Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 3: Depletion of antioxidant defenses

Our plain-English summary of Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 3: Depletion of antioxidant defenses, by E. Gazzano, C. Riganti, M. Tomatis, et al (Journal of Toxicology and Environmental Health. Part a, 2005).

The study

• Authors: E. Gazzano, C. Riganti, M. Tomatis, F. Turci, A. Bosia, B. Fubini, D. Ghigo
• Journal: Journal of Toxicology and Environmental Health. Part a
• Published: 2005;68(1):41-9
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The asbestiform fibrous silicate balangeroite exhibits cytotoxic and oxidative properties similar to those exerted by crocidolite asbestos. In human lung epithelial cells A549, balangeroite, like crocidolite, inhibited the pentose phosphate pathway (PPP), one of the main antioxidant intracellular tools; this inhibition was exerted also when PPP was activated by the redox-cycling compound menadione. PPP inhibition may be accounted for by the inhibition of its rate-limiting enzyme, glucose-6-phosphate dehydrogenase (G6PD). Reduced glutathione (GSH), the most important intracellular antioxidant molecule, was decreased by both balangeroite and crocidolite incubation. This effect was not related to any increased content of oxidized glutathione, or to any enhanced efflux of glutathione, suggesting that balangeroite fibers, like crocidolite, might favor the reaction of GSH with other molecules.

In plain English

This laboratory study tested balangeroite, an asbestiform fibrous mineral associated with chrysotile in the Balangero mine in Italy, on human lung epithelial cells (A549). Cells were exposed for 24 hours to balangeroite at 2.4 or 12 micrograms per square centimetre, or to crocidolite asbestos at 12 as a comparison. The authors measured the pentose phosphate pathway, a cell process supporting antioxidant defenses, its key enzyme G6PD, and glutathione, a main antioxidant inside cells. Balangeroite significantly reduced pathway activity, with an effect matching crocidolite's. In control cells the chemical menadione raised pathway activity 10-fold; balangeroite strongly inhibited this increase and crocidolite abolished it. Both fibers significantly lowered G6PD activity, but not a second enzyme, 6PGD, and both lowered reduced glutathione. This drop was not matched by a rise in oxidized glutathione or by glutathione leaving the cells. The authors wrote that, taken as a whole, their data suggest that balangeroite exerts the same adverse effects as crocidolite in cultured cells. They proposed that such oxidative stress might partly explain the pleural mesothelioma increase reported in earlier studies of Balangero workers. This study did not examine people.

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) cell culture experiment, with crocidolite asbestos as the positive control
• Who was studied: Human lung epithelial cells of the A549 line, cultured in a laboratory at the University of Torino, Italy; n = 6 experiments for pathway and enzyme measurements, n = 3 for glutathione
• Exposure: Balangeroite fibers (from the Balangero mine, where the mineral is associated with chrysotile) at 2.4 or 12 micrograms per square centimetre, and UICC crocidolite at 12 micrograms per square centimetre, for 24 hours. Menadione (100 micromolar) was used to stimulate the pathway. Tert-butyl hydroperoxide (100 micromolar, 3 hours) was used as a check of the oxidized glutathione measurement. Enzyme and glutathione tests used the 12 microgram dose only.
• Main results:
  • After 24 hours, balangeroite significantly decreased pentose phosphate pathway activity in A549 cells, with an effect the same as that of crocidolite
  • Menadione increased pathway activity 10-fold. Balangeroite dramatically inhibited this increase and crocidolite completely abolished it.
  • Like crocidolite, balangeroite (12 micrograms per square centimetre) significantly inhibited the enzyme G6PD but not the enzyme 6PGD in cell lysates
  • After 24 hours, both balangeroite and crocidolite significantly decreased intracellular reduced glutathione (GSH)
  • The fall in GSH was not accompanied by a rise in intracellular oxidized glutathione (GSSG). Tert-butyl hydroperoxide did raise GSSG under the same conditions, which the authors took to mean the method was working.
  • There was no increased transport of GSH or GSSG out of the cells
• The authors' conclusion: The authors wrote that, taken as a whole, their data suggest that balangeroite exerts the same adverse effects as crocidolite in cultured cells. They suggested that the fibers might favor the reaction of glutathione with other molecules. They also proposed that increased oxidative stress might partly account for the increase in pleural mesothelioma reported in earlier epidemiological studies of Balangero miners and employees.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Balangero mine, Balangero, about 20 km north of Turin, Piedmont

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Crocidolite.

Medical terms in this study, explained in our Lexicon: Asbestiform, Balangeroite, Silicate, Crocidolite, Glutathione (GSH).

Related studies

• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 2: Oxidant activity of the fibers — F. Turci, M. Tomatis, et al. (2005)
• Potential toxicity of nonregulated asbestiform minerals: balangeroite from the western Alps. Part 1: Identification and characterization — C. Groppo, M. Tomatis, et al. (2005)
• The effect of weathering on ecopersistence, reactivity, and potential toxicity of naturally occurring asbestos and asbestiform minerals — S. Enrico Favero-Longo, F. Turci, et al. (2009)
• Role of associated mineral fibres in chrysotile asbestos health effects: the case of balangeroite — F. Turci, M. Tomatis, et al. (2009)
• Iron-loaded synthetic chrysotile: a new model solid for studying the role of iron in asbestos toxicity — E. Gazzano, F. Turci, et al. (2007)
• Long and short fiber amosite asbestos alters at a different extent the redox metabolism in human lung epithelial cells — C. Riganti, E. Aldieri, et al. (2003)

Browse more research in Journal of Toxicology and Environmental Health. Part a, or return to medical research.