Comparative Analysis of Temporal and Dose-Dependent TCDD-Elicited Gene Expression in Human, Mouse, and Rat Primary Hepatocytes

Abstract

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)-elicited time- and dose-dependent differential gene expression was compared in human, mouse, and rat primary hepatocytes. Comprehensive time course (10 nM TCDD or dimethyl sulfoxide vehicle control for 1, 2, 4, 8, 12, 24, and 48h) studies identified 495, 2305, and 711 differentially expressed orthologous genes in human, mouse, and rat hepatocytes, respectively. However, only 16 orthologs were differentially expressed across all three species, with the majority of orthologs exhibiting species-specific expression (399 human, 2097 mouse, and 533 rat), consistent with species-specific expression reported in other in vitro and in vivo comparative studies. TCDD also elicited the dose-dependent induction of 397 human, 100 mouse, and 443 rat genes at 12h and 615 human, 426 mouse, and 314 rat genes at 24h. Comparable EC50 values were obtained for AhR battery genes including Cyp1a1 (0.1 nM human, 0.05 nM mouse, 0.08 nM rat at 24h) and Tiparp (0.97 nM human, 0.63 nM mouse, 0.14 nM rat at 12h). Overrepresented functions and pathways included amino acid metabolism in humans, immune response in mice, and energy homeostasis in rats. Differentially expressed genes functionally associated with lipid transport, processing, and metabolism were overrepresented in all three species but exhibited species-specific expression consistent with the induction of hepatic steatosis in mice but not in rats following a single oral gavage of TCDD. Furthermore, human primary hepatocytes showed lipid accumulation following 48h of treatment with TCDD, suggesting that AhR-mediated steatosis in mice more closely resembles human hepatic fat accumulation compared with that in rats. Collectively, these results suggest that species-specific gene expression profiles mediate the species-specific effects of TCDD despite the conservation of the AhR and its signaling mechanism.

Loss of the Mono-ADP-ribosyltransferase, Tiparp, Increases Sensitivity to Dioxin-induced Steatohepatitis and Lethality

“…11) (25). Because of the known differences in affinities of AHR agonists for human AHR compared with mouse Ahr b1 and the differential gene expression profiles observed between mouse and human hepatocytes in response to dioxin (47), it will be important to determine whether TIPARP influences lipid uptake and AHR signaling in human hepatocytes or other human primary cells. Moreover, it will be necessary to determine whether some of the SNPs in TIPARP, particularly those that were found to increase or decrease the ability of TIPARP to repress AHR in a reporter gene assay can affect other AHR-dependent outcomes.…”

Two persistent organic pollutants which act through different xenosensors (alpha-endosulfan and 2,3,7,8 tetrachlorodibenzo-p-dioxin) interact in a mixture and downregulate multiple genes involved in human hepatocyte lipid and glucose metabolism

“…Rankerank hypergeometric overlap was also used to identify statistically significant overlap between gene expression signatures [62]. The lists of genes were derived from an analysis of publicly available (literature or public repositories) genome-wide expression data obtained from exposure of primary human hepatocytes [63,64], HepaRG [42] or mouse primary hepatocytes [65] to TCDD or 17b-estradiol. Raw data were renormalized with the plier module in R and robust averages calculated with Tukey's Bi weight average algorithm [66].…”

“…Differentially expressed genes were those having a fold change >2 and p < 0.05. The data from supplementary files 11 and 17 from Forgacs et al [64] were filtered as indicated in the files. Murine expression data from Flaveny et al [65] were also analyzed with Focus.…”

“…We, thus, compared our results following exposure of HepaRG to TCDD or aendosulfan alone with results published in the literature. None of the studies employ conditions that are identical to our work, but a similar study evaluated the effect of exposure of HepaRG cells to 10 nM TCDD or 30 mM 17b-estradiol for 12 or 48 h [42] and two other analyses employed primary human hepatocytes exposed to several concentrations of TCDD for different times [63,64]. Several of the up-and down-regulated gene sets derived from these studies were enriched in the most strongly up-and down-regulated genes in our own ranked list when analyzed by the gene set enrichment analysis algorithm (Fig.…”

Differential Regulation of Gene Expression by Cholesterol Biosynthesis Inhibitors That Reduce (Pravastatin) or Enhance (Squalestatin 1) Nonsterol Isoprenoid Levels in Primary Cultured Mouse and Rat Hepatocytes

“…Speciesspecific responses to pharmacologic and toxicologic agents are generally accepted and have been well reported (Forgacs et al, 2013). To understand the key biologic pathways affected by isoprenoid accumulation that are conserved across species and that therefore likely represent core functions of isoprenoids on hepatocellular physiology, we further processed lists of regulated genes among species to identify treatment-specific orthologs, as depicted in Fig.…”