Induction of oxidative stress in Trypanosoma brucei by the antitrypanosomal dihydroquinoline OSU-40.
Dihydroquinoline derivative OSU-40 (1-benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate) is selectively potent against Trypanosma brucei rhodesiense in vitro (50% inhibitory concentration [IC(50)], 14 nM; selectivity index, 1,700) and has been proposed to cause the formation of reactive oxygen species (ROS) in African trypanosomes (J. Fotie et al., J. Med. Chem. 53:966-982, 2010). In the present study, we sought to provide further support for the hypothesis that OSU-40 kills trypanosomes through oxidative stress. Inducible RNA interference (RNAi) was applied to downregulate key enzymes in parasite antioxidant defense, including T. brucei trypanothione synthetase (TbTryS) and superoxide dismutase B (TbSODB). Both TbTryS RNAi-induced and TbSODB RNAi-induced cells showed impaired growth and increased sensitivity toward OSU-40 by 2.4-fold and 3.4-fold, respectively. Decreased expression of key parasite antioxidant enzymes was thus associated with increased sensitivity to OSU-40, consistent with the hypothesis that OSU-40 acts through oxidative stress. Finally, the dose-dependent formation of free radicals was observed after incubation of T. brucei with OSU-40 utilizing electron spin resonance (ESR) spectroscopy. These data support the notion that the mode of antitrypanosomal action for this class of compounds is to induce oxidative stress.
Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, Ohio, USA.
Shanshan
S
He
Alex
A
Dayton
Periannan
P
Kuppusamy
Karl A
KA
Werbovetz
Mark E
ME
Drew
D000085:Acetates / Q000494:pharmacology*; D019732:Amide Synthases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002478:Cells, Cultured; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D020128:Inhibitory Concentration 50; D018384:Oxidative Stress / Q000187:drug effects; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011806:Quinolinium Compounds / Q000494:pharmacology*; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014344:Trypanocidal Agents / Q000494:pharmacology*; D016833:Trypanosoma brucei rhodesiense / Q000187:drug effects* / Q000201:enzymology; D014353:Trypanosomiasis, African / Q000188:drug therapy / Q000469:parasitology
C560080:1-benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate; D000085:Acetates; D015800:Protozoan Proteins; D011806:Quinolinium Compounds; D017382:Reactive Oxygen Species; D014344:Trypanocidal Agents; D013482:Superoxide Dismutase; D019732:Amide Synthases; C064407:trypanothione synthetase