Late stage assay provider results from the probe development effort to identify inhibitors of plasma platelet activating factor acetylhydrolase (pPAFAH): absorbance-based cell-based dose response assay to determine cytotoxicity of inhibitor compounds
Name: Late stage assay provider results from the probe development effort to identify inhibitors of plasma platelet activating factor acetylhydrolase (pPAFAH): absorbance-based cell-based dose response assay to determine cytotoxicity of inhibitor compounds. ..more
BioActive Compounds: 2
Source (MLPCN Center Name): The Scripps Research Institute Molecular Screening Center (SRIMSC)
Center Affiliation: The Scripps Research Institute (TSRI)
Assay Providers: Brian Bahnson (Univ. of Delaware); Benjamin Cravatt, (TSRI)
Network: Molecular Libraries Probe Production Centers Network (MLPCN)
Grant Proposal Number: 1R01HL084366
Grant Proposal PI: Brian Bahnson
External Assay ID: 293TCYTOX_INH_ABSORB_5XCC50
Name: Late stage assay provider results from the probe development effort to identify inhibitors of plasma platelet activating factor acetylhydrolase (pPAFAH): absorbance-based cell-based dose response assay to determine cytotoxicity of inhibitor compounds.
This project aims to develop specific inhibitors of plasma platelet activating factor acetylhydrolase (pPAFAH), and three associated members of the serine hydrolase family of enzymes-PAFAH2, PAFAH1b2, and PAFAH1b3. pPAFAH, an enzyme linked to the inflammatory pathways involved in atherosclerosis, asthma, anaphylactic shock, and other allergic reactions (1,2), is a lipoprotein-associated group VIIA phospholipase A2 that reduces the levels of the signaling molecule platelet activating factor (PAF) (3,4), a potent pro-inflammatory phospholipid signaling molecule (5), and other pro-inflammatory agents, such as oxidized phospholipids, through hydrolysis. A large number of studies have been published over the years since pPAFAH was first discovered linking an increase in pPAFAH concentration and/or activity to an increased risk of various cardiovascular diseases (6,7). The biological function of pPAFAH in the development of coronary heart diseases (CHD) is controversial, with both anti- and pro-inflammatory roles attributed to it (8,9). Dr. Bahnson and colleagues recently reported the first high-resolution crystal structure of the pPAFAH enzyme (10), and would like to expand their studies to co-crystallize pPAFAH with substrate-mimetic inhibitors to further define the active site and substrate specificity of pPAFAH. While one selective pPAFAH inhibitor has been reported (11), its properties are not suitable for the proposed studies. Given the complex biology of the pPAFAH enzymes, a complete characterization of their patho/physiological roles in lipid metabolism is necessary to maximize the success of therapeutic intervention. Towards this goal, development of selective inhibitors would significantly advance our understanding of these enzymes' substrate specificity and contribution to inflammatory disease processes including atherosclerosis, asthma, and rheumatoid arthritis. Pan-PAFAH inhibitors might be of heightened therapeutic value.
1. Karasawa, K., Harada, A., Satoh, N., Inoue, K., and Setaka, M. (2003) Plasma platelet activating factor-acetylhydrolase (PAF-AH), Prog Lipid Res 42, 93-114.
2. Leitinger, N. (2005) Oxidized phospholipids as triggers of inflammation in atherosclerosis, Molecular Nutrition & Food Research 49, 1063-1071.
3. Blank, M. L., Lee, T., Fitzgerald, V., and Snyder, F. (1981) A specific acetylhydrolase for 1-alkyl-2- acetyl-sn-glycero-3-phosphocholine (a hypotensive and platelet-activating lipid), J Biol Chem 256, 175-178.
4. Farr, R. S., Cox, C. P., Wardlow, M. L., and Jorgensen, R. (1980) Preliminary studies of an acid labile factor (ALF) in human sera that inactivates platelet-activating factor (PAF), Clin Immunol Immunopathol 15, 318-330.
5. Zimmerman, G. A., McIntyre, T. M., Prescott, S. M., and Stafforini, D. M. (2002) The plateletactivating factor signaling system and its regulators in syndromes of inflammation and thrombosis, Crit Care Med 30, S294-301.
6. Anderson, J. L. (2008) Lipoprotein-associated phospholipase A2: an independent predictor of coronary artery disease events in primary and secondary prevention, Am J Cardiol 101, 23F-33F.
7. Sudhir, K. (2005) Clinical review: Lipoprotein-associated phospholipase A2, a novel inflammatory biomarker and independent risk predictor for cardiovascular disease, J Clin Endocrinol Metab 90, 3100-3105.
8. Wilensky, R. L., and Macphee, C. H. (2009) Lipoprotein-associated phospholipase A(2) and atherosclerosis, Curr Opin Lipidol 20, 415-420.
9. Karabina, S. A., and Ninio, E. (2006) Plasma PAF-acetylhydrolase: an unfulfilled promise?, Biochim Biophys Acta 1761, 1351-1358.
10. Samanta, U., and Bahnson, B. J. (2008) Crystal structure of human plasma platelet-activating factor acetylhydrolase: structural implication to lipoprotein binding and catalysis, J Biol Chem 283, 31617-31624.
