Exposure to coplanar PCBs induces endothelial cell inflammation through epigenetic regulation of NF-?B subunit p65.
ABSTRACT: Epigenetic modifications of DNA and histones alter cellular phenotypes without changing genetic codes. Alterations of epigenetic marks can be induced by exposure to environmental pollutants and may contribute to associated disease risks. Here we test the hypothesis that endothelial cell dysfunction induced by exposure to polychlorinated biphenyls (PCBs) is mediated in part though histone modifications. In this study, human vascular endothelial cells were exposed to physiologically relevant concentrations of several PCBs congeners (e.g., PCBs 77, 118, 126 and 153) followed by quantification of inflammatory gene expression and changes of histone methylation. Only exposure to coplanar PCBs 77 and 126 induced the expression of histone H3K9 trimethyl demethylase jumonji domain-containing protein 2B (JMJD2B) and nuclear factor-kappa B (NF-?B) subunit p65, activated NF-?B signaling as evidenced by nuclear translocation of p65, and up-regulated p65 target inflammatory genes, such as interleukin (IL)-6, C-reactive protein (CRP), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and IL-1?/?. The increased accumulation of JMJD2B in the p65 promoter led to a depletion of H3K9me3 repression mark, which accounts for the observed up-regulation of p65 and associated inflammatory genes. JMJD2B gene knockdown confirmed a critical role for this histone demethylase in mediating PCB-induced inflammation of the vascular endothelium. Finally, it was determined, via chemical inhibition, that PCB-induced up-regulation of JMJD2B was estrogen receptor-alpha (ER-?) dependent. These data suggest that coplanar PCBs may exert endothelial cell toxicity through changes in histone modifications.
Project description:Anti-inflammatory polyphenols, such as epigallocatechin-3-gallate (EGCG), have been shown to protect against the toxicity of environmental pollutants. It is well known that bioactive food compounds such as polyphenols may exert their protection by modulating inflammatory pathways regulated through nuclear factor-kappa B (NF-?B) signaling. EGCG has been reported to inhibit NF-?B activation. We hypothesize that EGCG can protect against polychlorinated biphenyl (PCB)-induced endothelial inflammation in part through epigenetic regulation of NF-?B-regulated inflammatory genes. In order to test this hypothesis, human endothelial cells (EA.hy926) were exposed to physiologically relevant levels of coplanar PCB 126 and/or 15 or 30 ?M of EGCG, followed by quantification of NF-?B subunit p65, histone acetyltransferase p300 and histone deacetylases (HDACs) accumulation through chromatin immunoprecipitation assay in the promoter region of inflammatory genes. In addition, the enrichment of the acetylated H3 was also quantified. PCB 126 exposure increased the expression of vascular inflammatory mediators, including interleukin (IL)-6, C-reactive protein, intercellular adhesion molecule-1, vascular cell adhesion molecule-1 and IL-1?/?, which were prevented by pretreatment with EGCG. This inhibitory effect by EGCG correlated with abolished nuclear import of p65, decreased chromatin binding of p65 and p300, as well as increased chromatin binding of HDAC 1/2. Furthermore, EGCG induced hypoacetylation of H3, which accounts for deactivation of downstream genes. These data suggest that EGCG-induced epigenetic modifications can decrease PCB-induced vascular toxicity.
Project description:Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that contribute to the initiation of cardiovascular disease. Exercise has been shown to reduce the risk of cardiovascular disease; however, whether exercise can modulate PCB-induced vascular endothelial dysfunction and associated cardiovascular risk factors is unknown. We examined the effects of exercise on coplanar PCB-induced cardiovascular risk factors including oxidative stress, inflammation, impaired glucose tolerance, hypercholesteremia, and endothelium-dependent relaxation. Male ApoE(-/-) mice were divided into sedentary and exercise groups (voluntary wheel running) over a 12-week period. Half of each group was exposed to vehicle or PCB 77 at weeks 1, 2, 9, and 10. For ex vivo studies, male C57BL/6 mice exercised via voluntary wheel training for 5 weeks and then were administered with vehicle or PCB 77 24 h before vascular reactivity studies were performed. Exposure to coplanar PCB increased risk factors associated with cardiovascular disease, including oxidative stress and systemic inflammation, glucose intolerance, and hypercholesteremia. The 12-week exercise intervention significantly reduced these proatherogenic parameters. Exercise also upregulated antioxidant enzymes including phase II detoxification enzymes. Sedentary animals exposed to PCB 77 exhibited endothelial dysfunction as demonstrated by significant impairment of endothelium-dependent relaxation, which was prevented by exercise. Lifestyle modifications such as aerobic exercise could be utilized as a therapeutic approach for the prevention of adverse cardiovascular health effects induced by environmental pollutants such as PCBs.
