The diamidine DB75 targets the nucleus of Plasmodium falciparum.
BACKGROUND
DB289, [2,5-bis(4-amidinophenyl)furan bis-O-methylamidoxime], is a broad spectrum anti-parasitic compound which has been shown to be effective against malaria in recent clinical trials. DB75, [2,5-bis(4-amidinophenyl)furan], is the active metabolite of this drug. The objective of this study was to determine the mechanism of action of DB75 in Plasmodium falciparum.


METHODS
Live parasites were observed by confocal microscopy after treatment with organelle specific dyes and DB75, an inherently fluorescent compound. Parasites were exposed to DB75 and assessed for growth and morphological changes over time using blood smears and light microscopy. Also, to determine if DB75 affects gene transcription, real time PCR was used to monitor transcript levels over time for six developmentally expressed genes, including trophozoite antigen R45-like (PFD1175w), lactate dehydrogenase (PF13_0141), DNA primase (PFI0530c), isocitrate dehydrogenase (PF13_0242), merozoite surface protein-1 (PFI1475w), and merozoite surface protein-7 (PF13_0197).


RESULTS
The results show that DB75 localizes in the parasite nucleus but not in other organelles. Once rings are exposed, parasites mature to the trophozoite stage and stall. No stage-dependent or gene-specific inhibition of transcription was seen. However, DB75 delayed peak transcription of trophozoite-stage genes.


CONCLUSIONS
Taken together, DB75 appears to concentrate in the nucleus and delay parasite maturation.
Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA. purfield@med.unc.edu
Anne E
AE
Purfield
Richard R
RR
Tidwell
Steven R
SR
Meshnick
D000818:Animals; D000962:Antimalarials / Q000494:pharmacology; D001550:Benzamidines / Q000493:pharmacokinetics / Q000494:pharmacology*; D002467:Cell Nucleus / Q000187:drug effects; D003470:Culture Media; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D008856:Microscopy, Fluorescence; D015388:Organelles / Q000187:drug effects / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D016133:Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects*; D014344:Trypanocidal Agents / Q000493:pharmacokinetics / Q000494:pharmacology*
D000962:Antimalarials; D001550:Benzamidines; D003470:Culture Media; D005456:Fluorescent Dyes; D014344:Trypanocidal Agents; C033286:furamidine