Expression of hypoxia-inducible factor-1alpha in the cutaneous lesions of BALB/c mice infected with Leishmania amazonensis

HIF-α signaling regulates the macrophage inflammatory response during Leishmania major infection

Cutaneous leishmaniasis (CL) contributes significantly to the global burden of neglected tropical diseases, with 12 million people currently infected with Leishmania parasites. CL encompasses a range of disease manifestations, from self-healing skin lesions to permanent disfigurations. Currently there is no vaccine available, and many patients are refractory to treatment, emphasizing the need for new therapeutic targets. Previous work demonstrated macrophage HIF-α-mediated lymphangiogenesis is necessary to achieve efficient wound resolution during murine L. major infection. Here, we investigate the role of macrophage HIF-α signaling independent of lymphangiogenesis. We sought to determine the relative contributions of the parasite and the host-mediated inflammation in the lesional microenvironment to myeloid HIF-α signaling. Because HIF-α activation can be detected in infected and bystander macrophages in leishmanial lesions, we hypothesize it is the host's inflammatory response and microenvironment, rather than the parasite, that triggers HIF-α activation. To address this, macrophages from mice with intact HIF-α signaling (LysMCreARNTf/+) or mice with deleted HIF-α signaling (LysMCreARNTf/f) were subjected to RNASequencing after L. major infection and under pro-inflammatory stimulus. We report that L. major infection alone is enough to induce some minor HIF-α-dependent transcriptomic changes, while infection with L. major in combination with pro-inflammatory stimuli induces numerous transcriptomic changes that are both dependent and independent of HIF-α signaling. Additionally, by coupling transcriptomic analysis with several pathway analyses, we found HIF-α suppresses pathways involved in protein translation during L. major infection in a pro-inflammatory environment. Together these findings show L. major induces a HIF-α-dependent transcriptomic program, but HIF-α only suppresses protein translation in a pro-inflammatory environment. Thus, this work indicates the host inflammatory response, rather than the parasite, largely contributes to myeloid HIF-α signaling during Leishmania infection.

Hypoxia and collagen deposition in the kidneys infected with Acanthamoeba sp

Acanthamoeba spp. are facultative, opportunistic pathogens that are found in diverse environments. In the hosts, they lead to multi-organ disease. Recent studies reported that they may induce changes in the kidneys of hosts. The aim of the study was to determine the influence of Acanthamoeba sp. on hypoxia and collagen deposition in the kidneys of immunocompetent and immunosuppressed mice infected with Acanthamoeba sp. The results strongly suggest that Acanthamoeba sp. induces hypoxia in mice with normal and reduced immune response by increasing gene and/or protein expression of HIF1α as well as HIF2α. Additionally, the activation of these factors is probably induced via NOX2/ROS. Hypoxia promotes vessel formation, and we found that angiogenesis occurs in the kidneys of mice infected with the parasite regardless of their immunological status. The proangiogenic factors released in hypoxic conditions cause modulation and inflammation in the kidney cells, which in turn leads to collagen deposition via TGF-β. This work reveals mechanisms occurring in the hosts infected with Acanthamoeba sp., highlights as well as supports the relevance of pathophysiology in the kidneys in hosts with systematic acanthamoebiasis.

Increased Abnormal Erythrocytes Caused by Spleen Filtration Deficiency Provide a Hypoxic Environment for the Occurrence of Psoriasis

Psoriasis is a chronic autoimmune disease with a long disease course and frequent relapse characteristics. It is now recognised to be associated with epidermal environments of inflammatory cytokines. However, its pathogenesis is still not completely clear. We found the haemorheology of psoriatic patients to be abnormal, and ageing and deformed erythrocytes increased in the blood. The abnormal erythrocytes were more likely to induce psoriasis, which was confirmed in a mouse model induced by different blood components of psoriatic patients/healthy volunteers. Spleen filtration dysfunction, which caused abnormal erythrocytes, was also more likely to induce psoriasis, which was confirmed in a mouse model induced by splenectomy. The mechanism was the weakening of the 'eat me' function of spleen macrophages phagocytizing ageing and deformed erythrocytes, resulting in the dysfunction of spleen filtration and the increase of ageing and deformed erythrocytes in the body. Additionally, the decreased oxygen-carrying capacity and the declined antioxidant capacity of those erythrocytes led to the hypoxia environment, making psoriasis more likely to be induced. These findings demonstrate that spleen filtration dysfunction contributes to the pathogenesis of psoriasis and suggest that improving it may be an effective therapy for psoriasis and control its relapse.

HIF-α signaling regulates the macrophage inflammatory response during Leishmania major infection

Cutaneous leishmaniasis (CL) contributes significantly to the global burden of neglected tropical diseases, with 12 million people currently infected with Leishmania parasites. CL encompasses a range of disease manifestations, from self-healing skin lesions to permanent disfigurations. Currently there is no vaccine available, and many patients are refractory to treatment, emphasizing the need for new therapeutic targets. Previous work demonstrated macrophage HIF-α-mediated lymphangiogenesis is necessary to achieve efficient wound resolution during murine L. major infection. Here, we investigate the role of macrophage HIF-α signaling independent of lymphangiogenesis. We sought to determine the relative contributions of the parasite and the host-mediated inflammation in the lesional microenvironment to myeloid HIF-α signaling. Because HIF-α activation can be detected in infected and bystander macrophages in leishmanial lesions, we hypothesize it is the host's inflammatory response and microenvironment, rather than the parasite, that triggers HIF-α activation. To address this, macrophages from mice with intact HIF-α signaling (LysM Cre ARNT f/+ ) or mice with deleted HIF-α signaling (LysM Cre ARNT f/f ) were subjected to RNASequencing after L. major infection and under pro-inflammatory stimulus. We report that L. major infection alone is enough to induce some minor HIF-α-dependent transcriptomic changes, while infection with L. major in combincation with pro-inflammatory stimuli induces numerous transcriptomic changes that are both dependent and independent of HIF-α signaling. Additionally, by coupling transcriptomic analysis with several pathway analyses, we found HIF-α suppresses pathways involved in protein translation during L. major infection in a pro-inflammatory environment. Together these findings show L. major induces a HIF-α-dependent transcriptomic program, but HIF-α only suppresses protein translation in a pro-inflammatory environment. Thus, this work indicates the host inflammatory response, rather than the parasite, largely contributes to myeloid HIF-α signaling during Leishmania infection.

Neutrophil-mediated hypoxia drives pathogenic CD8+ T cell responses in cutaneous leishmaniasis

Cutaneous leishmaniasis caused by Leishmania parasites exhibits a wide range of clinical manifestations. Although parasites influence disease severity, cytolytic CD8+ T cell responses mediate disease. Although these responses originate in the lymph node, we found that expression of the cytolytic effector molecule granzyme B was restricted to lesional CD8+ T cells in Leishmania-infected mice, suggesting that local cues within inflamed skin induced cytolytic function. Expression of Blimp-1 (Prdm1), a transcription factor necessary for cytolytic CD8+ T cell differentiation, was driven by hypoxia within the inflamed skin. Hypoxia was further enhanced by the recruitment of neutrophils that consumed oxygen to produce ROS and ultimately increased the hypoxic state and granzyme B expression in CD8+ T cells. Importantly, lesions from patients with cutaneous leishmaniasis exhibited hypoxia transcription signatures that correlated with the presence of neutrophils. Thus, targeting hypoxia-driven signals that support local differentiation of cytolytic CD8+ T cells may improve the prognosis for patients with cutaneous leishmaniasis, as well as for other inflammatory skin diseases in which cytolytic CD8+ T cells contribute to pathogenesis.

Pathogenic CD8 T cell responses are driven by neutrophil-mediated hypoxia in cutaneous leishmaniasis

Cutaneous leishmaniasis caused by Leishmania parasites exhibits a wide range of clinical manifestations. Although parasites influence disease severity, cytolytic CD8 T cell responses mediate disease. While these responses originate in the lymph node, we find that expression of the cytolytic effector molecule granzyme B is restricted to lesional CD8 T cells in Leishmania - infected mice, suggesting that local cues within inflamed skin induce cytolytic function. Expression of Blimp-1 ( Prdm1 ), a transcription factor necessary for cytolytic CD8 T cell differentiation, is driven by hypoxia within the inflamed skin. Hypoxia is further enhanced by the recruitment of neutrophils that consume oxygen to produce reactive oxygen species, ultimately increasing granzyme B expression in CD8 T cells. Importantly, lesions from cutaneous leishmaniasis patients exhibit hypoxia transcription signatures that correlate with the presence of neutrophils. Thus, targeting hypoxia-driven signals that support local differentiation of cytolytic CD8 T cells may improve the prognosis for patients with cutaneous leishmaniasis, as well as other inflammatory skin diseases where cytolytic CD8 T cells contribute to pathogenesis.

