PubMed Health⌕ Search

Biomedical subjects

M H Suh

Publications and source records attributed to M H Suh.

At least 19 recordsLinked to original sources
PubMed2001

The green tea polyphenol (-)-epigallocatechin gallate attenuates beta-amyloid-induced neurotoxicity in cultured hippocampal neurons.

Previous evidence has indicated that the neuronal toxicity of amyloid beta (betaA) protein is mediated through oxygen free radicals and can be attenuated by antioxidants and free radical scavengers. Recent studies have shown that green tea polyphenols reduced free radical-induced lipid peroxidation. The purpose of this study was to investigate whether (-)-epigallocatechin gallate (EGCG) would prevent or reduce the death of cultured hippocampal neuronal cells exposed to betaA because EGCG has a potent antioxidant property as a green tea polyphenol. Following exposure of the hippocampal neuronal cells to betaA for 48 hours, a marked hippocampal neuronal injuries and increases in malondialdehyde (MDA) level and caspase activity were observed. Co-treatment of cells with EGCG to betaA exposure elevated the cell survival and decreased the levels of MDA and caspase activity. Proapoptotic (p53 and Bax), Bcl-XL and cyclooxygenase (COX) proteins have been implicated in betaA-induced neuronal death. However, in this study the protective effects of EGCG seem to be independent of the regulation of p53, Bax, Bcl-XL and COX proteins. Taken together, the results suggest that EGCG has protective effects against betaA-induced neuronal apoptosis through scavenging reactive oxygen species, which may be beneficial for the prevention of Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed2001

Immune response induced by immunization with Hepatitis B virus core DNA isolated from chronic active hepatitis patients.

There are many mutations in the gene encoding Hepatitis B virus (HBV) core antigen of chronic active hepatitis patients, and such mutations are most likely to be related to the severity of disease. Here, we constructed plasmids containing wild-type and deletion type of HBV core gene (HBc) to develop an experimental DNA vaccine and to compare immunogenicity of two types of HBc vaccine. Twenty-nine wild-types and seven deletion types of HBc were detected in sera of 32 Korean patients with chronic active hepatitis. Four wild-types (W1, W2, W4, W6) and two deletion types (D3, D4) of HBc were cloned into the pcDNA3 vector. Intramuscular immunization with wild-type HBc efficiently increased serum anti-HBc antibody response in a dose-dependent manner. Anti-HBc antibody response in mice injected with W6 increased 14 days after immunization, and peaked after 30 days and was maintained at least up to 50 days. W6 immunization induced a specific cytotoxic T lymphocyte response to W6-transfected 3LL (3LL-W6), and reduced the sizes of tumor mass of mice challenged with 3LL-W6 or 3LL transfected with D4. However, intramuscular immunization with D3 and D4 did not show antibody response at all. D3 and D4 have 157 bp (from 331 to 491 bp) and 122 bp (from 327 to 448 bp) gene deletion, respectively, and these encode class II MHC-restricted T-cell epitope. Altogether, these results suggest that mutant virus that has deleted HBc gene may evade immune systems due to loss of T-cell epitope.

Animals↗
PubMed2001

Chemopreventive agent resveratrol, a natural product derived from grapes, reversibly inhibits progression through S and G2 phases of the cell cycle in U937 cells.

Resveratrol, a natural product derived from grapes, has been shown to prevent carcinogenesis in murine models. We report here that resveratrol induces antiproliferation and arrests the S phase in human histiocytic lymphoma U937 cells. Resveratrol induces arrest in the S phase at low concentrations (30-60 microM), but high concentrations do not induce S phase accumulation in U937 cells. Removal of resveratrol from the culture medium stimulates U937 cells to reenter the cell cycle synchronously, as judged by the expression patterns of cyclin E, A and by fluorescent activated cell sorting analysis. These data demonstrate that resveratrol causes S phase arrest and reversible cell cycle arrest. Thus, resveratrol provides an important new cell cycle blocker as well as a cancer chemopreventive agent.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Hepatitis C virus core protein promotes cell proliferation through the upregulation of cyclin E expression levels.

AIMS/BACKGROUND: The hepatitis C virus (HCV) core protein is known to play an important role in hepatocarcinogenesis. Recent studies have suggested that the increased proliferation rate of hepatocytes is a major risk factor for the development of hepatocellular carcinoma. In this study, we investigated whether the HCV core protein promotes the cell growth rate through the modulation of cyclin E expression levels. METHODS/RESULTS: HCV core stable transfectant Rat-1 cell lines showed a markedly increased proliferation rate compared to mock cells. Cyclin E expression and its associated kinase activities were remarkably increased in HCV core stable transfectants. Cyclin E mRNA levels were also upregulated in these cell lines. CONCLUSIONS: Our data suggest that the HCV core protein promotes cell proliferation through upregulation of the cyclin E expression levels, implying this property of HCV core protein plays an important role in hepatocarcinogenesis.

