Recombinant Transthyretin Purification and Competitive Binding with Organohalogen Compounds in Two Gull Species (Larus argentatus and Larus hyperboreus)

National Wildlife Research Centre, Carleton University, Ottawa, Ontario, K1A 0H3, Canada.
Toxicological Sciences (Impact Factor: 3.85). 12/2008; 107(2):440-50. DOI: 10.1093/toxsci/kfn240
Source: PubMed

ABSTRACT

Glaucous gulls (Larus hyperboreus) from Svalbard, Norway (marine), and herring gulls (Larus argentatus) from the Laurentian Great Lakes (freshwater) of North America are differentially exposed to persistent and bioaccumulative anthropogenic contaminants, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ether (PBDE) flame retardants and metabolic products. Such compounds can potentially perturb hormone transport via binding interactions with proteins such as transthyretin (TTR, prealbumin). In this present study, we isolated, cloned and sequenced TTR cDNA from the brain and liver of two species (herring and glaucous gull), which, to our knowledge, is the first report describing the TTR nucleic acid and amino acid sequences from any gull species. Identical TTR nucleotide and amino acid sequences were obtained from both gull species (liver and brain). Recombinant TTR (rTTR) was expressed and purified, and determined as a monomer of 18 kDa and homodimer of 36 kDa that putatively is comprised of the two protein monomers. Concentration dependent, competitive TTR-binding curves with each of the natural TTR ligands 3,5,3'-triiodothyronine (T(3)) and thyroxine (T(4)) were generated as well as by treatment with a range of concentrations (10(-3)-10(5)nM) of 2,2',3,4',5,5',6-heptaCB (CB187), 2,2',4,4'-tetrabromoDE (BDE47), and hydroxyl- (OH) and methoxyl (MeO)-containing analogs (i.e., 4-OH-CB187, 6-OH-BDE47, 4'-OH-BDE49, 4-MeO-CB187, and 6-MeO-BDE47). Relative to the nonsubstituted BDE47 and CB187 and their MeO-substituted analogs, the OH-substituted analogs all had lower K(i) and K(d) values, indicating greater affinity and more potent competitive binding to both T(3) and T(4). The OH-substitution position and/or the diphenyl ether substitution of the four bromine atoms resulted in more potent, greater affinity, and greater relative potency for 4'-OH-BDE49 relative to 6-OH-BDE47. CB187 was more comparable in binding potency and affinity to 4-OH-CB187, then was 6-OH-BDE47 and 4'-OH-BDE49 relative to BDE47 where the binding potency and affinity was several orders of magnitude greater for 6-OH-BDE47 and 4'-OH-BDE49. This indicated that the combination of the more thyroid hormone-like brominated diphenyl ether backbone (relative to the chlorinated biphenyl backbone), and in combination of having an OH-group, results in a more effective competitive ligand on gull TTR relative to both T(3) and T(4). Known circulating levels of 4-OH-CB187, 6-OH-BDE47, and 4'-OH-BDE49 in the plasma of free-ranging Svalbard glaucous gulls were comparable to the concentration of in vitro competitive potency of T(3) and T(4) with gull TTR. These results suggest that environmentally relevant and selected OH-containing PCB, and to a lesser extent PBDE congeners have the potential to be physiologically effective in these gull species via perturbation of T(4) and T(3) transport.

Download full-text

Full-text

Available from: Geir Wing Gabrielsen
  • Source
    • "Some xenobiotics can compete with the T4 carrier proteins in the plasma (TTR proteins) and bind with them. As a result they stop the T4 from binding to such proteins and prevent their transport in the plasma (Purkey et al., 2004; Ucán-Marín et al., 2009). Binding the BaP with the TTR proteins during acute stress can induce changes in the T4 levels, consequently changing the T3 levels with prolonged stress. "

