Intraneuronal advanced glycation endproducts in presenilin-1 Alzheimer's disease

The most frequently mutated gene resulting in dominantly inherited Alzheimer's disease is presenilin-1. We have used antibodies against advanced glycation endproducts (AGE) in brain tissue sections of four patients with three different presenilin I mutations. Accumulation of intracellular AGE was observed in 75-95% of pyramidal neurons in patients with presenilin-1 mutations, far exceeding the percentage of presenilin-1-, tau- or ubiquitin-positive neurons. This high level of AGE-modified proteins in vulnerable neurons is most likely explained by higher levels of their precursors (reactive (di)carbonyl products) or a slower turnover of the participating proteins. These conditions of carbonyl stress may contribute to increased neuronal dysfunction and vulnerability leading to the early disease onset.     

Involvement of advanced glycation end-products (AGEs) in Alzheimer's disease

The advanced stage of the glycation process (one of the post-translational modifications of proteins) leads to the formation of advanced glycation end-products (AGEs) and plays an important role in the pathogenesis of angiopathy in diabetic patients. It has recently become clear that AGEs also influence physiological aging and neurodegenerative diseases such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Recently we have provided direct immunochemical evidence for the existence of six distinct AGE structures within the AGE-modified proteins and peptides that circulate in the serum of diabetic patients on hemodialysis (DM-HD). We showed a direct toxic effect of the synthetic AGE-2 (glyceraldehyde-derived AGEs) on cortical neuronal cells and provided evidence for a toxic effect of AGE-2 present in DM-HD serum. These results indicate that of the various types of AGE structures that can form in vivo, the AGE-2 structure is likely to play an important role in the pathophysiological processes associated with AGE formation. In AD brains, AGE-2 epitope was mainly present in the cytosol of neurons in the hippocampus and para-hippocampal gyrus. Protein cross-linking by AGE structures results in the formation of protease-resistant aggregates. Such protein aggregates may interfere with both axonal transport and intracellular protein traffic in neuron. In this review, we provide an outline of AGEs formation in vivo and propose that the novel structural epitope AGE-2 is an important toxic moiety for neuronal cells in AD.     

Effect of advanced glycation endproducts on cell cycle and their relevance for Alzheimer's disease

In Alzheimer's disease, neurons in affected regions re-enter the cell cycle, leave the G0 state and appear to be arrested at both the G1/S and G2/M phase with resulting cell death, predominantly by apoptosis. Further hallmarks of AD are crosslinked protein deposits (amyloid plaques and neurofibrillary tangles), which time-dependently become modified by "advanced glycation endproducts (AGEs)". Since AGEs activate both mitogenic and redox-sensitive pathways, they might be involved both in cell cycle re-entry and arrest.     

The role of receptor for advanced glycation end products (RAGE) in neuronal differentiation

The receptor for advanced glycation end products (RAGE) is a multiligand receptor protein thought to play an important role in neuronal differentiation. RAGE can bind a number of ligands and activate a variety of signalling pathways that lead to diverse downstream effects. Amphoterin and S100B are endogenous ligands, the interaction of which with RAGE is known to be involved in defined physiological processes. The present study investigated the spatiotemporal pattern of the expression for RAGE and its ligands, amphoterin and S100B, during neuronal differentiation of NT2/D1 cells. In this study, all three proteins were shown to increase with progression of neuronal differentiation as determined by Western blotting, raising the possibility that both amphoterin and S100B may interact with RAGE and have important functions during the process of cell differentiation. Moreover, blocking the activation of RAGE with neutralizing antibody in the presence of retinoic acid disrupted the progression of normal neuronal differentiation. Immunocytochemistry (ICC) studies showed that amphoterin partially colocalized with RAGE within differentiating NT2 cells, whereas S100B showed a high degree of colocalization. This result suggests that S100B is more likely to be the principal ligand for RAGE during the differentiation process and that RAGE and amphoterin might have both independent and combined roles. Moreover, RAGE was expressed only in cells that were committed to a neuronal phenotype, suggesting direct involvement of RAGE in mediating cellular changes within differentiating neuronal cells. Further detailed studies are now required to characterize fully the role of RAGE during the neuronal differentiation period.     

Plasma levels of soluble receptor for advanced glycation end products in Alzheimer's disease

Background: A decreased plasma level of soluble form of the receptor for advanced glycation end products (sRAGE) in patients with Alzheimer's disease (AD) has been reported. However, no evidence has shown whether the sRAGE plasma level of AD patients may differentiate from other types of dementia. Methods: Our study assessed sRAGE concentrations in the following 121 individuals in Chongqing area: 36 patients with AD, 12 with vascular dementia (VaD), 14 with mixed dementia (MD), 24 with other dementia (OD) including Parkinson's disease dementia, frontotemporal dementia, paralytic dementia and 35 cognitively normal controls. The total plasma level of sRAGE was determined using sandwich ELISA method. Results: sRAGE concentration in AD is significantly decreased compared with healthy controls. However, the receiver operating characteristic curve analysis of sRAGE between the AD and the control shows a low diagnostic accuracy. Conclusions: Our results demonstrate that sRAGE may assist the diagnosis of AD from normal individuals, but cannot differentiate AD from VaD, MD or OD.     

Altered intracellular signaling and reduced viability of Alzheimer's disease neuronal cybrids is reproduced by beta-amyloid peptide acting through receptor for advanced glycation end products (RAGE)

Activation of apoptosis by increased production of amyloid beta peptides (Abeta) has been implicated in neuronal cell death of Alzheimer's disease (AD). We used mitochondrial transgenic cybrid models of sporadic AD (SAD), which overproduce Abeta compared to control (CTL) cybrids, to investigate the effects of endogenously generated Abeta on intracellular signaling pathways and viability. Reducing SAD Abeta production with gamma-secretase inhibition altered the total phosphorylation profile of SAD cybrid to one similar to CTL cybrids and enhanced viability to approximately CTL cybrid levels. Treating CTL cybrids with exogenous Abeta or conditioned media (CM) from SAD cybrids activated the signaling pathways active in SAD cybrids under basal condition and decreased viability. Antibodies against receptor for advanced glycation end products (RAGE) blocked Abeta-induced activation of the p38, JNK pathways, and NF-kappaB in CTL cybrids and offered protection against the neurotoxic effects of Abeta. Expression of SAD mitochondrial genes in cybrids activates stress-related signaling pathways and reduces viability. This SAD phenotype is produced by endogenously generated Abeta and can be replicated by exogenous Abeta acting through RAGE.     

Toxic advanced glycation end products (TAGE) theory in Alzheimer's disease

Several epidemiological studies have reported moderately increased risks of Alzheimer's disease (AD) in diabetic patients compared with general population. In diabetes mellitus, the formation and accumulation of advanced glycation end products (AGEs) progress more rapidly. Recent understanding of this process has confirmed that interactions between AGEs and their receptor (RAGE) may play a role in the pathogenesis of diabetic complications and AD. The authors have recently found that glyceraldehyde-derived AGEs (AGE-2), which is predominantly the structure of toxic AGEs (TAGE), show significant toxicity on cortical neuronal cells and that the neurotoxic effect of diabetic serum is completely blocked by neutralizing antibody against the AGE-2 epitope. Moreover, in human AD brains, AGE-2 is distributed in the cytosol of neurons in the hippocampus and parahippocampal gyrus. These results suggest that TAGE is involved in the pathogenesis of AD as well as other age-related diseases. In this review, the authors discuss the molecular mechanisms of AD, especially focusing on TAGE-RAGE system.     

晚期糖基化终产物受体在脑缺血损伤中的表达及作用机制

目的 通过研究RAGE在大鼠及人的缺血脑组织中的表达情况,结合体外神经细胞OGD模型中S100B、RAGE与TNF-α的相互作用结果,探讨RAGE在脑缺血损伤中的作用及相关机制.方法 采用免疫组织化学方法检测RAGE在不同缺血时间点实验大鼠和患者脑组织中的表达;建立体外神经细胞OGD模型,用ELISA方法检测TNF-α的表达.结果 （1）大鼠永久性MCAO 1h、6h、12h、24h、2d、6d缺血侧RAGE表达均明显高于非缺血侧（P＜0.01）,脑梗死患者＜2d组、3～5d组及＞5d组脑病理切片中缺血侧与非缺血侧对比RAGE表达均有显著性差异（P＜0.05）;（2）OGD培养的神经细胞,TNF-α表达量显著增加,与正常培养组相比P＜0.01;用S100B蛋白刺激神经细胞并OGD培养,可以引起神经细胞表达TNF-α的量增加S100B（P＜0.01）;阻断神经细胞表达RAGE后,TNF-α表达量也相应地下降（P＜0.01）.结论 RAGE参与脑缺血损伤过程,缺氧缺糖培养的神经细胞其损伤过程可以通过RAGE表达上调引起TNF-α表达来实现.     

Immunohistochemical localization of receptor for advanced glycation end (RAGE) products in the R6/2 mouse model of Huntington's disease

The receptor for advanced glycation end (RAGE) products is a multi-ligand receptor that belongs to the immunoglobulin superfamily of cell surface receptors, whose ligands are known to be upregulated in neuropathological conditions. RAGE upregulation has been described in neurodegenerative diseases, such as Alzheimer's disease, Creutzfeldt-Jakob's disease and Huntington's disease (HD). To analyze in detail the implication of RAGE in HD, we studied the immunohistochemical distribution of RAGE in the striatum of the R6/2 mouse model of HD, with particular attention to the neuronal subpopulations and their relative vulnerability to HD neurodegeneration. We show that RAGE immunoreactivity is evenly distributed to the cytoplasm of neurons in the wild type mouse, while it is finely granular in the cytoplasm of striatal neurons of R6/2 mouse. RAGE is distributed in 98% of spiny projection neurons, both in the normal mouse and in the R6/2. RAGE co-localizes with all of the striatal interneuron subsets both in the wild-type and in the R6/2 mouse. However, the intensity of RAGE immunoreactivity is significantly higher in the spiny neurons and in the PARV neurons of R6/2 mouse, whereas it is comparable between R6/2 and wild-type in the cholinergic and somatostatinergic interneurons. These data support the concept that RAGE is upregulated in the neurodegenerative process of HD, and suggests that its activation is related to the individual vulnerability of the striatal neuronal subtype.     

血清晚期糖基化终末产物和可溶性晚期糖基化终末产物受体与阿尔茨海默病及血管性痴呆关系的研究

目的探讨血清中晚期糖基化终末产物(AGEs)、可溶性晚期糖基化终末产物受体(sRAGE)的水平与阿尔茨海默病(AD)、血管性痴呆(Va D)的关系。方法收集兰州大学第二医院神经内科2017年2月到2018年1月收治的149例患者,根据MMSE量表及相应的纳入排除标准,将患者进行分组,其中AD组34例,脑梗死后痴呆(Va D)组64例,脑梗死非痴呆(N-Va D)组51例,选择同期在性别、年龄、文化程度上无差异、无严重疾病的住院体检者31例作为正常对照组。比较4组间的一般资料及简易智能精神状态检查量表(MMSE)评分,比较血清AGEs、sRAGE在不同组别之间的差异,并分析其与AD和Va D的关系。结果 AD组和N-Va D组的AGEs水平高于Va D组和正常对照组,差异有统计学意义(P 0. 05)。Va D组和正常对照组之间,AD组和N-Va D组之间的AGEs水平比较,差异无统计学意义(P 0. 05)。ROC曲线分析显示血清AGEs对AD有较低诊断价值。Spearman秩相关法分析显示,年龄(r=-0. 168,P 0. 05)与MMSE评分呈负相关;体重指数(r=0. 151,P 0. 05)与MMSE评分呈正相关。4组在性别、年龄、糖尿病方面不存在显著性差异(P 0. 05)。4组间sRAGE水平比较无显著性差异(P 0. 05)。结论血清AGEs可能与AD的发生、发展有关; AGEs对AD有较低的诊断价值。     

Immunohistochemical distribution of the receptor for advanced glycation end products in neurons and astrocytes in Alzheimer's disease

Advanced glycation end products (AGE) and the receptor for AGE (RAGE) have been implicated in the chronic complications of diabetes mellitus (DM), and have been reported to play an important role in the pathogenesis of Alzheimer's disease (AD). In this study, we established a polyclonal anti-RAGE antibody, and examined the immunohistochemical localization of amyloid beta protein (Abeta), AGE, and RAGE in neurons and astrocytes from patients with AD and DM. Our anti-RAGE antibody recognized full-length RAGE (50 kd) and N-terminal RAGE (35 kd) in human brain tissue. Abeta-, AGE-, and RAGE-positive granules were identified in the perikaryon of hippocampal neurons (especially from CA3 and CA4) in all subjects. The distribution and staining pattern of these immunopositive granules showed good concordance with each antibody. In AD, most astrocytes contained both AGE-and RAGE-positive granules and their distribution was almost the same. Abeta-positive granules were less common, but Abeta-, AGE-, and RAGE-positive granules were colocalized in one part of a single astrocyte. In DM patients and control cases, AGE-and RAGE-positive astrocytes were very rare. These finding support the hypothesis that glycated Abeta is taken up via RAGE and is degraded through the lysosomal pathway in astrocytes. In addition to the presence of AGE, the process of AGE degradation and receptor-mediated reactions may contribute to neuronal dysfunction and promote the progression of AD.     

Receptor for advanced glycation end products (RAGE) mediates neuronal differentiation and neurite outgrowth

The receptor for advanced glycation end products (RAGE) plays a crucial role in several disease processes, such as diabetes, inflammation, and neurodegeneration. In this article we report multiple roles of RAGE in neuronal differentiation and neurite outgrowth. In retinoic-induced P19 embryonic carcinoma stem cells, silencing the expression of RAGE by RNA interference (RNAi) blocked differentiation of the P19 cells into neuronal cells and enhanced the formation of vimentin-positive fibroblast-like cells. RAGE knockdown inhibited retinoic acid-induced activation and blocked nuclear translocation of NF-kappaB, suggesting RAGE regulates activation of NF-kappaB. RAGE was also shown to be involved in survival of P19 cells during retinoic acid differentiation. Additionally, knockdown of RAGE strongly inhibited neurite outgrowth in retinoic acid-differentiated P19 cells, indicating that RAGE is required for neurite outgrowth of differentiated P19 cells. Retinoic acid-treated P19 cells activated GTPases, Rac1, and Cdc42. This activation of the GTPases was inhibited in RAGE-knockdown cells. In primary cerebellar granule neurons, the knockdown of RAGE also inhibited neurite outgrowth. In these cells, overexpression of dominant-negative forms of Rac1 and Cdc42 inhibited neurite outgrowth, whereas overexpression of constitutively active forms of Rac1 and Cdc42 in RAGE-deficient neurons restored neurite outgrowth, indicating that RAGE mediated neurite outgrowth through the Rac1/Cdc42 pathway. This is the first report on the role of RAGE in cell lines and primary neurons, as determined by RNAi knockdown.     

Prothrombin kringle-2,a mediator of microglial activation:new insight in Alzheimer's disease pathogenesis

Microglial activation in Alzheimer's disease(AD):In 1907,Dr.Alois Alzheimer,a Bavarian-born German psychiatrist and neuropathologist,published an article descri...     

Soluble receptor for advanced glycation end products in multiple sclerosis: a potential marker of disease severity

OBJECTIVES: To compare serum levels of the receptor for advanced glycation end products (sRAGE) between multiple sclerosis (MS) patients and healthy control subjects, and to investigate whether serum sRAGE levels correlate with MS disease severity as indicated by the Kurtzke Expanded Disability Status Scale (EDSS). METHOD: 37 patients with clinical diagnosis of MS and 22 healthy control subjects were investigated in a cross-sectional study using enzyme-linked immunosorbent assays (ELISA). RESULTS: Serum levels of sRAGE were found to be significantly lower in MS patients compared to levels in healthy controls (p = 0.005). A trend toward lower levels of serum sRAGE was observed in female MS patients compared to their male counterparts (p = 0.05). A relationship between sRAGE and EDSS, and sRAGE and rate of clinical relapse was observed (p = 0.012). CONCLUSION: The significant reduction of sRAGE in MS patients relative to healthy controls supports the potential role for RAGE axis in MS clinical pathology. Lower levels of sRAGE may be associated with enhanced inflammatory responses. Based on these observations, further investigations into the role of sRAGE in MS clinical pathology is warranted.     

Tetrahydrohyperforin (IDN5706)targets the endoplasmic reticulum for autophagy activation: potential mechanism for Alzheimer's disease therapy

正Alzheimer’s disease(AD)is the most common form of dementia worldwide among the older population.To date,there is no therapy to stop the destruction of brain cells and all the available treatments only compensate for the loss of synaptic transmission,thus resulting in marginal benefits to patients.     

Expression of the receptor for advanced glycation end products in Huntington's disease caudate nucleus

The accumulation of amyloid-beta and increased expression of its receptor RAGE (the receptor for advanced glycation end products) have been implicated in the pathogenesis of Alzheimer's disease (AD). Here we have used immunohistochemistry and double labelling to localize RAGE expression in Huntington's disease (HD) caudate nucleus (CN). Results showed that RAGE is expressed in at least two cell types in the CN, medium spiny projection neurons and astrocytes, with stronger staining in astrocytes than in neurons. The percentage of the total number of neurons positive for RAGE was significantly higher in G2 and G3 HD CN when compared with controls. What is more interesting however was the heterogeneous distribution of RAGE staining in CN. In controls, astrocytic RAGE staining was seen only in the superficial layer of the subependymal layer (SEL). In G1 HD cases, staining was seen throughout the entire width of SEL but extended into the CN in G2, 3 and 4. Neuronal RAGE staining was stronger in the medial CN than in the lateral CN in control and G1 cases. In G2, 3 and 4 cases, this staining gradient was not observed; more neuronal RAGE staining was however seen in the dorsal part of the CN when compared with the ventral part. The distribution of RAGE staining in neurons appeared to correlate with the ordered cell death seen in HD CN. Identification of the ligand for RAGE in HD brain and further functional studies are needed to clarify the role of RAGE in the pathogenesis of HD.     

Involvement of insulin receptor substrates in cognitive impairment and Alzheimer's disease

Type 2 diabetes—associated with impaired insulin/insulin-like growth factor-1(IGF1) signaling(IIS)—is a risk factor for cognitive impairment and dementia including Alzheimer's disease(AD). The insulin receptor substrate(IRS) proteins are major components of IIS, which transmit upstream signals via the insulin receptor and/or IGF1 receptor to multiple intracellular signaling pathways, including AKT/protein kinase B and extracellular-signal-regulated kinase cascades. Of the four IRS proteins in mammals, IRS1 and IRS2 play key roles in regulating growth and survival, metabolism, and aging. Meanwhile, the roles of IRS1 and IRS2 in the central nervous system with respect to cognitive abilities remain to be clarified. In contrast to IRS2 in peripheral tissues, inactivation of neural IRS2 exerts beneficial effects, resulting in the reduction of amyloid β accumulation and premature mortality in AD mouse models. On the other hand, the increased phosphorylation of IRS1 at several serine sites is observed in the brains from patients with AD and animal models of AD or cognitive impairment induced by type 2 diabetes. However, these serine sites are also activated in a mouse model of type 2 diabetes, in which the diabetes drug metformin improves memory impairment. Because IRS1 and IRS2 signaling pathways are regulated through complex mechanisms including positive and negative feedback loops, whether the elevated phosphorylation of IRS1 at specific serine sites found in AD brains is a primary response to cognitive dysfunction remains unknown. Here, we examine the associations between IRS1/IRS2-mediated signaling in the central nervous system and cognitive decline.