Why should neuroscientists worry about iron? The emerging role of ferroptosis in the pathophysiology of neuroprogressive diseases

Cellular iron deposition patterns predict clinical subtypes of multiple system atrophy

BACKGROUND

Multiple system atrophy (MSA) is a primary oligodendroglial synucleinopathy, characterized by elevated iron burden in early-affected subcortical nuclei. Although neurotoxic effects of brain iron deposition and its relationship with α-synuclein pathology have been demonstrated, the exact role of iron dysregulation in MSA pathogenesis is unknown. Therefore, advancing the understanding of iron dysregulation at the cellular level is critical, especially in relation to α-synuclein cytopathology.

METHODS

Iron burden in subcortical and brainstem regions were histologically mapped in human post-mortem brains of 4 MSA-parkinsonian (MSA-P), 4 MSA-cerebellar (MSA-C), and 1 MSA case with both parkinsonian and cerebellar features. We then performed the first cell type-specific evaluation of pathological iron deposition in α-synuclein-affected and -unaffected cells of the globus pallidus, putamen, and the substantia nigra, regions of highest iron concentration, using a combination of iron staining with immunolabelling. Selective regional and cellular vulnerability patterns of iron deposition were compared between disease subtypes. In 7 MSA cases, expression of key iron- and closely related oxygen-homeostatic genes were examined.

RESULTS

MSA-P and MSA-C showed different patterns of regional iron burden across the pathology-related systems. We identified subcortical microglia to predominantly accumulate iron, which was more distinct in MSA-P. MSA-C showed relatively heterogenous iron accumulation, with greater or similar deposition in astroglia. Iron deposition was also found outside cellular bodies. Cellular iron burden associated with oligodendrocytic, and not neuronal, α-synuclein cytopathology. Gene expression analysis revealed dysregulation of oxygen homeostatic genes, rather than of cellular iron. Importantly, hierarchal cluster analysis revealed the pattern of cellular vulnerability to iron accumulation, distinctly to α-synuclein pathology load in the subtype-related systems, to distinguish MSA subtypes.

CONCLUSIONS

Our comprehensive evaluation of iron deposition in MSA brains identified distinct regional, and for the first time, cellular distribution of iron deposition in MSA-P and MSA-C and revealed cellular vulnerability patterns to iron deposition as a novel neuropathological characteristic that predicts MSA clinical subtypes. Our findings suggest distinct iron-related pathomechanisms in MSA clinical subtypes that are therefore not a consequence of a uniform down-stream pathway to α-synuclein pathology, and inform current efforts in iron chelation therapies at the disease and cellular-specific levels.

Exploring the anti-ferroptosis mechanism of Kai-Xin-San against Alzheimer's disease through integrating network pharmacology, bioinformatics, and experimental validation strategy in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Kai Xin San (KXS), first proposed by Sun Simiao during the Tang Dynasty, has been utilized to treat dementia by tonifying qi and dispersing phlegm.

AIM OF THE STUDY

This study aimed to elucidate the mechanism by which KXS exerts its therapeutic effects on Alzheimer's disease (AD) by targeting ferroptosis, using a combination of network pharmacology, bioinformatics, and experimental validation strategies.

MATERIALS AND METHODS

The active target sites and the further potential mechanisms of KXS in protecting against AD were investigated through molecular docking, molecular dynamics simulation, and network pharmacology, and combined with the validation of animal experiments.

RESULTS

Computational and experimental findings provide the first indication that KXS significantly improves learning and memory defects and inhibits neuronal ferroptosis by repairing mitochondria damage and upregulating the protein expression of ferroptosis suppressor protein 1 (FSP1) in vivo APP/PS1 mice AD model. According to bioinformatics analysis, the mechanism by which KXS inhibits ferroptosis may involve SIRT1. KXS notably upregulated the mRNA and protein expression of SIRT1 in both vivo APP/PS1 mice and in vitro APP-overexpressed HT22 cells. Additionally, KXS inhibited ferroptosis induced by APP-overexpression in HT22 cells through activating the SIRT1-FSP1 signal pathway.

CONCLUSIONS

Collectively, our findings suggest that KXS may inhibit neuronal ferroptosis through activating the SIRT1/FSP1 signaling pathway. This study reveals the scientific basis and underlying modern theory of replenishing qi and eliminating phlegm, which involves the inhibition of ferroptosis. Moreover, it highlights the potential application of SIRT1 or FSP1 activators in the treatment of AD and other ferroptosis-related diseases.

Polycytosine RNA-binding protein 1 regulates osteoblast function via a ferroptosis pathway in type 2 diabetic osteoporosis

BACKGROUND

Recently, type 2 diabetic osteoporosis (T2DOP) has become a research hotspot for the complications of diabetes, but the specific mechanism of its occurrence and development remains unknown. Ferroptosis caused by iron overload is con-sidered an important cause of T2DOP. Polycytosine RNA-binding protein 1 (PCBP1), an iron ion chaperone, is considered a protector of ferroptosis.

AIM

To investigate the existence of ferroptosis and specific role of PCBP1 in the development of type 2 diabetes.

METHODS

A cell counting kit-8 assay was used to detect changes in osteoblast viability under high glucose (HG) and/or ferroptosis inhibitors at different concentrations and times. Transmission electron microscopy was used to examine the morphological changes in the mitochondria of osteoblasts under HG, and western blotting was used to detect the expression levels of PCBP1, ferritin, and the ferroptosis-related protein glutathione peroxidase 4 (GPX4). A lentivirus silenced and overexpressed PCBP1. Western blotting was used to detect the expression levels of the osteoblast functional proteins osteoprotegerin (OPG) and osteocalcin (OCN), whereas flow cytometry was used to detect changes in reactive oxygen species (ROS) levels in each group.

RESULTS

Under HG, the viability of osteoblasts was considerably decreased, the number of mitochondria undergoing atrophy was considerably increased, PCBP1 and ferritin expression levels were increased, and GPX4 expression was decreased. Western blotting results demonstrated that infection with lentivirus overexpressing PCBP1, increased the expression levels of ferritin, GPX4, OPG, and OCN, compared with the HG group. Flow cytometry results showed a reduction in ROS, and an opposite result was obtained after silencing PCBP1.

CONCLUSION

PCBP1 may protect osteoblasts and reduce the harm caused by ferroptosis by promoting ferritin expression under a HG environment. Moreover, PCBP1 may be a potential therapeutic target for T2DOP.

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

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

Whole brain pattern of iron accumulation in REM sleep behavior disorder

Isolated REM sleep behavior disorder (iRBD) is an early stage of synucleinopathy with most patients progressing to Parkinson's disease (PD) or related conditions. Quantitative susceptibility mapping (QSM) in PD has identified pathological iron accumulation in the substantia nigra (SN) and variably also in basal ganglia and cortex. Analyzing whole-brain QSM across iRBD, PD, and healthy controls (HC) may help to ascertain the extent of neurodegeneration in prodromal synucleinopathy. 70 de novo PD patients, 70 iRBD patients, and 60 HCs underwent 3 T MRI. T1 and susceptibility-weighted images were acquired and processed to space standardized QSM. Voxel-based analyses of grey matter magnetic susceptibility differences comparing all groups were performed on the whole brain and upper brainstem levels with the statistical threshold set at family-wise error-corrected p-values <.05. Whole-brain analysis showed increased susceptibility in the bilateral fronto-parietal cortex of iRBD patients compared to both PD and HC. This was not associated with cortical thinning according to the cortical thickness analysis. Compared to iRBD, PD patients had increased susceptibility in the left amygdala and hippocampal region. Upper brainstem analysis revealed increased susceptibility within the bilateral SN for both PD and iRBD compared to HC; changes were located predominantly in nigrosome 1 in the former and nigrosome 2 in the latter group. In the iRBD group, abnormal dopamine transporter SPECT was associated with increased susceptibility in nigrosome 1. iRBD patients display greater fronto-parietal cortex involvement than incidental early-stage PD cohort indicating more widespread subclinical neuropathology. Dopaminergic degeneration in the substantia nigra is paralleled by susceptibility increase, mainly in nigrosome 1.

Ferroptosis regulation through Nrf2 and implications for neurodegenerative diseases

This article provides an overview of the background knowledge of ferroptosis in the nervous system, as well as the key role of nuclear factor E2-related factor 2 (Nrf2) in regulating ferroptosis. The article takes Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) as the starting point to explore the close association between Nrf2 and ferroptosis, which is of clear and significant importance for understanding the mechanism of neurodegenerative diseases (NDs) based on oxidative stress (OS). Accumulating evidence links ferroptosis to the pathogenesis of NDs. As the disease progresses, damage to the antioxidant system, excessive OS, and altered Nrf2 expression levels, especially the inhibition of ferroptosis by lipid peroxidation inhibitors and adaptive enhancement of Nrf2 signaling, demonstrate the potential clinical significance of Nrf2 in detecting and identifying ferroptosis, as well as targeted therapy for neuronal loss and mitochondrial dysfunction. These findings provide new insights and possibilities for the treatment and prevention of NDs.

Ferroptosis and Pyroptosis in Epilepsy

Epilepsy is sudden, recurrent, and transient central nervous system dysfunction caused by abnormal discharge of neurons in the brain. Ferroptosis and pyroptosis are newly discovered ways of programmed cell death. One of the characteristics of ferroptosis is the oxidative stress generated by lipid peroxides. Similarly, pyroptosis has unique pro-inflammatory properties. As both oxidative stress and neuroinflammation are significant contributors to the pathogenesis of epilepsy, increasing evidence shows that ferroptosis and pyroptosis are closely related to epilepsy. This article reviews the current comprehension of ferroptosis and pyroptosis and elucidates potential mechanisms by which ferroptosis and pyroptosis may contribute to epilepsy. In addition, we also highlight the possible interactions between ferroptosis and pyroptosis because they reportedly coexist in many diseases, and increasing studies have demonstrated the convergence of pathways between the two. This is of great significance for explaining the occurrence and development of epilepsy and provides a new therapeutic perspective for the treatment of epilepsy.

Ferroptosis in early brain injury after subarachnoid hemorrhage: review of literature

Spontaneous subarachnoid hemorrhage (SAH), mainly caused by ruptured intracranial aneurysms, is a serious acute cerebrovascular disease. Early brain injury (EBI) is all brain injury occurring within 72 h after SAH, mainly including increased intracranial pressure, decreased cerebral blood flow, disruption of the blood-brain barrier, brain edema, oxidative stress, and neuroinflammation. It activates cell death pathways, leading to neuronal and glial cell death, and is significantly associated with poor prognosis. Ferroptosis is characterized by iron-dependent accumulation of lipid peroxides and is involved in the process of neuron and glial cell death in early brain injury. This paper reviews the research progress of ferroptosis in early brain injury after subarachnoid hemorrhage and provides new ideas for future research.

Folic acid blocks ferroptosis induced by cerebral ischemia and reperfusion through regulating folate hydrolase transcriptional adaptive program

Cerebral ischemia-reperfusion (I/R) injury is notably linked with folic acid (FA) deficiency. The aim of our investigation was to explore the effects and underlying mechanisms by which FA mitigates I/R, specifically through regulating the GCPII transcriptional adaptive program. Initially, we discovered that following cerebral I/R, levels of FA, methionine synthase (MTR), and methylenetetrahydrofolate reductase (MTHFR) were decreased, while GCPII expression was elevated. Secondly, administering FA could mitigate cognitive impairment and neuronal damage induced by I/R. Thirdly, the mechanism of FA supplementation involved suppressing the transcriptional factor Sp1, subsequently inhibiting GCPII transcription, reducing Glu content, obstructing cellular ferroptosis, and alleviating cerebral I/R injury. In summary, our data demonstrate that FA affords protection against cerebral I/R injury by inhibiting the GCPII transcriptional adaptive response. These findings unveil that targeting GCPII might be a viable therapeutic strategy for cerebral I/R.

Ferroptosis as a Therapeutic Target in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a cerebrovascular disorder with significant mortality and morbidity. Neural injury in SAH is mediated through a variety of pathophysiological processes. Currently available treatments are either nonspecific in targeting the basic pathophysiological mechanisms that result in neural damage in SAH, or merely focus on vasospasm. Ferroptosis is a type of programmed iron dependent cell death, which has received attention due to its possible role in neural injury in SAH. Herein, we review how intracellular iron overload mediates the production of reactive free radicals and lipid peroxidation through a variety of biochemical pathways in SAH. This in turn results in induction of ferroptosis, as well as exacerbation of vasospasm. We also discuss several therapeutic agents that have been shown to inhibit ferroptosis through targeting different steps of the process. Such agents have proven effective in ameliorating vasospasm, neural damage, and neurobehavioral outcomes in animal models of SAH. Human studies to test the safety and efficacy of intrathecal or parenteral administration of the inhibitors of ferroptosis in improving outcomes of SAH patients are warranted. There are currently a few ongoing clinical trials pursuing this therapeutic concept, the results of which will be critical to determine the value of ferroptosis as a novel therapeutic target in SAH.

Deeper insight into ferroptosis: association with Alzheimer's, Parkinson's disease, and brain tumors and their possible treatment by nanomaterials induced ferroptosis

Ferroptosis is an emerging and novel type of iron-dependent programmed cell death which is mainly caused by the excessive deposition of free intracellular iron in the brain cells. This deposited free iron exerts a ferroptosis pathway, resulting in lipid peroxidation (LiPr). There are mainly three ferroptosis pathways viz. iron metabolism-mediated cysteine/glutamate, and LiPr-mediated. Iron is required by the brain as a redox metal for several physiological activities. Due to the iron homeostasis balance disruption, the brain gets adversely affected which further causes neurodegenerative diseases (NDDs) like Parkinson's and Alzheimer's disease, strokes, and brain tumors like glioblastoma (GBS), and glioma. Nanotechnology has played an important role in the prevention and treatment of these NDDs. A synergistic effect of nanomaterials and ferroptosis could prove to be an effective and efficient approach in the field of nanomedicine. In the current review, the authors have highlighted all the latest research in the field of ferroptosis, specifically emphasizing on the role of major molecular key players and various mechanisms involved in the ferroptosis pathway. Moreover, here the authors have also addressed the correlation of ferroptosis with the pathophysiology of NDDs and theragnostic effect of ferroptosis and nanomaterials for the prevention and treatment of NDDs.

DJ-1 inhibits ferroptosis in cerebral ischemia-reperfusion via ATF4/HSPA5 pathway

DJ-1 has been confirmed to have neuroprotective effects. Ferroptosis is an iron-dependent programmed cell death mode associated with ischemic stroke. The ATF4/HSPA5 pathway has been shown to play an important role in the regulation of ferroptosis. To explore the role and possible mechanism of DJ-1 in regulating ferroptosis in cerebral ischemia-reperfusion injury. In this study, Middle cerebral artery occlusion/reperfusion (MCAO/R) was used to simulate cerebral ischemia-reperfusion injury in vivo. Detected ferroptosis-related indicators and observed mitochondrial morphology in brain tissue using transmission electron microscopy. ATF4 was subsequently interfered to observe the effect of DJ-1 on ferroptosis. The results suggest that after interfering with DJ-1, the iron content and malondialdehyde (MDA) content of ferroptosis-related indicators increased, the GSH content decreased, and the mitochondrial structure was severely damaged. We then found that DJ-1 attenuated ferroptosis following ATF4 reduction. In this study, we found that the neuroprotective effect of DJ-1 is related to the inhibition of ferroptosis, and its molecular mechanism is closely related to the ATF4/HSPA5 pathway, which may play a key role in inhibiting brain ischemia-reperfusion (I/R) ferroptosis.

Drug Selection and Posology, Optimal Therapies and Risk/Benefit Assessment in Medicine: The Paradigm of Iron-Chelating Drugs

The design of clinical protocols and the selection of drugs with appropriate posology are critical parameters for therapeutic outcomes. Optimal therapeutic protocols could ideally be designed in all diseases including for millions of patients affected by excess iron deposition (EID) toxicity based on personalised medicine parameters, as well as many variations and limitations. EID is an adverse prognostic factor for all diseases and especially for millions of chronically red-blood-cell-transfused patients. Differences in iron chelation therapy posology cause disappointing results in neurodegenerative diseases at low doses, but lifesaving outcomes in thalassemia major (TM) when using higher doses. In particular, the transformation of TM from a fatal to a chronic disease has been achieved using effective doses of oral deferiprone (L1), which improved compliance and cleared excess toxic iron from the heart associated with increased mortality in TM. Furthermore, effective L1 and L1/deferoxamine combination posology resulted in the complete elimination of EID and the maintenance of normal iron store levels in TM. The selection of effective chelation protocols has been monitored by MRI T2* diagnosis for EID levels in different organs. Millions of other iron-loaded patients with sickle cell anemia, myelodysplasia and haemopoietic stem cell transplantation, or non-iron-loaded categories with EID in different organs could also benefit from such chelation therapy advances. Drawbacks of chelation therapy include drug toxicity in some patients and also the wide use of suboptimal chelation protocols, resulting in ineffective therapies. Drug metabolic effects, and interactions with other metals, drugs and dietary molecules also affected iron chelation therapy. Drug selection and the identification of effective or optimal dose protocols are essential for positive therapeutic outcomes in the use of chelating drugs in TM and other iron-loaded and non-iron-loaded conditions, as well as general iron toxicity.