Low expression of hypoxia-inducible factor-1α and differential expression of immune mediators during experimental infection with Leishmania (Viannia) spp

Leishmania (Viannia) species are the major agents of cutaneous leishmaniasis (CL) in the Americas. Ulcerative stigmatizing skin lesions generally characterize CL. The microenvironment during Leishmania infection is rich in inflammatory cells and molecules, which contrasts with low oxygen levels. The hypoxia-inducible factor (HIF)-1α activates several genes in response to hypoxia and inflammatory reactions, but its role in the CL course is poorly understood. We investigated the expression pattern of the genes HIF-1α, arginase, inducible NO synthase (iNOS), interferon (IFN)-γ, interleukin (IL)-12, and IL-10 in skin lesions and lymph nodes of golden hamsters infected with L. braziliensis, L. lainsoni, and L. naiffi. The animals were infected and followed for 105 days, with paw volume measurements and photos taken weekly. Euthanasia was performed at 0, 15, 56, and 105 days post-infection. The parasite load of paw and lymph node tissues were measured through absolute quantification at real-time PCR (qPCR), and reverse transcription qPCR (RT-qPCR) was applied to demonstrate the relative mRNA expression of the target genes. Among groups, animals infected with L. braziliensis had the highest parasite load in paws and lymph nodes. HIF-1α mRNA was down-regulated during chronic Leishmania (Viannia) infection but demonstrated less inhibition in hamsters infected with L. lainsoni and L. naiffi. Arginase was the most detectable gene in animals infected by L. braziliensis; IFN-γ and IL-10 genes were the most detectable in L. lainsoni and L. naiffi-infected animals. HIF-1α gene transcription seemed to be down-modulated byL. (Viannia)infection and was less inhibited by L. lainsoni and L. naiffi when compared toL. braziliensis. Animals with L. lainsoni and L. naiffi showed better control of the disease. Further studies are necessary to evaluate the mechanism influencing HIF-1α expression and its role on CL protection; such research could elucidate potential use of HIF-1α as a therapeutic target.

Transcription Factors Interplay Orchestrates the Immune-Metabolic Response of Leishmania Infected Macrophages

Leishmaniasis is a group of heterogenous diseases considered as an important public health problem in several countries. This neglected disease is caused by over 20 parasite species of the protozoa belonging to the Leishmania genus and is spread by the bite of a female phlebotomine sandfly. Depending on the parasite specie and the immune status of the patient, leishmaniasis can present a wide spectrum of clinical manifestations. As an obligate intracellular parasite, Leishmania colonize phagocytic cells, mainly the macrophages that orchestrate the host immune response and determine the fate of the infection. Once inside macrophages, Leishmania triggers different signaling pathways that regulate the immune and metabolic response of the host cells. Various transcription factors regulate such immune-metabolic responses and the associated leishmanicidal and inflammatory reaction against the invading parasite. In this review, we will highlight the most important transcription factors involved in these responses, their interactions and their impact on the establishment and the progression of the immune response along with their effect on the physiopathology of the disease.

The Activin Receptor, Activin-Like Kinase 4, Mediates Toxoplasma Gondii Activation of Hypoxia Inducible Factor-1

To grow and cause disease, intracellular pathogens modulate host cell processes. Identifying these processes as well as the mechanisms used by the pathogens to manipulate them is important for the development of more effective therapeutics. As an example, the intracellular parasite Toxoplasma gondii induces a wide variety of changes to its host cell, including altered membrane trafficking, cytoskeletal reorganization, and differential gene expression. Although several parasite molecules and their host targets have been identified that mediate- these changes, few are known to be required for parasite replication. One exception is the host cell transcription factor, hypoxia-inducible factor-1 (HIF-1), which is required for parasite replication in an oxygen-dependent manner. Toxoplasma activates HIF-1 by stabilizing the HIF-1α subunit, and this is dependent on the signaling from the Activin-Like Kinase (ALK) receptor superfamily. Here, we demonstrate that specific overexpression of the ALK family member, ALK4, increased HIF-1 activity in Toxoplasma-infected cells, and this increase required ALK4 kinase activity. Moreover, Toxoplasma stimulated ALK4 to dimerize with its co-receptor, ActRII, and also increased ALK4 kinase activity, thereby demonstrating that Toxoplasma activates the ALK4 receptor. ALK4 activation of HIF-1 was independent of canonical SMAD signaling but rather was dependent on the non-canonical Rho GTPase and JNK MAP kinase signaling pathways. Finally, Toxoplasma increased rates of ALK4 ubiquitination and turnover. These data provide the first evidence indicating that ALK4 signaling is a target for a microbial pathogen to manipulate its host cell.

