乳铁蛋白和脑铁代谢参与阿尔茨海默病

阿尔茨海默病(AD)是一种以脑内β-淀粉样蛋白(Aβ)逐渐沉积形成老年斑和tau蛋白过度磷酸化形成神经原纤维缠结为主要病理特征的神经退行性疾病。脑铁代谢紊乱促进阿尔茨海默病的发病进程,铁代谢异常能够促进AD脑内Aβ的沉积、tau蛋白过度磷酸化以及氧化应激反应等神经病理过程;而金属离子螯合剂如去铁敏等,可通过调节脑内铁离子代谢平衡,阻止Aβ的产生、tau蛋白磷酸化并改善学习记忆能力。乳铁蛋白(lactoferrin,LF)是一种具有铁螯合和抗炎作用的糖蛋白,在AD患者和转基因小鼠大脑Aβ斑块和神经原纤维缠结内均有明显表达,提示LF可能具有抑制AD脑内神经病理特征的产生的作用。因此,LF可能成为防治AD的候选药物之一。     

小胶质细胞及其在阿尔茨海默病中的作用

阿尔茨海默病(AD)是一种常见的老年神经变性疾病,病因十分复杂。目前多数学者认为：β-淀粉样蛋白沉积使得神经胶质细胞活化引起脑内慢性炎症反应可能是AD发病的核心病理机制之一。在AD炎症过程中,渉及到诸多细胞如小胶质细胞、星形胶质细胞及神经元参与,小胶质细胞则是其最主要的炎症细胞,小胶质细胞被β-淀粉样蛋白（Aβ）激活,产生大量致炎性细胞因子和神经元毒性介质,从而诱发脑内炎症反应,导致神经元损伤、死亡。Aβ的持续存在,小胶质细胞被持续激活,形成炎症发生和持续的恶性循环,最后导致AD的发生发展。     

DMT1在APP/PS1转基因小鼠大脑皮层老年斑内的定位研究

目的研究二价金属离子转运体1(divalent metal transporter 1,DMT1)在APP/PS1转基因小鼠大脑皮层内的定位分布,探讨DMT1异常表达影响脑铁代谢平衡从而参与AD发病的可能机制。方法应用免疫组织化学方法观察DMT1在9月龄APPsw/PS1小鼠大脑皮层的阳性分布;应用免疫荧光双标技术和共聚焦激光扫描显微镜观察DMT1蛋白和β淀粉样蛋白(β-amyloid peptide,Aβ)在APP/PS1转基因小鼠大脑皮层老年斑内的一致性分布和位置关系。结果APP/PS1转基因小鼠大脑皮层老年斑内均有DMT1阳性表达;DMT1和Aβ免疫双标发现DMT1免疫阳性产物与Aβ共存于老年斑,二者分布具有一致性。结论DMT1在APP/PS1转基因小鼠大脑皮层老年斑内大量表达,其分布与Aβ具有一致性,提示DMT1可能参与AD脑内Aβ沉积和老年斑形成。     

银杏叶提取物对Alzheimer‘s病样大鼠的治疗作用

Alzheimer’s病(AD)的重要病理特征为脑内老年斑沉积,主要临床表现为进行性记忆和认知力减退。研究表明,β淀粉样蛋白(Aβ)是老年斑的主要成分,聚集态Aβ或其活性片断如 Aβ25-35具有神经毒性,脑内注射聚集态Aβ25-35可引起学习记忆损害,并被作为AD的动物模型。本研究向大鼠海马注射聚集态     

用MALDI成像质谱法观察β-淀粉样肽类在阿尔茨海默病脑中的差异性沉积

正脑中β-淀粉样蛋白(amyloidβ,Aβ)沉积是阿尔茨海默病(Alzheimer’s disease,AD)早期并贯穿始终的一个特征。在发病前,老年斑(senile plaques,SP)中可检测到不溶性Aβ的沉积。此外,Aβ也沉积在脑毛细血管和动脉壁中并引起脑淀粉样血管病(cerebral amyloid angiopathy,CAA)。Aβ肽包含大约40个氨基酸,并由淀粉样前体蛋白(amyloid precursor protein,     

锌转运体ZNT1在人阿尔茨海默病大脑的定位

目的研究锌转运体-1(zinc transporter 1,ZNT1)在阿尔茨海默病(Alzheimer's Disease,AD)尸检大脑皮层内的定位分布,探讨ZNT1影响脑锌平衡从而参与AD发病的可能机制。方法应用免疫组织化学、免疫荧光和共聚焦激光扫描显微镜观察ZNT1蛋白和β-淀粉样蛋白(β-amyloid,Aβ)在AD患者大脑内的分布和二者之间的位置关系。结果ZNT1免疫阳性反应产物主要定位于AD大脑皮层老年斑内。几乎所有的Aβ老年斑内均有不同程度ZNT1表达。ZNT1和β-淀粉样蛋白免疫双标结果进一步证实ZNT1免疫产物与Aβ共存于AD患者的老年斑内。结论AD患者大脑皮质Aβ老年斑内有大量ZNT1蛋白表达,提示ZNT1可能参与AD大脑皮质Aβ老年斑的形成。     

以Tau蛋白为靶点治疗阿尔茨海默病的药物发展

阿尔茨海默病(Alzheimer’disease，AD)是老年人中痴呆最主要的原因。以不可逆进行性记忆和认知功能障碍为主要临床症状。目前AD的病因和发病机制尚未完全阐明，其主要神经病理特征包括：神经细胞外以β-淀粉样蛋白(A8)沉积为核心形成的老年斑(senile plaques，SP)；神经细胞内以过磷酸化的tau蛋白为核心形成的神经元纤维缠结(neurofibrillary tangle．NFT)和神经细胞丢失。     

阿尔茨海默病与β-淀粉样蛋白相关性研究现状

阿尔茨海默病(AD)是一种中枢神经系统变性病,常伴随有认知障碍、记忆力减退、人格改变等。AD的病因和发病机制尚不明确,由β淀粉样蛋白沉积(amyloid-β,Aβ)所积聚的细胞外老年斑(SP),tau蛋白过度磷酸化产生的神经细胞内神经原纤维缠结(NFT)和神经元丢失伴胶质细胞增生是AD发生的病理学基础。本文综述归纳了AD与Aβ相关性的最新进展情况。     

小胶质细胞在阿尔茨海默病中的作用及潜在的应用价值

<正>阿尔茨海默病(Alzheimer disease,AD)是神经退行性疾病的一种。全世界的痴呆症患者数约为5 000万，每年新增的痴呆症人数约为1 000万，AD是痴呆症中患病率最高的疾病，AD患者占痴呆症患者的60%～80%^[1]。AD的发病机制目前尚不明确，其病理特征主要为脑内β-淀粉样蛋白(amyloid β-protein,Aβ)聚集成的淀粉样斑块沉积和τ蛋白(tau protein)过度磷酸化产生的神经纤维缠结(neurofibrillary tangles,NFTs)，     

β淀粉样肽代谢与阿尔兹海默病

老年痴呆是当代医学界关注的焦点之一，其中阿尔兹海默病(Alazheimer's disease,AD)在65岁老人中患病率可高达5%，成为第4位死亡原因。AD的发病机理极为复杂，目前已确知4种基因突变与该病有关，它们是β淀粉样肽前体蛋白(APP)基因、早老1(PS1)基因、早老2(PS2)基因和ApoE基因。此外，其它病因学危险因子已达150余种或许将来可能发现得更多，而AD的神经病理学以脑内聚集大量的老年斑(SP)及神经纤维缠结(NFT)为其主要特征，这两者之间有无关系目前还不十分清楚，但大多数学者还是认为β淀粉样肽(β-amyloid,Aβ)的大量沉积是AD病理机制的核心问题。事实上，无论是Aβ还是其前体APP均具有正常的生理功能。是什么因素使它们从正常功能状态转变为病理因子，这正是引起人们兴趣的所在。本文仅对APP和Aβ的研究近况作一简要概述。     

Iron, zinc and copper in the Alzheimer's disease brain: a quantitative meta-analysis. Some insight on the influence of citation bias on scientific opinion

