Switching on Endogenous Metal Binding Proteins in Parkinson's Disease

Metallothionein: A Comprehensive Review of Its Classification, Structure, Biological Functions, and Applications

Metallothionein is a cysteine-rich protein with a high metal content that is widely found in nature. In addition to heavy metal detoxification, metallothionein is well known as a potent antioxidant. The high sulfhydryl content of metallothionein confers excellent antioxidant activity, enabling it to effectively scavenge free radicals and mitigate oxidative stress damage. In addition, metallothionein can play a neuroprotective role by alleviating oxidative damage in nerve cells, have an anticancer effect by enhancing the ability of normal cells to resist unfavorable conditions through its antioxidant function, and reduce inflammation by scavenging reactive oxygen species. Due to its diverse biological functions, metallothionein has a broad potential for application in alleviating environmental heavy metal pollution, predicting and diagnosing diseases, and developing skin care products and health foods. This review summarizes the recent advances in the classification, structure, biological functions, and applications of metallothionein, focusing on its powerful antioxidant effects and related functions.

Dyshomeostasis of Iron and Its Transporter Proteins in Cypermethrin-Induced Parkinson's Disease

The etiology of Parkinson's disease (PD) is highly complex and is still indefinable. However, a number of studies have indicated the involvement of pesticides and transition metals. Copper, magnesium, iron, and zinc have emerged as important metal contributors. Exposure to pesticides causes an accumulation of transition metals in the substantia nigra (SN) region of the brain. The cypermethrin model of PD is characterized by mitochondrial dysfunction, autophagy impairment, oxidative stress, etc. However, the effect of cypermethrin on metal homeostasis is not yet explored. The study was designed to delineate the role of metals and their transporter proteins in cypermethrin-induced animal and cellular models of PD. The level of copper, magnesium, iron, and zinc was checked in the nigrostriatal tissue and serum by atomic absorption spectroscopy. Since cypermethrin consistently increased iron content in the nigrostriatal tissue and serum after 12 weeks of exposure, the level of iron transporter proteins, such as divalent metal transporter-1 (DMT-1), ceruloplasmin, transferrin, ferroportin, and hepcidin, and their in silico interaction with cypermethrin were checked. 3,3'-Diaminobenzidine-enhanced Perl's staining showed an elevated number of iron-positive cells in the SN of cypermethrin-treated rats. Molecular docking studies revealed a strong binding affinity between cypermethrin and iron transporter protein receptors of humans and rats. Furthermore, cypermethrin increased the expression of DMT-1 and hepcidin while reducing the expression of transferrin, ceruloplasmin, and ferroportin in the nigrostriatal tissue and human neuroblastoma cells. These observations suggest that cypermethrin alters the expression of iron transporter proteins leading to iron dyshomeostasis, which could contribute to dopaminergic neurotoxicity.

Multifunctional Metallothioneins as a Target for Neuroprotection in Parkinson's Disease

Parkinson's disease (PD) is characterized by motor symptoms based on a loss of nigrostriatal dopaminergic neurons and by non-motor symptoms which precede motor symptoms. Neurodegeneration accompanied by an accumulation of α-synuclein is thought to propagate from the enteric nervous system to the central nervous system. The pathogenesis in sporadic PD remains unknown. However, many reports indicate various etiological factors, such as oxidative stress, inflammation, α-synuclein toxicity and mitochondrial impairment, drive neurodegeneration. Exposure to heavy metals contributes to these etiopathogenesis and increases the risk of developing PD. Metallothioneins (MTs) are cysteine-rich metal-binding proteins; MTs chelate metals and inhibit metal-induced oxidative stress, inflammation and mitochondrial dysfunction. In addition, MTs possess antioxidative properties by scavenging free radicals and exert anti-inflammatory effects by suppression of microglial activation. Furthermore, MTs recently received attention as a potential target for attenuating metal-induced α-synuclein aggregation. In this article, we summarize MTs expression in the central and enteric nervous system, and review protective functions of MTs against etiopathogenesis in PD. We also discuss neuroprotective strategies for the prevention of central dopaminergic and enteric neurodegeneration by targeting MTs. This review highlights multifunctional MTs as a target for the development of disease-modifying drugs for PD.

