Leishmania and its quest for iron: An update and overview

Cutaneous leishmaniasis and iron metabolism: current insights and challenges

Leishmaniasis is a vector-borne parasitic infection induced by protozoa of the genus Leishmania. The disease spectrum ranges from skin lesions to visceral leishmaniasis, which is fatal if untreated. The cutaneous leishmaniasis is characterized by a clinical polymorphism of lesions with a broad range of severity ranging from a self-limited lesion to multiple disfiguring lesions stigmatizing the patient for life. Although iron is required for several process of Leishmania infection including survival, growth and virulence, the number of studies on host iron metabolism during this infection remains limited. Iron homeostasis in the body is finely regulated by hepcidin, a hyposideremic peptide highly expressed in the liver. In infectious contexts, hepcidin plays additionally an antimicrobial role, acting through various mechanisms such as retaining iron in tissues, modulating the immune response, and operating as a defensin against gram-negative bacteria. This review mainly summarizes the most important interconnections between iron metabolism, hepcidin and leishmaniasis. A deeper understanding of iron metabolism in this context could help in developing innovative treatment strategies that target the parasite while simultaneously reinforcing host defenses.

Enhanced anticancer effect of thymidylate synthase dimer disrupters by promoting intracellular accumulation

Introduction

Thymidylate synthase (TS) plays a crucial role in cellular growth, proliferation, DNA synthesis, and repair, thus gaining attention for targeted therapies in cancer. TS overexpression and the altered pharmacokinetics of anti-TS drugs are among the most prominent causes of cellular resistance. Decreased drug influx and/or efficient efflux result in reduced drug access to the intracellular targets.

Results

In this study, we have evaluated and demonstrated the increased cytotoxic efficacy of novel TS dimer disrupters (Ddis) in the presence of specific inhibitors of drug efflux protein pumps in ovarian and colon cancer cells, suggesting that these compounds are substrates of the cellular drug extruders. A second strategy adopted to favor intracellular accumulation was to employ, as a drug delivery system, a molecular tool able to help less lipophilic compounds to cross the cell membrane. The Ddis were delivered through the SAINT-Protein transfection agent. The observed cell-killing effects agreed with the reduction of TS protein level and cell cycle perturbation.

Conclusion

Overall, this preclinical study suggests that the innovative TS dimer disrupters can be optimized by increasing their intracellular accumulation by both inhibiting their outflow and/or enhancing cellular uptake.

Hemoglobin uptake and utilization by human protozoan parasites: a review

The protozoan disease is a major global health concern. Amoebiasis, leishmaniasis, Chagas disease, and African sleeping sickness affect several million people worldwide, leading to millions of deaths annually and immense social and economic problems. Iron is an essential nutrient for nearly all microbes, including invading pathogens. The majority of iron in mammalian hosts is stored intracellularly in proteins, such as ferritin and hemoglobin (Hb). Hb, present in blood erythrocytes, is a very important source of iron and amino acids for pathogenic microorganisms ranging from bacteria to eukaryotic pathogens, such as worms, protozoa, yeast, and fungi. These organisms have developed adequate mechanisms to obtain Hb or its byproducts (heme and globin) from the host. One of the major virulence factors identified in parasites is parasite-derived proteases, essential for host tissue degradation, immune evasion, and nutrient acquisition. The production of Hb-degrading proteases is a Hb uptake mechanism that degrades globin in amino acids and facilitates heme release. This review aims to provide an overview of the Hb and heme-uptake mechanisms utilized by human pathogenic protozoa to survive inside the host.

The Possible Role of Selected Vitamins and Minerals in the Therapeutic Outcomes of Leishmaniasis

Leishmaniasis is a protozoal disease declared as an endemic in areas suffering from severe malnutrition and poverty. The factors associated with poverty like low income, ecological factors, and malnutrition cause disruption in immunity and host defense increasing risk of infection. Altered resistance to infection and host susceptibility are associated with low micronutrient levels in undernourished patients. Malnutrition has been recognized as a poor predictive marker for leishmaniasis, in particular the deficiency of trace elements like zinc, iron, and vitamin A, B, C, D which has a prominent function in the regulation of innate and adaptive immunity, cell proliferation, human physiology, etc. Malnourishment can exacerbate host sensitivity and pathophysiologic intensity to infection in variety of ways, whereas infection can enhance underlying poor nutrition or enhance host vulnerability and sandfly's urge to attack specific hosts. The intensity of leishmaniasis can be influenced by body mass and micronutrient availability in the blood. Vitamin D, C, zinc, and iron are proved effective in inhibiting the growth of leishmaniasis in both amastigote or promastigote forms, either directly or by acting as precursor for a pathway which inhibits the parasite growth. This article elucidates a new perception to the crucial role of micronutrients and their probable role in the therapeutic outcomes of leishmaniasis. Since there is requirement of novel drugs to fight drug resistance and relapse of leishmaniasis, this article may pave way to understand the importance of micronutrients and their role in therapeutic outcomes of leishmaniasis.

Label-Free Mass Spectrometry Proteomics Reveals Different Pathways Modulated in THP-1 Cells Infected with Therapeutic Failure and Drug Resistance Leishmania infantum Clinical Isolates

As the world is facing increasing difficulties to treat leishmaniasis with current therapies, deeper investigation into the molecular mechanisms responsible for both drug resistance and treatment failure (TF) is essential in drug discovery and development. So far, few available drugs cause severe side effects and have developed several resistance mechanisms. Drug resistance and TF parasite strains from clinical isolates may have acquired altered expression of proteins that characterize specific mechanisms leading to therapy inefficacy. This work aims to identify the biochemical pathways of THP-1 human monocytes infected by different Leishmania infantum clinical isolates from patients with either resistance or with TF outcome, using whole cell differential Mass Spectrometry proteomics. We have adopted network enrichment analysis to integrate the transcriptomics and the proteomic results of infected cells studies. Transferrin receptor C (TFRC) and nucleoside diphosphate kinase 3 (NDK3) were discovered as overexpressed proteins in THP-1 cells infected with paromomycin, antimony, and miltefosine resistant L. infantum lines. The overall achievements represent founding concepts to confirm new targets involved in the parasitic drug resistance and TF mechanisms, and to consider in perspective the importance of a dual host-guest pharmacological approach to treat the acute stage of the disease.

Ein Update zur Leishmaniose des Hundes: Diagnostik, Therapie und Monitoring

Aufgrund von steigenden Importzahlen von Hunden aus dem Ausland, zunehmendem Reiseverkehr sowie den Veränderungen klimatischer Bedingungen in Europa gewinnen Infektionen mit Leishmania (L.) infantum bei Hunden in Deutschland zunehmend an Bedeutung. Daher sollten auch Hunde aus dem Ausland, die keine klinischen Symptome zeigen, direkt nach Import sowie erneut 6 Monate später auf vektorübertragene Infektionserreger getestet werden. Bei Hunden mit klinischer Symptomatik, die hinweisend auf eine Leishmaniose sind, werden direkte und indirekte Nachweisverfahren sowie eine hämatologische und biochemische Untersuchung unter Einbezug von Serumeiweißelektrophorese sowie Bestimmung des C-reaktiven Proteins empfohlen. Als Leitfaden für die Therapie sowie das Monitoring stehen die LeishVet-Guidelines zur Verfügung. Es stehen leishmanizide und leishmaniostatische Wirkstoffe zur Verfügung, die in first-line, second-line und third-line unterschieden werden. Zur Anpassung der Allopurinol-Dosierung wird der Stufenplan empfohlen. Aufgrund der Veränderung der klimatischen Bedingungen kommt es zu einer Ausbreitung der Habitate von Sandmücken, die als Vektoren der Leishmaniose bekannt sind. Als weitere Infektionsquellen sind Deckakte, transplazentare Infektionen, Bisswunden und Bluttransfusionen beschrieben. Leishmania infantum hat zoonotisches Potential und ist daher auch in Hinblick auf den „One-Health“-Gedanken bedeutend.

Exploring the paradox of defense between host and Leishmania parasite

Leishmaniasis, a neglected tropical disease, still remains a global concern for the healthcare sector. The primary causative agents of the disease comprise diverse leishmanial species, leading to recurring failures in disease diagnosis and delaying the initiation of appropriate chemotherapy. Various species of the Leishmania parasite cause diverse clinical manifestations ranging from skin ulcers to systemic infections. Therefore, host immunity in response to different forms of infecting species of Leishmania becomes pivotal in disease progression or regression. Thus, understanding the paradox of immune arsenals during host and parasite interface becomes crucial to eliminate this deadly disease. In the present review, we have elaborated on the immunological perspectives of the disease and discussed primary host immune cells that form a defense line to counteract parasite infection. Furthermore, we also have shed light on the immune cells and effector molecules responsible for parasite survival in host lethal milieu/ environment. Next, we have highlighted recent molecules/compounds showing potent leishmanicidal activities pertaining to their pro-oxidant and immuno-modulatory mechanisms. This review addresses an immuno-biological overview of the factors influencing the parasitic disease, as this knowledge can aid in the unraveling/ identification of potential biomarkers, novel therapeutics, and vaccine candidates against leishmaniasis.

Arginine sensing in intracellular parasitism of Leishmania

Protozoa of the genus Leishmania are intracellular parasites that cause human leishmaniasis, a disease spread mostly in the tropics and subtropics. Leishmania cycle between the midgut of female sand flies and phagolysosome of mammalian macrophages. During their life cycle they constantly encounter changing nutritional environments. To monitor the external concentration of essential nutrients, the invading parasites employ sensors that report on the availability of these nutrients; but to-date only a few sensing pathways have been identified in Leishmania. This review focuses on the Arginine Deprivation Response, which both extracellular and intracellular Leishmania utilize to monitor environmental arginine and adjust their arginine transporter (AAP3) levels accordingly.

Caryocar coriaceum Wittm. fruit extracts as Leishmania inhibitors: in-vitro and in-silico approaches

Leishmaniasis is a group of neglected diseases caused by parasites of the Leishmania genus. The treatment of Leishmaniasis represents a great challenge, because the available drugs present high toxicity and none of them is fully effective. Caryocar is a botanical genus rich in phenolic compounds, which leaves extracts have already been described by its antileishmanial action. Thus, we investigated the effect of pulp and peel extracts of the Caryocar coriaceum fruit on promastigote and amastigote forms of Leishmania amazonensis. Both extracts had antipromastigote effect after 24, 48, and 72 h, and this effect was by apoptosis-like process induction, with reactive oxygen species (ROS) production, damage to the mitochondria and plasma membrane, and phosphatidylserine exposure. Knowing that the fruit extracts did not alter the viability of macrophages, we observed that the treatment reduced the infection of these cells. Thereafter, in the in vitro infection context, the extracts showed antioxidant proprieties, by reducing NO, ROS, and MDA levels. Besides, both peel and pulp extracts up-regulated Nrf2/HO-1/Ferritin expression and increase the total iron-bound in infected macrophages, which culminates in a depletion of available iron for L. amazonensis replication. In silico, the molecular modeling experiments showed that the three flavonoids presented in the C. coriaceum extracts can act as synergistic inhibitors of Leishmania proteins, and compete for the active site. Also, there is a preference for rutin at the active site due to its greater interaction binding strength.

Evaluation of the Pharmacophoric Role of the O-O Bond in Synthetic Antileishmanial Compounds: Comparison between 1,2-Dioxanes and Tetrahydropyrans

Leishmaniases are neglected diseases that can be treated with a limited drug arsenal; the development of new molecules is therefore a priority. Recent evidence indicates that endoperoxides, including artemisinin and its derivatives, possess antileishmanial activity. Here, 1,2-dioxanes were synthesized with their corresponding tetrahydropyrans lacking the peroxide bridge, to ascertain if this group is a key pharmacophoric requirement for the antileishmanial bioactivity. Newly synthesized compounds were examined in vitro, and their mechanism of action was preliminarily investigated. Three endoperoxides and their corresponding tetrahydropyrans effectively inhibited the growth of Leishmania donovani promastigotes and amastigotes, and iron did not play a significant role in their activation. Further, reactive oxygen species were produced in both endoperoxide- and tetrahydropyran-treated promastigotes. In conclusion, the peroxide group proved not to be crucial for the antileishmanial bioactivity of endoperoxides, under the tested conditions. Our findings reveal the potential of both 1,2-dioxanes and tetrahydropyrans as lead compounds for novel therapies against Leishmania.

Mathematical Modelling Using Predictive Biomarkers for the Outcome of Canine Leishmaniasis upon Chemotherapy

Prediction parameters of possible outcomes of canine leishmaniasis (CanL) therapy might help with therapeutic decisions and animal health care. Here, we aimed to develop a diagnostic method with predictive value by analyzing two groups of dogs with CanL, those that exhibited a decrease in parasite load upon antiparasitic treatment (group: responders) and those that maintained high parasite load despite the treatment (group: non-responders). The parameters analyzed were parasitic load determined by q-PCR, hemogram, serum biochemistry and immune system-related gene expression signature. A mathematical model was applied to the analysis of these parameters to predict how efficient their response to therapy would be. Responder dogs restored hematological and biochemical parameters to the reference values and exhibited a Th1 cell activation profile with a linear tendency to reach mild clinical alteration stages. Differently, non-responders developed a mixed Th1/Th2 response and exhibited markers of liver and kidney injury. Erythrocyte counts and serum phosphorus were identified as predictive markers of therapeutic response at an early period of assessment of CanL. The results presented in this study are highly encouraging and may represent a new paradigm for future assistance to clinicians to interfere precociously in the therapeutic approach, with a more precise definition in the patient's prognosis.

Iron trafficking in patients with Indian Post kala-azar dermal leishmaniasis

Background

During infections involving intracellular pathogens, iron performs a double-edged function by providing the pathogen with nutrients, but also boosts the host’s antimicrobial arsenal. Although the role of iron has been described in visceral leishmaniasis, information regarding its status in the dermal sequel, Post Kala-azar Dermal Leishmaniasis (PKDL) remains limited. Accordingly, this study aimed to establish the status of iron within monocytes/macrophages of PKDL cases.

Methodology/Principal findings

The intramonocytic labile iron pool (LIP), status of CD163 (hemoglobin-haptoglobin scavenging receptor) and CD71 (transferrin receptor, Tfr) were evaluated within CD14⁺ monocytes by flow cytometry, and soluble CD163 by ELISA. At the lesional sites, Fe³⁺ status was evaluated by Prussian blue staining, parasite load by qPCR, while the mRNA expression of Tfr (TfR1/CD71), CD163, divalent metal transporter-1 (DMT-1), Lipocalin-2 (Lcn-2), Heme-oxygenase-1 (HO-1), Ferritin, Natural resistance-associated macrophage protein (NRAMP-1) and Ferroportin (Fpn-1) was evaluated by droplet digital PCR. Circulating monocytes demonstrated elevated levels of CD71, CD163 and soluble CD163, which corroborated with an enhanced lesional mRNA expression of TfR, CD163, DMT1 and Lcn-2. Additionally, the LIP was raised along with an elevated mRNA expression of ferritin and HO-1, as also iron exporters NRAMP-1 and Fpn-1.

Conclusions/Significance

In monocytes/macrophages of PKDL cases, enhancement of the iron influx gateways (TfR, CD163, DMT-1 and Lcn-2) possibly accounted for the enhanced LIP. However, enhancement of the iron exporters (NRAMP-1 and Fpn-1) defied the classical Ferritin^low/Ferroportin^high phenotype of alternatively activated macrophages. The creation of such a pro-parasitic environment suggests incorporation of chemotherapeutic strategies wherein the availability of iron to the parasite can be restricted.

Post kala-azar dermal leishmaniasis (PKDL), a dermal sequel of Visceral Leishmaniasis (VL) is caused by the digenetic protozoan parasite Leishmania donovani. The parasite infects humans and replicates intracellularly within macrophages, cells normally engaged in protecting the host from pathogens. Iron plays a crucial role in microbes and mammalian cells, being needed by the former for its growth and survival, while the latter uses it for activation of the immune system by facilitating generation of reactive oxygen species. Therefore, the availability of iron needs to be tightly regulated to ensure its accessibility for core biological functions, and yet prevent its utilization by intracellular pathogens. Here we investigated the status of intra-macrophage iron along with expression of its transporters in patients with PKDL. Our study suggests that within monocytes/macrophages there is an enhanced entry of iron via the upregulation of CD71 and CD163 that translates into an enhanced labile iron pool and Ferritin. However, the concomitant increase in expression of iron exporters NRAMP-1 and Fpn-1 suggested the host’s attempt to deny the pathogen access to iron. This Ferritin^high/Ferroportin^high phenotype was in contrast to the conventional Ferritin^low/Ferroportin^high phenotype present in alternatively activated M2 macrophages. Taken together, the control of iron homeostasis is one of the contributors in the host-pathogen interplay as it influences the course of an infectious disease by favouring either the mammalian host or the invading pathogen.

Proteomic Analysis Reveals a Predominant NFE2L2 (NRF2) Signature in Canonical Pathway and Upstream Regulator Analysis of Leishmania-Infected Macrophages

CBA mice macrophages (MØ) control infection by Leishmania major and are susceptive to Leishmania amazonensis, suggesting that both parasite species induce distinct responses that play important roles in infection outcome. To evaluate the MØ responses to infection arising from these two Leishmania species, a proteomic study using a Multidimensional Protein Identification Technology (MudPIT) approach with liquid chromatography tandem mass spectrometry (LC-MS/MS) was carried out on CBA mice bone-marrow MØ (BMMØ). Following SEQUEST analysis, which revealed 2,838 proteins detected in BMMØ, data mining approach found six proteins significantly associated with the tested conditions. To investigate their biological significance, enrichment analysis was performed using Ingenuity Pathway Analysis (IPA). A three steps IPA approach revealed 4 Canonical Pathways (CP) and 7 Upstream Transcriptional Factors (UTFs) strongly associated with the infection process. NRF2 signatures were present in both CPs and UTFs pathways. Proteins involved in iron metabolism, such as heme oxigenase 1 (HO-1) and ferritin besides sequestosome (SQSMT1 or p62) were found in the NRF2 CPs and the NRF2 UTFs. Differences in the involvement of iron metabolism pathway in Leishmania infection was revealed by the presence of HO-1 and ferritin. Noteworty, HO-1 was strongly associated with L. amazonensis infection, while ferritin was regulated by both species. As expected, higher HO-1 and p62 expressions were validated in L. amazonensis-infected BMMØ, in addition to decreased expression of ferritin and nitric oxide production. Moreover, BMMØ incubated with L. amazonensis LPG also expressed higher levels of HO-1 in comparison to those stimulated with L. major LPG. In addition, L. amazonensis-induced uptake of holoTf was higher than that induced by L. major in BMMØ, and holoTf was also detected at higher levels in vacuoles induced by L. amazonensis. Taken together, these findings indicate that NRF2 pathway activation and increased HO-1 production, together with higher levels of holoTf uptake, may promote permissiveness to L. amazonensis infection. In this context, differences in protein signatures triggered in the host by L. amazonensis and L. major infection could drive the outcomes in distinct clinical forms of leishmaniasis.

Susceptibility to leishmaniasis is affected by host SLC11A1 gene polymorphisms: a systematic review and meta-analysis

Leishmaniases are cutaneous, mucocutaneous, and visceral diseases affecting humans and domesticated animals mostly in the tropical and subtropical areas of the planet. Host genetics have been widely investigated for their role in developing various infectious diseases. The SLC11A1 gene has been reported to play a role in neutrophil function and is associated with susceptibility to infectious and inflammatory diseases such as tuberculosis or rheumatoid arthritis. In the present meta-analysis, we investigate the genetic association of SLC11A1 polymorphisms with susceptibility to leishmaniasis. Genotypes and other risk-related data were collected from 13 case-control and family-based studies (after literature search). Conventional random-effects meta-analysis was performed using STATA 13. To pool case-control and family-based data, the weighted Stouffer's method was also applied. Eight polymorphisms were investigated: rs2276631, rs3731865, rs3731864, rs17221959, rs201565523, rs2279015, rs17235409, and rs17235416. We found that rs17235409 (D543N) and rs17235416 (1729 + 55del4) are significantly associated with a risk for cutaneous leishmaniasis (CL), whereas rs17221959, rs2279015, and rs17235409 are associated with visceral leishmaniasis (VL). Our results suggest that polymorphisms in SLC11A1 affect susceptibility to CL and VL. These findings open new pathways in understanding macrophage response to Leishmania infection and the genetic factors predisposing to symptomatic CL or VL that can lead to the usage of predictive biomarkers in populations at risk.

Caffeic acid has antipromastigote activity by apoptosis-like process; and anti-amastigote by TNF-α/ROS/NO production and decreased of iron availability

BACKGROUND

Leishmaniasis is a disease caused by protozoan parasites of the Leishmania genus whose current treatment has high cost, highly toxic, and difficult administration, which makes it very important to find alternative natural compounds of high efficiency and low cost.

PURPOSE

This study assessed the in vitro effect of caffeic acid (CA) on promastigotes and L. amazonensis-infected macrophages.

METHODS

Evaluation of the in vitro leishmanicidal activity of CA against promastigotes and L. amazonensis infected peritoneal macrophages, as well its microbicide mechanisms.

RESULTS

CA 12.5-100 µg/ml were able to inhibit promastigotes proliferation at all tested periods. The IC₅₀, 12.5 µg/ml, also altered promastigote cell morphology and cell volume accompanied by loss of mitochondrial integrity, increase in reactive oxygen species (ROS) production, phosphatidylserine exposure, and loss of plasma membrane integrity - characterizing the apoptosis-like process. Moreover, CA reduced the percentage of infected macrophages and the number of amastigotes per macrophages increasing TNF-α, ROS, NO and reducing IL-10 levels as well as iron availability.

CONCLUSION

CA showed in vitro antipromastigote and antiamostigote by increasing oxidant and inflammatory response important to eliminate the parasite.

Grandiflorenic acid promotes death of promastigotes via apoptosis-like mechanism and affects amastigotes by increasing total iron bound capacity

BACKGROUND

American tegumentary leishmaniasis (ATL) is a zoonotic disease caused by protozoa of the genus Leishmania. The high toxicity, high costs and resistance of some strains to current drugs has prompted the search for therapeutic alternatives for the management of this disease. Sphagneticola trilobata is a plant that has diterpenes as main constituents, including grandiflorenic acid (GFA) that has antiinflammatory, antiprotozoal, antibacterial and antinociceptive activity.

PURPOSE

The aim of our study was to determine the effect of GFA on both the promastigotes and the amastigotes of Leishmania amazonensis.

