Plasma and cerebrospinal fluid alpha1-antichymotrypsin levels in Alzheimer's disease: correlation with cognitive impairment

Prediction Value of Initial Serum Levels of SERPINA3 in Intracranial Pressure and Long-Term Neurological Outcomes in Traumatic Brain Injury

Traumatic brain injury (TBI) is a severe neurological condition characterized by inflammation in the central nervous system. SERPINA3 has garnered attention as a potential biomarker for assessing this inflammation. Our study aimed to explore the predictive value of postoperative serum SERPINA3 levels in identifying the risk of cerebral edema and its prognostic implications in TBI. This study is a prospective observational study, including 37 patients with TBI who finally met our criteria. The Glasgow Outcome Scale (GOS), Levels of Cognitive Functioning (LCF), Disability Rating Scale (DRS), and Early Rehabilitation Barthel Index (ERBI) scores at six months after trauma were defined as the main study endpoint. We further calculated the ventricle-to-intracranial-volume ratio (VBR) at 6 months from CT scans. The study included patients with Glasgow Coma Scale (GCS) scores ranging from 3 to 8, who were subsequently categorized into two groups: the critical TBI group (GCS 3-5 points) and the severe TBI group (GCS 6-8 points). Within the critical TBI group, SERPINA3 levels were notably lower. However, among patients with elevated SERPINA3 levels, both the peak intracranial pressure (ICP) and average mannitol consumption were significantly reduced compared with those of patients with lower SERPINA3 levels. In terms of the 6-month outcomes measured via the GOS, LCF, DRS, and ERBI, lower levels of SERPINA3 were indicative of poorer prognosis. Furthermore, we found a negative correlation between serum SERPINA3 levels and the VBR. The receiver operating characteristic (ROC) curve and decision curve analysis (DCA) demonstrated the predictive performance of SERPINA3. In conclusion, incorporating the novel biomarker SERPINA3 alongside traditional assessment tools offers neurosurgeons an effective and easily accessible means, which is readily accessible early on, to predict the risk of intracranial pressure elevation and long-term prognosis in TBI patients.

Regulation of CNS pathology by Serpina3n/SERPINA3: The knowns and the puzzles

Neuroinflammation, blood-brain barrier (BBB) dysfunction, neuron and glia injury/death and myelin damage are common central nervous system (CNS) pathologies observed in various neurological diseases and injuries. Serine protease inhibitor (Serpin) clade A member 3n (Serpina3n), and its human orthologue SERPINA3, is an acute-phase inflammatory glycoprotein secreted primarily by the liver into the bloodstream in response to systemic inflammation. Clinically, SERPINA3 is dysregulated in brain cells, cerebrospinal fluid and plasma in various neurological conditions. Although it has been widely accepted that Serpina3n/SERPINA3 is a reliable biomarker of reactive astrocytes in diseased CNS, recent data have challenged this well-cited concept, suggesting instead that oligodendrocytes and neurons are the primary sources of Serpina3n/SERPINA3. The debate continues regarding whether Serpina3n/SERPINA3 induction represents a pathogenic or a protective mechanism. Here, we propose possible interpretations for previously controversial data and present perspectives regarding the potential role of Serpina3n/SERPINA3 in CNS pathologies, including demyelinating disorders where oligodendrocytes are the primary targets. We hypothesise that the 'good' or 'bad' aspects of Serpina3n/SERPINA3 depend on its cellular sources, its subcellular distribution (or mis-localisation) and/or disease/injury types. Furthermore, circulating Serpina3n/SERPINA3 may cross the BBB to impact CNS pathologies. Cell-specific genetic tools are critically important to tease out the potential roles of cell type-dependent Serpina3n in CNS diseases/injuries.

Dispensable regulation of brain development and myelination by Serpina3n

Serine protease inhibitor clade A member 3n (Serpina3n) or its human orthologue SERPINA3 is a secretory glycoprotein expressed primarily in the liver and brain under homeostatic conditions and dysregulated in various CNS pathologies. Yet its cellular expression profile and physiological significance in postnatal development remain elusive. Here, we showed that Serpina3n protein is expressed predominantly in oligodendroglial lineage cells in the postnatal CNS and that oligodendrocytes (OLs) responded to oxidative injury by upregulating Serpina3n production and secretion. Using loss-of-function genetic tools, we found that Serpina3n conditional knockout (cKO) from Olig2-expressing cells did not affect motor and cognitive functions in mice. Serpina3n depletion in Olig2-expressing cells did not appear to interfere with oligodendrocyte differentiation and developmental myelination nor affect the population of other glial cells and neurons in vivo. In vitro primary cell culture showed that Serpina3n-sufficient and -deficient oligodendroglial progenitor cells (OPCs) differentiated into myelin gene-expressing OLs comparatively. Together, these data suggest that Serpina3n plays a minor role, if any, in regulating brain neural cell development and myelination under homeostatic conditions and raise interests in pursuing its functional significance in CNS diseases and injuries.

Hippocampal delivery of neurotrophic factor-α1/carboxypeptidase E gene prevents neurodegeneration, amyloidosis, memory loss in Alzheimer's Disease male mice

Alzheimer's Disease (AD) is a prevalent neurodegenerative disease characterized by tau hyperphosphorylation, Aβ1-42 aggregation and cognitive dysfunction. Therapeutic agents directed at mitigating tau aggregation and clearing Aβ1-42, and delivery of growth factor genes (BDNF, FGF2), have ameliorated cognitive deficits, but these approaches did not prevent or stop AD progression. Here we report that viral-(AAV) delivery of Neurotrophic Factor-α1/Carboxypeptidase E (NF-α1/CPE) gene in hippocampus at an early age prevented later development of cognitive deficits as assessed by Morris water maze and novel object recognition assays, neurodegeneration, and tau hyperphosphorylation in male 3xTg-AD mice. Additionally, amyloid precursor protein (APP) expression was reduced to near non-AD levels, and insoluble Aβ1-42 was reduced significantly. Pro-survival proteins: mitochondrial Bcl2 and Serpina3g were increased; and mitophagy inhibitor Plin4 and pro-inflammatory protein Card14 were decreased in AAV-NF-α1/CPE treated versus untreated AD mice. Thus NF-α1/CPE gene therapy targets many regulatory components to prevent cognitive deficits in 3xTg-AD mice and has implications as a new therapy to prevent AD progression by promoting cell survival, inhibiting APP overexpression and tau hyperphosphorylation.

SERPINA3: Stimulator or Inhibitor of Pathological Changes

SERPINA3, also called α-1-antichymotrypsin (AACT, ACT), is one of the inhibitors of serine proteases, one of which is cathepsin G. As an acute-phase protein secreted into the plasma by liver cells, it plays an important role in the anti-inflammatory response and antiviral response. Elevated levels of SERPINA3 have been observed in heart failure and neurological diseases such as Alzheimer's disease or Creutzfeldt-Jakob disease. Many studies have shown increased expression levels of the SERPINA3 gene in various types of cancer, such as glioblastoma, colorectal cancer, endometrial cancer, breast cancer, or melanoma. In this case, the SERPINA3 protein is associated with an antiapoptotic function implemented by adjusting the PI3K/AKT or MAPK/ERK 1/2 signal pathways. However, the functions of the SERPINA3 protein are still only partially understood, mainly in the context of cancerogenesis, so it seems necessary to summarize the available information and describe its mechanism of action. In particular, we sought to amass the existing body of research focusing on the description of the underlying mechanisms of various diseases not related to cancer. Our goal was to present an overview of the correct function of SERPINA3 as part of the defense system, which unfortunately easily becomes the "Fifth Column" and begins to support processes of destruction.

Deciphering the enigmatic crosstalk between prostate cancer and Alzheimer's disease: A current update on molecular mechanisms and combination therapy

Alzheimer's disease (AD) and prostate cancer (PCa) are considered the leading causes of death in elderly people worldwide. Although both these diseases have striking differences in their pathologies, a few underlying mechanisms are similar when cell survival is considered. In the current study, we employed an in-silico approach to decipher the possible role of bacterial proteins in the initiation and progression of AD and PCa. We further analyzed the molecular connections between these two life-threatening diseases. The androgen deprivation therapy used against PCa has been shown to promote castrate resistant PCa as well as AD. In addition, cell signaling pathways, such as Akt, IGF, and Wnt contribute to the progression of both AD and PCa. Besides, various proteins and genes are also common in disease progression. One such similarity is mTOR signaling. mTOR is the common downstream target for many signaling pathways and plays a vital role in both PCa and AD. Targeting mTOR can be a favorable line of treatment for both AD and PCa. However, drug resistance is one of the challenges in effective drug therapy. A few drugs that target mTOR have now become ineffective due to the development of resistance. In that regard, phytochemicals can be a rich source of novel drug candidates as they can act via multiple mechanisms. This review also presents mTOR targeting phytochemicals with promising anti-PCa, anti-AD activities, and approaches to overcome the issues associated with phytochemical-based therapies in clinical trials.

