Differential protein folding and chemical changes in lung tissues exposed to asbestos or particulates

Our plain-English summary of Differential protein folding and chemical changes in lung tissues exposed to asbestos or particulates, by L. Pascolo, V. Borelli, V. Canzonieri, et al (Scientific Reports, 2015).

The study

• Authors: L. Pascolo, V. Borelli, V. Canzonieri, A. Gianoncelli, G. Birarda, D.E. Bedolla, M. Salomé, L. Vaccari, C. Calligaro, M. Cotte, B. Hesse, F. Luisi, G. Zabucchi, M. Melato, C. Rizzardi
• Journal: Scientific Reports
• Published: 2015;5:12129
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Environmental and occupational inhalants may induce a large number of pulmonary diseases, with asbestos exposure being the most risky. The mechanisms are clearly related to chemical composition and physical and surface properties of materials. A combination of X-ray fluorescence (μXRF) and Fourier Transform InfraRed (μFTIR) microscopy was used to chemically characterize and compare asbestos bodies versus environmental particulates (anthracosis) in lung tissues from asbestos exposed and control patients. μXRF analyses revealed heterogeneously aggregated particles in the anthracotic structures, containing mainly Si, K, Al and Fe. Both asbestos and particulates alter lung iron homeostasis, with a more marked effect in asbestos exposure. μFTIR analyses revealed abundant proteins on asbestos bodies but not on anthracotic particles. Most importantly, the analyses demonstrated that the asbestos coating proteins contain high levels of β-sheet structures. The occurrence of conformational changes in the proteic component of the asbestos coating provides new insights into long-term asbestos effects.

In plain English

This laboratory study used X-ray fluorescence and infrared microscopy to compare the chemistry of lung tissue taken at autopsy from eight people. Four were men with asbestosis who had been naval shipyard workers in Monfalcone, Italy. Four had anthracosis (black dust deposits in the lung) and had died with cancers other than lung cancer. Asbestos bodies extracted from a further exposed worker were also examined. Where their core fibres could be analysed, they were mostly amosite, with crocidolite in a few cases. Iron was most concentrated in asbestos bodies, and the iron signal over dust particles was 5 to 10 times lower. Iron was also spread through the tissue near both. The dust contained high levels of silicon, potassium and aluminium, with significant iron and traces of chromium and titanium. Protein was higher on asbestos bodies than in the surrounding tissue, and lower on dust. The proteins coating asbestos bodies showed more beta-sheet structure, whereas commercial ferritin showed mainly alpha-helix structure. The authors concluded that asbestos and dust both alter iron balance in the lung, more so with asbestos. They described their series as limited.

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 microscopy and spectroscopy study of post-mortem human lung tissue, comparing asbestosis with anthracosis
• Who was studied: Eight autopsy cases from Italy. Four were men aged 74 to 93 with asbestosis (patients A1 to A4, from St. Polo Hospital of Monfalcone). Four had anthracosis (three men and one woman aged 71 to 77, from CRO Aviano) and had died with gastric, breast, colon or renal cancer. Frozen tissue from one further asbestos-exposed man (autopsy n. 60, aged 69) was used to extract asbestos bodies.
• Exposure: Occupational asbestos exposure in naval shipyard workers at Monfalcone, chosen from a cohort of 200 former shipyard workers who died of asbestos-related diseases. The comparison group had environmental particulates (anthracosis, described as from generic urban pollution); no occupational data were recorded for them. Lung asbestos body counts per gram of dry tissue were 1,209,375, 25,600, 1,400 and 2,700 for patients A1 to A4, and 110,000 for autopsy n. 60.
• Main results:
  • In tissue containing both asbestos bodies and dust, iron was most concentrated at the asbestos bodies. The iron signal over the particulate regions was 5 to 10 times lower.
  • A diffuse iron signal, seen in tissue around asbestos bodies, was also present close to the anthracotic material.
  • The anthracotic structures contained high levels of silicon, potassium and aluminium, together with significant iron concentrations and traces of chromium and titanium.
  • Calcium and phosphorus, which outline the asbestos body coating, were not abundant in anthracosis.
  • Compared with the surrounding tissue, protein content was lower over anthracotic material and higher over asbestos bodies.
  • At asbestos bodies in tissue, the infrared spectra showed an increased relative abundance of parallel beta-sheet protein structure.
  • In asbestos bodies extracted from frozen tissue, beta-sheet and random-coil components appeared more abundant than alpha-helix (data not shown in the article).
  • Commercial human ferritin, used for comparison, showed alpha-helix folding.
  • Among extracted bodies whose core fibre could be analysed, the core fibres were mostly amosite, with crocidolite in a few cases (data not shown).
• The authors' conclusion: The authors concluded that asbestos and dust material in general alter iron balance (homeostasis) in the lung, with a more pronounced effect for asbestos exposure.
• Limitations the authors state:
  • The authors refer to their series of cases as limited.
  • The authors state that further in vitro studies are needed to demonstrate and understand the protein shape changes caused by asbestos, and whether other pollutants do the same.
  • Some spots of anthracotic material showing co-localized phosphorus, calcium and iron may hide unrecognizable asbestos-derived structures.
  • An endogenous (body-derived) source of the potassium found in anthracosis could not be excluded.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Asbestos Bodies, Anthracosis.

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