mRNA expression of proteins involved in iron homeostasis in brain regions is altered by age and by iron overloading in the neonatal period

Chalcone-based Turn-Off Chemosensor for Selective and Susceptible Detection of Fe2+ Ions: Spectroscopic and DFT Investigations

Herein, in this report we are introducing newly synthesized chalcone derivative, "(E)-1-phenyl-3-(4-((5-(((Z)-thiophen-2-ylmethylene)amino)-1,3,4-thiadiazol-2-yl)thio)phenyl)prop-2-en-1-one" (5), as a chemosensor to detect Fe2+ metal ions in HEPES buffer solution of pH 7.5. Spectroscopic techniques were used to confirm the synthesized sensor. To determine the chemical reactivity and molecular stability of the probe, a frontier molecular orbitals investigation was carried out. A molecular electrostatic potential map was investigated to know the binding site of 5 for metal ion coordination. The theoretical absorption and fluorescence emission properties were estimated and correlated with the experimental observations. The sensor showed excellent selectivity for Fe2+ compared to all other studied metal ions. The fluorescence binding studies were carried out by adding different amounts of Fe2+ ions for a fixed concentration of probe 5. The inclusion of Fe2+ ions resulted in a decrease in fluorescence intensity with a bathochromic shift of emission wavelength of 5 due to the 5-Fe2+ complexation. The binding affinity value for the probe was found to be 576.2 M-1 with the help of the Stern-Volmer plot. The Job's plot and mass spectra supported the 2:1 (5: Fe2+) stoichiometry of complex formation. The detection limit and limit of quantification of 5 for Fe2+ were calculated to be 4.79 × 10-5 M and 14.54 × 10-5 M. Further, in addition to this, the photophysical parameters such as fluorescence lifetime of 5 and 5-Fe2+ complex measured to be 0.1439 and 0.1574 ns. The quantum yield of 5 and 5-Fe2+ was found to be 0.0398 and 0.0376. All these experimental findings revealed that probe 5 has excellent selectivity and sensitivity for Fe2+ ions.

A Solvent-Mediated Excited-State Intermolecular Proton Transfer Fluorescent Probe for Fe3+ Sensing and Cell Imaging

Constructing excited-state intermolecular proton transfer (ESIPT-e) fluorophores represents significant challenges due to the harsh requirement of bearing a proton donor-acceptor (D-A) system and their matching proton donating-accepting ability in the same molecule. Herein, we synthesized a new-type ESIPT-e fluorophor (2-APC) using the "four-component one-pot" reaction. By the installing of a cyano-group on pyridine scaffold, the proton donating ability of -NH2 was greatly enhanced, enabling 2-APC to undergo ESIPT-e process. Surprisingly, 2-APC exhibited dual-emissions in protic solvents ethanol and normal fluorescence in aprotic solvents, which is vastly different from that of conventional ESIPT-a dyes. The ESIPT emission can be obviously suppressed by Fe3+ due to the coordination reaction of Fe3+ with the A-D system in 2-APC. From this basis, a highly sensitive and selective method was established using 2-APC as a fluorescent probe, which offers the sensitive detection of Fe3+ ranging from 0 to 13 μM with the detection limit of 7.5 nM. The recovery study of spiked Fe3+ measured by the probe showed satisfactory results (97.2103.4%) with the reasonable RSD ranging from 3.1 to 3.8%. Moreover, 2-APC can also exhibit aggregation-induced effect in poor solvent or solid-state, eliciting strong red fluorescence. 2-APC was also applied to cell-imaging, exhibiting good cell-permeability, biocompatibility and color rendering. This multi-mode emission of 2-APC is significant departure from that of conventional extended p-conjugated systems and ESIPT dyes based on a flat and rigid molecular design. The "one-pot synthesis" strategy for the construction of ESIPT molecules pioneered a new route to achieve tricolor-emissive fluorophores.

Postnatal Iron Supplementation with Ferrous Sulfate vs. Ferrous Bis-Glycinate Chelate: Effects on Iron Metabolism, Growth, and Central Nervous System Development in Sprague Dawley Rat Pups

Iron-fortified formulas and iron drops (both usually ferrous sulfate, FS) prevent early life iron deficiency, but may delay growth and adversely affect neurodevelopment by providing excess iron. We used a rat pup model to investigate iron status, growth, and development outcomes following daily iron supplementation (10 mg iron/kg body weight, representative of iron-fortified formula levels) with FS or an alternative, bioavailable form of iron, ferrous bis-glycinate chelate (FC). On postnatal day (PD) 2, sex-matched rat litters (n = 3 litters, 10 pups each) were randomly assigned to receive FS, FC, or vehicle control until PD 14. On PD 15, we evaluated systemic iron regulation and CNS mineral interactions and we interrogated iron loading outcomes in the hippocampus, in search of mechanisms by which iron may influence neurodevelopment. Body iron stores were elevated substantially in iron-supplemented pups. All pups gained weight normally, but brain size on PD 15 was dependent on iron source. This may have been associated with reduced hippocampal oxidative stress but was not associated with CNS mineral interactions, iron regulation, or myelination, as these were unchanged with iron supplementation. Additional studies are warranted to investigate iron form effects on neurodevelopment so that iron recommendations can be optimized for all infants.

Nitrogen-doped carbon dots for sensitive detection of ferric ions and monohydrogen phosphate by the naked eye and imaging in living cells

Nitrogen doped carbon dots (N-CDs) have been prepared via a one-pot hydrothermal method by using formamide and o-phenylenediamine as the carbon precursors. The as-fabricated N-CDs display excellent water dispersibility, good biocompatibility and anti-photobleaching properties. A strong emission band with an emission maximum (λ ^fl _max) of 556 nm is observed under 450 nm excitation, and a large Stokes shift of 106 nm is presented. However, the fluorescence is quenched by the addition of Fe³⁺; a good linearity is shown in the range of 0-65 μM with a detection limit as low as 0.85 μM. Fortunately, the quenched fluorescence could be recovered rapidly by the addition of monohydrogen phosphate (HPO₄ ^2-) due to the formation of the stable [N-CDs-Fe³⁺-HPO₄ ^2-] complex, and a good linearity is exhibited in the range of 0-60 μM with a low detection limit of 0.80 μM for HPO₄ ^2-. A novel "on-off-on" fluorescence response is seen with an obvious color change from yellow-crimson-yellow by the naked eye. In addition, the confocal microscopy images suggest that the as-synthesized N-CDs could serve as a sensitive nanosensor for Fe³⁺ and HPO₄ ^2- detection, implying the diverse potential application of N-CDs in the biomedical field.

Chromene–triazole-pyrimidine based chemosensor therapeutics for the in vivo and in vitro detection of Fe3+ ions

MCR and click synthesis of selective and sensitive Fe³⁺ sensors that can interact with CDK2 proteins and cytotoxicity against the human cervical cancer cell line HeLa is developed.

The neurophysiological effects of iron in early life stages of zebrafish

Trace metal/ion homeostasis, neurophysiological performance, and molecular responses to iron (Fe) exposure were investigated in the model organism zebrafish (Danio rerio). The findings demonstrated that exposure to a sublethal concentration of ferric iron (Fe³⁺) increased Fe contents in both the whole body and head region of developing zebrafish. Among the various trace metals and major ion examined, a dysregulation in manganese, zinc, nickel, and calcium balance was also observed in Fe-exposed larvae. Further biochemical assay and in-vivo imaging revealed that Fe exposure resulted in possible oxidative stress-induced damage, and an increased generation of reactive oxygen species in specific regions of the larvae. Using a droplet digital PCR (ddPCR) technology, it was found that the expression levels of various oxidative stress-responsive genes were temporally modulated by Fe exposure. Additionally, Fe-exposed larvae exhibited an impairment in escape response and a decrease in swimming activity. These larvae also appeared to exhibit a reduced anxiety-like behaviour. Together, our research suggested that larvae experiencing an increased Fe loading exhibited a dysregulation in metal homeostasis and a decrease in neurophysiological performance. These results suggested that neurophysiological assessments are sensitive methods to evaluate Fe toxicity in developing fish.

