Ginsenoside RK1 Induces Ferroptosis in Hepatocellular Carcinoma Cells through an FSP1-Dependent Pathway.

BACKGROUND: Hepatocellular carcinoma (HCC), currently ranking as the third most lethal malignancy, poses a grave threat to human health. Ferroptosis, a form of programmed cell demise, has emerged as a promising therapeutic target in HCC treatment. In this study, we investigated the impact of ginsenoside RK1 on ferroptosis induction in HCC cells and elucidated the underlying mechanisms. METHODS: The HCC cell line HepG2 was utilized to evaluate the effects of ginsenoside RK1. Distinct dosages of ginsenoside RK1 (25 µM, 50 µM, and 100 µM) were selected based on half-maximal inhibitory concentration (IC50) values. Cellular viability was assessed using a CCK8 assay, cytotoxicity was measured via lactate dehydrogenase (LDH) release assay, and colony-forming ability was evaluated using the clone formation assay. Various inhibitors targeting apoptosis (Z-VAD-FMK 20 µM), necrosis (Nec-1, 10 µM), and ferroptosis (Fer-1, 10 µM; Lip-1, 1 µM) were employed to assess ginsenoside RK1's impact on cell demise. Intracellular levels of key ions, including glutathione (GSH), malondialdehyde (MDA), and iron ions, were quantified, and the protein expression levels of ferroptosis-related genes were evaluated. The sensitivity of HCC cells to ferroptosis induction by ginsenoside RK1 was examined following the overexpression and silencing of the aforementioned target genes. RESULTS: Ginsenoside RK1 exhibited an inhibitory effect on HCC cells with an IC50 value of approximately 20 µM. It attenuated cellular viability and colony-forming capacity in a dose-dependent manner, concurrently reducing intracellular GSH levels and increasing intracellular Malondialdehyde (MDA) and iron ion contents. Importantly, cell demise induced by ginsenoside RK1 was specifically counteracted by ferroptosis inhibitors. Furthermore, the modulation of Ferroptosis suppressor protein 1 (FSP1) expression influenced the ability of ginsenoside RK1 to induce ferroptosis. FSP1 overexpression or silencing enhanced or inhibited ferroptosis induction by ginsenoside RK1, respectively. CONCLUSIONS: Ginsenoside RK1 enhances ferroptosis in hepatocellular carcinoma through an FSP1-dependent pathway.

SENP3 sensitizes macrophages to ferroptosis via de-SUMOylation of FSP1.

Ferroptosis, driven by an imbalance in redox homeostasis, has recently been identified to regulate macrophage function and inflammatory responses. SENP3 is a redox-sensitive de-SUMOylation protease that plays an important role in macrophage function. However, doubt remains on whether SENP3 and SUMOylation regulate macrophage ferroptosis. For the first time, the results of our study suggest that SENP3 sensitizes macrophages to RSL3-induced ferroptosis. We showed that SENP3 promotes the ferroptosis of M2 macrophages to decrease M2 macrophage proportion in vivo. Mechanistically, we identified the ferroptosis repressor FSP1 as a substrate for SUMOylation and confirmed that SUMOylation takes place mainly at its K162 site. We found that SENP3 sensitizes macrophages to ferroptosis by interacting with and de-SUMOylating FSP1 at the K162 site. In summary, our study describes a novel type of posttranslational modification for FSP1 and advances our knowledge of the biological functions of SENP3 and SUMOylation in macrophage ferroptosis.

The dual role of FSP1 in programmed cell death: resisting ferroptosis in the cell membrane and promoting necroptosis in the nucleus of THP-1 cells.

