Pendrin mediates uptake of perchlorate in a mammalian in vitro system
Highlights
► This study was designed to determine whether or not pendrin is able to mediate perchlorate uptake. ► A mammalian in vitro system was generated and used to assess perchlorate uptake by pendrin. ► The recombinant cells expressing pendrin accumulate iodide and perchlorate intracellularly. ► We conclude that pendrin might be involved in the uptake of perchlorate.
Introduction
The iodide-containing hormones triiodothyronine (T3) and its precursor thyroxine (T4) are synthesized in the thyroid and are essential for normal development, growth and regulation of several metabolic pathways (Zoeller, 2007). A variety of industrial chemicals reduce circulating levels of thyroid hormone, thus behaving as endocrine disruptors and resulting in adverse health outcomes. Perchlorate is one of these chemicals. It is an inorganic anion (ClO4−) that behaves as endocrine disruptor by blocking iodine uptake into the thyroid. In a cross sectional study of the US population, perchlorate has been associated with decreased serum thyroxine levels in women with low iodine levels (Blount et al., 2006).
Perchlorate derives from both natural and anthropogenic sources and is a widespread, environmentally stable contaminant found in both irrigation and drinking waters and therefore in vegetables such as lettuce, tomatoes and soybeans as well as in dairy milk and breast milk (ATSDR, 2008). Contamination from anthropogenic sources results mostly from its use as an oxidant in solid rocket propellants, fireworks and airbag deployment systems. Because of its environmental stability, it can be found in many regions of the United States.
In humans, the primary concern with regard to perchlorate exposure is the potential of reduction of iodide uptake into the thyroid gland and subsequent decrease of thyroid hormone production. This effect is mediated by the ability of perchlorate to competitively inhibit the sodium-iodide symporter (NIS), which is located at the basolateral membrane of thyroid follicular cells and transports iodide into the cytoplasm (Dohán et al., 2003, Dohán et al., 2007). Indeed, perchlorate is a potent NIS inhibitor and is itself transported into the thyroid. Its potency, when compared to the NIS inhibitors thiocyanate and nitrate, has been estimated to be 15 and 240 times higher, respectively, on a molar concentration basis (Tonacchera et al., 2004). However, in addition to iodide transport by NIS, synthesis of the thyroid hormone requires several additional steps, some of these also involved in iodide transport (Scinicariello et al., 2005).
Pendrin is an iodide transporter expressed at the apical membrane of thyroid follicular cells and mediates efflux of iodide across this membrane (Yoshida et al., 2002). Structurally, it is a glycoprotein composed of 780 amino acids and is encoded by the SLC26A4 gene, which contains 21 exons with an open reading frame of 2343 bp. It consists of 12 transmembrane domains with both amino and carboxy termini located inside the cytosol (Coyle et al., 1996, Sheffield et al., 1996). Once iodide reaches the cell-colloid interface following pendrin-mediated transport, it is oxidized and rapidly organified by incorporation into selected tyrosyl residues of thyroglobulin (Scinicariello et al., 2005). It might be possible that, once inside the thyrocyte following NIS-mediated transport, perchlorate is then transported by pendrin. Therefore, the objective of this study was to ascertain whether or not pendrin is involved in the uptake of perchlorate. To accomplish this objective, the human HeLa cell line was engineered to express recombinant human pendrin by transfection with human SLC26A4 cDNA and cultured in presence of perchlorate and iodide. Intracellular levels of perchlorate and iodide were then measured by ion chromatography tandem mass spectrometry.
Section snippets
Amplification, cloning, and sequence analysis of human pendrin cDNA
Human SLC26A4 cDNA was isolated from the human mammary MCF-7 cell line grown in presence of prolactin, as previously described (Rillema and Hill, 2003). Total RNA was extracted from the cultured cells using the QIAamp RNA Blood MiniKit (Qiagen), and reverse transcribed into cDNA using oligo(dT)17 primers, followed by primer extension with the AMV reverse transcriptase (Roche Diagnostic Systems). PCR amplification of cDNA was performed with Expand High Fidelity polymerase (Roche Diagnostic
Results and discussion
A variety of industrial chemicals interfere with thyroid function and reduce circulating levels of thyroid hormone by acting at different steps of hormone synthesis, release, transport, metabolism and clearance. In many instances, the mechanisms responsible for the interference with the action of thyroid hormones are not well understood. The main function of the thyroid gland is to concentrate iodide (the form of iodine that enters the cell) and make it available for biosynthesis of thyroid
Acknowledgment
The authors thank Dr. Amy Delinsky at CDC for laboratory assistance.
