Showing papers by "Takashi Saito published in 2003"

Negative feedback of T cell activation through inhibitory adapters and costimulatory receptors.

Abstract: Antigen recognition by the T cell receptor (TCR) complex induces the formation of a TCR signalosome by recruiting various signaling molecules, generating the recognition signals for T cell activation. The activation status and functional outcome are positively and negatively regulated by dynamic organization of the signalosome and by costimulation signals. We have studied the negative regulation of T cell activation, particularly through inhibitory adapters and costimulation receptors that are little expressed in resting cells but are induced upon T cell activation. We described Grb-associated binder 2 (Gab2) and cytotoxic T lymphocyte antigen-4 (CTLA-4) as a representative inhibitory adapter and a negative costimulation receptor, respectively, both of which exhibit negative feedback. Gab2 functions as a signal branch for activation vs. inhibition, as phosphorylation of either Src homology 2 (SH2) domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) or Gab2 by zeta-associated protein of 70 kDa (ZAP-70) determines the fate of the response. As a professional inhibitory receptor, CTLA-4 inhibits T cell response by competition of ligand binding with positive costimulator receptor CD28, and also induces inhibitory signaling. The trafficking and the cell surface expression of CTLA-4 are dynamically regulated and induced. CTLA-4 is accumulated in lysosomes and secreted to the T cell-APC contact site upon TCR stimulation. As T cell activation proceeds, these inhibitory adapters and costimulation receptors are induced and suppress/regulate the responses as negative feedback.

Fc receptor-independent development of autoimmune glomerulonephritis in lupus-prone MRL/lpr mice.

Abstract: Objective To determine the role of Fc receptors (FcR), which play crucial roles in antibody and immune complex–mediated inflammation and autoimmunity, including glomerulonephritis (GN), in the development of autoimmune GN and vasculitis in MRL/lpr mice, one of the most widely used lupus-prone mouse models. Methods FcRγ−/− MRL/lpr mice were generated by backcrossing for 8 generations. The development of GN and vasculitis of various sized vessels was analyzed histopathologically in the kidney, lung, and skin. Autoantibody and immune complex levels were determined biochemically at 16–24 weeks of age and compared with the findings in FcRγ+ MRL/lpr mice. The lifespan of the mice was also recorded. Results Diffuse proliferative GN, with deposition of IgG and C3, developed in both FcRγ−/− and FcRγ+ MRL/lpr mice. There was no difference in the survival rate and degree of proteinuria between FcRγ+ and FcRγ−/− MRL/lpr mice. Regardless of the level of FcR expression, there were no significant differences in the levels of serum IgG, anti-DNA antibody, or circulating immune complexes between the two types of mice. Necrotizing vasculitis in medium-sized arteries of the kidneys and lungs as well as small-vessel vasculitis in the skin was observed in both in FcRγ+ and FcRγ−/− MRL/lpr mice. In contrast, the Arthus reaction was induced in FcRγ+ MRL/lpr mice, but not in FcRγ−/− MRL/lpr mice. Conclusion Unlike (NZB × NZW)F1, the other strain of lupus-prone mice that develops GN in an FcR-dependent manner, the development of autoimmune GN and vasculitis in MRL/lpr mice was FcR-independent, implying heterogeneity of the contribution of FcR to the development of autoimmune disease.

Gads/Grb2-mediated association with LAT is critical for the inhibitory function of Gab2 in T cells.

Abstract: A docking protein, Gab2, is recruited to the vicinity of the TCR complex and inhibits downstream signaling by interaction with negative regulators. However, the molecular mechanisms of this recruitment remain unclear. We have found that Gab2 associates with LAT upon TCR stimulation and that LAT is essential for Gab2 phosphorylation. By analysis of several Gab2 mutants, the c-Met binding domain (MBD) of Gab2 was found to be both necessary and sufficient for stimulation-induced LAT binding. Within the MBD domain, a novel Grb2 SH3 binding motif, PXXXR, is critical for constitutive association with Gads/Grb2. Through this association, Gab2 is recruited to the lipid raft after TCR ligation and exerts inhibitory function. The in vivo significance of this association is illustrated by the fact that T-cell responses are impaired in transgenic mice expressing wild-type Gab2 but not in mice expressing mutant Gab2 lacking the motif. Furthermore, T cells from Gab2-deficient mice showed enhanced proliferative responses upon TCR stimulation. These results indicate that Gads/Grb2-mediated LAT association is critical for the inhibitory function of Gab2, implying that Gab2 induced in stimulated T cells may exert an efficient negative feedback loop by recruiting inhibitory molecules to the lipid raft and competing with SLP-76 through Gads binding.

