Biomedical subjects

Y Kitamura

Publications and source records attributed to Y Kitamura.

At least 307 records · Page 17Linked to original sources

PubMed1997

Absence of mast cell involvement in leukocyte adhesion and emigration induced by inhibition of nitric oxide synthase.

Leukocyte adhesion on venules and their emigration to extravascular connective tissue are induced by administration of a nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester. In the present study, the involvement of mast cells in the process was examined in genetically mast cell-deficient and normal rats by intravital microscopy. Superfusion of the NOS inhibitor into the mesentery induced partial degranulation of mast cells in normal rats. However, leukocyte adhesion on mesenteric venules and emigration to extravascular connective tissue occurred even in mast cell-deficient rats, with no significant difference from the normal rats. When the reverse-passive Arthus reaction, characterized by generalized antigen-antibody complex formation, was induced in the rat mesentery, the immune complex increased both the adhesion and emigration in normal rats but not in mast cell-deficient rats. These results show that mast cells are not involved in the leukocyte adhesion and emigration induced by NOS inhibition, but are in the reverse-passive Arthus reaction.

Animals↗

PubMed1996

Functional properties of murine macrophages promoted by nerve growth factor.

The stimulating effect of nerve growth factor (NGF) on phagocytosis, parasite killing, and interleukin-1beta (IL-1beta) production of murine peritoneal macrophages was assessed. In the presence of various doses of NGF, macrophages showed the increased phagocytosis of both nonspecific hydrophilic microspheres and sheep red blood cells (SRBC) opsonized with anti-SRBC antibodies (Ab) or complement in a dose-dependent manner. NGF also enhanced killing of Leishmania donovani promastigotes by macrophages, and its ability was comparable with that of an optimal dose of recombinant granulocyte-macrophage colony-stimulating factor or recombinant interferon-gamma. The addition of NGF to peritoneal macrophages and monocyte-macrophage J774A.1 cells led to a significant release of IL-1beta in a dose-dependent manner and expression of IL-1beta mRNA. Because pretreatment of peritoneal macrophages and J774A.1 cells with K-252a, a tyrosine kinase inhibitor, completely suppressed these NGF-mediated stimulating effects and p140trk phosphorylation and because flow cytometric analysis with specific Ab against two distinct NGF receptors showed the expression of p140trk, unlike p75LNGFR, on the surface of macrophages, the stimulating activity of NGF to murine macrophages may be mediated through p140trk. Thus, NGF may act as an activator for murine macrophages in the process of inflammatory and immune actions.

3T3 Cells↗

PubMed1996

Mechanism of resistance to NO-induced neurotoxicity in cultured rat dopaminergic neurons.

We previously reported that mesencephalic dopaminergic neurons are resistant to cytotoxicity induced by nitric oxide (NO). This study investigated the intracellular mechanism that protects dopaminergic neurons against NO toxicity in rat mesencephalic cultures. Peroxynitrite anion, an active metabolite of NO, caused significant cytotoxic effects against dopaminergic and nondopaminergic neurons, but NO caused cytotoxic effects restricted to nondopaminergic neurons. In addition, we studied the effects of ascorbate, an anti-oxidant, on NO-induced neurotoxicity against dopaminergic neurons and found that coadministration of ascorbate failed to affect resistance against NO-induced neurotoxicity. These findings suggest that the protecting mechanism from NO neurotoxicity in dopaminergic neurons is based on inhibition of conversion of NO to peroxynitrite anion, is independent of the NO redox state, and is possibly due to suppression of superoxide anion production. Furthermore, we investigated NO-induced neurotoxicity with or without pretreatment with sublethal doses of methylphenylpyridium ion (MPP+). Following pretreatment with 1 microM MPP+, which did not show significant cytotoxic effects against dopaminergic neurons, NO demonstrated significant cytotoxicity. Therefore, MPP+ may inhibit the protecting systems from NO neurotoxicity in dopaminergic neurons.

