Background: 新生兒缺氧窒息腦病變是造成嬰幼兒神經病變最常見的原因,除了嚴重威脅新生兒的生命，在存活者中也常導致永久性的神經缺陷諸如腦性麻痺、智能障礙和癲癇。然而，至今仍然沒有非常有效的治療方法。近年來一些研究指出，在一些神經退化性疾病如阿茲海默或是腦中風的動物實驗中發現，藉由抑制劑抑制去乙醯基酵素(HDAC)活性而增加組織蛋白(histone)上的乙醯化可以有治療的效果。而去乙醯基酵素的抑制劑提供的保護機制可能是藉由使組織蛋白上的乙醯化增加，進而促使細胞中一些促活基因被轉錄出來。
Hypothesis因此在我們的研究中，我們提出一個假設想證明藉由丁酸鈉(sodium butyrate；SB)增加組織蛋白上的乙醯化，可以提供1)神經保護以抵抗缺氧窒息的傷害2)透過增加組蛋白上的乙醯化修飾增加神經細胞在缺氧後的可塑性(neuroplasticity)和促活基因的表現。
Materials and methods: 在前處理的部分，從幼鼠出生的第一天到第七天，我們每天利用腹腔注射的方式注射丁酸鈉(劑量:1.2和1.8克/公斤)到幼鼠體內，另以注射生理食鹽水的組別做為對照組。在第七天時，經過單側右頸動脈結紮缺血以及兩小時，8%氧氣缺氧處理。後續利用western blotting分析組蛋白的乙醯化、細胞凋亡、發炎反應，以及利用Morris water maze和inhibitory avoidance test觀察注射丁酸鈉之後學習及記憶能力是否有改善，另外也利用Nissl staining染色來觀察老鼠的腦傷程度。在後處理的部分，我們在老鼠出生第7天缺氧，在第42到49天連續四週注射丁酸鈉，然後同樣在42到49天時利用行為實驗觀察老鼠的學習記憶能力和腦傷程度。
Results: 在前處理的部分，我們發現相較於對照組，注射1.8克/公斤丁酸鈉的幼鼠能有效的減緩在不同腦區如大腦皮層(cortex)、海馬迴(hippocampus)以及紋狀體(striatum)的傷害，而且使幼鼠在行為實驗中有更好的表現，相較於對照組。在western blotting中也發現，丁酸鈉的前處理可以明顯的增加細胞中組蛋白上的乙醯化如histone H3, H4並降低細胞凋亡(caspase-3, PARP)和發炎反應(cox-2, p53)。丁酸鈉的前處理也增加了Bcl-xL和HSP70的mRNA表現。我們更進一步發現丁酸鈉處理也增加了調控HSP70的轉錄因子Sp1的乙醯化。在丁酸鈉後處理的實驗中，我們發現丁酸鈉無法提供在組織學上及學習記憶上的保護。
Conclusion: 丁酸鈉在缺氧前的前處理可以對新生幼鼠的腦部提供有效的神經保護，這個保護可能是藉由抑制細胞凋亡和發炎反應的發生，以及可能透過增加Sp1乙醯化提高HSP70的表現達到的。相對地，在缺氧的丁酸鈉後處理不法提供增加神經可塑性的而產生保護效果。

Background: Hypoxic-ischemia (HI) encephalopathy is a major cause of neonatal mortality and subsequent neurodevelopmental disability in the surviving infants, however, there is still no effective treatment. Recent studies have showed that increased histone acetylation by inhibitors of histone deacetylase (HDAC) protects against neurodegenerative disorders and acute cerebral ischemia in adult animals. The neuroprotective effect of HDAC inhibitors involves transcription activation through increasing histone acetylation of prosurvival genes.
Hypothesis: This study was to test the hypotheses that increased histone acetylation by a HDAC inhibitor- sodium butyrate (SB): 1) provides neuroprotection against HI, and 2) increases neuroplasticity after HI in the neonatal rat brain through chromatin remodeling and upregulating protective factors.
Materials and methods: In the pre-treatment part, we intraperitoneally injected SB (1.2 and 1.8 g/kg) or vehicle (normal saline) daily in SD rat pups from postnatal (P) day 1 to P7. On P7, rats were subjected to HI induced by permanent ligation of unilateral carotid artery followed by 2 hours of 8% O2 hypoxia at 37°C. Histone acetylation, apoptosis and inflammatory marker activity were investigated by western blotting before and after HI. Behavior test was performed by Morris water maze ,and inhibitory avoidance test from P42 to P49, and brain injury was investigated by pathology on P49. In the post-treatment part, we treated the pups with SB or vehicle daily after HI from P14 to P42. Behavior test measured by Morris water maze test and inhibitory avoidance test was done from P42 to P49 and brain injury by pathology on P49.
Results: In the pretreatment part, compared with vehicle, SB pretreatment (1.8g/kg) significantly reduced HI injury in the cortex (P<0.001), striatum (P<0.05) and hippocampus (P<0.01) and improved learning and memory performance (P <0.05). SB pretreatment (1.2g/kg) didn’t show protective effect in pathology and learning and memory performance, compared with vehicle group. Western blotting analysis showed that SB (1.8g/kg) increased acetylation levels of histone H3 and H4, and down-regulated apoptotic (caspase-3, PARP) and inflammatory (COX-2, p53) markers after HI. SB also increased Bcl-xL mRNA expression (3.2 fold) and heat shock protein 70 (HSP70) mRNA and protein levels. We also found that SB upregulated acetylation levels of Sp1, a transcription factor of HSP70. In the post-HI treatment part, SB post-treatment did not provide protective effect at pathology and behavioral levels.
Conclusion: SB treatment before HI provides neuroprotection in the neonatal rat brain in association with down-regulating apoptotic and inflammatory responses and up-regulating HSP70 possibly through Sp1 acetylation. In contrast, SB post-treatment after HI does not upregulate neuroplasticity.

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