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Morphological changes in the respiratory system of mice after inhalation of mosquito-coil smoke
Abstract:
Male ICR mice were exposed to mosquito-coil smoke with d-allethrin or without d-allethrin at airborne particles concentration of 1.27 mg/m3, 7 h/day, 7 days/week for 1, 3, 6, and 12 months. Additional groups of air exposure animals served as controls. At 1 month after exposure, the histopathological lesions included the loss of cilia, and the alteration of the alveolar pattern in the treated and the sham mice. Volume fractions of the type I and II cells were smaller (0.028 +/- 0.006, 0.044 +/- 0.002) in the treated group than those of the controls (0.049 +/- 0.008, 0.059 +/- 0.003). Fractions of the lumina of vessels and the vessel wall decreased in both the treated and the sham groups as compared to the control group. However, the volume fraction of alveolar air space increased significantly in both treated and sham groups as compared to the controls (0.619 +/- 0.022, 0.685 +/- 0.018 vs. 0.507 +/- 0.025). After 3- and 6-months exposure, the lesions observed in the trachea persisted. The intercellular fibrosis in the lung was increased in both the treated and sham groups at 6 months and became more severe at the later stages. At 12-months exposure, an increase in vascularity of the alveolar wall was observed and fine granular debris was frequently present in the alveolar space. The fraction volumes of the type II cells in the treated group and the type I cells in the sham group were significantly increased (0.059 +/- 0.010, 0.042 +/- 0.003) compared with those of the controls (0.038 +/- 0.008, 0.033 +/- 0.003). However, the fraction volume of air space and vessel lumen were not different among the three groups. Finally, there were no differences in the morphologic appearance of the airways and the lung periphery between the treated and the sham-exposed animals.
Insights
Mosquito-coil smoke exposure, with or without d-allethrin, caused lung damage in mice, including airway lesions and altered alveolar structure. These effects persisted and worsened over time, indicating significant respiratory toxicity from smoke inhalation.
Area of Science:
- Environmental Toxicology
- Pulmonary Pathology
- Inhalation Toxicology
Background:
- Mosquito-coil smoke is a common indoor air pollutant.
- Exposure to combustion products can lead to respiratory issues.
Purpose of the Study:
- To investigate the long-term pulmonary effects of mosquito-coil smoke exposure in mice.
- To compare the toxicity of mosquito-coil smoke with and without d-allethrin.
Main Methods:
- Male ICR mice were exposed to mosquito-coil smoke (with or without d-allethrin) or filtered air for up to 12 months.
- Histopathological examination and stereological analysis of lung tissues were performed at various time points.
Main Results:
- Early lesions included loss of cilia and altered alveolar patterns. Intercellular fibrosis in the lung increased with exposure duration.
- Exposure led to decreased vessel lumen fraction and increased alveolar air space fraction, particularly at early time points.
- While some cell type volume fractions changed, no significant morphologic differences were observed between smoke-exposed groups and controls at the 12-month mark.
Conclusions:
- Mosquito-coil smoke induces progressive histopathological changes in the mouse lung, including fibrosis and altered air space.
- The presence of d-allethrin did not lead to distinct differences in lung morphology compared to smoke alone.
- Long-term exposure to mosquito-coil smoke poses a risk for respiratory toxicity.