Particles of different sizes and shapes induce neutrophil necroptosis followed by the release of neutrophil extracellular trap-like chromatin

Our plain-English summary of Particles of different sizes and shapes induce neutrophil necroptosis followed by the release of neutrophil extracellular trap-like chromatin, by J. Desai, O. Foresto-Neto, M. Honarpisheh, et al (Scientific Reports, 2017).

The study

• Authors: J. Desai, O. Foresto-Neto, M. Honarpisheh, S. Steiger, D. Nakazawa, B. Popper, E.M. Buhl, P. Boor, S.R. Mulay, H.J. Anders
• Journal: Scientific Reports
• Published: 2017;7(1):15003
• Cited by: 97 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The human body is exposed to a wide range of particles of industrial, environmental or internal origin such as asbestos, alum, silica or crystals of urate, calcium phosphate, calcium oxalate, cystine or cholesterol. Phagocytic clearance of such particles involves neutrophils and macrophages. Here we report that neutrophils encountering such particles of diverse sizes and shapes undergo necrotic cell death, a process associated with the formation of neutrophil extracellular trap (NET)-like extracellular DNA. In human neutrophils receptor-interacting protein kinase (RIPK)-1 inhibition with necrostatin-1s or mixed lineage kinase domain-like (MLKL) inhibition with necrosulfonamide abrogated cell death and associated-neutrophil extracellular DNA release induced by all of the aforementioned particles. Similar results were obtained with Mlkl-deficient mice neutrophils for all particles in vitro. Furthermore, Mlkl-deficient mice lacked tophus formation upon injection of MSU crystals into subcutaneous air pouches. These findings imply that nano- or microparticle-induced neutrophil extracellular DNA release is the consequence of neutrophil necroptosis, a regulated form of cell necrosis defined by RIPK1-RIPK3-MLKL signaling. Interestingly, this finding was consistent across different particle sizes and shapes. The RIPK1-RIPK3-MLKL signaling pathway may represent a potential therapeutic target in nano- or microparticle-related diseases (crystallopathies).

In plain English

This was a laboratory study, not a study of people's health. The authors exposed neutrophils, a type of white blood cell, to several kinds of particles for 2 hours. The cells came from healthy human blood donors and from mice. The particles were crystals of calcium oxalate, monosodium urate (the crystal of gout), cystine, calcium phosphate, cholesterol and silica, plus crocidolite asbestos fibers. The authors reported that all of the particles caused the neutrophils to die and to release DNA outside the cell (called NET-like extracellular DNA). Markers of this DNA and of cell damage rose significantly compared with untreated cells. Two drugs that block a regulated form of cell death called necroptosis partially suppressed this cell death. Mouse neutrophils lacking a protein called MLKL released much less DNA with all particles tested, including asbestos. In a separate experiment with urate crystals only, a tophus-like mass formed in normal mice but not in MLKL-deficient mice. The article gives n = 5 for this experiment without saying whether that is per group or in total. The authors concluded that particles induce this DNA release downstream of neutrophil necroptosis.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiments on isolated human and mouse neutrophils, plus an animal experiment (mouse air pouch model) using urate crystals
• Who was studied: Neutrophils isolated from healthy human blood donors (purity above 95%; number of donors not stated) and from wild type and Mlkl-deficient mice. The air pouch experiment used 6-week-old female C57BL/6 wild type and Mlkl-deficient mice. The article gives n = 5 without saying whether this is per group or in total.
• Exposure: Crystals of calcium oxalate, monosodium urate, cystine (written as cysteine in places), calcium phosphate, cholesterol and silica, and crocidolite asbestos fibers. Concentrations were 0.2 mg/ml in the figure experiments (200 to 500 µg/ml for electron microscopy), applied for 2 hours. The mouse air pouch experiment used 2.5 mg of urate crystals only.
• Main results:
  • In human neutrophils, all particles significantly increased complexes of myeloperoxidase with DNA (a marker of NET-like DNA release) in the culture fluid compared with medium control.
  • Electron microscopy showed signs of cell death in human neutrophils exposed to particles, including membrane rupture and release of cell contents, but not in controls.
  • All particles significantly increased release of LDH, a marker of cell membrane rupture, from human neutrophils.
  • Pretreatment with necrostatin-1s (100 µM) or necrosulfonamide (5 µM), drugs that block necroptosis, partially suppressed human neutrophil death induced by the particles.
  • Neutrophils from MLKL-deficient mice showed drastically reduced extracellular DNA release and NET formation with all particles. The particles shown for this experiment include asbestos at 0.2 mg/ml.
  • 24 hours after urate crystal injection into air pouches, tophus formation was seen in wild type mice but not in Mlkl-deficient mice.
  • Mouse genotype did not affect the number of neutrophils drawn into the air pouch.
• The authors' conclusion: The authors concluded that particles induce NET-like extracellular DNA release downstream of neutrophil necroptosis. They suggested that RIPK1, RIPK3 and MLKL could be molecular targets to limit crystal- and microparticle-related inflammation.
• Limitations the authors state:
  • The authors could not fully exclude that the inhibitor drugs affected neutrophil survival through unknown off-target effects. For this reason they repeated the experiments with MLKL-deficient mouse neutrophils.
  • The authors noted that most current techniques for documenting NET formation cannot distinguish NET formation from neutrophil death.

Topics

Medical terms in this study, explained in our Lexicon: Macrophage, Necrosis.

Related studies

• Heterogenous presence of neutrophil extracellular traps in human solid tumours is partially dependent on IL-8 — C.E. de Andrea, M.C. Ochoa, et al. (2021)
• Neutrophil chemotactic factor release and neutrophil alveolitis in asbestos-exposed individuals — A.A. Hayes, A.H. Rose, et al. (1988)
• Pifithrin-μ induces necroptosis through oxidative mitochondrial damage but accompanies epithelial-mesenchymal transition-like phenomenon in malignant mesothelioma cells under lactic acidosis — Y.J. Lee, K.S. Park, et al. (2019)
• The sizes, shapes, and mineralogy of asbestos structures that induce lung tumors or mesothelioma in AF/HAN rats following inhalation — D.W. Berman, K.S. Crump, et al. (1995)
• Diarachidonoylphosphoethanolamine induces necrosis/necroptosis of malignant pleural mesothelioma cells — Y. Kaku, A. Tsuchiya, et al. (2015)
• Neutrophil elastase promotes myofibroblast differentiation in lung fibrosis — A.D. Gregory, C.R. Kliment, et al. (2015)

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