Project description:Endothelial cells play an important role in maintenance of the vascular system and the repair after injury. Under proinflammatory conditions, endothelial cells can acquire a mesenchymal phenotype by a process named endothelial-to-mesenchymal transition (EndMT), which affects the functional properties of endothelial cells. Here, we investigated the epigenetic control of EndMT. We show that the histone demethylase JMJD2B is induced by EndMT-promoting, proinflammatory, and hypoxic conditions. Silencing of JMJD2B reduced TGF-?2-induced expression of mesenchymal genes, prevented the alterations in endothelial morphology and impaired endothelial barrier function. Endothelial-specific deletion of JMJD2B in vivo confirmed a reduction of EndMT after myocardial infarction. EndMT did not affect global H3K9me3 levels but induced a site-specific reduction of repressive H3K9me3 marks at promoters of mesenchymal genes, such as Calponin (CNN1), and genes involved in TGF-? signaling, such as AKT Serine/Threonine Kinase 3 (AKT3) and Sulfatase 1 (SULF1). Silencing of JMJD2B prevented the EndMT-induced reduction of H3K9me3 marks at these promotors and further repressed these EndMT-related genes. Our study reveals that endothelial identity and function is critically controlled by the histone demethylase JMJD2B, which is induced by EndMT-promoting, proinflammatory, and hypoxic conditions, and supports the acquirement of a mesenchymal phenotype.
Project description:Posttranslational histone modifications serve to store epigenetic information and control both nucleosome assembly and recruitment of non-histone proteins. Histone methylation occurs on arginine and lysine residues and is involved in the regulation of gene transcription. A dynamic control of these modifications is exerted by histone methyltransferases and the recently discovered histone demethylases. Here we show that the hypoxia-inducible factor HIF-1alpha binds to specific recognition sites in the genes encoding the jumonji family histone demethylases JMJD1A and JMJD2B and induces their expression. Accordingly, hypoxic cells express elevated levels of JMJD1A and JMJD2B mRNA and protein. Furthermore, we find increased expression of JMJD1A and JMJD2B in renal cancer cells that have lost the von Hippel Lindau tumor suppressor protein VHL and therefore display a deregulated expression of hypoxia-inducible factor. Studies on ectopically expressed JMJD1A and JMJD2B indicate that both proteins retain their histone lysine demethylase activity in hypoxia and thereby might impact the hypoxic gene expression program.
Project description:<h4>Background</h4>Both coplanar and noncoplanar polychlorinated biphenyls (PCBs) exhibit neurotoxic effects in animal studies, but individual congeners do not always produce the same effects as PCB mixtures. Humans genetically have > 60-fold differences in hepatic cytochrome P450 1A2 (CYP1A2)-uninduced basal levels and > 12-fold variability in aryl hydrocarbon receptor (AHR)affinity; because CYP1A2 is known to sequester coplanar PCBs and because AHR ligands include coplanar PCBs, both genotypes can affect PCB response.<h4>Objectives</h4>We aimed to develop a mouse paradigm with extremes in Cyp1a2 and Ahr genotypes to explore genetic susceptibility to PCB-induced developmental neurotoxicity using an environmentally relevant mixture of PCBs.<h4>Methods</h4>We developed a mixture of eight PCBs to simulate human exposures based on their reported concentrations in human tissue, breast milk, and food supply. We previously characterized specific differences in PCB congener pharmacokinetics and toxicity, comparing high-affinity-AHR Cyp1a2 wild-type [Ahrb1_Cyp1a2(+/+)], poor-affinity-AHR Cyp1a2 wild-type [Ahrd_Cyp1a2(+/+)], and high-affinity-AHR Cyp1a2 knockout [Ahrb1_Cyp1a2(-/-)] mouse lines [Curran CP, Vorhees CV, Williams MT, Genter MB, Miller ML, Nebert DW. 2011. In utero and lactational exposure to a complex mixture of polychlorinated biphenyls: toxicity in pups dependent on the Cyp1a2 and Ahr genotypes. Toxicol Sci 119:189-208]. Dams received a mixture of three coplanar and five noncoplanar PCBs on gestational day 10.5 and postnatal day (PND) 5. In the present study we conducted behavioral phenotyping of exposed offspring at PND60, examining multiple measures of learning, memory, and other behaviors.<h4>Results</h4>We observed the most significant deficits in response to PCB treatment in Ahrb1_Cyp1a2(-/-) mice, including impaired novel object recognition and increased failure rate in the Morris water maze. However, all PCB-treated genotypes showed significant differences on at least one measure of learning or behavior.<h4>Conclusions</h4>High levels of maternal hepatic CYP1A2 offer the most important protection against deficits in learning and memory in offspring exposed to a mixture of coplanar and noncoplanar PCBs. High-affinity AHR is the next most important factor in protection of offspring.
Project description:<h4>Background</h4>Previous studies demonstrated that coplanar polychlorinated biphenyls (PCBs) promote proinflammatory gene expression in adipocytes. PCBs are highly lipophilic and accumulate in adipose tissue, a site of insulin resistance in persons with type 2 diabetes.<h4>Objectives</h4>We investigated the in vitro and in vivo effects of coplanar PCBs on adipose expression of tumor necrosis factor ? (TNF-?) and on glucose and insulin homeostasis in lean and obese mice.<h4>Methods</h4>We quantified glucose and insulin tolerance, as well as TNF-? levels, in liver, muscle, and adipose tissue of male C57BL/6 mice administered vehicle, PCB-77, or PCB-126 and fed a low fat (LF) diet. Another group of mice administered vehicle or PCB-77 were fed a high fat (HF) diet for 12 weeks; the diet was then switched from HF to LF for 4 weeks to induce weight loss. We quantified glucose and insulin tolerance and adipose TNF-? expression in these mice. In addition, we used in vitro and in vivo studies to quantify aryl hydrocarbon receptor (AhR)-dependent effects of PCB-77 on parameters of glucose homeostasis.<h4>Results</h4>Treatment with coplanar PCBs resulted in sustained impairment of glucose and insulin tolerance in mice fed the LF diet. In PCB-77-treated mice, TNF-? expression was increased in adipose tissue but not in liver or muscle. PCB-77 levels were strikingly higher in adipose tissue than in liver or serum. Antagonism of AhR abolished both in vitro and in vivo effects of PCB-77. In obese mice, PCB-77 had no effect on glucose homeostasis, but glucose homeostasis was impaired after weight loss.<h4>Conclusions</h4>Coplanar PCBs impaired glucose homeostasis in lean mice and in obese mice following weight loss. Adipose-specific elevations in TNF-? expression by PCBs may contribute to impaired glucose homeostasis.
Project description:Strong sorption of planar nonionic organic chemicals by clay minerals has been observed for important classes of organic contaminants including polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dioxins, and such affinity was hypothesized to relate to the interlayer hydrophobicity of smectite clays. In batch sorption experiments of two trichlorobiphenyls on homoionic Na-, K-, Cs-montmorillonites, considerably greater sorption coefficient (Kw) was observed for coplanar 3,3',5-trichlorobiphenyl (PCB 36); log Kw for Na-, K-, and Cs-montmorillonite were 3.69, 3.72, and 4.53 for coplanar PCB 36 vs 1.21, 1.46, and 0.87 for the nonplanar 2,2',6-trichlorobiphenyl (PCB 19). MD simulations were conducted utilizing X-ray diffraction determined clay interlayer distances (d-spacing). The trajectory, density distribution, and radial distribution function of interlayer cation, water, and PCBs collectively indicated that the hydrophobic nature of the interlayer regions was determined by the hydration status of exchangeable cations and the associated d-spacing. The sorption free energies calculated for both coplanar and nonplanar PCB molecules by adaptive biasing force (ABF) method with an extended interlayer-micropore two-phase model consisting of cleaved clay hydrates and "bulk water" are consistent with the Gibbs free energies derived from the measured log Kw, manifesting enhanced sorption of coplanar PCBs was attributed to shape selectivity and hydrophobic interactions.
