Free radicals and inflammation: superoxide-dependent activation of a neutrophil chemotactic factor in plasma.

The intravenous administration of superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) to animals with induced inflammation suppresses the inflammatory response and inhibits leukocyte infiltration into the challenged site, suggesting that neutrophil-generated superoxide reacts with an extracellular precursor to generate a substance chemotactic for neutrophils. Plasma exposed to superoxide in vitro becomes potently chemotactic. The appearance of chemotactic activity is inhibited by superoxide dismutase but not by catalase. The chemotactic factor does not stimulate superoxide production or degranulation in neurtrophils. Intradermal injection of superoxide-treated plasma or of a superoxide-generating system causes heavy infiltration of neutrophils to the injection site but does not cause overt signs of inflammation. The chemotactic factor consists of a chloroform-extractable component bound to serum albumin. The superoxide-dependent chemotactic factor appears to play a major role in communication in neutrophil-mediated inflammatory events. Prevention of production of this factor appears to be the major anti-inflammatory action of superoxide dismutase.