Alterations In Alzheimer's Disease Research Articles

The Memory Benefit to Aged APP/PS1 Mice from Long-Term Intranasal Treatment of Low-Dose THC.

THC has been used as a promising treatment approach for neurological disorders, but the highly psychoactive effects have largely warned off many scientists from pursuing it further. We conducted an intranasal treatment using low-dose THC on 12-month-old APP/PS1 mice daily for 3 months to overcome any potential psychoactive response induced by the systemic delivery. Our results demonstrate that the THC nasal treatment at 0.002 and 0.02 mg/kg significantly slowed the memory decline compared to that in the vehicle-treated transgenic mouse control group. An enzyme-linked immunosorbent assay showed that the Aβ1–40 and 1–42 peptides decreased in the THC-treated groups. The Western blot data indicate that long-term low-dose THC intranasal administration promoted p-tau level reduction and mitochondrial function marker redistribution. The blood biochemical parameter data demonstrate some insignificant changes in cytokine, immunoglobulin, and immune cell profiles during intranasal THC treatment. Intranasal delivery is a non-invasive and convenient method that rapidly targets therapeutics to the brain, minimizing systemic exposure to avoid unwanted adverse effects. Our study provides new insights into the role of low-dose THC intranasal treatment as a pharmacological strategy to counteract alterations in Alzheimer’s disease-related cognitive performance.

Brain Metabolic Alterations in Alzheimer's Disease.

The brain is one of the most energy-consuming organs in the body. Satisfying such energy demand requires compartmentalized, cell-specific metabolic processes, known to be complementary and intimately coupled. Thus, the brain relies on thoroughly orchestrated energy-obtaining agents, processes and molecular features, such as the neurovascular unit, the astrocyte–neuron metabolic coupling, and the cellular distribution of energy substrate transporters. Importantly, early features of the aging process are determined by the progressive perturbation of certain processes responsible for adequate brain energy supply, resulting in brain hypometabolism. These age-related brain energy alterations are further worsened during the prodromal stages of neurodegenerative diseases, namely Alzheimer’s disease (AD), preceding the onset of clinical symptoms, and are anatomically and functionally associated with the loss of cognitive abilities. Here, we focus on concrete neuroenergetic features such as the brain’s fueling by glucose and lactate, the transporters and vascular system guaranteeing its supply, and the metabolic interactions between astrocytes and neurons, and on its neurodegenerative-related disruption. We sought to review the principles underlying the metabolic dimension of healthy and AD brains, and suggest that the integration of these concepts in the preventive, diagnostic and treatment strategies for AD is key to improving the precision of these interventions.

Neurofilament light chain: defining the analyte.

This scientific commentary refers to 'A map of neurofilament light chain species in brain and cerebrospinal fluid and alterations in Alzheimer's disease' by Budelier et al. (https://doi.org/10.1093/braincomms/fcac045).

Temporal dynamics of animacy categorization in the brain of patients with mild cognitive impairment.

Electroencephalography (EEG) has been commonly used to measure brain alterations in Alzheimer's Disease (AD). However, reported changes are limited to those obtained from using univariate measures, including activation level and frequency bands. To look beyond the activation level, we used multivariate pattern analysis (MVPA) to extract patterns of information from EEG responses to images in an animacy categorization task. Comparing healthy controls (HC) with patients with mild cognitive impairment (MCI), we found that the neural speed of animacy information processing is decreased in MCI patients. Moreover, we found critical time-points during which the representational pattern of animacy for MCI patients was significantly discriminable from that of HC, while the activation level remained unchanged. Together, these results suggest that the speed and pattern of animacy information processing provide clinically useful information as a potential biomarker for detecting early changes in MCI and AD patients.

The Cardiac Dysfunction Caused by Metabolic Alterations in Alzheimer's Disease.

A progressive defect in the energy generation pathway is implicated in multiple aging-related diseases, including cardiovascular conditions and Alzheimer's Disease (AD). However, evidence of the pathogenesis of cardiac dysfunction in AD and the associations between the two organ diseases need further elucidation. This study aims to characterize cellular defects resulting in decreased cardiac function in AD-model. 5XFAD mice, a strain expressing five mutations in human APP and PS1 that shows robust Aβ production with visible plaques at 2 months and were used in this study as a model of AD. 5XFAD mice and wild-type (WT) counterparts were subjected to echocardiography at 2-, 4-, and 6-month, and 5XFAD had a significant reduction in cardiac fractional shortening and ejection fraction compared to WT. Additionally, 5XFAD mice had decreased observed electrical signals demonstrated as decreased R, P, T wave amplitudes. In isolated cardiomyocytes, 5XFAD mice showed decreased fraction shortening, rate of shortening, as well as the degree of transient calcium influx. To reveal the mechanism by which AD leads to cardiac systolic dysfunction, the immunoblotting analysis showed increased activation of AMP-activated protein kinase (AMPK) in 5XFAD left ventricular and brain tissue, indicating altered energy metabolism. Mito Stress Assays examining mitochondrial function revealed decreased basal and maximal oxygen consumption rate, as well as defective pyruvate dehydrogenase activity in the 5XFAD heart and brain. Cellular inflammation was provoked in the 5XFAD heart and brain marked by the increase of reactive oxygen species accumulation and upregulation of inflammatory mediator activities. Finally, AD pathological phenotype with increased deposition of Aβ and defective cognitive function was observed in 6-month 5XFAD mice. In addition, elevated fibrosis was observed in the 6-month 5XFAD heart. The results implicated that AD led to defective mitochondrial function, and increased inflammation which caused the decrease in contractility of the heart.

A map of neurofilament light chain species in brain and cerebrospinal fluid and alterations in Alzheimer's disease.

Neurofilament light is a well-established marker of both acute and chronic neuronal damage and is increased in multiple neurodegenerative diseases. However, the protein is not well characterized in brain tissue or body fluids, and it is unknown what neurofilament light species are detected by commercial assays and whether additional species exist. We developed an immunoprecipitation-mass spectrometry assay using custom antibodies targeting various neurofilament light domains, including antibodies targeting Coil 1A/1B of the rod domain (HJ30.13), Coil 2B of the rod domain (HJ30.4) and the tail region (HJ30.11). We utilized our assay to characterize neurofilament light in brain tissue and CSF of individuals with Alzheimer’s disease dementia and healthy controls. We then validated a quantitative version of our assay and measured neurofilament light concentrations using both our quantitative immunoprecipitation-mass spectrometry assay and the commercially available immunoassay from Uman diagnostics in individuals with and without Alzheimer’s disease dementia. Our validation cohort included CSF samples from 30 symptomatic amyloid-positive participants, 16 asymptomatic amyloid-positive participants, 10 symptomatic amyloid-negative participants and 25 amyloid-negative controls. We identified at least three major neurofilament light species in CSF, including N-terminal and C-terminal truncations, and a C-terminal fragment containing the tail domain. No full-length neurofilament light was identified in CSF. This contrasts with brain tissue, which contained mostly full-length neurofilament and a C-terminal tail domain fragment. We observed an increase in neurofilament light concentrations in individuals with Alzheimer’s disease compared with healthy controls, with larger differences for some neurofilament light species than for others. The largest differences were observed for neurofilament light fragments including NfL165 (in Coil 1B), NfL324 (in Coil 2B) and NfL530 (in the C-terminal tail domain). The Uman immunoassay correlated most with NfL324. This study provides a comprehensive evaluation of neurofilament light in brain and CSF and enables future investigations of neurofilament light biology and utility as a biomarker.

Spatial Training Attenuates Long-Term Alzheimer's Disease-Related Pathogenic Processes in APP/PS1 Mice.

Alzheimer's disease (AD), with cognitive impairment as the main clinical manifestation, is a progressive neurodegenerative disease. The assembly of amyloid-β (Aβ) as senile plaques is one of the most well-known histopathological alterations in AD. Several studies reported that cognitive training reduced Aβ deposition and delayed memory loss. However, the long-term benefits of spatial training and the underlying neurobiological mechanisms have not yet been elucidated. To explore the long-term effects of spatial training on AD-related pathogenic processes in APP/PS1 mice. We used Morris water maze (MWM), Open Field, Barnes Maze, western blotting, qPCR, and immunofluorescence. One-month MWM training in APP/PS1 mice at 2.5 months of age could attenuate Aβ deposition and decrease the expression of β-secretase (BACE1) and amyloid-β protein precursor (AβPP) with long-term effects. Simultaneously, regular spatial training increased the expression of synapse-related proteins in the hippocampus. Moreover, MWM training increased adult hippocampal neurogenesis in AD model mice. Nonetheless, cognitive deficits in APP/PS1 transgenic mice at 7 months of age were not attenuated by MWM training at an early stage. Our study demonstrates that MWM training alleviates amyloid plaque burden and adult hippocampal neurogenesis deficits with long-term effects in AD model mice.

Endothelial Progenitor Cells and Vascular Alterations in Alzheimer's Disease.

Alzheimer’s disease (AD) is a neurodegenerative disease representing the most common type of dementia worldwide. The early diagnosis of AD is very difficult to achieve due to its complexity and the practically unknown etiology. Therefore, this is one of the greatest challenges in the field in order to develop an accurate therapy. Within the different etiological hypotheses proposed for AD, we will focus on the two-hit vascular hypothesis and vascular alterations occurring in the disease. According to this hypothesis, the accumulation of β-amyloid protein in the brain starts as a consequence of damage in the cerebral vasculature. Given that there are several vascular and angiogenic alterations in AD, and that endothelial progenitor cells (EPCs) play a key role in endothelial repair processes, the study of EPCs in AD may be relevant to the disease etiology and perhaps a biomarker and/or therapeutic target. This review focuses on the involvement of endothelial dysfunction in the onset and progression of AD with special emphasis on EPCs as a biomarker and potential therapeutic target.

Advances in Genetics and Epigenetic Alterations in Alzheimer's Disease: A Notion for Therapeutic Treatment.

Alzheimer’s disease (AD) is a disabling neurodegenerative disorder that leads to long-term functional and cognitive impairment and greatly reduces life expectancy. Early genetic studies focused on tracking variations in genome-wide DNA sequences discovered several polymorphisms and novel susceptibility genes associated with AD. However, despite the numerous risk factors already identified, there is still no fully satisfactory explanation for the mechanisms underlying the onset of the disease. Also, as with other complex human diseases, the causes of low heritability are unclear. Epigenetic mechanisms, in which changes in gene expression do not depend on changes in genotype, have attracted considerable attention in recent years and are key to understanding the processes that influence age-related changes and various neurological diseases. With the recent use of massive sequencing techniques, methods for studying epigenome variations in AD have also evolved tremendously, allowing the discovery of differentially expressed disease traits under different conditions and experimental settings. This is important for understanding disease development and for unlocking new potential AD therapies. In this work, we outline the genomic and epigenomic components involved in the initiation and development of AD and identify potentially effective therapeutic targets for disease control.

Investigating epigenetic loci implicated in Alzheimer’s disease via the CRISPR‐Cas9 system

AbstractBackgroundDifferentially methylated positions (DMPs) identified by Epigenome‐wide association studies (EWAS) of Alzheimer’s disease (AD) were modified by the CRISPR‐Cas9 system to investigate the role of epigenetic alterations in AD pathogenesis.MethodCell lines of neuronal phenotype (SH‐SY5Y) and microglial phenotype (IHM‐SV40) were used to explore the functional consequence of loci demethylation, where removal of the methyl groups was achieved by the modified CRISPR‐dCas9 system. Lentiviral delivery of the dCas9‐TET1CD demethylase tool and guide RNA (gRNA) constructs targeting the CpG sites associated with differential expression of ANK1 and BIN1 in AD was validated by fluorescence‐activated cell sorting (FACS). Bisulphite pyrosequencing was applied to confirm the DNA methylation edit.ResultHigh transduction efficiencies were observed during FACS of SH‐SY5Y cells transduced with CRISPR‐dCas9 constructs targeting the BIN1 locus and IHM‐SV40 cells with constructs against the ANK1 locus. Methylation analysis of these target regions in the modified cell lines demonstrated a reduction in methylation when compared to the untreated control cells. This modification was maintained over a three‐week period.ConclusionDelivery and activity of our CRISPR‐dCas9 fusion constructs was demonstrated in cell line models of AD. In the future, we intend to profile the epigenome and transcriptome of these modified cell lines to identify any off‐target effects of the CRISPR‐dCas9 system and determine differences in mRNA transcript variant levels of our target genes.

Neurobiological role of Alzheimer's disease genetic risk factor ApoE on early synaptic changes in Alzheimer-like models.

The presence of an apolipoprotein E4 (ApoE4) genotype is the major genetic risk factor for Alzheimer's disease (AD). Astrocytes are the main source of ApoE in the brain, however ApoE can also be produced by neurons and microglia. ApoE plays a role in many cell types and processes related to AD, however, it remains unclear which mechanism(s) and cellular source of ApoE are most critical for AD. One of the earliest changes in AD are early cellular changes such as endosomal and synaptic alterations. ApoE4 has been associated with impaired endosomal trafficking and dysregulated synaptic plasticity. Neuronal hyperexcitability has been reported in mice expressing human ApoE4, a dysregulation that is also seen in AD transgenic mice. Although ApoE seems to play a crucial role in neuronal changes linked to early AD, ApoE's synaptic localization and mechanisms remain poorly understood. In this study, the aim is to determine the role of ApoE, in particular ApoE4, on synaptic alterations in AD models. Mouse neurons and astrocytes are derived from wild-type, ApoE knock-out (KO), humanized ApoE3 and ApoE4 knock-in mice. Astrocyte-conditioned medium from mouse astrocytes expressing human ApoE and recombinant ApoE are used as a source for human ApoE to treat ApoE KO, wild-type and AD transgenic APP/PS1 neurons. Additionally, ApoE KO and humanized ApoE neurons are treated with synthetic Aβ or vehicle control. Analysis is performed using immunofluorescence, confocal and live cell imaging. Exogenously added and endogenously produced human ApoE is shown to be present at neurites and synaptic terminals of cultured neurons. Differences in neuronal activity are observed among different ApoE conditions using Ca2+ live cell microscopy, both in the presence and absence of elevated human Aβ. Added recombinant and endogenous ApoE appear to be present in the endosome-lysosome system of neurons. ApoE appears to localize at synapses and endosomes, sites associated with early cellular changes in AD, and seems to play a role in neuronal excitability. Determining the neurobiology of ApoE, in particular in connection with cellular sites vulnerable to early changes in AD, can contribute to a better understanding of the role of ApoE in AD.

Investigating epigenetic loci implicated in Alzheimer's disease via the CRISPR-Cas9 system.

Differentially methylated positions (DMPs) identified by Epigenome-wide association studies (EWAS) of Alzheimer's disease (AD) were modified by the CRISPR-Cas9 system to investigate the role of epigenetic alterations in AD pathogenesis. Cell lines of neuronal phenotype (SH-SY5Y) and microglial phenotype (IHM-SV40) were used to explore the functional consequence of loci demethylation, where removal of the methyl groups was achieved by the modified CRISPR-dCas9 system. Lentiviral delivery of the dCas9-TET1CD demethylase tool and guide RNA (gRNA) constructs targeting the CpG sites associated with differential expression of ANK1 and BIN1 in AD was validated by fluorescence activated cell sorting (FACS). Bisulphite pyrosequencing was applied to confirm the DNA methylation edit and RT-qPCR was performed to assess changes in mRNA expression. High transduction efficiencies were observed during FACS of SH-SY5Y cells transduced with CRISPR-dCas9 constructs targeting the BIN1 locus and IHM-SV40 cells with constructs against the ANK1 locus. Methylation analysis of these target regions in the modified cell lines demonstrated a reduction in methylation when compared to the untreated control cells. Full-length transcript expression levels of ANK1 and BIN1 showed no significant differences between experimental conditions. Delivery and activity of our CRISPR-dCas9 fusion constructs was demonstrated in cell line models of AD.

The metabolic landscape of brain alterations in Alzheimer's disease.

Impairment of brain glucose metabolism has been frequently described in Alzheimer's disease (AD). Moreover, the strongest predictor of the lifetime incidence of AD is the ε4 allele of APOE, a protein involved in lipid metabolism. These connections between AD and metabolism provide motivation to perform an in-depth metabolic profiling of human brain tissue for different stages of AD pathophysiology. Brain tissue samples were obtained from the Religious Orders Study and Memory and Aging Project (ROS/MAP) at the Rush Alzheimer's Disease Center. Furthermore, ROS/MAP collects extensive phenotyping of the participants' cognitive trajectories as well as postmortem pathology. Metabolic profiling was performed on Metabolon's untargeted platform, yielding 1,055 quantified metabolites. Generalized linear models with appropriate linkage functions for continuous or categorical AD-related phenotypes were used to discover the association of metabolic profiles with AD-related phenotypes, such as amount of amyloid and tangles in brain, global burden of pathology, NIA-Reagan score, diagnosis (derived from Braak and CERAD scores), clinical diagnosis at the time of death, global cognition assessed during the visit before death, estimated decline of global cognition over lifetime. The models included confounder correction for age, gender, body mass index, years of education, post mortem interval, number of APOEε4 alleles, and medications. We found 263 metabolites to be significantly associated (adjusted p-value <0.05) with one of the AD phenotypes. 137 of these metabolites were significantly associated with three or more phenotypes. Of these, nine could be replicated using an independent autopsy cohort from Mayo Clinic, five could also be replicated using a published study based on Baltimore Longitudinal Study of Aging cohort. The associated metabolites are involved in various metabolic processes known to be involved in AD pathogenesis, such as amino acid metabolism, urea cycle, and polyamine metabolism. In addition, we have identified several novel associations that could uncover the interdependence of different AD-associated metabolic processes. We have generated a comprehensive landscape of AD-associated metabolites and associated processes. These will be instrumental to fill the gap in our understanding of the metabolic components of AD pathophysiology.

Proliferating microglia exhibit unique transcriptomal and functional alterations in Alzheimer’s disease

Proliferation of microglia is a common process occurring in several neurodegenerative disorders including Alzheimer disease (AD). However, the effect of proliferation on microglial function and disease progression remains unclear to date. We hypothesize that microglial proliferation in a neurodegenerative environment will generate different subpopulations contributing to the transition from acute to chronic neuroinflammation METHOD: Proliferating microglia was studied in APP/PS1 mice and in human brain tissue. Phagocytic capacity of proliferating microglia was assessed in vivo by methoxy-X04 injection and Ki67+ staining in WT and APP/PS1 mice at 6m and 12m of age. Genetic signature of proliferating microglia in these groups was investigated sorting CD11b+/CD45+/Ki67+ microglia and performing RNA-seq. First, we confirmed increased microglial proliferation both in human AD and in a mouse model of the disease (APP/PS1). We observed these cells specially neighbouring the sites of beta-amyloid deposition. We provide evidence that newly proliferated microglia do not phagocyte beta-amyloid in vivo. We identified a unique transcriptomic signature of these cells at 6 and 12 months of age, which was characterized by an enrichment of immune system-related pathways. Performing network reconstruction analysis, we defined a set of 3 key genes upregulated in proliferating microglia at 12 months of age and we then validated their role in microglia activation and beta-amyloid phagocytosis in vitro. Our results argue for a novel concept by which phenotypic and functional microglial changes occur as a response to accelerated proliferation in a neurodegenerative environment. In this work, we dissected the phenotype and function of proliferating microglia in AD and pointed out targets that might serve as new therapeutic approaches not only in AD but also in other CNS disorders, harboring a chronic inflammatory component, as microglia proliferation is a recurrent event in both acute injuries and neurodegeneration.

It Is Time to Study Overlapping Molecular and Circuit Pathophysiologies in Alzheimer's and Lewy Body Disease Spectra.

Alzheimer’s disease (AD) is the leading cause of dementia due to neurodegeneration and is characterized by extracellular senile plaques composed of amyloid β1–42 (Aβ) as well as intracellular neurofibrillary tangles consisting of phosphorylated tau (p-tau). Dementia with Lewy bodies constitutes a continuous spectrum with Parkinson’s disease, collectively termed Lewy body disease (LBD). LBD is characterized by intracellular Lewy bodies containing α-synuclein (α-syn). The core clinical features of AD and LBD spectra are distinct, but the two spectra share common cognitive and behavioral symptoms. The accumulation of pathological proteins, which acquire pathogenicity through conformational changes, has long been investigated on a protein-by-protein basis. However, recent evidence suggests that interactions among these molecules may be critical to pathogenesis. For example, Aβ/tau promotes α-syn pathology, and α-syn modulates p-tau pathology. Furthermore, clinical evidence suggests that these interactions may explain the overlapping pathology between AD and LBD in molecular imaging and post-mortem studies. Additionally, a recent hypothesis points to a common mechanism of prion-like progression of these pathological proteins, via neural circuits, in both AD and LBD. This suggests a need for understanding connectomics and their alterations in AD and LBD from both pathological and functional perspectives. In AD, reduced connectivity in the default mode network is considered a hallmark of the disease. In LBD, previous studies have emphasized abnormalities in the basal ganglia and sensorimotor networks; however, these account for movement disorders only. Knowledge about network abnormalities common to AD and LBD is scarce because few previous neuroimaging studies investigated AD and LBD as a comprehensive cohort. In this paper, we review research on the distribution and interactions of pathological proteins in the brain in AD and LBD, after briefly summarizing their clinical and neuropsychological manifestations. We also describe the brain functional and connectivity changes following abnormal protein accumulation in AD and LBD. Finally, we argue for the necessity of neuroimaging studies that examine AD and LBD cases as a continuous spectrum especially from the proteinopathy and neurocircuitopathy viewpoints. The findings from such a unified AD and Parkinson’s disease (PD) cohort study should provide a new comprehensive perspective and key data for guiding disease modification therapies targeting the pathological proteins in AD and LBD.

Distinct Functional and Metabolic Alterations of DMN Subsystems in Alzheimer's Disease: A Simultaneous FDG-PET/fMRI Study.

The default mode network (DMN) dysfunction has been widely identified in Alzheimer's disease (AD). Increasing evidence has shown that the functional heterogeneity of DMN has been associated with distinct cognitive functions. The pathophysiological changes of these two DMN subsystems, i.e., anterior DMN (aDMN) and posterior DMN (pDMN), also showed different patterns in the AD patients. Yet the underlying metabolic mechanism remains not clear. In this work, we performed a simultaneous FDG-PET/fMRI study, to investigate the distinct functional and metabolic alterations of DMN subsystems in AD. Significantly decreased functional connectivity strength (FCS) in pDMN but not aDMN was found in AD patients. The retaining connectivity in aDMN might represent a compensatory strategy. Concurrently, significant glucose hypometabolism was shown in pDMN and aDMN of AD patients, respectively. Moreover, the reduction of FCS in pDMN was positively correlated with MMSE score of patients. Our study suggests that resting state functional connectivity and glucose metabolism changed differently in the aDMN and pDMN of AD. Our findings brought new insights in understanding the underlying metabolism changes along with functional alterations in AD.

Interdependence of neural network dysfunction and microglial alterations in Alzheimer’s disease-related models

SummaryNonconvulsive epileptiform activity and microglial alterations have been detected in people with Alzheimer’s disease (AD) and related mouse models. However, the relationship between these abnormalities remains to be elucidated. We suppressed epileptiform activity by treatment with the antiepileptic drug levetiracetam or by genetic ablation of tau and found that these interventions reversed or prevented aberrant microglial gene expression in brain tissues of aged human amyloid precursor protein transgenic mice, which simulate several key aspects of AD. The most robustly modulated genes included multiple factors previously implicated in AD pathogenesis, including TREM2, the hypofunction of which increases disease risk. Genetic reduction of TREM2 exacerbated epileptiform activity after mice were injected with kainate. We conclude that AD-related epileptiform activity markedly changes the molecular profile of microglia, inducing both maladaptive and adaptive alterations in their activities. Increased expression of TREM2 seems to support microglial activities that counteract this type of network dysfunction.

Multimodal mechanisms of human socially reinforced learning across neurodegenerative diseases.

Social feedback can selectively enhance learning in diverse domains. Relevant neurocognitive mechanisms have been studied mainly in healthy persons, yielding correlational findings. Neurodegenerative lesion models, coupled with multimodal brain measures, can complement standard approaches by revealing direct multidimensional correlates of the phenomenon.To this end, we assessed socially reinforced and non-socially reinforced learning in 40 healthy participants as well as persons with behavioural variant frontotemporal dementia (n = 21), Parkinson’s disease (n = 31) and Alzheimer’s disease (n = 20). These conditions are typified by predominant deficits in social cognition, feedback-based learning and associative learning, respectively, although all three domains may be partly compromised in the other conditions. We combined a validated behavioural task with ongoing EEG signatures of implicit learning (medial frontal negativity) and offline MRI measures (voxel-based morphometry).In healthy participants, learning was facilitated by social feedback relative to non-social feedback. In comparison with controls, this effect was specifically impaired in behavioural variant frontotemporal dementia and Parkinson’s disease, while unspecific learning deficits (across social and non-social conditions) were observed in Alzheimer’s disease. EEG results showed increased medial frontal negativity in healthy controls during social feedback and learning. Such a modulation was selectively disrupted in behavioural variant frontotemporal dementia. Neuroanatomical results revealed extended temporo-parietal and fronto-limbic correlates of socially reinforced learning, with specific temporo-parietal associations in behavioural variant frontotemporal dementia and predominantly fronto-limbic regions in Alzheimer’s disease. In contrast, non-socially reinforced learning was consistently linked to medial temporal/hippocampal regions. No associations with cortical volume were found in Parkinson’s disease. Results are consistent with core social deficits in behavioural variant frontotemporal dementia, subtle disruptions in ongoing feedback-mechanisms and social processes in Parkinson’s disease and generalized learning alterations in Alzheimer’s disease. This multimodal approach highlights the impact of different neurodegenerative profiles on learning and social feedback.Our findings inform a promising theoretical and clinical agenda in the fields of social learning, socially reinforced learning and neurodegeneration.

Involvement of cerebrovascular abnormalities in the pathogenesis and progression of Alzheimer's disease: an adrenergic approach.

Alzheimer’s disease (AD), as the most common neurodegenerative disease in elder population, is pathologically characterized by β-amyloid (Aβ) plaques, neurofibrillary tangles composed of highly-phosphorylated tau protein and consequently progressive neurodegeneration. However, both Aβ and tau fails to cover the whole pathological process of AD, and most of the Aβ- or tau-based therapeutic strategies are all failed. Increasing lines of evidence from both clinical and preclinical studies have indicated that age-related cerebrovascular dysfunctions, including the changes in cerebrovascular microstructure, blood-brain barrier integrity, cerebrovascular reactivity and cerebral blood flow, accompany or even precede the development of AD-like pathologies. These findings may raise the possibility that cerebrovascular changes are likely pathogenic contributors to the onset and progression of AD. In this review, we provide an appraisal of the cerebrovascular alterations in AD and the relationship to cognitive impairment and AD pathologies. Moreover, the adrenergic mechanisms leading to cerebrovascular and AD pathologies were further discussed. The contributions of early cerebrovascular factors, especially through adrenergic mechanisms, should be considered and treasured in the diagnostic, preventative, and therapeutic approaches to address AD.

Tau phosphorylation and OPA1 proteolysis are unrelated events: Implications for Alzheimer's Disease

The neuropathological hallmarks of Alzheimer's Disease are plaques and neurofibrillary tangles. Yet, Alzheimer's is a complex disease with many contributing factors, such as energy-metabolic changes, which have been documented in autopsy brains from individuals with Alzheimer's and animal disease models alike. One conceivable explanation is that the interplay of age-related extracellular and intracellular alterations pertaining to Alzheimer's, such as cerebrovascular changes, protein aggregates and inflammation, evoke a mitochondrial response. However, it is not clear if and how mitochondria can contribute to Alzheimer's pathophysiology. This study focuses on one particular aspect of this question by investigating the functional interaction between the microtubule-associated protein tau and the mitochondrial inner membrane fusion machinery, which shows alterations in Alzheimer's brains. OPA1 is an essential inner membrane-fusion protein regulated by the two membrane proteases OMA1 and YME1L1. Assessment of OPA1 proteolysis—usually found in dividing mitochondria—and posttranslational tau modifications in mouse and human neuroblastoma cells under different experimental conditions clarified the relationship between these two pathways: OPA1 hydrolysis and phosphorylation or dephosphorylation of tau may coincide, but are not causally related. OPA1 cleavage did not alter tau's phosphorylation pattern. Conversely, tau's phosphorylation state did not induce nor correlate with OPA1 proteolysis. These results irrefutably demonstrate that there is no direct functional interaction between posttranslational tau modifications and the regulation of the OMA1-OPA1 pathway, which implies a common root cause modulating both pathways in Alzheimer's.