Publications

The problems associated with the drugs currently used to treat leishmaniasis, including resistance, toxicity, and the high cost of some formulations, call for the urgent identification of new therapeutic agents with novel modes of action. The aggregated protein dye YAT2150 has been found to be a potent antileishmanial compound, with a half-maximal inhibitory concentration (IC50) of approximately 0.5 mu M against promastigote and amastigote stages of Leishmania infantum. The encapsulation in liposomes of YAT2150 significantly improved its in vitro IC50 to 0.37 and 0.19 mu M in promastigotes and amastigotes, respectively, and increased the half-maximal cytotoxic concentration in human umbilical vein endothelial cells to >50 mu M. YAT2150 became strongly fluorescent when binding intracellular protein deposits in Leishmania cells. This fluorescence pattern aligns with the proposed mode of action of this drug in the malaria parasite Plasmodium falciparum, the inhibition of protein aggregation. In Leishmania major, YAT2150 rapidly reduced ATP levels, suggesting an alternative antileishmanial mechanism. To the best of our knowledge, this first-in-class compound is the only one described so far having significant activity against both Plasmodium and Leishmania, thus being a potential drug for the treatment of co-infections of both parasites.

JTD Keywords: Animal, Animals, Antileishmanial drugs, Antiprotozoal agent, Antiprotozoal agents, Axenic amastigotes, Colocalization, Differentiation, Discovery, Endothelial cells, Endothelium cell, Human, Humans, Identification, Leishmania, Leishmania infantum, Leishmaniasis, Parasite, Parasites, Protein aggregation, Yat2150, Yeast

The second-line antileishmanial compound pentamidine is administered intramuscularly or, preferably, by intravenous infusion, with its use limited by severe adverse effects, including diabetes, severe hypoglycemia, myocarditis and renal toxicity. We sought to test the potential of phospholipid vesicles to improve the patient compliance and efficacy of this drug for the treatment of leishmaniasis by means of aerosol therapy. The targeting to macrophages of pentamidine-loaded liposomes coated with chondroitin sulfate or heparin increased about twofold (up to ca. 90%) relative to noncoated liposomes. The encapsulation of pentamidine in liposomes ameliorated its activity on the amastigote and promastigote forms of Leishmania infantum and Leishmania pifanoi, and it significantly reduced cytotoxicity on human umbilical endothelial cells, for which the concentration inhibiting 50% of cell viability was 144.2 ± 12.7 µM for pentamidine-containing heparin-coated liposomes vs. 59.3 ± 4.9 µM for free pentamidine. The deposition of liposome dispersions after nebulization was evaluated with the Next Generation Impactor, which mimics human airways. Approximately 53% of total initial pentamidine in solution reached the deeper stages of the impactor, with a median aerodynamic diameter of ~2.8 µm, supporting a partial deposition on the lung alveoli. Upon loading pentamidine in phospholipid vesicles, its deposition in the deeper stages significantly increased up to ~68%, and the median aerodynamic diameter decreased to a range between 1.4 and 1.8 µm, suggesting a better aptitude to reach the deeper lung airways in higher amounts. In all, nebulization of liposome-encapsulated pentamidine improved the bioavailability of this neglected drug by a patient-friendly delivery route amenable to self-administration, paving the way for the treatment of leishmaniasis and other infections where pentamidine is active.

JTD Keywords: aerosol therapy, delivery-systems, drug encapsulation, drugs, ex-vivo models, formulation, leishmania infantum, leishmania pifanoi, leishmaniasis, liposomes, macrophages, miltefosine, pentamidine, pharmacology, pulmonary absorption, visceral leishmaniasis, Amphotericin-b treatment, Leishmania infantum, Pentamidine

Nanotechnological devices for therapeutic applications are massively addressed to diseases prevalent in the developed world, particularly cancer, because of the wrong assumption (for both ethical and technical reasons) that nanomedicines are too expensive and thus they can not be applied to diseases of poverty. Here we have applied quantum dots to study at the cellular level the delivery of the contents of liposomes to erythrocytes infected by the malaria parasite Plasmodium falciparum, and to macrophages infected by the leishmaniasis causative agent Leishmania infantum. A number of works have reported on the encapsulation in liposomes of drugs against both diseases as a strategy to increase therapeutic efficacy and decrease unspecific toxicity. Liposome-carried drugs end up inside Plasmodium-infected red blood cells (pRBCs) and in the phagolysosome system of Leishmania-infected macrophages but some knowledge gaps still obscure subcellular events related to these processes. As a proof of concept, we have used confocal fluorescence microscopy to follow the fate in pRBCs and infected macrophages of quantum dots encapsulated in liposomes, and of lysosomes, leishmaniasis and malaria parasites, nuclei, and phagosomes. Our data indicate that liposomes merge their lipid bilayers with pRBC plasma membranes but are engulfed by macrophages, where they fuse with lysosomes. Lysosomes have not been observed to join with phagosomes harboring single Leishmania parasites, whereas in phagosomes where the parasite has divided there is lysosome-specific fluorescence with a concomitant disappearance of lysosomes from the cytosol. In later stages, all the lysosome-specific label is found inside phagosomes whereas the phagosomal marker cadaverine strongly stains the macrophage nucleus, suggesting that Leishmania infection induces in its later stages nuclear degeneration and, possibly, apoptosis of the host cell. These results indicate that induction of macrophage apoptosis should be explored as a possible strategy used by Leishmania to prepare its egress.

JTD Keywords: Leishmania infantum, Leishmaniasis Liposomes, Malaria, Nanomedicine, Nanotechnology, Plasmodium falciparum, Quantum dots

Nanotechnological devices for therapeutic applications are massively addressed to diseases prevalent in the developed world, particularly cancer, because of the wrong assumption (for both ethical and technical reasons) that nanomedicines are too expensive and thus they can not be applied to diseases of poverty. Here we have applied quantum dots to study at the cellular level the delivery of the contents of immunoliposomes to erythrocytes infected by the malaria parasite Plasmodium falciparum, and to macrophages infected by the leishmaniasis causative agent Leishmania infantum. A number of works have reported on the encapsulation in liposomes of drugs against both diseases as a strategy to increase therapeutic efficacy and decrease unspecific toxicity. Liposome-carried drugs end up inside Plasmodium-infected red blood cells (pRBCs) and in the phagolysosome system of Leishmania-infected macrophages but some knowledge gaps still obscure subcellular events related to these processes. As a proof of concept, we have used confocal fluorescence microscopy to follow the fate in pRBCs and L. infantum-infected macrophages of quantum dots encapsulated in liposomes, and of lysosomes, Leishmania and Plasmodium parasites, nuclei, and phagosomes. Our data indicate that liposomes merge their lipid bilayers with pRBC plasma membranes but are engulfed by macrophages, where they fuse with lysosomes. Lysosomes have not been observed to join with phagosomes harboring single L. infantum parasites, whereas in phagosomes where the parasite has divided there is lysosome-specific fluorescence with a concomitant disappearance of lysosomes from the cytosol. In later stages, all the lysosome-specific label is found inside phagosomes whereas the phagosomal marker cadaverine strongly stains the macrophage nucleus, suggesting that L. infantum infection induces in its later stages nuclear degeneration and possibly, apoptosis of the host cell. These results indicate that induction of macrophage apoptosis should be explored as a possible strategy used by L. infantum to prepare its egress.

JTD Keywords: Leishmania infantum, Leishmaniasis, Liposomes, Malaria, Nanomedicine, Nanotechnology, Plasmodium falciparum, Quantum dots