title: Bleomycin induces cellular senescence in alveolar epithelial cells.
abstract: Cellular senescence is a state of irreversible growth arrest. In this paper the authors examined whether bleomycin, an agent that causes pulmonary fibrosis, induces the senescence of alveolar epithelial cells. Type II-like alveolar epithelial (A549) cells or rat primary type II cells were exposed to bleomycin and then evaluated for markers of cellular senescence. Bleomycin was also administered intratracheally in C57BL/6 mice. The authors found that exposure to bleomycin induced cellular senescence in A549 cells and rat primary type II cells. The senescence was characterised by a dose- and time-dependent increase in senescence-associated beta-galactosidase activity, senescence-associated changes in cell morphology, an increase in cell size and lysosomal mass, the overexpression of p21 protein, and irreversible growth arrest. The intratracheal injection of bleomycin in mice induced an increase in senescence-associated beta-galactosidase activity in type II epithelial cells, reaching a maximum at day 7. These results suggest that bleomycin induces a phenotype that is indistinguishable from that of senescence in alveolar epithelial cells. The induction of epithelial senescence by bleomycin may contribute to the pathway of impaired re-epithelialisation leading to pulmonary fibrosis.
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001761:Bleomycin / Q000494:pharmacology*; D002460:Cell Line; D016922:Cellular Senescence / Q000187:drug effects*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects*; D015151:Immunoblotting; D007150:Immunohistochemistry; D008168:Lung / Q000166:cytology / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects*; D011658:Pulmonary Fibrosis / Q000139:chemically induced; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration; D013997:Time Factors; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; C493957:Cdkn1a protein, mouse; C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D001761:Bleomycin; D001616:beta-Galactosidase