School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
Department of Pharmacology and Toxicology, Pharmacy College, University of Elmergib, Al Khums, Libya.
Front Cell Infect Microbiol. 2023 Dec 15;13:1320160. doi: 10.3389/fcimb.2023.1320160. eCollection 2023.
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 as a drug target. Whereas uptake of [H]-cytidine and particularly [H]-thymidine was at most marginal, [H]-uracil and [H]-uridine were readily taken up. Kinetic analysis of uridine uptake was consistent with a single transporter with a K of 3.3 ± 0.8 µM, which was inhibited by uracil with high affinity (K = 1.15 ± 0.07 µM) but not by thymidine or 5-methyluridine, showing that the 5-Me group is incompatible with uptake by . Conversely, [H]-uracil transport displayed a K of 2.05 ± 0.40 µM, not significantly different from the uracil K on uridine transport, and was inhibited by uridine with a K of 2.44 ± 0.59 µM, also not significantly different from the experimental uridine K. 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 [H]-uracil with a K of 6.80 ± 2.12 µM ( > 0.05 compared to uracil K). Indeed, we found that 5F-Uridine, 5F-uracil and 5F,2'-deoxyuridine were all potent antimetabolites against with EC values well below that of the current first line treatment, sulfadiazine. 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.
弓形虫病是一种常见的原生动物感染，在免疫功能低下和怀孕期间可能会产生严重后果，但治疗选择有限。最近，核苷酸代谢作为新抗原生动物药物的靶点受到了广泛关注，在这里我们重点关注嘧啶补救由作为药物靶点。虽然 [H]-胞苷和特别是 [H]-胸苷的摄取最多是微不足道的，但 [H]-尿嘧啶和 [H]-尿苷很容易被摄取。尿苷摄取的动力学分析与具有 K 的单个转运蛋白一致。3.3 ± 0.8 µM，被尿嘧啶高亲和力（K = 1.15 ± 0.07 µM）抑制，但不被胸苷或 5-甲基尿嘧啶抑制，表明 5-Me 基团与摄取不兼容。相反，[H]-尿嘧啶转运显示 K 为 2.05 ± 0.40 µM，与尿嘧啶转运的尿嘧啶 K 无显著差异，并且被尿苷以 K 抑制。2.44 ± 0.59 µM，与实验尿苷 K 无显著差异。相互的，完全抑制，显示出大约 -1 的希尔斜率，强烈表明尿嘧啶和尿嘧啶共享一个具有相似亲和力的单个转运蛋白，我们将其命名为尿嘧啶/尿嘧啶转运蛋白 1（TgUUT1）。虽然 TgUUT1 排除了 5-甲基取代，但较小的 5F 取代是可以容忍的，因为 5F-尿嘧啶以 K 抑制 [H]-尿嘧啶的摄取。6.80 ± 2.12 µM（与尿嘧啶 K 相比 > 0.05）。事实上，我们发现 5F-尿嘧啶、5F-尿嘧啶和 5F、2'-脱氧尿嘧啶都是针对弓形虫的有效的抗代谢物，EC 值远低于当前的一线治疗药物磺胺嘧啶。5F-尿嘧啶和 5F、2'-脱氧尿嘧啶的评价也表明，它们与磺胺嘧啶一样有效对抗急性弓形虫病。我们的初步结论是，TgUUT1 介导的潜在新抗弓形虫药物具有优于当前治疗的活性。
