Immunometabolic Pathways and Its Therapeutic Implication in Autoimmune Diseases

Mechanism of Jinteng Qingbi granules in the treatment of rheumatoid arthritis using metabolomics analysis

This study investigated the differential metabolites after rheumatoid arthritis (RA) rats were treated with Jinteng Qingbi granules. Collagen-induced arthritis rats were divided into three groups, namely normal group, model group, and Jinteng Qingbi granules group. Serum compounds were identified, annotated, and classified using metabolomics to explain the physicochemical properties and biological functions. The metabolites were screened using univariate and multivariate statistical analyses. There were differences in serum metabolites between RA and normal rats; Jinteng Qingbi granules improved RA and recovered the metabolite levels to normal. Compared to the normal group, 51 differential ions were screened, and 108 ions were changed in the Jinteng Qingbi granules group compared to the RA model. Eight metabolites were upregulated in the RA model group compared to the normal group, whereas 10 metabolites were downregulated. Treatment with Jinteng Qingbi granules increased the levels of 12 metabolites such as cinnamate and decreased the levels of 16 metabolites such as allamandin in the RA model. Differential ion enrichment was mainly related to the histidine metabolic pathway in amino acid metabolism. Jinteng Qingbi granules resulted in improvements in the RA model, which were mainly associated with lipids and lipid-like molecules, organic acids, and derivatives, providing a new possibility and basis for screening biomarkers for the diagnosis and treatment of RA.

Glycolysis, a driving force of rheumatoid arthritis

Resident synoviocytes and synovial microvasculature, together with immune cells from circulation, contribute to pannus formation, the main pathological feature of rheumatoid arthritis (RA), leading to destruction of adjacent cartilage and bone. Seeds, fibroblast-like synoviocytes (FLSs), macrophages, dendritic cells (DCs), B cells, T cells and endothelial cells (ECs) seeds with high metabolic demands undergo metabolic reprogramming from oxidative phosphorylation to glycolysis in response to poor soil of RA synovium with hypoxia, nutrient deficiency and inflammatory stimuli. Glycolysis provides rapid energy supply and biosynthetic precursors to support pathogenic growth of these seeds. The metabolite lactate accumulated during this process in turn condition the soil microenvironment and affect seeds growth by modulating signalling pathways and directing lactylation modifications. This review explores in depth the survival mechanism of seeds with high metabolic demands in the poor soil of RA synovium, providing useful support for elucidating the etiology of RA. In addition, we discuss the role and major post-translational modifications of proteins and enzymes linked to glycolysis to inspire the discovery of novel anti-rheumatic targets.

A new look at angiogenesis inhibition of geniposide in experimental arthritis by blocking angiopoietin-2 exocytosis

Angiogenesis is a key player in the pathogenesis of rheumatoid arthritis. Exocytosis from Weibel-Palade bodies is a prerequisite for angiopoietin-2 (Ang-2) to activate endothelial cells and initiate angiogenesis. Geniposide (GE) was previously reported to exert anti-angiogenic effects. The aim of this study was to shed light on whether and how GE regulates Ang-2 exocytosis. A rat model of adjuvant arthritis (AA) was established to evaluate the therapeutic effect of GE (60 and 120 mg/kg) especially in synovial angiogenesis. In addition, the Matrigel plug assay was used to detect the effect of GE (120 and 240 mg/kg) on angiogenesis in AA mice. In vitro, sphingosine-1-phosphate (S1P)-stimulated human umbilical vein endothelial cells (HUVECs) were used to investigate the effect and mechanism of GE on Ang-2 exocytosis. It was found that GE improved the symptoms of AA rats and inhibited angiogenesis in AA, which may be related to the down-regulation of S1P receptors 1, 3 (S1PR1, S1PR3), phospholipase Cβ3 (PLCβ3), inositol 1,4,5-trisphosphate receptor (IP3 R) and Ang-2 expression. The results of in vitro experiments showed that S1P induced rapid release of Ang-2 from HUVECs with multigranular exocytosis. Suppression of the S1P/S1PR1/3/PLCβ3/Ca2+ signal axis by the S1PR1/3 inhibitor VPC23019 and the IP3 R inhibitor 2-APB blocked Ang-2 exocytosis, accompanied by diminished angiogenesis in vitro. GE dose-dependently weakened S1P/S1PR1/3/PLCβ3/Ca2+ signal axis activation, Ang-2 exocytosis and angiogenesis in HUVECs (p < 0.05, p < 0.01). Overall, these findings revealed that angiogenesis inhibition of GE was partly attributed to the intervention of Ang-2 exocytosis through negatively modulating the S1P/S1PR1/3/PLCβ3/Ca2+ signal axis, providing a novel strategy for rheumatoid arthritis anti-angiogenic therapy.

New sights of immunometabolism and agent progress in colitis associated colorectal cancer

Colitis associated colorectal cancer is a disease with a high incidence and complex course that develops from chronic inflammation and deteriorates after various immune responses and inflammation-induced attacks. Colitis associated colorectal cancer has the characteristics of both immune diseases and cancer, and the similarity of treatment models contributes to the similar treatment dilemma. Immunometabolism contributes to the basis of life and is the core of many immune diseases. Manipulating metabolic signal transduction can be an effective way to control the immune process, which is expected to become a new target for colitis associated colorectal cancer therapy. Immune cells participate in the whole process of colitis associated colorectal cancer development by transforming their functional condition via changing their metabolic ways, such as glucose, lipid, and amino acid metabolism. The same immune and metabolic processes may play different roles in inflammation, dysplasia, and carcinoma, so anti-inflammation agents, immunomodulators, and agents targeting special metabolism should be used in combination to prevent and inhibit the development of colitis associated colorectal cancer.

Decoding the mitochondrial connection: development and validation of biomarkers for classifying and treating systemic lupus erythematosus through bioinformatics and machine learning

BACKGROUND

Systemic lupus erythematosus (SLE) is a multifaceted autoimmune disease characterized by clinical and pathological diversity. Mitochondrial dysfunction has been identified as a critical pathogenetic factor in SLE. However, the specific molecular aspects and regulatory roles of this dysfunction in SLE are not fully understood. Our study aims to explore the molecular characteristics of mitochondria-related genes (MRGs) in SLE, with a focus on identifying reliable biomarkers for classification and therapeutic purposes.

METHODS

We sourced six SLE-related microarray datasets (GSE61635, GSE50772, GSE30153, GSE99967, GSE81622, and GSE49454) from the Gene Expression Omnibus (GEO) database. Three of these datasets (GSE61635, GSE50772, GSE30153) were integrated into a training set for differential analysis. The intersection of differentially expressed genes with MRGs yielded a set of differentially expressed MRGs (DE-MRGs). We employed machine learning algorithms-random forest (RF), support vector machine (SVM), and least absolute shrinkage and selection operator (LASSO) logistic regression-to select key hub genes. These genes' classifying potential was validated in the training set and three other validation sets (GSE99967, GSE81622, and GSE49454). Further analyses included differential expression, co-expression, protein-protein interaction (PPI), gene set enrichment analysis (GSEA), and immune infiltration, centered on these hub genes. We also constructed TF-mRNA, miRNA-mRNA, and drug-target networks based on these hub genes using the ChEA3, miRcode, and PubChem databases.

RESULTS

Our investigation identified 761 differentially expressed genes (DEGs), mainly related to viral infection, inflammatory, and immune-related signaling pathways. The interaction between these DEGs and MRGs led to the identification of 27 distinct DE-MRGs. Key among these were FAM210B, MSRB2, LYRM7, IFI27, and SCO2, designated as hub genes through machine learning analysis. Their significant role in SLE classification was confirmed in both the training and validation sets. Additional analyses included differential expression, co-expression, PPI, GSEA, immune infiltration, and the construction of TF-mRNA, miRNA-mRNA, and drug-target networks.

CONCLUSIONS

This research represents a novel exploration into the MRGs of SLE, identifying FAM210B, MSRB2, LYRM7, IFI27, and SCO2 as significant candidates for classifying and therapeutic targeting.

Phosphoproteome reveals long-term potentiation deficit following treatment of ultra-low dose soman exposure in mice

Soman, a warfare nerve agent, poses a significant threat by inducing severe brain damage that often results in death. Nonetheless, our understanding of the biological changes underlying persistent neurocognitive dysfunction caused by low dosage of soman remains limited. This study used mice to examine the effects of different doses of soman over time. Phosphoproteomic analysis of the mouse brain is the first time to be used to detect toxic effects of soman at such low or ultra-low doses, which were undetectable based on measuring the activity of acetylcholinesterase at the whole-animal level. We also found that phosphoproteome alterations could accurately track the soman dose, irrespective of the sampling time. Moreover, phosphoproteome revealed a rapid and adaptive cellular response to soman exposure, with the points of departure 8-38 times lower than that of acetylcholinesterase activity. Impaired long-term potentiation was identified in phosphoproteomic studies, which was further validated by targeted quantitative proteomics, immunohistochemistry, and immunofluorescence analyses, with significantly increased levels of phosphorylation of protein phosphatase 1 in the hippocampus following soman exposure. This increase in phosphorylation inhibits long-term potentiation, ultimately leading to long-term memory dysfunction in mice.

The Promise of Molecular Imaging: Focus on Central Nervous System Infections

Central nervous system (CNS) infections can lead to high mortality and severe morbidity. Diagnosis, monitoring, and assessing response to therapy of CNS infections is particularly challenging with traditional tools, such as microbiology, due to the dangers associated with invasive CNS procedures (ie, biopsy or surgical resection) to obtain tissues. Molecular imaging techniques like positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging have long been used to complement anatomic imaging such as computed tomography (CT) and magnetic resonance imaging (MRI), for in vivo evaluation of disease pathophysiology, progression, and treatment response. In this review, we detail the use of molecular imaging to delineate host-pathogen interactions, elucidate antimicrobial pharmacokinetics, and monitor treatment response. We also discuss the utility of pathogen-specific radiotracers to accurately diagnose CNS infections and strategies to develop radiotracers that would cross the blood-brain barrier.

B cell metabolism in autoimmune diseases: signaling pathways and interventions

Autoimmune diseases are heterogeneous disorders believed to stem from the immune system's inability to distinguish between auto- and foreign- antigens. B lymphocytes serve a crucial role in humoral immunity as they generate antibodies and present antigens. Dysregulation of B cell function induce the onset of autoimmune disorders by generating autoantibodies and pro-inflammatory cytokines, resulting in an imbalance in immune regulation. New research in immunometabolism shows that cellular metabolism plays an essential role in controlling B lymphocytes immune reactions by providing the energy and substrates for B lymphocytes activation, differentiation, and function. However, dysregulated immunometabolism lead to autoimmune diseases by disrupting self-tolerance mechanisms. This review summarizes the latest research on metabolic reprogramming of B lymphocytes in autoimmune diseases, identifying crucial pathways and regulatory factors. Moreover, we consider the potential of metabolic interventions as a promising therapeutic strategy. Understanding the metabolic mechanisms of B cells brings us closer to developing novel therapies for autoimmune disorders.

Role of T cells in the pathogenesis of systemic lupus erythematous: Focus on immunometabolism dysfunctions

Evidence demonstrates that T cells are implicated in developing SLE, and each of them dominantly uses distinct metabolic pathways. Indeed, intracellular enzymes and availability of specific nutrients orchestrate fate of T cells and lead to differentiation of regulatory T cells (Treg), memory T cells, helper T cells, and effector T cells. The function of T cells in inflammatory and autoimmune responses is determined by metabolic processes and activity of their enzymes. Several studies were conducted to determine metabolic abnormalities in SLE patients and clarify how these modifications could control the functions of the involved T cells. Metabolic pathways such as glycolysis, mitochondrial pathways, oxidative stress, mTOR pathway, fatty acid and amino acid metabolisms are dysregulated in SLE T cells. Moreover, immunosuppressive drugs used in treating autoimmune diseases, including SLE, could affect immunometabolism. Developing drugs to regulate autoreactive T cell metabolism could be a promising therapeutic approach for SLE treatment. Accordingly, increased knowledge about metabolic processes paves the way to understanding SLE pathogenesis better and introduces novel therapeutic options for SLE treatment. Although monotherapy with metabolic pathways modulators might not be sufficient to prevent autoimmune disease, they may be an ideal adjuvant to reduce administration doses of immunosuppressive drugs, thus reducing drug-associated adverse effects. This review summarized emerging data about T cells that are involved in SLE pathogenesis, focusing on immunometabolism dysregulation and how these modifications could affect the disease development.

