Biomedical subjects

H Hatanaka

Publications and source records attributed to H Hatanaka.

At least 19 recordsLinked to original sources

PubMed1999

Brain-derived neurotrophic factor prevents low-frequency inputs from inducing long-term depression in the developing visual cortex.

Brain-derived neurotrophic factor (BDNF) is reported to enhance synaptic transmission and to play a role in long-term potentiation in hippocampus and neocortex. If so, a shortage or blockade of BDNF might lead to another form of synaptic plasticity, long-term depression (LTD). To test this possibility and to elucidate mechanisms if it is the case, EPSCs evoked by test stimulation of layer IV were recorded from layer II/III neurons in visual cortical slices of young rats in the whole-cell voltage-clamp mode. LTD was induced by low-frequency stimulation (LFS) at 1 Hz for 10-15 min if each pulse of the LFS was paired with depolarization of neurons to -30 mV but was not induced if their membrane potentials were kept at -70 mV. Such an LTD was blocked by exogenously applied BDNF, probably through presynaptic mechanisms. Suppression of endogenous BDNF activity by the anti-BDNF antibody or an inhibitor for BDNF receptors made otherwise ineffective stimuli (LFS without postsynaptic depolarization) effective for LTD induction, suggesting that endogenous BDNF may prevent low-frequency inputs from inducing LTD in the developing visual cortex.

Aging↗

PubMed1999

Inhibition of phosphatidylinositol 3-kinase activity elevates c-Jun N-terminal kinase activity in apoptosis of cultured cerebellar granule neurons.

Cerebellar granule neurons maintained in medium containing 26 mM potassium or in medium (5 mM potassium) with 50 ng/ml brain-derived neurotrophic factor (BDNF) undergo an apoptotic cell death when exposed to 10 microM LY294002, an inhibitor of phosphatidylinositol 3-kinase (PI3-K). To investigate the intracellular signaling mechanism of LY294002-induced apoptosis, the activities of Akt and c-Jun N-terminal kinase (JNK) were measured in cells in HK (26 mM potassium) medium or LK+ (5 mM potassium) medium containing BDNF, with or without 10 microM LY294002. Akt activity decreased following the addition of 10 microM LY294002. In addition, we found that LY294002 increased the JNK activity, which is known to mediate some types of cell death in PNS neurons. We also observed elevated expression of c-Jun by LY294002 in HK+ BDNF. These findings demonstrated that apoptosis induced by inhibition of PI3-K activity involves suppression of the Akt activity and elevation of the JNK activity in cerebellar granule neurons. Our results suggested that the PI3-K-Akt pathway suppresses the activation of JNK and c-Jun expression, and as a result prevents the neuronal cell death in cerebellar granule neurons.

Animals↗

PubMed1999

Solution structure of human acidic fibroblast growth factor and interaction with heparin-derived hexasaccharide.

Fibroblast growth factors (FGFs) bind to extracellular matrices, especially heparin-like carbohydrates of heparan-sulfate proteoglycans which stabilize FGFs to protect against inactivation by heat, acid, proteolysis and oxidation. Moreover, binding of FGFs to cell surface proteoglycans promotes to form oligomers, which is essential for receptor oligomerization and activation. In the present study, we determined the solution structure of acidic FGF using a series of triple resonance multi-dimensional NMR experiments and simulated annealing calculations. Furthermore, we prepared the sample complexed with a heparin-derived hexasaccharide which is a minimum unit for aFGF binding. From the chemical shift differences between free aFGF and aFGF-heparin complex, we concluded that the major heparin binding site was located on the regions 110-131 and 17-21. The binding sites are quite similar to those observed for bFGF-heparin hexasaccharide complex, showing that both FGFs recognize heparin-oligosaccharides in a similar manner.

Amino Acid Sequence↗

PubMed1999

Thrombospondin 2 expression is correlated with inhibition of angiogenesis and metastasis of colon cancer.

Two subtypes of thrombospondin (TSP-1 and TSP-2) have inhibitory roles in angiogenesis in vitro, although the biological significance of these TSP isoforms has not been determined in vivo. We examined TSP-1 and TSP-2 gene expression by reverse transcription polymerase chain reaction (RT-PCR) analysis in 61 colon cancers. Thirty-eight of these 61 colon cancers were positive for TSP-2 expression and showed hepatic metastasis at a significantly lower incidence than those without TSP-2 expression (P = 0.02). TSP-2 expression was significantly associated with M0 stage in these colon cancers (P = 0.03), whereas TSP-1 expression showed no apparent correlation with these factors. The colon cancer patients with TSP-2 expression showed a significantly low frequency of liver metastasis correlated with the cell-associated isoform of vascular endothelial growth factor (VEGF-189) (P = 0.0006). Vascularity was estimated by CD34 staining, and TSP-2(-)/VEGF-189(+) colon cancers showed significantly increased vessel counts and density in the stroma (P < 0.0001). TSP-2(-)/VEGF-189(+) colon cancer patients also showed significantly poorer prognosis compared with those with TSP-2(+)/VEGF-189(-) (P = 0.0014). These results suggest that colon cancer metastasis is critically determined by angiogenesis resulting from the balance between the angioinhibitory factor TSP-2 and angiogenic factor VEGF-189.

Analysis of Variance↗

PubMed1999

Expression of the thrombospondin 1 receptor CD36 is correlated with decreased stromal vascularisation in colon cancer.

Vascularisation is determined by the balance between various angiogenic and angio-inhibitory factors in cancer stroma. CD36 is a cell adhesion receptor shown to interact with the ligand thrombospondin 1 (TSP1). It has not been determined whether the interaction of TSP1 and its receptor CD36 is correlated with vascularisation or clinical outcome of malignant tumours in vivo. We studied the correlations between expression of TSP1, CD36 and vascularisation and prognosis in 65 colon cancers. Various levels of TSP1 gene expression were observed in 27 of 65 colon cancers. CD36 expression was detected in 33 of 65 cancers, and was significantly correlated with decreased stromal vascularisation (P<0.001). The colon cancers expressing CD36 showed better prognosis (P<0.01). TSP1 expression levels did not affect CD36 expression. These results suggested that CD36 expression which decreased stromal vascularisation is correlated with better prognosis of colon cancer.

CD36 Antigens↗

PubMed1998

High potassium enhances secretion of neurotrophic factors from cultured astrocytes.

Elevation of extracellular potassium concentration ([K+]o) in the central nervous system (CNS), which is observed such after physiological stimuli and during ischemia, is known to be regulated by astrocytes. We suspected that in response to increased [K+]o, astrocytes might secrete some neurotrophic factor(s) to promote the survival of active and/or ischemically damaged neurons. In the present study, we examined neurotrophic activity contained in HK-ACM, i.e., astrocyte-conditioned medium (ACM) obtained after culturing astrocytes in 40 mM potassium-containing medium (HK medium). Addition of HK-ACM to basal forebrain cultures from postnatal 2-week-old (P2w) rats increased both the choline acetyltransferase (ChAT) activity (4.40-fold) and the number of ChAT-positive neurons (2.01-fold) as compared with non-conditioned HK medium. On the other hand, the neurotrophic effects of LK-ACM, i.e., ACM collected after culturing astrocytes in 4 mM potassium-containing medium (LK medium), were much weaker (2.85- and 1.41-fold for ChAT activity and number of ChAT-positive neurons, respectively) than those of HK-ACM. The neurotrophic effects of ACMs increased in a manner dependent on potassium concentration and on astrocyte culture time. Addition of an antibody against nerve growth factor (NGF) neutralized the neurotrophic effects of HK- and LK-ACMs. Direct quantification of NGF protein in ACMs by the two-site ELISA method demonstrated that a high concentration of potassium enhanced NGF secretion from cultured astrocytes. These results suggested that astrocytes secrete NGF in response to [K+]o elevation in the CNS.

Animals↗

PubMed1998

Synthetic lipid products of PI3-kinase which are added to culture medium prevent low K+-induced apoptosis of cerebellar granule neurons via Akt kinase activation.

To examine which lipid product of phosphatidylinositol 3-kinase (PI3-K) is essential for the survival-promoting pathway in cultured cerebellar granule neurons, three synthetic derivatives of lipid products of PI3-K were added to culture medium containing a low concentration (5 mM) of potassium (LK+) which induces apoptotic cell death. We found that dipalmitoylphosphatidylinositol 3,4-bisphosphate and dipalmitoylphosphatidylinositol 3,4,5-trisphosphate, but not dipalmitoylphosphatidylinositol 3-monophosphate, effectively blocked the LK+-induced apoptosis. These two synthetic phospholipids increased Akt activity but not that of PI3-K. These findings demonstrated that specific lipid products of PI3-K which are added to culture medium activate Akt/PKB without modulating PI3-K itself, and as a result prevent neuronal cell death in cerebellar granule neurons.

Animals↗

PubMed1998

Brain-derived neurotrophic factor induces rapid and transient release of glutamate through the non-exocytotic pathway from cortical neurons.

There is increasing interest in the involvement of neurotrophins in neural transmission and plasticity. Thus, we investigated the effects of brain-derived neurotrophic factor (BDNF) on glutamate release from cortical neurons. Treatment of cultured cortical neurons with BDNF induced rapid and transient release of glutamate. This effect was suggested to be mediated by TrkB activation because K252a inhibited the release of glutamate and BDNF phosphorylated TrkB within 30 s. BDNF-induced glutamate release was observed even when using Ca2+-free assay buffer but was inhibited by BAPTA-AM, a cell-permeable Ca2+ chelator. Therefore, BDNF-induced glutamate release was independent of extracelluar Ca2+ but dependent on intracellular Ca2+. Because normal neurotransmitter release is exocytotic, the involvement of the exocytotic pathway in BDNF-induced glutamate release was examined. As botulinum toxin is known to cleave exocytosis-associated proteins, thereby inhibiting exocytosis, it was applied to neurons prior to the release assay. Although botulinum toxin B cleaved VAMP2 and inhibited Ca2+-triggered glutamate release, it did not inhibit the BDNF-induced release of glutamate. These results strongly suggested that BDNF induces rapid and transient release of glutamate from cortical neurons through a non-exocytotic pathway.

Animals↗

PubMed1998

Changes in c-Jun but not Bcl-2 family proteins in p53-dependent apoptosis of mouse cerebellar granule neurons induced by DNA damaging agent bleomycin.

Tumor suppressor gene p53 is a critical regulator of the cellular response to DNA damage. To examine the function of p53 in postmitotic CNS neurons, we cultured cerebellar granule cells from 15-day-old wild type and p53-deficient mice, and analyzed changes of protein expression in apoptosis elicited by DNA damage. When cerebellar granule cells from wild type mice were treated with bleomycin, a DNA strand-break inducing agent, neuronal death occurred. In contrast, cells from p53-deficient mice were resistant to bleomycin-induced neuronal death. Furthermore, cells from p53 heterozygous mice showed an intermediate resistance between wild type and p53-deficient mice. These results show that p53 is required for the bleomycin-induced cerebellar granule cell death. To examine which proteins are involved in this apoptosis, we examined changes in protein levels of the Bcl-2 family, including Bcl-2, Bcl-X and Bax. The relative amounts of these proteins did not change after bleomycin treatment, suggesting that the changes in the levels of these Bcl-2 family proteins are not necessary for apoptosis in this system. In contrast, the levels of c-Jun protein significantly increased 6 h after treatment with bleomycin in wild type but not in p53-deficient cerebellar granule cells. These results raise the possibility that c-Jun is required for p53-dependent neuronal apoptosis induced by bleomycin.

Animals↗

PubMed1998

Solution structure of Der f 2, the major mite allergen for atopic diseases.

House dust mites cause heavy atopic diseases such as asthma and dermatitis. Among allergens from Dermatophagoides farinae, Der f 2 shows the highest positive rate for atopic patients, but its biological function in mites has been perfectly unknown, as well as the functions of its homologs in human and other animals. We have determined the tertiary structure of Der f 2 by multidimensional nuclear magnetic resonance spectroscopy. Der f 2 was found to be a single-domain protein of immunoglobulin fold, and its structure was the most similar to those of the two regulatory domains of transglutaminase. This fact, binding to the bacterial surface, and other small pieces of information hinted that Der f 2 is related to the innate antibacterial defense system in mites. The immunoglobulin E epitopes are also discussed on the basis of the tertiary structure.

Allergens↗

PubMed1998

Growth stimulation of non-small cell lung cancer xenografts by granulocyte-macrophage colony-stimulating factor (GM-CSF).

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been suggested to be involved in the carcinogenesis of some types of tumours by autocrine or paracrine mechanisms. We examined GM-CSF/GM-CSF receptor (GM-CSFR) gene expression in 20 human non-small cell lung cancer (NSCLC) xenografts. The stimulatory effects of GM-CSF were examined using GM-CSF transgenic severe combined immunodeficient (SCID) mice (GM-Tg-SCID), which produce abundant human GM-CSF. A NSCLC xenograft (LC11-JCK), expressed GM-CSFR but not GM-CSF, and showed more rapid growth in GM-Tg-SCID than non-GM-CSF transgenic SCID mice (non-Tg-SCID). GM-CSF gene expression was detected in 48 of 90 (53%) primary NSCLC human specimens and GM-CSFR gene expression was detected in 42 specimens (47%). GM-CSF expression was detected in 13 of 30 squamous cell carcinoma specimens (43%) and GM-CSFR expression was detected in 10 specimens (33%). Patients with squamous cell carcinoma coexpressing GM-CSF and GM-CSFR showed significantly poorer prognosis than those expressing neither GM-CSF nor GM-CSFR (P < 0.05, Cox-Mantel test). These results suggest that GM-CSF can have a stimulatory effect on some NSCLC.

Animals↗

PubMed1998

Oxygen toxicity induces apoptosis in neuronal cells.

1. A high oxygen atmosphere induced apoptosis in cultured neuronal cells including PC12 cells and rat embryonic cortical, hippocampal, and basal forebrain neurons associated with DNA fragmentation and nuclear condensation. 2. The sensitivity of CNS neurons to a high-oxygen atmosphere was the following order; cortex > basal forebrain > hippocampus. 3. Cycloheximide and actinomycin-D inhibited the apoptosis, indicating that it depends on new macromolecular synthesis. In contrast, cultured postnatal CNS neurons were resistant to oxidative stress. 4. Neurotrophic factors such as nerve growth factor (NGF), fibroblast growth factor (FGF), and epidermal growth factor (EGF) blocked the apoptosis induced by a high-oxygen atmosphere.

Animals↗

PubMed1998

Production of reactive oxygen species and release of L-glutamate during superoxide anion-induced cell death of cerebellar granule neurons.

Enhanced production of superoxide anion (O2-) is considered to play a pivotal role in the pathogenesis of CNS neurons. Here, we report that O2- generated by xanthine (XA) + xanthine oxidase (XO) triggered cell death associated with nuclear condensation and DNA fragmentation in cerebellar granule neuron. XA + XO induced significant increases in amounts of intracellular reactive oxygen species (ROS) before initiating loss of cell viability, as determined by measurement of 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA) for O2- and other ROS and hydroethidine (HEt) specifically for O2- by using fluorescence microscopy and flow cytometry. Catalase, but not superoxide dismutase (SOD), significantly protected granule neurons from the XA + XO-induced cell death. Catalase effectively reduced C-DCDHF-DA but not HEt fluorescence, whereas SOD reduced HEt but not C-DCDHF-DA fluorescence, indicating that HEt and C-DCDHF-DA fluorescence correlated with O2- and hydrogen peroxide, respectively. The NMDA antagonist MK-801 prevented the death. XA + XO induced an increase in L-glutamate release from cerebellar granule neurons. These results indicate that elevation of O2- induces cell death associated with increasing ROS production in cerebellar granule neurons and that XA + XO enhanced release of L-glutamate.

Animals↗

PubMed1998

MS-430, a synthetic pyrimidine derivative, influences the intracellular signal transduction pathway leading to neuronal differentiation of PC12h cells.

Although NGF (nerve growth factor) induces neuronal differentiation of PC12 cells, EGF (epidermal growth factor) acts as a mitogen for these cells. We have studied the effects of a synthetic pyrimidine derivative, MS-430, on the NGF and EGF actions on PC12h cells. We found that MS-430 accelerated NGF-induced neurite extension of PC12h cells and that, in the presence of MS-430, PC12h cells extended neurites in response to EGF. Next, we investigated the tyrosine phosphorylation of NGF receptor TrkA and the EGF receptor (EGFR) as well as mitogen-activated protein kinase (MAPK), which is a key protein in the intracellular signal transduction pathway. It was found that MS-430 prolonged the EGF-induced phosphorylation of EGFR and MAPK compared to that without MS-430. MS-430 also prolonged the NGF-induced phosphorylation of MAPK, but the phosphorylation of TrkA induced by NGF was not affected by MS-430. These results suggest that MS-430 influences the intracellular signal transduction pathway which causes the neuronal differentiation of PC12h cells.

Acetylcholinesterase↗

PubMed1998

Comparison of survival-promoting effects of brain-derived neurotrophic factor and neurotrophin-3 on PC12h cells stably expressing TrkB receptor.

We obtained two PC12h cell lines, PC-pAB1 and PC-pAB2, stably expressing TrkB receptor and investigated the effects of BDNF and NT-3 in these cell lines. The cells differentiated into neuron-like cells in response to BDNF as well as NGF, neurite extension being more rapid in the former case. These TrkB-expressing cells also extended neurites in response to NT-3, which is a nonpreferred ligand of TrkB. Next, we examined the survival-promoting effects of NGF, BDNF, and NT-3 under apoptotic conditions of oxygen toxicity in naive cells and NGF deprivation in differentiated cells. In both cases, BDNF prevented cell death similarly to NGF. NT-3 prevented cell death induced by oxygen toxicity in naive cells, but not that induced by NGF deprivation in differentiated cells. NT-3 induced the tyrosine phosphorylation of TrkB in naive cells, but not in differentiated cells. These results indicate that NT-3 has survival-promoting effects on naive TrkB-expressing PC12h cells, but not on differentiated cells because of its inability to induce the tyrosine phosphorylation of TrkB.

Animals↗

PubMed1998

Increased expression of human histocompatibility leukocyte antigen-G in colorectal cancer cells.

Human histocompatibility leukocyte antigen (HLA)-G is a nonclassical major histocompatibility complex class I molecule. HLA-G is known to provide tolerance from recognition by natural killer cells. We studied HLA-G expression in 39 human colorectal cancers and 23 extra-neoplastic colon tissue samples by RT-PCR. The expression of HLA-G mRNA was significantly more frequent in colorectal cancer (34 of 39 cases) than in the extraneoplastic tissue (10 of 23 specimens; chi2 test, p = 0.0003). HLA-G expression was also confirmed on the cancer cells immunohistochemically. These results suggested that HLA-G on colorectal cancer cells may be correlated with escape from immunological surveillance during colon cancer development.

Colon↗

PubMed1998

Expression of cell-associated isoform of vascular endothelial growth factor 189 and its prognostic relevance in non-small cell lung cancer.

Vascular endothelial growth factor (VEGF) has four isoforms (VEGF121, VEGF165, VEGF189, VEGF206). We examined the expression patterns of VEGF isoforms in non-small cell lung cancer (NSCLC) by RT-PCR. The cell-associated isoform VEGF189 was more frequently expressed in NSCLC (90.5%) than in extraneoplastic lung tissue (57.6%, p=0.00004). Immunohistochemical examination confirmed VEGF protein expression in 33 of 76 NSCLC expressing VEGF189 (V189p+ group). The V189p+ group showed significantly poorer prognosis than those without VEGF189 mRNA and protein (V189p- group, p=0.01722). These results suggest that expression of the cell-associated isoform VEGF189 is closely associated with progression of NSCLC.

Carcinoma, Non-Small-Cell Lung↗

PubMed1998

Brain-specific angiogenesis inhibitor 1 expression is inversely correlated with vascularity and distant metastasis of colorectal cancer.

Brain-specific angiogenesis inhibitor (BAI) 1 was recently isolated as a novel p53 inducible gene. BAI1 has been suggested to play a significant role in angiostasis. We studied the expression of BAI1 in 49 colorectal cancer specimens by RT-PCR. BAI1 expression was significantly reduced in colorectal cancers as compared to the extraneoplastic tissues (X(2) test, p=0.041). BAI1 expression was inversely correlated with vascular invasion and metastasis (Fisher's exact test, p 0.045). Moreover, vascularity in the colorectal cancer was inversely correlated with BAI1 gene expression (Mann-Whitney U-test, p=0.0003). These observations suggested that BAI1 expression might inhibit angiogenesis and metastasis of colorectal cancer.

Angiogenesis Inhibitors↗