Mi-Kyung Song

Modified composites based on mesostructured iron oxyhydroxide and synthetic minerals: a potential material for the treatment of various toxic heavy metals and its toxicity.

The composites of mesostructured iron oxyhydroxide and/or commercial synthetic zeolite were investigated for use in the removal of toxic heavy metals, such as cadmium, copper, lead and arsenic, from aqueous solution. Four types of adsorbents, dried alginate beads (DABs), synthetic-zeolite impregnated beads (SZIBs), meso-iron-oxyhydroxide impregnated beads (MIOIBs) and synthetic-zeolite/meso-iron-oxyhydroxide composite beads (SZMIOIBs), were prepared for heavy metal adsorption tests. Laboratory experiments were conducted to investigate the removal efficiencies of cations and anions of heavy metals and the possibility of regenerating the adsorbents. Among these adsorbents, the MIOIBs can simultaneously remove cations and anions of heavy metals; they have high adsorption capacities for lead (60.1mgg(-1)) and arsenic (71.9mgg(-1)) compared with other adsorbents, such as DABs (158.1 and 0.0mgg(-1)), SZIB (42.9 and 0.0mgg(-1)) and SZMIOIB (54.0 and 5.9mgg(-1)) for lead and arsenic, respectively. Additionally, the removal efficiency was consistent at approximately 90%, notwithstanding repetitive regeneration. The characteristics of meso-iron-oxyhydroxide powder were confirmed by X-ray diffraction, Brunauer-Emmett-Teller and transmission electron microscopy. We also performed a comparative toxicity study that indicated that much lower concentrations of the powdered form of mesostructured iron oxyhydroxide had stronger cytotoxicity than the granular form. These results suggest that the granular form of meso iron oxyhydroxide is a more useful and safer adsorbent for heavy metal treatment than the powdered form. This research provides promising results for the application of MIOIBs as an adsorbent for various heavy metals from wastewater and sewage.

Genotoxicity of nano-silica in mammalian cell lines

Nanomaterials are defined by the U.S. National Nanotechnology Initiative as materials that have at least one dimension in the 1- to 100-nm range. Due to their unique physical and chemical characteristics, nanotechnology has become one of the leading technologies over the past 10 years. This study represents data on genotoxic effects of nanoparticles and their application for assessing human health risks. Silica (SiO2) is a multi-functional ceramic material that is being used in various industries to improve surfaces and mechanical properties of diverse materials, such as paints and coatings, plastics, synthetic rubber, adhesives, sealants, or insulation materials. However, recent studies have shown that nano-sized silica (nano-silica) (10 nm in diameter) can generate adverse effects, like liver injury and inflammation. The cytotoxicity and genotoxicity of nano-silica were investigated using the dye exclusion assay, comet assay, and mouse lymphoma thymidine kinase (tk+/−) mouse lymphoma assay (MLA). IC20 of nano-silica in L5178Y cells was determined to be of 2,441.41 μg/mL and 2,363.28 μg/mL without and with S-9, respectively. Also IC20 of nano-silica in BEAS-2B cells was determined to be of 2,324.23 μg/mL and 537.11 μg/mL without and with S-9, respectively. In the comet assay, treating L5178Y cells and BEAS-2B cells with nanosilica treatment induced approximately 2-fold increases in tail moment (P<0.05) without and with S-9. Also, the mutant frequencies in the nano-silica treated L5178Y cells were not significantly increased compared to the solvent controls. The results of this study indicate that nano-silica can cause primary DNA damage and cytotoxicity but not mutagenicity in cultured mammalian cells.

Application of carbon foam for heavy metal removal from industrial plating wastewater and toxicity evaluation of the adsorbent

Electroplating wastewater contains various types of toxic substances, such as heavy metals, solvents, and cleaning agents. Carbon foam was used as an adsorbent for the removal of heavy metals from real industrial plating wastewater. Its sorption capacity was compared with those of a commercial ion-exchange resin (BC258) and a heavy metal adsorbent (CupriSorb™) in a batch system. The experimental carbon foam has a considerably higher sorption capacity for Cr and Cu than commercial adsorbents for acid/alkali wastewater and cyanide wastewater. Additionally, cytotoxicity test showed that the newly developed adsorbent has low cytotoxic effects on three kinds of human cells. In a pilot plant, the carbon foam had higher sorption capacity for Cr (73.64 g kg(-1)) than for Cu (14.86 g kg(-1)) and Ni (7.74 g kg(-1)) during 350 h of operation time. Oxidation pretreatments using UV/hydrogen peroxide enhance heavy metal removal from plating wastewater containing cyanide compounds.

Gene Expression Analysis Identifies DNA Damage-related Markers of Benzo(a)pyrene Exposure in HepG2 Human Hepatocytes

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) that is carcinogenic to humans. Although the environmental distribution and metabolism of BaP have been reported and many researchers are performing risk-assessment and toxicological studies of BaP by means of physical and chemical measurements, only a few studies have examined the expression of mRNAs and their functions in BaP-induced toxicity. Toxicogenomic technology, a new paradigm in toxicity screening, is a useful approach for evaluating the toxic properties of environmental pollutants. We analyzed gene expression profiles using human oligonucleotide chips and identified genes in human hepatocellular carcinoma (HepG2) cells whose expression changed > 1.5-fold after exposure to BaP. The expression of 4,048 and 3,926 genes was up-and down-regulated > 1.5-fold (P < 0.01), respectively, after exposure. Gene ontology (GO) analysis of these genes revealed significant enrichment in several key biological processes related to DNA damage, including DNA repair, cell cycle arrest, and apoptosis. We also performed a contrastive study of cellular effects in HepG2 cells exposed to BaP, and identified increased expression of related genes, cell cycle arrest, and apoptotic cells. These results suggest that genetic markers of BaP-induced toxicity may be molecular blueprints that can be more widely implemented in combination with more traditional techniques for assessment and prediction.

Gene expression analysis identifies potential biomarkers of phenanthrene in human hepatocytes (HepG2)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquious in the environment both as natural products and as environmental contaminants. Among PAHs, phenanthrene (PH) that is ubiquitously distributed throughout the environment was subjected in this study. Although environmental distribution and metabolism of PH have been well reported, there are only a few studies examined the expression of mRNA and their functions on PH-induced toxicity. A new paradigm in toxicity screening, toxicogenomic technology represents a useful approach for evaluating the toxic properties of environmental pollutants. In this respect, we elicited the genes which were changed more than 2-fold by analysis of gene expression profiles in human hepatocellular carcinoma (HepG2) cells, exposed to PH by using human oligonucleotide chip. 913 up- and 814 down-regulated genes changed their expression by more than 2-fold and p-values 0.05 through PH exposure. Gene Ontology (GO) analysis on these genes revealed significant enrichments in the several key biological processes related to the hepatotoxicity such as cell migration, wound healing, cytoskeleton organization, microtubule-based process, apoptosis, and cell cycle checkpoint. In conclusion, the present study suggests that PH exerts its toxicity by modulating the mRNA expression in HepG2 cells. we suggest that genes expressed by PH as a molecular signature which can be used more widely implemented in combination with more traditional techniques for assessment and prediction of toxicity by exposure to PH.

Analysis of dose-response to hexanal-induced gene expression in A549 human alveolar cells

The problems of analyzing dose effects on gene expression are gaining attention in toxicological research. Determining how gene expression profiles change with toxicant dose will improve the utility of arrays in identifying biomarkers and elucidating their modes of toxic action. In the present study, we focused on determining the dose-dependent alterations of gene expression profiles with hexanal exposure and we identified the possible biomarkers of hexanal in A549 human alveolar cells. A549 cells were exposed to a 5% inhibitory concentration (IC5) and a 20% inhibitory concentration (IC20) of hexanal for 48 h. Through microarray analysis using an oligonucleotide chip, we identified that the gene expression patterns were differentially shown in the control group and the hexanalexposed groups. The hexanal-exposed groups are more sensitive to gene alteration than the control group, and gene expressions are more significantly altered in the IC20 exposure group than in the IC5 exposure group. With clustering analysis of gene expression profiles, we identified 2,929 IC5− and 3,678 IC20-specific genes, and 302 dose-dependently expressed genes. Gene ontology (GO) analysis with 246 annotated genes of the 302 dosedependent expressed genes showed correlation with the key biological processes involved in neurological system processes, immune system development, cell activation, and cell-cell signaling. In conclusion, current study describes alterations in gene expression profiles in response to exposure to different doses of hexanal and related toxic pathways induced by significantly expressed genes. Moreover, novel genes and pathways that could potentially play a role in the prevention of respiratory disease due to aldehydes are identified.

Integrative analysis of mRNA and microRNA expression of a human alveolar epithelial cell(A549) exposed to water and organic-soluble extract from particulate matter (PM)2.5

MicroRNA (miRNA) is now attracting attention as a powerful negative regulator of messenger RNA(mRNA) levels, and is implicated in the modulation of important mRNA networks involved in toxicity. In this study, we assessed the effects of particulate matter 2.5 (PM2.5), one of the most significant air pollutants, on miRNA and target gene expression. We exposed human alveolar epithelial cell (A549) to two types of PM2.5[water (W‐PM2.5) and organic (O‐PM2.5) soluble extracts] and performed miRNA microarray analysis. A total of 37 miRNAs and 62 miRNAs were altered 1.3‐fold in W‐PM2.5 and O‐PM2.5, respectively. Integrated analyses of miRNA and mRNA expression profiles identified negative correlations between miRNA and mRNA in both W‐PM2.5 and O‐PM2.5 exposure groups. Gene ontology and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses showed that the 35 W‐PM2.5 target genes are involved in responses to nutrients, positive regulation of biosynthetic processes, positive regulation of nucleobase, nucleoside, and nucleotide, and nucleic acid metabolic processes; while the 69 O‐PM2.5 target genes are involved in DNA replication, cell cycle processes, the M phase, and the cell cycle check point. We suggest that these target genes may play important roles in PM2.5‐induced respiratory toxicity by miRNA regulation. These results demonstrate an integrated miRNA‐mRNA approach for identifying molecular events induced by environmental pollutants in an in vitro human model.

Transcriptome profile analysis of saturated aliphatic aldehydes reveals carbon number-specific molecules involved in pulmonary toxicity.

In the current study, we aimed to investigate the transcriptomic responses and identify specific molecular signatures of low-molecular-weight saturated aliphatic aldehydes (LSAAs). To evaluate the change in gene expression levels, A549 human alveolar epithelial cells were exposed to six LSAAs (propanal, butanal, pentanal, hexanal, heptanal, and octanal) for 48 h. Clustering analysis of gene expression data show that the low carbon number group (LCG; propanal, butanal, and pentanal) was distinguished from the high carbon number group (HCG; hexanal, heptanal, and octanal). Also, transcriptomic profiling indicates that the LCG exposure group was more sensitive in gene alterations than the HCG group. Supervised analysis revealed 703 LCG specific genes and 55 HCG specific genes. After gene ontology (GO) analysis on LCG specific genes, we determined several key pathways which are known as being related to increase pulmonary toxicity such as cytokine-cytokine receptor interaction and chemokine signaling pathway. However, we did not find pulmonary toxicity-related pathways through GO analysis on HCG specific genes. Genes that are expressed in only the low carbon LSAA exposure group were regarded as biomarkers of aldehyde-induced pulmonary toxicity. In conclusion, this study describes changes in gene expression profiles in the in vitro respiratory system in response to exposure to 6 LSAAs with different carbon numbers and relates these gene alterations to pulmonary toxicity-related pathways. Moreover, novel carbon number-specific genes and pathways can be more widely implemented in combination with the traditional technique for assessment and prediction of exposure to environmental toxicants.

