Iron transport across cell membranes: molecular understanding of duodenal and placental iron uptake

A Large Proportion of the Neonatal Iron Pool Is Acquired from the Gestational Diet in a Murine Model

BACKGROUND

Iron is crucial for growth and development, but excess iron is harmful. Neonatal mice have elevated concentrations of circulating iron, but the source of this iron is unclear. This lack of understanding makes it difficult to optimize early life iron balance.

OBJECTIVES

Identify the origins of neonatal tissue-specific iron pools using dietary manipulation and cross-fostering murine models.

METHODS

To determine whether tissue-specific neonatal iron was primarily acquired during gestation or after birth, pups born to iron-sufficient or iron-deficient dams were cross-fostered, and tissues were harvested at postnatal days 3-5 to measure iron content. A separate set of female mice were fed a diet enriched with the stable iron isotope 57 (57Fe) for 4 generations to replace naturally abundant liver iron isotope 56 (56Fe) stores with 57Fe. To quantify the proportions of neonatal iron acquired during gestation, pups born to dams with 56Fe or 57Fe stores were cross-fostered, and tissues were harvested at postnatal day 3-5 to determine 56Fe:57Fe ratios by inductively coupled plasma mass spectrometry. Finally, to quantify the proportion of neonatal iron acquired from the maternal diet, female mice with 56Fe or 57Fe stores switched diets upon mating, and pup tissues were harvested on P0 to determine 56Fe:57Fe ratios by inductively coupled plasma mass spectrometry.

RESULTS

Perinatal iron deficiency resulted in smaller pups, and gestational iron deficiency resulted in lower neonatal serum and liver iron. Cross-fostering between dams with 56Fe and 57Fe stores demonstrated that ≤70% of neonatal serum, liver, and brain iron were acquired during gestation. Dietary manipulation experiments using dams with 56Fe and 57Fe stores showed that over half of neonatal serum, liver, and brain iron were from the dam's gestational diet rather than preconception iron stores.

CONCLUSIONS

This study provides quantitative values for the sources of neonatal iron, which may inform approaches to optimize neonatal iron status.

Biomarkers of Brain Dysfunction in Perinatal Iron Deficiency

Iron deficiency in the fetal and neonatal period (perinatal iron deficiency) bodes poorly for neurodevelopment. Given its common occurrence and the negative impact on brain development, a screening and treatment strategy that is focused on optimizing brain development in perinatal iron deficiency is necessary. Pediatric societies currently recommend a universal iron supplementation strategy for full-term and preterm infants that does not consider individual variation in body iron status and thus could lead to undertreatment or overtreatment. Moreover, the focus is on hematological normalcy and not optimal brain development. Several serum iron indices and hematological parameters in the perinatal period are associated with a risk of abnormal neurodevelopment, suggesting their potential use as biomarkers for screening and monitoring treatment in infants at risk for perinatal iron deficiency. A biomarker-based screening and treatment strategy that is focused on optimizing brain development will likely improve outcomes in perinatal iron deficiency.

Maternal Mineral Nutrition Regulates Fetal Genomic Programming in Cattle: A Review

Maternal mineral nutrition during the critical phases of fetal development may leave lifetime impacts on the productivity of an individual. Most research within the developmental origins of the health and disease (DOHaD) field is focused on the role of macronutrients in the genome function and programming of the developing fetus. On the other hand, there is a paucity of knowledge about the role of micronutrients and, specifically, minerals in regulating the epigenome of livestock species, especially cattle. Therefore, this review will address the effects of the maternal dietary mineral supply on the fetal developmental programming from the embryonic to the postnatal phases in cattle. To this end, we will draw a parallel between findings from our cattle model research with data from model animals, cell lines, and other livestock species. The coordinated role and function of different mineral elements in feto-maternal genomic regulation underlies the establishment of pregnancy and organogenesis and, ultimately, affects the development and functioning of metabolically important tissues, such as the fetal liver, skeletal muscle, and, importantly, the placenta. Through this review, we will delineate the key regulatory pathways involved in fetal programming based on the dietary maternal mineral supply and its crosstalk with epigenomic regulation in cattle.

In Vitro and In Vivo Sucrosomial® Berberine Activity on Insulin Resistance

Background: Berberine is a natural alkaloid with hypoglycemic properties. However, its therapeutic use is limited by a very low oral bioavailability. Here we developed a new oral formulation of berberine based on Sucrosomial^® technology and tested its effect on insulin resistance. Methods: Sucrosomial^® berberine was first tested in vitro in the hepatoma cell line Huh7 to assess its effect on proteins involved in glucose homeostasis and insulin resistance. The pharmacokinetics and efficacy on insulin resistance were then studied in C57BL/6 mice fed with standard (SD) and high-fat diet (HFD) for 16 weeks and treated daily during the last 8 weeks with oral gavage of Sucrosomial^® berberine or berberine. Results: Sucrosomial^® berberine did not affect Huh7 cell viability at concentrations up to 40 µM. Incubation of Huh7 with 20 µM of Sucrosomial^® and control berberine induced glucokinase (GK) and the phosphorylation of 5′-adenosine monophosphate (AMP)-activated protein kinase (AMPK), both known targets for the control of insulin resistance. In vivo, we observed an 8-fold higher plasma concentration after 3 weeks of oral administration of 50 mg/kg/day of Sucrosomial^® formulation compared to berberine. HFD, compared to SD, induced insulin resistance in mice as determined by oral glucose tolerance test (OGTT). The treatment with a 6.25 mg/kg/daily dose of Sucrosomial^® berberine significantly reduced the area under the curve (AUC) of OGTT (73,103 ± 8645 vs. 58,830 ± 5597 mg/dL × min), while control berberine produced the same effects at 50 mg/Kg/day (51518 ± 1984 mg/dL × min). Under these conditions, the two formulations resulted in similar berberine plasma concentration in mice. Nevertheless, a different tissue distribution of metabolites was observed with a significant accumulation of reduced, demethylated and glucuronide berberine in the brain after the oral administration of the Sucrosomial^® form. Glucuronide berberine plasma concentration was higher with Sucrosomial^® berberine compared to normal berberine. Finally, we observed similar increases of AMPK phosphorylation in the liver in response to the treatment with Sucrosomial^® berberine and berberine. Conclusions: The Sucrosomial^® formulation is an innovative and effective technology to improve berberine gastrointestinal (GI) absorption with proven in vitro and in vivo activity on insulin resistance.

Expression of iron transport protein Divalent metal transporter 1 (DMT1) increases in response to maternal iron deficiency anemia in near term to term placenta

INTRODUCTION

Iron deficiency anemia (IDA) is the most prevalent nutritional deficiency disorder in pregnant women. During pregnancy, placental transport protein Divalent metal transporter1 (DMT1) plays a crucial role in transit of iron across placenta. The developing fetus is observed to be immune to anemia despite presence of anemia in the mother. Hence, we planned the present study to explore the effect of maternal IDA on the expression of DMT1 in the placenta.

MATERIALS AND METHODS

Two hundred pregnant women recruited, were divided into anemic and nonanemic groups based on their predelivery hemoglobin levels (<11 g/dL and ≥11 g/dL respectively). After delivery, placental expression of DMT1 was studied by immunohistochemistry and mRNA analysis and neonatal anthropometry was performed.

RESULTS

Of the 200 women recruited, 58.8% were anemic with 60.35% having moderate anemia. Most of the red cell parameters were observed to be higher in cord blood than mothers. DMT1 protein immunohistochemical expression showed a statistically significant increase with increasing severity of anemia. Similarly, placental mRNA expression levels of DMT1 gene were observed to be higher in anemic mothers in comparison with nonanemic mothers.

CONCLUSION

Our study thus demonstrated a definite increase in expression of DMT1 at both protein and mRNA levels in term placenta, in maternal IDA.

Iron Metabolism in Normal and Pathological Pregnancies and Fetal Consequences

Iron is required for energy production, DNA synthesis, and cell proliferation, mainly as a component of the prosthetic group in hemoproteins and as part of iron-sulfur clusters. Iron is also a critical component of hemoglobin and plays an important role in oxygen delivery. Imbalances in iron metabolism negatively affect these vital functions. As the crucial barrier between the fetus and the mother, the placenta plays a pivotal role in iron metabolism during pregnancy. Iron deficiency affects 1.2 billion individuals worldwide. Pregnant women are at high risk of developing or worsening iron deficiency. On the contrary, in frequent hemoglobin diseases, such as sickle-cell disease and thalassemia, iron overload is observed. Both iron deficiency and iron overload can affect neonatal development. This review aims to provide an update on our current knowledge on iron and heme metabolism in normal and pathological pregnancies. The main molecular actors in human placental iron metabolism are described, focusing on the impact of iron deficiency and hemoglobin diseases on the placenta, together with normal metabolism. Then, we discuss data concerning iron metabolism in frequent pathological pregnancies to complete the picture, focusing on the most frequent diseases.

Impact of maternal iron deficiency anaemia on the expression of the newly discovered multi-copper ferroxidase, Zyklopen, in term placentas

In the present study, we investigated the effect of maternal iron deficiency anaemia (IDA) on expression of the newly discovered iron transporter, Zyklopen in term placenta, in 200 pregnant women. Placental expression of Zyklopen was studied by mRNA analysis and immunohistochemistry for the protein. In addition neonatal anthropometric parameters were also analysed. 58.8% of 200 subjects were anaemic. Both Zyklopen mRNA as well as protein expression in the placenta showed a statistically significant increase with increasing severity of anaemia. Although all the neonatal anthropometric parameters were lower in newborns of anaemic mothers, none showed any statistical significance. Zp mRNA levels did not show any significant correlation with newborn and placental parameters (except newborn skinfold thickness and head circumference). Similar to mRNA expression, Zp IHC expression correlated positively, albiet non-significantly, with newborn length and Hb levels, the correlation was however negative with birth weight, head circumference, mid-arm circumference unlike the mRNA expression, where it positively correlated with the above parameters. Our study for the first time demonstrated a definite increase in expression of Zyklopen at both mRNA and protein levels in term placenta, in maternal IDA.IMPACT STATEMENTWhat is already known on this subject? Iron deficiency anaemia (IDA) in a pregnant mother can lead to anaemia in the developing foetus; which is frequently observed to be of lesser severity than that in the mother. Recently a copper-containing oxidase called Zyklopen was discovered which was involved in iron efflux in BeWo cells. The gene encoding Zyklopen has been identified with a putative C-terminal membrane-spanning sequence and high sequence identitical to hephaestin (Heph) and ceruloplasmin (Cp), the other known vertebrate multicopper ferroxidase (MCF). Protein expression of this new MCF was observed in multiple diverse mouse tissues, including placenta and mammary gland.What do the results of this study add? Zyklopen protein immunohistochemical expression showed a statistically significant increase with increasing severity of anaemia. Similarly, placental mRNA expression of the Zyklopen gene was observed to be higher in anaemic mothers when compared to non-anaemic mothers. Our study for the first time demonstrated a definite increase in expression of Zyklopen at both protein and mRNA levels in term placenta, in maternal IDA.What are the implications of these findings for clinical practice and/or further research? This study will help us to understand better, the increased potential for influx of iron from mother to foetus in the condition of maternal iron deficiency. This study will help to determine how placental iron transport proteins can be regulated in response to maternal and neonatal iron status and will further our existing knowledge on relationships between maternal and neonatal iron status and mechanisms by which placental iron transport is modified in relation to these parameters.

Effect of Maternal Iron Deficiency Anaemia on the Expression of Iron Transport Proteins in the Third Trimester Placenta

BackgroundDuring pregnancy, iron is transferred from mother to fetus with placental iron transport proteins (Transferrin receptor, Divalent metal transporter/DMT1, ferroportin/FPN1 and Zyklopen). The aim of the study was to evaluate the effect of maternal iron deficiency anemia on placental iron transporters. Study Design: Two hundred pregnant women, in third trimester of pregnancy were divided into anemic (Hemoglobin/Hb < 11g/dl) and non-anemic groups (Hb ≥ 11 g/dl). After delivery, placental expression of iron transport proteins were studied by immunohistochemistry and by mRNA analysis. Results: Of the 200 subjects, 59% were anemic. All 3 placental proteins showed statistically significant increase in immunohistochemical expression, proportionate to the severity of maternal anemia. The mRNA expression of DMT-1 gene was only significantly elevated in placentas of anemic mothers. Conclusion: Although in our study mRNA expression of only the DMT-1 gene was significantly high, immunohistochemically however all the 3 proteins showed significantly higher expression in placentas of anemic mothers.

From the Ocean to the Lab-Assessing Iron Limitation in Cyanobacteria: An Interface Paper

Iron is an essential, yet scarce, nutrient in marine environments. Phytoplankton, and especially cyanobacteria, have developed a wide range of mechanisms to acquire iron and maintain their iron-rich photosynthetic machinery. Iron limitation studies often utilize either oceanographic methods to understand large scale processes, or laboratory-based, molecular experiments to identify underlying molecular mechanisms on a cellular level. Here, we aim to highlight the benefits of both approaches to encourage interdisciplinary understanding of the effects of iron limitation on cyanobacteria with a focus on avoiding pitfalls in the initial phases of collaboration. In particular, we discuss the use of trace metal clean methods in combination with sterile techniques, and the challenges faced when a new collaboration is set up to combine interdisciplinary techniques. Methods necessary for producing reliable data, such as High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS), Flow Injection Analysis Chemiluminescence (FIA-CL), and 77K fluorescence emission spectroscopy are discussed and evaluated and a technical manual, including the preparation of the artificial seawater medium Aquil, cleaning procedures, and a sampling scheme for an iron limitation experiment is included. This paper provides a reference point for researchers to implement different techniques into interdisciplinary iron studies that span cyanobacteria physiology, molecular biology, and biogeochemistry.

