Biomedical subjects

Dong-Kwon Rhee

Publications and source records attributed to Dong-Kwon Rhee.

At least 19 recordsLinked to original sources

PubMed2006

Allicin, a major component of garlic, inhibits apoptosis of macrophage in a depleted nutritional state.

OBJECTIVE: Allicin is believed to be the main component responsible for the biological activity of garlic. The regulation of cell death might have therapeutic potential in many diseases, and previous studies have demonstrated that allicin stimulates the functional activity of macrophages. Therefore, this study examined the effects of allicin on the apoptosis of macrophages induced by serum- and amino acid-free culture. METHODS: The apoptosis of peritoneal macrophages was examined after pretreating them with allicin and incubating them in a depleted nutritional state. The rate of apoptosis was determined using propidium iodide staining analysis using flow cytometry, DNA fragmentation, and a caspase-3 assay. Western blot analysis was used to examine the changes in the pro- or antiapoptotic protein expression levels. RESULTS: DNA fragmentation and propidium iodide staining analyses revealed that allicin decreased the malnutrition-induced apoptosis of macrophages. The level of Bax expression, the amount of cytochrome-c released from the mitochondria, and the caspase-3 activity were also lower in the allicin-treated macrophages than in the untreated macrophages in a depleted nutritional state. Moreover, the MEK (mitogen-activated protein kinase/extracellular signal-regulated kinase-kinase) inhibitor suppressed the allicin-induced inhibition of apoptosis in a depleted nutritional state and allicin increased the level of ERK1/2 phosphorylation. CONCLUSION: Allicin inhibits the apoptosis of macrophages in a depleted nutritional state through the MEK/extracellular signal-regulated kinase pathway.

Animals↗

PubMed2006

Inhibition of ICAM-1 expression by garlic component, allicin, in gamma-irradiated human vascular endothelial cells via downregulation of the JNK signaling pathway.

Ionizing radiation used in cancer therapy frequently exerts damaging effects on normal tissues and induces a complex response including inflammation. Since the upregulation of adhesion molecules on endothelial cell surface has been known to be associated with inflammation and our previous data showed that irradiation enhanced adhesion molecules expression, interfering with the expression of adhesion molecules may be an important therapeutic target of inflammatory diseases. We examined the effect of allicin, a major component of garlic, on the induction of intercellular adhesion molecule-1 (ICAM-1) by gamma-irradiation (gamma IR) and the mechanisms of its effect in gamma-irradiated human umbilical vein endothelial cells (HUVECs). HUVECs were pretreated for 20 h with allicin (0.01-1 micro g/ml) and then exposed to 8 Gy radiation. Allicin significantly inhibited gamma IR-induced surface expression of ICAM-1 and ICAM mRNA in a dose-dependent manner. In addition, pretreatment with allicin resulted in the decrease of AP-1 activation and phosphorylation of the c-Jun NH2-terminal kinase (JNK) induced by gamma IR. These results suggest that allicin downregulates gamma IR-induced ICAM-1 expression via inhibition of both AP-1 activation and the JNK pathway and may be considered in therapeutic strategies for the management of patients treated with radiation therapy.

Cell Adhesion↗

PubMed2006

Analyses of single nucleotide polymorphisms and haplotype linkage of the human ABCB1 (MDR1) gene in Korean.

Single nucleotide polymorphisms (SNPs) in the MDR1 gene that are responsible for drug efflux can cause toxicity. Therefore, this study determined the SNPs of the Korean MDR1 gene, and analyzed the haplotypes and a linkage disequilibrium (LD) of the SNPs determined. The frequency of 9 SNPs from the MDR1 gene was determined by PCR-RFLP analyses of 100 to 500 healthy individuals. The frequcies of the SNPs were C3435T (47.7%), G2677T (37.6%), G2677A (4.4%), T1236C (21.7%), T129C (8%), A2956G (2.5%), T307C (1.5%), A41aG (9.2%), C145G (0%), and G4030C (0 %). Analyses of the haplotype structure and an estimation of the LD of the combined polymorphisms demonstrated that the frequency of the 1236T-2677G-3435T haplotype is much higher in Koreans (14.1%) than in Chinese and western black Africans and the C3435T SNP in Koreans appears to have LD with T129C in Koreans for the first time. These results provide insight into the genetic variation of MDR1 in Koreans, and demonstrated the possibility of a new LD in this gene.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2006

Gamma-irradiation-induced intercellular adhesion molecule-1 (ICAM-1) expression is associated with catalase: activation of Ap-1 and JNK.

The ionizing radiation used in cancer therapy frequently produces damage to normal tissues and induces complex responses, including inflammation. The upregulation of the intercellular adhesion molecule-1 (ICAM-1) in response to numerous inducing factors is associated with inflammation. Therefore, this study examined the molecular mechanisms responsible for ICAM-1 expression induced by gamma-irradiation (gammaIR). ICAM-1 mRNA and cell surface expression were induced in A549 human lung epithelial cells after exposing them to gammaIR. Catalase expression and activity were also increased in gammaIR-treated cells. Treatment of the gammaIR-treated cells with catalase resulted in a significant increase in the ICAM-1 cell surface expression level. The catalase inhibitor 3-amino-1,2,4-triazole (AT) reduced the level of ICAM-1. Electrophoretic mobility shift assay (EMSA) analysis showed that activating protein 1 (AP-1) was activated by gammaIR, whereas NF-kappaB was not. Specific Jun N-terminal kinase (JNK) inhibition attenuated the upregulation of gammaIR stimulated ICAM-1. Western blot analysis revealed a marked elevation in activation of JNK. In addition, pretreatment with AT resulted in a decrease in the level of JNK phosphorylation and AP-1 activation. Overall, data suggest that induction of ICAM-1 expression by gammaIR is associated with catalase. Furthermore, catalase, JNKs, and AP-1 activation induce ICAM-1 upregulation through a sequential process.

Catalase↗

PubMed2006

Regulation of insulin secretion and beta-cell mass by activating signal cointegrator 2.

Activating signal cointegrator 2 (ASC-2) is a transcriptional coactivator of many nuclear receptors (NRs) and other transcription factors and contains two NR-interacting LXXLL motifs (NR boxes). In the pancreas, ASC-2 is expressed only in the endocrine cells of the islets of Langerhans, but not in the exocrine cells. Thus, we examined the potential role of ASC-2 in insulin secretion from pancreatic beta-cells. Overexpressed ASC-2 increased glucose-elicited insulin secretion, whereas insulin secretion was decreased in islets from ASC-2+/- mice. DN1 and DN2 are two dominant-negative fragments of ASC-2 that contain NR boxes 1 and 2, respectively, and block the interactions of cognate NRs with the endogenous ASC-2. Primary rat islets ectopically expressing DN1 or DN2 exhibited decreased insulin secretion. Furthermore, relative to the wild type, ASC-2+/- mice showed reduced islet mass and number, which correlated with increased apoptosis and decreased proliferation of ASC-2+/- islets. These results suggest that ASC-2 regulates insulin secretion and beta-cell survival and that the regulatory role of ASC-2 in insulin secretion appears to involve, at least in part, its interaction with NRs via its two NR boxes.

Amino Acid Motifs↗

PubMed2005

Methamphetamine administration produces immunomodulation in mice.

The abuse of methamphetamine (MA) is an increasingly growing problem globally and produces serious side effects. In the present study, the immunomodulating effects of MA were examined on the immune system after MA (5 mg/kg body weight) was administered daily orally for 14 d. The immune system was evaluated by the antibody response to sheep red blood cells (SRBC; plaque assay and serum immunoglobulin [Ig] G), natural killer (NK) activity, lymphocyte subpopulations in the spleen and thymus, and concanavalin A (Con A)- and lipopolysaccharide (LPS)-stimulated lymphocyte proliferation using splenocytes. Body weight, spleen weight, and thymus weight generally decreased in MA-treated mice. MA treatment induced an increase in the percentage of CD4(+) cells with simultaneous decrease in the percentages of CD8(+) and double-positive CD4(+)CD8(+) in thymus. MA inhibited the IgM plaque-forming cell number, and lowered the level of IgG, the proliferation of mitogen-stimulated B and T cells, and the growth of granulocyte-macrophage colony-forming units (CFU-GM). Exposure to MA also decreased interleukin-2 production by splenocytes. In contrast, splenic NK activity in exposed mice was significantly enhanced. Taken together, data indicate that the immune system was suppressed by oral MA exposure.

