Regional siderosis: a new challenge for iron chelation therapy

Ironing out the Links: Ferroptosis in epilepsy and SUDEP

Iron is a crucial element for almost all organisms because it plays a vital role in oxygen transport, enzymatic processes, and energy generation due to its electron transfer capabilities. However, its dysregulation can lead to a form of programmed cell death known as ferroptosis, which is characterized by cellular iron accumulation, reactive oxygen species (ROS) production, and unrestricted lipid peroxidation. Both iron and ferroptosis have been identified as key players in the pathogenesis of various neurodegenerative diseases. While in epilepsy this phenomenon remains relatively understudied, seizures can be considered hypoxic-ischemic episodes resulting in increased ROS production, lipid peroxidation, membrane disorganization, and cell death. All of this is accompanied by elevated intracellular free Fe2+ concentration and hemosiderin precipitation, as existing reports suggest a significant accumulation of iron in the brain and heart associated with epilepsy. Generalized tonic-clonic seizures (GTCS), a primary risk factor for Sudden Unexpected Death in Epilepsy (SUDEP), not only have an impact on the brain but also lead to cardiogenic dysfunctions associated with "Iron Overload and Cardiomyopathy" (IOC) and "Epileptic heart" characterized by electrical and mechanical dysfunction and a high risk of malignant bradycardia. In line with this phenomenon, studies conducted by our research group have demonstrated that recurrent seizures induce hypoxia in cardiomyocytes, resulting in P-glycoprotein (P-gp) overexpression, prolonged Q-T interval, severe bradycardia, and hemosiderin precipitation, correlating with an elevated spontaneous death ratio. In this article, we explore the intricate connections among ferroptosis, epilepsy, and SUDEP. By synthesizing current knowledge and drawing insights from recent publications, this study provides a comprehensive understanding of the molecular underpinnings. Furthermore, this review offers insights into potential therapeutic avenues and outlines future research directions.

Mapping the Research of Ferroptosis in Parkinson's Disease from 2013 to 2023: A Scientometric Review

Methods

Related studies on PD and ferroptosis were searched in Web of Science Core Collection (WOSCC) from inception to 2023. VOSviewer, CiteSpace, RStudio, and Scimago Graphica were employed as bibliometric analysis tools to generate network maps about the collaborations between authors, countries, and institutions and to visualize the co-occurrence and trends of co-cited references and keywords.

Results

A total of 160 original articles and reviews related to PD and ferroptosis were retrieved, produced by from 958 authors from 162 institutions. Devos David was the most prolific author, with 9 articles. China and the University of Melbourne had leading positions in publication volume with 84 and 12 publications, respectively. Current hot topics focus on excavating potential new targets for treating PD based on ferroptosis by gaining insight into specific molecular mechanisms, including iron metabolism disorders, lipid peroxidation, and imbalanced antioxidant regulation. Clinical studies aimed at treating PD by targeting ferroptosis remain in their preliminary stages.

Conclusion

A continued increase was shown in the literature within the related field over the past decade. The current study suggested active collaborations among authors, countries, and institutions. Research into the pathogenesis and treatment of PD based on ferroptosis has remained a prominent topic in the field in recent years, indicating that ferroptosis-targeted therapy is a potential approach to halting the progression of PD.

Iron Deposition in Parkinson's Disease: A Mini-Review

Iron deposition is crucial pathological changes observed in patients with Parkinson's disease (PD). Recently, scientists have actively explored therapeutic approaches targeting iron deposition in PD. However, several clinical studies have failed to yield consistent results. In this review, we provide an overview of iron deposition in PD, from both basic research and clinical perspectives. PD patients exhibit abnormalities in various iron metabolism-related proteins, leading to disruptions in iron distribution, transport, storage, and circulation, ultimately resulting in iron deposition. Excess iron can induce oxidative stress and iron-related cell death, and exacerbate mitochondrial dysfunction, contributing to the progression of PD pathology. Magnetic resonance imaging studies have indicated that the characteristics of iron deposition in the brains of PD patients vary. Iron deposition correlates with the clinical symptoms of PD, and patients with different disease courses and clinical presentations display distinct patterns of iron deposition. These iron deposition patterns may contribute to PD diagnosis. Iron deposition is a promising target for PD treatment. However, further research is required to elucidate the underlying mechanisms and their impacts on PD.

Therapeutic inhibition of ferroptosis in neurodegenerative disease

Iron accumulation has been associated with the etiology and progression of multiple neurodegenerative diseases (NDDs). The exact role of iron in these diseases is not fully understood, but an iron-dependent form of regulated cell death called ferroptosis could be key. Although there is substantial preclinical and clinical evidence that ferroptosis plays a role in NDD, there are still questions regarding how to target ferroptosis therapeutically, including which proteins to target, identification of clinically relevant biomarkers, and which patients might benefit most. Clinical trials of iron- and ferroptosis-targeted therapies are beginning to provide some answers, but there is growing interest in developing new ferroptosis inhibitors. We describe newly identified ferroptosis targets, opportunities, and challenges in NDD, as well as key considerations for progressing new therapeutics to the clinic.

Trial of Deferiprone in Parkinson's Disease

BACKGROUND

Iron content is increased in the substantia nigra of persons with Parkinson's disease and may contribute to the pathophysiology of the disorder. Early research suggests that the iron chelator deferiprone can reduce nigrostriatal iron content in persons with Parkinson's disease, but its effects on disease progression are unclear.

METHODS

We conducted a multicenter, phase 2, randomized, double-blind trial involving participants with newly diagnosed Parkinson's disease who had never received levodopa. Participants were assigned (in a 1:1 ratio) to receive oral deferiprone at a dose of 15 mg per kilogram of body weight twice daily or matched placebo for 36 weeks. Dopaminergic therapy was withheld unless deemed necessary for symptom control. The primary outcome was the change in the total score on the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS; range, 0 to 260, with higher scores indicating more severe impairment) at 36 weeks. Secondary and exploratory clinical outcomes at up to 40 weeks included measures of motor and nonmotor disability. Brain iron content measured with the use of magnetic resonance imaging was also an exploratory outcome.

RESULTS

A total of 372 participants were enrolled; 186 were assigned to receive deferiprone and 186 to receive placebo. Progression of symptoms led to the initiation of dopaminergic therapy in 22.0% of the participants in the deferiprone group and 2.7% of those in the placebo group. The mean MDS-UPDRS total score at baseline was 34.3 in the deferiprone group and 33.2 in the placebo group and increased (worsened) by 15.6 points and 6.3 points, respectively (difference, 9.3 points; 95% confidence interval, 6.3 to 12.2; P<0.001). Nigrostriatal iron content decreased more in the deferiprone group than in the placebo group. The main serious adverse events with deferiprone were agranulocytosis in 2 participants and neutropenia in 3 participants.

CONCLUSIONS

In participants with early Parkinson's disease who had never received levodopa and in whom treatment with dopaminergic medications was not planned, deferiprone was associated with worse scores in measures of parkinsonism than those with placebo over a period of 36 weeks. (Funded by the European Union Horizon 2020 program; FAIRPARK-II ClinicalTrials.gov number, NCT02655315.).

Novel Antidepressant-Like Properties of the Iron Chelator Deferiprone in a Mouse Model of Depression

Depressed individuals who carry the short allele for the serotonin-transporter-linked promotor region of the gene are more vulnerable to stress and have reduced response to first-line antidepressants such as selective serotonin reuptake inhibitors. Since depression severity has been reported to correlate with brain iron levels, the present study aimed to characterise the potential antidepressant properties of the iron chelator deferiprone. Using the serotonin transporter knock-out (5-HTT KO) mouse model, we assessed the behavioural effects of acute deferiprone on the Porsolt swim test (PST) and novelty-suppressed feeding test (NSFT). Brain and blood iron levels were also measured following acute deferiprone. To determine the relevant brain regions activated by deferiprone, we then measured c-Fos expression and applied network-based analyses. We found that deferiprone reduced immobility time in the PST in 5-HTT KO mice and reduced latency to feed in the NSFT in both genotypes, suggesting potential antidepressant-like effects. There was no effect on brain or blood iron levels following deferiprone treatment, potentially indicating an acute iron-independent mechanism. Deferiprone reversed the increase in c-Fos expression induced by swim stress in 5-HTT KO mice in the lateral amygdala. Functional network analyses suggest that hub regions of activity in mice treated with deferiprone include the caudate putamen and prefrontal cortex. The PST-induced increase in network modularity in wild-type mice was not observed in 5-HTT KO mice. Altogether, our data show that the antidepressant-like effects of deferiprone could be acting via an iron-independent mechanism and that these therapeutic effects are underpinned by changes in neuronal activity in the lateral amygdala.

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.

Keeping Cell Death Alive: An Introduction into the French Cell Death Research Network

Since the Nobel Prize award more than twenty years ago for discovering the core apoptotic pathway in C. elegans, apoptosis and various other forms of regulated cell death have been thoroughly characterized by researchers around the world. Although many aspects of regulated cell death still remain to be elucidated in specific cell subtypes and disease conditions, many predicted that research into cell death was inexorably reaching a plateau. However, this was not the case since the last decade saw a multitude of cell death modalities being described, while harnessing their therapeutic potential reached clinical use in certain cases. In line with keeping research into cell death alive, francophone researchers from several institutions in France and Belgium established the French Cell Death Research Network (FCDRN). The research conducted by FCDRN is at the leading edge of emerging topics such as non-apoptotic functions of apoptotic effectors, paracrine effects of cell death, novel canonical and non-canonical mechanisms to induce apoptosis in cell death-resistant cancer cells or regulated forms of necrosis and the associated immunogenic response. Collectively, these various lines of research all emerged from the study of apoptosis and in the next few years will increase the mechanistic knowledge into regulated cell death and how to harness it for therapy.

Cerebral Iron Deposition in Neurodegeneration

Disruption of cerebral iron regulation appears to have a role in aging and in the pathogenesis of various neurodegenerative disorders. Possible unfavorable impacts of iron accumulation include reactive oxygen species generation, induction of ferroptosis, and acceleration of inflammatory changes. Whole-brain iron-sensitive magnetic resonance imaging (MRI) techniques allow the examination of macroscopic patterns of brain iron deposits in vivo, while modern analytical methods ex vivo enable the determination of metal-specific content inside individual cell-types, sometimes also within specific cellular compartments. The present review summarizes the whole brain, cellular, and subcellular patterns of iron accumulation in neurodegenerative diseases of genetic and sporadic origin. We also provide an update on mechanisms, biomarkers, and effects of brain iron accumulation in these disorders, focusing on recent publications. In Parkinson’s disease, Friedreich’s disease, and several disorders within the neurodegeneration with brain iron accumulation group, there is a focal siderosis, typically in regions with the most pronounced neuropathological changes. The second group of disorders including multiple sclerosis, Alzheimer’s disease, and amyotrophic lateral sclerosis shows iron accumulation in the globus pallidus, caudate, and putamen, and in specific cortical regions. Yet, other disorders such as aceruloplasminemia, neuroferritinopathy, or Wilson disease manifest with diffuse iron accumulation in the deep gray matter in a pattern comparable to or even more extensive than that observed during normal aging. On the microscopic level, brain iron deposits are present mostly in dystrophic microglia variably accompanied by iron-laden macrophages and in astrocytes, implicating a role of inflammatory changes and blood–brain barrier disturbance in iron accumulation. Options and potential benefits of iron reducing strategies in neurodegeneration are discussed. Future research investigating whether genetic predispositions play a role in brain Fe accumulation is necessary. If confirmed, the prevention of further brain Fe uptake in individuals at risk may be key for preventing neurodegenerative disorders.

Brain iron enrichment attenuates α-synuclein spreading after injection of preformed fibrils

Regional iron accumulation and α-synuclein (α-syn) spreading pathology within the central nervous system are common pathological findings in Parkinson's disease (PD). Whereas iron is known to bind to α-syn, facilitating its aggregation and regulating α-syn expression, it remains unclear if and how iron also modulates α-syn spreading. To elucidate the influence of iron on the propagation of α-syn pathology, we investigated α-syn spreading after stereotactic injection of α-syn preformed fibrils (PFFs) into the striatum of mouse brains after neonatal brain iron enrichment. C57Bl/6J mouse pups received oral gavage with 60, 120, or 240 mg/kg carbonyl iron or vehicle between postnatal days 10 and 17. At 12 weeks of age, intrastriatal injections of 5-µg PFFs were performed to induce seeding of α-syn aggregates. At 90 days post-injection, PFFs-injected mice displayed long-term memory deficits, without affection of motor behavior. Interestingly, quantification of α-syn phosphorylated at S129 showed reduced α-syn pathology and attenuated spreading to connectome-specific brain regions after brain iron enrichment. Furthermore, PFFs injection caused intrastriatal microglia accumulation, which was alleviated by iron in a dose-dependent way. In primary cortical neurons in a microfluidic chamber model in vitro, iron application did not alter trans-synaptic α-syn propagation, possibly indicating an involvement of non-neuronal cells in this process. Our study suggests that α-syn PFFs may induce cognitive deficits in mice independent of iron. However, a redistribution of α-syn aggregate pathology and reduction of striatal microglia accumulation in the mouse brain may be mediated via iron-induced alterations of the brain connectome.

Cell Death-Osis of Dopaminergic Neurons and the Role of Iron in Parkinson's Disease

Significance: There is still no cure for neurodegenerative diseases, such as Parkinson's disease (PD). Current treatments are based on the attempt to reduce dopaminergic neuronal loss, and multidisciplinary approaches have been used to provide only a temporary symptoms' relief. In addition to the difficulties of drugs developed against PD to access the brain, the specificity of those inhibitory compounds could be a concern. This because neurons might degenerate by activating distinct signaling pathways, which are often initiated by the same stimulus. Recent Advances: Apoptosis, necroptosis, and ferroptosis were shown to significantly contribute to PD progression and, so far, are the main death programs described as capable to alter brain homeostasis. Their activation is characterized by different biochemical and morphological features, some of which might even share the same molecular players. Critical Issues: If there is a pathological need to engage, in PD, multiple death programs, sequentially or simultaneously, is not clear yet. Possibly the activation of apoptosis, necroptosis, and/or ferroptosis correlates to different PD stages and symptom severities. This would imply that the efficacy of therapeutic approaches against neuronal death might depend on the death program they target and the relevance of this death pathway on a specific PD phase. Future Directions: In this review, we describe the molecular mechanisms underlying the activation of apoptosis, necroptosis, and ferroptosis in PD. Understanding the interrelationship between different death pathways' activation in PD is of utmost importance for the development of therapeutic approaches against disease progression. Antioxid. Redox Signal. 35, 453-473.

Copper, Iron, and Manganese Toxicity in Neuropsychiatric Conditions

Copper, manganese, and iron are vital elements required for the appropriate development and the general preservation of good health. Additionally, these essential metals play key roles in ensuring proper brain development and function. They also play vital roles in the central nervous system as significant cofactors for several enzymes, including the antioxidant enzyme superoxide dismutase (SOD) and other enzymes that take part in the creation and breakdown of neurotransmitters in the brain. An imbalance in the levels of these metals weakens the structural, regulatory, and catalytic roles of different enzymes, proteins, receptors, and transporters and is known to provoke the development of various neurological conditions through different mechanisms, such as via induction of oxidative stress, increased α-synuclein aggregation and fibril formation, and stimulation of microglial cells, thus resulting in inflammation and reduced production of metalloproteins. In the present review, the authors focus on neurological disorders with psychiatric signs associated with copper, iron, and manganese excess and the diagnosis and potential treatment of such disorders. In our review, we described diseases related to these metals, such as aceruloplasminaemia, neuroferritinopathy, pantothenate kinase-associated neurodegeneration (PKAN) and other very rare classical NBIA forms, manganism, attention-deficit/hyperactivity disorder (ADHD), ephedrone encephalopathy, HMNDYT1-SLC30A10 deficiency (HMNDYT1), HMNDYT2-SLC39A14 deficiency, CDG2N-SLC39A8 deficiency, hepatic encephalopathy, prion disease and “prion-like disease”, amyotrophic lateral sclerosis, Huntington’s disease, Friedreich’s ataxia, and depression.

Parkinson's disease: Alterations in iron and redox biology as a key to unlock therapeutic strategies

A plethora of studies indicate that iron metabolism is dysregulated in Parkinson's disease (PD). The literature reveals well-documented alterations consistent with established dogma, but also intriguing paradoxical observations requiring mechanistic dissection. An important fact is the iron loading in dopaminergic neurons of the substantia nigra pars compacta (SNpc), which are the cells primarily affected in PD. Assessment of these changes reveal increased expression of proteins critical for iron uptake, namely transferrin receptor 1 and the divalent metal transporter 1 (DMT1), and decreased expression of the iron exporter, ferroportin-1 (FPN1). Consistent with this is the activation of iron regulator protein (IRP) RNA-binding activity, which is an important regulator of iron homeostasis, with its activation indicating cytosolic iron deficiency. In fact, IRPs bind to iron-responsive elements (IREs) in the 3ꞌ untranslated region (UTR) of certain mRNAs to stabilize their half-life, while binding to the 5ꞌ UTR prevents translation. Iron loading of dopaminergic neurons in PD may occur through these mechanisms, leading to increased neuronal iron and iron-mediated reactive oxygen species (ROS) generation. The "gold standard" histological marker of PD, Lewy bodies, are mainly composed of α-synuclein, the expression of which is markedly increased in PD. Of note, an atypical IRE exists in the α-synuclein 5ꞌ UTR that may explain its up-regulation by increased iron. This dysregulation could be impacted by the unique autonomous pacemaking of dopaminergic neurons of the SNpc that engages L-type Ca+2 channels, which imparts a bioenergetic energy deficit and mitochondrial redox stress. This dysfunction could then drive alterations in iron trafficking that attempt to rescue energy deficits such as the increased iron uptake to provide iron for key electron transport proteins. Considering the increased iron-loading in PD brains, therapies utilizing limited iron chelation have shown success. Greater therapeutic advancements should be possible once the exact molecular pathways of iron processing are dissected.

Linking chronic kidney disease and Parkinson's disease: a literature review

Chronic kidney disease (CKD) has been typically implicated in cardiovascular risk, considering the function the kidney has related to blood pressure, vitamin D, red blood cell metabolism, and electrolyte and acid-base regulation. However, neurological consequences are also attributed to this disease. Among these, recent large epidemiological studies have demonstrated an increased risk for Parkinson's disease (PD) in patients with CKD. Multiple studies have evaluated individually the association of blood pressure, vitamin D, and red blood cell dysmetabolism with PD, however, no study has reviewed the potential mechanisms related to these components in context of CKD and PD. In this review, we explored the association of CKD and PD and linked the components of the former to propose potential pathways explaining a future increased risk for PD, where renin-angiotensin system, oxidative stress, and inflammation have a main role. Potential preventive and therapeutic interventions based on these associations are also explored. More preclinical studies are needed to confirm the potential link of CKD conditions and future PD risk, whereas more interventional studies targeting this association are warranted to confirm their potential benefit in PD.

Ferroptosis in Neurological Diseases

Ferroptosis is mechanism for non-apoptotic, iron-dependent, oxidative cell death that is characterized by glutathione consumption and lipid peroxides accumulation. Ferroptosis is crucially involved in neurological diseases, including neurodegeneration, stroke and neurotrauma. This review provides detailed discussions of the ferroptosis mechanisms in these neurological diseases. Moreover, it summarizes recent drugs that target ferroptosis for neurological disease treatment. Furthermore, it compares the differences and relationships among the various cell death mechanisms involved in neurological diseases. Elucidating the ferroptosis role in the brain can improve the understanding of neurological disease mechanism and provide potential prevention and treatment interventions for acute and chronic neurological diseases.

Cerebellar Astrocytes: Much More Than Passive Bystanders In Ataxia Pathophysiology

Ataxia is a neurodegenerative syndrome, which can emerge as a major element of a disease or represent a symptom of more complex multisystemic disorders. It comprises several forms with a highly variegated etiology, mainly united by motor, balance, and speech impairments and, at the tissue level, by cerebellar atrophy and Purkinje cells degeneration. For this reason, the contribution of astrocytes to this disease has been largely overlooked in the past. Nevertheless, in the last few decades, growing evidences are pointing to cerebellar astrocytes as crucial players not only in the progression but also in the onset of distinct forms of ataxia. Although the current knowledge on this topic is very fragmentary and ataxia type-specific, the present review will attempt to provide a comprehensive view of astrocytes’ involvement across the distinct forms of this pathology. Here, it will be highlighted how, through consecutive stage-specific mechanisms, astrocytes can lead to non-cell autonomous neurodegeneration and, consequently, to the behavioral impairments typical of this disease. In light of that, treating astrocytes to heal neurons will be discussed as a potential complementary therapeutic approach for ataxic patients, a crucial point provided the absence of conclusive treatments for this disease.

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.

Metal Chelation Therapy and Parkinson's Disease: A Critical Review on the Thermodynamics of Complex Formation between Relevant Metal Ions and Promising or Established Drugs

The present review reports a list of approximately 800 compounds which have been used, tested or proposed for Parkinson's disease (PD) therapy in the year range 2014-2019 (April): name(s), chemical structure and references are given. Among these compounds, approximately 250 have possible or established metal-chelating properties towards Cu(II), Cu(I), Fe(III), Fe(II), Mn(II), and Zn(II), which are considered to be involved in metal dyshomeostasis during PD. Speciation information regarding the complexes formed by these ions and the 250 compounds has been collected or, if not experimentally available, has been estimated from similar molecules. Stoichiometries and stability constants of the complexes have been reported; values of the cologarithm of the concentration of free metal ion at equilibrium (pM), and of the dissociation constant Kd (both computed at pH = 7.4 and at total metal and ligand concentrations of 10-6 and 10-5 mol/L, respectively), charge and stoichiometry of the most abundant metal-ligand complexes existing at physiological conditions, have been obtained. A rigorous definition of the reported amounts is given, the possible usefulness of this data is described, and the need to characterize the metal-ligand speciation of PD drugs is underlined.

Striking while the iron is hot: Iron metabolism and ferroptosis in neurodegeneration

Perturbations in iron homeostasis and iron accumulation feature in several neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD) and Amyotrophic lateral sclerosis (ALS). Proteins such as α-synuclein, tau and amyloid precursor protein that are pathologically associated with neurodegeneration are involved in molecular crosstalk with iron homeostatic proteins. Quantitative susceptibility mapping, an MRI based non-invasive technique, offers proximal evaluations of iron load in regions of the brain and powerfully predicts cognitive decline. Further, small molecules that target elevated iron have shown promise against PD and AD in preclinical studies and clinical trials. Despite these strong links between altered iron homeostasis and neurodegeneration the molecular biology to describe the association between enhanced iron levels and neuron death, synaptic impairment and cognitive decline is ill defined. In this review we discuss the current understanding of brain iron homeostasis and how it may be perturbed under pathological conditions. Further, we explore the ramifications of a novel cell death pathway called ferroptosis that has provided a fresh impetus to the "metal hypothesis" of neurodegeneration. While lipid peroxidation plays a central role in the execution of this cell death modality the removal of iron through chelation or genetic modifications appears to extinguish the ferroptotic pathway. Conversely, tissues that harbour elevated iron may be predisposed to ferroptotic damage. These emerging findings are of relevance to neurodegeneration where ferroptotic signalling may offer new targets to mitigate cell death and dysfunction.

Iron in Neurodegeneration - Cause or Consequence?

Iron dyshomeostasis can cause neuronal damage to iron-sensitive brain regions. Neurodegeneration with brain iron accumulation reflects a group of disorders caused by iron overload in the basal ganglia. High iron levels and iron related pathogenic triggers have also been implicated in sporadic neurodegenerative diseases including Alzheimer’s disease (AD), Parkinson’s disease (PD), and multiple system atrophy (MSA). Iron-induced dyshomeostasis within vulnerable brain regions is still insufficiently understood. Here, we summarize the modes of action by which iron might act as primary or secondary disease trigger in neurodegenerative disorders. In addition, available treatment options targeting brain iron dysregulation and the use of iron as biomarker in prodromal stages are critically discussed to address the question of cause or consequence.

The Role of Iron in Friedreich's Ataxia: Insights From Studies in Human Tissues and Cellular and Animal Models

Friedreich's ataxia (FRDA) is a rare early-onset degenerative disease that affects both the central and peripheral nervous systems, and other extraneural tissues, mainly the heart and endocrine pancreas. This disorder progresses as a mixed sensory and cerebellar ataxia, primarily disturbing the proprioceptive pathways in the spinal cord, peripheral nerves and nuclei of the cerebellum. FRDA is an inherited disease with an autosomal recessive pattern caused by an insufficient amount of the nuclear-encoded mitochondrial protein frataxin, which is an essential and highly evolutionary conserved protein whose deficit results in iron metabolism dysregulation and mitochondrial dysfunction. The first experimental evidence connecting frataxin with iron homeostasis came from Saccharomyces cerevisiae; iron accumulates in the mitochondria of yeast with deletion of the frataxin ortholog gene. This finding was soon linked to previous observations of iron deposits in the hearts of FRDA patients and was later reported in animal models of the disease. Despite advances made in the understanding of FRDA pathophysiology, the role of iron in this disease has not yet been completely clarified. Some of the questions still unresolved include the molecular mechanisms responsible for the iron accumulation and iron-mediated toxicity. Here, we review the contribution of the cellular and animal models of FRDA and relevance of the studies using FRDA patient samples to gain knowledge about these issues. Mechanisms of mitochondrial iron overload are discussed considering the potential roles of frataxin in the major mitochondrial metabolic pathways that use iron. We also analyzed the effect of iron toxicity on neuronal degeneration in FRDA by reactive oxygen species (ROS)-dependent and ROS-independent mechanisms. Finally, therapeutic strategies based on the control of iron toxicity are considered.

Emerging disease-modifying strategies targeting α-synuclein for the treatment of Parkinson's disease

Parkinson's disease is the most common neurodegenerative movement disorder. It arises as a result of neuronal cell death in specific brain regions, notably the substantia nigra pars compacta, and is characterized by the accumulation of α-synuclein in these brain regions. Current pharmacological therapies alleviate the motor symptoms of the disease and are particularly effective in the early stages of the disease. Ongoing drug development efforts focus on disease-modifying strategies that aim to halt or slow disease progression. In this review, we explore a number of emerging disease-modifying strategies with a focus on direct and indirect targeting of α-synuclein dysfunction. We summarize newer classes of small molecules and biological agents intended to attenuate protein aggregation or to target enzymes that may increase the degradation of the pathogenic forms of α-synuclein. Finally, we discuss emerging strategies that are demonstrating the potential for disease modification at the preclinical stage.

Deferiprone Rescues Behavioral Deficits Induced by Mild Iron Exposure in a Mouse Model of Alpha-Synuclein Aggregation

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, and its causes remain unknown. A major hallmark of the disease is the increasing presence of aggregated alpha-synuclein (aSyn). Furthermore, there is a solid consensus on iron (Fe) accumulation in several regions of PD brains during disease progression. In our study, we focused on the interaction of Fe and aggregating aSyn in vivo in a transgenic mouse model overexpressing human aSyn bearing the A53T mutation (prnp.aSyn.A53T). We utilized a neonatal iron-feeding model to exacerbate the motor phenotype of the transgenic mouse model. Beginning from day 100, mice were treated with deferiprone (DFP), a ferric chelator that is able to cross the blood-brain barrier and is currently used in clinics as treatment for hemosiderosis. Our paradigm resulted in an impairment of the learning abilities in the rotarod task and the novel object recognition test. DFP treatment significantly improved the performance in both tasks. Although this was not accompanied by alterations in aSyn aggregation, our results support DFP as possible therapeutic option in PD.

[New therapy approaches for Parkinson's disease]

Over the last years major advances have been made in the identification of specific pathways underlying the pathophysiology of subgroups of patients with Parkinson' disease. These pathways include mitochondrial and lysosomal dysfunction as well as inflammatory patterns and represent the basis for new causative and disease-modifying treatment strategies, possibly not only for the respective subgroups of patients but hopefully also for the majority of patients with idiopathic Parkinson's disease. This article highlights the main treatment strategies focusing on causative and disease course-modifying strategies as well as quality of life.

Iron chelation in the treatment of neurodegenerative diseases

Disturbance of cerebral iron regulation is almost universal in neurodegenerative disorders. There is a growing body of evidence that increased iron deposits may contribute to degenerative changes. Thus, the effect of iron chelation therapy has been investigated in many neurological disorders including rare genetic syndromes with neurodegeneration with brain iron accumulation as well as common sporadic disorders such as Parkinson's disease, Alzheimer's disease, and multiple sclerosis. This review summarizes recent advances in understanding the role of iron in the etiology of neurodegeneration. Outcomes of studies investigating the effect of iron chelation therapy in neurodegenerative disorders are systematically presented in tables. Iron chelators, particularly the blood brain barrier-crossing compound deferiprone, are capable of decreasing cerebral iron in areas with abnormally high concentrations as documented by MRI. Yet, currently, there is no compelling evidence of the clinical effect of iron removal therapy on any neurological disorder. However, several studies indicate that it may prevent or slow down disease progression of several disorders such as aceruloplasminemia, pantothenate kinase-associated neurodegeneration or Parkinson's disease.

Newly Diagnosed Anemia Increases Risk of Parkinson's disease: A Population-Based Cohort Study

Anemia and low hemoglobin have been identified to increase Parkinson’s disease (PD) risk. This population-based cohort study investigated PD risk in newly diagnosed anemic patients by using data from the Taiwan National Health Insurance Research Database. All newly diagnosed anemic patients (n = 86,334) without a history of stroke, neurodegenerative diseases, traumatic brain injury, major operations, or blood loss diseases were enrolled. A cohort of nonanemic controls, 1:1 matched with anemic patients on the basis of the demographics and pre-existing medical conditions, was also included. Competing risk analysis was used to evaluate PD risk in anemic patients compared with that in their matched controls. The adjusted hazard ratio (aHR) of PD risk in the anemic patients was 1.36 (95% confidence interval [CI]: 1.22–1.52, p < 0.001). Iron deficiency anemia (IDA) patients tended to exhibit a higher PD risk (aHR: 1.49; 95% CI: 1.24–1.79, p < 0.001). Furthermore, Iron supplement did not significantly affect the PD risk: the aHRs for PD risk were 1.32 (95% CI: 1.07–1.63, p < 0.01) and 1.86 (95% CI: 1.46–2.35, p < 0.001) in IDA patients with and without iron supplementation, respectively. The population-based cohort study indicated newly diagnosed anemia increases PD risk.

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.

Mitochondrial iron overload: causes and consequences

Pathological overload of iron in the mitochondrial matrix has been observed in numerous diseases, including sideroblastic anemias, which have many causes, and in genetic diseases that affect iron-sulfur cluster biogenesis, heme synthesis, and mitochondrial protein translation and its products. Although high expression of the mitochondrial iron importer, mitoferrin, appears to be an underlying common feature, it is unclear what drives high mitoferrin expression and what other proteins are involved in trapping excess toxic iron in the mitochondrial matrix. Numerous examples of human diseases and model systems suggest that mitochondrial iron homeostasis is coordinated through transcriptional remodeling. A cytosolic/nuclear molecule may affect a transcriptional factor to coordinate the events that lead to iron accumulation, but no candidates for this role have yet been identified.

Iron Homeostasis in Health and Disease

Iron is required for the survival of most organisms, including bacteria, plants, and humans. Its homeostasis in mammals must be fine-tuned to avoid iron deficiency with a reduced oxygen transport and diminished activity of Fe-dependent enzymes, and also iron excess that may catalyze the formation of highly reactive hydroxyl radicals, oxidative stress, and programmed cell death. The advance in understanding the main players and mechanisms involved in iron regulation significantly improved since the discovery of genes responsible for hemochromatosis, the IRE/IRPs machinery, and the hepcidin-ferroportin axis. This review provides an update on the molecular mechanisms regulating cellular and systemic Fe homeostasis and their roles in pathophysiologic conditions that involve alterations of iron metabolism, and provides novel therapeutic strategies to prevent the deleterious effect of its deficiency/overload.