The role of metalloproteases in Leishmania species infection in the New World: a systematic review

This is a systematic review on the role of metalloproteases in the pathogenicity of the American tegumentary leishmaniasis (ATL) caused by New World Leishmania species. The review followed the PRISMA method, searching for articles in PubMed, EMBASE, LILACS and ISI Web of Science, by employing the following terms: 'leishmaniasis', 'cutaneous leishmaniasis', 'mucocutaneous leishmaniasis', 'diffuse cutaneous leishmaniasis', 'Leishmania' and 'metalloproteases'. GP63 of New World Leishmania species is a parasite metalloproteases involved in the degradation and cleavage of many biological molecules as kappa-B nuclear factor, fibronectin, tyrosine phosphatases. GP63 is capable of inhibiting the activity of the complement system and reduces the host's immune functions, allowing the survival of the parasite and its dissemination. High serological/tissue levels of host matrix metalloproteases (MMP)-9 have been associated with tissue damage during the infection, while high transcriptional levels of MMP-2 related with a satisfactory response to treatment. Host MMPs serological and tissue levels have been investigated using Western Blot, zymography, and Real Time polymerase chain reaction. GP63 detection characterizes species and virulence in promastigotes isolated from lesions samples using techniques mentioned previously. The monitoring of host MMPs levels and GP63 in Leishmania isolated from host samples could be used on the laboratory routine to predict the prognostic and treatment efficacy of ATL.

Leishmania donovani Activates Hypoxia Inducible Factor-1α and miR-210 for Survival in Macrophages by Downregulation of NF-κB Mediated Pro-inflammatory Immune Response

Micro RNAs (miRNAs) have emerged as a critical regulator of several biological processes in both animals and plants. They have also been associated with regulation of immune responses in many human diseases during recent years. Visceral leishmaniasis (VL) is the most severe form of leishmaniasis, which is characterized by impairment of both innate and adaptive immune responses. In the present study, we observed that Leishmania establishes hypoxic environment in host macrophages that induces the expression of hypoxia inducible factor-1α (HIF-1α) and miRNA-210. Further, the expression of miRNA-210 was found to be dependent on activation of HIF-1α expression. The HIF-1α silencing by siRNA resulted in significantly (p < 0.001) decreased expression of miR-210 in parasites infected macrophages. We also observed that in siHIF-1α or antagomir-210 treated L. donovani infected macrophages, the parasitic load and percentage infectivity were significantly (p < 0.001) decreased. Furthermore, we found that inhibition of miR-210 leads to activation of NF-κB subunit p50, and it forms heterodimer with p65 and translocates into the nucleus from the cytoplasm. This significantly (p < 0.05) induced the transcription of pro-inflammatory cytokines genes such as TNF-α and IL-12 in miRNA-210 inhibited macrophages compared to uninhibited macrophages whereas the level of IL-10, an anti-inflammatory cytokine, was found to be significantly decreased (p < 0.001). These findings suggested that L. donovani infection induces hypoxic environment inside the macrophages that activates HIF-1α. Further, HIF-1α upregulates miR-210, which eventually establishes a suitable environment for the survival of parasite inside the host macrophages by downregulating NF-κB mediated pro-inflammatory immune responses.

Effects of nanoemulsions prepared with essential oils of copaiba- and andiroba against Leishmania infantum and Leishmania amazonensis infections

Plant products are an important source of bioactive agents against parasitic diseases, including leishmaniasis. Among these products, vegetable oils have gained ground in the pharmaceutical field. Here we report the development of nanoemulsions as a delivery system for copaiba and andiroba oils (nanocopa and nanoandi) in order to test their effects on Leishmania infantum and L. amazonensis. The nanocopa and nanoandi had an average particle size of 76.1 and 88.1, respectively with polydispersity index 0.14 to 0.16 and potential zeta -2.54 to -3.9. The data indicated toxic activity of nanocopa and nanoandi against promastigotes of both Leishmania species ultrastructural analyses by scanning electron microscopy revealed that exposition to nanoemulsions induced oval cell shape and retracted flagella. The treatment with nanocopa and nanoandi led to a reduction in L. infantum and L. amazonensis infection levels in macrophage cultures. The nanoemulsions treatment have significant beneficial effects on all the parameters evaluated in lesions induced by L. amazonensis (lesion size, parasite burden and histopathology) on BALB/c mice. The treatment of L. infantum-infected BALB/c mice with nanoemulsions also showed promising results reducing parasite burden in spleen and liver and improving histopathological features.