Mitochondrial fusion induced by transforming growth factor-β1 serves as a switch that governs the metabolic reprogramming during differentiation of regulatory T cells

Although metabolic reprogramming during the differentiation of regulatory T cells (Treg cells) has been extensively studied, the molecular switch to alter energy metabolism remains undefined. The present study explores the critical role of mitochondrial dynamics in the reprogramming and consequent generation of Treg cells. The results showed that during Treg cell differentiation, mitochondrial fusion but not fission led to elevation of oxygen consumption rate values, facilitation of metabolic reprogramming, and increase of number of Treg cells and expression of Foxp3 in vitro and in vivo. Mechanistically, mitochondrial fusion favored fatty acid oxidation but restricted glycolysis in Treg cells through down-regulating the expression of HIF-1α. Transforming growth factor-β1 (TGF-β1) played a crucial role in the induction of mitochondrial fusion, which activated Smad2/3, promoted the expression of PGC-1α and therefore facilitated the expression of mitochondrial fusion proteins. In conclusion, during Treg cell differentiation, TGF-β1 promotes PGC-1α-mediated mitochondrial fusion, which drives metabolic reprogramming from glycolysis to fatty acid oxidation via suppressing HIF-1α expression, and therefore favors the generation of Treg cells. The signals and proteins involved in mitochondrial fusion are potential therapeutic targets for Treg cell-related diseases.

Bioinformatics analysis of the pathogenic link between Epstein-Barr virus infection, systemic lupus erythematosus and diffuse large B cell lymphoma

Epstein-Barr virus (EBV) is a risk factor for diffuse large B-cell lymphoma (DLBCL) and systemic lupus erythematosus (SLE). While prior research has suggested a potential correlation between SLE and DLBCL, the molecular mechanisms remain unclear. The present study aimed to explore the contribution of EBV infection to the pathogenesis of DLBCL in the individuals with SLE using bioinformatics approaches. The Gene Expression Omnibus database was used to compile the gene expression profiles of EBV-infected B cells (GSE49628), SLE (GSE61635), and DLBCL (GSE32018). Altogether, 72 shared common differentially expressed genes (DEGs) were extracted and enrichment analysis of the shared genes showed that p53 signaling pathway was a common feature of the pathophysiology. Six hub genes were selected using protein-protein interaction (PPI) network analysis, including CDK1, KIF23, NEK2, TOP2A, NEIL3 and DEPDC1, which showed preferable diagnostic values for SLE and DLBCL and involved in immune cell infiltration and immune responses regulation. Finally, TF-gene and miRNA-gene regulatory networks and 10 potential drugs molecule were predicted. Our study revealed the potential molecular mechanisms by which EBV infection contribute to the susceptibility of DLBCL in SLE patients for the first time and identified future biomarkers and therapeutic targets for SLE and DLBCL.

RBP-RNA interactions in the control of autoimmunity and autoinflammation

Autoimmunity and autoinflammation arise from aberrant immunological and inflammatory responses toward self-components, contributing to various autoimmune diseases and autoinflammatory diseases. RNA-binding proteins (RBPs) are essential for immune cell development and function, mainly via exerting post-transcriptional regulation of RNA metabolism and function. Functional dysregulation of RBPs and abnormities in RNA metabolism are closely associated with multiple autoimmune or autoinflammatory disorders. Distinct RBPs play critical roles in aberrant autoreactive inflammatory responses via orchestrating a complex regulatory network consisting of DNAs, RNAs and proteins within immune cells. In-depth characterizations of RBP-RNA interactomes during autoimmunity and autoinflammation will lead to a better understanding of autoimmune pathogenesis and facilitate the development of effective therapeutic strategies. In this review, we summarize and discuss the functions of RBP-RNA interactions in controlling aberrant autoimmune inflammation and their potential as biomarkers and therapeutic targets.

Emerging role of hypoxia-inducible factor-1α in inflammatory autoimmune diseases: A comprehensive review

Hypoxia-inducible factor-1α (HIF-1α) is a primary metabolic sensor, and is expressed in different immune cells, such as macrophage, dendritic cell, neutrophil, T cell, and non-immune cells, for instance, synovial fibroblast, and islet β cell. HIF-1α signaling regulates cellular metabolism, triggering the release of inflammatory cytokines and inflammatory cells proliferation. It is known that microenvironment hypoxia, vascular proliferation, and impaired immunological balance are present in autoimmune diseases. To date, HIF-1α is recognized to be overexpressed in several inflammatory autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and function of HIF-1α is dysregulated in these diseases. In this review, we narrate the signaling pathway of HIF-1α and the possible immunopathological roles of HIF-1α in autoimmune diseases. The collected information will provide a theoretical basis for the familiarization and development of new clinical trials and treatment based on HIF-1α and inflammatory autoimmune disorders in the future.