Iron and oxidative stress in cardiomyopathy in thalassemia

With repeated blood transfusions, patients with thalassemia major rapidly become loaded with iron, often surpassing hepatic metal accumulation capacity within ferritin shells and infiltrating heart and endocrine organs. That pathological scenario contrasts with the physiological one, which is characterized by an efficient maintenance of all plasma iron bound to circulating transferrin, due to a tight control of iron ingress into plasma by the hormone hepcidin. Within cells, most of the acquired iron becomes protein-associated, as once released from endocytosed transferrin, it is used within mitochondria for the synthesis of protein prosthetic groups or it is incorporated into enzyme active centers or alternatively sequestered within ferritin shells. A few cell types also express the iron extrusion transporter ferroportin, which is under the negative control of circulating hepcidin. However, that system only backs up the major cell regulated iron uptake/storage machinery that is poised to maintain a basal level of labile cellular iron for metabolic purposes without incurring potentially toxic scenarios. In thalassemia and other transfusion iron-loading conditions, once transferrin saturation exceeds about 70%, labile forms of iron enter the circulation and can gain access to various types of cells via resident transporters or channels. Within cells, they can attain levels that exceed their ability to chemically cope with labile iron, which has a propensity for generating reactive oxygen species (ROS), thereby inducing oxidative damage. This scenario occurs in the heart of hypertransfused thalassemia major patients who do not receive adequate iron-chelation therapy. Iron that accumulates in cardiomyocytes forms agglomerates that are detected by T2* MRI. The labile forms of iron infiltrate the mitochondria and damage cells by inducing noxious ROS formation, resulting in heart failure. The very rapid relief of cardiac dysfunction seen after intensive iron-chelation therapy in some patients with thalassemia major is thought to be due to the relief of the cardiac mitochondrial dysfunction caused by oxidative stress or to the removal of labile iron interference with calcium fluxes through cardiac calcium channels. In fact, improvement occurs well before there is any significant improvement in the total level of cardiac iron loading. The oral iron chelator deferiprone, because of its small size and neutral charge, demonstrably enters cells and chelates labile iron, thereby rapidly reducing ROS formation, allowing better mitochondrial activity and improved cardiac function. Deferiprone may also rapidly improve arrhythmias in patients who do not have excessive cardiac iron. It maintains the flux of iron in the direction hemosiderin to ferritin to free iron, and it allows clearance of cardiac iron in the presence of other iron chelators or when used alone. To date, the most commonly used chelator combination therapy is deferoxamine plus deferiprone, whereas other combinations are in the process of assessment. In summary, it is imperative that patients with thalassemia major have iron chelators continuously present in their circulation to prevent exposure of the heart to labile iron, reduce cardiac toxicity, and improve cardiac function.

An unusual case of iron deficiency anemia is associated with extremely low level of transferrin receptor

A case study of a female patient, diagnosed with iron deficiency anemia, was unresponsive to oral iron treatment and only partially responsive to parenteral iron therapy, a clinical profile resembling the iron-refractory iron deficiency anemia (IRIDA) disorder. However, the patient failed to exhibit microcytic phenotype, one of the IRIDA hallmarks. Biochemical assays revealed that serum iron, hepcidin, interluekin 6, and transferrin saturation were within the normal range of references or were comparable to her non-anemic offspring. Iron contents in serum and red blood cells and hemoglobin levels were measured, which confirmed the partial improvement of anemia after parenteral iron therapy. Strikingly, serum transferrin receptor in patient was almost undetectable, reflecting the very low activity of bone-marrow erythropoiesis. Our data demonstrate that this is not a case of systemic iron deficiency, but rather cellular iron deficit due to the low level of transferrin receptor, particularly in erythroid tissue.

Ceruloplasmin activity and iron chelation treatment of patients with Parkinson's disease

Background

Growing body of evidence suggests that Parkinson’s disease (PD) is associated with oxidative damage via iron accumulation in the substantia nigra (SN). Low ceruloplasmin (CP)-ferroxidase activity has been identified in the SN and the cerebrospinal fluid (CSF) of patients with PD. The iron chelator, deferiprone, reduces the abnormally high levels of iron in the SN. In order to determine CP’s involvement in iron accumulation in SN and PD progression, we aim to compare the ability of iron chelation treatment to reducing both SN iron levels and motor handicap in PD patients according to the level of ceruloplasmin activity.

Methods

We used a moderate chelation protocol with deferiprone (DFP) based on a, 6-month delayed-start paradigm, randomized placebo controlled clinical trial in 40 PD patients. CP-ferroxidase activity was determined in blood and CSF together with the D544E gene polymorphism (rs701753). Iron levels were determined by R2* MRI sequence and the motor handicap by the UPDRS motor score.

Results

After 6 to 12 months of DFP treatment, greater reductions in SN iron levels and UPDRS motor scores were obtained in patients with higher serum and CSF levels of CP-ferroxidase activity. After 6 months of DFP treatment, the AT genotype group displayed greater reduction of iron level in the SN with greater CSF and serum levels of CP activity than the AA genotype group.

Conclusion

Although most of the DFP-treated patients displayed clinical and radiological improvements, those with the lower CP activity appeared to respond better to iron chelation. Larger RCTs are now needed to establish whether pharmacological modulation of CP activity could be an innovative neuroprotective strategy in PD.

Trial registration

FAIR-PARK study (ClinicalTrials.gov reference: NCT00943748; French national reference number: 2008−006842−25). This study was approved by the French Drug Agency (ANSM) and the local institutional review board (“Comité de Protection des Personnes of Lille”).

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-015-0331-3) contains supplementary material, which is available to authorized users.

