NET-targeted therapy: effects, limitations, and potential strategies to enhance treatment efficacy

Single-cell atlas of human gingiva unveils a NETs-related neutrophil subpopulation regulating periodontal immunity

INTRODUCTION

Exaggerated neutrophil recruitment and activation are the major features of pathological alterations in periodontitis, in which neutrophil extracellular traps (NETs) are considered to be responsible for inflammatory periodontal lesions. Despite the critical role of NETs in the development and progression of periodontitis, their specific functions and mechanisms remain unclear.

OBJECTIVES

To demonstrate the important functions and specific mechanisms of NETs involved in periodontal immunopathology.

METHODS

We performed single-cell RNA sequencing on gingival tissues from both healthy individuals and patients diagnosed with periodontitis. High-dimensional weighted gene co-expression network analysis and pseudotime analysis were then applied to characterize the heterogeneity of neutrophils. Animal models of periodontitis were treated with NETs inhibitors to investigate the effects of NETs in severe periodontitis. Additionally, we established a periodontitis prediction model based on NETs-related genes using six types of machine learning methods. Cell-cell communication analysis was used to identify ligand-receptor pairs among the major cell groups within the immune microenvironment.

RESULTS

We constructed a single-cell atlas of the periodontal microenvironment and obtained nine major cell populations. We further identified a NETs-related subgroup (NrNeu) in neutrophils. An in vivo inhibition experiment confirmed the involvement of NETs in gingival inflammatory infiltration and alveolar bone absorption in severe periodontitis. We further screened three key NETs-related genes (PTGS2, MME and SLC2A3) and verified that they have the potential to predict periodontitis. Moreover, our findings revealed that gingival fibroblasts had the most interactions with NrNeu and that they might facilitate the production of NETs through the MIF-CD74/CXCR4 axis in periodontitis.

CONCLUSION

This study highlights the pathogenic role of NETs in periodontal immunity and elucidates the specific regulatory relationship by which gingival fibroblasts activate NETs, which provides new insights into the clinical diagnosis and treatment of periodontitis.

PAD4 inhibition impacts immune responses in SARS-CoV-2 infection

Protein arginine deiminase 4 (PAD4) has emerged as a potential therapeutic target for various diseases due to its role in promoting neutrophil extracellular trap (NET) formation. NETs, composed of DNA and antimicrobial proteins, serve as a defense mechanism against pathogens but can also drive lung injury, particularly in SARS-CoV-2 infection. In this study, we examined the effects of PAD4 inhibition on clinical outcomes and adaptive immunity within the context of SARS-CoV-2 infection. Our results show that PAD4 pharmacological inhibition reduced lung NET concentration and improved clinical outcomes, similar to treatment with recombinant human DNase (rhDNase), which degrades NET structure. However, in contrast to rhDNase, PAD4 targeting diminished virus-specific T cell responses by impairing dendritic cell antigen presentation and reducing IL-2 signaling by affecting its production by T cells. In line with these observations, PAD4 pharmacological inhibition diminished antigen-specific T cell responses in a model of lung inflammation. These findings highlight the importance of carefully evaluating PAD4 as a therapeutic target in COVID-19, given its potential to compromise adaptive immune responses crucial for fighting the virus.

NETs-CD44-IL-17A Feedback Loop Drives Th17-Mediated Inflammation in Behçet's Uveitis

Behçet's uveitis (BU) is a severe ocular manifestation of Behçet's disease, typically accompanied by abnormal neutrophil infiltration and hyperactivation. However, the underlying causes of excessive neutrophil extracellular traps (NETs) production and mechanisms by which NETs contribute to the pathogenesis of BU remain incompletely understood. Neutrophils from BU patients exhibit a higher propensity for NETs release compared to healthy controls. In the experimental autoimmune uveitis (EAU), neutrophils are observed to exert pro-inflammatory effects through NETs. Clearing NETs can inhibit T helper 17 (Th17) cell differentiation and significantly alleviate EAU symptoms. In vivo and in vitro experiments demonstrate neutralizing IL-17A markedly reducing neutrophil infiltration and NETs formation in EAU. Single-cell RNA sequencing confirms that CD44 plays a key role in mediating interactions between NETs and Th17 cells. Antagonizing CD44 inhibits the proportion of Th17 cells and NETs formation. Multiplex immunofluorescence and cell communication analyses further demonstrate interactions and colocalization between NETs and CD44highCD4+T cells in EAU. NETs induce Th17 differentiation via upregulating CD44, and in turn, Th17 cells secrete IL-17A to recruit neutrophils and promote NETs formation. Interrupting NETs-CD44-IL-17A feedback loop may be a potential therapeutic target for BU.

