Alzheimer disease

Microglial response to aging and neuroinflammation in the development of neurodegenerative diseases

ABSTRACT

Cellular senescence and chronic inflammation in response to aging are considered to be indicators of brain aging; they have a great impact on the aging process and are the main risk factors for neurodegeneration. Reviewing the microglial response to aging and neuroinflammation in neurodegenerative diseases will help understand the importance of microglia in neurodegenerative diseases. This review describes the origin and function of microglia and focuses on the role of different states of the microglial response to aging and chronic inflammation on the occurrence and development of neurodegenerative diseases, including Alzheimer's disease, Huntington's chorea, and Parkinson's disease. This review also describes the potential benefits of treating neurodegenerative diseases by modulating changes in microglial states. Therefore, inducing a shift from the neurotoxic to neuroprotective microglial state in neurodegenerative diseases induced by aging and chronic inflammation holds promise for the treatment of neurodegenerative diseases in the future.

Biotechnological potential of actinomycetes in the 21st century: a brief review

This brief review aims to draw attention to the biotechnological potential of actinomycetes. Their main uses as sources of antibiotics and in agriculture would be enough not to neglect them; however, as we will see, their biotechnological application is much broader. Far from intending to exhaust this issue, we present a short survey of the research involving actinomycetes and their applications published in the last 23 years. We highlight a perspective for the discovery of new active ingredients or new applications for the known metabolites of these microorganisms that, for approximately 80 years, since the discovery of streptomycin, have been the main source of antibiotics. Based on the collected data, we organize the text to show how the cosmopolitanism of actinomycetes and the evolutionary biotic and abiotic ecological relationships of actinomycetes translate into the expression of metabolites in the environment and the richness of biosynthetic gene clusters, many of which remain silenced in traditional laboratory cultures. We also present the main strategies used in the twenty-first century to promote the expression of these silenced genes and obtain new secondary metabolites from known or new strains. Many of these metabolites have biological activities relevant to medicine, agriculture, and biotechnology industries, including candidates for new drugs or drug models against infectious and non-infectious diseases. Below, we present significant examples of the antimicrobial spectrum of actinomycetes, which is the most commonly investigated and best known, as well as their non-antimicrobial spectrum, which is becoming better known and increasingly explored.

Mechanisms of synapse-to-nucleus calcium signalling in striatal neurons and impairments in Huntington's disease

Huntington's disease (HD) is a monogenic disorder with autosomal dominant inheritance. In HD patients, neurons in the striatum and cortex degenerate, leading to motor, psychiatric and cognitive disorders. Dysregulated synaptic function and calcium handling are common in many neurodegenerative diseases, including HD. N-methyl-D-aspartate (NMDA) receptor function is enhanced in HD at extrasynaptic sites, altering the balance of calcium-dependent neuronal survival versus death signalling pathways. Endoplasmic reticulum (ER) calcium handling is also abnormal in HD. The ER, which is continuous with the nuclear envelope, is purportedly involved in nuclear calcium signalling; based on this, we hypothesised that nuclear calcium signalling is altered in HD. We explored this hypothesis with calcium imaging techniques, including simultaneous epifluorescent imaging of cytosolic and nuclear calcium using jRCaMP1b and GCaMP3 sensors, respectively, in striatal spiny projection neurons in cortical-striatal co-cultures from the YAC128 mouse model of HD. Our data show contributions from a variety of calcium channels to nuclear calcium signalling. NMDA receptors (NMDARs) play an essential role in initiating action potential-dependent calcium signalling to the nucleus, and ryanodine receptors (RyR) contribute to both cytosolic and nuclear calcium signals. Unlike previous reports in glutamatergic hippocampal and cortical neurons, we found that in GABAergic striatal neurons, L-type voltage-gated calcium channels (CaV) contribute to cytosolic, but not nuclear calcium signalling. Calcium imaging also suggests impairments in nuclear calcium signalling in HD striatal neurons, where spontaneous action potential-dependent calcium transients in the nucleus were smaller in YAC128 striatal neurons compared to those of wild-type (WT). Our results elucidate mechanisms involved in action potential-dependent nuclear calcium signalling in GABAergic striatal neurons, and have revealed a clear deficit in this signalling in HD.

Personalized Protein-Protein Interaction Networks Towards Unraveling the Molecular Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD) is a highly heterogenous neurodegenerative disease, and several omic-based datasets were generated in the last decade from the patients with the disease. However, the vast majority of studies evaluate these datasets in bulk by considering all the patients as a single group, which obscures the molecular differences resulting from the heterogeneous nature of the disease. In this study, we adopted a personalized approach and analyzed the transcriptome data from 403 patients individually by mapping the data on a human protein-protein interaction network. Patient-specific subnetworks were discovered and analyzed in terms of the genes in the subnetworks, enriched functional terms, and known AD genes. We identified several affected pathways that could not be captured by the bulk comparison. We also showed that our personalized findings point to patterns of alterations consistent with the recently suggested AD subtypes.

Erythrocyte membrane-coated nanocarriers modified by TGN for Alzheimer's disease

Alzheimer's disease (AD) is an aging-related neurodegenerative disease, and the main pathological feature was β-amyloid protein (Aβ) deposition. Recently, bioactive materials-based drug delivery system has been widely investigated for the treatment of AD. In this study, we developed a red blood cells (RBC) membrane-coated polycaprolactone (PCL) nanoparticles (NPs) loading with a therapeutic agent for AD, curcumin (Cur). A functional peptide TGNYKALHPHN (TGN) was conjugated to the surface of membrane for blood-brain barrier (BBB) transport (TGN-RBC-NPs-Cur). TGN peptide can be recognized by receptors on the BBB and has great potential for brain transport. To confirm the targeted delivery of Cur to the brain, a cell co-culturing immortalized human cerebral microvascular endothelial cells and human brain astrocytes glioblastoma (hCMEC/D3 and U-118MG) in vitro model was established. As a result, the BBB transporting ratio of TGN-RBC-NPs-FITC was 29.64% at 12 h which was approximately eight-fold than RBC-NPs-FITC. The improvement of drug accumulation in the AD lesion was confirmed by the NPs modified with the BBB-penetrating peptide in the fluorescence imaging and quantitative analysis with UPLC-MS/MS in vivo. The neuroprotective effects were evaluated with new object recognition behavioral test, in vitro AD cell model, dendritic spine stain, GFAP and IBA1 immunofluorescence stain. The spatial learning and memory abilities of the AD model mice treated with TGN-RBC-NPs-Cur were obviously enhanced compared with the AD control mice and were also better than Cur at the same dosage. These results were consistent with the values of protection index of rat adrenal pheochromocytoma cells (PC12 cells) treated by Aβ25-35. TGN-RBC-NPs-Cur increased the dendritic segments densities and restrained activation of microglia and astrocytes of AD mice, as well as reversed cognitive function of AD mice. All of the results demonstrated TGN-RBC-NPs-Cur a promising therapeutic strategy for delaying the progression of AD by designing biomimetic nanosystems to deliver drugs into the brain.

Transgenic amyloid precursor protein mouse models of amyloidosis. Incomplete models for Alzheimer's disease but effective predictors of anti-amyloid therapies

INTRODUCTION

Amyloid precursor protein (APP) transgenic mice are models of Alzheimer's disease (AD) amyloidosis, not all of AD. Diffuse, compacted, and vascular deposits in APP mice mimic those found in AD cases.

METHODS

Most interventional studies in APP mice start treatment early in the process of amyloid deposition, consistent with a prevention treatment regimen. Most clinical trials treat patients with established amyloid deposits in a therapeutic treatment regimen.

RESULTS

The first treatment to reduce amyloid and cognitive impairment in mice was immunotherapy. The APP mouse models not only predicted efficacy, but presaged the vascular leakage called ARIA. The recent immunotherapy clinical trials that removed amyloid and slowed cognitive decline confirms the utility of these early APP models when used in therapeutic designs.

DISCUSSION

New mouse models of AD pathologies will add to the research armamentarium, but the early models have accurately predicted responses to amyloid therapies in humans.

Histological and Memory Alterations in an Innovative Alzheimer's Disease Animal Model by Vanadium Pentoxide Inhalation

Background

Previous work from our group has shown that chronic exposure to Vanadium pentoxide (V2O5) causes cytoskeletal alterations suggesting that V2O5 can interact with cytoskeletal proteins through polymerization and tyrosine phosphatases inhibition, causing Alzheimer's disease (AD)-like hippocampal cell death.

Objective

This work aims to characterize an innovative AD experimental model through chronic V2O5 inhalation, analyzing the spatial memory alterations and the presence of neurofibrillary tangles (NFTs), amyloid-β (Aβ) senile plaques, cerebral amyloid angiopathy, and dendritic spine loss in AD-related brain structures.

Methods

20 male Wistar rats were divided into control (deionized water) and experimental (0.02 M V2O5 1 h, 3/week for 6 months) groups (n = 10). The T-maze test was used to assess spatial memory once a month. After 6 months, histological alterations of the frontal and entorhinal cortices, CA1, subiculum, and amygdala were analyzed by performing Congo red, Bielschowsky, and Golgi impregnation.

Results

Cognitive results in the T-maze showed memory impairment from the third month of V2O5 inhalation. We also noted NFTs, Aβ plaque accumulation in the vascular endothelium and pyramidal neurons, dendritic spine, and neuronal loss in all the analyzed structures, CA1 being the most affected.

Conclusions

This model characterizes neurodegenerative changes specific to AD. Our model is compatible with Braak AD stage IV, which represents a moment where it is feasible to propose therapies that have a positive impact on stopping neuronal damage.

Stroke and Vascular Cognitive Impairment: The Role of Intestinal Microbiota Metabolite TMAO

The gut microbiome interacts with the brain bidirectionally through the microbiome-gutbrain axis, which plays a key role in regulating various nervous system pathophysiological processes. Trimethylamine N-oxide (TMAO) is produced by choline metabolism through intestinal microorganisms, which can cross the blood-brain barrier to act on the central nervous system. Previous studies have shown that elevated plasma TMAO concentrations increase the risk of major adverse cardiovascular events, but there are few studies on TMAO in cerebrovascular disease and vascular cognitive impairment. This review summarized a decade of research on the impact of TMAO on stroke and related cognitive impairment, with particular attention to the effects on vascular cognitive disorders. We demonstrated that TMAO has a marked impact on the occurrence, development, and prognosis of stroke by regulating cholesterol metabolism, foam cell formation, platelet hyperresponsiveness and thrombosis, and promoting inflammation and oxidative stress. TMAO can also influence the cognitive impairment caused by Alzheimer's disease and Parkinson's disease via inducing abnormal aggregation of key proteins, affecting inflammation and thrombosis. However, although clinical studies have confirmed the association between the microbiome-gut-brain axis and vascular cognitive impairment (cerebral small vessel disease and post-stroke cognitive impairment), the molecular mechanism of TMAO has not been clarified, and TMAO precursors seem to play the opposite role in the process of poststroke cognitive impairment. In addition, several studies have also reported the possible neuroprotective effects of TMAO. Existing therapies for these diseases targeted to regulate intestinal flora and its metabolites have shown good efficacy. TMAO is probably a new target for early prediction and treatment of stroke and vascular cognitive impairment.

Caspases in Alzheimer's Disease: Mechanism of Activation, Role, and Potential Treatment

With the aging of the population, treatment of conditions emerging in old age, such as neurodegenerative disorders, has become a major medical challenge. Of these, Alzheimer's disease, leading to cognitive dysfunction, is of particular interest. Neuronal loss plays an important role in the pathophysiology of this condition, and over the years, a great effort has been made to determine the role of various factors in this process. Unfortunately, until now, the exact pathomechanism of this condition remains unknown. However, the most popular theories associate AD with abnormalities in the Tau and β-amyloid (Aβ) proteins, which lead to their deposition and result in neuronal death. Neurons, like all cells, die in a variety of ways, among which pyroptosis, apoptosis, and necroptosis are associated with the activation of various caspases. It is worth mentioning that Tau and Aβ proteins are considered to be one of the caspase activators, leading to cell death. Moreover, the protease activity of caspases influences both of the previously mentioned proteins, Tau and Aβ, converting them into more toxic derivatives. Due to the variety of ways caspases impact the development of AD, drugs targeting caspases could potentially be useful in the treatment of this condition. Therefore, there is a constant need to search for novel caspase inhibitors and evaluate them in preclinical and clinical trials.

Potential Modifying Effect of the APOEε4 Allele on Age of Onset and Clinical Manifestations in Patients with Early-Onset Alzheimer's Disease with and without a Pathogenic Variant in PSEN1 in a Sample of the Mexican Population

In Alzheimer's disease (AD), the age of onset (AoO) exhibits considerable variability, spanning from 40 to 90 years. Specifically, individuals diagnosed with AD and exhibiting symptoms prior to the age of 65 are typically classified as early onset (EOAD) cases. Notably, the apolipoprotein E (APOE) ε4 allele represents the most extensively studied genetic risk factor associated with AD. We clinically characterized and genotyped the APOEε4 allele from 101 individuals with a diagnosis of EOAD, and 69 of them were affected carriers of the autosomal dominant fully penetrant PSEN1 variant c.1292C>A (rs63750083, A431E) (PSEN1+ group), while there were 32 patients in which the genetic cause was unknown (PSEN1- group). We found a correlation between the AoO and the APOEε4 allele; patients carrying at least one APOEε4 allele showed delays, in AoO in patients in the PSEN1+ and PSEN1- groups, of 3.9 (p = 0.001) and 8.6 years (p = 0.012), respectively. The PSEN1+ group presented higher frequencies of gait disorders compared to PSEN1- group, and apraxia was more frequent with PSEN1+/APOE4+ than in the rest of the subgroup. This study shows what appears to be an inverse effect of APOEε4 in EOAD patients, as it delays AoO and modifies clinical manifestations.

Reduced synaptic proteins and SNARE complexes in Down syndrome with Alzheimer's disease and the Dp16 mouse Down syndrome model: Impact of APP gene dose

INTRODUCTION

Synaptic failure, a hallmark of Alzheimer's disease (AD), is correlated with reduced levels of synaptic proteins. Though people with Down syndrome (DS) are at markedly increased risk for AD (AD-DS), few studies have addressed synapse dysfunction.

METHODS

Synaptic proteins were measured in the frontal cortex of DS, AD-DS, sporadic AD cases, and controls. The same proteins were examined in the Dp16 model of DS.

RESULTS

A common subset of synaptic proteins were reduced in AD and AD-DS, but not in DS or a case of partial trisomy 21 lacking triplication of APP gene. Pointing to compromised synaptic function, the reductions in AD and AD-DS were correlated with reduced SNARE complexes. In Dp16 mice reductions in syntaxin 1A, SNAP25 and the SNARE complex recapitulated findings in AD-DS; reductions were impacted by both age and increased App gene dose.

DISCUSSION

Synaptic phenotypes shared between AD-DS and AD point to shared pathogenetic mechanisms.

Long-term use of metformin and Alzheimer's disease: beneficial or detrimental effects

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by extracellular deposition of amyloid beta (Aβ) leading to cognitive decline. Evidence from epidemiological studies has shown the association between type 2 diabetes mellitus (T2DM) and the development of AD. T2DM and peripheral insulin resistance (IR) augment the risk of AD with the development of brain IR with inhibition of neuronal insulin receptors. These changes impair clearance of Aβ, increase secretion of Aβ_1-42, reduce brain glucose metabolism, and abnormal deposition of Aβ plaques. Insulin-sensitizing drug metformin inhibits aggregation of Aβ by increasing the activity of the insulin-degrading enzyme (IDE) and neprilysin (NEP) levels. Additionally, different studies raised conflicting evidence concerning long-term metformin therapy in T2DM patients, as it may increase the risk of AD or it may prevent the progression of AD. Therefore, the objective of this review was to clarify the beneficial and detrimental effects of long-term metformin therapy in T2DM patients and risk of AD. Evidence from clinical trial studies revealed the little effect of metformin on AD. Various animal studies showed that metformin increases Aβ formation by activation of amyloid precursor protein (APP)-cleaving enzymes with the generation of insoluble tau species. Of note, the metformin effect on cognitive function relative to AD pathogenesis is mostly assessed in animal model studies. The duration of metformin therapy was short in most animal studies, this finding cannot apply to the long-term duration of metformin in humans. Therefore, large-scale prospective and comparative studies involving long-term metformin therapy in both diabetic and non-diabetic patients are required to exclude the effect of T2DM-induced AD.

Biomarkers: Role and Scope in Neurological Disorders

Neurological disorders pose a great threat to social health and are a major cause for mortality and morbidity. Effective drug development complemented with the improved drug therapy has made considerable progress towards easing symptoms associated with neurological illnesses, yet poor diagnosis and imprecise understanding of these disorders has led to imperfect treatment options. The scenario is complicated by the inability to extrapolate results of cell culture studies and transgenic models to clinical applications which has stagnated the process of improving drug therapy. In this context, the development of biomarkers has been viewed as beneficial to easing various pathological complications. A biomarker is measured and evaluated in order to gauge the physiological process or a pathological progression of a disease and such a marker can also indicate the clinical or pharmacological response to a therapeutic intervention. The development and identification of biomarkers for neurological disorders involves several issues including the complexity of the brain, unresolved discrepant data from experimental and clinical studies, poor clinical diagnostics, lack of functional endpoints, and high cost and complexity of techniques yet research in the area of biomarkers is highly desired. The present work describes existing biomarkers for various neurological disorders, provides support for the idea that biomarker development may ease our understanding underlying pathophysiology of these disorders and help to design and explore therapeutic targets for effective intervention.

Asiatic Acid Fabricated Nanoconstructs to Mitigate Amyloid Beta1-42 Induced Injury in SH-SY5Y Cells In-Vitro and Ameliorates Cognitive Impairment by Dual Cholinesterase Inhibition and Attenuation of Oxidative Stress In-Vivo

PURPOSE

Asiatic acid (AA) is reported for its neuroprotective potential in Alzheimer's disease (AD). This present work aimed to develop AA loaded nanostructured lipid carriers (AAN) for targeting the delivery of AA into the brain and ameliorating the cognitive deficits in AD rats.

METHODS

AAN was optimized using the Box-Behnken design, considering 3 factors (soya lecithin, tween 80, and high pressure homogenizer (HPH) pressure) as independent variables while particle size (PS), zeta potential (ZP) and entrapment efficiency (EE) were dependent variables. Cytotoxicity assay and internalization studies of AAN were evaluated in SH-SY5Y cells and further neuroprotective efficiency on intracellular amyloid beta (Aβ) aggregation was evaluated in Aβ _1-42 treated cells with thioflavin T (ThT). The behavioral acquisition effects were evaluated in Aβ _1-42 (5 µg/ 5 µL, intracerebroventricular (ICV), unilateral) induced AD model followed by the histology and quantification of neurotransmitters levels.

RESULTS

The optimized AAN revealed desired PS (44.1 ± 12.4 nm), ZP (- 47.1 ± 0.017 mv) and EE (73.41 ± 2.53%) for brain targeting delivery of AA. In-vitro, AAN exhibited better neuroprotective potential than AA suspension (AAS). AA content was 1.28 folds and 2.99 folds heightened in plasma and brain respectively after the i.p. administration of AAN as compared to AAS. The results of pharmacodynamic studies manifested the AAN treatment significantly (p < 0.05) ameliorated the cognitive deficits.

CONCLUSIONS

Hence, developed AAN has neuroprotective potential and should be further considered as an unconventional platform in preclinical model for the management of AD.

Comparative analysis of transcriptome remodeling in plaque-associated and plaque-distant microglia during amyloid-β pathology progression in mice

Background

Research in recent years firmly established that microglial cells play an important role in the pathogenesis of Alzheimer's disease (AD). In parallel, a series of studies showed that, under both homeostatic and pathological conditions, microglia are a heterogeneous cell population. In AD, amyloid-β (Aβ) plaque-associated microglia (PAM) display a clearly distinct phenotype compared to plaque-distant microglia (PCM), suggesting that these two microglia subtypes likely differently contribute to disease progression. So far, molecular characterization of PAM was performed indirectly using single cell RNA sequencing (scRNA-seq) approaches or based on markers that are supposedly up-regulated in this microglia subpopulation.

Methods

In this study based on a well-characterized AD mouse model, we combined cell-specific laser capture microdissection and RNA-seq analysis to i) identify, without preconceived notions of the molecular and/or functional changes that would affect these cells, the genes and gene networks that are dysregulated in PAM or PCM at three critical stages of the disease, and ii) to investigate the potential contribution of both plaque-associated and plaque-distant microglia.

Results

First, we established that our approach allows selective isolation of microglia, while preserving spatial information and preventing transcriptome changes induced by classical purification approaches. Then, we identified, in PAM and PCM subpopulations, networks of co-deregulated genes and analyzed their potential functional roles in AD. Finally, we investigated the dynamics of microglia transcriptomic remodeling at early, intermediate and late stages of the disease and validated select findings in postmortem human AD brain.

Conclusions

Our comprehensive study provides useful transcriptomic information regarding the respective contribution of PAM and PCM across the Aβ pathology progression. It highlights specific pathways that would require further study to decipher their roles across disease progression. It demonstrates that the proximity of microglia to Aβ-plaques dramatically alters the microglial transcriptome and reveals that these changes can have both positive and negative impacts on the surrounding cells. These opposing effects may be driven by local microglia heterogeneity also demonstrated by this study. Our approach leads to molecularly define the less well studied plaque-distant microglia. We show that plaque-distant microglia are not bystanders of the disease, although the transcriptomic changes are far less striking compared to what is observed in plaque-associated microglia. In particular, our results suggest they may be involved in Aβ oligomer detection and in Aβ-plaque initiation, with increased contribution as the disease progresses.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02581-0.

Arsenic Induces GSK3β-dependent p-tau, neuronal apoptosis and cognitive impairment via an interdependent hippocampal ERα and IL-1/IL-1R1 mechanism in female rats

Arsenic is an environmental contaminant with potential neurotoxicity. We previously reported that arsenic promoted hippocampal neuronal apoptosis, inducing cognitive loss. Here, we correlated it with tau pathology. We observed that environmentally relevant arsenic exposure increased tau phosphorylation and the principal tau kinase, glycogen synthase kinase-3 beta (GSK3β), in the female rat hippocampal neurons. We detected the same in primary hippocampal neurons. Since a regulated estrogen receptor (ER) level and inflammation contributed to normal hippocampal functions, we examined their levels following arsenic exposure. Our ER screening data revealed that arsenic down-regulated hippocampal neuronal ERα. We also detected an up-regulated hippocampal interleukin-1 (IL-1) and its receptor, IL-1R1. Further, co-treating arsenic with the ERα agonist, 4,4',4''-(4-Propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT), or IL-1R antagonist (IL-1Ra) resulted in reduced GSK3β and p-tau, indicating involvement of decreased ERα and increased IL-1/IL-1R1 in tau hyperphosphorylation. We then checked whether ERα and IL-1/IL-1R1 had linkage, and detected that while PPT reduced IL-1 and IL-1R1, the IL-1Ra restored ERα, suggesting their arsenic-induced interdependence. We finally correlated this pathway with apoptosis and cognition. We observed that PPT, IL-1Ra and the GSK3β inhibitor, LiCl, reduced hippocampal neuronal cleaved caspase-3 and TUNEL+ve apoptotic count, and decreased the number of errors during learning and increased the saving-memory for Y-Maze Test and retention performance for Passive avoidance test in arsenic-treated rats. Thus, our study reveals a novel mechanism of arsenic-induced GSK3β-dependent tau pathology via interdependent ERα and IL-1/IL-1R1 signaling. It also envisages the protective role of ERα agonist and IL-1 inhibitor against arsenic-induced neurotoxicity.

The Effect of Cannabidiol Coated by Nano-Chitosan on Learning and Memory, Hippocampal CB1 and CB2 Levels, and Amyloid Plaques in an Alzheimer's Disease Rat Model

INTRODUCTION

Using nanoparticle (NP) drugs can have better effects on the target tissue in various diseases. Alzheimer's disease (AD) is one of the degenerative neurological diseases that due to its high prevalence, requires the use of more appropriate treatments. Therefore, the aim of this study was consideration of the effect of cannabidiol (CBD) coated by nano-chitosan on learning and memory, hippocampal cannabinoid receptor type 1 (CB1) and cannabinoid receptor type 1 (CB2) levels, and amyloid plaques in an AD rat model.

MATERIAL AND METHODS

Thirty-five male Wistar rats were randomly divided into 5 groups (n = 7 in each): control, Alzheimer's disease model that received the beta-amyloid (Aβ) peptide (Alz), Alz + nano-chitosan (NP) Alz + CBD, and Alz + NP + CBD. Alz was induced by injection of the Aβ1-42 peptide into the hippocampal area cornu ammonis1. After confirmation of Alz, 1 μL of CBD and NP + CBD were administered by oral gavage daily in rats for 1 month. The Morris water maze (MWM) test was used to assess learning and memory of animals. Cresyl violet staining was used for consideration of dead cells. Gene and protein expression of CB1 and CB2 was performed by real-time PCR and immunohistochemistry methods.

RESULTS

Induction of Alz significantly increased Aβ plaques and dead cells compared to the control group (p < 0.001). Results of MWM in the day test show that Alz + NP + CBD significantly decrease escape latency (p < 0.01), travelled distance (p < 0.001), and significantly increased spending time (p < 0.001) compared to the Alz group. Protein expression of CB1 and CB2 significantly increased in Alz + CBD and Alz + NP + CBD compared to the Alz group (p < 0.05).

CONCLUSION

It seems that CBD coated by nano-chitosan has good potential for reducing Aβ plaques, increasing brain CB1 and levels CB2, and improving learning and memory in Alz rats.

Intestinal Microflora Changes in Patients with Mild Alzheimer's Disease in a Chinese Cohort

BACKGROUND

Understanding the relationship between Alzheimer's disease (AD) and intestinal flora is still a major scientific topic that continues to advance.

OBJECTIVE

To determine characterized changes in the intestinal microbe community of patients with mild AD.

METHODS

Comparison of the 16S ribosomal RNA (rRNA) high-throughput sequencing data was obtained from the Illumina MiSeq platform of fecal microorganisms of the patients and healthy controls (HC) which were selected from cohabiting caregivers of AD patients to exclude environmental and dietary factors.

RESULTS

We found that the abundance of several bacteria taxa in AD patients was different from that in HC at the genus level, such as Anaerostipes, Mitsuokella, Prevotella, Bosea, Fusobacterium, Anaerotruncus, Clostridium, and Coprobacillus. Interestingly, the abundance of Akkermansia, an emerging probiotic, increased significantly in the AD group compared with that in the HC group. Meanwhile, the quantity of traditional probiotic Bifidobacteria of the AD group also rose.

CONCLUSION

These alterations in fecal microbiome of the AD group indicate that patients with mild AD have unique gut microbial characteristics. These specific AD-associated intestinal microbes could serve as novel potential targets for early intervention of AD.

Transgenic Mouse Models of Alzheimer's Disease: An Integrative Analysis

Alzheimer's disease (AD) constitutes the most prominent form of dementia among elderly individuals worldwide. Disease modeling using murine transgenic mice was first initiated thanks to the discovery of heritable mutations in amyloid precursor protein (APP) and presenilins (PS) genes. However, due to the repeated failure of translational applications from animal models to human patients, along with the recent advances in genetic susceptibility and our current understanding on disease biology, these models have evolved over time in an attempt to better reproduce the complexity of this devastating disease and improve their applicability. In this review, we provide a comprehensive overview about the major pathological elements of human AD (plaques, tauopathy, synaptic damage, neuronal death, neuroinflammation and glial dysfunction), discussing the knowledge that available mouse models have provided about the mechanisms underlying human disease. Moreover, we highlight the pros and cons of current models, and the revolution offered by the concomitant use of transgenic mice and omics technologies that may lead to a more rapid improvement of the present modeling battery.

Characterization of Altered Molecular Pathways in the Entorhinal Cortex of Alzheimer’s Disease Patients and In Silico Prediction of Potential Repurposable Drugs

Alzheimer’s disease (AD) is the most common cause of dementia worldwide and is characterized by a progressive decline in cognitive functions. Accumulation of amyloid-β plaques and neurofibrillary tangles are a typical feature of AD neuropathological changes. The entorhinal cortex (EC) is the first brain area associated with pathologic changes in AD, even preceding atrophy of the hippocampus. In the current study, we have performed a meta-analysis of publicly available expression data sets of the entorhinal cortex (EC) in order to identify potential pathways underlying AD pathology. The meta-analysis identified 1915 differentially expressed genes (DEGs) between the EC from normal and AD patients. Among the downregulated DEGs, we found a significant enrichment of biological processes pertaining to the “neuronal system” (R-HSA-112316) and the “synaptic signaling” (GO:0099536), while the “regulation of protein catabolic process” (GO:00042176) and “transport of small molecules” (R-HSA-382551) resulted in enrichment among both the upregulated and downregulated DEGs. Finally, by means of an in silico pharmacology approach, we have prioritized drugs and molecules potentially able to revert the transcriptional changes associated with AD pathology. The drugs with a mostly anti-correlated signature were: efavirenz, an anti-retroviral drug; tacrolimus, a calcineurin inhibitor; and sirolimus, an mTOR inhibitor. Among the predicted drugs, those potentially able to cross the blood-brain barrier have also been identified. Overall, our study found a disease-specific set of dysfunctional biological pathways characterizing the EC in AD patients and identified a set of drugs that could in the future be exploited as potential therapeutic strategies. The approach used in the current study has some limitations, as it does not account for possible post-transcriptional events regulating the cellular phenotype, and also, much clinical information about the samples included in the meta-analysis was not available. However, despite these limitations, our study sets the basis for future investigations on the pathogenetic processes occurring in AD and proposes the repurposing of currently used drugs for the treatment of AD patients.

Stereotaxic-assisted gene therapy in Alzheimer's and Parkinson's diseases: therapeutic potentials and clinical frontiers

INTRODUCTION

Alzheimer's disease (AD) and Parkinson's disease (PD) are neurodegenerative disorders causing cognitive deficits and motor difficulties in the elderly. Conventional treatments are mainly symptomatic with little ability to halt disease progression. Gene therapies to correct or silence genetic mutations predisposing to AD or PD are currently being developed in preclinical studies and clinical trials, relying mostly on systemic delivery, which reduces their effectiveness. Imaging-guided stereotaxic procedures are used to locally deliver therapeutic cargos to well-defined brain sites, hence raising the question whether stereotaxic-assisted gene therapy has therapeutic potentials.

AREAS COVERED

The authors summarize the studies that investigated the use of gene therapy in PD and AD in animal and clinical studies over the past five years, with a special emphasis on the combinatorial potential with stereotaxic delivery. The advantages, limitations and futuristic challenges of this technique are discussed.

EXPERT OPINION

Robotic stereotaxis combined with intraoperative imaging has revolutionized brain surgeries. While gene therapies are bringing huge innovations to the medical field and new hope to AD and PD patients and medical professionals, the efficient and targeted delivery of such therapies is a bottleneck. We propose that careful application of stereotaxic delivery of gene therapies can improve PD and AD management. [Figure: see text].

Effects of electroacupuncture on DNA methylation of the TREM2 gene in senescence-accelerated mouse prone 8 mice

OBJECTIVE

To explore the mechanism by which electroacupuncture (EA) upregulates triggering receptor expressed on myeloid cells 2 (TREM2) protein in the hippocampus of Alzheimer's disease (AD) model animals from the perspective of TREM2 DNA methylation.

METHODS

In total, 24 eight-month-old senescence-accelerated mouse prone 8 (SAMP8) mice were divided into an (untreated) AD group (n = 8), donepezil group (receiving donepezil treatment, n = 8) or EA group (receiving an EA intervention, n = 8). A healthy control group comprising 8-month-old senescence-accelerated mouse resistant 1 (SAMR1) mice (n = 8) was also included. Western blotting, bisulfite sequencing, and oxidative bisulfite sequencing were applied to test the relative expression of TREM2 protein and the methylation levels of the TREM2 gene.

RESULTS

EA significantly upregulated the relative expression of TREM2 protein (p < 0.01), downregulated the 5-methylcytosine level (p < 0.01) and upregulated the 5-hydroxymethylcytosine level (p < 0.05) in the hippocampus.

CONCLUSION

Downregulation of 5-methylcytosine levels and upregulation of 5-hydroxymethylcytosine levels in the TREM2 gene might be the mechanism by which EA promotes the expression of TREM2 protein.

Nose-to-brain drug delivery for the treatment of Alzheimer's Disease: Current advancements and challenges

INTRODUCTION

The irreversible destruction of neurons, progressive loss of memory and cognitive behavior, high cost of therapy, and impact on society desire a better, effective, and affordable treatment of AD. The nose-to-brain drug delivery approach holds a great potential to access the brain without any hindrance of BBB and result in higher bioavailability thus better therapeutic efficacy of anti-AD drugs.

AREAS COVERED

The present review article highlighted the current facts and worldwide statistics of AD and its detailed etiology. Followed by barriers to brain delivery, nose-to-brain delivery, their limitations, and amalgamation with various novel carrier systems. We have emphasized recent advancements in nose-to-brain delivery using mucoadhesive, stimuli-responsive carriers, polymeric nanoparticles, lipid nanoparticles, protein/peptide delivery for treatment of AD.

EXPERT OPINION

The available therapies are symptomatic, mitigate the symptoms of AD at the initial stages. In this lieu, nose-to-brain delivery has the ability to overcome these limitations and increase drug bioavailability in the brain. Various novel strategies including stimuli-responsive systems, nanoparticles, etc. enhance the nasal drug permeation, protects the drug, and enhance its therapeutic potency. Although, successful preclinical data does not assure the clinical success of the therapy and hence exhaustive clinical investigations are needed to make the therapy available for patients.

News about Therapies of Alzheimer’s Disease: Extracellular Vesicles from Stem Cells Exhibit Advantages Compared to Other Treatments

Upon its discovery, Alzheimer’s, the neurodegenerative disease that affects many millions of patients in the world, remained without an effective therapy. The first drugs, made available near the end of last century, induced some effects, which remained only marginal. More promising effects are now present, induced by two approaches. Blockers of the enzyme BACE-1 induce, in neurons and glial cells, decreased levels of Aβ, the key peptide of the Alzheimer’s disease. If administered at early AD steps, the BACE-1 blockers preclude further development of the disease. However, they have no effect on established, irreversible lesions. The extracellular vesicles secreted by mesenchymal stem cells induce therapy effects analogous, but more convenient, than the effects of their original cells. After their specific fusion to target cells, the action of these vesicles depends on their ensuing release of cargo molecules, such as proteins and many miRNAs, active primarily on the cell cytoplasm. Operationally, these vesicles exhibit numerous advantages: they exclude, by their accurate selection, the heterogeneity of the original cells; exhibit molecular specificity due to their engineering and drug accumulation; and induce effective actions, mediated by variable concentrations of factors and molecules and by activation of signaling cascades. Their strength is reinforced by their combination with various factors and processes. The recent molecular and operations changes, induced especially by the stem cell target cells, result in encouraging and important improvement of the disease. Their further development is expected in the near future.

Neurodegenerative Disorders of Alzheimer, Parkinsonism, Amyotrophic Lateral Sclerosis and Multiple Sclerosis: An Early Diagnostic Approach for Precision Treatment

Neurodegenerative diseases (NDs) are characterised by progressive dysfunction of synapses, neurons, glial cells and their networks. Neurodegenerative diseases can be classified according to primary clinical features (e.g., dementia, parkinsonism, or motor neuron disease), anatomic distribution of neurodegeneration (e.g., frontotemporal degenerations, extrapyramidal disorders, or spinocerebellar degenerations), or principal molecular abnormalities. The most common neurodegenerative disorders are amyloidosis, tauopathies, a-synucleinopathy, and TAR DNA-binding protein 43 (TDP-43) proteopathy. The protein abnormalities in these disorders have abnormal conformational properties along with altered cellular mechanisms, and they exhibit motor deficit, mitochondrial malfunction, dysfunctions in autophagic-lysosomal pathways, synaptic toxicity, and more emerging mechanisms such as the roles of stress granule pathways and liquid-phase transitions. Finally, for each ND, microglial cells have been reported to be implicated in neurodegeneration, in particular, because the microglial responses can shift from neuroprotective to a deleterious role. Growing experimental evidence suggests that abnormal protein conformers act as seed material for oligomerization, spreading from cell to cell through anatomically connected neuronal pathways, which may in part explain the specific anatomical patterns observed in brain autopsy sample. In this review, we mention the human pathology of select neurodegenerative disorders, focusing on how neurodegenerative disorders (i.e., Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis) represent a great healthcare problem worldwide and are becoming prevalent because of the increasing aged population. Despite many studies have focused on their etiopathology, the exact cause of these diseases is still largely unknown and until now with the only available option of symptomatic treatments. In this review, we aim to report the systematic and clinically correlated potential biomarker candidates. Although future studies are necessary for their use in early detection and progression in humans affected by NDs, the promising results obtained by several groups leads us to this idea that biomarkers could be used to design a potential therapeutic approach and preclinical clinical trials for the treatments of NDs.

Loganin substantially ameliorates molecular deficits, pathologies and cognitive impairment in a mouse model of Alzheimer's disease

Alzheimer’s disease (AD) is the most common age-related neurodegenerative disease threatening the health of the elderly, but the available therapeutic and preventive drugs remain suboptimal. Loganin, an iridoid glycoside extracted from Cornus officinalis, is reported to have anti-inflammatory and memory-enhancing properties. This study is aimed to explore the influence of loganin on cognitive function in 3xTg-AD mice and the underlying mechanism associated with its neuroprotection. According to the results of behavioral tests, we found that administration of loganin could significantly alleviate anxiety behavior and improve memory deficits of 3xTg-AD mice. Furthermore, immunohistochemical analysis displayed that there were decreased Aβ deposition in the hippocampus and cortex of 3xTg-AD mice treated with loganin compared with the control mice. Importantly, the Aβ-related pathological change was mainly involved in altering APP expression and processing. And loganin was also found to reduce the levels of phosphorylated tau (i.e. pTau^S396 and pTau^S262) in 3xTg-AD mice. By performing 2D-DIGE combined with MALDI-TOF-MS/MS, we revealed 28 differentially expressed proteins in the 3xTg-AD mice treated with loganin compared with the control mice. Notably, 10 proteins largely involved in energy metabolism, synaptic proteins, inflammatory response, and ATP binding were simultaneously detected in 3xTg-AD mice compared to WT mice. The abnormal changes of energy metabolism (PAGM1 and ENO1), synaptic proteins (SYN2 and Cplx2), inflammatory response (1433Z) were verified by western blot. Overall, our study suggested that loganin could be used as a feasible candidate drug to ameliorate molecular deficits, pathologies and cognitive impairment for prevention and treatment of AD.

Novel insights into the relationship between cerebellum and dementia: A narrative review as a toolkit for clinicians

The role of the cerebellum in neurodegenerative disorders that target cognitive functions has been a subject of increasing interest over the past years. However, a review focused on making clinicians more aware of the role of the cerebellum in dementia is still missing. This narrative review explores the possible factors explaining the involvement of the cerebellum in different kinds of dementia by providing more insights on how this structure can be relevant in clinical practice. It emerged that, despite overlapping in specific areas, structural cerebellar alterations in dementia show a certain degree of disease-specificity. Furthermore, the relevance of cerebellar changes in dementia is corroborated by correlations observed between their topography and cognitive symptomatology, as well as by its previously ignored involvement of the cerebellum in early stages of dementia. Despite needing further investigations, these findings could become a useful diagnostic aid for clinicians that should not be overlooked, in particular for those individuals who do not show distinct and manifest brain or neuropsychological alterations, but that still make clinicians suspect the presence of a neurocognitive disease.

Engeletin Attenuates Aβ1-42-Induced Oxidative Stress and Neuroinflammation by Keap1/Nrf2 Pathway

Alzheimer's disease (AD) is a serious neuropathologic disease characterized by aggregation of amyloid-β (Aβ) peptide. Aβ-mediated oxidative stress and neuroinflammation play crucial role in the development of AD. Engeletin is a flavononol glycoside that possesses anti-inflammatory effect. However, the effects of engeletin on AD have not been investigated. In the present study, we investigated the role of engeletin in AD using an in vitro AD model. Murine microglia BV-2 cells were stimulated with Aβ1-42 (5 μM) for 24 h to induce oxidative stress and inflammation. Our results showed that treatment with engeletin suppressed Aβ1-42-induced viability reduction and lactate dehydrogenase (LDH) release in BV-2 cells. Engeletin attenuated Aβ1-42-induced oxidative stress in BV-2 cells, as proved by decreased production of reactive oxygen species (ROS) and malonaldehyde (MDA) and increased glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities. Aβ1-42-induced nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression were inhibited by engeletin treatment. Besides, engeletin inhibited Aβ1-42-induced production and mRNA levels of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6). Engeletin enhanced Aβ1-42-induced activation of Kelch-like ECH-associated protein 1 (Keap1)/nuclear transcription factor E2-related factor 2 (Nrf2) signaling pathway in BV-2 cells. Inhibition of Keap1/Nrf2 signaling pathway reversed the inhibitory effects of engeletin on Aβ1-42-induced oxidative stress and inflammation in BV-2 cells. Taken together, engeletin attenuated Aβ1-42-induced oxidative stress and inflammation in BV-2 cells via regulating the of Keap1/Nrf2 pathway. These findings indicated that engeletin might be served as a therapeutic agent for the treatment of AD.

Peptides Derived from Growth Factors to Treat Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by progressive neuron losses in memory-related brain structures. The classical features of AD are a dysregulation of the cholinergic system, the accumulation of amyloid plaques, and neurofibrillary tangles. Unfortunately, current treatments are unable to cure or even delay the progression of the disease. Therefore, new therapeutic strategies have emerged, such as the exogenous administration of neurotrophic factors (e.g., NGF and BDNF) that are deficient or dysregulated in AD. However, their low capacity to cross the blood-brain barrier and their exorbitant cost currently limit their use. To overcome these limitations, short peptides mimicking the binding receptor sites of these growth factors have been developed. Such peptides can target selective signaling pathways involved in neuron survival, differentiation, and/or maintenance. This review focuses on growth factors and their derived peptides as potential treatment for AD. It describes (1) the physiological functions of growth factors in the brain, their neuronal signaling pathways, and alteration in AD; (2) the strategies to develop peptides derived from growth factor and their capacity to mimic the role of native proteins; and (3) new advancements and potential in using these molecules as therapeutic treatments for AD, as well as their limitations.

Aminopeptidase A contributes to biochemical, anatomical and cognitive defects in Alzheimer's disease (AD) mouse model and is increased at early stage in sporadic AD brain

One of the main components of senile plaques in Alzheimer's disease (AD)-affected brain is the Aβ peptide species harboring a pyroglutamate at position three pE3-Aβ. Several studies indicated that pE3-Aβ is toxic, prone to aggregation and serves as a seed of Aβ aggregation. The cyclisation of the glutamate residue is produced by glutaminyl cyclase, the pharmacological and genetic reductions of which significantly alleviate AD-related anatomical lesions and cognitive defects in mice models. The cyclisation of the glutamate in position 3 requires prior removal of the Aβ N-terminal aspartyl residue to allow subsequent biotransformation. The enzyme responsible for this rate-limiting catalytic step and its relevance as a putative trigger of AD pathology remained yet to be established. Here, we identify aminopeptidase A as the main exopeptidase involved in the N-terminal truncation of Aβ and document its key contribution to AD-related anatomical and behavioral defects. First, we show by mass spectrometry that human recombinant aminopeptidase A (APA) truncates synthetic Aβ1-40 to yield Aβ2-40. We demonstrate that the pharmacological blockade of APA with its selective inhibitor RB150 restores the density of mature spines and significantly reduced filopodia-like processes in hippocampal organotypic slices cultures virally transduced with the Swedish mutated Aβ-precursor protein (βAPP). Pharmacological reduction of APA activity and lowering of its expression by shRNA affect pE3-42Aβ- and Aβ1-42-positive plaques and expressions in 3xTg-AD mice brains. Further, we show that both APA inhibitors and shRNA partly alleviate learning and memory deficits observed in 3xTg-AD mice. Importantly, we demonstrate that, concomitantly to the occurrence of pE3-42Aβ-positive plaques, APA activity is augmented at early Braak stages in sporadic AD brains. Overall, our data indicate that APA is a key enzyme involved in Aβ N-terminal truncation and suggest the potential benefit of targeting this proteolytic activity to interfere with AD pathology.

Altered metabolic pathways in a transgenic mouse model suggest mechanistic role of amyloid precursor protein overexpression in Alzheimer's disease

INTRODUCTION

The mechanistic role of amyloid precursor protein (APP) in Alzheimer's disease (AD) remains unclear.

OBJECTIVES

Here, we aimed to identify alterations in cerebral metabolites and metabolic pathways in cortex, hippocampus and serum samples from Tg2576 mice, a widely used mouse model of AD.

METHODS

Metabolomic profilings using liquid chromatography-mass spectrometry were performed and analysed with MetaboAnalyst and weighted correlation network analysis (WGCNA).

RESULTS

Expressions of 11 metabolites in cortex, including hydroxyphenyllactate-linked to oxidative stress-and phosphatidylserine-lipid metabolism-were significantly different between Tg2576 and WT mice (false discovery rate < 0.05). Four metabolic pathways from cortex, including glycerophospholipid metabolism and pyrimidine metabolism, and one pathway (sulphur metabolism) from hippocampus, were significantly enriched in Tg2576 mice. Network analysis identified five pathways, including alanine, aspartate and glutamate metabolism, and mitochondria electron transport chain, that were significantly correlated with AD genotype.

CONCLUSIONS

Changes in metabolite concentrations and metabolic pathways are present in the early stage of APP pathology, and may be important for AD development and progression.

System-Level Analysis of Alzheimer's Disease Prioritizes Candidate Genes for Neurodegeneration

Alzheimer’s disease (AD) is a debilitating neurodegenerative disorder. Since the advent of the genome-wide association study (GWAS) we have come to understand much about the genes involved in AD heritability and pathophysiology. Large case-control meta-GWAS studies have increased our ability to prioritize weaker effect alleles, while the recent development of network-based functional prediction has provided a mechanism by which we can use machine learning to reprioritize GWAS hits in the functional context of relevant brain tissues like the hippocampus and amygdala. In parallel with these developments, groups like the Alzheimer’s Disease Neuroimaging Initiative (ADNI) have compiled rich compendia of AD patient data including genotype and biomarker information, including derived volume measures for relevant structures like the hippocampus and the amygdala. In this study we wanted to identify genes involved in AD-related atrophy of these two structures, which are often critically impaired over the course of the disease. To do this we developed a combined score prioritization method which uses the cumulative distribution function of a gene’s functional and positional score, to prioritize top genes that not only segregate with disease status, but also with hippocampal and amygdalar atrophy. Our method identified a mix of genes that had previously been identified in AD GWAS including APOE, TOMM40, and NECTIN2(PVRL2) and several others that have not been identified in AD genetic studies, but play integral roles in AD-effected functional pathways including IQSEC1, PFN1, and PAK2. Our findings support the viability of our novel combined score as a method for prioritizing region- and even cell-specific AD risk genes.

Amyloid pathology arrangements in Alzheimer's disease brains modulate in vivo seeding capability

Amyloid-β (Aβ) misfolding is one of the hallmark pathological features of Alzheimer's disease (AD). AD can manifest with diverse symptomatology including variable rates of cognitive decline, duration of clinical disease, and other detrimental changes. Several reports suggest that conformational diversity in misfolded Aβ is a leading factor for clinical variability in AD, analogous to what it has been described for prion strains in prion diseases. Notably, prion strains generate diverse patterns of misfolded protein deposition in the brains of affected individuals. Here, we tested the in vivo prion-like transmission features of four AD brains displaying particular patterns of amyloidosis. AD brains induced different phenotypes in recipient mice, as evaluated by their specific seeding activity, as well as the total amount of Aβ deposited surrounding vascular structures and the reactivity of amyloid pathology to thioflavin S. Our results support the notion that AD-subtypes are encoded in disease-associated Aβ. Further research exploring whether AD include a spectrum of different clinical conditions or syndromes may pave the way to personalized diagnosis and treatments.

Is γ-secretase a beneficial inactivating enzyme of the toxic APP C-terminal fragment C99?

Genetic, biochemical, and anatomical grounds led to the proposal of the amyloid cascade hypothesis centered on the accumulation of amyloid beta peptides (Aβ) to explain Alzheimer's disease (AD) etiology. In this context, a bulk of efforts have aimed at developing therapeutic strategies seeking to reduce Aβ levels, either by blocking its production (γ- and β-secretase inhibitors) or by neutralizing it once formed (Aβ-directed immunotherapies). However, so far the vast majority of, if not all, clinical trials based on these strategies have failed, since they have not been able to restore cognitive function in AD patients, and even in many cases, they have worsened the clinical picture. We here propose that AD could be more complex than a simple Aβ-linked pathology and discuss the possibility that a way to reconcile undoubted genetic evidences linking processing of APP to AD and a consistent failure of Aβ-based clinical trials could be to envision the pathological contribution of the direct precursor of Aβ, the β-secretase-derived C-terminal fragment of APP, βCTF, also referred to as C99. In this review, we summarize scientific evidences pointing to C99 as an early contributor to AD and postulate that γ-secretase should be considered as not only an Aβ-generating protease, but also a beneficial C99-inactivating enzyme. In that sense, we discuss the limitations of molecules targeting γ-secretase and propose alternative strategies seeking to reduce C99 levels by other means and notably by enhancing its lysosomal degradation.

Anxiolytic, Promnesic, Anti-Acetylcholinesterase and Antioxidant Effects of Cotinine and 6-Hydroxy-L-Nicotine in Scopolamine-Induced Zebrafish (Danio rerio) Model of Alzheimer's Disease

Cotinine (COT) and 6-hydroxy-L-nicotine (6HLN) are two nicotinic derivatives that possess cognitive-improving abilities and antioxidant properties in different rodent models of Alzheimer's disease (AD), eluding the side-effects of nicotine (NIC), the parent molecule. In the current study, we evaluated the impact of COT and 6HLN on memory deterioration, anxiety, and oxidative stress in the scopolamine (SCOP)-induced zebrafish model of AD. For this, COT and 6HLN were acutely administered by immersion to zebrafish that were treated with SCOP before testing. The memory performances were assessed in Y-maze and object discrimination (NOR) tasks, while the anxiety-like behavior was evaluated in the novel tank diving test (NTT). The acetylcholinesterase (AChE) activity and oxidative stress were measured from brain samples. The RT-qPCR analysis was used to evaluate the npy, egr1, bdnf, and nrf2a gene expression. Our data indicated that both COT and 6HLN attenuated the SCOP-induced anxiety-like behavior and memory impairment and reduced the oxidative stress and AChE activity in the brain of zebrafish. Finally, RT-qPCR analysis indicated that COT and 6HLN increased the npy, egr1, bdnf, and nrf2a gene expression. Therefore, COT and 6HLN could be used as tools for improving AD conditions.

The Cholinergic System, the Adrenergic System and the Neuropathology of Alzheimer's Disease

Neurodegenerative diseases are a major public health problem worldwide with a wide spectrum of symptoms and physiological effects. It has been long reported that the dysregulation of the cholinergic system and the adrenergic system are linked to the etiology of Alzheimer’s disease. Cholinergic neurons are widely distributed in brain regions that play a role in cognitive functions and normal cholinergic signaling related to learning and memory is dependent on acetylcholine. The Locus Coeruleus norepinephrine (LC-NE) is the main noradrenergic nucleus that projects and supplies norepinephrine to different brain regions. Norepinephrine has been shown to be neuroprotective against neurodegeneration and plays a role in behavior and cognition. Cholinergic and adrenergic signaling are dysregulated in Alzheimer’s disease. The degeneration of cholinergic neurons in nucleus basalis of Meynert in the basal forebrain and the degeneration of LC-NE neurons were reported in Alzheimer’s disease. The aim of this review is to describe current literature on the role of the cholinergic system and the adrenergic system (LC-NE) in the pathology of Alzheimer’s disease and potential therapeutic implications.

Molecular mechanisms of neurodegeneration in the entorhinal cortex that underlie its selective vulnerability during the pathogenesis of Alzheimer's disease

The entorhinal cortex (EC) is a vital component of the medial temporal lobe, and its contributions to cognitive processes and memory formation are supported through its extensive interconnections with the hippocampal formation. During the pathogenesis of Alzheimer's disease (AD), many of the earliest degenerative changes are seen within the EC. Neurodegeneration in the EC and hippocampus during AD has been clearly linked to impairments in memory and cognitive function, and a growing body of evidence indicates that molecular and functional neurodegeneration within the EC may play a primary role in cognitive decline in the early phases of AD. Defining the mechanisms underlying molecular neurodegeneration in the EC is crucial to determining its contributions to the pathogenesis of AD. Surprisingly few studies have focused on understanding the mechanisms of molecular neurodegeneration and selective vulnerability within the EC. However, there have been advancements indicating that early dysregulation of cellular and molecular signaling pathways in the EC involve neurodegenerative cascades including oxidative stress, neuroinflammation, glia activation, stress kinases activation, and neuronal loss. Dysfunction within the EC can impact the function of the hippocampus, which relies on entorhinal inputs, and further degeneration within the hippocampus can compound this effect, leading to severe cognitive disruption. This review assesses the molecular and cellular mechanisms underlying early degeneration in the EC during AD. These mechanisms may underlie the selective vulnerability of neuronal subpopulations in this brain region to the disease development and contribute both directly and indirectly to cognitive loss.This paper has an associated Future Leader to Watch interview with the first author of the article.

Novel Phosphorylation-State Specific Antibodies Reveal Differential Deposition of Ser26 Phosphorylated Aβ Species in a Mouse Model of Alzheimer's Disease

Aggregation and deposition of amyloid-β (Aβ) peptides in extracellular plaques and in the cerebral vasculature are prominent neuropathological features of Alzheimer's disease (AD) and closely associated with the pathogenesis of AD. Amyloid plaques in the brains of most AD patients and transgenic mouse models exhibit heterogeneity in the composition of Aβ deposits, due to the occurrence of elongated, truncated, and post-translationally modified Aβ peptides. Importantly, changes in the deposition of these different Aβ variants are associated with the clinical disease progression and considered to mark sequential phases of plaque and cerebral amyloid angiopathy (CAA) maturation at distinct stages of AD. We recently showed that Aβ phosphorylated at serine residue 26 (pSer26Aβ) has peculiar characteristics in aggregation, deposition, and neurotoxicity. In the current study, we developed and thoroughly validated novel monoclonal and polyclonal antibodies that recognize Aβ depending on the phosphorylation-state of Ser26. Our results demonstrate that selected phosphorylation state-specific antibodies were able to recognize Ser26 phosphorylated and non-phosphorylated Aβ with high specificity in enzyme-linked immunosorbent assay (ELISA) and Western Blotting (WB) assays. Furthermore, immunofluorescence analyses with these antibodies demonstrated the occurrence of pSer26Aβ in transgenic mouse brains that show differential deposition as compared to non-phosphorylated Aβ (npAβ) or other modified Aβ species. Notably, pSer26Aβ species were faintly detected in extracellular Aβ plaques but most prominently found intraneuronally and in cerebral blood vessels. In conclusion, we developed new antibodies to specifically differentiate Aβ peptides depending on the phosphorylation state of Ser26, which are applicable in ELISA, WB, and immunofluorescence staining of mouse brain tissues. These site- and phosphorylation state-specific Aβ antibodies represent novel tools to examine phosphorylated Aβ species to further understand and dissect the complexity in the age-related and spatio-temporal deposition of different Aβ variants in transgenic mouse models and human AD brains.

MicroRNAs Regulating Autophagy in Neurodegeneration

Social and economic impacts of neurodegenerative diseases (NDs) become more prominent in our constantly aging population. Currently, due to the lack of knowledge about the aetiology of most NDs, only symptomatic treatment is available for patients. Hence, researchers and clinicians are in need of solid studies on pathological mechanisms of NDs. Autophagy promotes degradation of pathogenic proteins in NDs, while microRNAs post-transcriptionally regulate multiple signalling networks including autophagy. This chapter will critically discuss current research advancements in the area of microRNAs regulating autophagy in NDs. Moreover, we will introduce basic strategies and techniques used in microRNA research. Delineation of the mechanisms contributing to NDs will result in development of better approaches for their early diagnosis and effective treatment.

Dysbiosis is one of the risk factor for stroke and cognitive impairment and potential target for treatment

More than 50 million people have various forms of cognitive impairment basically caused by neurodegenerative diseases, such as Alzheimer's, Parkinson's, and cerebrovascular diseases as well as stroke. Often these conditions coexist and exacerbate one another. The damaged area in post-stroke dementia may lead to neurodegenerative lesions. Gut microbiome functions like an endocrine organ by generating bioactive metabolites that can directly or indirectly impact human physiology. An alteration in the composition and function of intestinal flora, i.e. gut dysbiosis, is implicated in neurodegenerative and cerebrovascular diseases. Additionally, gut dysbiosis may accelerate the progression of cognitive impairment. Dysbiosis may result from obesity; metabolic disorders, cardiovascular disease, and sleep disorders, Lack of physical activity is associated with dysbiosis as well. These may coexist in various patterns in older people, enhancing the risk, incidence, and progression of cerebrovascular lesions, neurodegenerative disorders, and cognitive impairment, creating a vicious circle. Recently, it has been reported that several metabolites produced by gut microbiota (e.g., trimethylamine/trimethylamine N-oxide, short-chain fatty acids, secondary bile acids) may be linked to neurodegenerative and cerebrovascular diseases. New treatment modalities, including prebiotic and probiotics, may normalize the gut microbiota composition, change the brain-gut barrier, and decrease the risk of the pathology development. Fecal microbiota transplantation, sometimes in combination with other methods, is used for remodeling and replenishing the symbiotic gut microbiome. This promising field of research is associated with basic findings of bidirectional communication between body organs and gut microbiota that creates new possibilities of pharmacological treatments of many clinical conditions. The authors present the role of gut microbiota in physiology, and the novel therapeutic targets in modulation of intestinal microbiota Personalized therapies based on their personal genome make up could offer benefits by modulating microbiota cross-talk with brain and cardiovascular system. A healthy lifestyle, including pre and probiotic nutrition is generally recommended. Prevention may also be enhanced by correcting gut dysbiosis resulting a reduced risk of post-stroke cognitive impairment including dementia.

Body Fluid Biomarkers for Alzheimer's Disease-An Up-To-Date Overview

Neurodegeneration is a highly complex process which is associated with a variety of molecular mechanisms related to ageing. Among neurodegenerative disorders, Alzheimer's disease (AD) is the most common, affecting more than 45 million individuals. The underlying mechanisms involve amyloid plaques and neurofibrillary tangles (NFTs) deposition, which will subsequently lead to oxidative stress, chronic neuroinflammation, neuron dysfunction, and neurodegeneration. The current diagnosis methods are still limited in regard to the possibility of the accurate and early detection of the diseases. Therefore, research has shifted towards the identification of novel biomarkers and matrices as biomarker sources, beyond amyloid-β and tau protein levels within the cerebrospinal fluid (CSF), that could improve AD diagnosis. In this context, the aim of this paper is to provide an overview of both conventional and novel biomarkers for AD found within body fluids, including CSF, blood, saliva, urine, tears, and olfactory fluids.

Human Pluripotent Stem Cell-Derived Neural Cells as a Relevant Platform for Drug Screening in Alzheimer's Disease

Extracellular amyloid-beta deposition and intraneuronal Tau-laden neurofibrillary tangles are prime features of Alzheimer's disease (AD). The pathology of AD is very complex and still not fully understood, since different neural cell types are involved in the disease. Although neuronal function is clearly deteriorated in AD patients, recently, an increasing number of evidences have pointed towards glial cell dysfunction as one of the main causative phenomena implicated in AD pathogenesis. The complex disease pathology together with the lack of reliable disease models have precluded the development of effective therapies able to counteract disease progression. The discovery and implementation of human pluripotent stem cell technology represents an important opportunity in this field, as this system allows the generation of patient-derived cells to be used for disease modeling and therapeutic target identification and as a platform to be employed in drug discovery programs. In this review, we discuss the current studies using human pluripotent stem cells focused on AD, providing convincing evidences that this system is an excellent opportunity to advance in the comprehension of AD pathology, which will be translated to the development of the still missing effective therapies.

Effects of a Nutritional Formulation Containing Caprylic and Capric Acid, Phosphatidylserine, and Docosahexaenoic Acid in Streptozotocin-Lesioned Rats

Background

It has been studied that nutrition can influence Alzheimer's disease (AD) onset and progression. Some studies on rodents using intraventricular streptozotocin (STZ) injection showed that this toxin changes cerebral glucose metabolism and insulin signaling pathways.

Objective

The aim of the present study was to evaluate whether a nutritional formulation could reduce cognitive impairment in STZ-induced animals.

Methods

The rats were randomly divided into two groups: sham and STZ. The STZ group received a single bilateral STZ-ICV injection (1 mg/kg). The sham group received a bilateral ICV injection of 0.9% saline solution. The animals were treated with AZ1 formulation (Instanth^® NEO, Prodiet Medical Nutrition) (1 g/kg, PO) or its vehicle (saline solution) for 30 days, once a day starting one day after the stereotaxic surgery (n = 6-10). The rats were evaluated using the open field test to evaluate locomotor activity at day 27 after surgery. Cognitive performance was evaluated at day 28 using the object recognition test and the spatial version of the Y-maze test. At day 30, the rats were anesthetized with chloral hydrate (400 mg/kg, i.p) and euthanized in order to evaluate IBA1 in the hippocampus. The differences were analyzed using one-way ANOVA with Bonferroni's or Kruskal Wallis with Dunn's post-hoc test.

Results/Conclusion

STZ-lesioned rats present memory impairment besides the increased microglial activation. The treatment with AZ1 formulation reversed the memory impairment observed in the object recognition test and Y-maze and also reduced IBA1 in CA1 and DG.

Sleep, Noninvasive Brain Stimulation, and the Aging Brain: Challenges and Opportunities

As we age, sleep patterns undergo severe modifications of their micro and macrostructure, with an overall lighter and more fragmented sleep structure. In general, interventions targeting sleep represent an excellent opportunity not only to maintain life quality in the healthy aging population, but also to enhance cognitive performance and, when pathology arises, to potentially prevent/slow down conversion from e.g. Mild Cognitive Impairment (MCI) to Alzheimer's Disease (AD). Sleep abnormalities are, in fact, one of the earliest recognizable biomarkers of dementia, being also partially responsible for a cascade of cortical events that worsen dementia pathophysiology, including impaired clearance systems leading to build-up of extracellular amyloid-β (Aβ) peptide and intracellular hyperphosphorylated tau proteins. In this context, Noninvasive Brain Stimulation (NiBS) techniques, such as transcranial electrical stimulation (tES) and transcranial magnetic stimulation (TMS), may help investigate the neural substrates of sleep, identify sleep-related pathology biomarkers, and ultimately help patients and healthy elderly individuals to restore sleep quality and cognitive performance. However, brain stimulation applications during sleep have so far not been fully investigated in healthy elderly cohorts, nor tested in AD patients or other related dementias. The manuscript discusses the role of sleep in normal and pathological aging, reviewing available evidence of NiBS applications during both wakefulness and sleep in healthy elderly individuals as well as in MCI/AD patients. Rationale and details for potential future brain stimulation studies targeting sleep alterations in the aging brain are discussed, including enhancement of cognitive performance, overall quality of life as well as protein clearance.

From the Entorhinal Region via the Prosubiculum to the Dentate Fascia: Alzheimer Disease-Related Neurofibrillary Changes in the Temporal Allocortex

The pathological process underlying Alzheimer disease (AD) unfolds predominantly in the cerebral cortex with the gradual appearance and regional progression of abnormal tau. Intraneuronal tau pathology progresses from the temporal transentorhinal and entorhinal regions into neocortical fields/areas of the temporal allocortex. Here, based on 95 cases staged for AD-related neurofibrillary changes, we propose an ordered progression of abnormal tau in the temporal allocortex. Initially, abnormal tau was limited to distal dendritic segments followed by tau in cell bodies of projection neurons of the transentorhinal/entorhinal layer pre-α. Next, abnormal distal dendrites accumulated in the prosubiculum and extended into the CA1 stratum oriens and lacunosum. Subsequently, altered dendrites developed in the CA2/CA3 stratum oriens and stratum lacunosum-moleculare, combined with tau-positive thorny excrescences of CA3/CA4 mossy cells. Finally, granule cells of the dentate fascia became involved. Such a progression might recapitulate a sequence of transsynaptic spreading of abnormal tau from 1 projection neuron to the next: From pre-α cells to distal dendrites in the prosubiculum and CA1; then, from CA1 or prosubicular pyramids to CA2 principal cells and CA3/CA4 mossy cells; finally, from CA4 mossy cells to dentate granule cells. The lesions are additive: Those from the previous steps persist.

Slow Wave Sleep Is a Promising Intervention Target for Alzheimer's Disease

Alzheimer's disease (AD) is the major cause of dementia, characterized by the presence of amyloid-beta plaques and neurofibrillary tau tangles. Plaques and tangles are associated with sleep-wake cycle disruptions, including the disruptions in non-rapid eye movement (NREM) slow wave sleep (SWS). Alzheimer's patients spend less time in NREM sleep and exhibit decreased slow wave activity (SWA). Consistent with the critical role of SWS in memory consolidation, reduced SWA is associated with impaired memory consolidation in AD patients. The aberrant SWA can be modeled in transgenic mouse models of amyloidosis and tauopathy. Animal models exhibited slow wave impairments early in the disease progression, prior to the deposition of amyloid-beta plaques, however, in the presence of abundant oligomeric amyloid-beta. Optogenetic rescue of SWA successfully halted the amyloid accumulation and restored intraneuronal calcium levels in mice. On the other hand, optogenetic acceleration of slow wave frequency exacerbated amyloid deposition and disrupted neuronal calcium homeostasis. In this review, we summarize the evidence and the mechanisms underlying the existence of a positive feedback loop between amyloid/tau pathology and SWA disruptions that lead to further accumulations of amyloid and tau in AD. Moreover, since SWA disruptions occur prior to the plaque deposition, SWA disruptions may provide an early biomarker for AD. Finally, we propose that therapeutic targeting of SWA in AD might lead to an effective treatment for Alzheimer's patients.

Umbilical cord-derived mesenchymal stem cells in neurodegenerative disorders: from literature to clinical practice

Mesenchymal stem cells (MSCs) have provided a promising tool for cell therapy. Umbilical cord (UC) is one of the best sources of MSCs since its collection is noninvasive, and effortless, and the cells from this source are more capable and prolific. It has been proven that the differentiation, migration and protective properties of UC-MSCs are superior compared with other kinds of stem cells. Moreover, incurable neurodegenerative diseases, such as Alzheimer's disease, multiple sclerosis, Parkinson's disease and Huntington, encourage scientists to apply UC-MSCs transplantation in order to find a definite treatment. This review will focus on the preclinical and clinical use of mesenchymal stem cells derived from human umbilical cord in the treatment of neurodegenerative disorders.