Molecular biology and genetics of Alzheimer's disease

Cross-sectional and longitudinal associations between late-life depressive symptoms and cognitive deficits: 20-year follow-up of the Kuakini Honolulu-Asia aging study

OBJECTIVE

To examine depressed affect, somatic complaints, and positive affect as longitudinal predictors of fluid, crystallized and global cognitive performance in the Kuakini Honolulu-Asia Aging Study (HAAS), a large prospective cohort study of Japanese-American men.

METHODS

We assessed 3,088 dementia-free Kuakini-HAAS participants aged 71-93 (77.1 ± 4.2) years at baseline (1991-1993). Depressive symptoms were evaluated by the Center for Epidemiologic Studies Depression (CES-D) Scale. Baseline CES-D depression subscales (depressed and positive affects; somatic complaints) were computed. The Cognitive Abilities Screening Instrument (CASI) measured cognitive performance on a 100-point scale; fluid and crystallized cognitive abilities were derived from CASI factor analysis. Cognition was also evaluated at 4 follow-up examinations over a 20-year period. Multiple regression assessed baseline CES-D subscales as predictors of cognitive change. The baseline covariates analyzed were CASI, age, education, prevalent stroke, APOE ε4 presence, and the longevity-associated FOXO3 genotype.

RESULTS

Cross-sectionally, baseline CES-D subscales were related to cognitive measures; e.g., higher depressed affect was associated with lower crystallized ability (β = -0.058, p ≤ 0.01), and somatic complaints were linked to poorer fluid ability (β = -0.045, p ≤ 0.05) and to worse global cognitive function as measured by total CASI score (β = -0.038, p ≤ 0.05). However, depression subscales did not significantly or consistently predict fluid ability, crystallized ability, or global cognitive performance over time.

CONCLUSION

Psychological and physical well-being were associated with contemporaneous but not subsequent cognitive functioning. Assessment of depressive symptoms may identify individuals who are likely to benefit from interventions to improve mood and somatic health and thereby maintain or enhance cognition.

Potentially Pathogenic SORL1 Mutations Observed in Autosomal-Dominant Cases of Alzheimer's Disease Do Not Modulate APP Physiopathological Processing

The SORL1 gene encodes LR11/SorLA, a protein that binds β-amyloid precursor protein (APP) and drives its intracellular trafficking. SORL1 mutations, occurring frequently in a subset of familial cases of Alzheimer's disease (AD), have been documented, but their pathogenic potential is not yet clear and questions remain concerning their putative influence on the physiopathological processing of APP. We have assessed the influence of two SORL1 mutations that were described as likely disease-causing and that were associated with either benign (SorLA924) or severe (SorLA511) AD phenotypes. We examined the influence of wild-type and mutants SorLA in transiently transfected HEK293 cells expressing either wild-type or Swedish mutated APP on APP expression, secreted Aβ and sAPPα levels, intracellular Aβ 40 and Aβ42 peptides, APP-CTFs (C99 and C83) expressions, α-, β- and γ-secretases expressions and activities as well as Aβ and CTFs-degrading enzymes. These paradigms were studied in control conditions or after pharmacological proteasomal modulation. We also established stably transfected CHO cells expressing wild-type SorLA and established the colocalization of APP and either wild-type or mutant SorLA. SorLA mutations partially disrupt co-localization of wild-type sorLA with APP. Overall, although we mostly confirmed previous data concerning the influence of wild-type SorLA on APP processing, we were unable to evidence significant alterations triggered by our set of SorLA mutants, whatever the cells or pharmacological conditions examined. Our study , however, does not rule out the possibility that other AD-linked SORL1 mutations could indeed affect APP processing, and that pathogenic mutations examined in the present study could interfere with other cellular pathways/triggers in AD.

TBX21, the Master regulator of the type 1 immune response, overexpresses in the leukocytes of peripheral blood in patients with late-onset Alzheimer's disease

BACKGROUND

The involvement of the peripheral immune system in the etiology of neurodegenerative diseases has recently been emphasized. Genome-wide association studies (GWAS) have recently identified several candidate immune genes linked to development of both Alzheimer's disease (AD) and depression. TBX21 (T-bet) which drives the Th1 immune response, is linked to the major depressive disorder (MDD) phenotype. This study investigated the association between the TBX21 immune gene and the possibility of late-onset Alzheimer's disease (LOAD) incidence in 194 LOAD and 200 control subjects using the real-time qPCR and the Tetra-ARMS-PCR methods. We also used an in silico approach to analyze the potential effects imparted by TBX21 rs17244587 and rs41515744 polymorphisms in LOAD pathogenesis.

RESULTS

We found that the TBX21 "immune gene" had significantly elevated mRNA expression levels in the leukocytes of peripheral blood in patients with LOAD (P < 0.0001). We also found an upward trend in TBX21 expression with increasing age in LOAD patients compared to the control group (P < 0.05; CI = 95%). We noticed that the TT genotype of rs41515744 plays a protective role in LOAD incidence, as it attenuates the expression of TBX21 in the control group. We observed that the dominant model of rs41515744 represented a substantial association with LOAD (P = 0.019).

CONCLUSIONS

Our results show for the first time the likely impact of the TBX21 (T-bet) immune gene in LOAD development and that the elevated TBX21 mRNAs in the WBCs of LOAD patients may represent a new easy diagnostic test for Alzheimer's disease.

Scanning Ion-Conductance Microscopy for Studying β-Amyloid Aggregate Formation on Living Cell Surfaces

β-Amyloid aggregation on living cell surfaces is described as responsible for the neurotoxicity associated with different neurodegenerative diseases. It is suggested that the aggregation of β-amyloid (Aβ) peptide on neuronal cell surface leads to various deviations of its vital function due to myriad pathways defined by internalization of calcium ions, apoptosis promotion, reduction of membrane potential, synaptic activity loss, etc. These are associated with structural reorganizations and pathologies of the cell cytoskeleton mainly involving actin filaments and microtubules and consequently alterations of cell mechanical properties. The effect of amyloid oligomers on cells' Young's modulus has been observed in a variety of studies. However, the precise connection between the formation of amyloid aggregates on cell membranes and their effects on the local mechanical properties of living cells is still unresolved. In this work, we have used correlative scanning ion-conductance microscopy (SICM) to study cell topography, Young's modulus mapping, and confocal imaging of Aβ aggregate formation on living cell surfaces. However, it is well-known that the cytoskeleton state is highly connected to the intracellular level of reactive oxygen species (ROS). The effect of Aβ leads to the induction of oxidative stress, actin polymerization, and stress fiber formation. We measured the reactive oxygen species levels inside single cells using platinum nanoelectrodes to demonstrate the connection of ROS and Young's modulus of cells. SICM can be successfully applied to studying the cytotoxicity mechanisms of Aβ aggregates on living cell surfaces.

Update on Nonhuman Primate Models of Brain Disease and Related Research Tools

The aging of the population is an increasingly serious issue, and many age-related illnesses are on the rise. These illnesses pose a serious threat to the health and safety of elderly individuals and create a serious economic and social burden. Despite substantial research into the pathogenesis of these diseases, their etiology and pathogenesis remain unclear. In recent decades, rodent models have been used in attempts to elucidate these disorders, but such models fail to simulate the full range of symptoms. Nonhuman primates (NHPs) are the most ideal neuroscientific models for studying the human brain and are more functionally similar to humans because of their high genetic similarities and phenotypic characteristics in comparison with humans. Here, we review the literature examining typical NHP brain disease models, focusing on NHP models of common diseases such as dementia, Parkinson's disease, and epilepsy. We also explore the application of electroencephalography (EEG), magnetic resonance imaging (MRI), and optogenetic study methods on NHPs and neural circuits associated with cognitive impairment.

Evaluation of Anti-Alzheimer Activity of Synthetic Coumarins by Combination of in Vitro and in Silico Approaches

Series of synthetic coumarin derivatives (1-16) were tested against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), two enzymes linked to the pathology of Alzheimer's disease (AD). Compound 16 was the most active AChE inhibitor with IC₅₀ 32.23±2.91 μM, while the reference (galantamine) had IC₅₀ =1.85±0.12 μM. Compounds 9 (IC₅₀ 75.14±1.82 μM), 13 (IC₅₀ =16.14±0.43 μM), were determined to be stronger BChE inhibitors than the reference galantamine (IC₅₀ =93.53±2.23 μM). The IC₅₀ value of compound 16 for BChE inhibition (IC₅₀ =126.56±11.96 μM) was slightly higher than galantamine. The atomic interactions between the ligands and the key amino acids inside the binding cavities were simulated to determine their ligand-binding positions and free energies. The three inhibitory coumarins (9, 13, 16) were next tested for their effects on the genes associated with AD using human neuroblastoma (SH-SY5Y) cell lines. Our data indicate that they could be considered for further evaluation as new anti-Alzheimer drug candidates.

Involvement of molecular chaperone in protein-misfolding brain diseases

Protein misfolding causes aggregation and build-up in a variety of brain diseases. There are numeral molecules that are linked with the protein homeostasis mechanism. Molecular chaperones are one of such molecules that are responsible for protection against protein misfolded and aggregation-induced neurotoxicity. Many studies have explored the participation of molecular chaperones in Parkinson's disease, Alzheimer's disease, Amyotrophic lateral sclerosis, and Huntington's diseases. In this review, we highlighted the constructive role of molecular chaperones in neurological diseases characterized by protein misfolding and aggregation and their capability to control aberrant protein interactions at an early stage thus successfully suppressing pathogenic cascades. A comprehensive understanding of the protein misfolding associated with brain diseases and the molecular basis of involvement of chaperone against aggregation-induced cellular stress might lead to the progress of new therapeutic intrusion-related to protein misfolding and aggregation.

Nanonization of Magnoflorine-Encapsulated Novel Chitosan-Collagen Nanocapsules for Neurodegenerative Diseases: In Vitro Evaluation

Neurodegeneration is one of the most common diseases in the aged population, characterized by the loss in the function of neuronal cells and their ultimate death. One of the common features in the progression of this type of diseases is the oxidative stress. Drugs which are currently being used have been found to show lateral side effects, which is partly due to their inefficiency to cross blood-brain barrier. Nanoencapsulation of bioactive compounds is a profound approach in this direction and has become a method of choice nowadays. This study involved the evaluation of the anti-oxidative properties of magnoflorine (MF), which is an aporphine quaternary alkaloid, and synthesis of MF-loaded chitosan-collagen nanocapsules (MF-CCNc) for its better efficacy as a potent anti-oxidant. Physiochemical characterization of the synthesized nanocapsules was done by using dynamic light scattering and transmission electron microscopy. It revealed that the synthesized nanocapsules are of small size range, as small as 12 ± 2 nm, and are more or less of spherical shape. Sustained release was shown by MF in the in vitro drug release studies. Both MF and MF-CCNc were found to have good anti-oxidant potential with IC₅₀ < 25 μg/mL. No major cytotoxicity was shown by the synthesized nanocapsules on SH-SY5Y cells. In silico anti-acetylcholinesterase (AChE) studies were also done, and they revealed that MF can be a potent inhibitor of AChE.

Synthesis and biological evaluation of 2-arylbenzofuran derivatives as potential anti-Alzheimer's disease agents

Alzheimer's disease (AD) is a type of progressive dementia caused by degeneration of the nervous system. A single target drug usually does not work well. Therefore, multi-target drugs are designed and developed so that one drug can specifically bind to multiple targets to ensure clinical effectiveness and reduce toxicity. We synthesised a series of 2-arylbenzofuran derivatives and evaluated their in vitro activities. 2-Arylbenzofuran compounds have good dual cholinesterase inhibitory activity and β-secretase inhibitory activity. The IC50 value of compound 20 against acetylcholinesterase inhibition (0.086 ± 0.01 µmol·L-1) is similar to donepezil (0.085 ± 0.01 µmol·L-1) and is better than baicalein (0.404 ± 0.04 µmol·L-1). And most of the compounds have good BACE1 inhibitory activity, of which 3 compounds (8, 19 and 20) show better activity than baicalein (0.087 ± 0.03 µmol·L-1). According to experimental results, 2-arylbenzofuran compounds provide an idea for drug design to develop prevention and treatment for AD.

Using multielectrode arrays to investigate neurodegenerative effects of the amyloid-beta peptide

BACKGROUND

Multielectrode arrays are widely used to analyze the effects of potentially toxic compounds, as well as to evaluate neuroprotective agents upon the activity of neural networks in short- and long-term cultures. Multielectrode arrays provide a way of non-destructive analysis of spontaneous and evoked neuronal activity, allowing to model neurodegenerative diseases in vitro. Here, we provide an overview on how these devices are currently used in research on the amyloid-β peptide and its role in Alzheimer's disease, the most common neurodegenerative disorder.

MAIN BODY

Most of the studies analysed here indicate fast responses of neuronal cultures towards aggregated forms of amyloid-β, leading to increases of spike frequency and impairments of long-term potentiation. This in turn suggests that this peptide might play a crucial role in causing the typical neuronal dysfunction observed in patients with Alzheimer's disease.

CONCLUSIONS

Although the number of studies using multielectrode arrays to examine the effect of the amyloid-β peptide onto neural cultures or whole compartments is currently limited, they still show how this technique can be used to not only investigate the interneuronal communication in neural networks, but also making it possible to examine the effects onto synaptic currents. This makes multielectrode arrays a powerful tool in future research on neurodegenerative diseases.

Possible Preventive Effect of Donepezil and Hyoscyamoside by Reduction of Plaque Formation and Neuroinflammation in Alzheimer's Disease

Background:

Alzheimer disease (AD) is the most common age-dependent dementia. The complex natural accumulation of amyloid beta (Aβ) precursor protein in hippocampus neurons is regarded as the earliest pathological feature of AD, although there are cholinergic assumptions and effective inflammation in AD. In this animal experimental study, we evaluated the preventive effect of hyoscyamoside (Hyo) and donepezil (Dz) on plaque formation and improvement of neurogenic inflammation in AD rats.

Methods:

Dz was prepared and Hyo (steroidal saponin) was isolated from Hyoscymus niger. Then, Wistar rats divided into five groups including negative and positive controls, AD, Dz, and Hyo treatment groups based on the drug exposure and their behavioral alternation was examined using Morris water maze (MWM) test. Bielschowsky staining was used to detect the nerve fibers. Serum levels of interleukin (IL)-4 and IL-6 were evaluated by ELISA. The RNA expression of cyclin-dependent kinase CDK11-P58 in peripheral blood lymphocytes was performed using quantitative PCR.

Results:

The MWM test showed significant changes in time the models spent to find the hidden platform. The Hyo treatment group showed a notable speed change (P < 0.01). The histopathological analysis of the hippocampal tissue revealed the inhibition of Aβ formation in the treatment groups. The treatment groups had a significant decline in the serum level of IL-6, and the IL-4 serum level was increased in the Hyo and Dz treated groups. The expression levels of CDK11-P58 was significantly decreased in the treatment groups.

Conclusions:

In sum, the therapeutic effects of Hyo is comparable with that of Dz in AD rats by suppressing neuroinflammation. Thus, these compounds could be considered as a preventive agent in the AD therapy.

Diabetes and inflammatory diseases: An overview from the perspective of Ca2+/3'-5'-cyclic adenosine monophosphate signaling

A large amount of evidence has supported a clinical link between diabetes and inflammatory diseases, e.g., cancer, dementia, and hypertension. In addition, it is also suggested that dysregulations related to Ca²⁺ signaling could link these diseases, in addition to 3'-5'-cyclic adenosine monophosphate (cAMP) signaling pathways. Thus, revealing this interplay between diabetes and inflammatory diseases may provide novel insights into the pathogenesis of these diseases. Publications involving signaling pathways related to Ca²⁺ and cAMP, inflammation, diabetes, dementia, cancer, and hypertension (alone or combined) were collected by searching PubMed and EMBASE. Both signaling pathways, Ca²⁺ and cAMP signaling, control the release of neurotransmitters and hormones, in addition to neurodegeneration, and tumor growth. Furthermore, there is a clear relationship between Ca²⁺ signaling, e.g., increased Ca²⁺ signals, and inflammatory responses. cAMP also regulates pro- and anti-inflammatory responses. Due to the experience of our group in this field, this article discusses the role of Ca²⁺ and cAMP signaling in the correlation between diabetes and inflammatory diseases, including its pharmacological implications. As a novelty, this article also includes: (1) A timeline of the major events in Ca²⁺/cAMP signaling; and (2) As coronavirus disease 2019 (COVID-19) is an emerging and rapidly evolving situation, this article also discusses recent reports on the role of Ca²⁺ channel blockers for preventing Ca²⁺ signaling disruption due to COVID-19, including the correlation between COVID-19 and diabetes.

The Interactions Between Alzheimer's Disease and Major Depression: Role of Ca2+ Channel Blockers and Ca2+/cAMP Signalling

BACKGROUND

The interactions between Alzheimer's Disease (AD) and major depression can be translated into clinical data showing that depressive patients have had an enhanced risk for developing AD (later in life). The cellular mechanisms involved in these interactions remain under intensive debate in the literature. In addition, the role of a Ca²⁺ homeostasis dysregulation in the pathogenesis of neurodegenerative diseases, like AD, and major depression has been under intensive discussion.

OBJECTIVE

Thus, revealing the interplay between AD and major depression may provide novel insights into the pathogenesis of these diseases.

METHODS

Publications involving Ca²⁺ signalling pathways, AD, and major depression (alone or combined) were collected by searching multiple databases to find the maximum number of relevant citations (using a search strategy with high sensitivity for studies of etiology).

RESULTS

Ca²⁺ Channel Blockers (CCBs), classically prescribed for hypertensive patients, have been demonstrating neuroprotective effects, such as decreasing the incidence of AD in hypertensive patients, including alleviating major depression symptoms. A mechanism under debate is focused on the restoration of the Ca²⁺ homeostasis. Indeed, previous studies of our own have correlated Ca²⁺ and cAMP signalling pathways (Ca²⁺/cAMP signalling) in controlling both the neurotransmitter release and neuronal death. These studies also observed that CCBs can affect Ca²⁺/cAMP signalling.

CONCLUSION

This review discussed the plausible role of Ca²⁺/cAMP signalling in the neuroprotective effects of CCBs, including the participation of Ca²⁺/cAMP signalling in the interactions between major depression and AD. Considering both AD and major depression have become highly prevalent medical problems in the world, the comprehension of the interactions between these diseases could improve drug development.

Correction of microtubule defects within Aβ plaque-associated dystrophic axons results in lowered Aβ release and plaque deposition

The hallmark pathologies of the Alzheimer's disease (AD) brain are amyloid beta (Aβ)-containing senile plaques and neurofibrillary tangles formed from the microtubule (MT)-binding tau protein. Tau becomes hyperphosphorylated and disengages from MTs in AD, with evidence of resulting MT structure/function defects. Brain-penetrant MT-stabilizing compounds can normalize MTs and axonal transport in mouse models with tau pathology, thereby reducing neuron loss and decreasing tau pathology. MT dysfunction is also observed in dystrophic axons adjacent to Aβ plaques, resulting in accumulation of amyloid precursor protein (APP) and BACE1 with the potential for enhanced localized Aβ generation. We have examined whether the brain-penetrant MT-stabilizing compound CNDR-51657 might decrease plaque-associated axonal dystrophy and Aβ release in 5XFAD mice that develop an abundance of Aβ plaques. Administration of CNDR-51657 to 1.5-month-old male and female 5XFAD mice for 4 or 7 weeks led to decreased soluble brain Aβ that coincided with reduced APP and BACE1 levels, resulting in decreased formation of insoluble Aβ deposits. These data suggest a vicious cycle whereby initial Aβ plaque formation causes MT disruption in nearby axons, resulting in the local accumulation of APP and BACE1 that facilitates additional Aβ generation and plaque deposition. The ability of a MT-stabilizing compound to attenuate this cycle, and also reduce deficits resulting from reduced tau binding to MTs, suggests that molecules of this type hold promise as potential AD therapeutics.

A Simple Differentiation Protocol for Generation of Induced Pluripotent Stem Cell-Derived Basal Forebrain-Like Cholinergic Neurons for Alzheimer's Disease and Frontotemporal Dementia Disease Modeling

The study of neurodegenerative diseases using pluripotent stem cells requires new methods to assess neurodevelopment and neurodegeneration of specific neuronal subtypes. The cholinergic system, characterized by its use of the neurotransmitter acetylcholine, is one of the first to degenerate in Alzheimer’s disease and is also affected in frontotemporal dementia. We developed a differentiation protocol to generate basal forebrain-like cholinergic neurons (BFCNs) from induced pluripotent stem cells (iPSCs) aided by the use of small molecule inhibitors and growth factors. Ten iPSC lines were successfully differentiated into BFCNs using this protocol. The neuronal cultures were characterised through RNA and protein expression, and functional analysis of neurons was confirmed by whole-cell patch clamp. We have developed a reliable protocol using only small molecule inhibitors and growth factors, while avoiding transfection or cell sorting methods, to achieve a BFCN culture that expresses the characteristic markers of cholinergic neurons.

Therapeutic Potentials of Scavenger Receptor CD36 Mediated Innate Immune Responses Against Infectious and Non-Infectious Diseases

CD36 is a multifunctional glycoprotein, expressed in different types of cells and known to play a significant role in the pathophysiology of the host. The structural studies revealed that the scavenger receptor consists of short cytosolic domains, two transmembrane domains, and a large ectodomain. The ectodomain serves as a receptor for a diverse number of endogenous and exogenous ligands. The CD36-specific ligands are involved in regulating the immune response during infectious and non-infectious diseases in the host. The role of CD36 in regulating the innate immune response during Pneumonia, Tuberculosis, Malaria, Leishmaniasis, HIV, and Sepsis in a ligand- mediated fashion. Apart from infectious diseases, it is also considered to be involved in metabolic disorders such as Atherosclerosis, Alzheimer's, cancer, and Diabetes. The ligand binding to scavenger receptor modulates the CD36 down-stream innate immune response, and it can be exploited to design suitable immuno-modulators. Hence, the current review focused on the role of the CD36 in innate immune response and therapeutic potentials of novel heterocyclic compounds as CD36 ligands during infectious and non-infectious diseases.

