Biomedical subjects

Noboru Suzuki

Publications and source records attributed to Noboru Suzuki.

26 records · Page 2Linked to original sources

PubMed2003

Abnormal killer inhibitory receptor expression on natural killer cells in patients with Behçet's disease.

Viral infection has been assigned some role in the pathogenesis of Behçet's disease (BD). Defects in natural killer (NK) cell repertoire may be involved in impaired antiviral immunity, leading to the development of BD. We studied killer inhibitory receptor (KIR) expression in 40 patients with BD. CD94 and CD158b expression of NK cells was normal in a great majority of BD patients. NKB1 expression was reduced in eight and increased in six. Twelve of these 14 patients (86%) had severe eye disease. Some had reduced NKB1 and enhanced CD158a expression simultaneously, or enhanced NKB1 and reduced CD158a simultaneously, suggesting a skewed NK cell repertoire in BD. Collectively, KIR expression was abnormal in the BD patients with severe eye disease. This may result from genetic predisposition, or certain viruses may affect the KIR repertoire formation in BD patients. Abnormal KIR expression of NK cells may be associated with the development of BD.

Adult↗

PubMed2003

Possible involvement of P2Y2 metabotropic receptors in ATP-induced transient receptor potential vanilloid receptor 1-mediated thermal hypersensitivity.

The capsaicin receptor transient receptor potential V1 (TRPV1; also known as vanilloid receptor 1) is a sensory neuron-specific ion channel that serves as a polymodal detector of pain-producing chemical and physical stimuli. It has been reported that extracellular ATP potentiates the TRPV1 currents evoked by capsaicin or protons and reduces the temperature threshold for its activation through metabotropic P2Y receptors in a PKC-dependent pathway, suggesting that TRPV1 activation could trigger the sensation of pain at normal body temperature in the presence of ATP. Here, we show that ATP-induced thermal hyperalgesia was abolished in mice lacking TRPV1, suggesting the functional interaction between ATP and TRPV1 at a behavioral level. However, thermal hyperalgesia was preserved in P2Y1 receptor-deficient mice. Patch-clamp analyses using mouse dorsal root ganglion neurons indicated the involvement of P2Y2 rather than P2Y1 receptors. Coexpression of TRPV1 mRNA with P2Y2 mRNA, but not P2Y1 mRNA, was determined in the rat lumbar DRG using in situ hybridization histochemistry. These data indicate the importance of metabotropic P2Y2 receptors in nociception through TRPV1.

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PubMed2003

Transplantation of motoneuron-enriched neural cells derived from mouse embryonic stem cells improves motor function of hemiplegic mice.

Embryonic stem (ES) cells are expected to be a potential donor source for neural transplantation. We have obtained motoneuron-enriched neural progenitor cells by culturing mouse ES cells with retinoic acid (RA). The cells also expressed mRNA of a neurotrophic factor, neurotrophin-3 (NT-3). The left motor cortex area of mice was damaged by cryogenic brain injury, and the neural cells were transplanted underneath the injured motor cortex, neighboring to the paraventricular region. We found that the cells expressing neuronal phenotypes not only remained close to the implantation site, but also exhibited substantial migration penetrating into the damaged lesion, in a seemingly directed manner up to cortical region. We found that some of the neural cells differentiated into Islet1-positive motoneurons. It seems likely that the ability of the ES cell-derived neural progenitor cells to respond in vivo to guidance cues and signals that can direct their migration and differentiation may contribute to functional recovery of the recipient mice. We found that an "island of the mature neuronal cells" of recipient origin emerged in the damaged motor cortex. This may be associated with the neuroprotective effects of the ES cell-derived neural cells. The ES cells differentiated into CD31+ vasculoendothelial cells with the RA treatment in vitro. Furthermore, the grafted cells may provide sufficient neurotrophic factors such as NT-3 for neuroprotection and regeneration. The grafted neural cells that migrated into residual cortex and differentiated into neurons had purposefully elongated axons that were stained with anti-neurofilament middle chain (NFM) antibody. Our study suggests that motoneurons can be induced from ES cells, and ES cells become virtually an unlimited source of cells for experimental and clinical neural cell transplantation.

Animals↗

PubMed2002

IL-18 contributes to the spontaneous development of atopic dermatitis-like inflammatory skin lesion independently of IgE/stat6 under specific pathogen-free conditions.

Atopic dermatitis (AD) is a pruritic inflammatory skin disease. Because IL-18 directly stimulates T cells and mast cells to release AD-associated molecules, Th2 cytokines, and histamine, we investigated the capacity of IL-18 to induce AD-like inflammatory skin disease by analyzing KIL-18Tg and KCASP1Tg, which skin-specifically overexpress IL-18 and caspase-1, respectively. They spontaneously developed relapsing dermatitis with mastocytosis and Th2 cytokine accumulation accompanied by systemic elevation of IgE and histamine. Stat6-deficient KCASP1Tg displayed undetectable levels of IgE but manifested the same degree of cutaneous changes, whereas IL-18-deficient KCASP1Tg evaded the dermatitis, suggesting that IL-18 causes the skin changes in the absence of IgE/stat6. KIL-18Tg and IL-1-deficient KCASP1Tg took longer to display the lesion than KCASP1Tg. Thus, AD-like inflammation is initiated by overrelease of IL-18 and accelerated by IL-1. Our present study might provide insight into understanding the pathogenesis of and establishing therapeutics for chronic inflammatory skin diseases including AD.

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PubMed2002

Txk, a member of nonreceptor tyrosine kinase of Tec family, acts as a Th1 cell-specific transcription factor and regulates IFN-gamma gene transcription.

Precise mechanisms responsible for Th1 cell activation and differentiation are not fully elucidated. We have recently reported that Txk, a member of Tec family nonreceptor tyrosine kinase, is expressed on Th1/Th0 cells, and Txk regulates specifically IFN-gamma gene expression. In this study, we found that Txk bound to IFN-gamma promoter region. Txk transfection increased transcriptional activity of IFN-gamma promoter plus luciferase constructs severalfold, including IFN-gamma promoter -538, -208, and -53. IFN-gamma promoter -39 was refractory to the Txk transfection. The actual site to which Txk bound was the element consisting of -53 and -39 bp from the transcription start site of human IFN-gamma gene, a site distinct from several previously characterized binding sites. We found that the entire -53/-39 region was necessary for the binding to and function of Txk, because mutant promoter oligoDNA that contained contiguous five base substitutions dispersed throughout the -53/-39 inhibited the binding, and the mutant promoters did not respond to the Txk transfection. Similar sequences of this element are found within the 5' flanking regions of several Th1 cell-associated protein genes. Thus, Txk is expressed on Th1/Th0 cells with the IFN-gamma production and acts as a Th1 cell-specific transcription factor.

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PubMed2002

Flk1+ cells derived from mouse embryonic stem cells reconstitute hematopoiesis in vivo in SCID mice.

OBJECTIVE: Embryonic stem (ES) cells are pluripotent and can differentiate into any cell type, including the hematopoietic lineage. We examined whether hematopoietic progenitor cells derived from ES cells reconstitute hematopoiesis in irradiated SCID mice. MATERIALS AND METHODS: ES cells (E14.1, H2K(b)) were cultured for 4 days in semisolid medium containing methylcellulose. Irradiated SCID mice were used as recipients of hematopoietic progenitor cells. Cell surface antigen expression was analyzed by flow cytometry. The spleens of the recipient mice were studied by hematoxylin and eosin staining and immunohistochemical staining. RESULTS: After cell culture of ES cells in methylcellulose for 4 days, the cells expressing Flk1 (VEGF receptor 2), a tentative marker of hemangioblasts, were increased, whereas cells expressing CD31 (PECAM-1) and E-cadherin (nonmesodermal adhesion molecule) were dramatically reduced. Flk1+ cells expressed c-kit predominantly. Circulating leukocytes and thrombocytes were increased in irradiated SCID (H2K(d)) mice transplanted with ES cell-derived Flk1+ cells compared with vehicle-injected control mice. H2K(b+) and VE-cadherin(+) vascular endothelial cells were prominent in spleens of the recipient mice. Flow cytometric analysis demonstrated that H2K(b+) cells were increased in the bone marrow of recipient mice. In addition, Flk1+ cells accompanying enhanced c-kit expression preferentially repopulated in the bone marrow, and leukopoiesis and thrombopoiesis of the recipient mice were evident. CONCLUSION: The Flk1+ hematopoietic cells derived from ES cells reconstitute hematopoiesis in vivo and may become an alternative donor source for bone marrow transplantation.

