Hiroyuki Ohta

Takeda Pharmaceutical Company Limited, Ōsaka-shi, Osaka-fu, Japan

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Publications (4)5.81 Total impact

  • Source
    Yasushi Shintani, Yasuko Terao, Hiroyuki Ohta
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    ABSTRACT: Stroke is a dynamic event in the brain involving heterogeneous cells. There is now compelling clinical evidence that prolonged, moderate cerebral hypothermia initiated within a few hours after severe ischemia can reduce subsequent neuronal death and improve behavioral recovery. The neuroprotective role of hypothermia is also well established in experimental animals. However, the mechanism of hypothermic neuroprotection remains unclear, although, presumably involves the ability of hypothermia to suppress a broad range of injurious factors. In this paper, we addressed this issue by utilizing comprehensive gene and protein expression analyses of ischemic rat brains. To predict precise target molecules, we took advantage of the therapeutic time window and duration of hypothermia necessary to exert neuroprotective effects. We proposed that hypothermia contributes to protect neuroinflammation, and identified candidate molecules such as MIP-3α and Hsp70 that warrant further investigation as targets for therapeutic drugs acting as "hypothermia-like neuroprotectants."
    Stroke research and treatment. 01/2010; 2011:809874.
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    ABSTRACT: Although hypothermia is one of the most robust neuroprotectants clinically available, its underlying mechanisms remain unclear. Through microarray gene expression analysis, we previously identified several key molecules potentially involved in the efficacy of hypothermia in a 2h middle cerebral artery occlusion (MCAO) rat model, including cytokine and chemokine genes. The present study demonstrated that the expressions of 2 genes, macrophage inflammatory protein-3alpha (MIP-3alpha) and its receptor, CC-chemokine receptor 6 (CCR6), were upregulated in the model and were suppressed by hypothermia. To investigate the role of cerebral MIP-3alpha, it was administered into the rat striatum; dose- and time-dependent induction of CCR6 gene expression was observed. Interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha injection also induced sequential expressions of MIP-3alpha and CCR6. MIP-3alpha was found to be produced by proinflammatory cytokines in rat astrocytes, while it was suppressed by hypothermia. In turn, MIP-3alpha stimulated IL-1beta and inducible nitric oxide synthase expressions in rat microglia and rat brains. Furthermore, intracerebroventricular administration of an anti-rat MIP-3alpha-neutralizing antibody significantly reduced the infarct in MCAO rat brains. These findings suggest that MIP-3alpha plays a pivotal role in inflammatory cascades in ischemic brains, and may be a novel therapeutic target for cerebral ischemia.
    Neuroscience Research 06/2009; 64(1):75-82. · 2.20 Impact Factor
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    ABSTRACT: Although moderate hypothermia is one of the most robust and effective techniques available for reducing ischemic injury, its key mechanism still remains unclear. Our proteomic analysis of the brains of rats treated with a 2-h middle cerebral artery occlusion showed that postischemic hypothermia markedly potentiated a sustained increase in heat-shock protein 70 (Hsp70). The elevated Hsp70 level was confirmed by enzyme-linked immunosorbent assay, western blot analysis, and immunohistochemical staining. Expression of other Hsp proteins was unaffected by hypothermia. Interestingly, hypothermia did not increased, even decreased, the upregulation of hsp70 mRNA expression by ischemia, suggesting that Hsp70 abundance is controlled by an unknown posttranscriptional regulation. As Hsp70 exerts a protective role against ischemic damage, the specific increase in Hsp70 production may contribute to the neuroprotective effect of hypothermia.
    Neuroreport 05/2009; 20(8):745-9. · 1.40 Impact Factor
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    ABSTRACT: Hypothermia is the only neuroprotective therapy proven to be clinically effective. Identifying the molecules that play important roles in the efficacy of hypothermia, we developed a multi-channel computer-controlled system, in which the brain temperatures of freely moving rats were telemetrically monitored and maintained below 35 degrees C, and examined the time window necessary to exert its significant neuroprotective effects. Eight-week-old SD rats were subjected to a 2h middle cerebral artery occlusion (MCAO) with an intraluminal filament, and post-ischemic hypothermia was introduced at 0, 2, 4, or 6h after reperfusion until the rats were killed 2 days after MCAO. Since a significant protection was observed when hypothermia was started within 4h after reperfusion, it was concluded that the therapeutic time window of mild hypothermia lasts for 4h after reperfusion in our model. On the basis of the window, comprehensive gene expression analyses using oligonucleotide microarrays were conducted and identified potential genes related to the efficacy of hypothermia, which included inflammatory genes like osteopontin, early growth response-1, or macrophage inflammatory protein-3alpha. Therefore, the neuroprotective effects of post-ischemic mild hypothermia were strongly suggested to be mainly associated with the reduction of neuronal inflammation.
    Neuroscience Research 04/2007; 57(3):424-33. · 2.20 Impact Factor

Publication Stats

81 Citations
5.81 Total Impact Points

Institutions

  • 2007
    • Takeda Pharmaceutical Company Limited
      • Pharmaceutical Research Division
      Ōsaka-shi, Osaka-fu, Japan