Priming of human neutrophils by peroxynitrite: potential role in enhancement of the local inflammatory response

Peroxynitrite is a potent oxidant generated from the reaction of nitric oxi de (NO) and superoxide anion (O-2(-)), both of which can be produced in inf lammatory tissues, In these studies, we analyzed what direct effect peroxyn itrite had on neutrophil (PMN) function, We found that peroxynitrite Tvas a n effective priming agent for PMNs, as demonstrated by enhanced O-2(-) prod uction on subsequent activation with low doses of PMA or N-folmyl-methionin e-leucine-phenylalanine (fMLF), changes in the expression of PMN surface ma rkers (L-selectin, Mac-1, flavocytochrome b, and fMLF receptor), and increa sed intracellular calcium levels, Analysis of the mechanism of PMN priming by peroxynitrite demonstrated that peroxynitrite resulted in minimal oxidat ion of protein sulfhydryl groups and subsequent protein cross-linking, In c ontrast, treatment of PMNs with peroxynitrite resulted in significant nitra tion of tyrosine residues on neutrophil proteins, In addition, inhibition o f tyrosine nitration with a pyrrolopyrimidine antioxidant blocked the major ity of peroxynitrite-induced priming effects, further suggesting that PMN p riming was mediated primarily by nitration of tyrosine residues on PMN prot eins. The ability of peroxynitrite to serve as an effective priming agent f or PMN's at sites of inflammation may play a key role in modulating the hos t-defense process.