title: Inhibitory effect of porcine surfactant on the respiratory burst oxidase in human neutrophils. Attenuation of p47phox and p67phox membrane translocation as the mechanism.
abstract: Surfactant has been shown to inhibit the production of reactive oxygen intermediates by various cells including alveolar macrophages and peripheral blood neutrophils. Superoxide O2-. production by the respiratory burst oxidase in isolated plasma membranes prepared from PMA-treated human neutrophils was significantly attenuated by prior treatment with native porcine surfactant. The effect was concentration dependent with half-maximal inhibition seen at approximately 0.050 mg surfactant phospholipid/ml. Kinetic analyses of the membrane-bound enzyme prepared from neutrophils stimulated by PMA in the presence or absence of surfactant demonstrated that surfactant treatment led to a decrease in the maximal velocity of O2-. production when NADPH was used as substrate, but there was no effect on enzyme substrate affinity. Immunoblotting studies demonstrated that surfactant treatment induced a decrease in the association of two oxidase components, p47phox and p67phox, with the isolated plasma membrane. In contrast, surfactant treatment of the cells did not alter the phosphorylation of p47phox. A mixture of phospholipids (phosphatidylcholine and phosphatidylglycerol in a 7:3 ratio) showed similar inhibition of the PMA-induced O2-. generation. Taken together, these data suggest the mechanism of surfactant-induced inhibition of O2-. production by human neutrophils involves attenuation of translocation of cytosolic components of the respiratory burst oxidase to the plasma membrane. The phospholipid components of surfactant appear to play a significant role in this mechanism.
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of California, San Diego 92093, USA.
authors.forename: W
authors.initials: W
authors.lastname: Chao
authors.forename: R G
authors.initials: RG
authors.lastname: Spragg
authors.forename: R M
authors.initials: RM
authors.lastname: Smith
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007525:Isoelectric Focusing; D007700:Kinetics; D008081:Liposomes; D009247:NADH, NADPH Oxidoreductases / Q000097:blood* / Q000187:drug effects; D009249:NADP / Q000378:metabolism; D019255:NADPH Oxidases; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010750:Phosphoproteins / Q000097:blood* / Q000302:isolation & purification; D010766:Phosphorylation; D011510:Proteolipids / Q000302:isolation & purification / Q000494:pharmacology*; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000302:isolation & purification / Q000494:pharmacology*; D013481:Superoxides / Q000097:blood; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D008081:Liposomes; D010750:Phosphoproteins; D011510:Proteolipids; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; C079789:neutrophil cytosol factor 67K; D013481:Superoxides; D009249:NADP; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; C022709:superoxide-forming enzyme; D013755:Tetradecanoylphorbol Acetate