TRPM7 channel inhibition attenuates rheumatoid arthritis articular chondrocyte ferroptosis by suppression of the PKCα-NOX4 axis

Dysregulation of Calcium Homeostasis: An Important Factor Leading to Ferroptosis in Cardiovascular Diseases

Cardiovascular disease is a circulatory system disease involving the heart and blood vessels, which is one of the main causes of human health loss and even life-threatening. Ca2+ is an important signal molecule. Free calcium ions in the cytoplasm are involved in various physiological and biochemical reactions of cells. Ferroptosis is a programmed cell death driven by lipid peroxidation dependent on free ferrous ions. The essence of ferroptosis is the accumulation of lipid peroxide caused by the increase of intracellular ferrous ion content, which leads to the damage of the phospholipid membrane and eventually cell death. Studies have shown that calcium homeostasis and ferroptosis are involved in the occurrence and development of cardiovascular diseases, but the relationship between them remains to be clarified. This article reviews the various pathways regulating calcium homeostasis in cells and the occurrence and development mechanism of ferroptosis, and discusses the relationship between the two in cardiovascular diseases, which is expected to provide novel and important strategies for alleviating and treating cardiovascular diseases.

Iron metabolism in rheumatic diseases

Iron is a crucial element for living organism in terms of oxygen transport, hematopoiesis, enzymatic activity, mitochondrial respiratory chain function and also immune system function. The human being has evolved a mechanism to regulate body iron. In some rheumatic diseases such as rheumatoid arthritis (RA), systemic lupus erythematous (SLE), systemic sclerosis (SSc), ankylosing spondylitis (AS), and gout, this balanced iron regulation is impaired. Altered iron homeostasis can contribute to disease progression through ROS production, fibrosis, inflammation, abnormal bone homeostasis, NETosis and cell senescence. In this review, we have focused on the iron metabolism in rheumatic disease and its role in disease progression.

Glutathione Decreases Parkinsonism-Induced Ferroptosis and Oxidative Stress Through the Inhibition of the TRPM2 Channel in Neuronal Cells

Parkinson's disease (PD) is the most prevalent neurodegenerative disease. Previously, it was believed that aberrant iron metabolism, leading to ferroptosis due to glutathione (GSH) depletion, excessive Ca2+ influx, mitochondrial (mROS), and cytosolic (cROS) free reactive oxygen species in the brain, was a contributing factor to PD. ADP-ribose (ADPR), mROS, and cROS activate the TRPM2 cation channel. It is yet unclear how TRPM2 contributes to the development of neuronal damage induced by the rise in ferroptosis in PD. Our aim in this study was to examine the function of TRPM2 and the protective effect of GSH in the dopaminergic human SH-SY5Y neuronal cells that had been exposed to 1-methyl 4-phenylpyridinium (MPP) to produce parkinsonism. The SH-SY5Y cells were divided into six groups: control, MPP, MPP + erastin, MPP + erastin + ferrostatin-1, MPP + erastin + glutathione (GSH), and MPP + erastin + TRPM2 blocker (ACA). In the MPP and MPP + erastin groups, the concentrations of Ca2+, ADPR-induced TRPM2 current density, mitochondrial membrane dysfunction, mROS, cROS, lipid peroxidation, mitochondrial Zn2+, cytosolic Zn2+, and cytosolic Fe2+ were increased, although glutathione peroxidase, GSH, cell viability, and cell number were decreased. The changes were higher in the MPP + erastin group than in MPP group only. However, their concentrations were modulated by the changes in the MPP + erastin + ferrostatin-1, MPP + erastin + GSH, and MPP + erastin + ACA groups. In conclusion, the increase in death and ferroptosis in parkinsonism (MPP)-induced SH-SY5Y cells was attributed to TRPM2 activation. By regulating cytosolic oxidant/antioxidant balance, GSH regulates TRPM2 channel activity and lowers neuronal death and ferroptosis.

Ferroptosis: New Strategies for Clinical Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that can lead to joint deformities, functional loss, and a significant reduction in patients' quality of life. It also imposes a considerable medical and socio-economic burden. Iron-induced cell death, or ferroptosis, is a unique form of programmed cell death characterized by dysregulated iron metabolism and the accumulation of lipid peroxides resulting from increased reactive oxygen species (ROS) and reduced activity of glutathione peroxidase 4 (GPX4). The accumulation of lipid peroxides can cause cellular damage, promotes inflammatory responses and joint destruction. This process not only plays a crucial role in the pathogenesis of RA, but also provides new therapeutic targets for its treatment. In this review, we summarize the regulatory mechanisms of ferroptosis in the pathogenesis of RA. These include its roles in regulating oxidative stress and lipid peroxidation, inhibiting the abnormal proliferation of synovial fibroblasts (FLSs), preventing cartilage erosion, restoring immune homeostasis and inflammatory responses, and other aspects. Finally, we also discuss the potential clinical applications, and future prospects of ferroptosis-based therapies for RA treatment.

An angiotensin-converting enzyme inhibitory peptide (Val-Trp) from cauliflower by-products exerts an antihypertensive effect via the eNOS/NO/cGMP pathway

Val-Trp (VW) has been identified as an angiotensin-converting enzyme (ACE) inhibitory peptide from cauliflower by-products by our previous research. The aim of this study is to investigate the antihypertensive activity and mechanism of VW. The results showed that oral administration of VW (40 mg kg-1) could effectively reduce the systolic and diastolic blood pressure in SHRs. The underlying mechanisms of VW were further investigated. The generation of cGMP was promoted by VW in an Ang I-induced HUVEC model, leading to a decrease in intracellular calcium concentration, thus facilitating vascular relaxation and lowering blood pressure. Additionally, VW significantly increased the content of the vasodilator factor NO, inhibited the production of the vasoconstrictor factor ET-1, and induced eNOS phosphorylation. Based on these findings, it can be inferred that VW exerted its antihypertensive effects by inhibition of ACE and activation of the eNOS/NO/cGMP signaling pathway. Furthermore, the inhibitory mechanism of VW on ACE was investigated. Isothermal titration calorimetry results revealed that the binding of VW to ACE was a spontaneous exothermic process driven by enthalpy and entropy, which involved hydrogen bonding and hydrophobic effects. The peptide VW had a static fluorescence quenching effect on ACE, involving secondary structure changes, and molecular docking showed that VW attached to the active pocket of ACE, consequently preventing the substrate from binding to ACE. The present study provides evidence for the antihypertensive effect of VW through the ACE-mediated eNOS/NO/cGMP pathway, and promotes the recycling of cauliflower by-products.

The Antifungal Effects of Equol Against Candida albicans Involve Mitochondrial Dysfunction

Novel antifungal agents are urgently needed because of the increasing number of drug-resistant Candida strains encountered in clinical practice and the limited variety of available antifungal drugs. Equol, a metabolite of soy isoflavone glycosides, exhibits antifungal activities. In this study, Equol had good inhibitory activity against Candida species. The lowest inhibitory concentration of 125-500 μg/mL was confirmed by the gradient dilution method. In addition, transmission electron microscopy and the relative content assay showed that Equol altered the cell wall and membrane of Candida albicans. Further studies found that Equol treatment increased the intracellular levels of reactive oxygen species and Ca2+. Subsequent experiments suggested that Equol treatment depolarized the membrane potential of C. albicans and up-regulated the expression of the apoptosis-inducing factor gene. These results confirmed that Equol damaged the cell wall and membrane, dysregulated the intracellular components, induced oxidative stress and Ca2+ accumulation, and ultimately resulted in mitochondrial dysfunction. Collectively, these findings demonstrated that Equol is a potential antifungal agent.

β-Diketone Functionalized Microspheres Chelate Reactive Iron via Metal Coordination for Cartilage Repair

Excessive intracellular iron accumulation can induce mitochondrial dysfunction, leading to chondrocyte ferroptosis, a key contributor to cartilage damage in osteoarthritis (OA). Here, micelle-microfluidic hydrogel microspheres, featuring keto-enol-thiol bridged nano-sized secondary structures that disintegrate within the intracellular peroxidative environment to reveal β-diketone groups with metal chelation capabilities, are utilized for the in situ removal of reactive iron, thereby facilitating cartilage repair through the restoration of mitochondrial homeostasis. The relevant experiments demonstrate that the microspheres reduce iron influx by downregulating transferrin receptor (TfR1) expression and decrease mitochondrial iron uptake by upregulating mitochondrial outer membrane iron-sulfur cluster protein (CISD1), thus restoring intracellular mitochondrial iron homeostasis. Furthermore, the antioxidant properties of the ketone-thioether segments synergistically mitigate chondrocyte phospholipid peroxidation via Nrf2/SLC7A11/GPX4 axis, inhibiting ferroptosis and slowing OA progression. In summary, this system that in situ sustainably chelates reactive iron via metal coordination exhibits great potential in the minimally invasive treatment of OA and other ferroptosis-mediated diseases.

Preparation of hydrogel microsphere and its application in articular cartilage injury

In recent years, hydrogel microspheres have garnered significant attention due to their unique structure and functionality, demonstrating substantial potential in articular cartilage injury repair. This paper provides a comprehensive overview of current strategies for cartilage injury repair and summarizes the materials and preparation methods of hydrogel microspheres. Furthermore, it highlights the multiple roles of hydrogel microspheres in cartilage repair, including inflammation control, regulation of chondrocyte metabolism, drug and cell delivery, lubrication improvement, and recruitment of endogenous stem cells. Finally, the paper discusses the application prospects of hydrogel microspheres, identifies current limitations and challenges, and offers insights to guide future research and practical applications in cartilage injury repair.

A Matrigel-Free 3D Chondrocytic Spheroid Model for Rheumatoid Arthritis-Associated Synoviocytes Invasion Studies

Background

The primary pathology of rheumatoid arthritis (RA) involves the invasion of the extracellular matrix (ECM) of articular cartilage by inflammation-activated fibroblast-like synoviocytes (FLS), a process targeted by most RA therapeutic drugs. However, the absence of an efficient in vitro model for evaluating FLS invasion hinders relevant drug screening and mechanism research. To address this, a novel three-dimensional (3D) chondrocytic spheroid model that mimics cartilage ECM has been developed, along with corresponding indices to quantify synoviocytes invasion.

Methods

The matrigel-free 3D chondrocytic spheroid model was developed using an ultra-low attachment plate. The model was characterized using transcriptome sequencing, immunofluorescent staining. To explore the feasibility of this 3D chondrocytic spheroid model for evaluating the invasive capacity of synoviocytes, multi-interference strategies, including ADAMTS5 gene overexpression, inflammatory cytokine stimulation, and anti-inflammatory drug (Etanercept) treatment were involved. Additionally, specific indices-Invasion Depth Ratio (IDR), Invasion Counts (IC), Invasion Ratio (IR), and Invasion Area Ratio (IAR)-were designed to quantify synoviocytes invasion.

Results

The 3D culture environment is more suitable for cartilage ECM synthesis by increasing cartilage anabolism-related gene (COL2A1) and reducing catabolism-related genes (ADAMTS5, MMP3, CCL2 and CDKN2A) expression. Moreover, the optimal conditions for developing the 3D chondrocytic spheroid model were identified. This model was sensitive to gene, inflammation and drug interference. Increased IDR, IC, IR and IAR was observed in ADAMTS5 overexpressed- and IL-1β-treated chondrocytic spheroid. Further, Etanercept could inhibit TNF-α induced synoviocytes invasion of chondrocytic spheroid.

Conclusion

This matrigel-free 3D chondrocytic spheroid model offers an ideal platform for innovative drug screening and pathogenesis studies focused on synoviocytes invasion of cartilage.

Ferroptosis: A New Strategy for the Treatment of Fibrotic Diseases

Ferroptosis is a new type of cell death characterized by iron dependence and the excessive accumulation of lipid reactive oxygen species (lipid ROS) that has gradually become better characterized. There is sufficient evidence indicating that ferroptosis is associated with a variety of human life activities and diseases, such as tumor suppression, ischemic organ injury, and degenerative disorders. Notably, ferroptosis is also involved in the initiation and development of fibrosis in various organs, including liver fibrosis, pulmonary fibrosis, renal fibrosis, and cardiac fibrosis, which is usually irreversible and refractory. Although a large number of patients with fibrosis urgently need to be treated, the current treatment options are still limited and unsatisfactory. Organ fibrosis involves a series of complex and orderly processes, such as parenchymal cell damage, recruitment of inflammatory cells and activation of fibroblasts, which ultimately leads to the accumulation of extracellular matrix (ECM) and the formation of fibrosis. An increasing number of studies have confirmed the close association between these pathological processes and ferroptosis. This review summarizes the role and function of ferroptosis in fibrosis and proposes several potential therapeutic strategies and pathways based on ferroptosis.

Immunological landscape of periodontitis and rheumatoid arthritis and their molecular crosstalk

BACKGROUND

The association between periodontitis (PT) and rheumatoid arthritis (RA) is well-established; however, the molecular mechanisms underlying this relationship remain poorly understood. This study aims to delineate shared genetic and molecular features between PT and RA to uncover potential common pathways involved in their pathogenesis.

METHODS

Gene expression data sets for PT and RA were retrieved from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) and co-expressed gene modules were identified using weighted gene co-expression network analysis (WGCNA) and the DESeq2 package. Enrichment analyses, including KEGG and Gene Ontology (GO) pathways, as well as immune cell infiltration profiling, were performed to explore shared biological pathways. A protein-protein interaction (PPI) network was constructed to pinpoint key genes linking PT and RA. Functional assays were conducted by overexpressing the identified core gene, PTPRC, in MH7A cells via lentiviral transfection, followed by cell viability (CCK-8), migration, and invasion assays. In addition, transcription factor enrichment and connectivity map (cMAP) analyses were employed to identify common transcriptional regulators and potential therapeutic targets for both conditions.

RESULTS

WGCNA and DESeq2 analyses revealed 154 shared DEGs between PT and RA, predominantly enriched in immune and inflammatory response pathways. PTPRC emerged as a pivotal shared gene, exhibiting significantly higher expression in PT patients compared to controls. In vitro assays confirmed that PTPRC overexpression enhanced fibroblast proliferation, migration, and invasion. Furthermore, transcription factor enrichment analysis and cMAP identified overlapping transcriptional regulators and potential pharmacological agents for both diseases.

CONCLUSIONS

This study provides novel insights into shared gene expression profiles and molecular mechanisms linking PT and RA, identifying PTPRC as a potential key regulator. These findings suggest that targeting PTPRC could offer therapeutic opportunities for RA driven by PT.

RND1 Induces Ferroptosis to Alleviate Inflammatory Response, Proliferation, Invasion, and Migration of Rheumatoid Synoviocytes

Background

Ferroptosis is involved in the occurrence and development of inflammatory arthritis. RND1 has been reported to possess pro-ferroptosis activity.

Objective

This study was designed to explore the role and the molecular mechanism of RND1 in rheumatoid arthritis (RA).

Methods

DBA/1 mice were exposed to type II collagen immunization. The pathological damage of the knee joints of mice was observed with H&E staining and RND1 expression in synovial tissues was detected using Western blot. In vitro, Western blot was used to measure RND1, ferroptosis-, migration- and inflammation-related proteins. The cell proliferation, migration and invasion were detected using CCK-8 method, EdU staining, wound healing and transwell assays. The levels of inflammatory factors were detected with ELISA and RT-qPCR. Relative iron level, GSH and MDA concentrations were detected with corresponding assay kits. BODIPY 581/591 C11 kit measured lipid ROS. 4-HNE and GPX4 expression were detected using immunofluorescence assay.

Results

This study found that RND1 expression was reduced in the synovial tissues of RA mice and human fibroblast-like MH7A synoviocytes. It was also found that the upregulation of RND1 inhibited the proliferation, migration, invasion and inflammatory response in rheumatoid synovial cells via ferroptosis.

Conclusion

Collectively, RND1 exerted protective impacts on RA, which might be mediated by ferroptosis.

Programmed Cell Death in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, progressive, systemic autoimmune disease characterised by synovial inflammation, synovial pannus formation and subsequent destruction of articular cartilage and bone. Programmed cell death (PCD), encompassing apoptosis, autophagy, pyroptosis, necroptosis, and ferroptosis, plays a pivotal role in the pathogenesis of RA. An imbalance in PCD causes a variety of immune cells to release large amounts of inflammatory factors and mediators that exacerbate not only chronic synovial inflammation, but also bone and joint damage. The purpose of this article is to review the relevant studies between PCD and RA, with the aim of providing further insights and considerations for a deeper understanding of the pathogenesis of RA and to guide clinical management.

Chronic Kidney Disease and Osteoarthritis: Current Understanding and Future Research Directions

Chronic kidney disease (CKD) is a significant public health concern. Osteoarthritis (OA), a common form of arthritis, has been shown to have a dramatically increased prevalence, particularly among individuals aged 40-50 and older, in the presence of CKD. Furthermore, CKD may exacerbate the progression and impact of OA. A survey study revealed that 53.9% of CKD patients undergoing long-term hemodialysis were diagnosed with OA. These findings underscore the potential association between CKD and OA. Uremic toxins, such as indoxyl sulfate, p-cresyl sulfate, transforming growth factor-β, and advanced glycation end-products, are regarded as potential risk factors in various CKD-related conditions, affecting bone and joint metabolism. However, whether these factors serve as a bridging mechanism between CKD and OA comorbidities, as well as their detailed roles in this context, remains unclear. Addressing the progression of OA in CKD patients and identifying effective treatment and prevention strategies is an urgent challenge that warrants immediate attention. This review focuses on describing and discussing the molecular pathological mechanisms underlying CKD-associated OA and the possible therapeutic strategies.

