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Biomedical subjects

M Horiuchi

Publications and source records attributed to M Horiuchi.

At least 73 records · Page 4Linked to original sources
PubMed1999

Increased vasoconstrictor response of the mouse lacking angiotensin II type 2 receptor.

The angiotensin II (Ang II) type 1 receptor mediates various actions of Ang II, whereas the function of the type 2 (AT2) receptor is not well understood. In the mice lacking the gene encoding the AT2 receptor, the pressor response to Ang II was increased although the underlying mechanism is unknown. We tested the hypothesis that vasoconstrictor response is exaggerated in the AT2 receptor null mice. We measured hemodynamic parameters and evaluated systemic vascular resistance (SVR) in the anesthetized open-chest wild-type and AT2 receptor null mice. Ang II infusion caused dose-dependent increases in SVR in both strains, while the response was significantly higher at 0.5 microgram/kg Ang II in the AT2 receptor null mice (305 +/- 53% of baseline) than in the wild-type mice (179 +/- 27% of baseline). To investigate further the vascular contractility, we examined contraction of aortic rings in vitro. The contraction induced by 1 microM Ang II was increased in the AT2 receptor null mice compared with that in the wild-type mice (0.82 +/- 0.11 vs. 0.54 +/- 0.12 g). Ang II-induced contraction was still greater in the AT2 receptor null mice when calibrated by the maximum tension induced by 90 mM KCl. These data suggest that the AT2 receptor modulates vascular contractility, which may influence blood pressure.

Angiotensin II↗
PubMed1999

Specific binding of normal prion protein to the scrapie form via a localized domain initiates its conversion to the protease-resistant state.

In the transmissible spongiform encephalopathies, normal prion protein (PrP-sen) is converted to a protease-resistant isoform, PrP-res, by an apparent self-propagating activity of the latter. Here we describe new, more physiological cell-free systems for analyzing the initial binding and subsequent conversion reactions between PrP-sen and PrP-res. These systems allowed the use of antibodies to map the sites of interaction between PrP-sen and PrP-res. Binding of antibodies (alpha219-232) to hamster PrP-sen residues 219-232 inhibited the binding of PrP-sen to PrP-res and the subsequent generation of PK-resistant PrP. However, antibodies to several other parts of PrP-sen did not inhibit. The alpha219-232 epitope itself was not required for PrP-res binding; thus, inhibition by alpha219-232 was likely due to steric blocking of a binding site that is close to, but does not include the epitope in the folded PrP-sen structure. The selectivity of the binding reaction was tested by incubating PrP-res with cell lysates or culture supernatants. Only PrP-sen was observed to bind PrP-res. This highly selective binding to PrP-res and the localized nature of the binding site on PrP-sen support the idea that PrP-sen serves as a critical ligand and/or receptor for PrP-res in the course of PrP-res propagation and pathogenesis in vivo.

Animals↗
PubMed1999

Activation of the de novo biosynthesis of sphingolipids mediates angiotensin II type 2 receptor-induced apoptosis.

This study examines the role of sphingolipids in mediating the apoptosis of PC12W cells induced by the angiotensin II type 2 (AT2) receptor. PC12W cells express abundant AT2 receptor but not angiotensin II type 1 receptor and undergo apoptosis when stimulated by angiotensin II. AT2 receptor-induced ceramide accumulation preceded the onset of caspase 3 activation and DNA fragmentation. AT2 receptor-induced ceramide accumulation did not result from the degradation of complex sphingolipids (SL) such as sphingomyelin or glycosphingolipids, as no changes in neutral or acidic sphingomyelinase activities, sphingomyelin level, nor in cellular glycolipid composition were observed. AT2 receptor activated serine palmitoyltransferase with a maximum time of 24 h after angiotensin II stimulation. The AT2 receptor-induced accumulation of ceramide was blocked by inhibitors of the de novo pathway of SL synthesis, beta-chloro-L-alanine and fumonisin B1. Inhibition of the de novo biosynthesis of SLs by fumonisin B1 and beta-chloro-L-alanine completely abrogated the AT2 receptor-mediated apoptosis. Pertussis toxin and orthovanadate blocked AT2 receptor-mediated ceramide production. Taken together our data demonstrate that in PC12W cells the stimulation of AT2 receptor induces the activation of de novo pathway, and a metabolite of this pathway, possibly ceramide, mediates AT2 receptor-induced apoptosis.

Acyltransferases↗
PubMed1999

Cloning and characterization of ATRAP, a novel protein that interacts with the angiotensin II type 1 receptor.

The carboxyl-terminal cytoplasmic domain of the angiotensin II type 1 (AT1) receptor has recently been shown to interact with several classes of cytoplasmic proteins that regulate different aspects of AT1 receptor physiology. Employing yeast two-hybrid screening of a mouse kidney cDNA library with the carboxyl-terminal cytoplasmic domain of the murine AT1a receptor as a bait, we have isolated a novel protein with a predicted molecular mass of 18 kDa, which we have named ATRAP (for AT1 receptor-associated protein). ATRAP interacts specifically with the carboxyl-terminal domain of the AT1a receptor but not with those of angiotensin II type 2 (AT2), m3 muscarinic acetylcholine, bradykinin B2, endothelin B, and beta2-adrenergic receptors. The mRNA of ATRAP was abundantly expressed in kidney, heart, and testis but was poorly expressed in lung, liver, spleen, and brain. The ATRAP-AT1a receptor association was confirmed by affinity chromatography, by specific co-immunoprecipitation of the two proteins, and by fluorescence microscopy, showing co-localization of these proteins in intact cells. Overexpression of ATRAP in COS-7 cells caused a marked inhibition of AT1a receptor-mediated activation of phospholipase C without affecting m3 receptor-mediated activation. In conclusion, we have isolated a novel protein that interacts specifically with the carboxyl-terminal cytoplasmic domain of the AT1a receptor and affects AT1a receptor signaling.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1999

Effects of mitogen-activated protein kinase inhibitors or phosphodiesterase inhibitors on interleukin-1-induced cytokines production in synovium-derived cells.

The effects of mitogen-activated protein (MAP) kinase inhibitors or phosphodiesterase (PDE) inhibitors on interleukin (IL)-1-induced cytokines production in synovium-derived cells were investigated. Human synoviocyte (HS) or synovial sarcoma (SW982) stimulated by IL-1beta (100 ng/ml) produced various cytokines including IL-6, IL-8, GROalpha, VEGF, basic FGF and tumor necrosis factor alpha (TNFalpha) in vitro. SB202190 or SB203580, an inhibitor of p38 MAP kinase, inhibited all cytokines production in both cells. PD98059, an inhibitor of MAP kinase kinase (MEK), inhibited IL-6, IL-8 and basic FGF production in HS and all cytokines production except basic FGF in SW982. However, many of its effects were weaker than those of SB202190 or SB203580. Quazinone, an inhibitor of cyclic GMP-inhibited PDE, scarcely affected cytokines production in both cells. Rolipram or R0201724, an inhibitor of cyclic AMP-specific PDE, inhibited IL-8 and basic FGF production in HS and TNFalpha production in SW982, however, it enhanced the other cytokines production in SW982. These results suggest that the activation of MAP kinase cascade may be important for IL-1-induced cytokines production in synovium-derived cells. On the other hand, the role of cyclic AMP may be dependent on cell and cytokine types.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1999

Transcription factor decoy to study the molecular mechanism of negative regulation of renin gene expression in the liver in vivo.

Renin is synthesized in high quantities in the juxtaglomerular cells of the kidney, but little or none is synthesized in the liver. Our previous in vitro and biochemical studies have demonstrated that tissue-specific expression of the mouse renin gene is regulated by the specific interaction between negative regulatory element (NRE) in the 5'-flanking region of the renin gene and NRE binding protein (NREB). In this study, we examined the hypothesis that this interaction between the NRE in the promoter region of the rat renin gene and the NREB in the liver contributes to the suppressed renin gene expression in this tissue in vivo. We used in vivo transfection of NRE transcription factor decoy (TFD) double-stranded oligonucleotide into the rat liver via portal vein infusion. A gel mobility shift assay showed that transfected NRE TFD blocked endogenous NREB binding with the rat renin gene. This resulted in enhanced hepatic renin mRNA expression, immunohistochemical detection of renin in the liver, and consequently, increased plasma renin concentration. Taken together, these results document the importance of NREB in the inhibition of renin gene expression in rat liver in vivo and suggest the possibility of in vivo renin gene modulation by the TFD approach.

Animals↗
PubMed1999

Stimulation of different subtypes of angiotensin II receptors, AT1 and AT2 receptors, regulates STAT activation by negative crosstalk.

Angiotensin II type 2 (AT2) receptor exerts an inhibitory action on cell growth. In the present study, we report that the stimulation of AT2 receptor in AT2 receptor cDNA-transfected rat adult vascular smooth muscle cells (VSMCs) inhibited angiotensin II type 1 (AT1) receptor-mediated tyrosine phosphorylation of STAT (signal transducers and activators of transcription) 1alpha/beta, STAT2, and STAT3 without influence on Janus kinase. AT2 receptor activation also inhibited the tyrosine phosphorylation of STAT1alpha/beta induced by interferon-gamma, epidermal growth factor, and platelet-derived growth factor. Similar effects of AT2 receptor were observed in R3T3 fibroblast and mouse fetal VSMCs, which express endogenous AT2 receptor. Moreover, AT2 receptor inhibited serine phosphorylation of STAT1alpha and STAT3 via the inhibition of extracellular signal-regulated kinase (ERK) activation. Stimulation of AT2 receptor inhibited the binding of STATs with sis-inducing element in c-fos promoter, resulting in decreased c-fos expression. Taken together, our results suggest that AT2 receptor can crosstalk negatively with multiple families of growth receptors by inhibiting ERK and STAT activation.

Animals↗
PubMed1999

Cardiomegaly in the juvenile visceral steatosis (JVS) mouse is reduced with acute elevation of heart short-chain acyl-carnitine level after L-carnitine injection.

The long-term administration of L-carnitine was very effective in preventing cardiomegaly in juvenile visceral steatosis (JVS) mice, which was confirmed by heart weight as well as the lipid contents in heart tissue. After i.p. injection of L-carnitine, the concentration of free carnitine in heart remained constant, although serum free carnitine level increased up to 80-fold. On the other hand, a significant increase in short-chain acyl-carnitine level in heart was observed. These results suggest that increased levels of short-chain acyl-carnitine, not free carnitine, might be a key compound in the protective effect of L-carnitine administration in JVS mice.

Aging↗
PubMed1999

Pyruvate dehydrogenase kinase 4 mRNA is increased in the hypertrophied ventricles of carnitine-deficient juvenile visceral steatosis (JVS) mice.

We isolated a mouse homologue cDNA of pyruvate dehydrogenase (PDH) kinase 4 (PDK4) with differential mRNA display as an up-regulated gene in the hypertrophied ventricles of juvenile visceral steatosis (JVS) mice with systemic carnitine deficiency. The PDK4 mRNA level was 5 times higher in JVS mice than in control mice under fed conditions. After 24 h starvation, this level increased to 20 times in JVS and 7 times in control, compared with the control fed level. On the other hand, carnitine administration reduced the high level of PDK4 mRNA in JVS mice to the control fed level. In control mice, the change in PDK4 mRNA was inversely correlated with the change in PDH activity. In JVS mice, however, the PDK4 mRNA level was not always correlated with the active-form PDH level.

Amino Acid Sequence↗
PubMed1999

Involvement of a cis-acting element in the suppression of carbamoyl phosphate synthetase I gene expression in the liver of carnitine-deficient mice.

The expression of carbamoyl phosphate synthetase I (CPS) gene is suppressed in the liver of carnitine-deficient juvenile visceral steatosis (JVS) mice at weaning and under starvation at adult age. To clarify the suppression mechanism, we produced CPSL transgenic JVS mice carrying a transgene composed of the chloramphenicol acetyltransferase (CAT) gene with the upstream region (-12 kb to +138) of the rat CPS gene and CPSE transgenic JVS mice carrying a transgene composed of the luciferase gene with minimal promoter (299 bp from -161 to +138) and enhancer (469 bp around -6.3 kb) fragments of the rat gene. The expression of the CAT gene as well as the endogenous CPS was suppressed in CPSL transgenic JVS mice, but luciferase gene expression was not suppressed in CPSE transgenic JVS mice. We isolated the 5'-upstream region of the mouse CPS gene and identified an activator protein-1 (AP-1) site downstream of the minimum enhancer region of both rat and mouse CPS genes. In conjunction with the 313-bp mouse promoter region, the 714-bp mouse enhancer fragment conferred a cell-type-dependent hormone responsiveness. In rat primary cultured hepatocytes, the addition of oleic acid suppressed reporter gene expression induced by dexamethasone in the construct containing the enhancer fragment of 714 bp with the AP-1 site, but not in its AP-1 site mutants or in 519 bp without the AP-1 site. These results strongly suggest that direct protein-protein interaction between AP-1 and glucocorticoid receptor is not involved in the suppression of the CPS gene in JVS mice and that the AP-1 element is the cis-element which is responsible for the suppression.

Animals↗
PubMed1999

Effects of S-8510, a benzodiazepine receptor partial inverse agonist, on event-related potentials (P300) in monkeys.

The present study investigated the effects of a novel benzodiazepine inverse agonist, S-8510 [2-(3-isoxazolyl)-3, 6, 7, 9-tetrahydroimidazo [4, 5-d] pyrano [4,3-b] pyridine monophosphate monohydrate], on the P300 components of the event-related potential (ERP) in monkeys. Late positive potentials (P300-like potentials) from the cortex (Pz) and hippocampus recorded using the auditory oddball paradigm in combination with electrical reinforcement can be measured in rhesus monkeys. The latency of this P300-like potential recorded from the monkey cortex was 330 ms, and the amplitude was 13 microV. It was prolonged in both the cortex (Pz) and hippocampus by SC injection of 10 microg/kg scopolamine, a muscarinic receptor antagonist. Oral administration of S-8510 (3, 10 mg/kg) had no effect on the latency in normal monkeys. However, S-8510 reversed the scopolamine-induced prolongation of P300-like potentials on the cortex (Pz) and hippocampus. These results show that S-8510 can attenuate the effects induced by scopolamine on P300-like potentials associated with cognitive function in monkeys, suggesting that S-8510 may be useful as a therapeutic drug in disease-associated cognitive dysfunctions of the central nervous system.

Animals↗
PubMed1999

Immunohistochemical study of some cytoskeletal proteins in hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle.

We have investigated the expression, using immunohistochemical and Western blot methods, of some cytoskeletal proteins including desmin, vimentin, actin, alpha-actinin, and ubiquitin in hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle (the histochemical and electron microscopical aspects have been previously reported). Immunohistochemically, the expression of desmin was observed strongly in the subsarcolemmal regions, but was lacking or faint in the area corresponding to the core-like structures. Vimentin showed almost the same localization as desmin, but no activity could be observed in the core-like structures. In addition, the core-like structures showed strong immunoreactivity for actin and ubiquitin, but no immunoreactivity for alpha-actinin. F-actin stained with phalloidin-tetramethyl-rhodamine was strongly positive in irregular spots that corresponded to the core-like structures, but was negative for desmin-positive regions. Western blot analysis of the diseased muscles revealed a significant increase in the amount of desmin and vimentin immunoreactivities and similar amounts of actin and alpha-actinin compared with the control muscles. Two-dimensional electrophoresis revealed no isoforms of desmin, suggesting the absence of abnormal phosphorylated forms of desmin. Since the co-localization of desmin and vimentin and the absence of phosphorylated desmin suggest that the overexpression of desmin may be reflected in the reactive change or regenerating process, the present myopathy should be regarded as an entity separate from desmin-storage myopathy or desmin-related myopathies. We also discuss the possibility that the present myopathy could be considered as myofibrillar myopathy, a recently proposed nosological entity.

Actinin↗
PubMed1999

Detection methods of possible prion contaminants in collagen and gelatin.

We describe methods for the preparation of collagen and gelatin samples to detect possible prion contaminants using Western blotting of a major component of prions, PrPSc. A commercially available collagen solution containing 2% athero-collagen was spiked with rodent adapted scrapie prion and used as the prion-contaminating collagen. The methods developed center on the enzymatic reduction of the collagen solution viscosity with protease treatments and on the concentration of the prion from the protease-digests with polyethylene glycol-#6000 and NaCl. Recovery of the spiked prion as a partially protease-resistant core fragment of PrPSc fluctuated from 30% to 46% of the input amount.

Animals↗
PubMed1999

Involvement of leukotriene B4 in arthritis models.

We investigated the role of leukotriene B4 (LTB4) in murine arthritis models using a leukotriene A4 (LTA4) hydrolase inhibitor, SA6541. SA6541 inhibited the severity of collagen-induced arthritis and muramyl dipeptide (MDP)-induced hyperproliferation of synovial cells in vivo. SA6541 also inhibited LTA4-induced hyperproliferation of synovial stromal cells in vitro. These results suggest that LTB4 may play an important role in arthritis models.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1999

Catecholamine metabolism inhibitors and receptor blockades only partially suppress cardiac hypertrophy of juvenile visceral steatosis mice with systemic carnitine deficiency.

To clarify the mechanism of cardiac hypertrophy in carnitine-deficient JVS mice, we studied the possible role of catecholamine metabolism. Cardiac hypertrophy occurs 2 weeks after birth. The turnover of norepinephrine in the ventricles of JVS mice at 2 weeks was 3 times that of control, but it was not different from control at 5 days when the heart weight was not changed. To evaluate the accelerated norepinephrine turnover, we examined the effects of catecholamine metabolism inhibitors (alpha-methyltyrosine and 6-hydroxydopamine) and catecholamine receptor blockades (propranolol, prazosin and yohimbine) on the ratio of heart weight to body weight (HW/BW) and on the augmented expression of atrial natriuretic peptide (ANP) and the down-regulated carnitine deficiency-associated gene expressed in ventricle (CDV-1). The HW/BW ratio in JVS mice treated with catecholamine metabolism inhibitors and receptor blockades was significantly lower than in JVS mice without treatment, but still higher than in controls treated with each drug and in JVS mice treated with carnitine. The HW/BW ratio of JVS mice with propranolol was not significantly different from that of JVS mice treated with catecholamine metabolism inhibitors and was significantly lower than that of JVS mice treated with prazosin and yohimbine. Northern blot analysis showed that the altered expression of ANP and CDV-1 was not corrected in the ventricles of JVS mice treated with any of the drugs except carnitine. These results suggest that the catecholamine metabolism accelerated in JVS mice ventricles at 2 weeks is not the major cause of cardiac hypertrophy, but probably promotes cardiac hypertrophy mainly through the beta-adrenergic signaling pathway. The aberrant gene expression of ANP and CDV-1 found in JVS mice seems to be independent of catecholamine metabolism, and mediated primarily by the systemic carnitine deficiency.

Adrenergic Antagonists↗
PubMed1999

Chiral separation and quantitation of pentazocine enantiomers in pharmaceuticals by capillary zone electrophoresis using maltodextrins.

The chiral separation of pentazocine was achieved by capillary electrophoresis using oligosaccharides. Enantiomers were separated on 100 mM Tris/H3PO4 buffer (pH 2.5) with 5% maltodextrin as a chiral selector, and migration behavior was monitored at 200 nm. Under these conditions, (-)- and (+)-pentazocine and dextromethorphan (internal standard) migrated within 9 min, and the resolution of pentazocine enantiomers was 2.54. Linear calibration curves were obtained in the range 5-50 microg/ml(-1) for each enantiomer. The detection limit of pentazocine enantiomers was 29 pg, and the recoveries of(-)- and (+)-pentazocine were 98.9 (R.S.D., 3.4%) and 101.4% (R.S.D., 4.3%) with 10 microg/ml(-1), respectively.

Analgesics, Opioid↗
PubMed1999

Signaling Mechanism of the AT2 Angiotensin II Receptor: Crosstalk between AT1 and AT2 Receptors in Cell Growth.

The peptide angiotensin (Ang) II exerts a range of actions in the cardiovascular, renal, reproductive and central nervous systems. At least two distinct Ang II receptor subtypes have been defined and designated as type 1 (AT1) and type 2 (AT2). The function and signaling mechanism of these receptor subtypes are quite different, and these receptors exert opposite effects on cell growth.

Journal Article↗