Pyrrolidine dithiocarbamate (PDTC) blocks apoptosis and promotes ionizing radiation-induced necrosis of freshly-isolated normal mouse spleen cells

John S. Thompson, Reto Asmis, Andrea A. Tapp, Brandy Nelson, Yanxia Chu, Judith Glass, Micheal Moneyhon, Stephen A. Brown

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Ionizing radiation (IR) is a pro-oxidant that kills cells by both apoptotic and necrotic mechanisms. Pyrrolidine dithiocarbamate (PDTC) is a thiol-containing compound that may act either as a pro-or anti-oxidant depending on the experimental conditions. This study was designed to determine whether PDTC would reduce or enhance IR-induced cell death of freshly-isolated normal mouse B6/129 spleen cells (NMSC). We determined the effect of increasing doses of IR, PDTC alone and PDTC followed by IR on the viability of NMSC. Annexin V and propidium iodide (Annexin V/PI) staining demonstrated a dose and time-dependent relationship in which PDTC enhanced the percentage of IR-induced apoptotic/necroticNMSC. Trypan blue dye inclusion confirmed that a loss of membrane integrity was occurring 1 h after incubation with PDTC plus IR. Reduction in the glutathione (GSH)/glutathione disul-fide (GSSG) ratio and GSH demonstrated that both IR (8.5 Gy) and PDTC acted as pro-oxidants, but their mechanisms of action differed: In contrast to IR, which promoted p53 activation and caspase 3/7-mediated apoptosis, PDTC inhibited IR-induced p53 and caspase 3/7 activity. However, PDTC increased H2O2 formation and necrosis, resulting in an overall increase in IR-induced cell death. Catalase prevented the PDTC-induced increase in IR cytotoxicity implicating the generation of H2O2 as a major factor in this mechanism. These results demonstrate that in NMSC PDTC acts as pro-oxidant and enhances IR-induced cell cytotoxicity by increasing H2O2formation and thiol oxidation. As such, they strongly suggest that the use of PDTC as an adjunct to reduce radiation toxicity should be avoided.

Original languageEnglish (US)
Pages (from-to)705-714
Number of pages10
JournalApoptosis
Volume15
Issue number6
DOIs
StatePublished - Jun 1 2010

Keywords

  • Caspase
  • Catalase
  • Hydrogen peroxide
  • Ionizing radiation
  • Pyrrolidine dithiocarbamate

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Cancer Research

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