Myeloid Cell-Derived HIF-1α Promotes Control of Leishmania major

Hypoxia-inducible factor-1α (HIF-1α), which accumulates in mammalian host organisms during infection, supports the defense against microbial pathogens. However, whether and to what extent HIF-1α expressed by myeloid cells contributes to the innate immune response against Leishmania major parasites is unknown. We observed that Leishmania-infected humans and L. major-infected C57BL/6 mice exhibited substantial amounts of HIF-1α in acute cutaneous lesions. In vitro, HIF-1α was required for leishmanicidal activity and high-level NO production by IFN-γ/LPS-activated macrophages. Mice deficient for HIF-1α in their myeloid cell compartment had a more severe clinical course of infection and increased parasite burden in the skin lesions compared with wild-type controls. These findings were paralleled by reduced expression of type 2 NO synthase by lesional CD11b⁺ cells. Together, these data illustrate that HIF-1α is required for optimal innate leishmanicidal immune responses and, thereby, contributes to the cure of cutaneous leishmaniasis.

Hostile takeover: Manipulation of HIF-1 signaling in pathogen-associated cancers (Review)

Hypoxia-inducible factor (HIF)-1 is a central regulator in the adaptation process of cell response to hypoxia (low oxygen). Emerging evidence has demonstrated that HIF-1 plays an important role in the development and progression of many types of human diseases, including pathogen-associated cancers. In the present review, we summarize the recent understandings of how human pathogenic agents including viruses, bacteria and parasites deregulate cellular HIF-1 signaling pathway in their associated cancer cells, and highlight the common molecular mechanisms of HIF-1 signaling activated by these pathogenic infection, which could act as potential diagnostic markers and new therapeutic strategies against human infectious cancers.

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.

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.

Macrophage arginase-1 controls bacterial growth and pathology in hypoxic tuberculosis granulomas

Lung granulomas develop upon Mycobacterium tuberculosis (Mtb) infection as a hallmark of human tuberculosis (TB). They are structured aggregates consisting mainly of Mtb-infected and -uninfected macrophages and Mtb-specific T cells. The production of NO by granuloma macrophages expressing nitric oxide synthase-2 (NOS2) via l-arginine and oxygen is a key protective mechanism against mycobacteria. Despite this protection, TB granulomas are often hypoxic, and bacterial killing via NOS2 in these conditions is likely suboptimal. Arginase-1 (Arg1) also metabolizes l-arginine but does not require oxygen as a substrate and has been shown to regulate NOS2 via substrate competition. However, in other infectious diseases in which granulomas occur, such as leishmaniasis and schistosomiasis, Arg1 plays additional roles such as T-cell regulation and tissue repair that are independent of NOS2 suppression. To address whether Arg1 could perform similar functions in hypoxic regions of TB granulomas, we used a TB murine granuloma model in which NOS2 is absent. Abrogation of Arg1 expression in macrophages in this setting resulted in exacerbated lung granuloma pathology and bacterial burden. Arg1 expression in hypoxic granuloma regions correlated with decreased T-cell proliferation, suggesting that Arg1 regulation of T-cell immunity is involved in disease control. Our data argue that Arg1 plays a central role in the control of TB when NOS2 is rendered ineffective by hypoxia.

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.

Immunohistochemical profile of HIF-1α, VEGF-A, VEGFR2 and MMP9 proteins in tegumentary leishmaniasis

BACKGROUND

Leishmaniasis is one of the most important infectious diseases worldwide. Our study can provide more knowledge about angiogenic and hypoxic events in leishmaniasis. We attempted to verify whether the HIF-1 α protein expression may be associated to VEGF-A, VEGFR2 and MMP9 in leishmanial lesions.

OBJECTIVES

Besides understanding the pathway, we performed the correlation of VEGF-A, VEGFR2 and MMP9 proteins.

METHODS

In this study, we gathered 54 paraffin blocks taken from skin lesions in patients from northern Minas Gerais, Brazil, with confirmed diagnosis of tegumentary leishmaniasis. Immunohistochemistry was used to evaluate the expression of the proteins. The expression of HIF-1α was categorized into two groups according to the median: HIF-1 α lower and HIF-1 α higher.

