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PM2.5 inhibits system Xc- activity to induce ferroptosis by activating the AMPK-Beclin1 pathway in acute lung injury
Abstract
Urban airborne fine particulate matter (PM2.5) is a global pollution source that has been strongly related to multiple respiratory diseases involving various types of regulated cell death (RCD). However, the role of ferroptosis, a novel form of RCD, in PM2.5-induced acute lung injury (ALI), has not been elucidated. Herein, we define the role and mechanism of ferroptosis in a PM2.5-induced ALI model. First, we demonstrated that lipid peroxidation and iron accumulation were significantly enhanced in ALI models and were accompanied by activation of the AMP-activated protein kinase (AMPK)-Beclin1 signaling pathway and inhibition of the key subunit SLC7A11 of System Xc-. However, these abnormalities were partially reversed by ferroptosis inhibitors. We further revealed that Beclin1 knockdown or overexpression ameliorated or exacerbated PM2.5-induced ferroptosis, respectively. Mechanistically, we verified that Beclin1 blocks System Xc- activity to trigger ferroptosis by directly binding to SLC7A11. Finally, knockdown of Beclin1 by AAV-shRNA or inhibition of AMPK, an upstream activator of Beclin1, ameliorated PM2.5-induced ferroptosis and ALI. Taken together, our results revealed that ferroptosis plays a novel role in PM2.5-induced ALI and elucidated the specific mechanism involving the AMPK-Beclin1 pathway and System Xc-, which may provide new insight into the toxicological effects of PM2.5 on respiratory problems.
... Ferroptosis, distinct from necrosis, autophagy, and apoptosis, is an emerging form of programmed cell death primarily marked by lipid peroxidation as well as the accumulation of iron intracellularly. These processes ultimately culminate in oxidative stress and subsequent cell demise [7]. The process of ferroptosis involves multiple signaling pathways and three major metabolic pathways (amino acid metabolism, iron metabolism and lipid metabolism) [8]. ...
Background
Chronic obstructive pulmonary disease (COPD), a prevalent respiratory condition, is characterized by long‐term airway inflammation, which can lead to airway remodeling and persistent airflow restriction. Exposure to cigarette smoke is known as a major contributor to COPD development. Research has confirmed that ferroptosis and m6A modification are closely related to various inflammatory‐related diseases. However, the correlation between m6A methylation and ferroptosis in COPD has not been confirmed. In this study, combined with bioinformatics analysis and molecular biology methods we investigated how m6A methylation was correlated to ferroptosis‐associated genes (SLC7A11 and NQO‐1) in cigarette smoke induced 16HBES cells.
Methods
Two microarray datasets (GSE30063 and GSE64614) were combined to identify differentially expressed genes (DEGs) through the application of bioinformatics techniques. A cigarette smoke (CS)‐induced 16HBE cells model was established. The ROS, GSH, MDA, and total iron content were detected by relevant detection kits. The expression levels associated with ferroptosis and m6A methylation modification‐related genes were determined via reverse transcription‐quantitative polymerase chain reaction and western blot.
Results
Overall, 529 DEGs were identified in the above two databases. For COPD patients, significant changes were observed in FAGs (GCLC, NQO‐1, SLC7A11) and m6A methylation‐related genes (FTO). A negative correlation was also noted between the expression level of genes linked to ferroptosis (SLC7A11 and NQO‐1) and that of the m6A methylation gene (FTO). The in vitro experiments results indicate that SLC7A11 and NQO‐1 were significantly downregulated, and FTO were significantly upregulated. In addition, cigarette smoke stimulation increased the levels of MDA, LPO, and ROS, while reducing the content of GSH and total iron content in 16HBE cells.
Conclusion
Our findings explored the relationship between ferroptosis and m6A methylation in COPD, and screened out SLC7A11, NQO‐1 and FTO may be critical in the pathogenesis of COPD.
Environmental pollution represents a significant public health concern, with the potential health risks associated with environmental pollutants receiving considerable attention over an extended period. In recent years, a substantial body of research has been dedicated to this topic. Since the discovery of ferroptosis, an iron-dependent programmed cell death typically characterized by lipid peroxidation, in 2012, there have been significant advances in the study of its role and mechanism in various diseases. A growing number of recent studies have also demonstrated the involvement of ferroptosis in the damage caused to the organism by environmental pollutants, and the molecular mechanisms involved have been partially elucidated. The targeting of ferroptosis has been demonstrated to be an effective means of ameliorating the health damage caused by PM2.5, organic and inorganic pollutants, and ionizing radiation. This review begins by providing a summary of the most recent and important advances in ferroptosis. It then proceeds to offer a critical analysis of the health effects and molecular mechanisms of ferroptosis induced by various environmental pollutants. Furthermore, as is the case with all rapidly evolving research areas, there are numerous unanswered questions and challenges pertaining to environmental pollutant-induced ferroptosis, which we discuss in this review in an attempt to provide some directions and clues for future research in this field.
Fine particulate matter (PM2.5) is increasingly recognized for its detrimental effects on human health, with substantial evidence linking exposure to various forms of cell death and dysfunction across multiple organ systems. This review examines key cell death mechanisms triggered by PM2.5, including PANoptosis, necroptosis, autophagy, and ferroptosis, while other forms such as oncosis, paraptosis, and cuprotosis remain unreported in relation to PM2.5 exposure. Mitochondria, endoplasmic reticulum, and lysosomes emerge as pivotal organelles in the disruption of cellular homeostasis, with mitochondrial dysfunction particularly implicated in metabolic dysregulation and the activation of pro-apoptotic pathways. Although PM2.5 primarily affects the nucleus, cytoskeleton, mitochondria, endoplasmic reticulum, and lysosomes, other organelles like ribosomes, Golgi apparatus, and peroxisomes have received limited attention. Interactions between these organelles, such as endoplasmic reticulum-associated mitochondrial membranes, lysosome-associated mitophagy, and mitochondria-nuclei retro-signaling may significantly contribute to the cytotoxic effects of PM2.5. The mechanisms of PM2.5 toxicity, encompassing oxidative stress, inflammatory responses, and metabolic imbalances, are described in detail. Notably, PM2.5 activates the NLRP3 inflammasome, amplifying inflammatory responses and contributing to chronic diseases. Furthermore, PM2.5 exposure disrupts genetic and epigenetic regulation, often resulting in cell cycle arrest and exacerbating cellular damage. The composition, concentration, and seasonal variability of PM2.5 modulate these effects, underscoring the complexity of PM2.5-induced cellular dysfunction. Despite significant advances in understanding these pathways, further research is required to elucidate the long-term effects of chronic PM2.5 exposure, the role of epigenetic regulation, and potential strategies to mitigate its harmful impact on human health.
The HBV core protein (HBc) is an important viral protein of HBV that plays an indispensable role in the lifecycle of HBV, including capsid assembly and transport, reverse transcription and virus release. In recent years, evidence has shown that HBc may be involved in the malignant progression of HCC. Thus, HBc is an attractive target for antiviral agents and provides a new strategy for the treatment of HBV-related HCC. Here, we identified a novel anti‐HBc compound—colchicine, an alkaloid compound—that promoted selective autophagic degradation of HBc through the AMPK/mTOR/ULK1 signalling pathway. We further confirmed that colchicine promoted the selective autophagy of HBc by enhancing the binding of HBc to the autophagy receptor p62. Finally, we evaluated the effects of colchicine on HBV replication and HBc-mediated HCC metastasis in vitro and in vivo. Our research indicated that the inhibitory effects of colchicine on HBV and HBV-related HCC depend on the selective autophagic degradation of HBc. Thus, colchicine is not only a promising therapeutic strategy for chronic hepatitis B but also a new treatment for HBV-related HCC.
Exposure to fine particulate matter (PM2.5) has been associated with the development and progression of renal disease. Peroxisome proliferator-activated receptor gamma (PPARγ), a key transcription factor involved in inflammation as well as lipid and glucose metabolism, helps maintain the integrity of tubular epithelial cells. However, the precise role of PPARγ in PM2.5-induced tubular injury remains unclear. In this study, we investigated the regulatory effects of PPARγ on PM2.5-induced ferroptotic stress and epithelial–mesenchymal transition (EMT) in tubular (HK-2) cells. We found that downregulation of PPARγ expression was correlated with EMT in PM2.5-exposed cells. Pretreatment with the PPARγ agonist 15d-PGJ2 protected the cells from EMT by reducing ferroptotic stress, whereas that with the PPARγ antagonist GW9662 promoted EMT. Furthermore, pretreatment with ferrostatin-1 (Fer-1) significantly prevented PM2.5-induced EMT and downregulation of PPARγ expression. Notably, overexpression of PPARγ blocked PM2.5-induced downregulation of E-cadherin and GPX4 expression and upregulation of α-SMA expression. This study highlights the complex associations of PPARγ with ferroptosis and EMT in PM2.5-exposed tubular cells. Our findings suggest that PPARγ activation confers protection against PM2.5-induced renal injury.
