title: Hydroxyl radical-induced apoptosis in human tumor cells is associated with telomere shortening but not telomerase inhibition and caspase activation.
abstract: Reactive oxygen species (ROS) have been found to trigger apoptosis in tumor cells. At the same time, telomerase is found to be associated with malignancy and reduced apoptosis. However little is known about the linkage between ROS such as *OH and telomerase/telomere. To address the interrelations between *OH and telomerase/telomere in tumor cell killing, HeLa, 293 and MW451 cells were induced to undergo apoptosis with *OH radicals generated via Fe(2+)-mediated Fenton reactions (0.1 mM FeSO(4) plus 0.3-0.9 mM H2O2) and telomerase activity, telomere length were measured during apoptosis. We found that during *OH-induced apoptosis, telomere shortening took place while no changes in telomerase activity were observed. Our results suggest that *OH-induced telomere shortening is not through telomerase inhibition but possibly a direct effect of *OH on telomeres themselves indicating that telomere shortening but not telomerase inhibition is the primary event during *OH-induced apoptosis. Strikingly, we also found that *OH-induced apoptosis in HeLa cells is caspase-3-independent but is associated with reduction of mitochondrial transmembrane potential. Our results indicate that *OH triggers apoptotic tumor cell death through a telomere-related, caspase-independent pathway.
authors.affiliation: Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing, PR China.
authors.forename: J G
authors.initials: JG
authors.lastname: Ren
authors.forename: H L
authors.initials: HL
authors.lastname: Xia
authors.forename: T
authors.initials: T
authors.lastname: Just
authors.forename: Y R
authors.initials: YR
authors.lastname: Dai
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism / Q000494:pharmacology*; D020287:In Situ Nick-End Labeling; D008564:Membrane Potentials / Q000187:drug effects; D008854:Microscopy, Electron; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016615:Telomere / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D061945:Caspase Inhibitors; D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D019098:Telomerase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione