Difference in hydrogen peroxide release between human neutrophils and neutrophil cytoplasts following calcium ionophore activation. A role of the subcellular granule in activation of the NADPH-oxidase in human neutrophils?
The role of subcellular granule in the capacity to generate reactive oxygen metabolites in human granulocytes was studied using normal cells and organell-free neutrophil cytoplasts. The cytoplasts are devoid of granules but have an intact ligand-receptor coupling mechanism. Both the chemotactic peptide formylmethionylleucylphenylalanine (FMLP) and the ionophore ionomycin induced a chemiluminescence response in normal cells, but only FMLP stimulation was associated with any notable hydrogen peroxide production. However, in the presence of azide, a potent inhibitor of the hydrogen peroxide-consuming enzymes, catalase and myeloperoxidase, a pronounced release of hydrogen peroxide was also induced by ionomycin. The response of cytoplasts to FMLP proceeded with a rate and time-course similar to those seen in intact cells, whereas in response to ionomycin they produced very low quantities of hydrogen peroxide, even in the presence of azide. Analysis of the data presented in this study leads to the following conclusion: (i) FMLP, which acts through cell surface receptors, causes the cells to produce oxygen metabolites, which, to a large extent, are released from the cells, a process that is not dependent on subcellular granule; and (ii) ionomycin, which bypasses cell surface receptors, is also capable of stimulating hydrogen peroxide formation that is granule-dependent and that is retained inside the cells.
Dahlgren
C
C
Department of Medical Microbiology, University of Linköping, Sweden.
Johansson
A
A
Orselius
K
K
D001386:Azides / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism; D004789:Enzyme Activation; D004987:Ethers / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000097:blood*; D015759:Ionomycin; D008163:Luminescent Measurements; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009247:NADH, NADPH Oxidoreductases / Q000097:blood*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000378:metabolism*; D010101:Oxygen Consumption; D009195:Peroxidase / Q000378:metabolism
D001386:Azides; D004987:Ethers; D015759:Ionomycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases