Project description:Hexavalent chromium (Cr(VI)) is a highly toxic contaminant, some bacteria are able to transform it to less toxic and less soluble trivalent chromium (Cr(III)). Klebsiella sp. strain AqSCr, isolated from Cr(VI)-polluted groundwater, reduces Cr(VI) both aerobically and anaerobically, and resists up 35 mM of Cr(VI); Subculturing of AqSCr in the presence of Cr(VI) conduces to adaptation. In this study, we performed RNA-Seq of Cr(VI) adapted stage, finding 255 genes upregulated and 240 downregulated with respect to controls without Cr(VI). Genes differentially expressed are mostly associated with oxidative stress response, DNA repair and replication, sulfur starvation response, envelope-osmotic stress response, fatty acid metabolism, ribosomal subunits and energy metabolism. Among them, genes not previously associated with chromium resistance as cybB, encoding a putative superoxide oxidase, gltA2, encoding an alternative citrate synthase, and des, encoding a fatty acid desaturase were upregulated. The alternative sigma factors fecl, rpoE and rpoS were upredgulated in Cr(VI) adapted cells, then they participate in orchestate the Cr(VI)-resistance mechanisms in AqSCr strain
Project description:Cr(VI) is a common bioavailable toxic metal that can cause oxidative stress, DNA adducts, and perturb normal gene expression. Changes in gene expression are useful biomarkers of toxicant exposure that provide information about the health of an organism, its ability to adapt to its environment, and indicate potential toxicant-specific effects. Therefore, we developed a toxicology array to the estuarine sentinel species Fundulus heteroclitus, or mummichog. Juvenile mummichog were exposed to potassium dichromate for thirty days at concentrations from 0 to 24 mg/L of Cr(VI), and growth was measured to determine the NOEC (1.5 mg/L or 0.0288 mM) and LOEC (3 mg/L or 0.0577 mM). Body burdens from Cr(VI) exposed fish demonstrated a dose dependent increase and were inversely correlated to body weight. Cr(VI)-exposed juvenile mummichog differentially expressed greater than 20 genes in a dose-dependent manner, including hepatic glucose transporter 2, liver fatty acid binding protein, ATPase synthase 8, type II keratin, TBT binding protein, and complement component C3-2. Many of these genes are involved in energy metabolism or growth, which is consistent with the reduced growth caused by Cr(VI). Keywords: dose response
Project description:Cr(VI) is a common bioavailable toxic metal that can cause oxidative stress, DNA adducts, and perturb normal gene expression. Changes in gene expression are useful biomarkers of toxicant exposure that provide information about the health of an organism, its ability to adapt to its environment, and indicate potential toxicant-specific effects. Therefore, we developed a toxicology array to the estuarine sentinel species Fundulus heteroclitus, or mummichog. Adults males were exposed to Cr(VI) for 7-days at 0, 1.5 (NOEC), or 3 mg/L (LOEC). Livers were excised and RNA isolated. Adults are used in the laboratory experiments so that we can compare laboratory studies to fish caught at chromium-contaminated field sites. Cr(VI) altered the expression of 12 genes in adult liver, including hepatic growth factor activator, heart fatty acid binding protein, and complement component C3-2. Keywords: dose response
Project description:Although the consequences of genotoxic injury include cell cycle arrest and apoptosis, cell survival responses after genotoxic injury can produce intrinsic death-resistance and contribute to the development of a transformed phenotype. Protein tyrosine phosphatases (PTPs) are integral components of key survival pathways, and are responsible for their inactivation, while PTP inhibition is are often associated with enhanced cell proliferation. Our aim was to elucidate signaling events that modulate cell survival after genotoxin exposure. Diploid human lung fibroblasts (HLF) were treated with Cr(VI) (as Na2CrO4), a well known human respiratory carcinogen that induces a wide spectrum of DNA damage, in the presence and absence of a broad-range PTP inhibitor, sodium orthovanadate. Notably, PTP inhibition abrogated Cr(VI)-induced clonogenic lethality. The enhanced survival of Cr(VI)-exposed cells after PTP inhibition was predominantly due to a bypass of cell cycle arrest and was not due to decreased Cr uptake as evidenced by unchanged Cr-DNA adduct burden. Additionally, the bypass of Cr-induced growth arrest by PTP inhibition, was accompanied by a decrease in Cr(VI)-induced expression of cell cycle inhibiting genes, and an increase in the Cr(VI)-induced expression of cell cycle promoting genes. Importantly, PTP inhibition resulted in an increase in forward mutations at the HPRT locus, supporting the hypothesis that PTP inhibition in the presence of DNA damage may lead to genomic instability, via bypass of cell cycle checkpoints.
Project description:Detailed analysis of genome-wide transcriptome profiling in rice root is reported here, following Cr-plant interaction. Such studies are important for the identification of genes responsible for tolerance, accumulation and defense response in plants with respect to Cr stress. Rice root metabolome analysis was also carried out to relate differential transcriptome data to biological processes affected by Cr (VI) stress in rice. The rice variety IR-64 was germinated and allowed to grow for 5 d at 37 C and then transferred to Hewitt solution for growth. After 10 d of growth, seedlings of uniform size and growth were treated with 100 µM of Cr (VI), As (V), Cd, and Pb under standard physiological conditions of 16 h light (115 μmol m−2 s−1) and 8 h dark photoperiod at 25 ± 2 C for 24 h. Total RNA was extracted from the treated rice roots and microarray was performed using one-cycle target labeling and control reagents (Affymetrix platform).
Project description:Detailed analysis of genome-wide transcriptome profiling in rice root is reported here, following Cr-plant interaction. Such studies are important for the identification of genes responsible for tolerance, accumulation and defense response in plants with respect to Cr stress. Rice root metabolome analysis was also carried out to relate differential transcriptome data to biological processes affected by Cr (VI) stress in rice.
Project description:Using ChIP-seq, we characterize the differential binding of CTCF following 48 hours of low-dose, Cr(VI) treatment. Differentially-bound sites are enriched in regions near genes that are actively transcribed in the basal state and strength of initial binding may be a factor in determining the directionality of binding affinity fluctuations. CTCF and cohesin samples were used to predict intra-TAD chromatin loops in an effort to provide an initial characterization of how Cr(VI) potentially disrupts chromatin-chromatin contacts important for the regulation of transcription, serving as a foundation for future studies.
Project description:Living organisms are exposed on a daily basis to widespread mixtures of toxic compounds. Mixtures pose a major problem in the assessment of health effects because they often generate substance-specific effects that cannot be attributed to a single mechanism. Two compounds often found together in the environment are the heavy metal chromium and the polycyclic aromatic hydrocarbon benzo[a]pyrene (B[a]P). We have examined how long-term exposure to a low concentration of Cr(VI) affects the transcriptional response to B[a]P, a second toxicant with an unrelated mechanism of action. Growth of mouse hepatoma cells for 20 passages in medium with 0.1 or 0.5 uM Cr(VI) increases DNA damage and apoptosis and decreases clonogenic ability. These cells also show transcriptome changes indicative of increased expression of DNA damage response and repair genes. In them, B[a]P activates cancer progression pathways, unlike cells never exposed to Cr(VI), where B[a]P activates mostly xenobiotic metabolism pathways. Cells grown in Cr(VI) for 20 passages and then cultured for an additional 5 passages in the absence of Cr(VI) recover from some but not all the chromium effects. They show B[a]P-dependent transcriptome changes strongly weighted towards xenobiotic metabolism, similar to those in B[a]P-treated cells that had no previous Cr(VI) exposure, but retain a high level of Cr(VI)-induced DNA damage and silence the expression of DNA damage and cancer progression genes. We conclude that the combined effect of these two toxicants appears to be neither synergistic nor cumulative, generating a toxic/adaptive condition that cannot be predicted from the effect of each toxicant alone. Mouse Hepa-1 cells treated with Cr, Bap, Cr+Bap and untreated were profiled using RNAseq in duplicates.
Project description:Living organisms are exposed on a daily basis to widespread mixtures of toxic compounds. Mixtures pose a major problem in the assessment of health effects because they often generate substance-specific effects that cannot be attributed to a single mechanism. Two compounds often found together in the environment are the heavy metal chromium and the polycyclic aromatic hydrocarbon benzo[a]pyrene (B[a]P). We have examined how long-term exposure to a low concentration of Cr(VI) affects the transcriptional response to B[a]P, a second toxicant with an unrelated mechanism of action. Growth of mouse hepatoma cells for 20 passages in medium with 0.1 or 0.5 uM Cr(VI) increases DNA damage and apoptosis and decreases clonogenic ability. These cells also show transcriptome changes indicative of increased expression of DNA damage response and repair genes. In them, B[a]P activates cancer progression pathways, unlike cells never exposed to Cr(VI), where B[a]P activates mostly xenobiotic metabolism pathways. Cells grown in Cr(VI) for 20 passages and then cultured for an additional 5 passages in the absence of Cr(VI) recover from some but not all the chromium effects. They show B[a]P-dependent transcriptome changes strongly weighted towards xenobiotic metabolism, similar to those in B[a]P-treated cells that had no previous Cr(VI) exposure, but retain a high level of Cr(VI)-induced DNA damage and silence the expression of DNA damage and cancer progression genes. We conclude that the combined effect of these two toxicants appears to be neither synergistic nor cumulative, generating a toxic/adaptive condition that cannot be predicted from the effect of each toxicant alone.