Schlüsselwörter
(Englisch)
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parasitoses; intestinal protozoan infection; giardiasis; chemotherapy; thiazolides; nitroimidazoles; drug design; drug resistance; drug target identification
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Forschungsprogramme
(Englisch)
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COST-Action B22 - Drug development for parasitic diseases
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Kurzbeschreibung
(Englisch)
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In the planned project, we will use the protozoan Giardia lamblia as a model intestinal parasite for in vitro studies to gene-rate information on the mode of action of, and the mechanisms involved in, resistance to thiazolides. In cooperation with an industrial partner, we will also design novel thiazolides and subsequently test these compounds regarding their efficacy in chemotherapy of giardiasis (and other protozoan ([and possibly helminthic] diseases). The results from our examination are expected to shed light on the molecular and biological effects of thiazolide on target cells and thus provide a basis for the development of safe chemotherapeutical formulations with high antiparasitic activity and a minimized potential to in-duce resistance as a consequence of wide-spread application.
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Weitere Hinweise und Angaben
(Englisch)
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Full name of research-institution/enterprise: Universität Bern Institut für Parasitologie der Veterinärmedizinischen und der Medizinischen Fakultät
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, CH, CZ, DE, DK, ES, FR, GR, IE, IL, IT, LT, LU, NL, PT, SE, SK, UK
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Abstract
(Englisch)
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In our project, the protozoan Giardia lamblia has been used as a model intestinal parasite for in vitro studies to generate information on the mode of action of, and the mechanisms involved in resistance to, antigiardial drugs. Since several years, metronidazole (MET), albendazole or the thiazolide nitazoxanide (NTZ) have been used as therapy of choice against giardiasis. In our pharmacological studies, we investigated in detail the antigiardial activity of NTZ and a number of other modified thiazolides. Thiazolides are composed of a thiazole moiety and a salicylic acid moiety. Based on our data, we developed a preliminary model for the mode of action of these compounds suggesting a strict involvement of both moieties in antigardial activity. In a second part of our study, we generated in vitro G. lamblia clones resistant to NTZ and/or MET. While the clone selected under MET pressure was only resistant to MET the clone selected in presence of NTZ exhibited 'cross-resistance' to MET. Our molecular biological analyses revealed that resistance formation in Giardia against NTZ and MET is linked, and possibly mediated by, altered gene expression in drug-resistant strains as compared to non-resistant strains. Most importantly, alterations in the expression of genes encoding protein disulphide isomerases (PDIs), now identified by us as proteins with potential thiazolide-binding function, as well as in genes (vsp genes) involved in surface antigenic variation of the parasite have been observed. Most recently, our gene microarray studies revealed that resistance formation towards NTZ was associated with elevated expression levels of those genes that contribute to the cellular stress response e.g. including an upregulation of heat-shock proteins and chaperonins. Interestingly, respective trophozoites also exhibited an increased thermotolerance. These observations indicated that the parasite has adopted the capacity to efficiently alter, or fine tune, its gene expression pattern in order to resist drug exposure but also other 'environmental challenges' such as temperature changes. This assumption was confirmed in a further study indicating that the parasite is able to rapidly adapt to cytotoxic concentrations of phytocompounds (e.g. isoflavones) with high antigiardial activity. In future, we will assess if complex generegulatory mechnisms, such as epigenetic control mechanisms, mediate in vitro (multi-)drug resistance formation of the parasite.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C05.0104
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