Neuroferritinopathy

Microglia ferroptosis is regulated by SEC24B and contributes to neurodegeneration

Iron dysregulation has been implicated in multiple neurodegenerative diseases, including Parkinson's disease (PD). Iron-loaded microglia are frequently found in affected brain regions, but how iron accumulation influences microglia physiology and contributes to neurodegeneration is poorly understood. Here we show that human induced pluripotent stem cell-derived microglia grown in a tri-culture system are highly responsive to iron and susceptible to ferroptosis, an iron-dependent form of cell death. Furthermore, iron overload causes a marked shift in the microglial transcriptional state that overlaps with a transcriptomic signature found in PD postmortem brain microglia. Our data also show that this microglial response contributes to neurodegeneration, as removal of microglia from the tri-culture system substantially delayed iron-induced neurotoxicity. To elucidate the mechanisms regulating iron response in microglia, we performed a genome-wide CRISPR screen and identified novel regulators of ferroptosis, including the vesicle trafficking gene SEC24B. These data suggest a critical role for microglia iron overload and ferroptosis in neurodegeneration.

Conservative Iron Chelation for Neuroferritinopathy

BACKGROUND

Neuroferritinopathy is a rare inherited neurodegenerative disease with brain iron accumulation characterized by brain iron overload resulting in progressive movement disorders. No treatment is currently available.

OBJECTIVE

We assessed conservative iron chelation with deferiprone at 30 mg/kg/day on the disease progression with controlled periods of discontinuation.

METHODS

Four patients with confirmed molecular diagnosis of neuroferritinopathy were given deferiprone at different stages of disease progression and with clinical and biological monitoring to control benefit and risk.

RESULTS

The four patients showed slight to high improvement. In one case, we managed to stabilize disease progression for more than 11 years. In another case, we were able to reverse symptoms after a few months of treatment. The earliest the treatment was started, the most efficient it was on disease progression.

CONCLUSIONS

Conservative iron chelation should be further assessed in neuroferritinopathy. © 2022 International Parkinson and Movement Disorder Society.

Review: Insights into molecular mechanisms of disease in neurodegeneration with brain iron accumulation: unifying theories

Neurodegeneration with brain iron accumulation (NBIA) is a group of disorders characterized by dystonia, parkinsonism and spasticity. Iron accumulates in the basal ganglia and may be accompanied by Lewy bodies, axonal swellings and hyperphosphorylated tau depending on NBIA subtype. Mutations in 10 genes have been associated with NBIA that include Ceruloplasmin (Cp) and ferritin light chain (FTL), both directly involved in iron homeostasis, as well as Pantothenate Kinase 2 (PANK2), Phospholipase A2 group 6 (PLA2G6), Fatty acid hydroxylase 2 (FA2H), Coenzyme A synthase (COASY), C19orf12, WDR45 and DCAF17 (C2orf37). These genes are involved in seemingly unrelated cellular pathways, such as lipid metabolism, Coenzyme A synthesis and autophagy. A greater understanding of the cellular pathways that link these genes and the disease mechanisms leading to iron dyshomeostasis is needed. Additionally, the major overlap seen between NBIA and more common neurodegenerative diseases may highlight conserved disease processes. In this review, we will discuss clinical and pathological findings for each NBIA-related gene, discuss proposed disease mechanisms such as mitochondrial health, oxidative damage, autophagy/mitophagy and iron homeostasis, and speculate the potential overlap between NBIA subtypes.

Preparation of iron-enriched baker's yeast and its efficiency in recovery of rats from dietary iron deficiency

OBJECTIVES

Iron is an important mineral, essential for the health and function of mammalian cells. Despite its key role, iron deficiency in humans is common worldwide, often leading to significant health issues within the population. The aim of this study was to evaluate the potential of using iron-enriched baker's yeast as a source of iron, especially for the protection and recovery from conditions related to anemia.

METHODS

Iron-enriched yeast was prepared by cultivating cells on basal medium comprising different iron concentrations. The effects of iron supplementation on animal health were assessed by feeding anemic rats with a variety of diets containing either inorganic iron or iron-enriched yeast. Body weight, iron bioavailability, blood parameters, and the activity of iron-containing enzymes (catalase) were studied.

RESULTS

Iron accumulation in yeast cells increased with iron concentration, reaching a maximum of 15 mg/g when 32 mM iron was applied. Rat groups fed iron-enriched yeast had the highest feed efficiency, iron bioavailability, and hemoglobin concentration. The source of iron supplementation influenced catalase activity in kidney tissues, increasing from 70 U/g tissue in anemic rats to 90 U/g tissue (inorganic iron salt), 110 U/g tissue (inorganic iron salt and non-enriched dry yeast), 145 U/g tissue (iron-enriched yeast 15 mg/g iron) and 115 U/g tissue (iron-enriched yeast 30 mg/g iron). The histologic study of tissues from liver, kidney, heart, and spleen of rats from different groups showed that the damage observed in tissues of anemic rats, was not observed after feeding with iron-enriched yeasts.

CONCLUSION

The results demonstrated that ingestion of iron-enriched yeast is more efficient than inorganic treatment in recovery from iron deficiency, including tissue recovery in rats.

The IRP/IRE system in vivo: insights from mouse models

Iron regulatory proteins 1 and 2 (IRP1 and IRP2) post-transcriptionally control the expression of several mRNAs encoding proteins of iron, oxygen and energy metabolism. The mechanism involves their binding to iron responsive elements (IREs) in the untranslated regions of target mRNAs, thereby controlling mRNA translation or stability. Whereas IRP2 functions solely as an RNA-binding protein, IRP1 operates as either an RNA-binding protein or a cytosolic aconitase. Early experiments in cultured cells established a crucial role of IRPs in regulation of cellular iron metabolism. More recently, studies in mouse models with global or localized Irp1 and/or Irp2 deficiencies uncovered new physiological functions of IRPs in the context of systemic iron homeostasis. Thus, IRP1 emerged as a key regulator of erythropoiesis and iron absorption by controlling hypoxia inducible factor 2α (HIF2α) mRNA translation, while IRP2 appears to dominate the control of iron uptake and heme biosynthesis in erythroid progenitor cells by regulating the expression of transferrin receptor 1 (TfR1) and 5-aminolevulinic acid synthase 2 (ALAS2) mRNAs, respectively. Targeted disruption of either Irp1 or Irp2 in mice is associated with distinct phenotypic abnormalities. Thus, Irp1(-/-) mice develop polycythemia and pulmonary hypertension, while Irp2(-/-) mice present with microcytic anemia, iron overload in the intestine and the liver, and neurologic defects. Combined disruption of both Irp1 and Irp2 is incombatible with life and leads to early embryonic lethality. Mice with intestinal- or liver-specific disruption of both Irps are viable at birth but die later on due to malabsorption or liver failure, respectively. Adult mice lacking both Irps in the intestine exhibit a profound defect in dietary iron absorption due to a "mucosal block" that is caused by the de-repression of ferritin mRNA translation. Herein, we discuss the physiological function of the IRE/IRP regulatory system.

Abnormal brain iron metabolism in Irp2 deficient mice is associated with mild neurological and behavioral impairments

Iron Regulatory Protein 2 (Irp2, Ireb2) is a central regulator of cellular iron homeostasis in vertebrates. Two global knockout mouse models have been generated to explore the role of Irp2 in regulating iron metabolism. While both mouse models show that loss of Irp2 results in microcytic anemia and altered body iron distribution, discrepant results have drawn into question the role of Irp2 in regulating brain iron metabolism. One model shows that aged Irp2 deficient mice develop adult-onset progressive neurodegeneration that is associated with axonal degeneration and loss of Purkinje cells in the central nervous system. These mice show iron deposition in white matter tracts and oligodendrocyte soma throughout the brain. A contrasting model of global Irp2 deficiency shows no overt or pathological signs of neurodegeneration or brain iron accumulation, and display only mild motor coordination and balance deficits when challenged by specific tests. Explanations for conflicting findings in the severity of the clinical phenotype, brain iron accumulation and neuronal degeneration remain unclear. Here, we describe an additional mouse model of global Irp2 deficiency. Our aged Irp2^−/− mice show marked iron deposition in white matter and in oligodendrocytes while iron content is significantly reduced in neurons. Ferritin and transferrin receptor 1 (TfR1, Tfrc), expression are increased and decreased, respectively, in the brain from Irp2^−/− mice. These mice show impairments in locomotion, exploration, motor coordination/balance and nociception when assessed by neurological and behavioral tests, but lack overt signs of neurodegenerative disease. Ultrastructural studies of specific brain regions show no evidence of neurodegeneration. Our data suggest that Irp2 deficiency dysregulates brain iron metabolism causing cellular dysfunction that ultimately leads to mild neurological, behavioral and nociceptive impairments.

Update on neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) defines a heterogeneous group of progressive neurodegenerative disorders characterized by excessive iron accumulation in the brain, particularly affecting the basal ganglia. In the recent years considerable development in the field of neurodegenerative disorders has been observed. Novel genetic methods such as autozygosity mapping have recently identified several genetic causes of NBIA. Our knowledge about clinical spectrum has broadened and we are now more aware of an overlap between the different NBIA disorders as well as with other diseases. Neuropathologic point of view has also been changed. It has been postulated that pantothenate kinase-associated neurodegeneration (PKAN) is not synucleinopathy. However, exact pathologic mechanism of NBIA remains unknown. The situation implicates a development of new therapies, which still are symptomatic and often unsatisfactory. In the present review, some of the main clinical presentations, investigational findings and therapeutic results of the different NBIA disorders will be presented.

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.

Biological metals and metal-targeting compounds in major neurodegenerative diseases

Metals are functionally essential, but redistribute in neurodegenerative disease where they induce protein aggregates, catalyze radical formation, and lose bioavailability.

Human L-ferritin deficiency is characterized by idiopathic generalized seizures and atypical restless leg syndrome

Human L-ferritin deficiency causes reduced cellular iron availability and increased ROS production with enhanced oxidized proteins, which results in idiopathic generalized seizures and atypical restless leg syndrome.

The ubiquitously expressed iron storage protein ferritin plays a central role in maintaining cellular iron homeostasis. Cytosolic ferritins are composed of heavy (H) and light (L) subunits that co-assemble into a hollow spherical shell with an internal cavity where iron is stored. The ferroxidase activity of the ferritin H chain is critical to store iron in its Fe3+ oxidation state, while the L chain shows iron nucleation properties. We describe a unique case of a 23-yr-old female patient affected by a homozygous loss of function mutation in the L-ferritin gene, idiopathic generalized seizures, and atypical restless leg syndrome (RLS). We show that L chain ferritin is undetectable in primary fibroblasts from the patient, and thus ferritin consists only of H chains. Increased iron incorporation into the FtH homopolymer leads to reduced cellular iron availability, diminished levels of cytosolic catalase, SOD1 protein levels, enhanced ROS production and higher levels of oxidized proteins. Importantly, key phenotypic features observed in fibroblasts are also mirrored in reprogrammed neurons from the patient’s fibroblasts. Our results demonstrate for the first time the pathophysiological consequences of L-ferritin deficiency in a human and help to define the concept for a new disease entity hallmarked by idiopathic generalized seizure and atypical RLS.

Iron metabolism in the CNS: implications for neurodegenerative diseases

Abnormal accumulation of brain iron has been detected in various neurodegenerative diseases, but the contribution of iron overload to pathology remains unclear. In a group of distinctive brain iron overload diseases known as 'neurodegeneration with brain iron accumulation' (NBIA) diseases, nine disease genes have been identified. Brain iron accumulation is observed in the globus pallidus and other brain regions in NBIA diseases, which are often associated with severe dystonia and gait abnormalities. Only two of these diseases, aceruloplasminaemia and neuroferritinopathy, are directly caused by abnormalities in iron metabolism, mainly in astrocytes and neurons, respectively. Understanding the early molecular pathophysiology of these diseases should aid insights into the role of iron and the design of specific therapeutic approaches.