Ferroptosis is implicated in the pathogenesis of multiple diseases, including neurodegenerative diseases, cardiovascular diseases, kidney pathologies, ischemia-reperfusion injury, and cancer. The current review article highlights the involvement of ferroptosis in traumatic brain injury, acute kidney damage, ethanol-induced liver injury, and PM2.5-induced lung injury. Melatonin, a molecule produced by the pineal gland and many other organs, is well known for its anti- aging, anti-inflammatory, and anticancer properties and is used in the treatment of different diseases. Melatonin's ability to activate anti-ferroptosis pathways including sirtuin (SIRT)6/p- nuclear factor erythroid 2-related factor 2 (Nrf2), Nrf2/ antioxidant responsive element (ARE)/ heme oxygenase (HO-1)/SLC7A11/glutathione peroxidase (GPX4)/ prostaglandin-endoperoxide synthase 2 (PTGS2), extracellular signal-regulated kinase (ERK)/Nrf2, ferroportin (FPN), Hippo/ Yes-associated protein (YAP), Phosphoinositide 3-kinase (PI3K)/ protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) and SIRT6/ nuclear receptor coactivator 4 (NCOA4)/ ferritin heavy chain 1 (FTH1) signaling pathways suggests that it could serve as a valuable therapeutic agent for preventing cell death associated with ferroptosis in various diseases. Further research is needed to fully understand the precise mechanisms by which melatonin regulates ferroptosis and its potential as a therapeutic target.
Autophagy is a process in which cells degrade intracellular substances and play a variety of roles in cells, such as maintaining intracellular homeostasis, preventing cell overgrowth, and removing pathogens. It is highly conserved during the evolution of eukaryotic cells. So far, the study of autophagy is still a hot topic in the field of cytology. Ferroptosis is an iron‐dependent form of cell death, accompanied by the accumulation of reactive oxygen species and lipid peroxides. With the deepening of research, it has been found that ferroptosis, like autophagy, is involved in the occurrence and development of cardiovascular diseases. The relationship between autophagy and ferroptosis is complex, and the association between the two in cardiovascular disease remains to be clarified. This article reviews the mechanism of autophagy and ferroptosis and their correlation, and discusses the relationship between them in cardiovascular diseases, which is expected to provide new and important treatment strategies for cardiovascular diseases.
As a life‐threatening disease, acute lung injury (ALI) may progress to chronic pulmonary fibrosis. For the treatment of lung injury, Tempol is a superoxide dismutase mimetic and intracellular redox agent that can be a potential drug. This study investigated the regulatory mechanism of Tempol in the treatment of ALI. A mouse model of ALI was established, and HE staining was used to examine histomorphology. The CCK‐8 assay was used to measure cell viability, and oxidative stress was assessed by corresponding kits. Flow cytometry and dichlorodihydrofluorescein diacetate staining assays were used to detect reactive oxygen species (ROS) levels. Protein expression levels were measured by Western blot analysis and ELISA. Pulmonary vascular permeability was used to measure the lung wet/dry weight ratio. The level of oxidative stress was increased in ALI mice, and the level of ferroptosis was upregulated. Tempol inhibited this effect and alleviated ALI. The administration of Tempol alleviated the pathological changes in ALI, inhibited pulmonary vascular permeability, and improved lung injury in ALI mice. The upregulation of genes essential for glutathione (GSH) metabolism induced by lipopolysaccharide (LPS) was inhibited by Tempol. In addition, nuclear factor‐related factor 2 (Nrf2) is activated by Tempol therapy to regulate the de novo synthesis pathway of GSH, thereby alleviating LPS‐induced lung epithelial cell damage. The results showed that Tempol alleviated ALI by activating the Nrf2 pathway to inhibit oxidative stress and ferroptosis in lung epithelial cells. In conclusion, this study demonstrates that Tempol alleviates ALI by inhibiting ferroptosis in lung epithelial cells through the effect of Nrf2 on GSH synthesis.
Background
PM 2.5 is a well-known harmful air pollutant that can lead to acute exacerbation and aggravation of respiratory diseases. Although ferroptosis is involves in the pathological process of pulmonary disease, the potential mechanism of ferroptosis in PM 2.5 -caused lung inflammation and fibrosis need to be further clarified. Quercetin is a phenolic compound that can inhibit ferroptosis in various diseases. Hence, this study explores the role of ferroptosis in lung injury induced by PM 2.5 in order to further elucidate the beneficial effect of quercetin and its underlying mechanism.
Methods
C57BL/6J mice were treated with either saline or PM 2.5 by intratracheal instillation 20 times (once every two days). Additionally, PM 2.5 -treated mice were supplemented with two doses of quercetin. Lung injury, lipid peroxidation, iron content and ferroptosis marker protein expression and the Nrf2 signaling pathway were evaluated. In vitro , cell experiments were applied to verify the mechanisms underlying the links between Nrf2 signaling pathway activation and ferroptosis as well as between ferroptosis and inflammation.
Results
In vivo , PM 2.5 increased lung inflammation and caused lung fibrosis and increased lipid peroxidation contents, iron contents and ferroptosis markers in lung tissues; these effects were significantly reversed by quercetin. Additionally, quercetin upregulated the nuclear Nrf2 expression and downregulated Keap1 expression in lung tissues of PM 2.5 -exposed mice. Quercetin decreased lipid peroxidation products, iron contents and ferroptosis levels and increased the nuclear translocation of Nrf2 and the degradation of Keap1 in PM 2.5 -exposed BEAS-2B cells. Moreover, we found that quercetin and dimethyl fumarate markedly decreased lipid peroxidation production and ferroptosis by activating the Nrf2-Keap1 pathway in PM 2.5 -exposed cells. Furthermore, quercetin reduced inflammatory cytokines and TGF- β 1 in PM 2.5 -exposed cells.
Conclusion
Our data suggested that Nrf2 is involved in ferroptosis in PM 2.5 -induced lung injury, and quercetin can alleviate these adverse effects via activating Nrf2-Keap1 signaling pathway.
Liver fibrosis is primarily driven by the activation of hepatic stellate cells (HSCs), a process associated with ferroptosis. Ginsenoside Rb1 (GRb1), a major active component extracted from Panax ginseng, inhibits HSC activation. However, the potential role of GRb1 in mediating HSC ferroptosis remains unclear. This study examined the effect of GRb1 on liver fibrosis both in vivo and in vitro, using CCl4-induced liver fibrosis mouse model and primary HSCs, LX-2 cells. The findings revealed that GRb1 effectively inactivated HSCs in vitro, reducing alpha-smooth muscle actin (α-SMA) and Type I collagen (Col1A1) levels. Moreover, GRb1 significantly alleviated CCl4-induced liver fibrosis in vivo. From a mechanistic standpoint, the ferroptosis pathway appeared to be central to the antifibrotic effects of GRb1. Specifically, GRb1 promoted HSC ferroptosis both in vivo and in vitro, characterized by increased glutathione depletion, malondialdehyde production, iron overload, and accumulation of reactive oxygen species (ROS). Intriguingly, GRb1 increased Beclin 1 (BECN1) levels and decreased the System Xc-key subunit SLC7A11. Further experiments showed that BECN1 silencing inhibited GRb1-induced effects on HSC ferroptosis and mitigated the reduction of SLC7A11 caused by GRb1. Moreover, BECN1 could directly interact with SLC7A11, initiating HSC ferroptosis. In conclusion, the suppression of BECN1 counteracted the effects of GRb1 on HSC inactivation both in vivo and in vitro. Overall, this study highlights the novel role of GRb1 in inducing HSC ferroptosis and promoting HSC inactivation, at least partly through its modulation of BECN1 and SLC7A11.
Pulmonary epithelial cells act as the first line of defense against various air pollutant particles. Previous studies have reported that particulate matter 2.5 (PM2.5) could trigger pulmonary inflammation and fibrosis by inducing pulmonary epithelial senescence and ferroptosis. Sirtuin 3 (SIRT3) is one of critical the mitochondrial NAD+-dependent deacetylases, exerting antioxidant and anti-aging effects in multiple diseases. The present study aimed to explore the role of SIRT3 in PM2.5-induced lung injury as well as possible mechanisms. The role of SIRT3 in PM2.5-induced lung injury was investigated by SIRT3 genetic depletion, adenovirus-mediated overexpression in type II alveolar epithelial (AT2) cells, and pharmacological activation by melatonin. The protein level and activity of SIRT3 in lung tissues and AT2 cells were significantly downregulated after PM2.5 stimulation. SIRT3 deficiency in AT2 cells aggravated inflammatory response and collagen deposition in PM2.5-treated lung tissues. RNA-sequence and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the differentially expressed genes (DEGs) between SIRT3 flox and SIRT3 CKO mice were mainly enriched in ferroptosis and cellular longevity. Western blot further showed that SIRT3 deficiency in AT2 cells significantly upregulated the proteins associated with ferroptosis and cell senescence in PM2.5-treated lung tissues. In vitro experiments also showed that SIRT3 overexpression could decrease the levels of ferroptosis and cell senescence in PM2.5-treated AT2 cells. In addition, we found that PM2.5 could increase the acetylation of P53 via triggering DNA damage in AT2 cells. And SIRT3 could deacetylate P53 at lysines 320 (K320), thus reducing its transcriptional activity. PM2.5 decreased the protein level of SIRT3 by inducing proteasome pathway through downregulating USP3. Finally, we found that SIRT3 agonist, melatonin treatment could alleviate PM2.5-induced senescence and ferroptosis in mice. In conclusion, targeting USP3-SIRT3-P53 axis may be a novel therapeutic strategy against PM2.5-induced pulmonary inflammation and fibrosis by decreasing pulmonary epithelial senescence and ferroptosis.
Chronic obstructive pulmonary disease (COPD), a heterogeneous disease, is the leading cause of death worldwide. In recent years, air pollution, especially particulate matter (PM), has been widely studied as a contributing factor to COPD. As an essential component of PM, PM2.5 is associated with COPD prevalence, morbidity, and acute exacerbations. However, the specific pathogenic mechanisms were still unclear and deserve further research. The diversity and complexity of PM2.5 components make it challenging to get its accurate effects and mechanisms for COPD. It has been determined that the most toxic PM2.5 components are metals, polycyclic aromatic hydrocarbons (PAHs), carbonaceous particles (CPs), and other organic compounds. PM2.5-induced cytokine release and oxidative stress are the main mechanisms reported leading to COPD. Nonnegligibly, the microorganism in PM 2.5 may directly cause mononuclear inflammation or break the microorganism balance contributing to the development and exacerbation of COPD. This review focuses on the pathophysiology and consequences of PM2.5 and its components on COPD.
Previous studies have indicated that allergens such as house dust mites (HDM) in the environment can induce allergic asthma. Ferroptosis is a newly discovered form of regulatory cell death characterized by aberrant lipid peroxidation and the accumulation of reactive oxygen species (ROS) in cells. However, whether ferroptosis participates in the pathological process of asthma remains to be elucidated. The present study used a HDM-induced mouse asthma model to determine the effect of HDM exposure on allergic asthma and its underlying mechanisms. Female BALB/c mice were intranasally exposed to HDM to induce allergic asthma. Airway hyperresponsiveness (AHR), lung inflammation, mucus secretion, IgE levels, cytokine levels and inflammatory cell counts in bronchoalveolar lavage fluid (BALF) were investigated. In addition, the morphological changes of mitochondria, ROS levels, glutathione (GSH) levels and changes in ferroptosis pathway proteins were also determined in murine lungs. As a result, HDM exposure significantly increased AHR, inflammatory cell infiltration and mucus secretion around the airways. Furthermore, elevated IgE levels in the BALF, lung eosinophilia and a concomitant increase in IL-13 and IL-5 levels in BALF were observed. HDM inhalation increased ROS and decreased GSH levels in the lungs. HDM inhalation induced dysmorphic small mitochondria with decreased crista, as well as condensed, ruptured outer membranes. Western blotting demonstrated that the activities of glutathione peroxidase 4 and catalytic subunit solute carrier family 7 member 11 were significantly decreased, and that protein expression levels of acyl-CoA synthetase long-chain family member 4 and 15 lipoxygenase 1 were upregulated compared with mice in the normal control group. Overall, these results indicated that the AHR, airway inflammation, lipid peroxidation and ROS levels increased in HDM-induced asthma, and that HDM inhalation induced ferroptosis in the lungs, which helped to form an improved understanding of the pathogenesis of allergic asthma.
Background: Idiopathic pulmonary fibrosis (IPF) is a chronic progressive disease with unknown etiology and unfavorable prognosis. Ferroptosis is a form of regulated cell death with an iron-dependent way that is involved in the development of various diseases. Whereas the prognostic value of ferroptosis-related genes (FRGs) in IPF remains uncertain and needs to be further elucidated.
Methods: The FerrDb database and the previous studies were screened to explore the FRGs. The data of patients with IPF were obtained from the GSE70866 dataset. Wilcoxon's test and univariate Cox regression analysis were applied to identify the FRGs that are differentially expressed between normal and patients with IPF and associated with prognosis. Next, a multigene signature was constructed by the least absolute shrinkage and selection operator (LASSO)-penalized Cox model in the training cohort and evaluated by using calibration and receiver operating characteristic (ROC) curves. Then, 30% of the dataset samples were randomly selected for internal validation. Finally, the potential function and pathways that might be affected by the risk score-related differently expressed genes (DEGs) were further explored.
Results: A total of 183 FRGs were identified by the FerrDb database and the previous studies, and 19 of them were differentially expressed in bronchoalveolar lavage fluid (BALF) between IPF and healthy controls and associated with prognosis ( p < 0.05). There were five FRGs (aconitase 1 [ACO1], neuroblastoma RAS viral (v-ras) oncogene homolog [NRAS], Ectonucleotide pyrophosphatase/phosphodiesterase 2 [ENPP2], Mucin 1 [MUC1], and ZFP36 ring finger protein [ZFP36]) identified as risk signatures and stratified patients with IPF into the two risk groups. The overall survival rate in patients with high risk was significantly lower than that in patients with low risk ( p < 0.001). The calibration and ROC curve analysis confirmed the predictive capacity of this signature, and the results were further verified in the validation group. Risk score-related DEGs were found enriched in ECM-receptor interaction and focal adhesion pathways.
Conclusion: The five FRGs in BALF can be used for prognostic prediction in IPF, which may contribute to improving the management strategies of IPF.
Ferroptosis is a new type of programmed cell death characterized by intracellular iron accumulation and lipid peroxidation that leads to oxidative stress and cell death. The metabolism of iron, lipids, and amino acids and multiple signalling pathways precisely regulate the process of ferroptosis. Emerging evidence has demonstrated that ferroptosis participates in the occurrence and progression of various pathological conditions and diseases, such as infections, neurodegeneration, tissue ischaemia-reperfusion injury and immune diseases. Recent studies have also indicated that ferroptosis plays a critical role in the pathogenesis of acute lung injury, chronic obstructive pulmonary disease, pulmonary fibrosis, pulmonary infection and asthma. Herein, we summarize the latest knowledge on the regulatory mechanism of ferroptosis and its association with iron, lipid and amino acid metabolism as well as several signalling pathways. Furthermore, we review the contribution of ferroptosis to the pathogenesis of lung diseases and discuss ferroptosis as a novel therapeutic target for various lung diseases.
Macroautophagy/autophagy and necroptosis represent two opposing cellular s tress responses. Whereas autophagy primarily fulfills a cyto-protective function, necroptosis is a form of regulated cell death induced via death receptors. Here, we aimed at investigating the molecular crosstalk between these two pathways. We observed that RIPK3 directly associates with AMPK and phosphorylates its catalytic subunit PRKAA1/2 at T183/T172. Activated AMPK then phosphorylates the autophagy-regulating proteins ULK1 and BECN1. However, the lysosomal degradation of autophagosomes is blocked by TNF-induced necroptosis. Specifically, we observed dysregulated SNARE complexes upon TNF treatment; e.g., reduced levels of full-length STX17. In summary, we identified RIPK3 as an AMPK-activating kinase and thus a direct link between autophagy- and necroptosis-regulating kinases.
Abbreviations ACACA/ACC: acetyl-CoA carboxylase alpha; AMPK: AMP-activated protein kinase; ATG: autophagy-related; BECN1: beclin 1; GFP: green fluorescent protein; EBSS: Earle’s balanced salt solution; Hs: Homo sapiens; KO: knockout; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; MLKL: mixed lineage kinase domain like pseudokinase; Mm: Mus musculus; MTOR: mechanistic target of rapamycin kinase; MVB: multivesicular body; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4/VPS15: phosphoinositide-3-kinase regulatory subunit 4; PLA: proximity ligation assay; PRKAA1: protein kinase AMP-activated catalytic subunit alpha 1; PRKAA2: protein kinase AMP-activated catalytic subunit alpha 2; PRKAB2: protein kinase AMP-activated non-catalytic subunit beta 2; PRKAG1: protein kinase AMP-activated non-catalytic subunit gamma 1; PtdIns3K: phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; RIPK1: receptor interacting serine/threonine kinase 1; RIPK3: receptor interacting serine/threonine kinase 3; SNAP29: synaptosome associated protein 29; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; STK11/LKB1: serine/threonine kinase 11; STX7: syntaxin 7; STX17: syntaxin 17; TAX1BP1: Tax1 binding protein 1; TNF: tumor necrosis factor; ULK1: unc-51 like autophagy activating kinase 1; VAMP8: vesicle associated membrane protein 8; WT: wild-type.
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Oxidative stress has been implicated in the pathogenesis of Alzheimer’s disease (AD). Mitochondrial dysfunction is linked to oxidative stress and reactive oxygen species (ROS) in neurotoxicity during AD. Impaired mitochondrial metabolism has been associated with mitochondrial dysfunction in brain damage of AD. While the role of NADPH oxidase 4 (NOX4), a major source of ROS, has been identified in brain damage, the mechanism by which NOX4 regulates ferroptosis of astrocytes in AD remains unclear. Here, we show that the protein levels of NOX4 were significantly elevated in impaired astrocytes of cerebral cortex from patients with AD and APP/PS1 double-transgenic mouse model of AD. The levels of 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA), a marker of oxidative stress-induced lipid peroxidation, were significantly also elevated in impaired astrocytes of patients with AD and mouse AD. We demonstrate that the over-expression of NOX4 significantly increases the impairment of mitochondrial metabolism by inhibition of mitochondrial respiration and ATP production via the reduction of five protein complexes in the mitochondrial ETC in human astrocytes. Moreover, the elevation of NOX4 induces oxidative stress by mitochondrial ROS (mtROS) production, mitochondrial fragmentation, and inhibition of cellular antioxidant process in human astrocytes. Furthermore, the elevation of NOX4 increased ferroptosis-dependent cytotoxicity by the activation of oxidative stress-induced lipid peroxidation in human astrocytes. These results suggest that NOX4 promotes ferroptosis of astrocytes by oxidative stress-induced lipid peroxidation via the impairment of mitochondrial metabolism in AD.
