CLEC5A is critical in Pseudomonas aeruginosa-induced acute lung injury

The natural compound PEITC ameliorates imiquimod-induced psoriasis in mice by suppressing neutrophil extracellular traps formation

Neutrophil extracellular traps (NETs) play a key role in the development of psoriasis, a chronic inflammatory skin condition. We demonstrate the effects and possible mechanisms of phenethyl isothiocyanate (PEITC) in inhibiting NETs and alleviating psoriasis. In response to imiquimod (IMQ), multiple symptoms including scaly plaques and associated skin inflammations were induced in mice. IMQ additionally promotes the formation of NETs and the levels of inflammatory factors. Interestingly, a natural compound PEITC exerted an intensive activity in the treatment of psoriasis. It improved lesions and ameliorated ischemic coagulation symptoms in the dorsal skin of mice. PEITC also significantly reduced the expression of inflammatory factors in mice skin with an inhibition on NETs-related molecules, such as myeloperoxidase, neutrophil elastase and citrullinated histone H3. 16S rRNA sequencing analysis demonstrated that IMQ treatment induced significant gut microbiota dysbiosis in mice, suggesting potential detrimental effects on intestinal microbial homeostasis. However, PEITC administration did not show a statistically significant ameliorative effect on this IMQ-induced microbial imbalance. In vitro experiments demonstrated that PEITC significantly suppressed lipopolysaccharide (LPS)-induced NET formation, suggesting that its therapeutic effects in psoriasis may be due to the inhibition of bacterially driven neutrophil activation. Therefore, we identified PAD4, an important enzyme for post-translational modification of proteins in the production of NETs, as a new potential target of PEITC. Taken together, our findings suggest that PEITC could be a novel potential therapeutic drug to relieve psoriasis via the inhibition of NETs both in vitro and in vivo.

Intrapulmonary-administered myeloid derived suppressor cells rescue mice from Pseudomonas aeruginosa infection and promote a regulatory/repair phenotype

Pseudomonas aeruginosa (P.aeruginosa) is a pathogenic opportunistic bacterium, classified as a priority by the WHO for the research of new treatments. As this bacterium is harmful through the inflammation and tissue damage it causes, we investigated the role of Myeloid Derived Suppressor Cells (MDSC) in P.aeruginosa infections and their potential as a therapeutic tool. Using both 'classically' obtained MDSC (through mice bone-marrow differentiation), and a new procedure developed here (using the ER-Hoxb8 hematopoietic cell line), we observed that after administering intra-nasally a lethal dose of P.aeruginosa (PAO1), intra-pulmonary transfer of MDSC, in both prophylactic and therapeutic protocols, markedly improves survival of P.aeruginosa infected animals. Mechanistically, with a sub-lethal dose of P.aeruginosa, we observed that MDSC transfer modulated lung tissue injury, down-regulated inflammatory responses and elicited lung repair. We further showed that WT-PAO1 and MDSC (and their subtypes PMN-MDSC and M-MDSC) could interact directly in vitro and in vivo, and that both PMN- and M-MDSC gene expression (assessed through RNA sequencing) was modulated after in vitro P.aeruginosa infection, and that WT-PAO1 (but not ΔFlic-PAO1) infection led to inhibition of T cell proliferation and promoted epithelial cell wound healing. Furthermore, we showed that the transcription factor Nr4A1 was up-regulated in both PMN- and M-MDSC- infected cells and may be an important mediator in the process. Altogether, we highlight a potential beneficial role of MDSC in P.aeruginosa infection responses and suggest that the unique properties of these cells make them attractive potential new therapeutic tools for patients with acute or chronic inflammatory diseases.

Activating Dectin-1/SOCS1 signaling attenuates pseudomonas aeruginosa-induced lung injury

OBJECTIVE

To investigate the role of Dectin-1 in alleviating Pseudomonas aeruginosa (PA)-induced lung injury and its underlying mechanism.

METHODS

Wild-type and Dectin-1 knockout (KO) C57BL/6 mice were exposed to PAvia intratracheal instillation. PAO1 strains were cultured, inactivated, and quantified. MHS cells were used in vitro. Curdlan was employed to activate Dectin-1 signaling, and SOCS1 expression was modulated through genetic manipulation. Levels of Dectin-1, Syk, p-Syk, SOCS1, p-p65, and p65 were assessed. Lung injury was evaluated using H&E and TUNEL staining, cell counts and protein content in bronchoalveolar lavage fluid (BALF), the lung tissue wet/dry ratio, and seven-day survival rates. Bacterial burden in the lung was assessed by PA colony formation. Inflammatory responses were measured by TNF-α, IL-6, and IL-1β levels in BALF, as well as the p-p65/p65 ratio in lung or cell lysates. Apoptosis rates in cells were determined by flow cytometry.

RESULTS

Dectin-1 expression was downregulated in the lungs and MHS cells following PA infection. Dectin-1 depletion exacerbated PA-induced lung injury. Activation of Dectin-1 by curdlan significantly alleviated PA-induced lung injury. PA infection reduced SOCS1 expression, and SOCS1 interference exacerbated the inflammatory response and apoptosis in MHS cells, nullifying the protective effects of curdlan. Overexpression of SOCS1 significantly reduced inflammation and apoptosis in both MHS cells and Dectin-1 KO mice.

CONCLUSIONS

Activation of Dectin-1 significantly mitigates PA-induced lung injury, with SOCS1 playing a critical role in this process.

