Tau Protein Phosphorylated at Threonine 181 in CSF as a Neurochemical Biomarker in Alzheimer's Disease: Original Data and Review of the Literature

Parsimonious EBM: Generalising the event-based model of disease progression for simultaneous events

The event-based model of disease progression (EBM) infers a temporal ordering of biomarker abnormalities, defining different disease stages, from cross-sectional data. A key modelling choice of the EBM is that biomarker abnormalities, termed events, are serially ordered. However, this choice enforces a strict equality between the number of input biomarkers and the number of modelled disease stages, limiting the EBM's ability to infer simple staging systems and identify latent disease processes driving multiple biomarker changes. To overcome this, we introduce the parsimonious event-based model of disease progression (P-EBM). The P-EBM generalises the EBM to allow multiple new biomarker abnormalities, termed "simultaneous events", at each model stage. We evaluate the P-EBM performance in simulated data and demonstrate its ability to reconstruct event orderings with arbitrary arrangements under realistic experimental conditions. In sporadic AD data from the Alzheimer's Disease Neuroimaging Initiative, the P-EBM estimated a sequence with 7 model stages from a dataset of 12 biomarkers that more closely fitted the data than the EBM. The inferred sets of simultaneous events, such as decreased cerebrospinal fluid total tau and p-tau181, correspond closely to known underlying disease processes. P-EBM patient stages were strongly associated with clinical diagnosis at baseline and future conversion and could be accurately estimated from a smaller number of biomarkers than the EBM. The P-EBM enables the data-driven discovery of simple disease staging systems which could highlight new latent disease processes and suggest practical strategies for patient staging.

Alzheimer's disease: a review on the current trends of the effective diagnosis and therapeutics

The most prevalent cause of dementia is Alzheimer's disease. Cognitive decline and accelerating memory loss characterize it. Alzheimer's disease advances sequentially, starting with preclinical stages, followed by mild cognitive and/or behavioral impairment, and ultimately leading to Alzheimer's disease dementia. In recent years, healthcare providers have been advised to make an earlier diagnosis of Alzheimer's, prior to individuals developing Alzheimer's disease dementia. Regrettably, the identification of early-stage Alzheimer's disease in clinical settings can be arduous due to the tendency of patients and healthcare providers to disregard symptoms as typical signs of aging. Therefore, accurate and prompt diagnosis of Alzheimer's disease is essential in order to facilitate the development of disease-modifying and secondary preventive therapies prior to the onset of symptoms. There has been a notable shift in the goal of the diagnosis process, transitioning from merely confirming the presence of symptomatic AD to recognizing the illness in its early, asymptomatic phases. Understanding the evolution of disease-modifying therapies and putting effective diagnostic and therapeutic management into practice requires an understanding of this concept. The outcomes of this study will enhance in-depth knowledge of the current status of Alzheimer's disease's diagnosis and treatment, justifying the necessity for the quest for potential novel biomarkers that can contribute to determining the stage of the disease, particularly in its earliest stages. Interestingly, latest clinical trial status on pharmacological agents, the nonpharmacological treatments such as behavior modification, exercise, and cognitive training as well as alternative approach on phytochemicals as neuroprotective agents have been covered in detailed.

CKG-IMC: An inductive matrix completion method enhanced by CKG and GNN for Alzheimer's disease compound-protein interactions prediction

Alzheimer's disease (AD) is one of the most prevalent chronic neurodegenerative disorders globally, with a rapidly growing population of AD patients and currently no effective therapeutic interventions available. Consequently, the development of therapeutic anti-AD drugs and the identification of AD targets represent one of the most urgent tasks. In this study, in addition to considering known drugs and targets, we explore compound-protein interactions (CPIs) between compounds and proteins relevant to AD. We propose a deep learning model called CKG-IMC to predict Alzheimer's disease compound-protein interaction relationships. CKG-IMC comprises three modules: a collaborative knowledge graph (CKG), a principal neighborhood aggregation graph neural network (PNA), and an inductive matrix completion (IMC). The collaborative knowledge graph is used to learn semantic associations between entities, PNA is employed to extract structural features of the relationship network, and IMC is utilized for CPIs prediction. Compared with a total of 16 baseline models based on similarities, knowledge graphs, and graph neural networks, our model achieves state-of-the-art performance in experiments of 10-fold cross-validation and independent test. Furthermore, we use CKG-IMC to predict compounds interacting with two confirmed AD targets, 42-amino-acid β-amyloid (Aβ42) protein and microtubule-associated protein tau (tau protein), as well as proteins interacting with five FDA-approved anti-AD drugs. The results indicate that the majority of predictions are supported by literature, and molecular docking experiments demonstrate a strong affinity between the predicted compounds and targets.

Novel Biomarkers for Alzheimer's Disease: Plasma Neurofilament Light and Cerebrospinal Fluid

Neurodegenerative disorders such as Alzheimer's disease (AD) represent an increasingly significant public health concern. As clinical diagnosis faces challenges, biomarkers are becoming increasingly important in research, trials, and patient assessments. While biomarkers like amyloid-β peptide, tau proteins, CSF levels (Aβ, tau, and p-tau), and neuroimaging techniques are commonly used in AD diagnosis, they are often limited and invasive in monitoring and diagnosis. For this reason, blood-based biomarkers are the optimal choice for detecting neurodegeneration in brain diseases due to their noninvasiveness, affordability, reliability, and consistency. This literature review focuses on plasma neurofilament light (NfL) and CSF NfL as blood-based biomarkers used in recent AD diagnosis. The findings revealed that the core CSF biomarkers of neurodegeneration (T-tau, P-tau, and Aβ42), CSF NFL, and plasma T-tau were strongly associated with Alzheimer's disease, and the core biomarkers were strongly associated with mild cognitive impairment due to Alzheimer's disease. Elevated levels of plasma and cerebrospinal fluid NfL were linked to decreased [18F]FDG uptake in corresponding brain areas. In participants with Aβ positivity (Aβ+), NfL correlated with reduced metabolism in regions susceptible to Alzheimer's disease. In addition, CSF NfL levels correlate with brain atrophy and predict cognitive changes, while plasma total tau does not. Plasma P-tau, especially in combination with Aβ42/Aβ40, is promising for symptomatic AD stages. Though not AD-exclusive, blood NfL holds promise for neurodegeneration detection and assessing treatment efficacy. Given the consistent levels of T-tau, P-tau, Aβ42, and NFL in CSF, their incorporation into both clinical practice and research is highly recommended.

Phosphorylated tau in Alzheimer's disease

There is a need for blood biomarkers to detect individuals at different Alzheimer's disease (AD) stages because obtaining cerebrospinal fluid-based biomarkers is invasive and costly. Plasma phosphorylated tau proteins (p-tau) have shown potential as such biomarkers. This systematic review was conducted according to the PRISMA guidelines and aimed to determine whether quantification of plasma tau phosphorylated at threonine 181 (p-tau181), threonine 217 (p-tau217) and threonine 231 (p-tau231) is informative in the diagnosis of AD. All p-tau isoforms increase as a function of Aβ-accumulation and discriminate healthy individuals from those at preclinical AD stages with high accuracy. P-tau231 increases earliest, followed by p-tau181 and p-tau217. In advanced stages, all p-tau isoforms are associated with the clinical classification of AD and increase with disease severity, with the greatest increase seen for p-tau217. This is also reflected by a better correlation of p-tau217 with Aβ scans, whereas both, p-tau217 and p-tau181 correlated equally with tau scans. However, at the very advanced stages, p-tau181 begins to plateau, which may mirror the trajectory of the Aβ pathology and indicate an association with a more intermediate risk of AD. Across the AD continuum, the incremental increase in all biomarkers is associated with structural changes in widespread brain regions and underlying cognitive decline. Furthermore, all isoforms differentiate AD from non-AD neurodegenerative disorders, making them specific for AD. Incorporating p-tau181, p-tau217 and p-tau231 in clinical use requires further studies to examine ideal cut-points and harmonize assays.

