Induction of neutrophil extracellular traps (NETs) by the pneumococcal toxin, pneumolysin (Ply) (original) (raw)
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Pneumolysin activates neutrophil extracellular trap formation
The primary objective of the current study was to investigate the potential of the pneumococcal toxin, pneumolysin (Ply), to activate neutrophil extracellular trap (NET) formation in vitro. Isolated human blood neutrophils were exposed to recombinant Ply (5-20 ng ml21) for 30–90 min at 378C and NET formation measured using the following procedures to detect extracellular DNA: (i) flow cytometry using VybrantVR DyeCycleTM Ruby; (ii) spectrofluorimetry using the fluorophore, SytoxVR Orange (5 lM); and (iii) NanoDropVR technology. These procedures were complemented by fluorescence microscopy using 40, 6-diamino-2-phenylindole (DAPI) (nuclear stain) in combination with anti-citrullinated histone monoclonal antibodies to visualize nets. Exposure of neutrophils to Ply resulted in relatively rapid (detected within 30–60 min), statistically significant (P < 005) dose- and time-related increases in the release of cellular DNA impregnated with both citrullinated histone and myeloperoxidase. Microscopy revealed that NETosis appeared to be restricted to a subpopulation of neutrophils, the numbers of NET-forming cells in the control and Ply-treated systems (10 and 20 ng ml21) were 43 (42), 14.3 (99) and 165 (75), respectively (n 5 4, P < 00001 for comparison of the control with both Ply-treated systems). Ply-induced NETosis occurred in the setting of retention of cell viability, and apparent lack of involvement of reactive oxygen species and Toll-like receptor 4. In conclusion, Ply induces vital NETosis in human neutrophils, a process which may either contribute to host defence or worsen disease severity, depending on the intensity of the inflammatory response during pneumococcal infection.
Neutrophil extracellular traps (NETs) - formation and implications
Acta Biochimica Polonica, 2013
Neutrophils are cells of the immune system which freely circulate in blood vessels and are recruited to the inflammation sites when the human organism responds to microbial infections. One of the mechanisms of neutrophil action is the formation of neutrophil extracellular traps (NETs) The process of NET generation, called netosis, is a specific type of cell death, different from necrosis and apoptosis. NETs are formed by neutrophils upon contact with various bacteria or fungi as well as with activated platelets or under the influence of numerous inflammatory stimuli, and this process is associated with dramatic changes in the morphology of the cells. The main components of NETs, DNA and granular antimicrobial proteins, determine their antimicrobial properties. The pathogens trapped in NETs are killed by oxidative and non-oxidative mechanisms. On the other hand, it was also discovered that chromatin and proteases released into the circulatory system during NET formation can regulate ...
Microbial Pathogenesis, 2019
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Neutrophil Extracellular Traps in Infectious Human Diseases
Role of Neutrophils in Disease Pathogenesis, 2017
Neutrophils, as the main cells of the first line of host defense against microbial pathogens, are responsible for pathogen recognition, inhibition of pathogen spreading into the host tissue, and finally, killing the invader cells. Neutrophils carry out these functions via numerous mechanisms, including a relatively recently described activity based on a release of neutrophil extracellular traps (NETs), a process called netosis. NETs are structures composed of DNA backbone, decorated with antimicrobial factors, derived from neutrophil granules. The structure of NETs and their enzymatic and microbicidal inclusions enable efficient trapping and killing of microorganisms within the neutrophil extracellular space. However, the efficiency of NETs depends on neutrophil ability to recognize pathogen signals and to trigger rapid responses. In this chapter, we focus on possible pathways involved in the release of NETs and summarize the current knowledge on triggers of this process during bacterial, fungal, protozoan, and viral infections. We also consider the mechanisms used by microorganisms to evade NET-killing activity and analyze the harmful potential of NETs against the host cells and the contribution of NETs to noninfectious human diseases.
Diverse stimuli engage different neutrophil extracellular trap pathways
eLife, 2017
Neutrophils release neutrophil extracellular traps (NETs) which ensnare pathogens and have pathogenic functions in diverse diseases. We examined the NETosis pathways induced by five stimuli; PMA, the calcium ionophore A23187, nigericin, Candida albicans and Group B Streptococcus. We studied NET production in neutrophils from healthy donors with inhibitors of molecules crucial to PMA induced NETs including protein kinase C, calcium, reactive oxygen species, the enzymes myeloperoxidase (MPO) and neutrophil elastase. Additionally, neutrophils from chronic granulomatous disease patients, carrying mutations in the NADPH oxidase complex or a MPO-deficient patient were examined. We show that PMA, C. albicans and GBS use a related pathway for NET induction whereas ionophores require an alternative pathway but that NETs produced by all stimuli are proteolytically active, kill bacteria and composed mainly of chromosomal DNA. Thus, we demonstrate that NETosis occurs through several signalling ...
Neutrophil extracellular traps in physiology and pathology
Central European Journal of Immunology, 2014
Neutrophil extracellular traps (NETs) are developed by nature to protect the body from furious invaders. on the other hand nets can play an important role in human pathology. recent studies have shown that neutrophils are able to perform beneficial suicide to create an unique microbicidal net composed from cellular content attached to chromatic frame. it is a powerful tool that primary serve as protector from severe infections, but this weapon is also a double ended sword of the immunity. if overproduced nets provoke certain autoimmune diseases, coagulation disorders and even cancer metastases. Moreover, due to the competition between host and pathogens, the microorganism have developed a width repertoire of sophisticated evading mechanisms, like creation of polysaccharide capsule or changes in cell wall charge. therefore it is important to increase the knowledge about paths underlying nets formation and degradation processes if we want to efficiently fight with bacterial infections and certain diseases.
Neutrophil Extracellular Trap (NET): The Interplay Between Infection, Inflammation and Thrombosis
While the observation that the interactions between infection and thrombosis is a well-known fact, the mechanism behind this connection was not clear. Also, it was known for a long period that thrombus contains neutrophils within its skeleton. Histon an intranuclear component, was known to have a very strong microbicidal property, the question was how could it reach its target? Could the discovery of this new mechanism in neutrophil biology; namely neutrophil extracellular trap (NET), answer these issues? Hopefully it could. This review will focus on the production of NET (NETosis), its implications in different diseases, its role in understanding the connection between infection, inflammation and thrombosis, finally we will look for the potentials of targeting it, for therapeutic benefits.