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Biomedical subjects

Y Yazaki

Publications and source records attributed to Y Yazaki.

At least 199 records · Page 11Linked to original sources
PubMed1998

Effect of the Pro12Ala variant of the human peroxisome proliferator-activated receptor gamma 2 gene on adiposity, fat distribution, and insulin sensitivity in Japanese men.

To examine the role of the Pro12Ala variant of the human PPARgamma2 gene on adiposity and insulin resistance, we studied the effect of the variant on fat distribution assessed by CT scan, plasma glucose, and insulin levels during a 75g oral glucose load in 215 non-diabetic Japanese men. The allele frequency of the variant was 0. 03 in this population. There were no differences in body mass index (BMI), subcutaneous fat area (S), visceral fat area (V), V/S ratio, fasting plasma insulin levels, or insulin resistance index in homeostatic model assessment between 203 subjects who were homozygous for the wild-type Pro12 allele and 12 subjects with the variant Ala12 allele (11 heterozygotes and one homozygote). These data suggest that the Pro12Ala variant is not a major contributor to adiposity, fat distribution, or insulin resistance in Japanese men.

Adipose Tissue↗
PubMed1998

Mechanical stretch induces hypertrophic responses in cardiac myocytes of angiotensin II type 1a receptor knockout mice.

Many lines of evidence have suggested that angiotensin II (AngII) plays an important role in the development of cardiac hypertrophy through AngII type 1 receptor (AT1). To determine whether AngII is indispensable for the development of mechanical stress-induced cardiac hypertrophy, we examined the activity of mitogen-activated protein kinase (MAPK) family and the expression of the c-fos gene as hypertrophic responses after stretching cultured cardiac myocytes of AT1a knockout (KO) mice. When cardiac myocytes were stretched by 20% for 10 min, extracellular signal-regulated protein kinases (ERKs) were strongly activated in KO cardiomyocytes as well as wild type (WT) myocytes. Both basal and stimulated levels of ERKs were higher in cardiomyocytes of KO mice than in those of WT mice. Activation of another member of the MAPK family, p38(MAPK), and expression of the c-fos gene were also induced by stretching cardiac myocytes of both types of mice. An AT1 antagonist attenuated stretch-induced activation of ERKs in WT cardiomyocytes but not in KO cardiomyocytes. Down-regulation of protein kinase C inhibited stretch-induced ERK activation in WT cardiomyocytes, whereas a broad spectrum tyrosine kinase inhibitor (genistein) and selective inhibitors of epidermal growth factor receptor (tyrphostin, AG1478, and B42) suppressed stretch-induced activation of ERKs in KO cardiac myocytes. Epidermal growth factor receptor was phosphorylated at tyrosine residues by stretching cardiac myocytes of KO mice. These results suggest that mechanical stretch could evoke hypertrophic responses in cardiac myocytes that lack the AT1 signaling pathway possibly through tyrosine kinase activation.

Animals↗
PubMed1998

Expression of costimulatory molecule CD40 in murine heart with acute myocarditis and reduction of inflammation by treatment with anti-CD40L/B7-1 monoclonal antibodies.

Evidence has accumulated that antigen-specific T cells infiltrate the heart and play an important role in the pathogenesis of viral myocarditis. Costimulatory molecules such as B7s and CD40 expressed on antigen-presenting cells are known to play a critical role for antigen-specific T-cell activation to occur. To investigate the role for a costimulatory molecule, CD40, in the development of acute viral myocarditis, we first analyzed the expression of CD40 in the hearts of mice with acute viral myocarditis induced by Coxsackievirus B3. We also evaluated the induction of CD40 in cultured cardiac myocytes treated with interferon gamma in vitro. Second, we analyzed the cytokine production by cultured cardiac myocytes by stimulation with anti-CD40 monoclonal antibody (mAb) in vitro. Third, we examined the effects of in vivo administration of anti-CD40L/B7-1 mAbs on the development of acute viral myocarditis. We found that Coxsackievirus B3-induced murine acute myocarditis results in enhanced expression of CD40 on cardiac myocytes. The expression of CD40 on cardiac myocytes could be induced by interferon gamma in vitro. We also found that the production of interleukin-6 by cardiac myocytes was stimulated with anti-CD40 mAb and that in vivo anti-CD40L/B7-1 mAb treatment significantly decreased the myocardial inflammation. Our findings strongly suggest that CD40 plays an important role in the development of acute viral myocarditis and raise the possibility of immunotherapy with anti-CD40L/B7-1 mAbs to prevent T cell-mediated myocardial damage in viral myocarditis.

