Reaction-Based Color-Convertible Fluorescent Probe for Ferroptosis Identification

Exploring Ferroptosis in Allergic Inflammatory Diseases: Emerging Mechanisms and Therapeutic Perspectives

Ferroptosis, a unique form of regulated cell death driven by iron accumulation and lipid peroxidation, has emerged as a critical process in various diseases. Recent evidence suggests its involvement in the pathogenesis of allergic diseases, including asthma, allergic rhinitis, and atopic dermatitis. These conditions are characterized by chronic inflammation, oxidative stress, and immune dysregulation, all of which intersect with the molecular mechanisms of ferroptosis. Key regulators, such as glutathione peroxidase 4 (GPX4), the cystine/glutamate antiporter system Xc-, and iron metabolism pathways, play pivotal roles in ferroptotic processes and their contribution to allergic disease progression. This review explores the mechanistic link between ferroptosis and allergic diseases, emphasizing how oxidative damage and iron overload exacerbate inflammation and tissue injury. We also highlight emerging diagnostic biomarkers, including lipid peroxidation products and iron regulators, which could improve disease monitoring and stratification. Therapeutic strategies targeting ferroptosis, such as GPX4 activators, iron chelators, and lipid peroxidation inhibitors, show promise in preclinical\ studies, offering potential new avenues for treating allergic diseases. However, challenges remain in translating these findings into clinical applications. By integrating current knowledge, this review underscores the need for further research into ferroptosis as both a biomarker and therapeutic target in allergic diseases.

Monitoring Dynamic Changes of Cellular Membrane GSH During Stroke via an ESIPT-Based Near-Infrared Fluorescent Probe

Stroke, primarily ischemic (85%), results from inadequate blood supply and is worsened by ferroptosis, characterized by free radical generation and lipid peroxidation. Monitoring ferroptosis is essential for understanding its mechanisms and developing treatments. Glutathione (GSH) is a key ferroptosis biomarker, but current probes are limited by short excitation/emission wavelengths, small Stokes shifts, and inability to monitor dynamic GSH changes at the cellular membrane, where ferroptosis plays a crucial role. To address these issues, we developed the PM-Red-GSH, a novel near-infrared (NIR) probe based on the Excited-state intramolecular proton transfer (ESIPT) mechanism. It shows strong NIR emission (715 nm), large Stokes shift (290 nm), and enhanced membrane binding (PCC = 0.95) due to its alkyl group. PM-Red-GSH enables dynamic GSH monitoring in an MCAO mouse model. These findings offer new insights into ferroptosis and stroke treatment.

ONOO- Activatable Fluorescent Sulfur Dioxide Donor for a More Accurate Assessment of Cell Ferroptosis

Ferroptosis is critical in the treatment of tumor therapies. Thus, monitoring reactive oxygen species (ROS) is of great significance for accurate assessment in ferroptosis without any interference. However, current probes for monitoring ROS during ferroptosis suffer from a drawback in that the probes consume ROS during detection, which inhibits the ferroptosis process and thus affects the accuracy and effectiveness of monitoring the process of ferroptosis. Herein, a new fluorescent donor probe, TFMU-SO2D, with the combination of the moiety of the SO2 donor is designed and synthesized by introducing the aryl boronate moieties that could give it the ability to effectively recognize ONOO-. The released SO2 could consume excess glutathione and regulate oxidative stress by elevating ROS levels, which would offset the ROS depletion by TFMU-SO2D and ensure accuracy in monitoring the ferroptosis process. The experimental results demonstrated that TFMU-SO2D possessed satisfactory performance for monitoring ONOO- as well as simultaneously releasing SO2 in oxidative stress stimulated by monensin and ferroptosis stimulated by erastin and RSL3. Additionally, the capability of SO2 synergized with ferroptosis to inhibit the viability of cancer cells was demonstrated by the CCK8 assay, which may be due to the fact that SO2 can potentiate ferroptosis cell death by increasing the ROS level. Overall, these combined results indicated that TFMU-SO2D possesses the excellent ability to precisely monitor ONOO- during ferroptosis without interference, which is significant for accurately accessing ferroptosis, cancer treatment, and drug development.

Ferroptosis boosted oral cancer photodynamic therapy by carrier-free Sorafenib-Ce6 self-assembly nanoparticles

Oral cancer is a disease with high morbidity and mortality worldwide and greatly impacts the quality of life, especially in patients with advanced stages. Photodynamic therapy (PDT) is one of the most effective clinical treatments for oral cancers. However, most clinically applied photosensitizers have several deficiencies, including oxygen dependence, poor aqueous solubility, and a lack of tumor-targeting ability. Herein, the carrier-free multifunctional Sorafenib (Sor), chlorin e6 (Ce6), and Fe3+ self-assembly co-delivery nanoparticles (Sor-Ce6 NPs) were constructed via combining a ferroptosis inducer Sor and a photosensitizer Ce6 for synergetic therapy. The as-synthesized Sor-Ce6 NPs presented excellent colloidal stability and water dispersity with good in vivo tumor-targeting ability. More significantly, the low dose of Sor-Ce6 NPs had little dark toxicity but produced significantly enhanced ROS and supplied O2 sustainably to increase phototoxicity through ferroptosis pathway. Notably, the Sor-Ce6 NPs showed significantly higher in vitro and in vivo anti-tumor efficacy than the Sor/Ce6 mixture due to the improvement of cellular uptake and the incorporation of foreign Fe ions in the system, which also confer the T1 magnetic resonance-guided imaging ability to the formed Sor-Ce6 NPs. Our study demonstrates a promising self-assembled strategy for overcoming hypoxia-related PDT resistance for oral cancer treatment.

Ferroptosis, Metabolic Rewiring, and Endometrial Cancer

Ferroptosis is a newly discovered form of regulated cell death. The main feature of ferroptosis is excessive membrane lipid peroxidation caused by iron-mediated chemical and enzymatic reactions. In normal cells, harmful lipid peroxides are neutralized by glutathione peroxidase 4 (GPX4). When GPX4 is inhibited, ferroptosis occurs. In mammalian cells, ferroptosis serves as a tumor suppression mechanism. Not surprisingly, in recent years, ferroptosis induction has gained attention as a potential anticancer strategy, alone or in combination with other conventional therapies. However, sensitivity to ferroptosis inducers depends on the metabolic state of the cell. Endometrial cancer (EC) is the sixth most common cancer in the world, with more than 66,000 new cases diagnosed every year. Out of all gynecological cancers, carcinogenesis of EC is mostly dependent on metabolic abnormalities. Changes in the uptake and catabolism of iron, lipids, glucose, and glutamine affect the redox capacity of EC cells and, consequently, their sensitivity to ferroptosis-inducing agents. In addition to this, in EC cells, ferroptosis-related genes are usually mutated and overexpressed, which makes ferroptosis a promising target for EC prediction, diagnosis, and therapy. However, for a successful application of ferroptosis, the connection between metabolic rewiring and ferroptosis in EC needs to be deciphered, which is the focus of this review.

CA9 knockdown enhanced ionizing radiation-induced ferroptosis and radiosensitivity of hypoxic glioma cells

PURPOSE

Ferroptosis is a type of regulatory cell death, caused by excessive lipid peroxidation This study aimed to explore whether ionizing radiation could induce ferroptosis in glioma cells and whether carbonic anhydrase 9 (CA9) knockdown could enhance the killing effect of ionizing radiation on hypoxic glioma cells through ferroptosis.

MATERIALS AND METHODS

The protein levels of Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4) were detected by Western blot in glioma cells irradiated by different doses of X-ray. The relative mRNA levels of ferroptosis markers and intracellular iron-associated proteins were detected by Real-time qPCR. Lipid peroxidation of glioma cells was detected by oxidation-sensitive probe C11-BODIPY581/591 staining. CCK-8 Assay was used to detect cell viability after X-ray irradiation. Cloning formation assay was used to assess the radiosensitivity of glioma cells. The exposure of cell surface calreticulin was measured by immunofluorescence staining.

