Early transcriptional changes in response to low dose radiation exposure

One of the most likely risks astronauts on long duration space missions face is exposure to ionizing radiation associated with highly energetic and charged heavy (HZE) particles. Since access to medical expertise on such a mission is limited at best, early diagnosis and mitigation of such exposure is critical. In order to accurately determine the time since exposure and dosage of exposure, dose- and time-dependent “biomarkers” are needed. Therefore, we performed a dose- and time-course transcriptional analysis for radiation exposure at 0, 0.15, 0.30, and 1.5 Gy with corresponding time points at 1 hour (hr) post-exposure as well as 2 hr and 6 hr using Affymetrix® Human PrimeArrayTM chips. The analysis of our data suggests a set of sensitive genetic biomarkers specific to each radiation level as well as generic radiation response biomarkers. Upregulated biomarkers can then be used within lab-on-a-chip (LOC) systems to detect exposure to ionizing radiation. A total of 100 human samples representing radiation exposure at levels 0 Gy, 0.15 Gy, 0.30 Gy and 1.5 Gy at time points 1 hour (hr), 2 hr, and 6 hr post-exposure were constructed. Blood samples were extracted from ten human volunteers, and were irradiated. Leukocytes were extracted, and gene expression was measured. Samples for all ten volunteers were measured at 1 hr and 2 hr for all four dose levels, while samples from volunteers 1,2,3,4, and 7 were measured at 6 hr, resulting in 10 replicates at 1 hr and 2 hr for each dosage, and 5 replicates at 6 hr post-exposure. Thus, a total of 25 samples at each of the four radiation levels were sampled, yielding the total of 100 samples.