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1.
Catalysis of Template-Directed Nonenzymatic RNA Copying by Iron(II).
Jin, L, Engelhart, AE, Zhang, W, Adamala, K, Szostak, JW
Journal of the American Chemical Society. 2018;(44):15016-15021
Abstract
The study of nonenzymatic template-directed RNA copying is the experimental basis for the search for chemistry and reaction conditions consistent with prebiotic RNA replication. The most effective model systems for RNA copying have to date required a high concentration of Mg2+. Recently, Fe2+, which was abundant on the prebiotic anoxic Earth, was shown to promote the folding of RNA in a manner similar to the case of Mg2+, as a result of the two cations having similar interactions with phosphate groups. These observations raise the question of whether Fe2+ could have promoted RNA copying on the prebiotic Earth. Here, we demonstrate that Fe2+ is a better catalyst and promotes faster nonenzymatic RNA primer extension and ligation than Mg2+ when using 2-methylimidazole activated nucleotides in slightly acidic to neutral pH solutions. Thus, it appears likely that Fe2+ could have facilitated RNA replication and evolution in concert with other metal cations on the prebiotic Earth.
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Redox Sensing by Fe2+ in Bacterial Fur Family Metalloregulators.
Pinochet-Barros, A, Helmann, JD
Antioxidants & redox signaling. 2018;(18):1858-1871
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Abstract
SIGNIFICANCE Iron is required for growth and is often redox active under cytosolic conditions. As a result of its facile redox chemistry, iron homeostasis is intricately involved with oxidative stress. Bacterial adaptation to iron limitation and oxidative stress often involves ferric uptake regulator (Fur) proteins: a diverse set of divalent cation-dependent, DNA-binding proteins that vary widely in both metal selectivity and sensitivity to metal-catalyzed oxidation. Recent Advances: Bacteria contain two Fur family metalloregulators that use ferrous iron (Fe2+) as their cofactor, Fur and PerR. Fur functions to regulate iron homeostasis in response to changes in intracellular levels of Fe2+. PerR also binds Fe2+, which enables metal-catalyzed protein oxidation as a mechanism for sensing hydrogen peroxide (H2O2). CRITICAL ISSUES To effectively regulate iron homeostasis, Fur has an Fe2+ affinity tuned to monitor the labile iron pool of the cell and may be under selective pressure to minimize iron oxidation, which would otherwise lead to an inappropriate increase in iron uptake under oxidative stress conditions. Conversely, Fe2+ is bound more tightly to PerR but exhibits high H2O2 reactivity, which enables a rapid induction of peroxide stress genes. FUTURE DIRECTIONS The features that determine the disparate reactivity of these proteins with oxidants are still poorly understood. A controlled, comparative analysis of the affinities of Fur/PerR proteins for their metal cofactors and their rate of reactivity with H2O2, combined with structure/function analyses, will be needed to define the molecular mechanisms that have facilitated this divergence of function between these two paralogous regulators.
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Oral administration of 5-aminolevulinic acid induces heme oxygenase-1 expression in peripheral blood mononuclear cells of healthy human subjects in combination with ferrous iron.
Ito, H, Nishio, Y, Hara, T, Sugihara, H, Tanaka, T, Li, XK
European journal of pharmacology. 2018;:25-33
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Heme oxygenase-1 (HO-1) is a major anti-inflammatory enzyme and a key regulator that induces immune tolerance through affecting the differentiation of dendritic cells. The aim of this study is to determine whether the combination of 5-aminolevulinic acid (ALA) and iron induces HO-1 expression in healthy human peripheral blood mononuclear cells (PBMC). The study was an open labeled, non-randomized, non-placebo-controlled trial using healthy male adults and consisted of three parts. Study A aimed to find the peak HO-1 expression at 0, 1, 2, 3, 4, 6, 8, 12, 16, and 24 h after administration. Study B aimed to examine HO-1 dose dependency at 150, 300, and 600 mg of ALA and the need for iron supplementation. Study C aimed to investigate HO-1 changes during a three-day, repetitive administration of ALA and iron. The combination of ALA 600 mg and sodium ferrous citrate (SFC) 942 mg upregulated HO-1 in PBMC at 8 h after administration while sole administration of ALA or SFC was unable to induce HO-1. HO-1 in blood myeloid and plasmacytoid dendritic cells was also upregulated with ALA+SFC. Clear dose dependency of ALA+SFC was not detected, and a slight tendency towards a cumulative effect of HO-1 after three-day, repetitive administration was observed. ALA, which is already approved for use in several countries as a diagnosis agent for cancer, has the potential to become a novel therapeutic drug for diseases stemming from unwanted immune response such as autoimmune diseases and the rejection response following organ transplantation.
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Toward a mechanistic understanding of Feo-mediated ferrous iron uptake.
Sestok, AE, Linkous, RO, Smith, AT
Metallomics : integrated biometal science. 2018;(7):887-898
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Abstract
Virtually all organisms require iron and have evolved to obtain this element in free or chelated forms. Under anaerobic or low pH conditions commonly encountered by numerous pathogens, iron predominantly exists in the ferrous (Fe2+) form. The ferrous iron transport (Feo) system is the only widespread mechanism dedicated solely to bacterial ferrous iron import, and this system has been linked to pathogenic virulence, bacterial colonization, and microbial survival. The canonical feo operon encodes for three proteins that comprise the Feo system: FeoA, a small cytoplasmic β-barrel protein; FeoB, a large, polytopic membrane protein with a soluble G-protein domain capable of hydrolyzing GTP; and FeoC, a small, cytoplasmic protein containing a winged-helix motif. While previous studies have revealed insight into soluble and fragmentary domains of the Feo system, the chief membrane-bound component FeoB remains poorly studied. However, recent advances have demonstrated that large quantities of intact FeoB can be overexpressed, purified, and biophysically characterized, revealing glimpses into FeoB function. Two models of full-length FeoB have been published, providing starting points for hypothesis-driven investigations into the mechanism of FeoB-mediated ferrous iron transport. Finally, in vivo studies have begun to shed light on how this system functions as a unique multicomponent complex. In light of these new data, this review will summarize what is known about the Feo system, including recent advancements in FeoB structure and function.
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Microbial anaerobic Fe(II) oxidation - Ecology, mechanisms and environmental implications.
Bryce, C, Blackwell, N, Schmidt, C, Otte, J, Huang, YM, Kleindienst, S, Tomaszewski, E, Schad, M, Warter, V, Peng, C, et al
Environmental microbiology. 2018;(10):3462-3483
Abstract
Iron is the most abundant redox-active metal in the Earth's crust. The one electron transfer between the two most common redox states, Fe(II) and Fe(III), plays a role in a huge range of environmental processes from mineral formation and dissolution to contaminant remediation and global biogeochemical cycling. It has been appreciated for more than a century that microorganisms can harness the energy of this Fe redox transformation for their metabolic benefit. However, this is most widely understood for anaerobic Fe(III)-reducing or aerobic and microaerophilic Fe(II)-oxidizing bacteria. Only in the past few decades have we come to appreciate that bacteria also play a role in the anaerobic oxidation of ferrous iron, Fe(II), and thus can act to form Fe(III) minerals in anoxic settings. Since this discovery, our understanding of the ecology of these organisms, their mechanisms of Fe(II) oxidation and their role in environmental processes has been increasing rapidly. In this article, we bring these new discoveries together to review the current knowledge on these environmentally important bacteria, and reveal knowledge gaps for future research.
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Microaerophilic Fe(II)-Oxidizing Zetaproteobacteria Isolated from Low-Fe Marine Coastal Sediments: Physiology and Composition of Their Twisted Stalks.
Laufer, K, Nordhoff, M, Halama, M, Martinez, RE, Obst, M, Nowak, M, Stryhanyuk, H, Richnow, HH, Kappler, A
Applied and environmental microbiology. 2017;(8)
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Abstract
Microaerophilic Fe(II) oxidizers are commonly found in habitats containing elevated Fe(II) and low O2 concentrations and often produce characteristic Fe mineral structures, so-called twisted stalks or tubular sheaths. Isolates originating from freshwater habitats are all members of the Betaproteobacteria, while isolates from marine habitats belong almost exclusively to the Zetaproteobacteria So far, only a few isolates of marine microaerophilic Fe(II) oxidizers have been described, all of which are obligate microaerophilic Fe(II) oxidizers and have been thought to be restricted to Fe-rich systems. Here, we present two new isolates of marine microaerophilic Fe(II)-oxidizing Zetaproteobacteria that originate from typical coastal marine sediments containing only low Fe concentrations (2 to 11 mg of total Fe/g of sediment [dry weight]; 70 to 100 μM dissolved Fe2+ in the porewater). The two novel Zetaproteobacteria share characteristic physiological properties of the Zetaproteobacteria group, even though they come from low-Fe environments: the isolates are obligate microaerophilic Fe(II) oxidizers and, like most isolated Zetaproteobacteria, they produce twisted stalks. We found a low organic carbon content in the stalks (∼0.3 wt%), with mostly polysaccharides and saturated aliphatic chains (most likely lipids). The Fe minerals in the stalks were identified as lepidocrocite and possibly ferrihydrite. Immobilization experiments with Ni2+ showed that the stalks can function as a sink for trace metals. Our findings show that obligate microaerophilic Fe(II) oxidizers belonging to the Zetaproteobacteria group are not restricted to Fe-rich environments but can also be found in low-Fe marine environments, which increases their overall importance for the global biogeochemical Fe cycle.IMPORTANCE So far, only a few isolates of benthic marine microaerophilic Fe(II) oxidizers belonging to the Zetaproteobacteria exist, and most isolates were obtained from habitats containing elevated Fe concentrations. Consequently, it was thought that these microorganisms are important mainly in habitats with high Fe concentrations. The two novel isolates of Zetaproteobacteria that are presented in the present study were isolated from typical coastal marine sediments that do not contain elevated Fe concentrations. This increases the knowledge about possible habitats in which Zetaproteobacteria can exist. Furthermore, we show that the physiology and the typical organo-mineral structures (twisted stalks) that are produced by the isolates do not notably differ from the physiology and the cell-mineral structures of isolates from environments with high Fe concentrations. We also showed that the organo-mineral structures can function as a sink for trace metals.
