Relationships between polybrominated diphenyl ethers and transcription and activity of type 1 deiodinase in a gull highly exposed to flame retardants

Abstract

Deca-brominated diphenyl ether (deca-BDE), composed mainly of BDE-209, is subject to usage restrictions in North America and Europe, although global action on its continued use has yet to be undertaken. Relatively large concentrations of polybrominated diphenyl ethers (PBDEs), especially BDE-209 and its higher brominated degradation products, have been reported in tissues of ring-billed gulls (Larus delawarensis) breeding near the densely populated city of Montreal (QC, Canada). There is limited knowledge of BDE-209 biotransformation and toxicokinetics in birds. Deiodinases, a class of enzymes catalyzing thyroid hormone conversion, have been suggested to be involved in BDE-209 debromination in birds. The objective of the present study was to investigate the relationships between PBDE concentrations and type 1 deiodinase (D1) transcription and in vitro activity (microsomes) in livers of Montreal-breeding ring-billed gulls. The ring-billed gulls exhibiting the highest D1 activity in liver microsomes accumulated the greatest liver concentrations of hepta-BDEs and octa-BDEs. Activity of D1 was inversely related to concentration ratios of BDE-209 to octa-BDEs and ∑hepta-BDE. An even stronger inverse relation was found between D1 activity and BDE-209 to ∑nona + octa + hepta-BDE concentration ratios. The messenger ribonucleic acid (mRNA) levels of D1 in gull livers were inversely associated with liver concentrations of ∑octa-BDE. The present study's findings suggest that D1 is potentially involved in BDE-209 biotransformation and accumulation of higher brominated PBDEs in livers of ring-billed gulls. Environ Toxicol Chem 2016;35:2215-2222. © 2016 SETAC.

Cell changes and differential proteomic analysis during biodegradation of decabromodiphenyl ether (BDE-209) byPseudomonas aeruginosa

“…However, it is still produced and used in large quantities in some parts of the world. 3,4 Due to the widespread use, chemical persistence and bioaccumulation, BDE-209 has been detected as the predominant BDE congener in atmosphere, water, soil, sediment, dust, especially in biota and humans, and its level has been increasing since 1970s. 5 Many toxicological studies have demonstrated that exposure to BDE-209 can lead to neurobehavioral toxicity, thyroid hormone disruption, cancer and reproductive toxicity.…”

Halogen Bonding Interactions of Haloaromatic Endocrine Disruptors and the Potential for Inhibition of Iodothyronine Deiodinases

“…Highly substituted PBDEs that XB to MeSe À with similar strength to THs have been shown to be debrominated by Dio proteins. [80,81] However, PCDDs are substantially weaker, even for the most substituted congeners, and would not be expected to undergo dehalogenation by Dios, nor have these products been observed experimentally.…”

“…The range of XB strengths for polybrominated aromatics overlap with that expected for iodothyronines (ΔE zpe =−21–−33 kcal/mol) with at least one position of several highly substituted polybrominated aromatics similar to that of 3‐T 1 (e. g., Se‐4‐HpBDD (−23.7 kcal/mol), Se‐1‐OBDD (−24.9 kcal/mol), Se‐2‐PBB‐207 (−25.2 kcal/mol), and Se‐1‐PBP (−25.6 kcal/mol)) suggesting the potential for debromination of these molecules. Highly substituted PBDEs that XB to MeSe − with similar strength to THs have been shown to be debrominated by Dio proteins [80,81] . However, PCDDs are substantially weaker, even for the most substituted congeners, and would not be expected to undergo dehalogenation by Dios, nor have these products been observed experimentally.…”

Dietary Intake of Endocrine Disrupting Substances Presents in Environment and Their Impact on Thyroid Function

“…Chemicals alter some TH regulatory proteins. In addition, they disrupt gene expression and secretion, and then transport and degradation, and they affect TH receptors Other studies also confirm that D1 may be involved in the biotransformation of other BDE-209 congeners [ 137 , 138 ].…”