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Y Yazaki

Publications and source records attributed to Y Yazaki.

At least 55 records · Page 3Linked to original sources
PubMed2000

beta-Adrenergic pathway induces apoptosis through calcineurin activation in cardiac myocytes.

Apoptosis of cardiac myocytes is one of the causes of heart failure. Here we examine the mechanism by which the activation of beta-adrenergic receptor induces cardiomyocyte apoptosis. Terminal deoxynucleotide transferase-mediated dUTP nick end labeling and DNA ladder analyses revealed that isoproterenol (Iso) induced the apoptosis of cardiac myocytes of neonatal rats through an increase in intracellular Ca(2+) levels. The Iso-induced cardiomyocyte apoptosis was strongly inhibited by the L-type Ca(2+) channel antagonist nifedipine and by the calcineurin inhibitors cyclosporin A and FK506. Iso reduced the phosphorylation levels of the proapoptotic Bcl-2 family protein Bad and induced cytochrome c release from mitochondria to the cytosol through calcineurin activation. Infusion of Iso increased calcineurin activity by approximately 3-fold in the hearts of wild-type mice but not in the hearts of transgenic mice that overexpress dominant negative mutants of calcineurin. Terminal deoxynucleotide transferase-mediated dUTP nick end labeling analysis revealed that infusion of Iso induced apoptosis of cardiac myocytes and that the number of apoptotic cardiomyocytes was significantly less in the hearts of the transgenic mice compared with the wild-type mice. These results suggest that calcineurin plays a critical role in Iso-induced apoptosis of cardiac myocytes, possibly through dephosphorylating Bad.

Animals↗
PubMed2000

Constitutive tyrosine phosphorylation of ErbB-2 via Jak2 by autocrine secretion of prolactin in human breast cancer.

Overexpression of the oncogene for ErbB-2 is an unfavorable prognostic marker in human breast cancer. Its oncogenic potential appears to depend on the state of tyrosine phosphorylation. However, the mechanisms by which ErbB-2 is constitutively tyrosine-phosphorylated in human breast cancer are poorly understood. We now show that human breast carcinoma samples with ErbB-2 overexpression have higher proliferative and metastatic activity in the presence of autocrine secretion of prolactin (PRL). By using a neutralizing antibody or dominant negative (DN) strategies or specific inhibitors, we also show that activation of Janus kinase Jak2 by autocrine secretion of PRL is one of the significant components of constitutive tyrosine phosphorylation of ErbB-2, its association with Grb2 and activation of mitogen-activated protein (MAP) kinase in human breast cancer cell lines that overexpress ErbB-2. Furthermore, the neutralizing anti-PRL antibody or erbB-2 antisense oligonucleotide or DN Jak2 or Jak2 inhibitor or DNRas or MAP kinase kinase inhibitor inhibits the proliferation of both untreated and PRL-treated cells. Our results indicate that autocrine secretion of PRL stimulates tyrosine phosphorylation of ErbB-2 by Jak2, provides docking sites for Grb2 and stimulates Ras-MAP kinase cascade, thereby causing unrestricted cellular proliferation. The identification of this novel cross-talk between ErbB-2 and the autocrine growth stimulatory loop for PRL may provide new targets for therapeutic and preventive intervention of human breast cancer.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Calcineurin inhibitor attenuates the development and induces the regression of cardiac hypertrophy in rats with salt-sensitive hypertension.

BACKGROUND: It remains unclear how hemodynamic overload induces cardiac hypertrophy. Recently, activation of calcium-dependent phosphatase, calcineurin, has been elucidated to induce cardiac hypertrophy. In the present study, we examined the role of calcineurin in load-induced cardiac hypertrophy by using Dahl salt-sensitive (DS) rats, which develop both pressure and volume overload when fed a high salt diet. METHODS AND RESULTS: In the DS rat heart, the activity of calcineurin was increased and cardiac hypertrophy was induced by high salt diet. Treatment of DS rats with the calcineurin inhibitor FK506 (0.1 or 0.01 mg/kg twice daily) from the age of 6 weeks to 12 weeks inhibited the activation of calcineurin in the heart in a dose-dependent manner and attenuated the development of load-induced cardiac hypertrophy and fibrosis without change of hemodynamic parameters. Additionally, treatment with 0.1 mg/kg twice daily but not with 0.01 mg/kg twice daily of FK506 from the age of 12 weeks to 16 weeks induced regression of cardiac hypertrophy in DS rats. Load-induced reprogramming of gene expression was also suppressed by the FK506 treatment. CONCLUSIONS: These results suggest that calcineurin is involved in the development of cardiac hypertrophy in rats with salt-sensitive hypertension and that inhibition of calcineurin could induce regression of cardiac hypertrophy.