This work was supported in part by the Research Program Enhancement from the Georgia State University Office of Research and Sponsored Programs, and by the Georgia Research Alliance.
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Agency for Toxic Substances and Disease Registry and of the Centers for Disease Control and Prevention.
References (33)
- et al.
The BeWo choriocarcinoma cell line as a model of iodide transport by placenta
Placenta
(2005) - et al.
SLC26 chloride/base exchangers in the kidney in health and disease
Semin. Nephrol.
(2006) - Agency for Toxic Substances and Disease Registry (ATSDR), 2008. Toxicological Profile for Perchlorates. Atlanta, GA:...
- et al.
Expression of Na+/I− symporter and Pendred syndrome genes in trophoblast cells
J. Clin. Endocrinol. Metab.
(2000) - et al.
Urinary perchlorate and thyroid hormone levels in adolescent and adult men and women living in the United States
Environ. Health Perspect.
(2006) - et al.
Perinatal exposure to perchlorate. Thiocyanate, and nitrate in New Jersey mothers and newborns
Environ. Sci. Technol.
(2009) - et al.
Pendred syndrome (goitre and sensorineural hearing loss) maps to chromosome 7 in the region containing the nonsyndromic deafness gene DFNB4
Nat. Genet.
(1996) - et al.
The sodium/iodide symporter (NIS): characterization, regulation and medical significance
Endocr. Rev.
(2003) - et al.
The Na+/I symporter (NIS) mediates electroneutral active transport of the environmental pollutant perchlorate
Proc. Natl Acad. Sci. USA
(2007) - et al.
Expression pattern of the mouse ortholog of the Pendred’s syndrome gene (Pds) suggests a key role for pendrin in the inner ear
Proc. Natl. Acad. Sci. USA.
(1999)
Fetal thyroid function: diagnosis and management of fetal thyroid disorders
Clin. Obstet. Gynecol.
Perchlorate and iodide in dairy and breast milk
Environ. Sci. Technol.
Temporal patterns in perchlorate, thiocyanate, and iodide excretion in human milk
Environ. Health Perspect.
The SLC26 gene family of multifunctional anion exchangers
Pflugers Arch.
Breast milk iodine and perchlorate concentrations in lactating Boston-area women
J. Clin. Endocrinol. Metab.
Cited by (11)
Evaluation of perchlorate removal from aqueous solution by cross-linked magnetic chitosan/poly (vinyl alcohol) particles
2016, Journal of the Taiwan Institute of Chemical EngineersCitation Excerpt :Perchlorate is an inorganic endocrine disruptor because it is a potent competitive inhibitor of sodium-iodide symporter on the basolateral membrane of thyroid cells [6]. It can interfere with natural iodine uptake by the thyroid gland, inhibit thyroid hormone production, disturb normal metabolism, and subsequently lead to a series of diseases [7]. Because of its harm to human health, the United States Environmental Protection Agency set an Interim Drinking Water Health Advisory level of 15 µg/L in 2008, and some states in the United States have established lower action levels [8].
Spatial distribution of perchlorate, iodide and thiocyanate in the aquatic environment of Tianjin, China: Environmental source analysis
2014, ChemosphereCitation Excerpt :Perchlorate (ClO4−) is an extremely water soluble and environmentally stable anion. Perchlorate has been used as an oxidizer in solid propellants, rockets, missiles, fireworks, and some munitions (Attanasio et al., 2011). Since the 1950s, the total production of perchlorate over 4 × 108 kg in the U.S. has been estimated (Dasgupta et al., 2006).
Removal of perchlorate from aqueous solution by cross-linked Fe(III)-chitosan complex
2014, Journal of Environmental Sciences (China)Seasonal variation and factors influencing perchlorate in water, snow, soil and corns in Northeastern China
2013, ChemosphereCitation Excerpt :Perchlorate and its salts are widely used in rocket fuels, propellants, explosives and some consumer products (Attanasio et al., 2011).
Montmorillonite modified with hexadecylpyridinium chloride as highly efficient anion exchanger for perchlorate ion
2012, Chemical Engineering JournalCitation Excerpt :The perchlorate ion is similar in size to an iodide ion, and can therefore be taken up in place of iodide ions by the mammalian thyroid gland. In this way, perchlorate ions can disrupt the production of thyroid hormones, and can therefore disrupt metabolism [3,7]. Several processes have been reported for removal of perchlorate ion in water: ion exchange [8–14], biological treatment [15], adsorption by activated carbon [16] or carbon tailored with cationic surfactants [17–19], and chemical and electrochemical processes [20–24].
Efficiency of magnetic chitosan supported on graphene for removal of perchlorate ions from wastewater
2021, Environmental Technology (United Kingdom)