title: Inhibition of protein kinase C of human neutrophils by phosphatidylcholines.
abstract: Pulmonary surfactant phospholipids, particularly phosphatidylcholines (PCs), inhibit superoxide generation in neutrophils. The activation of neutrophils is in part dependent on protein kinase C (PKC). To investigate the mechanism of action of PCs in inhibition of neutrophil activation, we studied the effect of PCs, commonly found in pulmonary surfactant, on the distribution of PKC in intact resting and stimulated neutrophils as well as on their kinase activity in vitro. In general, in contrast to PCs with saturated fatty acyl moieties, PCs with unsaturated fatty acyl moieties inhibited PKC activity in vitro. To determine the effect of PCs on the activation of PKC in intact neutrophils, neutrophils preincubated with PCs for 2 hours were stimulated by 1,2-sn-dioctanoylglycerol (diC8) or 4-beta-phorbol 12-beta-myristate 13-alpha-acetate (PMA). The cytosolic PKC activity did not change in cells preincubated with PCs after stimulation with diC8 (3.76 +/- 0.83 units vs 3.90 +/- 1.48 units), as would be expected in control cells (3.06 +/- 0.41 units to 1.01 +/- 0.29 units). In contrast to diC8, PMA-induced translocation of PKC to the membrane was unaffected by PCs. These data suggest that specific PCs not only inhibit neutrophil PKC in vitro but can also affect its translocation in response to stimulation by diacylglycerol in intact neutrophils.
authors.affiliation: John B. Pierce Laboratory, Yale University School of Medicine, New Haven, CT 06519.
authors.forename: K
authors.initials: K
authors.lastname: Yoshida
authors.forename: V
authors.initials: V
authors.lastname: Mohsenin
mesh_terms: D000704:Analysis of Variance; D002118:Calcium / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D004075:Diglycerides / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D010713:Phosphatidylcholines / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D004075:Diglycerides; D010713:Phosphatidylcholines; C044295:1,2-dioctanoylglycerol; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium