Protective effects of DA antagonists Vs METH induced toxicity in rats

甲基苯丙胺是一种被广泛滥用的非法有毒精神刺激剂。它的毒性作用依赖于释放过量的多巴胺(DA)来激活纹状体DA受体。用DA D1受体拮抗剂SCH23390抑制DA介导的神经传递，可对抗冰毒诱导的神经元凋亡。本研究的初步目的是利用基因芯片技术研究SCH23390对单次注射冰毒后2小时和4小时大鼠纹状体转录反应的影响。我们在总共22,227个基因中确定了545个是冰毒反应基因。这些基因包括与细胞凋亡途径、内质网应激、转录调控等有关的基因。在这些基因中，共有172个基因显示SCH23390诱导的冰毒介导的变化受到抑制。在这些SCH23390响应基因中，有几个基因在内质网应激过程中受到调控，即ATF3、HSP27、Hmox1、Hsp40和CHOP/Gadd153。这项研究的第二个目标是研究DAD1受体刺激对参与内质网应激介导的分子事件的基因表达的作用。因此，我们使用定量聚合酶链式反应来确认通过微阵列分析确定的甲基反应性ER基因的变化。我们还测量了这些基因以及ATF4、ATF6、Bip/GRP78和Gadd34在更长时间内的表达。SCH23390减弱或阻断了冰毒诱导的大部分这些基因的表达增加。Western印迹分析显示，冰毒诱导的抗氧化蛋白Hmox1的表达增加，并在注射冰毒后持续约24小时。此外，METH还导致依赖DA D1受体的Hmox1调节蛋白Nrf2从胞浆转移到核部分，在那里该蛋白发挥其调节功能。综上所述，这些发现表明，SCH23390可以通过抑制METH介导的DA D1受体介导的ER应激来保护大鼠纹状体神经元的凋亡。我们的数据还表明，冰毒诱导的毒性可能是一个有用的模型，可以用来剖析啮齿动物大脑中参与内质网应激依赖事件的分子机制。干预这些受体激活的治疗可能有助于对抗人类成瘾者的神经毒性。 表观遗传修饰的作用也在强迫性寻求甲基苯丙胺和使用脚部电击作为不良后果的模型中进行评估。

Methamphetamine (METH) is an illicit toxic psychostimulant which is widely abused. Its toxic effects depend on the release of excessive levels of dopamine (DA) that activates striatal DA receptors. Inhibition of DA-mediated neurotransmission by the DA D1 receptor antagonist, SCH23390, protects against METH-induced neuronal apoptosis. The initial purpose of the present study was to investigate, using microarray analyses, the influence of SCH23390 on transcriptional responses in the rat striatum caused by a single METH injection at 2 and 4 hours after drug administration. We identified 545 out of a total of 22,227 genes as METH-responsive. These include genes which are involved in apoptotic pathways, endoplasmic reticulum (ER) stress, and in transcription regulation, among others. Of these, a total of 172 genes showed SCH23390-induced inhibition of METH-mediated changes. Among these SCH23390-responsive genes were several genes that are regulated during ER stress, namely ATF3, HSP27, Hmox1, HSP40, and CHOP/Gadd153. The secondary goal of the study was to investigate the role of DA D1 receptor stimulation on the expression of genes that participate in ER stress-mediated molecular events. We thus used quantitative PCR to confirm changes in the METH-responsive ER genes identified by the microarray analyses. We also measured the expression of these genes and of ATF4, ATF6, BiP/GRP78, and of GADD34 over a more extended time course. SCH23390 attenuated or blocked METH-induced increases in the expression of the majority of these genes. Western blot analysis revealed METH-induced increases in the expression of the antioxidant protein, Hmox1, which lasted for about 24 hours after the METH injection. Additionally, METH caused DA D1 receptor-dependent transit of the Hmox1 regulator protein, Nrf2, from cytosolic into nuclear fractions where the protein exerts its regulatory functions. When taken together, these findings indicate that SCH23390 can provide protection against neuronal apoptosis by inhibiting METH-mediated DA D1 receptor-mediated ER stress in the rat striatum. Our data also suggest that METH-induced toxicity might be a useful model to dissect molecular mechanisms involved in ER stress-dependent events in the rodent brain. Therapies that interefere with actvitation of these receptors might be helpful to combat neurotxicity in human addicts. The role of epigenetic modifications are also being evaluated in models of compulsive methamphetamine seeking and taking using foot shock as adverse consequences.