Cytotoxicity of dust particles on colony-forming capacity of pulmonary alveolar macrophages

Cytotoxic effects of fibrogenic dust particles on the colony-forming capacity of murine pulmonary alveolar macrophages (PAM) were tested to define the possibility that the proliferation and the maintenance of PAM population could be affected by inhaled substances. Intratracheal instillation of crocidolite asbestos or Min-u-sil silica particles into mice induced significant and persistent reduction of alveolar macrophage colony -forming cells detected in vitro during the period of 1 to 6 months after treatments as compared to untreated control or groups of mice administered with non-fibrogenic TiO2 particles. Total numbers of PAM recovered by bronchoalveolar lavage, however, were not significantly different from the controls after asbestos- or silica-instillation. Instead, inflammatory exudation of polymorphonuclear leukocytes, Iymphocytes and monocytes significantly increased in the groups of asbestos- or silica-instilled animals, but not in TiO2-instilled mice. These data suggest that instilled fibrogenic particles have a cytotoxicity on the proliferation and differentiation of PAM, while total PAM population could be maintained by recruitments of monocytes following inflammation or chemotactic events.