Oxygen radical-mediated DNA damage by redox-active Cr(III) complexes.

Area of Science:

• Environmental toxicology
• Biochemistry
• Molecular biology

Background:

• Chromium(III) is the biologically active form of chromium, but its mechanism of DNA damage remains unclear.
• Understanding chromium-induced mutagenesis is crucial for assessing its health risks.

Purpose of the Study:

• To identify mutagenic chromium(III) complexes using the Salmonella reversion assay.
• To elucidate the redox kinetics and DNA interaction mechanisms of mutagenic chromium(III) species.
• To investigate the role of ligands in directing the biological activity of chromium(III) complexes.

Main Methods:

• Salmonella reversion assay for mutagenicity testing.
• Cyclic voltammetry to analyze redox kinetics.
• Plasmid relaxation assays to assess DNA interaction in vitro.

Main Results:

• Mutagenic chromium(III) complexes exhibited reversible redox behavior and positive shifts in the Cr(III)/Cr(II) couple, indicating electron-donating capacity.
• These mutagenic complexes induced supercoiled DNA relaxation in vitro, suggesting single-strand breaks.
• Nonmutagenic complexes showed irreversible redox kinetics, more negative potentials, and no DNA relaxation.
• Ligand properties were shown to influence the redox activity and DNA-damaging potential of chromium(III) complexes.

Conclusions:

• The mechanism of chromium(III)-induced mutagenesis likely involves oxygen radicals generated via a Fenton-like reaction.
• The electrochemical properties and DNA-relaxing ability of chromium(III) complexes are directly linked to their mutagenicity.
• Ligands play a critical role in modulating the redox behavior and biological activity of chromium(III) complexes.