Fiber-induced hydroxyl radical formation: correlation with mesothelioma induction in rats and humans

Our plain-English summary of Fiber-induced hydroxyl radical formation: correlation with mesothelioma induction in rats and humans, by K.R. Maples, N.F. Johnson (Carcinogenesis, 1992).

The study

• Authors: K.R. Maples, N.F. Johnson
• Journal: Carcinogenesis
• Published: 1992;13(11):2035-9
• Cited by: 35 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

As part of a program to study the effects of inhaled fibers, we characterized the capacity of various fibers to initiate hydroxyl radical (.OH) formation from hydrogen peroxide in a non-cellular system. We studied five natural fibers (erionite, crocidolite, amosite, anthophyllite and chrysotile) and two man-made fibers (JM code 100 glass fibers and glass wool). The fibers were incubated for 5 min at 37 degrees C with hydrogen peroxide and salicylic acid in pH 7.0 aqueous solutions. The salicylate reacted with any .OH formed in these mixtures to produce stable addition products. The amount of .OH addition products formed during the incubations was determined by the salicylate assay which uses HPLC with electrochemical detection. Erionite, JM code 100 and glass wool were the most effective initiators of .OH formation, followed, in order, by crocidolite, amosite and chrysotile. When the capacity of the natural fibers to initiate .OH formation was plotted versus either the values for tumor rates of rats that received pleural inoculations of fibers or the literature values for the human mesothelioma mortality rates, positive correlations (r2 > or = 0.896) were found. Similar correlations with man-made fibers were not found. No positive correlation could be made between .OH formation capacity versus the tumor rates of rats that received peritoneal injections of either type of fibers.

In plain English

In this cell-free laboratory study, the authors measured how readily seven fibers triggered hydroxyl radicals, a highly reactive form of oxygen, from hydrogen peroxide. They tested erionite, crocidolite, amosite, anthophyllite and chrysotile, and two man-made fibers, JM code 100 fine glass fibers and glass wool. Erionite, JM code 100 and glass wool produced the most. All except anthophyllite gave results significantly above the no-fiber control. The authors compared these results with rat tumor rates and human mesothelioma death rates from earlier published studies. For the natural fibers, radical formation correlated with rat tumor rates after injection into the chest (pleural) cavity (r2 = 0.896) and with human mesothelioma mortality rates (r2 = 0.990). The glass fibers did not fit, and there was no correlation with rat tumor rates after injection into the abdominal (peritoneal) cavity. The authors offered, as one interpretation, that free radicals play a role in causing mesothelioma. They noted that their fibers were not totally equivalent to those inhaled in the human studies.

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: In vitro (cell-free) laboratory experiment, with the results compared against rat tumor rates and human mesothelioma mortality rates taken from previously published studies
• Who was studied: No people or animals were studied. Seven fiber samples were tested at the Inhalation Toxicology Research Institute, Albuquerque, NM, USA: UICC anthophyllite, amosite, chrysotile and crocidolite; erionite; JM code 100 fine glass fibers (Johns Manville); and glass wool (Owens Corning). The rat and human comparison data came from earlier published studies.
• Exposure: Each fiber (1 mg/ml) was incubated at 37°C and pH 7.0 with salicylate (1 mM) and hydrogen peroxide (20 mM). Hydroxyl radical formation was measured by the salicylate assay and expressed as µM Fe(II) equivalents.
• Main results:
  • Erionite, JM code 100 and glass wool were the fibers most capable of initiating hydroxyl radical formation.
  • Erionite, JM code 100, glass wool, crocidolite, amosite and chrysotile gave significantly elevated hydroxyl radical formation compared with the no-fiber control (P less than 0.05). Anthophyllite was not among them.
  • Hydroxyl radical formation capacity in µM Fe(II) equivalents (mean plus or minus SE, three to six determinations): erionite 5.75 ± 1.30; crocidolite 2.56 ± 0.29; amosite 2.09 ± 0.52; chrysotile 1.35 ± 0.15; anthophyllite 1.02 ± 0.14; glass wool 5.19 ± 1.13; JM code 100 4.57 ± 0.17; no-fiber control 0.77 ± 0.17.
  • For the natural fibers, hydroxyl radical formation capacity correlated positively with published tumor rates in rats given pleural inoculations (r2 = 0.896).
  • For the natural fibers, hydroxyl radical formation capacity correlated positively with published human mesothelioma mortality rates (r2 = 0.990).
  • The man-made glass fibers (JM code 100 and glass wool) did not match the correlation for natural fibers.
  • No positive correlation was found between hydroxyl radical formation capacity and tumor rates in rats given peritoneal injections, for either natural or man-made fibers.
  • When crocidolite and erionite fibers were filtered out before hydrogen peroxide was added, no hydroxyl radical products were detected.
• The authors' conclusion: The authors stated that one interpretation of the correlations for natural fibers is that free radicals play a role in the induction of mesotheliomas.
• Limitations the authors state:
  • The fibers tested were not totally equivalent to those inhaled in the human studies used for comparison.
  • The no-fiber control showed background hydroxyl radical formation, probably from trace metal contamination of the reaction flasks.
  • The rat peritoneal tumor rates came from a single study.

Topics

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

Medical terms in this study, explained in our Lexicon: Hydroxyl Radical, Mesothelioma, erionite, Crocidolite, Amosite, Anthophyllite, Chrysotile.

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