Sulforaphane inhibits PDGF-induced proliferation of rat aortic vascular smooth muscle cell by up-regulation of p53 leading to G1/S cell cycle arrest.

Vascular diseases such as atherosclerosis and restenosis artery angioplasty are associated with vascular smooth muscle cell (VSMC) proliferation and intimal thickening arterial walls. In the present study, we investigated the inhibitory effects of sulforaphane, an isothiocyanate produced in cruciferous vegetables, on VSMC proliferation and neointimal formation in a rat carotid artery injury model. Sulforaphane at the concentrations of 0.5, 1.0, and 2.0 µM significantly inhibited platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation in a concentration-dependent manner, determined by cell count. The IC50 value of sulforaphane-inhibited VSMC proliferation was 0.8 µM. Sulforaphane increased the cyclin-dependent kinase inhibitor p21 and p53 levels, while it decreased CDK2 and cyclin E expression. The effects of sulforaphane on vascular thickening were determined 14 days after the injury to the rat carotid artery. The angiographic mean luminary diameters of the group treated with 2 and 4 µM sulforaphane were 0.25±0.1 and 0.09±0.1 mm², respectively, while the value of the control groups was 0.40±0.1 mm², indicating that sulforaphane may inhibit neointimal formation. The expression of PCNA, maker for cell cycle arrest, was decreased, while that of p53 and p21 was increased, which showed the same pattern as one in in-vitro study. These results suggest that sulforaphane-inhibited VSMC proliferation may occur through the G1/S cell cycle arrest by up-regulation of p53 signaling pathway, and then lead to the decreased neointimal hyperplasia thickening. Thus, sulforaphane may be a promising candidate for the therapy of atherosclerosis and post-angiography restenosis.

Camptothecin inhibits platelet-derived growth factor-BB-induced proliferation of rat aortic vascular smooth muscle cells through inhibition of PI3K/Akt signaling pathway.

The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial wall is a major cause of vascular disorders such as atherosclerosis and restenosis after angioplasty. In this study, we investigated not only the inhibitory effects of camptothecin (CPT) on PDGF-BB-induced VSMC proliferation, but also its molecular mechanism of this inhibition. CPT significantly inhibited proliferation with IC50 value of 0.58 µM and the DNA synthesis of PDGF-BB-stimulated VSMCs in a dose-dependent manner (0.5-2 µM ) without any cytotoxicity. CPT induced the cell cycle arrest at G0/G1 phase. Also, CPT decreased the expressions of G0/G1-specific regulatory proteins including cyclin-dependent kinase (CDK)2, cyclin D1 and PCNA in PDGF-BB-stimulated VSMCs. Pre-incubation of VSMCs with CPT significantly inhibited PDGF-BB-induced Akt activation, whereas CPT did not affect PDGF-receptor beta phosphorylation, extracellular signal-regulated kinase (ERK) 1/2 phosphorylation and phospholipase C (PLC)-γ1 phosphorylation in PDGF-BB signaling pathway. Our data showed that CPT pre-treatment inhibited VSMC proliferation, and that the inhibitory effect of CPT was enhanced by LY294002, a PI3K inhibitor, on PDGF-BB-induced VSMC proliferation. In addition, inhibiting the PI3K/Akt pathway by LY294002 significantly enhanced the suppression of PCNA expression and Akt activation by CPT. These results suggest that the anti-proliferative activity of CPT is mediated in part by downregulating the PI3K/Akt signaling pathway.

Clitocybin A, a novel isoindolinone, from the mushroom Clitocybe aurantiaca, inhibits cell proliferation through G1 phase arrest by regulating the PI3K/Akt cascade in vascular smooth muscle cells.

