Detection of biomarkers with a multiplex quantitative proteomic platform in cerebrospinal fluid of patients with neurodegenerative disorders

Abstract

Biomarkers are needed to assist in the diagnosis and medical management of various neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and dementia with Lewy body (DLB). We have employed a multiplex quantitative proteomics method, iTRAQ (isobaric Tagging for Relative and Absolute protein Quantification), in conjunction with multidimensional chromatography, followed by tandem mass spectrometry (MS/MS), to simultaneously measure relative changes in the proteome of cerebrospinal fluid (CSF) obtained from patients with AD, PD, and DLB compared to healthy controls. The diagnosis of AD and DLB was confirmed by autopsy, whereas the diagnosis of PD was based on clinical criteria. The proteomic findings showed quantitative changes in AD, PD, and DLB as compared to controls; among more than 1,500 identified CSF proteins, 136, 72, and 101 of the proteins displayed quantitative changes unique to AD, PD, and DLB, respectively. Eight unique proteins were confirmed by Western blot analysis, and the sensitivity at 95% specificity was calculated for each marker alone and in combination. Several panels of unique makers were capable of distinguishing AD, PD and DLB patients from each other as well as from controls with high sensitivity at 95% specificity. Although these preliminary findings must be validated in a larger and different population of patients, they suggest that a roster of proteins may be generated and developed into specific biomarkers that could eventually assist in clinical diagnosis and monitoring disease progression of AD, PD and DLB.

Vitamin D-binding protein interacts with Aβ and suppresses Aβ-mediated pathology

“…Although the level of DBP in CSF has been known to be increased in AD patients, and several lines of evidence have suggested that DBP plays a role in AD, 11,15,16,32 there is no direct evidence of whether or how DBP affects AD-related pathology. Our data clearly show that DBP interacts directly with Ab and reduces the formation of aggregated Ab.…”

“…As many Ab-binding proteins, such as TTR, apoE, apoJ, and apoA1, are known to accumulate with Ab in amyloid No Ab bands were detected in the littermate mice; n ¼ 4 each cases deposits 5,17 and the level of DBP in CSF is increased in AD patients, 11,15,16 we examined whether DBP is present in the amyloid plaques of brains from AD patients and transgenic animal model of AD. We double-stained human AD and control brain with antibodies against Ab (4G8) and DBP.…”

“…32,38,39 Many studies have also shown alterations in the concentration of DBP in the CSF of AD patients, who demonstrated upregulation of DBP expression. 11,15,16 Based on these reports, Ab-binding proteins, including DBP, might provide effective diagnostic tools or biomarkers for AD. 32,38,39 It has been suggested that upregulation of neuroprotective and Ab-sequestering proteins, such as ADNP and cystatin C, in response to AD represents an intrinsic compensatory response that may counteract the progression of the disease.…”

“…Several other studies also have shown that the level of DBP in CSF is increased in AD patients and suggested that this plays a role in the pathology of AD. 15,16 However, the functions of extracellular DBP in AD have not yet been elucidated.…”

P1–206: Quantitative label‐free proteomics for discovery of biomarkers in cerebrospinal fluid: Assessment of technical and inter‐individual variation

“…10). It is also encouraging that many of the 81 proteins have already been reported as potential biomarkers for AD by multiple independent groups [2,20,28,31,36,[58][59][60][61]. Indeed, because none of these previously reported candidate biomarkers have been vetted sufficiently to be applied in clinical trials, they will have to be studied further: individually and in combination; in larger cohorts and in different diseases.…”