Makoto Ojika

Nagoya University, Nagoya, Aichi, Japan

Are you Makoto Ojika?

Claim your profile

Publications (174)400.01 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: One of the current obstacles to stem cell therapy is the tumorigenic potential of residual undifferentiated stem cells. The present study reports rediscovery of a synthetic derivative of okadaic acid, a marine polyether toxin, as a reagent that selectively induces the death of human pluripotent stem cells. Cell-based screening of 333 cytotoxic compounds identified methyl 27-deoxy-27-oxookadaate (molecule 1) as a substrate of two ATP-binding cassette (ABC) transporters, ABCB1 (MDR1) and ABCG2 (BCRP), whose expression is repressed in human embryonic stem cells and induced pluripotent stem cells. The results demonstrate that selective elimination of human pluripotent stem cells can be achieved by designing cytotoxic small molecules with appropriate ABC-transporter selectivity.
    Journal of the American Chemical Society 07/2014; · 10.68 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Racemic RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol, RD) was used as a topical skin whitening agent until it was recently reported to induce leukoderma. We then showed that oxidation of RD with mushroom tyrosinase rapidly produces RD-quinone, which is quickly converted to RD-cyclic quinone and RD-hydroxy-p-quinone. In this study, we examined whether either or both of the enantiomers of RD can be oxidized by human tyrosinase. Using a chiral HPLC column, racemic RD was resolved optically to R(-)-RD and S(+)-RD enantiomers. In the presence of a catalytic amount of L-dopa, human tyrosinase, which can oxidize L-tyrosine but not D-tyrosine, was found to oxidize both R(-)- and S(+)-RD to give RD-catechol and its oxidation products. S(+)-RD was more effectively oxidized than L-tyrosine while R(-)-RD was less effective. These results support the notion that the melanocyte toxicity of RD depends on its tyrosinase-catalyzed conversion to toxic quinones and the concomitant production of reactive oxygen species.This article is protected by copyright. All rights reserved.
    Pigment Cell & Melanoma Research 07/2014; · 5.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: RS-4-(4-Hydroxyphenyl)-2-butanol (rhododendrol, RD) was used as a skin whitening agent until it was reported to induce leukoderma in July, 2013. To explore the mechanism underlying its melanocyte toxicity, we characterized the tyrosinase-catalyzed oxidation of RD using spectrophotometry and HPLC. Oxidation of RD with mushroom tyrosinase rapidly produced RD-quinone, which was quickly converted to 2-methylchromane-6,7-dione (RD-cyclic quinone) and RD-hydroxy-p-quinone through cyclization and addition of water molecule, respectively. RD-quinone and RD-cyclic quinone were identified as RD-catechol and RD-cyclic catechol after NaBH4 reduction. Autoxidation of RD-cyclic catechol produced superoxide radical. RD-quinone and RD-cyclic quinone quantitatively bound to thiols such as cysteine and GSH. These results suggest that the melanocyte toxicity of RD is caused by its tyrosinase-catalyzed oxidation through production of RD-cyclic quinone which depletes cytosolic GSH and then binds to essential cellular proteins through their sulfhydryl groups. The production of ROS through autoxidation of RD-cyclic catechol may augment the toxicity. (148 words) This article is protected by copyright. All rights reserved.
    Pigment Cell & Melanoma Research 06/2014; · 5.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Neuromelanin (NM) is produced in dopaminergic neurons of the substantia nigra (SN) and in noradrenergic neurons of the locus coeruleus (LC). The synthesis of NM in those neurons is a component of brain aging and there is the evidence that this pigment can be involved in the pathogenesis of neurodegenerative diseases such as Parkinson's disease. NM is believed to derive from the oxidative polymerization of dopamine (DA) or norepinephrine (NE) with the participation of cysteine, dolichols and proteins. However, there are still unknown aspects in the chemical structure of NM from SN (SN-NM) and LC (LC-NM). In this study, we designed a new method to synthesize o-aminophenol compounds as putative degradation products of catecholamines and their metabolites which may be incorporated into NM. Those compounds are aminohydroxyphenylethylamine (AHPEA) isomers, aminohydroxyphenylacetic acid (AHPAA) isomers and aminohydroxyethylbenzene (AHEB) isomers, which are expected to arise from DA or NE, 3,4-dihydroxyphenylacetic acid (DOPAC) or 3,4-dihydroxyphenylmandelic acid (DOMA) and 3,4-dihydroxyphenylethanol (DOPE) or 3,4-dihydroxyphenylethyleneglycol (DOPEG), respectively. These o-aminophenol compounds were synthesized by the nitration of phenol derivatives followed by reduction with hydroiodic acid (HI), and they could be identified by HPLC in HI hydrolysates of SN-NM and LC-NM. This degradative approach by HI hydrolysis allows the identification of catecholic precursors unique to SN-NM and LC-NM, which are present in catecholaminergic neurons.
