Host: The Japanese Society of Toxicology
Cigarette smoke (CS) causes chronic diseases, particularly lung diseases such as chronic obstructive pulmonary disease (COPD), lung cancer, and desquamative interstitial pneumonia. The present study aimed to assess the effects of repeated exposure to CS in polyhexamethylene guanidine (PHMG)-induced pulmonary fibrosis. Mice were exposed nose-only inhalation to CS (300 mg/m3) for 4 hours/day, 14 days/week. The following four experimental groups were evaluated: vehicle control (VC), PHMG, CS, and PHMG + CS. Animals in the PHMG group exhibited increased the numbers of total cells and inflammatory cells in the bronchoalveolar lavage fluid (BALF), lung hydroxyproline (HP) content, and histopathological changes, including macrophage infiltration and granulomatous inflammation/fibrosis in the lung. These parameters were exacerbated in mice in the PHMG + CS group. In contrast, mice in the CS group alone displayed only minimal macrophage infiltration in pulmonary tissue. The expression of fibrogenic mediators was significantly elevated in lungs of mice in the PHMG group compared with that VC. Further, the expression of fibrogenic mediators was enhanced in pulmonary tissue in mice administered PHMG + CS. These results demonstrate that repeated exposure to CS may enhance the development of PHMG-induced pulmonary fibrosis.
