N-Acetylcysteine Effect on the Luminol-dependent Chemiluminescence Pattern of Reactive Oxygen Species Generation by Human Polymorphonuclear Leukocytes

Abstract

The evidence of the effect of N-acetylcysteine on reactive oxygen species produced by human polymorphonuclear leukocytes (PMNs) is often contradictory, as thiol compounds may react with not only reactive oxygen and nitrogen species but also they may influence intracellular glutathione levels. The effect of 20, 100 and 200μM N-aceylcysteine (NAC) on luminol dependent chemiluminescence (LDCL) of human PMNs (106 cells/ml phospate buffered saline (PBS)) and whole blood to N-formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol-12-myristate-13-acetate (PMA) was studied. Further, the ability of NAC to increase PMNs intracellular thiols and affect subsequent PMNs, stimulation was assessed. NAC 100 and 200μM, but not 20μM, was found to attenuate the kinetic parameters of initial phase of fMLP-stimulated PMNs oxidative burst. NAC at the concentration of 100 and 200μM decreased the rate, maximum and integrated value of PMNs response to fMLP. The integrated value of PMA-induced PMNs and fMLP-induced whole blood LDCL response was also decreased by 100 and 200μM NAC. Furthermore, all tested NAC concentrations decreased LDCL of resting PMNs suspension.The chemiluminescence pattern of reactive oxygen species (ROS) generation by PMNs stimulated with fMLP or PMA did not differ significantly from those preincubated with either 20, 100, or 200μM NAC. Similarly, NAC did not increase the concentration of intracellular thiols in resting PMNs. However, addition of 200μM NAC to PMA-stimulated PMNs prevented the decline in intracellular thiols pool. Both PMA- and fMLP-activated PMNs oxidized extracellular NAC. These results indicate that NAC decreases the intensity of PMNs oxidative burst by direct scavenger activity.