小胶质细胞在AD中的作用机制研究进展

阿尔茨海默病(Alzheimer's disease,AD)是一种慢性神经退行性疾病,发病机制复杂,近些年来小胶质细胞介导的慢性神经炎症反应越来越受到人们的重视。小胶质细胞表达范围广,是一种中枢神经系统的免疫细胞,能够识别内源性或外源性中枢神经系统的损伤,从而引发免疫反应。AD患者中β淀粉样蛋白(Aβ)大量沉积也能够诱发小胶质细胞的激活,过度活化的小胶质细胞一方面可以吞噬病原体,另一方面也表达或释放具有细胞毒性的细胞因子和炎症介质,是加重AD的重要原因。本文就小胶质细胞在AD发病机制中的作用及其调控机制作一综述。     

以Tau蛋白为靶点的抗阿尔茨海默症药物研发进展

阿尔茨海默病(Alzheimer's Disease,AD)是一种神经退行性疾病,主要发病特征为学习记忆下降和认知损伤.关于其发病机制主要有神经递质失调假说、β淀粉样蛋白假说、Tau蛋白假说以及慢性炎症假说等.目前,尚未有药物可以阻止和逆转AD的病情,本文主要综述了Tau蛋白假说的临床药物研发现状,为进一步研究开发靶向...     

阿尔茨海默病中β淀粉样蛋白作用机制的研究进展

阿尔茨海默病(Alzheimer disease,AD)是一种常见的中枢神经系统退行性病变,老年人是高发人群,严重影响老年人的健康及生活质量。AD患者脑内形成神经炎性淀粉斑,即老年斑(senile plaque,SP)是其病理特征之一,SP主要由细胞外的β淀粉样蛋白(Amyloid-β,Aβ)沉积而成。Aβ是一个具有β片层的二级结构多肽,由淀粉样前体蛋白(APP)经水解产生后在脑内聚集,引发相应的神经毒性,造成神经元死亡,从而导致AD的发生和发展。Aβ在AD发病过程中起着重要作用,但其具体作用机制尚未明确。本文就近年来对Aβ的产生、分布与清除、传递与运输的研究进展作一综述。     

EGFR通路在胶质瘤发病机制中的研究进展

胶质瘤是目前最为常见的一种恶性肿瘤,约占我国中枢神经系统癌症的五分之二.EGFR受体是一种由上皮生长因子(egf)细胞扩增增殖和信号传导的酪氨酸激酶型受体,其扩增和过度表达对胶质癌的早期发生和扩散发育过程当中产生了巨大的作用,并且与肿瘤的等级呈正相关,EGFR与其受体的结合可以引起参加和调控细胞的分化、生长、迁移和凋亡...     

长链非编码RNA对阿尔茨海默病作用机制的研究进展

阿尔茨海默病(Alzheimer disease,AD)是一种典型的神经退行性疾病。其病程呈进行性发展,临床上主要表现为进行性记忆障碍、认知障碍、人格改变及语言障碍等;AD的病理特征为细胞外β-淀粉样蛋白(extracellularβ-amyloid protein deposition,Aβ)沉积、神经元纤维缠结(neurofibrillary tangles,NFTs)、神经元丢失、突触性和营养不良性神经炎。然而,上述病理变化的发病机制及分子谱目前尚不清楚,给AD的早期诊断及治疗带来了很大的挑战。长链非编码RNA(long non-coding RNA,LncRNA)是一类长度大于200个核苷酸单位的RNA,参与许多神经退行性疾病的发生及发展,如帕金森病(Parkinson,s disease,PD)和AD。越来越多的研究发现,LncRNA与AD间存在密切关系。为了深入了解LncRNA在AD中的作用及机制,本文对BACE1-AS、NEAT1、51A、BC200、EBF3-AS等LncRNA在AD中的作用作一综述,以期为AD的早期诊断及临床治疗提供依据。     

浅谈胶质细胞在帕金森病中的双重作用

帕金森病是中老年人常见的中枢神经系统变性疾病。胶质细胞与帕金森病相关,一方面,它能促进神经元的存活;另一方面,它又参与多巴胺能神经元的变性,促进帕金森病的发生和发展。该文就胶质细胞在帕金森病中可能发生的保护和毒性作用及其机制作一综述。     

多糖的共价键合对7S球蛋白凝胶性能的影响

引入细胞学说中的大分子拥挤体系并在该体系通过Maillard反应制备了大豆7S球蛋白(b-conglycinin,7S)和葡聚糖(dextran,Dex)的共价复合物,利用转谷氨酰胺酶(transglutaminase,TGase)的交联作用制得蛋白-多糖共价复合物凝胶.对其流变学、质构特性及微结构进行分析.结果表明,在大分子拥挤环境下,7S-葡聚糖比例为2:1的共价复合物制得具有致密且孔洞分布均匀的凝胶网络结构.单纯的蛋白自聚集或者与多糖的共混状态时形成的凝胶弹性模量都较高,但蛋白过度的聚集并不能得到孔洞均匀的凝胶网络结构,共价复合物制备的凝胶中葡聚糖的共价键合作用抑制了TGase交联过程中蛋白质分子间发生过度的相互作用.形貌学观察表明,共价复合物制备的凝胶形成了网络孔径均匀且非常致密的凝胶网络结构.     

β-淀粉样蛋白的聚集及其调控

β-淀粉样蛋白（amyloid β-protein,Aβ）的自发聚集形成大量毒性的寡聚体,导致脑内神经元死亡,从而引发认知障碍,即阿尔茨海默病（Alzheimer's disease,AD）,严重威胁着人类的健康。Aβ聚集过程呈现复杂的多尺度自组装特性,目前尚缺乏对Aβ聚集过程多尺度寡聚体的认识,严重制约Aβ聚集抑制剂的设计开发。本文首先简述Aβ聚集的基本理论以及与介尺度科学的关系,分类介绍Aβ自组装过程中所产生的各种介尺度寡聚体及其介导的细胞毒性;之后归纳各种Aβ聚集抑制剂的设计策略、作用原理和作用效果;最后总结Aβ聚集及其调控研究中存在的主要挑战,并提出了进一步研究的重点方向。     

小胶质细胞在神经退行性疾病发生发展中的作用研究进展

小胶质细胞作为中枢神经系统的免疫细胞,在胚胎期和出生后早期神经系统的发育及维持中枢神经系统微环境稳定中发挥重要作用。当神经元在衰老或神经退行性疾病中出现损伤时,小胶质细胞发生活化并通过释放趋化因子、神经传递素、细胞因子、生长因子等改变细胞微环境,发挥修复或保护神经元的作用。在修复或保护神经元的同时,活化的小胶质细胞也会释放前炎性细胞因子,通过炎性反应杀灭对神经元有毒有害的病原体等物质。小胶质细胞介导的炎性反应也会对神经元和其他正常细胞产生损害。神经退行性疾病是以神经元变性为主要病理改变的一类疾病,包括阿尔茨海默病、帕金森病和亨廷顿病。研究证实,小胶质细胞活化在神经退行性疾病的发生发展中发挥重要作用。本综述拟对小胶质细胞功能及其在神经退行性疾病的发生发展中发挥作用的研究进展进行探讨和总结。     

猪链球菌2型主要毒力因子研究进展

猪链球菌2型的毒力因子主要包括荚膜多糖(CPS)、溶菌酶释放蛋白(MRP)、细胞外因子(EF)、溶血素(HLY)以及多种具有毒性作用的蛋白片段。荚膜多糖是猪链球菌2型抵抗巨噬细胞吞噬的重要物质,也是猪链球菌进行分型的标志。溶菌酶释放蛋白和细胞外因子多出现于高致病力的毒株中,MRP和EF阳性菌株一般具有较高的毒力。溶血素具有较强的细胞毒性作用,其对微血管内皮细胞的破坏作用有利于细菌在组织内的扩散。其他多种毒力因子虽也具有致病作用和免疫原性,但还有待于进一步研究。由于猪链球菌2型致病机理复杂,毒株表型多样,尚未发现可区分毒力株、弱毒力株和无毒力株的标志性因子。对猪链球菌2型的毒力因子进行深入研究,对于阐明猪链球菌2型的致病机理,寻找到快速有效的诊断治疗方法以及疫苗的构建都有重要意义。     

Targeting Microglia-Synapse Interactions in Alzheimer’s Disease

In this review, we focus on the emerging roles of microglia in the brain, with particular attention to synaptic plasticity in health and disease. We present evidence that ramified microglia, classically believed to be “resting” (i.e., inactive), are instead strongly implicated in dynamic and plastic processes. Indeed, there is an intimate relationship between microglia and neurons at synapses which modulates activity-dependent functional and structural plasticity through the release of cytokines and growth factors. These roles are indispensable to brain development and cognitive function. Therefore, approaches aimed at maintaining the ramified state of microglia might be critical to ensure normal synaptic plasticity and cognition. On the other hand, inflammatory signals associated with Alzheimer’s disease are able to modify the ramified morphology of microglia, thus leading to synapse loss and dysfunction, as well as cognitive impairment. In this context, we highlight microglial TREM2 and CSF1R as emerging targets for disease-modifying therapy in Alzheimer’s disease (AD) and other neurodegenerative disorders.     

NLRP3 and Infections: β-Amyloid in Inflammasome beyond Neurodegeneration

Amyloid beta (Aβ)-induced abnormal neuroinflammation is recognized as a major pathological feature of Alzheimer’s disease (AD), which results in memory impairment. Research exploring low-grade systemic inflammation and its impact on the development and progression of neurodegenerative disease has increased. A particular research focus has been whether systemic inflammation arises only as a secondary effect of disease, or it is also a cause of pathology. The inflammasomes, and more specifically the NLRP3 inflammasome, are crucial components of the innate immune system and are usually activated in response to infection or tissue damage. Although inflammasome activation plays critical roles against various pathogens in host defense, overactivation of inflammasome contributes to the pathogenesis of inflammatory diseases, including acute central nervous system (CNS) injuries and chronic neurodegenerative diseases, such as AD. This review summarizes the current literature on the role of the NLRP3 inflammasome in the pathogenesis of AD, and its involvement in infections, particularly SARS-CoV-2. NLRP3 might represent the crossroad between the hypothesized neurodegeneration and the primary COVID-19 infection.     

Alzheimer’s Disease Animal Models: Elucidation of Biomarkers and Therapeutic Approaches for Cognitive Impairment

Alzheimer’s disease (AD) is an age-related and progressive neurodegenerative disorder. It is widely accepted that AD is mainly caused by the accumulation of extracellular amyloid β (Aβ) and intracellular neurofibrillary tau tangles. Aβ begins to accumulate years before the onset of cognitive impairment, suggesting that the benefit of currently available interventions would be greater if they were initiated in the early phases of AD. To understand the mechanisms of AD pathogenesis, various transgenic mouse models with an accelerated accumulation of Aβ and tau tangles have been developed. However, none of these models exhibit all pathologies present in human AD. To overcome these undesirable phenotypes, APP knock-in mice, which were presented with touchscreen-based tasks, were developed to better evaluate the efficacy of candidate therapeutics in mouse models of early-stage AD. This review assesses several AD mouse models from the aspect of biomarkers and cognitive impairment and discusses their potential as tools to provide novel AD therapeutic approaches.     

Targeting MicroRNA-485-3p Blocks Alzheimer’s Disease Progression

Alzheimer’s disease (AD) is a form of dementia characterized by progressive memory decline and cognitive dysfunction. With only one FDA-approved therapy, effective treatment strategies for AD are urgently needed. In this study, we found that microRNA-485-3p (miR-485-3p) was overexpressed in the brain tissues, cerebrospinal fluid, and plasma of patients with AD, and its antisense oligonucleotide (ASO) reduced Aβ plaque accumulation, tau pathology development, neuroinflammation, and cognitive decline in a transgenic mouse model of AD. Mechanistically, miR-485-3p ASO enhanced Aβ clearance via CD36-mediated phagocytosis of Aβ in vitro and in vivo. Furthermore, miR-485-3p ASO administration reduced apoptosis, thereby effectively decreasing truncated tau levels. Moreover, miR-485-3p ASO treatment reduced secretion of proinflammatory cytokines, including IL-1β and TNF-α, and eventually relieved cognitive impairment. Collectively, our findings suggest that miR-485-3p is a useful biomarker of the inflammatory pathophysiology of AD and that miR-485-3p ASO represents a potential therapeutic candidate for managing AD pathology and cognitive decline.     

Apoptosis Signal Regulating Kinase 1 (ASK1): Potential as a Therapeutic Target for Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common form of dementia, characterized by a decline in memory and cognitive function. Clinical manifestations of AD are closely associated with the formation of senile plaques and neurofibrillary tangles, neuronal loss and cognitive decline. Apoptosis signal regulating kinase 1 (ASK1) is a mediator of the MAPK pathway, which regulates various cellular responses such as apoptosis, cell survival, and differentiation. Accumulating evidence indicates that ASK1 plays a key role in the pathogenesis of neurodegenerative disorders such as Huntington’s disease and AD. Of particular interest, ASK1 is associated with many signaling pathways, which include endoplasmic reticulum (ER) stress-mediated apoptosis, Aβ-induced neurotoxicity, tau protein phosphorylation, and insulin signal transduction. Here, we review experimental evidence that links ASK1 signaling and AD pathogenesis and propose that ASK1 might be a new point of therapeutic intervention to prevent or treat AD.     

Activation of Endogenous Retrovirus,Brain Infections and Environmental Insults in Neurodegeneration and Alzheimer’s Disease

Chronic neurodegenerative diseases are complex, and their pathogenesis is uncertain. Alzheimer’s disease (AD) is a neurodegenerative brain alteration that is responsible for most dementia cases in the elderly. AD etiology is still uncertain; however, chronic neuroinflammation is a constant component of brain pathology. Infections have been associated with several neurological diseases and viruses of the Herpes family appear to be a probable cause of AD neurodegenerative alterations. Several different factors may contribute to the AD clinical progression. Exogeneous viruses or other microbes and environmental pollutants may directly induce neurodegeneration by activating brain inflammation. In this paper, we suggest that exogeneous brain insults may also activate retrotransposons and silent human endogenous retroviruses (HERVs). The initial inflammation of small brain areas induced by virus infections or other brain insults may activate HERV dis-regulation that contributes to neurodegenerative mechanisms. Chronic HERV activation in turn may cause progressive neurodegeneration that thereafter merges in cognitive impairment and dementia in genetically susceptible people. Specific treatment for exogenous end endogenous pathogens and decreasing pollutant exposure may show beneficial effect in early intervention protocol to prevent the progression of cognitive deterioration in the elderly.     

Neuroprotective Studies of Evodiamine in an Okadaic Acid-Induced Neurotoxicity

Background: Alzheimer’s disease (AD) is the most common neurodegenerative disease, and it manifests as progressive memory loss and cognitive decline. However, there are no effective therapies for AD, which is an urgent problem to solve. Evodiamine, one of the main bioactive ingredients of Evodia rutaecarpa, has been reported to ameliorate blood–brain barrier (BBB) permeability and improve cognitive impairment in ischemia and AD mouse models. However, whether evodiamine alleviates tauopathy remains unclear. This study aimed to examine whether evodiamine ameliorates tau phosphorylation and cognitive deficits in AD models. Methods: A protein phosphatase 2A inhibitor, okadaic acid (OA), was used to induce tau phosphorylation to mimic AD-like models in neuronal cells. Protein expression and cell apoptosis were detected using Western blotting and flow cytometry, respectively. Spatial memory/cognition was assessed using water maze, passive avoidance tests, and magnetic resonance imaging assay in OA-induced mice models, and brain slices were evaluated further by immunohistochemistry. Results: The results showed that evodiamine significantly reduced the expression of phosphor-tau, and further decreased tau aggregation and neuronal cell death in response to OA treatment. This inhibition was found to be via the inhibition of glycogen synthase kinase 3β, cyclin-dependent kinase 5, and mitogen-activated protein kinase pathways. In vivo results indicated that evodiamine treatment ameliorated learning and memory impairments in mice, whereas Western blotting and immunohistochemical analysis of the mouse brain also confirmed the neuroprotective effects of evodiamine. Conclusions: Evodiamine can decrease the neurotoxicity of tau aggregation and exhibit a neuroprotective effect. Our results demonstrate that evodiamine has a therapeutic potential for AD treatment.     

Microglial Heterogeneity and Its Potential Role in Driving Phenotypic Diversity of Alzheimer’s Disease

Alzheimer’s disease (AD) is increasingly recognized as a highly heterogeneous disorder occurring under distinct clinical and neuropathological phenotypes. Despite the molecular determinants of such variability not being well defined yet, microglial cells may play a key role in this process by releasing distinct pro- and/or anti-inflammatory cytokines, potentially affecting the expression of the disease. We carried out a neuropathological and biochemical analysis on a series of AD brain samples, gathering evidence about the heterogeneous involvement of microglia in AD. The neuropathological studies showed differences concerning morphology, density and distribution of microglial cells among AD brains. Biochemical investigations showed increased brain levels of IL-4, IL-6, IL-13, CCL17, MMP-7 and CXCL13 in AD in comparison with control subjects. The molecular profiling achieved by measuring the brain levels of 25 inflammatory factors known to be involved in neuroinflammation allowed a stratification of the AD patients in three distinct “neuroinflammatory clusters”. These findings strengthen the relevance of neuroinflammation in AD pathogenesis suggesting, in particular, that the differential involvement of neuroinflammatory molecules released by microglial cells during the development of the disease may contribute to modulate the characteristics and the severity of the neuropathological changes, driving—at least in part—the AD phenotypic diversity.     

Artemisinin Attenuates Amyloid-Induced Brain Inflammation and Memory Impairments by Modulating TLR4/NF-κB Signaling

The abnormal immune response is an early change in the pathogenesis of Alzheimer’s disease (AD). Microglial activation is a crucial regulator of the immune response, which contributes to progressive neuronal injury by releasing neurotoxic products. Therefore, finding effective drugs to regulate microglial homeostasis and neuroinflammation has become a new AD treatment strategy. Artemisinin has potent anti-inflammatory and immune activities. However, it is unclear whether Artemisinin contributes to the regulation of microglial activation, thereby improving AD pathology. This study found that Artemisinin significantly reduced amyloid beta-peptide 1–42 (Aβ_1–42)-induced increases in nitric oxide and reactive oxygen species and inflammatory factors in BV2 cells. In addition, Artemisinin inhibited the migration of microglia and prevented the expansion of the inflammatory cascade. The mechanical studies showed Artemisinin inhibited neuroinflammation and exerted neuroprotective effects by regulating the Toll-like receptor 4 (TLR4)/Nuclear factor-kappa B (NF-κB) signaling pathway. Similar results were obtained in AD model mice, in which Artemisinin administration attenuated Aβ_1–42-induced neuroinflammation and neuronal injury, reversing spatial learning and memory deficits. The anti-inflammatory effect of Artemisinin is also accompanied by the activation of the TLR4/NF-κB signaling pathway in the animal model. Our results indicate that Artemisinin attenuated Aβ_1–42-induced neuroinflammation and neuronal injury by stimulating the TLR4/NF-κB signaling pathway. These findings suggest that Artemisinin is a potential therapeutic agent for AD.     

Exosomes Derived from Human Amniotic Fluid Mesenchymal Stem Cells Preserve Microglia and Neuron Cells from Aβ

Background: Neuroinflammation is involved in neuronal cell death that occurs in neurodegenerative diseases such as Alzheimer’s disease (AD). Microglia play important roles in regulating the brain amyloid beta (Aβ) levels, so immunomodulatory properties exerted by mesenchymal stem cells may be exploited to treat this pathology. The evidence suggests that the mechanism of action of human amniotic fluid stem cells (hAFSCs) is through their secretome, which includes exosomes (exo). Methods: We examined the effect of exosomes derived from human amniotic fluid stem cells (hAFSCs-exo) on activated BV-2 microglia cells by lipopolysaccharide (LPS) as a neuroinflammation model. To investigate the exo effect on the interplay between AD neurons and microglia, SH-SY5Y neuroblastoma cells treated with Aβ were exposed to a conditioned medium (CM) obtained from activated BV-2 or co-culture systems. Results: We found that the upregulation of the markers of pro-inflammatory microglia was prevented when exposed to hAFSC-exo whereas the markers of the anti-inflammatory macrophage phenotype were not affected. Interestingly, the hAFSC-exo pretreatment significantly inhibited the oxidative stress rise and apoptosis occurring in the neurons in presence of both microglia and Aβ. Conclusion: We demonstrated that hAFSC-exo mitigated an inflammatory injury caused by microglia and significantly recovered the neurotoxicity, suggesting that hAFSC-exo may be a potential therapeutic agent for inflammation-related neurological conditions, including AD.