PLoS ONE, Jan 28, 2016, Vol.11(1)
Background In response to DNA double-strand breaks, the histone protein H2AX becomes phosphorylated at its C-terminal serine 139 residue, referred to as [gamma]-H2AX. Formation of [gamma]-H2AX foci is associated with recruitment of p53-binding protein 1 (53BP1), a regulator of the cellular response to DNA double-strand breaks. [gamma]-H2AX expression in peripheral blood mononuclear cells (PBMCs) was recently proposed as a diagnostic and disease activity marker for multiple sclerosis (MS). Objective To evaluate the significance of [gamma]-H2AX and 53BP1 foci in PBMCs as diagnostic and disease activity markers in patients with clinically isolated syndrome (CIS) and early relapsing-remitting MS (RRMS) using automated [gamma]-H2AX and 53BP1 foci detection. Methods Immunocytochemistry was performed on freshly isolated PBMCs of patients with CIS/early RRMS (n = 25) and healthy controls (n = 27) with [gamma]-H2AX and 53BP1 specific antibodies. Nuclear [gamma]-H2AX and 53BP1 foci were determined using a fully automated reading system, assessing the numbers of [gamma]-H2AX and 53BP1 foci per total number of cells and the percentage of cells with foci. Patients underwent contrast enhanced 3 Tesla magnetic resonance imaging (MRI) and clinical examination including expanded disability status scale (EDSS) score. [gamma]-H2AX and 53BP1 were also compared in previously frozen PBMCs of each 10 CIS/early RRMS patients with and without contrast enhancing lesions (CEL) and 10 healthy controls. Results The median (range) number of [gamma]-H2AX (0.04 [0-0.5]) and 53BP1 (0.005 [0-0.2]) foci per cell in freshly isolated PBMCs across all study participants was low and similar to previously reported values of healthy individuals. For both, [gamma]-H2AX and 53BP1, the cellular focus number as well as the percentage of positive cells did not differ between patients with CIS/RRMS and healthy controls. [gamma]-H2AX and 53BP1 levels neither correlated with number nor volume of T2-weighted lesions on MRI, nor with the EDSS. Although [gamma]-H2AX, but not 53BP1, levels were higher in previously frozen PBMCs of patients with than without CEL, [gamma]-H2AX values of both groups overlapped and [gamma]-H2AX did not correlate with the number or volume of CEL. Conclusion [gamma]-H2AX and 53BP1 foci do not seem to be promising diagnostic or disease activity biomarkers in patients with early MS. Lymphocytic DNA double-strand breaks are unlikely to play a major role in the pathophysiology of MS.
Dna Damage -- Physiological Aspects ; Dna Damage -- Research ; Multiple Sclerosis -- Development And Progression ; Multiple Sclerosis -- Genetic Aspects ; Multiple Sclerosis -- Research
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