Ferroptosis contributes to isoflurane-induced neurotoxicity and learning and memory impairment

Sevoflurane promotes neuronal ferroptosis via upregulation of PLIN4 to modulate the hippo signaling pathway

BACKGROUND

Sevoflurane is a widely used inhalation anesthetic associated with neuronal damage, cognitive impairment and neurodegenerative diseases, with iron overload reported to contribute to these adverse effects. However, the mechanisms of iron-dependent cell death (ferroptosis) in sevoflurane-induced neurotoxicity remain poorly understood.

METHODS

The role of PLIN4, a protein associated with neurodegeneration, in sevoflurane-induced neuronal damage was investigated using cultured mouse hippocampal neurons (HT22). PLIN4 knockdown or overexpression was performed through vector transfection, and PLIN4 transcription and expression levels after sevoflurane treatment and knockdown experiments were assessed via RT-qPCR, immunostaining, and western blot to evaluate its impact on ferroptosis. Transmission electron microscopy was used to assess cellular morphology and measure Fe2+ levels.

RESULTS

Sevoflurane treatment significantly increased PLIN4 expression in hippocampal neurons and induced ferroptosis. Silencing PLIN4 reduced ferroptosis and partially reversed sevoflurane's inhibition of the Hippo signaling pathway. Specifically, sevoflurane treatment led to a 2.9-fold increase in PLIN4 mRNA levels. Furthermore, higher PLIN4 levels upregulated ferroptosis in hippocampal neurons by inhibiting the Hippo pathway.

CONCLUSION

Our study indicates that sevoflurane promotes ferroptosis in neurons by upregulating PLIN4 and modulating the Hippo signaling pathway. These findings provide insights into the potential development of interventions to prevent anesthesia-related cognitive impairments and neurodegeneration.

Ferroptosis involvement in the neurotoxicity of flunitrazepam in zebrafish

In recent years, psychoactive drugs such as benzodiazepines (BZDs) have been frequently detected in water environments, however, there is still limited understanding regarding their potential impact on neurological health and underlying mechanisms. This study evaluated the neurotoxicity of the typical BZD drug flunitrazepam (FLZ, 0.2 and 5 μg/L) in zebrafish embryos and adults, and investigated the relationship between ferroptosis and FLZ-induced neurotoxicity. The results indicated that acute exposure to FLZ significantly inhibited zebrafish embryo hatching and promotes death, induced larval deformities, and led to abnormal neurobehavioral responses in larvae, likely due to ferroptosis induction. Results from a 30-day subacute exposure to FLZ showed that it decreased motor function and induced cognitive impairment in adult zebrafish. Immunofluorescence of brain tissues revealed a reduction in neurons in the telencephalon and an increase in microglia in the mesencephalon of the zebrafish exposed to FLZ. The ultrastructure of brain mitochondria showed serious damage. Besides, FLZ exposure increased iron levels, reduced GSH/GSSG and increased LPO in brain tissue, which is related to the abnormal expression of genes associated with ferroptosis. In the rescue experiments with co-exposure to deferoxamine (DFO), the motor-related parameters and biochemical indexes related to ferroptosis were restored, suggesting that FLZ can induce ferroptosis. The molecular docking results indicated that FLZ had a higher affinity with transferrin. This study elucidates the close relationship between ferroptosis and FLZ-induced neurotoxicity, which is significant for understanding the physiological damage caused by psychoactive substances and assessing environmental risks.

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.

MEF2C Alleviates Postoperative Cognitive Dysfunction by Repressing Ferroptosis

BACKGROUND

Ferroptosis, a form of programmed cell death featured by lipid peroxidation, has been proposed as a potential etiology for postoperative cognitive dysfunction (POCD). Myocyte-specific enhancer factor 2C (MEF2C), a transcription factor expressed in various brain cell types, has been implicated in cognitive disorders. This study sought to ascertain whether MEF2C governs postoperative cognitive capacity by affecting ferroptosis.

METHODS

Transcriptomic analysis of public data was used to identify MEF2C as a candidate differentially expressed gene in the hippocampus of POCD mice. The POCD mouse model was established via aseptic laparotomy under isoflurane anesthesia after treatment with recombinant adeno-associated virus 9 (AAV9)-mediated overexpression of MEF2C and/or the glutathione peroxidase 4 (GPX4) inhibitor RSL3. Cognitive performance, Nissl staining, and ferroptosis-related parameters were assessed. Dual-luciferase reporter gene assays and chromatin immunoprecipitation assays were implemented to elucidate the mechanism by which MEF2C transcriptionally activates GPX4.

RESULTS

MEF2C mRNA and protein levels decreased in the mouse hippocampus following anesthesia and surgery. MEF2C overexpression ameliorated postoperative memory decline, hindered lipid peroxidation and iron accumulation, and enhanced antioxidant capacity, which were reversed by RSL3. Additionally, MEF2C was found to directly bind to the Gpx4 promoter and activate its transcription.

CONCLUSIONS

Our findings suggest that MEF2C may be a promising therapeutic target for POCD through its negative modulation of ferroptosis.

Comprehensive review of perioperative factors influencing ferroptosis

The perioperative period encompasses all phases of patient care from the decision to perform surgery until full recovery. Ferroptosis, a newly identified type of regulated cell death, influences a wide array of diseases, including those affecting the prognosis and regression of surgical patients, such as ischemia-reperfusion injury and perioperative cognitive dysfunction. This review systematically examines perioperative factors impacting ferroptosis such as surgical trauma-induced stress, tissue hypoxia, anesthetics, hypothermia, and blood transfusion. By analyzing their intrinsic relationships, we aim to improve intraoperative management, enhance perioperative safety, prevent complications, and support high-quality postoperative recovery, ultimately improving patient outcomes.

Overview of ferroptosis and pyroptosis in acute liver failure

In this editorial, we comment on the article by Zhou et al published in a recent issue. We specifically focus on the crucial roles of ferroptosis and pyroptosis in acute liver failure (ALF), a disease with high mortality rates. Ferroptosis is the result of increased intracellular reactive oxygen species due to iron accumulation, glutathione (GSH) depletion, and decreased GSH peroxidase 4 activity, while pyroptosis is a procedural cell death mediated by gasdermin D which initiates a sustained inflammatory process. In this review, we describe the characteristics of ferroptosis and pyroptosis, and discuss the involvement of the two cell death modes in the onset and development of ALF. Furthermore, we summarize several interfering methods from the perspective of ferroptosis and pyroptosis for the alleviation of ALF. These observations might provide new targets and a theoretical basis for the treatment of ALF, which are also crucial for improving the prognosis of patients with ALF.

Propofol ameliorates cognitive deficits following splenectomy in aged rats by inhibiting ferroptosis via the SIRT1/Nrf2/GPX4 pathway

The aim of this study was to investigate the mechanism by which propofol reduces postoperative cognitive dysfunction after splenectomy in aged rats. The rats in the model group and propofol group were subjected to splenectomy, and anesthetized with isoflurane and propofol, respectively. Utilizing the western blotting to assess the expression of sirtuin-1 (SIRT1) in the hippocampus. Molecular docking technology was used to predict the binding ability of propofol and SIRT1. Behavioral tests were performed using the Morris water maze, and the hippocampus was isolated for mechanistic investigations. Molecular docking showed that propofol and SIRT1 had a strong binding affinity. The expression of SIRT1 and its related proteins Nrf2, HO-1, NQO1, and GPX4 in the model rats was decreased compared with the sham group. Moreover, the model group exhibited cognitive decline, such as extended escape latency and decreased number of platform crossings. Pathological analysis showed that the number of apoptotic neurons, the levels of oxidative stress and neuroinflammation, the iron deposition, and the expressions of ACSL4 and TFR1 were increased, while the expressions of SLC7A11 and FTH1 were decreased in the hippocampal CA1 region within the model group. These pathological changes in the propofol group were, however, less than those in the model group. Nevertheless, the SIRT1 inhibitor increased these pathological changes compared with the propofol group. Compared with isoflurane, propofol inhibits ferroptosis in the hippocampus of splenectomized rats by causing less downregulation of the SIRT1/Nrf2/GPX4 pathway, thereby reducing the negative impact on cognitive function.

Unveiling the hidden dangers: a review of non-apoptotic programmed cell death in anesthetic-induced developmental neurotoxicity

Anesthetic-induced developmental neurotoxicity (AIDN) can arise due to various factors, among which aberrant nerve cell death is a prominent risk factor. Animal studies have reported that repeated or prolonged anesthetic exposure can cause significant neuroapoptosis in the developing brain. Lately, non-apoptotic programmed cell deaths (PCDs), characterized by inflammation and oxidative stress, have gained increasing attention. Substantial evidence suggests that non-apoptotic PCDs are essential for neuronal cell death in AIDN compared to apoptosis. This article examines relevant publications in the PubMed database until April 2024. Only original articles in English that investigated the potential manifestations of non-apoptotic PCD in AIDN were analysed. Specifically, it investigates necroptosis, pyroptosis, ferroptosis, and parthanatos, elucidating the signaling mechanisms associated with each form. Furthermore, this study explores the potential relevance of these non-apoptotic PCDs pathways to the pathological mechanisms underlying AIDN, drawing upon their distinctive characteristics. Despite the considerable challenges involved in translating fundamental scientific knowledge into clinical therapeutic interventions, this comprehensive review offers a theoretical foundation for developing innovative preventive and treatment strategies targeting non-apoptotic PCDs in the context of AIDN.

Ferroptosis implication in environmental-induced neurotoxicity

Neurotoxicity, stemming from exposure to various chemical, biological, and physical agents, poses a substantial threat to the intricate network of the human nervous system. This article explores the implications of ferroptosis, a regulated form of programmed cell death characterized by iron-dependent lipid peroxidation, in environmental-induced neurotoxicity. While apoptosis has historically been recognized as a primary mechanism in neurotoxic events, recent evidence suggests the involvement of additional pathways, including ferroptosis. The study aims to conduct a comprehensive review of the existing literature on ferroptosis induced by environmental neurotoxicity across diverse agents such as natural toxins, insecticides, particulate matter, acrylamide, nanoparticles, plastic materials, metal overload, viral infections, anesthetics, chemotherapy, and radiation. The primary objective is to elucidate the diverse mechanisms through which these agents trigger ferroptosis, leading to neuronal cell death. Furthermore, the article explores potential preventive or therapeutic strategies that could mitigate ferroptosis, offering insights into protective measures against neurological damage induced by environmental stressors. This comprehensive review contributes to our evolving understanding of neurotoxicological processes, highlighting ferroptosis as a significant contributor to neuronal cell demise induced by environmental exposures. The insights gained from this study may pave the way for the development of targeted interventions to protect against ferroptosis-mediated neurotoxicity and ultimately safeguard public health.

The Impact of the Combined Effect of Inhalation Anesthetics and Iron Dextran on Rats' Systemic Toxicity

Disruption of any stage of iron homeostasis, including uptake, utilization, efflux, and storage, can cause progressive damage to peripheral organs. The health hazards associated with occupational exposure to inhalation anesthetics (IA) in combination with chronic iron overload are not well documented. This study aimed to investigate changes in the concentration of essential metals in the peripheral organs of rats after iron overload in combination with IA. The aim was also to determine how iron overload in combination with IA affects tissue metal homeostasis, hepcidin-ferritin levels, and MMP levels according to physiological, functional, and tissue features. According to the obtained results, iron accumulation was most pronounced in the liver (19×), spleen (6.7×), lungs (3.1×), and kidneys (2.5×) compared to control. Iron accumulation is associated with elevated heavy metal levels and impaired essential metal concentrations due to oxidative stress (OS). Notably, the use of IA increases the iron overload toxicity, especially after Isoflurane exposure. The results show that the regulation of iron homeostasis is based on the interaction of hepcidin, ferritin, and other proteins regulated by inflammation, OS, free iron levels, erythropoiesis, and hypoxia. Long-term exposure to IA and iron leads to the development of numerous adaptation mechanisms in response to toxicity, OS, and inflammation. These adaptive mechanisms of iron regulation lead to the inhibition of MMP activity and reduction of oxidative stress, protecting the organism from possible damage.

Fer-1 Protects against Isoflurane-Induced Ferroptosis in Astrocytes and Cognitive Impairment in Neonatal Mice

Early and prolonged exposure to anesthetic agents could cause neurodevelopmental disorders in children. Astrocytes, heavily outnumber neurons in the brain, are crucial regulators of synaptic formation and function during development. However, how general anesthetics act on astrocytes and the impact on cognition are still unclear. In this study, we investigated the role of ferroptosis and GPX4, a major hydroperoxide scavenger playing a pivotal role in suppressing the process of ferroptosis, and their underlying mechanism in isoflurane-induced cytotoxicity in astrocytes and cognitive impairment. Our results showed that early 6 h isoflurane anesthesia induced cognitive impairment in mice. Ferroptosis-relative genes and metabolic changes were involved in the pathological process of isoflurane-induced cytotoxicity in astrocytes. The level of GPX4 was decreased while the expression of 4-HNE and generation of ROS were elevated after isoflurane exposure. Selectively blocking ferroptosis with Fer-1 attenuated the abovementioned cytotoxicity in astrocytes, paralleling with the reverse of the changes in GPX4, ROS and 4-HNE secondary to isoflurane anesthesia. Fer-1 attenuated the cognitive impairment induced by prolonged isoflurane exposure. Thus, ferroptosis conduced towards isoflurane-induced cytotoxicity in astrocytes via suppressing GPX4 and promoting lipid peroxidation. Fer-1 was expected to be an underlying intervention for the neurotoxicity induced by isoflurane in the developing brain, and to alleviate cognitive impairment in neonates.

MT-TN mutations lead to progressive mitochondrial encephalopathy and promotes mitophagy

Mitochondrial encephalopathy is a neurological disorder caused by impaired mitochondrial function and energy production. One of the genetic causes of this condition is the mutation of MT-TN, a gene that encodes the mitochondrial transfer RNA (tRNA) for asparagine. MT-TN mutations affect the stability and structure of the tRNA, resulting in reduced protein synthesis and complex enzymatic deficiency of the mitochondrial respiratory chain. Our patient cohort manifests with epileptic encephalopathy, ataxia, hypotonia, and bilateral basal ganglia calcification, which differs from previously reported cases. MT-TN mutation deficiency leads to decreased basal and maximal oxygen consumption rates, disrupted spare respiratory capacity, declined mitochondrial membrane potential, and impaired ATP production. Moreover, MT-TN mutations promote mitophagy, a process of selective degradation of damaged mitochondria by autophagy. Excessive mitophagy further leads to mitochondrial biogensis as a compensatory mechanism. In this study, we provided evidence of pathogenicity for two MT-TN mutations, m.5688 T > C and m.G5691A, explored the molecular mechanisms, and summarized the clinical manifestations of MT-TN mutations. Our study expanded the genotype and phenotypic spectrum and provided new insight into mt-tRNA (Asn)-associated mitochondrial encephalopathy.

HSP90 Inhibition Attenuated Isoflurane-Induced Neurotoxicity in Mice and Human Neuroglioma Cells

Isoflurane, a widely used inhalation anesthetic in clinical practice, is associated with an increased risk of neuronal injury. Heat shock protein 90 (HSP90) plays a crucial role in maintaining neuronal homeostasis under stress conditions; however, its role during isoflurane exposure remains poorly understood. In this study, we aimed to investigate the protective effects of HSP90 inhibition and explore the regulatory mechanisms underlying these effects during isoflurane exposure. We found that the HSP90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17 AAG) has great protective effects in mitigating isoflurane-induced ferroptosis of mouse hippocampus and cultured neuronal cells. We focused on the activity of the crucial protein GPX4 in ferroptosis and found that 17 AAG exerted protective effects, preserving the physiological GPX4 activity under isoflurane exposure; further, 17 AAG restored the protein level of GPX4. Further, we observed that the chaperone-mediated autophagy (CMA) pathway was activated; 17 AAG also mediated GPX4 degradation under isoflurane exposure. Additionally, it interfered with the formation of complexes between HSP90 and Lamp-2a, inhibiting CMA activity, followed by the blockade of GPX4 degradation, further affecting the isoflurane-induced ferroptosis. Based on these findings, we proposed HSP90 inhibition as a protective mechanism against isoflurane-induced ferroptosis in neurons.

