NPGB-induced inhibition of superoxide anion production by normal Lewis rat macrophages

The treatment of Lewis rat peritoneal macrophages with p¹-nitrophenyl p-guanidinobenzoate (NPGB) inhibited the superoxide anion production stimulated with phorbol myristate acetate (PMA). The addition of NPGB at the time of maximum superoxide generation was still able to block the superoxide release. It appears from these findings that NPGB may block either the activation process of the membrane bound NAD(P)H oxidase or directly on the active enzyme. Other protease inhibitors such as, epsilon-amino caproic acid (EACA), pepstatin, trans aminomethyl cyclohexane carboxylic acid (AMCA), aprotinin, and leupeptin did not inhibit the superoxide release. The superoxide anion release by the xanthine-xanthine oxidase system was not inhibited by NPGB. This finding indicates that NPGB does not itself react with superoxide. It has been also demonstrated that NPGB is a good reactant toward sulfhydryl group. The relevance of these finding to experimental allergic encephalomyelitis (EAE) is discussed.