Increased serum mitogenic activity for arterial smooth muscle cells associated with relaxation and low educational level in human subjects with high but not low hostility traits: implications for atherogenesis

Sesamin Inhibits PDGF-Mediated Proliferation of Vascular Smooth Muscle Cells by Upregulating p21 and p27

Sesamin, an active ingredient of Asiasarum heterotropoides, is known to exhibit many bioactive functions, but the effect thereof on vascular smooth muscle cell (VSMC) proliferation remains poorly understood. Hence, we explored the antiproliferative action of sesamin on VSMCs and the underlying mechanism thereof, focusing on possible effects of sesamin on cell cycle progression. Sesamin significantly inhibited platelet-derived growth factor (PDGF)-induced VSMC proliferation (inhibition percentage at 1, 5, and 10 μM sesamin was 49.8 ± 22.0%, 74.6 ± 19.9%, and 87.8 ± 13.0%, respectively) in the absence of cytotoxicity and apoptosis, and PDGF-induced DNA synthesis; and arrested cell cycle progression in the G0/G1-to-S phase. Sesamin potently inhibited cyclin D1 and CDK4 expression, pRb phosphorylation, and expression of the proliferating cell nuclear antigen (PCNA); and upregulated p27(KIP1), p21(CIP1), and p53. The results thus indicate that the antiproliferative effect of sesamin on PDGF-stimulated VSMCs is attributable to arrest of the cell cycle in G0/G1 caused, in turn, by upregulation of p27(KIP1), p21(CIP1), and p53, and inhibition of cyclin E-CDK2 and cyclin D1-CDK4 expression.

Inhibitory effects of docetaxel on platelet-derived growth factor (PDGF)-BB-induced proliferation of vascular smooth muscle cells through blocking PDGF-receptor β phosphorylation

The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial wall is an important pathogenic factor for vascular disorders such as atherosclerosis and restenosis after angioplasty. The present study was designed to investigate the inhibitory effects of docetaxel on VSMC proliferation, as well as the molecular mechanism of this inhibition. Docetaxel at 10, 20 and 40 µM significantly inhibited both the proliferation and the DNA synthesis of fetal bovine serum (FBS)- and platelet-derived growth factor (PDGF)-BB-stimulated VSMCs in a concentration-dependent manner. In accordance with these findings, docetaxel blocked the FBS- and PDGF-BB-induced progression of synchronized cells through the G0/G1 phase of the cell cycle. Docetaxel also decreased the expressions of cell cycle-related proteins, including cyclin-dependent kinase (CDK) 2, cyclin E, CDK4, cyclin D1, retinoblastoma protein, and proliferative cell nuclear antigen in PDGF-BB-stimulated VSMCs. Docetaxel significantly inhibited the phosphorylation of extracellular signal-regulated kinase 1/2, Akt, and phospholipase C-γ1, downstream molecule in the PDGF-BB signaling pathway. Docetaxel suppressed the phosphorylation of PDGF receptor (PDGF-R) β, the upstream molecule in PDGF-BB signaling cascade, suggesting that the inhibitory effect of docetaxel on the proliferation of VSMCs may occur by blocking PDGF-Rβ phosphorylation. Thus, docetaxel may be a potential antiproliferative agent for the treatment of atherosclerosis and angioplasty restenosis.[Supplementary Figures: available only at http://dx.doi.org/10.1254/jphs.10276FP].

Epothilone D, a microtubule-stabilizing compound, inhibits neointimal hyperplasia after rat carotid artery injury by cell cycle arrest via regulation of G1-checkpoint proteins

Epothilone D (Epo-D) is a paclitaxel-like microtubule-stabilizing agent that was isolated from the myxobacterium Sorangium cellulosum. Although Epo-D can inhibit proliferation in multiple tumor cell lines, the effect of Epo-D on neointimal hyperplasia after angioplasty has not been reported. The aim of the present study was to investigate the effects of Epo-D on neointimal hyperplasia using an in vivo rat carotid artery injury model. We demonstrated that local Epo-D treatment significantly reduced neointimal hyperplasia after in vivo rat carotid artery injury, and Epo-D potently inhibited DNA synthesis, cell cycle progression and cell proliferation after FBS- and PDGF-BB-stimulation; PDGF-BB has been identified as the most potent growth factor for stimulating the proliferation of activated rat aortic smooth muscle cells (RASMCs). To clarify the specific effects of Epo-D on cell cycle machinery, we examined its effects on cyclin-dependent kinase (CDK)2, CDK4, cyclin E, p27, and retinoblastoma (Rb) proteins as cell cycle-related proteins in cellular lysates from PDGF-BB-stimulated RASMCs. Epo-D treatment significantly decreased the level of CDK2 protein, but did not change the levels of CDK4 and cyclin E proteins. Furthermore, Epo-D inhibited the phosphorylation of Rb, a key regulator of the G1 to S phase transition in the cell cycle. These findings suggest that Epo-D may regulate the cell cycle G1-checkpoint proteins as its major molecular mechanism for inhibiting neointimal hyperplasia after in vivo rat carotid artery injury.

