MECHANISMS OF ACTION OF PSYCHOACTIVE DRUGS

精神活性药物的作用机制

• 批准号: 6290538
• 负责人: DE-MAW CHUANG
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF MENTAL HEALTH
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6290538
• 关键词: NMDA receptors; apoptosis; cAMP response element binding protein; calcium flux; carbamazepine; cerebellum; drug interactions; excitatory aminoacid; gel mobility shift assay; glutamates; granule cell; hippocampus; laboratory rat; lithium; neuropharmacology; neuroprotectants; neurotoxins; phenytoin; serotonin receptor; tissue /cell culture

Lithium was introduced into psychiatry 50 years ago and remains to be the most commonly used drug for the treatment of manic depressive illness. The precise mechanisms underlying its clinical efficacy remain to be defined. We have previously shown that long-term treatment of cerebellar granule cells (CGCs) with relatively low doses of lithium increases the mRNA level of the immediate early gene product, c-Fos, and up-regulates the expression and function of m3-muscarinic receptors in these neurons. Since AP-1 and cAMP-responsive element (CRE) are key elements of transcriptional regulation for a variety of proteins with neurophysiological importance, we have investigated the effects of lithium on gene transcription in cultured CGCs and in rats by measuring transcription factor binding to AP-1 and CRE sites. We found that treatment of CGCs with lithium chloride induces a time- and concentration-dependent increase in AP-1 and CRE binding activities. Chronic dietary treatment of rats with lithium carbonate for 4 weeks also significantly increases AP-1 and CRE binding activity in the frontal cortex, hippocampus, amygdala and cerebellum. p-CREB, Jun D and Fos family proteins are present in the AP-1 binding sites in the rat brain and in CGCs. In a parallel study, we explored the neuroprotective effects of lithium against excitotoxicity elicited by glutamate, a major excitatory amino acid neurotransmitter involved in the synaptic plasticity and pathogenesis of neurodegenerative and neuropsychiatric disorders. We found that long-term exposure to lithium chloride dramatically protects cultured rat CGCs, cerebral cortical and hippocampal neurons against glutamate-induced excitotoxicity which involves apoptosis mediated by N-methyl-D-aspartate (NMDA) receptors. This neuroprotection occurs at therapeutically relevant concentrations (0.5-5.0 mM) and requires treatment for 6-7 days for complete protection to occur, while a 24-hr treatment is ineffective. The protection is specific for glutamate-induced excitotoxicity and can be attributed to inhibition of NMDA receptor-mediated calcium influx. The long-term effects of lithium are not due to down-regulation of NMDA receptor sites, nor are they related to its known ability to block inositol monophosphatase activity. Our results suggest that modulation of glutamate receptor hyperactivity represents, at least in part, the molecular mechanisms by which lithium alters brain function and exerts its clinical efficacy in the treatment for manic depressive illness. These novel actions of lithium also suggest that excessive glutamatergic neurotransmission may be the pathogenic mechanism underlying bipolar illness. In a related study, we found that lithium also robustly protects against carbamazepine and phenytoin-induced apoptosis and modestly inhibits age-induced death of CGCs. However, unlike the protection against glutamate excitotoxicity, this effect of lithium on anticonvulsant-induced neurotoxicity does not require long-term treatment and occurs at relatively high concentrations (less than or equale to 5 mM). This neuroprotective effect of lithium is inhibited by a phosphatidylinositol 3-kinase (PI 3-K) inhibitor, LY294002. The inhibition of carbamazepine neurotoxicity by lithium may have clinical implications, as combined treatment with lithium and carbamazepine is known to potentiate the effect of either drug alone in the treatment of manic depressive illness. We have studied the role of expression of genes involved in pro- apoptosis and cytoprotection. In CGCs, treatment with neuroprotective concentrations of lithium induces a time- dependent increase in the levels of mRNA and protein of the cytoprotective gene Bcl-2. Conversely, the levels of mRNA and protein of the pro-apoptotic genes, Bax and p53 are decreased by lithium. The ratio of Bcl-2/Bax is increased by about 6-fold after treatment with 3 mM LiCl for 7 days. In contrast, glutamate treatment induces a rapid increase in the levels of Bax and p53 mRNA and protein. Pretreatment with lithium suppresses the glutamate-induced increase in Bax and p53 and maintains Bcl-2 at an elevated level. Lithium also blocks glutamate-elicited cytochrome c release from mitochondria and the cleavage of the caspase-3 substrate, lamin B. In a parallel study, we found that glutamate induces a rapid, reversible decrease in the activity of a cell survival factor, Akt, through enhanced dephosphorylation due to activation of protein phosphatase(s). In contrast, lithium activates the PI 3-K/Akt signalling pathway and enhances the phosphorylation of glycogen synthase kinase 3-beta. Pretreatment with lithium facilitates the recovery of glutamate-induced loss of Akt activity. Taken together, our results suggest that lithium-induced up-regulation of cytoprotective gene products and down-regulation of pro- apoptotic gene products play a prominent role in its neuroprotective actions. We have expanded from our in vitro cell culture studies by using animal models of cerebral ischemia and Huntingtons disease. We found that subcutaneous injection of rats with LiCl for 16 days reduces the size of ischemic brain infarct volume by more than 50% in rats subjected to occlusion of the left middle cerebral artery. The focal ischemia-induced neurological deficits such as abnormal posture and hemiplegia, measured at 24 hr after middle artery occlusion, are significantly reduced by chronic lithium