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Biomedical subjects

M Namba

Publications and source records attributed to M Namba.

At least 19 recordsLinked to original sources
PubMed2006

Dominant-negative c-Jun inhibits rat cardiac hypertrophy induced by angiotensin II and hypertension.

Cardiac activator protein-1 (AP-1), composed of c-Jun, is significantly activated by hypertension or angiotensin II (AngII). This study was undertaken to elucidate whether c-Jun could be the potential target for treatment of cardiac hypertrophy. We constructed recombinant adenovirus carrying dominant-negative mutant of c-Jun (Ad.DN-c-Jun). Using catheter-based technique of adenoviral gene transfer, we achieved global myocardial transduction of DN-c-Jun in rats, to specifically inhibit cardiac AP-1. (1) AngII (200 ng/kg/min) infusion in rats caused cardiac hypertrophy, increased cardiac p70S6 kinase activity by 1.3-fold (P<0.05) and enhanced the gene expression of cardiac hypertrophic markers. Ad.DN-c-Jun, which was transferred to the heart 2 days before AngII infusion, prevented cardiac hypertrophy (P<0.01), decreased p70S6 kinase phosphorylation (P<0.05), and suppressed cardiac gene expression of brain natriuretic peptide, collagen I, III, and IV, monocyte chemoattractant protein-1 (MCP-1) and plasminogen activator inhibitor-1 (PAI-1) (P<0.01). (2) In genetically hypertensive rats with cardiac hypertrophy, cardiac gene transfer of Ad.DN-c-Jun, without affecting hypertension, regressed cardiac hypertrophy (P<0.05), and suppressed p70S6 kinase phosphorylation by 20% (P<0.05) and suppressed the enhanced expression of collagen I, III, and IV, MCP-1 and PAI-1. These results provided the first evidence that in vivo blockade of cardiac c-Jun inhibits pathologic cardiac hypertrophy.

Adenoviridae↗
PubMed2006

Clinical significance of circulating hepatocyte growth factor, a new risk marker of carotid atherosclerosis in patients with Type 2 diabetes.

AIMS: Recent studies have provided increasing evidence that hepatocyte growth factor (HGF) has a pathophysiological role in the development of diabetic complications. We set out to determine the relationship between serum HGF and risk factors for macroangiopathy including carotid atherosclerosis. Carotid atherosclerosis is an established and important risk factor for both cerebral and coronary artery diseases. METHODS: We studied 89 patients (48 males, 41 females, mean age 62.5 +/- 10.3 years) with Type 2 diabetes (DM). RESULTS: Serum levels of HGF correlated positively with both intimal-media thickness (IMT) (r = 0.24, P = 0.0248) and plaque score (r = 0.27, P = 0.0126). In multiple regression analysis, serum HGF was associated independently with IMT (standardized beta = 0.28, P = 0.0499). We also found that both IMT and plaque score were higher in patients with ischaemic heart disease (IHD) than in patients without IHD, and that plaque score in patients with lacunar infarcts was higher than in patients without lacunar infarcts. CONCLUSIONS: Serum HGF concentration may be a new marker of atherosclerotic complications in patients with Type 2 DM.

Age Factors↗
PubMed2004

Midkine promoter-driven suicide gene expression and -mediated adenovirus replication produced cytotoxic effects to immortalised and tumour cells.

We examined possible application of a regulatory region of midkine (MK) gene, which is frequently upregulated in a number of human tumours but not in normal cells, to cancer gene therapy. We examined transcriptional activity of the MK genomic fragments in paired cell lines, immortalized cells and their parental normal fibroblasts, and found that the MK fragments activated a fused reporter or a suicide gene preferentially in the immortalized cells. Recombinant adenoviruses (Ad), in which the MK fragment was inserted upstream to the E1A gene (AdMK), replicated preferentially in the immortalized cells and were cytotoxie to them. Human hepatocellular carcinoma cells were significantly susceptible to AdMK compared with human normal fibroblasts in vitro and the replication of AdMK was less than that of wild-type Ad in the infected fibroblasts. Hepatocellular carcinoma cells infected with AdMK did not form tumours in immunocompromised mice and intratumoural injection of AdMK into the hepatocellular carcinoma developed in mice retarded the subsequent tumour growth. Expression of E1A and necrosis of tumours were detected in AdMK-injected but not control Ad-injected cases. The MK promoter-driven suicide gene therapy and -mediated replicative Ad can thereby produce cytotoxic effects to immortalized and tumour cells with minimal damage to normal cells.

Adenoviridae↗
PubMed2003

Identification of a novel variant in the phosphoenolpyruvate carboxykinase gene promoter in Japanese patients with type 2 diabetes.

Phospho enolpyruvate carboxykinase (PEPCK) plays an important role in gluconeogenesis and hepatic glucose production. To test the hypothesis that mutations of the PEPCK gene promoter contribute to the increased hepatic glucose production that leads to diabetes, we screened for polymorphisms of the PEPCK promoter region in 252 Japanese type 2 diabetic patients and 188 non-diabetic control subjects. A novel variant at position - 232 (C to G) was found at a similar frequency in type 2 diabetes patients (32 %) and control subjects (35 %) (p = 0.26). However, patients with the - 232 G/G genotype had an earlier age of onset than those with the - 232 C/C or - 232 C/G genotypes (p = 0.028). As the variant might well otherwise influence hormonal action, we transfected PEPCK-luciferase fusion gene constructs with the variant into human hepatoma cells and examined the response to dexamethasone, insulin, and cAMP. The reporter assay showed no significant difference in hormonal responses with the fusion gene containing the variant. Accordingly, the single-base variant at position - 232 of the PEPCK gene promoter is most probably not a major contributor to the pathogenesis of type 2 diabetes. However, this variation may be useful as a genetic marker for other metabolic disorders, especially in Japanese.

Aged↗
PubMed2001

Antiproliferative activity of REIC/Dkk-3 and its significant down-regulation in non-small-cell lung carcinomas.

We recently reported the cloning of the REIC/Dkk-3 gene, whose expression was shown to be down-regulated in many human immortalized and tumor-derived cell lines [T. Tsuji et al. (2000) Biochem. Biophys. Res. Commun. 268, 20-24]. In the present study, we demonstrated that expression of the exogenous REIC/Dkk-3 gene in tumor cells inhibited cell growth. Furthermore, the level of REIC/Dkk-3 mRNA in normal human cells was lowest in the late G(1) phase during the cell cycle. Then we found that the expression of REIC/Dkk-3 was significantly down-regulated in surgically resected non-small-cell lung carcinomas. We determined the REIC/Dkk-3 locus on chromosome 11p15, where loss of heterozygosity has frequently been observed in human tumors. These findings indicate that REIC/Dkk-3 may function as a tumor suppressor.

Adaptor Proteins, Signal Transducing↗
PubMed2001

a4, a unique kidney-specific isoform of mouse vacuolar H+-ATPase subunit a.

The vacuolar-type H+ -ATPase (V-ATPase) translocates protons across membranes. Here, we have identified a mouse cDNA coding for a fourth isoform (a4) of the membrane sector subunit a of V-ATPase. This isoform was specifically expressed in kidney, but not in the heart, brain, spleen, lung, liver, muscle, or testis. Immunoprecipitation experiments, together with sequence similarities for other isoforms (a1, a2, and a3), indicate that the a4 isoform is a component of V-ATPase. Moreover, histochemical studies show that a4 is localized in the apical and basolateral plasma membranes of cortical alpha- and beta-intercalated cells, respectively. These results suggest that the V-ATPase, with the a4 isoform, is important for renal acid/base homeostasis.

Acid-Base Equilibrium↗
PubMed2001

Gene transfer of dominant-negative mutants of extracellular signal-regulated kinase and c-Jun NH2-terminal kinase prevents neointimal formation in balloon-injured rat artery.

We previously reported that extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK), belonging to mitogen-activated protein kinases, are rapidly activated in balloon-injured artery. Therefore, we examined the role of these kinase activations in neointimal formation by using an in vivo gene transfer technique. We made the dominant-negative mutants of ERK (DN-ERK) and JNK (DN-JNK) to specifically inhibit endogenous ERK and JNK activation, respectively. Before balloon injury, these mutants were transfected into rat carotid artery using the hemagglutinating virus of Japan liposome method. In vivo transfection of DN-ERK and DN-JNK significantly suppressed the activation of ERK and JNK, respectively, after balloon injury, confirming successful expression of the transfected genes. Neointimal formation at 14 and 28 days after injury was prevented by gene transfer of DN-ERK or DN-JNK. Furthermore, bromodeoxyuridine labeling index and total cell-counting analysis at 7 days showed that either DN-ERK or DN-JNK remarkably suppressed smooth muscle cell (SMC) proliferation in both the intima and the media after injury. Gene transfer of wild-type ERK (W-ERK) or JNK (W-JNK) significantly enhanced neointimal hyperplasia at 14 days after injury. Furthermore, DN-ERK and DN-JNK significantly suppressed serum-induced SMC proliferation in vitro. We obtained the first evidence that in vivo gene transfer of DN-ERK or DN-JNK prevented neointimal formation in balloon-injured artery by inhibiting SMC proliferation. Thus, ERK and JNK activation triggers SMC proliferation, leading to neointimal formation. These kinases may be the new therapeutic targets for prevention of vascular diseases.

