Biomedical subjects

Kazuhiro Nakamura

Publications and source records attributed to Kazuhiro Nakamura.

At least 55 records · Page 3Linked to original sources

PubMed2004

Independent inputs by VGLUT2- and VGLUT3-positive glutamatergic terminals onto rat sympathetic preganglionic neurons.

To characterize glutamatergic axon terminals onto sympathetic preganglionic neurons (SPNs), we visualized immunohistochemically three vesicular glutamate transporters (VGLUTs) in the intermediolateral cell column (IML) of rat thoracic spinal cord. VGLUT2 and VGLUT3 immunoreactivities but not VGLUT1 immunoreactivity were distributed in the IML and found in terminals making asymmetric synapses and apposed to dendrites immunopositive for choline acetyltransferase, an SPN marker. VGLUT2 and VGLUT3 immunoreactivities were not co-localized with each other. A population of VGLUT2-immunoreactive but not VGLUT3-immunoreactive terminals were adrenergic or noradrenergic. Some of VGLUT3-immunoreactive but not VGLUT2-immunoreactive terminals contained serotonin. These results indicate at least two independent glutamatergic terminal populations, which include a distinct monoaminergic subpopulation, making excitatory inputs onto SPNs.

Adrenergic Fibers↗

PubMed2004

Gain-of-function polymorphism in mouse and human Ltk: implications for the pathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE), a complex multigenic disease, is a typical antibody-mediated autoimmune disease characterized by production of autoantibodies against a variety of autoantigens and immune complex-type tissue inflammation, most prominently in the kidney. Evidence suggests that genetic factors predisposing to aberrant proliferation/maturation of self-reactive B cells initiate and propagate the disease. In SLE-prone New Zealand Black (NZB) mice and their F1 cross with New Zealand White (NZW) mice, B cell abnormalities can be ascribed mainly to self-reactive CD5+ B1 cells. Our genome-wide scans to search for susceptibility genes for aberrant activation of B1 cells in these mice showed evidence that the gene, Ltk, encoding leukocyte tyrosine kinase (LTK), is a possible candidate. LTK is a receptor-type protein tyrosine kinase, belonging to the insulin receptor superfamily, and is mainly expressed in B lymphocyte precursors and neuronal tissues. Sequence and functional analyses of the gene revealed that NZB has a gain-of-function polymorphism in the LTK kinase domain near YXXM, a binding motif of the p85 subunit of phosphatidylinositol 3-kinase (PI3K). SLE patients also had this type of Ltk polymorphism with a significantly higher frequency compared with the healthy controls. Our findings suggest that these polymorphic LTKs cause up-regulation of the PI3K pathway and possibly form one genetic component of susceptibility to abnormal proliferation of self-reactive B cells in SLE.

Adult↗

PubMed2004

Transgene-mediated hyper-expression of IL-5 inhibits autoimmune disease but increases the risk of B cell chronic lymphocytic leukemia in a model of murine lupus.

IL-5 preferentially activates B1 cells to produce natural antibodies cross-reactive to self antigens. To determine the role of IL-5 in antibody-mediated autoimmune disease, we generated systemic lupus erythematosus (SLE)-prone (NZB x NZW)F1 mice congenic for IL-5 transgene (TG-F1). The transgene unexpectedly reduced the incidence of lupus nephritis. Anti-DNA antibodies in sera and those produced by splenic B cells in vitro were markedly decreased in TG-F1 mice, while total polyclonal Ig levels were comparable to those in IL-5 transgene-negative (NZB x NZW)F1 (non-TG-F1) littermates. Flow cytometry-sorted splenic B1 cells showed a significant reduction of anti-DNA antibody synthesis in response to IL-5, while proliferative responses to IL-5 did not significantly differ between TG-F1 and non-TG-F1 mice. As TG-F1 mice aged, frequencies of peripheral B1 cells progressively increased, and the mice frequently developed B cell chronic lymphocytic leukemia (B-CLL). Our results suggest that dysregulated, continuous high expression of IL-5 in SLE-prone mice may directly or indirectly mediate a skewed signaling of proliferation/differentiation of self-antigen-activated B1 cells, leading to suppression of autoimmune disease, but instead to aberrant expansion of B1 cells, giving rise to B-CLL. Thus, this model may provide a clue to the pathogenesis of both SLE and B-CLL.

