Copper and iron ions accelerate the prion-like propagation of α-synuclein: A vicious cycle in Parkinson's disease

Modulating α-synuclein propagation and decomposition: Implications in Parkinson's disease therapy

α-Synuclein (α-Syn) is closely related to the pathogenesis of Parkinson's disease (PD). Under pathological conditions, the conformation of α-syn changes and different forms of α-syn lead to neurotoxicity. According to Braak stages, α-syn can propagate in different brain regions, inducing neurodegeneration and corresponding clinical manifestations through abnormal aggregation of Lewy bodies (LBs) and lewy axons in different types of neurons in PD. So far, PD lacks early diagnosis biomarkers, and treatments are mainly targeted at some clinical symptoms. There is no effective therapy to delay the progression of PD. This review first summarized the role of α-syn in physiological and pathological states, and the relationship between α-syn and PD. Then, we focused on the origin, secretion, aggregation, propagation and degradation of α-syn as well as the important regulatory factors in these processes systematically. Finally, we reviewed some potential drug candidates for alleviating the abnormal aggregation of α-syn in order to provide valuable targets for the treatment of PD to cope with the occurrence and progression of this disease.

α-Synuclein pathology from the body to the brain: so many seeds so close to the central soil

ABSTRACT

α-Synuclein is a protein that mainly exists in the presynaptic terminals. Abnormal folding and accumulation of α-synuclein are found in several neurodegenerative diseases, including Parkinson's disease. Aggregated and highly phosphorylated α-synuclein constitutes the main component of Lewy bodies in the brain, the pathological hallmark of Parkinson's disease. For decades, much attention has been focused on the accumulation of α-synuclein in the brain parenchyma rather than considering Parkinson's disease as a systemic disease. Recent evidence demonstrates that, at least in some patients, the initial α-synuclein pathology originates in the peripheral organs and spreads to the brain. Injection of α-synuclein preformed fibrils into the gastrointestinal tract triggers the gut-to-brain propagation of α-synuclein pathology. However, whether α-synuclein pathology can occur spontaneously in peripheral organs independent of exogenous α-synuclein preformed fibrils or pathological α-synuclein leakage from the central nervous system remains under investigation. In this review, we aimed to summarize the role of peripheral α-synuclein pathology in the pathogenesis of Parkinson's disease. We also discuss the pathways by which α-synuclein pathology spreads from the body to the brain.

The Irony of Iron: The Element with Diverse Influence on Neurodegenerative Diseases

Iron accumulation in the brain is a common feature of many neurodegenerative diseases. Its involvement spans across the main proteinopathies involving tau, amyloid-beta, alpha-synuclein, and TDP-43. Accumulating evidence supports the contribution of iron in disease pathologies, but the delineation of its pathogenic role is yet challenged by the complex involvement of iron in multiple neurotoxicity mechanisms and evidence supporting a reciprocal influence between accumulation of iron and protein pathology. Here, we review the major proteinopathy-specific observations supporting four distinct hypotheses: (1) iron deposition is a consequence of protein pathology; (2) iron promotes protein pathology; (3) iron protects from or hinders protein pathology; and (4) deposition of iron and protein pathology contribute parallelly to pathogenesis. Iron is an essential element for physiological brain function, requiring a fine balance of its levels. Understanding of disease-related iron accumulation at a more intricate and systemic level is critical for advancements in iron chelation therapies.

Unveiling the role of iPLA2β in neurodegeneration: From molecular mechanisms to advanced therapies

Calcium-independent phospholipase A2β (iPLA2β), a member of the phospholipase A2 (PLA2s) superfamily, is encoded by the PLA2G6 gene. Mutations in the PLA2G6 gene have been identified as the primary cause of infantile neuroaxonal dystrophy (INAD) and, less commonly, as a contributor to Parkinson's disease (PD). Recent studies have revealed that iPLA2β deficiency leads to neuroinflammation, iron accumulation, mitochondrial dysfunction, lipid dysregulation, and other pathological changes, forming a complex pathogenic network. These discoveries shed light on potential mechanisms underlying PLA2G6-associated neurodegeneration (PLAN) and offer valuable insights for therapeutic development. This review provides a comprehensive analysis of the fundamental characteristics of iPLA2β, its association with neurodegeneration, the pathogenic mechanisms involved in PLAN, and potential targets for therapeutic intervention. It offers an overview of the latest advancements in this field, aiming to contribute to ongoing research endeavors and facilitate the development of effective therapies for PLAN.

