Iron Deficiency and Iron Excess Differently Affect Dendritic Architecture of Pyramidal Neurons in the Hippocampus of Piglets

Overexpression of Nfs1 Cysteine Desulphurase Relieves Sevoflurane-Induced Neurotoxicity and Cognitive Dysfunction in Neonatal Mice Via Suppressing Oxidative Stress and Ferroptosis

Clinical evidence suggests that multiple exposures to sevoflurane in young people may be detrimental to cognitive development. Iron accumulation in the hippocampus is associated with sevoflurane-induced neurotoxicity and cognitive deficits. The cysteine desulphurase, Nfs1, the rate-limiting enzyme for the biosynthesis of iron-sulphur clusters, plays a role in cellular iron homeostasis. However, the impact of Nfs1-mediated ferroptosis on sevoflurane-induced neurotoxicity and cognitive impairments in neonatal mice remains undetermined. Neonatal mice at postnatal Day 6 received 3% sevoflurane daily for 3 consecutive days. Cognitive function was assessed using the Morris water maze test, and neurotoxicity was evaluated through terminal deoxynucleotidyl transferase dUTP nick end labeling and immunofluorescence staining. Here, HT22 hippocampal neurons were employed for in-vitro experiments, and Fe2+ accumulation was measured. Ferroptosis-related genes, including glutathione peroxidase 4 (GPX4), transferrin receptor 1 (TFR1) and ferritin, in the hippocampus and HT22 cells were observed, along with oxidative stress-related indicators such as reactive oxygen species (ROS), methionine adenosyltransferase (MAT), glutathione (GSH) and lipid peroxidation (LPO). Transmission electron microscopy was utilized to examine the mitochondrial microstructure. Sevoflurane exposure significantly decreased Nfs1 expression in the hippocampus of mice and HT22 cells. This exposure resulted in cognitive impairments and neuronal damage in the hippocampus, which were alleviated by overexpression of Nfs1. Intracellular and mitochondrial iron accumulation occurred in HT22 cells following sevoflurane treatment. Sevoflurane exposure also significantly reduced GSH levels and increased levels of malondialdehyde, ROS and LPO in the hippocampus or HT22 cells. Additionally, sevoflurane exposure decreased GPX4 expression but increased TFR1 and ferritin expression in the hippocampus or HT22 cells. Overexpression of Nfs1 reversed the sevoflurane-induced alterations in ferroptosis-related genes and oxidative stress-related indicators. Furthermore, overexpression of Nfs1 alleviated sevoflurane-induced mitochondrial dysfunction. However, Nfs1 knockdown alone did not result in cognitive impairments, ferroptosis or oxidative stress. The overexpression of Nfs1 mitigated sevoflurane-induced neurotoxicity and cognitive impairment by modulating oxidative stress and ferroptosis through the regulation of iron metabolism and transport.

Bridging the gap: Prenatal nutrition, myelination, and schizophrenia etiopathogenesis

Schizophrenia (SZ) is a complex mental illness characterized by disturbances in thinking, emotionality, and behavior, significantly impacting the quality of life for individuals affected and those around them. The etiology of SZ involves intricate interactions between genetic and environmental factors, although the precise mechanisms remain incompletely understood. Genetic predisposition, neurotransmitter dysregulation (particularly involving dopamine and serotonin), and structural brain abnormalities, including impaired prefrontal cortex function, have been implicated in SZ development. However, increasing evidence reveals the role of environmental factors, such as nutrition, during critical periods like pregnancy and lactation. Epidemiological studies suggest that early malnutrition significantly increases the risk of SZ symptoms manifesting in late adolescence, a crucial period coinciding with peak myelination and brain maturation. Prenatal undernutrition may disrupt myelin formation, rendering individuals more susceptible to SZ pathology. This review explores the potential relationship between prenatal undernutrition, myelin alterations, and susceptibility to SZ. By delineating the etiopathogenesis, examining genetic and environmental factors associated with SZ, and reviewing the relationship between SZ and myelination disorders, alongside the impact of malnutrition on myelination, we aim to examine how malnutrition might be linked to SZ by altering myelination processes, which contribute to increasing the understanding of SZ etiology and help identify targets for intervention and management.

