title: Identification of a host cell target for the thiazolide class of broad-spectrum anti-parasitic drugs.
abstract: The thiazolide nitazoxanide (NTZ) and some derivatives exhibit considerable in vitro activities against a broad range of parasites, including the apicomplexans Neospora caninum and Toxoplasma gondii tachyzoites. In order to identify potential molecular targets for this compound in both parasites, RM4847 was coupled to epoxy-agarose and affinity chromatography was performed. A protein of approximately 35 kDa was eluted upon RM4847-affinity-chromatography from extracts of N. caninum-infected human foreskin fibroblasts (HFF) and non-infected HFF, but no protein was eluted when affinity chromatography was performed with T. gondii or N. caninum tachyzoite extracts. Mass spectrometry analysis identified the 35 kDa protein as human quinone reductase NQO1 (P15559; QR). Within 8h after infection of HFF with N. caninum tachyzoites, QR transcript expression levels were notably increased, but no such increase was observed upon infection with T. gondii tachyzoites. Treatment of non-infected HFF with RM4847 did also lead to an increase of QR transcript levels. The enzymatic activity of 6-histidine-tagged recombinant QR (recQR) was assayed using menadione as a substrate. The thiazolides NTZ, tizoxanide and RM4847 inhibited recQR activity on menadione in a concentration-dependent manner. Moreover, a small residual reducing activity was observed when these thiazolides were offered as substrates.
authors.affiliation: Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland. joachim.mueller@ipa.unibe.ch
authors.forename: Joachim
authors.initials: J
authors.lastname: Müller
authors.forename: Andrew
authors.initials: A
authors.lastname: Hemphill
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000737:chemistry / Q000145:classification / Q000494:pharmacology*; D002522:Chlorocebus aethiops; D002846:Chromatography, Affinity; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000469:parasitology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000187:drug effects* / Q000378:metabolism; D018688:Neospora / Q000187:drug effects*; D013844:Thiazoles / Q000737:chemistry / Q000145:classification / Q000494:pharmacology*; D014122:Toxoplasma / Q000187:drug effects*; D014709:Vero Cells
chemical_list: D000977:Antiparasitic Agents; D013844:Thiazoles; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human