Heavy Metal Mediated Progressive Degeneration and Its Noxious Effects on Brain Microenvironment

Heavy metals, including lead (Pb), cadmium (Cd), arsenic (As), cobalt (Co), copper (Cu), manganese (Mn), zinc (Zn), and others, have a significant impact on the development and progression of neurodegenerative diseases in the human brain. This comprehensive review aims to consolidate the recent research on the harmful effects of different metals on specific brain cells such as neurons, microglia, astrocytes, and oligodendrocytes. Understanding the potential influence of these metals in neurodegeneration is crucial for effectively combating the ongoing advancement of these diseases. Metal-induced neurodegeneration involves molecular mechanisms such as apoptosis induction, dysregulation of metabolic and signaling pathways, metal imbalance, oxidative stress, loss of synaptic transmission, pathogenic peptide aggregation, and neuroinflammation. This review provides valuable insights by compiling the supportive evidence from recent research findings. Additionally, we briefly discuss the modes of action of natural neuroprotective compounds. While this comprehensive review aims to consolidate the recent research on the harmful effects of various metals on specific brain cells, it may not cover all studies and findings related to metal-induced neurodegeneration. Studies that are done using bioinformatics tools, microRNAs, long non-coding RNAs, emerging disease models, and studies based on the modes of exposure to toxic metals are a future prospect to be explored.

The mechanism of cuproptosis in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease with an increased morbidity. The pathogenesis PD has not been fully elucidated, and whatever mechanism is involved, it ultimately leads to dopamine (DA) neuronal apoptosis. Cuproptosis is a novel form of cell death. Its morphology, biochemical properties, and mechanism of action differ from known forms of cell death, such as apoptosis, autophagy, necrosis and pyroptosis. Copper binds to the lipoylated components of the tricarboxylic acid cycle, causing proteotoxic stress that ultimately leads to cellular cuproptosis. PD has biochemical features such as mitochondrial dysfunction and decreased levels of copper and glutathione in brain regions. This is closely related to the cuproptosis mechanism. However, the specific link between the pathogenesis of PD and cuproptosis is unclear. Herein, we summarizes cuproptosis as the cause of DA neuronal death in PD, and the relationship between cuproptosis and the PD pathogenesis. This article provides a research basis for targeted cuproptosis for PD.

Exploring Caenorhabditis elegans as Parkinson's Disease Model: Neurotoxins and Genetic Implications

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world, the first being Alzheimer's disease. Patients with PD have a loss of dopaminergic neurons in the substantia nigra of the basal ganglia, which controls voluntary movements, causing a motor impairment as a result of dopaminergic signaling impairment. Studies have shown that mutations in several genes, such as SNCA, PARK2, PINK1, DJ-1, ATP13A2, and LRRK2, and the exposure to neurotoxic agents can potentially increase the chances of PD development. The nematode Caenorhabditis elegans (C. elegans) plays an important role in studying the risk factors, such as genetic factors, aging, exposure to chemicals, disease progression, and drug treatments for PD. C. elegans has a conserved neurotransmission system during evolution; it produces dopamine, through the eight dopaminergic neurons; it can be used to study the effect of neurotoxins and also has strains that express human α-synuclein. Furthermore, the human PD-related genes, LRK-1, PINK-1, PDR-1, DJR-1.1, and CATP-6, are present and functional in this model. Therefore, this review focuses on highlighting and discussing the use of C. elegans an in vivo model in PD-related studies. Here, we identified that nematodes exposed to the neurotoxins, such as 6-OHDA, MPTP, paraquat, and rotenone, had a progressive loss of dopaminergic neurons, dopamine deficits, and decreased survival rate. Several studies have reported that expression of human LRRK2 (G2019S) caused neurodegeneration and pink-1, pdr-1, and djr-1.1 deletion caused several effects PD-related in C. elegans, including mitochondrial dysfunctions. Of note, the deletion of catp-6 in nematodes caused behavioral dysfunction, mitochondrial damage, and reduced survival. In addition, nematodes expressing α-synuclein had neurodegeneration and dopamine-dependent deficits. Therefore, C. elegans can be considered an accurate animal model of PD that can be used to elucidate to assess the underlying mechanisms implicated in PD to find novel therapeutic targets.

Cell senescence induced by toxic interaction between α-synuclein and iron precedes nigral dopaminergic neuron loss in a mouse model of Parkinson's disease

Cell senescence has been implicated in the pathology of Parkinson's disease (PD). Both abnormal α-synuclein aggregation and iron deposition are suggested to be the triggers, facilitators, and aggravators during the development of PD. In this study, we investigated the involvement of α-synuclein and iron in the process of cell senescence in a mouse model of PD. In order to overexpress α-syn-A53T in the substantia nigra pars compacta (SNpc), human α-syn-A53T was microinjected into both sides of the SNpc in mice. We found that overexpression of α-syn-A53T for one week induced significant pro-inflammatory senescence-associated secretory phenotype (SASP), increased cell senescence-related proteins (β-gal, p16, p21, H2A.X and γ-H2A.X), mitochondrial dysfunction accompanied by dysregulation of iron-related proteins (L-ferritin, H-ferritin, DMT1, IRP1 and IRP2) in the SNpc. In contrast, significant loss of nigral dopaminergic neurons and motor dysfunction were only observed after overexpression of α-syn-A53T for 4 weeks. In PC12 cells stably overexpressing α-syn-A53T, iron overload (ferric ammonium citrate, FAC, 100 μM) not only increased the level of reactive oxygen species (ROS), p16 and p21, but also exacerbated the processes of oxidative stress and cell senescence signalling induced by α-syn-A53T overexpression. Interestingly, reducing the iron level with deferoxamine (DFO) or knockdown of transferrin receptor 1 (TfR1) significantly improved both the phenotypes and dysregulated proteins of cell senescence induced by α-syn-A53T overexpression. All these evidence highlights the toxic interaction between iron and α-synuclein inducing cell senescence, which precedes nigral dopaminergic neuronal loss in PD. Further investigation on cell senescence may yield new therapeutic agents for the prevention or treatment of PD.

