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Biomedical subjects

Satoshi Omura

Publications and source records attributed to Satoshi Omura.

At least 19 recordsLinked to original sources
PubMed2003

Total synthesis and adjuvant activity of all stereoisomers of pinellic acid.

Pinellic acid is a novel and potentially useful oral adjuvant when used in conjunction with intranasal inoculation of influenza HA vaccines. All stereoisomers of pinellic acid have been synthesized via regioselective asymmetric dihydroxylation, regioselective inversion, and stereoselective reduction, and their adjuvant activities were characterized. Among this series of isomers, 9S, 12S, 13S compound has the most potent adjuvant activity. Structure-activity relationships are discussed.

Adjuvants, Immunologic↗
PubMed2003

Atpenins, potent and specific inhibitors of mitochondrial complex II (succinate-ubiquinone oxidoreductase).

Enzymes in the mitochondrial respiratory chain are involved in various physiological events in addition to their essential role in the production of ATP by oxidative phosphorylation. The use of specific and potent inhibitors of complex I (NADH-ubiquinone reductase) and complex III (ubiquinol-cytochrome c reductase), such as rotenone and antimycin, respectively, has allowed determination of the role of these enzymes in physiological processes. However, unlike complexes I, III, and IV (cytochrome c oxidase), there are few potent and specific inhibitors of complex II (succinate-ubiquinone reductase) that have been described. In this article, we report that atpenins potently and specifically inhibit the succinate-ubiquinone reductase activity of mitochondrial complex II. Therefore, atpenins may be useful tools for clarifying the biochemical and structural properties of complex II, as well as for determining its physiological roles in mammalian tissues.

Animals↗
PubMed2003

Core structure in roselipins essential for eliciting inhibitory activity against diacylglycerol acyltransferase.

Fungal roselipins, discovered as inhibitors of diacylglycerol acyltransferase (DGAT), consist of three parts; highly methylated C20 fatty acid, mannose and arabinitol. Demannosyl and/or dearabinitoyl roselipins were prepared chemically or enzymatically. Demannnosyl roselipins conserved the DGAT inhibitory activity, but the others lost the activity, indicating that the arabinitoyl fatty acid core is essential for eliciting the activity.

Acyltransferases↗
PubMed2002

Suppression of bone resorption by madindoline A, a novel nonpeptide antagonist to gp130.

IL-6 is a multifunctional cytokine involved in regulation of differentiation, antibody production, and growth of certain types of tumor cells. Its excessive production plays a major role in pathogenesis of multiple myeloma and postmenopausal osteoporosis. In the course of a screening program aimed at IL-6 inhibitor from microbial products, we found madindoline A (MDL-A) and madindoline B, which have a fuloindoline structure with diketocyclopentene bound to the methyl group. MDL-A has no cytotoxic activities. It inhibited only activities of both IL-6 and IL-11 without affecting the IL-6-specific signal transduction cascade, JAK2/STAT3. In a dose-dependent manner [(3)H]MDL-A binds to gp130, which is a signal transducing 130-kDa glycoprotein, but formation of the trimeric complex IL-6/IL-6 receptor/gp130 was not inhibited, suggesting that MDL-A suppresses dimerization of trimeric complexes. Not only did MDL-A markedly inhibit IL-6- and IL-11-induced osteoclastogenesis in vitro, but it also inhibited IL-6-stimulated serum amyloid A production and bone resorption in an experimental model of postmenopausal osteoporosis in vivo by a different mechanism from that of 17beta-estradiol. Here we show that MDL-A has a highly selective inhibitory effect on IL-6 and IL-11 activities by inhibiting a gp130 activity while suppressing bone loss in ovariectomized mice. MDL-A is anticipated as a lead compound for treatment of hormone-dependent postmenopausal osteoporosis, which has no serious side effects, and as a new mechanism of action, gp130 blocking.

Animals↗
PubMed2002

Remarkable influence of the aromatic substructure in 9-methoxystrobilurin derivatives on their antifungal activity.

9-Methoxystrobilurin-type beta-methoxyacrylate antibiotics (MOSBs) having various aromatic substructures were synthesized. The antifungal activity of the synthesized MOSBs against pathogenic and non-pathogenic fungi was examined, and the obtained results revealed that the antifungal activity of MOSBs was highly dependent on the aromatic substructures. However, no significant correlation was observed between cytotoxicity against human fibroblasts-like cell line and their structural properties. In addition, our results suggested that the strong growth-inhibitory activity of 9-methoxystrobilurin K against human-derived cell lines should be related to its hindered ether-type substructure.

