Original research

The cysteine proteinase inhibitor Z-Phe-Ala-CHN₂ alters cell morphology and cell division activity of Trypanosoma brucei bloodstream forms in vivo

Stefan Scory¹, York-Dieter Stierhof^2,4, Conor R Caffrey^3,5 and Dietmar Steverding^1,6

¹Abteilung Parasitologie, Hygiene-Institut der Ruprecht Karls-Universität, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany

²Abteilung Membranbiochemie, Max-Planck-Institut für Biologie, Corrensstraße 38, 72076 Tübingen, Germany

³Abteilung Tropenhygiene und Öffentliches Gesundheitswesen, Hygiene-Institut der Ruprecht Karls-Universität, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany

⁴Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität, Auf der Morgenstelle 1, 72076 Tübingen, Germany

⁵Sandler Center for Basic Research in Parasitic Diseases, California Institute for Quantitative Biomedical Research, Byers Hall, University of California San Francisco, 1700 4th Street, San Francisco, CA94158-2330, USA

⁶Present address: BioMedical Research Centre, School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK

Kinetoplastid Biology and Disease 2007, 6:2doi:10.1186/1475-9292-6-2

Published:	28 February 2007

Abstract

Background

Current chemotherapy of human African trypanosomiasis or sleeping sickness relies on drugs developed decades ago, some of which show toxic side effects. One promising line of research towards the development of novel anti-trypanosomal drugs are small-molecule inhibitors of Trypanosoma brucei cysteine proteinases.

Results

In this study, we demonstrate that treatment of T. brucei-infected mice with the inhibitor, carbobenzoxy-phenylalanyl-alanine-diazomethyl ketone (Z-Phe-Ala-CHN₂), alters parasite morphology and inhibits cell division. Following daily intra-peritoneal administration of 250 mg kg^-1 of Z-Phe-Ala-CHN₂ on days three and four post infection (p.i.), stumpy-like forms with enlarged lysosomes were evident by day five p.i. In addition, trypanosomes exposed to the inhibitor had a 65% greater protein content than those from control mice. Also, in contrast to the normal 16% of parasites containing two kinetoplasts – a hallmark of active mitosis, only 4% of trypanosomes exposed to the inhibitor were actively dividing, indicating cell cycle-arrest.

Conclusion

We suggest that inhibition of endogenous cysteine proteinases by Z-Phe-Ala-CHN₂ depletes the parasite of essential nutrients necessary for DNA synthesis, which in turn, prevents progression of the cell cycle. This arrest then triggers differentiation of the long-slender into short-stumpy forms.