Engineered nanoplatform mediated gas therapy enhanced ferroptosis for tumor therapy in vivo

The high glutathione (GSH) environment poses a significant challenge for inducing ferroptosis in tumor cells, necessitating the development of nanoplatforms that can deplete intracellular GSH. In this study, we developed an engineered nanoplatform (MIL-100@Era/L-Arg-HA) that enhances ferroptosis through gas therapy. First, we confirmed that the Fe element in the nanoplatform undergoes valence changes under the influence of high GSH and H2O2 in tumor cells. Meanwhile, L-Arg generates NO gas in the presence of intracellular H2O2, which reacts with GSH. Additionally, Erastin depletes GSH by inhibiting the cystine/glutamate antiporter system, reducing cystine uptake and impairing GPX4, while also increasing intracellular H2O2 levels by activating NOX4 protein expression. Through these combined GSH-depletion mechanisms, we demonstrated that MIL-100@Era/L-Arg-HA effectively depletes GSH levels, disrupts GPX4 function, and increases intracellular lipid ROS levels in vitro. Furthermore, this nanoplatform significantly inhibited tumor cell growth and extended the survival time of tumor-bearing mice in vivo. This engineered nanoplatform, which enhances ferroptosis through gas therapy, shows significant promise for ferroptosis-based cancer therapy and offers potential strategies for clinical tumor treatment.

Inhibition of ASIC1a reduces ferroptosis in rheumatoid arthritis articular chondrocytes via the p53/NRF2/SLC7A11 pathway

The activation of acid-sensing ion channel 1a (ASIC1a) in response to extracellular acidification leads to an increase in extracellular calcium influx, thereby exacerbating the degeneration of articular chondrocytes in rheumatoid arthritis (RA). It has been suggested that the inhibition of extracellular calcium influx could potentially impede chondrocyte ferroptosis. The cystine transporter, solute carrier family 7 member 11 (SLC7A11), is recognized as a key regulator of ferroptosis. Recent studies suggest that the tumor suppressor gene p53 facilitates the induction of ferroptosis by suppressing the upregulation of SLC7A11. This process is mediated by the nuclear factor erythroid 2-related factor 2 (NRF2), a key transcription factor integral to the maintenance of cellular redox homeostasis and the regulation of inflammatory responses. This study aims to investigate the role of ASIC1a in the ferroptosis of RA chondrocytes and to determine the involvement of the p53/NRF2/SLC7A11 pathway in its underlying mechanism. In vitro experiments revealed that acidosis induces ferroptosis and reduces the expression of NRF2 and SLC7A11 in chondrocytes. Moreover, acidification significantly increased p53 protein levels in chondrocytes. Pifithrin-α (PFN-α), a p53 inhibitor, mitigated acidosis-induced ferroptosis and restored the diminished expression of NRF2 and SLC7A11. Furthermore, PcTx-1, an ASIC1a inhibitor, inhibited acidification-induced ferroptosis, enhanced the protein levels of SLC7A11 and NRF2, and reduced p53 expression. In vivo experiments demonstrated that the ASIC1a-specific inhibitor PcTx-1 ameliorated histopathological characteristics of ankle joints in collagen-induced arthritis (CIA) mice, decreased p53 expression, and enhanced NRF2 and SLC7A11 expression in chondrocytes. These findings suggest that ASIC1a inhibition may mitigate acidification-induced ferroptosis in articular chondrocytes in RA, potentially via the p53/NRF2/SLC7A11 pathway.

Sea buckthorn extract mitigates chronic obstructive pulmonary disease by suppression of ferroptosis via scavenging ROS and blocking p53/MAPK pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Sea buckthorn (Hippophae rhamnoides), a traditional Tibetan medicinal herb, exhibits protective effects against cardiovascular and respiratory diseases. Although Sea buckthorn extract (SBE) has been confirmed to alleviate airway inflammation in mice, its therapeutic effect and underlying mechanism on chronic obstructive pulmonary disease (COPD) requires further clarification.

AIM OF THE STUDY

To elucidate the alleviative effect and molecular mechanism of SBE on lipopolysaccharides (LPS)/porcine pancreatic elastase (PPE)-induced COPD by blocking ferroptosis.

METHODS

The anti-ferroptotic effects of SBE were evaluated in human BEAS-2B bronchial epithelial cells using CCK8, RT-qPCR, western blotting, and transmission electron microscopy. Transwell was employed to detect chemotaxis of neutrophils. COPD model was induced by intranasally administration of LPS/PPE in mice and measured by alterations of histopathology, inflammation, and ferroptosis. RNA-sequencing, western blotting, antioxidant examination, flow cytometry, DARTS, CETSA, and molecular docking were then used to investigate its anti-ferroptotic mechanisms.

RESULTS

In vitro, SBE not only suppressed erastin- or RSL3-induced ferroptosis by suppressing lipid peroxides (LPOs) production and glutathione (GSH) depletion, but also suppressed ferroptosis-induced chemotactic migration of neutrophils via reducing mRNA expression of chemokines. In vivo, SBE ameliorated LPS/PPE-induced COPD phenotypes, and inhibited the generation of LPOs, cytokines, and chemokines. RNA-sequencing showed that p53 pathway and mitogen-activated protein kinases (MAPK) pathway were implicated in SBE-mediated anti-ferroptotic action. SBE repressed erastin- or LPS/PPE-induced overactivation of p53 and MAPK pathway, thereby decreasing expression of diamine acetyltransferase 1 (SAT1) and arachidonate 15-lipoxygenase (ALOX15), and increasing expression of glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11). Mechanistically, erastin-induced elevation of reactive oxygen species (ROS) was reduced by SBE through directly scavenging free radicals, thereby contributing to its inhibition of p53 and MAPK pathways. CETSA, DARTS, and molecular docking further showed that ROS-generating enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) may be the target of SBE. Overexpression of NOX4 partially impaired the anti-ferroptotic activity of SBE.

CONCLUSION

Our results demonstrated that SBE mitigated COPD by suppressing p53 and MAPK pro-ferroptosis pathways via directly scavenging ROS and blocking NOX4. These findings also supported the clinical application of Sea buckthorn in COPD therapy.

Blocking the isoflavone chemoreceptor in Phytophthora sojae to prevent disease

Inhibiting pathogen chemotaxis is a promising strategy for reducing disease pressure. However, this strategy is currently in the proof-of-concept stage. Here, Phytophthora sojae was used as a model, as its biflagellated zoospores could sense genistein, a soybean root exudate, to navigate host and initiate infection. We identify P. sojae IRK1 (isoflavone-insensitive receptor kinase 1) as a receptor for genistein, with PsIRK2 functioning as a coreceptor that enhances the binding affinity of PsIRK1 to genistein and regulates chemotaxis by phosphorylating G protein α subunit. Last, we identify an antagonist, esculetin, which disrupts the PsIRK1-genistein interaction, thereby preventing P. sojae infection by repelling zoospores. Our findings reveal the mechanism by which P. sojae senses host genistein and demonstrate a strategy for disease prevention by targeting the chemoreceptor.

[Knockdown of nuclear protein 1 delays pathological pro-gression of osteoarthritis through inhibiting chondrocyte ferroptosis]

OBJECTIVES

To investigate the effect of nuclear protein (Nupr) 1 on the pathological progression of osteoarthritis and its relationship with ferroptosis of chondrocytes.

METHODS

Chondrocytes from mouse knees were divided into small interfering RNA (siRNA) control group, small interfering RNA targeting Nupr1 (siNupr1) group, siRNA control+IL-1β group (siRNA control interference for 24 h followed by 10 ng/mL IL-1β) and siNupr1+IL-1β group (siNupr1 interference for 24 h followed by 10 ng/mL IL-1β). The protein and mRNA expressions of Nupr1 were detected by Western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR). Cell proliferation viabilities were measured using the cell counting kit-8 method. The levels of ferrous ions were detected by FerroOrange staining. Lipid peroxidation levels were detected by C11-BODIPY-591 fluorescence imaging. The contents of malondialdehyde (MDA) and glutathione (GSH) were detected by enzyme-linked immunosorbent assay. The protein expressions of acyl-CoA synthetase long-chain family (ACSL) 4, P53, glutathione peroxidase (GPX) 4 and solute carrier family 7 member 11 gene (SLC7A11) were detected by Western blotting. The osteoarthritis model was constructed by destabilization of the medial meniscus (DMM) surgery in 7-week-old male C57BL/6J mice. The mice were randomly divided into four groups with 10 animals in each group: sham surgery (Sham)+adeno-associated virus serotype 5 (AAV5)-short hairpin RNA (shRNA) control group, Sham+AAV5-shRNA control targeting Nupr1 (shNupr1) group, DMM+AAV5-shRNA control group, and DMM+AAV5-shNupr1 group. Hematoxylin and eosin staining and Safranin O-Fast Green staining were used to observe the morphological changes in cartilage tissue. The Osteoarthritis Research Society International (OARSI) osteoarthritis cartilage histopathology assessment system was used to evaluate the degree of cartilage degeneration in mice. The mRNA expressions of matrix metallopeptidase (MMP) 13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) 5, cyclooxy-genase (COX) 2, and GPX4 were detected by qRT-PCR.

RESULTS

In vitro experiments showed that knocking down Nupr1 alleviated the decrease of chondrocyte proliferation activity induced by IL-1β, reduced iron accumulation in mouse chondrocytes, lowered lipid peroxidation, downregulated ACSL4 and P53 protein expression and upregulated GPX4 and SLC7A11 protein expression (all P<0.01), thereby inhibiting ferroptosis in mouse chondrocytes. Meanwhile, in vivo animal experiments demonstrated that knocking down Nupr1 delayed the degeneration of articular cartilage in osteoarthritis mice, improved the OARSI score, slowed down the degradation of the extracellular matrix in osteoarthritis cartilage, and reduced the expression of the key ferroptosis regulator GPX4 (all P<0.01).

CONCLUSIONS

Knockdown of Nupr1 can delay the pathological progression of osteoarthritis through inhibiting ferroptosis in mouse chondrocytes.

Ferroptosis: mechanisms and therapeutic targets

Ferroptosis is a nonapoptotic form of cell death characterized by iron-dependent lipid peroxidation in membrane phospholipids. Since its identification in 2012, extensive research has unveiled its involvement in the pathophysiology of numerous diseases, including cancers, neurodegenerative disorders, organ injuries, infectious diseases, autoimmune conditions, metabolic disorders, and skin diseases. Oxidizable lipids, overload iron, and compromised antioxidant systems are known as critical prerequisites for driving overwhelming lipid peroxidation, ultimately leading to plasma membrane rupture and ferroptotic cell death. However, the precise regulatory networks governing ferroptosis and ferroptosis-targeted therapy in these diseases remain largely undefined, hindering the development of pharmacological agonists and antagonists. In this review, we first elucidate core mechanisms of ferroptosis and summarize its epigenetic modifications (e.g., histone modifications, DNA methylation, noncoding RNAs, and N6-methyladenosine modification) and nonepigenetic modifications (e.g., genetic mutations, transcriptional regulation, and posttranslational modifications). We then discuss the association between ferroptosis and disease pathogenesis and explore therapeutic approaches for targeting ferroptosis. We also introduce potential clinical monitoring strategies for ferroptosis. Finally, we put forward several unresolved issues in which progress is needed to better understand ferroptosis. We hope this review will offer promise for the clinical application of ferroptosis-targeted therapies in the context of human health and disease.

Injectable bioadhesive hydrogel as a local nanomedicine depot for targeted regulation of inflammation and ferroptosis in rheumatoid arthritis

Medicine intervention is the major clinical treatment used to relieve the symptoms and delay the progression of rheumatoid arthritis (RA), but is limited by its poor targeted delivery and short therapeutic duration. Herein, we developed an injectable and bioadhesive gelatin-based (Gel) hydrogel as a local depot of leonurine (Leon)-loaded and folate-functionalized polydopamine (FA-PDA@Leon) nanoparticles for anti-inflammation and chondroprotection in RA. The nanoparticles could protect Leon and facilitate its entry into the M1 phenotype macrophage for intracellular delivery of Leon, while the hydrogel tightly adhered to the tissues in the joint cavity and prolonged the retention of FA-PDA@Leon nanoparticles, thus achieving higher availability and therapeutic efficiency of Leon. In vitro and in vivo experiments demonstrated that the Gel/FA-PDA@Leon hydrogel could strongly suppress the inflammatory response by down-regulating the JAK2/STAT3 signaling pathway in macrophages and protect the chondrocytes from ferritinophagy/ferroptosis. This contributed to maintaining the structural integrity of articular cartilage and accelerating the joint functional recovery. This work provides an effective and convenient strategy to achieve higher bioavailability and long-lasting therapeutic duration of medicine intervention in arthritis diseases.

Potential Roles of IP3 Receptors and Calcium in Programmed Cell Death and Implications in Cardiovascular Diseases

Inositol 1,4,5-trisphosphate receptors (IP3Rs) play a crucial role in maintaining intracellular/cytosolic calcium ion (Ca2+i) homeostasis. The release of Ca2+ from IP3Rs serves as a second messenger and a modulatory factor influencing various intracellular and interorganelle communications during both physiological and pathological processes. Accumulating evidence from in vitro, in vivo, and clinical studies supports the notion that the overactivation of IP3Rs is linked to the pathogenesis of various cardiac conditions. The overactivation of IP3Rs results in the dysregulation of Ca2+ concentration ([Ca2+]) within cytosolic, mitochondrial, and nucleoplasmic cellular compartments. In cardiovascular pathologies, two isoforms of IP3Rs, i.e., IP3R1 and IP3R2, have been identified. Notably, IP3R1 plays a pivotal role in cardiac ischemia and diabetes-induced arrhythmias, while IP3R2 is implicated in sepsis-induced cardiomyopathy and cardiac hypertrophy. Furthermore, IP3Rs have been reported to be involved in various programmed cell death (PCD) pathways, such as apoptosis, pyroptosis, and ferroptosis underscoring their multifaceted roles in cardiac pathophysiology. Based on these findings, it is evident that exploring potential therapeutic avenues becomes crucial. Both genetic ablation and pharmacological intervention using IP3R antagonists have emerged as promising strategies against IP3R-related pathologies suggesting their potential therapeutic potency. This review summarizes the roles of IP3Rs in cardiac physiology and pathology and establishes a foundational understanding with a particular focus on their involvement in the various PCD pathways within the context of cardiovascular diseases.

SPG21, a potential oncogene targeted by miR-128-3p, amplifies HBx-induced carcinogenesis and chemoresistance via activation of TRPM7-mediated JNK pathway in hepatocellular carcinoma

PURPOSE

Chronic hepatitis B virus (HBV) infection is the primary risk factor for the malignant progression of hepatocellular carcinoma (HCC). It has been reported that HBV X protein (HBx) possesses oncogenic properties, promoting hepatocarcinogenesis and chemoresistance. However, the detailed molecular mechanisms are not fully understood. Here, we aim to investigate the effects of miR-128-3p/SPG21 axis on HBx-induced hepatocarcinogenesis and chemoresistance.

METHODS

The expression of SPG21 in HCC was determined using bioinformatics analysis, quantitative real-time PCR (qRT-PCR), western blotting, and immunohistochemistry (IHC). The roles of SPG21 in HCC were elucidated through a series of in vitro and in vivo experiments, including real-time cellular analysis (RTCA), matrigel invasion assay, and xenograft mouse model. Pharmacologic treatment and flow cytometry were performed to demonstrate the potential mechanism of SPG21 in HCC.

RESULTS

SPG21 expression was elevated in HCC tissues compared to adjacent non-tumor tissues (NTs). Moreover, higher SPG21 expression correlated with poor overall survival. Functional assays revealed that SPG21 fostered HCC tumorigenesis and invasion. MiR-128-3p, which targeted SPG21, was downregulated in HCC tissues. Subsequent analyses showed that HBx amplified TRPM7-mediated calcium influx via miR-128-3p/SPG21, thereby activating the c-Jun N-terminal kinase (JNK) pathway. Furthermore, HBx inhibited doxorubicin-induced apoptosis by engaging the JNK pathway through miR-128-3p/SPG21.

CONCLUSION

The study suggested that SPG21, targeted by miR-128-3p, might be involved in enhancing HBx-induced carcinogenesis and doxorubicin resistance in HCC via the TRPM7/Ca2+/JNK signaling pathway. This insight suggested that SPG21 could be recognized as a potential oncogene, offering a novel perspective on its role as a prognostic factor and a therapeutic target in the context of HCC.

Macrophage membrane-camouflaged biomimetic nanoparticles for rheumatoid arthritis treatment via modulating macrophage polarization

Rheumatoid arthritis (RA) is a debilitating autoimmune disease characterized by chronic joint inflammation and cartilage damage. Current therapeutic strategies often result in side effects, necessitating the development of targeted and safer treatment options. This study introduces a novel nanotherapeutic system, 2-APB@DGP-MM, which utilizes macrophage membrane (MM)-encapsulated nanoparticles (NPs) for the targeted delivery of 2-Aminoethyl diphenylborinate (2-APB) to inflamed joints more effectively. The NPs are designed with a matrix metalloproteinase (MMP)-cleavable peptide, allowing for MMP-responsive drug release within RA microenvironment. Comprehensive in vitro and in vivo assays confirmed the successful synthesis and loading of 2-APB into the DSPE-GPLGVRGC-PEG (DGP) NPs, as well as their ability to repolarize macrophages from a pro-inflammatory M1 to an anti-inflammatory M2 phenotype. The NPs demonstrated high biocompatibility, low cytotoxicity, and enhanced cellular uptake. In a collagen-induced arthritis (CIA) mouse model, intra-articular injection of 2-APB@DGP-MM significantly reduced synovial inflammation and cartilage destruction. Histological analysis corroborated these findings, demonstrating marked improvements in joint structure and delayed disease progression. Above all, the 2-APB@DGP-MM nanotherapeutic system offers a promising and safe approach for RA treatment by modulating macrophage polarization and delivering effective agents to inflamed joints.

