The lysosome as a master regulator of iron metabolism

Programmed cell death in nasopharyngeal carcinoma: Mechanisms and therapeutic targets

Programmed cell death is a type of autonomic and orderly cell death mode controlled by genes that maintain homeostasis and growth. Tumor is a typical manifestation of an imbalance in environmental homeostasis in the human body. Currently, several tumor treatments are designed to trigger the death of tumor cells. Nasopharyngeal carcinoma is one of the most common malignant tumors in China. It displays obvious regional and ethnic differences in its incidence, being typically high in the south and low in the north of China. Nasopharyngeal carcinoma is currently considered to be a polygenic inherited disease and is often mediated by the interaction between multiple genes or between genes and the environment. Apoptosis has long been considered the key to tumor treatment, while other cell death pathways have often been overlooked. The current study provides an overview of the relationship among apoptosis, autophagy, pyroptosis, necroptosis, ferroptosis, and nasopharyngeal carcinoma, and the regulatory pathways of nasopharyngeal carcinoma based on five cell death modes were synthesized from the view of molecule. We hope this review will help explore additional, novel programmed cell death targets for the treatment of nasopharyngeal carcinoma and thus promote in-depth research.

Metal Ion Signaling in Biomedicine

Complex multicellular organisms are composed of distinct tissues involving specialized cells that can perform specific functions, making such life forms possible. Species are defined by their genomes, and differences between individuals within a given species directly result from variations in their genetic codes. While genetic alterations can give rise to disease-causing acquisitions of distinct cell identities, it is now well-established that biochemical imbalances within a cell can also lead to cellular dysfunction and diseases. Specifically, nongenetic chemical events orchestrate cell metabolism and transcriptional programs that govern functional cell identity. Thus, imbalances in cell signaling, which broadly defines the conversion of extracellular signals into intracellular biochemical changes, can also contribute to the acquisition of diseased cell states. Metal ions exhibit unique chemical properties that can be exploited by the cell. For instance, metal ions maintain the ionic balance within the cell, coordinate amino acid residues or nucleobases altering folding and function of biomolecules, or directly catalyze specific chemical reactions. Thus, metals are essential cell signaling effectors in normal physiology and disease. Deciphering metal ion signaling is a challenging endeavor that can illuminate pathways to be targeted for therapeutic intervention. Here, we review key cellular processes where metal ions play essential roles and describe how targeting metal ion signaling pathways has been instrumental to dissecting the biochemistry of the cell and how this has led to the development of effective therapeutic strategies.

Mitochondrial dysfunction, cause or consequence in neurodegenerative diseases?

Neurodegenerative diseases encompass a spectrum of conditions characterized by the gradual deterioration of neurons in the central and peripheral nervous system. While their origins are multifaceted, emerging data underscore the pivotal role of impaired mitochondrial functions and endolysosomal homeostasis to the onset and progression of pathology. This article explores whether mitochondrial dysfunctions act as causal factors or are intricately linked to the decline in endolysosomal function. As research delves deeper into the genetics of neurodegenerative diseases, an increasing number of risk loci and genes associated with the regulation of endolysosomal and autophagy functions are being identified, arguing for a downstream impact on mitochondrial health. Our hypothesis centers on the notion that disturbances in endolysosomal processes may propagate to other organelles, including mitochondria, through disrupted inter-organellar communication. We discuss these views in the context of major neurodegenerative diseases including Alzheimer's and Parkinson's diseases, and their relevance to potential therapeutic avenues.

Ferroptosis: Latest evidence and perspectives on plant-derived natural active compounds mitigating doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is a chemotherapy drug widely used in clinical settings, acting as a first-line treatment for various malignant tumors. However, its use is greatly limited by the cardiotoxicity it induces, including doxorubicin-induced cardiomyopathy (DIC). The mechanisms behind DIC are not fully understood, but its potential biological mechanisms are thought to include oxidative stress, inflammation, energy metabolism disorders, mitochondrial damage, autophagy, apoptosis, and ferroptosis. Recent studies have shown that cardiac injury induced by DOX is closely related to ferroptosis. Due to their high efficacy, availability, and low side effects, natural medicine treatments hold strong clinical potential. Currently, natural medicines have been shown to mitigate DOX-induced ferroptosis and ease DIC through various functions such as antioxidation, iron ion homeostasis correction, lipid metabolism regulation, and mitochondrial function improvement. Therefore, this review summarizes the mechanisms of ferroptosis in DIC and the regulation by natural plant products, with the expectation of providing a reference for future research and development of inhibitors targeting ferroptosis in DIC. This review explores the mechanisms of ferroptosis in doxorubicin-induced cardiomyopathy (DIC) and summarizes how natural plant products can alleviate DIC by inhibiting ferroptosis through reducing oxidative stress, correcting iron ion homeostasis, regulating lipid metabolism, and improving mitochondrial function.

Infection of Helicobacter pylori contributes to the progression of gastric cancer through ferroptosis

Helicobacter pylori (H. pylori) is a gram-negative pathogen that colonizes gastric epithelial cells, and its chronic infection is the primary risk factor for the development of gastric cancer (GC). Ferroptosis is an iron-dependent form of cell death characterized by intracellular lipid peroxide accumulation and reactive oxygen species (ROS) imbalance. There is evidence suggesting that pathogens can manipulate ferroptosis to facilitate their replication, transmission, and pathogenesis. However, the interaction between ferroptosis and H. pylori infection requires further elucidation. We reviewed the mechanism of ferroptosis and found that H. pylori virulence factors such as cytotoxin-associated gene A (CagA), vacuolating cytotoxin A (VacA), neutrophil-activating protein A (NapA), superoxide dismutase B (SodB), γ-glutamyl transpeptidase (gGT), lipopolysaccharide (LPS), and outer inflammatory protein A (OipA) affected glutathione (GSH), ROS, and lipid oxidation to regulate ferroptosis. It also affected the progression of GC by regulating ferroptosis-related indicators through abnormal gene expression after H. pylori infected gastric mucosa cells. Finally, we discuss the potential application value of ferroptosis inducers, inhibitors and other drugs in treating H. pylori-infected GC patients while acknowledging that their interactions are still not fully understood.

Emerging mechanisms of lipid peroxidation in regulated cell death and its physiological implications

Regulated cell death (RCD) refers to the form of cell death that can be regulated by various biomacromolecules. Each cell death modalities have their distinct morphological changes and molecular mechanisms. However, intense evidences suggest that lipid peroxidation can be the common feature that initiates and propagates the cell death. Excessive lipid peroxidation alters the property of membrane and further damage the proteins and nucleic acids, which is implicated in various human pathologies. Here, we firstly review the classical chain process of lipid peroxidation, and further clarify the current understanding of the myriad roles and molecular mechanisms of lipid peroxidation in various RCD types. We also discuss how lipid peroxidation involves in diseases and how such intimate association between lipid peroxidation-driven cell death and diseases can be leveraged to develop rational therapeutic strategies.

Dual Role of Lysosome in Cancer Development and Progression

Lysosomes are essential intracellular catabolic organelles that contain digestive enzymes involved in the degradation and recycle of damaged proteins, organelles, etc. Thus, they play an important role in various biological processes, including autophagy regulation, ion homeostasis, cell death, cell senescence. A myriad of studies has shown that the dysfunction of lysosome is implicated in human aging and various age-related diseases, including cancer. However, what is noteworthy is that the modulation of lysosome-based signaling and degradation has both the cancer-suppressive and cancer-promotive functions in diverse cancers depending on stage, biology, or tumor microenvironment. This dual role limits their application as targets in cancer therapy. In this review, we provide an overview of lysosome and autophagy-lysosomal pathway and outline their critical roles in many cellular processes, including cell death. We highlight the different functions of autophagy-lysosomal pathway in cancer development and progression, underscoring its potential as a target for effective cancer therapies.

Into the deep: Exploring the molecular mechanisms of hyperactive behaviour induced by three rare earth elements in early life-stages of the deep-sea scavenging amphipod Tmetonyx cicada (Lysianassidae)

With increasing socio-economic importance of the rare earth elements and yttrium (REY), Norway has laid out plans for REY mining, from land-based to deep-sea mining, thereby enhancing REY mobility in the marine ecosystem. Little is known about associated environmental consequences, especially in the deep ocean. We explored the toxicity and modes of action of a light (Nd), medium (Gd) and heavy (Yb) REY-Cl3 at four concentrations (3, 30, 300, and 3000 μg L-1) in the Arcto-boreal deep-sea amphipod Tmetonyx cicada. At the highest concentration, REY solubility was limited and increased with atomic weight (Nd < Gd < Yb). Lethal effects were practically restricted to this treatment, with the lighter elements being more acutely toxic than Yb (from ∼50 % mortality in the Gd-group at dissolved 689-504 μg L-1 to <20 % in the Yb-group at ca. 2000 μg L-1), which could be a function of bioavailability. All three REY induced hyperactivity at the low-medium concentrations. Delving into the transcriptome of T. cicada allowed us to determine a whole array of potential (neurotoxic) mechanisms underlying this behaviour. Gd induced the vastest response, affecting serotonin-synthesis; sphingolipid-synthesis; the renin-angiotensin system; mitochondrial and endoplasmic reticulum functioning (Gd, Nd); and lysosome integrity (Gd, Yb); as well as the expression of hemocyanin, potentially governing REY-uptake (Gd, Yb). While Nd and Yb shared only few pathways, suggesting a link between mode of action and atomic weight/radius, almost all discussed mechanisms imply the disruption of organismal Ca-homeostasis. Despite only fragmental genomic information available for crustaceans to date, our results provide novel insight into the toxicophysiology of REY in marine biota. The neurotoxic/behavioural effects in T. cicada at concentrations with potential environmental relevance warn about the possibility of bottom-up ecological consequences in mining exposed fjords and deep-sea ecosystems, calling for follow-up studies and regulatory measures prior to the onset of REY mining in Norway.

Identification of a divalent metal transporter required for cellular iron metabolism in malaria parasites

Plasmodium falciparum malaria parasites invade and multiply inside red blood cells (RBCs), the most iron-rich compartment in humans. Like all cells, P. falciparum requires nutritional iron to support essential metabolic pathways, but the critical mechanisms of iron acquisition and trafficking during RBC infection have remained obscure. Parasites internalize and liberate massive amounts of heme during large-scale digestion of RBC hemoglobin within an acidic food vacuole (FV) but lack a heme oxygenase to release porphyrin-bound iron. Although most FV heme is sequestered into inert hemozoin crystals, prior studies indicate that trace heme escapes biomineralization and is susceptible to nonenzymatic degradation within the oxidizing FV environment to release labile iron. Parasites retain a homolog of divalent metal transporter 1 (DMT1), a known mammalian iron transporter, but its role in P. falciparum iron acquisition has not been tested. Our phylogenetic studies indicate that P. falciparum DMT1 (PfDMT1) retains conserved molecular features critical for metal transport. We localized this protein to the FV membrane and defined its orientation in an export-competent topology. Conditional knockdown of PfDMT1 expression is lethal to parasites, which display broad cellular defects in iron-dependent functions, including impaired apicoplast biogenesis and mitochondrial polarization. Parasites are selectively rescued from partial PfDMT1 knockdown by supplementation with exogenous iron, but not other metals. These results support a cellular paradigm whereby PfDMT1 is the molecular gatekeeper to essential iron acquisition by blood-stage malaria parasites and suggest that therapeutic targeting of PfDMT1 may be a potent antimalarial strategy.

Endo-Lysosomal Network Disorder Reprograms Energy Metabolism in SorL1-Null Rat Hippocampus

Sortilin-related receptor 1 (SorL1) deficiency is a genetic predisposition to familial Alzheimer's disease (AD), but its pathology is poorly understood. In SorL1-null rats, a disorder of the global endosome-lysosome network (ELN) is found in hippocampal neurons. Deletion of amyloid precursor protein (APP) in SorL1-null rats could not completely rescue the neuronal abnormalities in the ELN of the hippocampus and the impairment of spatial memory in SorL1-null young rats. These in vivo observations indicated that APP is one of the cargoes of SorL1 in the regulation of the ELN, which affects hippocampal-dependent memory. When SorL1 is depleted, the endolysosome takes up more of the lysosome flux and damages lysosomal digestion, leading to pathological lysosomal storage and disturbance of cholesterol and iron homeostasis in the hippocampus. These disturbances disrupt the original homeostasis of the material-energy-subcellular structure and reprogram energy metabolism based on fatty acids in the SorL1-null hippocampus, instead of glucose. Although fatty acid oxidation increases ATP supply, it cannot reduce the levels of the harmful byproduct ROS during oxidative phosphorylation, as it does in glucose catabolism. Therefore, the SorL1-null rats exhibit hippocampal degeneration, and their spatial memory is impaired. Our research sheds light on the pathology of SorL1 deficiency in AD.

Gastrodin ameliorates oxidative stress-induced RPE damage by facilitating autophagy and phagocytosis through PPARα-TFEB/CD36 signal pathway

Age-related macular degeneration (AMD), the leading cause of irreversible blindness in the elderly, is primarily characterized by the degeneration of the retinal pigment epithelium (RPE). However, effective therapeutic options for dry AMD are currently lacking, necessitating further exploration into preventive and pharmaceutical interventions. This study aimed to investigate the protective effects of gastrodin on RPE cells exposed to oxidative stress. We constructed an in vitro oxidative stress model of 4-hydroxynonenal (4-HNE) and performed RNA-seq, and demonstrated the protective effect of gastrodin through mouse experiments. Our findings reveal that gastrodin can inhibit 4-HNE-induced oxidative stress, effectively improving the mitochondrial and lysosomal dysfunction of RPE cells. We further elucidated that gastrodin promotes autophagy and phagocytosis through activating the PPARα-TFEB/CD36 signaling pathway. Interestingly, these outcomes were corroborated in a mouse model, in which gastrodin maintained retinal integrity and reduced RPE disorganization and degeneration under oxidative stress. The accumulation of LC3B and SQSTM1 in mouse RPE-choroid was also reduced. Moreover, activating PPARα and downstream pathways to restore autophagy and phagocytosis, thereby countering RPE injury from oxidative stress. In conclusion, this study demonstrated that gastrodin maintains the normal function of RPE cells by reducing oxidative stress, enhancing their phagocytic function, and restoring the level of autophagic flow. These findings suggest that gastrodin is a novel formulation with potential applications in the development of AMD disease.

Downregulation of heat shock protein 47 caused lysosomal dysfunction leading to excessive chondrocyte apoptosis

Heat shock protein 47 (HSP47) is a collagen-specific chaperone present in several regions of the endoplasmic reticulum and cytoplasm. Elevated HSP47 expression in cells causes various cancers and fibrotic disorders. However, the consequences of HSP47 downregulation leading to chondrocyte death, as well as the underlying pathways, remain largely unclear. This study presents the first experimental evidence of the localization of HSP47 on lysosomes. Additionally, it successfully designed and generated shRNA HSP47 target sequences to suppress the expression of HSP47 in ATDC5 chondrocytes using lentiviral vectors. By employing a chondrocyte model that has undergone stable downregulation of HSP47, we observed that HSP47 downregulation in chondrocytes, disturbs the acidic homeostatic environment of chondrocyte lysosomes, causes hydrolytic enzyme activity dysregulation, impairs the lysosome-mediated autophagy-lysosome pathway, and causes abnormal expression of lysosomal morphology, number, and functional effector proteins. This implies the significance of the presence of HSP47 in maintaining proper lysosomal function. Significantly, the inhibitor CA-074 Me, which can restore the dysfunction of lysosomes, successfully reversed the negative effects of HSP47 on the autophagy-lysosomal pathway and partially reduced the occurrence of excessive cell death in chondrocytes. This suggests that maintaining proper lysosomal function is crucial for preventing HSP47-induced apoptosis in chondrocytes. The existence of HSP47 is crucial for preserving optimal lysosomal function and autophagic flux, while also inhibiting excessive apoptosis in ATDC5 chondrocytes.

Treatment of polyethylene microplastics degraded by ultraviolet light irradiation causes lysosome-deregulated cell death

BACKGROUND

Microplastics (MPs), plastic particles < 5 mm in size, are prevalent in the environment, and human exposure to them is inevitable. To assess the potential risk of MPs on human health, it is essential to consider the physicochemical properties of environmental MPs, including polymer types, size, shape, and surface chemical modifications. Notably, environmental MPs undergo degradation due to external factors such as ultraviolet (UV) rays and waves, leading to changes in their surface characteristics. However, limited knowledge exists regarding the health effects of MPs, with a specific focus on their surface degradation. This study concentrates on cytotoxic MPs with surface degradation through UV irradiation, aiming to identify the mechanisms underlying their cell toxicity.

RESULTS

Polyethylene (PE) and surface-degraded PE achieved through UV light irradiation were employed as model MPs in this study. We explored the impact of PE and degraded PE on cell death in murine macrophage cell line RAW264.7 cells and human monocyte cell line THP-1 cells. Flow cytometric analysis revealed that degraded PE induced programmed cell death without activating caspase 3, while non-degraded PE did not trigger programmed cell death. These findings suggest that degraded PE might induce programmed cell death through mechanisms other than caspase-driven apoptosis. To understand the mechanisms of cell death, we investigated how cells responded to degraded PE-induced cellular stress. Immunofluorescence and western blotting analyses demonstrated that degraded PE induced autophagosome formation and increased p62 expression, indicating inhibited autophagy flux after exposure to degraded PE. Furthermore, degraded PE exposure led to a decrease in acidic lysosomes, indicating lysosomal dysregulation. These results imply that degraded PE induces lysosomal dysfunction, subsequently causing autophagy dysregulation and cell death.

CONCLUSIONS

This study unveils that UV-induced degradation of PE results in cell death attributed to lysosomal dysfunction. The findings presented herein provide novel insights into the effects of surface-degraded MPs on biological responses.

Dynamic death decisions: How mitochondrial dynamics shape cellular commitment to apoptosis and ferroptosis

The incorporation of mitochondria into early eukaryotes established organelle-based biochemistry and enabled metazoan development. Diverse mitochondrial biochemistry is essential for life, and its homeostatic control via mitochondrial dynamics supports organelle quality and function. Mitochondrial crosstalk with numerous regulated cell death (RCD) pathways controls the decision to die. In this review, we will focus on apoptosis and ferroptosis, two distinct forms of RCD that utilize divergent signaling to kill a targeted cell. We will highlight how proteins and processes involved in mitochondrial dynamics maintain biochemically diverse subcellular compartments to support apoptosis and ferroptosis machinery, as well as unite disparate RCD pathways through dual control of organelle biochemistry and the decision to die.

Lysosomal iron accumulation and subsequent lysosomes-mitochondria iron transmission mediate PFOS-induced hepatocyte ferroptosis

Perfluorooctane sulfonate (PFOS) is known as a persistent organic pollutant. A significant correlation between PFOS and liver ferroptosis has been unveiled, but the precise mechanism needs to be elucidated. In prior research, we found that PFOS treatment provoked mitochondrial iron overload. In this study, we observed a gradual increase in lysosomal iron in L-O2 cells after exposure to PFOS for 0.5-24 h. In PFOS-exposed L-O2 cells, suppressing autophagy relieved the lysosomal iron overload. Inhibiting transient receptor potential mucolipin 1 (TRPML1), a calcium efflux channel on the lysosomal membrane, led to a further rise in lysosomal iron levels and decreased mitochondrial iron overload during PFOS treatment. Suppressing VDAC1, a subtype of voltage-dependent anion-selective channels (VDACs) on the outer mitochondrial membrane, had no impact on PFOS-triggered mitochondrial iron overload, whereas restraining VDAC2/3 relieved this condition. Although silencing VDAC2 relieved PFOS-induced mitochondrial iron overload, it had no effect on PFOS-triggered lysosomal iron overload. Silencing VDAC3 alleviated PFOS-mediated mitochondrial iron overload and led to an additional increase in lysosomal iron. Therefore, we regarded VDAC3 as the specific VDACs subtype that mediated the lysosomes-mitochondria iron transfer. Additionally, in the presence of PFOS, an enhanced association between TRPML1 and VDAC3 was found in mice liver tissue and L-O2 cells. Our research unveils a novel regulatory mechanism of autophagy on the iron homeostasis and the effect of TRPML1-VDAC3 interaction on lysosomes-mitochondria iron transfer, giving an explanation of PFOS-induced ferroptosis and shedding some light on the role of classic calcium channels in iron transmission.

Role of ferroptosis in the pathogenesis of heart disease

Ferroptosis is a new form of regulated necrosis characterized by iron-dependent lipid peroxidation, leading to irreparable lipid damage, membrane permeabilization, and necrotic cell death. Ferroptosis has recently been implicated in the pathogenesis of multiple forms of heart disease such as myocardial infarction, cardiac hypertrophy, heart failure, and various cardiomyopathies. Important progress has also been made regarding how ferroptosis is regulated in vitro and in vivo as well as its role in cardiac homeostasis and disease pathogenesis. In this review, we discuss molecular mechanisms that regulates ferroptosis in the heart, including pathways leading to iron overload and lipid peroxidation as well as the roles of key organelles in this process. We also discuss recent findings pertaining to the new pathogenic role of ferroptosis in various forms of heart disease as well as genetic and pharmacologic strategies targeting ferroptosis in the heart.

Bortezomib elevates intracellular free Fe2+ by enhancing NCOA4-mediated ferritinophagy and synergizes with RSL-3 to inhibit multiple myeloma cells

Iron contributes to tumor initiation and progression; however, excessive intracellular free Fe2+ can be toxic to cancer cells. Our findings confirmed that multiple myeloma (MM) cells exhibited elevated intracellular iron levels and increased ferritin, a key protein for iron storage, compared with normal cells. Interestingly, Bortezomib (BTZ) was found to trigger ferritin degradation, increase free intracellular Fe2+, and promote ferroptosis in MM cells. Subsequent mechanistic investigation revealed that BTZ effectively increased NCOA4 levels by preventing proteasomal degradation in MM cells. When we knocked down NCOA4 or blocked autophagy using chloroquine, BTZ-induced ferritin degradation and the increase in intracellular free Fe2+ were significantly reduced in MM cells, confirming the role of BTZ in enhancing ferritinophagy. Furthermore, the combination of BTZ with RSL-3, a specific inhibitor of GPX4 and inducer of ferroptosis, synergistically promoted ferroptosis in MM cell lines and increased cell death in both MM cell lines and primary MM cells. The induction of ferroptosis inhibitor liproxstatin-1 successfully counteracted the synergistic effect of BTZ and RSL-3 in MM cells. Altogether, our findings reveal that BTZ elevates intracellular free Fe2+ by enhancing NCOA4-mediated ferritinophagy and synergizes with RSL-3 by increasing ferroptosisin MM cells.

V-ATPase Dysfunction in the Brain: Genetic Insights and Therapeutic Opportunities

Vacuolar-type ATPase (v-ATPase) is a multimeric protein complex that regulates H+ transport across membranes and intra-cellular organelle acidification. Catabolic processes, such as endocytic degradation and autophagy, strictly rely on v-ATPase-dependent luminal acidification in lysosomes. The v-ATPase complex is expressed at high levels in the brain and its impairment triggers neuronal dysfunction and neurodegeneration. Due to their post-mitotic nature and highly specialized function and morphology, neurons display a unique vulnerability to lysosomal dyshomeostasis. Alterations in genes encoding subunits composing v-ATPase or v-ATPase-related proteins impair brain development and synaptic function in animal models and underlie genetic diseases in humans, such as encephalopathies, epilepsy, as well as neurodevelopmental, and degenerative disorders. This review presents the genetic and functional evidence linking v-ATPase subunits and accessory proteins to various brain disorders, from early-onset developmental epileptic encephalopathy to neurodegenerative diseases. We highlight the latest emerging therapeutic strategies aimed at mitigating lysosomal defects associated with v-ATPase dysfunction.

Iron Dyshomeostasis in Neurodegeneration with Brain Iron Accumulation (NBIA): Is It the Cause or the Effect?

Iron is an essential metal ion implicated in several cellular processes. However, the reactive nature of iron renders this metal ion potentially dangerous for cells, and its levels need to be tightly controlled. Alterations in the intracellular concentration of iron are associated with different neuropathological conditions, including neurodegeneration with brain iron accumulation (NBIA). As the name suggests, NBIA encompasses a class of rare and still poorly investigated neurodegenerative disorders characterized by an abnormal accumulation of iron in the brain. NBIA is mostly a genetic pathology, and to date, 10 genes have been linked to familial forms of NBIA. In the present review, after the description of the principal mechanisms implicated in iron homeostasis, we summarize the research data concerning the pathological mechanisms underlying the genetic forms of NBIA and discuss the potential involvement of iron in such processes. The picture that emerges is that, while iron overload can contribute to the pathogenesis of NBIA, it does not seem to be the causal factor in most forms of the pathology. The onset of these pathologies is rather caused by a combination of processes involving the interplay between lipid metabolism, mitochondrial functions, and autophagic activity, eventually leading to iron dyshomeostasis.

Unveiling the shield: Troglitazone's impact on epilepsy-induced nerve injury through ferroptosis inhibition

BACKGROUND

Epilepsy is a widespread central nervous system disorder with an estimated 50 million people affected globally. It is characterized by a bimodal incidence peak among infants and the elderly and is influenced by a variety of risk factors, including a significant genetic component. Despite the use of anti-epileptic drugs (AEDs), drug-refractory epilepsy develops in about one-third of patients, highlighting the need for alternative therapeutic approaches.

AIMS

The primary aim of this study was to evaluate the neuroprotective effects of troglitazone (TGZ) in epilepsy and to explore the potential mechanisms underlying its action.

