The lysosomotropic drug LeuLeu-OMe induces lysosome disruption and autophagy-independent cell death in Trypanosoma brucei

Authors:

Hazel Xinyu Koh1,2, Htay Mon Aye1, Kevin S. W. Tan2 and Cynthia Y. He1

doi: 10.15698/mic2015.08.217
Volume 2, pp. 288 to 298, published 30/07/2015.

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Affiliations:

1 Department of Biological Sciences, National University of Singapore.

2 Department of Microbiology, National University of Singapore.

Keywords: 

Trypanosoma brucei, LeuLeu-OMe, lysosome, lysosomotropic, necrosis, autophagy

Corresponding Author(s):

Kevin S. W. Tan, kevin_tan@nuhs.edu.sg

Conflict of interest statement:

The authors do not have any commercial or other associations that might constitute a conflict of interest.

Please cite this article as:

Hazel Xinyu Koh, Htay Mon Aye, Kevin S. W. Tan and Cynthia Y. He (2015). The lysosomotropic drug LeuLeu-OMe induces lysosome disruption and autophagy-independent cell death in Trypanosoma brucei. Microbial Cell 2(8): 288-298.

© 2015 Koh et al. This is an open-access article released under the terms of the Creative Commons Attribution (CC BY) license, which allows the unrestricted use, distribution, and reproduction in any medium, provided the original author and source are acknowledged.

Abstract:

Background: Trypanosoma brucei is 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 form T. brucei cell death via lysosome destabilization. Methods: We measured drug concentrations that inhibit cell proliferation by 50% (IC50) for several compounds, chosen based on their lysosomotropic effects previously reported in Plasmodium 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 against T. brucei with minimal toxicity to human cell lines in 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 of T. brucei.