Enhancement of chemoattractant-induced oxidative activation during phagocytosis of Staphylococcus aureus by human neutrophils
(English)Manuscript (preprint) (Other academic)
Several studies have shown that the production of oxygen radicals in human neutrophils can be influenced by prior exposure to different priming agents, but the mechanism underlying priming is not fully understood. The present study shows that under reduced Ca2+-conditions, phagocytosis of viable, but not heat-killed S. aureus can prepare Ca2+-depleted neutrophils for an increased oxidative activation when stimulated with fMLP in the presence of Ca2+. This enhancement of the produced oxygen radicals, induced by viable S. aureus, was not due to differences in phagocytic uptake between viable or heat-killed bacteria by the neutrophils. We could neither detect any difference in the upregulation of chemoattractant receptors such as the fMLP receptor or complement receptor 3 (CR3) to the neutrophil cell surface. Phagocytosis of viable S. aureus by Ca2+-depleted neutrophils under reduced Ca2+-conditions, induced tyrosine phosphorylation of two proteins identified as phospholipase Cγ2 (PLCγ2) and Syk. Pretreatment of neutrophils with U-73122 or piceatannol, to selectively inhibit PLC and Syk, respectively, resulted in a marked suppression of the oxidative response in primed neutrophils. In addition, PP1, a drug known to selectively inhibit Srcfamily protein kinases inhibited the oxidative response in primedneutrophils. Moreover, bacterial uptake activated the Src- family protein kinase Lyn, which was inhibited by PPl. Phagocytosis of viable or heatkilled S. aureus did not show any difference in activation of p38 mitogenactivated protein kinase (MAPK) and inhibition of this kinase by SB203580 did not suppress the fMLP-induced oxidative activation inprimed neutrophils. The findings demonstrate that both priming and the induction of tyrosine phosphorylation of PLCγ2, Syk and Lyn are Ca2+-independent events, thus indicating that the phosphorylation of these intracellular targets plays a central role during the neutrophil priming by S. aureus.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-79589OAI: oai:DiVA.org:liu-79589DiVA: diva2:543864