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Daily home fortification with iron as ferrous fumarate versus NaFeEDTA: a randomised, placebo-controlled, non-inferiority trial in Kenyan children.
Teshome, EM, Andang'o, PEA, Osoti, V, Terwel, SR, Otieno, W, Demir, AY, Prentice, AM, Verhoef, H
BMC medicine. 2017;(1):89
Abstract
BACKGROUND We aimed to show the non-inferiority of home fortification with a daily dose of 3 mg iron in the form of iron as ferric sodium ethylenediaminetetraacetate (NaFeEDTA) compared with 12.5 mg iron as encapsulated ferrous fumarate in Kenyan children aged 12-36 months. In addition, we updated a recent meta-analysis to assess the efficacy of home fortification with iron-containing powders, with a view to examining diversity in trial results. METHODS We gave chemoprevention by dihydroartemisinin-piperaquine, albendazole and praziquantel to 338 afebrile children with haemoglobin concentration ≥70 g/L. We randomly allocated them to daily home fortification for 30 days with either placebo, 3 mg iron as NaFeEDTA or 12.5 mg iron as encapsulated ferrous fumarate. We assessed haemoglobin concentration (primary outcome), plasma iron markers, plasma inflammation markers and Plasmodium infection in samples collected at baseline and after 30 days of intervention. We conducted a meta-analysis of randomised controlled trials in pre-school children to assess the effect of home fortification with iron-containing powders on anaemia and haemoglobin concentration at end of intervention. RESULTS A total of 315 children completed the 30-day intervention period. At baseline, 66.9% of children had inflammation (plasma C-reactive protein concentration >5 mg/L or plasma α 1-acid glycoprotein concentration >1.0 g/L); in those without inflammation, 42.5% were iron deficient. There was no evidence, either in per protocol analysis or intention-to-treat analysis, that home fortification with either of the iron interventions improved haemoglobin concentration, plasma ferritin concentration, plasma transferrin receptor concentration or erythrocyte zinc protoporphyrin-haem ratio. We also found no evidence of effect modification by iron status, anaemia status and inflammation status at baseline. In the meta-analysis, the effect on haemoglobin concentration was highly heterogeneous between trials (I 2: 84.1%; p value for test of heterogeneity: <0.0001). CONCLUSIONS In this population, home fortification with either 3 mg iron as NaFeEDTA or 12.5 mg iron as encapsulated ferrous fumarate was insufficiently efficacious to assess non-inferiority of 3 mg iron as NaFeEDTA compared to 12.5 mg iron as encapsulated ferrous fumarate. Our finding of heterogeneity between trial results should stimulate subgroup analysis or meta-regression to identify population-specific factors that determine efficacy. TRIAL REGISTRATION The trial was registered with ClinicalTrials.gov ( NCT02073149 ) on 25 February 2014.
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Iron supplementation in singleton pregnancy: Is there a benefit to doubling the dose of elemental iron in iron-deficient pregnant women? a randomized controlled trial.
Shinar, S, Skornick-Rapaport, A, Maslovitz, S
Journal of perinatology : official journal of the California Perinatal Association. 2017;(7):782-786
Abstract
OBJECTIVE To assess the efficacy of doubling the 30 mg dose of iron in women with iron deficiency anemia (IDA) in singleton pregnancies. STUDY DESIGN Prospective randomized controlled trial. Iron-deficient women were randomized during the second trimester to receive one or two capsules of daily iron supplement, containing 34 mg of ferrous sulfate, from 17 weeks until 6 weeks postpartum. The primary outcome was hemoglobin (Hgb) at 35 weeks. Secondary outcomes included ferritin at 35 weeks, Hgb during pregnancy and postpartum, birth weights, preterm birth rate, gastrointestinal side effects, intravenous iron administration and compliance. RESULTS In all, 160 women were randomized to receive one capsule and 164 received two capsules. Both groups had similar Hgb (10.1 g dl-1) and ferritin (9.3 and 9.4 ng l-1) at allocation. Hgb concentration in both groups was similar at 35 weeks (10.8 g dl-1). There were no significant differences in any of the secondary outcomes. CONCLUSION In IDA pregnant women, a single dose of iron is as effective as a double dose.