The clinical effect of deferoxamine mesylate on edema after intracerebral hemorrhage

Background and Purpose

It has been shown that 3 days of 62 mg/kg/day deferoxamine infusion (maximum dose not to exceed 6000 mg/day) is safe and tolerated by intracerebral hemorrhage (ICH) patients. The aim of this study was to investigate the efficacy of deferoxamine mesylate for edema resolution and hematoma absorption after ICH.

Methods

From February 2013 to May 2014, spontaneous ICH patients diagnosed by computed tomography (CT) within 18 hours of onset were evaluated. Patients were randomly divided into two groups: an experimental group and a control group. The treatment of the two groups was similar except that the experimental group received deferoxamine mesylate. Patients were evaluated by CT and neurology scale at the time of admission, and on the fourth, eighth, and fifteenth day (or at discharge) after admission. Patients were followed up for the first 30 days and clinical data of the two groups were compared.

Results

Forty-two patients completed 30 days of follow-up by May 2014; 21 cases in the experimental group and 21 cases in the control group. The control group’s relative edema volume on the fifteenth day (or discharge) was 10.26 ± 17.54, which was higher than the experimental group (1.91 ± 1.94; P < 0.05). The control group’s 1–8 day and 8–15 day relative hematoma absorption were greater than the experimental group (P < 0.05).The control group’s relative edema volume on the fourth, eighth, and fifteenth day (or discharge) was higher than the experimental group (P < 0.05). Neurological scores between the two groups were not statistically different on the fifteenth day (or discharge) or on the thirtieth day.

Conclusions

Deferoxamine mesylate may slow hematoma absorption and inhibit edema after ICH, although further investigation is required to form definitive conclusions.

Trial Registration

Chinese Clinical Trial Registry ChiCTR-TRC-14004979

Iron-induced damage in cardiomyopathy: oxidative-dependent and independent mechanisms

The high incidence of cardiomyopathy in patients with hemosiderosis, particularly in transfusional iron overload, strongly indicates that iron accumulation in the heart plays a major role in the process leading to heart failure. In this context, iron-mediated generation of noxious reactive oxygen species is believed to be the most important pathogenetic mechanism determining cardiomyocyte damage, the initiating event of a pathologic progression involving apoptosis, fibrosis, and ultimately cardiac dysfunction. However, recent findings suggest that additional mechanisms involving subcellular organelles and inflammatory mediators are important factors in the development of this disease. Moreover, excess iron can amplify the cardiotoxic effect of other agents or events. Finally, subcellular misdistribution of iron within cardiomyocytes may represent an additional pathway leading to cardiac injury. Recent advances in imaging techniques and chelators development remarkably improved cardiac iron overload detection and treatment, respectively. However, increased understanding of the pathogenic mechanisms of iron overload cardiomyopathy is needed to pave the way for the development of improved therapeutic strategies.

Deferoxamine attenuates lipopolysaccharide-induced neuroinflammation and memory impairment in mice

Background

Neuroinflammation often results in enduring cognitive impairment and is a risk factor for postoperative cognitive dysfunction. There are currently no effective treatments for infection-induced cognitive impairment. Previous studies have shown that the iron chelator deferoxamine (DFO) can increase the resistance of neurons to injury and disease by stimulating adaptive cellular stress responses. However, the impact of DFO on the cognitive sequelae of neuroinflammation is unknown.

Methods

A mouse model of lipopolysaccharide (LPS)-induced cognitive impairment was established to evaluate the neuroprotective effects of DFO against LPS-induced memory deficits and neuroinflammation. Adult C57BL/6 mice were treated with 0.5 μg of DFO 3 days prior to intracerebroventricular microinjection of 2 μg of LPS. Cognitive function was assessed using a Morris water maze from post-injection days 1 to 3. Animal behavioral tests, as well as pathological and biochemical assays were performed to evaluate the LPS-induced hippocampal damage and the neuroprotective effect of DFO.

Results

Treatment of mice with LPS resulted in deficits in cognitive performance in the Morris water maze without changing locomotor activity, which were ameliorated by pretreatment with DFO. DFO prevented LPS-induced microglial activation and elevations of IL-1β and TNF-α levels in the hippocampus. Moreover, DFO attenuated elevated expression of caspase-3, modulated GSK3β activity, and prevented LPS-induced increases of MDA and SOD levels in the hippocampus. DFO also significantly blocked LPS-induced iron accumulation and altered expression of proteins related to iron metabolism in the hippocampus.

Conclusions

Our results suggest that DFO may possess a neuroprotective effect against LPS-induced neuroinflammation and cognitive deficits via mechanisms involving maintenance of less brain iron, prevention of neuroinflammation, and alleviation of oxidative stress and apoptosis.

The neurotoxicity of iron, copper and manganese in Parkinson's and Wilson's diseases

Impaired cellular homeostasis of metals, particularly of Cu, Fe and Mn may trigger neurodegeneration through various mechanisms, notably induction of oxidative stress, promotion of α-synuclein aggregation and fibril formation, activation of microglial cells leading to inflammation and impaired production of metalloproteins. In this article we review available studies concerning Fe, Cu and Mn in Parkinson's disease and Wilson's disease. In Parkinson's disease local dysregulation of iron metabolism in the substantia nigra (SN) seems to be related to neurodegeneration with an increase in SN iron concentration, accompanied by decreased SN Cu and ceruloplasmin concentrations and increased free Cu concentrations and decreased ferroxidase activity in the cerebrospinal fluid. Available data in Wilson's disease suggest that substantial increases in CNS Cu concentrations persist for a long time during chelating treatment and that local accumulation of Fe in certain brain nuclei may occur during the course of the disease. Consequences for chelating treatment strategies are discussed.