Iron Metabolism in Oligodendrocytes and Astrocytes, Implications for Myelination and Remyelination

Perilipin-2 mediates ferroptosis in oligodendrocyte progenitor cells and myelin injury after ischemic stroke

JOURNAL/nrgr/04.03/01300535-202507000-00024/figure1/v/2024-09-09T124005Z/r/image-tiff Differentiation of oligodendrocyte progenitor cells into mature myelin-forming oligodendrocytes contributes to remyelination. Failure of remyelination due to oligodendrocyte progenitor cell death can result in severe nerve damage. Ferroptosis is an iron-dependent form of regulated cell death caused by membrane rupture induced by lipid peroxidation, and plays an important role in the pathological process of ischemic stroke. However, there are few studies on oligodendrocyte progenitor cell ferroptosis. We analyzed transcriptome sequencing data from GEO databases and identified a role of ferroptosis in oligodendrocyte progenitor cell death and myelin injury after cerebral ischemia. Bioinformatics analysis suggested that perilipin-2 (PLIN2) was involved in oligodendrocyte progenitor cell ferroptosis. PLIN2 is a lipid storage protein and a marker of hypoxia-sensitive lipid droplet accumulation. For further investigation, we established a mouse model of cerebral ischemia/reperfusion. We found significant myelin damage after cerebral ischemia, as well as oligodendrocyte progenitor cell death and increased lipid peroxidation levels around the infarct area. The ferroptosis inhibitor, ferrostatin-1, rescued oligodendrocyte progenitor cell death and subsequent myelin injury. We also found increased PLIN2 levels in the peri-infarct area that co-localized with oligodendrocyte progenitor cells. Plin2 knockdown rescued demyelination and improved neurological deficits. Our findings suggest that targeting PLIN2 to regulate oligodendrocyte progenitor cell ferroptosis may be a potential therapeutic strategy for rescuing myelin damage after cerebral ischemia.

Alterations in magnetic susceptibility correlate with higher cerebral blood flow in the right amygdala of patients with major depressive disorder

BACKGROUND

The amygdala plays a crucial role in emotion processing and is a key target for understanding the mechanisms underlying major depressive disorder (MDD). This study aimed to investigate the magnetic susceptibility of the amygdala in MDD and examine its association with structural and cerebral blood flow (CBF) changes.

METHODS

A total of 158 individuals were included in the study, comprising 86 patients with MDD and 72 healthy controls. Depression severity was assessed using Hamilton Depression Rating Scale. Quantitative susceptibility mapping (QSM), T1-weighted, and arterial spin labeling scans were conducted to measure amygdala magnetic susceptibility, volume, and CBF, respectively. Group differences were compared, and associations between susceptibility, volume, and CBF were examined.

RESULTS

The median susceptibility of the amygdala was significantly higher in MDD patients than in controls (all p < 0.01). In the MDD group, increased QSM value in the right amygdala was associated with higher CBF (r = 0.28, p = 0.01), whereas no significant correlation was found between QSM value and volume (p = 0.76). Increased QSM value in the right amygdala was associated with worse depressed mood (r = 0.30, p < 0.01).

LIMITATION

Retrospective cross-sectional study conducted at a single center.

CONCLUSION

The magnetic susceptibility of the amygdala was higher in MDD patients with than in controls. QSM changes in the right amygdala correlated with increased CBF and worse depressed mood, indicating both microstructural and functional alterations. Our results encourage further use of the QSM technique in the elucidation of MDD pathophysiology.

Sex-differences in brain multimodal estimates of white matter microstructure during early adolescence: Sex-specific associations with biological factors

Adolescence is marked by significant maturation of brain white matter microstructure, with evidence for sex-specific maturational trajectory. Most studies have examined conventional diffusion tensor imaging (DTI) metrics, which lack specificity to the underlying tissue modifications. In this study, we characterized sex-differences in white matter microstructure cross-sectionally using DTI, advanced diffusion spectrum imaging (DSI) and diffusion kurtosis imaging (DKI), as well as the white matter tract integrity-Watson (WMTI-W) biophysical model. We also aimed to explore the effect of age and biological systems undergoing sex-specific changes during adolescence, namely pubertal hormones, hypothalamic-pituitary-adrenal (HPA)-axis function, and glutathione-redox cycle homeostasis. The results indicate widespread sex-differences in all the white matter derived metrics, suggesting more advanced maturation in females compared to males as well as distinct tissue modifications underlying white matter maturation between males and females during this narrow developmental period. Additionally, the three biological factors explored appeared to be associated with indices of white matter maturation in females specifically, emphasizing this period as critical in female white matter development and sensitivity to environmental factors.

Functional Specificity of Astrocyte Subtypes in Alzheimer's Disease: Decoding Disease Mechanisms Through Network-based Analysis of Integrated Single-Nuclei Multi-Omic Data

Alzheimer's disease (AD) is the most common cause of dementia. Recent studies have revealed incontrovertible roles of astrocytes in the pathology of AD. Considering the conflicting behaviours of astrocytes in AD brain, they have been proposed to have subtypes. In this study, astrocytes from two publicly available single-nuclei transcriptome datasets were integrated to provide in-depth characterization of astrocyte subtypes in AD. Differentially expressed genes within each astrocyte subtype were analyzed by mapping them onto a human protein-protein interaction network to discover subnetworks with biologically relevant genes. Integrating single-nuclei datasets and using network-based analysis approach led to higher sensitivity in capturing AD-related genes compared to traditional approaches. One of the identified subtypes was highly representative of neurotoxic reactive astrocytes in AD. The results show that A1 reactive astrocytes could have an enhancing role for the amyloid beta and neurofibrillary tangle accumulation through MAPK10, MAPT, and TMED10, which were all found to be differentially expressed in this subtype during AD in our analysis. Moreover, single-nuclei ATAC-Seq data from the same tissue was re-analyzed to evaluate astrocyte subtypes at multi-omic level. It was found that astrocyte subtypes underwent epigenetic reprogramming during AD. Potential transcription factors were also identified for the regulation of the genes that exhibited alterations in both promoter accessibility and gene expression in AD. Comparative analysis of single-nuclei RNA-Seq and ATAC-Seq datasets showed that PTN gene, which was reported to be important for AD pathology, is likely regulated by ATF3 transcription factor in subtype-specific manner in astrocytes.

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.

Nigrostriatal iron accumulation in the progression of Parkinson's disease

Iron deposition in the nigrostriatal system plays a pivotal role in Parkinson's disease (PD) onset and progression. This study explored the time course of nigrostriatal iron accumulation in 54 PD patients at early to moderately advanced stages and 20 age-matched healthy controls. Using multi-echo T2*-MRI and R2* relaxometry, iron content was assessed in the substantia nigra pars compacta (SNpc) and striatum. In vivo findings were contrasted with histological analyses in a progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism model involving six non-human primates (NHPs) and two controls using Perls' Prussian blue staining. Complementarily, dopaminergic degeneration was quantified by 6-[18F]-fluoro-L-dopa PET in humans and TH immunohistochemistry in NHPs. Results showed progressive iron accumulation in the SNpc correlating with striatal dopaminergic denervation and neuronal loss. Striatal iron followed a V-shaped progression, decreasing initially and increasing later. Iron in the SNpc may serve as a marker of neurodegeneration in PD, while decreased striatal iron may indicate pathological susceptibility to dopaminergic loss.

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.

Neurodevelopmental Impairments as Long-term Effects of Iron Deficiency in Early Childhood: A Systematic Review

Background

Numerous studies have reported neurodevelopmental disorders in children with a history of early-life iron deficiency (ID), though findings vary.

Aims

To evaluate the long-term impact of early childhood ID on neurodevelopmental outcomes.

Study Design

Systematic review.

Methods

A literature search was conducted across five electronic databases (PubMed, Cochrane, Scopus, Sage, and Embase) using the keywords “iron deficiency anemia” and “infant.” The JBI critical appraisal tool for cohort studies was used to evaluate study quality.

Results

Seventeen relevant cohort studies were identified through the systematic search. Of these, 14 were rated as high quality, while 3 were classified as moderate quality. The neurodevelopmental domains assessed included cognitive deficits (seven studies), motor deficits (four studies), verbal deficits (seven studies), behavioral deficits (nine studies), auditory function (one study), and neuroendocrine function (two studies).

Conclusion

Early-life ID disrupts neurodevelopment, leading to persistent cognitive, motor, behavioral, and neuroendocrine impairments. Children with a history of early childhood ID demonstrate poorer cognitive, motor, and behavioral outcomes compared with their non-ID counterparts. Preventing ID within the first 1,000 days of life is essential to mitigate irreversible deficits in motor, cognitive, and behavioral functions.

Tau, amyloid, iron, oligodendrocytes ferroptosis, and inflammaging in the hippocampal formation of aged rats submitted to an aerobic exercise program

Alzheimer's disease is a progressive neurodegenerative disease affecting memory, language, and thinking with no curative treatment. Symptoms appear gradually, and pathological brain changes may occur twenty years before the physical and psychological signs, pointing to the urgent development of preventive interventions. Physical activity has been investigated as a preventive tool to defeat the main biological features of AD: pathological amyloid protein plaques, tau tangles, myelin degeneration, and iron deposits in the brain. This work quantifies tau tangles, amyloid, iron, and ferroptosis in oligodendrocytes in the aged rat hippocampal formation and statistically correlates neuron-neuron, neuron-glia, and glia-glia crosstalk and the effect of physical exercise on it. Our results indicate that iron overload in the oligodendrocytes is an inducer of ferroptosis; physical exercise reduces inflammaging, and improves axon-myelin volume relations; tau, amyloid, iron, and hippocampal formation cells present statistical correlations. Our data suggest the beneficial effects of physical exercise in AD and a mathematical relationship between the hippocampal formation cells in sedentary and active individuals, which should be considered in human and animal studies as a guide to a better understanding of crosstalk physiology.

Dopamine degrades ferritin by chaperone-mediated autophagy to elevate mitochondrial iron level in astroglial cells

Iron accumulation and mitochondrial dysfunction in astroglia are reported in Parkinson's disease (PD). Astroglia control iron availability in neurons in which dopamine (DA) synthesis is affected in PD. Despite their intimate relationship the role of DA in astroglial iron homeostasis is limited. Here we show that DA degrades iron storage protein ferritin in astroglial cells involving lysosomal proteolysis. Lysosomal ferritinophagy is mainly associated with macroautophagy; however, we revealed the involvement of chaperone-mediated autophagy (CMA) in DA-induced ferritin degradation. In CMA, cytosolic proteins containing a specific pentapeptide motif bind with HSC70 to be transported to lysosome mediated by LAMP2A. We identified the conserved pentapeptide motif in ferritin-H (Ft-H), mutations of which resulted loss of its interaction with HSC70. Pharmacological inhibitors of HSC70 or LAMP2/2A knockdown blocks DA-induced Ft-H degradation. DA also induces cytosolic cargo NCOA4 for ferritinophagy. We further reveal that DA promotes cathepsin B to lysis ferritin within the lysosome. Inhibitor of cathepsin B, knocking down of LAMP2, or HSC70 inhibitor attenuate DA-induced elevated mitochondrial iron level. Our results establish a direct role of DA on astroglial iron homeostasis and novel involvement of CMA in ferritin degradation in response to a biological stimulus. These results also may help in better understanding iron dyshomeostasis and mitochondrial dysfunction reported in PD.

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.

Neurovascular unit impairment in iron deficiency anemia

Iron is one of the crucial elements for CNS development and function and its deficiency (ID) is the most common worldwide nutrient deficit in the world. Iron deficiency anemia (IDA) in pregnant women and infants is a worldwide health problem due to its high prevalence and its irreversible long-lasting effects on brain development. Even with iron supplementation, IDA during pregnancy and/or breastfeeding can result in irreversible cognitive, motor, and behavioral impairments. The neurovascular unit (NVU) plays an important role in iron transport within the CNS as well as in the blood brain-barrier (BBB) formation and maturation, vasculogenesis/angiogenesis, neurovascular coupling and metabolic waste clearance. In animal models of IDA, significant changes have been observed at the capillary level, including alterations in iron transport, vasculogenesis, astrocyte endfeet, and pericytes. Despite these findings, the role of the NVU in IDA remains poorly understood. This review summarizes the potential effects of ID/IDA on brain development, myelination and neuronal function and discusses the role of NVU cells in iron metabolism, BBB, vasculogenesis/angiogenesis, neurovascular coupling and metabolic waste clearance. Furthermore, it emphasizes the need to view the NVU as a whole and as a potential target for ID/IDA. However, it remains unclear to what extent NVU alterations contribute to neuronal dysfunction, myelination abnormalities, and synaptic disturbances described in IDA.

Neonatal sevoflurane exposures inhibits DHHC5-mediated palmitoylation of TfR1 in oligodendrocytes, leading to hypomyelination and neurological impairments

INTRODUCTION

Neonatal anesthesia-related neurological impairments are of significant concern, closely linked to oligodendrocyte dysfunction. However, there is a notable temporal discrepancy between the sustained development of oligodendrocytes (myelination) and the short-term vulnerability to anesthesia exposures.

OBJECTIVES

Given the significant rise in iron demand by oligodendrocytes during neonatal period, our objective was to clarify the potential roles and underlying mechanisms of iron homeostasis, particularly focusing on transferrin receptor 1 (TfR1), in governing the transient susceptibility to anesthesia.

METHODS

Sevoflurane (3 %, 2 h/day) was administered to wildtype or Pdgfrα-CreERT mice from postnatal day (P)6 to P8. Subsequently, behavioral tests, genetic modulation, co-immunoprecipitation assays, Acyl-resin assisted capture assay and single-cell RNA sequencing were employed on P8 and/or P32.

RESULTS

Following neonatal exposure to sevoflurane, the observed cognitive impairments and hypomyelination at P32 were attributed to iron accumulation and ferroptosis, particularly within oligodendrocytes of the corpus callosum (CC). This ferroptosis was mediated by enhanced endocytosis of transiently expressed TfR1, rather than its overexpression, due to inhibited palmitoylation. Among the 21 palmitoyltransferases, only Asp-His-His-Cys5 (DHHC5) was down-regulated in oligodendrocytes, reducing palmitoylation of TfR1 at the C98 cysteine site. Furthermore, specific overexpression of DHHC5 in oligodendrocytes significantly restored TfR1 endocytosis, hypomyelination, and ferroptosis, thereby preventing neuronal ferroptosis across multiple brain regions by decreasing iron transport, ultimately mitigating neurological impairments.

CONCLUSION

We discovered that decreased DHHC5 in oligodendrocytes promotes TfR1 associated ferroptosis, resulting in hypomyelination and initiating neuronal ferroptosis, thereby impairing cognition following neonatal sevoflurane exposures. The transiently expressed TfR1 may mediate the critical period for neonatal anesthesia vulnerability. These findings highlight the pivotal role of TfR1-associated ferroptosis in neonatal anesthesia-associated neurotoxicity and oligodendrocyte-neuron interaction, while providing new perspect to understand temporary neurotoxicity of anesthesia. DHHC5 may represent promising therapeutic target to enhance the safety of neonatal anesthesia and iron-related oligodendrocytes disorders.

AKRs confer oligodendrocytes resistance to differentiation-stimulated ferroptosis

Ferroptosis is a recently characterized form of cell death that has gained attention for its roles in both pathological and physiological contexts. The existence of multiple anti-ferroptotic pathways in both neoplastic and healthy cells, along with the critical regulation of iron metabolism involved in lipid peroxides (lipid-ROS) production-the primary mediators of this cell death process-underscores the necessity of precisely controlling or preventing accidental/unwanted ferroptosis. Conversely, dysregulated iron metabolism and alterations in the expression or activity of key anti-ferroptotic components are linked to the development and progression of various human diseases, including multiple sclerosis (MS). In MS, the improper activation of ferroptosis has been associated with the progressive loss of myelinating oligodendrocytes (myOLs). Our study demonstrates that the physiological and maturation-dependent increase in iron accumulation within oligodendrocytes acts as a pro-ferroptotic signal, countered by the concurrent expression of AKR1C1. Importantly, MS-related neuroinflammation contributes to the down-regulation of AKR1C1 through miRNA-mediated mechanisms, rendering mature oligodendrocytes more vulnerable to ferroptosis. Together, these findings highlight the role of ferroptosis in MS-associated oligodendrocyte loss and position AKR1C1 as a potential therapeutic target for preserving oligodendrocyte integrity and supporting neuronal function in MS patients.