METHODS

We employed both in vitro and in vivo models to assess TGZ's effects. The in vitro model involved glutamate-induced toxicity in HT22 mouse hippocampal neurons, while the in vivo model used kainic acid (KA) to induce epilepsy in mice. A range of methods, including Hoechst/PI staining, CCK-8 assay, flow cytometry, RT-PCR analysis, Nissl staining, scanning electron microscopy, and RNA sequencing, were utilized to assess various parameters such as cellular damage, viability, lipid-ROS levels, mitochondrial membrane potential, mRNA expression, seizure grade, and mitochondrial morphology.

RESULTS

Our results indicate that TGZ, at doses of 5 or 20 mg/kg/day, significantly reduces KA-induced seizures and neuronal damage in mice by inhibiting the process of ferroptosis. Furthermore, TGZ was found to prevent changes in mitochondrial morphology. In the glutamate-induced HT22 cell damage model, 2.5 μM TGZ effectively suppressed neuronal ferroptosis, as shown by a reduction in lipid-ROS accumulation, a decrease in mitochondrial membrane potential, and an increase in PTGS2 expression. The anti-ferroptotic effect of TGZ was confirmed in an erastin-induced HT22 cell damage model as well. Additionally, TGZ reversed the upregulation of Plaur expression in HT22 cells treated with glutamate or erastin. The downregulation of Plaur expression was found to alleviate seizures and reduce neuronal damage in the mouse hippocampus.

CONCLUSION

This study demonstrates that troglitazone has significant therapeutic potential in the treatment of epilepsy by reducing epileptic seizures and the associated brain damage through the inhibition of neuronal ferroptosis. The downregulation of Plaur expression plays a crucial role in TGZ's anti-ferroptotic effect, offering a promising avenue for the development of new epilepsy treatments.

Analysis of mechanism, therapeutic strategies, and potential natural compounds against atherosclerosis by targeting iron overload-induced oxidative stress

Ferroptosis is a novel form of cell demise characterized primarily by the reduction of trivalent iron to divalent iron, leading to the release of reactive oxygen species (ROS) and consequent induction of intense oxidative stress. In atherosclerosis (AS), highly accumulated lipids are modified by ROS to promote the formation of lipid peroxides, further amplifying cellular oxidative stress damage to influence all stages of atherosclerotic development. Macrophages are regarded as pivotal executors in the progression of AS and the handling of iron, thus targeting macrophage iron metabolism holds significant guiding implications for exploring potential therapeutic strategies against AS. In this comprehensive review, we elucidate the potential interplay among iron overload, inflammation, and lipid dysregulation, summarizing the potential mechanisms underlying the suppression of AS by alleviating iron overload. Furthermore, the application of Traditional Chinese Medicine (TCM) is increasingly widespread. Based on extant research and the pharmacological foundations of active compounds of TCM, we propose alternative therapeutic agents for AS in the context of iron overload, aiming to diversify the therapeutic avenues.

Targeting ferritinophagy impairs quiescent cancer stem cells in acute myeloid leukemia in vitro and in vivo models

Acute myeloid leukemia (AML) remains a challenging hematological malignancy with poor prognosis and limited treatment options. Leukemic stem cells (LSCs) contribute to therapeutic failure, relapse, and adverse outcome. This study investigates the role of quiescence and related molecular mechanisms in AML pathogenesis and LSC functions to identify potential therapeutic targets. Transcriptomic analysis revealed that the LSC-enriched quiescent cell population has a distinct gene signature with prognostic relevance in patients with AML. Mechanistically, quiescent blasts exhibit increased autophagic activity, which contributes to their sustained viability. Proteomic profiling uncovered differential requirements for iron metabolism between quiescent and cycling cells, revealing a unique dependence of quiescent cells on ferritinophagy, a selective form of autophagy mediated by nuclear receptor coactivator 4 (NCOA4), which regulates iron bioavailability. We evaluated the therapeutic potential of inhibiting NCOA4-mediated ferritinophagy using genetic knockdown and chemical inhibition approaches. In vitro assays showed that suppression of NCOA4 was toxic to leukemic blasts, particularly the CD34+CD38- LSC-enriched population, without affecting normal CD34+ hematopoietic progenitors. In vivo studies using murine patient-derived xenograft (PDX) models of AML confirmed that NCOA4 inhibition reduced tumor burden and impaired LSC viability and self-renewal, indicating a specific vulnerability of these cells to ferritinophagy disruption. Our findings underscore the role of NCOA4-mediated ferritinophagy in maintaining LSC quiescence and function and suggest that targeting this pathway may be an effective therapeutic strategy for AML. This study highlights the potential of NCOA4 inhibition to improve AML outcomes and paves the way for future research and clinical development.

Nutrient vitamins enabled metabolic regulation of ferroptosis via reactive oxygen species biology

Vitamins are dietary components necessary for cellular metabolic balance, especially redox homeostasis; deficient or excessive supply may give rise to symptoms of psychiatric disorders. Exploring the nutritional and metabolic pathways of vitamins could contribute to uncovering the underlying pathogenesis of ferroptosis-associated diseases. This mini-review aims to provide insights into vitamins closely linked to the regulation of ferroptosis from the perspective of cellular reactive oxygen species biology. The mainstream reprogramming mechanisms of ferroptosis are overviewed, focusing on unique biological processes of iron metabolism, lipid metabolism, and amino acid metabolism. Moreover, recent breakthroughs in therapeutic interventions targeting ferroptosis via fully utilizing vitamin-based pharmacological tools were overviewed, covering vitamins (B, C, E, and K). Finally, mechanism insight related to vitamin-associated nutrient signaling was provided, highlighting the pharmacological benefits of metabolically reprogramming ferroptosis-associated diseases.

Emerging roles of ferroptosis in pulmonary fibrosis: current perspectives, opportunities and challenges

Pulmonary fibrosis (PF) is a chronic interstitial lung disorder characterized by abnormal myofibroblast activation, accumulation of extracellular matrix (ECM), and thickening of fibrotic alveolar walls, resulting in deteriorated lung function. PF is initiated by dysregulated wound healing processes triggered by factors such as excessive inflammation, oxidative stress, and coronavirus disease (COVID-19). Despite advancements in understanding the disease's pathogenesis, effective preventive and therapeutic interventions are currently lacking. Ferroptosis, an iron-dependent regulated cell death (RCD) mechanism involving lipid peroxidation and glutathione (GSH) depletion, exhibits unique features distinct from other RCD forms (e.g., apoptosis, necrosis, and pyroptosis). Imbalance between reactive oxygen species (ROS) production and detoxification leads to ferroptosis, causing cellular dysfunction through lipid peroxidation, protein modifications, and DNA damage. Emerging evidence points to the crucial role of ferroptosis in PF progression, driving macrophage polarization, fibroblast proliferation, and ECM deposition, ultimately contributing to alveolar cell death and lung tissue scarring. This review provides a comprehensive overview of the latest findings on the involvement and signaling mechanisms of ferroptosis in PF pathogenesis, emphasizing potential novel anti-fibrotic therapeutic approaches targeting ferroptosis for PF management.

Boswellia carterii n-hexane extract suppresses breast cancer growth via induction of ferroptosis by downregulated GPX4 and upregulated transferrin

Breast cancer (BC) remains a significant health concern for women globally, prompting the relentless pursuit of novel therapeutic modalities. As a traditional Chinese medicine, Boswellia carterii has been extensively used to treat various cancers, such as BC. However, the anti-BC effect and underlying mechanism of Boswellia carterii remain largely unclear. The aim of this study is to explore the therapeutic effect of Boswellia carterii n-hexane extract (BCHE) against BC as well as its underlying mechanism. The present study showed that BCHE significantly suppressed the viability of human BC cells. Moreover, BCHE exhibited potent anti-BC activity in vivo with no significant toxic effects. Additionally, BCHE induced ferroptosis via increased Transferrin expression and the intracellular accumulation of Fe2+, as well as decreased glutathione peroxidase 4 (GPX4) expression and the upregulation of reactive oxygen species (ROS)-induced lipid peroxidation in BC cells. In vivo experimental results also demonstrated that BCHE effectively induced ferroptosis through GPX4 downregulation and Transferrin upregulation in tumor-bearing mice. Overall, BCHE inhibited the growth of BC cells by inducing ferroptosis mediated by modulating the iron accumulation pathway and the lipid peroxidation pathway. Therefore, BCHE could serve as a potential ferroptosis-targeting drug for treating BC.

