Yasuhiro Katou
Tohoku University
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Featured researches published by Yasuhiro Katou.
Organic Letters | 2011
Haruhisa Kikuchi; Masato Isobe; Mizuki Sekiya; Yuko Abe; Tsuyoshi Hoshikawa; K. Ueda; Shoichiro Kurata; Yasuhiro Katou; Yoshiteru Oshima
Innate immunity is the front line of self-defense against microbial infection. After searching for natural substances that regulate innate immunity using an ex vivo Drosophila culture system, we identified a novel dimeric chromanone, gonytolide A, as an innate immune promoter from the fungus Gonytrichum sp. along with gonytolides B and C. Gonytolide A also increased TNF-α-stimulated production of IL-8 in human umbilical vein endothelial cells.
Organic Letters | 2009
Haruhisa Kikuchi; Mizuki Sekiya; Yasuhiro Katou; K. Ueda; Takahiro Kabeya; Shoichiro Kurata; Yoshiteru Oshima
After searching for natural substances that regulate innate immunity using the ex vivo Drosophila culture system, a benzoyl pyrrole-type compound, celastramycin A, was identified and isolated as a potent suppressor. By synthesizing the previously reported structure 1 and another benzoyl pyrrole-type compound 2 reported in a Japanese patent, the correct structure of celastramycin A was confirmed to be 2. Compound 2 suppressed the production of IL-8 (IC(50) 0.06 microg/mL) in human umbilical vein endothelial cells (HUVECs).
Bioorganic & Medicinal Chemistry | 2013
Haruhisa Kikuchi; Yuzuru Kubohara; Van Hai Nguyen; Yasuhiro Katou; Yoshiteru Oshima
Cellular slime molds are expected to have the huge potential for producing secondary metabolites including polyketides, and we have studied the diversity of secondary metabolites of cellular slime molds for their potential utilization as new biological resources for natural product chemistry. From the methanol extract of fruiting bodies of Polysphondylium filamentosum, we obtained new chlorinated benzofurans Pf-1 (4) and Pf-2 (5) which display multiple biological activities; these include stalk cell differentiation-inducing activity in the well-studied cellular slime mold, Dictyostelium discoideum, and inhibitory activities on cell proliferation in mammalian cells and gene expression in Drosophila melanogaster.
European Journal of Medicinal Chemistry | 2011
Haruhisa Kikuchi; Kaori Okazaki; Mizuki Sekiya; Yasuyuki Uryu; K. Ueda; Yasuhiro Katou; Shoichiro Kurata; Yoshiteru Oshima
Innate immunity is the front line of self-defense against infectious microorganisms. In mammals, innate immunity interacts with adaptive immunity and plays a key role in regulating the immune response. Therefore, innate immunity is a good pharmaceutical target for the development of immune regulators. After searching for natural substances that regulate innate immunity using an ex vivo Drosophila culture system, we identified a cyclopentanediol-type compound 1 as an immunosuppressor. In this study, we synthesized and evaluated 1 and its derivatives. Several methylamide- or phenylamide-containing derivatives showed effects that were 20-25 times more potent than those of 1.
Journal of Natural Products | 2016
Haruhisa Kikuchi; Tsuyoshi Hoshikawa; Shoichiro Kurata; Yasuhiro Katou; Yoshiteru Oshima
Gonytolide A (1), a dimeric chromanone substituted with the γ-lactone, shows promoting activity of innate immune responses. However, biological studies on this compound have been limited by the low amounts of 1 available from natural resources and the difficulty of its synthesis. In this study, we designed and synthesized structure-simplified gonytolide derivatives. Bischromone 10 and biflavone 13 both promoted the mammalian TNF-α signaling pathway and Drosophila innate immunity. They did not contain a chiral center and were easy to synthesize. Hence, they can be used as lead compounds for a new type of immunostimulating drugs and as research reagents.
Life Sciences | 2014
Yasuhiro Katou; Naoya Endo; Toshiyuki Suzuki; Jiang Yu; Haruhisa Kikuchi; Yoshiteru Oshima; Yoshimi Homma
AIMS Metarhizin A was originally isolated from Metarhizium flavoviride as a potent inhibitor of the growth of insect and mammalian cells. In this study, we aimed to understand the molecular targets of metarhizin A involved in its anti-proliferative activity against human cells. MAIN METHODS Cell cycle regulators and signaling molecules were examined by immunoblotting using specific antibodies. A mitochondria-enriched fraction was prepared from mouse liver, and mitochondrial activity was monitored using an oxygen electrode. Enzyme activity was measured using purified cytochrome c oxidase and permeabilized cells. KEY FINDINGS Metarhizin A inhibits the growth of MCF-7 cells with an IC50 value of ~0.2 μM and other cells in a similar manner; a cell cycle-dependent kinase inhibitor, p21, is selectively induced. Significant amounts of reactive oxygen species (ROS) are generated and ERK1/2 is activated in cells treated with metarhizin A. Metarhizin A completely suppresses oxygen consumption by mitochondria, and potently inhibits the activity of cytochrome c oxidase. It induces cell death when MCF-7 cells are cultured under limiting conditions. SIGNIFICANCE Metarhizin A is a potent inhibitor of cytochrome c oxidase and activates the MAPK pathway through the generation of ROS, which induces growth arrest of cells, and, under some conditions, enhances cell death. The cytochrome c oxidase system is a possible molecular target of metarhizin A.
Journal of Natural Products | 2015
Haruhisa Kikuchi; Tsuyoshi Hoshikawa; Shimpei Fujimura; Noriaki Sakata; Shoichiro Kurata; Yasuhiro Katou; Yoshiteru Oshima
Innate immunity is the front line of self-defense against microbial infection. After searching for natural compounds that regulate innate immunity using an ex vivo Drosophila culture system, we identified a new cyclic depsipeptide, aspergillicin F, from the fungus Aspergillus sp., as an innate immune suppressor. The total synthesis and biological evaluation of the aspergillicin family, including aspergillicin F, were performed, revealing that slight structural differences in the side chains of amino acid residues alter innate immunity-regulating activity.
Tetrahedron | 2009
Haruhisa Kikuchi; Tomoko Hoshi; Minoru Kitayama; Mizuki Sekiya; Yasuhiro Katou; K. Ueda; Yuzuru Kubohara; Hiroki Sato; Mitsuaki Shimazu; Shoichiro Kurata; Yoshiteru Oshima
Tetrahedron | 2012
Haruhisa Kikuchi; Yusuke Matsuo; Yasuhiro Katou; Yuzuru Kubohara; Yoshiteru Oshima
Tetrahedron | 2012
Haruhisa Kikuchi; Masato Isobe; Shoichiro Kurata; Yasuhiro Katou; Yoshiteru Oshima