Frequency of MDR1-related p-gp overexpression in Greek Leishmania isolates.

In this work, we investigated Greek Leishmania isolates (n = 70) for their individual MDR1-gene-related p-gp (belonging to the ABC-B subfamily of permeases) expression levels by means of flow cytometric analysis of Rhodamine 123 extrusion kinetics. Of all used isolates, 5.71% express this drug-extruding ABC-transporter at alarming levels and are distributed widely over the country. Some 33% of all examined isolates originated on the island of Crete though none of the strains showed vastly elevated p-gp extrusion activity, indicating a reasonable implementation of anti-leishmanial compounds in this part of the country. Compared to isolates obtained from canine tissue, human Leishmania isolates were superior both in size and in subcellular differentiation in flow cytometry. Furthermore, a specific t test confirmed verapamil hydrochloride to be a highly potent p-gp reversal agent with p < 0.0001. In a second test series, the loading of Leishmania with Rhodamine 123 was moreover reduced when occurring under influence of verapamil hydrochloride, a known p-gp reversal agent, indicating an ATP-dependant influx of the fluorescent dye and therewith the drug itself. In a final, third experiment series, it was shown that Sb(V) does not act upon the promastigote form of Leishmania.