Animals↗
PubMed2000

Transcriptional regulation of human cardiac homeobox gene CSX1.

Cardiac homeobox gene Csx/Nkx-2.5 is essential for normal heart development and morphogenesis and is the earliest marker for cardiogenesis. To elucidate the regulatory mechanisms of Csx/Nkx-2.5 expression, we have isolated and characterized the upstream regulatory region of human Csx/Nkx-2.5 (CSX1). Transfection of the reporter gene containing a 965-bp CSX1 5' flanking region indicated that this region confers cardiomyocyte-predominant expression of CSX1. Deletion and mutational analyses revealed two positive cis-regulatory elements in this region that are essential for CSX1 expression in cardiomyocytes. Electrophoretic mobility shift assay revealed that nuclear proteins prepared from cardiac myocytes bound to these elements in a sequence-specific manner. The identification of cis-regulatory sequences of the Csx/Nkx-2.5 gene will facilitate further analysis for the upstream regulatory factors that control the expression of Csx/Nkx-2.5 and the process of vertebrate heart development.

Animals↗
PubMed2000

The evi-1 oncoprotein inhibits c-Jun N-terminal kinase and prevents stress-induced cell death.

Evi-1 encodes a nuclear protein involved in leukemic transformation of hematopoietic cells. Evi-1 possesses two sets of zinc finger motifs separated into two domains, and its characteristics as a transcriptional regulator have been described. Here we show that Evi-1 acts as an inhibitor of c-Jun N-terminal kinase (JNK), a class of mitogen-activated protein kinases implicated in stress responses of cells. Evi-1 physically interacts with JNK, although it does not affect its phosphorylation. This interaction is required for inhibition of JNK. Evi-1 protects cells from stress-induced cell death with dependence on the ability to inhibit JNK. These results reveal a novel function of Evi-1, which provides evidence for inhibition of JNK by a nuclear oncogene product. Evi-1 blocks cell death by selectively inhibiting JNK, thereby contributing to oncogenic transformation of cells.

Adaptation, Biological↗
PubMed2000

p110beta is up-regulated during differentiation of 3T3-L1 cells and contributes to the highly insulin-responsive glucose transport activity.

Activation of p85/p110 type phosphatidylinositol kinase is essential for aspects of insulin-induced glucose metabolism, including translocation of GLUT4 to the cell surface and glycogen synthesis. The enzyme exists as a heterodimer containing a regulatory subunit (e.g. p85alpha) and one of two widely distributed isoforms of the p110 catalytic subunit: p110alpha or p110beta. In the present study, we compared the two isoforms in the regulation of insulin action. During differentiation of 3T3-L1 cells into adipocytes, p110beta was up-regulated approximately 10-fold, whereas expression of p110alpha was unaltered. The effects of the increased p110 expression were further assessed by expressing epitope tagged p110beta and p110alpha in 3T3-L1 cells using adenovirus transduction systems, respectively. In vitro, the basal lipid kinase activity of p110beta was lower than that of p110alpha. When p110alpha and p110beta were overexpressed in 3T3-L1 adipocytes, exposing cells to insulin induced each of the subunits to form complexes with p85alpha and tyrosine-phosphorylated IRS-1 with similar efficiency. However, whereas the kinase activity of p110beta, either endogenous or exogeneous, was markedly enhanced by insulin stimulation, only very small increases of the activity of p110alpha were observed. Interestingly, overexpression of p110beta increased insulin-induced glucose uptake by 3T3-L1 cells without significantly affecting basal glucose transport, whereas overexpression of p110alpha increased both basal and insulin-stimulated glucose uptake. Finally, microinjection of anti-p110beta neutralizing antibody into 3T3-L1 adipocytes abolished insulin-induced translocation of GLUT4 to the cell surface almost completely, whereas anti-p110alpha neutralizing antibody did only slightly. Together, these findings suggest that p110beta plays a crucial role in cellular activities evoked acutely by insulin.

3T3 Cells↗
PubMed2000

Ca2+/calmodulin-dependent kinase II and calcineurin play critical roles in endothelin-1-induced cardiomyocyte hypertrophy.

Endothelin-1 (ET-1) induces cardiac hypertrophy. Because Ca(2+) is a major second messenger of ET-1, the role of Ca(2+) in ET-1-induced hypertrophic responses in cultured cardiac myocytes of neonatal rats was examined. ET-1 activated the promoter of the beta-type myosin heavy chain gene (beta-MHC) (-354 to +34 base pairs) by about 4-fold. This activation was inhibited by chelation of Ca(2+) and the blocking of protein kinase C activity. Similarly, the beta-MHC promoter was activated by Ca(2+) ionophores and a protein kinase C activator. beta-MHC promoter activation induced by ET-1 was suppressed by pretreatment with the calmodulin inhibitor, W7, the Ca(2+)/calmodulin-dependent kinase II (CaMKII) inhibitor, KN62, and the calcineurin inhibitor, cyclosporin A. beta-MHC promoter activation by ET-1 was also attenuated by overexpression of dominant-negative mutants of CaMKII and calcineurin. ET-1 increased the activity of CaMKII and calcineurin in cardiac myocytes. Pretreatment with KN62 and cyclosporin A strongly suppressed ET-1-induced increases in [(3)H]phenylalanine uptake and in cell size. These results suggest that Ca(2+) plays a critical role in ET-1-induced cardiomyocyte hypertrophy by activating CaMKII- and calcineurin-dependent pathways.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2000

Hypotension and resistance to lipopolysaccharide-induced shock in transgenic mice overexpressing adrenomedullin in their vasculature.

BACKGROUND: Adrenomedullin (AM) is a vasodilating peptide involved in the regulation of circulatory homeostasis and in the pathophysiology of certain cardiovascular diseases. To determine the extent to which chronic AM overproduction affects circulatory physiology under normal and pathological conditions, we used a preproendothelin-1 promoter to establish transgenic mouse lines overexpressing AM in their vasculature. METHODS AND RESULTS: Transgenic mice overexpressing AM mainly in vascular endothelial and smooth muscle cells exhibited significantly lower blood pressure (BP) and higher plasma cGMP levels than their wild-type littermates. Blockade of NO synthase with N(G)-monomethyl-L-arginine elevated BP to a greater degree in AM transgenic mice, offsetting the BP difference between the 2 groups. Despite their lower basal BP, administration of bacterial lipopolysaccharide elicited smaller declines in BP and less severe organ damage in AM transgenic mice than in wild-type mice. Furthermore, the 24-hour survival rate after induction of lipopolysaccharide shock was significantly higher in the transgenic mice. CONCLUSIONS: A chronic increase in vascular AM production reduces BP at least in part via an NO-dependent pathway. In addition, smaller responses to LPS in transgenic mice suggest that AM is protective against the circulatory collapse, organ damage, and mortality characteristic of endotoxic shock.

Adrenomedullin↗
PubMed2000

Up-regulation of natriuretic peptides in the ventricle of Csx/Nkx2-5 transgenic mice.

A cardiac homeobox-containing gene Csx/Nkx2-5, which is essential for cardiac development, is abundantly expressed in the adult heart as well as in the heart primordia. Targeted disruption of this gene results in embryonic lethality due to abnormal heart morphogenesis. To elucidate the role of Csx/Nkx2-5 in the adult heart, we generated transgenic mice which overexpress human Csx/Nkx2-5. The transgene was expressed abundantly in the heart and the skeletal muscle. mRNA levels of several cardiac genes including natriuretic peptides, CARP, MLC2v, and endogenous Csx/Nkx2-5 were increased in the ventricle of the transgenic mice. Electron microscopic analysis revealed that the ventricular myocardium of the transgenic mice had many secretory granules, which disappeared after administration of vasopressin. These results suggest that Csx/Nkx2-5 regulates many cardiac genes and induces formation of secretory granules in the adult ventricle.

Animals↗
PubMed2000

Acquired loss of p53 induces blastic transformation in p210(bcr/abl)-expressing hematopoietic cells: a transgenic study for blast crisis of human CML.

