Neutrophils, the most abundant circulating leukocyte, are critical for host defense. Granulopoiesis is under the control of transcriptional factors and culminates in mature neutrophils with a broad ...armamentarium of antimicrobial pathways. These pathways include nicotinamide adenine dinucleotide phosphate oxidase, which generates microbicidal reactive oxidants, and nonoxidant pathways that target microbes through several mechanisms. Activated neutrophils can cause or worsen tissue injury, underscoring the need for calibration of activation and resolution of inflammation when infection has been cleared. Acquired neutrophil disorders are typically caused by cytotoxic chemotherapy or immunosuppressive agents. Primary neutrophil disorders typically result from disabling mutations of individual genes that result in impaired neutrophil number or function, and provide insight into basic mechanisms of neutrophil biology. Neutrophils can also be activated by noninfectious causes, including trauma and cellular injury, and can have off-target effects in which pathways that typically defend against infection exacerbate injury and disease. These off-target effects include acute organ injury, autoimmunity, and variable effects on the tumor microenvironment that can limit or worsen tumor progression. A greater understanding of neutrophil plasticity in these conditions is likely to pave the way to new therapeutic approaches.
NADPH oxidase (NOX) isoforms together have multiple functions that are important for normal physiology and have been implicated in the pathogenesis of a broad range of diseases, including ...atherosclerosis, cancer and neurodegenerative diseases. The phagocyte NADPH oxidase (NOX2) is critical for antimicrobial host defence. Chronic granulomatous disease (CGD) is an inherited disorder of NOX2 characterized by severe life-threatening bacterial and fungal infections and by excessive inflammation, including Crohn's-like inflammatory bowel disease (IBD). NOX2 defends against microbes through the direct antimicrobial activity of reactive oxidants and through activation of granular proteases and generation of neutrophil extracellular traps (NETs). NETosis involves the breakdown of cell membranes and extracellular release of chromatin and neutrophil granular constituents that target extracellular pathogens. Although the immediate effects of oxidant generation and NETosis are predicted to be injurious, NOX2, in several contexts, limits inflammation and injury by modulation of key signalling pathways that affect neutrophil accumulation and clearance. NOX2 also plays a role in antigen presentation and regulation of adaptive immunity. Specific NOX2-activated pathways such as nuclear factor erythroid 2-related factor 2 (Nrf2), a transcriptional factor that induces antioxidative and cytoprotective responses, may be important therapeutic targets for CGD and, more broadly, diseases associated with excessive inflammation and injury.
It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or ...special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.
Summary
Neutrophils are the first responders to infection and injury and are critical for antimicrobial host defense. Through the generation of reactive oxidants, activation of granular constituents ...and neutrophil extracellular traps, neutrophils target microbes and prevent their dissemination. While these pathways are beneficial in the context of trauma and infection, their off‐target effects in the context of tumor are variable. Tumor‐derived factors have been shown to reprogram the marrow, skewing toward the expansion of myelopoiesis. This can result in stimulation of both neutrophilic leukocytosis and the release of immature granulocytic populations that accumulate in circulation and in the tumor microenvironment. While activated neutrophils have been shown to kill tumor cells, there is growing evidence for neutrophil activation driving tumor progression and metastasis through a number of pathways, including stimulation of thrombosis and angiogenesis, stromal remodeling, and impairment of T cell‐dependent anti‐tumor immunity. There is also growing appreciation of neutrophil heterogeneity in cancer, with distinct neutrophil populations promoting cancer control or progression. In addition to the effects of tumor on neutrophil responses, anti‐neoplastic treatment, including surgery, chemotherapy, and growth factors, can influence neutrophil responses. Future directions for research are expected to result in more mechanistic knowledge of neutrophil biology in the tumor microenvironment that may be exploited as prognostic biomarkers and therapeutic targets.
SARS-CoV-2 vaccines are effective in preventing COVID-19. Patients with cancer are at high risk for severe COVID-19 and are appropriately prioritized for vaccination. Several studies in this issue of ...Cancer Cell add to our knowledge of the heterogeneity of immune responses to vaccination among patients with cancer and identify important areas for future research.
SARS-CoV-2 vaccines are effective in preventing COVID-19. Patients with cancer are at high risk for severe COVID-19 and are appropriately prioritized for vaccination. Several studies in this issue of Cancer Cell add to our knowledge of the heterogeneity of immune responses to vaccination among patients with cancer and identify important areas for future research.
