title: Plasmodium falciparum: food vacuole localization of nitric oxide-derived species in intraerythrocytic stages of the malaria parasite.
abstract: Nitric oxide (NO) has diverse biological functions. Numerous studies have documented NO's biosynthetic pathway in a wide variety of organisms. Little is known, however, about NO production in intraerythrocytic Plasmodium falciparum. Using diaminorhodamine-4-methyl acetoxymethylester (DAR-4M AM), a fluorescent indicator, we obtained direct evidence of NO and NO-derived reactive nitrogen species (RNS) production in intraerythrocytic P. falciparum parasites, as well as in isolated food vacuoles from trophozoite stage parasites. We preliminarily identified two gene sequences that might be implicated in NO synthesis in intraerythrocytic P. falciparum. We showed localization of the protein product of one of these two genes, a molecule that is structurally similar to a plant nitrate reductase, in trophozoite food vacuole membranes. We confirmed previous reports on the antiproliferative effect of NOS (nitric oxide synthase) inhibitors in P. falciparum cultures; however, we did not obtain evidence that NOS inhibitors had the ability to inhibit RNS production or that there is an active NOS in mature forms of the parasite. We concluded that a nitrate reductase activity produce NO and NO-derived RNS in or around the food vacuole in P. falciparum parasites. The food vacuole is a critical parasitic compartment involved in hemoglobin degradation, heme detoxification and a target for antimalarial drug action. Characterization of this relatively unexplored synthetic activity could provide important clues into poorly understood metabolic processes of the malaria parasite.
authors.affiliation: Biophysical and Biochemical Parasitology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA. gostera@niaid.nih.gov
authors.forename: Graciela
authors.initials: G
authors.lastname: Ostera
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Tokumasu
authors.forename: Fabiano
authors.initials: F
authors.lastname: Oliveira
authors.forename: Juliana
authors.initials: J
authors.lastname: Sa
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Furuya
authors.forename: Clarissa
authors.initials: C
authors.lastname: Teixeira
authors.forename: James
authors.initials: J
authors.lastname: Dvorak
mesh_terms: D000818:Animals; D002172:Canavanine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000469:parasitology*; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D008859:Microscopy, Polarization; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009952:Ornithine / Q000031:analogs & derivatives / Q000494:pharmacology; D010963:Plasmodium falciparum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D026361:Reactive Nitrogen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012235:Rhodamines; D014617:Vacuoles / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D012333:RNA, Messenger; D026361:Reactive Nitrogen Species; D012235:Rhodamines; C508638:diaminorhodamine-4M; D009569:Nitric Oxide; C065027:N(G)-iminoethylornithine; D002172:Canavanine; D009952:Ornithine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester