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-1␣ 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. IntroductionA genetic basis for resistance to infection by intracellular pathogens was proposed several years ago. [1][2][3][4][5][6] This concept was confirmed upon the positional cloning of the dominant autosomal gene Ity/Lsh/Bcg based on its ability to confer on inbred mice an innate resistance to infection by diverse intracellular pathogens. 7 These include Salmonella typhimurium, 2 Leishmania donovani, 3 and some species of Mycobacterium such as M bovis 5 and M intracellulare. 8 Targeted ablation of Ity/Lsh/ Bcg 9 or allelic exchange in susceptible mice 10 confirmed its requirement for resistance to infection. Ity/Lsh/Bcg encodes the phagocyte-specific solute carrier 11a1 protein Slc11a1 (formerly Nramp1), 11-13 which restricts pathogen replication by inducing the expression of major histocompatibility complex (MHC) class II molecules, cytokines (eg, TNF␣), and chemokines. 14 SLC11A1/Slc11a1 belongs to a family of polytopic membrane proteins whose functions include divalent cation acquisition in mammals (DCT1/DMT1/NRAMP2), 15 taste perception in the fruit fly (malvolio), 16 and stress signal transduction in plants (EIN2). 17 In mice, a single nonsynonymous mutation in Slc11a1 codon 169 determines resistance (Gly169) or susceptibility (Asp169) to intracellular bacterial and leishmanial infections. 7 Compared with susceptible mice, macrophages from mice that are resistant to infection also show increased oxidative burst and expression of the MHC class...

In the present study, we compared the effect of 5% oxygen tension (hypoxia) with a normal tension of 21% oxygen (normoxia) on macrophage infection by the protozoan parasite Leishmania amazonensis. Macrophages from different sources (human cell line U937, murine cell line J774, and murine peritoneal macrophages) exposed to hypoxia showed a reduction of the percentage of infected cells and the number of intracellular parasites per cell. Observations on the kinetics of infection indicated that hypoxia did not depress L. amazonensis phagocytosis but induced macrophages to reduce intracellular parasitism. Furthermore, hypoxia did not act synergistically with gamma-interferon and bacterial lipopolysaccharides in macrophages to induce killing of parasites. Experiments also indicated no correlation between nitric oxide production and control of infection in macrophages under hypoxic condition. Thus, we have provided the first evidence that hypoxia, which occurs in various pathological conditions, can alter macrophage susceptibility to a parasitic infection.

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Hypoxia, a microenvironmental factor present in diseased tissues, has been recognized as a specific metabolic stimulus or a signal of cellular response. Experimental hypoxia has been reported to induce adaptation in macrophages such as differential migration, elevation of proinflammatory cytokines and glycolytic enzyme activities, and decreased phagocytosis of inert particles. In this study we demonstrate that although exposure to hypoxia (5% O₂, 5% CO₂, and balanced N₂) did not change macrophage viability, or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cleavage and proliferation, it significantly reduced expression of the 70-kD heat shock protein (HSP70), which was restored to prehypoxia levels after reoxygenation. The influence of low oxygen tension on macrophage functional activity was also studied, i.e. the ability of these cells to maintain or resist infection by a microorganism. We demonstrate that macrophages from two different sources (a murine cell line and primary cells) exposed to hypoxia were efficiently infected with Leishmania amazonensis, but after 24 h showed a reduction in the percentage of infected cells and of the number of intracellular parasites per macrophage, indicating that hypoxia induced macrophages to kill the intracellular parasites. These results support the notion that hypoxia, a microenvironmental factor, can modulate macrophage protein expression and functional activity.

BackgroundCerebral 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 FindingsC57BL/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/SignificanceThe 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.

Hypoxia (low oxygen tension) is a common feature of inflamed and infected tissues. The influence of hypoxia on macrophage responses to micro‐organisms has only recently been studied. This study demonstrates that hypoxia induced macrophages to control Leishmania amazonensis, an intracellular parasite that causes cutaneous and cutaneous metastatic lesions. The mechanisms that contribute to the control of macrophages against L. amazonensis infection under a hypoxic microenvironment are not known. Nitric oxide, TNF‐α, IL‐10 or IL‐12 is not responsible for the decrease in parasitism under hypoxia. Live L. amazonensis entry or exocytosis of internalized particles as well as energetic metabolism was not impaired in infected macrophages; no apoptosis‐like death was detected in intracellular parasites. Reactive oxygen species (ROS) is likely to be involved, because treatment with antioxidants N‐acetylcysteine (NAC) and ebselen inhibits the leishmanicidal effect of macrophages under hypoxia. Leishmania amazonensis infection induces macrophages to express hypoxia‐inducible factor‐1 (HIF‐1α) and ‐2 (HIF‐2α). Data indicate that hypoxia affects the microbial activities and protein expression of macrophages leading to a different phenotype from that of the normoxic counterpart and that it plays a role in modulating Leishmania infection.

Leishmaniasis caused by the intracellular protozoan parasite of mononuclear phagocytes Leishmania is endemic in 88 countries [1]. Leishmania amazonensis, a species transmitted mainly in the Amazon region, has been associated with localized cutaneous lesions, diffuse cutaneous disease, and mucosal infection [1,2]. The disease is neglected by the pharmaceutical industry, even though no vaccine exists, and significant side effects and signs of increasing resistance continue to occur with the use of the few effective drugs available [3,4].More recently, the pharmaceutical proprieties of tellurane compounds were investigated [5,6]. Several tellurides show antioxidative and immunomodulating proprieties and antitumor activities [5][6][7][8][9][10][11][12]. Clinical trials with a tellurane compound are presently underway [13,14]. The synthetic organotellurane compound RT-01 ( Fig. 1) has been previously shown to inhibit cathepsin B, a cysteine protease involved in tumor invasion, and presents a cytotoxic effect on cancer cells [7]. In an attempt to find new leishmanial drugs, RT-01 was tested both in vitro and in vivo against L. amazonensis. The results reported here suggest that RT-01 is effective against the flagellate and nonflagellate parasitic forms and in L. amazonensis-infected BALB/c mice. MATERIALS AND METHODS Organotellurane compound (RT-01)The organotellurane RT-01 used to evaluate the effects in vitro against L. amazonensis and in vivo in L. amazonensis-infected mice was prepared by the reaction of tellurium tetrachloride with propargyl alcohol in benzene followed by complexation with triethylbenzylammonium chloride, as described previously [7,15] (Fig. 1). The compound was dissolved in DMSO and diluted in phosphate buffer pH 7.4, medium or saline. The final concentration of DMSO in vitro and in vivo experiments was 0.1%. A Novel Organotellurium Compound (RT-01) as a New Antileishmanial AgentKorean J Parasitol. Vol. 47, No. 3: 213-218, September 2009 DOI: 10.3347/kjp.2009 213 Abstract: 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 μ g/kg/day); mice showed significant delay in the development of cutaneous lesions and decreased numbers of parasites ob...

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