Direct stimulation of superoxide output in neutrophils by lipid A of Escherichia coli.
Two different results have been published in regard to the superoxide-stimulating activity of lipopolysaccharide or Lipid A in neutrophils: first, a direct stimulation after a lag time of about 30-60 sec and second, the inactivity of Lipid A if applied alone, being able only to "prime" the cells for a second challenge during a longer incubation period. In order to achieve clarity regarding these two different opinions, we asked the questions whether: (a) Lipid A is able to stimulate PMN directly, i.e. without a preincubation and a second stimulus; (b) fMLP and Lipid A show a synergistic effect; (c) a preincubation ("priming") of the PMN with Lipid A really increases the superoxide output after a second challenge. We observed (a) a direct stimulation of the chemiluminescence with Lipid A without an additional second challenge, accompanied by a seemingly unimodal kinetics of the superoxide output, i.e. mainly the second phase of the usually bimodal kinetics has been stimulated. As for question (b), a clearly detectable synergism between Lipid A and fMLP could be measured. Regarding question (c), a preincubation ("priming") with Lipid A was of no beneficial effect; the chemiluminescence count could be equally well increased without a "priming" compound.
Tarnok
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Department of Immunochemistry and Microbial Biochemistry, Research Institute Borstel, Federal Republic of Germany.
Tarnok
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D004357:Drug Synergism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008050:Lipid A / Q000494:pharmacology*; D008163:Luminescent Measurements; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
D008050:Lipid A; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine