Biomedical subjects

Hye Kyung Kim

Publications and source records attributed to Hye Kyung Kim.

At least 19 recordsLinked to original sources

PubMed2007

Activation effects of Allium tuberosum Rottl. on choline acetyltransferase.

An ethanolic extract of Allium tuberosum Rottl. demonstrated potent choline acetytrasferase (ChAT) activating activity (45%) among 30 screened Korean edible plants. The ChAT activator of A. tuberoum Rottl. was purified and identified as ferulic acid [4-hydroxy-3-methoxycinnamic acid] via silica-gel open-column chromatography, HPLC, EI-MS, and 1H/13C-NMR. The ferulic acid from A. tuberoum Rottl. exhibited ChAT activity in a dose-dependent manner and showed notoxicity in a cell viability assay (MTT assay). We suggest that the ferulic acid from A. tuberoum Rottl. was the strong ChAT activator.

Cell Line↗

PubMed2006

Ganoderma lucidum extract stimulates glucose uptake in L6 rat skeletal muscle cells.

The effect of Ganoderma lucidum extract on glucose uptake was studied in L6 rat skeletal muscle cells. G. lucidum extract increased glucose uptake about 2-fold compared to control. The extract stimulated the activity of phosphatidylinositol (PI) 3-kinase which is a major regulatory molecule in the glucose uptake pathway. About 7-fold increased activity of a PI 3-kinase was observed after treatment with G. lucidum extract, whereas PI 3-kinase inhibitor, LY294002, blocked the G. lucidum extract-stimulated PI 3-kinase activity in L6 skeletal muscle cells. Protein kinase B, a downstream mediator of PI 3-kinase, was also activated by G. lucidum extract. We then assessed the activity of AMP-activated protein kinase (AMPK), another regulatory molecule in the glucose uptake pathway. G. lucidum extract increased the phosphorylation level of both AMPK alpha1 and alpha2. Activity of p38 MAPK, a downstream mediator of AMPK, was also increased by G. lucidum extract. Taken together, these results suggest that G. lucidum extract may stimulate glucose uptake, through both PI 3-kinase and AMPK in L6 skeletal muscle cells thereby contributing to glucose homeostasis.

AMP-Activated Protein Kinases↗

PubMed2006

Anti-diabetic effects of electrolyzed reduced water in streptozotocin-induced and genetic diabetic mice.

Oxidative stress is produced under diabetic conditions and is likely involved in progression of pancreatic beta-cell dysfunction found in diabetes. Both an increase in reactive oxygen free radical species (ROS) and a decrease in the antioxidant defense mechanism lead to the increase in oxidative stress in diabetes. Electrolyzed reduced water (ERW) with ROS scavenging ability may have a potential effect on diabetic animals, a model for high oxidative stress. Therefore, the present study examined the possible anti-diabetic effect of ERW in two different diabetic animal models. The genetically diabetic mouse strain C57BL/6J-db/db (db/db) and streptozotocin (STZ)-induced diabetic mouse were used as insulin deficient type 1 and insulin resistant type 2 animal model, respectively. ERW, provided as a drinking water, significantly reduced the blood glucose concentration and improved glucose tolerance in both animal models. However, ERW fail to affect blood insulin levels in STZ-diabetic mice whereas blood insulin level was markedly increased in genetically diabetic db/db mice. This improved blood glucose control could result from enhanced insulin sensitivity, as well as increased insulin release. The present data suggest that ERW may function as an orally effective anti-diabetic agent and merit further studies on its precise mechanism.

Animals↗

PubMed2006

The purification, crystallization and preliminary diffraction of a glycerophosphodiesterase from Enterobacter aerogenes.

The metallo-glycerophosphodiesterase from Enterobacter aerogenes (GpdQ) has been cloned, expressed in Escherichia coli and purified. Initial screening of crystallization conditions for this enzyme resulted in the identification of needles from one condition in a sodium malonate grid screen. Removal of the metals from the enzyme and subsequent optimization of these conditions led to crystals that diffracted to 2.9 angstroms and belonged to space group P2(1)3, with unit-cell parameter a = 164.1 angstroms. Self-rotation function analysis and V(M) calculations indicated that the asymmetric unit contains two copies of the monomeric enzyme, corresponding to a solvent content of 79%. It is intended to determine the structure of this protein utilizing SAD phasing from transition metals or molecular replacement.

