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毒性精神兴奋剂。它的毒性作用依赖于过量多巴胺（DA）的释放，多巴胺（DA）激活纹状体DA受体。DA D1受体拮抗剂SCH23390对DA介导的神经传递的抑制作用可保护甲基安非他命诱导的神经元凋亡。本研究的最初目的是利用微阵列分析，研究SCH23390对在给药后2和4小时单次注射甲基苯丙胺引起的大鼠纹状体转录反应的影响。我们在总共22227个基因中鉴定出545个对甲基甲醚敏感。这些基因包括参与凋亡途径、内质网（ER）应激和转录调节等。其中，共有172个基因显示出sch23390诱导的甲基甲醚介导的变化抑制。在这些sch23390应答基因中，有几个在内质网应激中受到调控的基因，分别是ATF3、HSP27、Hmox1、HSP40和CHOP/Gadd153。本研究的第二个目的是研究DA D1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PCR来确认微阵列分析鉴定的甲基甲醚反应性ER基因的变化。我们还在更长的时间内测量了这些基因以及ATF4、ATF6、BiP/GRP78和GADD34的表达。SCH23390可以减弱或阻断甲基甲醚诱导的这些基因的表达增加。Western blot分析显示，注射甲基安非他明后，抗氧化蛋白Hmox1表达增加，持续约24小时。此外,冰毒DA D1 receptor-dependent交通Hmox1监管机构引起的蛋白质,Nrf2,从胞质核分数的蛋白质发挥其监管职能。综上所述，这些发现表明SCH23390可以通过抑制甲基甲氧嘧啶介导的DA D1受体介导的纹状体内质网应激来保护神经元凋亡。我们的数据还表明，甲基苯丙胺诱导的毒性可能是一个有用的模型，可以用来解剖啮齿动物大脑内质网应激依赖事件的分子机制。干扰这些受体激活的疗法可能有助于对抗人类成瘾者的神经毒性。

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.