Project description:Ligand-activated liver X receptor ? (LXR?) upregulates the expression of hepatic lipogenic genes, which leads to triglyceride (TG) accumulation, resulting in nonalcoholic fatty liver disease (NAFLD). Thus, LXR? regulation may provide a novel therapeutic target against NAFLD. However, histone methylation-mediated epigenetic regulation involved in LXR?-dependent lipogenesis is poorly understood. In this study, we investigated the functional role of the histone demethylase Jumonji domain-containing protein 2B (JMJD2B) in LXR?-dependent lipogenesis. JMJD2B expression level was upregulated in HepG2 cells treated with LXR? agonist T0901317 or palmitate and the liver of mice administered with T0901317 or fed a high-fat diet. Knockdown of JMJD2B using siRNA abrogated T0901317-induced LXR?-dependent lipogenic gene expression and lowered intracellular TG accumulation. Conversely, overexpression of JMJD2B in HepG2 cells upregulated the expression of LXR?-dependent lipogenic genes, in line with increased intracellular TG levels. JMJD2B overexpression or T0901317 treatment induced the recruitment of JMJD2B and LXR? to LXR response elements (LXRE) in the promoter region of LXR?-target gene and reduced the enrichment of H3K9me2 and H3K9me3 in the vicinity of the LXRE. Furthermore, JMJD2B enhanced T0901317 or LXR?-induced transcriptional activities of reporters containing LXRE. A co-immunoprecipitation assay revealed that JMJD2B interacted with activated LXR?. Moreover, overexpression of JMJD2B in mice resulted in upregulation of hepatic LXR?-dependent lipogenic genes, consistent with development of hepatic steatosis. Taken together, these results indicate that JMJD2B plays a role in LXR?-mediated lipogenesis via removing the repressive histone marks, H3K9me2 and H3K9me3, at LXRE, which might contribute to hepatic steatosis.
Project description:It is well-documented that the methylation of histone H3 lysine 4 (H3K4) and of H3K9 are mutually exclusive, an epigenetic phenomenon conserved from yeast to humans. How this opposed methylation modification is accomplished and coordinated in mammalian cells is poorly understood. Here we report that the H3K9 trimethyl demethylase JMJD2B is an integral component of the H3K4-specific methyltransferase, the mixed-lineage leukemia (MLL) 2 complex. We show that the JMJD2B/MLL2 complex is copurified with estrogen receptor ? (ER?) and is required for ER?-regulated transcription. We demonstrate that H3K9 demethylation and H3K4 methylation are coordinated in ER?-activated transcription such that H3K9 demethylation is a prerequisite for H3K4 methylation. Significantly, depletion of JMJD2B impairs the estrogen-induced G(1)/S transition of the cell cycle in vitro and inhibits breast tumorigenesis in vivo. Interestingly, JMJD2B itself is an ER? target gene, and forms a feed-forward regulatory loop in regulation of the hormone response. Our results provide a molecular basis for the coordinated H3K4 methylation/H3K9 demethylation in transcription activation, link the trimethyl demethylase JMJD2B to euchromatin functions, and provide a mechanism for JMJD2B in breast carcinogenesis.
Project description:Endothelial cells play an important role in maintenance of the vascular system and the repair after injury. Under pro-inflammatory conditions, endothelial cells can acquire a mesenchymal phenotype by a process named endothelial-to-mesenchymal transition (EndMT), which affects the functional properties of endothelial cells. Here, we investigated the epigenetic control of EndMT. We show that the histone demethylase JMJD2B is induced by EndMT promoting pro-inflammatory and hypoxic conditions. Silencing of JMJD2B reduced TGF-β2-induced expression of mesenchymal genes and prevented the alterations in endothelial morphology and impaired endothelial barrier function. Endothelial-specific deletion of JMJD2B in vivo confirmed a reduction of EndMT after myocardial infarction. EndMT did not affect global H3K9me3 levels but induced a site-specific reduction of repressive H3K9me3 marks at promoters of mesenchymal genes, such as Calponin (CNN1), and genes involved in TGF-β signaling, such as AKT Serine/Threonine Kinase 3 (AKT3) and sulfatase 1 (SULF1). Silencing of JMJD2B prevented the EndMT-induced reduction of H3K9me3 marks at these promotors and further repressed these EndMT-related genes. Our study reveals that endothelial identity and function is critically controlled by the histone demethylase JMJD2B, which is induced by EndMT-promoting pro-inflammatory and hypoxic conditions and support the acquirement of a mesenchymal phenotype. Overall design: Affymetrix Human Exon 1.0 ST Array of HUVEC cells in full- and differentiation medium under control and JMJD2B knockdown.