Radiographic changes and lung function in relation to activity of the glutathione transferases theta and mu among asbestos cement workers

Our plain-English summary of Radiographic changes and lung function in relation to activity of the glutathione transferases theta and mu among asbestos cement workers, by K. Jakobsson, A. Rannug, A.K. Alexandrie, et al (Toxicology Letters, 1995).

The study

• Authors: K. Jakobsson, A. Rannug, A.K. Alexandrie, M. Warholm, L. Rylander, L. Hagmar
• Journal: Toxicology Letters
• Published: 1995;77(1-3):363-9
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Experimental data indicate that active oxygen species may be casually involved in the development of asbestos-related disease. Thus, it was hypothesized that individual differences in glutathione transferase activity, which may affect the ability to inactivate molecules formed in relation to oxidative stress, could influence the biological response to asbestos exposure. We could, however, not demonstrate an increased risk for radiographic changes or reduced lung function among asbestos cement workers deficient for glutathione transferase theta (GSTT1), glutathione transferase mu (GSTM1), or having a combined deficiency of enzyme activity.

In plain English

This study asked whether inherited differences in two detoxifying enzymes, glutathione transferase theta (GSTT1) and glutathione transferase mu (GSTM1), were linked to chest X-ray changes or reduced lung function in asbestos-exposed workers. It extended the authors' earlier GSTM1 work on the same group by adding GSTT1. The study base was 95 male former asbestos cement workers with at least 10 years of employment at an asbestos cement plant. Blood samples for enzyme testing came from 78 of them. Asbestos exposure was estimated in fibre-years. Of the men tested, 18% lacked GSTT1, 54% lacked GSTM1 and 10% lacked both. X-ray abnormalities of the lung tissue and pleura were similarly distributed between deficient and non-deficient groups. The share of men with lung function in the lowest third was smallest in the deficient groups, but none of the differences were statistically significant. The authors concluded they could not show that either deficiency, or both together, increased the risk. They noted that the study was small for GSTT1 and for combined deficiency, that GSTT1-deficient men were younger and more often lifelong non-smokers, and that true differences may exist.

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: Cross-sectional comparison within a group of former asbestos cement workers, relating enzyme genotype or activity to X-ray and lung function findings. It extends the authors' earlier GSTM1 study of the same workers.
• Who was studied: 95 male asbestos cement workers with at least 10 years of employment at an asbestos cement plant, for whom chest X-ray and lung function data from after the end of employment were available. Blood samples were obtained from 78 of them. The plant's location and the study dates are not stated in this text.
• Exposure: Work at an asbestos cement plant. Individual cumulative asbestos doses were estimated in fibre-years, and average intensity in fibres per ml was calculated by dividing cumulative dose by employment time. Fiber types are not named in this text.
• Main results:
  • Among the 78 men tested, 18% lacked GSTT1 (GSTT1-negative), 54% were GSTM1-negative, and 10% were deficient for both enzymes.
  • Radiographic abnormalities in the lung tissue (parenchyma) and in the pleura were similarly distributed between the groups, for GSTT1 alone, GSTM1 alone and the combined deletion.
  • Nominally, the proportions of men with parenchymal abnormality were smallest among the enzyme-deficient men.
  • The fractions of men with vital capacity (VC) and FEV1 in the lowest third were smallest among the deficient groups. None of these differences were statistically significant.
  • The proportion of men in the higher estimated cumulative dose category differed between groups, but none of the differences were statistically significant. The figures were 29% for GSTT1-negative vs 41% for GSTT1-positive, 45% vs 21% for GSTM1 deficient vs non-deficient, and 38% vs 33% for combined deletion vs non-deficient.
  • The GSTT1-negative group was younger (P = 0.06), as was the combined-deletion group (P = 0.04). Lifelong non-smokers were more common in the GSTT1-negative group than in the GSTT1-positive group (P = 0.02).
• The authors' conclusion: The authors concluded that they could not show an increased risk of radiographic changes or reduced lung function from GSTT1 deletion alone or from combined GSTT1 and GSTM1 deletion. Their earlier study had likewise not shown an increased risk for GSTM1 deficiency.
• Limitations the authors state:
  • The authors stated that the study was small when GSTT1 alone and the combined deficiency were considered.
  • The GSTT1-negative men were younger, included more lifelong non-smokers and had somewhat lower estimated exposure. The authors said this called for caution in interpreting the small-opacity results, although lung function results, which were adjusted for age and smoking, were similar.
  • Only a small fraction of the men had radiographic changes of ILO grade 1/1 or higher.
  • The authors stated that true differences in outcome between enzyme groups may exist but could not be evaluated in this study group.

Topics

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

Medical terms in this study, explained in our Lexicon: Glutathione (GSH), Asbestos-Cement, Oxidative Stress, Asbestos Exposure.

Related studies

• Genetic polymorphism for glutathione-S-transferase mu in asbestos cement workers — K. Jakobsson, A. Rannug, et al. (1994)
• Polymorphism of glutathione S-transferase M1 and lung cancer risk among African-Americans and Caucasians in Los Angeles County, California — S.J. London, A.K. Daly, et al. (1995)
• Effect of chrysotile asbestos on cytochrome P-450-dependent monooxygenase and glutathione-S-transferase activities in rat lung — Q. Rahman, S.G. Khan, et al. (1990)
• Glutathione S-transferase and N-acetyltransferase genotypes and asbestos-associated pulmonary disorders — A. Hirvonen, S.T. Saarikoski, et al. (1996)
• Are glutathione S transferases involved in DNA damage signalling? Interactions with DNA damage and repair revealed from molecular epidemiology studies — M. Dusinska, M. Staruchova, et al. (2012)
• Glutathione S-transferases GSTM1 and GSTT1 polymorphisms and asbestosis — A. Franko, M. Dodic-Fikfak, et al. (2007)

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