Intracellular thiol depletion causes mitochondrial permeability transition in ebselen-induced apoptosis

Cheng Feng Yang, Han Ming Shen, Choon Nam Ong

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

Ebselen, a selenoorganic compound, has recently been shown to display a novel property of inducing apoptosis through rapid depletion of intracellular thiols in human hepatoma cells, HepG2. The present study was thus designed to explore the mechanism of how ebselen triggers apoptosis upon depletion of intracellular thiols. The results demonstrated that ebselen treatment triggered mitochondrial permeability transition rather rapidly as revealed by redistribution of calcein green fluorescence from cytosol into mitochondria. Ebselen treatment also caused a dose- and time-dependent loss of mitochondrial membrane potential (MMP) and release of cytochrome c. Pretreatment with N-acetylcysteine, a precursor of intracellular reduced glutathione (GSH) synthesis, significantly attenuated the ebselen-induced MMP disruption and subsequently inhibited the apoptosis. In contrast, pretreatment with buthionine sulfoximine, a specific inhibitor of intracellular GSH synthesis, significantly augmented the ebselen-induced MMP alteration, and enhanced the apoptosis. Although ebselen treatment significantly increased the intracellular superoxide radical and calcium concentrations, superoxide dismutase, and BAPTA (a calcium chelator), however, failed to prevent ebselen-induced MMP loss and apoptosis. Neither caspase-9 nor caspase-3 activation was detected in ebselen-treated cells. Z-VAD-FMK, a general caspase inhibitor, also had no effect on ebselen-induced MMP decrease and apoptosis. The overall findings thus suggest that mitochondrial permeability transition resulted from intracellular thiol depletion is a critical event in ebselen-induced apoptosis. (C) 2000 Academic Press.

Original languageEnglish
Pages (from-to)319-330
Number of pages12
JournalArchives of Biochemistry and Biophysics
Volume380
Issue number2
DOIs
StatePublished - Aug 15 2000

Bibliographical note

Funding Information:
The authors thank Mr. H. Y. Ong, Mr. W. X. Ding, Ms. W. X. Xu, Ms. C. Er, Ms. B. L. Ng, and Ms. W. Xiong for their technical assistances. Y.C.F. is supported by a Research Scholarship from the National University of Singapore. This research was supported by the National Medical Research Council of Singapore (RP 3970301N).

Keywords

  • Calcium
  • Caspase
  • Cytochrome c
  • Mitochondrial membrane potential
  • Superoxide radical

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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