A low blood copper concentration is a co-morbidity burden factor in Parkinson’s disease development

Homeostasis and metabolism of iron and other metal ions in neurodegenerative diseases

As essential micronutrients, metal ions such as iron, manganese, copper, and zinc, are required for a wide range of physiological processes in the brain. However, an imbalance in metal ions, whether excessive or insufficient, is detrimental and can contribute to neuronal death through oxidative stress, ferroptosis, cuproptosis, cell senescence, or neuroinflammation. These processes have been found to be involved in the pathological mechanisms of neurodegenerative diseases. In this review, the research history and milestone events of studying metal ions, including iron, manganese, copper, and zinc in neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), will be introduced. Then, the upstream regulators, downstream effector, and crosstalk of mental ions under both physiologic and pathologic conditions will be summarized. Finally, the therapeutic effects of metal ion chelators, such as clioquinol, quercetin, curcumin, coumarin, and their derivatives for the treatment of neurodegenerative diseases will be discussed. Additionally, the promising results and limitations observed in clinical trials of these metal ion chelators will also be addressed. This review will not only provide a comprehensive understanding of the role of metal ions in disease development but also offer perspectives on their modulation for the prevention or treatment of neurodegenerative diseases.

Molecular basis of the development of Parkinson's disease

Parkinson's disease is one of the most prevalent neurodegenerative motor disorders worldwide with postural instability, bradykinesia, resting tremor and rigidity being the most common symptoms of the disease. Despite the fact that the molecular mechanisms of Parkinson's disease pathogenesis have already been well described, there is still no coherent picture of the etiopathogenesis of this disease. According to modern concepts, neurodegeneration is induced mainly by oxidative stress, neuroinflammation, dysregulation of cerebral proteostasis, apoptotic dysregulation, and impaired autophagy. This review describes how various factors contribute to neurodegeneration in Parkinson's disease. Understanding the factors affecting fundamental cellular processes and responsible for disease progression may help develop therapeutic strategies to improve the quality of life of patients suffering from the disease. The review also discusses the role of calpains in the development of Parkinson's disease. It is known that α-synuclein is a substrate of calcium-dependent proteases of the calpain family. Truncated forms of α-synuclein are not only involved in the process of formation of the aggregates, but also increase their toxicity.

Associations of Dietary Intakes with Parkinson's Disease: Findings from a Cross-Sectional Study

BACKGROUND

Parkinson's disease (PD) is a chronic progressive neurodegenerative disease, and the exact etiology of PD has not been fully elucidated. Changes in dietary patterns play an important role in the onset and progression of PD. However, the association between specific dietary factors and PD remains unclear.

METHODS

A total of 14,309 subjects from the National Health and Nutrition Examination Survey (NHANES) (2007-2016) were included. Logistic regression was used to analyze the association between 34 nutrients and PD. The regression model was adjusted for potential confounders and effect modifiers including age, gender, race, education, hypertension, and stroke.

RESULTS

The data showed negative associations of the intake of protein (0.99 (0.98, 1.00), p = 0.018), fiber (0.96 (0.93, 0.99), p = 0.003), vitamin E (0.91 (0.86, 0.97), p = 0.005), copper (0.55 (0.36, 0.86), p = 0.009) with PD. Alpha carotene (p = 0.042), beta-carotene (p = 0.006), phosphorus (p = 0.018), magnesium (p = 0.002), sodium (p = 0.035), potassium (p = 0.001) had a potential negative correlation with PD. The intake of carbohydrate, sugars, fat, cholesterol, vitamin A, beta-cryptoxanthin, lycopene, lutein zeaxanthin, vitamin B1, vitamin B2, niacin, vitamin B6, folate, vitamin B12, vitamin C, vitamin D, vitamin K, calcium, iron, zinc, selenium, caffeine, theobromine, alcohol was not associated with PD (p > 0.05).

CONCLUSIONS

Some specific dietary elements are associated with PD, and supplementation of dietary elements may have potentially beneficial effects. However, the observed associations between dietary factors and PD may be influenced by changes in diet resulting from the disease itself, rather than diet influencing PD risk. Further longitudinal studies are needed to establish causal relationships and directionality.

Primary Nucleation of Polymorphic α-Synuclein Dimers Depends on Copper Concentrations and Definite Copper-Binding Site

The primary nucleation process of α-synuclein (AS) that forms toxic oligomeric species is the early stage of the pathological cause of Parkinson's disease. It is well-known that copper influences this primary nucleation process. While significant efforts have been made to solve the structures of polymorphic AS fibrils, the structures of AS oligomers and the copper-bound AS oligomers at the molecular level and the effect of copper concentrations on the primary nucleation are elusive. Here, we propose and demonstrate new molecular mechanism pathways of primary nucleation of AS that are tuned by distinct copper concentrations and by a specific copper-binding site. We present the polymorphic AS dimers bound to different copper-binding sites at the atomic resolution in high- and low-copper concentrations, using extensive molecular dynamics simulations. Our results show the complexity of the primary nucleation pathways that rely on the copper concentrations and the copper binding site. From a broader perspective, our study proposes a new strategy to control the primary nucleation of other toxic amyloid oligomers in other neurodegenerative diseases.

Metals linked with the most prevalent primary neurodegenerative dementias in the elderly: A narrative review

The ageing population has been steadily increasing worldwide, leading to a higher risk of cognitive decline and dementia. Environmental toxicants, particularly metals, have been identified as modifiable risk factors for cognitive impairment. Continuous exposure to metals occurs mainly through dietary sources, with older adults being particularly vulnerable. However, imbalances in the gut microbiota, known as dysbiosis, have also been associated with dementia. A literature review was conducted to explore the potential role of metals in the development of cognitive decline and the most prevalent primary neurodegenerative dementias, as well as their interaction with the gut microbiota. High levels of iron (Fe) and copper (Cu) are associated with mild cognitive impairment (MCI) and Alzheimer's disease (AD), while low selenium (Se) levels are linked to poor cognitive status. Parkinson's disease dementia (PDD) is associated with elevated levels of iron (Fe), manganese (Mn), and zinc (Zn), but the role of copper (Cu) remains unclear. The relationship between metals and Lewy body dementia (LBD) requires further investigation. High aluminium (Al) exposure is associated with frontotemporal dementia (FTD), and elevated selenium (Se) levels may be linked to its onset. Challenges in comparing studies arise from the heterogeneity of metal analysis matrices and analytical techniques, as well as the limitations of small study cohorts. More research is needed to understand the influence of metals on cognition through the gut microbiota (GMB) and its potential relevance in the development of these diseases.

Abnormalities in Copper Status Associated with an Elevated Risk of Parkinson's Phenotype Development

In the last 15 years, among the many reasons given for the development of idiopathic forms of Parkinson's disease (PD), copper imbalance has been identified as a factor, and PD is often referred to as a copper-mediated disorder. More than 640 papers have been devoted to the relationship between PD and copper status in the blood, which include the following markers: total copper concentration, enzymatic ceruloplasmin (Cp) concentration, Cp protein level, and non-ceruloplasmin copper level. Most studies measure only one of these markers. Therefore, the existence of a correlation between copper status and the development of PD is still debated. Based on data from the published literature, meta-analysis, and our own research, it is clear that there is a connection between the development of PD symptoms and the number of copper atoms, which are weakly associated with the ceruloplasmin molecule. In this work, the link between the risk of developing PD and various inborn errors related to copper metabolism, leading to decreased levels of oxidase ceruloplasmin in the circulation and cerebrospinal fluid, is discussed.

