Cancer chemopreventive oltipraz generates superoxide anion radical

doi:10.1016/j.abb.2004.11.028

Archives of Biochemistry and Biophysics

Volume 435, Issue 1, 1 March 2005, Pages 83-88

https://doi.org/10.1016/j.abb.2004.11.028 Get rights and content

Abstract

The cancer chemopreventive actions of oltipraz, a member of a class of 1,2-dithiolethiones, have been primarily associated with the induction of phase 2 enzymes mediated by a 41 bp enhancer element known as the anti-oxidant response element in the promoter regions of many phase 2 genes. It has been suggested that oxygen radical formation by oltipraz may be a critical mechanism by which it exerts chemoprevention. Therefore, in the present work, studies were performed to directly determine if oltipraz generates oxygen free radicals. Electron paramagnetic resonance (EPR) spin trapping demonstrated that oltipraz slowly reacts in the presence of oxygen to generate the superoxide anion radical. This formation of superoxide by oltipraz was concentration- and time-dependent. EPR oximetry studies showed that oxygen was also slowly consumed paralleling the process of superoxide formation. Thus, oltipraz induced superoxide formation occurs and could be involved in the mechanism by which it exerts chemoprotection.

Section snippets

Materials

Oltipraz was a generous gift of Dr. James Crowell, Chemoprevention Branch, National Cancer Institute, NIH. Oltipraz was kept in the freezer in a tightly sealed container. All other reagents were obtained from commercial sources and typically ACS grade. Bovine erythrocyte copper,zinc-superoxide dismutase (SOD1) was purchased from Sigma (98% enzyme, 4000–5800 U/mg). 2,2,6,6-Tetramethylpiperidino-1-oxy (TEMPO), diethylenetriaminepentaacetic acid (DTPA), and methyl sulfoxide (DMSO) were obtained

Results and discussion

In the presence of the spin trap DMPO, EPR analysis of solutions of oltipraz in phosphate-buffered aqueous media (PB) containing the metal ion chelator DTPA indicates the formation of the spin trap radical adduct DMPO-OH. The spectrum in Fig. 2B, a 1:2:2:1 quartet that is absent in the absence of oltipraz (Fig. 2A), exhibits isotropic hyperfine splitting of 14.9 G (a_N = a_H), characteristic of the hydroxyl radical adduct of DMPO, DMPO-OH [31]. Oltipraz stimulated formation of DMPO-OH is dependent

Acknowledgments

The authors thank Drs. R.P. Pandian and P. Kuppusamy, and Anna Bratasz for the generous gift of lithium octa-n-butoxy naphthalocyanine and human kidney 293 cells, respectively. We thank Dr. Govindasamy Ilangovan for helpful discussions. This work was supported by RO1 CA91032-01 (J.C.F.) and NIH Grants, EB00890, RR12190/EB00306, and GM58582/EB00254 (J.L.Z.).

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Cancer chemopreventive oltipraz generates superoxide anion radical

Abstract

Section snippets

Materials

Results and discussion

Acknowledgments

Pharmacol. Ther.

Cancer Lett.

Food Chem. Toxicol.

J. Biol. Chem.

Tetrahedron

Biochem. Pharmacol.

Tetrahedron Lett.

Biochem. Pharmacol.

Free Radic. Biol. Med.

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Anal. Biochem.

Free Radic. Biol. Med.

J. Biol. Chem.

Cancer Epidemiol. Biomarkers Prev.

Cancer Epidemiol. Biomarkers Prev.

Cancer Epidemiol. Biomarkers Prev.

J. Natl. Cancer Inst.

Brit. Med. J.

Environ. Health Perspect.

J. Intern. Med.

Curr. Med. Chem.

Chem. Res. Toxicol.