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Biomedical subjects

Satoshi Fujii

Publications and source records attributed to Satoshi Fujii.

At least 55 records · Page 3Linked to original sources
PubMed2004

ATP- and adenosine-mediated signaling in the central nervous system: the role of extracellular ATP in hippocampal long-term potentiation.

Application of 10 microM ATP for 10 min transiently depressed, then slowly augmented, synaptic transmission in CA1 neurons, leading to long-term potentiation (LTP) (ATP-induced LTP). This ATP-induced LTP was blocked by addition of an N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, D,L-2-amino-5-phosphonovalerate (5 microM). For ATP-induced LTP, delivery of test synaptic inputs once every 20 s to CA1 neurons could be substituted by application of 100 nM NMDA during ATP perfusion. In addition, ATP-induced LTP was blocked by co-application of an ecto-protein kinase inhibitor, K-252b (40 nM), whereas a P2X purinoceptor antagonist, pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid 4-sodium (50 microM), or a P2Y purinoceptor antagonist, basilen blue (10 microM), had no effect. These results, therefore, indicate that the mechanisms of ATP-induced LTP involve the modulation of NMDA receptors / Ca(2+) channels and the phosphorylation of extracellular domains of synaptic membrane proteins, one of which could be the NMDA receptor / Ca(2+) channel.

Adenosine↗
PubMed2004

[Procoagulant activity and hypofibrinolysis in metabolic syndrome].

Atherosclerosis and cardiovascular diseases(CVD) are complex pathological processes involving many genes and their products in complicated interactions with environmental factors such as life-style changes. Recent advances in integrated molecular physiology have convincingly shown that increased coagulation, decreased fibrinolysis and inflammation integrate with each other under pathological conditions and contribute to CVD in metabolic syndrome. Thus, human responses to rapidly changing Westernization of Japanese life-styles can provide enormous damages that result in CVD. By intervening these processes we can modify the course of CVD. Vigorous research activities to implement therapeutic means and to improve preventive measures are needed to successfully interrupt pathogenetic processes such as vascular remodeling and thrombus formation without interrupting physiological defense activities such as wound healing and hemostasis.

Blood Coagulation↗
PubMed2003

Phosphorylation by aurora kinase A induces Mdm2-mediated destabilization and inhibition of p53.

Aurora kinase A (also called STK15 and BTAK) is overexpressed in many human cancers. Ectopic overexpression of aurora kinase A in mammalian cells induces centrosome amplification, chromosome instability and oncogenic transformation, a phenotype characteristic of loss-of-function mutations of p53. Here we show that aurora kinase A phosphorylates p53 at Ser315, leading to its ubiquitination by Mdm2 and proteolysis. p53 is not degraded in the presence of inactive aurora kinase A or ubiquitination-defective Mdm2. Destabilization of p53 by aurora kinase A is abrogated in the presence of mutant Mdm2 that is unable to bind p53 and after repression of Mdm2 by RNA interference. Silencing of aurora kinase A results in less phosphorylation of p53 at Ser315, greater stability of p53 and cell-cycle arrest at G2-M. Cells depleted of aurora kinase A are more sensitive to cisplatin-induced apoptosis, and elevated expression of aurora kinase A abolishes this response. In a sample of bladder tumors with wild-type p53, elevated expression of aurora kinase A was correlated with low p53 concentration. We conclude that aurora kinase A is a key regulatory component of the p53 pathway and that overexpression of aurora kinase A leads to increased degradation of p53, causing downregulation of checkpoint-response pathways and facilitating oncogenic transformation of cells.

Apoptosis↗
PubMed2003

Inhibition of influenza A virus sialidase activity by sulfatide.

Sulfatide, which binds to influenza A viruses and prevents the viral infection, was found to inhibit the sialidase activities of influenza A viruses in a pH-dependent manner. The kinetic parameters of the effect of sulfatide on the sialidase activities of human influenza A viruses using fluorometric assay indicated that sulfatide was a powerful and non-competitive type inhibitor in low-pH conditions.

