title: The lysosomotropic drug LeuLeu-OMe induces lysosome disruption and autophagy-independent cell death inTrypanosoma brucei.
abstract: BACKGROUND
  Trypanosoma bruceiis a blood-borne, protozoan parasite that causes African sleeping sickness in humans and nagana in animals. The current chemotherapy relies on only a handful of drugs that display undesirable toxicity, poor efficacy and drug-resistance. In this study, we explored the use of lysosomotropic drugs to induce bloodstream formT. bruceicell death via lysosome destabilization.
  
  
  METHODS
  We measured drug concentrations that inhibit cell proliferation by 50% (IC<sub>50<sub>) for several compounds, chosen based on their lysosomotropic effects previously reported inPlasmodium falciparum. The lysosomal effects and cell death induced by L-leucyl-L-leucyl methyl ester (LeuLeu-OMe) were further analyzed by flow cytometry and immunofluorescence analyses of different lysosomal markers. The effect of autophagy in LeuLeu-OMe-induced lysosome destabilization and cytotoxicity was also investigated in control and autophagy-deficient cells.
  
  
  RESULTS
  LeuLeu-OMe was selected for detailed analyses due to its strong inhibitory profile againstT. bruceiwith minimal toxicity to human cell linesin vitro. Time-dependent immunofluorescence studies confirmed an effect of LeuLeu-OMe on the lysosome. LeuLeu-OMe-induced cytotoxicity was also found to be dependent on the acidic pH of the lysosome. Although an increase in autophagosomes was observed upon LeuLeu-OMe treatment, autophagy was not required for the cell death induced by LeuLeu-OMe. Necrosis appeared to be the main cause of cell death upon LeuLeu-OMe treatment.
  
  
  CONCLUSIONS
  LeuLeu-OMe is a lysosomotropic agent capable of destabilizing lysosomes and causing necrotic cell death in bloodstream form ofT. brucei.
authors.affiliation: Department of Biological Sciences, National University of Singapore. ; Department of Microbiology, National University of Singapore.
authors.forename: Hazel X
authors.initials: HX
authors.lastname: Koh
authors.affiliation: Department of Biological Sciences, National University of Singapore.
authors.forename: Htay M
authors.initials: HM
authors.lastname: Aye
authors.affiliation: Department of Microbiology, National University of Singapore.
authors.forename: Kevin S W
authors.initials: KS
authors.lastname: Tan
authors.affiliation: Department of Biological Sciences, National University of Singapore.
authors.forename: Cynthia Y
authors.initials: CY
authors.lastname: He
keywords: LeuLeu-OMe; Trypanosoma brucei; autophagy; lysosome; lysosomotropic; necrosis