Proteomic analysis of normal mouse thyroids after 131I administration

Sammanfattning

Iodine is essential for the normal function of the thyroid gland, which in turn is susceptible to cellular damage after treatment with the β-emitter radioiodine (131I). Individuals exposed to 131I at a young age via contaminated food or nuclear crises such as the Chernobyl nuclear accident are at greater risk of developing e.g. thyroid cancer and other thyroid disorders later on in life. These factors may therefore have clinical implications for patients receiving 131I-based radionuclide therapy. The aim of this study was to identify potential biomarkers in normal thyroid tissue that are induced by 131I administration. Non-tumor-bearing female Balb/c nude mice were i.v. injected with 490 kBq 131I or physiological saline and killed 24 h after injection. The mean absorbed dose to the thyroid was calculated to 32 Gy. Protein lysates were extracted from surgically excised thyroids and analyzed using liquid chromatography tandem-mass spectrometry (LC-MS/MS), followed by database-dependent protein identification and relative quantification. The LC-MS/MS analysis identified 17 differentially expressed proteins (p<0.05), of which 13 showed down-regulation in the 131I-treated group compared to the controls. There was an enrichment of proteins associated with hypoxia/ischemia, oxygen transport/erythrocyte development, regulation of cell cycle, and metabolism. Interestingly, Hypoxia up-regulated protein 1 (HYOU1), known to be up-regulated during hypoxic conditions, was up-regulated in treated samples. In addition, five proteins associated with oxygen transport/erythrocyte development were identified, all of which were down-regulated, i.e. Bisphosphoglycerate mutase (PMGE), Ankyrin-1 (ANK1), and Hemoglobin subunits beta-1 (HBB1), beta-2 (HBB2), alpha (HBA). Taken together, these findings suggest the presence of hypoxic conditions and reduced oxygen transport in normal mouse thyroids 24 h after 131I administration. However, further studies are needed to determine whether these effects are time- and/or dose-dependent.