Novel Exosome Biomarker Candidates for Alzheimer's Disease Unravelled Through Mass Spectrometry Analysis

Exosomes are small extracellular vesicles (EVs) present in human biofluids that can transport specific disease-associated molecules. Consequently blood-derived exosomes have emerged as important peripheral biomarker sources for a wide range of diseases, among them Alzheimer’s disease (AD). Although there is no effective cure for AD, an accurate diagnosis, relying on easily accessible peripheral biofluids, is still necessary to discriminate this disease from other dementias, test potential therapies and even monitor rate of disease progression. The ultimate goal is to produce a cost-effective and widely available alternative, which can also be employed as a first clinical screen. In this study, EVs with exosome-like characteristics were isolated from serum of Controls and AD cases through precipitation- and column-based methods, followed by mass spectrometry analysis. The resulting proteomes were characterized by Gene Ontology (GO) and multivariate analyses. Although GO terms were similar for exosomes’ proteomes of Controls and ADs, using both methodologies, a clear segregation of disease cases was obtained when using the precipitation-based method. Nine significantly different abundant proteins were identified between Controls and AD cases, representing putative biomarker candidate targets. Among them are AACT and C4BPα, two Aβ-binding proteins, whose exosome levels were further validated in individuals from independent cohorts using antibody-based approaches. The findings discussed represent an important contribution to the identification of novel exosomal biomarker candidates useful as potential blood-based tools for AD diagnosis.

Transient response of serpinA3 during cellular stress

We demonstrated that serpinA3c/k relocates from the cytoplasm to the apical tubular membrane (ATM) in chronic kidney disease (CKD), suggesting its secretion in luminal space in pathophysiological contexts. Here, we studied serpinA3c/k expression and secretion under different stressful conditions in vitro and in vivo. HEK-293 cells were transfected with a FLAG-tagged serpinA3c/k clone and exposed to H₂ O₂ or starvation. Both stressors induced serpinA3c/k secretion but with a higher molecular weight. Glycanase treatment established that serpinA3c/k is glycosylated. Site-directed mutagenesis for each of the four glycosylation sites was performed. During cellular stress, serpinA3c/k secretion increased with each mutant except in the quadruple mutant. In rats and patients suffering acute kidney injury (AKI), an atypical urinary serpinA3c/k excretion (uSerpinA3c/k) was observed. In rats with AKI, the greater the induced kidney damage, the greater the uSerpinA3 c/k, together with relocation toward ATM. Our findings show that: (1) serpinA3c/k is glycosylated and secreted, (2) serpinA3c/k secretion increases during cellular stress, (3) its appearance in urine reveals a pathophysiological state, and (4) urinary serpinA3 excretion could become a potential biomarker for AKI.

Biosensor approaches on the diagnosis of neurodegenerative diseases: Sensing the past to the future

Early diagnosis of neurodegeneration-oriented diseases that develop with the aging world is essential for improving the patient's living conditions as well as the treatment of the disease. Alzheimer's and Parkinson's diseases are prominent examples of neurodegeneration characterized by dementia leading to the death of nerve cells. The clinical diagnosis of these diseases only after the symptoms appear, delays the treatment process. Detection of biomarkers, which are distinctive molecules in biological fluids, involved in neurodegeneration processes, has the potential to allow early diagnosis of neurodegenerative diseases. Studies on biosensors, whose main responsibility is to detect the target analyte with high specificity, has gained momentum in recent years with the aim of high detection of potential biomarkers of neurodegeneration process. This study aims to provide an overview of neuro-biosensors developed on the basis of biomarkers identified in biological fluids for the diagnosis of neurodegenerative diseases such as Alzheimer's disease (AD), and Parkinson's disease (PD), and to provide an overview of the urgent needs in this field, emphasizing the importance of early diagnosis in the general lines of the neurodegeneration pathway. In this review, biosensor systems developed for the detection of biomarkers of neurodegenerative diseases, especially in the last 5 years, are discussed.

Role of Inflammatory Cytokines in the Conversion of Mild Cognitive Im- pairment to Dementia: A Prospective Study

BACKGROUND

The effect that cytokines can exert on the progression from mild cognitive impairment (MCI) to ongoing dementia is a matter of debate and the results obtained so far are controversial.

OBJECTIVE

The aim of the study is to analyze the influence of markers of subclinical inflammation on the progression of MCI to dementia.

METHODS

A prospective study involving a cohort of patients ≥ 65 years of age diagnosed with MCI and followed for 3 years was conducted. 105 patients were enrolled, and serum concentrations of several subclinical inflammatory markers were determined.

RESULTS

After 3.09 (2 - 3.79) years of follow-up, 47 (44.76%) patients progressed to dementia. Alpha 1-antichymotrypsin (ACT) was found to be significantly higher in patients who progressed to dementia (486.45 ± 169.18 vs. 400.91 ± 163.03; p = 0.012), and observed to significantly increase the risk of developing dementia in patients with mild cognitive impairment (1.004, 1.001-1.007; p= 0.007). IL-10 levels were significantly higher in those who remained stable (6.69 ± 18.1 vs. 32.54 ± 89.6; p = 0.04). Regarding the type of dementia to which our patients progressed, we found that patients who developed mixed dementia had higher IL-4 levels than those who converted to AD (31.54 ± 63.6 vs. 4.43 ± 12.9; p = 0.03). No significant differences were observed between the groups with regard to the ESR and LPa, CRP, IL-1 and TNF-α levels.

CONCLUSION

ACT levels have a significant predictive value in the conversion of MCI to dementia. IL-10 levels could be a protective factor. It is necessary to conduct studies with serial determinations of these and other inflammatory markers in order to determine their effect on the progression of MCI to dementia.

Extracellular protein components of amyloid plaques and their roles in Alzheimer's disease pathology

Alzheimer's disease (AD) is pathologically defined by the presence of fibrillar amyloid β (Aβ) peptide in extracellular senile plaques and tau filaments in intracellular neurofibrillary tangles. Extensive research has focused on understanding the assembly mechanisms and neurotoxic effects of Aβ during the last decades but still we only have a brief understanding of the disease associated biological processes. This review highlights the many other constituents that, beside Aβ, are accumulated in the plaques, with the focus on extracellular proteins. All living organisms rely on a delicate network of protein functionality. Deposition of significant amounts of certain proteins in insoluble inclusions will unquestionably lead to disturbances in the network, which may contribute to AD and copathology. This paper provide a comprehensive overview of extracellular proteins that have been shown to interact with Aβ and a discussion of their potential roles in AD pathology. Methods that can expand the knowledge about how the proteins are incorporated in plaques are described. Top-down methods to analyze post-mortem tissue and bottom-up approaches with the potential to provide molecular insights on the organization of plaque-like particles are compared. Finally, a network analysis of Aβ-interacting partners with enriched functional and structural key words is presented.

Exosomal Aβ-Binding Proteins Identified by "In Silico" Analysis Represent Putative Blood-Derived Biomarker Candidates for Alzheimer´s Disease

The potential of exosomes as biomarker resources for diagnostics and even for therapeutics has intensified research in the field, including in the context of Alzheimer´s disease (AD). The search for disease biomarkers in peripheral biofluids is advancing mainly due to the easy access it offers. In the study presented here, emphasis was given to the bioinformatic identification of putative exosomal candidates for AD. The exosomal proteomes of cerebrospinal fluid (CSF), serum and plasma, were obtained from three databases (ExoCarta, EVpedia and Vesiclepedia), and complemented with additional exosomal proteins already associated with AD but not found in the databases. The final biofluids’ proteomes were submitted to gene ontology (GO) enrichment analysis and the exosomal Aβ-binding proteins that can constitute putative candidates were identified. Among these candidates, gelsolin, a protein known to be involved in inhibiting Abeta fibril formation, was identified, and it was tested in human samples. The levels of this Aβ-binding protein, with anti-amyloidogenic properties, were assessed in serum-derived exosomes isolated from controls and individuals with dementia, including AD cases, and revealed altered expression patterns. Identification of potential peripheral biomarker candidates for AD may be useful, not only for early disease diagnosis but also in drug trials and to monitor disease progression, allowing for a timely therapeutic intervention, which will positively impact the patient’s quality of life.

