Hye Joo Chung

Influence of CYP2D6*10 on the pharmacokinetics of metoprolol in healthy Korean volunteers

Background and objective:  Genetic polymorphism of CYP2D6 leads to differences in pharmacokinetics of CYP2D6 substrates. The CYP2D6*10 allele is clinically important in Koreans because of its high frequency in Asians. We investigated whether the pharmacokinetics of metoprolol was altered by the presence of the CYP2D6*10 allele in Korean subjects.

Changes of miRNA and mRNA expression in HepG2 cells treated by epigallocatechin gallate

Epigallocatechin gallate (EGCG), a major type of green tea polyphenol, has been reported to cause hepatotoxicity when used in excess. Micro-RNAs (miRNAs) are small non-coding RNA molecules that functions as negative regulators of gene expression. They play an important role in the regulation of genes involved in the cellular and molecular responses to toxicants. To examine miRNA regulatory effect on global gene expression in EGCG-treated HepG2 cells, we performed pair-wise correlation coefficient analysis on expression levels of 22 miRNA and 27,419 mRNA, and observed negative correlations (r< −0.7) between miRNA and mRNA. We identified a total of 234 negative correlated miRNA-mRNA pairs. Gene Ontology analysis on the miRNA-correlated genes revealed significant enrichment in the several biological processes related to organic acid metabolic process, carboxylic acid metabolic process and cellular protein catabolic process. Connectivity map analysis also revealed that the expression signatures of EGCG were very similar to those of polyphenol gossypol which is hepatotoxic to animal and human.

Modulation of immune response induced by co-administration of DNA vaccine encoding HBV surface antigen and HCV envelope antigen in BALB/c mice

Plasmid DNA vaccines encoding the hepatitis B virus (HBV) surface and hepatitis C virus (HCV) envelope antigens, respectively, were constructed, and attempt were made to find the possibility of a divalent vaccine against HBV and HCV. The expression of each plasmid in Cos-1 cells was confirmed using immunocytochemistry. To measure the induced immune response by these plasmidsin vivo, female BALB/c mice were immunized intramuscularly with 100 μg of either both or just one of the plasmids. Anti-HBV and HCV-specific antibodies and related cytokines were evaluated to investigate the generation of both humoral and cellular immune responses. As a result, specific anti-HBV and anti-HCV serum antibodies from mice immunized with these plasmids were observed using immunoblot. The levels of IL-2 and RANTES showing a Th1 immune response were significantly increased, but there was no change in the level of IL-4 (Th2 immune response) in any of the immunized groups. Compared with each plasmid DNA vaccine, the combined vaccine elicited similar immune responses in both humoral and cell-mediated immunities. These results suggest that the combined DNA vaccine can induce not only comparable immunity experimentally without antigenic interference, but also humoral and Th1 dominant cellular immune responses. Therefore, they could serve as candidates for a simultaneous bivalent vaccine against HBV and HCV infections.

High-concentration Epigallocatechin Gallate Treatment Causes Endoplasmic Reticulum Stress-mediated Cell Death in HepG2 Cells

Epigallocatechin gallate (EGCG), a well-known antioxidant molecule, has been reported to cause hepatotoxicity when used in excess. However, the mechanism underlying EGCG-induced hepatotoxicity is still unclear. To better understand the mode of action of EGCG-induced hepatotoxicity, we examined the effect of EGCG on human hepatic gene expression in HepG2 cells using microarrays. Analyses of microarray data revealed more than 1300 differentially expressed genes with a variety of biological processes. Upregulated genes showed a primary involvement with protein-related biological processes, such as protein synthesis, protein modification, and protein trafficking, while downregulated genes demonstrated a strong association with lipid transport. Genes involved in cellular stress responses were highly upregulated by EGCG treatment, in particular genes involved in endoplasmic reticulum (ER) stress, such as GADD153, GADD34, and ATF3. In addition, changes in genes respo nsible for cholesterol synthesis and lipid transport were also observed, which explains the high accumulation of EGCG-induced lipids. We also identified other regulatory genes that might aid in clarifying the molecular mechanism underlying EGCG-induced hepatotoxicity.

Gene expression profiles during the activation of rat hepatic stellate cells evaluated by cDNA microarray

Hepatic stellate cells (HSCs) are activated by producing potentially injurious connective tissue components during hepatic fibrosis, thereby exerting a pivotal action in the development of liver fibrogenesis. The aim of this study was to investigate differences in gene expression patterns during the activation of HSCs using complementary cDNA microarrays. HSCs were isolated from normal rat livers and cultured for 0 (3 h), 3, 5 and 7 d. RNA was extracted from cultured cells at each point. The target RNA was hybridized to gene-specific sequence probes immobilized on chips. The hybridization signal was assessed using a confocal laser scanner. Comparison of hybridization signals and patterns allows the identification of mRNAs that are expressed differentially. Statistical analysis was used to classify and cluster the genes according to their up- or downregulation. As a result, 33 upregulated early-stage and 36 upregulated late-stage gene candidates were identified. This time-based study revealed a number of newly discovered genes involved in fibrogenesis during the activation of HSCs.

