Biomedical subjects

Tetsuya Yamamoto

Publications and source records attributed to Tetsuya Yamamoto.

At least 91 records · Page 5Linked to original sources

PubMed2003

STAP-2/BKS, an adaptor/docking protein, modulates STAT3 activation in acute-phase response through its YXXQ motif.

As a c-fms-interacting protein, we cloned a novel adaptor molecule, signal-transducing adaptor protein-2 (STAP-2), which contains pleckstrin homology- and Src homology 2-like (PH and SRC) domains and a proline-rich region. STAP-2 is structurally related to STAP-1/BRDG1 (BCR downstream signaling-1), which we had cloned previously from hematopoietic stem cells. STAP-2 is a murine homologue of a recently identified adaptor molecule, BKS, a substrate of BRK tyrosine kinase. STAP-2 was tyrosine-phosphorylated and translocated to the plasma membrane in response to epidermal growth factor when overexpressed in fibroblastic cells. To define the function of STAP-2, we generated mice lacking the STAP-2 gene. STAP-2 mRNA was strongly induced in the liver in response to lipopolysaccharide and in isolated hepatocytes in response to interleukin-6. In the STAP-2(-/-) hepatocytes, the interleukin-6-induced expression of acute-phase (AP) genes and the tyrosine-phosphorylation level of STAT3 were reduced specifically at the late phase (6-24 h) of the response. These data indicate that STAP-2 plays a regulatory role in the AP response in systemic inflammation. STAP-2 contains a YXXQ motif in the C-terminal region that is a potential STAT3-binding site. Overexpression of wild-type STAP-2, but not of mutants lacking this motif, enhanced the AP response element reporter activity and an AP protein production. These data suggest that STAP-2 is a new class of adaptor molecule that modulates STAT3 activity through its YXXQ motif.

Acute-Phase Reaction↗

PubMed2003

Limitin, an interferon-like cytokine, transduces inhibitory signals on B-cell growth through activation of Tyk2, but not Stat1, followed by induction and nuclear translocation of Daxx.

OBJECTIVE: Limitin, an interferon-like cytokine, suppresses B lymphopoiesis through ligation of the interferon-alpha/beta (IFN-alpha/beta) receptor. The aim of this study was to examine the intracellular signal transduction pathways activated by limitin. MATERIALS AND METHODS: The effects of limitin on cell growth, the activation of Jak kinase and Stat proteins, and the induction of interferon regulatory factor-1 (IRF-1) and Daxx were examined using the mouse pre-B-cell line 18.81, wild-type, and Tyk2-deficient mouse bone marrow cells. In addition, the change of localization of the Daxx protein after limitin treatment in wild-type and Tyk2-deficient mice was examined. RESULTS: Limitin phosphorylates Tyk2, Jak1, Stat1, and Stat2 and rapidly induces IRF-1 mRNA production. Phosphorylation of Stat1 by limitin is partially dependent on Tyk2. Suppression of B-cell growth by limitin, however, is severely impaired in the absence of Tyk2, whereas it is unaffected by the absence of Stat1. Limitin also induces the expression and nuclear translocation of Daxx, which is essential for IFN-alpha-induced inhibition of B-lymphocyte development. The absence of Tyk2 abrogates this induction of Daxx expression and nuclear translocation. CONCLUSIONS: Limitin suppresses B-cell growth through activation of Tyk2, resulting in the up-regulation and nuclear translocation of Daxx. This limitin-mediated signaling pathway does not require Stat1.

Active Transport, Cell Nucleus↗

PubMed2003

Characteristics of visual field progression in patients with normal-tension glaucoma with optic disk hemorrhages.

PURPOSE: To study the characteristics of visual field progression in patients with normal-tension glaucoma (NTG) with optic disk hemorrhages. DESIGN: Observational study. METHODS: Fifty-eight eyes of 58 untreated patients with NTG who had at least five reliable visual fields of the Humphrey Field Analyzer (central 30-2) within the follow-up period of more than 24 months were enrolled. Of these, 27 eyes had optic disk hemorrhages in their clinical courses. Pointwise linear regression analysis was done using total deviation values of the fields at each of 74 test locations in each patient. Progression was defined as the points of negative slopes with P <.01. A whole visual field was concentrically divided into three clusters: the areas within 10 degrees, 10 to 20 degrees, and 20 to 30 degrees. Percentages of the progressed points of the three clusters and a whole field were compared between the groups with and without optic disk hemorrhages. RESULTS: No significant differences were found in patients' backgrounds, including initial mean deviation values, follow-up periods, and the number of visual field examinations between the 27 patients with optic disk hemorrhages and the 31 without. The group with optic disk hemorrhages showed significantly higher percentages of progressed points within the 10-degree area compared with the group without optic disk hemorrhages (mean +/- SD: 13.1 +/- 13.7%; 5.1 +/- 8.5%, respectively; P =.0086, Student t test), whereas no significant differences were found in the other two clusters or in a whole field. CONCLUSIONS: Patients with NTG with optic disk hemorrhages tend to show visual field progression in areas within 10 degrees.

Adult↗

PubMed2003

Evaluation of optineurin sequence variations in 1,048 patients with open-angle glaucoma.

PURPOSE: To investigate the association of sequence variations in the optineurin (OPTN) gene in patients with open-angle glaucoma. DESIGN: Prospective case control study. METHODS: The OPTN gene was screened for sequence variations using a combination of single-strand conformational polymorphism analysis and automated DNA sequencing. A total of 1,299 subjects (1048 glaucoma patients and 251 controls) were screened for variations in the four portions of the gene that had been previously associated with glaucoma. A subset of these subjects (376 patients and 176 controls) was screened for variations in the entire coding sequence. Twenty-four percent of the patients and 35% of the controls were Japanese, whereas the remainder were predominantly Caucasian. Allele frequencies were compared with the Fisher exact test. RESULTS: The OPTN sequence variations were not significantly associated with any form of high-tension open-angle glaucoma. One proband with familial normal-tension glaucoma was found to harbor the previously reported Glu50Lys variation. Another previously reported change, Met98Lys, was associated with normal-tension glaucoma in Japanese but not in Caucasian patients. CONCLUSIONS: This study provides some additional evidence for the association of the Glu50Lys OPTN sequence variation with familial normal tension glaucoma. However, because familial normal-tension glaucoma is so rare, this change seems to be responsible for less than 0.1% of all open-angle glaucoma. The Arg545Gln variation is likely to be a nondisease-causing polymorphism. The Met98Lys change may be associated with a fraction of normal-tension glaucoma in patients of Japanese ethnicity.

Base Sequence↗

PubMed2003

Identification of a new point mutation in the human molybdenum cofactor sulferase gene that is responsible for xanthinuria type II.

A 43-year-old xanthinuric female was referred to our department because of hypouricemia. Routine laboratory data showed hypouricemia, a high level of plasma oxypurines, decreased urinary uric acid excretion, and increased urinary oxypurine excretion, with xanthine dehydrogenase activity in the duodenal mucosa below the limits of detection. In addition, allopurinol was not metabolized. From these findings, the patient was diagnosed with xanthinuria type II. To investigate the properties of xanthine dehydrogenase/xanthine oxidase (XDH/XO) deficiency, a cDNA sequence encoding XDH/XO, aldehyde oxidase (AO), and molybdenum cofactor sulferase (MCS), as well as immunoblotting analysis for XDH/XO protein, obtained from duodenal mucosa samples were performed. The XDH/XO cDNA and AO cDNA sequences of the xanthinuric patient were consistent with previously reported ones, whereas the MCS cDNA sequence revealed a point mutation of G to C in nucleotide 466, which changed codon 156 from GCC (Ala) to CCC (Pro). In addition, the MCS genomic DNA sequence including the site of the mutation revealed the same, suggesting that the xanthinuric patient was homozygous for this mutation. Such findings have not been previously reported for patients with xanthinuria type II.

Adult↗

PubMed2003

Lipopolysaccharide signal transduction in oral keratinocytes--involvement of CD59 but not CD14.

