Leandro S. Sangenito

The potent cell permeable calpain inhibitor MDL28170 affects the interaction of Leishmania amazonensis with macrophages and shows anti-amastigote activity

Since the discovery of the28 first drugs used in leishmaniasis treatment up to now, the search for compounds with anti-Leishmania activity without toxic effects and able to overcome the emergency of resistant strains remains a major goal to combat this neglected disease. With this in mind, in the present work, we evaluated the effects of the calpain inhibitor MDL28170 on the interaction process of Leishmania amazonensis promastigote forms with murine peritoneal macrophages and on the intracellular amastigotes. Our results showed that the calpain inhibitor MDL28170 at 15 and 30μM significantly reduced the interaction process of promastigotes with macrophages by 16% and 41%, respectively. The inhibitor was also able to drastically reduce the number of infected macrophages in a time- and dose-dependent manner: after only 24h, MDL28170 was able to significantly diminish the infection rate, presenting an IC50 value of 18.2μM for amastigotes. The treatment with MDL28170 did not alter the nitric oxide production, but the production of TNF-α was significantly raised. Altogether, the results presented here contribute to the search of new proteolytic inhibitors able to act in a selective and effective manner against the diseases caused by trypanosomatids.

Deciphering the effects of nelfinavir and lopinavir on epimastigote forms of Trypanosoma cruzi

• Some aspects of T. cruzi epimastigotes physiology and biochemistry are demonstrated.

Rutin derivatives obtained by transesterification reactions catalyzed by Novozym 435: Antioxidant properties and absence of toxicity in mammalian cells

Flavonoids are one of the most important and diversified phenolic groups among products of natural origin. An important property of this metabolite class is the antioxidant action. This study evaluated the antioxidant and cytotoxic activities and oxidative stress of transesterification products of the flavonoid rutin, catalyzed by Novozym® 435. The presence of monoacetate and diacetate was confirmed by quantitative evaluation of the retention times (rutin, 15.68 min; rutin monoacetate, 18.14 min; and rutin diacetate, 18.57 min) and by the data from LC-MS and NMR 1H and 13C. The experiment showed excellent conversion values of 96% in total acetates (rutin monoacetate and diacetate). These results confirmed that rutin derivatives have antioxidant potential, as evaluated by the ORAC method (rutin standard: 0.53 ± 0.08 μM Trolox/g and rutin derivatives: 2.33 ± 1.08 μM Trolox/g) and also show low cytotoxicity in human and animal cells. Rutin derivatives reduced the production of reactive oxygen species in RAW macrophages as well. Many qualities attributed to rutin derivatives make them promising potential candidates for use as nutraceuticals, including their high amounts of antioxidants, biological potential and low toxicity, which contribute to the reduction of oxidative stress.

Ultrastructural viewpoints on the interaction events of Scedosporium apiospermum conidia with lung and macrophage cells

BACKGROUND Scedosporium apiospermum is a ubiquitous, emerging and multidrug-resistant fungal pathogen with still rather unknown virulence mechanisms. OBJECTIVES/METHODS The cellular basis of the in vitro interaction between fungi and host cells/tissues is the determinant factor for the development of a successful in vivo infection. Herein, we evaluated the interaction of S. apiospermum conidia with lung epithelial (A549), lung fibroblast (MRC-5) and RAW 264.7 macrophages by light and scanning/transmission electron microscopy. FINDINGS After 4 h of fungi-host cell contact, the percentage of infected mammalian cells and the number of fungi per infected cell was measured by light microscopy, and the following association indexes were calculated for A549, MRC-5 and macrophage cells: 73.2 ± 25.9, 69.7 ± 22.5 and 59.7 ± 11.1, respectively. Both conidia and germinated conidia were regularly observed interacting with the evaluated cells, with a higher prevalence of non-germinated conidia. Interestingly, nests of germinated conidia were evidenced at the surface of lung cells by scanning electron microscopy. Some germination projections and hyphae were seen penetrating/evading the mammalian cells. Furthermore, internalised conidia were seen within vacuoles as visualised by transmission electron microscopy. MAIN CONCLUSIONS The present study contributes to a better understanding of S. apiospermum pathogenesis by demonstrating the first steps of the infection process of this opportunistic fungus.

Primary evidence of the mechanisms of action of HIV aspartyl peptidase inhibitors on Trypanosoma cruzi trypomastigote forms

The development of HIV aspartyl peptidase inhibitors (HIV-PIs) and their introduction into AIDS therapy preceded a significant decrease in the incidence, morbidity and mortality of relevant protozoan co-infections. However, few data are available about how HIV-PIs act on pathogenic parasites, such as Trypanosoma cruzi, the etiological agent of Chagas disease. Therefore, the aim of the present work was to evaluate different physiological aspects of the treatment of the infective trypomastigote forms of T. cruzi with the HIV-PIs, nelfinavir and lopinavir. At the LD50/4 h doses, both HIV-PIs significantly reduced the trypomastigote size and markedly increased the granularity/complexity. Transmission electron microscopy analysis associated to biochemical assays permitted definition of the main HIV-PIs targets in the parasite. Lopinavir and nelfinavir induced (i) plasma membrane shedding, particularly in the flagellar region, which drastically affected parasite integrity; (ii) strong mitochondrial swelling with rare matrix fragmentation, which were linked to severely reduced hydrolytic activity of dehydrogenases and organelle membrane depolarization; (iii) increased generation of reactive oxygen species (ROS); (iv) dilation of both nuclear envelope (without DNA disruption) and endoplasmic reticulum (with formation of autophagosomes), and (v) accumulation of intracellular lipid droplets, revealing a typical lipid metabolism disorder. Collectively, our study demonstrated that nelfinavir and lopinavir target vital cellular structures of trypomastigotes, culminating in irreversible metabolic injuries that lead to T. cruzi death.

Asymmetric peptidomimetics containing L-tartaric acid core inhibit the aspartyl peptidase activity and growth of Leishmania amazonensis promastigotes

Aspartyl-type peptidases are promising chemotherapeutic targets in protozoan parasites. In the present work, we identified an aspartyl peptidase activity from the soluble extract of Leishmania amazonensis promastigotes, which cleaved the fluorogenic peptide 7-methoxycoumarin-4-acetyl-Gly-Lys-Pro-Ile-Leu-Phe-Phe-Arg-Leu-Lys(DNP)-D-Arg-amide (cathepsin D substrate) under acidic pH conditions at 37°C, showing a KM of 0.58 μM and Vmax of 129.87 fluorescence arbitrary units/s mg protein. The leishmanial aspartyl peptidase activity was blocked by pepstatin A (IC50 = 6.8 μM) and diazo-acetyl-norleucinemetilester (IC50 = 10.2 μM), two classical aspartyl peptidase inhibitors. Subsequently, the effects of 6 asymmetric peptidomimetics, containing L-tartaric acid core, were tested on both aspartyl peptidase and growth of L. amazonensis promastigotes. The peptidomimetics named 88, 154 and 158 promoted a reduction of 50% on the leishmanial aspartyl peptidase activity at concentrations ranging from 40 to 85 μM, whereas the peptidomimetic 157 was by far the most effective, presenting IC50 of 0.04 μM. Furthermore, the peptidomimetics 157 and 154 reduced the parasite proliferation in a dose-dependent manner, displaying IC50 values of 33.7 and 44.5 µM, respectively. Collectively, the peptidomimetic 157 was the most efficient compound able to arrest both aspartyl peptidase activity and leishmanial proliferation, which raises excellent perspectives regarding its use against this human pathogenic protozoan.