Role of Dietary Flavonoids in Iron Homeostasis

Balancing systemic iron levels within narrow limits is critical for human health, as both iron deficiency and overload lead to serious disorders. There are no known physiologically controlled pathways to eliminate iron from the body and therefore iron homeostasis is maintained by modifying dietary iron absorption. Several dietary factors, such as flavonoids, are known to greatly affect iron absorption. Recent evidence suggests that flavonoids can affect iron status by regulating expression and activity of proteins involved the systemic regulation of iron metabolism and iron absorption. We provide an overview of the links between different dietary flavonoids and iron homeostasis together with the mechanism of flavonoids effect on iron metabolism. In addition, we also discuss the clinical relevance of state-of-the-art knowledge regarding therapeutic potential that flavonoids may have for conditions that are low in iron such as anaemia or iron overload diseases.

Placental iron transport: The mechanism and regulatory circuits

As the interface between the fetal and maternal circulation, the placenta facilitates both nutrient and waste exchange for the developing fetus. Iron is essential for healthy pregnancy, and transport of iron across the placenta is required for fetal growth and development. Perturbation of this transfer can lead to adverse pregnancy outcomes. Despite its importance, our understanding of how a large amount of iron is transported across placental membranes, how this process is regulated, and which iron transporter proteins function in different placental cells remains rudimentary. Mechanistic studies in mouse models, including placenta-specific deletion or overexpression of iron-related proteins will be essential to make progress. This review summarizes our current understanding about iron transport across the syncytiotrophoblast under physiological conditions and identifies areas for further investigation.

New Perspectives on Iron Uptake in Eukaryotes

All eukaryotic organisms require iron to function. Malfunctions within iron homeostasis have a range of physiological consequences, and can lead to the development of pathological conditions that can result in an excess of non-transferrin bound iron (NTBI). Despite extensive understanding of iron homeostasis, the links between the “macroscopic” transport of iron across biological barriers (cellular membranes) and the chemistry of redox changes that drive these processes still needs elucidating. This review draws conclusions from the current literature, and describes some of the underlying biophysical and biochemical processes that occur in iron homeostasis. By first taking a broad view of iron uptake within the gut and subsequent delivery to tissues, in addition to describing the transferrin and non-transferrin mediated components of these processes, we provide a base of knowledge from which we further explore NTBI uptake. We provide concise up-to-date information of the transplasma electron transport systems (tPMETSs) involved within NTBI uptake, and highlight how these systems are not only involved within NTBI uptake for detoxification but also may play a role within the reduction of metabolic stress through regeneration of intracellular NAD(P)H/NAD(P)⁺ levels. Furthermore, we illuminate the thermodynamics that governs iron transport, namely the redox potential cascade and electrochemical behavior of key components of the electron transport systems that facilitate the movement of electrons across the plasma membrane to the extracellular compartment. We also take account of kinetic changes that occur to transport iron into the cell, namely membrane dipole change and their consequent effects within membrane structure that act to facilitate transport of ions.

Interactions between chromium(III) and iron(III), molybdenum(III) or nickel(II): Cytotoxicity, genotoxicity and mutagenicity studies

The aim of this study was to examine the effect of chromium(III) and iron(III) and molybdenum(III) and nickel(II) and their combinations on cyto-, genotoxicity and mutagenicity in BALB/3T3 and HepG2 cells. The results obtained from cytotoxicity assays indicate that there are differences between BALB/3T3 and HepG2 cell lines in their sensitivity to chromium chloride, iron chloride, molybdenum trioxide and nickel chloride. The statistically significant increase of DNA damage of all used microelements in both cell lines was observed. The micronucleus assay performed with the use of all concentrations shows statistically significant induction of chromosomal aberrations in all tested microelements in both cell lines. Moreover, treated cells display characteristic apoptosis in comparison to control cells. In all tested microelements, the increase of number of reverse mutations was observed with and without metabolic activation. Additions of Cr(III) at 200 μM plus Fe(III) at 1000 μM showed synergistic effect in decrease of cell viability and increase of comets, micronuclei and number of revertants in both cell lines. In case of Cr(III) at 200 μM plus Mo(III) at 1000 μM, a protective effect of chromium against molybdenum at 1000 μM toxicity in both cell lines (assessed by MTT, LDH and NRU, comet, micronucleus and Ames assays) was observed. The protective effect of Cr(III) in decrease of cell viability was observed in pair of Cr(III) at 200 μM and Ni(II) at 1000 μM in BALB/3T3 and HepG2 cell lines assessed by MTT, LDH and NRU, comet, micronucleus and Ames assays.

