Contribution of nitric oxide synthase to human neutrophil chemiluminescence

A chemiluminescence (CL) assay has been used to measure the reactive oxygen species (ROS)-generating capacity of phagocytes. Primed neutrophils produce ROS and nitric oxide (NO) upon induction of nitric oxide synthase (NOS) activity. NO and superoxide (O2^-) form peroxynitrite (ONOO^-), and emit CL. We examined the involvement of NOS in the CL response of neutrophils using a method based on the modulation of enzyme activity of NOS by the substrate L-arginine and an inhibitor; L-NAME. We used lipopolysaccharide (LPS) as the neutrophil-priming agent. Addition of sodium azide (NaN₃) with horseradish peroxidase (HRP) to luminol-dependent CL, gave a CL response that was significantly enhanced when 10 mmol/L L-arginine was present (p <0.05). suggesting that NOS activity contributed to the CL response of human neutrophils. LPS-primed luminol-dependent CL was significantly inhibited by L-NAME compared with D-NAME. The proportion of the difference between the two inhibitors in luminol-dependent CL was 12.3 ± 15.0%. Therefore, approximately 12% of the LPS-primed luminol-dependent CL decrease induced by L-NAME indicated the contribution of NOS activity to the CL response.