189 research outputs found

    Structures, targets and recent approaches in anti-leishmanial drug discovery and development.

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    Recent years have seen a significant improvement in available treatment options for leishmaniasis. Two new drugs, miltefosine and paromomycin, have been registered for the treatment of visceral leishmaniasis (VL) in India since 2002. Combination therapy is now explored in clinical trials as a new treatment approach for VL to reduce the length of treatment and potentially prevent selection of resistant parasites. However there is still a need for new drugs due to safety, resistance, stability and cost issues with existing therapies. The search for topical treatments for cutaneous leishmaniasis (CL) is ongoing. This review gives a brief overview of recent developments and approaches in anti-leishmanial drug discovery and development

    Noncovalent complexation of amphotericin-B with Poly(α-glutamic acid).

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    A noncovalent complex of amphotericin B (AmB) and poly(α-glutamic acid) (PGA) was prepared to develop a safe and stable formulation for the treatment of leishmaniasis. The loading of AmB in the complex was in the range of ∼20-50%. AmB was in a highly aggregated state with an aggregation ratio often above 2.0. This complex (AmB-PGA) was shown to be stable and to have reduced toxicity to human red blood cells and KB cells compared to the parent compound; cell viability was not affected at an AmB concentration as high as 50 and 200 μg/mL respectively. This AmB-PGA complex retained AmB activity against intracellular Leishmania major amastigotes in the differentiated THP-1 cells with an EC50 of 0.07 ± 0.03-0.08 ± 0.01 μg/mL, which is similar to Fungizone (EC50 of 0.06 ± 0.01 μg/mL). The in vitro antileishmanial activity of the complex against Leishmania donovani was retained after storage at 37 °C for 7 days in the form of a solution (EC50 of 0.27 ± 0.03 to 0.35 ± 0.04 μg/mL) and for 30 days as a solid (EC50 of 0.41 ± 0.07 to 0.63 ± 0.25 μg/mL). These encouraging results indicate that the AmB-PGA complex has the potential for further development

    LETM1-Mediated K+ and Na+ Homeostasis Regulates Mitochondrial Ca2+ Efflux

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    HIGHLIGHTS \u2022 Monovalent cation homeostasis is dysregulated upon LETM1 depletion \u2022 K+/H+ exchange activity is decreased in LETM1 knockdown cells \u2022 LETM1 depletion results in K+ accumulation in the mitochondrial matrix \u2022 LETM1 knockdown does not affect expression of major mitochondrial Ca2+ transport modulators \u2022 LETM1-regulated mitochondrial Ca2+ fluxes are dependent on Na+ Ca2+ transport across the inner membrane of mitochondria (IMM) is of major importance for their functions in bioenergetics, cell death and signaling. It is therefore tightly regulated. It has been recently proposed that LETM1\u2014an IMM protein with a crucial role in mitochondrial K+/H+ exchange and volume homeostasis\u2014also acts as a Ca2+/H+ exchanger. Here we show for the first time that lowering LETM1 gene expression by shRNA hampers mitochondrial K+/H+ and Na+/H+ exchange. Decreased exchange activity resulted in matrix K+ accumulation in these mitochondria. Furthermore, LETM1 depletion selectively decreased Na+/Ca2+ exchange mediated by NCLX, as observed in the presence of ruthenium red, a blocker of the Mitochondrial Ca2+ Uniporter (MCU). These data confirm a key role of LETM1 in monovalent cation homeostasis, and suggest that the effects of its modulation on mitochondrial transmembrane Ca2+ fluxes may reflect those on Na+/H+ exchange activity

    Psycho-historical rivalry of complexes in mentality of the Russian autocracy

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    Статья посвящена оригинальной психоаналитической интерпретации становления российской государственности и самодержавия, которая ранее не проводилась в материале русского Средневековья. Автор впервые обращается к психоисторической концепции генезиса самодержавия: от формирования Московского централизованного государства до наших дней. Этот подход опирается на зарубежные психоисторические исследования, начатые Л. Де Мозом, и представляет новую и актуальную стратегию социокультурных исследований. Результаты. История страны предстает как хронология бессознательной конкуренции ведущих психических комплексов российской ментальности. Во-первых, это «новгородский комплекс неполноценности московской аристократии» - итог активного противостояния Москвы и Новгорода, вплоть до падения вечевой республики. Вторым сценарием, вытесняющим «новгородский комплекс», стал «западный комплекс превосходства». Он воспроизводил колониальное отношение империи к своей территории. Третья грань психоистории самодержавия связана с многовековым противостоянием татаро-монгольскому нашествию. Социально-политический уклад татар и других степняков очень сильно повлиял на отечественную культуру, язык и политическую традицию. Он проявился в абсолютно бессознательном комплексе «завистнического сравнения», открытом Т. Вебленом. Московская аристократия без централизованного государства вынуждена сублимировать психоисторический конфликт в форме рационализированной, православно- адаптированной идеологии. В ней была сублимирована и кочевая модель управления геополитическими пространствами, принудительно наложенная на традиционный земледельческий общинно- родовой уклад Древней и Средневековой Руси. Последующая история XV−XVI вв. лишь подтверждает факт сублимации комплексов неполноценности и завистнического сравнения по отношению к татарам.Horde on Moscow Rus predetermined the strategy of «envious» sublimation of the «steppe complex» by Moscow elite, and final abandonment of sociocultural lessons and historical perspective of the «Novgorod complex»

    Pharmacodynamics and Biodistribution of Single-Dose Liposomal Amphotericin B at Different Stages of Experimental Visceral Leishmaniasis.