There are a variety of dermal and mucosal lesions involving keratinocytes. We examined here the signal transduction of lipopolysaccharide (LPS) in oral keratinocytes. Oral keratinocytes did not express CD14, but expression of CD58 and CD59 was observed by flow cytometry and reverse transcription-PCR. The binding between LPS and keratinocytes was strongly inhibited by pretreatment of keratinocytes with anti-CD59 monoclonal antibody (mAb) or phosphatidylinositol-specific phospholipase C (PI-PLC) but was not inhibited by anti-CD14 or anti-CD58 mAb. In LPS-treated keratinocytes, nuclear translocation of nuclear factor-kappa B (NF-kappaB) was induced and generation of granulocyte-macrophage colony-stimulating factor, interleukin-6 and tumour necrosis factor-alpha was enhanced. These upregulations in nuclear translocation of NF-kappaB and cytokine generation were not suppressed by anti-CD14 mAb or anti-CD58 mAb but were suppressed by anti-CD59 mAb and PI-PLC. Moreover, the transfection of CD59 antisense oligonucleotide into keratinocytes markedly suppressed LPS-induced nuclear translocation of NF-kappaB and cytokine generation. These results indicate that, through CD59, the LPS signal is transduced into the nucleus via NF-kappaB activation inducing cytokine generation, which may be involved in dermal and mucosal inflammatory diseases.

Antibodies↗

PubMed2003

Apoptosis induction by interleukin-2-activated cytotoxic lymphocytes in a squamous cell carcinoma cell line and Daudi cells - involvement of reactive oxygen species-dependent cytochrome c and reactive oxygen species-independent apoptosis-inducing factors.

Investigation of the induction of apoptosis by cytotoxic lymphocytes has mainly focused on the signalling associated with Fas and its adaptor proteins. The signal pathway via mitochondria, however, has not been sufficiently elucidated in cytotoxic lymphocyte-induced apoptosis. We examined the release of mitochondrial proapoptotic factors by lymphokine-activated killer (LAK) cells in two cell lines. LAK cell-induced DNA fragmentation of the target cells was suppressed to approximately 50% of control levels by the addition of neutralizing monoclonal antibody to Fas and a granzyme B inhibitor. When intracellular reactive oxygen species (ROS) were scavenged, the LAK cell-induced DNA fragmentation was decreased to approximately 60% of the non-treated cell level. Co-cultivation of Daudi cells with LAK cells increased cytosolic and mitochondrial ROS levels. Activation of procaspase-3 and apoptosis by treatment of oral squamous cell carcinoma cells (OSC) with LAK cells was partially inhibited by pretreatment of OSC cells with ROS scavengers and mitochondrial complex inhibitors. Furthermore, cytochrome c and apoptosis-inducing factor (AIF) were released from mitochondria by OSC cell treatment with supernatants of LAK cells. The supernatant-induced cytochrome c release was suppressed by mitochondrial complex inhibitors, but the inhibitors did not inhibit the release of AIF. These results indicate that LAK cells induce target cell apoptosis via not only the Fas/Fas ligand system and granzyme B, but also ROS-dependent cytochrome c and ROS-independent AIF release.

Apoptosis↗

PubMed2003

Elevated levels of interleukin-18 and tumor necrosis factor-alpha in serum of patients with type 2 diabetes mellitus: relationship with diabetic nephropathy.

To compare levels of interleukin (IL)-18, tumor necrosis factor-alpha (TNF-alpha), and IL-6 in serum, we studied 151 type 2 diabetes mellitus patients with various degrees of nephropathy, as well as 80 healthy volunteers. IL-18, TNF-alpha, and IL-6 in serum were measured using an enzyme-linked immunosorbent assay (ELISA) with the respective mouse monoclonal antibodies. Significant differences in serum levels of IL-18 and TNF-alpha were observed between the patients and control subjects (IL-18, 278.0 +/- 11.9 pg/mL v 172.8 +/- 7.7 pg/mL, P <.0001; TNF-alpha, 2.41 +/- 0.18 pg/mL v 0.46 +/- 0.18 pg/mL, P <.0001), whereas that of IL-6 was not different between the two groups (0.73 +/- 0.10 pg/mL v 0.65 +/- 0.08 pg/mL, difference not significant [NS]), although patients with nephropathy showed higher levels. In addition, IL-18 levels were increased in diabetic patients with the development of urinary albumin excretion, with the highest found in those with microalbuminuria (<30 micro g/mg creatinine, 252.7 +/- 16.4 pg/mL; 30 to >300 micro g/mg creatinine, 352.7 +/- 35.2 pg/mL; >>300 micro g/mg creatinine, 350.0 +/- 16.0 pg/mL). Similarly, TNF-alpha and IL-6 in diabetic patients with microalbuminuria or clinical albuminuria were significantly increased as compared with those without albuminuria (TNF-alpha, 3.20 +/- 0.41 pg/mL v 1.94 +/- 0.18 pg/mL; IL-6, 1.64 +/- 1.11 pg/mL v 0.51 +/- 0.05 pg/mL, P <.05, respectively). These results suggest that serum levels of IL-18, TNF-alpha, and IL-6 may have some etiopathogenic roles in diabetic nephropathy.

Adult↗

PubMed2003

A mechanism-based in vitro anticancer drug screening approach for phenolic phytochemicals.

Plant-derived phenolic compounds, including polyphenols (e.g., tannins), flavonoids, and phenolic acids, have been under investigation for their anticancer therapeutic and chemoprevention properties. Recently, certain mechanisms underlying the differential effects of green tea polyphenols (GTPPs) on tumor versus normal cells have been determined. These suggest that GTPPs may simultaneously activate multiple pathways. However, existing screening methods are insufficient for the identification of agents that possess both a cytotoxic effect on tumor cells and a protective effect on normal cells. The current study describes the establishment of an in vitro survival/apoptosis testing system based on detecting these mechanisms by a double-fluorescence method. This system is able to screen potential chemopreventive or therapeutic agents from (but not limited to) plant-derived compounds based on the pathways differentially activated by the agents. Tumor cell death and normal cell survival are detected simultaneously, in a device that co-cultures normal human cells adjacent to human tumor cells.

Antineoplastic Agents↗

PubMed2003

Polymorphic mutations of the Mn-SOD gene in intact human lymphocytes and oral squamous cell carcinoma cell lines.

Mutations of the superoxide dismutase (SOD) genes are associated with neoplastic and non-neoplastic diseases. However, the existence of polymorphic mutations of manganese SOD (Mn-SOD) has not been explored in squamous cell carcinoma (SCC) cells or in normal cells. In the present study, we examined mutations in the 5' flanking region of the Mn-SOD gene and Mn-SOD mRNA using 10 human oral SCC (OSC) cell lines and intact lymphocytes obtained from 10 healthy donors and one patient with OSC. The polymerase chain reaction products of DNA obtained from lymphocytes revealed insertions at many sites (-1833, -1575, -1093, -1056, -325, -318, and -310) in 10 of the 11 donors. Transitions and (or) transversions were also observed at -1638 and -216 in lymphocytes from six donors and one donor, respectively. In DNA obtained from OSC cells, insertions and transitions and (or) transversions were more frequent than those in DNA from lymphocytes. In addition, deletions at -1341 and -1288 were observed in all lines except for one line. In these mutations, the transcription factor binding sites were not involved except for the AP-2 binding site (-102) in three cell lines. In Mn-SOD mRNA, Val at -9 position was varied to Ala in lymphocytes from two donors and three OSC cell lines, respectively. In the remaining cell lines, Mn-SOD mRNA from lymphocytes and OSC cell lines revealed heterozygosity (Ala/Val) and homozygosity (Val/Nal), respectively. The Mn-SOD activities in lymphocytes were 3.8-5.8 x 10(-4) U/10(6) cells and the activities in OSC cell lines were 1.8-8.3 x 10(-4) U/10(6) cells. These Mn-SOD activities were not correlated with the mutations of DNA and mRNA. From these results, it is indicated that polymorphic mutations of Mn-SOD exist in human normal cells and that the deletions might be obtained in the course of malignant transformation of OSC although decrease in Mn-SOD activity is not involved in the transformation.

5' Flanking Region↗

PubMed2003

Characteristic cytokine generation patterns in cancer cells and infiltrating lymphocytes in oral squamous cell carcinomas and the influence of chemoradiation combined with immunotherapy on these patterns.