Angioplasty, Balloon↗
PubMed2001

Identification of a phosphoprotein that is downregulated in immortalized human fibroblasts.

Many lines of evidence indicate that the immortalization step is critical for the neoplastic transformation of normal human cells. Once normal human cells have been immortalized, they are relatively easily transformed into neoplastic cells. In order to understand these phenomena, patterns of protein phosphorylation in proliferating normal human fibroblast cell strains and their immortalized cell lines were compared by using two-dimensional polyacrylamide gel electrophoresis. It was found that the expression and phosphorylation levels of the human heat shock protein 27 (HSP27) were predominantly downregulated in the immortalized cells compared with those in their normal counterparts. In the normal cells, HSP27 expression and phosphorylation were markedly increased by physiological and nonphysiological stresses, such as serum addition, treatment with a carcinogenic agent like 4-nitroquinoline-1-oxide, and a high osmotic pressure. This may be a normal defense against acute changes of cellular environment and cytotoxic effects. However, these stresses had no effects on the expression and phosphorylation of HSP27 in the immortalized cells. These results suggest that an abnormal regulation of HSP27 expression and phosphorylation may be one of the reasons for easy neoplastic transformation of the immortalized cells by the treatment with carcinogenic agents.

Amino Acid Sequence↗
PubMed2001

Photo-cross-linked oligonucleotide duplex as a decoy-DNA for inhibition of restriction endonuclease activity.

As a novel type of regulator molecule for DNA-recognizing proteins, a photo-cross-linked oligonucleotide duplex was designed and synthesized. The molecule regulated the activity of a restriction endonuclease by being recognized as a substrate. This type of regulating molecule is regarded as a decoy-DNA. 4,5',8-[4-Aminoethylaminomethyl]-trioxalen (aeAMT) was conjugated with an oligodeoxyribonucleotide (ODN) at the 5'-end and the aeAMT was cross-linked with the thymine residue of the complementary oligonucleotide upon UVA irradiation. The terminally cross-linked oligonucleotides, singly clipped (SC) decoy-DNA, acquired thermal stability. An oligonucleoside phosphorothioate (OPT) was also introduced as one or both components, yielding three types of decoy-DNAs, SC-ODN-ODN (SC.DD), SC-OPT-ODN (SC.SD), and SC-OPT-OPT (SC.SS). The SC decoy-DNAs inhibited the function of the restriction endonuclease, AatII, in a sequence-specific and concentration-dependent manner with an appreciable IC50 value (1.3 microM for SC.DD, 0.016 microM for SC.SD, 0.002 microM for SC.SS). The SC decoy-DNAs were found to be effective for regulating the DNA recognizing proteins.

DNA↗
PubMed2001

Establishment of a human hepatocyte line (OUMS-29) having CYP 1A1 and 1A2 activities from fetal liver tissue by transfection of SV40 LT.

Immortalized human hepatocytes that can retain functions of drug-metabolizing enzymes would be useful for medical and pharmacological studies and for constructing an artificial liver. The aim of this study was to establish immortalized human hepatocyte lines having differentiated liver-specific functions. pSVneo deoxyribonucleic acid, which contains large and small T genes in the early region of simian virus 40, was introduced into hepatocytes that had been obtained from the liver of a 21-wk-old fetus. Neomycin-resistant immortalized colonies were cloned and expanded to mass cultures to examine hepatic functions. Cells were cultured in a chemically defined serum-free medium, ASF104, which contains no peptides other than recombinant human transferrin and insulin. As a result, an immortal human hepatocyte cell line (OUMS-29) having liver-specific functions was established from one of the 13 clones. Expression of CYP 1A1 and 1A2 messenger ribonucleic acid by the cells was induced by treatment with benz[a]pyrene, 3-methylcholanthrene, and benz[a]anthracene. OUMS-29 cells had both the polycyclic aromatic hydrocarbon receptor (AhR) and AhR nuclear translocator. Consequently 7-ethoxyresorufin deethylase activity of the cells was induced time- and dose-dependently by these polycyclic aromatic hydrocarbons. This cell line is expected to be instrumental as an alternative method in animal experiments for studying hepatocarcinogenesis, drug metabolisms of liver cells, and hepatic toxicology.

