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Carrageenan-induced pulmonary emphysema of rabbit
T Mitsuhashi1, H Kuwahara, Y Ikura
1Department of Pathology, Osaka City University Medical School, Japan.
Abstract:
A transbronchial injection of 0.75% carrageenan in physiologic saline induced pneumonia followed by emphysema in the insulted lobe. In the stages of pneumonia, scattered infiltration of polymorphonuclear leukocytes was seen throughout the affected lobe within a few days of treatment; later this was replaced by the accumulation of carrageenan-laden macrophages, which lasted for one to two months. Enlargement of alveoli and alveolar ducts appeared 2 weeks to 2 months after the treatment, and pulmonary emphysema was observed at 4 months. The lobes that were not treated with carrageenan were normal in appearance during both the pneumonia and the emphysema. Morphometric analysis of the lung at 4 months showed decrease of the alveoli and/or alveolar ducts and enlargement of their luminal spaces, also suggesting the development of emphysema. In contrast to various kinds of elastases that are known to produce emphysematous changes in animals, the elastolytic activity of carrageenan solution did not show any such effects, although in the homogenate of the lobes given carrageenan, a moderate but significant increase in the proteinase activities of alveolar macrophages are said to occur (Bowers et al. 1985). It was suggested that carrageenan-induced emphysema is a chronic disorder associated with both carrageenan toxicity and accumulated carrageenan-laden macrophages in the insulted lobes.
Insights
Carrageenan injection in the lung causes pneumonia and emphysema. This chronic lung disorder involves carrageenan toxicity and macrophages, distinct from elastase-induced emphysema.
Area of Science:
- Pulmonary Pathology
- Toxicology
- Cell Biology
Background:
- Emphysema is a chronic lung disease characterized by alveolar damage.
- Investigating novel models for emphysema is crucial for understanding disease mechanisms.
- Carrageenan is known to induce inflammation and has been used to model lung injury.
Purpose of the Study:
- To investigate the induction of pneumonia and subsequent emphysema using transbronchial carrageenan injection.
- To characterize the cellular and structural changes associated with carrageenan-induced lung disease.
- To compare carrageenan-induced emphysema with elastase-induced models.
Main Methods:
- Transbronchial injection of 0.75% carrageenan in saline into a lung lobe.
- Histological and morphometric analysis of lung tissue at various time points.
- Assessment of cellular infiltration (polymorphonuclear leukocytes, macrophages) and alveolar structure.
Main Results:
- Carrageenan induced pneumonia characterized by polymorphonuclear leukocytes, followed by macrophages.
- Alveolar enlargement and emphysematous changes were observed 2 weeks to 4 months post-injection.
- Morphometric analysis confirmed alveolar destruction and luminal enlargement, indicative of emphysema.
- Carrageenan itself showed no elastolytic activity, but increased proteinase activity in macrophages was noted.
Conclusions:
- Transbronchial carrageenan injection is a viable model for inducing pneumonia and subsequent chronic pulmonary emphysema.
- Carrageenan-induced emphysema is associated with carrageenan toxicity and the accumulation of carrageenan-laden macrophages.
- This model offers a distinct pathway for emphysema development compared to elastase-induced models.