In the present work, we have investigated the effect of essential oils obtained from Origanum vulgare L. (oregano) and Thymus vulgaris L. (thyme) on growth and ultrastructure of diverse evolutive forms of Trypanosoma cruzi. Culture epimastigotes and bloodstream trypomastigotes were incubated for 24 h with different concentrations of oregano or thyme essential oils and with thymol (the main constituent of thyme), and the inhibitory concentration (IC)(50) was determined by cell counting. Crude extract of oregano essential oil inhibited epimastigote growth (IC(50)/24 h = 175 microg/ml) and also induced trypomastigote lysis (IC(50)/24 h = 115 microg/ml). Thyme essential oil presented IC(50)/24 h values of 77 microg/ml for epimastigotes and 38 mug/ml for trypomastigotes, while treatment with thymol resulted in an IC(50)/24 h of 62 microg/ml for epimastigotes and 53 microg/ml for trypomastigotes. Scanning electron microscopy of treated cells showed few morphological alterations at the plasma membrane. Observation by transmission electron microscopy showed cytoplasmic swelling with occasional morphological alterations in plasma and flagellar membrane. Our data indicate that oregano and thyme essential oils are effective against T. cruzi, with higher activity of thyme, and that thymol may be the main component responsible for the trypanocidal activity.

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This study analyses the anti-proliferative effect of lemongrass essential oil and its main constituent (citral) on all 3 evolutive forms of Trypanosoma cruzi. Steam distillation was used to obtain lemongrass essential oil, with chemical composition determined by gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS). The IC50/24 h (concentration that reduced the parasite population by 50%) of the oil and of citral upon T. cruzi was determined by cell counting in a Neubauer chamber, while morphological alterations were visualized by scanning and transmission electron microscopy. Treatment with the essential oil resulted in epimastigote growth inhibition with IC50=126.5 microg/ml, while the IC50 for trypomastigote lysis was 15.5 microg/ml. The IC50/48 h for the Association Index (% macrophage infection x number of amastigotes per cell) was 5.1 microg/ml, with a strong inhibition of intracellular amastigote proliferation. Ultrastructural analysis demonstrated cytoplasmic and nuclear extraction, while the plasma membrane remained morphologically preserved. Our data show that lemongrass essential oil is effective against T. cruzi trypomastigotes and amastigotes, and that its main component, citral, is responsible for the trypanocidal activity. These results indicate that essential oils can be promising anti-parasitic agents, opening perspectives to the discovery of more effective drugs of vegetal origin for treatment of parasitic diseases. However, additional cytotoxicity experiments on different cell lines and tests in a T. cruzi-mouse model are needed to support these data.

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In order to contribute to the search for new therapeutic agents for leishmaniasis, we report the effect of several essential oils on the growth of Leishmania infantum promastigotes. Eight of the tested essential oils revealed activity below 150 mg/ml, the most active being Cymbopogon citratus, Juniperus oxycedrus berries and Thymus capitelatus oils, with 50% effective concentration values in the range 16-51 mg/ml. The results support the concept that several essential oils or some of their constituents can become useful in the research of new therapeutic agents for leishmaniasis and in the clinical management of this parasitic disease.

Infection by the protozoan parasite Toxoplasma gondii is highly prevalent worldwide and may have serious clinical manifestations in immunocompromised patients. T. gondii is an obligate intracellular parasite that infects almost any cell type in mammalian hosts, including immune cells. The immune cells express purinergic P2 receptors in their membrane – subdivided into P2Y and P2X subfamilies - whose activation is important for infection control. Here, we examined the effect of treatment with UTP and UDP in mouse peritoneal macrophages infected with T. gondii tachyzoites. Treatment with these nucleotides reduced parasitic load by 90%, but did not increase the levels of the inflammatory mediators NO and ROS, nor did it modulate host cell death by apoptosis or necrosis. On the other hand, UTP and UDP treatments induced early egress of tachyzoites from infected macrophages, in a Ca2+-dependent manner, as shown by scanning electron microscopy analysis, and videomicroscopy. In subsequent infections, prematurely egressed parasites had reduced infectivity, and could neither replicate nor inhibit the fusion of lysosomes to the parasitophorous vacuole. The use of selective agonists and antagonists of the receptor subtypes P2Y2 and P2Y4 and P2Y6 showed that premature parasite egress may be mediated by the activation of these receptor subtypes. Our results suggest that the activity of P2Y host cell receptors controls T. gondii infection in macrophages, highlighting the importance of pyrimidinergic signaling for innate immune system response against infection. Finally the P2Y receptors should be considered as new target for the development of drugs against T. gondii infection.

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Previously, we showed that treating macrophages with ATP impairs the intracellular growth of Leishmania amazonensis, and that the P2X7 purinergic receptor is overexpressed during leishmaniasis. In the present study, we directly evaluated the effect of periodate-oxidized ATP (oATP) on parasite control in Leishmania-infected macrophages. We found that oATP impaired the attachment/entrance of L. amazonensis promastigotes to C57BL/6 mouse macrophages in a P2X7 receptor-independent manner, as macrophages from P2X7(-/-) mice were similarly affected. Although oATP directly inhibited the growth of axenic promastigotes in culture, promoted rapid ultrastructural alterations, and impaired Leishmania internalization by macrophages, it did not affect intracellular parasite multiplication. Upon infection, phagosomal acidification was diminished in oATP-treated macrophages, accompanied by reduced endosomal proteolysis. Likewise, MHC class II molecules expression and ectoATPase activity was decreased by oATP added to macrophages at the time of parasite infection. These inhibitory effects were not due to a cytotoxic effect, as no additional release of lactate dehydrogenase was detected in culture supernatants. Moreover, the capacity of macrophages to produce nitric oxide and reactive oxygen species was not affected by the presence of oATP during infection. We conclude that oATP directly affects extracellular parasite integrity and macrophage functioning.