Abstract
Thrombomodulin (TM) modulates the activation of protein C and coagulation. Additionally, TM regulates monocyte migration and inflammation. However, its role on monocyte differentiation is still unknown. We investigated the effects of TM on monocyte differentiation. First, we found that TM was increased when THP-1 cells were treated with phorbol-12-myristate-13-acetate (PMA). Overexpression of TM enhanced the macrophage markers, CD14 and CD68 expression in PMA-induced THP-1. TM siRNA depressed the PMA-induced increase of p21Cip1/WAF1 via ERK1/2-NF-kB p65 signaling. TM regulated cytoskeletal reorganization via its interaction with paxillin, cofilin, LIMK1, and PYK2. In addition, PMA-induced p21Cip1/WAF1 expression, CD14-positive cell labeling intensity and ERK1/2 phosphorylation were markedly inhibited when protein kinase C-δ (PKCδ) was knocked down. We identified that TM directly interacts with PKCδ. PKCδ was highly expressed in human atherosclerotic arteries and colocalized with TM in CD68-positive infiltrated macrophages of plaques, indicating that the coordination between TM and PKCδ in macrophages participated in atherogenesis. TM may act as a scaffold for PKCδ docking, which keeps PKCδ in the region close to the monocyte membrane to promote the activation of ERK1/2. Taken together, our findings suggest that TM-PKCδ interaction may contribute to cardiovascular disorders by affecting monocye differentiation, which may develop future therapeutic applications.
Highlights
Monocytes undergo transendothelial migration and differentiate into macrophages[1], which take on the morphology and functional properties that are characteristic of the tissue they enter[2]
The results showed that knockdown of TM significantly decreased PMA-induced monocyte differentiation by 26.1 ± 4.5% (1305 ± 225 differentiated cells/per 5000 THP-1 cells)
PMA may trigger the activation of PKCδ, and make PKCδcolocalized with TM in peripheral blood mononuclear cells (PBMCs) (Fig. 5D). These results indicate that ERK1/2 activation regulates p21Cip1/WAF1 expression and PKCδinteracts with TM in PMA-stimulated PBMCs, which is consistent with those results in THP-1 cells
Summary
Monocytes undergo transendothelial migration and differentiate into macrophages[1], which take on the morphology and functional properties that are characteristic of the tissue they enter[2]. Human THP-1 monocytic cells can be induced to differentiate into macrophages by treatment with phorbol-12-myristate-13-acetate (PMA), after which they can be converted into foam cells by exposure to oxLDL12. PMA treatment, which activates protein kinase C (PKC), induces a greater degree of differentiation in THP-1 cells, as is reflected by their increased adherence and expression of macrophage differentiation-associated surface markers[13]. A previous study[28] reported that exposure of THP-1 cells to recombinant human soluble thrombomodulin (rTM) induced growth arrest and differentiation in THP-1 cells by activating JNK/c-Jun signaling, suggesting that rTM is a positive regulator of THP-1 differentiation. We suggested that the mechanisms underlying TM-regulated monocyte differentiations are likely to be mediated through a direct interaction with PKCδ, which is thought to induce ERK1/2 activation and to cause THP-1 cell differentiation. This study may provide a new view of the role of endogenous TM in macrophage differentiation in atherogenesis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
