A case study of the translocation, bioprocessing and tissue interactions of EMP following inhalation exposure

Our plain-English summary of A case study of the translocation, bioprocessing and tissue interactions of EMP following inhalation exposure, by U.M. Graham, G. Oberdörster, B. Case, et al (Toxicology and Applied Pharmacology, 2018).

The study

• Authors: U.M. Graham, G. Oberdörster, B. Case, A. Dozier
• Journal: Toxicology and Applied Pharmacology
• Published: 2018;361:81-88
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Human autopsied lung sections from a resident in the Quebec asbestos region were examined. The study utilized high resolution transmission electron microscopy, scanning transmission electron microscopy (HRTEM/STEM) with the analytical capabilities of electron energy loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) detectors. We report the first analytical ultrastructural characteristics of EMPs, detailing chemical concentration gradients inside the iron-protein coatings and lateral elemental gradients in the local tissue regions. It is shown that the EMPs are subjected to bioprocessing which involves physicochemical transformations and also an elemental transport mechanism that alters the inhaled EMP as well as the surrounding cellular matrix. At high resolution imaging the iron-rich coating around the EMP was observed to have a distinct channel-like nanostructure with some parallel aligned nanofibrils that are reminiscent of tooth enamel which consists of biomineralized nanocomposites with alternating organic/inorganic matrices.

Copyright © 2018 Elsevier Inc. All rights reserved.

In plain English

This case study examined autopsied lung tissue from one resident of a Quebec asbestos mining region. The autopsy was done over 40 years earlier, and the person's cause of death and occupation were unknown. The authors used high-resolution electron microscopy to study elongated mineral particles (EMP) and the tissue around them. Standard slides showed no typical asbestos bodies. The tissue showed extensive pulmonary fibrosis but a noticeable lack of asbestos fibers. The EMP seen were mostly small and not identified as asbestos, and very few were longer than 1 μm. EMP lay in or next to alveolar macrophages, which also held metal oxide nanoparticles, commonly zinc, titanium and manganese. Clouds of tiny iron particles, most likely ferritin, surrounded some EMP. Some EMP had an iron- and carbon-rich crust with a layered structure the authors likened to tooth enamel. The authors concluded that bioprocessing may occur in some silicon-based EMPs. They called their chemical mapping findings preliminary and said more work is needed to identify whether the EMP fragments are related to asbestos.

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: case study: electron microscopy and chemical analysis (HRTEM/STEM with EELS and EDS) of autopsy lung tissue from one person
• Who was studied: Lung tissue (paraffin blocks) from one anonymized person who lived in a Quebec asbestos mining region, taken at an autopsy done over 40 years ago in a hospital there; cause of death and occupation not known
• Exposure: Elongated mineral particles (EMP) found in the lung, which the authors measured as silicon-magnesium-iron rich but did not identify as asbestos; the person lived in an asbestos mining region; non-fibrous metal oxide nanoparticles were also present
• Main results:
  • Light microscopy of standard stained and iron-stained slides found no typical asbestos bodies
  • The tissue showed extensive pulmonary fibrosis but a noticeable lack of asbestos fibers
  • Electron imaging showed many smaller EMP that were not identified as asbestos, along with submicron iron deposits
  • Only very few EMP were longer than 1 μm (about a quarter micron in diameter), and these were always surrounded by nanoscale iron particles
  • All EMP identified had aspect ratios of 3:1 or above and were inside or next to alveolar macrophages
  • The macrophages also contained non-fibrous metal oxide nanoparticles; commonly observed metals were zinc, titanium and manganese
  • Some EMP were surrounded by diffuse clouds of uniform iron oxide nanoparticles (about 3 to 10 nm) that the authors considered most likely to be ferritin
  • Some EMP fragments had an iron coating made of iron nanocrystals lined up perpendicular to the particle's long axis
  • Elemental mapping of one EMP showed a thick iron-, oxygen- and carbon-containing crust around a more silicon-rich interior
  • Calcium and phosphorus were enriched where the EMP met the surrounding cells
  • At high magnification the iron-carbon coating had parallel aligned nanofibrils that the authors compared to tooth enamel
• The authors' conclusion: The authors concluded that their work suggests bioprocessing may occur in some silicon-based EMPs and in the formation of nanoscale iron-rich crusts on the EMP and the nearby tissue
• Limitations the authors state:
  • The origin of the iron nanoparticle accumulations could not be determined
  • The chemical mapping findings are preliminary and need further work
  • It was not established whether the EMP fragments are related to asbestos
  • The person's cause of death and occupation were unknown
  • The source of the magnesium in the mapped EMP is not known

Topics

Medical terms in this study, explained in our Lexicon: Translocation, Bioprocessing, Transmission Electron Microscopy (TEM), HRTEM, STEM, electron energy loss spectroscopy (EELS), energy dispersive X-ray spectroscopy (EDS).

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