beta-amyloid peptides enhance alpha-synuclein accumulation and neuronal deficits in a transgenic mouse model linking Alzheimer's disease and Parkinson's disease

Correlation between decreased CSF α-synuclein and Aβ₁₋₄₂ in Parkinson disease

Accumulation of misfolded α-synuclein (α-syn) protein in Lewy bodies and neurites is the cardinal pathologic feature of Parkinson disease (PD), but abnormal deposition of other proteins may also play a role. Cerebrospinal fluid (CSF) levels of proteins known to accumulate in PD may provide insight into disease-associated changes in protein metabolism and their relationship to disease progression. We measured CSF α-syn, amyloid β₁₋₄₂ (Aβ₁₋₄₂), and tau from 77 nondemented PD and 30 control participants. CSF α-syn and Aβ₁₋₄₂ were significantly lower in PD compared with controls. In contrast with increased CSF tau in Alzheimer disease, CSF tau did not significantly differ between PD and controls. CSF protein levels did not significantly correlate with ratings of motor function or performance on neuropsychological testing. As expected, CSF Aβ₁₋₄₂ inversely correlated with [(11)C]-Pittsburgh compound B (PiB) mean cortical binding potential, with PiB(+) PD participants having lower CSF Aβ₁₋₄₂ compared with PiB(-) PD participants. Furthermore, CSF α-syn positively correlated with Aβ₁₋₄₂ in PD participants but not in controls, suggesting a pathophysiologic connection between the metabolisms of these proteins in PD.

CSF beta-amyloid 1-42 - what are we measuring in Alzheimer's disease?

Objective

To characterize biological and technical factors which influence cerebrospinal fluid (CSF) Alzheimer's disease (AD) biomarker levels, including the presence of apolipoprotein E (APOE) ε4 allele, AD diagnosis, Aβ-binding proteins, sample processing, and preanalytical handling.

Methods

CSF was collected from 140 subjects with normal cognition, mild cognitive impairment, AD, and non-AD dementia. CSF levels of beta-amyloid 1–42 (Aβ42), total Tau (t-Tau), and Tau phosphorylated at threonine 181 (p-Tau181) were analyzed following the standard and modified protocols. CSF levels of apoJ, apoE, albumin, and α-synuclein were measured in a subgroup (n = 69), and their effects on measured AD biomarker levels were also determined in vitro using human CSF samples.

Results

CSF Aβ42 levels measured using the AD Neuro-imaging Initiative (ADNI) protocol (which we call suspended Aβ42 or susAβ) were lower than total measurable CSF Aβ42 in all groups, and on average represents 57% of the latter. Logistic regression analysis showed this proportion (% susAβ) to be directly correlated with CSF Aβ42 and apoJ levels, but inversely correlated with CSF t-Tau levels. Finally, we showed in vitro that increasing apoE and apoJ levels directly increased % susAβ.

Conclusion

CSF susAβ levels are influenced by biological and technical factors, and may represent a marker of Aβ susceptible to lipoprotein-mediated clearance. Clinical trials should include total measurable Aβ42 and susAβ to better inform outcomes.

What is the Clinical Significance of Cerebrospinal Fluid Biomarkers in Parkinson's disease? Is the Significance Diagnostic or Prognostic?

The clinical diagnostic criteria of Parkinson's disease (PD) have limitations in detecting the disease at early stage and in differentiating heterogeneous clinical progression. The lack of reliable biomarker(s) for early diagnosis and prediction of prognosis is a major hurdle to achieve optimal clinical care of patients and efficient design of clinical trials for disease-modifying therapeutics. Numerous efforts to discover PD biomarkers in CSF were conducted. In this review, we describe the molecular pathogenesis of PD and discuss its implication to develop PD biomarkers in CSF. Next, we summarize the clinical utility of CSF biomarkers including alpha-synuclein for early and differential diagnosis, and prediction of PD progression. Given the heterogeneity in the clinical features of PD and none of the CSF biomarkers for an early diagnosis have been developed, research efforts to develop biomarkers to predict heterogeneous disease progression is on-going. Notably, a rapid cognitive decline followed by the development of dementia is a risk factor of poor prognosis in PD. In connection to this, CSF levels of Alzheimer's disease (AD) biomarkers have received considerable attention. However, we still need long-term longitudinal observational studies employing large cohorts to evaluate the clinical utility of CSF biomarkers reflecting Lewy body pathology and AD pathology in the brain. We believe that current research efforts including the Parkinson's Progression Markers Initiative will resolve the current needs of early diagnosis and/or prediction of disease progression using CSF biomarkers, and which will further accelerate the development of disease-modifying therapeutics and optimize the clinical management of PD patients.

Differences in the binding of copper(I) to α- and β-synuclein

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the presence of abnormal α-synuclein (αS) deposits in the brain. Alterations in homeostasis and metal-induced oxidative stress may play a crucial role in the progression of αS amyloid assembly and pathogenesis of PD. Contrary to αS, β-synuclein (βS) is not involved in the PD etiology. However, it has been suggested that the βS/αS ratio is altered in PD, indicating that a correct balance of these two proteins is implicated in the inhibition of αS aggregation. αS and βS share similar abilities to coordinate Cu(II). In this study, we investigated and compared the interaction of Cu(I) with the N-terminal portion of βS and αS by means of NMR, circular dichroism, and X-ray absorption spectroscopies. Our data show the importance of M10K mutation, which induces different Cu(I) chemical environments. Coordination modes 3S1O and 2S2O were identified for βS and αS, respectively. These new insights into the bioinorganic chemistry of copper and synuclein proteins are a basis to understand the molecular mechanism by which βS might inhibit αS aggregation.

Protein Transmission, Seeding and Degradation: Key Steps for α-Synuclein Prion-Like Propagation

Converging lines of evidence suggest that cell-to-cell transmission and the self-propagation of pathogenic amyloidogenic proteins play a central role in the initiation and the progression of several neurodegenerative disorders. This "prion-like" hypothesis has been recently reported for α-synuclein, a presynaptic protein implicated in the pathogenesis of Parkinson's disease (PD) and related disorders. This review summarizes recent findings on α-synuclein prion-like propagation, focusing on its transmission, seeding and degradation and discusses some key questions that remain to be explored. Understanding how α-synuclein exits cells and propagates from one brain region to another will lead to the development of new therapeutic strategies for the treatment of PD, aiming at slowing or stopping the disease progression.

The ongoing pursuit of neuroprotective therapies in Parkinson disease

Many agents developed for neuroprotective treatment of Parkinson disease (PD) have shown great promise in the laboratory, but none have translated to positive results in patients with PD. Potential neuroprotective drugs, such as ubiquinone, creatine and PYM50028, have failed to show any clinical benefits in recent high-profile clinical trials. This 'failure to translate' is likely to be related primarily to our incomplete understanding of the pathogenic mechanisms underlying PD, and excessive reliance on data from toxin-based animal models to judge which agents should be selected for clinical trials. Restricted resources inevitably mean that difficult compromises must be made in terms of trial design, and reliable estimation of efficacy is further hampered by the absence of validated biomarkers of disease progression. Drug development in PD dementia has been mostly unsuccessful; however, emerging biochemical, genetic and pathological evidence suggests a link between tau and amyloid-β deposition and cognitive decline in PD, potentially opening up new possibilities for therapeutic intervention. This Review discusses the most important 'druggable' disease mechanisms in PD, as well as the most-promising drugs that are being evaluated for their potential efficiency in treatment of motor and cognitive impairments in PD.

Evaluating the relationship between amyloid-β and α-synuclein phosphorylated at Ser129 in dementia with Lewy bodies and Parkinson's disease

Introduction

Lewy body and Alzheimer-type pathologies often co-exist. Several studies suggest a synergistic relationship between amyloid-β (Aβ) and α-synuclein (α-syn) accumulation. We have explored the relationship between Aβ accumulation and the phosphorylation of α-syn at serine-129 (pSer129 α-syn), in post-mortem human brain tissue and in SH-SY5Y neuroblastoma cells transfected to overexpress human α-syn.

