Superoxide radical-initiated apoptotic signalling pathway in selenite-treated HepG2 cells: Mitochondria serve as the main target

Han Ming Shen, Cheng Feng Yang, Wen Xing Ding, Jin Liu, Choon Nam Ong

Research output: Contribution to journalArticlepeer-review

121 Scopus citations


The exact role of superoxide radicals (O2·-) in apoptosis is still a matter of debate. The main objective of the present study is to evaluate the apoptotic signalling pathway initiated by O2·-. The reductive reaction of sodium selenite with glutathione was used as the intracellular O2·--generating system. When cells were exposed to 5 to 25 μM selenite, a temporal pattern of apoptotic events was observed following the elevation of O2·-, in which cytochrome c release and mitochondrial depolarization preceded caspase-3 activation and DNA fragmentation. The simultaneous treatment with N-acetylcysteine and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl markedly reduced O2·- level and suppressed the mitochondrial changes and the downstream apoptotic events. Moreover, pretreatment with cyclosporin A plus trifluoperazine, two mitochondrial permeability transition (MPT) inhibitors, was capable of attenuating O2·--mediated cytochrome c release and mitochondrial depolarization, and subsequently inhibiting apoptosis. Thus, the present results provide convincing evidence that O2·- generated from the reductive reaction of selenite with GSH is capable of triggering a mitochondria-dependent apoptotic pathway. Such knowledge may not only help to obtain a better understanding of the apoptotic effect of selenite per se, but of the role of O2·- in initiation and execution of apoptosis.

Original languageEnglish
Pages (from-to)9-21
Number of pages13
JournalFree Radical Biology and Medicine
Issue number1
StatePublished - Jan 1 2001

Bibliographical note

Funding Information:
We would like to thank Ms. B. L. Ng and C. Er for their excellent technical support in flow cytometry and confocal microscopy analysis, and Prof. B. Halliwell for his critical reading of the manuscript. C.F.Y., W.X.D., and J.L. are recipients of research scholarships from the National University of Singapore (NUS). This work was supported by the Centre for Occupational and Environmental Health Research, NUS, and a research grant from the National Medical Research Council of Singapore (RP3970301N).


  • Apoptosis
  • Caspase
  • Cytochrome c
  • Free radicals
  • Mitochondria
  • Selenite
  • Superoxide radical

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)


Dive into the research topics of 'Superoxide radical-initiated apoptotic signalling pathway in selenite-treated HepG2 cells: Mitochondria serve as the main target'. Together they form a unique fingerprint.

Cite this