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    Visceral leishmaniasis is a neglected tropical disease that causes significant morbidity and mortality worldwide. Characterization of the pharmacokinetics and pharmacodynamics of antileishmanial drugs in preclinical models is important for drug development and use. Here we investigated the pharmacodynamics and drug distribution of liposomal amphotericin B (AmBisome) in Leishmania donovani-infected BALB/c mice at three different dose levels and two different time points after infection. We additionally compared drug levels in plasma, liver, and spleen in infected and uninfected BALB/c mice over time. At the highest administered dose of 10 mg/kg AmBisome, >90% parasite inhibition was observed within 2 days after drug administration, consistent with drug distribution from blood to tissue within 24 h and a fast rate of kill. Decreased drug potency was observed in the spleen when AmBisome was administered on day 35 after infection, compared to day 14 after infection. Amphotericin B concentrations and total drug amounts per organ were lower in liver and spleen when AmBisome was administered at the advanced stage of infection and compared to those in uninfected BALB/c mice. However, the magnitude of difference was lower when total drug amounts per organ were estimated. Differences were also noted in drug distribution to L. donovani-infected livers and spleens. Taken together, our data suggest that organ enlargement and other pathophysiological factors cause infection- and organ-specific drug distribution and elimination after administration of single-dose AmBisome to L. donovani-infected mice. Plasma drug levels were not reflective of changes in drug levels in tissues

    Pharmacodynamics and cellular accumulation of amphotericin B and miltefosine in Leishmania donovani-infected primary macrophages.

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    Objectives: We examined the in vitro pharmacodynamics and cellular accumulation of the standard anti-leishmanial drugs amphotericin B and miltefosine in intracellular Leishmania donovani amastigote-macrophage drug assays. Methods: Primary mouse macrophages were infected with L. donovani amastigotes. In time-kill assays infected macrophages were exposed to at least six different concentrations of serially diluted drugs and the percentage of infected macrophages was determined after 6, 12, 24, 48, 72 and 120 h of exposure. Cellular drug accumulation was measured following exposure to highly effective drug concentrations for 1, 6, 24, 48 and 72 h. Data were analysed through a mathematical model, relating drug concentration to the percentage of infected cells over time. Host cell membrane damage was evaluated through measurement of lactate dehydrogenase release. The effect of varying the serum and albumin concentrations in medium on the cellular accumulation levels of miltefosine was measured. Results: Amphotericin B was more potent than miltefosine (EC50 values of 0.65 and 1.26 μM, respectively) and displayed a wider therapeutic window in vitro. The kinetics of the cellular accumulation of amphotericin B was concentration- and formulation-dependent. At an extracellular concentration of 10 μM miltefosine maximum cellular drug levels preceded maximum anti-leishmanial kill. Miltefosine induced membrane damage in a concentration-, time- and serum-dependent manner. Its cellular accumulation levels increased with decreasing amounts of protein in assay medium. Conclusions: We have developed a novel approach to investigate the cellular pharmacology of anti-leishmanial drugs that serves as a model for the characterization of new drug candidates

    Distinct activation mechanisms trigger the trypanocidal activity of DNA damaging prodrugs

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    Quinone-based compounds have been exploited to treat infectious diseases and cancer, with such chemicals often functioning as inhibitors of key metabolic pathways or as prodrugs. Here, we screened an aziridinyl 1,4-benzoquinone (ABQ) library against the causative agents of trypanosomiasis, and cutaneous leishmaniasis, identifying several potent structures that exhibited EC50 values of <100 nM. However, these compounds also displayed significant toxicity towards mammalian cells indicating that they are not suitable therapies for systemic infections. Using anti-T. brucei ABQs as chemical probes, we demonstrated that these exhibit different trypanocidal modes of action. Many functioned as type I nitroreductase (TbNTR) or cytochrome P450 reductase (TbCPR) dependent prodrugs that, following activation, generate metabolites which promote DNA damage, specifically interstrand crosslinks (ICLs). Trypanosomes lacking TbSNM1, a nuclease that specifically repairs ICLs, are hypersensitive to most ABQ prodrugs, a phenotype exacerbated in cells also engineered to express elevated levels of TbNTR or TbCPR. In contrast, ABQs that contain substituent groups on the biologically active aziridine do not function as TbNTR or TbCPR-activated prodrugs and do not promote DNA damage. By unravelling how ABQs mediate their activities, features that facilitate the desired anti-parasitic growth inhibitory effects could be incorporated into new, safer compounds targeting these neglected tropical diseases

    Shape transformations of giant vesicles : extreme sensitivity to bilayer asymmetry

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    Shape transformations of vesicles of lecithin (DMPC) in water are induced by changing the temperature which effectively changes the volume-to-area ratio. Three different routes are found which include i) symmetric-asymmetric re-entrant transitions from a dumbbell to pear-shaped state, ii) the expulsion of a smaller vesicle (budding), and iii) discocytestomatocyte transitions. All of these shape transformations are explained within a model for the bending energy of the bilayer which assumes i) that the two monolayers do not exchange lipid molecules, and ii) that the two adjacent monolayers exhibit a small difference in their thermal expansivities which is easily produced, e.g., by residual impurities

    Vesicle shapes and shape transformations: a systematic study

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    In our contribution we report a systematic experimental and theoretical study on shape transformations. In order to avoid the above mentioned complications we have investigated vesicles which consist of electrically neutral lipids (that is phosphatidylcholine) in Millipore water. We find, that even for such a simple system a change in temperature can lead to three different types of shape transformations. Theoretically, we discuss shape transformations within two well established curvature models, (i) the bilayer coupling model of Svetina and Zeks and (ii) the spontaneous curvature model of Helfrichs.A comparison leads to the conclusion that the observed shape transformations can well be explained within the bilayer coupling model provided a small asymmetry in the thermal expansivities of both monolayers is assumed. In some cases, such an asymmetry is not required