Acrylates↗
PubMed2002

Accelerated degradation of mislocalized UDP-glucuronosyltransferase family 1 (UGT1) proteins in Gunn rat hepatocytes.

Gunn rat is a hyperbilirubinemic rat strain that is inherently deficient in the activity of UDP-glucuronosyltransferase form 1A1 (UGT1A1). A premature termination codon is predicted to produce truncated UGT1 proteins that lack the COOH-terminal 116 amino acids in Gunn rat. Pulse-chase experiments using primary cell cultures showed that the truncated UGT1A1 protein in Gunn rat hepatocytes was synthesized similarly to wild-type UGT1A1 protein in normal Wistar rat hepatocytes. However, the truncated UGT1A1 protein was degraded rapidly with a half-life of about 50 min, whereas the wild-type UGT1A1 protein had a much longer half-life of about 10 h. The rapid degradation of truncated UGT1A1 protein was inhibited partially but not completely by treating Gunn rat hepatocytes with proteasome inhibitors such as carbobenzoxy-Leu-Leu-leucinal and lactacystin. By contrast, neither the lysosomal cysteine protease inhibitor nor the calpain inhibitor slowed the degradation. Our findings show that the absence of UGT1 protein from Gunn rat hepatocytes is due to rapid degradation of the truncated UGT1 protein by the proteasome and elucidate the molecular basis underlying the deficiency in bilirubin glucuronidation.

Acetylcysteine↗
PubMed2002

High-resolution structures of a chitinase complexed with natural product cyclopentapeptide inhibitors: mimicry of carbohydrate substrate.

Over the past years, family 18 chitinases have been validated as potential targets for the design of drugs against human pathogens that contain or interact with chitin during their normal life cycles. Thus far, only one potent chitinase inhibitor has been described in detail, the pseudotrisaccharide allosamidin. Recently, however, two potent natural-product cyclopentapeptide chitinase inhibitors, argifin and argadin, were reported. Here, we describe high-resolution crystal structures that reveal the details of the interactions of these cyclopeptides with a family 18 chitinase. The structures are examples of complexes of a carbohydrate-processing enzyme with high-affinity peptide-based inhibitors and show in detail how the peptide backbone and side chains mimic the interactions of the enzyme with chitooligosaccharides. Together with enzymological characterization, the structures explain why argadin shows an order of magnitude stronger inhibition than allosamidin, whereas argifin shows weaker inhibition. The peptides bind to the chitinase in remarkably different ways, which may explain the differences in inhibition constants. The two complexes provide a basis for structure-based design of potent chitinase inhibitors, accessible by standard peptide chemistry.

Animals↗
PubMed2002

Macrosphelide B suppressed metastasis through inhibition of adhesion of sLe(x)/E-selectin molecules.

Macrosphelide B (MSB), a 16-membered macrolide from Microsphaeropsis sp. FO-5050, inhibits adhesion of sialyl Lewis(x) (sLe(x))-expressing HL-60 cells to LPS-activated (E-selectin-expressing) human umbilical vein endothelial cells (HUVECs) in vitro. This study examines MSB effects on metastasis of B16/BL6 mouse melanoma cells (B16/BL6 cells) and L5178Y-ML mouse lymphoma cells in vivo and analyzes the MSB antimetastatic activity mechanism. When administered MSB at 20 mg/kg/day, lung metastatic nodules of B16/BL6 cells were significantly decreased (T/C = 45%). However, no inhibition of metastasis of L5178Y-ML cells to the spleen and liver was observed. Flow cytometry analysis showed that B16/BL6 cells expressed high levels of sLe(x) antigen, whereas expression on L5178Y-ML cells was low. Under in vitro conditions, B16/BL6 cells demonstrated a greater degree of adhesion to LPS-activated HUVECs than L5178Y-ML cells, but adhesion was significantly inhibited by MSB and sLe(x) antibody. Combined therapy of MSB and cisplatin (CDDP) induced remarkable lung metastasis inhibition without adverse effects of CDDP to the host. All these findings suggest that MSB suppresses lung metastasis of B16/BL6 cells by inhibiting cell adhesion to endothelial cells through the sLe(x) molecule.

Animals↗
PubMed2002

Short total synthesis of (+)-madindolines A and B.

[reaction: see text] A short and efficient total synthesis of (+)-madindolines A (1) and B (2), potent and selective inhibitors of interleukin 6, has been achieved. The synthesis features a key chelation-controlled 1,4-diastereoselective acylation to generate the quaternary carbon and an intramolecular acylation of allylsilane to build up the cyclopentene unit.

