The effect of synthetic iron chelators on bacterial growth in human serum

Abstract The effect of synthetic iron chelators of the 1-alkyl-3-hydroxy-2-methylpyrid-4-one class (the L1 series) and 1-hydroxypyrid-2-one (L4) on bacterial growth in human serum was compared with those of the plant iron chelators mimosine and maltol and of the microbial siderophore desferrioxamine. None of the synthetic chelators enhanced growth of 3 Gram-negative organisms ( Yersinia enterocolitica, Escherichia coli and Pseudomonas aeruginosa ); in some cases they were even inhibitory. L4 strongly stimulated growth of Staphylococcus epidermidis , but the L1 series had only a marginal effect. Maltol was mildly inhibitory to all 4 bacterial species, while mimosine enhanced the growth of S. epidermidis and Y. enterocolitica but had little effect on E. coli or P. aeruginosa . Desferrioxamine enhanced the growth chelators of synthetic or plant origin may carry less risk of increasing susceptibility to bacterial infection in patients undergiong chelation therapy for iron overload than does desferrioxamine, the drug currently in clinical use.     

Unmasking of a potassium leak in resealed human red blood cell ghosts

A selective potassium leak is observed in resealed, human red blood cell ghosts when hemolysis is performed with distilled water at pH 6.5, 0° C. The leak, which has a maximum near pH 6.7, is suppressed when either magnesium or a chelating agent is present in the hemolysing medium. The potassium leak has the additional property that it can be suppressed after resealing by washing the ghost membranes in a medium containing a low concentration of ATP or EDTA. The data suggest that through the dilution of endogenous chelating agents at hemolysis a potassium leak may be unmasked.     

Iron homeostasis and eye disease

Background

Iron is necessary for life, but excess iron can be toxic to tissues. Iron is thought to damage tissues primarily by generating oxygen free radicals through the Fenton reaction.

Methods

We present an overview of the evidence supporting iron's potential contribution to a broad range of eye disease using an anatomical approach.

Results

Iron can be visualized in the cornea as iron lines in the normal aging cornea as well as in diseases like keratoconus and pterygium. In the lens, we present the evidence for the role of oxidative damage in cataractogenesis. Also, we review the evidence that iron may play a role in the pathogenesis of the retinal disease age-related macular degeneration. Although currently there is no direct link between excess iron and development of optic neuropathies, ferrous iron's ability to form highly reactive oxygen species may play a role in optic nerve pathology. Lastly, we discuss recent advances in prevention and therapeutics for eye disease with antioxidants and iron chelators.

General significance

Iron homeostasis is important for ocular health.     

Relationship of chloroquine-induced redistribution of a neutral aminopeptidase to hemoglobin accumulation in malaria parasites

To study the relationship between neutral aminopeptidase activity and hemoglobin accumulation in malaria parasites, we treated mice infected with Plasmodium berghei NYU-2 with chloroquine intraperitoneally in doses ranging from 0.3 to 3 micromol per 25 g mouse. Preparations of infected erythrocytes (normalized to represent 1000 parasites per 1000 erythrocytes) hydrolyzed 1200 nmol of leucine-p-nitroanilide per minute per milliliter of packed erythrocytes, which was 10x more than that of uninfected preparations. The activity in infected preparations was distinguished by resistance to ferriprotoporphyrin IX and puromycin and susceptibility to inhibition by ethanol and Tris. Chloroquine treatment caused the activity in unwashed membrane ghosts of infected preparations to decrease by 50% despite an increase in total activity. Concomitantly, hemoglobin in washed membrane ghosts increased. Electron microscopy revealed that the hemoglobin was retained in endocytic vesicles. Chloroquine-induced redistribution of a neutral aminopeptidase may be the cause of hemoglobin accumulation in endocytic vesicles of malaria parasites.     

Stem cell engineering might be protective against severe malaria

Hemoglobin variants are associated with protection from malaria. Stem cell engineering may yield erythrocytes with new modified hemoglobin which might protect against severe malaria.     

