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Lung cell reactions in guinea pigs after inhalation of asbestos (amosite)
M Sjöstrand1, R Rylander, R Bergström
1Department of Environmental Hygiene, University of Gothenburg, Sweden.
Abstract:
To study the long-term effect of inhaled asbestos, guinea-pigs were exposed to airborne amosite at a concentration of 49 mg/m3, 2 h/day for 3 or 6 weeks and examined up to 2 years after exposure. Macrophages in lung lavage fluid (LLF) were increased at 16, 24 and 93 weeks and lymphocytes at 24 weeks. Examination of lung wall cells (LWC) 2 years after exposure compared to cells obtained by LLF showed higher proportions of LWC lymphocytes and neutrophils. Percoll gradient centrifugation of these cells showed a higher proportion of high density macrophages in LLF from the amosite-exposed animal and an increased number of low density lymphocytes in the LW. Cathepsin D was increased in LLF at 8 and 24 weeks and in alveolar macrophages 24 weeks and 2 years after exposure. Fibroblast cultures exposed to LLF did not show any statistical significant changes in their collagen synthesis. Histology 93 weeks after exposure showed macrophage and mediastinal lymph node accumulation of asbestos, as well as collagen in alveolar walls. Granulomas were found in the vicinity of blood vessels and in connection with the bronchioles. The data suggest that amosite at low doses ultimately causes fibrosis with a reaction pattern different from that seen in silicosis. The inflammation and fibrosis seems to develop only within the interstitium.
Insights
Inhaled amosite asbestos exposure in guinea pigs led to long-term lung inflammation and fibrosis, distinct from silicosis. The study observed asbestos accumulation and granuloma formation up to two years post-exposure.
Area of Science:
- Environmental Health
- Toxicology
- Pulmonary Pathology
Background:
- Asbestos exposure is a known cause of lung disease.
- Understanding the long-term effects of specific asbestos types like amosite is crucial for risk assessment.
Purpose of the Study:
- To investigate the chronic pulmonary effects of inhaled amosite asbestos in a guinea pig model.
- To characterize the cellular and histological changes in the lungs following amosite exposure over a two-year period.
Main Methods:
- Guinea pigs were exposed to airborne amosite asbestos.
- Lung lavage fluid (LLF) and lung wall cells (LWC) were analyzed at various time points up to two years.
- Cellular composition, density, and cathepsin D levels were assessed.
- Histological examination identified asbestos accumulation, collagen deposition, and granuloma formation.
Main Results:
- Increased macrophages and lymphocytes in LLF, with higher lymphocyte and neutrophil proportions in LWC.
- Amosite exposure altered cell densities in LLF and LW.
- Elevated cathepsin D in LLF and alveolar macrophages.
- Histology revealed asbestos accumulation, collagen in alveolar walls, and granulomas.
Conclusions:
- Low-dose amosite asbestos exposure induces interstitial fibrosis with a unique reaction pattern.
- The observed fibrosis and inflammation are confined to the lung interstitium.
- The findings suggest a distinct fibrotic response compared to silicosis.