11. Blackie, J. A., Bloomer, J. C., Brown, M. J. B., Cheng, H. Y., Hammond, B., Hickey, D. M. B., Ife, R. J., Leach, C. A., Lewis, V. A., Macphee, C. H., Milliner, K. J., Moores, K. E., Pinto, I. L., Smith, S. A., Stansfield, I. G., Stanway, S. J., Taylor, M. A., and Theobald, C. J. (2003) The identification of clinical candidate SB-480848: A potent inhibitor of lipoprotein-associated phospholipase A(2), Bioorganic & Medicinal Chemistry Letters 13, 1067-1070.
late stage, late stage AID, assay provider, low throughput, secondary, PLA2G7, pPAFAH, serine hydrolase, platelet activating factor acetylhydrolase, inflammation, atherosclerosis, powders, fluorescence, competitive activity-based protein profiling, ABPP, gel-based, inhibitor, cytotoxicity, rhodamine-conjugated fluorophosphonate, FP-Rh, Scripps, The Scripps Research Institute Molecular Screening Center, SRIMSC, Molecular Libraries Probe Production Centers Network, MLPCN
The purpose of this assay is to determine cytotoxicity of powder samples of synthetic inhibitor compounds belonging to the carbamate scaffold. In this assay, 293T Hek cells in either serum-free media (Assay 1) or media containing fetal calf serum (FCS) (Assay 2) are incubated with test compounds, followed by determination of cell viability. The assay utilizes the WST-1 substrate which is converted into colorimetric formazan dye by the metabolic activity of viable cells. The amount of formed formazan directly correlates to the number of metabolically active cells in the culture. As designed, compounds that reduce cell viability will result in decreased absorbance of the dye. Compounds were tested in a 7-point 1:5 dilution series starting at a nominal test concentration of 50 uM (n = 5 per concentration).
This assay was started by dispensing 293T Hek cells in DMEM media (100 uL, 15,000 cells/well) into a 96-well plate. Both serum-free media (Assay 1) and media supplemented with 10% FCS (Assay 2) were tested. Compound (10 uL of 11x stocks in media containing 10% DMSO) was added to each well, giving final compound concentrations of 0-50 uM (7-point 1:5 dilution series). Cells were incubated for 48 hours at 37 C in a humidified incubator and cell viability was determined by the WST-1 assay (Roche) according to manufacturer instructions.
%_Cell_Viability = ( ABS_Test_Compound - Median_ABS_Low_Control ) / ( Median_ABS_High_Control - Median_ABS_Low_Control ) * 100
Test_Compound is defined as wells containing cells in the presence of test compound.
High_Control is defined as wells containing cells treated with media only (no compound).
Low_Control is defined as wells containing no cells (media only).
For each test compound, percent inhibition was plotted against the log of the compound concentration. A three parameter equation describing a sigmoidal dose-response curve was then fitted using GraphPad Prism (GraphPad Software Inc). The software-generated CC50 values are reported.
PubChem Activity Outcome and Score:
The following applies to each panel in this assay:
Compounds with CC50 less than or equal to 5 uM were considered active (cytotoxic). Compounds with CC50 greater than 5 uM were considered inactive (non-cytotoxic).
Any compound with a percent activity value less than 50% at all test concentrations was assigned an activity score of zero. Any compound with a percent activity value greater than or equal to 50% at any test concentration was assigned an activity score greater than zero.
Activity score was then ranked by the potency of the compounds with fitted curves, with the most potent compounds assigned the highest activity scores.
Serum-free medium Score: The PubChem Activity Score range for active compounds is 100-74, and for inactive compounds 1-1.
Serum-containing medium Score: The PubChem Activity Score range for inactive compounds is 100-1. There are no active compounds.
Overall Outcome and Score:
The overall outcome was active if the compound was active in at least one panel, inactive otherwise.
The overall score is 0 if the compound was inactive, otherwise the score is taken as the fraction of panels where the compound is active, multiplied by 100.
The PubChem Activity Score range for active compounds is 50-50, and for inactive compounds 0-0.
List of Reagents:
293T Hek cells (provided by Assay Provider)
DMEM Media (CellGro 10-017-CV)
FCS (Omega Scientific, FB-01)
WST-1 reagent (Roche)
96-well plates (Corning)
This assay was performed by the assay provider with powder samples of synthesized test compounds.
Categorized Comment - additional comments and annotations
From BioAssay Depositor:
BAO: assay format: biochemical format: protein format: single protein format
BAO: bioassay specification: assay biosafety level: bsl1
BAO: bioassay specification: assay measurement type: endpoint assay
BAO: bioassay specification: assay readout content: assay readout method: regular screening
BAO: bioassay specification: assay readout content: content readout type: single readout
BAO: bioassay specification: assay stage: secondary: alternate confirmatory
BAO: detection technology: fluorescence: fluorescence intensity
BAO: meta target detail: binding reporter specification: interaction: protein-small molecule
BAO: meta target: molecular target: protein target: enzyme: generic hydrolase
BAO: version: 1.4b1090
Assay Format: Cell-based
Assay Type: Toxicity
Assay Cell Type: HEK 293T
* Activity Concentration. ** Test Concentration. § Panel component ID.