用基因芯片研究高苯丙氨酸诱导神经元基因表达谱的改变

Alteration of gene expression profiles of cultured embryo rat cortex induced by phenylalanine

为深入了解苯丙酮尿症患者高苯丙氨酸损伤神经元的可能机制,我们将体外培养3 d的胚鼠神经元随机分为两组:高苯丙氨酸组和对照组。高苯丙氨酸组加入0.9 mmol/L苯丙氨酸诱导12 h,对照组加入等体积的培养液,抽提RNA,与大鼠神经生物学芯片U34杂交,检测胚鼠原代神经元高苯丙氨酸作用下表达谱的改变,并用实时荧光定量聚合酶链式反应方法验证基因芯片的结果。发现芯片上1323条总探针组合数中有167条基因表达增加(12.6％),表达下调的已知基因数为7条,占总探针组合数的0.5％。按基因功能,表达上升的基因可分为信号转导相关基因、神经元相关基因、细胞骨架基因、代谢相关基因、离子通道基因、转录相关基因、细胞因子基因、凋亡相关基因等。研究结果证实了以前的报道,如Na+、K+-ATP酶、凋亡、氧化应激、NMDA受体、Ca2+参与了高苯丙氨酸对神经元的损伤过程。结果还显示,在高苯丙氨酸环境下,CaMK Ⅱ、Ras、P38、钙通道基因表达上升,部分与囊泡形成、神经递质释放有关的基因表达增强,与神经递质谷氨酸有关的受体和转运体基因表达上升。我们推测高苯丙氨酸可能激活轴NMDR-Ca2+-CaMK Ⅱ-Ras.-P38,引起神经元突起异常;高苯丙氨酸环境下,神经递质释放可能异常;兴奋性神经递质谷氨酸可能参与了高苯丙氨酸引起的神经元损伤。

To have more insight into the mechanism of neuronal injury in phenylketonuria patients, gene expression profiles were studied in cell culture of embryonic rat cortical neurons induced by phenylalanine. Randomly chosen cortical cultures for 3 d were treated by 0.9 mmol/ L phenylalanine for 12 h. Control group of the same batch was treated with the same volume of medium. Total RNA was extracted and hybridized with the Affymetrix gene chip U34 according to the protocol provided by the Affymetrix Company. Real-time PCR was used to further confirm the result. We found that the hybridization signals of 167 genes were increased among the total 1323 probes plotted on the chip. The 167 increased genes could be functionally categorized into signal transduction, neuron related, cytoskeleton, metabolism, ion channels, transcription factors, cytokines, and apoptosis related. Signals of 7 probes were decreased, which accounted to 0.5% of the total number. A series of genes that were not reported before were up-regulated by phenylalanine, including Ca2+ /calmodulin-dependent protein kinase, Brain type II (CaMK Ⅱ), Ras, P38 MAP kinase, L-voltage dependent calcium channel, some genes related to vesicle formation and transmitter release, some glutamate receptor subunits and glutamate transporters. According to the gene expression profile, it is likely that multi-processes are involved in the neuronal injury induced by high phenylalanine, such as the activation of the NMDR Ca2+- CaMK Ⅱ - Ras- P38 axis, the abnormality in neurotransmitter release. Our study also suggests that the excitatory neurotransmitter glutamate may play a role in the neural pathology of phenylketonuria.