Glatiramer acetate (copaxone) modulates platelet activation and inhibits thrombin-induced calcium influx: possible role of copaxone in targeting platelets during autoimmune neuroinflammation.
BACKGROUND
Glatiramer acetate (GA, Copaxone, Copolymer-1) is an FDA approved drug for the treatment of MS and it is very effective in suppressing neuroinflammation in experimental autoimmune encephalitis (EAE), an animal model of MS. Although this drug was designed to inhibit pathogenic T cells, the exact mechanism of EAE/MS suppression by GA is still not well understood. Previously we presented evidence that platelets become activated and promote neuroinflammation in EAE, suggesting a possible pathogenic role of platelets in MS and EAE. We hypothesized that GA could inhibit neuroinflammation by affecting not only immune cells but also platelets.


RESULTS
We investigated the effect of GA on the activation of human platelets in vitro: calcium influx, platelet aggregation and expression of activation markers. Our results in human platelets were confirmed by in-vitro and in-vivo studies of modulation of functions of platelets in mouse model. We found that GA inhibited thrombin-induced calcium influx in human and mouse platelets. GA also decreased thrombin-induced CD31, CD62P, CD63, and active form of αIIbβ3 integrin surface expression and formation of platelet aggregates for both mouse and human platelets, and prolonged the bleeding time in mice by 2.7-fold. In addition, we found that GA decreased the extent of macrophage activation induced by co-culture of macrophages with platelets.


CONCLUSIONS
GA inhibited the activation of platelets, which suggests a new mechanism of GA action in suppression of EAE/MS by targeting platelets and possibly preventing their interaction with immune cells such as macrophages. Furthermore, the reduction in platelet activation by GA may have additional cardiovascular benefits to prevent thrombosis.
Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America; Institute for Medical Immunology and NeuroCure, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Sarah C
SC
Starossom
School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Tatyana
T
Veremeyko
School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Marina
M
Dukhinova
School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Amanda W Y
AW
Yung
Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America; School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Eugene D
ED
Ponomarev
D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D051940:B7-2 Antigen / Q000378:metabolism; D001760:Bleeding Time; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018920:Coculture Techniques; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000097:blood / Q000517:prevention & control; D000068717:Glatiramer Acetate; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism; D008810:Mice, Inbred C57BL; D009103:Multiple Sclerosis / Q000097:blood / Q000517:prevention & control; D019007:P-Selectin / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D015539:Platelet Activation / Q000187:drug effects*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*
D000276:Adjuvants, Immunologic; D051940:B7-2 Antigen; D000949:Histocompatibility Antigens Class II; D019007:P-Selectin; D010455:Peptides; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D000068717:Glatiramer Acetate; D013917:Thrombin; D002118:Calcium