The Involvement of Glucose and Lipid Metabolism Alteration in Rheumatoid Arthritis and Its Clinical Implication

Obviously, immune cells like T cells and macrophages play a major role in rheumatoid arthritis (RA). On one hand, the breakdown of immune homeostasis directly induces systemic inflammation; on the other hand, these cells initiate and perpetuate synovitis and tissue damages through the interaction with fibroblast-like synoviocytes (FLS). In recent years, the pathological link between metabolic disorders and immune imbalance has received increasing attention. High energy demand of immune cells leads to the accumulation of metabolic byproducts and inflammatory mediators. They act on various metabolism-sensitive signal pathways as well as relevant transcription factors, such as HIF-1α, and STATs. These molecular events will impact RA-related effectors like circulating immune cells and joint-resident cells in return, allowing the continuous progression of systemic inflammation, arthritic manifestations, and life-threatening complications. In other words, metabolic complications are secondary pathological factors for the progression of RA. Therefore, the status of energy metabolism may be an important indicator to evaluate RA severity, and in-depth explorations of the mechanisms underlying the mystery of how RA-related metabolic disorders develop will provide useful clues to further clarify the etiology of RA, and inspire the discovery of new anti-rheumatic targets. This article reviews the latest research progress on the interactions between immune and metabolism systems in the context of RA. Great importance is attached to the changes in certain pathways controlling both immune and metabolism functions during RA progression.

Mitochondria in innate immunity signaling and its therapeutic implications in autoimmune diseases

Autoimmune diseases are characterized by vast alterations in immune responses, but the pathogenesis remains sophisticated and yet to be fully elucidated. Multiple mechanisms regulating cell differentiation, maturation, and death are critical, among which mitochondria-related cellular organelle functions have recently gained accumulating attention. Mitochondria, as a highly preserved organelle in eukaryotes, have crucial roles in the cellular response to both exogenous and endogenous stress beyond their fundamental functions in chemical energy conversion. In this review, we aim to summarize recent findings on the function of mitochondria in the innate immune response and its aberrancy in autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, etc., mainly focusing on its direct impact on cellular metabolism and its machinery on regulating immune response signaling pathways. More importantly, we summarize the status quo of potential therapeutic targets found in the mitochondrial regulation in the setting of autoimmune diseases and wish to shed light on future studies.

Saussurea involucrata oral liquid regulates gut microbiota and serum metabolism during alleviation of collagen‐induced arthritis in rats

Saussurea involucrata oral liquid (SIOL) can clinically relieve symptoms, such as joint pain and swelling, and morning stiffness, in patients with rheumatoid arthritis (RA). However, the mechanism of action remains unclear. This study used a combination of gut microbiota and serum metabolomics analysis to investigate the effects and potential mechanisms of SIOL intervention on rats with RA induced by type II bovine collagen and Freund's complete adjuvant. Results showed that SIOL treatment consequently improved the degree of ankle joint swelling, joint histopathological changes, joint pathological score, and expression of serum-related inflammatory cytokines (interleukin (IL)-1β, IL-4, IL-6, IL-10, and tumor necrosis factor-α) in RA model rats. 16 S rRNA sequencing results showed that SIOL increased the relative richness of the Lactobacillus and Bacteroides genus and decreased the relative richness of Romboutsia, Alloprevotella, Blautia, and Helicobacter genus. Serum nontargeted metabolomic results indicated that SIOL could regulate metabolites related to metabolic pathways, such as glycine, serine, threonine, galactose, cysteine, and methionine metabolism. Spearman correlation analysis showed that the regulatory effects of SIOL on the tricarboxylic acid (TCA) cycle, phenylalanine metabolism, phenylalanine, tyrosine, and tryptophan biosynthesis, and glyoxylate and dicarboxylate metabolism pathways were correlated with changes in the richness of the Lactobacillus, Romboutsia, Bacteroides, and Alloprevotella genus in the gut microbiome. In conclusion, this study revealed the ameliorative effects of SIOL on RA and suggested that the therapeutic effects of SIOL on RA may be related to the regulation of the community richness of the Lactobacillus, Romboutsia, Bacteroides, and Alloprevotella genus, thereby improving the TCA cycle; phenylalanine metabolism; phenylalanine, tyrosine, and tryptophan biosynthesis, and glyoxylate and dicarboxylate metabolism-related pathways.

