Project description:We have previously shown that in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-elicited NAFLD progression, central carbon, glutaminolysis and serine/folate metabolism are reprogrammed to support NADPH production and ROS defenses. To further investigate underlying dose-dependent responses associated with TCDD-induced fibrosis, female C57BL/6 mice were gavaged with TCDD every 4 days (d) for 28d or 92d. RNA-Seq, ChIP-Seq (2hr), and 28d metabolomic (urine, serum, and hepatic extract) analyses were conducted with complementary serum marker assessments at 92d. Additional vehicle and 30 µg/kg treatment groups were allowed to recover for 36d following the 92d treatment regimen to examine recovery from TCDD-elicited fibrosis. Histopathology revealed dose-dependent increases in hepatic fat accumulation, inflammation, and periportal collagen deposition at 92d, with increased fibrotic severity in the recovery group. Serum proinflammatory and profibrotic interleukins-1β, -2, -4, -6, and -10, as well as TNFα and IFNγ, exhibited dose-dependent induction. An increase in glucose tolerance was observed with a concomitant 3.0-fold decrease in hepatic glycogen linked to increased ascorbic acid biosynthesis and proline metabolism, consistent with increased fibrosis. RNA-Seq identified differential expression of numerous matrisome genes including an 8.8-fold increase in Tgfb2 indicating myofibroblast activation. Further analysis suggests reprogramming of glycogen, ascorbic acid, and amino acid metabolism in support of collagen deposition and the use of proline as a substrate for ATP production via the proline cycle. Conclusion: In addition to metabolic reprogramming in support of NADPH production for ROS defense, we demonstrate that glycogen, ascorbic acid, and amino acid metabolism are also reorganized to support remodeling of the extracellular matrix, progressing to hepatic fibrosis in response to chronic injury from TCDD.
Project description:2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) dose-dependently induces the development of hepatic fat accumulation and inflammation with fibrosis in mice initially in the portal region. Conversely, differential gene and protein expression is first detected in the central region. To further investigate cell-specific and spatially resolved dose-dependent changes in gene expression elicited by TCDD, single-nuclei RNA sequencing and spatial transcriptomics were used for livers of male mice gavaged with TCDD every 4 days for 28 days. The proportion of 11 cell (sub)types across 131,613 nuclei dose-dependently changed with 68% of all portal and central hepatocyte nuclei in control mice being overtaken by macrophages following TCDD treatment. We identified 368 (portal fibroblasts) to 1,339 (macrophages) differentially expressed genes. Spatial analyses revealed initial loss of portal identity that eventually spanned the entire liver lobule with increasing dose. Induction of R-spondin 3 (Rspo3) and pericentral Apc, suggested dysregulation of the Wnt/β-catenin signaling cascade in zonally resolved steatosis. Collectively, the integrated results suggest disruption of zonation contributes to the pattern of TCDD-elicited NAFLD pathologies.
Project description:Dose-dependent jejunal epithelial gene expression was examined following repeated exposure (every 4 days for 28 days) to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). These data were used to examine the effect of repeated TCDD exposure on jejunal differential gene expression, in order to investigate the role of the jejunum in TCDD-elicited steatohepatitis in C57BL/6.
Project description:2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent aryl hydrocarbon receptor (AhR) agonist that elicits a broad spectrum of dose-dependent effects in the liver, including hepatic lipid accumulation coupled with inflammation. To determine the role of inflammatory lipid mediators in TCDD-mediated hepatotoxicity, eicosanoid metabolism was investigated in female Sprague-Dawley (SD) rats. Rats were gavaged with sesame oil vehicle or 0.01-10 µg/kg TCDD every 4 days for 28 days. Hepatic RNA-Seq data from female SD rats was compared with data from female C57BL/6 mice and functionally annotated to determine key toxicogenomic differences between the two species regarding TCDD exposure. Hepatic RNA-Seq data from female SD rats integrated with untargeted metabolomics of liver, serum, and urine identified dose-dependent changes in linoleic acid (LA) and arachidonic acid (AA) metabolism. TCDD also elicited dose-dependent differential gene expression associated with cyclooxygenase, lipoxygenase, and cytochrome P450 epoxidation/ hydroxylation pathways with corresponding changes in omega-6 (e.g. AA and LA) and omega-3 polyunsaturated fatty acids (PUFAs) as well as their eicosanoid metabolites. Overall, total omega-6 PUFAs increased, while total omega-3 PUFAs decreased. Phospholipase A2 (Pla2g12a) was induced 6-fold consistent with increased AA metabolism, while AA utilization by lipoxygenases Alox5 (2-fold) and Alox15 (10-fold) increased leukotrienes (LTs), important mediators signaling an inflammatory response. More specifically, TCDD increased pro-inflammatory eicosanoids, including leukotriene (LT) B4 (3-fold), and LTB3 (5-fold), known signals for the recruitment of neutrophils to areas of tissue damage. Dose-response modeling of metabolite and gene expression changes suggests the cytochrome P450 hydroxylase/epoxygenase and the lipoxygenase pathways are the most sensitive to TCDD. While several differentially expressed genes (DEGs) associated with eicosanoid biosynthesis contained putative dioxin response elements (pDRE) within their regulatory region, ChIP-Seq analysis showed little AhR enrichment, suggesting TCDD-elicited induction of eicosanoid biosynthesis is not a direct effect of AhR activation.
