Structure- and Ligand-Based Approaches to Evaluate Aporphynic Alkaloids from Annonaceae as Multi-Target Agent Against Leishmania donovani.

BACKGROUND: Leishmaniasis is a neglected disease that affects 15 million people around the world. Many limitations are associated to the treatment as high cost and toxicity. Several classes of natural substances with proven leishmanicidal activity were reported in the literature. Phytochemsitry study of Anaxagorea dolichocarpa (Annonacea) reported the isolation of aporphine alkaloids. METHODS: In this study, we evaluate the potential activity of the azaphenanthrene alkaloids eupolaramine, imbiline 1, imbiline 4, sampangine, 3-metoxisampangine and 4- metoxisampangine, isolated from A. dolichocarpa, together with a homemade databank of 142 aporphynic alkaloids isolated from Annonaceae, through ligand-based and structurebased virtual screening (VS) against Leishmania donovani. A diverse set selected from CHEMBL databank of 1397 structures, with tested antileishmanial activity against promastigote L. donovani, were classified according pIC50 values in order to generate and validate Random Forest model that show higher statistical indices values. The structure of six different L. donovani enzymes were downloaded from PDB databank and alkaloids structures were submitted to molecular docking. RESULTS: From the six azaphenanthrene alkaloids, sampangine, 3-methoxy, and 4-methoxy were indicated as potential actives by the RF model. Docking results gave similar values for all six azaphenanthrene alkaloids. So, we performed in vitro tests with sampangine, imbiline 1, imbiline 4, and eupolaramine, which are available in our laboratory, and that show significant values of pIC50 (> 5.26). CONCLUSION: Combined approach of VS allowed us to select that aporphynic alkaloid xyloguyelline as potential multitarget compound for leishmanial treatment, presenting activity against five strategic enzymes to treatment with probability of activity over 60% by RF model.

Violacein induces cell death by triggering mitochondrial membrane hyperpolarization in vitro.

BACKGROUND: Violacein is a purple pigment from Chromobacterium violaceum that possesses diverse biological and pharmacological properties. Among these, pro-oxidant and antioxidant activities have been suggested. However, the cytotoxic mechanisms induced by violacein are poorly understood and the improvement in knowledge regarding these cell death mechanisms will be useful to develop new therapeutic approaches. Considering this, in our work, we investigated the pro-oxidant effects of violacein in non-tumor (CHO-K1 and MRC-5) and tumor (HeLa) cell lines, searching for a better understanding of reactive oxygen species (ROS) production and cell death induction. RESULTS: Cytotoxicity induced by violacein was observed in the three cell lines; however, MRC-5 and HeLa cells were shown to be more sensitive to violacein treatment. Although punctual alterations in the antioxidant apparatus and increase in oxidative stress biomarkers was observed in some violacein concentrations, no association was found between increased oxidative stress and induction of cell death. However, the increase of mitochondrial membrane potential was observed. CONCLUSIONS: In fact, the increase of mitochondrial membrane potential in MRC-5 and HeLa cells suggests that mitochondrial membrane hyperpolarization might be the main cause of cell death triggered by violacein.

Toll receptors type-2 and CR3 expression of canine monocytes and its correlation with immunohistochemistry and xenodiagnosis in visceral leishmaniasis.

The aim of the present study was to investigate TLR2 expression in peripheral blood monocytes from dogs naturally infected with Leishmania (Leishmania) infantum to determine whether it correlates with CD11b/CD18 (CR3) expression, and to evaluate the potential of dogs as sources of infection using phlebotomine xenodiagnosis. Forty eight dogs were serologically diagnosed with L. infantum infection by indirect immunofluorescence antibody test (IFAT) and enzyme linked immunosorbent assay (ELISA). Parasitological exams from bone-marrow aspirates were positive by PCR analysis. All dogs were clinical defined as symptomatic. Ear skin tissue samples were obtained for immunohistochemistry (IHQ) analysis. The potential of these dogs as a source of infection using phlebotomine xenodiagnosis (XENO) was evaluated. Flow cytometry was carried out on peripheral blood mononuclear cells using superficial receptors including CD14, CD11b, TLR2 and MHCII. IHQ ear skin tissue parasite load and XENO where done where we found a strict correlation (r = 0.5373). Dogs with higher expression of MFI of CD11b inside CD14 monocytes were represented by dogs without parasite ear tissue load that were unable to infect phlebotomines (IHQ⁻/XENO⁻). Dogs with lower expression of MFI of CD11b inside CD14 monocytes were represented by dogs with parasite ear tissue load and able to infect phlebotomines (IHQ⁺/XENO⁺) (p = 0,0032). Comparable results were obtained for MFI of MHCII (p = 0.0054). In addition, considering the population frequency of CD11b⁺TLR2⁺ and CD11b⁺MHCII⁺, higher values were obtained from dogs with IHQ⁻/XENO⁻ than dogs with IHQ⁺/XENO⁺ (p = 0.01; p = 0.0048, respectively). These data, together with the TLR2 and NO assays results (CD11b⁺TLR2⁺ and NO with higher values for dogs with IHQ⁻/XENO⁻ than dogs with IHQ⁺/XENO⁺, led to the conclusion that IHQ⁻/XENO⁻ dogs are more resistant or could modulate the cellular immune response essential for Leishmania tissue clearance.