Therapeutic potential of induced iron depletion using iron chelators in Covid-19

Ferritin, which includes twenty-four light and heavy chains in varying proportions in different tissues, is primarily responsible for maintaining the body's iron metabolism. Its normal value is between 10 and 200 ngmL^?1 in men and between 30 and 300 ngmL^?1 in women. Iron is delivered to the tissue via them, and they act as immunomodulators, signaling molecules, and inflammatory markers. When ferritin level exceeds 1000 µgL^-1, the patient is categorized as having hyperferritinemia. Iron chelators such as deferiprone, deferirox, and deferoxamine are currently FDA approved to treat iron overload. The inflammation cascade and poor prognosis of COVID-19 may be attributed to high ferritin levels. Critically ill patients can benefit from deferasirox, an iron chelator administered orally at 20–40 mgkg^?1 once daily, as well as intravenous deferoxamine at 1000 mg initially followed by 500 mg every 4 to 12 h. It can be combined with monoclonal antibodies, antioxidants, corticosteroids, and lactoferrin to make iron chelation therapy effective for COVID-19 victims. In this article, we analyze the antiviral and antifibrotic activity of iron chelators, thereby promoting iron depletion therapy as a potentially innovative treatment strategy for COVID-19.     

Medicinal plants as a fight against murine blood-stage malaria

ObjectiveMalaria is an infectious parasitic disease affecting most of countries worldwide. Due to antimalarial drug resistance, researchers are seeking to find another safe efficient source for treatment of malaria. Since many years ago, medicinal plants were widely used for the treatment of several diseases. In general, most application is done first on experimental animals then human. In this article, medicinal plants as antimalarial agents in experimental animals were reviewed from January 2000 until November 2020.Materials and methodsIn this systematic review published articles were reviewed using the electronic databases NCBI, ISI Web of knowledge, ScienceDirect and Saudi digital library to check articles and theses for M.Sc/Ph.D. The name of the medicinal plant with its taxon ID and family, the used Plasmodium species, plant part used and its extract type and the country of harvest were described.Results and conclusionThe reviewed plants belonged to 83 families. Medicinal plants of families Asteraceae, Meliaceae Fabaceae and Lamiaceae are the most abundant for use in laboratory animal antimalarial studies. According to region, published articles from 33 different countries were reviewed. Most of malaria published articles are from Africa especially Nigeria and Ethiopia. Leaves were the most common plant part used for the experimental malaria research. In many regions, research using medicinal plants to eliminate parasites and as a defensive tool is popular.     

Control of hemoglobin synthesis in erythroid differentiating K562 cells: II. Studies of iron mobilization in erythroid cells by high-performance liquid chromatography–electrochemical detection

We have demonstrated that iron controls hemoglobin (Hb) synthesis in erythroid differentiating K562 cells by enhancing the activity of a key enzyme of the Hb synthesis, δ-aminolevulinate synthase (ALAS). In the present study, we studied iron mobilization and the role of iron in erythroid differentiating cells by measuring the level of iron by means of high-performance liquid chromatography using electrochemical detection (HPLC–ED). After treatment of K562 cells with sodium butyrate, the expression of transferrin receptor (TfR) increased initially, followed by an increase in the levels of both total iron and Hb as well as the ALAS activity. However, no increase could be found in the levels of non-heme iron, low-molecular-mass iron (LMMFe) and ferritin. Addition of diferric transferrin (FeTf) enhanced both δ-aminolevulinic acid (ALA) and Hb synthesis. In contrast, addition of hemin elevated the levels of all iron species as well as the Hb synthesis but reduced the TfR expression and ALA contents in both butyrate treated and untreated cells. These results suggest that Hb synthesis is controlled by TfR expression, and that the ALA synthesis is suppressed by iron released from heme and/or Hb due to lowered expression of TfR.     

Identification of a ubiquitin family protein as a novel neutrophil chemotactic factor

Neutrophil chemotaxis is a process that is essential for the recruitment of neutrophils to an inflamed site. In the present study, we found a remarkable increase in neutrophil chemotactic activity in the lysate of red blood cells (RBC) of mice infected with murine malaria, Plasmodium yoelii. A neutrophil chemotactic factor with an apparent molecular weight of 17 kDa (IP17) was isolated from RBC by a combination of anion-exchange chromatography on DE52 and cation-exchange chromatography on Mono S. A comprehensive GenBank database search of N-terminal amino acid sequences and MALDI-TOF mass analysis of IP17 revealed that IP17 is identical to a murine homologue of ISG15/UCRP, a member of the ubiquitin family of proteins that are inducible by interferon-beta. Recombinant mouse ISG15 showed neutrophil chemotactic activity comparable to that of natural IP17. IP17 showed specific chemotactic activity forward neutrophils and activated neutrophils to induce the release of eosinophil chemotactic factors. These results suggest that the ubiquitin family protein ISG15/UCRP has novel functions in neutrophil-mediated immune mechanisms.     

Critical role of Erythrocyte Binding-Like protein of the rodent malaria parasite Plasmodium yoelii to establish an irreversible connection with the erythrocyte during invasion

Plasmodium malaria parasites multiply within erythrocytes and possess a repertoire of proteins whose function is to recognize and invade these vertebrate host cells. One such protein involved in erythrocyte invasion is the micronemal protein, Erythrocyte Binding-Like (EBL), which has been studied as a potential target of vaccine development in Plasmodium vivax (PvDBP) and Plasmodium falciparum (EBA-175). In the rodent malaria parasite model Plasmodium yoelii, specific substitutions in the EBL regions responsible for intracellular trafficking (17XL parasite line) or receptor recognition (17X1.1pp. parasite line), paradoxically increase invasion ability and virulence rather than abolish EBL function. Attempts to disrupt the ebl gene locus in the 17XL and 17XNL lines were unsuccessful, suggesting EBL essentiality. To understand the mechanisms behind these potentially conflicting outcomes, we generated 17XL-based transfectants in which ebl expression is suppressed with anhydrotetracycline (ATc) and investigated merozoite behavior during erythrocyte invasion. In the absence of ATc, EBL was secreted to the merozoite surface, whereas following ATc administration parasitemia was negligible in vivo. Merozoites lacking EBL were unable to invade erythrocytes in vitro, indicating that EBL has a critical role for erythrocyte invasion. Quantitative time-lapse imaging revealed that with ATc administration a significant number of merozoites were detached from the erythrocyte after the erythrocyte deformation event and no echinocytosis was observed, indicating that EBL is required for merozoites to establish an irreversible connection with erythrocytes during invasion.     

Gametocytocidal and sporontocidal effects of antimalarial drugs on malaria parasites. I. Effect of single and multiple doses of primaquine on Plasmodium cynomolgi

A study was undertaken to determine the gametocytocidal and sporontocidal activity of primaquine against blood-induced Plasmodium cynomolgi infections in seven rhesus monkeys (Macaca mulatta). Infected animals were treated orally with single (1.95 mg/kg primaquine base) or multiple doses of primaquine (0.65 mg/kg/day × 5 primaquine base). The effect of the drug on the sporogonic stages of the parasite was observed in Anopheles maculatus mosquitoes fed at appropriate intervals before and after treatment began. Mosquitoes were also fed on control untreated monkeys on a parallel feeding schedule. The results indicated that primaquine given in the above doses exerted a marked sporontocidal activity within 4 hr after initial medication whereas its gametocytocidal effect first became obvious 2–3 days later. Single doses of primaquine were less effective as compared to multiple doses in the sense that full mosquito infectivity was restored as early as 3 days after single dosage treatment. Primaquine (as base) given in much smaller amounts (0.08 mg/kg/day × 5 or 0.24 mg/kg × 1) acted exclusively as a sporontocidal agent. The sporontocidal action of primaquine was very rapid. Its gametocytocidal effect was less apparent.     