Project description:2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent aryl hydrocarbon receptor (AhR) agonist that elicits a broad spectrum of dose-dependent effects in the liver, including hepatic lipid accumulation coupled with inflammation. To determine the role of inflammatory lipid mediators in TCDD-mediated hepatotoxicity, eicosanoid metabolism was investigated in female Sprague-Dawley (SD) rats. Rats were gavaged with sesame oil vehicle or 0.01-10 µg/kg TCDD every 4 days for 28 days. Hepatic RNA-Seq data from female SD rats was compared with data from female C57BL/6 mice and functionally annotated to determine key toxicogenomic differences between the two species regarding TCDD exposure. Hepatic RNA-Seq data from female SD rats integrated with untargeted metabolomics of liver, serum, and urine identified dose-dependent changes in linoleic acid (LA) and arachidonic acid (AA) metabolism. TCDD also elicited dose-dependent differential gene expression associated with cyclooxygenase, lipoxygenase, and cytochrome P450 epoxidation/ hydroxylation pathways with corresponding changes in omega-6 (e.g. AA and LA) and omega-3 polyunsaturated fatty acids (PUFAs) as well as their eicosanoid metabolites. Overall, total omega-6 PUFAs increased, while total omega-3 PUFAs decreased. Phospholipase A2 (Pla2g12a) was induced 6-fold consistent with increased AA metabolism, while AA utilization by lipoxygenases Alox5 (2-fold) and Alox15 (10-fold) increased leukotrienes (LTs), important mediators signaling an inflammatory response. More specifically, TCDD increased pro-inflammatory eicosanoids, including leukotriene (LT) B4 (3-fold), and LTB3 (5-fold), known signals for the recruitment of neutrophils to areas of tissue damage. Dose-response modeling of metabolite and gene expression changes suggests the cytochrome P450 hydroxylase/epoxygenase and the lipoxygenase pathways are the most sensitive to TCDD. While several differentially expressed genes (DEGs) associated with eicosanoid biosynthesis contained putative dioxin response elements (pDRE) within their regulatory region, ChIP-Seq analysis showed little AhR enrichment, suggesting TCDD-elicited induction of eicosanoid biosynthesis is not a direct effect of AhR activation.
Project description:TCDD is an environmental contaminant that elicits a number of hepatic effects including fat accumulation, inflammation, and fibrosis that can progress to hepatocellular carcinoma. RNA-Seq and targeted metabolomics were integrated with complementary dioxin response element (DRE) location and aryl hydrocarbon receptor (AhR) ChIP-Seq data to further investigate the hepatotoxicity of TCDD. Our integrative analysis identified changes similar to the Warburg effect observed in cancer cells, including pyruvate kinase isoform switching (PKM1 to PKM2), and an increase in the glutaminase (GLS1) GAC:KGA isoform ratio. Consequently, metabolites are redirected towards the pentose phosphate pathway, serine biosynthesis, and glutaminolysis. We propose that the effects of TCDD on central carbon and amino acid metabolism represents AhR-mediated hepatic metabolic reprogramming in order to increase NADPH production as an oxidative stress counter-measure.
