Chen Pei-Yi, Wu Ming-Jiuan, Chang Heng-Yuan, Tai Mi-Hsueh, Ho Chi-Tang, Yen Jui-Hung
†Center of Medical Genetics, Buddhist Tzu Chi General Hospital, Hualien 970, Taiwan.
‡Department of Biotechnology, Chia-Nan University of Pharmacy and Science, Tainan 717, Taiwan.
J Agric Food Chem. 2015 Apr 29;63(16):4148-59. doi: 10.1021/acs.jafc.5b01005. Epub 2015 Apr 20.
Luteolin (3',4',5,7-tetrahydroxyflavone), a flavonoid found in several vegetables and fruits, has been reported to possess neurotrophic activities that are associated with its capacity to promote neuronal survival and differentiation. In the present study, we report for the first time a genomewide screen for microRNAs (miRNAs) regulated during the luteolin-mediated neurite outgrowth of PC12 cells. We found that after luteolin treatment, the abundance of 16 miRNAs was markedly up-regulated and that of 3 miRNAs was down-regulated in PC12 cells. The induction of miR-34a by luteolin was the most pronounced among these differentially expressed miRNAs. The correlation between miR-34a down-regulation and decreased luteolin-mediated neurite outgrowth may indicate a mechanism by which miR-34a may act as a modulator of neuronal differentiation. Furthermore, we found that luteolin enhanced the phosphorylation of p53 at Ser15, which was associated with the promotion of miR-34a transcription and neurite outgrowth. Moreover, the level of sirtuin 1 (SIRT1), a known miR-34a target, was reduced during luteolin-induced neurite outgrowth. In turn, the level of acetylated p53, a substrate of SIRT1, was correspondingly increased in luteolin-treated PC12 cells. In addition to p53 activation, we further identified that luteolin-induced miR-34a transcription and neurite outgrowth involved the activation of the JNK and p38 MAPK pathways. However, the inhibition of JNK and p38 MAPK activation did not block luteolin-induced p53 activation in PC12 cells. Our findings suggested that the activation of both p53-dependent and p53-independent miR-34a/SIRT1 pathways plays a critical role in the mechanisms underlying luteolin-induced neuritogenesis.
木犀草素（3'，4'，5，7 - 四羟基黄酮）是一种存在于多种蔬菜和水果中的类黄酮，据报道具有神经营养活性，这与其促进神经元存活和分化的能力有关。在本研究中，我们首次报告了在木犀草素介导的PC12细胞神经突生长过程中受调控的 microRNA（miRNA）的全基因组筛选。我们发现，木犀草素处理后，PC12细胞中16种miRNA的丰度显著上调，3种miRNA的丰度下调。在这些差异表达的miRNA中，木犀草素对miR - 34a的诱导最为明显。miR - 34a下调与木犀草素介导的神经突生长减少之间的相关性可能表明miR - 34a可能作为神经元分化调节剂的一种机制。此外，我们发现木犀草素增强了p53在Ser15位点的磷酸化，这与miR - 34a转录和神经突生长的促进有关。此外，在木犀草素诱导的神经突生长过程中，已知的miR - 34a靶标沉默调节蛋白1（SIRT1）的水平降低。相应地，在木犀草素处理的PC12细胞中，SIRT1的底物乙酰化p53的水平升高。除了p53激活外，我们进一步确定木犀草素诱导的miR - 34a转录和神经突生长涉及JNK和p38 MAPK通路的激活。然而，JNK和p38 MAPK激活的抑制并未阻断木犀草素诱导的PC12细胞中p53的激活。我们的研究结果表明，p53依赖性和p53非依赖性miR - 34a/SIRT1通路的激活在木犀草素诱导神经突形成的机制中起关键作用。