CAPN1 Promotes Pseudomonas aeruginosa-Induced Infection by Interacting with TFEB and Inhibiting Autophagy

INTRODUCTION

Autophagy-lysosome pathways play a crucial role in the intracellular killing of pathogenic microorganisms. This study aimed to explore the mechanism by which acute lung injury (ALI) of Pseudomonas aeruginosa affects the autophagy-lysosome pathway.

METHODS

ALI mouse models were induced by lipopolysaccharide and P. aeruginosa strain K (PAK). Lung tissue sections were stained with hematoxylin-eosin for observation. Flow cytometry was used to analyze bacteria and inflammatory cell infiltration. ELISA was performed to measure inflammatory factor levels. Transmission electron microscopy evaluated autolysosome quantity. Western blot detected levels of related proteins. Immunofluorescence evaluated LC3 expression, and the localization of TFEB in cells was observed. Co-immunoprecipitation and pull-down experiments confirmed the interaction between CAPN1 and TFEB. qRT-PCR measured capn1 and tfeb expression.

RESULTS

Mouse experiments revealed that PAK infection led to the suppression of autolysosomes in mouse lung tissue, along with increased CAPN1 expression and decreased TFEB in the lung tissue of PAK-induced pneumonia mice. CAPN1-deficient mice could reverse the impact of PAK infection on autolysosomes in mouse lung tissue. These findings were further verified by cell experiments. At a mechanistic level, CAPN1 can interact with TFEB after PAK infection and prevent its entry into the nucleus, thereby inhibiting the autophagolysosomal pathway.

CONCLUSION

CAPN1 promotes PAK-induced ALI by inhibiting the autophagy-lysosome pathway by targeting TFEB.

INTRODUCTION

Autophagy-lysosome pathways play a crucial role in the intracellular killing of pathogenic microorganisms. This study aimed to explore the mechanism by which acute lung injury (ALI) of Pseudomonas aeruginosa affects the autophagy-lysosome pathway.

METHODS

ALI mouse models were induced by lipopolysaccharide and P. aeruginosa strain K (PAK). Lung tissue sections were stained with hematoxylin-eosin for observation. Flow cytometry was used to analyze bacteria and inflammatory cell infiltration. ELISA was performed to measure inflammatory factor levels. Transmission electron microscopy evaluated autolysosome quantity. Western blot detected levels of related proteins. Immunofluorescence evaluated LC3 expression, and the localization of TFEB in cells was observed. Co-immunoprecipitation and pull-down experiments confirmed the interaction between CAPN1 and TFEB. qRT-PCR measured capn1 and tfeb expression.

RESULTS

Mouse experiments revealed that PAK infection led to the suppression of autolysosomes in mouse lung tissue, along with increased CAPN1 expression and decreased TFEB in the lung tissue of PAK-induced pneumonia mice. CAPN1-deficient mice could reverse the impact of PAK infection on autolysosomes in mouse lung tissue. These findings were further verified by cell experiments. At a mechanistic level, CAPN1 can interact with TFEB after PAK infection and prevent its entry into the nucleus, thereby inhibiting the autophagolysosomal pathway.

CONCLUSION

CAPN1 promotes PAK-induced ALI by inhibiting the autophagy-lysosome pathway by targeting TFEB.

Coordination of Neutrophil and Apoptosis-Inducing Ligand in Inflammatory Diseases

As the most abundant innate immune cells, neutrophils play a key role in host's anti-infective activity and tissue damage/repair process of sterile inflammation. Due to the restriction of apoptosis and other regulatory mechanisms, neutrophils have a short survival time in vivo. Because of the death domain of cytoplasmic regions, some members of tumor necrosis factor receptor superfamily (TNFRSF) are defined as death receptors, such as TNFR-I, Fas and DR4/DR5. TNF-α, FasL and TRAIL, which are known as apoptosis-inducing ligand, can bind to death receptors and activate intracellular apoptosis pathways to induce apoptosis. Accumulating studies found that these three apoptosis-inducing ligands play an important role in the immune system by coordinating with neutrophil, which including neutrophil recruitment/infiltration and function performing. In this review, we summarize existing studies targeting neutrophils as diagnosis and treatment for diseases, and focus on the involvement of neutrophils which regulated by apoptosis-inducing ligands in inflammatory diseases under current cognition.

NAT10 induces mitochondrial dysfunction in lung epithelial cells by acetylating HMGB1 to exacerbate Pseudomonas aeruginosa-induced acute lung injury

BACKGROUND

Pseudomonas aeruginosa (PA) is a major pathogen that causes pneumonia and acute lung injury (ALI). Dysregulated NAT10 expression is associated with inflammatory and infectious diseases, but its role in PA-induced ALI remains unclear.

METHODS

A mouse pneumonia model was established by intratracheal injection of PA, and lentivirus-mediated NAT10 interference and HMGB1 overexpression vectors were administered via the tail vein. Lung mechanics, protein content, total cell counts, neutrophil counts, inflammatory factor levels in bronchoalveolar lavage fluid (BALF), and lung bacterial load were assessed 24 h after PA injection. HE staining was performed to evaluate lung structural damage. Intracellular oxidative stress levels in mouse lung epithelial cells (TC-1 cells) were measured by detecting ROS and MDA levels. Mitochondrial function was analyzed by testing the mitochondrial membrane potential, cytoplasmic accumulation of cytochrome C, mtDNA copy number, and ATP production. An N4-acetylcytidine (ac4C)-RNA immunoprecipitation assay was conducted to assess the ac4C level of HMGB1 mRNA.

RESULTS

NAT10 deficiency hindered PA infection-induced increases in immune cell infiltration, inflammatory factor levels, bacterial load, and ultimately lung structural and functional damage. However, upregulation of HMGB1 effectively antagonized the protective effects of NAT10 silencing in vivo. NAT10 knockdown suppressed PA-induced oxidative stress, mitochondrial dysfunction, and apoptosis in vitro. Whereas, HMGB1 overexpression reversed the inhibitory effects of NAT10 downregulation on PA-induced TC-1 cell injury. Mechanistically, as an acetyltransferase, NAT10 enhanced HMGB1 mRNA stability and protein expression by promoting HMGB1 mRNA ac4C modification.

CONCLUSION

NAT10 facilitated mitochondrial dysfunction in lung epithelial cells and exacerbated PA-induced ALI by promoting the N4-acetylcytidine of HMGB1 mRNA.

Fatty Acids Derived from Royal Jelly Exert Anti-Inflammatory and Antibacterial Activities in the Treatment of Pseudomonas aeruginosa-Induced Acute Pneumonia

Pseudomonas aeruginosa, an opportunistic pathogen, commonly causes hospital-acquired pneumonia. Royal jelly fatty acids (RJFAs), a mixture of various fatty acids extracted from royal jelly, exhibit antibacterial and anti-inflammatory properties in treating many infectious diseases. Nevertheless, the therapeutic mechanisms of RJFAs in treatment of acute P. aeruginosa pulmonary infection are still unclear. Herein, we initially extracted the fatty acids from royal jelly and characterized their chemical constituents using headspace gas chromatography-mass spectrometry. Furthermore, we examined the antibacterial effect of RJFAs in vitro and explored its therapeutic effect and molecular mechanisms in treating acute P. aeruginosa pulmonary infection in vivo. The in vitro antibacterial studies revealed that RJFAs significantly inhibited P. aeruginosa growth. Moreover, the in vivo studies showed that the RJFAs effectively mitigated the lung damage and inflammation induced by P. aeruginosa through impairing neutrophil infiltration, reducing the bacterial load in lung and diminishing the production of proinflammatory cytokines, including tumor necrosis factor (TNF-α), interleukin (IL-1β), IL-6, and macrophage inflammatory protein-2 (MIP-2). In addition, the mice treated with RJFAs exhibited reduced phosphorylation of extracellular signal-regulated kinase (ERK), p38, c-Jun N-terminal kinase (JNK), c-Jun, and nuclear factor-kappa B (NF-κB) p65 in the lung tissues in comparison with that of the mice without drug treatment. These findings demonstrated that RJFAs exhibited significant antibacterial and anti-inflammatory effects in treating the P. aeruginosa-induced acute pneumonia, and the anti-inflammatory effects were exerted through suppressing the mitogen-activated protein kinase/activator protein-1 (MAPK/AP-1) pathway and NF-κB activation, suggesting a promising therapeutic potential of RJFAs against acute bacterial pneumonia.

The deficient CLEC5A ameliorates the behavioral and pathological deficits via the microglial Aβ clearance in Alzheimer's disease mouse model

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disease that causes cognitive dysfunction in older adults. One of the AD pathological factors, β-Amyloid (Aβ), triggers inflammatory responses and phagocytosis of microglia. C-type lectin domain family 5 member A (CLEC5A) induces over-reactive inflammatory responses in several virus infections. Yet, the role of CLEC5A in AD progression remains unknown. This study aimed to elucidate the contribution of CLEC5A to Aβ-induced microglial activation and behavioral deficits.

METHODS

The AD mouse model was crossed with Clec5a knockout mice for subsequent behavioral and pathological tests. The memory deficit was revealed by the Morris water maze, while the nociception abnormalities were examined by the von Frey filament and hotplate test. The Aβ deposition and microglia recruitment were identified by ELISA and immunohistochemistry. The inflammatory signals were identified by ELISA and western blotting. In the Clec5a knockdown microglial cell model and Clec5a knockout primary microglia, the microglial phagocytosis was revealed using the fluorescent-labeled Aβ.

RESULTS

The AD mice with Clec5a knockout improved Aβ-induced memory deficit and abnormal nociception. These mice have reduced Aβ deposition and increased microglia coverage surrounding the amyloid plaque, suggesting the involvement of CLEC5A in AD progression and Aβ clearance. Moreover, the phagocytosis was also increased in the Aβ-stressed Clec5a knockdown microglial cell lines and Clec5a knockout primary microglia.

CONCLUSION

The Clec5a knockout ameliorates AD-like deficits by modulating microglial Aβ clearance. This study implies that targeting microglial Clec5a could offer a promising approach to mitigate AD progression.