Animals↗

PubMed2005

Immunomodulatory function of murine NK cell activity by alginate.

The in vivo immunomodulatory function of the activity of murine natural killer (NK) cells induced by high mannuronic acid-containing alginate (HMA) was examined. HMA was injected i.p at doses of 25 and 100 mg/kg. The NK activity was 3 times higher with 100 mg/kg HMA than the baseline. In addition, in vitro studies of splenocytes cultured with HMA for 20 h showed a significant increase in NK activity at E:T ratio of 100:1; a 160% and 210% increase at 10 and 100 microg/mL, respectively. There was a six fold increase in interferon-gamma production in a postculture of splenocytes with 100 microg/mL HMA. HMA had no suppressive effects on the lymphocyte function in the presence or absence of mitogens. This suggests that HMA is useful in cancer immunotherapy.

Alginates↗

PubMed2005

Comparison of the rabbit pyrogen test and Limulus amoebocyte lysate (LAL) assay for endotoxin in hepatitis B vaccines and the effect of aluminum hydroxide.

The rabbit pyrogen test and Limulus amoebocyte lysate (LAL) assay have been used to detect endotoxins in vaccines, but interactions between the endotoxins and proteins or aluminum hydroxide can interfere with the results. Currently, the rabbit pyrogen test is used to detect endotoxin in hepatitis B (HB) vaccines even though the HB surface protein, the active ingredient, is over-expressed in and purified from eukaryotic cells which lack endotoxin. Therefore, we examined the possibility of replacing the animal tests with the more efficient LAL test. To this end, we determined whether the aluminum hydroxide in the HB vaccines affects the rabbit pyrogen test and the LAL assay. HB vaccines and HB protein solutions spiked with lipopolysaccharide (LPS) produced almost the same dose-dependent temperature rise in rabbits, indicating that the aluminum hydroxide in the HB vaccine does not interfere with the pyrogenic response in rabbit. In contrast, a spike recovery study showed that aluminum hydroxide interfered with the LAL clot and kinetic assays; however, the LAL clot assay was effective at detecting endotoxin without loss of LAL activity after serial dilution of the samples. Furthermore, there was good correlation in the LAL clot assay between the amount of LPS added and the amount recovered. However, both turbidimetric and chromogenic kinetic assays displayed no correlation between the LPS amount added and recovered. Our results suggest that the LAL clot assay is sensitive and reliable when samples are properly prepared, and can be used to replace the rabbit pyrogen test for the detection of endotoxin in HB vaccines.

Aluminum Hydroxide↗

PubMed2005

Ca2+-dependent expression of the CIRCE regulon in Streptococcus pneumoniae.

DnaK and GroEL play a pivotal role in protein folding, and promote cell proliferation and survival. In Gram-positive and several Gram-negative bacteria, HrcA represses the transcription of dnaK and groE operons by binding to the highly conserved CIRCE (controlling inverted repeat of chaperone expression) operator sequence in the presence of GroEL. HrcA may respond to environmental stress and various other factors that modulate the transcription of the dnaK and groE operons. However, the mechanisms by which these factors modulate the activity of HrcA remain elusive. Here, we show that the thermoresistance of Streptococcus pneumoniae is significantly repressed in the presence of Ca2+. Furthermore, heat shock-induced expression of the CIRCE regulon in S. pneumoniae is repressed in the presence of Ca2+, although to a lesser degree than in the hrcA mutant, strongly suggesting that HrcA inhibits expression of the CIRCE regulon in a Ca2+-dependent manner. Although HrcA does not bind directly to Ca2+, its hydrophobicity is increased in the presence of the metal ion. Taken together, our observations suggest that Ca2+ induces conformational changes, such as exposure of the hydrophobic surfaces of HrcA, which facilitate binding to GroEL. Alternatively, the presence of Ca2+ may facilitate GroEL in interacting freely with HrcA. This, in turn, enhances access to CIRCE and leads to repression of the dnaK and groE operons in S. pneumoniae.

