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

BOTH THE INFECTION STATUS AND INFLAMMATORY MICROENVIRONMENT INDUCE TRANSCRIPTIONAL REMODELING IN MACROPHAGES IN MURINE LEISHMANIAL LESIONS

Cutaneous leishmaniasis is caused by infection with the protozoan parasite Leishmania, which resides intracellularly in dermal macrophages (Mø), producing lesions. The skin lesions are characterized by proinflammatory cytokines and growth factors as well as inflammatory hypoxia, creating a stressful microenvironment for Mø. Of importance, not all Mø in lesions harbor parasites. To distinguish the influence of the parasite from the inflammatory microenvironment after Leishmania major (LM) infection on the Mø, we performed single-cell RNA sequencing and compared Mø associated with LM transcripts (or 'infected' Mø) with Mø not associated with LM transcripts (or 'bystander' Mø) within the lesions. Our findings show coordinated lysosomal expression and regulation signaling with increased cathepsin and H+-ATPase transcripts are upregulated in infected compared with bystander Mø. Additionally, eukaryotic initiation factor 2 (EIF2) signaling is downregulated in infected compared with bystander Mø, which includes many small and large ribosomal subunit (Rps and Rpl) transcripts being decreased in Mø harboring parasites. Furthermore, we also find EIF2 signaling including EIF, Rps, and Rpl transcripts being downregulated in bystander Mø compared with Mø from naïve skin. These data suggest that both the parasite and the inflammatory host microenvironment affect the transcription of ribosomal machinery in lesional Mø, thereby potentially affecting the ability of these cells to perform translation, protein synthesis, and thus function. Altogether, these results suggest that both the parasite and host inflammatory microenvironment independently drive transcriptional remodeling in Mø during LM infection in vivo.

Hypoxia-Inducible Factor-1 Alpha Stabilization in Human Macrophages during Leishmania major Infection Is Impaired by Parasite Virulence

Hypoxia-inducible factor-1 alpha (HIF-1α) is one of the master regulators of immune and metabolic cellular functions. HIF-1α, a transcriptional factor whose activity is closely related to oxygen levels, is a target for understanding infectious disease control. Several studies have demonstrated that HIF-1α plays an important role during the infectious process, while its role in relation to parasite virulence has not been addressed. In this work, we studied the expression levels of HIF-1α and related angiogenic vascular endothelial growth factor A (VEGF-A) in human macrophages infected with promastigotes of hypo- or hyper-virulent Leishmania major human isolates. L. major parasites readily subverted host macrophage functions for their survival and induced local oxygen consumption at the site of infection. In contrast to hypo-virulent parasites that induce high HIF-1α expression levels, hyper-virulent L. major reduced HIF-1α expression in macrophages under normoxic or hypoxic conditions, and consequently impeded the expression of VEGF-A mRNA. HIF-1α may play a key role during control of disease chronicity, severity, or outcome.

Hypoxia-Inducible Factor Signaling in Macrophages Promotes Lymphangiogenesis in Leishmania major Infection

Vascular remodeling is a phenomenon seen in the cutaneous lesions formed during infection with Leishmania parasites. Within the lesion, Leishmania major infection leads to the infiltration of inflammatory cells, including macrophages, and is associated with hypoxic conditions and lymphangiogenesis in the local site. This low-oxygen environment is concomitant with the expression of hypoxic inducible factors (HIFs), which initiate the expression of vascular endothelial growth factor-A (VEGF-A) in macrophages during the infection. Here, we found that macrophage hypoxia is elevated in the skin, and the HIF target Vegfa is preferentially expressed at the site of infection. Further, transcripts indicative of both HIF-1α and HIF-2α activation were increased at the site of infection. Given that HIF mediates VEGF-A and that VEGF-A/VEGFR-2 signaling induces lymphangiogenesis, we wanted to investigate the link between myeloid HIF activation and lymphangiogenesis during L. major infection. We show that myeloid aryl hydrocarbon receptor nuclear translocator (ARNT)/HIF/VEGF-A signaling promotes lymphangiogenesis (the generation of newly formed vessels within the local lymphatic network), which helps resolve the lesion by draining away inflammatory cells and fluid. Concomitant with impaired lymphangiogenesis, we find the deletion of myeloid ARNT/HIF signaling leads to an exacerbated inflammatory response associated with a heightened CD4⁺ Th1 immune response following L. major infection. Altogether, our data suggest that VEGF-A-mediated lymphangiogenesis occurs through myeloid ARNT/HIF activation following Leishmania major infection and this process is critical in limiting immunopathology.

miR-548d-3p Alters Parasite Growth and Inflammation in Leishmania (Viannia) braziliensis Infection

American Tegumentary Leishmaniasis (ATL) is an endemic disease in Latin America, mainly caused in Brazil by Leishmania (Viannia) braziliensis. Clinical manifestations vary from mild, localized cutaneous leishmaniasis (CL) to aggressive mucosal disease. The host immune response strongly determines the outcome of infection and pattern of disease. However, the pathogenesis of ATL is not well understood, and host microRNAs (miRNAs) may have a role in this context. In the present study, miRNAs were quantified using qPCR arrays in human monocytic THP-1 cells infected in vitro with L. (V.) braziliensis promastigotes and in plasma from patients with ATL, focusing on inflammatory response-specific miRNAs. Patients with active or self-healed cutaneous leishmaniasis patients, with confirmed parasitological or immunological diagnosis, were compared with healthy controls. Computational target prediction of significantly-altered miRNAs from in vitro L. (V.) braziliensis-infected THP-1 cells revealed predicted targets involved in diverse pathways, including chemokine signaling, inflammatory, cellular proliferation, and tissue repair processes. In plasma, we observed distinct miRNA expression in patients with self-healed and active lesions compared with healthy controls. Some miRNAs dysregulated during THP-1 in vitro infection were also found in plasma from self-healed patients, including miR-548d-3p, which was upregulated in infected THP-1 cells and in plasma from self-healed patients. As miR-548d-3p was predicted to target the chemokine pathway and inflammation is a central to the pathogenesis of ATL, we evaluated the effect of transient transfection of a miR-548d-3p inhibitor on L. (V.) braziliensis infected-THP-1 cells. Inhibition of miR-548d-3p reduced parasite growth early after infection and increased production of MCP1/CCL2, RANTES/CCL5, and IP10/CXCL10. In plasma of self-healed patients, MCP1/CCL2, RANTES/CCL5, and IL-8/CXCL8 concentrations were significantly decreased and MIG/CXCL9 and IP-10/CXCL10 increased compared to patients with active disease. These data suggest that by modulating miRNAs, L. (V.) braziliensis may interfere with chemokine production and hence the inflammatory processes underpinning lesion resolution. Our data suggest miR-548d-3p could be further evaluated as a prognostic marker for ATL and/or as a host-directed therapeutic target.

The role of vascular endothelium and exosomes in human protozoan parasitic diseases

The vascular endothelium is a vital component in maintaining the structure and function of blood vessels. The endothelial cells (ECs) mediate vital regulatory functions such as the proliferation of cells, permeability of various tissue membranes, and exchange of gases, thrombolysis, blood flow, and homeostasis. The vascular endothelium also regulates inflammation and immune cell trafficking, and ECs serve as a replicative niche for many bacterial, viral, and protozoan infectious diseases. Endothelial dysfunction can lead to vasodilation and pro-inflammation, which are the hallmarks of many severe diseases. Exosomes are nanoscale membrane-bound vesicles that emerge from cells and serve as important extracellular components, which facilitate communication between cells and maintain homeostasis during normal and pathophysiological states. Exosomes are also involved in gene transfer, inflammation and antigen presentation, and mediation of the immune response during pathogenic states. Protozoa are a diverse group of unicellular organisms that cause many infectious diseases in humans. In this regard, it is becoming increasingly evident that many protozoan parasites (such as Plasmodium, Trypanosoma, Leishmania, and Toxoplasma) utilize exosomes for the transfer of their virulence factors and effector molecules into the host cells, which manipulate the host gene expression, immune responses, and other biological activities to establish and modulate infection. In this review, we discuss the role of the vascular endothelium and exosomes in and their contribution to pathogenesis in malaria, African sleeping sickness, Chagas disease, and leishmaniasis and toxoplasmosis with an emphasis on their actions on the innate and adaptive immune mechanisms of resistance.

Leishmania infantum transfected with toxic plasmid induces protection in mice infected with wild type L. infantum or L. amazonensis

Leishmania infantum infection may cause visceral leishmaniasis (VL), a fatal disease having worldwide distribution, that may be silent or asymptomatic. The latter indicates that immunity is naturally developed in some individuals, and, therefore, a vaccine against VL would be possible. Molecular mechanisms of gene expression are being understood in Leishmania, and this knowledge may be useful for vaccine development. The aim of this study was developing an attenuated strain by regulating the expression of toxic proteins in a stage specific manner. For that purpose, the 3' UTR of an amastin gene, known by its increased expression in the amastigote phase, was selected for direct the expression of exogenous proteins. This construct (pFL-AMA), firstly, was proved effective for the expression of mCherry specifically in the intracellular form of L. infantum, as demonstrated by fluorescence microscopy, flow cytometry and Western blotting. Afterwards, mCherry coding sequence was replaced, in the pFL-AMA plasmid, by either egg avidin or the active form of bovine trypsin. Viability of transfected parasites was evaluated in promastigote axenic cultures and in in vitro infection of macrophages. Both lines of transfected parasites showed a limited capacity to multiply inside macrophages. BALB/c mice were inoculated intraperitoneally (i.p.) with a single dose consisting of 2 × 10⁶L. infantum promastigotes transfected with plasmids bearing the toxic genes. After 10 weeks post-inoculation, no parasites were recovered by limiting dilution in either liver or spleen, but a specific immunological response was detected. The immunization with transfected parasites induced cellular and humoral immune responses with activation of TCD4⁺, TCD8⁺ and B cells, having a TH1-type response with increased levels of pro-inflammatory cytokines such as IFN-γ, TNF-α and IL-6. In parallel groups of mice, a challenge consisting on 1 × 10⁶ virulent parasites of either L. infantum (inoculated i.p.) or L. amazonensis subcutaneously (s.c.) was performed. Vaccinated mice, challenged with L. infantum, showed lower parasite burdens in liver, spleen and bone marrow than infected mice with WT L. infantum (non-vaccinated); similarly, vaccinated mice developed smaller footpad inflammation than control group. These data support this strategy as an efficient immunization system aimed to the development of vaccines against different forms of leishmaniasis.

Tandem Mass Tag Proteomic Analysis of in Vitro and in Vivo Models of Cutaneous Leishmaniasis Reveals Parasite-Specific and Nonspecific Modulation of Proteins in the Host

Cutaneous leishmaniasis, the most common form of leishmaniasis, is endemic in several regions of the world, and if not treated properly, it can cause disfiguring scars on the skin. Leishmania spp. infection causes an inflammatory response in its host, and it modulates the host metabolism differently depending on the Leishmania species. Since Leishmania spp. has begun to develop resistance against current therapies, we believe efforts to identify new possibilities for treatment are critical for future control of the disease. Proteomics approaches such as isobaric labeling yield accurate relative quantification of protein abundances and, when combined with chemometrics/statistical analysis, provide robust information about protein modulation across biological conditions. Using a mass spectrometry-based proteomics approach and tandem mass tag labeling, we have investigated protein modulation in murine macrophages (in vitro model) and skin biopsies after exposure to Leishmania spp. (in vivo murine model). Infections induced by L. amazonensis (endemic in the New World) and L. major (endemic in the Old World) were compared to an inflammation model to search for Leishmania-specific and nonspecific protein modulation in the host. After protein extracts obtained from in vitro and in vivo experiments were digested, the resulting peptides were labeled with isobaric tags and analyzed by liquid chromatography-MS (LC-MS). Several proteins that were found to be changed upon infection with Leishmania spp. provide interesting candidates for further investigation into disease mechanism and development of possible immunotherapies.