The Beta Amyloid Dysfunction (BAD) Hypothesis for Alzheimer's Disease

Beta amyloid, Aβ 1–42, originally named as Amyloid A4 protein, is one of the most investigated peptides in neuroscience and has attracted substantial interest since its discovery as the main insoluble fibril-type protein in cerebrovascular amyloid angiopathy (Glenner and Wong, 1984; Masters et al., 1985) of Alzheimer’s disease (AD). From the very beginning, Aβ was regarded per se as a “bad molecule,” triggering the so-called “beta amyloid cascade hypothesis” (Hardy and Higgins, 1992). This hypothesis ignored any physiological function for in situ generated Aβ monomer with normal production and turnover rate (Bateman et al., 2006). Accordingly, pan-Aβ-related therapeutic approaches were designed to eliminate or lower the three structural isoforms in parallel: (1) the pre-amyloid monomer, (2) the misfolded oligomer, and (3) the final fibril. While we already knew about poor correlations between plaques and cognitive decline quite early (Terry et al., 1991), data for an essential benign physiological role for Aβ monomer at low concentrations were also not considered to be relevant. Here, a different Beta Amyloid hypothesis is described, the so-called “Beta Amyloid Dysfunction hypothesis,” which, in contrast to the “Beta Amyloid Cascade hypothesis,” builds on the homeostasis of essential Aβ monomer in the synaptic vesicle cycle (SVC). Disease-relevant early pathology emerges through disturbance of the Aβ homeostasis by so far unknown factors leading to the formation of misfolded Aβ oligomers. These early species interfere with the synaptic physiological Aβ monomer regulation and exert their neurotoxicity via various receptors for sticky oligomer-type Aβ aggregates. The Beta Amyloid Dysfunction (BAD) hypothesis is introduced and shown to explain negative clinical results of Gamma-secretase and Beta-secretase (BACE) inhibitors as well as pan-Aβ isotype unselective immunotherapies. This hypothesis gives guidance to what needs to be done therapeutically to revive successful clinical testing in AD for this highly validated target. The BAD hypothesis will need further refinement in particular through more detailed exploration for the role of physiological Aβ monomer.

Circulatory Levels of Toxic Metals (Aluminum, Cadmium, Mercury, Lead) in Patients with Alzheimer's Disease: A Quantitative Meta-Analysis and Systematic Review

BACKGROUND

Environmental exposure to toxic metals has been postulated to play a role in the pathophysiological processes of Alzheimer's disease (AD). However, the circulatory levels of toxic metals in AD patients are not consistent in previous studies.

OBJECTIVE

To systematically assess levels of toxic metals (aluminum, mercury, cadmium, lead) in the circulation (blood, serum/plasma) of AD patients and controls.

METHODS

PubMed, Web of Science, Science Direct, Cochrane Library, and the China National Knowledge Infrastructure (CNKI) were systematically searched to identify studies published up to January 1, 2017. Meta-analyses were performed using random-effects models and the pooled standardized mean difference (SMD) were reported with 95% confidence intervals (CI).

RESULTS

We identified 17, 7, 8, and 10 studies for aluminum, mercury, cadmium, and lead, respectively. Meta-analyses showed significantly elevated circulatory levels of aluminum (SMD = 1.08, 95% CI: 0.66, 1.50), mercury (SMD = 0.55, 95% CI, 0.15, 0.95), and cadmium (SMD = 0.62, 95% CI: 0.12, 1.11), whereas lower levels of lead (SMD = -0.23, 95% CI: -0.38, -0.07) in AD patients than in controls. Publication bias was only observed for aluminum studies, but the "trim and fill" analysis showed that the publication bias did not alter the direction of the effect. Sensitivity analyses showed no studies from the pooled analysis changed the results.

CONCLUSION

Compared to controls, circulatory levels of aluminum, mercury, and cadmium are significantly higher but the levels of lead were reduced in AD patients. These findings suggest that elevated aluminum, mercury, and cadmium in the circulation, especially in serum may play a role in the progression of AD.

Relationship of polymorphisms and haplotype in interleukin-16 and adiponectin gene with late-onset Alzheimer's disease risk

Aims

To investigate the impact of Interleukin-16 (IL- 16) and Adiponectin (ANP) gene single nucleotide polymorphisms (SNPs), gene- gene interactions and haplotype on late-onset Alzheimer’s disease (LOAD) risk.

Methods

Hardy-Weinberg equilibrium (HWE), haplotype and pairwise linkage disequilibrium (LD) analysis were investigated by using SNPstats (available online at http://bioinfo.iconcologia.net/SNPstats). Generalized multifactor dimensionality reduction (GMDR) was used to examine interaction among 4 SNPs, odds ratio (OR) and 95% confident interval (95%CI) were calculated by logistic regression model.

Results

LOAD risk was significantly higher in carriers of rs266729- G allele than those with CC genotype (CG+ GG versus CC), OR (95%CI) =1.61 (1.26-1.96), and higher in carriers of rs1501299- T allele, OR (95%CI) = 1.62 (1.32-2.12), lower in carriers of rs4072111- T allele, adjusted OR (95%CI) =0.65 (0.44-0.93). We also found a significant gene- gene interaction between rs266729 and rs4072111. Participants with CG or GG of rs266729 and CC of rs4072111 genotype have the highest LOAD risk, OR (95%CI) = 2.62 (1.64 -3.58). Haplotype containing the rs266729- G and rs1501299- T alleles were associated with increased LOAD risk, OR (95%CI)= 1.83 (1.32- 2.43), and haplotype containing the rs1131445- C and rs4072111- T alleles were associated with decreased LOAD risk, OR (95%CI)= 0.53 (0.18- 0.95).

Conclusions

We concluded that rs266729 and rs1501299 minor alleles were associated with increased LOAD risk, but rs4072111 minor allele was associated with decreased LOAD risk. We also found that interaction involving rs266729 and rs4072111, and haplotype combinations were associated with LOAD risk.

Do anti-amyloid beta protein antibody cross reactivities confound Alzheimer disease research?

Background

Alzheimer disease (AD) research has focussed mainly on the amyloid beta protein (Aβ). However, many Aβ-and P3-type peptides derived from the amyloid precursor protein (APP) and peptides thought to derive from Aβ catabolism share sequence homology. Additionally, conformations can change dependent on aggregation state and solubility leading to significant uncertainty relating to interpretations of immunoreactivity with antibodies raised against Aβ. We review evidence relating to the reactivities of commonly used antibodies including 6F3D, 6E10 and 4G8 and evaluate their reactivity profiles with respect to AD diagnosis and research.

Results

Antibody cross-reactivities between Aβ-type, P3-type and Aβ-catabolic peptides confound interpretations of immunoreactivity. More than one antibody is required to adequately characterise Aβ. The relationships between anti-Aβ immunoreactivity, neuropathology and proposed APP cleavages are unclear.

Conclusions

We find that the concept of Aβ lacks clarity as a specific entity. Anti-Aβ antibody cross-reactivities lead to significant uncertainty in our understanding of the APP proteolytic system and its role in AD with profound implications for current research and therapeutic strategies.

Altered microtubule dynamics in neurodegenerative disease: Therapeutic potential of microtubule-stabilizing drugs

Many neurodegenerative diseases are characterized by deficiencies in neuronal axonal transport, a process in which cellular cargo is shuttled with the aid of molecular motors from the cell body to axonal termini and back along microtubules (MTs). Proper axonal transport is critical to the normal functioning of neurons, and impairments in this process could contribute to the neuronal damage and death that is characteristic of neurodegenerative disease. Although the causes of axonal transport abnormalities may vary among the various neurodegenerative conditions, in many cases it appears that the transport deficiencies result from a diminution of axonal MT stability. Here we review the evidence of MT abnormalities in a number of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and traumatic brain injury, and highlight the potential benefit of MT-stabilizing agents in improving axonal transport and nerve function in these diseases. Moreover, we discuss the challenges associated with the utilization of MT-stabilizing drugs as therapeutic candidates for neurodegenerative conditions.

Phosphorylation of the amyloid β-peptide at Ser26 stabilizes oligomeric assembly and increases neurotoxicity

Aggregation and toxicity of the amyloid β-peptide (Aβ) are considered as critical events in the initiation and progression of Alzheimer's disease (AD). Recent evidence indicated that soluble oligomeric Aβ assemblies exert pronounced toxicity, rather than larger fibrillar aggregates that deposit in the forms of extracellular plaques. While some rare mutations in the Aβ sequence that cause early-onset AD promote the oligomerization, molecular mechanisms that induce the formation or stabilization of oligomers of the wild-type Aβ remain unclear. Here, we identified an Aβ variant phosphorylated at Ser26 residue (pSer26Aβ) in transgenic mouse models of AD and in human brain that shows contrasting spatio-temporal distribution as compared to non-phosphorylated Aβ (npAβ) or other modified Aβ species. pSer26Aβ is particularly abundant in intraneuronal deposits at very early stages of AD, but much less in extracellular plaques. pSer26Aβ assembles into a specific oligomeric form that does not proceed further into larger fibrillar aggregates, and accumulates in characteristic intracellular compartments of granulovacuolar degeneration together with TDP-43 and phosphorylated tau. Importantly, pSer26Aβ oligomers exert increased toxicity in human neurons as compared to other known Aβ species. Thus, pSer26Aβ could represent a critical species in the neurodegeneration during AD pathogenesis.

The new β amyloid-derived peptide Aβ1-6A2V-TAT(D) prevents Aβ oligomer formation and protects transgenic C. elegans from Aβ toxicity

One attractive pharmacological strategy for Alzheimer's disease (AD) is to design small peptides to interact with amyloid-β (Aβ) protein reducing its aggregation and toxicity. Starting from clinical observations indicating that patients coding a mutated Aβ variant (AβA2V) in the heterozygous state do not develop AD, we developed AβA2V synthetic peptides, as well as a small peptide homologous to residues 1-6. These hindered the amyloidogenesis of Aβ and its neurotoxicity in vitro, suggesting a basis for the design of a new small peptide in D-isomeric form, linked to the arginine-rich TAT sequence [Aβ1-6A2V-TAT(D)], to allow translocation across biological membranes and the blood-brain barrier. Aβ1-6A2V-TAT(D) was resistant to protease degradation, stable in serum and specifically able to interfere with Aβ aggregation in vitro, reducing the appearance of toxic soluble species and protecting transgenic C. elegans from toxicity related to the muscular expression of human Aβ. These observations offer a proof of concept for future pharmacological studies in mouse models of AD, providing a foundation for the design of AβA2V-based peptidomimetic molecules for therapeutic purposes.

Alzheimer's as a Systems-Level Disease Involving the Interplay of Multiple Cellular Networks

Alzheimer's disease (AD), and many neurodegenerative disorders, are multifactorial in nature. They involve a combination of genomic, epigenomic, interactomic and environmental factors. Progress is being made, and these complex diseases are beginning to be understood as having their origin in altered states of biological networks at the cellular level. In the case of AD, genomic susceptibility and mechanisms leading to (or accompanying) the impairment of the central Amyloid Precursor Protein (APP) processing and tau networks are widely accepted as major contributors to the diseased state. The derangement of these networks may result in both the gain and loss of functions, increased generation of toxic species (e.g., toxic soluble oligomers and aggregates) and imbalances, whose effects can propagate to supra-cellular levels. Although well sustained by empirical data and widely accepted, this global perspective often overlooks the essential roles played by the main counteracting homeostatic networks (e.g., protein quality control/proteostasis, unfolded protein response, protein folding chaperone networks, disaggregases, ER-associated degradation/ubiquitin proteasome system, endolysosomal network, autophagy, and other stress-protective and clearance networks), whose relevance to AD is just beginning to be fully realized. In this chapter, an integrative perspective is presented. Alzheimer's disease is characterized to be a result of: (a) intrinsic genomic/epigenomic susceptibility and, (b) a continued dynamic interplay between the deranged networks and the central homeostatic networks of nerve cells. This interplay of networks will underlie both the onset and rate of progression of the disease in each individual. Integrative Systems Biology approaches are required to effect its elucidation. Comprehensive Systems Biology experiments at different 'omics levels in simple model organisms, engineered to recapitulate the basic features of AD may illuminate the onset and sequence of events underlying AD. Indeed, studies of models of AD in simple organisms, differentiated cells in culture and rodents are beginning to offer hope that the onset and progression of AD, if detected at an early stage, may be stopped, delayed, or even reversed, by activating or modulating networks involved in proteostasis and the clearance of toxic species. In practice, the incorporation of next-generation neuroimaging, high-throughput and computational approaches are opening the way towards early diagnosis well before irreversible cell death. Thus, the presence or co-occurrence of: (a) accumulation of toxic Aβ oligomers and tau species; (b) altered splicing and transcriptome patterns; (c) impaired redox, proteostatic, and metabolic networks together with, (d) compromised homeostatic capacities may constitute relevant 'AD hallmarks at the cellular level' towards reliable and early diagnosis. From here, preventive lifestyle changes and tailored therapies may be investigated, such as combined strategies aimed at both lowering the production of toxic species and potentiating homeostatic responses, in order to prevent or delay the onset, and arrest, alleviate, or even reverse the progression of the disease.

The cell-permeable Aβ1-6A2VTAT(D) peptide reverts synaptopathy induced by Aβ1-42wt

Alzheimer disease (AD) is the most prevalent form of dementia. Loss of hippocampal synapses is the first neurodegenerative event in AD. Synaptic loss has been associated with the accumulation in the brain parenchyma of soluble oligomeric forms of amyloid β peptide (Aβ1-42wt). Clinical observations have shown that a mutation in the APP protein (A673V) causes an early onset AD-type dementia in homozygous carriers while heterozygous carriers are unaffected. This mutation leads to the formation of mutated Aβ peptides (Aβ1-42A2V) in homozygous patients, while in heterozygous subjects both Aβ1-42wt and Aβ1-42A2V are present. To better understand the impact of the A673V mutation in AD, we analyzed the synaptotoxic effect of oligomers formed by aggregation of different Aβ peptides (Aβ1-42wt or Aβ1-42A2V) and the combination of the two Aβ1-42MIX (Aβ1-42wt and Aβ1-42A2V) in an in vitro model of synaptic injury. We showed that Aβ1-42A2V oligomers are more toxic than Aβ1-42wt oligomers in hippocampal neurons, confirming the results previously obtained in cell lines. Furthermore, we reported that oligomers obtained by the combination of both wild type and mutated peptides (Aβ1-42MIX) did not exert synaptic toxicity. We concluded that the combination of Aβ1-42wt and Aβ1-42A2V peptides hinders the toxicity of Aβ1-42A2V and counteracts the manifestation of synaptopathy in vitro. Finally we took advantage of this finding to generate a cell-permeable peptide for clinical application, by fusing the first six residues of the Aβ1-42A2V to the TAT cargo sequence (Aβ1-6A2VTAT(D)). Noteworthy, the treatment with Aβ1-6A2VTAT(D) confers neuroprotection against both in vitro and in vivo synaptopathy models. Therefore Aβ1-6A2VTAT(D) may represent an innovative therapeutic tool to prevent synaptic degeneration in AD.

Hippocampal neurogenesis in the APP/PS1/nestin-GFP triple transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is one of the most common causes of dementia. Although the exact mechanisms of AD are not entirely clear, the impairment in adult hippocampal neurogenesis has been reported to play a role in AD. To assess the relationship between AD and neurogenesis, we studied APP/PS1/nestin-green fluorescent protein (GFP) triple transgenic mice, a well-characterized mouse model of AD, which express GFP under the control of the nestin promoter. Different ages of AD mice and their wild-type littermates (WT) were used in our study. Immunofluorescent staining showed that neurogenesis occurred mainly in the subgranular zone (SGZ) of the dentate gyrus (DG) and subventricular zone (SVZ) of the lateral ventricles (LVs). The expression of neural stem cells (NSCs) (nestin) and neural precursors such as doublecortin (DCX) and GFAP in AD mice were decreased with age, as well as there being a reduction in 5-bromo-2-deoxyuridine (BrdU)-positive cells, when compared to WT. However, the number of maturate neurons (NeuN) was not significantly different between AD mice and wild-type controls, and NeuN changed only slightly with age. By Golgi-Cox staining, the morphologies of dendrites were observed, and significant differences existed between AD mice and wild-type controls. These results suggest that AD has a far-reaching influence on the regulation of adult hippocampal neurogenesis, leading to a gradual decrease in the generation of neural progenitors (NPCs), and inhibition of the differentiation and maturation of neurons.

Association between polymorphisms in Interleukin-16 gene and risk of late-onset Alzheimer's disease

Cytokines play important roles in the inflammation pathways. Alzheimer's disease (AD) is an inflammatory disease, and it is suggested that cytokines are able to influence AD. We investigated the association between IL16 polymorphisms and risk of AD in an Iranian population. The case group consisted of 144 individuals with AD and the control group included 173 healthy individuals. Genotyping of the IL16 rs4072111 C>T and rs1131445 T>C polymorphisms was determined using PCR-RFLP method. The frequency of rs4072111 CT genotype was significantly lower (P=0.007; OR=0.5, 95% CI: 0.3-0.8) in the patients (17.3%) than the control group (30%). The rs4072111 T allele was significantly lower (P=0.008; OR=0.5, 95% CI: 0.3-0.9) in the cases (8.6%) compared with the control group (15.6%). The IL16 rs4072111 polymorphism may be associated with susceptibility to AD and the T allele may have a protective role in the progression of AD in an Iranian population.

Genetic Modifiers of Age at Onset in Carriers of the G206A Mutation in PSEN1 With Familial Alzheimer Disease Among Caribbean Hispanics

IMPORTANCE

The present study identified potential genetic modifiers that may delay or accelerate age at onset of familial Alzheimer disease (AD) by examining age at onset in PSEN1 mutation carrier families, and further investigation of these modifiers may provide insight into the pathobiology of AD and potential therapeutic measures.

OBJECTIVE

To identify genetic variants that modify age at onset of AD.

DESIGN, SETTING, AND PARTICIPANTS

Using a subset of Caribbean Hispanic families that carry the PSEN1 p.G206A mutation, we performed a 2-stage genome study. The mutation carrier families from an ongoing genetic study served as a discovery set, and the cohort of those with LOAD served as a confirmation set. To identify candidate loci, we performed linkage analysis using 5 p.G206A carrier families (n = 56), and we also performed whole-exome association analysis using 31 p.G206A carriers from 26 families. To confirm the genetic modifiers identified from the p.G206A carrier families, we analyzed the GWAS data for 2888 elderly individuals with LOAD. All study participants were Caribbean Hispanics.

MAIN OUTCOMES AND MEASURES

Age at onset of AD.

RESULTS

Linkage analysis of AD identified the strongest linkage support at 4q35 (LOD [logarithm of odds] score, 3.69), and the GWAS of age at onset identified variants on 1p13.1, 2q13, 4q25, and 17p11. In the confirmation stage, genewise analysis identified SNX25, PDLIM3, and 3 SH3 domain genes (SORBS2, SH3RF3, and NPHP1) to be significantly associated with LOAD. Subsequent allelic association analysis confirmed SNX25, PDLIM3, and SORBS2 as genetic modifiers of age at onset of EOAD and LOAD and provided modest support for SH3RF3 and NPHP1.

CONCLUSIONS AND RELEVANCE

Our 2-stage analysis revealed that SNX25, PDLIM3, and SORBS2 may serve as genetic modifiers of age at onset in both EOAD and LOAD.

Eleutheroside B or E enhances learning and memory in experimentally aged rats

Eleutheroside B or E, the main component of Acanthopanax, can relieve fatigue, enhance memory, and improve human cognition. Numerous studies have confirmed that high doses of acetylcholine significantly attenuate clinical symptoms and delay the progression of Alzheimer's disease. The present study replicated a rat model of aging induced by injecting quinolinic acid into the hippocampal CA1 region. These rats were intraperitoneally injected with low, medium and high doses of eleutheroside B or E (50, 100, 200 mg/kg), and rats injected with Huperzine A or PBS were used as controls. At 4 weeks after administration, behavioral tests showed that the escape latencies and errors in searching for the platform in a Morris water maze were dose-dependently reduced in rats treated with medium and high-dose eleutheroside B or E. Hematoxylin-eosin staining showed that the number of surviving hippocampal neurons was greater and pathological injury was milder in three eleutheroside B or E groups compared with model group. Hippocampal homogenates showed enhanced cholinesterase activity, and dose-dependent increases in acetylcholine content and decreases in choline content following eleutheroside B or E treatment, similar to those seen in the Huperzine A group. These findings indicate that eleutheroside B or E improves learning and memory in aged rats. These effects of eleutheroside B or E may be mediated by activation of cholinesterase or enhanced reuse of choline to accelerate the synthesis of acetylcholine in hippocampal neurons.

Alzheimer's disease and HLA-A2: linking neurodegenerative to immune processes through an in silico approach

There is a controversial relationship between HLA-A2 and Alzheimer's disease (AD). It has been suggested a modifier effect on the risk that depends on genetic loadings. Thus, the aims of this study were to evaluate this relationship and to reveal genes associated with both concepts the HLA-A gene and AD. Consequently, we did first a classical systematic review and a meta-analysis of case-control studies. Next, by means of an in silico approach, we used experimental knowledge of protein-protein interactions to evaluate the top ranked genes shared by both concepts, previously found through text mining. The meta-analysis did not show a significant pooled OR (1.11, 95% CI: 0.98 to 1.24 in Caucasians), in spite of the fact that four of the included studies had a significant OR > 1 and none of them a significant OR < 1. In contrast, the in silico approach retrieved nonrandomly shared genes by both concepts (P = 0.02), which additionally encode truly interacting proteins. The network of proteins encoded by APP, ICAM-1, ITGB2, ITGAL, SELP, SELL, IL2, IL1B, CD4, and CD8A linked immune to neurodegenerative processes and highlighted the potential roles in AD pathogenesis of endothelial regulation, infectious diseases, specific antigen presentation, and HLA-A2 in maintaining synapses.

The FAM3 superfamily member ILEI ameliorates Alzheimer's disease-like pathology by destabilizing the penultimate amyloid-β precursor

Accumulation of amyloid-β peptide (Aβ) in the brain underlies the pathogenesis of Alzheimer's disease (AD). Aβ is produced by β- and γ-secretase-mediated sequential proteolysis of amyloid-β precursor protein (APP). Here we identify a secretory protein named interleukin-like epithelial-mesenchymal transition inducer (ILEI, also known as FAM3 superfamily member C) as a negative regulator of Aβ production. ILEI destabilizes the β-secretase-cleaved APP carboxy-terminal fragment, the penultimate precursor of Aβ, by binding to the γ-secretase complex and interfering with its chaperone properties. Notch signalling and γ-secretase activity are not affected by ILEI. We also show neuronal expression of ILEI and its induction by transforming growth factor-β signalling. The level of secreted ILEI is markedly decreased in the brains of AD patients. Transgenic (Tg) overexpression of ILEI significantly reduces the brain Aβ burden and ameliorates the memory deficit in AD model mice. ILEI may be a plausible target for the development of disease-modifying therapies.

Disease-related mutations among Caribbean Hispanics with familial dementia

Pathogenic mutations in the three known genes – the amyloid precursor protein (APP), presenilin 1 (PSEN1), presenilin 2 (PSEN2) – are known to cause familial Alzheimer's disease (AD) and tend to be associated with early-onset AD. However, the frequency and risk associated with these mutations vary widely. In addition, mutations in the frontotemporal lobar degeneration (FTLD) genes – the microtubule-associated protein tau (MAPT), granulin (GRN) – have also been found to be associated with clinical AD. Here, we conducted targeted resequencing of the exons in genes encoding APP, PSEN1, PSEN2, GRN, and MAPT in 183 individuals from families with four or more affected relatives, presumed to be AD, and living in the Dominican Republic and Puerto Rico. We then performed linkage and family-based association analyses in carrier families, and genotyped 498 similarly aged unrelated controls from the same ethnic background. Twelve potentially pathogenic mutations were found to be associated with disease in 53 individuals in the five genes. The most frequently observed mutation was the p.Gly206Ala variant in PSEN1 present in 30 (57%) of those sequenced. In the combined linkage and association analyses several rare variants were associated with dementia. In Caribbean Hispanics with familial AD, potentially pathogenic variants were present in 29.2%, four were novel mutations, while eight had been previously observed. In addition, some family members carried variants in the GRN and MAPT genes which are associated with FTLD.

The sodium leak channel, NALCN, in health and disease

Ion channels are crucial components of cellular excitability and are involved in many neurological diseases. This review focuses on the sodium leak, G protein-coupled receptors (GPCRs)-activated NALCN channel that is predominantly expressed in neurons where it regulates the resting membrane potential and neuronal excitability. NALCN is part of a complex that includes not only GPCRs, but also UNC-79, UNC-80, NLF-1 and src family of Tyrosine kinases (SFKs). There is growing evidence that the NALCN channelosome critically regulates its ion conduction. Both in mammals and invertebrates, animal models revealed an involvement in many processes such as locomotor behaviors, sensitivity to volatile anesthetics, and respiratory rhythms. There is also evidence that alteration in this NALCN channelosome can cause a wide variety of diseases. Indeed, mutations in the NALCN gene were identified in Infantile Neuroaxonal Dystrophy (INAD) patients, as well as in patients with an Autosomal Recessive Syndrome with severe hypotonia, speech impairment, and cognitive delay. Deletions in NALCN gene were also reported in diseases such as 13q syndrome. In addition, genes encoding NALCN, NLF- 1, UNC-79, and UNC-80 proteins may be susceptibility loci for several diseases including bipolar disorder, schizophrenia, Alzheimer's disease, autism, epilepsy, alcoholism, cardiac diseases and cancer. Although the physiological role of the NALCN channelosome is poorly understood, its involvement in human diseases should foster interest for drug development in the near future. Toward this goal, we review here the current knowledge on the NALCN channelosome in physiology and diseases.

Overexpression of the IGF-II/M6P receptor in mouse fibroblast cell lines differentially alters expression profiles of genes involved in Alzheimer's disease-related pathology

Alzheimer’s disease (AD) is the most common type of senile dementia affecting elderly people. The processing of amyloid precursor protein (APP) leading to the generation of β-amyloid (Aβ) peptide contributes to neurodegeneration and development of AD pathology. The endocytic trafficking pathway, which comprises of the endosomes and lysosomes, acts as an important site for Aβ generation, and endocytic dysfunction has been linked to increased Aβ production and loss of neurons in AD brains. Since insulin-like growth factor-II (IGF-II) receptor plays a critical role in the transport of lysosomal enzymes from the trans-Golgi network to endosomes, it is likely that the receptor may have a role in regulating Aβ metabolism in AD pathology. However, very little is known on how altered levels of the IGF-II receptor can influence the expression/function of various molecules involved in AD pathology. To address this issue, we evaluated the expression profiles of 87 selected genes related to AD pathology in mouse fibroblast MS cells that are deficient in murine IGF-II receptor and corresponding MS9II cells overexpressing ∼500 times the human IGF-II receptors. Our results reveal that an elevation in IGF-II receptor levels alters the expression profiles of a number of genes including APP as well as enzymes regulating Aβ production, degradation and clearance mechanisms. Additionally, it influences the expression of various lysosomal enzymes and protein kinases that are involved in Aβ toxicity. IGF-II receptor overexpression also alters expression of several genes involved in intracellular signalling as well as cholesterol metabolism, which play a critical role in AD pathology. The altered gene profiles observed in this study closely match with the corresponding protein levels, with a few exceptions. These results, taken together, suggest that an elevation in IGF-II receptor levels can influence the expression profiles of transcripts as well as proteins that are involved in AD pathogenesis.

Cross-talk of membrane lipids and Alzheimer-related proteins

Alzheimer’s disease (AD) is neuropathologically characterized by the combined occurrence of extracellular β-amyloid plaques and intracellular neurofibrillary tangles in the brain. While plaques contain aggregated forms of the amyloid β-peptide (Aβ), tangles are formed by fibrillar forms of the microtubule associated protein tau. All mutations identified so far to cause familial forms of early onset AD (FAD) are localized close to or within the Aβ domain of the amyloid precursor protein (APP) or in the presenilin proteins that are essential components of a protease complex involved in the generation of Aβ. Mutations in the tau gene are not associated with FAD, but can cause other forms of dementia. The genetics of FAD together with biochemical and cell biological data, led to the formulation of the amyloid hypothesis, stating that accumulation and aggregation of Aβ is the primary event in the pathogenesis of AD, while tau might mediate its toxicity and neurodegeneration.

The generation of Aβ involves sequential proteolytic cleavages of the amyloid precursor protein (APP) by enzymes called β-and γ-secretases. Notably, APP itself as well as the secretases are integral membrane proteins. Thus, it is very likely that membrane lipids are involved in the regulation of subcellular transport, activity, and metabolism of AD related proteins.

Indeed, several studies indicate that membrane lipids, including cholesterol and sphingolipids (SLs) affect Aβ generation and aggregation. Interestingly, APP and other AD associated proteins, including β-and γ-secretases can, in turn, influence lipid metabolic pathways. Here, we review the close connection of cellular lipid metabolism and AD associated proteins and discuss potential mechanisms that could contribute to initiation and progression of AD.

Decreased cognitive function in extended family members from the single late-onset-Alzheimer's-disease pedigree

A family history of dementia is associated with an increased risk of developing Alzheimer's disease (AD) late in life (LOAD). This study marked the first attempt to assess the familial contribution to differences in cognitive performance in a large family-based group in the Chinese community. We enrolled 168 participants without dementia from a single pedigree with 9 probable AD patients diagnosed after age 65. These participants were evaluated with a comprehensive neuropsychological battery, the Chinese version of the Mini Mental State Examination, and the Alzheimer Disease Assessment Scale-Cognitive Subscale. Analyses found that extended family members of the LOAD pedigree showed similar performance on measures of global cognitive function and semantic memory compared to controls, but lower scores on episodic memory, attention, and executive function measures. These results indicate that the genetic influences on certain sub-cognitive domains are more detectable despite normal global cognitive function, and that family members with the LOAD pedigree are at risk for developing LOAD by virtue of their family history with an additive risk due to increased age. The findings in this study support the importance of documenting if there is a positive family history of AD in clinical evaluations.

Curcumin and its derivatives: their application in neuropharmacology and neuroscience in the 21st century

Curcumin (diferuloylmethane), a polyphenol extracted from the plant Curcuma longa, is widely used in Southeast Asia, China and India in food preparation and for medicinal purposes. Since the second half of the last century, this traditional medicine has attracted the attention of scientists from multiple disciplines to elucidate its pharmacological properties. Of significant interest is curcumin's role to treat neurodegenerative diseases including Alzheimer's disease (AD), and Parkinson's disease (PD) and malignancy. These diseases all share an inflammatory basis, involving increased cellular reactive oxygen species (ROS) accumulation and oxidative damage to lipids, nucleic acids and proteins. The therapeutic benefits of curcumin for these neurodegenerative diseases appear multifactorial via regulation of transcription factors, cytokines and enzymes associated with (Nuclear factor kappa beta) NFκB activity. This review describes the historical use of curcumin in medicine, its chemistry, stability and biological activities, including curcumin's anti-cancer, anti-microbial, anti-oxidant, and anti-inflammatory properties. The review further discusses the pharmacology of curcumin and provides new perspectives on its therapeutic potential and limitations. Especially, the review focuses in detail on the effectiveness of curcumin and its mechanism of actions in treating neurodegenerative diseases such as Alzheimer's and Parkinson's diseases and brain malignancies.

An intracellular threonine of amyloid-β precursor protein mediates synaptic plasticity deficits and memory loss

Mutations in Amyloid-ß Precursor Protein (APP) and BRI2/ITM2b genes cause Familial Alzheimer and Danish Dementias (FAD/FDD), respectively. APP processing by BACE1, which is inhibited by BRI2, yields sAPPß and ß-CTF. ß-CTF is cleaved by gamma-secretase to produce Aß. A knock-in mouse model of FDD, called FDDKI, shows deficits in memory and synaptic plasticity, which can be attributed to sAPPß/ß-CTF but not Aß. We have investigated further the pathogenic function of ß-CTF focusing on Thr(668) of ß-CTF because phosphorylation of Thr(668) is increased in AD cases. We created a knock-in mouse bearing a Thr(668)Ala mutation (APP(TA) mice) that prevents phosphorylation at this site. This mutation prevents the development of memory and synaptic plasticity deficits in FDDKI mice. These data are consistent with a role for the carboxyl-terminal APP domain in the pathogenesis of dementia and suggest that averting the noxious role of Thr(668) is a viable therapeutic strategy for human dementias.

S14G-humanin inhibits Aβ1-42 fibril formation, disaggregates preformed fibrils, and protects against Aβ-induced cytotoxicity in vitro

The aggregation of soluble amyloid-beta (Aβ) peptide into oligomers/fibrils is one of the key pathological features in Alzheimer's disease (AD). The Aβ aggregates are considered to play a pivotal role in the pathogenesis of AD. Therefore, inhibiting Aβ aggregation and destabilizing preformed Aβ fibrils would be an attractive therapeutic target for prevention and treatment of AD. S14G-humanin (HNG), a synthetic derivative of Humanin (HN), has been shown to be a strong neuroprotective agent against various AD-related insults. Recent studies have shown that HNG can significantly improve cognitive deficits and reduce insoluble Aβ levels as well as amyloid plaque burden without affecting amyloid precursor protein processing and Aβ production in transgenic AD models. However, the potential mechanisms by which HNG reduces Aβ-related pathology in vivo remain obscure. In the present study, we found that HNG could significantly inhibit monomeric Aβ1-42 aggregation into fibrils and destabilize preformed Aβ1-42 fibrils in a concentration-dependent manner by Thioflavin T fluorescence assay. In transmission electron microscope study, we observed that HNG was effective in inhibiting Aβ1-42 fibril formation and disrupting preformed Aβ1-42 fibrils, exhibiting various types of amorphous aggregates without identifiable Aβ fibrils. Furthermore, HNG-treated monomeric or fibrillar Aβ1-42 was found to significantly reduce Aβ1-42-mediated cytotoxic effects on PC12 cells in a dose-dependent manner by MTT assay. Collectively, our results demonstrate for the first time that HNG not only inhibits Aβ1-42 fibril formation but also disaggregates preformed Aβ1-42 fibrils, which provides the novel evidence that HNG may have anti-Aβ aggregation and fibrillogenesis, and fibril-destabilizing properties. Together with previous studies, we concluded that HNG may have promising therapeutic potential as a multitarget agent for the prevention and/or treatment of AD.

Epigenetics in Parkinson's and Alzheimer's diseases

Neurodegenerative disorders, such as Parkinson's and Alzheimer's disease, are highly complex, due to their multifactorial origin, not only depending on genetic but also on environmental factors. Several genetic risk factors have already been associated with both the diseases, however, the precise way through which the environment contributes to neurodegeneration is still unclear.Recently, epigenetic mechanisms, such as DNA methylation, chromatin remodeling or miRNAs, which may induce alterations in genes expression, have started to be implicated in both AD and PD. Epigenetic modulation is present since pre-natal stages and throughout lifetime, and depends on lifestyle conditions and environmental exposures, and consequently could represent the missing link between risk factors and the development of sporadic disorders. This chapter will discusses the role of epigenetics in AD and PD.

Genetic influences on atrophy patterns in familial Alzheimer's disease: a comparison of APP and PSEN1 mutations

Mutations in the presenilin1 (PSEN1) and amyloid β-protein precursor (APP) genes account for the majority of cases of autosomal dominantly inherited Alzheimer's disease (AD). We wished to assess and compare the patterns of cerebral loss produced by these two groups of mutations. Volumetric magnetic resonance imaging and neuropsychological assessments were performed in individuals with clinical AD carrying mutations in the APP (n = 10) and PSEN1 (n = 18) genes and in healthy controls (n = 18). Voxel-based morphometry (VBM), cortical thickness, and region of interest analyses were performed. Mini-Mental State Examination scores were similar in the two disease groups suggesting similar levels of disease severity. There was evidence that APP subjects have smaller hippocampal volume compared with PSEN1 subjects (p = 0.007), and weak evidence that they have larger whole-brain and grey matter volumes (both p = 0.07). Although there was no evidence of statistically significant differences between APP and PSEN1 in VBM or cortical thickness analyses, effect-maps were suggestive of APP subjects having more medial temporal lobe atrophy and conversely PSEN1 subjects showing more neocortical loss. Neuropsychological data were consistent with these regional differences and suggested greater memory deficits in the APP patients and greater impairment in non-memory domains in the PSEN1 group, although these differences were not statistically significant. We conclude that the mechanisms by which APP and PSEN1 mutations cause neuronal loss may differ which furthers our understanding of the neuropathology underlying AD and may inform future therapeutic strategies and trial designs.