The role of iron in brain ageing and neurodegenerative disorders

Iron metabolism and ferroptosis in health and diseases: The crucial role of mitochondria in metabolically active tissues

Iron is essential in various physiological processes, but its accumulation leads to oxidative stress and cell damage, thus iron homeostasis has to be tightly regulated. Ferroptosis is an iron-dependent non-apoptotic regulated cell death characterized by iron overload and reactive oxygen species accumulation. Mitochondria are organelles playing a crucial role in iron metabolism and involved in ferroptosis. MitoNEET, a protein of mitochondrial outer membrane, is a key element in this process. Ferroptosis, altering iron levels in several metabolically active organs, is linked to several non-communicable diseases. For example, iron overload in the liver leads to hepatic fibrosis and cirrhosis, accelerating non-alcholic fatty liver diseases progression, in the muscle cells contributes to oxidative damage leading to sarcopenia, and in the brain is associated to neurodegeneration. The aim of this review is to investigate the intricate balance of iron regulation focusing on the role of mitochondria and oxidative stress, and analyzing the ferroptosis implications in health and disease.

Unraveling the mystery of citrate transporters in Alzheimer's disease: An updated review

A key molecule in cellular metabolism, citrate is essential for lipid biosynthesis, energy production, and epigenetic control. The etiology of Alzheimer's disease (AD), a progressive neurodegenerative illness marked by memory loss and cognitive decline, may be linked to dysregulated citrate transport, according to recent research. Citrate transporters, which help citrate flow both inside and outside of cells, are becoming more and more recognized as possible participants in the molecular processes underlying AD. Citrate synthase (CS), a key enzyme in the tricarboxylic acid (TCA) cycle, supports mitochondrial function and neurotransmitter synthesis, particularly acetylcholine (ACh), essential for cognition. Changes in CS activity affect citrate availability, influencing energy metabolism and neurotransmitter production. Choline, a precursor for ACh, is crucial for neuronal function. Lipid metabolism, oxidative stress reactions, and mitochondrial function can all be affected by aberrant citrate transport, and these changes are linked to dementia. Furthermore, the two main pathogenic characteristics of AD, tau hyperphosphorylation and amyloid-beta (Aβ) aggregation, may be impacted by disturbances in citrate homeostasis. The goal of this review is to clarify the complex function of citrate transporters in AD and provide insight into how they contribute to the development and course of the illness. We aim to provide an in-depth idea of which particular transporters are dysregulated in AD and clarify the functional implications of these dysregulated transporters in brain cells. To reduce neurodegenerative processes and restore metabolic equilibrium, we have also discussed the therapeutic potential of regulating citrate transport. Gaining insight into the relationship between citrate transporters and the pathogenesis of AD may help identify new indicators for early detection and creative targets for treatment. This study offers hope for more potent ways to fight this debilitating illness and is a crucial step in understanding the metabolic foundations of AD.

Absence of astrocytic ceruloplasmin reverses the senescence process with aging of learning and memory abilities

Ceruloplasmin (CP) is a multi-copper ferroxidase mainly synthesized by liver, secreted into the peripheral blood, playing a critical role in regulating the iron homeostasis. In the central nervous system (CNS), the CP expressed by astrocytes plays an important role in the transportation of iron from the blood across the blood-brain barrier (BBB) into the brain. Our previous study showed that conditional knockout of astrocytic CP with Cre-LoxP system (CpGfapcKO) not only improved the learning and memory abilities of elderly mice, but also impaired the learning and memory abilities of young mice. In order to further investigate the effects of CP on learning and memory with aging, we constructed mice model with tamoxifen-induced astrocyte specific knockout of CP, induced CP knockout at 12 months old, and observed the effects on mouse learning and memory at 18 months old. We were delighted to found that ablation of astrocytic CP by tamoxifen at 12 months old could similarly enhance the learning, memory and recognition abilities in 18-month-old mice. Iron deposition in the hippocampus associated with aging was mitigated, leading to a reduction in oxidative stress. The MAPK/JNK pathway exhibited attenuation, while the PI3K/Akt/GSK3 pathway showed enhancement. This combination is expected to result in the reduction of the phosphorylation level of MYC and the elevation of the nuclear translocation of MYC, which might then contribute to reduced cellular senescence. Additionally, the ROS/MAPK/Erk and ROS/MAPK/p38 pathways-dependent cell apoptosis in hippocampus was diminished. The hallmarks of Alzheimer's Disease (AD) were all significantly reduced. Ultimately, the alleviated cellular senescence along with the reduction in AD-related markers, coincided with an improvement in learning, memory, and recognition abilities. These findings further elucidated the role of CP in brain iron metabolism, offering a novel target and strategy for the prevention and treatment of neurodegenerative diseases, such as AD associated with aging.

Exploring morphological and microstructural signatures across the Alzheimer's spectrum and risk factors

Neural alterations, including myelin degeneration and inflammation-related iron burden, may accompany early Alzheimer's disease (AD) pathophysiology. This study aims to identify multi-modal signatures associated with MRI-derived atrophy and quantitative MRI (qMRI) measures of myelin and iron in a unique dataset of 158 participants across the AD spectrum, including those without cognitive impairment, at familial risk for AD, with mild cognitive impairment, and with AD dementia. Our results revealed a brain pattern with decreased cortical thickness, indicating increased neuronal death, and compromised hippocampal integrity due to reduced myelin content. This pattern was associated with lifestyle factors such as smoking, high blood pressure, high cholesterol, and anxiety, as well as older age, AD progression, and APOE-ɛ4 carrier status. These findings underscore the value of qMRI metrics as a non-invasive tool, offering sensitivity to lifestyle-related modifiable risk factors and medical history, even in preclinical stages of AD.

The role of microglia in neurodegenerative diseases: from the perspective of ferroptosis

Iron plays a pivotal role in numerous fundamental biological processes in the brain. Among the various cell types in the central nervous system, microglia are recognized as the most proficient cells in accumulating and storing iron. Nonetheless, iron overload can induce inflammatory phenotype of microglia, leading to the production of proinflammatory cytokines and contributing to neurodegeneration. A growing body of evidence shows that disturbances in iron homeostasis in microglia is associated with a range of neurodegenerative disorders. Recent research has revealed that microglia are highly sensitive to ferroptosis, a form of iron-dependent cell death. How iron overload influences microglial function? Whether disbiosis in iron metabolism and ferroptosis in microglia are involved in neurodegenerative disorders and the underlying mechanisms remain to be elucidated. In this review we focus on the recent advances in research on microglial iron metabolism as well as ferroptosis in microglia. Meanwhile, we provide a comprehensive overview of the involvement of microglial ferroptosis in neurodegenerative disorders from the perspective of crosstalk between microglia and neuron, with a focus on Alzheimer's disease and Parkinson's disease.

Selenoprotein K Confers Protection against Iron Dyshomeostasis-Related Neurotoxicity by Regulating the Palmitoylation of TfR-1

Selenoprotein K (SELENOK), a protein residing in the endoplasmic reticulum (ER), is modulated by dietary selenium and is expressed at elevated levels in neurons. SELENOK has been shown to participate in cellular antioxidant activity and posttranslational palmitoylation. This study presents both in vivo and in vitro evidence that SELENOK deficiency reduces the palmitoylation of TfR-1, thereby impairing transferrin transport and ultimately leading to a decrease in the intracellular iron content, impaired mitochondrial respiratory chain activity and decreased ATP production. Remarkably, restoring SELENOK levels significantly enhanced TfR-1 palmitoylation, increased intracellular iron levels, and restored mitochondrial function, thus ameliorating cognitive deficits in 7 month-old SELENOK knockout mice. Consistent with these findings, iron supplementation also improved mitochondrial function by elevating intracellular iron levels, thereby improving cognitive deficits in 7 month-old SELENOK knockout mice. Therefore, SELENOK exerts its neuroprotective effect by regulating the palmitoylation of TfR-1 to maintain iron homeostasis, thereby protecting mitochondrial function in neurons.

Identifying brain degeneration patterns in early-stage Parkinson's disease: a multimodal MRI study

Parkinson's disease (PD) is a highly heterogeneous neurodegenerative disorder. This study aimed to identify different patterns of early brain degeneration in PD patients and investigate their clinical relevance. 179 early-stage PD patients and 115 healthy controls were included. We assessed cortical morphology, white matter microstructure, and subcortical iron metabolism using multimodal magnetic resonance imaging and employed clustering techniques to identify subtypes. Two subtypes were identified: the early-deterioration subtype, characterized by fronto-temporal atrophy, parietal thickening, widespread reductions in fractional anisotropy (FA) values, and increased subcortical iron content, which exhibited more severe baseline symptoms and a trend of faster memory decline; and the early-compensatory subtype, characterized by rostral middle frontal atrophy, parietal-occipital thickening, increased FA values, and normal iron content, which exhibited milder symptoms initially but experienced faster progression of both motor and non-motor symptoms. These discoveries provided new insights into disease heterogeneity and facilitated the exploration of early neurodegenerative mechanisms.