Methods

We measured levels of Aβ40, Aβ42, α-syn and pSer129 α-syn by sandwich enzyme-linked immunosorbent assay, in soluble and insoluble fractions of midfrontal, cingulate and parahippocampal cortex and thalamus, from cases of Parkinson’s disease (PD) with (PDD; n = 12) and without dementia (PDND; n = 23), dementia with Lewy bodies (DLB; n = 10) and age-matched controls (n = 17). We also examined the relationship of these measurements to cognitive decline, as measured by time-to-dementia and the mini-mental state examination (MMSE) score in the PD patients, and to Braak tangle stage.

Results

In most brain regions, the concentration of insoluble pSer129 α-syn correlated positively, and soluble pSer129 α-syn negatively, with the levels of soluble and insoluble Aβ. Insoluble pSer129 α-syn also correlated positively with Braak stage. In most regions, the levels of insoluble and soluble Aβ and the proportion of insoluble α-syn that was phosphorylated at Ser129 were significantly higher in the PD and DLB groups than the controls, and higher in the PDD and DLB groups than the PDND brains. In PD, the MMSE score correlated negatively with the level of insoluble pSer129 α-syn. Exposure of SH-SY5Y cells to aggregated Aβ42 significantly increased the proportion of α-syn that was phosphorylated at Ser129 (aggregated Aβ40 exposure had a smaller, non-significant effect).

Conclusions

Together, these data show that the concentration of pSer129 α-syn in brain tissue homogenates is directly related to the level of Aβ and Braak tangle stage, and predicts cognitive status in Lewy body diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-014-0077-y) contains supplementary material, which is available to authorized users.

Regional Multiple Pathology Scores Are Associated with Cognitive Decline in Lewy Body Dementias

Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) are characterized by the presence of α‐synuclein‐containing Lewy bodies and Lewy neurites. However, both dementias also show variable degrees of Alzheimer's disease (AD) pathology (senile plaques and neurofibrillary tangles), particularly in areas of the cortex associated with higher cognitive functions. This study investigates the contribution of the individual and combined pathologies in determining the rate of cognitive decline. Cortical α‐synuclein, phosphorylated tau (phosphotau) and Aβ plaque pathology in 34 PDD and 55 DLB patients was assessed semi‐quantitatively in four regions of the neocortex. The decline in cognition, assessed by Mini Mental State Examination, correlated positively with the cortical α‐synuclein load. Patients also had varying degrees of senile Aβ plaque and phosphotau pathology. Regression analyses pointed to a combined pathology (Aβ plaque plus phosphotau plus α‐synuclein‐positive features), particularly in the prefrontal cortex (BA9) and temporal lobe neocortex with the superior and middle temporal gyrus (BA21, 22), being a major determining factor in the development of dementia. Thus, cognitive decline in Lewy body dementias is not a consequence of α‐synuclein‐induced neurodegeneration alone but senile plaque and phosphorylated tau pathology also contribute to the overall deficits.

Current Challenges Towards the Development of a Blood Test for Parkinson's Disease

Parkinson’ disease (PD) is the second most prevalent neurodegenerative disease worldwide. To date, there is no disease-modifying agent, and current medical treatment only provides symptomatic benefits. Early diagnosis of PD would be useful in clinical practice to identify patients for clinical trials, test potential drugs and neuroprotective agents and track their therapeutic effect. Considerable progress has been made in the discovery and validation of diagnostic biomarkers for PD. In particular, blood-based biomarkers have shown promise in identifying PD patients in samples from independent clinical trials. Evaluation of these biomarkers in de novo patients and individuals at risk for PD remains a top priority. Here, we review the current advances and challenges toward the clinical translation of these biomarkers into a blood-based test for PD.

(1)H NMR-based metabolomics study on a goldfish model of Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

A goldfish (Carassius auratus) model of Parkinson's disease (PD) was constructed by a single dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) according to previously reported methods. Global metabolite changes in brain of the MPTP induced goldfish model of PD were investigated. (1)H NMR-based metabolomics combined with various statistical methods such as orthogonal partial least squares discriminant analysis (OPLS-DA) and two-dimensional statistical total correlation spectroscopy (2D-STOCSY) found significant increase of leucine, isoleucine, valine, alanine, alanylalanine, creatinine, myo-inositol, 18:2 fatty acid, total fatty acids, arachic alcohol, taurine and significant decrease of N-acetylaspartate, (phospho)creatine, (phospho)choline, betaine, glutamine, 3-hexenedioate, acetamide, malonate, isocitrate, scyllo-inositol, phosphatidylcholines, cholesterols, n-3 fatty acids, polyunsaturated fatty acids (PUFAs) in brain of MPTP induced PD goldfish. These disturbed metabolite levels were involved in oxidative stress, energy failure, neuronal cell injury and death, consistent with those observed in clinical PD patients, and rodents and primates model of PD, indicating that the acute MPTP model of goldfish was an ideal and valuable model for PD research. In addition, several unusual metabolites in brain were significantly changed between MPTP induced PD and control goldfish, which might also play an important role in the pathogenesis of PD. This study also demonstrated the applicability and potential of (1)H NMR-based metabolomics approach for evaluation of animal models of disease induced by chemicals, such as MPTP-induced PD goldfish.

Cross dimerization of amyloid-β and αsynuclein proteins in aqueous environment: a molecular dynamics simulations study

Self-assembly of the intrinsically unstructured proteins, amyloid beta (Aβ) and alpha synclein (αSyn), are associated with Alzheimer's Disease, and Parkinson's and Lewy Body Diseases, respectively. Importantly, pathological overlaps between these neurodegenerative diseases, and the possibilities of interactions between Aβ and αSyn in biological milieu emerge from several recent clinical reports and in vitro studies. Nevertheless, there are very few molecular level studies that have probed the nature of spontaneous interactions between these two sequentially dissimilar proteins and key characteristics of the resulting cross complexes. In this study, we have used atomistic molecular dynamics simulations to probe the possibility of cross dimerization between αSyn1-95 and Aβ1-42, and thereby gain insights into their plausible early assembly pathways in aqueous environment. Our analyses indicate a strong probability of association between the two sequences, with inter-protein attractive electrostatic interactions playing dominant roles. Principal component analysis revealed significant heterogeneity in the strength and nature of the associations in the key interaction modes. In most, the interactions of repeating Lys residues, mainly in the imperfect repeats 'KTKEGV' present in αSyn1-95 were found to be essential for cross interactions and formation of inter-protein salt bridges. Additionally, a hydrophobicity driven interaction mode devoid of salt bridges, where the non-amyloid component (NAC) region of αSyn1-95 came in contact with the hydrophobic core of Aβ1-42 was observed. The existence of such hetero complexes, and therefore hetero assembly pathways may lead to polymorphic aggregates with variations in pathological attributes. Our results provide a perspective on development of therapeutic strategies for preventing pathogenic interactions between these proteins.

New α- and γ-synuclein immunopathological lesions in human brain

Introduction

Several neurodegenerative diseases are classified as proteopathies as they are associated with the aggregation of misfolded proteins. Synucleinopathies are a group of neurodegenerative disorders associated with abnormal deposition of synucleins. α-Synucleinopathies include Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy. Recently accumulation of another member of the synuclein family- γ−synuclein in neurodegenerative diseases compelled the introduction of the term γ−synucleinopathy. The formation of aggregates and deposits of γ−synuclein is facilitated after its oxidation at methionine 38 (Met³⁸).