NS8593 inhibits chondrocyte ferroptosis and alleviates cartilage injury in rat adjuvant arthritis through TRPM7 / HO-1 pathway

Ferroptosis is an emerging target in rheumatoid arthritis (RA). We previously reported that transient receptor potential melastatin 7 (TRPM7) expression is correlated with RA cartilage destruction and demonstrated that TRPM7 mediates ferroptosis in chondrocytes. Here, we further determined the role and mechanism of (R)-N-(Benzimidazol-2-yl)-1,2,3,4-tetrahydro-1-naphthylamine (NS8593), a TRPM7 inhibitor, in chondrocyte ferroptosis of RA. We established in vitro models of ferroptosis in human chondrocytes (C28/I2 cells) by using ferroptosis inducer Erastin. The results showed that NS8593 could protect C28/I2 cells from ferroptosis by inhibiting TRPM7 channel, which was manifested by restoring cell viability, reducing cytotoxicity, affecting the expression of ferroptosis marker protein, and restoring redox balance to alleviate Erastin-induced oxidative stress injury. Mechanistically, the Heme oxygenase-1 (HO-1) axis responded to Erastin stimulation, which resulted in TRPM7-mediated chondrocyte ferroptosis, NS8593 could reduce the expression of HO-1 by inhibiting TRPM7 channel. Moreover, NS8593 alleviated articular cartilage destruction and inhibited chondrocyte ferroptosis in AA rats. In conclusion, NS8593 mitigated articular cartilage damage and chondrocyte ferroptosis through the TRPM7/HO-1 pathway, suggesting that NS8593 may be a potential novel drug for the treatment of RA.

Androgen receptor deficiency-induced TUG1 in suppressing ferroptosis to promote benign prostatic hyperplasia through the miR-188-3p/GPX4 signal pathway

Benign prostatic hyperplasia (BPH), characterized by the non-malignant enlargement of the prostate, exhibits a pronounced association with inflammation resulting from androgen receptor (AR) deficiency. Ferroptosis, a cell death mechanism triggered by iron-dependent lipid peroxidation and closely linked to inflammation, has yet to be fully understood in the context of BPH. Using RNA sequencing, we observed a significant elevation of taurine-upregulated gene 1 (TUG1) long noncoding RNA (lncRNA) in BPH tissues compared to normal prostate tissue. High levels of TUG1 exhibited a discernible correlation with both prostate volume and the extent of inflammatory infiltration in BPH patients. The suppression of TUG1 not only led to a reduction in prostate size but also ameliorated AR-deficiency-induced prostatic hyperplasia. Mechanistically, a decrease in AR in prostate luminal cells prompted macrophage aggregation and the release of IL-1β, subsequently fostering the transcription of TUG1 via MYC. Induced TUG1, through competitive binding with miR-188-3p, facilitated the expression of GPX4, thereby diminishing intracellular ROS levels and impeding ferroptosis in prostate luminal cells. Notably, the ferroptosis inducer JKE-1674 alleviated inflammation-induced prostatic hyperplasia in vivo. Together, these findings suggest that AR deficiency crucially inhibits ferroptosis, promoting BPH via the TUG1/miR-188-3p/GPX4 signaling axis, and making ferroptosis induction a promising therapeutic strategy for BPH patients with AR deficiency.

Vitamin D3 Attenuates Neuropathic Pain via Suppression of Mitochondria-Associated Ferroptosis by Inhibiting PKCα/NOX4 Signaling Pathway

AIMS

Neuropathic pain remains a significant unmet medical challenge due to its elusive mechanisms. Recent clinical observations suggest that vitamin D (VitD) holds promise in pain relief, yet its precise mechanism of action is still unclear. This study explores the therapeutical role and potential mechanism of VitD3 in spared nerve injury (SNI)-induced neuropathic pain rat model.

METHODS

The analgesic effects and underlying mechanisms of VitD3 were evaluated in SNI and naïve rat models. Mechanical allodynia was assessed using the Von Frey test. Western blotting, immunofluorescence, biochemical assay, and transmission electron microscope (TEM) were employed to investigate the molecular and cellular effects of VitD3.

RESULTS

Ferroptosis was observed in the spinal cord following SNI. Intrathecal administration of VitD3, the active form of VitD, activated the vitamin D receptor (VDR), suppressed ferroptosis, and alleviated mechanical nociceptive behaviors. VitD3 treatment preserved spinal GABAergic interneurons, and its neuroprotective effects were eliminated by the ferroptosis inducer RSL3. Additionally, VitD3 mitigated aberrant mitochondrial morphology and oxidative metabolism in the spinal cord. Mechanistically, VitD3 inhibited SNI-induced activation of spinal PKCα/NOX4 signaling. Inhibition of PKCα/NOX4 signaling alleviated mechanical pain hypersensitivity, accompanied by reduced ferroptosis and mitochondrial dysfunction in SNI rats. Conversely, activation of PKCα/NOX4 signaling in naïve rats induced hyperalgesia, ferroptosis, loss of GABAergic interneurons, and mitochondrial dysfunction in the spinal cord, all of which were reversed by VitD3 treatment.

CONCLUSIONS

Our findings provide evidence that VitD3 attenuates neuropathic pain by preserving spinal GABAergic interneurons through the suppression of mitochondria-associated ferroptosis mediated by PKCα/NOX4 signaling, probably via VDR activation. VitD, alone or in combination with existing analgesics, presents an innovative therapeutic avenue for neuropathic pain.

Ferroptosis in health and disease

Ferroptosis is a pervasive non-apoptotic form of cell death highly relevant in various degenerative diseases and malignancies. The hallmark of ferroptosis is uncontrolled and overwhelming peroxidation of polyunsaturated fatty acids contained in membrane phospholipids, which eventually leads to rupture of the plasma membrane. Ferroptosis is unique in that it is essentially a spontaneous, uncatalyzed chemical process based on perturbed iron and redox homeostasis contributing to the cell death process, but that it is nonetheless modulated by many metabolic nodes that impinge on the cells' susceptibility to ferroptosis. Among the various nodes affecting ferroptosis sensitivity, several have emerged as promising candidates for pharmacological intervention, rendering ferroptosis-related proteins attractive targets for the treatment of numerous currently incurable diseases. Herein, the current members of a Germany-wide research consortium focusing on ferroptosis research, as well as key external experts in ferroptosis who have made seminal contributions to this rapidly growing and exciting field of research, have gathered to provide a comprehensive, state-of-the-art review on ferroptosis. Specific topics include: basic mechanisms, in vivo relevance, specialized methodologies, chemical and pharmacological tools, and the potential contribution of ferroptosis to disease etiopathology and progression. We hope that this article will not only provide established scientists and newcomers to the field with an overview of the multiple facets of ferroptosis, but also encourage additional efforts to characterize further molecular pathways modulating ferroptosis, with the ultimate goal to develop novel pharmacotherapies to tackle the various diseases associated with - or caused by - ferroptosis.

Ion channels in osteoarthritis: emerging roles and potential targets

Osteoarthritis (OA) is a highly prevalent joint disease that causes substantial disability, yet effective approaches to disease prevention or to the delay of OA progression are lacking. Emerging evidence has pinpointed ion channels as pivotal mediators in OA pathogenesis and as promising targets for disease-modifying treatments. Preclinical studies have assessed the potential of a variety of ion channel modulators to modify disease pathways involved in cartilage degeneration, synovial inflammation, bone hyperplasia and pain, and to provide symptomatic relief in models of OA. Some of these modulators are currently being evaluated in clinical trials. This review explores the structures and functions of ion channels, including transient receptor potential channels, Piezo channels, voltage-gated sodium channels, voltage-dependent calcium channels, potassium channels, acid-sensing ion channels, chloride channels and the ATP-dependent P2XR channels in the osteoarthritic joint. The discussion spans channel-targeting drug discovery and potential clinical applications, emphasizing opportunities for further research, and underscoring the growing clinical impact of ion channel biology in OA.

Asiatic acid induces ferroptosis of RA-FLS via the Nrf2/HMOX1 pathway to relieve inflammation in rheumatoid arthritis

BACKGROUND

Ferroptosis is a distinct iron-dependent non-apoptotic type of programmed cell death that is implicated in the pathophysiology of rheumatoid arthritis (RA). Although asiatic acid (AA) is documented to have significant anti-inflammatory effects in various diseases, it is not known whether it can regulate RA via ferroptosis.

METHODS

The effects of AA on rheumatoid arthritis fibroid-like synoviocytes (RA-FLS) were assessed in vitro, and a rat model of type II collagen-induced arthritis (CIA) was established to evaluate the effectiveness of AA treatment in vivo.

RESULTS

AA significantly reduced both viability and colony formation in cultured RA-FLS, while increasing the levels of reactive oxygen species (ROS), ferrous iron (Fe2+), malondialdehyde (MDA), and lactate dehydrogenase (LDH), as well as the expression of COX2. Furthermore, AA induced ferroptosis in RA-FLS by promoting Fe2+ accumulation through downregulation of the expression of Keap1 and FTH1 and upregulation of Nrf2 and HMOX1. In vivo, AA treatment was found to reduce toe swelling and the arthritis score in CIA rats, as well as relieve inflammation and ankle damage and significantly upregulate the expression of Nrf2 and HMOX1 in the synovial fluid.

CONCLUSION

Treatment with AA significantly reduced the viability of RA-FLS and triggered ferroptosis by promoting accumulation of Fe2+via the Nrf2-HMOX1 pathway, and was effective in relieving inflammation in CIA model rats. These findings suggest that the use of AA may be a promising strategy for the clinical treatment of RA.

Diagnostic and Therapeutic Roles of Extracellular Vesicles and Their Enwrapped ncRNAs in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory disease whose precise pathogenesis remains mysterious. The involvement of epigenetic regulation in the pathogenesis of RA is one of the most anticipated findings, among which non-coding RNAs (ncRNAs) hold great application promise as diagnostic and therapeutic biomarkers for RA. Extracellular vesicles (EVs) are a heterogeneous group of nano-sized, membrane-enclosed vesicles that mediate intercellular communication and substance exchange, especially the transfer of ncRNAs from donor cells, thereby regulating the functional activities and biological processes of recipient cells. In light of the significant correlation between EVs, ncRNAs, and RA, we first documented expression levels of EVs and their-encapsulated ncRNAs in RA individuals, and methodically discussed their-implicated signaling pathways and phenotypic changes. The last but not least, we paied special attention to the therapeutic benefits of gene therapy reagents specifically imitating or silencing candidate ncRNAs with exosomes as carriers on RA animal models, and briefly highlighted their clinical application advantage and foreground. In conclusion, the present review may be conducive to a deeper comprehension of the diagnostic and therapeutic roles of EVs-enwrapped ncRNAs in RA, with special emphasis on exosomal ncRNAs, which may offer hints for the monitoring and treatment of RA.

Exploration and validation of therapeutic molecules for rheumatoid arthritis based on ferroptosis-related genes

AIMS

This study aimed to identify hub ferroptosis-related genes (FRGs) and investigate potential therapy for RA based on FRGs.

MAIN METHODS

The differentially expressed FRGs in synovial tissue of RA patients were obtained from the dataset GSE12021 (GPL96). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were conducted to investigate the potential signaling pathways associated with FRGs. Hub genes were identified through topological analysis. The expression levels of these hub genes as well as their diagnostic accuracies were further evaluated. Connectivity Map (CMap) database was utilized to analyze the top 10 FRGs-guided potential drugs for RA. In vitro and in vivo experiments were carried out for further validation.

KEY FINDINGS

2 hub genes among 58 FRGs were identified (EGR1 and CDKN1A), and both were down regulated in RA synovial tissue. GPx4 expression was also decreased in the RA synovial tissue. The natural compound withaferin-a exhibited the highest negative CMap score. In-vitro and in-vivo experiments demonstrated anti-arthritic effects of withaferin-a.

SIGNIFICANCE

Ferroptosis participates in pathogenesis of RA, ferroptosis-related genes EGR1 and CDKN1A can be used as diagnostic and therapeutic targets for RA. Withaferin-a can be used as potential anti-arthritic treatment.

Sensory nerve regulation of bone homeostasis: Emerging therapeutic opportunities for bone-related diseases

Understanding the intricate interplay between sensory nerves and bone tissue cells is of paramount significance in the field of bone biology and clinical medicine. The regulatory role of sensory nerves in bone homeostasis offers a novel perspective for the development of targeted therapeutic interventions for a spectrum of bone-related diseases, including osteoarthritis, osteoporosis, and intervertebral disc degeneration. By elucidating the mechanisms through which sensory nerves and their neuropeptides influence the differentiation and function of bone tissue cells, this review aims to shed light on emerging therapeutic targets that harness the neuro-skeletal axis for the treatment and management of debilitating bone disorders. Moreover, a comprehensive understanding of sensory nerve-mediated bone regulation may pave the way for the development of innovative strategies to promote bone health and mitigate the burden of skeletal pathologies in clinical practice.

Ferroptosis in Arthritis: Driver of the Disease or Therapeutic Option?

Ferroptosis is a form of iron-dependent regulated cell death caused by the accumulation of lipid peroxides. In this review, we summarize research on the impact of ferroptosis on disease models and isolated cells in various types of arthritis. While most studies have focused on rheumatoid arthritis (RA) and osteoarthritis (OA), there is limited research on spondylarthritis and crystal arthropathies. The effects of inducing or inhibiting ferroptosis on the disease strongly depend on the studied cell type. In the search for new therapeutic targets, inhibiting ferroptosis in chondrocytes might have promising effects for any type of arthritis. On the other hand, ferroptosis induction may also lead to a desired decrease of synovial fibroblasts in RA. Thus, ferroptosis research must consider the cell-type-specific effects on arthritis. Further investigation is needed to clarify these complexities.

Iron metabolism and arthritis: Exploring connections and therapeutic avenues

ABSTRACT

Iron is indispensable for the viablility of nearly all living organisms, and it is imperative for cells, tissues, and organisms to acquire this essential metal sufficiently and maintain its metabolic stability for survival. Disruption of iron homeostasis can lead to the development of various diseases. There is a robust connection between iron metabolism and infection, immunity, inflammation, and aging, suggesting that disorders in iron metabolism may contribute to the pathogenesis of arthritis. Numerous studies have focused on the significant role of iron metabolism in the development of arthritis and its potential for targeted drug therapy. Targeting iron metabolism offers a promising approach for individualized treatment of arthritis. Therefore, this review aimed to investigate the mechanisms by which the body maintains iron metabolism and the impacts of iron and iron metabolism disorders on arthritis. Furthermore, this review aimed to identify potential therapeutic targets and active substances related to iron metabolism, which could provide promising research directions in this field.

Ferroptosis and endoplasmic reticulum stress in rheumatoid arthritis

Ferroptosis is an iron-dependent mode of cell death distinct from apoptosis and necrosis. Its mechanisms mainly involve disordered iron metabolism, lipid peroxide deposition, and an imbalance of the antioxidant system. The endoplasmic reticulum is an organelle responsible for protein folding, lipid metabolism, and Ca2+ regulation in cells. It can be induced to undergo endoplasmic reticulum stress in response to inflammation, oxidative stress, and hypoxia, thereby regulating intracellular environmental homeostasis through unfolded protein responses. It has been reported that ferroptosis and endoplasmic reticulum stress (ERS) have an interaction pathway and jointly regulate cell survival and death. Both have also been reported separately in rheumatoid arthritis (RA) mechanism studies. However, studies on the correlation between ferroptosis and ERS in RA have not been reported so far. Therefore, this paper reviews the current status of studies and the potential correlation between ferroptosis and ERS in RA, aiming to provide a research reference for developing treatments for RA.

3-methyladenine ameliorates acute lung injury by inhibiting oxidative damage and apoptosis

Background

Acute lung injury (ALI) is a condition characterized by inflammation and oxidative damage. 3-methyladenine (3-MA) has great potential for regulating apoptosis, but its regulatory role in ALI is unknown.

Methods

Lipopolysaccharide (LPS)-treated mice and tert-butyl hydroperoxide (TBHP)-treated bronchial epithelial cells were used to simulate in vivo and in vitro ALI models, respectively. In vivo, lung injury was assessed by histopathological analysis and lung injury scoring. The total cell count, protein content, and inflammatory factors in bronchoalveolar lavage fluid (BALF) were examined. The level of apoptosis in lung tissue was assessed through TUNEL staining. In the vitro ALI model, cell viability and levels of reactive oxygen species and apoptosis were assessed.

Results

3-MA pretreatment ameliorated lung injury, including intra-alveolar hemorrhage and inflammatory cell accumulation, both in vitro and in vivo. 3-MA pretreatment also decreased inflammatory factor levels in the BALF. 3-MA pretreatment alleviated oxidative damage, decreased reactive oxygen species levels, and attenuated morphological changes. TUNEL and Annexin V-FITC/PI staining revealed that pretreatment with 3-MA reduced the level of apoptosis. 3-MA pretreatment significantly decreased the expression of caspase-3 and Bax but increased the expression of Bcl-2 in ALI. Mechanistically, 3-MA pretreatment also affected the PKCα/NOX4 and Nrf2 pathways, which decreased the level of apoptosis in ALI.

Conclusions

3-MA pretreatment inhibited inflammation and oxidative damage in ALI and inhibited apoptosis to mitigate ALI in part by inhibiting the PKCα/NOX4 pathway and activating the Nrf2 pathway. Based on these results, 3-MA might be a viable medication to treat with ALI.

Advances in research on immunocyte iron metabolism, ferroptosis, and their regulatory roles in autoimmune and autoinflammatory diseases

Autoimmune diseases commonly affect various systems, but their etiology and pathogenesis remain unclear. Currently, increasing research has highlighted the role of ferroptosis in immune regulation, with immune cells being a crucial component of the body's immune system. This review provides an overview and discusses the relationship between ferroptosis, programmed cell death in immune cells, and autoimmune diseases. Additionally, it summarizes the role of various key targets of ferroptosis, such as GPX4 and TFR, in immune cell immune responses. Furthermore, the release of multiple molecules, including damage-associated molecular patterns (DAMPs), following cell death by ferroptosis, is examined, as these molecules further influence the differentiation and function of immune cells, thereby affecting the occurrence and progression of autoimmune diseases. Moreover, immune cells secrete immune factors or their metabolites, which also impact the occurrence of ferroptosis in target organs and tissues involved in autoimmune diseases. Iron chelators, chloroquine and its derivatives, antioxidants, chloroquine derivatives, and calreticulin have been demonstrated to be effective in animal studies for certain autoimmune diseases, exerting anti-inflammatory and immunomodulatory effects. Finally, a brief summary and future perspectives on the research of autoimmune diseases are provided, aiming to guide disease treatment strategies.

Scavenger Receptor Class B Type I Deficiency Induces Iron Overload and Ferroptosis in Renal Tubular Epithelial Cells via Hypoxia-Inducible Factor-1α/Transferrin Receptor 1 Signaling Pathway

Aims: Scavenger receptor class B type I (SRBI) promotes cell cholesterol efflux and the clearance of plasma cholesterol. Thus, SRBI deficiency causes abnormal cholesterol metabolism and hyperlipidemia. Studies have suggested that ferroptosis is involved in lipotoxicity; however, whether SRBI deficiency could induce ferroptosis remains to be investigated. Results: We knocked down or knocked out SRBI in renal HK-2 cells and C57BL/6 mice to determine the expression levels of ferroptosis-related regulators. Our results demonstrated that SRBI deficiency upregulates transferrin receptor 1 (TFR1) expression and downregulates ferroportin expression, which induces iron overload and subsequent ferroptosis in renal tubular epithelial cells. TFR1 is known to be regulated by hypoxia-inducible factor-1α (HIF-1α). Next, we investigated whether SRBI deletion affected HIF-1α. SRBI deletion upregulated the mRNA and protein expression of HIF-1α, and promoted its translocation to the nucleus. To determine whether HIF-1α plays a key role in SRBI-deficiency-induced ferroptosis, we used HIF-1α inhibitor and siHIF-1α in HK-2 cells, and found that downregulation of HIF-1α prevented SRBI-silencing-induced TFR1 upregulation and iron overload, and eventually reduced ferroptosis. The underlying mechanism of HIF-1α activation was explored next, and the results showed that SRBI knockout or knockdown may upregulate the expression of HIF-1α, and promote HIF-1α translocation from the cytoplasm into the nucleus via the PKC-β/NF-κB signaling pathway. Innovation and Conclusion: Our study showed, for the first time, that SRBI deficiency induces iron overload and subsequent ferroptosis via the HIF-1α/TFR1 pathway.

α-Ketoglutarate alleviates osteoarthritis by inhibiting ferroptosis via the ETV4/SLC7A11/GPX4 signaling pathway

Osteoarthritis (OA) is the most common degenerative joint disorder that causes disability in aged individuals, caused by functional and structural alterations of the knee joint. To investigate whether metabolic drivers might be harnessed to promote cartilage repair, a liquid chromatography-mass spectrometry (LC-MS) untargeted metabolomics approach was carried out to screen serum biomarkers in osteoarthritic rats. Based on the correlation analyses, α-ketoglutarate (α-KG) has been demonstrated to have antioxidant and anti-inflammatory properties in various diseases. These properties make α-KG a prime candidate for further investigation of OA. Experimental results indicate that α-KG significantly inhibited H2O2-induced cartilage cell matrix degradation and apoptosis, reduced levels of reactive oxygen species (ROS) and malondialdehyde (MDA), increased superoxide dismutase (SOD) and glutathione (GSH)/glutathione disulfide (GSSG) levels, and upregulated the expression of ETV4, SLC7A11 and GPX4. Further mechanistic studies observed that α-KG, like Ferrostatin-1 (Fer-1), effectively alleviated Erastin-induced apoptosis and ECM degradation. α-KG and Fer-1 upregulated ETV4, SLC7A11, and GPX4 at the mRNA and protein levels, decreased ferrous ion (Fe2+) accumulation, and preserved mitochondrial membrane potential (MMP) in ATDC5 cells. In vivo, α-KG treatment inhibited ferroptosis in OA rats by activating the ETV4/SLC7A11/GPX4 pathway. Thus, these findings indicate that α-KG inhibits ferroptosis via the ETV4/SLC7A11/GPX4 signaling pathway, thereby alleviating OA. These observations suggest that α-KG exhibits potential therapeutic properties for the treatment and prevention of OA, thereby having potential clinical applications in the future.

Ferroptosis: principles and significance in health and disease

Ferroptosis, an iron-dependent form of cell death characterized by uncontrolled lipid peroxidation, is governed by molecular networks involving diverse molecules and organelles. Since its recognition as a non-apoptotic cell death pathway in 2012, ferroptosis has emerged as a crucial mechanism in numerous physiological and pathological contexts, leading to significant therapeutic advancements across a wide range of diseases. This review summarizes the fundamental molecular mechanisms and regulatory pathways underlying ferroptosis, including both GPX4-dependent and -independent antioxidant mechanisms. Additionally, we examine the involvement of ferroptosis in various pathological conditions, including cancer, neurodegenerative diseases, sepsis, ischemia-reperfusion injury, autoimmune disorders, and metabolic disorders. Specifically, we explore the role of ferroptosis in response to chemotherapy, radiotherapy, immunotherapy, nanotherapy, and targeted therapy. Furthermore, we discuss pharmacological strategies for modulating ferroptosis and potential biomarkers for monitoring this process. Lastly, we elucidate the interplay between ferroptosis and other forms of regulated cell death. Such insights hold promise for advancing our understanding of ferroptosis in the context of human health and disease.

Efferocytosis: Unveiling its potential in autoimmune disease and treatment strategies

Efferocytosis is a crucial process whereby phagocytes engulf and eliminate apoptotic cells (ACs). This intricate process can be categorized into four steps: (1) ACs release "find me" signals to attract phagocytes, (2) phagocytosis is directed by "eat me" signals emitted by ACs, (3) phagocytes engulf and internalize ACs, and (4) degradation of ACs occurs. Maintaining immune homeostasis heavily relies on the efficient clearance of ACs, which eliminates self-antigens and facilitates the generation of anti-inflammatory and immunosuppressive signals that maintain immune tolerance. However, any disruptions occurring at any of the efferocytosis steps during apoptosis can lead to a diminished efficacy in removing apoptotic cells. Factors contributing to this inefficiency encompass dysregulation in the release and recognition of "find me" or "eat me" signals, defects in phagocyte surface receptors, bridging molecules, and other signaling pathways. The inadequate clearance of ACs can result in their rupture and subsequent release of self-antigens, thereby promoting immune responses and precipitating the onset of autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes, and multiple sclerosis. A comprehensive understanding of the efferocytosis process and its implications can provide valuable insights for developing novel therapeutic strategies that target this process to prevent or treat autoimmune diseases.

Comprehensive analysis and prediction model of mitophagy and ferroptosis in primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is linked to specific pathogenic mechanisms, yet its relationship with mitophagy and ferroptosis is poorly understood. This study aimed to identify new biomarkers and explore the role of mitophagy and ferroptosis in ITP pathogenesis. Techniques such as differential analysis, Mfuzz expression pattern clustering, machine learning, gene set enrichment analysis, single-cell RNA sequencing (scRNA-seq) and immune infiltration analysis were employed to investigate the molecular pathways of pivotal genes. Two-sample Mendelian randomization (TSMR) assessed the causal effects in ITP. Key genes identified in the training set included GABARAPL1, S100A8, LIN28A, and GDF9, which demonstrated diagnostic potential in validation sets. Functional analysis indicated these genes' involvement in ubiquitin phosphorylation, PPAR signalling pathway and T-cell differentiation. Immune infiltration analysis revealed increased macrophage presence in ITP, related to the critical genes. scRNA-seq indicated reduced GABARAPL1 expression in ITP bone marrow macrophages. TSMR linked S100A8 with ITP diagnosis, presenting an OR of 0.856 (95% CI = 0.736-0.997, p = 0.045). The study pinpointed four central genes, GABARAPL1, S100A8, LIN28A, and GDF9, tied to mitophagy and ferroptosis in ITP. It posits that diminished GABARAPL1 expression may disrupts ubiquitin phosphorylation and PPAR signalling, impairing mitophagy and inhibiting ferroptosis, leading to immune imbalance.

