p53, Cip1, and Gadd153 expression following treatment of A549 cells with natural and man-made vitreous fibers.

Abstract

DNA damage induced by chemicals and ionizing radiation is associated with the expression of negative regulators of the cell cycle. The arrest of cells in Gl and G2 phases of the cell cycle provides time for DNA repair. Asbestos fibers are carcinogenic when inhaled by both humans and animals; however, the mechanism by which the fibers exert their effect is unknown. This work was undertaken to determine whether the expression of DNA damage-inducible genes differs between crocidolite, a fiber positive for lung tumors, and JM 100 glass microfiber, which is negative for lung tumors when inhaled by rats. Temporal and dose-related expressions of p53, Cipl, and Gadd153 proteins were determined in cultured A549 cells treated with either Union Internationale Contre le Cancer crocidolite or JM 100 for 20 hr and cultured in fresh media. Immunolabeled cells were analyzed by flow cytometry, and the increased number of proteinexpressing cells was determined by subtracting the expression in unexposed cells from exposed cells. Crocidolite induced the expression of all three proteins with a maximum expression after approximately 18 hr in fresh media. At a similar time point, JM 100 did not markedly induce the three proteins. Crocidolite also induced a dose-dependent increase in the number of cells in the G2 phase of the cell cycle. These results show that asbestos behaves like ionizing radiation and genotoxic chemicals by inducing proteins associated with DNA damage and cell-cycle arrest. The clear difference in response between crocidolite and JM 100 may help elucidate the mechanism of action of toxic and nontoxic fibers.

P53 Mediates Amosite Asbestos–Induced Alveolar Epithelial Cell Mitochondria-Regulated Apoptosis

“…Asbestos-induced p53 protein expression was first evident at 4 h and remained elevated at 24 h (Figure 4). These findings are consistent with the work of others showing that asbestos induces A549 and mesothelial cell p53 expression, upregulates p21 (a downstream gene activated by p53), inhibits cellular proliferation, and promotes apoptosis (17)(18)(19). Similar to these studies, we have observed that amosite asbestos causes dose-dependent inhibition of A549 cell proliferation as assessed by a colony forming unit assay (unpublished observation).…”

“…Increased p53 protein expression occurs in the bronchiolar and alveolar epithelium of humans with idiopathic pulmonary fibrosis and in rodents exposed to asbestos (14)(15)(16). It is established that asbestos induces p53 and p21 expression in lung epithelial and mesothelial cells and that this results in cell cycle arrest (17)(18)(19). Crocidolite asbestos induces p53 gene mutations predominantly in exons 9 through 11 in BALB/c-3T3 cells (20).…”

Molecular Basis of Asbestos-Induced Lung Disease

“…Asbestos activates p53 and p21 expression in lung epithelial and mesothelial cells that result in cell-cycle arrest (104–108). Furthermore, increased p53 levels are detected in lung cancers of patients with asbestosis (109), and p53 point mutations are present in the lung epithelium of smokers and asbestos-exposed individuals (110).…”

Nanoparticle-driven DNA damage mimics irradiation-related carcinogenesis pathways

“…JOHNSON et al [44] demonstrated that exposure of A549 cells to asbestos fibres induced a dosedependent increase in the G2 phase cell numbers. Aneuploidy was associated with an increase in the protein levels of genes such as p53, Cip1 and Gadd45, which are induced by DNA damage.…”