    Full-text · Article · Jan 2016
  • Source
    • "In vitro studies suggested that in humans, meta-and para-OH-substituted PBDEs have relative binding potencies toward transthyretin (TTR) 160–1600 times higher than BDE-47 itself (Hamers et al., 2008). It has also been reported that OH-PBDEs have greater affinity and more potent competitive binding to gull TTR compared to the natural ligands (Ucán-Marín et al., 2009). Studies have shown that some ortho-substituted OH-PBDEs and MeO-PBDEs (6-OH-BDE-47, 6- OH-BDE-99, 6-MeO-BDE-47) have an inhibitory effect on aromatase (CYP19) activity at low micromolar concentrations in the H295R human adrenocortical carcinoma cells, and 6-OH-BDE47 also causes a statistically significant increase in cytotoxicity at concentrations >2.5 lM (Song et al., 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The structural analogues of polybrominated diphenyl ethers (PBDEs), hydroxylated PBDEs (OH-PBDEs) and methoxylated PBDEs (MeO-PBDEs) have been attracting increasing concern in recent years. Five bivalve species (blue mussel, short-necked clam, surf clam, ark shell and razor clam) were collected from Beijing markets, and the concentrations of seven PBDEs, four OH-PBDEs and fourteen MeO-PBDEs in the bivalves were measured. The seasonal variations of these three types of polybrominated compound in blue mussels were also monitored. The results indicate that the levels of ΣPBDEs in this study were comparable to those in short-necked clams from Liaodong Bay, China, with BDE47 as the dominant congener. For the ortho-MeO-PBDEs, 6-MeO-BDE47 was found at higher concentrations than the others, while for the meta- and para-MeO-PBDEs, 4'-MeO-BDE17 was found at higher concentrations. 6-OH-BDE-47 was the most abundant congener among the 4 measured OH-PBDEs, followed by 6-OH-BDE-137 and 6-OH-BDE-85. The levels of OH-PBDEs and MeO-PBDEs in bivalves from Beijing markets were much lower than the corresponding compounds in blue mussels from the Baltic Sea. In the blue mussels collected in April, June and September of 2012, apparent seasonal variations were observed for these three types of polybrominated compounds, but the acidic components displayed different trends from the neutral components, with PBDEs and MeO-PBDEs showing the highest concentrations in June, while OH-PBDEs had the lowest concentrations in June. This difference in seasonal variations between the neutral components and the acidic components may be explained by their different sources and transformation/elimination mechanisms.
    Full-text · Article · Mar 2014 · Chemosphere
    • "PBDEs have 209 congers and share the basic chemical structure with polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs). Despite the chemical structure similarity, PBDEs cannot activate AhR, a nuclear receptor of polychlorinated dibenzo-pdioxins (PCDDs) and PCBs, demonstrated by a study with primary hepatocytes and hepatic cell lines (Wahl et al., 2010), and the observed AhR-mediated effects of commercial PBDE mixtures are generally considered to be caused by trace amounts of brominated dioxins and furans (Sanders et al., 2005;Wahl et al., 2008)., PBDEs, particularly OH-PBDEs, can bind thyroid hormone transport proteins and thyroid receptors then disrupt thyroid homeostasis and function (Meerts et al., 2000;Ucan-Marin et al., 2009). Other toxicological effects of PBDEs, such as reproductive and genetic toxicity , have also been studied (vanBoxtel et al., 2008;Kodavanti et al., 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants and are banned around the world as potent environmental contaminants. PBDE-47 is the most concerned PBDE with its environmental prevalence and various toxicity characteristics including neurotoxicity. In this paper, we studied larval zebrafish behavioral alterations caused by PBDE-47 neurotoxicity. The light-dark cycle stimulation was used to investigate the locomotor changes of zebrafish larvae at different ages (4-6day post-fertilization, dpf) after PBDE-47 exposure (5, 50, 500μgL(-1)). Three exposure modes, namely continuous exposure, early pulse exposure and interval exposure, were adopted to assess and compare the impacts of exposure modes on larval zebrafish locomotion. Our results showed that locomotor effects upon PBDE exposure depended on the specific exposure mode studied. In the early pulse exposure mode, the locomotion of zebrafish larvae did not change significantly at all PBDE-47 concentrations tested. In contrast, for both the continuous exposure and interval exposure modes, the highest dose of PBDE-47 (500μgL(-1)) elicited pronounced hypoactivity at 5dpf during dark periods except for the initial one. However, at 6dpf, hypoactivity was only observed in the continuously exposed zebrafish larvae (to an even higher degree compared to 5dpf), but not in the interval exposure treatment group. Our results suggested that the conventional, continuous exposure mode might not be enough to evaluate the toxicity of chemicals in the real environments.
    No preview · Article · Sep 2013 · Chemosphere
Show more