Nicotine induces neutrophil extracellular traps Hosseinzadeh, Ava; Thompson, Paul R; Segal, Brahm H ...
Journal of leukocyte biology,
November 2016, Letnik:
100, Številka:
5
Journal Article
Recenzirano
Odprti dostop
NETs serve to ensnare and kill microbial pathogens. However, NETs can at the same time contribute to tissue damage and excessive inflammation. Nicotine is a major toxic agent and has been associated ...with exacerbated inflammatory diseases. The current study aimed at investigating the role of nicotine, the addictive component of tobacco and electronic cigarettes, on triggering NET formation. We report that nicotine induces neutrophils to release NETs in a dose-dependent manner. Nicotine-induced NET formation is mediated via nicotine acetylcholine receptors, depends on Akt and PAD4 activation, but is Nox2-independent, as demonstrated by pharmacological inhibition of Nox2 and by use of Nox2-deficient mouse neutrophils. These findings demonstrate that nicotine induces NETs, which may in turn contribute to smoking-related diseases.
It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or ...special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.
Reactive oxygen species (ROS) activate NF-E2-related transcription factor 2 (Nrf2), a key transcriptional regulator driving antioxidant gene expression and protection from oxidant injury. Here, we ...report that in response to elevation of intracellular ROS above a critical threshold, Nrf2 stimulates expression of transcription Kruppel-like factor 9 (Klf9), resulting in further Klf9-dependent increases in ROS and subsequent cell death. We demonstrated that Klf9 independently causes increased ROS levels in various types of cultured cells and in mouse tissues and is required for pathogenesis of bleomycin-induced pulmonary fibrosis in mice. Mechanistically, Klf9 binds to the promoters and alters the expression of several genes involved in the metabolism of ROS, including suppression of thioredoxin reductase 2, an enzyme participating in ROS clearance. Our data reveal an Nrf2-dependent feedforward regulation of ROS and identify Klf9 as a ubiquitous regulator of oxidative stress and lung injury.
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•High intracellular ROS trigger a Nrf2-dependent increase in ROS levels•Nrf2 binds to the promoter and activates expression of the Klf9 gene•Klf9 reduces oxidative stress resistance by suppressing Trxrd2•Klf9 deficiency reduces bleomycin-induced pulmonary fibrosis in mice
Nrf2 is a key suppressor of oxidative stress. In this issue, Zucker et al. report that, paradoxically, Nrf2 increases oxidative stress when reactive oxygen species elevate above a critical threshold. Under these conditions, Nrf2 induces expression of transcription factor Klf9, resulting in Klf9-dependent suppression of antioxidant defenses and cell death.
Neutrophil extracellular traps (NETs) are critical for anti-bacterial activity of the innate immune system. We have previously shown that mitochondrial damage-associated molecular patterns (mtDAMPs), ...including mitochondrial DNA (mtDNA), are released into the circulation after injury. We therefore questioned whether mtDNA is involved in trauma-induced NET formation. Treatment of human polymorphoneutrophils (PMN) with mtDNA induced robust NET formation, though in contrast to phorbol myristate acetate (PMA) stimulation, no NADPH-oxidase involvement was required. Moreover, formation of mtDNA-induced NETs was completely blocked by TLR9 antagonist, ODN-TTAGGG. Knowing that infective outcomes of trauma in elderly people are more severe than in young people, we measured plasma mtDNA and NET formation in elderly and young trauma patients and control subjects. MtDNA levels were significantly higher in the plasma of elderly trauma patients than young patients, despite lower injury severity scores in the elderly group. NETs were not visible in circulating PMN isolated from either young or old control subjects. NETs were however, detected in PMN isolated from young trauma patients and to a lesser extent from elderly patients. Stimulation by PMA induced widespread NET formation in PMN from both young volunteers and young trauma patients. NET response to PMA was much less pronounced in both elderly volunteers' PMN and in trauma patients' PMN. We conclude that mtDNA is a potent inducer of NETs that activates PMN via TLR9 without NADPH-oxidase involvement. We suggest that decreased NET formation in the elderly regardless of higher mtDNA levels in their plasma may result from decreased levels of TLR9 and/or other molecules, such as neutrophil elastase and myeloperoxidase that are involved in NET generation. Further study of the links between circulating mtDNA and NET formation may elucidate the mechanisms of trauma-related organ failure as well as the greater susceptibility to secondary infection in elderly trauma patients.
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