Takemichi Nakamura

Platelet-derived growth factor BB secreted from osteoclasts acts as an osteoblastogenesis inhibitory factor.

Osteoclasts and osteoblasts are responsible for strict bone maintenance with a balance between bone formation and resorption by interacting with each other. Recently, it has been revealed that osteoblasts/stromal cells regulate differentiation of osteoclasts/hematopoietic cells by two factors, the receptor activator of nuclear factor‐κB (NF‐κB) ligand (RANKL) on the plasma membrane, and secreted osteoprotegerin (OPG). However, no factors have yet been reported by which osteoclasts/hematopoietic cells regulate osteoblasts/stromal cells. To elucidate the possibility of signal transduction from osteoclasts to osteoblasts, we studied the conditioned medium of mouse osteoclast‐like myeloma cell line RAW264.7 treated with RANKL. We found that this medium contains a factor that inhibits differentiation of mouse osteoblast precursor‐like cell line MC3T3‐E1 to osteoblasts induced by bone morphogenetic protein 4 (BMP‐4) and named this factor osteoblastogenesis inhibitory factor (OBIF). OBIF was purified by successive three‐step chromatography by heparin affinity, anion exchange, and reversed‐phase columns. Osteoblastogenesis inhibitory activity made one peak in each chromatography step, showing the factor is a single entity. Active fractions were loaded on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and bands of proteins were excised, digested by trypsin, and analyzed by liquid chromatography equipped with tandem mass spectrometry (LC/MS/MS). Consequently, we have identified this factor to be platelet‐derived growth factor BB (PDGF BB) homodimer. Furthermore, this identification of PDGF BB as OBIF was confirmed by neutralization of the inhibitory activity of the medium with anti‐PDGF antibody. These results show, for the first time, that osteoclasts regulate osteoblasts directly and suggest that PDGF BB is a key factor in bone remodeling.

Fellutamides A and B, cytotoxic peptides from a marine fish-possessing fungus Penicillium fellutanum

Abstract Two cytotoxic peptides, fellutamides A and B, have been isolated from the cultured fungus Penicillium fellutanum Biourge which was isolated from the gastrointestine of the marine fish Apogon endekataenia Bleeker, and the structures were elucidated to be 1 and 2 by two-dimensional NMR and FAB MS/MS data.

Hymenamides A and B, new proline-rich cyclic heptapeptides from the Okinawan marine sponge Hymeniacidon sp.

Abstract New cyclic heptapeptides, hymenamides A and B, with a prolyproline segment have been isolated from the Okinawan marine sponge Hymeniacidon sp. and the structures elucidated on the basis of 2D NMR and FAB MS/MS data.

Systematic syntheses of influenza neuraminidase inhibitors: a series of carbosilane dendrimers uniformly functionalized with thioglycoside-type sialic acid moieties.

In order to develop novel influenza sialidase inhibitors, we constructed a library of glycoclusters composed of twelve types of sialylated dendrimers with thioglycosidic linkage that are resistant to hydrolysis by the sialidases. These sialodendrimers were synthesized by condensation reaction between a thiosialoside modified on the aglycon terminal end by a thioacetyl group and twelve types of carbosilane dendrimers having brominated terminal ends under deacetylation conditions, and temporal re-protection was performed for purification. Removal of all protection of the glycodendrimers was accomplished by transesterification and subsequent saponification to provide corresponding water-soluble glycodendrimers in good yields. For investigation of the structure-activity relationship, dendrimer scaffolds having differences in number of the sugar moieties, such as 3-, 4-, 6- and 12-functionalized dendrimers, and in linkage patterns, such as normal aliphatic linkage, ether- and amide-linkages. Biological evaluations of these glycodendrimers showed that all of the ether- and amide-elongated compounds had inhibitory potencies for the influenza sialidases in the mM range, while compounds having normal aliphatic linkage did not have any activities except for a 12-functionalized compound.

Hymenamide F, new cyclic heptapeptide from marine sponge Hymeniacidon sp

Abstract A new cyclic heptapeptide, hymenamide F (1), was isolated from an Okinawan marine sponge Hymeniacidon sp. and the structure was elucidated on the basis of spectroscopic data of [Mso]-hymenamide F (2). The absolute configuration of each amino acid residue was determined by Marfeys method. The conformation in the solution of 2 is discussed on the basis of NMR data as well as molecular calculation.

Keramamide A, a novel peptide from the Okinawan marine sponge Theonella sp.

A novel peptide, keramamide A 1, has been isolated from the Okinawan marine sponge Theonella sp. and the structure established as a unique hexapeptide containing a hitherto unknown amino acid 6-chloro-5-hydroxy-N-methyltryptophan, and possessing an unusual ureido bond. The structural assignment was made on the basis of spectroscopic results (two-dimensional NMR: 1H–1H COSY, NOESY, ROESY, COLOC, HMQC, HMBC and HOHAHA; and FAB MS/MS).

Allelopathic effects of p-menthane-3,8-diols in Eucalyptus citriodora

Abstract The relationship between the allelopathic p-menthane-3,8-diols and the ontogenetic age in Eucalyptus citriodora was elucidated. The diols in the soil from a Eucalyptus grove were analysed by mass chromatography. Germination and growth inhibitory activities of the cis-diol against several higher plants were examined.

RK-1355A and B, novel quinomycin derivatives isolated from a microbial metabolites fraction library based on NPPlot screening.

Two novel quinomycin derivatives, RK-1355A (1) and B (2), and one known quinomycin derivative, UK-63,598 (3), were isolated from a microbial metabolites fraction library of Streptomyces sp. RK88-1355 based on Natural Products Plot screening. The structural elucidation of 1 and 2 was established through two-dimensional NMR and mass spectrometric measurements. They belong to a class of quinomycin antibiotics family having 3-hydroxyquinaldic acid and a sulfoxide moiety. They are the first examples for natural products as a quinoline type quinomycin having a sulfoxide on the intramolecular cross-linkage. They showed potent antiproliferative activities against various cancer cell lines and they were also found to exhibit moderate antibacterial activity.

Structural analysis of O-glycans of mucin from jellyfish (Aurelia aurita) containing 2-aminoethylphosphonate

The structure of O-glycan in qniumucin (Q-mucin), which is a novel mucin extracted from jellyfish, was analyzed by a combination of NMR and ESI-MS/MS. A previously unidentified monosaccharide involved in the glycan chains was determined to be N-acetylgalactosamine (GalNAc) substituted by 2-aminoethylphosphonate (AEP) at the C-6. The O-glycans in Q-mucin from Aurelia aurita were proved to be mainly composed of three monosaccharides: GalNAc, AEP-(O-->6)-GalNAc, and P-6-GalNAc. To the best of our knowledge, this is the first example of an O-glycan structure of glycoproteins containing AEP. This exceptionally simple structure of Q-mucin and its potential use in material science and technology are revealed.

Structure determination of phosphonosphingolipids by fast atom bombardment and tandem mass spectrometry

Abstract Tandem mass spectrometry (MS/MS) and the fast atom bombardment (FAB) ionization method were used to determine the structures of phosphonophingolipids. Water-soluble components, aminoethylphosphonic acid and N-methylaminoethylphosphonic acid, were distinguished easily by the ions at m/z 126 and 140, respectively, in positive ion mode FAB mass spectra and the ions at m/z 124 and 138, respectively, in the negative ion mode. The molecular species of the ceramide moiety could also be determined from collisionally activated decomposition (CAD) spectra of each ceramide ion. Long-chain base ions could be clearly detected in positive ion mode FAB/MS.