title: Drug resistance in natural isolates of Leishmania donovani s.l. promastigotes is dependent of Pgp170 expression.
abstract: Resistance of pathogens to drugs is a growing concern regarding many diseases. Parasites like Leishmania, Plasmodium and Entamoeba histolytica; and neoplastic cells, present the multidrug-resistant phenotype rendering chemotherapy ineffective. The acquired resistance of Leishmania to antimony has generated intense research on the mechanisms involved but the question has not yet been resolved. To test the hypothesis that drug efflux in Leishmania, as measured by flow cytometry using the fluorescent dye Rhodamine-123, is largely dependent on the number of efflux pumps an isolate can express, the amount of Pgp 170 molecules was assessed in ten field isolates (5 "resistant" and 5 "susceptible") using: Western Blotting, Confocal and Transmission Electron Microscopy, and proteomics. Their survival after exposure to three antileishmanial drugs, in vitro, was evaluated and clinical data were compared to the in vitro results. All isolates were resistant to Glucantime but susceptible to Miltefosine, whilst Amphotericin B was more effective on the "susceptible" isolates. The MDR gene, expressing the transmembrane efflux pump Pgp 170, appears to play a key role in the phenomenon of drug resistance. When "susceptible" versus "resistant" parasites were compared, it was shown that the higher the number of Pgp 170 molecules the higher the Rhodamine-123 efflux from the parasite body and, when exposed to the drug, the number of efflux pumps increased. However, the rate of this increase was not linear and it is possible that there is a maximum number of Pgp 170 molecules an isolate can express. Nevertheless, the phenomenon is a complex one and other factors and proteins are involved in which the HSP-70 group proteins, detected in the "resistant" isolates, may play a significant role.
authors.affiliation: Laboratory of Clinical Bacteriology, Parasitology, Zoonoses and Geographical Medicine, Faculty of Medicine, University of Crete, Crete, Greece.
authors.forename: Ippokratis
authors.initials: I
authors.lastname: Messaritakis
authors.forename: Vasiliki
authors.initials: V
authors.lastname: Christodoulou
authors.forename: Apostolos
authors.initials: A
authors.lastname: Mazeris
authors.forename: Eleni
authors.initials: E
authors.lastname: Koutala
authors.forename: Antonia
authors.initials: A
authors.lastname: Vlahou
authors.forename: Sevasti
authors.initials: S
authors.lastname: Papadogiorgaki
authors.forename: Maria
authors.initials: M
authors.lastname: Antoniou
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D004351:Drug Resistance; D007893:Leishmania donovani / Q000187:drug effects* / Q000378:metabolism*; D008536:Meglumine / Q000494:pharmacology; D000077485:Meglumine Antimoniate; D008565:Membrane Proteins / Q000378:metabolism*; D009942:Organometallic Compounds / Q000494:pharmacology; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000494:pharmacology; D015800:Protozoan Proteins / Q000378:metabolism*; D020112:Rhodamine 123 / Q000378:metabolism
chemical_list: D000981:Antiprotozoal Agents; D008565:Membrane Proteins; D009942:Organometallic Compounds; D015800:Protozoan Proteins; D010767:Phosphorylcholine; D020112:Rhodamine 123; C039128:miltefosine; D008536:Meglumine; D000077485:Meglumine Antimoniate; D000666:Amphotericin B