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Real-time Imaging of Heterotypic Platelet-neutrophil Interactions on the Activated Endothelium During Vascular Inflammation and Thrombus Formation in Live Mice
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Real-time Imaging of Heterotypic Platelet-neutrophil Interactions on the Activated Endothelium During Vascular Inflammation and Thrombus Formation in Live Mice

Published on: April 2, 2013

Platelet CD40L mediates thrombotic and inflammatory processes in atherosclerosis

Dirk Lievens1, Alma Zernecke, Tom Seijkens

  • 1Department of Pathology, Maastricht Center for Atherosclerosis Research, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands.

Blood
|August 14, 2010
PubMed

CD40 ligand (CD40L), identified as a costimulatory molecule expressed on T cells, is also expressed and functional on platelets. We investigated the thrombotic and inflammatory contributions of platelet CD40L in atherosclerosis. Although CD40L-deficient (Cd40l(-/-)) platelets exhibited impaired platelet aggregation and thrombus stability, the effects of platelet CD40L on inflammatory processes in atherosclerosis were more remarkable. Repeated injections of activated Cd40l(-/-) platelets into Apoe(-/-) mice strongly decreased both platelet and leukocyte adhesion to the endothelium and decreased plasma CCL2 levels compared with wild-type platelets. Moreover, Cd40l(-/-) platelets failed to form proinflammatory platelet-leukocyte aggregates. Expression of CD40L on platelets was required for platelet-induced atherosclerosis as injection of Cd40l(-/-) platelets in contrast to Cd40l(+/+) platelets did not promote lesion formation. Remarkably, injection of Cd40l(+/+), but not Cd40l(-/-), platelets transiently decreased the amount of regulatory T cells (Tregs) in blood and spleen. Depletion of Tregs in mice injected with activated Cd40l(-/-) platelets abrogated the athero-protective effect, indicating that CD40L on platelets mediates the reduction of Tregs leading to accelerated atherosclerosis. We conclude that platelet CD40L plays a pivotal role in atherosclerosis, not only by affecting platelet-platelet interactions but especially by activating leukocytes, thereby increasing platelet-leukocyte and leukocyte-endothelium interactions.

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