Metal Exposure and Risk of Parkinson Disease: A Systematic Review and Meta-Analysis

Metal exposure has been suggested as a possible environmental risk factor for Parkinson disease (PD). We searched the PubMed, EMBASE, and Cochrane databases to systematically review the literature on the relationship between metal exposure and PD risk and to examine the overall quality of each study and the exposure assessment method. A total of 83 case-control studies and 5 cohort studies published during the period 1963-July 2021 were included, of which 73 were graded as being of low or moderate overall quality. Investigators in 69 studies adopted self-reported exposure and biomonitoring after disease diagnosis for exposure assessment approaches. The meta-analyses showed that concentrations of copper and iron in serum and concentrations of zinc in either serum or plasma were lower, while concentrations of magnesium in CSF and zinc in hair were higher, among PD cases as compared with controls. Cumulative lead levels in bone were found to be associated with increased risk of PD. We did not find associations between other metals and PD. The current level of evidence for associations between metals and PD risk is limited, as biases from methodological limitations cannot be ruled out. High-quality studies assessing metal levels before disease onset are needed to improve our understanding of the role of metals in the etiology of PD.

Copper oxide nanoparticles: In vitro and in vivo toxicity, mechanisms of action and factors influencing their toxicology

Copper oxide nanoparticles (CuO NPs) have received increasing interest due to their distinctive properties, including small particle size, high surface area, and reactivity. Due to these properties, their applications have been expanded rapidly in various areas such as biomedical properties, industrial catalysts, gas sensors, electronic materials, and environmental remediation. However, because of these widespread uses, there is now an increased risk of human exposure, which could lead to short- and long-term toxicity. This review addresses the underlying toxicity mechanisms of CuO NPs in cells which include reactive oxygen species generation, leaching of Cu ion, coordination effects, non-homeostasis effect, autophagy, and inflammation. In addition, different key factors responsible for toxicity, characterization, surface modification, dissolution, NPs dose, exposure pathways and environment are discussed to understand the toxicological impact of CuO NPs. In vitro and in vivo studies have shown that CuO NPs cause oxidative stress, cytotoxicity, genotoxicity, immunotoxicity, neurotoxicity, and inflammation in bacterial, algal, fish, rodents, and human cell lines. Therefore, to make CuO NPs a more suitable candidate for various applications, it is essential to address their potential toxic effects, and hence, more studies should be done on the long-term and chronic impacts of CuO NPs at different concentrations to assure the safe usage of CuO NPs.

Microglial Activation in Metal Neurotoxicity: Impact in Neurodegenerative Diseases

Neurodegenerative processes encompass a large variety of diseases with different pathological patterns and clinical features, such as Alzheimer's and Parkinson's diseases. Exposure to metals has been hypothesized to increase oxidative stress in brain cells leading to cell death and neurodegeneration. Neurotoxicity of metals has been demonstrated by several in vitro and in vivo experimental studies, and most probably, each metal has its specific pathway to trigger cell death. As a result, exposure to essential metals, such as manganese, iron, copper, zinc, and cobalt, and nonessential metals, including lead, aluminum, and cadmium, perturbs metal homeostasis at the cellular and organism levels leading to neurodegeneration. In this contribution, a comprehensive review of the molecular mechanisms by which metals affect microglia physiology and signaling properties is presented. Furthermore, studies that validate the disruption of microglia activation pathways as an essential mechanism of metal toxicity that can contribute to neurodegenerative disease are also presented and discussed.