Cell Line↗
PubMed2001

IL-1beta-induced expression of matrix metalloproteinases and gliostatin/platelet-derived endothelial cell growth factor (GLS/PD-ECGF) in a chondrosarcoma cell line (OUMS-27).

The purpose of this study was to examine how chondrocytes are involved in the molecular mechanism of inflammation in rheumatoid arthritis (RA). A chondrosarcoma cell line (OUMS-27) was cultured and treated with interleukin-1beta (IL-1beta). Changes in the expression levels of matrix metalloproteinase-1 (MMP-1), metalloproteinase-13 (MMP-13), and gliostatin/platelet-derived endothelial cell growth factor (GLS/PD-ECGF) were assessed by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assays. IL-1beta induced the expressions of MMP-1, MMP-13, and GLS mRNAs and proteins in a dose-dependent manner. Selective inhibition of the p38 mitogen-activated protein kinase (p38 MAPK) pathway with SB 203580 and SB 202190 blocked the expression of MMP-1, MMP-13, and GLS more strongly than selective in hibition of the extracellular signal-regulated kinase 1 and 2 (ERK1/2) pathway by PD 98059. These findings suggest that chondrocytes may intensify cartilage destruction and inflammation in RA by the induction of MMP-1, MMP-13, and GLS by IL-1beta and that the p38 MAPK pathway plays an important role in these inductions.

Base Sequence↗
PubMed2001

A 10-year-old boy with Marfan syndrome exhibiting cerebrovascular abnormalities.

A young male with Marfan syndrome, diagnosed at the age of 10 years, presented with conspicuous elongation and tortuosity of the internal carotid, middle cerebral, vertebral and basilar arteries on cranial magnetic resonance and computed tomography angiography. There is a little mention of cerebral blood vessel examinations in the guidelines of the American Academy of Pediatrics for Marfan syndrome. Guidelines may be provided for the evaluation of cerebrovascular system for the patients with Marfan syndrome who have family history of Marfan syndrome as well as a family history of death from subarachnoid hemorrhage.

Cerebrovascular Disorders↗
PubMed2001

Two-dimensional gel electrophoretic studies on the cellular aging: accumulation of alpha-2-macroglobulin in human fibroblasts with aging.

To understand the mechanisms that control life span and age-related phenotypes, we used two-dimensional (2D) gel electrophoresis to study the intracellular proteins whose amounts change during the process of cellular aging. We found that the amount of an alpha-2-macroglobulin (A2M) fragment derived from culture medium increased in the cells with aging. A2M is linked to Alzheimer's disease both genetically and functionally. This is the first report of accumulation of an A2M fragment in senescent fibroblasts. We also studied 2D gel profiles of human fibroblasts immortalized by treatment with either 60Co gamma rays or 4-nitroquinoline 1-oxide. As immortalized cells overcome cellular senescence to gain an unlimited life span, the proteins whose amounts change after immortalization may be relevant to the age-related phenotypes. 2D gel analysis revealed that the A2M fragment was down-regulated in the immortalized cells, compared with their normal counterparts, regardless of their passage. We also found that the other four proteins increased in amount with aging and decreased in amount after immortalization. Our results suggest: (1) the A2M incorporation into the cells is increased in the process of cellular aging; and (2) A2M may be linked to the age-related phenotypes that were lost during the process of immortalization of human cells.

Cell Line↗
PubMed2001

Up-regulation of S100C in normal human fibroblasts in the process of aging in vitro.

S100 proteins belonging to the EF-hand Ca(2+)-binding protein family regulate a variety of cellular processes via interaction with different target proteins. Several diseases, including cancer and Alzheimer's disease, are related to a disorder of multifunctional S100 proteins, which are expressed in cell- and tissue-specific manners. We previously demonstrated that S100C could move to and accumulate in the nuclei of normal human fibroblasts but not in the nuclei of immortalized and neoplastic cells. In addition, we found that its nuclear accumulation resulted in suppression of DNA synthesis in normal cells at a confluent stage. In the present study, we investigated whether S100C was associated with cellular senescence in vitro. We found that S100C expression increased in normal human fibroblasts in the process of aging in culture and was accompanied by accumulation of its protein in the nuclei of senescent fibroblasts. In addition, the nuclear accumulation of S100C increased expression of a cyclin-dependent kinase inhibitor p21(Sdi1), a strong inhibitor of cell growth. These findings suggest that an increase in the cells having nuclear accumulation of S100C is closely related to the process of cellular senescence of normal human fibroblasts.

