Inhibition of VDAC1 Protects Against Glutamate-Induced Oxytosis and Mitochondrial Fragmentation in Hippocampal HT22 Cells

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.

A critical appraisal of ferroptosis in Alzheimer's and Parkinson's disease: new insights into emerging mechanisms and therapeutic targets

Neurodegenerative diseases represent a pressing global health challenge, and the identification of novel mechanisms underlying their pathogenesis is of utmost importance. Ferroptosis, a non-apoptotic form of regulated cell death characterized by iron-dependent lipid peroxidation, has emerged as a pivotal player in the pathogenesis of neurodegenerative diseases. This review delves into the discovery of ferroptosis, the critical players involved, and their intricate role in the underlying mechanisms of neurodegeneration, with an emphasis on Alzheimer's and Parkinson's diseases. We critically appraise unsolved mechanistic links involved in the initiation and propagation of ferroptosis, such as a signaling cascade resulting in the de-repression of lipoxygenase translation and the role played by mitochondrial voltage-dependent anionic channels in iron homeostasis. Particular attention is given to the dual role of heme oxygenase in ferroptosis, which may be linked to the non-specific activity of P450 reductase in the endoplasmic reticulum. Despite the limited knowledge of ferroptosis initiation and progression in neurodegeneration, Nrf2/Bach1 target genes have emerged as crucial defenders in anti-ferroptotic pathways. The activation of Nrf2 and the inhibition of Bach1 can counteract ferroptosis and present a promising avenue for future therapeutic interventions targeting ferroptosis in neurodegenerative diseases.

GRP75-dependent mitochondria-ER contacts ensure cell survival during early mouse thymocyte development

Mitochondria and endoplasmic reticulum contacts (MERCs) control multiple cellular processes, including cell survival and differentiation. Based on the observations that MERCs were specifically enriched in the CD4-CD8- double-negative (DN) stage, we studied their role in early mouse thymocyte development. We found that T cell-specific knockout of Hspa9, which encodes GRP75, a protein that mediates MERC formation by assembling the IP3R-GRP75-VDAC complex, impaired DN3 thymocyte viability and resulted in thymocyte developmental arrest at the DN3-DN4 transition. Mechanistically, GRP75 deficiency induced mitochondrial stress, releasing mitochondrial DNA (mtDNA) into the cytosol and triggering the type I interferon (IFN-I) response. The IFN-I pathway contributed to both the impairment of cell survival and DN3-DN4 transition blockage, while increased lipid peroxidation (LPO) played a major role downstream of IFN-I. Thus, our study identifies the essential role of GRP75-dependent MERCs in early thymocyte development and the governing facts of cell survival and differentiation in the DN stage.

Pore-Forming VDAC Proteins of the Outer Mitochondrial Membrane: Regulation and Pathophysiological Role

Voltage-dependent anion channels (VDAC1-3) of the outer mitochondrial membrane are a family of pore-forming β-barrel proteins that carry out controlled "filtration" of small molecules and ions between the cytoplasm and mitochondria. Due to the conformational transitions between the closed and open states and interaction with cytoplasmic and mitochondrial proteins, VDACs not only regulate the mitochondrial membrane permeability for major metabolites and ions, but also participate in the control of essential intracellular processes and pathological conditions. This review discusses novel data on the molecular structure, regulatory mechanisms, and pathophysiological role of VDAC proteins, as well as future directions in this area of research.

Resveratrol Inhibits VDAC1-Mediated Mitochondrial Dysfunction to Mitigate Pathological Progression in Parkinson's Disease Model

An increase in α-synuclein (α-syn) levels and mutations in proteins associated with mitochondria contribute to the development of familial Parkinson's disease (PD); however, the involvement of α-syn and mitochondria in idiopathic PD remains incompletely understood. The voltage-dependent anion channel I (VDAC1) protein, which serves as a crucial regulator of mitochondrial function and a gatekeeper, plays a pivotal role in governing cellular destiny through the control of ion and respiratory metabolite flux. The ability of resveratrol (RES), which is a potent phytoalexin with antioxidant and anti-inflammatory properties, to regulate VDAC1 in PD is unknown. The objective of this study was to evaluate the role of VDAC1 in the pathological process of PD and to explore the mechanism by which resveratrol protects dopaminergic neurons by regulating VDAC1 to maintain the mitochondrial permeability transition pore (mPTP) and calcium ion balance. The effects of RES on the motor and cognitive abilities of A53T mice were evaluated by using small animal behavioral tests. Various techniques, including immunofluorescence staining, transmission electron microscopy, enzyme-linked immunoadsorption, quantitative polymerase chain reaction (PCR), and Western blotting, among others, were employed to assess the therapeutic impact of RES on neuropathy associated with PD and its potential in regulating mitochondrial VDAC1. The findings showed that RES significantly improved motor and cognitive dysfunction and restored mitochondrial function, thus reducing oxidative stress levels in A53T mice. A significant positive correlation was observed between the protein expression level of VDAC1 and mitochondrial α-syn expression, as well as disease progression, whereas no such correlation was found in VDAC2 and VDAC3. Administration of RES resulted in a significant decrease in the protein expression of VDAC1 and in the protein expression of α-syn both in vivo and in vitro. In addition, we found that RES prevents excessive opening of the mPTP in dopaminergic neurons. This may prevent the abnormal aggregation of α-syn in mitochondria and the release of mitochondrial apoptosis signals. Furthermore, the activation of VDAC1 reversed the resveratrol-induced decrease in the accumulation of α-syn in the mitochondria. These findings highlight the potential of VDAC1 as a therapeutic target for PD and identify the mechanism by which resveratrol alleviates PD-related pathology by modulating mitochondrial VDAC1.