METHODS

Isolation by chromatographic methods and chemical identification of GFA, then evaluation of the in vitro leishmanicidal activity of this compound against Leishmania amazonensis promastigotes and L. amazonensis infected peritoneal Balb/c macrophages, as well its action and microbicide mechanisms.

RESULTS

GFA treatment significantly inhibited the proliferation of promastigotes. This antiproliferative effect was accompanied by morphological changes in the parasite with 25 nM GFA. Afterwards, we investigated the mechanisms involved in the death of the protozoan; there was an increase in the production of reactive oxygen species (ROS), phosphatidylserine exposure, permeabilization of the plasma membrane and decreased mitochondrial depolarization. In addition, we observed that the treatment caused a reduction in the percentage of infected cells and the number of amastigotes per macrophage, without showing cytotoxicity in low doses to peritoneal macrophages and sheep erythrocytes. GFA increased IL-10 and total iron bound to transferrin in infected macrophages. Our results showed that GFA treatment acts on promastigote forms through an apoptosis-like mechanism and on intracellular amastigote forms, dependent of regulatory cytokine IL-10 modulation with increase in total iron bound to transferrin.

CONCLUSION

GFA showed in vitro antileishmanial activity on L. amazonensis promastigotes forms and on L. amazonensis-infected macrophages.

A MFS-like plasma membrane transporter required for Leishmania virulence protects the parasites from iron toxicity

Iron is essential for many cellular processes, but can generate highly toxic hydroxyl radicals in the presence of oxygen. Therefore, intracellular iron accumulation must be tightly regulated, by balancing uptake with storage or export. Iron uptake in Leishmania is mediated by the coordinated action of two plasma membrane proteins, the ferric iron reductase LFR1 and the ferrous iron transporter LIT1. However, how these parasites regulate their cytosolic iron concentration to prevent toxicity remains unknown. Here we characterize Leishmania Iron Regulator 1 (LIR1), an iron responsive protein with similarity to membrane transporters of the major facilitator superfamily (MFS) and plant nodulin-like proteins. LIR1 localizes on the plasma membrane of L. amazonensis promastigotes and intracellular amastigotes. After heterologous expression in Arabidopsis thaliana, LIR1 decreases the iron content of leaves and worsens the chlorotic phenotype of plants lacking the iron importer IRT1. Consistent with a role in iron efflux, LIR1 deficiency does not affect iron uptake by L. amazonensis but significantly increases the amount of iron retained intracellularly in the parasites. LIR1 null parasites are more sensitive to iron toxicity and have drastically impaired infectivity, phenotypes that are reversed by LIR1 complementation. We conclude that LIR1 functions as a plasma membrane iron exporter with a critical role in maintaining iron homeostasis and promoting infectivity in L. amazonensis.

Modulation of mitochondrial metabolism as a biochemical trait in blood feeding organisms: the redox vampire hypothesis redux

Hematophagous organisms undergo remarkable metabolic changes during the blood digestion process, increasing fermentative glucose metabolism, and reducing respiratory rates, both consequence of functional mitochondrial remodeling. Here, we review the pathways involved in energy metabolism and mitochondrial functionality in a comparative framework across different hematophagous species, and consider how these processes regulate redox homeostasis during blood digestion. The trend across distinct species indicate that a switch in energy metabolism might represent an important defensive mechanism to avoid the potential harmful interaction of oxidants generated from aerobic energy metabolism with products derived from blood digestion. Indeed, in insect vectors, blood feeding transiently reduces respiratory rates and oxidant production, irrespective of tissue and insect model. On the other hand, a different scenario is observed in several unrelated parasite species when exposed to blood digestion products, as respiratory rates reduce and mitochondrial oxidant production increase. The emerging picture indicates that re-wiring of energy metabolism, through reduced mitochondrial function, culminates in improved tolerance to redox insults and seems to represent a key step for hematophagous organisms to cope with the overwhelming and potentially toxic blood meal.