Lung Progenitor and Stem Cell Transplantation as a Potential Regenerative Therapy for Lung Diseases

Chronic lung diseases are debilitating illnesses ranking among the top causes of death globally. Currently, clinically available therapeutic options capable of curing chronic lung diseases are limited to lung transplantation, which is hindered by donor organ shortage. This highlights the urgent need for alternative strategies to repair damaged lung tissues. Stem cell transplantation has emerged as a promising avenue for regenerative treatment of the lung, which involves delivery of healthy lung epithelial progenitor cells that subsequently engraft in the injured tissue and further differentiate to reconstitute the functional respiratory epithelium. These transplanted progenitor cells possess the remarkable ability to self-renew, thereby offering the potential for sustained long-term treatment effects. Notably, the transplantation of basal cells, the airway stem cells, holds the promise for rehabilitating airway injuries resulting from environmental factors or genetic conditions such as cystic fibrosis. Similarly, for diseases affecting the alveoli, alveolar type II cells have garnered interest as a viable alveolar stem cell source for restoring the lung parenchyma from genetic or environmentally induced dysfunctions. Expanding upon these advancements, the use of induced pluripotent stem cells to derive lung progenitor cells for transplantation offers advantages such as scalability and patient specificity. In this review, we comprehensively explore the progress made in lung stem cell transplantation, providing insights into the current state of the field and its future prospects.

CLEC5A Promotes Neuronal Pyroptosis in Rat Spinal Cord Injury Models by Interacting with TREM1 and Elevating NLRC4 Expression

Pyroptosis, an inflammatory programmed cell death, has recently been found to play an important role in spinal cord injury (SCI). C-type lectin domain family 5 member A (CLEC5A), triggering receptor expressed on myeloid cells 1 (TREM1), and NLR-family CARD-containing protein 4 (NLRC4) have been reported to be associated with neuronal pyroptosis, but few studies have clarified their functions and regulatory mechanisms in SCI. In this study, CLEC5A, TREM1, and NLRC4 were highly expressed in lidocaine-induced SCI rat models, and their knockdown alleviated lidocaine-induced SCI. The elevation of pyroptosis-related indicators LDH, ASC, GSDMD-N, IL-18, caspase-1, and IL-1β levels in SCI rats was attenuated after silencing of CLEC5A, TREM1, or NLRC4. Lidocaine-induced decrease in cell viability and the elevation in cell death were partly reversed after CLEC5A, TREM1, or NLRC4 silencing. Lidocaine-mediated effects on the levels of LDH, ASC, GSDMD-N, IL-18, caspase-1, and IL-1β in lidocaine-induced PC12 cells were weakened by downregulating CLEC5A, TREM1, or NLRC4. CLEC5A could interact with TREM1 to mediate NLRC4 expression, thus accelerating neuronal pyroptosis, ultimately leading to SCI exacerbation. In conclusions, CLEC5A interacted with TREM1 to increase NLRC4 expression, thus promoting neuronal pyroptosis in rat SCI models, providing new insights into the role of neuronal pyroptosis in SCI.

Data-driven analysis that integrates bioinformatics and machine learning uncovers PANoptosis-related diagnostic genes in early pediatric septic shock

Objectives

Sepsis is one of the leading causes of death for children worldwide. Additionally, refractory septic shock is one of the most significant groups that contributes to a high death rate. The interaction of pyroptosis, apoptosis, and necroptosis results in a unique inflammatory cell death mechanism known as PANoptosis. An increasing amount of evidence suggests that PANoptosis can be brought on by several stimuli, including cytokine storms, malignancy, and bacterial or viral infections. The goal of this study is to improve the diagnostic significance of the PANoptosis-related gene signature in early pediatric septic shock.

Design and methods

We examined children with septic shock from the GSE66099 discovery cohort and looked at differentially expressed genes (DEGs). To filter the important modules, weighted gene co-expression network analysis (WCGNA) was employed. In the end, random forest analysis and the least absolute shrinkage and selection operator (LASSO) were used to determine the PANoptosis diagnostic signature genes. To determine the PANoptosis signature genes, we also found four validation cohorts: GSE26378, GSE26440, GSE8121, and GSE13904. The area under the curve (AUC) of the receiver operating characteristic curves (ROCs), along with sensitivity, specificity, positive predictive value, and negative predictive value, were used to assess the diagnostic efficacy of these signature genes.

Results

From GSE66099, 1142 DEGs in total were tested. Following the WGCNA clustering of the data into 16 modules, the MEgrey module showed a significant correlation with pediatric septic shock (p < 0.0001). Following the use of LASSO and random forest algorithms to identify the PANoptosis-related signature genes, which include ANXA3, S100A9, TXN, CLEC5A, and TMEM263. These signature genes' receiver operating characteristic curves (ROCs) were confirmed in the external dataset from GSE26378, GSE26440, GSE8121, and GSE13904, and were 0.994 (95 % CI 0.987-0.999), 0.987 (95 % CI 0.974-0.997), 0.957 (95 % CI 0.927-0.981), 0.974 (95 % CI 0.954-0.988), 0.897 (95 % CI 0.846-0.941), respectively.

Conclusion

In summary, the discovery of PANoptosis genes, ANXA3, S100A9, TXN, CLEC5A, and TMEM263 proved to be quite helpful in the early detection of pediatric septic shock patients. These early results, which need to be further confirmed in basic and clinical research, are extremely important for understanding immune cell infiltration in the pathophysiology of pediatric septic shock.