RESULTS

We observed increase of VEGFR2 and MMP9 protein expressions in HIF-1 α higher group of epithelial cells. Spearman analyses in epithelial cells showed correlation between VEGF-A and MMP9, VEGFR2 and MMP9 protein expression.

CONCLUSIONS

HIF-1 α higher group showed increase of VEGFR2 and MMP9 proteins. In epithelial cells, VEGF-A was correlated to MMP9 protein. Furthermore, considering leukocyte cells, VEGFR2 was negatively correlated to MMP9 protein levels. This pathway possibly prepares the cells for a higher activity in a hypoxic or an angiogenic microenvironment. Other in vitro and in vivo studies may clarify the activation mechanism and the response from the proteins HIF-1 α, VEGFR2 and MMP-9 in tegumentary leishmaniasis.

Infection by Leishmania amazonensis in mice: a potential model for chronic hypoxia

Hypoxia is a common feature of injured and infected tissues. Hypoxia inducible factors 1α and 2α (HIF-1α, HIF-2α) are heterodimeric transcription factors mediating the cellular responses to hypoxia and also the vascular endothelial growth factor (VEGF). VEGF is a cytokine which can be induced by hypoxia, whose pathogenic mechanisms are still unclear and which is the subject of debate. Murine cutaneous lesions during Leishmania amazonensis parasite infection are chronic, although they are small and self-controlled in C57BL/6 mice and severe in BALB/c mice. In the present study we examined the presence of hypoxia, HIF-1α, HIF-2α and VEGF during the course of infection in both mouse strains. Hypoxia was detected in lesions from BALB/c mice by pimonidazole marking, which occurred earlier than in lesions from C57Bl/6 mice. The lesions in the BALB/c mice showed HIF-1α and HIF-2α expression in the cytoplasm of macrophages and failed to promote any VEGF expression, while lesions in the C57BL/6 mice showed HIF-2α nuclear accumulation and subsequent VEGF expression. In conclusion, the animal models of leishmaniasis demonstrated a diversity of patterns of expression, cell localization and activity of the main transducers of hypoxia and may be useful models for studying the pathogenic mechanisms of HIF-1α and HIF-2α during chronic hypoxic diseases.

Transcriptomic signature of Leishmania infected mice macrophages: a metabolic point of view

We analyzed the transcriptional signatures of mouse bone marrow-derived macrophages at different times after infection with promastigotes of the protozoan parasite Leishmania major. Ingenuity Pathway Analysis revealed that the macrophage metabolic pathways including carbohydrate and lipid metabolisms were among the most altered pathways at later time points of infection. Indeed, L. major promastiogtes induced increased mRNA levels of the glucose transporter and almost all of the genes associated with glycolysis and lactate dehydrogenase, suggesting a shift to anaerobic glycolysis. On the other hand, L. major promastigotes enhanced the expression of scavenger receptors involved in the uptake of Low-Density Lipoprotein (LDL), inhibited the expression of genes coding for proteins regulating cholesterol efflux, and induced the synthesis of triacylglycerides. These data suggested that Leishmania infection disturbs cholesterol and triglycerides homeostasis and may lead to cholesterol accumulation and foam cell formation. Using Filipin and Bodipy staining, we showed cholesterol and triglycerides accumulation in infected macrophages. Moreover, Bodipy-positive lipid droplets accumulated in close proximity to parasitophorous vacuoles, suggesting that intracellular L. major may take advantage of these organelles as high-energy substrate sources. While the effect of infection on cholesterol accumulation and lipid droplet formation was independent on parasite development, our data indicate that anaerobic glycolysis is actively induced by L. major during the establishment of infection.

Leishmania are obligated intracellular pathogens that develop almost exclusively in macrophages. Experimental leishmaniasis in mice is one of the most extensively studied models of intracellular infections both at the level of the parasite and host immune responses. We took advantage of Balb/c mice model to investigate gene expression profile through Affymetrix oligonucleotide arrays. In order to have a general and dynamic picture of the complex biological events that are acting in the context of Leishmania intracellular parasitism, we investigated the mouse macrophage response to initial invasion of L. major over a time course that extended from one to 24 hours post-infection. Our results reveal the alteration of several biological processes and metabolic changes. Indeed, similarly to different other pathogens, Leishmania induces cholesterol accumulation and foam cell formation that have been confirmed by confocal microscopy experiments. Whether Leishmania parasites take advantage of this high-energy source is now under investigation. Our findings provided further understandings in host responses to Leishmania infection.

