Iron: a new target for pharmacological intervention in neurodegenerative diseases

Implications of Iron in Ferroptosis, Necroptosis, and Pyroptosis as Potential Players in TBI Morbidity and Mortality

Iron is a critical transition metal required to sustain a healthy central nervous system. Iron is involved in metabolic reactions, enzymatic activity, myelinogenesis, and oxygen transport. However, in several pathological conditions such as cancer, neurodegeneration, and neurotrauma iron becomes elevated. Excessive iron can have deleterious effects leading to reactive oxygen species (ROS) via the Fenton reaction. Iron-derived ROS are known to drive several mechanisms such as cell death pathways including ferroptosis, necroptosis, and pyroptosis. Excessive iron present in the post-traumatic brain could trigger these harmful pathways potentiating the high rates of morbidity and mortality. In the present review, we will discuss how iron plays an intricate role in initiating ferroptosis, necroptosis, and pyroptosis, examine their potential link to traumatic brain injury morbidity and mortality, and suggest therapeutic targets.

Realizing brain therapy with "smart medicine": mechanism and case report of molecular hydrogen inhalation for Parkinson's disease

The Michael J. Fox Foundation has been funding research on Parkinson's disease for 35 years, but has yet to find a cure. This is due to a problem with the philosophy behind the development of modern medical treatments. In this paper, we will introduce "smart medicine" with a substance that can solve all the problems of central nervous system drugs. The substance is the smallest diatomic molecule, the hydrogen molecule. Due to their size, hydrogen molecules can easily penetrate the cell membrane and enter the brain. In the midbrain of Parkinson's disease patients, hydroxyl radicals generated by the Fenton reaction cause a chain reaction of oxidation of dopamine, but hydrogen entering the midbrain can convert the hydroxyl radicals into water molecules and inhibit the oxidation of dopamine. In this paper, we focus on the etiology of neurological diseases, especially Parkinson's disease, and present a case in which hydrogen inhalation improves the symptoms of Parkinson's disease, such as body bending and hand tremor. And we confidently state that if Michael J. Fox encountered "smart medicine" that could be realized with molecular hydrogen, he would not be a "lucky man" but a "super-lucky man."

Ferroptosis in Parkinson's disease -- The iron-related degenerative disease

Parkinson's disease (PD) is a prevalent and advancing age-related neurodegenerative disorder, distinguished by the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Iron regional deposit in SNpc is a significant pathological characteristic of PD. Brain iron homeostasis is precisely regulated by iron metabolism related proteins, whereas disorder of these proteins can damage neurons and glial cells in the brain. Additionally, growing studies have reported iron metabolism related proteins are involved in the ferroptosis progression in PD. However, the effect of these proteins in the ferroptosis of PD has not been systematically summarized. This review focuses on the roles of iron metabolism related proteins in the ferroptosis of PD. Finally, we put forward the iron early diagnosis according to the observation of iron deposits in the brain and showed the recent advances in iron chelation therapy in PD.

Identification of the bacterial metabolite aerugine as potential trigger of human dopaminergic neurodegeneration

The causes of nigrostriatal cell death in idiopathic Parkinson's disease are unknown, but exposure to toxic chemicals may play some role. We followed up here on suggestions that bacterial secondary metabolites might be selectively cytotoxic to dopaminergic neurons. Extracts from Streptomyces venezuelae were found to kill human dopaminergic neurons (LUHMES cells). Utilizing this model system as a bioassay, we identified a bacterial metabolite known as aerugine (C10H11NO2S; 2-[4-(hydroxymethyl)-4,5-dihydro-1,3-thiazol-2-yl]phenol) and confirmed this finding by chemical re-synthesis. This 2-hydroxyphenyl-thiazoline compound was previously shown to be a product of a wide-spread biosynthetic cluster also found in the human microbiome and in several pathogens. Aerugine triggered half-maximal dopaminergic neurotoxicity at 3-4 µM. It was less toxic for other neurons (10-20 µM), and non-toxic (at <100 µM) for common human cell lines. Neurotoxicity was completely prevented by several iron chelators, by distinct anti-oxidants and by a caspase inhibitor. In the Caenorhabditis elegans model organism, general survival was not affected by aerugine concentrations up to 100 µM. When transgenic worms, expressing green fluorescent protein only in their dopamine neurons, were exposed to aerugine, specific neurodegeneration was observed. The toxicant also exerted functional dopaminergic toxicity in nematodes as determined by the "basal slowing response" assay. Thus, our research has unveiled a bacterial metabolite with a remarkably selective toxicity toward human dopaminergic neurons in vitro and for the dopaminergic nervous system of Caenorhabditis elegans in vivo. These findings suggest that microbe-derived environmental chemicals should be further investigated for their role in the pathogenesis of Parkinson's disease.

The Neuroprotective Activities of the Novel Multi-Target Iron-Chelators in Models of Alzheimer's Disease, Amyotrophic Lateral Sclerosis and Aging

The concept of chelation therapy as a valuable therapeutic approach in neurological disorders led us to develop multi-target, non-toxic, lipophilic, brain-permeable compounds with iron chelation and anti-apoptotic properties for neurodegenerative diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD), age-related dementia and amyotrophic lateral sclerosis (ALS). Herein, we reviewed our two most effective such compounds, M30 and HLA20, based on a multimodal drug design paradigm. The compounds have been tested for their mechanisms of action using animal and cellular models such as APP/PS1 AD transgenic (Tg) mice, G93A-SOD1 mutant ALS Tg mice, C57BL/6 mice, Neuroblastoma × Spinal Cord-34 (NSC-34) hybrid cells, a battery of behavior tests, and various immunohistochemical and biochemical techniques. These novel iron chelators exhibit neuroprotective activities by attenuating relevant neurodegenerative pathology, promoting positive behavior changes, and up-regulating neuroprotective signaling pathways. Taken together, these results suggest that our multifunctional iron-chelating compounds can upregulate several neuroprotective-adaptive mechanisms and pro-survival signaling pathways in the brain and might function as ideal drugs for neurodegenerative disorders, such as PD, AD, ALS, and aging-related cognitive decline, in which oxidative stress and iron-mediated toxicity and dysregulation of iron homeostasis have been implicated.

Fiscalin Derivatives as Potential Neuroprotective Agents

Neurodegenerative diseases (ND) share common molecular/cellular mechanisms that contribute to their progression and pathogenesis. In this sense, we are here proposing new neuroprotection strategies by using marine-derived compounds as fiscalins. This work aims to evaluate the protective effects of fiscalin derivatives towards 1-methyl-4-phenylpyridinium (MPP⁺)- and iron (III)-induced cytotoxicity in differentiated SH-SY5Y cells, an in vitro disease model to study ND; and on P-glycoprotein (P-gp) transport activity, an efflux pump of drugs and neurotoxins. SH-SY5Y cells were simultaneously exposed to MPP⁺ or iron (III), and noncytotoxic concentrations of 18 fiscalin derivatives (0–25 μM), being the cytotoxic effect of both MPP⁺ and iron (III) evaluated 24 and 48 h after exposure. Fiscalins 1a and 1b showed a significant protective effect against MPP⁺-induced cytotoxicity and fiscalins 1b, 2b, 4 and 5 showed a protective effect against iron (III)-induced cytotoxicity. Fiscalins 4 and 5 caused a significant P-gp inhibition, while fiscalins 1c, 2a, 2b, 6 and 11 caused a modest increase in P-gp transport activity, thus suggesting a promising source of new P-gp inhibitors and activators, respectively. The obtained results highlight fiscalins with promising neuroprotective effects and with relevance for the synthesis of new derivatives for the treatment/prevention of ND.

Variable histopathology features of neuronal dyslamination in the cerebral neocortex adjacent to epilepsy-associated vascular malformations suggest complex pathogenesis of focal cortical dysplasia ILAE type IIIc

Focal cortical dysplasia type IIIc (FCD‐IIIc) is histopathologically defined by the International League Against Epilepsy's classification scheme as abnormal cortical organization adjacent to epilepsy‐associated vascular malformations (VM). However, the incidence of FCD‐IIIc, its pathogenesis, or association with the epileptogenic condition remains to be clarified. We reviewed a retrospective series of surgical brain specimens from 14 epilepsy patients with leptomeningeal angiomatosis of Sturge‐Weber syndrome (LMA‐SWS; n = 6), cerebral cavernous malformations (CCM; n = 7), and an arteriovenous malformation (AVM; n = 1) to assess the histopathological spectrum of FCD‐IIIc patterns in VM. FCD‐IIIc was observed in all cases of LMA‐SWS and was designated as cortical pseudolaminar sclerosis (CPLS). CPLS showed a common pattern of horizontally organized layer abnormalities, including neuronal cell loss and astrogliosis, either manifesting predominantly in cortical layer (L) 3 extending variably to deeper areas with or without further extension to L2 and/or L4. Another pattern was more localized, targeting mainly L4 with extension to L3 and/or L5. Abnormal cortical layering characterized by a fusion of L2 and L3 or L4–L6 was also noted in two LMA‐SWS cases and the AVM case. No horizontal or vertical lamination abnormalities were observed in the specimens adjacent to the CCM, despite the presence of vascular congestion and dilated parenchymal veins in all VM. These findings suggest that FCD‐IIIc depends on the type of the VM and developmental timing. We further conclude that FCD‐IIIc represents a secondary lesion acquired during pre‐ and/or perinatal development rather than following a pathomechanism independent of LMA‐SWS. Further studies will be necessary to address the selective vulnerability of the developing cerebral neocortex in LMA‐SWS, including genetic, encephaloclastic, hemodynamic, or metabolic events.

Management of Iron Overload in Resource Poor Nations: A Systematic Review of Phlebotomy and Natural Chelators

Iron is an essential element and the most abundant trace metal in the body involved in oxygen transport and oxygen sensing, electron transfer, energy metabolism, and DNA synthesis. Excess labile and unchelated iron can catalyze the formation of tissue-damaging radicals and induce oxidative stress. English abstracts were identified in PubMed and Google Scholar using multiple and various search terms based on defined inclusion and exclusion criteria. Full-length articles were selected for systematic review, and secondary and tertiary references were developed. Although bloodletting or phlebotomy remains the gold standard in the management of iron overload, this systematic review is an updated account of the pitfalls of phlebotomy and classical synthetic chelators with scientific justification for the use of natural iron chelators of dietary origin in resource-poor nations.

Conservative iron chelation for neurodegenerative diseases such as Parkinson's disease and amyotrophic lateral sclerosis

Focal iron accumulation associated with brain iron dyshomeostasis is a pathological hallmark of various neurodegenerative diseases (NDD). The application of iron-sensitive sequences in magnetic resonance imaging has provided a useful tool to identify the underlying NDD pathology. In the three major NDD, degeneration occurs in central nervous system (CNS) regions associated with memory (Alzheimer's disease, AD), automaticity (Parkinson's disease, PD) and motor function (amyotrophic lateral sclerosis, ALS), all of which require a high oxygen demand for harnessing neuronal energy. In PD, a progressive degeneration of the substantia nigra pars compacta (SNc) is associated with the appearance of siderotic foci, largely caused by increased labile iron levels resulting from an imbalance between cell iron import, storage and export. At a molecular level, α-synuclein regulates dopamine and iron transport with PD-associated mutations in this protein causing functional disruption to these processes. Equally, in ALS, an early iron accumulation is present in neurons of the cortico-spinal motor pathway before neuropathology and secondary iron accumulation in microglia. High serum ferritin is an indicator of poor prognosis in ALS and the application of iron-sensitive sequences in magnetic resonance imaging has become a useful tool in identifying pathology. The molecular pathways that cascade down from such dyshomeostasis still remain to be fully elucidated but strong inroads have been made in recent years. Far from being a simple cause or consequence, it has recently been discovered that these alterations can trigger susceptibility to an iron-dependent cell-death pathway with unique lipoperoxidation signatures called ferroptosis. In turn, this has now provided insight into some key modulators of this cell-death pathway that could be therapeutic targets for the NDD. Interestingly, iron accumulation and ferroptosis are highly sensitive to iron chelation. However, whilst chelators that strongly scavenge intracellular iron protect against oxidative neuronal damage in mammalian models and are proven to be effective in treating systemic siderosis, these compounds are not clinically suitable due to the high risk of developing iatrogenic iron depletion and ensuing anaemia. Instead, a moderate iron chelation modality that conserves systemic iron offers a novel therapeutic strategy for neuroprotection. As demonstrated with the prototype chelator deferiprone, iron can be scavenged from labile iron complexes in the brain and transferred (conservatively) either to higher affinity acceptors in cells or extracellular transferrin. Promising preclinical and clinical proof of concept trials has led to several current large randomized clinical trials that aim to demonstrate the efficacy and safety of conservative iron chelation for NDD, notably in a long-term treatment regimen.

Hepcidin and its therapeutic potential in neurodegenerative disorders

Abnormally high brain iron, resulting from the disrupted expression or function of proteins involved in iron metabolism in the brain, is an initial cause of neuronal death in neuroferritinopathy and aceruloplasminemia, and also plays a causative role in at least some of the other neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, and Friedreich's ataxia. As such, iron is believed to be a novel target for pharmacological intervention in these disorders. Reducing iron toward normal levels or hampering the increases in iron associated with age in the brain is a promising therapeutic strategy for all iron-related neurodegenerative disorders. Hepcidin is a crucial regulator of iron homeostasis in the brain. Recent studies have suggested that upregulating brain hepcidin levels can significantly reduce brain iron content through the regulation of iron transport protein expression in the blood-brain barrier and in neurons and astrocytes. In this review, we focus on the discussion of the therapeutic potential of hepcidin in iron-associated neurodegenerative diseases and also provide a systematic overview of recent research progress on how misregulated brain iron metabolism is involved in the development of multiple neurodegenerative disorders.

Compound of icariin, astragalus, and puerarin mitigates iron overload in the cerebral cortex of Alzheimer's disease mice

Increasing evidence indicates that disruption of normal iron homeostasis may contribute to pathological development of Alzheimer's disease. Icariin, astragalus, and puerarin have been shown to suppress iron overload in the cerebral cortex and improve spatial learning and memory disorders in Alzheimer's disease mice, although the underlying mechanism remains unclear. In the present study, APPswe/PS1ΔE9 transgenic mice were administered icariin, astragalus, and puerarin (120, 80, and 80 mg/kg, respectively, once a day, for 3 months). Iron levels were detected by flame atomic absorption spectroscopy. Interleukin-1β, interleukin-6, and tumor necrosis factor-α levels were measured in the cerebral cortex by enzyme linked immunosorbent assay. Glutathione peroxidase and superoxide dismutase activity and malondialdehyde content were determined by colorimetry. Our results demonstrate that after treatment, iron levels and malondialdehyde content are decreased, while glutathione peroxidase and superoxide dismutase activities are increased. Further, interleukin-1β, interleukin-6, and tumor necrosis factor-α levels were reduced. These results confirm that compounds of icariin, astragalus, and puerarin may alleviate iron overload by reducing oxidative stress and the inflammatory response.

The novel multitarget iron chelating and propargylamine drug M30 affects APP regulation and processing activities in Alzheimer's disease models

In many of the neurodegenerative diseases, such as Alzheimer's disease (AD) and AD-related disorders, as well as in the regular ageing process, excessive generation of oxidative stress (OS) and accumulation of iron levels and deposition have been observed in specific affected-brain regions and thus, regarded as contributing factors to the pathogenesis of the diseases. In AD, iron promotes amyloid β (Aβ) neurotoxicity by producing free radical damage and OS in brain areas affected by neurodegeneration, presumably by facilitating the aggregation of Aβ. In addition, it was shown that iron modulates intracellular levels of the holo amyloid precursor protein (APP) by iron-responsive elements (IRE) RNA stem loops in the 5' untranslated region (5'UTR) of the APP transcript. As a consequence of these observations, iron chelation is one of the major new therapeutic strategies for the treatment of AD. This review describes the benefits and importance of the multimodal brain permeable chimeric iron-chelating/propargylamine drug M30, concerning its neuroprotective/neurorestorative inter-related activities relevant of the pathological features ascribed to AD, with a special focus on the effect of the drug on APP regulation and processing.

Targeting Free Radicals in Oxidative Stress-Related Human Diseases

Cancer and Alzheimer's disease (AD) are characterized by (i) opposing biological mechanisms, (ii) an inverse correlation between their incidences, and (iii) oxidative stress being a common denominator of both diseases. Increased formation of reactive oxygen species (ROS) in cancer cells from oncogenic signaling and/or metabolic disturbances leads to upregulation of cellular antioxidant capacity to maintain ROS levels below a toxic threshold. Combining drugs that induce high levels of ROS with compounds that suppress cellular antioxidant capacity by depleting antioxidant systems [glutathione (GSH), superoxide dismutase (SOD), and thioredoxin (TRX)] and/or targeting glucose metabolism represents a potential anticancer strategy. In AD, free metals and/or Aβ:metal complexes may cause damage to biomolecules in the brain (via Fenton reaction), including DNA. Metal chelation, based on the application of selective metal chelators or metal delivery, may induce neuroprotective signaling and represents a promising therapeutic strategy. This review examines therapeutic strategies based on the modulation of oxidative stress in cancer and AD.

New Insights into the Crosstalk between NMDARs and Iron: Implications for Understanding Pathology of Neurological Diseases

Both iron dyshomeostasis and N-methyl-D-aspartate receptors (NMDARs)-mediated neurotoxicity have been shown to have an important role in neurological diseases such as Parkinson’s disease (PD) and Alzheimer’s disease (AD). Evidence proved that activation of NMDARs could promote iron overload and iron-induced neurotoxicity by enhancing iron importer divalent metal transporter 1 (DMT1)-mediated iron uptake and iron releasing from lysosome. Also, iron overload could regulate NMDARs-mediated synaptic transmission. This indicates that there might be a possible relationship between iron and activation of NMDARs in neurological diseases. Understanding this interaction between iron and activation of NMDARs may provide new therapeutic avenues for a more targeted neurotherapeutic strategy for these diseases. Therefore, in this review article, we will describe the dysfunction of iron metabolism and NMDARs in neurological diseases including PD and AD, and summarize the new insight into the mechanisms underlying the interaction between iron and activation of NMDARs.

Clinical Experience With Deferiprone Treatment for Friedreich Ataxia

Friedreich ataxia is an inherited disorder characterized by degeneration of the peripheral and central nervous system and hypertrophic cardiomyopathy. Homozygous mutations in the frataxine (FXN) gene reduce expression of frataxin and cause accumulation of iron in the mitochondria. Deferiprone, an oral iron chelator, has been shown effective in cell and animal models of Friedreich ataxia. The results of a 6-month randomized, double blind placebo-controlled study suggested that deferiprone 20 mg/kg/day may reduce disease progression. The authors present their experience of 5 Friedreich ataxia patients treated with deferiprone (20 mg/kg/day), in addition to idebenone treatment, followed over a period of 10-24 months, under off-label authorization. The patients were monitored for laboratory parameters, cardiac assessment, neurological evaluations, and quality of life. The authors conclude that combined therapy of a low dose of deferiprone with idebenone is relatively safe, might improve neurological function, and seems to improve heart hypertrophy, warranting further studies.

Expression of RNAs Coding for Metal Transporters in Blood of Patients with Huntington's Disease

Recent studies have demonstrated elevated levels of iron (Fe) in brains of patients with Huntington's disease (HD). Striatal cells carrying mutated Huntingtin presented increased sensitivity to cadmium (Cd) toxicity, decreased sensitivity to manganese (Mn) toxicity and deficits in Mn uptake. The hypothesis arose that the observed alterations result from the altered expression and/or activity of proteins engaged in the transport of these metals, that is: transferrin (TF), transferrin receptor (TFR), divalent metal transporter 1 (DMT1) and ZIP8 protein. Here we examined the expression levels of genes encoding these proteins in blood of HD patients and control subjects. A decreasing tendency in the level of TF transcript and increasing tendency of SLC11A2 mRNA encoding DMT1 was observed in the blood of HD patients compared to the control subjects, but neither attained statistical significance. No changes were found in the levels of TFRC coding for TFR and SLC39A8 coding for ZIP8 between HD patients and controls. The results indicate that HD-associated changes in metal homeostasis occur are not related to mechanisms other than the expression level of the here analyzed metal transporters.

Synthesis, spectral characterization, computational calculations and biological activity of complexes designed from NNO donor Schiff-base ligand

A new series of Co(II), Ni(II) and Cu(II) complexes of (Z)-2-oxo-2-(phenylamino)-N'-(1-(pyridin-2-yl)ethylidene)acetohydrazide (H2OPPAH) have been prepared and characterized by conventional techniques. The spectral data indicated that the ligand acts as neutral or mononegative NNO tridentate. On the basis of magnetic and electronic spectral data an octahedral geometry for Ni(II) and Cu(II) complexes and a tetrahedral geometry for Co(II) complex have been proposed. The molecular modeling using DFT method are drawn showing the bond length, bond angle, chemical reactivity, energy components (kcal/mol) and binding energy (kcal/mol) for all title compounds. The Kinetic parameters were determined for each thermal degradation stages of the ligand and its complexes using Coats-Redfern and Horowitz-Metzger methods. Also, the compounds were screened for antioxidant activity using ABTS free radical, anti-hemolytic, and in vitro cytotoxic assay. H2OPPAH showed the potent antioxidant activity followed by Co(II) and Cu(II) complexes. On the other hand Ni(II) complex exhibited weak antioxidant activity using ABTS free radical and Erlich and strong erythrocyte hemolysis activity.

Polymeric nanocarriers for the treatment of systemic iron overload

Desferrioxamine (DFO), deferiprone (L1) and desferasirox (ICL-670) are clinically approved iron chelators used to treat secondary iron overload. Although iron chelators have been utilized since the 1960s and there has been much improvement in available therapy, there is still the need for new drug candidates due to limited long-term efficacy and drug toxicity. Moreover, all currently approved iron chelators are of low molecular weight (MW) (<600 Da) and the objectives reported for the "ideal" chelator of low MW, including possessing the ability to promote iron excretion without causing toxic side effects, has proven difficult to realize in practice. With prolonged iron chelator use, patients may develop toxicities or become insensitive. In contrast, the limited research that has been geared towards developing higher MW, polymeric, long circulating iron chelators has shown promise. The inherent potential of polymeric iron chelators toward longer plasma half-lives and reduction in toxicity provides optimism and may be a significant addition to the currently available low MW iron chelators. This article reviews knowledge pertaining to this theme, highlights some unique advantages that these nanomedicines have in treating systemic iron overload as well as their potential utility in the treatment of other disease states.

Polymeric nanocarriers for the treatment of systemic iron overload

Desferrioxamine (DFO), deferiprone (L1) and desferasirox (ICL-670) are clinically approved iron chelators used to treat secondary iron overload. Although iron chelators have been utilized since the 1960s and there has been much improvement in available therapy, there is still the need for new drug candidates due to limited long-term efficacy and drug toxicity. Moreover, all currently approved iron chelators are of low molecular weight (MW) (<600 Da) and the objectives reported for the “ideal” chelator of low MW, including possessing the ability to promote iron excretion without causing toxic side effects, has proven difficult to realize in practice. With prolonged iron chelator use, patients may develop toxicities or become insensitive. In contrast, the limited research that has been geared towards developing higher MW, polymeric, long circulating iron chelators has shown promise. The inherent potential of polymeric iron chelators toward longer plasma half-lives and reduction in toxicity provides optimism and may be a significant addition to the currently available low MW iron chelators. This article reviews knowledge pertaining to this theme, highlights some unique advantages that these nanomedicines have in treating systemic iron overload as well as their potential utility in the treatment of other disease states.

Relationship between iron accumulation and white matter injury in multiple sclerosis: a case-control study

Despite the increasing development and applications of iron imaging, the pathophysiology of iron accumulation in multiple sclerosis (MS), and its role in disease progression and development of clinical disability, is poorly understood. The aims of our study were to determine the presence and extent of iron in T2 visible lesions and gray and white matter using magnetic field correlation (MFC) MRI and correlate with microscopic white matter (WM) injury as measured by diffusion tensor imaging (DTI). This is a case-control study including a series of 31 patients with clinically definite MS. The mean age was 39 years [standard deviation (SD) = 9.55], they were 11 males and 20 females, with a disease duration average of 3 years (range 0-13) and a median EDSS of 2 (0-4.5). Seventeen healthy volunteers (6 males and 11 females) with a mean age of 36 years (SD = 11.4) were recruited. All subjects underwent MR imaging on a 3T scanner using T2-weighted sequence, 3D T1 MPRAGE, MFC, single-shot DTI and post-contrast T1. T2-lesion volumes, brain volumetry, DTI parameters and iron quantification were calculated and multiple correlations were exploited. Increased MFC was found in the putamen (p = 0.061), the thalamus (p = 0.123), the centrum semiovale (p = 0.053), globus pallidus (p = 0.008) and gray matter (GM) (p = 0.004) of MS patients compared to controls. The mean lesional MFC was 121 s(-2) (SD = 67), significantly lower compared to the GM MFC (<0.0001). The GM mean diffusivity (MD) was inversely correlated with the MFC in the centrum semiovale (p < 0.001), and in the splenium of the corpus callosum (p < 0.001). Patients with MS have increased iron in the globus pallidus, putamen and centrum with a trend toward increased iron in all the brain structures. Quantitative iron evaluation of WM and GM may improve the understanding of MS pathophysiology, and might serve as a surrogate marker of disease progression.

Neuroprotective effect of the active components of three Chinese herbs on brain iron load in a mouse model of Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative brain disorder and the most common cause of dementia. New treatments for AD are required due to its increasing prevalence in aging populations. The present study evaluated the effects of the active components of Epimedium, Astragalus and Radix Puerariae on learning and memory impairment, β-amyloid (Aβ) reduction and brain iron load in an APP_swe/PS1_ΔE9 transgenic mouse model of AD. Increasing evidence indicates that a disturbance of normal iron homeostasis may contribute to the pathology of AD. However, the underlying mechanisms resulting in abnormal iron load in the AD brain remain unclear. It has been hypothesized that the brain iron load is influenced by the deregulation of certain proteins associated with brain iron metabolism, including divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1). The present study investigated the effects of the active components of Epimedium, Astragalus and Radix Puerariae on the expression levels of DMT1 and FPN1. The treatment with the active components reduced cognitive deficits, inhibited Aβ plaque accumulation, reversed Aβ burden and reduced the brain iron load in AD model mice. A significant increase was observed in the levels of DMT1-iron-responsive element (IRE) and DMT1-nonIRE in the hippocampus of the AD mouse brain, which was reduced by treatment with the active components. In addition, the levels of FPN1 were significantly reduced in the hippocampus of the AD mouse brain compared with those of control mice, and these levels were increased following treatment with the active components. Thus, the present study indicated that the active components of Epimedium, Astragalus and Radix Puerariae may exert a neuroprotective effect against AD by reducing iron overload in the AD brain and may provide a novel approach for the development of drugs for the treatment of AD.

Synthesis, spectral characterization, molecular modeling and in vitro antibacterial activity of complexes designed from OO, NO and NN donor Schiff-base ligand [corrected]

A new chelating agent, N'-(4-methoxybenzylidene)-2-oxo-2-(phenylamino)acetohydrazide (H2OMPH) and its complexes with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Hg(II) and U(IV)O2(2+) ions have been prepared and characterized by conventional techniques. The spectral data indicated that the ligand coordinates as neutral bidentate with Cu(II), Mn(II), U(IV)O2(2+) and Hg(II), neutral tridentate with Ni(II), mononegative tridentate with Co(II) and binegative tetradentate with Zn(II) ions. On basis of magnetic and electronic spectral data an octahedral geometry for Mn(II), Co(II) and Ni(II) complexes and a square planar geometry for Cu(II) complex have been proposed and confirmed by applying geometry optimization and conformational analysis. The protonation constants of H2OMPH and the stepwise stability constants of its complexes are calculated at 298, 308 and 318 k as well as their thermodynamic parameters. Also, the Kinetic parameters (Ea, A, ΔH(*), ΔS(*) and ΔG(*)) were determined for each thermal degradation stage of some complexes using Coats-Redfern and Horowitz-Metzger methods. Moreover, the ligand and some complexes were screened for in vitro antibacterial activity against Staphylococcus epidermalies (St. epid); Streptococcus pyagenies (Strp. py.) as Gram +ve bacteria and Escherichia coli (E. coli); Klebsiella spp. (kleb. spp.) as Gram -ve bacteria using inhibition zone diameter.

Synthesis, characterization and biological activity of 2-acetylpyridine-α naphthoxyacetylhydrazone and its metal complexes [corrected]

A new series of complexes of Ni(II), Co(II), Cu(II), Cd(II), Mn(II), Hg(II) and UO2(2+) derived from 2-acetylpyridine-α-naphthoxyacetylhydrazone (HA2PNA) have been prepared and characterized by elemental analyses, spectral (IR, UV-visible, ESR and (1)H NMR) as well as magnetic and thermal measurements. The data revealed that the ligand acts as neutral NO, NN and NNO or mono-negative NNO chelate. On the basis of electronic spectral and magnetic moment data, an octahedral geometry is suggested for Mn(II), Co(II), Ni(II) and UO2(2+) complexes and a square planar arrangement for Cu(II) complex. The bond length, bond angle, HOMO, LUMO, dipole moment and charges on the atoms have been calculated to confirm the geometry of the ligand and the investigated complexes. The kinetic parameters were determined for thermal degradation stages of some complexes using Coats-Redfern and Horowitz-Metzger methods. Also, the ligand and its complexes were screened against antibacterial, antioxidant using DPPH radical and antitumor activities using in vitro Ehrlich ascites assay.

Iron and copper in progressive demyelination--New lessons from Skogholt's disease

The pathophysiological mechanisms of progressive demyelinating disorders including multiple sclerosis are incompletely understood. Increasing evidence indicates a role for trace metals in the progression of several neurodegenerative disorders. The study of Skogholt disease, a recently discovered demyelinating disease affecting both the central and peripheral nervous system, might shed some light on the mechanisms underlying demyelination. Cerebrospinal fluid iron and copper concentrations are about four times higher in Skogholt patients than in controls. The transit into cerebrospinal fluid of these elements from blood probably occurs in protein bound form. We hypothesize that exchangeable fractions of iron and copper are further transferred from cerebrospinal fluid into myelin, thereby contributing to the pathogenesis of demyelination. Free or weakly bound iron and copper ions may exert their toxic action on myelin by catalyzing production of oxygen radicals. Similarities to demyelinating processes in multiple sclerosis and other myelinopathies are discussed.

Hepcidin Suppresses Brain Iron Accumulation by Downregulating Iron Transport Proteins in Iron-Overloaded Rats

Iron accumulates progressively in the brain with age, and iron-induced oxidative stress has been considered as one of the initial causes for Alzheimer's disease (AD) and Parkinson's disease (PD). Based on the role of hepcidin in peripheral organs and its expression in the brain, we hypothesized that this peptide has a role to reduce iron in the brain and hence has the potential to prevent or delay brain iron accumulation in iron-associated neurodegenerative disorders. Here, we investigated the effects of hepcidin expression adenovirus (ad-hepcidin) and hepcidin peptide on brain iron contents, iron transport across the brain-blood barrier, iron uptake and release, and also the expression of transferrin receptor-1 (TfR1), divalent metal transporter 1 (DMT1), and ferroportin 1 (Fpn1) in cultured microvascular endothelial cells and neurons. We demonstrated that hepcidin significantly reduced brain iron in iron-overloaded rats and suppressed transport of transferrin-bound iron (Tf-Fe) from the periphery into the brain. Also, the peptide significantly inhibited expression of TfR1, DMT1, and Fpn1 as well as reduced Tf-Fe and non-transferrin-bound iron uptake and iron release in cultured microvascular endothelial cells and neurons, while downregulation of hepcidin with hepcidin siRNA retrovirus generated opposite results. We concluded that, under iron-overload, hepcidin functions to reduce iron in the brain by downregulating iron transport proteins. Upregulation of brain hepcidin by ad-hepcidin emerges as a new pharmacological treatment and prevention for iron-associated neurodegenerative disorders.

Role of iron in UPS impairment model of Parkinson's disease

Iron homeostasis requires the regulation of iron influx, iron efflux and iron storage, which are all essential to the execution of the multiple functions of the central nervous system. Abnormal accumulation of iron in the brain has been implicated in several neurodegenerative diseases, including Parkinson's disease (PD) and neurodegeneration with brain iron accumulation (NBIA). Although the cause of the neurodegenerative process in PD remains unclear, recent evidence suggests that failure of the ubiquitin-proteasome system (UPS) may play an important role in the pathogenesis of this disease. Our studies have shown that injection of the proteasome inhibitor lactacystin in the substantia nigra (SN) of rodents causes significant loss of dopamine (DA) neurons and induces intracellular inclusion body formation, which is accompanied by excessive iron accumulation in the midbrain. In the in vitro model, lactacystin causes a marked increase in labile iron, reactive oxygen species, alteration of iron regulatory protein (IRP)/iron response element expression levels, and an increase in the aggregation of ubiquitin-conjugated proteins prior to cell injury and death. Furthermore, we have demonstrated that synthetic iron chelators and a genetic iron chelator are neuroprotective against proteasome inhibitor-induced DA neuron degeneration, suggesting that iron chelation might be a promising therapeutic target for PD.

Brain iron homeostasis: from molecular mechanisms to clinical significance and therapeutic opportunities

Iron has emerged as a significant cause of neurotoxicity in several neurodegenerative conditions, including Alzheimer's disease (AD), Parkinson's disease (PD), sporadic Creutzfeldt-Jakob disease (sCJD), and others. In some cases, the underlying cause of iron mis-metabolism is known, while in others, our understanding is, at best, incomplete. Recent evidence implicating key proteins involved in the pathogenesis of AD, PD, and sCJD in cellular iron metabolism suggests that imbalance of brain iron homeostasis associated with these disorders is a direct consequence of disease pathogenesis. A complete understanding of the molecular events leading to this phenotype is lacking partly because of the complex regulation of iron homeostasis within the brain. Since systemic organs and the brain share several iron regulatory mechanisms and iron-modulating proteins, dysfunction of a specific pathway or selective absence of iron-modulating protein(s) in systemic organs has provided important insights into the maintenance of iron homeostasis within the brain. Here, we review recent information on the regulation of iron uptake and utilization in systemic organs and within the complex environment of the brain, with particular emphasis on the underlying mechanisms leading to brain iron mis-metabolism in specific neurodegenerative conditions. Mouse models that have been instrumental in understanding systemic and brain disorders associated with iron mis-metabolism are also described, followed by current therapeutic strategies which are aimed at restoring brain iron homeostasis in different neurodegenerative conditions. We conclude by highlighting important gaps in our understanding of brain iron metabolism and mis-metabolism, particularly in the context of neurodegenerative disorders.