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

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

PPM1K mediates metabolic disorder of branched-chain amino acid and regulates cerebral ischemia-reperfusion injury by activating ferroptosis in neurons

Ischemic stroke is a neurological disorder caused by vascular stenosis or occlusion, accounting for approximately 87% of strokes. Clinically, the most effective therapy for ischemic stroke is vascular recanalization, which aims to rescue neurons undergoing ischemic insults. Although reperfusion therapy is the most effective treatment for ischemic stroke, it still has limited benefits for many patients, and ischemia-reperfusion (I/R) injury is a widely recognized cause of poor prognosis. Here, we aim to investigate the mechanism of protein phosphatase Mg2+/Mn2+ dependent 1 K (PPM1K) mediates metabolic disorder of branched-chain amino acids (BCAA) by promoting fatty acid oxidation led to ferroptosis after cerebral I/R injury. We established the I/R model in mice and used BT2, a highly specific BCAA dehydrogenase (BCKD) kinase inhibitor to promote BCAA metabolism. It was further verified by lentivirus knocking down PPM1K in neurons. We found that BCAA levels were elevated after I/R injury due to dysfunctional oxidative degradation caused by phosphorylated BCKD E1α subunit (BCKDHA). Additionally, the level of phosphorylated BCKDHA was determined by decreased PPM1K in neurons. We next demonstrated that BCAA could induce oxidative stress, lipid peroxidation, and ferroptosis in primary cultured cortical neurons in vitro. Our results further showed that BT2 could reduce neuronal ferroptosis by enhancing BCAA oxidation through inhibition of BCKDHA phosphorylation. We further found that defective BCAA catabolism could induce neuronal ferroptosis by PPM1K knockdown. Furthermore, BT2 was found to alleviate neurological behavior disorders after I/R injury in mice, and the effect was similar to ferroptosis inhibitor ferrostatin-1. Our findings reveal a novel role of BCAA in neuronal ferroptosis after cerebral ischemia and provide a new potential target for the treatment of ischemic stroke.

Metabolomics: A useful tool for ischemic stroke research

Ischemic stroke (IS) is a multifactorial and heterogeneous disease. Despite years of studies, effective strategies for the diagnosis, management and treatment of stroke are still lacking in clinical practice. Metabolomics is a growing field in systems biology. It is starting to show promise in the identification of biomarkers and in the use of pharmacometabolomics to help patients with certain disorders choose their course of treatment. The development of metabolomics has enabled further and more biological applications. Particularly, metabolomics is increasingly being used to diagnose diseases, discover new drug targets, elucidate mechanisms, and monitor therapeutic outcomes and its potential effect on precision medicine. In this review, we reviewed some recent advances in the study of metabolomics as well as how metabolomics might be used to identify novel biomarkers and understand the mechanisms of IS. Then, the use of metabolomics approaches to investigate the molecular processes and active ingredients of Chinese herbal formulations with anti-IS capabilities is summarized. We finally summarized recent developments in single cell metabolomics for exploring the metabolic profiles of single cells. Although the field is relatively young, the development of single cell metabolomics promises to provide a powerful tool for unraveling the pathogenesis of IS.

Modulation of NRF2/KEAP1 Signaling in Preeclampsia

Placentation is a key and tightly regulated process that ensures the normal development of the placenta and fetal growth. Preeclampsia (PE) is a hypertensive pregnancy-related disorder involving about 5-8% of all pregnancies and clinically characterized by de novo maternal hypertension and proteinuria. In addition, PE pregnancies are also characterized by increased oxidative stress and inflammation. The NRF2/KEAP1 signaling pathway plays an important role in protecting cells against oxidative damage due to increased reactive oxygen species (ROS) levels. ROS activate NRF2, allowing its binding to the antioxidant response element (ARE) region present in the promoter of several antioxidant genes such as heme oxygenase, catalase, glutathione peroxidase and superoxide dismutase that neutralize ROS, protecting cells against oxidative stress damages. In this review, we analyze the current literature regarding the role of the NRF2/KEAP1 pathway in preeclamptic pregnancies, discussing the main cellular modulators of this pathway. Moreover, we also discuss the main natural and synthetic compounds that can regulate this pathway in in vivo and in vitro models.

Metal Complexes of Omadine (N-Hydroxypyridine-2-thione): Differences of Antioxidant and Pro-Oxidant Behavior in Light and Dark Conditions with Possible Toxicity Implications

Omadine or N-hydroxypyridine-2-thione and its metal complexes are widely used in medicine and show bactericidal, fungicidal, anticancer, and photochemical activity. The redox activity of omadine complexes with iron, copper, and zinc on lipid peroxidation under light and dark conditions has been investigated. The monitoring of the oxidation of linoleic acid micelles, resembling a model of lipid membrane, was carried out using nuclear magnetic resonance (¹H-NMR). It has been shown that the omadine-zinc complex can induce the oxidation of linoleic acid under light irradiation, whereas the complexes with iron and copper are photochemically stable. All the chelating complexes of omadine appear to be redox-inactive in the presence of hydrogen peroxide under dark conditions. These findings suggest that omadine can demonstrate antioxidant behavior in processes involving reactive oxygen species generation induced by transition metals (Fenton and photo-Fenton reactions). However, the omadine complex with zinc, which is widely used in shampoos and ointments, is photochemically active and may cause oxidative cell membrane damage when exposed to light, with possible implications to health.

The Effects of Programmed Cell Death of Mesenchymal Stem Cells on the Development of Liver Fibrosis

Mesenchymal stem cells have shown noticeable potential for unlimited self-renewal. They can differentiate into specific somatic cells, integrate into target tissues via cell-cell contact, paracrine effects, exosomes, and other processes and then regulate the target cells and tissues. Studies have demonstrated that transplantation of MSCs could decrease the expression and concentration of collagen in the liver, thereby reducing liver fibrosis. A growing body of evidence indicates that apoptotic MSCs could inhibit harmful immune responses and reduce inflammatory responses more effectively than viable MSCs. Accumulating evidence suggests that mitochondrial transfer from MSCs is a novel strategy for the regeneration of various damaged cells via the rescue of their respiratory activities. This study is aimed at reviewing the functions of MSCs and the related roles of the programmed cell death of MSCs, including autophagy, apoptosis, pyroptosis, and ferroptosis, as well as the regulatory pathogenic mechanisms of MSCs in liver fibrosis. Research has demonstrated that the miR-200B-3p gene is differentially expressed gene between LF and normal liver samples, and that the miR-200B-3p gene expression is positively correlated with the degree of liver fibrosis, suggesting that MSCs could inhibit liver fibrosis through pyroptosis. It was confirmed that circulating monocytes could deliver MSC-derived immunomodulatory molecules to different sites by phagocytosis of apoptotic MSCs, thereby achieving systemic immunosuppression. Accordingly, it was suggested that characterization of the programmed cell death-mediated immunomodulatory signaling pathways in MSCs should be a focus of research.

Perturbed iron biology in the prefrontal cortex of people with schizophrenia

Despite loss of grey matter volume and emergence of distinct cognitive deficits in young adults diagnosed with schizophrenia, current treatments for schizophrenia do not target disruptions in late maturational reshaping of the prefrontal cortex. Iron, the most abundant transition metal in the brain, is essential to brain development and function, but in excess, it can impair major neurotransmission systems and lead to lipid peroxidation, neuroinflammation and accelerated aging. However, analysis of cortical iron biology in schizophrenia has not been reported in modern literature. Using a combination of inductively coupled plasma-mass spectrometry and western blots, we quantified iron and its major-storage protein, ferritin, in post-mortem prefrontal cortex specimens obtained from three independent, well-characterised brain tissue resources. Compared to matched controls (n = 85), among schizophrenia cases (n = 86) we found elevated tissue iron, unlikely to be confounded by demographic and lifestyle variables, by duration, dose and type of antipsychotic medications used or by copper and zinc levels. We further observed a loss of physiologic age-dependent iron accumulation among people with schizophrenia, in that the iron level among cases was already high in young adulthood. Ferritin, which stores iron in a redox-inactive form, was paradoxically decreased in individuals with the disorder. Such iron-ferritin uncoupling could alter free, chemically reactive, tissue iron in key reasoning and planning areas of the young-adult schizophrenia cortex. Using a prediction model based on iron and ferritin, our data provide a pathophysiologic link between perturbed cortical iron biology and schizophrenia and indicate that achievement of optimal cortical iron homeostasis could offer a new therapeutic target.