BACKGROUND: Acute monocytic leukemia-M5 (AML-M5) remains a challenging disease due to its high morbidity and poor prognosis. In addition to the evidence mentioned earlier, several studies have shown that programmed cell death (PCD) serves a critical function in treatment of AML-M5. However, the role and relationship between ferroptosis and necroptosis in AML-M5 remains unclear. METHODS: THP-1 cells were mainly treated with Erastin and IMP-366. The changes of ferroptosis and necroptosis levels were detected by CCK-8, western blot, quantitative real-time PCR, and electron microscopy. Flow cytometry was applied to detect the ROS and lipid ROS levels. MDA, 4-HNE, GSH and GSSG were assessed by ELISA kits. Intracellular distribution of FSP1 was studied by immunofluorescent staining and western blot. RESULTS: The addition of the myristoylation inhibitor IMP-366 to erastin-treated acute monocytic leukemia cell line THP-1 cell not only resulted in greater susceptibility to ferroptosis characterized by lipid peroxidation, glutathione (GSH) depletion and mitochondrial shrinkage, as the FSP1 position on membrane was inhibited, but also increased p-RIPK1 and p-MLKL protein expression, as well as a decrease in caspase-8 expression, and triggered the characteristic necroptosis phenomena, including cytoplasmic translucency, mitochondrial swelling, membranous fractures by FSP1 migration into the nucleus via binding importin α2. It is interesting to note that ferroptosis inhibitor fer-1 reversed necroptosis. CONCLUSION: We demonstrated that inhibition of myristoylation by IMP-366 is capable of switching ferroptosis and ferroptosis-dependent necroptosis in THP-1 cells. In these findings, FSP1-mediated ferroptosis and necroptosis are described as alternative mechanisms of PCD of THP-1 cells, providing potential therapeutic strategies and targets for AML-M5.

Nrf2/FSP1/CoQ10 axis-mediated ferroptosis is involved in sodium aescinate-induced nephrotoxicity.

Sodium aescinate (SA), an active compound found in horse chestnut seeds, is widely used in clinical practice. Recently, the incidence of SA-induced adverse events, particularly renal impairment, has increased. Our previous work demonstrated that SA causes severe nephrotoxicity via nephrocyte ferroptosis; however, the underlying mechanism remains to be fully elucidated. In the current study, we investigated additional molecular pathways involved in SA-induced nephrotoxicity. Our results showed that SA inhibited cell viability, disrupted cellular membrane integrity, and enhanced reactive oxygen species (ROS), ferrous iron (Fe2+), and malondialdehyde (MDA) levels, as well as lipid peroxidation in rat proximal renal tubular epithelial cell line (NRK-52E) cells. SA also depleted coenzyme Q10 (CoQ10, ubiquinone) and nicotinamide adenine dinucleotide (NADH) and reduced ferroptosis suppressor protein 1 (FSP1) and polyprenyltransferase (coenzyme Q2, COQ2) activity, triggering lipid peroxidation and ROS accumulation in mouse kidneys and NRK-52E cells. The overexpression of COQ2, FSP1, or CoQ10 (ubiquinone) supplementation effectively attenuated SA-induced ferroptosis, whereas iFSP1 or 4-formylbenzoic acid (4-CBA) pretreatment exacerbated SA-induced nephrotoxicity. Additionally, SA decreased nuclear factor-erythroid-2-related factor 2 (Nrf2) levels and inhibited Nrf2 binding to the -1170/-1180 bp ARE site in FSP1 promoter, resulting in FSP1 suppression. Overexpression of Nrf2 or its agonist dimethyl fumarate (DMF) promoted FSP1 expression, thereby improving cellular antioxidant capacity and alleviating SA-induced ferroptosis. These results suggest that SA-triggers renal injury through oxidative stress and ferroptosis, driven by the suppression of the Nrf2/FSP1/CoQ10 axis.

Idebenone alleviates doxorubicin-induced cardiotoxicity by stabilizing FSP1 to inhibit ferroptosis.

Doxorubicin (DOX)-mediated cardiotoxicity can exacerbate mortality in oncology patients, but related pharmacotherapeutic measures are relatively limited. Ferroptosis was recently identified as a major mechanism of DOX-induced cardiotoxicity. Idebenone, a novel ferroptosis inhibitor, is a well-described clinical drug widely used. However, its role and pathological mechanism in DOX-induced cardiotoxicity are still unclear. In this study, we demonstrated the effects of idebenone on DOX-induced cardiotoxicity and elucidated its underlying mechanism. A single intraperitoneal injection of DOX (15 mg/kg) was administrated to establish DOX-induced cardiotoxicity. The results showed that idebenone significantly attenuated DOX-induced cardiac dysfunction due to its ability to regulate acute DOX-induced Fe2+ and ROS overload, which resulted in ferroptosis. CESTA and BLI further revealed that idebenone's anti-ferroptosis effect was mediated by FSP1. Interestingly, idebenone increased FSP1 protein levels but did not affect Fsp1 mRNA levels in the presence of DOX. Idebenone could form stable hydrogen bonds with FSP1 protein at K355, which may influence its association with ubiquitin. The results confirmed that idebenone stabilized FSP1 protein levels by inhibiting its ubiquitination degradation. In conclusion, this study demonstrates idebenone attenuated DOX-induced cardiotoxicity by inhibiting ferroptosis via regulation of FSP1, making it a potential clinical drug for patients receiving DOX treatment.

Inhibition of FSP1: A new strategy for the treatment of tumors (Review).

Ferroptosis, a regulated form of cell death, is intricately linked to iron­dependent lipid peroxidation. Recent evidence strongly supports the induction of ferroptosis as a promising strategy for treating cancers resistant to conventional therapies. A key player in ferroptosis regulation is ferroptosis suppressor protein 1 (FSP1), which promotes cancer cell resistance by promoting the production of the antioxidant form of coenzyme Q10. Of note, FSP1 confers resistance to ferroptosis independently of the glutathione (GSH) and glutathione peroxidase­4 pathway. Therefore, targeting FSP1 to weaken its inhibition of ferroptosis may be a viable strategy for treating refractory cancer. This review aims to clarify the molecular mechanisms underlying ferroptosis, the specific pathway by which FSP1 suppresses ferroptosis and the effect of FSP1 inhibitors on cancer cells.

Regulation of FSP1 myristoylation by NADPH: A novel mechanism for ferroptosis inhibition.

Excitotoxicity is a prevalent pathological event in neurodegenerative diseases. The involvement of ferroptosis in the pathogenesis of excitotoxicity remains elusive. Transcriptome analysis has revealed that cytoplasmic reduced nicotinamide adenine dinucleotide phosphate (NADPH) levels are associated with susceptibility to ferroptosis-inducing compounds. Here we show that exogenous NADPH, besides being reductant, interacts with N-myristoyltransferase 2 (NMT2) and upregulates the N-myristoylated ferroptosis suppressor protein 1 (FSP1). NADPH increases membrane-localized FSP1 and strengthens resistance to ferroptosis. Arg-291 of NMT2 is critical for the NADPH-NMT2-FSP1 axis-mediated suppression of ferroptosis. This study suggests that NMT2 plays a pivotal role by bridging NADPH levels and neuronal susceptibility to ferroptosis. We propose a mechanism by which the NADPH regulates N-myristoylation, which has important implications for ferroptosis and disease treatment.

TRPV3 facilitates lipolysis and attenuates diet-induced obesity via activation of the NRF2/FSP1 signaling axis.

Transient receptor potential vanilloid (TRPV) ion channels play a crucial role in various cellular functions by regulating intracellular Ca2+ levels and have been extensively studied in the context of several metabolic diseases. However, the regulatory effects of TRPV3 in obesity and lipolysis are not well understood. In this study, utilizing a TRPV3 gain-of-function mouse model (TRPV3G568V/G568V), we assessed the metabolic phenotype of both TRPV3G568V/G568V mice and their control littermates, which were randomly assigned to either a 12-week high-fat diet or a control diet. We investigated the potential mechanisms underlying the role of TRPV3 in restraining obesity and promoting lipolysis both in vivo and in vitro. Our findings indicate that a high-fat diet led to significant obesity, characterized by increased epididymal and inguinal white adipose tissue weight and higher fat mass. However, the gain-of-function mutation in TRPV3 appeared to counteract these adverse effects by enhancing lipolysis in visceral fat through the upregulation of the major lipolytic enzyme, adipocyte triglyceride lipase (ATGL). In vitro experiments using carvacrol, a TRPV3 agonist, demonstrated the promotion of lipolysis and antioxidation in 3T3-L1 adipocytes after TRPV3 activation. Notably, carvacrol failed to stimulate Ca2+ influx, lipolysis, and antioxidation in 3T3-L1 adipocytes treated with BAPTA-AM, a cell-permeable calcium chelator. Our results revealed that TRPV3 activation induced the action of transcriptional factor nuclear factor erythroid 2-related factor 2 (NRF2), resulting in increased expression of ferroptosis suppressor protein 1 (FSP1) and superoxide dismutase2 (SOD2). Moreover, the inhibition of NRF2 impeded carvacrol-induced lipolysis and antioxidation in 3T3-L1 adipocytes, with downregulation of ATGL, FSP1, and SOD2. In summary, our study suggests that TRPV3 promotes visceral fat lipolysis and inhibits diet-induced obesity through the activation of the NRF2/FSP1 signaling axis. We propose that TRPV3 may be a potential therapeutic target in the treatment of obesity.

Ironing out the role of ferroptosis in immunity.

