Cleavage of cystatin C is not associated with multiple sclerosis

Molecular biomarkers in multiple sclerosis

Multiple sclerosis (MS) is a highly heterogenous disease regarding radiological, pathological, and clinical characteristics and therapeutic response, including both the efficacy and safety profile of treatments. Accordingly, there is a high demand for biomarkers that sensitively and specifically apprehend the distinctive aspects of the MS heterogeneity, and that can aid in better understanding of the disease diagnosis, prognosis, prediction of the treatment response, and, finally, in the development of new treatments. Currently, clinical characteristics (e.g., relapse rate and disease progression) and magnetic resonance imaging play the most important role in the clinical classification of MS and assessment of its course. Molecular biomarkers (e.g., immunoglobulin G (IgG) oligoclonal bands, IgG index, anti-aquaporin-4 antibodies, neutralizing antibodies against interferon-beta and natalizumab, anti-varicella zoster virus and anti-John Cunningham (JC) virus antibodies) complement these markers excellently. This review provides an overview of exploratory, validated and clinically useful molecular biomarkers in MS which are used for prediction, diagnosis, disease activity and treatment response.

Cystatin C Plays a Sex-Dependent Detrimental Role in Experimental Autoimmune Encephalomyelitis

The cysteine protease inhibitor Cystatin C (CST3) is highly expressed in the brains of multiple sclerosis (MS) patients and C57BL/6J mice with experimental autoimmune encephalomyelitis (EAE; a model of MS), but its roles in the diseases are unknown. Here, we show that CST3 plays a detrimental function in myelin oligodendrocyte glycoprotein 35–55 (MOG_35–55)-induced EAE but only in female animals. Female Cst3 null mice display significantly lower clinical signs of disease compared to wild-type (WT) littermates. This difference is associated with reduced interleukin-6 production and lower expression of key proteins (CD80, CD86, major histocompatibility complex [MHC] II, LC3A/B) involved in antigen processing, presentation, and co-stimulation in antigen-presenting cells (APCs). In contrast, male WT and Cst3^−/− mice and cells show no differences in EAE signs or APC function. Further, the sex-dependent effect of CST3 in EAE is sensitive to gonadal hormones. Altogether, we have shown that CST3 has a sex-dependent role in MOG_35–55-induced EAE.

Cystatin C (CST3) is increased in the brains of multiple sclerosis patients, but its role is unknown. In a mouse model of the disease, Hoghooghi et al. find that CST3 has a detrimental function but only in female animals. The effect is related to activation of antigen-presenting cells of the immune system.

A Cystatin C Cleavage ELISA Assay as a Quality Control Tool for Determining Sub-Optimal Storage Conditions of Cerebrospinal Fluid Samples in Alzheimer's Disease Research

Background:

An N-terminal octapeptide cleavage of the cystatin C protein was discovered by mass spectrometry when cerebrospinal fluid (CSF) was stored at –20°C for 3 months, which did not occur when CSF was stored at –80°C.

Objective:

The aim was to develop an immunoassay as quality assessment tool to detect this –20°C cleavage of cystatin C in CSF and support Alzheimer’s disease research.

Methods:

A specific monoclonal antibody and a double indirect sandwich ELISA were developed: one assay quantifies the octapeptide uncleaved protein specifically and the other quantifies the total cystatin C present in the biological fluid (both cleaved and uncleaved forms). The ratio of these concentrations was calculated to assess the extent of cleavage of cystatin C. The novel ELISA was validated and applied in a short-term (up to 4 weeks) and mid-term (up to one year) stability study of CSF stored at 4°C, –20°C, –80°C, and liquid nitrogen. Impact of freeze-thaw cycles, adsorption, and protease inhibitors were tested.

Results:

The ratio of truncated protein was modified following –20°C storage and seemed to reach a plateau after 6 months. The ratio was impacted neither by freeze-thaw cycles nor adsorption. The –20°C specific cleavage was found to be protease related.

