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Toxins 2010, 2(7), 1825-1847; doi:10.3390/toxins2071825
Article

Identification of Small Molecule Inhibitors of Clostridium perfringens ε-Toxin Cytotoxicity Using a Cell-Based High-Throughput Screen

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Received: 14 May 2010 / Revised: 23 June 2010 / Accepted: 6 July 2010 / Published: 9 July 2010
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Abstract

The Clostridium perfringens epsilon toxin, a select agent, is responsible for a severe, often fatal enterotoxemia characterized by edema in the heart, lungs, kidney, and brain. The toxin is believed to be an oligomeric pore-forming toxin. Currently, there is no effective therapy for countering the cytotoxic activity of the toxin in exposed individuals. Using a robust cell-based high-throughput screening (HTS) assay, we screened a 151,616-compound library for the ability to inhibit e-toxin-induced cytotoxicity. Survival of MDCK cells exposed to the toxin was assessed by addition of resazurin to detect metabolic activity in surviving cells. The hit rate for this screen was 0.6%. Following a secondary screen of each hit in triplicate and assays to eliminate false positives, we focused on three structurally-distinct compounds: an N-cycloalkylbenzamide, a furo[2,3-b]quinoline, and a 6H-anthra[1,9-cd]isoxazol. None of the three compounds appeared to inhibit toxin binding to cells or the ability of the toxin to form oligomeric complexes. Additional assays demonstrated that two of the inhibitory compounds inhibited ε-toxin-induced permeabilization of MDCK cells to propidium iodide. Furthermore, the two compounds exhibited inhibitory effects on cells pre-treated with toxin. Structural analogs of one of the inhibitors identified through the high-throughput screen were analyzed and provided initial structure-activity data. These compounds should serve as the basis for further structure-activity refinement that may lead to the development of effective anti-ε-toxin therapeutics.
Keywords: bacterial toxins; Clostridium perfringens; cell membrane permeability; small molecule libraries; structure-activity relationship; drug evaluation; preclinical bacterial toxins; Clostridium perfringens; cell membrane permeability; small molecule libraries; structure-activity relationship; drug evaluation; preclinical
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Lewis, M.; Weaver, C.D.; McClain, M.S. Identification of Small Molecule Inhibitors of Clostridium perfringens ε-Toxin Cytotoxicity Using a Cell-Based High-Throughput Screen. Toxins 2010, 2, 1825-1847.

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