| In Vitro | In vitro activity: U0126-EtOH functionally antagonizes AP- 1 transcriptional activity and blocks the production of a variety of cytokines and metalloproteinases involved in the inflammatory response. U0126-EtOH inhibits T cell proliferation in response to antigenic stimulation or cross-linked anti-CD3 plus anti-CD28 Abs without effect on IL-2-induced proliferation by down-regulating IL-2 mRNA levels. A recent study shows that U0126-EtOH antagonizes resveratrol-induced apoptosis in castration-resistant human prostate cancer C4-2 cells, inhibits mitochondrial function and shifts cells to aerobic glycolysis independently of MEK.
Kinase Assay: The amount of immunoprecipitated wild type MEK used in these assays is adjusted to give a similar amount of activity units as obtained with 10 nM recombinant MEK. Reaction velocities are measured using a 96-well nitrocellulose filter apparatus as described below. Unless otherwise noted, reactions are carried out at an enzyme concentration of 10 nM, in 20 mM Hepes, 10 mM MgCl2, 5 mM β-mercaptoethanol, 0.1 mg/mL BSA, pH 7.4, at room temperature. Reactions are initiated by the addition of [γ-33P]ATP into the premixed MEK/ERK/inhibitor reaction mixture, and an aliquot of 100 μL is taken every 6 minutes and transferred to the 96-well nitrocellulose membrane plate which has 50 mM EDTA to stop the reaction. The membrane plate is drawn and washed 4 times with buffer under vacuum. Wells are then filled with 30 μL of Microscint-20 scintillation fluid, and the radioactivity of 33P-phosphorylated ERK is counted with a Top Count scintillation counter. Velocities are obtained from the slopes of radioactivity versus time plots. Concentrations of ERK and ATP are 400 nM and 40 μM, respectively, unless otherwise indicated. For all of the in vitro enzyme assays, the percent inhibition is calculated 100 (1 –Vi/Vo) where Vi and Vo are the initial reaction velocities in the presence and absence of inhibitor, respectively. The data are then plotted as percent inhibition as a function of inhibitor concentration and fit, by nonlinear least squares regression, to the standard equation for a Langmuir isotherm to determine the IC50. As reported, enzyme concentrations are based upon molecular weights and mass of protein used in the final assay volume and not on active site titration. Thus, the actual enzyme active site concentration may differ from that reported.
Cell Assay: A.E7 or Th17 cells are incubated with mitomycin C-treated B10.BR or BALB/c splenocytes plus varying concentrations of pigeon cytochrome c or PR8 Ag, or with 5 U/mL human rIL-2. In addition, some assays contains U0126 or an inactive analogue, U0124, to determine direct effects of MEK inhibition on T cell proliferation. Two days after culture initiation, each well is pulsed with 1 μCi of [3H]TdR and harvested the following day. The incorporation of [3H]TdR into DNA is quantitated on a Packard Matrix 96 direct beta counter without the use of liquid scintillation mixtures. |
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