pretreatment. In the Huntingtons disease animal model, we injected quinolinic acid, a partial agonist of the NMDA receptor, into the left side of rat striatum. This treatment results in about 70% lesion of the striatum which involves the loss of GABAnergic neurons expressing dopamine D-1 receptors. This quinolinic acid-induced lesion requires activation of the transcription factor NF-kB and induction of p53 and c-Myc. Our results show that chronic lithium treatment or one day pretreatment decreases the size of striatal lesion by 40-50%. Moreover, lithium neuroprotection effects are associated with over-expression of Bcl-2 in affected areas and other brain structures. Thus, our in vitro and in vivo studies raise the possibility that lithium, in addition to its use for bipolar depressive illness, may have expanded use for the treatment of neurodegenerative diseases, particularly those linked to excitotoxicity.

锂于50年前被引入精神病学，仍然是治疗躁狂抑郁疾病的最常用药物。其临床疗效的基础机制仍有待定义。我们先前已经表明，对小脑颗粒细胞（CGC）的长期治疗相对较低，锂相对较低，会增加这些神经元中M3-穆斯羟inic受体的表达和功能，从而增加了早期基因产物的mRNA水平。由于AP-1和CAMP响应元件（CRE）是对各种具有神经生理学意义的蛋白质转录调节的关键要素，因此我们通过测量转录因子与AP-1和CRE位点的结合来研究锂对培养的CGC和大鼠基因转录的影响。我们发现，用氯化锂对CGC进行处理会诱导AP-1和CRE结合活性的时间和浓度依赖性增加。用碳酸锂对大鼠进行长期饮食治疗4周，还显着增加了额叶皮质，海马，杏仁核和小脑的AP-1和CRE结合活性。 P-CREB，JUN D和FOS家族蛋白存在于大鼠脑和CGC中的AP-1结合位点中。在一项平行研究中，我们探讨了锂对谷氨酸引起的兴奋性毒素的神经保护作用，谷氨酸是一种主要的兴奋性氨基酸神经递质，涉及神经退行性和神经精神疾病的突触可塑性和发病机理。我们发现，长期暴露于氯化锂可以极大地保护培养的大鼠CGC，脑皮质和海马神经元针对谷氨酸诱导的兴奋性毒性毒性，涉及由N-甲基-D-大众（NMDA）受体介导的凋亡。这种神经保护发生在治疗相关的浓度（0.5-5.0 mm）下，需要进行6-7天的治疗才能进行完全保护，而24小时治疗则无效。该保护是针对谷氨酸诱导的兴奋性毒性的特异性，可以归因于NMDA受体介导的钙涌入的抑制。锂的长期作用并不是由于NMDA受体位点的下调，也不与已知的阻断肌醇单磷酸酶活性的能力有关。我们的结果表明，谷氨酸受体多动的调节至少部分代表了锂可以改变脑功能并在躁狂抑郁疾病治疗中施加临床功效的分子机制。锂的这些新作用还表明，过度的谷氨酸能神经传递可能是双极疾病的致病机制。在一项相关研究中，我们发现锂还可以牢固地保护卡马西平和苯妥英钠诱导的凋亡，并适度抑制CGC的年龄诱导死亡。但是，与防止谷氨酸兴奋性毒性的保护不同，锂对抗惊厥药诱导的神经毒性的影响不需要长期治疗，并且以相对较高的浓度（小于或等于5 mm）发生。锂的这种神经保护作用被磷脂酰肌醇3-激酶（PI 3-K）抑制剂LY294002抑制。锂对卡马西平神经毒性的抑制可能具有临床意义，因为众所周知，与锂和卡马西平的联合治疗可以增强任何一种药物对躁狂抑郁疾病治疗的影响。我们研究了与凋亡和细胞保护作用有关的基因表达的作用。在CGC中，用神经保护浓度的锂治疗可诱导细胞保护基因Bcl-2的mRNA和蛋白质水平的时间依赖性增加。相反，锂，Bax和p53的mRNA和蛋白质水平通过锂降低。用3 mM licl治疗7天后，Bcl-2/BAX的比率增加了约6倍。相反，谷氨酸治疗诱导BAX和p53 mRNA和蛋白质的水平迅速增加。用锂预处理抑制谷氨酸诱导的BAX和p53的增加，并将Bcl-2保持在升高的水平。 Lithium also blocks glutamate-elicited cytochrome c release from mitochondria and the cleavage of the caspase-3 substrate, lamin B. In a parallel study, we found that glutamate induces a rapid, reversible decrease in the activity of a cell survival factor, Akt, through enhanced dephosphorylation due to activation of protein phosphatase(s).相反，锂激活PI 3-K/AKT信号通路并增强糖原合酶激酶3-β的磷酸化。锂预处理促进了谷氨酸诱导的AKT活性丧失的恢复。综上所述，我们的结果表明，锂诱导的细胞保护基因产物上调和凋亡基因产物的下调在其神经保护作用中起着重要作用。我们通过使用脑缺血和亨廷顿氏病的动物模型从体外细胞培养研究扩展。我们发现，用LICL皮下注射16天的大鼠可在受到闭塞的大脑中间动脉的大鼠中减少缺血性脑梗塞体积的大小超过50％。局部缺血诱导的神经系统缺陷，例如异常姿势和偏瘫，在中动脉闭塞后24小时测量，通过慢性锂预处理大大降低。在Huntingtons病动物模型中，我们将NMDA受体的部分激动剂（NMDA受体的部分激动剂）注入了大鼠纹状体的左侧。这种治疗可导致大约70％的纹状体病变，涉及表达多巴胺D-1受体的GABAN能神经元的丧失。这种喹啉酸诱导的病变需要激活转录因子NF-KB并诱导p53和c-Myc。我们的结果表明，慢性锂治疗或一天预处理可将纹状体病变的大小降低40-50％。此外，锂神经保护作用与受影响区域和其他大脑结构中Bcl-2的过表达有关。因此，我们的体外和体内研究增加了锂除了用于双极抑郁疾病的使用外，还可能扩大用于治疗神经退行性疾病的使用，尤其是与兴奋性毒性相关的疾病。