OBJECTIVES: Cytokines produced by tumor cells and tumor-infiltrating lymphocytes (TIL) appear to regulate tumor cell growth and the cytotoxic activity of TIL. The objectives of the present study were to investigate cytokine generation patterns in tumor cells and TIL and to examine the influence of cancer therapy on this cytokine production and the cytotoxic activity of TIL. METHODS: We determined the levels of cytokines produced by tumor cells and TIL in vitro and measured the cytotoxic activity of TIL against Daudi cells in patients with oral squamous cell carcinoma (OSC) before and 1 week after the start of concomitant chemo-radio-immunotherapy. RESULTS: Before the therapy, OSC cells generated higher levels of granulocyte-macrophage colony-stimulating factor, tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) than did oral keratinocytes isolated from the noninflamed gingivae of healthy individuals, but both kinds of cells generated similar levels of interleukin (IL)-1beta and IL-6. Compared with peripheral blood mononuclear cells (PBMC) of the patients, TIL produced higher levels of IL-1beta, IL-6, IL-10, TNF-alpha and TGF-beta, whereas their production of IL-12 and interferon-gamma (IFN-gamma) was only slightly higher than that in PBMC. After 1 week of therapy, the cytokine production by OSC cells had largely decreased, while the production of TNF-alpha, IFN-gamma, TGF-beta and IL-12 by TIL had increased greatly, although other cytokine levels were almost constant during the investigations. The cytotoxic activity of TIL was higher than that of PBMC before the therapy, and this activity was strongly increased by 1 week of therapy. CONCLUSIONS: These results suggest that the cytokine productivities of TIL and tumor cells differ from those of PBMC and normal keratinocytes, respectively, and that chemo-radio-immunotherapy modulates in situ cytokine generation, which is advantageous for inhibition of tumor cell growth and activation of TIL.

Adult↗

PubMed2003

Allopurinol improves cardiac dysfunction after ischemia-reperfusion via reduction of oxidative stress in isolated perfused rat hearts.

It has been reported that the xanthine oxidase inhibitor, allopurinol, has a protective effect on ischemia - reperfusion injury, but the precise mechanism of its action is still unclear. Therefore, in the present study the mechanisms of the myocardial protection of allopurinol were evaluated in isolated perfused rat hearts. Allopurinol significantly inhibited myocardial xanthine oxidase activity, and improved left ventricular dysfunction after ischemia - reperfusion. In addition, the lactate dehydrogenase content in the coronary effluent obtained after reperfusion was significantly decreased. ATP, ADP, AMP and IMP significantly decreased, whereas inosine, hypoxanthine and xanthine significantly increased after ischemia in both the control and allopurinol groups. The concentration of xanthine was significantly decreased after ischemia - reperfusion in the allopurinol group; however, allopurinol did not affect the other purine metabolites. To evaluate the accumulation of oxidative stress, thiobarbituric acid reactive substances (TBARS) production in myocardial tissue was measured and allopurinol significantly decreased TBARS formation after ischemia - reperfusion. Finally, myocardial hydroxyl radicals were directly measured by electron spin resonance spectroscopy with the nitroxide radical 4-hydroxy-2, 2,6,6-tetramethyl-piperidine-N-oxyl. Hydroxyl radicals significantly increased immediately after reperfusion, but were significantly decreased in the allopurinol group. In conclusion, allopurinol reduced myocardial injury after ischemia-reperfusion by suppressing oxidative stress, but not by salvage of ATP. These findings may lead to the development of new therapeutic strategies for myocardial ischemia - reperfusion injury.

Adenine Nucleotides↗

PubMed2003

Characterization of neutron beams for boron neutron capture therapy: in-air radiobiological dosimetry.

The survival curves and the RBE for the dose components generated in boron neutron capture therapy (BNCT) were determined separately in neutron beams at Japan Research Reactor No. 4. The surviving fractions of V79 Chinese hamster cells with or without 10B were obtained using an epithermal neutron beam (ENB), a mixed thermal-epithermal neutron beam (TNB-1), and a thermal (TNB-2) neutron beam; these beams were used or are planned for use in BNCT clinical trials. The cell killing effect of the neutron beam in the presence or absence of 10B was highly dependent on the neutron beam used and depended on the epithermal and fast-neutron content of the beam. The RBEs of the boron capture reaction for ENB, TNB-1 and TNB-2 were 4.07 +/- 0.22, 2.98 +/- 0.16 and 1.42 +/- 0.07, respectively. The RBEs of the high-LET dose components based on the hydrogen recoils and the nitrogen capture reaction were 2.50 +/- 0.32, 2.34 +/- 0.30 and 2.17 +/- 0.28 for ENB, TNB-1 and TNB-2, respectively. The RBEs of the neutron and photon components were 1.22 +/- 0.16, 1.23 +/- 0.16, and 1.21 +/- 0.16 for ENB, TNB-1 and TNB-2, respectively. The approach to the experimental determination of RBEs outlined in this paper allows the RBE-weighted dose calculation for each dose component of the neutron beams and contributes to an accurate inter-beam comparison of the neutron beams at the different facilities employed in ongoing and planned BNCT clinical trials.

Air↗

PubMed2003