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Biomedical subjects

Yukio Hirata

Publications and source records attributed to Yukio Hirata.

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

Antioxidant effect of adrenomedullin on angiotensin II-induced reactive oxygen species generation in vascular smooth muscle cells.

Recent adrenomedullin (AM) gene-targeting studies have proposed a novel concept that AM plays a protective role against oxidative stress in vivo. The present study was undertaken to explore the underlying molecular mechanism of the putative antioxidant action of AM against angiotensin II (Ang II)induced reactive oxygen species (ROS) generation in rat vascular smooth muscle cells (VSMCs). Intracellular ROS levels were measured by dichlorofluoroscein fluorescence. Redox-sensitive c-Jun amino-terminal kinase (JNK) and ERK1/2 activation and gene expression induced by Ang II in VSMCs were also studied. AM dose-relatedly (10(-8)-10(-7) m) inhibited intracellular ROS generation stimulated by Ang II (10(-7) m), as mimicked by dibutyl-cAMP, the effect of which was inhibited by the pretreatment with N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide hydrochloride, a protein kinase A inhibitor, and calcitonin gene-related peptide(8-37), an AM/calcitonin gene-related peptide receptor antagonist. Ang II induced JNK and ERK1/2 activation via a redox-sensitive manner, whereas AM inhibited JNK, but not ERK1/2, activation by Ang II. Furthermore, AM inhibited Ang II-induced redox-sensitive gene expression (plasminogen activator inhibitor-1 and monocyte chemoattractant protein-1) in the same manner as N-acetyl-l-cysteine, a potent antioxidant. AM also inhibited Ang II-induced up-regulation of Nox1, a critical membrane-bound component of reduced nicotinamide adenine dinucleotide phosphate oxidase in VSMCs, in the same degree as N-acetyl-l-cysteine. Our study demonstrates for the first time that AM directly inhibits intracellular ROS generation via an AM receptor-mediated and c-AMP-protein kinase A-dependent mechanism in VSMCs and that AM with its potent antioxidant action inhibits redox-sensitive JNK activation and gene expression induced by Ang II. These data suggest that AM plays a protective role as an endogenous antioxidant in Ang II-induced vascular injury.

Adrenomedullin↗
PubMed2004

Involvement of the 3'-untranslated region of cyclooxygenase-2 gene in its post-transcriptional regulation through the glucocorticoid receptor.

Functional roles of the 3'-untranslated region (3'-UTR) of the human Cyclooxygenase-2 (COX-2) gene were evaluated by transient transfection using luciferase (Luc) reporter vectors into bovine arterial endothelial cells (BAEC). Insertion of the 3'-UTR into the downstream of a Luc coding region resulted in decreased reporter activity (23%), although insertion into the upstream was no effect. The reporter activity of the downstream insertion but not the upstream insertion was induced by bacterial lipopolysaccharide (LPS). Moreover, LPS selectively stabilized COX-2 mRNA. Next, to evaluate the role of the 3'-UTR together with glucocorticoid receptor (GR), a GR-expression vector was cotransfected with the reporter vector of the downstream insertion of the 3'-UTR. As a result, the LPS-induced reporter activity was suppressed by dexamethasone in a dose-dependent manner. These data suggest that the 3'-UTR of the COX-2 gene is involved in not only the induction by LPS but also the suppression by DEX of COX-2 expression at the post-transcriptional level.

3' Untranslated Regions↗
PubMed2004

Separation of fatty acid methyl esters by comprehensive two-dimensional supercritical fluid chromatography with packed columns and programming of sampling duration.

Fatty acid methyl esters from various fats and oils were separated by comprehensive two-dimensional supercritical fluid chromatography with conventional packed columns and FID detection. The first dimension was a silica gel column and the second dimension was an ODS column. This combination was largely orthogonal for the separation of fatty acid methyl esters. The first dimension separations were primarily based on the number of double bonds while the second dimension separations were based on the chain length. The highly-ordered chromatograms and improved resolution allowed the easy detection and identification of minor components. Although the first dimension separations were performed under isobaric conditions where the peak width increased in proportion to the retention, the programming of the sampling duration allowed us to maintain the optimum re-injection frequency (3-4 times) per peak into the second dimension and so to minimize the total analysis time without deteriorating the resolution.

Animals↗
PubMed2004

Role of urotensin II in peripheral tissue as an autocrine/paracrine growth factor.