Animals↗
PubMed2003

Induction of Tissue Factor Expression in Endothelial Cells by Basic Fibroblast Growth Factor and its Modulation by Fenofibric acid.

BACKGROUND: Tissue factor (TF), expressed in endothelial cells (ECs) and enriched in human atherosclerotic lesions, acts as a critical initiator of blood coagulation in acute coronary syndrome. Basic fibroblast growth factor (bFGF) induces the proliferation and migration of ECs and plays a role in angiogenesis and restoration of endothelial integrity. As TF is implicated in angiogenesis, we studied the effect of bFGF on TF gene and protein expression. Methods: Human umbilical vein ECs (HUVECs) were exposed to bFGF. TF mRNA was assessed by Northern blot and TF protein was assessed by Western blot. TF promoter activity was assessed by transient transfection assay and transcription factor was identified by electro mobility shift assay. RESULTS: bFGF increased TF mRNA and protein expression in HUVECs. Increased TF mRNA was attenuated by inhibition of extracellular signal-regulated kinase kinase in human ECV304 cells. Transient transfection assays of the human TF promoter-luciferase construct (-786/+121 bp) demonstrated that bFGF induced transcription was dependent on the elements within the -197 to -176 bp relative to the transcription start site of the human TF gene. This region contains NF-kappaB like binding site. Electro mobility shift assay showed that bFGF increased nuclear translocation or DNA binding of NF-kappaB transcription factor to TF promoter. Nucleotide substitution to disrupt NF-kappaB like site reduced bFGF stimulated promoter activity. Fenofibric acid, an agonist ligand for the peroxisome proliferator activated receptor-alpha, reduced basal and bFGF stimulated TF expression. CONCLUSIONS: These results indicate that bFGF may increase TF production in ECs through activation of transcription at NF-kappaB binding site, and control coagulation in vessel walls. Fibrate can inhibit TF expression and therefore reduce the thrombogenecity of human atherosclerotic lesions.

Journal Article↗
PubMed2003

Reactivation of the silenced and imprinted alleles of ARHI is associated with increased histone H3 acetylation and decreased histone H3 lysine 9 methylation.

ARHI has been identified as a maternally imprinted tumor suppressor gene that maps to chromosome 1p31 and whose expression is markedly down-regulated in breast cancer. To explore possible mechanisms that could silence ARHI expression, we have tested the importance of DNA methylation, histone acetylation and histone methylation in regulating ARHI expression. We found that treatment with CpG demethylating agents and/or histone deacetylase inhibitors could reactivate both the silenced and the imprinted alleles of this tumor suppressor gene. Reactivation of ARHI expression by these reagents is related to the methylation status of the CpG islands in the ARHI promoter, especially CpG island II. Chromatin immunoprecipitation assays revealed that histone H3 lysine 9/18 acetylation levels associated with ARHI in normal cells were significantly higher than those in breast cancer cell lines that lacked ARHI expression. Treatment with a CpG demethylating agent and/or histone deacetylase inhibitor could increase ARHI expression in breast cancer cells, with a corresponding increase in histone H3 lysine 9/18 acetylation and decrease in histone H3 lysine 9 methylation.

Acetylation↗
PubMed2003

Aberrant methylation and silencing of ARHI, an imprinted tumor suppressor gene in which the function is lost in breast cancers.

ARHI is a maternally imprinted tumor suppressor gene that maps to a site on chromosome 1p31 where loss of heterozygosity has been observed in 40% of human breast and ovarian cancers. ARHI is expressed in normal ovarian and breast epithelial cells, but ARHI expression is lost in a majority of ovarian and breast cancers. Expression of ARHI from the paternal allele can be down-regulated by multiple mechanisms in addition to loss of heterozygosity. This article explores the role of DNA methylation in silencing ARHI expression. There are three CpG islands in the ARHI gene. CpG islands I and II are located in the promoter region, whereas CpG island III is located in the coding region. Consistent with imprinting, we have found that all three CpG islands were partially methylated in normal human breast epithelial cells. Additional confirmation of imprinting has been obtained by studying DNA methylation and ARHI expression in murine A9 cells that carry either the maternal or the paternal copy of human chromosome 1. All three CpG islands were methylated, and ARHI was not expressed in A9 cells that contained the maternal allele. Conversely, CpG islands were not methylated and ARHI was expressed in A9 cells that contained the paternal allele of human chromosome 1. Aberrant methylation was found in several breast cancer cell lines that exhibited decreased ARHI expression. Hypermethylation was detected in 67% (6 of 9) of breast cancer cell lines at CpG island I, 33% (3 of 9) at CpG island II, and 56% (5 of 9) at CpG island III. Hypomethylation was observed in 44% (4 of 9) of breast cancer cell lines at CpG island II. When methylation of CpG islands was studied in 20 surgical specimens, hypermethylation was not observed in CpG island I, but 3 of 20 cases exhibited hypermethylation in CpG island II (15%), and 4 of 20 cases had hypermethylation in CpG island III (20%). Treatment with 5-aza-2'-deoxycytidine, a methyltransferase inhibitor, could reverse aberrant hypermethylation of CpG island I, II and III and partially restore ARHI expression in some, but not all of the cell lines. Treatment with 5-aza-2'-deoxycytidine partially reactivated ARHI expression in cell lines with hypermethylation of CpG islands I and II but not in cell lines with partial methylation or hypomethylation of these CpG islands. To test the impact of CpG island methylation on ARHI promoter activity more directly, constructs were prepared with the ARHI promoter linked to a luciferase reporter and transfected into SKBr3 and human embryo kidney 293 cells. Methylation of the entire construct destroyed promoter activity. Selective methylation of CpG island II alone or in combination with CpG island I also abolished ARHI promoter activity. Methylation of CpG I alone partially inhibited promoter activity of ARHI. Thus, hypermethylation of CpG island II in the promoter region of ARHI is associated with the complete loss of ARHI expression in breast cancer cells. Other epigenetic modifications such as hypermethylation in CpG island III may also contribute to the loss of ARHI expression.

Alleles↗
PubMed2003

Intracellular signal transduction modulating expression of plasminogen activator inhibitor-1 in adipocytes.

The concentrations in blood of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis and proteolysis, are elevated in obese and insulin-resistant subjects, predispose them to the risk of thrombosis, and may accelerate atherogenesis. Adipose tissue is a prominent source. Accordingly, intracellular signaling pathways that may influence PAI-1 expression in adipocytes have been the focus of considerable study. Rho, a small GTP binding and GTPase protein, when activated in turn activates its target, Rho-associated coiled-coil forming protein, to yield an active kinase, Rho-kinase, an effector in the Rho pathway. Rho-kinase exerts calcium-sensitizing effects in vascular smooth muscle cells and inhibitory effects on transforming growth factor-beta (TGF-beta) expression in chicken embryonic heart cells. Because TGF-beta is a powerful agonist of PAI-1 expression, we characterized the effects of inhibition of Rho-kinase in 3T3-L1 adipocytes. PAI-1 mRNA was determined by Northern blotting, and PAI-1 protein was determined by Western blotting. The Rho-kinase inhibitor, Y-27632 [(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide], increased PAI-1 expression markedly. Although genistein, a flavonoid tyrosine kinase, attenuated the increase of PAI-1 induced by Y-27632, other non-flavonoid tyrosine kinase inhibitors did not. However, another flavonoid, daidzein, which lacks tyrosine kinase activity, decreased basal PAI-1 expression and attenuated the induction of PAI-1 expression by Y-27632. Thus, the Rho/Rho-kinase system inhibits PAI-1 expression by a flavonoid-sensitive mechanism in adipocytes. Therefore, flavonoids may be useful in decreasing elevated PAI-1 expression in adipose tissue and its consequent pathophysiologic sequelae.

3T3 Cells↗
PubMed2003

Long-term potentiation and long-term depression induced by local application of ATP to hippocampal CA1 neurons of the guinea pig.

The present study has investigated the role of ATP in the induction of synaptic plasticity, using local application of ATP by picopump administration into the stratum radiatum of guinea pig hippocampal region CA1. Excitatory postsynaptic currents (EPSCs) evoked by stimulation of Schaffer collateral/commissural afferents synapsing on CA1 pyramidal cells of hippocampal slices were monitored in voltage-clamp mode, using whole-cell recording. Brief local application of ATP (1 mM) induced an inward current, usually consisting of early- and late-phase components. Because the late-phase component of an ATP-induced current was largely inhibited by Ca2+-free solution, this component is supposed to depend on extracellular Ca2+. After local application of ATP, long-term synaptic modification of EPSCs was induced: LTP was detected in neurons exhibiting a small late Ca2+ current, while LTD was obtained from recordings showing a large late Ca2+ current in response to ATP application. There was a statistically significant correlation between the magnitude of long-term plastic changes and the size of Ca2+ currents in response to ATP application. Furthermore, there was significant difference between the average size of the Ca2+ current in the LTP group and the size in the LTD group. These results suggest that a small Ca2+ influx in response to ATP application induces LTP, whereas a large one induces LTD in guinea pig hippocampal CA1 neurons.

Adenosine Triphosphate↗
PubMed2003

Cooperativity between activation of metabotropic glutamate receptors and NMDA receptors in the induction of LTP in hippocampal CA1 neurons.

In CA1 neurons of guinea pig hippocampal slices, long-term potentiation (LTP) was induced by 10 min application of 10 microM aminocyclopentane-1S, 3R-dicarboxylic acid (ACPD), the metabotropic glutamate receptor (mGluR) agonist, in the presence of test synaptic inputs (once every 20 s). In contrast, long-term depression (LTD) was induced by application of 10 microM ACPD in the absence of test inputs. When 10 microM ACPD was applied in the presence of test inputs, co-application of the N-methyl-D-aspartate (NMDA) receptor antagonist, D,L-2-amino-5-phosphonovalerate resulted in LTD induction when used at 50 microM. In ACPD-induced LTP, the delivery of test synaptic inputs to CA1 neurons could be replaced by co-application of NMDA (100 nM) during ACPD perfusion. These results suggest that, in CA1 neurons, a co-operative effect involving the activation of both mGluRs and NMDA receptors is required to trigger the process involved in ACPD-induced LTP. In addition, ACPD-induced LTD was blocked by co-application of an inositol 1,4,5-trisphosphate (IP3) receptor inhibitor, 2-aminotheoxydiphenyl borate (10 microM), which had no effect on ACPD-induced LTP. The results of the present study, therefore, indicate that ACPD-induced LTP involves NMDA receptors, but not IP3 receptors, whereas the converse applies to ACPD-induced LTD.

2-Amino-5-phosphonovalerate↗
PubMed2003

Coronary capillary network remodeling and hypofibrinolysis in aged obese diabetic rats: implications for increased myocardial vulnerability to ischemia.

Despite the known abnormalities of cardiac function in patients with overt non-insulin dependent diabetes mellitus (NIDDM) the temporal changes of coronary capillary network remodeling leading to potential microcirculatory dysfunction have not been elucidated. To this end, left ventricular subendocardial capillary network of Otsuka Long-Evans Tokushima Fatty (OLETF) rats, characterized by hypertension, obesity, hyperglycemia, hyperinsulinemia and mild NIDDM, and control Long-Evans Tokushima (LETO) rats were investigated. Total capillary density in OLETF was significantly higher than that in LETO at 20 weeks, suggesting compensatory improvement of O2 transport at early stages of NIDDM. The increase in capillary density in OLETF was lost at 40 and 60 weeks due to the decreases of intermediate capillary portions and venular capillary portions. Although capillary domain area (area innervated by single capillary) in OLETF was lower than that in LETO at 20 weeks, the values were similar between OLETF and LETO at 40 and 60 weeks, suggesting that adaptive improvement in the capacity for 02 transport with a high perfusion was lost in late stages of NIDDM. Activity of plasma plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of proteo(fibrino)lysis, in OLETF was higher than that in LETO at 40 and 60 weeks, suggesting that increase of PAI-1 may downregulate compensatory adaptive capillary network remodeling by inhibiting proteolysis and angiogenesis in the cardiac interstitium. Loss of adaptive myocardial microcirculation may therefore contribute to increased vulnerability in ischemic injury and to cardiac dysfunction in NIDDM.

