Major trauma enhances store-operated calcium influx in human neutrophils

Purpose: Chemotaxins from inflammatory sites prime or activate neutrophils (PMN) by using cytosolic calcium ([Ca 2+ ] i ) fluxes as second messengers. [Ca 2+ ] i can be mobilized rapidly by receptor-mediated entry or store-release, or more slowly by store-operated calcium influx (SOCI). We studied [Ca 2+ ] i mobilization by chemotaxins and how trauma impacts the calcium entry mechanisms used by chemotaxins. Methods: [Ca 2+ ] i flux was studied by spectrofluorometry. The contributions of early and late [Ca 2+ ] i currents to net calcium flux were compared after stimulation by more potent (fMLP, C5a, PAF) or less potent (IL-8, GRO-a, and LTB4) agonists. Store operated [Ca 2+ ] i mobilization was reflected by the ratio of area under the [Ca 2+ ] i efflux curve to peak [Ca 2+ ] i (efflux curve). PMN from trauma patients (ISS > 25) and pair-matched volunteer (n = 7 pairs) were then primed and stimulated with thapsigargin to compare cell calcium stores and SOCI. Results: Late [Ca 2+ ] i mobilization made more important contributions to fMLP, PAF, and C5a signals than to IL-8, GRO-a, or LTB4 (p < 0.01 all comparisons). Calcium stores and store release were only marginally lower after injury (p = not significant), but trauma PMN showed far higher [Ca 2+ ] i influx after thapsigargin (p = 0.007), and greater net SOCI (p = 0.034). Conclusions: SOCI may play an important role in PMN activation, and trauma increases PMN SOCI. Prolonged elevations of [Ca 2+ ] i due to enhanced SOCI may alter stimulus-response coupling to chemotaxins and contribute to PMN dysfunction after injury.