Dysregulation of iron homeostasis and ferroptosis in sevoflurane and isoflurane associated perioperative neurocognitive disorders

In recent years, sevoflurane and isoflurane are the most popular anesthetics in general anesthesia for their safe, rapid onset, and well tolerant. Nevertheless, many studies reported their neurotoxicity among pediatric and aged populations. This effect is usually manifested as cognitive impairment such as perioperative neurocognitive disorders. The wide application of sevoflurane and isoflurane during general anesthesia makes their safety a major health concern. Evidence indicates that iron dyshomeostasis and ferroptosis may establish a role in neurotoxicity of sevoflurane and isoflurane. However, the mechanisms of sevoflurane- and isoflurane-induced neuronal injury were not fully understood, which poses a barrier to the treatment of its neurotoxicity. We, therefore, reviewed the current knowledge on mechanisms of iron dyshomeostasis and ferroptosis and aimed to promote a better understanding of their roles in sevoflurane- and isoflurane-induced neurotoxicity.

Co-exposure to Fe, Zn, and Cu induced neuronal ferroptosis with associated lipid metabolism disorder via the ERK/cPLA2/AA pathway

Excessive amounts of iron (Fe), zinc (Zn), and copper (Cu) can be toxic to neuronal cells, even though these are essential trace elements for animals and humans. However, the precise mechanisms underlying the neurotoxicity of exposure to mixtures of Fe, Zn, and Cu are still mostly unclear. The research aimed to investigate the influence of co-exposure to iron, zinc and copper and the related mechanisms in HT22 murine hippocampal neuronal cells. Intracellular metal content, markers of oxidative damage, and biomarkers of ferroptosis were respectively detected. Afterward, metabolomic analyses were performed to obtain a comprehensive understanding of the metal mixtures on metabolism, and the functions of key enzymes on metabolic pathways were validated. The results showed that metal co-exposure resulted in cellular iron overload and increased lipid peroxidation, accompanied by significant pathological damage and mitochondrial abnormalities in HT22 cells. Meanwhile, it was found that GSH depletion, decreased GPX4, and increased expression of the lipid metabolism gene ACSL4 play important roles in ferroptosis induced by metal mixture. Further, metabolomic analysis revealed metal co-exposure induced significant alterations in metabolite levels, especially in the glycerophospholipid metabolism pathway and the arachidonic acid metabolism pathway. The levels of cPLA2 and its metabolite, arachidonic acid, were significantly increased after metal co-exposure. Then, inhibition of cPLA2 decreased the level of arachidonic acid and attenuated ferroptosis in neuronal cells. Collectively, our findings unveiled ferroptosis induced by metal co-exposure associated with crucial molecular changes in neuronal cells, providing a novel perspective on the comprehensive toxicity risk assessment of metal mixtures.

Targeting Pro-Oxidant Iron with Exogenously Administered Apotransferrin Provides Benefits Associated with Changes in Crucial Cellular Iron Gate Protein TfR in a Model of Intracerebral Hemorrhagic Stroke in Mice

We have previously demonstrated that the post-stroke administration of iron-free transferrin (apotransferrin, ATf) is beneficial in different models of ischemic stroke (IS) through the inhibition of the neuronal uptake of pro-oxidant iron. In the present study, we asked whether ATf is safe and also beneficial when given after the induction of intracerebral hemorrhage (ICH) in mice, and investigated the underlying mechanisms. We first compared the main iron actors in the brain of IS- or collagenase-induced ICH mice and then obtained insight into these iron-related proteins in ICH 72 h after the administration of ATf. The infarct size of the IS mice was double that of hemorrhage in ICH mice, but both groups showed similar body weight loss, edema, and increased ferritin and transferrin levels in the ipsilateral brain hemisphere. Although the administration of human ATf (hATf) to ICH mice did not alter the hemorrhage volume or levels of the classical ferroptosis GPX4/system xc- pathways, hATf induced better neurobehavioral performance, decreased 4-hydroxynonenal levels and those of the second-generation ferroptosis marker transferrin receptor (TfR), and restored the mRNA levels of the recently recognized cytosolic iron chaperone poly(RC) binding protein 2. In addition, hATf treatment lowered the ICH-induced increase in both endogenous mouse transferrin mRNA levels and the activation of caspase-2. In conclusion, hATf treatment provides neurobehavioral benefits post-ICH associated with the modulation of iron/oxidative players.

Novel Mechanisms of Perioperative Neurocognitive Disorders: Ferroptosis and Pyroptosis

Perioperative neurocognitive disorders (PNDs) are some of the most common postoperative complications among the elderly and susceptible individuals, which significantly worsens the clinical outcome of patients. However, the prevention and treatment strategies of PNDs are difficult to determine and implement since the pathogenesis of PNDs is not well understood. The development of living organisms is associated with active and organized cell death, which is essential for maintaining the homeostasis of life. Ferroptosis is a programmed cell death (different from apoptosis and necrosis) mainly caused by an imbalance in the generation and degradation of intracellular lipid peroxides due to iron overload. Pyroptosis is an inflammatory cell death characterized by the creation of membrane holes mediated by the gasdermin (GSDM) family, followed by cell lysis and the release of pro-inflammatory cytokines. Ferroptosis and pyroptosis are involved in the pathogenesis of various central nervous system (CNS) diseases. Furthermore, ferroptosis and pyroptosis are closely associated with the occurrence and development of PNDs. This review summarizes the main regulatory mechanisms of ferroptosis and pyroptosis and the latest related to PNDs. Based on the available evidence, potential intervention strategies that can alleviate PNDs by inhibiting ferroptosis and pyroptosis have also been provided.

Role of ferroptosis in effects of anesthetics on multiple organ diseases: A literature review

Anesthesiologists are often faced with patients combined with a series of organ injuries, such as acute lung injury, myocardial ischemia-reperfusion injury, and neurodegenerative diseases. With the in-depth study of these diseases, we are more aware of the choice and rational use of anesthetics for the prognosis of these patients. Ferroptosis is a new type of programmed cell death. This unique pattern of cell death, driven by an imbalance between oxides and antioxidants, is regulated by multiple cellular metabolic events, including redox homeostasis, iron handling, mitochondrial activity, and lipids peroxidation. Numerous studies confirmed that anesthetics modulate ferroptosis by interfering its machineries such as cystine-import-glutathione-glutathione peroxidase 4 axis, Heme oxygenase 1, nuclear factor erythroid 2-related factor 2, and iron homeostasis system. In this literature review, we systemically illustrated possible involvement of ferroptosis in effects of anesthetics and adjuvant drugs on multiple organ diseases, hoping our work may serve as a basis for further studies on regulating ferroptosis through anesthetics related pharmacological modulation and promoting the rational use of anesthetics.

Multiple sevoflurane exposures during mid-trimester induce neurotoxicity in the developing brain initiated by 15LO2-Mediated ferroptosis

AIMS

Mid-gestational sevoflurane exposure may induce notable long-term neurocognitive impairment in offspring. This study was designed to investigate the role and potential mechanism of ferroptosis in developmental neurotoxicity induced by sevoflurane in the second trimester.

METHODS

Pregnant rats on day 13 of gestation (G13) were treated with or without 3.0% sevoflurane, Ferrostatin-1 (Fer-1), PD146176, or Ku55933 on three consecutive days. Mitochondrial morphology, ferroptosis-relative proteins, malondialdehyde (MDA) levels, total iron content, and glutathione peroxidase 4 (GPX4) activities were measured. Hippocampal neuronal development in offspring was also examined. Subsequently, 15-lipoxygenase 2 (15LO2)-phosphatidylethanolamine binding protein 1 (PEBP1) interaction and expression of Ataxia telangiectasia mutated (ATM) and its downstream proteins were also detected. Furthermore, Morris water maze (MWM) and Nissl's staining were applied to estimate the long-term neurotoxic effects of sevoflurane.

RESULTS

Ferroptosis mitochondria were observed after maternal sevoflurane exposures. Sevoflurane elevated MDA and iron levels while inhibiting GPX4 activity, and resultant long-term learning and memory dysfunction, which were alleviated by Fer-1, PD146176, and Ku55933. Sevoflurane could enhance 15LO2-PEBP1 interaction and activate ATM and its downstream P53/SAT1 pathway, which might be attributed to excessive p-ATM nuclear translocation.

CONCLUSION

This study proposes that 15LO2-mediated ferroptosis might contribute to neurotoxicity induced by maternal sevoflurane anesthesia during the mid-trimester in the offspring and its mechanism may be ascribed to hyperactivation of ATM and enhancement of 15LO2-PEBP1 interaction, indicating a potential therapeutic target for ameliorating sevoflurane-induced neurotoxicity.

The effects of general anesthetics on mitochondrial structure and function in the developing brain

The use of general anesthetics in modern clinical practice is commonly regarded as safe for healthy individuals, but exposures at the extreme ends of the age spectrum have been linked to chronic cognitive impairments and persistent functional and structural alterations to the nervous system. The accumulation of evidence at both the epidemiological and experimental level prompted the addition of a warning label to inhaled anesthetics by the Food and Drug Administration cautioning their use in children under 3  years of age. Though the mechanism by which anesthetics may induce these detrimental changes remains to be fully elucidated, increasing evidence implicates mitochondria as a potential primary target of anesthetic damage, meditating many of the associated neurotoxic effects. Along with their commonly cited role in energy production via oxidative phosphorylation, mitochondria also play a central role in other critical cellular processes including calcium buffering, cell death pathways, and metabolite synthesis. In addition to meeting their immense energy demands, neurons are particularly dependent on the proper function and spatial organization of mitochondria to mediate specialized functions including neurotransmitter trafficking and release. Mitochondrial dependence is further highlighted in the developing brain, requiring spatiotemporally complex and metabolically expensive processes such as neurogenesis, synaptogenesis, and synaptic pruning, making the consequence of functional alterations potentially impactful. To this end, we explore and summarize the current mechanistic understanding of the effects of anesthetic exposure on mitochondria in the developing nervous system. We will specifically focus on the impact of anesthetic agents on mitochondrial dynamics, apoptosis, bioenergetics, stress pathways, and redox homeostasis. In addition, we will highlight critical knowledge gaps, pertinent challenges, and potential therapeutic targets warranting future exploration to guide mechanistic and outcomes research.

Lycopene ameliorates atrazine-induced spatial learning and memory impairments by inhibiting ferroptosis in the hippocampus of mice

Atrazine (ATR) is a commercially available herbicide that is used worldwide. The intensive use of ATR poses potential risks to animals' and humans' health. Lycopene (LYC) is an anti-oxidative phytochemical that normalizes health hazards triggered by environmental factors. In this study, we aimed to investigate the toxic effects of ATR on the hippocampus and its amelioration by LYC. Male mice were exposed to ATR (50 mg/kg/day or 200 mg/kg/d) and/or LYC (5 mg/kg/d) for 21 days. The results showed that ATR exposure induced hippocampus-dependent learning and memory impairments. ATR-induced ferroptosis in hippocampal cells affects the homeostasis of lipid metabolism, whereas LYC ameliorates the neurotoxic effects of ATR in the hippocampus. LYC inhibited ATR-induced ferroptosis by increasing the expression of HO-1, Nrf2 and SLC7A11. Therefore, this study established that LYC ameliorates ATR-induced spatial learning and memory impairments by inhibiting ferroptosis in the hippocampus and also provides a novel approach for the treatment in contradiction of environmental pollutants.

Ferroptosis contributes to nickel-induced developmental neurotoxicity in zebrafish

Nickel (Ni) is a widely utilized heavy metal that can cause environmental pollution and health hazards. Its safety has attracted the attention of both the environmental ecology and public health fields. While the central nervous system (CNS) is one of the main targets of Ni, its neurotoxicity and the underlying mechanisms remain unclear. Here, by taking advantage of the zebrafish model for live imaging, genetic analysis and neurobehavioral studies, we reveal that the neurotoxic effects induced by exposure to environmentally relevant levels of Ni are closely related to ferroptosis, a newly-described form of iron-mediated cell death. In vivo two-photon imaging, neurobehavioral analysis and transcriptome sequencing consistently demonstrate that early neurodevelopment, neuroimmune function and vasculogenesis in zebrafish larvae are significantly affected by environmental Ni exposure. Importantly, exposure to various concentrations of Ni activates the ferroptosis pathway, as demonstrated by physiological/biochemical tests, as well as the expression of ferroptosis markers. Furthermore, pharmacological intervention of ferroptosis via deferoxamine (DFO), a classical iron chelating agent, strongly implicates iron dyshomeostasis and ferroptosis in these Ni-induced neurotoxic effects. Thus, this study elucidates the cellular and molecular mechanisms underlying Ni neurotoxicity, with implications for our understanding of the physiologically damaging effects of other environmental heavy metal pollutants.

Avenanthramide-C Activates Nrf2/ARE Pathway and Inhibiting Ferroptosis Pathway to Improve Cognitive Dysfunction in Aging Rats

Postoperative neurocognitive impairment (POCD) is a common complication after surgery and anesthesia, especially in elderly patients. Avenanthramide-C (AVC) test is a vascular endothelial cell adhesion molecule inhibitor with strong anti-inflammatory and antioxidant effects. The aim of this study was to investigate the effect and mechanism of AVC on POCD in aged rats to clarify the effect of AVC on POCD in aged rats. The aging rat model was established by continuous 200 mg/kg propofol anesthesia. Repeated propofol anesthesia could severely impair spatial learning ability, memory and cognitive function, and could promote hippocampal apoptosis, oxidative stress injury, neuroinflammation and ferroptosis in aging rats. In addition, AVC not only improved cognitive dysfunction, but also significantly inhibited apoptosis, neuroinflammatory response, ferroptosis and oxidative stress level in the hippocampus of aging rats induced by repeated anesthesia. Further mechanistic studies manifested that the above protective effects of AVC on aging rats induced by repeated propofol anesthesia may be achieved by activating Nrf2/ARE pathway activity. AVC pretreatment has a preventive effect on cognitive dysfunction induced by repeated propofol anesthesia in aging rats, and the preventive effect of AVC may be realized by activating the Nrf2/ARE signaling pathway activity. Our results demonstrate that AVC preconditioning reduces postoperative neuronal loss and neuroinflammation, activates the Nrf2/ARE pathway, reduces oxidative stress injury, and improves POCD in aged rats.

Depletion of PSMD14 suppresses bladder cancer proliferation by regulating GPX4

Objective

The aim of this study was to investigate the role of deubiquitinase (DUB) 26S proteasome non-ATPase regulatory subunit 14 (PSMD14) in patients with bladder cancer.

Methods

From 2016 to 2018, 181 patients diagnosed with primary bladder cancer at the Affiliated Hospital of Qingdao University were recruited. The expression of PSMD14 in bladder cancer tissues was tested by immunochemistry. The association between PSMD14 expression and clinical and pathological data and outcomes of bladder cancer patients was determined. Overexpression and knockdown cells were constructed to evaluate the effects of PSMD14 on proliferation of bladder cancer cells.

Results

Our results showed that PSMD14 was significantly overexpressed in bladder cancer tissues compared to adjacent non-tumor tissues (76.24% vs 23.76%, P = 0.02). The expression of PSMD14 was significantly higher in patients with larger tumor diameters (85.14% vs 70.09%, P = 0.019) and patients with a family history of cancer (92.16% vs 70.00%, P = 0.002). Patients with high expression of PSMD14 had poor disease-free survival (DFS) (HR = 2.89, 95% CI [1.247-6.711], P = 0.013). Gain and loss of function experiments demonstrated that PSMD14 deficiency inhibited bladder cancer cell proliferation. Additionally, depletion of PSMD14 suppressed bladder cancer cell growth via down-regulation of GPX4, and the promotion of PSMD14-induced cell growth was observably reversed by the GPX4 inhibitor RSL3.

Conclusion

We determined that PSMD14 is highly expressed in bladder cancer tissues, and that PSMD14 expression correlated with poor disease-free survival. Depletion of PSMD14 could inhibit the proliferation of bladder cancer cells through the downregulation of GPX4. Therefore, PSMD14 may be an effective target for the treatment of bladder cancer.

Research progress on molecular mechanisms of general anesthetic-induced neurotoxicity and cognitive impairment in the developing brain

General anesthetics-induced neurotoxicity and cognitive impairment in developing brains have become one of the current research hotspots in the medical science community. The underlying mechanisms are complex and involve various related molecular signaling pathways, cell mediators, autophagy, and other pathological processes. However, few drugs can be directly used to treat neurotoxicity and cognitive impairment caused by general anesthetics in clinical practice. This article reviews the molecular mechanism of general anesthesia-induced neurotoxicity and cognitive impairment in the neonatal brain after surgery in the hope of providing critical references for the treatments of clinical diseases.

Anesthesia and developing brain: What have we learned from recent studies

Anesthesia is unavoidable in surgical procedures. However, whether the general anesthetics are neurotoxic to immature brains remains undefined. Neurodevelopmental impairment induced by anesthesia has been a critical health issue and topic of concern. This review summarizes recent progress made in clinical and preclinical studies to provide useful suggestions and potential therapeutic targets for the protection of the immature brain. On the one hand, clinical researchers continue the debate about the effect of single and multiple exposures to anesthesia on developing brains. On the other hand, preclinical researchers focus on exploring the mechanisms of neurotoxic effects of general anesthesia on immature brains and seeking novel solutions. Rodent models have always been used in preclinical studies, but it is still unclear whether the mechanisms observed in rodent models have clinical relevance. Compared with these models, non-human primates (NHPs) are more genetically similar to humans. However, few research institutions in this area can afford to use NHP models in their studies. One way to address both problems is by combining single-cell sequencing technologies to screen differential gene expression in NHPs and perform in vivo validation in rodents. The mechanism of anesthesia-induced neurotoxicity still requires further elucidation in primates.

The effect of narcotics on ferroptosis-related molecular mechanisms and signalling pathways

Ferroptosis is a novel programmed cell death form characterized by iron-mediated reactive oxygen species-induced lipid peroxidation and subsequent cell damage that is distinct from apoptosis, necroptosis, pyroptosis, and autophagy. Most studies on ferroptosis are based on its function and mechanism, but there have been relatively few studies on the effects of drugs, especially anaesthetics, on ferroptosis. Therefore, we summarized the recent literature on the effects of anaesthetics on ferroptosis to understand the underlying mechanism. In particular, we focused on the targets of various anaesthetics in different mechanisms of ferroptosis and the effects of ferroptosis induction or inhibition by narcotics on various diseases. The aims of this review are to provide a relatively reasonable drug regimen for clinicians, to explore potential ferroptosis protection drugs and targets, to reduce perioperative complications and to improve the postoperative performance of patients, especially those who are critically ill.

Acutely increased aquaporin-4 exhibits more potent protective effects in the cortex against single and repeated isoflurane-induced neurotoxicity in the developing rat brain

Damage to hippocampus, cerebellum, and cortex associated with cognitive functions due to anesthetic-induced toxicity early in life may cause cognitive decline later. Aquaporin 4 (AQP4), a key protein in waste clearance pathway of brain, is involved in synaptic plasticity and neurocognition. We investigated the effects of single and repeated isoflurane (Iso) anesthesia on AQP4 levels and brain damage. Postnatal-day (P)7 Wistar albino rats were randomly assigned to Iso or Control (C) groups. For single-exposure, pups were exposed to 1.5% Iso in 30% oxygenated-air for 3-h at P7 (Iso₁). For repeated-exposure, pups were exposed to Iso for 3 days, 3-h each day, at 1-day intervals (P7 + 9+11) starting at P7 (Iso₃). C₁ and C₃ groups received only 30% oxygenated-air. Based on HE-staining and immunoblotting (Bax/Bcl-2, cleaved-caspase3 and PARP1) analyses, Iso exposures caused a higher degree of apoptosis in hippocampus. Anesthesia increased 4HNE, oxidative stress marker; the highest ROS accumulation was determined in cerebellum. Increased inflammation (TNF-α, NF-κB) was detected. Multiple Iso-exposures caused more significant damage than single exposure. Moreover, 4HNE and TNF-α contributed synergistically to Iso-induced neurotoxicity. After anesthesia, higher expression of AQP4 was detected in cortex than hippocampus and cerebellum. There was an inverse correlation between increased AQP4 levels and apoptosis/ROS/inflammation. Correlation analysis indicated that AQP4 had a more substantial protective profile against oxidative stress than apoptosis. Remarkably, acutely increased AQP4 against Iso exhibited a more potent neuroprotective effect in cortex, especially frontal cortex. These findings promote further research to understand better the mechanisms underlying anesthesia-induced toxicity in the developing brain.

Ferroptosis is involved in regulating perioperative neurocognitive disorders: emerging perspectives

Since the twenty-first century, the development of technological advances in anesthesia and surgery has brought benefits to human health. However, the adverse neurological effects of perioperative-related factors (e.g., surgical trauma, anesthesia, etc.) as stressors cannot be ignored as well. The nervous system appears to be more "fragile" and vulnerable to damage in developing and aging individuals. Ferroptosis is a novel form of programmed cell death proposed in 2012. In recent years, the regulation of ferroptosis to treat cancer, immune system disorders, and neurodegenerative diseases have seen an unprecedented surge of interest. The association of ferroptosis with perioperative neurocognitive disorders has also received much attention. Cognitive impairment can not only affect the individual's quality of life, but also impose a burden on the family and society. Therefore, the search for effective preventive and therapeutic methods to alleviate cognitive impairment caused by perioperative-related factors is a challenge that needs to be urgently addressed. In our review, we first briefly describe the connection between iron accumulation in neurons and impairment of brain function during development and aging. It is followed by a review of the pathways of ferroptosis, mainly including iron metabolism, amino acid metabolism, and lipid metabolism pathway. Furthermore, we analyze the connection between ferroptosis and perioperative-related factors. The surgery itself, general anesthetic drugs, and many other relevant factors in the perioperative period may affect neuronal iron homeostasis. Finally, we summarize the experimental evidence for ameliorating developmental and degenerative neurotoxicity by modulating ferroptosis. The suppression of ferroptosis seems to provide the possibility to prevent and improve perioperative neurocognitive impairment.

Sevoflurane exposure during the second trimester induces neurotoxicity in offspring rats by hyperactivation of PARP-1

RATIONALE

Fetal exposure to general anesthesia may cause noteworthy neurocognitive impairment, but the mechanisms are unclear.

OBJECTIVES

Our study designed to explore the potential mechanism of neurotoxicity in offspring rats after sevoflurane exposure to the pregnant rats during the second trimester.

METHODS

Pregnant rats (G14 day) were administrated with or without 3.5% sevoflurane, 40 mg/kg 3-aminobenzamide (3-AB), inhibitor of poly ADP ribose polymerase 1 (PARP-1), or 10 mg/kg TC-2153, inhibitor of striatal-enriched phosphatase 61 (STEP61). Afterwards, the effects on expression of β-tubulin (TUJ1), neurite outgrowth inhibitor A (Nogo-A), parthanatos-related and STEP61/proline-rich tyrosine kinase 2 (Pyk2) pathway-associated proteins, and reactive oxygen species (ROS) levels were examined by immunofluorescence staining, Western blot, and dihydroethidium (DHE) staining, respectively. Moreover, morphological changes in the hippocampal CA3 region and neuronal cell death were tested by glycine silver staining and TUNEL and immunofluorescence double staining, respectively. Furthermore, spatial learning and memory functions of rats on postnatal 28-33 days (PND 28-33) were evaluated by morris water maze (MWM).

RESULTS

Mid-pregnancy exposure to sevoflurane led to excessive PARP-1 activation, poly (ADP-ribose) (PAR) polymer accumulation, apoptosis-inducing factor (AIF) nuclear translocation, and Nogo-A accumulation. Besides, sevoflurane significantly inhibited neurite growth and increased cell death in the fetal rat brain. Additionally, sevoflurane activated STEP61/Pyk2 pathway and increased ROS levels. However, 3-AB or TC-2153 significantly alleviated cell death, promoted neurites growth, and improved sevoflurane-induced spatial learning and memory impairment.

CONCLUSION

This study proposes that sevoflurane exposure during the second trimester incudes neurotoxicity in offspring rats by hyperactivation of PARP-1 via STEP61/Pyk2 pathway.

Activation of the P62-Keap1-NRF2 Pathway Protects against Ferroptosis in Radiation-Induced Lung Injury

Radiation-induced lung injury (RILI) is one of the most common, serious, and dose-limiting toxicities of thoracic radiotherapy. A primary cause for this is the radiation-induced cell death. Ferroptosis is a recently recognized form of regulated cell death, characterized by the accumulation of lipid peroxidation products and lethal reactive oxygen species (ROS). The ROS generated by irradiation might be the original trigger of ferroptosis in RILI. In addition, activation of the P62-Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (NRF2) pathway has been shown to blunt ferroptosis and thus acts as a protective factor. Therefore, this study aimed to explore the protective effect of the P62-Keap1-NRF2 pathway against radiation-induced ferroptosis in alveolar epithelial cells. First, we found that radiation induced ferroptosis in vitro using a RILI cell model, which could be significantly reduced by ferrostatin-1 (Fer-1), a specific ferroptosis inhibitor. Additionally, overexpression of P62 interacted with Keap1 to facilitate the translocation of NRF2 into the nucleus and promote the expression of its target proteins, including quinone oxidoreductase 1 (NQO1), heme oxygenase 1 (HO1), and ferritin heavy chain 1 (FTH1). In summary, our results demonstrated that the activation of the P62-Keap1-NRF2 pathway prevents radiation-induced ferroptosis in RILI cells, providing a theoretical basis of finding a potential therapeutic approach for RILI.

The role of ferroptosis in organ toxicity

Ferroptosis, an iron-dependent form of programmed cell death, is characterized by iron overload, increased reactive oxygen species (ROS) generation, and depletion of glutathione (GSH) and lipid peroxidation. Lipophilic antioxidants and iron chelators can prevent ferroptosis. GSH-dependent glutathione peroxidase 4 (GPX4) prevents lipid ROS accumulation. Ferroptosis is thought to be initiated through GPX4 inactivation. Moreover, mitochondrial iron overload derived from the degradation of ferritin is involved in increasing ROS generation. Ferroptosis has been suggested to explain the mechanism of action of organ toxicity induced by several drugs and chemicals. Inhibition of ferroptosis may provide novel therapeutic opportunities for treatment and even prevention of such organ toxicities.

Pachypodol protects newborn rats from anaesthesia-induced apoptosis in the developing brain by regulating the JNK/ERK pathway

Anaesthesia exposure causes changes in the developing brain and affects behaviour and memory. This study examined the beneficial effect of pachypodol against isoflurane (ISF)-induced neuronal injury. Seven-day-old rats were treated with 10 mg/kg and 30 mg/kg intravenous pachypodol 30 min before exposure to ISF (0.75%) for 6 h. Oxidative stress and other biochemical parameters were assessed in the brain tissue and serum using enzyme-linked immunosorbent assay. Additionally, a terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay was performed to assess neuronal cell apoptosis in several regions of the hippocampus. Cognitive function and neurological scores were determined in the pachypodol-treated neuron-injured rats. Cytokine levels and oxidative stress were reduced in the pachypodol-treated group compared with the ISF group. In addition, cognitive deterioration was reversed in pachypodol-treated compared with ISF-treated rats. Thus, treatment with pachypodol reduced neuronal apoptosis in neuron-injured rats. Moreover, pachypodol ameliorated changes to the JNK/ERK/Akt pathway in brain-injured rats. In conclusion, pachypodol treatment prevents neuronal apoptosis in ISF-treated rats by regulating the JNK/ERK pathway.