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.
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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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-1 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.
Exposure to cobalt causes transcriptomic and proteomic changes in two rat liver derived cell lines.
Cell lineView Samples
Protein synthesis belongs to the most energy consuming processes in the cell. Lowering oxygen tension below normal (hypoxia) causes a rapid inhibition of global mRNA translation due to the decreased availability of energy. Interestingly, subsets of mRNAs pursue active translation under such circumstances. In human fibrosarcoma cells (HT1080) exposed to prolonged hypoxia (36 h, 1% oxygen) we observed that transcripts are either increasingly or decreasingly associated with ribosomes localized at the endoplasmic reticulum (ER). In a global setting it turned out that only 31% of transcripts showing elevated total-RNA levels were also increasingly present at the ER in hypoxia. These genes, regulated by its expression as well as its ER-localization, belong to the gene ontologys hypoxia response, glycolysis and HIF-1 transcription factor network supporting the view of active mRNA translation at the ER during hypoxia. Interestingly, a large group of RNAs was found to be unchanged at the expression level, but translocate to the ER in hypoxia. Among these are transcripts encoding translation factors and >180 ncRNAs. In summary, we provide evidence that protein synthesis is favoured at the ER and, thus, partitioning of the transcriptome between cytoplasmic and ER associated ribosomes mediates adaptation of gene expression in hypoxia.
Hypoxia-induced gene expression results from selective mRNA partitioning to the endoplasmic reticulum.
Specimen part, Cell lineView Samples
Expression profiling of cultured HL-1 cardiomyocytes subjected to hypoxia for 8 hours.
The VLDL receptor promotes lipotoxicity and increases mortality in mice following an acute myocardial infarction.
Cell lineView Samples
We used microarray analysis to investigate if keratinocytes excert an immuno-inflammatory response towards streptococcal M1 protein.
Vigilant keratinocytes trigger pathogen-associated molecular pattern signaling in response to streptococcal M1 protein.
Specimen part, Cell lineView Samples
Predicting liver injury after exposure to toxic industrial chemicals is complicated by the large number of potential environmental contaminants, mixtures, and exposure dose and route scenarios. Identifying indicators of end organ injury can complement exposure-based assays and improve predictive power. A multiplexed approach was used to experimentally evaluate a panel of 67 genes predicted to be fibrogenic by computationally mining DrugMatrix, a publicly available repository of gene microarray data. Five-day oral gavage studies in male Sprague-Dawley rats dosed with varying concentrations of three fibrogenic compounds (allyl alcohol, carbon tetrachloride, and 4,4-methylenedianiline) and two non-fibrogenic compounds (bromobenzene and dexamethasone) were conducted. Fibrosis was definitively diagnosed by histopathology. Transcriptomics data matched the predictions made using the DrugMatrix data with greater than 90% accuracy. Microarray data were verified using a 67-plex panel Bioplex assay, confirming that the 67-plex panel constituted a biomolecular signature of hepatic fibrosis (Figure). Necrosis and inflammatory infiltration were comorbid with fibrosis. Interaction analysis identified 24 genes specific for the fibrosis phenotype. The protein product of the gene most strongly correlated with the fibrosis phenotype (Pcolce) was dose-dependently elevated in plasma from animals administered fibrogenic chemicals (p<0.05). PCOLCE is a novel biomarker candidate of fibrotic injury. These results support the development of gene panels for liver injury and may suggest bridging biomarkers for molecular mediators linked to histopathology.
Gene Expression Patterns Associated With Histopathology in Toxic Liver Fibrosis.
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We used the flu mutant of Arabidopsis and a transgenic line that overexpresses the thylakoid-bound ascorbate peroxidase (tAPX) to address the interactions between different reactive oxygen species (ROS) signaling pathways. The conditional flu mutant of Arabidopsis accumulates excess protochlorophyllide in the dark within chloroplast membranes that upon illumination acts as a photosensitizer and generates singlet oxygen (1O2). Immediately after the release of singlet oxygen rapid changes in nuclear gene expression occur. Distinct sets of genes were activated that were different from those induced by other reactive oxygen species, superoxide or hydrogen peroxide (H2O2), suggesting that different types of active oxygen species activate distinct signaling pathways. It was not known whether the pathways operate separately or interact with each other. We have addressed this problem by modulating noninvasively the level of H2O2 in plastids by means of a transgenic line that overexpresses the thylakoid-bound ascorbate peroxidase (tAPX, line 14/2 PMID: 15165186). In the flu mutant overexpressing tAPX, the expression of most of the nuclear genes that were rapidly activated after the release of 1O2 was significantly higher in flu plants overexpressing tAPX, whereas in wild-type plants, overexpression of tAPX had only a very minor impact on nuclear gene expression. The results suggest that H2O2 antagonizes the 1O2-mediated signaling of stress responses as seen in the flu mutant. This cross-talk between H2O2- and 1O2-dependent signaling pathways might contribute to the overall stability and robustness of wild-type plants exposed to adverse environmental stress conditions.
