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Masanori Yoshida

Publications and source records attributed to Masanori Yoshida.

At least 19 recordsLinked to original sources
PubMed2007

High glucose activates pituitary proopiomelanocortin gene expression: possible role of free radical-sensitive transcription factors.

BACKGROUND: Hyperglycemia is recognized as a metabolic stress, and indeed it is known to stimulate hypothalamo-pituitary-adrenal (HPA) axis, a representative anti-stress system, in patients with diabetes mellitus or in animal models of hyperglycemia. Thus, we tried to clarify the molecular mechanism of glucose-induced HPA axis activation. METHODS: We studied the effect of high glucose on the transcriptional regulation of proopiomelanocortin (POMC) gene that encodes adrenocorticotropic hormone, a central mediator of HPA axis, using AtT20 corticotroph cell line in vitro. RESULTS: We found that high glucose concentration (24 mM) significantly stimulated the 5'-promoter activity of POMC gene. The effect was promoter-specific, and was mimicked by nuclear factor-kappaB (NF-kappaB)- or AP1-responsive promoters but not by cAMP-responsive element or serum-response element-containing promoters. Furthermore, the stimulatory effect of high glucose on POMC gene was eliminated by NF-kappaB and AP1 inhibitors, suggesting the involvement of the transcriptional factors. The POMC 5'-promoter has the canonical NF-kappaB consensus sequence, and gel shift assay showed the binding of NF-kappaB to the element. Finally, the effect of high glucose was completely abolished by treatment with a radical quencher 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL). CONCLUSIONS: Our data suggest that hyperglycemia activates POMC gene expression, at least partly, via NF-kappaB/AP1, and that high-glucose-induced free radical generation may mediate the activation of these transcription factors, which in turn stimulates the transcription of POMC gene.

Animals↗
PubMed2006

Molecular mechanisms for corticotropin-releasing hormone gene repression by glucocorticoid in BE(2)C neuronal cell line.

The molecular mechanisms for the suppression of corticotropin-releasing hormone (CRH) gene expression by glucocorticoid remain to be clarified albeit the well-known physiological role of the glucocorticoid-induced negative feedback regulation of the gene. In this study, we examined the effect of glucocorticoid on CRH gene transcription using the human BE(2)C neuronal cell line, which expresses the CRH gene and produces CRH peptide intrinsically. Dexamethasone, a specific ligand for the glucocorticoid receptor (GR), potently suppressed human CRH 5'-promoter activity. The effect was GR-dependent, and was completely antagonized by antiglucocorticoid RU38486. Treatment with neither sodium butyrate nor trichostatin A abolished the suppression, thus making the possible involvement of histone deacetylase (HDACs) unlikely. The suppression was not influenced by the deletion or mutation of the proposed negative glucocorticoid-response element (nGRE) but was completely eliminated by that of cAMP-response element. Finally, overexpression of protein kinase A catalytic subunit antagonized the glucocorticoid suppression, whereas overexpression of GR enhanced it. Taken together, our data suggest that: (1) glucocorticoid exerts its negative effect on CRH gene transcription in a GR-dependent manner, but the GR-mediated inhibition appears to be independent of the nGRE; (2) HDACs do not play a significant role in the glucocorticoid repression; (3) some of the inhibitory events may take place through transrepression of protein kinase A by GR.

Cell Line, Tumor↗
PubMed2006

Enantioselective organocatalytic amine conjugate addition.

The first enantioselective organocatalytic amine conjugate addition has been successfully developed. The application of LUMO-lowering iminium catalysis has enabled the highly chemo- and enantioselective 1,4-addition of a rationally designed N-silyloxycarbamate nucleophile (HOMO-raised) to alpha,beta-unsaturated aldehydes. Imidazolidinone 2*pTSA was found to catalyze the addition of various orthogonally N-protected silyloxycarbamate nucleophiles to a range of alpha,beta-unsaturated aldehydes, affording synthetically useful beta-amino aldehyde intermediates. The synthetic utility of the protocol was demonstrated in the rapid synthesis of enantioenriched beta-amino acids in one operation and 1,3-amino alcohol derivatives in three operations.

Aldehydes↗
PubMed2006

Stereoselective generation of (E)- and (Z)-2-fluoroalkylidene-type carbenoids from (2-fluoro-1-alkenyl)iodonium salts and their application for stereoselective synthesis of fluoroalkenes.

Alkylidene-type carbenoids, generated from (Z)- or (E)-(2-fluoro-1-alkenyl)iodonium salts by treatment with LDA, reacted with trialkylboranes to give (E)- or (Z)-(fluoroalkenyl)boranes stereoselectively. The resulting (fluoroalkenyl)borane can be used for the selective synthesis of (E)- or (Z)-fluoroalkenes, (E)- or (Z)-fluoroiodoalkenes, and alpha-fluoroketones. [reaction: see text]

Journal Article↗
PubMed2006

Identification of a functional AP1 element in the rat vasopressin gene promoter.

Arginine vasopressin (AVP) is expressed in paraventricular, supraoptic, and suprachiasmatic nuclei of the hypothalamus, where transcription of the AVP gene is activated by various forms of stress, such as hyperosmolality, inflammation, and photic stimulation. In vasopressinergic neurons, the expression of the Fos/Jun family proteins is known to be rapidly induced after these stimuli as well. However, it is still unknown whether these proteins actually mediate AVP gene expression. In this study we examined in vitro the role of Fos/Jun protein in transcriptional regulation of the AVP gene using the BE(2)M17 neuroblastoma cell line. We found that 5'-promoter activity of the rat AVP gene (-803/+26) markedly increased when all combinations of the Fos/Jun family proteins were overexpressed. Coexpression of the cAMP-responsive element-binding protein-binding protein and steroid receptor coactivator-1a further enhanced the Fos/Jun-mediated transcription. Using site-directed mutagenesis and EMSA techniques, we identified an activation protein 1 (AP1)-like element (-134/-128; TGAATCA) in the AVP gene 5'-promoter region, which is the sole responsible site for the Fos/Jun-mediated transcription. We also found that 12-O-tetradecarbonyl phorbol 13-acetate stimulates AVP gene transcription partly via the AP1 site through the activation of ERK signaling. Together, these results suggest that a variety of Fos/Jun family member proteins stimulate transcription of the AVP gene through the AP1 site we identified. Furthermore, this effect may be activated by both protein kinase A and protein kinase C signaling pathways.

Animals↗
PubMed2005

Inhibition of 11beta-hydroxysteroid dehydrogenase eliminates impaired glucocorticoid suppression and induces apoptosis in corticotroph tumor cells.

Cushing's disease is characterized by persistent ACTH secretion under hypercortisolemia. In an attempt to clarify the molecular mechanism, we examined the effect of 11beta-hydroxysteroid dehydrogenase (HSD) inhibition on glucocorticoid suppression of ACTH release using murine corticotroph tumor cells. We found that 11beta-HSD2, as well as -HSD1, was expressed in the cells and that its inhibition by carbenoxolone significantly improved the negative feedback effect of glucocorticoid. Carbenoxolone also enhanced apoptosis induced by cortisol. These effects are most likely attributable to inhibition of 11beta-HSD2 because only cortisol, a substrate of 11beta-HSD2, was present in these experimental conditions. We conclude that ectopic expression of 11beta-HSD2 is, at least in part, responsible for the impaired glucocorticoid suppression in corticotroph adenoma. Inhibition of 11beta-HSD2 may be applicable to the medical therapy for Cushing's disease.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2005

Improvement of foam breaking and oxygen-transfer performance in a stirred-tank fermenter.

This study examined a stirred-tank fermenter (STF) containing low-viscosity foaming liquids with an agitation impeller and foam-breaking impeller mounted on the same shaft. Results showed that the performance of the foam-breaking impeller can be improved by changing a conventional six-blade turbine impeller into a rod impeller as the agitation impeller. The volumetric oxygen-transfer coefficient, kLa, in the mechanical foam-control method (MFM) using a six-blade vaned disk as the foam-breaking impeller in the STF with the rod impeller was approximately five times greater than that of the chemical foam-control method (CFM) adding an anti-foaming agent in the STF with the six-blade turbine impeller. Application of the present method to the cultivation of Saccharomyces cerevisiae K-7 demonstrated that the cultivation time up to the maximum cell concentration was remarkably shorter than that achieved using a conventional CFM.

Bioreactors↗
PubMed2004

Nuclear factor of activated T cells (NFAT) is involved in the depolarization-induced activation of growth hormone-releasing hormone gene transcription in vitro.

GHRH plays a pivotal role in the regulation of both synthesis and secretion of GH in the anterior pituitary. In this study, we examined the molecular mechanism of depolarization-induced GHRH gene transcription using the hypothalamus cell line, Gsh+/+, revealing the involvement of the transcription factor called nuclear factor of activated T cells (NFAT). GHRH, NFAT1, NFAT4, and related genes were endogenously expressed in Gsh+/+ cells and the rat arcuate nucleus, where NFAT1 and GHRH were colocalized. Cellular excitation with high potassium potently stimulated endogenous GHRH gene 5'-promoter activity as well as the NFAT-mediated gene transcription, the former being further enhanced by coexpression of NFAT. On the other hand, cyclosporin A (a calcineurin-NFAT inhibitor) or EGTA (a calcium chelator) significantly blocked the depolarization-induced GHRH gene transcription. EMSA and site-directed mutagenesis experiments showed the direct binding of NFAT at five sites of the GHRH promoter, among which the relative importance of three distal sites (-417/-403, -402/-387, -317/-301) was suggested. Finally, elimination of all five sites completely abolished the NFAT-induced GHRH gene up-regulation. Altogether, our results suggest that the transcription factor NFAT is involved in the depolarization-induced transcriptional activation of GHRH gene in the neuronal cells.

Animals↗
PubMed2004

Effects of hormones targeting nuclear receptors on transcriptional regulation of the growth hormone gene in the MtT/S rat somatotrope cell line.

We have examined the effects of nuclear receptor hormones such as glucocorticoid, gonadal steroid hormones, thyroid hormone and retinoids on the transcriptional regulation of the 5'-promoter activity of growth hormone (GH) gene using the MtT/S rat pure somatotrope cell line or MtT/SGL, a subclone of MtT/S in which the rat GH gene 5'-promoter (1.7 Kb)-luciferase fusion gene was stably incorporated. RT-PCR analyses revealed that receptors for all the hormones except androgen receptor were expressed in the cell line. Triiodothyronine (T(3), 10 nM) transiently but significantly stimulated the promoter activity of GH gene, whereas retinoic acids (9-cis and all-trans, both 1 microM) showed sustained stimulation. There were no additive effects among the T(3), all-trans, and9-cis retinoic acids. Synthetic glucocorticoid hormone dexamethasone (100 nM) showed an inhibitory effect but, interestingly, significantly enhanced T(3)-stimulated GH promoter activity during long-term incubation. Among the gonadal steroid hormones tested, estradiol and estriol had significant stimulatory effects, and deletion analysis showed that the estrogen effect was maintained with the shortest construct examined (-150 to +6, +1 denotes the transcription start site). These results suggest that thyroid hormone and retinoids stimulate the transcription of GH gene, probably through a common response element, whereas glucocorticoid has both negative and positive effects on GH expression, depending on the combination with other hormones and the time of exposure. Estrogens also have direct stimulatory effects through the proximal promoter region of GH gene.

Analysis of Variance↗
PubMed2004

Nilvadipine inhibits nuclear factor-kappaB-dependent transcription in hepatic cells.

BACKGROUND: Recent findings suggest that some dihydropyridine-type calcium channel blockers, widely used as anti-hypertensive drugs, have direct anti-atherogenic action through their antioxidant properties. METHODS: We examined the effect of nilvadipine on the activity of a representative radical-sensitive transcription factor, nuclear factor kappa-B (NF-kappaB), in the human hepatocyte cell line HuH7 in vitro. RESULTS: Nilvadipine potently inhibited NF-kappaB-dependent transcription in a dose- and time-dependent manner, with a minimal effective concentration of 50 nmol/l. The effect was specific because no similar effects were found in the prototype dihydropyridine nifedipine. Electromobility shift assay showed reduced protein binding to the NF-kappaB-consensus sequence in nilvadipine-treated cells. Nilvadipine also reduced the expression of fibrinogen and plasminogen activator inhibitor-1 (PAI-1). CONCLUSIONS: Since NF-kappaB-mediated gene products, such as fibrinogen and PAI-1, are known to facilitate hypercoagulation, thrombosis and vascular events, we suggest that nilvadipine has a direct beneficial effect separate from its anti-hypertensive properties by inhibiting NF-kappaB-dependent gene expression and eventually inhibiting atherosclerosis.

Arteriosclerosis↗
PubMed2004

Akt activation protects rat liver from ischemia/reperfusion injury.

BACKGROUND: Apoptosis as well as necrosis may play an important role in hepatic ischemia/reperfusion (I/R) injury. Akt, a serine-threonine protein kinase, is known to promote cell survival. We investigated whether gene transfer of constitutively active or dominant negative Akt could affect hepatic I/R injury. MATERIALS AND METHODS: Hepatic I/R injury was induced in rats by Pringle's maneuver for 20 min followed by reperfusion. Adenoviruses encoding a constitutively active form of Akt (myrAkt), a dominant negative form of Akt (dnAkt), or beta-galactosidase (LacZ) were injected through the tail vein 72 h before hepatic I/R. RESULTS: Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) staining demonstrated a significant increase in the positive cells 240 min after reperfusion. Immunoblotting with phospho-Akt antibody showed phosphorylation of Akt from 90 to 180 min after reperfusion. The expression of myrAkt reduced the number of TUNEL-positive cells and hepatic necrosis around the central veins in the liver after reperfusion. This expression also significantly inhibited the increase in serum alanine aminotransferase (297 +/- 131 IU/L, P < 0.05) 120 min after I/R, compared with increases in uninfected (1761 +/- 671 IU/L), LacZ adenovirus (1528 +/- 671 IU/L)-, and dnAkt adenovirus (1342 +/- 485 IU/L)-infected rats. MyrAkt expression phosphorylated Bad and inhibited the release of cytochrome-c after reperfusion. No difference in nuclear translocation of nuclear factor (NF)-kappaB, p65 was seen among the three groups of rats, however. CONCLUSION: Adenoviral gene transfer of myrAkt could inhibit apoptotic cell death and subsequent hepatic I/R injury in the rat, through Bad, not NF-kappaB.

Adenoviridae↗
PubMed2004

Dehydroepiandrosterone-sulfate inhibits nuclear factor-kappaB-dependent transcription in hepatocytes, possibly through antioxidant effect.

Dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS), the representative sex steroid precursors, are postulated to have antiinflammatory effects, although the molecular background remains unknown. In this study, we examined the effects of these sex steroid precursors on cytokine-induced, nuclear factor-kappaB (NF-kappaB)-mediated transcription. The HuH7 human hepatocyte cell line was stably transfected with an NF-kappaB-luciferase reporter gene or transiently transfected with other representative response elements-luciferase fusion genes, and the effects of DHEA/DHEAS on proinflammatory cytokine-induced transcription were estimated by luciferase assay. The results showed that DHEA/DHEAS potently inhibited TNF-alpha-induced NF-kappaB-dependent transcription in a time- and dose-dependent manner. The effect was more obvious for DHEAS than for DHEA, and both steroids preferentially inhibited the cytokine-stimulated rather than basal NF-kappaB-mediated transcription. Similar effects were observed in activator protein-1-dependent but not constitutive Rous sarcoma virus promoter-dependent transcription. Two major downstream products of the sex steroid precursors, estradiol and testosterone, had no effect, indicating that the observed suppressive effect is not mediated by these metabolites. In contrast, glucocorticoids showed inhibitory effects on both basal and stimulated transcription and had an additive effect with DHEAS, suggesting the independent mechanisms of action of these steroid hormones. Finally, DHEAS eliminated hydroxyradical-induced activation of NF-kappaB-dependent transcription as well. Altogether, these results suggest that DHEA/DHEAS have an antiinflammatory effect in such a way that they inhibit proinflammatory cytokine-stimulated, NF-kappaB-mediated transcription, at least partly through their antioxidant properties.

Antioxidants↗
PubMed2004

High brachial-ankle pulse wave velocity is an independent predictor of the presence of coronary artery disease in men.

Pulse wave velocity (PWV) is an index of arterial stiffness, and a simple device for measuring brachial-ankle PWV (baPWV) has recently been developed. However, the clinical application of baPWV in patients with coronary artery disease (CAD) remains to be fully evaluated. This cross-sectional study was conducted to evaluate whether a higher baPWV predicts the presence of CAD. The baPWV was measured in 123 patients (77 males, 46 females; 63.5+/-11.8 years) who were undergoing coronary angiography. CAD was defined as >50% diameter stenosis. Hemodynamic data and cardiovascular risk factors were examined according to the presence or absence of CAD. Patients with CAD were significantly older across both sexes. The presence of hypertension and chest pain, but not baPWV, was correlated with CAD in females. The baPWV, and the presence of diabetes, hyperlipidemia, and chest pain were related to the presence of CAD in males. Multivariate logistic regression analysis in male patients showed that baPWV, diabetes, hyperlipidemia, and chest pain were independent risk factors for the presence of CAD. Furthermore, high baPWV in males with or without chest pain had a positive predictive value of 81.8% and 71.7% for the presence of CAD, respectively. In conclusion, high baPWV was shown to be a good independent predictor for the presence of CAD in men.

Adult↗
PubMed2003

Possible involvement of ryanodine receptor-mediated intracellular calcium release in the effect of corticotropin-releasing factor on adrenocorticotropin secretion.

We examined the role of intracellular calcium release in the regulation of CRH-induced ACTH secretion using the AtT20 corticotroph cell line. We found that ruthenium red, an inhibitor of ryanodine receptor, substantially diminished the secretory response, whereas Xestospongin C, an inositol 1,4,5-triphosphate receptor antagonist, had no effect. Expression of two ryanodine receptor subtypes (RyR1 and RyR3) was confirmed by RT-PCR. We also found that caffeine, a ryanodine receptor agonist, significantly stimulated, whereas thapsigargin, which causes depletion of intracellular calcium store, markedly diminished, the ACTH release. These results suggest that ryanodine receptor-mediated calcium-induced calcium release is involved in the regulation of CRH-induced ACTH release.

Adrenocorticotropic Hormone↗