Effects of reactive oxygen and nitrogen metabolites on eotaxin-induced eosinophil chemotactic activity in vitro

Peroxynitrite, an oxidant generated by the interaction between superoxide a nd nitric oxide (NO), has been implicated in the etiology of numerous disea se processes. Several studies have shown that peroxynitrite-induced protein nitration may compromise enzyme and protein function. We hypothesized that peroxynitrite may regulate cytokine function during inflammation. To test this hypothesis, the eosinophil chemotactic responses of eotaxin incubated with and without peroxynitrite were evaluated. Peroxynitrite attenuated eot axin-induced eosinophil chemotactic activity (ECA) in a dose-dependent mann er (P < 0.05). The inhibitory effects were not significant on ECA induced b y leukotriene B-4 or complement-activated serum incubated with peroxynitrit e. The reducing agents deferoxamine and dithiothreitol reversed the ECA inh ibition by peroxynitrite, and exogenous L-tyrosine abrogated the inhibition by peroxynitrite. PAPA-NONOate (an NO donor) or a combination of xanthine and xanthine oxidase to generate superoxide did not show an inhibitory effe ct on ECA induced by eotaxin. In contrast, 3-morpholinosydnonimine, a perox ynitrite generator, caused a concentration-dependent inhibition of ECA by e otaxin. Consistent with its capacity to reduce EGA, peroxynitrite treatment reduced eotaxin binding to eosinophils, Nitrotyrosine was detected in the eotaxin incubated with peroxynitrite. These findings are consistent with ni tration of tyrosine by peroxynitrite with subsequent inhibition of eotaxin binding to eosinophils and a reduction in EGA. These data demonstrate that peroxynitrite modulates the eosinophil migration by eotaxin, and suggest th at oxidants may play an important role in regulation of eotaxin-induced eos inophil chemotaxis.