Nanomolar arachidonic acid influences the respiratory burst in eosinophils and neutrophils induced by GTP-binding protein. A comparative study of the respiratory burst in bovine eosinophils and neutrophils.
To investigate a possible role of phospholipase A2 (PLA2) in the respiratory burst in bovine eosinophilic and neutrophilic leukocytes dependent on GTP-binding protein (G-protein), we permeabilized these cells with Staphylococcus aureus alpha-toxin and induced NADPH oxidase activity with the non-hydrolysable GTP analogue GTP[S] or the aluminium tetrafluoro complex AlF4-. Under same experimental conditions, cells responded with different onset times. The onset time for eosinophils was 50-200 s, for neutrophils it was only a few seconds. GTP[S] stimulated in neutrophils only 5% of the respiratory burst compared to eosinophils, whereas AlF4(-)-induced comparable responses (neutrophils 120% of eosinophils). GDP inhibited these responses with an IC50 value of 2.4 mM. Arachidonic acid showed, with the exception of AlF4- stimulated neutrophils, on both stimuli and cell types an enhancing effect (150%) that reached its maximum at 0.1-1 microM. The PLA2 inhibitor 4-bromophenacylbromide reduced the GTP[S]- and AlF4(-)-induced response almost completely (10 microM) and the inhibition was not significantly different for eosinophils and neutrophils (IC50 1-3 microM). If the respiratory burst was reduced with 4-bromophenacylbromide to 1-4% of the original value, 10% of the basal NADPH oxidase activity could be restored by addition of only 20-100 nM arachidonic acid. In addition, the PLA2 activator adriamycin enhanced the response in a dose-dependent manner and in the same order as arachidonic acid did. The results presented above suggest that the respiratory burst may be regulated by different low-molecular-mass and/or heterotrimeric G-proteins and an active role for arachidonic acid or its metabolites in the activation and the maintenance of the direct G-protein-stimulated respiratory burst in bovine eosinophils and neutrophils.
Aebischer
C P
CP
Institute of Biochemistry, University of Fribourg, Switzerland.
Pasche
I
I
Jörg
A
A
D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D002417:Cattle; D004317:Doxorubicin / Q000494:pharmacology; D004789:Enzyme Activation; D004790:Enzyme Induction; D004804:Eosinophils / Q000187:drug effects* / Q000378:metabolism; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D066298:In Vitro Techniques; D008163:Luminescent Measurements; D008165:Luminol / Q000494:pharmacology; D009247:NADH, NADPH Oxidoreductases / Q000096:biosynthesis / Q000378:metabolism; D019255:NADPH Oxidases; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000502:physiology; D054467:Phospholipases A2; D016897:Respiratory Burst / Q000187:drug effects*; D013211:Staphylococcus aureus / Q000378:metabolism; D010738:Type C Phospholipases / Q000494:pharmacology
D017607:Aluminum Compounds; C050992:tetrafluoroaluminate; D016718:Arachidonic Acid; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D008165:Luminol; D004317:Doxorubicin; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D005459:Fluorides