Project description:[Original title] In utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces disruption of the prostate glands and fibrosis in rhesus monkeys. We investigated the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure on the prostate in rhesus monkey offspring. Dams received 0, 30 or 300 ng/kg TCDD subcutaneously on Day 20 of gestation, and then 5% of the initial dose was injected every 30 days until Day 90 after delivery. The offspring were maintained until reaching sexual maturity, and examined histopathologically. Dose-dependent decreases in the prostate glands and widespread fibrosis were observed in offspring. It is noteworthy that 7 years from the final lactational TCDD exposure, inflammatory cell infiltration and disruption of the prostate glands were also observed. Differential mRNA expression associated with fibrosis, inflammatory response and disruption of cell components were demonstrated by microarray analysis, and up-regulation of TGM4, TGFB1, COL1A1 and MMP2 was confirmed with Real-time PCR. In conclusion, in utero and lactational exposure to TCDD induced dose-proportional prostatic fibrosis, indicating prostatic dysfunction and inducible semen quality reduction in second-generation rhesus monkeys.
Project description:[Original title] In utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces disruption of the prostate glands and fibrosis in rhesus monkeys. We investigated the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure on the prostate in rhesus monkey offspring. Dams received 0, 30 or 300 ng/kg TCDD subcutaneously on Day 20 of gestation, and then 5% of the initial dose was injected every 30 days until Day 90 after delivery. The offspring were maintained until reaching sexual maturity, and examined histopathologically. Dose-dependent decreases in the prostate glands and widespread fibrosis were observed in offspring. It is noteworthy that 7 years from the final lactational TCDD exposure, inflammatory cell infiltration and disruption of the prostate glands were also observed. Differential mRNA expression associated with fibrosis, inflammatory response and disruption of cell components were demonstrated by microarray analysis, and up-regulation of TGM4, TGFB1, COL1A1 and MMP2 was confirmed with Real-time PCR. In conclusion, in utero and lactational exposure to TCDD induced dose-proportional prostatic fibrosis, indicating prostatic dysfunction and inducible semen quality reduction in second-generation rhesus monkeys. Dam received 0, 30 or 300 ng/kg TCDD subcutaneously on Day 20 of gestation, and then 5% of the initial dose was injected every 30 days until Day 90 after delivery. The offspring were maintained until reaching sexual maturity, and the prostates from 3 offspring in each group were evalutated by histopathological examination, microarray analysis and Real-time quantitative PCR. Supplementary file: Fold_change comparison results of 'control group vs 30 ng/kg group' and 'control group vs 300 ng/kg group'.
Project description:2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental contaminant which induces diverse biological and toxic effects, including the reprograming of intermediate metabolism, mediated by the aryl hydrocarbon receptor (AHR). Targeted LC-MS analysis of hepatic extracts from mice gavaged with TCDD every 4 days for 28 days detected an increase in S-(2-carboxyethyl)-L-cysteine, a conjugate produced following the spontaneous reaction between the sulfhydryl group of cysteine and highly reactive acrylyl-CoA, an intermediate in the cobalamin (Cbl)-independent β–oxidation-like metabolism of propionyl-CoA. In addition to repressing genes in both the canonical Cbl-dependent carboxylase and the alternate Cbl-independent β–oxidation-like pathways at 30 µg/kg TCDD, methylmalonyl-CoA mutase (MUT) activity was inhibited at lower doses. Moreover, TCDD decreased serum Cbl levels and hepatic cobalt levels while eliciting negligible effects on gene expression associated with Cbl absorption, transport, trafficking, or the derivatization to 5’-deoxy-adenosylcobalamin (AdoCbl), the required MUT cofactor. In addition to inducing Acod1 that encodes for aconitate decarboxylase 1, the enzyme responsible for the decarboxylation cis-aconitate to itaconate, TCDD also dose-dependently increased itaconate levels in hepatic extracts. MUT inhibition is consistent with itaconate activation to itaconyl-CoA, a MUT suicide inactivator that adducts AdoCbl, that in turn, inhibits MUT activity and reduces Cbl levels. Collectively, these results suggest the decrease in MUT activity is due to Cbl depletion following TCDD treatment that redirected propionyl-CoA metabolism to the alternate Cbl-independent β–oxidation-like pathway. The resulting hepatic accumulation of acrylyl-CoA likely contributes to TCDD-elicited hepatotoxicity and the multi-hit progression of steatosis to steatohepatitis with fibrosis.