The influence of CLEC5A on early macrophage-mediated inflammation in COPD progression

Chronic obstructive pulmonary disease (COPD) is a complex syndrome with poorly understood mechanisms driving its early progression (GOLD stages 1-2). Elucidating the genetic factors that influence early-stage COPD, particularly those related to airway inflammation and remodeling, is crucial. This study analyzed lung tissue sequencing data from patients with early-stage COPD (GSE47460) and smoke-exposed mice. We employed Weighted Gene Co-Expression Network Analysis (WGCNA) and machine learning to identify potentially pathogenic genes. Further analyses included single-cell sequencing from both mice and COPD patients to pinpoint gene expression in specific cell types. Cell-cell communication and pseudotemporal analyses were conducted, with findings validated in smoke-exposed mice. Additionally, Mendelian randomization (MR) was used to confirm the association between candidate genes and lung function/COPD. Finally, functional validation was performed in vitro using cell cultures. Machine learning analysis of 30 differentially expressed genes identified 8 key genes, with CLEC5A emerging as a potential pathogenic factor in early-stage COPD. Bioinformatics analyses suggested a role for CLEC5A in macrophage-mediated inflammation during COPD. Two-sample Mendelian randomization linked CLEC5A single nucleotide polymorphisms (SNPs) with Forced Expiratory Volume in One Second (FEV1), FEV1/Forced Vital Capacity (FVC) and early/later on COPD. In vitro, the knockdown of CLEC5A led to a reduction in inflammatory markers within macrophages. Our study identifies CLEC5A as a critical gene in early-stage COPD, contributing to its pathogenesis through pro-inflammatory mechanisms. This discovery offers valuable insights for developing early diagnosis and treatment strategies for COPD and highlights CLEC5A as a promising target for further investigation.

REEP5 mediates the function of CLEC5A to alleviate myocardial infarction by inhibiting endoplasmic reticulum stress-induced apoptosis

MI (myocardial infarction) often triggers severe heart failure and is one of the leading causes of death worldwide. Receptor expression-enhancing protein 5 (REEP5), a member of REEPs, acts as regulators of endoplasmic reticulum (ER) affecting cardiac functions. Based on GSE114695 profile data, REEP5 was decreased in the left ventricle of MI mice. However, its role and potential mechanism in MI remain to be investigated. In the present study, the mouse MI model was established by ligation of the left anterior descending artery. REEP5 expression was downregulated in the infarct penumbra area of MI mice. Next, its role during MI was explored by gain-of-function. Interestingly, REEP5 overexpression improved left ventricular function of mice with MI, accompanied with reduced infarct size. In cardiomyocytes, REEP5 overexpression inhibited ER stress, accompanied with repressive phosphorylation of PERK and IRE1α, and the decreased nuclear translocation of ATF6. Subsequently, REEP5 overexpression downregulated the levels of Chop and cleaved caspase-12, further alleviating ER stress-induced apoptosis, which was consistent with the in vivo results. Moreover, REEP5 was found to bind to C-type lectin member 5 A (CLEC5A), a protein that triggers cardiac dysfunction. CLEC5A, whose expression was elevated in hypoxia-induced cell models, led to cardiomyocyte apoptosis. Noteworthily, REEP5 overexpression markedly abolished the effects of CLEC5A on ER stress-induced apoptosis. Taken together, REEP5 mediated the function of CLEC5A to relieve MI via inhibiting ER stress-induced apoptosis in vivo and in vitro. REEP5 may be a promising target for treating MI.

ARAP3 protects from excessive formylated peptide-induced microvascular leakage by acting on endothelial cells and neutrophils

Vascular permeability is temporarily heightened during inflammation, but excessive inflammation-associated microvascular leakage can be detrimental, as evidenced in the inflamed lung. Formylated peptides regulate vascular leakage indirectly via formylated peptide receptor-1 (FPR1)-mediated recruitment and activation of neutrophils. Here we identify how the GTPase-activating protein ARAP3 protects against formylated peptide-induced microvascular permeability via endothelial cells and neutrophils. In vitro, Arap3-/- endothelial monolayers were characterised by enhanced formylated peptide-induced permeability due to upregulated endothelial FPR1 and enhanced vascular endothelial cadherin internalisation. In vivo, enhanced inflammation-associated microvascular leakage was observed in Arap3-/- mice. Leakage of plasma protein into the lungs of Arap3-/- mice increased within hours of formylated peptide administration. Adoptive transfer experiments indicated this was dependent upon ARAP3 deficiency in both immune and non-immune cells. Bronchoalveolar lavages of formylated peptide-challenged Arap3-/- mice contained neutrophil extracellular traps (NETs). Pharmacological inhibition of NET formation abrogated excessive microvascular leakage, indicating a critical function of NETs in this context. The observation that Arap3-/- mice developed more severe influenza suggests these findings are pertinent to pathological situations characterised by abundant formylated peptides. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Endothelial ERG programs neutrophil transcriptome for sustained anti-inflammatory vascular niche

Neutrophils (PMNs) reside as a marginated pool within the vasculature, ready for deployment during infection. However, how endothelial cells (ECs) control PMN extravasation and activation to strengthen tissue homeostasis remains ill-defined. Here, we found that the vascular ETS-related gene (ERG) is a generalized mechanism regulating PMN activity in preclinical tissue injury models and human patients. We show that ERG loss in ECs rewired PMN-transcriptome, enriched for genes associated with the CXCR2-CXCR4 signaling. Rewired PMNs compromise mice survival after pneumonia and induced lung vascular inflammatory injury following adoptive transfer into naïve mice, indicating their longevity and inflammatory activity memory. Mechanistically, EC-ERG restricted PMN extravasation and activation by upregulating the deubiquitinase A20 and downregulating the NFκB-IL8 cascade. Rescuing A20 in EC-Erg -/- endothelium or suppressing PMN-CXCR2 signaling rescued EC control of PMN activation. Findings deepen our understanding of EC control of PMN-mediated inflammation, offering potential avenues for targeting various inflammatory diseases.

Highlights

ERG regulates trans-endothelial neutrophil (PMN) extravasation, retention, and activationLoss of endothelial (EC) ERG rewires PMN-transcriptomeAdopted transfer of rewired PMNs causes inflammation in a naïve mouse ERG transcribes A20 and suppresses CXCR2 function to inactivate PMNs.

In brief/blurb

The authors investigated how vascular endothelial cells (EC) control polymorphonuclear neutrophil (PMN) extravasation, retention, and activation to strengthen tissue homeostasis. They showed that EC-ERG controls PMN transcriptome into an anti-adhesive and anti-inflammatory lineage by synthesizing A20 and suppressing PMNs-CXCR2 signaling, defining EC-ERG as a target for preventing neutrophilic inflammatory injury.

Neutrophil Infiltration and Function in the Pathogenesis of Inflammatory Airspace Disease

Neutrophils are an important cell type often considered the body's first responders to inflammatory insult or damage. They are recruited to the tissue of the lungs in patients with inflammatory airspace diseases and have unique and complex functions that range from helpful to harmful. The uniqueness of these functions is due to the heterogeneity of the inflammatory cascade and retention in the vasculature. Neutrophils are known to marginate, or remain stagnant, in the lungs even in nondisease conditions. This review discusses the ways in which the recruitment, presence, and function of neutrophils in the airspace of the lungs are unique from those of other tissues, and the complex effects of neutrophils on pathogenesis. Inflammatory mediators produced by neutrophils, such as neutrophil elastase, proresolving mediators, and neutrophil extracellular traps, dramatically affect the outcomes of patients with disease of the lungs.

Myeloid C-type lectin receptors in innate immune recognition

C-type lectin receptors (CLRs) expressed by myeloid cells constitute a versatile family of receptors that play a key role in innate immune recognition. Myeloid CLRs exhibit a remarkable ability to recognize an extensive array of ligands, from carbohydrates and beyond, and encompass pattern-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), and markers of altered self. These receptors, classified into distinct subgroups, play pivotal roles in immune recognition and modulation of immune responses. Their intricate signaling pathways orchestrate a spectrum of cellular responses, influencing processes such as phagocytosis, cytokine production, and antigen presentation. Beyond their contributions to host defense in viral, bacterial, fungal, and parasitic infections, myeloid CLRs have been implicated in non-infectious diseases such as cancer, allergies, and autoimmunity. A nuanced understanding of myeloid CLR interactions with endogenous and microbial triggers is starting to uncover the context-dependent nature of their roles in innate immunity, with implications for therapeutic intervention.

Pyroptosis-related signatures predict immune characteristics and prognosis in IPF

The purpose of this work was to use integrated bioinformatics analysis to screen for pyroptosis-related genes (PRGs) and possible immunological phenotypes linked to the development and course of IPF. Transcriptome sequencing datasets GSE70866, GSE47460 and GSE150910 were obtained from GEO database. From the GSE70866 database, 34 PRGs with differential expression were found in IPF as compared to healthy controls. In addition, a diagnostic model containing 4 genes PRGs (CAMP, MKI67, TCEA3 and USP24) was constructed based on LASSO logistic regression. The diagnostic model showed good predictive ability to differentiate between IPF and healthy, with ROC-AUC ranging from 0.910 to 0.997 in GSE70866 and GSE150910 datasets. Moreover, based on a combined cohort of the Freiburg and the Siena cohorts from GSE70866 dataset, we identified ten PRGs that might predict prognosis for IPF. We constructed a prognostic model that included eight PRGs (CLEC5A, TREM2, MMP1, IRF2, SEZ6L2, ADORA3, NOS2, USP24) by LASSO Cox regression and validated it in the Leuven cohort. The risk model divided IPF patients from the combined cohort into high-risk and low-risk subgroups. There were significant differences between the two subgroups in terms of IPF survival and GAP stage. There is a close correlation between leukocyte migration, plasma membrane junction, and poor prognosis in a high-risk subgroup. Furthermore, a high-risk score was associated with more plasma cells, activated NK cells, monocytes, and activated mast cells. Additionally, we identified HDAC inhibitors in the cMAP database that might be therapeutic for IPF. To summarize, pyroptosis and its underlying immunological features are to blame for the onset and progression of IPF. PRG-based predictive models and drugs may offer new treatment options for IPF.

Demethyleneberberine alleviates Pseudomonas aeruginosa-induced acute pneumonia by inhibiting the AIM2 inflammasome and oxidative stress

BACKGROUND

Acute pneumonia induced by Pseudomonas aeruginosa is characterized by massive infiltration of inflammatory cell and the production of reactive oxygen species (ROS), which lead to severe and transient pulmonary inflammation and acute lung injury. However, P.aeruginosa infection is resistant to multiple antibiotics and causes high mortality in clinic, the search for alternative prophylactic and therapeutic strategies is imperative.

PURPOSE

This study was aimed to investigate the anti-inflammatory and antioxidant effects of DMB, a novel derivative of berberine, and explore the role of AIM2 inflammasome in P. aeruginosa-induced acute pneumonia.

