Alteration of DBP levels in CSF of patients with MS by proteomics analysis

Abstract

Objective: The diagnosis of multiple sclerosis (MS) is still challenging recently due to the lack of a specific diagnostic test. Proteomics analysis was applied to biomarkers discovery and their pathways study.

Methods: First, the proteins of CSF from MS patients and control group were analyzed individually with 2D-DIGE technology (two-dimensional difference gel electrophoresis). Then, protein spots were found out with DeCyder6.0 software which showed different expression levels in the gel images between the two groups. The information regarding these proteins was collected based on MALDI-TOF/MS and related database searches. Lastly, interaction between these proteins was further analyzed by using Metacore software.

Results: There were 13 proteins that showed more than 1.5-fold difference in expression levels between the two groups. Furthermore, the identification made by MALDI-TOF/MS revealed that one of the most significant differential proteins was DBP (vitamin D-binding protein), which decreased in the experimental group. This result was confirmed by ELISA (P < 0.01). Moreover, network between the 13 proteins were partially got, which showed some biological interactions.

Conclusion: These results support a correlation between the level of DBP and MS. DBP may be a potential useful biomarker for diagnosis or a medicine target for treatment of MS.

Fig. 1

DIA of CSF from patients with MS versus NODs analyzed by 2-D DIGE and DeCyder 6.0 Difference Analysis Software; MS sample pool labeled Cy3 (a), ONDs sample pool labeled Cy5 (b), and 13 spots with >1.5-fold differences as a result of comparison between MS and ONDs are shown

Fig. 2

Part and 3D simulation figures of protein spots acquired gel images by 2D-DGE DeCyder 6.0 software. The (a, b) showed spot 1 identified as DBP was down-regulated in CSF of MS. The (c, d) showed spot 1 identified as DBP was up-regulated in CSF of ONDs

Fig. 3

The result of ELISA for DBP in control group. The left post represented the DBP concentrations of MS CSF [0.61 ± 0.31 mg/l] and the right one represented that of normal CSF [0.86 ± 0.23 mg/l]

Fig. 4

A typical MALDI-TOF peptide mass fingerprint spectrum of spot 1 identified as DBP which is decreased in CSF of MS. The x-axis represents mass-to-charge ratio (m/z), whereas the y-axis represents relative abundance

Fig. 5

Biological network analysis of DBP(VDB)with other proteins in CSF using MetaCore mapping tool. The network was generated using shortest path algorithm to map interaction between the proteins. Nodes represent proteins, lines between the nodes indicate direct protein–protein interaction