Animals↗
PubMed2003

Allograft inflammatory factor-1 regulates trinitrobenzene sulphonic acid-induced colitis.

The expression of allograft inflammatory factor-1 (AIF-1) in 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis, a model for T helper 1 (Th1) type disease, was investigated in BALB/c mice. The AIF-1 expression was significantly increased in the colitis lesion compared to that in the normal colon. We then prepared AIF-1 transgenic mice (Tgm) with the BALB/c background that express high levels of AIF-1 in lymphoid tissues and the colon. When AIF-1 Tgm were administrated TNBS, the TNBS-induced colitis was ameliorated compared with that in non-transgenic littermates. The amelioration of colitis was associated with the low expression of interleukin-1beta in the colon. The present findings suggest that AIF-1 regulates Th1-type inflammatory responses.

Animals↗
PubMed2003

Structural characterization of adenine moiety in functional RNA molecules.

RNA molecules express the specific structure containing A-form helices and non-helical regions, such as loops and bulges. The adenosine moiety plays a key role in helical packing and/or loop and/or bulge interactions. It is well known as A-platform, tetraloop, and A-minor motif. For the formation of these motifs, there are specific interactions to the adjacent RNA segments and/or protein and/or metal ions beside the specific base sequences. The database focusing on adenine's structural roles, structural information about the assemblage and the space distribution of base moieties can be a useful tool. The user can obtain the selected list with the several descriptors including kink parameters for the structure definition and sequence properties. In addition to this nucleic acid system, RNA-drug related compound system would be included.

Adenine↗
PubMed2003

The Colletotrichum lagenariu Ste12-like gene CST1 is essential for appressorium penetration.

Colletotrichum lagenarium is the causal agent of anthracnose of cucumber. This fungus produces a darkly melanized infection structure, appressoria, to penetrate the host leaves. The C. lagenarium CMK1 gene, a homologue of the Saccharomyces cerevisiae FUS3/KSS1 mitogen-activated protein (MAP) kinase genes, was shown to regulate conidial germination, appressorium formation, and invasive growth. In S. cerevisiae, Ste12p is known to be a transcriptional factor downstream of Fus3p/Kss1p MAP kinases. To evaluate the CMK1 MAP kinase pathway, we isolated the Ste12 homologue CST1 gene from C. lagenarium and characterized. The cst1delta strains were nonpathogenic on intact host leaves, but could form lesions when inoculated on wounded leaves. Conidia of the cst1delta strains could germinate and form melanized appressoria on both host leaf surface and artificial cellulose membrane, but could not produce infectious hyphae from appressoria, suggesting that CST1 is essential for appressorium penetration in C. lagenarium. In addition, matured appressoria of the cst1delta strains contained an extremely low level of lipid droplets compared with that of the wild-type strain. Lipid droplets were abundant in conidia of the cst1delta strains, but rapidly disappeared during appressorium formation. This misscheduled lipid degradation might be related to the failure of appressorium penetration in the cst1delta strain.

Amino Acid Sequence↗
PubMed2003

Epigenetic regulation of ARHI in breast and ovarian cancer cells.

