Iron Dysregulation in Parkinson's Disease: Focused on the Autophagy-Lysosome Pathway

Fluoride Induces Neurocytotoxicity by Disrupting Lysosomal Iron Metabolism and Membrane Permeability

The detrimental effects of fluoride on neurotoxicity have been widely recorded, yet the detailed mechanisms underlying these effects remain unclear. This study explores lysosomal iron metabolism in fluoride-related neurotoxicity, with a focus on the Steap3/TRPML1 axis. Utilizing sodium fluoride (NaF)-treated human neuroblastoma (SH-SY5Y) and mouse hippocampal neuron (HT22) cell lines, our research demonstrates that NaF enhances the accumulation of ferrous ions (Fe2+) in these cells, disrupting lysosomal iron metabolism through the Steap3/TRPML1 axis. Notably, NaF exposure upregulated ACSL4 and downregulated GPX4, accompanied by reduced glutathione (GSH) levels and superoxide dismutase (SOD) activity and increased malondialdehyde (MDA) levels. These changes indicate increased vulnerability to ferroptosis within neuronal cells. The iron chelator deferoxamine (DFO) mitigates this disruption. DFO binds to lysosomal Fe2+ and inhibits the Steap3/TRPML1 axis, restoring normal lysosomal iron metabolism, preventing lysosomal membrane permeabilization (LMP), and reducing neuronal cell ferroptosis. Our findings suggest that interference in lysosomal iron metabolism may mitigate fluoride-induced neurotoxicity, underscoring the critical role of the Steap3/TRPML1 axis in this pathological process.

Autophagy-associated non-coding RNAs: Unraveling their impact on Parkinson's disease pathogenesis

BACKGROUND

Parkinson's disease (PD) is a degenerative neurological condition marked by the gradual loss of dopaminergic neurons in the substantia nigra pars compacta. The precise etiology of PD remains unclear, but emerging evidence suggests a significant role for disrupted autophagy-a crucial cellular process for maintaining protein and organelle integrity.

METHODS

This review focuses on the role of non-coding RNAs (ncRNAs) in modulating autophagy in PD. We conducted a comprehensive review of recent studies to explore how ncRNAs influence autophagy and contribute to PD pathophysiology. Special attention was given to the examination of ncRNAs' regulatory impacts in various PD models and patient samples.

RESULTS

Findings reveal that ncRNAs are pivotal in regulating key processes associated with PD progression, including autophagy, α-synuclein aggregation, mitochondrial dysfunction, and neuroinflammation. Dysregulation of specific ncRNAs appears to be closely linked to these pathogenic processes.

CONCLUSION

ncRNAs hold significant therapeutic potential for addressing autophagy-related mechanisms in PD. The review highlights innovative therapeutic strategies targeting autophagy-related ncRNAs and discusses the challenges and prospective directions for developing ncRNA-based therapies in clinical practice. The insights from this study underline the importance of ncRNAs in the molecular landscape of PD and their potential in novel treatment approaches.

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.

Examining the Role of a Functional Deficiency of Iron in Lysosomal Storage Disorders with Translational Relevance to Alzheimer's Disease

The recently presented Azalea Hypothesis for Alzheimer's disease asserts that iron becomes sequestered, leading to a functional iron deficiency that contributes to neurodegeneration. Iron sequestration can occur by iron being bound to protein aggregates, such as amyloid β and tau, iron-rich structures not undergoing recycling (e.g., due to disrupted ferritinophagy and impaired mitophagy), and diminished delivery of iron from the lysosome to the cytosol. Reduced iron availability for biochemical reactions causes cells to respond to acquire additional iron, resulting in an elevation in the total iron level within affected brain regions. As the amount of unavailable iron increases, the level of available iron decreases until eventually it is unable to meet cellular demands, which leads to a functional iron deficiency. Normally, the lysosome plays an integral role in cellular iron homeostasis by facilitating both the delivery of iron to the cytosol (e.g., after endocytosis of the iron-transferrin-transferrin receptor complex) and the cellular recycling of iron. During a lysosomal storage disorder, an enzyme deficiency causes undigested substrates to accumulate, causing a sequelae of pathogenic events that may include cellular iron dyshomeostasis. Thus, a functional deficiency of iron may be a pathogenic mechanism occurring within several lysosomal storage diseases and Alzheimer's disease.

TFEB regulates cellular labile iron and prevents ferroptosis in a TfR1-dependent manner

Autophagy is a major clearance pathway for misfolded α-synuclein which promotes ferroptosis through NCOA4-mediated ferritin degradation. The regulation of these two processes to achieve improved neuroprotection in Parkinson's disease (PD) must be elucidated. Transcription factor EB (TFEB) is a master regulator of both autophagy and lysosome biogenesis, and lysosomes are important cellular iron storage organelles; however, the role of TFEB in ferroptosis and iron metabolism remains unclear. In this study, TFEB overexpression promoted the clearance of misfolded α-synuclein and prevented ferroptosis and iron overload. TFEB overexpression up-regulated transferrin receptor 1 (TfR1) synthesis and increased the localization of TfR1 in the lysosome, facilitating lysosomal iron import and transient lysosomal iron storage. TFEB overexpression increased the levels of cellular iron-safe storage proteins (both ferritin light and heavy chains). These functions in iron metabolism maintain the cellular labile iron at a low level and electrical activity, even under iron overload conditions. Notably, lower levels of cellular labile iron and the upregulation of ferritin light and heavy chains were reversed after TfR1 knockdown in cells overexpressing TFEB, indicating that TFEB regulates cellular labile iron and suppresses ferroptosis in a TfR1 dependent manner. Taken together, this evidence of the regulation of iron metabolism enriches our understanding of the function of TFEB. In addition, TFEB overexpression protects against ferroptosis and iron overload and provides a new direction and perspective for autophagy regulation in PD.

Identification of the bacterial metabolite aerugine as potential trigger of human dopaminergic neurodegeneration

The causes of nigrostriatal cell death in idiopathic Parkinson's disease are unknown, but exposure to toxic chemicals may play some role. We followed up here on suggestions that bacterial secondary metabolites might be selectively cytotoxic to dopaminergic neurons. Extracts from Streptomyces venezuelae were found to kill human dopaminergic neurons (LUHMES cells). Utilizing this model system as a bioassay, we identified a bacterial metabolite known as aerugine (C10H11NO2S; 2-[4-(hydroxymethyl)-4,5-dihydro-1,3-thiazol-2-yl]phenol) and confirmed this finding by chemical re-synthesis. This 2-hydroxyphenyl-thiazoline compound was previously shown to be a product of a wide-spread biosynthetic cluster also found in the human microbiome and in several pathogens. Aerugine triggered half-maximal dopaminergic neurotoxicity at 3-4 µM. It was less toxic for other neurons (10-20 µM), and non-toxic (at <100 µM) for common human cell lines. Neurotoxicity was completely prevented by several iron chelators, by distinct anti-oxidants and by a caspase inhibitor. In the Caenorhabditis elegans model organism, general survival was not affected by aerugine concentrations up to 100 µM. When transgenic worms, expressing green fluorescent protein only in their dopamine neurons, were exposed to aerugine, specific neurodegeneration was observed. The toxicant also exerted functional dopaminergic toxicity in nematodes as determined by the "basal slowing response" assay. Thus, our research has unveiled a bacterial metabolite with a remarkably selective toxicity toward human dopaminergic neurons in vitro and for the dopaminergic nervous system of Caenorhabditis elegans in vivo. These findings suggest that microbe-derived environmental chemicals should be further investigated for their role in the pathogenesis of Parkinson's disease.

A ratiometric fluorescent probe based on spiropyran in situ switching for tracking dynamic changes of lysosomal autophagy and anticounterfeiting

Autophagy is the controlled breakdown of cellular components that dysfunctional or nonessential, and the decomposition products are further recycled and synthesized for the normal physiological activities of cells. Lysosomal autophagy has been implicated in cancer, neurological disorders, Parkinson's disease, etc. Therefore, it is necessary to develop a fluorescent probe that can clearly describe the process of lysosomal autophagy. However, there are currently limited fluorescent probes for ratiometric monitoring of the autophagic process in dual channels. To solve this problem, a fluorescent probe based on spiropyran with lysosomal targeting and pH response for ratiometric monitoring the autophagy process of lysosomes were designed. The sensitive response of the probe to pH in vitro was verified by UV and fluorescence spectrum tests. Meanwhile, the probe demonstrated the ability to monitor the intracellular pH fluctuations. In addition, the application of Lyso-SD in the field of anti-counterfeiting has been proposed based on the obvious photoluminescence ability of Lyso-SD under UV irradiation.

