Post-translational modifications in extracellular microvesicles from plasma of rheumatoid arthritis patients following anti-TNFα therapy

Autoantibodies targeting post-translational modified proteins represent key immunological hallmarks of Rheumatoid Arthritis (RA). In a previous study we demonstrated the presence of citrullinated and carbamylated proteins in extracellular microvesicles (EMVs) from plasma of RA patients. Since the pivotal role of TNFα in sustaining inflammatory and oxidative processes that promote protein modification, in this study we investigated the patterns of these post-translational modifications in EMVs isolated from RA patients before and after anti-TNFα treatment. Twelve consecutive RA patients, naïve to biological therapy, were enrolled and subjected to anti-TNFα therapy, which remained stable throughout the 8-month follow-up. EMVs, isolated from baseline (T0) and 8 months of follow-up (T8) plasma of RA patients, were measured by Nanoparticle Tracking Analysis or lysed and subjected to western blot analysis, using anti-citrulline or anti-carbamyl lysine antibodies. Anti-citrullinated and anti-carbamylated protein antibodies were also detected. Anti-TNFα treatment induced a significant reduction in the concentration of EMVs isolated from plasma of RA patients after 8 months of anti-TNFα treatment (P < 0.01). Moreover, in EMVs extracts citrullinated and carbamylated protein levels were significantly lower at T8, as compared to T0 (P < 0.01). Anti-TNFα treatment also induced a significant decrease of both anti-citrullinated and anti-carbamylated protein antibody levels, as well as of activity scores (SDAI and DAS28). These findings suggest the role of EMVs, as well as of citrullinated and carbamylated protein levels, as potential indicators of RA activity.