Ferroptosis of CD163+ tissue-infiltrating macrophages and CD10+ PC+ epithelial cells in lupus nephritis

Disrupting the immune homeostasis: the emerging role of macrophage ferroptosis in autoimmune diseases

Autoimmune diseases are a class of chronic disorders characterized by the aberrant activation of the immune system, where macrophages play a central role in regulating immune responses during disease onset and progression. Ferroptosis, a form of iron-dependent programmed cell death, has recently attracted significant interest due to its involvement in various pathological conditions. In macrophages, ferroptosis not only compromises cell viability but also disrupts immune homeostasis by promoting pro-inflammatory responses and suppressing anti-inflammatory pathways, thereby intensifying inflammation and exacerbating disease severity. While substantial progress has been made in elucidating macrophage ferroptosis in atherosclerosis and oncology, its precise mechanistic role in autoimmune diseases remains largely unexplored. This review systematically summarizes the molecular mechanisms of macrophage ferroptosis and its regulatory effects on immune homeostasis, with particular emphasis on its role in autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD), multiple sclerosis (MS), and systemic sclerosis (SSc). Furthermore, we discuss potential therapeutic targets related to macrophage ferroptosis in these conditions. By integrating current knowledge, this review aims to provide a theoretical framework and novel perspectives for developing innovative therapeutic strategies targeting autoimmune diseases.

The CD163 + tissue-infiltrating macrophages regulate ferroptosis in thyroid-associated ophthalmopathy orbital fibroblasts via the TGF-β/Smad2/3 signaling pathway

BACKGROUND

Thyroid-associated ophthalmopathy (TAO) is a thyroid function-related, organ-specific autoimmune disease that primarily leads to specific reactive changes and tissue remodeling in the periocular region. The exact pathogenesis of TAO remains unclear.

METHODS

High-throughput gene expression datasets related to TAO were comprehensively retrieved from the Gene Expression Omnibus (GEO) database, selecting GSE174139 and GSE158464 for analysis. Differentially expressed genes (DEGs) between TAO patients and healthy controls were identified, and ferroptosis-related genes (FRGs) were obtained from the FerrDb database. The intersection of DEGs and FRGs yielded ferroptosis-related genes associated with TAO.The transcriptional expression of FRGs was validated using real-time quantitative polymerase chain reaction (RT-qPCR) on orbital adipose tissue samples from TAO patients and healthy controls. Single-cell sequencing of six human tissue samples further analyzed changes in cellular subpopulations within the TAO microenvironment.Additionally, a co-culture model of CD163 + macrophages and TAO orbital fibroblasts, along with an in vitro TGF-β1-induced orbital fibroblast (OF) model, was constructed to validate the role of the TGF-β1/SMAD2/3 axis in ferroptosis regulation. Finally, potential clinical drugs targeting CD163 + macrophages with high ferroptosis activity in TAO were predicted using the Random Walk with Restart (RWR) algorithm combined with the DGIdb database.

RESULTS

We first utilized TAO-related datasets from the GEO database, combined with the FerrDb ferroptosis database, to identify changes in iron metabolism genes during TAO progression through differential expression analysis, screening 7 key ferroptosis-related proteins. In vitro validation revealed that all but AOPQ and LGMN, which were upregulated, exhibited downregulated expression.Single-cell sequencing of orbital connective tissue from 4 TAO patients and 2 healthy controls identified 16,364 cells spanning 18 cell types. Analysis of the 7 key ferroptosis-related proteins revealed that fibroblasts and macrophages displayed elevated ferroptosis signaling during TAO progression. Subcluster analysis of macrophages identified 4 distinct subpopulations, with the C2 subpopulation-characterized by high expression of CD163 and CCL18-exhibiting prominent ferroptosis activation signals.Further validation using clinical tissue samples, a co-culture model of CD163 + macrophages and TAO orbital fibroblasts, and an in vitro TGF-β1-induced orbital fibroblast (OF) model confirmed aberrant activation of the TGF-β1/SMAD2/3 pathway as a key regulator of ferroptosis. Hub gene analysis of C2 subpopulation marker genes, combined with the DGIdb database, predicted potential clinical drugs targeting the C2 macrophages.

