Cytotoxicity of 2,2',3,5',6-Pentachlorobiphenyl (PCB95) and its metabolites in the chicken embryo liver cells of laying hens

Thyroid hormone transporters binding affinity of methoxypoly chlorinated biphenyls: Insights from molecular simulations and fluorescence competitive binding experiment

Triiodothyronine (T3) and thyroxine (T4) are essential for regulating cell metabolic rate and promoting the development and differentiation of brain tissue, especially in fetuses and newborns. In particular, it has been proved that MeO-PCBs have high binding to thyroid hormone transporters and can competitively bind to thyroid carrier proteins, thus destroying the transport of the thyroid hormone. Fluorescence competition binding experiments and docking results showed that the binding affinity decreased with the increase in number of chlorine atoms of MeO-PCBs. The interaction mechanism of MeO-PCBs with thyroid transporter (TTR) and thyroid binding globulin (TBG) was compared by computational simulation and the binding free energies were calculated by the molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) method. Electrostatic potential analysis, Hirshfeld surface analysis and electron density difference maps confirmed the existence of electrostatic interactions. Secondly, noncovalent interaction (NCI) analysis further indicated that the main driving force for the combination of MeO-PCBs to TTR and TBG were electrostatic interaction and van der Waals interaction. The conformational changes of the protein after binding were studied by a molecular dynamic simulation.

Genome analysis reveals hepatic transcriptional reprogramming changes mediated by enhancers during chick embryonic development

The liver undergoes a slow process for lipid deposition during chick embryonic period. However, the underlying physiological and molecular mechanisms are still unclear. Therefore, the aim of the current study was to reveal the epigenetic mechanism of hepatic transcriptional reprogramming changes based on the integration analysis of RNA-seq and H3K27ac labeled CUT&Tag. Results showed that lipid contents increased gradually with the embryonic age (E) 11, E15, and E19 based on morphological analysis of Hematoxylin-eosin and Oil Red O staining as well as total triglyceride and cholesterol detection. The hepatic protein level of SREBP-1c was higher in E19 when compared with that in E11 and E15, while H3K27ac and H3K4me2 levels declined from E11 to E19. Differential expression genes (DEGs) among these 3 embryonic ages were determined by transcriptome analysis. A total of 107 and 46 genes were gradually upregulated and downregulated respectively with the embryonic age. Meanwhile, differential H3K27ac occupancy in chromatin was investigated. But the integration analysis of RNA-seq and CUT&Tag data showed that the overlap genes were less between DEGs and target genes of differential peaks in the promoter regions. Further, some KEGG pathways enriched from target genes of typical enhancer were overlapped with those from DEGs in transcriptome analysis such as insulin, FoxO, MAPK signaling pathways which were related to lipid metabolism. DNA motif analysis identify 8 and 10 transcription factors (TFs) based on up and down differential peaks individually among E11, E15, and E19 stages where 7 TFs were overlapped including COUP-TFII, FOXM1, FOXA1, HNF4A, RXR, ERRA, FOXA2. These results indicated that H3K27ac histone modification is involved in the transcriptional reprogramming regulation during embryonic development, which could recruit TFs binding to mediate differential enhancer activation. Differential activated enhancer impels dynamic transcriptional reprogramming towards lipid metabolism to promote the occurrence of special phenotype of hepatic lipid deposition.

Comparative In Vitro and In Vivo Hydroxylation Metabolization of Polychlorinated Biphenyl 101 in Laying Hens: A Pilot Study

Polychlorinated biphenyls (PCBs) can be metabolized into hydroxylated PCBs (OH-PCBs) that exhibit greater toxicity than their parent compounds. In particular, 2,2',4,5,5'-pentachlorobiphenyl (PCB 101) is commonly found in chicken feeds and breeding environments, although information on the biotransformation of this PCB in chickens is lacking. In this study, the hydroxylation metabolization of PCB 101 was assessed based on in vitro trials with Sanhuang chicken liver microsomes and in vivo experiments with Hy-Line Brown hens. The para-substituted metabolite 4'-OH-PCB 101 is the predominant metabolite of PCB 101. 4'-OH-PCB 101 is preferentially retained in the chicken bloodstream and partly distributed into different tissues of laying hens. The blood-brain barrier can effectively prevent the OH-PCB from entering the brain, and the adipose tissue contains a relatively low residue concentration of the OH-PCB. The laying hen can deplete the OH-PCB via laying eggs and excrement. The ratio of 4'-OH-PCB 101/PCB 101 in egg yolk is about 1:2. These results first provide definite evidence for the previous hypothesis of the PCB 101 metabolism by chickens. They could assist in predicting the environmental fate of PCBs, and in the risk assessment of PCBs and OH-PCBs in chicken-based foodstuffs.

Study on toxicity effects of environmental pollutants based on metabolomics: A review

In the past few decades, the toxic effects of environmental pollutants on non-target organisms have received more and more attention. As a new omics technology, metabolomics can clarify the metabolic homeostasis of the organism at the overall level by studying the changes in the relative contents of endogenous metabolites in the organism. Recently, a large number of studies have used metabolomics technology to study the toxic effects of environmental pollutants on organisms. In this review, we reviewed the analysis processes and data processes of metabolomics and its application in the study of the toxic effects of environmental pollutants including heavy metals, pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers and microplastics. In addition, we emphasized that the combination of metabolomics and other omics technologies will help to explore the toxic mechanism of environmental pollutants and provide new research ideas for the toxicological evaluation of environmental pollutants.

Hepatic toxicity of fluorene-9-bisphenol (BHPF) on CD-1 mice

Fluorene-9-bisphenol (BHPF), a substitute for bisphenol A (BPA), has been widely used in the synthesis of polyester polymers. Studies have reported multiple BHPF toxicities but its effect on the liver remains unknown. In this study, we performed short-term and subchronic toxicity tests, as well as primary hepatocyte experiments, to investigate the hepatic toxicity of BHPF using CD-1 mice. And microarray was used to analyze the changes of global gene expression in the liver of mice treated with BHPF. The results showed that the liver coefficient and the activities of serum aminotransferases were obviously elevated by BHPF at doses of 27.8 mg/kg body weight (bw)/day or higher in mice treated for 10 days. Histological analysis showed obvious changes, including narrowed hepatic sinuses, dilated central vein, leucocyte infiltration, and cytoplasmic vacuolation, in the livers of mice treated with BHPF at dosages of 2 mg/kg bw/3-day and higher for 36 days. Microarray analyses revealed 2623 differentially expressed genes (DEGs) in the livers of mice treated with 50 mg/kg bw/day of BHPF for 3 days, which could be enriched in GO terms of T cell activation, leukocyte migration, and leukocyte chemotaxis and KEGG pathways of natural killer cell-mediated cytotoxicity and autoimmune thyroid disease. The top 10 hub DEGs, including LTF and MMP8, were observed in the protein-protein interaction network obtained via STRING database analysis, and are proposed as potential biomarkers for liver injury studies. Primary hepatocyte experiments demonstrated the hepatotoxicity of BHPF at concentrations of 10^-6 M and higher. This study indicates that BHPF could cause liver injury at relatively low levels, suggesting that the risk of human BHPF exposure should be of concern.

Three widely used pesticides and their mixtures induced cytotoxicity and apoptosis through the ROS-related caspase pathway in HepG2 cells

Difenoconazole, cypermethrin and triazophos are widely used pesticides in agricultural production and frequently detected in foods. The aim of this study was to determine the effect of these pesticides and their mixtures on cell viability, reactive oxygen species (ROS), lactate dehydrogenase (LDH) content, apoptosis rate and DNA fragmentation and synthesis in human hepatocellular carcinoma cells (HepG2). The order of inhibitory effects for the individual pesticides was ranked as difenoconazole > cypermethrin > triazophos. The enhanced expression of caspase-3, caspase-7 and PARP activity was observed in HepG2 cells, which was 1.7, 1.3 and 1.6-fold higher than the control, respectively, along with significant protein cleavage; and induced apoptosis in a concentration-dependent manner. Further, the pesticide mixtures significantly increased ROS level (up to 1.3-fold), induced DNA fragmentation (up to 1.8-fold), inhibited DNA synthesis (up to 53%), and damaged the cells by destroying the cell membrane and producing a large amount of LDH at concentration range of 10-30 μM. Specifically, mixtures containing difenoconazole showed stronger toxicities than individual pesticides, implying higher health risks associated with mixtures. Our results show that three widely used pesticides exhibited cytotoxicity and apoptosis through the ROS-related caspase pathway, providing a basis for evaluation of health risks from pesticide mixtures via food consumption.