Sucrosomial® iron absorption studied by in vitro and ex-vivo models

This paper presents a comparative evaluation of different oral ferric iron formulations for ability to retain Fe³⁺ in simulated gastric fluid (SGF), be internalized by cells lining intestinal epithelium, and cross it to reach the bloodstream. In all formulations iron was ferric pyrophosphate, the excipients were different types and fractions of lecithin plus sucrose esters of fatty acids matrix (Sideral® RM; PRT1; PRT2) or lecithin without sucrester (SUN). Dissolution kinetics of formulations in SGF was studied by USP method. The ability of the formulations to promote iron intestinal absorption was evaluated by the Caco-2 cell model, measuring cellular ferritin content, and by the excised rat intestine model, yielding apparent permeability parameters (P_app). All formulations limited iron release in SGF to ≤10%. Sideral® RM was by far the most absorbed by Caco-2, as ferritin content was in the order: Sideral® RM≫PRT2>PRT1>SUN>control. The Fe³⁺ crossing the intestinal barrier was in part reduced to Fe²⁺ by epithelial enzymes, in part it was carried by formulation rearrangement into nano-structures able to protect it from reduction and apt for internalization by epithelium cells. P_app parameters were in the order: Sideral® RM≫PRT1>PRT2>SUN=control. Relevance of transepithelial Fe²⁺carrier, DMT-1, to Fe³⁺ transport was ruled out using a DMT-1 inhibitor. In conclusion, Sideral® RM retains iron in SGF, and is the most suitable for Fe³⁺ internalization by Caco-2 cells, Fe³⁺ protection from enzymatic reduction and promotion of Fe³⁺ absorption across intestinal epithelium, non-mediated by DMT-1.

Association between weather seasonality and blood parameters in riverine populations of the Brazilian Amazon

OBJECTIVE

To analyze the seasonality of blood parameters related to iron homeostasis, inflammation, and allergy in two riverine populations from the Brazilian Amazon.

METHODS

This was a cross-sectional study of 120 children and adolescents of school age, living in riverine communities of Porto Velho, Rondonia, Brazil, describing the hematocrit, hemoglobin, ferritin, serum iron, total white blood cell count, lymphocytes, eosinophils, C-reactive protein, and immunoglobulin E levels in the dry and rainy seasons. The chi-squared test and the prevalence ratio were used for the comparison of proportions and mean analysis using paired Student's t-test.

RESULTS

Hemoglobin (13.3g/dL) and hematocrit (40.9%) showed higher average values in the dry season. Anemia prevalence was approximately 4% and 12% in the dry and rainy seasons, respectively. Serum iron was lower in the dry season, with a mean of 68.7 mcg/dL. The prevalence of iron deficiency was 25.8% in the dry season and 9.2% in the rainy season. Serum ferritin did not show abnormal values in both seasons; however, the mean values were higher in the dry season (48.5ng/mL). The parameters of eosinophils, lymphocytes, global leukocyte count, C-reactive protein and immunoglobulin E showed no seasonal differences. C-reactive protein and immunoglobulin E showed abnormal values in approximately 7% and 60% of the examinations, respectively.

CONCLUSION

Hematological parameters of the red cell series and blood iron homeostasis had seasonal variation, which coincided with the dry season in the region, in which an increase in atmospheric pollutants derived from fires is observed.

Chronic maternal hyperglycemia induced during mid-pregnancy in rats increases RAGE expression, augments hippocampal excitability, and alters behavior of the offspring

Maternal diabetes during pregnancy may increase the risk of neurodevelopmental disorders in the offspring by increasing inflammation. A major source of inflammatory signaling observed in diabetes is activation of the receptor for advanced glycation end-products (RAGE), and increased RAGE expression has been reported in psychiatric disorders. Thus, we sought to examine whether maternal diabetes creates a proinflammatory state, triggered largely by RAGE signaling, that alters normal brain development and behavior of the offspring. We tested this hypothesis in rats using the streptozotocin (STZ; 50mg/kg; i.p.) model of diabetes induced during mid-pregnancy. Following STZ treatment, we observed a significant increase in RAGE protein expression in the forebrain of the offspring (postnatal day 1). Data obtained from whole-cell patch clamping of hippocampal neurons in cultures from the offspring of STZ-treated dams revealed a striking increase in excitability. When tested in a battery of behavioral tasks in early adulthood, the offspring of STZ-treated dams had significantly lower prepulse inhibition, reduced anxiety-like behavior, and altered object-place preference when compared to control offspring. In an operant-based strategy set-shifting task, STZ offspring did not differ from controls on an initial visual discrimination or reversal learning but took significantly longer to shift to a new strategy (i.e., set-shift). Insulin replacement with an implantable pellet in the dams reversed the effects of maternal diabetes on RAGE expression, hippocampal excitability, prepulse inhibition and object-place memory, but not anxiety-like behavior or set-shifting. Taken together, these results suggest that chronic maternal hyperglycemia alters normal hippocampal development and behavior of the offspring, effects that may be mediated by increased RAGE signaling in the fetal brain.

Iron deficiency during pregnancy: the consequences for placental function and fetal outcome

This review examines the importance of the placenta in iron metabolism during development and the effect of iron deficiency on maternal and fetal physiology. Iron is an essential micronutrient, required for a wide variety of biological processes. During pregnancy, the mother has to deplete her iron stores in order to provide the baby with adequate amounts. Trans-placental iron transfer involves binding transferrin (Tf)-bound iron to the Tf receptor, uptake into an endosome, acidification, release of iron through divalent metal transporter 1, efflux across the basolateral membrane through ferroportin and oxidation of Fe(II) by zyklopen. An additional haem transport system has been hypothesised, which may explain why certain gene knockouts are not lethal for the developing fetus. Iron deficiency is a common phenomenon during pregnancy, and the placenta adapts by up-regulating its transfer systems, maintaining iron at the expense of the mother. Despite these adaptations, deficiency cannot be completely prevented, and the offspring suffers both short- and long-term consequences. Some of these, at least, may arise from decreased expression of genes involved in the cell cycle and altered expression of transcription factors, such as c-myc, which in turn can produce, for example, kidneys with reduced numbers of nephrons. The mechanism whereby these changes are induced is not certain, but may simply be as a result of the reduced availability of iron resulting in decreased enzyme activity. Since these changes are so significant, and because some of the changes are irreversible, we believe that iron prophylaxis should be considered in all pregnancies.

Evolution of Placental Function in Mammals: The Molecular Basis of Gas and Nutrient Transfer, Hormone Secretion, and Immune Responses

Placenta has a wide range of functions. Some are supported by novel genes that have evolved following gene duplication events while others require acquisition of gene expression by the trophoblast. Although not expressed in the placenta, high-affinity fetal hemoglobins play a key role in placental gas exchange. They evolved following duplications within the beta-globin gene family with convergent evolution occurring in ruminants and primates. In primates there was also an interesting rearrangement of a cassette of genes in relation to an upstream locus control region. Substrate transfer from mother to fetus is maintained by expression of classic sugar and amino acid transporters at the trophoblast microvillous and basal membranes. In contrast, placental peptide hormones have arisen largely by gene duplication, yielding for example chorionic gonadotropins from the luteinizing hormone gene and placental lactogens from the growth hormone and prolactin genes. There has been a remarkable degree of convergent evolution with placental lactogens emerging separately in the ruminant, rodent, and primate lineages and chorionic gonadotropins evolving separately in equids and higher primates. Finally, coevolution in the primate lineage of killer immunoglobulin-like receptors and human leukocyte antigens can be linked to the deep invasion of the uterus by trophoblast that is a characteristic feature of human placentation.

Iron transportation across the placenta

According to the classification of placental types among animals, the transfer of iron through the placenta can occur via: absorption connected to transferin through the outer surface of the trophoblast in direct contact with circulating maternal blood; absorption of the erythrocytes by the chorionic epithelium in direct contact with accumulation of blood extravased from haemotophagous areas; absorption by the chorionic epithelium in direct contact with iron enriched secretions from the endometrial glands and absorption by extravasations of the blood in the maternal-fetal surface and the subsequent phagocytosis of the erythrocytes by trophoblast cells described in bovine, small ruminants, canine and feline. The function of erythrophagocytosis observed after the extravasation of blood in the maternal-fetal interface is undefined in several species. Possibly, the iron is transferred to the fetus through the trophoblastic erythrophagocytosis in the hemophogous area of the placenta and also in the endometrial glands. In this literature survey, new methods of studies regarding placental transfer involving iron and other nutrients necessary for survival and maintenance of embryonic fetus to birth are proposed.

