title: Kinetics of the cell biological changes occurring in the progression of DNA damage-induced senescence.
abstract: Cellular senescence is characterized by cell-cycle arrest accompanied by various cell biological changes. Although these changes have been heavily relied on as senescence markers in numerous studies on senescence and its intervention, their underlying mechanisms and relationship to each other are poorly understood. Furthermore, the depth and the reversibility of those changes have not been addressed previously. Using flow cytometry coupled with confocal microscopy and Western blotting, we quantified various senescence-associated cellular changes and determined their time course profiles in MCF-7 cells undergoing DNA damage-induced senescence. The examined properties changed with several different kinetics patterns. Autofluorescence, side scattering, and the mitochondria content increased progressively and linearly. Cell volume, lysosome content, and reactive oxygen species (ROS) level increased abruptly at an early stage. Meanwhile, senescence associated β-galactosidase activity increased after a lag of a few days. In addition, during the senescence progression, lysosomes exhibited a loss of integrity, which may have been associated with the accumulation of ROS. The finding that various senescence phenotypes matured at different rates with different lag times suggests multiple independent mechanisms controlling the expression of senescence phenotypes. This type of kinetics study would promote the understanding of how cells become fully senescent and facilitate the screening of methods that intervene in cellular senescence.
authors.affiliation: Department of Life Science, University of Seoul, Seoul, 130-743, Korea.
authors.forename: Sohee
authors.initials: S
authors.lastname: Cho
authors.forename: Jihoon
authors.initials: J
authors.lastname: Park
authors.forename: Eun Seong
authors.initials: ES
authors.lastname: Hwang
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D048429:Cell Size / Q000187:drug effects; D016922:Cellular Senescence / Q000187:drug effects*; D004249:DNA Damage / Q000187:drug effects*; D004317:Doxorubicin / Q000494:pharmacology; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008062:Lipofuscin / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D008062:Lipofuscin; D000643:Ammonium Chloride; D013481:Superoxides; D004317:Doxorubicin; C061901:GLB1 protein, human; D001616:beta-Galactosidase