Cell Division↗
PubMed2001

Establishment of the transformants expressing human cytochrome P450 subtypes in HepG2, and their applications on drug metabolism and toxicology.

Transformants with stable expression of a series of human cytochrome P450 (CYP) subtypes in the human hepatic cell line, HepG2, were established. These transformants are designated Hepc/1A1.4, Hepc/1A2.9, Hepc/2A6L.14, Hepc/2B6.68, Hepc/2C8.46, Hepc/2C9.1, Hepc/2C19.12, Hepc/2D6.39, Hepc/2E1.3-8 and Hepc/3A4.2-30, which stably expressed human CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4, respectively. The expression of the CYP subtypes in the transformants was confirmed by both determination of enzyme activities and the reverse transcriptase polymerase chain reaction (RT-PCR) procedure. The apparent K(m) values of the expressed CYP subtypes for their specific substrates were close to those of human liver microsomes. In addition to their CYP activities, these transformants retained glucuronide- and sulfate-conjugating activities. Furthermore, the activities of CYP2C9, CYP2D6 and CYP3A4 were inhibited by their specific inhibitors. The cytotoxicity of acetaminophen (APAP), cyclophosphamide (CPA) and benz[a]anthracene (BA) were analyzed by CYP-expressing transformants. The cytotoxicity depended on the expression of CYP subtypes and increased in a dose-dependent manner. These results show the metabolic activation of APAP, CPA and BA by the specific CYP subtypes expressed in the transformants and demonstrate the usefulness of these transformants for in vitro metabolic and toxicological studies in human liver.

Acetaminophen↗
PubMed2001

High quality RNA isolation from tumours with low cellularity and high extracellular matrix component for cDNA microarrays: application to chondrosarcoma.

AIMS: High quality RNA isolation from cartilaginous tissue is considered difficult because of relatively low cellularity and the abundance of extracellular matrix rich in glycosaminoglycans and collagens. Given the growing interest and technical possibilities to study RNA expression at a high throughput level, research on tissue with these characteristics is hampered by the lack of an efficient method for obtaining sufficient amounts of high quality RNA. METHODS: This paper presents a robust protocol combining two RNA isolation procedures, based on a combination of Trizol and RNA specific columns, which has been developed to obtain high molecular weight RNA from fresh frozen and stored tissue of normal cartilage and cartilaginous tumours. Using this method, RNA was isolated from normal cartilage, peripheral chondrosarcoma, and central chondrosarcoma. RESULTS: The yields ranged from 0.1 to 0.5 microg RNA/mg tissue. RNA isolated with this method was stable and of high molecular weight. RNA samples from normal cartilage and from two chondrosarcomas isolated using this method were applied successfully in cDNA microarray experiments. The number of genes that give interpretable results was in the range of what would be expected from microarray results obtained on chondrosarcoma cell line RNA. Signal to noise ratios were good and differential expression between tumour and normal cartilage was detectable for a large number of genes. CONCLUSION: With this newly developed isolation method, high quality RNA can be obtained from low cellular tissue with a high extracellular matrix component. These procedures can also be applied to other tumour material.

Bone Neoplasms↗
PubMed2001

Loss of nuclear localization of the S100C protein in immortalized human fibroblasts.

It is well known that cancer develops through a multistep process. In vitro transformation studies of normal human cells have shown that the immortalization step is critical for neoplastic transformation of cells. Furthermore, studies of cell fusion between normal and immortalized cells have indicated that the normal phenotype is dominant and the immortal phenotype is recessive. Thus we looked for cellular proteins that were down-regulated in immortalized human cells by two-dimensional gel electrophoresis to elucidate the mechanisms of immortalization of human cells. We found that the S100C protein was down-regulated in immortalized cells. This protein was localized in the cytoplasm of cells at the semiconfluent stage, while at the confluent stage it moved into the nuclei of normal cells but not into those of immortalized cells. Microinjection of an S100C antibody into normal confluent cells diminished the level of nuclear S100C protein, resulting in DNA synthesis. Taken together, loss of nuclear localization of the S100C protein, which may be related to DNA synthesis, is thought to be one of the mechanisms of immortalization.

Amino Acid Sequence↗