Copper trafficking systems in cells: insights into coordination chemistry and toxicity

Transition metal ions, such as copper, are indispensable components in the biological system. Copper ions which primarily exist in two major oxidation states Cu(I) and Cu(II) play crucial roles in various cellular processes including antioxidant defense, biosynthesis of neurotransmitters, and energy metabolism, owing to their inherent redox activity. The disturbance in copper homeostasis can contribute to the development of copper metabolism disorders, cancer, and neurodegenerative diseases, highlighting the significance of understanding the copper trafficking system in cellular environments. This review aims to offer a comprehensive overview of copper homeostatic machinery, with an emphasis on the coordination chemistry of copper transporters and trafficking proteins. While copper chaperones and the corresponding metalloenzymes are thoroughly discussed, we also explore the potential existence of low-molecular-mass metal complexes within cellular systems. Furthermore, we summarize the toxicity mechanisms originating from copper deficiency or accumulation, which include the dysregulation of oxidative stress, signaling pathways, signal transduction, and amyloidosis. This perspective review delves into the current knowledge regarding the intricate aspects of the copper trafficking system, providing valuable insights into potential treatment strategies from the standpoint of bioinorganic chemistry.

Low-dose Cu exposure enhanced α-synuclein accumulation associates with mitochondrial impairments in mice model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that mainly affects the elder population, and its etiology is enigmatic. Both environmental risks and genetics may influence the development of PD. Excess copper causes neurotoxicity and accelerates the progression of neurodegenerative diseases. However, the underlying mechanisms of copper-induced neurotoxicity remain controversial. In this study, A53T transgenic α-synuclein (A53T) mice and their matching wild-type (WT) mice were treated with a low dose of copper (0.13 ppm copper chlorinated drinking water, equivalent to the copper exposure of human daily copper intake dose) for 4 months, and copper poisoning was performed on human A53T mutant SHSY5Y cells overexpressed with α-synuclein (dose of 1/4 IC50), to test the effects of copper exposure on the body. The results of the open field test showed that the moto function of Cu-treated mice was impaired. Proteomics revealed changes in neurodevelopment, transport function, and mitochondrial membrane-related function in Cu-treated WT mice, which were associated with reduced expression of mitochondrial complex (NDUFA10, ATP5A), dopamine neurons (TH), and dopamine transporter (DAT). Mitochondrial function, nervous system development, synaptic function, and immune response were altered in Cu-treated A53T mice. These changes were associated with increased mitochondrial splitting protein (Drp1), decreased mitochondrial fusion protein (OPA1, Mfn1), abnormalities in mitochondrial autophagy protein (LC3BII/I, P62), decreased dopamine neuron (TH) expression, increased α-synuclein expression, inflammatory factors (IL-6, IL-1β, and TNF-α) release and microglia (Iba1) activation. In addition, we found that Cu2+ (30 μM) induced excessive ROS production and reduced mitochondrial ATP production in human A53T mutant α-synuclein overexpressing SHSY5Y cells by in vitro experiments. In conclusion, low-dose copper treatment altered critical proteins involved in mitochondrial, neurodevelopmental, and inflammatory responses and affected mitochondria's ROS and ATP production levels.

Unveiling the Effects of Copper Ions in the Aggregation of Amyloidogenic Proteins

Amyloid diseases have become a global concern due to their increasing prevalence. Transition metals, including copper, can affect the aggregation of the pathological proteins involved in these diseases. Copper ions play vital roles in organisms, but the disruption of their homeostasis can negatively impact neuronal function and contribute to amyloid diseases with toxic protein aggregates, oxidative stress, mitochondrial dysfunction, impaired cellular signaling, inflammation, and cell death. Gaining insight into the imbalance of copper ions and its impact on protein folding and aggregation is crucial for developing focused therapies. This review examines the influence of copper ions on significant amyloid proteins/peptides, offering a comprehensive overview of the current understanding in this field.

A renal YY1-KIM1-DR5 axis regulates the progression of acute kidney injury

Acute kidney injury (AKI) exhibits high morbidity and mortality. Kidney injury molecule-1 (KIM1) is dramatically upregulated in renal tubules upon injury, and acts as a biomarker for various renal diseases. However, the exact role and underlying mechanism of KIM1 in the progression of AKI remain elusive. Herein, we report that renal tubular specific knockout of Kim1 attenuates cisplatin- or ischemia/reperfusion-induced AKI in male mice. Mechanistically, transcription factor Yin Yang 1 (YY1), which is downregulated upon AKI, binds to the promoter of KIM1 and represses its expression. Injury-induced KIM1 binds to the ECD domain of death receptor 5 (DR5), which activates DR5 and the following caspase cascade by promoting its multimerization, thus induces renal cell apoptosis and exacerbates AKI. Blocking the KIM1-DR5 interaction with rationally designed peptides exhibit reno-protective effects against AKI. Here, we reveal a YY1-KIM1-DR5 axis in the progression of AKI, which warrants future exploration as therapeutic targets.

The Role of Exercise in Maintaining Mitochondrial Proteostasis in Parkinson's Disease

Parkinson's disease (PD) is the second most common rapidly progressive neurodegenerative disease and has serious health and socio-economic consequences. Mitochondrial dysfunction is closely related to the onset and progression of PD, and the use of mitochondria as a target for PD therapy has been gaining traction in terms of both recognition and application. The disruption of mitochondrial proteostasis in the brain tissue of PD patients leads to mitochondrial dysfunction, which manifests as mitochondrial unfolded protein response, mitophagy, and mitochondrial oxidative phosphorylation. Physical exercise is important for the maintenance of human health, and has the great advantage of being a non-pharmacological therapy that is non-toxic, low-cost, and universally applicable. In this review, we investigate the relationships between exercise, mitochondrial proteostasis, and PD and explore the role and mechanisms of mitochondrial proteostasis in delaying PD through exercise.

Proximity to residential and workplace pesticides application and the risk of progression of Parkinson's diseases in Central California

BACKGROUND

Pesticide exposure has consistently been associated with Parkinson's disease (PD) onset. Yet, fewer epidemiologic studies have examined whether pesticides influence PD motor and non-motor symptom progression.

OBJECTIVES

Using a geographic information system tool that integrates agricultural pesticide use reports and land use records to derive ambient exposures at residences and workplaces, we assessed associations between specific pesticides previously related to PD onset with PD symptom progression in two PD patient cohorts living in agricultural regions of California.

METHODS

We calculated the pounds of pesticide applied agriculturally near each participant's residential or occupational addresses from 1974 to the year of PD diagnosis, using a geographic information system tool that links the California Pesticide Use Reports database to land use data. We examined 53 pesticides selected a priori as they have previously been associated with PD onset. We longitudinally followed two PD patient cohorts (PEG1 N = 242, PEG2 N = 259) for an average of 5.0 years (SD ± 3.5) and 2.7 years (SD ± 1.6) respectively and assessed PD symptoms using the movement disorder specialist-administered Unified Parkinson's disease Rating Scale part III (UPDRS), Mini-Mental State Examination (MMSE), and Geriatric Depression Scale (GDS). Weighted time-to-event regression models were implemented to estimate effects.

RESULTS

Ten agricultural pesticides, including copper sulfate (pentahydrate), 2-methyl-4-chlorophenoxyacetic acid (MCPA) dimethylamine salt, tribufos, sodium cacodylate, methamidophos, ethephon, propargite, bromoxynil octanoate, monosodium methanearsonate (MSMA), and dicamba, were associated with faster symptom progression. Among these pesticides, residential or workplace proximity to higher amounts of copper sulfate (pentahydrate) and MCPA (dimethylamine salt) was associated with all three progression endpoints (copper sulfate: HRs = 1.22-1.36, 95 % CIs = 1.03-1.73; MCPA: HRs = 1.27-1.35, 95 % CIs = 1.02-1.70).

CONCLUSIONS

Our findings suggest that pesticide exposure may not only be relevant for PD onset but also PD progression phenotypes. We have implicated ten specific pesticide active ingredients in faster PD motor and non-motor decline.

Probing the interactions between amyloidogenic proteins and bio-membranes

Protein misfolding diseases (PMDs) in humans are characterized by the deposition of protein aggregates in tissues, including Alzheimer's disease, Parkinson's disease, type 2 diabetes, and amyotrophic lateral sclerosis. Misfolding and aggregation of amyloidogenic proteins play a central role in the onset and progression of PMDs, and these processes are regulated by multiple factors, especially the interaction between proteins and bio-membranes. Bio-membranes induce conformational changes in amyloidogenic proteins and affect their aggregation; on the other hand, the aggregates of amyloidogenic proteins may cause membrane damage or dysfunction leading to cytotoxicity. In this review, we summarize the factors that affect the binding of amyloidogenic proteins and membranes, the effects of bio-membranes on the aggregation of amyloidogenic proteins, mechanisms of membrane disruption by amyloidogenic aggregates, technical approaches for detecting these interactions, and finally therapeutic strategies targeting membrane damage caused by amyloidogenic proteins.

The Strategies of Development of New Non-Toxic Inhibitors of Amyloid Formation

In recent years, due to the aging of the population and the development of diagnostic medicine, the number of identified diseases associated with the accumulation of amyloid proteins has increased. Some of these proteins are known to cause a number of degenerative diseases in humans, such as amyloid-beta (Aβ) in Alzheimer's disease (AD), α-synuclein in Parkinson's disease (PD), and insulin and its analogues in insulin-derived amyloidosis. In this regard, it is important to develop strategies for the search and development of effective inhibitors of amyloid formation. Many studies have been carried out aimed at elucidating the mechanisms of amyloid aggregation of proteins and peptides. This review focuses on three amyloidogenic peptides and proteins-Aβ, α-synuclein, and insulin-for which we will consider amyloid fibril formation mechanisms and analyze existing and prospective strategies for the development of effective and non-toxic inhibitors of amyloid formation. The development of non-toxic inhibitors of amyloid will allow them to be used more effectively for the treatment of diseases associated with amyloid.

Structural Insights of Fe3+ Induced α-synuclein Fibrillation in Parkinson's Disease

Amyloid aggregation of α-synuclein (α-syn) in Lewy bodies (LBs) is the pathological hallmark of Parkinson's disease (PD). Iron, especially Fe³⁺, is accumulated in substantia nigra of PD patients and co-deposited with α-syn in LBs. However, how Fe³⁺ modulates α-syn fibrillation at molecular level remains unclear. In this study, we found that Fe³⁺ can promote α-syn fibrillation at low concentration while inhibit its fibrillation at high concentration. NMR titration study shows poor interaction between α-syn monomer and Fe³⁺. Instead, we found that Fe³⁺ binds to α-syn fibrils. By using cryo-electron microscopy (cryo-EM), we further determined the atomic structure of α-syn fibril in complex with Fe³⁺ at the resolution of 2.7 Å. Strikingly, two extra electron densities adjacent to His50 and Glu57 were observed as putative binding sites of Fe³⁺ and water molecules, suggesting that Fe³⁺ binds to the negative cleft of the fibril and stabilizes the fibril structure for promoting α-syn aggregation. Further mutagenesis study shows mutation of His50 abolishes the Fe³⁺-facilitated fibrillation of α-syn. Our work illuminates the structural basis of the interaction of Fe³⁺ and α-syn in both monomeric and fibrillar forms, and sheds light on understanding the pathological role of Fe³⁺ in α-syn aggregation in PD.

Machine learning-based characterization of cuprotosis-related biomarkers and immune infiltration in Parkinson's disease

Background: Parkinson's disease (PD) is a neurodegenerative disease commonly seen in the elderly. On the other hand, cuprotosis is a new copper-dependent type of cell death that can be observed in various diseases. Methods: This study aimed to identify potential novel biomarkers of Parkinson's disease by biomarker analysis and to explore immune cell infiltration during the onset of cuprotosis. Gene expression profiles were retrieved from the GEO database for the GSE8397, GSE7621, GSE20163, and GSE20186 datasets. Three machine learning algorithms: the least absolute shrinkage and selection operator (LASSO), random forest, and support vector machine-recursive feature elimination (SVM-RFE) were used to screen for signature genes for Parkinson's disease onset and cuprotosis-related genes (CRG). Immune cell infiltration was estimated by ssGSEA, and cuprotosis-related genes associated with immune cells and immune function were examined using spearman correlation analysis. Nomogram was created to validate the accuracy of these cuprotosis-related genes in predicting PD disease progression. Classification of Parkinson's specimens using consensus clustering methods. Result: Three PD datasets from the Gene Expression Omnibus (GEO) database were combined after eliminating batch effects. By ssGSEA, we identified three cuprotosis-related genes ATP7A, SLC31A1, and DBT associated with immune cells or immune function in PD and more accurate for the diagnosis of Parkinson's disease course. Patients could benefit clinically from a characteristic line graph based on these genes. Consistent clustering analysis identified two subtypes, with the C2 subtype exhibiting higher immune cell infiltration and immune function. Conclusion: In conclusion, our study reveals that several newly identified cuprotosis-related genes intervene in the progression of Parkinson's disease through immune cell infiltration.

Modelling Parkinson's Disease in C. elegans: Strengths and Limitations

Parkinson's disease (PD) is a common neurodegenerative disease that affects the motor system and progressively worsens with age. Current treatment options for PD mainly target symptoms, due to our limited understanding of the etiology and pathophysiology of PD. A variety of preclinical models have been developed to study different aspects of the disease. The models have been used to elucidate the pathogenesis and for testing new treatments. These models include cell models, non-mammalian models, rodent models, and non-human primate models. Over the past few decades, Caenorhabditis elegans (C. elegans) has been widely adopted as a model system due to its small size, transparent body, short generation time and life cycle, fully sequenced genome, the tractability of genetic manipulation and suitability for large scale screening for disease modifiers. Here, we review studies using C. elegans as a model for PD and highlight the strengths and limitations of the C. elegans model. Various C. elegans PD models, including neurotoxin-induced models and genetic models, are described in detail. Moreover, met.