Bacterial Proteins↗

PubMed2006

Crystal structure of 2-nitropropane dioxygenase complexed with FMN and substrate. Identification of the catalytic base.

Nitroalkane compounds are widely used in chemical industry and are also produced by microorganisms and plants. Some nitroalkanes have been demonstrated to be carcinogenic, and enzymatic oxidation of nitroalkanes is of considerable interest. 2-Nitropropane dioxygenases from Neurospora crassa and Williopsis mrakii (Hansenula mrakii), members of one family of the nitroalkane-oxidizing enzymes, contain FMN and FAD, respectively. The enzymatic oxidation of nitroalkanes by 2-nitropropane dioxygenase operates by an oxidase-style catalytic mechanism, which was recently shown to involve the formation of an anionic flavin semiquinone. This represents a unique case in which an anionic flavin semiquinone has been experimentally observed in the catalytic pathway for oxidation catalyzed by a flavin-dependent enzyme. Here we report the first crystal structure of 2-nitropropane dioxygenase from Pseudomonas aeruginosa in two forms: a binary complex with FMN and a ternary complex with both FMN and 2-nitropropane. The structure identifies His(152) as the proposed catalytic base, thus providing a structural framework for a better understanding of the catalytic mechanism.

Amino Acid Sequence↗

PubMed2006

Improvement of lipid profile by amaranth (Amaranthus esculantus) supplementation in streptozotocin-induced diabetic rats.

BACKGROUND/AIMS: Lipid disorders may exacerbate some complications of diabetes. Amaranth has been reported to exhibit a cholesterol-lowering effect in hyperlipidemic animals. The present study was designed to investigate the effect of amaranth on serum glucose and the lipid profile in diabetic rats. METHODS: Male Sprague-Dawley rats were assigned to normal control, diabetic control, diabetic amaranth-grain (AG)-supplemented (500 g/kg diet) and diabetic amaranth-oil (AO)-supplemented (90 g/kg diet) groups and fed experimental diets for 3 weeks. Effects were monitored on glucose tolerance, serum and liver lipids, and fecal excretions of lipids and bile acids. RESULTS: Fasting serum glucose levels and the glucose tolerance of diabetic rats were improved by AG and AO supplementation. Serum and liver lipids such as total cholesterol, triglyceride (TG) and very-low-density lipoprotein cholesterol concentrations were also lowered in diabetic animals by AG and AO consumption. Fecal excretions of cholesterol, TG and bile acid were markedly reduced in diabetic rats, and these parameters were dramatically increased by AG and AO supplementation. CONCLUSION: AG and AO supplementation improve the glucose and lipid metabolism in streptozotocin-induced diabetic rats.

Amaranthus↗

PubMed2006

Effects of ephedrae herba on melanogenesis and gene expression profiles using cDNA microarray in B16 melanocytes.

Ephedrae Herba (EH) is obtained by drying the stems of Ephedra sinica Stapf (family Ephedraceae). EH has been used clinically to treat colds and to reduce edema in skin. The effects of EH on melanogenesis were studied in B16 murine melanocytes. The tyrosinase activity and melanin content were measured after incubation with EH. Both reverse transcription-polymerase chain reaction and cDNA microarray analysis were used to study the mechanism of EH action. EH decreased tyrosinase activity and melanin content in a dose-dependent manner. EH decreased microphthalmia-associated transcription factor (MITF) and tyrosinase gene expression. These effects were controlled by MITF-mediated regulation of tyrosinase gene expression. EH also altered the expression of about 100 other genes. These results suggest that EH may be used clinically to treat freckles and liver spots.

Animals↗

PubMed2006

Protective effect of Rosa laevigata against amyloid beta peptide-induced oxidative stress.

