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.

Development of Harmaline-induced Tremor in a Swine Model.

Background: In the field of translational neuroscience research, it is critical to utilize a large animal model to test the feasibility, safety, and functionality of novel therapies. Here, we describe a protocol for the development of a large animal model of tremor. Methods: In a pig model, tremor was induced with harmaline and measured with wireless accelerometers attached to the limbs. Three different doses of harmaline were tested and three repetitive injections were made at 72-hour intervals. To fully characterize the drug-induced tremor, onset time, tremor amplitude, maintained duration, and peak tremor frequency were analyzed. Results: Harmaline-induced tremor appeared immediately following intravenous injection of harmaline. Tremor was maintained over 2 hours. Its frequency was 10-16 Hz, which was independent of doses. Dose-dependent responses were observed in tremor amplitude, triggering time, and tremor-maintained duration. Repetitive injection of harmaline desensitized the harmaline effect. Discussion: We provide a detailed protocol for training, drug injection, device selection, and tremor recording optimized to create a swine model of tremor with harmaline. Our protocol provides reliable tremor in pigs and suggests pig as a valid translational large animal model of tremor.

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.