Chronic myelogenous leukemia (CML) begins with an indolent chronic phase but inevitably progresses to a fatal blast crisis. Although the Philadelphia chromosome, which generates p210(bcr/abl), is a unique chromosomal abnormality in the chronic phase, additional chromosomal abnormalities are frequently detected in the blast crisis, suggesting that superimposed genetic events are responsible for disease progression. To investigate whether loss of p53 plays a role in the evolution of CML, we crossmated p210(bcr/abl)-transgenic (BCR/ABL(tg/-)) mice with p53-heterozygous (p53(+/-)) mice and generated p210(bcr/abl)-transgenic, p53-heterozygous (BCR/ABL(tg/-)p53(+/-)) mice, in which a somatic alteration in the residual normal p53 allele directly abrogates p53 function. The BCR/ABL(tg/-)p53(+/-) mice died in a short period compared with their wild-type (BCR/ABL(-/-)p53(+/+)), p53 heterozygous (BCR/ABL(-/-)p53(+/-)), and p210(bcr/abl) transgenic (BCR/ABL(tg/-)p53(+/+)) litter mates. They had rapid proliferation of blast cells, which was preceded by subclinical or clinical signs of a myeloproliferative disorder resembling human CML. The blast cells were clonal in origin and expressed p210(bcr/abl) with an increased kinase activity. Interestingly, the residual normal p53 allele was frequently and preferentially lost in the tumor tissues, implying that a certain mechanism facilitating the loss of p53 allele exists in p210(bcr/abl)-expressing hematopoietic cells. Our study presents in vivo evidence that acquired loss of p53 contributes to the blastic transformation of p210(bcr/abl)-expressing hematopoietic cells and provides insights into the molecular mechanism for blast crisis of human CML. (Blood. 2000;95:1144-1150)

Animals↗
PubMed2000

Association of methylenetetrahydrofolate reductase (MTHFR) polymorphism with bone mineral density in postmenopausal Japanese women.

The pathogenesis of osteoporosis is controlled by genetic and environmental factors. Considering the high prevalence of osteoporosis in homocystinuria, abnormal homocysteine metabolism would contribute to the pathogenesis of osteoporosis. It is known that the polymorphism of methylenetetrahydrofolate reductase (MTHFR), the enzyme catalyzing the reduction of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, correlates with hyperhomocysteinemia. In this study, we examined the association of this polymorphism with bone mineral density (BMD). BMD was measured by dual-energy X-ray absorptiometry (DXA) in 307 postmenopausal women. MTHFR A/V polymorphism was analyzed using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). We compared BMD, clinical characteristics, and bone metabolic markers among MTHFR groups (AA, AV, VV). The groups did not differ in terms of baseline data. The values of lumbar spine BMD and total body BMD were as follows: lumbar spine: AA, 0.91 +/- 0.18, AV, 0.88 +/- 0.16, VV, 0.84 +/- 0.14 g/cm(2); total body: AA, 0.97 +/- 0.11, AV, 0.96 +/- 0.11, VV, 0.93 +/- 0.09 g/cm(2). In the VV genotype, lumbar spine BMD values were significantly lower than those of the women with the AA genotype (P = 0.016) and total body BMD was significantly lower than those of the women with AA genotype (P = 0.03) and AV genotype (P = 0.04). This is the first report that suggests that the VV genotype of MTHFR is one of the genetic risk factors for low BMD.

Aged↗
PubMed2000

Molecular basis of cardiac hypertrophy.

Cardiac hypertrophy is an adaptive process to an increased hemodynamic overload. When cardiomyocytes cultured on silicone dishes were stretched, second messengers such as protein kinase C (PKC), Raf-1 kinase, and mitogen-activated protein (MAP) kinases were activated, which were followed by increased protein synthesis. Moreover, pretreatment with an angiotensin II (AngII) type 1 receptor antagonist dimished an increase in protein synthesis, MAP kinase activity, and c-fos gene expression induced by the stretching of cardiomyocytes. These suggest the linkage of the cardiac renin-angiotensin system to the formation of pressure-overload hypertrophy. Indeed, in the stretch-conditioned medium the levels of AngII concentration were increased. Also, mechanical stretch enhanced endothelin (ET)-1 release from the cardiomyocytes and activated the Na(+)/H(+) exchanger independently of these vasoactive peptides. In the second part, we examined AngII-induced signaling pathways both in cardiac myocytes and in cardiac fibroblasts. AngII-evoked signal transduction pathways differed between cell types. In cardiac fibroblasts AngII activated MAP kinases through a pathway including the Gbetagamma subunit of Gi protein, Src, Shc, Grb2, and Ras, while Gq and PKC activation was necessary in cardiac myocytes. We further explored norepinephrine (NE)-induced signaling pathways in cardiac myocytes. NE activated Raf-1 kinase and MAP kinases and increased amino acid uptake in cardiomyocytes of neonatal rats. beta-adrenoceptor (AR) stimulation as well and alpha1-AR stimulation was involved in NE-induced MAP kinase activation. It is noteworthy that unlike in other cell types not only PKC activation but also protein kinase A (PKA) activation increased the activities of Raf-1 kinase and MAP kinases in cardiac myocytes and induced cell growth. Finally, we observed that beta-AR-induced activation of MAP kinases is dependent on both Gs/cAMP/PKA and Gi/Src/Ras signaling pathways and that phosphorylation of beta-AR is critical to the cross talk between these signaling pathways.

