Protection from radiation-induced DNA single-strand breaks by induction of nuclear metallothionein

V. Vukovic, Say Ry Pheng, Alexander Keith Stewart, C. H. Vik, D. W. Hedley

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Purpose: To examine the extent to which nuclear metallothionein protects from radiation-induced DNA damage under aerobic and hypoxic conditions. Materials and methods: A semiquantitative fluorescence image analysis method measured the nuclear content of metallothionein (MT) in ME180 and SiHa human squamous cervical carcinoma cell lines under normal growth conditions, and following MT induction by zinc. The extent of initial DNA damage following 60Co irradiation under aerobic and hypoxic conditions was assessed using the alkaline comet assay. Results: Provided that cells were maintained at 37°C, most of the cellular content of MT was in the nucleus. Incubation at 4°C: caused the rapid translocation of MT from the nucleus into the cytoplasm in both cell lines, with no net loss of cellular MT. Baseline nuclear MT levels were about four times greater in ME180 cells, and were much more readily induced by treatment with 100 μM zinc acetate, compared with SiHa cells. Under aerobic conditions, MT induction by zinc resulted in no protection in either of the cell lines. Under hypoxic conditions, however, the number of DNA single-strand breaks in zinc-treated cells was reduced by ~ 40% in ME180, but not in SiHa cells, when compared with non-induced controls. Conclusions: Nuclear MT can exert a significant level of protection from radiation by a mechanism that involves competition with oxygen for DNA radical sites and/or scavenging of free radicals. Because increased MT levels have been reported in hypoxic micro-regions of some solid tumours, this protective mechanism might have clinical relevance. .

Original languageEnglish (US)
Pages (from-to)757-762
Number of pages6
JournalInternational Journal of Radiation Biology
Volume76
Issue number6
StatePublished - 2000
Externally publishedYes

Fingerprint

Single-Stranded DNA Breaks
Radiation Protection
Metallothionein
metallothionein
strands
induction
DNA
deoxyribonucleic acid
Radiation
zinc
cultured cells
radiation
cells
aerobic conditions
Zinc
Cells
anaerobic conditions
damage
nuclei
Cell Line

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology
  • Nuclear Energy and Engineering
  • Radiation

Cite this

Protection from radiation-induced DNA single-strand breaks by induction of nuclear metallothionein. / Vukovic, V.; Pheng, Say Ry; Stewart, Alexander Keith; Vik, C. H.; Hedley, D. W.

In: International Journal of Radiation Biology, Vol. 76, No. 6, 2000, p. 757-762.

Research output: Contribution to journalArticle

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abstract = "Purpose: To examine the extent to which nuclear metallothionein protects from radiation-induced DNA damage under aerobic and hypoxic conditions. Materials and methods: A semiquantitative fluorescence image analysis method measured the nuclear content of metallothionein (MT) in ME180 and SiHa human squamous cervical carcinoma cell lines under normal growth conditions, and following MT induction by zinc. The extent of initial DNA damage following 60Co irradiation under aerobic and hypoxic conditions was assessed using the alkaline comet assay. Results: Provided that cells were maintained at 37°C, most of the cellular content of MT was in the nucleus. Incubation at 4°C: caused the rapid translocation of MT from the nucleus into the cytoplasm in both cell lines, with no net loss of cellular MT. Baseline nuclear MT levels were about four times greater in ME180 cells, and were much more readily induced by treatment with 100 μM zinc acetate, compared with SiHa cells. Under aerobic conditions, MT induction by zinc resulted in no protection in either of the cell lines. Under hypoxic conditions, however, the number of DNA single-strand breaks in zinc-treated cells was reduced by ~ 40{\%} in ME180, but not in SiHa cells, when compared with non-induced controls. Conclusions: Nuclear MT can exert a significant level of protection from radiation by a mechanism that involves competition with oxygen for DNA radical sites and/or scavenging of free radicals. Because increased MT levels have been reported in hypoxic micro-regions of some solid tumours, this protective mechanism might have clinical relevance. .",
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AB - Purpose: To examine the extent to which nuclear metallothionein protects from radiation-induced DNA damage under aerobic and hypoxic conditions. Materials and methods: A semiquantitative fluorescence image analysis method measured the nuclear content of metallothionein (MT) in ME180 and SiHa human squamous cervical carcinoma cell lines under normal growth conditions, and following MT induction by zinc. The extent of initial DNA damage following 60Co irradiation under aerobic and hypoxic conditions was assessed using the alkaline comet assay. Results: Provided that cells were maintained at 37°C, most of the cellular content of MT was in the nucleus. Incubation at 4°C: caused the rapid translocation of MT from the nucleus into the cytoplasm in both cell lines, with no net loss of cellular MT. Baseline nuclear MT levels were about four times greater in ME180 cells, and were much more readily induced by treatment with 100 μM zinc acetate, compared with SiHa cells. Under aerobic conditions, MT induction by zinc resulted in no protection in either of the cell lines. Under hypoxic conditions, however, the number of DNA single-strand breaks in zinc-treated cells was reduced by ~ 40% in ME180, but not in SiHa cells, when compared with non-induced controls. Conclusions: Nuclear MT can exert a significant level of protection from radiation by a mechanism that involves competition with oxygen for DNA radical sites and/or scavenging of free radicals. Because increased MT levels have been reported in hypoxic micro-regions of some solid tumours, this protective mechanism might have clinical relevance. .

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