Ai Asaoka

National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan

Are you Ai Asaoka?

Claim your profile

Publications (16)41.56 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: RGD peptides are popular drug delivery tools in treating integrin αVβ3-expressing malignant tumors and tumor vasculature cells. We investigated the specific delivery and pharmacological potential of enantiomeric mitochondria-disruptive peptides (RLYLRIGRR-NH(2), RLRLRIGRR-NH(2), ALYLAIRRR-NH(2), and RLLLRIGRR-NH(2)) after conjugation with an integrin αVβ3-homing peptide, cyclic pentameric RGD peptide. The cyclic RGD-conjugated mitochondria-disruptive peptides exhibited specific internalization, apoptosis induction, and cytotoxicity against integrin αVβ3-high-expressing human umbilical vein endothelial cells. Our findings indicate that these novel peptide complexes might prove good anti-angiogenesis reagents.
    Bioscience Biotechnology and Biochemistry 11/2012; · 1.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The 9-mer peptides RLYLRIGRR and RLLLRIGRR were immobilized to amino-functionalized cotton fibers by a modification of the SPOT synthesis technique. The antibacterial activities of the peptide-immobilized cotton fibers against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) were investigated. Antibacterial assays revealed that these fibers inhibit the growth of MRSA and the antibacterial activities were maintained after washing and sterilization by autoclaving. The anticancer effect of the peptide-immobilized fiber was also investigated with mouse myeloma cells and human leukemia cells. These results indicate that these fibers have strong growth inhibition activity against bacteria and cancer cells.
    Biomacromolecules 03/2011; 12(5):1540-5. · 5.37 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel antimicrobial peptide, Bactrocerin-1, was purified and characterized from an immunized dipteran insect, Bactrocera dorsalis. Bactrocerin-1 has 20 amino acid residues with a mass of 2,325.95 Da. The amino acid sequence of Bactrocerin-1 showed very high similarity to the active fragment (46V-65S-NH(2)) of Coleoptericin A. The composition of amino acid residues revealed that Bactrocerin-1 is a hydrophobic, positively charged, and Lys/Ile/Gly-rich peptide. Minimal growth inhibition concentration (MIC) measurements for synthesized Bactrocerin-1 showed a very broad spectrum of anti-microbial activity against Gram-positive bacteria, Gram-negative bacteria, and fungi. Bactrocerin-1 did not show hemolytic activity toward mouse red blood cells even at a concentration of 50 microM. Analysis of the Helical-wheel projection and the CD spectrum suggested that Bactrocerin-1 contains the amphipathic alpha-helix.
    Archives of Insect Biochemistry and Physiology 06/2009; 71(3):117-29. · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Four enantiomeric 9-mer peptides named d-peptide A, B, C and D were designed and synthesized on the basis of 43-mer insect defensins from two beetles. The d-9-mer peptides maintained bacterial membrane disruptive activity similar to the original peptides and also showed various extents of growth inhibitory activity against different cancer cell lines. Of these peptides, d-peptide B exhibited the highest selective cancer cell cytotoxicity against the mouse myeloma cell line, P3-X63-Ag8.653. Flow cytometric and scanning electron microscopic analysis revealed d-peptide B disrupts mouse myeloma membrane construction, whereas no cytotoxic effect on normal leukocytes was observed. Moreover, a strong correlation between negatively charged phosphatidylserine (PS) density in cancer cell membrane surface and sensitivity to d-9-mer peptides were observed in various cancer cell lines. These results suggest that d-9-mer peptides have negative charge-dependent selective cancer cell cytotoxicity targeting PS in the cancer cell membrane. In addition, synergic growth inhibitory activity against mouse myeloma was observed in combinations of d-peptide B and dexamethasone. These results suggest d-9-mer peptides are promising candidates for novel anticancer drugs.
    Peptides 01/2009; · 2.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A genome-wide analysis of innate immunity-related genes and gene families was conducted using the silkworm, Bombyx mori. We identified orthologs for a large number of genes involved in insect immunity that have been reported from Drosophila melanogaster (Diptera), Anopheles gambiae (Diptera), Apis mellifera (Hymenoptera) and Tribolium castaneum (Coleoptera). B. mori has a unique recognition gene and antimicrobial peptide genes that are not present in the Drosophila, Anopheles, Apis and Tribolium genomes, suggesting a lineage-specific gene evolution for lepidopteran insects. The comparative analysis of the insect immune repertoires indicated a dynamic and flexible gene expansion in recognition, modulation and effector mechanisms due to different selection pressures. Differential gene regulation by different bacterial species was found in PGRP and Serpin genes, suggesting that Bombyx has a highly selective gene regulation system depending on bacterial species.
    Insect biochemistry and molecular biology 10/2008; 38(12):1087-110. · 3.25 Impact Factor
  • Source
    01/2007;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Synthetic peptides, peptides A (Arg-Leu-Tyr-Leu-Arg-Ile-Gly-Arg-Arg-NH(2)) and B (Arg-Leu-Arg-Leu-Arg-Ile-Gly-Arg-Arg-NH(2)), derived from the beetle Allomyrina dichotoma defensin, have antimicrobial activities. Immunotoxicological effect of these peptides was evaluated by cytotoxicity of mouse peritoneal macrophages. In addition, antigenicity of these peptides was studied by evaluating antibody responses in mice immunized with these peptides. The toxicity of peptide A toward mouse peritoneal cells was less than that of polymyxin B, when morphologically evaluated in a cytotoxicity test. Almost all of mice injected intraperitoneally (i.p.) with either peptide A or B at 50-150 mg/kg survived, whereas all mice injected i.p. with polymyxin B at the doses of more than 25 mg/kg died within 24 h. Interestingly, almost all of mice injected intravenously with these peptides at the doses of 10 and 25 mg/kg also survived. Furthermore, mice immunized with these peptides conjugated with keyhole limpet hemocyanin (KLH) showed little or negligible anti-peptide A or B antibody production, although anti-KLH antibody was significantly produced. The results indicated that peptides A and B were less cytotoxic than polymyxin B and also had poor antigenicity to produce specific antibody in mice.
    International Immunopharmacology 12/2006; 6(11):1748-53. · 2.42 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Synthetic peptides, Arg-Leu-Tyr-Leu-Arg-Ile-Gly-Arg-Arg-NH2 (peptide A) and Arg-Leu-Arg-Leu-Arg-Ile-Gly-Arg-Arg-NH2 (peptide B), derived from the beetle Allomyrina dichotoma defensin, have not only antimicrobial activities but also anti-inflammatory effects by inhibiting tumour necrosis factor-alpha(TNF-alpha) production. In the present study, we evaluated the lipopolysaccharide (LPS)-binding activities and the protective effects of these peptides on LPS-induced lethal shock in d-galactosamine (GalN)-sensitized mice. These peptides were shown to bind to erythrocytes coated with LPS and the binding activity of peptide A to LPS was significantly higher than those of peptide B and polymyxin B. Mice were injected intraperitoneally with peptide A or B at doses of 25, 50, 100 and 150 mg/kg before an injection of Salmonella abortusequi LPS (5 microg/kg) and GalN (1 g/kg) (LPS+GalN). All of wild-type mice died within 24 h after challenged with LPS+GalN. All of TNF-alpha-deficient mice challenged with LPS+GalN survived. An injection of peptide A immediately after challenge with LPS+GalN resulted in significantly improved survival rates in a dose dependent manner. Peptide B showed only minor protection. The levels of TNF-alpha in the ameliorated mice by peptide A were significantly lower than those of challenge control, suggesting a suppressive effect of peptide A on TNF-alpha production. Furthermore, peptide A-treated mice showed significantly lower levels of asparate aminotransferase and alanine aminotransferase when compared to challenge control. Concordantly, hemorrhage and necrosis in the liver of peptide A-treated mice were less apparent than those of untreated control mice. These results suggest that peptide A has a protective effect on LPS-induced mortality in this mouse model.
    International Immunopharmacology 03/2006; 6(2):234-40. · 2.42 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Anti-bacterial activity of two synthesized oligopeptides, RLYLRIGRR-NH2 (peptide A) and RLRLRIGRR-NH2 (peptide B), both which based on a putative active site of defensin, an anti-bacterial peptide from the beetle Allomyrina dichotoma, was examined by macroscopic and histopathologic assessment during the course of infection in mice inoculated with methicillin-resistant Staphylococcus aureus (MRSA) in vivo. Both peptides A and B decreased the mortality of mice inoculated with MRSA. Peptides A and B decreased the macroscopical and histopathological lesions by MRSA infection in mice even seven days after the challenge. The anti-bacterial activity of peptides A and B has a therapeutic effect on MRSA infection in mice even seven days after being challenged.
    Journal of Veterinary Medical Science 11/2005; 67(10):1005-11. · 0.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An antibacterial peptide was isolated from a lepidopteran insect, Spodoptera litura. The molecular mass of this peptide was determined to be 4489.55 by matrix assisted laser desorption/ionization-time of flight mass (MALDI-TOF MS) spectrometry. The peptide consists of 42 amino acids and the sequence has 69-98% identity to those of moricin-related peptides, antibacterial peptides from lepidopetran insects. Thus, the peptide was designated S. litura (Sl) moricin. Sl moricin showed a broad antibacterial spectrum against Gram-positive and negative bacteria. Sl moricin gene was inducible by bacterial injection and expressed tissue-specifically in the fat body and hemocytes. Furthermore, the solution structure of Sl moricin was determined by two-dimensional (2D) 1H-nuclear magnetic resonance (NMR) spectroscopy and hybrid distance geometry-simulated annealing calculation. The tertiary structure revealed a long alpha-helix containing eight turns along nearly the full length of the peptide like that of moricin, confirming that Sl moricin is a new moricin-like antibacterial peptide. These results suggest that moricin is present not only in B. mori but also in other lepidopteran insects forming a gene family.
    Biochimica et Biophysica Acta 09/2005; 1752(1):83-92. · 4.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We previously reported that synthetic peptides, RLYLRIGRR-NH2 (peptide A) and RLRLRIGRR-NH2 (peptide B), derived from the beetle Allomyrina dichotoma defensin, showed antimicrobial activity against both Gram-positive and negative bacteria and suppressed lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-alpha) mRNA expression in a murine macrophage cell line. In this study, inhibitory effects of these peptides in LPS-induced mouse peritoneal macrophage activation were investigated. The supplement of peptide A to macrophages cultured with LPS resulted in a significant decrease in nitric oxide and TNF-alpha production. Furthermore, NF-kappaB activation was also blocked by addition of peptide A. These results indicated that peptide A blocked macrophage activation induced by LPS.
    Journal of Veterinary Medical Science 04/2004; 66(3):319-22. · 0.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A protein showing strong antiviral activity against Bombyx mori nucleopolyhedrovirus (BmNPV) was purified from the digestive juice of B. mori larvae. The molecular mass of this protein was 24271 Da. Partial N-terminal amino acid sequence of the protein was determined and cDNA was cloned based on the amino acid sequence. A homology search of the deduced amino acid sequence of the cDNA showed 94% identity with B. mori serine protease so the protein was designated B. mori serine protease-2 (BmSP-2). Analysis of BmSP-2 gene expression showed that this gene is expressed in the midgut but not in other tissues. In addition, BmSP-2 gene was shown to not be expressed in the molting and wandering stages, indicating that the gene is hormonally regulated. Our results suggest that BmSP-2, an insect digestive enzyme, can be a potential antiviral factor against BmNPV at the initial site of viral infection.
    Virology 04/2004; 321(1):154-62. · 3.37 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The novel peptides based on a putative active site of defensin, an anti-bacterial peptide from the beetle Allomyrina dichotoma, were synthesized. These synthetic oligopeptides exhibited strong anti-bacterial activity in vitro, even against antibiotic-resistant pathogenic bacteria. Then, anti-bacterial activity of two newly synthesized peptides, RLYLRIGRR-NH(2) (peptide A) and RLRLRIGRR-NH(2) (peptide B) was also examined by macroscopic and histopathologic assessment during the course of infection in mice inoculated with antibiotic-resistant pathogenic Escherichia coli (E. coli) in vivo. Peptide B decreased the mortality of mice inoculated with antibiotic-resistant pathogenic E. coli. The results of macroscopic and histopathologic examinations revealed that peptide B could protect the mice from infection. In contrast, peptide A failed to protect mice from infection with antibiotic-resistant pathogenic E. coli. Also, modified peptides A and B produced no toxicity or side effects in mice. These results suggest that peptide B is useful for developing novel antibiotics against antibiotic-resistant pathogenic bacteria.
    Journal of Veterinary Medical Science 03/2004; 66(2):137-42. · 0.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Defensins are a major group of antimicrobial peptides and are found widely in vertebrates, invertebrates and plants. Invertebrate defensins have been identified from insects, scorpions, mussels and ticks. In this study, chemically synthesized tick defensin was used to further investigate the activity spectrum and mode of action of natural tick defensin. Synthetic tick defensin showed antibacterial activity against many Gram-positive bacteria but not Gram-negative bacteria and low hemolytic activity, characteristic of invertebrate defensins. Furthermore, bactericidal activity against pathogenic Gram-positive bacteria including Bacillus cereus, Enterococcus faecalis and methicillin-resistant Staphylococcus aureus was observed. However, more than 30 min was necessary for tick defensin to completely kill bacteria. The interaction of tick defensin with the bacterial cytoplasmic membrane and its ability to disrupt the membrane potential was analyzed. Tick defensin was able to disrupt the membrane potential over a period of 30-60 min consistent with its relatively slow killing. Transmission electron microscopy of Micrococcus luteus treated with tick defensin showed lysis of the cytoplasmic membrane and leakage of cellular cytoplasmic contents. These findings suggest that the primary mechanism of action of tick defensin is bacterial cytoplasmic membrane lysis. In addition, incomplete cell division with multiple cross-wall formation was occasionally seen in tick defensin-treated bacteria showing pleiotropic secondary effects of tick defensin.
    Biochimica et Biophysica Acta 01/2004; 1624(1-3):125-30. · 4.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A protein showing strong antiviral activity against Bombyx mori nucleopolyhedrovirus (BmNPV) was purified from the digestive juice of B. mori larvae. A homology search of the deduced amino acid sequence of the protein cDNA revealed 56% homology with Drosophila melanogaster lipase and 21% homology with human lipase. As lipase activity of the protein was confirmed in vitro, this protein was designated Bmlipase-1. Northern blot analysis showed that the Bmlipase-1 gene is expressed in the midgut but not in other tissues, nor is it activated by BmNPV infection. In addition, the Bmlipase-1 gene was shown not to be expressed in the molting and wandering stages, indicating that the gene is hormonally regulated. Our results suggest that an insect digestive enzyme has potential as a physiological barrier against BmNPV at the initial site of viral infection.
    Journal of Virology 11/2003; 77(19):10725-9. · 5.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel antifungal peptide, scarabaecin (4080Da), was isolated from the coconut rhinoceros beetle, Oryctes rhinoceros. Scarabaecin cDNA was cloned by reverse transcriptase-polymerase chain reactions (RT-PCR) using a primer based on the N-terminal amino acid sequence. The amino acid sequence deduced from scarabaecin cDNA showed no significant similarity to those of reported proteins. Chemically synthesized scarabaecin indicated antifungal activity against phytopathogenic fungi such as Pyricularia oryzae, Rhizoctonia solani, and Botrytis cinerea, but not against phytopathogenic bacteria. It showed weak activity against Bauberia bassiana, an insect pathogenic fungus, and Staphylococcus aureus, a pathogenic bacterium. Scarabaecin showed chitin binding property and its K(d) was 1.315 microM. A comparison of putative chitin-binding domains among scarabaecin, invertebrate, and plant chitin-binding proteins suggests that scarabaecin is a new member of chitin-binding antimicrobial proteins.
    Biochemical and Biophysical Research Communications 08/2003; 307(2):261-6. · 2.41 Impact Factor

Publication Stats

332 Citations
41.56 Total Impact Points

Institutions

  • 2003–2009
    • National Institute of Agrobiological Sciences
      Tsukuba, Ibaraki, Japan
  • 2004–2006
    • National Institute of Animal Health
      Tsukuba, Ibaraki, Japan
    • University of Tsukuba
      • Institute of Agriculture and Forestry
      Tsukuba, Ibaraki, Japan
  • 2005
    • Biotechnology and Biological Sciences Research Council
      Swindon, England, United Kingdom