Abnormal proliferation of vascular smooth muscle cells (VSMCs) plays an essential role in the pathogenesis of vascular diseases, such as atherosclerosis, hypertension, and restenosis. Clitocybin A, a novel isoindolinone, isolated from the culture broth of mushroom Clitocybe aurantiaca has been reported to possess free radical scavenging activity. However, the antiproliferative effects of clitocybin A on VSMCs are unknown. In the present study, we investigated the effect of clitocybin A on platelet-derived growth factor (PDGF)-BB-induced proliferation of VSMCs and examined the molecular basis of the underlying mechanism. Clitocybin A inhibited DNA synthesis and cell proliferation. In accordance with these findings, clitocybin A blocked the PDGF-BB-inducible progression through G0/G1 to S phase of the cell cycle in synchronized cells and decreased the expression of cyclin-dependent kinase (CDK) 2, CDK4, cyclin D1, cyclin E, and proliferative cell nuclear antigen. In addition, clitocybin A inhibited the PDGF-BB-induced phosphorylation of phosphatidylinositol 3 kinase (PI3K) / Akt kinase. However, clitocybin A did not change the expression levels of extracellular signal-related kinase (ERK) 1/2, phospholipase C-γ1, and PDGF-Rß phosphorylation. These results indicate that clitocybin A may inhibit VSMCs proliferation through G1 phase arrest by regulating the PI3K/Akt pathway.

Clitocybin B inhibits rat aortic smooth muscle cell proliferation through suppressing PDGF-Rß phosphorylation.

The increased proliferation of vascular smooth muscle cells (VSMCs) in the arterial wall is a critical pathogenic factor for vascular diseases such as atherosclerosis and restenosis after angioplasty. Clitocybin B was reported to have either a potent free radical scavenging effect or effects that were isolated from the culture broth of mushroom Clitocybe aurantiaca. The present study was designed to investigate the effects of clitocybin B on VSMC proliferation and its possible molecular mechanism. Clitocybin B significantly inhibited the proliferation and the DNA synthesis of PDGF-BB-stimulated VSMCs in a concentration-dependent manner. In agreement with these findings, clitocybin B suppressed the PDGF-BB-induced progression through G0/G1 to S phase of cell cycle. Clitocybin B also down-regulated the expressions of cell cycle-related proteins, including cyclin-dependent kinase (CDK)2, cyclin E, CDK4, cyclin D1, and proliferative cell nuclear antigen in PDGF-BB-stimulated VSMCs. Clitocybin B significantly inhibited the phosphorylation of Akt, extracellular signal-regulated kinase 1/2, and phospholipase C-γ1, in the PDGF-BB signaling pathway. Clitocybin B suppressed the PDGF-Rß activation in PDGF-BB signaling cascade. These results suggested that the inhibitory effect of clitocybin B on the proliferation of VSMCs may be associated with suppressing PDGF-Rß phosphorylation. Thus, clitocybin B may be an effective antiproliferative agent for the prevention of atherosclerosis and restenosis.

Phosphorylation of Smac by JNK3 attenuates its interaction with XIAP.

Here we demonstrate that JNK3 can phosphorylate Smac. Smac phosphorylation attenuates its ability to activate apoptosome activity in HeLa S-100 cell lysates. Addition of the X-linked inhibitor of apoptosis protein (XIAP) to the S-100 markedly suppresses apoptosome activity, and this suppressive effect of XIAP is neutralized by adding unphosphorylated Smac, but not phosphorylated Smac. Furtherover, JNK3-mediated phosphorylation of Smac markedly attenuates the interaction between Smac and XIAP, as measured by BIACORE assays and non-denaturing gel shift assays. When JNK3 activity is down-regulated in etoposide-induced HeLa cells by transiently overexpressing a dominant negative version of JNK3 (DN-JNK3), the caspase-3 activity as well as PARP cleavages are markedly enhanced. And the interaction of Smac with XIAP also increases by down-regulating JNK3 activity under the same conditions. These results suggest that JNK3 activity can attenuate the progression of apoptosis through a novel mechanism of action, the down-regulation of interaction between Smac and XIAP.