Bacterial Proteins↗

PubMed2004

Caspase-independent cell death by allicin in human epithelial carcinoma cells: involvement of PKA.

Allicin, the major component of Garlic (Allium sativum) was examined for the ability to induce apoptosis and the mechanism of the induction of apoptosis in human epithelial carcinoma cells. Allicin inhibited cell growth and induced apoptosis in gastric epithelial cells. Treatment with allicin resulted in morphological changes, DNA fragmentation, hypodiploid DNA contents and the translocation of Bax to mitochondria. The release of cytochrome c from mitochondria into the cytosol, which is an initiator of the activation of caspase cascades, was observed in allicin-treated cells. However, pretreatment with Z-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk), a broad spectrum of caspase inhibitor, could not rescue apoptotic cells from allicin toxicity. Coincidently, caspase-3 activation and cleavage of PARP were not detected. In addition, caspase independent apoptosis-inducing factor (AIF) was released from mitochondria after treatment with allicin. After pre-incubation of cells with the protein kinase A (PKA) inhibitor H-89, allicin was not capable of inducing an increase of the rate of apoptosis with affecting the expression levels of Bax and AIF. These data demonstrate that allicin induces a caspase-independent apoptotic pathway mediated by mitochondrial release of AIF and PKA appears to be involved in allicin-induced apoptosis in gastric epithelial cells.

Apoptosis↗

PubMed2004

Modulation of murine macrophage function by methamphetamine.

The abuse of methamphetamine (MA) is an increasingly growing problem globally and produces serious side effects. In the present study, the immunomodulating effects of MA were examined on murine peritoneal macrophages after MA (5 mg/kg body weight) was administered daily orally for 2 wk. When purified macrophages were stimulated with lipopolysaccharide (LPS), the tumoricidal activity induced by LPS was significantly suppressed by MA. MA also inhibited poly I:C-induced antiviral activity in macrophages and decreased the number of peritoneal macrophages. FACS analysis showed that the expression of CD14 was markedly decreased by MA in LPS-stimulated macrophages. The production of nitric oxide (NO) and tumor necrosis factor (TNF)-alpha: which are known to be major effector molecules in macrophage-mediated cytotoxicity, was decreased by MA. MA produced a significant effect on phagocytosis and interleukin-1 (IL-1) and IL-6 at 14 d. In addition, the level of hydrogen peroxide (H2O2) was not altered by MA. Taken together, these data indicate that MA has a differential immunomodulating effect on macrophage secretory and cellular activities.

Animals↗

PubMed2004

The ClpP protease of Streptococcus pneumoniae modulates virulence gene expression and protects against fatal pneumococcal challenge.

Streptococcus pneumoniae usually colonizes the nasopharynx of humans asymptomatically but occasionally translocates from this niche to the lungs, the brain, and the blood, causing potentially fatal infections. Spread to other host tissues requires a significant morphological change and the expression of virulence factors, such as capsular polysaccharide, and virulence proteins, such as pneumolysin (Ply), PspA, and CbpA. Modulation of the expression of pneumococcal virulence genes by heat shock and by heat shock proteins ClpL and ClpP, as well as the attenuation of virulence of a clpP mutant in a murine intraperitoneal infection model, was demonstrated previously. In this study, we further investigated the underlying mechanism of virulence attenuation by the clpP mutation. The half-lives of the mRNAs of ply and of the first gene of the serotype 2 capsule synthesis locus [cps2A] in the clpP mutant were more than twofold longer than those of the parent after heat shock, suggesting that the mRNA species were regulated posttranscriptionally by ClpP. In addition, the clpP mutant was defective in colonization of the nasopharynx and survival in the lungs of mice after intranasal challenge. The mutant was also killed faster than the parent in the murine macrophage RAW264.7 cell line, indicating that ClpP is required for colonization and intracellular survival in the host. Furthermore, fractionation studies demonstrated that ClpP was translocated into the cell wall after heat shock, and immunization of mice with ClpP elicited a protective immune response against fatal systemic challenge with S. pneumoniae D39, making ClpP a potential vaccine candidate for pneumococcal disease.

Adenosine Triphosphatases↗

PubMed2004

Vitamin C blocks TNF-alpha-induced NF-kappaB activation and ICAM-1 expression in human neuroblastoma cells.

Interactions of the cell adhesion molecules are known to play important roles in mediating inflammation. The proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), activates the NF-kappaB signaling pathway, which induces the expression of various genes, such as intercellular adhesion molecule-1 (ICAM-1). In this study, the effect of vitamin C on the ICAM-1 expression induced by TNF-alpha in a human neuroblastoma cell line, SK-N-SH was investigated. Treatment with vitamin C resulted in the downregulation of the TNF-alpha-induced surface expression and ICAM-1 mRNA levels in a concentration-dependent manner. Moreover, a gel shift analysis indicated that vitamin C dose-dependently inhibited the NF-kappaB activation and IkappaBalpha degradation induced by TNF-alpha. Taken together, these results suggest that vitamin C downregulates TNF-alpha-induced ICAM-1 expression via the inhibition of NF-kappaB activation.

Antioxidants↗

PubMed2003

Immune alterations in mice exposed to the herbicide simazine.

Simazine, a triazine herbicide, was investigated for its in vivo immunomodulatory properties. Male C57Bl/6 mice were treated with vehicle or 300 or 600 mg/kg body weight (bw) simazine daily orally for 4 wk. The immune system was evaluated by the antibody response to sheep red blood cells (SRBC; plaque assay and serum immunoglobulin G), natural killer (NK) and macro-phage activities, lymphocyte subpopulations in the spleen and thymus, and concanavalin A (Con A)- and lipopolysaccharide (LPS)-stimulated lymphocyte proliferation using splenocytes. Body weight and spleen and thymus weight decreased generally in simazine-treated mice, while the weight of adrenal glands was higher than in the control. Simazine treatment (600 mg/kg) induced an increase in the percentage of CD4(+) cells in spleen and CD8 + in thymus. Simazine inhibited the IgM plaque-forming cell numbers and lowered the level of IgG and the proliferation of mitogen-stimulated B cells and T cells. In addition, splenic NK and peritoneal macrophage activities in exposed mice were significantly decreased. Exposure to simazine also decreased cytokine production by macrophages, such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF-alpha). Taken together, data indicate that the immune system was suppressed by oral simazine exposure.

Administration, Oral↗

PubMed2003

Reversal of P-glycoprotein-mediated multidrug resistance by ginsenoside Rg(3).

Multidrug resistance has been a major problem in cancer chemotherapy. In this study, in vitro and in vivo modulations of MDR by ginsenoside Rg(3), a red ginseng saponin, were investigated. In flow cytometric analysis using rhodamine 123 as an artificial substrate, Rg(3) promoted accumulation of rhodamine 123 in drug-resistant KBV20C cells in a dose-dependent manner, but it had no effect on parental KB cells. Additionally Rg(3) inhibited [3H]vinblastine efflux and reversed MDR to doxorubicin, COL, VCR, and VP-16 in KBV20C cells. Reverse transcriptase-polymerase chain reaction and immuno-blot analysis after exposure of KBV20C cells to Rg(3) showed that inhibition of drug efflux by Rg(3) was due to neither repression of MDR1 gene expression nor Pgp level. Photo-affinity labeling study with [3H]azidopine, however, revealed that Rg(3) competed with [3H]azidopine for binding to the Pgp demonstrating that Rg(3) competed with anticancer drug for binding to Pgp thereby blocking drug efflux. Furthermore, Rg(3) increased life span in mice implanted with DOX-resistant murine leukemia P388 cells in vivo and inhibited body weight increase significantly.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

Modulation of TNF-alpha-induced ICAM-1 expression, NO and H2O2 production by alginate, allicin and ascorbic acid in human endothelial cells.