Brain transcriptome perturbations in the Hfe(-/-) mouse model of genetic iron loading

Severe disruption of brain iron homeostasis can cause fatal neurodegenerative disease, however debate surrounds the neurologic effects of milder, more common iron loading disorders such as hereditary hemochromatosis, which is usually caused by loss-of-function polymorphisms in the HFE gene. There is evidence from both human and animal studies that HFE gene variants may affect brain function and modify risks of brain disease. To investigate how disruption of HFE influences brain transcript levels, we used microarray and real-time reverse transcription polymerase chain reaction to assess the brain transcriptome in Hfe(-/-) mice relative to wildtype AKR controls (age 10 weeks, n≥4/group). The Hfe(-/-) mouse brain showed numerous significant changes in transcript levels (p<0.05) although few of these related to proteins directly involved in iron homeostasis. There were robust changes of at least 2-fold in levels of transcripts for prominent genes relating to transcriptional regulation (FBJ osteosarcoma oncogene Fos, early growth response genes), neurotransmission (glutamate NMDA receptor Grin1, GABA receptor Gabbr1) and synaptic plasticity and memory (calcium/calmodulin-dependent protein kinase IIα Camk2a). As previously reported for dietary iron-supplemented mice, there were altered levels of transcripts for genes linked to neuronal ceroid lipofuscinosis, a disease characterized by excessive lipofuscin deposition. Labile iron is known to enhance lipofuscin generation which may accelerate brain aging. The findings provide evidence that iron loading disorders can considerably perturb levels of transcripts for genes essential for normal brain function and may help explain some of the neurologic signs and symptoms reported in hemochromatosis patients.

MRI findings in neuroferritinopathy

Neuroferritinopathy is a neurodegenerative disease which demonstrates brain iron accumulation caused by the mutations in the ferritin light chain gene. On brain MRI in neuroferritinopathy, iron deposits are observed as low-intensity areas on T2WI and as signal loss on T2∗WI. On T2WI, hyperintense abnormalities reflecting tissue edema and gliosis are also seen. Another characteristic finding is the presence of symmetrical cystic changes in the basal ganglia, which are seen in the advanced stages of this disorder. Atrophy is sometimes noted in the cerebellar and cerebral cortices. The variety in the MRI findings is specific to neuroferritinopathy. Based on observations of an excessive iron content in patients with chronic neurologic disorders, such as Parkinson disease and Alzheimer disease, the presence of excess iron is therefore recognized as a major risk factor for neurodegenerative diseases. The future development of multimodal and advanced MRI techniques is thus expected to play an important role in accurately measuring the brain iron content and thereby further elucidating the neurodegenerative process.

Neurodegeneration with brain iron accumulation - clinical syndromes and neuroimaging

Iron participates in a wide array of cellular functions and is essential for normal neural development and physiology. However, if inappropriately managed, the transition metal is capable of generating neurotoxic reactive oxygen species. A number of hereditary conditions perturb body iron homeostasis and some, collectively referred to as neurodegeneration with brain iron accumulation (NBIA), promote pathological deposition of the metal predominantly or exclusively within the central nervous system (CNS). In this article, we discuss seven NBIA disorders with emphasis on the clinical syndromes and neuroimaging. The latter primarily entails magnetic resonance scanning using iron-sensitive sequences. The conditions considered are Friedreich ataxia (FA), pantothenate kinase 2-associated neurodegeneration (PKAN), PLA2G6-associated neurodegeneration (PLAN), FA2H-associated neurodegeneration (FAHN), Kufor-Rakeb disease (KRD), aceruloplasminemia, and neuroferritinopathy. An approach to differential diagnosis and the status of iron chelation therapy for several of these entities are presented. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Childhood disorders of neurodegeneration with brain iron accumulation (NBIA)

Neurodegeneration with brain iron accumulation (NBIA) comprises a heterogeneous group of progressive complex motor disorders characterized by the presence of high brain iron, particularly within the basal ganglia. A number of autosomal recessive NBIA syndromes can present in childhood, most commonly pantothenate kinase-associated neurodegeneration (PKAN; due to mutations in the PANK2 gene) and phospholipase A2 group 6-associated neurodegeneration (PLAN; associated with genetic defects in PLA2G6). Mutations in the genes that cause these two neuroaxonal dystrophies are thought to disrupt the normal cellular functions of phospholipid remodelling and fatty acid metabolism. A significant proportion of children with an NBIA phenotype have no genetic diagnosis and there are, no doubt, additional as yet undiscovered genes that account for a number of these cases. NBIA disorders can be diagnostically challenging as there is often phenotypic overlap between the different disease entities. This review aims to define the clinical, radiological, and genetic features of such disorders, providing the clinician with a stepwise approach to appropriate neurological and genetic investigation, as well as a clinical management strategy for these neurodegenerative syndromes.

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.

Juvenile parkinsonism: epidemiology, diagnosis and treatment

Juvenile parkinsonism, with onset prior to age 21 years, is a relatively rare syndrome. It is caused by a group of heterogeneous entities that can present with a clinical picture similar to idiopathic Parkinson's disease or manifest parkinsonism as part of a spectrum of other signs. Diagnostic testing is guided by the presenting symptoms and aimed at uncovering potentially reversible and/or treatable causes. If an underlying condition is found, treatment is tailored accordingly. Otherwise, treatment is symptomatic and relies on medications commonly employed to treat idiopathic Parkinson's disease. Juvenile parkinsonism patients tend to be plagued by treatment-induced complications, so caution must be employed.

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.

Cytosolic and mitochondrial ferritins in the regulation of cellular iron homeostasis and oxidative damage

BACKGROUND

Ferritin structure is designed to maintain large amounts of iron in a compact and bioavailable form in solution. All ferritins induce fast Fe(II) oxidation in a reaction catalyzed by a ferroxidase center that consumes Fe(II) and peroxides, the reagents that produce toxic free radicals in the Fenton reaction, and thus have anti-oxidant effects. Cytosolic ferritins are composed of the H- and L-chains, whose expression are regulated by iron at a post-transcriptional level and by oxidative stress at a transcriptional level. The regulation of mitochondrial ferritin expression is presently unclear.

SCOPE OF REVIEW

The scope of the review is to update recent progress regarding the role of ferritins in the regulation of cellular iron and in the response to oxidative stress with particular attention paid to the new roles described for cytosolic ferritins, to genetic disorders caused by mutations of the ferritin L-chain, and new findings on mitochondrial ferritin.

MAJOR CONCLUSIONS

The new data on the adult conditional knockout (KO) mice for the H-chain and on the hereditary ferritinopathies with mutations that reduce ferritin functionality strongly indicate that the major role of ferritins is to protect from the oxidative damage caused by iron deregulation. In addition, the study of mitochondrial ferritin, which is not iron-regulated, indicates that it participates in the protection against oxidative damage, particularly in cells with high oxidative activity.

GENERAL SIGNIFICANCE

Ferritins have a central role in the protection against oxidative damage, but they are also involved in non-iron-dependent processes.

Challenges associated with metal chelation therapy in Alzheimer's disease

A close association between brain metal dishomeostasis and the onset and/or progression of Alzheimer's disease (AD) has been clearly established in a number of studies, although the underlying biochemical mechanisms remain obscure. This observation renders chelation therapy an attractive pharmacological option for the treatment of this disease. However, a number of requirements must be fulfilled in order to adapt chelation therapy to AD so that the term "metal targeted strategies" seems now more appropriate. Indeed, brain metal redistribution rather than brain metal scavenging and removal is the major goal of this type of intervention. The most recent developments in metal targeted strategies for AD will be discussed using, as useful examples, clioquinol, curcumin, and epigallocatechin, and the future perspectives will also be outlined.

