Lack of the brain-specific isoform of apoptosis-inducing factor aggravates cerebral damage in a model of neonatal hypoxia-ischemia

Emerging ferroptosis inhibitors as a novel therapeutic strategy for the treatment of neonatal hypoxic-ischemic encephalopathy

Neonatal hypoxia-ischemia encephalopathy (NHIE), an oxygen deprivation-mediated brain injury due to birth asphyxia or reduced cerebral blood perfusion, often leads to lifelong sequelae, including seizures, cerebral palsy, and mental retardation. NHIE poses a significant health challenge, as one of the leading causes of neonatal morbidity and mortality globally. Despite this, available therapies are limited. Numerous studies have recently demonstrated that ferroptosis, an iron-dependent non-apoptotic regulated form of cell death characterized by lipid peroxidation (LPO) and iron dyshomeostasis, plays a role in the genesis of NHIE. Moreover, recently discovered compounds have been shown to exert potential therapeutic effects on NHIE by inhibiting ferroptosis. This comprehensive review summarizes the fundamental mechanisms of ferroptosis contributing to NHIE. We focus on various emerging therapeutic compounds exhibiting characteristics of ferroptosis inhibition and delineate their pharmacological benefits for the treatment of NHIE. This review suggests that pharmacological inhibition of ferroptosis may be a potential therapeutic strategy for NHIE.

Polyethylene microplastics cause apoptosis via the MiR-132/CAPN axis and inflammation in carp ovarian

Microplastics (MPs) are widely distributed pollutants in the environment and accumulate in the aquatic environment due to human activities. Carp, a common edible aquatic organism, has been found to accumulate MPs in body. MicroRNA (miRNAs) is a non-coding short RNA that regulates protein expression by binding to target genes in various physiological processes such as proliferation, differentiation and apoptosis. The ovary is a crucial role in carp reproduction. In this study, we established a model of carp exposed to polyethylene microplastics (PE-MPs) in the aquatic environment to investigate the specific mechanism of PE-MPs causing ovarian injury and the involvement of miR-132/calpain (CAPN) axis. H&E stained sections revealed that PE-PMs induced inflammation in ovarian tissues and impaired oocyte development. TUNEL analysis showed an increased rate of apoptosis in ovarian cells treated with PE-PMs. RT-PCR and Western Blot assays confirmed that exposure to PE-MPs significantly decreased miR-132 expression while increasing CAPN expression at both mRNA and protein levels. The concentration of calcium ions was significantly increased in tissues, leading to CAPN enzyme activity increase. The expression of mitochondrial damage-related genes (bax, AIF, cyt-c, caspase-7, caspase-9, and caspase-3) was higher while the expression of anti-apoptotic genes (bcl-2 and bcl-xl) was lower. Protein levels of bax, AIF, caspase-3, bcl-2 and bcl-xl changed accordingly with the genetic alterations. Additionally, we discovered that PE-MPs can activate the p65 factor through the TRAF6/NF-kB pathway resulting in elevated production of pro-inflammatory factors IL-6, IL-1β and TNF-a which contribute to ovarian inflammation development. This study investigates the impact of PE-MPs on carp ovarian function and provides insights into miRNAs' role and their target genes.

Dying transplanted neural stem cells mediate survival bystander effects in the injured brain

Neural stem and progenitor cell (NSPC) transplants provide neuroprotection in models of acute brain injury, but the underlying mechanisms are not fully understood. Here, we provide evidence that caspase-dependent apoptotic cell death of NSPCs is required for sending survival signals to the injured brain. The secretome of dying NSPCs contains heat-stable proteins, which protect neurons against glutamate-induced toxicity and trophic factor withdrawal in vitro, and from ischemic brain damage in vivo. Our findings support a new concept suggesting a bystander effect of apoptotic NSPCs, which actively promote neuronal survival through the release of a protective "farewell" secretome. Similar protective effects by the secretome of apoptotic NSPC were also confirmed in human neural progenitor cells and neural stem cells but not in mouse embryonic fibroblasts (MEF) or human dopaminergic neurons, suggesting that the observed effects are cell type specific and exist for neural progenitor/stem cells across species.

Linoleic Acid-Glucosamine Hybrid for Endogenous Iron-Activated Ferroptosis Therapy in High-Grade Serous Ovarian Cancer

As the most common subtype in ovarian malignancies, high-grade serous ovarian cancer (HGSOC) made less therapeutic progress in past decades due to the lack of effective drug-able targets. Herein, an effective linoleic acid (LA) and glucosamine (GlcN) hybrid (LA-GlcN) was synthesized for the treatment of HGSOC. The GlcN was introduced to recognize the glucose transporter 1 (GLUT 1) overexpressed in tumor cells to enhance the uptake of LA-GlcN, and the unsaturated LA was employed to trigger ferroptosis by iron-dependent lipid peroxidation. Since the iron content of HGSOC was ∼5 and 2 times, respectively, higher than that of the normal ovarian cells and low-grade serous ovarian cancer cells, these excess irons make them a good target to enhance the ferroptosis of LA-GlcN. The in vitro study demonstrated that LA-GlcN could selectively kill HGSOC cells without affecting normal cells; the in vivo study revealed that LA-GlcN at the dose of 50 mg kg^-1 achieved a comparable tumor inhibition as doxorubicin hydrochloride (4 mg kg^-1) while the overall survival of mice was extended largely due to the low toxicity, and when the dose was increased to 100 mg kg^-1, the therapeutic outcomes could be improved further. This dietary hybrid which targets the excess endogenous iron to activate ferroptosis represents a promising drug for HGSOC treatment.

Ferroptosis: A Promising Therapeutic Target for Neonatal Hypoxic-Ischemic Brain Injury

Ferroptosis is a type of programmed cell death caused by phospholipid peroxidation that has been implicated as a mechanism in several diseases resulting from ischemic-reperfusion injury. Most recently, ferroptosis has been identified as a possible key injury mechanism in neonatal hypoxic-ischemic brain injury (HIBI). This review summarizes the current literature regarding the different ferroptotic pathways, how they may be activated after neonatal HIBI, and which current or investigative interventions may attenuate ferroptotic cell death associated with neonatal HIBI.

6-Gingerol Alleviates Neonatal Hypoxic-Ischemic Cerebral and White Matter Injury and Contributes to Functional Recovery

Hypoxic-ischemic encephalopathy (HIE) is one main cause of neonatal death and disability, causing substantial injury to white and gray matter, which can lead to severe neurobehavioral dysfunction, including intellectual disability and dyskinesia. Inflammation, nerve cell death, and white matter injury are important factors in the pathological process of HIE. 6-Gingerol is a ginger extract, which reduces inflammatory response and cell death. However, the role of 6-Gingerol in neonatal hypoxic-ischemic brain injury (HIBI) remains unknown. In this study, we constructed a mouse HIBI model and analyzed the protective effect of 6-Gingerol on HIBI by using behavioral tests, histological staining, qPCR and western blot. Here, we found that 6-Gingerol treatment could alleviate HIBI and improve short-term reflex performance, which is closely related to cell death and neuroinflammation. Additionally, 6-Gingerol reduced neuronal apoptosis, pro-inflammatory factor release, as well as microglial activation. Furthermore, 6-Gingerol significantly improved motor disability, which is associated with white matter damage. Thus, our results showed that 6-Gingerol could reduce the loss of myelin sheaths, alleviate cell death of oligodendrocytes, and stimulate the maturation of oligodendrocytes. In terms of mechanism, we found that 6-Gingerol decreased histone H3K27me3 levels, activated AKT pathway and inhibited the activation of ERK and NF-κB pathway at 3 days post-HIBI. Taken together, our data clearly indicate that 6-Gingerol plays a neuroprotective role against HIBI by epigenetic modification and regulation of AKT, ERK, and NF-κB pathways, inhibiting inflammatory responses and reducing cell death.

Extracellular Vesicle-Derived microRNA-410 From Mesenchymal Stem Cells Protects Against Neonatal Hypoxia-Ischemia Brain Damage Through an HDAC1-Dependent EGR2/Bcl2 Axis

Hypoxia-ischemia brain damage (HIBD) is a neurological disorder occring in neonates, which is exacerbated by neuronal apoptosis. Mesenchymal stem cells (MSCs)-derived extracellular vesicles (EVs) have been proposed as a promising strategy for treating or preventing ischemia-related diseases. However, their mechanisms in HIBD remain unclear. Thus, we aimed to address the role of EV-derived microRNA (miR)-410 in HIBD. Neonatal HIBD mouse model was constructed using HI insult, from which neurons were isolated, followed by exposure to oxygen glucose deprivation (OGD). EVs were isolated from human umbilical cord (hUC)-derived MSCs. In silico analyses, dual-luciferase reporter gene and chromatin immunoprecipitation assays were adopted to determine relationships among miR-410, histone deacetylase 1 (HDAC1), early growth response protein 2 (EGR2), and B cell lymphoma/leukemia 2 (Bcl2). The functional roles of EV-derived miR-410 were determined using loss- and gain-of functions experiments, and by evaluating neuronal viability, cell-cycle distribution and neuronal apoptosis in vitro as well as modified neurological severity score (mNSS), edema formation, and cerebral infarction volume in vivo. hUC-MSCs-derived EVs protected against HIBD in vivo and inhibited the OGD-induced neuronal apoptosis in vitro. miR-410 was successfully delivered to neurons by hUC-MSCs-EVs and negatively targeted HDAC1, which inversely mediated the expression of EGR2/Bcl2. Upregulation of EV-derived miR-410 promoted the viability but inhibited apoptosis of neurons, which was reversed by HDAC1 overexpression. EV-derived miR-410 elevation reduced mNSS, edema formation, and cerebral infarction volume by increasing EGR2/Bcl2 expression through downregulating HDAC1 expression in vivo. In summary, EV-derived miR-410 impeded neuronal apoptosis by elevating the expression of EGR2/Bcl2 via HDAC1 downregulation, thereby providing a potential strategy for treating or preventing HIBD.

Role of apoptosis-inducing factor in perinatal hypoxic-ischemic brain injury

Perinatal complications, such as asphyxia, can cause brain injuries that are often associated with subsequent neurological deficits, such as cerebral palsy or mental retardation. The mechanisms of perinatal brain injury are not fully understood, but mitochondria play a prominent role not only due to their central function in metabolism but also because many proteins with apoptosis-related functions are located in the mitochondrion. Among these proteins, apoptosis-inducing factor has already been shown to be an important factor involved in neuronal cell death upon hypoxia-ischemia, but a better understanding of the mechanisms behind these processes is required for the development of more effective treatments during the early stages of perinatal brain injury. In this review, we focus on the molecular mechanisms of hypoxic-ischemic encephalopathy, specifically on the importance of apoptosis-inducing factor. The relevance of apoptosis-inducing factor is based not only because it participates in the caspase-independent apoptotic pathway but also because it plays a crucial role in mitochondrial energetic functionality, especially with regard to the maintenance of electron transport during oxidative phosphorylation and in oxidative stress, acting as a free radical scavenger. We also discuss all the different apoptosis-inducing factor isoforms discovered, focusing especially on apoptosis-inducing factor 2, which is only expressed in the brain and the functions of which are starting now to be clarified. Finally, we summarized the interaction of apoptosis-inducing factor with several proteins that are crucial for both apoptosis-inducing factor functions (pro-survival and pro-apoptotic) and that are highly important in order to develop promising therapeutic targets for improving outcomes after perinatal brain injury.

Inhibiting the interaction between apoptosis-inducing factor and cyclophilin A prevents brain injury in neonatal mice after hypoxia-ischemia

The interaction between apoptosis-inducing factor (AIF) and cyclophilin A (CypA) has been shown to contribute to caspase-independent apoptosis. Blocking the AIF/CypA interaction protects against glutamate-induced neuronal cell death in vitro, and the purpose of this study was to determine the in vivo effect of an AIF/CypA interaction blocking peptide (AIF(370-394)-TAT) on neonatal mouse brain injury after hypoxia-ischemia (HI). The pups were treated with AIF (370-394)-TAT peptide intranasally prior to HI. Brain injury was significantly reduced at 72 h after HI in the AIF(370-394)-TAT peptide treatment group compared to vehicle-only treatment for both the gray matter and the subcortical white matter, and the neuroprotection was more pronounced in males than in females. Neuronal cell death was evaluated in males at 8 h and 24 h post-HI, and it was decreased significantly in the CA1 region of the hippocampus and the nucleus habenularis region after AIF(370-394)-TAT treatment. Caspase-independent apoptosis was decreased in the cortex, striatum, and nucleus habenularis after AIF(370-394)-TAT treatment, but no significant change was found on caspase-dependent apoptosis as indicated by the number of active caspase-3-labeled cells. Further analysis showed that both AIF and CypA nuclear accumulation were decreased after treatment with the AIF(370-394)-TAT peptide. These results suggest that AIF(370-394)-TAT inhibited AIF/CypA translocation to the nucleus and reduced HI-induced caspase-independent apoptosis and brain injury in young male mice, suggesting that blocking AIF/CypA might be a potential therapeutic target for neonatal brain injury.

Transfer of mitochondria from mesenchymal stem cells derived from induced pluripotent stem cells attenuates hypoxia-ischemia-induced mitochondrial dysfunction in PC12 cells

Mitochondrial dysfunction in neurons has been implicated in hypoxia-ischemia-induced brain injury. Although mesenchymal stem cell therapy has emerged as a novel treatment for this pathology, the mechanisms are not fully understood. To address this issue, we first co-cultured 1.5 × 10⁵ PC12 cells with mesenchymal stem cells that were derived from induced pluripotent stem cells at a ratio of 1:1, and then intervened with cobalt chloride (CoCl₂) for 24 hours. Reactive oxygen species in PC12 cells was measured by Mito-sox. Mitochondrial membrane potential (?Ψm) in PC12 cells was determined by JC-1 staining. Apoptosis of PC12 cells was detected by terminal deoxynucleotidal transferase-mediated dUTP nick end-labeling staining. Mitochondrial morphology in PC12 cells was examined by transmission electron microscopy. Transfer of mitochondria from the mesenchymal stem cells derived from induced pluripotent stem cells to damaged PC12 cells was measured by flow cytometry. Mesenchymal stem cells were induced from pluripotent stem cells by lentivirus infection containing green fluorescent protein in mitochondria. Then they were co-cultured with PC12 cells in Transwell chambers and treated with CoCl₂ for 24 hours to detect adenosine triphosphate level in PC12 cells. CoCl₂-induced PC12 cell damage was dose-dependent. Co-culture with mesenchymal stem cells significantly reduced apoptosis and restored ?Ψm in the injured PC12 cells under CoCl₂ challenge. Co-culture with mesenchymal stem cells ameliorated mitochondrial swelling, the disappearance of cristae, and chromatin margination in the injured PC12 cells. After direct co-culture, mitochondrial transfer from the mesenchymal stem cells stem cells to PC12 cells was detected via formed tunneling nanotubes between these two types of cells. The transfer efficiency was greatly enhanced in the presence of CoCl₂. More importantly, inhibition of tunneling nanotubes partially abrogated the beneficial effects of mesenchymal stem cells on CoCl₂-induced PC12 cell injury. Mesenchymal stem cells reduced CoCl₂-induced PC12 cell injury and these effects were in part due to efficacious mitochondrial transfer.

AIF meets the CHCHD4/Mia40-dependent mitochondrial import pathway

In the mitochondria of healthy cells, Apoptosis-Inducing factor (AIF) is required for the optimal functioning of the respiratory chain machinery, mitochondrial integrity, cell survival, and proliferation. In all analysed species, it was revealed that the downregulation or depletion of AIF provokes mainly the post-transcriptional loss of respiratory chain Complex I protein subunits. Recent progress in the field has revealed that AIF fulfils its mitochondrial pro-survival function by interacting physically and functionally with CHCHD4, the evolutionarily-conserved human homolog of yeast Mia40. The redox-regulated CHCHD4/Mia40-dependent import machinery operates in the intermembrane space of the mitochondrion and controls the import of a set of nuclear-encoded cysteine-motif carrying protein substrates. In addition to their participation in the biogenesis of specific respiratory chain protein subunits, CHCHD4/Mia40 substrates are also implicated in the control of redox regulation, antioxidant response, translation, lipid homeostasis and mitochondrial ultrastructure and dynamics. Here, we discuss recent insights on the AIF/CHCHD4-dependent protein import pathway and review current data concerning the CHCHD4/Mia40 protein substrates in metazoan. Recent findings and the identification of disease-associated mutations in AIF or in specific CHCHD4/Mia40 substrates have highlighted these proteins as potential therapeutic targets in a variety of human disorders.

Astragaloside IV alleviates ischemia reperfusion-induced apoptosis by inhibiting the activation of key factors in death receptor pathway and mitochondrial pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Apoptosis plays an important role in cerebral ischemia-reperfusion injury and triggers a series of pathological changes which may even be life-threatening. Astragaloside-IV (AS-IV), a natural compound extracted from Astragalus (Astragalus membranaceus (Fisch.) Bunge., Leguminosae, Huangqi in Chinese), showed neuroprotective effects in the study of cerebral ischemia-reperfusion injury. In this study we investigate the effects of AS-IV on apoptosis induced by transient cerebral ischemia and reperfusion in rats, as well as the associated regulatory factors.

METHODS

AS-IV was administrated to male Sprague-Dawley (SD) rats after transient cerebral ischemia and reperfusion surgery (12.5, 25, and 50 mg/kg, once per day, continued for 7 days after surgey). After seven days of continuous administration, neurological function, cerebral infarction volume, and pathological changes of brain tissue were detected. Fas, FasL, Caspase-8, Bax, and Bcl-2 mRNA levels were determined by real-time PCR. Caspase-8, Bid, Cytochrome C (Cyto C), cleaved Caspase-3 proteins were determined by western blot and immunohistochemistry was used to quantify Cyto C.

RESULTS

AS-IV significantly attenuated the neurological deficit in rats with ischemica-reperfusion injury, and reduced cerebral infarction and neuronal apoptosis. AS-IV inhibited the mRNA upregulation of Fas, FasL, Caspase-8, and Bax/Bcl-2. Furthermore, the protein level of apoptosis cytokines Caspase-8, Bid, cleaved Caspase-3 and Cyto C were also inhibited after ischemia reperfusion, suggesting that AS-IV might alleviate ischemia reperfusion-induced apoptosis by inhibiting the activation of key factors in death receptor pathway and mitochondrial pathway.

Overexpression of apoptosis inducing factor aggravates hypoxic-ischemic brain injury in neonatal mice

Apoptosis inducing factor (AIF) has been shown to be a major contributor to neuron loss in the immature brain after hypoxia-ischemia (HI). Indeed, mice bearing a hypomorphic mutation causing reduced AIF expression are protected against neonatal HI. To further investigate the possible molecular mechanisms of this neuroprotection, we generated an AIF knock-in mouse by introduction of a latent transgene coding for flagged AIF protein into the Rosa26 locus, followed by its conditional activation by a ubiquitously expressed Cre recombinase. Such AIF transgenic mice overexpress the pro-apoptotic splice variant of AIF (AIF1) at both the mRNA (5.9 times higher) and protein level (2.4 times higher), but not the brain-specific AIF splice-isoform (AIF2). Excessive AIF did not have any apparent effects on the phenotype or physiological functions of the mice. However, brain injury (both gray and white matter) after neonatal HI was exacerbated in mice overexpressing AIF, coupled to enhanced translocation of mitochondrial AIF to the nucleus as well as enhanced caspase-3 activation in some brain regions, as indicated by immunohistochemistry. Altogether, these findings corroborate earlier studies demonstrating that AIF plays a causal role in neonatal HI brain injury.

Neuroprotective effects of irisin against cerebral ischemia/ reperfusion injury via Notch signaling pathway

Irisin, a 112-amino acid peptide induced with exercise in mice and human is thought to have correlation with the short-term outcomes of patients in ischemic stroke. In the present study, the neuroprotective effects of irisin were evaluated in vivo and in vitro and its underlying mechanism was also explored. The global cerebral ischemia/reperfusion (I/R) model was established by bilateral common carotid artery occlusion for 20 min and reperfusion for 24 h in mice and oxygen-glucose deprivation/reperfusion in HT22 cells. Neurological function was scored and then the mice were sacrificed. The brains were harvested for HE staining and detection of brain water content (BWC). The percentage of neuronal apoptosis was evaluated by TUNEL and flow cytometry analysis. The mRNA expression of TNF-α and IL-1β was detected by RT-PCR analysis. The Notch intracellular domain (NICD) was detected by double immunofluorescence staining and western blot, and the protein expression of Notch1 and Hes 1 was detected by western blot. It was observed that irisin could alleviate morphological damage and improve neurological function after global cerebral I/R injury in mice. The apoptosis of hippocampal neurons reduced in the presence of irisin in vivo and in vitro. Additionally irisin could downregulate the expression of IL-1β and TNF-α and upregulate the expression of NICD, Notch1 and Hes 1 in vitro and in vivo. After the application of γ-secretase inhibitor DAPT, all the morphological, neurological and biochemical changes were reversed. Taken together, these results suggest that irisin could regulate the Notch signaling pathway that leads to the alleviation of transient global cerebral I/R injury.

Sex differences in neonatal mouse brain injury after hypoxia-ischemia and adaptaquin treatment

Hypoxia-inducible factor prolyl 4-hydroxylases (HIF-PHDs) are important targets against oxidative stress. We hypothesized that inhibition HIF-PHD by adaptaquin reduces hypoxic-ischemic brain injury in a neonatal mouse model. The pups were treated intraperitoneally immediately with adaptaquin after hypoxia-ischemia (HI) and then every 24 h for 3 days. Adaptaquin treatment reduced infarction volume by an average of 26.3% at 72 h after HI compared to vehicle alone, and this reduction was more pronounced in males (34.8%) than in females (11.7%). The protection was also more pronounced in the cortex. The subcortical white matter injury as measured by tissue loss volume was reduced by 24.4% in the adaptaquin treatment group, and this reduction was also more pronounced in males (28.4%) than in females (18.9%). Cell death was decreased in the cortex as indicated by Fluoro-Jade labeling, but not in other brain regions with adaptaquin treatment. Furthermore, in the brain injury area, adaptaquin did not alter the number of cells positive for caspase-3 activation or translocation of apoptosis-inducing factor to the nuclei. Adaptaquin treatment increased glutathione peroxidase 4 mRNA expression in the cortex but had no impact on 3-nitrotyrosine, 8-hydroxy-2 deoxyguanosine, or malondialdehyde production. Hif1α mRNA expression increased after HI, and adaptaquin treatment also stimulated Hif1α mRNA expression, which was also more pronounced in males than in females. However, nuclear translocation of HIF1α protein was decreased after HI, and adaptaquin treatment had no influence on HIF1α expression in the nucleus. These findings demonstrate that adaptaquin treatment is neuroprotective, but the potential mechanisms need further investigation. Read the Editorial Highlight for this article on page 645.