CD63 is Regulated by Iron via the IRE-IRP System and is Important for Ferritin Secretion by Extracellular Vesicles

Selenoprotein K Confers Protection against Iron Dyshomeostasis-Related Neurotoxicity by Regulating the Palmitoylation of TfR-1

Selenoprotein K (SELENOK), a protein residing in the endoplasmic reticulum (ER), is modulated by dietary selenium and is expressed at elevated levels in neurons. SELENOK has been shown to participate in cellular antioxidant activity and posttranslational palmitoylation. This study presents both in vivo and in vitro evidence that SELENOK deficiency reduces the palmitoylation of TfR-1, thereby impairing transferrin transport and ultimately leading to a decrease in the intracellular iron content, impaired mitochondrial respiratory chain activity and decreased ATP production. Remarkably, restoring SELENOK levels significantly enhanced TfR-1 palmitoylation, increased intracellular iron levels, and restored mitochondrial function, thus ameliorating cognitive deficits in 7 month-old SELENOK knockout mice. Consistent with these findings, iron supplementation also improved mitochondrial function by elevating intracellular iron levels, thereby improving cognitive deficits in 7 month-old SELENOK knockout mice. Therefore, SELENOK exerts its neuroprotective effect by regulating the palmitoylation of TfR-1 to maintain iron homeostasis, thereby protecting mitochondrial function in neurons.

Susceptibility of Brca1(L63X/+) rat to ovarian reserve dissipation by chemotherapeutic agents to breast cancer

BRCA1 is one of the causative genes for hereditary breast and ovarian cancer syndrome with a high risk of early-onset breast cancer. Whereas olaparib (OLA), an inhibitor of poly-ADP-ribose polymerase, has been applied as adjuvant therapy to those cancer patients, its effect on ovarian reproductive function remains unelucidated. Recently, a rat model (MUT; Brca1(L63X/+) mutation) mimicking a human BRCA1 pathogenic variant has been established. Using this model, we evaluated the effects of OLA on ovarian reproductive function in comparison with the wild-type (WT) rats. MUT showed a significantly reduced number of primordial follicles and subfertility in accordance with aging. Oxidative stress was significantly elevated in the young MUT granulosa cells (GCs) accompanied by increased mTOR but decreased PTEN signals. OLA administration in MUT further decreased primordial follicles, with gene set enrichment analysis, indicating upregulated DNA repair pathways. Furthermore, a combination of OLA and cyclophosphamide (CPA) induced empty primordial follicles, recognized as CPA-induced severe ovarian toxicity. Whereas OLA + CPA caused greater reduction in primordial follicles both in MUT and WT in comparison with CPA alone, MUT ovaries were more susceptible to oxidative stress, potentially depleting primordial follicles via activation of GCs and inducing oocyte death due to accumulated DNA damage by OLA treatment. Our findings in this preclinical model underscore the importance of evaluating ovarian reserve prior to chemotherapy by performing reproductive consultation with female patients with BRCA1 pathogenic variants.

Expulsion of iron-rich ferritin via CD63-mediated exosome drives ferroptosis resistance in ovarian cancer cells

Introduction

Ferroptosis is a promising new target for ovarian cancer (OVCA) treatment. However, some OVCA cell types resist the induction of ferroptosis by limiting the intracellular accumulation of the labile iron pool (LIP).

Methods

HEY, COV318 and PEO4 were treated with erastin and assessed for cell viability by using PI flow cytometry assays. Erastin-affected iron metabolism was analysed by using FerroOrange assay, Western Blot (WB) analysis of ferritin heavy chain (FtH), transferrin receptor (CD71), and ferroportin (FPN). Mitochondrial reactive oxygen species (mitROS) and lipid peroxidation were quantified via MitoSOX and BODIPY-C11 flow cytometry assays, respectively. Exosomes (EVs) were collected from cell culture media through ultracentrifugation and then enumerated and analyzed by Nanoparticale Tracking Analysis (NTA) and transmission electron microscopy (TEM). CD63 protein expression in EVs was measured through WB by using CD9 as a loading control. Loss-of-function assays for FtH and CD63 were performed by using siRNA-mediated transient transfection.

Results

We demonstrate that erastin treatment (8 µM, 8 h) is accompanied by the release of iron-rich ferritin via EV pathway in COV318 and PEO4 OVCA cells, thus failing to exert cytotoxic effects. Mechanistically, erastin causes the upregulation of CD63, a tetraspanin involved in forming multivesicular bodies (MVBs) and EVs, and the increase of MBVs assessed by transmission electron microscopy. Consistent with these findings, EV isolation followed by nanoparticle tracking analysis revealed a significant increase in EVs/cell in erastin-treated COV318 and PEO4 cells. Notably, EVs harvested from these cells contained CD63 and FtH, a major iron-storage protein. Inhibition of EV biogenesis with GW4869 prevented FtH release and restored LIP accumulation, lipid peroxidation, and ferroptosis sensitivity in COV318 and PEO4 cells.

Discussion

Overall, our results indicate that OVCA cells can utilize CD63+ EVs to secrete iron-rich ferritin as a mechanism to evade erastin-induced ferroptosis. These findings suggest that combining erastin with EV inhibitors could offer promising strategy for overcoming ferroptosis resistance in OVCA.

Capacity of fullerenols to modulate neurodegeneration induced by ferroptosis: Focus on multiple sclerosis

Multiple sclerosis is an inflammatory disease of the central nervous system (CNS), characterized by oligodendrocyte loss and demyelination of axons leading to neurodegeneration and severe neurological disability. Despite the existing drugs that have immunomodulatory effects an adequate therapy that slow down or stop neuronal death has not yet been found. Oxidative stress accompanied by excessive release of iron into the extracellular space, mitochondrial damage and lipid peroxidation are important factors in the controlled cell death named ferroptosis, latterly recognized in MS. As the fullerenols exhibit potent antioxidant activity, recent results imply that they could have protective effects by suppressing ferroptosis. Based on the current knowledge we addressed the main mechanisms of the protective effects of fullerenols in the CNS in relation to ferroptosis. Inhibition of inflammation, iron overload and lipid peroxidation through the signal transduction mechanism of Nuclear Factor Erythroid 2-Related Factor 2 (NRF2), chelation of heavy metals and free radical scavenging using fullerenols are proposed as benefitial strategy preventing MS progression. Current review connects ferroptosis molecular targets and important factors of MS progression, with biomedical properties and mechanisms of fullerenols' actions, to propose new treatment strategies that could be addaptobale in other neurodegenerative diseases.

Crosstalk between ferroptosis and innate immune in diabetic kidney disease: mechanisms and therapeutic implications

Diabetic kidney disease (DKD) is a prevalent complication of diabetes mellitus (DM), and its incidence is increasing alongside the number of diabetes cases. Effective treatment and long-term management of DKD present significant challenges; thus, a deeper understanding of its pathogenesis is essential to address this issue. Chronic inflammation and abnormal cell death in the kidney closely associate with DKD development. Recently, there has been considerable attention focused on immune cell infiltration into renal tissues and its inflammatory response's role in disease progression. Concurrently, ferroptosis-a novel form of cell death-has emerged as a critical factor in DKD pathogenesis, leading to increased glomerular filtration permeability, proteinuria, tubular injury, interstitial fibrosis, and other pathological processes. The cardiorenal benefits of SGLT2 inhibitors (SGLT2-i) in DKD patients have been demonstrated through numerous large clinical trials. Moreover, further exploratory experiments indicate these drugs may ameliorate serum and urinary markers of inflammation, such as TNF-α, and inhibit ferroptosis in DKD models. Consequently, investigating the interplay between ferroptosis and innate immune and inflammatory responses in DKD is essential for guiding future drug development. This review presents an overview of ferroptosis within the context of DKD, beginning with its core mechanisms and delving into its potential roles in DKD progression. We will also analyze how aberrant innate immune cells, molecules, and signaling pathways contribute to disease progression. Finally, we discuss the interactions between ferroptosis and immune responses, as well as targeted therapeutic agents, based on current evidence. By analyzing the interplay between ferroptosis and innate immunity alongside its inflammatory responses in DKD, we aim to provide insights for clinical management and drug development in this area.

Decoding the molecular enigma behind asbestos and fibrous nanomaterial-induced carcinogenesis

OBJECTIVES

The natural fibrous mineral, asbestos, has been useful in industry for many centuries. In the 1960s, epidemiology recognized the association between asbestos exposure and mesothelioma, and in 1987 the International Agency for Research on Cancer designated all kinds of asbestos as Group 1 carcinogens. However, various scientific enigmas remained regarding the molecular mechanisms of asbestos-induced mesothelial carcinogenesis. This review article was undertaken to reveal and summarize recent discoveries to resolve those enigmas.

METHODS

We collected recent important findings from our own laboratory and others to explain why mesothelial cells are the target for asbestos-induced carcinogenesis and what are the key molecular mechanisms.

RESULTS

The long incubation period of 30-40 years for mesothelial carcinogenesis after asbestos exposure allows the asbestos fibers to go through the pulmonary parenchyma from the central to peripheral portions and ultimately reach the parietal mesothelium by piercing visceral pleura. Asbestos fibers have affinity for hemoglobin and histones, thus accumulating iron on the surface while traveling through the lung. Mesothelial cells are phagocytic cells, engulfing iron-coated asbestos fibers. Accordingly, homozygous deletion of the p16INK4a tumor suppressor gene, a signature of excess iron-induced carcinogenesis, is acquired through oxidative DNA damage. Recently, exosome-dependent iron transfer from asbestos-fed macrophages to mesothelial cells was reported. Similar molecular mechanisms are observed with multiwalled carbon nanotubes of ~50-nm diameter.

CONCLUSIONS

Physical dimensions, biopersistence, and affinity to iron/histones are essential for fibrous material to be carcinogenic to mesothelial cells. Therefore, local iron reduction may be a strategy to prevent mesothelial carcinogenesis.

Iron regulates MT1-MMP-mediated proMMP-2 activation and cancer cell invasion

Cellular iron plays a crucial role in many crucial physiological processes. Excessive iron retention due to iron influx and efflux imbalance contributes to cancer development and proliferation, as well as malignant conversion. Membrane-type 1 matrix metalloproteinase (MT1-MMP) plays a crucial role in tumor invasion and metastasis, because this enzyme can degrade various extracellular matrix components and cleave membrane tethered proteins on the cell surface. Herein, we demonstrate that cellular iron regulates MT1-MMP-mediated proMMP-2 activation and thereby cancer cell invasion. Iron depletion downregulated MT1-MMP expression in cancer cells, accompanied by inhibition of proMMP-2 activation. Conversely, iron loading stimulated MT1-MMP expression and MT1-MMP-containing extracellular vesicle secretion, thereby promoting proMMP-2 activation, which was inhibited through antioxidant treatment. Iron chelator deferasirox suppressed cancer cell invasion but not fibroblasts. Thus, this study indicated that iron accumulation in cancer may contribute to not only cell proliferation but also invasion by activating the MT1-MMP-MMP-2 axis.

Extracellular NCOA4 is a mediator of septic death by activating the AGER-NFKB pathway

Sepsis, a life-threatening condition resulting from a dysregulated response to pathogen infection, poses a significant challenge in clinical management. Here, we report a novel role for the autophagy receptor NCOA4 in the pathogenesis of sepsis. Activated macrophages and monocytes secrete NCOA4, which acts as a mediator of septic death in mice. Mechanistically, lipopolysaccharide, a major component of the outer membrane of Gram-negative bacteria, induces NCOA4 secretion through autophagy-dependent lysosomal exocytosis mediated by ATG5 and MCOLN1. Moreover, bacterial infection with E. coli or S. enterica leads to passive release of NCOA4 during GSDMD-mediated pyroptosis. Upon release, extracellular NCOA4 triggers the activation of the proinflammatory transcription factor NFKB/NF-κB by promoting the degradation of NFKBIA/IκB molecules. This process is dependent on the pattern recognition receptor AGER, rather than TLR4. In vivo studies employing endotoxemia and polymicrobial sepsis mouse models reveal that a monoclonal neutralizing antibody targeting NCOA4 or AGER delays animal death, protects against organ damage, and attenuates systemic inflammation. Furthermore, elevated plasma NCOA4 levels in septic patients, particularly in non-survivors, correlate positively with the sequential organ failure assessment score and concentrations of lactate and proinflammatory mediators, such as TNF, IL1B, IL6, and HMGB1. These findings demonstrate a previously unrecognized role of extracellular NCOA4 in inflammation, suggesting it as a potential therapeutic target for severe infectious diseases. Abbreviation: BMDMs: bone marrow-derived macrophages; BUN: blood urea nitrogen; CLP: cecal ligation and puncture; ELISA: enzyme-linked immunosorbent assay; LPS: lipopolysaccharide; NO: nitric oxide; SOFA: sequential organ failure assessment.

Deep Learning and Single-Cell Sequencing Analyses Unveiling Key Molecular Features in the Progression of Carotid Atherosclerotic Plaque

Rupture of advanced carotid atherosclerotic plaques increases the risk of ischaemic stroke, which has significant global morbidity and mortality rates. However, the specific characteristics of immune cells with dysregulated function and proven biomarkers for the diagnosis of atherosclerotic plaque progression remain poorly characterised. Our study elucidated the role of immune cells and explored diagnostic biomarkers in advanced plaque progression using single-cell RNA sequencing and high-dimensional weighted gene co-expression network analysis. We identified a subcluster of monocytes with significantly increased infiltration in the advanced plaques. Based on the monocyte signature and machine-learning approaches, we accurately distinguished advanced plaques from early plaques, with an area under the curve (AUC) of 0.899 in independent external testing. Using microenvironment cell populations (MCP) counter and non-negative matrix factorisation, we determined the association between monocyte signatures and immune cell infiltration as well as the heterogeneity of the patient. Finally, we constructed a convolutional neural network deep learning model based on gene-immune correlation, which achieved an AUC of 0.933, a sensitivity of 92.3%, and a specificity of 87.5% in independent external testing for diagnosing advanced plaques. Our findings on unique subpopulations of monocytes that contribute to carotid plaque progression are crucial for the development of diagnostic tools for clinical diseases.

Exosomes Induce Crosstalk Between Multiple Types of Cells and Cardiac Fibroblasts: Therapeutic Potential for Remodeling After Myocardial Infarction

Recanalization therapy can significantly improve the prognosis of patients with acute myocardial infarction (AMI). However, infarction or reperfusion-induced cardiomyocyte death, immune cell infiltration, fibroblast proliferation, and scarring formation lead to cardiac remodeling and gradually progress to heart failure or arrhythmia, resulting in a high mortality rate. Due to the inability of cardiomyocytes to regenerate, the healing of infarcted myocardium mainly relies on the formation of scars. Cardiac fibroblasts, as the main effector cells involved in repair and scar formation, play a crucial role in maintaining the structural integrity of the heart after MI. Recent studies have revealed that exosome-mediated intercellular communication plays a huge role in myocardial repair and signaling transduction after myocardial infarction (MI). Exosomes can regulate the biological behavior of fibroblasts by activating or inhibiting the intracellular signaling pathways through their contents, which are derived from cardiomyocytes, immune cells, endothelial cells, mesenchymal cells, and others. Understanding the interactions between fibroblasts and other cell types during cardiac remodeling will be the key to breakthrough therapies. This review examines the role of exosomes from different sources in the repair process after MI injury, especially the impacts on fibroblasts during myocardial remodeling, and explores the use of exosomes in the treatment of myocardial remodeling after MI.

Bile from the hemojuvelin-deficient mouse model of iron excess is enriched in iron and ferritin

Iron is an essential nutrient but is toxic in excess. Iron deficiency is the most prevalent nutritional deficiency and typically linked to inadequate intake. Iron excess is also common and usually due to genetic defects that perturb expression of hepcidin, a hormone that inhibits dietary iron absorption. Our understanding of iron absorption far exceeds that of iron excretion, which is believed to contribute minimally to iron homeostasis. Prior to the discovery of hepcidin, multiple studies showed that excess iron undergoes biliary excretion. We recently reported that wild-type mice raised on an iron-rich diet have increased bile levels of iron and ferritin, a multi-subunit iron storage protein. Given that genetic defects leading to excessive iron absorption are much more common causes of iron excess than dietary loading, we set out to determine if an inherited form of iron excess known as hereditary hemochromatosis also results in bile iron loading. We employed mice deficient in hemojuvelin, a protein essential for hepcidin expression. Mutant mice developed bile iron and ferritin excess. While lysosomal exocytosis has been implicated in ferritin export into bile, knockdown of Tfeb, a regulator of lysosomal biogenesis and function, did not impact bile iron or ferritin levels. Bile proteomes differed between female and male mice for wild-type and hemojuvelin-deficient mice, suggesting sex and iron excess impact bile protein content. Overall, our findings support the notion that excess iron undergoes biliary excretion in genetically determined iron excess.

Exosome-based nanoparticles and cancer immunotherapy

Over the past decades, cancer immunotherapy has encountered challenges such as immunogenicity, inefficiency, and cytotoxicity. Consequently, exosome-based cancer immunotherapy has gained rapid traction as a promising alternative. Exosomes, a type of extracellular vesicles (EVs) ranging from 50 to 150 nm, are self-originating and exhibit fewer side effects compared to traditional therapies. Exosome-based immunotherapy encompasses three significant areas: cancer vaccination, co-inhibitory checkpoints, and adoptive T-cell therapy. Each of these fields leverages the inherent advantages of exosomes, demonstrating substantial potential for individualized tumor therapy and precision medicine. This review aims to elucidate the reasons behind the promise of exosome-based nanoparticles as cancer therapies by examining their characteristics and summarizing the latest research advancements in cancer immunotherapy.

The use of hydrogel microspheres as cell and drug delivery carriers for bone, cartilage, and soft tissue regeneration

Bone, cartilage, and soft tissue regeneration is a complex process involving many cellular activities across various cell types. Autografts remain the "gold standard" for the regeneration of these tissues. However, the use of autografts is associated with many disadvantages, including donor scarcity, the requirement of multiple surgeries, and the risk of infection. The development of tissue engineering techniques opens new avenues for enhanced tissue regeneration. Nowadays, the expectations of tissue engineering scaffolds have gone beyond merely providing physical support for cell attachment. Ideal scaffolds should also provide biological cues to actively boost tissue regeneration. As a new type of injectable biomaterial, hydrogel microspheres have been increasingly recognised as promising therapeutic carriers for the local delivery of cells and drugs to enhance tissue regeneration. Compared to traditional tissue engineering scaffolds and bulk hydrogel, hydrogel microspheres possess distinct advantages, including less invasive delivery, larger surface area, higher transparency for visualisation, and greater flexibility for functionalisation. Herein, we review the materials characteristics of hydrogel microspheres and compare their fabrication approaches, including microfluidics, batch emulsion, electrohydrodynamic spraying, lithography, and mechanical fragmentation. Additionally, based on the different requirements for bone, cartilage, nerve, skin, and muscle tissue regeneration, we summarize the applications of hydrogel microspheres as cell and drug delivery carriers for the regeneration of these tissues. Overall, hydrogel microspheres are regarded as effective therapeutic delivery carriers to enhance tissue regeneration in regenerative medicine. However, significant effort is required before hydrogel microspheres become widely accepted as commercial products for clinical use.

Ferroptosis at the nexus of metabolism and metabolic diseases

Ferroptosis, an iron-dependent form of regulated cell death, is emerging as a crucial regulator of human physiology and pathology. Increasing evidence showcases a reciprocal relationship between ferroptosis and dysregulated metabolism, propagating a pathogenic vicious cycle that exacerbates pathology and human diseases, particularly metabolic disorders. Consequently, there is a rapidly growing interest in developing ferroptosis-based therapeutics. Therefore, a comprehensive understanding of the intricate interplay between ferroptosis and metabolism could provide an invaluable resource for mechanistic insight and therapeutic development. In this review, we summarize the important metabolic substances and associated pathways in ferroptosis initiation and progression, outline the cascade responses of ferroptosis in disease development, overview the roles and mechanisms of ferroptosis in metabolic diseases, introduce the methods for ferroptosis detection, and discuss the therapeutic perspectives of ferroptosis, which collectively aim to illustrate a comprehensive view of ferroptosis in basic, translational, and clinical science.

Distinct phenotypes induced by acute hypoxia and TGF-β1 in human adult cardiac fibroblasts

Myocardial infarction (MI) causes hypoxic injury to downstream myocardial tissue, which initiates a wound healing response that replaces injured myocardial tissue with a scar. Wound healing is a complex process that consists of multiple phases, in which many different stimuli induce cardiac fibroblasts to differentiate into myofibroblasts and deposit new matrix. While this process is necessary to replace necrotic tissue, excessive and unresolved fibrosis is common post-MI and correlated with heart failure. Therefore, defining how cardiac fibroblast phenotypes are distinctly regulated by stimuli that are prevalent in the post-MI microenvironment, such as hypoxia and transforming growth factor-beta (TGF-β), is essential for understanding and ultimately mitigating pathological fibrosis. In this study, we acutely treated primary human adult cardiac fibroblasts with TGF-β1 or hypoxia and then characterized their phenotype through immunofluorescence, quantitative RT-PCR, and proteomic analysis. We found that fibroblasts responded to low oxygen with increased localization of hypoxia inducible factor 1 (HIF-1) to the nuclei after 4h, which was followed by increased gene expression of vascular endothelial growth factor A (VEGFA), a known target of HIF-1, by 24h. Both TGF-β1 and hypoxia inhibited proliferation after 24h. TGF-β1 treatment also upregulated various fibrotic pathways. In contrast, hypoxia caused a reduction in several protein synthesis pathways, including collagen biosynthesis. Collectively, these data suggest that TGF-β1, but not acute hypoxia, robustly induces the differentiation of human cardiac fibroblasts into myofibroblasts. Discerning the overlapping and distinctive outcomes of TGF-β1 and hypoxia treatment is important for elucidating their roles in fibrotic remodeling post-MI and provides insight into potential therapeutic targets.

Lipid droplets and small extracellular vesicles: More than two independent entities

Despite increasing knowledge about small extracellular vesicle (sEV) composition and functions in cell-cell communication, the mechanism behind their biogenesis remains unclear. Here, we reveal for the first time that sEV biogenesis and release into the microenvironment are tightly connected with another important organelle, Lipid Droplets (LDs). The correlation was observed in several human cancer cell lines as well as patient-derived colorectal cancer stem cells (CR-CSCs). Our results demonstrated that external stimuli such as radiation, pH, hypoxia or lipid-interfering drugs, known to affect the number of LDs/cell, similarly influenced sEV secretion. Importantly, through multiple omics data, at both mRNA and protein levels, we revealed RAB5C as a potential important molecular player behind this organelle connection. Altogether, the potential to fine-tune sEV biogenesis by targeting LDs could significantly impact the amount, cargos and properties of these sEVs, opening new clinical perspectives.

Xenogenous implanted dental follicle stem cells promote periodontal regeneration through inducing the N2 phenotype of neutrophils

BACKGROUND

Periodontal tissue loss is the main reason for tooth mobility and loss caused by periodontal disease. Dental follicle stem cells (DFSCs) have significant therapeutic potential in periodontal regeneration, which maybe mainly depends on their potent immunomodulatory capacity. Consequently, this study aims to elucidate the impact of implanted xenogenous DFSCs on innate immune responses during early and late stages in the periodontal defect repair period.

METHODS

To trace and investigate the immunomodulation mechanisms of DFSCs in vivo, DFSCs were engineered (E-DFSCs) using lentiviral vectors expressing CD63-enhanced green fluorescent protein (CD63-EGFP) and β-Actin-mCherry protein (ACTB-mCherry) to exhibit green and red fluorescence. The biological characteristics and functions of E-DFSCs were verified by proliferation, differentiation, and co-culture experiments in vitro. In vivo, the periodontal regeneration capacity of E-DFSCs was detected by implantation of murine periodontal defect model, and the response of innate immune cells was detected at the 1st, 3rd, and 5th days (early stage) and 4th week (late stage) after implantation.

RESULTS

In vitro assessments showed that E-DFSCs retain similar properties to their non-engineered counterparts but exhibit enhanced macrophage immunomodulation capability. In mice models, four-week micro-CT and histological evaluations indicated that E-DFSCs have equivalent efficiency to DFSCs in periodontal defect regeneration. At the early stage of repair in mice periodontal defect, fluorescence tracking showed that implanted E-DFSCs might primarily activate endogenous cells through direct contact and indirect actions, and most of these cells are myeloperoxidase-positive neutrophils. Additionally, compared with the control group, the neutrophilic infiltration and conversion of N2-type were significantly increased in the E-DFSC group. At the late stage of defect regeneration, more M2-type macrophages, fewer TRAP + osteoclasts, and an upregulated OPG/RANKL ratio were detected in the E-DFSC group compared to the control group, which indicated that immune balance tilts towards healing and bone formation.

CONCLUSION

The xenogenous implanted DFSCs can induce the N2 phenotype of neutrophils in the early stage, which can activate the innate immune mechanism of the host to promote periodontal tissue regeneration.

The molecular conversations of sarcomas: exosomal non-coding RNAs in tumor's biology and their translational prospects

Exosomes mediate cell-to-cell crosstalk involving a variety of biomolecules through an intricate signaling network. In recent years, the pivotal role of exosomes and their non-coding RNAs cargo in the development and progression of several cancer types clearly emerged. In particular, tumor bulk and its microenvironment co-evolve through cellular communications where these nanosized extracellular vesicles are among the most relevant actors. Knowledge about the cellular, and molecular mechanisms involved in these communications will pave the way for novel exosome-based delivery of therapeutic RNAs as well as innovative prognostic/diagnostic tools. Despite the valuable therapeutic potential and clinical relevance of exosomes, their role on sarcoma has been vaguely reported because the rarity and high heterogeneity of this type of cancer. Here, we dissected the scientific literature to unravel the multifaceted role of exosomal non-coding RNAs as mediator of cell-to-cell communications in the sarcoma subtypes.

Scaffold design considerations for peripheral nerve regeneration

Peripheral nerve injury (PNI) represents a serious clinical and public health problem due to its high incurrence and poor spontaneous recovery. Compared to autograft, which is still the best current practice for long-gap peripheral nerve defects in clinics, the use of polymer-based biodegradable nerve guidance conduits (NGCs) has been gaining momentum as an alternative to guide the repair of severe PNI without the need of secondary surgery and donor nerve tissue. However, simple hollow cylindrical tubes can barely outperform autograft in terms of the regenerative efficiency especially in critical sized PNI. With the rapid development of tissue engineering technology and materials science, various functionalized NGCs have emerged to enhance nerve regeneration over the past decades. From the aspect of scaffold design considerations, with a specific focus on biodegradable polymers, this review aims to summarize the recent advances in NGCs by addressing the onerous demands of biomaterial selections, structural designs, and manufacturing techniques that contributes to the biocompatibility, degradation rate, mechanical properties, drug encapsulation and release efficiency, immunomodulation, angiogenesis, and the overall nerve regeneration potential of NGCs. In addition, several commercially available NGCs along with their regulation pathways and clinical applications are compared and discussed. Lastly, we discuss the current challenges and future directions attempting to provide inspiration for the future design of ideal NGCs that can completely cure long-gap peripheral nerve defects.

The emerging role of nuclear receptor coactivator 4 in health and disease: a novel bridge between iron metabolism and immunity

Nuclear receptor coactivator 4 (NCOA4) has recently been recognized as a selective cargo receptor of ferritinophagy participating in ferroptosis. However, NCOA4 is also a coactivator that modulates the transcriptional activity of many vital nuclear receptors. Recent novel studies have documented the role of NCOA4 in healthy and pathogenic conditions via its modulation of iron- and non-iron-dependent metabolic pathways. NCOA4 exhibits non-ferritinophagic and iron-independent features such as promoting tumorigenesis and erythropoiesis, immunomodulation, regulating autophagy, and participating in DNA replication and mitosis. Full-length human-NCOA4 is composed of 614 amino acids, of which the N-terminal (1-237) contains nuclear-receptor-binding domains, while the C-terminal (238-614) principally contains a ferritin-binding domain. The exploration of the protein structure of NCOA4 suggests that NCOA4 possesses additional significant and complex functions based on its structural domains. Intriguingly, another three isoforms of NCOA4 that are produced by alternative splicing have been identified, which may also display disparate activities in physiological and pathological processes. Thus, NCOA4 has become an important bridge that encompasses interactions between immunity and metabolism. In this review, we outline the latest advances in the important regulating mechanisms underlying NCOA4 actions in health and disease conditions, providing insights into potential therapeutic interventions.

Magnetic Particle Imaging Reveals that Iron-Labeled Extracellular Vesicles Accumulate in Brains of Mice with Metastases

The incidence of breast cancer remains high worldwide and is associated with a significant risk of metastasis to the brain that can be fatal; this is due, in part, to the inability of therapeutics to cross the blood-brain barrier (BBB). Extracellular vesicles (EVs) have been found to cross the BBB and further have been used to deliver drugs to tumors. EVs from different cell types appear to have different patterns of accumulation and retention as well as the efficiency of bioactive cargo delivery to recipient cells in the body. Engineering EVs as delivery tools to treat brain metastases, therefore, will require an understanding of the timing of EV accumulation and their localization relative to metastatic sites. Magnetic particle imaging (MPI) is a sensitive and quantitative imaging method that directly detects superparamagnetic iron. Here, we demonstrate MPI as a novel tool to characterize EV biodistribution in metastatic disease after labeling EVs with superparamagnetic iron oxide (SPIO) nanoparticles. Iron-labeled EVs (FeEVs) were collected from iron-labeled parental primary 4T1 tumor cells and brain-seeking 4T1BR5 cells, followed by injection into the mice with orthotopic tumors or brain metastases. MPI quantification revealed that FeEVs were retained for longer in orthotopic mammary carcinomas compared to SPIOs. MPI signal due to iron could only be detected in brains of mice bearing brain metastases after injection of FeEVs, but not SPIOs, or FeEVs when mice did not have brain metastases. These findings indicate the potential use of EVs as a therapeutic delivery tool in primary and metastatic tumors.

Advance in Iron Metabolism, Oxidative Stress and Cellular Dysfunction in Experimental and Human Kidney Diseases

Kidney diseases pose a significant global health issue, frequently resulting in the gradual decline of renal function and eventually leading to end-stage renal failure. Abnormal iron metabolism and oxidative stress-mediated cellular dysfunction facilitates the advancement of kidney diseases. Iron homeostasis is strictly regulated in the body, and disturbance in this regulatory system results in abnormal iron accumulation or deficiency, both of which are associated with the pathogenesis of kidney diseases. Iron overload promotes the production of reactive oxygen species (ROS) through the Fenton reaction, resulting in oxidative damage to cellular molecules and impaired cellular function. Increased oxidative stress can also influence iron metabolism through upregulation of iron regulatory proteins and altering the expression and activity of key iron transport and storage proteins. This creates a harmful cycle in which abnormal iron metabolism and oxidative stress perpetuate each other, ultimately contributing to the advancement of kidney diseases. The crosstalk of iron metabolism and oxidative stress involves multiple signaling pathways, such as hypoxia-inducible factor (HIF) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways. This review delves into the functions and mechanisms of iron metabolism and oxidative stress, along with the intricate relationship between these two factors in the context of kidney diseases. Understanding the underlying mechanisms should help to identify potential therapeutic targets and develop novel and effective therapeutic strategies to combat the burden of kidney diseases.

Iron Absorption: Molecular and Pathophysiological Aspects

Iron is an essential nutrient for growth among all branches of life, but while iron is among the most common elements, bioavailable iron is a relatively scarce nutrient. Since iron is fundamental for several biological processes, iron deficiency can be deleterious. On the other hand, excess iron may lead to cell and tissue damage. Consequently, iron balance is strictly regulated. As iron excretion is not physiologically controlled, systemic iron homeostasis is maintained at the level of absorption, which is mainly influenced by the amount of iron stores and the level of erythropoietic activity, the major iron consumer. Here, we outline recent advances that increased our understanding of the molecular aspects of iron absorption. Moreover, we examine the impact of these recent insights on dietary strategies for maintaining iron balance.

Abnormal mitochondrial iron metabolism damages alveolar type II epithelial cells involved in bleomycin-induced pulmonary fibrosis

Rationale: Pulmonary fibrosis is a chronic progressive lung disease with limited therapeutic options. We previously revealed that there is iron deposition in alveolar epithelial type II cell (AECII) in pulmonary fibrosis, which can be prevented by the iron chelator deferoxamine. However, iron in the cytoplasm and the mitochondria has two relatively independent roles and regulatory systems. In this study, we aimed to investigate the role of mitochondrial iron deposition in AECII injury and pulmonary fibrosis, and to find potential therapeutic strategies. Methods: BLM-treated mice, MLE-12 cells, and primary AECII were employed to establish the mouse pulmonary fibrosis model and epithelial cells injury model, respectively. Mitochondrial transplantation, siRNA and plasmid transfection, western blotting (WB), quantitative real-time polymerase chain reaction (RT-qPCR), polymerase chain reaction (PCR), immunofluorescence, immunoprecipitation (IP), MitoSOX staining, JC-1 staining, oxygen consumption rate (OCR) measurement, and Cell Counting Kit-8 (CCK8) assay were utilized to elucidate the role of mitochondrial iron deposition in cell and lung fibrosis and determine its mechanism. Results: This study showed that prominent mitochondrial iron deposition occurs within AECII in bleomycin (BLM)-induced pulmonary fibrosis mouse model and in BLM-treated MLE-12 epithelial cells. Further, the study revealed that healthy mitochondria rescue BLM-damaged AECII mitochondrial iron deposition and cell damage loss. Mitoferrin-2 (MFRN2) is the main transporter that regulates mitochondrial iron metabolism by transferring cytosolic iron into mitochondria, which is upregulated in BLM-treated MLE-12 epithelial cells. Direct overexpression of MFRN2 causes mitochondrial iron deposition and cell damage. In this study, decreased ubiquitination of the ubiquitin ligase F-box/LRR-repeat protein 5 (FBXL5) degraded iron-reactive element-binding protein 2 (IREB2) and promoted MFRN2 expression as well as mitochondrial iron deposition in damaged AECII. Activation of the prostaglandin E2 receptor EP4 subtype (EP4) receptor signaling pathway counteracted mitochondrial iron deposition by downregulating IREB2-MFRN2 signaling through upregulation of FBXL5. This intervention not only reduced mitochondrial iron content but also preserved mitochondrial function and protected against AECII damage after BLM treatment. Conclusion: Our findings highlight the unexplored roles, mechanisms, and regulatory approaches of abnormal mitochondrial iron metabolism of AECII in pulmonary fibrosis. Therefore, this study deepens the understanding of the mechanisms underlying pulmonary fibrosis and offers a promising strategy for developing effective therapeutic interventions using the EP4 receptor activator.

