Department of Pharmacology, College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Gu, Seoul 151-742, Republic of Korea.
Neurosci Res. 2011 Mar;69(3):214-22. doi: 10.1016/j.neures.2010.11.008. Epub 2010 Dec 8.
Oroxylin A (5,7-dihydroxy-6-methoxyfavone) is a flavonoid compound originated from the root of Scutellaria baicalensis Georgi. Our previous reports suggested that oroxylin A improves memory function in rat, at least in part, by its antagonistic effects on GABA(A) receptor. In addition, oroxylin A protects neurons from ischemic damage by mechanisms currently not clear. In this study we determined whether oroxylin A modulates the level of brain derived neurotrophic factor (BDNF) in primary rat cortical neuronal culture, which is well known for its role on neuronal survival, neurogenesis, differentiation of neurons and synapses and learning and memory. Treatment of oroxylin A for 3-48h increased BDNF expression which was analyzed by ELISA assay and Western blot analysis. Oroxylin A induced slow but sustained increases in intracellular calcium level and activated ERK1/2 mitogen activated protein kinase (MAPK). In addition, oroxylin A phosphorylated cyclic AMP response element binding protein (CREB) at Ser 133 in concentration and time dependent manner. Pretreatment with the MAPK inhibitor PD98059 (10μM) attenuated phosphorylation of ERK1/2 and CREB as well as BDNF production, which suggests that oroxylin A regulates BDNF production by activating MAPK-CREB pathway. GABA(A) antagonist bicuculline mimicked the effects of oroxylin A on BDNF production as well as MAPK-CREB pathway. Increase in intracellular Ca(2+) concentration, phosphorylation of ERK1/2 and CREB, and BDNF expression by oroxylin A was blocked by NMDA receptor inhibitor MK-801 (10μM) as well as tetrodotoxin (TTX, 0.5 and 1μM). The results from the present study suggest that the calcium and p-CREB dependent induction of BDNF expression, possibly via activation of synaptic NMDA receptor through the blockade of GABA(A) activity in cortical neuronal circuitry, might be responsible for the neuroprotective or memory enhancing effects of oroxylin A.
盐酸小檗碱（5,7-二羟基-6-甲氧基黄酮）是一种来源于黄芩根的黄酮类化合物。我们之前的报告表明，盐酸小檗碱通过其对 GABA(A)受体的拮抗作用改善大鼠的记忆功能。此外，盐酸小檗碱通过目前尚不清楚的机制保护神经元免受缺血性损伤。在这项研究中，我们确定盐酸小檗碱是否调节原代大鼠皮质神经元培养物中脑源性神经营养因子（BDNF）的水平，BDNF 因其在神经元存活、神经发生、神经元和突触的分化以及学习和记忆中的作用而广为人知。用盐酸小檗碱处理 3-48 小时可增加 BDNF 的表达，通过 ELISA 分析和 Western blot 分析进行分析。盐酸小檗碱诱导细胞内钙水平缓慢但持续增加，并激活 ERK1/2 丝裂原活化蛋白激酶（MAPK）。此外，盐酸小檗碱以浓度和时间依赖性方式磷酸化环磷酸腺苷反应元件结合蛋白（CREB）的丝氨酸 133。用 MAPK 抑制剂 PD98059（10μM）预处理可减弱 ERK1/2 和 CREB 的磷酸化以及 BDNF 的产生，这表明盐酸小檗碱通过激活 MAPK-CREB 途径调节 BDNF 的产生。GABA(A)拮抗剂荷包牡丹碱模拟了盐酸小檗碱对 BDNF 产生以及 MAPK-CREB 途径的影响。盐酸小檗碱引起的细胞内 Ca(2+)浓度增加、ERK1/2 和 CREB 的磷酸化以及 BDNF 的表达被 NMDA 受体抑制剂 MK-801（10μM）和河豚毒素（TTX，0.5 和 1μM）阻断。本研究结果表明，BDNF 表达的钙依赖性和 p-CREB 依赖性诱导，可能通过阻断皮质神经元回路中的 GABA(A)活性激活突触 NMDA 受体，可能是盐酸小檗碱的神经保护或增强记忆作用的原因。