The amyloid beta (Abeta) peptide is known to increase free radical production in nerve cells, leading to cell death. To investigate the effect of Rosa laevigata against Abeta-induced oxidative damage, in vitro assays and in vivo behavioral tests were performed. R. laevigata showed cell protective effects against oxidative stress-induced cytotoxicity. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) reduction assay exhibited significant increase in cell viability when rat pheochromocytoma (PC 12) cells were treated with R. laevigata extracts. Administration of R. laevigata extracts to mice significantly reversed the Abeta-induced learning and memory impairment in in vivo behavioral tests. These results suggest that R. laevigata extracts can reduce the cytotoxicity of Abeta in PC 12 cells, possibly by the reduction of oxidative stress, and these extracts may be useful in the prevention of Alzheimer's disease.

Amyloid beta-Peptides↗

PubMed2006

Antihypertensive effects of Gynura procumbens extract in spontaneously hypertensive rats.

Aqueous extracts of Gynura procumbens (Lour.) Merr. were orally administered to spontaneously hypertensive (SHR) rats for 4 weeks, and antihypertensive effects were determined. Oral administration of 500 mg/kg of G. procumbens (Lour.) Merr. extract (GPE) resulted in significantly lower blood pressure in SHR rats compared with SHR rats not given GPE (P < .05). Furthermore, GPE-administered rats had significantly lower serum lactate dehydrogenase, creatine phosphate kinase, and increased nitric oxide (NO), a known vasodilator, compared with the non-GPE-administered SHR group (P < .05). These results suggest that oral administration of aqueous GPE may be useful for prevention and treatment of hypertension through increasing NO production in blood vessels.

Animals↗

PubMed2006

Suppressive effect of Punica granatum on the production of tumor necrosis factor (Tnf) in BV2 microglial cells.

While the anti-oxidant properties of Punica granatum methanol extract (PGMF) are well documented, little is known concerning the anti-inflammatory effect of Punica granatum. PGMF was pretreated in BV2 microglial cells and cells were stimulated to induce inflammation by lipopolysaccharide (LPS). The effect of PGME on the production and expression of tumor necrosis factor alpha (Tnf, previously known as Tnf alpha) was determined by enzyme-linked immunosorbent assay (ELISA), western blotting, and reverse transcription-polymerase chain reaction (RT-PCR). In addition, the expression of nuclear factor kappa b (Nfkappab) was measured using an electrophoretic mobility shift assay (EMSA). By ELISA, PGME at the concentrations of 1, 5, 10, and 50 microg/ml inhibited Tnf production in LPS-stimulated cells by 30.2, 42.3, 57.6, and 88.4%, respectively, compared to LPS-stimulated cells. The LPS-stimulated Tnf production was reduced with a dose-dependent manner. Immuno blot and RT-PCR analyses revealed that PGME of 5 and 50 microg/ml inhibited the expression of both protein and mRNA levels of Tnf compared to LPS-stimulated cells. EMSA revealed that PGME of 5 and 50 microg/ml blocked the LPS-stimulated activation of Nfkappab. These data suggest that PGME may suppress LPS-stimulated Tnf production through inhibition of Nfkappab in BV2 microglia cells.

Animals↗

PubMed2005

Following directed evolution with crystallography: structural changes observed in changing the substrate specificity of dienelactone hydrolase.

The enzyme dienelactone hydrolase (DLH) has undergone directed evolution to produce a series of mutant proteins that have enhanced activity towards the non-physiological substrates alpha-naphthyl acetate and p-nitrophenyl acetate. In terms of steady-state kinetics, the mutations caused a drop in the K(m) for the hydrolysis reaction with these two substrates. For the best mutant, there was a 5.6-fold increase in k(cat)/K(m) for the hydrolysis of alpha-naphthyl acetate and a 3.6-fold increase was observed for p-nitrophenyl acetate. For alpha-naphthyl acetate the pre-steady-state kinetics revealed that the rate constant for the formation of the covalent intermediate had increased. The mutations responsible for the rate enhancements map to the active site. The structures of the starting and mutated proteins revealed small changes in the protein owing to the mutations, while the structures of the same proteins with an inhibitor co-crystallized in the active site indicated that the mutations caused significant changes in the way the mutated proteins recognized the substrates. Within the active site of the mutant proteins, the inhibitor was rotated by about 180 degrees with respect to the orientation found in the starting enzyme. This rotation of the inhibitor caused the displacement of a large section of a loop on one side of the active site. Residues that could stabilize the transition state for the reaction were identified.

Binding Sites↗

PubMed2005

Citrus Reticulata blanco induces apoptosis in human gastric cancer cells SNU-668.

Citrus fruits have been known to reduce the proliferation of many cancer cells. The antiproliferative effects of Citrus reticulata Blanco (CR) extract, the immature tangerine peel, on human gastric cancer cell line SNU-668 were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, 4,6-diamidineo-2-phenylindole staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, reverse transcription-polymerase chain reaction expressions of BCL-2, BAX and CASP-3 genes, caspase-3 activity, and immunocytochemistry of caspase-3. From the results of the morphological and biochemical assays, CR (50 microg/ml) increased the apoptosis of human gastric cancer cells with typical apoptotic characteristics, including morphological changes of chromatin condensation and apoptotic body formation. CR (50 microg/ml) reduced the expression of BCL-2, whereas the expression of BAX and CASP-3 was increased compared with the control group. Furthermore, caspase-3 activity and caspase-3 protein expression in the CR-treated group was significantly increased compared with that in control group. These results suggest that CR may induce the apoptosis through the caspase-3 pathway in human gastric cancer cells.

Antineoplastic Agents↗

PubMed2005

Protective effects of aucubin isolated from Eucommia ulmoides against UVB-induced oxidative stress in human skin fibroblasts.

Ultraviolet-B (UVB) irradiation has been demonstrated to produce reactive oxygen species (ROS) in the cells and skin, which induces the synthesis of matrix metalloproteinases (MMPs), causing skin photoaging. Using the human skin fibroblast HS68 cell line in the present study, we investigated the photoprotective effects of aucubin from Eucommia ulmoides. Pretreatment with aucubin significantly inhibited the production of MMP-1 by 57% when compared to the UVB-irradiated cells. Additionally, the senescence-associated beta-galactosidase (SA beta-gal) activity was markedly decreased in the presence of aucubin, which indicates it as an antiphoto-induced aging compound. As the effect of aucubin was determined against ROS, the inhibited ROS formation and malondialdehyde (MDA) levels, and the increased cell viability and glutathione (GSH) level were observed with aucubin under UVB irradiation. Based upon these results, it was suggested that aucubin might play an important role in the cellular defense mechanism against UV radiation-induced photoaging. An understanding of the antioxidant properties of aucubin could, in part, act to elucidate its protective mechanism on the human skin photoaging.

Eucommiaceae↗

PubMed2005

Increased expression of hypothalamic NADPH-diaphorase neurons in mice with iron supplement.

Iron deficiency is known as the most important nutritional problem in the world. The loss of appetite is a common characteristic of iron deficiency. Iron-containing heme is required as a cofactor for nitric oxide synthase (NOS) which produces nitric oxide (NO). NOS in the central nervous system has been suggested to regulate food intake. Hence, we examined the expression of hypothalamic NOS at various levels of dietary iron. ICR mice (n = 30) were randomly divided into three groups based on the level of dietary iron and fed experimental diets for 4 weeks: the normal-iron diet group (7 mg/kg diet, n = 10), the low-iron diet group (21 mg/kg diet, n = 10) and the high-iron diet group (42 mg/kg diet, n = 10). Expression of NOS in the paraventricular nucleus (PVN) and lateral hypothalamic area (LHA) of hypothalamus was examined by histochemistry for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-diaphorase). The high-iron diet mice showed significantly higher staining intensity of NADPH-diaphorase-positive neurons in the PVN and LHA than the normal- and low-iron diet mice.

Animals↗

PubMed2005

Dissimilarity in Fos and Jun immunoreactivity in hypothalamic regions between obese and lean Zucker rats.

