Background: Thyroid iodide uptake, mediated by the sodium-iodide symporter (NIS), is essential for thyroid hormone synthesis and also for treatment of thyroid diseases, such as thyroid cancer, through radioiodine therapy. Therefore, compounds able to increase thyroid iodide uptake could be clinically useful, and it is of great importance to unravel the mechanisms underlying such an effect. It has been shown previously that the flavonoid rutin increases thyroid radioiodide uptake in vivo in rats. This study aimed to investigate the mechanisms involved in the stimulatory effect of rutin on iodide uptake.
Methods: This study evaluated iodide uptake, NIS expression and its subcellular distribution, iodide efflux, reactive oxygen species levels, and the intracellular pathways involved in NIS regulation in a rat thyroid PCCL3 cell line treated with rutin.
Results: Similar to previous results found in vivo, rutin increased radioiodide uptake in PCCL3 cells, which was accompanied by increased NIS expression (at both the mRNA and protein levels) and a reduction of radioiodide efflux. Moreover, the results suggest that rutin could regulate NIS subcellular distribution, leading to higher levels of NIS at the cell membrane. In addition, rutin decreased the levels of intracellular reactive oxygen species and phospho-5'-adenosine monophosphate-activated protein kinase.
Conclusions: The flavonoid rutin seems to be an important stimulator of radioiodide uptake, acting at multiple levels, an effect that can be due to decreased oxidative stress, reduced 5'-adenosine monophosphate-activated protein kinase activation, or both. Since thyroid iodide uptake is crucial for effective radioiodine therapy, the results suggest that rutin could be useful as an adjuvant in radioiodine therapy.
Keywords: AMPK; NIS; ROS; antioxidant; flavonoid; rutin.