Identification of a divalent metal transporter required for cellular iron metabolism in malaria parasites

Plasmodium falciparum malaria parasites invade and multiply inside red blood cells (RBCs), the most iron-rich compartment in humans. Like all cells, P. falciparum requires nutritional iron to support essential metabolic pathways, but the critical mechanisms of iron acquisition and trafficking during RBC infection have remained obscure. Parasites internalize and liberate massive amounts of heme during large-scale digestion of RBC hemoglobin within an acidic food vacuole (FV) but lack a heme oxygenase to release porphyrin-bound iron. Although most FV heme is sequestered into inert hemozoin crystals, prior studies indicate that trace heme escapes biomineralization and is susceptible to non-enzymatic degradation within the oxidizing FV environment to release labile iron. Parasites retain a homolog of divalent metal transporter 1 (DMT1), a known mammalian iron transporter, but its role in P. falciparum iron acquisition has not been tested. Our phylogenetic studies indicate that P. falciparum DMT1 (PfDMT1) retains conserved molecular features critical for metal transport. We localized this protein to the FV membrane and defined its orientation in an export-competent topology. Conditional knockdown of PfDMT1 expression is lethal to parasites, which display broad cellular defects in iron-dependent functions, including impaired apicoplast biogenesis and mitochondrial polarization. Parasites are selectively rescued from partial PfDMT1 knockdown by supplementation with exogenous iron, but not other metals. These results support a cellular paradigm whereby PfDMT1 is the molecular gatekeeper to essential iron acquisition by blood-stage malaria parasites and suggest that therapeutic targeting of PfDMT1 may be a potent antimalarial strategy.

The role of labile iron on brain proteostasis; could it be an early event of neurodegenerative disease?

Iron deposits in the brain are a natural consequence of aging. Iron accumulation, especially in the form of labile iron, can trigger a cascade of adverse effects, eventually leading to neurodegeneration and cognitive decline. Aging also increases the dysfunction of cellular proteostasis. The question of whether iron alters proteostasis is now being pondered. Herein, we investigated the effect of ferric citrate, considered as labile iron, on various aspects of proteostasis of neuronal cell lines, and also established an animal model having a labile iron diet in order to evaluate proteostasis alteration in the brain along with behavioral effects. According to an in vitro study, labile iron was found to activate lysosome formation but inhibits lysosomal clearance function. Furthermore, the presence of labile iron can alter autophagic flux and can also induce the accumulation of protein aggregates. RNA-sequencing analysis further reveals the upregulation of various terms related to proteostasis along with neurodegenerative disease-related terms. According to an in vivo study, a labile iron-rich diet does not induce iron overload conditions and was not detrimental to the behavior of male Wistar rats. However, an iron-rich diet can promote iron accumulation in a region-dependent manner. By staining for autophagic markers and misfolding proteins in the cerebral cortex and hippocampus, an iron-rich diet was actually found to alter autophagy and induce an accumulation of misfolding proteins. These findings emphasize the importance of labile iron on brain cell proteostasis, which could be implicated in developing of neurological diseases.

Recent advancements in nanomaterial-mediated ferroptosis-induced cancer therapy: Importance of molecular dynamics and novel strategies

Ferroptosis is a novel type of controlled cell death resulting from an imbalance between oxidative harm and protective mechanisms, demonstrating significant potential in combating cancer. It differs from other forms of cell death, such as apoptosis and necrosis. Molecular therapeutics have hard time playing the long-acting role of ferroptosis induction due to their limited water solubility, low cell targeting capacity, and quick metabolism in vivo. To this end, small molecule inducers based on biological factors have long been used as strategy to induce cell death. Research into ferroptosis and advancements in nanotechnology have led to the discovery that nanomaterials are superior to biological medications in triggering ferroptosis. Nanomaterials derived from iron can enhance ferroptosis induction by directly releasing large quantities of iron and increasing cell ROS levels. Moreover, utilizing nanomaterials to promote programmed cell death minimizes the probability of unfavorable effects induced by mutations in cancer-associated genes such as RAS and TP53. Taken together, this review summarizes the molecular mechanisms involved in ferroptosis along with the classification of ferroptosis induction. It also emphasized the importance of cell organelles in the control of ferroptosis in cancer therapy. The nanomaterials that trigger ferroptosis are categorized and explained. Iron-based and noniron-based nanomaterials with their characterization at the molecular and cellular levels have been explored, which will be useful for inducing ferroptosis that leads to reduced tumor growth. Within this framework, we offer a synopsis, which traverses the well-established mechanism of ferroptosis and offers practical suggestions for the design and therapeutic use of nanomaterials.

Inhibition of lysosomal TRPML1 channel eliminates breast cancer stem cells by triggering ferroptosis

Cancer stem cells (CSCs) are a sub-population of cells possessing high tumorigenic potential, which contribute to therapeutic resistance, metastasis and recurrence. Eradication of CSCs is widely recognized as a crucial factor in improving patient prognosis, yet the effective targeting of these cells remains a major challenge. Here, we show that the lysosomal cation channel TRPML1 represents a promising target for CSCs. TRPML1 is highly expressed in breast cancer cells and exhibits sensitivity to salinomycin, a drug known to selectively eliminate CSCs. Pharmacological inhibition and genetic depletion of TRPML1 promote ferroptosis in breast CSCs, reduce their stemness, and enhance the sensitivity of breast cancer cells to chemotherapy drug doxorubicin. The inhibition and knockout of TRPML1 also demonstrate significant suppression of tumor formation and growth in the mouse xenograft model. These findings suggest that targeting TRPML1 to eliminate CSCs may be an effective strategy for the treatment of breast cancer.

Fluoride Induces Neurocytotoxicity by Disrupting Lysosomal Iron Metabolism and Membrane Permeability

The detrimental effects of fluoride on neurotoxicity have been widely recorded, yet the detailed mechanisms underlying these effects remain unclear. This study explores lysosomal iron metabolism in fluoride-related neurotoxicity, with a focus on the Steap3/TRPML1 axis. Utilizing sodium fluoride (NaF)-treated human neuroblastoma (SH-SY5Y) and mouse hippocampal neuron (HT22) cell lines, our research demonstrates that NaF enhances the accumulation of ferrous ions (Fe2+) in these cells, disrupting lysosomal iron metabolism through the Steap3/TRPML1 axis. Notably, NaF exposure upregulated ACSL4 and downregulated GPX4, accompanied by reduced glutathione (GSH) levels and superoxide dismutase (SOD) activity and increased malondialdehyde (MDA) levels. These changes indicate increased vulnerability to ferroptosis within neuronal cells. The iron chelator deferoxamine (DFO) mitigates this disruption. DFO binds to lysosomal Fe2+ and inhibits the Steap3/TRPML1 axis, restoring normal lysosomal iron metabolism, preventing lysosomal membrane permeabilization (LMP), and reducing neuronal cell ferroptosis. Our findings suggest that interference in lysosomal iron metabolism may mitigate fluoride-induced neurotoxicity, underscoring the critical role of the Steap3/TRPML1 axis in this pathological process.

Glucose starvation causes ferroptosis-mediated lysosomal dysfunction

Lysosomes, the hub of metabolic signaling, are associated with various diseases and participate in autophagy by supplying nutrients to cells under nutrient starvation. However, their function and regulation under glucose starvation remain unclear and are studied herein. Under glucose starvation, lysosomal protein expression decreased, leading to the accumulation of damaged lysosomes. Subsequently, cell death occurred via ferroptosis and iron accumulation due to DMT1 degradation. GPX4, a key factor in ferroptosis inhibition located on the outer membrane of lysosomes, accumulated in lysosomes, especially under glucose starvation, to protect cells from ferroptosis. ALDOA, GAPDH, NAMPT, and PGK1 are also located on the outer membrane of lysosomes and participate in lysosomal function. These enzymes did not function effectively under glucose starvation, leading to lysosomal dysfunction and ferroptosis. These findings may facilitate the treatment of lysosomal-related diseases.

Transformable Supramolecular Self-Assembled Peptides for Cascade Self-Enhanced Ferroptosis Primed Cancer Immunotherapy

Immunotherapy has received widespread attention for its effective and long-term tumor-eliminating ability. However, for immunogenic "cold" tumors, such as prostate cancer (PCa), the low immunogenicity of the tumor itself is a serious obstacle to efficacy. Here, this work reports a strategy to enhance PCa immunogenicity by triggering cascade self-enhanced ferroptosis in tumor cells, turning the tumor from "cold" to "hot". This work develops a transformable self-assembled peptide TEP-FFG-CRApY with alkaline phosphatase (ALP) responsiveness and glutathione peroxidase 4 (GPX4) protein targeting. TEP-FFG-CRApY self-assembles into nanoparticles under aqueous conditions and transforms into nanofibers in response to ALP during endosome/lysosome uptake into tumor cells, promoting lysosomal membrane permeabilization (LMP). On the one hand, the released TEP-FFG-CRAY nanofibers target GPX4 and selectively degrade the GPX4 protein under the light irradiation, inducing ferroptosis; on the other hand, the large amount of leaked Fe2+ further cascade to amplify the ferroptosis through the Fenton reaction. TEP-FFG-CRApY-induced immunogenic ferroptosis improves tumor cell immunogenicity by promoting the maturation of dendritic cells (DCs) and increasing intratumor T-cell infiltration. More importantly, recovered T cells further enhance ferroptosis by secreting large amounts of interferon-gamma (IFN-γ). This work provides a novel strategy for the molecular design of synergistic molecularly targeted therapy for immunogenic "cold" tumors.

Rational design of a lysosome-targeted fluorescent probe for monitoring the generation of hydroxyl radicals in ferroptosis pathways

Ferroptosis is a newly discovered iron-dependent form of regulated cell death associated with high levels of hydroxyl radical (˙OH) production. Meanwhile, lysosome dysfunction has been shown to be one of the causes of ferroptosis. Although a variety of ˙OH-responsive fluorescent probes have been developed for detecting intracellular ˙OH in living cells, there are still only few lysosome-targeted probes to monitor the variation in lysosomal ˙OH levels during ferroptosis. Herein, we report a novel ˙OH-specific fluorescent probe HCy-Lyso, which is composed of the hydrocyanine and morpholine moiety. Upon treatment with ˙OH, its hydrocyanine unit was converted to the corresponding cyanine group, thus leading to a large π-conjugation extension of HCy-Lyso, accompanied by a significant fluorescence off-on response. Moreover, after reacting with ˙OH in an acidic environment, the protonation product of HCy-Lyso exhibits a higher fluorescence enhancement, which is suitable for detecting lysosomal ˙OH variation. HCy-Lyso has been utilized for imaging endogenous ˙OH in living cells under phorbol myristate acetate (PMA) stimuli and monitoring the changes in lysosomal ˙OH levels during ferroptosis. Thus, our study proposes a new strategy to design lysosome-targeted and ˙OH-responsive fluorescent probes to investigate the relationship between lysosomes and ferroptosis.

Pharmacological approaches for targeting lysosomes to induce ferroptotic cell death in cancer

Lysosomes are crucial organelles responsible for the degradation of cytosolic materials and bulky organelles, thereby facilitating nutrient recycling and cell survival. However, lysosome also acts as an executioner of cell death, including ferroptosis, a distinctive form of regulated cell death that hinges on iron-dependent phospholipid peroxidation. The initiation of ferroptosis necessitates three key components: substrates (membrane phospholipids enriched with polyunsaturated fatty acids), triggers (redox-active irons), and compromised defence mechanisms (GPX4-dependent and -independent antioxidant systems). Notably, iron assumes a pivotal role in ferroptotic cell death, particularly in the context of cancer, where iron and oncogenic signaling pathways reciprocally reinforce each other. Given the lysosomes' central role in iron metabolism, various strategies have been devised to harness lysosome-mediated iron metabolism to induce ferroptosis. These include the re-mobilization of iron from intracellular storage sites such as ferritin complex and mitochondria through ferritinophagy and mitophagy, respectively. Additionally, transcriptional regulation of lysosomal and autophagy genes by TFEB enhances lysosomal function. Moreover, the induction of lysosomal iron overload can lead to lysosomal membrane permeabilization and subsequent cell death. Extensive screening and individually studies have explored pharmacological interventions using clinically available drugs and phytochemical agents. Furthermore, a drug delivery system involving ferritin-coated nanoparticles has been specifically tailored to target cancer cells overexpressing TFRC. With the rapid advancements in understandings the mechanistic underpinnings of ferroptosis and iron metabolism, it is increasingly evident that lysosomes represent a promising target for inducing ferroptosis and combating cancer.

HERV-K (HML-2) Envelope Protein Induces Mitochondrial Depolarization and Neurotoxicity via Endolysosome Iron Dyshomeostasis

Human endogenous retroviruses (HERVs) are associated with the pathogenesis of amyotrophic lateral sclerosis (ALS); a disease characterized by motor neuron degeneration and cell death. The HERV-K subtype HML-2 envelope protein (HERV-K Env) is expressed in the brain, spinal cord, and cerebrospinal fluid of people living with ALS and through CD98 receptor-linked interactions causes neurodegeneration. HERV-K Env-induced increases in oxidative stress are implicated in the pathogenesis of ALS, and ferrous iron (Fe2+) generates reactive oxygen species (ROS). Endolysosome stores of Fe2+ are central to iron trafficking and endolysosome deacidification releases Fe2+ into the cytoplasm. Because HERV-K Env is an arginine-rich protein that is likely endocytosed and arginine is a pH-elevating amino acid, it is important to determine HERV-K Env effects on endolysosome pH and whether HERV-K Env-induced neurotoxicity is downstream of Fe2+ released from endolysosomes. Here, we showed using SH-SY5Y human neuroblastoma cells and primary cultures of human cortical neurons (HCNs, information on age and sex was not available) that HERV-K Env (1) is endocytosed via CD98 receptors, (2) concentration dependently deacidified endolysosomes, (3) decreased endolysosome Fe2+ concentrations, (4) increased cytosolic and mitochondrial Fe2+ and ROS levels, (5) depolarized mitochondrial membrane potential, and (6) induced cell death, effects blocked by an antibody against the CD98 receptor and by the endolysosome iron chelator deferoxamine. Thus, HERV-K Env-induced increases in cytosolic and mitochondrial Fe2+ and ROS as well as cell death appear to be mechanistically caused by HERV-K Env endocytosis, endolysosome deacidification, and endolysosome Fe2+ efflux into the cytoplasm.

Iron imbalance in neurodegeneration

Iron is an essential element for the development and functionality of the brain, and anomalies in its distribution and concentration in brain tissue have been found to be associated with the most frequent neurodegenerative diseases. When magnetic resonance techniques allowed iron quantification in vivo, it was confirmed that the alteration of brain iron homeostasis is a common feature of many neurodegenerative diseases. However, whether iron is the main actor in the neurodegenerative process, or its alteration is a consequence of the degenerative process is still an open question. Because the different iron-related pathogenic mechanisms are specific for distinctive diseases, identifying the molecular mechanisms common to the various pathologies could represent a way to clarify this complex topic. Indeed, both iron overload and iron deficiency have profound consequences on cellular functioning, and both contribute to neuronal death processes in different manners, such as promoting oxidative damage, a loss of membrane integrity, a loss of proteostasis, and mitochondrial dysfunction. In this review, with the attempt to elucidate the consequences of iron dyshomeostasis for brain health, we summarize the main pathological molecular mechanisms that couple iron and neuronal death.

The role of lysosomes in airborne particulate matter-induced pulmonary toxicity

An investigation of the potential role of lysosomes in airborne particulate matter (APM) induced health risks is essential to fully comprehend the pathogenic mechanisms of respiratory diseases. It is commonly accepted that APM-induced lung injury is caused by oxidative stress, inflammatory responses, and DNA damage. In addition, there exists abundant evidence that changes in lysosomal function are essential for cellular adaptation to a variety of particulate stimuli. This review emphasizes that disruption of the lysosomal structure/function is a key step in the cellular metabolic imbalance induced by APMs. After being ingested by cells, most particles are localized within lysosomes. Thus, lysosomes become the primary locus where APMs accumulate, and here they undergo degradation and release toxic components. Recent studies have provided incontrovertible evidence that a wide variety of APMs interfere with the normal function of lysosomes. After being stimulated by APMs, lysosome rupture leads to a loss of lysosomal acidic conditions and the inactivation of proteolytic enzymes, promoting an inflammatory response by activating the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. Moreover, APMs interfere with autophagosome production or block autophagic flux, resulting in autophagy dysfunction. Additionally, APMs disrupt the normal function of lysosomes in iron metabolism, leading to disruption on iron homeostasis. Therefore, understanding the impacts of APM exposure from the perspective of lysosomes will provide new insights into the detrimental consequences of air pollution.

K, Koner AL. Review on Lysosomal Metal Ion Detection Using Fluorescent Probes

Metal ions are indispensable and play an important role in living systems. Metal ions coordinated to metalloenzymes pocket activate the bound substrate and labile metal ions maintaining the ionic balance. The amount of metal ions present in various subcellular compartments of the cells is highly regulated for maintaining cellular homeostasis. An imbalance in the metal ion concentration is related to several diseases and results in serious pathological conditions. Mostly the internalized metal ions are processed in the lysosomal compartment of the cell. A delicate regulation of metal ions in the lysosomal compartment can modulate the lysosomal pH and inhibit hydrolytic enzymes, which ultimately causes lysosomal storage disorders. In the past decade, the understanding and regulation of lysosomal metal ions based on fluorometric methods have gained significant attention. In this review, we have comprehensively summarized the development of various fluorescent reporters over the past five years for a selective and sensitive estimation of lysosomal metal ion concentration. We believe this consolidated and timely review will help researchers working in the areas associated with lysosomal metal ions.

Magnetic modulation of lysosomes for cancer therapy

Lysosomes play a central role in biochemical signal transduction and oxidative stress in cells. Inducing lysosome membrane penetration (LMP) to cause lysosomal-dependent cell death (LCD) in tumor cells is an effective strategy for cancer therapy. Chemical drugs can destroy the stability of lysosomes by neutralizing protons within the lysosomes or enhancing the fragility of the lysosomal membranes. However, there remain several unsolved problems of traditional drugs in LMP induction due to insufficient lysosomal targeting, fast metabolism, and toxicity in normal cells. With the development of nanotechnology, magnetic nanoparticles have been demonstrated to target lysosomes naturally, providing a versatile tool for lysosomal modulation. Combined with excellent tissue penetration and spatiotemporal manipulability of magnetic fields, magnetic modulation of lysosomes progresses rapidly in inducing LMP and LCD for cancer therapy. This review comprehensively discussed the strategies of magnetic modulation of lysosomes for cancer therapy. The intrinsic mechanisms of LMP-induced LCD were first introduced. Then, the modulation of lysosomes by diverse physical outputs of magnetic fields was emphatically discussed. Looking forward, this review will shed the light on the prospect of magnetic modulation of lysosomes, inspiring future research of magnetic modulation strategy in cancer therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

A Lysosome-Targeted Magnetic Nanotorquer Mechanically Triggers Ferroptosis for Breast Cancer Treatment

Targeting ferroptosis has attracted exponential attention to eradicate cancer cells with high iron-dependent growth. Increasing the level of intracellular labile iron pool via small molecules and iron-containing nanomaterials is an effective approach to induce ferroptosis but often faces insufficient efficacy due to the fast drug metabolism and toxicity issues on normal tissues. Therefore, developing a long-acting and selective approach to regulate ferroptosis is highly demanded in cancer treatment. Herein, a lysosome-targeted magnetic nanotorquer (T7-MNT) is proposed as the mechanical tool to dynamically induce the endogenous Fe2+ pool outbreak for ferroptosis of breast cancer. T7-MNTs target lysosomes via the transferrin receptor-mediated endocytosis in breast cancer cells. Under the programmed rotating magnetic field, T7-MNTs generate torques to trigger endogenous Fe2+ release by disrupting the lysosomal membrane. This magneto-mechanical manipulation can induce oxidative damage and antioxidant defense imbalance to boost frequency- and time-dependent lipid peroxidization. Importantly, in vivo studies show that T7-MNTs can efficiently trigger ferroptosis under the magnetic field and play as a long-acting physical inducer to boost ferrotherapy efficacy in combination with RSL3. It is anticipated that this dynamic targeted strategy can be coupled with current ferroptosis inducers to achieve enhanced efficacy and inspire the design of mechanical-based ferroptosis inducers for cancer treatment.

Weak base drug-induced endolysosome iron dyshomeostasis controls the generation of reactive oxygen species, mitochondrial depolarization, and cytotoxicity

Objectives

Approximately 75 % of marketed drugs have the physicochemical property of being weak bases. Weak-base drugs with relatively high pKa values enter acidic organelles including endosomes and lysosomes (endolysosomes), reside in and de-acidify endolysosomes, and induce cytotoxicity. Divalent cations within endolysosomes, including iron, are released upon endolysosome de-acidification. Endolysosomes are "master regulators of iron homeostasis", and neurodegeneration is linked to ferrous iron (Fe2+)-induced reactive oxygen species (ROS) generation via Fenton chemistry. Because endolysosome de-acidification-induced lysosome-stress responses release endolysosome Fe2+, it was crucial to determine the mechanisms by which a functionally and structurally diverse group of weak base drugs including atropine, azithromycin, fluoxetine, metoprolol, and tamoxifen influence endolysosomes and cause cell death.

Methods

Using U87MG astrocytoma and SH-SY5Y neuroblastoma cells, we conducted concentration-response relationships for 5 weak-base drugs to determine EC50 values. From these curves, we chose pharmacologically and therapeutically relevant concentrations to determine if weak-base drugs induced lysosome-stress responses by de-acidifying endolysosomes, releasing endolysosome Fe2+ in sufficient levels to increase cytosolic and mitochondria Fe2+ and ROS levels and cell death.

Results

Atropine (anticholinergic), azithromycin (antibiotic), fluoxetine (antidepressant), metoprolol (beta-adrenergic), and tamoxifen (anti-estrogen) at pharmacologically and therapeutically relevant concentrations (1) de-acidified endolysosomes, (2) decreased Fe2+ levels in endolysosomes, (3) increased Fe2+ and ROS levels in cytosol and mitochondria, (4) induced mitochondrial membrane potential depolarization, and (5) increased cell death; effects prevented by the endocytosed iron-chelator deferoxamine.

Conclusions

Weak-base pharmaceuticals induce lysosome-stress responses that may affect their safety profiles; a better understanding of weak-base drugs on Fe2+ interorganellar signaling may improve pharmacotherapeutics.

A Self-Homing and Traceable Cardiac Patch Leveraging Ferumoxytol for Spatiotemporal Therapeutic Delivery

Mesenchymal stem cell (MSC)-based cardiac patches are envisioned to be a promising treatment option for patients with myocardial infarction. However, their therapeutic efficacy and duration are hampered due to their limited retention on the epicardium. We engineered a scaffold-free MSC sheet with an inherent ability to migrate into the infarcted myocardium, a strategy enabled by actively establishing a sustained intracellular hypoxic environment through the endocytosis of our FDA-approved ferumoxytol. This iron oxide nanoparticle stabilized hypoxia-induced factor-1α, triggering upregulation of the CXC chemokine receptor and subsequent MSC chemotaxis. Thus, MSCs integrated into 2/3 depth of the left ventricular anterior wall in a rat model of acute myocardial infarction and persisted for at least 28 days. This led to spatiotemporal delivery of paracrine factors by MSCs, enhancing cardiac regeneration and function. Ferumoxytol also facilitated the noninvasive MRI tracking of implanted MSCs. Our approach introduces a strategy for mobilizing MSC migration, holding promise for rapid clinical translation in myocardial infarction treatment.

The application of approaches in detecting ferroptosis

Ferroptosis is a regulatory cell death (RCD) caused by iron-dependent lipid peroxidation, which is the backbone of regulating various diseases such as tumor, nervous system diseases and so on. Despite ferroptosis without specific detection methods currently, there are numerous types of detection technology commonly used, including flow cytometry, cell activity assay, microscopic imaging, western blotting, quantitative polymerase chain reaction (qPCR). In addition, ferroptosis could be detected by quantifying oxygen-free radicals reactive oxygen species (ROS), the lipid metabolite (malondialdehyde ((MDA)), related pathways and observing mitochondrial damage. In the face of numerous detection methods, how to choose appropriate detection methods based on experimental purposes has become a problem that needs to be solved at present. In this review, we summarized the commonly used detection methods of the critical substances in the process of ferroptosis, in the hope of facilitating the comprehensive study of ferroptosis, with a view to providing a guidance for subsequent related research.

Development and validation of a novel lysosome-related LncRNA signature for predicting prognosis and the immune landscape features in colon cancer

Lysosomes are essential components for managing tumor microenvironment and regulating tumor growth. Moreover, recent studies have also demonstrated that long non-coding RNAs could be used as a clinical biomarker for diagnosis and treatment of colorectal cancer. However, the influence of lysosome-related lncRNA (LRLs) on the progression of colon cancer is still unclear. This study aimed to identify a prognostic LRL signature in colon cancer and elucidated potential biological function. Herein, 10 differential expressed lysosome-related genes were obtained by the TCGA database and ultimately 4 prognostic LRLs for conducting a risk model were identified by the co-expression, univariate cox, least absolute shrinkage and selection operator analyses. Kaplan-Meier analysis, principal-component analysis, functional enrichment annotation, and nomogram were used to verify the risk model. Besides, the association between the prognostic model and immune infiltration, chemotherapeutic drugs sensitivity were also discussed in this study. This risk model based on the LRLs may be promising for potential clinical prognosis and immunotherapeutic responses related indicator in colon cancer patients.

Glycine recalibrates iron homeostasis of lens epithelial cells by blocking lysosome-dependent ferritin degradation

One of the major pathological processes in cataracts has been identified as ferroptosis. However, studies on the iron metabolism mechanism in lens epithelial cells (LECs) and the methods of effectively alleviating ferroptosis in LECs are scarce. Along these lines, we found that in the ultraviolet radiation b (UVB) induced cataract model in vitro and in vivo, the ferritin of LECs is over-degraded by lysosomes, resulting in the occurrence of iron homeostasis disorder. Glycine can affect the ferritin degradation through the proton-coupled amino acid transporter (PAT1) on the lysosome membrane, further upregulating the content of nuclear factor erythrocyte 2 related factor 2 (Nrf2) to reduce the damage of LECs from two aspects of regulating iron homeostasis and alleviating oxidative stress. By co-staining, we further demonstrate that there is a more sensitive poly-(rC)-binding protein 2 (PCBP2) transportation of iron ions in LECs after UVB irradiation. Additionally, this study illustrated the increased expression of nuclear receptor coactivator 4 (NCOA4) in NRF2-KO mice, indicating that Nrf2 may affect ferritin degradation by decreasing the expression of NCOA4. Collectively, glycine can effectively regulate cellular iron homeostasis by synergistically affecting the lysosome-dependent ferritin degradation and PCBP2-mediated ferrous ion transportation, ultimately delaying the development of cataracts.

STING modulates iron metabolism to promote liver injury and inflammation in acute immune hepatitis

The pathogenesis of Autoimmune Hepatitis (AIH) is closely associated with perturbations in iron ion metabolism, during which Stimulator of Interferon Genes (STING) plays an important role. However, the precise regulatory mechanism remains elusive. In this study, we investigated the relationship between iron dysregulation and STING activation in Concanavalin A (ConA)-induced AIH liver injury. STING knockout (STING-/-) mice and AAV (Adeno-Associated virus)-Sting1-RNAi-treated mice were involved and subjected in AIH. We observed that increased iron dysregulation was linked with STING activation, but this effect was effectively reversed by the administration of iron chelating agent Desferoxamine (DFO) and the antioxidant Ferrostatin-1 (Fer-1). Notably, the iron transport protein Transferrin (TF) and Transferrin Receptor (TfR) exhibited significant accumulation in AIH along with upregulated expression of ferritin protein. Additionally, the deficiency of STING reduced hepatic iron accumulation, mitigated oxidative stress, and attenuated macrophage activation during ConA treatment. Furthermore, liver-specific knockdown of STING using AAV-Sting1-RNAi significantly ameliorated liver iron dysregulation and oxidative stress response induced by Kupffer cells (KCs). KC-derived STING exacerbates liver damage severity in AIH through promoting disturbances in hepatic iron ion metabolism as well as oxidative stress response. These findings provide valuable insights into the pathogenesis of AIH and may pave the way for potential therapeutic strategies targeting STING and iron metabolism in the future.

Transferrin receptor levels and its rare variant are associated with human obesity

AIM

Iron homeostasis is critical for functional respiratory chain complex of mitochondrial, thus potentially contributing to fat biology and energy homeostasis. Transferrin receptor (Tfrc) binds to transferrin for extracellular iron uptake and is recently reported to be involved in brown fat development and functionality. However, whether TFRC levels and variants are associated with human obesity is unknown.

METHODS

To investigate the association of TFRC levels and variants with human obesity, fat biopsies were obtained from surgery. Exon-sequencing and genetic assessments were conducted of a case-control study. For TFRC levels assessment in fat biopsy, 9 overweight and 12 lean subjects were involved. For genetic study, obese (n = 1271) and lean subjects (n = 1455) were involved. TFRC levels were compared in abdominal mesenteric fat of pheochromocytoma patients versus control subjects, and overweight versus lean subjects. For genetic study, whole-exome sequencing of obese and matched control subjects were conducted and analyzed. In addition, the possible disruption in protein stability of TFRC variant was assessed by structural and molecular analysis.

RESULTS

TFRC levels are increased in human browning adipose tissue and decreased in fat of overweight patients. Besides, TFRC levels are negatively correlated with body mass index and positively correlated with uncoupling protein 1 levels. Furthermore, a rare heterozygous missense variant p.I337V in TFRC shows a tendency to enrich in obese subjects. Structural and functional study reveals impaired protein stability of the TFRC variant compared to wild-type.

CONCLUSIONS

Reduced TFRC levels and its rare variant p.I337V with protein instability are associated with human obesity.

Chronic cadmium exposure triggered ferroptosis by perturbing the STEAP3-mediated glutathione redox balance linked to altered metabolomic signatures in humans

Cadmium (Cd), a predominant environmental pollutant, is a canonical toxicant that acts on the kidneys. However, the nephrotoxic effect and underlying mechanism activated by chronic exposure to Cd remain unclear. In the present study, male mice (C57BL/6J, 8 weeks) were treated with 0.6 mg/L cadmium chloride (CdCl2) administered orally for 6 months, and tubular epithelial cells (TCMK-1 cells) were treated with low-dose (1, 2, and 3 μM) CdCl2 for 72 h (h). Our study results revealed that environmental Cd exposure triggered ferroptosis and renal dysfunction. Spatially resolved metabolomics enabled delineation of metabolic profiles and visualization of the disruption to glutathione homeostasis related to ferroptosis in mouse kidneys. Multiomics analysis revealed that chronic Cd exposure induced glutathione redox imbalance that depended on STEAP3-driven lysosomal iron overload. In particular, glutathione metabolic reprogramming linked to ferroptosis emerged as a metabolic hallmark in the blood of Cd-exposed workers. In conclusion, this study provides the first evidence indicating that chronic Cd exposure triggers ferroptosis and renal dysfunction that depend on STEAP3-mediated glutathione redox imbalance, greatly increasing our understanding of the metabolic reprogramming induced by Cd exposure in the kidneys and providing novel clues linking chronic Cd exposure to nephrotoxicity.

Acid Ceramidase Inhibitor LCL-805 Antagonizes Akt Signaling and Promotes Iron-Dependent Cell Death in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy requiring urgent treatment advancements. Ceramide is a cell-death-promoting signaling lipid that plays a central role in therapy-induced cell death. We previously determined that acid ceramidase (AC), a ceramide-depleting enzyme, is overexpressed in AML and promotes leukemic survival and drug resistance. The ceramidase inhibitor B-13 and next-generation lysosomal-localizing derivatives termed dimethylglycine (DMG)-B-13 prodrugs have been developed but remain untested in AML. Here, we report the in vitro anti-leukemic efficacy and mechanism of DMG-B-13 prodrug LCL-805 across AML cell lines and primary patient samples. LCL-805 inhibited AC enzymatic activity, increased total ceramides, and reduced sphingosine levels. A median EC50 value of 11.7 μM was achieved for LCL-805 in cell viability assays across 32 human AML cell lines. As a single agent tested across a panel of 71 primary AML patient samples, a median EC50 value of 15.8 μM was achieved. Exogenous ceramide supplementation with C6-ceramide nanoliposomes, which is entering phase I/II clinical trial for relapsed/refractory AML, significantly enhanced LCL-805 killing. Mechanistically, LCL-805 antagonized Akt signaling and led to iron-dependent cell death distinct from canonical ferroptosis. These findings elucidated key factors involved in LCL-805 cytotoxicity and demonstrated the potency of combining AC inhibition with exogenous ceramide.

Assessing the effects of single and binary exposures of copper and lead on Mytilus galloprovincialis: Physiological and genotoxic approaches

It is becoming increasingly recognised that contaminants are not isolated in their threats to the aquatic environment, with recent shifts towards studying the effects of chemical mixtures. In this study, adult marine mussels (Mytilus galloprovincialis) were exposed to two aqueous concentrations of the essential trace metal, Cu (5 and 32 μg L-1), and the non-essential metal, Pb (5 and 25 μg L-1), both individually and in binary mixtures. After a 14-day exposure, metal accumulation was determined in the digestive gland, gill and mantle tissues by inductively coupled plasma-mass spectrometry following acid digestion, and a number of biochemical, neurotoxic and physiological markers were assessed. These included measurements of DNA damage using comet assay, total glutathione concentration, acetylcholinesterase (AChE) activity and clearance rate. Metal accumulation was greater in the digestive gland and gill than in the mantle, and based on computed free ion concentrations, was greater for Pb than for Cu. Copper exhibited an inhibitory effect on Pb accumulation but Pb did not appear to affect Cu accumulation. Comet assay results revealed DNA damage (i.e., genotoxic effects) in all treatments but differences between the exposures were not significant (p > 0.05), and there were no significant differences in AChE activities between treatments. The most distinctive impacts were a reduction in clearance rate resulting from the higher concentration of Cu, with and without Pb, and an increase in glutathione in the gill resulting from the higher concentration of Cu without Pb. Multivariate analysis facilitated the development of a conceptual model based on the current findings and previously published data on the toxicity and intracellular behaviour of Cu and Pb that will assist in the advancement of regulations and guidelines regarding multiple metal contaminants in the environment.