Increased expression of TF in BMP-7-treated human mononuclear cells depends on activation of select MAPK signaling pathways

Abstract

Bone morphogenetic protein (BMP)-7 regulates atherosclerotic plaque calcification, and it contributes to increased thrombogenicity of lipid-rich lesions by enhancement of TF expression in monocytes/macrophages by unknown mechanism. Since Erk1/2, JNK and p38 mitogen activated protein kinases (MAPKs) regulate TF expression, we studied involvement of MAPK pathways in BMP-7-induced activation of TF in human mononuclear cells (MNCs). Whole blood from healthy volunteers was treated with BMP-7, MNCs were isolated, and TF expression was assessed by western blot (WB) and In-Cell Western assay. Phosphorylation and nuclear translocation of Smad1/5/8 in response to BMP-7 stimulation of MNCs was evaluated by WB and confocal microscopy. Activation of MAPKs was judged by measuring the levels of phoshorylated Erk1/2, JNK, and p38 in the lysates of MNCs. The impact of Erk1/2 and p38 activation was studied by use of PD98059 and SB203580 inhibitors, respectively. Stimulation of whole blood with BMP-7 increased the levels of TF in the lysates of MNCs by 7-fold as compared to 12-fold after LPS stimulation. It was followed by elevation in TF fuctional activity. It was accompanied by elevated levels of phosphorylated Smad 1/5/8 and nuclear translocation of Smad1/5/8 proteins. Treatment of whole blood with BMP-7 led to a phosphorylation of Erk1/2, JNK and p38 MAPKs. BMP-7-induced TF expression was partially inhibited by Erk1/2 inhibitor, whereas TF expression was completely abolished by p38 inhibitor. BMP-7-dependent activation of TF in human MNCs by BMP-7 is accompanied by activation of canonic Smad1/5/8 signaling pathway and depends on activation of Erk1/2 and p38.