Alzheimer's disease, neuropeptides, neuropeptidase, and amyloid-beta peptide metabolism.

Abstract: Amyloid-beta peptide (Abeta), the pathogenic agent of Alzheimer's disease (AD), is a physiological metabolite in the brain. We have focused our attention and effort on elucidating the unresolved aspect of Abeta metabolism: proteolytic degradation. Among a number of Abeta-degrading enzyme candidates, we used a novel in vivo paradigm to identify a member of the neutral endopeptidase family, neprilysin, as the major Abeta catabolic enzyme. Neprilysin deficiency results in defects in the metabolism of endogenous Abeta 40 and 42 in a gene dose-dependent manner. Our observations suggest that even partial down-regulation of neprilysin activity, which could be caused by aging, can contribute to AD development by promoting Abeta accumulation. Moreover, we discuss the fact that an aging-dependent decline of neprilysin activity, which leads to elevation of Abeta concentrations in the brain, is a natural process that precedes AD pathology. In this Perspective, we hypothesize that neprilysin down-regulation has a role in sporadic AD (SAD) pathogenesis, and we propose that this knowledge be used for developing preventive and therapeutic strategies through use of a G protein-coupled receptor (GPCR).

Effect of human urotensin-II infusion on hemodynamics and cardiac function

Abstract: Recent studies have shown that the vasoactive peptide urotensin-II (U-II) exerts a wide range of action on the cardiovascular system of various species. In the present study, we determined the in vivo effects of U-II on basal hemodynamics and cardiac function in the anesthetized intact rat. Intravenous bolus injection of human U-II resulted in a dose-dependent decrease in mean arterial pressure and left ventricular systolic pressure. Cardiac contractility repre - sented by ±dP/dt was decreased after injection of U-II. However, there was no significant change in heart rate or dia - stolic pressure. The present study suggests that upregulation of myocardial U-II may contribute to impaired myocardial function in disease conditions such as congestive heart failure.

IL-1R-associated kinase 4 is required for lipopolysaccharide-induced activation of APC.

Abstract: The bacterial product LPS is a critical stimulus for the host immune system in the response against the corresponding bacterial infection. LPS provides an activation stimulus for macrophages and a maturation signal for dendritic cells to set up innate and adaptive immune responses, respectively. The signaling cascade of myeloid differentiation factor 88→IL-1R-associated kinase (IRAK)→TNFR-associated factor 6 has been implicated in mediating LPS signaling. In this report, we studied the function of IRAK-4 in various LPS-induced signals. We found that IRAK-4-deficient cells were severely impaired in producing some IFN-regulated genes as well as inflammatory cytokines in response to LPS. Among the critical downstream signaling pathways induced by LPS, NF-κB activation but not IFN regulatory factor 3 or STAT1 activation was defective in cells lacking IRAK-4. IRAK-4 was also required for the proper maturation of dendritic cells by LPS stimulation, particularly in terms of cytokine production and the ability to stimulate Th cell differentiation. Our results demonstrate that IRAK-4 is critical for the LPS-induced activations of APCs.

IgE-Mediated Activation of NK Cells Through FcγRIII

Abstract: NK cells express FcγRIII (CD16), which is responsible for IgG-dependent cell cytotoxicity and for production of several cytokines and chemokines. Whereas FcγRIII on NK cells is composed of both FcγRIIIα and FcRγ chains, that on mast cells is distinct from NK cells and made of FcγRIIIα, FcRβ, and FcRγ. Mast cells show degranulation and release several mediators, which cause anaphylactic responses upon cross-linking of FcγRIII as well as FceRI with aggregated IgE. In this paper, we examined whether IgE activates NK cells through FcγRIII on their cell surface. We found that NK cells produce several cytokines and chemokines related to an allergic reaction upon IgE stimulation. Furthermore, NK cells exhibited cytotoxicity against IgE-coated target cells in an FcγRIII-dependent manner. These effects of IgE through FcγRIII were not observed in NK cells from FcRγ-deficient mice lacking FcγRIII expression. Collectively, these results demonstrate that NK cells can be activated with IgE through FcγRIII and exhibit both cytokine/chemokine production and Ab-dependent cell cytotoxicity. These data imply that not only mast cells but also NK cells may contribute to IgE-mediated allergic responses.