Impact of Zn,Cu, and Fe on the Activity of Carbonic Anhydrase of Erythrocytes in Ducks

The impact of zinc, copper, and iron on the duck erythrocyte carbonic anhydrase (CA) activity and the hemoglobin content in vitro culture were studied. The increase of zinc or iron addition at a low level induced the rise of CA activity, and the CA activity was inhibited by zinc or iron at a high addition level. The duck erythrocyte CA was strongly inhibited by cupric ion. The inhibition constant of duck erythrocyte CA to cupric ion is about 3.5 μM. Carbonic anhydrase compared to hemoglobin is more sensitive to zinc and copper in the environment. These findings suggest that some characteristics of duck erythrocyte CA are different from both CAI and CAII of mammals. The increase of Fe addition below 8 μM in the minimal essential medium brought about the rise of CA activity and resulted in the maximum of CA activity exceeding that induced by Zn. It provided a new evidence for the role of ferrous ion in CA.     

Lipopeptides as anti-infectives: a practical perspective

Lipopeptide antibiotics represent an old class of antibiotics that were discovered over 50 years ago, which includes the old polymyxins but also new entries, such as the recently approved daptomycin. They generally consist of a hydrophilic cyclic peptide portion attached to a fatty acid chain which facilitates insertion into the lipid bilayer of bacterial membranes. This review presents an overview of this class of antibiotics, focusing on their therapeutic applications and putting particular emphasis on chemical modifications introduced to improve their activity.     

Novel diaroylhydrazine ligands as iron chelators: coordination chemistry and biological activity

The search for orally effective drugs for the treatment of iron overload disorders is an important goal in improving the health of patients suffering diseases such as β-thalassemia major. Herein, we report the syntheses and characterization of some new members of a series of N-aroyl-N′-picolinoyl hydrazine chelators (the H₂IPH analogs). Both 1:1 and 1:2 Fe^III:L complexes were isolated and the crystal structures of Fe(HPPH)Cl₂, Fe(4BBPH)Cl₂, Fe(HAPH)(APH) and Fe(H3BBPH)(3BBPH) were determined (H₂PPH=N,N′-bis-picolinoyl hydrazine; H₂APH=N-4-aminobenzoyl-N′-picolinoyl hydrazine, H₂3BBPH=N-3-bromobenzoyl-N′-picolinoylhydrazine and H₂4BBPH=N-(4-bromobenzoyl)-N′-(picolinoyl)hydrazine). In each case, a tridentate N,N,O coordination mode of each chelator with Fe was observed. The Fe^III complexes of these ligands have been synthesized and their structural, spectroscopic and electrochemical characterization are reported. Five of these new chelators, namely H₂BPH (N-(benzoyl)-N′-(picolinoyl)hydrazine), H₂TPH (N-(2-thienyl)-N′-(picolinoyl)-hydrazine), H₂PPH, H₂3BBPH and H₂4BBPH, showed high efficacy at mobilizing ⁵⁹Fe from cells and inhibiting ⁵⁹Fe uptake from the serum Fe transport protein, transferrin (Tf). Indeed, their activity was much greater than that found for the chelator in current clinical use, desferrioxamine (DFO), and similar to that observed for the orally active chelator, pyridoxal isonicotinoyl hydrazone (H₂PIH). The ability of the chelators to inhibit ⁵⁹Fe uptake could not be accounted for by direct chelation of ⁵⁹Fe from ⁵⁹Fe–Tf. The most effective chelators also showed low antiproliferative activity which was similar to or less than that observed with DFO, which is important in terms of their potential use as agents to treat Fe-overload disease.     

Iron trafficking as an antimicrobial target

Iron is essential for the survival of most organisms. Microbial iron acquisition depends on multiple, sometimes complex steps, many of which are not shared by higher eukaryotes. Depriving pathogenic microbes of iron is therefore a potential antimicrobial strategy. The following minireview briefly describes general elements in microbial iron uptake pathways and summarizes some of the current work aiming at their medicinal inhibition.     

