Epigenetic Factors in Cancer Risk: Effect of Chemical Carcinogens on Global DNA Methylation Pattern in Human TK6 Cells

In the current study, we assessed the global DNA methylation changes in human lymphoblastoid (TK6) cells in vitro in response to 5 direct and 10 indirect-acting genotoxic agents. TK6 cells were exposed to the selected agents for 24 h in the presence and/or absence of S9 metabolic mix. Liquid chromatography-mass spectrometry was used for quantitative profiling of 5-methyl-2′-deoxycytidine. The effect of exposure on 5-methyl-2′-deoxycytidine between control and exposed cultures was assessed by applying the marginal model with correlated residuals on % global DNA methylation data. We reported the induction of global DNA hypomethylation in TK6 cells in response to S9 metabolic mix, under the current experimental settings. Benzene, hydroquinone, styrene, carbon tetrachloride and trichloroethylene induced global DNA hypomethylation in TK6 cells. Furthermore, we showed that dose did not have an effect on global DNA methylation in TK6 cells. In conclusion we report changes in global DNA methylation as an early event in response to agents traditionally considered as genotoxic

Effect of Chemical Mutagens and Carcinogens on Gene Expression Profiles in Human TK6 Cells

Characterization of toxicogenomic signatures of carcinogen exposure holds significant promise for mechanistic and predictive toxicology. In vitro transcriptomic studies allow the comparison of the response to chemicals with diverse mode of actions under controlled experimental conditions. We conducted an in vitro study in TK6 cells to characterize gene expression signatures of exposure to 15 genotoxic carcinogens frequently used in European industries. We also examined the dose-responsive changes in gene expression, and perturbation of biochemical pathways in response to these carcinogens. TK6 cells were exposed at 3 dose levels for 24 h with and without S9 human metabolic mix. Since S9 had an impact on gene expression (885 genes), we analyzed the gene expression data from cells cultures incubated with S9 and without S9 independently. The ribosome pathway was affected by all chemical-dose combinations. However in general, no similar gene expression was observed among carcinogens. Further, pathways, i.e. cell cycle, DNA repair mechanisms, RNA degradation, that were common within sets of chemical-dose combination were suggested by clustergram. Linear trends in dose–response of gene expression were observed for Trichloroethylene, Benz[a]anthracene, Epichlorohydrin, Benzene, and Hydroquinone. The significantly altered genes were involved in the regulation of (anti-) apoptosis, maintenance of cell survival, tumor necrosis factor-related pathways and immune response, in agreement with several other studies. Similarly in S9+ cultures, Benz[a]pyrene, Styrene and Trichloroethylene each modified over 1000 genes at high concentrations. Our findings expand our understanding of the transcriptomic response to genotoxic carcinogens, revealing the alteration of diverse sets of genes and pathways involved in cellular homeostasis and cell cycle control

Impact of lung surfactant on wettability and cytotoxicity of nanoparticles

The importance of nanoparticle characterization for nanotoxicology has been extensively emphasized and it has been universally agreed that the most important parameters for characterizing nanomaterials are specific surface area and surface properties (chemistry, hydro-philicity/phobicity, charge etc.). This study is proposing the use of enthalpy of wetting which depends on both specific surface area and surface properties, is easily measurable and proves to be highly relevant for predicting nanoparticles' dispersion state and their interaction with the lungs. It also shows the conditioning effect of the lung surfactant main component, DPPC on the surface of particles when used in concentrations which mimic pulmonary exposure more closely

Assessment of Experimental Techniques That Facilitate Human Granuloma Formation in an In Vitro System: A Systematic Review

The process of granuloma formation is complex, and due to species differences, the validity of animal studies is somewhat questioned. Moreover, the large number of animals needed to observe the different stages of development also raises ethical questions. Therefore, researchers have explored the use of human peripheral blood mononuclear cells (PBMCs), a heterogeneous population of immune cells, in an in vitro model. This review included in vitro studies that focused on exposing PBMCs—from healthy, sensitized, or diseased individuals—to antigens derived from infectious agents—such as mycobacteria or Schistosoma spp.—or inorganic antigens—such as beryllium. The reviewed studies mainly explored how human in vitro granuloma models can contribute towards understanding the pathogenesis of granulomatous diseases, especially during the early stages of granuloma formation. The feasibility of granuloma modelling was thus largely assessed via experimental techniques including (1) granuloma scoring indices (GI), (2) cell surface markers and (3) cytokine secretion profiling. While granuloma scoring showed some similarities between studies, a large variability of culture conditions and endpoints measured have been identified. The lack of any standardization currently impedes the success of a human in vitro granuloma model

Dermal exposure determines the outcome of repeated airway exposure in a long-term chemical-induced asthma-like mouse model

Background: Exposure to diisocyanates is an important cause of occupational asthma (OA) in the industrialized world. Since OA occurs after long-term exposure to diisocyanates, we developed a chronic mouse model of chemical-induced asthma where toluene diisocyanate (TDI) was administered at two different exposure sites. Objectives: Evaluating the effect of long-term respiratory isocyanate exposure - with or without prior dermal exposure- on sensitization, inflammatory responses and airway hyperreactivity (AHR). Methods: On days 1 and 8, BALB/c mice were dermally treated (20 mu 1/ear) with 0.5% 2,4-toluene diisocyanate TDI or the vehicle acetone olive oil (AOO) (3:2). Starting from day 15, mice received intranasal instillations with 0.1% TDI of vehicle five times in a week, for five successive weeks. One day after the last instillation airway hyperreactivity (AHR) to methacholine was assessed, followed by an evaluation of pulmonary inflammation and structural lung changes. Immune-related parameters were assessed in the lungs (BAL and tissue), blood, cervical-and auricular lymph nodes. Results: Mice repeatedly intranasally exposed to TDI showed systemic sensitization and a mixed Th1/Th2 type immune response, without the presence of AHR. However, when mice are first dermally sensitized with TDI, followed by repeated intranasal TDI challenges, this results in a pronounced Th2 response and AHR. Conclusion: Dermal exposure to TDI determines airway hyperreactivity after repeated airway exposure to TDI

Synthesis, characterization and toxicity assessment of a new polymeric nanoparticle, L-glutamic acid-g-p(HEMA)

Hoet, Peter/0000-0002-0292-6603; Karabay Yavasoglu, N.Ulku/0000-0002-7483-0184WOS: 000514572800010PubMed: 31669216The toxic effects of poly(HEMA)-based polymeric nanoparticles must be analyzed before their biomedical applications as drug delivery systems. the aim of the study was to characterize and evaluate the toxicity for its biocompatibility of a newly synthesized L-glutamic acid-g-p(HEMA) polymeric nanoparticle the nanoparticle was synthesized with surfactant-free emulsion polymerization and grafting techniques. Grafting efficiency was estimated at 58%. the nanoparticle shape was verified as nearly spherical by scanning electron microscopy. Atomic force microscopy images showed a rough surface topography. the nanoparticle had an average size of similar to 194.6 nm on zeta analysis, and the zeta potential value was -18 mV. Fourier transformed infrared spectroscopy revealed spectra from 750 to 4000 cm(-1) and characteristic peaks of stretching bands. the swelling ratio was 46%. With 24-h exposure, p(HEMA) and L-glutamic acid-g-p(HEMA) did not have cytotoxic effects on a human bronchial epithelial cell line (16HBE) and human monocyte cell line by water-soluble tetrazolium salt 1 (WST-1) assay and lactate dehydrogenase assay (LDH). It did not show genotoxic potential by comet assay and did not have mutagenic effects on Salmonella typhimurium TA98, TA100, TA1535 and TA1537 strains by Ames test. the nanoparticle at 160 mu g/ml showed 2% hemolytic activity on erythrocytes. on cell migration assay, the percentage closure difference between exposed and control cells was estimated at 21%. We found no irritation effect on Hen's egg test-chorioallantoic membrane test. We determined that the polymeric nanoparticle L-glutamic acid-g-p(HEMA) was biocompatible and has potential for use in a drug delivery system.Ege University, Scientific Research ProjectEge University [2015/FEN/010]; TUBITAK 2214-A - PhD Abroad Research Scholarship Program, TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)The study was supported by Ege University, Scientific Research Project (Project number is 2015/FEN/010) and TUBITAK 2214-A - PhD Abroad Research Scholarship Program, Turkey