Phosphorylation of Cyclic Adenosine Monophosphate Response Element Binding Protein in Oligodendrocytes in the Corpus Callosum after Focal Cerebral Ischemia in the Rat

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  • Kortaro Tanaka
    Department of Neurology, School of Medicine, Keio University, Tokyo, Japan
  • Shigeru Nogawa
    Department of Neurology, School of Medicine, Keio University, Tokyo, Japan
  • Daisuke Ito
    Department of Neurology, School of Medicine, Keio University, Tokyo, Japan
  • Shigeaki Suzuki
    Department of Neurology, School of Medicine, Keio University, Tokyo, Japan
  • Tomohisa Dembo
    Department of Neurology, School of Medicine, Keio University, Tokyo, Japan
  • Arifumi Kosakai
    Department of Neurology, School of Medicine, Keio University, Tokyo, Japan
  • Yasuo Fukuuchi
    Department of Neurology, School of Medicine, Keio University, Tokyo, Japan

抄録

<jats:p> Phosphorylation of cyclic adenosine monophosphate (AMP) response element binding protein (CREB) was examined immunohistochemically in the corpus callosum of the rat brain at various time points after 90-minute focal cerebral ischemia. Focal ischemia was induced by occlusion of the middle cerebral artery (MCA) using the intraluminal suture method. Sham animals showed that numerous oligodendrocytes (OLGs) constitutively express unphosphorylated CREB. Local cerebral blood flow (lCBF) measured by the<jats:sup>14</jats:sup> C-iodoantipyrine method was reduced from 44.2 ± 15.4 (mL 100 g<jats:sup>−1</jats:sup> min<jats:sup>−1</jats:sup>) to 18.4 ± 3.8 and from 53.9 ± 14.4 to 4.8 ± 4.5 in the medial and the lateral regions of the corpus callosum, respectively, during MCA occlusion (MCAO). After release of the MCAO, lCBF recovered to the control level in each region. The medial region of the corpus callosum showed a marked increase in phosphorylated CREB-positive OLGs at 3.5 hours of recirculation, and it remained increased until 2 weeks of recirculation as it gradually declined. The activation of CREB phosphorylation in the OLGs was accompanied by expression of antiapoptotic protein bcl-2, normal staining with cresyl violet, and negative TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling) staining. Myelination detected by immunostaining with anti-myelin basic protein (MBP) antibody and anti-myelin associated glycoprotein (MAG) antibody remained normal in the medial region of the corpus callosum. The lateral region of the corpus callosum showed a significant but only transient increase in phosphorylated CREB-positive OLGs at 3.5 hours of recirculation, which was followed by a rapid decrease during the subsequent recirculation period. Expression of bcl-2 was suppressed in this region, and demyelination became apparent. These findings suggest that signal transduction through CREB phosphorylation may be closely associated with survival of OLGs and maintenance of myelination in the corpus callosum after cerebral ischemia. </jats:p>

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