Myeloid thrombomodulin lectin-like domain inhibits osteoclastogenesis and inflammatory bone loss

Abstract

Osteoclastogenesis is an essential process during bone metabolism which can also be promoted by inflammatory signals. Thrombomodulin (TM), a transmembrane glycoprotein, exerts anti-inflammatory activities such as neutralization of proinflammatory high-mobility group box 1 (HMGB1) through TM lectin-like domain. This study aimed to identify the role of myeloid TM (i.e., endogenous TM expression on the myeloid lineage) in osteoclastogenesis and inflammatory bone loss. Using human peripheral blood mononuclear cells and mouse bone marrow-derived macrophages, we observed that the protein levels of TM were dramatically reduced as these cells differentiated into osteoclasts. In addition, osteoclastogenesis and extracellular HMGB1 accumulation were enhanced in primary cultured monocytes from myeloid-specific TM-deficient mice (LysMcre/TMflox/flox) and from TM lectin-like domain deleted mice (TMLeD/LeD) compared with their respective controls. Micro-computerized tomography scans showed that ovariectomy-induced bone loss was more pronounced in TMLeD/LeD mice compared with controls. Finally, the inhibiting effects of recombinant TM lectin-like domain (rTMD1) on bone resorption in vitro, and bone loss in both the ovariectomized model and collagen antibody-induced arthritis model has been detected. These findings suggested that the myeloid TM lectin-like domain may inhibit osteoclastogenesis by reducing HMGB1 signaling, and rTMD1 may hold therapeutic potential for inflammatory bone loss.

Role of non-macrophage cell-derived HMGB1 in oxaliplatin-induced peripheral neuropathy and its prevention by the thrombin/thrombomodulin system in rodents: negative impact of anticoagulants

“…There is in vitro evidence that TMα consisting of TM’s D1–D3, produced by the Chinese hamster ovary (CHO) cell engineering system, sequesters HMGB1 with D1 and then promotes its degradation by thrombin binding to D2 [14–16]. Although TM’s D1 alone appears to exhibit anti-inflammatory activity [38, 39], our in vivo studies employing mice have clearly demonstrated that TMα-induced prevention of the allodynia following intraplantar injection of HMGB1 requires endogenous thrombin [16] and that yeast-generated TM’s D1–D3, but not D1 or D2 alone, mimics the preventive effect of the CHO-generated TMα against HMGB1-induced allodynia [15]. Therefore, it is quite understandable that the preventive effect of TMα against the oxaliplatin-induced neuropathic allodynia was abolished or attenuated by systemic administration of argatroban and dabigatran, parenteral and oral direct thrombin inhibitors, respectively, in the present study (see Fig.…”

Thrombomodulin Regulation of Mitogen-Activated Protein Kinases

“…Decreased expression of TM on monocytes was reported in patients with DIC [60], coronary artery bypass graft surgery [61] and during osteoclastogenesis (inflammatory bone loss) [37]. These pathological conditions are associated with increased activation of MAPKs including p38, JNK and ERK1/2 [62,63].…”

“…These pathological conditions are associated with increased activation of MAPKs including p38, JNK and ERK1/2 [62,63]. Osteoclastogenesis was also observed in macrophages derived from myeloid TM deleted mice, suggesting an anti-inflammatory role for TM in circulating cells [37]. Use of recombinant TM protein improves the survival of DIC patients [64] and attenuates the inflammatory bone loss in collagen antibody-induced arthritis and ovariectomy-induced mice models [37].…”

“…Osteoclastogenesis was also observed in macrophages derived from myeloid TM deleted mice, suggesting an anti-inflammatory role for TM in circulating cells [37]. Use of recombinant TM protein improves the survival of DIC patients [64] and attenuates the inflammatory bone loss in collagen antibody-induced arthritis and ovariectomy-induced mice models [37]. Apart from these direct effects, TM mediated generation of APC has been shown to reduce LPS-induced secretion of TNFα, IL-1β, IL-6, and IL-8 from human monocytes and THP-1 cell line [65].…”

Thrombomodulin Functional Domains Support Osteoblast Differentiation and Bone Healing in Diabetes in Mice

“…In our previous work, we showed that the protein levels of TM are reduced as myeloid‐derived monocytes/macrophages differentiate into osteoclasts. ( 14 ) Using myeloid‐specific TM‐deficient mice (LysMcre/TM flox/flox ) and TM lectin‐like domain deleted mice (TM LeD/LeD ), we showed that lack of TM in these leukocytes leads to elevated secretion of the proinflammatory high mobility group box 1 (HMGB1), with increased bone resorption and ovariectomy‐induced bone loss. Treatment with recombinant TMD1 (rTMD1) inhibited osteoclastogenesis through blockade of HMGB1 signaling.…”