title: Inhibitory action of marine algae extracts on the Trypanosoma cruzi dihydroorotate dehydrogenase activity and on the protozoan growth in mammalian cells.
abstract: Trypanosoma cruzi, the causative agent of Chagas' disease, replicates in mammalian cells and relies on the de novo pyrimidine biosynthetic pathway that supplies essential precursors for nucleic acid synthesis. The protozoan dihydroorotate dehydrogenase (DHOD), the fourth enzyme of the pathway catalyzing production of orotate from dihydroorotate, markedly differs from the human enzyme. This study was thus aimed to search for potent inhibitors against T. cruzi DHOD activity, and a number of methanol extracts prepared from green, brown, and red algae were assayed. The extracts from two brown algae, Fucus evanescens and Pelvetia babingtonii, yielded 59 and 58% decrease in the recombinant DHOD activity, respectively, at the concentration of 50 microg/ml. Inhibition by these extracts was noncompetitive with respect to dihydroorotate, with apparent Ki values of 35.3+/-5.9 and 10.3+/-4.4 microg/ml, respectively. Further, in an in vitro T. cruzi-HeLa cell infection system, ethanol-reconstituted F. evanescens and P. babingtonii extracts at the concentration of 1 microg/ml, respectively, decreased significantly the infection rate of host cells and the average parasite number per infected cell. These results imply that F. evanescens and P. babingtonii contain inhibitor(s) against the T. cruzi DHOD activity and against the protozoan infection and proliferation in mammalian cells. Identification of inhibitor(s) in these two brown algae and further screening of other marine algae may facilitate the discovery of new, anti-trypanosomal lead compounds.
authors.affiliation: Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421, Japan. tnara@med.juntendo.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nara
authors.forename: Yuto
authors.initials: Y
authors.lastname: Kamei
authors.forename: Akiko
authors.initials: A
authors.lastname: Tsubouchi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Annoura
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Hirota
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Iizumi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Dohmoto
authors.forename: Takeaki
authors.initials: T
authors.lastname: Ono
authors.forename: Takashi
authors.initials: T
authors.lastname: Aoki
mesh_terms: D000818:Animals; D000090722:Dihydroorotate Dehydrogenase; D004791:Enzyme Inhibitors / Q000494:pharmacology; D056890:Eukaryota / Q000737:chemistry*; D044645:Fucus / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000459:Phaeophyceae / Q000737:chemistry; D012623:Seawater / Q000382:microbiology; D014349:Trypanosoma cruzi / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity
chemical_list: D000090722:Dihydroorotate Dehydrogenase; D004791:Enzyme Inhibitors; D044925:Oxidoreductases Acting on CH-CH Group Donors