Conclusion:

Using this novel double indirect sandwich ELISA, absolute levels of the total and uncleaved cystatin C and the ratio of truncated cystatin C can be measured. This assay is an easily applicable tool which can be used to confirm that CSF biospecimen are fit-for-purpose for Alzheimer’s disease research.

Proteomics of Multiple Sclerosis: Inherent Issues in Defining the Pathoetiology and Identifying (Early) Biomarkers

Multiple Sclerosis (MS) is a demyelinating disease of the human central nervous system having an unconfirmed pathoetiology. Although animal models are used to mimic the pathology and clinical symptoms, no single model successfully replicates the full complexity of MS from its initial clinical identification through disease progression. Most importantly, a lack of preclinical biomarkers is hampering the earliest possible diagnosis and treatment. Notably, the development of rationally targeted therapeutics enabling pre-emptive treatment to halt the disease is also delayed without such biomarkers. Using literature mining and bioinformatic analyses, this review assessed the available proteomic studies of MS patients and animal models to discern (1) whether the models effectively mimic MS; and (2) whether reasonable biomarker candidates have been identified. The implication and necessity of assessing proteoforms and the critical importance of this to identifying rational biomarkers are discussed. Moreover, the challenges of using different proteomic analytical approaches and biological samples are also addressed.

Stabilized Human Cystatin C Variant L47C/G69C Is a Better Reporter Than the Wild-Type Inhibitor for Characterizing the Thermodynamics of Binding to Cysteine Proteases

Human cystatin C (HCC) binds and inhibits all types of cysteine proteases from the papain family, including cathepsins (a group of enzymes that participate in a variety of physiological processes), which are some of its natural targets. The affinities of diverse proteases for HCC, expressed as equilibrium binding constants (K_b), range from 10⁶ to 10¹⁴ M^-1. Isothermal titration calorimetry (ITC) is one of the most useful techniques to characterize the thermodynamics of molecular associations, making it possible to dissect the binding free energy into its enthalpic and entropic components. This information, together with the structural changes that occur during the different associations, could enable better understanding of the molecular basis of affinity. Notwithstanding the high sensitivity of modern calorimeters, ITC requires protein concentrations in at least the 10-100 μM range to obtain reliable data, and it is known that HCC forms oligomers in this concentration range. We present herein a comparative study of the structural, thermal stability, and oligomerization properties of HCC and its stabilized variant (sHCC) L47C/G69C (which possesses an additional disulfide bridge) as well as their binding thermodynamics to the protease chymopapain, analyzed by ITC. The results show that, because sHCC remains monomeric, it is a better reporter than wild-type HCC to characterize the thermodynamics of binding to cysteine proteases.

Utility of Two-Dimensional Difference Gel Electrophoresis in Diagnosis of Multiple Sclerosis

Two-dimensional difference gel electrophoresis (2D-DIGE) has been used for identification of possible biomarkers in the cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients. However, in different studies inconsistent results have been obtained. We wanted to analyze the diagnostic value of 2D-DIGE in early MS patients by comparing protein patterns between single and pooled samples of MS patients and controls. CSF samples of 20 MS patients and 10 control subjects were processed with 2D-DIGE. The so obtained protein patterns were analyzed with DeCyder 6.5 software, whereby we described variation of patterns presented in one gel as well as between different gels. Even when running single samples of patients of the same group in one gel, variation of protein patterns was high. The number of identified spots with different protein level varied between 4 and 30, depending on which sample batches were compared. We did not find a consistent pattern throughout all possible batch combinations. The inter-individual variation of protein expression as well as the susceptibility of 2D-DIGE for methodological variations makes use of 2D-DIGE as a diagnostic tool for MS and for detection of possible candidate biomarkers difficult, since detected proteins vary depending on which samples are compared.

