Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Exposure to Nickel, Chromium, or Cadmium Causes Distinct Changes in the Gene Expression Patterns of a Rat Liver Derived Cell Line

ABSTRACT: Many heavy metals, including nickel (Ni), cadmium (Cd), and chromium (Cr) are toxic industrial chemicals with an exposure risk in both occupational and environmental settings that may cause harmful outcomes. While these substances are known to produce adverse health effects leading to disease or health problems, the detailed mechanisms remain unclear. To elucidate the processes involved in the of toxicity of nickel, cadmium, and chromium at the molecular level and to perform a comparative analysis, H4-II-E-C3 rat liver-derived cell lines were treated with soluble salts of each metal using concentrations derived from viability assays, and gene expression patterns were determined with DNA microarrays. We identified both common and unique biological responses to exposure to the three metals. Nickel, cadmium, chromium all induced oxidative stress with both similar and unique genes and pathways responding to this stress. Although all three metals are known to be genotoxic, evidence for DNA damage in our study only exists in response to chromium. Nickel induced a hypoxic response as well as inducing genes involved in chromatin structure, perhaps by replacing iron in key proteins. Cadmium distinctly perturbed genes related to endoplasmic reticulum stress and invoked the unfolded protein response leading to apoptosis. With these studies, we have completed the first gene expression comparative analysis of nickel, cadmium, and chromium in H4-II-E-C3 cells. H4-II-E-C3 cells were were exposed to nickel (II) chloride (NiCl2), cadmium chloride (CdCl2), or sodium dichromate (Na2Cr2O7) for 24 hours. The cells were treated with a low, mid, and high concentration of each chemical and shared a control for each biological replicated, and we exposed 4 biologcial replicates for a total of 44 samples.

ORGANISM(S): Rattus norvegicus

SUBMITTER: John Lewis

PROVIDER: E-GEOD-31503 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:A convergence of technological breakthroughs in the past decade has facilitated the development of rapid screening tools for biomarkers of toxicant exposure and effect. Platforms using the whole adult organism to evaluate the genome-wide response to toxicants are especially attractive. Recent work demonstrates the feasibility of this approach in vertebrates using the experimentally robust zebrafish model. In the present study, we evaluated gene expression changes in whole adult zebrafish following an acute 24 hour exposure to three metals with known human health risks. Male adult zebrafish were exposed to nickel chloride, cobalt chloride, and sodium dichromate concentrations corresponding to their respective 96 hr LC20, LC40 and LC60. Histopathology was performed on a subset of metal-exposed zebrafish to phenotypically anchor transcriptional changes associated with each metal. Comparative analysis identified subsets of differentially expressed transcripts both overlapping and unique to each metal. Application of gene ontology (GO) and transcription factor enrichment algorithms revealed a number of key biological processes perturbed by metal exposures and the master transcriptional regulators mediating gene expression changes. Metal exposures differentially activated biological processes associated with ribosome biogenesis, proteosomal degradation and p53 signaling cascades, while repressing oxygen-generating pathways associated with amino acid and lipid metabolism. Despite appreciable effects on gene regulation, nickel exposures did not induce any morphological alterations in zebrafish organs and tissues. Histopathological effects of cobalt remained confined to the olfactory system, while chromium targeted the gills, pharynx and intestinal mucosa. A number of enriched transcription factors mediate the observed gene response to metal exposure, including known targets such as p53, HIF1M-oM-^AM-! and the myc oncogene and novel regulatory factors such as XBP1, GATA6 and HNF3M-oM-^AM-". This work uses an experimentally innovative approach to capture global responses to metal exposures and provides mechanistic insights into metal toxicity mechanisms. Metal induced changes in gene expression in zebrafish were measured after 24 h exposures to each of three metals (nickel, chromium or cobalt). A total of 48 arrays were processed - 16 arrays per metal with 4 replicates for each exposure condition (control, low, mid, and high).

Project description:Cobalt is a transition group metal present in trace amounts in the human diet, but in larger doses it can be acutely toxic or cause adverse health effects in chronic, long term exposures. Its use in many industrial processes and alloys worldwide presents opportunities for occupational exposures, as well as exposures to military personnel. While the toxic effects of cobalt have been widely studied, the exact mechanisms of toxicity remain unclear. In order to further elucidate these mechanisms and identify potential biomarkers of exposure or effect, we exposed two rat liver-derived cell lines, H4-II-E-C3 and MH1C1, to two concentrations of cobalt chloride. We examined changes in gene expression using DNA microarrays in both cell lines and examined changes in cytoplasmic protein abundance in MH1C1 cells using mass spectrometry. We chose to closely examine differentially expressed genes and proteins changing in abundance in both cells lines in order to remove cell line specific effects. We identified enriched pathways, networks, and biological functions using commercial bioinformatic tools and manual annotation. Many of the genes, proteins, and pathways modulated by exposure to cobalt appear to be due to an induction of a hypoxic-like response and oxidative stress. Genes that may be differentially expressed due to a hypoxic-like response are involved in Hif-1Î± signaling, glycolysis, gluconeogenesis, and other energy metabolism related processes. Gene expression changes linked to oxidative stress are also known to be involved in the NRF2-mediated response, protein degradation, and glutathione production. Using microarray and mass spectrometry analysis, we were able to identify modulated genes and proteins, further elucidate the mechanisms of toxicity of cobalt, and identify biomarkers of exposure and effect in vitro, providing targets for focused in vitro studies. H4-II-E-C3 and MH1C1 cells were treated with two doses of CoCl2 for 24 h in serum free DMEM. For each condition, we ran four biological replicates, with each replicate having its own untreated control. Therefore, this study contains 24 samples.

Project description:A convergence of technological breakthroughs in the past decade has facilitated the development of rapid screening tools for biomarkers of toxicant exposure and effect. Platforms using the whole adult organism to evaluate the genome-wide response to toxicants are especially attractive. Recent work demonstrates the feasibility of this approach in vertebrates using the experimentally robust zebrafish model. In the present study, we evaluated gene expression changes in whole adult zebrafish following an acute 24 hour exposure to three metals with known human health risks. Male adult zebrafish were exposed to nickel chloride, cobalt chloride, and sodium dichromate concentrations corresponding to their respective 96 hr LC20, LC40 and LC60. Histopathology was performed on a subset of metal-exposed zebrafish to phenotypically anchor transcriptional changes associated with each metal. Comparative analysis identified subsets of differentially expressed transcripts both overlapping and unique to each metal. Application of gene ontology (GO) and transcription factor enrichment algorithms revealed a number of key biological processes perturbed by metal exposures and the master transcriptional regulators mediating gene expression changes. Metal exposures differentially activated biological processes associated with ribosome biogenesis, proteosomal degradation and p53 signaling cascades, while repressing oxygen-generating pathways associated with amino acid and lipid metabolism. Despite appreciable effects on gene regulation, nickel exposures did not induce any morphological alterations in zebrafish organs and tissues. Histopathological effects of cobalt remained confined to the olfactory system, while chromium targeted the gills, pharynx and intestinal mucosa. A number of enriched transcription factors mediate the observed gene response to metal exposure, including known targets such as p53, HIF1 and the myc oncogene and novel regulatory factors such as XBP1, GATA6 and HNF3. This work uses an experimentally innovative approach to capture global responses to metal exposures and provides mechanistic insights into metal toxicity mechanisms.

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Exposure to Nickel, Chromium, or Cadmium Causes Distinct Changes in the Gene Expression Patterns of a Rat Liver Derived Cell Line

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