Reduced expression of membrane-bound (m)RAGE is a biomarker of multiple sclerosis disease progression.

ABSTRACT

OBJECTIVES: This study is one in series measuring RAGE axis (receptor for advanced glycation end products, its isoforms, and ligands) as a biomarker in multiple sclerosis (MS). We identified and quantified membrane-bound RAGE (mRAGE) expression levels on freshly isolated PBMCs and its subpopulation (monocytes and T cells), and determined the relationship between mRAGE expression levels and MS disease severity. MATERIALS AND METHODS: mRAGE expression was determined for 28 MS patients and 16HCs, by flow cytometry, using fluorochrome unconjugated primary RAGE monoclonal antibody and a polyclonal secondary antibody conjugated to R-Phycoerythrin (PE). RESULTS: After adjusting for multiple comparisons and correcting for group differences in age and gender, MS patients showed higher percentages of mRAGE-positive on PBMCs (12.4±2.1 vs. 4.08±0.8, P=0.02), monocytes (37.4±5.8 vs. 20.1±5.0, P=0.08) and T cells (4.1±1.2 vs. 2.1±0.3, P=0.05). SPMS patients' showed lower percentages of RAGE-positive monocytes (13.7±5.5 vs. 49.5±6.6, P=0.0006) and RAGE-positive T cells (4.1±1.8 vs. 6.6±1.5, P=0.04) than RRMS patients. We observed a negative relationship between the percentages of mRAGE-positive PBMCs and MS severity scale (MSSS) (r=-0.39, P=0.04), monocytes and EDSS (r=-0.48, P=0.01), monocytes and MSSS (r=-0.58, P=0.001), and T cells and MSSS (r=-0.40, P=0.04). Monocytes expression of mRAGE showed 0.811 area under the curve (95% CI 0.64-0.98) sensitivity/specificity for MSSS. CONCLUSION: The reduced mRAGE expression on PBMCs in general, and on monocytes in particular, can be used as biomarker of MS disease severity and progression.