title: Mitochondrial DNA-depleted A549 cells are resistant to bleomycin.
abstract: Alveolar epithelial cells are considered to be the primary target of bleomycin-induced lung injury, leading to interstitial fibrosis. The molecular mechanisms by which bleomycin causes this damage are poorly understood but are suspected to involve generation of reactive oxygen species and DNA damage. We studied the effect of bleomycin on mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) in human alveolar epithelial A549 cells. Bleomycin caused an increase in reactive oxygen species production, DNA damage, and apoptosis in A549 cells; however, bleomycin induced more mtDNA than nDNA damage. DNA damage was associated with activation of caspase-3, cleavage of poly(ADP-ribose) polymerase, and cleavage and activation of protein kinase D1 (PKD1), a newly identified mitochondrial oxidative stress sensor. These effects appear to be mtDNA-dependent, because no caspase-3 or PKD1 activation was observed in mtDNA-depleted (ρ(0)) A549 cells. Survival rate after bleomycin treatment was higher for A549 ρ(0) than A549 cells. These results suggest that A549 ρ(0) cells are more resistant to bleomycin toxicity than are parent A549 cells, likely in part due to the depletion of mtDNA and impairment of mitochondria-dependent apoptotic pathways.
authors: Laboratory of Respiratory Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA.
authors: Sukhdev S
authors: SS
authors: Brar
authors: Joel N
authors: JN
authors: Meyer
authors: Carl D
authors: CD
authors: Bortner
authors: Bennett
authors: B
authors: Van Houten
authors: William J
authors: WJ
authors: Martin
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D001761:Bleomycin / Q000633:toxicity*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects; D004249:DNA Damage; D004272:DNA, Mitochondrial / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000473:pathology; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport / Q000187:drug effects; D059748:Proteolysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D050396:TRPP Cation Channels / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D000255:Adenosine Triphosphate; D000903:Antibiotics, Antineoplastic; D001761:Bleomycin; D053148:Caspase 3; D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species; D050396:TRPP Cation Channels; D051028:bcl-2-Associated X Protein; C494826:BAX protein, human; C505407:CASP3 protein, human