毒蕈碱受体激动剂治疗阿尔茨海默病的研究进展

毒蕈碱 (M )受体激动剂 ,尤其是M1 受体选择性激动剂对治疗阿尔茨海默病具有潜在的应用前景 ,不仅能提高脑内胆碱能神经系统的功能 ,还可促进分泌性β淀粉样前体蛋白的分泌和tau蛋白的去磷酸化 ,改善脑内胆碱能神经系统的退变。     

M1受体激动剂介导的神经保护作用机制

阿尔茨海默病(AD)是老年期常见的一类慢性、进行性神经细胞退行性病变。应用毒蕈碱M1受体激动剂是治疗AD的策略之一。M1受体激动剂可通过对抗淀粉样β蛋白产生的神经毒性,减少tau蛋白的过度磷酸化,产生神经生长因子样作用,以及缩短后超极化时程等机制而产生神经保护作用。     

肝素类药物防治阿尔采末病的研究进展

本文分析了阿尔采末病(AD)的病理机制,对肝素类药物神经保护机制的进展进行了综述。阐明了肝素类药物可通过调节IP3受体介导的细胞内钙释放,影响淀粉样蛋白(Aβ)沉积及其毒性、调节tau蛋白的磷酸化状态,保护胆碱能神经元等发挥神经保护作用,从而延缓AD的发生与发展。     

阿尔茨海默病与胆碱能系统损害

阿尔茨海默病(AD)是包括遗传因素、慢性感染、免疫缺陷和环境毒素等多种原因引起的脑退行性疾病,以Aβ的老年斑、异常磷酸化tau蛋白构成的神经纤维缠结和突触变性、皮质及皮质下神经元变性为特征。中枢胆碱能神经是构成学习记忆的重要生物学基础,早在上个世纪七、八十年代就发现AD患者的脑中胆碱能神经元相对选择性退变,从而提出胆碱能假说。尽管后来证明AD是一种发病机制非常复杂的疾病,难以用一种假说完全解释清楚,但脑内胆碱能神经元退变被认为是造成AD的最重要的病理因素之一。     

毒蕈碱受体激动剂治疗阿尔茨海默病的研？…

毒蕈碱（Ｍ）受体激动剂,尤其是Ｍ１受休选择性激动剂对治疗阿尔茨海默病具有在的应用前景,不仅能提高脑内胆碱能神经系统的功能,还可促进分泌性β淀粉样前体蛋白的分泌和ｔａｕ蛋白的去磷酸化,改善脑内胆碱能神经系统的退变。     

以病理特征为靶点的抗阿尔茨海默病药物的研究进展

阿尔茨海默病（AD）是一种起病隐匿的神经系统退行性疾病，主要的发病机制包括胆碱能假说、β-淀粉样蛋白假说和Tau蛋白假说等。本文从AD病理特征出发，主要介绍了乙酰胆碱及Sigma-1受体激动剂及以β-淀粉样蛋白、Tau蛋白为靶点的抗AD药物的研究进展，为新药研发提供参考。     

β-淀粉样蛋白对大鼠学习记忆、病理及tau蛋白磷酸化的影响

目的研究大鼠海马区内注射β-淀粉样蛋白（Aβ）的神经毒性,建立阿尔茨海默病（AD）动物模型,探讨Aβ毒性机制。方法选取雌性成年SD大鼠24只,随机分为止常对照组、生理盐水组、AD组,每组8只。Morris水迷宫检测大鼠学习记忆功能,HE染色及B ielschowsk i染色法观察海马神经元形态,免疫组化法观察tau蛋白异常磷酸化变化。结果与正常对照组大鼠相比,AD组大鼠水迷富测试结果明显减退（P〈0.01）;海马CA1区神经元纤维形态紊乱,tau蛋白磷酸化阳性细胞数明显增多（P〈0.01）。结论大鼠海马内注射凝集态Aβ可产生神经毒性作用,能较好地模拟AD行为和病理表现,其神经毒性可能是通过tau蛋白的异常磷酸化起作用。     

阿尔采末病胆碱能学说研究进展

中枢胆碱能系统参与调节哺乳动物的神经元兴奋性、皮质可塑性以及学习记忆过程 ,与脑认知功能密切相关。阿尔采末病 (Alzheimersdisease ,AD)是老年性痴呆的最常见原因 ,主要表现为进行性的认知功能下降。基底前脑胆碱能损伤导致的中枢胆碱能系统功能低下是AD患者认知功能障碍的基础。在AD病程中存在一个恶性循环 ,即脑内的胆碱能神经传递早期受损 ,导致神经退行性病变的易损区内Aβ的大量产生以及tau蛋白过度磷酸化 ,而Aβ又进一步削弱胆碱能神经传递的效应 ,中枢胆碱能功能障碍可能是AD患者认知功能障碍的根源     

多作用点乙酰胆碱酯酶抑制剂研究进展

阿尔茨海默病(AD)又名早老性痴呆,是中老年人群中最常见的痴呆形式。主要临床表现为记忆能力减退,持续性认知能力下降以及运动障碍等,并伴随有一系列精神病症状。AD的3个神经病理学特征为:以β2淀粉蛋白(Aβ)为沉积核心的老年斑,细胞内高度磷酸化的微管蛋白组成的神经元纤维缠结和前脑基底部胆碱能神经元的退化和丢失[1]。在胆碱能假说(cholinergic hypothesis)提出后,人们想出了一系列治疗AD办法:使用乙酰胆碱前体药物,M和N受体激动剂以及乙酰胆碱酯酶(AChE)抑制剂等[2]。到目前为止,用于临床治疗AD的主要是乙酰胆碱酯酶抑制剂(AChE…     

金属离子在阿尔茨海默病发病机制的作用

现有研究表明,大脑中金属离子动态平衡的改变与阿尔茨海默病(AD)的形成和病理改变密切相关。AD患者大脑神经元外出现的淀粉样蛋白(Aβ)沉积形成老年斑,伴有金属离子浓度升高异常。AD的其他病理特征,如神经元纤维缠结、神经元丢失、神经突触可塑性降低等也与金属离子有关。金属离子平衡紊乱已被认为是AD发病机制中的重要因素之一。大脑中的Fe3+,Cu2+和Zn2+参与突触神经活性,维持各种金属蛋白的生物学功能,Ca2+是普遍存在的第二信使,这些金属离子在脑内的稳态平衡对于维持大脑正常生理功能至关重要。本文对铁、铜、锌、钙等金属离子在AD发病机制中的作用从以下4个方面进行了系统性综述。(1)金属离子与蛋白异常:多项研究表明,铁、铜、锌、钙等金属离子等在不同脑区的错误沉积可促进Aβ的聚集与tau蛋白的过度磷酸化,而相关金属转运蛋白的异常是导致金属离子在脑中错误分布的关键因素。(2)金属离子与氧化应激:神经元对破坏性自由基的攻击极为敏感,AD患者大脑中存在的病变(如DNA损伤、蛋白质氧化、脂质过氧化和高级糖基化终产物),通常与自由基的攻击和金属离子失衡相关。金属离子失衡可引起氧化应激,使神经元中tau蛋白磷酸化、Aβ沉积,神经细胞受损、神经纤维交联等,与AD发病关系密切。(3)金属离子与细胞自噬:由于过度刺激的自噬和损耗造成细胞过度损伤以致细胞死亡,这是AD的标志。自噬-溶酶体缺陷发生在AD发病早期,被认为是AD发病的重要原因之一。溶酶体降解蛋白依赖于其内部的水解酶,抑制溶酶体蛋白水解酶活性,同时增加自噬囊泡的数量,降解异常蛋白沉积和损伤细胞。因此自噬可能成为改善AD神经元发病机制的潜在治疗靶点。(4)金属离子与神经突触:突触丢失是AD的病理特征之一。突触结构功能改变造成的神经系统紊乱会导致认知功能的障碍,且突触密度下降与AD认知功能障碍减退程度明显相关。而金属离子稳态对维持突触功能至关重要。综上所述,金属离子的作用在AD的发病机制中至关重要,所以近年来金属离子在AD发病机制中所起的作用也越来越受关注。金属离子螯合剂可能会减轻AD患者的病理特征,这些研究和发现将为治疗AD提供新的研究方向和思路。     

Therapeutic strategies in Alzheimer's disease: M1 muscarinic agonists

The cholinergic hypofunction in Alzheimer's disease (AD) appears to be linked with two other major hallmarks of this disease, beta-amyloid and hyperphosphorylated tau protein. Formation of beta-amyloids might impair the coupling of M1 muscarinic acetylcholine receptors (mAChR) with G-proteins. This can lead to decreased signal transduction, a decrease of trophic and non-amyloidogenic amyloid precursor protein (APPs) and generation of more beta-amyloids, aggravating further the cholinergic deficiency. This review is an attempt to explore the M1 mAChR regulation of beta-amyloid metabolism, tau hyperphosphorylation and cognitive functions. The therapeutic potential of M1-selective muscarinic agonists including AF102B, AF150(S), AF267B (the AF series) is evaluated and compared, when possible, with several FDA-approved acetylcholinesterase inhibitors. These M1 agonists can elevate APPs, decrease tau protein phosphorylation/hyperphosphorylation in vitro and in vivo and restore cognitive impairments in several animal models for AD. Except for the M1 agonists, no other compounds were reported yet with combined effects; e.g., amelioration of cognition dysfunction and beneficial modulation of APPs/beta-amyloid together with tau hyperphosphorylation/phosphorylation. This property of M1 agonists to alter different aspects associated with AD pathogenesis could represent the most remarkable clinical value of such drugs.     

Muscarinic agonists for the treatment of Alzheimer's disease: progress and perspectives

Much interest has focused on the development of selective muscarinic agonists for the treatment of Alzheimer's disease (AD). Cholinergic replacement therapy is thought to be beneficial in alleviating some of the cognitive dysfunctions in this disorder. The cholinergic neuronal tracts are involved in memory and learning processes, and the extent of the degeneration of the cortical projections correlates with the severity of the dementia. An M1 selective muscarinic agonist may be effective in treating at least some of the cognitive symptoms in AD. Highly selective M1 agonists, producing cellular excitation, should be beneficial in AD, regardless of the extent of degeneration of presynaptic cholinergic projections to the frontal cortex or hippocampus. Functional abnormalities in AD may also occur along various signal transduction pathways mediated, in part, at least, by muscarinic receptors. In general, activities associated with mAChR subtypes and m1 receptors, in particular, indicate that M1 agonists may also be useful for this aspect of AD. Mismetabolism of amyloid precursor proteins (APPs) may induce AD. Recent studies indicate that the formation of the b-amyloid peptide (Abeta) and amyloid plaques is linked to the loss of cholinergic function in AD. New data on the activation of m1 mAChRs in conjunction with recent findings that the induction of such receptors stimulates neurotrophic-like activities, decreases tau phosphorylation and inhibits apoptosis indicate that restoring the cholinergic tone in AD may be useful both in improving memory function and in altering the onset and progression of AD dementia. This article focuses on the recent, promising developments in this field and assesses the value of muscarinic agonists currently under development for the treatment of AD.     

Muscarinic agonists for the treatment of Alzheimer’s disease: progress and perspectives

Much interest has focused on the development of selective muscarinic agonists for the treatment of Alzheimer's disease (AD). Cholinergic replacement therapy is thought to be beneficial in alleviating some of the cognitive dysfunctions in this disorder. The cholinergic neuronal tracts are involved in memory and learning processes, and the extent of the degeneration of the cortical projections correlates with the severity of the dementia. An M1 selective muscarinic agonist may be effective in treating at least some of the cognitive symptoms in AD. Highly selective M1 agonists, producing cellular excitation, should be beneficial in AD, regardless of the extent of degeneration of presynaptic cholinergic projections to the frontal cortex or hippocampus. Functional abnormalities in AD may also occur along various signal transduction pathways mediated, in part, at least, by muscarinic receptors. In general, activities associated with mAChR subtypes and m1 receptors, in particular, indicate that M1 agonists may also be useful for this aspect of AD. Mismetabolism of amyloid precursor proteins (APPs) may induce AD. Recent studies indicate that the formation of the b-amyloid peptide (Ab) and amyloid plaques is linked to the loss of cholinergic function in AD. New data on the activation of m1 mAChRs in conjunction with recent findings that the induction of such receptors stimulates neurotrophic-like activities, decreases tau phosphorylation and inhibits apoptosis indicate that restoring the cholinergic tone in AD may be useful both in improving memory function and in altering the onset and progression of AD dementia. This article focuses on the recent, promising developments in this field and assesses the value of muscarinic agonists currently under development for the treatment of AD.     

Characteristics and consequences of muscarinic receptor activation by tau protein

It was recently suggested that tau protein released as a result of neuronal death is toxic to neighbouring cells, an effect that is mediated through the activation of muscarinic M1 and/or M3 receptors. Nevertheless, why tau protein and not other native muscarinic agonists, like ACh, can induce this neurotoxicity remains unknown. To clarify this issue, we analysed the different responses and properties of muscarinic receptors in response to stimulation by tau or ACh. The results revealed that the tau protein has an affinity for muscarinic receptors of around one order of magnitude higher than that of ACh. Furthermore, while the repeated stimulation with ACh induces desensitization of the muscarinic receptors, reiterate stimulation with tau failed to produce this phenomenon. Finally, we found the tau protein to be very stable in the extracellular milieu. These studies provide valuable information to help understand tau toxicity on neural cells bearing M1 or M3 muscarinic receptors and its contribution to neurodegenerative progression in tauopathies.     

Rationale for the development of cholinesterase inhibitors as anti-Alzheimer agents

Alzheimer's disease (AD) is characterized by progressive dementia caused by the loss of the presynaptic markers of the cholinergic system in the brain areas related to memory and learning and brain deposits of amyloid beta peptide (A beta) and neurofibrillary tangles (NFT). A small fraction of early onset familial AD (FAD) is caused by mutations in genes, such as the beta-amyloid precursor protein (APP) and presenilins that increase the load of A beta in the brain. These studies together with findings that A beta is neurotoxic in vitro, provide evidence that some aggregates of this peptide are the key to the pathogenesis of AD. The yield of A beta and the processing and turnover of APP are regulated by a number of pathways including apolipoprotein E, cholesterol and cholinergic agonists. Early studies showed that muscarinic agonists increased APP processing within the A beta sequence (sAPP alpha). More recently, we have presented evidence showing that some, but not all, anticholinesterases reduce secretion of sAPP alpha as well as A beta into the media suggesting that cholinergic agonists modulate A beta levels by multiple mechanisms. Herein we review the recent advances in understanding the function of cholinesterase (ChE) in the brain and the use of ChE-inhibitors in AD. We propose and support the position that the influence of cholinergic stimulation on amyloid formation is critical in light of the early targeting of the cholinergic basal forebrain in AD and the possibility that maintenance of this cholinergic tone might slow amyloid deposition. In this context, the dual action of certain cholinesterase inhibitors on their ability to increase acetylcholine levels and decrease amyloid burden assumes significance as it may identify a single drug to both arrest the progression of the disease as well as treat its symptoms. A new generation of acetyl- and butyryl cholinesterase inhibitors is being studied and tested in human clinical trials for AD. We critically discuss recent trends in AD research, from molecular and genetic to clinical areas, as it relates to the effects of cholinergic agents and their secondary effects on A beta. Finally, we examine different neurobiological mechanisms that provide the basis of new targets for AD drug development.     

Muscarinic receptor agonists and antagonists

Although four different subtypes of the muscarinic acetylcholine (ACh) receptor with functional correlates are known to exist (function for M5 is still unclear), all muscarinic agonists and antagonists in clinical practice only show very weak selectivity. Therefore, intensive investigations are in progress to develop subtype selective ligands. This review describes the first M1 agonists and antagonists of the presynaptic M2 receptor, which can be used in the treatment of Alzheimer’s disease (AD), and M3 antagonists, which will be useful in the treatment of urinary urge incontinence. In addition, muscarinic agonists were found to exhibit analgesic effects and M4 antagonists may be useful in the treatment of movement disorders. However, the latter two pharmacological findings will need more research work to become established in clinical trials.     

Functional comparison of muscarinic partial agonists at muscarinic receptor subtypes hM1, hM2, hM3, hM4 and hM5 using microphysiometry.

1. This study describes the pharmacological comparison of the muscarinic partial agonists sabcomeline, xanomeline and milameline at human cloned muscarinic receptor subtypes (hM1-5). 2. Radioligand binding studies at the hM1-5 muscarinic receptor subtypes were compared with functional studies using microphysiometry using carbachol as the standard full agonist. 3. In binding assays none of the compounds studied displayed preferential affinity for the M1,3,4 or M5 subtypes although carbachol was less potent at hM1 than hM3,4,5. 4. In functional studies, all of the compounds studied displayed similar levels of efficacy across the muscarinic receptors with the exception of M3, where there was a large apparent receptor reserve and the compounds behaved essentially as full agonists. 5. Sabcomeline was the most potent agonist in functional studies but also showed the lowest efficacy. In terms of potency, xanomeline showed some selectivity for M1 over M2 receptors and milameline showed some selectivity for M2 over M1 receptors. 6. These results show the value of microphysiometry in being able to compare receptor pharmacology across subtypes irrespective of the signal transduction pathway. 7. None of the partial agonists showed functional selectivity for M1 receptors, or indeed any muscarinic receptor, in the present study.     

Modulation of beta-amyloid precursor protein processing and tau phosphorylation by acetylcholine receptors

Neurofibrillary lesions and senile plaques that are composed mainly of hyperphosphorylated tau protein and the amyloid-beta peptide derived from the amyloid precursor protein, respectively, are classical hallmarks of Alzheimer's disease. A number of studies strongly suggests that amyloid-beta formation and amyloid depositions are linked to the pathogenesis of Alzheimer's disease. Recent findings suggest that very low concentrations of the amyloid-beta can inhibit various cholinergic neurotransmitter functions independently of apparent neurotoxicity. Many factors have been shown to influence the processing of amyloid precursor protein, including activation of muscarinic and nicotinic receptors. This review focus on some recent studies concerning the regulation of amyloid precursor protein processing and modulation of tau phosphorylation by acetylcholine receptor stimulation and how cholinergic deficits and amyloid-beta might be related to one another.     

Muscarinic receptor agonists and antagonists in the treatment of Alzheimer's disease

One of the consistent findings in the brains of Alzheimer's Disease (AD) patients is loss of cholinergic function. The cholinergic approach to treatment of AD involves counteracting this loss in cholinergic activity by pharmacological intervention to increase cholinergic transmission. The cognitive effects of acetylcholine are mediated via the muscarinic M1 receptor. Direct stimulation of this receptor using muscarinic M1 agonists improves cognition in animal models and improves performance in cognitive tests in Alzheimer's patients. Alternatively, antagonists of central presynaptic M2 receptors improves cognition by increasing the central release of acetylcholine. Both approaches require high selectivity for one muscarinic receptor sub-type both for efficacy and to avoid cholinergic side effects. In this review summarizes recent progress in the identification and characterization of selective muscarinic receptor ligands for the treatment of Alzheimer's disease.     

匹伐他汀对阿尔兹海默症作用机制的研究进展

阿尔兹海默症(AD)的主要病理学特征为β淀粉样蛋白(Aβ)沉积和tau蛋白过度磷酸化致神经纤维缠结,因此Aβ和tau是开发阿尔兹海默症药物的两大靶点。近些年的基础和临床研究,已证实他汀类药物对阿尔兹海默症有疗效。其中,匹伐他汀是他汀类新一代药,对AD的药理作用机制有:以Aβ为靶点的降胆固醇降脂作用、缓解氧化应激造成的细胞损伤作用、减少炎症反应作用、以及对神经血管和神经细胞及突触的保护作用,和以tau为靶点的减少tau蛋白总水平及其磷酸化水平,这些基础研究为相关临床研究提供了充分的依据。目前已有大量关于他汀类药物对AD疗效的临床报道,而对于匹伐他汀改善AD等神经疾病的相关研究还处于探索阶段,因此还未见具体匹伐他汀相关临床报道。