Ferroptosis in Alzheimer's Disease: The Regulatory Role of Glial Cells

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the formation of amyloid plaques, neurofibrillary tangles and progressive cognitive decline. Amyloid-beta peptide (Aβ) monoclonal antibody therapeutic clinical trials have nearly failed, raising significant concerns about other etiological hypotheses about AD. Recent evidence suggests that AD patients also exhibit persistent neuronal loss and neuronal death accompanied by brain iron deposition or overload-related oxidative stress. Ferroptosis is a type of cell death that depends on iron, unlike autophagy and apoptosis. Inhibiting neuronal ferroptosis function is effective in improving cognitive impairment in AD. Notably, new research shows that ferroptosis in AD is crucially dependent on glial cell activation. This review examines the relationship between the imbalance of iron metabolism, the regulation of iron homeostasis in glial cells and neuronal death in AD pathology. Finally, the review summarizes some current drug research in AD targeting iron homeostasis, many novel iron-chelating compounds and natural compounds showing potential AD-modifying properties that may provide therapeutic targets for treating AD.

Induction of Ferroptotic Cell Death by Neuromelanin Pigments in Dopaminergic Cells

Neuromelanin (NM) is an iron-rich, insoluble brown or black pigment that exhibits protective properties. However, its accumulation over time may render it a source of free radicals. In Parkinson's disease, dopaminergic neurons with the highest NM levels and increased iron content are preferentially vulnerable to degeneration. Considering NM's iron binding capacity and the critical role of iron in ferroptosis, we aimed to investigate the interplay between neuromelanin and ferroptosis in dopaminergic cells. We prepared two NM pigments: iron-free NM (ifNM) and iron-containing NM (Fe3+NM) and, exposed to cells. After verifying NM accumulation, cell viability was assessed in the absence or presence of antioxidants (NAC (1 mM), Trolox (100 μM)) and specific inhibitors of cell death types. Ferroptosis-related parameters, including lipid peroxidation byproducts (4-HNE), lipid ROS, glutathione, intracellular iron, GPX4, and ACSL4, and cellular iron metabolism-related proteins (TfR1, ferroportin, ferritin, IREB2) were evaluated following ifNM and Fe3+NM treatments, with or without Ferrostatin-1, Liproxstatin-1 and deferoxamine. Both NMs induced cell death via distinct mechanisms. Ferroptotic cell death by ifNM and Fe3+NM was reversed by ferrostatin-1 and NAC (p < 0.05). Significant alterations in lipid peroxidation, GPX4 levels, and iron metabolism were observed independent of NM's iron composition (p < 0.05). Ferritin levels increased following ifNM treatment, reflecting an adaptive response to iron overload, while Fe3+NM treatment led to ferritin depletion, possibly via ferritinophagy. Our findings reveal a distinct role of iron-rich and iron-free neuromelanin in modulating ferroptotic pathways, highlighting the potential of targeting neuromelanin-iron interactions as a therapeutic strategy to mitigate neuronal ferroptosis in Parkinson's disease.

Increased cortical iron deposition in glioma patients: a quantitative susceptibility mapping study

OBJECTIVES

This study aimed to evaluate how cortical gray matter iron, measured using quantitative susceptibility mapping (QSM), changes in glioma patients and its relationship to cognitive scores.

MATERIALS AND METHODS

This study included 121 glioma patients (45.42 ± 11.59 years; 61 females and 60 males) and 42 healthy controls (39.93 ± 10.37 years; 19 females and 23 males). The participants underwent cognitive assessment and brain magnetic resonance imaging using a 3D multi-echo gradient-echo sequence on a 3.0 T scanner. ITK-SNAP was used to measure the susceptibility values reflecting the iron content in the regions of interest (ROIs). We used analysis of covariance to investigate the differences in susceptibility between glioma patients and healthy controls in each brain region. Pearson's correlation analysis assessed the relationship between cortical magnetic susceptibility values and cognitive scores (MoCA).

RESULTS

The frontal (p < 0.001), precentral gyrus (p < 0.001), postcentral gyrus (p < 0.001), parietal (p < 0.001), insular (p < 0.001), occipital (p < 0.001), and temporal cortices (p < 0.001) showed higher magnetic susceptibility in glioma patients than in healthy controls. There was a negative correlation between MoCA scores and magnetic susceptibility values in each brain region, precentral gyrus with significant differences (r = -0.253, p = 0.028).

CONCLUSION

We quantified cortical magnetic susceptibility values reflecting the iron content in glioma patients using QSM and assessed participants' cognitive function using MoCA, and found that cortical iron deposition was increased in different brain regions and that cognitive decline in glioma patients may be associated with elevated iron content in the precentral gyrus.

Oxidant-Based Cytotoxic Agents During Aging: From Disturbed Energy Metabolism to Chronic Inflammation and Disease Progression

In humans, aging is an inevitable consequence of diminished growth processes after reaching maturity. The high order of biomolecules in cells and tissues is continuously disturbed by numerous physical and chemical destructive impacts. Host-derived oxidant-based cytotoxic agents (reactive species, transition free metal ions, and free heme) contribute considerably to this damage. These agents are under the control of immediately acting antagonizing principles, which are important to ensure cell and tissue homeostasis. In this review, I apply the concept of host-derived cytotoxic agents and their interplay with antagonizing principles to the aging process. During aging, energy metabolism and the supply of tissues with dioxygen and nutrients are increasingly disturbed. In addition, a chronic inflammatory state develops, a condition known as inflammaging. The balance between oxidant-based cytotoxic agents and protective mechanisms is analyzed depending on age-based physiological alterations in ATP production. Disturbances in this balance are associated with the development of age-related diseases and comorbidities. An enhanced production of reactive species from dysfunctional mitochondria, alterations in cellular redox homeostasis, and adaptations to hypoxia are highlighted. Examples of how disturbances between oxidant-based cytotoxic agents and antagonizing principles contribute to the pathogenesis of diseases in persons of advanced age are given.

Inhaled Lead Nanoparticles Enter the Brain through the Olfactory Pathway and Induce Neurodegenerative Changes Resembling Tauopathies

Lead nanoparticles (PbNPs) in air pollution pose a significant threat to human health, especially due to their neurotoxic effects. In this study, we exposed mice to lead(II) oxide nanoparticles (PbONPs) in inhalation chambers to mimic real-life exposure and assess their impact on the brain. PbONPs caused the formation of Hirano bodies and pathological changes related to neurodegenerative disorders through cytoskeletal disruptions without the induction of inflammation. Damage to astrocytic endfeet and capillary endothelial cells indicated a compromised blood-brain barrier (BBB), allowing PbONPs to enter the brain. Additionally, NPs were detected along the olfactory pathway, including fila olfactoria, suggesting that at least a proportion of PbNPs enter the brain directly by passing through the olfactory epithelium. PbNP inhalation severely damaged the apical parts of olfactory epithelial cells, including the loss of microtubules in their ciliary distal segments. Inhalation of PbONPs led to the rapid accumulation of lead in the brain, while more soluble lead(II) nitrate NPs did not accumulate significantly until 11 weeks of exposure. PbNPs induced disruption of the BBB at multiple levels, ranging from ultrastructural changes to functional impairments of the barrier; however, they did not induce systemic inflammation in the brain. The clearance ability of the brain to remove Pb was very low for both types of NPs, with significant pathological effects persisting even after a long clearance period. Cation-binding proteins (ZBTB20 and calbindin1) were distributed unevenly in the brain, with the strongest signal located in the hippocampus, which exhibited the greatest defects in nuclear architecture, indicating that this area is the most sensitive structure for PbNP exposure. PbNP exposure also altered the PI3K/Akt/mTOR signaling pathway, and tau phosphorylation in the hippocampus and inhibition of tau phosphorylation by GSK-3 inhibitor rescued the negative effect of PbONPs on the intracellular calcium level in trigeminal ganglion cultures. In zebrafish larvae, PbONPs affected locomotor activity and reduced calcium levels in the medium enhanced negative effect of PbONP on animal mobility, even increasing lethality. These findings suggest that cytoskeletal disruption and calcium dysregulation are key factors in PbNP-induced neurotoxicity, providing potential targets for therapeutic intervention to prevent neurodegenerative changes following PbNP exposure.

Air Pollution-Induced Neurotoxicity: The Relationship Between Air Pollution, Epigenetic Changes, and Neurological Disorders

Air pollution is a major global health threat, responsible for over 8 million deaths in 2021, including 700,000 fatalities among children under the age of five. It is currently the second leading risk factor for mortality worldwide. Key pollutants, such as particulate matter (PM2.5, PM10), ozone, sulfur dioxide, nitrogen oxides, and carbon monoxide, have significant adverse effects on human health, contributing to respiratory and cardiovascular diseases, as well as neurodevelopmental and neurodegenerative disorders. Among these, particulate matter poses the most significant threat due to its highly complex mixture of organic and inorganic compounds with diverse sizes, compositions, and origins. Additionally, it can penetrate deeply into tissues and cross the blood-brain barrier, causing neurotoxicity which contributes to the development of neurodegenerative diseases. Although the link between air pollution and neurological disorders is well documented, the precise mechanisms and their sequence remain unclear. Beyond causing oxidative stress, inflammation, and excitotoxicity, studies suggest that air pollution induces epigenetic changes. These epigenetic alterations may affect the expression of genes involved in stress responses, neuroprotection, and synaptic plasticity. Understanding the relationship between neurological disorders and epigenetic changes induced by specific air pollutants could aid in the early detection and monitoring of central nervous system diseases.

Dexmedetomidine Improves Long-term Neurological Outcomes by Promoting Oligodendrocyte Genesis and Myelination in Neonatal Rats Following Hypoxic-ischemic Brain Injury

Neonatal hypoxic-ischemic brain injury (HIBI) can lead to white matter damage, which significantly contributes to cognitive dysfunction, emotional disorders, and sensorimotor impairments. Although dexmedetomidine enhances neurobehavioral outcomes, its impact on oligodendrocyte genesis and myelination following hypoxic-ischemic events, as well as the underlying mechanisms, remain poorly understood. Dexmedetomidine was administered 15 min post-HIBI. We assessed neurobehavioral deficits using various tests: surface righting, negative geotaxis, forelimb grip strength, cliff avoidance, sensory reflexes, novel object recognition, T-maze, and three-chamber social interaction. We also investigated the relationship between myelination and neurobehavioral outcomes. Measurements included oligodendrocyte precursor cell (OPC) proliferation and survival 24 h post-injury, early myelination, and oligodendrocyte differentiation by postnatal day 14. Furthermore, we evaluated microglial activation towards the M2 phenotype and the extent of neuroinflammation during the acute phase. Dexmedetomidine significantly ameliorated long-term neurological deficits caused by HIBI. Pearson linear regression analysis revealed a strong correlation between long-term neurological outcomes and myelin maturity. The treatment notably mitigated the long-term deterioration of myelin formation and maturation following HIBI. This protective effect was primarily due to enhanced OPC proliferation and survival post-HIBI during the acute phase and, to a lesser extent, to the modulation of microglial activity towards the M2 phenotype and a reduction in neuroinflammation. Dexmedetomidine offers substantial protection against long-term neurobehavioral disabilities induced by HIBI, primarily by revitalizing the impaired survival and maturation of oligodendrocyte progenitor cells and promoting myelination.

Cognitive implications and associated transcriptomic signatures of distinct regional iron depositions in cerebral small vessel disease

INTRODUCTION

Regional brain iron dyshomeostasis is observed in cerebral small vessel disease (cSVD) and other neurodegeneration processes. However, its spatial patterns, cognitive impact, and underlying pathological mechanisms remain unclear.

METHODS

Voxel-based analysis of quantitative susceptibility mapping (QSM) was used to detect regional susceptibility changes, and their correlations with cognitive function were assessed using linear regression. We combined the microarray dataset from the Allen Human Brain Atlas (AHBA) to explore the pathological mechanisms of iron deposition patterns.

RESULTS

A total of 87 cSVD patients and 80 controls were included in the study. Increased QSM values in the bilateral putamen and caudate were associated with cognitive decline in cSVD. Gene set enrichment analysis revealed the enrichment of gene sets related to central nervous system integrity.

DISCUSSION

Iron deposition in deep gray matter may indicate cognitive changes in cSVD and could be linked to the disruption of brain structural and functional integrity.

HIGHLIGHTS

Increased susceptibility values, indicating focal iron deposition, were observed in the deep gray matter of patients with cerebral small vessel disease (cSVD). Regional iron concentration in the deep gray nuclei was associated with cognitive impairment in cSVD patients. Imaging transcriptomics suggests that cSVD-related iron deposition is linked to the structural and functional integrity of the brain. An open-source script for imaging transcriptomics focusing on regional gene expression was developed and proposed.

Impact of Nutrition on the Gut Microbiota: Implications for Parkinson's Disease

Parkinson's disease (PD) is a multifactorial neurodegenerative disease that is characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta and by the anomalous accumulation of α-synuclein aggregates into Lewy bodies and Lewy neurites. Research suggests 2 distinct subtypes of PD: the brain-first subtype if the pathology arises from the brain and then spreads to the peripheral nervous system (PNS) and the body-first subtype, where the pathological process begins in the PNS and then spreads to the central nervous system. This review primarily focuses on the body-first subtype. The influence of the gut microbiota on the development of PD has been the subject of growing interest among researchers. It has been suggested that gut inflammation may be closely associated with pathogenesis in PD, therefore leading to the hypothesis that gut microbiota modulation could play a significant role in this process. Nutrition can influence gut health and alter the risk and progression of PD by altering inflammatory markers. This review provides an overview of recent research that correlates variations in gut microbiota composition between patients with PD and healthy individuals with the impact of certain nutrients and dietary patterns, including the Mediterranean diet, the Western diet, and the ketogenic diet. It explores how these diets influence gut microbiota composition and, consequently, the risk of PD. Last, it examines fecal transplantation and the use of prebiotics, probiotics, or synbiotics as potential therapeutic strategies to balance the gut microbiome, aiming to reduce the risk or delay the progression of PD.

Depthwise cortical iron relates to functional connectivity and fluid cognition in healthy aging

Age-related differences in fluid cognition have been associated with both the merging of functional brain networks, defined from resting-state functional magnetic resonance imaging (rsfMRI), and with elevated cortical iron, assessed by quantitative susceptibility mapping (QSM). Limited information is available, however, regarding the depthwise profile of cortical iron and its potential relation to functional connectivity. Here, using an adult lifespan sample (n = 138; 18-80 years), we assessed relations among graph theoretical measures of functional connectivity, column-based depthwise measures of cortical iron, and fluid cognition (i.e., tests of memory, perceptual-motor speed, executive function). Increased age was related both to less segregated functional networks and to increased cortical iron, especially for superficial depths. Functional network segregation mediated age-related differences in memory, whereas depthwise iron mediated age-related differences in general fluid cognition. Lastly, higher mean parietal iron predicted lower network segregation for adults younger than 45 years of age. These findings suggest that functional connectivity and depthwise cortical iron have distinct, complementary roles in the relation between age and fluid cognition in healthy adults.

Ferroptosis: when metabolism meets cell death

We present here a comprehensive update on recent advancements in the field of ferroptosis, with a particular emphasis on its metabolic underpinnings and physiological impacts. After briefly introducing landmark studies that have helped to shape the concept of ferroptosis as a distinct form of cell death, we critically evaluate the key metabolic determinants involved in its regulation. These include the metabolism of essential trace elements such as selenium and iron; amino acids such as cyst(e)ine, methionine, glutamine/glutamate, and tryptophan; and carbohydrates, covering glycolysis, the citric acid cycle, the electron transport chain, and the pentose phosphate pathway. We also delve into the mevalonate pathway and subsequent cholesterol biosynthesis, including intermediate metabolites like dimethylallyl pyrophosphate, squalene, coenzyme Q (CoQ), vitamin K, and 7-dehydrocholesterol, as well as fatty acid and phospholipid metabolism, including the biosynthesis and remodeling of ester and ether phospholipids and lipid peroxidation. Next, we highlight major ferroptosis surveillance systems, specifically the cyst(e)ine/glutathione/glutathione peroxidase 4 axis, the NAD(P)H/ferroptosis suppressor protein 1/CoQ/vitamin K system, and the guanosine triphosphate cyclohydrolase 1/tetrahydrobiopterin/dihydrofolate reductase axis. We also discuss other potential anti- and proferroptotic systems, including glutathione S-transferase P1, peroxiredoxin 6, dihydroorotate dehydrogenase, glycerol-3-phosphate dehydrogenase 2, vitamin K epoxide reductase complex subunit 1 like 1, nitric oxide, and acyl-CoA synthetase long-chain family member 4. Finally, we explore ferroptosis's physiological roles in aging, tumor suppression, and infection control, its pathological implications in tissue ischemia-reperfusion injury and neurodegeneration, and its potential therapeutic applications in cancer treatment. Existing drugs and compounds that may regulate ferroptosis in vivo are enumerated.

