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Infection and Immunity, December 2008, p. 5706-5713, Vol. 76, No. 12
0019-9567/08/$08.00+0 doi:10.1128/IAI.00935-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Platelet Antistaphylococcal Responses Occur through P2X1 and P2Y12 Receptor-Induced Activation and Kinocidin Release
Darin A. Trier,1
Kimberly D. Gank,1
Deborah Kupferwasser,1
Nannette Y. Yount,1
William J. French,1,2
Alan D. Michelson,4
Leon I. Kupferwasser,1,
Yan Q. Xiong,1,3
Arnold S. Bayer,1,3 and
Michael R. Yeaman1,3*
Division of Infectious Diseases, LAC-Harbor UCLA Medical Center, Torrance, California 90509,1 Division of Cardiology, LAC-Harbor UCLA Medical Center, Torrance, California 90509,2 David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90024,3 Center for Platelet Function Studies, University of Massachusetts Medical School, Worcester, Massachusetts 016554
Received 27 July 2008/ Accepted 11 September 2008
Platelets (PLTs) act in antimicrobial host defense by releasing PLT microbicidal proteins (PMPs) or PLT kinocidins (PKs). Receptors mediating staphylocidal efficacy and PMP or PK release versus isogenic PMP-susceptible (ISP479C) and -resistant (ISP479R) Staphylococcus aureus strains were examined in vitro. Isolated PLTs were incubated with ISP479C or ISP479R (PLT/S. aureus ratio range, 1:1 to 10,000:1) in the presence or absence of a panel of PLT inhibitors, including P2X and P2Y receptor antagonists of increasingly narrow specificity, and PLT adhesion receptors (CD41, CD42b, and CD62P). PLT-to-S. aureus exposure ratios of 
10:1 yielded significant reductions in the viability of both strains. Results from reversed-phase high-performance liquid chromatography indicated that staphylocidal PLT releasates contained PMPs and PKs. At ratios below 10:1, the PLT antistaphylococcal efficacy relative to the intrinsic S. aureus PMP-susceptible or -resistant phenotype diminished. Apyrase (an agent of ADP degradation), suramin (a general P2 receptor antagonist), pyridoxal 5'-phosphonucleotide derivative (a specific P2X1 antagonist), and cangrelor (a specific P2Y12 antagonist) mitigated the PLT staphylocidal response against both strains, correlating with reduced levels of PMP and PK release. Specific inhibition occurred in the presence and absence of homologous plasma. The antagonism of the thromboxane A2, cyclooxygenase-1/cyclooxygenase-2, or phospholipase C pathway or the hindrance of surface adhesion receptors failed to impede PLT anti-S. aureus responses. These results suggest a multifactorial PLT anti-S. aureus response mechanism involving (i) a PLT-to-S. aureus ratio sufficient for activation; (ii) the ensuing degranulation of PMPs, PKs, ADP, and/or ATP; (iii) the activation of P2X1/P2Y12 receptors on adjacent PLTs; and (iv) the recursive amplification of PMP and PK release from these PLTs.
* Corresponding author. Mailing address: Division of Infectious Diseases, David Geffen School of Medicine at UCLA, LAC-Harbor UCLA Medical Center, 1124 West Carson St., RB-2, Torrance, CA 90502. Phone: (310) 222-6428. Fax: (310) 782-2016. E-mail: mryeaman{at}ucla.edu
Published ahead of print on 29 September 2008.
Previous address: Division of Cardiology, Cedars Sinai Medical Center, Los Angeles, CA 90048.
Infection and Immunity, December 2008, p. 5706-5713, Vol. 76, No. 12
0019-9567/08/$08.00+0 doi:10.1128/IAI.00935-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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