H Obata

Publications (3)20.13 Total impact

• Article: Apolipoprotein J/clusterin is induced in vascular smooth muscle cells after vascular injury.

  M Miyata, S Biro, H Kaieda, H Eto, K Orihara, T Kihara, H Obata, N Matsushita, T Matsuyama, C Tei
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  ABSTRACT: Understanding the precise molecular mechanisms underlying the phenomenon of restenosis after PTCA may help us to develop a new strategy for the treatment of restenosis after PTCA. The purpose of this study was to identify the genes involved in vascular restenosis. Applying a differential hybridization method to a model of the balloon-injured rabbit aorta, we identified 6 cDNA clones that were upregulated after injury. Northern blot showed that 5 genes, but not apolipoprotein J (apoJ)/clusterin, were constitutively expressed in noninjured aorta and upregulated after balloon injury. ApoJ mRNA was not detectable in noninjured aorta (control), began to be expressed at 6 hours after injury, showed a peak level at 24 hours (a 48-fold increase), gradually declined, and returned to the control level at 24 weeks. Western blot and immunohistochemistry demonstrated no expression of apoJ protein in noninjured aorta, an expression of apoJ at 2 days after balloon injury, and a peak level (a 55-fold increase) at 2 to 8 weeks. The expression of apoJ protein continued until 24 weeks after injury. In situ hybridization revealed that apoJ mRNA was expressed in smooth muscle cells (SMCs) of media at 2 days after injury and in SMCs of media and neointima at 2 weeks. To analyze the function of apoJ, stably transfected rabbit SMCs were created. The expression of apoJ stimulated proliferation and migration of SMCs. ApoJ is dramatically induced in media and neointima after vascular injury, suggesting that apoJ contributes to restenosis after angioplasty.
  Circulation 10/2001; 104(12):1407-12. · 14.74 Impact Factor
• Article: NF-kappaB involvement in the activation of primary adult T-cell leukemia cells and its clinical implications.

  N Arima, K Matsushita, H Obata, H Ohtsubo, H Fujiwara, K Arimura, T Kukita, Y Suruga, S Wakamatsu, S Hidaka, C Tei
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  ABSTRACT: The HTLV-I provirus-encoded Tax protein induces NF-kappaB in Tax-transfected Jurkat T cells or HTLVL-I- infected T cells in vitro. Tax induction of NF-kappaB is presumed to be involved in proliferation and activation of primary leukemia cells in vivo. Recent studies have demonstrated that NF-kappaB activities in human T cells are mediated by at least four c-Rel-related DNA binding proteins - p50, p55, p75 and p85. We examined the significance of NF-kappaB induction in primary adult T cell leukemia cells and the induction kinetics of each of the four NF-kappaB species. Marked NF-kappaB activity was detected using an electrophoretic mobility shift assay (EMSA) in the primary cells of patients with acute disease, but little activity was noted in the cells of chronic patients. NF-kappaB activity was enhanced in a time-dependent manner in acute type cells cultured with mitogen-free medium; there was no induction of activity in chronic type cells. UV crosslinking demonstrated all four species of NFkappaB complex - high levels of p50 and lower levels of p55 and p75, in acute type cells; chronic type cells showed only the p50. As a control, normal resting T cells similarly showed only p50; control cells showed little change in activity when cultured without mitogenic stimulation, analogous to chronic type ATL. Northern blotting revealed enhancement of c-rel (encoding p85) and KBFI (encoding p50 and p55) expression in acute type cells during culture, while there was no significant enhancement of mRNAs in chronic type ATL cells or unstimulated normal T cells. Northern blotting also revealed that Tax is upregulated at the mRNA level in acute- but not chronic-type cells during culture. Expression of c-rel and KBF1 mRNAs in acute type cells appeared to be related to Tax mRNA expression. These results suggest that Tax is capable of inducing nuclear expression of all four NF-kappaB species in primary ATL cells of acute type patients, with marked effects on p55, p75, and p85. Tax induction of NF-kappaB species is regulated, at least in part, at a pretranslational level involving increases in c-rel and KBF1 mRNA.
  Experimental Hematology 08/1999; 27(7):1168-75. · 2.90 Impact Factor
• Article: NF-kappa B is induced in the nuclei of cultured rat aortic smooth muscle cells by stimulation of various growth factors.

  H Obata, S Biro, N Arima, H Kaieda, T Kihara, H Eto, M Miyata, H Tanaka
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  ABSTRACT: We investigated whether induction of transcription factor NF-kappa B is involved in the proliferation of cultured rat aortic smooth muscle cell using electrophoretic mobility shift assay and immunocytochemistry. NF-kappa B was induced in the nucleus in a dose-dependent manner when the smooth muscle cells were stimulated by various growth factors such as PDGF-BB, bFGF, EGF and IGF-1, but not growth inhibitors such as TGF-beta and IFN-gamma. Among growth factors, PDGF-BB and bFGF, more potent growth stimulators, induced higher kappa B binding activity than EGF or IGF-1. These evidences were also supported by the results obtained with immunocytochemistry. Immunocytochemistry also showed that the induced NF-kappa B contained p50 and p65. These results suggest that NF-kappa B induction may be involved in the proliferation of vascular smooth muscle cell.
  Biochemical and Biophysical Research Communications 08/1996; 224(1):27-32. · 2.48 Impact Factor