Recombinant Thrombomodulin Inhibits Lipopolysaccharide-Induced Inflammatory Response by Blocking the Functions of CD14

Abstract

CD14, a multiligand pattern-recognition receptor, is involved in the activation of many TLRs. Thrombomodulin (TM), a type I transmembrane glycoprotein, originally was identified as an anticoagulant factor that activates protein C. Previously, we showed that the recombinant TM lectin-like domain binds to LPS and inhibits LPS-induced inflammation, but the function of the recombinant epidermal growth factor–like domain plus serine/threonine-rich domain of TM (rTMD23) in LPS-induced inflammation remains unknown. In the current study, we found that rTMD23 markedly suppressed the activation of intracellular signaling pathways and the production of inflammatory cytokines induced by LPS. The anti-inflammatory activity of rTMD23 was independent of activated protein C. We also found that rTMD23 interacted with the soluble and membrane forms of CD14 and inhibited the CD14-mediated inflammatory response. Knockdown of CD14 in macrophages suppressed the production of inflammatory cytokines induced by LPS, and rTMD23 inhibited LPS-induced IL-6 production in CD14-knockdown macrophages. rTMD23 suppressed the binding of LPS to macrophages by blocking the association between monocytic membrane-bound TM and CD14. The administration of rTMD23 in mice, both pretreatment and posttreatment, significantly increased the survival rate and reduced the inflammatory response to LPS. Notably, the serine/threonine-rich domain is essential for the anti-inflammatory activity of rTMD23. To summarize, we show that rTMD23 suppresses the LPS-induced inflammatory response in mice by targeting CD14 and that the serine/threonine-rich domain is crucial for the inhibitory effect of rTMD23 on LPS-induced inflammation.

Thrombomodulin Attenuates Inflammatory Damage Due to Liver Ischemia and Reperfusion Injury in Mice in Toll-Like Receptor 4–Dependent Manner

“…Activated protein C not only works as an anticoagulant factor but also has indirect inflammatory activities . D‐2/3 also exhibits an anti‐inflammatory effect , and rTM has a protective effect in the murine liver resection model . In our study, pretreatment with rTMD1 demonstrated the suppression of sALT and serum HMGB‐1 levels in liver IRI to the same extent as rTM treatment.…”

C‐type lectin domain group 14 proteins in vascular biology, cancer and inflammation

“…Conversely, human leucocytes have been suggested to directly recognise the mucin-like region of thrombomodulin through leucocyte adhesion integrins lymphocyte function-associated antigen-1 (LFA-1) and Mac-1 in vitro [58]. Thrombomodulin EGF domains were found to markedly suppress LPS-induced inflammatory signalling pathways in macrophages by associating with the pattern recognition receptor CD14, and that this inhibitory effect was also dependent on the serine threoninerich domain [59]. Thrombomodulin EGF5 also has the capacity to engage T-cells bearing GPR15 [60].…”

The science of vaccine adjuvants: advances in TLR4 ligand adjuvants

“…Most importantly, monophosphorylated LPS derived from commensal or pathogenic bacteria triggers less CD14 activation, TLR4/MD-2 dimerization and endocytosis as compared to diphophorylated LPS [31]. The synergy between CD14 and thrombomodulin [32] or complement C5 [33] that leads to TLR4 activation and inflammatory responses also suggests that switching CD14 activation ON/OFF may be crucial to designing next generation adjuvants.…”