Dysfunctional homeostasis of transition metals is believed to play a role in the pathogenesis of Alzheimer's disease (AD). Although questioned by some, brain copper, zinc, and particularly iron overload are widely accepted features of AD which have led to the hypothesis that oxidative stress generated from aberrant homeostasis of these transition metals might be a pathogenic mechanism behind AD. This meta-analysis compiled and critically assessed available quantitative data on brain iron, zinc and copper levels in AD patients compared to aged controls. The results were very heterogeneous. A series of heavily cited articles from one laboratory reported a large increase in iron in AD neocortex compared to age-matched controls (p<0.0001) while seven laboratories failed to reproduce these findings reporting no significant difference between the groups (p=0.76). A more than three-fold citation bias was found to favor outlier studies reporting increases in iron and this bias was particularly prominent among narrative review articles. Additionally, while zinc was not significantly changed in the neocortex (p=0.29), copper was significantly depleted in AD (p=0.0003). In light of these findings, it will be important to re-evaluate the hypothesis that transition metal overload accounts for oxidative injury noted in AD.     

Iron,copper, and iron regulatory protein 2 in Alzheimer's disease and related dementias

Accumulating evidence implicates a role for altered iron and copper metabolism in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD). However, imbalances in the levels of the various forms of iron at different stages of AD have not been examined. In this pilot study we extracted and measured the levels of loosely bound, non-heme and total iron and copper in the frontal cortex and hippocampus of patients with mild–moderate AD (n = 3), severe AD (n = 8) and dementia with Lewy bodies (DLB, n = 6), using graphite furnace atomic absorption spectrometry (GFAAS). Additionally, the expression of iron regulatory protein 2 (IRP2) was examined in relation to the pathological hallmarks of AD and DLB, amyloid plaques, neurofibrillary tangles (NFT), and Lewy bodies, by immunohistochemistry. We found significantly decreased loosely bound iron in the hippocampal white matter of mild–moderate and severe AD patients and a trend towards increased non-heme iron in the hippocampal gray matter of severe AD patients. Furthermore, decreased levels of total copper were seen in severe AD and DLB frontal cortex compared to controls, suggesting an imbalance in brain metal levels in both AD and DLB. The decrease in loosely bound iron in mild–moderate AD patients may be associated with myelin breakdown seen in the beginning stages of AD and implicates that iron dysregulation is an early event in AD pathogenesis.     

Evidence for a novel heme-binding protein, HasAh, in Alzheimer disease

Multiple lines of evidence indicate that oxidative stress is an integral component of the pathogenesis of Alzheimer disease (AD). The precipitating cause of such oxidative stress may be misregulated iron homeostasis because there are profound alterations in heme oxygenase-1 (HO-1), redox-active iron, and iron regulatory proteins. In this regard, HasA, a recently characterized bacterial protein involved in heme acquisition and iron metabolism, may also be important in the generation of reactive oxygen species (ROS) given its ability to bind heme and render iron available for free radical generation through the Fenton reaction. To study further the role of heme binding and iron metabolism in AD, we show an abnormal localization of anti-HasA to the neurofibrillary pathology of AD, but not in normal-appearing neurons in the brains of cases of AD or in age-matched controls. These results suggest the increased presence in AD of a HasA homologue or protein sharing a common epitope with HasA, which we term HasAh. We conclude that heme binding of HasAh is a potential source of free soluble iron and therefore toxic free radicals in AD and in aging. This furthers the evidence that redox-active iron and subsequent Fenton reaction generating reactive oxygen are critical factors in the pathogenesis of AD.     

A morphometric study of the blood-brain barrier in Alzheimer's disease.

BACKGROUND: Abnormalities in the human blood-brain barrier may contribute to the pathogenesis of Alzheimer disease (AD). EXPERIMENTAL DESIGN: Morphometric parameters relevant to integrity of the blood-brain barrier (cerebral capillary endothelium) were assessed in brain biopsies from patients with AD and compared with values from age-matched nondemented controls. RESULTS: Alzheimer patients showed diminished mitochondrial density and area within cerebral capillary endothelium, an increased number of capillary profiles containing pericytes (a possible second line of defense when the capillary endothelium fails), and features of inter-endothelial junctions that suggest 'leakiness' of the blood-brain barrier. CONCLUSIONS: The data indicate subtle but definite abnormalities suggesting compromise of the blood-brain barrier in AD that may contribute to its pathogenesis, and support neuropharmacologic and morphologic studies that suggest that a form of denervation microangiopathy may occur in AD brain, possibly secondary to loss of neurons from the pontine locus ceruleus. The changes may also play a role in the deposition of A4 Alzheimer amyloid within cerebral microvessel walls.     

Bifunctional drug derivatives of MAO-B inhibitor rasagiline and iron chelator VK-28 as a more effective approach to treatment of brain ageing and ageing neurodegenerative diseases

Degeneration of nigrostriatal dopamine neurons and cholinergic cortical neurones are the main pathological features of Parkinson's disease (PD) and for the cognitive deficit in dementia of the Alzheimer' type (AD) and in dementia with Lewy bodies (DLB), respectively. Many PD and DLB subjects have dementia and depression resulting from possible degeneration of cholinergic and noradrenergic and serotonergic neurons. On the other hand, AD patients may also develop extrapyramidal features as well as depression. In both PD and AD there is, respectively, accumulation of iron within the melanin containing dopamine neurons of pars compacta and with in the plaques and tangle. It has been suggested that iron accumulation may contribute to the oxidative stress induced apoptosis reported in both diseases. This may result from increased glia hydrogen peroxide producing monoamine oxidase (MAO) activity that can generate of reactive hydroxyl radical formed from interaction of iron and hydrogen peroxide. We have therefore prepared a series of novel bifunctional drugs from the neuroprotective-antiapoptotic antiparkinson monoamine oxidase B inhibitor, rasagiline, by introducing a carbamate cholinesterase (ChE) inhibitory moiety into it. Ladostigil (TV-3326, N-propargyl-3R-aminoindan-5yl)-ethyl methylcarbamate), has both ChE and MAO-AB inhibitory activity, as potential treatment of AD and DLB or PD subjects with dementia Being a brain selective MAO-AB inhibitor it has limited potentiation of the pressor response to oral tyramine and exhibits antidepressant activity similar to classical non-selective MAO inhibitor antidepressants by increasing brain serotonin and noradrenaline. Ladostigil inhibits brain acetyl and butyrylcholinesterase in rats and antagonizes scopolamine-induced inhibition of spatial learning. Ladostigil like MAO-B inhibitor it prevents MPTP Parkinsonism in mice model and retains the in vitro and in vivo neuroprotective activity of rasagiline. Ladostigil, rasagiline and other propargylamines have been demonstrated to have neuroprotective activity in several in vitro and in vivo models, which have been shown be associated with propargylamines moiety, since propargylamines itself possess these properties. The mechanism of neuroprotective activity has been attributed to the ability of propargylamines-inducing the antiapoptotic family proteins Bcl-2 and Bcl-xl, while decreasing Bad and Bax and preventing opening of mitochondrial permeability transition pore. Iron accumulates in brain regions associated with neurodegenerative diseases of PD, AD, amyotrophic lateral sclerosis and Huntington disease. It is thought to be involved in Fenton chemistry oxidative stress observed in these diseases. The neuroprotective activity of propargylamines led us to develop several novel bifunctional iron chelator from our prototype brain permeable iron chelators, VK-28, possessing propargylamine moiety (HLA-20, M30 and M30A) to iron out iron from the brain. These compounds have been shown to have iron chelating and monoamine oxidase A and B selective brain inhibitory and neuroprotective-antiapoptotic actions.     

Reducing iron in the brain: a novel pharmacologic mechanism of huperzine A in the treatment of Alzheimer's disease

Huperzine A (HupA), a natural inhibitor of acetylcholinesterase derived from a plant, is a licensed anti-Alzheimer's disease (AD) drug in China and a nutraceutical in the United States. In addition to acting as an acetylcholinesterase inhibitor, HupA possesses neuroprotective properties. However, the relevant mechanism is unknown. Here, we showed that the neuroprotective effect of HupA was derived from a novel action on brain iron regulation. HupA treatment reduced insoluble and soluble beta amyloid levels, ameliorated amyloid plaques formation, and hyperphosphorylated tau in the cortex and hippocampus of APPswe/PS1dE9 transgenic AD mice. Also, HupA decreased beta amyloid oligomers and amyloid precursor protein levels, and increased A Disintegrin And Metalloprotease Domain 10 (ADAM10) expression in these treated AD mice. However, these beneficial effects of HupA were largely abolished by feeding the animals with a high iron diet. In parallel, we found that HupA decreased iron content in the brain and demonstrated that HupA also has a role to reduce the expression of transferrin-receptor 1 as well as the transferrin-bound iron uptake in cultured neurons. The findings implied that reducing iron in the brain is a novel mechanism of HupA in the treatment of Alzheimer's disease.     

A damaged microcirculation contributes to neuronal cell death in Alzheimer's disease

Alzheimer's disease (AD) involves multiple etiologic factors and a complex pathogenesis. Vascular factors are increasingly implicated in the pathogenesis of AD. In this paper we review evidence that AD brain microvessels are biochemically altered and contribute to neuronal injury and death by release of factors directly injurious to neurons. Our data show that when brain microvessels are "injured" by anoxia they produce high levels of reactive oxygen species. Comparisons of isolated brain microvessels from AD and age-matched controls show specific abnormalities in alpha(1) and beta receptors and in protein kinase C and protein kinase A signaling pathways. In AD but not in controls, the cerebral microcirculation expresses the inflammatory mediator CAP37 and over produces nitric oxide. Finally, we demonstrate that AD microvessels secrete toxic factors that cause neuronal cell death in vitro. These latter experiments showing that AD brain microvessels, in co-culture or vessel-conditioned media, cause lethal injury to neurons in culture, establish a direct link between endothelial cell products and neuronal cell death in this disease.     

Intranasal deferoxamine reverses iron-induced memory deficits and inhibits amyloidogenic APP processing in a transgenic mouse model of Alzheimer's disease

Increasing evidence indicates that a disturbance of normal iron homeostasis and an amyloid-β (Aβ)-iron interaction may contribute to the pathology of Alzheimer's disease (AD), whereas iron chelation could be an effective therapeutic intervention. In the present study, transgenic mice expressing amyloid precursor protein (APP) and presenilin 1 and watered with high-dose iron served as a model of AD. We evaluated the effects of intranasal administration of the high-affinity iron chelator deferoxamine (DFO) on Aβ neuropathology and spatial learning and memory deficits created in this AD model. The effects of Fe, DFO, and combined treatments were also evaluated in vitro using SHSY-5Y cells overexpressing the human APP Swedish mutation. In vivo, no significant differences in the brain concentrations of iron, copper, or zinc were found among the treatment groups. We found that high-dose iron (deionized water containing 10 mg/mL FeCl₃) administered to transgenic mice increased protein expression and phosphorylation of APP695, enhanced amyloidogenic APP cleavage and Aβ deposition, and impaired spatial learning and memory. Chelation of iron via intranasal administration of DFO (200 mg/kg once every other day for 90 days) inhibited iron-induced amyloidogenic APP processing and reversed behavioral alterations. DFO treatment reduced the expression and phosphorylation of APP protein by shifting the processing of APP to the nonamyloidogenic pathway, and the reduction was accompanied by attenuating the Aβ burden, and then significantly promoted memory retention in APP/PS1 mice. The effects of DFO on iron-induced amyloidogenic APP cleavage were further confirmed in vitro. Collectively, the present data suggest that intranasal DFO treatment may be useful in AD, and amelioration of iron homeostasis is a potential strategy for prevention and treatment of this disease.     

Is mitochondrial DNA depletion involved in Alzheimer's disease?

Several studies have suggested that mitochondrial metabolism disturbances and mitochondrial DNA (mtDNA) abnormalities may contribute to the progression of the pathology of Alzheimer's disease (AD).In this study we have investigated whether the amount of mtDNA is modified in different brain regions (cerebellum, hippocampus and frontal cortex) of confirmed AD necropsies and in blood of living AD patients. We used a real-time PCR method to analyse the mtDNA relative abundance in brain regions from 12 AD and seven controls and from a group of blood samples (17 living AD patients and 11 controls). MtDNA from blood samples together with hippocampus and cerebellum brain areas did not show differences between controls and AD. However, AD patients showed a 28% decrease in the amount of mtDNA in the frontal cortex when compared to controls for this specific area. Since frontal cortex is a severely affected region in AD, our results support the hypothesis that mitochondrial defects may play a role in the pathogenesis of AD.