The role of neutrophil extracellular traps in Crohn's disease

Crohn's disease (CD) is an idiopathic and chronic inflammation of the gastrointestinal (GI) tract. The underlying pathogenesis of CD is multifaceted, with complex interactions between genetic predisposition, environmental triggers, and abnormalities within the immune system. Neutrophil extracellular traps (NETs) have gained significant attention as a novel component in the pathogenesis of CD. NETs are intricate structures fashioned from DNA, histones, and granule proteins, and are actively released by neutrophils to entangle and eliminate pathogenic microbes. This review article delves into the intricate role of NETs in the pathogenesis of CD. We examine how NETs may serve as a pivotal mechanism for the recruitment of immune cells to the site of inflammation. NETs are known to influence the function of epithelial cells, which line the GI tract, potentially contributing to the structural integrity and barrier dysfunction observed in CD. NETs stimulate inflammation, a hallmark of the disease, by releasing pro-inflammatory molecules and activating immune cells. We also investigate the promising therapeutic potential of targeting NETs in CD. By intercepting the formation or function of NETs, it may be possible to mitigate the chronic inflammation, reduce tissue damage, and alleviate the symptoms associated with CD. Strategies to inhibit NET formation, such as the use of DNase I and approaches to disrupt NET-mediated signaling pathways, are discussed in CD therapeutics. Understanding the detailed mechanisms of NETs is crucial for the development of targeted treatments that could potentially revolutionize the management of CD.

Identification of a biomarker to predict doxorubicin/cisplatin chemotherapy efficacy in osteosarcoma patients using primary, recurrent and metastatic specimens

BACKGROUND

Doxorubicin and cisplatin are both first-line chemotherapeutics for osteosarcoma (OS) treatment. However, the efficacy of doxorubicin/cisplatin chemotherapy varies considerably. Thus, identifying an efficient diagnostic biomarker to distinguish patients with good and poor responses to doxorubicin/cisplatin chemotherapy is of paramount importance.

METHODS

To predict the efficacy of doxorubicin/cisplatin chemotherapy, we analyzed the differentially expressed proteins in 37 resected OS samples, which were categorized into the primary group (PG), the recurrent group (RG) and the metastatic group (MG). The characteristics of the enriched differentially expressed proteins were assessed via GO and KEGG analyses. Protein‒protein interactions were identified to determine the relationships among the differentially expressed proteins. Receiver operating characteristic (ROC) curve analyses were performed to explore the clinical significance of the differentially expressed proteins. Parallel reaction monitoring (PRM) was used to validate the candidate proteins. Immunohistochemical (IHC) staining was performed to confirm the expression of cathepsin (CTSG) in patients with good and poor response to doxorubicin/cisplatin.

RESULTS

A total of 9458 proteins were identified and quantified, among which 143 and 208 exhibited significant changes (|log2FC|>1, p < 0.05) in the RG and MG compared with the PG, respectively. GO and KEGG enrichment led to the identification of neutrophil extracellular traps (NETs). ROC curve analyses revealed 74 and 86 proteins with areas under the curve greater than 0.7 in the RG and MG, respectively. PRM validation revealed the statistical significance of CTSG, which is involved in NET formation, at the protein level in both the RG and MG. IHC staining of another cohort revealed that CTSG was prominently upregulated in the poor response group after treatment with doxorubicin/cisplatin.

CONCLUSION

CTSG and its associated NETs are potential biomarkers with which the efficacy of doxorubicin/cisplatin chemotherapy could be predicted in OS patients.

Calcinosis in dermatomyositis

PURPOSE OF REVIEW

To provide the most recent literature on our understanding behind the pathogenesis and the treatment of calcinosis in dermatomyositis.

RECENT FINDINGS

Early diagnosis and controlling the overall disease activity are cornerstones to prevent calcinosis in juvenile dermatomyositis. Observational cohort studies showed that prolonged state of inflammation and features of vascular dysfunction like digital ulcers and abnormal nailfold capillaries are associated with calcinosis. Neutrophil activation and mitochondrial dysfunction have recently emerged as potential mechanistic pathways involved in calcinosis pathogenesis. Few recent case series have alluded to the efficacy of topical and intralesional sodium thiosulfate, while JAK inhibitors appear to be newer promising therapy in juvenile dermatomyositis.

SUMMARY

Calcinosis in dermatomyositis consists of deposition of insoluble calcium compounds in the skin and other tissues. It is prevalent in up to 75% of patients with juvenile dermatomyositis and up to 20% in adult dermatomyositis. While it leads to significant patient morbidity, we do not yet understand the pathogenesis in its entirety. Surgical excision although palliative is the mainstay of treatment and should be offered to patients. All available treatment options are only based on very low level of evidence.

