Proteomic analysis of peripheral leukocytes in Alzheimer's disease patients treated with divalproex sodium

Human peripheral blood mononuclear cells as a valuable source of disease-related biomarkers: Evidence from comparative proteomics studies

PURPOSE

The discovery of specific and sensitive disease-associated biomarkers for early diagnostic purposes of many diseases is still highly challenging due to various complex molecular mechanisms triggered, high variability of disease-related interactions, and an overlap of manifestations among diseases. Human peripheral blood mononuclear cells (PBMCs) contain protein signatures corresponding to essential immunological interplay. Certain diseases stimulate PBMCs and contribute towards modulation of their proteome which can be effectively identified and evaluated via the comparative proteomics approach.

EXPERIMENTAL DESIGN

In this review, we made a detailed survey of the PBMCS-derived protein biomarker candidates for a variety of diseases, published in the last 15 years. Articles were preselected to include only comparative proteomics studies.

RESULTS

PBMC-derived biomarkers were investigated for cancer, glomerular, neurodegenerative/neurodevelopmental, psychiatric, chronic inflammatory, autoimmune, endocrinal, infectious, and other diseases. A detailed review of these studies encompassed the proteomics platforms, proposed candidate biomarkers, their immune cell type specificity, and potential clinical application.

CONCLUSIONS

Overall, PBMCs have shown a solid potential in giving early diagnostic and prognostic biomarkers for many diseases. The future of PBMC biomarker research should reveal its full potential through well-designed comparative studies and extensive testing of the most promising protein biomarkers identified so far.

Nanoparticle-Enabled Enrichment of Longitudinal Blood Proteomic Fingerprints in Alzheimer's Disease

Blood-circulating biomarkers have the potential to detect Alzheimer's disease (AD) pathology before clinical symptoms emerge and to improve the outcomes of clinical trials for disease-modifying therapies. Despite recent advances in understanding concomitant systemic abnormalities, there are currently no validated or clinically used blood-based biomarkers for AD. The extremely low concentration of neurodegeneration-associated proteins in blood necessitates the development of analytical platforms to address the "signal-to-noise" issue and to allow an in-depth analysis of the plasma proteome. Here, we aimed to discover and longitudinally track alterations of the blood proteome in a transgenic mouse model of AD, using a nanoparticle-based proteomics enrichment approach. We employed blood-circulating, lipid-based nanoparticles to extract, analyze and monitor AD-specific protein signatures and to systemically uncover molecular pathways associated with AD progression. Our data revealed the existence of multiple proteomic signals in blood, indicative of the asymptomatic stages of AD. Comprehensive analysis of the nanoparticle-recovered blood proteome by label-free liquid chromatography-tandem mass spectrometry resulted in the discovery of AD-monitoring signatures that could discriminate the asymptomatic phase from amyloidopathy and cognitive deterioration. While the majority of differentially abundant plasma proteins were found to be upregulated at the initial asymptomatic stages, the abundance of these molecules was significantly reduced as a result of amyloidosis, suggesting a disease-stage-dependent fluctuation of the AD-specific blood proteome. The potential use of the proposed nano-omics approach to uncover information in the blood that is directly associated with brain neurodegeneration was further exemplified by the recovery of focal adhesion cascade proteins. We herein propose the integration of nanotechnology with already existing proteomic analytical tools in order to enrich the identification of blood-circulating signals of neurodegeneration, reinvigorating the potential clinical utility of the blood proteome at predicting the onset and kinetics of the AD progression trajectory.

Efficacy and safety of valproic acid in dementia: A systematic review with meta-analysis

INTRODUCTION

The neuroprotective effect of valproic acid has been observed in the animal models of neurodegeneration, which suggests it as a potential candidate for clinical trials. In this paper, we aimed to systematically analyze the efficacy and safety of valproic acid in the treatment of dementia.

METHODS

We searched the electronic databases PubMed, EMBASE, CINAHL, Cochrane Library and China National Knowledge Infrastructure until March 2020 for the eligible randomized controlled trials, as well as the unpublished and ongoing trials. We pooled the results using a random-effects model.

RESULTS

We included seven studies with 770 randomized patients with dementia, which compared valproic acid with placebo. Indeed, there were no significant differences found in the scores of Mini-mental State Examination, Cohen-Mansfield Agitation Inventory and number of patients with adverse events. Valproic acid is generally well-tolerated in patients with dementia, even in long-term therapy for 24 months.

CONCLUSION

Insufficient evidences are found to support valproic acid in the treatment of dementia for cognitive, psychiatric symptoms or disease-modifying. The anticipations for a success in the trial of valproic acid for dementia in the future look not optimistic based on the available evidence.

Identification of Blood Biomarkers for Alzheimer's Disease Through Computational Prediction and Experimental Validation

Background: Alzheimer's disease (AD) is the major cause of dementia in population aged over 65 years, accounting up to 70% dementia cases. However, validated peripheral biomarkers for AD diagnosis are not available up to present. In this study, we adopted a new strategy of combination of computational prediction and experimental validation to identify blood protein biomarkers for AD.

Methods: First, we collected tissue-based gene expression data of AD patients and healthy controls from GEO database. Second, we analyzed these data and identified differentially expressed genes for AD. Third, we applied a blood-secretory protein prediction program on these genes and predicted AD-related proteins in blood. Finally, we collected blood samples of AD patients and healthy controls to validate the potential AD biomarkers by using ELISA experiments and Western blot analyses.

Results: A total of 2754 genes were identified to express differentially in brain tissues of AD, among which 296 genes were predicted to encode AD-related blood-secretory proteins. After careful analysis and literature survey on these predicted blood-secretory proteins, ten proteins were considered as potential AD biomarkers, five of which were experimentally verified with significant change in blood samples of AD vs. controls by ELISA, including GSN, BDNF, TIMP1, VLDLR, and APLP2. ROC analyses showed that VLDLR and TIMP1 had excellent performance in distinguishing AD patients from controls (area under the curve, AUC = 0.932 and 0.903, respectively). Further validation of VLDLR and TIMP1 by Western blot analyses has confirmed the results obtained in ELISA experiments.

Conclusion: VLDLR and TIMP1 had better discriminative abilities between ADs and controls, and might serve as potential blood biomarkers for AD. To our knowledge, this is the first time to identify blood protein biomarkers for AD through combination of computational prediction and experimental validation. In addition, VLDLR was first reported here as potential blood protein biomarker for AD. Thus, our findings might provide important information for AD diagnosis and therapies.

Alzheimer's disease: are blood and brain markers related? A systematic review

OBJECTIVE

Peripheral protein biomarkers of Alzheimer's disease (AD) may help identify novel treatment avenues by allowing early diagnosis, recruitment to clinical trials, and treatment initiation. The purpose of this review was to determine which proteins have been found to be differentially expressed in the AD brain and whether these proteins are also found within the blood of AD patients.

METHODS

A two-stage approach was conducted. The first stage involved conducting a systematic search to identify discovery-based brain proteomic studies of AD. The second stage involved comparing whether proteins found to be differentially expressed in AD brain were also differentially expressed in the blood.

RESULTS

Across 11 discovery based brain proteomic studies 371 proteins were at different levels in the AD brain. Nine proteins were frequently found, defined as appearing in at least three separate studies. Of these proteins heat-shock cognate 71 kDa, ubiquitin carboxyl-terminal hydrolase isozyme L1, and 2',3'-cyclic nucleotide 3' phosphodiesterase alone were found to share a consistent direction of change, being consistently upregulated in studies they appeared in. Eighteen proteins seen as being differentially expressed within the AD brain were present in blood proteomic studies of AD. Only complement C4a was seen multiple times within both the blood and brain proteomic studies.

INTERPRETATION

We report a number of proteins appearing in both the blood and brain of AD patients. Of these proteins, C4a may be a good candidate for further follow-up in large-scale replication efforts.

