CSF Biomarkers Profile in CADASIL-A Model of Pure Vascular Dementia: Usefulness in Differential Diagnosis in the Dementia Disorder

Cerebrospinal Fluid Biomarkers for Alzheimer's Disease in the Era of Disease-Modifying Treatments

Correct in vivo diagnosis of Alzheimer’s disease (AD) helps to avoid administration of disease-modifying treatments in non-AD patients, and allows the possible use of such treatments in clinically atypical AD patients. Cerebrospinal fluid (CSF) biomarkers offer a tool for AD diagnosis. A reduction in CSF β-amyloid (marker of amyloid plaque burden), although compatible with Alzheimer’s pathological change, may also be observed in other dementing disorders, including vascular cognitive disorders due to subcortical small-vessel disease, dementia with Lewy bodies and normal-pressure hydrocephalus. Thus, for the diagnosis of AD, an abnormal result of CSF β-amyloid may not be sufficient, and an increase in phospho-tau (marker of tangle pathology) is also required in order to confirm AD diagnosis in patients with a typical amnestic presentation and reveal underlying AD in patients with atypical or mixed and diagnostically confusing clinical presentations.

Role of Notch signaling in neurovascular aging and Alzheimer's disease

The Notch signaling pathway is an evolutionarily conserved cell signaling system known to be involved in vascular development and function. Recent evidence suggests that dysfunctional Notch signaling could play a critical role in the pathophysiology of neurodegenerative diseases. We reviewed current literature on the role of Notch signaling pathway, and specifically Notch receptor genes and proteins, in aging, cerebrovascular disease and Alzheimer's disease. We hypothesize that Notch signaling may represent a key point of overlap between age-related vascular and Alzheimer's pathophysiology contributing to their comorbidity and combined influence on cognitive decline and dementia. Numerous findings from studies of genetics, neuropathology and cell culture models all suggest a link between altered Notch signaling and Alzheimer's pathophysiology. Age-related changes in Notch signaling may also trigger neurovascular dysfunction, contributing to the development of neurodegenerative diseases; however, additional studies are warranted. Future research directly exploring the influence of aberrant Notch signaling in the development of Alzheimer's disease is needed to better understand this mechanism.

Dabigatran reduces thrombin-induced neuroinflammation and AD markers in vitro: Therapeutic relevance for Alzheimer's disease

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Thrombin treatment induced proteins linked to neuroinflammation in SH-SY5Y cells.

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Thrombin exposure elevated the expression/ levels of proteins of AD pathway.

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EMSA showed dabigatran reduced activation of NFκB in SH-SY5Y cells.

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Dabigatran reduced thrombin-driven neuroinflammation and downstream AD pathology.

Background

Vascular risk factors such as atherosclerosis, diabetes, and elevated homocysteine levels are strongly correlated with onset of Alzheimer's disease (AD). Emerging evidence indicates that blood coagulation protein thrombin is associated with vascular and non-vascular risk factors of AD. Here, we examined the effect of thrombin and its direct inhibitor dabigatran on key mediators of neuro-inflammation and AD pathology in the retinoic acid (RA)-differentiated human neuroblastoma cell line SH-SY5Y.

Methods

SH-SY5Y cells exposed to thrombin concentrations (10–100 nM) +/- 250 nM dabigatran for 24 h were analyzed for protein and gene expression. Electrophoretic mobility shift assay (EMSA) was used to determine DNA binding of NFkB. Western blotting, qRT-PCR and ELISA were used to measure the protein, mRNA, and activity levels of known AD hallmarks and signaling molecules.

Results

Dabigatran treatment attenuated thrombin-induced increase in DNA binding of NFκB by 175% at 50 nM and by 77% at 100 nM thrombin concentration. Thrombin also augmented accumulation of Aβ protein expression and phosphorylation of p38 MAPK, a downstream molecule in the signaling cascade, expression of pro-apoptotic mediator caspase 3, APP, tTau and pTau. Additionally, thrombin increased BACE1 activity, GSK3β expression, and APP, BACE1, Tau and GSK3β mRNA levels. Co-incubation with dabigatran attenuated thrombin-induced increases in the protein, mRNA, and activities of the aforesaid molecules to various extents (between −31% and −283%).

Conclusion

Our data demonstrates that thrombin promotes AD-related pathological changes in neuronal cultures and suggests that use of direct oral anticoagulants may provide a therapeutic benefit against thrombin-driven neuroinflammation and downstream pathology in AD.