Ferroptosis is a type of regulated cell death that drives the pathophysiology of many diseases. Oxidative stress is detectable in many types of regulated cell death, but only ferroptosis involves lipid peroxidation and iron dependency. Ferroptosis originates and propagates from several organelles, including the mitochondria, endoplasmic reticulum, Golgi, and lysosomes. Recent data have revealed that immune cells can both induce and undergo ferroptosis. A mechanistic understanding of how ferroptosis regulates immunity is critical to understanding how ferroptosis controls immune responses and how this is dysregulated in disease. Translationally, more work is needed to produce ferroptosis-modulating immunotherapeutics. This review focuses on the role of ferroptosis in immune-related diseases, including infection, autoimmune diseases, and cancer. We discuss how ferroptosis is regulated in immunity, how this regulation contributes to disease pathogenesis, and how targeting ferroptosis may lead to novel therapies.

Ferroptosis inhibitor alleviates sorafenib-induced cardiotoxicity by attenuating KLF11-mediated FSP1-dependent ferroptosis.

Sorafenib is a standard first-line drug for advanced hepatocellular carcinoma, but the serious cardiotoxic effects restrict its therapeutic applicability. Here, we show that iron-dependent ferroptosis plays a vital role in sorafenib-induced cardiotoxicity. Remarkably, our in vivo and in vitro experiments demonstrated that ferroptosis inhibitor application neutralized sorafenib-induced heart injury. By analyzing transcriptome profiles of adult human sorafenib-treated cardiomyocytes, we found that Krüppel-like transcription factor 11 (KLF11) expression significantly increased after sorafenib stimulation. Mechanistically, KLF11 promoted ferroptosis by suppressing transcription of ferroptosis suppressor protein 1 (FSP1), a seminal breakthrough due to its ferroptosis-repressing properties. Moreover, FSP1 knockdown showed equivalent results to glutathione peroxidase 4 (GPX4) knockdown, and FSP1 overexpression counteracted GPX4 inhibition-induced ferroptosis to a substantial extent. Cardiac-specific overexpression of FSP1 and silencing KLF11 by an adeno-associated virus serotype 9 markedly improved cardiac dysfunction in sorafenib-treated mice. In summary, FSP1-mediated ferroptosis is a crucial mechanism for sorafenib-provoked cardiotoxicity, and targeting ferroptosis may be a promising therapeutic strategy for alleviating sorafenib-induced cardiac damage.

Knockdown of NADK promotes LUAD ferroptosis via NADPH/FSP1 axis.

BACKGROUND: Lung cancer is a serious threat to human health and is the first leading cause of cancer death. Ferroptosis, a newly discovered form of programmed cell death associated with redox homeostasis, is of particular interest in the lung cancer, given the high oxygen environment of lung cancer. NADPH has reducing properties and therefore holds the potential to resist ferroptosis. Resistance to ferroptosis exists in lung cancer, but the role of NADK in regulating ferroptosis in lung cancer has not been reported yet. METHODS: Immunohistochemistry (IHC) was used to analyse the expression of NADK in 86 cases of lung adenocarcinoma(LUAD) and adjacent tissues, and a IHC score was assigned to each sample. Chi-square and kaplan-meier curve was performed to analyse the differences in metastasis and five-year survival between the two groups with NADK high or low scores. Proliferation of NADK-knockdown LUAD cell lines was detected in vivo and vitro. Furthermore, leves of ROS, MDA and Fe2+ were measured to validate the effect and mechanism of NADK on ferroptosis in LUAD. RESULTS: The expression of NADK was significantly evaluated in LUAD tissues as compared to adjacent non-cancerous tissues. The proliferation of NADK-knockdown cells was inhibited both in vivo and vitro, and increasing levels of intracellular ROS, Fe2+ and lipid peroxide products (MDA) were observed. Furthermore, NADK-knockdown promoted the ferroptosis of LUAD cells induced by Erastin/RSL3 by regulating the level of NADPH and the expression of FSP1. Knockdown of NADK enhanced the sensitivities of LUAD cells to Erastin/RSL3-induced ferroptosis by regulating NADPH level and FSP1 expression. CONCLUSIONS: NADK is over-expressed in LUAD patients. Knockdown of NADK inhibited the proliferation of LUAD cells both in vitro and in vivo and promotes the Erastin/RSL3-induced ferroptosis of LUAD cells by down-regulating the NADPH/FSP1 axis.

BRD4 inhibitors broadly promote erastin-induced ferroptosis in different cell lines by targeting ROS and FSP1.

Ferroptosis, an iron-dependent form of programmed cell death, is a promising strategy for cancer treatment. Bromodomain-containing protein 4 (BRD4) is an epigenetic reader and a promising target for cancer therapeutics. However, the role of BRD4 in ferroptosis is controversial and the value of the interaction between BRD4 inhibitors and ferroptosis inducers remains to be explored. Here, we found that BRD4 inhibition greatly enhanced erastin-induced ferroptosis in different types of cells, including HEK293T, HeLa, HepG2, RKO, and PC3 cell lines. Knocking down BRD4 in HEK293T and HeLa cells also promoted erastin-induced cell death. BRD4 inhibition by JQ-1 and I-BET-762 or BRD4 knockdown resulted in substantial accumulation of reactive oxygen species (ROS) in both HEK293T and HeLa cells. The effect of BRD4 inhibition on ferroptosis-associated genes varied in different cells. After using BRD4 inhibitors, the expression of FTH1, Nrf2, and GPX4 increased in HEK293T cells, while the levels of VDAC2, VDAC3, and FSP1 decreased. In HeLa cells, the expression of FTH1, VDAC2, VDAC3, Nrf2, GPX4, and FSP1 was reduced upon treatment with JQ-1 and I-BET-762. Consistently, the level of FSP1 was greatly reduced in HEK293T and HeLa cells with stable BRD4 knockdown compared to control cells. Furthermore, ChIP-sequencing data showed that BRD4 bound to the promoter of FSP1, but the BRD4 binding was greatly reduced upon JQ-1 treatment. Our results suggest that ROS accumulation and FSP1 downregulation are common mechanisms underlying increased ferroptosis with BRD4 inhibitors. Thus, BRD4 inhibitors might be more effective in combination with ferroptosis inducers, especially in FSP1-dependent cancer cells.

Penthorum chinense Pursh inhibits ferroptosis in cellular and Caenorhabditis elegans models of Alzheimer's disease.

BACKGROUND: Ferroptosis, a unique type of cell death triggered by iron-dependent lipid peroxidation, plays a critical role in the pathogenesis of Alzheimer's disease (AD), a debilitating condition marked by memory loss and cognitive impairment due to the accumulation of beta-amyloid (Aß) and hyperphosphorylated Tau protein. Increasing evidence suggests that inhibitors of ferroptosis could be groundbreaking in the treatment of AD. METHOD: In this study, we established in vitro ferroptosis using erastin-, RSL-3-, hemin-, and iFSP1-induced PC-12 cells. Using MTT along with Hoechst/PI staining, we assessed cell viability and death. To determine various aspects of ferroptosis, we employed fluorescence probes, including DCFDA, JC-1, C11 BODIPY, Mito-Tracker, and PGSK, to measure ROS production, mitochondrial membrane potential, lipid peroxidation, mitochondrial morphology, and intracellular iron levels. Additionally, Western blotting, biolayer interferometry technology, and shRNA were utilized to investigate the underlying molecular mechanisms. Furthermore, p-CAX APP Swe/Ind- and pRK5-EGFP-Tau P301L overexpressing PC-12 cells, along with Caenorhabditis elegans (C. elegans) strains CL4176, CL2331, and BR5270, were employed to examine ferroptosis in AD models. RESULTS: Here, we conducted a screening of our natural medicine libraries and identified the ethanol extract of Penthorum chinense Pursh (PEE), particularly its ethyl acetate fraction (PEF), displayed inhibitory effects on ferroptosis in cells. Specifically, PEF inhibited the generation of ROS, lipid peroxidation, and intracellular iron levels. Furthermore, PEF demonstrated protective effects against H2O2-induced cell death, ROS production, and mitochondrial damage. Mechanistic investigations unveiled PEF's modulation of intracellular iron accumulation, GPX4 expression and activity, and FSP1 expression. In p-CAX APP Swe/Ind and pRK5-EGFP-Tau P301L overexpressing PC-12 cells, PEF significantly reduced cell death, as well as ROS and lipid peroxidase production. Moreover, PEF ameliorated paralysis and slowing rate in Aß and Tau transgenic C. elegans models, while inhibiting ferroptosis, as evidenced by decreased DHE intensity, lipid peroxidation levels, iron accumulation, and expression of SOD-3 and gst-4. CONCLUSION: Our findings highlight the suppressive effects of PEF on ferroptosis in AD cellular and C. elegans models. This study helps us better understand how ferroptosis affects AD and emphasizes the potential of PCP as a candidate for AD intervention.