1-Methyl-4-phenylpyridinium↗

PubMed1996

150-kD oxygen-regulated protein is expressed in human atherosclerotic plaques and allows mononuclear phagocytes to withstand cellular stress on exposure to hypoxia and modified low density lipoprotein.

The 150-kD oxygen-regulated protein (ORP150) was initially characterized based on its selective expression in astrocytes subjected to oxygen deprivation (Kuwabara, K., M. Matsumoto, J. Ikeda, O. Hori, S. Ogawa, Y. Maeda, K. Kitagawa, N. Imuta, K. Kinoshita, D.M. Stern, et al. 1996. J. Biol. Chem. 279:5025-5032). We have found that exposure of cultured human aortic smooth muscle cells and mononuclear phagocytes (MPs) to hypoxia (pO2 approximately 12-14 torr) induces ORP150 transcripts and production of the antigen, whereas incubation with either hydrogen peroxide, sodium arsenite, heat shock, or 2-deoxyglucose was without effect. Tissue extracts prepared from human atherosclerotic lesions demonstrated expression of ORP150 mRNA and antigen, vs lack of ORP150 in samples from nonatherosclerotic areas. In situ hybridization using ORP150 riboprobes showed the mRNA to be predominantly [correction of predominately] present in macrophages in in atherosclerotic plaques. Furthermore, autoantibody to ORP150 was demonstrated in the serum of patients with severe atherosclerosis, consistent with inducible in vivo expression of ORP150. Introduction of antisense oligonucleotide for ORP150 selectively diminished hypoxia-mediated induction of ORP150 antigen and reduced the viability of hypoxic MPs, especially in the presence of modified (oxidized/acetylated) LDL. In support of a role for ORP150 in the MPs' response to the microenvironment of an atheroma, the presence of oxidized LDL enhanced by approximately 10-fold ORP150 expression in hypoxic cultures. These data indicate that cells of the atherosclerotic vessel wall express ORP150 as part of a protective mechanism, potentially triggered by local hypoxia/hypoxemia and augmented by modified lipoproteins. The presence of antibody to ORP150 in sera of patients with severe atherosclerosis emphasizes the possibility that ORP150 may be a marker of vascular pathology.

Adolescent↗

PubMed1996

Cyclic GMP elevation by 5-hydroxytryptamine is due to nitric oxide derived from endogenous nitrosothiol in NG108-15 cells.

To clarify the involvement of nitric oxide (NO) derived from nitrosothiols (RSNO) in 5-hydroxytryptamine (5-HT)-induced Ca(2+)-independent cGMP formation (CIGF) in NG108-15 cells, we investigated the effects of 5-HT on intracellular contents of RSNO as well as of NO metabolites. 5-HT stimulation resulted in an increase in the intracellular contents of nitrate and cGMP. RSNO was detected in NG108-15 cells and was decreased by 5-HT stimulation. Furthermore, the time course of nitrate increase was coincident with that of RSNO decrease. CarboxyPTIO inhibited 5-HT-induced CIGF, whereas oxyhemoglobin failed to inhibit it. The data suggest that NO is stored in a stable form as RSNO and that 5-HT stimulates NO generation from endogenous RSNO, which is followed by elevation of cGMP via activation of cytosolic guanylyl cyclase by NO in NG108-15 cells. We suggest the existence of a novel 5-HT signal transduction pathway involved in NO generation in NG108-15 cells.

Animals↗

PubMed1996

Regulation of mouse mast cell protease 6 gene expression by transcription factor encoded by the mi locus.

The mi locus of mice encodes a member of the basic-helix-loop-helix-leucine zipper (bHLH-Zip) protein family of transcription factors (hereafter called MITF). Because the expression of the mouse mast cell protease 6 (MMCP-6) gene is remarkably reduced in mast cells of mi/mi mutant mice, we investigated the effect of MITF on the transcription of the MMCP-6 gene. First, we introduced the normal (+) MITF cDNA into mi/mi cultured mast cells using the retroviral vector. Overexpression of +-MITF but not mi-MITF normalized the expression of the MMCP-6 gene, indicating the involvement of +-MITF in the MMCP-6 gene transactivation. Second, we analyzed the promoter of the MMCP-6 gene by the transient cotransfection assay. The luciferase construct under the control of the MMCP-6 promoter and the cDNA encoding +-MITF or mi-MITF were cotransfected into NIH/ 3T3 fibroblasts. The coexpression of +-MITF but not mi-MITF increased the luciferase activity 10-fold. We found a CACATG and a CATCTG motif in the MMCP-6 promoter, both of which are generally recognized by bHLH-Zip-type transcription factors. We also found a GACCTG motif that was strongly bound by +-MITF. These three motifs were necessary for the 10-fold transactivation ability of the MMCP-6 promoter by +-MITF. Mutations of each motif significantly reduced the transactivation, suggesting that +-MITF directly transactivated the MMCP-6 gene through these three motifs.

3T3 Cells↗

PubMed1996

Inhibition of thymidylate synthase and thymidine kinase by okadaic acid in regenerating rat liver after partial hepatectomy.

The effects of okadaic acid, a potent and specific inhibitor of protein phosphatases 1 and 2A, on liver regeneration after partial (70%) hepatectomy were investigated. The injection of okadaic acid (25 micrograms/kg body weight) inhibited the increases in the activities of thymidylate synthase and thymidine kinase in regenerating rat liver at 24 hr after partial hepatectomy, with a concomitant reduction in DNA content. Northern blot analysis showed that the suppression of thymidylate synthase and thymidine kinase activities was caused by comparable decreases in their mRNA levels. The protein levels of thymidylate synthase and thymidine kinase were confirmed by immunoblotting assay to be proportional to the activity and mRNA levels. These findings suggest that okadaic acid-sensitive protein phosphatases are involved in transcriptional control of the dTMP-synthesizing enzymes during liver regeneration.

Animals↗

PubMed1996

Defects of B-cell lymphopoiesis and bone-marrow myelopoiesis in mice lacking the CXC chemokine PBSF/SDF-1.

The chemokines are a large family of small, structurally related cytokines. The physiological importance of most members of this family has yet to be elucidated, although some are inducible inflammatory mediators that determine leukocyte chemotaxis. Pre-B-cell growth-stimulating factor/stromal cell-derived factor-1 (PBSF/SDF-1) is a member of the CXC group of chemokines PBSF/SDF-1 stimulates proliferation of B-cell progenitors in vitro and is constitutively expressed in bone-marrow-derived stromal cells. Here we investigate the physiological roles of PBSF/SDF-1 by generating mutant mice with a targeted disruption of the gene encoding PBSF/SDF-1. We found that mice lacking PBSF/SDF-1 died perinatally and that although the numbers of B-cell progenitors in mutant embryos were severely reduced in fetal liver and bone marrow, myeloid progenitors were reduced only in the bone marrow but not in the fetal liver, indicating that PBSF/SDF-1 is responsible for B-cell lymphopoiesis and bone-marrow myelopoiesis. In addition, the mutants had a cardiac ventricular septal defect. Hence, we have shown that the chemokine PBSF/SDF-1 has several essential functions in development.

Animals↗

PubMed1996

Involvement of transcription factor encoded by the mi locus in the expression of c-kit receptor tyrosine kinase in cultured mast cells of mice.

The mi locus of mice encodes a member of the basic-helix-loop-helix-leucine zipper (bHLH-Zip) protein family of transcription factors (hereafter called MITF). Cultured mast cells of mi/mi genotype (mi/mi CMCs) did not normally respond to stem cell factor (SCF), a ligand for the c-kit receptor tyrosine kinase. The poor response of mi/mi CMCs to SCF was attributed to the deficient expression of c-kit both the mRNA and protein levels. The purpose of the present study is to investigate the effect of MITF on the transcription of the c-kit gene. First, we introduced cDNA encoding normal (+) MITF or mutant (mi) MITF into mi/mi CMCs using the retroviral vector. Overexpression of (+)-MITF but not mi-MITF normalized the expression of the c-kit and the poor response of mi/mi CMCs to SCF, indicating the involvement of (+)-MITF in the c-kit gene transactivation. Second, we analyzed the promoter of the c-kit gene. Three CANNTG motifs recognized by bHLH-Zip-type transcription factors were conserved between the mouse and human c-kit promoters. Among these three CANNTG motifs, only the CACCTG motif (nt -356 to -351) was specifically bound by (+)-MITF. When the luciferase gene under the control of the c-kit promoter was contransfected into NIH/3T3 fibroblasts with cDNA encoding (+)-MITF or mi-MITF, the luciferase activity significantly increased only when (+)-MITF cDNA was cotransfected. The deletion of the promoter region containing the CACCTG motif or the mutation of the CACCTG to CTCCAG abolished the transactivation effect of (+)-MITF, indicating that (+)-MITF transactivated the c-kit gene through the CACCTG motif. When the luciferase gene under the control of the c-kit promoter was introduced into the FMA3 mastocytoma and FEC-P1 myeloid cell lines, remarkable luciferase activity was observed only in FMA3 cells. Thus, the involvement of (+)-MITF in the c-kit transactivation appeared to be specific to the mast cell lineage.

Animals↗

PubMed1996

Neoplastic transformation of normal hematopoietic cells by constitutively activating mutations of c-kit receptor tyrosine kinase.

The c-kit proto-oncogene encodes a receptor tyrosine kinase that is crucial to hematopoiesis, melanogenesis, and gametogeneis. Although the enzymatic activity of the c-kit product (KIT) is regulated by its ligand, both the Val559-->Gly (G559) mutation in the juxtamembrane domain and the Asp814-->Val (V814) mutation in the phosphotransferase domain lead to constitutive activation of KIT. By retroviral infection of hematopoietic progenitor cells with KIT(G559) or KIT(V814), KIT(G559) induced development of granulocyte/macrophage and mast-cell colonies in vitro without the addition of exogenous growth factors. KIT(V814) induced factor-independent growth of various types of hematopoietic progenitor cells, resulting in the development of mixed erythroid/myeloid colonies in addition to granulocyte/macrophage and mast-cell colonies. Furthermore, transplantation of KIT(G559) and KIT(V814)-infected bone marrow cells led to development of acute leukemia in one of 10 and six of 10 transplanted mice, respectively. No mice developed hematologic malignancies after transplantation of wild-type KIT-infected cells. Furthermore, transgenic mice expressing KIT(V814) developed acute leukemia or malignant lymphoma. These results demonstrate a direct role of the mutant KITs, particularly KIT(V814), in tumorigenesis of hematopoietic cells and suggest that similar mutations may contribute to the development of human hematologic malignancies.

Animals↗

PubMed1996

Kyotorphin (L-tyrosyl-L-arginine) as a possible substrate for inducible nitric oxide synthase in rat glial cells.

L-Arginine (L-Arg) is an endogenous substrate for nitric oxide synthase (NOS). In the present study, we examined whether L-tyrosyl-L-Arg (kyotorphin), an endogenous analgesic neuropeptide, might be a substrate for inducible NOS (iNOS) in the brain. Both kyotorphin and L-Arg caused an accumulation of nitrites in lipopolysaccharide (LPS)-treated glial cells cultured from infant rat brains. However, such accumulation of nitrites was not induced by NG-nitro-L-Arg (a NOS inhibitor), L-tyrosyl-D-Arg (D-kyotorphin) or D-Arg. L-Leucyl-L-Arg (an antagonist for kyotorphin receptors) or bestatin (an inhibitor for kyotorphin-hydrolyzing peptidase) did not inhibit the kyotorphin-induced accumulation of nitrites in LPS-treated cells. On the contrary, L-Leucyl-L-Arg caused an accumulation of nitrites in a concentration-dependent manner. The results indicate that nitric oxide (NO) is produced in LPS-treated glial cells directly from kyotorphin through the catalytic action of iNOS.

Analgesics↗

PubMed1996

Senescence-accelerated mouse. Neurochemical studies on aging.

Senescence-accelerated mouse (SAMP8) is known as a murine model of accelerated aging and memory dysfunction. The binding activity of [3H] 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK-11195) as a neurochemical marker of gliosis markedly increased with aging in the cerebral cortex and hippocampus of SAMP8. Immunoreactivity for glial fibrillary acidic protein (GFAP) was also enhanced. A beta-amyloid precursor protein (APP)-like immunoreactivity and 27-kDa-carboxyl terminal fragments of APP increased in SAMP8 brain. In addition, anti-APP antibody stained reactive astrocytes surrounding spongy degeneration in brain stern of SAMP8. These results suggest that astrocytosis and production of APP-derived fragments occur markedly in SAMP8 brains.

Aging↗

PubMed1996

Possible involvement of Janus kinase Jak2 in interferon-gamma induction of nitric oxide synthase in rat glial cells.

To clarify the induction pathway of inducible nitric oxide (NO) synthase in the brain, we examined the effects of interferon-gamma and lipopolysaccharide on the induction of inducible NO synthase in glial cells cultured from neonatal rats, compared to those in the macrophage cell line RAW264.7 which was derived from Abelson leukemia virus-induced BALB/c lymphocytic lymphoma. NO synthase activity (NO2- accumulation) and 130 kDa protein of inducible NO synthase were induced 24 h after treatment with interferon-gamma or lipopolysaccharide in both glial cells and RAW264.7 macrophages. These induction activities were inhibited by a tyrosine kinase inhibitor, herbimycin A. Immunoprecipitation assay using antibodies against Janus kinases, and the signal transducer and activator of transcription-1 (STAT1), revealed that interferon-gamma induced tyrosine phosphorylation of the just another kinase-2 (Jak2) and STAT1 alpha but did not induced the phosphorylation of Jak1, the non-receptor tyrosine kinase-2 (Tyk2) and STAT1 beta. Tyrosine phosphorylation of Jak2 and STAT1 alpha induced by interferon-gamma was also inhibited by herbimycin A, while lipopolysaccharide did not induce any tyrosine phosphorylation of Janus kinases and STAT1 at all. These results suggest that the interferon-gamma-induced inducible NO synthase induction involves activation of Jak2-STAT1 alpha pathway in both glial cells and macrophages.

Animals↗

PubMed1996

The disruption of spatial cognition and changes in brain amino acid, monoamine and acetylcholine in rats with transient cerebral ischemia.

We investigated the disruption of spatial cognition due to transient forebrain ischemia using an 8-arm radial arm maze task in rats. Five or 10 min of ischemia did not affect the task acquisition. When rats established spatial cognition by daily training of the task, 10 min of ischemia significantly decreased the number of correct choices and increased the errors in the task when performed 24 h after reperfusion. These changes, however, returned to the normal level after about 4 days of daily training. Glutamic acid (Glu) and acetylcholine (ACh) release from the dorsal hippocampus (DH) was observed to transiently increase during ischemia. However, neither the content of noradrenaline (NA) nor the release of NA in the DH changed during ischemia. The NA and ACh release from the DH, however, gradually decreased during reperfusion, and the decrease became significant at 24 h after reperfusion. The NA content of the frontal cortex (FC) and the DH increased 7 days after reperfusion. These results suggest that the disruption of spatial cognition induced by 10 min of ischemia may be attributed to a greater degree to the dysfunction of the hippocampal ACh and NA, and cortical NA systems, rather than to the development of neuronal cell death in these areas.

Acetylcholine↗

PubMed1996

Role of aspartic acid 814 in the function and expression of c-kit receptor tyrosine kinase.