RESULTS

X-ray induced lipid peroxidation and ferroptosis markers expression in U251 and GL261 glioma cells. Knockdown of CA9 in hypoxic glioma cells significantly altered the expression of iron regulation-related proteins and enhanced X-ray-induced ferroptosis and radiosensitivity. The ferroptosis inhibitor significantly improved the survival of cells irradiated by X-ray, while ferroptosis inducers (FINs) enhanced the lethal effect of X-ray on cells. Enhancing ferroptosis in glioma cells promoted the exposure and release of damage-associated molecular patterns (DAMPs).

CONCLUSIONS

Ionizing radiation can induce ferroptosis in glioma cells. CA9 knockdown can enhance the radiosensitivity of hypoxic glioma cells and overcome the resistance of ferroptosis under hypoxia. Enhancing ferroptosis will become a new idea to improve the efficacy of radiotherapy for glioma.

Two-photon imaging for visualizing polarity in lipid droplets during chemotherapy induced Ferroptosis

As a novel pattern of regulated cell death (RCD), Ferroptosis is induced by lipid peroxide-dependent iron accumulation, which is associated with reactive oxygen species (ROS). Ferroptosis regulates cell death via ROS accumulation-related lipid peroxides accumulation, affecting the structure and polarity of lipid droplets (LDs). Compared with reactive fluorescent probes, environment-sensitive fluorescent probes allow for maximum preservation of the intracellular environment while monitoring metabolic activity in situ, resulting in more accurate monitoring results. In this study, a polarity-sensitive two-photon fluorescent probe with anchoring capacity in LDs, LIP-Pola, is reported and applied to monitor the polarity of LDs during cell Ferroptosis by in situ imaging analysis of cell Ferroptosis via LDs polarity changes. Additionally, Paclitaxel is shown to increase the Ferroptosis level from data of cells and tumor tissue sections, suggesting that Paclitaxel may deactivate tumor cells by regulating Ferroptosis.

Fluorescent probes for ferroptosis bioimaging: advances, challenges, and prospects

Ferroptosis is a form of regulatory cell death distinct from caspase-dependent apoptosis and plays an important role in life entities. Since ferroptosis involves a variety of complex regulatory factors, the levels of certain biological species and microenvironments would change during this process. Thus, the investigation of the level fluctuation of key target analytes during ferroptosis is of great significance for disease treatment and drug design. Toward this aim, multiple organic fluorescent probes with simple preparation and non-destructive detection have been developed, and research over the past decade has uncovered a vast array of homeostasis and other physiological characteristics of ferroptosis. However, this significant and cutting-edge topic has not yet been reviewed. In this work, we aim to highlight the latest breakthrough results of fluorescent probes for monitoring various bio-related molecules and microenvironments during ferroptosis at the cellular, tissue and in vivo levels. Accordingly, this tutorial review has been organized according to the target molecules identified by the probes including ionic species, reactive sulfur species, reactive oxygen species, biomacromolecules, microenvironment, and others. In addition to providing new insights into the findings of each fluorescent probe in ferroptosis studies, we also discuss the defects and limitations of the probes developed, and highlight the potential challenges and further prospects in this domain. We anticipate that this review will convey profound implications for designing powerful fluorescent probes to decrypt changes in key molecules and microenvironments during ferroptosis.

An Activity-Based Photosensitizer to Reverse Hypoxia and Oxidative Resistance for Tumor Photodynamic Eradication

Photodynamic therapy (PDT) has been a well-accepted clinical treatment for malignant tumors owing to its noninvasiveness and high spatiotemporal selectivity. However, the treatment outcome of current PDT applications is hindered by hypoxia and intracellular oxidative resistance of solid tumors. Recent studies have shown that inhibiting histone deacetylases (HDACs) can induce cell ferroptosis, reverse hypoxia, and elevate oxidative status. Theoretically, the design and synthesis of activity-based photosensitizers that target HDACs can address the bottlenecks of PDT. Herein, the concept of an activity-based photosensitizer is presented for targeting HDACs, which is designed based on a quinoxalinone scaffold through a pharmacophore migration strategy. The developed activity-based photosensitizer can inhibit HDACs, and overcome hypoxia and intracellular oxidative resistance, realizing the full potential of photosensitizers for malignant tumor treatment. The molecular design strategy proposed in this project should provide theoretical guidance for the development of ideal photosensitizers for practical applications.

