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

Abstract

Background Sepsis is a life‐threatening condition often manifested as marked inflammation and severe coagulopathy. Toll‐like receptors (TLRs) 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, TLR2−/− and TLR7−/− CLP mice showed preserved MCF and platelet counts, and near‐normal plasma TF levels. Bone marrow–derived macrophages treated with a TLR2 agonist Pam3cys‐Ser‐(Lys)4 (Pam3cys) or a TLR7 agonist (R837) showed marked increases in TF gene expression and protein expression. MicroRNA‐146a, a newly identified proinflammatory mediator that is upregulated during sepsis, induced TF production via a TLR7‐dependent mechanism. Conclusions Murine sepsis leads to an increased procoagulant response, thrombocytopenia, and global coagulopathy. TLR2 and TLR7 play an important role in procoagulant production and in SIC.

Innate Receptor Activation Patterns Involving TLR and NLR Synergisms in COVID-19, ALI/ARDS and Sepsis Cytokine Storms: A Review and Model Making Novel Predictions and Therapeutic Suggestions

“…In sum, all that can be said in general about innate activation in sepsis is that TLR2, TLR4, TLR5, TLR7 and NLRP3 [102] can be, but are not necessarily, activated, while TLR9 may or may not be downregulated [103][104][105]. The same generalizations can be made about murine polymicrobial sepsis models [91,[106][107][108], suggesting that sepsis is not a single, definable disease [97]. Table 1 summarizes these data, demonstrating that cytokine release syndromes share only partial overlaps in their innate receptor activation profiles, which provides a possible clue as to why their cytokine release profiles also differ and, therefore, why it has been difficult to define a clear set of diagnostic criteria for them or to devise a comprehensive or universal approach to treatment.…”

Six-gene Signature Based on Metabolism Is Closely Related to the Prognosis and Immune Infiltration of Patients With Sepsis

“…Previous studies have shown that the expression of ELANE is able to reflect the leukocyte function during sepsis, which is able to provide more prognostic information than leukocyte counting [21]. Brittney Williams et al found that TLR2 and TLR7 are involved in coagulation dysfunction in murine sepsis, which may be an important reason for the high mortality of sepsis [28].The regulatory axis of GDF / SMAD2 / SMAD3 in sepsis that can promote macrophage polarization toward M2 phenotype leading to immunosuppression, and activation of this regulatory axis may be associated with high lethality in sepsis [26]. CD3E, as part of the TCR-CD3 complex, is present on the surface of T-lymphocytes and plays an important role in adaptive immunity [29].…”

Platelet Innate Immune Receptors and TLRs: A Double-Edged Sword

“…Similarly, lipoteichoic acid, a membrane component of Gram-positive bacteria, was shown to inhibit platelet aggregation in human platelets [ 201 ] and reduce platelet thrombus formation in vitro [ 202 ], which may not cause thrombotic complications, but could be of advantage to the bacteria that would not be trapped in a thrombus. In addition, TLR3 and TLR4 could be of particular importance in platelet responses during sepsis, because a deficiency in either of these receptors is associated with more severe thrombocytopenia during polymicrobial sepsis induced by a cecal ligation and puncture procedure, while TLR2- and TLR7-deficient mice displayed a less severe coagulopathy, suggesting a different pattern of TLR involvement in murine polymicrobial sepsis [ 203 ]. Finally, another innate immunity receptor, C-type lectin-like-2/CLEC-2, found on platelets could be beneficial during sepsis by downregulating inflammation and leukocyte infiltration in tissues and reducing organ damage, further illustrating that the contribution of platelets to sepsis pathophysiology is not unequivocal [ 204 ].…”