LPS directly induces oxygen radical production in human monocytes via LPS binding protein and CD14.
In human monocytes, superoxide (O2-) generation accompanies phagocytosis and is important for bactericidal activity. It also contributes to tissue damage in inflammation. In the present study we investigated, whether lipopolysaccharide (LPS) directly stimulates monocyte O2- production with kinetics known for other LPS effects and, if so, by which mechanism. LPS caused a time- and dose-dependent O2- release in nonadherent purified monocytes. The effect appeared after 5 min, peaked at 30 min, and disappeared after 2 h. It was maximal with 10 ng/ml lipid A (+148 +/- 22%, P < .001), 1 ng/ml LPS Escherichia coli Re (+226 +/- 68%, P < .001), and 100 ng/ml LPS Salmonella abortus equi sm (+272 +/- 52%, P < .001), respectively. The effect was not observed in buffer, even when using 10 micrograms/ml LPS. It was dependent on the presence of heat-inactivated AB serum, with a maximal effect at > or = 0.5%. Serum could be replaced by LPS-binding protein (LBP). Polymyxin B and anti-LBP antiserum, respectively, blocked the LPS effect. LPS-induced O2- generation was also completely blocked by anti-CD14 antibodies (3C10 and 63D3) and by their corresponding F(ab')2 fragments. Monocytes treated with phosphoinositol-specific phospholipase C and monocytes from patients with paroxysmal nocturnal hemoglobinuria, lacking the phosphatidylinositol-anchored CD14, did not respond to LPS stimulation with O2- production. Similarly to LPS, E. coli caused stronger O2- production with heat-inactivated serum than without, and this effect was blocked by anti-CD14 antibodies. In conclusion, these data indicate that LPS directly stimulates O2- production in human monocytes via CD14 depending on LBP.
Landmann
R
R
Department of Research, University Hospital, Basel, Switzerland.
Scherer
F
F
Schumann
R
R
Link
S
S
Sansano
S
S
Zimmerli
W
W
D000209:Acute-Phase Proteins; D015703:Antigens, CD / Q000378:metabolism*; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004926:Escherichia coli; D006801:Humans; D066298:In Vitro Techniques; D008050:Lipid A / Q000494:pharmacology; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008562:Membrane Glycoproteins; D009000:Monocytes / Q000378:metabolism*; D011112:Polymyxin B / Q000494:pharmacology; D012475:Salmonella; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000099231:Lipopolysaccharide-Binding Protein
D000209:Acute-Phase Proteins; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D002352:Carrier Proteins; D008050:Lipid A; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011112:Polymyxin B; D013481:Superoxides; D013755:Tetradecanoylphorbol Acetate; D000099231:Lipopolysaccharide-Binding Protein