In vitro RABiT measurement of dose rate effects on radiation induction of micronuclei in human peripheral blood lymphocytes

Abstract

Developing new methods for radiation biodosimetry has been identified as a high priority need in case of a radiological accident or nuclear terrorist attacks. A large-scale radiological incident would result in an immediate critical need to assess the radiation doses received by thousands of individuals. Casualties will be exposed to different doses and dose-rates due to their geographical position and sheltering conditions, and dose-rate is one of the principal factors that determine the biological consequences of a given absorbed dose. In these scenarios high-throughput platforms are required to identify the biological dose in a large number of exposed individuals for clinical monitoring and medical treatment. The RABiT (Rapid Automated Biodosimetry Tool) is designed to be completely automated from the input of blood sample into the machine to the output of a dose estimate. The primary goal of this paper was to quantify the dose-rate effects for RABiT-measured micronuclei in vitro in human lymphocytes. Blood samples from healthy volunteers were exposed in vitro to different doses of X-rays to acute and protracted doses over a period up to 24 hours. The acute dose (ADR) was delivered at ∼1.03Gy/min and the low dose rate (LDR) exposure at ∼0.31Gy/min. The results showed that the yield of micronuclei decreases with decreasing dose-rate starting at 2Gy, whereas response was indistinguishable from that of acute exposure in the low dose region, up to 0.5Gy. The results showed a linear-quadratic dose-response relationship for the occurrence of micronuclei for the acute exposure and a linear dose-response relationship for the low dose-rate exposure.

Mice and the A-Bomb: Irradiation Systems for Realistic Exposure Scenarios

“…Similarly gene expression patterns in both mouse (50) and ex vivo irradiated blood (48) showed gene signatures that were independent of dose rate as well as signatures that were dose rate dependent. As expected, micronuclei (47) showed a linear dose response for LDR and a quadratic dose response for HDR, indicating repair of sublethal damage in the former.…”

“…Using this low-dose-rate irradiator we have studied a variety of cytogenetic (46, 47), transcriptomic (48, 50) and metabolomic (49) endpoints. We have seen that both HDR and LDR perturb the same general metabolic pathways but that individual metabolites may be used to discriminate between high- and low-dose rates (49).…”

“…At our facility, we have modified an X-Rad 320 (Precision X Ray Inc., North Branford, CT) to support long term irradiations of mice and blood (46, 47). An important requirement in beam preparation is that the radiation quality be the same in both high-dose-rate (HDR) and low-dose-rate (LDR) modes.…”

“…To fulfill this requirement, we built a custom incubator (47–49) (Fig. 4a) mainly made of plastic to minimize scattered radiation.…”

THE DECADE OF THE RABiT (2005–15)

“…At this point developments transitioned to optimization of the existing system (7,19) , developing novel bioassays could be performed on the RABiT and testing the existing assays under complex radiation exposure scenarios (20)(21)(22) . The gamma-H2AX and CBMN RABiT assays were transitioned to BARDA funding for further development and rigorous validation in preparation for licensing by the Food and Drug Administration.…”