| In Vitro | In vitro activity: GW4869 inhibits N-SMase not only in vitro but also in a cellular model. GW4869 does not significantly impair TNF-induced NF-κB translocation to nuclei. Therefore, GW4869 does not interfere with other key TNF-mediated signaling effects. GW4869 is able, in a dose-dependent manner, to significantly protect from cell death as measured by nuclear condensation, caspase activation, PARP degradation, and trypan blue uptake. These protective effects are accompanied by significant inhibition of cytochrome c release from mitochondria and caspase 9 activation, therefore localizing N-SMase activation upstream of mitochondrial dysfunction. At up to 150 μM, GW4869 does not inhibit the cloned human A-SMase. GW4869 shows no or minor inhibitory activity versus other hydrolytic enzymes, such as bacterial phosphatidylcholine-PLC and bovine protein phosphatase 2A, and it shows significantly higher activity versus the rat brain enzyme compared with the human lyso-PAF PLC
Kinase Assay: B. cereu sphosphatidylcholine-PLC is incubated in the presence or absence of 10 μM GW4869 in a reaction mixture containing 100 mM Tris, pH 7.2, 25% glycerol, 20 mM p-nitrophenyl/phosphorylcholine, and production of p-nitrophenol is quantified spectrophotometrically at 410 nm. Protein phosphatase 2A from bovine kidney is incubated in the presence or absence of GW4869 in buffer containing 50 mM Tris, pH 7.4, 1 mM dithiothreitol, 100 μM MnCl2, and 20% glycerol, and phosphatase activity is measured.
Cell Assay: MCF7 human breast cancer cells are routinely cultured in RPMI 1640 containing 10% FBS at 37 °C in 5% CO2. Unless otherwise indicated, for treatment, cells are seeded at 1.7 × 106 cells/10-cm culture dish in 10 ml of complete medium; after 24 h, the medium is replaced with 7 ml of RPMI 1640 containing 2% FBS and 25 mM Hepes, pH 7.5, and the cells are rested for 2 h prior to treatment. GW4869 is routinely stored at –80 °C as a 1.5 mM stock suspension in Me2SO. Right before use, the suspension is solubilized by the addition of 5% methane sulfonic acid (MSA) (2.5 μl of 5% MSA in sterile double-distilled H2O are added to 50 μl of GW4869 stock suspension; therefore, the concentration of the GW4869 stock solution at the time of the experiments is 1.43 mM). The suspension is mixed and warmed up at 37 °C until clear. Cells are preincubated with the inhibitor for 30 min prior to treatment with TNF. Control cells are treated with Me2SO containing 5% MSA, similarly to the samples receiving the GW4869 solution. When different doses of GW4869 are tested, amounts of vehicle solution are added in order to equal the volume of GW4869 used for the highest dose. |
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