Pancreatic melatonin enhances anti-tumor immunity in pancreatic adenocarcinoma through regulating tumor-associated neutrophils infiltration and NETosis

Tumor microenvironment contributes to poor prognosis of pancreatic adenocarcinoma (PAAD) patients. Proper regulation could improve survival. Melatonin is an endogenous hormone that delivers multiple bioactivities. Here we showed that pancreatic melatonin level is associated with patients' survival. In PAAD mice models, melatonin supplementation suppressed tumor growth, while blockade of melatonin pathway exacerbated tumor progression. This anti-tumor effect was independent of cytotoxicity but associated with tumor-associated neutrophils (TANs), and TANs depletion reversed effects of melatonin. Melatonin induced TANs infiltration and activation, therefore induced cell apoptosis of PAAD cells. Cytokine arrays revealed that melatonin had minimal impact on neutrophils but induced secretion of Cxcl2 from tumor cells. Knockdown of Cxcl2 in tumor cells abolished neutrophil migration and activation. Melatonin-induced neutrophils presented an N1-like anti-tumor phenotype, with increased neutrophil extracellular traps (NETs) causing tumor cell apoptosis through cell-to-cell contact. Proteomics analysis revealed that this reactive oxygen species (ROS)-mediated inhibition was fueled by fatty acid oxidation (FAO) in neutrophils, while FAO inhibitor abolished the anti-tumor effect. Analysis of PAAD patient specimens revealed that CXCL2 expression was associated with neutrophil infiltration. CXCL2, or TANs, combined with NET marker, can better predict patients' prognosis. Collectively, we discovered an anti-tumor mechanism of melatonin through recruiting N1-neutrophils and beneficial NET formation.

Research advances on the relationship between infectious diseases and programmed cell death / 中华临床感染病杂志

In recent years, with the progress of research on the molecular mechanism of cell death, it has been discovered that there are many new types of programmed cell death, including non-apoptotic (10 types) and apoptotic (2 types), which are widely involved in the pathogenesis of infectious diseases and tumors. It is also a frontier research topic and provides new ideas for disease prevention and treatment. This article reviews the published literature on programmed cell death, focusing on the characteristics of cell necrosis, apoptosis, pyroptosis, ferroptosis, neutrophil inflammatory cell death (NETosis), cuproptosis, and widespread apoptosis (PANoptosis), as well as their relationship with infectious diseases.

Hypervirulent Klebsiella pneumoniae serotype K1 induces liver abscess through activating NLRP3 inflammasome / 中华微生物学和免疫学杂志

Objective:To investigate whether the hypervirulent Klebsiella pneumoniae (hvKP) induces liver abscess through activating NLRP3 inflammasome. Methods:K1-hvKP and K35-non-hvKP bacterial suspensions were intraperitoneally injected into C57BL/6 mice to establish the models of liver abscess. Human peripheral blood neutrophils were sorted by immunomagnetic beads with CD45 + and Gr-1 + , and the purity was detected by flow cytometry. The concentrations of capsular polysaccharide of K1-hvKP and K35-non-hvKP were detected by total carbohydrate assay kit. The expression of IL-18 and IL-33 by neutrophils at mRNA and protein levels was detected by real-time fluorescence quantitative PCR and ELISA, respectively. The activation of NLRP3 inflammasome in neutrophils was detected by Western blot. Neutrophil extracellular trap formation (NETosis) was observed under confocal laser scanning microscope. Results:The C57BL/6 mice with K1-hvKP infection had significantly serious liver abscess as compared with the K35-non-hvKP-infected mice. The purity of human neutrophils was more than 95%. The concentration of capsular polysaccharide in K1-hvKP was significantly higher than that in K35-non-hvKP. Compared with K35-non-hvKP, K1-hvKP significantly promoted the neutrophils to express IL-18 and IL-33 at both mRNA and protein levels, enhanced the activation of NLRP3 and induced NETosis.Conclusions:This study suggested that hvKP could promote NETosis by activating NLRP3 inflammasome to cause liver abscess.

Neutrophil extracellular traps in autoimmune diseases / Trampas extracelulares de neutrófilos en enfermedades autoinmunes

ABSTRACT Neutrophils play an important role in immune defence against several pathogens. These cells actively participate in the innate immune response through different functions, such as chemotaxis, phagocytosis, oxidative burst and degranulation, which have been widely studied. However, in the last few years, a new function has been described; activated neutrophils are able to release web-like chromatin structures known as neutrophil extracellular traps (NETs). These structures formed by DNA, histones, and proteins, immobilize and kill microorganisms. Disruption in NET formation is associated with the pathophysiology of several disorders, including the autoimmune diseases. NETs are an important source of the autoantigens involved in the production of autoantibodies and maintenance of the inflammatory milieu. This review provides a summary of the contribution of NETs to the pathogenesis of anti-neutrophil cytoplasmic antibodies-associated vasculitis, systemic lupus erythematosus, and rheumatoid arthritis. The preliminary findings on NETs components in Sjögren.'s syndrome will also be described.

RESUMEN Los neutrófilos juegan un papel muy importante en la defensa inmune contra diferentes patógenos. Estas células participan activamente en la respuesta inmune innata a través de diferentes funciones como quimiotaxis, fagocitosis, estallido oxidativo y degranulación, las cuales han sido estudiadas ampliamente. Sin embargo, en los últimos años se ha descrito una nueva función; los neutrófilos activados son capaces de liberar redes de cromatina llamadas trampas extracelulares de neutrófilos (NETs). Estas estructuras están formadas por ADN, histonas y proteínas capaces de inmovilizar y matar microorganismos. Alteraciones en la formación de estas NETs están asociadas con la fisiopatología de varios trastornos, incluyendo las enfermedades autoinmunes (EAI). Las NETs son consideradas una fuente de autoantígenos que ayudan a la producción de autoanticuerpos y al mantenimiento de un ambiente inflamatorio. Esta revisión resume la contribución de las NETs a la patogénesis de vasculitis asociada a anticuerpos contra el citoplasma de los neutrófilos, lupus eritematoso sistémico y artritis reumatoide. Adicionalmente, se describirán los resultados preliminares de la detección de componentes de las NETs en pacientes con síndrome de Sjögren.

NETosis in Autoimmune Diseases

Neutrophils are the major antimicrobial cells of the innate immune system, which are recruited rapidly to the sites of infection and provide the primary defense against pathogens. Recent evidence suggests that neutrophils undergo a distinct cell death mechanism called NETosis, which not only contributes to the host defense, but also leads to severe pathological immune responses in cases of dysregulation. Here, we review the general features of NETosis as well as the generation of autoantigens and damage-associated molecular patterns by NETosis in autoimmune diseases. This review discusses the pathogenic role of NETosis in rheumatoid arthritis and systemic lupus erythematosus, where neutrophils may play a key role in the pathogenesis of these diseases, and suggest the possibility of neutrophil extracellular traps as biomarkers and therapeutic targets for the treatment of autoimmune diseases.