Department of Chemistry, Mass Spectrometry Centre, University of Aveiro, Aveiro, Portugal.
J Neurochem. 2012 Mar;120(6):998-1013. doi: 10.1111/j.1471-4159.2011.07636.x. Epub 2012 Feb 10.
Tacrine is an acetylcholinesterase (AChE) inhibitor used as a cognitive enhancer in the treatment of Alzheimer's disease (AD). However, its low therapeutic efficiency and a high incidence of side effects have limited its clinical use. In this study, the molecular mechanisms underlying the impact on brain activity of tacrine and two novel tacrine analogues (T1, T2) were approached by focusing on three aspects: (i) their effects on brain cholinesterase activity; (ii) perturbations on electron transport chain enzymes activities of non-synaptic brain mitochondria; and (iii) the role of mitochondrial lipidome changes induced by these compounds on mitochondrial bioenergetics. Brain effects were evaluated 18 h after the administration of a single dose (75.6 μmol/kg) of tacrine or tacrine analogues. The three compounds promoted a significant reduction in brain AChE and butyrylcholinesterase (BuChE) activities. Additionally, tacrine was shown to be more efficient in brain AChE inhibition than T2 tacrine analogue and less active than T1 tacrine analogue, whereas BuChE inhibition followed the order: T1 > T2 > tacrine. The studies using non-synaptic brain mitochondria show that all the compounds studied disturbed brain mitochondrial bioenergetics mainly via the inhibition of complex I activity. Furthermore, the activity of complex IV is also affected by tacrine and T1 treatments while FoF(1) -ATPase is only affected by tacrine. Therefore, the compounds' toxicity as regards brain mitochondria, which follows the order: tacrine >> T1 > T2, does not correlate with their ability to inhibit brain cholinesterase enzymes. Lipidomics approaches show that phosphatidylethanolamine (PE) is the most abundant phospholipids (PL) class in non-synaptic brain mitochondria and cardiolipin (CL) present the greatest diversity of molecular species. Tacrine induced significant perturbations in the mitochondrial PL profile, which were detected by means of changes in the relative abundance of phosphatidylcholine (PC), PE, phosphatidylinositol (PI) and CL and by the presence of oxidized phosphatidylserines. Additionally, in both the T1 and T2 groups, the lipid content and molecular composition of brain mitochondria PL are perturbed to a lesser extent than in the tacrine group. Abnormalities in CL content and the amount of oxidized phosphatidylserines were associated with significant reductions in mitochondrial enzymes activities, mainly complex I. These results indicate that tacrine and its analogues impair mitochondrial function and bioenergetics, thus compromising the activity of brain cells.
他克林是一种乙酰胆碱酯酶 (AChE) 抑制剂，用于治疗阿尔茨海默病 (AD) 时作为认知增强剂。然而，其治疗效率低和副作用发生率高限制了其临床应用。在这项研究中，通过关注三个方面，研究了他克林和两种新型他克林类似物 (T1、T2) 对大脑活动影响的分子机制：(i) 它们对脑胆碱酯酶活性的影响；(ii) 对非突触脑线粒体电子传递链酶活性的干扰；和 (iii) 这些化合物引起的线粒体脂质组变化对线粒体生物能的作用。在给予他克林或他克林类似物单剂量 (75.6 μmol/kg) 18 小时后，评估了脑效应。这三种化合物均显著降低了大脑中的乙酰胆碱酯酶和丁酰胆碱酯酶 (BuChE) 活性。此外，与 T2 他克林类似物相比，他克林对脑 AChE 的抑制作用更为有效，而与 T1 他克林类似物相比则不那么活跃，而 BuChE 抑制则遵循以下顺序：T1 > T2 > 他克林。使用非突触脑线粒体的研究表明，所有研究的化合物均通过抑制复合物 I 活性来干扰脑线粒体生物能。此外，Tacrine 和 T1 处理还会影响复合物 IV 的活性，而 FoF(1)-ATPase 仅受 Tacrine 影响。因此，化合物对脑线粒体的毒性，其顺序为：他克林> > T1 > T2，与它们抑制脑胆碱酯酶的能力无关。脂质组学方法表明，磷脂酰乙醇胺 (PE) 是非突触脑线粒体中最丰富的磷脂 (PL) 类，而心磷脂 (CL) 则具有最大的分子多样性。他克林诱导了线粒体 PL 谱的显著改变，这是通过相对丰度的变化来检测的，其中包括磷脂酰胆碱 (PC)、PE、磷脂酰肌醇 (PI) 和 CL 的变化以及氧化的磷脂酰丝氨酸的存在。此外，在 T1 和 T2 组中，脑线粒体 PL 的脂质含量和分子组成受到的干扰程度均小于他克林组。CL 含量和氧化磷脂酰丝氨酸的异常与线粒体酶活性的显著降低有关，主要是复合物 I。这些结果表明，他克林及其类似物会损害线粒体功能和生物能，从而影响脑细胞的活性。
