Critical importance of the de novo pyrimidine biosynthesis pathway for Trypanosoma cruzi growth in the mammalian host cell cytoplasm.

The intracellular parasitic protist Trypanosoma cruzi is the causative agent of Chagas disease in Latin America. In general, pyrimidine nucleotides are supplied by both de novo biosynthesis and salvage pathways. While epimastigotes-an insect form-possess both activities, amastigotes-an intracellular replicating form of T. cruzi-are unable to mediate the uptake of pyrimidine. However, the requirement of de novo pyrimidine biosynthesis for parasite growth and survival has not yet been elucidated. Carbamoyl-phosphate synthetase II (CPSII) is the first and rate-limiting enzyme of the de novo biosynthetic pathway, and increased CPSII activity is associated with the rapid proliferation of tumor cells. In the present study, we showed that disruption of the T. cruzi cpsII gene significantly reduced parasite growth. In particular, the growth of amastigotes lacking the cpsII gene was severely suppressed. Thus, the de novo pyrimidine pathway is important for proliferation of T. cruzi in the host cell cytoplasm and represents a promising target for chemotherapy against Chagas disease.

Monoterpene hydroperoxides with trypanocidal activity from Chenopodium ambrosioides.

Four monoterpene hydroperoxides were isolated from aerial parts of Chenopodium ambrosioides along with ascaridole (1), the anthelmintic principle of this plant, as anti-trypanosomal compounds. The structures of these monoterpenes were determined to be (-)-(2S,4S)- and (-)-(2R,4S)-p-mentha-1(7),8-dien-2-hydroperoxide (2a and 3a) and (-)-(1R,4S)- and (-)-(1S,4S)-p-mentha-2,8-dien-1-hydroperoxide (4a and 5a) on the basis of spectroscopic methods and chemical correlations. In vitro trypanocidal activities of ascaridole (1) and these hydroperoxides (2a-5a) against epimastigotes of Trypanosoma cruzi were 23, 1.2, 1.6, 3.1, and 0.8 microM, respectively. Fresh leaves of C. ambrosioides also contained isomeric hydroperoxides 6a and 7a, and the content ratio of 2a-7a suggested that these hydroperoxides were formed through the singlet-oxygen oxidation of limonene.