Bridged Bicyclo Compounds, Heterocyclic↗
PubMed2002

Streptomyces avermectinius sp. nov., an avermectin-producing strain.

We propose the establishment of a new species, Streptomyces avermectinius, based on characterization of strain MA-4680(T) and morphological and phylogenetic comparisons with closely related members of the genus Streptomyces. The 16S rDNA sequence was obtained from this strain and used to place it among Streptomyces species using the variable alpha region and the nearly complete 16S rDNA sequence. Four Streptomyces species were selected as related species from phenotypic data, three species from phylogenetic databases on alpha region sequences and two species from phylogenetic data using nearly complete 16S rDNA sequences. Analysis of DNA-DNA hybridization tests distinguished strain MA-4680(T) from these eight Streptomyces species. The type strain is strain MA-4680(T) (= ATCC 31267(T) = NRRL 8165(T)).

Anthelmintics↗
PubMed2002

Fourteen-member macrolides suppress interleukin-8 production but do not promote apoptosis of activated neutrophils.

A 14-member macrolide was found to inhibit interleukin-8 (IL-8) synthesis in lipopolysaccharide-stimulated neutrophils but did not accelerate apoptosis in activated neutrophils. These data suggest that 14-member macrolides achieve clinical efficacy for chronic airway diseases partly by suppressing IL-8 production by activated neutrophils, but not by enhancing apoptosis in these cells.

Anti-Bacterial Agents↗
PubMed2002

Selective production of fungal beauveriolide I or III by fermentation in amino acid-supplemented media.

Beauveriolides I and III, cyclic depsipeptides composed of L-Phe, L-Ala, D-Leu and (3S,4S)-3-hydroxy-4-methyloctanoic acid, and L-Phe, L-Ala, L-allo-Ile and (3S,4S)-3-hydroxy-4-methyloctanoic acid, respectively, were previously isolated from the culture broth of fungal Beauveria sp. FO-6979 as inhibitors of macrophage foam cell formation. To improve the production of these compounds by fermentation, the culture conditions were studied. The production of both beauveriolides was increased five to ten folds by fermentation in the culture media containing tryptone. Further study revealed that addition of L-Leu/L-Ile, but not D-Leu/D-allo-Ile, to the culture medium yielded a high and selective production of beauveriolide I or III. As a result, regardless of their separation difficulty due to the similar physico-chemical properties, a large amount of beauveriolide I or III was prepared from the culture broth obtained from L-Leu- or L-Ile-supplemented fermentation, respectively, by one step purification using silica gel column chromatography.

Amino Acids↗
PubMed2002

Funicone-related compounds, potentiators of antifungal miconazole activity, produced by Talaromycesflavus FKI-0076.

Talaromyces flavus FKI-0076, a soil isolate, was found to produce compounds which reinforce the anti-Candida albicans activity of miconazole. Four structurally related compounds, a novel one, designated actofunicone, and the knowns deoxyfunicone, vermistatin and NG-012, were isolated from the culture broth by solvent extraction, ODS column chromatography and HPLC. The structure of actofunicone was elucidated as benzoic acid, 3,5-dimethoxy-2-[[4-oxo-6-(2-acetyloxy propyl)-4H-pyran-3-yl]carbonyl]-, methyl ester by various spectroscopic analyses including NMR experiments. These compounds potentiated the anti-C. albicans activity of miconazole, decreasing the IC50 value of miconazole from 19 microM to 1.6 approximately 3.7 microM in the presence of the funicones.

Antifungal Agents↗
PubMed2002

New antibiotics miyakamides produced by a fungus.

New antibiotics, miyakamides A1, A2, B1, and B2, were isolated from the cultured broth of Aspergillus flavus Link var. columnaris FKI-0739 together with known compounds, parasiticolide A, hydroxyaspergillic acid, and kojic acid. The structure of miyakamide A1 is N-acetyl-L-phenylalanyl-N-methyl-L-phenylalanyl-(alphaZ)-alpha,beta-didehydrotryptamine, and miyakamide A2 is E isomer of A1 at didehydrotryptamine. The structure of miyakamide B1 is N-acetyl-L-tyrosyl-N-methyl-L-phenylalanyl-(alphaZ)-alpha,beta-didehydrotryptamine, and B2 is E isomer of B1. Both miyakamides A1 and B1 existed as equilibrium isomers in solvents, and this isomerism was associated with cis-trans rotation of the amide bond between two amino acids. Conformational isomerism between two amino acids of miyakamides A2 and B2 is cis-form. Miyakamides showed growth inhibitory activity against brine shrimp, Artemia salina.

Animals↗