CARBON-CENTERED FREE-RADICAL FORMATION DURING THE METABOLISM OF HYDRAZINE DERIVATIVES BY NEUTROPHILS

The neutrophil-catalyzed metabolism of hydrazine derivatives to carbon-centered radicals was investigated by the spin-trapping technique using alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Oxidation of methylhydrazine (MeH), dimethylhydrazine (DMH), phenylethylhydrazine or procarbazine by neutrophils from rat peritoneal exudates led to the formation of alkyl radicals. The monosubstituted hydrazine oxidation by phorbol ester (PMA)- or Zymocel-activated neutrophils generated, on average, 2- to 4-fold more POBN-alkyl adducts than di-substituted hydrazines. Supernatant from sonicated neutrophils generated similar yields of radicals. Azide, an inhibitor of myeloperoxidase, effectively reduced the neutrophil-catalyzed radical yield from the oxidation of MeH but not DMH. On the other hand, superoxide dismutase and catalase effectively inhibited radical formation in DMH metabolism by PMA-activated neutrophils, in contrast to MeH metabolism. Our results show that neutrophils are able to metabolize hydrazine derivatives, the pathway depending on the hydrazine substitution. Alkyl radical production during the oxidation of mono-substituted derivatives, such as MeH, was mediated mainly by myeloperoxidase, and that of di-substituted derivatives, such as DMH, was mediated mainly by active oxygen species.