Update on the Neurobiology of Vascular Cognitive Impairment: From Lab to Clinic

In the last years, there has been a significant growth in the literature exploring the pathophysiology of vascular cognitive impairment (VCI). As an "umbrella term" encompassing any degree of vascular-related cognitive decline, VCI is deemed to be the most common cognitive disorder in the elderly, with a significant impact on social and healthcare expenses. Interestingly, some of the molecular, biochemical, and electrophysiological abnormalities detected in VCI seem to correlate with disease process and progression, eventually promoting an adaptive plasticity in some patients and a maladaptive, dysfunctional response in others. However, the exact relationships between vascular lesion, cognition, and neuroplasticity are not completely understood. Recent findings point out also the possibility to identify a panel of markers able to predict cognitive deterioration in the so-called "brain at risk" for vascular or mixed dementia. This will be of pivotal importance when designing trials of disease-modifying drugs or non-pharmacological approaches, including non-invasive neuromodulatory techniques. Taken together, these advances could make VCI a potentially preventable cause of both vascular and degenerative dementia in late life. This review provides a timely update on the recent serological, cerebrospinal fluid, histopathological, imaging, and neurophysiological studies on this "cutting-edge" topic, including the limitations, future perspectives and translational implications in the diagnosis and management of VCI patients.

Update on the Neurobiology of Vascular Cognitive Impairment: From Lab to Clinic

In the last years, there has been a significant growth in the literature exploring the pathophysiology of vascular cognitive impairment (VCI). As an "umbrella term" encompassing any degree of vascular-related cognitive decline, VCI is deemed to be the most common cognitive disorder in the elderly, with a significant impact on social and healthcare expenses. Interestingly, some of the molecular, biochemical, and electrophysiological abnormalities detected in VCI seem to correlate with disease process and progression, eventually promoting an adaptive plasticity in some patients and a maladaptive, dysfunctional response in others. However, the exact relationships between vascular lesion, cognition, and neuroplasticity are not completely understood. Recent findings point out also the possibility to identify a panel of markers able to predict cognitive deterioration in the so-called "brain at risk" for vascular or mixed dementia. This will be of pivotal importance when designing trials of disease-modifying drugs or non-pharmacological approaches, including non-invasive neuromodulatory techniques. Taken together, these advances could make VCI a potentially preventable cause of both vascular and degenerative dementia in late life. This review provides a timely update on the recent serological, cerebrospinal fluid, histopathological, imaging, and neurophysiological studies on this "cutting-edge" topic, including the limitations, future perspectives and translational implications in the diagnosis and management of VCI patients.

The Apolipoprotein E ε4 Allele-Dependent Relationship Between Serum Lipid Levels and Cognitive Function: A Population-Based Cross-sectional Study

Objectives: Till now, the effect of serum lipid levels on cognitive function is still controversial. The apolipoprotein E (APOE) ε4 allele is the most critical genetic risk factor for Alzheimer’s disease (AD) and cognitive impairment. Additionally, APOE ε4 allele has a major impact on lipid metabolism. The aim of this study was to investigate the APOE genotype-dependent relationship between peripheral serum lipid levels and cognitive impairment.

Methods: A total of 1,273 subjects aged 40–86 years participated in this cross-sectional study. Serum lipid levels and the APOE genotype were detected. Mini-Mental State Examination was used to diagnose the cognitive impairment or not. Univariate and multivariate analyses were used to analyze the relationships between APOE genotype, serum lipid levels, and cognition function.

Results: After controlling for all possible covariates, a significant interaction between low serum high-density lipoprotein and the APOE ε4 allele on cognitive impairment (Wald’s χ² = 4.269, df = 1, OR = 20.094, p = 0.039) was found in the total participants. In APOE ε4 carriers, low serum high-density lipoprotein was positively associated with cognitive impairment (Wald’s χ² = 8.200, df = 1, OR = 60.335, p = 0.004) and serum high-density lipoprotein levels were positively correlated with Mini-Mental State Examination score (r = 0.217, df = 176, p = 0.004). There was no significant correlation between serum total cholesterol (TC), low-density lipoprotein, triglycerides (TG) levels, and cognitive impairment in either the total participants or APOE ε4 carriers/non-carriers.

Conclusions: APOE ε4 carriers, but not non-carriers, with lower serum high-density lipoprotein had a higher prevalence of cognitive impairment and a lower Mini-Mental State Examination score. These results suggest that the APOE ε4 allele may affect the relationship between serum lipid levels and cognitive impairment. However, the specific mechanism needs to be further elucidated.

Serum Neurofilament light correlates with CADASIL disease severity and survival

Objective

To validate whether serum Neurofilament Light‐chain (NfL) levels correlate with disease severity in CADASIL, and to determine whether serum NfL predicts disease progression and survival.

Methods

Fourty‐one (pre‐) manifest individuals with CADASIL causing NOTCH3 mutations and 22 healthy controls were recruited from CADASIL families. At baseline, MRI‐lesion load and clinical severity was determined and serum was stored. Disease progression was measured in 30/41 patients at 7‐year follow‐up, and survival of all individuals was determined at 17‐year follow‐up. Serum NfL levels were quantified using an ultra‐sensitive molecule array. Generalized estimated equation regression (GEE) was used to analyze association between serum NfL, MRI‐lesion load, disease severity, and disease progression. With GEE‐based Cox regression, survival was analyzed.

Results

At baseline, serum NfL levels correlated with MRI‐lesion load [lacune count (s = 0.64, P = 0.002), brain atrophy (r = −0.50, P = 0.001), and microbleed count (s = 0.48, P = 0.044)], cognition [CAMCOG (s = −0.45, P = 0.010), MMSE (r = −0.61, P = 0.003), GIT (r = −0.61, P < 0.001), TMT‐A (r = 0.70, P < 0.001)) and disability (mRS (r = 0.70, P = 0.002)]. Baseline serum NfL predicted 7‐year changes in disability (B = 0.34, P < 0.001) and cognition (CAMCOG B = −4.94, P = 0.032), as well as 17‐year survival. Higher NfL levels were associated with increased mortality (HR=1.8 per twofold increase in NfL levels, P = 0.006).

Interpretation

Serum NfL levels correlate with disease severity, disease progression and 17‐year survival in CADASIL patients. Serum NfL is a promising biomarker to monitor and predict disease course in CADASIL, as well as potentially assessing therapeutic response in future clinical trials.

Biomarkers in Alzheimer's, Frontotemporal, Lewy Body, and Vascular Dementias

This article reviews the current evidence base for biomarkers of the most common causes of dementia in later life: Alzheimer's disease (AD), frontotemporal lobar degenerations, Lewy body dementias, and vascular cognitive impairment and dementia. Biomarkers are objectively measurable indicators of normal physiology, pathological processes, or response to an intervention. Ideally, they are sensitive, specific, easy to obtain, and closely reflect the underlying biological processes of interest. While such markers are well established and in broad clinical use for common disorders in general medicine (e.g., thallium stress tests for coronary artery disease or serum blood urea nitrogen and creatinine for renal failure), analogous, validated markers for AD or other common dementias are limited, although biomarkers in research settings and specialty dementia clinics are progressing toward clinical use. By way of introducing current and future biomarkers for dementias of later life, this article will benefit the practicing clinician by increasing awareness of the availability and utility of current and emerging biomarkers in dementia diagnosis and prognosis and for monitoring new disease-modifying therapeutics that arrive in the clinic over the coming decade.

N-Terminal Prosomatostatin and Risk of Vascular Dementia

BACKGROUND

Increased somatostatin plasma concentration has been found in patients with vascular dementia. However, it is unknown whether or not somatostatin levels may predict dementia development in the general population. To this end, we sought to assess the association of circulating N-terminal prosomatostatin (NT-proSST) with incident dementia among community-dwelling older adults.

METHODS

In the prospective population-based Malmö Preventive Project, 5,347 study participants (mean age: 69 ± 6years; 70% men) provided plasma for the determination of NT-proSST concentration. Of these, 373 participants (7%) were diagnosed with dementia (120 Alzheimer's disease, 83 vascular, 102 mixed, and 68 other aetiology) during a follow-up period of 4.6 ± 1.3 years. The association of NT-proSST with the risk of dementia and its subtypes was studied using multivariable-adjusted Cox regression models controlling for age, gender, body mass index, systolic blood pressure, antihypertensive treatment, smoking, diabetes, lipid levels and prevalent stroke.

RESULTS

Higher levels of NT-proSST were significantly associated with an increased risk of vascular dementia (hazard ratio [HR] per 1 SD: 1.29; 95% CI 1.05-1.59; p = 0.016), whereas no association was observed with Alzheimer's disease (HR per 1 SD: 0.99; 95% CI 0.81-1.20; p = 0.91), all-cause dementia (HR per 1 SD: 1.04; 95% CI 0.94-1.16; p = 0.44), and mixed dementia (HR per 1 SD: 0.98; 95% CI 0.79-1.21; p = 0.84). Levels of NT-proSST above 563 pmol/L (highest quartile) conferred distinctly increased risk of vascular dementia (HR 1.66; 95% CI 1.05-2.63; p = 0.029) compared with lower values.