Alpha 1-antichymotrypsin may be a biomarker for the progression of amnestic mild cognitive impairment

Alpha 1-antichymotrypsin (ACT), an acute-phase protein, has been reported to be increased in the brain and blood of Alzheimer's disease (AD) patients. However, few previous studies have focused on amnestic mild cognitive impairment (aMCI) patients. The aim of our study was to investigate the changing trend in ACT concentrations during the progression of aMCI. Hence, we measured the cerebrospinal fluid (CSF) and serum levels of ACT in aMCI subjects and normal controls (NC) at 2-year follow-up assessments using ELISA and Western blot. Forty-four NCs, 28 stable aMCI (sMCI) patients, and 20 progressive aMCI (pMCI) patients finished the follow-up assessments, and their data were used for analysis. We found that CSF and serum ACT levels of both sMCI and pMCI patients increased over time, while those of NCs remained stable; CSF and serum ACT levels were significantly higher in both sMCI and pMCI patients than in NCs, except for baseline serum ACT. In pMCI patients prior to developing AD, CSF and serum ACT levels were already significantly higher than those in sMCI patients. The ROC curve results demonstrated that combining CSF and serum ACT levels can distinguish aMCI patients from NCs with high specificity and sensitivity. Our data suggest that ACT may be a biomarker for diagnosing aMCI.

CSF SERPINA3 Levels Are Elevated in Patients With Progressive MS

Objective

To identify biomarkers associated with progressive phases of MS and with neuroprotective potential.

Methods

Combined analysis of the transcriptional and proteomic profiles obtained in CNS tissue during chronic progressive phases of experimental autoimmune encephalomyelitis (EAE) with the transcriptional profile obtained during the differentiation of murine neural stem cells into neurons. Candidate biomarkers were measured by ELISA in the CSF of 65 patients with MS (29 with relapsing-remitting MS [RRMS], 20 with secondary progressive MS, and 16 with primary progressive MS [PPMS]) and 30 noninflammatory neurologic controls (NINCs).

Results

Integrative analysis of gene and protein expression data identified 2 biomarkers, the serine protease inhibitor Serpina3n and the calcium-binding protein S100A4, which were upregulated in chronic progressive EAE and whose expression was induced during neuronal differentiation. Immunofluorescence studies revealed a primarily neuronal expression of S100A4 and Serpina3n during EAE. CSF levels of SERPINA3, the human ortholog of murine Serpina3n, and S100A4 were increased in patients with MS compared with NINCs (SERPINA3: 1,320 vs 838.6 ng/mL, p = 0.0001; S100A4: 1.6 vs 0.8 ng/mL, p = 0.02). Within the MS group, CSF SERPINA3 levels were significantly elevated in patients with progressive forms, mainly patients with PPMS compared with patients with RRMS (1,617 vs 1,129 ng/mL, p = 0.02) and NINCs (1,617 vs 838.6 ng/mL, p = 0.0001). Of interest, CSF SERPINA3 levels significantly correlated with CSF neurofilament light chain levels only in the PPMS group (r = 0.62, p = 0.01).

Conclusion

These results point to a role of SERPINA3 as a biomarker associated with the progressive forms of MS, particularly PPMS.

Exploration of the Role of Serine Proteinase Inhibitor A3 in Alcohol Dependence Using Gene Expression Omnibus Database

Background: Alcohol dependence is an overall health-related challenge; however, the specific mechanisms underlying alcohol dependence remain unclear. Serine proteinase inhibitor A3 (SERPINA3) plays crucial roles in multiple human diseases; however, its role in alcohol dependence clinical practice has not been confirmed. Methods: We screened Gene Expression Omnibus (GEO) expression profiles, and identified differentially expressed genes (DEGs). Protein-protein interaction (PPI) networks were generated using STRING and Cytoscape, and the key clustering module was identified using the MCODE plugin. SERPINA3-based target microRNA prediction was performed using online databases. Functional enrichment analysis was performed. Fifty-eight patients with alcohol dependence and 20 healthy controls were recruited. Clinical variables were collected and follow-up was conducted for 8 months for relapse. Results: SERPINA3 was identified as a DEG. ELANE and miR-137 were identified after PPI analysis. The enriched functions and pathways included acute inflammatory response, response to stress, immune response, and terpenoid backbone biosynthesis. SERPINA3 concentrations were significantly elevated in the alcohol dependence group than in healthy controls (P < 0.001). According to the median value of SERPINA3 expression level in alcohol dependence group, patients were divided into high SERPINA3 (≥2677.33 pg/ml, n = 29) and low SERPINA3 groups (<2677.33 pg/ml, n = 29). Binary logistic analysis indicated that IL-6 was statistically significant (P = 0.015) Kaplan-Meier survival analysis did not indicate any difference in event-free survival between patients with low and high SERPINA3 levels (P = 0.489) after 8 months of follow-up. Receiver characteristic curve analysis revealed that SERPINA3 had an area under the curve of 0.921 (P < 0.0001), with a sensitivity and specificity of 93.1 and 80.0%, respectively. Cox regression analysis revealed that aspartate transaminase level was a negative predictor of relapse (β = 0.003; hazard ratio = 1.003; P = 0.03). Conclusions: SERPINA3 level was remarkably elevated in patients with alcohol dependence than healthy controls, indicating that SERPINA3 is correlated with alcohol dependence. However, SERPINA3 may not be a potential predictive marker of relapse with patients in alcohol dependence.

Alzheimer's Amyloidopathy: An Alternative Aspect

The ‘amyloid hypothesis’ dominates Alzheimer’s disease (AD) research but has failed to deliver effective therapies. Amyloid precursor protein (APP) and presenilin-1 (PSEN1) genetic mutations are undoubtedly pathogenic, albeit by unclear mechanisms. Conversely, high dose B-vitamins convincingly slow brain atrophy in a pre-stage state of sporadic AD. Here we suggest a link between sporadic and genetic AD: 1) Increased serum homocysteine, a marker of B-vitamin deficiencies, is a significant risk factor for sporadic AD. It also correlates with elevated levels of antichymotrypsin, a serine protease inhibitor. 2) Family members with codon 717 APP mutations and dementia have low serum vitamin B₁₂ values. Overexpression of the APP domain coding for a Kunitz type serine protease inhibitor might explain this. 3) PSEN1 mutations disrupt lysosomal function due to reduced proteolytic activity. They also trap cobalamin (B₁₂) within lysosomes, leading to intracellular deficiency of the vitamin. In summary, APP and PSEN1 mutations both confer a risk for reduced protease activity and B₁₂ bio-availability. Comparably, sporadic AD features a constellation of increased protease inhibition and B-vitamin deficiencies, the central part of which is believed to be B₁₂. These concordant observations in three disparate AD etiologies suggest a common neuropathogenic pathway. This hypothesis is evaluable in laboratory and clinical trials.

Prevention of Early Alzheimer's Disease by Erinacine A-Enriched Hericium erinaceus Mycelia Pilot Double-Blind Placebo-Controlled Study

Objective

To investigate the efficacy and safety of three H. erinaceus mycelia (EAHE) capsules (350 mg/capsule; containing 5 mg/g erinacine A active ingredient) per day for the treatment of patients with mild Alzheimer’s Disease (AD).

Methods

This study comprised a 3-week no-drug screening period, followed by a 49-week double-blind treatment period with 2-parallel groups in which eligible patients were randomized to either three 5 mg/g EAHE mycelia capsules per day or identical appearing placebo capsules. Cognitive assessments, ophthalmic examinations, biomarker collection, and neuroimaging were followed throughout the study period.

Results

After 49 weeks of EAHE intervention, a significant decrease in Cognitive Abilities Screening Instrument score was noted in the placebo group, a significant improvement in Mini-Mental State Examination score was observed in the EAHE group and a significant Instrumental Activities of Daily Living score difference were found between the two groups. In addition, EAHE group achieved a significantly better contrast sensitivity when compared to the placebo group. Moreover, only the placebo group observed significantly lowered biomarkers such as calcium, albumin, apolipoprotein E4, hemoglobin, and brain-derived neurotrophic factor and significantly elevated alpha1-antichymotrypsin and amyloid-beta peptide 1–40 over the study period. Using diffusion tensor imaging, the mean apparent diffusion coefficient (ADC) values from the arcuate fasciculus region in the dominant hemisphere significantly increased in the placebo group while no significant difference was found in the EAHE group in comparison to their baselines. Moreover, ADC values from the parahippocampal cingulum region in the dominant hemisphere significantly decreased in the EAHE group whereas no significant difference was found in the placebo group when compared to their baselines. Lastly, except for four subjects who dropped out of the study due to abdominal discomfort, nausea, and skin rash, no other adverse events were reported.

Conclusion

Three 350 mg/g EAHE capsules intervention for 49 weeks demonstrated higher CASI, MMSE, and IADL scores and achieved a better contrast sensitivity in patients with mild AD when compared to the placebo group, suggesting that EAHE is safe, well-tolerated, and may be important in achieving neurocognitive benefits.

Clinical Trial Registration

ClinicalTrials.gov, identifier NCT04065061.

Inflammatory markers in Alzheimer's disease and mild cognitive impairment: a meta-analysis and systematic review of 170 studies

OBJECTIVE

Inflammation plays a crucial role in the pathogenesis of mild cognitive impairment (MCI) and Alzheimer's disease (AD). Our study aimed to analyse previous inconsistent results of inflammatory markers in AD and MCI quantitatively.

METHODS

Studies reporting concentrations of peripheral or cerebrospinal fluid (CSF) markers were included, and eligible data on AD, MCI and control were extracted. Pooled Hedges's g was adopted to illustrate comparisons, and various confounding factors were used to explore sources of heterogeneity.

RESULTS

A total of 170 studies were included in the meta-analysis and systematic review, which demonstrated increased peripheral levels of high-sensitivity C reactive protein (Hedges's g 0.281, p<0.05), interleukin-6 (IL-6) (0.429, p<0.005), soluble tumour necrosis factor receptor 1 (sTNFR1) (0.763, p<0.05), soluble tumour necrosis factor receptor 2 (sTNFR2) (0.354, p<0.005), alpha1-antichymotrypsin (α1-ACT) (1.217, p<0.005), IL-1β (0.615, p<0.05) and soluble CD40 ligand (0.868, p<0.005), and CSF levels of IL-10 (0.434, p<0.05), monocyte chemoattractant protein-1 (MCP-1) (0.798, p<0.005), transforming growth factor-beta 1 (1.009, p<0.05), soluble triggering receptor expressed on myeloid cells2 (sTREM2) (0.587, p<0.001), YKL-40 (0.849, p<0.001), α1-ACT (0.638, p<0.001), nerve growth factor (5.475, p<0.005) and visinin-like protein-1 (VILIP-1) (0.677, p<0.005), in AD compared with the control. Higher levels of sTNFR2 (0.265, p<0.05), IL-6 (0.129, p<0.05) and MCP-1 (0.779, p<0.05) and lower levels of IL-8 (-1.293, p<0.05) in the periphery, as well as elevated concentrations of YKL-40 (0.373, p<0.05), VILIP-1 (0.534, p<0.005) and sTREM2 (0.695, p<0.05) in CSF, were shown in MCI compared with the control. Additionally, increased peripheral sTNFR1 (0.582, p<0.05) and sTNFR2 (0.254, p<0.05) levels were observed in AD compared with MCI.

CONCLUSION

Significantly altered levels of inflammatory markers were verified in comparison between AD, MCI and control, supporting the notion that AD and MCI are accompanied by inflammatory responses in both the periphery and CSF.

Increased free prostate specific antigen serum levels in Alzheimer's disease, correlation with Cognitive Decline

BACKGROUND/AIMS

Prostate specific antigen (PSA) is regulated by steroid hormones, such as testosterone, the serum levels of which are altered in patients with Alzheimer's disease (AD).This pilot study compared serum levels of the free (f) PSA between AD, mild cognitive impairment (MCI), and control subjects, and evaluated the relationship between fPSA serum levels and cognitive assessment tests and neuroimaging data. In addition, in a subgroup of AD patients, we correlated fPSA serum levels with the existing data on serum levels of amyloid-beta (Aβ), and iron-related proteins, including hepcidin and ferritin.

METHODS

Frozen serum samples from the Oregon Tissue Bank were used to measure serum levels of fPSA using enzyme-linked immunosorbent assay.

RESULTS

fPSA serum levels calculated as median ± SD were higher in AD males (663.6 ± 821.0 pg/ml) compared to control males (152.0 ± 207.0 pg/ml), p = 0.003. A similar Pattern emerged when comparing MCI males (310.7 ± 367.0 pg/ml) to control males (P = 0.02). Correlation studies showed a significant association between fPSA and CDR (r = 0.56, P = 0.006) and CDR-SOB (r = 0.54, P = 0.009) in AD males.

CONCLUSION

Additional studies in a larger cohort are required for determining whether fPSA can be used as biomarker of AD disease progression and whether it has the potential to identify male subjects at risk of AD dementia.

Proteomics Analysis of Blood Serums from Alzheimer's Disease Patients Using iTRAQ Labeling Technology

Alzheimer' disease (AD) is the most common form of dementia affecting up to 6% of the population over the age of 65. In order to discover differentially expressed proteins that might serve as potential biomarkers, the serums from AD patients and healthy controls were compared and analyzed using the proteomics approach of isobaric tagging for relative and absolute quantitation (iTRAQ). For the first time, AD biomarkers in serums are investigated in the Han Chinese population using iTRAQ labeled proteomics strategy. Twenty-two differentially expressed proteins were identified and out of which nine proteins were further validated with more sample test. Another three proteins that have been reported in the literature to be potentially associated with AD were also investigated for alteration in expression level. Functions of those proteins were mainly related to the following processes: amyloid-β (Aβ) metabolism, cholesterol transport, complement and coagulation cascades, immune response, inflammation, hemostasis, hyaluronan metabolism, and oxidative stress. These results support current views on the molecular mechanism of AD. For the first time, differential expression of zinc-alpha-2-glycoprotein (AZGP1), fibulin-1 (FBLN1), platelet basic protein (PPBP), thrombospondin-1 (THBS1), S100 calcium-binding protein A8 (S100A8), and S100 calcium-binding protein A9 (S100A9) were detected in the serums of AD patients compared with healthy controls. These proteins might play a role in AD pathophysiology and serve as potential biomarkers for AD diagnosis. Specifically, our results strengthened the crucial role of Aβ metabolism and blood coagulation in AD pathogenesis and proteins related to these two processes may be used as peripheral blood biomarkers for AD.

Remarkable increases of α1-antichymotrypsin in brain tissues of rodents during prion infection

α1-Antichymotrypsin (α1-ACT) belongs to a kind of acute-phase inflammatory protein. Recently, such protein has been proved exist in the amyloid deposits which is the hallmark of Alzheimer's disease, but limitedly reported in prion disease. To estimate the change of α1-ACT during prion infection, the levels of α1-ACT in the brain tissues of scrapie agents 263K-, 139A- and ME7-infected rodents were analyzed, respectively. Results shown that α1-ACT levels were significantly increased in the brain tissues of the three kinds of scrapie-infected rodents, displaying a time-dependent manner during prion infection. Immunohistochemistry assays revealed the increased α1-ACT mainly accumulated in some cerebral regions of rodents infected with prion, such as cortex, thalamus and cerebellum. Immunofluorescent assays illustrated ubiquitously localization of α1-ACT with GFAP positive astrocytes, Iba1-positive microglia and NeuN-positive neurons. Moreover, double-stained immunofluorescent assays and immunohistochemistry assays using series of brain slices demonstrated close morphological colocalization of α1-ACT signals with that of PrP and PrP^Sc in the brain slices of 263K-infected hamster. However, co-immunoprecipitation does not identify any detectable molecular interaction between the endogenous α1-ACT and PrP either in the brain homogenates of 263K-infected hamsters or in the lysates of prion-infected cultured cells. Our data here imply that brain α1-ACT is increased abnormally in various scrapie-infected rodent models. Direct molecular interaction between α1-ACT and PrP seems not to be essential for the morphological colocalization of those two proteins in the brain tissues of prion infection.

Midlife systemic inflammatory markers are associated with late-life brain volume: The ARIC study

OBJECTIVE

To clarify the temporal relationship between systemic inflammation and neurodegeneration, we examined whether a higher level of circulating inflammatory markers during midlife was associated with smaller brain volumes in late life using a large biracial prospective cohort study.

METHODS

Plasma levels of systemic inflammatory markers (fibrinogen, albumin, white blood cell count, von Willebrand factor, and Factor VIII) were assessed at baseline in 1,633 participants (mean age 53 [5] years, 60% female, 27% African American) enrolled in the Atherosclerosis Risk in Communities Study. Using all 5 inflammatory markers, an inflammation composite score was created for each participant. We assessed episodic memory and regional brain volumes, using 3T MRI, 24 years later.

RESULTS

Each SD increase in midlife inflammation composite score was associated with 1,788 mm3 greater ventricular (p = 0.013), 110 mm3 smaller hippocampal (p = 0.013), 519 mm3 smaller occipital (p = 0.009), and 532 mm3 smaller Alzheimer disease signature region (p = 0.008) volumes, and reduced episodic memory (p = 0.046) 24 years later. Compared to participants with no elevated (4th quartile) midlife inflammatory markers, participants with elevations in 3 or more markers had, on average, 5% smaller hippocampal and Alzheimer disease signature region volumes. The association between midlife inflammation and late-life brain volume was modified by age and race, whereby younger participants and white participants with higher levels of systemic inflammation during midlife were more likely to show reduced brain volumes subsequently.

CONCLUSIONS

Our prospective findings provide evidence for what may be an early contributory role of systemic inflammation in neurodegeneration and cognitive aging.

Cerebrospinal Fluid Markers of Alzheimer's Disease Pathology and Microglial Activation are Associated with Altered White Matter Microstructure in Asymptomatic Adults at Risk for Alzheimer's Disease

BACKGROUND

The immune response in Alzheimer's disease (AD) involves activation of microglia which may remove amyloid-β (Aβ). However, overproduction of inflammatory compounds may exacerbate neural damage in AD. AD pathology accumulates years before diagnosis, yet the extent to which neuroinflammation is involved in the earliest disease stages is unknown.

OBJECTIVE

To determine whether neuroinflammation exacerbates neural damage in preclinical AD.

METHODS

We utilized cerebrospinal fluid (CSF) and magnetic resonance imaging collected in 192 asymptomatic late-middle-aged adults (mean age = 60.98 years). Neuroinflammatory markers chitinase-3-like protein 1 (YKL-40) and monocyte chemoattractant protein-1 (MCP-1) in CSF were utilized as markers of neuroinflammation. Neural cell damage was assessed using CSF neurofilament light chain protein (NFL), CSF total tau (T-Tau), and neural microstructure assessed with diffusion tensor imaging (DTI). With regard to AD pathology, CSF Aβ42 and tau phosphorylated at threonine 181 (P-Tau181) were used as markers of amyloid and tau pathology, respectively. We hypothesized that higher YKL-40 and MCP-1 in the presence of AD pathology would be associated with higher NFL, T-Tau, and altered microstructure on DTI.

RESULTS

Neuroinflammation was associated with markers of neural damage. Higher CSF YKL-40 was associated with both higher CSF NFL and T-Tau. Inflammation interacted with AD pathology, such that greater MCP-1 and lower Aβ42 was associated with altered microstructure in bilateral frontal and right temporal lobe and that greater MCP-1 and greater P-Tau181 was associated with altered microstructure in precuneus.

CONCLUSION

Inflammation may play a role in neural damage in preclinical AD.

Progranulin deficiency induces overactivation of WNT5A expression via TNF-α/NF-κB pathway in peripheral cells from frontotemporal dementia-linked granulin mutation carriers

BACKGROUND

Loss-of-function progranulin gene (GRN) mutations have been identified as the major cause of frontotemporal lobar degeneration with transactive response (TAR) DNA-binding protein 43 (TDP-43) pathology (frontotemporal lobar degeneration [FTLD]-TDP); however, little is known about the association between progranulin (PGRN) deficiency and neuronal loss in individuals with FTLD-TDP. Previously we reported enhanced proliferative activity associated with the activation of WNT5A/CDK6/pRb signalling in PGRN-deficient cells. The objective of this work was to elucidate the association between PGRN deficiency, WNT5A signalling and cell proliferation in immortalized lymphoblasts from carriers of the c.709-1G > A GRN mutation (asymptomatic and FTLD-TDP).

METHODS

We assessed cell proliferation in carriers of the c.709-1G > A GRN gene mutation and controls without GRN mutation and without sign of neurologic degeneration by cell counting or using an MTT assay. We used a luciferase assay to measure the nuclear factor-κ (NF-κ) activity. We evaluated messenger RNA levels using quantitative real-time polymerase chain reaction and protein levels by immunoblotting. Co-immunoprecipitation was used to analyze the interaction between PGRN and its receptors.

RESULTS

We enrolled 19 carriers of the GRN gene mutation and 10 controls in this study. The PGRN-deficient cells showed increased expression of WNT5A due to NF-κB signalling overactivation. We observed a competition between PGRN and tumour necrosis factor-α (TNF-α) for binding both TNF receptors (TNFR) I and II. Blocking NF-κB signalling using wedelolactone or specific antibodies against TNFRs inhibited WNT5A overexpression and proliferation of PGRN-deficient cells. Conversely, the activation of NF-κB signalling by TNF-α increased WNT5A-dependent proliferation of control cells.

LIMITATIONS

All cell lines were derived from individuals harboring the same splicing GRN mutation. Nevertheless, most of the known GRN mutations lead to haploinsufficiency of the protein.

CONCLUSION

Our results revealed an important role of NF-κB signalling in PGRN-associated FTLD-TDP and confirm that PGRN can bind to TNF-α receptors regulating the expression of WNT5A, suggesting novel targets for treatment of FTLD-TDP linked to GRN mutations.

Increased plasma TACE activity in subjects with mild cognitive impairment and patients with Alzheimer's disease

Evidence suggests that the tumor necrosis factor receptor (TNFR)-signaling pathway contributes to the pathogenesis of Alzheimer's disease (AD). TNF-α converting enzyme (TACE/ADAM-17) can cleave both pro-TNF-α and TNF receptors. Recently, we have shown that TACE activity in the cerebrospinal fluid (CSF) of subjects with mild cognitive impairment (MCI) and AD patients is significantly higher than that of cognitively healthy controls (HC). To date, it is not clear whether TACE activity could be detected in the human plasma and whether TACE activity in MCI and AD patients is different from that in HC. We analyzed TACE expression and activity in a large clinical sample of 64 patients with AD, 88 subjects with MCI, and 50 age-matched HC recruited from two distinct academic centers. Plasma TACE protein levels did not differ significantly in the three study groups (AD, MCI, and HC). However, plasma TACE activity in subjects with MCI and AD patients was significantly higher than that in HC. Moreover, in MCI and AD groups, we found a significant correlation between plasma TACE activity and CSF t-tau and Aβ42 levels and CSF Aβ42/tau ratios. In AD patients, the levels of plasma TACE activity correlated significantly and negatively with cognition. These findings further support the role of the TNF-α receptor complex in AD-related neuroinflammation and propose TACE plasma activity as a promising hypothesis-driven biomarker candidate for detection, diagnosis, and prognosis of prodromal and clinical AD.

Biomarker modelling of early molecular changes in Alzheimer's disease

The preclinical phase of Alzheimer's disease (AD) occurs years, possibly decades, before the onset of clinical symptoms. Being able to detect the very earliest stages of AD is critical to improving understanding of AD biology, and identifying individuals at greatest risk of developing clinical symptoms with a view to treating AD pathophysiology before irreversible neurodegeneration occurs. Studies of dominantly inherited AD families and longitudinal studies of sporadic AD have contributed to knowledge of the earliest AD biomarkers. Here we appraise this evidence before reviewing novel, particularly fluid, biomarkers that may provide insights into AD pathogenesis and relate these to existing hypothetical disease models.

Body fluid cytokine levels in mild cognitive impairment and Alzheimer's disease: a comparative overview

This article gives a comprehensive overview of cytokine and other inflammation associated protein levels in plasma, serum and cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). We reviewed 118 research articles published between 1989 and 2013 to compare the reported levels of 66 cytokines and other proteins related to regulation and signaling in inflammation in the blood or CSF obtained from MCI and AD patients. Several cytokines are evidently regulated in (neuro-) inflammatory processes associated with neurodegenerative disorders. Others do not display changes in the blood or CSF during disease progression. However, many reports on cytokine levels in MCI or AD are controversial or inconclusive, particularly those which provide data on frequently investigated cytokines like tumor necrosis factor alpha (TNF-α) or interleukin-6 (IL-6). The levels of several cytokines are possible indicators of neuroinflammation in AD. Some of them might increase steadily during disease progression or temporarily at the time of MCI to AD conversion. Furthermore, elevated body fluid cytokine levels may correlate with an increased risk of conversion from MCI to AD. Yet, research results are conflicting. To overcome interindividual variances and to obtain a more definite description of cytokine regulation and function in neurodegeneration, a high degree of methodical standardization and patients collective characterization, together with longitudinal sampling over years is essential.

The Postprandial Effects of a Moderately High-Fat Meal on Lipid Profiles and Vascular Inflammation in Alzheimer's Disease Patients: A Pilot Study

Objective

Alzheimer’s disease (AD) is a neurodegenerative disease of aging with unknown causative factors. Accumulating evidence suggests that inflammation and neurovascular dysfunction play important roles in AD. The postprandial period following a moderately high-fat meal is associated with vascular inflammation in young, healthy individuals; however, this relationship has not been investigated in Alzheimer’s patients despite their exaggerated inflammatory state.

Methods

Patients with AD and age-matched control subjects were recruited through the UC Davis Alzheimer’s Disease Center. All subjects consumed a moderately high-fat breakfast meal. Fasting and postprandial blood samples were collected for lipid, lipoprotein, and oxylipin analyses, as well as assays for cytokine levels and monocyte activation.

Results

The plasma lipid analyses revealed similar levels of triglycerides and esterified oxylipins between groups, but there was an interaction between postprandial non-esterified fatty acid (NEFA) levels and body mass index in the AD group compared to the control subjects. The AD group also had increased behenic acid and decreased linoleic and oleic acids in the postprandial period; however, these were not significantly different. Inflammatory assays revealed elevated fasting levels of interleukin (IL)-10 and IL-12 p70, but no change in monocyte activation in the AD group.

Conclusion

The postprandial period following a moderately high-fat meal is not associated with an exaggerated inflammatory state in Alzheimer’s patients, and basal esterified oxylipin profiles do not indicate elevated oxidative stress. However, the baseline inflammatory state during fasting in AD patients includes elevated levels of plasma IL-10 and IL-12 p70, which may indicate a balance between immune responses mediated by these interleukins.

Alzheimer’s disease, cerebrovascular disease, and the β-amyloid cascade

Alzheimer’s disease (AD), considered the commonest neurodegenerative cause of dementia, is associated with hallmark pathologies including extracellular amyloid-β protein (Aβ) deposition in extracellular senile plaques and vessels, and intraneuronal tau deposition as neurofibrillary tangles. Although AD is usually categorized as neurodegeneration distinct from cerebrovascular disease (CVD), studies have shown strong links between AD and CVD. There is evidence that vascular risk factors and CVD may accelerate Aβ 40-42 production/ aggregation/deposition and contribute to the pathology and symptomatology of AD. Aβ deposited along vessels also causes cerebral amyloid angiopathy. Amyloid imaging allows in vivo detection of AD pathology, opening the way for prevention and early treatment, if disease-modifying therapies in the pipeline show safety and efficacy. In this review, we review the role of vascular factors and Aβ, underlining that vascular risk factor management may be important for AD prevention and treatment.

Assessing candidate serum biomarkers for Alzheimer's disease: a longitudinal study

Because of the growing impact of late onset cognitive loss, considerable effort has been directed toward the development of improved diagnostic techniques for Alzheimer's disease (AD) that may pave the way for earlier (and more effective) therapeutic efforts. Serum-based biomarkers are the least expensive and invasive modality for screening and routine monitoring. We systematically reviewed the literature to assemble a list of serum biomarkers relevant to AD. In parallel, we conducted a proteomic LC-MS/MS analysis of serum collected from neurologically normal subjects and subjects with mild cognitive impairment (MCI) and early AD (n = 6 in all). Complement C3 and alpha-2-macroglobulin were identified from both the literature review and our proteomic screen for further validation. For these two candidates, ELISA was performed on serum collected from a small independent cohort of subjects for longitudinal analysis. Serum was serially collected from neurologically normal subjects (n = 5) and subjects with MCI who were subsequently followed for a period of two years (n = 5) and regrouped into stable MCI and progressive MCI or AD (n = 6). The ability of each marker to predict which subjects with MCI would progress to dementia and which would remain cognitively stable was assessed. Patients with probable cerebral amyloid angiopathy were also identified (n = 3). This preliminary analysis tested the most-promising serum protein biomarkers for AD and we concluded that none are yet ready for use in the clinical diagnosis and management of dementia. However, a more thorough assessment in longitudinal studies with higher statistical power is warranted.

Gene Expression Profiling of Tuberculous Meningitis Co-infected with HIV

Tuberculous meningitis (TBM) is a fatal form of Mycobacterium tuberculosis infection of the central nervous system (CNS). The similarities in the clinical and radiological findings in TBM cases with or without HIV make the diagnosis very challenging. Identification of genes, which are differentially expressed in brain tissues of HIV positive and HIV negative TBM patients, would enable better understanding of the molecular aspects of the infection and would also serve as an initial platform to evaluate potential biomarkers. Here, we report the identification of 796 differentially regulated genes in brain tissues of TBM patients co-infected with HIV using oligonucleotide DNA microarrays. We also performed immunohistochemical validation and confirmed the abundance of four gene products-glial fibrillary acidic protein (GFAP), serpin peptidase inhibitor, clade A member 3 (SERPINA3), thymidine phosphorylase (TYMP/ECGF1) and heat shock 70 kDa protein 8 (HSPA8). Our study paves the way for understanding the mechanism of TBM in HIV positive patients and for further validation of potential disease biomarkers.

Upcoming candidate cerebrospinal fluid biomarkers of Alzheimer's disease

Dementia due to Alzheimer's disease (AD) is estimated to reach epidemic proportions by the year 2030. Given the limited accuracy of current AD clinical diagnosis, biomarkers of AD pathologies are currently being sought. Reductions in cerebrospinal fluid levels of β-amyloid 42 (a marker of amyloid plaques) and elevations in tau species (markers of neurofibrillary tangles and/or neurodegeneration) are well-established as biomarkers useful for AD diagnosis and prognosis. However, novel markers for other features of AD pathophysiology (e.g., β-amyloid processing, neuroinflammation and neuronal stress/dysfunction) and for other non-AD dementias are required to improve the accuracy of AD disease diagnosis, prognosis, staging and therapeutic monitoring (theragnosis). This article discusses the potential of several promising novel cerebrospinal fluid analytes, highlights the next steps critical for advancement in the field, and provides a prediction on how the field may evolve in 5-10 years.

Inactivation of CDK/pRb pathway normalizes survival pattern of lymphoblasts expressing the FTLD-progranulin mutation c.709-1G>A

BACKGROUND

Mutations in the progranulin (PGRN) gene, leading to haploinsufficiency, cause familial frontotemporal lobar degeneration (FTLD-TDP), although the pathogenic mechanism of PGRN deficit is largely unknown. Allelic loss of PGRN was previously shown to increase the activity of cyclin-dependent kinase (CDK) CDK6/pRb pathway in lymphoblasts expressing the c.709-1G>A PGRN mutation. Since members of the CDK family appear to play a role in neurodegenerative disorders and in apoptotic death of neurons subjected to various insults, we investigated the role of CDK6/pRb in cell survival/death mechanisms following serum deprivation.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a comparative study of cell viability after serum withdrawal of established lymphoblastoid cell lines from control and carriers of c.709-1G>A PGRN mutation, asymptomatic and FTLD-TDP diagnosed individuals. Our results suggest that the CDK6/pRb pathway is enhanced in the c.709-1G>A bearing lymphoblasts. Apparently, this feature allows PGRN-deficient cells to escape from serum withdrawal-induced apoptosis by decreasing the activity of executive caspases and lowering the dissipation of mitochondrial membrane potential and the release of cytochrome c from the mitochondria. Inhibitors of CDK6 expression levels like sodium butyrate or the CDK6 activity such as PD332991 were able to restore the vulnerability of lymphoblasts from FTLD-TDP patients to trophic factor withdrawal.

CONCLUSION/SIGNIFICANCE

The use of PGRN-deficient lymphoblasts from FTLD-TDP patients may be a useful model to investigate cell biochemical aspects of this disease. It is suggested that CDK6 could be potentially a therapeutic target for the treatment of the FTLD-TDP.

Blood-based protein biomarkers for diagnosis and classification of neurodegenerative diseases: current progress and clinical potential

Biomarker research is a rapidly advancing field in medicine. Recent advances in genomic, genetic, epigenetic, neuroscientific, proteomic, and metabolomic knowledge and technologies have opened the way to thriving research. In the most general sense, a biomarker refers to any useful characteristic that can be measured and used as an indicator of a normal biologic process, a pathogenic process, or a pharmacologic response to a therapeutic agent. Despite the extensive resources concentrated on this area, there are very few biomarkers currently available that qualify and are satisfactorily validated for mental disorders, and there is still a major lack of biomarkers for typifying neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. This article provides an overview of this field of research and focuses on recent advances in biomarker research in Alzheimer's disease and Parkinson's disease.

Biomarkers in Alzheimer's disease drug development

Developing new therapies for Alzheimer's disease (AD) is critically important to avoid the impending public health disaster imposed by this common disorder. Means must be found to prevent, delay the onset, or slow the progression of AD. These goals will be achieved by identifying disease-modifying therapies and testing them in clinical trials. Biomarkers play an increasingly important role in AD drug development. In preclinical testing, they assist in decisions to develop an agent. Biomarkers in phase I provide insights into toxic responses and drug metabolism and in Phase II proof-of-concept trials they facilitate go/no-go decisions and dose finding. Biomarkers can play a role in identifying presymptomatic patients or specific patient subgroups. They can provide evidence of target engagement before clinical changes can be expected. Brain imaging can serve as a primary outcome in Phase II trials and as a key secondary outcome in Phase III trials. Magnetic resonance imaging is currently best positioned for use in large multicenter clinical trials. Cerebrospinal fluid (CSF) measures of amyloid beta protein (Aβ), tau protein, and hyperphosphorylated tau (p-tau) protein are sensitive and specific to the diagnosis of AD and may serve as inclusion criteria and possibly as outcomes in clinical trials targeting relevant pathways. Plasma measures of Aβ are of limited diagnostic value but may provide important information as a measure of treatment response. A wide variety of measures of detectable products of cellular processes are being developed as possible biomarkers accessible in the cerebrospinal fluid and plasma or serum. Surrogate markers that can function as outcomes in pivotal trials and reliably predict clinical outcomes are needed to facilitate primary prevention trials of asymptomatic persons where clinical measures may be of limited value. Fit-for-purpose biomarkers are increasingly available to guide AD drug development decisions.

Identification and validation of novel cerebrospinal fluid biomarkers for staging early Alzheimer's disease

BACKGROUND

Ideally, disease modifying therapies for Alzheimer disease (AD) will be applied during the 'preclinical' stage (pathology present with cognition intact) before severe neuronal damage occurs, or upon recognizing very mild cognitive impairment. Developing and judiciously administering such therapies will require biomarker panels to identify early AD pathology, classify disease stage, monitor pathological progression, and predict cognitive decline. To discover such biomarkers, we measured AD-associated changes in the cerebrospinal fluid (CSF) proteome.

METHODS AND FINDINGS

CSF samples from individuals with mild AD (Clinical Dementia Rating [CDR] 1) (n = 24) and cognitively normal controls (CDR 0) (n = 24) were subjected to two-dimensional difference-in-gel electrophoresis. Within 119 differentially-abundant gel features, mass spectrometry (LC-MS/MS) identified 47 proteins. For validation, eleven proteins were re-evaluated by enzyme-linked immunosorbent assays (ELISA). Six of these assays (NrCAM, YKL-40, chromogranin A, carnosinase I, transthyretin, cystatin C) distinguished CDR 1 and CDR 0 groups and were subsequently applied (with tau, p-tau181 and Aβ42 ELISAs) to a larger independent cohort (n = 292) that included individuals with very mild dementia (CDR 0.5). Receiver-operating characteristic curve analyses using stepwise logistic regression yielded optimal biomarker combinations to distinguish CDR 0 from CDR>0 (tau, YKL-40, NrCAM) and CDR 1 from CDR<1 (tau, chromogranin A, carnosinase I) with areas under the curve of 0.90 (0.85-0.94 95% confidence interval [CI]) and 0.88 (0.81-0.94 CI), respectively.

CONCLUSIONS

Four novel CSF biomarkers for AD (NrCAM, YKL-40, chromogranin A, carnosinase I) can improve the diagnostic accuracy of Aβ42 and tau. Together, these six markers describe six clinicopathological stages from cognitive normalcy to mild dementia, including stages defined by increased risk of cognitive decline. Such a panel might improve clinical trial efficiency by guiding subject enrollment and monitoring disease progression. Further studies will be required to validate this panel and evaluate its potential for distinguishing AD from other dementing conditions.

Biomarkers of oxidative damage and inflammation in Alzheimer's disease

Oxidative damage and inflammation are important features of the brain pathology of Alzheimer's disease (AD). Oxidative damage can be found in membranes (lipid peroxidation), proteins (nitrosylation and other post-translational changes) and nucleic acids. Inflammatory changes include activation of microglia and astrocytes, with increased levels of proinflammatory cytokines. Not all of these changes are specific to AD, and occur in other neurodegenerative disorders. Both oxidative stress and inflammation are potential therapeutic targets in AD, and biomarkers could help to identify and monitor key pathways in patients with AD. This article summarizes progress in developing cerebrospinal fluid biomarkers related to oxidative stress and inflammation, problems and pitfalls related to systemic (blood- or urine-based) biomarkers in this area, and future research directions and applications.

Peripheral expression of key regulatory kinases in Alzheimer's disease and Parkinson's disease

Alteration of key regulatory kinases may cause aberrant protein phosphorylation and aggregation in Alzheimer's disease (AD) and Parkinson's disease (PD). In this study, we investigated expression and phosphorylation status of glycogen synthase kinase 3 (GSK-3), protein kinase B (Akt) and tau protein in peripheral blood lymphocytes of 20 AD, 25 PD patients and 20 healthy controls. GSK-3 was increased in AD and PD patients. In these latter, GSK-3 levels were positively correlated with daily L-Dopa intake. Phosphorylated Akt expression was augmented in both groups; total Akt levels were increased only in AD patients and were positively correlated with disease duration and severity. Total and phosphorylated tau were increased only in AD, with phospho-tau levels being positively correlated with levels of total tau, Akt, and disease duration. No correlations between protein levels and clinical variables were found in PD patients. Investigation of peripheral changes in the expression of specific kinases may, therefore, lead to the development of innovative biomarkers of neurodegeneration, particularly for AD.

Challenges to demonstrating disease-modifying effects in Alzheimer's disease clinical trials

Progress in understanding the molecular biology of Alzheimer's disease (AD) has provided a number of plausible therapeutic targets for disease-modifying interventions. To advance these agents toward eventual US Food and Drug Administration (FDA) approval and incorporation into clinical practice by physicians and acceptance by patients and caregivers it is necessary to reach consensus on the meaning of disease modification and on what information is needed to provide a compelling factual basis for distinguishing disease modification from symptomatic treatment effects. Disease modification requires that the intervention have an impact of underlying pathology and pathophysiology of AD; disease course modification, illness modification or disability sparing are alternate terminologies that could be applied to symptomatic agents that do not affect the underlying neurobiology of AD. A variety of trial designs have been proposed to provide information supporting disease modification including change from baseline designs, survival type designs, staggered start designs, and staggered withdrawal designs. Each of these has shortcomings, and by themselves trial designs are not likely to provide sufficient information to conclusively prove that disease modification has occurred. Incorporation of a biomarker into clinical trials will support the claim for disease modification. Such a surrogate marker ideally should respond to the intervention, predict the clinical response to the intervention, and be compellingly related to the neurobiology of AD in the pathway affected by the intervention. A third axis of information supportive of disease modification is derived from observation of the effect of treatment in animal models of AD. The triad of a clinical outcome consistent with disease modification, support from a surrogate marker incorporated into the clinical trial, and basic science information indicating the effect of the therapy on a model of AD would combine to make a convincing case for disease modification.

Multimodal techniques for diagnosis and prognosis of Alzheimer's disease

Alzheimer's disease affects millions of people around the world. Currently, there are no treatments that prevent or slow the disease. Like other neurodegenerative diseases, Alzheimer's disease is characterized by protein misfolding in the brain. This process and the associated brain damage begin years before the substantial neurodegeneration that accompanies dementia. Studies using new neuroimaging techniques and fluid biomarkers suggest that Alzheimer's disease pathology can be detected preclinically. These advances should allow the design of new clinical trials and early mechanism-based therapeutic intervention.