Intraperitoneal injection of iron dextran induces peripheral iron overload and mild neurodegeneration in the nigrostriatal system in C57BL/6 mice

AIMS

Elevated iron levels in the affected areas of brain are linked to several neurodegenerative diseases including Parkinson's disease (PD). This study investigated the influence of peripheral iron overload in peripheral tissues, as well as its entry into the brain regions on lysosomal functions. The survival of dopaminergic neurons in the nigrostriatal system and motor coordination were also investigated.

MAIN METHODS

An intraperitoneal injection of iron dextran (FeDx) mouse model was established. Western blot was used to detect iron deposition and lysosomal functions in the liver, spleen, hippocampal (HC), striatum (STR), substantia nigra (SN) and olfactory bulb (OB). Iron in serum and cerebrospinal fluid (CSF) was determined by an iron assay kit. Immunofluorescence and immunohistochemical staining were applied to detect dopaminergic neurons and fibers. Motor behavior was evaluated by gait analysis.

KEY FINDINGS

Iron was deposited consistently in the liver and spleen, and serum iron was elevated. While iron deposition occurred late in the HC, STR and SN, without apparently affecting CSF iron levels. Although cathepsin B (CTSB), cathepsin D (CTSD), glucocerebrosidase (GCase) and lysosome integrated membrane protein 2 (LIMP-2) protein levels were dramatically up-regulated in the liver and spleen, they were almost unchanged in the brain regions. However, CTSB was up-regulated in acute iron-overloaded OB and primary cultured astrocytes. The number of dopaminergic neurons in the SN remained unchanged, and mice did not exhibit significant motor incoordination.

SIGNIFICANCE

Intraperitoneal injection of FeDx in mice induces largely peripheral iron overload while not necessarily sufficient to cause severe disruption of the nigrostriatal system.

PM2.5 exposure triggers cell death through lysosomal membrane permeabilization and leads to ferroptosis insensitivity via the autophagy dysfunction/p62-KEAP1-NRF2 activation in neuronal cells

PM2.5 exposure can be associated with the onset of neurodegenerative diseases, with oxidative stress-induced cellular homeostasis disruption and cell death as one of the main mechanisms. However, the exact cellular and molecular processes are still rarely investigated. Autophagy and KEAP1-NRF2 (Kelch-like ECH-Associating protein 1-nuclear factor erythroid 2 related factor 2) signaling pathway are two main cellular defense systems for maintaining cellular homeostasis and resisting oxidative stress. In this study, we primarily investigated the role of autophagy and KEAP1-NRF2 in regulating cell death resulting from PM2.5 exposure in mouse neuroblastoma N2a cells. Our results showed that PM2.5 exposure disrupted autophagic flux by impairing lysosomal function, including lysosomal alkalinization, increased lysosome membrane permeabilization (LMP), and Cathepsin B release. Furthermore, dysregulated autophagy enhances NRF2 activity in a p62-dependent manner, which then initiates the expression of a series of antioxidant genes and increases cellular insensitivity to ferroptosis. Meanwhile, autophagy dysfunction impairs the intracellular degradation of ferroptosis related proteins such as GPX4 and ferritin. As these proteins accumulate, cells also become less sensitive to ferroptosis. LMP-associated cell death may be the main mechanism of PM2.5-induced N2a cytotoxicity. Our results may provide insights into the mechanisms of PM2.5-induced neurotoxicity and predict effective prevention and treatment strategies.

Attenuated iron stress and oxidative stress may participate in anti-seizure and neuroprotective roles of xenon in pentylenetetrazole-induced epileptogenesis

The previous studies have demonstrated the excellent neuroprotective effects of xenon. In this study, we verified the anti-seizure and neuroprotective roles of xenon in epileptogenesis and evaluated the involvement of oxidative stress and iron accumulation in the protective roles of xenon. Epileptogenesis was induced by pentylenetetrazole (PTZ) treatment in Sprague-Dawley rats. During epileptogenesis, we found increased levels of iron and oxidative stress accompanied by elevated levels of divalent metal transporter protein 1 and iron regulatory protein 1, which are closely associated with iron accumulation. Meanwhile, the levels of autophagy and mitophagy increased, alongside significant neuronal damage and cognitive deficits. Xenon treatment reversed these effects: oxidative stress and iron stress were reduced, neuronal injury and seizure severity were attenuated, and learning and memory deficits were improved. Thus, our results confirmed the neuroprotective and anti-seizure effects of xenon treatment in PTZ-induced epileptogenesis. The reduction in oxidative and iron stress may be the main mechanisms underlying xenon treatment. Thus, this study provides a potential intervention strategy for epileptogenesis.

The critical role of ferritinophagy in human disease

Ferritinophagy is a type of autophagy mediated by nuclear receptor activator 4 (NCOA4), which plays a role in inducing ferroptosis by regulating iron homeostasis and producing reactive oxygen species in cells. Under physiological conditions, ferritinophagy maintains the stability of intracellular iron by regulating the release of free iron. Studies have demonstrated that ferritinophagy is necessary to induce ferroptosis; however, under pathological conditions, excessive ferritinophagy results in the release of free iron in large quantities, which leads to lipid peroxidation and iron-dependent cell death, known as ferroptosis. Ferritinophagy has become an area of interest in recent years. We here in review the mechanism of ferritinophagy and its association with ferroptosis and various diseases to provide a reference for future clinical and scientific studies.

6-Hydroxydopamine Induces Abnormal Iron Sequestration in BV2 Microglia by Activating Iron Regulatory Protein 1 and Inhibiting Hepcidin Release

Disrupted iron homeostasis in the substantia nigra pars compacta (SNpc) is an important pathological mechanism in Parkinson’s disease (PD). It is unclear what role microglia play in iron metabolism and selective iron deposition in the SNpc of PD brain. In this study, we observed that 6-hydroxydopamine (6-OHDA) induced the expression of divalent metal transporter-1 (DMT1) and iron influx in BV2 microglia cells, which might be associated with the upregulation of iron regulatory protein 1 (IRP1) expression. Moreover, we found that 6-OHDA had no significant effect on the expression of ferroportin 1 (FPN1) and iron efflux in BV2 microglial cells, which might be the combined action of IRP1 upregulation and reduced hepcidin levels. Furthermore, 6-OHDA treatment activated BV2 microglia and enhanced the release of pro-inflammatory cytokines. Interestingly, iron overloading suppressed IRP1 expression, thus downregulating DMT1 and upregulating FPN1 levels in these microglial cells. On the contrary, iron deficiency activated IRP1, leading to increased expression of DMT1 and decreased expression of FPN1—which indicates that activated IRP1 induces iron overloading in 6-OHDA-treated microglia, but not iron overloading modulates the expression of IRP1. Taken together, our data suggest that 6-OHDA can regulate the expression of DMT1 and FPN1 by activating IRP1 and inhibiting hepcidin release, thus leading to abnormal iron sequestration in microglia. In addition, 6-OHDA can activate microglia, which leads to increased release of pro-inflammatory factors that can further induce genome damage in dopaminergic neurons.

Desferrioxamine Ameliorates Lipopolysaccharide-Induced Lipocalin-2 Upregulation via Autophagy Activation in Primary Astrocytes

Lipocalin-2 (LCN2) is an important regulator of both neuroinflammation and iron homeostasis. Upregulated LCN2 was observed in reactive astrocytes in the Parkinson's disease (PD) models. In the present study, we reported iron chelator deferoxamine (DFO) abolished lipopolysaccharide (LPS)-induced LCN2 upregulation in primary astrocytes, although iron overload had no effects. The suppressive effects of DFO were consistent with autophagy inducer rapamycin or carfilzomib, blocked by autophagy inhibitor 3-methyladenine rather than chloroquine or bafilomycin A1, meanwhile, while were not dependent on proteasome system and NF-κB pathway. DFO was not able to ameliorate LCN2 upregulation in α-synuclein-treated astrocytes, because DFO failed to induce autophagy in these cells. We further demonstrated that DFO could not enhance autophagy lysosomal degradation, however promoted secretory autophagy in primary astrocytes with LPS insults. These data suggest that DFO could serve as an autophagy activator, capable of ameliorating the upregulation of LCN2 in astrocytes by acting on the formation of autophagosomes and secretory autophagy. This provides better understandings of DFO-mediated neuroprotection against neuroinflammation and provides new insights that autophagy activation could be beneficial approaches in PD.

iTRAQ and PRM-Based Proteomic Analysis Provides New Insights into Mechanisms of Response to Triple Therapy in Patients with Rheumatoid Arthritis

Background

Approximately 30% of patients with rheumatoid arthritis (RA) respond poorly to combination therapy of multiple drugs. The molecular mechanisms of different responses to methotrexate + leflunomide + infliximab therapy in patients with RA were explored in this study.

Methods

Infliximab was administered to patients with RA whose disease activity score was higher than 5.1 after 1 month of combination therapy with methotrexate and leflunomide. After 14 weeks of undergoing triple therapy, patients with RA were classified as responders and non-responders. Protein profiles at baseline and 14th week were investigated via isobaric tags for relative and absolute quantification (iTRAQ), and proteins with significant differences ≥1.2 folds change or ≤0.8 folds change were defined as differentially expressed proteins (DEPs). Overlapping DEPs between responders and non-responders were confirmed by parallel reaction monitoring (PRM). Bioinformatic analyses were performed for DEPs.

Results

The results revealed 5 non-responders (NRs) and 15 responders (Rs). iTRAQ analysis indicated 13 overlapping DEPs and included 6 opposite change DEPs such as testicular tissue protein Li 70, cofilin 1, fibrinogen beta chain, galectin-10, serotransferrin (TF) and albumin. The difference in serotransferrin between responders and non-responders confirmed by PRM was significant. Verification by PRM indicated that TF was elevated in the Rs group and was reduced in the NRs group. Bioinformatic analysis indicated that serotransferrin was involved in the hypoxia-inducible factor-1 pathway and ferroptosis.

Conclusion

Serotransferrin-related molecular mechanism may be a new direction to study refractory RA.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Vibrational Fingerprint Analysis of an Azo-based Resonance Raman Scattering Probe for Imaging Proton Distribution in Cellular Lysosomes

Due to the fundamental mechanism of vibrational state transitions for chemical bonds, the spectra of Raman scattering are narrow-banded and photostable signals capable of probing specific reactions. In the case of protonation/deprotonation reactions, certain chemical bonds are broken and new bonds are formed. Based on the changes of the vibrational modes for the corresponding bonds, fingerprint analysis of multiple Raman bands may allow for the in situ visualization of proton distribution in live cells. However, Raman scattering faces the well-known challenge of low sensitivity. To perform the vibrational fingerprint analysis of Raman scattering by overcoming this challenge, we developed an azo-based resonance Raman pH probe. It was an azobenzene-featured small molecule responsive to protons with the inherent Raman signal ∼10⁴-fold more intense than that of the conventional alkyne-type Raman reporter 5-ethynyl-2'-deoxyuridine. Through the substitution of the electron-donating and -withdrawing entities to the azobenzene group, the effect of resonance Raman scattering and fluorescence quenching was obtained. This effect resulted in a significant Raman enhancement factor of ∼10³ compared to the counterpart molecules without the molecular design. Based on the enhanced Raman sensitivity of the azo-based resonance Raman pH probe, the identification of vibrational fingerprint changes at the azo group was achieved during the protonation/deprotonation reactions, and the vibrational fingerprint analysis resolved a pH difference of less than 0.2 unit. The method enabled sensitive hyperspectral cell imaging that clearly visualized the change of proton distribution in autophagic cells.

Neuroprotective Activities of Curcumin in Parkinson's Disease: A Review of the Literature

Parkinson's disease (PD) is a slowly progressive multisystem disorder affecting dopaminergic neurons of the substantia nigra pars compacta (SNpc), which is characterized by a decrease of dopamine (DA) in their striatal terminals. Treatment of PD with levodopa or DA receptor agonists replaces the function of depleted DA in the striatum. Prolonged treatment with these agents often has variable therapeutic effects and leads to the development of undesirable dyskinesia. Consequently, a crucial unmet demand in the management of Parkinson's disease is the discovery of new approaches that could slow down, stop, or reverse the process of neurodegeneration. Novel potential treatments involving natural substances with neuroprotective activities are being developed. Curcumin is a polyphenolic compound isolated from the rhizomes of Curcuma longa (turmeric). It has been demonstrated to have potent anti-inflammatory, antioxidant, free radical scavenging, mitochondrial protecting, and iron-chelating effects, and is considered a promising therapeutic and nutraceutical agent for the treatment of PD. However, molecular and cellular mechanisms that mediate the pharmacological actions of curcumin remain largely unknown. Stimulation of nicotinic receptors and, more precisely, selective α7 nicotinic acetylcholine receptors (α7-nAChR), have been found to play a major modulatory role in the immune system via the "cholinergic anti-inflammatory pathway". Recently, α7-nAChR has been proposed to be a potential therapeutic approach in PD. In this review, the detailed mechanisms of the neuroprotective activities of curcumin as a potential therapeutic agent to help Parkinson's patients are being discussed and elaborated on in detail.

Blood-Derived α-Synuclein Aggregated in the Substantia Nigra of Parabiotic Mice

As a pathological biomarker of Parkinson’s disease, α-synuclein is thought to be a prion-like protein, but evidence for the transmission of α-synuclein from blood to the brain is unclear. The goals of this study were to determine whether blood-derived α-synuclein could enter the brains of mice and whether α-synuclein in the brain could be cleared by parabiosis. Heterochronic parabiosis was performed on SNCA^A53T transgenic mice (A53T mice) and wildtype mice. The levels of human α-synuclein in the blood and substantia nigra of wildtype mice were significantly increased after 4-month parabiosis with A53T mice. Moreover, the expression of α-synuclein filament, but not of total α-synuclein, was significantly increased in the substantia nigra of wildtype mice that were paired with A53T mice. However, the levels of human α-synuclein displayed no significant change in the serum, blood, or substantia nigra of A53T mice. These results provide direct evidence that pathological α-synuclein can be transmitted from blood to the brain in the heterochronic parabiosis system; however, it appears to be difficult to clear it from the brain in a short period of time.

Corynoxine Protects Dopaminergic Neurons Through Inducing Autophagy and Diminishing Neuroinflammation in Rotenone-Induced Animal Models of Parkinson's Disease

Recent studies have shown that impairment of autophagy is related to the pathogenesis of Parkinson's disease (PD), and small molecular autophagy enhancers are suggested to be potential drug candidates against PD. Previous studies identified corynoxine (Cory), an oxindole alkaloid isolated from the Chinese herbal medicine Uncaria rhynchophylla (Miq.) Jacks, as a new autophagy enhancer that promoted the degradation of α-synuclein in a PD cell model. In this study, two different rotenone-induced animal models of PD, one involving the systemic administration of rotenone at a low dosage in mice and the other involving the infusion of rotenone stereotaxically into the substantia nigra pars compacta (SNpc) of rats, were employed to evaluate the neuroprotective effects of Cory. Cory was shown to exhibit neuroprotective effects in the two rotenone-induced models of PD by improving motor dysfunction, preventing tyrosine hydroxylase (TH)-positive neuronal loss, decreasing α-synuclein aggregates through the mechanistic target of the rapamycin (mTOR) pathway, and diminishing neuroinflammation. These results provide preclinical experimental evidence supporting the development of Cory into a potential delivery system for the treatment of PD.

An anthracene–quinoline based dual-mode fluorometric–colorimetric sensor for the detection of Fe3+ and its application in live cell imaging

A highly sensitive anthracene–quinoline based dual-mode sensor has been synthesized and used for the fluorometric and colorimetric detection of Fe³⁺ and in live cell imaging.

Attenuation of the mutual elevation of iron accumulation and oxidative stress may contribute to the neuroprotective and anti-seizure effects of xenon in neonatal hypoxia-induced seizures

Previous studies have suggested that xenon inhalation has neuroprotective and antiepileptic effects; however, the underlying mechanisms involved remain unclear. This study aimed to investigate the possible xenon inhalation mechanisms involved in the neuroprotection and antiepileptic effects. A neonatal hypoxic C57BL/6J mouse model was used for the experiments. Immediately after hypoxia treatment, the treatment group inhaled a xenon mixture (70% xenon/21% oxygen/9% nitrogen) for 60 min, while the hypoxia group inhaled a non-xenon mixture (21% oxygen/79% nitrogen) for 60 min. Seizure activity was recorded at designated time points using electroencephalography. Oxidative stress levels, iron levels, neuronal injury, and learning and memory functions were also studied. The results showed that hypoxia increased the levels of iron, oxidative stress, mitophagy, and neurodegeneration, which were accompanied by seizures and learning and memory disorders. In addition, our results confirmed that xenon treatment significantly attenuated the hypoxia-induced seizures and cognitive defects in neonatal C57 mice. Moreover, the increased levels of iron, oxidative stress, mitophagy, and neuronal injury were reduced in xenon-treated mice. This study confirms the significant protective effects of a xenon mixture on hypoxia-induced damage in neonatal mice. Furthermore, our results suggest that reducing oxidative stress levels and iron accumulation may be the underlying mechanisms of xenon activity. Studying the protective mechanisms of xenon will advance its applications in potential therapeutic strategies.