Neuroinflammation and iron metabolism after intracerebral hemorrhage: a glial cell perspective

Intracerebral hemorrhage (ICH) is the most common subtype of hemorrhagic stroke causing significant morbidity and mortality. Previously clinical treatments for ICH have largely been based on a single pathophysiological perspective, and there remains a lack of curative interventions. Following the rupture of cerebral blood vessels, blood metabolites activate resident immune cells such as microglia and astrocytes, and infiltrate peripheral immune cells, leading to the release of a series of inflammatory mediators. Degradation of hemoglobin produces large amounts of iron ions, leading to an imbalance of iron homeostasis and the production of large quantities of harmful hydroxyl radicals. Neuroinflammation and dysregulation of brain iron metabolism are both important pathophysiological changes in ICH, and both can exacerbate secondary brain injury. There is an inseparable relationship between brain iron metabolism disorder and activated glial cells after ICH. Glial cells participate in brain iron metabolism through various mechanisms; meanwhile, iron accumulation exacerbates neuroinflammation by activating inflammatory signaling pathways modulating the functions of inflammatory cells, and so on. This review aims to explore neuroinflammation from the perspective of iron metabolism, linking the complex pathophysiological changes, delving into the exploration of treatment approaches for ICH, and offering insights that could enhance clinical management strategies.

Soma and neurite density abnormalities of paramagnetic rim lesions and core-sign lesions in multiple sclerosis

BACKGROUND

In multiple sclerosis (MS), susceptibility-weighted imaging (SWI) may reveal white matter lesions (WML) with a paramagnetic rim ("paramagnetic rim lesions" [PRLs]) or diffuse hypointensity ("core-sign lesions"), reflecting different stages of WML evolution.

OBJECTIVE

Using the soma and neurite density imaging (SANDI) model on diffusion-weighted magnetic resonance imaging (MRI), we characterized microstructural abnormalities of MS PRLs and core-sign lesions and their clinical relevance.

METHODS

Forty MS patients and 20 healthy controls (HC) underwent a 3 T brain MRI. Using SANDI, the fractions of neurite (fneurite) and soma (fsoma) and size of soma (rsoma) were quantified in PRLs (including their core and rim separately), and core-sign lesions identified on SWI-phase.

RESULTS

Among 1811 WMLs, 122 (6.7%) core-sign lesions and 97 (5.4%) PRLs were identified. Compared to HC and MS normal-appearing white matter, all MS WML showed significantly lower fneurite and fsoma and higher rsoma (FDR-p < 0.001). Compared to SWI-isointense WML, core-sign lesions showed a significantly higher fneurite, and lower fsoma and rsoma (FDR-p ≤ 0.005). Compared to SWI-isointense WML and core-sign lesions, PRLs showed a significantly lower fneurite, higher fsoma, and higher rsoma (FDR-p ≤ 0.001). The PRL-core showed significantly lower fneurite, and higher rsoma than PRL-rim (FDR-p < 0.001). Lower PRL fneurite (β ≤ -0.006, FDR-p ≤ 0.015) and higher rsoma (β ≥ 0.032, FDR-p ≤ 0.024) were significantly associated with a longer disease duration and more severe disability.

CONCLUSIONS

In PRLs, the significant and clinically relevant neurite loss and increased soma fraction and size possibly reflect increased astrogliosis and activated microglia. Core-sign lesions exhibit milder axonal loss, microglia density and astrogliosis, supporting their less destructive nature.

Limited Changes in Red Blood Cell Parameters After Probiotic Supplementation in Depressive Individuals: Insights from a Secondary Analysis of the PRO-DEMET Randomized Controlled Trial

Background: Depression often coexists with anemia, potentially sharing common pathways, highlighting the need for treatments addressing both conditions simultaneously. This study evaluated the effect of probiotics on red blood cell (RBC) parameters in adults with depressive disorder. We hypothesized that probiotics would positively influence RBC parameters, potentially modulated by baseline inflammation or dietary intake, with improved RBC function correlating with better antidepressant outcomes. Methods: This secondary analysis of a two-arm, randomized, double-blind, controlled trial involved 116 adults with depressive disorder. Participants received a probiotic formulation containing Lactobacillus helveticus Rosell®-52 and Bifidobacterium longum Rosell®-175 or a placebo for 60 days. Data from 97 subjects were analyzed for RBC parameters, including hemoglobin (HGB), RBC count, hematocrit (HCT), mean corpuscular volume (MCV), mean hemoglobin concentration (MCH), mean corpuscular hemoglobin concentration (MCHC), and RBC distribution width (RDW). Results: Probiotic supplementation did not result in significant changes in RBC parameters compared to the placebo. However, probiotics may help stabilize HGB, HCT, MCH, and MCHC levels, potentially preventing fluctuations observed in the placebo group. Conclusions: While probiotics showed potential benefits for depressive symptoms, significant changes in RBC parameters were not observed. Larger studies are needed to clarify the mechanisms and clinical implications.

In defence of ferroptosis

Rampant phospholipid peroxidation initiated by iron causes ferroptosis unless this is restrained by cellular defences. Ferroptosis is increasingly implicated in a host of diseases, and unlike other cell death programs the physiological initiation of ferroptosis is conceived to occur not by an endogenous executioner, but by the withdrawal of cellular guardians that otherwise constantly oppose ferroptosis induction. Here, we profile key ferroptotic defence strategies including iron regulation, phospholipid modulation and enzymes and metabolite systems: glutathione reductase (GR), Ferroptosis suppressor protein 1 (FSP1), NAD(P)H Quinone Dehydrogenase 1 (NQO1), Dihydrofolate reductase (DHFR), retinal reductases and retinal dehydrogenases (RDH) and thioredoxin reductases (TR). A common thread uniting all key enzymes and metabolites that combat lipid peroxidation during ferroptosis is a dependence on a key cellular reductant, nicotinamide adenine dinucleotide phosphate (NADPH). We will outline how cells control central carbon metabolism to produce NADPH and necessary precursors to defend against ferroptosis. Subsequently we will discuss evidence for ferroptosis and NADPH dysregulation in different disease contexts including glucose-6-phosphate dehydrogenase deficiency, cancer and neurodegeneration. Finally, we discuss several anti-ferroptosis therapeutic strategies spanning the use of radical trapping agents, iron modulation and glutathione dependent redox support and highlight the current landscape of clinical trials focusing on ferroptosis.

Ablation of lipocalin-2 reduces neuroinflammation in a mouse model of Krabbe disease

Lipocalin-2 (LCN2) is an acute-phase secretory molecule significantly upregulated in various neuroinflammatory and demyelinating conditions. Krabbe disease (KD) is a neurodegenerative lysosomal disorder caused by a galactosylceramidase (GALC) deficiency, accumulating cytotoxic psychosine in nervous systems, and subsequent neuroinflammation. Here, we show that LCN2 is highly overexpressed in GALC-deficient astrocytes. To further understand if the elevated LCN2 is critical for KD progression, we globally deleted Lcn2 in the Galc-knockout (KO) mouse model. Interestingly, the Galc and Lcn2 double KO mice showed dramatically reduced neuroinflammation including gliosis. Pro-inflammatory cytokines such as TNF-α, MMP3, and MCP-1 were significantly downregulated in the brain of the double KO mice compared to Galc-KO. In addition, the ablation of Lcn2 marginally increased the survival and attenuated disease progression in Galc-KO mice. However, the accumulation of psychosine was not altered in the brain by LCN2 deficiency. Our findings suggest that the upregulation of LCN2 is crucial for the aggravation of neuroinflammation in a mouse model of Krabbe disease.

