Effects of reactive oxygen and nitrogen metabolites on MCP-1-induced monocyte chemotactic activity in vitro

Peroxynitrite, an oxidant generated by the interaction between super-oxide and nitric oxide (NO), can nitrate tyrosine residues, resulting in compromi sed protein function. Monocyte chemoattractant protein-1 (MCP-1) is a chemo kine that attracts monocytes and has a tyrosine residue critical for functi on. We hypothesized that peroxynitrite would alter MCP-1 activity. Peroxyni trite attenuated MCP-l-induced monocyte chemotactic activity (MCA) in a dos e-dependent manner (P < 0.05) but did not attenuate leukotriene Bq or compl ement-activated serum MCA. The reducing agents dithionite, deferoxamine, an d dithiothreitol reversed the MCA inhibition by peroxynitrite, and exogenou s L-tyrosine abrogated the inhibition by peroxynitrite. PAPA-NONOate, an NO donor, or superoxide generated by xanthine and xanthine oxidase did not sh ow an inhibitory effect on MCA. induced by MCP-1. The peroxynitrite generat or 3-morpholinosydnonimine caused a concentration-dependent inhibition of M CA by MCP-1. Peroxynitrite reduced MCP-1 binding to monocytes and resulted in nitrotyrosine formation. These findings are consistent with nitration of tyrosine by peroxynitrite, with subsequent inhibition of MCP-1 binding to monocytes, and suggest that peroxynitrite may play a role in regulation of MCP-l-induced monocyte chemotaxis.