Human microglial cells synthesize albumin in brain

Albumin has been implicated in Alzheimer's disease since it can bind to and transport amyloid beta, the causative agent; albumin is also a potent inhibitor of amyloid beta polymerization. In a pilot phase study of Human Brain Proteome Project, we found evidence that albumin may be synthesized in immortalized human microglial cells, human primary microglial cells, and human fetal and adult brain tissues. We also found the synthesis and secretion is enhanced upon microglial activation by Amyloid [beta]~1-42~, lipopolysaccharide treatment or human Alzheimer's brain

Modulating Amyloid Beta Clearance by Altering Cellular and Whole Brain Apolipoprotein E Metabolism

The aggregation and accumulation of the amyloid beta peptide in the brain is hypothesized to be an initial necessary event in the pathogenesis of Alzheimer\u27s disease (AD). Since the level of monomeric soluble amyloid beta as well as amyloid beta-binding molecules determine the onset and amount of amyloid beta aggregation, significant attention has been devoted to defining the molecular and systemic pathways that modulate amyloid beta synthesis and clearance in the brain. Extensive evidence exists that both the isoform and amount of apolipoprotein E (apoE), an amyloid beta-binding molecule, influence amyloid beta aggregation and clearance from the brain. Therefore, studying how the molecular mechanisms that modulate apoE levels in the brain affect amyloid beta clearance will enhance our insight into the disease process. The apoE receptor low-density lipoprotein receptor (LDLR) and ATP-binding cassette transporter A1 (ABCA1), a protein that regulates apoE lipidation, have previously been shown to modulate brain amyloid beta levels. In the work presented in this dissertation, we found that increasing LDLR levels enhanced the cellular uptake and degradation of amyloid beta by primary astrocytes, and increased amyloid beta transport to lysosomes. The effect of LDLR on amyloid beta uptake and clearance occurred independently of apoE, and potentially involved a direct interaction between amyloid beta and LDLR. To measure the clearance of apoE and amyloid beta in the mouse brain, we developed a technique that couples stable isotope-labeling kinetics (SILK) with mass spectrometry. We validated this technique by demonstrating that apoE clearance is enhanced in the brains of mice overexpressing LDLR. We also applied this technique to measure apoE clearance rates in the brains of human apoE targeted-replacement mice. Finally, we analyzed the effect of ABCA1 on apoE and amyloid beta clearance from the mouse brain. The fractional clearance rate of apoE was increased in amyloid precursor protein (APP) transgenic mice that either lacked or overexpressed ABCA1, while ABCA1 levels had no effect on amyloid beta clearance. Therefore, ABCA1 likely influences amyloid beta aggregation in vivo through a process other than modulating amyloid beta clearance. These data further our understanding of how proteins involved in apoE metabolism influence AD pathogenesis, and have important implications for future therapeutic strategies that target brain apoE levels and function

Differentiating amyloid beta spread in autosomal dominant and sporadic Alzheimer\u27s disease

Amyloid-beta deposition is one of the hallmark pathologies in both sporadic Alzheimer\u27s disease and autosomal-dominant Alzheimer\u27s disease, the latter of which is caused by mutations in genes involved in amyloid-beta processing. Despite amyloid-beta deposition being a centrepiece to both sporadic Alzheimer\u27s disease and autosomal-dominant Alzheimer\u27s disease, some differences between these Alzheimer\u27s disease subtypes have been observed with respect to the spatial pattern of amyloid-beta. Previous work has shown that the spatial pattern of amyloid-beta in individuals spanning the sporadic Alzheimer\u27s disease spectrum can be reproduced with high accuracy using an epidemic spreading model which simulates the diffusion of amyloid-beta across neuronal connections and is constrained by individual rates of amyloid-beta production and clearance. However, it has not been investigated whether amyloid-beta deposition in the rarer autosomal-dominant Alzheimer\u27s disease can be modelled in the same way, and if so, how congruent the spreading patterns of amyloid-beta across sporadic Alzheimer\u27s disease and autosomal-dominant Alzheimer\u27s disease are. We leverage the epidemic spreading model as a data-driven approach to probe individual-level variation in the spreading patterns of amyloid-beta across three different large-scale imaging datasets (2 sporadic Alzheimer\u27s disease, 1 autosomal-dominant Alzheimer\u27s disease). We applied the epidemic spreading model separately to the Alzheimer\u27s Disease Neuroimaging initiative (n = 737), the Open Access Series of Imaging Studies (n = 510) and the Dominantly Inherited Alzheimer\u27s Network (n = 249), the latter two of which were processed using an identical pipeline. We assessed inter-and intra-individual model performance in each dataset separately and further identified the most likely subject-specific epicentre of amyloid-beta spread. Using epicentres defined in previous work in sporadic Alzheimer\u27s disease, the epidemic spreading model provided moderate prediction of the regional pattern of amyloid-beta deposition across all three datasets. We further find that, whilst the most likely epicentre for most amyloid-beta-positive subjects overlaps with the default mode network, 13% of autosomal-dominant Alzheimer\u27s disease individuals were best characterized by a striatal origin of amyloid-beta spread. These subjects were also distinguished by being younger than autosomal-dominant Alzheimer\u27s disease subjects with a default mode network amyloid-beta origin, despite having a similar estimated age of symptom onset. Together, our results suggest that most autosomal-dominant Alzheimer\u27s disease patients express amyloid-beta spreading patterns similar to those of sporadic Alzheimer\u27s disease, but that there may be a subset of autosomal-dominant Alzheimer\u27s disease patients with a separate, striatal phenotype

