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(PP261) Radioprotective effects of a super oxide dismutase mimetic on V79-4 micronucleus formation and survival.
Serra, Virginia*,1, Ortloff, Leticia2, Jobe, Marlene2, Pandya, Pinal1, Green, Lora1, 2, 3, 1 Department of Microbiology, Loma Linda, Ca, USA2 Radiobiology Program-Radiation Medicine, Loma Linda, Ca, USA3 Research, Loma Linda, CA, USA
ABSTRACT- Low linear energy transfer radiation, such as, gamma rays causes the majority of its damage to cellular components indirectly through the generation of oxygen radicals. The role of reactive oxygen species generated in response to irradiation and its contribution to radiation induced damage is part of our research focus. In this particular study we investigated superoxide/superoxide dismutase (SOD) in V79-4 cells using an SOD mimetic. The radiobiologic endpoints were micronucleus formation and survival.
The formation of micronuclei and survival were judged following exposure to 1, 3, 5 and 7 Gy gamma rays plus/minus various concentrations of an added superoxide dismutase mimetic (MnTMPyP). The micronucleus assay was conducted using cytochalasin B and scoring a minimum of 500 binucleated cells per condition in duplicate. Survival of the V79-4 was determined by the traditional colony counting method. The level of micronuclei above background was 20% and apoptosis was at a 30% at 48 hours post a 3 Gy gamma ray exposure. The addition of the SOD mimetic at a concentration of 5 ug/ml (median concentration used) added 30 minutes prior to irradiation was able to reduce the level of micronuclei formed and apoptosis at 3 Gy by 50%. However, at 7 Gy there was no sparing effect from the added mimetic. There was measurable toxicity from the mimetic alone at the concentrations employed, suggesting that the combined toxicity and damage at 7 Gy outweighed any protection the presence of additional SOD could impart.
In conclusion, at this point in the investigation we have found that increasing the concentration of SOD was able to reduce the chromosomal damage, in the form of micronuclei, caused by gamma radiation. However, the protective effects were dose and concentration dependent. We are currently conducting survival assays and repeating the micronucleus assay at lower concentrations of the mimetic.
Key words: super oxide dismutase mimetic, ionizing radiation, V79-4, chromosomal damage
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