A Defined Diet Combined with Sonicated Inoculum Provides a High Incidence, Moderate Severity Form of Experimental Autoimmune Encephalomyelitis (EAE)

BACKGROUND

Myelin oligodendrocyte glycoprotein 35-55 (MOG35-55)-peptide induced experimental autoimmune encephalomyelitis (EAE) is a model for inflammation of the brain and spinal cord. However, its severity and incidence vary within and between laboratories. Severe scores can lead to premature termination and are both unnecessary for readouts and detrimental to animal welfare. Ideally, the model would have high incidence, moderate severity, and low interindividual variability to fulfill the "Refine" aspect of the 3R concept. Nevertheless, most efforts to increase incidence also increase the severity. When the effects of potential therapies are tested, moderate severity is sufficient to detect useful drug effects as long as variation is low. Low variation can also reduce group sizes, which supports the "Reduce" aspect of 3R approaches in disease modeling. We set out to reduce variation and control severity by assessing the effects of mouse age, dietary fiber, antigen emulsion, and the dose of MOG and pertussis toxin on incidence, variability, and severity in the MOG-EAE model.

METHODS

We compared 14- and 33-week-old female C57BL/6 mice and varied the diet and inoculum in two studies. We measured disease signs in vivo as well as gene expression in the brain and spinal cord and histology by immunofluorescence. Ordinary one-way ANOVA was used for multiple comparisons.

RESULTS

The most reliable induction conditions were with a low-fermentative/fiber diet (AIN 93M) combined with a sonicated emulsion of the MOG35-55-peptide. High-dose pertussis toxin increased EAE severity and incidence in 14-week-old mice (25% survival) while being more moderate in mature mice (100% survival). Varying all parameters suggests that duration of prefeeding defined diet, emulsion quality, and mouse maturity were factors that increase uniformity of response allowing incidence to reach 100% without excess severity. Microglia and astrocyte-associated markers were upregulated proportionally to score consistent with known EAE pathology.

CONCLUSIONS

A defined fiber/high-sugar diet with sonicated inoculum provides for a moderate severity, high incidence, and less variable EAE. The resulting uniformity in animal response and associated cytokine patterns, and the strong link to a defined diet, suggest that this may be a more clinically translatable protocol for the induction of EAE. This is consistent with reported effects of low-fermentable diets on immune modulation in human patients with autoimmune diseases.

Spontaneous mutation in 2310061I04Rik results in reduced expression of mitochondrial genes and impaired brain myelination

Here, we describe a spontaneous mouse mutant with a deletion in a predicted gene 2310061I04Rik (Rik) of unknown function located on chromosome 17. A 59 base pair long deletion occurred in the first intron of the Rik gene and disrupted its expression. Riknull mice were born healthy and appeared anatomically normal up to two weeks of age. After that, these mice showed inhibited growth, ataxic gait, and died shortly after postnatal day 24 (P24). Transcriptome analysis at P14 and P23 revealed significantly reduced expression of mitochondrial genes in Riknull brains compared to wild type controls including mt-Nd4, mt-Cytb, mt-Nd2, mt-Co1, mt-Atp6, and others. Similarly, genes specific for myelinating oligodendrocytes also showed reduced expression in P23 Riknull brains compared to controls. Histological examination of anterior thalamic nuclei demonstrated decreased myelination of anteroventral nuclei but not of anterodorsal nuclei in P23 Riknull mice. Myelination of the anterior commissure was also impaired and displayed extensive vacuolation. Consistently with these findings, immunohistochemistry showed reduced expression of Opalin, a glycoprotein expressed in differentiated oligodendrocytes. Taken together, these results suggest that RIK is important for oligodendrocyte maturation and myelination in the developing brain.

Ferritin loss in astrocytes reduces spinal cord oxidative stress and demyelination in the experimental autoimmune encephalomyelitis (EAE) model

Demyelinating diseases such as multiple sclerosis (MS) cause myelin degradation and oligodendrocyte death, resulting in the release of toxic iron and iron-induced oxidative stress. Astrocytes have a large capacity for iron transport and storage, however the role of astrocytic iron homeostasis in demyelinating disorders is not completely understood. Here we investigate whether astrocytic iron metabolism modulates neuroinflammation, oligodendrocyte survival, and oxidative stress following demyelination. To this aim, we conditionally knock out ferritin in astrocytes and induce experimental autoimmune encephalomyelitis (EAE), an autoimmune-mediated model of demyelination. Ferritin ablation in astrocytes reduced the severity of disease in both the acute and chronic phases. The day of onset, peak disease severity, and cumulative clinical score were all significantly reduced in ferritin KO animals. This corresponded to better performance on the rotarod and increased mobility in ferritin KO mice. Furthermore, the spinal cord of ferritin KO mice display decreased numbers of reactive astrocytes, activated microglia, and infiltrating lymphocytes. Correspondingly, the size of demyelinated lesions, iron accumulation, and oxidative stress were attenuated in the CNS of ferritin KO subjects, particularly in white matter regions of the spinal cord. Thus, deleting ferritin in astrocytes reduced neuroinflammation, oxidative stress, and myelin deterioration in EAE animals. Collectively, these findings suggest that iron storage in astrocytes is a potential therapeutic target to lessen CNS inflammation and myelin loss in autoimmune demyelinating diseases.

Promoting remyelination in central nervous system diseases: Potentials and prospects of natural products and herbal medicine

Myelin damage is frequently associated with central nervous system (CNS) diseases and is a critical factor influencing neurological function and disease prognosis. Nevertheless, the majority of current treatments for the CNS concentrate on gray matter injury and repair strategies, while clinical interventions specifically targeting myelin repair remain unavailable. In recent years, natural products and herbal medicine have achieved considerable progress in the domain of myelin repair, given their remarkable curative effect and low toxic side effects, demonstrating significant therapeutic potential. In this review, we present a rather comprehensive account of the mechanisms underlying myelin formation, injury, and repair, with a particular emphasis on the interactions between oligodendrocytes and other glial cells. Furthermore, we summarize the natural products and herbal medicine currently employed in remyelination along with their mechanisms of action, highlighting the potential and challenges of certain natural compounds to enhance myelin repair. This review aims to facilitate the expedited development of innovative therapeutics derived from natural products and herbal medicine and furnish novel insights into myelin repair in the CNS.

Should We Consider Neurodegeneration by Itself or in a Triangulation with Neuroinflammation and Demyelination? The Example of Multiple Sclerosis and Beyond

Neurodegeneration is preeminent in many neurological diseases, and still a major burden we fail to manage in patient's care. Its pathogenesis is complicated, intricate, and far from being completely understood. Taking multiple sclerosis as an example, we propose that neurodegeneration is neither a cause nor a consequence by itself. Mitochondrial dysfunction, leading to energy deficiency and ion imbalance, plays a key role in neurodegeneration, and is partly caused by the oxidative stress generated by microglia and astrocytes. Nodal and paranodal disruption, with or without myelin alteration, is further involved. Myelin loss exposes the axons directly to the inflammatory and oxidative environment. Moreover, oligodendrocytes provide a singular metabolic and trophic support to axons, but do not emerge unscathed from the pathological events, by primary myelin defects and cell apoptosis or secondary to neuroinflammation or axonal damage. Hereby, trophic failure might be an overlooked contributor to neurodegeneration. Thus, a complex interplay between neuroinflammation, demyelination, and neurodegeneration, wherein each is primarily and secondarily involved, might offer a more comprehensive understanding of the pathogenesis and help establishing novel therapeutic strategies for many neurological diseases and beyond.

Ferroptosis in Parkinson's disease -- The iron-related degenerative disease

Parkinson's disease (PD) is a prevalent and advancing age-related neurodegenerative disorder, distinguished by the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Iron regional deposit in SNpc is a significant pathological characteristic of PD. Brain iron homeostasis is precisely regulated by iron metabolism related proteins, whereas disorder of these proteins can damage neurons and glial cells in the brain. Additionally, growing studies have reported iron metabolism related proteins are involved in the ferroptosis progression in PD. However, the effect of these proteins in the ferroptosis of PD has not been systematically summarized. This review focuses on the roles of iron metabolism related proteins in the ferroptosis of PD. Finally, we put forward the iron early diagnosis according to the observation of iron deposits in the brain and showed the recent advances in iron chelation therapy in PD.

Transcriptional profiling of retinal astrocytes identifies a specific marker and points to functional specialization

Astrocyte heterogeneity is an increasingly prominent research topic, and studies in the brain have demonstrated substantial variation in astrocyte form and function, both between and within regions. In contrast, retinal astrocytes are not well understood and remain incompletely characterized. Along with optic nerve astrocytes, they are responsible for supporting retinal ganglion cell axons and an improved understanding of their role is required. We have used a combination of microdissection and Ribotag immunoprecipitation to isolate ribosome-associated mRNA from retinal astrocytes and investigate their transcriptome, which we also compared to astrocyte populations in the optic nerve. Astrocytes from these regions are transcriptionally distinct, and we identified retina-specific astrocyte genes and pathways. Moreover, although they share much of the "classical" gene expression patterns of astrocytes, we uncovered unexpected variation, including in genes related to core astrocyte functions. We additionally identified the transcription factor Pax8 as a highly specific marker of retinal astrocytes and demonstrated that these astrocytes populate not only the retinal surface, but also the prelaminar region at the optic nerve head. These findings are likely to contribute to a revised understanding of the role of astrocytes in the retina.

Progress in the Pathogenesis of Diabetic Encephalopathy: The Key Role of Neuroinflammation

Diabetic encephalopathy (DE) is a severe complication that occurs in the central nervous system (CNS) and leads to cognitive impairment. DE involves various pathophysiological processes, and its pathogenesis is still unclear. This review summarised current research on the pathogenesis of diabetic encephalopathy, which involves neuroinflammation, oxidative stress, iron homoeostasis, blood-brain barrier disruption, altered gut microbiota, insulin resistance, etc. Among these pathological mechanisms, neuroinflammation has been focused on. This paper summarises some of the molecular mechanisms involved in neuroinflammation, including the Mammalian Target of Rapamycin (mTOR), Lipocalin-2 (LCN-2), Pyroptosis, Advanced Glycosylation End Products (AGEs), and some common pro-inflammatory factors. In addition, we discuss recent advances in the study of potential therapeutic targets for the treatment of DE against neuroinflammation. The current research on the pathogenesis of DE is progressing slowly, and more research is needed in the future. Further study of neuroinflammation as a mechanism is conducive to the discovery of more effective treatments for DE in the future.

Iron Dyshomeostasis in Neurodegeneration with Brain Iron Accumulation (NBIA): Is It the Cause or the Effect?

Iron is an essential metal ion implicated in several cellular processes. However, the reactive nature of iron renders this metal ion potentially dangerous for cells, and its levels need to be tightly controlled. Alterations in the intracellular concentration of iron are associated with different neuropathological conditions, including neurodegeneration with brain iron accumulation (NBIA). As the name suggests, NBIA encompasses a class of rare and still poorly investigated neurodegenerative disorders characterized by an abnormal accumulation of iron in the brain. NBIA is mostly a genetic pathology, and to date, 10 genes have been linked to familial forms of NBIA. In the present review, after the description of the principal mechanisms implicated in iron homeostasis, we summarize the research data concerning the pathological mechanisms underlying the genetic forms of NBIA and discuss the potential involvement of iron in such processes. The picture that emerges is that, while iron overload can contribute to the pathogenesis of NBIA, it does not seem to be the causal factor in most forms of the pathology. The onset of these pathologies is rather caused by a combination of processes involving the interplay between lipid metabolism, mitochondrial functions, and autophagic activity, eventually leading to iron dyshomeostasis.

Loss of primary cilia and dopaminergic neuroprotection in pathogenic LRRK2-driven and idiopathic Parkinson's disease

Activating leucine-rich repeat kinase 2 (LRRK2) mutations cause Parkinson's and phosphorylation of Rab10 by pathogenic LRRK2 blocks primary ciliogenesis in cultured cells. In the mouse brain, LRRK2 blockade of primary cilia is highly cell type specific: For example, cholinergic interneurons and astrocytes but not medium spiny neurons of the dorsal striatum lose primary cilia in LRRK2-pathway mutant mice. We show here that the cell type specificity of LRRK2-mediated cilia loss is also seen in human postmortem striatum from patients with LRRK2 pathway mutations and idiopathic Parkinson's. Single nucleus RNA sequencing shows that cilia loss in mouse cholinergic interneurons is accompanied by decreased glial-derived neurotrophic factor transcription, decreasing neuroprotection for dopamine neurons. Nevertheless, LRRK2 expression differences cannot explain the unique vulnerability of cholinergic neurons to LRRK2 kinase as much higher LRRK2 expression is seen in medium spiny neurons that have normal cilia. In parallel with decreased striatal dopaminergic neurite density, LRRK2 G2019S neurons show increased autism-linked CNTN5 adhesion protein expression; glial cells show significant loss of ferritin heavy chain. These data strongly suggest that loss of cilia in specific striatal cell types decreases neuroprotection for dopamine neurons in mice and human Parkinson's.

Myelin endocytosis by brain endothelial cells causes endothelial iron overload and oligodendroglial iron hunger in hypoperfusion-induced white matter injury

AIMS

Hypoperfusion induces significant white matter injury in cerebral vascular disorders, including arteriosclerotic cerebral small vessel disease (aCSVD), which is prevalent among the elderly. Iron transport by blood vessel endothelial cells (BVECs) from the periphery supports oligodendrocyte maturation and white matter repair. This study aims to elucidate the association between iron homeostasis changes and white matter injury severity, and explore the crosstalk between BVECs and oligodendroglial lineage cells.

METHODS

In vivo: C57BL/6 mice were subjected to unilateral common carotid artery occlusion (UCCAO). In vitro: BVECs with myelin pretreatment were co-cultured with oligodendrocyte progenitor cells (OPCs) or organotypic cerebellar slices subjected to oxygen and glucose deprivation.

RESULTS

Circulatory iron tends to be stored in aCSVD patients with white matter injury. Myelin debris endocytosis by BVECs impairs iron transport, trapping iron in the blood and away from the brain, worsening oligodendrocyte iron deficiency in hypoperfusion-induced white matter injury. Iron accumulation in BVECs triggers ferroptosis, suppressing iron transport and hindering white matter regeneration. Intranasal holo-transferrin (hTF) administration bypassing the BBB alleviates oligodendrocyte iron deficiency and promotes myelin regeneration in hypoperfusion-induced white matter injury.

CONCLUSION

The iron imbalance between BVECs and oligodendroglial lineage cells is a potential therapeutic target in hypoperfusion-induced white matter injury.

Heavy Metal Interactions with Neuroglia and Gut Microbiota: Implications for Huntington's Disease

Huntington's disease (HD) is a rare but progressive and devastating neurodegenerative disease characterized by involuntary movements, cognitive decline, executive dysfunction, and neuropsychiatric conditions such as anxiety and depression. It follows an autosomal dominant inheritance pattern. Thus, a child who has a parent with the mutated huntingtin (mHTT) gene has a 50% chance of developing the disease. Since the HTT protein is involved in many critical cellular processes, including neurogenesis, brain development, energy metabolism, transcriptional regulation, synaptic activity, vesicle trafficking, cell signaling, and autophagy, its aberrant aggregates lead to the disruption of numerous cellular pathways and neurodegeneration. Essential heavy metals are vital at low concentrations; however, at higher concentrations, they can exacerbate HD by disrupting glial-neuronal communication and/or causing dysbiosis (disturbance in the gut microbiota, GM), both of which can lead to neuroinflammation and further neurodegeneration. Here, we discuss in detail the interactions of iron, manganese, and copper with glial-neuron communication and GM and indicate how this knowledge may pave the way for the development of a new generation of disease-modifying therapies in HD.

Central Vein Sign and Paramagnetic Rim Lesions: Susceptibility Changes in Brain Tissues and Their Implications for the Study of Multiple Sclerosis Pathology

Multiple sclerosis (MS) is the most common acquired inflammatory and demyelinating disease in adults. The conventional diagnostic of MS and the follow-up of inflammatory activity is based on the detection of hyperintense foci in T2 and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) and lesions with brain-blood barrier (BBB) disruption in the central nervous system (CNS) parenchyma. However, T2/FLAIR hyperintense lesions are not specific to MS and the MS pathology and inflammatory processes go far beyond focal lesions and can be independent of BBB disruption. MRI techniques based on the magnetic susceptibility properties of the tissue, such as T2*, susceptibility-weighted images (SWI), and quantitative susceptibility mapping (QSM) offer tools for advanced MS diagnostic, follow-up, and the assessment of more detailed features of MS dynamic pathology. Susceptibility-weighted techniques are sensitive to the paramagnetic components of biological tissues, such as deoxyhemoglobin. This capability enables the visualization of brain parenchymal veins. Consequently, it presents an opportunity to identify veins within the core of multiple sclerosis (MS) lesions, thereby affirming their venocentric characteristics. This advancement significantly enhances the accuracy of the differential diagnostic process. Another important paramagnetic component in biological tissues is iron. In MS, the dynamic trafficking of iron between different cells, such as oligodendrocytes, astrocytes, and microglia, enables the study of different stages of demyelination and remyelination. Furthermore, the accumulation of iron in activated microglia serves as an indicator of latent inflammatory activity in chronic MS lesions, termed paramagnetic rim lesions (PRLs). PRLs have been correlated with disease progression and degenerative processes, underscoring their significance in MS pathology. This review will elucidate the underlying physical principles of magnetic susceptibility and their implications for the formation and interpretation of T2*, SWI, and QSM sequences. Additionally, it will explore their applications in multiple sclerosis (MS), particularly in detecting the central vein sign (CVS) and PRLs, and assessing iron metabolism. Furthermore, the review will discuss their role in advancing early and precise MS diagnosis and prognostic evaluation, as well as their utility in studying chronic active inflammation and degenerative processes.

Quantitative susceptibility mapping in the brain reflects spatial expression of genes involved in iron homeostasis and myelination

Quantitative susceptibility mapping (QSM) is an MRI modality used to non-invasively measure iron content in the brain. Iron exhibits a specific anatomically varying pattern of accumulation in the brain across individuals. The highest regions of accumulation are the deep grey nuclei, where iron is stored in paramagnetic molecule ferritin. This form of iron is considered to be what largely contributes to the signal measured by QSM in the deep grey nuclei. It is also known that QSM is affected by diamagnetic myelin contents. Here, we investigate spatial gene expression of iron and myelin related genes, as measured by the Allen Human Brain Atlas, in relation to QSM images of age-matched subjects. We performed multiple linear regressions between gene expression and the average QSM signal within 34 distinct deep grey nuclei regions. Our results show a positive correlation (p < .05, corrected) between expression of ferritin and the QSM signal in deep grey nuclei regions. We repeated the analysis for other genes that encode proteins thought to be involved in the transport and storage of iron in the brain, as well as myelination. In addition to ferritin, our findings demonstrate a positive correlation (p < .05, corrected) between the expression of ferroportin, transferrin, divalent metal transporter 1, several gene markers of myelinating oligodendrocytes, and the QSM signal in deep grey nuclei regions. Our results suggest that the QSM signal reflects both the storage and active transport of iron in the deep grey nuclei regions of the brain.

Potential of ferroptosis and ferritinophagy in migraine pathogenesis

Objective

To assess the potential of ferroptosis and ferritinophagy in migraine pathogenesis.

Background

Ferroptosis and ferritinophagy are related to increased cellular iron concentration and have been associated with the pathogenesis of several neurological disorders, but their potential in migraine pathogenesis has not been explored. Increased iron deposits in some deep brain areas, mainly periaqueductal gray (PAG), are reported in migraine and they have been associated with the disease severity and chronification as well as poor response to antimigraine drugs.

Results

Iron deposits may interfere with antinociceptive signaling in the neuronal network in the brain areas affected by migraine, but their mechanistic role is unclear. Independently of the location, increased iron concentration may be related to ferroptosis and ferritinophagy in the cell. Therefore, both phenomena may be related to increased iron deposits in migraine. It is unclear whether these deposits are the reason, consequence, or just a correlate of migraine. Still, due to migraine-related elevated levels of iron, which is a prerequisite of ferroptosis and ferritinophagy, the potential of both phenomena in migraine should be explored. If the iron deposits matter in migraine pathogenesis, they should be mechanically linked with the clinical picture of the disease. As iron is an exogenous essential trace element, it is provided to the human body solely with diet or supplements. Therefore, exploring the role of iron in migraine pathogenesis may help to determine the potential role of iron-rich/poor dietary products as migraine triggers or relievers.

Conclusion

Ferroptosis and ferritinophagy may be related to migraine pathogenesis through iron deposits in the deep areas of the brain.

CoQ10 targeted hippocampal ferroptosis in a status epilepticus rat model

Status epilepticus (SE), the most severe form of epilepsy, leads to brain damage. Uncertainty persists about the mechanisms that lead to the pathophysiology of epilepsy and the death of neurons. Overloading of intracellular iron ions has recently been identified as the cause of a newly recognized form of controlled cell death called ferroptosis. Inhibiting ferroptosis has shown promise as a treatment for epilepsy, according to recent studies. So, the current study aimed to assess the possible antiepileptic impact of CoQ10 either alone or with the standard antiepileptic drug sodium valproate (SVP) and to evaluate the targeted effect of COQ10 on hippocampal oxidative stress and ferroptosis in a SE rat model. Using a lithium-pilocarpine rat model of epilepsy, we evaluated the effect of SVP, CoQ10, or both on seizure severity, histological, and immunohistochemical of the hippocampus. Furthermore, due to the essential role of oxidative stress and lipid peroxidation in inducing ferroptosis, we evaluated malonaldehyde (MDA), reduced glutathione (GSH), glutathione peroxidase 4 (GPX4), and ferritin in tissue homogenate. Our work illustrated that ferroptosis occurs in murine models of lithium-pilocarpine-induced seizures (epileptic group). Nissl staining revealed significant neurodegeneration. A significant increase in the number of astrocytes stained with an astrocyte-specific marker was observed in the hippocampus. Effective seizure relief can be achieved in the seizure model by administering CoQ10 alone compared to SVP. This was accomplished by lowering ferritin levels and increasing GPX4, reducing MDA, and increasing GSH in the hippocampus tissue homogenate. In addition, the benefits of SVP therapy for regulating iron stores, GPX4, and oxidative stress markers were amplified by incorporating CoQ10 as compared to SVP alone. It was concluded that CoQ10 alone has a more beneficial effect than SVP alone in restoring histological structures and has a targeted effect on hippocampal oxidative stress and ferroptosis. In addition, COQ10 could be useful as an adjuvant to SVP in protecting against oxidative damage and ferroptosis-related damage that result from epileptic seizures.

The Emerging Role of Microglial Hv1 as a Target for Immunomodulation in Myelin Repair

In the central nervous system (CNS), the myelin sheath ensures efficient interconnection between neurons and contributes to the regulation of the proper function of neuronal networks. The maintenance of myelin and the well-organized subtle process of myelin plasticity requires cooperation among myelin-forming cells, glial cells, and neural networks. The process of cooperation is fragile, and the balance is highly susceptible to disruption by microenvironment influences. Reactive microglia play a critical and complicated role in the demyelination and remyelination process. Recent studies have shown that the voltage-gated proton channel Hv1 is selectively expressed in microglia in CNS, which regulates intracellular pH and is involved in the production of reactive oxygen species, underlying multifaceted roles in maintaining microglia function. This paper begins by examining the molecular mechanisms of demyelination and emphasizes the crucial role of the microenvironment in demyelination. It focuses specifically on the role of Hv1 in myelin repair and its therapeutic potential in CNS demyelinating diseases.

Brain iron concentration in childhood ADHD: A systematic review of neuroimaging studies

Iron deficiency may play a role in the pathophysiology of Attention Deficit/Hyperactivity Disorder (ADHD). Due to its preponderant function in monoamine catecholamine and myelin synthesis, brain iron concentration may be of primary interest in the investigation of iron dysregulation in ADHD. This study reviewed current evidence of brain iron abnormalities in children and adolescents with ADHD using magnetic resonance imaging methods, such as relaxometry and quantitative susceptibility mapping, to assess brain iron estimates. The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A literature search was performed for studies published between January 1, 2008 and July 7, 2023 in Medline, Scopus and Proquest. Regions of interest, brain iron index values and phenotypical information were extracted from the relevant studies. Risk of bias was assessed using a modified version of the National Heart, Lung, and Blood Institute quality assessment tool. Seven cross-sectional studies comparing brain iron estimates in children with ADHD with neurotypical children were included. Significantly reduced brain iron content in medication-naïve children with ADHD was a consistent finding. Two studies found psychostimulant use may increase and normalize brain iron concentration in children with ADHD. The findings were consistent across the studies despite differing methodologies and may lay the early foundation for the recognition of a potential biomarker in ADHD, although longitudinal prospective neuroimaging studies using larger sample sizes are required. Lastly, the effects of iron supplementation on brain iron concentration in children with ADHD need to be elucidated.

