Gene expression of surfactant protein-A and thyroid transcription factor-1 in lungs of rats exposed to silicon-carbide whisker in vivo

Our plain-English summary of Gene expression of surfactant protein-A and thyroid transcription factor-1 in lungs of rats exposed to silicon-carbide whisker in vivo, by Y. Morimoto, L. Ding, T. Oyabu, et al (Journal of Occupational Health, 2003).

The study

• Authors: Y. Morimoto, L. Ding, T. Oyabu, H. Kim, A. Ogami, M. Hirohashi, H. Nagatomo, H. Yamato, I. Akiyama, H. Hori, T. Higashi, I. Tanaka
• Journal: Journal of Occupational Health
• Published: 2003;45(5):307-12
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Intratracheal instillation studies have shown that exposure to silicon carbide whisker (SiCW), an asbestos substitute, produces pulmonary fibrotic changes, suggesting that SICW might have a fibrogenic potential. It is thought that surfactant protein is a good biomarker of lung injury and pulmonary fibrotic activity. In order to explore whether or not surfactant protein is associated with lung disorder through exposure to SiCW, we examined the expression of SP-A, SP-C and thyroid transcription factor-1 (TTF-1), a common transcription factor of SP-A and SP-C mRNA in lungs exposed to SiCW. Male Wistar rats were administered 2 mg or 10 mg of SiCW suspended in saline by a single intratracheal instillation, and were sacrificed at 3 d, 1 wk, 1 month, 3 months and 6 months after the intratracheal instillation. RNA was subsequently extracted from the lungs, and expression of SP-A, SP-C and TTF-1 mRNA from the lungs was observed by reverse transcription-polymerase chain reaction (RT-PCR). Exposure to 2 mg of SiCW showed a decrease in mRNA of SP-A and TTF-1 at 6 months, but exposure to 10 mg of SiCW showed decreased levels of SP-A and TTF-1 mRNA at 3 d and 6 months. On the other hand, 2 mg of SiCW increased the level of SP-C mRNA from 3 d to 3 months, and 10 mg of SiCW decreased the levels of SP-C mRNA in the rat lungs at 3 d, 1 month and 6 months. No clear tendency to the expression of SP-C was observed, but the patterns of expression of TTF-1 and SP-A were similar. These data suggest that SP-A and TTF-1 are associated with not only the acute phase but also the chronic phase in lungs exposed to SiCW.

In plain English

This animal experiment tested silicon carbide whisker (SiCW), a man-made fiber the authors called an asbestos substitute. Asbestos was not tested. Male Wistar rats received a single dose of 2 mg or 10 mg of SiCW, or saline as controls, into the windpipe (five rats per group). They were examined from 3 days to 6 months later. The authors measured gene activity for two lung surfactant proteins, SP-A and SP-C, and for TTF-1, a factor that regulates them. At 10 mg, SP-A and TTF-1 activity was significantly lower than in controls at 3 days and 6 months. At 2 mg, TTF-1 was significantly lower only at 6 months, and SP-A was reported decreased at 6 months. SP-C fell at 10 mg at 3 days, 1 month and 6 months, but was higher than in controls at 2 mg through 3 months. Lung inflammation was greatest at 3 days and lessened over time, with occasional slight collagen deposits. The authors concluded that SP-A and TTF-1 are associated with both early and later phases of lung changes after SiCW exposure.

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, with serial measurements over time)
• Who was studied: Male Wistar rats, 10 weeks old, purchased from Kyudo (Kumamoto, Japan). They were divided into 2 mg-exposed (n=5), 10 mg-exposed (n=5) and saline control (n=5) groups for each time point, and kept for 3 days, 1 week, 1 month, 3 months or 6 months after instillation. Study dates are not given.
• Exposure: Silicon carbide whisker (SiCW), a fiber composed of silicon and carbon, supplied by the Japan Fibrous Material Research Association. Geometric mean diameter was 0.3 µm (SD 1.5) and geometric mean length 5.1 µm (SD 2.3). It was given as 2 mg or 10 mg in 0.4 ml saline by a single intratracheal instillation. No asbestos was tested.
• Main results:
  • In the 10 mg SiCW group, SP-A mRNA in the lung was significantly decreased at 3 days and 6 months after instillation.
  • At 3 months, SP-A mRNA was significantly increased in the exposed groups compared with controls. The text does not say which dose group.
  • In the 2 mg SiCW group, SP-A mRNA was reported decreased only at 6 months.
  • SP-C mRNA decreased in the 10 mg-exposed lungs at 3 days, 1 month and 6 months.
  • In the 2 mg-exposed groups, SP-C mRNA was higher than in controls at 3 days, 1 week, 1 month and 3 months.
  • TTF-1 mRNA was significantly decreased in the 10 mg-exposed groups at 3 days and 6 months, compared with controls.
  • TTF-1 mRNA was significantly lower in the 2 mg-exposed groups than in saline controls at 6 months. There were no significant differences at the other time points.
  • On lung tissue examination, inflammatory cell infiltration was greatest at 3 days and decreased with time. Slight amounts of collagenous material were occasionally deposited in thickened alveolar ducts and nearby alveoli. The dose group is not specified.
• The authors' conclusion: The authors concluded that the data suggest SP-A and TTF-1 are associated with both the acute phase and the chronic phase in lungs exposed to SiCW.
• Limitations the authors state:
  • The authors stated it is unclear why the SP-C expression pattern differed from the SP-A pattern, given that they expected the two to be similar.

Topics

Medical terms in this study, explained in our Lexicon: Thyroid Transcription Factor-1 (TTF-1), Fibrogenic, Biomarker.

Related studies

• Expression of Clara cell secretory protein in the lungs of rats exposed to silicon carbide whisker in vivo — Y. Morimoto, L. Ding, et al. (2003)
• Pulmonary effects and biopersistence of deposited silicon carbide whisker after 1-year inhalation in rats — I. Akiyama, A. Ogami, et al. (2007)
• Napsin A and thyroid transcription factor-1 expression in carcinomas of the lung, breast, pancreas, colon, kidney, thyroid, and malignant mesothelioma — J.A. Bishop, R. Sharma, et al. (2010)
• Expression of thyroid transcription factor-1 in malignant pleural effusions — A. Khoor, A.L. Byrd-Gloster, et al. (2011)
• Histopathological changes in rat lung following intratracheal instillation of silicon carbide whiskers and potassium octatitanate whiskers — A. Ogami, Y. Morimoto, et al. (2007)
• Pulmonary response, in vivo, to silicon carbide whiskers — G.L. Vaughan, S.A. Trently, et al. (1993)

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