METHODS

Acute pneumonia mice were established by tracheal injection of P. aeruginosa suspension. Pathological changes of lung tissue were observed by its appearance and H&E staining. The lung coefficient ratio was measured to evaluate pulmonary edema. Inflammatory factors were detected by qRT-PCR, western blotting and immunohistochemistry. ROS and other indicators of oxidative damage were analyzed by flow cytometry and specific kit. Proteins related to AIM2 inflammasome were detected by western blotting.

RESULTS

Compared with the P. aeruginosa-induced group, DMB ameliorated pulmonary edema, hyperemia, and pathological damage based on its appearance and H&E staining in DMB groups. First, DMB attenuated the inflammatory response induced by P.aeruginosa. Compared with the P. aeruginosa-induced group, the lung coefficient ratio was decreased by 31.5%, the MPO activity of lung tissue was decreased by 44.0%, the mRNA expression levels of TNF-α, IL-1β and IL-6 were decreased by 64.8%, 51.2% and 64.0% respectively, and those protein expression levels were decreased by 40.1%, 42.8% and 47.8% respectively, and the number of white blood cells, neutrophils and monocytes were decreased by 53.5%, 29.4% and 13.7% in high dose (200 mg/kg) DMB group. Second, DMB alleviates oxidative stress in the lung tissue during P. aeruginosa-induced acute pneumonia. Compared with the P. aeruginosa-induced group, the level of GSH was increased by 42.5% and MDA was decreased by 49.5% in high dose DMB group. Moreover, the western blotting results showed that DMB markedly suppressed the expression of AIM2, ASC, Cleaved caspase1 and decreased the secretion of IL-1β. Additionally, these results were also confirmed by in vitro experiments using MH-S and BEAS-2B cell lines.

CONCLUSIONS

Taken together, these results indicated that DMB ameliorates P. aeruginosa-induced acute pneumonia through anti-inflammatory, antioxidant effects, and inhibition of AIM2 inflammasome activation.

Erythropoietin inhibits neutrophil extracellular traps formation to ameliorate lung injury in a pneumonia model

BACKGROUND

Severe pneumonia is a kind of disease that develops from lung inflammation, and new drugs are still required to treat the same. Erythropoietin (EPO) is widely used to treat anemia in patients. However, there are fewer studies on the role of EPO in neutrophil extracellular trappings (NETs) and pneumonia, and the mechanism is unclear.

OBJECTIVE

To investigate the possible effects of EPO on the formation of NETs and progression of pneumonia.

METHODS

Mice pneumonia model was induced by tracheal lipopolysaccharide (LPS) administration. Hematoxylin and eosin (H&E) staining and automatic blood cell analysis were performed in this model to confirm the effects of EPO on lung injury. Flow cytometry, enzyme-linked immunosorbent serological assay, and immunostaining assay were conducted to detect the effects of EPO on the inflammation as well as formation of NETs in mice. Immunoblot was further conducted to confirm the mechanism.

RESULTS

EPO alleviated LPS-induced lung injury. EPO reduced the release of inflammatory factors induced by LPS. In addition, EPO inhibited the formation of NETs. Mechanically, EPO inhibited tumor necrosis factor (TNF) receptor associated factor 2 (TRAF2)/nuclear factor kappa-B (NF-κB) activity in mouse models, and therefore suppressed the progression of pneumonia.

CONCLUSION

EPO inhibited formation of NETs to ameliorate lung injury in a pneumonia model, and could serve as a drug of pneumonia.

IL-8 Triggers Neutrophil Extracellular Trap Formation Through an Nicotinamide Adenine Dinucleotide Phosphate Oxidase- and Mitogen-Activated Protein Kinase Pathway-Dependent Mechanism in Uveitis

Purpose

To explore the mechanism underlying IL-8-induced neutrophil extracellular trap (NET) formation in patients with ocular-active Behçet's disease (BD) and the effect of inhibiting NET formation on the severity of inflammation in experimental autoimmune uveitis (EAU) mice.

Methods

The serum extracellular DNA and neutrophil elastase (NE) and IL-8 levels in patients with ocular-active BD, the expression of myeloperoxidase, NE, and histone H3Cit in IL-8-induced neutrophils isolated from healthy controls, and the effects of NETs on HMC3 cells were detected. Female C57BL/6J mice were immunized with IRBP651-670 to induce EAU and EAU mice received intravitreal injection of the CXCR2 (IL-8 receptor) antagonist SB225002 or PBS. The serum levels of extracellular DNA, NE, and keratinocyte-derived chemokine (the mouse ortholog of human IL-8) and expression of myeloperoxidase, NE, and histone H3Cit in mouse retinas were detected. Disease severity was evaluated by clinical and histopathological scores.

Results

Serum keratinocyte-derived chemokine expression levels in EAU mice and IL-8 expression levels in patients with ocular-active BD increased. IL-8 notably increased NET formation in a dose-dependent manner through an nicotinamide adenine dinucleotide phosphate oxidase and mitogen-activated protein kinase pathway dependent mechanism. IL-8-induced NET formation damaged HMC3 cells in vitro. Pretreatment with SB225002 notably ameliorated the production of NETs in EAU mice.

