Nanomaterial exposure and sterile inflammatory reactions

Our plain-English summary of Nanomaterial exposure and sterile inflammatory reactions, by V. Leso, L. Fontana, I. Iavicoli (Toxicology and Applied Pharmacology, 2018).

The study

• Authors: V. Leso, L. Fontana, I. Iavicoli
• Journal: Toxicology and Applied Pharmacology
• Published: 2018;355:80-92
• Type of article: Review
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

"Sterile inflammation" is a type of pathogen-free inflammation which may be induced by various physical, chemical, or metabolic insults, including environmental particles e.g. silica dioxide crystals and asbestos. The possible role of nanomaterials as danger signals able to trigger sterile inflammatory responses is not yet fully understood. Therefore, the aim of this review was to investigate conditions of sterile inflammation induced by nanomaterial exposure with a specific focus on possible modes of action. Metal-, metal-oxide- and carbon-based nanomaterials may trigger a sterile inflammatory cascade by means of different damage-associated molecular patterns, including chromatin associated protein high-mobility group box-1 secretion, ATP, ADP and adenosine purinergic signaling, interleukin-1α alarmin, and NLPR-3 inflammasome activation. However, such preliminary results do not enable us to draw definite conclusions regarding the sterile inflammatory potential of nanomaterials and possible underlying molecular mechanisms. Therefore, further research is required to understand the complex "interplay" between the multitude of nanomaterial intrinsic or acquired physico-chemical properties and the extremely changeable immunological competence of organisms. The identification of possible nanomaterial modes of action in sterile inflammation could provide early indicators of the biological reactivity of nano-sized chemicals and could direct "safe by design" efforts for improving occupational safety and that of the general population. Moreover, the possible pathological consequences of nanomaterial-induced sterile inflammatory reactions need to be clarified in order to define suitable preventive measures to protect the health of chronically exposed subjects.

Copyright © 2018 Elsevier Inc. All rights reserved.

In plain English

This article was a review, not a new experiment. The authors searched three databases for laboratory studies published up to December 2017 on "sterile inflammation" (inflammation without infection) caused by nanomaterials. They reviewed 23 publications of cell and animal experiments. Asbestos and silica crystals were mentioned only as background examples of causes of this inflammation; asbestos itself was not studied, but silica nanoparticles were among the reviewed exposures. The reviewed work covered metal, metal-oxide and carbon-based nanomaterials, such as titanium dioxide, silica, zinc oxide and silver particles and multi-walled carbon nanotubes. According to the authors, nanomaterials from all three classes were reported to affect release of a danger-signal protein, HMGB-1, and most investigated nanomaterials could activate an inflammation pathway, the NLRP-3 inflammasome. Particle size, a long needle-like shape and surface coatings were reported to change the response. In one reviewed study, an effect of carbon nanotubes was largely due to nickel contamination. The authors concluded that these preliminary results did not allow definite conclusions about the mechanisms. They called for more research, including on long-term, low-dose exposure.

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: Literature review of in vitro (cell) and in vivo (animal) experimental studies, found by searching PubMed, ISI Web of Science and Scopus
• Who was studied: 23 published experimental studies (cell and animal experiments) on nanomaterial-induced sterile inflammation, published up to December 2017
• Exposure: Engineered nanomaterials: metal-, metal oxide- and carbon-based (for example titanium dioxide, silica, zinc oxide, silver, indium-tin-oxide, nickel oxide and tungsten oxide nanoparticles, quantum dots, multi-walled carbon nanotubes and fullerene nanowhiskers). Asbestos and silica dioxide crystals were mentioned only as background examples. Neither was an exposure studied in this review.
• Main results:
  • According to the authors, nanomaterials from each of the three classes (metal, metal-oxide and carbon-based) were reported to affect secretion of HMGB-1, a danger-signal protein that can start an inflammatory cascade
  • Most of the nanomaterials investigated in the reviewed studies were able to activate the NLRP-3 inflammasome
  • In one reviewed study (Mishra et al.), 10 nm silver nanoparticles were more active in inducing caspase-1 and IL-1 beta than 50 and 100 nm silver nanoparticles
  • In the reviewed studies, a high aspect ratio and a needle-like shape were linked to greater biological reactivity of longer multi-walled carbon nanotubes
  • In the reviewed studies, surface functionalization (coatings or chemical groups) changed the inflammatory profile of nanomaterials
  • In one reviewed study (Hamilton et al. 2012), lysosomal disruption caused by multi-walled carbon nanotubes in mouse alveolar macrophages was largely due to nickel contamination of the preparations
• The authors' conclusion: The authors concluded that the preliminary results did not allow definite conclusions about how differently characterized nanomaterials cause sterile inflammation, and that further research is needed
• Limitations the authors state:
  • The initial search on the main terms yielded only 2 eligible studies, so the authors had to broaden the search terms
  • The authors noted that research is needed under long-term, low-dose exposure conditions like those experienced by the general and occupationally exposed population
  • The authors noted that separating the contribution of each particle property is difficult because of protein corona formation on particles inside the body

Topics

Medical terms in this study, explained in our Lexicon: Inflammation.

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