Animals↗
PubMed1998

Comparison of clinical features and prognosis of cardiac sarcoidosis and idiopathic dilated cardiomyopathy.

In the present study, clinical findings of 15 patients with cardiac sarcoidosis presenting as dilated cardiomyopathy were compared with those of 30 consecutive patients with idiopathic dilated cardiomyopathy. The sarcoidosis patients had different clinical features, including female predominance, a high incidence of grave conduction disturbance and abnormal wall thickness, uneven wall motion abnormalities, and perfusion defects preferentially affecting the anteroseptal and apical regions, and poor prognosis compared with those with idiopathic dilated cardiomyopathy.

Adult↗
PubMed1998

Ethidium bromide-induced inhibition of mitochondrial gene transcription suppresses glucose-stimulated insulin release in the mouse pancreatic beta-cell line betaHC9.

Recently, a mitochondrial mutation was found to be associated with maternally inherited diabetes mellitus (Kadowaki, T., Kadowaki, H., Mori, Y., Tobe, K., Sakuta, R., Suzuki, Y., Tanabe, Y, Sakura, H., Awata, T., Goto, Y., Hayakawa, T., Matsuoka, K., Kawamori, R., Kamada, T., Horai, S., Nonaka, I., Hagura, R., Akanuma, Y., and Yazaki, Y. (1994) N. Engl. J. Med. 330, 962-968). In order to elucidate its etiology, we have investigated the involvement of mitochondrial function in insulin secretion. Culture of the pancreatic beta-cell line, betaHC9, with low dose ethidium bromide (EB) (0.4 microg/ml) for 2-6 days resulted in a substantial decrease in the transcription level of mitochondrial DNA (to 10-20% of the control cells) without changing its copy number, whereas the transcription of nuclear genes was grossly unaffected. Electron microscopic analysis revealed that treatment by EB caused morphological changes only in mitochondria and not in other organelles such as nuclei, endoplasmic reticula, Golgi bodies, or secretory granules. When the cells were treated with EB for 6 days, glucose (20 mM) could no longer stimulate insulin secretion, while glibenclamide (1 microM) still did. When EB was removed after 3- or 6-day treatment, mitochondrial gene transcription recovered within 2 days, and the profiles of insulin secretion returned to normal within 7 days. Studies with fura-2 indicated that in EB-treated cells, glucose (20 mM) failed to increase intracellular Ca2+, while the effect of glibenclamide (1 microM) was maintained. Our system provides a unique way to investigate the relationship between mitochondrial function and insulin secretion.

Animals↗
PubMed1998

Cloning, functional expression, and chromosomal localization of the human and mouse gp180-carboxypeptidase D-like enzyme.

We previously reported that a host cell glycoprotein, gp180, binds duck hepatitis B virus particles, and is encoded by a member of the carboxypeptidase gene family (Kuroki, K., Eng, F., Ishikawa, T., Turck, C., Harada, F., Ganem, D., 1995. gp180, a host cell glycoprotein that binds duck hepatitis B virus particles, is encoded by a member of the carboxypeptidase gene family. J. Biol. Chem. 270, 15022-15028). After that report, carboxypeptidase D (CPD) was subsequently purified from bovine pituitary and characterized as a novel carboxypeptidase E (CPE)-like enzyme, with many characteristics in common with duck gp180 (Song, L., Fricker, L.D., 1995. Purification and characterization of carboxypeptidase D, a novel carboxypeptidase E-like enzyme, from bovine pituitary. J. Biol. Chem. 270, 25007-25013). CPD is now supposed to play an important role in a secretory pathway. To clarify the function of gp180 further, we have isolated and analyzed human and mouse homologues of duck gp180. cDNA clones derived from human HepG2 cells and mouse livers have been isolated on the basis of homology to the duck gp180. The suggested open reading frames of the human and mouse cDNA encode 1380 and 1377 amino acid proteins, respectively and have three carboxypeptidase homologous domains (A, B, and C). Domains A and B have completely conserved the residues known to have the enzymatic activity of carboxypeptidase, but domain C in each cDNA does not. Northern blotting revealed a ubiquitous tissue distribution of human gp180 mRNA with several transcript species. Expression of human gp180 cDNA in transfected 293T cells exhibited carboxypeptidase activity upon radiometric assay. The human and mouse homologues of duck gp180 have many characteristics in common with bovine CPD. Fluorescence in-situ hybridization reveals that the gene encoding human gp180 is located in region 17q11.2.

Amino Acid Sequence↗
PubMed1998

Cholesterol lowering in low density lipoprotein receptor knockout mice overexpressing apolipoprotein E.

