Formation of Hydroxyl Radicals from Hydrogen Peroxide and Iron Salts by Superoxide- and Ascorbate-Dependent Mechanisms: Relevance to the Pathology of Rheumatoid Disease

Publisher Website
Google Scholar
Abstract
Superoxide and H2O2 are formed by activated phagocytes and react together in the presence of Fe salts to form the hydroxyl [OH] radical, which attacks hyaluronic acid. Ascorbic acid also interacts with H2O2 and Fe salts to form OH radical in a reaction independent of superoxide. Since Fe salts, ascorbate and activated phagocytes are present in the rheumatoid joint, experiments were designed to see whether ascorbate-dependent or superoxide-dependent formation of OH radicals would be more important in vivo. Addition of ascorbate to a superoxide-generating system at concentrations of 100 .mu.mol/l provoked a superoxide-independent formation of OH radicals for a short period. Lower concentrations of ascorbate did not do this. Apparently, the superoxide-dependent reaction is probably more important. Evidently, destruction of ascorbate by oxygen radicals formed by activated phagocytes accounts for the previously reported low concentrations of this compound in the serum and synovial fluid of rheumatoid patients.