Different iron deposition patterns in Parkinson's disease subtypes: a quantitative susceptibility mapping study

Background

Parkinson's disease (PD) is a heterogeneous neurodegenerative disorder with various subtypes and uncertain pathogenesis. Iron deposition is considered to be involved in the pathological mechanisms of PD. The present study aimed to investigate the iron deposition in deep gray matter in patients with different PD subtypes using quantitative susceptibility mapping (QSM).

Methods

Forty-six PD patients and 22 healthy controls (HCs) were recruited for the study. PD patients were allocated to the tremor-dominant (TD) group (n=22), postural instability and gait disorder-dominant (PIGD) group (n=19), and intermediate group (n=5). Susceptibility values in deep gray matter nuclei measured by QSM among the PD-TD and PD-PIGD groups and the HCs, as well as the relationship between iron accumulation and clinical motor features, were investigated.

Results

Susceptibility values in the dentate nucleus (DN) were greater in the PD-TD (118.73±70.45) group than in the PD-PIGD (72.14±39.85, P=0.02) group and HCs (78.26±41.38, P=0.042). Further, a significant positive correlation was observed between the DN susceptibility values and tremor scores (r=0.324, P=0.028). Compared with the HCs (182.60±85.35), both the PD-TD (282.00±102.49, P=0.006) and PD-PIGD groups (284.91±118.54, P=0.007) exhibited greater susceptibility values in the substantia nigra (SN) pars reticulata. The susceptibility values in the SN pars compacta were also greater in the PD-PIGD group (164.51±89.44) than in the HCs (107.78±63.11, P=0.048).

Conclusions

The present study demonstrated various iron deposition patterns in different PD phenotypes. These findings give insight into the pathophysiology underlying different PD phenotypes, and potentially illustrate the involvement of iron deposition in the PD-TD and PD-PIGD subtypes.

MSTN Attenuates Cardiac Hypertrophy through Inhibition of Excessive Cardiac Autophagy by Blocking AMPK /mTOR and miR-128/PPARγ/NF-κB

Cardiac hypertrophy, a response of the heart to increased workload, is a major risk factor for heart failure. Myostatin (MSTN) is an inhibitor of myogenesis, regulating the number and size of skeletal myocytes. In recent years, cardiomyocyte autophagy also has been considered to be involved in controlling the hypertrophic response. However, less is known about the detailed mechanism of MSTN on cardiac hypertrophy via regulation of cardiomyocyte autophagy. In this study, we found that the deletion of MSTN potentiated abdominal aorta coarctation (AAC) and angiotensin II (Ang II)-induced pathological cardiac hypertrophy and cardiac autophagy; however, AAC and Ang II-induced cardiac hypertrophic phenotype and cardiac autophagy were dramatically diminished by MSTN in vivo and in vitro. Mechanistically, the anti-hypertrophic and anti-autophagic effects mediated by MSTN in response to pathological stimuli were associated with the direct inactivation of activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) and activation of the peroxisome proliferator-activated receptor gamma (PPARγ)/nuclear factor κB (NF-κB) signaling pathway. Additionally, miR-128 aggravated the progression of cardiac hypertrophy through suppressing its target PPARγ. Furthermore, MSTN downregulated miR-128 expression induced by AAC and Ang II. Taken together, MSTN significantly blunts pathological cardiac hypertrophy and dysfunction, at least in part, by inhibiting excessive cardiac autophagy via blocking AMPK/mTOR and miR-128/PPARγ/NF-κB signaling pathways.

Evaluation of serum iron overload, AST:ALT ratio and log10ferritin:AST ratio among schizophrenia patients in the Kumasi Metropolis, Ghana: a case-control study

OBJECTIVE

The association between unbalanced iron indices and the conditions of schizophrenia are not well understood. Liver dysfunction which has been linked to iron metabolism might be a contributing factor. This case-control study evaluated serum iron indices and liver function in treatment-naïve schizophrenia patients and those already on treatment at the Psychiatric Department of the Komfo Anokye Teaching Hospital (KATH), Kumasi-Ghana.