With the increasingly serious problem of environmental pollution, the health problems caused by PM2.5 are gradually coming into our line of sight. Previous researches have indicated that air pollution is nearly related to various diseases, but few studies have focused on the exact function mediated by particulate matter less than 2.5 (PM2.5) in these diseases. PM2.5 is known to induce multiple ways of cell death, including autophagy, necrosis, apoptosis, pyroptosis and ferroptosis. Therefore, it is of much importance to understand the different ways of cell death caused by PM2.5 in the pathogenesis and treatment of PM2.5-related diseases. This present review is an insight of multiple ways of PM2.5‑induced cell death in different diseases.
Amino acid transporters mediate substrates across cellular membranes and their fine-tuned regulations are critical to cellular metabolism, growth, and death. As the functional component of system Xc-, which imports extracellular cystine with intracellular glutamate release at a ratio of 1:1, SLC7A11 has diverse functional roles in regulating many pathophysiological processes such as cellular redox homeostasis, ferroptosis, and drug resistance in cancer. Notably, accumulated evidence demonstrated that SLC7A11 is overexpressed in many types of cancers and is associated with patients' poor prognosis. As a result, SLC7A11 becomes a new potential target for cancer therapy. In this review, we first briefly introduce the structure and function of SLC7A11, then discuss its pathological role in cancer. We next summarize current available data of how SLC7A11 is subjected to fine regulations at multiple levels. We further describe the potential inhibitors of the SLC7A11 and their roles in human cancer cells. Finally, we propose novel insights for future perspectives on the modulation of SLC7A11, as well as possible targeted strategies for SLC7A11-based anti-cancer therapies.
Cell death can be executed through different subroutines. Since the description of ferroptosis as an iron-dependent form of non-apoptotic cell death in 2012, there has been mounting interest in the process and function of ferroptosis. Ferroptosis can occur through two major pathways, the extrinsic or transporter-dependent pathway and the intrinsic or enzyme-regulated pathway. Ferroptosis is caused by a redox imbalance between the production of oxidants and antioxidants, which is driven by the abnormal expression and activity of multiple redox-active enzymes that produce or detoxify free radicals and lipid oxidation products. Accordingly, ferroptosis is precisely regulated at multiple levels, including epigenetic, transcriptional, posttranscriptional and posttranslational layers. The transcription factor NFE2L2 plays a central role in upregulating anti-ferroptotic defense, whereas selective autophagy may promote ferroptotic death. Here, we review current knowledge on the integrated molecular machinery of ferroptosis and describe how dysregulated ferroptosis is involved in cancer, neurodegeneration, tissue injury, inflammation, and infection.
Air pollution can highly impact the respiratory system in healthy individuals. Studies have indicated that particles with an aerodynamic diameter of ≤2.5 µm (PM2.5) can be considered to be harmful for lung alveoli and bronchial epithelium cells. PM2.5 can be directly inhaled and can deeply penetrate into the lung alveoli, causing lung dysfunction. However, the toxicological mechanism mediated by PM2.5 for respiratory disease has still not been clearly determined. The purpose of the current study was to investigate the effects of PM2.5 on mouse bronchial epithelium cells (MBECs) and explored the possible mechanism mediated by PM2.5 in MBECs. The results of the current study indicated that PM2.5 markedly decreased lung function, including total lung capacity, residual volume, vital capacity and airway resistance in experimental mice. The results demonstrated that PM2.5 markedly induced inflammatory responses, oxidative injury and MBEC apoptosis. PM2.5 increased interleukin (IL)-1β and IL-6 expression, and reactive oxygen species production in MBECs. Furthermore, PM2.5 specifically induced PI3K, AKT and mTOR expression in MBECs. Disruption of PI3K/AKT/mTOR signaling was also indicated to effectively inhibit apoptosis of MBECs. In conclusion, the results of the current study systematically demonstrated the role of apoptosis-mediated MBEC apoptosis in PM2.5-treated mice, and provides a potential strategy for preclinical intervention in patients with PM2.5-induced lung diseases.
Ferroptosis is a form of regulated cell death that is characterized by iron-dependent oxidative damage and subsequent plasma membrane ruptures and the release of damage-associated molecular patterns. Due to the role of iron in mediating the production of reactive oxygen species and enzyme activity in lipid peroxidation, ferroptosis is strictly controlled by regulators involved in many aspects of iron metabolism, such as iron uptake, storage, utilization, and efflux. Translational and transcriptional regulation of iron homeostasis provide an integrated network to determine the sensitivity of ferroptosis. Impaired ferroptosis is implicated in various iron-related pathological conditions or diseases, such as cancer, neurodegenerative diseases, and ischemia-reperfusion injury. Understanding the molecular mechanisms underlying the regulation of iron metabolism during ferroptosis may provide effective strategies for the treatment of ferroptosis-associated diseases. Indeed, iron chelators effectively prevent the occurrence of ferroptosis, which may provide new approaches for the treatment of iron-related disorders. In this review, we summarize recent advances in the theoretical modeling of iron-dependent ferroptosis, and highlight the therapeutic implications of iron chelators in diseases.
Many new types of regulated cell death have been recently implicated in human health and disease. These regulated cell deaths have different morphological, genetic, biochemical, and functional hallmarks. Ferroptosis was originally described as a carcinogenic RAS-dependent non-apoptotic cell death, and is now defined as a type of regulated necrosis characterized by iron accumulation, lipid peroxidation, and the release of damage-associated molecular patterns (DAMPs). Multiple oxidative and antioxidant systems, acting together autophagy machinery, shape the process of lipid peroxidation during ferroptosis. In particular, the production of reactive oxygen species (ROS) that depends on the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and the mitochondrial respiratory chain promotes lipid peroxidation by lipoxygenase (ALOX) or cytochrome P450 reductase (POR). In contrast, the glutathione (GSH), coenzyme Q10 (CoQ10), and tetrahydrobiopterin (BH4) system limits oxidative damage during ferroptosis. These antioxidant processes are further transcriptionally regulated by nuclear factor, erythroid 2-like 2 (NFE2L2/NRF2), whereas membrane repair during ferroptotic damage requires the activation of endosomal sorting complexes required for transport (ESCRT)-III. A further understanding of the process and function of ferroptosis may provide precise treatment strategies for disease.
Erastin is a small molecular compound that induces ferroptosis by binding to voltage-dependent anion-selective channel protein (VDAC)2, VDAC3 and solute carrier family 7 member 5 inhibiting the cystine/glutamate antiporter. However, to the best of our knowledge, the mechanism of erastin-induced breast cancer cell death remains unclear. In present study aimed to explore the underlying mechanisms of the antitumor effects of erastin on breast cancer cells. Cellular viability was assessed using an MTT assay, a lactate dehydrogenase cytotoxicity assay kit was used to determine the cell death rate, the intracellular Fe2+ levels were determined using an iron colorimetric assay kit and western blotting was used to estimate the changes of autophagy-associated proteins levels. The present study demonstrated that erastin inhibited the viability of breast cancer cells and induced breast cancer cell death in a dose-dependent manner. Additionally, autophagy was activated by erastin, as demonstrated by upregulated expression levels of autophagy-associated proteins in breast cancer cells. Bafilomycin A1, 3-methyladenine and knockdown of autophagy related (ATG)5 with small interfering RNA prevented erastin-induced breast cancer cell death and inhibited the erastin-induced changes in the expression levels of the autophagy-associated proteins beclin1, ATG5, ATG12, microtubule-associated proteins 1A/1B light chain 3B (LC3B) and P62. Furthermore, erastin-induced breast cancer cell death was inhibited by an iron chelator, deferoxamine, which inhibited the increases of erastin-induced iron levels and inhibited the erastin-induced changes in the expression levels of the autophagy-related proteins beclin1, ATG5, ATG12, LC3B and P62. In summary, erastin triggered autophagic death in breast cancer cells by increasing intracellular iron levels.
Background:
Epidemiological studies and mice models have demonstrated that air pollution containing particulate matter smaller than 2.5 μm (PM2.5) exacerbates acute episodes of asthma in both children and adults.
Objectives:
The aim of the study was to investigate the effect of continuous PM2.5 treatment on asthma regulation mechanism behind this effect.
Material and methods:
In this study, the effects of continuous exposure to PM2.5 on asthma and eosinophil recruitment was compared to the effect of a single pre-ovalbumin (OVA)-sensitization exposure to PM2.5. Wild-type mice were either challenged once with PM2.5 + OVA before sensitization and asthma induction over a 27-day period, or with 5 times of PM2.5 + OVA treatment and sensitization/asthma induction over the same period.
Results:
Continuous exposure to PM2.5 significantly increased total plasma immunoglobulin E (IgE), bronchial alveolar lavage fluid (BALF) cell numbers, eosinophils, and macrophages, leading to increased lung injury. This effect was regulated through increased production of chemokines and cytokines, such as interleukin (IL)-1β, monocyte chemoattractant protein 1 (MCP-1), IL-12, IL-5, IL-13, and prostaglandin D2 (PGD2). Eosinophil recruitment during continuous PM2.5 treatment was regulated through phosphorylation of the JAK/STAT6 pathway. As this study shows, continuous PM2.5 treatment significantly worsens asthma as compared to single exposure to PM2.5 or OVA exposure alone.
Conclusions:
Our findings reveal that continuous exposure of PM2.5 exacerbates OVA-induced asthma in mouse lung through JAK-STAT6 signaling pathway.
Background:
Ferroptosis is a newly recognized type of cell death, which is different from traditional necrosis, apoptosis or autophagic cell death. However, the position of ferroptosis in lipopolysaccharide (LPS)-induced acute lung injury (ALI) has not been explored intensively so far. In this study, we mainly analyzed the relationship between ferroptosis and LPS-induced ALI.
Methods:
In this study, a human bronchial epithelial cell line, BEAS-2B, was treated with LPS and ferrostatin-1 (Fer-1, ferroptosis inhibitor). The cell viability was measured using CCK-8. Additionally, the levels of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), and iron, as well as the protein level of SLC7A11 and GPX4, were measured in different groups. To further confirm the in vitro results, an ALI model was induced by LPS in mice, and the therapeutic action of Fer-1 and ferroptosis level in lung tissues were evaluated.
Results:
The cell viability of BEAS-2B was down-regulated by LPS treatment, together with the ferroptosis markers SLC7A11 and GPX4, while the levels of MDA, 4-HNE and total iron were increased by LPS treatment in a dose-dependent manner, which could be rescued by Fer-1. The results of the in vivo experiment also indicated that Fer-1 exerted therapeutic action against LPS-induced ALI, and down-regulated the ferroptosis level in lung tissues.
Conclusions:
Our study indicated that ferroptosis has an important role in the progression of LPS-induced ALI, and ferroptosis may become a novel target in the treatment of ALI patients.
Energy stress depletes ATP and induces cell death. Here we identify an unexpected inhibitory role of energy stress on ferroptosis, a form of regulated cell death induced by iron-dependent lipid peroxidation. We found that ferroptotic cell death and lipid peroxidation can be inhibited by treatments that induce or mimic energy stress. Inactivation of AMP-activated protein kinase (AMPK), a sensor of cellular energy status, largely abolishes the protective effects of energy stress on ferroptosis in vitro and on ferroptosis-associated renal ischaemia–reperfusion injury in vivo. Cancer cells with high basal AMPK activation are resistant to ferroptosis and AMPK inactivation sensitizes these cells to ferroptosis. Functional and lipidomic analyses further link AMPK regulation of ferroptosis to AMPK-mediated phosphorylation of acetyl-CoA carboxylase and polyunsaturated fatty acid biosynthesis. Our study demonstrates that energy stress inhibits ferroptosis partly through AMPK and reveals an unexpected coupling between ferroptosis and AMPK-mediated energy-stress signalling.
Non-small cell lung cancer (NSCLC) has long been one of the most lethal types of cancer due to its lack of typical clinical symptoms at early stages and high risk of tumour recurrence, even following complete surgical resection. Multicourse chemotherapy based on cisplatin (CDDP) is the standard adjuvant treatment for NSCLC; however, its benefits for the overall survival of patients are limited. In this study, NSCLC cells possessing CDDP-resistant characteristics (N5CP cells), obtained from surgical resection of clinical specimens of patients with NSCLC, were cultured and screened to generate research models. This study aimed to identify the mechanism underlying tumour cell resistance to CDDP and to identify a novel treatment for NSCLC following CDDP failure. CDDP-mediated NF-E2 related factor 2 (Nrf2)/light chain of System xc- (xCT) pathway activation was associated with the resistance of cells to CDDP. Therefore, erastin/sorafenib regulation of Nrf2 or xCT expression may alter the sensitivity of tumour cells to CDDP. The small molecules erastin and sorafenib effectively induced N5CP cell ferroptosis, which was mediated by the accumulation of intracellular lipid reactive oxygen species. Additionally, low doses of erastin or sorafenib could be used in association with CDDP to effectively trigger N5CP cell ferroptosis. Furthermore, it was indicated that erastin and sorafenib, alone or in combination with a low dose of CDDP, effectively inhibited the growth of N5CP cells in vivo. Therefore, ferroptosis inducers, including erastin and sorafenib, may be considered a novel treatment regimen for patients with NSCLC, particularly patients with CDDP failure.
Ferroptosis is a novel form of programmed cell death in which the accumulation of intracellular iron promotes lipid peroxidation, leading to cell death. Recently, the induction of autophagy has been suggested during ferroptosis. However, this relationship between autophagy and ferroptosis is still controversial and the autophagy-inducing mediator remains unknown. In this study, we confirmed that autophagy is indeed induced by the ferroptosis inducer erastin. Furthermore, we show that autophagy leads to iron-dependent ferroptosis by degradation of ferritin and induction of transferrin receptor 1 (TfR1) expression, using wild-type and autophagy-deficient cells, BECN1+/− and LC3B−/−. Consistently, autophagy deficiency caused depletion of intracellular iron and reduced lipid peroxidation, resulting in cell survival during erastin-induced ferroptosis. We further identified that autophagy was triggered by erastin-induced reactive oxygen species (ROS) in ferroptosis. These data provide evidence that ROS-induced autophagy is a key regulator of ferritin degradation and TfR1 expression during ferroptosis. Our study thus contributes toward our understanding of the ferroptotic processes and also helps resolve some of the controversies associated with this phenomenon.
Ferroptosis, a newly discovered form of iron-dependent regulated cell death, has been implicated in traumatic brain injury (TBI). MiR-212-5p has previously been reported to be downregulated in extracellular vesicles following TBI. To investigate whether miR-212-5p is involved in the ferroptotic neuronal death in TBI mice, we first examined the accumulation of malondialdehyde (MDA) and ferrous ion, and the expression of ferroptosis-related molecules at 6 h, 12 h, 24 h, 48 h and 72 h following controlled cortical impact (CCI) in mice. There was a significant upregulation in the expression of Gpx4 and Acsl4 at 6 h, Slc7a11 from 12 h to 72 h, and Nox2 and Sat1 from 6 h to 72 h post injury. Similarly, an upregulation in the expression of Gpx4 at 6 h, Nox2 from 6 h to 72 h, xCT from 12 h to 72 h, and Sat1 at 72 h after CCI was observed at the protein level. Interestingly, MDA and ferrous ion were increased whereas miR-212-5p was decreased in the CCI group compared to the sham group. Furthermore, we found that overexpression of miR-212-5p attenuated ferroptosis while downregulation of miR-212-5p promoted ferroptotic cell death partially by targeting prostaglandin-endoperoxide synthase-2 (Ptgs2) in HT-22 and Neuro-2a cell lines. In addition, administration of miR-212-5p in CCI mice significantly improved learning and spatial memory. Collectively, these findings indicate that miR-212-5p may protect against ferroptotic neuronal death in CCI mice partially by targeting Ptgs2.
Ferroptosis is a necrotic form of regulated cell death (RCD) mediated by phospholipid peroxidation in association with free iron-mediated Fenton reactions. Disrupted iron homeostasis resulting in excessive oxidative stress has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Here, we demonstrate the involvement of ferroptosis in COPD pathogenesis. Our in vivo and in vitro models show labile iron accumulation and enhanced lipid peroxidation with concomitant non-apoptotic cell death during cigarette smoke (CS) exposure, which are negatively regulated by GPx4 activity. Treatment with deferoxamine and ferrostatin-1, in addition to GPx4 knockdown, illuminate the role of ferroptosis in CS-treated lung epithelial cells. NCOA4-mediated ferritin selective autophagy (ferritinophagy) is initiated during ferritin degradation in response to CS treatment. CS exposure models, using both GPx4-deficient and overexpressing mice, clarify the pivotal role of GPx4-regulated cell death during COPD. These findings support a role for cigarette smoke-induced ferroptosis in the pathogenesis of COPD.
Heart failure (HF) is the single largest cause for increased hospitalization after fine particulate matter (PM2.5) exposure. Patients with left HF often progress to right ventricular (RV) failure even with optimal medical care. An increase of PM2.5 of 10 μg per cubic meter was associated with a 76% increase in the risk of death from cardiovascular disease in 4 years' period. However, the role and mechanism of PM2.5 in HF progression are not known. Here we investigated the role of PM2.5 exposure in mice with existing HF mice produced by transverse aortic constriction (TAC). TAC-induced HF caused lung inflammation, vascular remodeling and RV hypertrophy. We found increased PM2.5 profoundly exacerbated lung oxidative stress in mice with existing left HF. To our surprise, PM2.5 exposure had no effect on LV hypertrophy and function, but profoundly exacerbated lung inflammation, vascular remodeling, and RV hypertrophy in mice with existing left HF. These striking findings demonstrate that PM2.5 and/or air pollution is a critical factor for overall HF progression by regulating lung oxidative stress, inflammation and remodeling as well as RV hypertrophy. Improving air quality may save HF patients from a dismal fate.
