The neutrophil to lymphocyte ratio associates with markers of Alzheimer's disease pathology in cognitively unimpaired elderly people

BACKGROUND

An elevated neutrophil-lymphocyte ratio (NLR) in blood has been associated with Alzheimer's disease (AD). However, an elevated NLR has also been implicated in many other conditions that are risk factors for AD, prompting investigation into whether the NLR is directly linked with AD pathology or a result of underlying comorbidities. Herein, we explored the relationship between the NLR and AD biomarkers in the cerebrospinal fluid (CSF) of cognitively unimpaired (CU) subjects. Adjusting for sociodemographics, APOE4, and common comorbidities, we investigated these associations in two cohorts: the Alzheimer's Disease Neuroimaging Initiative (ADNI) and the M.J. de Leon CSF repository at NYU. Specifically, we examined associations between the NLR and cross-sectional measures of amyloid-β42 (Aβ42), total tau (t-tau), and phosphorylated tau181 (p-tau), as well as the trajectories of these CSF measures obtained longitudinally.

RESULTS

A total of 111 ADNI and 190 NYU participants classified as CU with available NLR, CSF, and covariate data were included. Compared to NYU, ADNI participants were older (73.79 vs. 61.53, p < 0.001), had a higher proportion of males (49.5% vs. 36.8%, p = 0.042), higher BMIs (27.94 vs. 25.79, p < 0.001), higher prevalence of hypertensive history (47.7% vs. 16.3%, p < 0.001), and a greater percentage of Aβ-positivity (34.2% vs. 20.0%, p = 0.009). In the ADNI cohort, we found cross-sectional associations between the NLR and CSF Aβ42 (β = -12.193, p = 0.021), but not t-tau or p-tau. In the NYU cohort, we found cross-sectional associations between the NLR and CSF t-tau (β = 26.812, p = 0.019) and p-tau (β = 3.441, p = 0.015), but not Aβ42. In the NYU cohort alone, subjects classified as Aβ + (n = 38) displayed a stronger association between the NLR and t-tau (β = 100.476, p = 0.037) compared to Aβ- subjects or the non-stratified cohort. In both cohorts, the same associations observed in the cross-sectional analyses were observed after incorporating longitudinal CSF data.

CONCLUSIONS

We report associations between the NLR and Aβ42 in the older ADNI cohort, and between the NLR and t-tau and p-tau in the younger NYU cohort. Associations persisted after adjusting for comorbidities, suggesting a direct link between the NLR and AD. However, changes in associations between the NLR and specific AD biomarkers may occur as part of immunosenescence.

Heparan sulfate proteoglycans: Mediators of cellular and molecular Alzheimer's disease pathogenic factors via tunnelling nanotubes?

Neurological disorders impact around one billion individuals globally (15 % approx.), with significant implications for disability and mortality with their impact in Australia currently amounts to 6.8 million deaths annually. Heparan sulfate proteoglycans (HSPGs) are complex extracellular molecules implicated in promoting Tau fibril formation resulting in Tau tangles, a hallmark of Alzheimer's disease (AD). HSPG-Tau protein interactions contribute to various AD stages via aggregation, toxicity, and clearance, largely via interactions with the glypican 1 and syndecan 3 core proteins. The tunnelling nanotubes (TNTs) pathway is emerging as a facilitator of intercellular molecule transport, including Tau and Amyloid β proteins, across extensive distances. While current TNT-associated evidence primarily stems from cancer models, their role in Tau propagation and its effects on recipient cells remain unclear. This review explores the interplay of TNTs, HSPGs, and AD-related factors and proposes that HSPGs influence TNT formation in neurodegenerative conditions such as AD.

Murine Traumatic Brain Injury Model Comparison: Closed Head Injury Versus Controlled Cortical Impact

INTRODUCTION

Various murine models have been utilized to study TBI, including closed head injury (CHI) and controlled cortical impact (CCI), without direct comparison. The aim of our study was to evaluate these models to determine differences in neurological and behavioral outcomes postinjury.

METHODS

Male C57B/6 mice (9-10 wk) were separated into six groups including: untouched, sham craniotomy (4 mm), CCI 0.9 mm depth of impact, CCI 1.6 mm, CCI 2.2 mm, and CHI. CCI was performed using a 3 mm impact tip at a velocity of 5 m/s, dwell time of 250 ms, and depth as noted above. CHI was completed with a centered 400 g weight drop from 1 cm height. Mice were survived to 14-d (n = 5 per group) and 30-d (n = 5 per group) respectively for histological analysis of p-tau within the hippocampus. These mice underwent Morris Water Maze memory testing and Rotarod motor testing. Serum was collected from a separate cohort of mice (n = 5 per group) including untouched, isoflurane only, CCI 1.6 mm, CHI at 1, 4, 6, and 24 h for analysis of neuron specific enolase and glial fibrillary acidic protein (GFAP) via ELISA. Laser speckle contrast imaging was analyzed prior to and after impact in the CHI and CCI 1.6 mm groups.

RESULTS

There were no significant differences in Morris Water Maze or Rotarod testing times between groups at 14- or 30-d. P-tau was significantly elevated in all groups except CCI 1.6 mm contralateral and CCI 2.2 mm ipsilateral compared to untouched mice at 30-d. P-tau was also significantly elevated in the CHI group at 30 d compared to CCI 1.6 mm contralateral and CCI 2.2 mm on both sides. GFAP was significantly increased in mice undergoing CHI (9959 ± 91 pg/mL) compared to CCI (2299 ± 1288 pg/mL), isoflurane only (133 ± 75 pg/mL), and sham (86 ± 58 pg/mL) at 1-h post TBI (P < 0.0001). There were no differences in serum neuron specific enolase levels between groups. Laser doppler imaging demonstrated similar decreases in cerebral blood flow between CHI and CCI; however, CCI mice had a reduction in blood flow with craniotomy only that did not significantly decrease further with impact.

CONCLUSIONS

Based on our findings, CHI leads to increased serum GFAP levels and increased p-tau within the hippocampus at 30-d postinjury. While CCI allows the comparison of one cerebral hemisphere to the other, CHI may be a better model of TBI as it requires less technical expertise and has similar neurological outcomes in these murine models.

The neutrophil to lymphocyte ratio associates with markers of Alzheimer's disease pathology in cognitively unimpaired elderly people

Background

An elevated neutrophil-lymphocyte ratio (NLR) in blood has been associated with Alzheimer's disease (AD). However, an elevated NLR has also been implicated in many other conditions that are risk factors for AD, prompting investigation into whether the NLR is directly linked with AD pathology or a result of underlying comorbidities. Herein, we explored the relationship between the NLR and AD biomarkers in the cerebrospinal fluid (CSF) of cognitively unimpaired (CU) subjects. Adjusting for sociodemographics, APOE4, and common comorbidities, we investigated these associations in two cohorts: the Alzheimer's Disease Neuroimaging Initiative (ADNI) and the M.J. de Leon CSF repository at NYU. Specifically, we examined associations between the NLR and cross-sectional measures of amyloid-β42 (Aβ42), total tau (t-tau), and phosphorylated tau181 (p-tau), as well as the trajectories of these CSF measures obtained longitudinally.

Results

A total of 111 ADNI and 190 NYU participants classified as CU with available NLR, CSF, and covariate data were included. Compared to NYU, ADNI participants were older (73.79 vs. 61.53, p < 0.001), had a higher proportion of males (49.5% vs. 36.8%, p = 0.042), higher BMIs (27.94 vs. 25.79, p < 0.001), higher prevalence of hypertensive history (47.7% vs. 16.3%, p < 0.001), and a greater percentage of Aβ-positivity (34.2% vs. 20.0%, p = 0.009). In the ADNI cohort, we found cross-sectional associations between the NLR and CSF Aβ42 (β=-12.193, p = 0.021), but not t-tau or p-tau. In the NYU cohort, we found cross-sectional associations between the NLR and CSF t-tau (β = 26.812, p = 0.019) and p-tau (β = 3.441, p = 0.015), but not Aβ42. In the NYU cohort alone, subjects classified as Aβ+ (n = 38) displayed a stronger association between the NLR and t-tau (β = 100.476, p = 0.037) compared to Aβ- subjects or the non-stratified cohort. In both cohorts, the same associations observed in the cross-sectional analyses were observed after incorporating longitudinal CSF data.

Conclusions

We report associations between the NLR and Aβ42 in the older ADNI cohort, and between the NLR and t-tau and p-tau181 in the younger NYU cohort. Associations persisted after adjusting for comorbidities, suggesting a direct link between the NLR and AD. However, changes in associations between the NLR and specific AD biomarkers may occur as part of immunosenescence.

Regional differences in synaptic degeneration are linked to alpha-synuclein burden and axonal damage in Parkinson's disease and dementia with Lewy bodies

Regional differences in synaptic degeneration may underlie differences in clinical presentation and neuropathological disease progression in Parkinson's Disease (PD) and Dementia with Lewy bodies (DLB). Here, we mapped and quantified synaptic degeneration in cortical brain regions in PD, PD with dementia (PDD) and DLB, and assessed whether regional differences in synaptic loss are linked to axonal degeneration and neuropathological burden. We included a total of 47 brain donors, 9 PD, 12 PDD, 6 DLB and 20 non-neurological controls. Synaptophysin+ and SV2A+ puncta were quantified in eight cortical regions using a high throughput microscopy approach. Neurofilament light chain (NfL) immunoreactivity, Lewy body (LB) density, phosphorylated-tau and amyloid-β load were also quantified. Group differences in synaptic density, and associations with neuropathological markers and Clinical Dementia Rating (CDR) scores, were investigated using linear mixed models. We found significantly decreased synaptophysin and SV2A densities in the cortex of PD, PDD and DLB cases compared to controls. Specifically, synaptic density was decreased in cortical regions affected at Braak α-synuclein stage 5 in PD (middle temporal gyrus, anterior cingulate and insula), and was additionally decreased in cortical regions affected at Braak α-synuclein stage 4 in PDD and DLB compared to controls (entorhinal cortex, parahippocampal gyrus and fusiform gyrus). Synaptic loss associated with higher NfL immunoreactivity and LB density. Global synaptophysin loss associated with longer disease duration and higher CDR scores. Synaptic neurodegeneration occurred in temporal, cingulate and insular cortices in PD, as well as in parahippocampal regions in PDD and DLB. In addition, synaptic loss was linked to axonal damage and severe α-synuclein burden. These results, together with the association between synaptic loss and disease progression and cognitive impairment, indicate that regional synaptic loss may underlie clinical differences between PD and PDD/DLB. Our results might provide useful information for the interpretation of synaptic biomarkers in vivo.

Factors affecting the GABAergic synapse function in Alzheimer's disease: Focus on microRNAs

Alzheimer's disease (AD) is a progressive neurological disease characterized by the loss of cognitive function, confusion, and memory deficit. Accumulation of abnormal proteins, amyloid beta (Aß), and phosphorylated Tau (p-tau) forms plaques and tangles that deteriorate synapse function, resulting in neurodegeneration and cognitive decline in AD. The human brain is composed of different types of neurons and/or synapses that are functionally defective in AD. The GABAergic synapse, the most abundant inhibitory neuron in the human brain was found to be dysfunctional in AD and contributes to disrupting neurological function. This study explored the types of GABA receptors associated with neurological dysfunction and various biological and environmental factors that cause GABAergic neuron dysfunction in AD, such as Aβ, p-tau, aging, sex, astrocytes, microglia, APOE, mental disorder, diet, physical activity, and sleep. Furthermore, we explored the role of microRNAs (miRNAs) in the regulation of GABAergic synapse function in neurological disorders and AD states. We also discuss the molecular mechanisms underlying GABAergic synapse dysfunction with a focus on miR-27b, miR-30a, miR-190a/b, miR-33, miR-51, miR-129-5p, miR-376-3p, miR-376c, miR-30b and miR-502-3p. The purpose of our article is to highlight the recent research on miRNAs affecting the regulation of GABAergic synapse function and factors that contribute to the progression of AD.

Co-administration of dl-3-n-butylphthalide and neprilysin is neuroprotective in Alzheimer disease associated with mild traumatic brain injury

dl-3-n-Butylphthalide is a potent synthetic Chinese celery extract that is highly efficient in inducing neuroprotection in concussive head injury (CHI), Parkinson's disease, Alzheimer's disease, stroke as well as depression, dementia, anxiety and other neurological diseases. Thus, there are reasons to believe that dl-3-n-butylphthalide could effectively prevent Alzheimer's disease brain pathology. Military personnel during combat operation or veterans are often the victims of brain injury that is a major risk factor for developing Alzheimer's disease in their later lives. In our laboratory we have shown that CHI exacerbates Alzheimer's disease brain pathology and reduces the amyloid beta peptide (AβP) inactivating enzyme neprilysin. We have used TiO2 nanowired-dl-3-n-butylphthalide in attenuating Parkinson's disease brain pathology exacerbated by CHI. Nanodelivery of dl-3-n-butylphthalide appears to be more potent as compared to the conventional delivery of the compound. Thus, it would be interesting to examine the effects of nanowired dl-3-n-butylphthalide together with nanowired delivery of neprilysin in Alzheimer's disease model on brain pathology. In this investigation we found that nanowired delivery of dl-3-n-butylphthalide together with nanowired neprilysin significantly attenuated brain pathology in Alzheimer's disease model with CHI, not reported earlier. The possible mechanism and clinical significance is discussed based on the current literature.

Nanowired delivery of antibodies to tau and neuronal nitric oxide synthase together with cerebrolysin attenuates traumatic brain injury induced exacerbation of brain pathology in Parkinson's disease

Concussive head injury (CHI) is one of the major risk factors for developing Parkinson's disease in later life of military personnel affecting lifetime functional and cognitive disturbances. Till date no suitable therapies are available to attenuate CHI or PD induced brain pathology. Thus, further exploration of novel therapeutic agents are highly warranted using nanomedicine in enhancing the quality of life of veterans or service members of US military. Since PD or CHI induces oxidative stress and perturbs neurotrophic factors regulation associated with phosphorylated tau (p-tau) deposition, a possibility exists that nanodelivery of agents that could enhance neurotrophic factors balance and attenuate oxidative stress could be neuroprotective in nature. In this review, nanowired delivery of cerebrolysin-a balanced composition of several neurotrophic factors and active peptide fragments together with monoclonal antibodies to neuronal nitric oxide synthase (nNOS) with p-tau antibodies was examined in PD following CHI in model experiments. Our results suggest that combined administration of nanowired antibodies to nNOS and p-tau together with cerebrolysin significantly attenuated CHI induced exacerbation of PD brain pathology. This combined treatment also has beneficial effects in CHI or PD alone, not reported earlier.

Concordance of Alzheimer's Disease-Related Biomarkers Between Intraventricular and Lumbar Cerebrospinal Fluid in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

Alzheimer's disease cerebrospinal fluid (CSF) biomarkers amyloid-β 1-42 (Aβ42), total tau (T-tau), and phosphorylated tau 181 (P-tau181) are widely used. However, concentration gradient of these biomarkers between intraventricular (V-CSF) and lumbar CSF (L-CSF) has been demonstrated in idiopathic normal pressure hydrocephalus (iNPH), potentially affecting clinical utility.

OBJECTIVE

Here we aim to provide conversion factors for clinical and research use between V-CSF and L-CSF.

METHODS

Altogether 138 iNPH patients participated. L-CSF samples were obtained prior to shunt surgery. Intraoperative V-CSF samples were obtained from 97 patients. Post-operative follow-up L- and V-CSF (shunt reservoir) samples of 41 patients were obtained 1-73 months after surgery and then after 3, 6, and 18 months. CSF concentrations of Aβ42, T-tau, and P-tau181 were analyzed using commercial ELISA assays.

RESULTS

Preoperative L-CSF Aβ42, T-tau, and P-tau181 correlated to intraoperative V-CSF (ρ= 0.34-0.55, p < 0.001). Strong correlations were seen between postoperative L- and V-CSF for all biomarkers in every follow-up sampling point (ρs Aβ42: 0.77-0.88, T-tau: 0.91-0.94, P-tau181: 0.94-0.96, p < 0.0001). Regression equations were determined for intraoperative V- and preoperative L-CSF (Aβ42: V-CSF = 185+0.34*L-CSF, T-tau: Ln(V-CSF) = 3.11+0.49*Ln(L-CSF), P-tau181: V-CSF = 8.2+0.51*L-CSF), and for postoperative V- and L-CSF (Aβ42: V-CSF = 86.7+0.75*L-CSF, T-tau: V-CSF = 86.9+0.62*L-CSF, P-tau181: V-CSF = 2.6+0.74*L-CSF).

CONCLUSION

Aβ42, T-tau, and P-tau181 correlate linearly in-between V- and L-CSF, even stronger after CSF shunt surgery. Equations presented here, provide a novel tool to use V-CSF for diagnostic and prognostic entities relying on the L-CSF concentrations and can be applicable to clinical use when L-CSF samples are not available or less invasively obtained shunt reservoir samples should be interpreted.

Anesthesia and surgery-induced elevation of CSF sTREM2 is associated with early cognitive dysfunction after thoracoabdominal aortic dissection surgery

PURPOSE

Soluble triggering receptor expressed on myeloid cells 2 (sTREM2) concentration is increased in cerebrospinal fluid (CSF) in early symptomatic phase of Alzheimer's disease (AD). This study investigated whether CSF sTREM2 has a relationship with early cognitive dysfunction following surgery in cardiac surgery patients.

METHODS

A total of 82 patients undergoing thoracoabdominal aortic replacement were recruited in this study. Neuropsychological testing battery was conducted before and after surgery. Postoperative cognitive dysfunction (POCD) was defined as a Z-score > 1.96 on at least 2 different tests or Telephone Interviews for Cognitive Status-Modified (TICS-M) score < 27. The CSF and serum sTREM2, Aβ₄₂, T-tau and P-tau were collected and measured by ELISA on day before surgery and postoperative day 3.

RESULTS

Patients were classified into POCD (n = 34) and non-POCD (n = 48) groups according to Z-score. Compared to non-POCD group, the levels of CSF sTREM2 (p < 0.001) and serum sTREM2 (p = 0.001) were significantly higher in POCD group on postoperative day 3. The levels of Aβ₄₂ (p = 0.005) and Aβ₄₂/T-tau ratio (p = 0.036) were significantly lower in POCD group on postoperative day 3. Multivariate logistic regression analysis revealed that higher value of postoperative CSF sTREM2 (odds ratio: 1.06, 95% confidence interval: 1.02-1.11, p = 0.009), age (OR: 1.15, 95%CI: 1.03-1.28, p = 0.014) and POD duration (OR: 2.47, 95%CI: 1.15-5.29, p = 0.02) were the risk factors of POCD.

CONCLUSION

This study indicates that anesthesia and surgery-induced elevation of CSF sTREM2 is associated with an increased risk of early cognitive dysfunction following surgery.

CSF p-tau as a potential cognition impairment biomarker in ALS

Background

Cerebrospinal fluid (CSF) and serum tau (t-tau, p-tau) are potential biomarkers for neurodegeneration in Alzheimer disease (AD), but their role in amyotrophic lateral sclerosis (ALS) is unclear.

Objectives

The aim of our study was to evaluate CSF and serum p-tau and t-tau in patients with ALS and to analyze the correlation and clinical parameters between them.

Methods

CSF and serum samples were obtained from 90 patients with ALS, 48 other neurological disease (OND), and 20 with AM (ALS mimic, AM) diseases. The levels of p-tau and t-tau in the CSF and serum were assessed with an enzyme-linked immunosorbent assay, and disease progression parameters, including the duration, the ALSFRS-R score, disease progression rate (DPR), the upper motor neuron (UMN) score, the Mini-mental State Examination (MMSE) score, the Montreal Cognitive Assessment (MoCA) score, and the Edinburgh Cognitive and Behavioral ALS Screen (ECAS) results, were analyzed by registered neurologists. Statistical analyses were performed using Prism software.

Results

Compared with controls, patients with ALS displayed significantly lower levels of CSF p-tau and p-tau:t-tau ratio. The CSF p-tau level in patients with ALS and cognition impairment was higher than that in patients with ALS who did not have cognition impairment. CSF p-tau level was negatively correlated with MMSE, MoCA, and ECAS total score and the specific score of ECAS in patients with ALS and cognition impairment.

Conclusions

The CSF p-tau level and p-tau:t-tau ratio were lower in patients with ALS than patients with OND and AM. Results suggest that CSF p-tau may be used as an index of cognition impairment in patients with ALS.

Plasma p-tau181 shows stronger network association to Alzheimer's disease dementia than neurofilament light and total tau

INTRODUCTION

We examined the ability of plasma hyperphosphorylated tau (p-tau)181 to detect cognitive impairment due to Alzheimer's disease (AD) independently and in combination with plasma total tau (t-tau) and neurofilament light (NfL).

METHODS

Plasma samples were analyzed using the Simoa platform for 235 participants with normal cognition (NC), 181 with mild cognitive impairment due to AD (MCI), and 153 with AD dementia. Statistical approaches included multinomial regression and Gaussian graphical models (GGMs) to assess a network of plasma biomarkers, neuropsychological tests, and demographic variables.

RESULTS

Plasma p-tau181 discriminated AD dementia from NC, but not MCI, and correlated with dementia severity and worse neuropsychological test performance. Plasma NfL similarly discriminated diagnostic groups. Unlike plasma NfL or t-tau, p-tau181 had a direct association with cognitive diagnosis in a bootstrapped GGM.

DISCUSSION

These results support plasma p-tau181 for the detection of AD dementia and the use of blood-based biomarkers for optimal disease detection.

Blood-based biomarkers for Alzheimer's disease

Neurodegenerative disorders such as Alzheimer's disease (AD) represent a mounting public health challenge. As these diseases are difficult to diagnose clinically, biomarkers of underlying pathophysiology are playing an ever-increasing role in research, clinical trials, and in the clinical work-up of patients. Though cerebrospinal fluid (CSF) and positron emission tomography (PET)-based measures are available, their use is not widespread due to limitations, including high costs and perceived invasiveness. As a result of rapid advances in the development of ultra-sensitive assays, the levels of pathological brain- and AD-related proteins can now be measured in blood, with recent work showing promising results. Plasma P-tau appears to be the best candidate marker during symptomatic AD (i.e., prodromal AD and AD dementia) and preclinical AD when combined with Aβ42/Aβ40. Though not AD-specific, blood NfL appears promising for the detection of neurodegeneration and could potentially be used to detect the effects of disease-modifying therapies. This review provides an overview of the progress achieved thus far using AD blood-based biomarkers, highlighting key areas of application and unmet challenges.

The Interplay of Tau Protein and β-Amyloid: While Tauopathy Spreads More Profoundly Than Amyloidopathy, Both Processes Are Almost Equally Pathogenic

Alzheimer's disease (AD) is a neurodegenerative disorder, in which amyloid precursor protein (APP) misprocessing and tau protein hyperphosphorylation are well-established pathogenic cascades. Despite extensive considerations, the central mediator of neuronal cell death upon AD remains under debate. Therefore, we examined the direct interplay between tauopathy and amyloidopathy processes. We employed primary culture neurons and examined pathogenic P-tau and Aβ oligomers upon hypoxia treatment by immunofluorescence and immunoblotting. We observed both tauopathy and amyloidopathy processes upon the hypoxia condition. We also applied Aβ1-42 or P-tau onto primary cultured neurons. We overexpressed P-tau in SH-SY5Y cells and found Aβ accumulation. Furthermore, adult male rats received Aβ1-42 or pathogenic P-tau in the dorsal hippocampus and were examined for 8 weeks. Learning and memory performance, as well as anxiety behaviors, were assessed by Morris water maze and elevated plus-maze tests. Both Aβ1-42 and pathogenic P-tau significantly induced learning and memory deficits and enhanced anxiety behavior after treatment 2 weeks. Aβ administration induced robust tauopathy distribution in the cortex, striatum, and corpus callosum as well as CA1. On the other hand, P-tau treatment developed Aβ oligomers in the cortex and CA1 only. Our findings indicate that Aβ1-42 and pathogenic P-tau may induce each other and cause almost identical neurotoxicity in a time-dependent manner, while tauopathy seems to be more distributable than amyloidopathy.

The validation status of blood biomarkers of amyloid and phospho-tau assessed with the 5-phase development framework for AD biomarkers

PURPOSE

The development of blood biomarkers that reflect Alzheimer's disease (AD) pathophysiology (phosphorylated tau and amyloid-β) has offered potential as scalable tests for dementia differential diagnosis and early detection. In 2019, the Geneva AD Biomarker Roadmap Initiative included blood biomarkers in the systematic validation of AD biomarkers.

METHODS

A panel of experts convened in November 2019 at a two-day workshop in Geneva. The level of maturity (fully achieved, partly achieved, preliminary evidence, not achieved, unsuccessful) of blood biomarkers was assessed based on the Biomarker Roadmap methodology and discussed fully during the workshop which also evaluated cerebrospinal fluid (CSF) and positron emission tomography (PET) biomarkers.

RESULTS

Plasma p-tau has shown analytical validity (phase 2 primary aim 1) and first evidence of clinical validity (phase 3 primary aim 1), whereas the maturity level for Aβ remains to be partially achieved. Full and partial achievement has been assigned to p-tau and Aβ, respectively, in their associations to ante-mortem measures (phase 2 secondary aim 2). However, only preliminary evidence exists for the influence of covariates, assay comparison and cut-off criteria.

CONCLUSIONS

Despite the relative infancy of blood biomarkers, in comparison to CSF biomarkers, much has already been achieved for phases 1 through 3 - with p-tau having greater success in detecting AD and predicting disease progression. However, sufficient data about the effect of covariates on the biomarker measurement is lacking. No phase 4 (real-world performance) or phase 5 (assessment of impact/cost) aim has been tested, thus not achieved.

Time Trends of Cerebrospinal Fluid Biomarkers of Neurodegeneration in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

Longitudinal changes in cerebrospinal fluid (CSF) biomarkers are seldom studied. Furthermore, data on biomarker gradient between lumbar (L-) and ventricular (V-) compartments seems to be discordant.

OBJECTIVE

To examine alteration of CSF biomarkers reflecting Alzheimer's disease (AD)-related amyloid-β (Aβ) aggregation, tau pathology, neurodegeneration, and early synaptic degeneration by CSF shunt surgery in idiopathic normal pressure hydrocephalus (iNPH) in relation to AD-related changes in brain biopsy. In addition, biomarker levels in L- and V-CSF were compared.

METHODS

L-CSF was collected prior to shunt placement and, together with V-CSF, 3-73 months after surgery. Thereafter, additional CSF sampling took place at 3, 6, and 18 months after the baseline sample from 26 iNPH patients with confirmed Aβ plaques in frontal cortical brain biopsy and 13 iNPH patients without Aβ pathology. CSF Amyloid-β42 (Aβ42), total tau (T-tau), phosphorylated tau (P-tau181), neurofilament light (NFL), and neurogranin (NRGN) were analyzed with customized ELISAs.

RESULTS

All biomarkers but Aβ42 increased notably by 140-810% in L-CSF after CSF diversion and then stabilized. Aβ42 instead showed divergent longitudinal decrease between Aβ-positive and -negative patients in L-CSF, and thereafter increase in Aβ-negative iNPH patients in both L- and V-CSF. All five biomarkers correlated highly between V-CSF and L-CSF (Aβ42 R = 0.87, T-tau R = 0.83, P-tau R = 0.92, NFL R = 0.94, NRGN R = 0.9; all p < 0.0001) but were systematically lower in V-CSF (Aβ42 14 %, T-tau 22%, P-tau 20%, NFL 32%, NRGN 19%). With APOE genotype-grouping, only Aβ42 showed higher concentration in non-carriers of allele ɛ4.

CONCLUSION

Longitudinal follow up shows that after an initial post-surgery increase, T-tau, P-tau, and NRGN are stable in iNPH patients regardless of brain biopsy Aβ pathology, while NFL normalized toward its pre-shunt levels. Aβ42 as biomarker seems to be the least affected by the surgical procedure or shunt and may be the best predictor of AD risk in iNPH patients. All biomarker concentrations were lower in V- than L-CSF yet showing strong correlations.

2020 update on the clinical validity of cerebrospinal fluid amyloid, tau, and phospho-tau as biomarkers for Alzheimer's disease in the context of a structured 5-phase development framework

Purpose

In the last decade, the research community has focused on defining reliable biomarkers for the early detection of Alzheimer’s disease (AD) pathology. In 2017, the Geneva AD Biomarker Roadmap Initiative adapted a framework for the systematic validation of oncological biomarkers to cerebrospinal fluid (CSF) AD biomarkers—encompassing the 42 amino-acid isoform of amyloid-β (Aβ42), phosphorylated-tau (P-tau), and Total-tau (T-tau)—with the aim to accelerate their development and clinical implementation. The aim of this work is to update the current validation status of CSF AD biomarkers based on the Biomarker Roadmap methodology.