Animals↗

PubMed2004

Traumatic acute subdural hygroma mimicking acute subdural hematoma.

Subdural hygroma is a frequent delayed complication of head trauma. Most hygromas are clinically 'silent' and a few cases have shown slow deterioration in the chronic stage. We report a case of subdural hygroma showing unique radiological findings and rapid deterioration. A 74-years-old female presented with a mild headache and consciousness disturbance after head injury. Computed tomography showed a midline shift as a result of two components piling up in the subdural space; the outer components showed low density, the inner components high density. Magnetic resonance imaging demonstrated that these two subdural components were subdural hygroma and subarachnoid hematoma. Simple burr hole irrigation, rather than large craniotomy, was thought to be more appropriate treatment to reduce the mass effect. Simple burr hole irrigation was performed to remove the subdural hygroma and the patient showed an excellent recovery. Careful examination of the radiological findings prevented an unnecessary procedure in this case. A possible mechanism of this phenomenon is discussed.

Acute Disease↗

PubMed2004

Is state-dependent alternation of slow dynamics in central single neurons during sleep present in the rat ventroposterior thalamic nucleus?

Based upon our previous results in cats, we hypothesized that neurons in the central processor systems of the brain generally exhibit state-dependent dynamics alternation of slow fluctuations in spontaneous activity during sleep. To test the validity of this hypothesis across species, we recorded single neuronal activity during sleep from the ventroposterior (VP) thalamic nucleus in unanesthetized, head-restrained rats. Spectral analysis was performed on successive spike-counts of neuronal activity recorded during three stages of the sleep-wakefulness cycle: wakefulness (W, n=6), slow-wave sleep (SWS, n=20), and paradoxical sleep (PS, n=32). We found that firing of VP neurons displayed white-noise-like dynamics over the range of 0.04-1.0 Hz during SWS and 1/f-noise-like dynamics over the same range during PS. We also demonstrated for the first time that the slow dynamics of neuronal activity during quiet wakefulness (but not drowsiness) are white-noise-like. These results suggest that our hypothesis is true across species. During W and SWS, the brain may be considered as under global inhibition. Conversely, PS may represent a state of global disinhibition in the brain, where neuronal activity exhibits 1/f-noise-like dynamics. Fluctuations observed in living organisms may be involved in essential processes in generation and function of sleep states.

Action Potentials↗

PubMed2004

Wiring diagrams of MAPK regulation by MEKK1, 2, and 3.

Mitogen-activated protein kinase (MAPK) pathways are activated by a plethora of stimuli. The literature is filled with papers describing the activation of different MAPKs by almost any stimulus or insult imaginable to cells. In this review, we use signal transduction wiring diagrams to illustrate putative upstream regulators for the MAPK kinase kinases, MEKK1, 2, and 3. Targeted gene disruption of MEKK1, 2, or 3 defined phenotypes for each MEKK associated with loss of specific MAPK regulation. Genetic analysis of MEKK function clearly defines specific components of the wiring diagram that require MEKK1, 2, or 3 for physiological responses. We propose that signal transduction network wiring diagrams are valuable tools for hypothesis building and filtering physiologically relevant phenotypic responses from less connected protein relations in the regulation of MAPK pathways.

Animals↗

PubMed2003

Magnetic resonance spectra of hyperpolarized (129)xe in human blood and living rat chest.

We constructed a gas polarization system to test the feasibility of using hyperpolarized (129)Xe gas as an NMR (nuclear magnetic resonance) probe to explore brain function. Both in vitro and in vivo experiments were performed with a 4.7 T NMR spectrometer. Xenon spectra from human blood confirmed the existence of two peaks corresponding to red blood cells and plasma. In rat studies, three peaks at around 200 ppm were observed. Our results are consistent with previously reported data.

Animals↗

PubMed2003

PB1 domains of MEKK2 and MEKK3 interact with the MEK5 PB1 domain for activation of the ERK5 pathway.

