Pyrimidine salvage in Toxoplasma gondii as a target for new treatment

Elati, H. A.A. , Goerner, A. L., Martorelli Di Genova, B., Sheiner, L. and De Koning, H. P. (2023) Pyrimidine salvage in Toxoplasma gondii as a target for new treatment. Frontiers in Cellular and Infection Microbiology, 13, 1320160. (doi: 10.3389/fcimb.2023.1320160) (PMID:38162577) (PMCID:PMC10755004)

Abstract

Toxoplasmosis is a common protozoan infection that can have severe outcomes in the immunocompromised and during pregnancy, but treatment options are limited. Recently, nucleotide metabolism has received much attention as a target for new antiprotozoal agents and here we focus on pyrimidine salvage by Toxoplasma gondii as a drug target. Whereas uptake of [3H]-cytidine and particularly [3H]-thymidine was at most marginal, [3H]-uracil and [3H]-uridine were readily taken up. Kinetic analysis of uridine uptake was consistent with a single transporter with a Km of 3.3 ± 0.8 µM, which was inhibited by uracil with high affinity (Ki = 1.15 ± 0.07 µM) but not by thymidine or 5-methyluridine, showing that the 5-Me group is incompatible with uptake by T. gondii. Conversely, [3H]-uracil transport displayed a Km of 2.05 ± 0.40 µM, not significantly different from the uracil Ki on uridine transport, and was inhibited by uridine with a Ki of 2.44 ± 0.59 µM, also not significantly different from the experimental uridine Km. The reciprocal, complete inhibition, displaying Hill slopes of approximately -1, strongly suggest that uridine and uracil share a single transporter with similarly high affinity for both, and we designate it uridine/uracil transporter 1 (TgUUT1). While TgUUT1 excludes 5-methyl substitutions, the smaller 5F substitution was tolerated, as 5F-uracil inhibited uptake of [3H]-uracil with a Ki of 6.80 ± 2.12 µM (P > 0.05 compared to uracil Km). Indeed, we found that 5F-Uridine, 5F-uracil and 5F,2’-deoxyuridine were all potent antimetabolites against T. gondii with EC50 values well below that of the current first line treatment, sulfadiazine. In vivo evaluation also showed that 5F-uracil and 5F,2’-deoxyuridine were similarly effective as sulfadiazine against acute toxoplasmosis. Our preliminary conclusion is that TgUUT1 mediates potential new anti-toxoplasmosis drugs with activity superior to the current treatment.

• Item Type: Articles
• Additional Information: HE was supported by a studentship from the government of Libya. This work was supported by the Wellcome Trust as part of the core funding for the Wellcome Centre for Integrative Parasitology [grant number 104111] .
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Elati, Hamza Ali Abd and De Koning, Professor Harry and Sheiner, Professor Lilach

Creator Roles

Elati, H. A. A.: Formal analysis, Funding acquisition, Investigation, Methodology, Writing – original draft
Sheiner, L.: Methodology, Supervision, Writing – review and editing
De Koning, H.: Conceptualization, Formal analysis, Methodology, Project administration, Resources, Supervision, Writing – review and editing

• Authors: Elati, H. A.A., Goerner, A. L., Martorelli Di Genova, B., Sheiner, L., and De Koning, H. P.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: Frontiers in Cellular and Infection Microbiology
• Publisher: Frontiers Media
• ISSN: 2235-2988
• ISSN (Online): 2235-2988
• Copyright Holders: Copyright: © 2023 Elati, Goerner, Martorelli Di Genova, Sheiner and de Koning.
• First Published: First published in Frontiers in Cellular and Infection Microbiology 13: 1320160
• Publisher Policy: Reproduced under a Creative Commons licence

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
170547		The Wellcome Centre for Molecular Parasitology ( Core Support )	Andrew Waters	Wellcome Trust (WELLCOTR)	104111/Z/14/Z	SII - Parasitology