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 the potent oxidant peroxynitrite (ONOO-) was shown to react with luminol to yield CL in a cellfree system. We evaluated the role of the image-arginine/NOS pathway in luminol CL by phorbol ester-activated human polymorpho-nuclear (PMN) leukocytes using the NOS inhibitors NG-monomethyl-image-arginine (image-NMMA) and N-iminoethyl-image-omithine (image-NIO). Nitric oxide (·NO) release was determined by oxidation of oxymyoglobin. In addition, the effect of NOS inhibitors on superoxide anion O2-) production was measured. Luminol CL was notably diminished by image-NMMA in a dose-dependent manner. Superoxide dismutase (SOD) also decreased luminol CL and image-NMMA potentiated light emission decrease produced by SOD. Nitric oxide and O2·- production was significantly decreased by image-NMMA; moreover, luminol-dependent CL but not O2·- production was attenuated by image-NIO. These data suggest that products of catalytic activity of both ·NO 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.