Apo E is a key molecule in the lipoprotein metabolism; thus, genetic manipulation of apo E may prove useful in the treatment of hypercholesterolemia. To test the feasibility of this idea, we have generated low density lipoprotein receptor (LDLR) knockout mice that overexpress the rat apo E transgene (ETg+/+:LDLRKO), and compared their plasma lipoprotein profiles with those of nonexpressing LDLR knockout mice (ETg-/-:LDLRKO). On a normal chow diet, the mean plasma cholesterol level of ETg+/+:LDLRKO mice was significantly lower than that of ETg-/-:LDLRKO mice (189 versus 240 mg/dl, P < 0. 01). The LDL fraction was selectively reduced in the ETg+/+:LDLRKO mice. Despite the challenge with an atherogenic diet, cholesterol lowering was persistently observed and fatty streak lesions in the aortic sinus were significantly suppressed in the mice overexpressing apo E. These results imply that stimulation of hepatic production of apo E may be used as a promising adjunctive therapy for homozygous familial hypercholesterolemia.

Animals↗
PubMed1998

The oncoprotein Evi-1 represses TGF-beta signalling by inhibiting Smad3.

Evi-1 encodes a zinc-finger protein that may be involved in leukaemic transformation of haematopoietic cells. Evi-1 has two zinc-finger domains, one with seven repeats of a zinc-finger motif and one with three repeats, and it has characteristics of a transcriptional regulator. Although Evi-1 is thought to be able to promote growth and to block differentiation in some cell types, its biological functions are poorly understood. Here we study the mechanisms that underlie oncogenesis induced by Evi-1 by investigating whether Evi-1 perturbs signalling through transforming growth factor-beta (TGF-beta), one of the most studied growth-regulatory factors, which inhibits proliferation of a wide range of cell types. We show that Evi-1 represses TGF-beta signalling and antagonizes the growth-inhibitory effects of TGF-beta. Two separate regions of Evi-1 are responsible for this repression; one of these regions is the first zinc-finger domain. Through this domain, Evi-1 interacts with Smad3, an intracellular mediator of TGF-beta signalling, thereby suppressing the transcriptional activity of Smad3. These results define a new function of Evi-1 as a repressor of signalling through TGF-beta.

Animals↗
PubMed1998

Growth hormone and prolactin stimulate tyrosine phosphorylation of insulin receptor substrate-1, -2, and -3, their association with p85 phosphatidylinositol 3-kinase (PI3-kinase), and concomitantly PI3-kinase activation via JAK2 kinase.

Growth hormone (GH) and prolactin (PRL) binding to their receptors, which belong to the cytokine receptor superfamily, activate Janus kinase (JAK) 2 tyrosine kinase, thereby leading to their biological actions. We recently showed that GH mainly stimulated tyrosine phosphorylation of epidermal growth factor receptor and its association with Grb2, and concomitantly stimulated mitogen-activated protein kinase activity in liver, a major target tissue. Using specific antibodies, we now show that GH was also able to induce tyrosine phosphorylation of insulin receptor substrate (IRS)-1/IRS-2 in liver. In addition, the major tyrosine-phosphorylated protein in anti-p85 phosphatidylinositol 3-kinase (PI3-kinase) immunoprecipitate from liver of wild-type mice was IRS-1, and IRS-2 in IRS-1 deficient mice, but not epidermal growth factor receptor. These data suggest that tyrosine phosphorylation of IRS-1 may be a major mechanism for GH-induced PI3-kinase activation in physiological target organ of GH, liver. We also show that PRL was able to induce tyrosine phosphorylation of both IRS-1 and IRS-2 in COS cells transiently transfected with PRLR and in CHO-PRLR cells. Moreover, we show that tyrosine phosphorylation of IRS-3 was induced by both GH and PRL in COS cells transiently transfected with IRS-3 and their cognate receptors. By using the JAK2-deficient cell lines or by expressing a dominant negative JAK2 mutant, we show that JAK2 is required for the GH- and PRL-dependent tyrosine phosphorylation of IRS-1, -2, and -3. Finally, a specific PI3-kinase inhibitor, wortmannin, completely blocked the anti-lipolytic effect of GH in 3T3 L1 adipocytes. Taken together, the role of IRS-1, -2, and -3 in GH and PRL signalings appears to be phosphorylated by JAK2, thereby providing docking sites for p85 PI3-kinase and activating PI3-kinase and its downstream biological effects.

Androstadienes↗
PubMed1998

A potential molecular approach to ex vivo hematopoietic expansion with recombinant epidermal growth factor receptor-expressing adenovirus vector.