The role of myelin in neurodegeneration: implications for drug targets and neuroprotection strategies

Myelination of axons in the central nervous system offers numerous advantages, including decreased energy expenditure for signal transmission and enhanced signal speed. The myelin sheaths surrounding an axon consist of a multi-layered membrane that is formed by oligodendrocytes, while specific glycoproteins and lipids play various roles in this formation process. As beneficial as myelin can be, its dysregulation and degeneration can prove detrimental. Inflammation, oxidative stress, and changes in cellular metabolism and the extracellular matrix can lead to demyelination of these axons. These factors are hallmark characteristics of certain demyelinating diseases including multiple sclerosis. The effects of demyelination are also implicated in primary degeneration in diseases such as glaucoma and Alzheimer's disease, as well as in processes of secondary degeneration. This reveals a relationship between myelin and secondary processes of neurodegeneration, including resultant degeneration following traumatic injury and transsynaptic degeneration. The role of myelin in primary and secondary degeneration is also of interest in the exploration of strategies and targets for remyelination, including the use of anti-inflammatory molecules or nanoparticles to deliver drugs. Although the use of these methods in animal models of diseases have shown to be effective in promoting remyelination, very few clinical trials in patients have met primary end points. This may be due to shortcomings or considerations that are not met while designing a clinical trial that targets remyelination. Potential solutions include diversifying disease targets and requiring concomitant interventions to promote rehabilitation.

Identity and Maturity of iPSC-Derived Oligodendrocytes in 2D and Organoid Systems

Oligodendrocytes originating in the brain and spinal cord as well as in the ventral and dorsal domains of the neural tube are transcriptomically and functionally distinct. These distinctions are also reflected in the ultrastructure of the produced myelin, and the susceptibility to myelin-related disorders, which highlights the significance of the choice of patterning protocols in the differentiation of induced pluripotent stem cells (iPSCs) into oligodendrocytes. Thus, our first goal was to survey the different approaches applied to the generation of iPSC-derived oligodendrocytes in 2D culture and in organoids, as well as reflect on how these approaches pertain to the regional and spatial fate of the generated oligodendrocyte progenitors and myelinating oligodendrocytes. This knowledge is increasingly important to disease modeling and future therapeutic strategies. Our second goal was to recap the recent advances in the development of oligodendrocyte-enriched organoids, as we explore their relevance to a regional specification alongside their duration, complexity, and maturation stages of oligodendrocytes and myelin biology. Finally, we discuss the shortcomings of the existing protocols and potential future explorations.

Myelin Pathology in Alzheimer's Disease: Potential Therapeutic Opportunities

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by memory loss and cognitive decline. Despite significant efforts over several decades, our understanding of the pathophysiology of this disease is still incomplete. Myelin is a multi-layered membrane structure ensheathing neuronal axons, which is essential for the fast and effective propagation of action potentials along the axons. Recent studies highlight the critical involvement of myelin in memory consolidation and reveal its vulnerability in various pathological conditions. Notably, apart from the classic amyloid hypothesis, myelin degeneration has been proposed as another critical pathophysiological feature of AD, which could occur prior to the development of amyloid pathology. Here, we review recent works supporting the critical role of myelin in cognition and myelin pathology during AD progression, with a focus on the mechanisms underlying myelin degeneration in AD. We also discuss the complex intersections between myelin pathology and typical AD pathophysiology, as well as the therapeutic potential of pro-myelinating approaches for this disease. Overall, these findings implicate myelin degeneration as a critical contributor to AD-related cognitive deficits and support targeting myelin repair as a promising therapeutic strategy for AD.

Iron metabolism disorder and multiple sclerosis: a comprehensive analysis

Background

Multiple sclerosis (MS) is the most common chronic inflammatory disease of the central nervous system. Currently, the pathological mechanisms of MS are not fully understood, but research has suggested that iron metabolism disorder may be associated with the onset and clinical manifestations of MS.

Methods and materials

The study utilized publicly available databases and bioinformatics techniques for gene expression data analysis, including differential expression analysis, weighted correlation network analysis, gene enrichment analysis, and construction of logistic regression models. Subsequently, Mendelian randomization was used to assess the causal relationship between different iron metabolism markers and MS.

Results

This study identified IREB2, LAMP2, ISCU, ATP6V1G1, ATP13A2, and SKP1 as genes associated with multiple sclerosis (MS) and iron metabolism, establishing their multi-gene diagnostic value for MS with an AUC of 0.83. Additionally, Mendelian randomization analysis revealed a potential causal relationship between transferrin saturation and MS (p=2.22E-02; OR 95%CI=0.86 (0.75, 0.98)), as well as serum transferrin and MS (p=2.18E-04; OR 95%CI=1.22 (1.10, 1.36)).

Conclusion

This study comprehensively explored the relationship between iron metabolism and MS through integrated bioinformatics analysis and Mendelian randomization methods. The findings provide important insights for further research into the role of iron metabolism disorder in the pathogenesis of MS and offer crucial theoretical support for the treatment of MS.

Contrasting Iron Metabolism in Undifferentiated Versus Differentiated MO3.13 Oligodendrocytes via IL-1β-Induced Iron Regulatory Protein 1

Parkinson's disease (PD) is a prevalent neurodegenerative disorder characterized by the loss of dopaminergic neurons and the accumulation of iron in the substantia nigra. While iron accumulation and inflammation are implicated in PD pathogenesis, their impact on oligodendrocytes, the brain's myelin-forming cells, remains elusive. This study investigated the influence of interleukin-1β (IL-1β), an elevated proinflammatory cytokine in PD, on iron-related proteins in MO3.13 oligodendrocytes. We found that IL-1β treatment in undifferentiated MO3.13 oligodendrocytes increased iron regulatory protein 1 and transferrin receptor 1 (TfR1) expression while decreasing ferroportin 1 (FPN1) expression. Consequently, iron uptake was enhanced, and iron release was reduced, leading to intracellular iron accumulation. Conversely, IL-1β treatment in differentiated MO3.13 oligodendrocytes exhibited the opposite effect, with decreased TfR1 expression, increased FPN1 expression, and reduced iron uptake. These findings suggest that IL-1β-induced dysregulation of iron metabolism in oligodendrocytes may contribute to the pathological processes observed in PD. IL-1β can increase the iron content in undifferentiated oligodendrocytes, thus facilitating the differentiation of undifferentiated MO3.13 oligodendrocytes. In differentiated oligodendrocytes, IL-1β may facilitate iron release, providing a potential source of iron for neighboring dopaminergic neurons, thereby initiating a cascade of deleterious events. This study provides valuable insights into the intricate interplay between inflammation, abnormal iron accumulation, and oligodendrocyte dysfunction in PD. Targeting the IL-1β-mediated alterations in iron metabolism may hold therapeutic potential for mitigating neurodegeneration and preserving dopaminergic function in PD.

Identification of Immune Infiltration and Iron Metabolism-Related Subgroups in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder with a broad spectrum of symptoms and prognoses. Effective therapy requires understanding this variability. ASD children's cognitive and immunological development may depend on iron homoeostasis. This study employs a machine learning model that focuses on iron metabolism hub genes to identify ASD subgroups and describe immune infiltration patterns. A total of 97 control and 148 ASD samples were obtained from the GEO database. Differentially expressed genes (DEGs) and an iron metabolism gene collection achieved the intersection of 25 genes. Unsupervised cluster analysis determined molecular subgroups in individuals with ASD based on 25 genes related to iron metabolism. We assessed gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, gene set variation analysis (GSVA), and immune infiltration analysis to compare iron metabolism subtype effects. We employed machine learning to identify subtype-predicting hub genes and utilized both training and validation sets to assess gene subtype prediction accuracy. ASD can be classified into two iron-metabolizing molecular clusters. Metabolic enrichment pathways differed between clusters. Immune infiltration showed that clusters differed immunologically. Cluster 2 had better immunological scores and more immune cells, indicating a stronger immune response. Machine learning screening identified SELENBP1 and CAND1 as important genes in ASD's iron metabolism signaling pathway. These genes express in the brain and have AUC values over 0.8, implying significant predictive power. The present study introduces iron metabolism signaling pathway indicators to predict ASD subtypes. ASD is linked to immune cell infiltration and iron metabolism disorders.

The Role of Calcium and Iron Homeostasis in Parkinson's Disease

Calcium and iron are essential elements that regulate many important processes of eukaryotic cells. Failure to maintain homeostasis of calcium and iron causes cell dysfunction or even death. PD (Parkinson's disease) is the second most common neurological disorder in humans, for which there are currently no viable treatment options or effective strategies to cure and delay progression. Pathological hallmarks of PD, such as dopaminergic neuronal death and intracellular α-synuclein deposition, are closely involved in perturbations of iron and calcium homeostasis and accumulation. Here, we summarize the mechanisms by which Ca2+ signaling influences or promotes PD progression and the main mechanisms involved in ferroptosis in Parkinson's disease. Understanding the mechanisms by which calcium and iron imbalances contribute to the progression of this disease is critical to developing effective treatments to combat this devastating neurological disorder.

Loss of primary cilia and dopaminergic neuroprotection in pathogenic LRRK2-driven and idiopathic Parkinson's disease

Activating LRRK2 mutations cause Parkinson's disease. Previously, we showed that cholinergic interneurons and astrocytes but not medium spiny neurons of the dorsal striatum lose primary cilia in LRRK2 mutant mice. Single nucleus RNA sequencing shows that cilia loss in cholinergic interneurons correlates with higher LRRK2 expression and decreased glial derived neurotrophic factor transcription. Nevertheless, much higher LRRK2 expression is seen in medium spiny neurons that have normal cilia in mice and humans. In parallel with decreased striatal dopaminergic neurite density, LRRK2 G2019S neurons show increased autism-linked CNTN5 adhesion protein expression; glial cells show significant loss of ferritin heavy chain. Human striatal tissue from LRRK2 pathway mutation carriers and idiopathic Parkinson's disease show similar cilia loss in cholinergic interneurons and astrocytes and overall loss of such neurons. These data strongly suggest that loss of cilia in specific striatal cell types decreases neuroprotection for dopamine neurons in mice and human Parkinson's disease.

A maternal high-fat diet during pregnancy and lactation induced depression-like behavior in offspring and myelin-related changes in the rat prefrontal cortex

In accordance with the developmental origins of health and disease, early-life environmental exposures, such as maternal diet, can enhance the probability and gravity of health concerns in their offspring in the future. Over the past few years, compelling evidence has emerged suggesting that prenatal exposure to a maternal high-fat diet (HFD) could trigger neuropsychiatric disorders in the offspring, such as depression. The majority of brain development takes place before birth and during lactation. Nevertheless, our understanding of the impact of HFD on myelination in the offspring's brain during both gestation and lactation remains limited. In the present study, we investigated the effects of maternal HFD (60% energy from fat) on depressive-like and myelin-related changes in adolescent and adult rat offspring. Maternal HFD increased immobility time during the forced swimming test in both adolescent and adult offspring. Correspondingly, the depressive-like phenotype in offspring correlated with dysregulation of several genes and proteins in the prefrontal cortex, especially of myelin-oligodendrocyte glycoprotein (MOG), myelin and lymphocyte protein (MAL), 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase), kallikrein 6, and transferrin in male offspring, as well as of MOG and kallikrein 6 in female offspring, which persist even into adulthood. Maternal HFD also induced long-lasting adaptations manifested by the reduction of immature and mature oligodendrocytes in the prefrontal cortex in adult offspring. In summary, maternal HFD-induced changes in myelin-related genes are correlated with depressive-like behavior in adolescent offspring, which persists even to adulthood.

Local Administrations of Iron Oxide Nanoparticles in the Prefrontal Cortex and Caudate Putamen of Rats Do Not Compromise Working Memory and Motor Activity

Iron oxide nanoparticles (IONPs) have come into focus for their use in medical applications although possible health risks for humans, especially in terms of brain functions, have not yet been fully clarified. The present study investigates the effects of IONPs on neurobehavioural functions in rats. For this purpose, we infused dimercaptosuccinic acid-coated IONPs into the medial prefrontal cortex (mPFC) and caudate putamen (CPu). Saline (VEH) and ferric ammonium citrate (FAC) were administered as controls. One- and 4-week post-surgery mPFC-infused animals were tested for their working memory performance in the delayed alternation T-maze task and in the open field (OF) for motor activity, and CPu-infused rats were tested for their motor activity in the OF. After completion of the experiments, the brains were examined histologically and immunohistochemically. We did not observe any behavioural or structural abnormalities in the rats after administration of IONPs in the mPFC and the CPu. In contrast, administration of FAC into the CPu resulted in decreased motor activity and increased the number of microglia in the mPFC. Perls' Prussian blue staining revealed that FAC- and IONP-treated rats had more iron-containing ramified cells than VEH-treated rats, indicating iron uptake by microglia. Our results demonstrate that local infusions of IONPs into selected brain regions have no adverse impact on locomotor behaviour and working memory.

Ferroptosis of Microglia in Aging Human White Matter Injury

OBJECTIVE

Because the role of white matter (WM) degenerating microglia (DM) in remyelination failure is unclear, we sought to define the core features of this novel population of aging human microglia.

METHODS

We analyzed postmortem human brain tissue to define a population of DM in aging WM lesions. We used immunofluorescence staining and gene expression analysis to investigate molecular mechanisms related to the degeneration of DM.

RESULTS

We found that DM, which accumulated myelin debris were selectively enriched in the iron-binding protein light chain ferritin, and accumulated PLIN2-labeled lipid droplets. DM displayed lipid peroxidation injury and enhanced expression for TOM20, a mitochondrial translocase, and a sensor of oxidative stress. DM also displayed enhanced expression of the DNA fragmentation marker phospho-histone H2A.X. We identified a unique set of ferroptosis-related genes involving iron-mediated lipid dysmetabolism and oxidative stress that were preferentially expressed in WM injury relative to gray matter neurodegeneration.

INTERPRETATION

Ferroptosis appears to be a major mechanism of WM injury in Alzheimer's disease and vascular dementia. WM DM are a novel therapeutic target to potentially reduce the impact of WM injury and myelin loss on the progression of cognitive impairment. ANN NEUROL 2023;94:1048-1066.

New frontiers in neonatal red blood cell transfusion research

Red blood cell (RBC) transfusions are common in neonates requiring intensive care. Recent studies have compared restricted versus liberal transfusion guidelines, but limitations exist on evaluations of outcomes in populations that never required a transfusion compared to those receiving any transfusion. Although there are well-established risks associated with RBC transfusions, new data has emerged that suggests additional clinically relevant associations, including adverse neurodevelopmental outcomes, donor sex differences, and inflammation or immunosuppression. Further research is needed to delineate the magnitude of these risks and to further improve the safety of transfusions. The goal of this review is to highlight underappreciated, yet clinically important risks associated with neonatal RBC transfusions and to introduce several areas in which neonates may uniquely benefit from alterations in practice.

Research progress in the molecular mechanism of ferroptosis in Parkinson's disease and regulation by natural plant products

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder of the central nervous system after Alzheimer's disease. The current understanding of PD focuses mainly on the loss of dopamine neurons in the substantia nigra region of the midbrain, which is attributed to factors such as oxidative stress, alpha-synuclein aggregation, neuroinflammation, and mitochondrial dysfunction. These factors together contribute to the PD phenotype. Recent studies on PD pathology have introduced a new form of cell death known as ferroptosis. Pathological changes closely linked with ferroptosis have been seen in the brain tissues of PD patients, including alterations in iron metabolism, lipid peroxidation, and increased levels of reactive oxygen species. Preclinical research has demonstrated the neuroprotective qualities of certain iron chelators, antioxidants, Fer-1, and conditioners in Parkinson's disease. Natural plant products have shown significant potential in balancing ferroptosis-related factors and adjusting their expression levels. Therefore, it is vital to understand the mechanisms by which natural plant products inhibit ferroptosis and relieve PD symptoms. This review provides a comprehensive look at ferroptosis, its role in PD pathology, and the mechanisms underlying the therapeutic effects of natural plant products focused on ferroptosis. The insights from this review can serve as useful references for future research on novel ferroptosis inhibitors and lead compounds for PD treatment.