Endocrine Abstracts

Regulation of gene expression mediated by thyroid hormones (THs) plays an essential role in variety of physiological processes. It is known that large group of natural and synthetic compounds, generally termed endocrine disruptors, can interfere with endocrine system and thus disrupt homeostasis of hormonal regulation processes in human organism. In order to screen for substances with potential disrupting effects on TH pathway, we developed and characterized human luciferase reporter gene cell line for assessment of thyroid receptor (TR) transcriptional activity – PZ-TR. PZ-TR cell line was derived from human hepatocellular carcinoma cells HepG2, which were stably transfected with reporter plasmid containing two copies of tandem thyroid response elements (TREs) upstream of reporter gene for luciferase. Dose–response analyses showed that triiodothyronine (T₃), natural ligand of TR, induced luciferase activity in PZ-TR cells in dose-dependent manner and sensitivity of luciferase assays allowed detection of T₃ in nanomolar range of concentrations. Maximum fold induction of luciferase activity ranged from 2.5× to almost 3× after 24 h of exposure to T₃. We did not observe unspecific induction of luciferase activity by other steroid hormones and VDR ligands, only exception was partial increase of luciferase activity after treatment of PZ-TR cells with retinoic acids. Cryopreservation of PZ-TR cells did not influence their functionality, similarly responsivity to T₃ and cell morphology maintained unaffected even after long-term cultivation. Novel PZ-TR cell line was used for evaluation of effects of organic tin compounds on transcriptional activity of TR. We found that both, tributyltin derivatives and triphenyltin derivatives induced luciferase activity in PZ-TR cells. These findings indicate that organic tin compounds have potential to interfere with TR-mediated regulation of gene expression and thus influence physiological activity of THs.

This work was supported by the European Social Fund and the Ministry of Education, Youth and Sports of the Czech Republic, Project No. CZ.1.07/2.3.00/30.0004 (POST-UP).

Disclosure: This work was supported by the European Social Fund and the Ministry of Education, Youth and Sports of the Czech Republic, Project No. CZ.1.07/2.3.00/30.0004 (POST-UP).