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Calcium requirements for vitronectin-mediated phagocytosis of Staphylococcus aureus by human neutrophils
Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper we have shown that the intracellular free calcium concentration ([Ca2+]i) in human neutrophils regulates phagocytosis of Staphylococcus aureus adherent to vitronectin-coated surfaces. When neutrophils were allowed to phagocytose bacteria bound to vitronectin- or albumin-coated surfaces in tbe presence of Ca2+, there were no obvious differences in the phagocytic activity. Ca2+-depleted neut:ropbils showed a reduced phagocytic activity on vitronectin-coated surfaces. However, the phagocytosis on albumin-coated surfaces was unaffected. Adding extracellularly Ca2+ restored the reduced phagocytic activity in Ca2+-depleted neutrophils on vitronectincoated surfaces. Similarly, using a GRGDSP-peptide to block tbe RGDmediated integrin attachment of tbe neutrophils to vitronectin restored tbe reduced phagocytic activity in Ca2+-depleted cells. Studying phagocytosis in non-migrating neutrophils adherent to vitronectin showed that ingestion of S. aureus occurred independently of Ca2+. This indicate that Ca2+ regulate the phagocytic activity of neutrophils on vitronectin-coated surfaces by regulating integrin-dependent cell directed motility.

National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-79588OAI: oai:DiVA.org:liu-79588DiVA: diva2:543861
Available from: 2012-08-10 Created: 2012-08-10 Last updated: 2012-08-10Bibliographically approved
In thesis
1. On the interaction between human neutrophils and Staphylococcus aureus
Open this publication in new window or tab >>On the interaction between human neutrophils and Staphylococcus aureus
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Intracellular free calcium is a key second messenger and has been shown to regulate several crucial functions in human neutrophils. The results show that a rise in [Ca2+], is an absolute requirement for efficient killing of serum-opsonized Staphylococcus aureus by human neutrophils. The reduced killing in the absence of Ca2+ was not due to an inhibited ingestion of the S. aureus bacteria but to impairment of the subsequent production of oxygen radicals.

S. aureus is a bacterium which binds to extracellular matrix proteins such as vitronectin. When studying the role of Ca2+ during phagocytosis of S. aureus adherent to vitronectin-coated surfaces, the results show that a rise in [Ca2+], is not a prerequisite for ingestion per se. However, Ca2+ control neutrophil migration on vitronectin, by regulating reversible integrindependent adhesion of the neutrophils.

The intracellular signalling events of the neutrophils induced by S. aureus were also evaluated. The results demonstrate that S. aureus induces both priming and apoptosis in the neutrophils. This was restricted to viable and not heat-killed bacteria. During priming tyrosine phosphorylation of PLCγ2 and Syk is increased. In addition, the Src-family protein kinase Lyn is activated as well by these bacteria. Inhibition of these proteins by selective drugs abrogates priming of the neutrophils, indicating that these proteins participate in neutrophil priming. Interaction of neutrophils with S. aureus as well as a S. aureus-derived factor induces apoptosis in the neutrophils, and this is regulated by p38 MAPK.

Taken together, this investigation shows that the Ca2+-dependent processing of bacteria by human neutrophils leads to several cellular responses affecting inflammation, such as oxidative activation, tyrosine phosphorylation, priming and apoptosis.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2000. 60 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 634
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28652 (URN)13808 (Local ID)91-7219-735-8 (ISBN)13808 (Archive number)13808 (OAI)
Public defence
2000-05-30, Elsa Brändströmssalen, Hälsouniversitetet, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-08-10Bibliographically approved

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Wilsson, ÅsaMajeed, MeythamStendahl, Olle

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