Phosphorus-Doped Carbon Quantum Dots as Fluorometric Probes for Iron Detection

Carbon quantum dots (CQDs), a novel fluorescent nanomaterial, have been extensively employed/explored in various applications, that is, biosensors, bioimaging, nanomedicine, therapeutics, photocatalysis, electrocatalysis, energy storage system, and so forth. In this study, we report the synthesis, characterization, and the application of phosphorus-doped CQDs (PCQDs), synthesized using trisodium citrate and phosphoric acid by the hydrothermal method. The effect of phosphorus doping on optical features and the formation of PCQDs have been explored elaborately by controlling the concentrations of precursors, reaction time, and the temperature. The fluorescent quantum yield for PCQDs was determined to be 16.1% at an excitation/emission wavelength of 310/440 nm. Also, the optical and structural properties of PCQDs were determined by using various spectroscopic and microscopic techniques. Static quenching of fluorescence was determined upon the addition of Fe3+ to PCQDs because of the formation of the fluorescent inactive complex (PCQDs-Fe3+). Hence, this chemistry leads to the development of a new fluorometric assay for the detection of Fe3+. The lower limit of Fe3+ detection is determined to be 9.5 nM (3σ/slope), with the linear fit from 20 nM to 3.0 μM (R 2 = 0.99). We have validated this new assay in the raw, ejected, and purified water samples of the RO plant by the standard addition method. These results suggest the possibility of developing a new commercial assay for Fe3+ detection in blood, urine, and various industrial waste and sewage water samples. Furthermore, recycling the pollutant water into the freshwater using filters that consist of PCQDs offers a great deal.

Isocyanoacetate-Aldehyde Polymerization: A Facile Tool toward Functional Oxazoline-Containing Polymers

As an important nitrogen source, isocyanides have been involved in numerous organic reactions. As a result, many complicated compounds have been successfully synthesized through isocyanide chemistry. However, compared with its popular research in organic reactions, the application of isocyanides in polymerization is less investigated. In this work, a new polymerization based on isocyanide monomers is established. By simply mixing diisocyanoacetates and dialdehydes in the presence of a catalytic system of CuCl/PPh₃ /organobase in dichloromethane at room temperature readily produces soluble and thermally stable oxazoline-containing polymers with moderate weight-averaged molecular weights (M_w up to 11 200) in excellent yields (up to 97%) after 6 h. Furthermore, introducing the tetraphenylethene moiety into the main chains endows the resultant polymers with aggregation-induced emission, which can function as fluorescent probes for Fe³⁺ ion detection with high sensitivity and selectivity. This work not only enriches the family of isocyanide-based polymerizations but also provides an efficient tool for the preparation of functional heterocycle-containing polymers.

Self-Assembly Fluorescent Cationic Cellulose Nanocomplex via Electrostatic Interaction for the Detection of Fe3+ Ions

In this work, an aggregation-induced emission (AIE) sensor for the detection of Fe3+ ions was fabricated through the electrostatic interaction between 1,1,2-triphenyl-2-[4-(3-sulfonatopropoxyl)-phenyl]-ethene sodium salt (SPOTPE) and quaternized cellulose (QC). The structure and properties of the SPOTPE/QC nanocomplex were studied by using ¹H NMR, spectrofluorophotometer, transmission electron microscopy (TEM), and dynamic laser light scattering (DLS). An aqueous solution of SPOTPE and QC resulted in a remarkably enhanced cyan fluorescence in comparison to that of the SPOTPE solution. Strong through-space electrostatic interaction between SPOTPE and QC is the main cause for the fluorescence emerging. The fluorescence of the SPOTPE/QC solutions show good stability over a wide pH range of 5.0⁻10.0. When introducing Fe3+ ions into the SPOTPE/QC solution, the fluorescence quenched within 5 s. SPOTPE/QC solutions exhibited high selectivity and sensitivity for the detection of Fe3+ ions with ignored interferences from other ions, and the detection limit was determined to be 2.92 × 10-6 M. The quenching mechanism was confirmed to be the consequence of the binding interactions between Fe3+ ions and SPOTPE/QC complex.

Antiapoptotic effects of cannabidiol in an experimental model of cognitive decline induced by brain iron overload

Iron accumulation in the brain has been recognized as a common feature of both normal aging and neurodegenerative diseases. Cognitive dysfunction has been associated to iron excess in brain regions in humans. We have previously described that iron overload leads to severe memory deficits, including spatial, recognition, and emotional memory impairments in adult rats. In the present study we investigated the effects of neonatal iron overload on proteins involved in apoptotic pathways, such as Caspase 8, Caspase 9, Caspase 3, Cytochrome c, APAF1, and PARP in the hippocampus of adult rats, in an attempt to establish a causative role of iron excess on cell death in the nervous system, leading to memory dysfunction. Cannabidiol (CBD), the main non-psychotropic component of Cannabis sativa, was examined as a potential drug to reverse iron-induced effects on the parameters analyzed. Male rats received vehicle or iron carbonyl (30 mg/kg) from the 12th to the 14th postnatal days and were treated with vehicle or CBD (10 mg/kg) for 14 days in adulthood. Iron increased Caspase 9, Cytochrome c, APAF1, Caspase 3 and cleaved PARP, without affecting cleaved Caspase 8 levels. CBD reversed iron-induced effects, recovering apoptotic proteins Caspase 9, APAF1, Caspase 3 and cleaved PARP to the levels found in controls. These results suggest that iron can trigger cell death pathways by inducing intrinsic apoptotic proteins. The reversal of iron-induced effects by CBD indicates that it has neuroprotective potential through its anti-apoptotic action.

A pyrene based fluorescent turn-on chemosensor: aggregation-induced emission enhancement and application towards Fe3+ and Fe2+ recognition

A pyrene-based probe bearing benzothiazole ionophore (Py-BTZ) was synthesised as a "turn-on" fluorescent chemosensor for the detection of Fe³⁺ and Fe²⁺ ions in CH₃CN : H₂O (1 : 1, v/v) solvent mixes. The chemosensor showed optical as well as colorimetric changes towards Fe³⁺ and Fe²⁺ ions along with a remarkable enhancement in fluorescence emission. The detection limit of Py-BTZ towards Fe³⁺ and Fe²⁺ ions was found to be 2.61 μM and 2.06 μM, respectively. The binding of Py-BTZ with Fe³⁺ and Fe²⁺ was determined by using FT-IR experiments. Interestingly, Py-BTZ shows aggregation induced emission enhancement (AIEE) properties in polar solvent mixes such as CH₃CN : H₂O (1 : 1, v/v).

Excess iron intake as a factor in growth, infections, and development of infants and young children

The provision of iron via supplementation or the fortification of foods has been shown to be effective in preventing and treating iron deficiency and iron deficiency anemia in infants and young children. However, iron is a pro-oxidative element and can have negative effects on biological systems even at moderate amounts. An increasing number of studies have reported adverse effects of iron that was given to infants and young-children populations who initially were iron replete. These effects include decreased growth (both linear growth and weight), increased illness (usually diarrhea), interactions with other trace elements such as copper and zinc, altered gut microbiota to more pathogenic bacteria, increased inflammatory markers, and impaired cognitive and motor development. If these results can be confirmed by larger and well-controlled studies, it may have considerable programmatic implications (e.g., the necessity to screen for iron status before interventions to exclude iron-replete individuals). A lack of understanding of the mechanisms underlying these adverse outcomes limits our ability to modify present supplementation and fortification strategies. This review summarizes studies on the adverse effects of iron on various outcomes; suggests possible mechanisms that may explain these observations, which are usually made in clinical studies and intervention trials; and gives examples from animal models and in vitro studies. With a better understanding of these mechanisms, it may be possible to find novel ways of providing iron in a form that causes fewer or no adverse effects even when subjects are iron replete. However, it is apparent that our understanding is limited, and research in this area is urgently needed.

Pyrene-Phosphonate Conjugate: Aggregation-Induced Enhanced Emission, and Selective Fe3+ Ions Sensing Properties

A new pyrene-phosphonate colorimetric receptor 1 has been designed and synthesized in a one-step process via amide bond formation between pyrene butyric acid chloride and phosphonate-appended aniline. The pyrene-phosphonate receptor 1 showed aggregation-induced enhanced emission (AIEE) properties in water/acetonitrile (ACN) solutions. Dynamic light scattering (DLS) characterization revealed that the aggregates of receptor 1 at 80% water fraction have an average size of ≈142 nm. Field emission scanning electron microscopy (FE-SEM) analysis confirmed the formation of spherical aggregates upon solvent evaporation. The sensing properties of receptor 1 were investigated by UV-vis, fluorescence emission spectroscopy, and other optical methods. Among the tested metal ions, receptor 1 is capable of recognizing the Fe³⁺ ion selectively. The changes in spectral measurements were explained on the basis of complex formation. The composition of receptor 1 and Fe³⁺ ions was determined by using Job's plot and found to be 1:1. The receptor 1-Fe³⁺ complex showed a reversible UV-vis response in the presence of EDTA.