Synthesis, determination, and bio-application in cellular and biomass-bamboo imaging of natural cinnamaldehyde derivatives

Cinnamon essential oil (CEO) is the main ingredient in the renewable biomass of cinnamon, which contains natural cinnamaldehyde. To valorize the value of cinnamaldehyde, two simple and useful compounds (1 and 2) from CEO were synthesized using a Schiff-base reaction and characterized by infrared spectra (IR), nuclear magnetic resonance (NMR), and high-resolution mass spectrometry (HRMS). Compound 1 was used to confirm the presence of Fe³⁺ and ClO⁻ in solution, as well as compound 2. Using fluorescence enhancement phenomena, it offered practicable linear relationship of 1’s fluorescence intensity and Fe³⁺ concentrations: (0–8.0 × 10⁻⁵ mol/L), y = 36.232x + 45.054, R² = 0.9947, with a limit of detection (LOD) of 0.323 μM, as well as compound 2. With increasing fluorescence, F₄₀₄/F₄₂₆ of 1 and the ClO⁻ concentration (0–1.0 × 10⁻⁴ mol/L) also had a linear relationship: y = 0.0392x + 0.5545, R² = 0.9931, LOD = 0.165 μM. However, the fluorescence intensity of 2 (596 nm) was quenched by a reduced concentration of ClO⁻, resulting in a linear. In addition, compounds 1 and 2 were used to image human astrocytoma MG (U-251), brain neuroblastoma (LN-229) cells, and bamboo tissue by adding Fe³⁺ or ClO⁻, with clear intracellular fluorescence. Thus, the two compounds based on CEO could be used to dye cells and bamboo tissues by fluorescence technology.

Role of heavy metals (copper (Cu), arsenic (As), cadmium (Cd), iron (Fe) and lithium (Li)) induced neurotoxicity

Parkinson's disease (PD) is a neurodegenerative condition characterized by the dopamine (DA) neuronal loss in the substantia nigra. PD impairs motor controls symptoms such as tremor, rigidity, bradykinesia and postural imbalance gradually along with non-motor problems such as olfactory dysfunction, constipation, sleeping disorder. Though surplus of factors and mechanisms have been recognized, the precise PD etiopathogenesis is not yet implied. Reports suggest that various environmental factors play a crucial role in the causality of the PD cases. Epidemiological studies have reported that heavy metals has a role in causing defects in substantia nigra region of brain in PD. Though the reason is unknown, exposure to heavy metals is reported to be an underlying factor in PD development. Metals are classified as either essential or non-essential, and they have a role in physiological processes such protein modification, electron transport, oxygen transport, redox reactions, and cell adhesion. Excessive metal levels cause oxidative stress, protein misfolding, mitochondrial malfunction, autophagy dysregulation, and apoptosis, among other things. In this review, we check out the link between heavy metals like copper (Cu), arsenic (As), cadmium (Cd), iron (Fe), and lithium (Li) in neurodegeneration, and how it impacts the pathological conditions of PD. In conclusion, increase or decrease in heavy metals involve in regulation of neuronal functions that have an impact on neurodegeneration process. Through this review, we suggest that more research is needed in this stream to bring more novel approaches for either disease modelling or therapeutics.

Understanding the Inhibitory and Antioxidant Effects of Pyrroloquinoline Quinone (PQQ) on Copper(II)-Induced α-Synuclein-119 Aggregation

Parkinson's disease (PD) is associated with the aggregation and misfolding of a-synuclein (a-syn) protein in dopaminergic neurons. The misfolding process is heavily linked to copper dysregulation in PD. Experimental evidence supports the hypothesis that the co-presence of Cu(II) and α-syn facilitates the aggregation of α-syn, affecting the pathological development of PD. Recent literature has shown that pyrroloquinoline quinone (PQQ) contains strong neuroprotective activity by reducing the reactive oxygen species (ROS) production by α-syn. Despite these known facts, minimal studies have been done on the antioxidant effect of PQQ against ROS formation in the presence of Cu(II) and α-syn-119. Thus, it is of great significance to study the interaction between all three components, PQQ, Cu(II), and α-syn-119. In this proof-of-concept study, a variety of chemical techniques were employed to examine the antioxidant effect of PQQ on ROS that α-syn-119 produced in the presence of Cu(II). Our results showed that PQQ effectively prevented ROS formation in SH-SY5Y human differentiated neuronal cells. Thioflavin T (ThT) fluorescence assay, circular dichroism (CD) spectroscopy, and transmission electron microscopy (TEM) were applied, where PQQ was able to actively prevent fibrillation of α-syn-119 in the presence of Cu(II). This finding was further confirmed using electrochemical impedance spectroscopy (EIS), where the binding of PQQ to the α-syn-119 suppressed the aggregation process on the electrode surface. With these encouraging results, we envisage that PQQ and its derivatives can be a promising candidate for further studies as a multitarget therapeutic agent toward PD therapy.

Inhibiting protein aggregation with nanomaterials: The underlying mechanisms and impact factors

Protein aggregation is correlated with the onset and progression of protein misfolding diseases (PMDs). Inhibiting the generation of toxic aggregates of misfolded proteins has been proposed as a therapeutic approach for PMDs. Due to their unique properties, nanomaterials have been extensively investigated for their ability to inhibit protein aggregation and have shown great potential in the diagnosis and treatment of PMDs. However, the precise mechanisms by which nanomaterials interact with amyloidogenic proteins and the factors influencing these interactions remain poorly understood. Consequently, developing a rational design strategy for nanomaterials that target specific proteins in PMDs has been challenging. In this review, we elucidate the effects of nanomaterials on protein aggregation and describe the mechanisms through which nanomaterials interfere with protein aggregation. The major factors impacting protein-nanomaterial interaction such as size, charge, concentration, surface modification and morphology that can be rationally addressed to achieve the desired effects of nanomaterials on protein aggregation are summarized. The prospects and challenges to the clinical application of nanomaterials for the treatment of PMDs are also discussed.

Parkinson's Disease Dementia: Synergistic Effects of Alpha-Synuclein, Tau, Beta-Amyloid, and Iron

Parkinson’s disease dementia (PDD) is a common complication of Parkinson’s disease that seriously affects patients’ health and quality of life. At present, the process and pathological mechanisms of PDD remain controversial, which hinders the development of treatments. An increasing number of clinical studies have shown that alpha-synuclein (α-syn), tau, beta-amyloid (Aβ), and iron are closely associated with PDD severity. Thus, we inferred the vicious cycle that causes oxidative stress (OS), due to the synergistic effects of α-syn, tau, Aβ, and, iron, and which plays a pivotal role in the mechanism underlying PDD. First, iron-mediated reactive oxygen species (ROS) production can lead to neuronal protein accumulation (e.g., α-syn andAβ) and cytotoxicity. In addition, regulation of post-translational modification of α-syn by iron affects the aggregation or oligomer formation of α-syn. Iron promotes tau aggregation and neurofibrillary tangles (NFTs) formation. High levels of iron, α-syn, Aβ, tau, and NFTs can cause severe OS and neuroinflammation, which lead to cell death. Then, the increasing formation of α-syn, Aβ, and NFTs further increase iron levels, which promotes the spread of α-syn and Aβ in the central and peripheral nervous systems. Finally, iron-induced neurotoxicity promotes the activation of glycogen synthase kinase 3β (GSK3β) related pathways in the synaptic terminals, which in turn play an important role in the pathological synergistic effects of α-syn, tau and Aβ. Thus, as the central factor regulating this vicious cycle, GSK3β is a potential target for the prevention and treatment of PDD; this is worthy of future study.

A novel multi-target strategy to attenuate the progression of Parkinson's disease by diamine hybrid AGE/ALE inhibitor

Instead of a conventional 'one-drug-one-target approach', this article presents a novel multi-target approach with a concept of trapping simultaneously as many detrimental factors as possible involved in the progression of Parkinson's disease. These factors include reactive carbonyl species, reactive oxygen species, Fe^3+/Cu²⁺ and ortho-quinones (o-quinone), in particular. Different from the known multi-target strategies for Parkinson's disease, it is a sort of 'vacuum cleaning' strategy. The new agent consists of reactive carbonyl species scavenging moiety and reactive oxygen species scavenging and metal chelating moiety linked by a spacer. Provided that the capacity of scavenging o-quinones is demonstrated, this type of agent can further broaden its potential therapeutic profile. In order to support this new hypothetical approach, a number of simple in vitro experiments are proposed.

All Roads Lead to Rome: Different Molecular Players Converge to Common Toxic Pathways in Neurodegeneration

Multiple neurodegenerative diseases (NDDs) such as Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) and Huntington’s disease (HD) are being suggested to have common cellular and molecular pathological mechanisms, characterized mainly by protein misfolding and aggregation. These large inclusions, most likely, represent an end stage of a molecular cascade; however, the soluble misfolded proteins, which take part in earlier steps of this cascade, are the more toxic players. These pathological proteins, which characterize each specific disease, lead to the selective vulnerability of different neurons, likely resulting from a combination of different intracellular mechanisms, including mitochondrial dysfunction, ER stress, proteasome inhibition, excitotoxicity, oxidative damage, defects in nucleocytoplasmic transport, defective axonal transport and neuroinflammation. Damage within these neurons is enhanced by damage from the nonneuronal cells, via inflammatory processes that accelerate the progression of these diseases. In this review, while acknowledging the hallmark proteins which characterize the most common NDDs; we place specific focus on the common overlapping mechanisms leading to disease pathology despite these different molecular players and discuss how this convergence may occur, with the ultimate hope that therapies effective in one disease may successfully translate to another.

Research progress of adsorption and removal of heavy metals by chitosan and its derivatives: A review

Chitosan has received widespread attention as an adsorbent for pollutants because of its low cost and great adsorption potentials. Chitosan has abundant hydroxyl and amino groups that can bind heavy metal ions. However, it has defects such as sensitivity to pH, low thermal stability, and low mechanical strength, which limit the application of chitosan in wastewater treatment. The functional groups of chitosan can be modified to improve its performance via crosslinking and graft modification. The porosity and specific surface area of chitosan in powder form are not ideal, therefore, physical modification has been attempted to generate chitosan nanoparticles and hydrogel. Chitosan has also been integrated with other materials (e.g. graphene, zeolite) resulting in composite materials with improved adsorption performance. This review mainly focuses on reports about the application of chitosan and its derivatives to remove different heavy metals. The preparation strategy, adsorption mechanism, and factors affecting the adsorption performance of adsorbents for each type of heavy metal are discussed in detail. Recent reports on important organic pollutants (dyes and phenol) removal by chitosan and its derivatives are also briefly discussed.

Kidney injury molecule-1 is a potential receptor for SARS-CoV-2

COVID-19 patients present high incidence of kidney abnormalities, which are associated with poor prognosis and mortality. The identification of SARS-CoV-2 in the kidney of COVID-19 patients suggests renal tropism of SARS-CoV-2. However, whether there is a specific target of SARS-CoV-2 in the kidney remains unclear. Herein, by using in silico simulation, coimmunoprecipitation, fluorescence resonance energy transfer, fluorescein isothiocyanate labeling, and rational design of antagonist peptides, we demonstrate that kidney injury molecule-1 (KIM1), a molecule dramatically upregulated upon kidney injury, binds with the receptor-binding domain (RBD) of SARS-CoV-2 and facilitates its attachment to cell membrane, with the immunoglobulin variable Ig-like (Ig V) domain of KIM1 playing a key role in this recognition. The interaction between SARS-CoV-2 RBD and KIM1 is potently blockaded by a rationally designed KIM1-derived polypeptide AP2. In addition, our results also suggest interactions between KIM1 Ig V domain and the RBDs of SARS-CoV and MERS-CoV, pathogens of two severe infectious respiratory diseases. Together, these findings suggest KIM1 as a novel receptor for SARS-CoV-2 and other coronaviruses. We propose that KIM1 may thus mediate and exacerbate the renal infection of SARS-CoV-2 in a ‘vicious cycle’, and KIM1 could be further explored as a therapeutic target.

Nano-based approaches in the development of antiviral agents and vaccines

Outbreaks and the rapid transmission of viruses, such as coronaviruses and influenza viruses, are serious threats to human health. A major challenge in combating infectious diseases caused by viruses is the lack of effective methods for prevention and treatment. Nanotechnology has provided a basis for the development of novel antiviral strategies. Owing to their large modifiable surfaces that can be functionalized with multiple molecules to realize sophisticated designs, nanomaterials have been developed as nanodrugs, nanocarriers, and nano-based vaccines to effectively induce sufficient immunologic memory. From this perspective, we introduce various nanomaterials with diverse antiviral mechanisms and summarize how nano-based antiviral agents protect against viral infection at the molecular, cellular, and organismal levels. We summarize the applications of nanomaterials for defense against emerging viruses by trapping and inactivating viruses and inhibiting viral entry and replication. We also discuss recent progress in nano-based vaccines with a focus on the mechanisms by which nanomaterials contribute to immunogenicity. We further describe how nanotechnology may improve vaccine efficacy by delivering large amounts of antigens to target immune cells and enhancing the immune response by mimicking viral structures and activating dendritic cells. Finally, we provide an overview of future prospects for nano-based antiviral agents and vaccines.

Regulation of SIRT3 on mitochondrial functions and oxidative stress in Parkinson's disease

Sirtuin-3 (SIRT3) is a NAD⁺-dependent protein deacetylase that is located in mitochondria, regulating mitochondrial proteins and maintaining cellular antioxidant status. Increasing evidence demonstrates that SIRT3 plays a role in degenerative disorders including Parkinson's disease (PD), which is a devastating nervous system disease currently with no effective treatments available. Although the etiology of PD is still largely ambiguous, substantial evidence indicates that mitochondrial dysfunction and oxidative stress play major roles in the pathogenesis of PD. The imbalance of reactive oxygen species (ROS) production and detoxification leads to oxidative stress that can accelerate the progression of PD. By causing conformational changes in the deacetylated proteins SIRT3 modulates the activities and biological functions of a variety of proteins involved in mitochondrial antioxidant defense and various mitochondrial functions. Increasingly more studies have suggested that upregulation of SIRT3 confers beneficial effect on neuroprotection in various PD models. This review discusses the mechanism by which SIRT3 regulates intracellular oxidative status and mitochondrial function with an emphasis in discussing in detail the regulation of SIRT3 on each component of the five complexes of the mitochondrial respiratory chain and mitochondrial antioxidant defense, as well as the pharmacological regulation of SIRT3 in light of therapeutic strategies for PD.