Animals↗
PubMed2001

p21(WAF1) is associated with CDK2 and CDK4 protein during HL-60 cell differentiation by TPA treatment.

TPA-treated HL-60 cells are mainly arrested in G1 by p21(WAF1) accumulation. We investigate the downstream changes following such accumulation. Increased p21(WAF1) is associated with CDK2 and CDK4. pRb is dephosphorylated in the presence of p21-CDK2/4 complexes, and the Rb-E2F1 complex increases after TPA treatment, whereas the Rb-HDAC1 complex decreases slightly. Our results suggest that increased p21(WAF1) is associated with CDK2/4, and that these complexes induce pRb dephosphorylation. In turn, hypophosphorylated pRb are mainly complexed with E2F1, but HDAC1 appears not to be a key component in this process.

CDC2-CDC28 Kinases↗
PubMed2001

Bcl-2 overexpression attenuates resveratrol-induced apoptosis in U937 cells by inhibition of caspase-3 activity.

Resveratrol has been shown to induce anti-proliferation and apoptosis of human cancer cell lines. In the present study, we determined the effect of high intracellular levels of the anti-apoptosis protein Bcl-2 on caspase-3 activation, PLC-gamma1 degradation and cytochrome c release during resveratrol-induced apoptosis. For this, we used U937/vector and U937/Bcl-2 cells, which were generated by transfection of the cDNA of the Bcl-2 gene. As compared with U937/vector, U937/Bcl-2 cells exhibited a 4-fold greater expression of Bcl-2. Treatment with 60 or 100 microM resveratrol for 24 h produced morphological features of apoptosis and DNA fragmentation in U937/vector cells, respectively. This was associated with caspase-3 activation and PLC-gamma1 degradation. In contrast, resveratrol-induced caspase-3 activation and PLC-gamma1 degradation and apoptosis were significantly inhibited in U937/Bcl-2 cells. Bcl-2 overexpressing cells exhibited less cytochrome c release and sustained expression levels of the IAP proteins during resveratrol-induced apoptosis. In addition, these findings indicate that Bcl-2 inhibits resveratrol-induced apoptosis by a mechanism that interferes with cytochrome c release and activity of caspase-3 that is involved in the execution of apoptosis.

Apoptosis↗
PubMed2001

The levels of MDM2 protein are decreased by a proteasome-mediated proteolysis prior to caspase-3-dependent pRb and PARP cleavages.

MDM2 is a substrate of caspase-3 in p53-mediated apoptosis. In addition, MDM2 mediates its own ubiquitination in a RING finger-dependent manner. Thus, we investigated whether MDM2 is degraded through a ubiquitin-dependent proteasome pathway in the absence of p53. When HL-60 cells, p53 null, were treated with etoposide, MDM2 was markedly decreased prior to caspase-3-dependent retinoblastoma tumor suppressor protein (pRb) and poly (ADP- ribose) polymerase (PARP) cleavages. Moreover, down-regulation of MDM2 level was not coupled with its mRNA down-regulation. However, the level of MDM2 was partially restored by proteasome inhibitors such as LLnL and lactacystin, even in the presence of etoposide. Our results suggest that, in the p53 null status, MDM2 protein level is decreased by proteasome-mediated proteolysis prior to caspase-3-dependent PARP and pRb cleavages.

Antineoplastic Agents, Phytogenic↗
PubMed2000

5-Aza-2'-deoxycytidine leads to down-regulation of aberrant p16INK4A RNA transcripts and restores the functional retinoblastoma protein pathway in hepatocellular carcinoma cell lines.

The inactivation of the cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor p16INK4A may be caused by gene deletion, mutation or promoter hypermethylation. We have previously reported that p16INK4A in hepatocellular carcinoma (HCC) tissues and cell lines is inactivated predominantly by promoter hypermethylation rather than genomic aberrations. In the present experiments, we have studied the effects of the demethylating agent, 5-aza-2'-deoxycytidine (5-AZA/decitabine), on the expression of aberrant p16INK4A RNA transcripts and the CDK-retinoblastoma gene pathway in HCC cell lines with p16INK4A promoter hypermethylation. The expression of aberrant p16INK4A RNA transcripts was down-regulated and p16INK4A protein was strongly re-expressed in the HCC cell lines, SNU 354, 398, 423 and 475 after 5-AZA/decitabine treatment for 5 days. The re-expressed p16INK4A was functional, because it bound to and inhibited CDK4 kinase activity, and increased the concentrations of the hypophosphorylated form of retinoblastoma protein (pRB) in cells with a wild type RB gene. Moreover, treatment with the demethylating agent led not only to G1 cell cycle arrest, but also to the increased expression of the senescence-associated marker beta-galactosidase. This up-regulation of p16INK4A mRNA and protein correlated with demethylation of the p16INK4A promoter, and with the down-regulation or disappearance of aberrant p16INK4A transcripts. These results suggest that the aberrant p16INK4A RNA transcript can be transcribed from the methylated p16INK4A gene, and endogenous reactivation of functional p16INK4A mRNA by a demethylating agent can restore the pRB pathway in HCC, and foster the terminal differentiation of the malignant cells. Therefore, demethylating agents, such as 5-AZA/decitabine, may have potential in the treatment of HCC.

Azacitidine↗
PubMed2000

Lack of mutation at p16INK4A gene but expression of aberrant p16INK4A RNA transcripts in human ovarian carcinoma.

Alterations of the p16INK4A gene are frequent in various human cancers. We investigated p16INK4A gene status in 20 ovarian carcinomas by PCR (polymerase chain reaction), PCR-SSCP (polymerase chain reaction-single strand conformation polymorphism) and sequencing techniques. None of the primary tumors showed any mutational or deletional events. However, 19 out of 20 tumors displayed both a methylated and an unmethylated p16INK4A promoter. In some of these samples, we detected aberrant p16INK4A transcripts, with partial deletions of both exons 1 and 2, which could not encode a functional p16INK4A protein. The sequences of the aberrant mRNA revealed common 4-7 nucleotide sequences before and after the deleted region, which might cause abnormal splicing of mRNA transcripts. These results suggest that both promoter methylation and aberrant mRNA processing may interfere with p16INK4A expression in ovarian tumors.

Base Sequence↗
PubMed2000

Isolation and characterization of nifDK::kanamycin and nitrogen fixation proficient Azotobacter vinelandii strain, and its implication on the status of multiple chromosomes in Azotobacter.

Several lines of experimental analyses on the ploidy status of Azotobacter vinelandii genome lead to the conclusion that it contains more than 40 copies of its chromosome and therefore it is a polyploid organism. The genetic evidence argues against the existence of polyploidy in these cells since the segregation pattern of genetic markers under lack of selection pressure mimic that of haploids. However, when A. vinelandii was made Nif- by inserting a kanamycin resistance marker gene in the nifDK sequence and the cells were selected for kanamycin resistance and Nif+ phenotype, we were able to score colonies that are both kanamycin resistant and Nif+. Therefore, when the cells were subjected to forced double selection of the same locus, they behaved as if they carried at least two chromosomes, one carrying the kanamycin resistance marker in the nifDK genes and the other carrying the intact nifDK genes. These analyses suggested that at least a diploidy status can be induced in these cells under selection pressure.

Azotobacter vinelandii↗
PubMed2000

p53 codon 72 polymorphism and risk of cervical carcinoma in Korean women.

A common polymorphism of the wild type p53 is known at codon 72 of exon 4, with 2 alleles encoding either arginine (CGC, p53Arg) or proline (CCC, p53Pro). A recent study suggested that this polymorphism affects the susceptibility of p53 protein to human papillomavirus E6 oncoprotein mediated degradation and that individuals homozygous for p53Arg are seven times more susceptible to HPV-associated carcinogenesis of the cervix than heterozygotes. To examine whether the p53Arg genotype could be a risk factor for HPV-associated cervical carcinomas in the Korean population, we analyzed the p53 codon 72 polymorphism status of HPV-positive invasive cervical carcinomas from 52 Korean women and 103 healthy control samples. The proportion of individuals homozygous for p53Arg, homozygous for p53Pro, and heterozygous for the two alleles were 40%, 19%, and 41% in normal healthy controls; 42%, 17%, and 40% in women with HPV-positive invasive cervical carcinoma. There were no significant differences in the distribution of p53 genotypes between controls and cervical carcinomas. This finding indicates that the p53Arg genotype is not associated with an increased susceptibility to cervical carcinoma in Korean women.

Alleles↗
PubMed1999

DNA-mediated immunization of mice with plasmid encoding HBs antigen.

In order to develop an experimental DNA vaccine for the prevention and treatment of hepatitis B virus infection, hepatitis B virus surface antigen (HBsAg) DNA was subcloned into an E. coli-eukaryotic cell shuttle vector and was expressed in the Baculovirus expression system. Intramuscular, intradermal, and intraperitoneal injections of 30 microg of the plasmid DNA expressing HBsAg induced humoral and cellular immune responses in ICR mice. The first IgG antibodies were detected after ten days and specific IgG antibody titers peaked after two months of a single intramuscular DNA injection. Anti-HBs antibody titers gradually increased and peaked at four months following intradermal DNA injection, and in case of intraperitoneal injection they peaked at seven months. Generation of HBs-specific helper T lymphocytes was also investigated through the production of interleukin-2 by T helper cells. Boosting effects of HBs DNA were investigated without much results. In general, DNA-mediated HBs immunization induced humoral and cellular immune responses in mice that appears to simulate immune responses in human during the course of HBV vaccination.

Animals↗
PubMed1998

Persistent expression of Fas/FasL mRNA in the mouse hippocampus after a single NMDA injection.

Synaptic reorganization plays a very important role in brain adaptations to environmental stimuli, diseases, and aging processes. The NMDA model of excitotoxic injury was used to investigate the long-term molecular changes in the surviving neural cells in the mouse hippocampus. We demonstrated that a single intraperitoneal injection of NMDA produces persistent expression of c-fos, c-jun, Fas, and Fas ligand (FasL) mRNA in the hippocampus for 5 months. To determine the cellular origin of those gene transcripts in our in vivo model, a glial cell line and primary fetal neuronal culture were used to investigate the inducibility of the c-fos, c-jun, Fas, and FasL mRNA by NMDA. Both c-fos and Fas mRNA expression was observed in the NMDA-treated glial or neuronal cultures; however, c-jun and FasL mRNA was undetectable in this study. In our in vivo model, mossy fiber sprouting and apoptosis were also observed up to 40 days after the NMDA injection. Therefore, we hypothesize that the observed long-term expression of c-fos, c-jun, Fas, and FasL mRNAs may reflect the ongoing synaptic reorganization.

Animals↗
PubMed1995

Identification of CD44 splice variant in Korean colorectal cancers and cell lines.

CD44 is a glycoprotein expressed in a wide variety of cell types. Recently expression of some alternatively-spliced variants of CD44 transcripts (CD44v) has been suggested to play a potential role in tumor metastasis and the detection of CD44v containing exon 6 to 11 may be helpful for the diagnosis of cancers. Expressions of CD44v containing exon 6 to 11 were investigated in 20 human colorectal cancer samples, peripheral blood leukocytes isolated from colorectal cancer patients, and 4 colorectal cancer cell lines using reverse transcription-polymerase chain reaction and Southern blot analysis. The standard form of CD44 transcripts was expressed in all samples tested. CD44v containing exon 6 to 11 was expressed in 18 cases of colorectal cancers (sensitivity = 90%), 3 out of 4 cell lines, and one normal tissue (specificity = 95%). These results suggest that the expression of CD44v containing exon 6 to 11 can be regarded as tumor specific and that this marker may be helpful for the early diagnosis of colon cancers, if specimens from the early stage are available.

Adenocarcinoma↗
PubMed1994

Decreased expression of collagen and fibronectin genes in striae distensae tissue.

Striae distensae are characterized by a thinning of connective tissue stroma to produce linear, atrophic-appearing skin. Excessive adrenocortical activity, genetic factors and inherited defects of connective tissues, etc. are important causative factors in the formation of striae distensae, but the basic aetiology is not known. Total RNA was extracted from skin biopsies of five patients with striae distensae. The expression of genes coding for types I and III procollagen, elastin, fibronectin and beta-actin were studied and compared with those of four sex- and age-matched healthy individuals. The percentages of types I and III procollagen mRNA were 9.9 +/- 2.9% (mean +/- s.d.) and 10.6 +/- 1.6%, respectively, of the corresponding controls. The value for fibronectin mRNA in striae distensae was 7.3 +/- 1.8% of the control. The steady-state ratio fibronectin/type I procollagen mRNAs was 0.12 +/- 0.01 in striae distensae and 0.18 +/- 0.01 in the control. These observations suggest that expression of collagens, elastin and fibronectin genes are apparently decreased, and that there is a marked alteration of fibroblast metabolism, in striae distensae.

Adolescent↗
PubMed1991

Collagen mRNA expression detected by in situ hybridization in keloid tissue.

The keloid fibroblasts exhibited increased extracellular matrix gene expression, and prominent elevated type I procollagen mRNA when compared to control fibroblasts cultured from the uninvolved skin of normal people. It also showed markedly elevated type I/III procollagen mRNA ratios, but no synthesis of type IV procollagen mRNA by keloid fibroblasts was observed. By in situ hybridization in keloid tissue, high levels of type I and type III procollagen mRNAs were detected in most of the fibroblasts, suggesting the presence of a subpopulation responsible for the increased collagen production. The levels of type I and type III procollagen mRNAs in these fibroblasts were clearly elevated compared to control skin specimens. And concentration of type I procollagen mRNA was found more predominantly than was type III. These results suggest that deposition of collagen in keloid could result from activation of certain fibroblasts responsible for type I procollagen production.

Adult↗