Alveolar Macrophage Chemokine Secretion Mediates Neutrophilic Lung Injury in Nox2-Deficient Mice

Bioinformatic analysis reveals the relationship between macrophage infiltration and Cybb downregulation in hyperoxia-induced bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common sequela of prematurity and is characterized by alveolar simplification and lung angiogenesis failure. The aim of this study was to explore the immune signatures of BPD. Differentially expressed gene analysis and immune infiltration analysis were conducted to identify key immune cell types and related genes by using the mRNA-seq dataset GSE25286. The expression patterns of key genes were validated in the scRNA-seq dataset GSE209664 and in experiments. The cell-cell crosstalk of key immune cells was explored with CellChat. We found that differentially expressed genes between BPD mice and controls were mostly enriched in leukocyte migration and M1 macrophages were highly enriched in BPD lungs. Hub genes (Cybb, Papss2, F7 and Fpr2) were validated at the single-cell level, among which the downregulation of Cybb was most closely related to macrophage infiltration. The reduced mRNA and protein levels of Cybb were further validated in animal experiments. Colocalization analysis of Cybb and macrophage markers demonstrated a significant decrease of Cybb in M1 macrophages. Cell-cell crosstalk found that alveolar epithelial cells interacted actively with macrophages through MIF-(CD74 + CD44) signalling. In conclusion, M1 macrophages played important roles in promoting BPD-like lung injury, which was correlated with a specific reduction of Cybb in macrophages and the potential activation of MIF signalling.

Investigation of the miRNA-mRNA Regulatory Circuits and Immune Signatures Associated with Bronchopulmonary Dysplasia

Background

Bronchopulmonary dysplasia (BPD) has become a major cause of morbidity and mortality in preterm infants worldwide, yet its pathogenesis and underlying mechanisms remain poorly understood. The present study sought to explore microRNA-mRNA regulatory networks and immune cells involvement in BPD through a combination of bioinformatic analysis and experimental validation.

Methods

MicroRNA and mRNA microarray datasets were obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed microRNAs (DEMs) were identified in BPD patients compared to control subjects, and their target genes were predicted using miRWalk, miRNet, miRDB, and TargetScan databases. Subsequently, protein-protein interaction (PPI) and functional enrichment analyses were conducted on the target genes. 30 hub genes were screened using the Cytohubba plugin of the Cytoscape software. Additionally, mRNA microarray data was utilized to validate the expression of hub genes and to perform immune infiltration analysis. Finally, real-time PCR (RT-PCR), immunohistochemistry (IHC), and flow cytometry were conducted using a mouse model of BPD to confirm the bioinformatics findings.

Results

Two DEMs (miR-15b-5p and miR-20a-5p) targeting genes primarily involved in the regulation of cell cycle phase transition, ubiquitin ligase complex, protein serine/threonine kinase activity, and MAPK signaling pathway were identified. APP and four autophagy-related genes (DLC1, PARP1, NLRC4, and NRG1) were differentially expressed in the mRNA microarray dataset. Analysis of immune infiltration revealed significant differences in levels of neutrophils and naive B cells between BPD patients and control subjects. RT-PCR and IHC confirmed reduced expression of APP in a mouse model of BPD. Although the proportion of total neutrophils did not change appreciably, the activation of neutrophils, marked by loss of CD62L, was significantly increased in BPD mice.

Conclusion

Downregulation of APP mediated by miR-15b-5p and miR-20a-5p may be associated with the development of BPD. Additionally, increased CD62L- neutrophil subset might be important for the immune-mediated injury in BPD.

Significance of Pyroptosis in Immunoregulation and Prognosis of Patients with Acute Respiratory Distress Syndrome: Evidence from RNA-Seq of Alveolar Macrophages

Objective

This study aimed to investigate the role of pyroptosis in alveolar macrophages regarding the immune microenvironment of acute respiratory distress syndrome (ARDS) and its prognosis.

Methods

ARDS Microarray data were downloaded from Gene Expression Omnibus (GEO). Support vector machine (SVM) and random forest (RF) models were applied to identify hub pyroptosis-related genes (PRGs) with prognostic significance in ARDS. RT-PCR was used to detect the relative expression of PRGs mRNA in alveolar macrophages of ARDS mice. Consensus clustering analysis was conducted based on the expression of the PRGs to identify pyroptosis modification patterns. Bioinformatic algorithms were used to study the immune traits and biological functions of the pyroptosis patterns. Finally, protein-protein interaction (PPI) networks were established to identify hub regulatory proteins with implications for the pyroptosis patterns.