Assessment by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry of the Effects of Preanalytical Variables on Serum Peptidome Profiles Following Long-Term Sample Storage

PURPOSE

Human serum and plasma are often used as clinical specimens in proteomics analyses, and peptidome profiling of human serum is a promising tool for identifying novel disease-associated biomarkers. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used for peptidomic biomarker discovery. Careful sample collection and handling are required as either can have a profound impact on serum peptidome patterns, yet the effects of preanalytical variables on serum peptidome profiles have not been completely elucidated. The present study investigated the effects of preanalytical variables, including storage temperature, duration (up to 12 months), and thawing methods, on MALDI-TOF MS-based serum peptidome patterns.

EXPERIMENTAL DESIGN

Aliquots of serum samples were pretreated with weak cation exchanger magnetic beads using an automated ClinProtRobot system and then analyzed by MALDI-TOF MS.

RESULTS

A number of significant differences in peak intensities were observed depending on sample processing variables.

CONCLUSIONS AND CLINICAL RELEVANCE

These peaks can be used as sample quality markers to assess the effects of long-term storage on serum peptidome profiles using MALDI-TOF MS.

Direct Assessment of Plasma/Serum Sample Quality for Proteomics Biomarker Investigation

Blood proteome analysis for biomarker discovery represents one of the most challenging tasks to be achieved through clinical proteomics due to the sample complexity, such as the extreme heterogeneity of proteins in very dynamic concentrations, and to the observation of proper sampling and storage conditions. Quantitative and qualitative proteomics profiling of plasma and serum could be useful both for the early detection of diseases and for the evaluation of pathological status. Two main sources of variability can affect the precision and accuracy of the quantitative experiments designed for biomarker discovery and validation. These sources are divided into two categories, pre-analytical and analytical, and are often ignored; however, they can contribute to consistent errors and misunderstanding in biomarker research. In this chapter, we review critical pre-analytical and analytical variables that can influence quantitative proteomics. According to guidelines accepted by proteomics community, we propose some recommendations and strategies for a proper proteomics analysis addressed to biomarker studies.

Cystatins: a versatile family

Cystatins are small proteins, typically composed of 100-120 amino acids, which together with similar proteins devoid of inhibitory properties, belong to a cystatin 'superfamily'. Cystatins can do more than just inhibit proteases: two important aspects described here are aggregation properties linked to misfolding diseases and the unique ability of monellin, a plant cystatin, to elicit sweet taste. The explanation of the puzzling phenomenon of 'sweet proteins' required an in-depth structural study of monellin, also regarding the causes of the high thermal stability of its single chain structure. The detailed mechanisms by which cystatins aggregate could be relevant in the study of misfolding diseases involving cystatins. They are reviewed here with emphasis on 3D domain swapping, typical of aggregating cystatins. While studying monellin, we noticed that it aggregates in a conventional way, probably through the cross-β spine mechanism. However, several cystatins derived from oryzacystatin_I to emulate the taste behavior of monellin aggregate via different mechanisms.

Biobanking of Cerebrospinal Fluid for Biomarker Analysis in Neurological Diseases

Cerebrospinal fluid (CSF) reflects pathophysiological aspects of neurological diseases, where neuroprotective strategies and biomarkers are urgently needed. Therefore, biobanking is very relevant for biomarker discovery and evaluation for these neurological diseases.An important aspect of CSF biobanking is quality control, needed for e.g. consistent patient follow-up and the exchange of patient samples between research centers. Systematic studies to address effects of pre-analytical and storage variation on a broad range of CSF proteins are needed and initiated.Important features of CSF biobanking are intensive collaboration in international networks and the tight application of standardized protocols. The current adoption of standardized protocols for CSF and blood collection and for biobanking of these samples, as presented in this chapter, enables biomarker studies in large cohorts of patients and controls.In conclusion, biomarker research in neurodegenerative diseases has entered a new era due to the collaborative and multicenter efforts of many groups. The streamlining of biobanking procedures, including sample collection, quality control, and the selection of optimal control groups for investigating biomarkers is an important improvement to perform high quality biomarker studies.