The neuropathologic basis for translational biomarker development in the macaque model of late-onset Alzheimer's disease

BackgroundAccurate placement of the macaque within the Alzheimer's disease (AD) research framework is essential to discover early-stage predictive biomarkers.ObjectiveTo assess utility of the aging macaque in advancing translational biomarker development for preclinical AD, we evaluated relative signal strength of comparable neuropathologic phenomena in macaques and patients.MethodsWe compared pathology in patient and macaque formalin-fixed paraffin embedded (FFPE) tissues using identical criteria. We quantified expression of amyloid-β (Aβ), pTau, and inflammatory and senescence markers across species. Distribution of AD-relevant markers were compared in FFPE and perfused frozen macaque brain to assess expression of labile proteins that could inform in-life fluid biomarkers.ResultsAβ pathology in macaques closely approximated patient pathology. Complex plaque composition in macaques implied significant disruption of synaptic connectivity. In FFPE tissue, pretangle pTau immunoreactivity placed the macaque in Braak Stage 1b. In perfused frozen tissue, soluble pTau distribution approximated Braak Stage III-IV. In macaque, Aβ, pTau, and acetylcholinesterase labeling co-localized to AD-vulnerable circuits. Significant association of glial fibrillary acidic protein with Aβ occurred in humans only. The senescence marker p16 correlated positively with pTau expression and negatively with Aβ in patients only. Macaques lacked neuropathologic co-morbidities.ConclusionsAD-relevant neuropathologic signals in the macaque support biomarker discovery in the areas of Aβ plaque evolution and associated synaptic disruption as well as early-stage tau phosphorylation. Relative protection from accumulation of senescence markers, fibrillar tau and neuropathologic co-morbidities in macaque implicate species difference in rates of biological brain aging. We provide over 4000 digital slides for further study.

Oxidative Stress and Redox Imbalance: Common Mechanisms in Cancer Stem Cells and Neurodegenerative Diseases

Oxidative stress (OS) is an established hallmark of cancer and neurodegenerative disorders (NDDs), which contributes to genomic instability and neuronal loss. This review explores the contrasting role of OS in cancer stem cells (CSCs) and NDDs. Elevated levels of reactive oxygen species (ROS) contribute to genomic instability and promote tumor initiation and progression in CSCs, while in NDDs such as Alzheimer's and Parkinson's disease, OS accelerates neuronal death and impairs cellular repair mechanisms. Both scenarios involve disruption of the delicate balance between pro-oxidant and antioxidant systems, which leads to chronic oxidative stress. Notably, CSCs and neurons display alterations in redox-sensitive signaling pathways, including Nrf2 and NF-κB, which influence cell survival, proliferation, and differentiation. Mitochondrial dynamics further illustrate these differences: enhanced function in CSCs supports adaptability and survival, whereas impairments in neurons heighten vulnerability. Understanding these common mechanisms of OS-induced redox imbalance may provide insights for developing interventions, addressing aging hallmarks, and potentially mitigating or preventing both cancer and NDDs.

Reevaluating the role of amyloid β-peptides in Alzheimer's disease: from pathogenic agents to protective chelation mechanisms

Alzheimer's disease (AD) is a multifaceted neurodegenerative disorder with complex etiology, often associated with histological markers of oxidative stress, inflammation, and disturbances in calcium homeostasis. Traditionally, amyloid β-peptides (Aβ) have been considered key contributors to these pathological processes. However, emerging evidence suggests a protective role for Aβ and the enzymes involved in its production. This article further explores the hypothesis published by us a decade before that posits amyloid β-peptides and the β-secretase enzyme (BACE1) are part of an intentionally designed cellular defense mechanism against metal toxicity. This challenges the conventional understanding of their roles in AD pathogenesis. It is not until this BACE1 system, primarily the associated amyloid plaque deposit sites, are saturated with heavy and other metals and the exposure to these cations continues to influx oxidative ions into the brain, do the indications of neurodegeneration begin to become symptomatic. Until this metal oversaturation takes place, the system - Aβ and the enzymes involved in its production and conveyance - keeps the oxidative potential of the metal toxins sequestered extracellularly and out of the way of the neuron's intracellular activities.

Iron Overload, Microbleeding and the Role of Bilirubin in Alzheimer's Disease Brain: Revisiting the Vascular Hypothesis

Alzheimer's disease (AD) and vascular dementia (VaD) are the two most prevalent forms of dementia, sharing overlapping clinical features yet distinct pathophysiological mechanisms. While AD is primarily driven by amyloid-beta (Aβ) plaques and tau neurofibrillary tangles, VaD results from cerebrovascular pathology, including ischemic lesions and chronic hypoperfusion. However, accumulating evidence suggests that vascular dysfunction is a crucial contributor to both conditions, bridging neurodegenerative and cerebrovascular pathologies. In this review, we explore the interplay between AD and VaD, focusing on shared pathways such as blood-brain barrier (BBB) breakdown, neuroinflammation, and microvascular damage. Notably, cerebral microbleeds have emerged as a common feature in both AD and VaD, further linking vascular pathology to neurodegeneration. Microbleeding contributes to BBB disruption, iron deposition, and exacerbated oxidative stress, creating a vicious cycle that accelerates cognitive decline. We highlight the role of iron dysregulation as a key driver in AD, exacerbating Aβ accumulation, tau hyperphosphorylation, and ferroptosis. Conversely, bilirubin emerges as a molecule with theranostic potential, acting as both a biomarker and a neuroprotective agent due to its antioxidant and anti-inflammatory properties. Despite its protective role, bilirubin's dysregulation under pathological conditions may contribute to oxidative damage and neurovascular dysfunction. In this context, the accumulation of iron from recurrent microbleeds may further disrupt bilirubin homeostasis, amplifying oxidative injury and inflammation. We propose a vascular hypothesis that integrates iron metabolism and bilirubin homeostasis, suggesting that their imbalance plays a central role in AD pathogenesis and worsening. Understanding the intricate molecular interplay between neurodegeneration and vascular dysfunction could provide novel insights into targeted interventions aimed at mitigating cognitive decline. Finally, we discuss the potential of bilirubin-based therapeutic strategies, including its role in counteracting oxidative stress and modulating neuroinflammatory pathways, offering promising avenues for future research and precision medicine in dementia.

Cerebral iron accumulation in multiple sclerosis: Pathophysiology and therapeutic implications

Multiple sclerosis (MS) is a chronic autoimmune disorder of the central nervous system characterized by demyelination, neuroinflammation, and neurodegeneration. Recent studies highlight the role of cerebral iron (Fe) accumulation in exacerbating MS pathophysiology. Fe, essential for neural function, contributes to oxidative stress and inflammation when dysregulated, particularly in the brain's gray matter and demyelinated lesions. Advanced imaging techniques, including susceptibility-weighted and quantitative susceptibility mapping, have revealed abnormal Fe deposition patterns in MS patients, suggesting its involvement in disease progression. Iron's interaction with immune cells, such as microglia, releases pro-inflammatory cytokines, further amplifying neuroinflammation and neuronal damage. These findings implicate Fe dysregulation as a significant factor in MS progression, contributing to clinical manifestations like cognitive impairment. Therapeutic strategies targeting Fe metabolism, including Fe chelation therapies, show promise in reducing Fe-related damage, instilling optimism about the future of MS treatment. However, challenges such as crossing the blood-brain barrier and maintaining Fe homeostasis remain. Emerging approaches, such as Fe-targeted nanotherapeutics and biologics, offer new possibilities for personalized treatments. However, the journey is far from over. Continued research into the molecular mechanisms of Fe-induced neuroinflammation and oxidative damage is essential. Through this research, we can develop effective interventions that could slow MS progression and improve patient outcomes.

Heterologous Expression of Either Human or Soya Bean Ferritins in Budding Yeast Reveals Common Functions Protecting Against Oxidative Agents and Counteracting Double-Strand Break Accumulation

Ferritins are globular proteins that, upon self-assembly in nanocages, are capable of bio-safely storing huge concentrations of bioavailable iron. They are present in most cell types and organisms; one of the exceptions is yeast. Heterologous expression of either human or vegetal ferritins in Saccharomyces cerevisiae revealed new and unknown functions for soya bean ferritins; validated this model by confirming previously characterized functions in human ferritins and also demonstrated that, like human H chain, vegetal H1, and H2 chains also shown a tendency to localize in the nucleus when expressed in an eukaryotic cell model lacking plastids and chloroplasts. Furthermore, when expressed in the system budding yeast, the four ferritins (human H and L and soya bean H1 and H2 chains) present equivalent and relevant functions as protectors against oxidative damage and against the accumulation of double-strand breaks in the DNA. We present evidence demonstrating that these effects are exclusively observed with oxidative agents that operate through the Fenton reaction, such as H2O2. Here, we also discuss the ferritin requirement for N-glycosylation to exert these functions. We believe that our approach might contribute to extending the knowledge around ferritin function and its consequent relevance to human health.

Iron deposition in subcortical nuclei of Parkinson's disease: A meta-analysis of quantitative iron-sensitive magnetic resonance imaging studies

BACKGROUND

Iron deposition plays a crucial role in the pathophysiology of Parkinson's disease (PD), yet the distribution pattern of iron deposition in the subcortical nuclei has been inconsistent across previous studies. We aimed to assess the difference patterns of iron deposition detected by quantitative iron-sensitive magnetic resonance imaging (MRI) between patients with PD and patients with atypical parkinsonian syndromes (APSs), and between patients with PD and healthy controls (HCs).