Effect of goji berry on the formation of extracellular senile plaques of Alzheimer\u27s disease

BACKGROUND: Alzheimer\u27s disease (AD) is the most common neurodegenerative disease and a major source of morbidity and mortality. Currently, no therapy nor drug can cure or modify AD progression, but recent studies suggest that nutritional compounds in certain foods can delay or prevent the onset of AD. Diets with high antioxidants is one of the examples which is believed to influence AD pathogenesis through direct effect on amyloid beta levels. Compared to other fruits and vegetables, goji berry (GB) has high levels of polyphenolic substances with antioxidant activities which have shown some positive effects on cognitive function while its mechanism on neuroprotection is yet to be explored. We investigated whether GB would decrease the quantity of amyloid beta in cell culture model of AD. OBJECTIVE: To assess the protective effects of GB against amyloid beta toxicity in M17 cells using different techniques. METHODS: Goji berry powder (GBP) at different concentrations was treated with 20 μM amyloid beta-induced neuronal cells. MTS assay (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium), bicinchoninic acid (BCA) assay, Western blot analysis, enzyme-linked immunosorbent assay (ELISA) and atomic force microscopy (AFM) were performed to identify how GB affected amyloid beta. RESULTS: MTS assay indicated that GBP significantly increased cell viability up to 105% when GBP was at 1.2 μg/ mL. Western blot showed significant reduction of amyloid beta up to 20% in cells treated with 1.5 μg/ mL GBP. GBP at 1.5 μg/ mL was the most effective concentration with 17% reduction of amyloid beta in amyloid beta-induced neuronal cells compared to control (amyloid beta only) based on ELISA results. AFM images further confirmed increasing GBP concentration led to decreased aggregation of amyloid beta. CONCLUSION: GB can be a promising anti-aging agent and warrants further investigating due to its effect on reduction of amyloid beta toxicity

Estrogen protects neuronal cells from amyloid beta-induced apoptosis via regulation of mitochondrial proteins and function

BACKGROUND: Neurodegeneration in Alzheimer's disease is associated with increased apoptosis and parallels increased levels of amyloid beta, which can induce neuronal apoptosis. Estrogen exposure prior to neurotoxic insult of hippocampal neurons promotes neuronal defence and survival against neurodegenerative insults including amyloid beta. Although all underlying molecular mechanisms of amyloid beta neurotoxicity remain undetermined, mitochondrial dysfunction, including altered calcium homeostasis and Bcl-2 expression, are involved in neurodegenerative vulnerability. RESULTS: In this study, we investigated the mechanism of 17β-estradiol-induced prevention of amyloid beta-induced apoptosis of rat hippocampal neuronal cultures. Estradiol treatment prior to amyloid beta exposure significantly reduced the number of apoptotic neurons and the associated rise in resting intracellular calcium levels. Amyloid beta exposure provoked down regulation of a key antiapoptotic protein, Bcl-2, and resulted in mitochondrial translocation of Bax, a protein known to promote cell death, and subsequent release of cytochrome c. E(2 )pretreatment inhibited the amyloid beta-induced decrease in Bcl-2 expression, translocation of Bax to the mitochondria and subsequent release of cytochrome c. Further implicating the mitochondria as a target of estradiol action, in vivo estradiol treatment enhanced the respiratory function of whole brain mitochondria. In addition, estradiol pretreatment protected isolated mitochondria against calcium-induced loss of respiratory function. CONCLUSION: Therefore, we propose that estradiol pretreatment protects against amyloid beta neurotoxicity by limiting mitochondrial dysfunction via activation of antiapoptotic mechanisms

Investigating the Modulation of Aggregating Amyloid Beta 40

Amyloid beta protein has been linked to the formation of Alzheimer’s disease in patients.¹ Plaques form from amyloid beta fibrils. The formation of these plaques between neural connections in the brain are associated with Alzheimer’s disease.² The reduction of the formation of fibrils can be linked to utilizing protein mimics. The protocols that are used to reproduce the simulation of amyloid beta in the brain can be very important. Also, the structure of the protein mimic that is being used to inhibit the formation of fibrils can determine how the amyloid beta plaques are reduced. The structure of sequence KLLFFLFFLLK peptoid was synthesized to test with amyloid beta. The amyloid beta must first be monomerized to the desired monomer 40 or 42 which are believed to be the main amino acid residues associated with the formation of plaques.³ This was accomplished through both 1,1,1,3,3,3 hexaprop-2-flouro treatment and fast protein liquid chromatography. The peptoid was synthesized by hand, purified by high pressure liquid chromatography, and tested by matrix-assisted laser desorption/ionization

Non-natural protein mimetics for the treatment of Alzheimer\u27s disease

Alzheimer\u27s disease (AD) is a slow degenerative disease that causes memory loss and eventually leads to death. AD is caused by the aggregation of the amyloid-beta protein, found on the outside of brain cells; once the amyloid-beta protein begins to aggregate it forms plaques on the extracellular part of the neural cells. To date there is no AD medication commercially available that breaks up the amyloid-beta aggregates. Current research has found that certain molecules bind to the amyloid-beta protein and prevent aggregation. The purpose of this research project is to engineer a peptoid-based molecule to stop the aggregation of the amyloid-beta protein. Peptoids have been found to form strong helices, have high bioactivity, and are easy and cost-effective to synthesize. Three peptoids with different chemistries at only the 6th side chain have been designed; the first peptoid is neutral, the second peptoid is positive, and the third peptoid is negative. The binding ability of the peptoids with the amyloid-beta protein will be tested at the University of South Carolina in the laboratory of Dr. Melissa Moss. Currently the peptoids have been synthesized and are in the process of purification and characterization. The peptoids binding ability with the amyloid-beta protein will provide important information regarding their use for the therapeutic treatment of AD

Inflammation, neurodegeneration and protein aggregation in the retina as ocular biomarkers for Alzheimer’s Disease in the 3xTg-AD mouse model

Alzheimer's disease (AD) is the most common cause of dementia in the elderly. In the pathogenesis of AD a pivotal role is played by two neurotoxic proteins that aggregate and accumulate in the central nervous system: amyloid beta and hyper-phosphorylated tau. Accumulation of extracellular amyloid beta plaques and intracellular hyper-phosphorylated tau tangles, and consequent neuronal loss begins 10-15 years before any cognitive impairment. In addition to cognitive and behavioral deficits, sensorial abnormalities have been described in AD patients and in some AD transgenic mouse models. Retina can be considered a simple model of the brain, as some pathological changes and therapeutic strategies from the brain may be observed or applicable to the retina. Here we propose new retinal biomarkers that could anticipate the AD diagnosis and help the beginning and the follow-up of possible future treatments. We analyzed retinal tissue of triple-transgenic AD mouse model (3xTg-AD) for the presence of pathological hallmarks during disease progression. We found the presence of amyloid beta plaques, tau tangles, neurodegeneration, and astrogliosis in the retinal ganglion cell layer of 3xTg-AD mice, already at pre-symptomatic stage. Moreover, retinal microglia in pre-symptomatic mice showed a ramified, anti-inflammatory phenotype which, during disease progression, switches to a pro-inflammatory, less ramified one, becoming neurotoxic. We hypothesize retina as a window through which monitor AD-related neurodegeneration process

Cognitive and brain cytokine profile of non-demented individuals with cerebral amyloid-beta deposition

Brain inflammation has been increasingly associated with early amyloid accumulation in Alzheimer's disease models; however, evidence of its occurrence in humans remains scarce. To elucidate whether amyloid deposition is associated with neuroinflammation and cognitive deficits, we studied brain inflammatory cytokine expression and cognitive decline in non-demented elderly individuals with and without cerebral amyloid-beta deposition. Global cognition, episodic, working, and semantic memory, perceptual speed, visuospatial ability, and longitudinal decline (5.7 ± 3.6 years) in each cognitive domain were compared between elderly individuals (66-79 years) with and without cerebral amyloid-beta deposition. The expression of 20 inflammatory cytokines was analyzed in frozen temporal, parietal, and frontal cortices and compared between older individuals with and without amyloid-beta deposition in each brain region. Correlation analyses were performed to analyze associations between amyloid-beta load, cytokine expression, and cognitive decline. Individuals with cortical amyloid-beta deposition displayed deficits and a faster rate of cognitive decline in perceptual speed as compared with those individuals without amyloid-beta. This decline was positively associated with cortical amyloid-beta levels. Elderly individuals with amyloid-beta deposition had higher levels of IL-1β, IL-6, and eotaxin-3 in the temporal cortex accompanied by an increase in MCP-1 and IL-1β in the parietal cortex and a trend towards higher levels of IL-1β and MCP-1 in the frontal cortex as compared with age-matched amyloid-free individuals. Brain IL-1β levels displayed a positive association with cortical amyloid burden in each brain region. Finally, differential cytokine expression in each cortical region was associated with cognitive decline. Elderly individuals with amyloid-beta neuropathology but no symptomatic manifestation of dementia, exhibit cognitive decline and increased brain cytokine expression. Such observations suggest that increased cytokine expression might be an early event in the Alzheimer's continuum. The online version contains supplementary material available at 10.1186/s12974-021-02169-0

A data-driven study of Alzheimer's disease related amyloid and tau pathology progression

Amyloid-beta is thought to facilitate the spread of tau throughout the neocortex in Alzheimer's disease, though how this occurs is not well understood. This is because of the spatial discordance between amyloid-beta, which accumulates in the neocortex, and tau, which accumulates in the medial temporal lobe during aging. There is evidence that in some cases amyloid-beta-independent tau spreads beyond the medial temporal lobe where it may interact with neocortical amyloid-beta. This suggests that there may be multiple distinct spatiotemporal subtypes of Alzheimer's-related protein aggregation, with potentially different demographic and genetic risk profiles. We investigated this hypothesis, applying data-driven disease progression subtyping models to post-mortem neuropathology and in vivo PET based measures from two large observational studies: the Alzheimer's Disease Neuroimaging Initiative and the Religious Orders Study and Rush Memory and Aging Project. We consistently identified 'amyloid-first' and 'tau-first' subtypes using cross-sectional information from both studies. In the amyloid-first subtype, extensive neocortical amyloid-beta precedes the spread of tau beyond the medial temporal lobe, while in the tau-first subtype mild tau accumulates in medial temporal and neocortical areas prior to interacting with amyloid-beta. As expected, we found a higher prevalence of the amyloid-first subtype among apolipoprotein E (APOE) ε4 allele carriers while the tau-first subtype was more common among APOE ε4 non-carriers. Within tau-first APOE ε4 carriers, we found an increased rate of amyloid-beta accumulation (via longitudinal amyloid PET), suggesting that this rare group may belong within the Alzheimer's disease continuum. We also found that tau-first APOE ε4 carriers had several fewer years of education than other groups, suggesting a role for modifiable risk factors in facilitating amyloid-beta-independent tau. Tau-first APOE ε4 non-carriers, in contrast, recapitulated many of the features of Primary Age-related Tauopathy. The rate of longitudinal amyloid-beta and tau accumulation (both measured via PET) within this group did not differ from normal aging, supporting the distinction of Primary Age-related Tauopathy from Alzheimer's disease. We also found reduced longitudinal subtype consistency within tau-first APOE ε4 non-carriers, suggesting additional heterogeneity within this group. Our findings support the idea that amyloid-beta and tau may begin as independent processes in spatially disconnected regions, with widespread neocortical tau resulting from the local interaction of amyloid-beta and tau. The site of this interaction may be subtype-dependent: medial temporal lobe in amyloid-first, neocortex in tau-first. These insights into the dynamics of amyloid-beta and tau may inform research and clinical trials that target these pathologies