Subversion of Immunity by Leishmania amazonensis Parasites: Possible Role of Phosphatidylserine as a Main Regulator

Leishmania amazonensis parasites cause progressive disease in most inbred mouse strains and are associated with the development of diffuse cutaneous leishmaniasis in humans. The poor activation of an effective cellular response is correlated with the ability of these parasites to infect mononuclear phagocytic cells without triggering their activation or actively suppressing innate responses of these cells. Here we discuss the possible role of phosphatidylserine exposure by these parasites as a main regulator of the mechanism underlying subversion of the immune system at different steps during the infection

New Insights on the Inflammatory Role of Lutzomyia longipalpis Saliva in Leishmaniasis

When an haematophagous sand fly vector insect bites a vertebrate host, it introduces its mouthparts into the skin and lacerates blood vessels, forming a hemorrhagic pool which constitutes an intricate environment of cell interactions. In this scenario, the initial performance of host, parasite, and vector “authors” will heavily influence the course of Leishmania infection. Recent advances in vector-parasite-host interaction have elucidated “co-authors” and “new roles” not yet described. We review here the stimulatory role of Lutzomyia longipalpis saliva leading to inflammation and try to connect them in an early context of Leishmania infection

Lutzomyia longipalpis Saliva Triggers Lipid Body Formation and Prostaglandin E2 Production in Murine Macrophages

After the injection of saliva into the host's skin by sand flies, a transient erythematous reaction is observed, which is related to an influx of inflammatory cells and the release of various molecules that actively facilitate the blood meal. It is important to understand the specific mechanisms by which sand fly saliva manipulates the host's inflammatory responses. Herein, we report that saliva from Lutzomyia (L.) longipalpis, a widespread Leishmania vector, induces early production of eicosanoids. Intense formation of intracellular organelles called lipid bodies (LBs) was noted within those cells that migrated to the site of saliva injection. In vitro and ex vivo, sand fly saliva was able to induce LB formation and PGE2 release by macrophages. Interestingly, PGE2 production induced by L. longipalpis saliva was dependent on intracellular mechanisms involving phosphorylation of signaling proteins such as PKC-α and ERK-1/2 and subsequent activation of cyclooxygenase-2. Thus, this study provides new insights into the pharmacological properties of sand fly saliva and opens new opportunities for intervening with the induction of the host's inflammatory pathways by L. longipalpis bites

Cooperation between Apoptotic and Viable Metacyclics Enhances the Pathogenesis of Leishmaniasis

Mimicking mammalian apoptotic cells by exposing phosphatidylserine (PS) is a strategy used by virus and parasitic protozoa to escape host protective inflammatory responses. With Leishmania amazonensis (La), apoptotic mimicry is a prerogative of the intramacrophagic amastigote form of the parasite and is modulated by the host. Now we show that differently from what happens with amastigotes, promastigotes exposing PS are non-viable, non-infective cells, undergoing apoptotic death. As part of the normal metacyclogenic process occurring in axenic cultures and in the gut of sand fly vectors, a sub-population of metacyclic promastigotes exposes PS. Apoptotic death of the purified PS-positive (PSPOS) sub-population was confirmed by TUNEL staining and DNA laddering. Transmission electron microscopy revealed morphological alterations in PSPOS metacyclics such as DNA condensation, cytoplasm degradation and mitochondrion and kinetoplast destruction, both in in vitro cultures and in sand fly guts. TUNELPOS promastigotes were detected only in the anterior midgut to foregut boundary of infected sand flies. Interestingly, caspase inhibitors modulated parasite death and PS exposure, when added to parasite cultures in a specific time window. Efficient in vitro macrophage infections and in vivo lesions only occur when PSPOS and PS-negative (PSNEG) parasites were simultaneously added to the cell culture or inoculated in the mammalian host. The viable PSNEG promastigote was the infective form, as shown by following the fate of fluorescently labeled parasites, while the PSPOS apoptotic sub-population inhibited host macrophage inflammatory response. PS exposure and macrophage inhibition by a subpopulation of promastigotes is a different mechanism than the one previously described with amastigotes, where the entire population exposes PS. Both mechanisms co-exist and play a role in the transmission and development of the disease in case of infection by La. Since both processes confer selective advantages to the infective microorganism they justify the occurrence of apoptotic features in a unicellular pathogen

Parasite Killing of Leishmania (V) braziliensis by Standardized Propolis Extracts

