Expression of heme oxygenase-1 in the lungs of rats exposed to potassium octatitanate whiskers

Our plain-English summary of Expression of heme oxygenase-1 in the lungs of rats exposed to potassium octatitanate whiskers, by Y. Obata, Y. Morimoto, M. Hirohashi, et al (Journal of Occupational Health, 2011).

The study

• Authors: Y. Obata, Y. Morimoto, M. Hirohashi, A. Ogami, T. Oyabu, T. Myojo, S. Kawanami, S. Horie, H. Nagatomo, M. Murakami, I. Tanaka
• Journal: Journal of Occupational Health
• Published: 2011;53(4):267-73
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Oxidative stress is thought to be the pathogenesis of pulmonary fibrosis induced by asbestos, and heme oxygenase-1 (HO-1) protects lung tissue against oxidative stress. We hypothesized that HO-1 is also associated with oxidative lung injury caused by exposure to potassium octatitanate whiskers (PT1), which is one of the asbestos substitutes.

Methods: Male Wistar rats were administered 1 mg or 2 mg PT1 suspended in saline by a single intratracheal instillation and were sacrificed after recovery for 3 days, 1 wk, 1 mo, 3 mo or 6 mo. Gene expression of HO-1 protein and mRNA and immunostaining were investigated in rat lungs.

Results: HO-1 protein expression was increased from 3 days to 1 mo and at 6 mo in the 1 or 2 mg PT1-exposed groups, and the gene expression of HO-1 mRNA was also increased at 3 days and from 1 mo to 6 mo. HO-1-positive cells were mainly found in the alveolar macrophages and the bronchial epithelial cells in immunostaining.

Conclusions: These findings suggest that HO-1 is involved in lung damage caused by PT1.

In plain English

This animal experiment studied potassium octatitanate whiskers (PT1), a man-made fiber used as an asbestos substitute. Male Wistar rats received a single dose of 1 mg or 2 mg PT1 in saline, or saline alone, placed directly into the windpipe. They were examined 3 days, 1 week, 1 month, 3 months or 6 months later, in groups of 5. The authors measured heme oxygenase-1 (HO-1), a protective protein linked to oxidative stress. HO-1 protein in the PT1-exposed groups was significantly higher than in controls from 3 days to 1 month and at 6 months, but not significantly at 3 months. In the 1 mg groups the increases were smaller early on and not significant from 1 to 6 months. HO-1 gene activity was significantly raised at 3 days and from 1 to 6 months. Nitric oxide products did not rise significantly. HO-1 was found mainly in alveolar macrophages (lung scavenger cells), with some in alveolar and bronchial lining cells. The authors concluded that HO-1 is involved in lung damage caused by PT1. Their comparisons with crocidolite, chrysotile and silica came from earlier studies, not this experiment.

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: animal experiment (single intratracheal instillation in rats, compared with saline-treated control groups)
• Who was studied: Male Wistar rats, 10 weeks old, obtained from Kyudo (Kumamoto, Japan). There were exposed and control groups of 5 rats each for each dose and each recovery time (3 days, 1 week, 1 month, 3 months, 6 months). Figures report n=4 to 5 per group.
• Exposure: Potassium octatitanate whiskers (PT1), a man-made fiber used as an asbestos substitute, given as a single dose of 1 mg or 2 mg in 0.4 ml saline. Fibers had a geometric mean length of 4.4 µm and a geometric average diameter of 0.35 µm.
• Main results:
  • In the PT1-exposed groups, HO-1 protein in lung tissue was significantly increased compared with controls from 3 days to 1 month and at 6 months. At 3 months it was increased but not significantly.
  • In the 1 mg PT1 groups, HO-1 protein rose less than in the 2 mg groups at 3 days and 1 week. From 1 month to 6 months the increases were not statistically significant.
  • HO-1 mRNA (gene activity) in the PT1-exposed groups was significantly increased compared with controls at 3 days and from 1 month to 6 months.
  • Nitric oxide products (nitrite and nitrate) showed no significant increase in either the 1 mg or the 2 mg PT1 groups compared with controls.
  • Inflammatory cells (mainly neutrophils and alveolar macrophages) were partly seen in the 2 mg groups at 3 days. The authors report this tended to fade by 6 months.
  • HO-1-positive cells were found mainly in alveolar macrophages, especially those that had engulfed PT1 fibers, with some in alveolar and bronchial lining cells.
  • The authors' impression was that HO-1-positive macrophages were markedly more numerous up to 3 months and decreased at 6 months, while bronchial lining cells were markedly more often positive at 6 months.
• The authors' conclusion: The authors concluded that HO-1 is involved in lung damage caused by PT1. They described HO-1 expression as increased mildly and persistently over the observation period. Their statements comparing PT1 with silica, crocidolite and titanium dioxide rely on their earlier studies, not on groups in this experiment.

Topics

Medical terms in this study, explained in our Lexicon: Oxidative Stress, Pulmonary Fibrosis, Alveolar Macrophage.

Related studies

• Expression of heme oxygenase-1 in the lungs of rats exposed to crocidolite asbestos — H. Nagatomo, Y. Morimoto, et al. (2005)
• Histopathological changes in rat lung following intratracheal instillation of silicon carbide whiskers and potassium octatitanate whiskers — A. Ogami, Y. Morimoto, et al. (2007)
• The effect of lung burden on biopersistence and pulmonary effects in rats exposed to potassium octatitanate whiskers by inhalation — T. Oyabu, H. Yamato, et al. (2004)
• The effect of lung burden on biopersistence and pulmonary effects in rats exposed to potassium octatitanate whiskers by intratracheal instillation — T. Oyabu, H. Yamato, et al. (2006)
• Change of heme oxygenase-1 expression in lung injury induced by chrysotile asbestos in vivo and in vitro — H. Nagatomo, Y. Morimoto, et al. (2007)
• Potassium octatitanate fibers induce persistent lung and pleural injury and are possibly carcinogenic in male Fischer 344 rats — M. Abdelgied, A.M. El-Gazzar, et al. (2018)

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