Metallothionein Transcription Research Articles

Mercury accumulation and biomarkers of exposure in two popular recreational fishes in Hawaiian waters

Mercury (Hg) exposure has not been examined in many recreational nearshore fish species that are commonly consumed around the Hawaiian Islands. Specific gene transcripts, such as metallothionein (MET) and thioredoxin reductase (TrxR), can be used to examine Hg exposure responses in aquatic organisms. This study measured total mercury (THg) in four species from two groups of Hawaiian nearshore fishes: giant trevally (Caranx ignobilis, n = 13), bluefin trevally (C. melampygus, n = 4), sharp jaw bonefish (Albula virgata, n = 2), and round jaw bonefish (A. glossodonta, n = 19). Total Hg accumulation and abundance profiles of MET and TrxR were evaluated for muscle, liver, and kidney tissues. Total Hg in round jaw bonefish and giant trevally tissues accumulated with length and calculated age. In round jaw bonefish tissues, mean THg was greater in kidney (1156 ng/g wet mass (wm)) than liver (339 ng/g wm) and muscle (330 ng/g wm). Giant trevally muscle (187 ng/g wm) and liver (277 ng/g wm) mean THg did not differ significantly. Fish species in this study were compared to commercial and local fish species with state and federal muscle tissue consumption advisories based on THg benchmarks developed by the U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA). Both bonefishes had mean muscle THg that exceeded benchmarks suggesting consumption advisories should be considered. MET transcript in round jaw bonefish kidney tissue and kidney THg exhibited a marginally significant positive correlation, while TrxR transcript in liver tissue negatively correlated with increasing liver THg. These results contribute to our understanding of Hg exposure associated health effects in fish.

Single-Cell Gene Network Analysis and Transcriptional Landscape of MYCN-Amplified Neuroblastoma Cell Lines.

Neuroblastoma (NBL) is a pediatric cancer responsible for more than 15% of cancer deaths in children, with 800 new cases each year in the United States alone. Genomic amplification of the MYC oncogene family member MYCN characterizes a subset of high-risk pediatric neuroblastomas. Several cellular models have been implemented to study this disease over the years. Two of these, SK-N-BE-2-C (BE2C) and Kelly, are amongst the most used worldwide as models of MYCN-Amplified human NBL. Here, we provide a transcriptome-wide quantitative measurement of gene expression and transcriptional network activity in BE2C and Kelly cell lines at an unprecedented single-cell resolution. We obtained 1105 Kelly and 962 BE2C unsynchronized cells, with an average number of mapped reads/cell of roughly 38,000. The single-cell data recapitulate gene expression signatures previously generated from bulk RNA-Seq. We highlight low variance for commonly used housekeeping genes between different cells (ACTB, B2M and GAPDH), while showing higher than expected variance for metallothionein transcripts in Kelly cells. The high number of samples, despite the relatively low read coverage of single cells, allowed for robust pathway enrichment analysis and master regulator analysis (MRA), both of which highlight the more mesenchymal nature of BE2C cells as compared to Kelly cells, and the upregulation of TWIST1 and DNAJC1 transcriptional networks. We further defined master regulators at the single cell level and showed that MYCN is not constantly active or expressed within Kelly and BE2C cells, independently of cell cycle phase. The dataset, alongside a detailed and commented programming protocol to analyze it, is fully shared and reusable.

Utilization of Cratoxylum formosum crude extract for synthesis of ZnO nanosheets: Characterization, biological activities and effects on gene expression of nonmelanoma skin cancer cell

Cratoxylum formosum Dyer is a medicinal plant widely found in Asia and commonly consumed for food and folk medicine. It is rich in phenolic compounds. The present study utilized water crude extract of C. formosum leaves to synthesize zinc oxide nanoparticles (ZnO NPs) by green synthesis. The synthesized ZnO NPs with the average electronic band gap ∼3 eV were obtained and found to either have spherical shape or sheet-like structures depending on synthesis process and concentration of crude extract. Higher concentration of C. formosum extract also eliminates impurity of Zn(OH)2 during the synthesis. Results from an agar disk diffusion assay demonstrated that all synthesized ZnO samples inhibited growth of Gram-positive bacteria, Bacillus subtilis and Staphylococcus epidermidis and Gram-negative bacterium, Escherichia coli. Furthermore, all synthesized ZnO demonstrated potent anti-cancer activity against non-melanoma skin cancer cells (A431) and the intermediary of cancerous keratinocytes (HaCaT) without affecting normal cell lines (Vero). In addition, we observed that the ZnO nanosheet offered stronger cytotoxicity effects against A431 than spherical shaped ZnO particles. Analysis of RNA-sequencing data revealed that synthesized ZnO nanosheets altered the number of genes in pathways involved in cancer and MAPK signaling pathways in A431 cells. Several isoforms of metallothionein transcripts were upregulated including transcripts involved in inflammatory responses whereas transcripts promoted cell proliferation and apoptosis were downregulated. Therefore, these studies firstly reported potential usage of the green-synthesized ZnO nanosheets from C. formosum extract for development of antibacterial substances or anticancer drugs.

Assessment of Suitable Reference Genes for RT-qPCR Normalization with Developmental Samples in Pacific Abalone Haliotis discus hannai

Potential utility of 14 candidate housekeeping genes as normalization reference for RT-qPCR analysis with developmental samples (fertilized eggs to late veliger larvae) in Pacific abalone Haliotis discus hannai was evaluated using four different statistical algorithms (geNorm, NormFinder, BestKeeper and comparative ΔCT method). Different algorithms identified different genes as the best candidates, and geometric mean-based final ranking from the most to the least stable expression was as follow: RPL5, RPL4, RPS18, RPL8, RPL7, UBE2, RPL7A, GAPDH, RPL36, PPIB, EF1A, ACTB and B-TU. The findings were further validated via relative quantification of metallothionein (MT) transcripts using the stable and unstable reference genes, and expression levels of MT were greatly influenced according to the choice of reference genes. In overall, our data suggest that RPL5 and RPS18, either singly or in combination, are appropriate for normalizing gene expression in developmental samples of this abalone species, whereas ACTB, B-TU and EF1A are less stable and not recommended. In addition, our findings propose that standard deviations in geometric ranking as well as geometric mean itself should also be taken into account for the final selection of reference gene(s). This study could be a useful basis to facilitate the generation of accurate and reliable RT-qPCR data with developmental samples in this abalone species.

Environmentally relevant concentrations of arsenite induces developmental toxicity and oxidative responses in the early life stage of zebrafish

Arsenic (As) present in water is a nonignorable environmental issue, even at low concentrations (≤150 μg L−1). To evaluate the toxic effect of low concentrations of As, zebrafish at early life stage were exposed to 0, 25, 50, 75, or 150 μg L−1 AsIII for 120 h. Our results indicated that low concentration of AsIII decreased zebrafish larvae’s survival rate to 85%, 89% and 86% at 50, 75 and 150 μg L−1. Furthermore, low concentrations of AsIII exposure caused oxidative stress (elevated superoxide dismutase (SOD) activity and influenced the mRNA transcriptional levels of Cu/ZnSOD and MnSOD) and damage (increased malondialdehyde levels). Meanwhile, zebrafish larvae regulated the mRNA transcription of metallothionein and heat shock protein 70 to alleviate toxicity caused by AsIII. These results revealed lower concentrations (≤150 μg L−1) of AsIII had a detriment effect on the survival of fish at early life stage, moreover, oxidative stress caused by AsIII posed potential risk for the zebrafish. This study provides novel insight into low concentration AsIII-induced toxicity in zebrafish.

The effect of CTCF binding sites destruction by CRISPR/Cas9 on transcription of metallothionein gene family in liver hepatocellular carcinoma

Chromatin spatial organization is essential for transcriptional modulation and stabilization. The pattern of DNA distal interplay form the multiple topological associating domains (TADs), and further assemble the functional compartmentalization with open and expression-active chromatin ("A" compartments) or closed and expression-inactive chromatin ("B" compartments) in genome, whose boundaries were defined by the high enrichment of CCCTC-binding factor (CTCF). Nevertheless, As a potential therapeutic strategy, changing the local chromatin architecture via adding or removing the CTCF binding sites in situ to regulate the transcription activity of genes within one TAD in cancer cells is poorly explored. In present study, we observed that the metallothionein (MT) family were all remarkably decreased in HCC of TCGA database, and MT genes family were located within a TAD of 1.2 Mb at 16q13 in order, and CTCF binding sites were distributed at the both sites of MT gene clusters. Furthermore, CRISPR/Cas9 was employed to destroy the CTCF binding sites at the vicinity of the MT family in human liver hepatocellular carcinoma (HCC) cell lines Huh-7 and HepG2. And the presence of up-regulated transcription of MTs were observed in Huh-7 and HepG2 cells compared to normal liver CRL-12461 cells. Moreover, the presence of the varying DNA interplay as well as H3K4me3 and H3K9me3 modification on different MT genes were observed after CTCF binding domain destruction compared to the control using chromosome conformation capture (3C) and chromatin immunoprecipitation (ChIP). Our results determined a potential way to regulate the transcription of a series of genes via changing the local genomic organization for diseases treatment.

Stress response of NAD+-dependent formate dehydrogenase in Gossypium hirsutum L. grown under copper toxicity.

Cotton (Gossypium hirsutum L.), which is not directly involved in the food chain, appears to be a suitable candidate to remove heavy metals from the food chain and to be a commercial plant which could be planted in contaminated soils. The key point of this approach is selection of the right genotype, which has heavy metal resistance or hyperaccumulation properties. Therefore, in the present study, two G. hirsutum genotypes, Erşan-92 and N-84S, were grown under copper stress and investigated to obtain further insights about the heavy metal tolerance mechanisms of plants by focusing on the expression of NAD+-dependent formate dehydrogenase (FDH). In accordance with the results, which were obtained from RT-PCR analysis and activity measurements, in the Erşan-92 root tissue, FDH activity increased significantly with increasing metal concentrations and a 6.35-fold higher FDH activity was observed in the presence of 100-μM Cu. As opposed to Erşan-92, the maximum FDH activity in the roots of N-84S, which were untreated with copper as the control plants, was measured as 0.0141-Umg-1g-1 FW, and the activity decreased significantly with the increasing metal concentrations. The metallothionein (GhMT3a) transcript level of the plants grown in a medium containing different Cu concentrations showed nearly the same pattern as that of the FDH gene transcription. It was observed that while the tolerance of N-84S in the lower Cu concentration reduces remarkably, Erşan-92 continues to struggle up to 100-μM Cu. The results of the SOD analysis also confirm this activity of Erşan-92 against the Cu stress.

Metallothionein cDNA Cloning and Metallothionein Expression in Sea Cucumber (Apostichopus japonicus, Slenka) from the WeiHai Coast of China

The aims of this work were (1) the identification of the metallothionein (MT) gene cDNA sequence in Apostichopus japonicus and (2) the quantification of MT mRNA expression in the intestine, body wall and respiratory tree of A. japonicas after exposure to cadmium or zinc. Using RT-PCR and RACE-PCR, we cloned the MT complete cDNA sequence of A. japonicus using the RNA extracted from Cadmium-exposed intestines. The 1351 bp MT cDNA consisted of a 126 bp 5’ untranslated region, a 1069 bp 3’ untranslated region, and a 156 bp open reading frame coding for 51 amino acids, including 16 cysteines. The MT sequence of A. japonicus was 47% identical to the sequence of MT from Strongylocentrotus purpuratus. Through real-time quantitative PCR analysis, we found that the MT expression levels were significantly higher when the specimens were exposed to heavy metals, and the response to combined metal ions exposure occurred earlier than that for single metal ion exposure. Additionally, the induction of MT transcription was more responsive to zinc and can be envisaged as a potential biomarker for zinc contamination.

Toxicity of copper hydroxide nanoparticles, bulk copper hydroxide, and ionic copper to alfalfa plants: A spectroscopic and gene expression study

Bulk Cu compounds such as Cu(OH)2 are extensively used as pesticides in agriculture. Recent investigations suggest that Cu-based nanomaterials can replace bulk materials reducing the environmental impacts of Cu. In this study, stress responses of alfalfa (Medicago sativa L.) seedlings to Cu(OH)2 nanoparticle or compounds were evaluated. Seeds were immersed in suspension/solutions of a Cu(OH)2 nanoform, bulk Cu(OH)2, CuSO4, and Cu(NO3)2 at 25 and 75 mg/L. Six days later, the germination, seedling growth, and the physiological and biochemical responses of sprouts were evaluated. All Cu treatments significantly reduced root elongation (average = 63%). The ionic compounds at 25 and 75 mg/L caused a reduction in all elements analyzed (Ca, K, Mg, P, Zn, and Mn), excepting for S, Fe and Mo. The bulk-Cu(OH)2 treatment reduced K (48%) and P (52%) at 75 mg/L, but increased Zn at 25 (18%) and 75 (21%) mg/L. The nano-Cu(OH)2 reduced K (46%) and P (48%) at 75 mg/L, and also P (37%) at 25 mg/L, compared with control. Confocal microscopy images showed that all Cu compounds, at 75 mg/L, significantly reduced nitric oxide, concurring with the reduction in root growth. Nano Cu(OH)2 at 25 mg/L upregulated the expression of the Cu/Zn superoxide dismutase gene (1.92-fold), while ionic treatments at 75 mg/L upregulated (∼10-fold) metallothionein (MT) transcripts. Results demonstrated that nano and bulk Cu(OH)2 compounds caused less physiological impairments in comparison to the ionic ones in alfalfa seedlings.

Metallothionein I as a direct link between therapeutic hematopoietic stem/progenitor cells and cerebral protection in stroke.

Stroke continues to be a leading cause of death and disability worldwide, yet effective treatments are lacking. Previous studies have indicated that stem-cell transplantation could be an effective treatment. However, little is known about the direct impact of transplanted cells on injured brain tissue. We wanted to help fill this knowledge gap and investigated effects of hematopoietic stem/progenitor cells (HSPCs) on the cerebral microcirculation after ischemia-reperfusion injury (I/RI). Treatment of HSPCs in I/RI for up to 2 wk after cerebral I/RI led to decreased mortality rate, decreased infarct volume, improved functional outcome, reduced microglial activation, and reduced cerebral leukocyte adhesion. Confocal microscopy and fluorescence-activated cell sorting analyses showed transplanted HSPCs emigrate preferentially into ischemic cortex brain parenchyma. We isolated migrated HSPCs from the brain; using RNA sequencing to investigate the transcriptome, we found metallothionein (MT, particularly MT-I) transcripts were dramatically up-regulated. Finally, to confirm the significance of MT, we exogenously administered MT-I after cerebral I/RI and found that it produced neuroprotection in a manner similar to HSPC treatment. These findings provide novel evidence that the mechanism through which HSPCs promote repair after stroke maybe via direct action of HSPC-derived MT-I and could therefore be exploited as a useful therapeutic strategy for stroke.-Smith, H. K., Omura, S., Vital, S. A., Becker, F., Senchenkova, E. Y., Kaur, G., Tsunoda, I., Peirce, S. M., Gavins, F. N. E. Metallothionein I as a direct link between therapeutic hematopoietic stem/progenitor cells and cerebral protection in stroke.

Intermittent hypoxia-induced cardiomyopathy and its prevention by Nrf2 and metallothionein

The mechanism for intermittent hypoxia (IH)-induced cardiomyopathy remains obscure. We reported the prevention of acute and chronic IH-induced cardiac damage by selective cardiac overexpression of metallothionein (MT). Herein we defined that MT-mediated protection from IH-cardiomyopathy is via activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a critical redox-balance controller in the body. For this, mice were exposed to IH for 3 days (acute) or 4 or 8 weeks (chronic). Cardiac Nrf2 and MT expression in response to IH were significantly increased acutely yet decreased chronically. Interestingly, cardiac overexpression (Nrf2-TG) or global deletion of the Nrf2 gene (Nrf2-KO) made mice highly resistant or highly susceptible, respectively, to IH-induced cardiomyopathy and MT expression. Mechanistically, 4-week IH exposure significantly decreased cardiac Nrf2 binding to the MT gene promoter, and thus, depressed both MT transcription and translation in WT mice but not Nrf2-TG mice. Likewise, cardiac MT overexpression prevented chronic IH-induced cardiomyopathy and down-regulation of Nrf2 likely via activation of a PI3K/Akt/GSK-3β/Fyn-dependent signaling pathway. These results reveal an integrated relationship between cardiac Nrf2 and MT expression in response to IH -- acute compensatory up-regulation followed by chronic down-regulation and cardiomyopathy. Cardiac overexpression of either Nrf2 or MT offered cardioprotection from IH via complicated PI3K/Akt/GSK3B/Fyn signaling. Potential therapeutics may target either Nrf2 or MT to prevent chronic IH-induced cardiomyopathy.

Unravelling the Role of Metallothionein on Development, Reproduction and Detoxification in the Wall Lizard Podarcis sicula.

Metallothioneins (MTs) are an evolutionary conserved multigene family of proteins whose role was initially identified in binding essential metals. The physiological role of MT, however, has been revealed to be more complex than expected, since not only are MTs able to bind to toxic heavy metals, but many isoforms have shown specialized and alternative functions. Within this uncertainty, the information available on MTs in non-mammalian vertebrates, particularly in neglected tetrapods such as the reptiles, is even more scant. In this review, we provide a summary of the current understanding on metallothionein presence and function in the oviparous lizard Podarcis sicula, highlighting the results obtained by studying MT gene expression in most representative adult and embryonic tissues. The results demonstrate that in adults, cadmium induces MT transcription in a dose- and tissue-specific manner. Thus, the MT mRNAs appear, at least in some cases, to be an unsuitable tool for detecting environmental ion contamination. In early embryos, maternal RNAs sustain developmental needs for MT protein until organogenesis is well on its way. At this time, transcription starts, but again in a tissue- and organ-specific manner, suggesting an involvement in alternative roles. In conclusion, the spatiotemporal distribution of transcripts in adults and embryos definitively confirms that MT has deserved the title of elusive protein.

Metallothionein expression and synthesis in the testis of the lizard Podarcis sicula under natural conditions and following estrogenic exposure.

Metallothionein (MT) is the main protein involved in the homeostasis of metallic micronutrients and in cellular defence against heavy metals and reactive oxygen species. Found in almost all vertebrate tissues, MT presence and localization in the testis has been controversial. In the present study, by using in situ hybridization and immunohistochemical analysis we assessed the localization of both MT transcript and protein in Podarcis sicula testes during two different phases of the reproductive cycle: the autumnal resumption and the springearly summer mating period. In addition, with the same methodological approach, we verified the effect of estradiol-1711and nonylphenol, a potent xenoestrogen, on MT expression and synthesis. These results, the first collected in a non-mammalian oviparous vertebrate, demonstrated that the expression profile of MT mRNA and protein changes during the reproductive cycle. In the fall resumption, MT transcripts are absent in spermatogonia and present in all the other cells of tubules, including spermatozoa; vice versa, the MT protein is evident only in spermatozoa and somatic cells. In the mating period, both MT transcripts and proteins are present in spermatogonia, spermatocytes and spermatids, whereas in the spermatozoa only the proteins are detected, thus suggesting that the MTs translated in the earlier germinal stages are stored up to spermatozoa. Results also demonstrated that in lizard testis the expression of MT gene undergoes a cell-specific regulation after estrogenic exposure; the possible role and the mechanism by which this regulation occurs have been discussed.

Hepatic transcriptional responses to copper in the three-spined stickleback are affected by their pollution exposure history

Some fish populations inhabiting contaminated environments show evidence of increased chemical tolerance, however the mechanisms contributing to this tolerance, and whether this is heritable, are poorly understood. We investigated the responses of two populations of wild three-spined stickleback (Gasterosteus aculeatus) with different histories of contaminant exposure to an oestrogen and copper, two widespread aquatic pollutants. Male stickleback originating from two sites, the River Aire, with a history of complex pollution discharges, and Siblyback Lake, with a history of metal contamination, were depurated and then exposed to copper (46μg/L) and the synthetic oestrogen ethinyloestradiol (22ng/L). The hepatic transcriptomic response was compared between the two populations and to a reference population with no known history of exposure (Houghton Springs, Dorset). Gene responses included those typical for both copper and oestrogen, with no discernable difference in response to oestrogen between populations. There was, however, some difference in the magnitude of response to copper between populations. Siblyback fish showed an elevated baseline transcription of genes encoding metallothioneins and a lower level of metallothionein induction following copper exposure, compared to those from the River Aire. Similarly, a further experiment with an F1 generation of Siblyback fish bred in the laboratory found evidence for elevated transcription of genes encoding metallothioneins in unexposed fish, together with an altered transcriptional response to 125μg/L copper, compared with F1 fish originating from the clean reference population exposed to the same copper concentration. These data suggest that the stickleback from Siblyback Lake have a differential response to copper, which is inherited by the F1 generation in laboratory conditions, and for which the underlying mechanism may include an elevation of baseline transcription of genes encoding metallothioneins. The genetic and/or epigenetic mechanisms contributing to this inherited alteration of metallothionein transcription have yet to be established.

Analysis of hematologic alterations, immune responses and metallothionein gene expression in Nile tilapia (Oreochromis niloticus) exposed to silver nanoparticles

In this study, Nile tilapia (Oreochromis niloticus) fingerlings were used as a model to examine acute and chronic toxicity of silver nanoparticles (AgNP). Expression levels of metallothionein (MT) transcripts in fish exposed to 0, 1 or 100 mg AgNP/kg fish were investigated by quantitative real-time RT-PCR. The results showed MT expression levels were significantly decreased 0.3–0.7-fold in the liver and spleen of fish exposed to 1 or 100 mg AgNP/kg after 6–48 h. In contrast, during this period, MT mRNA expression levels were increased 2–3-fold in the head kidney of the fish exposed to either level of AgNP. Investigations of effects of AgNP on the fish immune responses and hematological parameters revealed that phagocytic activity, the amount of red blood cells (RBC) and the percent hematocrit (%Hct) in fish exposed to AgNP were decreased significantly 1 week after exposure, especially those exposed to 100 mg AgNP/kg. Fish immunized with Streptococcus agalactiae vaccine and simultaneously exposed to 100 mg AgNP/kg presented decreased antibody titers during the early phase. Lastly, a challenge test showed that vaccinated fish exposed to AgNP, regardless of concentration, remained protected against S. agalactiae infection, with a lower mortality (10–20%) compared to 70% in control fish. These findings indicated that expression patterns of the MT gene in the liver, spleen and head kidney at different timepoints could be used to assess acute and chronic exposure of Nile tilapia to AgNP. Additionally, changes in innate immune responses and hematological parameters in fish may prove useful for evaluation of AgNP toxicity. Data obtained in this study strongly support the use of Nile tilapia as an animal model to potentially serve as a bio-indicator of environment contamination caused by AgNP.

Hypoxia drives apoptosis independently of p53 and metallothionein transcript levels in hemocytes of the whiteleg shrimp Litopenaeus vannamei

The cellular mechanisms used by the shrimp Litopenaeus vannamei to respond to hypoxia have been studied from the energetic metabolism and antioxidant angles. We herein investigated the participation of p53 and metallothionein (MT) in the apoptotic process in response to hypoxia in shrimp hemocytes. The Lvp53 or LvMT genes were efficiently silenced by injection of double stranded RNA for p53 or MT. The effects of silencing on apoptosis were measured as caspase-3 activity and flow cytometry in hemocytes after 24 and 48 h of hypoxia (1.5 mg DO L−1). Hemocytes from unsilenced animals had significantly higher apoptosis levels upon both times of hypoxia. The apoptotic levels were diminished but not suppressed in dsp53-silenced but not dsMT-silenced hemocytes after 24 h of hypoxia, indicating a contribution of Lvp53 to apoptosis. Apoptosis in normoxia was significantly higher in dsp53-and dsMT-silenced animals compared to the unsilenced controls, pointing to a possible cytoprotective role of LvMT and Lvp53 during the basal apoptotic program in normoxia. Overall, these results indicate that hypoxia augments apoptosis in shrimp hemocytes and high mRNA levels of Lvp53 and LvMT are not necessary for this response.

Low-dose oral cadmium increases airway reactivity and lung neuronal gene expression in mice.