Adherence to iron supplementation during the first year of life infants in Izmir, Turkey

To determine the prevalence of adherence to iron supplementation and the risk factors for incomplete adherence during the first year of life of infants in Izmir, Turkey. In this cross-sectional study, a total of 511 infants aged 2 to 12 months who presented to the Pediatrics outpatient clinics of Ege University Children's Hospital were included. Mothers (n = 511) who agreed to participate in the study were interviewed face-to-face and a comprehensive questionnaire including questions about the sociodemographic characteristics of the children and the family, and their adherence to iron supplementation was administered. The data obtained from 471 (92.2%) mothers who used iron supplements for their babies were subjected to further statistical analysis. Analyses were performed with SPSS 25.0. Chi-square test was used for univariate analysis and logistic regression analysis was used to determine the independent factors associated with incomplete adherence to iron supplementation. A total of 511 mothers were surveyed. Among the infants of mothers who participated in the study, 471 (92.2%) were taking iron supplementation. Of the infants who received iron supplementation, 58.3% were given iron supplementation with complete adherence. The percentage of complete adherence with iron supplementation was 35.1% between 2 and 4 months, 66.3% between 5 and 8 months, and 52.4% between 9 to 12 months. In univariate analysis, statistically significant differences were found between complete and incomplete adherence to iron supplementation in terms of infant age, time of birth, family income, maternal education, and maternal employment status (P < .001). When the data were analyzed using multivariate analysis, only maternal education level and infant age group were found to be statistically significant independent variables for complete and incomplete adherence to iron supplementation (P < .001). In populations with a high prevalence of ID, incomplete adherence to iron supplementation is a serious risk factor for ID/IDA. Although iron supplements are routinely given to infants by the Ministry of Health in Turkey, the prevalence of complete adherence to iron supplementation is low. Therefore, in order to increase the rate of complete adherence to iron supplementation, the iron supplementation status of infants should be reviewed in detail at each health child visit and families should be informed about the importance of supplementation to prevent iron deficiency.

Brain Iron Metabolism, Redox Balance and Neurological Diseases

The incidence of neurological diseases, such as Parkinson's disease, Alzheimer's disease and stroke, is increasing. An increasing number of studies have correlated these diseases with brain iron overload and the resulting oxidative damage. Brain iron deficiency has also been closely linked to neurodevelopment. These neurological disorders seriously affect the physical and mental health of patients and bring heavy economic burdens to families and society. Therefore, it is important to maintain brain iron homeostasis and to understand the mechanism of brain iron disorders affecting reactive oxygen species (ROS) balance, resulting in neural damage, cell death and, ultimately, leading to the development of disease. Evidence has shown that many therapies targeting brain iron and ROS imbalances have good preventive and therapeutic effects on neurological diseases. This review highlights the molecular mechanisms, pathogenesis and treatment strategies of brain iron metabolism disorders in neurological diseases.

Benefits and Risks of Early Life Iron Supplementation

Infants are frequently supplemented with iron to prevent iron deficiency, but iron supplements may have adverse effects on infant health. Although iron supplements can be highly effective at improving iron status and preventing iron deficiency anemia, iron may adversely affect growth and development, and may increase risk for certain infections. Several reviews exist in this area; however, none has fully summarized all reported outcomes of iron supplementation during infancy. In this review, we summarize the risks and benefits of iron supplementation as they have been reported in controlled studies and in relevant animal models. Additionally, we discuss the mechanisms that may underly beneficial and adverse effects.

Trace Element Interactions, Inflammatory Signaling, and Male Sex Implicated in Reduced Growth Following Excess Oral Iron Supplementation in Pre-Weanling Rats

Iron supplements are frequently provided to infants in high-income countries despite low incidence of iron deficiency. There is growing concern regarding adverse health and development outcomes of excess iron provision in early life. Excess iron may directly damage developing organs through the formation of reactive oxygen species, alter systemic inflammatory signaling, and/or dysregulate trace mineral metabolism. To better characterize the in vivo effects of excess iron on development, we utilized a pre-weanling rat pup model. Lewis rat litters were culled to eight pups (four males and four females) and randomly assigned to daily supplementation groups receiving either vehicle control (CON; 10% w/v sucrose solution) or ferrous sulfate (FS) iron at one of the following doses: 10, 30, or 90 mg iron/kg body weight—FS-10, FS-30, and FS-90, respectively—from postnatal day (PD) 2 through 9. FS-90 litters, but not FS-30 or FS-10, failed to thrive compared to CON litters and had smaller brains on PD 10. Among the groups, FS-90 liver iron levels were highest, as were white blood cell counts. Compared to CON, circulating MCP-1 and liver zinc were increased in FS-90 pups, whereas liver copper was decreased. Growth defects due to excess FS provision in pre-weanling rats may be related to liver injury, inflammation, and altered trace mineral metabolism.

Mitochondria-Related Ferroptosis Drives Cognitive Deficits in Neonatal Mice Following Sevoflurane Administration

Multiple sevoflurane exposure may result in cognitive deficits in neonatal animals. This study attempted to investigate the potential mechanism of sevoflurane-induced neurotoxicity in developing hippocampus. Neonatal animals received sevoflurane anesthesia, then the behavioral tests and Golgi-Cox staining were employed to detect the effect of sevoflurane inhalation in adult mice. And the mitochondrial function was evaluated using MitoSOX staining, Fluo calcium indicators, mitochondrial permeability transition pore (mPTP) assay, and JC-1 probe after sevoflurane administration. Meanwhile, mitochondrial lipid hydroperoxide and ferroptosis were measured by MitoPeDPP and Mito-FerroGreen signals following sevoflurane exposure. Moreover, the ferroptosis and behavioral performance were assessed after deferiprone (DFP) treatment. The results showed that sevoflurane administration induced cognitive impairment accompanied by reducing dendritic length, density, and nodes. Additionally, sevoflurane exposure elevated mitochondrial ROS production and cytoplasm calcium levels, triggered the opening of mPTP, and decreased the mitochondrial membrane potential (MMP). However, supplement of elamipretide (SS-31) effectively reversed mitochondrial dysfunction. Mitochondrial lipid hydroperoxide production was increased after sevoflurane administration, whereas Fer-1 treatment reduced lipid hydroperoxide formation. Sevoflurane exposure induced mitochondrial iron overload, whereas Mito-Tempo treatment reduced iron accumulation. Prussian blue staining showed that the hippocampal iron deposition was apparently increased after sevoflurane inhalation. Additionally, the ferroptosis-related protein expression (including ACSL4, COX2, GPX4, and FTH1) was significantly changed, whereas DFP effectively suppressed ferroptosis and enhanced sevoflurane-induced behavioral malfunction. These findings demonstrated that sevoflurane administration elicited mitochondrial dysfunction and iron dyshomeostasis and eventually resulted in cognitive impairments, whereas protecting mitochondrial function and chelating neurotoxic iron effectively reversed these pathological processes.

Small Extracellular Vesicles in Milk Cross the Blood-Brain Barrier in Murine Cerebral Cortex Endothelial Cells and Promote Dendritic Complexity in the Hippocampus and Brain Function in C57BL/6J Mice

Human milk contains large amounts of small extracellular vesicles (sEVs) and their microRNA cargos, whereas infant formulas contain only trace amounts of sEVs and microRNAs. We assessed the transport of sEVs across the blood-brain barrier (BBB) and sEV accumulation in distinct regions of the brain in brain endothelial cells and suckling mice. We further assessed sEV-dependent gene expression profiles and effects on the dendritic complexity of hippocampal granule cells and phenotypes of EV depletion in neonate, juvenile and adult mice. The transfer of sEVs across the BBB was assessed by using fluorophore-labeled bovine sEVs in brain endothelial bEnd.3 monolayers and dual chamber systems, and in wild-type newborn pups fostered to sEV and cargo tracking (ECT) dams that express sEVs labeled with a CD63-eGFP fusion protein for subsequent analysis by serial two-photon tomography and staining with anti-eGFP antibodies. Effects of EVs on gene expression and dendritic architecture of granule cells was analyzed in hippocampi from juvenile mice fed sEV and RNA-depleted (ERD) and sEV and RNA-sufficient (ERS) diets by using RNA-sequencing analysis and Golgi-Cox staining followed by integrated neuronal tracing and morphological analysis of neuronal dendrites, respectively. Spatial learning and severity of kainic acid-induced seizures were assessed in mice fed ERD and ERS diets. bEnd.3 cells internalized sEVs by using a saturable transport mechanism and secreted miR-34a across the basal membrane. sEVs penetrated the entire brain in fostering experiments; major regions of accumulation included the hippocampus, cortex and cerebellum. Two hundred ninety-five genes were differentially expressed in hippocampi from mice fed ERD and ERS diets; high-confidence gene networks included pathways implicated in axon guidance and calcium signaling. Juvenile pups fed the ERD diet had reduced dendritic complexity of dentate granule cells in the hippocampus, scored nine-fold lower in the Barnes maze test of spatial learning and memory, and the severity of seizures was 5-fold higher following kainic acid administration in adult mice fed the ERD diet compared to mice fed the ERS diet. We conclude that sEVs cross the BBB and contribute toward optimal neuronal development, spatial learning and memory, and resistance to kainic acid-induced seizures in mice.

Synergistic gene regulation by thyroid hormone and glucocorticoid in the hippocampus

The hippocampus is considered the center for learning and memory in the brain, and its development and function is greatly affected by the thyroid and stress axes. Thyroid hormone (TH) and glucocorticoids (GC) are known to have a synergistic effect on developmental programs across several vertebrate species, and their effects on hippocampal structure and function are well-documented. However, there are few studies that focus on the processes and genes that are cooperatively regulated by the two hormone axes. Cross-regulation of the thyroid and stress axes in the hippocampus occurs on multiple levels such that TH can regulate the expression of the GC receptor (GR) while GC can modulate tissue sensitivity to TH by controlling the expression of TH receptor (TR) and enzymes involved in TH biosynthesis. Thyroid hormone and GC are also known to synergistically regulate the transcription of genes associated with neuronal function and development. Synergistic gene regulation by TH and GC may occur through the direct, cooperative action of TR and GR on common target genes, or by indirect mechanisms involving gene regulatory cascades activated by TR and GR. In this chapter, we describe the known physiological effects and underlying molecular mechanisms of TH and GC synergistic gene regulation in the hippocampus.

Quantitative Susceptibility Mapping of the Basal Ganglia and Thalamus at 9.4 Tesla

The thalamus (Th) and basal ganglia (BG) are central subcortical connectivity hubs of the human brain, whose functional anatomy is still under intense investigation. Nevertheless, both substructures contain a robust and reproducible functional anatomy. The quantitative susceptibility mapping (QSM) at ultra-high field may facilitate an improved characterization of the underlying functional anatomy in vivo. We acquired high-resolution QSM data at 9.4 Tesla in 21 subjects, and analyzed the thalamic and BG by using a prior defined functional parcellation. We found a more substantial contribution of paramagnetic susceptibility sources such as iron in the pallidum in contrast to the caudate, putamen, and Th in descending order. The diamagnetic susceptibility sources such as myelin and calcium revealed significant contributions in the Th parcels compared with the BG. This study presents a detailed nuclei-specific delineation of QSM-provided diamagnetic and paramagnetic susceptibility sources pronounced in the BG and the Th. We also found a reasonable interindividual variability as well as slight hemispheric differences. The results presented here contribute to the microstructural knowledge of the Th and the BG. In specific, the study illustrates QSM values (myelin, calcium, and iron) in functionally similar subregions of the Th and the BG.