CONCLUSION

This study, integrating single-cell RNA-Seq and bulk transcriptome analysis, revealed the involvement of CD163 + tissue-infiltrating macrophages in regulating ferroptosis of orbital fibroblasts during TAO progression and identified therapeutic candidates targeting macrophage ferroptosis signaling in TAO. Furthermore, in vitro experiments demonstrated that activation of the TGF-β1/SMAD2/3 axis promotes ferroptosis in TAO orbital fibroblasts, highlighting a novel pathway for potential therapeutic intervention.

Ferroptosis contributes to immunosuppression

As a novel form of cell death, ferroptosis is mainly regulated by the accumulation of soluble iron ions in the cytoplasm and the production of lipid peroxides and is closely associated with several diseases, including acute kidney injury, ischemic reperfusion injury, neurodegenerative diseases, and cancer. The term "immunosuppression" refers to various factors that can directly harm immune cells' structure and function and affect the synthesis, release, and biological activity of immune molecules, leading to the insufficient response of the immune system to antigen production, failure to successfully resist the invasion of foreign pathogens, and even organ damage and metabolic disorders. An immunosuppressive phase commonly occurs in the progression of many ferroptosis-related diseases, and ferroptosis can directly inhibit immune cell function. However, the relationship between ferroptosis and immunosuppression has not yet been published due to their complicated interactions in various diseases. Therefore, this review deeply discusses the contribution of ferroptosis to immunosuppression in specific cases. In addition to offering new therapeutic targets for ferroptosis-related diseases, the findings will help clarify the issues on how ferroptosis contributes to immunosuppression.

HMGA1 influence on iron-induced cell death in Tfh cells of SLE patients

The autoimmune disorder known as Systemic Lupus Erythematosus (SLE) exhibits intricate features with abnormal immune responses leading to tissue injury. The generation of antibodies and the disruption of immune regulation heavily depend on the pivotal function of T follicular helper (Tfh) cells. Iron dysregulation is significant in autoimmune diseases, impacting immune cell function and disease progression. Our study investigates the role of the HMGA1/EZH2/STAT3/GPX4 axis in modulating Tfh cells and iron homeostasis in SLE. Abnormal Tfh cell populations in SLE patients demonstrate reduced susceptibility to iron-induced cell death, with HMGA1 identified as a key player in Tfh cell proliferation and sensitivity to iron-induced death. Experimental interventions reveal the inhibitory role of the HMGA1 axis in Tfh cells' susceptibility to iron-induced death, suggesting therapeutic avenues for SLE and related autoimmune disorders. Our study underscores the importance of iron homeostasis in autoimmune conditions, providing novel insights and treatment strategies for further research in this field.

Research advancements in the association between prevalent trace metals and connective tissue diseases

Connective tissue diseases (CTD) encompass a spectrum of autoimmune disorders, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS), inflammatory myopathy (IIM), systemic sclerosis (SSc), among others. Recent research has highlighted the significant role of trace metals in the pathogenesis of connective tissue diseases. This article provides an overview of recent advancements in understanding the correlation between common trace metals such as iron, copper, zinc and CTD, aiming to offer novel insights for the diagnosis and treatment of these conditions. Iron is implicated in the pathogenesis of SLE through various mechanisms, including alterations in serum iron concentration, disturbances in iron metabolism and homeostasis, as well as involvement in ferroptosis. Disorders affecting iron metabolism, ferroptosis, and the expression and regulation of associated genes and proteins contribute to the development and progression of RA. Elevated serum copper levels are observed in patients with both SLE and RA compared to healthy controls. Cuproptosis, a novel form of cell death, is also considered to be linked to their pathogenesis. Decreased serum zinc concentration is evident in patients with SLE, RA, and SS. Zinc finger proteins play a crucial role in the pathogenesis of these diseases.