Andrographolide attenuates sepsis-induced acute kidney injury by inhibiting ferroptosis through the Nrf2/FSP1 pathway.

Sepsis is a systemic inflammatory response syndrome caused by infection, which causes renal dysfunction known as sepsis-associated acute kidney injury (S-AKI). Ferroptosis is a form of lipid peroxidation dependent on iron and reactive oxygen species that differs from other forms of programmed cell death at the morphological and biochemical levels. Andrographolide (AG), a natural diterpenoid lactone compound extracted from Andrographis paniculata, has been shown to have therapeutic effects in kidney disease. In this study, we investigated the novel mechanism by which AG attenuates septic acute kidney injury by inhibiting ferroptosis in renal tubular epithelial cells (HK-2) through the Nrf2/FSP1 pathway. Cecum ligation and puncture (CLP)-induced septic rats and lipopolysaccharide (LPS)-induced HK-2 cells were used for in vivo and in vitro experiments. Firstly, in septic rats and HK-2 cells, AG effectively decreased the levels of kidney injury indicators, including blood creatinine, urea nitrogen, and markers of kidney injury such as neutrophil gelatinase-associated lipid transport protein and kidney injury molecule-1 (KIM-1). In addition, AG prevented ferroptotosis, by avoiding the accumulation of iron and lipid peroxidation, and an increase in SLC7A11 and GPX4 in AG-treated HK-2 cells. Furthermore, AG attenuated mitochondrial damage, including mitochondrial swelling, outer membrane rupture, and a reduction in mitochondrial cristae in LPS-treated HK-2 cells. Ferrostatin-1 (Fer-1), a ferroptosis inhibitor, significantly inhibited LPS-induced ferroptosis in HK-2 cells. Importantly, our results confirm that Nrf2/FSP1 is an important pathway for ferroptosis resistance. Nrf2 siRNA hindered the effect of AG in attenuating acute kidney injury and inhibiting ferroptosis. These findings demonstrate that Nrf2/FSP1-mediated HK-2 ferroptosis is associated with AG, alleviates septic acute kidney injury, and indicates a novel avenue for therapeutic interventions in the treatment of acute kidney injury in sepsis.

Co-catalpol alleviates fluoxetine-induced main toxicity: Involvement of ATF3/FSP1 signaling-mediated inhibition of ferroptosis.

BACKGROUND: Fluoxetine is often used as a well-known first-line antidepressant. However, it is accompanied with hepatogenic injury as its main organ toxicity, thereby limiting its application despite its superior efficacy. Fluoxetine is commonly traditionally used combined with some Chinese antidepressant prescriptions containing Rehmannia glutinosa (Dihuang) for depression therapy and hepatoprotection. Our previous experiments showed that co-Dihuang can alleviate fluoxetine-induced liver injury while efficiencies, and catalpol may be the key ingredient to characterize the toxicity-reducing and synergistic effects. However, whether co-catalpol can alleviate fluoxetine-induced liver injury and its toxicity-reducing mechanism remain unclear. PURPOSE: On the basis of the first recognition of the dose and duration at which pre-fluoxetine caused hepatic injury, co-catalpol's alleviation of fluoxetine-induced hepatic injury and its pathway was comprehensively elucidated. METHOD AND RESULTS: The hepatoprotection of co-catalpol was evaluated by serum biochemical indexes sensitive to hepatic injury and multiple staining techniques for hepatic pathologic analysis. Subsequently, the pathway by which catalpol alleviated fluoxetine-induced hepatic injury was predicted by network pharmacology to be predominantly the inhibition of ferroptosis. These were validated and confirmed in subsequent experiments with key technologies and diagnostic reagents related to ferroptosis. Further molecular docking showed that activating transcription factor 3 (ATF3) and ferroptosis suppressor protein 1 (FSP1) were the the most prospective molecules for catalpol and fluoxetine among many ferroptosis-related molecules. The critical role of ATF3/FSP1 signaling was further observed by surface plasmon resonance, diagnostic reagents, transmission electron microscopy, Western blot, real-time PCR, immunofluorescence, and immunohistochemistry. Results showed that fluoxetine directly bound to ATF3 and FSP1; agonisting ATF3 or blocking FSP1 abolished the alleviation of catalpol on fluoxetine-induced liver injury, and both exacerbated ferroptosis. Moreover, co-catalpol significantly enhanced the antidepressant efficacy of fluoxetine against depressive behaviours in mice. CONCLUSION: The hepatic impairment properties of fluoxetine were largely dependent on ATF3/FSP1 target-mediated ferroptosis. Co-catalpol alleviated fluoxetine-induced hepatic injury while enhancing its antidepressant efficacy, and that ATF3/FSP1 signaling-mediated inhibition of ferroptosis was involved in its co-administration detoxification mechanism. This study was the first to reveal the hepatotoxicity characteristics, targets, and mechanisms of fluoxetine; provide a detoxification and efficiency regimen by co-catalpol; and elucidate the detoxification mechanism.

