Synthesis, inhibition potency, binding mode, and antiprotozoal activities of fluorescent inhibitors of trypanothione reductase based on mepacrine-conjugated diaryl sulfide scaffolds.
Trypanothione reductase (TR) is a flavoenzyme unique to trypanosomatid parasites and a target for lead discovery programs. Various inhibitor scaffolds have emerged in the past, exhibiting moderate affinity for the parasite enzyme. Herein we show that the combination of two structural motifs of known TR inhibitors - diaryl sulfides and mepacrine - enables the simultaneous addressing of two hydrophobic patches in the active site. The binding efficacy of these conjugates is enhanced over that of the respective parent inhibitors. They show K(ic) values for the parasite enzyme down to 0.9+/-0.1 microm and exhibit high selectivity for TR over human glutathione reductase (GR). Despite their considerable molecular mass and in some cases permanent positive charges, in vitro studies revealed IC(50) values in the low micromolar to sub-micromolar range against Trypanosoma brucei rhodesiense and Trypanosoma cruzi, as well as the malaria parasite Plasmodium falciparum, which lack trypanothione metabolism. The inhibitors exhibit strong fluorescence due to their aminoacridine moiety. This feature allows visualization of the drugs in the parasite where high accumulation was observed by fluorescence microscopy even after short exposure times.
Eberle
Christian
C
Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich, Switzerland.
Burkhard
Johannes A
JA
Stump
Bernhard
B
Kaiser
Marcel
M
Brun
Reto
R
Krauth-Siegel
R Luise
RL
Diederich
François
F
D000585:Aminacrine / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D000981:Antiprotozoal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D005980:Glutathione Reductase / Q000378:metabolism; D006801:Humans; D015394:Molecular Structure; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology*; D011485:Protein Binding; D011796:Quinacrine / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013440:Sulfides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D014344:Trypanocidal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D014345:Trypanosoma / Q000187:drug effects / Q000201:enzymology*
D000981:Antiprotozoal Agents; D005456:Fluorescent Dyes; D013440:Sulfides; D014344:Trypanocidal Agents; D000585:Aminacrine; D009247:NADH, NADPH Oxidoreductases; C049608:trypanothione reductase; D005980:Glutathione Reductase; D011796:Quinacrine