High-throughput screening against thioredoxin glutathione reductase identifies novel inhibitors with potential therapeutic value for schistosomiasis.
BACKGROUND
Schistosomiasis, a parasitic disease also known as bilharzia and snail fever, is caused by different species of flatworms, such as Schistosoma mansoni (S. mansoni). Thioredoxin glutathione reductase (TGR) from S. mansoni (SmTGR) is a well-characterized drug target for schistosomiasis, yet no anti-SmTGR compounds have reached clinical trials, suggesting that therapeutic development against schistosomiasis might benefit from additional scaffolds targeting this enzyme.


METHODS
A high-throughput screening (HTS) assay in vitro against SmTGR was developed and applied to a diverse compound library. SmTGR activity was quantified with ThioGlo®, a reagent that fluoresces upon binding to the free sulfhydryl groups of the reaction product GSH (reduced glutathione).


RESULTS
We implemented an HTS effort against 59,360 synthetic compounds. In the primary screening, initial hits (928 or 1.56 %) showing greater than 90 % inhibition on SmTGR activity at a final concentration of 10 μM for each compound were identified. Further tests were carried out to confirm the effects of these hits and to explore the concentration-dependent response characteristics. As a result, 74 of them (0.12 %) representing 17 chemical scaffolds were confirmed and showed a great concentration-dependent inhibitory trend against SmTGR, including structures previously shown to be lethal to schistosomal growth. Of these, two scaffolds displayed a limited structure-activity relationship. When tested in cultured larvae, 39 compounds had cidal activity in 48 h, and five of them killed larvae completely at 3.125 μM. Of these, three compounds also killed adult worms ex vivo at concentrations between 5 μM and 10 μM.


CONCLUSIONS
These confirmed hits may serve as starting points for the development of novel therapeutics to combat schistosomiasis.
The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. lichangxin911@163.com.
Ting
T
Li
Department of Immunology and Microbiology, Rush University Medical Center, Chicago, IL, 60612, USA. peter_ziniel@rush.edu.
Peter D
PD
Ziniel
Division of Allergy and Infectious Diseases, University of Washington, Seattle, WA, 98195, USA. panqinghe@yahoo.com.
Pan-Qing
PQ
He
Department of Immunology and Microbiology, Rush University Medical Center, Chicago, IL, 60612, USA. vpkommer@gmail.com.
Valerie P
VP
Kommer
Division of Allergy and Infectious Diseases, University of Washington, Seattle, WA, 98195, USA. crowther@uw.edu.
Gregory J
GJ
Crowther
The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. ylhemin@163.com.
Min
M
He
The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. qliu@simm.ac.cn.
Qing
Q
Liu
Division of Allergy and Infectious Diseases, University of Washington, Seattle, WA, 98195, USA. WVanVoorhis@medicine.washington.edu.
Wesley C
WC
Van Voorhis
Department of Immunology and Microbiology, Rush University Medical Center, Chicago, IL, 60612, USA. David_Williams@rush.edu.
David L
DL
Williams
The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China. mwwang@simm.ac.cn.
Ming-Wei
MW
Wang
D000818:Animals; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D057166:High-Throughput Screening Assays / Q000379:methods / Q000592:standards; D006801:Humans; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors*; D021261:Parasitic Sensitivity Tests; D015203:Reproducibility of Results; D012550:Schistosoma mansoni / Q000187:drug effects* / Q000201:enzymology*; D012552:Schistosomiasis / Q000188:drug therapy; D012556:Schistosomicides / Q000494:pharmacology*; D054852:Small Molecule Libraries
D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D012556:Schistosomicides; D054852:Small Molecule Libraries; D009247:NADH, NADPH Oxidoreductases; C466433:thioredoxin glutathione reductase