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Cell Biology International (2000) 24, 9–23 (Printed in Great Britain)

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HYDROGEN PEROXIDE INDUCES APOPTOSIS IN HUMAN HEPATOMA CELLS AND ALTERS CELL REDOX STATUS

Ji Li^a,f2, Chung‑Yang Huang^b, Rong‑Liang Zheng^a,f1, Kai‑Rong Cui^a and Jian‑Feng Li^a

^aDepartment of Biology, Lanzhou University, Lanzhou, 730000, P.R. China
^bMederi Research Institute, Taipei, Taiwan, R.O.C.

Abstract

Direct exposure of human hepatoma cell line SMMC-7721 to hydrogen peroxide (H2O2) can induce apoptosis. Apoptosis induced by H2O2was inhibited by cycloheximide, actinomycin D, 3-aminobenzamide, EGTA or Zn2+. H2O2can increase the level of intracellular Ca2+, downregulate GSH levels, slightly induce lipid peroxidation, and lead to change in the ratio of reduced ion components to oxidized ion components of cells. Analysis of flow cytometry indicates that H2O2decreases the level of Bcl-2. The data indicate that H2O2-induced apoptosis requires new mRNA and protein syntheses; H2O2can activate Ca2+/Mg2+-dependent endonuclease leading to internucleosomal DNA fragmentation and activation of poly (ADP-ribose) polymerase interfering with the energy metabolism of the cell. The H2O2downregulation of GSH may be more important for apoptosis than H2O2induction of lipid peroxidation, and the H2O2induced changes in redox status of the cell may be among the original events which lead up to other biochemical changes.

Key words: hydrogen peroxide, human hepatoma cell line SMMC-7721, apoptosis, redox status Bcl-2.

^f2Current address: College of Basic Medical Sciences, West China University of Medical Sciences, Chengdu 610041, P.R. China.

^f1To whom correspondence should be addressed: Department of Biology, Lanzhou University, Lanzhou 730000, P.R. China. E-mail:zhengrl@lzu.edu.cn

Received 1 April 1999; accepted 9 August 1999