Abstract
Accurate dose assessment and correct identification of irradiated from non-irradiated people are goals of biological dosimetry in radiation accidents. Changes in the FDXR and the RAD51 gene expression (GE) levels were here analyzed in response to total body exposure (TBE) to a 6 MV x-ray beam in rats. We determined the accuracy for absolute quantification of GE to predict the dose at 24 hours. For this in vivo experimental study, using simple randomized sampling, peripheral blood samples were collected from a total of 20 Wistar rats at 24 hours following exposure of total body to 6 MV X-ray beam energy with doses (0.2, 0.5, 2 and 4 Gy) for TBE in Linac Varian 2100C/D (Varian, USA) in Golestan Hospital, in Ahvaz, Iran. Also, 9 rats was irradiated with a 6MV X-ray beam at doses of 1, 2, 3 Gy in 6MV energy as a validation group. A sham group was also included. After RNA extraction and DNA synthesis, GE changes were measured by the QRT-PCR technique and an absolute quantification strategy by taqman methodology in peripheral blood from rats. ROC analysis was used to distinguish irradiated from non-irradiated samples (qualitative dose assessment) at a dose of 2 Gy. The best fits for mean of responses were polynomial equations with a R2 of 0.98 and 0.90 (for FDXR and RAD51 dose response curves, respectively). Dose response of the FDXR gene produced a better mean dose estimation of irradiated "validation" samples compared to the RAD51 gene at doses of 1, 2 and 3 Gy. FDXR gene expression separated the irradiated rats from controls with a sensitivity, specificity and accuracy of 87.5%, 83.5% and 81.3%, respectively, 24 hours after dose of 2 Gy. These values were significantly (p<0.05) higher than the 75%, 75% and 75%, respectively, obtained using gene expression of RAD51 analysis at a dose of 2 Gy. Collectively, these data suggest that absolute quantification by gel purified quantitative RT-PCR can be used to measure the mRNA copies for GE biodosimetry studies at comparable accuracy to similar methods. In the case of TBE with 6MV energy, FDXR gene expression analysis is more precise than that with RAD51 for quantitative and qualitative dose assessment.
Highlights
In a situation of increasing concern about the possibility of large-scale acute exposure the ability to assess the extent of exposure is essential for decreasing morbidity and mortality through medical intervention (Bazan et al 2014; Forrester and Sprung. 2014; Min et al 2014; Tsuyama et al 2014)
PCR efficiencies were between 89% and 105% for ferodoxin reductase (FDXR) and RAD51 genes with R2 > 0.98, respectively
The Ct for FDXR and RAD51 genes was initiated from the cycles of 18 and 23 for the first concentration of standard samples and ended in the cycles of 32 and 34 for the last concentration of standard samples, respectively
Summary
In a situation of increasing concern about the possibility of large-scale acute exposure the ability to assess the extent of exposure is essential for decreasing morbidity and mortality through medical intervention (Bazan et al 2014; Forrester and Sprung. 2014; Min et al 2014; Tsuyama et al 2014). The changes in the GE and quantity of RNA transcripts in cells that have been exposed to ionizing radiation suggest the possibility of that the GE analysis providing qualitative assessments of dose and quantitative dose determination. It may provide high-throughput assessments of radiation exposure in a large number of exposed individuals (Filiano et al 2011). In the case of TBE with 6MV energy, FDXR gene expression analysis is more precise than that with RAD51 for quantitative and qualitative dose assessment
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