Immune imbalance in Lupus Nephritis: The intersection of T-Cell and ferroptosis

Ferroptosis is a novel form of cell death characterized by unlimited accumulation of iron-dependent lipid peroxides. It is often accompanied by disease, and the relationship between ferroptosis of immune cells and immune regulation has been attracting increasing attention. Initially, it was found in cancer research that the inhibition of regulatory T cell (Treg) ferroptosis and the promotion of CD8+ T cell ferroptosis jointly promoted the formation of an immune-tolerant environment in tumors. T-cell ferroptosis has subsequently been found to have immunoregulatory effects in other diseases. As an autoimmune disease characterized by immune imbalance, T-cell ferroptosis has attracted attention for its potential in regulating immune balance in lupus nephritis. This article reviews the metabolic processes within different T-cell subsets in lupus nephritis (LN), including T follicular helper (TFH) cells, T helper (Th)17 cells, Th1 cells, Th2 cells, and Treg cells, and reveals that these cellular metabolisms not only facilitate the formation of a T-cell immune imbalance but are also closely associated with the occurrence of ferroptosis. Consequently, we hypothesize that targeting the metabolic pathways of ferroptosis could become a novel research direction for effectively treating the immune imbalance in lupus nephritis by altering T-cell differentiation and the incidence of ferroptosis.

OTUB1 regulation of ferroptosis and the protective role of ferrostatin-1 in lupus nephritis

Lupus nephritis (LN) is a prevalent and severe manifestation of systemic lupus erythematosus (SLE), leading to significant morbidity and mortality. OTUB1, a deubiquitinating enzyme, has emerged as a potential therapeutic target due to its role in cellular protection and regulation of ferroptosis, a form of cell death linked to LN. Our study revealed significantly reduced OTUB1 expression in the glomeruli of LN patients and podocytes, correlated with disease severity. CRISPR/Cas9-mediated OTUB1 knockout in podocytes resulted in pronounced injury, indicated by decreased levels of nephrin and podocin. Ferrostatin-1 treatment effectively mitigated this injury, restoring SLC7A11 expression and significantly reducing MDA levels, Fe2+ levels, BODIPY C11 expression, and normalized cysteine and glutathione expression. In the MRL/lpr mouse model, Ferrostatin-1 significantly improved renal function decreased proteinuria, and ameliorated renal histopathological changes, including reduced glomerular endothelial swelling, mesangial cell proliferation, and leukocyte infiltration. These results underscore the protective role of Ferrostatin-1 in modulating the pathogenesis of LN. OTUB1 plays a crucial protective role against podocyte injury in LN by regulating ferroptosis. Ferrostatin-1 effectively mitigates podocyte damage induced by OTUB1 deficiency, suggesting that targeting ferroptosis could be a promising therapeutic strategy for LN.

Clinical significance of serum soluble scavenger receptor CD163 in patients with lupus nephritis

BACKGROUND

The soluble CD163 (sCD163) was elevated in systemic lupus erythematosus (SLE) patients.

PURPOSE

To study whether serum sCD163 could be used to predict the occurrence and prognosis of lupus nephritis (LN).

RESEARCH DESIGN

The recruited patients were classified into different groups according to standard identification criteria.

STUDY SAMPLE

The patients with LN.

DATA COLLECTION AND ANALYSIS

11 indices were analyzed and compared in SLE and LN patients. Furthermore, the level of serum sCD163 was detected using an enzyme-linked immunosorbent assay. Meanwhile, the receiver operating characteristic analysis was performed to evaluate the prediction effect of sCD163. Additionally, spearman correlation analysis of serum sCD163 with indices was conducted.

RESULTS

There were six positive indices and one negative risk factor correlated to LN. sCD163 was elevated in LN patients and could be used to diagnose LN. Importantly, sCD163 was increased in LN patients with a heavy SLE disease activity index. Finally, it was revealed that the level of sCD163 was higher in the LN patients with no response than that with complete or partial response, which also could predict the prognosis of LN.

CONCLUSIONS

Serum sCD163 was elevated in LN patients than in SLE patients, which could be used to predict the occurrence and prognosis of LN.