Results

In our study, a total of 12 PRGs with differential expression were obtained. Four hub PRGs, including GPX4, IL6, IL18 and NLRP3, were identified and proven to be predictive of ventilator-free days (VFDS) in ARDS patients. The AUC values of the 4 PRGs were 0.911 (GPX4), 0.879 (IL18), 0.851 (IL6) and 0.841 (NLRP3), respectively. In ARDS mice, GPX4 mRNA decreased significantly, while IL6, IL18, and NLRP3 mRNA increased. Functional analysis revealed that IL6 had the strongest positive correlation with the CCR pathway, while GPX4 exhibited the strongest negative correlation with the T co-inhibition pathway. Based on the expression of the 4 PRGs, three pyroptosis modification patterns representing different immune states were obtained, and pattern C might represent immune storm.

Conclusion

The results showed that pyroptosis plays an important regulatory role in the immune microenvironment of ARDS. This finding provides new insights into the pathogenesis, diagnosis, and treatment of ARDS.

Expression and prognostic value of MIP-1α in neonatal acute respiratory distress syndrome

OBJECTIVE

To investigate the expression and prognostic value of macrophage inflammatory protein 1α (MIP-1α) in neonatal acute respiratory distress syndrome (NRDS).

METHODS

In this retrospective analysis, 96 newborns with NRDS in Affiliated Lianyungang Hospital of Xuzhou Medical University from January 2018 to June 2021 were included in the experimental group (EG), while the other 60 normal neonates were included as the control group (CG). The concentration of MIP-1α in umbilical cord blood was tested by Elisa method. The clinical value of MIP-1α in diagnosing NRDS was assessed via receiver operating characteristic (ROC) curve. According to the 28-day survival data, children were divided into a survival group and a death group. The prognostic factors were assessed by Cox regression analysis. The correlation between MIP-1α and IL-1β, IL-6, TNF-α, SNAPPE-II scores were evaluated by Pearson test. The relationship between the MIP-1α level and the severity of the disease was assessed.

RESULTS

The MIF-1α level in cord blood of children in the EG was dramatically higher than that in the CG (P<0.05). Besides, ROC curve further found that the area of MIF-1α under the curve of diagnosing NRSD was 0.949. MIF-1α was positively correlated with the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α) and SNAPPE-II score (P<0.001). With the increase of NRDS, the serum MIF-1α level increased, showing a positive association (P<0.05). Cox regression analysis revealed that the severity and MIF-1α level were independent prognostic factors of survival (P<0.001). The survival rate of children with MIF-1α <281.58 pg/mL as well as children with I-II grade was higher than those with MIF-1α >281.58 pg/mL as well as children with III-IV grade (P<0.05).

CONCLUSION

The increase of serum MIP-1α level is relevant to the condition and prognosis of NRDS children. The level of cord blood MIP-1α level is expected to become a potential outcome measure.

MiR-217-5p inhibits smog (PM2.5)-induced inflammation and oxidative stress response of mouse lung tissues and macrophages through targeting STAT1

Objective: To explore the roles of macrophages’ miR-217-5p in the process of PM2.5 induced acute lung injury.

Methods: GEO database and KEGG pathway enrichment analysis as well as GSEA were used to predicted the miRNA and associated target signals. And then mice and RAW246.7 macrophages treated with PM2.5 to imitate PM2.5 induced acute lung injury environment and then transfected with miR-217-5p NC or miR-217-5p mimic. The levels of inflammatory factors TNF-α and anti-inflammatory factor IL-10 of mice serum were tested by ELISA. And the pathological changes and ROS level of mouse lung tissues were stained by HE and DHE staining. The proteins expression of phosphorylated-STAT1, total-STAT1, TNF-α, IFN-γ as well as p47, gp91, NOX4 in mice or RAW264.7 cells were tested by western blot or immunofluorescence of RAW264.7 cell slides.

Results: The results of bioinformatics analysis indicated the miR-217 as well as STAT1 were involved PM2.5 associated lung injury. After exposure to PM2.5, the decreased levels of serum TNF-α but not IL-10, consistent with reduced macrophages’ accumulation as well as decreased ROS levels in lung tissues in miR-217-5p mimic group vs miR-217-5p NC group mice, and moreover, the protein expression levels of phosphorylated--STAT1, total-STAT1, TNF-α, IFN-γ, p47, gp91 and NOX4 in mouse lung tissues and RTAW246.7 macrophages cells were all significantly reduced with miR-217-5p mimic administration. The above phenomena were reversed by specific STAT1-inhibitor HY-N8107.