Results

Several types of intracytoplasmic inclusions containing post-translationally modified α- and γ−synucleins are detected. Oxidized Met³⁸-γ-synuclein forms aberrant inclusions in amygdala and substantia nigra. Double staining revealed colocalization of oxidized-γ-synuclein with α-synuclein in the cytoplasm of neurons. Another type of synuclein positive inclusions in the amygdala of dementia with Lewy bodies patients has the appearance of Lewy bodies. These inclusions are immunoreactive when analyzed with antibodies to α-synuclein phosphorylated on serine 129, as well as with antibodies to oxidized-γ-synuclein. Some of these Lewy bodies have doughnut-like shape with round or elongated shape. The separate immunofluorescent images obtained with individual antibodies specific to oxidized-γ-synuclein and phospho-α-synuclein clearly shows the colocalization of these synuclein isoforms in substantia nigra inclusions. Phospho-α-synuclein is present almost exclusively at the periphery of these structures, whereas oxidized-γ-syn immunoreactivity is also located in the internal parts forming dot-like pattern of staining.

We also identified several types of oxidized-γ-syn positive astrocytes with different morphology and examined their immunohistochemical phenotypes. Some of them are compact cells with short processes, others have longer processes. Oxidized-γ-synuclein positive astrocytes may also display mixed morphological and immunocytochemical phenotypes between protoplasmic and fibrous astrocytes.

Conclusions

These results reveal new γ−synuclein positive lesions in human brain. Oxidized-γ-synuclein is colocalized with phospho-α-synuclein in doughnut-like inclusions. Several types of astrocytes with different morphology are immunopositive for oxidized-γ-synuclein.

Reducing C-terminal-truncated alpha-synuclein by immunotherapy attenuates neurodegeneration and propagation in Parkinson's disease-like models

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are common neurodegenerative disorders of the aging population, characterized by progressive and abnormal accumulation of α-synuclein (α-syn). Recent studies have shown that C-terminus (CT) truncation and propagation of α-syn play a role in the pathogenesis of PD/DLB. Therefore, we explored the effect of passive immunization against the CT of α-syn in the mThy1-α-syn transgenic (tg) mouse model, which resembles the striato-nigral and motor deficits of PD. Mice were immunized with the new monoclonal antibodies 1H7, 5C1, or 5D12, all directed against the CT of α-syn. CT α-syn antibodies attenuated synaptic and axonal pathology, reduced the accumulation of CT-truncated α-syn (CT-α-syn) in axons, rescued the loss of tyrosine hydroxylase fibers in striatum, and improved motor and memory deficits. Among them, 1H7 and 5C1 were most effective at decreasing levels of CT-α-syn and higher-molecular-weight aggregates. Furthermore, in vitro studies showed that preincubation of recombinant α-syn with 1H7 and 5C1 prevented CT cleavage of α-syn. In a cell-based system, CT antibodies reduced cell-to-cell propagation of full-length α-syn, but not of the CT-α-syn that lacked the 118-126 aa recognition site needed for antibody binding. Furthermore, the results obtained after lentiviral expression of α-syn suggest that antibodies might be blocking the extracellular truncation of α-syn by calpain-1. Together, these results demonstrate that antibodies against the CT of α-syn reduce levels of CT-truncated fragments of the protein and its propagation, thus ameliorating PD-like pathology and improving behavioral and motor functions in a mouse model of this disease.

Novel therapeutic strategy for neurodegeneration by blocking Aβ seeding mediated aggregation in models of Alzheimer's disease

Aβ accumulation plays a central role in the pathogenesis of Alzheimer's disease (AD). Recent studies suggest that the process of Aβ nucleated polymerization is essential for Aβ fibril formation, pathology spreading and toxicity. Therefore, targeting this process represents an effective therapeutic strategy to slow or block disease progression. To discover compounds that might interfere with the Aβ seeding capacity, toxicity and pathology spreading, we screened a focused library of FDA-approved drugs in vitro using a seeding polymerization assay and identified small molecule inhibitors that specifically interfered with Aβ seeding-mediated fibril growth and toxicity. Mitoxantrone, bithionol and hexachlorophene were found to be the strongest inhibitors of fibril growth and protected primary cortical neuronal cultures against Aβ-induced toxicity. Next, we assessed the effects of these three inhibitors in vivo in the mThy1-APPtg mouse model of AD (8-month-old mice). We found that mitoxantrone and bithionol, but not hexachlorophene, stabilized diffuse amyloid plaques, reduced the levels of Aβ42 oligomers and ameliorated synapse loss, neuronal damage and astrogliosis. Together, our findings suggest that targeting fibril growth and Aβ seeding capacity constitutes a viable and effective strategy for protecting against neurodegeneration and disease progression in AD.

Multiple pathogenic proteins implicated in neuronopathic Gaucher disease mice

Gaucher disease, a prevalent lysosomal storage disease (LSD), is caused by insufficient activity of acid β-glucosidase (GCase) and the resultant glucosylceramide (GC)/glucosylsphingosine (GS) accumulation in visceral organs (Type 1) and the central nervous system (Types 2 and 3). Recent clinical and genetic studies implicate a pathogenic link between Gaucher and neurodegenerative diseases. The aggregation and inclusion bodies of α-synuclein with ubiquitin are present in the brains of Gaucher disease patients and mouse models. Indirect evidence of β-amyloid pathology promoting α-synuclein fibrillation supports these pathogenic proteins as a common feature in neurodegenerative diseases. Here, multiple proteins are implicated in the pathogenesis of chronic neuronopathic Gaucher disease (nGD). Immunohistochemical and biochemical analyses showed significant amounts of β-amyloid and amyloid precursor protein (APP) aggregates in the cortex, hippocampus, stratum and substantia nigra of the nGD mice. APP aggregates were in neuronal cells and colocalized with α-synuclein signals. A majority of APP co-localized with the mitochondrial markers TOM40 and Cox IV; a small portion co-localized with the autophagy proteins, P62/LC3, and the lysosomal marker, LAMP1. In cultured wild-type brain cortical neural cells, the GCase-irreversible inhibitor, conduritol B epoxide (CBE), reproduced the APP/α-synuclein aggregation and the accumulation of GC/GS. Ultrastructural studies showed numerous larger-sized and electron-dense mitochondria in nGD cerebral cortical neural cells. Significant reductions of mitochondrial adenosine triphosphate production and oxygen consumption (28-40%) were detected in nGD brains and in CBE-treated neural cells. These studies implicate defective GCase function and GC/GS accumulation as risk factors for mitochondrial dysfunction and the multi-proteinopathies (α-synuclein-, APP- and Aβ-aggregates) in nGD.

(11)C-PIB-PET for the early diagnosis of Alzheimer's disease dementia and other dementias in people with mild cognitive impairment (MCI)

BACKGROUND

According to the latest revised National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (now known as the Alzheimer's Association) (NINCDS-ADRDA) diagnostic criteria for Alzheimer's disease dementia, the confidence in diagnosing mild cognitive impairment (MCI) due to Alzheimer's disease dementia is raised with the application of imaging biomarkers. These tests, added to core clinical criteria, might increase the sensitivity or specificity of a testing strategy. However, the accuracy of biomarkers in the diagnosis of Alzheimer's disease dementia and other dementias has not yet been systematically evaluated. A formal systematic evaluation of the sensitivity, specificity, and other properties of positron emission tomography (PET) imaging with the (11)C-labelled Pittsburgh Compound-B ((11)C-PIB) ligand was performed.

OBJECTIVES

To determine the diagnostic accuracy of the (11)C- PIB-PET scan for detecting participants with MCI at baseline who will clinically convert to Alzheimer's disease dementia or other forms of dementia over a period of time.

SEARCH METHODS

The most recent search for this review was performed on 12 January 2013. We searched MEDLINE (OvidSP), EMBASE (OvidSP), BIOSIS Previews (ISI Web of Knowledge), Web of Science and Conference Proceedings (ISI Web of Knowledge), PsycINFO (OvidSP), and LILACS (BIREME). We also requested a search of the Cochrane Register of Diagnostic Test Accuracy Studies (managed by the Cochrane Renal Group).No language or date restrictions were applied to the electronic searches and methodological filters were not used so as to maximise sensitivity.

SELECTION CRITERIA

We selected studies that had prospectively defined cohorts with any accepted definition of MCI with baseline (11)C-PIB-PET scan. In addition, we only selected studies that applied a reference standard for Alzheimer's dementia diagnosis for example NINCDS-ADRDA or Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criteria.

DATA COLLECTION AND ANALYSIS

We screened all titles generated by electronic database searches. Two review authors independently assessed the abstracts of all potentially relevant studies. The identified full papers were assessed for eligibility and data were extracted to create two by two tables. Two independent assessors performed quality assessment using the QUADAS 2 tool. We used the hierarchical summary receiver operating characteristic (ROC) model to produce a summary ROC curve.

MAIN RESULTS

Conversion from MCI to Alzheimer's disease dementia was evaluated in nine studies. The quality of the evidence was limited. Of the 274 participants included in the meta-analysis, 112 developed Alzheimer's dementia. Based on the nine included studies, the median proportion converting was 34%. The studies varied markedly in how the PIB scans were done and interpreted.The sensitivities were between 83% and 100% while the specificities were between 46% and 88%. Because of the variation in thresholds and measures of (11)C-PIB amyloid retention, we did not calculate summary sensitivity and specificity. Although subject to considerable uncertainty, to illustrate the potential strengths and weaknesses of (11)C-PIB-PET scans we estimated from the fitted summary ROC curve that the sensitivity was 96% (95% confidence interval (CI) 87 to 99) at the included study median specificity of 58%. This equated to a positive likelihood ratio of 2.3 and a negative likelihood ratio of 0.07. Assuming a typical conversion rate of MCI to Alzheimer's dementia of 34%, for every 100 PIB scans one person with a negative scan would progress and 28 with a positive scan would not actually progress to Alzheimer's dementia.There were limited data for formal investigation of heterogeneity. We performed two sensitivity analyses to assess the influence of type of reference standard and the use of a pre-specified threshold. There was no effect on our findings.

AUTHORS' CONCLUSIONS

Although the good sensitivity achieved in some included studies is promising for the value of (11)C-PIB-PET, given the heterogeneity in the conduct and interpretation of the test and the lack of defined thresholds for determination of test positivity, we cannot recommend its routine use in clinical practice.(11)C-PIB-PET biomarker is a high cost investigation, therefore it is important to clearly demonstrate its accuracy and standardise the process of the (11)C-PIB diagnostic modality prior to it being widely used.

Parkinson's disease--the debate on the clinical phenomenology, aetiology, pathology and pathogenesis

The definition of Parkinson’s disease (PD) is changing with the expansion of clinical phenomenology and improved understanding of environmental and genetic influences that impact on the pathogenesis of the disease at the cellular and molecular level. This had led to debate and discussion with as yet, no general acceptance of the direction that change should take either at the level of diagnosis or of what should and should not be sheltered under an umbrella of PD. This article is one contribution to this on-going discussion. There are two different themes running through the article - widening the definition of PD/LBD/synucleinopathies and the heterogeneity that exists within PD itself from a clinical, pathological and genetic per-spective. The conclusion reached is that in the future, further diagnostic categories will need to be recognized. These are likely to include - Parkinson’s syndrome, Parkinson’s syndrome likely to be Lewy body PD, clinical PD (defined by QSBB criteria), Lewy body disease (PD, LBD, REM SBD) and synucleinopathies (including LBD, MSA).

Evaluation of plant phenolic metabolites as a source of Alzheimer's drug leads

Epidemiological studies have proven an association between consumption of polyphenols and prevention of Alzheimer's disease, the most common form of dementia characterized by extracellular deposition of amyloid beta plaques. The aim of this study is pharmacological screening of the aqueous alcohol extract of Markhamia platycalyx leaves, Schotia brachypetala leaves and stalks, and piceatannol compared to aqueous alcohol extract of Camellia sinensis leaves as potential Alzheimer's disease drugs. LC-HRESI(-ve)-MSⁿ was performed to identify phenolics' profile of Schotia brachypetala stalks aqueous alcohol extract and revealed ten phenolic compounds as first report: daidzein, naringin, procyanidin isomers, procyanidin dimer gallate, quercetin 3-O-rhamnoside, quercetin 3-O-glucuronide, quercetin hexose gallic acid, quercetin hexose protocatechuic acid, and ellagic acid. Alzheimer's disease was induced by a single intraperitoneal injection of LPS. Adult male Swiss albino mice were divided into groups of 8–10 mice each receiving treatment for six days. In vivo behavioral tests (Y maze and object recognition) and in vitro estimation of amyloid beta 42 by ELISA showed significant differences between results of treated and nontreated animals.

Hippocampal neuronal cells that accumulate α-synuclein fragments are more vulnerable to Aβ oligomer toxicity via mGluR5--implications for dementia with Lewy bodies

BACKGROUND

In dementia with Lewy bodies (DLB) abnormal interactions between α-synuclein (α-syn) and beta amyloid (Aβ) result in selective degeneration of neurons in the neocortex, limbic system and striatum. However, factors rendering these neurons selectively vulnerable have not been fully investigated. The metabotropic glutamate receptor 5 (mGluR5) has been shown to be up regulated in DLB and might play a role as a mediator of the neurotoxic effects of Aβ and α-syn in vulnerable neuronal populations. In this context, the main objective of the present study was to investigate the role of mGluR5 as a mediator of the neurotoxic effects of α-syn and Aβ in the hippocampus.

RESULTS

We generated double transgenic mice over-expressing amyloid precursor protein (APP) and α-syn under the mThy1 cassette and investigated the relationship between α-syn cleavage, Aβ, mGluR5 and neurodegeneration in the hippocampus. We found that compared to the single tg mice, the α-syn/APP tg mice displayed greater accumulation of α-syn and mGluR5 in the CA3 region of the hippocampus compared to the CA1 and other regions. This was accompanied by loss of CA3 (but not CA1) neurons in the single and α-syn/APP tg mice and greater loss of MAP 2 and synaptophysin in the CA3 in the α-syn/APP tg. mGluR5 gene transfer using a lentiviral vector into the hippocampus CA1 region resulted in greater α-syn accumulation and neurodegeneration in the single and α-syn/APP tg mice. In contrast, silencing mGluR5 with a lenti-shRNA protected neurons in the CA3 region of tg mice. In vitro, greater toxicity was observed in primary hippocampal neuronal cultures treated with Aβ oligomers and over-expressing α-syn; this effect was attenuated by down-regulating mGluR5 with an shRNA lentiviral vector. In α-syn-expressing neuronal cells lines, Aβ oligomers promoted increased intracellular calcium levels, calpain activation and α-syn cleavage resulting in caspase-3-dependent cell death. Treatment with pharmacological mGluR5 inhibitors such as 2-Methyl-6-(phenylethynyl)pyridine (MPEP) and 3-((2-Methyl-4-thiazolyl)ethynyl)pyridine (MTEP) attenuated the toxic effects of Aβ in α-syn-expressing neuronal cells.

CONCLUSIONS

Together, these results support the possibility that vulnerability of hippocampal neurons to α-syn and Aβ might be mediated via mGluR5. Moreover, therapeutical interventions targeting mGluR5 might have a role in DLB.

System-based approaches to decode the molecular links in Parkinson's disease and diabetes

A growing body of evidence indicates an increased risk for developing Parkinson's disease (PD) among people with type 2 diabetes (T2DM). The relationship between the etiology and development of both chronic diseases is beginning to be uncovered and recent studies show that PD and T2DM share remarkably similar dysregulated pathways. It has been proposed that a cascade of events including mitochondrial dysfunction, impaired insulin signaling, and metabolic inflammation trigger neurodegeneration in T2DM models. Network-based approaches have elucidated a potential molecular framework linking both diseases. Further, transcriptional signatures that modulate the neurodegenerative phenotype in T2DM have been identified. Here we contextualize the current experimental approaches to dissect the mechanisms underlying the association between PD and T2DM and discuss the existing challenges toward the understanding of the coexistence of these devastating aging diseases.

Protein aggregation and prionopathies

Prion protein and prion-like proteins share a number of characteristics. From the molecular point of view, they are constitutive proteins that aggregate following conformational changes into insoluble particles. These particles escape the cellular clearance machinery and amplify by recruiting the soluble for of their constituting proteins. The resulting protein aggregates are responsible for a number of neurodegenerative diseases such as Creutzfeldt-Jacob, Alzheimer, Parkinson and Huntington diseases. In addition, there are increasing evidences supporting the inter-cellular trafficking of these aggregates, meaning that they are "transmissible" between cells. There are also evidences that brain homogenates from individuals developing Alzheimer and Parkinson diseases propagate the disease in recipient model animals in a manner similar to brain extracts of patients developing Creutzfeldt-Jacob's disease. Thus, the propagation of protein aggregates from cell to cell may be a generic phenomenon that contributes to the evolution of neurodegenerative diseases, which has important consequences on human health issues. Moreover, although the distribution of protein aggregates is characteristic for each disease, new evidences indicate the possibility of overlaps and crosstalk between the different disorders. Despite the increasing evidences that support prion or prion-like propagation of protein aggregates, there are many unanswered questions regarding the mechanisms of toxicity and this is a field of intensive research nowadays.

α-Synuclein in cerebrospinal fluid of Alzheimer's disease and mild cognitive impairment

In addition to amyloid-β (Aβ) and tau, α-synuclein, best known for its role in Parkinson's disease (PD), has been suggested to be involved in cognition and pathogenesis of Alzheimer's disease (AD). We investigate the potential of α-synuclein in cerebrospinal fluid (CSF) as a biomarker of cognitive decline in AD, and its prodromal phase, mild cognitive impairment (MCI). Using an established, sensitive Luminex assay, we measured α-synuclein levels in the CSF of a cohort of close to 400 healthy control, MCI, and AD subjects obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and factored in APOE genotype in data analysis. CSF α-synuclein levels were significantly higher in the MCI (p = 0.005) and AD (p < 0.001) groups, compared to controls. However, receiver operating characteristic (ROC) curve analysis suggests that CSF α-synuclein level on its own only offered modest sensitivity (65%) and specificity (74%) as a diagnostic marker of AD, with an area under the curve (AUC) value of 0.719 for AD versus controls. The effect of APOE genotype, if any, was quite subtle. However, there was a significant correlation between α-synuclein and cognition (p = 0.001), with increased α-synuclein levels associated with decreased Mini-Mental State Exam scores. Our results support a role for α-synuclein even in MCI, the early phase of AD, in addition to being a potential contributor in MCI and AD diagnosis or monitoring of disease progression.

Mutations in PRKN and SNCA Genes Important for the Progress of Parkinson's Disease

Although Parkinson’s disease (PD) was first described almost 200 years ago, it remains an incurable disease with a cause that is not fully understood. Nowadays it is known that disturbances in the structure of pathological proteins in PD can be caused by more than environmental and genetic factors. Despite numerous debates and controversies in the literature about the role of mutations in the SNCA and PRKN genes in the pathogenesis of PD, it is evident that these genes play a key role in maintaining dopamine (DA) neuronal homeostasis and that the dysfunction of this homeostasis is relevant to both familial (FPD) and sporadic (SPD) PD with different onset. In recent years, the importance of alphasynuclein (ASN) in the process of neurodegeneration and neuroprotective function of the Parkin is becoming better understood. Moreover, there have been an increasing number of recent reports indicating the importance of the interaction between these proteins and their encoding genes. Among others interactions, it is suggested that even heterozygous substitution in the PRKN gene in the presence of the variants +2/+2 or +2/+3 of NACP-Rep1 in the SNCA promoter, may increase the risk of PD manifestation, which is probably due to ineffective elimination of over-expressed ASN by the mutated Parkin protein. Finally, it seems that genetic testing may be an important part of diagnostics in patients with PD and may improve the prognostic process in the course of PD. However, only full knowledge of the mechanism of the interaction between the genes associated with the pathogenesis of PD is likely to help explain the currently unknown pathways of selective damage to dopaminergic neurons in the course of PD.

Next-generation active immunization approach for synucleinopathies: implications for Parkinson's disease clinical trials

Immunotherapeutic approaches are currently in the spotlight for their potential as disease-modifying treatments for neurodegenerative disorders. The discovery that α-synuclein (α-syn) can transmit from cell to cell in a prion-like fashion suggests that immunization might be a viable option for the treatment of synucleinopathies. This possibility has been bolstered by the development of next-generation active vaccination technology with short peptides-AFFITOPEs(®) (AFF)- that do not elicit an α-syn-specific T cell response. This approach allows for the production of long term, sustained, more specific, non-cross reacting antibodies suitable for the treatment of synucleinopathies, such as Parkinson's disease (PD). In this context, we screened a large library of peptides that mimic the C-terminus region of α-syn and discovered a novel set of AFF that identified α-syn oligomers. Next, the peptide that elicited the most specific response against α-syn (AFF 1) was selected for immunizing two different transgenic (tg) mouse models of PD and Dementia with Lewy bodies, the PDGF- and the mThy1-α-syn tg mice. Vaccination with AFF 1 resulted in high antibody titers in CSF and plasma, which crossed into the CNS and recognized α-syn aggregates. Active vaccination with AFF 1 resulted in decreased accumulation of α-syn oligomers in axons and synapses, accompanied by reduced degeneration of TH fibers in the caudo-putamen nucleus and by improvements in motor and memory deficits in both in vivo models. Clearance of α-syn involved activation of microglia and increased anti-inflammatory cytokine expression, further supporting the efficacy of this novel active vaccination approach for synucleinopathies.

Association of cerebrospinal fluid β-amyloid 1-42, T-tau, P-tau181, and α-synuclein levels with clinical features of drug-naive patients with early Parkinson disease

IMPORTANCE

We observed a significant correlation between cerebrospinal fluid (CSF) levels of tau proteins and α-synuclein, but not β-amyloid 1-42 (Aβ1-42), and lower concentration of CSF biomarkers, as compared with healthy controls, in a cohort of entirely untreated patients with Parkinson disease (PD) at the earliest stage of the disease studied so far.

OBJECTIVE

To evaluate the baseline characteristics and relationship to clinical features of CSF biomarkers (Aβ1-42, total tau [T-tau], tau phosphorylated at threonine 181 [P-tau181], and α-synuclein) in drug-naive patients with early PD and demographically matched healthy controls enrolled in the Parkinson's Progression Markers Initiative (PPMI) study.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study of the initial 102 research volunteers (63 patients with PD and 39 healthy controls) of the PPMI cohort.

MAIN OUTCOMES AND MEASURES

The CSF biomarkers were measured by INNO-BIA AlzBio3 immunoassay (Aβ1-42, T-tau, and P-tau181; Innogenetics Inc) or by enzyme-linked immunosorbent assay (α-synuclein). Clinical features including diagnosis, demographic characteristics, motor, neuropsychiatric, and cognitive assessments, and DaTscan were systematically assessed according to the PPMI study protocol.

RESULTS

Slightly, but significantly, lower levels of Aβ1-42, T-tau, P-tau181, α-synuclein, and T-tau/Aβ1-42 were seen in subjects with PD compared with healthy controls but with a marked overlap between groups. Using multivariate regression analysis, we found that lower Aβ1-42 and P-tau181 levels were associated with PD diagnosis and that decreased CSF T-tau and α-synuclein were associated with increased motor severity. Notably, when we classified patients with PD by their motor phenotypes, lower CSF Aβ1-42 and P-tau181 concentrations were associated with the postural instability-gait disturbance-dominant phenotype but not with the tremor-dominant or intermediate phenotype. Finally, we found a significant correlation of the levels of α-synuclein with the levels of T-tau and P-tau181.

CONCLUSIONS AND RELEVANCE

In this first report of CSF biomarkers in PPMI study subjects,we found that measures of CSF Aβ1-42, T-tau, P-tau181, and α-synuclein have prognostic and diagnostic potential in early-stage PD. Further investigations using the entire PPMI cohort will test the predictive performance of CSF biomarkers for PD progression

Confluence of α-synuclein, tau, and β-amyloid pathologies in dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is pathologically characterized by α-synuclein aggregates in the brain. Most patients with DLB also show cerebral Alzheimer disease-type pathology (i.e. β-amyloid plaques and hyperphosphorylated tau deposits). It is unclear whether this overlap is coincidental or driven by specific regional or cellular interactions. The aims of this study were to investigate the regional convergence of α-synuclein, tau, and β-amyloid and to identify patterns of cellular co-occurrence of tau and α-synuclein in DLB. The study group consisted of 22 patients who met clinical and neuropathologic criteria for DLB. Protein aggregates were assessed semiquantitatively in 17 brain areas. APOE and MAPT genotypes were determined. Cellular co-occurrence of tau and α-synuclein was evaluated by double immunofluorescence. We found that total β-amyloid pathology scores correlated positively with total α-synuclein pathology scores (ρ = 0.692, p = 0.001). The factors that correlated best with the amount of α-synuclein pathology were the severity of β-amyloid pathology and presence of the MAPT H1 haplotype. Tau and α-synuclein frequently colocalized in limbic areas, but no correlation between total pathology scores was observed. This study confirms and extends the role of β-amyloid deposition and the MAPT H1 haplotype as contributing factors in DLB pathogenesis and demonstrates the confluence of multiple agents in neurodegenerative diseases.

c-Abl phosphorylates α-synuclein and regulates its degradation: implication for α-synuclein clearance and contribution to the pathogenesis of Parkinson's disease

Increasing evidence suggests that the c-Abl protein tyrosine kinase could play a role in the pathogenesis of Parkinson's disease (PD) and other neurodegenerative disorders. c-Abl has been shown to regulate the degradation of two proteins implicated in the pathogenesis of PD, parkin and α-synuclein (α-syn). The inhibition of parkin's neuroprotective functions is regulated by c-Abl-mediated phosphorylation of parkin. However, the molecular mechanisms by which c-Abl activity regulates α-syn toxicity and clearance remain unknown. Herein, using NMR spectroscopy, mass spectrometry, in vitro enzymatic assays and cell-based studies, we established that α-syn is a bona fide substrate for c-Abl. In vitro studies demonstrate that c-Abl directly interacts with α-syn and catalyzes its phosphorylation mainly at tyrosine 39 (pY39) and to a lesser extent at tyrosine 125 (pY125). Analysis of human brain tissues showed that pY39 α-syn is detected in the brains of healthy individuals and those with PD. However, only c-Abl protein levels were found to be upregulated in PD brains. Interestingly, nilotinib, a specific inhibitor of c-Abl kinase activity, induces α-syn protein degradation via the autophagy and proteasome pathways, whereas the overexpression of α-syn in the rat midbrains enhances c-Abl expression. Together, these data suggest that changes in c-Abl expression, activation and/or c-Abl-mediated phosphorylation of Y39 play a role in regulating α-syn clearance and contribute to the pathogenesis of PD.

Transgenic rodent models to study alpha-synuclein pathogenesis, with a focus on cognitive deficits

The aggregation of alpha-synuclein (aSyn) has been implicated in a number of degenerative diseases collectively termed synucleinopathies. Although most cases of synucleinopathies are idiopathic in nature, there are familial cases of these diseases that are due to mutations or multiplications of the gene coding for aSyn. Two of the most common synucleinopathies are Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Both of these diseases present with cognitive deficits, though with different clinical and temporal features. In PD, cognitive deficits are subtle, may occur before the onset of the classical motor symptoms, and only occasionally lead to dementia in the later stages of the disease. In contrast, dementia is the dominating feature of DLB from the disease onset. The impact of aSyn pathology on the development of neurobiological and behavioral impairments can be investigated using rodent models. There are currently several lines of transgenic mice overexpressing wild-type or mutated aSyn under various promoters. This review will provide an updated synopsis of the mouse lines available, summarize their cognitive deficits, and reflect on how deficits observed in these mice relate to the disease process in humans. In addition, we will review mouse lines where knockout strategies have been applied to study the effects of aSyn on various cognitive tasks and comment on how these lines have been used in combination with other transgenic strains, or with human aSyn overexpression by viral vectors. Finally, we will discuss the recent advent of bacterial artificial chromosome (BAC) transgenic models of PD and their effectiveness in modeling cognitive decline in PD.

Integrative network analysis unveils convergent molecular pathways in Parkinson's disease and diabetes

Background

Shared dysregulated pathways may contribute to Parkinson's disease and type 2 diabetes, chronic diseases that afflict millions of people worldwide. Despite the evidence provided by epidemiological and gene profiling studies, the molecular and functional networks implicated in both diseases, have not been fully explored. In this study, we used an integrated network approach to investigate the extent to which Parkinson's disease and type 2 diabetes are linked at the molecular level.

Methods and Findings

Using a random walk algorithm within the human functional linkage network we identified a molecular cluster of 478 neighboring genes closely associated with confirmed Parkinson's disease and type 2 diabetes genes. Biological and functional analysis identified the protein serine-threonine kinase activity, MAPK cascade, activation of the immune response, and insulin receptor and lipid signaling as convergent pathways. Integration of results from microarrays studies identified a blood signature comprising seven genes whose expression is dysregulated in Parkinson's disease and type 2 diabetes. Among this group of genes, is the amyloid precursor protein (APP), previously associated with neurodegeneration and insulin regulation. Quantification of RNA from whole blood of 192 samples from two independent clinical trials, the Harvard Biomarker Study (HBS) and the Prognostic Biomarker Study (PROBE), revealed that expression of APP is significantly upregulated in Parkinson's disease patients compared to healthy controls. Assessment of biomarker performance revealed that expression of APP could distinguish Parkinson's disease from healthy individuals with a diagnostic accuracy of 80% in both cohorts of patients.

Conclusions

These results provide the first evidence that Parkinson's disease and diabetes are strongly linked at the molecular level and that shared molecular networks provide an additional source for identifying highly sensitive biomarkers. Further, these results suggest for the first time that increased expression of APP in blood may modulate the neurodegenerative phenotype in type 2 diabetes patients.

CSF α-synuclein improves diagnostic and prognostic performance of CSF tau and Aβ in Alzheimer's disease

Alzheimer's disease (AD) and Lewy body diseases (LBD), e.g., Parkinson's disease (PD) dementia and dementia with Lewy bodies (DLB), are common causes of geriatric cognitive impairments. In addition, AD and LBD are often found in the same patients at autopsy; therefore, biomarkers that can detect the presence of both pathologies in living subjects are needed. In this investigation, we report the assessment of α-synuclein (α-syn) in cerebrospinal fluid (CSF) and its association with CSF total tau (t-tau), phosphorylated tau181 (p-tau181), and amyloid beta1-42 (Aβ1-42) in subjects of the Alzheimer's Disease Neuroimaging Initiative (ADNI; n = 389), with longitudinal clinical assessments. A strong correlation was noted between α-syn and t-tau in controls, as well as in patients with AD and mild cognitive impairment (MCI). However, the correlation is not specific to subjects in the ADNI cohort, as it was also seen in PD patients and controls enrolled in the Parkinson's Progression Markers Initiative (PPMI; n = 102). A bimodal distribution of CSF α-syn levels was observed in the ADNI cohort, with high levels of α-syn in the subjects with abnormally increased t-tau values. Although a correlation was also noted between α-syn and p-tau181, there was a mismatch (α-syn-p-tau181-Mis), i.e., higher p-tau181 levels accompanied by lower α-syn levels in a subset of ADNI patients. We hypothesize that this α-syn-p-tau181-Mis is a CSF signature of concomitant LBD pathology in AD patients. Hence, we suggest that inclusion of measures of CSF α-syn and calculation of α-syn-p-tau181-Mis improves the diagnostic sensitivity/specificity of classic CSF AD biomarkers and better predicts longitudinal cognitive changes.

Assessing the causes and consequences of co-polymerization in amyloid formation

How, and why, different proteins form amyloid fibrils is most often studied in vitro using a single purified protein sequence. However, many amyloid diseases involve co-aggregation of different protein species, including proteins with/without post-translational modifications (e.g., different strains of PrP), proteins of different length (e.g., β₂-microglobulin and ΔN6, Aβ40, and Aβ42), sequence variants (e.g., Aβ and Aβ(ARC)), and proteins from different organisms (e.g., bovine PrP and human PrP). The consequences of co-aggregation of different proteins upon the structure, stability, species transmission and toxicity of the resulting amyloid aggregates is discussed here, including the role of co-aggregation in expanding the repertoire of oligomeric and fibrillar structures and how this can affect their biological and biophysical properties.

Parkinson's disease dementia: convergence of α-synuclein, tau and amyloid-β pathologies

Dementia is increasingly being recognized in cases of Parkinson's disease (PD); such cases are termed PD dementia (PDD). The spread of fibrillar α-synuclein (α-syn) pathology from the brainstem to limbic and neocortical structures seems to be the strongest neuropathological correlate of emerging dementia in PD. In addition, up to 50% of patients with PDD also develop sufficient numbers of amyloid-β plaques and tau-containing neurofibrillary tangles for a secondary diagnosis of Alzheimer's disease, and these pathologies may act synergistically with α-syn pathology to confer a worse prognosis. An understanding of the relationships between these three distinct pathologies and their resultant clinical phenotypes is crucial for the development of effective disease-modifying treatments for PD and PDD.

Mitochondrial dysfunction in psychiatric and neurological diseases: cause(s), consequence(s), and implications of antioxidant therapy

Mitochondrial dysfunction is at the base of development and progression of several psychiatric and neurologic diseases with different etiologies. MtDNA/nDNA mutational damage, failure of endogenous antioxidant defenses, hormonal malfunction, altered membrane permeability, metabolic dysregulation, disruption of calcium buffering capacity and ageing have been found to be the root causes of mitochondrial dysfunction in psychatric and neurodegenerative diseases. However, the overall consequences of mitochondrial dysfunction are only limited to increase in oxidative/nitrosative stress and cellular energy crises. Thus far, extensive efforts have been made to improve mitochondrial function through specific cause-dependent antioxidant therapy. However, owing to complex genetic and interlinked causes of mitochondrial dysfunction, it has not been possible to achieve any common, unique supportive antioxidant therapeutic strategy for the treatment of psychiatric and neurologic diseases. Hence, we propose an antioxidant therapeutic strategy for management of consequences of mitochondrial dysfunction in psychiatric and neurologic diseases. It is expected that this will not only reduces oxidative stress, but also promote anaerobic energy production.

Amyloid imaging with PET in early Alzheimer disease diagnosis

In vivo imaging of amyloid-β (Aβ) with positron emission tomography has moved from the research arena into clinical practice. Clinicians working with cognitive decline and dementia must become familiar with its benefits and limitations. Amyloid imaging allows earlier diagnosis of Alzheimer disease and better differential diagnosis of dementia and provides prognostic information for mild cognitive impairment. It also has an increasingly important role in therapeutic trial recruitment and for evaluation of anti-Aβ treatments. Longitudinal observations are required to elucidate the role of Aβ deposition in the course of Alzheimer disease and provide information needed to fully use the prognostic power of this investigation.

A progressive dopaminergic phenotype associated with neurotoxic conversion of α-synuclein in BAC-transgenic rats

Conversion of soluble α-synuclein into insoluble and fibrillar inclusions is a hallmark of Parkinson's disease and other synucleinopathies. Accumulating evidence points towards a relationship between its generation at nerve terminals and structural synaptic pathology. Little is known about the pathogenic impact of α-synuclein conversion and deposition at nigrostriatal dopaminergic synapses in transgenic mice, mainly owing to expression limitations of the α-synuclein construct. Here, we explore whether both the rat as a model and expression of the bacterial artificial chromosome construct consisting of human full-length wild-type α-synuclein could exert dopaminergic neuropathological effects. We found that the human promoter induced a pan-neuronal expression, matching the rodent α-synuclein expression pattern, however, with prominent C-terminally truncated fragments. Ageing promoted conversion of both full-length and C-terminally truncated α-synuclein species into insolube and proteinase K-resistant fibres, with strongest accumulation in the striatum, resembling biochemical changes seen in human Parkinson's disease. Transgenic rats develop early changes in novelty-seeking, avoidance and smell before the progressive motor deficit. Importantly, the observed pathological changes were associated with severe loss of the dopaminergic integrity, thus resembling more closely the human pathology.

The role of amyloidogenic protein oligomerization in neurodegenerative disease

A common pathological hallmark in many neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Huntington's disease, is the formation of fibrillar protein aggregates referred to as amyloids. The amyloidogenic aggregates were long thought to be toxic, but mounting evidence supports the notion that a variety of amyloid aggregate intermediates to fibril formation, termed oligomers, may in fact be the primary culprit leading to neuronal dysfunction and cell death. While amyloid formation is a complex, heterogeneous process, aggregates formed by diverse, diseases-related proteins share many conformational similarities, suggesting common toxic mechanisms among these diseases. Ideally, similar therapeutic strategies may be applicable. This review focuses on the potential role of amyloidogenic oligomers in neurodegenerative disease, highlighting some promising therapeutic strategies.

Neuropathological alterations in Alzheimer disease

The neuropathological hallmarks of Alzheimer disease (AD) include "positive" lesions such as amyloid plaques and cerebral amyloid angiopathy, neurofibrillary tangles, and glial responses, and "negative" lesions such as neuronal and synaptic loss. Despite their inherently cross-sectional nature, postmortem studies have enabled the staging of the progression of both amyloid and tangle pathologies, and, consequently, the development of diagnostic criteria that are now used worldwide. In addition, clinicopathological correlation studies have been crucial to generate hypotheses about the pathophysiology of the disease, by establishing that there is a continuum between "normal" aging and AD dementia, and that the amyloid plaque build-up occurs primarily before the onset of cognitive deficits, while neurofibrillary tangles, neuron loss, and particularly synaptic loss, parallel the progression of cognitive decline. Importantly, these cross-sectional neuropathological data have been largely validated by longitudinal in vivo studies using modern imaging biomarkers such as amyloid PET and volumetric MRI.

Quantitative appraisal of ventricular cerebrospinal fluid biomarkers in neuropathologically diagnosed Parkinson's disease cases lacking Alzheimer's disease pathology

Identifying biomarkers that distinguish Parkinson’s disease (PD) from normal control (NC) individuals has the potential to increase diagnostic sensitivity for the detection of early-stage PD. A previous proteomic study identified potential biomarkers in postmortem ventricular cerebrospinal fluid (V-CSF) from neuropathologically diagnosed PD subjects lacking Alzheimer’s disease (AD) neuropathology. In the present study, we assessed these biomarkers as well as p-tau¹⁸¹, Aβ42, and S100B by ELISA in PD (n = 43) and NC (n = 49) cases. The p-tau¹⁸¹/Aβ42 ratio and ApoA-1 showed statistically significant differences between groups. Multiple regression analysis demonstrated that p-tau¹⁸¹/Aβ42 had a significant odds ratio: OR = 1.42 (95% confidence interval [CI], 1.12–1.84), P = 0.006. Among the molecules investigated, intriguing correlations were observed that require further investigation. Our results suggest coexistent AD CSF biomarkers within the PD group notwithstanding that it was selected to minimize AD neuropathological lesions.

Accumulation of α-synuclein triggered by presynaptic dysfunction

Pathological examination of dementia with Lewy bodies patients identified the presence of abnormal α-synuclein (αSyn) aggregates in the presynaptic terminals. αSyn is involved in the regulation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex. Importantly, αSyn-transgenic mouse and postmortem examination of patients with Parkinson's disease have demonstrated the abnormal distribution of SNARE protein in presynaptic terminals. In this study, we investigated the effects of SNARE dysfunction on endogenous αSyn using Snap25(S187A/S187A) mutant mice. These mice have homozygous knock-in gene encoding unphosphorylatable S187A-substituted synaptosomal-associated protein of 25 kDa (SNAP-25). The mice displayed a significant age-dependent change in the distribution of αSyn and its Ser(129)-phosphorylated form in abnormally hypertrophied glutamatergic nerve terminals in the striatum. Electron-microscopic analysis revealed the abnormally condensed synaptic vesicles with concomitant mislocalization of αSyn protein to the periactive zone in the glutamatergic nerve terminals. However, the Snap25(S187A/S187A) mutant mouse harbored no abnormalities in the nigrostriatal dopaminergic neurons. Our present results suggest that SNARE dysfunction is the initial trigger of mislocalization and accumulation of αSyn, and probably is an important pathomechanism of α-synucleinopathies.

Toxicity of extracellular secreted alpha-synuclein: Its role in nitrosative stress and neurodegeneration

It has been demonstrated that both oligomerisation and accumulation of α-synuclein (ASN) are the key molecular processes involved in the pathophysiology of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease and other synucleinopathies. Alterations of ASN expression and impairment of its degradation can lead to the formation of intracellular deposits of this protein, called Lewy bodies. Overexpressed or misfolded ASN could be secreted to the extracellular space. Today the prion-like transmission of ASN oligomers to neighbouring cells is believed to be responsible for protein modification and propagation of neurodegeneration in the brain. It was presented that oxidative/nitrosative stress may play a key role in ASN secretion and spread of ASN pathology. Moreover, ASN-evoked protein oxidation, nitration and nitrosylation lead to disturbances in synaptic transmission and cell death. The interaction of secreted ASN with other amyloidogenic proteins and its involvement in irreversible mitochondrial disturbances and oxidative stress were also described. A better understanding of the mechanisms of ASN secretion and dysfunction may help to explain the molecular mechanisms of neurodegeneration and may be the basis for the development of novel therapeutic strategies.

Effect of α-synuclein on amyloid β-induced toxicity: relevance to Lewy body variant of Alzheimer disease

Alzheimer's disease, the most prevalent age-related neurodegenerative disease, is characterized by the presence of extracellular senile plaques composed of amyloid-beta (Aβ) peptide and intracellular neurofibrillary tangles. More than 50 % of Alzheimer's disease (AD) patients also exhibit abundant accumulation of α-synuclein (α-Syn)-positive Lewy bodies. This Lewy body variant of AD (LBV-AD) is associated with accelerated cognitive dysfunction and progresses more rapidly than pure AD. In addition, it has been suggested that Aβ and α-Syn can directly interact. In this study we investigated the effect of α-Syn on Aβ-induced toxicity in cortical neurons. In order to mimic the intracellular accumulation of α-Syn observed in the brain of LBV-AD patients, we used valproic acid (VPA) to increase its endogenous expression levels. The release of α-Syn from damaged presynaptic terminals that occurs during the course of the disease was simulated by challenging cells with recombinant α-Syn. Our results showed that either VPA-induced α-Syn upregulation or addition of recombinant α-Syn protect primary cortical neurons from soluble Aβ1-42 decreasing the caspase-3-mediated cell death. It was also found that neuroprotection against Aβ-induced toxicity mediated by α-Syn overexpression involves the PI3K/Akt cell survival pathway. Furthermore, recombinant α-Syn was shown to directly interact with Aβ1-42 and to decrease the levels of Aβ1-42 oligomers, which might explain its neuroprotective effect. In conclusion, we demonstrate that either endogenous or exogenous α-Syn can be neuroprotective against Aβ-induced cell death, suggesting a cell defence mechanism during the initial stages of the mixed pathology.

Enteric alpha-synuclein expression is increased in Parkinson's disease but not Alzheimer's disease

BACKGROUND AND OBJECTIVE

Alpha-synuclein (α-Syn) is immunohistochemically detectable in enteric neurons in some subjects. We determined its age distribution in the general autopsy population and in an age-matched subset investigated differences with Parkinson's (PD) and Alzheimer's diseases (AD).

METHODS

Archival autopsy samples of colon from 95 cases (77 general population, 10 PD, and 8 AD) were immunostained with monoclonal antibody KM51. α-Syn detectability was semiquantitatively graded 1 to 3.

RESULTS

α-Syn was detectable in 52% of the general population, and its level of expression did not change between ages 40 and 91. All PD subjects were α-Syn positive, with higher prevalence (P = 0.001) and grade (P = 0.003) than age-matched controls. AD subjects were no more likely to be α-Syn positive or have a higher grade than controls.

CONCLUSIONS

Either PD develops selectively in the enterically α-Syn-positive population subset or PD induces this expression. Absence of increased α-Syn expression in AD points to differences in pathogenesis.

Cerebrospinal fluid biomarker candidates for parkinsonian disorders

The Parkinsonian disorders are a large group of neurodegenerative diseases including idiopathic Parkinson’s disease (PD) and atypical Parkinsonian disorders (APD), such as multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, and dementia with Lewy bodies. The etiology of these disorders is not known although it is considered to be a combination of genetic and environmental factors. One of the greatest obstacles for developing efficacious disease-modifying treatment strategies is the lack of biomarkers. Reliable biomarkers are needed for early and accurate diagnosis, to measure disease progression, and response to therapy. In this review several of the most promising cerebrospinal biomarker candidates are discussed. Alpha-synuclein seems to be intimately involved in the pathogenesis of synucleinopathies and its levels can be measured in the cerebrospinal fluid and in plasma. In a similar way, tau protein accumulation seems to be involved in the pathogenesis of tauopathies. Urate, a potent antioxidant, seems to be associated to the risk of developing PD and with its progression. Neurofilament light chain levels are increased in APD compared with PD and healthy controls. The new “omics” techniques are potent tools offering new insights in the patho-etiology of these disorders. Some of the difficulties encountered in developing biomarkers are discussed together with future perspectives.

Pax6 interactions with chromatin and identification of its novel direct target genes in lens and forebrain

Pax6 encodes a specific DNA-binding transcription factor that regulates the development of multiple organs, including the eye, brain and pancreas. Previous studies have shown that Pax6 regulates the entire process of ocular lens development. In the developing forebrain, Pax6 is expressed in ventricular zone precursor cells and in specific populations of neurons; absence of Pax6 results in disrupted cell proliferation and cell fate specification in telencephalon. In the pancreas, Pax6 is essential for the differentiation of α-, β- and δ-islet cells. To elucidate molecular roles of Pax6, chromatin immunoprecipitation experiments combined with high-density oligonucleotide array hybridizations (ChIP-chip) were performed using three distinct sources of chromatin (lens, forebrain and β-cells). ChIP-chip studies, performed as biological triplicates, identified a total of 5,260 promoters occupied by Pax6. 1,001 (133) of these promoter regions were shared between at least two (three) distinct chromatin sources, respectively. In lens chromatin, 2,335 promoters were bound by Pax6. RNA expression profiling from Pax6^+/− lenses combined with in vivo Pax6-binding data yielded 76 putative Pax6-direct targets, including the Gaa, Isl1, Kif1b, Mtmr2, Pcsk1n, and Snca genes. RNA and ChIP data were validated for all these genes. In lens cells, reporter assays established Kib1b and Snca as Pax6 activated and repressed genes, respectively. In situ hybridization revealed reduced expression of these genes in E14 cerebral cortex. Moreover, we examined differentially expressed transcripts between E9.5 wild type and Pax6^−/− lens placodes that suggested Efnb2, Fat4, Has2, Nav1, and Trpm3 as novel Pax6-direct targets. Collectively, the present studies, through the identification of Pax6-direct target genes, provide novel insights into the molecular mechanisms of Pax6 gene control during mouse embryonic development. In addition, the present data demonstrate that Pax6 interacts preferentially with promoter regions in a tissue-specific fashion. Nevertheless, nearly 20% of the regions identified are accessible to Pax6 in multiple tissues.