Trauma to erythrocytes induced by long term in vitro pumping using a roller pump

The objective of this study is to investigate the impact of trauma on erythrocyte caused by long term in vitro pumping using roller pump. Ten bags of human blood (400 ml each) were provided by a local blood bank and they were divided into two groups with five bags in each group. Each blood bag was subject to pumping in a closed circuit, which was composed of silica gel tubes and a roller pump. Polystan and COBE pumps were used for the two groups, respectively. The blood was pumped for 16 h in vitro. Free hemoglobin (FHb), platelets (PLT), erythrocyte fragility (EF), and morphological analysis of erythrocytes observed under scanning electron microscope were measured to evaluate the impact of trauma on erythrocytes. A small amount of blood was collected for analysis before pumping, at the end of the 4th hour and then every 2 h till the end of the 16th hour. Some blood samples were also collected for electron microscope scanning before pumping and every 4 h during pumping. It was found that FHb and PLT linearly increased with the pumping time. There was a significant correlation between the two parameters (r=0.7745, p<0.001). The hemolysis indexes of the two groups were 0.296 and 0.3993 mg/L/h, respectively, with no significant difference. During the pumping process, EF changed slightly. The observation of scanning electron microscopy showed various deformed erythrocytes after pumping, including the distortion of cell membrane and the appearance of echinocytes, which increased with pumping time. This study demonstrated that long term pumping using roller pump not only caused the immediate rupture of red blood cells, i.e. the immediate hemolysis, but also caused sub-trauma to a large number of erythrocytes, which led to the delayed hemolysis. The change of erythrocyte morphology was the basis of the delayed hemolysis.     

Plasmodium gallinaceum: density dependent limits on infectivity to Aedes aegypti

In acute, blood-induced infections of chickens, the malarial parasite Plasmodium gallinaceum is most infective to the mosquito Aedes aegypti 1 day before gametocyte numbers peak. In an effort to account for this disynchrony , daily changes in parasite infectivity, parasitemia, hematocrit, and hemoglobin were measured during the course of infections. Three events were correlated with the loss of infectivity: (1) In the 24 hr between park infectivity and peak gametocytemia , schizont-induced hemolysis reduced the red blood cell volume 22%. (2) P. gallinaceum zygotes, fertilized in vitro and mixed with heavily infected red blood cells from which all viable, mature gametocytes had been removed, produced 67% fewer oocytes than when combined with uninfected red blood cells. (3) Zygotes fertilized in vitro on the day of peak parasitemia produced 47% fewer oocysts than zygotes prepared 24 hr earlier. It appears that high parasite density reduces infectiousness by destroying, through hemolysis and intraerythrocytic metabolism, a substance necessary to the sporogonic stages, and that there is also an intrinsic loss of infectivity, possibly due to decreased efficiency of fertilization.     

Subdomain 3 of Plasmodium falciparum VAR2CSA DBL3x Is Identified as a Minimal Chondroitin Sulfate A-binding Region

Molecular interactions between the VAR2CSA protein, expressed on the surface of Plasmodium falciparum-infected erythrocytes, and placental chondroitin sulfate A (CSA) are primarily responsible for pregnancy-associated malaria (PAM). Interrupting these interactions may prevent or ameliorate the severity of PAM. Several of the Duffy binding-like (DBL) domains of VAR2CSA, including the DBL3x domain, have been shown to bind CSA in vitro, but a more detailed understanding of how DBL domains bind CSA is needed. In this study, we demonstrate that subdomain 3 (S3), one of the three subdomains of VAR2CSA DBL3x by itself, is the major contributor toward CSA binding. NMR spectroscopy and flow cytometry analyses show that S3 and the intact DBL3x domain bind CSA similarly. Mutations within the S3 portion of DBL3x markedly affect CSA binding. Both recombinant molecules, S3 and DBL3x, are recognized by antibodies in the plasma of previously pregnant women living in malaria-endemic regions of Mali, but much less so by plasma from men of the same regions. As the S3 sequence is highly conserved in all known VAR2CSA proteins expressed by different parasite isolates obtained from various malaria endemic areas of the world, the identification of S3 as an independent CSA-binding region provides a compelling molecular basis for designing interventions against PAM.