Sonoko Ishizaki-Koizumi

Publications (3)13.42 Total impact

• Article: The glycine analogue, aminomethanesulfonic acid, inhibits LPS-induced production of TNF-alpha in isolated rat Kupffer cells and exerts hepatoprotective effects in mice.

  Sonoko Ishizaki-Koizumi, Ichiro Sonaka, Yoshiyuki Takei, Kenichi Ikejima, Nobuhiro Sato
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  ABSTRACT: The activation of Kupffer cells represents a central mechanism of liver injury involving the production of TNF-alpha. It is known that glycine prevents LPS-induced production of TNF-alpha in isolated Kupffer cells. In this study, the possibility that glycine analogues might affect Kupffer cells was investigated. As a result, aminomethanesulfonic acid (AMS) inhibited the production of TNF-alpha in LPS-stimulated Kupffer cells. Furthermore, LPS treatment caused a transient increase in intracellular calcium ([Ca(2+)](i)) which was blunted by AMS. Thus, the addition of AMS is protective against the LPS-induced increase [Ca(2+)](i) and subsequent production of TNF-alpha. Moreover, in vivo studies demonstrated that pretreatment of mice with AMS increased the rate of survival after injection with LPS/d-gal and reduced the TNF-alpha serum level and the mRNA level in the liver. These results indicate that intake of AMS attenuates the LPS-induced hepatotoxicity resulting from activation of Kupffer cells.
  Biochemical and Biophysical Research Communications 10/2004; 322(2):514-9. · 2.48 Impact Factor
• Article: Overexpression of human thioredoxin in transgenic mice controls oxidative stress and life span.

  Akira Mitsui, Junji Hamuro, Hajime Nakamura, Norihiko Kondo, Yoko Hirabayashi, Sonoko Ishizaki-Koizumi, Tadashi Hirakawa, Tohru Inoue, Junji Yodoi
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  ABSTRACT: Transgenic (Tg) mice overexpressing human thioredoxin (TRX), a small redox-active protein, were produced to investigate the role of the protein in a variety of stresses. Bone marrow cells from TRX-Tg mice were more resistant to ultraviolet C-induced cytocide compared with those from wild type (WT) C57BL/6 mice. TRX-Tg mice exhibited extended median and maximum life spans compared with WT mice. Telomerase activity in spleen tissues in TRX-Tg mice was higher than that in WT mice. These results suggest that overexpression of TRX results in resistance against oxidative stress and a possible extension of life span without apparent abnormality in mammals.
  Antioxidants and Redox Signaling 09/2002; 4(4):693-6. · 8.46 Impact Factor
• Article: Mechanisms of the protective effect of L-alanine to D-galactosamine-induced hepatocellular injury: comparative studies of L-alanine and pyruvate.

  Sonoko Ishizaki-Koizumi, Ichiro Sonaka, Shoji Fujitani, Shuhei Nishiguchi
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  ABSTRACT: The addition of L-alanine reduced lactate dehydrogenase leakage from primary cultured rat hepatocytes treated with galactosamine (D-gal), while D-alanine and other amino acids did not. However, the mechanisms have not yet been entirely clarified. In this study, we used various inhibitors of metabolism, i.e., aminooxyacetate, oligomycin, and quinolinic acid, to examine the relation between this protective effect and the metabolism of L-alanine. Quinolinic acid (10 mM) did not affect the hepatoprotective effect of L-alanine, while oligomycin (0.1 mug/ml) and aminooxyacetate (1 mM) eliminated the hepatoprotective effect of L-alanine. L-Alanine also increased the albumin secretion by cultured hepatocytes treated with D-gal, while pyruvate had little effect. It was revealed that the intracellular content of pyruvate did not increase as a result of addition of L-alanine. These results are consistent with the hypothesis that L-alanine metabolism is important for hepatoprotection, but pyruvate cannot be used as a substitute for L-alanine.
  Biochemical and Biophysical Research Communications 04/2002; 291(4):738-43. · 2.48 Impact Factor