Parapneumonic Effusions Are Characterized by Elevated Levels of Neutrophil Extracellular Traps

Neutrophil extracellular traps in homeostasis and disease

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

Neutrophil-mediated Inflammatory Plasminogen Degradation, Rather Than High Plasminogen-Activator Inhibitor-1, May Underly Failures and Inefficiencies of Intrapleural Fibrinolysis

BACKGROUND

Complex pleural space infections often require treatment with multiple doses of intrapleural tissue plasminogen activator (tPA) and deoxyribonuclease, with treatment failure frequently necessitating surgery. Pleural infections are rich in neutrophils, and neutrophil elastase degrades plasminogen, the target substrate of tPA, that is required to generate fibrinolysis. We hypothesized that pleural fluid from patients with pleural space infection would show high elastase activity, evidence of inflammatory plasminogen degradation, and low fibrinolytic potential in response to tPA that could be rescued with plasminogen supplementation.

RESEARCH QUESTION

Does neutrophil elastase degradation of plasminogen contribute to intrapleural fibrinolytic failure?

STUDY DESIGN AND METHODS

We obtained infected pleural fluid and circulating plasma from hospitalized adults (n = 10) with institutional review board approval from a randomized trial evaluating intrapleural fibrinolytics vs surgery for initial management of pleural space infection. Samples were collected before the intervention and on days 1, 2, and 3 after the intervention. Activity assays, enzyme-linked immunosorbent assays, and Western blot analysis were performed, and turbidimetric measurements of fibrinolysis were obtained from pleural fluid with and without exogenous plasminogen supplementation. Results are reported as median (interquartile range) or number (percentage) as appropriate, with an α value of .05.

RESULTS

Pleural fluid elastase activity was more than fourfold higher (P = .02) and plasminogen antigen levels were more than threefold lower (P = .04) than their corresponding plasma values. Pleural fluid Western blot analysis demonstrated abundant plasminogen degradation fragments consistent with elastase degradation patterns. We found that plasminogen activator inhibitor 1 (PAI-1), the native tPA inhibitor, showed high antigen levels before the intervention, but the overwhelming majority of this PAI-1 (82%) was not active (P = .003), and all PAI-1 activity was lost by day 2 after the intervention in patients receiving intrapleural tPA and deoxyribonuclease. Finally, using turbidity clot lysis assays, we found that the pleural fluid of 9 of 10 patients was unable to generate a significant fibrinolytic response when challenged with tPA and that plasminogen supplementation rescued fibrinolysis in all patients.

INTERPRETATION

Our findings suggest that inflammatory plasminogen deficiency, not high PAI-1 activity, is a significant contributor to intrapleural fibrinolytic failure.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03583931; URL: www.

CLINICALTRIALS

gov.

A review on gout: Looking back and looking ahead

Gout is a metabolic disease caused by the deposition of monosodium urate (MSU) crystals inside joints, which leads to inflammation and tissue damage. Increased concentration of serum urate is an essential step in the development of gout. Serum urate is regulated by urate transporters in the kidney and intestine, especially GLUT9 (SLC2A9), URAT1 (SLC22A12) and ABCG. Activation of NLRP3 inflammasome bodies and subsequent release of IL-1β by monosodium urate crystals induce the crescendo of acute gouty arthritis, while neutrophil extracellular traps (NETs) are considered to drive the self-resolving of gout within a few days. If untreated, acute gout may eventually develop into chronic tophaceous gout characterized by tophi, chronic gouty synovitis, and structural joint damage, leading the crushing burden of treatment. Although the research on the pathological mechanism of gout has been gradually deepened in recent years, many clinical manifestations of gout are still unable to be fully elucidated. Here, we reviewed the molecular pathological mechanism behind various clinical manifestations of gout, with a view to making contributions to further understanding and treatment.

Promising Neutrophil-Associated Biomarkers in Lung Diseases of Patients with Antisynthetase Syndrome and Dermatomyositis

Objectives

Antisynthetase syndrome (ASS) and dermatomyositis (DM) are serious autoimmune diseases, with lungs being the most frequently involved organ and sometimes fatal. This study is aimed at clarifying the role of neutrophil-associated biological markers in suggesting ASS and DM-associated respiratory infections and interstitial lung diseases.

Methods

We carried out a retrospective review of the medical records of 46 cases of ASS and DM diagnosed at the Second Hospital of Zhejiang University College of Medicine, between January 2017 and December 2020. Serum myeloperoxidase (MPO), neutrophil elastase (NE), α1 anti-trypsin (AAT), and interleukin-6 (IL-6) were also detected.

Results

Gottron's sign is characteristic of dermatomyositis, while polyarthritis is more characteristic of ASS. Pulmonary function is worse in ASS than in DM patients. Patients with ASS and DM had abnormal lymphocyte and neutrophil counts compared to healthy subjects, but not in relation to lung function and rapid progression of interstitial lung disease (RP-ILD). Elevated serum NE, MPO, and IL-6 levels are suggestive of respiratory infections, whereas decreased circulating IL-6 is predictive of RP-ILD.

Conclusion

Our study identified the neutrophil-associated biomarkers MPO, NE, and IL-6 as promising indicators with different suggestive roles in respiratory infections and interstitial lung diseases in patients with ASS and DM.

Influence of Malignant Pleural Fluid from Lung Adenocarcinoma Patients on Neutrophil Response

Simple Summary

This study provides novel information about the role of neutrophils in malignant pleural effusion (MPE) and hallmarks their clinical relevance. Since these cells have emerged as important regulators of cancer, we characterized their phenotype and functions in MPE microenvironment. We found that neutrophil-derived products (degranulation molecules and neutrophil extracellular traps (NETs)) were increased in MPE. In addition, NETs were associated with a worse outcome in lung adenocarcinoma patients with MPE.

Abstract

Malignant pleural effusion (MPE) is a common severe complication of advanced lung adenocarcinoma (LAC). Neutrophils, an essential component of tumor infiltrates, contribute to tumor progression and their counts in MPE have been associated with worse outcome in LAC. This study aimed to evaluate phenotypical and functional changes of neutrophils induced by MPE to determine the influence of MPE immunomodulatory factors in neutrophil response and to find a possible association between neutrophil functions and clinical outcomes. Pleural fluid samples were collected from 47 LAC and 25 heart failure (HF) patients. We measured neutrophil degranulation products by ELISA, oxidative burst capacity and apoptosis by flow cytometry, and NETosis by fluorescence. The concentration of degranulation products was higher in MPE-LAC than in PE-HF. Functionally, neutrophils cultured with MPE-LAC had enhanced survival and neutrophil extracellular trap (NET) formation but had reduced oxidative burst capacity. In MPE, NETosis was positively associated with MMP-9, P-selectin, and sPD-L1 and clinically related to a worse outcome. This is the first study associating NETs with a worse outcome in MPE. Neutrophils likely contribute to tumor progression through the release of NETs, suggesting that they are a potential therapeutic target in LAC.

Inflammation of the Pleural Cavity: A Review on Pathogenesis, Diagnosis and Implications in Tumor Pathophysiology

Pleural effusions are a common respiratory condition with many etiologies. Nonmalignant etiologies explain most pleural effusions and despite being nonmalignant, they can be associated with poor survival; thus, it is important to understand their pathophysiology. Furthermore, diagnosing a benign pleural pathology always harbors the uncertainty of a false-negative diagnosis for physicians and pathologists, especially for the group of non-specific pleuritis. This review aims to present the role of the inflammation in the development of benign pleural effusions, with a special interest in their pathophysiology and their association with malignancy.