Masakazu Takahashi

The silk protein, sericin, protects against cell death caused by acute serum deprivation in insect cell culture

Sericin is the silk protein that covers fibroin fibers and functions as a `glue in the cocoons of silkworms, and its most abundant component, Ser1, contains repeats of Ser- and Thr-rich 38 amino acid residues. The viability of Sf9 insect cells was 20, 57 and 49% on the fifth day and 41, 91 and 70% on the ninth day after serum deprivation in the presence of no additives, 3000xa0μg sericin hydrolysate and 350xa0μg SerD (the peptide containing the two repetitive units)xa0ml−1, respectively. Thus, the sericin samples were useful in preventing cell death and promoting cellular growth after acute serum deprivation.

A sericin-derived peptide protects Sf9 insect cells from death caused by acute serum deprivation

Sericin is the silk protein enveloping fibroin fibers in cocoons. Sericin hydrolysate protects cultured Sf9 insect cells from death caused by serum deprivation; the activity depends on the repeats of 38 amino acids. A partial peptide from the 38 residues, SGGSSTYGYS, inhibited serum-deprivation death as well. Cell viabilities in the presence of 10% (v/v) foetal calf serum, no additives and 1xa0mM SGGSSTYGYS were 96, 12 and 31% on the third day after inoculation, respectively. Aromatic residues seemed to be important because SGGSSTWGWS had the same activity as SGGSSTYGYS but SGGSSTAGAS had no activity.

Inhibitory Effects of 4-Hydroxyderricin and Xanthoangelol on Lipopolysaccharide-Induced Inflammatory Responses in RAW264 Macrophages

The Japanese herb, Ashitaba (Angelica keiskei Koidzumi), contains two prenylated chalcones, 4-hydroxyderricin and xanthoangelol, which are considered to be the major active compounds of Ashitaba. However, their effects on inflammatory responses are poorly understood. In the present study, we investigated the effects and underlying molecular mechanisms of 4-hydroxyderricin and xanthoangelol on lipopolysaccharide (LPS)-induced inflammatory responses in RAW264 mouse macrophages. LPS-mediated production of nitric oxide (NO) was markedly reduced by 4-hydroxyderricin (10 μM) and xanthoangelol (5 μM) compared with their parent compound, chalcone (25 μM). They also inhibited LPS-induced secretion of tumor necrosis factor-alpha (TNF-α) and expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). Although chalcone decreased the DNA-binding activity of both activator protein-1 (AP-1) and nuclear factor-kappa B (NF-κB), 4-hydroxyderricin and xanthoangelol suppressed only AP-1 and had no effect on NF-κB. On the other hand, all of the tested chalcones reduced the phosphorylation (at serine 536) level of the p65 subunit of NF-κB. 4-Hydroxyderricin and xanthoangelol may be promising for the prevention of inflammatory diseases.

Anti-analgesic and anti-amnesic effect of complement C3a

In the present study, we found that complement C3a exerted central effects after intracerebroventricular administration in mice. At doses of 3 and 10 pmol/mouse, the peptide showed an antagonistic effect on analgesia induced by morphine and U-50488H, known to be mu- and kappa-opioid receptor agonists, respectively. Moreover, complement C3a improved scopolamine- and ischemia-induced amnesia at a dose of 10 pmol/mouse. Anti-analgesia was not observed by C3a des-Arg at 10 pmol/mouse. The present findings suggest that complement C3a may act as a peptide with anti-opioid activity in the central nervous system.

Soybean extracts increase cell surface ZIP4 abundance and cellular zinc levels: A potential novel strategy to enhance zinc absorption by ZIP4 targeting

Dietary zinc deficiency puts human health at risk, so we explored strategies for enhancing zinc absorption. In the small intestine, the zinc transporter ZIP4 functions as an essential component of 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 via the intestine. In the present 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 that can 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, two apically localized 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.

1,2-Di-O-α-linolenoyl-3-O-β-galactosyl-sn-glycerol as a superoxide generation inhibitor from Perilla frutescens var. crispa.

Using a superoxide (O2 −) generation assay system with differentiated HL-60 cells, 1,2-di-O-α-linolenoyl-3-O-β-galactosyl-sn-glycerol (DLGG) was identified as an O2 − generation inhibitor from Perilla frutescens var. crispa (a local variety, kida-chirimen shiso). DLGG suppressed the O2 − level in a dose-dependent manner with an IC50 value of 21 μM, comparable to those of rosmarinic acid (RoA, IC50=29 μM) and caffeic acid (CA, IC50=30 μM). While RoA and CA also dose-dependently inhibited O2 − generation in a xanthine-xanthine oxidase system, DLGG had no effect in the same system. Thus DLGG appeared to decrease the O2 − level in the HL-60 assay system by mechanisms different from those of RoA and CA, which appeared to act as O2 − scavengers.

Simple and Rapid Separation of Soyasaponin Bb from a Soy Extract

A simple method to separate soyasaponin Bb from a soy extract is presented. This method is based on the difference in the solubility of soyasaponin Bb and Ba and other components into 3:7 and 1:1 (v/v) acetone-water mixed solvents. The crude soyasaponin consisting of soyasaponins Aa, Ab, Ba, and Bb at the 10 wt% level and other components was examined as the soy extract. A 10 mg quantity of the crude soyasaponin was mixed with 1 mL of the 3:7 acetone-water containing 0.1 mol/L HCl, and the supernatant was removed to obtain a precipitate, which was found to contain mainly soyasaponins Bb and Ba. The precipitate was mixed with 0.4 mL of the 1:1 acetone-water containing 0.1 mol/L HCl; the supernatant was transferred, and was mixed with 0.6 mL of water to obtain a precipitate, which was found to contain mainly soyasaponin Bb. The yield was ca. 30%, which may be much higher than that by the conventional preparative chromatographic approach. The separation method is rapid and easy to carry out, and is useful for the preparation of a soyasaponin Bb sample.

Triterpenoids Isolated from Ziziphus jujuba Enhance Glucose Uptake Activity in Skeletal Muscle Cells

Jujube (Ziziphus jujuba Mill.), a traditional folk medicine and functional food in China and South Korea, is known for its beneficial properties, which include anti-cancer, anti-oxidative, and anti-obesity effects. To assess the anti-hyperglycemic effect of jujube in this study, we investigated the glucose uptake-promoting activity of jujube in rat L6 myotubes. After determining that the jujube extract induces muscle glucose uptake, we identified the following active compounds by bioassay-guided fractionation: betulonic acid, betulinic acid, and oleanonic acid. Ursonic acid, known to be present in jujube, was semi-synthesized from ursolic acid and also observed to enhance glucose uptake. These four triterpenic acids induced glucose uptake in a glucose transporter 4-dependent manner. Comparison experiments of jujube fruits from three countries, namely, China, South Korea, and Japan, revealed that Japanese jujube has a higher content of active triterpenoids and is the most potent enhancer of glucose uptake.

The isoflavone fraction from soybean presents mRNA maturation inhibition activity

Recent findings indicate that mRNA splicing inhibitors can be potential anticancer candidates. We have previously established a screening system which monitors mRNA processing in order to identify mRNA processing inhibitors. Among a number of dietary resources, isoflavone fractions showed an inhibitory effect of mRNA processing. These findings demonstrate that a variety of dietary sources have an impact on mRNA biogenesis.