Effects of Low-Dose Gestational TCDD Exposure on Behavior and on Hippocampal Neuron Morphology and Gene Expression in Mice.

BACKGROUND: 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a persistent and toxic environmental pollutant. Gestational exposure to TCDD has been linked to cognitive and motor deficits, and increased incidence of autism spectrum disorder (ASD) traits in children. Most animal studies of these neurodevelopmental effects involve acute TCDD exposure, which does not model typical exposure in humans. OBJECTIVES: The aim of the study was to establish a dietary low-dose gestational TCDD exposure protocol and performed an initial characterization of the effects on offspring behavior, neurodevelopmental phenotypes, and gene expression. METHODS: Throughout gestation, pregnant C57BL/6J mice were fed a diet containing a low dose of TCDD (9 ng TCDD/kg body weight per day) or a control diet. The offspring were tested in a battery of behavioral tests, and structural brain alterations were investigated by magnetic resonance imaging. The dendritic morphology of pyramidal neurons in the hippocampal Cornu Ammonis (CA)1 area was analyzed. RNA sequencing was performed on hippocampi of postnatal day 14 TCDD-exposed and control offspring. RESULTS: TCDD-exposed females displayed subtle deficits in motor coordination and reversal learning. Volumetric difference between diet groups were observed in regions of the hippocampal formation, mammillary bodies, and cerebellum, alongside higher dendritic arborization of pyramidal neurons in the hippocampal CA1 region of TCDD-exposed females. RNA-seq analysis identified 405 differentially expressed genes in the hippocampus, enriched for genes with functions in regulation of microtubules, axon guidance, extracellular matrix, and genes regulated by SMAD3. DISCUSSION: Exposure to 9 ng TCDD/kg body weight per day throughout gestation was sufficient to cause specific behavioral and structural brain phenotypes in offspring. Our data suggest that alterations in SMAD3-regulated microtubule polymerization in the developing postnatal hippocampus may lead to an abnormal morphology of neuronal dendrites that persists into adulthood. These findings show that environmental low-dose gestational exposure to TCDD can have significant, long-term impacts on brain development and function. https://doi.org/10.1289/EHP7352

Effects of low-dose gestational tcdd exposure on behavior and on hippocampal neuron morphology and gene expression in mice

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a persistent and toxic environmental pollutant. Gestational exposure to TCDD has been linked to cognitive and motor deficits, and increased incidence of autism spectrum disorder (ASD) traits in children. Most animal studies of these neurodevelopmental effects involve acute TCDD exposure, which does not model typical exposure in humans.publishedVersio

Scientific Opinion on the safety and efficacy of Urea for ruminants

Urea supplementation to feed for ruminants provides non-protein nitrogen for microbial protein synthesis in the rumen and thus in part replaces other dietary protein sources. Urea supplementation of feed for ruminants at doses up to 1 % of complete feed DM (corresponding to 0.3 g/kg bw/day) is considered safe when given to animals with a well adapted ruminal microbiota and fed diets rich in easily digestible carbohydrates. Based on the metabolic fate of urea in ruminants, the use of urea in ruminant nutrition does not raise any concern for consumers\u2019 safety. Urea is considered to be non irritant to skin and eyes and its topical use suggests that it is not a dermal sensitiser. The risk of exposure by inhalation would be low. The substitution of protein by urea in well balanced feed for ruminants would not result in an increased environmental nitrogen load. Urea is an effective source of non-protein nitrogen substituting for dietary protein in ruminants

The ZIP6/ZIP10 heteromer is essential for the zinc-mediated trigger of mitosis

Zinc has been known to be essential for cell division for over 40 years but the molecular pathways involved remain elusive. Cellular zinc import across biological membranes necessitates the help of zinc transporters such as the SLC39A family of ZIP transporters. We have discovered a molecular process that explains why zinc is required for cell division, involving two highly regulated zinc transporters, as a heteromer of ZIP6 and ZIP10, providing the means of cellular zinc entry at a specific time of the cell cycle that initiates a pathway resulting in the onset of mitosis. Crucially, when the zinc influx across this heteromer is blocked by ZIP6 or ZIP10 specific antibodies, there is no evidence of mitosis, confirming the requirement for zinc influx as a trigger of mitosis. The zinc that influxes into cells to trigger mitosis additionally changes the phosphorylation state of STAT3 converting it from a transcription factor to a protein that complexes with this heteromer and pS38Stathmin, the form allowing microtubule rearrangement as required in mitosis. This discovery now explains the specific cellular role of ZIP6 and ZIP10 and how they have special importance in the mitosis process compared to other ZIP transporter family members. This finding offers new therapeutic opportunities for inhibition of cell division in the many proliferative diseases that exist, such as cancer

