Luminescence-based counterscreen for inhibitors of NADPH oxidase 1 (Nox1): biochemical high throughput screening assay to identify inhibitors of luminol (Maybridge Library)
Data Source (MLPCN Center Name): The Scripps Research Institute Molecular Screening Center (SRIMSC) Center Affiliation: The Scripps Research Institute, TSRI Assay Provider: Gary Bokoch, TSRI Network: Molecular Libraries Probe Production Center Network (MLPCN) Grant Proposal Number: 1 R03 MH083264-01A1 Grant Proposal PI: Gary Bokoch, TSRI External Assay ID: NOX1_INH_RAD_96_4X%INH_PDSP SCREEN_SET 2
Name: Late-stage radioligand binding assay to identify inhibitors of NADPH oxidase 1 (NOX1): PDSP screen Set 2
Description:
Host defense mechanisms are diverse and include receptor-initiated signaling pathways, antibody and cytokine production, and the generation of reactive oxygen species (ROS) such as hydroxyl radical and hypochlorus acid to kill microorganisms (1). In activated phagocytic cells, the membrane integrated protein gp91phox serves as the catalytic cytochrome b subunit of the respiratory burst oxidase used to generate superoxide in an NADPH-dependent manner for host defense (2). Generation of ROS has also been identified in non-phagocytic cells (3). One important enzyme involved in ROS production in non-leukocyte tissues is NADPH oxidase 1 (NOX1), a homolog of gp91phox. NOX1 is highly expressed in colon epithelial cells where it can generate ROS to interact with normal and pathogenic bacteria (3-5). However, excess ROS production is associated with damage to the intestinal mucosa, particularly in mucosal lesions of inflammatory bowel disease (IBD) (4). Studies showing that NOX1 levels are increased in human prostate cancer (6) and that cells overexpressing NOX1 have a transformed appearance, exhibit anchorage-independent growth, and induce vascularized tumor formation in athymic mice (3, 7), suggest that NOX1 may also play a role in angiogenesis, cell growth, and tumor pathogenesis (8, 9). The identification of inhibitors of NOX1 may lead to potential candidates for excess cell proliferation, cancer, and IBD.
References:
1. Takeya, R. and Sumimoto, H., Molecular mechanism for activation of superoxide-producing NADPH oxidases. Mol Cells, 2003. 16(3): p. 271-7. 2. Cheng, G., Cao, Z., Xu, X., van Meir, E.G., and Lambeth, J.D., Homologs of gp91phox: cloning and tissue expression of Nox3, Nox4, and Nox5. Gene, 2001. 269(1-2): p. 131-40. 3. Suh, Y.A., Arnold, R.S., Lassegue, B., Shi, J., Xu, X., Sorescu, D., Chung, A.B., Griendling, K.K., and Lambeth, J.D., Cell transformation by the superoxide-generating oxidase Mox1. Nature, 1999. 401(6748): p. 79-82. 4. Szanto, I., Rubbia-Brandt, L., Kiss, P., Steger, K., Banfi, B., Kovari, E., Herrmann, F., Hadengue, A., and Krause, K.H., Expression of NOX1, a superoxide-generating NADPH oxidase, in colon cancer and inflammatory bowel disease. J Pathol, 2005. 207(2): p. 164-76. 5. Rokutan, K., Kawahara, T., Kuwano, Y., Tominaga, K., Nishida, K., and Teshima-Kondo, S., Nox enzymes and oxidative stress in the immunopathology of the gastrointestinal tract. Semin Immunopathol, 2008. 30(3): p. 315-27. 6. Lim, S.D., Sun, C., Lambeth, J.D., Marshall, F., Amin, M., Chung, L., Petros, J.A., and Arnold, R.S., Increased Nox1 and hydrogen peroxide in prostate cancer. Prostate, 2005. 62(2): p. 200-7. 7. Arnold, R.S., Shi, J., Murad, E., Whalen, A.M., Sun, C.Q., Polavarapu, R., Parthasarathy, S., Petros, J.A., and Lambeth, J.D., Hydrogen peroxide mediates the cell growth and transformation caused by the mitogenic oxidase Nox1. Proc Natl Acad Sci U S A, 2001. 98(10): p. 5550-5. 8. Ushio-Fukai, M. and Nakamura, Y., Reactive oxygen species and angiogenesis: NADPH oxidase as target for cancer therapy. Cancer Lett, 2008. 266(1): p. 37-52. 9. Kobayashi, S., Nojima, Y., Shibuya, M., and Maru, Y., Nox1 regulates apoptosis and potentially stimulates branching morphogenesis in sinusoidal endothelial cells. Exp Cell Res, 2004. 300(2): p. 455-62.
Keywords:
NOX1, NADPH oxidase 1, cancer, inflammation, 96, inhibitor, inhibition, late stage, powders, Psychoactive Drug Screening Program, PDSP, radioligand, radioligand binding assay, receptor, transporter, ion channel, NIMH, Scripps, The Scripps Research Institute Molecular Screening Center, SRIMSC, Molecular Libraries Probe Production Center Network, MLPCN.
The purpose of this panel of radioligand binding assays performed by the NIMH Psychoactive Drug Screening Program (PDSP) is to identify a subset of potential receptors, transporters, ion channels, etc. for which the NOX1 inhibitor compound SID 57287864 displays affinity.
Protocol Summary:
Test and reference compounds are diluted to 5X final assay concentration (50 uM for a final assay concentration of 10 uM) in the appropriate radioligand binding buffer. Then, 50 uL aliquots of buffer (negative control), test compound, and reference compound (positive control) are added in quadruplicate to the wells of a 96-well plate, each of which contains 50 uL of 5X radioligand and 100 uL of buffer. Finally, receptor-containing, crude membrane fractions are resuspended in an appropriate volume of buffer and dispensed (50 mul per well) into the 96-well plate. Radioligand binding is allowed to equilibrate for 1.5 hours at room temperature, and then bound radioactivity is isolated by filtration onto 0.3% polyethyleneimine-treated, 96-well filter mats using a 96-well Filtermate harverster. The filter mats are dried, then scintillant is melted onto the filters and the radioactivity retained on the filters is counted in a Microbeta scintillation counter. As designed, membrane fractions to which substance SID 57287864 binds will bind less radioligand and decrease the radioactivity measured in the assay.
Raw data from the Microbeta counter are analyzed on the PDSP DB. Total bound radioactivity is estimated from quadruplicate wells containing no test or reference compound and adjusted to 100%; non-specifically bound radioactivity is assessed from quadruplicate wells containing 10 uM of a suitable reference compound and adjusted to 0%. The average bound radioactivity in the presence of the test compound is expressed on a percent scale. The percent inhibition of radioligand binding is calculated as follows:
%_Inhibition = 100% - %_radioactivity_bound
Inhibition of > 50% is considered significant. Negative inhibition represents a stimulation of binding.
The PDSP on-line data entry and analysis system calculates the variance of the quadruplicate determinations (for the total, non-specific, and test compound binding values) and variances greater than 20% are flagged for further inspection and assays are repeated if necessary. Additionally, % inhibition values that are greater than the total binding (i.e., 100%) by at least 20% are also flagged for inspection; such results could indicate allosteric modulation of radioligand binding.
List of Reagents:
Reagents were provided by the NIMH Psychoactive Drug Screening Program.