Reactive oxygen species and hyaluronate in serum and synovial fluid in arthritis

Oxygen-derived free radicals (ODFR) depolymerized synovial-fluid (SF) hyaluronic acid (HA) when hypoxanthine/xanthine oxidase (HX/XAO) was used as the radical generator. The molecular-weight distribution of ODFR-induced SF HA degradation products was determined using high performance liquid chromatography (HPLC) with TSK 5000 PW or TSK 6000 PW size-exclusion columns and simultaneously using 125I-labelled hyaluronate-binding protein (125I-HABP) assay. The exposure of SF HA to hydroxyl-radical flux resulted in the formation of a degradation product having a molecular weight of 13.5 X 10(3) daltons, from which no further degradation was achieved. If the iron chelator desferrioxamine and hydroxyl-radical scavenger mannitol were present in the reaction mixture, the HA peak decreased by 30-50%, as a result of reaction with superoxide radical and hydrogen peroxide. These results show that superoxide radical and hydroxyl radical may have different modes of action on SF HA. The molecular-weight distribution of serum HA from patients with rheumatoid arthritis varied in different individuals and ranged between 275 X 10(3) and 650 X 10(3).