Leishmanicidal activity of peroxynitrite

Nitric oxide reacts with superoxide to produce peroxynitrite which has been reported to be highly microbicidal to Trypanosoma cruzi in phosphate buffer but ineffective against Leishmania major in culture medium. This contradiction and the potential importance of peroxynitrite as a cytotoxic effector molecule of both macrophages and neutrophils led us to re-examine its leishmanicidal effects. Our results demonstrate that peroxynitrite inhibits growth of Leishmania amazonensis promastigotes in a concentration-dependent manner both in phosphate buffer and culture medium (DMEM containing 20% fetal calf serum). In the latter, 43% growth inhibition was observed with 4 mM peroxynitrite whereas in buffer a 70% inhibition was already observed with 0.5 mM peroxynitrite. Treated parasites presented reduced motility and became round in shape further confirming the leishmanicidal activity of peroxynitrite. The latter was attenuated by reduced glutathione supporting the view that peroxynitrite-mediated oxidation of critical thiol groups is a major mechanism accounting for its trypanocidal activity.

Evaluation of hypoxia inducible factor targeting pharmacological drugs as antileishmanial agents

OBJECTIVE

To evaluate whether hypoxia inducible factor (HIF-1α) targeting pharmacological drugs, echinomycin, resveratrol and CdCl2 which inhibit HIF-1α stimulation, and mimosine, which enhances the stability of HIF-1α present antileishmanial properties.

METHODS

The leishmanicidal effect of drugs was evaluated in mouse macrophages and Balb/c mouse model for cutaneous leishmaniosis.

RESULTS

Resveratrol and CdCl2 reduced the parasite load [IC50, (27.3 ± 2.25) μM and (24.8 ± 0.95) μM, respectively]. The IC50 value of echinomycin was (22.7 ± 7.36) nM and mimosine did not alter the parasite load in primary macrophages. The macrophage viability IC50 values for resveratrol, echinomycin and CdCl2 and mimosine were >40 μM, >100 nM, >200 μM and>2000 μM, respectively. In vivo no differences between cutaneous lesions from control, resveratrol- and echinomycin-treated Balb/c mice were detected.

CONCLUSIONS

Resveratrol, echinomycin and CdCl2 reduce parasite survival in vitro. The HIF-1α targeting pharmacological drugs require further study to more fully determine their anti-Leishmania potential and their role in therapeutic strategies.

HSP70 of Leishmania amazonensis alters resistance to different stresses and mitochondrial bioenergetics

The 70 kDa heat shock protein (HSP70) is a molecular chaperone that assists the parasite Leishmania in returning to homeostasis after being subjected to different types of stress during its life cycle. In the present study, we evaluated the effects of HSP70 transfection of L. amazonensis promastigotes (pTEX-HSP70) in terms of morphology, resistance, infectivity and mitochondrial bioenergetics. The pTEX-HSP70 promastigotes showed no ultrastructural morphological changes compared to control parasites. Interestingly, the pTEX-HSP70 promastigotes are resistant to heat shock, H2O2-induced oxidative stress and hyperbaric environments. Regarding the bioenergetics parameters, the pTEX-HSP70 parasites had higher respiratory rates and released less H2O2 than the control parasites. Nevertheless, the infectivity capacity of the parasites did not change, as verified by the infection of murine peritoneal macrophages and human macrophages, as well as the infection of BALB/c mice. Together, these results indicate that the overexpression of HSP70 protects L. amazonensis from stress, but does not interfere with its infective capacity.

Comparative in vitro toxicity of a graphene oxide-silver nanocomposite and the pristine counterparts toward macrophages

BACKGROUND

Graphene oxide (GO) is a highly oxidized graphene form with oxygen functional groups on its surface. GO is an excellent platform to support and stabilize silver nanoparticles (AgNP), which gives rise to the graphene oxide-silver nanoparticle (GOAg) nanocomposite. Understanding how this nanocomposite interacts with cells is a toxicological challenge of great importance for future biomedical applications, and macrophage cells can provide information concerning the biocompatibility of these nanomaterials. The cytotoxicity of the GOAg nanocomposite, pristine GO, and pristine AgNP was compared toward two representative murine macrophages: a tumoral lineage (J774) and peritoneal macrophages collected from Balb/c mouse. The production of reactive oxygen species (ROS) by J774 macrophages was also monitored. We investigated the internalization of nanomaterials by transmission electron microscopy (TEM). The quantification of internalized silver was carried out by inductively coupled plasma mass spectrometry (ICP-MS). Nanomaterial stability in the cell media was investigated overtime by visual observation, inductively coupled plasma optical emission spectrometry (ICP OES), and dynamic light scattering (DLS).

RESULTS

The GOAg nanocomposite was more toxic than pristine GO and pristine AgNP for both macrophages, and it significantly induced more ROS production compared to pristine AgNP. TEM analysis showed that GOAg was internalized by tumoral J774 macrophages. However, macrophages internalized approximately 60 % less GOAg than did pristine AgNP. The images also showed the degradation of nanocomposite inside cells.

CONCLUSIONS

Although the GOAg nanocomposite was less internalized by the macrophage cells, it was more toxic than the pristine counterparts and induced remarkable oxidative stress. Our findings strongly reveal a synergistic toxicity effect of the GOAg nanocomposite. The toxicity and fate of nanocomposites in cells are some of the major concerns in the development of novel biocompatible materials and must be carefully evaluated.

Pd surface and Pt subsurface segregation in Pt1-c Pd c nanoalloys

The structure and chemical arrangement of Pt1-c Pd c nanoalloys with the icosahedral and face centered cubic symmetry are studied using Monte Carlo simulations with a tight binding interatomic potential fitted to density-functional theory calculations. Pd surface segregation from the lowest to the highest coordinated sites is predicted by the theory together with a Pt enrichment at the subsurface, whatever the structure and the size of the nanoparticles, and which subsists when increasing the temperature. The onion-shell chemical configuration is found for both symmetries and is initiated from the Pd surface segregation. It is amplified in the icosahedral symmetry and small sizes but when considering larger sizes, the oscillating segregation profile occurs near the surface on about three to four shells whatever the structure. Pd segregation results from the significant lower cohesive energy of Pd as compared to Pt and the weak ordering tendency leads to the Pt subsurface segregation. The very weak size mismatch does not prevent the bigger atoms (Pt) from occupying subsurface sites which are in compression whereas the smaller ones (Pd) occupy the central site of the icosahedra where the compression is an order of magnitude higher.

Effectiveness of hyperbaric oxygen for experimental treatment of schistosomiasis mansoni using praziquantel-free and encapsulated into liposomes: assay in adult worms and oviposition

The treatment of schistosomiasis depends on a single drug: praziquantel (PZQ). However, this treatment presents limitations such as low and/or erratic bioavailability that can contribute to cases of tolerance. Improvements to the available drug are urgently needed and studies with a controlled system of drug release, like liposomes, have been gaining prominence. The present study evaluated the activity and synergy between liposomal-praziquantel (lip.PZQ) and hyperbaric oxygen therapy (HBO). Mice received doses of 60 or 100mg/kg PZQ or lip.PZQ, 50 days post-infection, and after the treatment, were exposed to HBO (3 atmosphere absolute - ATA) for 1h. The viability of adult worms and oviposition were analyzed, by necropsy and Kato-Katz examination performed after 15 days of treatment. A concentration of 100mg/kg of lip.PZQ+HBO was more effective (48.0% reduction of worms, 83.3% reduction of eggs/gram of feces) and 100% of the mice had altered of oograms (indicating interruption of oviposition) compared to other treatments and to the Control group (infected and untreated). It is known that PZQ requires participation of the host immune system to complete its antischistosomal activity and that HBO is able to stimulate the immune system. The drug became more available in the body when incorporated into liposomes and, used with HBO, the HBO worked as an adjuvant. This explains the decreases of oviposition and worms recovered form hepatic portal system.

Effects of hyperbaric oxygen on Pseudomonas aeruginosa susceptibility to imipenem and macrophages

BACKGROUND

The seriousness to treat burn wounds infected with Pseudomonas aeruginosa led us to examine whether the effect of the carbapenem antibiotic imipenem is enhanced by hyperbaric oxygen (HBO).

MATERIALS & METHODS

The effects of HBO (100% O2, 3 ATA, 5 h) in combination with imipenen on bacterial counts of six isolates of P. aeruginosa and bacterial ultrastructure were investigated. Infected macrophages were exposed to HBO (100% O2, 3 ATA, 90 min) and the production of reactive oxygen species monitored.

RESULTS

HBO enhanced the effects of imipenen. HBO increased superoxide anion production by macrophages and likely kills bacteria by oxidative mechanisms.

CONCLUSION

HBO in combination with imipenem can be used to kill P. aeruginosa in vitro and such treatment may be beneficial for the patients with injuries containing the P. aeruginosa.

Immunohistochemical evidence of stress and inflammatory markers in mouse models of cutaneous leishmaniosis

Leishmanioses are chronic parasitic diseases and host responses are associated with pro- or anti-inflammatory cytokines involved, respectively, in the control or exacerbation of infection. The relevance of other inflammatory mediators and stress markers has not been widely studied and there is a need to search for biomarkers to leishmaniasis. In this work, the stress and inflammatory molecules p38 mitogen-activated protein kinase, cyclooxygenase-2, migration inhibitory factor, macrophage inflammatory protein 2, heat shock protein 70 kDa, vascular endothelial factor (VEGF), hypoxia-inducible factors (HIF-1α and HIF-2α), heme oxygenase and galectin-3 expression were assessed immunohistochemically in self-controlled lesions in C57BL/6 mice and severe lesions in Balb/c mice infected with Leishmania amazonensis. The results indicated that the majority of molecules were expressed in the cutaneous lesions of both C57BL/6 and Balb/c mice during various phases of infection, suggesting no obvious correlation between the stress and inflammatory molecule expression and the control/exacerbation of leishmanial lesions. However, the cytokine VEGF was only detected in C57BL/6 footpad lesions and small lesions in Balb/c mice treated with antimonial pentavalent. These findings suggest that VEGF expression could be a predictive factor for murine leishmanial control, a hypothesis that should be tested in human leishmaniosis.

Standardization of histological procedures for the detection of toxic substances by immunohistochemistry in Dipteran larvae of forensic importance

Immunohistochemistry (IHC) technique is an alternative toxicological analysis to detect drugs in insects of forensic importance, but it requires thorough histological procedures. In this study, we tested different fixatives--phosphate-buffered paraformaldehyde 4% (PP), Carnoy's fluid (CF), Kahle's solution (KS), ethanol in different concentrations, and ethanol associated to PP and CF, time of fixation and histological processes for dipteran larvae's tissue, aiming to develop a sample preparation protocol for IHC application. A suitable fixation was achieved using PP for 12 and 24 h, CF for 3 h, 70% ethanol for 19 days, and 70% ethanol/CF for 2 h/3 h. Postfixation using negative pressure, two immersions in xylene for 30 min each, and one in xylene plus paraffin for 45 min increased tissue preservation. An immunohistochemical test for cocaine detection was performed using monoclonal benzoylecgonine antibody from mouse, peroxidase-conjugated anti-mouse IgG and visualized by 3,3'-diaminobenzidine method showed these histological procedures didn't compromise antigenicity.