A tangible method to assess native ferroptosis suppressor activity.

Ferroptosis, a regulated cell death hallmarked by unrestrained lipid peroxidation, plays a pivotal role in the pathophysiology of various diseases, making it a promising therapeutic target. Glutathione peroxidase 4 (GPX4) prevents ferroptosis by reducing (phospho)lipid hydroperoxides, yet evaluation of its actual activity has remained arduous. Here, we present a tangible method using affinity-purified GPX4 to capture a snapshot of its native activity. Next to measuring GPX4 activity, this improved method allows for the investigation of mutational GPX4 activity, exemplified by the GPX4U46C mutant lacking selenocysteine at its active site, as well as the evaluation of GPX4 inhibitors, such as RSL3, as a showcase. Furthermore, we apply this method to the second ferroptosis guardian, ferroptosis suppressor protein 1, to validate the newly identified ferroptosis inhibitor WIN62577. Together, these methods open up opportunities for evaluating alternative ferroptosis suppression mechanisms.

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

ETHNOPHARMACOLOGICAL RELEVANCE: Kai Xin San (KXS), first proposed by Sun Simiao during the Tang Dynasty, has been utilized to treat dementia by tonifying qi and dispersing phlegm. AIM OF THE STUDY: This study aimed to elucidate the mechanism by which KXS exerts its therapeutic effects on Alzheimer's disease (AD) by targeting ferroptosis, using a combination of network pharmacology, bioinformatics, and experimental validation strategies. MATERIALS AND METHODS: The active target sites and the further potential mechanisms of KXS in protecting against AD were investigated through molecular docking, molecular dynamics simulation, and network pharmacology, and combined with the validation of animal experiments. RESULTS: Computational and experimental findings provide the first indication that KXS significantly improves learning and memory defects and inhibits neuronal ferroptosis by repairing mitochondria damage and upregulating the protein expression of ferroptosis suppressor protein 1 (FSP1) in vivo APP/PS1 mice AD model. According to bioinformatics analysis, the mechanism by which KXS inhibits ferroptosis may involve SIRT1. KXS notably upregulated the mRNA and protein expression of SIRT1 in both vivo APP/PS1 mice and in vitro APP-overexpressed HT22 cells. Additionally, KXS inhibited ferroptosis induced by APP-overexpression in HT22 cells through activating the SIRT1-FSP1 signal pathway. CONCLUSIONS: Collectively, our findings suggest that KXS may inhibit neuronal ferroptosis through activating the SIRT1/FSP1 signaling pathway. This study reveals the scientific basis and underlying modern theory of replenishing qi and eliminating phlegm, which involves the inhibition of ferroptosis. Moreover, it highlights the potential application of SIRT1 or FSP1 activators in the treatment of AD and other ferroptosis-related diseases.

The crystal structure of human ferroptosis suppressive protein 1 in complex with flavin adenine dinucleotide and nicotinamide adenine nucleotide.

Ferroptosis is a recently discovered form of regulated cell death characterized by its distinct dependence on iron and the peroxidation of lipids within cellular membranes. Ferroptosis plays a crucial role in physiological and pathological situations and has attracted the attention of numerous scientists. Ferroptosis suppressive protein 1 (FSP1) is one of the main regulators that negatively regulates ferroptosis through the GPX4-independent FSP1-CoQ10-NAD(P)H axis and is a potential therapeutic target for ferroptosis-related diseases. However, the crystal structure of FSP1 has not been resolved, which hinders the development of therapeutic strategies targeting FSP1. To unravel this puzzle, we purified the human FSP1 (hFSP1) protein using the baculovirus eukaryotic cell expression system and solved its crystal structure at a resolution of 1.75 Å. Furthermore, we evaluated the oxidoreductase activity of hFSP1 with NADH as the substrate and identified E156 as the key amino acid in maintaining hFSP1 activity. Interestingly, our results indicated that hFSP1 exists and functions in a monomeric state. Mutagenesis analysis revealed the critical role of the C-terminal domain in the binding of substrate. These findings significantly enhance our understanding of the functional mechanism of FSP1 and provide a precise model for further drug development.