Differential Subcellular Localization of the Splice Variants of the Zinc Transporter ZnT5 Is Dictated by the Different C-Terminal Regions

Zinc is emerging as an important intracellular signaling molecule, as well as fulfilling essential structural and catalytic functions through incorporation in a myriad of zinc metalloproteins so it is important to elucidate the molecular mechanisms of zinc homeostasis, including the subcellular localizations of zinc transporters.Two splice variants of the human SLC30A5 Zn transporter gene (ZnT5) have been reported in the literature. These variants differ at their N- and C-terminal regions, corresponding with the use of different 5' and 3' exons. We demonstrate that full length human ZnT5 variant B is a genuine transcript in human intestinal cells and confirm expression of both variant A and variant B in a range of untreated human tissues by splice variant-specific RT-PCR. Using N- or C-terminal GFP or FLAG fusions of both isoforms of ZnT5 we identify that the differential subcellular localization to the Golgi apparatus and ER respectively is a function of their alternative C-terminal sequences. These different C-terminal regions result from the incorporation into the mature transcript of either the whole of exon 14 (variant B) or only the 5' region of exon 14 plus exons 15-17 (variant A).We thus propose that exons 15 to 17 include a signal that results in trafficking of ZnT5 to the Golgi apparatus and that the 3' end of exon 14 includes a signal that leads to retention in the ER

Cerebral gene expression in response to single or combined gestational exposure to methylmercury and selenium through the maternal diet

Controversy remains regarding the safety of consuming certain types of seafood, particularly during pregnancy. While seafood is rich in vital nutrients, it may also be an important source of environmental contaminants such as methylmercury (MeHg). Selenium (Se) is one essential element present in seafood, hypothesised to ameliorate MeHg toxicity. The aim of the present study was to ascertain the impact of Se on MeHg-induced cerebral gene expression in a mammalian model. Microarray analysis was performed on brain tissue from 15-day-old mice that had been exposed to MeHg throughout development via the maternal diet. The results from the microarray analysis were validated using qPCR. The exposure groups included: MeHg alone (2.6 mg kg−1), Se alone (1.3 mg kg−1), and MeHg + Se. MeHg was presented in a cysteinate form, and Se as Se–methionine, one of the elemental species occurring naturally in seafood. Eight genes responded to Se exposure alone, five were specific to MeHg, and 63 were regulated under the concurrent exposure of MeHg and Se. Significantly enriched functional classes relating to the immune system and cell adhesion were identified, highlighting potential ameliorating mechanisms of Se on MeHg toxicity. Key developmental genes, such as Wnt3 and Sparcl1, were also identified as putative ameliorative targets. This study, utilising environmentally realistic forms of toxicants, delivered through the natural route of exposure, in association with the power of transcriptomics, highlights significant novel information regarding putative pathways of selenium and MeHg interaction in the mammalian brain

Zinc uptake promotes myoblast differentiation via Zip7 transporter and activation of Akt signalling transduction pathway

[EN] Myogenic regeneration occurs through a chain of events beginning with the output of satellite cells from quiescent state, formation of competent myoblasts and later fusion and differentiation into myofibres. Traditionally, growth factors are used to stimulate muscle regeneration but this involves serious off-target effects, including alterations in cell homeostasis and cancer. In this work, we have studied the use of zinc to trigger myogenic differentiation. We show that zinc promotes myoblast proliferation, differentiation and maturation of myofibres. We demonstrate that this process occurs through the PI3K/Akt pathway, via zinc stimulation of transporter Zip7. Depletion of zinc transporter Zip7 by RNA interference shows reduction of both PI3K/Akt signalling and a significant reduction of multinucleated myofibres and myotubes development. Moreover, we show that mature myofibres, obtained through stimulation with high concentrations of zinc, accumulate zinc and so we hypothesise their function as zinc reservoirs into the cell.P.R. and R.S. acknowledges support from the Spanish Ministry of Economy and Competitiveness (MINECO) (MAT2015-69315-C3-1-R). P.R. acknowledges the Fondo Europeo de Desarrollo Regional (FEDER). CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. R.S. acknowledges the support from the Spanish MECD through the PRX16/00208 grant. MSS acknowledges support from the European Research Council (ERC - HealInSynergy 306990) and the UK Engineering and Physical Sciences Research Council (EPSRC - EP/P001114/1)Mnatsakanyan, H.; Sabater I Serra, R.; Rico Tortosa, PM.; Salmerón Sánchez, M. (2018). 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Molecular mechanisms of toxicity of silver nanoparticles in zebrafish embryos.

addresses: Biosciences, College of Life and Environmental Sciences, Geoffrey Pope Building, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK. [email protected]: Journal Article; Research Support, Non-U.S. Gov'tThis is an open access article that is freely available in ORE or from the publisher's web site. http://pubs.acs.org/doi/abs/10.1021/es401758d. Please cite the published version© 2013 American Chemical SocietySupporting Information: Further details on the methodology and results for the characterization of the silver particles used for the exposures, mortality curves, sequencing analysis, and a number of supporting figures and tables. This material is available free of charge via the Internet at http://pubs.acs.org.Silver nanoparticles cause toxicity in exposed organisms and are an environmental health concern. The mechanisms of silver nanoparticle toxicity, however, remain unclear. We examined the effects of exposure to silver in nano-, bulk-, and ionic forms on zebrafish embryos (Danio rerio) using a Next Generation Sequencing approach in an Illumina platform (High-Throughput SuperSAGE). Significant alterations in gene expression were found for all treatments and many of the gene pathways affected, most notably those associated with oxidative phosphorylation and protein synthesis, overlapped strongly between the three treatments indicating similar mechanisms of toxicity for the three forms of silver studied. Changes in oxidative phosphorylation indicated a down-regulation of this pathway at 24 h of exposure, but with a recovery at 48 h. This finding was consistent with a dose-dependent decrease in oxygen consumption at 24 h, but not at 48 h, following exposure to silver ions. Overall, our data provide support for the hypothesis that the toxicity caused by silver nanoparticles is principally associated with bioavailable silver ions in exposed zebrafish embryos. These findings are important in the evaluation of the risk that silver particles may pose to exposed vertebrate organisms.Natural Environment Research Council (NERC)NERC Biomolecular Analysis FacilityUK Environment AgencySystems Biology Seed fund, University of Exete

The Zinc Transporter SLC39A14/ZIP14 Controls G-Protein Coupled Receptor-Mediated Signaling Required for Systemic Growth

Aberrant zinc (Zn) homeostasis is associated with abnormal control of mammalian growth, although the molecular mechanisms of Zn's roles in regulating systemic growth remain to be clarified. Here we report that the cell membrane-localized Zn transporter SLC39A14 controls G-protein coupled receptor (GPCR)-mediated signaling. Mice lacking Slc39a14 (Slc39a14-KO mice) exhibit growth retardation and impaired gluconeogenesis, which are attributable to disrupted GPCR signaling in the growth plate, pituitary gland, and liver. The decreased signaling is a consequence of the reduced basal level of cyclic adenosine monophosphate (cAMP) caused by increased phosphodiesterase (PDE) activity in Slc39a14-KO cells. We conclude that SLC39A14 facilitates GPCR-mediated cAMP-CREB signaling by suppressing the basal PDE activity, and that this is one mechanism for Zn's involvement in systemic growth processes. Our data highlight SLC39A14 as an important novel player in GPCR-mediated signaling. In addition, the Slc39a14-KO mice may be useful for studying the GPCR-associated regulation of mammalian systemic growth