Journal of Leukocyte Biology
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Originally published online as doi:10.1189/jlb.0507276 on October 25, 2007

Published online before print October 25, 2007
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(Journal of Leukocyte Biology. 2008;83:139-148.)
© 2008 by Society for Leukocyte Biology

Serum amyloid A inhibits apoptosis of human neutrophils via a P2X7-sensitive pathway independent of formyl peptide receptor-like 1

Karin Christenson, Lena Björkman, Carolina Tängemo1 and Johan Bylund2

Department of Rheumatology and Inflammation Research, Göteborg University, Göteborg, Sweden

2 Correspondence: Department of Rheumatology and Inflammation Research, Göteborg University, Guldhedsgatan 10, 413 46 Göteborg, Sweden. E-mail: johan.bylund{at}rheuma.gu.se

Neutrophil apoptosis is important for the termination of inflammatory reactions, in that it ensures placid clearance of these potently cytotoxic cells. Various proinflammatory cytokines delay neutrophil apoptosis, which may result in accumulation of these cells, sometimes accompanied by tissue destruction, potentially leading to various inflammatory disease states. Rheumatoid arthritis (RA) is characterized frequently by elevated levels of the acute-phase reactant serum amyloid A (SAA) in circulation and in tissues. SAA is emerging as a cytokine-like molecule with the ability to activate various proinflammatory processes, many of which involve signaling via the formyl peptide receptor-like 1 (FPRL1). In this study, we show that SAA, purified from plasma from RA patients or in recombinant form, suppressed apoptosis of human neutrophils. Blocking FPRL1 did not lessen the antiapoptotic effects of SAA, implying the action of a receptor distinct from FPRL1. In contrast, antagonists of the nucleotide receptor P2X7 abrogated the antiapoptotic effect of SAA completely but did not block intracellular calcium transients evoked by SAA stimulation. Based on these results and also the finding that blocking P2X7 inhibited antiapoptotic actions of unrelated stimuli (LPS and GM-CSF), we propose that P2X7 is a general mediator of antiapoptotic signaling in neutrophils rather than a bona fide SAA receptor.

Key Words: acute-phase reactant • granulocyte • cell death • rheumatoid arthritis • nucleotide receptor




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Opposing regulation of neutrophil apoptosis through the formyl peptide receptor-like 1/lipoxin A4 receptor: implications for resolution of inflammation
J. Leukoc. Biol., September 1, 2008; 84(3): 600 - 606.
[Abstract] [Full Text] [PDF]


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