Effects of KTJ740, a Novel Antithrombotic Agent, on Platelet-Derived Growth Factor-Induced Rat Aortic Smooth Muscle Cell Proliferation and Cell Cycle Progression

Hyperproliferation of platelet-derived growth factor (PDGF)-BB-induced vascular smooth muscle cell (VSMC) is a hallmark of atherosclerosis and related vascular disorders. In the previous study, we reported that KTJ740 [2-chloro-3-(4-(ethylcarboxy)-phenyl)-amino-1,4-naphthoquinone], a newly synthesized vitamin K derivative, has potent antithrombotic effects in mice and antiplatelet activity in vitro and ex vivo. In the present study, we have tested that KTJ740 could inhibit PDGF-BB-stimulated VSMC proliferation. We have examined the potential inhibitory effect of this compound on rat aortic smooth muscle cells (RASMCs). Our results show that this compound significantly inhibits PDGF-BB-stimulated RASMC number and DNA synthesis in a concentration-dependent manner. Furthermore, we have examined its effect on cell cycle progression by flow cytometry. KTJ740 treatment resulted in a significant arrest in cell cycle progression of RASMCs induced by PDGF-BB, and this effect was achieved by suppressing activation of PDGF-beta receptor (PDGF-Rbeta) tyrosine kinase pathway. These results suggest that a possibility of KTJ740 can be a potential agent to control vascular disorders and its antiproliferative mechanism may be mediated through PDGF-Rbeta tyrosine kinase-dependent signaling pathway.

Epothilone B Inhibits Neointimal Formation after Rat Carotid Injury through the Regulation of Cell Cycle-Related Proteins

The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial walls is an important pathogenetic factor of vascular disorders such as atherosclerosis and restenosis after angioplasty. Epothilone B, a novel potential antitumor compound, has a potent effect on preventing postangioplasty restenosis. Therefore, we established an in vivo rat carotid injury model and examined the potential effects of epothilone B on cardiovascular disease. We found that epothilone B potently prevented neointimal formation and in vivo VSMCs proliferation. In addition, we also showed that epothilone B significantly inhibited 5% fetal bovine serum (FBS)- and 50 ng/ml platelet-derived growth factor (PDGF)-BB-induced proliferation and cell cycle progression in rat aortic VSMCs. Furthermore, FBS and PDGF-BB induced the activations of extracellular signal-regulated kinases 1 and 2, Akt, phospholipase C gamma 1, and PDGF-receptor beta chain tyrosine kinase were not changed by epothilone B. However, epothilone B treatment caused a significant decrease in the level of cyclin-dependent protein kinase (CDK) 2, whereas it caused no change in the levels of cyclin E and down-regulated the phosphorylation of retinoblastoma, which plays a critical role in cell cycle regulation. Furthermore, levels of p27, an inhibitor of cyclin E/CDK2 complex, were significantly increased in VSMCs treated with epothilone B, indicating that this might be a major molecular mechanism for the inhibitory effects of epothilone B on the proliferation and cell cycle of VSMCs. These findings suggest that epothilone B can inhibit neointimal formation via the cell cycle arrest by the regulation of the cell cycle-related proteins in VSMCs.

Vascular smooth muscle cell proliferation requires both p38 and BMK1 MAP kinases

Vascular smooth muscle cell (VSMC) proliferation is a key event in the progression of atherosclerosis. Induction of both c-fos (through the transcription factor Elk-1) and c-jun, both immediate early genes, is important for the stimulation of VSMC proliferation and migration. It was earlier found that p38 mitogen-activated protein (MAP) kinase upregulates c-jun gene transcription through phosphorylation of two myocyte enhancer factor 2 (MEF2) family transcription factors, MEF2A and MEF2C, while big MAP kinase 1 (BMK1) may upregulate c-jun gene transcription through MEF2A, MEF2C, and also MEF2D. Here, we report that inhibition of BMK1 by a dominant negative form of MEK5 or pharmacologic inhibition of p38 by SB 203580 additively suppress serum-induced VSMC proliferation. This additive effect of p38 and BMK1 inhibition implies that these two kinases coordinately regulate MEF2 transcription factors. The exclusive activation of MEF2D by BMK1 appears required for this cooperative upregulation of c-jun in VSMC, and coactivation of p38 and BMK1 also has additive effects on the activation of a reporter gene linked to the c-jun promoter in our experimental system. Thus, coordinate activity of both the p38 and BMK1 pathways appears necessary for optimal transcription of c-jun and, pari pasu, VSMC proliferation. These results may have implications for the future design of pharmacologic agents for inhibition of VSMC growth.