Plant nutrients are believed to provide protection against various diseases including inflammation. Since interactions of the cell adhesion molecules are known to play important roles in mediating inflammation, inhibiting adhesion protein upregulation is a possible therapeutic target. In this study, the interacellular adhesion molecule-1 (ICAM-1) was induced in human umbilical endothelial cells (HUVECs) after stimulation with TNF-alpha. In addition, alginate, ascorbic acid and allicin were demonstrated to inhibit the TNF-alpha induced expression of ICAM-1 on the HUVECs in a dose-dependent manner. These compounds also inhibited the production of NO and H2O2 induced by TNF-alpha, which suggests that the inhibition of ICAM-1 expression by the three compounds may be due to the modulated production of the reactive oxygen/nitrogen components. Overall, these results indicate that these dietary components have a therapeutic potential in the treatment of various inflammatory disorders associated with an increase in endothelial leukocyte adhesion molecules.

Alginates↗

PubMed2003

Antiviral and tumoricidal activities of alginate-stimulated macrophages are mediated by different mechanisms.

Macrophages play an important role in host defenses by killing tumors and virus infections and producing secretory products. High mannuronic acid (HMA) containing alginate was examined to determine the mechanisms by which HMA-activated macrophages resist infection with HSV-1 and inhibit the growth of tumor cells. The ability of macrophages to resist infection with HSV-1 or to inhibit the growth of tumor cells was assessed following treatment with HMA alginate in the presence of either antibodies to various cytokines or inhibitors/scavengers of toxic macrophage products. Only antibodies to IFN-alpha/beta were able to abrogate the protective effects of HMA alginate in macrophages infected with HSV-1, suggesting that the antiviral activity induced by this immunomodulator was mediated by the production of IFN-beta. In contrast, anti-TNF-alpha, anti-IFN and inhibitors of nitric oxide and reactive oxygen species were all able to partially abrogate HMA-induced cytostatic activity, suggesting that multiple mechanisms are involved in macrophage cytostasis. These results indicate that the HMA-induced intrinsic antiviral and extrinsic cytotoxic activites are mediated by different mechanisms.

Alginates↗

PubMed2003

Induction of apoptosis and expression of apoptosis related genes in human epithelial carcinoma cells by Helicobacter pylori VacA toxin.

Virulence factors produced by Helicobacter pylori have been known to be associated with serious gastroduodenal diseases. The aims of this study were to clarify the apoptosis-inducing properties of vacuolating cytotoxin (VacA) and examine the expression of apoptosis related proteins in human epithelial carcinoma cells expressing (AGS) or lacking (Kato III) p53. The midregion VacA homolog from H. pylori strain Q35 (Korean isolate) was cloned, expressed and sequenced. Recombinant VacA (VacA(418-799)) inhibited cell growth and induced apoptosis in gastric epithelial cells. Treatment with VacA(418-799) resulted in morphological changes and DNA fragmentation. Cell cycle analysis revealed subdiploid cells suggesting apoptosis, which was confirmed by the activation of caspase-3 and cleavage of PARP. VacA(418-799) also mediated a prolongation of the cell cycle progression in G1 phase. Furthermore, VacA(418-799) increased the expression of p53, p21(waf1/cip1) and Bax in AGS cells, but not in Kato III cells and did not affect the phosphorylation of Rb in both cell lines. These results indicate that recombinant VacA of H. pylori induces apoptosis in both Kato III and AGS cells, regardless of p53 status and suggest that VacA(418-799) mediate the development of gastric diseases through cell cycle arrest in the G1 phase. VacA(418-799) induction of apoptosis is associated with up-regulation of p53, p21(waf1/cip1), Bax in AGS cells and activation of caspase-3 in both cell lines.

Amino Acid Sequence↗