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_LUMI_384_3XIC50_Purchased Analogs

Name: Late-stage luminescence-based cell-based dose response assay to identify inhibitors of NADPH oxidase 1 (NOX1): Purchased analogs

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, 384, inhibitor, inhibition, late stage, dose response, HT29, luminol, ROS, chemiluminescence, Scripps, The Scripps Research Institute Molecular Screening Center, SRIMSC, Molecular Libraries Probe Production Center Network, MLPCN.

Assay Overview:

The purpose of this cell-based assay is to determine the potency of a set of purchased analog inhibitors of NADPH oxidase 1 (NOX1). This chemiluminescence assay employs a luminol probe to monitor intracellular ROS in the HT29 transformed colonic epithelial cell line. HT29 cells express high endogenous levels of known NOX1 components and no other NOX family members.

Protocol Summary:

In this assay, the cells are incubated with test compounds, cell-permeable luminol, and horseradish peroxidase. The interaction of luminol with NOX1-generated ROS/superoxide inside cells yields an unstable endoperoxide that generates light, leading to increased well luminescence. As designed, compounds that inhibit cellular NOX1 activity will reduce intracellular ROS and endoperoxide levels, leading to reduced luminol-ROS interactions, reduced endoperoxide production, reduced light emission, and reduced well luminescence. Test compounds were assayed in triplicate using a 10-point dilution series starting at a maximum concentration of 20 micromolar.

For each test compound, percent inhibition was plotted against compound concentration. The reported IC50 values were generated from fitted curves by solving for the X-intercept value at the 50% inhibition level of the Y-intercept value.

PubChem Activity Outcome and Score:

Compounds with an IC50 greater than 17 uM were considered inactive. Compounds with an IC50 equal to or less than 17 uM were considered active.

Any compound with a percent activity value <50% at all test concentrations was assigned an activity score of zero. Any compound with a percent activity value >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.

The PubChem Activity Score range for active compounds is 100-1, for inactive 0-0.

List of Reagents:

HT29 cells (provided by Assay Provider)
DMEM medium (GIBCO, part 25200)
Hank's Balanced Salt Solution (Invitrogen, part 14025-092)
100X Penicillin-Streptomycin mix (Invitrogen, part 15140)
Trypsin-EDTA solution (Invitrogen, part 25200-056)
Fetal Bovine Serum (Invitrogen, part 16140-071)
Luminol (Sigma, 09253-5g)
Horseradish peroxidase (EMD Bioscience, part 516531-5KU)
DPI (Sigma, D2926)
150 mm tissue culture dishes (Corning, part 430599)
384-well plates (Corning, 3704)

Possible artifacts of this assay can include, but are not limited to: dust or lint located in or on wells of the microtiter plate, compounds that non-specifically modulate luciferase activity, and compounds that quench or emit luminescence within the well.

Grant Number: 1 R03 MH083264-01A1