Revisiting the intersection of microglial activation and neuroinflammation in Alzheimer's disease from the perspective of ferroptosis

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by chronic neuroinflammation with amyloid beta-protein deposition and hyperphosphorylated tau protein. The typical clinical manifestation of AD is progressive memory impairment, and AD is considered a multifactorial disease with various etiologies (genetic factors, aging, lifestyle, etc.) and complicated pathophysiological processes. Previous research identified that neuroinflammation and typical microglial activation are significant mechanisms underlying AD, resulting in dysfunction of the nervous system and progression of the disease. Ferroptosis is a novel modality involved in this process. As an iron-dependent form of cell death, ferroptosis, characterized by iron accumulation, lipid peroxidation, and irreversible plasma membrane disruption, promotes AD by accelerating neuronal dysfunction and abnormal microglial activation. In this case, disturbances in brain iron homeostasis and neuronal ferroptosis aggravate neuroinflammation and lead to the abnormal activation of microglia. Abnormally activated microglia release various pro-inflammatory factors that aggravate the dysregulation of iron homeostasis and neuroinflammation, forming a vicious cycle. In this review, we first introduce ferroptosis, microglia, AD, and their relationship. Second, we discuss the nonnegligible role of ferroptosis in the abnormal microglial activation involved in the chronic neuroinflammation of AD to provide new ideas for the identification of potential therapeutic targets for AD.

Sodium hydrosulfide inhibits hemin-induced ferroptosis and lipid peroxidation in BV2 cells via the CBS/H2S system

Ferroptosis is a form of iron-dependent programmed cell death discovered in recent years that has been shown to be involved in diverse neurological disorders. Hydrogen sulfide (H₂S) is an important signaling molecule with neuroprotective effects, including antioxidation. However, whether the protective mechanism of H₂S is related to ferroptosis remains unknown. Therefore, in this study, we focused on the protective mechanisms of sodium hydrosulfide (NaHS, a donor of H₂S) against ferroptosis caused by intracerebral hemorrhage (ICH) using a hemin-induced BV2 cell injury model in vitro. Our results indicated that NaHS enhanced cell viability and reduced hemin-induced lactate dehydrogenase (LDH) release. NaHS suppressed ferroptosis after hemin treatment, which was confirmed by attenuated reactive oxygen species (ROS) and lipid peroxidation, maintained iron homeostasis, recovery of the expression of glutathione peroxidase 4 (GPX4) and solute carrier family 7-member 11 (SLC7A11), and increased glutathione (GSH) production. Moreover, we demonstrated that inhibiting ferroptosis improved cell survival and prevented hemin-induced oxidative stress. In addition, NaHS was also able to block ferroptosis inducer RSL3-induced ferroptotic cell death. We also found that NaHS increased cystathionine-β-synthase (CBS) expression and H₂S levels after hemin treatment. Furthermore, NaHS-induced ferroptosis reduction was inhibited by the CBS inhibitor aminooxyacetic acid (AOAA) as well as by CBS small interference RNA (siCBS). In summary, these findings demonstrated that NaHS protects against hemin-induced ferroptosis by reducing lipid peroxidation, inhibiting iron overload, increasing GSH production, and improving GPX4 and SLC7A11 via the CBS/H₂S system. The CBS/H₂S system may be a promising target for preventing ferroptosis after ICH.

Anti-Ferroptotic Effects of Nrf2: Beyond the Antioxidant Response

The transcription factor Nrf2 was originally identified as a master regulator of redox homeostasis, as it governs the expression of a battery of genes involved in mitigating oxidative and electrophilic stress. However, the central role of Nrf2 in dictating multiple facets of the cellular stress response has defined the Nrf2 pathway as a general mediator of cell survival. Recent studies have indicated that Nrf2 regulates the expression of genes controlling ferroptosis, an ironand lipid peroxidation-dependent form of cell death. While Nrf2 was initially thought to have anti-ferroptotic function primarily through regulation of the antioxidant response, accumulating evidence has indicated that Nrf2 also exerts anti-ferroptotic effects via regulation of key aspects of iron and lipid metabolism. In this review, we will explore the emerging role of Nrf2 in mediating iron homeostasis and lipid peroxidation, where several Nrf2 target genes have been identified that encode critical proteins involved in these pathways. A better understanding of the mechanistic relationship between Nrf2 and ferroptosis, including how genetic and/or pharmacological manipulation of Nrf2 affect the ferroptotic response, should facilitate the development of new therapies that can be used to treat ferroptosis-associated diseases.

Dihydroorotate dehydrogenase regulates ferroptosis in neurons after spinal cord injury via the P53-ALOX15 signaling pathway

BACKGROUND

Spinal cord injury (SCI) is a highly disabling condition in spinal surgery that leads to neuronal damage and secondary inflammation. Ferroptosis is a non-apoptotic type of cell death that has only recently been identified, which is marked primarily by iron-dependent and lipid-derived reactive oxygen species accumulation, and accompanied by morphological modifications such as mitochondrial atrophy and increase in membrane density. Dihydroorotate dehydrogenase (DHODH) is a powerful inhibitor of ferroptosis and has been demonstrated to inhibit cellular ferroptosis in tumor cells, but whether it can inhibit neuronal injury following spinal cord injury remains ambiguous.

METHODS

In this study, the effect of DHODH on neuronal ferroptosis was observed in vivo and in vitro using a rat spinal cord injury model and erastin-induced PC12 cells, respectively. A combination of molecular and histological approaches was performed to assess ferroptosis and explore the possible mechanisms in vivo and in vitro.

RESULTS

First, we confirmed the existence of neuronal ferroptosis after spinal cord injury and that DHODH attenuates neuronal damage after spinal cord injury. Second, we showed molecular evidence that DHODH inhibits the activation of ferroptosis-related molecules and reduces lipid peroxide production and mitochondrial damage, thereby reducing neuronal ferroptosis. Further analysis suggests that P53/ALOX15 may be one of the mechanisms regulated by DHODH. Importantly, we determined that DHODH inhibits ALOX15 expression by inhibiting P53.

CONCLUSIONS

Our findings reveal a novel function for DHODH in neuronal ferroptosis after spinal cord injury, suggesting a unique therapeutic target to alleviate the disease process of spinal cord injury.

Novel druggable mechanism of Parkinson's disease: Potential therapeutics and underlying pathogenesis based on ferroptosis

Genetics, age, environmental factors, and oxidative stress have all been implicated in the development of Parkinson's disease (PD); however, a complete understanding of its pathology remains elusive. At present, there is no cure for PD, and currently available therapeutics are insufficient to meet patient needs. Ferroptosis, a distinctive iron-dependent cell death mode characterized by lipid peroxidation and oxidative stress, has pathophysiological features similar to those of PD, including iron accumulation, reactive oxygen species-induced oxidative damage, and mitochondrial dysfunction. Ferroptosis has been identified as a specific pathway of neuronal death and is closely related to the pathogenesis of PD. Despite the similarities in the biological targets involved in PD pathogenesis and ferroptosis, the relationship between novel targets in PD and ferroptosis has been neglected in the literature. In this review, the mechanism of ferroptosis is discussed, and the potential therapeutic targets implicated in both PD and ferroptosis are compared. Furthermore, the anti-PD effects of several ferroptosis inhibitors, as well as clinical studies thereof, and the identification of novel lead compounds for the treatment of PD and the inhibition of ferroptosis are reviewed. It is hoped that this review can promote research to further elucidate the relationship between ferroptosis and PD and provide new strategies for the development of novel ferroptosis-targeting PD therapy.

Peripheral and Central Iron Measures in Alcohol Use Disorder and Aging: A Quantitative Susceptibility Mapping Pilot Study

Chronic excessive alcohol use has neurotoxic effects, which may contribute to cognitive decline and the risk of early-onset dementia. Elevated peripheral iron levels have been reported in individuals with alcohol use disorder (AUD), but its association with brain iron loading has not been explored. We evaluated whether (1) serum and brain iron loading are higher in individuals with AUD than non-dependent healthy controls and (2) serum and brain iron loading increase with age. A fasting serum iron panel was obtained and a magnetic resonance imaging scan with quantitative susceptibility mapping (QSM) was used to quantify brain iron concentrations. Although serum ferritin levels were higher in the AUD group than in controls, whole-brain iron susceptibility did not differ between groups. Voxel-wise QSM analyses revealed higher susceptibility in a cluster in the left globus pallidus in individuals with AUD than controls. Whole-brain iron increased with age and voxel-wise QSM indicated higher susceptibility with age in various brain areas including the basal ganglia. This is the first study to analyze both serum and brain iron loading in individuals with AUD. Larger studies are needed to examine the effects of alcohol use on iron loading and its associations with alcohol use severity, structural and functional brain changes, and alcohol-induced cognitive impairments.

Deferoxamine prevents poststroke memory impairment in female diabetic rats: potential links to hemorrhagic transformation and ferroptosis

Diabetes increases the risk of poststroke cognitive impairment (PSCI). Greater hemorrhagic transformation (HT) after stroke is associated with vasoregression and cognitive decline in male diabetic rats. Iron chelator deferoxamine (DFX) prevents vasoregression and improves outcomes. Although diabetic female rats develop greater HT, its impact on poststroke cerebrovascularization and cognitive outcomes remained unknown. We hypothesized that diabetes mediates pathological neovascularization, and DFX attenuates poststroke cerebrovascular remodeling and improves neurological outcomes in female diabetic rats. Female control and diabetic animals were treated with DFX or vehicle for 7 days after stroke. Vascular indices, microglial activation, and blood-brain barrier (BBB) integrity were evaluated on day 14. Results from diabetic female rats were partially compared with our previously published findings in male counterparts. Hemin-induced programmed cell death was studied in male and female brain microvascular endothelial cell lines (BMVEC). There was no vasoregression after stroke in either control or diabetic female animals. DFX prevented diabetes-mediated gliovascular remodeling and compromised BBB integrity while improving memory function in diabetes. Comparisons of female and male rats indicated sex differences in cognitive and vascular outcomes. Hemin mediated ferroptosis in both male and female BMVECs. DFX improved survival but had differential effects on ferroptosis signaling in female and male cells. These results suggest that stroke and associated HT do not affect cerebrovascularization in diabetic female rats, but iron chelation may provide a novel therapeutic strategy in the prevention of poststroke memory impairment in females with diabetes via the preservation of gliovascular integrity and improvement of endothelial cell survival.NEW & NOTEWORTHY The current study shows for the first time that diabetes does not promote aberrant cerebrovascularization in female rats. This contrasts with what we reported in male animals in various diabetes models. Deferoxamine preserved recognition memory function in diabetic female animals after stroke. The effect(s) of stroke and deferoxamine on cerebrovascular density and microglial activation also appear(s) to be different in female diabetic rats. Lastly, deferoxamine exerts detrimental effects on animals and BMVECs under control conditions.

Cerebroprotein hydrolysate attenuates neurodegenerative changes in Alzheimer's mice model via ferroptosis pathway

Introduction: Cerebroprotein hydrolysate has been proven to improve cognitive function in patients with Alzheimer's disease (AD). We explored the safety and effectiveness of the clinical administration of oral cerebroprotein hydrolysate in AD, and possible mechanisms related to the neuronal ferroptosis pathway. Methods: Three-month-old male APP/PS1 double-transgenic mice were randomly divided into AD model (n = 8) and intervention (n = 8) groups. Eight non-transgenic wild-type (WT) C57 mice were used as age-matched controls. The experiments were started at the age of 6 months. The intervention group was then administered cerebroprotein hydrolysate nutrient solution (11.9 mg/kg/day) via chronic gavage, the other groups received an identical volume of distilled water. Behavioural experiments were performed after 90 days of continuous administration. Serum and hippocampal tissues were then collected for histomorphological observation, tau and p-tau expression, and ferroptosis markers analysis. Results: Cerebroprotein hydrolysate simplified movement trajectories and shortened escape latencies of APP/PS1 mice in the Morris water maze test. Neuronal morphologies were restored in hippocampal tissues on haematoxylin-eosin staining. In the AD-model group, Aβ protein and p-tau/tau expression levels were elevated, plasma Fe²⁺ and malondialdehyde levels were elevated, GXP4 protein expression and plasma glutathione levels declined than controls. All indices improved after cerebroprotein hydrolysate intervention. Conclusion: Cerebroprotein hydrolysate improves learning and memory function, alleviates neuronal damage, and reduces the deposition of pathological AD markers in AD mice, which may be related to the inhibition of neuronal ferroptosis.

The emerging roles of ferroptosis in cells of the central nervous system

Ferroptosis is morphologically characterized by shrunken mitochondria and biochemically characterized by iron overload, lipid peroxidation and lipid reactive oxygen species (ROS) accumulation; these phenomena are suppressed by iron chelation, genetic inhibition of cellular iron uptake, and intervention on other pathways such as lipid metabolism. The induction of ferroptosis may be related to pathological cellular conditions in the central nervous system (CNS); thus, ferroptosis may cause disability via CNS damage. Here, we review the role of ferroptosis in the main cells of the CNS, including glial cells, neurons, and pericytes; in various diseases of the CNS; and in the interaction of glia and neurons in CNS diseases. Some small molecules and traditional Chinese drugs which inhibit ferroptosis in cells of the CNS are shown as potential therapeutic strategies for neurological diseases.

MicroRNA-27a Regulates Ferroptosis Through SLC7A11 to Aggravate Cerebral ischemia-reperfusion Injury

Cerebral ischemia-reperfusion (I/R) injury is an inevitable issue in the treatment of ischemic stroke, which has a high disability rate and seriously threatens the living quality of patients. Previous studies have demonstrated that ferroptosis, which plays a crucial role in ischemia-reperfusion injury, can be accelerated by microRNA-27a (miR-27a). However, the mechanism by which miR-27a regulates ferroptosis in cerebral ischemia-reperfusion injury remains unknown. In this study, Male Sprague-Dawley rats were subjected to a middle cerebral artery occlusion (MCAO), then restored blood flow. Neurological function score and TTC staining were used to evaluate brain tissue injury and the infarct volume. The relative expression level of miR-27a was detected by qPCR. The relative expression levels of glutathione peroxidase 4(GPx4), solute carrier family 7 member 11 (SLC7A11) proteins were analyzed by Western Blot. The contents of GSH, Fe and malonaldehyde (MDA) were detected by corresponding detection kits, and the target gene of miR-27a was confirmed by dual luciferase reporter gene technique. It was found the relative expression level of miR-27a was increased and ferroptosis was aggravated as reperfusion time went by. Also, brain tissue injury and ferroptosis were exacerbated with agomiR-27a intervention, while these effects were reversed with antagomiR-27a intervention. In addition, the combined intervention of agomiR-27a and Fer-1 alleviated the brain tissue injury and ferroptosis. The results of dual luciferase reporter gene technique indicated SLC7A11 as the target gene of miR-27a. In the current study, miR-27a upregulates ferroptosis to aggravate cerebral ischemia-reperfusion injury by SLC7A11.

Harnessing the Therapeutic Potential of the Nrf2/Bach1 Signaling Pathway in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative movement disorder characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Although a complex interplay of multiple environmental and genetic factors has been implicated, the etiology of neuronal death in PD remains unresolved. Various mechanisms of neuronal degeneration in PD have been proposed, including oxidative stress, mitochondrial dysfunction, neuroinflammation, α-synuclein proteostasis, disruption of calcium homeostasis, and other cell death pathways. While many drugs individually targeting these pathways have shown promise in preclinical PD models, this promise has not yet translated into neuroprotective therapies in human PD. This has consequently spurred efforts to identify alternative targets with multipronged therapeutic approaches. A promising therapeutic target that could modulate multiple etiological pathways involves drug-induced activation of a coordinated genetic program regulated by the transcription factor, nuclear factor E2-related factor 2 (Nrf2). Nrf2 regulates the transcription of over 250 genes, creating a multifaceted network that integrates cellular activities by expressing cytoprotective genes, promoting the resolution of inflammation, restoring redox and protein homeostasis, stimulating energy metabolism, and facilitating repair. However, FDA-approved electrophilic Nrf2 activators cause irreversible alkylation of cysteine residues in various cellular proteins resulting in side effects. We propose that the transcriptional repressor of BTB and CNC homology 1 (Bach1), which antagonizes Nrf2, could serve as a promising complementary target for the activation of both Nrf2-dependent and Nrf2-independent neuroprotective pathways. This review presents the current knowledge on the Nrf2/Bach1 signaling pathway, its role in various cellular processes, and the benefits of simultaneously inhibiting Bach1 and stabilizing Nrf2 using non-electrophilic small molecules as a novel therapeutic approach for PD.

Redox regulation of the immune response

The immune-inflammatory response is associated with increased nitro-oxidative stress. The aim of this mechanistic review is to examine: (a) the role of redox-sensitive transcription factors and enzymes, ROS/RNS production, and the activity of cellular antioxidants in the activation and performance of macrophages, dendritic cells, neutrophils, T-cells, B-cells, and natural killer cells; (b) the involvement of high-density lipoprotein (HDL), apolipoprotein A1 (ApoA1), paraoxonase-1 (PON1), and oxidized phospholipids in regulating the immune response; and (c) the detrimental effects of hypernitrosylation and chronic nitro-oxidative stress on the immune response. The redox changes during immune-inflammatory responses are orchestrated by the actions of nuclear factor-κB, HIF1α, the mechanistic target of rapamycin, the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, mitogen-activated protein kinases, 5' AMP-activated protein kinase, and peroxisome proliferator-activated receptor. The performance and survival of individual immune cells is under redox control and depends on intracellular and extracellular levels of ROS/RNS. They are heavily influenced by cellular antioxidants including the glutathione and thioredoxin systems, nuclear factor erythroid 2-related factor 2, and the HDL/ApoA1/PON1 complex. Chronic nitro-oxidative stress and hypernitrosylation inhibit the activity of those antioxidant systems, the tricarboxylic acid cycle, mitochondrial functions, and the metabolism of immune cells. In conclusion, redox-associated mechanisms modulate metabolic reprogramming of immune cells, macrophage and T helper cell polarization, phagocytosis, production of pro- versus anti-inflammatory cytokines, immune training and tolerance, chemotaxis, pathogen sensing, antiviral and antibacterial effects, Toll-like receptor activity, and endotoxin tolerance.

Molecular mechanisms of programmed cell death in methamphetamine-induced neuronal damage

Methamphetamine, commonly referred to as METH, is a highly addictive psychostimulant and one of the most commonly misused drugs on the planet. Using METH continuously can increase your risk for drug addiction, along with other health complications like attention deficit disorder, memory loss, and cognitive decline. Neurotoxicity caused by METH is thought to play a significant role in the onset of these neurological complications. The molecular mechanisms responsible for METH-caused neuronal damage are discussed in this review. According to our analysis, METH is closely associated with programmed cell death (PCD) in the process that causes neuronal impairment, such as apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. In reviewing this article, some insights are gained into how METH addiction is accompanied by cell death and may help to identify potential therapeutic targets for the neurological impairment caused by METH abuse.

The potential involvement of inhaled iron (Fe) in the neurotoxic effects of ultrafine particulate matter air pollution exposure on brain development in mice

BACKGROUND

Air pollution has been associated with neurodevelopmental disorders in epidemiological studies. In our studies in mice, developmental exposures to ambient ultrafine particulate (UFP) matter either postnatally or gestationally results in neurotoxic consequences that include brain metal dyshomeostasis, including significant increases in brain Fe. Since Fe is redox active and neurotoxic to brain in excess, this study examined the extent to which postnatal Fe inhalation exposure, might contribute to the observed neurotoxicity of UFPs. Mice were exposed to 1 µg/m³ Fe oxide nanoparticles alone, or in conjunction with sulfur dioxide (Fe (1 µg/m³) + SO₂ (SO₂ at 1.31 mg/m³, 500 ppb) from postnatal days 4-7 and 10-13 for 4 h/day.

RESULTS

Overarching results included the observations that Fe + SO₂ produced greater neurotoxicity than did Fe alone, that females appeared to show greater vulnerability to these exposures than did males, and that profiles of effects differed by sex. Consistent with metal dyshomeostasis, both Fe only and Fe + SO₂ exposures altered correlations of Fe and of sulfur (S) with other metals in a sex and tissue-specific manner. Specifically, altered metal levels in lung, but particularly in frontal cortex were found, with reductions produced by Fe in females, but increases produced by Fe + SO₂ in males. At PND14, marked changes in brain frontal cortex and striatal neurotransmitter systems were observed, particularly in response to combined Fe + SO2 as compared to Fe only, in glutamatergic and dopaminergic functions that were of opposite directions by sex. Changes in markers of trans-sulfuration in frontal cortex likewise differed in females as compared to males. Residual neurotransmitter changes were limited at PND60. Increases in serum glutathione and Il-1a were female-specific effects of combined Fe + SO2.

CONCLUSIONS

Collectively, these findings suggest a role for the Fe contamination in air pollution in the observed neurotoxicity of ambient UFPs and that such involvement may be different by chemical mixture. Translation of such results to humans requires verification, and, if found, would suggest a need for regulation of Fe in air for public health protection.

Role and Mechanism of Ferroptosis in Neurological Diseases

Background

Ferroptosis, as a new form of cell death, is different from other cell deaths such as autophagy or senescence. Ferroptosis involves in the pathophysiological progress of several diseases, including cancers, cardiovascular diseases, nervous system diseases, and kidney damage. Since oxidative stress and iron deposition are the broad pathological features of neurological diseases, the role of ferroptosis in neurological diseases has been widely explored.

Scope of review

Ferroptosis is mainly characterized by changes in iron homeostasis, iron-dependent lipid peroxidation, and glutamate toxicity accumulation, of which can be specifically reversed by ferroptosis inducers or inhibitors. The ferroptosis is mainly regulated by the metabolism of iron, lipids and amino acids through System Xc⁻, voltage-dependent anion channels, p53, p62-Keap1-Nrf2, mevalonate and other pathways. This review also focus on the regulatory pathways of ferroptosis and its research progress in neurological diseases.

Major conclusions

The current researches of ferroptosis in neurological diseases mostly focus on the key pathways of ferroptosis. At the same time, ferroptosis was found playing a bidirectional regulation role in neurological diseases. Therefore, the specific regulatory mechanisms of ferroptosis in neurological diseases still need to be further explored to provide new perspectives for the application of ferroptosis in the treatment of neurological diseases.

The key roles of organelles and ferroptosis in Alzheimer's disease

Alzheimer's disease (AD), an age-related neurodegenerative disease, is a striking global health problem. Ferroptosis is a newly discovered form of cell death characterized by iron-dependent lipid peroxidation products and the accumulation of lethal reactive oxygen species. Strict regulation of iron metabolism is essential to ensure neuronal homeostasis. Excess and deficiency of iron are both associated with neurodegeneration. Studies have shown that oxidative stress caused by cerebral iron metabolism disorders in the body is involved in the process of AD, ferroptosis may play an important role in the pathogenesis of AD, and regulating ferroptosis is expected to be a new direction for the treatment of AD. Various organelles are closely related to ferroptosis: mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosome are involved in the regulation of ferroptosis from the aspects of iron metabolism and redox imbalance. In this review, the relationship between AD and the dysfunction of organelles (including mitochondria, endoplasmic reticulum, lysosome, and Golgi apparatus) and the role of organelles in ferroptosis of AD were reviewed to provide insights for understanding the relationship between organelles and ferroptosis in AD and the treatment of AD.

The NSUN5-FTH1/FTL pathway mediates ferroptosis in bone marrow-derived mesenchymal stem cells

Ferroptosis is a type of cell death induced by the iron-dependent accumulation of lipid hydroperoxides and reactive oxygen species (ROS) in cells. Inhibiting ferroptosis is important for improving the survival of transplanted bone marrow-derived mesenchymal stem cells (BMSCs). Although it is known that NOP2/Sun RNA methyltransferase 5 (NSUN5) post-transcriptionally regulates ferroptosis in BMSCs through RNA methylation, the precise mechanisms underlying these effects have not been reported. In this study, we demonstrate that NSUN5 is downregulated in erastin-induced ferroptosis in BMSCs. Ferroptosis was inhibited by the overexpression of NSUN5 or ferritin heavy chain/light-chain (FTH1/FTL) and was enhanced by NSUN5 knockdown. RNA immunoprecipitation experiments revealed that NSUN5 binds to FTH1/FTL, while NSUN5 depletion reduced the levels of 5-methylcytosine in FTH1/FTL RNA and increased intracellular iron concentrations, resulting in the downregulation of glutathione peroxidase 4 (GPX4) and the accumulation of ROS and lipid peroxidation products. Co-immunoprecipitation experiments demonstrated that the recognition of FTH1 and FTL by NSUN5 is dependent on the recruitment of tumor necrosis factor receptor-associated protein 1 (TRAP1). These results suggested that the NSUN5-FTH1/FTL pathway mediates ferroptosis in BMSCs and that the therapeutic targeting of components of this pathway may promote resistance to ferroptosis and improve the survival of transplanted BMSCs.

Intertwined associations between oxidative and nitrosative stress and endocannabinoid system pathways: Relevance for neuropsychiatric disorders

The endocannabinoid system (ECS) appears to regulate metabolic, cardiovascular, immune, gastrointestinal, lung, and reproductive system functions, as well as the central nervous system. There is also evidence that neuropsychiatric disorders are associated with ECS abnormalities as well as oxidative and nitrosative stress pathways. The goal of this mechanistic review is to investigate the mechanisms underlying the ECS's regulation of redox signalling, as well as the mechanisms by which activated oxidative and nitrosative stress pathways may impair ECS-mediated signalling. Cannabinoid receptor (CB)1 activation and upregulation of brain CB2 receptors reduce oxidative stress in the brain, resulting in less tissue damage and less neuroinflammation. Chronically high levels of oxidative stress may impair CB1 and CB2 receptor activity. CB1 activation in peripheral cells increases nitrosative stress and inducible nitric oxide (iNOS) activity, reducing mitochondrial activity. Upregulation of CB2 in the peripheral and central nervous systems may reduce iNOS, nitrosative stress, and neuroinflammation. Nitrosative stress may have an impact on CB1 and CB2-mediated signalling. Peripheral immune activation, which frequently occurs in response to nitro-oxidative stress, may result in increased expression of CB2 receptors on T and B lymphocytes, dendritic cells, and macrophages, reducing the production of inflammatory products and limiting the duration and intensity of the immune and oxidative stress response. In conclusion, high levels of oxidative and nitrosative stress may compromise or even abolish ECS-mediated redox pathway regulation. Future research in neuropsychiatric disorders like mood disorders and deficit schizophrenia should explore abnormalities in these intertwined signalling pathways.

DJ-1 upregulates the Nrf2/GPX4 signal pathway to inhibit trophoblast ferroptosis in the pathogenesis of preeclampsia

Ferroptosis is a newly discovered mode of cell death that involves disorders in iron metabolism and the accumulation of reactive oxygen species (ROS) in the plasma membrane. Preeclampsia (PE) is a gestational idiopathic disease that is characterized by hypertension and albuminuria, begins after 20 weeks of pregnancy. DJ-1 is a prerequisite for activating and stabilizing Nrf2 to allow translocation to the nucleus to carry out further functions. Detecting the expression levels of DJ-1, the Nrf2/GPX4 signaling pathway and ferroptosis markers in placental tissues of pregnant women with and without PE. Analyzing the effects of the ferroptosis inducer (RSL3) and the inhibitor (Fer-1) on the mortality rate of BeWo cells and DJ-1+/+, DJ-1-/- BeWo cells. Ferroptosis markers (MDA concentration and morphology of trophoblast cells) and DJ-1 and its downstream the Nrf2/GPX4 signaling pathway increased significantly in PE pathological state. The expression levels of DJ-1 protein in the control group and the PE group were positively correlated with the expression levels of Nrf2/GPX4 signaling pathway protein, and negatively correlated with the MDA concentration. BeWo cells were sensitive to the ferroptosis inducer (RSL3) and the inhibitor (Fer-1). The high expression levels of DJ-1 in BeWo cells can resist ferroptosis by regulating the Nrf2/GPX4 signaling pathway. Ferroptosis is involved in the pathogenesis of PE. DJ-1 can mediate the trophoblast cells ferroptosis and play a protective role in the pathogenesis of preeclampsia by regulating the Nrf2/GPX4 signaling pathway.

Eriodictyol ameliorates cognitive dysfunction in APP/PS1 mice by inhibiting ferroptosis via vitamin D receptor-mediated Nrf2 activation

Background

Alzheimer’s disease (AD) is the most common type of neurodegenerative disease in the contemporary era, and it is still clinically incurable. Eriodictyol, a natural flavonoid compound that is mainly present in citrus fruits and some Chinese herbal medicines, has been reported to exert anti-inflammatory, antioxidant, anticancer and neuroprotective effects. However, few studies have examined the anti-AD effect and molecular mechanism of eriodictyol.

Methods

APP/PS1 mice were treated with eriodictyol and the cognitive function of mice was assessed using behavioral tests. The level of amyloid-β (Aβ) aggregation and hyperphosphorylation of Tau in the mouse brain were detected by preforming a histological analysis and Western blotting. HT-22 cells induced by amyloid-β peptide (1–42) (Aβ_1–42) oligomers were treated with eriodictyol, after which cell viability was determined and the production of p-Tau was tested using Western blotting. Then, the characteristics of ferroptosis, including iron aggregation, lipid peroxidation and the expression of glutathione peroxidase type 4 (GPX4), were determined both in vivo and in vitro using Fe straining, Western blotting and qPCR assays. Additionally, the expression level of vitamin D receptor (VDR) and the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling pathway were tested using Western blotting and qPCR assays. Afterward, HT-22 cells with VDR knockout were used to explore the potential mechanisms, and the relationship between VDR and Nrf2 was further assessed by performing a coimmunoprecipitation assay and bioinformatics analysis.

Results

Eriodictyol obviously ameliorated cognitive deficits in APP/PS1 mice, and suppressed Aβ aggregation and Tau phosphorylation in the brains of APP/PS1 mice. Moreover, eriodictyol inhibited Tau hyperphosphorylation and neurotoxicity in HT-22 cells induced by Aβ_1–42 oligomer. Furthermore, eriodictyol exerted an antiferroptosis effect both in vivo and in vitro, and its mechanism may be associated with the activation of the Nrf2/HO-1 signaling pathway. Additionally, further experiments explained that the activation of Nrf2/HO-1 signaling pathway by eriodictyol treatment mediated by VDR.

Conclusions

Eriodictyol alleviated memory impairment and AD-like pathological changes by activating the Nrf2/HO-1 signaling pathway through a mechanism mediated by VDR, which provides a new possibility for the treatment of AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00442-3.

Actions of Klotho on hippocampal neuronal cells

Klotho gene was originally recognized as a putative aging-suppressor and its prominent age-regulating effects are mostly attributed to the modulation of mineral homeostasis in the kidney. However, recent studies link alterations in hippocampal Klotho expression with cognitive impairment and neurodegenerative diseases. This suggests that hippocampal neurons require Klotho for health and proper functionality. Klotho protects against neuronal dysfunction and regulates several intracellular signaling pathways including oxidative stress response, inflammation, DNA damage, autophagy, endoplasmic reticulum stress response, and multiple types of cell death. Specifically, this chapter covers the current knowledge as to how Klotho protein affects the hippocampal neuronal cells, with special attention paid to underlying molecular mechanisms, and thus influences hippocampal development, hippocampal-dependent cognition, behavior, and motor skills as well as mediates neurodegenerative processes.

Novel Targets and Interventions for Cognitive Complications of Diabetes

Diabetes and cognitive dysfunction, ranging from mild cognitive impairment to dementia, often coexist in individuals over 65 years of age. Vascular contributions to cognitive impairment/dementia (VCID) are the second leading cause of dementias under the umbrella of Alzheimer's disease and related dementias (ADRD). Over half of dementia patients have VCID either as a single pathology or a mixed dementia with AD. While the prevalence of type 2 diabetes in individuals with dementia can be as high as 39% and diabetes increases the risk of cerebrovascular disease and stroke, VCID remains to be one of the less understood and less studied complications of diabetes. We have identified cerebrovascular dysfunction and compromised endothelial integrity leading to decreased cerebral blood flow and iron deposition into the brain, respectively, as targets for intervention for the prevention of VCID in diabetes. This review will focus on targeted therapies that improve endothelial function or remove iron without systemic effects, such as agents delivered intranasally, that may result in actionable and disease-modifying novel treatments in the high-risk diabetic population.

Iron homeostasis and organismal aging

Iron is indispensable for normal body functions across species because of its critical roles in red blood cell function and many essential proteins and enzymes required for numerous physiological processes. Regulation of iron homeostasis is an intricate process involving multiple modulators at the systemic, cellular, and molecular levels. Interestingly, emerging evidence has demonstrated that many modulators of iron homeostasis contribute to organismal aging and longevity. On the other hand, the age-related dysregulation of iron homeostasis is often associated with multiple age-related pathologies including bone resorption and neurodegenerative diseases such as Alzheimer's disease. Thus, a thorough understanding on the interconnections between systemic and cellular iron balance and organismal aging may help decipher the etiologies of multiple age-related diseases, which could ultimately lead to developing therapeutic strategies to delay aging and treat various age-related diseases. Here we present the current understanding on the mechanisms of iron homeostasis. We also discuss the impacts of aging on iron homeostatic processes and how dysregulated iron metabolism may affect aging and organismal longevity.

Iron Homeostasis Disorder and Alzheimer's Disease

Iron is an essential trace metal for almost all organisms, including human; however, oxidative stress can easily be caused when iron is in excess, producing toxicity to the human body due to its capability to be both an electron donor and an electron acceptor. Although there is a strict regulation mechanism for iron homeostasis in the human body and brain, it is usually inevitably disturbed by genetic and environmental factors, or disordered with aging, which leads to iron metabolism diseases, including many neurodegenerative diseases such as Alzheimer's disease (AD). AD is one of the most common degenerative diseases of the central nervous system (CNS) threatening human health. However, the precise pathogenesis of AD is still unclear, which seriously restricts the design of interventions and treatment drugs based on the pathogenesis of AD. Many studies have observed abnormal iron accumulation in different regions of the AD brain, resulting in cognitive, memory, motor and other nerve damages. Understanding the metabolic balance mechanism of iron in the brain is crucial for the treatment of AD, which would provide new cures for the disease. This paper reviews the recent progress in the relationship between iron and AD from the aspects of iron absorption in intestinal cells, storage and regulation of iron in cells and organs, especially for the regulation of iron homeostasis in the human brain and prospects the future directions for AD treatments.

Dauricine alleviated secondary brain injury after intracerebral hemorrhage by upregulating GPX4 expression and inhibiting ferroptosis of nerve cells

Intracerebral hemorrhage (ICH) is a severe stroke subtype with high disability and mortality, and no effective treatment is available. Previous research on intracerebral hemorrhage secondary brain injury drugs mainly targeted at cell apoptosis, inflammation and oxidative stress, but did not achieve good effects. In recent years, ferroptosis has become a focus concern in neurological diseases. Ferroptosis is a new type of programmed cell death caused by iron-dependent accumulation of lipid peroxides, in which glutathione peroxidase 4 (GPX4) is a key protein affecting ferroptosis. In this study, we used the STRING protein database to predict the proteins that may be co-expressed with GPX4, and studied the ability of Dauricine(Dau) to up-regulate the expression of GPX4 against ferroptosis and neuroprotection after intracerebral hemorrhage in normal cells in vitro, glutathione peroxidase 4 (GPX4) knockdown cells and collagenase injection in vivo in mouse models of intracerebral hemorrhage. The results showed that glutathione reductase (GSR) was a possible co-expression protein with GPX4. Dau could up-regulate the expression of glutathione peroxidase 4 (GPX4) in intracerebral hemorrhage(ICH) model, normal cells and GPX4 knockdown cells in vitro, and simultaneously up-regulate the expression of GSR in ICH mice. Dau could also reduce the levels of iron and lipid peroxidation, and have a neuroprotective effect on intracerebral hemorrhage(ICH) mice. It was tesified that Dauricine(Dau) could inhibit ferroptosis of nerve cells and alleviate brain injury after intracerebral hemorrhage by upregulating glutathione peroxidase 4 (GPX4) and glutathione reductase (GSR) co-expression. Therefore, Dau may be an effective drug for inhibiting ferroptosis and treating intracerebral hemorrhage.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.

Antioxidant Activity of Deferasirox and Its Metal Complexes in Model Systems of Oxidative Damage: Comparison with Deferiprone

Deferasirox is an orally active, lipophilic iron chelating drug used on thousands of patients worldwide for the treatment of transfusional iron overload. The essential transition metals iron and copper are the primary catalysts of reactive oxygen species and oxidative damage in biological systems. The redox effects of deferasirox and its metal complexes with iron, copper and other metals are of pharmacological, toxicological, biological and physiological importance. Several molecular model systems of oxidative damage caused by iron and copper catalysis including the oxidation of ascorbic acid, the peroxidation of linoleic acid micelles and the oxidation of dihydropyridine have been investigated in the presence of deferasirox using UV-visible and NMR spectroscopy. Deferasirox has shown antioxidant activity in all three model systems, causing substantial reduction in the rate of oxidation and oxidative damage. Deferasirox showed the greatest antioxidant activity in the oxidation of ascorbic acid with the participation of iron ions and reduced the reaction rate by about a 100 times. Overall, deferasirox appears to have lower affinity for copper in comparison to iron. Comparative studies of the antioxidant activity of deferasirox and the hydrophilic oral iron chelating drug deferiprone in the peroxidation of linoleic acid micelles showed lower efficiency of deferasirox in comparison to deferiprone.

Ferroptosis: A Trusted Ally in Combating Drug Resistance in Cancer

Ferroptosis, which is an iron-dependent, non-apoptotic cell death mechanism, has recently been proposed as a novel approach in cancer treatment. Bearing distinctive features and its exclusive mechanism have put forward the potential therapeutic benefit of triggering this newly discovered form of cell death. Numerous studies have indicated that apoptotic pathways are often deactivated in resistant cells, leading to a failure in therapy. Hence, alternative strategies to promote cell death are required. Mounting evidence suggests that drug-resistant cancer cells are particularly sensitive to ferroptosis. Given that cancer cells consume a higher amount of iron than healthy ones, ferroptosis not only stands as an excellent alternative to trigger cell death and reverse drug-resistance, but also provides selectivity in therapy. This review focuses specifically on overcoming drug-resistance in cancer through activating ferroptotic pathways and brings together the relevant chemotherapeutics-based and nanotherapeutics-based studies to offer a perspective for researchers regarding the potential use of this mechanism in developing novel therapeutic strategies.

Deferoxamine Treatment Prevents Post-Stroke Vasoregression and Neurovascular Unit Remodeling Leading to Improved Functional Outcomes in Type 2 Male Diabetic Rats: Role of Endothelial Ferroptosis

It is a clinically well-established fact that patients with diabetes have very poor stroke outcomes. Yet, the underlying mechanisms remain largely unknown. Our previous studies showed that male diabetic animals show greater hemorrhagic transformation (HT), profound loss of cerebral vasculature in the recovery period, and poor sensorimotor and cognitive outcomes after ischemic stroke. This study aimed to determine the impact of iron chelation with deferoxamine (DFX) on (1) cerebral vascularization patterns and (2) functional outcomes after stroke in control and diabetic rats. After 8 weeks of type 2 diabetes induced by a combination of high-fat diet and low-dose streptozotocin, male control and diabetic animals were subjected to thromboembolic middle cerebral artery occlusion (MCAO) and randomized to vehicle, DFX, or tPA/DFX and followed for 14 days with behavioral tests. Vascular indices (vascular volume and surface area), neurovascular remodeling (AQP4 polarity), and microglia activation were measured. Brain microvascular endothelial cells (BMVEC) from control and diabetic animals were evaluated for the impact of DFX on ferroptotic cell death. DFX treatment prevented vasoregression and microglia activation while improving AQP4 polarity as well as blood-brain barrier permeability by day 14 in diabetic rats. These pathological changes were associated with improvement of functional outcomes. In control rats, DFX did not have an effect. Iron increased markers of ferroptosis and lipid reactive oxygen species (ROS) to a greater extent in BMVECs from diabetic animals, and this was prevented by DFX. These results strongly suggest that (1) HT impacts post-stroke vascularization patterns and recovery responses in diabetes, (2) treatment of bleeding with iron chelation has differential effects on outcomes in comorbid disease conditions, and (3) iron chelation and possibly inhibition of ferroptosis may provide a novel disease-modifying therapeutic strategy in the prevention of post-stroke cognitive impairment in diabetes.