Pitavastatin inhibits upregulation of intermediate conductance calcium-activated potassium channels and coronary arteriolar remodeling induced by long-term blockade of nitric oxide synthesis.

Abstract: We have reported that intermediate conductance Ca2+-activated K+ channels (ImK) showed augmented expression in angiotensin II (AII) type 1 receptor-dependent manner in post-ische

Neoplasm image detecting method, and device therefor

Abstract: PROBLEM TO BE SOLVED: To provide a neoplasm image detecting method and a neoplasm image detecting device capable of not only measuring only own fluorescence to acquire an image of a lesion texture but also measuring fluorescence emitted from an oncotropic substance, and capable of conducting division of intensities of the fluorescences emitted from the own fluorescence and the oncotropic substance to measure thereby a neoplasm part precisely in a real time, in an operation. SOLUTION: This method/instrument has an oncotropic substance administration process S1, an irradiation process S2 for irradiation with an electromagnetic wave including a wavelength for exciting the oncotropic substance and a wavelength for exciting own fluorescence protein contained in a biotexture of the neoplasm part, the first measuring process S3 for measuring the fluorescence intensity emitted from the excited oncotropic substance, the second measuring process S4 for measuring the fluorescence intensity emitted from the excited own fluorescence protein, a computing process S5 for computing a ratio of the fluorescence intensity from the oncotropic substance to the fluorescence intensity from the own fluorescence protein, and a display process S6 for displaying the ratio of the fluorescence intensities. COPYRIGHT: (C)2005,JPO&NCIPI

Single crystal growth of Ca2-xNaxCuO2Cl2 and related compounds at high pressures of several GPa

Abstract: Single crystal samples of the oxychloride superconductor Ca 2-x Na x CuO 2 Cl 2 were obtained by flux method at high pressures of several GPa. The growth conditions were determined based on synchrotron powder X-ray diffraction studies at high pressure and high temperature conditions as in the case of (VO) 2 P 2 O 7 high pressure phase.

TNF-α Rapidly Antagonizes the β-Adrenergic Responses of the Chloride Current in Guinea-Pig Ventricular Myocytes

Abstract: The purpose of this study was to test the hypothesis that tumor necrosis factor-α (TNF-α) rapidly antagonizes the β-adrenergic responses of the chloride current and to clarify the intracellular mechanisms responsible for the anti-adrenergic action. The whole-cell patch-clamp technique was used to monitor the anti-adrenergic effects of TNF-α on the cAMP-dependent chloride current (ICl) recorded from isolated guinea-pig ventricular myocytes. Ramp pulses (±120 mV; dv/dt = ±0.4 V/s) were applied from the holding potential of -40 mV. TNF-α rapidly (<15 min) inhibited the isoproterenol (Iso, 0.1 μmol/L)-induced ICl in a concentration-dependent manner (30-1,000 U/ml, IC 50 = 144 U/ml, n=30). The inhibitory action of TNF-α was also observed when ICl had been previously stimulated by 1 μmol/L forskolin (n=5). Prior exposure of myocytes to 5 μg/ml pertussis toxin (PTX) hardly affected the anti-adrenergic action of TNF-α (n=4). However, when ICl was induced by both 8-bromo-cAMP (100 μmol/L) and isobutylmethylxanthine (0.1 mmol/L), TNF-α (1,000 U/ml) failed to decrease ICl amplitude (n=5). Prior exposure of myocytes to 5 mg/ml pertussis toxin (PTX) hardly affected the anti-adrenergic action of TNF-α (n=4). Furthermore, despite of the presence of nitro-L-arginine methyl ester (0.1 mmol/L), a nitric oxide synthase (NOS) inhibitor, TNF-α reversed the Iso-induced increase in ICl (n=5). These results suggest that TNF-α rapidly antagonizes the β-adrenergic responses of ICl by reducing cAMP concentration. This anti-adrenergic action is mediated by neither the PTX-sensitive G proteins regulatory pathway nor constitutive NOS activation. (Circ J 2003; 67: 347 - 353)

Distributed processing method and distributed processing system

Abstract: PROBLEM TO BE SOLVED: To provide a distributed processing method and a distributed processing system capable of reducing an economic cost and a temporal cost of communication. SOLUTION: In a center system 20 and a branch system 60, databases 30a and 30b having the same data are arranged individually. An application processing part 24 arranged in the center system 20 carries out processing using the database 30a. An application processing part 64 arranged in the branch system 60 carries out processing using the database 30b. When the application processing part is stopped, import/export subsystems 22 and 62 form downbound and upbound snap shot data respectively, and import/export subsystems 62 and 22 on the counterpart side read them respectively to reflect them on the database. COPYRIGHT: (C)2004,JPO

Method of forming mask pattern and manufacturing semiconductor device

Abstract: PROBLEM TO BE SOLVED: To provide a mask pattern forming method and a semiconductor device manufacturing method, which are capable of making a semiconductor device undergo the desired processing by thickening the thin part of a mask film that is used for processing such as etching of the semiconductor device. SOLUTION: An insulating film 2 is formed on a semiconductor board 1, and a photoresist film 3 is formed on the insulating film 2. The photoresist film 3 is formed by patterning into a first mask pattern containing a thin film part 3a. Then, a photoresist film 5 is formed on the first mask pattern so as to cover the thin film part 3a. A second mask pattern is formed by patterning the photoresist film 5, and a part of the photoresist film 5 is left on the thin film part 3a. The insulating film 2 is processed by the use of the first and second mask patterns. COPYRIGHT: (C)2004,JPO

Methode de mesure de l'activite de la neprilysine

Abstract: L'invention concerne une methode permettant de mesurer l'activite de la neprilysine, etc. Plus specifiquement, cette invention a trait a une methode permettant de mesurer l'activite de la neprilysine dans des cellules nerveuses, a une methode de criblage d'une proteine, d'un peptide ou d'un compose ameliorant l'activite ou l'expression de la neprilysine dans des cellules nerveuses par le biais de la mesure de l'activite de la neprilysine, a une methode d'amelioration de l'activite ou de l'expression de la neprilysine etc. On utilise un compose ameliorant l'activite ou l'expression de la neprilysine comme agent preventif et/ou remede a la maladie d'Alzheimer, ledit compose etant obtenu par le procede de criblage caracterise par l'utilisation de la methode de mesure de l'activite de la neprilysine susmentionnee. On peut employer la methode susmentionnee de mesure de l'activite dans le diagnostic de la maladie d'Alzheimer.

Photo-Dynamic Diagnosis of Brain Tumor Using Dual Emission Laser-Induced Fluorescence

Abstract: In the neurosurgery of brain tumor, patients' life after surgery crucially depends on completeness of malignant glioma resection. It is, therefore, quite necessary to construct real-time monitoring system of brain tumor. In this study, proposed is the novel optical measurement method of brain tumor demarcation. It has been well known that some phosphorescence luminophor dyes used in PDT can emit fluorescence. In addition, it has been recently reported that auto-fluorescence can be observed even in brain white matter tissue; moreover its intensity locally decreases in tumor region. Using phosphorescence and auto-fluorescence images, Dual Emission Laser-Induced Fluorescence technique was experimentally applied to the brain tumor detection. Consequently, it was confirmed that the contrast between tumor and normal region could be enhanced. Undesirable fluorescence variation, which was dependent on illumination intensity distribution and brain surface shape, could be reduced. The present method was clarified to be effective to brain tumor monitoring and quantitative delimitation.

Investigation of QTc Dispersion in Patients with Stractural Heart Diseases (Old Myocardial Infarction and Dilated Cardiomyopathy)

Abstract: 陳旧性心筋梗塞 (OMI) , 拡張型心筋症 (DCM) におけるQTc dispersion (QTcd) と心室性不整脈との関連性, QTcdとJTc dispersion (JTcd) および貫壁性のばらつきの指標とされるTransmural dispersion of repolarization (胸部誘導におけるT波頂点とT波終末点の差の最大値をTDRcmaxとして算出) との関連性, さらにQTcdと心機能との関連性について検討した, 対象はOMI: 61例, DCM: 20例 (男性59例, 女性22例, 平均年齢65.8±13.4歳) .12誘導心電図よりフクダ電子社製QT計測ソフトを用い, QTcdを自動計測し, JTcd, TDRcmaxを算出し, 心エコー図より左室駆出率, 左室拡張終期径を, OMIではasynergy scoreを算出した上OMI, DCMでは心室頻拍の有無に関するQTc dispersionのcut off値を70msecに設定することにより, 心室頻拍の有力な予知因子となる可能性が示唆された.OMlではQTcdはJTcd, TDRcmax, 心機能指標と有意な相関を示し, DCMではTDRcmaxを除く各指標と有意な相関を示した.OMI, DCMではQTcdは脱分極相より再分極相の不均一性を示し, また, 心機能指標としての有用性が示唆された.OMIでは貫壁性の再分極不均一性の存在が示唆された.