METHODS

A systematic literature search was conducted on PubMed, Embase, and Web of Science databases to identify studies investigating the iron content in PD patients using the iron-sensitive MRI techniques (R2 * and quantitative susceptibility mapping [QSM]), up until May 1, 2023. The quality assessment of case-control and cohort studies was performed using the Newcastle-Ottawa Scale, whereas diagnostic studies were assessed using the Quality Assessment of Diagnostic Accuracy Studies-2. Standardized mean differences and summary estimates of sensitivity, specificity, and area under the curve (AUC) were calculated for iron content, using a random effects model. We also conducted the subgroup-analysis based on the MRI sequence and meta-regression.

RESULTS

Seventy-seven studies with 3192 PD, 209 multiple system atrophy (MSA), 174 progressive supranuclear palsy (PSP), and 2447 HCs were included. Elevated iron content in substantia nigra (SN) pars reticulata ( P <0.001) and compacta ( P <0.001), SN ( P <0.001), red nucleus (RN, P <0.001), globus pallidus ( P <0.001), putamen (PUT, P = 0.021), and thalamus ( P = 0.029) were found in PD patients compared with HCs. PD patients showed lower iron content in PUT ( P <0.001), RN ( P = 0.003), SN ( P = 0.017), and caudate nucleus ( P = 0.017) than MSA patients, and lower iron content in RN ( P = 0.001), PUT ( P <0.001), globus pallidus ( P = 0.004), SN ( P = 0.015), and caudate nucleus ( P = 0.001) than PSP patients. The highest diagnostic accuracy distinguishing PD from HCs was observed in SN (AUC: 0.85), and that distinguishing PD from MSA was found in PUT (AUC: 0.90). In addition, the best diagnostic performance was achieved in the RN for distinguishing PD from PSP (AUC: 0.86).

CONCLUSIONS

Quantitative iron-sensitive MRI could quantitatively detect the iron content of subcortical nuclei in PD and APSs, while it may be insufficient to accurately diagnose PD. Future studies are needed to explore the role of multimodal MRI in the diagnosis of PD.

REGISTRISION

PROSPERO (CRD42022344413).

Proteomic Investigation of Neurotrophic trans-Banglene Reveals Potential Link to Iron Homeostasis

In an effort to gain insight into cellular systems impacted by neurotrophic trans-banglene (t-BG), global proteomic profiling and Western blot analyses were employed. Expression level changes in response to t-BG treatment were compared to those observed with nerve growth factor (NGF), a natural neurotrophic protein and functional analog to t-BG. Findings from these studies did not point to direct interception of NGF/TrkA signaling by t-BG. Instead, significant alterations in iron-binding and iron-regulating proteins were observed. While total iron levels showed no change across all treatments, intracellular iron measurements and mitochondrial iron measurements demonstrated lower ferrous (Fe2+) ion levels in t-BG treated cells but not in NGF treated cells. These results highlight a potential connection between iron regulation and neurotrophic activity, a relationship which has, to date, not been well studied. These results are also notable given that iron dysregulation occurs in most neurodegenerative disease settings, and that iron has been shown to facilitate protein aggregation and apoptotic mechanisms.

Melatonin alleviates ferroptosis triggered by cadmium via regulating ferritinophagy and iron metabolism in spermatogonia

Melatonin (Mel), a classical antioxidant, has the potential to mediate ferroptosis. Cadmium (Cd) poses a substantial threat to the male reproductive system, as it can induce testicular injury by triggering ferroptosis. The study aimed to explore the protective role and mechanism of Mel in Cd-induced ferroptosis in spermatogonia (spg). Our results demonstrated that Cd disrupted the mitochondrial ultrastructure and induced more autophagosomes in spg. Exposure to Cd resulted in a reduction of the mitochondrial membrane potential of the cells. The transcriptomics analysis revealed significant differences in gene expression associated with ferroptosis and autophagy. Mel could reverse the changes caused by Cd in the genes mentioned above. Furthermore, Cd increased cellular iron content and elevated reactive oxygen species levels, which induced oxidative stress in spg. Mel pretreatment reduced iron accumulation and oxidative damage caused by Cd exposure. Additional studies demonstrated that Cd exposure activated NCOA4-mediated ferritinophagy in spg. Mel pretreatment, as anticipated, inhibited the increased the mRNA and protein expression of ATG5, LC3B, and NCOA4 caused by Cd, ameliorated Cd-caused iron overload and oxidative stress, and protected spg from ferroptosis. Our study provides a therapeutic basis for the use of Mel to treat Cd-induced testicular injury.

Overcoming failure: improving acceptance and success of implanted neural interfaces

Implanted neural interfaces are electronic devices that stimulate or record from neurons with the purpose of improving the quality of life of people who suffer from neural injury or disease. Devices have been designed to interact with neurons throughout the body to treat a growing variety of conditions. The development and use of implanted neural interfaces is increasing steadily and has shown great success, with implants lasting for years to decades and improving the health and quality of life of many patient populations. Despite these successes, implanted neural interfaces face a multitude of challenges to remain effective for the lifetime of their users. The devices are comprised of several electronic and mechanical components that each may be susceptible to failure. Furthermore, implanted neural interfaces, like any foreign body, will evoke an immune response. The immune response will differ for implants in the central nervous system and peripheral nervous system, as well as over time, ultimately resulting in encapsulation of the device. This review describes the challenges faced by developers of neural interface systems, particularly devices already in use in humans. The mechanical and technological failure modes of each component of an implant system is described. The acute and chronic reactions to devices in the peripheral and central nervous system and how they affect system performance are depicted. Further, physical challenges such as micro and macro movements are reviewed. The clinical implications of device failures are summarized and a guide for determining the severity of complication was developed and provided. Common methods to diagnose and examine mechanical, technological, and biological failure modes at various stages of development and testing are outlined, with an emphasis on chronic in vivo characterization of implant systems. Finally, this review concludes with an overview of some of the innovative solutions developed to reduce or resolve the challenges faced by implanted neural interface systems.

Mild traumatic brain injury increases cortical iron: evidence from individual susceptibility mapping

Quantitative susceptibility mapping has been applied to map brain iron distribution after mild traumatic brain injury to understand properties of neural tissue which may be related to cellular dyshomeostasis. However, this is a heterogeneous injury associated with microstructural brain changes, and 'traditional' group-wise statistical approaches may lead to a loss of clinically relevant information, as subtle alterations at the individual level can be obscured by averages and confounded by within-group variability. More precise and individualized approaches are needed to characterize mild traumatic brain injury better and elucidate potential cellular mechanisms to improve intervention and rehabilitation. To address this issue, we use quantitative MRI to build individualized profiles of regional positive (iron-related) magnetic susceptibility across 34 bilateral cortical ROIs following mild traumatic brain injury. Healthy population templates were constructed for each cortical area using standardized Z-scores derived from 25 age-matched male controls aged between 16 and 32 years (M = 21.10, SD = 4.35), serving as a reference against which Z-scores of 35 males with acute (<14 days) sports-related mild traumatic brain injury were compared [M = 21.60 years (range: 16-33), SD = 4.98]. Secondary analyses sensitive to cortical depth and curvature were also generated to approximate the location of iron accumulation in the cortical laminae and the effect of gyrification. Primary analyses indicated that approximately one-third (11/35; 31%) of injured participants exhibited elevated positive susceptibility indicative of abnormal iron profiles relative to the healthy population, a finding that was mainly concentrated in regions within the temporal lobe. Injury severity was significantly higher (P = 0.02) for these participants than their iron-normal counterparts, suggesting a link between injury severity, symptom burden, and elevated cortical iron. Secondary exploratory analyses of cortical depth and curvature profiles revealed abnormal iron accumulation in 83% (29/35) of mild traumatic brain injury participants, enabling better localization of injury-related changes in iron content to specific loci within each region and identifying effects that may be more subtle and lost in region-wise averaging. Our findings suggest that individualized approaches can further elucidate the clinical relevance of iron in mild head injury. Differences in injury severity between iron-normal and iron-abnormal mild traumatic brain injury participants identified in our primary analysis highlight not only why precise investigation is required to understand the link between objective changes in the brain and subjective symptomatology, but also identify iron as a candidate biomarker for tissue pathology after mild traumatic brain injury.

Epigenetic regulation of iron metabolism and ferroptosis in Parkinson's disease: Identifying novel epigenetic targets

Parkinson's disease (PD) is a neurodegenerative disease, and emerging evidence has shown that iron deposition, ferroptosis and epigenetic modifications are implicated in the pathogenesis of PD. However, the interplay among these factors in PD has not been fully understood. In this review, we provide an overview of the current research progress on iron metabolism, ferroptosis and epigenetic alterations associated with PD. Furthermore, we present new frontiers concerning various epigenetic modifications related to iron metabolism and ferroptosis that might contribute to the pathology of PD. Notably, epigenetic modifications of iron metabolism and ferroptosis as both diagnostic and therapeutic targets in PD have been discussed. This opens new avenues for the regulation of iron homeostasis and ferroptosis in PD from epigenetic perspectives, and provides evidence for their potential implications in the diagnosis and treatment of PD.