In vivo and in vitro Leishmania amazonensis infection induces autophagy in macrophages

Autophagy is the primary mechanism of degradation of cellular proteins and at least two functions can be attributed to this biological phenomenon: increased nutrient supply via recycling of the products of autophagy under nutrient starvation; and antimicrobial response involved in the innate immune system. Many microorganisms induce host cell autophagy and it has been proposed as a pathway by which parasites compete with the host cell for limited resources. In this report we provide evidence that the intracellular parasite Leishmania amazonensis induces autophagy in macrophages. Using western blotting, the LC3II protein, a marker of autophagosomes, was detected in cell cultures with a high infection index. Macrophages infected with L. amazonensis were examined by transmission electronic microscopy, which revealed enlarged myelin-like structures typical late autophagosome and autolysosome. Other evidence indicating autophagy was Lysotracker red dye uptake by the macrophages. Autophagy also occurs in the leishmaniasis skin lesions of BALB/c mice, detected by immunohistochemistry with anti-LC3II antibody. In this study, autophagy inhibitor 3-methyladenine (3MA) reduced the infection index, while autophagy inductors, such as rapamycin or starvation, did not alter the infection index in cultivated macrophages, suggesting that one aspect of the role of autophagy could be the provision of nutritive support to the parasite.

Use of in vivo and in vitro systems to select Leishmania amazonensis expressing green fluorescent protein

Various Leishmania species were engineered with green fluorescent protein (GFP) using episomal vectors that encoded an antibiotic resistance gene, such as aminoglycoside geneticin sulphate (G418). Most reports of GFP-Leishmania have used the flagellated extracellular promastigote, the stage of parasite detected in the midgut of the sandfly vector; fewer studies have been performed with amastigotes, the stage of parasite detected in mammals. In this study, comparisons were made regarding the efficiency for in vitro G418 selection of GFP-Leishmania amazonensis promastigotes and amastigotes and the use of in vivo G418 selection. The GFP-promastigotes retained episomal plasmid for a prolonged period and G418 treatment was necessary and efficient for in vitro selection. In contrast, GFP-amastigotes showed low retention of the episomal plasmid in the absence of G418 selection and low sensitivity to antibiotics in vitro. The use of protocols for G418 selection using infected BALB/c mice also indicated low sensitivity to antibiotics against amastigotes in cutaneous lesions.

Potential utility of hyperbaric oxygen therapy and propolis in enhancing the leishmanicidal activity of glucantime

In this study we investigated the efficacy of hyperbaric oxygen (HBO) therapy, alone or combined with the pentavalent antimonial glucantime on Leishmania amazonensis infection. In parallel, the effect of Brazilian red propolis gel (propain) alone or combined with glucantime on L. amazonensis infection was evaluated. The inhibition of the infection in macrophages treated with glucantime in combination with HBO exposition was greater than that of macrophages treated with glucantime alone or HBO alone. The susceptible mouse strain BALB/c infected in the shaved rump with L. amazonensis treated with glucantime and exposed to HBO showed: time points in the course of the disease in which lesions were smaller than those of mice treated with glucantime alone and revascularization of the skin in the lesion site; interferon-gamma (IFN-g) levels were not elevated in lymph node cells from these animals. Propain alone was not efficient against lesions, although less exudative lesions were observed in animals treated with propain alone or combined with glucantime. These results reveal the potential value of HBO and red propolis in combination with glucantime for treating cutaneous leishmaniasis and encourage further studies on the effect of more aggressive HBO, propolis and glucantime therapies on different mouse models of leishmaniasis.

Hypoxia, hypoxia-inducible factor-1α and vascular endothelial growth factor in a murine model of Schistosoma mansoni infection

Schistosomiasis mansoni is a chronic parasitic disease where much of the symptomatology is attributed to granuloma formation, an immunopathological reaction against Schistosoma eggs. To more clearly understand the immunopathology of schistosomiasis, the tissue microenvironment generated by S. mansoni infected mice was investigated. Using the hypoxia marker pimonidazole, we provide immunohistochemical evidence that hypoxia occurred in inflammatory cells infiltrated around the eggs and cells surrounding granulomas in the liver, intestine, spleen and lungs of infected mice. Hypoxia-inducible factor-1α (HIF-1α) was mainly expressed in inflammatory cells surrounding the eggs and in hepatocytes surrounding cellular and fibrocellular granulomas in infected mouse liver. HIF-1α expression was also verified in granulomas in the other tissues tested (intestine, spleen and lungs). Vascular endothelial growth factor (VEGF) expression was observed in the extracellular space surrounding inflammatory cells in liver granuloma. The VEGF expression pattern verified in infected mouse liver was very similar to that observed in the other tissues tested. A strong positive correlation occurred between pimonidazole binding and HIF-1α and VEGF expression in the tissues tested, except for lung. This work is the first evidence that infection by a helminth parasite, S. mansoni, produces a hypoxic tissue microenvironment and induces HIF-1α and VEGF expression.

Tempol ameliorates murine viral encephalomyelitis by preserving the blood-brain barrier, reducing viral load, and lessening inflammation

Multiple sclerosis (MS) is a progressive inflammatory and/or demyelinating disease of the human central nervous system (CNS). Most of the knowledge about the pathogenesis of MS has been derived from murine models, such as experimental autoimmune encephalomyelitis and viral encephalomyelitis. Here, we infected female C57BL/6 mice with a neurotropic strain of the mouse hepatitis virus (MHV-59A) to evaluate whether treatment with the multifunctional antioxidant tempol (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy) affects the ensuing encephalomyelitis. In untreated animals, neurological symptoms developed quickly: 90% of infected mice died 10 days after virus inoculation and the few survivors presented neurological deficits. Treatment with tempol (24 mg/kg, ip, two doses on the first day and daily doses for 7 days plus 2 mM tempol in the drinking water ad libitum) profoundly altered the disease outcome: neurological symptoms were attenuated, mouse survival increased up to 70%, and half of the survivors behaved as normal mice. Not surprisingly, tempol substantially preserved the integrity of the CNS, including the blood-brain barrier. Furthermore, treatment with tempol decreased CNS viral titers, macrophage and T lymphocyte infiltration, and levels of markers of inflammation, such as expression of inducible nitric oxide synthase, transcription of tumor necrosis factor-alpha and interferon-gamma, and protein nitration. The results indicate that tempol ameliorates murine viral encephalomyelitis by altering the redox status of the infectious environment that contributes to an attenuated CNS inflammatory response. Overall, our study supports the development of therapeutic strategies based on nitroxides to manage neuroinflammatory diseases, including MS.

A novel organotellurium compound (RT-01) as a new antileishmanial agent

Leishmaniasis is a neglected disease and endemic in developing countries. A lack of adequate and definitive chemotherapeutic agents to fight against this infection has led to the investigation of numerous compounds. The aim of this study was to investigate the effect of RT-01, an organotellurane compound presenting biological activities, in 2 experimental systems against Leishmania amazonensis. The in vitro system consisted of promastigotes and amastigotes forms of the parasite, and the in vivo system consisted of L. amazonensis infected BALB/c mice, an extremely susceptible mouse strain. The compound proved to be toxic against promastigotes and amastigotes. The study also showed that treatment with RT-01 produces an effect similar to that treatment with the reference antimonial drug, Glucantime, in L. amazonensis infected mice. The best results were obtained following RT-01 intralesional administration (720 microg/kg/day); mice showed significant delay in the development of cutaneous lesions and decreased numbers of parasites obtained from the lesions. Significant differences in tissue pathology consisted mainly of no expressive accumulation of inflammatory cells and well-preserved structures in the skin tissue of RT-01-treated mice compared with expressive infiltration of infected cells replacing the skin tissue in lesions of untreated mice. These findings highlight the fact that the apparent potency of organotellurane compounds, together with their relatively simple structure, may represent a new avenue for the development of novel drugs to combat parasitic diseases.

Efficacy of pentavalent antimony, amphotericin B, and miltefosine in Leishmania amazonensis-infected macrophages under normoxic and hypoxic conditions

Recently, our group demonstrated that mouse lesions infected with Leishmania amazonensis are hypoxic. Evidence indicates the negative impact of hypoxia on the efficacy of a variety of chemotherapeutic agents against tumors, fungi, bacteria, and malaria parasites. In the present study, comparison of the effect of antileishmanial drugs on L. amazonensis-infected macrophages under normoxic and hypoxic conditions was performed. We compared the effect of 5% oxygen tension with a tension of 21% oxygen on peritoneal murine macrophage cultures infected with the parasite and treated with glucantime, amphotericin B, or miltefosine. Analysis of the infection index (percentage of infected macrophages x number of amastigotes per macrophage), dose-dependent efficacy of drugs, and IC(50) values demonstrated that hypoxia conferred a small, but significant, resistance to all 3 antileishmanial drugs. The present finding suggests that in vitro assays under hypoxia should not be neglected in drug studies.

Hyperbaric oxygen prevents early death caused by experimental cerebral malaria

Background

Cerebral malaria (CM) is a syndrome characterized by neurological signs, seizures and coma. Despite the fact that CM presents similarities with cerebral stroke, few studies have focused on new supportive therapies for the disease. Hyperbaric oxygen (HBO) therapy has been successfully used in patients with numerous brain disorders such as stroke, migraine and atherosclerosis.

Methodology/Principal Findings

C57BL/6 mice infected with Plasmodium berghei ANKA (PbA) were exposed to daily doses of HBO (100% O₂, 3.0 ATA, 1–2 h per day) in conditions well-tolerated by humans and animals, before or after parasite establishment. Cumulative survival analyses demonstrated that HBO therapy protected 50% of PbA-infected mice and delayed CM-specific neurological signs when administrated after patent parasitemia. Pressurized oxygen therapy reduced peripheral parasitemia, expression of TNF-α, IFN-γ and IL-10 mRNA levels and percentage of γδ and αβ CD4⁺ and CD8⁺ T lymphocytes sequestered in mice brains, thus resulting in a reduction of blood-brain barrier (BBB) dysfunction and hypothermia.

Conclusions/Significance

The data presented here is the first indication that HBO treatment could be used as supportive therapy, perhaps in association with neuroprotective drugs, to prevent CM clinical outcomes, including death.

Inhibition of in vivo leishmanicidal mechanisms by tempol: nitric oxide down-regulation and oxidant scavenging

Tempol (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy) has long been known to protect experimental animals from the injury associated with oxidative and inflammatory conditions. In the latter case, a parallel decrease in tissue protein nitration levels has been observed. Protein nitration represents a shift in nitric oxide actions from physiological to pathophysiological and potentially damaging pathways involving its derived oxidants such as nitrogen dioxide and peroxynitrite. In infectious diseases, protein tyrosine nitration of tissues and cells has been taken as evidence for the involvement of nitric oxide-derived oxidants in microbicidal mechanisms. To examine whether tempol inhibits the microbicidal action of macrophages, we investigated its effects on Leishmania amazonensis infection in vitro (RAW 264.7 murine macrophages) and in vivo (C57Bl/6 mice). Tempol was administered in the drinking water at 2 mM throughout the experiments and shown to reach infected footpads as the nitroxide plus the hydroxylamine derivative by EPR analysis. At the time of maximum infection (6 weeks), tempol increased footpad lesion size (120%) and parasite burden (150%). In lesion extracts, tempol decreased overall nitric oxide products and expression of inducible nitric oxide synthase to about 80% of the levels in control animals. Nitric oxide-derived products produced by radical mechanisms, such as 3-nitrotyrosine and nitrosothiol, decreased to about 40% of the levels in control mice. The results indicate that tempol worsened L. amazonensis infection by a dual mechanism involving down-regulation of iNOS expression and scavenging of nitric oxide-derived oxidants. Thus, the development of therapeutic strategies based on nitroxides should take into account the potential risk of altering host resistance to parasite infection.