Ferroptosis is an iron-dependent, oxidative cell death, and is characterized by iron-dependent accumulation of reactive oxygen species (ROS) within the cell. It has been implicated in various human diseases, including cancer. Recently, ferroptosis, as a non-apoptotic form of cell death, is emerging in specific cancer types; however, its relevance in colorectal cancer (CRC) is unexplored and remains unclear. Here, we showed that ferroptosis inducer RSL3 initiated cell death and ROS accumulation in HCT116, LoVo, and HT29 CRC cells over a 24 h time course. Furthermore, we found that ROS levels and transferrin expression were elevated in CRC cells treated with RSL3 accompanied by a decrease in the expression of glutathione peroxidase 4 (GPX4), indicating an iron-dependent cell death, ferroptosis. Overexpression GPX4 resulted in decreased cell death after RSL3 treatment. Therefore, RSL3 was able to induce ferroptosis on three different CRC cell lines in vitro in a dose- and time-dependent manner, which was due to increased ROS and an increase in the cellular labile iron pool. Moreover, this effect was able to be reversed by overexpression of GPX4. Taken together, our results suggest that the induction of ferroptosis contributed to RSL3-induced cell death in CRC cells and ferroptosis may be a pervasive and dynamic form of cell death for cancer treatment.
Cancer cells often upregulate nutrient transporters to fulfill their increased biosynthetic and bioenergetic needs, and to maintain redox homeostasis. One nutrient transporter frequently overexpressed in human cancers is the cystine/glutamate antiporter solute carrier family 7 member 11 (SLC7A11; also known as xCT). SLC7A11 promotes cystine uptake and glutathione biosynthesis, resulting in protection from oxidative stress and ferroptotic cell death. Recent studies have unexpectedly revealed that SLC7A11 also plays critical roles in glutamine metabolism and regulates the glucose and glutamine dependency of cancer cells. This review discusses the roles of SLC7A11 in regulating the antioxidant response and nutrient dependency of cancer cells, explores our current understanding of SLC7A11 regulation in cancer metabolism, and highlights key open questions for future studies in this emerging research area. A deeper understanding of SLC7A11 in cancer metabolism may identify new therapeutic opportunities to target this important amino acid transporter for cancer treatment.
Macroautophagy/autophagy is a conserved catabolic process that recycles cytoplasmic material during low energy conditions. BECN1/Beclin1 (beclin 1, autophagy related) is an essential protein for function of the class 3 phosphatidylinositol 3-kinase (PtdIns3K) complexes that play a key role in autophagy nucleation and elongation. Here, we show that AMP-activated protein kinase (AMPK) regulates autophagy by phosphorylating BECN1 at Thr388. Phosphorylation of BECN1 is required for autophagy upon glucose withdrawal. BECN1T388A, a phosphorylation defective mutant, suppresses autophagy through decreasing the interaction between PIK3C3 (phosphatidylinositol 3-kinase catalytic subunit type 3) and ATG14 (autophagy related 14). The BECN1T388A mutant has a higher affinity for BCL2 than its wild-type counterpart; the mutant is more prone to dimer formation. Conversely, a BECN1 phosphorylation mimic mutant, T388D, has stronger binding to PIK3C3 and ATG14, and promotes higher autophagy activity than the wild-type control. These findings uncover a novel mechanism of autophagy regulation.
Bisphenol A (BPA) is a common environmental contaminant, whose exposure is associated with the progression of various kidney diseases. BPA exposure has turned out to be associated with cytotoxicity to renal tubular epithelial cells, but its underlying mechanism remains unknown. Herein, we found that BPA induced ferroptosis in kidney and renal tubular epithelial cells, as showed by increased intracellular iron accumulation, lipid peroxidation and cells death upon BPA exposure. Additionally, utilization of ferrostatin-1 and desferrioxamine, typical ferroptosis inhibitors, can fundamentally diminish cells death. Intriguingly, we discovered that autophagy inhibitor chloroquine can shield renal tubular epithelial cells from BPA-caused ferroptosis. Furthermore, we found that ferritinophagy, a phenomenon that degradation of ferritin and inducing subsequent iron overload, occurred after BPA exposure and excessive iron promoted ferroptosis through Fenton reaction. We next demonstrated that BPA activated the AMPK-mTOR-ULK1 signaling pathway. In turn, AMPK, mTOR, and ULK1 knockdown dramatically mitigated BPA-induced TCMK-1 cells death, and decreased MDA and LC3 levels, but increased FTH protein content. These results indicate that activation of the AMPK-mTOR-ULK1 signaling is involved in BPA-induced ferritinophagy. In conclusion, renal dysfunction and renal tubular epithelial damage induced by BPA are linked to ferroptosis, which depends on the activation of ferritinophagy through AMPK-mTOR-ULK1 axis.
Background: Rising pollution plays a crucial role in worsening several respiratory diseases. Particulate Matter (PM)-induced asthma exacerbations are one of the most dangerous events.
Objectives: To assess the correlation between progressive particulate matter short-term exposure and asthma exacerbations, we investigated the role of PM levels on Emergency Department (ED) admissions and hospitalizations for these events in Brescia, an important industrial city located in northern Italy with high yearly levels of air pollution.
Methods: We analyzed 1050 clinical records of ED admissions for suspected asthma exacerbation, starting from January 2014 to December 2017. Daily PM levels were collected from the Environmental Protection Regional Agency. We performed a time-series analysis using a Poisson regression model with single and multiple day-lag. Results were expressed as Relative Risk (RR) and Excess of Relative Risk (ERR) of severe asthma exacerbation over a 10µg/m³ increase in PM10 and PM2.5 concentration.
Results: We selected and focused our analysis on 543 admissions for indisputable asthma exacerbation in ED and hospital. The time-series study showed an increase of the RR (CI95%) for asthma exacerbation-related ED admissions of 1.24 with an ERR of 24.2% for PM2.5 at lag0-1 (p < 0.05). We also estimated for PM2.5 a RR (CI95%) of 1.12 with an ERR of 12.5% at lag0-5 (p ≤ 0.05). Again, for PM2.5, an increase of the RR (CI95%) for asthma exacerbation-related hospitalizations of 1.31 with an ERR of 30.7% at lag0-1 (p < 0.05) has been documented. These findings were confirmed and even reinforced considering only the population living in the city.
Conclusions: Short-term PM exposure, especially for PM2.5, plays a critical role in inducing asthma exacerbation events leading to ED admission or hospitalization.
Alzheimer disease (AD) is usually accompanied by two prominent pathological features, cerebral accumulation of amyloid-β (Aβ) plaques and presence of MAPT/tau neurofibrillary tangles. Dysregulated clearance of Aβ largely contributes to its accumulation and plaque formation in the brain. Macroautophagy/autophagy is a lysosomal degradative process, which plays an important role in the clearance of Aβ. Failure of autophagic clearance of Aβ is currently acknowledged as a contributing factor to increased accumulation of Aβ in AD brains. In this study, we have identified crocetin, a pharmacologically active constituent from the flower stigmas of Crocus sativus, as a potential inducer of autophagy in AD. In the cellular model, crocetin induced autophagy in N9 microglial and primary neuron cells through STK11/LKB1 (serine/threonine kinase 11)-mediated AMP-activated protein kinase (AMPK) pathway activation. Autophagy induction by crocetin significantly increased Aβ clearance in N9 cells. Moreover, crocetin crossed the blood-brain barrier and induced autophagy in the brains’ hippocampi of wild-type male C57BL/6 mice. Further studies in transgenic male 5XFAD mice, as a model of AD, revealed that one-month treatment with crocetin significantly reduced Aβ levels and neuroinflammation in the mice brains and improved memory function by inducing autophagy that was mediated by AMPK pathway activation. Our findings support further development of crocetin as a pharmacological inducer of autophagy to prevent, slow down progression, and/or treat AD.
Objective
Cold exposure provokes cardiac remodeling and cardiac dysfunction. Autophagy participates in cold stress-induced cardiovascular dysfunction. This study was designed to examine the impact of Beclin1 haploinsufficiency (BECN+/−) in cold stress-induced cardiac geometric and contractile responses.
Methods and materials
Wild-type (WT) and BECN+/− mice were assigned to normal or cold exposure (4 °C) environment for 4 weeks prior to evaluation of cardiac geometry, contractile and mitochondrial properties. Autophagy, apoptosis and ferroptosis were evaluated.
Results
Our data revealed that cold stress triggered cardiac remodeling, compromised myocardial contractile capacity including ejection fraction, fractional shortening, peak shortening and maximal velocity of shortening/relengthening, duration of shortening and relengthening, intracellular Ca²⁺ release, intracellular Ca²⁺ decay, mitochondrial ultrastructural disarray, superoxide production, unchecked autophagy, apoptosis and ferroptosis, the effects of which were negated by Beclin1 haploinsufficiency. Circulating levels of corticosterone were elevated in both WT and BECN+/− mice. Treatment of corticosterone synthesis inhibitor metyrapone or ferroptosis inhibitor liproxstatins-1 rescued cold stress-induced cardiac dysfunction and mitochondrial injury. In vitro study noted that corticosterone challenge compromised cardiomyocyte function, provoked lipid peroxidation and mitochondrial injury, the effects of which were nullified by Beclin1 haploinsufficiency, inhibitors of lipoxygenase, ferroptosis and autophagy. In addition, ferroptosis inducer erastin abrogated Beclin1 deficiency-offered cardioprotection.
Conclusion
These data suggest that Beclin1 haploinsufficiency protects against cold exposure-induced cardiac dysfunction possibly through corticosterone- and ferroptosis-mediated mechanisms.
Acute lung injury (ALI) is a life-threatening disorder with high rates of morbidity and mortality. Reactive oxygen species and epithelial apoptosis are involved in the pathogenesis of acute lung injury. Ferroptosis, an iron-dependent non-apoptotic form of cell death, mediates its effects in part by promoting the accumulation of reactive oxygen species. The inhibition of ferroptosis decreases clinical symptoms in experimental models of ischemia/reperfusion-induced renal failure and heart injury. This study investigated the roles of inhibitor of apoptosis-stimulating protein of p53 (iASPP) and Nrf2 in ferroptosis and their potential therapeutic effects in intestinal ischemia/reperfusion-induced acute lung injury. Intestinal ischemia/reperfusion-induced ALI was induced in wild-type and Nrf2−/− mice. The mice were treated with erastin followed by liproxstatin-1. Ferroptosis-related factors in mice with ischemia/reperfusion-induced acute lung injury or in mouse lung epithelial-2 cells with hypoxia/regeneration (HR)-induced ALI were measured by western blotting, real-time PCR, and immunofluorescence. Ferroptosis contributed to intestinal ischemia/reperfusion-induced ALI in vivo. iASPP inhibited ferroptosis and alleviated intestinal ischemia/reperfusion-induced acute lung injury, and iASPP-mediated protection against ischemia/reperfusion-induced ALI was dependent on Nrf2 signaling. HR-induced acute lung injury enhanced ferroptosis in vitro in mouse lung epithelial-2 cells, and ferroptosis was modulated after the enhancement of intestinal ischemia/reperfusion in Nrf2−/− mice. iASPP mediated its protective effects against acute lung injury through the Nrf2/HIF-1/TF signaling pathway. Ferroptosis contributes to intestinal ischemia/reperfusion-induced ALI, and iASPP treatment inhibits ferroptosis in part via Nrf2. These findings indicate the therapeutic potential of iASPP for treating ischemia/reperfusion-induced ALI.
The widely used inhalation anesthetic, isoflurane, potentially induces neuronal injury in clinical practice. Previous studies showed multiple forms of cell death that resulted from isoflurane-induced cytotoxicity, but the precise underlying mechanism remains poorly understood. Ferroptosis has recently been identified as a non-apoptotic form of regulated cell death. Here, we found that ferroptosis inhibitors, ferrostatin-1 and deferoxamine mesylate (DFOM), showed great efficiency in maintaining cell viability in SH-SY5Y neuroblastoma cells exposed to a high concentration of isoflurane for 24 h. We also observed that cellular chelatable iron and lipid peroxidation were increased in a concentration-dependent manner in response to isoflurane. In addition, isoflurane upregulated Beclin1 phosphorylation, followed by the formation of a Beclin1-solute carrier family 7 member 11 (SLC7A11) complex, which affected the activity of cystine/glutamate antipoter and further regulated ferroptotic cell death. Accordingly, Beclin1 overexpression aggravated isoflurane-induced cell damage by upregulating ferroptosis. This phenomenon was significantly attenuated by silencing of Beclin1 in SH-SY5Y cells. These findings indicate that Beclin1 may regulate ferroptosis in a manner involving inhibition of glutamate exchange activity of system xc(-), which is implicated in isoflurane-induced toxicity. In particular, when isoflurane is administrated at high concentrations and for an extended duration, ferroptosis is more likely to play a crucial role in isoflurane-induced toxicity.
Ferroptosis is recognized as a new form of regulated cell death which is initiated by severe lipid peroxidation relying on reactive oxygen species (ROS) generation and iron overload. This iron-dependent cell death manifests evident morphological, biochemical and genetic differences from other forms of regulated cell death, such as apoptosis, autophagy, necrosis and pyroptosis. Ferroptosis was primarily characterized by condensed mitochondrial membrane densities and smaller volume than normal mitochondria, as well as the diminished or vanished of mitochondria crista and outer membrane ruptured. Mitochondria take the center role in iron metabolism, as well as substance and energy metabolism as it's the major organelle in iron utilization, catabolic and anabolic pathways. Interference of key regulators of mitochondrial lipid metabolism (e.g., ASCF2 and CS), iron homeostasis (e.g., ferritin, mitoferrin1/2 and NEET proteins), glutamine metabolism and other signaling pathways make a difference to ferroptotic sensitivity. Targeted induction of ferroptosis was also considered as a potential therapeutic strategy to some oxidative stress diseases, including neurodegenerative disorders, ischemia-reperfusion injury, traumatic spinal cord injury. However, the pertinence between mitochondria and ferroptosis is still in dispute. Here we systematic elucidate the morphological characteristics and metabolic regulation of mitochondria in the regulation of ferroptosis.
PM2.5 is becoming a worldwide environmental problem, which profoundly endangers public health, thus progressively capturing public attention this decade. As a fragile target of PM2.5, the underlying mechanisms of endothelial cell damage are still obscure. According to the previous microarray data and signaling pathway analysis, a new form of cell death termed ferroptosis in the current study is proposed following PM2.5 exposure. In order to verify the vital role of ferroptosis in PM2.5-induced endothelial lesion and further understand the potential mechanism involved, intracellular iron content, ROS release and lipid peroxidation, as well as biomarkers of ferroptosis were detected, respectively. As a result, uptake of particles increases cellular iron content and ROS production. Meanwhile, GSH depletion, and the decrease of GSH-Px and NADPH play significant roles in PM2.5-induced endothelial cell ferroptosis. Moreover, significantly changed expression of TFRC, FTL and FTH1 hinted that dysfunction of iron uptake and storage is a major inducer of ferroptosis. Importantly, index monitored above can be partially rescued by lipid peroxidation inhibitor ferrostatin-1 and iron chelator deferoxamine mesylate, which mediated antiferroptosis activity mainly depends on the restoration of antioxidant activity and iron metabolism. In conclusion, our data basically show that PM2.5 enhances ferroptosis sensitivity with increased ferroptotic events in endothelial cells, in which iron overload, lipid peroxidation and redox imbalance act pivotal roles.
One of the key challenges in cancer research is how to effectively kill cancer cells while leaving the healthy cells intact. Cancer cells often have defects in cell death executioner mechanisms, which is one of the main reasons for therapy resistance. To enable growth, cancer cells exhibit an increased iron demand compared with normal, non-cancer cells. This iron dependency can make cancer cells more vulnerable to iron-catalyzed necrosis, referred to as ferroptosis. The identification of FDA-approved drugs as ferroptosis inducers creates high expectations for the potential of ferroptosis to be a new promising way to kill therapy-resistant cancers.
Redox changes and generation of reactive oxygen species (ROS) are part of normal cell metabolism. While low ROS levels are implicated in cellular signaling pathways necessary for survival, higher levels play major roles in cancer development as well as cell death signaling and execution. A role for redox changes in apoptosis has been long established; however, several new modalities of regulated cell death have been brought to light, for which the importance of ROS production as well as ROS source and targets are being actively investigated. In this review, we summarize recent findings on the role of ROS and redox changes in the activation and execution of two major forms of regulated cell death, necroptosis and ferroptosis. We also discuss the potential of using modulators of these two forms of cell death to exacerbate ROS as a promising anticancer therapy.
Ferroptosis is a form of regulated cell death triggered by lipid peroxidation after inhibition of the cystine/glutamate antiporter system Xc-. However, key regulators of system Xc- activity in ferroptosis remain undefined. Here, we show that BECN1 plays a hitherto unsuspected role in promoting ferroptosis through directly blocking system Xc- activity via binding to its core component, SLC7A11 (solute carrier family 7 member 11). Knockdown of BECN1 by shRNA inhibits ferroptosis induced by system Xc- inhibitors (e.g., erastin, sulfasalazine, and sorafenib), but not other ferroptosis inducers including RSL3, FIN56, and buthionine sulfoximine. Mechanistically, AMP-activated protein kinase (AMPK)-mediated phosphorylation of BECN1 at Ser90/93/96 is required for BECN1-SLC7A11 complex formation and lipid peroxidation. Inhibition of PRKAA/AMPKα by siRNA or compound C diminishes erastin-induced BECN1 phosphorylation at S93/96, BECN1-SLC7A11 complex formation, and subsequent ferroptosis. Accordingly, a BECN1 phosphorylation-defective mutant (S90,93,96A) reverses BECN1-induced lipid peroxidation and ferroptosis. Importantly, genetic and pharmacological activation of the BECN1 pathway by overexpression of the protein in tumor cells or by administration of the BECN1 activator peptide Tat-beclin 1, respectively, increases ferroptotic cancer cell death (but not apoptosis and necroptosis) in vitro and in vivo in subcutaneous and orthotopic tumor mouse models. Collectively, our work reveals that BECN1 plays a novel role in lipid peroxidation that could be exploited to improve anticancer therapy by the induction of ferroptosis.
