A rapid assay of human thyroid peroxidase activity

Area of Science:

• Endocrinology
• Toxicology
• Biochemical Assays

Background:

• Thyroid hormones (THs) are crucial for development, and their disruption by chemicals can cause long-term health issues.
• Thyroid peroxidase (TPO) is essential for TH synthesis and a target for chemical disruption.
• Developing rapid, human-relevant assays is vital for assessing chemical risks to TH physiology.

Purpose of the Study:

• To engineer cell lines expressing active human TPO (hTPO) for a rapid TPO inhibition assay.
• To validate the assay's performance using reference chemicals with known TPO inhibitory activity.
• To evaluate the potential of cell line-derived hTPO as a substitute for animal-derived microsomes in screening assays.

Main Methods:

• Engineered CHO and LentiX-293 cell lines to express active human TPO (hTPO).
• Utilized a rapid assay employing Amplex UltraRed to detect TPO activity.
• Assessed assay performance by testing 19 reference chemicals with known TPO inhibition profiles.

Main Results:

• The hTPO assay consistently identified strong to moderate TPO inhibitors and inactive chemicals.
• Assay results showed less consistency for weak inhibitors, potentially indicating species-specific effects.
• The engineered cell lines expressing hTPO performed comparably to animal-derived thyroid microsomes.

Conclusions:

• Stably transfected cell lines expressing hTPO provide a viable alternative to animal-derived microsomes for TPO inhibition assays.
• This human-relevant assay is suitable for rapid, high-throughput screening of chemicals impacting thyroid hormone synthesis.
• The assay aids in identifying and characterizing TPO inhibitors, contributing to reduced chemical risks.