Dibutyl phthalate exposure induced mitochondria-dependent ferroptosis by enhancing VDAC2 in zebrafish ZF4 cells

Dibutyl phthalate (DBP) contamination has raised global concern for decades, while its health risk with toxic mechanisms requires further elaboration. This study used zebrafish ZF4 cells to investigate the toxicity of ferroptosis with underlying mechanisms in response to DBP exposure. Results showed that DBP induced ferroptosis, characterized by accumulation of ferrous iron, lipid peroxidation, and decrease of glutathione peroxidase 4 levels in a time-dependent manner, subsequently reduced cell viability. Transcriptome analysis revealed that voltage-dependent anion-selective channel (VDAC) in mitochondrial outer membrane was upregulated in ferroptosis signaling pathways. Protecting mitochondria with a VDAC2 inhibitor or siRNAs attenuated the accumulation of mitochondrial superoxide and lipid peroxides, the opening of mitochondrial permeability transition pore (mPTP), and the overload of iron levels, suggesting VDAC2 oligomerization mediated the influx of iron into mitochondria that is predominant and responsible for mitochondria-dependent ferroptosis under DBP exposure. Furthermore, the pivotal role of activating transcription factor 4 (ATF4) was identified in the transcriptional regulation of vdac2 by ChIP assay. And the intervention of atf4b inhibited DBP-induced VDAC2 upregulation and oligomerization. Taken together, this study reveals that ATF4-VDAC2 signaling pathway is involved in the DBP-induced ferroptosis in zebrafish ZF4 cells, contributing to the in-depth understanding of biotoxicity and the ecological risk assessment of phthalates.

Mapping the Research of Ferroptosis in Parkinson's Disease from 2013 to 2023: A Scientometric Review

Methods

Related studies on PD and ferroptosis were searched in Web of Science Core Collection (WOSCC) from inception to 2023. VOSviewer, CiteSpace, RStudio, and Scimago Graphica were employed as bibliometric analysis tools to generate network maps about the collaborations between authors, countries, and institutions and to visualize the co-occurrence and trends of co-cited references and keywords.

Results

A total of 160 original articles and reviews related to PD and ferroptosis were retrieved, produced by from 958 authors from 162 institutions. Devos David was the most prolific author, with 9 articles. China and the University of Melbourne had leading positions in publication volume with 84 and 12 publications, respectively. Current hot topics focus on excavating potential new targets for treating PD based on ferroptosis by gaining insight into specific molecular mechanisms, including iron metabolism disorders, lipid peroxidation, and imbalanced antioxidant regulation. Clinical studies aimed at treating PD by targeting ferroptosis remain in their preliminary stages.

Conclusion

A continued increase was shown in the literature within the related field over the past decade. The current study suggested active collaborations among authors, countries, and institutions. Research into the pathogenesis and treatment of PD based on ferroptosis has remained a prominent topic in the field in recent years, indicating that ferroptosis-targeted therapy is a potential approach to halting the progression of PD.

Mitochondrial iron dyshomeostasis and its potential as a therapeutic target for Parkinson's disease

Abnormal iron accumulation has been implicated in the etiology of Parkinson's disease (PD). Understanding how iron damages dopaminergic neurons in the substantia nigra (SN) of PD is particularly important for developing targeted neurotherapeutic strategies for the disease. However, it is still not fully understood how excess iron contributes to the neurodegeneration of dopaminergic neurons in PD. There has been increased attention on mitochondrial iron dyshomeostasis, iron-induced mitochondrial dysfunction and ferroptosis in PD. Therefore, this review begins with a brief introduction to describe cellular iron metabolism and the dysregulation of iron metabolism in PD. Then we provide an update on how iron is delivered to mitochondria and induces the damage of dopaminergic neurons in PD. In addition, we also summarize new research progress on iron-dependent ferroptosis in PD and mitochondria-localized proteins involved in ferroptosis. This will provide new insight into potential therapeutic strategies targeting mitochondrial iron dysfunction.

Tanshinone IIA confers protection against myocardial ischemia/reperfusion injury by inhibiting ferroptosis and apoptosis via VDAC1

Tanshinone IIA (TSN) extracted from danshen (Salvia miltiorrhiza) could protect cardiomyocytes against myocardial ischemia/reperfusion injury (IRI), however the underlying molecular mechanisms of action remain unclear. The aim of the present study was to identify the protective effects of TSN and its mechanisms of action through in vitro studies. An anoxia/reoxygenation (A/R) injury model was established using H9c2 cells to simulate myocardial IRI in vitro. Before A/R, H9c2 cardiomyoblasts were pretreated with 8 µM TSN or 10 µM ferrostatin‑1 (Fer‑1) or erastin. The cell counting kit 8 (CCK‑8) and lactate dehydrogenase (LDH) assay kit were used to detect the cell viability and cytotoxicity. The levels of total iron, glutathione (GSH), glutathione disulfide (GSSG), malondialdehyde (MDA), ferrous iron, caspase‑3 activity, and reactive oxygen species (ROS) were assessed using commercial kit. The levels of mitochondrial membrane potential (MMP), lipid ROS, cell apoptosis, and mitochondrial permeability transition pore (mPTP) opening were detected by flow cytometry. Transmission electron microscopy (TEM) was used to observed the mitochondrial damage. Protein levels were detected by western blot analysis. The interaction between TSN and voltage‑dependent anion channel 1 (VDAC1) was evaluated by molecular docking simulation. The results showed that pretreatment with TSN and Fer‑1 significantly decreased cell viability, glutathione peroxidase 4 (GPX4) protein and GSH expression and GSH/GSSG ratio and inhibited upregulation of LDH activity, prostaglandin endoperoxide synthase 2 and VDAC1 protein expression, ROS levels, mitochondrial injury and GSSG induced by A/R. TSN also effectively inhibited the damaging effects of erastin treatment. Additionally, TSN increased MMP and Bcl‑2/Bax ratio, while decreasing levels of apoptotic cells, activating Caspase‑3 and closing the mPTP. These effects were blocked by VDAC1 overexpression and the results of molecular docking simulation studies revealed a direct interaction between TSN and VDAC1. In conclusion, TSN pretreatment effectively attenuated H9c2 cardiomyocyte damage in an A/R injury model and VDAC1‑mediated ferroptosis and apoptosis served a vital role in the protective effects of TSN.

FDX1 regulates leydig cell ferroptosis mediates PM2.5-induced testicular dysfunction of mice

Epidemiological studies have established an association between chronic exposure to PM2.5 and male infertility. However, the underlying mechanisms were not fully revealed. In this study, we established mice models exposed to PM2.5 for 16 weeks, and a significant decrease in sperm quality accompanied by an increase in testosterone levels were observed after PM2.5 exposure. Moreover, treatment with ferrostatin-1 (Fer-1), a specific ferroptosis inhibitor, effectively mitigated PM2.5-induced testicular dysfunction in mice. And lipid peroxidation and ferritin accumulation were found to be significantly increased in Leydig cells of testes with a PM2.5-dose dependent manner. Further investigations revealed that TM-3 cells, a mouse Leydig cell line, were prone to ferroptosis after PM2.5 exposure, and the cell viability was partly rescued after the intervention of Fer-1. Furthermore, our results supported that the ferroptosis of TM-3 cells was attributed to the upregulation of ferredoxin 1 (FDX1), which was the protein transferring electrons to cytochrome P450 family 11 subfamily A member 1 to aid lysing cholesterol to pregnenolone at initial of steroidogenesis. Mechanically, PM2.5-induced FDX1 upregulation resulted in cellular ROS elevation and ferrous iron overload, which together initiated an autoxidation process of polyunsaturated fatty acids in the cell membrane of Leydig cells until the accumulated lipid peroxides triggered ferroptotic cell death. Simultaneously, upregulation of FDX1 promoted steroidogenesis and let to an increased level of testosterone. In summary, our work suggested that FDX1, a mediator involving steroidogenesis, was a key regulator in PM2.5-induced Leydig cells ferroptosis.

Trastuzumab-induced cardiomyopathy via ferroptosis-mediated mitochondrial dysfunction

Trastuzumab (TRZ) is a first-line chemotherapeutic agent for HER-2 (ErbB2)-positive breast cancer. Unfortunately, its clinical use is limited due to its cardiotoxicity, referred to as TRZ-induced cardiotoxicity (TIC). However, the exact molecular mechanisms underlying the development of TIC remain unclear. Iron and lipid metabolism and redox reactions participate in the development of ferroptosis. Here, we show that ferroptosis-mediated mitochondrial dysfunction is involved in TIC in vivo and in vitro. We first established TIC models with BALB/c mice or neonatal rat cardiomyocytes and confirmed cardiomyopathy with echocardiography and inhibition of cell viability with a cell counting kit-8 examination, respectively. We showed that TRZ downregulated glutathione peroxidase 4 (GPx4) and elevated lipid peroxidation by-products, 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA), by inactivating the ErbB2/PI3K/AKT/Nrf2 signalling pathway. Additionally, upregulated mitochondrial 4-HNE binds to voltage-dependent anion channel 1 (VDAC1), increases VDAC1 oligomerization, and subsequently induces mitochondrial dysfunction, as evidenced by mitochondrial permeability transition pore (mPTP) opening and decreased mitochondrial membrane potential (MMP) and ATP levels. Concomitantly, TRZ affected the mitochondrial levels of GSH/GSSG and iron ions and the stability of mitoGPx4. Ferroptosis inhibitors, such as ferrostatin-1 (Fer-1) or the iron chelator deferoxamine (DFO), ameliorate TRZ-induced cardiomyopathy. Overexpression of mitoGPx4 also suppressed mitochondrial lipid peroxidation and prevented TRZ-induced ferroptosis. Our study strongly suggests that targeting ferroptosis-mediated mitochondrial dysfunction is a potential cardioprotective strategy.

MIRO-1 interacts with VDAC-1 to regulate mitochondrial membrane potential in Caenorhabditis elegans

Precise regulation of mitochondrial fusion and fission is essential for cellular activity and animal development. Imbalances between these processes can lead to fragmentation and loss of normal membrane potential in individual mitochondria. In this study, we show that MIRO-1 is stochastically elevated in individual fragmented mitochondria and is required for maintaining mitochondrial membrane potential. We further observe a higher level of membrane potential in fragmented mitochondria in fzo-1 mutants and wounded animals. Moreover, MIRO-1 interacts with VDAC-1, a crucial mitochondrial ion channel located in the outer mitochondrial membrane, and this interaction depends on the residues E473 of MIRO-1 and K163 of VDAC-1. The E473G point mutation disrupts their interaction, resulting in a reduction of the mitochondrial membrane potential. Our findings suggest that MIRO-1 regulates membrane potential and maintains mitochondrial activity and animal health by interacting with VDAC-1. This study provides insight into the mechanisms underlying the stochastic maintenance of membrane potential in fragmented mitochondria.

Inhibition of extranodal NK/T-cell lymphoma by Chiauranib through an AIF-dependent pathway and its synergy with L-asparaginase

Extranodal NK/T-cell lymphoma (NKTL) is a rare and aggressive form of extranodal lymphoma with a poor prognosis. Currently, there are very limited treatment options for patients with advanced-stage disease or those with relapsed/recurrent disease. Here we show that Chiauranib, an orally small molecule inhibitor of select serine-threonine kinases (aurora B, VEGFRs, PDGFR, CSF1R, c-Kit), inhibited NKTL cell proliferation, induced cell cycle arrest, as well as suppressed the microvessel density in vitro and in vivo similar as in other types of cancer cells. Surprisingly, Chiauranib unfolded a new effect to induce apoptosis of NKTL cells by triggering AIF-dependent apoptosis other than the traditional cyt-c/caspase mitochondrial apoptosis pathway. The knockdown of AIF in vitro and in vivo dramatically blocked the efficacy of Chiauranib on NKTL. Mechanistically, the release of AIF from mitochondria is due to the upregulation of VDAC1 by the AKT-GSK3β pathway and activation of calcium-dependent m-calpain, which promotes the cleavage of VDAC1 and therefore permits the release of AIF. Notably, the low expression of Bax in both NKTL cells and patient tissues restrained the cyt-c release. It resulted in the inhibition of cyt-c/caspase mitochondrial pathway, suggesting that drugs targeting this traditional pathway may not be effective in NKTL. Furthermore, we found that L-asparaginase triggered CD95 (Fas/Apo-1)-caspase 8-caspase 3 apoptotic pathway in NKTL cells, and combination of Chiauranib and L-asparaginase exhibited a synergistic effect, suggesting a feasibility to combine these two drugs for effective treatment of NKTL. This study demonstrates Chiauranib's positive efficacy toward NKTL through the activation of the AIF-dependent apoptosis pathway for the first time. The novel and multi-targets of Chiauranib and the synergistic effect with L-asparaginase may provide a promising therapy for NKTL patients.

Activated AMPK-mediated glucose uptake and mitochondrial dysfunction is critically involved in the glutamate-induced oxidative injury in HT22 cell

BACKGROUND

Accumulation of glutamate damages neurons via the reactive oxygen species (ROS) injury, which was involved in the development of neurodegenerative diseases. However, the mechanism of neuronal oxidative stress damage caused by glutamate and the intervention targets still needs to be further studied. This study explored whether 5' adenosine monophosphate-activated protein kinase (AMPK)-induced glucose metabolic and mitochondrial dysfunction were related to glutamate-dependent ROS injury of the neuron.

