Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2016 Dec;6(1):48.
doi: 10.1186/s13550-016-0203-x. Epub 2016 Jun 3.

The effect of dimethyl sulfoxide on the induction of DNA strand breaks in plasmid DNA and colony formation of PC Cl3 mammalian cells by alpha-, beta-, and Auger electron emitters (223)Ra, (188)Re, and (99m)Tc

Roswitha Runge  1 , Liane Oehme  2 , Jörg Kotzerke  2 , Robert Freudenberg  2
Affiliations

The effect of dimethyl sulfoxide on the induction of DNA strand breaks in plasmid DNA and colony formation of PC Cl3 mammalian cells by alpha-, beta-, and Auger electron emitters (223)Ra, (188)Re, and (99m)Tc

Roswitha Runge et al. EJNMMI Res. 2016 Dec.

Abstract

Background: DNA damage occurs as a consequence of both direct and indirect effects of ionizing radiation. The severity of DNA damage depends on the physical characteristics of the radiation quality, e.g., the linear energy transfer (LET). There are still contrary findings regarding direct or indirect interactions of high-LET emitters with DNA. Our aim is to determine DNA damage and the effect on cellular survival induced by (223)Ra compared to (188)Re and (99m)Tc modulated by the radical scavenger dimethyl sulfoxide (DMSO).

Methods: Radioactive solutions of (223)Ra, (188)Re, or (99m)Tc were added to either plasmid DNA or to PC Cl3 cells in the absence or presence of DMSO. Following irradiation, single strand breaks (SSB) and double strand breaks (DSB) in plasmid DNA were analyzed by gel electrophoresis. To determine the radiosensitivity of the rat thyroid cell line (PC Cl3), survival curves were performed using the colony formation assay.

Results: Exposure to 120 Gy of (223)Ra, (188)Re, or (99m)Tc leads to maximal yields of SSB (80 %) in plasmid DNA. Irradiation with 540 Gy (223)Ra and 500 Gy (188)Re or (99m)Tc induced 40, 28, and 64 % linear plasmid conformations, respectively. DMSO prevented the SSB and DSB in a similar way for all radionuclides. However, with the α-emitter (223)Ra, a low level of DSB could not be prevented by DMSO. Irradiation of PC Cl3 cells with (223)Ra, (188)Re, and (99m)Tc pre-incubated with DMSO revealed enhanced survival fractions (SF) in comparison to treatment without DMSO. Protection factors (PF) were calculated using the fitted survival curves. These factors are 1.23 ± 0.04, 1.20 ± 0.19, and 1.34 ± 0.05 for (223)Ra, (188)Re, and (99m)Tc, respectively.

Conclusions: For (223)Ra, as well as for (188)Re and (99m)Tc, dose-dependent radiation effects were found applicable for plasmid DNA and PC Cl3 cells. The radioprotection by DMSO was in the same range for high- and low-LET emitter. Overall, the results indicate the contribution of mainly indirect radiation effects for each of the radionuclides regarding DNA damage and cell survival. In summary, our findings may contribute to fundamental knowledge about the α-particle induced DNA damage.

Keywords: Cellular survival; DMSO; LET; Plasmid DNA; α-emitter.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1
Dose response of 223Ra (a), 188Re (b), and 99mTc (c) in the absence or presence of DMSO. Dose-dependent increase in open circular DNA and linear DNA was accompanied by the loss of supercoiled DNA. The influence of DMSO on yields of DNA conformational changes shows prevention of SSB and DSB. Error bars present the standard errors of the means from three independent experiments
Fig. 2
Fig. 2
Calculated numbers of SSB (a, b) and DSB (c, d) per plasmid molecule in the absence (a, c) and presence (b, d) of 0.2 M DMSO for 223Ra, 188Re, and 99mTc. The mean numbers of SSB and DSB were calculated based on the fluorescence intensities shown in Fig. 1. Panel a shows only dose points up to 180 Gy because after higher doses, the SC plasmid forms disappeared. Error bars were calculated by the propagation of uncertainty of the standard error of the mean
Fig. 3
Fig. 3
Effect of the DMSO concentrations on open circular fractions of DNA (SSB). Plasmid samples were irradiated with 200 Gy 223Ra, 188Re, and 99mTc. The relative amount of SSB was determined at various DMSO concentrations. Error bars indicate the standard error of the mean from three independent experiments
Fig. 4
Fig. 4
Survival of PC Cl3 cells after exposure to 223Ra (a), 188Re (b), and 99mTc (c) in the presence or absence of DMSO (0.2 M). The amount of radioactivity was adjusted to reduce survival to about 1 % in the absence of DMSO. The curves were fitted to linear regression. Error bars are standard deviations from three independent experiments
Fig. 5
Fig. 5
Cytotoxic and radioprotective effects of DMSO. PC Cl3 cells were subjected to different DMSO concentrations (a) or irradiated with 223Ra, 188Re, or 99mTc in combination with DMSO (b). The ratio of surviving fractions SF+DMSO/SF−DMSO for the radionuclides are shown. Error bars are the standard error of the mean from three independent experiments
See this image and copyright information in PMC

References

    1. Giustranti C, Rousset S, Balanzat E, Sage E. Heavy ion-induced plasmid DNA damage in aerated or deaerated conditions. Biochimie. 2000;82:79–83. doi: 10.1016/S0300-9084(00)00186-3. - DOI - PubMed
    1. Peak JG, Ito T, Robb FT, Peak MJ. DNA damage produced by exposure of supercoiled plasmid DNA to high- and low-LET ionizing radiation: effects of hydroxyl radical quenchers. Int J Radiat Biol. 1995;67:1–6. doi: 10.1080/09553009514550011. - DOI - PubMed
    1. Taucher-Scholz G, Kraft G. Influence of radiation quality on the yield of DNA strand breaks in SV40 DNA irradiated in solution. Radiat Res. 1999;151:595–604. doi: 10.2307/3580036. - DOI - PubMed
    1. Urushibara A, Shikazono N, O’Neill P, Fujii K, Wada S, Yokoya A. LET dependence of the yield of single-, double-strand breaks and base lesions in fully hydrated plasmid DNA films by 4He(2+) ion irradiation. Int J Radiat Biol. 2008;84:23–33. doi: 10.1080/09553000701616072. - DOI - PubMed
    1. Ushigome T, Shikazono N, Fujii K, Watanabe R, Suzuki M, Tsuruoka C, et al. Yield of single- and double-strand breaks and nucleobase lesions in fully hydrated plasmid DNA films irradiated with high-LET charged particles. Radiat Res. 2012;177:614–27. doi: 10.1667/RR2701.1. - DOI - PubMed