In Vitro and In Vivo Activity of a Palladacycle Complex on Leishmania (Leishmania) amazonensis

Leishmaniasis is an important public health problem with an estimated annual incidence of 1.5 million of new human cases of cutaneous leishmaniasis and 500,000 of visceral leishmaniasis. Treatment of the diseases is limited by toxicity and parasite resistance to the drugs currently in use, validating the need to develop new leishmanicidal compounds. We evaluated the killing by the palladacycle complex DPPE 1.2 of Leishmania (Leishmania) amazonensis, an agent of human cutaneous leishmaniasis in the Amazon region, Brazil. DPPE 1.2 destroyed promastigotes of L. (L.) amazonensis in vitro at nanomolar concentrations, whereas intracellular amastigotes were killed at drug concentrations 10-fold less toxic than those displayed to macrophages. L. (L.) amazonensis-infected BALB/c mice treated by intralesional injection of DPPE 1.2 exhibited a significant decrease of foot lesion sizes and a 97% reduction of parasite burdens when compared to untreated controls. Additional experiments indicated the inhibition of the cathepsin B activity of L. (L.) amazonensis amastigotes by DPPE 1.2. Further studies are needed to explore the potential of DPPE 1.2 as an additional option for the chemotherapy of leishmaniasis

In Vitro and in Vivo Activity of an Organic Tellurium Compound on Leishmania (Leishmania) chagasi

Tellurium compounds have shown several biological properties and recently the leishmanicidal effect of one organotellurane was demonstrated. These findings led us to test the effect of the organotellurium compound RF07 on Leishmania (Leishmania) chagasi, the agent of visceral leishmaniasis in Latin America. in vitro assays were performed in L. (L.) chagasi-infected bone marrow derived macrophages treated with different concentrations of RF07. in in vivo experiments Golden hamsters were infected with L. (L.) chagasi and injected intraperitoneally with RF07 whereas control animals received either Glucantime or PBS. the effect of RF07 on cathepsin B activity of L. (L.) chagasi amastigotes was assayed spectrofluorometrically using fluorogenic substrates. the main findings were: 1) RF07 showed significant leishmanicidal activity against intracellular parasites at submicromolar concentrations (IC50 of 529.7+/-26.5 nM), and the drug displayed 10-fold less toxicity to macrophages (CC50 of 5,426+/-272.8 nM); 2) kinetics assays showed an increasing leishmanicidal action of RF07 at longer periods of treatment; 3) one month after intraperitoneal injection of RF07 L. (L.) chagasi-infected hamsters showed a reduction of 99.6% of parasite burden when compared to controls that received PBS; 4) RF07 inhibited the cathepsin B activity of L. (L.) chagasi amastigotes. the present results demonstrated that the tellurium compound RF07 is able to destroy L. (L.) chagasi in vitro and in vivo at concentrations that are non toxic to the host. We believe these findings support further study of the potential of RF07 as a possible alternative for the chemotherapy of visceral leishmaniasis

Molecular structure of organotellurane RF07.

<p>Molecular structure of organotellurane RF07.</p

Effect of RF07 on proteolytic activity of <i>L. (L.) chagasi</i> amastigotes.

<p>A - Fluorogenic substrates with different specificities for cathepsin-like proteases were incubated with extracts of <i>L. (L.) chagasi</i> amastigotes in the presence of DTT and increasing concentrations of RF07, as indicated. B and C - Fluorogenic substrate specific for cathepsin B-like proteases was incubated with extracts of <i>L. (L.) chagasi</i> in presence of increasing concentrations of either RF07 (B) or CA074 (C).</p

Toxicity evaluation in <i>L. (L.) chagasi</i>-infected hamster after treatment with RF07.

<p>Serum concentrations of albumin (A), transaminases (B) and creatinine (C) in <i>L. (L.) chagasi</i>-infected hamsters 15 days after treatment with either RF07 or Glucantime. The reference values are: albumin: 3.2–4.3 g/dl; transaminases: ALT: 53–202 UI/L, AST: 28–107 UI/L; creatinine: 0.5–0.6 mg/dl.</p

Kinetics of RF07 leishmanicidal activity on <i>L. (L.) chagasi</i>-infected macrophages.

<p>Macrophages were infected with amastigotes of <i>L. (L.) chagasi</i>, treated with the drugs for 3, 5 and 7 days and the infection index was calculated after each period. ^*<i>P</i><0.001 compared to control.</p

Treatment of <i>L. (L.) chagasi</i>-infected hamsters with RF07.

<p>Spleen parasite load of <i>L. (L.) chagasi</i>-infected hamsters treated with either different concentrations of RF07 or Glucantime was determined by the limiting dilution method one month after end of the treatment. ^*<i>P</i><0.001 compared to control.</p

Parasite load in foot lesions of <i>L. (L.) amazonenis</i>-infected BALB/c mice treated with DPPE 1.2.

<p>Number of parasites recovered by limiting dilution from <i>L. (L.) amazonensis</i>-infected mice treated with DPPE 1.2. Parasites were quantified one month after interruption of treatment. ^*<i>P</i><0.001.</p

Effect of DPPE 1.2 on proteolytic activity of <i>L. (L.) amazonensis</i>.

<p>A - Extracts of promastigotes (P) and amastigotes (AM) of <i>L. (L.) amazonensis</i> were separated by SDS-PAGE on a 10% acrylamide gel containing 0.1% gelatin under nonreducing conditions. Numbers at left indicate apparent molecular masses in kilodaltons. B - Fluorogenic substrates with different specificities for cathepsin-like proteases were incubated with extracts of <i>L. (L.) amazonensis</i> amastigotes in absence or presence of DPPE 1.2, as indicated. C – Fluorogenic substrate specific for cathepsin B-like proteases was incubated with extracts of <i>L. (L.) amazonensis</i> in presence of increasing concentrations of DPPE 1.2.</p