CONCLUSIONS

Higher levels of circulating N-terminal-prosomatostatin are associated with increased incidence of vascular dementia. Our findings might be of importance for the understanding of dementia development in older adults.

Analytical performance of reagent for assaying tau protein in human plasma and feasibility study screening neurodegenerative diseases

Immunomagnetic reduction (IMR), which involves the use of antibody-functionalized magnetic nanoparticles to specifically label target biomarkers, was utilized to develop an assay for total tau protein in human plasma. The analytic properties of the IMR assay on tau protein were investigated. The limit of detection was found to be 0.026 pg/ml. Other properties such as Hook effect, assay linearity, dilution recovery range, reagent stability, interference test, and spiked recovery were also characterized. The ultra-sensitive IMR assay was applied to detect the plasma tau protein levels of subjects with prevalent neurodegenerative diseases, such as Alzheimer's disease (AD), mild cognitive impairment (MCI) due to AD, Parkinson's disease (PD), frontotemporal dementia (FTD) and vascular dementia (VD). The concentrations of plasma tau protein in patients with VD, PD, MCI due to AD, FTD, and AD patients were higher than that of healthy controls. Using an ROC curve analysis, the cutoff value for discriminating dementia patients from healthy controls was 17.43 pg/ml, resulting in 0.856 and 0.727 for clinical sensitivity and specificity, respectively. The area under the ROC curve was 0.908. These results imply that the IMR plasma tau assay would be useful to screen for prevalent neurodegenerative diseases.

Tau proteins in the temporal and frontal cortices in patients with vascular dementia

We previously reported that, in the brains of older patients with vascular dementia (VaD), there is a distinctive accumulation of detergent-extractable soluble amyloid-β, with a predominance of Aβ42 species. It is unclear, however, if tau proteins also accumulate in the brains of older VaD subjects. Using antibody-specific immunoassays, we assessed concentrations of total tau (t-tau) and phosphorylated tau protein, measured at 3 phosphorylated sites (i.e. Thr181, Ser202/Thr205, and Ser262), as well as synaptophysin in the temporal and frontal cortices of 18 VaD, 16 Alzheimer disease (AD), and 16 normal age-matched control subjects. There was selective loss of t-tau protein in VaD compared with controls and AD subjects (p < 0.021 and p < 0.001, respectively). In contrast, phosphorylated tau levels were similar to controls in VaD in both regions, but they were increased in the temporal lobes of patients with AD (p < 0.01 and p < 0.0001 for Ser202/Thr205 and Ser262 phosphorylated sites, respectively). The reduced t-tau in the VaD group was unrelated to any low-level neurofibrillary or amyloid pathology or age at death. These findings suggest that breaches of microvascular or microstructural tissue integrity subsequent to ischemic injury in older age may modify tau protein metabolism or phosphorylation and have effects on the burden of neurofibrillary pathology characteristic of AD.

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

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

Neurovascular dysfunction, inflammation and endothelial activation: implications for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is an age-related disorder characterized by progressive cognitive decline and dementia. Alzheimer's disease is an increasingly prevalent disease with 5.3 million people in the United States currently affected. This number is a 10 percent increase from previous estimates and is projected to sharply increase to 8 million by 2030; it is the sixth-leading cause of death. In the United States the direct and indirect costs of Alzheimer's and other dementias to Medicare, Medicaid and businesses amount to more than $172 billion each year. Despite intense research efforts, effective disease-modifying therapies for this devastating disease remain elusive. At present, the few agents that are FDA-approved for the treatment of AD have demonstrated only modest effects in modifying clinical symptoms for relatively short periods and none has shown a clear effect on disease progression. New therapeutic approaches are desperately needed. Although the idea that vascular defects are present in AD and may be important in disease pathogenesis was suggested over 25 years ago, little work has focused on an active role for cerebrovascular mechanisms in the pathogenesis of AD. Nevertheless, increasing literature supports a vascular-neuronal axis in AD as shared risk factors for both AD and atherosclerotic cardiovascular disease implicate vascular mechanisms in the development and/or progression of AD. Also, chronic inflammation is closely associated with cardiovascular disease, as well as a broad spectrum of neurodegenerative diseases of aging including AD. In this review we summarize data regarding, cardiovascular risk factors and vascular abnormalities, neuro- and vascular-inflammation, and brain endothelial dysfunction in AD. We conclude that the endothelial interface, a highly synthetic bioreactor that produces a large number of soluble factors, is functionally altered in AD and contributes to a noxious CNS milieu by releasing inflammatory and neurotoxic species.