Conclusions

Our data confirm that NET formation is induced by IL-8. IL-8-induced NET formation was found to be related to mitogen-activated protein kinase and nicotinamide adenine dinucleotide phosphate pathways. Pretreatment with the CXCR2 antagonist SB225002 alleviated neutrophil infiltration and suppressed NET formation in EAU mice.

The perspectives of NETosis on the progression of obesity and obesity-related diseases: mechanisms and applications

Obesity is a disease commonly associated with urbanization and can also be characterized as a systemic, chronic metabolic condition resulting from an imbalance between energy intake and expenditure. The World Health Organization (WHO) has identified obesity as the most serious chronic disease that is increasingly prevalent in the world population. If left untreated, it can lead to dangerous health issues such as hypertension, hyperglycemia, hyperlipidemia, hyperuricemia, nonalcoholic steatohepatitis, atherosclerosis, and vulnerability to cardiovascular and cerebrovascular events. The specific mechanisms by which obesity affects the development of these diseases can be refined to the effect on immune cells. Existing studies have shown that the development of obesity and its associated diseases is closely related to the balance or lack thereof in the number and function of various immune cells, of which neutrophils are the most abundant immune cells in humans, infiltrating and accumulating in the adipose tissues of obese individuals, whereas NETosis, as a newly discovered type of neutrophil-related cell death, its role in the development of obesity and related diseases is increasingly emphasized. The article reviews the significant role that NETosis plays in the development of obesity and related diseases, such as diabetes and its complications. It discusses the epidemiology and negative impacts of obesity, explains the mechanisms of NETosis, and examines its potential as a targeted drug to treat obesity and associated ailments.

Spectrum of Thrombotic Complications in Fatal Cases of COVID-19: Focus on Pulmonary Artery Thrombosis In Situ

COVID-19-related thrombosis affects the venous and arterial systems. Data from 156 autopsies of COVID-19 patients were retrospectively analyzed to investigate the pattern of thrombotic complications and factors associated with pulmonary artery thrombosis and thromboembolism. Thrombotic complications were observed in a significant proportion (n = 68, 44%), with pulmonary artery thrombosis the most frequently identified thrombotic event (42, 27%). Multivariate analysis revealed that the length of hospital stay (OR 1.1, p = 0.004), neutrophil infiltration in the alveolar spaces (OR 3.6, p = 0.002), and the absence of hyaline membranes (OR 0.1, p = 0.01) were associated with thrombotic complications. Neutrophil infiltration in the alveolar spaces (OR 8, p < 0.001) and the absence of hyaline membranes (OR 0.1, p = 0.003) were also independent predictors of pulmonary artery thrombosis. The association of pulmonary artery thrombosis with an absence of hyaline membranes suggests it occurs later in the course of COVID-19 infection. As neutrophil infiltration in the alveolar spaces may indicate bacterial infection, our studies suggest the consideration of bacterial infections in these critically ill patients.

Gasdermins assemble; recent developments in bacteriology and pharmacology

The discovery of gasdermin D (GSDMD) as the terminal executioner of pyroptosis provided a large piece of the cell death puzzle, whilst simultaneously and firmly putting the gasdermin family into the limelight. In its purest form, GSDMD provides a connection between the innate alarm systems to an explosive, inflammatory form of cell death to jolt the local environment into immunological action. However, the gasdermin field has moved rapidly and significantly since the original seminal work and novel functions and mechanisms have been recently uncovered, particularly in response to infection. Gasdermins regulate and are regulated by mechanisms such as autophagy, metabolism and NETosis in fighting pathogen and protecting host. Importantly, activators and interactors of the other gasdermins, not just GSDMD, have been recently elucidated and have opened new avenues for gasdermin-based discovery. Key to this is the development of potent and specific tool molecules, so far a challenge for the field. Here we will cover some of these recently discovered areas in relation to bacterial infection before providing an overview of the pharmacological landscape and the challenges associated with targeting gasdermins.

Disulfiram accelerates diabetic foot ulcer healing by blocking NET formation via suppressing the NLRP3/Caspase-1/GSDMD pathway

Diabetic foot ulcer (DFU) is among the most frequent complications of diabetes and is associated with significant morbidity and mortality. Excessive neutrophil extracellular traps (NETs) delay wound healing in diabetic patients. Therefore, interventions targeting NET release need to be developed to effectively prevent NET-based wound healing impairment. Gasdermin D (GSDMD), a pore-forming protein acts as a central executioner of inflammatory cell death and can activate inflammasomes in neutrophils to release NETs. A precise understanding of the mechanism underlying NET-mediated delay in diabetic wound healing may be valuable in identifying potential therapeutic targets to improve clinical outcomes. In this study, we reported that neutrophils were more susceptible to NETosis in diabetic wound environments of patients with DFU. By in vitro experiments and using in vivo mouse models of diabetic wound healing (wide-type, Nlrp3^-/-, Casp-1^-/-, and Gsdmd^-/- mice), we demonstrated that NLRP3/caspase-1/GSDMD pathway on activation controls NET release by neutrophils in diabetic wound tissue. Furthermore, inhibition of GSDMD with disulfiram or genic deletion of Gsdmd abrogated NET formation, thereby accelerating diabetic wound healing. Disulfiram could inhibit NETs-mediated diabetic foot ulcer healing impairment by suppressing the NLRP3/Caspase-1/GSDMD pathway. In summary, our findings uncover a novel therapeutic role of disulfiram in inhibiting NET formation, which is of considerable value in accelerating wound healing in patients with DFU.