Molecular mechanism of green microalgae, Dunaliella salina, involved in attenuating balloon injury-induced neointimal formation.

The pathological mechanism of restenosis is primarily attributed to excessive proliferation of vascular smooth muscle cells (VSMC). The preventive effects of ethanol extract of Dunaliella salina (EDS) on balloon injury-induced neointimal formation were investigated. To explore its molecular mechanism in regulating cell proliferation, we first showed that EDS markedly reduced the human aortic smooth muscle cell proliferation via the inhibition of 5'-bromo-2'-deoxyuridine (BrdU) incorporation at 40 and 80 microg/ml. This was further supported by the G0/G1-phase arrest using a flow cytometric analysis. In an in vivo study, EDS at 40 and 80 microg/ml was previously administered to the Sprague-Dawley rats and found that the thickness of neointima, and the ratio of neointima:media were also reduced. EDS inhibited VSMC proliferation in a dose-dependent manner following stimulation of VSMC cultures with 15 % fetal bovine serum (FBS). Suppressed by EDS were 15 % FBS-stimulated intracellular Raf, phosphorylated extracellular signal-regulated kinases (p-Erk) involved in cell-cycle arrest and proliferating cell nuclear antigen. Phosphorylated focal adhesion kinase (p-FAK) was also suppressed by EDS. Also active caspase-9, caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) protein expression levels were increased by administration with EDS; the apoptotic pathway may play an important role in the regulatory effects of EDS on cell growth. These observations provide a mechanism of EDS in attenuating cell proliferation, thus as a potential intervention for restenosis.

Pipoxolan inhibits proliferation of HL-60 human leukaemia cancer cells by arresting the cell cycle at the G0/G1 phase.

1. The aim of the present study was to investigate the molecular mechanisms by which pipoxolan exerts its inhibitory effects and apoptotic activity in human leukaemia HL-60 cells. 2. The effects of pipoxolan on the proliferation of HL-60 cells and on the distribution of cells within different phases of the cell cycle were investigated indirectly using a Trypan blue assay and a flow cytometer, respectively. The effects of pipoxolan on the apoptosis of HL-60 cells was investigated using DNA fragmentation and flow cytometer. The expression of factors affecting the cell cycle and apoptosis, including p53, p21, Bax, Bcl2, cytochrome c, caspase 3 and caspase 9, was examined by western blotting. 3. At 6.25 microg/mL, pipoxolan significantly induced apoptosis in human leukaemia HL-60 cells after 24 h exposure. In addition, HL-60 cells were arrested in the G(0)/G(1) phase via the induction of p53/p21 by pipoxolan. Apoptosis was associated with an increased Bax/Bcl-2 ratio, cytochrome c release, cleavage of procaspases-9 and -3 and hydrolysis of poly(ADP-ribose) polymerase. Intracellular reactive oxygen species (ROS) seem to play a key role in the pipoxolan-induced apoptosis, because high levels of ROS were produced early in the drug treatment. Apoptosis was significantly abrogated by the free radical scavenger N-acetylcysteine (NAC).

Pipoxolan Exhibits Antitumor Activity Toward Oral Squamous Cell Carcinoma Through Reactive Oxygen Species-mediated Apoptosis.

Pipoxolan is frequently prescribed as a smooth muscle relaxant. Pipoxolan has also been shown to have anticancer activity. Our study investigated whether pipoxolan induced apoptosis in oral squamous cell carcinoma (OSCC). Cell cytotoxicity was evaluated by the MTT assay. Cell apoptosis and cell-cycle distribution were measured by annexin V/propidium iodide (PI) double staining and flow cytometry, respectively. Apoptotic-related proteins were assessed by western blotting. Reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP) were measured with fluorescent probes. Following exposure of TW206 OSCC cells to pipoxolan, a time-dependently decrease in MMP and an increase in ROS were observed. However, these effects were significantly abrogated by the free radical scavenger N-acetyl-L-cysteine. Since high levels of ROS were produced early in the treatment, intracellular ROS seemed to play a key role in pipoxolan-induced apoptosis. In HSC-3 OSCC cells, our results demonstrated that pipoxolan treatment caused a time-dependent increase of protein expression of active caspase-3 and -9, cytosolic cytochrome c, cleavage of poly (ADP-ribose) polymerase, and B-cell lymphoma 2 (BCL2)-like protein 4 (BAX). However, expression of BCL2 itself was reduced. Clearly, such an increase in BAX/BCL2 ratio would be associated with apoptosis. In addition, pipoxolan markedly suppressed the protein expression of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) and phosphorylation of protein kinase B (AKT). These data suggest that pipoxolan acts against HSC-3 in vitro via intrinsic apoptotic signaling pathways, and inhibition of PI3K/AKT signaling.