Thrombin Induces EGF Receptor Expression and Cell Proliferation via a PKC(δ)/c-Src-Dependent Pathway in Vascular Smooth Muscle Cells

Abstract

Objection-Thrombin upregulates expression of several proteins in vascular smooth muscle cells (VSMCs) which may contribute to atherosclerosis. Here, we investigated the mechanisms underlying thrombin-induced EGF receptor (EGFR) expression and its effect on VSMCs. Methods and Results-Normal rat VSMCs were used. First, Western blotting and RT-PCR analyses showed that thrombin induces the expression of EGFR at transcription and translation levels in VSMCs. Second, pharmacological inhibitors, dominant negative mutants, and short hairpin RNA interference (shRNA) technology enabled us to demonstrate that thrombin-induced EGFR expression is mediated through PKC(␦)/c-Src-dependent transactivation of EGFR linking to PI3K/Akt and ERK1/2. We further investigated whether the transcription factors AP-1 and NF-B are involved in this response by a promoter assay. Finally, data obtained by using EGFR shRNA technology and XTT assay demonstrated that thrombin-enhanced VSMC proliferation was mediated through upregulation of EGFR. Conclusions-Our

Thrombin induced connective tissue growth factor expression in rat vascular smooth muscle cells via the PAR-1/JNK/AP-1 pathway

“…In addition to this important JNK/AP-1 pathway, thrombin may act upon VSMCs through several other signaling pathways. Thrombin enhanced VSMC proliferation through epidermal growth factor receptor, ERK, and AP-1 pathways [41] . Thrombin also stimulated VSMC migration through an ROS-sensitive p38 MAPK pathway [42] .…”

Involvement of the ADAM 12 in Thrombin-Induced Rat's VSMCs Proliferation

“…Thr, a key player in the 'coagulation-atherogenesis' maze [10], exerts most of its proliferating effects though PAR-1 in VSMCs [17,29] and through direct proteolytic action, such as activation of pro MMP-2 that further supports VSMCs proliferation [30][31][32]. It is interesting to note here that Thr being capable of activating pro MMP-2 to MMP-2 under the association with heparin sulfate proteglycan, becomes a potent extracellular degrading enzyme [31].…”

“…Thr has also been associated with VSMCs proliferation, including mesenchymal cells [14,15] and human fibroblasts [16] through activation of its proteolytically activated receptors (PARs). Thr is a G-protein coupled receptor (GPCR) agonist that stimulates phospholipase C and results in intracellular Ca 2+ elevation and protein kinase C (PKC) activation and these events participate in the stimulation of extracellular signal-regulated protein kinase p42/44 (ERK1/2) cascade [17,18]. In several cell lines, it has been shown that Thr mediates cell proliferation through transactivation of the epidermal grown factor receptor (EGFR) via a metalloproteinasemediated cleavage and release of pro-heparin binding EGF-like factor (pro HB-EGF), which then binds to EGFR [15,19,20].…”

Matrix Metalloproteinase-1-mediated Up-regulation of Vascular Endothelial Growth Factor-2 in Endothelial Cells

“…The mechanism leading to increased expression of VEGFR2 in response to MMP-1 stimulation was also investigated in this study. It was previously shown that thrombin (a main activator of PAR-1) is able to stimulate NF-B and cause the up-regulation of multiple receptors (36,37). NF-B has also been shown to mediate KDR transcription (38).…”