Neutrophil-associated inflammatory responses in rats are inhibited by phenylarsine oxide

NADPH oxidase is a phagocyte-specific enzyme which produces O2- and so initiates a cascade of reactive oxygen species formation. Inflammatory diseases involve overproduction of reactive oxygen species which induce tissue damage. Phenylarsine oxide has been described previously as a complete and direct inhibitor of NADPH oxidase in vitro that acts by covalently binding to vicinal thiol groups of a membrane-associated component of the enzyme. In the present work, the potential anti-inflammatory effect of phenylarsine oxide was tested on two experimental models in rats, carrageenan-induced paw oedema and lipopolysaccharide-mediated lung inflammation. Intraperitoneal injection of phenylarsine oxide reduced (i) reactive oxygen species production by rat phagocytes, (ii) neutrophil infiltration into the lung after inhalation of lipopolysaccharide and (iii) neutrophil-dependent oedema induced by carrageenan in hindpaws. We conclude that phenylarsine oxide has anti-inflammatory properties which are probably exerted by its ability to inhibit neutrophil NADPH oxidase-dependent reactive oxygen species production. The present work provides the basis for the development of new anti-inflammatory, arsenic-free agents reacting at the phenylarsine oxide site, which seems to be the Achilles' heel of NADPH oxidase.