Studies on molecular regulation of phagocytosis and activation of the NADPH oxidase in neutrophils. IgG- and C3b-mediated ingestion and associated respiratory burst independent of phospholipid turnover and Ca2+ transients.
The role of messengers derived from hydrolysis of phosphoinositides and other phospholipids, of the basal level of [Ca2+]i and of the increase in [Ca2+]i in phagocytosis and respiratory burst was investigated, using normal neutrophils and neutrophils Ca2(+)-depleted by pretreatment with Quin2/AM and EGTA. 1) Phagocytosis and respiratory burst in control neutrophils challenged with yeast opsonized with IgG or C3b/bi were associated with a stimulation of the production of inositol phosphates, diacylglycerol, phosphatidic acid, arachidonic acid, and rise in [Ca2+]i. 2) In Ca2(+)-depleted neutrophils (basal [Ca2+]i 10 to 20 nM) the phagocytosis of yeast-IgG was similar to that in control neutrophils, the respiratory burst was slightly depressed (-30%), while the increase in [Ca2+]i and production of inositol phosphates, diacylglycerol, and phosphatidic and arachidonic acid did not occur. 3) In Ca2(+)-depleted neutrophils the phagocytosis of yeast-C3b/bi was slightly lower than that in control neutrophils, and the respiratory burst, related to the same number of particles ingested, was depressed by about 60%, whereas the increase in [Ca2+]i and production of inositol phosphates, diacylglycerol, phosphatidic acid, and arachidonic acid release did not occur. These findings demonstrate that transmembrane signaling pathways involving the hydrolysis of phosphoinositides by phospholipase C and D and of other phospholipids by phospholipase C and Az, and the rise in [Ca2+]i are not essential processes for triggering the ingestion of yeast particles opsonized with IgG and C3b/bi and the activation of the NADPH oxidase.
Della Bianca
V
V
Instituto di Patologia Generale, Universita di Verona, Italy.
Grzeskowiak
M
M
Rossi
F
F
D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D003179:Complement C3b / Q000502:physiology; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D007074:Immunoglobulin G / Q000502:physiology; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000502:physiology*; D010587:Phagocytosis; D010712:Phosphatidic Acids / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D015398:Signal Transduction
D001095:Arachidonic Acids; D004075:Diglycerides; D007074:Immunoglobulin G; D007295:Inositol Phosphates; D010712:Phosphatidic Acids; D010743:Phospholipids; D016718:Arachidonic Acid; D003179:Complement C3b; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D002118:Calcium