Urotensin II (UII), originally isolated from goby urophysis, has been shown to be an endogenous ligand for an orphan G-protein-coupled receptor, GPR14. Recent development of PCR quantitative method revealed that UII and UT receptor (GPR14) were expressed in a broad range of tissues and organs, including cardiovascular and renal system, and assumed to function as an autocrine/paracrine factor. UII is a potent vasoconstrictor peptide, whose potency is greater than any other vasoconstrictors thus far known. However, its physiological roles have been found to extend far beyond the regulation of vascular tone. In this review, we focused on the mitogenic action of UII and discuss its underlying cellular mechanisms and potential physiological/pathophysiological role in various human diseases.

Animals↗
PubMed2004

Endothelin-1 induces cyclooxygenase-2 expression and generation of reactive oxygen species in endothelial cells.

Since both endothelin-1 (ET-1) and aldosterone have been shown to induce expression of several pro-inflammatory genes, including cyclooxygenase-2 (COX-2), in the vasculature as a cardiovascular risk hormone, the present study was undertaken to examine the effects of ET-1 and aldosterone on COX-2 gene expression as measured by a real-time reverse transcriptase-polymerase chain reaction in aortic endothelial cells. Treatment with ET-1(10 M) markedly upregulated COX-2 mRNA levels in rat endothelial cells, whereas aldosterone (10 M) did not show any effect. The ET-1-induced COX-2 upregulation was inhibited by pretreatment with a non-selective endothelin receptor antagonist (TAK044), a protein kinase C inhibitor (GF109203X), and a MEK inhibitor (PD98059). Furthermore, ET-1 increased intracellular reactive oxygen species generation as estimated by the measurement of dichlorofluorescein fluorescence, whose effect was blocked by a COX-2 inhibitor (NS398). Our data show that ET-1 induces COX-2 upregulation in rat endothelial cells via a protein kinase C-dependent and extracellular signal-regulated kinase-dependent pathway, which may largely contribute to the generation of intracellular reactive oxygen species.

Aldosterone↗
PubMed2004

Laminar shear stress up-regulates inducible nitric oxide synthase in the endothelium.

Shear stress caused by blood flow is a potent physiological stimulus for the generation of nitric oxide (NO) in endothelial cells, which is believed to derive from the up-regulation and post-transcriptional activation of endothelial constitutive NO synthase (ecNOS). However, it has yet to be demonstrated that inducible NO synthase (iNOS) plays a significant role in shear stress-induced NO production from endothelial cells. We used parallel plate-type flow chambers that detect fluid shear stress to determine that shear stress, as quantified by a real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR), increased iNOS gene transcripts in cultured endothelial cells, which resulted in increased NO production. Shear stress-induced iNOS expression was inhibited by pyrrolidine dithiocarbamate (PDTC), an antioxidant and nuclear factor kappaB (NF-kappaB) blocker, and by MG132, an aldehyde peptide proteasome inhibitor that antagonizes I kappaB-kinase. Laminar shear stress increased the transcriptional activity of NF-kappaB, whereas over-expression of an I kappaB-alpha mutant that inhibits the activation of NF-KB in a dominant-negative fashion was found to attenuate the induction of endothelial iNOS by shear stress. The present results demonstrate that shear stress induces iNOS in the endothelium, mainly via the activation of NF-kappaB.

Animals↗
PubMed2004

[Anti-hypertensive drugs associated with the improvement of endothelial function].

Vascular endothelium is not merely a barrier between circulating blood and tissue, but also regulates vascular tone through the secretion of numerous vasoactive substances in response to hemodynamic changes. Thus endothelial injuries by hypertension and atherogenic risk factors play important pathogenic roles in the vascular disease state, and the protection of endothelial function leads to amelioration of progressive vascular disease. In this review, we describe the pathophysiology of endothelial dysfunction in vascular disease, and therapeutic significance of vaso-protective agents, especially in the cotex of endothelial protection.

Animals↗
PubMed2003

Regulation of multiple functions of SHPS-1, a transmembrane glycoprotein, by its cytoplasmic region.

SHPS-1 is a receptor-type transmembrane glycoprotein, which contains four tyrosine residues in its cytoplasmic region, and the phosphorylation of these tyrosine residues serves the binding sites for SHP-2 protein-tyrosine phosphatase. Its extracellular region interacts with another membrane protein, CD47, thereby constituting a cell-cell communication system. We analyzed this ligand-receptor interaction using Chinese hamster ovary (CHO) cells expressing wild-type (WT) or mutant SHPS-1. The binding affinity of an SHPS-1 mutant such as deltaCyto, that lacked most of cytoplasmic region, or 4F, in which all four tyrosine residues in cytoplasmic region were substituted with phenylalanine, for a recombinant CD47-Fc was greater than that of WT. In addition, oligomerization of deltaCyto or 4F mutant by binding of CD47-Fc was greater than WT. Chemical cross-linking of SHPS-1 indicated that SHPS-1 formed a cis-dimer. Furthermore, WT cells exhibited a less polarized cell shape with decreased formation of actin stress fibers, compared with parental CHO cells and mutant SHPS-1 expressing cells. Prominent lamellipodium formation and membrane ruffling were also observed at leading edges of migrating WT cells but not at those of other mutant SHPS-1 expressing cells. These results suggest that the binding affinity of SHPS-1 to CD47, clustering ability of SHPS-1, and cytoskeletal reorganization are regulated by the cytoplasmic region of SHPS-1.

Animals↗
PubMed2003

Salusins: newly identified bioactive peptides with hemodynamic and mitogenic activities.

The discovery of endogenous bioactive peptides has typically required a lengthy identification process. Computer-assisted analysis of cDNA and genomic DNA sequence information can markedly shorten the process. A bioinformatic analysis of full-length, enriched human cDNA libraries searching for previously unidentified bioactive peptides resulted in the identification and characterization of two related peptides of 28 and 20 amino acids, which we designated salusin-alpha and salusin-beta. Salusins are translated from an alternatively spliced mRNA of TOR2A, a gene encoding a protein of the torsion dystonia family. Intravenous administration of salusin-alpha or salusin-beta to rats causes rapid, profound hypotension and bradycardia. Salusins increase intracellular Ca2+, upregulate a variety of genes and induce cell mitogenesis. Salusin-beta stimulates the release of arginine-vasopressin from rat pituitary. Expression of TOR2A mRNA and its splicing into preprosalusin are ubiquitous, and immunoreactive salusin-alpha and salusin-beta are detected in many human tissues, plasma and urine, suggesting that salusins are endocrine and/or paracrine factors.

Adenosine Triphosphatases↗
PubMed2003

Adrenomedullin is an autocrine/paracrine growth factor for rat vascular smooth muscle cells.

Adrenomedullin is a potent vasodilator peptide secreted by vascular endothelial and smooth muscle cells. Adrenomedullin stimulates the proliferation of quiescent rat vascular smooth muscle cells (VSMCs) via p42/p44 ERK/MAP kinase activation. Recently, receptor-activity-modifying proteins (RAMPs) have been shown to transport calcitonin-receptor-like-receptor (CRLR) to the cell surface to present either as CGRP receptor or adrenomedullin receptor. We investigated whether adrenomedullin acts as an autocrine/paracrine growth factor for cultured rat VSMCs and whether coexpressions of RAMP isoform and CRLR may mediate p42/p44 ERK/MAP kinase activation by adrenomedullin. Adrenomedullin dose-dependently stimulated the proliferation of quiescent rat VSMCs, and this effect was inhibited by an adrenomedullin receptor antagonist, a MAP kinase kinase inhibitor and phosphatidylinositol 3-kinase inhibitors. Addition of either CGRP(8-37) or anti-adrenomedullin antibody to exponentially growing rat VSMCs inhibited the serum-induced cell proliferation, suggesting its role as an autocrine/paracrine growth factor. Cotransfection of RAMP2 or RAMP3 with CRLR into rat VSMCs potentiated activation of cAMP activity, but not of p42/p44 ERK/MAP kinase activity in response to adrenomedullin. Our results suggest that adrenomedullin is an autocrine/paracrine growth factor for rat VSMCs via p42/p44 ERK/MAP kinase and phosphatidylinositol 3-kinase pathways and that it is not mediated by human RAMP-CRLR receptors.

Adrenomedullin↗
PubMed2003

MR imaging of the thyroid: correlation between apparent diffusion coefficient and thyroid gland scintigraphy.

PURPOSE: To evaluate the usefulness of echo-planar MR imaging for assessing the thyroid function and confirm the clinical use of MR imaging for thyroid diseases. MATERIALS AND METHODS: Thirty-four patients with a variety of thyroid disorders (24 Graves disease; five subacute thyroiditis; five Hashimoto thyroiditis) were examined using T1-, T2-, and diffusion-weighted magnetic resonance (MR) imaging and thyroid scintigraphy with Tc-99m pertechnetate. RESULTS: The ADC values obtained from the diffusion-weighted images of the patients with Graves disease were significantly higher than those of patients with subacute hyroiditis and Hashimoto thyroiditis, though no difference among those disorders was observed on T1- and T2-weighted images. Based on the ADC value, anisotropy was not observed in the thyroid gland. An ADC value of 1.82 x 10(-3) mm(2)/second or higher indicated the presence of Graves disease (sensitivity 75%, specificity 80%). CONCLUSION: Diffusion-weighted MR images may be of value for the diagnosis of thyroid diseases and could be clinically important in the evaluation of thyroid function.

Diffusion Magnetic Resonance Imaging↗