Abnormalities of iron homeostasis and the dopaminergic system in Tourette syndrome revealed by 7T MRI and PET

While the implication of a dysfunctional dopaminergic system in Tourette syndrome (TS) is well established, the underlying pathophysiological mechanisms remain unclear. Apart from neurotransmitters, disturbed iron homeostasis and iron regulatory mechanisms are also suspected. Iron is a trace element of fundamental biological importance and is involved in the synthesis and metabolism of dopamine and its receptors and transporters. The goal of the current pre-registered, multi-modal, cross-sectional study was to investigate the relationship between potential iron homeostasis imbalances and dopaminergic system disturbances in patients with TS. Susceptibility-sensitive MRI at 7 Tesla was used to obtain surrogate measures for local brain iron in 25 patients with TS (age 30 ± 9 years, 6 female) and 40 matched control subjects. Additionally, dopamine D1 receptor availability was investigated with [11C]SCH23390 PET in a subgroup of 20 patients and 20 controls. Significantly reduced sub-cortical magnetic susceptibility, indicating reduced iron levels, was observed in TS patients in the caudate, pallidum, sub-thalamic nucleus, thalamus, red nucleus and substantia nigra. These reductions were accompanied by significant reductions of the [11C]SCH23390 binding potential indicating reduced availability of D1 receptors in the dorsal striatum. The D1 receptor abnormality correlated with tic severity. These results point to alterations of intra-synaptic dopamine release and reduced striatal D1 receptor binding, supporting the notion of disruption in multiple functional elements of the dopaminergic system. Such dopaminergic abnormalities appear to be associated with disturbances in iron homeostasis.

Iron content of glioblastoma tumours and role of ferrous iron in the hypoxic response in vitro

Introduction

Glioblastomas are an aggressive primary brain cancer, characterised by hypoxia and poor patient survival. Iron is the most abundant transition metal in the brain, yet data on the iron content of brain cancers is sparse. Ferrous iron is an essential cofactor for a super-family of enzymes, the iron- and 2-oxoglutarate-dependent dioxygenase enzymes (2-OGDD). These enzymes control the response to hypoxia via hydroxylation of the hypoxia-inducible factor-1α (HIF-1α), and DNA demethylation via hydroxylation of 5-methyl cytosines (5hmC).

Methods

This study used clinical glioblastoma samples from 40 patients to determine the relationship between 2-OGDD activity and iron. Elemental iron was measured using inductively coupled plasma mass spectrometry (ICP-MS) and ferrous iron was measured using the colorimetric ferrozine assay. Iron measurements were compared against patient survival and clinicopathological data, and 2-OGDD-dependent activity of HIF-1 activation and 5hmC.

Results and discussion

Elemental and ferrous iron levels were weakly related. Higher ferrous iron content of clinical glioblastoma tissue was associated with longer overall survival compared to lower ferrous iron content, but elemental iron showed no such relationship. Neither form of iron was related to clinicopathological data or markers of 2-OGDD activity. The impact of iron supplementation on the hypoxic response was assessed in three glioblastoma cell lines in vitro, similarly showing only a limited influence of iron on these 2-OGDD enzymes. Our data, together with prior studies in anaemic patients, highlight the importance of healthy iron levels in patients with glioblastoma, but further mechanistic studies are needed to elucidate the molecular pathways involved.

Characterizing positive and negative quantitative susceptibility values in the cortex following mild traumatic brain injury: a depth- and curvature-based study

Evidence has linked head trauma to increased risk factors for neuropathology, including mechanical deformation of the sulcal fundus and, later, perivascular accumulation of hyperphosphorylated tau adjacent to these spaces related to chronic traumatic encephalopathy. However, little is known about microstructural abnormalities and cellular dyshomeostasis in acute mild traumatic brain injury in humans, particularly in the cortex. To address this gap, we designed the first architectonically motivated quantitative susceptibility mapping study to assess regional patterns of net positive (iron-related) and net negative (myelin-, calcium-, and protein-related) magnetic susceptibility across 34 cortical regions of interest following mild traumatic brain injury. Bilateral, between-group analyses sensitive to cortical depth and curvature were conducted between 25 males with acute (<14 d) sports-related mild traumatic brain injury and 25 age-matched male controls. Results suggest a trauma-induced increase in net positive susceptibility focal to superficial, perivascular-adjacent spaces in the parahippocampal sulcus. Decreases in net negative susceptibility values in distinct voxel populations within the same region indicate a potential dual pathology of neural substrates. These mild traumatic brain injury-related patterns were distinct from age-related processes revealed by correlation analyses. Our findings suggest depth- and curvature-specific deposition of biological substrates in cortical tissue convergent with features of misfolded proteins in trauma-related neurodegeneration.

Gradients of Nigrostriatal Iron Deposition in Healthy Aging and Synucleinopathies

AIMS

To investigate the gradients of nigrostriatal iron deposition in aging, Parkinson's disease (PD), and multiple system atrophy (MSA).

METHODS

This study included 100 young healthy controls, 171 old healthy controls (OHC), 231 PD, and 24 MSA patients. The brain iron content was quantified by quantitative susceptibility mapping. A spatial function method was employed to map the iron gradient along the principal axis of the subcortical structure. General linear models were used to compare differences in iron gradients between groups. Partial correlation was used to analyze the relationship between iron content and symptoms of synucleinopathies.

RESULTS

Nigrostriatal iron deposition in all gradient directions was observed during aging (p < 0.05). Compared to OHC, iron deposition was significant in nearly all substantia nigra (SN) segments in both PD and MSA (p < 0.05). MSA showed significant iron deposition in the posterolateral putamen compared to PD (p < 0.05). Iron deposition in the SN in PD and putamen in MSA correlated with disease severity.

CONCLUSION

Iron deposition in all gradient directions occurred in the nigrostriatal system during healthy aging, and this was more evident in the SN in both PD and MSA, with MSA displaying additional iron deposition in the posterolateral putamen.

Ferroptosis in Osteoarthritis: Towards Novel Therapeutic Strategy

Osteoarthritis (OA) is a chronic, degenerative joint disease primarily characterised by damage to the articular cartilage, synovitis and persistent pain, and has become one of the most common diseases worldwide. In OA cartilage, various forms of cell death have been identified, including apoptosis, necroptosis and autophagic cell death. Ever-growing observations indicate that ferroptosis, a newly-discovered iron-dependent form of regulated cell death, is detrimental to OA occurrence and progression. In this review, we first analyse the pathogenetic mechanisms of OA by which iron overload, inflammatory response and mechanical stress contribute to ferroptosis. We then discuss how ferroptosis exacerbates OA progression, focusing on its impact on chondrocyte viability, synoviocyte populations and extracellular matrix integrity. Finally, we highlight several potential therapeutic strategies targeting ferroptosis that could be explored for the treatment of OA.

The role of ferritinophagy and ferroptosis in Alzheimer's disease

Iron is a crucial mineral element within human cells, serving as a pivotal cofactor for diverse biological enzymes. Ferritin plays a crucial role in maintaining iron homeostasis within the body through its ability to sequester and release iron. Ferritinophagy is a selective autophagic process in cells that specifically facilitates the degradation of ferritin and subsequent release of free iron, thereby regulating intracellular iron homeostasis. The nuclear receptor coactivator 4 (NCOA4) serves as a pivotal regulator in the entire process of ferritinophagy, facilitating its binding to ferritin and subsequent delivering to lysosomes for degradation, thereby enabling the release of free iron. The free iron ions within the cell undergo catalysis through the Fenton reaction, resulting in a substantial generation of reactive oxygen species (ROS). This process induces lipid peroxidation, thereby stimulating a cascade leading to cellular tissue damage and subsequent initiation of ferroptosis. Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive deterioration of emotional memory and cognitive function, accompanied by mental and behavioral aberrations. The pathology of the disease is characterized by aberrant deposition of amyloid β-protein (Aβ) and hyperphosphorylated tau protein. It has been observed that evident iron metabolism disorders and accumulation of lipid peroxides occur in AD, indicating a significant impact of ferritinophagy and ferroptosis on the pathogenesis and progression of AD. This article elucidates the process and mechanism of ferritinophagy and ferroptosis, investigating their implications in AD to identify novel targets for therapeutic intervention.

Oncogenic KRAS Promotes Ferroptosis in Pancreatic Cancer Through Regulation of the Fosl1-Tfrc Axis

ABSTRACT

Mutant KRAS activation occurs in most of pancreatic ductal adenocarcinoma (PDAC), which induce the sensitivity to ferroptosis of PDAC cells, but the underlying mechanism is still poorly understood. Here, we show how KRAS acts in signaling to activate transcription factor FOSL1, which promotes the expression of the iron uptake receptor TFRC. In PDAC cells, repression of TFRC by KRAS/FOSL1 signaling inhibited intracellular iron levels, thereby restricting the occurrence of ferroptosis. Furthermore, the KRAS/FOSL1/TFRC axis can make the PDAC cells vulnerable to alteration of the iron level in the tumor microenvironment. Our study highlights a pivotal mechanism of PDAC ferroptosis through iron metabolism and supports a new therapeutic strategy for PDAC with superior potential.

