The phagocyte chemiluminescence paradox: luminol can act as an inhibitor of neutrophil NADPH-oxidase activity.
The chemiluminescence system amplified by luminol or isoluminol is a sensitive and widely used method for determination of respiratory burst products generated by the NADPH-oxidase in phagocytes. The present study shows that luminol, but not isoluminol, can inhibit the release of oxygen metabolites generated by human neutrophil NADPH-oxidase. The difference in structure between luminol and isoluminol (rendering luminol more lipophilic than isoluminol, and thereby membrane-permeable), is suggested to determine indirectly whether or not the molecule is inhibitory. Luminol was shown to have an increased inhibitory effect after preincubation of neutrophils on a surface of aggregated IgG, suggesting that the cells can be transferred from a 'luminol-insensitive' to a 'luminol-sensitive' state. Since luminol had no inhibitory effect in a cell-free NADPH-oxidase system, it is likely that it interferes with the signal transduction pathway, leading to assembly and/or activation of the oxidase. As a consequence of the present results, showing that luminol but not isoluminol can inhibit NADPH-oxidase activity, we suggest that isoluminol is used in future studies of superoxide anion release from phagocytes.
Fäldt
J
J
Department of Medical Microbiology and Immunology, Göteborg University, Guldhedsgatan 10, S-413 46 Göteborg, Sweden. jenny.faldt@microbio.gu.se
Ridell
M
M
Karlsson
A
A
Dahlgren
C
C
D002474:Cell-Free System; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008163:Luminescent Measurements; D008165:Luminol / Q000031:analogs & derivatives / Q000494:pharmacology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors*; D010586:Phagocytes / Q000187:drug effects* / Q000201:enzymology*; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004791:Enzyme Inhibitors; D013481:Superoxides; C032487:isoluminol; D009240:N-Formylmethionine Leucyl-Phenylalanine; D008165:Luminol; D019255:NADPH Oxidases; D013755:Tetradecanoylphorbol Acetate