Mass spectrometry-based proteomics in Chest Medicine, Gerontology, and Nephrology: subgroups omics for personalized medicine

Mass spectrometry (MS) is currently the most promising tool for studying proteomics to investigate largescale proteins in a specific proteome. Emerging MS-based proteomics is widely applied to decipher complex proteome for discovering potential biomarkers. Given its growing usage in clinical medicine for biomarker discovery to predict, diagnose and confer prognosis, MS-based proteomics can benefit study of personalized medicine. In this review we introduce some fundamental MS theory and MS-based quantitative proteomic approaches as well as several representative clinical MS-based proteomics issues in Chest Medicine, Gerontology, and Nephrology.

New treatment strategies for Alzheimer's disease: is there a hope?

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disease, and corresponds to the most common cause of dementia worldwide. Although not fully understood, the pathophysiology of AD is largely represented by the neurotoxic events triggered by the beta-amyloid cascade and by cytoskeletal abnormalities subsequent to the hyperphosphorylation of microtubule-associated Tau protein in neurons. These processes lead respectively to the formation of neuritic plaques and neurofibrillary tangles, which are the pathological hallmarks of the disease. Clinical benefits of the available pharmacological treatment for AD with antidementia drugs (namely cholinesterase inhibitors and memantine) are unquestionable, although limited to a temporary, symptomatic support to cognitive and related functions. Over the past decade, substantial funding and research have been dedicated to the search and development of new pharmaceutical compounds with disease-modifying properties. The rationale of such approach is that by tackling key pathological processes in AD it may be possible to attenuate or even change its natural history. In the present review, we summarize the available evidence on the new therapeutic approaches that target amyloid and Tau pathology in AD, focusing on pharmaceutical compounds undergoing phase 2 and phase 3 randomized controlled trials.

Leukocyte p53 protein biosignature through standard-aligned two-dimensional immunoblotting

Peripheral leukocytes may reflect systemic disease and stress states through their gene expression profile. Subsequent protein analyses of leukocytes are hypothesized to provide essential information regarding systemic diseases. We have developed a protein biosignature analysis of the tumour suppressor and cell stress sensor p53 based on two-dimensional gel electrophoresis and immunoblotting, and utilize fluorescently labelled reference standards to significantly improve the alignment and comparison of biosignatures, including full-length p53 and isoforms p53β and p53γ. Analysis of the p53 biosignatures of peripheral blood mononuclear cells from 526 healthy individuals and 65 acute myeloid leukaemia patients indicated a novel putative p53 protein variant in a subset of individuals (227 of 526 healthy tested). The p53 variant was more distinct in the reference standard aligned biosignatures of healthy individuals, compared to the non-standard aligned leukaemia biosignatures. This approximately 2 kDa heavier variant of p53 appeared with similar frequency in leukemic and healthy test persons, without coinciding with known splice forms or post-translational modifications of p53. We propose that a standardized leukocyte protein biosignature of p53 provides a powerful research tool and indicate how p53 protein biosignatures may be used in future diagnostics. This article is part of a Special Issue entitled: Integrated omics.

Improved control of tuberculosis and activation of macrophages in mice lacking protein kinase R

Host factors that microbial pathogens exploit for their propagation are potential targets for therapeuic countermeasures. No host enzyme has been identified whose genetic absence benefits the intact mammalian host in vivo during infection with Mycobacterium tuberculosis (Mtb), the leading cause of death from bacterial infection. Here, we report that the dsRNA-dependent protein kinase (PKR) is such an enzyme. PKR-deficient mice contained fewer viable Mtb and showed less pulmonary pathology than wild type mice. We identified two potential mechanisms for the protective effect of PKR deficiency: increased apoptosis of macrophages in response to Mtb and enhanced activation of macrophages in response to IFN-gamma. The restraining effect of PKR on macrophage activation was explained by its mediation of a previously unrecognized ability of IFN-gamma to induce low levels of the macrophage deactivating factor interleukin 10 (IL10). These observations suggest that PKR inhibitors may prove useful as an adjunctive treatment for tuberculosis.

The role of Wnt signaling and its interaction with diverse mechanisms of cellular apoptosis in the pathophysiology of bipolar disorder

The neurobiology of Bipolar Disorder (BD) is not completely understood, although abnormalities in neuroplasticity and control of apoptosis have been considered as central events in its pathophysiology. The molecules of the Wnt family comprise a class of proteins that control essential developmental processes such as embryonic patterning, cell growth, migration, and differentiation with their actions largely exerted by modulating gene transcription. The Wnt signaling pathway has interface with some mediators with a well documented action in neuroplasticity and regulation of cell surviving. In addition, mood stabilizers such as lithium and valproate may have their neuroprotective properties in part mediated by the Wnt pathway. This article is an overview of how the Wnt signaling cascade might be involved in the pathogenesis of BD and also in details of intracellular events related to this pathway. Further studies of Wnt signaling may lead to a better comprehension of the neuroprotective actions of mood stabilizers and contribute to improving the therapeutics of BD.

Therapeutic anti-inflammatory potential of formyl-peptide receptor agonists

The need for novel anti-inflammatory drugs justifies the search for innovative targets that could satisfy this goal. For quite some time now, we have proposed the study of endogenous anti-inflammation as a distinctive approach to the discovery of new drugs. This approach requires development of new compounds that activate specific receptor targets to downregulate the cellular and tissue pathways operative in the host during inflammation. Here we dwell on a family of G-protein coupled receptors (GPCR) termed FPRs, acronym for formyl-peptide receptors. With three and seven members in man and mouse, respectively, these receptors harness many biological functions, spanning odour perception and hair growth, to the control of multiple facets (pain; cell migration; oxidative burst; xenobiotic engulfment) of the inflammatory reaction. We focus on FPR biology with particular attention to molecules able to produce pharmacological effects by interacting with these GPCRs, describing endogenous agonists of FPRs and, more relevantly, the current development of synthetic agonists. Besides being potential leads for the development of the anti-inflammatory therapeutics of the future, these compounds could also help clarify the properties and roles that each FPR might play in the complex network of pathways that is inflammation. We conclude that FPR2 agonists could be valid warhorses for defining a novel philosophy for anti-inflammatory drug discovery programmes: mimicking - with new compounds - the way our body disposes of inflammation could be a viable approach to regulate aberrant inflammatory responses as in the case of several chronic rheumatic and cardiovascular pathologies.

Blood-based biomarkers of Alzheimer's disease: challenging but feasible

Blood-based biomarkers present a considerable challenge: technically, as blood is a complex tissue and conceptually, as blood lacks direct contact with brain. Nonetheless, increasing evidence suggests that there is a blood protein signature, and possibly a transcript signature, that might act to increase confidence in diagnosis, be used to predict progression in either disease or prodromal states, and that may also be used to monitor disease progression. Evidence for this optimism comes partly from candidate protein studies, including those suggesting that amyloid-beta measures might have value in prediction and those studies of inflammatory markers that consistently show change in Alzheimer's disease, and partly from true proteomics studies that are beginning to identify markers in blood that replicate across studies and populations.

An update on clinical proteomics in Alzheimer's research

Alzheimer's disease (AD) is a pathologically complex and aetiologically multifactorial dementing disorder affecting millions of people worldwide. The pathological brain changes are assumed to occur decades prior to the onset of clinical symptoms. The diagnosis of early AD remains problematic and is mainly based on clinical and neuropsychological findings after the onset of symptoms. Currently available drugs are able to delay the symptom progression of the disease but not to attenuate the progression of pathological brain changes. Many studies exploring AD proteomes have been conducted as the middle of 1990s as a consequence of recent advances in the development of both gel-based and gel-free proteomics approaches. It is hoped that proteomics can contribute to improving the understanding, diagnosis, and follow-up of the progression of AD. In this review, we summarise the present status of proteome alterations, with emphasis on quantitative approaches, in AD brain, CSF and blood, and their relevance to dementia research.

