Sensitivities of Leishmania species to hexadecylphosphocholine (miltefosine), ET-18-OCH(3) (edelfosine) and amphotericin B

Successful Treatment with Miltefosine of Disseminated Cutaneous Leishmaniasis in a Severely Immunocompromised Patient Infected with HIV-1

We describe here a case of disseminated cutaneous leishmaniasis due to Leishmania major in a severely immunocompromised patient from Burkino Faso, Africa, who is infected with human immunodeficiency virus-1. The skin lesions failed to respond to full treatment courses of amphotericin B, sodium stibogluconate, and liposomal amphotericin B but were successfully treated with miltefosine, an alkylphosphocholine analogue.

Leishmanicidal activity of edelfosine, miltefosine and ilmofosine

The anti-proliferative action of three alkyl-lysophospholipid derivatives, edelfosine (ET-OCH), miltefosine (Hexadecylphosphocholine), and ilmofosine (BM 14.440) has been studied on the promastigotes and amastigotes of Leishmania donovani. The effect of the three drugs has previously been studied, but the action mode was not clearly elucidated. In this study the effect on the intracellular amastigote forms was evaluated by two different methods: the traditional method, counting the amastigotes within the macrophages stained with Giemsa; and by a new method, staining the nuclear macrophages and amastigotes with ethidium bromide and counting the different population by flow cytometry. This new method, based on the flow cytometry, shows an advantage for evaluating the anti-proliferative effects in intracellular parasites. The ED50 were calculated for the drug activity after 72 hr, and for the three alkyl-lysophospholipid derivatives it were in the range of 26.73-33.31 microM against promastigotes and in the range of 16.46-23.16 against amastigotes. Also, studying the effect against macrophages J774A1, the ED50 were in the range of 24.28-26.38 microM. The effect of the alkyl-lysophospholipids in the macromolecular biosynthesis of the Leishmania donovani, was studied comparing the incorporation of labelled analogues ([3H] thymidine, [3H] uridine and [3H] leucine), respectively, in the DNA, RNA, and proteins of the flagellates treated. Miltefosine was the most active of the alkyl-lysophospholipids, especially in the inhibition of the RNA synthesis. The three compounds studied show high in vitro activity against L. donovani promastigotes and amastigotes.

Antiprotozoal activity of Brazilian plant extracts from isoquinoline alkaloid-producing families

Leishmaniasis and Chagas disease afflict the poorest countries in the world. The Brazilian flora represents a rich source for the screening of potential antiparasitic compounds. In this work, we tested the total alkaloid and ethanol extracts of nine different plants from Brazilian families which produce isoquinoline alkaloids, to determine their in vitro antiparasitic effect against L. chagasi and T. cruzi parasites. Promastigotes of L. chagasi were shown to be susceptible only to the total alkaloid extracts of A. crassiflora (EC50 value = 24.89 microg/ml), A. coriacea (EC50 value = 41.60 microg/ml), C. ovalifolia (EC50 value = 63.88 microg/ml) and G. australis (EC50 value = 37.88 microg/ml). Except for the G. australis total alkaloids, all the three extracts presented a considerable activity when tested against intracellular amastigotes. The most effective alkaloid extracts were those from A. crassiflora and C. ovalifolia, which reduced the number of infected macrophages at 25 microg/ml by 86.1% and 89.8%, respectively. Among the 18 tested extracts, 16 showed anti-Trypanosoma activity. Eight extracts (A. crassiflora, A. coriacea, C. ovalifolia, D. furfuracea, D. lanceolata, S. guianensis, X. emarginata and G. australis) were the most effective against the trypomastigotes, killing approximately 100% of the parasites at the maximal concentration of 100 microg/ml. Cytotoxicity against mammalian cells was evaluated for all extracts, but potential ones showed little or no cytotoxicity and a considerable antiparasitic effect, including D. furfuracea, D. lanceolata, G. australis, S. guianensis and X. emarginata. Plants are a rich source of natural compounds, and a powerful tool for the development of new arsenals for the therapy of protozoan diseases.

