title: Appearance of 1-2 Mbp giant DNA fragments as an early common response leading to cell death induced by various substances that cause oxidative stress.
abstract: The effects of oxidative stress on double strand DNA breakage were examined in T-24 human bladder tumor cells using various active oxygen producing agents such as hydrogen peroxide (H2O2), bleomycin (BLM), neocarzinostatin (NCS), and x-ray irradiation. Analysis of the DNA by pulsed-field gel electrophoresis (PFGE) revealed that discrete giant DNA fragments of 1-2 Mbp and 200-800 kbp had accumulated in the nuclei of the treated cells. The 1-2 Mbp giant DNA fragments were first observed 2 h after the T-24 cells were exposed to the active oxygen producing agents, or irradiated with x-ray. The appearance and the amounts of 1-2 Mbp and 200-800 kbp giant DNA fragments seemed to depend on the concentration and the type of reagents used or the dose of x-ray. Following the accumulation of giant DNA fragments, another type of DNA fragmentation was detected and DNA fragments smaller than 100 kbp accumulated in the nuclei of the cells irradiated with x-ray or treated with NCS. In addition, DNA ladder formation, which is characteristic of apoptosis, was observed. The giant DNA fragments appeared to arise as a consequence of double-stranded DNA breakage, which occurred earlier than cell lysis, as assessed by 51Cr release. These findings indicate that the formation of giant DNA fragments is a specific characteristic of cells responding to oxidative stress, and it may be an initial event that leads to cell death.
authors.affiliation: Department of Pharmacology, Kanazawa University, School of Medicine, Ishikawa, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Higuchi
authors.forename: S
authors.initials: S
authors.lastname: Matsukawa
mesh_terms: D001761:Bleomycin / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects; D002857:Chromium / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D053938:DNA Fragmentation / Q000187:drug effects / Q000528:radiation effects; D004587:Electrophoresis, Agar Gel; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018384:Oxidative Stress; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms; D014965:X-Rays; D009353:Zinostatin / Q000494:pharmacology
chemical_list: D017382:Reactive Oxygen Species; D002857:Chromium; D001761:Bleomycin; D009353:Zinostatin; D006861:Hydrogen Peroxide