Cross-talk between singlet oxygen- and hydrogen peroxide-dependent signaling of stress responses in Arabidopsis thaliana.
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Climate change and disease have large negative impacts on poultry production, but little is known about the interactions of responses to these stressors in chickens. Fayoumi (heat and disease resistant) and broiler (heat and disease susceptible) chicken lines were stimulated at 22 days of age, using a 2x2x2 factorial design including: breed (Fayoumi or broiler), inflammatory stimulus [lipopolysaccharide (LPS) or saline], and temperature (35°C or 25°C). Transcriptional changes in spleens were analyzed using RNA-sequencing on the Illumina HiSeq 2500. Thirty-two individual cDNA libraries were sequenced (four per treatment) and an average of 22 million reads were generated per library. Stimulation with LPS induced more differentially expressed genes (DEG, log2 fold change = 2 and FDR = 0.05) in the broiler (N=283) than the Fayoumi (N=85), whereas heat treatment resulted in fewer DEG in broiler (N=22) compared to Fayoumi (N=107). The double stimulus of LPS+heat induced the largest numbers of changes in gene expression, for which broiler had 567 DEG and Fayoumi had 1471 DEG of which 399 were shared between breeds. Further analysis of DEG revealed pathways impacted by these stressors such as Remodelling of Epithelial Adherens Junctions due to heat stress, Granulocyte Adhesion and Diapedesis due to LPS, and Hepatic Fibrosis/Hepatic Stellate Cell Activation due to LPS+heat. The genes and pathways identified provide deeper understanding of the response to the applied stressors and may serve as biomarkers for genetic selection for heat and disease tolerant chickens. Overall design: At 22 days of age, divergent chicken breeds (Fayoumi and broiler) were treated with a thermal treatment (heat stress at 35C, or thermoneutral at 25C as a control) for 3.5 hours, then stimulated subcutaneously with an inflammatory stimulus (LPS, or saline as a control) for another 3.5 hours. Chickens were euthanized and spleens were harvested. A total of 32 indivudally coded cDNA libraries were prepared using TruSeq v2 library preparation kit which selects for polyA mRNA. In this 2x2x2 full factorial design with the factors of breed, thermal treatment, and inflammatory stimulus, there were a total of 8 treatment groups. Each treatment group had a total of 4 animal biological replicates. Therefore, a total of 32 individual barcoded samples were sequenced. A total of 8 individually barcoded cDNA libraries were sequenced per lane using the HiSeq Illumina 2500, and we used 4 lanes total. Reads were mapped to Galgal 2.0.
Unique genetic responses revealed in RNA-seq of the spleen of chickens stimulated with lipopolysaccharide and short-term heat.
Sle1c is a sublocus of the NZM2410-derived Sle1 major susceptibility locus. We have previously shown that Sle1c contributes to lupus pathogenesis by conferring CD4+ T cell-intrinsic hyperactivation and increased susceptibility to chronic graft-versus-host disease (cGVHD) that mapped to the centromeric portion of the locus. In this study, we have refined the centromeric sublocus to a 675Kb interval, termed Sle1c2. Recombinant congenic strains expressing Sle1c2 exhibited a T cell-intrinsic CD4+ T cell hyperactivation and cGVHD susceptibility, similar to mice with the parental Sle1c.
Murine lupus susceptibility locus Sle1c2 mediates CD4+ T cell activation and maps to estrogen-related receptor γ.
Sex, Age, Specimen partView Samples
A biobank collection of carotid plaque samples taken from patients undergoing endarterectomy operations.
Prediction of ischemic events on the basis of transcriptomic and genomic profiling in patients undergoing carotid endarterectomy.
Specimen part, Disease, SubjectView Samples