Investigation of the mechanism of action of mefloquine and derivatives against the parasite Echinococcus multilocularis.

Alveolar echinococcosis (AE) is caused by infection with the fox tapeworm E. multilocularis. The disease affects humans, dogs, captive monkeys, and other mammals, and it is caused by the metacestode stage of the parasite growing invasively in the liver. The current drug treatment is based on non-parasiticidal benzimidazoles. Thus, they are only limitedly curative and can cause severe side effects. Therefore, novel and improved treatment options for AE are needed. Mefloquine (MEF), an antimalarial agent, was previously shown to be effective against E. multilocularis in vitro and in experimentally infected mice. However, MEF is not parasiticidal and needs improvement for successful treatment of patients, and it can induce strong neuropsychiatric side-effects. In this study, the structure-activity relationship and mode of action of MEF was investigated by comparative analysis of 14 MEF derivatives. None of them showed higher activity against E. multilocularis metacestodes compared to MEF, but four compounds caused limited damage. In order to identify molecular targets of MEF and effective derivatives, differential affinity chromatography combined with mass spectrometry was performed with two effective compounds (MEF, MEF-3) and two ineffective compounds (MEF-13, MEF-22). 1'681 proteins were identified that bound specifically to MEF or derivatives. 216 proteins were identified as binding only to MEF and MEF-3. GO term enrichment analysis of these proteins and functional grouping of the 25 most abundant MEF and MEF-3 specific binding proteins revealed the key processes energy metabolism and cellular transport and structure, as well as stress responses and nucleic acid binding to be involved. The previously described ferritin was confirmed as an exclusively MEF-binding protein that could be relevant for its efficacy against E. multilocularis. The here identified potential targets of MEF will be further investigated in the future for a clear understanding of the pleiotropic effects of MEF, and improved therapeutic options against AE.

In vitro Assessment of Camphor Hydrazone Derivatives as an Agent Against Leishmania amazonensis.

PURPOSE: Due to serious problems with the treatment of leishmaniasis all around the world, here is an urgent need in the search for new drugs that are more effective and safer for the treatment of the various forms of leishmaniasis. Actual therapy is limited and lacks sufficient efficacy due to incomplete elimination of the parasites form of patients. In this sense, we decided to evaluate, by first-time, a series of seventeen camphor hydrazone derivatives (2a-2p) against Leishmania amazonensis. METHODS: The compounds previously synthesized from camphor, an abundant natural compound, were evaluated in vitro against the extra and intracellular forms of Leishmania amazonensis, and murine macrophages. RESULTS: The majority of compounds, fourteen, displayed activity against the intracellular form of the parasite (amastigote) with IC50 values ranging from 21.78 to 58.23 µM, being six compounds active for both forms of the parasite. The compound 2i exhibited higher activity against the amastigote form with the value of IC50 (21.78 µM) close to standard utilized miltefosine (12.74 µM) and selectivity index of at least 6.9. Six compounds displayed activity against promastigote form of Leishmania amazonensis 2g, 2j-2n (41.17-69.59 µM), with the compound 2m being the more active with IC50 = 41.17 µM, 1.9 times less active than the reference drug (IC50 = 21.39 µM). The compound 2m was the more selective to this form, with a selectivity index of at least 3.6. All the compounds were non-cytotoxic to macrophages. CONCLUSIONS: Most compounds showed activity against amastigote form of Leishmania amazonensis, being that they were not cytotoxic to macrophage at the maximum tested concentration, showing the selective property of these compounds. Since amastigotes are the parasite stages that cause the disease in humans, these results highlight the antileishmanial effect of the compounds. This study indicates the possible development of candidates to leishmanicidal drugs from an abundant natural compound of easy access.