Kazuhiro Irie

Kyoto University, Kioto, Kyoto, Japan

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Publications (178)583.46 Total impact

  • Kazuma Murakami · Kazuhiro Irie · Takahiko Shimizu
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    ABSTRACT: Emerging evidence supports an "oxidative stress" theory in the pathogenesis of Alzheimer's disease (AD). Amyloid β-protein (Aβ), one of the causative agents, forms a soluble oligomeric assembly to induce neurotoxicity, which is triggered by reactive oxygen species. Recent clinical studies suggest a preventive role of antioxidants during AD progression. Because vitamin C (VC) is a widely known nutrient or food used for its potent antioxidant properties, therapy using high-dose VC given by intravenous routes as well as dietary intake has benefits in the treatment of disease. Although there are numerous epidemiologic studies on the relevance of VC supplementation to lowering the risk of AD, the mechanism of how VC affects Aβ-induced pathologies remains entirely unclear. This short review documents recent findings on AD prevention by VC, including our own, and discusses the future directions that this research might take.
    No preview · Chapter · Dec 2015
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    ABSTRACT: The prevention of 42-mer amyloid β-protein (Aβ42) aggregation is promising for the treatment of Alzheimer's disease. We previously described the site-specific inhibitory mechanism for Aβ42 aggregation by a catechol-type flavonoid, (+)-taxifolin, targeting Lys16,28 after its autoxidation. In contrast, non-catechol-type flavonoids (morin, datiscetin, and kaempferol) inhibited Aβ42 aggregation without targeting Lys16,28 with almost similar potencies to that of (+)-taxifolin. We herein provided structural insights into their mechanisms for inhibiting Aβ42 aggregation. Physicochemical analyses revealed that their inhibition did not require autoxidation. The (1)H-(15)N SOFAST-HMQC NMR of Aβ42 in the presence of morin and datiscetin revealed the significant perturbation of chemical shifts of His13,14 and Gln15, which were close to the intermolecular β-sheet region, Gln15-Ala21. His13,14 also played a role in radical formation at Tyr10, thereby inducing the oxidation of Met35, which has been implicated in Aβ42 aggregation. These results suggest the direct interaction of morin and datiscetin with the Aβ42 monomer. Although only kaempferol was oxidatively-degraded during incubation, its degradation products as well as kaempferol itself suppressed Aβ42 aggregation. However, neither kaempferol nor its decomposed products perturbed the chemical shifts of the Aβ42 monomer. Aggregation experiments using 1,1,1,3,3,3-hexafluoro-2-propanol-treated Aβ42 demonstrated that kaempferol and its degradation products inhibited the elongation rather than nucleation phase, implying that they interacted with small aggregates of Aβ42, but not with the monomer. In contrast, morin and datiscetin inhibited both phases. The position and number of hydroxyl groups on the B-ring of non-catechol-type flavonoids could be important for their inhibitory potencies and mechanisms against Aβ42 aggregation.
    No preview · Article · Dec 2015 · Bioorganic & medicinal chemistry
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    ABSTRACT: Aplog-1 is a simplified analog of debromoaplysiatoxin (DAT) with potent tumor-promoting and proinflammatory activities. Aplog-1 and DAT exhibited anti-proliferative activities against several human cancer cell lines, whereas aplog-1 did not have tumor-promoting nor proinflammatory activities. We have recently found 10-methyl-aplog-1 (1) to have strong anti-proliferative activity compared with aplog-1. To further investigate the structural factors involved in the tumor-promoting, proinflammatory, and anti-proliferative activities, two dimethyl derivatives of aplog-1 (2, 3) were synthesized, where two methyl groups were installed at positions 4 and 10 or 10 and 12. 10,12-Dimethyl-aplog-1 (2) had stronger inhibitory effects on the growth of several human cancer cell lines than 1 and DAT, but exhibited no tumor-promoting and proinflammatory activities. In contrast, 4,10-dimethyl-aplog-1 (3) displayed weak tumor-promoting and proinflammatory activities along with anti-proliferative activity similar to that of 1 and DAT. Compound 2 would be the optimized seed for anticancer drugs among the simplified analogs of DAT.
    No preview · Article · Oct 2015 · Bioscience Biotechnology and Biochemistry
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    ABSTRACT: Peroxisome proliferator-activated receptor γ (PPARγ) is a ligand-activated transcriptional factor that plays an important role in adipogenesis and glucose metabolism. The ligand-binding pocket (LBP) of PPARγ has a large Y-shaped cavity with multiple subpockets where multiple ligands can simultaneously bind to and cooperatively activate PPARγ. Focusing on this unique property of the PPARγ LBP, we describe a novel two-step cell-based strategy to develop PPARγ ligands. First, a combination of ligands that cooperatively activates PPARγ was identified using a luciferase reporter assay. Second, hybrid ligands were designed and synthesized. For proof-of-concept we focused on covalent agonists, which activate PPARγ through a unique activation mechanism regulated by a covalent linkage with the Cys285 residue in the PPARγ LBP. Despite their biological significance and pharmacological potential, few covalent PPARγ agonists are known except for endogenous fatty acid metabolites. With our strategy, we determined that plant-derived cinnamic acid derivatives cooperatively activated PPARγ by combining with GW9662, an irreversible antagonist. GW9662 covalently reacts with the Cys285 residue. A docking study predicted that a cinnamic acid derivative can bind to the open cavity in GW9662-bound PPARγ LBP. Based on the putative binding mode, structures of both ligands were linked successfully to create a potent PPARγ agonist, which enhanced the transactivation potential of PPARγ at submicromolar levels through covalent modification of Cys285. Our approach could lead to the discovery of novel high-potency PPARγ agonists.
    No preview · Article · Sep 2015 · ACS Chemical Biology
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    ABSTRACT: Dietary zinc deficiency puts human health at risk. Therefore, we are exploring strategies for enhancing zinc absorption. In the small intestine, the zinc transporter ZIP4 functions as an essential component for zinc absorption. Overexpression of ZIP4 protein increases zinc uptake and thereby cellular zinc levels, suggesting that food components with the ability to increase ZIP4 could potentially enhance zinc absorption by the intestine. In this study, we used mouse Hepa cells, which regulate mouse Zip4 (mZip4) in a manner indistinguishable from that in intestinal enterocytes, to screen for suitable food components able to increase the abundance of ZIP4. Using this ZIP4-targeting strategy, two such soybean extracts were identified that were specifically able to decrease mZip4 endocytosis in response to zinc. These soybean extracts also effectively increased the abundance of apically localized mZip4 in transfected polarized Caco2 and Madin-Darby canine kidney cells and, moreover, apically localized two mZip4 acrodermatitis enteropathica mutants. Soybean components were purified from one extract and soyasaponin Bb was identified as an active component that increased both mZip4 protein abundance and zinc levels in Hepa cells. Finally, we confirmed that soyasaponin Bb is capable of enhancing cell surface endogenous human ZIP4 in human cells. Our results suggest that ZIP4 targeting may represent a new strategy to improve zinc absorption in humans.
    No preview · Article · Sep 2015 · Biochemical Journal
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    ABSTRACT: Amyloid fibrils in senile plaque mainly consist of the 40-mer and 42-mer amyloid β-proteins (Aβ40 and Aβ42). Although Aβ42 plays more important role in the pathogenesis of Alzheimer's disease (AD), Aβ40 could be involved in the progression of AD pathology because of its large amount. Recent studies revealed that variable sizes of Aβ oligomers contributed to the neuronal death and cognitive dysfunction. However, how large oligomeric species are responsible for AD pathogenesis remains unclear. We previously proposed a toxic dimer model of Aβ with turn structure at positions 22 and 23 using solid-state NMR and systematic proline replacement. Based on this model, we herein show the synthesis and biological activities of an E22P-Aβ40 dimer at position 30, which was connected to L,L-2,6-diaminopimeric acid. The E22P-Aβ40 dimer formed stable 6∼8-mer oligomers without amyloid fibrils, but was not neurotoxic on human neuroblastoma cells. On the other hand, E22P-Aβ40 generated high molecular-weight oligomers into fibrils, and showed the neurotoxicity. These results suggest that such kind of Aβ40 dimer with a parallel β-sheet might not be pathological.
    No preview · Article · Sep 2015 · Biochemical and Biophysical Research Communications
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    ABSTRACT: Aplog-1 is a simplified analog of the tumor-promoting aplysiatoxin with anti-proliferative and cytotoxic activities against several cancer cell lines. Our recent findings have suggested that protein kinase Cδ (PKCδ) could be one of the target proteins of aplog-1. In this study, we synthesized amide-aplog-1 (3), in which the C-1 ester group was replaced with an amide group, to improve chemical stability in vivo. Unfortunately, 3 exhibited seventy-fold weaker binding affinity to the C1B domain of PKCδ than that of aplog-1, and negligible anti-proliferative and cytotoxic activities even at 10(-4) M. A conformational analysis and density functional theory calculations indicated that the stable conformation of 3 differed from that of aplog-1. Since 27-methyl and 27-methoxy derivatives (1, 2) without the ability to bind to PKC isozymes exhibited marked anti-proliferative and cytotoxic activities at 10(-4) M, 3 may be an inactive control to identify the target proteins of aplogs.
    No preview · Article · Jan 2015 · Bioscience Biotechnology and Biochemistry
  • Masayuki Kikumori · Ryo C. Yanagita · Kazuhiro Irie
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    ABSTRACT: 10-Methyl-aplog-1 (1), a simplified analog of tumor-promoting aplysiatoxin, is a potential lead for cancer therapy that exhibits marked and selective growth inhibitory effects against several human cancer cell lines and negligible tumor-promoting activity in vivo. However, more detailed evaluations of its toxicity and anticancer activity in vivo are hampered by supply problems associated with a non-optimal synthetic method. We here addressed this issue through a more practical and reliable synthetic method that afforded several hundred milligrams of 1 with high purity (>98%) in 23 steps from commercially available m-hydroxycinnamic acid with an overall yield of 1.1%. The utilization of two key reactions, substrate-controlled epoxidation and the oxidative cleavage of alkene with a free hydroxyl group, successfully reduced the existing five synthetic steps and markedly improved the handling of large amounts of intermediates. We also demonstrated for the first time that such an analog was synthetically accessible in reliable quantities and also that this large supply could advance in vivo trials for the treatment of cancer.
    No preview · Article · Dec 2014 · Tetrahedron
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    ABSTRACT: The toxin-producing cyanobacterium, Moorea producens, is a known causative organism of food poisoning and seaweed dermatitis (also known as "swimmer's itch"). Two new toxic compounds were isolated and structurally elucidated from an ethyl acetate extract of M. producens collected from Hawaii. Analyses of HR-ESI-MS and NMR spectroscopies, as well as optical rotations and CD spectra indicated two new lyngbyatoxin derivatives, 2-oxo-3(R)-hydroxy-lyngbyatoxin A (1) and 2-oxo-3(R)-hydroxy-13-N-desmethyl-lyngbyatoxin A (2). The cytotoxicity and lethal activities of 1 and 2 were approximately 10- to 150-times less potent than lyngbyatoxin A. Additionally, the binding activities of 1 and 2 possessed 10,000-times lower affinity for the protein kinase Cδ (PKCδ)-C1B peptide when compared to lyngbyatoxin A. These findings suggest that these new lyngbyatoxin derivatives may mediate their acute toxicities through a non-PKC activation pathway.
    Full-text · Article · Dec 2014 · Marine Drugs
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    ABSTRACT: Amyloid assemblies are associated with a wide range of human disorders, including Alzheimer's and Parkinson's diseases. Here we identify protein kinase C (PKC) γ, a serine/threonine kinase mutated in the neurodegenerative disease spinocerebellar ataxia type 14 (SCA14), as a novel amyloidogenic protein with no previously characterized amyloid-prone domains. We found that overexpression of PKCγ in cultured cells, as well as in vitro incubation of PKCγ without heat or chemical denaturants, cause amyloid-like fibril formation of this protein. We also observed that SCA14-associated mutations in PKCγ accelerate the amyloid-like fibril formation both in cultured cells and in vitro. We show that the C1A and kinase domains of PKCγ are involved in its soluble dimer and aggregate formation, and that SCA14-associated mutations in the C1 domain cause its misfolding and aggregation. Furthermore, long-term time-lapse imaging indicates that aggregates of mutant PKCγ are highly toxic to neuronal cells. Based on these findings, we propose that PKCγ could form amyloid-like fibrils in physiological and/or pathophysiological conditions such as SCA14. More generally, our results provide novel insights into the mechanism of amyloid-like fibril formation by multi-domain proteins.
    Full-text · Article · Sep 2014 · Human Molecular Genetics
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    Preview · Article · Jul 2014
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    Preview · Article · Jul 2014 · Alzheimer's and Dementia
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    ABSTRACT: (-)-Indolactam-V (1) has the fundamental structure of potent tumor-promoting teleocidins. A new teleocidin-related metabolite, (-)-14-O-malonylindolactam-V (2), was isolated from the culture broth of Streptomyces blastmyceticum NA34-17 which produced a large quantity of 1 along with a small amount of (-)-14-O-acetylindolactam-V (3). Heat treatment of 2 in methanol readily produced 1 and 3, suggesting that S. blastmyceticum NA34-17 excreted 1 as a malonic acid conjugate to accumulate 1 and 3 in the culture broth during cultivation.
    Preview · Article · May 2014 · Bioscience Biotechnology and Biochemistry
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    ABSTRACT: Lyngbyatoxin A from the marine cyanobacterium Moorea producens (formerly Lyngbya majuscula) is known as the causative agent of "swimmer's itch" with its highly inflammatory effect. A new toxic compound was isolated along with lyngbyatoxin A from an ethyl acetate extract of M. producens collected from Hawaii. Analyses of HR-ESI-MS and NMR spectroscopies revealed the isolated compound had the same planar structure with that of lyngbyatoxin A. The results of optical rotation and CD spectra indicated that the compound was a new lyngbyatoxin A derivative, 12-epi-lyngbyatoxin A (1). While 12-epi-lyngbyatoxin A showed comparable toxicities with lyngbyatoxin A in cytotoxicity and crustacean lethality tests, it showed more than 100 times lower affinity for protein kinase Cδ (PKCδ) using the PKCδ-C1B peptide when compared to lyngbyatoxin A.
    Full-text · Article · May 2014 · Marine Drugs
  • Kazuhiro Irie · Ryo C Yanagita
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    ABSTRACT: Protein kinase C (PKC) isozymes play central roles in signal transduction on the cell surface and could serve as promising therapeutic targets of intractable diseases like cancer, Alzheimer's disease, and acquired immunodeficiency syndrome (AIDS). Although natural PKC ligands like phorbol esters, ingenol esters, and teleocidins have the potential to become therapeutic leads, most of them are potent tumor promoters in mouse skin. By contrast, bryostatin-1 (bryo-1) isolated from marine bryozoan is a potent PKC activator with little tumor-promoting activity. Numerous investigations have suggested bryo-1 to be a promising therapeutic candidate for the above intractable diseases. However, there is a supply problem of bryo-1 both from natural sources and by organic synthesis. Recent approaches on the synthesis of bryo-1 have focused on its simplification, without decreasing the ability to activate PKC isozymes, to develop new medicinal leads. Another approach is to use the skeleton of natural PKC ligands to develop bryo-1 surrogates. We have recently identified 10-methyl-aplog-1 (26), a simplified analog of tumor-promoting aplysiatoxin (ATX), as a possible therapeutic lead for cancer. This review summarizes recent investigations on the simplification of natural PKC ligands, bryo-1 and ATX, to develop potential medicinal leads.
    No preview · Article · Apr 2014 · The Chemical Record
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    ABSTRACT: 6-Octadecynoic acid (6-ODA), a fatty acid with a triple bond, was identified in the methanol extract of Marrubium vulgare L. as an agonist of peroxisome proliferator-activated receptor γ (PPARγ). Fibrogenesis caused by hepatic stellate cells is inhibited by PPARγ whose ligands are clinically used for the treatment of diabetes. Plant extracts of Marrubium vulgare L., were screened for activity to inhibit fibrosis in the hepatic stellate cell line HSC-T6 using Oil Red-O staining, which detects lipids that typically accumulate in quiescent hepatic stellate cells. A methanol extract with activity to stimulate accumulation of lipids was obtained. This extract was found to have PPARγ agonist activity using a luciferase reporter assay. After purification using several chromatographic methods, 6-ODA, a fatty acid with a triple bond, was identified as a candidate of PPARγ agonist. Synthesized 6-ODA and its derivative 9-octadecynoic acid (9-ODA), which both have a triple bond but in different positions, activated PPARγ in a luciferase reporter assay and increased lipid accumulation in 3T3-L1 adipocytes in a PPARγ-dependent manner. There is little information about the biological activity of fatty acids with a triple bond, and to our knowledge, this is the first report that 6-ODA and 9-ODA function as PPARγ agonists.
    Full-text · Article · Sep 2013 · Biochemical and Biophysical Research Communications
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    ABSTRACT: Aplog-1, a simplified analog of debromoaplysiatoxin with anti-proliferative activity, bound to and activated protein kinase Cδ (PKCδ), that is involved in tumor suppression and apoptosis. To examine the contribution of PKCδ to the anti-proliferative activity of aplog-1, we synthesized 27-methyl and 27-methoxy derivatives that differed in the ability to activate PKCδ. Activators of PKCδ like aplog-1 and 27-(R)-Me-aplog-1 strongly inhibited the growth of several cancer cell lines. On the other hand, 27-(S)-Me-aplog-1 and 27-O-Me-aplog-1 without the ability to activate PKCδ, exhibited only weak growth inhibitory activity against these cell lines. These results suggest indirectly that the activation of PKCδ might be involved in the anti-proliferative activity of aplog-1 against aplog-sensitive cancer cell lines.
    No preview · Article · Sep 2013 · Tetrahedron

  • No preview · Article · Jul 2013 · Alzheimer's and Dementia

  • No preview · Article · Jul 2013 · Alzheimer's and Dementia

  • No preview · Article · Jul 2013

Publication Stats

3k Citations
583.46 Total Impact Points


  • 1987-2015
    • Kyoto University
      • • Division of Food Science and Biotechnology
      • • Division of Applied Life Sciences
      Kioto, Kyoto, Japan
  • 2011
    • Tokyo University of Agriculture and Technology
      • Division of Applied Biological Chemistry
      Edo, Tōkyō, Japan
  • 1995-1999
    • Stanford University
      • Department of Chemistry
      Palo Alto, California, United States
  • 1996
    • Meijo University
      Nagoya, Aichi, Japan
  • 1991
    • Kyoto Prefectural University of Medicine
      Kioto, Kyōto, Japan
  • 1990
    • Hokkaido University
      • Department of Medicine II
      Sapporo, Hokkaido, Japan