Inhibition of MIP-1 alpha-induced human neutrophil and monocyte chemotactic activity by reactive oxygen and nitrogen metabolites

Peroxynitrite, formed by the reaction between nitric oxide (NO) and superox ide, has been implicated in the pathogenesis of numerous disease processes. Several studies have shown that peroxynitrite-induced protein nitration ma y compromise enzyme and protein function. We hypothesized that peroxynitrit e may regulate cytokine function during inflammation. To test this hypothes is, the neutrophil and monocyte chemotactic responses of macrophage inflamm atory protein-1 alpha (MIP-1 alpha) incubated with and without peroxynitrit e were evaluated. Peroxynitrite attenuated neutrophil chemotactic activity (NCA) and monocyte chemotactic activity (MCA) by MIP-1 alpha in a dose-depe ndent manner (P <.05). The inhibitory effects were not significant on NCA a nd MCA induced by leukotriene B4 or complement-activated serum incubated wi th peroxynitrite. The reducing agents deferoxamine, dithiothreitol, and exo genous L-tyrosine abrogated the NCA and MCA inhibition by peroxynitrite, Pa pa-NONOate, an NO donor, or a combination of xanthine and xanthine oxidase to generate superoxide, did not show an inhibitory effect on NCA and MCA in duced by MIP-1 alpha. In contrast, 3-morpholinosydnonimine (SIN-1), a perox ynitrite generator, elicited a concentration-dependent reduction in NCA and MCA induced by MIP-1 alpha. Consistent with its capacity to reduce NCA and MCA, peroxynitrite treatment reduced MIP-1 alpha binding to neutrophils an d monocytes. Nitrotyrosine was detected in the MIP-1 alpha incubated with p eroxynitrite, These findings are consistent with nitration of tyrosine by p eroxynitrite with subsequent inhibition of MIP-1 alpha binding to neutrophi ls and monocytes and a reduction in NCA and MCA. These data demonstrate tha t peroxynitrite modulates the inflammatory cell migration by MIP-1 alpha, a nd they suggest that oxidants may play an important role in the regulation of MIP-1 alpha-induced inflammatory cell chemotaxis.