The obese Zucker rat, whose genotype is transmitted in an autosomal recessive fashion, is an animal model widely used in the field of obesity. The expression of the nuclear transcription factors c-Fos and c-Jun in the paraventricular nucleus (PVN) and arcuate nucleus (ARC) of the hypothalamus of obese Zucker rats was studied using immunohistochemical methods. PVN and ARC in the hypothalamus are known as centers for the control of food intake. It was observed that the numbers of c-Fos-positive and c-Jun-positive neurons in these regions decreased in obese rats compared to lean rats, and that difference was more evident in the ARC than in the PVN which has to do with the regulation of body weight. The reduction in expression in the ARC of obese rats was greater for c-Jun than for c-Fos. These results suggest a possible difference in Fos immunoreactivity in hypothalamic resistance to circulating satiety factors in genetically obese Zucker rats.

Animals↗

PubMed2004

Crystallization and preliminary X-ray crystallographic analysis of a putative agmatinase from Deinococcus radiodurans.

Agmatine, which results from the decarboxylation of arginine by arginine decarboxylase, is a metabolic intermediate in the biosynthesis of putresine and higher polyamines. The enzyme agmatinase catalyses the hydrolysis of agmatine to putresine and urea. Recent studies indicate that agmatinase plays important roles in mammals. Human mitochondrial agmatinase shows a considerable level of sequence similarity to bacterial agmatinases, including a putative agmatinase from Deinococcus radiodurans. The putative agmatinase from D. radiodurans has been overexpressed in Escherichia coli and crystallized at 297 K using polyethylene glycol 3000 as a precipitant. X-ray diffraction data were collected to 1.80 A from a crystal grown in the presence of Mn2+ and 1,6-hexanediamine. The crystals are orthorhombic, belonging to the space group P2(1)2(1)2(1), with unit-cell parameters a = 81.77, b = 131.44, c = 168.85 A, alpha = beta = gamma = 90 degrees. A hexameric molecule is likely to be present in the asymmetric unit, giving a crystal volume per protein weight (VM) of 2.15 A3 Da(-1) and a solvent content of 41.8%.

Crystallization↗

PubMed2004

Melatonin increases cell proliferation in the dentate gyrus of maternally separated rats.

Melatonin in mammals, produced by the pineal gland and elsewhere, has shown antioxidant and neuroprotective properties in neuronal cells. We investigated whether melatonin would increase newly born cells (cell proliferation) in the dentate gyrus of maternally separated rats. To examine the effect of melatonin on cell proliferation of the dentate gyrus in maternally separated rats, 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry was performed. Rat pups were separated from their mothers and socially isolated on postnatal day 14. Melatonin (10 mg/kg, i.p.) and BrdU (50 mg/kg, i.p.) were given to them for 7 days. The number of BrdU-positive cells was significantly increased in the dentate gyrus of maternally separated pups with melatonin administration (P < 0.001). In addition, the expression of glucocorticoid receptor was significantly decreased in the dentate gyrus compared with maternally separated pups not given melatonin (P < 0.001). This is the first report that melatonin increases cell proliferation in the dentate gyrus of maternally separated rats.

Animals↗

PubMed2004

Coptidis rhizoma induces apoptosis in human colorectal cancer cells SNU-C4.

Coptidis rhizoma has been used as traditional herb medicine in gastrointestinal disorders in the Eastern Asia. We investigated whether the anticancer effects of the C. rhizoma induced apoptosis on human colorectal cancer cells SNU-C4. The cytotoxic effect of C. rhizoma was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. To determine apoptotic cell death, 4,6-diamidino-2-phenylindole (DAPI) staining, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay, reverse transcription-polymerase chain reaction (RT-PCR) and caspase-3 enzyme assay were performed. In this study, C. rhizoma treatment (100 microg/ml) revealed typical morphological apoptotic features. Additionally, C. rhizoma treatment (100 microg/ml) increased levels of BAX and CASPASE-3, and decreased levels of BCL-2. Caspase-3 enzyme activity by treatment of C. rhizoma (100 microg/ml) also significantly increased compared to the control (p < 0.05). These data indicate that C. rhizoma caused cell death by apoptosis through caspase pathways on human colorectal cancer cells SNU-C4.

Anticarcinogenic Agents↗