Preferential immunoglobulin oxidation in children with juvenile idiopathic arthritis

Objective: Juvenile idiopathic arthritis (JIA) is a rare chronic inflammatory disorder of the joints. There is strong evidence that oxidative damage occurs in rheumatoid diseases, including JIA. The increased level of protein oxidation products in total plasma proteins has recently been reported in children with diagnosed JIA. The objective of this study was to find out which fraction of plasma proteins is mostly damaged by oxidative stress and whether the damaging effect correlates with certain clinical or laboratory parameters. Methods: A new approach to estimate the carbonyl content of plasma protein fractions was developed, based on two-stage electrophoresis and immunochemical detection of the carbonyl derivatives of the proteins. This method allowed us to detect and quantitate carbonyl groups in the albumin, alpha-2, beta and gamma-globulin fractions. Sera of 25 children with JIA and 13 healthy controls were tested. Results: Albumin and gamma-globulins were found to be most modified by oxidation. In a group of children with systemic JIA, both albumin and gamma-globulins were oxidized while plasma gamma-globulin fraction damage was prevalent in pauciarticular JIA. Conclusions: Among plasma proteins of children with JIA, gamma-globulins were preferentially oxidized, whereas most of the other proteins did not seem to be affected. Oxidative modification of plasma proteins was correlated with the type of JIA. These findings may allow the use of carbonyls as clinical markers of inflammatory process activity in patients with different types of JIA. It is also a potential tool for monitoring oxidative protein damage in other diseases and therapies.