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Lactoferrin or ferrous salts for iron deficiency anemia in pregnancy: A meta-analysis of randomized trials.
Abu Hashim, H, Foda, O, Ghayaty, E
European journal of obstetrics, gynecology, and reproductive biology. 2017;:45-52
Abstract
This systematic review and meta-analysis aimed to evaluate the efficacy of daily oral bovine lactoferrin versus daily oral ferrous iron preparations for treatment of iron deficiency anemia (IDA) during pregnancy. Searches were conducted on PubMed, ScienceDirect, ClinicalTrials.gov and CENTRAL databases from inception to February 2017 and the bibliographies of retrieved articles were screened. The PRISMA Statement was followed. Published English language randomized trials comparing lactoferrin with oral ferrous iron preparations in pregnant women with iron deficiency anemia were included. Quasi-randomized, non- randomized or studies including other known cause of anemia, gestational or pre-existent maternal diseases were excluded. Accordingly, 4 eligible trials (600 women) were analyzed. Primary outcome was change in hemoglobin level at 4 weeks of treatment. Secondary outcomes were; change in serum ferritin and iron, rates of gastrointestinal side effects, preterm birth, low birthweight, neonatal death and mean birthweight. Quality assessment was performed by the Cochrane risk of bias tool. Odds ratio and mean difference were used to integrate dichotomous and continuous outcomes respectively. Pooled estimates for change in hemoglobin levels at four weeks favored daily oral lactoferrin over daily oral ferrous sulphate (mean difference 0.77; 95% confidence interval [CI] 0.04-1.55; P=0.04, 4 trials, 600 women). However, after subgroup analysis (degree of anemia), no significant difference in hemoglobin levels were found between both groups in mild anemia (mean difference 0.80; 95% CI -0.21 to 1.82, 3 trials, 372 women), but a significant increase favoring lactoferrin was reported in moderate anemia (mean difference 0.68; 95% CI 0.53-0.83; P<0.00001, one trial, 228 women). Significantly less gastrointestinal side effects were reported with lactoferrin treatment. No significant differences existed with regard to other outcomes. In conclusion, for pregnant women with IDA, daily oral bovine lactoferrin is just as good as ferrous sulfate in improving hematological parameters with fewer gastrointestinal side effects. Thereby, lactoferrin should be the iron replacement agent of choice for treatment of IDA in pregnancy.
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Consumption of a Double-Fortified Salt Affects Perceptual, Attentional, and Mnemonic Functioning in Women in a Randomized Controlled Trial in India.
Wenger, MJ, Murray-Kolb, LE, Nevins, JE, Venkatramanan, S, Reinhart, GA, Wesley, A, Haas, JD
The Journal of nutrition. 2017;(12):2297-2308
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Background: Iron deficiency and iron deficiency anemia have been shown to have negative effects on aspects of perception, attention, and memory.Objective: The purpose of this investigation was to assess the extent to which increases in dietary iron consumption are related to improvements in behavioral measures of perceptual, attentional, and mnemonic function.Methods: Women were selected from a randomized, double-blind, controlled food-fortification trial involving ad libitum consumption of either a double-fortified salt (DFS) containing 47 mg potassium iodate/kg and 3.3 mg microencapsulated ferrous fumarate/g (1.1 mg elemental Fe/g) or a control iodized salt. Participants' blood iron status (primary outcomes) and cognitive functioning (secondary outcomes) were assessed at baseline and after 10 mo at endline. The study was performed on a tea plantation in the Darjeeling district of India. Participants (n = 126; 66% iron deficient and 49% anemic at baseline) were otherwise healthy women of reproductive age, 18-55 y.Results: Significant improvements were documented for iron status and for perceptual, attentional, and mnemonic function in the DFS group (percentage of variance accounted for: 16.5%) compared with the control group. In addition, the amount of change in perceptual and cognitive performance was significantly (P < 0.05) related to the amount of change in blood iron markers (mean percentage of variance accounted for: 16.0%) and baseline concentrations of blood iron markers (mean percentage of variance accounted for: 25.0%). Overall, there was evidence that the strongest effects of change in iron status were obtained for perceptual and low-level attentional function.Conclusion: DFS produced measurable and significant improvements in the perceptual, attentional, and mnemonic performance of Indian female tea pickers of reproductive age. This trial was registered at clinicaltrials.gov as NCT01032005.