Copper-mediated DNA damage caused by purpurin, a natural anthraquinone

Hatasu Kobayashi; Yurie Mori; Ryo Iwasa; Yuichiro Hirao; Shinya Kato; Shosuke Kawanishi; Mariko Murata; Shinji Oikawa

doi:10.1186/s41021-022-00245-2

Copper-mediated DNA damage caused by purpurin, a natural anthraquinone

Genes Environ. 2022 May 9;44(1):15. doi: 10.1186/s41021-022-00245-2.

Authors

Hatasu Kobayashi¹, Yurie Mori^{1

2}, Ryo Iwasa¹, Yuichiro Hirao^{1

3}, Shinya Kato⁴, Shosuke Kawanishi⁵, Mariko Murata¹, Shinji Oikawa⁶

Affiliations

¹ Department of Environmental and Molecular medicine, Mie University Graduate School of Medicine, Edobashi 2-174, Tsu, Mie, 514-8507, Japan.
² Faculty of Pharmacy, Gifu University of Medical Science, 4-3-3 Nijigaoka, Kani, Gifu, 509-0293, Japan.
³ Mie Prefectural College of Nursing, Yumegaoka 1-1-1, Tsu, Mie, 514-0116, Japan.
⁴ Radioisotope Experimental Facility, Advanced Science Research Promotion Center, Mie University, Edobashi 2-174, Tsu, Mie, 514-8507, Japan.
⁵ Faculty of Pharmaceutical Science, Suzuka University of Medical Science, 3500-3, Minamitamagaki, Suzuka, Mie, 513-8670, Japan.
⁶ Department of Environmental and Molecular medicine, Mie University Graduate School of Medicine, Edobashi 2-174, Tsu, Mie, 514-8507, Japan. s-oikawa@med.mie-u.ac.jp.

Abstract

Background: Purpurin (1,2,4-trihydroxy-9,10-anthraquinone), a natural red anthraquinone pigment, has historically been used as a textile dye. However, purpurin induced urinary bladder tumors in rats, and displayed a mutagenic activity in assay using bacteria and mammalian cells. Many carcinogenic dyes are known to induce bladder cancers via DNA adduct formation, but carcinogenic mechanisms of purpurin remain unknown. In this study, to clarify the mechanism underlying carcinogenicity of purpurin, copper-mediated DNA damage induced by purpurin was examined using ³²P-labeled DNA fragments of human genes relevant to cancer. Furthermore, we also measured 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), an indicator of oxidative DNA damage, in calf thymus DNA.

Results: Purpurin plus Cu(II) cleaved ³²P-labeled DNA fragments only under piperidine treatment, indicating that purpurin caused base modification, but not breakage of the DNA backbone. In the absence of Cu(II), purpurin did not induce DNA cleavage even with piperidine treatment. Purpurin plus Cu(II) caused piperidine-labile sites predominantly at G and some T residues. Bathocuproine, a Cu(I) chelator, completely prevented the occurrence of piperidine-labile sites, indicating a critical role of Cu(I) in piperidine-labile sites induced by purpurin plus Cu(II). On the other hand, methional, a scavenger of a variety of reactive oxygen species (ROS) and catalase showed limited inhibitory effects on the induction of piperidine-labile sites, suggesting that ROS could not be major mediators of the purpurin-induced DNA damage. Considering reported DNA adduct formation by quinone metabolites of several carcinogenic agents, quinone form of purpurin, which is possibly generated via purpurin autoxidation accompanied by Cu(I)/Cu(II) redox cycle, might lead to DNA adducts and piperidine-labile sites. In addition, we measured contents of 8-oxodG. Purpurin moderately but significantly increased 8-oxodG in calf thymus DNA in the presence of Cu(II). The 8-oxodG formation was inhibited by catalase, methional and bathocuproine, suggesting that Cu(I)-hydroperoxide, which was generated via Cu(I) and H₂O₂, caused oxidative DNA base damage.

Conclusions: We demonstrated that purpurin induces DNA base damage possibly mediated by Cu(I)/Cu(II) redox cycle both with and without ROS generation, which are likely to play an important role in its carcinogenicity.

Keywords: Copper; DNA damage; Purpurin; Reactive oxygen species.

Abstract

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