Ferroptosis role in complexity of cell death: unrevealing mechanisms in Parkinson's disease and therapeutic approaches

Parkinson's disease (PD), a common neurodegenerative disorder, is characterized by progressive loss of dopaminergic neurons, and accumulation of α-synuclein in the substantial nigra. Emerging evidence identifies ferroptosis as a regulated iron-dependent cell death mechanism marked by excessive lipid peroxidation (LPO) as a key contributor to PD pathogenesis. Ferroptosis is intertwined with critical disease processes such as aggregation of α-synuclein protein, oxidative stress generation, mitochondrial alteration, iron homeostasis dysregulation, and neuroinflammation. This mechanism disrupts cellular homeostasis by impairing iron metabolism and antioxidant pathways like the xc-/glutathione/GPX4 axis and the CoQ10 pathway. This review consolidates current advancements in understanding ferroptosis in these mechanisms, increasing interest in contribution to PD pathology. In addition, it explores the latest developments in ferroptosis-targeting pharmacological agents, including their application in the preclinical and clinical study, and highlights their potential to revolutionize PD management. Unraveling the interplay between ferroptosis and PD offers a transformative perspective, paving the way for innovative therapies to combat this debilitating disease condition.

High correlation of quantitative susceptibility mapping and echo intensity measurements of nigral iron overload in Parkinson's disease

Quantitative susceptibility mapping (QSM) and transcranial sonography (TCS) offer proximal evaluations of iron load in the substantia nigra. Our prospective study aimed to investigate the relationship between QSM and TCS measurements of nigral iron content in patients with Parkinson's disease (PD). In secondary analyses, we wanted to explore the correlation of substantia nigra imaging data with clinical and laboratory findings. Eighteen magnetic resonance imaging and TCS examinations were performed in 15 PD patients at various disease stages. Susceptibility measures of substantia nigra were calculated from referenced QSM maps. Echogenicity of substantia nigra on TCS was measured planimetrically (echogenic area) and by digitized analysis (echo-intensity). Iron-related blood serum parameters were measured. Clinical assessments included the Unified PD Rating Scale and non-motor symptom scales. Substantia nigra susceptibility correlated with echogenic area (Pearson correlation, r = 0.53, p = 0.001) and echo-intensity (r = 0.78, p < 0.001). Individual asymmetry indices correlated between susceptibility and echogenic area measurements (r = 0.50, p = 0.042) and, more clearly, between susceptibility and echo-intensity measurements (r = 0.85, p < 0.001). Substantia nigra susceptibility (individual mean of bilateral measurements) correlated with serum transferrin saturation (Spearman test, r = 0.78, p < 0.001) and, by trend, with serum iron (r = 0.69, p = 0.004). Nigral echogenicity was not clearly related to serum values associated with iron metabolism. Susceptibility and echogenicity measurements were unrelated to PD duration, motor subtype, and severity of motor and non-motor symptoms. The present results support the assumption that iron accumulation is involved in the increase of nigral echogenicity in PD. Nigral echo-intensity probably reflects ferritin-bound iron, e.g. stored in microglia.

Iron metabolism dysfunction in neuropsychiatric disorders: Implications for therapeutic intervention

Iron is a trace metal that takes part in the maintenance of body homeostasis by, for instance, aiding in energy production and immunity. A body of evidence now demonstrates that dysfunction in iron metabolism can have detrimental effects and is intricately associated with the development of neuropsychiatric disorders, including Major Depressive Disorder (MDD), anxiety, and schizophrenia. For instance, changes in serum and central nervous system (CNS) levels of iron and in proteins mediating iron metabolism have been documented in patients grappling with the aforementioned diseases. By contrast, targeting iron metabolism by using iron chelators, for instance, has proven to be effective in alleviating disease burden. Therefore, here we review the state-of-the-art regarding the role of iron metabolism and its dysfunction in the context of neuropsychiatric disorders. Furthermore, we discuss how targeting iron metabolism can be an effective therapeutic option to tackle this class of diseases. Finally, we discuss the mechanisms linking this dysfunction to behavioral changes in these disorders. Harnessing the knowledge of iron metabolism is not only key to the characterization of novel molecular targets and disease biomarkers but also crucial to drug repurposing and drug design.

Iron homeostasis and ferroptosis in muscle diseases and disorders: mechanisms and therapeutic prospects

The muscular system plays a critical role in the human body by governing skeletal movement, cardiovascular function, and the activities of digestive organs. Additionally, muscle tissues serve an endocrine function by secreting myogenic cytokines, thereby regulating metabolism throughout the entire body. Maintaining muscle function requires iron homeostasis. Recent studies suggest that disruptions in iron metabolism and ferroptosis, a form of iron-dependent cell death, are essential contributors to the progression of a wide range of muscle diseases and disorders, including sarcopenia, cardiomyopathy, and amyotrophic lateral sclerosis. Thus, a comprehensive overview of the mechanisms regulating iron metabolism and ferroptosis in these conditions is crucial for identifying potential therapeutic targets and developing new strategies for disease treatment and/or prevention. This review aims to summarize recent advances in understanding the molecular mechanisms underlying ferroptosis in the context of muscle injury, as well as associated muscle diseases and disorders. Moreover, we discuss potential targets within the ferroptosis pathway and possible strategies for managing muscle disorders. Finally, we shed new light on current limitations and future prospects for therapeutic interventions targeting ferroptosis.

How neurons cope with oxidative stress

Neurons are highly dependent on mitochondrial respiration for energy, rendering them vulnerable to oxidative stress. Reactive oxygen species (ROS), by-products of oxidative phosphorylation, can damage lipids, proteins, and DNA, potentially triggering cell death pathways. This review explores the neuronal vulnerability to ROS, highlighting metabolic adaptations and antioxidant systems that mitigate oxidative damage. Balancing metabolic needs and oxidative stress defenses is critical for neurons, as disruptions are implicated in neurodegenerative diseases. Neurons uniquely modulate metabolic pathways, favoring glycolysis over oxidative phosphorylation in cell bodies, to minimize harmful ROS production. Key antioxidants, including superoxide dismutases and glutathione peroxidases, play crucial roles in neuronal protection, as evident from genetic studies linking deficiencies to neurodegeneration. Notably, neurons have the ability to adapt to oxidative conditions in compartment-specific manners and also utilize ROS as a signaling molecule to promote adaptive synaptic plasticity. Future research should aim to elucidate differential ROS signaling and antioxidant responses across neuronal compartments for improved therapeutic strategies.

The role of protein phosphorylation modifications mediated by iron metabolism regulatory networks in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a severe neurodegenerative disease characterized mainly by the formation of amyloid beta (Aβ) plaques and abnormal phosphorylation of tau. In recent years, an imbalance in iron homeostasis has been recognized to play a key role in the pathological process of AD. Abnormal iron accumulation can activate various kinases such as glycogen synthase kinase-3β, cyclin-dependent kinase 5, and mitogen-activated protein kinase, leading to abnormal phosphorylation of tau and amyloid precursor protein, and accelerating the formation of Aβ plaques and neurofibrillary tangles. In addition, iron-mediated oxidative stress not only triggers neuronal damage, but also exacerbates neuronal dysfunction by altering the phosphorylation of N-methyl-D-aspartate receptors and γ-aminobutyric acid type A receptors. Iron accumulation also affects the phosphorylation status of tyrosine hydroxylase, the rate-limiting enzyme for dopamine synthesis, interfering with the dopamine signaling pathway. On the other hand, iron affects iron transport and metabolism in the brain by regulating the phosphorylation of transferrin, further disrupting iron homeostasis. Therapeutic strategies targeting iron metabolism show promise by reducing iron accumulation, inhibiting oxidative stress, and reducing abnormal phosphorylation of key proteins. This article reviews the molecular mechanisms of phosphorylation modifications mediated by iron homeostasis imbalance in AD, and discusses the potential of interventions that regulate iron metabolism and related signaling pathways, providing a new theoretical basis for the treatment of AD.