RESULTS

The mean age of the respondents was 39.6 ± 0.8 years. Increased levels of serum iron, TS, AST, ALT and AST:ALT ratio and lower levels of UIBC, TIBC, Transferrin, and log Ferritin:AST ratio levels were observed among the treatment-naïve group compared to the control. The treatment-naïve and treatment groups showed significantly higher serum AST:ALT ratio, and lower log10ferrtin:AST ratio than the healthy controls. There was a significant correlation between log10ferritin and AST, and log10ferritin and GGT in both treatments (r = 0.343; p = 0.003, and r = 0.502; p = 0.001 respectively) and treatment-naïve groups (r = 0.348; p = 0.002, and r = 0.614; p < 0.001 respectively). Percentage transferrin saturation correlated significantly with GGT only, in the treatment-naïve group (r = 0.667; p < 0.001), and ALT and GGT in the treatment group (r = 0.252; p = 0.030 and r = 0.646; p = 0.014 respectively).

Iron dysregulation in vascular dementia: Focused on the AMPK/autophagy pathway

Recent researches suggested that iron dysregulation play an important role in the pathogenesis of vascular dementia (VD). Iron deposition had been found in hippocampus in vascular dementia model in recent research. Nevertheless, the underlying mechanisms of iron deposition and its neurotoxicity in vascular dementia was still unclear. Thus, our research was aimed at whether the neurotoxicity of iron was associated with autophagy regulation. We established a chronic cerebral hypoperfusion model in the rat brain in order to mimic the vascular dementia using permanent bilateral common carotid artery occlusion (2VO). The preparation of iron overloaded rats model by intraperitoneal injection of iron dextran. Following, we tested the learning and memory function of each group using Morris Water Maze. Consequently, we analyzed the iron content and iron transport related molecules (TFR1, DMT1) in hippocampus. Furthermore, we examined the effect of iron deposition on autophagy-related molecules including AMPK, Beclin1 and LC3 and the number of autophagosomes in hippocampus. Last, we tested the apoptosis of neurons in hippocampus. We found that iron deposition in hippocampus in model groups which accompanied the decline of learning and memory function. And the expression of TFR1 and DMT1 were up-regulated in model groups. Moreover, iron deposition up-regulated the expression of AMPK, Beclin1 and LC3 and increase the number of autophagosomes in hippocampus. And the expression of Bax was up-regulated and Bcl-2 was down-regulated in iron deposition groups. To sum up, our data suggested that iron deposition increased AMPK/autophagy pathway associated molecules in the hippocampus and promoted neuronal apoptosis, which might be a new pathogenesis in vascular dementia.

Rebalancing metal dyshomeostasis for Alzheimer's disease therapy

Alzheimer's disease (AD) is a type of neurodegenerative malady that is associated with the accumulation of amyloid plaques. Metal ions are critical for the development and upkeep of brain activity, but metal dyshomeostasis can contribute to the development of neurodegenerative diseases, including AD. This review highlights the association between metal dyshomeostasis and AD pathology, the feasibility of rebalancing metal homeostasis as a therapeutic strategy for AD, and a survey of current drugs that action via rebalancing metal homeostasis. Finally, we discuss the challenges that should be overcome by researchers in the future to enable the practical use of metal homeostasis rebalancing agents for clinical application.

Long-term iron exposure causes widespread molecular alterations associated with memory impairment in mice

Limited literature available indicates the neurotoxic effects of excessive iron, however, a deep understanding of iron neurotoxicity needs to be developed. In this study, we evaluated the toxic effects of excessive iron on learning and cognitive function in long-term iron exposure (oral, 10 mg/L, 6 months) of mice by behavioral tests including novel object recognition test, step-down passive avoidance test and Morris water maze test, and further analyzed differential expression of hippocampal proteins. The behavioral tests consistently showed that iron treatment caused cognitive defects of the mice. Proteomic analysis revealed 66 differentially expressed hippocampal proteins (30 increased and 36 decreased) in iron-treated mice as compared with the control ones. Bioinformatics analysis showed that the dysregulated proteins mainly included: synapse-associated proteins (i.e. synaptosomal-associated protein 25 (SNAP25), complexin-1 (CPLX1), vesicle-associated membrane protein 2 (VAMP2), neurochondrin (NCDN)); mitochondria-related proteins (i.e. ADP/ATP translocase 1 (SLC25A4), 14-3-3 protein zeta/delta (YWHAZ)); cytoskeleton proteins (i.e. neurofilament light polypeptide (NEFL), tubulin beta-2B chain (TUBB2B), tubulin alpha-4A chain (TUBA4A)). The findings suggest that the dysregulations of synaptic, mitochondrial, and cytoskeletal proteins may be involved in iron-triggered memory impairment. This study provides new insights into the molecular mechanisms of iron neurotoxicity.