NITRIC-OXIDE SYNTHASE INHIBITORS DECREASE HUMAN POLYMORPHONUCLEAR LEUKOCYTE LUMINOL-DEPENDENT CHEMILUMINESCENCE

Nitric oxide synthase (NOS) inhibitors have been reported to modulate luminol-dependent chemiluminescence (CL) in rat macrophages, whereas t he potent oxidant peroxynitrite (ONOO-) was shown to react with lumino l to yield CL in a cell-free system. We evaluated the role of the L-ar ginine/NOS pathway in luminol CL by phorbol ester-activated human poly morphonuclear (PMN) leukocytes using the NOS inhibitors NG-monomethyl- L-arginine (L-NMMA) and N-iminoethyl-L-ornithine (L-NIO). Nitric oxide ((NO)-N-.) release was determined by oxidation of oxymyoglobin. In ad dition, the effect of NOS inhibitors on superoxide anion O-2(.-)) prod uction was measured. Luminol CL was notably diminished by L-NMMA in a dose-dependent manner. Superoxide dismutase (SOD) also decreased lumin ol CL and L-NMMA potentiated light emission decrease produced by SOD. Nitric oxide and O-2(.-) production was significantly decreased by L-N MMA; moreover, luminol-dependent CL but not O-2(.-) production was att enuated by L-NIO. These data suggest that products of catalytic activi ty of both (NO)-N-. synthase and NADPH oxidase are required to elicit maximal luminol CL in this system. These studies demonstrate that the NOS synthase pathway is involved in luminol CL by human PMN, and they suggest that ONOO would be an unrecognized mediator in this phenomenon .