Stimulus-specific enhancement of luminol chemiluminescence in neutrophils by phosphatidylserine liposomes. |
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Authors: | M Takahashi H Ikeda E F Sato K Akimaru R Edamatsu M Inoue K Utsumi |
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Institution: | Department of Neuropsychiatry, Kochi Medical School, Japan. |
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Abstract: | When stimulated with different stimuli, neutrophils generate various active oxygen species. These active oxygen molecules can be analyzed by luminol chemiluminescence (LCL). Phosphatidylserine (PS)-liposomes increased the formylmethionyl-leucyl-phenylalanine-induced LCL of guinea pig peritoneal neutrophils without affecting their oxygen consumption and superoxide (O2.-) generation. Similar effects of PS-liposomes were also observed in LCL of neutrophils stimulated by phorbol myristate acetate or arachidonic acid but not by opsonized zymosan. Kinetic analysis revealed that the PS-liposome-induced increase in LCL depended on extracellulary generated O2.-. Moreover, the stimulatory effect of PS could be seen only when it formed liposomal membranes. The effect of PS-liposomes was also inhibited by superoxide dismutase, catalase, and deferoxamine, an iron chelator, but not by azide, an inhibitor of myeloperoxidase. Similar enhancement of stimulation-dependent LCL response was also observed with Fe3+ and ADP-Fe3+, but the degree of enhancement was much greater with PS-liposomes than with iron and its complex. The increase in hydroxyl radical generation by PS-liposome-treated neutrophils was confirmed by experiments with EPR spectrometry using spin-trapping agents. These results suggested that the interaction of neutrophils with PS-containing membrane surface might generate reactive oxygen species that enhance the stimulus-dependent LCL response of neutrophils. |
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