ARHI (Ras homologue member I) encodes a 26-kDa GTPase with 50-60% amino acid homology to Ras and Rap. ARHI and Ras share similar GTP/GDP binding domains, but exert opposite functions. ARHI is one of the first reported tumor suppressors in the ras superfamily. ARHI is expressed consistently in normal breast and ovarian epithelial cells, but not in breast or ovarian cancers. The loss of ARHI can be related to tumor progression. Reexpression of ARHI induces apoptosis of breast and ovarian cancer cells by a caspase-independent, calpain-dependent pathway. ARHI is consistently expressed in normal breast and ovarian epithelial cells but is dramatically downregulated in more then 70% of breast and ovarian cancers. ARHI is maternally imprinted with methylation of the three CpG islands in the maternal allele of normal cells. ARHI is expressed only from the paternal allele whose three CpG islands are not methylated. Loss of ARHI expression can occur through a genetic event, with loss of heterozygosity observed in 40% of breast, ovarian, and pancreatic cancers; but it can also occur through epigenetic mechanisms, including DNA methylation, histone deacetylation, histone methylation, and transcriptional regulation. Our data suggest that acetylation and methylation of chromatin associated with the ARHI promoter leads to loss of both ARHI expression and the ability to suppress tumor growth. Changes in chromatin that silence ARHI may be driven by methylation-dependent and -independent pathways. Reactivation of both the silenced paternal and imprinted maternal alleles can be achieved by demethylation and inhibition of histone deacetylation.

Acetylation↗
PubMed2003

Increased expression of plasminogen activator inhibitor-1 by mediators of the acute phase response: a potential progenitor of vasculopathy in hypertensives.

Hypertension is an important risk factor for coronary atherosclerosis, which is accelerated by inflammation and diminished fibrinolysis. We have previously shown that levels of plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of fibrinolysis, are increased with atherogenic metabolic derangement. Because the liver is one of the major sources of circulating PAI-1, we here examined the effects of two proinflammatory cytokines, interleukin (IL)-1beta, and IL-6, on PAI-1 production in a human hepatoma cell line, HepG2. IL-1beta (1 ng/ml) and IL-6 (1 ng/ml) increased the accumulation of PAI-1 in the conditioned media over 24 h (IL-1beta: 2.1 +/- 0.2 (mean +/- SD) fold over the control; IL-6:1.4 +/- 0.2 fold; Western blot, p < 0.05). The increase in PAI-1 protein accumulation correlated with the increased expression of PAI-1 mRNA (Northern blot). An HMG-CoA reductase inhibitor (mevastatin, 10 micromol/l) attenuated the PAI-1 production induced by IL-1beta and IL-6. The plasma PAI-1 activity level was higher in hypertensives than in normotensives (10.0 +/- 9.8 AU/ml vs. 6.2 +/- 4.5 AU/ml, p < 0.05). The plasma PAI-1 antigen level was also higher in hypertensives than in normotensives (30.9 +/- 22.4 ng/ml vs. 24.4 +/- 13.3 ng/ml, p < 0.05). Thus, 1) IL-1beta and IL-6 can increase PAI-1 production in hepatic cells and 2) mevastatin may exert anti-thrombotic effects by decreasing the PAI-1 protein production induced by these proinflammatory cytokines. These results provide further insights into how inflammation is involved in the atherothrombotic complications observed in hypertensives, which may be ameliorated by HMG-CoA reductase inhibitors.

Acute-Phase Reaction↗
PubMed2003

Brainstem congestion caused by direct carotid-cavernous fistula--case report.

A 41-year-old woman presented with tinnitus in the left ear and headache, followed by diplopia and pain in the left cheek. Angiography showed a left high-flow direct carotid-cavernous fistula (CCF), causing steal of the blood flow from the internal carotid artery into the cavernous sinus. A few days later, she rapidly developed right hemiparesis, dysarthria, and ocular conjugate deviation to the right, and became somnolent. Angiography at that time revealed occlusion of the superior petrosal sinus, causing engorgement of the veins in the surrounding brainstem. The CCF was completely embolized with interlocking detachable coils. Her consciousness disturbance and ophthalmoparesis dramatically improved within a few days, and the right hemiparesis and dysarthria gradually resolved. Magnetic resonance (MR) imaging after the treatment showed small pontine hemorrhage and perifocal edema but no ischemic lesions in the cerebral hemisphere. Re-evaluation of the MR imaging with gadolinium taken on admission demonstrated engorged veins in the brainstem parenchyma, which corresponded to the hemorrhagic lesion in the brainstem. Brainstem congestion caused by direct CCF is very rare, but it can be life-threatening. Good outcome can be expected if the CCF is completely occluded before congestive hemorrhage occurs.

Adult↗