Metal-mediated oxidative DNA damage induced by methylene blue.

Abstract

BACKGROUND:

Methylene blue (MB) is used for various clinical purposes, including chromoendoscopy and methemoglobinemia treatment. However, MB induces tumors of pancreatic islets and small intestine in experimental animals. This finding raises a possibility that MB induces carcinogenicity in these organs via light-independent mechanisms, although MB is known to cause light-dependent DNA damage.

METHODS:

We investigated the mechanism of MB-induced DNA damage using (32)P-5'-end-labeled DNA fragments of human tumor-relevant genes. We investigated the redox reaction of MB by UV-visible spectrometry.

RESULTS:

MB induced DNA damage at the 5'-ACG-3' sequence, a hot spot of the p53 gene, in the presence of NADH and Cu(II). DNA damage was inhibited by catalase and bathocuproine, a Cu(I)-specific chelator. MB induced DNA damage at every nucleotide in the presence of NADH and Fe(III)-ethylenediaminetetraacetic acid, which was inhibited by OH scavengers and catalase. MB significantly increased the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an oxidative DNA lesion, in the presence of NADH and metal ions. UV-visible spectrometry revealed that the absorbance of oxidized form of MB at 668nm was decreased by NADH, and the addition of metal ions attenuated the spectral change.

CONCLUSIONS:

MB undergoes NADH-dependent reduction followed by metal ion-mediated reoxidation. Reduced metal ions [Cu(I) and Fe(II)] interact with H2O2, generated during the redox reaction, to produce Cu(I)OOH and OH that cause DNA damage, respectively. These findings suggest that metal-mediated DNA damage contributes to MB-mediated carcinogenesis.

GENERAL SIGNIFICANCE:

This study would provide an insight into the mechanism of MB-induced carcinogenesis and its safety assurance for clinical use.

• Authors: Yusuke Hiraku, Hiroyuki Goto, Masaki Kohno, Shosuke Kawanishi, Mariko Murata
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1840 Issue 9 Pg. 2776-82 (Sep 2014) ISSN: 0006-3002 [Print] Netherlands
• PMID: 24792575 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical References

• Phenanthrolines
• Copper
• bathocuproine
• Hydrogen Peroxide
• Iron
• Methylene Blue

Topics

• Copper (chemistry)
• DNA Damage
• Humans
• Hydrogen Peroxide (chemistry)
• Iron (chemistry)
• Methylene Blue (chemistry)
• Oxidation-Reduction
• Phenanthrolines (chemistry)