Leishmania Infection Induces Macrophage Vascular Endothelial Growth Factor A Production in an ARNT/HIF-Dependent Manner

Cutaneous leishmaniasis is characterized by vascular remodeling. Following infection with Leishmania parasites, the vascular endothelial growth factor A (VEGF-A)/VEGF receptor 2 (VEGFR-2) signaling pathway mediates lymphangiogenesis, which is critical for lesion resolution. Therefore, we investigated the cellular and molecular mediators involved in VEGF-A/VEGFR-2 signaling using a murine model of infection. We found that macrophages are the predominant cell type expressing VEGF-A during Leishmania major infection. Given that Leishmania parasites activate hypoxia-inducible factor 1α (HIF-1α) and this transcription factor can drive VEGF-A expression, we analyzed the expression of HIF-1α during infection. We showed that macrophages were also the major cell type expressing HIF-1α during infection and that infection-induced VEGF-A production is mediated by ARNT/HIF activation. Furthermore, mice deficient in myeloid ARNT/HIF signaling exhibited larger lesions without differences in parasite numbers. These data show that L. major infection induces macrophage VEGF-A production in an ARNT/HIF-dependent manner and suggest that ARNT/HIF signaling may limit inflammation by promoting VEGF-A production and, thus, lymphangiogenesis during infection.

Comparative Proteomic Analysis of Murine Cutaneous Lesions Induced by Leishmania amazonensis or Leishmania major

Cutaneous leishmaniasisis is the most common clinical form of leishmaniasis and one of the most relevant neglected diseases. It is known that the progress of the disease is species specific and the host's immune response plays an important role in its outcome. However, the pathways that lead to parasite clearance or survival remain unknown. In this work, skin tissue from mice experimentally infected with L. amazonensis, one of the causative agents of cutaneous leishmaniasis in the Amazon region, L. major, another causative agent of cutaneous leishmaniasis in Africa, the Middle East, China, and India, or lipopolysaccharides from Escherichia coli as an inflammation model were investigated using label-free proteomics to unveil Leishmania-specific protein alterations. Proteomics is a powerful tool to investigate host-pathogen relationships to address biological questions. In this work, proteins from mice skin biopsies were identified and quantified using nano-LC coupled with tandem mass spectrometry analyses. Integrated Proteomics Pipeline was used for peptide/protein identification and quantification. Western blot was used for validation of protein quantification by mass spectrometry, and protein pathways were predicted using Ingenuity Pathway Analysis. In this proteomics study, several proteins were pointed out as hypothetical targets to guide future studies on Leishmania-specific modulation of proteins in the host. We identified hundreds of exclusively modulated proteins after Leishmania spp. infection and 17 proteins that were differentially modulated in the host after L. amazonensis or L. major infection.

Novel Nanosized Chitosan-Betulinic Acid Against Resistant Leishmania Major and First Clinical Observation of such parasite in Kidney

Regarding the antiparasitic effects of Betulinic acid (B) against Leishmaniasis, it was loaded into nanochitosan (K) for the first time in order to improve its therapeutic effects and decrease its side effects for the treatment of Leishmania major-infected Balb/c mice. Improvement the therapeutic efficacy of Bas an anti-leishmania agent through increasing the effective dose was achieved by using a novel solvent and phase separation method for K synthesis. The synthesized K with the size of 102 nm and Betulinic acid-nanochitosan (BK) with the size of 124 nm and drug loading efficiency of 93%, cellular uptake of 97.5% with the slow drug release pattern was prepared. To increase the therapeutic dose, a modified 10% acetic acid solvent was used. The in vitro and in vivo results showed that the nanodrug of BK was non toxic by 100% and BK20 mg/kg could completely performed the wound healing and inhibit the parasite in a large extent (P ˂ 0.001) compared to other groups. Therefore, BK could be considered as an alternative regimen for treatment of L. major.

Hypoxia, Hypoxia-Inducible Factor-1α, and Innate Antileishmanial Immune Responses

Low oxygen environments and accumulation of hypoxia-inducible factors (HIFs) are features of infected and inflamed tissues. Here, we summarize our current knowledge on oxygen levels found in Leishmania-infected tissues and discuss which mechanisms potentially contribute to local tissue oxygenation in leishmanial lesions. Moreover, we review the role of hypoxia and HIF-1 on innate antileishmanial immune responses.

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.