Examining the mechanisms that link β-amyloid and α-synuclein pathologies

Alpha-synuclein expression in oxytocin neurons of young and old bovine brains

Understanding of central nervous system mechanisms underlying age-related infertility remains limited. Fibril α-synuclein, distinct from its monomeric form, is implicated in age-related diseases. Notably, fibril α-synuclein spreads among neurons, similar to prions, from damaged old neurons in cortex and hippocampus to healthy neurons. However, less is known whether α-synuclein propagates into oxytocin neurons, which play crucial roles in reproduction. We compared α-synuclein expression in the oxytocin neurons in suprachiasmatic nucleus (SCN), supraoptic nucleus (SON), paraventricular hypothalamic nucleus (PVN), and posterior pituitary (PP) gland of healthy heifers and aged cows to determine its role in age-related infertility. We analyzed mRNA and protein expression, along with Congo red histochemistry and fluorescent immunohistochemistry for oxytocin and α-synuclein, followed by confocal microscopy with Congo red staining. Both mRNA and protein expressions of α-synuclein were confirmed in the bovine cortex, hippocampus, SCN, SON, PVN, and PP tissues. Significant differences in α-synuclein mRNA expressions were observed in the cortex and hippocampus between young heifers and old cows. Western blots showed five bands of α-synuclein, probably reflecting monomers, dimers, and oligomers, in the cortex, hippocampus, SCN, SON, PVN, and PP tissues, and there were significant differences in some bands between the young heifers and old cows. Bright-field and polarized light microscopy did not detect obvious amyloid deposition in the aged hypothalami; however, higher-sensitive confocal microscopy unveiled strong positive signals for Congo red and α-synuclein in oxytocin neurons in the aged hypothalami. α-synuclein was expressed in oxytocin neurons, and some differences were observed between young and old hypothalami.

Ultrasensitive detection of aggregated α-synuclein using quiescent seed amplification assay for the diagnosis of Parkinson's disease

BACKGROUND

Seed amplification assays (SAA) enable the amplification of pathological misfolded proteins, including α-synuclein (αSyn), in both tissue homogenates and body fluids of Parkinson's disease (PD) patients. SAA involves repeated cycles of shaking or sonication coupled with incubation periods. However, this amplification scheme has limitations in tracking protein propagation due to repeated fragmentation.

METHODS

We introduced a modified form of SAA, known as Quiescent SAA (QSAA), and evaluated biopsy and autopsy samples from individuals clinically diagnosed with PD and those without synucleinopathies (control group). Brain biopsy samples were obtained from 14 PD patients and 6 controls without synucleinopathies. Additionally, skin samples were collected from 214 PD patients and 208 control subjects. Data were analyzed from April 2019 to May 2023.

RESULTS

QSAA successfully amplified αSyn aggregates in brain tissue sections from mice inoculated with pre-formed fibrils. In the skin samples from 214 PD cases and 208 non-PD cases, QSAA demonstrated high sensitivity (90.2%) and specificity (91.4%) in differentiating between PD and non-PD cases. Notably, more αSyn aggregates were detected by QSAA compared to immunofluorescence with the pS129-αSyn antibody in consecutive slices of both brain and skin samples.

CONCLUSION

We introduced the new QSAA method tailored for in situ amplification of αSyn aggregates in brain and skin samples while maintaining tissue integrity, providing a streamlined approach to diagnosing PD with individual variability. The integration of seeding activities with the location of deposition of αSyn seeds advances our understanding of the mechanism underlying αSyn misfolding in PD.

Association of CSF α-Synuclein Seed Amplification Assay Positivity with Disease Progression and Cognitive Decline: A Longitudinal Alzheimer's Disease Neuroimaging Initiative Study

INTRODUCTION

CSF α-synuclein seed amplification assay (SAA) is a sensitive and specific tool for detecting Lewy body (LB) co-pathology in AD.

METHODS

1637 cross-sectional and 407 longitudinal CSF samples from ADNI were tested with SAA. We examined longitudinal dynamics of Aβ, α-synuclein seeds, and p-tau181, along with global and domain-specific cognition in stable SAA+, stable SAA-, and those who converted to SAA+ from SAA-.

RESULTS

SAA+ individuals had faster cognitive decline than SAA-, notably in MCI, and presented with earlier symptom onset. SAA+ conversion was associated with CSF Aβ42-positivity but did not impact progression of either Aβ42 or p-tau181 status. Aβ42, p-tau181, and α-syn SAA were all strong predictors of clinical progression, particularly Aβ42. In vitro α-syn SAA kinetic parameters were associated with participant demographics, clinical profiles, and cognitive decline.

DISCUSSION

These results highlight the interplay between Aβ and α-synuclein and their association with disease progression.

Neuroinflammation is associated with Alzheimer's disease co-pathology in dementia with Lewy bodies

BACKGROUND

Neuroinflammation and Alzheimer's disease (AD) co-pathology may contribute to disease progression and severity in dementia with Lewy bodies (DLB). This study aims to clarify whether a different pattern of neuroinflammation, such as alteration in microglial and astroglial morphology and distribution, is present in DLB cases with and without AD co-pathology.

METHODS

The morphology and load (% area of immunopositivity) of total (Iba1) and reactive microglia (CD68 and HLA-DR), reactive astrocytes (GFAP) and proteinopathies of alpha-synuclein (KM51/pser129), amyloid-beta (6 F/3D) and p-tau (AT8) were assessed in a cohort of mixed DLB + AD (n = 35), pure DLB (n = 15), pure AD (n = 16) and control (n = 11) donors in limbic and neocortical brain regions using immunostaining, quantitative image analysis and confocal microscopy. Regional and group differences were estimated using a linear mixed model analysis.

RESULTS

Morphologically, reactive and amoeboid microglia were common in mixed DLB + AD, while homeostatic microglia with a small soma and thin processes were observed in pure DLB cases. A higher density of swollen astrocytes was observed in pure AD cases, but not in mixed DLB + AD or pure DLB cases. Mixed DLB + AD had higher CD68-loads in the amygdala and parahippocampal gyrus than pure DLB cases, but did not differ in astrocytic loads. Pure AD showed higher Iba1-loads in the CA1 and CA2, higher CD68-loads in the CA2 and subiculum, and a higher astrocytic load in the CA1-4 and subiculum than mixed DLB + AD cases. In mixed DLB + AD cases, microglial load associated strongly with amyloid-beta (Iba1, CD68 and HLA-DR), and p-tau (CD68 and HLA-DR), and minimally with alpha-synuclein load (CD68). In addition, the highest microglial activity was found in the amygdala and CA2, and astroglial load in the CA4. Confocal microscopy demonstrated co-localization of large amoeboid microglia with neuritic and classic-cored plaques of amyloid-beta and p-tau in mixed DLB + AD cases.

CONCLUSIONS

In conclusion, microglial activation in DLB was largely associated with AD co-pathology, while astrocytic response in DLB was not. In addition, microglial activity was high in limbic regions, with prevalent AD pathology. Our study provides novel insights into the molecular neuropathology of DLB, highlighting the importance of microglial activation in mixed DLB + AD.

Practical use of DAT SPECT imaging in diagnosing dementia with Lewy bodies: a US perspective of current guidelines and future directions

Background

Diagnosing Dementia with Lewy Bodies (DLB) remains a challenge in clinical practice. The use of 123I-ioflupane (DaTscan™) SPECT imaging, which detects reduced dopamine transporter (DAT) uptake-a key biomarker in DLB diagnosis-could improve diagnostic accuracy. However, DAT imaging is underutilized despite its potential, contributing to delays and suboptimal patient management.

Methods

This review evaluates DLB diagnostic practices and challenges faced within the U.S. by synthesizing information from current literature, consensus guidelines, expert opinions, and recent updates on DaTscan FDA filings. It contrasts DAT SPECT with alternative biomarkers, provides recommendations for when DAT SPECT imaging may be indicated and discusses the potential of emerging biomarkers in enhancing diagnostic approaches.

Results

The radiopharmaceutical 123I-ioflupane for SPECT imaging was initially approved in Europe (2000) and later in the US (2011) for Parkinsonism/Essential Tremor. Its application was extended in 2022 to include the diagnosis of DLB. DaTscan's diagnostic efficacy for DLB, with its sensitivity, specificity, and predictive values, confirms its clinical utility. However, US implementation faces challenges such as insurance barriers, costs, access issues, and regional availability disparities.

Conclusion

123I-ioflupane SPECT Imaging is indicated for DLB diagnosis and differential diagnosis of Alzheimer's Disease, particularly in uncertain cases. Addressing diagnostic obstacles and enhancing physician-patient education could improve and expedite DLB diagnosis. Collaborative efforts among neurologists, geriatric psychiatrists, psychologists, and memory clinic staff are key to increasing diagnostic accuracy and care in DLB management.

Tau maturation in the clinicopathological spectrum of Lewy body and Alzheimer's disease

OBJECTIVE

Alzheimer's disease neuropathologic change and alpha-synucleinopathy commonly co-exist and contribute to the clinical heterogeneity of dementia. Here, we examined tau epitopes marking various stages of tangle maturation to test the hypotheses that tau maturation is more strongly associated with beta-amyloid compared to alpha-synuclein, and within the context of mixed pathology, mature tau is linked to Alzheimer's disease clinical phenotype and negatively associated with Lewy body dementia.

METHODS

We used digital histology to measure percent area-occupied by pathology in cortical regions among individuals with pure Alzheimer's disease neuropathologic change, pure alpha-synucleinopathy, and a co-pathology group with both Alzheimer's and alpha-synuclein pathologic diagnoses. Multiple tau monoclonal antibodies were used to detect early (AT8, MC1) and mature (TauC3) epitopes of tangle progression. We used linear/logistic regression to compare groups and test the association between pathologies and clinical features.

RESULTS

There were lower levels of tau pathology (β = 1.86-2.96, p < 0.001) across all tau antibodies in the co-pathology group compared to the pure Alzheimer's pathology group. Among individuals with alpha-synucleinopathy, higher alpha-synuclein was associated with greater early tau (AT8 β = 1.37, p < 0.001; MC1 β = 1.2, p < 0.001) but not mature tau (TauC3 p = 0.18), whereas mature tau was associated with beta-amyloid (β = 0.21, p = 0.01). Finally, lower tau, particularly TauC3 pathology, was associated with lower frequency of both core clinical features and categorical clinical diagnosis of dementia with Lewy bodies.

INTERPRETATION

Mature tau may be more closely related to beta-amyloidosis than alpha-synucleinopathy, and pathophysiological processes of tangle maturation may influence the clinical features of dementia in mixed Lewy-Alzheimer's pathology.

The Complex Interplay between Toxic Hallmark Proteins, Calmodulin-Binding Proteins, Ion Channels, and Receptors Involved in Calcium Dyshomeostasis in Neurodegeneration

Calcium dyshomeostasis is an early critical event in neurodegeneration as exemplified by Alzheimer's (AD), Huntington's (HD) and Parkinson's (PD) diseases. Neuronal calcium homeostasis is maintained by a diversity of ion channels, buffers, calcium-binding protein effectors, and intracellular storage in the endoplasmic reticulum, mitochondria, and lysosomes. The function of these components and compartments is impacted by the toxic hallmark proteins of AD (amyloid beta and Tau), HD (huntingtin) and PD (alpha-synuclein) as well as by interactions with downstream calcium-binding proteins, especially calmodulin. Each of the toxic hallmark proteins (amyloid beta, Tau, huntingtin, and alpha-synuclein) binds to calmodulin. Multiple channels and receptors involved in calcium homeostasis and dysregulation also bind to and are regulated by calmodulin. The primary goal of this review is to show the complexity of these interactions and how they can impact research and the search for therapies. A secondary goal is to suggest that therapeutic targets downstream from calcium dyshomeostasis may offer greater opportunities for success.

Role of Specific Autoantibodies in Neurodegenerative Diseases: Pathogenic Antibodies or Promising Biomarkers for Diagnosis

Neurodegenerative diseases (NDDs) affect millions of people worldwide. They develop due to the pathological accumulation and aggregation of various misfolded proteins, axonal and synaptic loss and dysfunction, inflammation, cytoskeletal abnormalities, defects in DNA and RNA, and neuronal death. This leads to the activation of immune responses and the release of the antibodies against them. Recently, it has become clear that autoantibodies (Aabs) can contribute to demyelination, axonal loss, and brain and cognitive dysfunction. This has significantly changed the understanding of the participation of humoral autoimmunity in neurodegenerative disorders. It is crucial to understand how neuroinflammation is involved in neurodegeneration, to aid in improving the diagnostic and therapeutic value of Aabs in the future. This review aims to provide data on the immune system's role in NDDs, the pathogenic role of some specific Aabs against molecules associated with the most common NDDs, and their potential role as biomarkers for monitoring and diagnosing NDDs. It is suggested that the autoimmune aspects of NDDs will facilitate early diagnosis and help to elucidate previously unknown aspects of the pathobiology of these diseases.

Evaluation of N- and O-Linked Indole Triazines for a Dual Effect on α-Synuclein and Tau Aggregation

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder underlying dementia in the geriatric population. AD manifests by two pathological hallmarks: extracellular amyloid-β (Aβ) peptide-containing senile plaques and intraneuronal neurofibrillary tangles comprised of aggregated hyperphosphorylated tau protein (p-tau). However, more than half of AD cases also display the presence of aggregated α-synuclein (α-syn)-containing Lewy bodies. Conversely, Lewy bodies disorders have been reported to have concomitant Aβ plaques and neurofibrillary tangles. Our drug discovery program focuses on the synthesis of multitarget-directed ligands to abrogate aberrant α-syn, tau (2N4R), and p-tau (1N4R) aggregation and to slow the progression of AD and related dementias. To this end, we synthesized 11 compounds with a triazine-linker and evaluated their effectiveness in reducing α-syn, tau isoform 2N4R, and p-tau isoform 1N4R aggregation. We utilized biophysical methods such as thioflavin T (ThT) fluorescence assays, transmission electron microscopy (TEM), photoinduced cross-linking of unmodified proteins (PICUP), and M17D intracellular inclusion cell-based assays to evaluate the antiaggregation properties and cellular protection of our best compounds. We also performed disaggregation assays with isolated Aβ-plaques from human AD brains. Our results demonstrated that compound 10 was effective in reducing both oligomerization and fibril formation of α-syn and tau isoform 2N4R in a dose-dependent manner via ThT and PICUP assays. Compound 10 was also effective at reducing the formation of recombinant α-syn, tau 2N4R, and p-tau 1N4R fibrils by TEM. Compound 10 reduced the development of α-syn inclusions in M17D neuroblastoma cells and stopped the seeding of tau P301S using biosensor cells. Disaggregation experiments showed smaller Aβ-plaques and less paired helical filaments with compound 10. Compound 10 may provide molecular scaffolds for further optimization and preclinical studies for neurodegenerative proteinopathies.

α-Synuclein Aggregation Is Triggered by Oligomeric Amyloid-β 42 via Heterogeneous Primary Nucleation

An increasing number of cases where amyloids of different proteins are found in the same patient are being reported. This observation complicates diagnosis and clinical intervention. Amyloids of the amyloid-β peptide or the protein α-synuclein are traditionally considered hallmarks of Alzheimer's and Parkinson's diseases, respectively. However, the co-occurrence of amyloids of these proteins has also been reported in patients diagnosed with either disease. Here, we show that soluble species containing amyloid-β can induce the aggregation of α-synuclein. Fibrils formed under these conditions are solely composed of α-synuclein to which amyloid-β can be found associated but not as part of the core of the fibrils. Importantly, by global kinetic analysis, we found that the aggregation of α-synuclein under these conditions occurs via heterogeneous primary nucleation, triggered by soluble aggregates containing amyloid-β.

Exploring the Potential of Aptamers in Targeting Neuroinflammation and Neurodegenerative Disorders: Opportunities and Challenges

Neuroinflammation is the precursor for several neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Targeting neuroinflammation has emerged as a promising strategy to address a wide range of CNS pathologies. These NDDs still present significant challenges in terms of limited and ineffective diagnosis and treatment options, driving the need to explore innovative and novel therapeutic alternatives. Aptamers are single-stranded nucleic acids that offer the potential for addressing these challenges through diagnostic and therapeutic applications. In this review, we summarize diagnostic and therapeutic aptamers for inflammatory biomolecules, as well as the inflammatory cells in NDDs. We also discussed the potential of short nucleotides for Aptamer-Based Targeted Brain Delivery through their unique features and modifications, as well as their ability to penetrate the blood-brain barrier. Moreover, the unprecedented opportunities and substantial challenges of using aptamers as therapeutic agents, such as drug efficacy, safety considerations, and pharmacokinetics, are also discussed. Taken together, this review assesses the potential of aptamers as a pioneering approach for target delivery to the CNS and the treatment of neuroinflammation and NDDs.

Natural Products as the Potential to Improve Alzheimer's and Parkinson's Disease

Alzheimer's disease and Parkinson's disease are the two most common neurodegenerative diseases in the world, and their incidence rates are increasing as our society ages. This creates a significant social and economic burden. Although the exact cause and treatment methods for these diseases are not yet known, research suggests that Alzheimer's disease is caused by amyloid precursor protein, while α-synuclein acts as a causative agent in Parkinson's disease. The accumulation of abnormal proteins such as these can lead to symptoms such as loss of protein homeostasis, mitochondrial dysfunction, and neuroinflammation, which ultimately result in the death of nerve cells and the progression of neurodegenerative diseases. The medications currently available for these diseases only delay their progression and have many adverse effects, which has led to increased interest in developing natural products with fewer adverse effects. In this study, we selected specific keywords and thesis content to investigate natural products that are effective in treating Alzheimer's and Parkinson's diseases. We reviewed 16 papers on natural products and found that they showed promising mechanisms of action such as antioxidant, anti-inflammatory, and mitochondrial function improvement. Other natural products with similar properties could also be considered potential treatments for neurodegenerative diseases, and they can be consumed as part of a healthy diet rather than as medicine.

Implications of fractalkine on glial function, ablation and glial proteins/receptors/markers—understanding its therapeutic usefulness in neurological settings: a narrative review

Background

Fractalkine (CX3CL1) is a chemokine predominantly released by neurons. As a signaling molecule, CX3CL1 facilitates talk between neurons and glia. CX3CL1 is considered as a potential target which could alleviate neuroinflammation. However, certain controversial results and ambiguous role of CX3CL1 make it inexorable to decipher the overall effects of CX3CL1 on the physiopathology of glial cells.

Main body of the abstract

Implications of cross-talk between CX3CL1 and different glial proteins/receptors/markers will give a bird eye view of the therapeutic significance of CX3CL1. Keeping with the need, this review identifies the effects of CX3CL1 on glial physiopathology, glial ablation, and gives a wide coverage on the effects of CX3CL1 on certain glial proteins/receptors/markers.

Short conclusion

Pinpoint prediction of the therapeutic effect of CX3CL1 on neuroinflammation needs further research. This is owing to certain obscure roles and implications of CX3CL1 on different glial proteins/receptors/markers, which are crucial under neurological settings. Further challenges are imposed due to the dichotomous roles played by CX3CL1. The age-old chemokine shows many newer scopes of research in near future. Thus, overall assessment of the effect of CX3CL1 becomes crucial prior to its administration in neuroinflammation.

The Neurodegenerative Elderly Syndrome (NES) hypothesis: Alzheimer and Parkinson are two faces of the same disease

Increasing evidence suggests that Alzheimer's disease (AD) and Parkinson's disease (PD) share monoamine and alpha-synuclein (αSyn) dysfunctions, often beginning years before clinical manifestations onset. The triggers for these impairments and the causes leading these early neurodegenerative processes to become AD or PD remain unclear. We address these issues by proposing a radically new perspective to frame AD and PD: they are different manifestations of one only disease we call "Neurodegenerative Elderly Syndrome (NES)". NES goes through three phases. The seeding stage, which starts years before clinical signs, and where the part of the brain-body affected by the initial αSyn and monoamine dysfunctions, influences the future possible progression of NES towards PD or AD. The compensatory stage, where the clinical symptoms are still silent thanks to compensatory mechanisms keeping monoamine concentrations homeostasis. The bifurcation stage, where NES becomes AD or PD. We present recent literature supporting NES and discuss how this hypothesis could radically change the comprehension of AD and PD comorbidities and the design of novel system-level diagnostic and therapeutic actions.

Glymphatic MRI techniques in sleep and neurodegenerative diseases

PURPOSE OF REVIEW

The purpose of this review article is to summarize the current in-vivo imaging techniques for the evaluation of the glymphatic function and discuss the factors influencing the glymphatic function and research directions in the future.

RECENT FINDINGS

The glymphatic system allows the clearance of metabolic waste from the central nervous system (CNS). The glymphatic pathway has been investigated using intrathecal or intravenous injection of a gadolinium-based contrast agent (GBCA) on MRI, so-called glymphatic MRI. The glymphatic MRI indirectly visualizes the dynamic CSF flow and evaluated the glymphatic function in the animal and human models. Several clinical and preclinical studies using glymphatic MRI have confirmed that the glymphatic function is impaired in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and idiopathic normal pressure hydrocephalus. Furthermore, physiologic process such as sleep facilitates the glymphatic clearance, thus clearing accumulation of protein deposition, such as amyloid or tau, potentially delaying the progression of neurodegenerative diseases.

SUMMARY

The glymphatic system plays a crucial role in clearing metabolic wastes in the brain. Glymphatic MR imaging using GBCA administration serves as a functional imaging tool to measure the glymphatic function and investigate various pathophysiologies of neurodegenerative diseases.

Novel pathophysiological roles of α-synuclein in age-related vascular endothelial dysfunction

Although α-synuclein (SNCA) is a well-known pathological molecule involved in synucleinopathy in neurons, its physiological roles remain largely unknown. We reported that serum SNCA levels have a close inverse correlation with blood pressure and age, which indicates the involvement of SNCA in age-related endothelial dysfunction. Therefore, this study aimed to elucidate the molecular functions of SNCA in the endothelium. We confirmed that SNCA was expressed in and secreted from endothelial cells (ECs). Exogenous treatment with recombinant SNCA (rSNCA) activated the Akt-eNOS axis and increased nitric oxide production in ECs. Treatment with rSNCA also suppressed TNF-α- and palmitic acid-induced NF-κB activation, leading to the suppression of VCAM-1 upregulation and restoration of eNOS downregulation in ECs. As for endogenous SNCA expression, replicative senescence resulted in the attenuation of SNCA expression in cultured ECs, similar to the effects of physiological aging on mice aortas. The siRNA-mediated silencing of SNCA consistently resulted in senescent phenotypes, such as eNOS downregulation, increased β-gal activity, decreased Sirt1 expression, and increased p53 expression, in ECs. Ex vivo assessment of endothelial functions using aortic rings revealed impaired endothelium-dependent acetylcholine-induced relaxation in SNCA knockout (KO) mice. Furthermore, SNCA KO mice, especially those on a high-fat diet, displayed elevated blood pressure compared with wild-type mice; this could be eNOS dysfunction-dependent because of the lower difference caused by L-NAME administration. These results indicate that exogenous and endogenous SNCA in ECs might physiologically maintain vascular integrity, and age-related endothelial dysfunction might be partially ascribed to loss-of-function of SNCA in ECs.

Amitriptyline Improves Cognitive and Neuronal Function in a Rat Model that Mimics Dementia with Lewy Bodies

Dementia with Lewy bodies (DLB), a highly prevalent neurodegenerative disorder, causes motor and cognitive deficits. The main pathophysiologies of DLB are glutamate excitotoxicity and accumulation of Lewy bodies comprising α-synuclein (α-syn) and β-amyloid (Aβ). Amitriptyline (AMI) promotes expression of glutamate transporter-1 and glutamate reuptake. In this study, we measured the effects of AMI on behavioral and neuronal function in a DLB rat model. We used rivastigmine (RIVA) as a positive control. To establish the DLB rat model, male Wistar rats were stereotaxically injected with recombinant adenoassociated viral vector with the SNCA gene (10μg/10μL) and Aβ (5μg/2.5μL) into the left ventricle and prefrontal cortex, respectively. AMI (10mg/kg/day, i.p.), RIVA (2mg/kg/day, i.p.), or saline was injected intraperitoneally after surgery. From the 29^th day, behavioral tests were performed to evaluate the motor and cognitive functions of the rats. Immunohistochemical staining was used to assess neuronal changes. We measured the α-syn level, number of newborn cells, and neuronal density in the hippocampus and in the nigrostriatal dopaminergic system. The DLB group exhibited deficit in object recognition. Both the AMI and RIVA treatments reversed these deficits. Histologically, the DLB rats exhibited cell loss in the substantia nigra pars compacta and in the hippocampal CA1 area. AMI reduced this cell loss, but RIVA did not. In addition, the DLB rats exhibited a lower number of newborn cells and higher α-syn levels in the dentate gyrus (DG). AMI did not affect α-syn accumulation but recovered neurogenesis in the DG of the rats, whereas RIVA reversed the α-syn accumulation but did not affect neurogenesis in the rats. We suggest that AMI may have potential for use in the treatment of DLB.

Differential Neuropathology, Genetics, and Transcriptomics in Two Kindred Cases with Alzheimer’s Disease and Lewy Body Dementia

Alzheimer’s disease (AD) and Lewy body dementia (LBD) are two different forms of dementia, but their pathology may involve the same cortical areas with overlapping cognitive manifestations. Nonetheless, the clinical phenotype is different due to the topography of the lesions driven by the different underlying molecular processes that arise apart from genetics, causing diverse neurodegeneration. Here, we define the commonalities and differences in the pathological processes of dementia in two kindred cases, a mother and a son, who developed classical AD and an aggressive form of AD/LBD, respectively, through a neuropathological, genetic (next-generation sequencing), and transcriptomic (RNA-seq) comparison of four different brain areas. A genetic analysis did not reveal any pathogenic variants in the principal AD/LBD-causative genes. RNA sequencing highlighted high transcriptional dysregulation within the substantia nigra in the AD/LBD case, while the AD case showed lower transcriptional dysregulation, with the parietal lobe being the most involved brain area. The hippocampus (the most degenerated area) and basal ganglia (lacking specific lesions) expressed the lowest level of dysregulation. Our data suggest that there is a link between transcriptional dysregulation and the amount of tissue damage accumulated across time, assessed through neuropathology. Moreover, we highlight that the molecular bases of AD and LBD follow very different pathways, which underlie their neuropathological signatures. Indeed, the transcriptome profiling through RNA sequencing may be an important tool in flanking the neuropathological analysis for a deeper understanding of AD and LBD pathogenesis.

Evolution of Clinical-Pathological Correlations in Early-Onset Alzheimer's Disease Over a 25-Year Period in an Academic Brain Bank

BACKGROUND

Early onset Alzheimer's disease (EOAD) represents a diagnostic challenge and is associated with a high diagnostic delay and misdiagnosis.

OBJECTIVE

To describe clinical and pathological data from a pathologically confirmed EOAD cohort and evaluate evolving trends in clinical-pathological correlation accuracy.

METHODS

Retrospective review of clinical and neuropathological data of pathologically confirmed EOAD patients (age at onset [AAO] < 60). Comparison between two periods: 1994- 2009 and 2010- 2018.

RESULTS

Eighty brain donors were included. Mean AAO, age at death, and diagnostic delay was 55, 66, and 3 years, respectively. Twenty-nine percent had a nonamnestic presentation. Sixteen percent were given a non-AD initial clinical diagnosis (initial misdiagnosis) and 14% received a final misdiagnosis. Nonamnestic presentation patients received more misdiagnoses than amnestic presentation ones (39% versus 7% and 39% versus 3.5%, on initial and final misdiagnosis, respectively). When comparing both time periods, a trend towards a higher diagnostic accuracy in the 2010- 2018 period was observed, mainly on initial misdiagnosis in nonamnestic presentation patients (53% versus 13%, p = 0.069). Diagnostic delay was similar between both periods. Cerebral amyloid angiopathy (96%) and Lewy body co-pathology (55%) were very frequent, while limbic-predominant age-related TDP-43 encephalopathy pathologic changes were only present in 12.5%.

CONCLUSION

In the last decade, there has been a trend towards improved diagnostic accuracy in EOAD, which might be explained by improved diagnostic criteria, increasing experience on EOAD and the beginning of the use of biomarkers, although diagnostic delay remains similar. Concomitant neuropathology was very frequent despite the relatively young age of brain donors.

Nutrient-sensing amyloid metastasis

Amyloids are organized suprastructural polypeptide arrangements. The prevalence of amyloid-related processes of pathophysiological relevance has been linked to aging-related degenerative diseases. Besides the role of genetic polymorphisms on the relative risk of amyloid diseases, the contributions of nongenetic ontogenic cluster of factors remain elusive. In recent decades, mounting evidences have been suggesting the role of essential micronutrients, in particular transition metals, in the regulation of amyloidogenic processes, both directly (such as binding to amyloid proteins) or indirectly (such as regulating regulatory partners, processing enzymes, and membrane transporters). The features of transition metals as regulatory cofactors of amyloid proteins and the consequences of metal dyshomeostasis in triggering amyloidogenic processes, as well as the evidences showing amelioration of symptoms by dietary supplementation, suggest an exaptative role of metals in regulating amyloid pathways. The self- and cross-talk replicative nature of these amyloid processes along with their systemic distribution support the concept of their metastatic nature. The role of amyloidosis as nutrient sensors would act as intra- and transgenerational epigenetic metabolic programming factors determining health span and life span, viability, which could participate as an evolutive selective pressure.

Therapeutic Potential of Astrocyte Transplantation

Cell transplantation is an attractive treatment strategy for a variety of brain disorders, as it promises to replenish lost functions and rejuvenate the brain. In particular, transplantation of astrocytes has come into light recently as a therapy for amyotrophic lateral sclerosis (ALS); moreover, grafting of astrocytes also showed positive results in models of other conditions ranging from neurodegenerative diseases of older age to traumatic injury and stroke. Despite clear differences in etiology, disorders such as ALS, Parkinson's, Alzheimer's, and Huntington's diseases, as well as traumatic injury and stroke, converge on a number of underlying astrocytic abnormalities, which include inflammatory changes, mitochondrial damage, calcium signaling disturbance, hemichannel opening, and loss of glutamate transporters. In this review, we examine these convergent pathways leading to astrocyte dysfunction, and explore the existing evidence for a therapeutic potential of transplantation of healthy astrocytes in various models. Existing literature presents a wide variety of methods to generate astrocytes, or relevant precursor cells, for subsequent transplantation, while described outcomes of this type of treatment also differ between studies. We take technical differences between methodologies into account to understand the variability of therapeutic benefits, or lack thereof, at a deeper level. We conclude by discussing some key requirements of an astrocyte graft that would be most suitable for clinical applications.

Deciphering the role of PGC-1α in neurological disorders: from mitochondrial dysfunction to synaptic failure

The onset and mechanisms underlying neurodegenerative diseases remain uncertain. The main features of neurodegenerative diseases have been related with cellular and molecular events like neuronal loss, mitochondrial dysfunction and aberrant accumulation of misfolded proteins or peptides in specific areas of the brain. The most prevalent neurodegenerative diseases belonging to age-related pathologies are Alzheimer's disease, Huntington's disease, Parkinson's disease and amyotrophic lateral sclerosis. Interestingly, mitochondrial dysfunction has been observed to occur during the early onset of several neuropathological events associated to neurodegenerative diseases. The master regulator of mitochondrial quality control and energetic metabolism is the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Additionally, it has been observed that PGC-1α appears to be a key factor in maintaining neuronal survival and synaptic transmission. In fact, PGC-1α downregulation in different brain areas (hippocampus, substantia nigra, cortex, striatum and spinal cord) that occurs in function of neurological damage including oxidative stress, neuronal loss, and motor disorders has been seen in several animal and cellular models of neurodegenerative diseases. Current evidence indicates that PGC-1α upregulation may serve as a potent therapeutic approach against development and progression of neuronal damage. Remarkably, increasing evidence shows that PGC-1α deficient mice have neurodegenerative diseases-like features, as well as neurological abnormalities. Finally, we discuss recent studies showing novel specific PGC-1α isoforms in the central nervous system that appear to exert a key role in the age of onset of neurodegenerative diseases and have a neuroprotective function in the central nervous system, thus opening a new molecular strategy for treatment of neurodegenerative diseases. The purpose of this review is to provide an up-to-date overview of the PGC-1α role in the physiopathology of neurodegenerative diseases, as well as establish the importance of PGC-1α function in synaptic transmission and neuronal survival.

Apolipoprotein E Genotype Contributes to Motor Progression in Parkinson's Disease

BACKGROUND

Emerging evidence indicates that the apolipoprotein E (APOE) ε4 exacerbates α-synuclein pathology.

OBJECTIVE

To determine whether APOE ε4 contributes to motor progression in early Parkinson's disease (PD).

METHODS

Longitudinal data were obtained from 384 patients with PD divided into APOE ε4 carriers (n = 85) and noncarriers (n = 299) in the Parkinson's Progression Marker Initiative. Participants underwent yearly motor assessments over a mean follow-up period of 78.9 months. Repeated measures and linear mixed models were used to test the effects of APOE ε4.

RESULTS

The motor progression was significantly more rapid in patients with PD carrying APOE ε4 than in noncarriers (β = 0.283, P = 0.026, 95% confidence interval: 0.033-0.532). Through subgroup analysis, we found that the effect of APOE ε4 was significant only in patients with high amyloid β burden (β = 0.761, P < 0.001, 95% confidence interval: 0.0356-1.167).

CONCLUSIONS

APOE ε4 may be associated with rapid motor progression in PD. © 2021 International Parkinson and Movement Disorder Society.

Soluble endogenous oligomeric α-synuclein species in neurodegenerative diseases: Expression, spreading, and cross-talk

There is growing recognition in the field of neurodegenerative diseases that mixed proteinopathies are occurring at greater frequency than originally thought. This is particularly true for three amyloid proteins defining most of these neurological disorders, amyloid-beta (Aβ), tau, and alpha-synuclein (αSyn). The co-existence and often co-localization of aggregated forms of these proteins has led to the emergence of concepts positing molecular interactions and cross-seeding between Aβ, tau, and αSyn aggregates. Amongst this trio, αSyn has received particular attention in this context during recent years due to its ability to modulate Aβ and tau aggregation in vivo, to interact at a molecular level with Aβ and tau in vivo and to cross-seed tau in mice. Here we provide a comprehensive, critical, and accessible review about the expression, role and nature of endogenous soluble αSyn oligomers because of recent developments in the understanding of αSyn multimerization, misfolding, aggregation, cross-talk, spreading and cross-seeding in neurodegenerative disorders, including Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, Alzheimer's disease, and Huntington's disease. We will also discuss our current understanding about the relative toxicity of endogenous αSyn oligomers in vivo and in vitro, and introduce potential opportunities to counter their deleterious effects.

Nanoaggregates Derived from Amyloid-beta and Alpha-synuclein Characterized by Sequential Quadruple Force Mapping

Overlapping of Alzheimer's disease and Parkinson's disease is associated with the formation of hetero-oligomers derived from amyloid-beta and alpha-synuclein. However, the structural identity of the hetero-oligomer has yet to be elucidated, particularly at high resolution. Here, with atomic force microscopy, the surface structure of hetero-oligomer was examined with four AFM tips tethering one of the selected antibodies recognizing N-terminus or C-terminus of each peptide. All aggregates were found to be hetero-oligomers, and probability of recognizing the termini is higher than that for the homo-oligomers, suggesting that the termini of the former have a greater tendency to be located at the surface or the termini have more freedom to be recognized, probably through loose packing. The methodology in this study provides us with a new approach to elucidate the structure of such aggregates at the single-molecule level, allowing the exploration of other intrinsically disordered proteins frequently found in nature.

Amyloid Oligomers: A Joint Experimental/Computational Perspective on Alzheimer's Disease, Parkinson's Disease, Type II Diabetes, and Amyotrophic Lateral Sclerosis

Protein misfolding and aggregation is observed in many amyloidogenic diseases affecting either the central nervous system or a variety of peripheral tissues. Structural and dynamic characterization of all species along the pathways from monomers to fibrils is challenging by experimental and computational means because they involve intrinsically disordered proteins in most diseases. Yet understanding how amyloid species become toxic is the challenge in developing a treatment for these diseases. Here we review what computer, in vitro, in vivo, and pharmacological experiments tell us about the accumulation and deposition of the oligomers of the (Aβ, tau), α-synuclein, IAPP, and superoxide dismutase 1 proteins, which have been the mainstream concept underlying Alzheimer's disease (AD), Parkinson's disease (PD), type II diabetes (T2D), and amyotrophic lateral sclerosis (ALS) research, respectively, for many years.

Lysozyme Fibrils Alter the Mechanism of Insulin Amyloid Aggregation

Protein aggregation into amyloid fibrils is linked to multiple disorders. The understanding of how natively non-harmful proteins convert to these highly cytotoxic amyloid aggregates is still not sufficient, with new ideas and hypotheses being presented each year. Recently it has been shown that more than one type of protein aggregates may co-exist in the affected tissue of patients suffering from amyloid-related disorders, sparking the idea that amyloid aggregates formed by one protein may induce another protein’s fibrillization. In this work, we examine the effect that lysozyme fibrils have on insulin amyloid aggregation. We show that not only do lysozyme fibrils affect insulin nucleation, but they also alter the mechanism of its aggregation.

Biophysical processes underlying cross-seeding in amyloid aggregation and implications in amyloid pathology

Abnormal aggregation of proteins into filamentous aggregates commonly associates with many diseases, such as Alzheimer's disease, Parkinson's disease and type-2 diabetes. These filamentous aggregates, also known as amyloids, can propagate their abnormal structures to either the same precursor molecules (seeding) or other protein monomers (cross-seeding). Cross-seeding has been implicated in the abnormal protein aggregation and has been found to facilitate the formation of physiological amyloids. It has risen to be an exciting area of research with a high volume of published reports. In this review article, we focus on the biophysical processes underlying the cross-seeding for some of the most commonly studied amyloid proteins. Here we will discuss the relevant literature related to cross-seeded polymerization of amyloid-beta, human islet amyloid polypeptide (hIAPP, or also known as amylin) and alpha-synuclein. SEVI (semen-derived enhancer of viral infection) amyloid formation by the cross-seeding between the bacterial curli protein and PAP248-286 is also briefly discussed.

Genome-Wide Association Studies of Cognitive and Motor Progression in Parkinson's Disease

BACKGROUND

There are currently no treatments that stop or slow the progression of Parkinson's disease (PD). Case-control genome-wide association studies have identified variants associated with disease risk, but not progression. The objective of the current study was to identify genetic variants associated with PD progression.

METHODS

We analyzed 3 large longitudinal cohorts: Tracking Parkinson's, Oxford Discovery, and the Parkinson's Progression Markers Initiative. We included clinical data for 3364 patients with 12,144 observations (mean follow-up 4.2 years). We used a new method in PD, following a similar approach in Huntington's disease, in which we combined multiple assessments using a principal components analysis to derive scores for composite, motor, and cognitive progression. These scores were analyzed in linear regression in genome-wide association studies. We also performed a targeted analysis of the 90 PD risk loci from the latest case-control meta-analysis.

RESULTS

There was no overlap between variants associated with PD risk, from case-control studies, and PD age at onset versus PD progression. The APOE ε4 tagging variant, rs429358, was significantly associated with composite and cognitive progression in PD. Conditional analysis revealed several independent signals in the APOE locus for cognitive progression. No single variants were associated with motor progression. However, in gene-based analysis, ATP8B2, a phospholipid transporter related to vesicle formation, was nominally associated with motor progression (P = 5.3 × 10^-6 ).

CONCLUSIONS

We provide early evidence that this new method in PD improves measurement of symptom progression. We show that the APOE ε4 allele drives progressive cognitive impairment in PD. Replication of this method and results in independent cohorts are needed. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Chinese nutraceuticals and physical activity; their role in neurodegenerative tauopathies

The onset of neurodegenerative disease has not only been a major cause of scientific worry, but of economic burden to the health system. This condition has been further attributed to mis-stability, deletion or mutation of tau protein, causing the onset of Corticobasal degeneration, Pick's diseases, Progressive supranuclear palsy, Argyrophilic grains disease, Alzheimer's diseases etc. as scientifically renowned. This is mainly related to dysregulation of translational machinery, upregulation of proinflammatory cytokines and inhibition of several essential cascades such as ERK signaling cascade, GSK3β, CREB, and PKA/PKB (Akt) signaling cascades that enhances protein processing, normal protein folding, cognitive function, and microtubule associated tau stability. Administration of some nutrients and/or bioactive compounds has a high tendency to impede tau mediated inflammation at neuronal level. Furthermore, prevention and neutralization of protein misfolding through modulation of microtubule tau stability and prevention of protein misfolding is by virtue few of the numerous beneficial effects of physical activity. Of utmost important in this study is the exploration of promising bioactivities of nutraceuticals found in china and the ameliorating potential of physical activity on tauopathies, while highlighting animal and in vitro studies that have been investigated for comprehensive understanding of its potential and an insight into the effects on human highly probable to tau mediated neurodegeneration.

Potential Role of Natural Polyphenols against Protein Aggregation Toxicity: In Vitro, In Vivo, and Clinical Studies

One of the main features of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease is the amyloidogenic behavior of disease-specific proteins including amyloid β, tau, α-synuclein, and mutant Huntingtin which participate in the formation, accumulation, and deposition of toxic misfolded aggregates. Consequently, these proteins not only associated with the progress of their respective neurodegenerative pathologies but also qualify as disease-specific biomarkers. The aim of using natural polyphenols is to target amyloid-dependent proteopathies by decreasing free radical damage and inhibiting and dissolving amyloid fibrils. We explore the effectiveness of the polyphenols epigallocatechin-3-gallate, oleuropein aglycone, and quercetin on their ability to inhibit aggregation of amyloid β, tau, and α-synuclein and mitigate other pathological features for Alzheimer's disease and Parkinson's disease. The analysis was carried from in vitro and cell line studies to animal models and clinical trials. This Review describes the use of phytochemical compounds as prophylactic agents for Alzheimer's disease, Parkinson's disease, and other proteopathies.

Loss of Midbrain Dopamine Neurons and Altered Apomorphine EEG Effects in the 5xFAD Mouse Model of Alzheimer's Disease

Cognitive malfunction, synaptic dysfunction, and disconnections in neural networks are core deficits in Alzheimer's disease (AD). 5xFAD mice, a transgenic model of AD, are characterized by an enhanced level of amyloid-β and abnormal neurotransmission. The dopaminergic (DA) system has been shown to be involved in amyloid-β transformations and neuronal plasticity; however, its role in functional network changes in familial AD still remains unclear. In 5xFAD and non-transgenic freely moving mice, electroencephalograms (EEGs) were simultaneously recorded from the secondary motor cortex (MC), superficial layers of the hippocampal CA1 area (HPC), substantia nigra (SN), and ventral tegmental area (VTA). EEGs and their frequency spectra were analyzed before and after systemic injection of a DA receptor agonist, apomorphine (APO). In the baseline EEG from MC and HPC of 5xFAD mice, delta and alpha oscillations were enhanced and beta activity was attenuated, compared to control mice. In VTA and SN of 5xFAD mice, delta-theta activity was decreased and beta oscillations dominated. In control mice, APO suppressed delta activity in VTA to a higher extent than in MC, whereas in 5xFAD mice, this difference was eliminated due to attenuation of the delta suppression in VTA. APO increased beta activity in MC of mice from both groups while significant beta suppression was observed in VTA of 5xFAD mice. These mice were characterized by significant decrease of tyrosine hydroxylase immunopositive cells in both VTA and SN and of DA transporter in MC and hippocampal dentate gyrus. We suggest that the EEG modifications observed in 5xFAD mice are associated with alterations in dopaminergic transmission, resulting in adaptive changes in the cerebral networks in the course of familial AD development.

POSCAbilities: The Application of the Prion Organotypic Slice Culture Assay to Neurodegenerative Disease Research

Prion diseases are fatal, transmissible neurodegenerative disorders whose pathogenesis is driven by the misfolding, self-templating and cell-to-cell spread of the prion protein. Other neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis and Huntington’s disease, share some of these prion-like features, with different aggregation-prone proteins. Consequently, researchers have begun to apply prion-specific techniques, like the prion organotypic slice culture assay (POSCA), to these disorders. In this review we explore the ways in which the prion phenomenon has been used in organotypic cultures to study neurodegenerative diseases from the perspective of protein aggregation and spreading, strain propagation, the role of glia in pathogenesis, and efficacy of drug treatments. We also present an overview of the advantages and disadvantages of this culture system compared to in vivo and in vitro models and provide suggestions for new directions.

Testing Amyloid Cross-Toxicity in the Vertebrate Brain

While amyloid proteins such as amyloid β (Aβ),α-synuclein, tau, and lysozyme are known to be prion-like; emerging data have revealed that they are also able to seed the misfolding of prion-like proteins differing in sequence. In the present study, we have developed a tool designed to test neurohistochemical outcomes associated with the entry of an amyloid protein into heterotypic neurons, i.e., neurons that do not express the invading amyloid and, instead, endogenously express amyloids differing in sequence. The stereotaxic introduction of Aβ into the rodent tegmental area of the mid-brain revealed that the foreign amyloid had infiltrated into nigral neurons. Furthermore, Aβ was found colocalized with α-synuclein, an amyloid endogenous to the substantia nigra and differing in sequence relative to Aβ. Disruption of α-synuclein status in the substantia nigra is associated with Parkinson's disease onset and progress. In addition to the study findings, a significant inroad to future neurodegenerative research was made via the stereotaxic introduction of the foreign amyloid. This technique limits the presence of confounding neurometabolic variables that may be prevalent in transgenic animal models of cross-toxicity and, thereby, better addresses the role of individual neuronal factors in cross-toxicity. Finally, the data from this work may help reconcile the high frequency of clinical comorbidity seen in neurodegenerative diseases.

On the Conformational Dynamics of β-Amyloid Forming Peptides: A Computational Perspective

Understanding the conformational dynamics of proteins and peptides involved in important functions is still a difficult task in computational structural biology. Because such conformational transitions in β-amyloid (Aβ) forming peptides play a crucial role in many neurological disorders, researchers from different scientific fields have been trying to address issues related to the folding of Aβ forming peptides together. Many theoretical models have been proposed in the recent years for studying Aβ peptides using mathematical, physicochemical, and molecular dynamics simulation, and machine learning approaches. In this article, we have comprehensively reviewed the developmental advances in the theoretical models for Aβ peptide folding and interactions, particularly in the context of neurological disorders. Furthermore, we have extensively reviewed the advances in molecular dynamics simulation as a tool used for studying the conversions between polymorphic amyloid forms and applications of using machine learning approaches in predicting Aβ peptides and aggregation-prone regions in proteins. We have also provided details on the theoretical advances in the study of Aβ peptides, which would enhance our understanding of these peptides at the molecular level and eventually lead to the development of targeted therapies for certain acute neurological disorders such as Alzheimer's disease in the future.

Pharmacological inhibition and knockdown of O-GlcNAcase reduces cellular internalization of α-synuclein preformed fibrils

The pathological hallmark of Parkinson's disease (PD) is Lewy bodies that form within the brain from aggregated forms of α-synuclein (α-syn). These toxic α-syn aggregates are transferred from cell to cell by release of fibrils from dying neurons into the extracellular environment, followed by their subsequent uptake by neighboring cells. This process leads to spreading of the pathology throughout the brain in a prion-like manner. Identifying new pathways that hinder the internalization of such α-syn fibrils is of high interest for their downstream potential exploitation as a way to create disease-modifying therapeutics for PD. Here, we show that Thiamet-G, a highly selective pharmacological agent that inhibits the glycoside hydrolase O-GlcNAcase (OGA), blunts the cellular uptake of α-syn fibrils. This effect correlates with increased nucleocytoplasmic levels of O-linked N-acetylglucosamine (O-GlcNAc)-modified proteins, and genetic knockdown of OGA expression closely phenocopies both these effects. These reductions in the uptake of α-syn fibrils caused by inhibition of OGA are both concentration- and time-dependent and are observed in multiple cell lines including mouse primary cortical neurons. Moreover, treatment of cells with the OGT inhibitor, 5SGlcNHex, increases the level of uptake of α-syn PFFs, further supporting O-GlcNAcylation of proteins driving these effects. Notably, this effect is mediated through an unknown mechanism that does not involve well-characterized endocytotic pathways. These data suggest one mechanism by which OGA inhibitors might exert their protective effects in prion-like neuropathologies and support exploration of OGA inhibitors as a potential disease-modifying approach to treat PD.

Dopaminergic Depletion, β-Amyloid Burden, and Cognition in Lewy Body Disease

OBJECTIVE

We aimed to determine the association between striatal dopaminergic depletion, cerebral β-amyloid deposition, and cognitive dysfunction in Lewy body disease (LBD).

METHODS

This cross-sectional study recruited 48 LBD patients (30 with dementia, 18 with mild cognitive impairment) and 15 control subjects from a university-based hospital. We measured the striatal dopamine transporter (DAT) activity and regional β-amyloid burden using N-(3-[¹⁸ F]fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) nortropane (FP-CIT) positron emission tomography (PET) and ¹⁸ F-florbetaben (FBB) PET, respectively. The relationship between striatal FP-CIT uptake, regional cortical FBB uptake, and cognitive function scores was evaluated using path analyses. We also investigated the effects of striatal FP-CIT uptake and cortical FBB uptake on the interval between motor symptom and dementia onset.

RESULTS

Reduced striatal FP-CIT uptake was associated with increased FBB uptake in the posterior cortical regions, most prominently in the occipital cortices. Reduced FP-CIT uptake in the anterior putamen was associated with visuospatial dysfunction with mediation of increased occipital FBB uptake. Reduced FP-CIT uptake in the posterior putamen and an increased parietal FBB uptake were independently associated with memory dysfunction. Reduced striatal FP-CIT uptake was associated with attention, language, and frontal/executive dysfunction, independent of amyloid deposition. Increased FBB uptake, especially in the parietal cortex, was associated with earlier onset of dementia.

INTERPRETATION

Our results suggest that occipital β-amyloid deposition may contribute to the association between striatal dopaminergic depletion and visuospatial dysfunction in LBD patients. Although the effects of reduced DAT activity are more prominent than those of β-amyloid burden on cognitive dysfunction, the latter affects the onset of cognitive dysfunction. ANN NEUROL 2020;87:739-750.

Characterization of the effects of calcitonin gene-related peptide receptor antagonist for Alzheimer's disease

Calcitonin gene-related peptide (cGRP) receptor antagonists effectively treat migraine through reducing neuroinflammation, vasoconstriction and possibly neruogenesis. Since neuroinflammation is also involved in the pathogenesis of Alzheimer's diseases (AD), we hypothesized and tested if a cGRP receptor antagonist, BIBN 4096 BS (BIBN), has effects on AD pathology. Using an AD mouse model, 5XFAD, with different ages, here we report that the BIBN treatment significantly increased the brain expression of PSD95, a postsynaptic protein, in both young and old AD mice. In parallel, BIBN improved learning and memory in the behavior test in the young, but not old, AD mice. The BIBN treatment reduced α-synuclein aggregation in both young and old AD mice. BIBN significantly decreased neuroinflammatory markers of ionized calcium binding adapter molecules-1 (Iba-1) and the p38 MAPK and NFκB signaling pathways in young, but not old, AD mice. The treatment also reduced the accumulation of amyloid-β (Aβ), and decreased tau phosphorylation through the pathway of CDK5/p25 in young mice only. Our study provides the evidence and suggests that the cGRP antagonists might be a therapeutic target to attenuate the pathological cascade and delay cognitive decline of AD in humans.

Amyloid-Beta (Aβ) Plaques Promote Seeding and Spreading of Alpha-Synuclein and Tau in a Mouse Model of Lewy Body Disorders with Aβ Pathology

Studies have shown an overlap of Aβ plaques, tau tangles, and α-synuclein (α-syn) pathologies in the brains of Alzheimer's disease (AD) and Parkinson's disease (PD) with dementia (PDD) patients, with increased pathological burden correlating with severity of cognitive and motor symptoms. Despite the observed co-pathology and concomitance of motor and cognitive phenotypes, the consequences of the primary amyloidogenic protein on the secondary pathologies remain poorly understood. To better define the relationship between α-syn and Aβ plaques, we injected α-syn preformed fibrils (α-syn mpffs) into mice with abundant Aβ plaques. Aβ deposits dramatically accelerated α-syn pathogenesis and spread throughout the brain. Remarkably, hyperphosphorylated tau (p-tau) was induced in α-syn mpff-injected 5xFAD mice. Finally, α-syn mpff-injected 5xFAD mice showed neuron loss that correlated with the progressive decline of cognitive and motor performance. Our findings suggest a "feed-forward" mechanism whereby Aβ plaques enhance endogenous α-syn seeding and spreading over time post-injection with mpffs.

Latest advances in cerebrospinal fluid and blood biomarkers of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease and its diagnosis has classically been based on clinical symptoms. Recently, a biological rather than a syndromic definition of the disease has been proposed that is based on biomarkers that reflect neuropathological changes. In AD, there are two main biomarker categories, namely neuroimaging and fluid biomarkers [cerebrospinal fluid (CSF) and blood]. As a complex and multifactorial disease, AD biomarkers are important for an accurate diagnosis and to stage the disease, assess the prognosis, test target engagement, and measure the response to treatment. In addition, biomarkers provide us with information that, even if it does not have a current clinical use, helps us to understand the mechanisms of the disease. In addition to the pathological hallmarks of AD, which include amyloid-β and tau deposition, there are multiple concomitant pathological events that play a key role in the disease. These include, but are not limited to, neurodegeneration, inflammation, vascular dysregulation or synaptic dysfunction. In addition, AD patients often have an accumulation of other proteins including α-synuclein and TDP-43, which may have a pathogenic effect on AD. In combination, there is a need to have biomarkers that reflect different aspects of AD pathogenesis and this will be important in the future to establish what are the most suitable applications for each of these AD-related biomarkers. It is unclear whether sex, gender, or both have an effect on the causes of AD. There may be differences in fluid biomarkers due to sex but this issue has often been neglected and warrants further research. In this review, we summarize the current state of the principal AD fluid biomarkers and discuss the effect of sex on these biomarkers.

Aβ, Tau, and α-Synuclein aggregation and integrated role of PARK2 in the regulation and clearance of toxic peptides

Alzheimer's and Parkinson's diseases are one of the world's leading causes of death. >50 million people throughout the world are suffering with these diseases. They are two distinct progressive neurodegenerative disorders affecting different regions of the brain with diverse symptoms, including memory and motor loss respectively, but with the advancement of diseases, both affect the whole brain and exhibit some common biological symptoms. For instance, >50% PD patients develop dementia in their later stages, though it is a hallmark of Alzheimer's disease. In fact, latest research has suggested the involvement of some common pathophysiological and genetic links between these diseases, including the deposition of pathological Aβ, Tau, and α-synuclein in both the cases. Therefore, it is pertinent to diagnose the shared biomarkers, their aggregation mechanism, their intricate relationships in the pathophysiology of disease and therapeutic markers to target them. This would enable us to identify novel markers for the early detection of disease and targets for the future therapies. Herein, we investigated molecular aspects of Aβ, Tau, and α-Synuclein aggregation, and characterized their functional partners involved in the pathology of AD and PD. Moreover, we identified the molecular-crosstalk between AD and PD associated with their pathogenic proteins- Aβ, Tau, and α-Synuclein. Furthermore, we characterized their ubiquitinational enzymes and associated interaction network regulating the proteasomal clearance of these pathological proteins.

Associations between cerebrovascular risk factors and parkinson disease

OBJECTIVE

To determine whether cerebrovascular risk factors are associated with subsequent diagnoses of Parkinson disease, and whether these associations are similar in magnitude to those with subsequent diagnoses of Alzheimer disease.

METHODS

This was a retrospective cohort study using claims data from a 5% random sample of Medicare beneficiaries from 2008 to 2015. The exposures were stroke, atrial fibrillation, coronary disease, hyperlipidemia, hypertension, sleep apnea, diabetes mellitus, heart failure, peripheral vascular disease, chronic kidney disease, chronic obstructive pulmonary disease, valvular heart disease, tobacco use, and alcohol abuse. The primary outcome was a new diagnosis of idiopathic Parkinson disease. The secondary outcome was a new diagnosis of Alzheimer disease. Marginal structural Cox models adjusting for time-dependent confounding were used to characterize the association between exposures and outcomes. We also evaluated the association between cerebrovascular risk factors and subsequent renal colic (negative control).

RESULTS

Among 1,035,536 Medicare beneficiaries followed for a mean of 5.2 years, 15,531 (1.5%) participants were diagnosed with Parkinson disease and 81,974 (7.9%) were diagnosed with Alzheimer disease. Most evaluated cerebrovascular risk factors, including prior stroke (hazard ratio = 1.55; 95% confidence interval = 1.39-1.72), were associated with the subsequent diagnosis of Parkinson disease. The magnitudes of these associations were similar, but attenuated, to the associations between cerebrovascular risk factors and Alzheimer disease. Confirming the validity of our analytical model, most cerebrovascular risk factors were not associated with the subsequent diagnosis of renal colic.

INTERPRETATION

Cerebrovascular risk factors are associated with Parkinson disease, an effect comparable to their association with Alzheimer disease. ANN NEUROL 2019;86:572-581.

Alzheimer's disease and other neurodegenerative dementias in comorbidity: A clinical and neuropathological overview

Neuropathological diagnostic criteria of neurodegenerative disorders are based on the presence of specific inclusions in a specific area of brain tissue that correlate with clinical manifestations. Concomitant neurodegenerative disorders correspond to a combination of two (or more) different fully developed diseases in the same patient. Concomitant neurodegenerative pathology represents the presence of definite neurodegeneration and deposits of pathological proteins specific for another disease, which is not, however, fully developed. Very frequent overlaps include Alzheimer's disease and alpha-synuclein inclusions. Nevertheless, careful neuropathological investigations reveal an increasing frequency of different co-pathologies in examined brains. In Alzheimer's disease, protein TDP-43 may co-aggregate, but it is not clear whether this is atypical isolated Alzheimer's disease or overlap of Alzheimer's disease with early frontotemporal lobar degeneration. Comorbidities of Alzheimer's disease and tauopathies are relatively rare. A combination of vascular pathology with primary neurodegeneration (mostly Alzheimer's disease or dementia with Lewy bodies) is historically called mixed dementia. Overlap of different neuropathologically confirmed neurodegenerations could lead to atypical and unusual clinical presentations and may be responsible for faster disease progression. Several CSF biomarkers have been evaluated for their utility in diagnostic processes in different neurodegenerative dementias; however, evidence regarding their role in neurodegenerative overlaps is still limited.

Use of Ceftriaxone in Treating Cognitive and Neuronal Deficits Associated With Dementia With Lewy Bodies

Dementia with Lewy bodies (DLB) is caused by accumulation of Lewy bodies, destruction of mitochondria, and excess of glutamate in synapses, which eventually leads to excitotoxicity, neurodegeneration, and cognitive impairments. Ceftriaxone (CEF) reduces excitotoxicity by increasing glutamate transporter 1 expression and glutamate reuptake. We investigated whether CEF can prevent cognitive decline and neurological deficits and increase neurogenesis in DLB rats. Male Wistar rats infused with viral vector containing human alpha-synuclein (α-syn) gene, SNCA, in the lateral ventricle were used as a rat model of DLB. CEF (100 mg/kg/day, i.p.) was injected in these rats for 27 days. The active avoidance test and object recognition test was performed. Finally, the brains of all the rats were immunohistochemically stained to measure α-syn, neuronal density, and newborn cells in the hippocampus and substantia nigra. The results revealed that DLB rats had learning and object recognition impairments and exhibited cell loss in the nigrostriatal dopaminergic system, and hippocampal CA1, and dentate gyrus (DG). Additionally, DLB rats had fewer newborn cells in the DG and substantia nigra pars reticulata and more α-syn immune-positive cells in the DG. Treatment with CEF improved cognitive function, reduced cell loss, and increased the number of newborn cells in the brain. To our knowledge, this is the first study showing that CEF prevents loss of neurogenesis in the brain of DLB rats. CEF may therefore has clinical potential for treating DLB.

Imaging in prodromal dementia with Lewy bodies: Where do we stand?

OBJECTIVES

The aim of this review was to provide an overview of the literature on imaging in prodromal dementia with Lewy bodies (DLB).

DESIGN

Systematic PubMed search and literature review.

RESULTS

Diagnostic classification of the prodromal DLB stage remains to be established but is likely to require imaging biomarkers to improve diagnostic accuracy. In subjects with mild cognitive impairment with Lewy body disease (MCI-LB) (here synonymous with prodromal DLB) and REM sleep behaviour disorder, a high risk condition for future conversion to a synucleinopathy, imaging modalities have assessed early structural brain changes, striatal dopaminergic integrity, metabolic brain, and cerebral perfusion alterations. It remains uncertain whether structural brain imaging can differentiate MCI-LB from mild cognitive impairment with Alzheimer disease (MCI-AD), but early right anterior insula thinning has been reported to occur in MCI-LB compared with MCI-AD. Dopaminergic deficits have been observed in a substantial proportion of MCI-LB subjects and have a high specificity for Lewy body disease at the pre-dementia stage. Cardiac sympathetic denervation, occipital hypometabolism, or hypoperfusion is less studied as this pre-dementia stage and it remains to be determined whether any imaging abnormalities antedate DLB.

CONCLUSION

Imaging studies in prodromal DLB are still in their infancy but offer great potential to study early in vivo structural and functional biological alterations. Future work should focus on longitudinal multimodal imaging studies with postmortem validation of diagnosis in order to develop and then validate criteria for prodromal DLB.