u-0126 and Arteriosclerosis

Tissue factor (TF) is the main initiator of coagulation in vivo. Recently, however, a role for TF as a cell receptor involved in signal transduction has been suggested. The aim of the present study was to assess whether activated factor VII (FVIIa) binding to TF could induce smooth muscle cell (SMC) proliferation and to clarify the possible intracellular mechanism(s) responsible for this proliferation.. Cell proliferation was induced by FVIIa in a dose-dependent manner, as assessed by [3H]thymidine incorporation and direct cell counting, whereas no response was observed with active site-inhibited FVIIa (FVIIai), which is identical to FVIIa but is devoid of enzymatic activity. Similarly, no proliferation was observed when binding of FVIIa to TF was prevented by the monoclonal anti-TF antibody AP-1. Activation of the p44/42 mitogen-activated protein (MAP) kinase (extracellular signal-regulated kinases 1 and 2 [ERK 1/2]) pathway on binding of FVIIa to TF was demonstrated by transient ERK phosphorylation in Western blots and by suppression of proliferation with the specific MEK (MAP kinase/ERK kinase) inhibitor UO126. ERK phosphorylation was not observed with FVIIai or when cells were pretreated with AP-1.. These data indicate a specific effect by which binding of FVIIa to TF on the surface of SMCs induces proliferation via a coagulation-independent mechanism and possibly indicate a new link between coagulation, inflammation, and atherosclerosis.

Topics: Animals; Antibodies, Monoclonal; Aorta, Thoracic; Arteriosclerosis; Binding Sites; Blood Coagulation; Butadienes; Cell Division; Cells, Cultured; Enzyme Activation; Enzyme Inhibitors; Factor VIIa; Humans; Inflammation; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Nitriles; Phosphorylation; Protein Binding; Protein Processing, Post-Translational; Rabbits; Recombinant Fusion Proteins; Signal Transduction; Thromboplastin

Resistin, a novel adipokine, is elevated in patients with type 2 diabetes and may play a role in the vascular complications of this disorder. One recent study has shown that resistin has a proinflammatory effect on endothelial cells. However, there is no information on whether resistin could also affect vascular smooth muscle cells (SMCs). Thus, the purpose of this study was to assess whether resistin could induce SMC proliferation and to study the mechanisms whereby resistin signals in SMCs.. Human aortic smooth muscle cells (HASMCs) were stimulated with increasing concentrations of resistin for 48 hours. Cell proliferation was induced by resistin in a dose-dependent manner as assessed by direct cell counting. To gain more insights into the mechanism of action of resistin, we investigated the extracellular signal-regulated kinase (ERK) and/or phosphatidylinositol 3-kinase (PI3K) signaling pathways. Transient phosphorylation of the p42/44 mitogen-activated protein kinase (ERK 1/2) occurred after addition of resistin to HASMCs. U0126, a specific inhibitor of ERK phosphorylation, significantly inhibited ERK 1/2 phosphorylation and reduced resistin-simulated proliferation of HASMCs. LY294002, a specific PI3K inhibitor, also significantly inhibited HASMC proliferation after resistin stimulation.. Our results demonstrate that resistin induces HASMC proliferation through both ERK 1/2 and Akt signaling pathways. The proliferative action exerted by resistin on HASMCs may account in part for the increased incidence of restenosis in diabetes patients.

Topics: Aorta; Arteriosclerosis; Butadienes; Cell Division; Cells, Cultured; Chromones; Diabetes Complications; Hormones, Ectopic; Imidazoles; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Morpholines; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Nitriles; p38 Mitogen-Activated Protein Kinases; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Pyridines; Recombinant Proteins; Resistin; Signal Transduction