METHODS

Neuronal oxidative stress injury was induced by glutamate treatment in HT-22 cells. Western blotting was used to evaluate the phosphorylation of the AMPK. The XF24 Flux Analyzer was used to measure the effect of glutamate and Compound C (a well-known pharmacological inhibitor of AMPK phosphorylation) on the cellular oxygen consumption rate (OCR) of HT-22 cells. Glucose uptake, intracellular ROS, mitochondrial potential, apoptosis and cell viability were quantified using biochemical assays.

RESULTS

Glutamate caused the phosphorylation of AMPK and subsequently promoted the glucose uptake. Furthermore, AMPK-mediated glucose uptake enhanced OCR and increased the intracellular ROS levels in neurons. The pharmacological inhibition of AMPK phosphorylation by Compound C attenuated glutamate-induced toxicity in HT22 cells by regulating the glucose uptake/mitochondrial respiration/ROS pathway.

CONCLUSIONS

The AMPK phosphorylation/glucose uptake/mitochondrial respiration/ROS pathway was involved in glutamate-induced excitotoxic injury in HT22 cells. The inhibition of AMPK phosphorylation may be a potential target for the development of therapeutic agents for treating the glutamate-induced neurotoxicity.

Inhibition of VDAC1 Rescues Aβ 1-42-Induced Mitochondrial Dysfunction and Ferroptosis via Activation of AMPK and Wnt/β-Catenin Pathways

Beta-amyloid (Aβ) accumulation in the brains of Alzheimer's disease (AD) patients leads to mitochondrial dysfunction and ferroptosis in neurons. Voltage-dependent anion channel 1 (VDAC1) is a major protein in the mitochondrial outer membrane. It has been reported that VDAC1 associated with mitochondrial dysfunction and ferroptosis. However, the mechanism by which VDAC1 regulates mitochondrial dysfunction and ferroptosis of neurons in AD remains unclear. This study is aimed at investigating the mechanism of action of VDAC1 in mitochondrial dysfunction and ferroptosis in neurons of the AD model. In this study, we determined cell viability after treatment with Aβ _1-42 via the MTT assay. The SOD, MDA, ROS, and MMP production was measured via the SOD kit, MDA kit, DCFDA staining, and JC-1 staining. The memory abilities of mice were detected via the Morris water maze test. The expression of AMPK/mTOR, Wnt/β-catenin, and GPX4 regulated by VDAC1 was detected via western blotting. Our present study showed that PC12 cells had decreased cell viability, increased LDH release, and decreased GPX4 expression after Aβ _1-42 treatment. Meanwhile, Aβ _1-42 induced MMP and SOD downregulation and increased MDA and ROS generation in PC12 cells. In addition, the expression of VDAC1 is increased in the brain tissue of AD mice and Aβ _1-42-treated PC12 cells. Further investigation of the role of VDAC1 in regulating AD found that all effects induced by Aβ _1-42 were reversed by inhibition of VDAC1. Additionally, inhibition of VDAC1 activates the AMPK/mTOR and Wnt/β-catenin pathways. Taken together, these findings demonstrate that inhibition of VDAC1 alleviates mitochondrial dysfunction and ferroptosis in AD neurons by activating AMPK/mTOR and Wnt/β-catenin.

Site-specific ubiquitination of VDAC1 restricts its oligomerization and mitochondrial DNA release in liver fibrosis

Mitochondrial DNA (mtDNA) released through protein oligomers, such as voltage-dependent anion channel 1 (VDAC1), triggers innate immune activation and thus contributes to liver fibrosis. Here, we investigated the role of Parkin, an important regulator of mitochondria, and its regulation of VDAC1-mediated mtDNA release in liver fibrosis. The circulating mitochondrial DNA (mtDNA) and protein levels of liver Parkin and VDAC1 were upregulated in patients with liver fibrosis. A 4-week CCl₄ challenge induced release of mtDNA, activation of STING signaling, a decline in autophagy, and apoptosis in mouse livers, and the knockout of Parkin aggravated these effects. In addition, Parkin reduced mtDNA release and prevented VDAC1 oligomerization in a manner dependent on its E3 activity in hepatocytes. We found that site-specific ubiquitination of VDAC1 at lysine 53 by Parkin interrupted VDAC1 oligomerization and prevented mtDNA release into the cytoplasm under stress. The ubiquitination-defective VDAC1 K53R mutant predominantly formed oligomers that resisted suppression by Parkin. Hepatocytes expressing VDAC1 K53R exhibited mtDNA release and thus activated the STING signaling pathway in hepatic stellate cells, and this effect could not be abolished by Parkin. We propose that the ubiquitination of VDAC1 at a specific site by Parkin confers protection against liver fibrosis by interrupting VDAC1 oligomerization and mtDNA release.

The E3 ubiquitin ligase NEDD4-1 protects against acetaminophen-induced liver injury by targeting VDAC1 for degradation

Acetaminophen (APAP) overdose is a major cause of liver injury. Neural precursor cell expressed developmentally downregulated 4-1 (NEDD4-1) is an E3 ubiquitin ligase that has been implicated in the pathogenesis of numerous liver diseases; however, its role in APAP-induced liver injury (AILI) is unclear. Thus, this study aimed to investigate the role of NEDD4-1 in the pathogenesis of AILI. We found that NEDD4-1 was dramatically downregulated in response to APAP treatment in mouse livers and isolated mouse hepatocytes. Hepatocyte-specific NEDD4-1 knockout exacerbated APAP-induced mitochondrial damage and the resultant hepatocyte necrosis and liver injury, while hepatocyte-specific NEDD4-1 overexpression mitigated these pathological events both in vivo and in vitro. Additionally, hepatocyte NEDD4-1 deficiency led to marked accumulation of voltage-dependent anion channel 1 (VDAC1) and increased VDAC1 oligomerization. Furthermore, VDAC1 knockdown alleviated AILI and weakened the exacerbation of AILI caused by hepatocyte NEDD4-1 deficiency. Mechanistically, NEDD4-1 was found to interact with the PPTY motif of VDAC1 through its WW domain and regulate K48-linked ubiquitination and degradation of VDAC1. Our present study indicates that NEDD4-1 is a suppressor of AILI and functions by regulating the degradation of VDAC1.

Mitochondrial event as an ultimate step in ferroptosis

In ferroptosis, the roles of mitochondria have been controversial. To explore the role of mitochondrial events in ferroptosis, we employed mitochondrial DNA-depleted ρ⁰ cells that are resistant to cell death due to enhanced expression of antioxidant enzymes. Expression of mitochondrial-type GPx4 (mGPx4) but no other forms of GPx4 was increased in SK-Hep1 ρ⁰ cells. Likely due to high mGPx4 expression, SK-Hep1 ρ⁰ cells were resistant to ferroptosis by erastin inhibiting xCT channel. In contrast, SK-Hep1 ρ⁰ cells were susceptible to cell death by a high concentration of RSL3 imposing ferroptosis by GPx4 inhibition. Accumulation of cellular ROS and oxidized lipids was observed in erastin- or RSL3-treated SK-Hep1 ρ⁺ cells but not in erastin-treated SK-Hep1 ρ⁰ cells. Mitochondrial ROS and mitochondrial peroxidized lipids accumulated in SK-Hep1 ρ⁺ cells not only by RSL3 but also by erastin acting on xCT on the plasma membrane. Mitochondrial ROS quenching inhibited SK-Hep1 ρ⁺ cell death by erastin or a high dose of RSL3, suggesting a critical role of mitochondrial ROS in ferroptosis. Ferroptosis by erastin or RSL3 was inhibited by a more than 20-fold lower concentration of MitoQ, a mitochondrial ROS quencher, compared to DecylQ, a non-targeting counterpart. Ferroptosis of SK-Hep1 ρ⁺ cells by erastin or RSL3 was markedly inhibited by a VDAC inhibitor, accompanied by significantly reduced accumulation of mitochondria ROS, total peroxidized lipids, and mitochondrial peroxidized lipids, strongly supporting the role of mitochondrial events in ferroptotic death and that of VDAC in mitochondrial steps of ferroptosis induced by erastin or RSL3. SK-Hep1 ρ⁺ cell ferroptosis by sorafenib was also suppressed by mitochondrial ROS quenchers, accompanied by abrogation of sorafenib-induced mitochondrial ROS and mitochondrial peroxidized lipid accumulation. These results suggest that SK-Hep1 ρ⁰ cells are resistant to ferroptosis due to upregulation of mGPx4 expression and mitochondrial events could be the ultimate step in determining final cell fate.

The Potential Role of Voltage-Dependent Anion Channel in the Treatment of Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative disease second only to Alzheimer’s disease in terms of prevalence. Previous studies have indicated that the occurrence and progression of PD are associated with mitochondrial dysfunction. Mitochondrial dysfunction is one of the most important causes for apoptosis of dopaminergic neurons. Therefore, maintaining the stability of mitochondrial functioning is a potential strategy in the treatment of PD. Voltage-dependent anion channel (VDAC) is the main component in the outer mitochondrial membrane, and it participates in a variety of biological processes. In this review, we focus on the potential roles of VDACs in the treatment of PD. We found that VDACs are involved in PD by regulating apoptosis, autophagy, and ferroptosis. VDAC1 oligomerization, VDACs ubiquitination, regulation of mitochondrial permeability transition pore (mPTP) by VDACs, and interaction between VDACs and α-synuclein (α-syn) are all promising methods for the treatment of PD. We proposed that inhibition of VDAC1 oligomerization and promotion of VDAC1 ubiquitination as an effective approach for the treatment of PD. Previous studies have proven that the expression of VDAC1 has a significant change in PD models. The expression levels of VDAC1 are decreased in the substantia nigra (SN) of patients suffering from PD compared with the control group consisting of normal individuals by using bioinformatics tools. VDAC2 is involved in PD mainly through the regulation of apoptosis. VDAC3 may have a similar function to VDAC1. It can be concluded that the functional roles of VDACs contribute to the therapeutic strategy of PD.

Impact of Calcium Influx on Endoplasmic Reticulum in Excitotoxic Neurons: Role of Chemical Chaperone 4-PBA

Excessive activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propoinic acid (AMPA) receptors instigates excitotoxicity via enhanced calcium influx in the neurons thus inciting deleterious consequences. Additionally, Endoplasmic Reticulum (ER) is pivotal in maintaining the intracellular calcium balance. Considering this, studying the aftermath of enhanced calcium uptake by neurons and its effect on ER environment can assist in delineating the pathophysiological events incurred by excitotoxicty. The current study was premeditated to decipher the role of ER pertaining to calcium homeostasis in AMPA-induced excitotoxicity. The findings showed, increased intracellular calcium levels (measured by flowcytometry and spectroflourimeter using Fura 2AM) in AMPA excitotoxic animals (male Sprague dawely rats) (intra-hippocampal injection of 10 mM AMPA). Further, ER resident proteins like calnexin, PDI and ERp72 were found to be upregulated, which further modulated the functioning of ER membrane calcium channels viz. IP3R, RyR, and SERCA pump. Altered calcium homeostasis further led to ER stress and deranged the protein folding capacity of ER post AMPA toxicity, which was ascertained by unfolded protein response (UPR) pathway markers such as IRE1α, eIF2α, and ATF6α. Chemical chaperone, 4-phenybutric acid (4-PBA), ameliorated the protein folding capacity and subsequent UPR markers. In addition, modulation of calcium channels and calcium regulating machinery of ER post 4-PBA administration restored the calcium homeostasis. Therefore the study reinforces the significance of ER stress, a debilitating outcome of impaired calcium homeostasis, under AMPA-induced excitotoxicity. Also, employing chaperone-based therapeutic approach to curb ER stress can restore the calcium imbalance in the neuropathological diseases.

Calcium Ions Aggravate Alzheimer's Disease Through the Aberrant Activation of Neuronal Networks, Leading to Synaptic and Cognitive Deficits

Alzheimer’s disease (AD) is a neurodegenerative disease that is characterized by the production and deposition of β-amyloid protein (Aβ) and hyperphosphorylated tau, leading to the formation of β-amyloid plaques (APs) and neurofibrillary tangles (NFTs). Although calcium ions (Ca²⁺) promote the formation of APs and NFTs, no systematic review of the mechanisms by which Ca²⁺ affects the development and progression of AD has been published. Therefore, the current review aimed to fill the gaps between elevated Ca²⁺ levels and the pathogenesis of AD. Specifically, we mainly focus on the molecular mechanisms by which Ca²⁺ affects the neuronal networks of neuroinflammation, neuronal injury, neurogenesis, neurotoxicity, neuroprotection, and autophagy. Furthermore, the roles of Ca²⁺ transporters located in the cell membrane, endoplasmic reticulum (ER), mitochondria and lysosome in mediating the effects of Ca²⁺ on activating neuronal networks that ultimately contribute to the development and progression of AD are discussed. Finally, the drug candidates derived from herbs used as food or seasoning in Chinese daily life are summarized to provide a theoretical basis for improving the clinical treatment of AD.

Protecting mitochondria via inhibiting VDAC1 oligomerization alleviates ferroptosis in acetaminophen-induced acute liver injury

Acetaminophen (APAP) overdose is a common cause of drug-induced liver injury (DILI). Ferroptosis has been recently implicated in APAP-induced liver injury (AILI). However, the functional role and underlying mechanisms of mitochondria in APAP-induced ferroptosis are unclear. In this study, the voltage-dependent anion channel (VDAC) oligomerization inhibitor VBIT-12 and ferroptosis inhibitors were injected via tail vein in APAP-injured mice. Targeted metabolomics and untargeted lipidomic analyses were utilized to explore underlying mechanisms of APAP-induced mitochondrial dysfunction and subsequent ferroptosis. As a result, APAP overdose led to characteristic changes generally observed in ferroptosis. The use of ferroptosis inhibitor ferrostatin-1 (or UAMC3203) and iron chelator deferoxamine further confirmed that ferroptosis was responsible for AILI. Mitochondrial dysfunction, which is associated with the tricarboxylic acid cycle and fatty acid β-oxidation suppression, may drive APAP-induced ferroptosis in hepatocytes. APAP overdose induced VDAC1 oligomerization in hepatocytes, and protecting mitochondria via VBIT-12 alleviated APAP-induced ferroptosis. Ceramide and cardiolipin levels were increased via UAMC3203 or VBIT-12 in APAP-induced ferroptosis in hepatocytes. Knockdown of Smpd1 and Taz expression responsible for ceramide and cardiolipin synthesis, respectively, aggravated APAP-induced mitochondrial dysfunction and ferroptosis in hepatocytes, whereas Taz overexpression protected against these processes. By immunohistochemical staining, we found that levels of 4-hydroxynonenal (4-HNE) protein adducts were increased in the liver biopsy samples of patients with DILI compared to that in those of patients with autoimmune liver disease, chronic viral hepatitis B, and non-alcoholic fatty liver disease (NAFLD). In summary, protecting mitochondria via inhibiting VDAC1 oligomerization attenuated hepatocyte ferroptosis by restoring ceramide and cardiolipin content in AILI.

Prokineticin-2 prevents neuronal cell deaths in a model of traumatic brain injury

Prokineticin-2 (Prok2) is an important secreted protein likely involved in the pathogenesis of several acute and chronic neurological diseases through currently unidentified regulatory mechanisms. The initial mechanical injury of neurons by traumatic brain injury triggers multiple secondary responses including various cell death programs. One of these is ferroptosis, which is associated with dysregulation of iron and thiols and culminates in fatal lipid peroxidation. Here, we explore the regulatory role of Prok2 in neuronal ferroptosis in vitro and in vivo. We show that Prok2 prevents neuronal cell death by suppressing the biosynthesis of lipid peroxidation substrates, arachidonic acid-phospholipids, via accelerated F-box only protein 10 (Fbxo10)-driven ubiquitination, degradation of long-chain-fatty-acid-CoA ligase 4 (Acsl4), and inhibition of lipid peroxidation. Mice injected with adeno-associated virus-Prok2 before controlled cortical impact injury show reduced neuronal degeneration and improved motor and cognitive functions, which could be inhibited by Fbxo10 knockdown. Our study shows that Prok2 mediates neuronal cell deaths in traumatic brain injury via ferroptosis.

Construction and validation of a 15-gene ferroptosis signature in lung adenocarcinoma

Background

Ferroptosis is a novel form of programmed cell death characterized by the excessive accumulation of intracellular iron and an increase in reactive oxygen species. Emerging studies have shown that ferroptosis plays a vital role in the progression of lung adenocarcinoma, but the effect of ferroptosis-related genes on prognosis has been poorly studied. The purpose of this study was to explore the prognostic value of ferroptosis-related genes.

Methods

Lung adenocarcinoma samples were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. The least absolute shrinkage and selection operator (LASSO) Cox regression algorithm was used to establish a predictive signature for risk stratification. Kaplan–Meier (K–M) survival analysis and receiver operating characteristic (ROC) curve analysis were conducted to evaluate the signature. We further explored the potential correlation between the risk score model and tumor immune status.

Results

A 15-gene ferroptosis signature was constructed to classify patients into different risk groups. The overall survival (OS) of patients in the high-risk group was significantly shorter than that of patients in the low-risk group. The signature could predict OS independent of other risk factors. Single-sample gene set enrichment analysis (ssGSEA) identified the difference in immune status between the two groups. Patients in the high-risk group had stronger immune suppression, especially in the antigen presentation process.

Conclusions

The 15-gene ferroptosis signature identified in this study could be a potential biomarker for prognosis prediction in lung adenocarcinoma. Targeting ferroptosis might be a promising therapeutic alternative for lung adenocarcinoma.

Ischemia Injury induces mPTP opening by reducing Sirt3

Mitochondrial permeability transition pore (mPTP) opening is critical to mitochondrial apoptosis during ischemic injury. Sirtuin 3 (Sirt3) is a mitochondrial deacetylase known to play a major role in stress resistance and cell death. Our previous studies have shown that Sirt3 activates superoxide dismutase 2 and forkhead box O3a to reduce cellular reactive oxygen species. However, it is unclear the interaction between Sirt3 and mPTP and the roles they play in ischemic stroke. We used the middle cerebral artery occlusion (MCAO) model, a mouse model of stroke, to examine Sirt3 and mPTP-related protein levels. We then applied lentivirus packaged Sirt3 overexpression in HT22 cells, a mouse hippocampal neuronal cell line, to investigate the underlying mechanism. We found Sirt3 protein level was decreased in the penumbra area in MCAO mice, along with an increase in mPTP related proteins, namely voltage-dependent anion channel 1 (VDAC1) and adenine nucleotide translocator 1 (ANT1). Sirt3 overexpression suppressed the increase in VDAC1, ANT1 and cleaved caspase 3 that were induced by the serum and glucose deprivation (SGD) condition. Our studies suggest that ischemic injury induced mPTP opening and apoptosis by reducing Sirt3. It helps to identify new therapeutic targets for ischemic stroke.

