Cross-species Comparisons of Transcriptomic Alterations in Human and Rat Primary Hepatocytes Exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin

The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709, USA.
Toxicological Sciences (Impact Factor: 3.85). 02/2012; 127(1):199-215. DOI: 10.1093/toxsci/kfs069
Source: PubMed


A toxicogenomics approach was used to qualitatively and quantitatively compare the gene expression changes in human and rat primary hepatocytes exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Hepatocytes from five individual rats and five individual humans were exposed for 24 h to 11 concentrations of TCDD ranging from 0.00001 to 100nM and a vehicle control. Gene expression changes were analyzed using whole-genome microarrays containing 13,002 orthologs. Significant changes in expression of individual orthologs at any concentration (fold change [FC] ± 1.5 and false discovery rate < 0.05) were higher in the rat (1547) compared with human hepatocytes (475). Only 158 differentially expressed orthologs were common between rats and humans. Enrichment analysis was performed on the differentially expressed orthologs in each species with 49 and 34 enriched human and rat pathways, respectively. Only 12 enriched pathways were shared between the two species. The results demonstrate significant cross-species differences in expression at both the gene and pathway level. Benchmark dose analysis of gene expression changes showed an average 18-fold cross-species difference in potency among differentially expressed orthologs with the rat more sensitive than the human. Similar cross-species differences in potency were observed for signaling pathways. Using the maximum FC in gene expression as a measure of efficacy, the human hepatocytes showed on average a 20% lower efficacy among the individual orthologs showing differential expression. The results provide evidence for divergent cross-species gene expression changes in response to TCDD and are consistent with epidemiological and clinical evidence showing humans to be less sensitive to TCDD-induced hepatotoxicity.

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Available from: Michael B Black, Oct 05, 2015
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    • "or an imbalance between mitochondrial and nuclear - encoded proteins , as shown in mouse hepatocytes treated with doxycycline ( Houtkooper et al . , 2013 ) or in mtDNA depleted ( rho 0 ) rat hepatoma cells ( Martinus et al . , 1996 ) . Even if it is known that sensitivity and response to drugs might differ between rodent and human hepato - cytes ( Black et al . , 2012 ; Kotokorpi et al . , 2007 ; Seok et al . , 2013 ) , in our hands , similar stresses increase neither HSPD1 nor ClpP expression despite testing four different models , of which one in three cancer cell lines as well as in primary human hepatocytes ( Figs . 2A , B , C , D , S1C , S2B ) . However , in the later case , the non - induction "
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    ABSTRACT: Mitochondria-to-nucleus communication, known as retrograde signaling, is important to adjust the nuclear gene expression in response to organelle dysfunction. Among the transcription factors described to respond to mitochondrial stress, CHOP-10 is activated by respiratory chain inhibition, mitochondrial accumulation of unfolded proteins and mtDNA mutations. In this study, we show that altered/impaired expression of mtDNA induces CHOP-10 expression in a signaling pathway that depends on the eIF2α/ATF4 axis of the integrated stress response rather than on the mitochondrial unfolded protein response.
    Mitochondrion 01/2015; 21. DOI:10.1016/j.mito.2015.01.005 · 3.25 Impact Factor
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    • "An underlying assumption is that PCDD/F congeners act through similar modes of action (MOAs), but differ in overall potency. Although there has been a wealth of data published on specific AHR-mediated events (eg, CYP1A1 transcription and activity), only recently data have been published on the relative effects of PCDD/F congeners on the transcriptome (Black et al., 2012; Boverhof et al., 2006; Carlson et al., 2009; Kopec et al., 2010; Rowlands et al., 2011). The most common genes examined for PCDD/F transcriptional effects are related to well-conserved enzyme induction for xenobiotic metabolism , such as CYP1A1 and CYP1A2 genes. "
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    ABSTRACT: Toxic equivalency factors (TEFs) for dioxin-like compounds (DLCs) are largely based on relative potency (REP) values derived from biochemical endpoints such as enzyme activity. As of yet, REPs based on gene expression changes have not been accounted for in the TEF values. In this study, primary rat hepatocytes were treated for 24 hours with 11 concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF), or 2,3,7,8-tetrachlorodibenzofuran (TCDF) ranging from 0.00001-100 nM. Differential changes in gene expression were analyzed using analysis of variance to assess the relative contributions of concentration, congener, and the interaction between concentration and congener for each gene. A total of 3,283 genes showed significant changes with concentration (FDR < 0.05 and fold-change ± 1.5 in at least one concentration for one congener). Among these genes, 399 were significant for both concentration and congener effects indicating parallel concentration response curves with significant differences in potency. Only eight genes showed a significant concentration and congener interaction term indicating a minority of genes show non-parallel dose response curves among the three congeners. Benchmark dose (BMD) modeling was used to derive BMD values for induced individual genes and signaling pathways. The REP values for 4-PeCDF and TCDF were generally three- to five-fold lower than the WHO TEF values on both a gene and pathway basis. These findings suggest that the WHO TEF values may possibly over-predict the potency of these PCDD/F congeners, and demonstrate the importance of identifying functional pathways relevant to the toxicological MOA for establishing pertinent REPs.
    Toxicological Sciences 12/2013; 136(2):595-604. DOI:10.1093/toxsci/kft203 · 3.85 Impact Factor
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    • "Since 1980s, it has been increasingly documented that dioxin-like compounds cause various biological effects in laboratory animals and human [2], [3]. Among them, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent toxicant and it is produced from both natural and anthropogenic processes including incineration of chlorine-containing substances, bleaching of paper, manufacturing of specific organochlorine chemicals, volcanoes, and forest fires [4]. As an aromatic hydrocarbon, TCDD has a long biological half-life and is heavily accumulated in the food chain, which causes adverse effects on human health at environmental levels [4], [5]. "
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    ABSTRACT: TCDD is one of the most persistent environmental toxicants in biological systems and its effect through aryl hydrocarbon receptor (AhR) has been well characterized. However, the information on TCDD-induced toxicity in other molecular pathways is rather limited. To fully understand molecular toxicity of TCDD in an in vivo animal model, adult zebrafish were exposed to TCDD at 10 nM for 96 h and the livers were sampled for RNA-sequencing based transcriptomic profiling. A total of 1,058 differently expressed genes were identified based on fold-change>2 and TPM (transcripts per million) >10. Among the top 20 up-regulated genes, 10 novel responsive genes were identified and verified by RT-qPCR analysis on independent samples. Transcriptomic analysis indicated several deregulated pathways associated with cell cycle, endocrine disruptors, signal transduction and immune systems. Comparative analyses of TCDD-induced transcriptomic changes between fish and mammalian models revealed that proteomic pathway is consistently up-regulated while calcium signaling pathway and several immune-related pathways are generally down-regulated. Finally, our study also suggested that zebrafish model showed greater similarity to in vivo mammalian models than in vitro models. Our study indicated that the zebrafish is a valuable in vivo model in toxicogenomic analyses for understanding molecular toxicity of environmental toxicants relevant to human health. The expression profiles associated with TCDD could be useful for monitoring environmental dioxin and dioxin-like contamination.
    PLoS ONE 10/2013; 8(10):e77292. DOI:10.1371/journal.pone.0077292 · 3.23 Impact Factor
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