MEKK2 and MEKK3 are MAPK kinase kinases that activate the ERK5 pathway by phosphorylating and activating the MAPK kinase, MEK5. Activated MEK5 then phosphorylates and activates ERK5. PB1 domains were first defined in the p67phox and Bem1p proteins and have been shown to mediate protein-protein heterodimerization. A PB1 domain is encoded within the N-terminal portion of MEKK2, MEKK3, and MEK5. Herein, we analyze the functional role of MEKK2, MEKK3, and MEK5 PB1 domains in the ERK5 activation pathway. The PB1 domains of MEKK2 and MEKK3 bind the PB1 domain of MEK5 but do not significantly homo- or heterodimerize with one another in vitro. Furthermore, co-immunoprecipitation of MEKK2 and MEK5 from cell lysates shows that they form a complex in vivo. Deletion or mutation of the MEKK2 PB1 domain abolishes MEKK2-MEK5 complexes, demonstrating that the PB1 domain interaction is required for MEKK2-MEK5 interactions. Expression in cells of the MEKK2 or MEKK3 PB1 domain inhibits ERK5 activation, whereas expression of a mutant MEKK2 unable to bind the MEK5 PB1 domain or expression of the p67phox PB1 domain has no effect on ERK5 activation. These findings demonstrate that the PB1 domain mediates the association of MEKK2 and MEKK3 with MEK5 and that the respective PB1 domains of these kinases are critical for regulation of the ERK5 pathway. The free PB1 domain of MEKK2 or MEKK3 functions effectively to inhibit the ERK5 pathway but not the p38 or JNK pathways, demonstrating the specific and unique requirement of the MEKK2 and MEKK3 PB1 domain in regulating ERK5 activation.

Amino Acid Sequence↗

PubMed2003

A monoclonal antibody to the alpha2 domain of murine major histocompatibility complex class I that specifically kills activated lymphocytes and blocks liver damage in the concanavalin A hepatitis model.

We earlier found that a rat monoclonal antibody (mAb) RE2 can induce rapid death of murine activated, but not resting, lymphocytes and lymphocyte cell lines, in a complement-independent manner, a cell death differing from typical apoptosis or necrosis. We here found that this cell death is independent of pathways involving Fas, caspase, and phosphoinositide-3 kinase. With the advantage of producing human B cell line transfectants with stable expression of human/mouse xeno-chimeric MHC class I genes, we found that RE2 epitope resides on the murine class I alpha2 domain. However, the alpha3 domain plays a key role in transducing the death signal, which mediates extensive aggregation of the MHC class I-integrin-actin filament system, giving rise to membrane blebs and pores. In mouse models with T/NKT cell activation-associated fulminant hepatitis, administration of mAb RE2 almost completely inhibited the development of liver cell injuries. Taken collectively, this form of cell death may be involved in homeostatic immune regulation, and induction of this form of cell death using the mAbs may be potentially therapeutic for subjects with immunological diseases mediated by activated lymphocytes.

Animals↗

PubMed2003

Overexpression of V-1 prevents nitric oxide-induced cell death: involvement of enhanced tetrahydrobiopterin biosynthesis.

Previously we reported that the synthesis of catecholamines, dopamine, and noradrenaline was enhanced by overexpression of V-1 protein, a neuronal protein active in the initial stage of development of the rat cerebellum, in the neuronal cell line PC12D, a model of dopamine cells (Yamakuni et al. [1998] J. Biol. Chem. 273:27051-27054). To investigate the physiological role of this protein, we examined the effect of V-1 overexpression on cell toxicity induced by nitric oxide (NO) used at low concentrations. Two clones of PC12D cells overexpressing V-1, transfectants termed V1-46 and V1-69, were significantly more resistant to NOR3 (an NO donor) but not to etoposide (an inhibitor of topoisomerase II)-induced apoptotic cell death than the control cells (termed C-7 and C-9) that had been transfected with the vector alone. The addition of L-DOPA, dopamine, or noradrenaline to the medium did not abolish NOR3-induced cell death in PC12D cells. Moreover, pretreatment of V1-46 and V1-69 cells with L-alpha-methyl-p-tyrosine (alpha-MPT), an inhibitor of tyrosine hydroxylase, to inhibit catecholamine biosynthesis did not affect the resistance to NO toxicity. These results indicate that the catecholamine levels increased by V-1 overexpression did not produce the protection against NOR3-induced toxicity. We further showed that overexpression of V-1 enhanced the synthesis of (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH(4)). In addition, pretreatment with BH(4) or with sepiapterin, which is converted to BH(4) intracellularly, significantly protected PC12D cells in a dose-dependent manner. The increased BH(4) synthesis by V-1 overexpression was dose dependently inhibited by pretreatment with diaminohydroxypyrimidine (DAHP), an inhibitor of GTP-cyclohydrolase I, which is the rate-limiting enzyme for the biosynthesis of BH(4), concomitantly with the loss of protective effect afforded by V-1 overexpression. Furthermore, the addition of BH(4) or sepiapterin to DAHP-pretreated V146 and V1-69 cells restored cell viability. Taken together, these results indicate that V1 protein plays an important role in protection against cell death induced by NO at low levels by promoting the synthesis of BH(4). Moreover, these findings suggest the up-regulation of V1 expression as a possible therapeutic target for protection against the insult of NO-induced oxidative stress.

