Metals in ALS TDP-43 Pathology

Which Environmental Pollutants Are Toxic to Our Ears?-Evidence of the Ototoxicity of Common Substances

Ototoxicity refers to the adverse effects of substances on auditory or vestibular functions. This study examines the evidence of ototoxicity's association with exposure to common environmental pollutants, as documented in toxicological profiles by the Agency for Toxic Substances and Disease Registry. Our aim was to evaluate whether the evidence supports modifying the charting of ototoxic effects in the summary tables of these toxicological profiles and providing a guide for scientists to access these data. Health outcomes of interest included hearing loss, vestibular effects, cochlear lesions, tonal alterations, cellular damage, and ototoxicity-related outcomes (neurological, nephrotoxic, hepatic, and developmental effects). We obtained ototoxicity information for 62 substances. Hearing-related effects were reported, along with neurological effects. Overall, 26 profiles reported strong evidence of ototoxicity, including 13 substances previously designated as ototoxic by other health and safety agencies. Commonly studied outcomes included hearing loss, damage to ear anatomy, and auditory dysfunction. Vestibular dysfunction and tinnitus are rarely studied. Our findings highlight the lack of conclusive evidence of ototoxic properties for many substances, especially for pesticides and herbicides. This review supports charting the evidence of ototoxicity separately in toxicological profiles' summary tables. Improving the communication of ototoxicity-related health effects might impact their recognition and prompt further research. A stronger evidence base could support improved prevention efforts in terms of serious health outcomes.

Hereditary Transthyretin Amyloidosis (hATTR) with Polyneuropathy Clusters Are Located in Ancient Mining Districts: A Possible Geochemical Origin of the Disease

Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy (FAP)) is an endemic amyloidosis involving the harmful aggregation of proteins, most commonly transthyretin (TTR) but sometimes also apolipoprotein A-1 or gelsolin. hATTR appears to be transmitted as an autosomal dominant trait. Over 100 point mutations have been identified, with the Val30Met substitution being the most common. Yet, the mechanism of pathogenesis and the overall origin of hATTR remain unclear. Here, we argue that hATTR could be related to harmful metal exposure. hATTR incidence is unevenly distributed globally, and the three largest defined clusters exist in Japan, Portugal, and Sweden. All three disease regions are also ancient mining districts with associated metal contamination of the local environment. There are two main mechanisms for how harmful metals, after uptake into tissues and body fluids, could induce hATTR. First, the metals could directly influence the expression, function, and/or aggregation of the proteins involved in hATTR pathology. Such metal-protein interactions might constitute molecular targets for anti-hATTR drug design. Second, metal exposure could induce hATTR -associated genetic mutations, which may have happened several generations ago. These two mechanisms can occur in parallel. In conclusion, the possibility that hATTR could be related to metal exposure in geochemically defined regions deserves further attention.

Glycyl-l-histidyl-l-lysine prevents copper- and zinc-induced protein aggregation and central nervous system cell death in vitro

Common features of neurodegenerative diseases are oxidative and inflammatory imbalances as well as the misfolding of proteins. An excess of free metal ions can be pathological and contribute to cell death, but only copper and zinc strongly promote protein aggregation. Herein we demonstrate that the endogenous copper-binding tripeptide glycyl-l-histidyl-l-lysine (GHK) has the ability to bind to and reduce copper redox activity and to prevent copper- and zinc-induced cell death in vitro. In addition, GHK prevents copper- and zinc-induced bovine serum albumin aggregation and reverses aggregation through resolubilizing the protein. We further demonstrate the enhanced toxicity of copper during inflammation and the ability of GHK to attenuate this toxicity. Finally, we investigated the effects of copper on enhancing paraquat toxicity and report a protective effect of GHK. We therefore conclude that GHK has potential as a cytoprotective compound with regard to copper and zinc toxicity, with positive effects on protein solubility and aggregation that warrant further investigation in the treatment of neurodegenerative diseases.

Trace Elements in Alzheimer's Disease and Dementia: The Current State of Knowledge

Changes in trace element concentrations are being wildly considered when it comes to neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease. This study aims to present the role that trace elements play in the central nervous system. Moreover, we reviewed the mechanisms involved in their neurotoxicity. Low zinc concentrations, as well as high levels of copper, manganese, and iron, activate the signalling pathways of the inflammatory, oxidative and nitrosative stress response. Neurodegeneration occurs due to the association between metals and proteins, which is then followed by aggregate formation, mitochondrial disorder, and, ultimately, cell death. In Alzheimer's disease, low Zn levels suppress the neurotoxicity induced by β-amyloid through the selective precipitation of aggregation intermediates. High concentrations of copper, iron and manganese cause the aggregation of intracellular α-synuclein, which results in synaptic dysfunction and axonal transport disruption. Parkinson's disease is caused by the accumulation of Fe in the midbrain dopaminergic nucleus, and the pathogenesis of multiple sclerosis derives from Zn deficiency, leading to an imbalance between T cell functions. Aluminium disturbs the homeostasis of other metals through a rise in the production of oxygen reactive forms, which then leads to cellular death. Selenium, in association with iron, plays a distinct role in the process of ferroptosis. Outlining the influence that metals have on oxidoreduction processes is crucial to recognising the pathophysiology of neurodegenerative diseases and may provide possible new methods for both their avoidance and therapy.

Consequences of Disturbing Manganese Homeostasis

Manganese (Mn) is an essential trace element with unique functions in the body; it acts as a cofactor for many enzymes involved in energy metabolism, the endogenous antioxidant enzyme systems, neurotransmitter production, and the regulation of reproductive hormones. However, overexposure to Mn is toxic, particularly to the central nervous system (CNS) due to it causing the progressive destruction of nerve cells. Exposure to manganese is widespread and occurs by inhalation, ingestion, or dermal contact. Associations have been observed between Mn accumulation and neurodegenerative diseases such as manganism, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. People with genetic diseases associated with a mutation in the gene associated with impaired Mn excretion, kidney disease, iron deficiency, or a vegetarian diet are at particular risk of excessive exposure to Mn. This review has collected data on the current knowledge of the source of Mn exposure, the experimental data supporting the dispersive accumulation of Mn in the brain, the controversies surrounding the reference values of biomarkers related to Mn status in different matrices, and the competitiveness of Mn with other metals, such as iron (Fe), magnesium (Mg), zinc (Zn), copper (Cu), lead (Pb), calcium (Ca). The disturbed homeostasis of Mn in the body has been connected with susceptibility to neurodegenerative diseases, fertility, and infectious diseases. The current evidence on the involvement of Mn in metabolic diseases, such as type 2 diabetes mellitus/insulin resistance, osteoporosis, obesity, atherosclerosis, and non-alcoholic fatty liver disease, was collected and discussed.

The amyotrophic lateral sclerosis exposome: recent advances and future directions

Amyotrophic lateral sclerosis (ALS) is a fatal disease of motor neuron degeneration with typical survival of only 2-5 years from diagnosis. The causes of ALS are multifactorial: known genetic mutations account for only around 70% of cases of familial ALS and 15% of sporadic cases, and heritability estimates range from 8% to 61%, indicating additional causes beyond genetics. Consequently, interest has grown in environmental contributions to ALS risk and progression. The gene-time-environment hypothesis posits that ALS onset occurs through an interaction of genes with environmental exposures during ageing. An alternative hypothesis, the multistep model of ALS, suggests that several hits, at least some of which could be environmental, are required to trigger disease onset, even in the presence of highly penetrant ALS-associated mutations. Studies have sought to characterize the ALS exposome - the lifetime accumulation of environmental exposures that increase disease risk and affect progression. Identifying the full scope of environmental toxicants that enhance ALS risk raises the prospect of preventing disease by eliminating or mitigating exposures. In this Review, we summarize the evidence for an ALS exposome, discussing the strengths and limitations of epidemiological studies that have identified contributions from various sources. We also consider potential mechanisms of exposure-mediated toxicity and suggest future directions for ALS exposome research.

Prion Protein Octarepeat Domain Forms Transient β-Sheet Structures upon Residue-Specific Binding to Cu(II) and Zn(II) Ions

Misfolding of the cellular prion protein (PrP^C) is associated with the development of fatal neurodegenerative diseases called transmissible spongiform encephalopathies (TSEs). Metal ions appear to play a crucial role in PrP^C misfolding. PrP^C is a combined Cu(II) and Zn(II) metal-binding protein, where the main metal-binding site is located in the octarepeat (OR) region. Thus, the biological function of PrP^C may involve the transport of divalent metal ions across membranes or buffering concentrations of divalent metal ions in the synaptic cleft. Recent studies have shown that an excess of Cu(II) ions can result in PrP^C instability, oligomerization, and/or neuroinflammation. Here, we have used biophysical methods to characterize Cu(II) and Zn(II) binding to the isolated OR region of PrP^C. Circular dichroism (CD) spectroscopy data suggest that the OR domain binds up to four Cu(II) ions or two Zn(II) ions. Binding of the first metal ion results in a structural transition from the polyproline II helix to the β-turn structure, while the binding of additional metal ions induces the formation of β-sheet structures. Fluorescence spectroscopy data indicate that the OR region can bind both Cu(II) and Zn(II) ions at neutral pH, but under acidic conditions, it binds only Cu(II) ions. Molecular dynamics simulations suggest that binding of either metal ion to the OR region results in the formation of β-hairpin structures. As the formation of β-sheet structures can be a first step toward amyloid formation, we propose that high concentrations of either Cu(II) or Zn(II) ions may have a pro-amyloid effect in TSE diseases.

Amyotrophic Lateral Sclerosis and Air Pollutants in the Province of Ferrara, Northern Italy: An Ecological Study

The etiopathogenesis of amyotrophic lateral sclerosis (ALS) is still largely unknown, but likely depends on gene-environment interactions. Among the putative sources of environmental exposure are air pollutants and especially heavy metals. We aimed to investigate the relationship between ALS density and the concentration of air pollution heavy metals in Ferrara, northern Italy. An ecological study was designed to correlate the map of ALS distribution and that of air pollutants. All ALS cases diagnosed between 2000 and 2017 (Ferrara University Hospital administrative data) were plotted by residency in 100 sub-areas, and grouped in 4 sectors: urban, rural, northwestern and along the motorway. The concentrations of silver, aluminium, cadmium, chrome, copper, iron, manganese, lead, and selenium in moss and lichens were measured and monitored in 2006 and 2011. Based on 62 ALS patients, a strong and direct correlation of ALS density was observed only with copper concentrations in all sectors and in both sexes (Pearson coefficient (ρ) = 0.758; p = 0.000002). The correlation was higher in the urban sector (ρ = 0.767; p = 0.000128), in women for the overall population (ρ = 0.782, p = 0.000028) and in the urban (ρ = 0.872, p = 0.000047) population, and for the older cohort of diagnosed patients (2000-2009) the assessment correlated with the first assessment of air pollutants in 2006 (ρ = 0.724, p = 0.008). Our data is, in part, consistent with a hypothesis linking copper pollution to ALS.

Shapeshifter TDP-43: Molecular mechanism of structural polymorphism, aggregation, phase separation and their modulators

TDP-43 is a nucleic acid-binding protein that performs physiologically essential functions and is known to undergo phase separation and aggregation during stress. Initial observations have shown that TDP-43 forms heterogeneous assemblies, including monomer, dimer, oligomers, aggregates, phase-separated assemblies, etc. However, the significance of each assembly of TDP-43 concerning its function, phase separation, and aggregation is poorly known. Furthermore, how different assemblies of TDP-43 are related to each other is unclear. In this review, we focus on the various assemblies of TDP-43 and discuss the plausible origin of the structural heterogeneity of TDP-43. TDP-43 is involved in multiple physiological processes like phase separation, aggregation, prion-like seeding, and performing physiological functions. However, the molecular mechanism behind the physiological process performed by TDP-43 is not well understood. The current review discusses the plausible molecular mechanism of phase separation, aggregation, and prion-like propagation of TDP-43.