Animals↗

PubMed2002

Aberrant Fas ligand expression in lymphocytes in patients with Behçet's disease.

BACKGROUND: Defects in immune responses have been reported in patients with Behçet's disease (BD). To further characterize the immune dysfunction and its contribution to the pathogenesis, we have studied Fas ligand (FasL) expression in peripheral blood lymphocytes (PBL) and mononuclear cells in the skin lesions in patients with BD. METHODS: FasL expression in PBL was studied with RT-PCR and immunoblotting with rabbit anti-human FasL antibody. We studied the expression of FasL in cryostat sections of biopsy specimens of erythema nodosum lesions from 4 patients with BD and of a genital ulcer lesion in another patient using immunohistochemical staining. Apoptotic cell death was detected with the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. RESULTS: We found that FasL mRNA and FasL protein expression was detected marginally in the unstimulated PBL, and was induced upon activation in normal individuals. PBL from patients with BD exhibited an enhanced expression of FasL mRNA and FasL protein without in vitro stimulation. Moreover, mitogen stimulation failed to augment FasL expression of their lymphocytes, suggesting a dysregulation of FasL expression of PBL in patients with BD. The skin biopsy specimens revealed that cells infiltrating into skin lesions expressed FasL and there were several TUNEL staining-positive cells in the lesions, suggesting that Fas/FasL-mediated apoptosis is involved in the development of the skin lesion and thus may be associated with the pathogenesis. CONCLUSIONS: We found an excessive expression of FasL in circulating as well as skin-infiltrating lymphocytes and the presence of apoptotic cells in the skin lesions, suggesting that lymphocytes expressing FasL aberrantly may play a role in the development and pathogenesis of BD.

Adult↗

PubMed2002

Evidence of autophosphorylation in Txk: Y91 is an autophosphorylation site.

We have previously shown that Txk, a member of Tec family tyrosine kinase, is expressed in Th1 and ThO cells and directly contributes to gene transcription of Th1-related proteins, including interferon (IFN)-gamma, through nuclear translocation in response to mitogenic stimuli. Btk, another member of Tec family tyrosine kinase, has been shown to have a Src family tyrosine kinase-dependent transphosphorylation site and an autophosphorylation site. However, little is known about the phosphorylation mechanism of Txk, except that 420 tyrosine residue was identified as the transphosphorylation site. In this study, we found that Txk autophosphorylated itself by using an in vitro kinase assay. To elucidate the role of phosphorylation in Txk function, we studied IFN-gamma secretion by Jurkat T cells expressing mutant Txk proteins. While transfection with the wild-type Txk resulted in increased IFN-gamma production, the function was abrogated by disruption of the ATP biding site, which is presumably involved in the autophosphorylation mechanism. The results suggest that phosphorylated Txk is an active form to promote IFN-gamma synthesis. The 91 tyrosine residue of Txk is deduced to be an autophosphorylation site by comparing its structure with Btk. In Jurkat cells transfected with Txk Y91A, IFN-gamma production was decreased in comparison with the wild-type Txk transfected Jurkat cells. These data suggest that phosphorylation of the 91 tyrosine residue in Txk plays a positive regulatory role in Txk function.

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