Methods

A panel of experts in AD biomarkers convened in November 2019 at a 2-day workshop in Geneva. The level of maturity (fully achieved, partly achieved, preliminary evidence, not achieved, unsuccessful) of CSF AD biomarkers was assessed based on the Biomarker Roadmap methodology before the meeting and presented and discussed during the workshop.

Results

By comparison to the previous 2017 Geneva Roadmap meeting, the primary advances in CSF AD biomarkers have been in the area of a unified protocol for CSF sampling, handling and storage, the introduction of certified reference methods and materials for Aβ42, and the introduction of fully automated assays. Additional advances have occurred in the form of defining thresholds for biomarker positivity and assessing the impact of covariates on their discriminatory ability.

Conclusions

Though much has been achieved for phases one through three, much work remains in phases four (real world performance) and five (assessment of impact/cost). To a large degree, this will depend on the availability of disease-modifying treatments for AD, given these will make accurate and generally available diagnostic tools key to initiate therapy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05258-7.

Longitudinal changes in blood-based biomarkers in chronic moderate to severe traumatic brain injury: preliminary findings

Objectives: This longitudinal study aims at 1) providing preliminary evidence of changes in blood-based biomarkers across time in chronic TBI and 2) relating these changes to outcome measures and cerebral structure and activity.Methods: Eight patients with moderate-to-severe TBI (7 males, 35 ± 7.6 years old, 5 severe TBI, 17.52 ± 3.84 months post-injury) were evaluated at monthly intervals across 6 time-points using: a) Blood-based biomarkers (GFAP, NSE, S100A12, SDBP145, UCH-L1, T-tau, P-tau, P-tau/T-tau ratio); b) Magnetic Resonance Imaging to evaluate changes in brain structure; c) Resting-state electroencephalograms to evaluate changes in brain function; and d) Outcome measures to assess cognition, emotion, and functional recovery (MOCA, RBANS, BDI-II, and DRS).Results: Changes in P-tau levels were found across time [p = .007]. P-tau was positively related to functional [p < .001] and cognitive [p = .006] outcomes, and negatively related to the severity of depression, 6 months later [R = -0.901; p =.006]. P-tau and P-tau/T-tau ratio were also positively correlated to shape change in subcortical areas such as brainstem [T(7) = 4.71, p = .008] and putamen [T(7) = 3.25, p = .012].Conclusions: Our study provides preliminary findings that suggest a positive relationship between P-tau and the recovery of patients with chronic TBI.

α-synuclein abnormalities trigger focal tau pathology, spreading to various brain areas in Parkinson disease

Parkinson disease (PD) is the second most common neurodegenerative disorder, whose prevalence is 2~3% in the population over 65. α-Synuclein aggregation is the major pathological hallmark of PD. However, recent studies have demonstrated enhancing evidence of tau pathology in PD. Despite extensive considerations, thus far, the actual spreading mechanism of neurodegeneration has remained elusive in a PD brain. This study aimed to further investigate the development of α-synuclein and tau pathology. We employed various PD models, including cultured neurons treated with either 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or with recombinant α-synuclein. Also, we studied dopaminergic neurons of cytokine Interferon-β knock-out. Moreover, we examined rats treated with 6-hydroxydopamine, Rhesus monkeys administrated with MPTP neurotoxin, and finally, human post-mortem brains. We found the α-synuclein phosphorylation triggers tau pathogenicity. Also, we observed more widespread phosphorylated tau than α-synuclein with prion-like nature in various brain areas. We optionally removed P-tau or P-α-synuclein from cytokine interferon-β knock out with respective monoclonal antibodies. We found that tau immunotherapy suppressed neurodegeneration more than α-synuclein elimination. Our findings indicate that the pathogenic tau could be one of the leading causes of comprehensive neurodegeneration triggered by PD. Thus, we can propose an efficient therapeutic target to fight the devastating disorder.

Erlangen Score Predicts Cognitive and Neuroimaging Progression in Mild Cognitive Impairment Stage of Alzheimer's Disease

BACKGROUND

To alleviate the interpretation of the core Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers, amyloid β1-42 (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau), the Erlangen Score (ES) interpretation algorithm has been proposed.

OBJECTIVE

In this study, we aim to assess the predictive properties of the ES algorithm on cognitive and neuroimaging outcomes in mild cognitive impairment (MCI).

METHODS

All MCI subjects with an available baseline CSF sample from ADNI-1 were included (n = 193), and assigned an ES between 0 and 4 based on their baseline CSF biomarker profile. Structural magnetic resonance imaging brain scans and MMSE and ADAS-Cog scores were collected at up to 7 times in follow-up examinations.

RESULTS

We observed strong and significant correlations between the ES at baseline and neuroimaging and cognitive results with patients with neurochemically probable AD (ES = 4) progressing significantly (p≤0.01) faster than those with a neurochemically improbable AD (ES = 0 or 1), and the subjects with neurochemically possible AD (ES = 2 or 3) in-between these two groups.

CONCLUSION

This study further demonstrates the utility of the ES algorithm as a as a tool in predicting cognitive and imaging progression in MCI patients.

Obstructive sleep apnea and longitudinal Alzheimer's disease biomarker changes

STUDY OBJECTIVES

To determine the effect of self-reported clinical diagnosis of obstructive sleep apnea (OSA) on longitudinal changes in brain amyloid PET and CSF biomarkers (Aβ42, T-tau, and P-tau) in cognitively normal (NL), mild cognitive impairment (MCI), and Alzheimer's disease (AD) elderly.

METHODS

Longitudinal study with mean follow-up time of 2.52 ± 0.51 years. Data were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. Participants included 516 NL, 798 MCI, and 325 AD elderly. Main outcomes were annual rate of change in brain amyloid burden (i.e. longitudinal increases in florbetapir PET uptake or decreases in CSF Aβ42 levels); and tau protein aggregation (i.e. longitudinal increases in CSF total tau [T-tau] and phosphorylated tau [P-tau]). Adjusted multilevel mixed effects linear regression models with randomly varying intercepts and slopes was used to test whether the rate of biomarker change differed between participants with and without OSA.

RESULTS

In NL and MCI groups, OSA+ subjects experienced faster annual increase in florbetapir uptake (B = .06, 95% CI = .02, .11 and B = .08, 95% CI = .05, .12, respectively) and decrease in CSF Aβ42 levels (B = -2.71, 95% CI = -3.11, -2.35 and B = -2.62, 95% CI = -3.23, -2.03, respectively); as well as increases in CSF T-tau (B = 3.68, 95% CI = 3.31, 4.07 and B = 2.21, 95% CI = 1.58, 2.86, respectively) and P-tau (B = 1.221, 95% CI = 1.02, 1.42 and B = 1.74, 95% CI = 1.22, 2.27, respectively); compared with OSA- participants. No significant variations in the biomarker changes over time were seen in the AD group.

CONCLUSIONS

In both NL and MCI, elderly, clinical interventions aimed to treat OSA are needed to test if OSA treatment may affect the progression of cognitive impairment due to AD.

PCSK9 Concentrations in Cerebrospinal Fluid Are Not Specifically Increased in Alzheimer's Disease

The role of PCSK9 in Alzheimer's disease (AD) is controversial. We compared cerebrospinal fluid (CSF) PCSK9 concentrations in 36 AD and 31 non-AD patients. CSF PCSK9 levels did not differ between AD and non-AD groups (2.80 versus 2.62 ng/mL). However, PCSK9 CSF levels were increased in AD and non-AD patients with other neurodegenerative process (non-AD ND, n = 20) compared to patients without neurodegenerative disorders (non-ND, n = 11): 2.80 versus 2.30 (p < 0.005) and 2.83 versus 2.30 ng/mL (p = NS), respectively. CSF PCSK9 were positively correlated with AD biomarkers (Aβ1-42, T-tau, and P-tau). PCSK9 concentrations in CSF are increased in neurodegenerative disorders rather than specifically in AD.

Phosphorylated human tau associates with mouse prion protein amyloid in scrapie-infected mice but does not increase progression of clinical disease

Tauopathies are a family of neurodegenerative diseases in which fibrils of human hyperphosphorylated tau (P-tau) are believed to cause neuropathology. In Alzheimer disease, P-tau associates with A-beta amyloid and contributes to disease pathogenesis. In familial human prion diseases and variant CJD, P-tau often co-associates with prion protein amyloid, and might also accelerate disease progression. To test this latter possibility, here we compared progression of amyloid prion disease in vivo after scrapie infection of mice with and without expression of human tau. The mice used expressed both anchorless prion protein (PrP) and membrane-anchored PrP, that generate disease associated amyloid and non-amyloid PrP (PrPSc) after scrapie infection. Human P-tau induced by scrapie infection was only rarely associated with non-amyloid PrPSc, but abundant human P-tau was detected at extracellular, perivascular and axonal deposits associated with amyloid PrPSc. This pathology was quite similar to that seen in familial prion diseases. However, association of human and mouse P-tau with amyloid PrPSc did not diminish survival time following prion infection in these mice. By analogy, human P-tau may not affect prion disease progression in humans. Alternatively, these results might be due to other factors, including rapidity of disease, blocking effects by mouse tau, or low toxicity of human P-tau in this model.

Effects of Bu Shen Yi sui capsule on NogoA/NgR and its signaling pathways RhoA/ROCK in mice with experimental autoimmune encephalomyelitis

Background

Axon growth inhibitory factors NogoA/Nogo receptor (NgR) and its signaling pathways RhoA/Rho kinase (ROCK) play a critical role in the repair of nerve damage in multiple sclerosis (MS). Bu Shen Yi Sui Capsule (BSYSC) is an effective Chinese formula utilized to treat MS in clinical setting and noted for its potent neuroprotective effects. In this study, we focus on the effects of BSYSC on promoting nerve repair and the underlying mechanisms in mice with experimental autoimmune encephalomyelitis (EAE), an animal model of MS.

Methods

The EAE mouse model was induced by injecting subcutaneously with myelin oligodendrocyte glycoprotein (MOG) _35–55 supplemented with pertussis toxin. BSYSC was orally administrated at dose of 3.0 g/kg once a day for 40 days. The levels of protein gene product (PGP) 9.5, p-Tau, growth associated protein (GAP) -43, KI67 and Nestin in the brain or spinal cord on 20 and 40 day post-induction (dpi) were detected via immunofluorescence and Western blot analysis. Furthermore, NogoA/NgR and RhoA/ROCK signaling molecules were studied by qRT-PCR and Western blot analysis.

Results

Twenty or 40 days of treatment with BSYSC increased markedly PGP9.5 and GAP-43 levels, reduced p-Tau in the brain or spinal cord of mice with EAE. In addition, BSYSC elevated significantly the expression of KI67 and Nestin in the spinal cord 40 dpi. Further study showed that the activation of NogoA/NgR and RhoA/ROCK were suppressed by the presence of BSYSC.

Conclusions

BSYSC could attenuate axonal injury and promote repair of axonal damage in EAE mice in part through the down-regulation of NogoA/NgR and RhoA/ROCK signaling pathways.

Aging, Alzheimer's, and APOE genotype influence the expression and neuronal distribution patterns of microtubule motor protein dynactin-P50

Reports from neural cell cultures and experimental animal studies provide evidence of age- and disease-related changes in retrograde transport of spent or misfolded proteins destined for degradation or recycling. However, few studies address these issues in human brain from those who either age without dementia and overt neuropathology, or succumb to Alzheimer's; especially as such propensity may be influenced by APOE genotype. We studied the expression and distribution of the dynein subunit dynactin-P50, the β amyloid precursor protein (βAPP), and hyperphosphorylated tau (P-tau) in tissues and tissue sections of brains from non-demented, neuropathology-free patients and from Alzheimer patients, with either APOE ε3,3 or APOE ε4,4. We found that advanced age in patients without dementia or neuropathological change was associated with coordinated increases in dynactin-P50 and βAPP in neurons in pyramidal layers of the hippocampus. In contrast, in Alzheimer's, βAPP and dynactin were significantly reduced. Furthermore, the dynactin-P50 and βAPP that was present was located primarily in dystrophic neurites in Aβ plaques. Tissues from Alzheimer patients with APOE ε3,3 had less P-tau, more βAPP, dynactin-P50, and synaptophysin than did tissues from Alzheimer patients carrying APOE ε4,4. It is logical to conclude, then, that as neurons age successfully, there is coordination between retrograde delivery and maintenance and repair, as well as between retrograde delivery and degradation and/or recycling of spent proteins. The buildup of proteins slated for repair, synaptic viability, transport, and re-cycling in neuron soma and dystrophic neurites suggest a loss of this coordination in Alzheimer neurons. Inheritance of APOE ε3,3 rather than APOE ε4,4, is associated with neuronal resilience, suggestive of better repair capabilities, more synapses, more efficient transport, and less hyperphosphorylation of tau. We conclude that even in disease the ε3 allele is neuroprotective.

Additional use of Aβ₄₂/Aβ₄₀ ratio with cerebrospinal fluid biomarkers P-tau and Aβ₄₂ increases the level of evidence of Alzheimer's disease pathophysiological process in routine practice

BACKGROUND

Cerebrospinal fluid (CSF) biomarkers have recently been included in the criteria for the diagnosis of Alzheimer's disease (AD). Since interpretation of CSF profile requires the combination of three parameters, biological data are not always conclusive and isolated elevation of phosphorylated tau (P-tau) or reduction of amyloid-β (Aβ)42 alone can be observed. In these cases, Aβ42/Aβ40 ratio could be more relevant than Aβ42 absolute values by considering inter-individual variations in the total amyloid load.

OBJECTIVE

The objective of this study was to assess the use of Aβ42/Aβ40 ratio to improve the accuracy of biological conclusions in the diagnosis of patients with ambiguous CSF Aβ42 or tau results.

METHODS

Among 386 lumbar punctures analyzed in the lab in 2 years, 122 showed ambiguous biological data that were completed by CSF Aβ40 quantification and Aβ42/Aβ40 ratio calculation. A biological conclusion was then made using 0.05 as the Aβ42/Aβ40 ratio cut-off.

RESULTS

Our results showed that one-third of the biological profiles of patients with atypical dementia were ambiguous. The addition of Aβ42/Aβ40 ratio increased the proportion of interpretable biological profiles from 69% to 87%, without changing the conclusion when usual biomarkers (Aβ42 and P-tau) were concordant.

CONCLUSION

Our results support the use of the Aβ42/Aβ40 ratio in addition to the usual CSF AD biomarkers for patients with ambiguous biological profiles. This method could be specifically directed to this population in order to improve the level of certainty for clinical routine practice.

Comparison of two methods for the analysis of CSF Aβ and tau in the diagnosis of Alzheimer's disease

INTRODUCTION

Biomarkers represent a promising adjunct to clinical techniques in the diagnosis of Alzheimer's Disease (AD) and other neurodegenerative diseases. At present, the potential of cerebrospinal fluid (CSF) biomarkers in diagnosing AD has been suggested but the degree of clinical utility is yet to be defined due to variability between studies. In this paper we compare the performance of two cerebrospinal fluid assay methods in predicting clinically diagnosed AD.

METHODS

CSF biomarker concentrations for Aβ1-42, P-tau181P and T-tau were analysed using INNOTEST (ELISA) and INNO-BIA AlzBio3 (Luminex) assay methods from Innogenetics, Belgium. Patients were clinically diagnosed based on NINCDS-ADRDA criteria supplemented with structural MRI, (18)F-fluorodeoxy-glucose positron emission tomography (FDG-PET) and cognitive profiling.

RESULTS

An abnormally low Aβ1-42 was the most useful biomarker in predicting clinical AD. Depending on the assay method, the predictive accuracy remained constant or improved slightly when abnormalities in P-tau181P and T-tau were considered in addition to Aβ1-42. The Luminex method with our optimised reference concentrations performed best for patients ≤ 65 years with sensitivity = 1 and a specificity = 0.60 for both Aβ1-42 and when one or more abnormal biomarkers were considered.

CONCLUSION

Given accurate, robust and reproducible CSF analytical methods, of which the Luminex method seems the most useful and practicable, our investigation suggests that measuring CSF Aβ1-42, P-tau and T-tau has utility in the diagnosis of probable AD and, when used with clinical diagnostic techniques, seems especially helpful in the diagnosis of AD with onset prior to the age of 65 years.

Revisiting the Role of Acetylcholinesterase in Alzheimer's Disease: Cross-Talk with P-tau and β-Amyloid

A common feature in the Alzheimer’s disease (AD) brain is the presence of acetylcholinesterase (AChE) which is commonly associated with β-amyloid plaques and neurofibrillary tangles (NFT). Although our understanding of the relationship between AChE and the pathological features of AD is incomplete, increasing evidence suggests that both β-amyloid protein (Aβ) and abnormally hyperphosphorylated tau (P-tau) can influence AChE expression. We also review recent findings which suggest the possible role of AChE in the development of a vicious cycle of Aβ and P-tau dysregulation and discuss the limited and temporary effect of therapeutic intervention with AChE inhibitors.