Animals↗
PubMed2000

Details of hyperplastic polyps of the stomach shrinking after anti-Helicobacter pylori therapy.

The precise etiology of hyperplastic polyps of the stomach is unknown, but recent studies suggest that they arise as a consequence of inflammation occurring in intimate association with Helicobacter pylori infection. The process of polyp regression after anti-H. pylori therapy, however, is unclear. Here we report a patient with large hyperplastic polyps of the stomach that regressed markedly after anti-H. pylori therapy. Histological examination of the regressed polyps revealed a decrease in the height of the hyperplastic foveolar epithelium and a decrease in the amount of inflammatory cell infiltration in the stroma. In addition, the percentage of Ki-67-positive hyperplastic epithelial cells markedly decreased after anti-H. pylori therapy, indicating that the epithelial cell proliferation rate had markedly decreased after treatment. At the same time, the degree of cyclooxygenase-2 expression in epithelial cells in the polyps decreased after treatment. Because cyclooxygenase-2 is expressed at sites of inflammation or neoplasm, these findings are consistent with a decrease in inflammatory cell infiltration, and represent resolving inflammation.

Anti-Bacterial Agents↗
PubMed2000

Protein-losing enteropathy associated with hypocomplementemia and anti-nuclear antibodies.

We report a case of protein-losing enteropathy associated with an autoimmune disorder, presumably systemic lupus erythematosus. Although typical manifestations of systemic lupus erythematosus were lacking, a high serum cholesterol level, a low serum complement level, positivity for anti-nuclear antibody, and positivity for anti-single-strand DNA antibody suggested an autoimmune mechanism as the cause of the condition. Although immunohistological examination of duodenal and ileal biopsy specimens failed to reveal deposits of immune complex or complement in the vessels, capillary hyperpermeability was suspected as the mechanism of the condition.

Adult↗
PubMed2000

Evaluation of the poly(ADP-ribose) polymerase gene in human stroke.

Nitric oxide (NO) and its reactant product, peroxynitrite, have been implied to mediate neuronal damage following cerebral ischemia. However, the cellular targets of these compounds remain unclear. Studies using poly(ADP-ribose) polymerase (PARP) inhibitors and PARP knock-out mice have recently demonstrated that excessive activation of this nuclear enzyme plays an important role in NO-induced neurotoxicity. To evaluate the relevance of this plausible candidate gene to human stroke, we undertook a case-control study in Japanese. Participants comprised 213 cerebral infarction cases and 374 age- and sex-matched controls. As a primary investigation, we screened polymorphic sites of the PARP gene, and newly identified a total of four polymorphisms in 1230-bp 5'-flanking sequence. None of them were, however, located on the known promoter components of the gene. Two bi-allelic polymorphisms selected and a CA-repeat polymorphism were subsequently characterized in the case-control study, but none were significantly associated with cerebral infarction in the present study. Our data thus suggest that the tested PARP polymorphisms do not principally contribute to cerebral infarction, although extensive searches would be required to clarify whether the PARP gene plays an important role in the pathogenesis of human stroke.

Adult↗
PubMed2000

Evidence for association between paraoxonase gene polymorphisms and atherosclerotic diseases.

Paraoxonase 1 (PON1) is proposed to have an anti-atherogenic action. Two polymorphisms at the PON1 (M/L55 and Q/R192) have been shown to be associated with coronary artery disease (CAD). This conclusion is not drawn universally, however, and specific ethnic characteristics may be important determinants in this association. Recently two homologues of PON1 - PON2 and PON3 - were identified and Sanghera et al. demonstrated C/S311 polymorphism at PON2 was associated with the risk of CAD. Within that context, we investigated the association between the aforementioned three polymorphisms and CAD and ischemic stroke in a Japanese population. The study population included 431 control subjects, 210 CAD patients, and 235 ischemic stroke patients. Genotype distributions and allele frequencies of M/L55 and C/S311 were similar among the control and patient groups, whereas the R192 allele frequency was significantly higher (P<0.001) in CAD (75%) and ischemic stroke (76%) patients than in control subjects (65%). When confounding influences of other risk factors were controlled for by multivariate analysis, R192 remained an independent risk determinant (additive model: OR (95% CI), P value CAD: 2.01 (1.45-2.79), 0.0001; ischemic stroke: 1.84 (1.34-2.52), 0.0002 (three genotypes into calculation)). Taken together, our data indicate that the Q/R192 is principally associated with both CAD and ischemic stroke in Japanese.

Aged↗