Identification of zyklopen, a new member of the vertebrate multicopper ferroxidase family, and characterization in rodents and human cells

We previously detected a membrane-bound, copper-containing oxidase that may be involved in iron efflux in BeWo cells, a human placental cell line. We have now identified a gene encoding a predicted multicopper ferroxidase (MCF) with a putative C-terminal membrane-spanning sequence and high sequence identity to hephaestin (Heph) and ceruloplasmin (Cp), the other known vertebrate MCF. Molecular modeling revealed conservation of all type I, II, and III copper-binding sites as well as a putative iron-binding site. Protein expression was observed in multiple diverse mouse tissues, including placenta and mammary gland, and the expression pattern was distinct from that of Cp and Heph. The protein possessed ferroxidase activity, and protein levels decreased in cellular copper deficiency. Knockdown with small interfering RNA in BeWo cells indicates that this gene represents the previously detected oxidase. We propose calling this new member of the MCF family "zyklopen."

A cohort study of haemoglobin and zinc protoporphyrin levels in term Zambian infants: effects of iron stores at birth, complementary food and placental malaria

OBJECTIVE

To examine zinc-protoporphyrin (ZPP) and haemoglobin levels, and to determine predictors of iron deficiency anaemia (IDA) in Zambian infants.

SUBJECTS AND METHODS

Ninety-one women and their normal birth weight (NBW) infants were followed bi-monthly during the first 6 months of life, and iron status, food intake, malaria parasitaemia and growth were monitored. At 4 months, the infants were divided into two groups, and the data were analysed according to whether or not they were exclusively breastfed.

RESULTS

Almost two-third of infants were born with low iron stores as defined by ZPP levels, and this proportion increased with age. Over 50% had developed IDA by 6 months. Exclusive breastfeeding at 4 months could be a protective factor for IDA (odds ratio (OR): 0.2; 95% confidence interval (CI): 0.0-1.1). Exclusively breastfed infants had higher haemoglobin values at 4 and 6 months (mean difference 0.6; 95% CI: 0.1-1.2 g/dl and mean difference 0.9; 95% CI: 0.2-1.7 g/dl, respectively), compared with infants with early complementary feeding. In univariate analysis, past or chronic placental malaria appeared to be a predictor of IDA at 4 and 6 months, but the significance was lost in multivariate analysis.

CONCLUSIONS

Zambian NBW infants are born with low iron stores and have a high risk to develop IDA in the first 6 months of life. Continuation of exclusive breastfeeding after 4 months is associated with a reduction of anaemia. The effect of placental malaria infection on increased risk of infant IDA could not be proven.

Oxidant/antioxidant status of placenta, blood, and cord blood samples from pregnant women supplemented with iron

OBJECTIVE

In this study, it was aimed to investigate oxidant/antioxidant status in placenta and in blood and cord blood samples from pregnant women supplemented with iron during pregnancy.

METHODS

For this purpose, 27 pregnant women at admission for delivery participated in the study. Fifteen of them did not take iron tablets and the others took oral iron supplements during pregnancy. Following delivery, part of the placenta and blood and cord blood samples were taken from the mothers. In these samples, oxidant parameters (malondialdehyde [MDA] levels and xanthine oxidase [XO] activities) and antioxidant parameters (antioxidant potential [AOP] values, superoxide dismutase [SOD], catalase [CAT] and glutathione peroxidase [GSH-Px] activities) were studied.

RESULTS

It was found that MDA level and SOD activities increased significantly in the placentas from the iron-supplemented group as compared with those from the control group. We also observed that activities of SOD and XO enzymes in maternal erythrocytes, XO in cord blood erythrocytes and GSH-Px activities in cord blood plasma decreased significantly. However, activities of CAT and GSH-Px enzymes in cord blood erythrocytes and MDA levels in maternal plasma increased in the iron-supplemented group as compared with those from the control group.

CONCLUSION

Increased MDA levels in the maternal plasma and the placenta in the iron-supplemented group suggests that iron supplementation may contribute to increased oxidative stress in women taking iron supplements during pregnancy.

