Transcriptional response of mouse thyroids following in vivo 211At exposure reveals distinct gene expression profiles. Mus musculus

Transcriptomic profiling of normal mouse thyroid tissue following 211At irradiation Astatine-211 (211At) is an alpha particle emitting halogen with almost optimal linear energy transfer (LET) for creating DNA double strand breaks, and is thus proposed for radionuclide therapy when bound to tumor-seeking agents. Un-bound 211At accumulates in the thyroid gland. The concept of basal radiation-induced biological effects in thyroid tissue is to a high degree unknown and is most valuable. Female BALB/c nude mice were i.v. injected with 0.064-42 kBq of 211At resulting in absorbed doses to the thyroid gland of 0.05-32 Gy. Thyroids were removed at 24 h after injection and total RNA was extracted from pooled thyroids and processed in triplicate using Illumina MouseRef-8 Whole-Genome Expression Beadchips. Nexus Expression 2.0 was used for data analysis. Thyroids exposed to 211At revealed distinctive gene expression profiles compared to non-irradiated controls. More genes were affected at low absorbed doses (0.05 and 0.5 Gy) compared to intermediate (1.4 Gy) and high absorbed doses (11 and 32 Gy) and the proportion of dose-specific genes increased with decreased absorbed dose. This result might be the manifestation of increased heterogeneous irradiation with decreasing absorbed dose, indicating a bystander effect. Also, 1.4 Gy often had an opposite regulation compared to the other absorbed doses. No inflammatory effects were seen while 0.05 and 11 Gy affected the immune system. Effects on the cellular response to outer stress and cell cycle regulation and proliferation were seen at 1.4 and 11 Gy. These results indicate that the cellular response to ionizing radiation is complex and differs with absorbed doses. Overall design: Total RNA was isolated from fresh-frozen tissue samples (Normal balb/c mouse thyroids)