Ex vivo expansion of hematopoietic stem cell (HSC) is an attractive technology for its potency of a variety of clinical applications. Such a technology has been achieved to some extent with combinations of various cytokines or continuous perfusion cultures. However, much more improvement is required especially for expansion of primitive hematopoietic progenitors. We propose here a novel molecular approach that might have the potential to compensate the current expansion. We designed an adenovirus vector to transiently express human epidermal growth factor receptor (EGFR), which is known to transduce only a mitogenic, but not a differentiation signal to mouse bone marrow cells on human purified CD34+ peripheral blood (PB) cells, and tried to expand these cells with EGF ex vivo. Because we found that exposure of CD34+ PB cells to cytokines induced surface expression of adenovirus-internalization receptor and rendered these cells permissive to adenovirus infection, we infected these cells with the adenovirus vector carrying EGFR gene in the presence of cytokines. Two-color flow cytometric analysis demonstrated that 60.3% +/- 22.4% of CD34+ cells expressed the adenovirus-mediated EGFR. Moreover, long-term culture-initiating cell assay showed that adenovirus vector could transduce more primitive progenitors. Subsequently, we tried to expand these cells in suspension culture with EGF for 5 days. Methylcellulose clonal assay showed that EGF induced 5.0- +/- 2.4-fold proliferation of the colony-forming unit pool during 5 days of expansion. The simple procedure of efficient adenovirus gene delivery to immature hematopoietic cells proved promising, and this technique was potentially applicable for a novel strategy aiming at ex vivo expansion of hematopoietic progenitors.

Adenoviridae↗
PubMed1998

Pressure overload induces cardiac hypertrophy in angiotensin II type 1A receptor knockout mice.

BACKGROUND: Many studies have suggested that the renin-angiotensin system plays an important role in the development of pressure overload-induced cardiac hypertrophy. Moreover, it has been reported that pressure overload-induced cardiac hypertrophy is completely prevented by ACE inhibitors in vivo and that the stored angiotensin II (Ang II) is released from cardiac myocytes in response to mechanical stretch and induces cardiomyocyte hypertrophy through the Ang II type 1 receptor (AT1) in vitro. These results suggest that the AT1-mediated signaling is critical for the development of mechanical stress-induced cardiac hypertrophy. METHODS AND RESULTS: To determine whether AT1-mediated signaling is indispensable for the development of pressure overload-induced cardiac hypertrophy, pressure overload was produced by constricting the abdominal aorta of AT1A knockout (KO) mice. Quantitative reverse transcriptase-polymerase chain reaction revealed that the cardiac AT1 (probably AT1B) mRNA levels in AT1A KO mice were <10% of those of wild-type (WT) mice and were not affected by pressure overload. Chronic treatment with subpressor doses of Ang II increased left ventricular mass in WT mice but not in KO mice. Pressure overload, however, fully induced cardiac hypertrophy in KO as well as WT mice. There were no significant differences between WT and KO mice in expression levels of fetal-type cardiac genes, in the left ventricular wall thickness and systolic function as revealed by the transthoracic echocardiogram, or in the histological changes such as myocyte hypertrophy and fibrosis. CONCLUSIONS: AT1-mediated Ang II signaling is not essential for the development of pressure overload-induced cardiac hypertrophy.

Angiotensin II↗
PubMed1998

Acute pressure overload could induce hypertrophic responses in the heart of angiotensin II type 1a knockout mice.

Increasing evidence has suggested that locally produced angiotensin II (Ang II) plays an important role in the development of cardiac hypertrophy through the Ang II type 1 receptor (AT1). We and others have recently reported that Ang II is critical for mechanical stress-induced hypertrophic responses in vitro. Using AT1a knockout (KO) mice, we examined whether Ang II is indispensable for pressure overload-induced cardiac hypertrophy in the present study. Reverse-transcriptase polymerase chain reaction analysis revealed that AT1 mRNA levels were <10% in the heart of KO mice compared with wild-type (WT) mice, but the Ang II type 2 receptor gene was expressed at almost the same levels in the hearts of both mice. Intravenous infusion of subpressor dose of Ang II induced c-fos gene expression in the hearts of WT mice but not KO mice. Acute pressure overload, however, induced expressions of immediate-early response genes and activations of mitogen-activated protein kinases in the hearts of KO mice as well as WT mice. Both basal and activated levels of all these responses were significantly higher in KO mice than in WT mice. Pressure overload markedly increased the heart weight-to-body weight ratio in both mice strains at 14 days after aortic banding. These results suggest that acute hypertrophic responses could be induced by pressure overload in the in vivo heart without AT1 signaling.

Angiotensin II↗
PubMed1998

Hypertension, hypertriglyceridemia, and impaired endothelium-dependent vascular relaxation in mice lacking insulin receptor substrate-1.

Insulin resistance is often associated with atherosclerotic diseases in subjects with obesity and impaired glucose tolerance. This study examined the effects of insulin resistance on coronary risk factors in IRS-1 deficient mice, a nonobese animal model of insulin resistance. Blood pressure and plasma triglyceride levels were significantly higher in IRS-1 deficient mice than in normal mice. Impaired endothelium-dependent vascular relaxation was also observed in IRS-1 deficient mice. Furthermore, lipoprotein lipase activity was lower than in normal mice, suggesting impaired lipolysis to be involved in the increase in plasma triglyceride levels under insulin-resistant conditions. Thus, insulin resistance plays an important role in the clustering of coronary risk factors which may accelerate the progression of atherosclerosis in subjects with insulin resistance.

Animals↗
PubMed1998

Type I phosphatidylinositol-4-phosphate 5-kinases. Cloning of the third isoform and deletion/substitution analysis of members of this novel lipid kinase family.

Type I phosphatidylinositol 4-phosphate (PtdIns(4)P) 5-kinases (PIP5K) catalyze the synthesis of phosphatidylinositol 4, 5-bisphosphate, an essential lipid molecule in various cellular processes. Here, we report the cloning of the third member (PIP5Kgamma) and the characterization of members of the type I PIP5K family. Type I PIP5Kgamma has two alternative splicing forms, migrating at 87 and 90 kDa on SDS-polyacrylamide gel electrophoresis. The amino acid sequence of the central portion of this isoform shows approximately 80% identity with those of the alpha and beta isoforms. Northern blot analysis revealed that the gamma isoform is highly expressed in the brain, lung, and kidneys. Among three isoforms, the beta isoform has the greatest Vmax value for the PtdIns(4)P kinase activity and the gamma isoform is most markedly stimulated by phosphatidic acid. By analyzing deletion mutants of the three isoforms, the minimal kinase core sequence of these isoforms were determined as an approximately 380-amino acid region. In addition, carboxyl-terminal regions of the beta and gamma isoforms were found to confer the greatest Vmax value and the highest phosphatidic acid sensitivity, respectively. It was also discovered that lysine 138 in the putative ATP binding motif of the alpha isoform is essential for the PtdIns(4)P kinase activity. As was the case with the alpha isoform reported previously (Shibasaki, Y., Ishihara, H., Kizuki, N., Asano, T., Oka, Y., Yazaki, Y. (1997) J. Biol. Chem. 272, 7578-7581), overexpression of either the beta or the gamma isoform induced an increase in short actin fibers and a decrease in actin stress fibers in COS7 cells. Surprisingly, a kinase-deficient substitution mutant also induced an abnormal actin polymerization, suggesting a role of PIP5Ks via structural interactions with other molecules.

Amino Acid Sequence↗
PubMed1998

Effects of in vivo administration of anti-B7-1/B7-2 monoclonal antibodies on murine acute myocarditis caused by coxsackievirus B3.

In viral myocarditis, we previously reported that antigen-specific T cells infiltrate the heart and play an important role in the pathogenesis of myocardial damage. For antigen-specific T-cell activation to occur, it is necessary for T cells to receive costimulatory signals provided by costimulatory molecules expressed on antigen-presenting cells as well as main signals provided by binding of T-cell receptors to antigens. To investigate the roles of costimulatory molecules B7-1 and B7-2 in the development of acute viral myocarditis, we first analyzed the expression of B7-1/B7-2 in the hearts of mice with acute viral myocarditis induced by coxsackievirus B3 (CVB3). Second, we evaluated the induction of B7-1/B7-2 in cultured cardiac myocytes treated with interferon gamma (IFN-gamma). Third, we examined the effects of in vivo administration of anti-B7-1/B7-2 monoclonal antibodies (mAbs) on the development of acute viral myocarditis. We found that CVB3-induced murine acute myocarditis resulted in enhanced expression of B7-1/B7-2 in cardiac myocytes. The expression of B7-1/B7-2 in cardiac myocytes could be induced in vitro by IFN-gamma. We found that in vivo anti-B7-1 mAb treatment markedly decreased myocardial inflammation, whereas anti-B7-2 mAb treatment abrogated the protective effect of anti-B7-1. Our findings indicate that distinct roles for B7-1 and B7-2 antigens are involved in the development of acute viral myocarditis and raise the possibility of immunotherapy with anti-B7-1 mAb to prevent T-cell-mediated myocardial damage in viral myocarditis.

Acute Disease↗