Human Rheumatoid Arthritis LC-MSMS

Malondialdehyde-modified epitopes (MDA-epitopes) can elicit specific autoantibody that expressed oxidative stress arising in rheumatoid arthritis (RA). The purpose of this study was to discover and validate MDA-peptide adducts as novel biomarkers using concanavalin A affinity chromatography, 1D SDS-PAGE, in-gel digestion, and label-free nano-LC-MS, and evaluate levels of serum MDA, MDA-protein adducts, proteins and autoantibody isotypes against an unmodified and MDA-peptide from Taiwanese female patients with RA and healthy controls (HCs). Levels of serum MDA and MDA-protein adducts were significantly higher in RA patients versus HCs. Four differentially expressed novel MDA-peptides were selected that relative modification ratio were 2-fold differences to examine protein levels and assess autoantibodies to MDA-peptides in RA patients compared with HCs. Four of peptides are autoantigens. Furthermore, 4 MDA-peptides can induce more autoantibody isotypes that are statistical significance in RA patients compared to HCs. Serum IgG and IgM against MDA-peptides showed excellent diagnostic performance in discriminating among RA patients and HCs: area under the curve (AUC, 0.96 ~ 0.98), sensitivity (88.9% ~ 97.8%) and specificity (88.9% ~ 100%). Autoantibodies to MDA-epitopes indicate oxidative modifications occurring in RA, and might be useful as clinical markers fro RA diagnosis if further investigated.