Expression of hypoxia-inducible factor 1alpha in mononuclear phagocytes infected with Leishmania amazonensis

Increasing evidence indicates that hypoxia-inducible factor 1alpha (HIF-1alpha) can be upregulated in different cell types by nonhypoxic stimuli such as growth factors, cytokines, nitric oxide, lipopolysaccharides and a range of infectious microorganisms. In this study, the ability of the following mononuclear phagocytes to express HIF-1alpha is reported: mouse macrophages (mMPhi), human macrophages (hMPhi) and human dendritic cells (DC), parasitized in vitro with Leishmania amazonensis; as assessed by immunofluorescence microscopy. A logical explanation for HIF-1alpha expression might be that the mononuclear phagocytes became hypoxic after L. amazonensis infection. Using the hypoxia marker pimonidazole, observation revealed that L. amazonensis-infected cells were not hypoxic. In addition, experiments using a HIF-1alpha inhibitor, CdCl(2), to treat L. amazonensis-infected macrophage cultures showed reduced parasite survival. These studies indicated that HIF-1alpha could play a role in adaptative and immune responses of mononuclear phagocytes presenting infection by the parasite L. amazonensis.

Effects of Brazilian propolis on Leishmania amazonensis

Leishmaniasis, an endemic parasitosis that leads to chronic cutaneous, mucocutaneous or visceral lesions, is part of those diseases, which still requires improved control tools. Propolis has shown activities against different bacteria, fungi, and parasites. In this study we investigated the effect of four ethanolic extracts of typified propolis collected in different Brazilian states, on Leishmania amazonensis performing assays with promastigote forms, extracellular amastigotes, and on infected peritoneal macrophages. Ethanolic extracts of all propolis samples (BRG, BRPG, BRP-1, and BRV) were capable to reduce parasite load as monitored by the percentage of infected macrophages and the number of intracellular parasites. BRV sample called red propolis, collected in the state of Alagoas, and containing high concentration of prenylated and benzophenones compounds, was the most active extract against L. amazonensis. The anti-Leishmania effect of BRV sample was increased in a concentration and time dependent manner. BRV treatment proved to be non-toxic to macrophage cultures. Since BRV extract at the concentration of 25 microg/ml reduced the parasite load of macrophages while presented no direct toxic to promastigotes and extracellular amastigotes, it was suggested that constituents of propolis intensify the mechanism of macrophage activation leading to killing of L. amazonensis. Our results demonstrate, for the first time, that ethanolic extracts of Brazilian propolis reduce L. amazonensis infection in macrophages, and encourage further studies of this natural compound in animal models of leishmaniasis.

HIF-1 regulates heritable variation and allele expression phenotypes of the macrophage immune response gene SLC11A1 from a Z-DNA forming microsatellite

The Ity/Lsh/Bcg locus encodes the macrophage protein Slc11a1/Nramp1, which protects inbred mice against infection by diverse intracellular pathogens including Leishmania, Mycobacterium, and Salmonella. Human susceptibility to infectious and inflammatory diseases, including rheumatoid arthritis, inflammatory bowel disease, and tuberculosis, shows allelic association with a highly polymorphic regulatory, Z-DNA-forming microsatellite of (GT/AC)n dinucleotides within the proximal SLC11A1 promoter. We surmised that cis-acting allelic polymorphisms may underlie heritable differences in SLC11A1 expression and phenotypic variation in disease risk. However, it is unclear what may underlie such variation in SLC11A1 allele expression. Here we show that hypoxia-inducible Factor 1 (HIF-1) regulates allelic variation in SLC11A1 expression by binding directly to the microsatellite during macrophage activation by infection or inflammation. Targeted Hif-1alpha ablation in murine macrophages attenuated Slc11a11 expression and responsiveness to S typhimurium infection. Our data also showed that HIF-1 may be functionally linked to complex prototypical inflammatory diseases associated with certain SLC11A1 alleles. As these alleles are highly polymorphic, our finding suggests that HIF-1 may influence heritable variation in SLC11A1-dependent innate resistance to infection and inflammation within and between populations. This report also suggests that microsatellites may play critical roles in the directional evolution of complex heritable traits by regulating gene expression phenotypes.