Therapeutic Potential of New Pt(II) and Ru(III) Triazole-Pyrimidine Complexes against Leishmania donovani

We have already established an in vitro culture system using murine macrophages infected with Leishmania donovani in which the time course of parasite growth is determined quantitatively. We adopted this system for the screening of three triazole-pyrimidine derivatives that would ideally prove to be effective against L. donovani with no toxicity to the host cell. Amphotericin B deoxycholate was used as the standard drug and gave a IC50 value of 3.89 microg/ml. The three triazole-pyrimidine compounds assayed have been reported to be potent growth inhibitors of L. donovani promastigote and amastigote stages. Compounds SPIV and SPVI exhibited the highest toxicity for extracellular forms of parasites, with IC50 values of 19.95 and 21.61 microg/ml, respectively. The triazole-pyrimidine SPV, although to a lower degree, also showed pronounced effects against promastigote forms with IC50 of 33.14 microg/ml. Drug activity was higher against amastigote than against promastigote stages. The compounds SPIV and SPVI interfered with the synthesis of macromolecules, affecting primarily DNA at the lower concentration tested (5 microg/ml), while SPV also showed interference, though to a lesser extent, and at a higher concentration (15 microg/ml) the percentage of inhibition rose considerably. The synthesis or RNA and proteins was also depressed significantly by these compounds at administration rates of 15 microg/ml. Ultrastructural alterations were evident in the main organelles of L. donovani (nucleus, kinetoplast, mitochondria), after the addition of the three compounds at a concentration of 5 microg/ml, to the in vitro culture. The in vitro promastigote forms of L. donovani can degrade glucose to carbon dioxide, and part of the carbon skeleton of the glucose is excreted as end metabolites. The excretion of these metabolites, mainly acetate, was also inhibited by the three compounds assayed, suggesting that this could be due to a direct effect on some of the enzymes related to this fermentation pathway or to the inhibition exerted by the compounds on enzyme synthesis.

Effect of the lysophospholipid analogues edelfosine, ilmofosine and miltefosine against Leishmania amazonensis

OBJECTIVES

Analysis of the effect of edelfosine, ilmofosine and miltefosine on Leishmania amazonensis and of potential targets of these lysophospholipid analogues.

METHODS

Quantification and ultrastructural analysis of the effect of lysophospholipid analogues on promastigote forms and on infected peritoneal macrophages, and flow cytometry analysis of treated promastigotes labelled with propidium iodide and rhodamine 123 (Rh123).

RESULTS

The lysophospholipid analogues presented potent antiproliferative activity with IC50/3 days of 1.9-3.4 microM for promastigotes and 4.2-9.0 microM for intracellular amastigotes. Treatment with these analogues in Schneider medium for 1 day led to a dose-dependent decrease in Rh123 fluorescence, an effect more accentuated in edelfosine-treated parasites, suggesting interference with the potential of the mitochondrial membrane. In both forms of L. amazonensis, edelfosine induced extensive mitochondrial damage, multinucleation and, in promastigotes, also led to plasma membrane alterations, formation of autophagic structures and membranous arrangements inside the flagellar pocket.

CONCLUSIONS

The alkylglycerophosphocholines edelfosine and ilmofosine were more active than the alkylphosphocholine miltefosine against promastigotes and intracellular amastigotes of L. amazonensis, and ultrastructural and flow cytometry data indicate the mitochondrion as a target of edelfosine.

Possible mechanism of miltefosine-mediated death of Leishmania donovani

Miltefosine causes leishmanial death, but the possible mechanism(s) of action is not known. The mode of action of miltefosine was investigated in vitro in Leishmania donovani promastigotes as well as in extra- and intracellular amastigotes. Here, we demonstrate that miltefosine induces apoptosis-like death in L. donovani based on observed phenomena such as nuclear DNA condensation, DNA fragmentation with accompanying ladder formation, and in situ labeling of DNA fragments by the terminal deoxyribonucleotidyltransferase-mediated dUTP-biotin nick end labeling method. Understanding of miltefosine-mediated death will facilitate the design of new therapeutic strategies against Leishmania parasites.

The efficacy of enrofloxacin, alone or combined with metronidazole, in the therapy of canine leishmaniasis

We evaluated the efficacy of enrofloxacin, alone or combined with metronidazole, against Leishmania infantum. The in vitro activity of this fluoroquinolone was assessed using two different methods: a direct test aimed at assessing the drug activity on the parasite, and an indirect test aimed at evaluating the drug effect on macrophage killing, lymphomonocyte activation and nitric oxide production. An in vivo test was also performed on 36 dogs with leishmaniasis, subdivided into three groups, one treated with enrofloxacin, another with enrofloxacin plus metronidazole, and a control group with meglumine antimoniate. The direct test did not show any action of enrofloxacin on the parasite, while the indirect testing showed an enhancement of macrophage killing and an increase in nitric oxide production. These findings show that enrofloxacin does not exert a direct anti-leishmanial activity in vitro. However, on the basis of the positive immunostimulation results shown in vitro and the clinical improvement, particularly of the cutaneous lesions, obtained in several dogs in the in vivo trial, the use of enrofloxacin in association with a specific anti-leishmanial drug can be proposed in the therapeutic protocol of canine leishmaniasis.

Miltefosine induces apoptosis-like death in Leishmania donovani promastigotes

Miltefosine (hexadecylphosphocholine [HePC]) has proved to be a potent oral treatment for human visceral leishmaniasis due to Leishmania donovani. The molecular mechanisms that contribute to the antileishmanial activity of HePC are still unknown. We report that in wild-type promastigotes of Leishmania donovani HePC is able to induce a cell death process with numerous cytoplasmic, nuclear, and membrane features of metazoan apoptosis, including cell shrinkage, DNA fragmentation into oligonucleosome-sized fragments, and phosphatidylserine exposure. None of these changes were detected in an HePC-resistant clone treated with the same drug concentration. Therefore, HePC does not appear to kill L. donovani promastigotes by a direct toxic mechanism but, rather, kills the promastigotes by an indirect one. Pretreatment of wild-type promastigotes with two broad caspase inhibitors, z-Val-Ala-DL-Asp(methoxy)-fluoromethylketone and Boc-Asp(methoxy)-fluoromethylketone, as well as a broad protease inhibitor, calpain inhibitor I, prior to drug exposure interfered with DNA fragmentation but did not prevent cell shrinkage or phosphatidylserine externalization. These data suggest that at least part of the apoptotic machinery operating in wild-type promastigotes involves proteases. Identification of the death-signaling pathways activated in HePC-sensitive parasites appears to be essential for a better understanding of the molecular mechanisms of action and resistance in these parasites.

Characterisation of Leishmania donovani promastigotes resistant to hexadecylphosphocholine (miltefosine)

Leishmania donovani promastigote lines resistant to hexadecylphosphocholine (HePC, miltefosine) at 2.5, 5.0, 10.0, 20.0 and 40.0 microM were developed in vitro by continuous step-wise drug pressure. The 40 microM line was 15 times more resistant to HePC than the wild-type clone and showed cross-resistance to the ether lipid ET-18-OCH3 (edelfosine) but not to the standard anti-leishmanial drugs. Resistance was stable up to 12 weeks in drug-free culture medium. No amplification of specific genes, including the multidrug resistance P-glycoprotein gene, could be detected in the resistant parasites.

Miltefosine (Impavido): the first oral treatment against leishmaniasis

Miltefosine is a novel antileishmanial drug that has significant selectivity in both in vitro and in vivo models. Clinical efficacy was demonstrated for the treatment of visceral leishmaniasis with the advantage of oral administration over the currently recommended antileishmanial drugs that require parenteral administration. Miltefosine produces high cure rates also in patients resistant to the standard antimonial therapy.

Lem3p is essential for the uptake and potency of alkylphosphocholine drugs, edelfosine and miltefosine

The alkylphosphocholine class of drugs, including edelfosine and miltefosine, has recently shown promise in the treatment of protozoal and fungal diseases, most notably, leishmaniasis. One of the major barriers to successful treatment of these infections is the development of drug resistance. To understand better the mechanisms underlying the development of drug resistance, we performed a combined mutant selection and screen in Saccharomyces cerevisiae, designed to identify genes that confer resistance to the alkylphosphocholine drugs by inhibiting their transport across the plasma membrane. Mutagenized cells were first selected for resistance to edelfosine, and the initial collection of mutants was screened a second time for defects in internalization of a short chain, fluorescent (7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD))-labeled phosphatidylcholine reporter. This approach identified mutations in a single gene, YNL323W/LEM3, that conferred resistance to alkylphosphocholine drugs and inhibited internalization of NBD-labeled phosphatidylcholine. Loss of YNL323W/LEM3 does not confer resistance to N-nitroquinilone N-oxide or ketoconazole and actually increases sensitivity to cycloheximide. The defect in internalization is specific to NBD-labeled phosphatidylcholine and phosphatidylethanolamine. Labeled phosphatidylserine is internalized at normal levels in lem3 strains. LEM3 is a member of an evolutionarily conserved family and has two homologues in S. cerevisiae. Single point mutations that produce resistance to alkylphosphocholine drugs and inhibition of NBD-labeled phosphatidylcholine internalization were identified in several highly conserved domains. These data demonstrate a requirement for Lem3p expression for normal phosphatidylcholine and alkylphosphocholine drug transport across the plasma membrane of yeast.

The activity of diguanidino and 'reversed' diamidino 2,5-diarylfurans versus Trypanosoma cruzi and Leishmania donovani

The in vitro activity of 20 dicationic molecules containing either diguanidino or reversed amidine cationic groups were evaluated versus Trypanosoma cruzi and Leishmania donovani. The most active compounds were in the reversed amidine series and six exhibited IC(50) values of less than 1 micro mol versus T. cruzi and five gave similar values versus L. donovani.

In vitro antileishmanial effects of antibacterial diterpenes from two Ethiopian Premna species: P. schimperi and P. oligotricha

BACKGROUND

Three antibacterial diterpenes: (5R,8R,9S,10R)-12-oxo-ent-3,13(16)-clerodien-15-oic acid (1), 16-hydroxy-clerod-3,13(14)-diene-15,16-olide (2) and ent-12-oxolabda-8,13(16)-dien-15-oic acid (3) were previously isolated form Premna schimperi and P. oligotricha. Since andrographolide and other structurally related diterpenes were shown to have antileishmanial activity, the aim of the present study was to assess the in vitro effect of premna diterpenes against Leishmania aethiopica; the causative agent of cutaneous leishmaniasis in Ethiopia.

RESULTS

The diterpenes showed potent concentration-dependant suppressive effect on the viability of axenically cultured amastigotes of L. aethiopica. The clerodane diterpenes 1 and 2 were most active (LD50 values 1.08 and 4.12 microg/ml respectively) followed by andrographolide and 3. Compounds 1 and 2 appear to be over 20 and 10-times respectively more selective to leishmania amastigotes than the permissive host cell line, THP-1 cells or the promastigotes stage of the parasites.

CONCLUSION

The clerodane diterpenes (1, 2) which were more potent and selective than labdanes (andrographolide and 3) are promising for further studies and/or development.

Antileishmanial ring-substituted ether phospholipids

Three series of ring-substituted ether phospholipids were synthesized carrying N,N,N-trimethylammonium, N-methylpiperidino, or N-methylmorpholino headgroups. The first series is substituted by 2-cyclohexyloxyethyl or 2-(4-alkylidenecyclohexyloxy)ethyl groups, the second series by cyclohexylidenealkyl or adamantylidenealkyl moieties, and the third series by 2-aryloxyethyl or 6-aryloxyhexyl groups in the alkyl portion of the molecule. The antileishmanial activity of the new compounds was evaluated in vitro against the promastigote forms of L. donovani and L. infantum using an MTT (3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide)-based microassay as a marker of cell viability. Analogues 12, 15, 24, 30, 32, 41, 43, and 45 were more potent than the control compound miltefosine (hexadecylphosphocholine) against both L. donovani and L. infantum while, derivatives 13 and 42 were equipotent to miltefosine. Analogues 16, 17, 19, 20 were more potent than miltefosine against L. infantumand compounds 27, 31, 44 were more active than miltefosine against L. donovani. Differential scanning calorimetry (DSC) was used to probe the role of individual ether phospholipids on the physicochemical properties of model membranes. The DSC scans showed that the active compounds have a more profound effect on the thermotropic properties of model membrane bilayers than the less active ones.

Antiprotozoal activities of phospholipid analogues

The antiprotozoal activity of phospholipid analogues, originally developed as anti-cancer drugs, has been determined in the past decade. The most susceptible parasites are Leishmania spp. and Trypanosoma cruzi with activity also shown against Trypanosoma brucei spp., Entamoeba histolytica and Acanthamoeba spp. Miltefosine, an alkylphosphocholine, was registered for the oral treatment of visceral leishmaniasis (VL) in India in March 2002. This review will focus on the biological activities of phospholipid analogues. Biochemical and molecular targets and mechanism(s) of action have been studied extensively in tumor cells but have not been determined in protozoa.

Proinflammatory and cytotoxic effects of hexadecylphosphocholine (miltefosine) against drug-resistant strains of Trypanosoma cruzi

The increased resistance of the protozoan parasite Trypanosoma cruzi to nitro derivatives is one of the major problems for the successful treatment of Chagas' disease. In the present study, we have tested the effects of 1-O-hexadecylphosphocholine (miltefosine) against strains of T. cruzi that are partially resistant (strain Y) and highly resistant (strain Colombiana) to the drugs in clinical use. As expected, epimastigotes of strain Colombiana showed higher levels of resistance to benznidazole than those of strain Y. However, the level of resistance to miltefosine was the same for both strains. This alkylphospholipid was also extremely toxic against intracellular amastigotes of both strains. This ether-lipid analogue induced in a dose-dependent manner the production of tumor necrosis factor alpha and nitric oxide (NO) radicals by infected and noninfected macrophages, suggesting that miltefosine may activate macrophages in vitro. Nevertheless, the cytotoxic effect of miltefosine against intracellular amastigotes was independent of the amount of NO produced by the infected macrophages since the same dose-response curves for miltefosine were observed when the NO production was blocked by the NO synthase inhibitor N(G)-monomethyl-L-arginine monoacetate. Preliminary in vivo studies with BALB/c mice infected with strain Y indicated that oral miltefosine promoted survival and reduced the parasitemia to levels comparable to those observed when benznidazole was used. Four months after treatment, no parasites were detected in the blood or spleen tissue sections maintained in culture. Together, these results support the hypothesis that miltefosine may be used for the treatment of Chagas' disease, including cases caused by resistant strains of T. cruzi.

Choline transport in Leishmania major promastigotes and its inhibition by choline and phosphocholine analogs

Phosphatidylcholine is the most abundant phospholipid in the membranes of the human parasite Leishmania. The metabolic pathways leading to its biosynthesis are likely to play a critical role in parasite development and survival and may offer a good target for antileishmanial chemotherapy. Phosphatidylcholine synthesis via the CDP-choline pathway requires transport of the choline precursor from the host. Here, we report the first characterization of choline transport in this parasite, which is carrier-mediated and exhibits Michaelis-Menten kinetics with an apparent K(m) value of 2.5 microM for choline. This process is Na(+)-independent and requires an intact proton gradient to be fully functional. Choline transport into Leishmania is highly specific for choline and is inhibited by the choline carrier inhibitor hemicholinium-3, the channel blocker quinacrine, the antimalarial aminoquinolines quinine and quinidine, the antileishmanial phosphocholine analogs, miltefosine and edelfosine, and by choline analogs, most of which have antimalarial activities. Most importantly, choline analogs kill the promastigote form of the parasite in vitro in the low micromolar range. These results set the stage for the use of choline analogs in antileishmanial chemotherapy and shed new lights on the mechanism of action of the leishmanicidal phosphocholine analogs.