Protocol for the isolation of GFP-expressing ferroptosis-dependent extracellular vesicles in in vitro cell culture models

Extracellular vesicles (EVs) are complex structures that transport various DNA, RNA, and protein. Recently, new EV secretion mechanisms have been identified through the iron regulatory system in mammalian cells. We revealed that ferroptosis increases EV secretion, which is named ferroptosis-dependent EVs (FedEVs). Here, we describe a step-by-step procedure to isolate GFP-expressing FedEVs for in vitro analysis. The FedEVs are further analyzed by imaging and flow cytometry analysis. For complete details on the use and execution of this protocol, please refer to Ito et al.1.

Tumor iron homeostasis and immune regulation

Abnormal iron metabolism has long been regarded as a key metabolic hallmark of cancer. As a critical cofactor, iron contributes to tumor progression by participating in various processes such as mitochondrial electron transport, gene regulation, and DNA synthesis or repair. Although the role of iron in tumor cells has been widely studied, recent studies have uncovered the interplay of iron metabolism between tumor cells and immune cells, which may affect both innate and adaptive immune responses. In this review, we discuss the current understanding of the regulatory networks of iron metabolism between cancer cells and immune cells and how they contribute to antitumor immunity, and we analyze potential therapeutics targeting iron metabolism. Also, we highlight several key challenges and describe potential therapeutic approaches for future investigations.

Sevoflurane causes cognitive impairment by inducing iron deficiency and inhibiting the proliferation of neural precursor cells in infant mice

AIMS

Numerous studies on animals have shown that exposure to general anesthetics in infant stage may cause neurocognitive impairment. However, the exact mechanism is not clear. The dysfunction of iron metabolism can cause neurodevelopmental disorders. Therefore, we investigated the effect of iron metabolism disorder induced by sevoflurane (Sev) on cognitive function and the proliferation of neural precursor cells (NPCs) and neural stem cells (NSCs) in infant mice.

METHODS

C57BL/6 mice of postnatal day 14 and neural stem cells NE4C were treated with 2% Sev for 6 h. We used the Morris water maze (MWM) to test the cognitive function of infant mice. The proliferation of NPCs was measured using bromodeoxyuridine (BrdU) label and their markers Ki67 and Pax6 in infant brain tissues 12 h after anesthesia. Meanwhile, we used immunohistochemical stain, immunofluorescence assay, western blot, and flow cytometer to evaluate the myelinogenesis, iron levels, and cell proliferation in cortex and hippocampus or in NE4C cells.

RESULTS

The results showed that Sev significantly caused cognitive deficiency in infant mice. Further, we found that Sev inhibited oligodendrocytes proliferation and myelinogenesis by decreasing MBP and CC-1 expression and iron levels. Meanwhile, Sev also induced the iron deficiency in neurons and NSCs by downregulating FtH and FtL expression and upregulating the TfR1 expression in the cortex and hippocampus, which dramatically suppressed the proliferation of NSCs and NPCs as indicated by decreasing the colocalization of Pax6+ and BrdU+ cells, and caused the decrease in the number of neurons. Interestingly, iron supplementation before anesthesia significantly improved iron deficiency in cortex and hippocampus and cognitive deficiency induced by Sev in infant mice. Iron therapy inhibited the decrease of MBP expression, iron levels in neurons and oligodendrocytes, and DNA synthesis of Pax6+ cells in hippocampus induced by Sev. Meanwhile, the number of neurons was partially recovered in hippocampus.

CONCLUSION

The results from the present study demonstrated that Sev-induced iron deficiency might be a new mechanism of cognitive impairment caused by inhaled anesthetics in infant mice. Iron supplementation before anesthesia is an effective strategy to prevent cognitive impairment caused by Sev in infants.

Mechanisms controlling cellular and systemic iron homeostasis

In mammals, hundreds of proteins use iron in a multitude of cellular functions, including vital processes such as mitochondrial respiration, gene regulation and DNA synthesis or repair. Highly orchestrated regulatory systems control cellular and systemic iron fluxes ensuring sufficient iron delivery to target proteins is maintained, while limiting its potentially deleterious effects in iron-mediated oxidative cell damage and ferroptosis. In this Review, we discuss how cells acquire, traffick and export iron and how stored iron is mobilized for iron-sulfur cluster and haem biogenesis. Furthermore, we describe how these cellular processes are fine-tuned by the combination of various sensory and regulatory systems, such as the iron-regulatory protein (IRP)-iron-responsive element (IRE) network, the nuclear receptor co-activator 4 (NCOA4)-mediated ferritinophagy pathway, the prolyl hydroxylase domain (PHD)-hypoxia-inducible factor (HIF) axis or the nuclear factor erythroid 2-related factor 2 (NRF2) regulatory hub. We further describe how these pathways interact with systemic iron homeostasis control through the hepcidin-ferroportin axis to ensure appropriate iron fluxes. This knowledge is key for the identification of novel therapeutic opportunities to prevent diseases of cellular and/or systemic iron mismanagement.

Site- and Structure-Specific Glycosylation Signatures of Bovine, Caprine, Porcine, and Human Milk-Derived Extracellular Vesicles

Extracellular vesicles (EVs) are membrane-bound vesicles released by living cells. As vesicles for macromolecule transmission and intercellular communication, EVs are broadly applied in clinical diagnosis and biomimetic drug delivery. Milk-derived EVs (MEVs) are an ideal choice for scale-up applications because they exhibit biocompatibility and are easily obtained. Herein, intact glycopeptides in MEVs from bovines, caprines, porcines, and humans were comprehensively analyzed by high-resolution mass spectrometry using the sceHCD, followed by the EThcD fragment method, revealing that protein glycosylation is abundant and heterogeneous in MEVs. The dominant glycans in all MEVs were sialic acid-modified N-linked glycans (over 50%). A couple of species-specific glycans were also characterized, which are potentially markers of different original EVs. Interestingly, the Neu5Gc-modified glycans were enriched in caprine milk-derived EVs (58 ± 2%). Heterogeneity of MEV protein glycosylation was observed for glycosites and glycan compositions, and the structural heterogeneity of protein glycosylation was also identified and validated. The glycosignatures of EV biogenesis- and endocytosis-related proteins (CD63 and MFGE8) were significantly different in these four species. Overall, we comprehensively characterized the glycosylation signature of MEVs from four different species and provided insight into protein glycosylation related to drug target delivery.

CD63-Snorkel tagging for isolation of exosomes

Exosomes (Exo) are important mediators of inter-cellular communications; however, no effective method is available for isolating, thus characterizing, cellular-specific exosomes in vivo. Since CD63 is a reliable marker for exosomes, we have developed a tagging strategy, term "CD63-Snorkel (CD63-SNKL)", in which CD63 at its intracellular C-terminus was fused to a fragment of PDGFRB that contains the transmembrane domain tethered to multiple epitope tags (HA, His, and FLAG) displayed in tandem on surface. We found that the CD63-SNKL protein has similar subcellular localizations as endogenous CD63 and can be effectively sorted into Exo. Furthermore, Exo secreted from CD63-SNKL-transduced cells can be effectively captured on anti-HA magnetic beads and eluted with HA peptides. Thus, CD63-SNKL may be engineered for isolating and tracking endogenous tissue-specific Exo in vivo.

New Perspectives on Circulating Ferritin: Its Role in Health and Disease

The diagnosis of iron disturbances usually includes the evaluation of serum parameters. Serum iron is assumed to be entirely bound to transferrin, and transferrin saturation-the ratio between the serum iron concentration and serum transferrin-usually reflects iron availability. Additionally, serum ferritin is commonly used as a surrogate of tissue iron levels. Low serum ferritin values are interpreted as a sign of iron deficiency, and high values are the main indicator of pathological iron overload. However, in situations of inflammation, serum ferritin levels may be very high, independently of tissue iron levels. This presents a particularly puzzling challenge for the clinician evaluating the overall iron status of the patient in the presence of an inflammatory condition. The increase in serum ferritin during inflammation is one of the enigmas regarding iron metabolism. Neither the origin, the mechanism of release, nor the effects of serum ferritin are known. The use of serum ferritin as a biomarker of disease has been rising, and it has become increasingly diverse, but whether or not it contributes to controlling the disease or host pathology, and how it would do it, are important, open questions. These will be discussed here, where we spotlight circulating ferritin and revise the recent clinical and preclinical data regarding its role in health and disease.

Extracellular vesicles modulate key signalling pathways in refractory wound healing

Chronic wounds are wounds that cannot heal properly due to various factors, such as underlying diseases, infection or reinjury, and improper healing of skin wounds and ulcers can cause a serious economic burden. Numerous studies have shown that extracellular vesicles (EVs) derived from stem/progenitor cells promote wound healing, reduce scar formation and have significant advantages over traditional treatment methods. EVs are membranous particles that carry various bioactive molecules from their cellular origins, such as cytokines, nucleic acids, enzymes, lipids and proteins. EVs can mediate cell-to-cell communication and modulate various physiological processes, such as cell differentiation, angiogenesis, immune response and tissue remodelling. In this review, we summarize the recent advances in EV-based wound healing, focusing on the signalling pathways that are regulated by EVs and their cargos. We discuss how EVs derived from different types of stem/progenitor cells can promote wound healing and reduce scar formation by modulating the Wnt/β-catenin, phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin, vascular endothelial growth factor, transforming growth factor β and JAK-STAT pathways. Moreover, we also highlight the challenges and opportunities for engineering or modifying EVs to enhance their efficacy and specificity for wound healing.

The role of extracellular vesicles on the occurrence of clinical complications in β-thalassemia

Thalassemia is the most common monogenic disorder of red blood cells (RBCs) caused by defects in the synthesis of globin chains. Thalassemia phenotypes have a wide spectrum of clinical manifestations and vary from severe anemia requiring regular blood transfusions to clinically asymptomatic states. Ineffective erythropoiesis and toxicity caused by iron overload are major factors responsible for various complications in thalassemia patients, especially patients with β-thalassemia major (β-TM). Common complications in patients with thalassemia include iron overload, thrombosis, cardiac morbidity, vascular dysfunction, inflammation, and organ dysfunction. Extracellular vesicles (EVs) are small membrane vesicles released from various cells' plasma membranes due to activation and apoptosis. Based on studies, EVs play a role in various processes, including clot formation, vascular damage, and proinflammatory processes. In recent years, they have also been studied as biomarkers in the diagnosis and prognosis of diseases. Considering the high concentration of EVs in thalassemia and their role in cellular processes, this study reviews the role of EVs in the common complications of patients with β-thalassemia for the first time.

Global Proteomics for Identifying the Alteration Pathway of Niemann-Pick Disease Type C Using Hepatic Cell Models

Niemann-Pick disease type C (NPC) is an autosomal recessive disorder with progressive neurodegeneration. Although the causative genes were previously identified, NPC has unclear pathophysiological aspects, and patients with NPC present various symptoms and onset ages. However, various novel biomarkers and metabolic alterations have been investigated; at present, few comprehensive proteomic alterations have been reported in relation to NPC. In this study, we aimed to elucidate proteomic alterations in NPC and perform a global proteomics analysis for NPC model cells. First, we developed two NPC cell models by knocking out NPC1 using CRISPR/Cas9 (KO1 and KO2). Second, we performed a label-free (LF) global proteomics analysis. Using the LF approach, more than 300 proteins, defined as differentially expressed proteins (DEPs), changed in the KO1 and/or KO2 cells, while the two models shared 35 DEPs. As a bioinformatics analysis, the construction of a protein-protein interaction (PPI) network and an enrichment analysis showed that common characteristic pathways such as ferroptosis and mitophagy were identified in the two model cells. There are few reports of the involvement of NPC in ferroptosis, and this study presents ferroptosis as an altered pathway in NPC. On the other hand, many other pathways and DEPs were previously suggested to be associated with NPC, supporting the link between the proteome analyzed here and NPC. Therapeutic research based on these results is expected in the future.

Engineered exosomes as drug and RNA co-delivery system: new hope for enhanced therapeutics?

Chemotherapy often faces some obstacles such as low targeting effects and drug resistance, which introduce the low therapeutic efficiency and strong side effects. Recent advances in nanotechnology allows the use of novel nanosystems for targeted drug delivery, although the chemically synthesized nanomaterials always show unexpected low biocompability. The emergence of exosome research has offered a better understanding of disease treatment and created novel opportunities for developing effective drug delivery systems with high biocompability. Moreover, RNA interference has emerged as a promising strategy for disease treatments by selectively knocking down or over-expressing specific genes, which allows new possibilities to directly control cell signaling events or drug resistance. Recently, more and more interests have been paid to develop optimal delivery nanosystems with high efficiency and high biocompability for drug and functional RNA co-delivery to achieve enhanced chemotherapy. In light of the challenges for developing drug and RNA co-delivery system, exosomes have been found to show very attractive prospects. This review aims to explore current technologies and challenges in the use of exosomes as drug and RNA co-delivery system with a focus on the emerging trends and issues associated with their further applications, which may contribute to the accelerated developments of exosome-based theraputics.

Evaluation of ferritin and TfR level in plasma neural-derived exosomes as potential markers of Parkinson's disease

Introduction

Early diagnosis of Parkinson's disease (PD) remains challenging. It has been suggested that abnormal brain iron metabolism leads to excessive iron accumulation in PD, although the mechanism of iron deposition is not yet fully understood. Ferritin and transferrin receptor (TfR) are involved in iron metabolism, and the exosome pathway is one mechanism by which ferritin is transported and regulated. While the blood of healthy animals contains a plentiful supply of TfR-positive exosomes, no studies have examined ferritin and TfR in plasma neural-derived exosomes.

Methods

Plasma exosomes were obtained from 43 patients with PD and 34 healthy controls. Neural-derived exosomes were isolated with anti-human L1CAM antibody immunoabsorption. Transmission electron microscopy and western blotting were used to identify the exosomes. ELISAs were used to quantify ferritin and TfR levels in plasma neural-derived exosomes of patients with PD and controls. Receivers operating characteristic (ROC) curves were applied to map the diagnostic accuracy of ferritin and TfR. Independent predictors of the disease were identified using logistic regression models.

Results

Neural-derived exosomes exhibited the typical exosomal morphology and expressed the specific exosome marker CD63. Ferritin and TfR levels in plasma neural-derived exosomes were significantly higher in patients with PD than controls (406.46 ± 241.86 vs. 245.62 ± 165.47 ng/μg, P = 0.001 and 1728.94 ± 766.71 vs. 1153.92 ± 539.30 ng/μg, P < 0.001, respectively). There were significant positive correlations between ferritin and TfR levels in plasma neural-derived exosomes in control group, PD group and all the individuals (rs = 0.744, 0.700, and 0.752, respectively). The level of TfR was independently associated with the disease (adjusted odds ratio 1.002; 95% CI 1.000-1.003). ROC performances of ferritin, TfR, and their combination were moderate (0.730, 0.812, and 0.808, respectively). However, no relationship was found between the biomarkers and disease progression.

Conclusion

It is hypothesized that ferritin and TfR in plasma neural-derived exosomes may be potential biomarkers for PD, and that they may participate in the mechanism of excessive iron deposition in PD.

New iron export pathways acting via holo-ferritin secretion

Ferritin is a spherical nanocage protein for iron storage, composed of 24 light- or heavy-polypeptide chain subunits. A single ferritin molecule can carry up to 4500 iron atoms in its core, which plays an important role in suppressing intracellular iron toxicity. Serum ferritin levels are used as a marker for the total amount of iron stored in the body. Most serum ferritin is iron-free (apo-ferritin) and it is unclear how ferritin is released from cells. Ferritin is secreted into serum via extracellular vesicles (EVs) or the secretory autophagy pathway but not via the classical endoplasmic reticulum (ER)-to-Golgi secretion pathway. We recently discovered that the level of tetraspanin CD63, a common EV marker, is post-transcriptionally regulated by the intracellular iron level and both CD63 and ferritin expression is induced by iron loading. Ferritin is incorporated into CD63(+)-EVs through the ferritin-specific autophagy adapter molecule, NCOA4, and then secreted from cells. EV production differs drastically depending on cell type and physiological conditions. Extracellular matrix detached cells express pentaspanin prominin 2 and prominin 2(+)-EVs secrete ferritin independently of NCOA4 trafficking. Ferritin is tightly bound to iron in EVs and functions as an iron-carrier protein in the extracellular environment. Cells can suppress ferroptosis by secreting holo-ferritin, which reduces intracellular iron concentration. However, this exposes the neighboring cells receiving the secreted holo-ferritin to a large excess of iron. This results in cellular toxicity through increased generation of reactive oxygen species (ROS). Here we review the machinery by which ferritin is incorporated into EVs and its role as an intercellular communication molecule.

Iron links endogenous and exogenous nanoparticles

Current progress in biology and medical science is based on the observation at the level of nanometers via electron microscopy and computation. Of note, the size of most cells in higher species exists in a limited range from 5 to 50 μm. Recently, it was demonstrated that endogenous extracellular nanoparticles play a role in communication among various cellular types in a variety of contexts. Among them, exosomes in serum have been established as biomarkers for human diseases by analyzing the cargo molecules. No life on the earth can survive without iron. However, excess iron can be a risk for carcinogenesis in rodents and humans. Nano-sized molecules may cause unexpected bioeffects, including carcinogenesis, which is a process to establish cellular iron addiction with ferroptosis-resistance. Asbestos and carbon nanotubes are the typical examples, leading to carcinogenesis by the alteration of iron metabolism. Recently, we found that CD63, one of the representative markers of exosomes, is under the regulation of iron-responsive element/iron-regulatory protein system. This is a safe strategy to share excess iron in the form of holo-ferritin between iron-sufficient and -deficient cells. On the other hand, damaged cells may secrete holo-ferritin-loaded exosomes as in the case of macrophages in ferroptosis after asbestos exposure. These holo-ferritin-loaded exosomes can cause mutagenic DNA damage in the recipient mesothelial cells. Thus, there is an iron link between exogenous and endogenous nanoparticles, which requires further investigation for better understanding and the future applications.

Development and validation of a differentiation-related signature based on single-cell RNA sequencing data of immune cells in spinal cord injury

Background

After spinal cord injury (SCI), the native immune surveillance function of the central nervous system is activated, resulting in a substantial infiltration of immune cells into the affected tissue. While numerous studies have explored the transcriptome data following SCI and revealed certain diagnostic biomarkers, there remains a paucity of research pertaining the identification of immune subtypes and molecular markers related to the immune system post-spinal cord injury using single-cell sequencing data of immune cells.

Methods

The researchers conducted an analysis of spinal cord samples obtained at three time points (3,10, and 21 days) following SCI using the GSE159638 dataset. The SCI subsets were delineated through pseudo-time analysis, and differentiation related genes were identified after principal component analysis (PCA), cell clustering, and annotation techniques. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were employed to assess the differentiation-related genes (DRGs) across different subsets. The molecular subtypes of SCI were determined using consensus clustering analysis. To further explore and validate the correlation between the molecular subtypes and the immune microenvironment, the CIBERSORT algorithm was employed. High-value diagnostic gene markers were identified using LASSO regression, and their diagnostic sensitivity was assessed using receiver operating characteristic curves (ROC) and quantitative real-time polymerase chain reaction (qRT-PCR).

Results

Three SCI subsets were obtained, and differentiation-related genes were characterized. Within these subsets, two distinct molecular subtypes, namely C1 and C2, were identified. These subtypes demonstrated significant variations in terms of immune cell infiltration levels and the expression of immune checkpoint genes. Through further analysis, three candidate biomarkers (C1qa, Lgals3 and Cd63) were identified and subsequently validated.

Conclusions

Our study revealed a diverse immune microenvironment in SCI samples, highlighting the potential significance of C1qa, Lgals3 and Cd63 as immune biomarkers for diagnosing SCI. Moreover, the identification of immune checkpoints corresponding to the two molecular subtypes suggests their potential as targets for immunotherapy to enhance SCI repair in future interventions.

Newly uncovered biochemical and functional aspects of ferritin

Iron homeostasis is strictly regulated at both the systemic and cellular levels by complex mechanisms because of its indispensability and toxicity. Among the various iron-regulatory proteins, ferritin is the earliest discovered regulator of iron metabolism and is a molecule that safely retains excess intracellular iron in the cores of its shells. Two types of ferritin, cytosolic ferritin and mitochondrial ferritin (FTMT), have been identified in a range of organisms from plants to humans. FTMT was identified approximately 60 years after the discovery of cytosolic ferritin. Cytosolic ferritin expression is regulated in an iron-responsive manner. Recently, the molecular mechanisms of iron-dependent degradation of cytosolic ferritin or its secretion into serum have been clarified. FTMT, which shares a high degree of sequence homology with cytosolic ferritin, has distinct functions and is regulated in different ways from cytosolic ferritin. Although knowledge of the physiological role of FTMT is still incomplete, recent studies have shed light on the function and regulation of FTMT. The accumulating biological evidence of both ferritins has made it possible to deepen our knowledge about iron metabolism and its significance in diseases. In this review, we discuss the biological properties of both ferritins, focusing on their newly uncovered behaviors.

Matrigel-based organoid culture of malignant mesothelioma reproduces cisplatin sensitivity through CTR1

Organoids are a three-dimensional (3D) culture system that simulate actual organs. Therefore, tumor organoids are expected to predict precise response to chemotherapy in patients. However, to date, few studies have studied the drug responses in organoids of malignant mesothelioma (MM). The poor prognosis of MM emphasizes the importance of establishing a protocol for generating MM-organoid for research and clinical use. Here, we established murine MM organoids from p53^+/- or wild-type C57BL/6 strain by intraperitoneal injection either with crocidolite or carbon nanotube. Established MM-organoids proliferated in Matrigel as spheroids. Subcutaneous injection assays revealed that the MM-organoids mimicked actual tissue architecture and maintained the original histological features of the primary MM. RNA sequencing and pathway analyses revealed that the significant expressional differences between the 2D- and 3D-culture systems were observed in receptor tyrosine kinases, including IGF1R and EGFR, glycosylation and cholesterol/steroid metabolism. MM-organoids exhibited a more sensitive response to cisplatin through stable plasma membrane localization of a major cisplatin transporter, copper transporter 1/Slc31A1 (Ctr1) in comparison to 2D-cultures, presumably through glycosylation and lipidation. The Matrigel culture system facilitated the localization of CTR1 on the plasma membrane, which simulated the original MMs and the subcutaneous xenografts. These results suggest that the newly developed protocol for MM-organoids is useful to study strategies to overcome chemotherapy resistance to cisplatin.

PTEN-induced kinase PINK1 supports colorectal cancer growth by regulating the labile iron pool

Mitophagy is a cargo-specific autophagic process that recycles damaged mitochondria to promote mitochondrial turnover. PTEN-induced putative kinase 1 (PINK1) mediates the canonical mitophagic pathway. However, the role of PINK1 in diseases where mitophagy has been purported to play a role, such as colorectal cancer, is unclear. Our results here demonstrate that higher PINK1 expression is positively correlated with decreased colon cancer survival, and mitophagy is required for colon cancer growth. We show that doxycycline-inducible knockdown (KD) of PINK1 in a panel of colon cancer cell lines inhibited proliferation, whereas disruption of other mitophagy receptors did not impact cell growth. We observed that PINK KD led to a decrease in mitochondrial respiration, membrane hyperpolarization, accumulation of mitochondrial DNA, and depletion of antioxidant glutathione. In addition, mitochondria are important hubs for the utilization of iron and synthesizing iron-dependent cofactors such as heme and iron sulfur clusters. We observed an increase in the iron storage protein ferritin and a decreased labile iron pool in the PINK1 KD cells, but total cellular iron or markers of iron starvation/overload were not affected. Finally, cellular iron storage and the labile iron pool are maintained via autophagic degradation of ferritin (ferritinophagy). We found overexpressing nuclear receptor coactivator 4, a key adaptor for ferritinophagy, rescued cell growth and the labile iron pool in PINK1 KD cells. These results indicate that PINK1 integrates mitophagy and ferritinophagy to regulate intracellular iron availability and is essential for maintaining intracellular iron homeostasis to support survival and growth in colorectal cancer cells.

Proteomic analysis of extracellular vesicles from tick hemolymph and uptake of extracellular vesicles by salivary glands and ovary cells

BACKGROUND

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures that are important mediators of intercellular communication. Arthropods transport nutrients, signaling molecules, waste and immune factors to all areas of the body via the hemolymph. Little is known about tick hemolymph EVs.

METHODS

Hemolymph was collected from partially fed Rhipicephalus haemaphysaloides and Hyalomma asiaticum ticks by making an incision with a sterile scalpel in the middle (between the femur and metatarsus) of the first pair of legs, which is known as leg amputation. EVs were isolated from hemolymph by differential centrifugation and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Proteins extracted from the hemolymph EVs were analyzed by 4D label-free proteomics. The EVs were also examined by western blot and immuno-electron microscopy analysis. Intracellular incorporation of PHK26-labeled EVs was tested by adding labeled EVs to tick salivary glands and ovaries, followed by fluorescence microscopy.

RESULTS

In this study, 149 and 273 proteins were identified by 4D label-free proteomics in R. haemaphysaloides and H. asiaticum hemolymph EVs, respectively. TEM and NTA revealed that the sizes of the hemolymph EVs from R. haemaphysaloides and H. asiaticum were 133 and 138 nm, respectively. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses of identified proteins revealed pathways related to binding, catalytic and transporter activity, translation, transport and catabolism, signal transduction and cellular community. The key EV marker proteins RhCD9, RhTSG101, Rh14-3-3 and RhGAPDH were identified using proteomics and western blot. The presence of RhFerritin-2 in tick hemolymph EVs was confirmed by western blot and immuno-electron microscopy. We demonstrated that PKH26-labeled hemolymph EVs are internalized by tick salivary glands and ovary cells in vitro.

CONCLUSIONS

The results suggest that tick EVs are secreted into, and circulated by, the hemolymph. EVs may play roles in the regulation of tick development, metabolism and reproduction.

An iron oxyhydroxide-based nanosystem sensitizes ferroptosis by a "Three-Pronged" strategy in breast cancer stem cells

The anti-apoptotic mechanism of breast cancer stem cells (BCSCs) makes it an obstacle to traditional apoptosis as the primary way of death. Ferroptosis is a recently reported mode of programmed cell death caused by the accumulation of iron-dependent lipid peroxidation (LPO) in cells. High dependence on iron makes BCSCs more sensitive to ferroptosis. However, the high level of the Prominin2 protein and high concentration of GSH in BCSCs make BCSCs able to efflux excess iron ions and clear LPO, which limits the therapeutic efficacy of ferroptosis in BCSCs. To overcome this obstacle, we designed a hyaluronic acid (HA)-coated siProminin2-loaded FeOOH nanoparticle (FeOOH/siPROM2@HA) to amplify ferroptosis. The FeOOH/siPROM2@HA is stable under physiologically neutral conditions but generates Fe³⁺ in an acidic microenvironment; meanwhile, the released siProminin2 inhibits its efflux, and then Fe³⁺ undergoes a redox reaction with endogenous GSH to produce Fe²⁺, which initiates the Fenton reaction-based ferroptosis by LPO elevation. Both in vitro and in vivo studies showed that these pH-sensitive NPs significantly inhibited tumor growth by downregulating glutathione peroxidase 4 (GPX4). Overall, this work demonstrates a "three-pronged" strategy for amplified ferroptotic therapy by simultaneously promoting intracellular iron, inhibiting iron efflux, and depleting GSH, which presents a potential strategy for CSC-targeted cancer therapy. STATEMENT OF SIGNIFICANCE: As the root of recurrence and metastasis, breast cancer stem cells (BCSCs) are resistant to traditional apoptotic death, so it is urgent to explore a new death mode for BCSCs. It has been reported that BCSCs are highly iron-dependent and, therefore, more sensitive to ferroptosis; however, the therapeutic efficacy is greatly limited by the overexpression of Prominin2 in BCSCs, which is correlated with resistance to ferroptosis by exocytosis of iron ions. In this work, we designed a hyaluronic acid-coated siProminin2-loaded FeOOH nano-drug (FeOOH/siPROM2@HA) to accelerate ferroptosis of BCSCs by simultaneously increasing iron ion content, inhibiting iron efflux, and scavenging GSH. This "three-pronged" strategy has significant implications for BCSC-targeted cancer therapy.

Iron-loaded extracellular vesicles: angel or demon?

Extracellular vesicles (EVs) are identified as a non-classical way to mediate iron efflux except ferroportin. Interestingly, recent studies indicated that EVs pathway is a novel way involved in iron efflux. Mitochondria-derived vesicles (MDVs) are the potential mediator to load mitochondrial iron into EVs. Additionally, iron-replete cells resist excess iron-induced damage by secreting iron-loaded EVs, and the uptake of these EVs induces oxidative damage in the recipient cell. Importantly, iron-loaded EVs play a key role in aberrant iron distribution, which drives the progress of diseases like nonalcoholic fatty liver disease (NAFLD) and neurodegenerative diseases. Herein, we summarize extant research on intracellular iron export with an emphasis on EVs and put our eyes on the relationship between iron-loaded EVs with both parent and target cells. Iron-loaded EVs will be an important avenue for later research on their vital role in iron redistribution.

Autophagy and exosomes coordinately mediate quercetin's protective effects on alcoholic liver disease

Alcoholic liver disease (ALD), a spectrum of liver abnormalities induced by chronic alcohol abuse, continues to be the major cause of life-threatening liver disease in developed countries. Autophagy and exosomes were individually confirmed to be involved in the pathogenesis of ALD. Here, we sought to identify the role of autophagy and exosomes in the liver protective effects of quercetin. We observed decreased hepatic LC3II/LC3I and increased p62 level in ethanol-fed mice, and these changes were alleviated by quercetin. Meanwhile, nanoparticle tracking analysis (NTA) showed elevated serum exosomes numbers in ethanol-fed mice, which was combated by quercetin. Ethanol induced elevated LDH, ALT, and AST in HepG2 supernatant, which was alleviated by cytochalasin D (exosomes uptake inhibitor). Moreover, quercetin reduced ethanol-induced LDH and ALT elevation in vitro, and the effects of quercetin were reversed by Rab27a overexpression (induce exosomes release) or wortmannin treatment (autophagy inhibitor). Transcriptomic analysis supported that quercetin reversed the change of lysosome related genes disturbed by ethanol. Meanwhile, western blot analysis exhibited decreased hepatic expression of LAMP2 and ATPA6V1B2, and active Cathepsin B/Cathepsin B by quercetin treatment, indicating quercetin alleviated lysosome dysfunction in ethanol-fed mice. Baf A treatment or transfection of siTFEB offset quercetin's effects in ethanol-induced LDH and ALT elevation, exosomes release, and autophagy inhibition (LC3II/I and p62 accumulation). Taken together, quercetin coordinately activates autophagy and combats exosomes release by restoring lysosome function, and further mitigates ethanol-induced liver damage.

An in vitro lipid-mixing assay to investigate the fusion between small extracellular vesicles and endosome

Small extracellular vesicles (sEVs) such as exosomes can efficiently deliver nucleic acids into the cytosol of recipient cells. However, the molecular mechanism of the subsequent fusion with an endosome is not well understood. In this study, we developed an in vitro lipid-mixing assay using an endosomal-mimicking anionic liposome to investigate the fusion between sEVs and endosomes. We observed that the particle number ratio between the sEVs and the anionic liposomes, the diameter of the liposomes, and the buffer pH were all important for fusion activity. Furthermore, we optimized the liposomal lipid composition and demonstrated that incorporating the anionic lipid bis(monooleoylglycero) phosphate and cholesterol was important for efficient and reliable fusion. Our in vitro assay suggested that a decrease in pH increased the fusion activity. Additionally, it was suggested that this pH-dependent increase in the fusion activity was predominantly due to a change in the sEVs. sEVs possess a larger fusion activity than artificial liposomes that mimic the physicochemical properties of exosomes. These results are consistent with those of previous in vivo studies, supporting the physiological relevance of our system. This study provides an important platform for further research to clarify the molecular mechanisms of fusion between sEVs and endosomes.

Advances in Ferritin Physiology and Possible Implications in Bacterial Infection

Due to its advantageous redox properties, iron plays an important role in the metabolism of nearly all life. However, these properties are not only a boon but also the bane of such life forms. Since labile iron results in the generation of reactive oxygen species by Fenton chemistry, iron is stored in a relatively safe form inside of ferritin. Despite the fact that the iron storage protein ferritin has been extensively researched, many of its physiological functions are hitherto unresolved. However, research regarding ferritin's functions is gaining momentum. For example, recent major discoveries on its secretion and distribution mechanisms have been made as well as the paradigm-changing finding of intracellular compartmentalization of ferritin via interaction with nuclear receptor coactivator 4 (NCOA4). In this review, we discuss established knowledge as well as these new findings and the implications they may have for host-pathogen interaction during bacterial infection.

Stimulation of Hepatic Ferritinophagy Mitigates Irp2 Depletion-Induced Anemia

Background: Iron regulatory proteins (IRPs) maintain cellular iron homeostasis. Due to aberrant tissue-iron distribution, Irp2-deficient mice suffer microcytic anemia and neurodegeneration, while iron overload occurs in the liver and intestine. We previously found that Irp2 deficiency-induced Hif2 plays an important role in neurodegeneration. Methods: To test the role of Hif2 in Irp2 deficiency-induced anemia, we used Irp2 global knockout mice. Following Hif2 inhibition, routine blood tests, iron availability in bone marrow, histological assays, and biochemical analysis were performed to assess anemia improvement and tissue iron distribution. Results: We found that Hif2 inhibition improved anemia. The increased iron bioavailability for erythropoiesis was mainly derived from hepatic iron release, and secondly from enhanced intestinal absorption. We further demonstrate that nuclear receptor coactivator 4 (Ncoa4) was upregulated for iron release via the process of ferritinophagy. The released iron was utilized not only for intracellular Fe-S biogenesis but also for erythropoiesis after being exported from the liver to circulation. The hepatic iron export reduced hepcidin expression to further support iron absorption through the hepcidin-ferroportin axis to alleviate intestinal iron overload. Conclusion: Irp2 not only regulates cellular iron homeostasis but also tissue iron distribution by managing the involvement of Hif2-Ncoa4.