Terahertz Wave Desensitizes Ferroptosis by Inhibiting the Binding of Ferric Ions to the Transferrin

Ferroptosis is a classic type of programmed cell death characterized by iron dependence, which is closely associated with many diseases such as cancer, intestinal ischemic diseases, and nervous system diseases. Transferrin (Tf) is responsible for ferric-ion delivery owing to its natural Fe3+ binding ability and plays a crucial role in ferroptosis. However, Tf is not considered as a classic druggable target for ferroptosis-associated diseases since systemic perturbation of Tf would dramatically disrupt blood iron homeostasis. Here, we reported a nonpharmaceutical, noninvasive, and Tf-targeted electromagnetic intervention technique capable of desensitizing ferroptosis with directivity. First, we revealed that the THz radiation had the ability to significantly decrease binding affinity between the Fe3+ and Tf via molecular dynamics simulations, and the modulation was strongly wavelength-dependent. This result provides theoretical feasibility for the THz modulation-based ferroptosis intervention. Subsequent extracellular and cellular chromogenic activity assays indicated that the THz field at 8.7 μm (i.e., 34.5 THz) inhibited the most Fe3+ bound to the Tf, and the wavelength was in good agreement with the simulated one. Then, functional assays demonstrated that levels of intracellular Fe2+, lipid peroxidation, malondialdehyde (MDA) and cell death were all significantly reduced in cells treated with this 34.5 THz wave. Furthermore, the iron deposition, lipid peroxidation, and MDA in the ferroptosis disease model induced by ischemia-reperfusion injury could be nearly eliminated by the same radiation, validating THz wave-induced desensitization of ferroptosis in vivo. Together, this work provides a preclinical exemplar for electromagnetic irradiation-stimulated desensitization of ferroptosis and predicts an innovative, THz wave-based therapeutic method for ferroptosis-associated diseases in the future.

Alpha-Lipoic Acid Reduces Neuroinflammation and Oxidative Stress Induced by Dapsone in an Animal Model

Background/Objectives: Chronic treatment with dapsone (DDS) has been linked to adverse reactions involving all organ systems, such as dapsone hypersensitivity syndrome, methemoglobinemia and hemolytic anemia, besides neuroinflammation and neurodegeneration due to iron accumulation and oxidative stress. These effects probably occur due to the presence of its toxic metabolite DDS-NOH, which can generate reactive oxygen species (ROS) and iron overload. In this sense, antioxidant compounds with chelating properties, such as alpha-lipoic acid (ALA), may be an interesting adjuvant therapy strategy in treating or preventing these effects. Thus, the aim of this study was to evaluate the effects of ALA on oxidative and neuroinflammatory changes caused by DDS treatment in the prefrontal cortex and hippocampus of mice. Materials and Methods:Mus musculus male mice that were pre-treated with DDS (40 mg/kg) and post-treated with ALA (25 mg/kg) underwent analyses for oxidative stress, antioxidant capacity, cytokine expression and microglial/astrocytic activity. Results: DDS did not activate macrophages/microglia or astrocytes in the prefrontal cortex but induced their activation in the hippocampus. ALA stimulated a protective microglial profile and reduced astrocyte reactivity, especially in the hippocampus. DDS increased the pro-inflammatory cytokine IL-1β and reduced brain-derived neurotrophic factor (BDNF), effects reversed by ALA. DDS also reduced antioxidant capacity (TEAC, GSH, SOD, CAT) and increased oxidative damage (lipid peroxidation, iron accumulation), while ALA restored antioxidant levels and reduced oxidative stress. Conclusions: ALA was able to reduce the effects of DDS, such as reducing microglial and astrocytic activation, as well as to decrease the levels of pro-inflammatory cytokines and increase BDNF, in addition to increasing antioxidant capacity and reducing oxidative damage caused by iron accumulation. Therefore, ALA is considered a useful and promising therapeutic alternative for the treatment of diseases related to oxidative stress and neuroinflammation.

Hyaluronic Acid-Based Therapy for Alleviating Early Lipid Peroxidation in Peripheral Nerve Compression Injury Repair

BACKGROUND

Peripheral nerve injuries compromise sensory and motor functions, severely affecting patients' quality of life. Early lipid peroxidation drives oxidative stress, disrupting the regenerative microenvironment. Hyaluronic acid (HA), an essential extracellular matrix component, shows promise in mitigating oxidative damage and fostering repair.

METHODS

In a rat sciatic nerve crush model, HA hydrogel was applied to enhance retention at the injury site. Transcriptomic analysis at 24 hours postinjury identified key pathways. In vitro assays examined HA's protective effects on Schwann cells against lipid peroxidation and oxidative stress. In vivo, HA hydrogel was administered immediately (0 hour) postcrush, followed by 4-methylumbelliferone-induced inhibition of endogenous HA synthesis and exogenous HA supplementation to clarify HA's role.

RESULTS

HA treatment reduced early lipid peroxidation, upregulated glutathione metabolism, and stimulated extracellular matrix receptor interactions, notably elevating CD44 expression. In vitro, HA lowered oxidative stress and maintained Schwann cell viability. In vivo, early HA intervention mitigated muscle atrophy, preserved myelin sheaths, and improved Sciatic Functional Index scores compared to delayed or untreated controls. Inhibiting endogenous HA synthesis impaired recovery, which was partially reversed by exogenous HA.

CONCLUSIONS

Early HA intervention modulates lipid peroxidation and oxidative stress via the HA/CD44 axis, establishing a supportive microenvironment for peripheral nerve regeneration and functional recovery. These findings underscore the potential of HA-based strategies to curb early lipid peroxidation, thereby expediting nerve repair and accelerating regeneration.

Cognitive Performance in Relation to Systemic and Brain Iron at Perimenopause

BACKGROUND

The literature on the relationships among blood iron levels, cognitive performance, and brain iron levels specific to women at the menopausal transition is ambiguous at best. The need to better understand these potential relationships in women for whom monthly blood loss (and thus iron loss) is ceasing is highlighted by iron's accumulation in brain tissue over time, thought to be a factor in the development of neurodegenerative disease.

METHODS

Non-anemic women who were either low in iron or had normal iron levels for their age and race/ethnicity provided blood samples, underwent MRI scans to estimate brain iron levels, and performed a set of cognitive tasks with concurrent EEG.

RESULTS

Cognitive performance and brain dynamics were positively related to iron levels, including measures associated with oxygen transport. There were no relationships between any of the blood measures of iron and brain iron.

CONCLUSIONS

Higher iron status was associated with better cognitive performance in a sample of women who were neither iron deficient nor anemic, without there being any indication that higher levels of systemic iron were related to higher levels of brain iron. Consequently, addressing low iron levels at the menopausal transition may be a candidate approach for alleviating the "brain fog" commonly experienced at menopause.

Cell type transcriptomics reveal shared genetic mechanisms in Alzheimer's and Parkinson's disease

Historically, Alzheimer's disease (AD) and Parkinson's disease (PD) have been investigated as two distinct disorders of the brain. However, a few similarities in neuropathology and clinical symptoms have been documented over the years. Traditional single gene-centric genetic studies, including GWAS and differential gene expression analyses, have struggled to unravel the molecular links between AD and PD. To address this, we tailor a pattern-learning framework to analyze synchronous gene co-expression at sub-cell-type resolution. Utilizing recently published single-nucleus AD (70,634 nuclei) and PD (340,902 nuclei) datasets from postmortem human brains, we systematically extract and juxtapose disease-critical gene modules. Our findings reveal extensive molecular similarities between AD and PD gene cliques. In neurons, disrupted cytoskeletal dynamics and mitochondrial stress highlight convergence in key processes; glial modules share roles in T-cell activation, myelin synthesis, and synapse pruning. This multi-module sub-cell-type approach offers insights into the molecular basis of shared neuropathology in AD and PD.

The Gut Microbiota Metabolite Butyrate Modulates Acute Stress-Induced Ferroptosis in the Prefrontal Cortex via the Gut-Brain Axis

Stress has been implicated in the onset of mental disorders such as depression, with the prefrontal cortex (PFC) playing a crucial role. However, the underlying mechanisms remain to be fully elucidated. Metabolites secreted by intestinal flora can enter the bloodstream and exert regulatory effects on the body. Consequently, this study aims to investigate the molecular mechanisms by which gut flora influences ferroptosis in PFC neurons, thereby affecting depression-like behavioral changes in mice subjected to acute stress. Initially, we established a mouse model of acute restraint stress (3-day duration) and verified that stress-induced ferroptosis of PFC neurons contributed to depression-like behavioral alterations in mice, as evidenced by morphological, behavioral, and molecular biology assessments. Subsequently, through fecal microbiota transplantation (FMT) experiments, we established a significant correlation between gut microbiota and ferroptosis of PFC neurons in acute stress-exposed mice. 16S rDNA sequencing identified butyric acid-producing bacteria, specifically g_Butyricimonas and its primary metabolite, butyric acid, as critical regulators of ferroptosis in PFC neurons in acutely stressed mice. Furthermore, the intervention of butyrate demonstrated its potential to ameliorate damage to the intestinal and blood-brain barriers in these mice. This intervention also mitigated depression-like behaviors induced by ferroptosis of PFC neurons by alleviating systemic inflammatory responses. The findings of this study indicate that acute stress-induced ferroptosis of PFC neurons plays a critical role in depression-like behavioral changes in mice. Additionally, the gut microbiota metabolite butyrate can modulate ferroptosis and depression-like behavioral changes through the gut-brain axis.