Reactive nitrogen and oxygen species attenuate interleukin-8-induced neutrophil chemotactic activity in vitro

Peroxynitrite, formed by the reaction between nitric oxide and superoxide, has been shown to induce protein nitration, which compromises protein funct ion. We hypothesized that peroxynitrite may regulate cytokine function duri ng inflammation. To test this hypothesis, the neutrophil chemotactic activi ty (NCA) of interleukin-8 (IL-8) incubated with peroxynitrite was evaluated . Peroxynitrite attenuated IL-8 NCA in a dose-dependent manner (p < 0.01) b ut did not significantly reduce NCA induced by leukotriene B-4 or complemen t-activated serum. The reducing agents, dithionite, deferoxamine, and dithi othreitol, reversed and exogenous L-tyrosine abrogated the peroxynitrite-in duced NCA inhibition. Papa-NONOate [N-(3-ammoniopropyl)-N-(n-propyl)amino]d iazen-1-ium-1,2-dialase or sodium nitroprusside, NO donors, or a combinatio n of xanthine and xanthine oxidase to generate superoxide did not show an i nhibitory effect on NCA induced by IL-8, In contrast, small amounts of SIN- 1, a peroxynitrite generator, caused a concentration-dependent inhibition o f NCA by IL-8, Consistent with its capacity to reduce NCA, peroxynitrite tr eatment reduced IL-8 binding to neutrophils. Nitrotyrosine was detected in the IL-8 incubated with peroxynitrite by enzyme-linked immunosorbent assay. These findings are consistent with nitration of tyrosine by peroxynitrite with subsequent inhibition of IL-8 binding to neutrophils and a reduction i n NCA and suggest that oxidants may play an important role in regulation of IL-8-induced neutrophil chemotaxis.