Submitted by Ana Maria Fiscina Sampaio ([email protected]) on 2018-04-04T18:41:34Z No. of bitstreams: 1 Silva JB Parasite Killing of by Standardized....pdf: 3616663 bytes, checksum: f9c22d8d7a23e97d508cb0e5c5666184 (MD5)Approved for entry into archive by Ana Maria Fiscina Sampaio ([email protected]) on 2018-04-04T19:00:54Z (GMT) No. of bitstreams: 1 Silva JB Parasite Killing of by Standardized....pdf: 3616663 bytes, checksum: f9c22d8d7a23e97d508cb0e5c5666184 (MD5)Made available in DSpace on 2018-04-04T19:00:54Z (GMT). No. of bitstreams: 1 Silva JB Parasite Killing of by Standardized....pdf: 3616663 bytes, checksum: f9c22d8d7a23e97d508cb0e5c5666184 (MD5) Previous issue date: 2017Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq (Process no. 309988/2014-4)Fundação Oswaldo Cruz. Instituto Gonçalo Moniz. Salvador, BA, Brasil / Universidade Federal da Bahia. Salvador, BA, Brasil.Fundação Oswaldo Cruz. Instituto Gonçalo Moniz. Salvador, BA, Brasil.Universidade Federal do Oeste da Bahia. Centro das Ciências Biológicas e da Saúde. Barreiras, BA, Brasil.Universidade Estadual Paulista. Instituto de Química. Araraquara, SP, Brasil / Universidade de Araraquara. Pós-Graduação em Biotecnologia. Araraquara, SP, Brasil.Fundação Oswaldo Cruz. Instituto Gonçalo Moniz. Salvador, BA, Brasil.Laboratório de Pesquisa, Desenvolvimento e Inovação. Apis Flora Industrial e Comercial Ltda. Ribeirão Preto, SP, Brasil / Universidade de São Paulo. Faculdade de Ciências Farmacêuticas de Ribeirão Preto. Departamento de Ciências Farmacêuticas. Ribeirão Preto, SP, Brasil.Fundação Oswaldo Cruz. Instituto Gonçalo Moniz. Salvador, BA, Brasil / Universidade Federal da Bahia. Salvador, BA, Brasil.Treatments based on antimonials to cutaneous leishmaniasis (CL) entail a range of toxic side effects. Propolis, a natural compound widely used in traditional medical applications, exhibits a range of biological effects, including activity against infectious agents. The aim of this study was to test the potential leishmanicidal effects of different propolis extracts againstLeishmania (Viannia) braziliensispromastigotes and intracellular amastigotes in vitro. Stationary-phaseL. (V) braziliensispromastigotes were incubated with medium alone or treated with dry, alcoholic, or glycolic propolis extract (10, 50, or 100 μg/mL) for 96 h. Our data showed that all extracts exhibited a dose-dependent effect on the viability ofL. (V) braziliensispromastigotes, while controlling the parasite burden inside infected macrophages. Dry propolis extract significantly modified the inflammatory profile of murine macrophages by downmodulating TGF-βand IL-10 production, while upmodulating TNF-α. All three types of propolis extract were found to reduce nitric oxide and superoxide levels in activatedL.braziliensis-infected macrophages. Altogether, our results showed that propolis extracts exhibited a leishmanicidal effect against both stages ofL. (V) braziliensis. The low cell toxicity and efficient microbicidal effect of alcoholic or glycolic propolis extracts make them candidates to an additive treatment for cutaneous leishmaniasis

Heme changes HIF-α, eNOS and nitrite production in HUVECs after simvastatin, HU, and ascorbic acid therapies

Submitted by Ana Maria Fiscina Sampaio ([email protected]) on 2016-05-10T15:54:44Z No. of bitstreams: 1 Guarda CC Heme changes....pdf: 517853 bytes, checksum: 521387a5f13e3781b0af22ec40769e20 (MD5)Approved for entry into archive by Ana Maria Fiscina Sampaio ([email protected]) on 2016-05-10T16:03:23Z (GMT) No. of bitstreams: 1 Guarda CC Heme changes....pdf: 517853 bytes, checksum: 521387a5f13e3781b0af22ec40769e20 (MD5)Made available in DSpace on 2016-05-10T16:03:23Z (GMT). No. of bitstreams: 1 Guarda CC Heme changes....pdf: 517853 bytes, checksum: 521387a5f13e3781b0af22ec40769e20 (MD5) Previous issue date: 2016Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, BrasilFundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, BrasilFundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, BrasilFundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, BrasilFundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, BrasilFundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, BrasilFundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, Brasil / Universidade Federal da Bahia. Faculdade de Farmácia. Departamento de Análises Clínicas e Toxicológicas. Salvador, BA, BrasilThe sickle cell disease (SCD) is a hemolytic genetic anemia characterized by free heme and hemoglobin release into intravascular spaces, with endothelial activation. Heme is a proinflammatory molecule able to directly activate vascular endothelium, thus, endothelial dysfunction and vascular disease are major chronic events described in SCD. The aim of this study was to evaluate the production of endothelial nitric oxide synthase (eNOS), nitrite and hypoxia inducible factor alpha (HIF-α) in HUVECs (human umbilical vein endothelial cells) activated by heme in response to simvastatin, hydroxyurea (HU), and ascorbic acid therapies. eNOS and HIF-α production were evaluated by ELISA and nitrite was measured by the Griess technique. The production of HIF-α increased when the cells were stimulated by heme (p b 0.01), while treatment with HU and simvastatin reduced the production (p b 0.01), and treatment with ascorbic acid increased HIF-1a production by the cells (p b 0.01). Hemeincreased eNOS production, (p b 0.01) but showed a heterogeneous pattern, and the lowest concentrations of all the treatments reduced the enzyme production (p b 0.01). The nitrite production by HUVECs was enhanced by stimulation with heme (p b 0.001) andwas reduced by treatment with HU (p b 0.001), ascorbic acid (p b 0.001) and simvastatin (p b 0.01). In summary, our results suggest that the hemolytic vascular microenvironment in SCD requires different therapeutic approaches to promote clinical improvement, and that a combination of therapies may be a viable strategy for treating patients