Direct analytical sample quality assessment for biomarker investigation: qualifying cerebrospinal fluid samples

Measurement of biochemical markers represents an important aid to clinicians in the early diagnosis and prognosis of neurological diseases. Many factors can contribute to increase the chances that a biomarker study becomes successful. In a cerebrospinal fluid analysis (CSF), more than 84% of laboratory errors can be attributed to several preanalytical variables that include CSF collection, storage, and freeze thawing cycles. In this concept paper, we focus on some critical issues arising from basic proteomics investigation in order to highlight some key elements of CSF quality control. Furthermore, we propose a direct assessment of sample quality (DASQ) by applying a fast MALDI-TOF-MS methodology to evaluate molecular features of sample degradation and oxidation. We propose DASQ as a fast and simple initial step to be included in large-scale projects for neurological biomarker studies. In fact, such a procedure will improved the development of standardized protocols in order to have well-characterized CSF biobanks.

Oxidative modifications of cerebral transthyretin are associated with multiple sclerosis

Transthyretin (TTR) is a homotetrameric protein of the CNS that plays a role of as the major thyroxine (T4) carrier from blood to cerebrospinal fluid (CSF). T4 physiologically helps oligodendrocyte precursor cells to turn into myelinating oligodendrocytes, enhancing remyelination after myelin sheet damage. We investigated post-translational oxidative modifications of serum and CSF TTR in multiple sclerosis subjects, highlighting high levels of S-sulfhydration and S-sulfonation of cysteine in position ten only in the cerebral TTR, which correlate with an anomalous TTR protein folding as well as with disease duration. Moreover, we found low levels of free T4 in CSF of multiple sclerosis patients, suggestive of a potential role of these modifications in T4 transport into the brain.

Proteomics technologies for biomarker discovery in multiple sclerosis

Multiple sclerosis is a disabling inflammatory and neurodegenerative disorder that predominantly affects young adults. There is a great need for biomarkers, which could elucidate pathology as well as provide prognosis of disease progression and therapy response in multiple sclerosis. Rapidly evolving, technology driven applications such as mass spectrometry based proteomics are currently being developed for this purpose. In this review, we will outline the current status of the field and detail a number of the bottlenecks as well as future prospects of this type of biomarker research.

Lipidomic investigations for the characterization of circulating serum lipids in multiple sclerosis

Multiple Sclerosis (MS) is a neurodegenerative autoimmune demyelinating disease affecting young adults. The aetiology still remains a mystery and diagnosis is impaired by the lack of defined molecular markers. Autoimmune response remains the main topic under investigation and recent studies suggest additional non-proteic mediators of brain inflammation such as lipids. We carried out an LC-MS based lipidomics approach to highlight serum lipids profiling in MS. Method was optimised and applied in a preliminary clinical cross-sectional investigation of MS patients vs Healthy Controls (HC) and patients with Other Neurological Diseases (OND). Ten significant metabolites were highlighted and tentatively identified by accurate mass and MS/MS experiments. Our most relevant data show altered level of lyso-glycerophosphatidylcholine (lysoPC) and glycerophosphatidylcholine (PC) species. Total lysoPC/PC ratio showed significant decrease in pathological groups (MS, OND) and, in addition, MS subjects had a relevant decrease of this ratio also in respect to OND. These findings suggest that there may be an altered phospholipid metabolism in MS that can be evaluated in serum. Some of these features are distinctive and may be considered specific for MS. Our lipidomics data show, for the first time, evidence in serum of a relationship between LysoPC/PC ratio and MS.

The effect of preanalytical factors on stability of the proteome and selected metabolites in cerebrospinal fluid (CSF)

To standardize the use of cerebrospinal fluid (CSF) for biomarker research, a set of stability studies have been performed on porcine samples to investigate the influence of common sample handling procedures on proteins, peptides, metabolites and free amino acids. This study focuses at the effect on proteins and peptides, analyzed by applying label-free quantitation using microfluidics nanoscale liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (chipLC-MS) as well as matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT-ICR-MS) and Orbitrap LC-MS/MS to trypsin-digested CSF samples. The factors assessed were a 30 or 120 min time delay at room temperature before storage at -80 degrees C after the collection of CSF in order to mimic potential delays in the clinic (delayed storage), storage at 4 degrees C after trypsin digestion to mimic the time that samples remain in the cooled autosampler of the analyzer, and repeated freeze-thaw cycles to mimic storage and handling procedures in the laboratory. The delayed storage factor was also analyzed by gas chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS) for changes of metabolites and free amino acids, respectively. Our results show that repeated freeze/thawing introduced changes in transthyretin peptide levels. The trypsin digested samples left at 4 degrees C in the autosampler showed a time-dependent decrease of peak areas for peptides from prostaglandin D-synthase and serotransferrin. Delayed storage of CSF led to changes in prostaglandin D-synthase derived peptides as well as to increased levels of certain amino acids and metabolites. The changes of metabolites, amino acids and proteins in the delayed storage study appear to be related to remaining white blood cells. Our recommendations are to centrifuge CSF samples immediately after collection to remove white blood cells, aliquot, and then snap-freeze the supernatant in liquid nitrogen for storage at -80 degrees C. Preferably samples should not be left in the autosampler for more than 24 h and freeze/thaw cycles should be avoided if at all possible.

Disease biomarkers in multiple sclerosis: potential for use in therapeutic decision making

Multiple sclerosis (MS) is an autoimmune disorder of the brain and spinal cord that predominantly affects white matter. MS has a variable clinical presentation and has no 'diagnostic' laboratory test; this often results in delays to definite diagnosis. In confronting the disease, early diagnosis and appropriate, timely therapeutic intervention are critical factors in ensuring favorable long-term outcomes. The availability of reliable biomarkers could radically alter our management of MS at critical phases of the disease spectrum. Identification of markers that could predict the development of MS in high-risk populations would allow for intervention strategies that may prevent evolution to definite disease. Work with anti-myelin antibodies and the ongoing analysis of microarray gene expression have thus far not yielded biomarkers that predict future disease development. Similarly, extensive studies with serum and cerebrospinal fluid (CSF) have not yielded a disease-specific and sensitive diagnostic biomarker for MS. Establishment of disease diagnosis always leads to questions about long-term prognosis because in an individual patient the natural history of the disease is clinically unpredictable. Biomarkers that correlate with myelin loss, spinal cord disease, grey matter and subcortical demyelination need to be developed in order to accurately predict the disease course. The bulk of effort in biomarker development in MS has been concentrated in the area of monitoring disease activity. At present, a disease 'activation' panel of CSF biomarkers would include the following: interleukin-6 or its soluble receptor, nitric oxide and nitric oxide synthase, osteopontin, and fetuin-A. Although disease activity in MS is predominantly inflammatory, disease progression is likely to be the result of neurodegeneration. Therefore, the roles of proteins indicative of neuronal, axonal, and glial loss such as neurofilaments, tau, 14-3-3 proteins, and N-acetylaspartate are all under investigation, as are proteins affecting remyelination and regeneration, such as Nogo-A. With the increasing awareness of cognition dysfunction in MS, molecules such as apolipoprotein and proteins in the amyloid precursor protein pathway implicated in dementia are also being examined. Serum biomarkers that help monitor therapeutic efficacy such as the titer of antibody to beta-interferon, a first-line medication in MS, are established in clinical practice. Ongoing work with biomarkers that reflect drug bioavailability and factors that distinguish between medication responders and nonresponders are also under investigation. The discovery of new biomarkers relies on applying advances in proteomics along with microarray gene and antigen analysis and will hopefully result in the establishment of specific biomarkers for MS.