Coagulopathy and acute pancreatitis: pathophysiology and clinical treatment

Coagulopathy is a critical pathophysiological mechanism of acute pancreatitis (AP), arising from the complex interplay between innate immune, endothelial cells and platelets. Although initially beneficial for the host, uncontrolled and systemic activation of coagulation cascade in AP can lead to thrombotic and hemorrhagic complications, ranging from subclinical abnormalities in coagulation tests to severe clinical manifestations, such as disseminated intravascular coagulation. Initiation of coagulation activation and consequent thrombin generation is caused by expression of tissue factor on activated monocytes and is ineffectually offset by tissue factor pathway inhibitor. At the same time, endothelial-associated anticoagulant pathways, in particular the protein C system, is impaired by pro-inflammatory cytokines. Also, fibrin removal is severely obstructed by inactivation of the endogenous fibrinolytic system, mainly as a result of upregulation of its principal inhibitor, plasminogen activator inhibitor type 1. Finally, increased fibrin generation and impaired break down lead to deposition of (micro) vascular clots, which may contribute to tissue ischemia and ensuing organ dysfunction. Despite the high burden of coagulopathy that have a negative impact on AP patients' prognosis, there is no effective treatment yet. Although a variety of anticoagulants drugs have been evaluated in clinical trials, their beneficial effects are inconsistent, and they are also characterized by hemorrhagic complications. Future studies are called to unravel the pathophysiologic mechanisms involved in coagulopathy in AP, and to test novel therapeutics block coagulopathy in AP.

Neutrophils: a key component in ECMO-related acute organ injury

Extracorporeal membrane oxygenation (ECMO), as an extracorporeal life support technique, can save the lives of reversible critically ill patients when conventional treatments fail. However, ECMO-related acute organ injury is a common complication that increases the risk of death in critically ill patients, including acute kidney injury, acute brain injury, acute lung injury, and so on. In ECMO supported patients, an increasing number of studies have shown that activation of the inflammatory response plays an important role in the development of acute organ injury. Cross-cascade activation of the complement system, the contact system, and the coagulation system, as well as the mechanical forces of the circuitry are very important pathophysiological mechanisms, likely leading to neutrophil activation and the production of neutrophil extracellular traps (NETs). NETs may have the potential to cause organ damage, generating interest in their study as potential therapeutic targets for ECMO-related acute organ injury. Therefore, this article comprehensively summarized the mechanism of neutrophils activation and NETs formation following ECMO treatment and their actions on acute organ injury.

Resveratrol prevents the release of neutrophil extracellular traps (NETs) by controlling hydrogen peroxide levels and nuclear elastase migration

Neutrophil extracellular traps (NETs) are defense mechanisms that trap and kill microorganisms and degrade cytokines. However, excessive production, dysregulation of suppression mechanisms, or inefficient removal of NETs can contribute to increased inflammatory response and the development of pathological conditions. Therefore, research has focused on identifying drugs that inhibit or delay the NET release process. Since reactive oxygen species (ROS) play a significant role in NET release, we aimed to investigate whether resveratrol (RSV), with a wide range of biological and pharmacological properties, could modulate NET release in response to different stimuli. Thus, human neutrophils were pretreated with RSV and subsequently stimulated with PMA, LPS, IL-8, or Leishmania. Our findings revealed that RSV reduced the release of NETs in response to all tested stimuli. RSV decreased hydrogen peroxide levels in PMA- and LPS-stimulated neutrophils, inhibited myeloperoxidase activity, and altered the localization of neutrophil elastase. RSV inhibition of NET generation was not mediated through A2A or A2B adenosine receptors or PKA. Based on the observed effectiveness of RSV in inhibiting NET release, our study suggests that this flavonoid holds potential as a candidate for treating NETs involving pathologies.

Role and Therapeutic Targeting Strategies of Neutrophil Extracellular Traps in Inflammation

Neutrophil extracellular traps (NETs) are large DNA reticular structures secreted by neutrophils and decorated with histones and antimicrobial proteins. As a key mechanism for neutrophils to resist microbial invasion, NETs play an important role in the killing of microorganisms (bacteria, fungi, and viruses). Although NETs are mostly known for mediating microbial killing, increasing evidence suggests that excessive NETs induced by stimulation of physical and chemical components, microorganisms, and pathological factors can exacerbate inflammation and organ damage. This review summarizes the induction and role of NETs in inflammation and focuses on the strategies of inhibiting NETosis and the mechanisms involved in pathogen evasion of NETs. Furthermore, herbal medicine inhibitors and nanodelivery strategies improve the efficiency of inhibition of excessive levels of NETs.