Mitochondrial calcium at the synapse

Mitochondria are dynamic organelles, which serve various purposes, including but not limited to the production of ATP and various metabolites, buffering ions, acting as a signaling hub, etc. In recent years, mitochondria are being seen as the central regulators of cellular growth, development, and death. Since neurons are highly specialized cells with a heavy metabolic demand, it is not surprising that neurons are one of the most mitochondria-rich cells in an animal. At synapses, mitochondrial function and dynamics is tightly regulated by synaptic calcium. Calcium influx during synaptic activity causes increased mitochondrial calcium influx leading to an increased ATP production as well as buffering of synaptic calcium. While increased ATP production is required during synaptic transmission, calcium buffering by mitochondria is crucial to prevent faulty neurotransmission and excitotoxicity. Interestingly, mitochondrial calcium also regulates the mobility of mitochondria within synapses causing mitochondria to halt at the synapse during synaptic transmission. In this review, we summarize the various roles of mitochondrial calcium at the synapse.

Endogenous glutamate determines ferroptosis sensitivity via ADCY10-dependent YAP suppression in lung adenocarcinoma

Rationale: Ferroptosis, a newly identified form of regulated cell death, can be induced following the inhibition of cystine-glutamate antiporter system X_C^- because of the impaired uptake of cystine. However, the outcome following the accumulation of endogenous glutamate in lung adenocarcinoma (LUAD) has not yet been determined. Yes-associated protein (YAP) is sustained by the hexosamine biosynthesis pathway (HBP)-dependent O-linked beta-N-acetylglucosaminylation (O-GlcNAcylation), and glutamine-fructose-6-phosphate transaminase (GFPT1), the rate-limiting enzyme of the HBP, can be phosphorylated and inhibited by adenylyl cyclase (ADCY)-mediated activation of protein kinase A (PKA). However, whether accumulated endogenous glutamate determines ferroptosis sensitivity by influencing the ADCY/PKA/HBP/YAP axis in LUAD cells is not understood.

Methods: Cell viability, cell death and the generation of lipid reactive oxygen species (ROS) and malondialdehyde (MDA) were measured to evaluate the responses to the induction of ferroptosis following the inhibition of system X_C^-. Tandem mass tags (TMTs) were employed to explore potential factors critical for the ferroptosis sensitivity of LUAD cells. Immunoblotting (IB) and quantitative RT-PCR (qPCR) were used to analyze protein and mRNA expression. Co-immunoprecipitation (co-IP) assays were performed to identify protein-protein interactions and posttranslational modifications. Metabolite levels were measured using the appropriate kits. Transcriptional regulation was evaluated using a luciferase reporter assay, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA). Drug administration and limiting dilution cell transplantation were performed with cell-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models. The associations among clinical outcome, drug efficacy and ADCY10 expression were determined based on data from patients who underwent curative surgery and evaluated with patient-derived primary LUAD cells and tissues.

Results: The accumulation of endogenous glutamate following system X_C^- inhibition has been shown to determine ferroptosis sensitivity by suppressing YAP in LUAD cells. YAP O-GlcNAcylation and expression cannot be sustained in LUAD cells upon impairment of GFPT1. Thus, Hippo pathway-like phosphorylation and ubiquitination of YAP are enhanced. ADCY10 acts as a key downstream target and diversifies the effects of glutamate on the PKA-dependent suppression of GFPT1. We also discovered that the protumorigenic and proferroptotic effects of ADCY10 are mediated separately. Advanced-stage LUADs with high ADCY10 expression are sensitive to ferroptosis. Moreover, LUAD cells with acquired therapy resistance are also prone to higher ADCY10 expression and are more likely to respond to ferroptosis. Finally, a varying degree of secondary labile iron increase is caused by the failure to sustain YAP-stimulated transcriptional compensation for ferritin at later stages further explains why ferroptosis sensitivity varies among LUAD cells.

Conclusions: Endogenous glutamate is critical for ferroptosis sensitivity following the inhibition of system X_C^- in LUAD cells, and ferroptosis-based treatment is a good choice for LUAD patients with later-stage and/or therapy-resistant tumors.

Cathepsin B is an executioner of ferroptosis

Ferroptosis is a necrotic form of cell death caused by inactivation of the glutathione system and uncontrolled iron-mediated lipid peroxidation. Increasing evidence implicates ferroptosis in a wide range of diseases from neurotrauma to cancer, highlighting the importance of identifying an executioner system that can be exploited for clinical applications. In this study, using pharmacological and genetic models of ferroptosis, we observed that lysosomal membrane permeabilization and cytoplasmic leakage of cathepsin B unleashes structural and functional changes in mitochondria and promotes a not previously reported cleavage of histone H3. Inhibition of cathepsin-B robustly rescued cellular membrane integrity and chromatin degradation. We show that these protective effects are independent of glutathione peroxidase-4 and are mediated by preventing lysosomal membrane damage. This was further confirmed when cathepsin B knockout primary fibroblasts remained unaffected in response to various ferroptosis inducers. Our work identifies new and yet-unrecognized aspects of ferroptosis and identifies cathepsin B as a mediator of ferroptotic cell death.

Development of Bisindole-Substituted Aminopyrazoles as Novel GSK-3β Inhibitors with Suppressive Effects against Microglial Inflammation and Oxidative Neurotoxicity

Development of glycogen synthase kinase-3β (GSK-3β) inactivation-centric agents with polypharmacological profiles is increasingly recognized as a promising therapeutic strategy against the multifactorial etiopathology of Alzheimer's disease (AD). In this respect, a series of disubstituted aminopyrazole derivatives were designed and synthesized as a new class of GSK-3β inhibitors. Most of these derivatives possess GSK-3β inhibitory activities with IC₅₀ values in the micromolar ranges, among which bisindole-substituted aminopyrazole derivative 6h displayed moderate GSK-3β inhibition (IC₅₀ = 1.76 ± 0.19 μM), and alleviative effects against lipopolysaccharide (LPS)-induced glial inflammation in BV-2 cells and glutamate-induced oxidative neurotoxicity in HT-22 cells. Further in vivo studies indicated that compound 6h had potent anti-inflammatory effect, by showing markedly reduced microglial activation and astrocyte proliferation in the brain of LPS-injected mice. Overall, the simultaneous modulation of 6h on multiple dysfunctions of disease network highlights this structural distinctively bisindole-substituted aminopyrazole could be a useful prototype for the discovery of novel therapeutic agents to tackle AD and other GSK-3β associated complex neurological syndromes.

The molecular mechanisms of MLKL-dependent and MLKL-independent necrosis

Necrosis, a type of unwanted and passive cell demise, usually occurs under the excessive external stress and is considered to be unregulated. However, under some special conditions such as caspase inhibition, necrosis is regulable in a well-orchestrated way. The term 'regulated necrosis' has been proposed to describe such programed necrosis. Recently, several forms of necrosis, including necroptosis, pyroptosis, ferroptosis, parthanatos, oxytosis, NETosis, and Na+/K+-ATPase-mediated necrosis, have been identified, and some crucial regulators governing regulated necrosis have also been discovered. Mixed lineage kinase domain-like pseudokinase (MLKL), a core regulator in necroptosis, acts as an executioner in response to ligands of death receptor family. Its activation requires the receptor-interacting protein kinases, RIP1 and RIP3. However, MLKL is only involved in necroptosis, i.e. MLKL is dispensable for necrosis. Therefore, this review is aimed at summarizing the molecular mechanisms of MLKL-dependent and MLKL-independent necrosis.

Ginsenoside Rh2 inhibits HeLa cell energy metabolism and induces apoptosis by upregulating voltage‑dependent anion channel 1

20(S)‑Ginsenoside Rh2 [20(S)‑GRh2], one of the main active components of Panax ginseng, induces apoptosis in a wide range of cancer cell types. The present study found that 20(S)‑GRh2 reduces mitochondrial membrane potential, decreases adenosine triphosphate generation and induces reactive oxygen species in HeLa cervical cancer cells. In addition, 20(S)‑GRh2 activated mitochondrion‑dependent apoptosis and inhibited both mitochondrial oxidative phosphorylation and glycolysis in HeLa cells. It was found that voltage‑dependent anion channel 1 (VDAC1) expression was significantly upregulated by 20(S)‑GRh2 treatment, while hexokinase 2 expression was downregulated and segregated from the mitochondria. Furthermore, 20(S)‑GRh2 promoted Bax transport from the cytoplasm to the mitochondria, and knockdown of VDAC1 inhibited Bax transport and apoptosis. These results suggest that VDAC1 is a novel target of 20(S)‑GRh2. The present study provides a better understanding of the mechanistic link between cervical cancer metabolism and growth control, and these results may facilitate the development of new treatments for cervical cancer.

Reactive Oxygen Species-Induced Lipid Peroxidation in Apoptosis, Autophagy, and Ferroptosis

Reactive oxygen species- (ROS-) induced lipid peroxidation plays a critical role in cell death including apoptosis, autophagy, and ferroptosis. This fundamental and conserved mechanism is based on an excess of ROS which attacks biomembranes, propagates lipid peroxidation chain reactions, and subsequently induces different types of cell death. A highly evolved sophisticated antioxidant system exists that acts to protect the cells from oxidative damage. In this review, we discussed how ROS propagate lipid peroxidation chain reactions and how the products of lipid peroxidation initiate apoptosis and autophagy in current models. We also discussed the mechanism of lipid peroxidation during ferroptosis, and we summarized lipid peroxidation in pathological conditions of critical illness. We aim to bring a more global and integrative sight to know how different ROS-induced lipid peroxidation occurs among apoptosis, autophagy, and ferroptosis.

Transmission Electron Microscopy Study of Mitochondria in Aging Brain Synapses

The brain is sensitive to aging-related morphological changes, where many neurodegenerative diseases manifest accompanied by a reduction in memory. The hippocampus is especially vulnerable to damage at an early stage of aging. The present transmission electron microscopy study examined the synapses and synaptic mitochondria of the CA1 region of the hippocampal layer in young-adult and old rats by means of a computer-assisted image analysis technique. Comparing young-adult (10 months of age) and old (22 months) male Fischer (CDF) rats, the total numerical density of synapses was significantly lower in aged rats than in the young adults. This age-related synaptic loss involved degenerative changes in the synaptic architectonic organization, including damage to mitochondria in both pre- and post-synaptic compartments. The number of asymmetric synapses with concave curvature decreased with age, while the number of asymmetric synapses with flat and convex curvatures increased. Old rats had a greater number of damaged mitochondria in their synapses, and most of this was type II and type III mitochondrial structural damage. These results demonstrate age-dependent changes in the morphology of synaptic mitochondria that may underlie declines in age-related synaptic function and may couple to age-dependent loss of synapses.

Global brain ischemia in rats is associated with mitochondrial release and downregulation of Mfn2 in the cerebral cortex, but not the hippocampus

Mitochondria are crucial for neuronal cell survival and death through their functions in ATP production and the intrinsic pathway of apoptosis. Mitochondrial dysfunction is considered to play a central role in several serious human diseases, including neurodegenerative diseases, such as Parkinson's and Alzheimer's disease and ischemic neurodegeneration. The aim of the present study was to investigate the impact of transient global brain ischemia on the expression of selected proteins involved in mitochondrial dynamics and mitochondria‑associated membranes. The main foci of interest were the proteins mitofusin 2 (Mfn2), dynamin‑related protein 1 (DRP1), voltage‑dependent anion‑selective channel 1 (VDAC1) and glucose‑regulated protein 75 (GRP75). Western blot analysis of total cell extracts and mitochondria isolated from either the cerebral cortex or hippocampus of experimental animals was performed. In addition, Mfn2 was localized intracellularly by laser scanning confocal microscopy. It was demonstrated that 15‑min ischemia, or 15‑min ischemia followed by 1, 3, 24 or 72 h of reperfusion, was associated with a marked decrease of the Mfn2 protein in mitochondria isolated from the cerebral cortex, but not in hippocampal mitochondria. Moreover, a translocation of the Mfn2 protein to the cytoplasm was documented immediately after global brain ischemia in the neurons of the cerebral cortex by laser scanning confocal microscopy. Mfn2 translocation was followed by decreased expression of Mfn2 during reperfusion. Markedly elevated levels of the VDAC1 protein were also documented in total cell extracts isolated from the hippocampus of rats after 15 min of global brain ischemia followed by 3 h of reperfusion, and from the cerebral cortex of rats after 15 min of global brain ischemia followed by 72 h of reperfusion. The mitochondrial Mfn2 release observed during the early stages of reperfusion may thus represent an important mechanism of mitochondrial dysfunction associated with neuronal dysfunction or death induced by global brain ischemia.