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Expression and functionality of Toll‐like receptor 3 in the megakaryocytic lineage
Author(s) -
D'Atri L. P.,
Etulain J.,
Rivadeneyra L.,
Lapponi M. J.,
Centurion M.,
Cheng K.,
Yin H.,
Schattner M.
Publication year - 2015
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.12842
Subject(s) - tlr3 , megakaryocyte , microbiology and biotechnology , platelet , pi3k/akt/mtor pathway , toll like receptor , protein kinase b , platelet activation , chemistry , biology , signal transduction , receptor , stem cell , innate immune system , haematopoiesis , immunology , biochemistry
Summary Background In addition to their key role in hemostasis, platelets and megakaryocytes regulate immune and inflammatory responses, in part through their expression of Toll‐like receptors ( TLR s). Among the TLR s, TLR 3 recognizes ds RNA associated with viral infection. Thrombocytopenia is a frequent complication of viral infection. However, the expression and functionality of TLR 3 in megakaryocytes and platelets is not yet well understood. Objective To study the expression and functionality of TLR 3 in the megakaryocytic lineage. Methods and results RT ‐ PCR , flow cytometric and immunofluorescence assays showed that TLR 3 is expressed in CD 34 + cells, megakaryocytes, and platelets. Immunoblotting assays showed that stimulation of megakaryocytes with two synthetic agonists of TLR 3, Poly(I:C) and Poly(A:U), activated the nuclear factor‐κB ( NF ‐κB), phosphoinositide 3‐kinase ( PI 3K)/Akt, extracellular signal‐related kinase ( ERK )1/2 and p38 pathways. TLR 3–megakaryocyte activation resulted in reduced platelet production in vitro and interferon‐β release through the PI 3K–Akt and NF ‐κB signaling pathways. TLR 3 ligands potentiated the aggregation mediated by classic platelet agonists. This effect was also observed for ATP release, but not for P‐selectin or CD 40L membrane exposure, indicating that TLR 3 activation was not involved in α‐granule release. In addition, TLR 3 agonists induced activation of the NF ‐κB, PI 3K–Akt and ERK 1/2 pathways in platelets. Reductions in platelet production and platelet fibrinogen binding mediated by Poly(I:C) or Poly(A:U) were prevented by the presence of an inhibitor of the TLR 3–ds RNA complex. Conclusions Our findings indicate that functional TLR 3 is expressed in CD 34 + cells, megakaryocytes, and platelets, and suggest a potential role for this receptor in the megakaryopoiesis/thrombopoiesis alterations that occur in viral infections.