis, proliferation of matrix proteins and impaired or dysfunctional regulatory pathways contribute as well. Our current understanding of the pathobiology, developmental stages, transition from hypertrophy to dilation and natural history of HCM with emphasis on the role of tissue-level inflammation in myocardial fibrosis and ventricular remodeling is summarized.

Effects of simvastatin on iNOS and caspase‑3 levels and oxidative stress following smoke inhalation injury

The overexpression of inducible nitric oxide synthase (iNOS) induces cell apoptosis through various signal transduction pathways and aggravates lung injury. Caspase‑3 is an important protein in the apoptotic pathway and its activation can exacerbate apoptosis. Simvastatin, a hydroxymethyl glutaryl‑A reductase inhibitor, protects against smoke inhalation injury by inhibiting the synthesis and release of inflammatory factors and decreasing cell apoptosis. Following the establishment of an animal model of smoke inhalation injury, lung tissue and serum were collected at different time points and the protein and mRNA expression of iNOS and caspase‑3 in lung tissue by immunochemistry, western blot and reverse transcription‑quantitative polymerase chain reaction, the malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in lung tissue and serum were analyzed using thiobarbituric acid method and the WST‑1 method. The results were statistically analyzed. The lung tissues of the rats in the saline group and the low‑, middle‑ and high‑dose groups exhibited clear edema and hemorrhage, and had significantly higher pathological scores at the various time points compared with the rats in the control group (P<0.05). Furthermore, lung tissue and serum samples obtained from these four groups had significantly higher mRNA and protein expression levels of iNOS and caspase‑3 (P<0.05), significantly lower SOD activity and higher MDA content (P<0.05). Compared with the saline group, the low‑, middle‑ and high‑dose groups had significantly lower pathological scores (P<0.05), significantly lower mRNA and protein expression levels of iNOS, caspase‑3 and MDA content in lung tissues (P<0.05) and significantly higher SOD activity in lung tissues and serum. The middle‑ and high‑dose groups had significantly lower pathological scores (P<0.05), significantly decreased iNOS and caspase‑3 mRNA and protein expression in lung tissues, significantly higher SOD activity in lung tissues and serum and a significantly lower MDA content (P<0.05) compared with the low‑dose group. With the exception of SOD activity in lung tissues at 24 and 72 h and MDA content in serum at 48 h, no significant differences were observed between the middle‑ and high‑dose groups. The present study demonstrated that there was an association between the therapeutic effect and dosage of simvastatin within a definitive range. In rats with smoke inhalation injury, simvastatin inhibited iNOS and caspase‑3 expression in lung tissues and mitigated oxidative stress, thereby exerting a protective effect. In addition, the effect and dose were associated within a definitive range.

Over-gene expression in the apoptotic, oxidative damage and liver injure in female rats exposed to butralin

The present study is the first report for studying the toxic effects of butralin herbicide on COX2, BAX, and Bcl2 gene expression, oxidative stress, and liver damage in female rats. Female rats were received butralin in drinking water for 28 days at concentration 4.16, 312, and 3120 mg/L that corresponded to the acceptable daily intake (ADI), no observed adverse effect level (NOAEL), and 10 NOAEL, respectively. Butralin decreased body weights and increased relative liver weight of female rats exposed to high dose. It caused significant elevation in liver function enzymes, lipid peroxidation, and reactive oxygen species (ROS). Antioxidant enzymes were decreased in liver tissue by increasing the dose. Butralin induced over-expression in the apoptotic related genes including COX2, BAX, and Bcl2 and pathological alteration in the liver of female rats especially at a high dose. It can be concluded that butralin induced oxidative damage and liver injure. The mechanism of damage could be due to generate reactive oxygen species, and increase lipid peroxidation that causes over-expression in the apoptotic related genes including COX2, BAX, and Bcl2. From the Benchmark dose (BMD) approach, there is dose-dependent manner in body weight, AST, ALT, and ALP, and ALT is a very sensitive parameter.

Emodin alleviates LPS-induced inflammatory response in lung injury rat by affecting the function of granulocytes

Background

Acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS) are critical life-threatening syndromes characterized by the infiltration of a large number of granulocytes (mainly neutrophils) that lead to an excessive inflammatory response. Emodin (Emo) is a naturally occurring anthraquinone derivative and an active ingredient of Chinese medicine. It is believed to have anti-inflammatory effects. In this study, we examined the impact of Emo on the pulmonary inflammatory response and the granulocytes function in a rat model of lipopolysaccharide (LPS)-induced ALI.

Results

Treatment with Emo protected rat against LPS-induced ALI. Compared to untreated rat, Emo-treated rat exhibited significantly ameliorated lung pathological changes and decreased tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). However, Emo has no protective effect on the rat model of acute lung injury with granulocyte deficiency. In addition, treatment with Emo enhanced the bactericidal capacity of LPS-induced granulocytes via the up-regulation of the ability of granulocytes to phagocytize bacteria and generate neutrophil extracellular traps (NETs). Emo also downregulated the respiratory burst and the expression of reactive oxygen species (ROS) in LPS-stimulated granulocytes, alleviating the damage of granulocytes to surrounding tissues. Finally, Emo can accelerate the resolution of inflammation by promoting apoptosis of granulocytes.

Conclusion

Our results provide the evidence that Emo could ameliorates LPS-induced ALI via its anti-inflammatory action by modulating the function of granulocytes. Emo may be a promising preventive and therapeutic agent in the treatment of ALI.

Anti-inflammatory effect of octyl gallate in alveolar macrophages cells and mice with acute lung injury

Acute lung injury (ALI) is an inflammatory process, and has high incidence and mortality. ALI and the acute respiratory distress syndrome are two common complications worldwide that result in acute lung failure, sepsis, and death. Pro-inflammatory substances, such as cytokines and chemokines, are responsible for activating the body's defense mechanisms and usually mediate inflammatory processes. Therefore, the research of substances that decrease the uncontrolled response of organism is seen as potential for patients with ALI. Octyl gallate (OG) is a phenolic compound with therapeutic actions namely antimicrobial, antiviral, and antifungal. In this study, we evaluated its action on lipopolysaccharide (LPS)-activated alveolar macrophages RAW 264.7 cells and ALI in male mice. Our results demonstrated protective effects of OG in alveolar macrophages activated with LPS and mice with ALI. The OG treatment significantly decreased the inflammatory markers in both studies in vitro and in vivo. The data suggested that OG can act as an anti-inflammatory agent for ALI.