Impact of high iron intake on cognition and neurodegeneration in humans and in animal models: a systematic review

Context

Accumulation of brain iron is linked to aging and protein-misfolding neurodegenerative diseases. High iron intake may influence important brain health outcomes in later life.

Objective

The aim of this systematic review was to examine evidence from animal and human studies of the effects of high iron intake or peripheral iron status on adult cognition, brain aging, and neurodegeneration.

Data Sources

MEDLINE, Scopus, CAB Abstracts, the Cochrane Central Register of Clinical Trials, and OpenGrey databases were searched.

Study Selection

Studies investigating the effect of elevated iron intake at all postnatal life stages in mammalian models and humans on measures of adult brain health were included.

Data Extraction

Data were extracted and evaluated by two authors independently, with discrepancies resolved by discussion. Neurodegenerative disease diagnosis and/or behavioral/cognitive, biochemical, and brain morphologic findings were used to study the effects of iron intake or peripheral iron status on brain health. Risk of bias was assessed for animal and human studies. PRISMA guidelines for reporting systematic reviews were followed.

Results

Thirty-four preclinical and 14 clinical studies were identified from database searches. Thirty-three preclinical studies provided evidence supporting an adverse effect of nutritionally relevant high iron intake in neonates on brain-health-related outcomes in adults. Human studies varied considerably in design, quality, and findings; none investigated the effects of high iron intake in neonates/infants.

Conclusions

Human studies are needed to verify whether dietary iron intake levels used in neonates/infants to prevent iron deficiency have effects on brain aging and neurodegenerative disease outcomes.

Self-Assembly of Fluorescent Organic Nanoparticles for Iron(III) Sensing and Cellular Imaging

Fluorescent organic nanoparticles have attracted increasing attentions for chemical or biological sensing and imaging due to their low-toxicity, facile fabrication and surface functionalization. In this work, we report novel fluorescent organic nanoparticles via facile self-assembly method in aqueous solution. First, the designed water-soluble fluorophore shows a weak and negligible intrinsic fluorescence in water. Upon binding with adenosine-5'-triphosphate (ATP), fluorescent nanoparticles were formed immediately with strongly enhanced fluorescence. These fluorescent nanoparticles exhibit high sensitivity and selectivity toward Fe(3+) sensing with detection limit of 0.1 nM. In addition, after incubation with HeLa cells, the fluorophore shows excellent imaging performance by interaction with entogenous ATP in cells. Finally, this fluorescent system is also demonstrated to be capable of Fe(3+) sensing via fluorescence quenching in cellular environment.

Design and synthesis of a novel rhodamine-based chemosensor and recognition study to Fe3+

A fluorescent and colorimetric chemosensor Rh1 for Fe3+ was synthesized by condensation reaction of rhodamine B hydrochloride and 2-aminothiazole, and its structure was confirmed by NMR, IR, HRMS and crystal data. Upon coordination with Fe3+ in CH3CN-H2O (1:1, v/v) solution, the spirolactam of Rh1 is opened, which results in a dramatic enhancement of fluorescence intensity as well as the color change of the solution. Most importantly, other metal ions show no obvious interference with the detection of Fe3+. Under the optimum conditions described, the fluorescence intensity is linearly proportional to the concentration of Fe3+ in the range of 2 μm ~ 7 μm. The Job’s plot indicates a 1:1 binding stoichiometry between Rh1 and Fe3+. The association constant (Ka) is 2.26 × 104m-1.

A reversible rhodamine 6G-based fluorescence turn-on probe for Fe3+ in water and its application in living cell imaging

A reversible fluorescent probe L based on rhodamine 6G was synthesized for the optical detection of Fe³⁺ in water.

A diarylethene-based fluorescent chemosensor for the sequential recognition of Fe3+ and cysteine

A new fluorescent chemosensor based on a diarylethene was designed and synthesized for sequential recognition of Fe³⁺ and cysteine.

Sleep patterns in male juvenile monkeys are influenced by gestational iron deprivation and monoamine oxidase A genotype

Individual differences in sleep patterns of children may have developmental origins. In the present study, two factors known to influence behavioural development, monoamine oxidase A (MAOA) genotype and prenatal Fe-deficient (ID) diet, were examined for their influences on sleep patterns in juvenile rhesus monkeys. Sleep patterns were assessed based on a threshold for inactivity as recorded by activity monitors. Pregnant monkeys were fed diets containing either 100 parts per million (ppm) Fe (Fe sufficient, IS) or 10 ppm Fe (ID). At 3-4 months of age, male offspring were genotyped for polymorphisms of the MAOA gene that lead to high or low transcription. At 1 and 2 years of age, sleep patterns were assessed. Several parameters of sleep architecture changed with age. At 1 year of age, monkeys with the low-MAOA genotype demonstrated a trend towards more sleep episodes at night compared with those with the high-MAOA genotype. When monkeys reached 2 years of age, prenatal ID reversed this trend; ID in the low-MAOA group resulted in sleep fragmentation, more awakenings at night and more sleep episodes during the day when compared with prenatal IS in this genotype. The ability to consolidate sleep during the dark cycle was disrupted by prenatal ID, specifically in monkeys with the low-MAOA genotype.

Novel fluorescent probes based on rhodamine for naked-eye detection of Fe3+ and their application of imaging in living cells

Novel fluorescent probes for Fe³⁺ and their application of imaging in living cells.

Noradrenergic-Dopaminergic Interactions Due to DSP-4-MPTP Neurotoxin Treatments: Iron Connection

The investigations of noradrenergic lesions and dopaminergic lesions have established particular profiles of functional deficits and accompanying alterations of biomarkers in brain regions and circuits. In the present account, the focus of these lesions is directed toward the effects upon dopaminergic neurotransmission and expression that are associated with the movement disorders and psychosis-like behavior. In this context, it was established that noradrenergic denervation, through administration of the selective noradrenaline (NA) neurotoxin, DSP-4, should be performed prior to the depletion of dopamine (DA) with the selective neurotoxin, MPTP. Employing this regime, it was shown that (i) following DSP-4 (50 mg/kg) pretreatment of C57/Bl6 mice, both the functional and neurochemical (DA loss) effects of MPTP (2 × 20 and 2 × 40 mg/kg) were markedly exacerbated, and (ii) following postnatal iron (Fe(2+), 7.5 mg/kg, on postnatal days 19-12), pretreatment with DSP-4 followed by the lower 2 × 20 mg/kg MPTP dose induced even greater losses of motor behavior and striatal DA. As yet, the combination of NA-DA depletions, and even more so Fe(2+)-NA-DA depletion, has been considered to present a movement disorder aspect although studies exploring cognitive domains are lacking. With intrusion of iron overload into this formula, the likelihood of neuropsychiatric disorder, as well, unfolds.

Novel BODIPY-based fluorescence turn-on sensor for Fe3+ and its bioimaging application in living cells

A novel boron-dipyrromethene (BODIPY) based fluorescence turn-on sensor for detecting Fe(3+) in aqueous media is reported with 23-fold fluorescence enhancement. The sensor is comprised of a combination of BODIPY fluorophore and a new Fe(3+)-recognizing cryptand that exhibits high selectivity, sensitivity, and reversibility toward Fe(3+) detection. Cell imaging studies demonstrate that this sensor is capable of sensing Fe(3+) in living cells.

Rhodamine-based "turn-on" fluorescent probe with high selectivity for Fe(2+) imaging in living cells

A rhodamine-based "turn-on" fluorescent probe 1 was synthesized with high yield. The recognizing behavior displays high selectivity of 1 toward Fe(2+) with a 2:1 complex, and 1 exhibits a stable response for Fe(2+) over a concentration range from 2 μM to 24 μM. Most importantly, probe is hardly interfered by other transition metal ions. Their fluorescent enhancement is observed in the presence of Fe(2+) because of the ring-open interactions of spirocyclic. All measurements are made in PBS buffer environments simulating biological conditions to make them suitable candidates for fluorescent labeling of biological systems. Confocal laser scanning microscopy experiments have proven that probe can be used to monitor Fe(2+) in living cells.

A mutation in the HFE gene is associated with altered brain iron profiles and increased oxidative stress in mice