    Molecules (Basel, Switzerland). 01/2014; 19(6):8039-8050.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using B16 melanoma cells for screening, we found that a marine sponge extract has a potent anti-pigmenting effect and identified arenarol as its major active compound. In normal human melanocytes (NHMs), arenarol significantly abrogated the endothelin 1 (EDN1) stimulated expression of tyrosinase, tyrosinase-related protein 1 and dopachrome tautomerase at the transcriptional, translational and enzymatic activity (only for tyrosinase) levels. That effect was accompanied by the attenuation of the increased expression level of microphthalmia-associated transcription factor (MITF) protein at the transcriptional and translational levels. Analysis of EDN1 signaling demonstrated that arenarol significantly suppressed the EDN1-induced phosphorylation of MEK, ERK, MITF and CREB but not of Raf-1s. In contrast, the forskolin-induced phosphorylation of CREB was not down-regulated by arenarol. As for the mode of action of the suppressed phosphorylation of MEK, Raf-1 activity was not directly inhibited by arenarol in vitro and pretreatment with the protein phosphatase inhibitor okadaic acid did not affect the down-regulated phosphorylation of MEK that was induced by arenarol in NHMs. The sum of these findings suggests that arenarol abrogates the EDN1-stimulated expression of melanocyte-specific proteins by interrupting MEK phosphorylation in an as yet unknown Raf-1 inactivation mechanism.
    Cytotechnology 05/2013; · 1.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Platelet-derived growth factor (PDGF) induces the proliferation and migration of vascular smooth muscle cells (VSMCs), leading to the development of various vascular disorders such as restenosis and atherosclerosis. Therefore, inhibitors of PDGF-induced cellular events would be candidate agents for treating these diseases. During the search for such inhibitors from marine sources, we isolated petrosiols A-D (1-4) and related compounds from the marine sponge Petrosia strongylata. These metabolites, which we previously reported as neurotrophic substances, showed an inhibitory effect on PDGF-induced DNA synthesis at IC(50) values of 0.69-2.2μM. Petrosiol A (1) inhibited PDGF-induced cell proliferation without remarkable cytotoxicity and arrested cell cycle progression from the G0/G1 to S phase by inducing the downregulation of the expression of G1 checkpoint proteins cyclin D1, cyclin E, cyclin-dependent kinases (CDK)2, and CDK4 and the upregulation of the expression of p21 and p27. In addition, petrosiol A (1) inhibited the phosphorylation of PDGF receptor-β and its downstream proteins such as phospholipase C (PLC)-γ1, Akt, and extracellular signal-regulated kinase (ERK)1/2. These results suggest that 1 inhibited PDGF-induced VSMC proliferation by interrupting the phosphorylation of PDGF receptor-β followed by downstream signal transduction. Furthermore, petrosiol A (1) suppressed PDGF-induced actin filament dissociation and cell migration, suggesting that 1 and its derivatives may be used for the prevention and treatment of vascular diseases.
    Bioorganic & medicinal chemistry 01/2013; · 2.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: From an extract of the Okinawan sponge Petrosia strongylata, five novel acetylenic metabolites, petrosiols A (1)–E (5), were isolated and chemically characterized. These compounds induced nerve growth factor (NGF)-like neuronal differentiation of PC12 cells. The structure–activity relationships of the petrosiols, their derivatives, and some related known compounds suggest the importance of the rare 2,4-diyne-1,6,7,8-tetraol fragment for the neurotrophic activity of the petrosiols.
    Tetrahedron. 01/2013; 69(1):101–106.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bioluminescence in fireflies and click beetles is produced by a luciferase-luciferin reaction. The luminescence property and protein structure of firefly luciferase have been investigated, and its cDNA has been used for various assay systems. The chemical structure of firefly luciferin was identified as the D-form in 1963 and studies on the biosynthesis of firefly luciferin began early in the 1970's. Incorporation experiments using (14)C-labeled compounds were performed, and cysteine and benzoquinone/hydroquinone were proposed to be biosynthetic component for firefly luciferin. However, there have been no clear conclusions regarding the biosynthetic components of firefly luciferin over 30 years. Incorporation studies were performed by injecting stable isotope-labeled compounds, including L-[U-(13)C3]-cysteine, L-[1-(13)C]-cysteine, L-[3-(13)C]-cysteine, 1,4-[D6]-hydroquinone, and p-[2,3,5,6-D]-benzoquinone, into the adult lantern of the living Japanese firefly Luciola lateralis. After extracting firefly luciferin from the lantern, the incorporation of stable isotope-labeled compounds into firefly luciferin was identified by LC/ESI-TOF-MS. The positions of the stable isotope atoms in firefly luciferin were determined by the mass fragmentation of firefly luciferin. We demonstrated for the first time that D- and L-firefly luciferins are biosynthesized in the lantern of the adult firefly from two L-cysteine molecules with p-benzoquinone/1,4-hydroquinone, accompanied by the decarboxylation of L-cysteine.
    PLoS ONE 01/2013; 8(12):e84023. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The novel cerebroside, termitomycesphin I (1), and two known cerebrosides (2 and 3) were isolated from the edible mushroom, Termitomyces titanicus. The structures of 1-3 were determined and identified by interpreting the spectroscopic data.
    Bioscience Biotechnology and Biochemistry 07/2012; 76(7):1407-9. · 1.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Metastatic melanoma is resistant to conventional therapies. N-propionyl-4-S-cysteaminylphenol (NPrCAP), an N-protected sulfur-amine analog of tyrosine, is a good substrate for tyrosinase and is selectively incorporated into melanoma cells, causing cytotoxicity in vitro and in vivo. We have recently shown that intratumoral injections of NPrCAP suppress not only the growth of primary B16F1 melanoma tumors but also of secondary, re-challenged tumors. The participation of CD8(+) T cells has been suggested for the NPrCAP-mediated anti-B16 melanoma immunity. In this study, the molecular mechanism of the NPrCAP cytotoxicity and immunogenicity was examined. The phenol NPrCAP was shown to be activated by mushroom tyrosinase to the ortho-quinone N-propionyl-4-S-cysteaminyl-1,2-benzoquinone (NPrCAQ), and the structure was confirmed by reducing it to the corresponding catechol. NPrCAQ reacted rapidly with biologically relevant sulfhydryl compounds such as cysteine, glutathione and bovine serum albumin. The NPrCAQ-thiol adduct formation was proven with a model thiol N-acetylcysteine by spectroscopic methods. The production and release of NPrCAQ-protein adducts was verified in B16F1 melanoma cells in vitro and in B16F1 melanoma-bearing mice in vivo through the detection of 5-S-cysteaminyl-3-S-cysteinylcatechol after acid hydrolysis of the protein fraction. These results suggest that the phenol NPrCAP, acting as a prohapten, can be activated in melanoma cells by tyrosinase to the quinone-hapten NPrCAQ, which binds to melanosomal proteins through their cysteine residues to form possible neo-antigens, thus triggering the immunological response. NPrCAP thus represents a potential new approach to immunotherapy against metastatic melanoma.
    Biochemical pharmacology 06/2012; 84(5):646-53. · 4.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A library of extracts established from hundreds of marine organisms was screened by a cytotoxicity test. The active organic extract of an Okinawan marine sponge of the genus Dysidea was subjected to bioassay-guided fractionation to give three new polyoxygenated steroids dysideasterols F-H (1-3), together with two known related compounds (4 and 5). Their structures were confirmed by NMR and mass spectroscopic analyses. A characteristic structural feature of 2, 4 and 5 is an allylic epoxide, whereas this epoxide undergoes ring-opening by a neighbouring hydroxyl group to give a tetrahydrofuran ring in 1 and 3. All compounds 1-5 exhibited a similar cytotoxic effect with IC50 values of 0.15-0.3 µM against human epidermoid carcinoma A431 cells, demonstrating that the allylic epoxide moiety was not responsible for this cytotoxic effect.
    Bioscience Biotechnology and Biochemistry 05/2012; 76(5):999-1002. · 1.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two new cerebrosides, termitomycesphins G and H, were isolated from the edible Chinese mushroom, Termitomyces albuminosus (Berk.) Herm., and exhibited neuritogenic activity against PC12 cells. Their structures and absolute stereochemistry were elucidated by spectroscopic methods and by a comparison of the specific rotation of the hydrogenated products from termitomycesphins H and C. These cerebrosides possessed a unique modification by a hydroxyl group at the middle of the long-chain base, like earlier congeners termitomycesphins A-F. Termitomycesphin G with a 16-carbon-chain fatty acid showed higher neuritogenic activity than that of termitomycesphin H with an 18-carbon-chain fatty acid. This effect was observed within the termitomycesphins, suggesting that the chain length of the fatty acyl moiety played a key role in the neuritogenic activity.
    Bioscience Biotechnology and Biochemistry 04/2012; 76(4):791-3. · 1.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Five cytotoxic macrolides, aplyronines D–H (4–8), were isolated from the Japanese sea hare Aplysia kurodai. They are new congeners of the antitumor compound aplyronine A (1), which was previously isolated from the same organism. Their structures were determined by spectroscopic analysis (NMR and MS). The cytotoxicity of these new compounds was evaluated in comparison with that of aplyronines A–C (1–3), suggesting the importance of the 7-O-seryl ester group for mediating the potent cytotoxicity of aplyronines.
    Tetrahedron. 01/2012; 68(4):982–987.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The mating hormones α1 and α2 induce sexual reproduction of the phytopathogenic genus Phytophthora. To demonstrate the structural elements responsible to hormonal activity, 17 derivatives of α1 and α2 were synthesized and their hormonal activity (oospore-inducing activity) was evaluated. The terminal ester derivatives of α1 (diacetate and dibenzoate) retained the hormonal activity, whereas a dicarbamate derivative completely suppressed the activity. Even monocarbamates showed weak activities; among them the 1-O-carbamate was less active than 16-O-carbamate, suggesting that the 1-OH group is a little more important than 16-OH. Dihydro, dehydro, and demethyl derivatives exhibited the minimum level of activity. Surviving activity of 15-epi-α1 suggested a less importance of this stereochemistry. Contrary to α1, not only the terminal diacetate derivative but also monoacetates of α2 exhibited no or little activity. Among the monoacetates, 1-O-acetyl-α2 exhibited little yet relatively better activity than the others. No activity was observed for mono- and dicarbamoyl derivatives of α2. Dihydro α2 with the saturated double bond lost most of the activity. These findings suggest that both the mating hormones α1 and α2 require most of the functional (hydroxyl, keto, and olefinic) groups they possess in their natural form for inducing the sexual reproduction of Phytophthora.
    Bioorganic & medicinal chemistry 12/2011; 20(2):681-6. · 2.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new 10-membered-ring diterpene, cyclolobatriene (1), along with three other known diterpenes, lobatriene (2), eunicol (3), and fuscol (4), were isolated from the Okinawan soft coral Lobophytum pauciflorum. Their structures were established by extensive NMR spectroscopic analyses. Cyclolobatriene (1) is an additional example of rare prenylated germacrenes. Although 1, due to a 10-membered-ring structure, exists as an equilibrium mixture of three conformers, the NMR measurement in CDCl(3) at 7°C enabled us to assign the NMR signals of the three, which is the first example of the complete NMR assignment of all the existing conformers of germacrene-type compounds. Cyclolobatriene (1) was thermally unstable and converted into 2 through Cope rearrangement upon heating at 70°C. Eunicol (3) also possesses the same prenylated germacrene structure as 1, showing similar physico-chemical properties to 1. All four compounds 1-4 showed cytotoxic effect with IC(50)'s of 0.64, 0.41, 0.35 and 0.52 μM, respectively, against human epidermoid carcinoma A431 cells.
    Bioorganic & medicinal chemistry 12/2011; 20(2):687-92. · 2.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have previously demonstrated that coffee and caffeine ameliorated hyperglycemia in spontaneously diabetic KK-A(y) mice. This present study evaluates the antidiabetic effects of coffee and caffeine on high-fat-diet-induced impaired glucose tolerance in C57BL/6J mice. C57BL/6J mice fed a high-fat diet were given regular drinking water (control group), or a 2.5-fold-diluted coffee or caffeine solution (200 mg/L) for 17 weeks. The ingestion of coffee or caffeine improved glucose tolerance, insulin sensitivity, and hyperinsulinemia when compared with mice in the control group. The adipose tissue mRNA levels of inflammatory adipocytokines (MCP-1 and IL-6) and the liver mRNA levels of genes related to fatty acid synthesis were lower in the coffee and caffeine groups than those in the control group. These results suggest that coffee and caffeine exerted an ameliorative effect on high-fat-diet-induced impaired glucose tolerance by improving insulin sensitivity. This effect might be attributable in part to the reduction of inflammatory adipocytokine expression.
    Bioscience Biotechnology and Biochemistry 12/2011; 75(12):2309-15. · 1.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ComX pheromone is an isoprenoidal oligopeptide containing a modified tryptophan residue, which stimulates natural genetic competence in gram-positive bacteria, Bacillus. We have reported the structure of the ComX(RO-E-2) pheromone, which is produced by the RO-E-2 strain of Bacillus subtilis. ComX(RO-E-2) analogs with substituted amino acids and isoprenoid modified tryptophan residues (e.g., prenyl, geranyl, and farnesyl), were synthesized and examined for biological activity. These results indicate that Phe-Trp(∗)(Ger)-NH(2) is the minimum pharmacophore of the ComX(RO-E-2) pheromone. Furthermore, the length of the isoprenoid moiety (i.e., modification style), and the presence of double bonds, are crucial for biological activity. The modification style of the ComX pheromone is more important than the peptide sequence with respect to biological activity.
    Bioorganic & medicinal chemistry letters 07/2011; 21(13):4041-4. · 2.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new steroidal saponin was isolated from Ophiopogon japonicus. This saponin possesses a modification by 2-hydroxy-3-methylvalerylation of the hydroxyl group at C-4' of the sugar, linked to C-1 of the aglycone. It exhibited significant neuritogenic activity for PC12 cells. The structure-activity relationship revealed the aglycone, rather than the sugar moieties and acylation, to be important for the neuritogenic activity.
    Bioscience Biotechnology and Biochemistry 06/2011; 75(6):1201-4. · 1.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Natural products provide a rich source of biological tools, but elucidating their molecular targets remains challenging. Here we report a cell morphological profiling of a natural product library, which permitted the identification of bisebromoamide and miuraenamide A as actin filament stabilizers. Automated high-content image analysis showed that these two structurally distinct marine natural products induce morphological changes in HeLa cells similar to those induced by known actin-stabilizing compounds. Bisebromoamide and miuraenamide A stabilized actin filaments in vitro, and fluorescein-conjugated bisebromoamide localized specifically to actin filaments in cells. Cell morphological profiling was also used to identify actin-stabilizing or -destabilizing natural products from marine sponge extracts, leading to the isolation of pectenotoxin-2 and lyngbyabellin C. Overall, the results demonstrate that high-content imaging of nuclei and cell shapes offers a sensitive and convenient method for detecting and isolating molecules that target actin.
    ACS Chemical Biology 02/2011; 6(5):425-31. · 5.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Four stereoisomers of Phytophthora mating hormone α2 were synthesized using both enantiomers of citronellol as starting materials. The absolute configuration of the natural product was determined to be 7S,11R,15R by oospore-inducing assays of the synthetic isomers. A concise synthetic procedure of α1 was also established using a common synthetic intermediate of α2.
    Tetrahedron. 01/2011; 67(46):8887-8894.

Publication Stats

1k Citations
400.01 Total Impact Points

Institutions

  • 1983–2014
    • Nagoya University
      • • Department of Applied Molecular Biosciences
      • • Graduate School of Bio-Agricultural Sciences
      • • Department of Chemistry
      Nagoya, Aichi, Japan
  • 2001–2010
    • AJINOMOTO CO., INC.
      Edo, Tōkyō, Japan
  • 2006
    • Shinshu University
      • Faculty of Textile Science and Technology
      Matsumoto, Nagano-ken, Japan
  • 1989
    • Tokyo Metropolitan Institute of Public Health
      • Department of Physiological Hygiene
      Edo, Tōkyō, Japan
  • 1985
    • Fujita Health University
      Nagoya, Aichi, Japan