Animals↗

PubMed2003

Genetic dissection of anxiety in autoimmune disease.

Systemic lupus erythematosus (SLE), a complex multigenic disease, is characterized by hypergammaglobulinemia, autoantibody production and immune complex-type lupus nephritis. In addition to these signs and symptoms in SLE, there can be symptoms of neurological disorders, including anxiety. To clarify mechanisms governing the anxiety seen in lupus, we carried out genome-wide scans, and found that the region including interferon-alpha (IFN-alpha) on NZB chromosome 4 is significantly linked to the anxiety-like behavior seen in SLE-prone New Zealand Black (NZB) x New Zealand White (NZW) F(1) (B/W F(1)) mice. This finding was confirmed by anxiety-like performances of mice with heterozygous NZB/NZW alleles in the susceptibility region onto the NZW background. In B/W F(1) mice, neuronal IFN-alpha levels were elevated, and blockade of the micro (1) opioid receptor or corticotropin-releasing hormone receptor 1, possible downstream effectors for IFN-alpha in the brain partially overcame the anxiety-like behavior seen in the B/W F(1) mice. Consistently, neuronal corticotropin-releasing hormone levels were higher in B/W F(1) than NZW mice. Furthermore, pretreatment of micro (1) opioid receptor antagonist abolished anxiety-like behaviour seen in IFN-alpha-treated NZW mice. Anxiety is shown to be mediated by multiple mediators. Our data suggest that a genetically determined endogenous excess amount of IFN-alpha in the brain may form one aspect of anxiety-like behavior seen in SLE-prone mice.

Alleles↗

PubMed2003

Galectin-9 induces apoptosis through the calcium-calpain-caspase-1 pathway.

Galectin-9 (Gal-9) induced the apoptosis of not only T cell lines but also of other types of cell lines in a dose- and time-dependent manner. The apoptosis was suppressed by lactose, but not by sucrose, indicating that beta-galactoside binding is essential for Gal-9-induced apoptosis. Moreover, Gal-9 required at least 60 min of Gal-9 binding and possibly de novo protein synthesis to mediate the apoptosis. We also assessed the apoptosis of peripheral blood T cells by Gal-9. Apoptosis was induced in both activated CD4(+) and CD8(+) T cells, but the former were more susceptible than the latter. A pan-caspase inhibitor (Z-VAD-FMK) inhibited Gal-9-induced apoptosis. Furthermore, a caspase-1 inhibitor (Z-YVAD-FMK), but not others such as Z-IETD-FMK (caspase-8 inhibitor), Z-LEHD-FMK (caspase-9 inhibitor), and Z-AEVD-FMK (caspase-10 inhibitor), inhibited Gal-9-induced apoptosis. We also found that a calpain inhibitor (Z-LLY-FMK) suppresses Gal-9-induced apoptosis, that Gal-9 induces calcium (Ca(2+)) influx, and that either the intracellular Ca(2+) chelator BAPTA-AM or an inositol trisphosphate inhibitor 2-aminoethoxydiphenyl borate inhibits Gal-9-induced apoptosis. These results suggest that Gal-9 induces apoptosis via the Ca(2+)-calpain-caspase-1 pathway, and that Gal-9 plays a role in immunomodulation of T cell-mediated immune responses.

