SFLLRN-induced P-Selectin Platelet Surface Expression Measured in Cell-Based System Using Flow Cytometry - 2016-03_Inhibitor_Dose_DryPowder_Activity_Set3
Keywords: Platelet, activation, P-selectin, SFLLRN, PAR1, thrombin receptor, alpha-granule, secretion ..more
BioActive Compounds: 5
Keywords: Platelet, activation, P-selectin, SFLLRN, PAR1, thrombin receptor, alpha-granule, secretion
Cell-based assay for inhibition of SFLLRN-induced P-selectin surface expression. Washed platelets obtained from individual donors were treated with a selection of compounds either at dose or at a single point of 10uM. Following compound addition, platelets were subsequently stimulated with 5 mM SFLLRN. After a 15-minute incubation, phycoerythrin-labeled anti-P-selectin antibody (BD Biosciences) was added for a 20-minute incubation. The samples were analyzed by flow cytometry to determine P-selectin expression on the surface of the platelets as a response to activation. Geometric mean values were collected for each sample.
This assay serves as a gate for the defined probe paths. A moderate decrease in the amount of P-selectin expressed on the surface of platelets will identify compounds that inhibit pathways that regulate granule secretion or G-protein coupled receptors (GPCR) expressed on the surface of platelets. Lack of substantial inhibition of surface expression of P-selectin is indicative of compounds that might selectively effect dense granule secretion. Additional secondary testing will further delineate the specificity of the probes.
1. Platelet samples (10 ul) were treated with compounds at dose or at a single point of 10uM.
2. 20 minutes following compound addition, platelets were stimulated with 5 uM thrombin-receptor-derived hexapeptide SFLLRN from 100 uM stock.
3. After a 15-minute incubation, phycoerythrin-labeled anti-P-selectin antibody (5 ul; BD Biosciences) was added. The samples were agitated gently.
4. After a 20-minute incubation, 500 ul of FACS buffer (BD Biosciences) was added to each of the samples.
5. Samples were then analyzed by flow cytometry to determine P-selectin expression on the surface of the platelets as a response to activation.
6. Geometric mean fluorescence values were collected for each sample.
PRESENCE OF CONTROLS: Neutral controls (NC) were included with every run.
EXPECTED OUTCOME: Active compounds result in decreasing readout signal.
ACTIVE CONCENTRATION LIMIT:
For each sample, the highest valid tested concentration (HVC) was determined and the active concentration limit (AC_limit) was set to equal (10)(HVC).
Percent inhibition of induced P-selectin expression was calculated based on the assumption that complete (100% ) inhibition is attainable, as:
100 - (100 * (Mean Fluorescence at dose/ Mean Fluorescence at DMSO))
PATTERN CORRECTION: No plate pattern correction algorithm from Genedata Condoseo (v.7.0.3) was applied.
MEASUREMENT USED TO DETERMINE ACTIVE CONCENTRATION(AC): AC50
AC values were calculated using the curve fitting strategies in Genedata Screener Condoseo (7.0.3).
AC values were calculated up to the active concentration limit described for each sample.
Activity_Outcome = 1 (inactive) when:
a) curve fit is constant where activity is > -30% and < 30% at all tested concentrations, or
b) AC > AC_limit, or
c) compound shows activity but in a direction opposite to the expected outcome
in these cases, values describing curve fitting parameters (Sinf, S0, Hill Slope, log_AC50, log_AC50_SE) are set to null
Activity_Outcome = 2 (active) when:
AC <= AC_limit
Activity_Outcome = 3 (inconclusive) when:
a) Curve fitting strategy resulted in a constant fit with activity >= -70% but <= -30%, or
b) The fit was not valid due to poor fit quality.
PUBCHEM_ACTIVITY_SCORE = 0 when PUBCHEM_ACTIVITY_OUTCOME = 1 (inactive) or 3 (inconclusive)
PUBCHEM_ACTIVITY_SCORE = (-10)[Log(AC)], where AC is in molar, when PUBCHEM_ACTIVITY_OUTCOME = 2 (active)
Scores relate to AC in this manner:
120 = 1 pM
90 = 1 nM
60 = 1 uM
30 = 1 mM
0 = 1 M
PUBCHEM_ACTIVITY_SCORE = 100 when the curve fit is constant and showing full inhibition at all tested concentrations.
* Activity Concentration. ** Test Concentration.
Data Table (Concise)