Inhibition of Gpx4-mediated ferroptosis alleviates cisplatin-induced hearing loss in C57BL/6 mice.

Cisplatin-induced hearing loss is a common side effect of cancer chemotherapy in clinics; however, the mechanism of cisplatin-induced ototoxicity is still not completely clarified. Cisplatin-induced ototoxicity is mainly associated with the production of reactive oxygen species, activation of apoptosis, and accumulation of intracellular lipid peroxidation, which also is involved in ferroptosis induction. In this study, the expression of TfR1, a ferroptosis biomarker, was upregulated in the outer hair cells of cisplatin-treated mice. Moreover, several key ferroptosis regulator genes were altered in cisplatin-damaged cochlear explants based on RNA sequencing, implying the induction of ferroptosis. Ferroptosis-related Gpx4 and Fsp1 knockout mice were established to investigate the specific mechanisms associated with ferroptosis in cochleae. Severe outer hair cell loss and progressive damage of synapses in inner hair cells were observed in Atoh1-Gpx4-/- mice. However, Fsp1-/- mice showed no significant hearing phenotype, demonstrating that Gpx4, but not Fsp1, may play an important role in the functional maintenance of HCs. Moreover, findings showed that FDA-approved luteolin could specifically inhibit ferroptosis and alleviate cisplatin-induced ototoxicity through decreased expression of transferrin and intracellular concentration of ferrous ions. This study indicated that ferroptosis inhibition through the reduction of intracellular ferrous ions might be a potential strategy to prevent cisplatin-induced hearing loss.

Targeting of FSP1 regulates iron homeostasis in drug-tolerant persister head and neck cancer cells via lipid-metabolism-driven ferroptosis.

BACKGROUND: Research has demonstrated that some tumor cells can transform into drug-tolerant persisters (DTPs), which serve as a reservoir for the recurrence of the disease. The persister state in cancer cells arises due to temporary molecular reprogramming, and exploring the genetic composition and microenvironment during the development of head and neck squamous cell carcinoma (HNSCC) can enhance our comprehension of the types of cell death that HNSCC, thus identifying potential targets for innovative therapies. This project investigated lipid-metabolism-driven ferroptosis and its role in drug resistance and DTP generation in HNSCC. METHODS: High levels of FSP1 were discovered in the tissues of patients who experienced relapse after cisplatin treatment. RNA sequencing indicated that a series of genes related to lipid metabolism were also highly expressed in tissues from these patients. Consistent results were obtained in primary DTP cells isolated from patients who experienced relapse. The Cancer Genome Atlas database confirmed this finding. This revealed that the activation of drug resistance in cancer cells is influenced by FSP1, intracellular iron homeostasis, and lipid metabolism. The regulatory roles of ferroptosis suppressor protein 1 (FSP1) in HNSCC metabolic regulation were investigated. RESULTS: We generated human oral squamous cell carcinoma DTP cells (HNSCC cell line) to cisplatin and observed higher expression of FSP1 and lipid-metabolism-related targets in vitro. The shFSP1 blockade attenuated HNSCC-DTP cell stemness and downregulated tumor invasion and the metastatic rate. We found that cisplatin induced FSP1/ACSL4 axis expression in HNSC-DTPC cells. Finally, we evaluated the HNSCC CSC-inhibitory functions of iFSP1 (a metabolic drug and ferroptosis inducer) used for neo-adjuvant chemotherapy; this was achieved by inducing ferroptosis in a patient-derived xenograft mouse model. CONCLUSIONS: The present findings elucidate the link between iron homeostasis, ferroptosis, and cancer metabolism in HNSCC-DTP generation and acquisition of chemoresistance. The findings may serve as a suitable model for cancer treatment testing and prediction of precision treatment outcomes. In conclusion, this study provides clinically oriented platforms for evaluating metabolism-modulating drugs (FSP1 inhibitors) and new drug candidates of drug resistance and ferroptotic biomarkers.