Inhibition of GRK2 ameliorates the pristane-induced mouse SLE model by suppressing plasma cells differentiation

Systemic lupus erythematosus (SLE) is a multifaceted autoimmune disorder characterized by diverse clinical manifestations and organ damage. Despite its elusive etiology, dysregulated subsets and functions of B cells are pivotal in SLE pathogenesis. Peoniflorin-6'-O-benzene sulfonate (CP-25), an esterification modification of Paeoniflorin, exhibits potent anti-inflammatory and immunomodulatory properties in autoimmune diseases (AID). However, the involvement of CP-25 and its target, GRK2, in SLE development has not been explored. In this study, we demonstrate that both genetic deficiency and pharmacological inhibition of GRK2 attenuate autoantibodies production, reduce systemic inflammation, and mitigate histopathological alterations in the spleen and kidney in the pristane-induced mouse SLE model. Importantly, our findings highlight that both genetic deficiency and pharmacological inhibition of GRK2 suppress plasma cells generation and restore dysregulated B-cell subsets by modulating two crucial transcription factors, Blimp1 and IRF4. Collectively, targeting GRK2 with CP-25 emerges as a promising therapeutic approach for SLE.

Promising roles of combined therapy based on immune response and iron metabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an intricate autoimmune disease with diverse manifestations. Immunometabolism reprogramming contributes to the progression of SLE by regulating the phenotype and function of immune cells. Dysregulated iron metabolism is implicated in SLE pathogenesis, affecting both systemic and immune cell-specific iron homeostasis. This review explores the systemic and cellular iron handling and regulation. Additionally, the advancements regarding iron metabolism in SLE with a focus on the distinct subsets of immune cells are highlighted. By gaining insight into the interplay between iron dysregulation and immune dysfunction, the potential therapeutic avenues may be unveiled. However, challenges remain in elucidating cell-specific iron metabolic reprogramming and its contribution to SLE pathogenesis needs further research for personalized therapeutic interventions and biomarker discovery. This review provides an in-depth understanding of immune cell-specific regulatory mechanisms of iron metabolism and new insights in current challenges as well as possible clinical applications.

Molecular and therapeutic landscape of ferroptosis in skin diseases

ABSTRACT

Regulated cell death (RCD) is a critical physiological process essential in maintaining skin homeostasis. Among the various forms of RCD, ferroptosis stands out due to its distinct features of iron accumulation, lipid peroxidation, and involvement of various inhibitory antioxidant systems. In recent years, an expanding body of research has solidly linked ferroptosis to the emergence of skin disorders. Therefore, understanding the mechanisms underlying ferroptosis in skin diseases is crucial for advancing therapy and prevention strategies. This review commences with a succinct elucidation of the mechanisms that underpin ferroptosis, embarks on a thorough exploration of ferroptosis's role across a spectrum of skin conditions, encompassing melanoma, psoriasis, systemic lupus erythematosus (SLE), vitiligo, and dermatological ailments precipitated by ultraviolet (UV) exposure, and scrutinizes the potential therapeutic benefits of pharmacological interventions aimed at modulating ferroptosis for the amelioration of skin diseases.

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.

Functional consequence of Iron dyshomeostasis and ferroptosis in systemic lupus erythematosus and lupus nephritis

Systemic lupus erythematosus (SLE) and its renal manifestation Lupus nephritis (LN) are characterized by a dysregulated immune system, autoantibodies, and injury to the renal parenchyma. Iron accumulation and ferroptosis in the immune effectors and renal tubules are recently identified pathological features in SLE and LN. Ferroptosis is an iron dependent non-apoptotic form of regulated cell death and ferroptosis inhibitors have improved disease outcomes in murine models of SLE, identifying it as a novel druggable target. In this review, we discuss novel mechanisms by which iron accumulation and ferroptosis perpetuate immune cell mediated pathology in SLE/LN. We highlight intra-renal dysregulation of iron metabolism and ferroptosis as an underlying pathogenic mechanism of renal tubular injury. The basic concepts of iron biology and ferroptosis are also discussed to expose the links between iron, cell metabolism and ferroptosis, that identify intracellular pro-ferroptotic enzymes and their protein conjugates as potential targets to improve SLE/LN outcomes.