Air quality data from a one year study at an urban roadside location in Rome are reported for major pollutants. Continuous concentration data of carbon monoxide, ozone, nitrogen dioxide, aromatic hydrocarbons and natural radioactivity were measured in the urban air of Rome from January 2016 to January 2017. Moreover, PM2.5 mass concentration and physico-chemical characteristics of single constituent particles are herein reported. Gaseous pollutants, except ozone, and PM2.5 showed maximum concentrations in December due to high atmospheric stability. O3 and NO2 trend analysis showed photochemical smog episodes in June and September. In September, during a photochemical smog episode the aromatic hydrocarbons contribution to ozone formation was experimentally proven. Pearson's coefficient among aromatic hydrocarbons and the ratio Toluene/Benzene (T/B) showed that pollutants were under the influence of vehicular traffic. Physico-chemical characterization of PM2.5 single particles, carried out by field emission scanning electron microscope combined with energy dispersive X-ray spectroscopy, displayed the presence of particle diversity from natural and anthropogenic origin. Four principal components in the PM2.5 were identified: carbonaceous particles, Ca-sulphates, soil dust and building structure particles, metal particles. The principal source of carbonaceous particles in this urban area consists of the motor vehicle exhausts and the heating systems in winter. Traces of S and sometimes S, Na, K were detected on varying percentages of carbonaceous particles. These data suggested that the carbonaceous particles act as vehicles for strong acids, prevalently H2SO4 and alkaline metal sulphates. A Saharan dust contribution to PM2.5 was found in different periods. Metal particles included iron oxide particles, metals oxide particles and Fe-rich metal compounds. The identification of chemical composition of individual particles provide useful information to determine their origin and formation processes.
Cells constantly adapt their metabolism to meet their energy needs and respond to nutrient availability. Eukaryotes have evolved a very sophisticated system to sense low cellular ATP levels via the serine/threonine kinase AMP-activated protein kinase (AMPK) complex. Under conditions of low energy, AMPK phosphorylates specific enzymes and growth control nodes to increase ATP generation and decrease ATP consumption. In the past decade, the discovery of numerous new AMPK substrates has led to a more complete understanding of the minimal number of steps required to reprogramme cellular metabolism from anabolism to catabolism. This energy switch controls cell growth and several other cellular processes, including lipid and glucose metabolism and autophagy. Recent studies have revealed that one ancestral function of AMPK is to promote mitochondrial health, and multiple newly discovered targets of AMPK are involved in various aspects of mitochondrial homeostasis, including mitophagy. This Review discusses how AMPK functions as a central mediator of the cellular response to energetic stress and mitochondrial insults and coordinates multiple features of autophagy and mitochondrial biology.
Recently, many researchers paid more attentions to the association between air pollution and respiratory system disease. In the past few years, levels of smog have increased throughout China resulting in the deterioration of air quality, raising worldwide concerns. PM2.5 (particles less than 2.5 micrometers in diameter) can penetrate deeply into the lung, irritate and corrode the alveolar wall, and consequently impair lung function. Hence it is important to investigate the impact of PM2.5 on the respiratory system and then to help China combat the current air pollution problems. In this review, we will discuss PM2.5 damage on human respiratory system from epidemiological, experimental and mechanism studies. At last, we recommend to the population to limit exposure to air pollution and call to the authorities to create an index of pollution related to health.
Many epidemiologic studies have documented variable relationships between ambient particulate matter (PM) and chronic obstructive pulmonary disease (COPD) hospitalizations and mortality in cities worldwide.
Comprehensive and systematic searches were performed in the electronic reference databases (PubMed, EMBASE, Google Scholar, Ovid, and Web of Science) with specific search terms and selection criteria for relevant studies. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were performed to evaluate the relationship between short-term PM2.5 exposure and COPD hospitalizations and mortality. The sources of heterogeneity and the effect of potential confounders were explored using subgroup analyses. Study findings were analyzed using random-effect model and fixed effect model in COPD hospitalizations and mortality, respectively.
The search yielded 12 studies suitable for meta-analysis of hospitalizations and six studies for the mortality meta-analysis during the period. A 10 ug/m3 increase in daily PM2.5 (lag days 0-7) was associated with a 3.1% (95% CI: 1.6%-4.6%) increase in COPD hospitalizations, and a 2.5% (95% CI: 1.5%-3.5%) increase in COPD mortality. Significant publication bias was not found in studies focusing on the relationship between short-term PM2.5 exposure and COPD hospitalizations and mortality.
Our combined analysis indicated that short-term exposure to 10 μg/m3 increment of ambient PM2.5 is associated with increased COPD hospitalizations and mortality. Further study is needed to elucidate to which extent this relationship is causal together with other factors and to elucidate the mechanism by which PM2.5 induces activation of cellular processes promoting COPD exacerbations.
The seasonal variation of PM2.5 carbonaceous aerosol was investigated in Beijing and Tangshan cities of China. The characteristics of carbonaceous aerosol (e.g., organic carbon, OC and elemental carbon, EC) under different weather conditions and their source apportionment were also examined. The annual average PM2.5 concentration in the study area reached 95.6-197.3 μg/m(3), showing seasonal and spatial variation. The carbonaceous materials accounted for 17.3-21.2 % of the PM2.5, and they had a much higher content under haze weather condition. It was found that the PM2.5 contained more OC than EC. Principal component analysis (PCA) results indicated that the carbonaceous components came from mixed emission sources of coal combustion, vehicle exhaust, and biomass burning. In Beijing, the vehicle emission made a contribution of 63.0 % to the carbonaceous components of PM2.5 in summer, which is higher than that in Tangshan. While in Tangshan, the coal combustion made a contribution of 30.3 %, which is much higher than that in Beijing.
The transition metal iron is essential for life, yet potentially toxic iron-catalyzed reactive oxygen species (ROS) are unavoidable in an oxygen-rich environment. Iron and ROS are increasingly recognized as important initiators and mediators of cell death in a variety of organisms and pathological situations. Here, we review recent discoveries regarding the mechanism by which iron and ROS participate in cell death. We describe the different roles of iron in triggering cell death, targets of iron-dependent ROS that mediate cell death and a new form of iron-dependent cell death termed ferroptosis. Recent advances in understanding the role of iron and ROS in cell death offer unexpected surprises and suggest new therapeutic avenues to treat cancer, organ damage and degenerative disease.
Nonapoptotic forms of cell death may facilitate the selective elimination of some tumor cells or be activated in specific pathological states. The oncogenic RAS-selective lethal small molecule erastin triggers a unique iron-dependent form of nonapoptotic cell death that we term ferroptosis. Ferroptosis is dependent upon intracellular iron, but not other metals, and is morphologically, biochemically, and genetically distinct from apoptosis, necrosis, and autophagy. We identify the small molecule ferrostatin-1 as a potent inhibitor of ferroptosis in cancer cells and glutamate-induced cell death in organotypic rat brain slices, suggesting similarities between these two processes. Indeed, erastin, like glutamate, inhibits cystine uptake by the cystine/glutamate antiporter (system x(c)(-)), creating a void in the antioxidant defenses of the cell and ultimately leading to iron-dependent, oxidative death. Thus, activation of ferroptosis results in the nonapoptotic destruction of certain cancer cells, whereas inhibition of this process may protect organisms from neurodegeneration.
Beclin1(Atg6) is a well-known key regulator of autophagy. Although Beclin1 is enzymatically inert, it governs the autophagic process by regulating PtdIns3KC3-dependent generation of phosphatidylinositol3-phosphate (PtdIns(3)P) and the subsequent recruitment of additional Atg proteins that orchestrate autophagosome formation. Furthermore, Beclin1 is implicated in numerous biological processes, including adaptation to stress, development, endocytosis, cytokinesis, immunity, tumorigenesis, ageing and cell death. Whether all of these processes involve only the autophagy-inducing function of Beclin1 is now being seriously questioned, because Beclin1 appears to exercise several non-autophagy functions. Therefore, we should broaden our view of Beclin1 as a specialized molecule in autophagy to that of a multifunctional protein. The central role of Beclin1 in multiple signaling events obviously requires tight regulation at multiple levels. Its function is kept in check by diverse mechanisms, such as epigenetic silencing, microRNA regulation, post-translational modifications, and protein-protein interactions. Interestingly, multiple diseases are associated with deficiency or malfunction of Beclin1, which makes it a potentially valuable target for various therapies, including anti-cancer treatment. In this review, we focus on Beclin1 as a multifunctional protein, discuss the variety of mechanisms by which it is controlled, and give an overview of Beclin1-associated pathologies.
Function of PM2.5 in the pathogenesis of lung cancer and chronic airway inflammatory diseases
- Li