Generation of reactive oxygen species in the enzymatic reduction of PbCrO4 and related DNA damage

Stephen S. Leonard, Val Vallyathan, Vince Castranova, Xianglin Shi

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Free radical reactions are believed to play an important role in the mechanism of Cr(VI)-induced carcinogenesis. Most studies concerning the role of free radical reactions have been limited to soluble Cr(VI). Various studies have shown that solubility is an important factor contributing to the carcinogenic potential of Cr(VI) compounds. Here, we report that reduction of insoluble PbCrO4 by glutathione reductase in the presence of NADPH as a cofactor generated hydroxyl radicals (.OH) and caused DNA damage. The .OH radicals were detected by electron spin resonance (ESR) using 5,5-dimethyl-N-oxide as a spin trap. Addition of catalase, a specific H2O2 scavenger, inhibited the .OH radical generation, indicating the involvement of H2O2 in the mechanism of Cr(VI)-induced .OH generation. Catalase reduced .OH radicals measured by electron spin resonance and reduced DNA strand breaks, indicating .OH radicals are involved in the damage measured. The H2O2 formation was measured by change in fluorescence of scopoletin in the presence of horseradish peroxidase. Molecular oxygen was used in the system as measured by oxygen consumption assay. Chelation of PbCrO4 impaired the generation of .OH radical. The results obtained from this study show that reduction of insoluble PbCrO4 by glutathione reductase/NADPH generates .OH radicals. The mechanism of .OH generation involves reduction of molecular oxygen to H2O2, which generates .OH radicals through a Fenton-like reaction. The .OH radicals generated by PbCrO4 caused DNA strand breakage.

Original languageEnglish
Pages (from-to)309-315
Number of pages7
JournalMolecular and Cellular Biochemistry
StatePublished - 2002

Bibliographical note

Funding Information:
The authors wish to thank Dr. Murali Rao for his critical reading of the manuscript. Research funded under Interagency Agreement number 98-18-00m2 between the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH). The views expressed in the paper are those of the authors and do not necessarily reflect the official position of OSHA or NIOSH.


  • Electron spin resonance (ESR)
  • Glutathione reductase
  • Hydroxyl radicals
  • PbCrO

ASJC Scopus subject areas

  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology


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