title: Evaluation of zinc (II) chelators for inhibiting p53-mediated apoptosis.
abstract: In a previous study, we reported that sodium orthovanadate (vanadate) is the first known inhibitor that is capable of protecting mice from death from the radiation-induced gastrointestinal syndrome via its ability to block both transcription-dependent and transcription-independent p53 apoptotic pathways. In this paper, we report that vanadate has a unique activity for inducing the denaturation of p53 relative to other known radioprotective p53 inhibitors, pifithrin-α (PFTα) and pifithrin-µ (PFTµ). This potent radioprotective effect of vanadate prompted us to undertake a more extensive search for p53 inhibitors that can induce p53 denaturation. Based on the fact that p53 denaturation can be induced by the dissociation of a zinc ion, which is used as a structural factor of p53, we screened some zinc (II) chelators for the suppression of the DNA binding activity of p53 in vitro and the inhibition of radiation-induced p53-dependent apoptosis in MOLT-4 cells. The findings indicate that two of five zinc (II) chelators also suppressed apoptosis. Among the inhibitors tested, Bispicen (N,N'-Bis(2-pyridylmethyl)-1,2-ethanediamine) had the highest inhibition activity. A mechanistic study using cells bearing different p53 status or functions (i.e., p53-knockdown MOLT-4 transformant and its revertants, p53 mutant cells, p53-null cells), and p53-independent apoptotic stimuli revealed that the suppressive effect of Bispicen on apoptosis is specifically mediated through p53. Moreover, Bispicen, similar to vanadate, induces the denaturation of p53 as well as the blocking of both transcription-dependent and -independent apoptotic pathways. Our findings indicate that the use of zinc (II) chelators represent a new approach for protecting against radiation-induced p53-dependent apoptosis through the inhibition of p53-dependent apoptotic pathways.
authors.affiliation: Department of Radiological Science, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Morita
authors.forename: Shinya
authors.initials: S
authors.lastname: Ariyasu
authors.forename: Soichiro
authors.initials: S
authors.lastname: Ohya
authors.forename: Ippei
authors.initials: I
authors.lastname: Takahashi
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.forename: Kaoru
authors.initials: K
authors.lastname: Tanaka
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Uchida
authors.forename: Haruna
authors.initials: H
authors.lastname: Okazaki
authors.forename: Kengo
authors.initials: K
authors.lastname: Hanaya
authors.forename: Atsushi
authors.initials: A
authors.lastname: Enomoto
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Nenoi
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ikekita
authors.forename: Shin
authors.initials: S
authors.lastname: Aoki
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hosoi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002413:Cations, Divalent / Q000378:metabolism; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology*; D051379:Mice; D011489:Protein Denaturation; D011837:Radiation-Protective Agents / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology*; D015032:Zinc / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D002614:Chelating Agents; D011837:Radiation-Protective Agents; D016159:Tumor Suppressor Protein p53; D014638:Vanadates; D015032:Zinc