Biological marker candidates of Alzheimer's disease in blood, plasma, and serum

At the earliest clinical stages of Alzheimer's disease (AD), when first symptoms are mild, making a reliable and accurate diagnosis is difficult. AD related brain pathology and underlying molecular mechanisms precede symptoms. Biological markers can serve as supportive early screening and diagnostic tools as well as indicators of presymptomatic biochemical change. Moreover, biomarkers cover a variety of roles and functions such as disease prediction, indicating disease acuity and progression, and may ensure biological mapping of treatment outcome. Early screening, detection, and diagnosis of AD would permit earlier disease modifying intervention at potentially reversible stages. To date, most established biological markers from both cerebrospinal fluid neurochemistry and structural and functional neuroimaging have not reached widespread clinical application. Crucial remaining problems, such as easy acceptance and application of a test, cost-effectiveness, and noninvasiveness, need to be resolved. The development and validation of precise, reliable, and robust tests and biomarkers in blood, plasma, or serum has therefore been for a long time the ultimate focus of many research groups worldwide. Blood-based testing will most likely be the prerequisite to future sensitive screening of large populations at risk of AD and the baseline in a diagnostic flow approach to AD. The status and emerging perspectives on hypothesis and exploratory-based candidate biomarkers derived from blood, plasma, and serum are reviewed and discussed.

Alpha1-antichymotrypsin induces TNF-alpha production and NF-kappaB activation in the murine N9 microglial cell line

Microglia are known to accumulate in senile plaques of Alzheimer's disease (AD) together with a set of proteins including alpha(1)-antichymotrypsin (ACT). To investigate the biological effects of the interaction between ACT and microglia, we examined cytokine production by the murine N9 microglial cell line after ACT treatment. Real-time PCR analysis and specific immunoassays demonstrate that ACT triggers mRNA expression and release of TNF-alpha by N9 microglial cells. Furthermore, we show that ACT induces a significant increase in NF-kappaB nuclear translocation. Taken together, these data demonstrate that ACT might contribute to the inflammatory mechanisms present in AD senile plaques.

Alzheimer's disease and infection: do infectious agents contribute to progression of Alzheimer's disease?

Infection with several important pathogens could constitute risk factors for cognitive impairment, dementia, and Alzheimer's disease (AD) in particular. This review summarizes the data related to infectious agents that appear to have a relationship with AD. Infections with herpes simplex virus type 1, picornavirus, Borna disease virus, Chlamydia pneumoniae, Helicobacter pylori, and spirochete were reported to contribute to the pathophysiology of AD or to cognitive changes. Based on these reports, it may be hypothesized that central nervous system or systemic infections may contribute to the pathogenesis or pathophysiology of AD, and chronic infection with several pathogens should be considered a risk factor for sporadic AD. If this hypothesis holds true, early intervention against infection may delay or even prevent the future development of AD.

CSF levels of PSA and PSA-ACT complexes in Alzheimer's disease

BACKGROUND

Prostate-specific antigen (PSA) is a serine protease that in serum, is predominantly found complexed to the serine protease inhibitor alpha1-antichymotrypsin (ACT). ACT co-localizes with amyloid plaques in Alzheimer's disease (AD) brain and both PSA and ACT are detectable in cerebrospinal fluid (CSF). Therefore, we aimed to determine whether PSA is produced in the brain and whether PSA and PSA-ACT complex levels in CSF can be used as a biomarker for AD.

METHODS

Levels of ACT and PSA-ACT were determined by sandwich enzyme-linked immunosorbent assay in CSF and serum samples of AD (n = 16), frontotemporal lobe dementia (FTLD) (n = 19), mild cognitively impaired (MCI) patients (n = 19) and controls (n = 12). Total PSA was determined in a non-competitive immunoassay. Reverse transcriptase-polymerase chain reaction (RT-PCR) for PSA was performed on postmortem hippocampus and temporal cortex specimens from control and AD cases.

RESULTS

PSA is expressed in the brain, as detected by RT-PCR. PSA and PSA-ACT complexes were detectable in CSF of almost all male and only very few female subjects. The levels of PSA and PSA-ACT complexes in CSF did not differ between AD, FTLD, MCI and control groups. PSA CSF/serum quotients highly correlated with albumin CSF/serum quotients. Furthermore, the hydrodynamic radius of PSA was found to be 3 nm and the theoretical PSA quotient, derived from the Felgenhauer plot, corresponded well with the measured PSA quotient.

CONCLUSIONS

PSA is locally produced in the human brain; however, brain PSA hardly contributes to the CSF levels of PSA. PSA and PSA-ACT levels in CSF are not suitable as a biomarker for AD.

Binding and uptake of A beta1-42 by primary human astrocytes in vitro

Clearance of the amyloid-beta peptide (A beta) as a remedy for Alzheimer's disease (AD) is a major target in on-going clinical trials. In vitro studies confirmed that A beta is taken up by rodent astrocytes, but knowledge on human astrocyte-mediated A beta clearance is sparse. Therefore, by means of flow cytometry and confocal laser scanning microscopy (CLSM), we evaluated the binding and internalization of A beta1-42 by primary human fetal astrocytes and adult astrocytes, isolated from nondemented subjects (n = 8) and AD subjects (n = 6). Furthermore, we analyzed whether alpha1-antichymotrypsin (ACT), which is found in amyloid plaques and can influence A beta fibrillogenesis, affects the A beta uptake by human astrocytes. Upon over night exposure of astrocytes to FAM-labeled A beta1-42 (10 microM) preparations, (80.7 +/- 17.7)% fetal and (52.9 +/- 20.9)% adult A beta-positive astrocytes (P = 0.018) were observed. No significant difference was found in A beta1-42 uptake between AD and non-AD astrocytes, and no influence of ApoE genotype on A beta1-42 uptake was observed in any group. There was no difference in the percentage of A beta-positive cells upon exposure to A beta1-42 (10 microM) combined with ACT (1,000:1, 100:1, and 10:1 molar ratio), versus A beta1-42 alone. CLSM revealed binding of A beta1-42 to the cellular surfaces and cellular internalization of smaller A beta1-42 fragments. Under these conditions, there was no increase in cellular release of the proinflammatory chemokine monocyte-chemoattractant protein 1, as compared with nontreated control astrocytes. Thus, primary human astrocytes derived from different sources can bind and internalize A beta1-42, and fetal astrocytes were more efficient in A beta1-42 uptake than adult astrocytes.

Multiple reaction monitoring-based, multiplexed, absolute quantitation of 45 proteins in human plasma

Mass spectrometry-based multiple reaction monitoring (MRM) quantitation of proteins can dramatically impact the discovery and quantitation of biomarkers via rapid, targeted, multiplexed protein expression profiling of clinical samples. A mixture of 45 peptide standards, easily adaptable to common plasma proteomics work flows, was created to permit absolute quantitation of 45 endogenous proteins in human plasma trypsin digests. All experiments were performed on simple tryptic digests of human EDTA-plasma without prior affinity depletion or enrichment. Stable isotope-labeled standard peptides were added immediately following tryptic digestion because addition of stable isotope-labeled standard peptides prior to trypsin digestion was found to generate elevated and unpredictable results. Proteotypic tryptic peptides containing isotopically coded amino acids ([(13)C(6)]Arg or [(13)C(6)]Lys) were synthesized for all 45 proteins. Peptide purity was assessed by capillary zone electrophoresis, and the peptide quantity was determined by amino acid analysis. For maximum sensitivity and specificity, instrumental parameters were empirically determined to generate the most abundant precursor ions and y ion fragments. Concentrations of individual peptide standards in the mixture were optimized to approximate endogenous concentrations of analytes and to ensure the maximum linear dynamic range of the MRM assays. Excellent linear responses (r > 0.99) were obtained for 43 of the 45 proteins with attomole level limits of quantitation (<20% coefficient of variation) for 27 of the 45 proteins. Analytical precision for 44 of the 45 assays varied by <10%. LC-MRM/MS analyses performed on 3 different days on different batches of plasma trypsin digests resulted in coefficients of variation of <20% for 42 of the 45 assays. Concentrations for 39 of the 45 proteins are within a factor of 2 of reported literature values. This mixture of internal standards has many uses and can be applied to the characterization of trypsin digestion kinetics and plasma protein expression profiling because 31 of the 45 proteins are putative biomarkers of cardiovascular disease.