Pre-analytical factors in clinical proteomics investigations: impact of ex vivo protein modifications for multiple sclerosis biomarker discovery

Serum proteome investigations have raised an incredible interest in the research of novel molecular biomarker, nevertheless few of the proposed evidences have been translated to the clinical practice. One of the limiting factors has been the lack of generally accepted guidelines for clinical proteomics studies and the lack of a robust analytical and pre-analytical ground for the proposed classification models. Pre-analytical issues may results in a deep impact for biomarker discovery campaign. In this study we present a systematic evaluation of sample storage and sampling conditions for clinical proteomics investigations. We have developed and validated a linear MALDI-TOF-MS protein profiling method to explore the low protein molecular weight region (5-20 kDa) of serum samples. Data normalization and processing was performed using optimise peak detection routine (LIMPIC) able to describe each group under investigation. Data were acquired either from healthy volunteers and from multiple sclerosis patients in order to highlight ex vivo protein profile alteration related to different physio-pathological conditions. Our data showed critical conditions for serum protein profiles depending on storage times and temperatures: 23 degrees C, 4 degrees C, -20 degrees C and -80 degrees C. We demonstrated that upon a -20 degrees C short term storage, characteristic degradation profiles are associated with different clinical groups. Protein signals were further identified after preparative HPLC separation by peptide sequencing on a nanoLC-Q-TOF TANDEM mass spectrometer. Apolipoprotein A-IV and complement C3 protein fragments, transthyretin and the oxidized isoforms in different apolipoprotein species represent the major molecular features of such a degradation pattern.

Quantitative matrix-assisted laser desorption ionization-fourier transform ion cyclotron resonance (MALDI-FT-ICR) peptide profiling and identification of multiple-sclerosis-related proteins

We introduce a matrix-assisted laser desorption ionization-Fourier transform ion cyclotron resonance (MALDI-FT-ICR) method for quantitative peptide profiling, using peak height as a measure for abundance. Relative standard deviations in peak height of peptides spiked over 3 orders of magnitude in concentration were below 10% and allowed for accurate comparisons between multiple sclerosis and controls. Application on a set of 163 cerebrospinal fluid (CSF) samples showed significantly differential abundant peptides, which were subsequently identified into proteins (e.g., chromogranin A, clusterin, and complement C3).

Cystatin C in cerebrospinal fluid as a biomarker of ALS

Amyotrophic lateral sclerosis (ALS) is diagnosed on the basis of progressive symptoms in both the upper and lower motor neurons. Because there are no specific biomarkers for ALS, it is difficult to diagnose this disease in its early stages. Cerebrospinal fluid (CSF) samples were obtained from 14 patients in the early stages of ALS, from 13 with polyneuropathy, and from 16 with other neurological disorders. The concentration of cystatin C in the CSF was measured using a sandwich enzyme-linked immunosorbent assay (ELISA) kit. The concentration of cystatin C in the CSF was significantly lower in ALS patients than in the control subjects who were patients with polyneuropathy or other neurological diseases (patients with ALS, polyneuropathy, and other diseases exhibited 5.5 +/- 0.3, 6.7 +/- 0.4, and 6.9 +/- 0.3 mg/L cystatin C, respectively; ALS patients vs. control subjects: p = 0.014 and ALS patients vs. polyneuropathy patients: p = 0.024). Cystatin C may be a useful biomarker of ALS and can be used to distinguish between ALS and polyneuropathy.

CSF proteome analysis in multiple sclerosis patients by two-dimensional electrophoresis

BACKGROUND AND PURPOSE

In recent years, different approaches have been used to investigate changes of cerebrospinal fluid (CSF) proteome in patients affected by multiple sclerosis (MS) with the aim to identify protein markers with potential diagnostic or prognostic value. Because of the lack of standardization of current proteomic techniques, contrasting results were achieved until now in different laboratories. In this study, we compare CSF proteome of 10 relapsing-remitting MS (RR-MS) patients, 11 patients with clinically isolated syndrome (CIS), and 10 control subjects without neurological or systemic diseases.