Because of the increasing evidence that H63D HFE polymorphism appears in higher frequency in neurodegenerative diseases, we evaluated the neurological consequences of H63D HFE in vivo using mice that carry H67D HFE (homologous to human H63D). Although total brain iron concentration did not change significantly in the H67D mice, brain iron management proteins expressions were altered significantly. The 6-month-old H67D mice had increased HFE and H-ferritin expression. At 12 months, H67D mice had increased H- and L-ferritin but decreased transferrin expression suggesting increased iron storage and decreased iron mobilization. Increased L-ferritin positive microglia in H67D mice suggests that microglia increase iron storage to maintain brain iron homeostasis. The 6-month-old H67D mice had increased levels of GFAP, increased oxidatively modified protein levels, and increased cystine/glutamate antiporter (xCT) and hemeoxygenase-1 (HO-1) expression indicating increased metabolic and oxidative stress. By 12 months, there was no longer increased astrogliosis or oxidative stress. The decrease in oxidative stress at 12 months could be related to an adaptive response by nuclear factor E2-related factor 2 (Nrf2) that regulates antioxidant enzymes expression and is increased in the H67D mice. These findings demonstrate that the H63D HFE impacts brain iron homeostasis, and promotes an environment of oxidative stress and induction of adaptive mechanisms. These data, along with literature reports on humans with HFE mutations provide the evidence to overturn the traditional paradigm that the brain is protected from HFE mutations. The H67D knock-in mouse can be used as a model to evaluate how the H63D HFE mutation contributes to neurodegenerative diseases.

Memory impairment induced by brain iron overload is accompanied by reduced H3K9 acetylation and ameliorated by sodium butyrate

Iron accumulation in the brain has been associated to the pathogenesis of neurodegenerative disorders. We have previously demonstrated that iron overload in the neonatal period results in severe and persistent memory deficits in adult rats. Alterations in histone acetylation have been associated with memory deficits in models of neurological disorders. Here we examine histone acetylation in the brain and the effects of the histone deacetylase inhibitor (HDACi) sodium butyrate (NaB) on memory in the neonatal iron overload model in rats. Rats received vehicle or 30.0-mg/kg Fe⁺² orally at postnatal days 12-14. When animals reached adulthood, they were given training in either novel object recognition or inhibitory avoidance. Histone acetylation in the dorsal hippocampus and the effects of NaB were examined in separate sets of rats. Iron overload led to a reduction in H3 lysine 9 acetylation in the hippocampus, without affecting the acetylation of other H3 and H4 lysine residues. A single systemic injection of NaB (1.2 g/kg) immediately after training ameliorated iron-induced memory impairments. The results suggest that a reduction in H3K9 acetylation might play a role in iron-induced memory impairment and support the view that HDACis can rescue memory dysfunction in models of brain disorders.

Iron and mechanisms of neurotoxicity

The accumulation of transition metals (e.g., copper, zinc, and iron) and the dysregulation of their metabolism are a hallmark in the pathogenesis of several neurodegenerative diseases. This paper will be focused on the mechanism of neurotoxicity mediated by iron. This metal progressively accumulates in the brain both during normal aging and neurodegenerative processes. High iron concentrations in the brain have been consistently observed in Alzheimer's (AD) and Parkinson's (PD) diseases. In this connection, metalloneurobiology has become extremely important in establishing the role of iron in the onset and progression of neurodegenerative diseases. Neurons have developed several protective mechanisms against oxidative stress, among them, the activation of cellular signaling pathways. The final response will depend on the identity, intensity, and persistence of the oxidative insult. The characterization of the mechanisms mediating the effects of iron-induced increase in neuronal dysfunction and death is central to understanding the pathology of a number of neurodegenerative disorders.

Molecular genetic approaches to understanding the roles and regulation of iron in brain health and disease

Iron is essential in the brain, yet too much iron can be toxic. Tight regulation of iron in the brain may involve intrinsic mechanisms that control internal homeostasis independent of systemic iron status. Iron abnormalities occur in various neurological disorders, usually with symptoms or neuropathology associated with movement impairment or behavioral disturbances rather than cognitive impairment or dementia. Consistent with this, polymorphisms in the HFE gene, associated with the iron overload disorder hemochromatosis, show stronger associations with the movement disorder amyotrophic lateral sclerosis (motor neuron disease) than with cognitive impairment. Such associations may arise because certain brain regions involved in movement or executive control are particularly iron-rich, notably the basal ganglia, and may be highly reliant on iron. Various mechanisms, including iron redistribution causing functional iron deficiency, lysosomal and mitochondrial abnormalities or oxidative damage, could underlie iron-related neuropathogenesis. Clarifying how iron contributes causatively to neurodegeneration may improve treatment options in a range of neurodegenerative disorders. This review considers how modern molecular genetic approaches can be applied to resolve the complex molecular systems and pathways by which brain iron homeostasis is regulated and the molecular changes that occur with iron dyshomeostasis and neuropathogenesis.