Nucleoside 5'-phosphorothioate derivatives are highly effective neuroprotectants

The brain is especially sensitive to oxidative stress due to its high rate of oxidative metabolism, relatively low levels of antioxidant enzymes, and high concentrations of Fe/Cu ions. During the neurodegeneration process, the aggregation of proteins Aβ, accompanies oxidative stress. We explored the potential of thiophosphate derivatives to rescue neurons from oxidative stress and Aβ toxicity. We evaluated the neuroprotective effect of ATP-γ-S, ADP-β-S, and GDP-β-S on primary cortical neuronal cells exposed to several insults, including treatment with FeSO4, co-application of H2O2 and FeSO4, and addition of Aβ42. Upon treatment with FeSO4, phosphorothioate analogues exhibited up to 3000-fold better neuroprotectant activity than the corresponding parent nucleotides. Likewise, phosphorothioate analogues proved to be up to 30-fold better neuroprotectants than the corresponding parent nucleotides upon treatment with both H2O2 and FeSO4. When we exposed primary neuron and astrocyte cultures to 50 μM Aβ42-induced cell death, we found that ATP-γ-S significantly improved cell morphology and maintained culture viability with an IC50 value of 0.8 μM. Finally, we evaluated the viability of neuroblastoma cells under hypoxic conditions in the presence of ATP-γ-S and found that the latter was involved in the regulation of HIF-1a and stabilized mRNA levels of vascular endothelial growth factor (VEGF) and glucose transporter 1 (GLUT-1), which promote cell survival and proliferation. Based on its high potency as a neuroprotectant, we propose ATP-γ-S as a highly promising, biocompatible, and water-soluble drug candidate for the treatment of neurodegenerative disorders.

[Iron metabolism in the central nervous system]

There are four cell types that have specific functions in iron metabolism; duodenal enterocytes, hepatocytes, erythroid cells, and reticuloendothelial macrophages. In these cells, iron absorption, storage, and export are critically regulated by several iron-metabolism proteins, including hepcidin. Iron is abundant in the brain, and iron homeostasis in the brain is relatively independent from that in other tissues because of the presence of the blood-brain barrier. Iron uptake and transport in the brain depends on interactions between the vascular endothelial cells and perivascular astrocytes. Transferrin-bound iron (Tf-Fe(3+)) binds to the transferrin receptor 1 (TR1) on the luminal membrane of the endothelial cells, and then Tf-Fe(3+)-TR1 complex is internalized in the endosomes. In the acidic environment of the endosomes, iron is liberated from Tf. The mechanism by which free iron in the endosomes is exported into the interstitial space is still controversial. GPI-anchored ceruloplasmin on the end-foot processes of astrocytes oxidizes newly released Fe(2+) to Fe(3+), which binds to Tf in brain interstitial fluid, and then Tf-Fe(3+) is taken up by neurons. Iron misregulation and abnormal iron accumulation are involved in several genetic and non-genetic neurological diseases through enhanced oxidative stress. Chelation therapy could be an effective disease-modifying approach for these conditions.

Deferiprone reduces amyloid-β and tau phosphorylation levels but not reactive oxygen species generation in hippocampus of rabbits fed a cholesterol-enriched diet

Accumulation of amyloid-β (Aβ) peptide and the hyperphosphorylation of tau protein are major hallmarks of Alzheimer's disease (AD). The causes of AD are not well known but a number of environmental and dietary factors are suggested to increase the risk of developing AD. Additionally, altered metabolism of iron may have a role in the pathogenesis of AD. We have previously demonstrated that cholesterol-enriched diet causes AD-like pathology with iron deposition in rabbit brain. However, the extent to which chelation of iron protects against this pathology has not been determined. In this study, we administered the iron chelator deferiprone in drinking water to rabbits fed with a 2% cholesterol diet for 12 weeks. We found that deferiprone (both at 10 and 50 mg/kg/day) significantly decreased levels of Aβ40 and Aβ42 as well as BACE1, the enzyme that initiates cleavage of amyloid-β protein precursor to yield Aβ. Deferiprone also reduced the cholesterol diet-induced increase in phosphorylation of tau but failed to reduce reactive oxygen species generation. While deferiprone treatment was not associated with any change in brain iron levels, it was associated with a significant reduction in plasma iron and cholesterol levels. These results demonstrate that deferiprone confers important protection against hypercholesterolemia-induced AD pathology but the mechanism(s) may involve reduction in plasma iron and cholesterol levels rather than chelation of brain iron. We propose that adding an antioxidant therapy to deferiprone may be necessary to fully protect against cholesterol-enriched diet-induced AD-like pathology.

Intranasal deferoxamine reverses iron-induced memory deficits and inhibits amyloidogenic APP processing in a transgenic mouse model of Alzheimer's disease

Increasing evidence indicates that a disturbance of normal iron homeostasis and an amyloid-β (Aβ)-iron interaction may contribute to the pathology of Alzheimer's disease (AD), whereas iron chelation could be an effective therapeutic intervention. In the present study, transgenic mice expressing amyloid precursor protein (APP) and presenilin 1 and watered with high-dose iron served as a model of AD. We evaluated the effects of intranasal administration of the high-affinity iron chelator deferoxamine (DFO) on Aβ neuropathology and spatial learning and memory deficits created in this AD model. The effects of Fe, DFO, and combined treatments were also evaluated in vitro using SHSY-5Y cells overexpressing the human APP Swedish mutation. In vivo, no significant differences in the brain concentrations of iron, copper, or zinc were found among the treatment groups. We found that high-dose iron (deionized water containing 10 mg/mL FeCl(3)) administered to transgenic mice increased protein expression and phosphorylation of APP695, enhanced amyloidogenic APP cleavage and Aβ deposition, and impaired spatial learning and memory. Chelation of iron via intranasal administration of DFO (200 mg/kg once every other day for 90 days) inhibited iron-induced amyloidogenic APP processing and reversed behavioral alterations. DFO treatment reduced the expression and phosphorylation of APP protein by shifting the processing of APP to the nonamyloidogenic pathway, and the reduction was accompanied by attenuating the Aβ burden, and then significantly promoted memory retention in APP/PS1 mice. The effects of DFO on iron-induced amyloidogenic APP cleavage were further confirmed in vitro. Collectively, the present data suggest that intranasal DFO treatment may be useful in AD, and amelioration of iron homeostasis is a potential strategy for prevention and treatment of this disease.

Iron homeostasis regulates the activity of the microRNA pathway through poly(C)-binding protein 2

MicroRNAs (miRNAs) control gene expression by promoting degradation or repressing translation of target mRNAs. The components of the miRNA pathway are subject to diverse modifications that can modulate the abundance and function of miRNAs. Iron is essential for fundamental metabolic processes, and its homeostasis is tightly regulated. Here we identified iron chelators as a class of activator of the miRNA pathway that could promote the processing of miRNA precursors. We show that cytosolic iron could regulate the activity of the miRNA pathway through poly(C)-binding protein 2 (PCBP2). PCBP2 is associated with Dicer and promotes the processing of miRNA precursors. Cytosolic iron could modulate the association between PCBP2 and Dicer, as well as the multimerization of PCBP2 and its ability to bind to miRNA precursors, which can alter the processing of miRNA precursors. Our findings reveal a role of iron homeostasis in the regulation of miRNA biogenesis.

Hypoxia inducible factor-1 as a target for neurodegenerative diseases

Hypoxia inducible factor-1 (HIF-1) is a transcriptional factor responsible for cellular and tissue adaption to low oxygen tension. HIF-1, a heterodimer consisting of a constitutively expressed β subunit and an oxygen-regulated α subunit, regulates a series of genes that participate in angiogenesis, iron metabolism, glucose metabolism, and cell proliferation/survival. The activity of HIF-1 is controlled by post-translational modifications on different amino acid residues of its subunits, mainly the alpha subunit. Besides in ischemic stroke (see review [1]), emerging evidence has revealed that HIF-1 activity and expression of its down-stream genes, such as vascular endothelial growth factor and erythropoietin, are altered in a range of neurodegenerative diseases. At the same time, experimental and clinical evidence has demonstrated that regulating HIF-1 might ameliorate the cellular and tissue damage in the neurodegenerative diseases. These new findings suggest HIF-1 as a potential medicinal target for the neurodegenerative diseases. This review focuses on HIF-1α protein modifications and HIF-1's potential neuroprotective roles in Alzheimer's (AD), Parkinson's (PD), Huntington's diseases (HD), and amyotrophic lateral sclerosis (ALS).

Silencing GADD153/CHOP gene expression protects against Alzheimer's disease-like pathology induced by 27-hydroxycholesterol in rabbit hippocampus

Endoplasmic reticulum (ER) stress is suggested to play a key role in the pathogenesis of neurodegenerative diseases including Alzheimer's disease (AD). Sustained ER stress leads to activation of the growth arrest and leucine zipper transcription factor, DNA damage inducible gene 153 (gadd153; also called CHOP). Activated gadd153 can generate oxidative damage and reactive oxygen species (ROS), increase β-amyloid (Aβ) levels, disturb iron homeostasis and induce inflammation as well as cell death, which are all pathological hallmarks of AD. Epidemiological and laboratory studies suggest that cholesterol dyshomeostasis contributes to the pathogenesis of AD. We have previously shown that the cholesterol oxidized metabolite 27-hydroxycholesterol (27-OHC) triggers AD-like pathology in organotypic slices. However, the extent to which gadd153 mediates 27-OHC effects has not been determined. We silenced gadd153 gene with siRNA and determined the effects of 27-OHC on AD hallmarks in organotypic slices from adult rabbit hippocampus. siRNA to gadd153 reduced 27-OHC-induced Aβ production by mechanisms involving reduction in levels of β-amyloid precursor protein (APP) and β-secretase (BACE1), the enzyme that initiates cleavage of APP to yield Aβ peptides. Additionally, 27-OHC-induced tau phosphorylation, ROS generation, TNF-α activation, and iron and apoptosis-regulatory protein levels alteration were also markedly reduced by siRNA to gadd153. These data suggest that ER stress-mediated gadd153 activation plays a central role in the triggering of AD pathological hallmarks that result from incubation of hippocampal slices with 27-OHC. Our results add important insights into cellular mechanisms that underlie the potential contribution of cholesterol metabolism in AD pathology, and suggest that preventing gadd153 activation protects against AD related to cholesterol oxidized products.

Synthetic and natural iron chelators: therapeutic potential and clinical use

Iron-chelation therapy has its origins in the treatment of iron-overload syndromes. For many years, the standard for this purpose has been deferoxamine. Recently, considerable progress has been made in identifying synthetic chelators with improved pharmacologic properties relative to deferoxamine. Most notable are deferasirox (Exjade(®)) and deferiprone (Ferriprox(®)), which are now available clinically. In addition to treatment of iron overload, there is an emerging role for iron chelators in the treatment of diseases characterized by oxidative stress, including cardiovascular disease, atherosclerosis, neurodegenerative diseases and cancer. While iron is not regarded as the underlying cause of these diseases, it does play an important role in disease progression, either through promotion of cellular growth and proliferation or through participation in redox reactions that catalyze the formation of reactive oxygen species and increase oxidative stress. Thus, iron chelators may be of therapeutic benefit in many of these conditions. Phytochemicals, many of which bind iron, may also owe some of their beneficial properties to iron chelation. This review will focus on the advances in iron-chelation therapy for the treatment of iron-overload disease and cancer, as well as neurodegenerative and chronic inflammatory diseases. Established and novel iron chelators will be discussed, as well as the emerging role of dietary plant polyphenols that effectively modulate iron biochemistry.

Ceruloplasmin protects against rotenone-induced oxidative stress and neurotoxicity

To clarify the neuroprotective property of ceruloplasmin and the pathogenesis of aceruloplasminemia, we generated ceruloplasmin-deficient (CP⁻/⁻) mice on the C57BL/10 genetic background and further treated them with a mitochondrial complex I inhibitor, rotenone. There was no iron accumulation in the brains of CP⁻/⁻ mice at least up to 60 weeks of age. Without rotenone treatment, CP⁻/⁻ mice showed slight motor dysfunction compared with CP⁺/⁺ mice, but there were no detectable differences in the levels of oxidative stress markers between these two groups. A low dose of rotenone did not affect the mitochondrial complex I activity in our mice, however, it caused a significant change in motor behavior, neuropathology, or the levels of oxidative stress markers in CP⁻/⁻ mice, but not in CP⁺/⁺ mice. Our data support that ceruloplasmin protects against rotenone-induced oxidative stress and neurotoxicity, probably through its antioxidant properties independently of its function of iron metabolism.