Resolvase-in vivo expression technology analysis of the Salmonella enterica serovar Typhimurium PhoP and PmrA regulons in BALB/c mice

Salmonella enterica modulates resistance to antimicrobial peptides in part via covalent modifications of the lipopolysaccharide (LPS). The two-component systems PhoP/PhoQ and PmrA/PmrB are activated during infection and regulate several genes involved in LPS modifications by responding to signals such as pH, iron, magnesium, and antimicrobial peptides. A recombination-based in vivo expression technology approach was adopted to analyze the spatial-temporal patterns of in vivo expression of genes of the PhoP and PmrA regulons and to identify the in vivo signals modulating their transcription. In vitro, we showed PhoP- and/or PmrA-dependent induction of pmrH (LPS aminoarabinose modification operon) by acidic pH, low levels of magnesium, or high levels of Fe(III). Upregulation in cultured J774A.1 macrophages was shown for pmrH, pagP (LPS palmitate addition), and ssaB (pathogenicity island II secretion) but not for prgH (pathogenicity island I secretion). Increased levels of pmrH, phoP, and prgH transcription but not ssaB were observed in bacteria isolated from the lumen of the distal ileum. Bacteria isolated from spleens of orally inoculated mice showed no further induction of prgH but had the highest expression of pmrH, pagP, and ssaB. In vivo induction of pmrH was fully dependent on pmrA and phoP, and buffering stomach acidity, iron chelation, or low-iron diets did not affect the expression of pmrH in the intestinal lumen. The observation of pmrH and pagP expression in the intestine refutes the paradigm of PhoP/PhoQ and PmrA/PmrB in vivo expression as solely intracellularly induced and supports previous data demonstrating peroral virulence attenuation of pmrH mutants.

Dysregulation of ferroportin 1 interferes with spleen organogenesis in polycythaemia mice

Regulatory interferences at the iron transporter ferroportin 1 (Fpn1) cause transient defects in iron homeostasis and erythropoiesis in polycythaemia(Pcm) mutant mice. The present study identified decreased Fpn1 expression in placental syncytiotrophoblast cells at late gestation as the mechanism of neonatal iron deficiency in Pcm mutants. Tissue specificity of embryonic Fpn1 dysregulation was evident from concomitant decreases in Fpn1 mRNA and protein expression in placenta and liver, as opposed to upregulation of Fpn1 protein despite decreased transcript levels in spleen, implicating post-transcriptional regulation of Fpn1. Dysregulation of Fpn1 and decreased iron levels in Pcm mutant spleens correlated with apoptotic cell death in the stroma, resulting in a semidominant spleen regression. At 7 weeks of age, a transient increase in spleen size in Pcm heterozygotes reflected a transient erythropoietin-mediated polycythemia. Structurally, Pcm mutant spleens displayed a severe defect in red pulp formation, including disruption of the sinusoidal endothelium, as well as discrete defects in white pulp organization during postnatal development. Reduced functional competence of the Pcmmutant spleen was manifested by an impaired response to chemically induced hemolytic anemia. Thus, aberrant Fpn1 regulation and iron homeostasis interferes with development of the spleen stroma during embryogenesis,resulting in a novel defect in spleen architecture postnatally.

Influence of gestational age and fetal iron status on IRP activity and iron transporter protein expression in third-trimester human placenta

Placental iron transport during the last trimester of pregnancy determines the iron endowment of the neonate. Iron transport is a function of the major iron transport proteins: transferrin receptor-1 (TfR-1) and ferroportin-1 (FPN-1). The mRNAs for TfR-1 and, potentially, FPN-1 are posttranscriptionally regulated by iron regulatory protein (IRP)-1 and IRP-2. We assessed the effect of gestational age and fetal iron status on IRP-1- and IRP-2-binding activity and on the localization and protein expression of TfR-1 and FPN-1 protein at 24-40 wk of gestation in 21 placentas obtained from iron-sufficient nonanemic mothers. Gestational age had no effect on cord serum ferritin concentration, IRP-2 RNA-binding activity, transporter protein location, and TfR-1 or FPN-1 protein expression. IRP-1 activity remained constant until full term, when it decreased (P = 0.01). Placental ferritin (r = 0.76, P < 0.001) and FPN-1 (r = 0.44, P < 0.05) expression increased with gestational age. Fetal iron status, as indexed by cord serum ferritin concentration, was inversely related to placental IRP-1 (r = -0.66, P < 0.001) and IRP-2 (r = -0.42, P = 0.05) activities. Placental ferritin protein expression correlated better with IRP-1 (r = -0.45, P = 0.04) than with IRP-2 (r = -0.35, P = 0.10) activity. Placental TfR-1 and FPN-1 protein expression was independent of fetal or placental iron status and IRP activities. Iron status had no effect on transport protein localization. We conclude that, toward the end of the third trimester of iron-sufficient human pregnancy, the placenta accumulates ferritin and potentially increases placental-fetal iron delivery through increased FPN-1 expression. IRP-1 may have a more dominant role than IRP-2 activity in regulating ferritin expression.