Development of a new alternative method to inhalation exposure: intratracheal instillation studies using molecular dispersion.

Toshiki MORIMOTO; Chinatsu NISHIDA; Hiroto IZUMI; Taisuke TOMONAGA; Kazuma SATO; Yasuyuki HIGASHI; Ke-Yong WANG; Takuma KOJIMA; Kazuo SAKURAI; Akihiro MORIYAMA; Jun-Ichi TAKESHITA; Kei YAMASAKI; Hidenori HIGASHI; Kazuhiro YATERA; Yasuo MORIMOTO

Return

Development of a new alternative method to inhalation exposure: intratracheal instillation studies using molecular dispersion.

Author: Toshiki MORIMOTO ¹ ; Chinatsu NISHIDA ² ; Hiroto IZUMI ³ ; Taisuke TOMONAGA ³ ; Kazuma SATO ³ ; Yasuyuki HIGASHI ¹ ; Ke-Yong WANG ⁴ ; Takuma KOJIMA ⁵ ; Kazuo SAKURAI ⁵ ; Akihiro MORIYAMA ⁶ ; Jun-Ichi TAKESHITA ⁶ ; Kei YAMASAKI ¹ ; Hidenori HIGASHI ² ; Kazuhiro YATERA ¹ ; Yasuo MORIMOTO ³
Author Information

1. Department of Respiratory Medicine, University of Occupational and Environmental Health, Japan.
2. Department of Environmental Health Engineering, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan.
3. Department of Occupational Pneumology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan.
4. Shared-Use Research Center, School of Medicine, University of Occupational and Environmental Health, Japan.
5. Department of Chemistry and Biochemistry, The University of Kitakyushu.
6. Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST).
Publication Type:Journal Article
Keywords: Dispersion; Organic compounds; Polyacrylic acid (PAA)
MeSH: Animals; Rats, Inbred F344; Acrylic Resins/adverse effects*; Rats; Inhalation Exposure/adverse effects*; Male; Pulmonary Fibrosis/pathology*; Pneumonia/pathology*; Lung/pathology*; Bronchoalveolar Lavage Fluid/cytology*
From:Environmental Health and Preventive Medicine 2025;30():69-69
CountryJapan
Language:English
Abstract: BACKGROUND:Organic chemicals have been known to cause allergic diseases such as bronchial asthma and hypersensitivity pneumonitis; however, the possibility that they do not cause irreversible pulmonary fibrosis has not been considered. Polyacrylic acid (PAA), an organic chemical, has caused irreversible progressive pulmonary fibrosis in exposed workers, indicating its potential to induce pulmonary inflammation and fibrosis. Although intratracheal instillation studies are commonly used for evaluating lung pathology, traditional methods face challenges with chemical substances, particularly nanoparticles, which tend to aggregate in suspension and prevent uniform pulmonary distribution. Such aggregation alters the qualitative and quantitative responses to lung injury, limiting accurate assessment of lung pathology. To overcome this limitation, we developed a 'molecular dispersion method' that uses pH modification to negative charges to PAA particles, maintaining their dispersion. Using this method, we investigated the effects of PAA on pulmonary inflammation and fibrosis in a rat model.
METHODS:F344 rats were intratracheally instilled with PAA using molecular dispersion (0.1 mg/rat, 1.0 mg/rat), PAA without molecular dispersion (1.0 mg/rat), and normal saline (control group). Rats were sacrificed at 3 days, 1 week, 1 month, 3 months, and 6 months after exposure to examine inflammatory and fibrotic responses.
RESULTS:PAA caused persistent increases in neutrophil influx in the bronchoalveolar lavage fluid (BALF) from 3 days to 1 month following instillation. In histopathological findings, the group with molecular dispersion had almost no inflammatory masses in the lung tissue compared to the group without molecular dispersion, and exhibited relatively uniform dispersion.
CONCLUSION:Intratracheal instillation of dispersed PAA induced neutrophil inflammation and fibrosis in the rat lung, suggesting that PAA might have pulmonary inflammogenicity and fibrogenicity. Intrapulmonary dispersion of PAA particles following intratracheal instillation studies using the molecular dispersion method was similar to that following inhalation studies.