Intracellular pathogen Leishmania donovani activates hypoxia inducible factor-1 by dual mechanism for survival advantage within macrophage

Recent evidence established a crucial role for mammalian oxygen sensing transcription factor hypoxia inducible factor-1 (HIF-1) in innate immunity against intracellular pathogens. In response to most of these pathogens host phagocytes increase transcription of HIF-1α, the regulatory component of HIF-1 to express various effector molecules against invaders. Leishmania donovani (LD), a protozoan parasite and the causative agent of fatal visceral leishmaniasis resides in macrophages within mammalian host. The mechanism of HIF-1 activation or its role in determining the fate of LD in infected macrophages is still not known. To determine that J774 macrophages were infected with LD and about four-fold increase in HIF-1 activity and HIF-1α expression were detected. A strong increase in HIF-1α expression and nuclear localization was also detected in LD-infected J774 cells, peritoneal macrophages and spleen derived macrophages of LD-infected BALB/c mice. A two-fold increase in HIF-1α mRNA was detected in LD-infected macrophages suggesting involvement of a transcriptional mechanism that was confirmed by promoter activity. We further revealed that LD also induced HIF-1α expression by depleting host cellular iron pool to affect prolyl hydroxylase activity resulting in to stabilization of HIF-1α. To determine the role of HIF-1 on intracellular LD, cells were transfected with HIF-1α siRNA to attenuate its expression and then infected with LD. Although, initial infection rate of LD in HIF-1α attenuated cells was not affected but intracellular growth of LD was significantly inhibited; while, over-expression of stabilized form of HIF-1α promoted intracellular growth of LD in host macrophage. Our results strongly suggest that LD activates HIF-1 by dual mechanism for its survival advantage within macrophage.

Modeling of leishmaniasis infection dynamics: novel application to the design of effective therapies

Background

The WHO considers leishmaniasis as one of the six most important tropical diseases worldwide. It is caused by parasites of the genus Leishmania that are passed on to humans and animals by the phlebotomine sandfly. Despite all of the research, there is still a lack of understanding on the metabolism of the parasite and the progression of the disease. In this study, a mathematical model of disease progression was developed based on experimental data of clinical symptoms, immunological responses, and parasite load for Leishmania amazonensis in BALB/c mice.

Results

Four biologically significant variables were chosen to develop a differential equation model based on the GMA power-law formalism. Parameters were determined to minimize error in the model dynamics and time series experimental data. Subsequently, the model robustness was tested and the model predictions were verified by comparing them with experimental observations made in different experimental conditions. The model obtained helps to quantify relationships between the selected variables, leads to a better understanding of disease progression, and aids in the identification of crucial points for introducing therapeutic methods.

Conclusions

Our model can be used to identify the biological factors that must be changed to minimize parasite load in the host body, and contributes to the design of effective therapies.

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.

Toxoplasma gondii activates hypoxia-inducible factor (HIF) by stabilizing the HIF-1alpha subunit via type I activin-like receptor kinase receptor signaling

Toxoplasma gondii is an intracellular protozoan parasite that can cause devastating disease in fetuses and immune-compromised individuals. We previously reported that the alpha subunit of the host cell transcription factor, hypoxia-inducible factor-1 (HIF-1), is up-regulated by infection and necessary for Toxoplasma growth. Under basal conditions, HIF-1alpha is constitutively expressed but rapidly targeted for proteasomal degradation after two proline residues are hydroxylated by a family of prolyl hydroxylases (PHDs). The PHDs are alpha-ketoglutarate-dependent dioxygenases that have low K(m) values for oxygen, making them important cellular oxygen sensors. Thus, when oxygen levels decrease, HIF-1alpha is not hydroxylated, and HIF-1 is activated. How Toxoplasma activates HIF-1 under normoxic conditions remains unknown. Here, we report that Toxoplasma infection increases HIF-1alpha stability by preventing HIF-1alpha prolyl hydroxylation. Infection significantly decreases PHD2 abundance, which is the key prolyl hydroxylase for regulating HIF-1alpha. The effects of Toxoplasma on HIF-1alpha abundance and prolyl hydroxylase activity require activin-like receptor kinase signaling. Finally, parasite growth is severely diminished when signaling from this family of receptors is inhibited. Together, these data indicate that PHD2 is a key host cell factor for T. gondii growth and represent a novel mechanism by which a microbial pathogen subverts host cell signaling and transcription to establish its replicative niche.

