Neuropathology and cognitive impairment in Alzheimer disease: a complex but coherent relationship

Defective Autophagy and Mitophagy in Alzheimer's Disease: Mechanisms and Translational Implications

The main histopathology of Alzheimer's disease (AD) is featured by the extracellular accumulation of amyloid-β (Aβ) plaques and intracellular tau neurofibrillary tangles (NFT) in the brain, which is likely to result from co-pathogenic interactions among multiple factors, e.g., aging or genes. The link between defective autophagy/mitophagy and AD pathologies is still under investigation and not fully established. In this review, we consider how AD is associated with impaired autophagy and mitophagy, and how these impact pathological hallmarks as well as the potential mechanisms. This complicated interplay between autophagy or mitophagy and histopathology in AD suggests that targeting autophagy or mitophagy probably is a promising anti-AD drug candidate. Finally, we review the implications of some new insights for induction of autophagy or mitophagy as the new therapeutic way that targets processes upstream of both NFT and Aβ plaques, and hence stops the neurodegenerative course in AD.

Dimethyl fumarate does not mitigate cognitive decline and β-amyloidosis in female APPPS1 mice

INTRODUCTION

Alzheimer's disease (AD) is the leading cause of dementia and a major global health issue. Currently, only limited treatment options are available to patients. One possibility to expand the treatment repertoire is repurposing of existing drugs such as dimethyl fumarate (DMF). DMF is approved for treatment of multiple sclerosis and previous animal studies have suggested that DMF may also have a beneficial effect for the treatment of AD.

METHODS

We used an APPPS1 transgenic model of senile β-amyloidosis and treated female mice orally with DMF in two treatment paradigms (pre and post onset). We quantified learning and memory parameters, β-amyloidosis, and neuroinflammation to determine the potential of DMF as AD therapeutics.

RESULTS

Treatment with DMF had no influence on water maze performance, β-amyloid accumulation, plaque formation, microglia activation, and recruitment of immune cells to the brain. Compared to vehicle-treated animals, oral DMF treatment could not halt or retard disease progression in the mice.

DISCUSSION

Our results do not favour the use of DMF as treatment for AD. While our results stand in contrast to previous findings in other models, they emphasize the importance of animal model selection and suggest further studies to elucidate the mechanisms leading to conflicting results.

Soluble amyloid beta-containing aggregates are present throughout the brain at early stages of Alzheimer's disease

Protein aggregation likely plays a key role in the initiation and spreading of Alzheimer's disease pathology through the brain. Soluble aggregates of amyloid beta are believed to play a key role in this process. However, the aggregates present in humans are still poorly characterized due to a lack of suitable methods required for characterizing the low concentration of heterogeneous aggregates present. We have used a variety of biophysical methods to characterize the aggregates present in human Alzheimer's disease brains at Braak stage III. We find soluble amyloid beta-containing aggregates in all regions of the brain up to 200 nm in length, capable of causing an inflammatory response. Rather than aggregates spreading through the brain as disease progresses, it appears that aggregation occurs all over the brain and that different brain regions are at earlier or later stages of the same process, with the later stages causing increased inflammation.

Insights into lncRNAs in Alzheimer's disease mechanisms

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common dementia among the elderly. The pathophysiology of AD is characterized by two hallmarks: amyloid plaques, produced by amyloid β (Aβ) aggregation, and neurofibrillary tangle (NFT), produced by accumulation of phosphorylated tau. The regulatory roles of non-coding RNAs (ncRNAs), particularly long noncoding RNAs (lncRNAs), have been widely recognized in gene expression at the transcriptional and posttranscriptional levels. Mounting evidence shows that lncRNAs are aberrantly expressed in AD progression. Here, we review the lncRNAs that implicated in the regulation of Aβ peptide, tau, inflammation, cell death, and other aspects which are the main mechanisms of AD pathology. We also discuss the possible clinical or therapeutic utility of lncRNA detection or targeting to help diagnose or possibly combat AD.

The impact of exercise, sleep, and diet on neurocognitive recovery from mild traumatic brain injury in older adults: A narrative review

Mild traumatic brain injury (mTBI) accounts for a large majority of traumatic brain injuries sustained globally each year. Older adults, who are already susceptible to age-related declines to neurocognitive health, appear to be at an increased risk of both sustaining an mTBI and experiencing slower or impaired recovery. There is also growing evidence that mTBI is a potential risk factor for accelerated cognitive decline and neurodegeneration. Lifestyle-based interventions are gaining prominence as a cost-effective means of maintaining cognition and brain health with age. Consequently, inter-individual variations in exercise, sleep, and dietary patterns could influence the trajectory of post-mTBI neurocognitive recovery, particularly in older adults. This review synthesises the current animal and human literature centred on the mechanisms through which lifestyle-related habits and behaviours could influence acute and longer-term neurocognitive functioning following mTBI. Numerous neuroprotective processes which are impacted by lifestyle factors have been established in animal models of TBI. However, the literature is characterised by a lack of translation to human samples and limited appraisal of the interaction between ageing and brain injury. Further research is needed to better establish the therapeutic utility of applying lifestyle-based modifications to improve post-mTBI neurocognitive outcomes in older adults.

Use of hypnosis in the field of dementia: A scoping review

BACKGROUND

Dementia has negative implications for the quality of life of person and lead to situations of distress. Hypnosis is effective in several health domains but its use in people with dementia is debated.

OBJECTIVE

The aim was to scope the research activity on the use of hypnosis with persons with dementia to manage their distress, symptoms or daily life.

METHOD

We used five international databases: PubMed/Medline, the Cochrane Library, ScienceDirect, PsycINFO, and Google Scholar.

RESULTS

Only seven articles were listed and three articles described the same longitudinal pilot study. Hypnosis was used either in one or several sessions, alone or as an adjunct and reinforced with daily self-hypnosis with or without audio tapes in people with dementia. The results show that they experienced moderate-to-high hypnotizability, but some adaptations were needed given their attention disabilities. They showed benefit on symptoms.  Nevertheless, some methodological weaknesses such as small heterogeneous samples, the use of non-validated tools for hypnotizability or outcomes, or the insufficient definition of the content of sessions limit the scope of the results.

CONCLUSION

Hypnosis seems feasible and acceptable for people with dementia and could provide interesting clinical benefits, but a randomized controlled trial with a large homogeneous sample would be highly informative.

Gene Ontology Curation of Neuroinflammation Biology Improves the Interpretation of Alzheimer's Disease Gene Expression Data

BACKGROUND

Gene Ontology (GO) is a major bioinformatic resource used for analysis of large biomedical datasets, for example from genome-wide association studies, applied universally across biological fields, including Alzheimer's disease (AD) research.

OBJECTIVE

We aim to demonstrate the applicability of GO for interpretation of AD datasets to improve the understanding of the underlying molecular disease mechanisms, including the involvement of inflammatory pathways and dysregulated microRNAs (miRs).

METHODS

We have undertaken a systematic full article GO annotation approach focused on microglial proteins implicated in AD and the miRs regulating their expression. PANTHER was used for enrichment analysis of previously published AD data. Cytoscape was used for visualizing and analyzing miR-target interactions captured from published experimental evidence.

RESULTS

We contributed 3,084 new annotations for 494 entities, i.e., on average six new annotations per entity. This included a total of 1,352 annotations for 40 prioritized microglial proteins implicated in AD and 66 miRs regulating their expression, yielding an average of twelve annotations per prioritized entity. The updated GO resource was then used to re-analyze previously published data. The re-analysis showed novel processes associated with AD-related genes, not identified in the original study, such as 'gliogenesis', 'regulation of neuron projection development', or 'response to cytokine', demonstrating enhanced applicability of GO for neuroscience research.

CONCLUSIONS

This study highlights ongoing development of the neurobiological aspects of GO and demonstrates the value of biocuration activities in the area, thus helping to delineate the molecular bases of AD to aid the development of diagnostic tools and treatments.

Staging Alzheimer's Disease in the Brain and Retina of B6.APP/PS1 Mice by Transcriptional Profiling

Alzheimer's disease (AD) is a common form of dementia characterized by amyloid plaque deposition, tau pathology, neuroinflammation, and neurodegeneration. Mouse models recapitulate some key features of AD. For instance, the B6.APP/PS1 model (carrying human transgenes for mutant forms of APP and PSEN1) shows plaque deposition and neuroinflammation involving both astrocytes and microglia beginning around 4-6 months of age. However, significant tau pathology and neurodegeneration are not apparent in this model even when assessed at old age. Therefore, this model is ideal for studying neuroinflammatory responses to amyloid deposition. Here, RNA sequencing of brain and retinal tissue, generalized linear modeling (GLM), functional annotation followed by validation by immunofluorescence was performed in B6.APP/PS1 mice to determine the earliest molecular changes prior to and around the onset of plaque deposition (2-6 months of age). Multiple pathways were shown to be activated in response to amyloid deposition including the JAK/STAT and NALFD pathways. Putative, cell-specific targets of STAT3, a central component of the JAK/STAT pathway, were identified that we propose provide more precise options for assessing the potential for targeting activation of the JAK/STAT pathway as a treatment for human AD. In the retina, GLM predicted activation of vascular-related pathways. However, many of the gene expression changes comparing B6 with B6.APP/PS1 retina samples occurred prior to plaque onset (2 months of age). This suggests retinal changes in B6.APP/PS1 mice may be an artefact of overexpression of mutant forms of APP and PSEN1 providing limited translatability to human AD. Therefore, caution should be taken when using this mouse model to assess the potential of using the eye as a window to the brain for AD.

Dysbiosis and Alzheimer's Disease: A Role for Chronic Stress?

Alzheimer’s disease (AD) is an incurable, neuropsychiatric, pathological condition that deteriorates the worth of geriatric lives. AD is characterized by aggregated senile amyloid plaques, neurofibrillary tangles, neuronal loss, gliosis, oxidative stress, neurotransmitter dysfunction, and bioenergetic deficits. The changes in GIT composition and harmony have been recognized as a decisive and interesting player in neuronal pathologies including AD. Microbiota control and influence the oxidoreductase status, inflammation, immune system, and the endocrine system through which it may have an impact on the cognitive domain. The altered and malfunctioned state of microbiota is associated with minor infections to complicated illnesses that include psychosis and neurodegeneration, and several studies show that microbiota regulates neuronal plasticity and neuronal development. The altered state of microbiota (dysbiosis) may affect behavior, stress response, and cognitive functions. Chronic stress-mediated pathological progression also has a well-defined role that intermingles at various physiological levels and directly impacts the pathological advancement of AD. Chronic stress-modulated alterations affect the well-established pathological markers of AD but also affect the gut–brain axis through the mediation of various downstream signaling mechanisms that modulate the microbial commensals of GIT. The extensive literature reports that chronic stressors affect the composition, metabolic activities, and physiological role of microbiota in various capacities. The present manuscript aims to elucidate mechanistic pathways through which stress induces dysbiosis, which in turn escalates the neuropathological cascade of AD. The stress–dysbiosis axis appears a feasible zone of work in the direction of treatment of AD.

Untapped endocannabinoid pharmacological targets: Pipe dream or pipeline?

It has been established that the endogenous cannabinoid (endocannabinoid) system plays key modulatory roles in a wide variety of pathological conditions. The endocannabinoid system comprises both cannabinoid receptors, their endogenous ligands including 2-arachidonoylglycerol (2-AG), N-arachidonylethanolamine (anandamide, AEA), and enzymes that regulate the synthesis and degradation of endogenous ligands which include diacylglycerol lipase alpha (DAGL-α), diacylglycerol lipase beta (DAGL-β), fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), α/β hydrolase domain 6 (ABHD6). As the endocannabinoid system exerts considerable involvement in the regulation of homeostasis and disease, much effort has been made towards understanding endocannabinoid-related mechanisms of action at cellular, physiological, and pathological levels as well as harnessing the various components of the endocannabinoid system to produce novel therapeutics. However, drug discovery efforts within the cannabinoid field have been slower than anticipated to reach satisfactory clinical endpoints and raises an important question into the validity of developing novel ligands that therapeutically target the endocannabinoid system. To answer this, we will first examine evidence that supports the existence of an endocannabinoid system role within inflammatory diseases, neurodegeneration, pain, substance use disorders, mood disorders, as well as metabolic diseases. Next, this review will discuss recent clinical studies, within the last 5 years, of cannabinoid compounds in context to these diseases. We will also address some of the challenges and considerations within the cannabinoid field that may be important in the advancement of therapeutics into the clinic.

Neuronal and Astrocytic Extracellular Vesicle Biomarkers in Blood Reflect Brain Pathology in Mouse Models of Alzheimer's Disease

Circulating neuronal extracellular vesicles (NEVs) of Alzheimer’s disease (AD) patients show high Tau and β-amyloid (Aβ) levels, whereas their astrocytic EVs (AEVs) contain high complement levels. To validate EV proteins as AD biomarkers, we immunocaptured NEVs and AEVs from plasma collected from fifteen wild type (WT), four 2xTg-AD, nine 5xFAD, and fifteen 3xTg-AD mice and assessed biomarker relationships with brain tissue levels. NEVs from 3xTg-AD mice had higher total Tau (p = 0.03) and p181-Tau (p = 0.0004) compared to WT mice. There were moderately strong correlations between biomarkers in NEVs and cerebral cortex and hippocampus (total Tau: cortex, r = 0.4, p = 0.009; p181-Tau: cortex, r = 0.7, p < 0.0001; hippocampus, r = 0.6, p < 0.0001). NEVs from 5xFAD compared to other mice had higher Aβ42 (p < 0.005). NEV Aβ42 had moderately strong correlations with Aβ42 in cortex (r = 0.6, p = 0.001) and hippocampus (r = 0.7, p < 0.0001). AEV C1q was elevated in 3xTg-AD compared to WT mice (p = 0.005); AEV C1q had moderate-strong correlations with C1q in cortex (r = 0.9, p < 0.0001) and hippocampus (r = 0.7, p < 0.0001). Biomarkers in circulating NEVs and AEVs reflect their brain levels across multiple AD mouse models supporting their potential use as a “liquid biopsy” for neurological disorders.

Serum tyrosine is associated with better cognition in Lewy body dementia

Amino acids' neuroactivity, and roles in excitotoxity and oxidative stress are linked to dementia. We aimed to investigate whether circulating amino acid concentrations were associated with cognitive decline in patients with mild Alzheimer's disease (AD) and Lewy body dementia (LBD). Baseline serum amino acid concentrations were measured in 89 patients with AD and 65 with LBD (13 with Parkinson's disease dementia and 52 with dementia with Lewy bodies). The Mini-Mental State Examination (MMSE) was administered at baseline and annually for five years. Associations between baseline amino acid concentrations and longitudinal MMSE score were assessed using a linear-mixed effects model stratified by diagnosis with adjustment for multiple comparisons. The results of the study indicated that serum tyrosine was positively associated with MMSE performance during the five-year follow-up period in patients with LBD (q-value = 0.012), but not AD. In conclusion, higher baseline serum concentrations of tyrosine, the precursor amino acid in dopamine and norepinephrine synthesis, was associated with better cognitive performance in patients with LBD, but not AD, throughout the 5-year follow-up period.

Aggregated Tau Measured by Visual Interpretation of Flortaucipir Positron Emission Tomography and the Associated Risk of Clinical Progression of Mild Cognitive Impairment and Alzheimer Disease: Results From 2 Phase III Clinical Trials

Questions

What is the association between flortaucipir positron emission tomography (PET) imaging visual classification using a clinically applicable and US Food and Drug Administration–approved method and 18-month cognitive and functional decline in patients with clinically diagnosed mild cognitive impairment and dementia owing to Alzheimer disease (AD)?

Findings

In this analysis of 2 open-label clinical trials, visual read of an advanced flortaucipir PET AD pattern was associated with an increased risk of 18-month cognitive and functional decline compared with other scan patterns.

Meaning

Clinically applicable visual reads of flortaucipir PET scans may provide valuable information regarding the risk of near-term clinical deterioration among patients with clinically diagnosed mild cognitive impairment or dementia owing to AD.

Importance

Flortaucipir positron emission tomography (PET) scans, rated with a novel, US Food and Drug Administration–approved, clinically applicable visual interpretation method, provide valuable information regarding near-term clinical progression of patients with Alzheimer disease (AD) or mild cognitive impairment (MCI).

Objective

To evaluate the association between flortaucipir PET visual interpretation and patients’ near-term clinical progression.

Design/Setting/Participants

Two prospective, open-label, longitudinal studies were conducted from December 2014 to September 2019. Study 1 screened 298 patients and enrolled 160 participants who had a flortaucipir scan at baseline visit. Study 2 selected 205 participants from the AMARANTH trial, which was terminated after futility analysis. Out of the 2218 AMARANTH participants, 424 had a flortaucipir scan around randomization, but 219 did not complete 18-month clinical dementia rating (CDR) assessments and thus were excluded. In both studies, all participants were diagnosed as clinically impaired, and they were longitudinally followed up for approximately 18 months after baseline.

Main Outcomes and Measures

Flortaucipir scans were rated as either advanced or nonadvanced AD pattern using a predetermined visual interpretation method. The CDR sum of box (CDR-SB) score was used as primary clinical end point measurement in both studies.

Results

Of the 364 study participants who had readable scans, 48% were female (n = 174 of 364), and the mean (SD) age was 71.8 (8.7) years. Two hundred forty participants were rated as having an advanced AD pattern. At 18 months follow-up, 70% of those with an advanced AD pattern (n = 147 of 210) had 1 point or more increase in CDR-SB, an event predefined as clinically meaningful deterioration. In contrast, only 46% of those with a nonadvanced AD pattern scan (n = 48 of 105) experienced the same event (risk ratio [RR], 1.40; 95% CI, 1.11-1.76; P = .005). The adjusted mean CDR-SB changes were 2.28 and 0.98 for advanced and nonadvanced AD pattern groups, respectively (P < .001). Analyses with other clinical end point assessments, as well as analyses with each individual study’s data, consistently indicated a higher risk of clinical deterioration associated with an advanced AD scan pattern.

Conclusions and Relevance

These results suggest that flortaucipir PET scans, when interpreted with an US Food and Drug Administration–approved, clinically applicable visual interpretation method, may provide valuable information regarding the risk of clinical deterioration over 18 months among patients with AD and MCI.

Trial Registration

ClinicalTrials.gov Identifier: NCT02016560 and NCT03901105

Administering crocin ameliorates anxiety-like behaviours and reduces the inflammatory response in amyloid-beta induced neurotoxicity in rat

Anxiety, hippocampus synaptic plasticity deficit, as well as pro-inflammatory cytokines, are involved in Alzheimer's disease (AD). The present study is designed to evaluate the possible therapeutic effect of crocin on anxiety-like behaviours, hippocampal synaptic plasticity and neuronal shape, as well as pro-inflammatory cytokines in the hippocampus using in vivo amyloid-beta (Aβ) models of AD. The Aβ peptide (1-42) was bilaterally injected into the frontal-cortex. Five hours after the surgery, the rats were given intraperitoneal (IP) crocin (30 mg/kg) daily up to 12 days. Elevated plus maze results showed that crocin treatment after bilateral Aβ injection significantly increased the percentage of spent time into open arms, frequency of entries, and percentage of entries into open arms as compared with the Aβ group. In the open field test, the Aβ+crocin group showed a higher percentage of spent time in the centre and frequency of entries into central zone as compare with the Aβ treated animals. Administering crocin increased the number of soma, dendrites and axonal arbores in the CA1 neurons among the rats with Aβ neurotoxicity. Cresyl violet (CV) staining showed that crocin increased the number of CV-positive cells in the CA1 region of the hippocampus compared with the Aβ group. Silver-nitrate staining indicated that crocin reduced neurofibrillary tangle formation induced by Aβ. Crocin treatment attenuated the expression of TNF-α and IL-1β mRNA in the hippocampus compared with the Aβ group. Our results suggest that crocin attenuated Aβ-induced anxiety-like behaviours and neuronal damage, and synaptic plasticity loss in hippocampal CA1 neurons may via its anti-inflammatory effects.

Synthesis of novel sulfonamides with anti-Alzheimer and antioxidant capacities

A series of novel dopamine analogs incorporating urea and sulfonamide functional groups was synthesized from 3,4-dimethoxyphenethylamine. The reaction of 3,4-dimethoxyphenethylamine with N,N-dimethylcarbamoyl chloride, followed by the sulfonyl chlorination of the urea derivative, gave benzene-1-sulfonyl chloride 9, which was reacted with NH₃ (aq) or N-alkyl amines to give related sulfonamides. The O-demethylation reaction of the subsequent compounds with BBr₃ afforded four novel phenolic dopamine analogs including sulfonamide and urea in the same structure. The anticholinergic and antioxidant effects of the synthesized compounds were examined. Compound 13 exhibited inhibition at the micromolar level for both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The IC₅₀ value of 13 was calculated as 298 ± 43 µM for AChE and 321 ± 29 µM for BChE. The antioxidant and antiradical effects of the molecules were investigated by five different methods. Among the synthesized compounds 10-18, the best antioxidant and antiradical activities belong to the phenolic compounds 15-18. Compounds 16 and 18 have a higher reducing power than the standards used, that is, butylated hydroxytoluene, butylated hydroxyanisole, Trolox, and α-tocopherol, for Fe³⁺ -Fe²⁺ and Cu²⁺ -Cu⁺ reducing activities. For the DPPH• radical scavenging method, compounds 16-18 have a much better scavenging power than the standard molecules. In addition, it has been determined by the induced-fit docking method that compound 13 is well-fitted in the active site of the enzymes. ADME studies reveal that the pharmacokinetic and physicochemical properties of all synthesized compounds are within an acceptable range.

Neuroinflammation in Alzheimer's disease and beneficial action of luteolin

Alzheimer's disease (AD), already the world's most common form of dementia, is projected to continue increasing in prevalence over the next several decades. The current lack of understanding of the pathogenesis of AD has hampered the development of effective treatments. Historically, AD research has been predicated on the amyloid cascade hypothesis (ACH), which attributes disease progression to the build-up of amyloid protein. However, multiple clinical studies of drugs interfering with ACH have failed to show any benefit demonstrating that AD etiology is more complex than previously thought. Here we review the current literature on the emerging key role of neuroinflammation, especially activation of microglia, in AD pathogenesis. Moreover, we provide compelling evidence that certain flavonoids, especially luteolin formulated in olive pomace oil together with hydroxytyrosol, offers a reasonable prophylactic treatment approach due to its many beneficial actions.

Differentiating traits and states identifies the importance of chronic neuropsychiatric symptoms for cognitive prognosis in mild dementia

INTRODUCTION

Neuropsychiatric symptoms (NPS) in dementia are associated with poor cognitive outcomes in longitudinal studies. Whether this is due to differences in symptom burden between persons (BP) or changes within persons (WP) is unknown.

METHODS

Patients with mild Alzheimer's disease (AD, n = 111) and Lewy-body dementia (LBD, n = 85) were assessed annually for 8 years. We modelled the association between NPS assessed by the Neuropsychiatric Inventory (NPI) and Mini-Mental State Examinations (MMSE) using Tobit mixed-effects model with NPS as individual means over time (BP) and its deviance (WP).

RESULTS

The association between higher NPS and poorer cognitive outcomes was mostly due to BP differences for the NPI-total score, and in particular for delusions, hallucinations, agitation, aberrant motor behavior, and apathy scores.

DISCUSSION

The NPS trait (BP) effect on cognitive decline is considerably stronger than the state effect (WP). Clinically, long-term rather than episodic NPS better identifies patients with poor cognitive outcomes.

Disclosure of preclinical Alzheimer's disease biomarker results in research and clinical settings: Why, how, and what we still need to know

Disclosure of personal disease-related information to asymptomatic adults has been debated over the last century in medicine and research. Recently, Alzheimer's disease (AD) has been conceptualized as a continuum that begins with a "preclinical" stage in which biomarkers are present in the absence of cognitive impairment. Studies have begun assessing the safety, psychological, and behavioral effects of disclosing both AD-related genetic and biomarker information to cognitively unimpaired older adults. Yet, debate continues over the appropriate circumstances and methods for returning such information. This article outlines concerns with and rationale for AD biomarker disclosure and summarizes findings from prior studies. Overall, this article aims to describe and respond to key questions concerning disclosure of amyloid positron emission tomography scan results to asymptomatic adults in a research setting. Moving forward, such conditions are important to consider as interventions target the preclinical phase of AD and normalize disclosing biomarker information to cognitively unimpaired persons.

Deep Brain Stimulation in Alzheimer's Disease: Targeting the Nucleus Basalis of Meynert

Alzheimer's disease (AD) is becoming a prevalent disease in the elderly population. Past decades have witnessed the development of drug therapies with varying targets. However, all drugs with a single molecular target fail to reverse or ameliorate AD progression, which ultimately results in cortical and subcortical network dysregulation. Deep brain stimulation (DBS) has been proven effective for the treatment of Parkinson's disease, essential tremor, and other neurological diseases. As such, DBS has also been gradually acknowledged as a potential therapy for AD. The current review focuses on DBS of the nucleus basalis of Meynert (NBM). As a critical component of the cerebral cholinergic system and the Papez circuit in the basal ganglia, the NBM plays an indispensable role in the subcortical regulation of memory, attention, and arousal state, which makes the NBM a promising target for modulation of neural network dysfunction and AD treatment. We summarized the intricate projection relations and functionality of the NBM, current approaches for stereotactic localization and evaluation of the NBM, and the therapeutic effects of NBM-DBS both in patients and animal models. Furthermore, the current shortcomings of NBM-DBS, such as variations in cortical blood flow, increased temperature in the target area, and stimulation-related neural damage, were presented.

Different Morphology of Neuritic Plaques in the Archicortex of Alzheimer's Disease with Comorbid Synucleinopathy: A Pilot Study

BACKGROUND

Bulbous neuritic changes in neuritic plaques have already been described, and their possible effect on the clinical course of the disease has been discussed.

OBJECTIVE

In our study, we focused on the location and density of these structures in patients with only Alzheimer's disease (AD) and patients with AD in comorbidity with synucleinopathies.

METHODS

Utilizing immunohistochemistry and confocal microscopy, we evaluated differences of neocortical and archicortical neuritic plaques and the frequency of bulbous changes in the archicortex of 14 subjects with Alzheimer's disease (AD), 10 subjects with the Lewy body variant of Alzheimer's disease (AD/DLB), and 4 subjects with Alzheimer's disease with amygdala Lewy bodies (AD/ALB). Also, the progression and density of neuritic changes over the time course of the disease were evaluated.

RESULTS

We found structural differences in bulbous dystrophic neurites more often in AD/DLB and AD/ALB than in pure AD cases. The bulbous neuritic changes were more prominent in the initial and progressive phases and were reduced in cases with a long clinical course.

CONCLUSION

Our results indicate that there is a prominent difference in the shape and composition of neocortical and archicortical neuritic plaques and, moreover, that bulbous neuritic changes can be observed at a higher rate in AD/DLB and AD/ALB subjects compared to pure AD subjects. This observation probably reflects that these subacute changes are more easily seen in the faster clinical course of AD patients with comorbidities.

Partial Inhibition of Mitochondrial Complex I Reduces Tau Pathology and Improves Energy Homeostasis and Synaptic Function in 3xTg-AD Mice

Background:

Accumulation of hyperphosphorylated tau (pTau) protein is associated with synaptic dysfunction in Alzheimer’s disease (AD). We previously demonstrated that neuroprotection in familial mouse models of AD could be achieved by targeting mitochondria complex I (MCI) and activating the adaptive stress response. Efficacy of this strategy on pTau-related pathology remained unknown.

Objective:

To investigate the effect of specific MCI inhibitor tricyclic pyrone compound CP2 on levels of human pTau, memory function, long term potentiation (LTP), and energy homeostasis in 18-month-old 3xTg-AD mice and explore the potential mechanisms.

Methods:

CP2 was administered to male and female 3xTg-AD mice from 3.5–18 months of age. Cognitive function was assessed using the Morris water maze. Glucose metabolism was measured in periphery using a glucose tolerance test and in the brain using fluorodeoxyglucose F18 positron-emission tomography (FDG-PET). LTP was evaluated using electrophysiology in the hippocampus. The expression of key proteins associated with neuroprotective mechanisms were assessed by western blotting.

Results:

Chronic CP2 treatment restored synaptic activity in female 3xTg-AD mice; cognitive function, levels of synaptic proteins, glucose metabolism, and energy homeostasis were improved in male and female 3xTg-AD mice. Significant reduction of human pTau in the brain was associated with increased activity of protein phosphatase of type 2A (PP2A), and reduced activity of cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3β (GSK3β).

Conclusion:

CP2 treatment protected against synaptic dysfunction and memory impairment in symptomatic 3xTg-AD mice, and reduced levels of human pTau, indicating that targeting mitochondria with small molecule specific MCI inhibitors represents a promising strategy for treating AD.

Inflammation Drives Alzheimer's Disease: Emphasis on 5-lipoxygenase Pathways

It is a known fact that inflammation affects several physiological processes, including the functioning of the central nervous system. Additionally, impairment of lipid mechanisms/pathways have been associated with a number of neurodegenerative disorders and Alzheimer's Disease (AD) is one of them. However, much attention has been given to the link between tau and beta- amyloid hypothesis in AD pathogenesis/prognosis. Increasing evidences suggest that biologically active lipid molecules could influence the pathophysiology of AD via a different mechanism of inflammation. This review intends to highlight the role of inflammatory responses in the context of AD with the emphasis on biochemical pathways of lipid metabolism enzyme, 5-lipoxygenase (5- LO).

Brain Α-Tocopherol Concentration is Inversely Associated with Neurofibrillary Tangle Counts in Brain Regions Affected in Earlier Braak Stages: A Cross-Sectional Finding in the Oldest Old

Objectives

Higher vitamin E status has been associated with lower risk of Alzheimer's disease (AD). However, evidence of the association of vitamin E concentration in neural tissue with AD pathologies is limited.

Design

The cross-sectional relationship between the human brain concentrations of α- and γ-tocopherol and the severity of AD pathologies - neurofibrillary tangle (NFT) and neuritic plaque (NP) - was investigated.

Setting & Participants

Brains from 43 centenarians (≥ 98 years at death) enrolled in the Phase III of the Georgia Centenarian Study were collected at autopsy.

Measurements

Brain α- and γ-tocopherol concentrations (previously reported) were averaged from frontal, temporal, and occipital cortices. NP and NFT counts (previously reported) were assessed in frontal, temporal, parietal, entorhinal cortices, amygdala, hippocampus, and subiculum. NFT topological progression was assessed using Braak staging. Multiple linear regression was performed to assess the relationship between tocopherol concentrations and NP or NFT counts, with and without adjustment for covariates.

Results

Brain α-tocopherol concentrations were inversely associated with NFT but not NP counts in amygdala (β = -2.67, 95% CI [-4.57, -0.79]), entorhinal cortex (β = -2.01, 95% CI [-3.72, -0.30]), hippocampus (β = -2.23, 95% CI [-3.82, -0.64]), and subiculum (β = -2.52, 95% CI [-4.42, -0.62]) where NFT present earlier in its topological progression, but not in neocortices. Subjects with Braak III-IV had lower α-tocopherol (median = 69,622 pmol/g, IQR = 54,389-72,155 pmol/g) than those with Braak I-II (median = 72,108 pmol/g, IQR = 64,056-82,430 pmol/g), but the difference was of borderline significance (p = 0.063). γ-Tocopherol concentrations were not associated with either NFT or NP counts in any brain regions assessed.

Conclusions

Higher brain α-tocopherol level is specifically associated with lower NFT counts in brain structures affected in earlier Braak stages. Our findings emphasize the possible importance of α-tocopherol intervention timing in tauopathy progression and warrant future clinical trials.

Extracellular Amyloid Deposits in Alzheimer's and Creutzfeldt-Jakob Disease: Similar Behavior of Different Proteins?

Neurodegenerative diseases are characterized by the deposition of specific protein aggregates, both intracellularly and/or extracellularly, depending on the type of disease. The extracellular occurrence of tridimensional structures formed by amyloidogenic proteins defines Alzheimer's disease, in which plaques are composed of amyloid β-protein, while in prionoses, the same term "amyloid" refers to the amyloid prion protein. In this review, we focused on providing a detailed didactic description and differentiation of diffuse, neuritic, and burnt-out plaques found in Alzheimer's disease and kuru-like, florid, multicentric, and neuritic plaques in human transmissible spongiform encephalopathies, followed by a systematic classification of the morphological similarities and differences between the extracellular amyloid deposits in these disorders. Both conditions are accompanied by the extracellular deposits that share certain signs, including neuritic degeneration, suggesting a particular role for amyloid protein toxicity.

Polymorphism in the MAGI2 Gene Modifies the Effect of Amyloid β on Neurodegeneration

INTRODUCTION

A weak association between amyloid β (Aβ) deposition and neurodegeneration biomarkers, such as brain atrophy, has been repeatedly reported in a subset of patients with Alzheimer disease, suggesting individual differences in response to Aβ deposition.

METHODS

Here, we performed a genome-wide interaction study to identify single-nucleotide polymorphism (SNP) that modify the effect of Aβ (measured by 18F-florbetapir positron emission tomography) on brain atrophy (measured by cortical thickness using magnetic resonance imaging). We used magnetic resonance imaging, positron emission tomography, cerebrospinal fluid, and genetic data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database [discovery cohort, ADNI-GO/2 (n=723) and replication cohort, ADNI-1 (n=129)].

RESULTS

We identified a genome-wide suggestive interaction of rs3807779 SNP (β=-0.14, SE=0.029, P=9.08×10-7) in the discovery cohort. The greater dosage of rs3807779 SNP increased the detrimental effect of Aβ deposition on cortical thickness. In replication analyses, the congruent results were replicated to confirm our findings. Furthermore, rs3807779 SNP augmented the detrimental effect of Aβ deposition on cognitive function. Genetic profiling showed that rs3807779 has chromatin interactions with the promoter region of MAGI2 gene, suggesting its association with MAGI2 expression.

CONCLUSIONS

These findings demonstrate that subjects carrying the rs3807779 SNP are more susceptible to Aβ-related neurodegeneration.

Telomeric alterations in the default mode network during the progression of Alzheimer's disease: Selective vulnerability of the precuneus

AIMS

Although telomere length (TL) and telomere maintenance proteins (shelterins) are markers of cellular senescence and peripheral blood biomarkers of Alzheimer's disease (AD), little information is available on telomeric alterations during the prodromal stage (MCI) of AD. We investigated TL in the default mode network (DMN), which underlies episodic memory deficits in AD, as well as shelterin protein and mRNA levels in the precuneus (PreC).

METHODS

Telomere length was evaluated in DMN hubs and visual cortex using quantitative PCR (qPCR). In the PreC, western blotting and NanoString nCounter expression analyses evaluated shelterin protein and mRNA levels, respectively, in cases with an antemortem clinical diagnosis of no cognitive impairment (NCI), MCI and AD.

RESULTS

TL was significantly reduced in the PreC in MCI and AD compared to NCI, but stable in frontal, inferior temporal, posterior cingulate and visual cortex. PreC TL correlated significantly with performance on cognitive tests. NCI cases with high vs low Braak scores displayed significantly shorter TL in posterior cingulate and frontal cortex, which correlated significantly with neuritic and diffuse amyloid-β plaque counts. Shelterin protein levels (TIN2, TRF1, TRF2 and POT1) declined in MCI and AD compared to NCI. The PreC displayed stable expression of shelterins TERF1, TERF2, POT1, RAP1 and TPP1, while TINF2 mRNA significantly increased in AD compared to NCI.

CONCLUSIONS

These findings indicate a selective vulnerability to telomere attrition within different nodes of the DMN in prodromal AD and in aged NCI individuals with high Braak scores highlighting a putative role in the pathogenesis of AD.

Anti-aging technoscience & the biologization of cumulative inequality: Affinities in the biopolitics of successful aging

This paper charts the emergence of under-remarked affinities between contemporary anti-aging technoscience and some social scientific work on biological aging. Both have recently sought to develop increasingly sophisticated operationalizations of age, aging and agedness as biological phenomena, in response to traditional notions of normal and chronological aging. Rather than being an interesting coincidence, these affinities indicate the influence of a biopolitics of successful aging on government, industry and social science. This biopolitics construes aging as a personal project that is mastered through specific forms of entrepreneurial individual action, especially consumption practices. Social scientists must remain alert to this biopolitics and its influence on their own work, because the individualization of cumulative inequalities provides intellectual and moral justifications for anti-aging interventions that exploit those inequalities.

Brain lipid peroxidation and alzheimer disease: Synergy between the Butterfield and Mattson laboratories

Brains from persons with Alzheimer disease (AD) and its earlier stage, amnestic mild cognitive impairment (MCI), exhibit high levels of oxidative damage, including that to phospholipids. One type of oxidative damage is lipid peroxidation, the most important index of which is protein-bound 4-hydroxy-2-trans-nonenal (HNE). This highly reactive alkenal changes the conformations and lowers the activities of brain proteins to which HNE is covalently bound. Evidence exists that suggests that lipid peroxidation is the first type of oxidative damage associated with amyloid β-peptide (Aβ), a 38-42 amino acid peptide that is highly neurotoxic and critical to the pathophysiology of AD. The Butterfield laboratory is one of, if not the, first research group to show that Aβ42 oligomers led to lipid peroxidation and to demonstrate this modification in brains of subjects with AD and MCI. The Mattson laboratory, particularly when Dr. Mattson was a faculty member at the University of Kentucky, also showed evidence for lipid peroxidation associated with Aβ peptides, mostly in in vitro systems. Consequently, there is synergy between our two laboratories. Since this special tribute issue of Aging Research Reviews is dedicated to the career of Dr. Mattson, a review of some aspects of this synergy of lipid peroxidation and its relevance to AD, as well as the role of lipid peroxidation in the progression of this dementing disorder seems germane. Accordingly, this review outlines some of the individual and/or complementary research on lipid peroxidation related to AD published from our two laboratories either separately or jointly.

RNA and Oxidative Stress in Alzheimer's Disease: Focus on microRNAs

Oxidative stress (OS) is one of the major pathomechanisms of Alzheimer's disease (AD), which is closely associated with other key events in neurodegeneration such as mitochondrial dysfunction, inflammation, metal dysregulation, and protein misfolding. Oxidized RNAs are identified in brains of AD patients at the prodromal stage. Indeed, oxidized mRNA, rRNA, and tRNA lead to retarded or aberrant protein synthesis. OS interferes with not only these translational machineries but also regulatory mechanisms of noncoding RNAs, especially microRNAs (miRNAs). MiRNAs can be oxidized, which causes misrecognizing target mRNAs. Moreover, OS affects the expression of multiple miRNAs, and conversely, miRNAs regulate many genes involved in the OS response. Intriguingly, several miRNAs embedded in upstream regulators or downstream targets of OS are involved also in neurodegenerative pathways in AD. Specifically, seven upregulated miRNAs (miR-125b, miR-146a, miR-200c, miR-26b, miR-30e, miR-34a, miR-34c) and three downregulated miRNAs (miR-107, miR-210, miR-485), all of which are associated with OS, are found in vulnerable brain regions of AD at the prodromal stage. Growing evidence suggests that altered miRNAs may serve as targets for developing diagnostic or therapeutic tools for early-stage AD. Focusing on a neuroprotective transcriptional repressor, REST, and the concept of hormesis that are relevant to the OS response may provide clues to help us understand the role of the miRNA system in cellular and organismal adaptive mechanisms to OS.

miR-149-5p inhibition reduces Alzheimer's disease β-amyloid generation in 293/APPsw cells by upregulating H4K16ac via KAT8

Alzheimer's disease (AD), the leading cause of age-related dementia, is characterized by abnormal β-amyloid accumulation. During learning, memory formation and consolidation, increased levels of histone H3 and H4 acetylation are observed. The present study reported significantly decreased level of H4K16ac in the plasma of patients with AD compared with healthy subjects via western blotting and reverse transcription-quantitative (RT-q)PCR. Lysine acetyltransferase 8 (KAT8) expression, the major lysine acetyltransferase responsible for the acetylation of H4K16, was significantly decreased in patients with AD compared with healthy subjects as determined via western blotting and RT-qPCR. The results indicated that aberrant expression patterns of H4K16ac and KAT8 might be associated with AD progression. Moreover, western blot analysis demonstrated that KAT8-overexpression cells displayed increased levels of H4K16ac, accompanied by higher levels of neuroprotective soluble amyloid precursor protein (sAPP)α and β-secretase (BACE)2, and decreased levels of sAPPβ and BACE1 compared with negative control and vector cells. In neurodegenerative disorders, microRNAs (miRNAs/miRs) are deregulated; however, the effect of miRNA dysregulation on histone acetylation is not completely understood. To the best of our knowledge, the present study identified a novel inhibitory interaction between miR-149-5p and KAT8 3'-UTR that contributed to the pathological alterations in an AD cell model for the first time, using bioinformatics and a dual-luciferase reporter assay. The western blotting results indicated that, compared with the inhibitor control group, miR-149-5p inhibitor markedly increased H4K16ac levels, which were significantly suppressed by co-transfection with KAT8 short hairpin (sh)RNA. KAT8 shRNA and miR-149-5p inhibitor co-transfection abolished the beneficial effects of miR-149-5p inhibitor. The results indicated that miR-149-5p regulated KAT8 and H4K16ac expression in an AD cell model, which may be associated with the pathological process of AD; therefore, miRNA may serve as a potential drug target for AD.

Clinico-Neuropathological Findings in the Oldest Old from the Georgia Centenarian Study

BACKGROUND

Centenarian studies are important sources for understanding of factors that contribute to longevity and healthy aging. Clinico-neuropathological finding is a key in identifying pathology and factors contributing to age-related cognitive decline and dementia in the oldest old.

OBJECTIVE

To characterize the cross-sectional relationship between neuropathologies and measures of premortem cognitive performance in centenarians.

METHODS

Data were acquired from 49 centenarians (≥98 years) from the Georgia Centenarian Study. Cognitive assessment from the time point closest to mortality was used (<1 year for all subjects) and scores for cognitive domains were established. Neuropathologies [cerebral atrophy, ventricular dilation, atherosclerosis, cerebral amyloid angiopathy (CAA), Lewy bodies, hippocampal sclerosis (HS), hippocampal TDP-43 proteinopathy, neuritic plaque (NP) and neurofibrillary tangle (NFT) counts, Braak staging, and National Institute on Aging-Reagan Institute (NIARI) criteria for the neuropathological diagnosis of Alzheimer's disease (AD)] were compared among subjects with different ratings of dementia. Linear regression was applied to evaluate the association between cognitive domain scores and neuropathologies.

RESULTS

Wide ranges of AD-type neuropathological changes were observed in both non-demented and demented subjects. Neocortical NFT and Braak staging were related to clinical dementia rating. Neocortical NFT and NP, Braak and NIARI staging, cerebral and ventricular atrophy, HS, CAA, and TDP-43 proteinopathy were differentially associated with poor performance in multiple cognitive domains and activities of daily living.

CONCLUSION

AD-type pathology was associated with severe dementia and poor cognition but was not the only variable that explained cognitive impairment, indicating the complexity and heterogeneity of pathophysiology of dementia in the oldest old.

Study of mitophagy and ATP-related metabolomics based on β-amyloid levels in Alzheimer's disease

The aggregation of β-amyloid (Aβ) peptide in Alzheimer's disease (AD) is characterized by mitochondrial dysfunction and mitophagy impairment. Mitophagy is a homeostatic mechanism by which autophagy selectively eliminates damaged mitochondria. Valinomycin is a respiratory chain inhibitor that activates mitophagy via the PINK1/Parkin signaling pathway. However, the mechanism underlying the association between mitophagy and valinomycin in Aβ formation has not been explored. Here, we demonstrate that genetically modified (N2a/APP695swe) cells overexpressing a mutant amyloid precursor protein (APP) serve as an in vitro model of AD for studying mitophagy and ATP-related metabolomics. Our results prove that valinomycin induced a time-dependent increase in the mitophagy activation of N2a/APP695swe cells as indicated by increased levels of PINK1, Parkin, and LC3II as well as increased the colocalization of Parkin-Tom20 and fewer mitochondria (indicated by decreased Tom20 levels). Valinomycin significantly decreased Aβ_1-42 and Aβ_1-40 levels after 3 h of treatment. ATP levels and ATP-related metabolites were significantly increased at this time. Our findings suggest that the elimination of impaired mitochondria via valinomycin-induced mitophagy ameliorates AD by decreasing Aβ and improving ATP levels.

Mitochondrial Oxidative and Nitrosative Stress and Alzheimer Disease

Oxidative and nitrosative stress are widely recognized as critical factors in the pathogenesis and progression of Alzheimer disease (AD) and its earlier stage, amnestic mild cognitive impairment (MCI). A major source of free radicals that lead to oxidative and nitrosative damage is mitochondria. This review paper discusses oxidative and nitrosative stress and markers thereof in the brain, along with redox proteomics, which are techniques that have been pioneered in the Butterfield laboratory. Selected biological alterations in-and oxidative and nitrosative modifications of-mitochondria in AD and MCI and systems of relevance thereof also are presented. The review article concludes with a section on the implications of mitochondrial oxidative and nitrosative stress in MCI and AD with respect to imaging studies in and targeted therapies toward these disorders. Taken together, this review provides support for the notion that brain mitochondrial alterations in AD and MCI are key components of oxidative and nitrosative stress observed in these two disorders, and as such, they provide potentially promising therapeutic targets to slow-and hopefully one day stop-the progression of AD, which is a devastating dementing disorder.

SFPQ and Tau: critical factors contributing to rapid progression of Alzheimer's disease

Dysfunctional RNA-binding proteins (RBPs) have been implicated in several neurodegenerative disorders. Recently, this paradigm of RBPs has been extended to pathophysiology of Alzheimer’s disease (AD). Here, we identified disease subtype specific variations in the RNA-binding proteome (RBPome) of sporadic AD (spAD), rapidly progressive AD (rpAD), and sporadic Creutzfeldt Jakob disease (sCJD), as well as control cases using RNA pull-down assay in combination with proteomics. We show that one of these identified proteins, splicing factor proline and glutamine rich (SFPQ), is downregulated in the post-mortem brains of rapidly progressive AD patients, sCJD patients and 3xTg mice brain at terminal stage of the disease. In contrast, the expression of SFPQ was elevated at early stage of the disease in the 3xTg mice, and in vitro after oxidative stress stimuli. Strikingly, in rpAD patients’ brains SFPQ showed a significant dislocation from the nucleus and cytoplasmic colocalization with TIA-1. Furthermore, in rpAD brain lesions, SFPQ and p-tau showed extranuclear colocalization. Of note, association between SFPQ and tau-oligomers in rpAD brains suggests a possible role of SFPQ in oligomerization and subsequent misfolding of tau protein. In line with the findings from the human brain, our in vitro study showed that SFPQ is recruited into TIA-1-positive stress granules (SGs) after oxidative stress induction, and colocalizes with tau/p-tau in these granules, providing a possible mechanism of SFPQ dislocation through pathological SGs. Furthermore, the expression of human tau in vitro induced significant downregulation of SFPQ, suggesting a causal role of tau in the downregulation of SFPQ. The findings from the current study indicate that the dysregulation and dislocation of SFPQ, the subsequent DNA-related anomalies and aberrant dynamics of SGs in association with pathological tau represents a critical pathway which contributes to rapid progression of AD.

The ubiquitin ligase UBE4B regulates amyloid precursor protein ubiquitination, endosomal trafficking, and amyloid β42 generation and secretion

The extracellular accumulation of amyloid β (Aβ) fragments of amyloid precursor protein (APP) in brain parenchyma is a pathological hallmark of Alzheimer's disease (AD). APP can be cleaved into Aβ on late endosomes/multivesicular bodies (MVBs). E3 ubiquitin ligases have been linked to Aβ production, but specific E3 ligases associated with APP ubiquitination that may affect targeting of APP to endosomes have not yet been described. Using cultured cortical neurons isolated from rat pups, we reconstituted APP movement into the internal vesicles (ILVs) of MVBs. Loss of endosomal sorting complexes required for transport (ESCRT) components inhibited APP movement into ILVs and increased endosomal Aβ42 generation, implying a requirement for APP ubiquitination. We identified an ESCRT-binding and APP-interacting endosomal E3 ubiquitin ligase, ubiquitination factor E4B (UBE4B) that regulates APP ubiquitination. Depleting UBE4B in neurons inhibited APP ubiquitination and internalization into MVBs, resulting in increased endosomal Aβ42 levels and increased neuronal secretion of Aβ42. When we examined AD brains, we found levels of the UBE4B-interacting ESCRT component, hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), were significantly decreased in AD brains. These data suggest that ESCRT components critical for membrane protein sorting in the endocytic pathway are altered in AD. These results indicate that the molecular machinery underlying endosomal trafficking of APP, including the ubiquitin ligase UBE4B, regulates Aβ levels and may play an essential role in AD progression.

Cerebrolysin in the therapy of mild cognitive impairment and dementia due to Alzheimer's disease: 30 years of clinical use

Alzheimer's disease (AD) is the most common neurocognitive disorder and a global health problem. The prevalence of AD is growing dramatically, especially in low- and middle-income countries, and will reach 131.5 million cases worldwide by 2050. Therefore, developing a disease-modifying therapy capable of delaying or even preventing the onset and progression of AD has become a world priority, and is an unmet need. The pathogenesis of AD, considered as the result of an imbalance between resilience and risk factors, begins many years before the typical clinical picture develops and involves multiple pathophysiological mechanisms. Since the pathophysiology of AD is multifactorial, it is not surprising that all attempts done to modify the disease course with drugs directed towards a single therapeutic target have been unsuccessful. Thus, combined modality therapy, using multiple drugs with a single mechanism of action or multi-target drugs, appears as the most promising strategy for both effective AD therapy and prevention. Cerebrolysin, acting as a multitarget peptidergic drug with a neurotrophic mode of action, exerts long-lasting therapeutic effects on AD that could reflect its potential utility for disease modification. Clinical trials demonstrated that Cerebrolysin is safe and efficacious in the treatment of AD, and may enhance and prolong the efficacy of cholinergic drugs, particularly in moderate to advanced AD patients. In this review, we summarize advances of therapeutic relevance in the pathogenesis and the biomarkers of AD, paying special attention to neurotrophic factors, and present results of preclinical and clinical investigations with Cerebrolysin in AD.

Race- and Sex-Based Disparities in Alzheimer's Disease Clinical Trial Enrollment in the United States and Canada: An Indigenous Perspective

Randomized clinical trials (RCT) involve labor-intensive, highly regulated, and controlled processes intended to transform scientific concepts into clinical outcomes. To be effective and targeted, it is imperative they include those populations who would most benefit from those outcomes. Alzheimer's disease (AD) is most detrimental to the aging population, and its clinical manifestation is influenced by socio-economic factors such as poverty, poor education, stress, and chronic co-morbidities. Indigenous populations in the United States and Canada are among the minority populations most influenced by poor socio-economic conditions and are prone to the ravages of AD, with Indigenous women carrying the added burden of exposure to violence, caregiving stresses, and increased risk by virtue of their sex. Race- and sex-based disparities in RCT enrollment has occurred for decades, with Indigenous men and women very poorly represented. In this review, we examined literature from the last twenty years that reinforce these disparities and provide some concrete suggestions and guidelines to increase the enrollment numbers in AD RCT among this vulnerable and poorly represented population.

Amygdala: Neuroanatomical and Morphophysiological Features in Terms of Neurological and Neurodegenerative Diseases

The amygdala is one of the most discussed structures of the brain. Correlations between its level of activity, size, biochemical organization, and various pathologies are the subject of many studies, and can serve as a marker of existing or future disease. It is hypothesized that the amygdala is not just a structural unit, but includes many other regions in the brain. In this review, we present the updated neuroanatomical and physiological aspects of the amygdala, discussing its involvement in neurodegenerative and neurological diseases. The amygdala plays an important role in the processing of input signals and behavioral synthesis. Lesions in the amygdala have been shown to cause neurological disfunction of ranging severity. Abnormality in the amygdala leads to conditions such as depression, anxiety, autism, and also promotes biochemical and physiological imbalance. The amygdala collects pathological proteins, and this fact can be considered to play a big role in the progression and diagnosis of many degenerative diseases, such as Alzheimer’s disease, chronic traumatic encephalopathy, Lewy body diseases, and hippocampal sclerosis. The amygdala has shown to play a crucial role as a central communication system in the brain, therefore understanding its neuroanatomical and physiological features can open a channel for targeted therapy of neurodegenerative diseases.

Invited Review - Understanding cause and effect in Alzheimer's pathophysiology: Implications for clinical trials

Alzheimer's disease (AD) pathology is multi-faceted, including extracellular accumulation of amyloid-β (Aβ), accumulation of tau within neurons, glial activation and loss of neurons and synapses. From a neuropathological perspective, usually at a single time-point and often at the end-stage of the disease, it is challenging to understand the cause and effect relationships between these components. There are at least four ways of trying to unravel these relationships. First, genetic studies demonstrate mutations that influence Aβ production, but not tau, can initiate AD; whereas genetic variants influencing AD risk are related to innate immunity and lipid metabolism. Second, studies at early time points show that pathology begins decades before the onset of dementia and indicate different anatomical locations for initiation of Aβ and tau accumulation. Third, cause and effect can be studied in experimental models, but most animal models do not fully replicate AD pathology. However, induced pluripotent stem cells (iPSCs) to study live human neurons has introduced a new perspective. Fourth, clinical trials may alter AD pathology giving insights into cause and effect relationships. Therefore, a sequence of (i) neocortical Aβ accumulation followed by (ii) a microglial inflammatory reaction to Aβ, causing neuritic dystrophy which promotes (iii) spread of tau from the limbic system to the neocortex with (iv) progressive tau accumulation and spread resulting in (v) neurodegeneration, explains the evidence. It is proposed that different therapeutic targets are required for different stages of the disease process: Aβ for primary prevention, microglia for secondary prevention, and tau for established disease.

Perspectives for New and More Efficient Multifunctional Ligands for Alzheimer's Disease Therapy

Despite tremendous research efforts at every level, globally, there is still a lack of effective drugs for the treatment of Alzheimer's disease (AD). The biochemical mechanisms of this devastating neurodegenerative disease are not yet clearly understood. This review analyses the relevance of multiple ligands in drug discovery for AD as a versatile toolbox for a polypharmacological approach to AD. Herein, we highlight major targets associated with AD, ranging from acetylcholine esterase (AChE), beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1), glycogen synthase kinase 3 beta (GSK-3β), N-methyl-d-aspartate (NMDA) receptor, monoamine oxidases (MAOs), metal ions in the brain, 5-hydroxytryptamine (5-HT) receptors, the third subtype of histamine receptor (H3 receptor), to phosphodiesterases (PDEs), along with a summary of their respective relationship to the disease network. In addition, a multitarget strategy for AD is presented, based on reported milestones in this area and the recent progress that has been achieved with multitargeted-directed ligands (MTDLs). Finally, the latest publications referencing the enlarged panel of new biological targets for AD related to the microglia are highlighted. However, the question of how to find meaningful combinations of targets for an MTDLs approach remains unanswered.

The potential role of pomegranate and its nano-formulations on cerebral neurons in aluminum chloride induced Alzheimer rat model

The oxidative stress leading to degenerative changes in the brain of Alzheimer's disease (AD) is evident. Our aim was to evaluate the therapeutic and protective effects of pomegranate extract (PE) and pomegranate extract-loaded nanoparticles (PE nano) in an AlCl 3-induced AD rat model. Nanoparticles were synthesized with a PE load of 0.68% w/w, and 70 male Wistar rats were divided into 7 groups: Group I was the control, Group II received PE., Group III received PE nano for 2 weeks, Group IV received AlCl 3 (50 mg/kg) daily orally for 4 weeks, Group V received PE for 2 weeks, Group VI received PE nano for 2 weeks, and Groups V and VI were started after AlCl 3 administration was stopped. Group VII received PE for 2 weeks and was stopped before AlCl 3 was administered. The Results revealed that the discrimination index in the novel object recognition test was the least in AD rat model but increased in cases protected with PE treated with PE nano. Similar results were shown based on calculating the brain weight/body weight percent. The biomarkers of antioxidant activity (catalase, glutathione and total antioxidant activity) in brain homogenate were significantly increased in groups treated with either PE or PE nano. The thiobarbituric acid reactive substance measured to estimate lipid peroxidation was significantly increased in AD rat model and decreased in groups protected with PE or treated with PE nano. Histopathological studies using hematoxylin and eosin, cresyl violet, and silver stains revealed hyaline degeneration, chromatolysis, and hallmarks of AD; neurofibrillary tangles and the senile plaques in brains of AD rat model. Restoration of the histological architecture, Nissl granules, and minimal appearance of hallmarks of AD characterized brains treated with PE or PE nano. In conclusion, PE was more effective as a protectant than a therapeutic measure in alleviating the antioxidant, lipid peroxidative effects and histopathological hallmarks in AD brains. But, the therapeutic PE-loaded nanoparticles increased the efficacy of active components and produced similar results as the protective PE.

Tau PET imaging with 18F-PI-2620 in aging and neurodegenerative diseases

PURPOSE

In vivo measurement of the spatial distribution of neurofibrillary tangle pathology is critical for early diagnosis and disease monitoring of Alzheimer's disease (AD).

METHODS

Forty-nine participants were scanned with ¹⁸F-PI-2620 PET to examine the distribution of this novel PET ligand throughout the course of AD: 36 older healthy controls (HC) (age range 61 to 86), 11 beta-amyloid+ (Aβ+) participants with cognitive impairment (CI; clinical diagnosis of either mild cognitive impairment or AD dementia, age range 57 to 86), and 2 participants with semantic variant primary progressive aphasia (svPPA, age 66 and 78). Group differences in brain regions relevant in AD (medial temporal lobe, posterior cingulate cortex, and lateral parietal cortex) were examined using standardized uptake value ratios (SUVRs) normalized to the inferior gray matter of the cerebellum.

RESULTS

SUVRs in target regions were relatively stable 60 to 90 min post-injection, with the exception of very high binders who continued to show increases over time. Robust elevations in ¹⁸F-PI-2620 were observed between HC and Aβ+ CI across all AD regions. Within the HC group, older age was associated with subtle elevations in target regions. Mildly elevated focal uptake was observed in the anterior temporal pole in one svPPA patient.

CONCLUSION

Preliminary results suggest strong differences in the medial temporal lobe and cortical regions known to be impacted in AD using ¹⁸F-PI-2620 in patients along the AD trajectory. This work confirms that ¹⁸F-PI-2620 holds promise as a tool to visualize tau aggregations in AD.

Comparison of regional flortaucipir PET with quantitative tau immunohistochemistry in three subjects with Alzheimer's disease pathology: a clinicopathological study

Background

The objective of this study was to make a quantitative comparison of flortaucipir PET retention with pathological tau and β-amyloid across a range of brain regions at autopsy.

Methods

Patients with dementia (two with clinical diagnosis of AD, one undetermined), nearing the end of life, underwent 20-min PET, beginning 80 min after an injection of ~370 mBq flortaucipir [¹⁸F]. Neocortical, basal ganglia, and limbic tissue samples were obtained bilaterally from 19 regions at autopsy and subject-specific PET regions of interest corresponding to the 19 sampled target tissue regions in each hemisphere were hand drawn on the PET images. SUVr values were calculated for each region using a cerebellar reference region. Abnormally phosphorylated tau (Ptau) and amyloid-β (Aβ) tissue concentrations were measured for each tissue region with an antibody capture assay (Histelide) using AT8 and H31L21 antibodies respectively.

Results

The imaging-to-autopsy interval ranged from 4–29 days. All three subjects had intermediate to high levels of AD neuropathologic change at autopsy. Mean cortical SUVr averaged across all three subjects correlated significantly with the Ptau immunoassay (Pearson r = 0.81; p < 0.0001). When Ptau and Aβ_1-42 were both included in the model, the Ptau correlation with flortaucipir SUVr was preserved but there was no correlation of Aβ_1-42 with flortaucipir. There was also a modest correlation between limbic (hippocampal/entorhinal and amygdala) flortaucipir SUVr and Ptau (Pearson r = 0.52; p < 0.080). There was no significant correlation between SUVr and Ptau in basal ganglia.

Conclusions

The results of this pilot study support a quantitative relationship between cortical flortaucipir SUVr values and quantitative measures of Ptau at autopsy. Additional research including more cases is needed to confirm the generalizability of these results.

Trial registration, NIH Clinicaltrials.gov NCT # 02516046. Registered August 27, 2015. https://clinicaltrials.gov/ct2/show/NCT02516046?term=02516046&draw=2&rank=1

Deep ensemble learning for Alzheimer's disease classification

Ensemble learning uses multiple algorithms to obtain better predictive performance than any single one of its constituent algorithms could. With the growing popularity of deep learning technologies, researchers have started to ensemble these technologies for various purposes. Few, if any, however, have used the deep learning approach as a means to ensemble Alzheimer's disease classification algorithms. This paper presents a deep ensemble learning framework that aims to harness deep learning algorithms to integrate multisource data and tap the 'wisdom of experts'. At the voting layer, two sparse autoencoders are trained for feature learning to reduce the correlation of attributes and diversify the base classifiers ultimately. At the stacking layer, a nonlinear feature-weighted method based on a deep belief network is proposed to rank the base classifiers, which may violate the conditional independence. The neural network is used as a meta classifier. At the optimizing layer, over-sampling and threshold-moving are used to cope with the cost-sensitive problem. Optimized predictions are obtained based on an ensemble of probabilistic predictions by similarity calculation. The proposed deep ensemble learning framework is used for Alzheimer's disease classification. Experiments with the clinical dataset from National Alzheimer's Coordinating Center demonstrate that the classification accuracy of our proposed framework is 4% better than six well-known ensemble approaches, including the standard stacking algorithm as well. Adequate coverage of more accurate diagnostic services can be provided by utilizing the wisdom of averaged physicians. This paper points out a new way to boost the primary care of Alzheimer's disease from the view of machine learning.

Diversity in Aβ deposit morphology and secondary proteome insolubility across models of Alzheimer-type amyloidosis

A hallmark pathology of Alzheimer's disease (AD) is the formation of amyloid β (Aβ) deposits that exhibit diverse localization and morphologies, ranging from diffuse to cored-neuritic deposits in brain parenchyma, with cerebral vascular deposition in leptomeningeal and parenchymal compartments. Most AD brains exhibit the full spectrum of pathologic Aβ morphologies. In the course of studies to model AD amyloidosis, we have generated multiple transgenic mouse models that vary in the nature of the transgene constructs that are expressed; including the species origin of Aβ peptides, the levels and length of Aβ that is deposited, and whether mutant presenilin 1 (PS1) is co-expressed. These models recapitulate features of human AD amyloidosis, but interestingly some models can produce pathology in which one type of Aβ morphology dominates. In prior studies of mice that primarily develop cored-neuritic deposits, we determined that Aβ deposition is associated with changes in cytosolic protein solubility in which a subset of proteins become detergent-insoluble, indicative of secondary proteome instability. Here, we survey changes in cytosolic protein solubility across seven different transgenic mouse models that exhibit a range of Aβ deposit morphologies. We find a surprisingly diverse range of changes in proteome solubility across these models. Mice that deposit human Aβ40 and Aβ42 in cored-neuritic plaques had the most robust changes in proteome solubility. Insoluble cytosolic proteins were also detected in the brains of mice that develop diffuse Aβ42 deposits but to a lesser extent. Notably, mice with cored deposits containing only Aβ42 had relatively few proteins that became detergent-insoluble. Our data provide new insight into the diversity of biological effects that can be attributed to different types of Aβ pathology and support the view that fibrillar cored-neuritic plaque pathology is the more disruptive Aβ pathology in the Alzheimer's cascade.

A multicentre longitudinal study of flortaucipir (18F) in normal ageing, mild cognitive impairment and Alzheimer's disease dementia

The advent of tau-targeted PET tracers such as flortaucipir (18F) (flortaucipir, also known as 18F-AV-1451 or 18F-T807) have made it possible to investigate the sequence of development of tau in relationship to age, amyloid-β, and to the development of cognitive impairment due to Alzheimer's disease. Here we report a multicentre longitudinal evaluation of the relationships between baseline tau, tau change and cognitive change, using flortaucipir PET imaging. A total of 202 participants 50 years old or older, including 57 cognitively normal subjects, 97 clinically defined mild cognitive impairment and 48 possible or probable Alzheimer's disease dementia patients, received flortaucipir PET scans of 20 min in duration beginning 80 min after intravenous administration of 370 MBq flortaucipir (18F). On separate days, subjects also received florbetapir amyloid PET imaging, and underwent a neuropsychological test battery. Follow-up flortaucipir scans and neuropsychological battery assessments were also performed at 9 and 18 months. Fifty-five amyloid-β+ and 90 amyloid-β- subjects completed the baseline and 18-month study visits and had valid quantifiable flortaucipir scans at both time points. There was a statistically significant increase in the global estimate of cortical tau burden as measured by standardized uptake value ratio (SUVr) from baseline to 18 months in amyloid-β+ but not amyloid-β- subjects (least squared mean change in flortaucipir SUVr : 0.0524 ± 0.0085, P < 0.0001 and 0.0007 ± 0.0024 P = 0.7850, respectively), and a significant association between magnitude of SUVr increase and baseline tau burden. Voxel-wise evaluations further suggested that the regional pattern of change in flortaucipir PET SUVr over the 18-month study period (i.e. which regions exhibited the greatest change) also varied as a function of baseline global estimate of tau burden. In subjects with lower global SUVr, temporal lobe regions showed the greatest flortaucipir retention, whereas in subjects with higher baseline SUVr, parietal and frontal regions were increasingly affected. Finally, baseline flortaucipir and change in flortaucipir SUVr were both significantly (P < 0.0001) associated with changes in cognitive performance. Taken together, these results provide a preliminary characterization of the longitudinal spread of tau in Alzheimer's disease and suggest that the amount and location of tau may have implications both for the spread of tau and the cognitive deterioration that may occur over an 18-month period.