Abstract
The appropriate amount of iodine is critical for normal function of thyroid cells synthesizing thyroid hormones. Although normal thyroid cell lines such as rat PCCL3 and FRTL5 and human Nthy-ori 3-1 have been widely used for in vitro studies on physiological and pathophysiological effects of iodine on thyroid cells, we have recently pointed out the critical differences between FRTL5/PCCL3 cells and Nthy-ori 3-1 cells. Therefore, we here directly compared some of the cellular characteristics—iodine uptake, differentiated status, iodine-induced cytotoxicity, and iodine-regulation of autophagy—between PCCL3 and Nthy-ori 3-1 cells. PCCL3 cells express messenger RNAs for thyrotropin receptor and sodium/iodine symporter and incorporate iodine in a thyrotropin-dependent manner, whereas Nthy-ori 3-1 cells do not either. Nevertheless, both cells were comparably resistant to iodine cytotoxicity: Only far excess iodine (5 × 10–2 M) killed 20% to 40% cells in 24 hours with perchlorate exhibiting no effect, suggesting this cytotoxic effect is due to extracellular iodine. In contrast, a wide range of iodine (5 × 10–9 to 5 × 10–2 M) induced autophagy in PCCL3 cells, which was abolished by perchlorate, indicating intracellular iodine-induction of autophagy, but this effect was not observed in Nthy-ori 3-1 cells. In conclusion, it is critical to discriminate the effect of iodine incorporated into cells from that of extracellular iodine on thyroid cells. Iodine-uptake competent thyroid cells such as PCCL3 and FRTL5 cells, not Nthy-ori 3-1 cells, should be used for studies on iodine effect on thyroid cells.
Highlights
The appropriate amount of iodine is critical for normal function of thyroid cells synthesizing thyroid hormones
Normal thyroid cell lines such as rat PCCL3 and FRTL5 and human Nthy-ori 3-1 have been widely used for in vitro studies on physiological and pathophysiological effects of iodine on thyroid cells, we have recently pointed out the critical differences between FRTL5/PCCL3 cells and Nthy-ori 3-1 cells
We have recently pointed out the critical differences between FRTL5/PCCL3 cells and Nthy-ori 3-1 cells and expressed our concern that the latter may not be suitable for studies on in vitro effect of iodine on thyroid cells [9]
Summary
A rat normal thyroid cell line PCCL3 [1] was previously described [14] and maintained in Coon’s modified F-12 medium supplemented with 5% fetal bovine serum (FBS), antibiotics and 3H (2 U/L bovine thyrotropin [TSH], 5 U/L insulin, and 5 mg/L transferrin) or 2H (insulin and transferrin) (all from Sigma-Aldrich). The former was spontaneously immortalized and its growth is totally TSH dependent, whereas the latter is derived from an HTori-3 cell line that was immortalized by transfection of simian virus 40 T-antigen and can grow without TSH [9]. Cell viability was measured using a Cell Counting Kit-8 (Dojindo) in accordance with the manufacturer’s protocol
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