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:The evolution of human diets led to preferences towards polyunsaturated fatty acid (PUFA) content with ‘Western’ diets enriched in ω-6 PUFAs. Mounting evidence points to ω-6 PUFA excess limiting metabolic and cognitive processes that define longevity in humans. When chosen during pregnancy, ω-6 PUFA-enriched ‘Western’ diets can reprogram maternal bodily metabolism with maternal nutrient supply precipitating the body-wide imprinting of molecular and cellular adaptations at the level of long-range intercellular signaling networks in the unborn fetus. Even though unfavorable neurological outcomes are amongst the most common complications of intrauterine ω6 PUFA excess, cellular underpinnings of life-long modifications to brain architecture remain unknown. Here, we show that nutritional ω-6 PUFA-derived endocannabinoids desensitize CB1 cannabinoid receptors, thus inducing epigenetic repression of transcriptional regulatory networks controlling neuronal differentiation. We found that cortical neurons lose their positional identity and axonal selectivity when mouse fetuses are exposed to excess ω-6 PUFAs in utero. Conversion of ω-6 PUFAs into endocannabinoids disrupted the temporal precision of signaling at neuronal CB1 cannabinoid receptors, chiefly deregulating Stat3-dependent transcriptional cascades otherwise required to execute neuronal differentiation programs. Global proteomics identified the immunoglobulin family of cell adhesion molecules (IgCAMs) as direct substrates, with DNA methylation and chromatin accessibility profiling uncovering epigenetic reprogramming at >1,400 sites in neurons after prolonged cannabinoid exposure. We found anxiety and depression-like behavioral traits to manifest in adult offspring, which is consistent with genetic models of reduced IgCAM expression, to suggest causality for cortical wiring defects. Overall, our data uncover a regulatory mechanism whose disruption by maternal food choices could limit an offspring’s brain function for life.

Project description:The optimal ratio of omega-6 to omega-3 polyunsaturated fatty acids (PUFAs) is important for keeping homeostasis of biological processes and metabolism, yet the underlying biological mechanism is poorly understood. The objective of this study was to identify changes in the pig liver transcriptome induced by a diet enriched with omega-6 and omega-3 fatty acids, and to characterize the biological mechanisms related to PUFA metabolism. Polish Landrace pigs (n =12) were fed diet enriched with linoleic acid (LA, omega-6) and alpha-linolenic acid (ALA, omega-3 family) or standard diet as a control. The fatty acids profiling was assayed in order to verify how feeding influenced the fatty acids content in liver, and subsequently next-generation sequencing (NGS) was used to identify differentially expressed genes (DEG) between transcriptomes between dietary groups. The biological mechanisms and pathway interaction networks were identified by analysis in DAVID and Cytoscape tools. Fatty acids profile analysis indicated a higher contribution of PUFAs in liver for LA and ALA-enriched diet group, particularly for the omega-3 fatty acids family, but not omega-6. Next-generation sequencing identified 3,565 DEG, 1,484 of which were induced and 2,081 were suppressed by PUFA supplemenation. Low ratio of omega-6/-3 fatty acids resulted in modulation of fatty acids metabolism pathways and over-representation of genes involved in membrane composition, signal transduction and immune response pathways. In conclusion, a diet enriched with omega-6 and omega-3 fatty acids altered the transcriptomic profile of the pig liver and affected a set of genes involved in metabolic pathways important to animal health status. Hepatic mRNA profiles of Polish Landrace pig breed fed two different diets, were generated by deep sequencing, using Illumina MiSeq. Experimental diet was enriched with polyunsaturated fatty acids (omega-6 and omega-3), while standard diet remain as a cotrol. 2 pooled samples each containing RNA extracts from 6 individuals livers were analyzed.

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