[Clinical features of neuroferritinopathy]

Neuroferritinopathy is an autosomal dominant basal ganglia disease with iron accumulation caused by a mutation of the gene encoding ferritin light polypeptide (FTL). Six pathogenic mutations in the FTL gene have so far been reported. One such mutation was found in a Japanese family, thus suggesting that a new mutation in the FTL gene can therefore occur anywhere in the world. The typical clinical features of neuroferritinopathy are dystonia (especially orofacial dystonia related to speech and leading to dysarthrophonia) and involuntary movement, but such features vary greatly among the affected individuals. The findings of excess iron storage and cystic changes involving the globus pallidus and the putamen on brain MRI. and low serum ferritin levels are characteristic in neuroferritinopathy. Brain histochemistry shows abnormal aggregates of ferritin and iron throughout the central nervous system. Iron atoms are stored in the central cavity of the ferritin polymer and the E-helices of ferritin play an important role in maintaining the central cavity. A mutation in exon 4 of the FTL gene is known to alter the structure of E-helices, thereby leading to the release of free iron and excessive oxidative stress. Iron depletion therapy by iron chelation in symptomatic patients has not been shown to be beneficial, however before the nset of clinical symptoms, such a treatment strategy may still have some benefit. Neuroferritinopathy should therefore be considered in all patients presenting with basal ganglia disorders of unknown origin. These characteristic MRI findings may help to differentiate neuroferritinopathy from other diseases showing similar clinical features.

Oxidative stress and cell death in cells expressing L-ferritin variants causing neuroferritinopathy

Neuroferritinopathies are dominantly inherited movement disorders associated with nucleotide insertions in the L-ferritin gene that modify the protein's C-terminus. The insertions alter physical and functional properties of the ferritins, causing an imbalance in brain iron homeostasis. We describe the effects produced by the over-expression in HeLa and neuroblastoma SH-SY5Y cells of two pathogenic L-ferritin variants, 460InsA and 498InsTC. Both peptides co-assembled with endogenous ferritins, producing molecules with reduced iron incorporation capacity, acting in a dominant negative manner. The cells showed an increase in cell death and a decrease in proteasomal activity. The formation of iron-ferritin aggregates became evident after 10 days of variant expression and was not associated with increased cell death. The addition of iron chelators or antioxidants restored proteasomal activity and reduced aggregate formation. The data indicate that cellular iron imbalance and oxidative damage are primary causes of cell death, while aggregate formation is a secondary effect.

Genetics of iron regulation and the possible role of iron in Parkinson's disease

Parkinson's disease (PD) is acknowledged as the second most common neurodegenerative disorder after Alzheimer's Disease. Older age may be the only unequivocal risk factor for PD although the male to female ratio is consistently greater than 1 in populations of European ancestry. Characteristic features of PD include dopaminergic neuron death in the substantia nigra (SN) pars compacta, accumulation of alpha-synuclein inclusions known as Lewy bodies in the SN, and brain iron accumulation beyond that observed in non-PD brains of a similar age. In this review article, we will provide an overview of human and animal studies investigating the contributions of iron in PD, a summary of human studies of iron-related genes in PD, a review of the literature on the genetics of iron metabolism, and some hypotheses on possible roles for iron in the pathogenic processes of PD including potential interactions between iron and other factors associated with Parkinson's disease.

Brain iron metabolism: neurobiology and neurochemistry

New findings obtained during the past years, especially the discovery of mutations in the genes associated with brain iron metabolism, have provided key insights into the homeostatic mechanisms of brain iron metabolism and the pathological mechanisms responsible for neurodegenerative diseases. The accumulated evidence demonstrates that misregulation in brain iron metabolism is one of the initial causes for neuronal death in some neurodegenerative disorders. The errors in brain iron metabolism found in these disorders have a multifactorial pathogenesis, including genetic and nongenetic factors. The disturbances of iron metabolism might occur at multiple levels, including iron uptake and release, storage, intracellular metabolism and regulation. It is the increased brain iron that triggers a cascade of deleterious events, leading to neuronal death in these diseases. In the article, the recent advances in studies on neurochemistry and neuropathophysiology of brain iron metabolism were reviewed.