Adjuvants, Immunologic↗

PubMed2003

In vivo cross-linking of nucleosomal histones catalyzed by nuclear transglutaminase in starfish sperm and its induction by egg jelly triggering the acrosome reaction.

A histone heterodimer, designated as p28, which contains an Nepsilon(gamma-glutamyl)lysine cross-link between Gln9 of histone H2B and Lys5 or Lys12 of histone H4, is present in starfish (Asterina pectinifera) sperm. Treatment of sperm nuclei with micrococcal nuclease produced soluble chromatin, which was size-fractionated by sucrose-gradient centrifugation to give p28-containing oligonucleosome and p28-free mononucleosome fractions, indicating that the cross-link is internucleosomal. When sperm nuclei were incubated with monodansylcadaverine, a fluorescent amine, in the presence or absence of Ca(2+), histone H2B was modified only in the presence of Ca(2+). Gln9, in the N-terminal region, was modified, but the other Gln residues located in the internal region were not, suggesting that the modification takes place on the surface of the nucleosome core by the in situ action of a Ca(2+)-dependent nuclear transglutaminase. Treatment of sperm with the egg jelly, which activates Ca(2+) influx to induce the acrosome reaction, resulted in a significant elevation of the p28 content in the nucleus. This is the first demonstration of an in vivo activation of transglutaminase leading to the formation of a cross-link in intracellular proteins.

Acrosome Reaction↗

PubMed2003

Neurons of the rat preoptic area and the raphe pallidus nucleus innervating the brown adipose tissue express the prostaglandin E receptor subtype EP3.

The major effector organ for thermogenesis during inflammation or experimental pyrogen-induced fever in rodents is the brown adipose tissue (BAT). Prostaglandin E2 (PGE2) microinjection into the medial preoptic area (POA) of rats leads to hyperthermia through an increase in BAT thermogenesis and induces pyrogenic signal transmission towards the raphe pallidus nucleus (RPa), a brainstem nucleus known to contain sympathetic premotor neurons for BAT control. The medial POA has a high expression of prostaglandin E receptor subtype EP3 (EP3R) on POA neurons, suggesting that these EP3R are main central targets of PGE2 to mediate BAT thermogenesis. To reveal central command neurons that contain EP3R and polysynaptically project to the BAT, we combined EP3R immunohistochemistry with the detection of transneuronally labelled neurons that were infected after injection of pseudorabies virus into the BAT. Neurons double-labelled with EP3R and viral surface antigens were particularly numerous in two brain regions, the medial POA and the RPa. Of all medial POA neurons that became virally infected 71 h after BAT inoculation, about 40% expressed the EP3R. This subpopulation of POA neurons is the origin of a complete neuronal chain that connects potential PGE2-sensitive POA neurons with the BAT. As for the efferent pathway of pyrogenic signal transmission, we hypothesize that neurons of this subpopulation of EP3R expressing POA neurons convey their pyrogenic signals towards the BAT via the RPa. We additionally observed that two-thirds of those RPa neurons that polysynaptically project to the interscapular BAT also expressed the EP3R, suggesting that RPa neurons themselves might possess prostaglandin sensitivity that is able to modulate BAT thermogenesis under febrile conditions.

Adipose Tissue, Brown↗

PubMed2003

Efficacy of prophylactic use of trimethoprim-sulfamethoxazole in autoimmune neutropenia in infancy.

PURPOSE: Most children with autoimmune neutropenia (AIN) have a benign clinical course because of the spontaneous resolution of neutropenia. The authors observed the clinical course of AIN in infancy accompanied by the prophylactic use of trimethoprim-sulfamethoxazole (TMP-SMX) during neutropenia. PATIENTS AND METHODS: Eight infants with AIN were followed by serial tests for antineutrophil antibodies and management of infectious complications. RESULTS: The spontaneous disappearance of antineutrophil antibodies that preceded the normalization of the neutrophil count was found in all patients. Until the resolution of neutropenia, TMP-SMX was administered in five patients, resulting in a reduction in the incidence of infection with no adverse effects. CONCLUSIONS: These observations demonstrate the possibility of the safety and usefulness of TMP-SMX treatment in patients with AIN.

Anti-Infective Agents↗

PubMed2003

Potential roles of galectins in myeloid differentiation into three different lineages.

Little is known about the roles of galectins, a family of beta-galactoside-binding lectins, in myeloid cell differentiation. In the present experiments, we used HL-60 cells as a model of myeloid cell differentiation. The HL-60 cells were differentiated into eosinophil-, monocyte-, and neutrophil-like cells by coculture with sodium butyrate under a mild alkaline condition, phorbol 12-myristate 13-acetate, and dimethyl sulfoxide, respectively. Thus, the expression of galectins in HL-60 cells during differentiation into three different lineages was assessed. Reverse transcriptase-polymerase chain reaction analyses revealed that undifferentiated HL-60 cells expressed galectin-1, -3, -8, -9, and -10 (identical to Charcot Leyden crystal) mRNAs, and galectin-2, -4, and -7 were negligible before and after the differentiations. We failed to detect evident changes in the mRNA levels of galectin-1 and -8 during the differentiations. However, during the eosinophilic differentiation, galectin-9 mRNA expression was gradually decreased, whereas galectin-10 mRNA expression was increased. During the course of monocytic differentiation, galectin-9 mRNA expression was down-regulated, whereas galectin-3 mRNA expression was up-regulated. Moreover, only galectin-10 mRNA expression was enhanced in the process of neutrophilic differentiation. These changes in galectin expressions were confirmed by Western blot and flow cytometry analyses. It is thus suggested that changes in the expressions of galectin-3, -9, and -10 are potentially important for myeloid cell differentiation into specific lineages.

Butyrates↗

PubMed2003

Dysregulation of transcriptions in primary granule constituents during myeloid proliferation and differentiation in patients with severe congenital neutropenia.

We examined the expression of granule constituent genes in myeloid progenitor cells during proliferation and differentiation in patients with severe congenital neutropenia (SCN). The heterozygous mutation of the neutrophil elastase gene was identified in two of four patients. The CD34+/granulocyte-colony stimulating factor receptor (G-CSFR)+ cells of SCN patients showed defective responsiveness to G-CSF in serum-deprived culture. The CD34+/G-CSFR+ cells expressed low levels of the granule constituent mRNAs. The transcription levels of primary granule enzyme genes in CD34+/G-CSFR+ cells were gradually enhanced and then decreased when cells were induced toward myeloid lineage with G-CSF in normal subjects. However, the primary up-regulation and the following down-regulation of these enzyme transcriptions were not clearly observed in SCN patients. No differences in expressions of the lactoferrin gene were seen between normal subjects and patients with SCN. We hypothesize that the abnormal regulation of the transcription in primary granule constituents might involve the defective proliferation and differentiation of myeloid cells in patients with SCN.

Bone Marrow Cells↗

PubMed2003

Multiple intracranial arterial stenoses around the circle of Willis in association with Graves' disease: report of two cases.

OBJECTIVE AND IMPORTANCE: The association of Graves' disease with multiple intracranial arterial stenoses is rare. CLINICAL PRESENTATION: We report on two Japanese women who experienced the concurrence of Graves' disease and cerebral ischemia attributable to multiple intracranial arterial stenoses around the circle of Willis. Clinically, these patients demonstrated hyperthyroidism, goiter, ophthalmopathy, and ensuing ischemic strokes. Cerebral angiography demonstrated multiple intracranial arterial stenoses around the circle of Willis in both cases. These cases did not meet the full diagnostic criteria for moyamoya disease, in that there were no abnormal, net-like, collateral vessels, but the other clinical and angiographic findings were consistent with this condition. INTERVENTION: After normalization of their hormonal conditions, the patients underwent cerebral revascularization procedures. Both patients achieved excellent recoveries and returned to normal daily life after treatment. CONCLUSION: Multiple intracranial arterial stenoses and Graves' disease may occur simultaneously. Such cases may offer new insights into the pathogenesis of these two conditions. It is important to study more patients with this dual condition, to obtain more evidence of the relationship between genetic and immunogenic backgrounds.

Adult↗