Dose dependent effects of platelet derived chondroitinsulfate A on the binding of CCL5 to endothelial cells.
BACKGROUND
Chemokines immobilized on endothelial cells play a central role in the induced firm adhesion and transendothelial migration of leukocytes. Activation of platelets at sites of vascular injury is considered to support leukocyte adhesion and extravasation. However, activated platelets also secrete soluble glycosaminoglycans that can interfere with immobilization of chemokines. We therefore analyzed the impact of platelet derived glycosaminoglycans on the immobilization of the chemokine CCL5 (RANTES) on human microvascular endothelial cells and their influence on CCL5-CCR5 interactions.


RESULTS
We confirm that undiluted serum in contrast to plasma decreases binding of CCL5 to endothelial cells. However, when lower concentrations of serum were used, CCL5-presentation on endothelial cells was markedly enhanced. This enhancement was neutralized if serum was digested with chondroinitase ABC. Using different chondroitinsulfate-subtypes we demonstrate that chondroitinsulfate A mediates the enhanced presentation of CCL5 on endothelial cells, whereas chondroitinsulfate B/C even at low concentrations block CCL5 binding. CCR5 downregulation on CCR5-transfected CHO cells or human monocytes is increased by preincubation of CCL5 with serum or chondroitinsulfate A.


CONCLUSIONS
We show that chondroitinsulfate A released from platelets increases the binding of chemokines to endothelial cells and supports receptor internalization in a dose dependent manner. These data help to understand the proinflammatory effects of activated platelets.
Weingart
Christian
C
Department of Internal Medicine II, University of Regensburg, Franz-Josef-Strauss Allee 11, 93042 Regensburg, Germany. christian.weingart@klinik.uni-regensburg.de
Nelson
Peter J
PJ
Krämer
Bernhard K
BK
Mack
Matthias
M
D000818:Animals; D019138:Antibodies, Blocking; D001792:Blood Platelets / Q000378:metabolism*; D016466:CHO Cells; D002450:Cell Communication / Q000276:immunology; D018946:Chemokine CCL5 / Q000276:immunology / Q000378:metabolism*; D002809:Chondroitin Sulfates / Q000276:immunology / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004306:Dose-Response Relationship, Immunologic; D015536:Down-Regulation / Q000276:immunology; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007111:Immunity, Cellular; D011485:Protein Binding; D019713:Receptors, CCR5 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D014162:Transfection
D019138:Antibodies, Blocking; D018946:Chemokine CCL5; D019713:Receptors, CCR5; D002809:Chondroitin Sulfates