Regulation of ionizing radiation-induced apoptosis by a manganese porphyrin complex

Hyup Lee Jin, Mie Lee You, Jeen Woo Park

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

Ionizing radiation induces the production of reactive oxygen species, which play an important causative role in apoptotic cell death. Therefore, compounds that scavenge reactive oxygen species may confer regulatory effects on apoptosis. Superoxide dismutase (SOD) mimetics have been shown to be protective against cell injury caused by reactive oxygen species. We investigated the effects of the manganese (III) tetrakis(N-methyl-2-pyridyl)porphyrin (MnTMPyP), a cell-permeable SOD mimetic, on ionizing radiation-induced apoptosis. Upon exposure to 2 Gy of γ-irradiation, there was a distinct difference between the control cells and the cells pre-treated with 5 μM MnTMPyP for 2 h with regard to apoptotic parameters, cellular redox status, mitochondria function, and oxidative damage to cells. MnTMPyP effectively suppressed morphological evidence of apoptosis and DNA fragmentation in U937 cells exposed to ionizing radiation. The [GSSG]/[GSH + GSSG] ratio and the generation of intracellular reactive oxygen species were higher and the [NADPH]/[NADP+ + NADPH] ratio was lower in control cells compared to MnTMPyP-treated cells. The ionizing radiation-induced mitochondrial damage reflected by the altered mitochondrial permeability transition, the increase in the accumulation of reactive oxygen species, and the reduction of ATP production were significantly higher in control cells compared to MnTMPyP-treated cells. MnTMPyP pre-treated cells showed significant inhibition of apoptotic features such as activation of caspase-3, up-regulation of Bax and p53, and down-regulation of Bcl-2 compared to control cells upon exposure to ionizing radiation. This study indicates that MnTMPyP may play an important role in regulating the apoptosis induced by ionizing radiation presumably through scavenging of reactive oxygen species.

Original languageEnglish
Pages (from-to)298-305
Number of pages8
JournalBiochemical and Biophysical Research Communications
Volume334
Issue number2
DOIs
StatePublished - 26 Aug 2005

Keywords

  • Apoptosis
  • Cellular redox status
  • Ionizing radiation
  • Reactive oxygen species
  • SOD mimetic

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