Dissociable contribution of plasma NfL and p-tau181 to cognitive impairment in Parkinson's disease

BACKGROUND

Cognitive dysfunction is a disabling complication in Parkinson's disease (PD). Accuracy of diagnosis of mild cognitive impairment in PD (PD-MCI) depends on the tests performed, which limits results generalization. Blood-based biomarkers could provide additional objective information for PD-MCI diagnosis and progression. Blood neurofilament light chain (NfL), a marker of neuronal injury, has shown good performance for PD disease stratification and progression. While NfL is not disease-specific, phosphorylated-tau at threonine-181 (p-tau181) in blood is a highly specific marker of concomitant brain amyloid-β and tau pathology.

METHODS

We investigated the potential of plasma NfL and p-tau181 levels as markers of cognitive impairment in a prospective cohort of 109 PD patients with and without PD-MCI (age 68.1 ± 7 years, education 12.2± 5 years), and 40 comparable healthy controls. After a follow-up of 4 years, we evaluated their predictive value for progression to dementia.

RESULTS

Although NfL and p-tau181 levels were significantly increased in PD compared with healthy controls, only NfL levels were significantly higher in PD-MCI compared with PD with normal cognition (PD-NC) at baseline. After a follow-up of 4 years, only NfL predicted progression to dementia (HR 1.23, 95% CI 1.02-1.53; p = 0.038). Significant correlations between fluid biomarkers and neuropsychological examination were only found with NfL levels.

CONCLUSIONS

Plasma NfL levels objectively differentiates PD-MCI from PD-NC patients, and may serve as a plasma biomarker for predicting progression to dementia in PD. Plasma levels of p-tau181 does not seem to help in differentiating PD-MCI or to predict future cognitive deterioration.

Discovery of MAO-B Inhibitor with Machine Learning, Topomer CoMFA, Molecular Docking and Multi-Spectroscopy Approaches

Alzheimer’s disease (AD) is the most common type of dementia and is a serious disruption to normal life. Monoamine oxidase-B (MAO-B) is an important target for the treatment of AD. In this study, machine learning approaches were applied to investigate the identification model of MAO-B inhibitors. The results showed that the identification model for MAO-B inhibitors with　K-nearest neighbor(KNN) algorithm had a prediction accuracy of 94.1% and 88.0% for the 10-fold cross-validation test and the independent test set, respectively. Secondly, a quantitative activity prediction model for MAO-B was investigated with the Topomer CoMFA model. Two separate cutting mode approaches were used to predict the activity of MAO-B inhibitors. The results showed that the cut model with q² = 0.612 (cross-validated correlation coefficient) and r² = 0.824 (non-cross-validated correlation coefficient) were determined for the training and test sets, respectively. In addition, molecular docking was employed to analyze the interaction between MAO-B and inhibitors. Finally, based on our proposed prediction model, 1-(4-hydroxyphenyl)-3-(2,4,6-trimethoxyphenyl)propan-1-one (LB) was predicted as a potential MAO-B inhibitor and was validated by a multi-spectroscopic approach including fluorescence spectra and ultraviolet spectrophotometry.

Plasma phosphorylated-tau181 levels reflect white matter microstructural changes across Alzheimer's disease progression

Alzheimer's Disease (AD) is characterized by cognitive impairments that hinder daily activities and lead to personal and behavioral problems. Plasma hyperphosphorylated tau protein at threonine 181 (p-tau181) has recently emerged as a new sensitive tool for the diagnosis of AD patients. We herein investigated the association of plasma P-tau181 and white matter (WM) microstructural changes in AD. We obtained data from a large prospective cohort of elderly individuals participating in the Alzheimer's Disease Neuroimaging Initiative (ADNI), which included baseline measurements of plasma P-tau181 and imaging findings. A subset of 41 patients with AD, 119 patients with mild cognitive impairments (MCI), and 43 healthy controls (HC) was included in the study, all of whom had baseline blood P-tau181 levels and had also undergone Diffusion Tensor Imaging. The analysis revealed that the plasma level of P-tau181 has a positive correlation with changes in Mean Diffusivity (MD), Radial Diffusivity (RD), and Axial Diffusivity (AxD), but a negative with Fractional Anisotropy (FA) parameters in WM regions of all participants. There is also a significant association between WM microstructural changes in different regions and P-tau181 plasma measurements within each MCI, HC, and AD group. In conclusion, our findings clarified that plasma P-tau181 levels are associated with changes in WM integrity in AD. P-tau181 could improve the accuracy of diagnostic procedures and support the application of blood-based biomarkers to diagnose WM neurodegeneration. Longitudinal clinical studies are also needed to demonstrate the efficacy of the P-tau181 biomarker and predict its role in structural changes.

Neurofilament Proteins as Biomarkers to Monitor Neurological Diseases and the Efficacy of Therapies

Biomarkers of neurodegeneration and neuronal injury have the potential to improve diagnostic accuracy, disease monitoring, prognosis, and measure treatment efficacy. Neurofilament proteins (NfPs) are well suited as biomarkers in these contexts because they are major neuron-specific components that maintain structural integrity and are sensitive to neurodegeneration and neuronal injury across a wide range of neurologic diseases. Low levels of NfPs are constantly released from neurons into the extracellular space and ultimately reach the cerebrospinal fluid (CSF) and blood under physiological conditions throughout normal brain development, maturation, and aging. NfP levels in CSF and blood rise above normal in response to neuronal injury and neurodegeneration independently of cause. NfPs in CSF measured by lumbar puncture are about 40-fold more concentrated than in blood in healthy individuals. New ultra-sensitive methods now allow minimally invasive measurement of these low levels of NfPs in serum or plasma to track disease onset and progression in neurological disorders or nervous system injury and assess responses to therapeutic interventions. Any of the five Nf subunits - neurofilament light chain (NfL), neurofilament medium chain (NfM), neurofilament heavy chain (NfH), alpha-internexin (INA) and peripherin (PRPH) may be altered in a given neuropathological condition. In familial and sporadic Alzheimer's disease (AD), plasma NfL levels may rise as early as 22 years before clinical onset in familial AD and 10 years before sporadic AD. The major determinants of elevated levels of NfPs and degradation fragments in CSF and blood are the magnitude of damaged or degenerating axons of fiber tracks, the affected axon caliber sizes and the rate of release of NfP and fragments at different stages of a given neurological disease or condition directly or indirectly affecting central nervous system (CNS) and/or peripheral nervous system (PNS). NfPs are rapidly emerging as transformative blood biomarkers in neurology providing novel insights into a wide range of neurological diseases and advancing clinical trials. Here we summarize the current understanding of intracellular NfP physiology, pathophysiology and extracellular kinetics of NfPs in biofluids and review the value and limitations of NfPs and degradation fragments as biomarkers of neurodegeneration and neuronal injury.

BMP4 overexpression induces the upregulation of APP/Tau and memory deficits in Alzheimer's disease

Alzheimer's disease (AD) is a chronic progressive degenerative disease of the nervous system. Its pathogenesis is complex and is related to the abnormal expression of the amyloid β (Aβ), APP, and Tau proteins. Evidence has demonstrated that bone morphogenetic protein 4 (BMP4) is highly expressed in transgenic mouse models of AD and that endogenous levels of BMP4 mainly affect hippocampal function. To determine whether BMP4 participates in AD development, transgenic mice were constructed that overexpress BMP4 under the control of the neuron-specific enolase (NSE) promoter. We also performed MTT, FACS, transfection, TUNEL, and Western blotting assays to define the role of BMP4 in cells. We found that middle-aged BMP4 transgenic mice exhibited impaired memory via the Morris water maze experiment. Moreover, their hippocampal tissues exhibited high expression levels of AD-related proteins, including APP, Aβ, PSEN-1, Tau, P-Tau (Thr181), and P-Tau (Thr231). Furthermore, in multiple cell lines, the overexpression of BMP4 increased the expression of AD-related proteins, whereas the downregulation of BMP4 demonstrated opposing effects. Consistent with these results, BMP4 modulation affected cell apoptosis via the regulation of BAX and Bcl-2 expression in cells. Our findings indicate that BMP4 overexpression might be a potential factor to induce AD.

Bridging the Gap Between Fluid Biomarkers for Alzheimer's Disease, Model Systems, and Patients

Alzheimer’s disease (AD) is a debilitating neurodegenerative disease characterized by the accumulation of two proteins in fibrillar form: amyloid-β (Aβ) and tau. Despite decades of intensive research, we cannot yet pinpoint the exact cause of the disease or unequivocally determine the exact mechanism(s) underlying its progression. This confounds early diagnosis and treatment of the disease. Cerebrospinal fluid (CSF) biomarkers, which can reveal ongoing biochemical changes in the brain, can help monitor developing AD pathology prior to clinical diagnosis. Here we review preclinical and clinical investigations of commonly used biomarkers in animals and patients with AD, which can bridge translation from model systems into the clinic. The core AD biomarkers have been found to translate well across species, whereas biomarkers of neuroinflammation translate to a lesser extent. Nevertheless, there is no absolute equivalence between biomarkers in human AD patients and those examined in preclinical models in terms of revealing key pathological hallmarks of the disease. In this review, we provide an overview of current but also novel AD biomarkers and how they relate to key constituents of the pathological cascade, highlighting confounding factors and pitfalls in interpretation, and also provide recommendations for standardized procedures during sample collection to enhance the translational validity of preclinical AD models.

Clinical significance of fluid biomarkers in Alzheimer's Disease

The number of patients with Alzheimer's Disease (AD) and other types of dementia disorders has drastically increased over the last decades. AD is a complex progressive neurodegenerative disease affecting about 14 million patients in Europe and the United States. The hallmarks of this disease are neurotic plaques consist of the Amyloid-β peptide (Aβ) and neurofibrillary tangles (NFTs) formed of hyperphosphorylated Tau protein (pTau). Currently, four CSF biomarkers: Amyloid beta 42 (Aβ42), Aβ42/40 ratio, Tau protein, and Tau phosphorylated at threonine 181 (pTau181) have been indicated as core neurochemical AD biomarkers. However, the identification of additional fluid biomarkers, useful in the prognosis, risk stratification, and monitoring of drug response is sorely needed to better understand the complex heterogeneity of AD pathology as well as to improve diagnosis of patients with the disease. Several novel biomarkers have been extensively investigated, and their utility must be proved and eventually integrated into guidelines for use in clinical practice. This paper presents the research and development of CSF and blood biomarkers for AD as well as their potential clinical significance. Upper panel: Aβ peptides are released from transmembrane Amyloid Precursor Protein (APP) under physiological conditions (blue arrow). In AD, however, pathologic accumulation of Aβ monomers leads to their accumulation in plaques (red arrow). This is reflected in decreased concentration of Aβ1-42 and decreased Aβ42/40 concentration ratio in the CSF. Lower panel: Phosphorylated Tau molecules maintain axonal structures; hyperphosphorylation of Tau (red arrow) in AD leads to degeneration of axons, and release of pTau molecules, which then accumulate in neurofibrillary tangles. This process is reflected by increased concentrations of Tau and pTau in the CSF.

Cerebrospinal fluid phospho-tau T217 outperforms T181 as a biomarker for the differential diagnosis of Alzheimer's disease and PET amyloid-positive patient identification

BACKGROUND

Cerebrospinal fluid biomarker profiles characterized by decreased amyloid-beta peptide levels and increased total and phosphorylated tau levels at threonine 181 (pT181) are currently used to discriminate between Alzheimer's disease and other neurodegenerative diseases. However, these changes are not entirely specific to Alzheimer's disease, and it is noteworthy that other phosphorylated isoforms of tau, possibly more specific for the disease process, have been described in the brain parenchyma of patients. The precise detection of these isoforms in biological fluids remains however a challenge.

METHODS

In the present study, we used the latest quantitative mass spectrometry approach, which achieves a sensitive detection in cerebrospinal fluid biomarker of two phosphorylated tau isoforms, pT181 and pT217, and first analyzed a cohort of probable Alzheimer's disease patients and patients with other neurological disorders, including tauopathies, and a set of cognitively normal controls. We then checked the validity of our results on a second cohort comprising cognitively normal individuals and patients with mild cognitive impairments and AD stratified in terms of their amyloid status based on PiB-PET imaging methods.

RESULTS

In the first cohort, pT217 but not pT181 differentiated between Alzheimer's disease patients and those with other neurodegenerative diseases and control subjects much more specificity and sensitivity than pT181. T217 phosphorylation was increased by 6.0-fold in patients with Alzheimer's disease whereas T181 phosphorylation was only increased by 1.3-fold, when compared with control subjects. These results were confirmed in the case of a second cohort, in which the pT217 cerebrospinal fluid levels marked out amyloid-positive patients with a sensitivity and a specificity of more than 90% (AUC 0.961; CI 0.874 to 0.995). The pT217 concentrations were also highly correlated with the PiB-PET values (correlation coefficient 0.72; P < 0.001).

CONCLUSIONS

Increased cerebrospinal fluid pT217 levels, more than those of pT181, are highly specific biomarkers for detecting both the preclinical and advanced forms of Alzheimer's disease. This finding should greatly improve the diagnosis of Alzheimer's disease, along with the correlations found to exist between pT217 levels and PiB-PET data. It also suggests that pT217 is a promising potential target for therapeutic applications and that a link exists between amyloid and tau pathology.

Uncovering the pathological functions of Ser404 phosphorylation by semisynthesis of a phosphorylated TDP-43 prion-like domain

Native and phosphorylated TDP-43 prion-like domains without any purification tags (wTDP PLD and pTDP PLD) were synthesized and studied.

Use of the tau protein-to-peptide ratio in CSF to improve diagnostic classification of Alzheimer's disease

Cerebrospinal fluid (CSF) tau and phospho-tau are well established biomarkers of Alzheimer's disease. While these measures are conventionally referred to as 'total tau' (T-tau) and 'phospho-tau' (P-tau), several truncated and modified tau forms exist that may relay additional diagnostic information. We evaluated the diagnostic performance of an endogenous tau peptide in CSF, tau 175-190, in the phosphorylated and non-phosphorylated state. A liquid chromatography-mass spectrometry (LC-MS) method was established to measure these peptides in CSF and was used to analyze two independent clinical cohorts; the first cohort included patients with Alzheimer's disease (AD, n = 15), Parkinson's disease (PD, n = 15), progressive supranuclear palsy (PSP, n = 15), and healthy controls (n = 15), the second cohort included AD patients (n = 16), and healthy controls (n = 24). In both cohorts T-tau and P-tau concentrations were determined by immunoassay. While tau 175-190 and P-tau 175-190 did not differentiate the study groups, the separation of AD and controls by T-tau (area under the ROC Curve (AUC) = 95%) and P-tau (AUC = 92%) was improved when normalizing the ELISA measurements to the concentrations of the endogenous peptides: T-tau/tau 175-190 (AUC = 100%), P-tau/P-tau 175-190 (AUC = 95%). The separation between patients and controls by T-tau (AUC = 88%) and P-tau (AUC = 82%) was similarly improved in the second cohort by taking the ratios of T-tau/tau 175-190 (AUC = 97%) and P-tau/P-tau 175-190 (AUC = 98%). In conclusion, our results suggest that the performance of the AD biomarkers T-tau and P-tau could be improved by normalizing their measurements to the endogenous peptides tau 175-190 and P-tau 175-190, possibly because these endogenous tau peptides serve to normalize for physiological, and disease-independent, secretion of tau from neurons to the extracellular space and the CSF. Finally, the observations made here add to the general applicability of mass spectrometry as a tool for rapid identification and accurate quantification of biomarker candidates.

LRRK2, alpha-synuclein, and tau: partners in crime or unfortunate bystanders?

The identification of genetic forms of Parkinson's disease (PD) has tremendously expanded our understanding of the players and mechanisms involved. Mutations in the genes encoding for alpha-synuclein (aSyn), LRRK2, and tau have been associated with familial and sporadic forms of the disease. aSyn is the major component of Lewy bodies and Lewy neurites, which are pathognomonic protein inclusions in PD. Hyperphosphorylated tau protein accumulates in neurofibrillary tangles in the brains of Alzheimer's disease patients but is also seen in the brains of PD patients. LRRK2 is a complex multi-domain protein with kinase and GTPase enzymatic activity. Since aSyn and tau are phosphoproteins, we review the possible interplay between the three proteins. Understanding the interplay between LRRK2, aSyn and tau is extremely important, as this may enable the identification of novel targets and pathways for therapeutic intervention.

Serum and cerebrospinal fluid tau protein level as biomarkers for evaluating acute spinal cord injury severity and motor function outcome

Tau protein, a microtubule-associated protein, has a high specific expression in neurons and axons. Because traumatic spinal cord injury mainly affects neurons and axons, we speculated that tau protein may be a promising biomarker to reflect the degree of spinal cord injury and prognosis of motor function. In this study, 160 female Sprague-Dawley rats were randomly divided into a sham group, and mild, moderate, and severe spinal cord injury groups. A laminectomy was performed at the T8 level to expose the spinal cord in all groups. A contusion lesion was made with the NYU-MASCIS impactor by dropping a 10 g rod from heights of 12.5 mm (mild), 25 mm (moderate) and 50 mm (severe) upon the exposed dorsal surface of the spinal cord. Tau protein levels were measured in serum and cerebrospinal fluid samples at 1, 6, 12, 24 hours, 3, 7, 14 and 28 days after operation. Locomotor function of all rats was assessed using the Basso, Beattie and Bresnahan locomotor rating scale. Tau protein concentration in the three spinal cord injury groups (both in serum and cerebrospinal fluid) rapidly increased and peaked at 12 hours after spinal cord injury. Statistically significant positive linear correlations were found between tau protein level and spinal cord injury severity in the three spinal cord injury groups, and between the tau protein level and Basso, Beattie, and Bresnahan locomotor rating scale scores. The tau protein level at 12 hours in the three spinal cord injury groups was negatively correlated with Basso, Beattie, and Bresnahan locomotor rating scale scores at 28 days (serum: r = −0.94; cerebrospinal fluid: r = −0.95). Our data suggest that tau protein levels in serum and cerebrospinal fluid might be a promising biomarker for predicting the severity and functional outcome of traumatic spinal cord injury.

Plasma neurofilament light as a potential biomarker of neurodegeneration in Alzheimer's disease

BACKGROUND

A growing body of evidence suggests that the plasma concentration of the neurofilament light chain (NfL) might be considered a plasma biomarker for the screening of neurodegeneration in Alzheimer's disease (AD).

METHODS

With a single molecule array method (Simoa, Quanterix), plasma NfL concentrations were measured in 99 subjects with AD at the stage of mild cognitive impairment (MCI-AD; n = 25) or at the stage of early dementia (ADD; n = 33), and in nondemented controls (n = 41); in all patients, the clinical diagnoses were in accordance with the results of the four core cerebrospinal fluid (CSF) biomarkers (amyloid β (Aβ)1-42, Aβ42/40, Tau, and pTau181), interpreted according to the Erlangen Score algorithm. The influence of preanalytical storage procedures on the NfL in plasma was tested on samples exposed to six different conditions.

RESULTS

NfL concentrations significantly increased in the samples exposed to more than one freezing/thawing cycle, and in those stored for 5 days at room temperature or at 4 °C. Compared with the control group of nondemented subjects (22.0 ± 12.4 pg/mL), the unadjusted plasma NfL concentration was highly significantly higher in the MCI-AD group (38.1 ± 15.9 pg/mL, p < 0.005) and even further elevated in the ADD group (49.1 ± 28.4 pg/mL; p < 0.001). A significant association between NfL and age (ρ = 0.65, p < 0.001) was observed; after correcting for age, the difference in NfL concentrations between AD and controls remained significant (p = 0.044). At the cutoff value of 25.7 pg/mL, unconditional sensitivity, specificity, and accuracy were 0.84, 0.78, and 0.82, respectively. Unadjusted correlation between plasma NfL and Mini Mental State Examination (MMSE) across all patients was moderate but significant (r = -0.49, p < 0.001). We observed an overall significant correlation between plasma NfL and the CSF biomarkers, but this correlation was not observed within the diagnostic groups.

CONCLUSIONS

This study confirms increased concentrations of plasma NfL in patients with Alzheimer's disease compared with nondemented controls.

Differential Hyperphosphorylation of Tau-S199, -T231 and -S396 in Organotypic Brain Slices of Alzheimer Mice. A Model to Study Early Tau Hyperphosphorylation Using Okadaic Acid

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder of the brain, characterized by extracellular aggregation of beta-amyloid (Aβ) and hyperphosphorylation of tau causing intraneuronal neurofibrillary tangles (NFTs). There is urgent need to study the interactions between Aβ and tau, especially to solve the question of the pathological cascade. In the present study, we aim to develop a model of organotypic brain slices in which both plaque and tau pathology can be examined. Organotypic brain slices (150 μm thick, coronal, at the hippocampal level) from adult (9 month) wildtype (WT, C57BL/6N) and transgenic AD mice (TG, APP_SweDI) were cultured for 2 weeks. To induce tau hyperphosphorylation 100 nM okadaic acid (OA), 10 μM wortmannin (WM) or both were added to the slices. Hyperphosphorylation of tau was tested at tau-S199, tau-T231 and tau-S396 using Western blot. Our data show that in TG mice with plaques a 50 kDa fragment of tau-S396 was hyperphosphorylated and that OA induced hyperphosphorylation of tau-S199. In WT mice (without plaques) OA caused hyperphosphorylation of a 50 kDa and a 38 kDa tau-T231 form and a 25 kDa sdftau-S396 fragment. The N-methyl-D-aspartate (NMDA) antagonist MK801 (1 μM) did not block these effects. Immunohistochemistry showed diffuse increased tau-S396 and tau-T231-like immunoreactivities at the hippocampal level but no formation of NFTs. Confocal microscopy indicated, that pTau-T231 was preferentially located in cytoplasma surrounding nuclei whereas pTau-S396 was found mainly in nerve fibers and strongly associated with plaques. In conclusion we provide a novel in vitro model to study both plaque and tau hyperphosphorylation but not NFTs, which could be useful to study pathological processes in AD and to screen for drugs.

Non-Phosphorylated Tau as a Potential Biomarker of Alzheimer's Disease: Analytical and Diagnostic Characterization

BACKGROUND

Virtually nothing is known about a potential diagnostic role of non-phospho-epitopes of Tau (Non-P-Tau) in cerebrospinal fluid (CSF).

OBJECTIVE

To establish and analytically and clinically characterize the first assay capable to measure concentrations of Non-P-Tau in human CSF.

METHODS

An antibody (1G2) was developed that selectively binds to the Tau molecule non-phosphorylated at the positions T175 and T181, and was used in establishing a sandwich ELISA capable to measure Non-P-Tau in human CSF, following analytical and clinical validation of the method.

RESULTS

The 1G2 antibody shows decreasing reactivity to tau peptides containing phosphorylation mainly at positions T175 and T181. Detection limit of the assay is 25 pg/ml; the coefficients of variation (CVs) of the optical densities of the repeated standard curves were between 3.6-15.9%. Median intra-assay imprecision of double measurements was 4.8%; inter-assay imprecision was in the range of 11.2% - 15.3%. Non-P-Tau concentrations are stable in the CSF samples sent to distinct laboratories under ambient temperature; inter-laboratory variation was approximately 30%. The Non-P-Tau CSF concentrations were highly significantly increased in patients with Alzheimer's disease in stage of mild cognitive impairment or dementia (AD/MCI, n = 58, 109.2±32.0 pg/mL) compared to the non-demented Controls (n = 42, 62.1±9.3 pg/mL, p < 0.001). At the cut-off of 78.3 pg/mL, the sensitivity and the specificity were 94.8% and 97.6%, respectively.

CONCLUSION

For the first time, an assay is reported to reliably measure concentrations of non-phosphorylated Tau in human CSF.

ReMAPping the microtubule landscape: How phosphorylation dictates the activities of microtubule-associated proteins

Classical microtubule-associated proteins (MAPs) were originally identified based on their co-purification with microtubules assembled from mammalian brain lysate. They have since been found to perform a range of functions involved in regulating the dynamics of the microtubule cytoskeleton. Most of these MAPs play integral roles in microtubule organization during neuronal development, microtubule remodeling during neuronal activity, and microtubule stabilization during neuronal maintenance. As a result, mutations in MAPs contribute to neurodevelopmental disorders, psychiatric conditions, and neurodegenerative diseases. MAPs are post-translationally regulated by phosphorylation depending on developmental time point and cellular context. Phosphorylation can affect the microtubule affinity, cellular localization, or overall function of a particular MAP and can thus have profound implications for neuronal health. Here we review MAP1, MAP2, MAP4, MAP6, MAP7, MAP9, tau, and DCX, and how each is regulated by phosphorylation in neuronal physiology and disease. Developmental Dynamics 247:138-155, 2018. © 2017 Wiley Periodicals, Inc.

Small molecular floribundiquinone B derived from medicinal plants inhibits acetylcholinesterase activity

Being a neurodegenerative disorder, Alzheimer's disease (AD) is the one of the most terrible diseases. And acetylcholinesterase (AChE) is considered as an important target for treating AD. Acetylcholinesterase inhibitors (AChEI) are considered to be one of the effective drugs for the treatment of AD. The aim of this study is to find a novel potential AChEI as a drug for the treatment of AD. In this study, instead of using the synthetic compounds, we used those extracted from plants to investigate the interaction between floribundiquinone B (FB) and AChE by means of both the experimental approach such as fluorescence spectra, ultraviolet-visible (UV-vis) absorption spectrometry, circular dichroism (CD) and the theoretical approaches such as molecular docking. The findings reported here have provided many useful clues and hints for designing more effective and less toxic drugs against Alzheimer's disease.

Microstructural white matter alterations in preclinical Alzheimer's disease detected using free water elimination diffusion tensor imaging

Brain changes associated with Alzheimer's disease (AD) begin decades before disease diagnosis. While β-amyloid plaques and neurofibrillary tangles are defining features of AD, neuronal loss and synaptic pathology are closely related to the cognitive dysfunction. Brain imaging methods that are tuned to assess degeneration of myelinated nerve fibers in the brain (collectively called white matter) include diffusion tensor imaging (DTI) and related techniques, and are expected to shed light on disease-related loss of structural connectivity. Participants (N = 70, ages 47-76 years) from the Wisconsin Registry for Alzheimer's Prevention study underwent DTI and hybrid diffusion imaging to determine a free-water elimination (FWE-DTI) model. The study assessed the extent to which preclinical AD pathology affects brain white matter. Preclinical AD pathology was determined using cerebrospinal fluid (CSF) biomarkers. The sample was enriched for AD risk (APOE ε4 and parental history of AD). AD pathology assessed by CSF analyses was significantly associated with altered microstructure on both DTI and FWE-DTI. Affected regions included frontal, parietal, and especially temporal white matter. The f-value derived from the FWE-DTI model appeared to be the most sensitive to the relationship between the CSF AD biomarkers and microstructural alterations in white matter. These findings suggest that white matter degeneration is an early pathological feature of AD that may have utility both for early disease detection and as outcome measures for clinical trials. More complex models of microstructural diffusion properties including FWE-DTI may provide increased sensitivity to early brain changes associated with AD over standard DTI.

2D-SAR and 3D-QSAR analyses for acetylcholinesterase inhibitors

Alzheimer's disease (AD) accounts for almost three quarters of dementia patients and interferes people's normal life. Great progress has been made recently in the study of Acetylcholinesterase (AChE), known as one of AD's biomarkers. In this study, acetylcholinesterase inhibitors (AChEI) were collected to build a two-dimensional structure-activity relationship (2D-SAR) model and three-dimensional quantitative structure-activity relationship (3D-QSAR) model based on feature selection method combined with random forest. After calculation, the prediction accuracy of the 2D-SAR model was 89.63% by using the tenfold cross-validation test and 87.27% for the independent test set. Three cutting ways were employed to build 3D-QSAR models. A model with the highest [Formula: see text] (cross-validated correlation coefficient) and [Formula: see text](non-cross-validated correlation coefficient) was obtained to predict AChEI activity. The mean absolute error (MAE) of the training set and the test set was 0.0689 and 0.5273, respectively. In addition, molecular docking was also employed to reveal that the ionization state of the compounds had an impact upon their interaction with AChE. Molecular docking results indicate that Ser124 might be one of the active site residues.

Cerebrospinal fluid biomarkers of infantile congenital hydrocephalus

Introduction

Hydrocephalus is a complex neurological disorder with a pervasive impact on the central nervous system. Previous work has demonstrated derangements in the biochemical profile of cerebrospinal fluid (CSF) in hydrocephalus, particularly in infants and children, in whom neurodevelopment is progressing in parallel with concomitant neurological injury. The objective of this study was to examine the CSF of children with congenital hydrocephalus (CHC) to gain insight into the pathophysiology of hydrocephalus and identify candidate biomarkers of CHC with potential diagnostic and therapeutic value.

Methods

CSF levels of amyloid precursor protein (APP) and derivative isoforms (sAPPα, sAPPβ, Aβ₄₂), tau, phosphorylated tau (pTau), L1CAM, NCAM-1, aquaporin 4 (AQP4), and total protein (TP) were measured by ELISA in 20 children with CHC. Two comparative groups were included: age-matched controls and children with other neurological diseases. Demographic parameters, ventricular frontal-occipital horn ratio, associated brain malformations, genetic alterations, and surgical treatments were recorded. Logistic regression analysis and receiver operating characteristic curves were used to examine the association of each CSF protein with CHC.

Results

CSF levels of APP, sAPPα, sAPPβ, Aβ₄₂, tau, pTau, L1CAM, and NCAM-1 but not AQP4 or TP were increased in untreated CHC. CSF TP and normalized L1CAM levels were associated with FOR in CHC subjects, while normalized CSF tau levels were associated with FOR in control subjects. Predictive ability for CHC was strongest for sAPPα, especially in subjects ≤12 months of age (p<0.0001 and AUC = 0.99), followed by normalized sAPPβ (p = 0.0001, AUC = 0.95), tau, APP, and L1CAM. Among subjects ≤12 months, a normalized CSF sAPPα cut-point of 0.41 provided the best prediction of CHC (odds ratio = 528, sensitivity = 0.94, specificity = 0.97); these infants were 32 times more likely to have CHC.

Conclusions

CSF proteins such as sAPPα and related proteins hold promise as biomarkers of CHC in infants and young children, and provide insight into the pathophysiology of CHC during this critical period in neurodevelopment.

Bamboo leaf extract improves spatial learning ability in a rat model with senile dementia

Senile dementia (SD) is a syndrome characterized by progressive neurological deterioration. Treatment for the disease is still under investigation. Bamboo leaf extract (B-extract) has been known for its biological efficacy in anti-oxidant and anti-cancer activities. However, study on B-extract for its protection against dementia is very limited. The effect of B-extract on a rat model with SD was examined. B-extract improved spatial learning ability of the dementia rats. The hippocampus of dementia model rats showed reduced levels of acetylcholine (ACh), epinephrine (E), norepinephrine (NE), and dopamine (DA), and increased activities of acetylcholine esterase (AChE) and monoamine oxidase (MAO). Treatment with B-extract 20 mg/(kg·d) for 7 weeks significantly inhibited the enzyme activity compared with untreated dementia rats, and raised the levels of ACh, E, and DA in the hippocampus. In addition, treatment with B-extract elevated the level of γ-aminobutyric acid (GABA), but reduced the level of glutamate (Glu) in the brain. These data suggest that B-extract might be a potential drug in treating impairment of spatial memory in dementia rats by regulating the central neurotransmitter function.

Fluorescent gold nanoclusters for in vivo target imaging of Alzheimer's disease

Fluorescent gold nanoclusters forin vivotarget imaging provides a new way for rapid and early diagnosis of Alzheimer's disease.

Biomarkers of Alzheimer's disease and mild cognitive impairment: a current perspective

A growing body of evidence supports the application of the neurochemical dementia diagnostics (NDD) biomarkers for the diagnosis of dementing conditions. Biomarkers of Alzheimer's disease (AD) were recently classified as these reflecting amyloid β pathology (decreased CSF concentrations of Aβ42 and/or positive Aβ PET scan) and these reflecting neurodegeneration (increased CSF Tau concentrations, decreased uptake of FDG on FDG-PET, and cerebral atrophy on structural MRI). Particularly important seems the role of the biomarkers in the early diagnosis of AD, as the first pathophysiologic events observable in the CSF and amyloid β-PET occur years and perhaps decades before the onset of the earliest clinical symptoms. Therefore, the NDD tools enable the diagnosis of AD already in the early preclinical stage. This review summarizes pathophysiology underlying the CSF biomarkers, following a discussion of their role in the current guidelines for the diagnostic procedures.

Validation of the Erlangen Score Algorithm for the Prediction of the Development of Dementia due to Alzheimer's Disease in Pre-Dementia Subjects

BACKGROUND

In previous studies, a dichotomous stratification of subjects into "cerebrospinal fluid (CSF) normal" and "CSF pathologic" was used to investigate the role of biomarkers in the prediction of progression to dementia in pre-dementia/mild cognitive impairment subjects. With the previously published Erlangen Score Algorithm, we suggested a division of CSF patterns into five groups, covering all possible CSF result combinations based on the presence of pathologic tau and/or amyloid-β CSF values.

OBJECTIVE

This study aimed to validate the Erlangen Score diagnostic algorithm based on the results of biomarkers analyses obtained in different patients cohorts, with different pre-analytical protocols, and with different laboratory analytical platforms.

METHODS

We evaluated the algorithm in two cohorts of pre-dementia subjects: the US-Alzheimer's Disease Neuroimaging Initiative and the German Dementia Competence Network.

RESULTS

In both cohorts, the Erlangen scores were strongly associated with progression to Alzheimer's disease. Neither the scores of the progressors nor the scores of the non-progressors differed significantly between the two projects, in spite of significant differences in the cohorts, laboratory methods, and the samples treatment.

CONCLUSIONS

Our findings confirm the utility of the Erlangen Score algorithm as a useful tool in the early neurochemical diagnosis of Alzheimer's disease.

CSF proteome: a protein repository for potential biomarker identification

Proteomic analysis is not limited to the analysis of serum or tissues. Synovial, peritoneal, pericardial and cerebrospinal fluid represent unique proteomes for disease diagnosis and prognosis. In particular, cerebrospinal fluid serves as a rich source of putative biomarkers that are not solely limited to neurologic disorders. Peptides, proteolytic fragments and antibodies are capable of crossing the blood-brain barrier, thus providing a repository of pathologic information. Proteomic technologies such as immunoblotting, isoelectric focusing, 2D gel electrophoresis and mass spectrometry have proven useful for deciphering this unique proteome. Cerebrospinal fluid proteins are generally less abundant than their corresponding serum counterparts, necessitating the development and use of sensitive analytical techniques. This review highlights some of the promising areas of cerebrospinal fluid proteomic research and their clinical applications.

Cerebrospinal fluid biomarkers in clinical subtypes of early-onset Alzheimer's disease

BACKGROUND/AIMS

Accurate diagnosis of sporadic early-onset Alzheimer's disease (EOAD) can be challenging, and cerebrospinal fluid (CSF) biomarkers may assist in this process. We compared CSF indices between three EOAD subtypes: amnestic, logopenic progressive aphasia (LPA), and posterior cortical atrophy (PCA).

METHODS

We identified 21 amnestic EOAD, 20 LPA, and 12 PCA patients with CSF data, which included amyloid β1-42 (Aβ42), total tau (t-tau), phospho-tau181 (p-tau), and Aβ42/t-tau index (ATI) levels.

RESULTS

Aβ42 and ATI levels were similar across groups, but t-tau and p-tau levels were significantly lower in PCA patients.

CONCLUSIONS

The Aβ42 and ATI data confirm the commonality of the Aβ pathology in EOAD. The lower tau indices in PCA patients may reflect differences in the distribution of neurofibrillary tangles or rates of neurodegeneration.

CSF p-Tau levels in the prediction of Alzheimer's disease

The two hallmarks of Alzheimer's disease (AD) are neurofibrillary tangles and amyloid plaques. Neurofibrillary tangles are formed due to the hyperphosphorylation of tau protein. There is an urgent need to develop a reliable biomarker for the diagnosis of AD. Cerebrospinal fluid (CSF) is surrounding the brain and reflects the major neuropathological features in the AD brain. Diagnosis, disease progression and drug actions rely on the AD biomarkers. Mainly CSF tau and phosphorylated tau (p-Tau) have been observed to serve the purpose for early AD. Keeping in view the early appearance of p-Tau in CSF, we analyzed p-Tau levels in 23 AD, 23 Non AD type dementia (NAD), 23 Neurological control (NC) and 23 Healthy control (HC) North Indian patients. The levels of p-Tau were found to be increased in AD patients (67.87±18.05 pg/ml, SEM 3.76) compared with NAD (47.55±7.85 pg/ml, SEM 1.64), NC (34.42±4.51 pg/ml, SEM 0.94) and HC (27.09±7.18 pg/ml, SEM 1.50). The resulting sensitivity for AD with NAD was 80.27% whereas with respect to the NAD, NC and HC was 85.40%. Therefore elevated levels of p-Tau in AD can be exploited as a predictive biomarker in North Indian AD patients.

Cerebrospinal fluid biomarkers of Alzheimer's disease in healthy elderly

Numerous studies have shown that Alzheimer's Disease (AD) pathology begins before the onset of clinical symptoms. Because therapies are likely to be more effective if they are implemented early in the disease progression, it is necessary to identify reliable biomarkers to detect AD pathology in the early stages of the disease, ideally in presymptomatic individuals. Recent research has identified three candidate cerebrospinal fluid (CSF) biomarkers that reflect AD pathology: amyloid beta, total tau protein (t-tau), and tau protein phosphorylated at AD-specific epitopes (p-tau). They are useful in supporting the AD diagnosis and have predictive value for AD when patients are in the stage of mild cognitive impairment (MCI). However, their predictive utility in cognitively healthy subjects is still being evaluated. We conducted a review of studies published between 1993 and 2011 and summarized their findings on the role of CSF biomarkers for AD in healthy elderly.

Alzheimer's therapeutics: continued clinical failures question the validity of the amyloid hypothesis-but what lies beyond?

The worldwide incidence of Alzheimer's disease (AD) is increasing with estimates that 115 million individuals will have AD by 2050, creating an unsustainable healthcare challenge due to a lack of effective treatment options highlighted by multiple clinical failures of agents designed to reduce the brain amyloid burden considered synonymous with the disease. The amyloid hypothesis that has been the overarching focus of AD research efforts for more than two decades has been questioned in terms of its causality but has not been unequivocally disproven despite multiple clinical failures, This is due to issues related to the quality of compounds advanced to late stage clinical trials and the lack of validated biomarkers that allow the recruitment of AD patients into trials before they are at a sufficiently advanced stage in the disease where therapeutic intervention is deemed futile. Pursuit of a linear, reductionistic amyloidocentric approach to AD research, which some have compared to a religious faith, has resulted in other, equally plausible but as yet unvalidated AD hypotheses being underfunded leading to a disastrous roadblock in the search for urgently needed AD therapeutics. Genetic evidence supporting amyloid causality in AD is reviewed in the context of the clinical failures, and progress in tau-based and alternative approaches to AD, where an evolving modus operandi in biomedical research fosters excessive optimism and a preoccupation with unproven, and often ephemeral, biomarker/genome-based approaches that override transparency, objectivity and data-driven decision making, resulting in low probability environments where data are subordinate to self propagating hypotheses.

Tau phosphorylation pathway genes and cerebrospinal fluid tau levels in Alzheimer's disease

Alzheimer's disease (AD) is characterized by the presence in the brain of amyloid plaques, consisting predominately of the amyloid β peptide (Aβ), and neurofibrillary tangles, consisting primarily of tau. Hyper-phosphorylated-tau (p-tau) contributes to neuronal damage, and both p-tau and total-tau (t-tau) levels are elevated in AD cerebrospinal fluid (CSF) compared to cognitively normal controls. Our hypothesis was that increased ratios of CSF phosphorylated-tau levels relative to total-tau levels correlate with regulatory region genetic variation of kinase or phosphatase genes biologically associated with the phosphorylation status of tau. Eighteen SNPs located within 5' and 3' regions of 5 kinase and 4 phosphatase genes, as well as two SNPs within regulatory regions of the MAPT gene were chosen for this analysis. The study sample consisted of 101 AD patients and 169 cognitively normal controls. Rs7768046 in the FYN kinase gene and rs913275 in the PPP2R4 phosphatase gene were both associated with CSF p-tau and t-tau levels in AD. These SNPs were also differentially associated with either CSF t-tau (rs7768046) or CSF p-tau (rs913275) relative to t-tau levels in AD compared to controls. These results suggest that rs7768046 and rs913275 both influence CSF tau levels in an AD-associated manner.

Neurochemical dementia diagnostics for Alzheimer’s disease and other dementias: an ISO 15189 perspective

Dementia is one of the most common causes of health problems in the elderly populations of Western industrialized countries. A combined analysis of cerebrospinal fluid-based neurochemical dementia diagnostics biomarkers (amyloid-β peptides, total tau and phosphorylated forms of tau) provides sensitivity and specificity in the range of 85% for the diagnosis of Alzheimer’s disease, the most common cause of dementia. The alterations occur very early in the course of neurodegeneration, enabling medical follow-up of persons with increased risk of developing dementia. With a growing number of laboratories performing neurochemical dementia diagnostics routinely, it is important to standardize protocols and laboratory performance to enable comparisons of results and their interpretations. Together with the recently published expert guidelines for sample handling and preparation, as well as the interpretation (post-analytical) algorithms developed by experienced centers, ISO 15189 norm provides an extremely useful tool for standardization of neurochemical dementia diagnostics.

Neurochemical dementia diagnostics in Alzheimer's disease: where are we now and where are we going?

Neurochemical dementia diagnostics (NDD) is a routine laboratory tool used in the diagnostic process for patients with neurodegenerative disorders, such as Alzheimer's disease. Currently, two groups of biomarkers analyzed in the cerebrospinal fluid are considered - namely amyloid-β peptides and Tau proteins - along with the hyperphosphorylated forms of the latter (pTau). Current directions in the development of NDD include the following: search for novel biomarkers with improved analytical or diagnostic performance; optimization of the analysis of the biomarkers already available (e.g., by improved quality control and interlaboratory comparison of results); applications of novel technologies enabling better management of patient samples; and search for biomarkers in the blood. This article presents the state-of-the-art in the field of cerebrospinal fluid-based NDD, and also summarizes some of the hypotheses of how the future development of NDD tools might look.

Increased concentration of the CSF Tau protein and its phosphorylated form in the late juvenile metachromatic leukodystrophy form: a case report

Metachromatic leukodystrophy (MLD) is an autosomal recessive, lysosomal storage disease due to deficiency or absence of arylsulfatase A enzyme (ASA) with sulfatide accumulation in the central and peripheral nervous system, kidneys, and gallbladder, leading to many dysfunctions. One of the clinical forms of the disease is a late juvenile MLD. To our best knowledge, this is the first report describing increased Tau/pTau and normal Aβ1-42 concentrations in the CSF of the late juvenile MLD patient.

[The future of biomarkers in dementia diagnostics]

Neurochemical dementia diagnostics (NDD) is a routine laboratory tool in the diagnostic process of patients with neurodegenerative disorders, such as Alzheimer's disease (AD). Currently, two groups of biomarkers analyzed in the cerebrospinal fluid (CSF) are being considered, namely amyloid β (Aβ) peptides and tau proteins, along with the hyperphosphorylated forms of the latter (p-tau). Current directions in the development of NDD include the following: 1. search for novel biomarkers with improved analytical or diagnostic performance; 2. search for biomarkers in the blood; 3. applications of novel technologies enabling better management of patient samples; 4. optimization of the analysis of the biomarkers already available (for example, by improved quality control and inter-laboratory comparison of results). This review presents the state of the art in the field of CSF-based NDD and also summarizes some of the hypotheses of how the future development of NDD tools might look.

Comparison of immunosorbent assays for the quantification of biomarkers for Alzheimer's disease in human cerebrospinal fluid

BACKGROUND

The clinical diagnosis of Alzheimer's disease in early stages may be substantiated by the quantification of the biomarkers Abeta42, Abeta40 and total-Tau (t-Tau) in cerebrospinal fluid (CSF). Different commercially available immunosorbent assays yield reliable results, yet the absolute values obtained may differ in between tests.

METHODS

We used CSF samples from patients that reported to our memory clinic. Enzyme-linked immunosorbent assays obtained from Innogenetics were used for the quantification of Abeta42 and t-Tau, test kits from IBL International were used to determine Abeta42 and Abeta40 concentrations. The multiplex assay system obtained from Mesoscale Discovery (MSD) Systems was used for the quantification of all three biomarkers.

RESULTS

For all biomarkers, the absolute values obtained with different test systems differ. However, the data sets highly correlate for all comparisons, with the MSD test system proving to be slightly more sensitive. Correlation coefficients (c) for the Abeta42 and Abeta40 quantifications lie between c = 0.80 and c = 0.87, and for the t-Tau quantifications we determined c = 0.99.

CONCLUSION

We conclude that all assays evaluated give reliable results, yet absolute values obtained have to be assessed differently within the framework of diagnostic procedures, depending on the system used.

Anesthesia in presymptomatic Alzheimer's disease: a study using the triple-transgenic mouse model

BACKGROUND

Experimental evidence suggests that anesthetics accelerate symptomatic neurodegenerative disorders such as Alzheimer's disease (AD). Because AD pathology precedes symptoms, we asked ourselves whether anesthetic exposure in the presymptomatic interval accelerated neuropathology and appearance of symptoms.

METHODS

Triple-transgenic AD mice were exposed to general aesthetics, either halothane or isoflurane, at 2, 4, and 6 months of age, they then underwent water maze cognitive testing 2 months later, and subsequently their brains were analyzed using enzyme-linked immunosorbent assay, immunoblots, and immunohistochemistry for amyloid and tau pathology and biomarkers.

RESULTS

Learning and memory improved after halothane exposure in the 2-month-old group relative to controls, but no changes were noted in the isoflurane group. When gender was examined in all age groups, females exposed to halothane performed better as compared with those exposed to isoflurane or controls. Therefore, improvement in the 2-month exposure group is most likely because of a gender effect. Level of phospho-tau in the hippocampus was significantly increased 2 months after anesthesia, especially in the 6-month exposure group, but changes in amyloid, caspase, microglia, or synaptophysin levels were not detected.

CONCLUSIONS

These results indicate that exposure to two different inhalation-type anesthetics during the presymptomatic phase of AD does not accelerate cognitive decline, after 2 months, and may cause a stress response, marked by hippocampal phosphorylated tau, resulting in preconditioning against the ongoing neuropathology, primarily in female mice.

Developing predictive CSF biomarkers-a challenge critical to success in Alzheimer's disease and neuropsychiatric translational medicine

The need to develop effective treatments for Alzheimer's disease has been confounded by repeated clinical failures where promising new chemical entities that have been extensively characterized in preclinical models of Alzheimer's disease have failed to show efficacy in the human disease state. This has been attributed to: the selection of drug targets that have yet to be shown as causal to the disease as distinct from being the result of the disease process, a lack of congruence in the animal models of Alzheimer's disease, wild-type and transgenic, to the human disease, and the enrollment of patients in proof of concept clinical trials who are at too advanced a stage of the disease to respond to any therapeutic. The development of validated biomarkers that can be used for disease diagnosis and progression is anticipated to improve patient enrollment in clinical trials, to develop new animal models and to identify new disease targets for drug discovery. The present review assesses the status of current efforts in developing CSF biomarkers for Alzheimer's disease and briefly discusses the status of CSF biomarker efforts in schizophrenia, depression, Parkinson's disease and multiple sclerosis.

Summary of cerebrospinal fluid routine parameters in neurodegenerative diseases

In neurodegenerative diseases, cerebrospinal fluid analysis (CSF) is predominantly performed to exclude inflammatory diseases and to perform a risk assessment in dementive disorders by measurement of tau proteins and amyloid beta peptides. However, large scale data on basic findings of CSF routine parameters are generally lacking. The objective of the study was to define a normal reference spectrum of routine CSF parameters in neurodegenerative diseases. Routine CSF parameters (white cell count, lactate and albumin concentrations, CSF/serum quotients of albumin (Q_alb), IgG, IgA, IgM, and oligoclonal IgG bands (OCB)) were retrospectively analyzed in an academic research setting. A total of 765 patients (Alzheimer’s disease (AD), Parkinson’s disease (PD), Parkinson’s disease dementia (PDD), vascular dementia (VD), frontotemporal lobar degeneration (FTLD), progressive supranuclear palsy (PSP), multisystem atrophy (MSA), motor neuron diseases (MND), spinocerebellar ataxia (SCA), Huntington’s disease (HD)) and non-demented control groups including a group of patients with muscular disorders (MD). The main outcome measures included statistical analyses of routine CSF parameters. Mildly elevated Q_alb were found in a small percentage of nearly all subgroups and in a higher proportion of patients with PSP, MSA, VD, PDD, and MND. With the exception of 1 MND patient, no intrathecal Ig synthesis was observed. Isolated OCBs in CSF were sometimes found in patients with neurodegenerative diseases without elevated cell counts; lactate levels were always normal. A slightly elevated Q_alb was observed in a subgroup of patients with neurodegenerative diseases and does not exclude the diagnosis. Extensive elevation of routine parameters is not characteristic and should encourage a re-evaluation of the clinical diagnosis.

Perfusion Imaging with SPECT in the Era of Pathophysiology-Based Biomarkers for Alzheimer's Disease

SPECT allows registration of regional cerebral blood flow (rCBF) which is altered in a characteristic temporoparietal pattern in Alzheimer's Dementia. Numerous studies have shown the diagnostic value of reduced cerebral blood flow and metabolic changes using perfusion SPECT and FDG-PEPT in AD diagnosis as well as in differential diagnosis against frontotemporal dementia, dementia with Lewy bodies and vascular disease. Recently more pathophysiology-based biomarkers in CSF and Amyloid-PET tracers have been developed that probably have a higher diagnostic accuracy than the more indirect rCBF changes seen in perfusion SPECT. In the paper review, we describe recent advances in AD biomarkers as well as improvements in the SPECT technique.

Altered serum glycomics in Alzheimer disease: a potential blood biomarker?

We investigated whether blood N-glycan changes can be used as a diagnostic biomarker for Alzheimer disease (AD). We used DNA sequencer-assisted, fluorophore-assisted carbohydrate electrophoresis (DSA-FACE) technology to assay N-glycans in sera from 79 autopsy-confirmed dementia patients and 149 healthy controls. One N-glycan (NA2F) was substantially decreased in AD patients but not in controls. Use of NA2F for discriminating AD between dementia patients and healthy controls showed a diagnostic accuracy of 85.7% +/- 2.8% with 92% specificity and 70% sensitivity. The decrease in the level of NA2F in AD patients compared to non-AD patients was more pronounced in females (p < 0.0001) than in males (p < 0.014). Use of NA2F to differentiate female AD from female non-AD patients reached a diagnostic accuracy of 90.7% +/- 4.8 %. Pearson correlation analysis showed that in female dementia patients, serum NA2F levels were significantly correlated with the cerebrospinal fluid (CSF) beta-amyloid peptide of 42 amino acids (Abeta(1-42)) and tau phosphorylated at threonine 181 (P-tau(181P)) levels, whereas in male dementia patients serum NA2F levels were significantly correlated only with CSF total tau protein (T-tau) level. Thus, we suggest that the serum N-glycan marker might be suitable for longitudinal and follow-up studies.

Biological markers and Alzheimer disease: a canadian perspective

Decreased β-amyloid_1-42 and increased phospho-tau protein levels in the cerebrospinal fluid (CSF) are currently the most accurate chemical neurodiagnostics of sporadic Alzheimer disease (AD). A report (2007) of the Third Canadian Consensus Conference on the Diagnosis and Treatment of Dementia (2006) recommended that biological markers should not be currently requisitioned by primary care physicians in the routine investigation of subjects with memory complaints. Consideration for such testing should prompt patient referral to a specialist engaged in dementia evaluations or a Memory Clinic. The specialist should consider having CSF biomarkers (β-amyloid_1-42 and phospho-tau) measured at a reputable facility in restricted cases presenting with atypical features and diagnostic confusion, but not as a routine procedure in all individuals with typical sporadic AD phenotypes. We submit that developments in the field of AD biomarker discovery since publication of the 3rd CCCDTD consensus data do not warrant revision of the 2007 recommendations.