Metal ratios as possible biomarkers for amyotrophic lateral sclerosis

BACKGROUND AND OBJECTIVES

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with unknown aetiology. Metals have been suspected to contribute to ALS pathogenesis since mid-19th century, yet studies on measured metal concentrations in ALS patients have often yielded conflicting results, with large individual variation in measured values. Calculating metal concentration ratios can unveil possible synergistic effects of neurotoxic metals in ALS pathogenesis. The aim of this study was to investigate if ratios of different metal concentrations in cerebrospinal fluid (CSF) and blood plasma, respectively, differ between ALS patients and healthy controls.

METHODS

Cerebrospinal fluid and blood plasma were collected from 17 ALS patients and 10 controls. Samples were analysed for 22 metals by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS), and all possible 231 metal ratios calculated in each body fluid.

RESULTS

Fifty-three metal ratios were significantly elevated in ALS cases as compared to controls (p < 0.05); five in blood plasma, and 48 in CSF. The finding of fewer elevated ratios in blood plasma may indicate specific transport of metals into the central nervous system. The elevated metal ratios in CSF include Cd/Se (p = 0.031), and 16 ratios with magnesium, such as Mn/Mg (p = 0.005) and Al/Mg (p = 0.014).

CONCLUSION

Metal ratios may be used as biomarkers in ALS diagnosis and as guidelines for preventive measures.

Risk factors of amyotrophic lateral sclerosis: a global meta-summary

Background

The etiology of amyotrophic lateral sclerosis (ALS) remains largely unknown. This study aimed to summarize the relationship between ALS and its genetic and non-genetic risk factors.

Method

A search of relevant literature from PubMed, Embase, and Cochrane Database from inception to December 2022 was performed. Random-effects or fixed-effects models were performed by Stata MP 15.0 to pool multivariate or adjusted ratios (OR). PROSPERO registration number: CRD42022301549.

Results

230 eligible studies were included, of which 67 involved 22 non-genetic factors, and 163 involved genetic factors. Four aspects of non-genetic factors, including lifestyle, environmental and occupational exposures, pre-existing diseases/comorbidity and medical exposures, and others, were analyzed. Exposure to heavy metals (OR = 1.79), pesticides (OR = 1.46), solvents (OR = 1.37), previous head trauma (OR = 1.37), military service (OR = 1.29), stroke (OR = 1.26), magnetic field (OR = 1.22) and hypertension (OR = 1.04) are significant risk factors, but use of antidiabetics (OR = 0.52), high BMI (OR = 0.60 for obese and overweight vs. normal and underweight), living in urban (OR = 0.70), diabetes mellitus (OR = 0.83), and kidney disease (OR = 0.84) decrease the risk for ALS. In addition, eight common ALS-related genes were evaluated, the mutation frequencies of these genes were ranked from highest to lowest as SOD1 (2.2%), C9orf72 (2.1%), ATXN2 (1.7%), FUS (1.7%), TARDBP (0.8%), VCP (0.6%), UBQLN2(0.6%) and SQSTM1 (0.6%) in all the ALS patients.

Conclusions

Our findings suggested that effective intervention for risk exposure and timely modification of lifestyle might prevent the occurrence of ALS. Genetic mutations are important risk factors for ALS and it is essential to detect genetic mutations correctly and scientifically.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=301549, identifier: CRD42022301549.

Studying Peptide-Metal Ion Complex Structures by Solution-State NMR

Metal chelation can provide structural stability and form reactive centers in metalloproteins. Approximately one third of known protein structures are metalloproteins, and metal binding, or the lack thereof, is often implicated in disease, making it necessary to be able to study these systems in detail. Peptide-metal complexes are both present in nature and can provide a means to focus on the binding region of a protein and control experimental variables to a high degree. Structural studies of peptide complexes with metal ions by nuclear magnetic resonance (NMR) were surveyed for all the essential metal complexes and many non-essential metal complexes. The various methods used to study each metal ion are presented together with examples of recent research. Many of these metal systems have been individually reviewed and this current overview of NMR studies of metallopeptide complexes aims to provide a basis for inspiration from structural studies and methodology applied in the field.

Effect of alpha-mangostin in the prevention of behavioural and neurochemical defects in methylmercury-induced neurotoxicity in experimental rats

Methylmercury (MeHg+) is a known neurotoxin that causes progressive motor neuron degeneration in the central nervous system. Axonal degeneration, oligodendrocyte degeneration, and myelin basic protein (MBP) deficits are among the neuropathological abnormalities caused by MeHg+ in amyotrophic lateral sclerosis (ALS). This results in demyelination and motor neuron death in both humans and animals. Previous experimental studies have confirmed that overexpression of the extracellular signalling regulated kinase (ERK1/2) signalling contributes to glutamate excitotoxicity, inflammatory response of microglial cells, and oligodendrocyte (OL) dysfunction that promotes myelin loss. Alpha-mangostin (AMG), an active ingredient obtained from the tree "Garcinia mangostana Linn," has been used in experimental animals to treat a variety of brain disorders, including Parkinson's and Huntington's disease memory impairment, Alzheimer's disease, and schizophrenia, including Parkinson's disease and Huntington's disease memory impairment, Alzheimer's disease, and schizophrenia. AMG has traditionally been used as an antioxidant, anti-inflammatory, and neuroprotective agent.Accordingly, we investigated the therapeutic potential of AMG (100 and 200 mg/kg) in experimental rats with methylmercury (MeHg+)-induced neurotoxicity. The neuroprotective effect of AMG on behavioural, cellular, molecular, and other gross pathological changes, such as histopathological alterations in MeHg+ -treated rat brains, is presented. The neurological behaviour of experimental rats was evaluated using a Morris water maze (MWM), open field test (OFT), grip strength test (GST), and force swim test (FST). In addition, we investigate AMG's neuroprotective effect by restoring MBP levels in cerebral spinal fluid and whole rat brain homogenate. The apoptotic, pro-inflammatory, and oxidative stress markers were measured in rat blood plasma samples and brain homogenate. According to the findings of this study, AMG decreases ERK-1/2 levels and modulates neurochemical alterations in rat brains, minimising MeHg+ -induced neurotoxicity.

Cognitive and Physical Intervention in Metals’ Dysfunction and Neurodegeneration

Metals—especially iron, copper and manganese—are important elements of brain functions and development. Metal-dysregulation homeostasis is associated with brain-structure damage to the motor, cognitive and emotional systems, and leads to neurodegenerative processes. There is more and more evidence that specialized cognitive and motor exercises can enhance brain function and attenuate neurodegeneration in mechanisms, such as improving neuroplasticity by altering the synaptic structure and function in many brain regions. Psychological and physical methods of rehabilitation are now becoming increasingly important, as pharmacological treatments for movement, cognitive and emotional symptoms are limited. The present study describes physical and cognitive rehabilitation methods of patients associated with metal-induced neurotoxicity such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, Huntington’s disease and Wilson’s disease. In our review, we describe physical (e.g., virtual-reality environments, robotic-assists training) and psychological (cognitive training, cognitive stimulation, neuropsychological rehabilitation and cognitive-behavioral and mindfulness-based therapies) methods, significantly improving the quality of life and independence of patients associated with storage diseases. Storage diseases are a diverse group of hereditary metabolic defects characterized by the abnormal cumulation of storage material in cells. This topic is being addressed due to the fact that rehabilitation plays a vital role in the treatment of neurodegenerative diseases. Unfortunately so far there are no specific guidelines concerning physiotherapy in neurodegenerative disorders, especially in regards to duration of exercise, type of exercise and intensity, as well as frequency of exercise. This is in part due to the variety of symptoms of these diseases and the various levels of disease progression. This further proves the need for more research to be carried out on the role of exercise in neurodegenerative disorder treatment.