Lipopolysaccharide priming of human neutrophils for an enhanced respiratory burst. Role of intracellular free calcium

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Abstract

Lipopolysaccharide (LPS) pretreatment 'primes' neutrophils to release increased amounts of superoxide anion (O2-) when stimulated. We investigated the molecular basis of this enhanced activity. Comparison of kinetic parameters of the respiratory burst NADPH oxidase in unstimulated LPS-primed and control neutrophils disclosed a similar K(m) for NADPH and no difference was seen in the content of cytochrome b. Pertussis toxin, which inhibits some G proteins, did not prevent priming. Change in membrane potential (Δψ) was five-fold greater in LPS-primed cells and paralleled the increased O2- release. Cytofluorographic analysis indicated that the increased change in Δψ was due to the creation of a new population of active cells. Changes in the concentration of intracellular free Ca2+ ([Ca2+](i)) are believed to antecede changes in Δψ. There was a consistent increment (67 ± 8%, n = 12) in resting [Ca2+](i) in cells preincubated with LPS compared with control. When stimulated, the peak [Ca2+](i) was significantly higher in LPS-primed cells. Ca2+-dependent protein kinase C activity was unaltered in resting and FMLP-stimulated neutrophils preexposed to LPS. Addition to cells of the intracellular Ca2+ chelator MAPTAM before preincubation with LPS blocked the changes in [Ca2+](i) and the enhanced respiratory burst that characterize LPS priming. The increased resting [Ca2+](i) in LPS-primed cells may enhance stimulus-induced cellular activity by modifying a Ca2+-dependent step in signal transduction.

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Forehand, J. R., Pabst, M. J., Phillips, W. A., & Johnston, R. B. (1989). Lipopolysaccharide priming of human neutrophils for an enhanced respiratory burst. Role of intracellular free calcium. Journal of Clinical Investigation, 83(1), 74–83. https://doi.org/10.1172/JCI113887

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