IL-18 contributes to susceptibility to Leishmania amazonensis infection by macrophage-independent mechanisms.

We evaluated the role of IL-18 during Leishmania amazonensis infection in C57BL/6 mice, using IL-18KO mice. We showed that IL-18 is involved in susceptibility to L. amazonensis, since IL-18KO mice presented reduced lesions and parasite loads. Because macrophages are the host cells of the parasite, we investigated if macrophages were involved in IL-18-mediated susceptibility to L. amazonensis. We showed that macrophages obtained from WT or IL-18KO responded similarly to L. amazonensis infection. Moreover, we showed that C57BL/6 macrophages do not respond to IL-18, since they do not express IL-18R. Therefore, macrophages are not involved in IL-18-mediated susceptibility to L. amazonensis.

Morphological and physiological changes in Leishmania promastigotes induced by yangambin, a lignan obtained from Ocotea duckei.

We have previously demonstrated that yangambin, a lignan obtained from Ocotea duckei Vattimo (Lauraceae), shows antileishmanial activity against promastigote forms of Leishmania chagasi and Leishmania amazonensis. The aim of this study was to determine the in vitro effects of yangambin against these parasites using electron and confocal microscopy. L. chagasi and L. amazonensis promastigotes were incubated respectively with 50 µg/mL and 65 µg/mL of pure yangambin and stained with acridine orange. Treated-parasites showed significant alterations in fluorescence emission pattern and cell morphology when compared with control cells, including the appearance of abnormal round-shaped cells, loss of cell motility, nuclear pyknosis, cytoplasm acidification and increased number of acidic vesicular organelles (AVOs), suggesting important physiological changes. Ultrastructural analysis of treated-promatigotes showed characteristics of cell death by apoptosis as well as by autophagy. The presence of parasites exhibiting multiples nuclei suggests that yangambin may also affect the microtubule dynamic in both Leishmania species. Taken together our results show that yangambin is a promising agent against Leishmania.

Yangambin cytotoxicity: a pharmacologically active lignan obtained from Ocotea duckei vattimo (Lauraceae).

The in vitro cytotoxic potential of yangambin was evaluated. Yangambin is a pharmacologically active furofuran lignan obtained from the leaves of Ocotea duckei. It is the major compound from the lignoids fraction. Yangambin presented low cytotoxicity in all in vitro models analyzed. Its cytotoxicity to murine macrophages was measured by the Trypan blue dye exclusion test and MTT reduction assay, resulting in high CC50 values of 187.0 microg/mL (383.3 microM) and 246.7 microg/mL (504.3 microM), respectively. The difference obtained in the inhibitory concentrations aforementioned can be explained, at least in part, by the different principles of the methods. While the MTT reduction assay evaluates the ability of yangambin to inhibit the activity of the mitochondrial enzyme succinate dehydrogenase, the Trypan blue dye exclusion test evaluates possible damages to the integrity of the cytoplasmic membrane which result in cell death. The capacity of yangambin to inhibit the sea urchin embryonic development showed that it has low antimitotic and teratogenic potential, once continued exposure of embryos to concentrations up to 500 microg/mL (1.025 microM) did not result in an inhibitory effect on the first egg cleavages. Such low in vitro cytotoxicity is correlated with the low acute toxicity previously studied. All these data, together with the various therapeutic properties of yangambin, make this lignan a promising one for a new drug.

Crude ethanolic extract, lignoid fraction and yangambin from Ocotea duckei (Lauraceae) show antileishmanial activity.

Crude ethanolic extract, lignoid fraction and the purified compound yangambin were obtained from Ocotea duckei (Lauraceae) and their antileishmanial activity was tested against promastigote forms of Leishmania chagasi and Leishmania amazonensis cultivated in Schneider medium, supplemented with 20% of fetal bovine serum. All substances presented antileishmanial activity with IC50 values of 135.7 microg/mL for the crude ethanolic extract, 26.5 microg/mL for the lignoid fraction and 49.0 microg/mL for yangambin on L. chagasi. For L. amazonensis the IC50 values were 143.7 microg/mL, 48.2 microg/mL and 64.9 microg/mL for the crude ethanolic extract, the lignoid fraction, and the purified compound yangambin, respectively. The crude ethanolic extract, lignoid fraction, and yangambin caused an inhibition higher than Glucantime, a reference drug used for the treatment of leishmaniasis.

Anti-mitotic activity towards sea urchin eggs of dichloromethane fraction obtained from Allamanda schottii Pohl (Apocynaceae) / Atividade anti-mitótica da fração diclorometano obtida de Allamanda schottii Pohl (Apocynaceae) sobre ovos do ouriço do mar

Allamanda (Apocynaceae) is a genus of climbing shrubs known for producing compounds with a range of biological activities. Previous works have shown the anti-proliferative effect of the ethanolic extract of Allamanda schottii on leukemic cells. The present work was conducted to evaluate the effects of dichloromethane fraction, obtained from Allamanda schottii, on sea urchin Echinometra lucunter eggs, as a multicellular model for evaluating anti-tumor activity. Our results show an inhibition of sea urchin development in a dose-dependent manner in the presence of dichloromethane fraction. The IC50 values for first and third cleavage and blastulae stage were 103.7 µg/mL, 33.1 µg/mL and 10.2 µg/mL, respectively. These results also demonstrate the cumulative effect of this fraction on sea urchin embryos. In the present work, the expressive anti-mitotic activity of dichloromethane fraction towards sea urchin eggs, a multicellular model, reinforces the anti-tumor potential of the Allamanda schotti.

Allamanda (Apocynacea) é um gênero de arbustos escandentes conhecido por produzir compostos com várias atividades biológicas. Trabalhos anteriores têm mostrado um efeito anti-proliferativo do extrato etanólico de Allamanda schottii sobre células leucêmicas. O presente trabalho foi realizado para avaliar o efeito da fração diclorometano, obtida de Allamanda schotti, sobre os ovos de ouriço-do-mar de Echinometra lucunter, como um modelo multicelular para estudar atividade anti-tumoral. Nossos resultados mostram uma inibição do desenvolvimento dos ovos de uma maneira dose-dependente na presença da fração diclorometano. Os valores de IC50 para a primeira e terceira clivagem e para o estágio de blástula foram de 103,7 µg/mL, 33.1 µg/mL e 10,2 µg/mL, respectivamente. Estes resultados também demonstram um efeito acumulativo da fração sobre os embriões do ouriço-do-mar. No presente trabalho, esta expressiva atividade anti-mitótica da fração diclorometano sobre o desenvolvimento embrionário do ouriço-do-mar, um modelo multicelular, reforça o potencial antitumoral de Allamanda schotti.