Impacts of Unregulated Novel Brominated Flame Retardants on Human Liver Thyroid Deiodination and Sulfotransferation
Citations Over TimeTop 14% of 2017 papers
Abstract
The inhibitory effects of five novel brominated flame retardants, 1,2-bis(2,4,5-tribromophenoxy)ethane (BTBPE), decabromodiphenylethane (DBDPE), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), bis(2-ethylhexyl)tetrabromophthalate (BEH-TEBP), and β-tetrabromoethylcyclohexane (β-TBECH), on thyroid hormone deiodinase (DIO) and sulfotransferase (SULT) activity were investigated using human in vitro liver microsomal and cytosolic bioassays. Enzymatic activity was measured by incubating active human liver subcellular fractions with thyroid hormones (T4 and rT3 separately) and measuring changes in thyroid hormone (T4, T3, rT3, and 3,3'-T2) concentrations. Only DBDPE showed inhibition of both outer and inner ring deiodination (O and IRD) of T3 and 3,3'-T2 formation from T4, respectively, with an estimated IC50 of 160 nM; no statistically significant inhibition of SULT activity was observed. ORD inhibition of 3,3'-T2 formation from rT3 was also observed (IC50 ∼ 100 nM). The kinetics of T4 O and IRD were also investigated, although a definitive mechanism could not be identified as the Michaelis-Menten parameters and maximal rate constants were not significantly different. Concentrations tested were intentionally above expected environmental levels, and this study suggests that these NBFRs are not potent human liver DIO and SULT inhibitors. To our knowledge, DBDPE is the first example of a nonhydroxylated contaminant inhibiting DIO activity, and further study of the mechanism of action is warranted.
Related Papers
- → Flame Retardant Applications in Camping Tents and Potential Exposure(2014)41 cited
- THE COMPARISON BETWEEN SYNERGISTIC EFFECT OF SB2O3 AND AL(OH)3 ON THE FLAME-RETARDANCY OF HIPS IN THE PRESENCE OF TETRABROMOBISPHENOL-A(2004)
- → Decomposition Behavior of Flame Retardant Plastics Containing Brominated Flame Retardant and Trioxide Antimony(2005)1 cited
- Preparation and Application of Brominated Flame Retardant Masterbatch of ABS(2012)
- → VECAP continues to effectively manage flame retardant chemicals(2008)