Cu2+ ions modulate the interaction between α-synuclein and lipid membranes

α-synuclein protein aggregates are the major constituent of Lewy bodies, which is a main pathogenic hallmark of Parkinson's disease. Both lipid membranes and Cu²⁺ ions can bind to α-synuclein and modulate its aggregation propensity and toxicity. However, the synergistic effect of copper ions and lipid membranes on α-synuclein remains to be explored. Here, we investigate how Cu²⁺ and α-synuclein simultaneously influence the lipidic structure of lipidic cubic phase(LCP) matrix by using small-angle X-ray scattering. α-Syn proteins destabilize the cubic-Pn3m phase of LCP that can be further recovered after the addition of Cu² ions even at a low stoichiometric ratio. By using circular dichroism and nuclear magnetic resonance, we also study how lipid membranes and Cu²⁺ ions impact the secondary structures of α-synuclein at an atomic level. Although the secondary structure of α-synuclein with lipid membranes is not significantly changed to a large extent in the presence of Cu²⁺ ions, lipid membranes promote the interaction between α-synuclein C-terminus and Cu²⁺ ions. The modulation of Cu²⁺ ions and lipid membranes on α-synuclein dynamics and structure may play an important role in the molecular pathogenesis of Parkinson's disease.

Higher baseline copper levels are associated with worse outcome in burn patients with overweight and obesity

INTRODUCTION

We examined the interactive effects of copper (Cu) and overweight (overweight) and obesity on outcomes of burn patients. We posited that higher baseline Cu among burn patients with overweight or obesity will be associated with poor clinical outcomes vs. patients with a normal weight.

METHODS

A retrospective review was conducted on patients with ≥20% total burn surface area (TBSA) with an initial measurement of Cu. Patients were grouped by body mass index (BMI). The interactions between baseline Cu and BMI groups on multiple burn patient outcomes were examined in a series of multiple regression models.

RESULTS

One-hundred-and-sixty patients met eligibility (age 43.9 ± 17.5, males 86.3%, normal weight:overweight:obesity = 53:38:69). BMI groups did not differ significantly on demographics, burn severity, or baseline biochemistry. Normal weight patients with higher baseline Cu had shorter ICU stay (ICUS), shorter length of stay (LOS), and had fewer operations (Ps < 0.05). In contrast, overweight and obese patients with higher baseline Cu had longer ICU stay (p = 0.001 and p = 0.034), LOS (p = 0.005 and p = 0.066), and increased operations (p = 0.001 and p = 0.067).

CONCLUSIONS

Higher baseline Cu seems associated with adverse outcomes in overweight and obese burn patients. Further research is needed to confirm this association and explore the direction of causality.

The molecular and cellular basis of copper dysregulation and its relationship with human pathologies

Copper (Cu) is an essential micronutrient required for the activity of redox-active enzymes involved in critical metabolic reactions, signaling pathways, and biological functions. Transporters and chaperones control Cu ion levels and bioavailability to ensure proper subcellular and systemic Cu distribution. Intensive research has focused on understanding how mammalian cells maintain Cu homeostasis, and how molecular signals coordinate Cu acquisition and storage within organs. In humans, mutations of genes that regulate Cu homeostasis or facilitate interactions with Cu ions lead to numerous pathologic conditions. Malfunctions of the Cu⁺ -transporting ATPases ATP7A and ATP7B cause Menkes disease and Wilson disease, respectively. Additionally, defects in the mitochondrial and cellular distributions and homeostasis of Cu lead to severe neurodegenerative conditions, mitochondrial myopathies, and metabolic diseases. Cu has a dual nature in carcinogenesis as a promotor of tumor growth and an inducer of redox stress in cancer cells. Cu also plays role in cancer treatment as a component of drugs and a regulator of drug sensitivity and uptake. In this review, we provide an overview of the current knowledge of Cu metabolism and transport and its relation to various human pathologies.

Plasma Cytokines Profile in Patients with Parkinson's Disease Associated with Mutations in GBA Gene

Plasma cytokine concentration in patients with Parkinson's disease and mutation in GBA gene, in patients with sporadic Parkinson's disease, and in healthy volunteers were measured by ELISA and multiplex analysis. In patients with Parkinson's disease and mutation in GBA gene, elevated plasma concentrations of IL-1β and TNFα were revealed by ELISA in comparison with both controls and patients with sporadic form of Parkinson's disease. Multiplex analysis revealed enhanced secretion of IL-1β, IL-2, IFNγ and reduced plasma levels of monocyte chemoattractant protein-1 (MCP-1) in patients with Parkinson's disease and mutation in GBA gene (in comparison with other groups) and increased plasma levels of IL-13 (only in comparison with the healthy volunteers). Our results support the hypothesis that the concentrations of inflammatory mediators are increased in patients with Parkinson's disease and mutation in GBA gene.

Copper Ions and Parkinson's Disease: Why Is Homeostasis So Relevant?

The involvement of copper in numerous physiological processes makes this metal ion essential for human life. Alterations in copper homeostasis might have deleterious consequences, and several neurodegenerative disorders, including Parkinson’s disease (PD), have been associated with impaired copper levels. In the present review, we describe the molecular mechanisms through which copper can exert its toxicity, by considering how it can interfere with other cellular processes known to play a role in PD, such as dopamine metabolism, oxidative stress, and α-synuclein aggregation. The recent experimental evidence that associates copper deficiency and the formation of superoxide dismutase 1 (SOD1) aggregates with the progression of PD is also discussed together with its therapeutic implication. Overall, the recent discoveries described in this review show how either copper deficiency or excessive levels can promote detrimental effects, highlighting the importance of preserving copper homeostasis and opening unexplored therapeutic avenues in the definition of novel disease-modifying drugs.

Case of Early-Onset Parkinson's Disease in a Heterozygous Mutation Carrier of the ATP7B Gene

In this paper, we report a clinically proven case of Parkinson’s disease (PD) with early onset in a patient who is a heterozygous mutation carrier of ATP7B (the Wilson’s disease gene). The patient was observed from 2011 to 2018 in the Center for Neurodegenerative Diseases, Institute of Experimental Medicine (St. Petersburg, Russia). During this period, the patient displayed aggravation of PD clinical symptoms that were accompanied by a decrease in the ceruloplasmin concentration (from 0.33 to 0.27 g/L) and an increase in serum nonceruloplasmin copper, which are typical of the late stages of Wilson’s disease. It was found that one of the alleles of exon 14 in the ATP7B gene, which partially codes of the nucleotide-binding domain (N-domain), carries a mutation not previously reported corresponding to Cys1079Gly substitution. Alignment of the ATP7B N-domain amino acid sequences of representative vertebrate species has shown that the Cys at 1079 position is conserved throughout the evolution. Molecular dynamic analysis of a polypeptide with Cys1079Gly substitution showed that the mutation causes profound conformational changes in the N-domain, which could potentially lead to impairment of its functions. The role of ATP7B gene mutations in PD development is discussed.

Switching on Endogenous Metal Binding Proteins in Parkinson's Disease

The formation of cytotoxic intracellular protein aggregates is a pathological signature of multiple neurodegenerative diseases. The principle aggregating protein in Parkinson’s disease (PD) and atypical Parkinson’s diseases is α-synuclein (α-syn), which occurs in neural cytoplasmic inclusions. Several factors have been found to trigger α-syn aggregation, including raised calcium, iron, and copper. Transcriptional inducers have been explored to upregulate expression of endogenous metal-binding proteins as a potential neuroprotective strategy. The vitamin-D analogue, calcipotriol, induced increased expression of the neuronal vitamin D-dependent calcium-binding protein, calbindin-D28k, and this significantly decreased the occurrence of α-syn aggregates in cells with transiently raised intracellular free Ca, thereby increasing viability. More recently, the induction of endogenous expression of the Zn and Cu binding protein, metallothionein, by the glucocorticoid analogue, dexamethasone, gave a specific reduction in Cu-dependent α-syn aggregates. Fe accumulation has long been associated with PD. Intracellularly, Fe is regulated by interactions between the Fe storage protein ferritin and Fe transporters, such as poly(C)-binding protein 1. Analysis of the transcriptional regulation of Fe binding proteins may reveal potential inducers that could modulate Fe homoeostasis in disease. The current review highlights recent studies that suggest that transcriptional inducers may have potential as novel mechanism-based drugs against metal overload in PD.