Monitoring of deiodinase deficiency based on transcriptomic responses in SH-SY5Y cells.

Iodothyronine deiodinase types I, II, and III (D1, D2, and D3, respectively), which constitute a family of selenoenzymes, activate and inactivate thyroid hormones through the removal of specific iodine moieties from thyroxine and its derivatives. These enzymes are important in the biological effects mediated by thyroid hormones. The expression of activating and inactivating deiodinases plays a critical role in a number of cell systems, including the neuronal system, during development as well as in adult vertebrates. To investigate deiodinase-disrupting chemicals based on transcriptomic responses, we examined differences in gene expression profiles between T3-treated and deiodinase-knockdown SH-SY5Y cells using microarray analysis and quantitative real-time RT-PCR. A total of 1,558 genes, consisting of 755 upregulated and 803 downregulated genes, were differentially expressed between the T3-treated and deiodinase-knockdown cells. The expression levels of 10 of these genes (ID2, ID3, CCL2, TBX3, TGOLN2, C1orf71, ZNF676, GULP1, KLF9, and ITGB5) were altered by deiodinase-disrupting chemicals (2,3,7,8-tetrachlorodibenzo-p-dioxin, polychlorinated biphenyls, propylthiouracil, iodoacetic acid, methylmercury, β-estradiol, methimazole, 3-methylcholanthrene, aminotriazole, amiodarone, cadmium chloride, dimethoate, fenvalerate, octylmethoxycinnamate, iopanoic acid, methoxychlor, and 4-methylbenzylidene-camphor). These genes are potential biomarkers for detecting deiodinase deficiency and predicting their effects on thyroid hormone production.

Dose-response functional gene analysis by exposure to 3 different polycyclic aromatic hydrocarbons in human hepatocytes

Polycyclic aromatic hydrocarbons (PAHs) are known as carcinogen and have been studied to show modulation of gene expression by exposure to various PAHs. However, few studies have been reported on microarray analysis of dose-response relationships of gene expression patterns. For comprehensive examination of dose-response effects of PAHs on gene expression, we elicited the genes which were changed more than 1.5-fold by analysis of gene expression profiles in human hepatocellular carcinoma (HepG2) cells, exposed for 48 h to nontoxic (NT) and IC20 doses of 3 different PAHs (benzo[a]anthracene (B[a]A), benzo[k]fluoranthene (B[k]F) and indeno[1,2,3-c,d]pyrene (IND)) by using human oligonucleotide chip. Transcriptomic profiling shows different gene expression patterns in NT and IC20 exposure groups and shows higher sensitivity to gene alteration in IC20 exposure group than NT group. Through the clustering analysis of gene expression profiles, we identified 7 up- and 3 down-regulated NT dose specific genes and 401 up- and 562 downregulated IC20 dose specific genes. After Gene Ontology (GO) analysis on IC20 dose specific genes, we determined several key pathways which are known as related to increase hepatotoxicity such as metabolism of xenobiotics by cytochrome P450, Jak-STAT signaling pathway, cytokine-cytokine receptor interaction and complement and coagulation cascade. But we did not find hepatotoxicity-related pathways through GO analysis on NT dose-specific genes. Genes that are expressed in only IC20 exposure group were regarded as biomarker of PAHs-induced hepatotoxicity. In conclusion, this study describes changes in gene expression profiles in hepatocytes in response to exposure to 3 PAHs with different doses and relates these gene expression changes to hepatotoxicity related pathways. Moreover, potential new leads to genes and pathways that could play a role in liver disease prevention by PAHs were identified.