Changes in expression profiles of internal jugular vein wall and plasma protein levels in multiple sclerosis

Abstract

Background: Multiple sclerosis (MS) is an inflammatory, demyelinating and degenerative disorder of the central nervous system (CNS). Several observations support interactions between vascular and neurodegenerative mechanisms in multiple sclerosis (MS). To investigate the contribution of the extracranial venous compartment, we analysed expression profiles of internal jugular vein (IJV), which drains blood from CNS, and related plasma protein levels.

Methods: We studied a group of MS patients (n = 19), screened by echo-color Doppler and magnetic resonance venography, who underwent surgical reconstruction of IJV for chronic cerebrospinal venous insufficiency (CCSVI). Microarray-based transcriptome analysis was conducted on specimens of IJV wall from MS patients and from subjects undergoing carotid endarterectomy, as controls. Protein levels were determined by multiplex assay in: i) jugular and peripheral plasma from 17 MS/CCSVI patients; ii) peripheral plasma from 60 progressive MS patients, after repeated sampling and iii) healthy individuals.

Results: Of the differentially expressed genes (≥ 2 fold-change, multiple testing correction, P < 0.05), the immune-related CD86 (8.5 fold-change, P = 0.002) emerged among the up regulated genes (N = 409). Several genes encoding HOX transcription factors and histones potentially regulated by blood flow, were overexpressed. Smooth muscle contraction and cell adhesion processes emerged among down regulated genes (N = 515), including the neuronal cell adhesion L1CAM as top scorer (5 fold-change, P = 5 × 10^{- 4}). Repeated measurements in jugular/peripheral plasma and overtime in peripheral plasma showed conserved individual plasma patterns for immune-inflammatory (CCL13, CCL18) and adhesion (NCAM1, VAP1, SELL) proteins, despite significant variations overtime (SELL P < 0.0001). Both age and MS disease phenotypes were determinants of VAP1 plasma levels. Data supported cerebral related-mechanisms regulating ANGPT1 levels, which were remarkably lower in jugular plasma and correlated in repeated assays but not between jugular/peripheral compartments.

Conclusions: This study provides for the first time expression patterns of the IJV wall, suggesting signatures of altered vascular mRNA profiles in MS disease also independently from CCSVI. The combined transcriptome-protein analysis provides intriguing links between IJV wall transcript alteration and plasma protein expression, thus highlighting proteins of interest for MS pathophysiology.

Keywords: Adhesion molecules; Chemokines; Chronic cerebrospinal venous insufficiency; Gene expression; Jugular plasma protein levels; Jugular vein wall; Multiple sclerosis; Multiplex protein assay; Venous abnormalities.

Fig. 1

Transcriptomic analysis in internal jugular vein walls. a Heat map representation of the 924 differentially expressed genes (1408 probes). Each column represents one RNA sample (MS/CCSVI and control jugular walls) and each row represents one gene (probe). Colors represent the expression level fold change: higher-red, lower- green and no difference-yellow. b Enriched biological processes and (c) pathways associated to the 924 genes differentially expressed between MS and control jugular walls. Significantly overrepresented terms (Benjamini test P < 0.05) were selected from DAVID bioinformatics 6.7 by the Functional Annotation Chart resource. *Pathway significantly overrepresented only among up-regulated genes

Fig. 2

Correlations and variations in protein plasma levels in the 1th MS population. r, Pearson coefficient of the correlation between jugular and peripheral plasma levels in MS patients. Δ JMS-PMS %, percentage difference between jugular and peripheral (100%) plasma levels in MS patients. Δ PMS-PHS %, percentage difference between MS and healthy (100%) peripheral plasma levels

Fig. 3

Correlations of protein plasma levels: relation between 1st and 2nd MS population values. X axis: Pearson coefficients (r) of the correlation between jugular and peripheral plasma in 1st MS population. Y axis: Pearson coefficients (r) of the correlation over 4 time points in the peripheral plasma of the 2nd MS population