Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


The Role of Platelets and CD40L in the Pathogenesis of Kawasaki Disease.

Arjmand2,  Parnian, Yeung1,  Rae S. M.

Hospital for Sick Children, Toronto, ON, Canada
University of Toronto, The Hospital for Sick Children, Toronto, ON, Canada

Background:

Kawasaki Disease (KD) is a disease of childhood characterized by systemic inflammation leading to coronary artery damage. Although its etiology remains unknown, superantigens are among the triggers of disease. Lactobacillus Casei Cell Wall Extract (LCWE) induces a disease in mice which mimics KD closely in time-course, histological changes and susceptibility in the young. LCWE contains both a superantigen and a TLR-2 ligand. KD is characterized by marked elevation in platelet numbers. Recent studies have found CD40L expression on platelets and CD4+ T cells to be associated with coronary artery aneurysms in children with KD. CD40L is a member of the TNF family of proteins which is expressed on T-cells. Interestingly, it is also stored in platelet granules and binds to an integrin receptor, gpIIIaIIb, on platelets. Platelets also store and release Matrix Metalleoprotease 9 (MMP-9) upon activation – an enzyme essential for coronary artery break-down and anuerysm formation in KD. Here, we aim to elucidate the role of platelets in the pathogenesis of KD: specifically, the effect of LCWE stimulation on platelet activation, CD40L and MMP-9 expression and release, and its role in coronary artery disease.

Methods:

In vivo and in vitro platelet activation (a-granular release, microparticle formation, aggregation, integrin receptor activation) is assayed using flow-cytometry. In vivo, blood is obtained from C57/BL6 mice injected with LCWE or PBS; in vitro, platelets are stimulated with LCWE and assayed. Platelet MMP-9 release is studied by determining protein and enzymatic activity using Western blots and zymography respectively. To differentiate between superantigenic versus TLR-2 agonistic activity of LCWE in stimulating platelets, blood is also drawn from TLR-2 knock-out mice or treated with a TLR-2 blocking mAb prior to analysis.

Results:

Stimulation of platelets with collagen and ADP agonists achieves maximal platelet CD40L and P-selectin upregulation in vitro.TLR2 ligand PAM3CSK4, LCWE and SEB are also able to induce CD40L and P-selectin upregulation, gpIIIaIIb activation, leukocyte aggregation and microparticle formation. Upregulation of these platelet activation markers were also observed in vivo after stimulation with the classic superantigen, SEB. Interestingly, LCWE induced platelet activation is unaffected in the absence of TLR-2 signaling, evidenced in assays using TLR2 deficient mice and also with addition of TLR-2 blocking antibody pointing superantigenic and not TLR2 activity as the trigger of platelet activation.

Conclusions:

Our results suggest that superantigenic stimulation with LCWE activates mouse platelets a-granular release, CD40L upregulation and integrin receptor gpIIIaIIb. Moreover, we show that TLR-2 signaling does not contribute to platelet activation. Establishing a role for platelets and CD40L in the pathogenesis of KD may have important implications in design of new therapeutic agents in KD.

To cite this abstract, please use the following information:
Arjmand, Parnian, Yeung, Rae S. M.; The Role of Platelets and CD40L in the Pathogenesis of Kawasaki Disease. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :267
DOI: 10.1002/art.28036

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