title: AS-2, a novel inhibitor of p53-dependent apoptosis, prevents apoptotic mitochondrial dysfunction in a transcription-independent manner and protects mice from a lethal dose of ionizing radiation.
abstract: In a previous study, we reported that some tetradentate zinc(II) chelators inhibit p53 through the denaturation of its zinc-requiring structure but a chelator, Bispicen, a potent inhibitor of in vitro apoptosis, failed to show any efficient radioprotective effect against irradiated mice because the toxicity of the chelator to mice. The unsuitability of using tetradentate chelators as radioprotectors prompted us to undertake a more extensive search for p53-inhibiting agents that are weaker zinc(II) chelators and therefore less toxic. Here, we show that an 8-hydroxyquinoline (8HQ) derivative, AS-2, suppresses p53-dependent apoptosis through a transcription-independent mechanism. A mechanistic study using cells with different p53 characteristics revealed that the suppressive effect of AS-2 on apoptosis is specifically mediated through p53. In addition, AS-2 was less effective in preventing p53-mediated transcription-dependent events than pifithrin-μ (PFTμ), an inhibitor of transcription-independent apoptosis by p53. Fluorescence visualization of the extranuclear distribution of AS-2 also supports that it is ineffective on the transcription-dependent pathway. Further investigations revealed that AS-2 suppressed mitochondrial apoptotic events, such as the mitochondrial release of intermembrane proteins and the loss of mitochondrial membrane potential, although AS-2 resulted in an increase in the mitochondrial translocation of p53 as opposed to the decrease of cytosolic p53, and did not affect the apoptotic interaction of p53 with Bcl-2. AS-2 also protected mice that had been exposed to a lethal dose of ionizing radiation. Our findings indicate that some types of bidentate 8HQ chelators could serve as radioprotectors with no substantial toxicity in vivo.
authors.affiliation: Department of Radiological Science, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan. Electronic address: morita@tokushima-u.ac.jp.
authors.forename: Akinori
authors.initials: A
authors.lastname: Morita
authors.affiliation: Center for Technologies against Cancer, Tokyo University of Science, Chiba 278-8510, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Ariyasu
authors.affiliation: Radiation Risk Reduction Research Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, Chiba 263-8555, Japan.
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Radiological Science, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Asanuma
authors.affiliation: Department of Radiological Science, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Onoda
authors.affiliation: Department of Medicinal and Life Science, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba 278-8510, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Sawa
authors.affiliation: Radiation Risk Reduction Research Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, Chiba 263-8555, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Ippei
authors.initials: I
authors.lastname: Takahashi
authors.affiliation: Department of Medicinal and Life Science, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba 278-8510, Japan.
authors.forename: Shotaro
authors.initials: S
authors.lastname: Togami
authors.affiliation: Radiation Risk Reduction Research Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, Chiba 263-8555, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Nenoi
authors.affiliation: Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Toshiya
authors.initials: T
authors.lastname: Inaba
authors.affiliation: Center for Technologies against Cancer, Tokyo University of Science, Chiba 278-8510, Japan; Department of Medicinal and Life Science, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba 278-8510, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Aoki
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002461:Cell Line, Transformed; D051379:Mice; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects* / Q000502:physiology; D011839:Radiation, Ionizing; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013463:Sulfuric Acid Esters / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: D011837:Radiation-Protective Agents; D013463:Sulfuric Acid Esters; D016159:Tumor Suppressor Protein p53; C111568:adociasulfate-2
keywords: Apoptosis; Mitochondria; Radioprotector; p53; p53 inhibitor