Proteomic changes in the crucian carp brain during exposure to anoxia

During exposure to anoxia, the crucian carp brain is able to maintain normal overall protein synthesis rates. However, it is not known if there are alterations in the synthesis or expression of specific proteins. This investigation addresses this issue by comparing the normoxic and anoxic brain proteome. Nine proteins were found to be reduced by anoxia. Reductions in the glycolytic pathway proteins creatine kinase, fructose biphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase, triosephosphate isomerase and lactate dehydrogenase reflect the reduced production and requirement for adenosine tri-phosphate during anoxia. In terms of neural protection, voltage-dependent anion channel, a protein associated with neuronal apoptosis, was reduced, along with gefiltin, a protein associated with the subsequent need for neuronal repair. Additionally the expression of proteins associated with neural degeneration and impaired cognitive function also declined; dihydropyrimidinase-like protein-3 and vesicle amine transport protein-1. One protein was found to be increased by anoxia; pre-proependymin, the precursor to ependymin. Ependymin fulfils multiple roles in neural plasticity, memory formation and learning, neuron growth and regeneration, and is able to reverse the possibility of apoptosis, thus further protecting the anoxic brain.

The role of proteomics in dementia and Alzheimer's disease

Proteomic analysis enables us to identify dementia-related protein profiles of both genetic and environmental origins. In this review, current proteomics technologies are described including many examples of clinical proteomics studies. Many of these studies present only results of the discovery phase. Progression to the validation phase was achieved by developing more advanced proteomics technologies such as fluorescence two-dimensional differential gel electrophoresis or isobaric tagging for relative and absolute protein quantification. These technologies will lead to the design of several new Alzheimer's disease-related protein panels for the analysis of CSF. On these new panels, established markers such as tau and Abeta42 will be used in combination with novel markers, for example beta-2-microglobulin, brain-derived neurotrophic factor 1 and fragments of cystatin C. However, there are still limitations to using proteomic assays. The preparation of homogeneous sample material is difficult due the complexity of brain tissue. Laser capture microdissection and recently developed more sensitive proteomics methods, for example fluorescence saturation labelling, will overcome these limitations. Combining proteomics with approaches at the level of the genome and transcriptome followed by interpretation by systems biology will soon shed further light on dementia-related pathogenesis.

Plasma biomarkers for mild cognitive impairment and Alzheimer's disease

PURPOSE OF REVIEW

With the move toward development of disease modifying treatments, there is a need for more specific diagnosis of early Alzheimer's disease (AD) and mild cognitive impairment (MCI), plasma biomarkers are likely to play an important role in this. We review the current state of knowledge on plasma biomarkers for MCI and AD, including unbiased proteomics and very recent longitudinal studies.

RECENT FINDINGS

With the use of proteomics methodologies, some proteins have been identified as potential biomarkers in plasma and serum of AD patients, including alpha-1-antitrypsin, complement factor H, alpha-2-macroglobulin, apolipoprotein J, apolipoprotein A-I. The findings of cross-sectional studies of plasma amyloid beta (A beta) levels are conflicting, but some recent longitudinal studies have shown that low plasma A beta 1-42 or A beta 1-40 levels, or A beta 1-42/A beta 1-40 ratio may be markers of cognitive decline. Other potential biomarkers for MCI and AD reflecting a variety of pathophysiological processes have been assessed, including isoprostanes and homocysteine (oxidative stress), total cholesterol and ApoE4 allele (lipoprotein metabolism), and cytokines and acute phase proteins (inflammation). A panel of 18 signal proteins was reported as markers of MCI and AD.

SUMMARY

A variety of potential plasma biomarkers for AD and MCI have been identified, however the findings need replication in longitudinal studies. This area of research promises to yield interesting results in the near future.

Chipping away at diagnostics for neurodegenerative diseases

Biomarkers are needed to overcome critical roadblocks in the development of disease-modifying therapeutics for neurodegenerative diseases. Evolving genome-wide expression technologies can comprehensively search for molecular biomarkers and allow fascinating insights into the expanding complexity of the human transcriptome. The technology has matured to the point where some applications are deemed reliable enough for use in patient care. In the neurosciences, it has led to the discoveries of osteopontin in multiple sclerosis and SORL1/LR11 in Alzheimer's, and recent studies indicate its potential for identifying neurogenomic biomarkers. Advances in pre-analytical and analytical methods are improving search efficiency and reproducibility and may lead to a pipeline of biomarker candidates suitable for development into future neurologic diagnostics.