METHODS

The differential expression of CSF proteins amongst these cohorts of patients was investigated by using two-dimensional electrophoresis and mass spectrometry.

RESULTS AND CONCLUSIONS

We found an overexpression of IgG free kappa light chain protein in both CIS and RR-MS patients, compared with control subjects and an increased expression of an apolipoprotein E isoform in RR-MS patients, compared with CIS and control groups. Our results confirm the presence of CSF proteome changes in MS patients. Future research should be aimed to investigate the role of these candidate CSF markers in larger cohorts of CIS and MS patients.

Clinical proteomics in neurodegenerative disorders

Neurodegenerative disorders are characterized by neuronal impairment that eventually leads to neuronal death. In spite of the brain's known capacity for regeneration, lost neurons are difficult to replace. Therefore, drugs aimed at inhibiting neurodegenerative processes are likely to be most effective if the treatment is initiated as early as possible. However, clinical manifestations in early disease stages are often numerous, subtle and difficult to diagnose. This is where biomarkers that specifically reflect onset of pathology, directly or indirectly, may have a profound impact on diagnosis making in the future. A triplet of biomarkers for Alzheimer's disease (AD), total and hyperphosphorylated tau and the 42 amino acid isoform of beta-amyloid, has already been established for early detection of AD before the onset of dementia. However, more biomarkers are needed both for AD and for other neurodegenerative disorders, such as Parkinson's disease, frontotemporal dementia and amyotrophic lateral sclerosis. This review provides an update on recent advances in clinical neuroproteomics, a biomarker discovery field that has expanded immensely during the last decade, and gives an overview of the most commonly used techniques and the major clinically relevant findings these techniques have lead to.

Multiple sclerosis-related proteins identified in cerebrospinal fluid by advanced mass spectrometry

A total of 164 cerebrospinal fluid (CSF) samples taken from neurological patients were classed into four groups according to the clinical diagnosis: multiple sclerosis (MScl, n = 44), clinically isolated syndrome of demyelination (CIS, n = 40), other inflammatory neurological disease (OIND, n = 26) and other neurological disease (OND, n = 54). After tryptic digestion, the samples were measured by MALDI-TOF MS. Spectra were analyzed using the R-project software package, in which a peak detection algorithm was developed. Subsequently, the peak lists were compared based on ranked data (non-parametric). Significant differences were observed in the comparisons of MScl vs. OND and CIS vs. OND. The comparisons of MScl vs. OIND, and CIS vs. OIND showed fewer significant differences. No significant differences were found in comparisons MScl vs. CIS and OIND vs. OND. MScl and CIS had strikingly similar profiles, probably a reflection of common pathological mechanisms. Three differentially expressed proteins in the comparison of MScl vs. OND were identified: chromogranin A, a potential marker for neurodegeneration; and two important factors in complement-mediated inflammatory reaction, clusterin and complement C3. CSF chromogranin A levels were confirmed to be significantly elevated in the MScl group using an ELISA.

Proteomic strategies in multiple sclerosis and its animal models

The early and precise diagnosis, the prognosis, and the clinical management of multiple sclerosis, remain a considerable challenge. In recent years, the development of novel and powerful proteomic techniques prompted the use of these approaches for the search of unique biomarkers in the cerebrospinal fluid of multiple sclerosis patients. A few studies have also utilized proteomics to delineate the profile of differentially expressed proteins in animal models of the human disease in order to gain global insights into affected pathways. The identification of differentially expressed proteins may be an initial step in the discovery of novel targets and mechanisms that play critical roles in the pathology of multiple sclerosis. Based on these findings, future investigations may elucidate the events leading to demyelination, axonal damage, and neurodegeneration, providing better insights into mechanisms governing the onset and progression of the disease. Although these proteomic studies provide valuable information, they are also faced with a number of challenges. The present review discusses some of the strengths and limitations of proteomic investigations as applied to multiple sclerosis.