Inhalation of cadmium (Cd) is associated with lung diseases, but less is known concerning pulmonary effects of Cd found in the diet. Cd has a decades‐long half‐life in humans and significant bioaccumulation occurs with chronic dietary intake. We exposed mice to low‐dose CdCl2 (10 mg/L in drinking water) for 20 weeks, which increased lung Cd to a level similar to that of nonoccupationally exposed adult humans. Cd‐treated mice had increased airway hyperresponsiveness to methacholine challenge, and gene expression array showed that Cd altered the abundance of 443 mRNA transcripts in mouse lung. In contrast to higher doses, low‐dose Cd did not elicit increased metallothionein transcripts in lung. To identify pathways most affected by Cd, gene set enrichment of transcripts was analyzed. Results showed that major inducible targets of low‐dose Cd were neuronal receptors represented by enriched olfactory, glutamatergic, cholinergic, and serotonergic gene sets. Olfactory receptors regulate chemosensory function and airway hypersensitivity, and these gene sets were the most enriched. Targeted metabolomics analysis showed that Cd treatment also increased metabolites in pathways of glutamatergic (glutamate), serotonergic (tryptophan), cholinergic (choline), and catecholaminergic (tyrosine) receptors in the lung tissue. Protein abundance measurements showed that the glutamate receptor GRIN2A was increased in mouse lung tissue. Together, these results show that in mice, oral low‐dose Cd increased lung Cd to levels comparable to humans, increased airway hyperresponsiveness and disrupted neuronal pathways regulating bronchial tone. Therefore, dietary Cd may promote or worsen airway hyperresponsiveness in multiple lung diseases including asthma.

Arbuscular mycorrhiza affects nickel translocation and expression of ABC transporter and metallothionein genes in Festuca arundinacea

Mycorrhizal fungi are key microorganisms for enhancing phytoremediation of soils contaminated with heavy metals. In this study, the effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae (=Glomus mosseae) on physiological and molecular mechanisms involved in the nickel (Ni) tolerance of tall fescue (Festuca arundinacea = Schedonorus arundinaceus) were investigated. Nickel addition had a pronounced negative effect on tall fescue growth and photosynthetic pigment contents, as well as on AMF colonization. Phosphorus content increased markedly in mycorrhizal plants (M) compared to non-inoculated (NM) ones. However, no significant difference was observed in root carbohydrate content between AMF-inoculated and non-inoculated plants. For both M and NM plants, Ni concentrations in shoots and roots increased according to the addition of the metal into soil, but inoculation with F. mosseae led to significantly lower Ni translocation from roots to the aboveground parts compared to non-inoculated plants. ABC transporter and metallothionein transcripts accumulated to considerably higher levels in tall fescue plants colonized by F. mosseae than in the corresponding non-mycorrhizal plants. These results highlight the importance of mycorrhizal colonization in alleviating Ni-induced stress by reducing Ni transport from roots to shoots of tall fescue plants.

Chromium (VI)-induced transformation is enhanced by Zn deficiency in BALB/c 3T3 cells.

Hexavalent chromium [Cr(VI)] is a carcinogenic heavy metal that is reduced to intermediate oxidation states, such as Cr(V) and Cr(IV), in the process of forming stable Cr(III) forms; it is these intermediate forms that are thought to be responsible for much of the DNA damage and mutations that are induced by Cr(VI). Metallothionein (MT), a heavy metal-binding protein, is induced by zinc and other heavy metals and protects cells from the toxic effects of these metals by sequestering them. MT cannot bind Cr, but by scavenging reactive oxygen species through its cysteine residues, it may act as a protective factor against Cr(VI)-induced DNA lesions by reducing Cr(VI) directly to Cr(III), thereby avoiding the creation of the toxic intermediates. Here, we showed that Zn deficiency decreased MT expression in BALB/3T3 clone A31-1-1 cells and caused them to become highly susceptible to Cr(VI)-induced transformation. To obtain Zn-deficient cultures, cells were cultured in medium supplemented with 10% Chelex(®)-100 chelating resin-treated FBS. The increase in susceptibility to transformation was abolished by culturing the cells with supplemental Zn (50 µM). Previously, we reported that Cr(VI) inhibits MT transcription by preventing the zinc-dependent formation of a complex of metal response element-binding transcription factor-1 (MTF-1) and the co-activator p300. Our results suggest that the carcinogenicity of Cr(VI) is enhanced by MTF-1 dysfunction.

Metallothionein transcripts are dynamic markers for brain disease in lysosomal disorders

Metallothionein transcripts are dynamic markers for brain disease in lysosomal disorders