Gene Expression Profiling in C57BL/6 Mice Treated with the Anorectic Drugs Sibutramine and Phendimetrazine and Their Mechanistic Implications

Recently, obesity has become a worldwide public health concern and the use of anorectic drugs has drastically increased. In this study, sibutramine and phendimetrazine, representative marketed anorectics, were repeatedly administered per os on a daily basis into C57BL/6 mice and the effects of these drugs on food intakes, body weight changes and gene expression profiles were monitored for up to following 7 days. Methamphetamine, which has a potent anorectic effect, was used as a positive control. Anorectic effects were sustained only for two days by phendimetrazine or methamphetamine, but for six days by sibutramine. The modulations of gene expressions in the hypothalamus and the striatum were investigated using microarrays on day 2 and day 7 post-administration, which corresponded to the anorectic period and a return of appetite respectively, for all three drugs tested. Differences in overall gene expression profiles in the stratum on day 2 for sibutramine and phendimetrazine seems to reflect difference between the two in terms of the onsets of drug tolerance. According to microarray findings, the Ankrd26 gene appears to have an important anorectic role, whereas the up-regulation of the olfaction system appeared to be involved in the drug tolerance of anorectics. The microarray data presented in this study demonstrates the usefulness of gene expression analysis for gathering information on the efficacy and safety of anorectic drugs.

Phototoxicity of melatonin

Melatonin (MLT), N-acetyl-5-methoxytryptamine, is mainly secreted by the pineal gland. The ultraviolet (UV), infrared (IR) and1H-NMR spectra of irradiated and non-irradiated MLT were measured, and phototoxicity tests of MLT, anthracene (positive control) and sodium lauryl sulfate (SLS, negative control) were performed. The methods employed include bothin vitro tests such as MTS assay using the human fibroblast cell and yeast growth inhibition assay usingCandida albicans andin vivo method using the skin of guinea pig. UV absorption spectra and1H-NMR spectra of MLT were changed by UVA (365 nm, 15 J/cm2), but IR spectra of MLT were not changed. The fifty percent inhibitory concentration (IC50) ratio (UV-/UV+) of MLT was 10. The inhibition zone of irradiated-paper disks treated with MLT was not observed. According to the results of histopathological examination, no pathologic lesion was observed in the non-irradiated group, but slight degeneration of keratinocytes in the epidermis, hemorrhage and vasodilation in dermis were observed in the irradiated group. These results indicate that the molecular structure of MLT is altered by UVA to unidentified photoproducts and a moderate phototoxicity of MLT is predicted.

Analysis of Gene Expression in Mouse Spinal Cord-derived Neural Precursor Cells During Neuronal Differentiation

The differentiation of neural precursor cells (NPCs) into neurons and astrocytes is a process that is tightly controlled by complicated and ill-defined gene networks. To extend our knowledge to gene networks, we performed a temporal analysis of gene expression during the differentiation (2, 4, and 8 days) of spinal cord-derived NPCs using oligonucleotide microarray technology. Out of 32,996 genes analyzed, 1878 exhibited significant changes in expression level (fold change>2, p

The application of Ion chromatographic method for bioavailability and stability test of iron preparations

Postabsorptive serum iron level was determined after oral administration of the compounds to human. In serum and whole blood, Fe3+ was measured by ion chromatography (IC) using a pyridine-2,6-dicarboxylic acid (PDCA) as an eluent. The serum sample solutions were pretreated with I N HCl and 50% TCA. The whole blood sample solutions were treated with 3 N HCl for 30 min at 125°C. The limit of detection (LOD) of the IC technique is 0.2 μM for Fe2+ and 0.1 μM for Fe3+ The area under concentration (AUC) can be obtained by the above analytical condition. In addition, to compare the stability of Fe2+ to that of Fe3+ in pharmaceutical preparations, accelerated stability test was carried out. After storing the samples under 40°C, 75%RH in light-resistant container for various time intervals, the contents of iron of different valencies were determined separately by the IC technique and the change and/or the interchange of among those iron species in preparations was investigated. Iron raw materials are stable, but Fe2+ in Fe3+ source materials was slightly converted to Fe3+ by oxidation. Fe2+ in Fe3+ source raw materials and Fe3+ in Fe2+ raw materials are determined as impurities. Therefore, IC technique is found to be an appropriate method for comparative evaluation of dissimilar bioavailability of Fe2+ and Fe3+, stability of Fe2+ and Fe3+ raw materials and preparations.

The activity of dopamine β-hydroxylase of central nervous system in genetically epilepsy prone rats

Abnormality in the central noradrenergic system may be related to the seizure prone state in the genetically epilepsy prone rats (GEPR). The present work deals with the characterization of the deficit in noradrenergic system if susceptitibility and intensity of seizure are dependent on central noradrenregic activities by comparing the activities of dopamine β-hydroxylase (DBH) which hydroxylates dopamine into noradrenaline. DBH activities were measured in 5 areas of brain of normal rats, naive GEPR, and severe GEPR. The results suggest that lower DBH activities in the midbrain of GEPRs may positively be coupled to the susceptibility to seizure, whereas the same characteristics of the naive or severe GEPR are not necessarily in parallel with the intensity of seizure.