Toll‐like receptors 2 and 7 mediate coagulation activation and coagulopathy in murine sepsis

Background Sepsis is a life‐threatening condition often manifested as marked inflammation and severe coagulopathy. Toll‐like receptors ( TLR s) play a pivotal role in inflammation, organ dysfunction and mortality in animal sepsis. Objectives To investigate the role of TLR signaling in mediating sepsis‐induced coagulopathy ( SIC ) in a mouse model. Methods Polymicrobial sepsis was created by cecal ligation and puncture ( CLP ) or fecal slurry peritoneal injection. To quantify global clotting function, two viscoelastic assays were performed with rotational thromboelastometry, and the results were presented as maximum clot firmness ( MCF ): ( a ) EXTEM to test tissue factor ( TF )‐initiated clot formation; and ( b ) FIBTEM to test EXTEM in the presence of a platelet inhibitor, cytochalasin D. Plasma coagulation factors were quantified with ELISA . TF gene expression and protein expression were determined with real‐time quantitative reverse transcription PCR and flow cytometry, respectively. Results Between 4 and 24 hours after CLP surgery, wild‐type mice showed significant MCF reduction in both EXTEM and FIBTEM tests. This was accompanied by marked thrombocytopenia and a significant increase in the levels of plasminogen activator inhibitor‐1, plasma TF , and D‐dimer. In comparison, TLR 2 −/− and TLR 7 −/− CLP mice showed preserved MCF and platelet counts, and near‐normal plasma TF levels. Bone marrow–derived macrophages treated with a TLR 2 agonist Pam3cys‐Ser‐(Lys)4 (Pam3cys) or a TLR 7 agonist (R837) showed marked increases in TF gene expression and protein expression. Micro RNA ‐146a, a newly identified proinflammatory mediator that is upregulated during sepsis, induced TF production via a TLR 7‐dependent mechanism. Conclusions Murine sepsis leads to an increased procoagulant response, thrombocytopenia, and global coagulopathy. TLR 2 and TLR 7 play an important role in procoagulant production and in SIC .