Conclusions: miR-217-5p suppressed the activated STAT1-signal induced inflammation and oxidative stress trigged by PM2.5 in macrophages and resulted in the decreased lung injure caused by PM2.5.

Macrophage NOX2 NADPH oxidase maintains alveolar homeostasis in mice

The leukocyte NADPH oxidase 2 (NOX2) plays a key role in pathogen killing and immunoregulation. Genetic defects in NOX2 result in chronic granulomatous disease (CGD), associated with microbial infections and inflammatory disorders, often involving the lung. Alveolar macrophages (AMs) are the predominant immune cell in the airways at steady state, and limiting their activation is important, given the constant exposure to inhaled materials, yet the importance of NOX2 in this process is not well understood. In this study, we showed a previously undescribed role for NOX2 in maintaining lung homeostasis by suppressing AM activation, in CGD mice or mice with selective loss of NOX2 preferentially in macrophages. AMs lacking NOX2 had increased cytokine responses to Toll-like receptor-2 (TLR2) and TLR4 stimulation ex vivo. Moreover, between 4 and 12 week of age, mice with global NOX2 deletion developed an activated CD11bhigh subset of AMs with epigenetic and transcriptional profiles reflecting immune activation compared with WT AMs. The presence of CD11bhigh AMs in CGD mice correlated with an increased number of alveolar neutrophils and proinflammatory cytokines at steady state and increased lung inflammation after insults. Moreover, deletion of NOX2 preferentially in macrophages was sufficient for mice to develop an activated CD11bhigh AM subset and accompanying proinflammatory sequelae. In addition, we showed that the altered resident macrophage transcriptional profile in the absence of NOX2 is tissue specific, as those changes were not seen in resident peritoneal macrophages. Thus, these data demonstrate that the absence of NOX2 in alveolar macrophages leads to their proinflammatory remodeling and dysregulates alveolar homeostasis.

TMT-Based proteomics analysis of LPS-induced acute lung injury

PURPOSE

The proteome during lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice is unclear.

MATERIALS AND METHODS

In this study, eight-week-old male C57BL/6 mice were intraperitoneally injected with LPS and sacrificed 18 hours after LPS administration to identify protein expression levels in lung tissue using tandem mass tag (TMT) analysis for relative quantification. Hematoxylin-eosin (HE) staining was used to evaluate lung injury in mice. Immunohistochemical staining was used to calculate the production of myeloperoxidase (MPO) and TUNEL staining was performed to detect apoptosis. GO functional clustering and KEGG pathway enrichment analyses were performed to determine functions of differentially expressed proteins (DEPs) and transduction pathways. Domain annotation and subcellular localization analysis of the DEPs were also performed. Furthermore, parallel reaction monitoring (PRM) analysis was used to verify the top 30 DEPs.

RESULTS

A total of 5188 proteins were found to be expressed in lung tissues from LPS- and saline-treated mice. Among these proteins, 293 were differentially expressed between the two groups; 255 proteins were upregulated in the LPS-treated ALI mice, while 38 were downregulated. GO analysis showed that the DEPs are mainly extracellular, and KEGG analysis suggested that the DEPs are mainly enriched in the NOD-like receptor signaling pathway, complement and coagulation cascades and natural killer cell-mediated cytotoxicity. Enrichment of the DEPs is mainly peptidase S1A, serine proteases, peptidase S1, and the serpin domain. 26.6% of the DEPs are in the nucleus, 24.6% are in the cytosol, 19.1% are in the extracellular space, and 18.8% are in the plasma membrane. PRM validation showed that the trend of 30 DEPs was same with TMT analysis. Among these, Cytochrome b-245 heavy chain (Cybb), Monocyte differentiation antigen CD14 (Cd14) and Neutrophil gelatinase-associated lipocalin (NGAL) were the most obvious change.

CONCLUSIONS

Our results may help to identify markers and therapeutic targets for LPS-induced ALI.

TLR4/TRAF6/NOX2 signaling pathway is involved in ventilation-induced lung injury via endoplasmic reticulum stress in murine model

In ventilation-induced lung injury (VILI), prolonged nonpathogen-mediated inflammation is triggered as a result of alveolar hyperinflation. In our previous study, we suggested that endoplasmic reticulum (ER) stress-mediated inflammation was involved in VILI, but how ER stress is triggered remains unknown. Toll-like receptor 4 (TLR4) activation plays an important role in mechanical ventilation (MV)-induced lung inflammation, however, it is unknown whether ER stress is activated by TLR4 to participate in VILI. In this study, C57BL/6 mice were exposed to MV with high tidal volumes (HTV 20 ml/kg). Mice were pretreated with TAK-242 the TLR4 inhibitor, C25-140, the TRAF6 inhibitor, or GSK2795039, the NOX2 inhibitor. Lung tissue and bronchoalveolar lavage fluid (BALF) were collected to measure lung injury, inflammatory responses and mRNA/protein expression associated with ER stress and the TLR4/TRAF6/NOX2 signaling pathway. Our results indicate that MV with HTV caused the TLR4/TRAF6/NOX2 signaling pathway activation and production of large amounts of ROS, which led to ER stress and NF-κB mediated inflammation in VILI. Furthermore, TLR4/TRAF6/NOX2 signaling pathway inhibition attenuated ER stress response and alleviate lung injury in mice.

The Role of Ferroptosis in Acute Respiratory Distress Syndrome

Ferroptosis is a newly discovered type of regulated cell death that is different from apoptosis, necrosis and autophagy. Ferroptosis is characterized by iron-dependent lipid peroxidation, which induces cell death. Iron, lipid and amino acid metabolism is associated with ferroptosis. Ferroptosis is involved in the pathological development of various diseases, such as neurological diseases and cancer. Recent studies have shown that ferroptosis is also closely related to acute lung injury (ALI)/ acute respiratory distress syndrome (ARDS), suggesting that it can be a novel therapeutic target. This article mainly introduces the metabolic mechanism related to ferroptosis and discusses its role in ALI/ARDS to provide new ideas for the treatment of these diseases.

Loss of Nucleobindin-2/Nesfatin-1 increases lipopolysaccharide-induced murine acute lung inflammation

NUCB2/nesfatin-1 is expressed in variety of tissues. Treatment with nesfatin-1 reduces inflammation in rat models of subarachnoid hemorrhage-induced oxidative brain damage and traumatic brain injury as well as myocardial injury. There is only one study showing anti-inflammatory actions of nesfatin-1 on acute lung inflammation. To more precisely determine the role of NUCB2/nesfatin-1 in acute lung inflammation, we conducted a study using NUCB2/nesfatin-1 knockout (NKO) mice as well as neutrophils isolated from the bone marrows of WT and NKO mice. Our findings suggest that the absence of NUCB2/nesfatin-1 significantly increases the accumulation of adherent neutrophils by approximately 3 times compared with WT within LPS-treated lungs. Integrating this with observations from both BALF and neutrophil cytokine expression, we propose that although neutrophils lacking NUCB2/nesfatin-1 individually secrete less pro-inflammatory cytokines compared with stimulated WT cells, the result of knocking out NUCB2/nesfatin-1 is net pro-inflammatory. No change was found in NUCB2/nesfatin-1 mRNA or protein expression comparing WT LPS and PBS-treated samples. Taken together, our results show that NUCB2/nesfatin-1 is constitutively expressed in mouse lungs and neutrophils and demonstrates anti-inflammatory properties in mouse lungs during acute lung injury, by inhibiting adherent neutrophil accumulation and inflammatory cytokine expression.

Mice Deficient in NOX2 Display Severe Thymic Atrophy, Lymphopenia, and Reduced Lymphopoiesis in a Zymosan-Induced Model of Systemic Inflammation

Patients with chronic granulomatous disease (CGD) who have mutated phagocyte NADPH oxidase are susceptible to infections due to reduced reactive oxygen species production and exhibit autoimmune and inflammatory diseases in the absence of evident infection. Neutrophils and macrophages have been extensively studied since phagocyte NADPH oxidase is mainly found only in them, while the impact of its deficiency on lymphocyte cellularity is less well characterized. We showed herein a zymosan-induced systemic inflammation model that CGD mice deficient in the phagocyte NADPH oxidase gp91phox subunit (NOX2) exhibited more severe thymic atrophy associated with peripheral blood and splenic lymphopenia and reduced lymphopoiesis in the bone marrow in comparison with the wild-type mice. Conversely, the zymosan-exposed CGD mice suffered from more remarkable neutrophilic lung inflammation, circulating and splenic neutrophilia, and enhanced granulopoiesis compared with those in zymosan-exposed wild-type mice. Overall, this study provided evidence that NOX2 deficiency exhibits severe thymic atrophy and lymphopenia concomitant with enhanced neutrophilic inflammation in a zymosan-induced systemic inflammation model.

Nox2 Regulates Platelet Activation and NET Formation in the Lung

The mortality rate of patients with critical illness has decreased significantly over the past two decades, but the rate of decline has slowed recently, with organ dysfunction as a major driver of morbidity and mortality. Among patients with the systemic inflammatory response syndrome (SIRS), acute lung injury is a common component with serious morbidity. Previous studies in our laboratory using a murine model of SIRS demonstrated a key role for NADPH oxidase 2 (Nox2)-derived reactive oxygen species in the resolution of inflammation. Nox2-deficient (gp91^phox−/y) mice develop profound lung injury secondary to SIRS and fail to resolve inflammation. Alveolar macrophages from gp91^phox−/y mice express greater levels of chemotactic and pro-inflammatory factors at baseline providing evidence that Nox2 in alveolar macrophages is critical for homeostasis. Based on the lung pathology with increased thrombosis in gp91^phox−/y mice, and the known role of platelets in the inflammatory process, we hypothesized that Nox2 represses platelet activation. In the mouse model, we found that platelet-derived chemokine (C-X-C motif) ligand 4 (CXCL4) and CXCL7 were increased in the bronchoalveolar fluid of gp91^phox−/y mice at baseline and 24 h post intraperitoneal zymosan-induced SIRS consistent with platelet activation. Activated platelets interact with leukocytes via P-selectin glycoprotein ligand 1 (PSGL-1). Within 2 h of SIRS induction, alveolar neutrophil PSGL-1 expression was higher in gp91^phox−/y mice. Platelet-neutrophil interactions were decreased in the peripheral blood of gp91^phox−/y mice consistent with movement of activated platelets to the lung of mice lacking Nox2. Based on the severe lung pathology and the role of platelets in the formation of neutrophil extracellular traps (NETs), we evaluated NET production. In contrast to previous studies demonstrating Nox2-dependent NET formation, staining of lung sections from mice 24 h post zymosan injection revealed a large number of citrullinated histone 3 (H3CIT) and myeloperoxidase positive cells consistent with NET formation in gp91^phox−/y mice that was virtually absent in WT mice. In addition, H3CIT protein expression and PAD4 activity were higher in the lung of gp91^phox−/y mice post SIRS induction. These results suggest that Nox2 plays a critical role in maintaining homeostasis by regulating platelet activation and NET formation in the lung.

Monocyte Chemoattractant Protein-1, a Possible Biomarker of Multiorgan Failure and Mortality in Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) leads to increased patients’ mortality and medical expenditure. Monocyte chemoattractant protein-1 (MCP-1) plays a role in the pathogenesis of lung inflammation and infection. Therefore, the plasma concentration of MCP-1 was assessed and correlated with the clinical course in VAP patients. This retrospective observational study recruited 45 healthy volunteers, 12 non-VAP subjects, and 30 VAP patients. The diagnostic criteria for VAP were based on the American Thoracic Society guidelines, and the level of plasma MCP-1 was determined by ELISA. Plasma MCP-1 concentration was significantly elevated in the acute stage in VAP patients when compared with the control (p < 0.0001) and non-VAP patient groups (p = 0.0006). Subsequently, it was remarkably decreased following antibiotic treatment. Moreover, plasma MCP-1 concentration was positively correlated with indices of pulmonary dysfunction, including the lung injury score (p = 0.02) and the oxygenation index (p = 0.02). When patients with VAP developed adult respiratory distress syndrome (ARDS), their plasma MCP-1 concentrations were significantly higher than those of patients who did not develop ARDS (p = 0.04). Moreover, plasma MCP-1 concentration was highly correlated with organ failure scores, including simplified acute physiology score II (SAPS II, p < 0.0001), sequential organ failure assessment score (SOFA, p < 0.0001), organ dysfunctions and/or infection (ODIN, p < 0.0001), predisposition, insult response and organ dysfunction (PIRO, p = 0.005), and immunodeficiency, blood pressure, multilobular infiltrates on chest radiograph, platelets and hospitalization 10 days before onset of VAP (IBMP-10, p = 0.004). Our results demonstrate that plasma MCP-1 is an excellent marker for recognizing VAP when the cut-off level is set to 347.18 ng/mL (area under the curve (AUC) = 0.936, 95% CI = 0.863–0.977). In conclusion, MCP-1 not only could be a biological marker related to pulmonary dysfunction, organ failure, and mortality in patients with VAP, but also could be used for early recognition of VAP.