The c-kit receptor tyrosine kinase (KIT) is constitutively activated in three different types of neoplastic mast cell lines by naturally occurring mutations that result in substitutions of Val or Tyr for Asp814 in the phosphotransferase domain. In an effort to characterize the role of the Asp814 residue, we have investigated the properties of mutant KITs in which the Asp814 residue was deleted or mutated to a series of other amino acids. With the exception of rare instances, mutant KITs with substitutions of Asp814 were found to be constitutively phosphorylated on tyrosine and activated in the absence of the ligand, stem cell factor (SCF), whereas a deletion mutant lacking Asp814 (KITDel-Asp-814) did not exhibit tyrosine phosphorylation and activation even after treatment with SCF. In addition to constitutive activation, furthermore, both highly activated substitution mutants (KITVal-814 and KITTyr-814) and modestly activated substitution mutants (KITGly-814 and KITHis-814) were continuously degraded in the absence of SCF, whereas wild-type KIT (KITWild) required SCF stimulation to undergo degradation. These results suggested that the Asp814 residue may play a crucial role in regulating enzymatic activity and expression of KIT and that various types of mutations at the Asp814 residue may generate oncogenic protein with constitutive activation and degradation.

Amino Acid Sequence↗

PubMed1996

Molecular cloning of p125Nap1, a protein that associates with an SH3 domain of Nck.

Binding proteins to the Src homology 3 (SH3) domains of Nck were screened by the use of glutathione S-transferase fusion proteins. Two proteins of 140 and 125 kDa were detected, both of which associated preferentially with the first SH3 domain of Nck. The 125-kDa protein, designated as Nap1 for Nck-associated protein 1, was purified and the corresponding rat cDNA was isolated. The predicted amino acid sequence revealed that p125Nap1 does not contain any known functional motif but shows sequence homology to Hem family gene. Using specific antibodies, p125Nap1 was shown to associate with Nck both in vitro and in intact cells. Further characterization of p125Nap1 may clarify the protein-protein interaction in the downstream signaling of Nck.

Adaptor Proteins, Signal Transducing↗

PubMed1996

Abundant expression of transcription factor GATA-2 in proliferating but not in differentiated mast cells in tissues of mice: demonstration by in situ hybridization.

Although GATA-binding transcription factors (GATA-1 and GATA-2) are strongly expressed in cultured mast cells (CMCs), their expression in mast cells within tissues has not been reported. We examined the expression of GATA-1 and GATA-2 in skin tissues of mice using Northern blot analysis and in situ hybridization. mRNA for GATA-2 but not for GATA-1 was expressed in skin mast cells of WB-+/+ embryos between days 15 and 17 postcoitum (pc). The expression was downregulated on and after day 18 pc. Skin mast cells did not express GATA-2 after birth either. When the number of skin mast cells was compared with the number of GATA-2 mRNA-expressing cells, GATA-2 mRNA appeared to be expressed by mast cells only when the number was increasing. When the mRNA expression of high-affinity IgE receptor beta-subunit and mast cell carboxypeptidase A was used as differentiation markers, the expression of these mRNAs continued even after the downregulation of GATA-2 expression. To clarify the relationship of the proliferation and GATA-2 expression, proliferating CMCs derived from WBB6F1-+/+ mice were transplanted into the peritoneal cavity of mast cell-deficient WBB6F1-W/Wv mice. The CMCs stopped both the proliferation and GATA-2 expression after the transplantation, suggesting the association of these two parameters in mast cells within tissues of mice.

Animals↗

PubMed1996

Effects of tactile interference stimulation on somatosensory evoked magnetic fields.

Tactile stimulation of the hand interferes with somatosensory evoked brain responses following electrical median nerve stimulation. This effect was studied in eight normal subjects by magnetonecephalography (MEG). When stimulation was applied to the hand ipsilateral to the stimulated nerve, only the third response (3M) was enhanced in five subjects, but other responses were attenuated in all subjects. These interference effects were probably due to interactions in areas 3b and 1. After stimulation of the contralateral hand, only the second response (2M) was enhanced in six subjects. This effect was probably due to the intracerebral interactions mediated through the corpus callosum.

Adult↗