An improved thyroid hormone reporter assay to determine the thyroid hormone-like activity of amiodarone, bithionol, closantel and rafoxanide.
A number of environmental chemicals have been reported to exhibit thyroid hormone-like activity. Since thyroid hormones play a crucial role in development, it is important to identify chemicals in the environment that are capable of endocrine disruption of thyroid hormone homeostasis. In order to detect thyroid hormone-like activity, the growth of pituitary cell lines has been commonly used as a sensitive marker, albeit with limited specificity to thyroid hormones. Reporter gene assays using the thyroid hormone responsive element (TRE) connected to the luciferase reporter gene have also been developed. Thus far however, this type of assay appears to have limited sensitivity compared to cell growth assays. In the present study, we developed a highly sensitive TRE reporter gene assay by using a pituitary cell line, MtT/E-2, and by culturing cells in a serum-free medium. Our assay was developed in order to detect T3 activity at a concentration of 10(-11)M. This assay identified thyroid hormone-like activity from the antiarrhythmic drug, amiodarone, and from three anti-parasitic drugs, bithionol, closantel and rafoxanide, all commonly used in veterinary medicine. Thyroid hormone-like activity of these compounds was further confirmed by the induction of BCL3 gene expression in MtT/E-2, which is known to be regulated by thyroid hormones. Our improved assay was proved to be a sensitive tool for assessing thyroid hormone-like activity of environmental chemicals.
Faculty of Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Hiroshima University, Japan.
Kana
K
Matsubara
Seigo
S
Sanoh
Shigeru
S
Ohta
Shigeyuki
S
Kitamura
Kazumi
K
Sugihara
Nariaki
N
Fujimoto
D000638:Amiodarone / Q000494:pharmacology; D000818:Animals; D000081242:B-Cell Lymphoma 3 Protein; D001681:Biological Assay / Q000379:methods*; D001735:Bithionol / Q000494:pharmacology; D002460:Cell Line; D052244:Endocrine Disruptors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter / Q000187:drug effects*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D010902:Pituitary Gland / Q000166:cytology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011888:Rafoxanide / Q000494:pharmacology; D051381:Rats; D020218:Response Elements / Q000187:drug effects; D012458:Salicylanilides / Q000494:pharmacology; D012680:Sensitivity and Specificity; D013963:Thyroid Hormones / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014284:Triiodothyronine / Q000378:metabolism
D000081242:B-Cell Lymphoma 3 Protein; D052244:Endocrine Disruptors; D011518:Proto-Oncogene Proteins; D012458:Salicylanilides; D013963:Thyroid Hormones; D014157:Transcription Factors; D014284:Triiodothyronine; D011888:Rafoxanide; D001735:Bithionol; D008156:Luciferases; C023342:closantel; D000638:Amiodarone