Effect of a specific iron chelating agent on animal models of inflammation

Iron is an important catalyst of oxidative radical reactions and promotes the formation of the hydroxyl radical from the superoxide anion radical and hydrogen peroxide. The stimulatory effect of the hydroxyl radical on lipid peroxidation prompted the speculation that free iron may directly promote inflammation and that iron chelating agents may have useful anti-inflammatory properties. This hypothesis is tested in animal models of inflammation with a specific iron chelating agent, desferrioxamine. At low doses (6 . 6 mg/kg) intraperitoneal desferrioxamine stimulated the induction of acute foot pad swelling in rats by monosodium urate but at higher doses (above 200 mg/kg) it suppressed this inflammatory reaction. A similar anti-inflammatory effect was observed in carrageenan-induced foot pad swelling. In guinea-pigs in which a Glynn-Dumonde synovitis was induced with bovine gammaglobulin, desferrioxamine (100 mg/kg) stimulated the acute inflammatory induction phase of this chronic allergic monoarthritis model. Repeated administration of desferrioxamine (100 mg/kg) from the seventh to the twelfth day after intra-articular challenge with bovine gammaglobulin markedly depressed the chronic inflammatory phase. In-vitro experiments suggest that desferrioxamine inhibits iron-catalysed lipid peroxidation when it is poorly saturated with iron, but loses this effect when it is iron saturated. Such an effect may explain our results with desferrioxamine in the animal studies and suggests that effective iron chelation and its removal may modify the inflammatory process in man.