Transcriptome analysis reveals PRKCA as a potential therapeutic target for overcoming cisplatin resistance in lung cancer through ferroptosis

Cisplatin-based chemotherapy is the current standard care for lung cancer patients; however, drug resistance frequently develops during treatment, thereby limiting therapeutic efficacy.The molecular mechanisms underlying cisplatin resistance remain elusive. In this study, we conducted an analysis of microarray data from the Gene Expression Omnibus (GEO) database under the accession numbers GSE21656, which encompassed expression profiling of cisplatin-resistant H460 (DDP-H460)and the parental cells (H460). Subsequently, we calculated the differentially expressed genes (DEGs) between DDP-H460 and H460. Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of DEGs demonstrated significant impact on the Rap1, PI3K/AKT and MAPK signaling pathways. Moreover, protein and protein interaction (PPI) network analysis identified PRKCA, DET1, and UBE2N as hub genes that potentially contribute predominantly to cisplatin resistance. Ultimately, PRKCA was selected for validation due to its significant prognostic effect, which predicts unfavorable overall survival and disease-free survival in patients with lung cancer. Network analysis conducted on The Cancer Genome Atlas (TCGA) database revealed a strong gene-level correlation between PRKCA and TP53, CDKN2A, BYR2, TTN, KRAS, and PIK3CA; whereas at the protein level, it exhibited a high correlation with EGFR, Lck, Bcl2, and Syk. The in vitro experiments revealed that PRKCA was upregulated in the cisplatin-resistant A549 cells (DDP-A549), while knockdown of PRKCA increased DDP-A549 apoptosis upon cisplatin treatment. Moreover, we observed that PRKCA knockdown attenuated DDP-A549 proliferation, migration and invasion ability. Western blot analysis demonstrated that PRKCA knockdown downregulated phosphorylation of PI3K expression while upregulated the genes involved in ferroptosis signaling. In summary, our results elucidate the role of PRKCA in acquiring resistance to cisplatin and underscore its potential as a therapeutic target for cisplatin-resistant lung cancer.

TRPM7 facilitates fibroblast-like synoviocyte proliferation, metastasis and inflammation through increasing IL-6 stability via the PKCα-HuR axis in rheumatoid arthritis

Transient receptor potential melastatin 7 (TRPM7) is a cation channel that plays a role in the progression of rheumatoid arthritis (RA), yet its involvement in synovial hyperplasia and inflammation has not been determined. We previously reported that TRPM7 affects the destruction of articular cartilage in RA. Herein, we further confirmed the involvement of TRPM7 in fibroblast-like synoviocyte (FLS) proliferation, metastasis and inflammation. We observed increased TRPM7 expression in FLSs derived from human RA patients. Pharmacological inhibition of TRPM7 protected primary RA-FLSs from proliferation, metastasis and inflammation. Furthermore, we found that TRPM7 contributes to RA-FLS proliferation, metastasis and inflammation by increasing the intracellular Ca2+ concentration. Mechanistically, the PKCα-HuR axis was demonstrated to respond to Ca2+ influx, leading to TRPM7-mediated RA-FLS proliferation, metastasis and inflammation. Moreover, HuR was shown to bind to IL-6 mRNA after nuclear translocation, which could be weakened by TRPM7 channel inhibition. Additionally, adeno-associated virus 9-mediated TRPM7 silencing is highly effective at alleviating synovial hyperplasia and inflammation in adjuvant-induced arthritis rats. In conclusion, our findings unveil a novel regulatory mechanism involved in the pathogenesis of RA and suggest that targeting TRPM7 might be a potential strategy for the prevention and treatment of RA.

Advances in exosome modulation of ferroptosis for the treatment of orthopedic diseases

Current treatments for orthopaedic illnesses frequently result in poor prognosis, treatment failure, numerous relapses, and other unpleasant outcomes that have a significant impact on patients' quality of life. Cell-free therapy has emerged as one of the most promising options in recent decades for improving the status quo. As a result, using exosomes produced from various cells to modulate ferroptosis has been proposed as a therapeutic method for the condition. Exosomes are extracellular vesicles that secrete various bioactive chemicals that influence disease treatment and play a role in the genesis and progression of orthopaedic illnesses. Ferroptosis is a recently defined kind of controlled cell death typified by large iron ion buildup and lipid peroxidation. An increasing number of studies indicate that ferroptosis plays a significant role in orthopaedic illnesses. Exosomes, as intercellular information transfer channels, have been found to play a significant role in the regulation of ferroptosis processes. Furthermore, accumulating research suggests that exosomes can influence the course of many diseases by regulating ferroptosis in injured cells. In order to better understand the processes by which exosomes govern ferroptosis in the therapy of orthopaedic illnesses. This review discusses the biogenesis, secretion, and uptake of exosomes, as well as the mechanisms of ferroptosis and exosomes in the therapy of orthopaedic illnesses. It focuses on recent research advances and exosome mechanisms in regulating iron death for the therapy of orthopaedic illnesses. The present state of review conducted both domestically and internationally is elucidated and anticipated as a viable avenue for future therapy in the field of orthopaedics.

Roles of TRP and PIEZO receptors in autoimmune diseases

Autoimmune diseases are pathological autoimmune reactions in the body caused by various factors, which can lead to tissue damage and organ dysfunction. They can be divided into organ-specific and systemic autoimmune diseases. These diseases usually involve various body systems, including the blood, muscles, bones, joints and soft tissues. The transient receptor potential (TRP) and PIEZO receptors, which resulted in David Julius and Ardem Patapoutian winning the Nobel Prize in Physiology or Medicine in 2021, attracted people's attention. Most current studies on TRP and PIEZO receptors in autoimmune diseases have been carried out on animal model, only few clinical studies have been conducted. Therefore, this study aimed to review existing studies on TRP and PIEZO to understand the roles of these receptors in autoimmune diseases, which may help elucidate novel treatment strategies.

The molecular mechanisms and potential drug targets of ferroptosis in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI), caused by the initial interruption and subsequent restoration of coronary artery blood, results in further damage to cardiac function, affecting the prognosis of patients with acute myocardial infarction. Ferroptosis is an iron-dependent, superoxide-driven, non-apoptotic form of regulated cell death that is involved in the pathogenesis of MIRI. Ferroptosis is characterized by the accumulation of lipid peroxides (LOOH) and redox disequilibrium. Free iron ions can induce lipid oxidative stress as a substrate of the Fenton reaction and lipoxygenase (LOX) and participate in the inactivation of a variety of lipid antioxidants including CoQ10 and GPX4, destroying the redox balance and causing cell death. The metabolism of amino acid, iron, and lipids, including associated pathways, is considered as a specific hallmark of ferroptosis. This review systematically summarizes the latest research progress on the mechanisms of ferroptosis and discusses and analyzes the therapeutic approaches targeting ferroptosis to alleviate MIRI.

Membrane Dynamics and Cation Handling in Ferroptosis

Ferroptosis, a regulated cell death hallmarked by excessive lipid peroxidation, is implicated in various (patho)physiological contexts. During ferroptosis, lipid peroxidation leads to a diverse change in membrane properties and the dysregulation of ion homeostasis via the cation channels, ultimately resulting in plasma membrane rupture. This review illuminates cellular membrane dynamics and cation handling in ferroptosis regulation.

Alleviated NCOA4-mediated ferritinophagy protected RA FLSs from ferroptosis in lipopolysaccharide-induced inflammation under hypoxia

OBJECTIVE

Ferroptosis is a reactive oxygen species (ROS)- and iron-dependent form of non-apoptotic cell death process. Previous studies have demonstrated that ferroptosis participates in the development of inflammatory arthritis. However, the role of ferroptosis in rheumatoid arthritis (RA) inflammatory hypoxic joints remains unclear. This study sought to explore the underlying mechanism of ferroptosis on lipopolysaccharide (LPS)-induced RA fibroblast-like synoviocytes (FLSs).

METHODS

FLSs, isolated from patients with RA, were treated with LPS and ferroptosis inducer (erastin and RSL-3), and ferroptosis inhibitor (Fer-1 and DFO), respectively. The cell viability was measured by CCK-8. The cell death was detected by flow cytometer. The proteins level were tested by Western blot. The cytosolic ROS and lipid peroxidation were determined using DCFH-DA and C11-BODIPY581/591 fluorescence probes, respectively. The small interfering RNA (siRNA) was used to knock down related proteins. The levels of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), iron, inflammatory cytokines (IL6 and IL8), and LDH were analyzed by commercial kits.

RESULTS

Ferroptosis was activated by LPS in RA FLS with increased cellular damage, ROS and lipid peroxidation, intracellular Fe and IL8, which can be further amplified by ferroptosis inducer (erastin and RSL-3) and inhibited by ferroptosis inhibitor (Fer-1 and DFO). Mechanistically, LPS triggered ferroptosis via NCOA4-mediated ferritinophagy in RA FLSs, and knockdown of NCOA4 strikingly prevent the process of ferroptosis. Intriguingly, LPS-induced RA FLSs became insensitive to ferroptosis and NCOA4-mediated ferritinophagy under hypoxia compared with normoxia. Knockdown of HIF-1α reverted ferroptosis and ferritinophagy evoking by LPS-induced RA FLSs inflammation under hypoxia. In addition, low dose of auranofin (AUR) induced re-sensitization of ferroptosis and ferritinophagy through inhibiting the expression of HIF-1α under hypoxia.

CONCLUSIONS

NCOA4-mediated ferritinophagy was a key driver of ferroptosis in inflammatory RA FLSs. The suppression of NCOA4-mediated ferritinophagy protected RA FLSs from ferroptosis in LPS-induced inflammation under hypoxia. Targeting HIF-1α/NCOA4 and ferroptosis could be an effective and valuable therapeutic strategy for synovium hyperplasia in the patients with RA.