Abstract
Iodotyrosine deiodinase (IYD) has an ability to salvage iodide from iodotyrosine that are generated as byproducts of thyroid hormone biosynthesis. This enzyme has also been discovered to act as a dehalogenase of bromo- and chlorotyrosine. Halogenated phenolic chemicals may disrupt thyroid hormone metabolism through the inhibition of IYD activity. The objective of this study was to clarify the effect of halogenated environmental chemicals on thyroid hormone metabolism, we investigated the inhibitory effects of these chemicals on IYD activity using HEK293T cells recombinant human IYD. Inhibition of IYD activity was detected by two flame retardants, 3,3’,5,5’-tetrachlorobisphenol A and 3,3’,5,5’-tetrabromobisphenol A, by the antimicrobial agent, triclosan, by antihyperuricemic drug, benzbromarone, by two antiparasitic drugs, bithionol and oxyclozanide, and by three food colorants, phloxine B, erythrosine B and rose bengal. These results suggest that the halogen substitution adjacent to hydroxyl group is structural requirement for the inhibition of IYD activity.