Interdependence of hypoxic and innate immune responses

Hypoxia-inducible factor (HIF) is an important transcriptional regulator of cell metabolism and the adaptation to cellular stress caused by oxygen deficiency (hypoxia). Phagocytic cells have an essential role in innate immune defence against pathogens and this is a battle that takes place mainly in the hypoxic microenvironments of infected tissues. It has now become clear that HIF promotes the bactericidal activities of phagocytic cells and supports the innate immune functions of dendritic cells, mast cells and epithelial cells. In response to microbial pathogens, HIF expression is upregulated through pathways involving the key immune response regulator nuclear factor-kappaB, highlighting an interdependence of the innate immune and hypoxic responses to infection and tissue damage. In turn, HIF-driven innate immune responses have important consequences for both the pathogen and the host, such that the tissue microenvironment fundamentally influences susceptibility to infectious disease.

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.

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.

Hyperbaric oxygen therapy reduces the size of Leishmania amazonensis-induced soft tissue lesions in mice

In this study we determined whether exposing mice to hyperbaric oxygen (HBO) would alter various disease parameters of a susceptible mouse strain infected with Leishmania amazonensis. BALB/c mice exposed to HBO (100% O2 at a pressure of 2.5 ATA, 1h before parasite inoculation and subsequently for 20 days) showed significant delay in lesion development and reduction in lesion parasite burdens compared with HBO-unexposed mice. Circulating levels of interferon gamma (IFN-gamma) and tumor necrosis factor (TNF-alpha) were significantly elevated in HBO-exposed as compared to HBO-unexposed mice. Concanavalin A-stimulated lymph nodes cultures from HBO-exposed mice released significantly more IFN-gamma and less interleukin 10 (IL-10) than cultures from HBO-unexposed mice, consistent with a skewed Th1 response. These results demonstrate, for the first time, that HBO can play a pathogen control role during leishmaniasis. Further studies are needed to elucidate whether hyperoxia alone or increased atmospheric pressure alone can exert a similar effect.

The host cell transcription factor hypoxia-inducible factor 1 is required for Toxoplasma gondii growth and survival at physiological oxygen levels

Toxoplasma gondii is an obligate intracellular protozoan pathogen. We previously found that genes mediating cellular responses to hypoxia were upregulated in Toxoplasma -infected cells but not in cells infected with another intracellular pathogen, Trypanosoma cruzi. The inducible expression of these genes is controlled by the hypoxia-inducible factor 1 (HIF1) transcription factor, which is the master regulator of cells exposed to low oxygen. Because this response may be important for parasites to grow at physiological oxygen levels, we tested the hypothesis that HIF1 is important for Toxoplasma growth. Here, we demonstrate that Toxoplasma infection rapidly increased the abundance of the HIF1alpha subunit and activated HIF1 reporter gene expression. In addition, we found that Toxoplasma growth and survival was severely reduced in HIF1alpha knockout cells at 3% oxygen. While HIF1alpha was not required for parasite invasion, we determined that HIF1 was required for parasite cell division and organelle maintenance at 3% oxygen. These data indicate that Toxoplasma activates HIF1 and requires HIF1 for growth and survival at physiologically relevant oxygen levels.

A soluble pyrophosphatase, a key enzyme for polyphosphate metabolism in Leishmania

We report the functional characterization in Leishmania amazonensis of a soluble pyrophosphatase (LaVSP1) that localizes in acidocalcisomes, a vesicular acidic compartment. LaVSP1 is preferentially expressed in metacyclic forms. Experiments with dominant negative mutants show the requirement of LaVSP1 functional expression for metacyclogenesis and virulence in mice. Depending on the pH and the cofactors Mg2+ or Zn2+, both present in acidocalcisomes, LaVSP1 hydrolyzes either inorganic pyrophosphate (Km = 92 microM, kcat = 125 s(-1)), tripolyphosphate (Km = 1153 microM, kcat = 131 s(-1)), or polyphosphate of 28 residues (Km = 123 microM, kcat = 8 s(-1)). Predicted structural analysis suggests that the structural orientation of the residue Lys78 in LaVSP1 accounts for the observed increase in Km compared with the yeast pyrophosphatase and for the ability of trypanosomatid VSP1 enzymes to hydrolyze polyphosphate. These results make the VSP1 enzyme an attractive drug target against trypanosomatid parasites.