Nimesulide as a downregulator of the activity of the neutrophil myeloperoxidase pathway : focus on the histoprotective potential of the drug during inflammatory processes

Neutrophils, recruited to tissue sites of inflammation, release a variety of oxidants and enzymes, which are responsible for tissue damage. Among the oxidants released are potent chlorinated compounds, such as hypochlorous acid and chloramines, which induce tissue cell damage and inactivate protease inhibitors, particularly α1-antitrypsin, the specific inhibitor of neutrophil elastase. In studying a rational approach to the pharmacological control of neutrophil-mediated tissue injury, we investigated the activity of the anti-inflammatory drug nimesulide. This agent reduced the function of the myeloperoxidase pathway (which generates hypochlorous acid), by exerting a cell-directed inhibitory activity, as shown by measurement of Superoxide anion and hydrogen peroxide production. Nimesulide also inactivated hypochlorous acid directly and protected α1-antitrypsin from the neutrophil-mediated oxidation. Thus, neutrophil elastolytic activity may be attenuated by nimesulide-spared α1-antitrypsin. The prevention of oxidative inactivation of α1-antitrypsin by nimesulide strictly correlates with the drug’s ability to suppress the extracellular availability of hypochlorous acid. Taken together, these data suggest that nimesulide may prevent tissue injury at sites of inflammation by maintaining natural host protective systems.