Recent advances in small-molecule fluorescent probes for studying ferroptosis

Ferroptosis is an iron-dependent, non-apoptotic form of programmed cell death driven by excessive lipid peroxidation (LPO). Mounting evidence suggests that the unique modality of cell death is involved in the development and progression of several diseases including cancer, cardiovascular diseases (CVDs), neurodegenerative disorders, etc. However, the pathogenesis and signalling pathways of ferroptosis are not fully understood, possibly due to the lack of robust tools for the highly selective and sensitive imaging of ferroptosis analytes in complex living systems. Up to now, various small-molecule fluorescent probes have been applied as promising chemosensors for studying ferroptosis through tracking the biomolecules or microenvironment-related parameters in vitro and in vivo. In this review, we comprehensively reviewed the recent development of small-molecule fluorescent probes for studying ferroptosis, with a focus on the analytes, design strategies and bioimaging applications. We also provided new insights to overcome the major challenges in this emerging field.

Aggregation-Induced Emission Luminogens for Cell Death Research

Cell death is closely related to various diseases, and monitoring and controlling cell death is a promising strategy to develop efficient therapy. Aggregation-induced emission luminogens (AIEgens) are ideal candidates for developing novel theranostic agents because of their intriguing properties in the aggregate state. The rational application of AIE materials in cell death-related research is still in its infancy but has shown great clinical potential. This review discussed the research frontier and our understanding of AIE materials in various subroutines of cell death, including apoptosis, necrosis, immunogenic cell death, pyroptosis, autophagy, lysosome-dependent cell death, and ferroptosis. We hope that the new insights can be offered to this growing field and attract more researchers to provide valuable contributions.

Near-infrared fluorescent probe for hydrogen sulfide: high-fidelity ferroptosis evaluation in vivo during stroke

Ferroptosis is closely associated with cancer, neurodegenerative diseases and ischemia-reperfusion injury and the detection of its pathological process is very important for early disease diagnosis. Fluorescence based sensing technologies have become excellent tools due to the real-time detection of cellular physiological or pathological processes. However, to date the detection of ferroptosis using reducing substances as markers has not been achieved since the reducing substances are not only present at extremely low concentrations during ferroptosis but also play a key role in the further development of ferroptosis. Significantly, sensors for reducing substances usually consume reducing substances, instigating a redox imbalance, which further aggravates the progression of ferroptosis. In this work, a H₂S triggered and H₂S releasing near-infrared fluorescent probe (HL-H₂S) was developed for the high-fidelity in situ imaging of ferroptosis. In the imaging process, HL-H₂S consumes H₂S and releases carbonyl sulfide, which is then catalyzed by carbonic anhydrase to produce H₂S. Importantly, this strategy does not intensify ferroptosis since it avoids disruption of the redox homeostasis. Furthermore, using erastin as an inducer for ferroptosis, the observed trends for Fe²⁺, MDA, and GSH, indicate that the introduction of the HL-H₂S probe does not exacerbate ferroptosis. In contrast, ferroptosis progression was significantly promoted when the release of H₂S from HL-H₂S was inhibited using AZ. These results indicate that the H₂S triggered and H₂S releasing fluorescent probe did not interfere with the progression of ferroptosis, thus enabling high-fidelity in situ imaging of ferroptosis.

A H₂S triggered and H₂S releasing near-infrared fluorescent probe (HL-H₂S) was developed. HL-H₂S does not interfere with the progression of ferroptosis by consuming H₂S, thus enabling high-fidelity in situ imaging of ferroptosis.

Ferroptosis: molecular mechanisms and health implications

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.

Epigenetic Regulation and Nonepigenetic Mechanisms of Ferroptosis Drive Emerging Nanotherapeutics in Tumor

Currently, traditional cancer therapy still falls far short of expectations. However, a variety of invasive cancers that are resistant to chemotherapy (such as platinum drugs, one of the most applied antineoplastics in clinic) and targeted agents are susceptible to ferroptosis. Ferroptosis is a form of cell death that is driven by cell metabolism and iron-dependent lipid peroxidation. Ferroptosis inducers can eliminate the drug resistance of tumor cells in the mesenchymal state, effectively inhibit the drug resistance of acquired tumor cells, and optimize cancer efficacy. Research based on the epigenetic mechanism of ferroptosis is still in the stage of screening and verifying the regulatory effect, and there is no complete regulatory mechanism network. In this review, we expound on the epigenetic regulation and nonepigenetic mechanisms of ferroptosis and review the epigenetic-based mechanisms of tumor therapy potential and emerging nonepigenetic-based therapies (nanotherapeutics).

Rational Design of a High-Performance Quinoxalinone-Based AIE Photosensitizer for Image-Guided Photodynamic Therapy

Because light exhibits excellent spatiotemporal resolution, photodynamic therapy (PDT) is becoming a promising method for cancer treatment. However, in a single photosensitizer (PS), it remains a big challenge to achieve all key properties including effective singlet oxygen (¹O₂) production under long-wavelength laser and bright near-infrared (NIR) emission without toxicity in the dark. In addition, clinically used traditional PSs encounter quenched fluorescence and decreased ¹O₂ production because of molecular aggregation in aqueous solution. To solve the aforementioned issues, quinoxalinone CN (QCN) with effective ¹O₂ generation under long-wavelength (530 nm) laser irradiation and aggregation-induced NIR emission is rationally designed by precise optimization of the quinoxalinone scaffold. After being encapsulated by an amphiphilic polymer (DSPE-PEG), the yielded nanoparticles exhibit highly efficient ¹O₂ production and stable NIR fluorescence located at 800 nm without obvious toxicity under the dark. Both in vitro and in vivo evaluation identify that QCN would be a promising PS for image-guided PDT of tumors.

Real-Time Imaging Redox Status in Biothiols and Ferric Metabolism of Cancer Cells in Ferroptosis Based on Switched Fluorescence Response of Gold Carbon Dots

Ferroptosis is an iron-dependent form of regulated cell death. In this study, a ratiometric fluorescent probe, gold carbon dots (GCDs) consisting of carbon skeleton and gold nanoclusters, was used for in situ imaging to monitor redox status in biothiols (glutathione and cysteine) and ferric metabolism of cancer cells in ferroptosis. The as-prepared GCDs can selectively respond to biothiols, interestingly, the fluorescence may be switched to sense ferric ions without interference by biothiols under proper conditions. The robust GCDs-probe exhibits excellent photobleaching resistance and can reversibly respond to intracellular biothiols/ferric ion with high temporal resolution. The 8 h real-time imaging of living cells was employed to track the fluctuation of biothiols, showing the change of redox status in ferroptosis. In addition, release of ferric ions in cells was monitored. The real-time imaging of depletion of biothiols and release of ferric ion in cells indicates the GCDs-probe can monitor how the ferroptosis regulates redox status in biothiols and ferric metabolism.

Recent progress in nanotechnology based ferroptotic therapies for clinical applications

Ferroptosis is a new iron and reactive oxygen species dependent programmed cell death process which is different from apoptosis, necrosis, and autophagy. It is closely related to a number of disease progression including cancers, neurodegenerative disease, cerebral hemorrhage, liver disease, and renal failure. The development of different ferroptotic inducers has been proved as an efficient therapeutic strategy for a variety of chemoradiotherapy-resistant cancer cells and cancer stem cells. In addition, the development of ferroptotic inhibitors is also becoming an emerging research hotspot for the treatment of many non-cancerous diseases. Furthermore, the combination of nanotechnology with ferroptotic therapies has exhibited additional advantages such as enhanced targeting and/or stimuli-responsive ability to tumor microenvironment, ameliorated drug solubility, ease of preparation and the integration of multifunctional theranostic platforms to develop synergetic combined therapies of great clinical importance. This paper reviews the latest advances of using tailored ferroptotic nanoparticles and ferroptotic molecular probes to be relevant for the accurate diagnosis and treatment of different diseases. Finally, the opportunities and challenges of this burgeoning field were spotlighted to promote the rational design of nano-ferroptotic drugs or theranostic probes in the near future.