Heavy metal stabilization remediation in polluted soils with stabilizing materials: a review

The remediation of soil contaminated by heavy metals has long been a concern of academics. This is due to the fact that heavy metals discharged into the environment as a result of natural and anthropogenic activities may have detrimental consequences for human health, the ecological environment, the economy, and society. Metal stabilization has received considerable attention and has shown to be a promising soil remediation option among the several techniques for the remediation of heavy metal-contaminated soils. This review discusses various stabilizing materials, including inorganic materials like clay minerals, phosphorus-containing materials, calcium silicon materials, metals, and metal oxides, as well as organic materials like manure, municipal solid waste, and biochar, for the remediation of heavy metal-contaminated soils. Through diverse remediation processes such as adsorption, complexation, precipitation, and redox reactions, these additives efficiently limit the biological effectiveness of heavy metals in soils. It should also be emphasized that the effectiveness of metal stabilization is influenced by soil pH, organic matter content, amendment type and dosage, heavy metal species and contamination level, and plant variety. Furthermore, a comprehensive overview of the methods for evaluating the effectiveness of heavy metal stabilization based on soil physicochemical properties, heavy metal morphology, and bioactivity has also been provided. At the same time, it is critical to assess the stability and timeliness of the heavy metals' long-term remedial effect. Finally, the priority should be on developing novel, efficient, environmentally friendly, and economically feasible stabilizing agents, as well as establishing a systematic assessment method and criteria for analyzing their long-term effects.

PCBP-1 Regulates the Transcription and Alternative Splicing of Inflammation and Ubiquitination-Related Genes in PC12 Cell

PCBP-1, a multifunctional RNA binding protein, is expressed in various human cell/tissue types and involved in post-transcriptional gene regulation. PCBP-1 has important roles in cellular Iron homeostasis, mitochondrial stability, and other cellular activities involved in the pathophysiological process of neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD). However, it remains enigmatic whether PCPB-1 is associated with the pathogenesis of PD. In this study, we cloned and constitutively overexpressed PCBP-1 in rat PC12 cells (PC12 cell is the common cell line studying neurodegenerative disease include PD). RNA-seq was performed to analyze PCBP-1-regulated differentially expressed genes (DEGs) and alternative splicing events (ASEs) between control and PCBP1-overexpressed cells. GO and KEGG pathway analyses were performed to identify functional DEGs and alternatively spliced genes. Consequently, we validated PCBP-1-regulated genes using RT-qPCR. Finally, we downloaded CLIP-seq data from GEO (GSE84700) to analyze the mechanisms of PCBP-1's regulation of gene expression and ASEs by revealing the binding profile of PCBP-1 on its target pre-mRNAs. Overexpression of PCBP-1 partially regulated the ASE and expression of genes enriched in neuroinflammation and protein ubiquitination, which were also associated with PD pathogenesis. Moreover, RT-qPCR assay verified the PCBP-1-modulated expression of neuroinflammatory genes, like LCN-2, and alternative splicing (AS) of ubiquitination-related gene WWP-2. Finally, CLIP-seq data analysis indicated that the first UC motif was the critical site for PCBP-1 binding to its targets. In this study, we provided evidence that PCBP-1 could regulate the expression of LCN-2 gene expression associated with neuroinflammation and AS of WWP-2 in relation to protein ubiquitination. These findings thus provided novel insights into the potential application of PCBP-1 as the disease pathophysiological or therapeutic target for neurodegenerative disease.

Investigating the Convergent Mechanisms between Major Depressive Disorder and Parkinson's Disease

Major depressive disorder (MDD) affects more than cognition, having a temporal relationship with neuroinflammatory pathways of Parkinson's disease (PD). Although this association is supported by epidemiological and clinical studies, the underlying mechanisms are unclear. Microglia and astrocytes play crucial roles in the pathophysiology of both MDD and PD. In PD, these cells can be activated by misfolded forms of the protein α-synuclein to release cytokines that can interact with multiple different physiological processes to produce depressive symptoms, including monoamine transport and availability, the hypothalamus-pituitary axis, and neurogenesis. In MDD, glial cell activation can be induced by peripheral inflammatory agents that cross the blood-brain barrier and/or c-Fos signalling from neurons. The resulting neuroinflammation can cause neurodegeneration due to oxidative stress and glutamate excitotoxicity, contributing to PD pathology. Astrocytes are another major link due to their recognized role in the glymphatic clearance mechanism. Research suggesting that MDD causes astrocytic destruction or structural atrophy highlights the possibility that accumulation of α-synuclein in the brain is facilitated as the brain cannot adequately clear the protein aggregates. This review examines research into the overlapping pathophysiology of MDD and PD with particular focus on the roles of glial cells and neuroinflammation.

Metals and Metal-Nanoparticles in Human Pathologies: From Exposure to Therapy

An increasing number of pathologies correlates with both toxic and essential metal ions dyshomeostasis. Next to known genetic disorders (e.g., Wilson's Disease and β-Thalassemia) other pathological states such as neurodegeneration and diabetes are characterized by an imbalance of essential metal ions. Metal ions can enter the human body from the surrounding environment in the form of free metal ions or metal-nanoparticles, and successively translocate to different tissues, where they are accumulated and develop distinct pathologies. There are no characteristic symptoms of metal intoxication, and the exact diagnosis is still difficult. In this review, we present metal-related pathologies with the most common onsets, biomarkers of metal intoxication, and proper techniques of metal qualitative and quantitative analysis. We discuss the possible role of drugs with metal-chelating ability in metal dyshomeostasis, and present recent advances in therapies of metal-related diseases.

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.

Pathogenic mechanism and modeling of neuroferritinopathy

Neuroferritinopathy is a rare autosomal dominant inherited movement disorder caused by alteration of the L-ferritin gene that results in the production of a ferritin molecule that is unable to properly manage iron, leading to the presence of free redox-active iron in the cytosol. This form of iron has detrimental effects on cells, particularly severe for neuronal cells, which are highly sensitive to oxidative stress. Although very rare, the disorder is notable for two reasons. First, neuroferritinopathy displays features also found in a larger group of disorders named Neurodegeneration with Brain Iron Accumulation (NBIA), such as iron deposition in the basal ganglia and extrapyramidal symptoms; thus, the elucidation of its pathogenic mechanism may contribute to clarifying the incompletely understood aspects of NBIA. Second, neuroferritinopathy shows the characteristic signs of an accelerated process of aging; thus, it can be considered an interesting model to study the progress of aging. Here, we will review the clinical and neurological features of neuroferritinopathy and summarize biochemical studies and data from cellular and animal models to propose a pathogenic mechanism of the disorder.

NEUROTOXICITY OF METAL MIXTURES

Environmental exposures and/or alterations in the homeostasis of essential transition metals (ETM), such as Fe, Cu, Zn or Mn, are known to contribute to neurodegenerative diseases (ND), such as Alzheimer's Disease (AD) and Parkinson's Disease (PD). Aberrant ETM homeostasis leads to altered distributions, as significant amounts may accumulate in specific brain areas, while causing metal deficiency in others. The disruption of processes reliant on the interplay between these ETM, may lead to loss of metal balance and the ensuing neurotoxicity via shared mechanisms, such as the induction of oxidative stress (OS). Both ETM imbalance and OS may play a role, via complex positive loop processes, in primary neuropathological signatures of AD, such as the accumulation of amyloid plaques and neurofibrillary tangles (NTF), and in PD, α-Syn aggregation and loss of dopamine(DA)rgic neurons. The association between ETM imbalance and ND is rarely approached under the view that metals such as Fe, Cu, Zn and Mn, can act as dangerous endogenous neurotoxic mixtures when their control mechanisms became disrupted. In fact, their presence as mixtures implies intricacies, which should be kept in mind when developing therapies for complex disorders of metal dyshomeostasis, which commonly occur in ND.

Neuron-Astrocyte Interactions in Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease. PD patients exhibit motor symptoms such as akinesia/bradykinesia, tremor, rigidity, and postural instability due to a loss of nigrostriatal dopaminergic neurons. Although the pathogenesis in sporadic PD remains unknown, there is a consensus on the involvement of non-neuronal cells in the progression of PD pathology. Astrocytes are the most numerous glial cells in the central nervous system. Normally, astrocytes protect neurons by releasing neurotrophic factors, producing antioxidants, and disposing of neuronal waste products. However, in pathological situations, astrocytes are known to produce inflammatory cytokines. In addition, various studies have reported that astrocyte dysfunction also leads to neurodegeneration in PD. In this article, we summarize the interaction of astrocytes and dopaminergic neurons, review the pathogenic role of astrocytes in PD, and discuss therapeutic strategies for the prevention of dopaminergic neurodegeneration. This review highlights neuron-astrocyte interaction as a target for the development of disease-modifying drugs for PD in the future.

Systematic Surveys of Iron Homeostasis Mechanisms Reveal Ferritin Superfamily and Nucleotide Surveillance Regulation to be Modified by PINK1 Absence

Iron deprivation activates mitophagy and extends lifespan in nematodes. In patients suffering from Parkinson’s disease (PD), PINK1-PRKN mutations via deficient mitophagy trigger iron accumulation and reduce lifespan. To evaluate molecular effects of iron chelator drugs as a potential PD therapy, we assessed fibroblasts by global proteome profiles and targeted transcript analyses. In mouse cells, iron shortage decreased protein abundance for iron-binding nucleotide metabolism enzymes (prominently XDH and ferritin homolog RRM2). It also decreased the expression of factors with a role for nucleotide surveillance, which associate with iron-sulfur-clusters (ISC), and are important for growth and survival. This widespread effect included prominently Nthl1-Ppat-Bdh2, but also mitochondrial Glrx5-Nfu1-Bola1, cytosolic Aco1-Abce1-Tyw5, and nuclear Dna2-Elp3-Pold1-Prim2. Incidentally, upregulated Pink1-Prkn levels explained mitophagy induction, the downregulated expression of Slc25a28 suggested it to function in iron export. The impact of PINK1 mutations in mouse and patient cells was pronounced only after iron overload, causing hyperreactive expression of ribosomal surveillance factor Abce1 and of ferritin, despite ferritin translation being repressed by IRP1. This misregulation might be explained by the deficiency of the ISC-biogenesis factor GLRX5. Our systematic survey suggests mitochondrial ISC-biogenesis and post-transcriptional iron regulation to be important in the decision, whether organisms undergo PD pathogenesis or healthy aging.

Membrane insertion exacerbates the α-Synuclein-Cu(II) dopamine oxidase activity: Metallothionein-3 targets and silences all α-synuclein-Cu(II) complexes

Copper binding to α-synuclein (α-Syn), the major component of intracellular Lewy body inclusions in substantia nigra dopaminergic neurons, potentiate its toxic redox-reactivity and plays a detrimental role in the etiology of Parkinson disease (PD). Soluble α-synuclein-Cu(II) complexes possess dopamine oxidase activity and catalyze ROS production in the presence of biological reducing agents via Cu(II)/Cu(I) redox cycling. These metal-centered redox reactivities harmfully promote the oxidation and oligomerization of α-Syn. While this chemistry has been investigated on recombinantly expressed soluble α-Syn, in vivo, α-Syn is acetylated at its N-terminus and is present in equilibrium between soluble and membrane-bound forms. This post-translational modification and membrane-binding alter the Cu(II) coordination environment and binding modes and are expected to affect the α-Syn-Cu(II) reactivity. In this work, we first investigated the reactivity of acetylated and membrane-bound complexes, and subsequently addressed whether the brain metalloprotein Zn₇-metallothionein-3 (Zn₇MT-3) possesses a multifaceted-role in targeting these aberrant copper interactions and consequent reactivity. Through biochemical characterization of the reactivity of the non-acetylated/N-terminally acetylated soluble or membrane-bound α-Syn-Cu(II) complexes towards dopamine, oxygen, and ascorbate, we reveal that membrane insertion dramatically exacerbates the catechol oxidase-like reactivity of α-Syn-Cu(II) as a result of a change in the Cu(II) coordination environment, thereby potentiating its toxicity. Moreover, we show that Zn₇MT-3 can efficiently target all α-Syn-Cu(II) complexes through Cu(II) removal, preventing their deleterious redox activities. We demonstrate that the Cu(II) reduction by the thiolate ligands of Zn₇MT-3 and the formation of Cu(I)₄Zn₄MT-3 featuring an unusual redox-inert Cu(I)₄-thiolate cluster is the molecular mechanism responsible for the protective effect exerted by MT-3 towards α-Syn-Cu(II). This work provides the molecular basis for new therapeutic interventions to control the deleterious bioinorganic chemistry of α-Syn-Cu(II).

A Multi-Scale Computational Model of Excitotoxic Loss of Dopaminergic Cells in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder caused by loss of dopaminergic neurons in substantia nigra pars compacta (SNc). Although the exact cause of cell death is not clear, the hypothesis that metabolic deficiency is a key factor has been gaining attention in recent years. In the present study, we investigated this hypothesis using a multi-scale computational model of the subsystem of the basal ganglia comprising the subthalamic nucleus (STN), globus pallidus externa (GPe), and SNc. The proposed model is a multiscale model in that interaction among the three nuclei are simulated using more abstract Izhikevich neuron models, while the molecular pathways involved in cell death of SNc neurons are simulated in terms of detailed chemical kinetics. Simulation results obtained from the proposed model showed that energy deficiencies occurring at cellular and network levels could precipitate the excitotoxic loss of SNc neurons in PD. At the subcellular level, the models show how calcium elevation leads to apoptosis of SNc neurons. The therapeutic effects of several neuroprotective interventions are also simulated in the model. From neuroprotective studies, it was clear that glutamate inhibition and apoptotic signal blocker therapies were able to halt the progression of SNc cell loss when compared to other therapeutic interventions, which only slowed down the progression of SNc cell loss.

The relationships of vitamin D, vitamin D receptor gene polymorphisms, and vitamin D supplementation with Parkinson's disease

In recent years, many studies have investigated the correlations between Parkinson's disease (PD) and vitamin D status, but the conclusion remains elusive. The present review focuses on the associations between PD and serum vitamin D levels by reviewing studies on the associations of PD with serum vitamin D levels and vitamin D receptor (VDR) gene polymorphisms from PubMed, Web of Science, Cochrane Library, and Embase databases. We found that PD patients have lower vitamin D levels than healthy controls and that the vitamin D concentrations are negatively correlated with PD risk and severity. Furthermore, higher vitamin D concentrations are linked to better cognitive function and mood in PD patients. Findings on the relationship between VDR gene polymorphisms and the risk of PD are inconsistent, but the FokI (C/T) polymorphism is significantly linked with PD. The occurrence of FokI (C/T) gene polymorphism may influence the risk, severity, and cognitive ability of PD patients, while also possibly influencing the effect of Vitamin D3 supplementation in PD patients. In view of the neuroprotective effects of vitamin D and the close association between vitamin D and dopaminergic neurotransmission, interventional prospective studies on vitamin D supplementation in PD patients should be conducted in the future.

Differential effects of Cu2+ and Fe3+ ions on in vitro amyloid formation of biologically-relevant α-synuclein variants

Alterations in metal ion homeostasis appear coupled to neurodegenerative disorders but mechanisms are unknown. Amyloid formation of the protein α-synuclein in brain cells is a hallmark of Parkinson's disease. α-Synuclein can bind several metal ions in vitro and such interactions may affect the assembly process. Here we used biophysical methods to study the effects of micromolar concentrations of Cu²⁺ and Fe³⁺ ions on amyloid formation of selected α-synuclein variants (wild-type and A53T α-synuclein, in normal and N-terminally acetylated forms). As shown previously, Cu²⁺ speeds up aggregation of normal wild-type α-synuclein, but not the acetylated form. However, Cu²⁺ has a minimal effect on (the faster) aggregation of normal A53T α-synuclein, despite that Cu²⁺ binds to this variant. Like Cu²⁺, Fe³⁺ speeds up aggregation of non-acetylated wild-type α-synuclein, but with acetylation, Fe³⁺ instead slows down aggregation. In contrast, for A53T α-synuclein, regardless of acetylation, Fe³⁺ slows down aggregation with the effect being most dramatic for acetylated A53T α-synuclein. The results presented here suggest a correlation between metal-ion modulation effect and intrinsic aggregation speed of the various α-synuclein variants.

Genetic Disorders Associated with Metal Metabolism

Genetic disorders associated with metal metabolism form a large group of disorders and mostly result from defects in the proteins/enzymes involved in nutrient metabolism and energy production. These defects can affect different metabolic pathways and cause mild to severe disorders related to metal metabolism. Some disorders have moderate to severe clinical consequences. In severe cases, these elements accumulate in different tissues and organs, particularly the brain. As they are toxic and interfere with normal biological functions, the severity of the disorder increases. However, the human body requires a very small amount of these elements, and a deficiency of or increase in these elements can cause different genetic disorders to occur. Some of the metals discussed in the present review are copper, iron, manganese, zinc, and selenium. These elements may play a key role in the pathology and physiology of the nervous system.

Stem Cell Modeling of Neuroferritinopathy Reveals Iron as a Determinant of Senescence and Ferroptosis during Neuronal Aging

Neuroferritinopathy (NF) is a movement disorder caused by alterations in the L-ferritin gene that generate cytosolic free iron. NF is a unique pathophysiological model for determining the direct consequences of cell iron dysregulation. We established lines of induced pluripotent stem cells from fibroblasts from two NF patients and one isogenic control obtained by CRISPR/Cas9 technology. NF fibroblasts, neural progenitors, and neurons exhibited the presence of increased cytosolic iron, which was also detectable as: ferritin aggregates, alterations in the iron parameters, oxidative damage, and the onset of a senescence phenotype, particularly severe in the neurons. In this spontaneous senescence model, NF cells had impaired survival and died by ferroptosis. Thus, non-ferritin-bound iron is sufficient per se to cause both cell senescence and ferroptotic cell death in human fibroblasts and neurons. These results provide strong evidence supporting the primary role of iron in neuronal aging and degeneration.

Emerging Approaches to Investigate the Influence of Transition Metals in the Proteinopathies

Transition metals have essential roles in brain structure and function, and are associated with pathological processes in neurodegenerative disorders classed as proteinopathies. Synchrotron X-ray techniques, coupled with ultrahigh-resolution mass spectrometry, have been applied to study iron and copper interactions with amyloid β (1–42) or α-synuclein. Ex vivo tissue and in vitro systems were investigated, showing the capability to identify metal oxidation states, probe local chemical environments, and localize metal-peptide binding sites. Synchrotron experiments showed that the chemical reduction of ferric (Fe³⁺) iron and cupric (Cu²⁺) copper can occur in vitro after incubating each metal in the presence of Aβ for one week, and to a lesser extent for ferric iron incubated with α-syn. Nanoscale chemical speciation mapping of Aβ-Fe complexes revealed a spatial heterogeneity in chemical reduction of iron within individual aggregates. Mass spectrometry allowed the determination of the highest-affinity binding region in all four metal-biomolecule complexes. Iron and copper were coordinated by the same N-terminal region of Aβ, likely through histidine residues. Fe³⁺ bound to a C-terminal region of α-syn, rich in aspartic and glutamic acid residues, and Cu²⁺ to the N-terminal region of α-syn. Elucidating the biochemistry of these metal-biomolecule complexes and identifying drivers of chemical reduction processes for which there is evidence ex-vivo, are critical to the advanced understanding of disease aetiology.

Intracellular and Intercellular Mitochondrial Dynamics in Parkinson's Disease

The appearance of alpha-synuclein-positive inclusion bodies (Lewy bodies) and the loss of catecholaminergic neurons are the primary pathological hallmarks of Parkinson's disease (PD). However, the dysfunction of mitochondria has long been recognized as a key component in the progression of the disease. Dysfunctional mitochondria can in turn lead to dysregulation of calcium homeostasis and, especially in dopaminergic neurons, raised mean intracellular calcium concentration. As calcium binding to alpha-synuclein is one of the important triggers of alpha-synuclein aggregation, mitochondrial dysfunction will promote inclusion body formation and disease progression. Increased reactive oxygen species (ROS) resulting from inefficiencies in the electron transport chain also contribute to the formation of alpha-synuclein aggregates and neuronal loss. Recent studies have also highlighted defects in mitochondrial clearance that lead to the accumulation of depolarized mitochondria. Transaxonal and intracytoplasmic translocation of mitochondria along the microtubule cytoskeleton may also be affected in diseased neurons. Furthermore, nanotube-mediated intercellular transfer of mitochondria has recently been reported between different cell types and may have relevance to the spread of PD pathology between adjacent brain regions. In the current review, the contributions of both intracellular and intercellular mitochondrial dynamics to the etiology of PD will be discussed.

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.