IAPs antagonist SM164 ameliorates experimental MPO-ANCA-associated vasculitis via enhancing fatty acid oxidation in neutrophils

OBJECTIVES

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of life-threatening autoimmune diseases. Inhibitors of apoptosis proteins (IAPs) are a class of molecules engaged in cell death and inflammation, interventions of which are proven effective in a number of inflammatory diseases. Here we tested whether targeting IAPs could ameliorate AAV and explored the potential mechanism.

METHODS

We collected 19 kidney specimens from patients with myeloperoxidase (MPO)-AAV to investigate the expression of IAPs. The IAPs pan-inhibitor SM164 was used to treat the experimental autoimmune vasculitis (EAV) rat model of AAV. RNA sequencing of renal cortex and enrichment analysis were developed to interpret gene expression. Functional experiments were performed to investigate the role of SM164 on neutrophils and endothelial cells.

RESULTS

The expressions of three IAPs (cIAP1, cIAP2 and XIAP) were upregulated in kidneys of AAV patients compared with normal controls. SM164 dramatically reduced renal injury in EAV rats. Transcriptomic analysis revealed prominent alterations in fatty acid oxidation and respiratory burst following SM164 treatment. Functional studies demonstrated that SM164 inhibited neutrophil activation induced by MPO-ANCA positive IgG or serum from MPO-AAV patients, and such inhibitory effect was abolished by gene silencing or pharmacological inhibition of fatty acid oxidation. SM164 also inhibited the adhesion of neutrophils to endothelial cells with little effect on the endothelial injury induced by serum from MPO-AAV patients.

CONCLUSION

Inhibition of IAPs with SM164 played a protective role in AAV through enhancing intracellular fatty acid oxidation in neutrophils.

IL-37 alleviates liver granuloma caused by Schistosoma japonicum infection by inducing alternative macrophage activation

Background

Hepatic macrophages regulate liver granuloma formation and fibrosis caused by infection with Schistosoma japonicum, with the manner of regulation dependent on macrophage activation state. Interleukin (IL)-37 may have immunomodulatory effects on macrophages. However, whether IL-37 can affect liver granuloma formation and fibrosis by affecting the polarization of macrophages in S. japonicum infection remains unclear. The aim of this study was to investigate IL-37-affected macrophage polarization in liver granuloma formation and fibrosis in S. japonicum infection.

Methods

An enzyme-linked immunosorbent assay (ELISA) was used to detect the expression of IL-37 in the serum of patients with acute S. japonicum infection and in the serum of healthy people. Recombinant IL-37 (rIL-37), CPP-IgG₂Fc-IL-37 and no CPP-IgG₂Fc-IL-37 proteins were injected into S. japonicum-infected mice every 3 days for a total of 6 times from day 24 post infection onwards. Subsequently, ELISA, quantitative reverse transcription-PCR, fluorescence-activated cell sorting and western blot were used to analyze whether IL-37 inhibits the formation of liver granulomas and the development of liver fibrosis by regulating the phenotypic transition of macrophages. Finally, the three IL-37 proteins and SIS3, a Smad3 inhibitor, were co-cultured in mouse peritoneal macrophages to explore the mechanism underlying the promotion of the polarization of M0 macrophages to the M2 phenotype by IL-37.

Results

Serum IL-37 levels were upregulated in schistosomiasis patients, and this increased level of IL-37 protein apparently alleviated the liver granuloma of mice in infection models. It also could induce liver and peritoneal macrophages to polarize to the M2 phenotype in S. japonicum-infected mice. The S. japonicum-infected mice injected with CPP-IgG₂Fc-IL-37 group exhibited the most obvious improvement in inflammatory reaction against the liver granuloma. The number and ratio of M2 macrophages in the liver and peritoneal cavity were significantly higher in the three IL-37 protein groups, especially in the CPP-IgG₂Fc-IL-37 group, compared to the controls. Similar results were also found regarding liver function damage. IL-37 induced macrophage M2 polarization by promoting AMP-activated protein kinase (AMPK) phosphorylation in vitro. Among all groups, the activation of AMPK was most significant in the CPP-IgG₂Fc-IL-37 group, and it was found that SMAD3 could enhance the anti-inflammatory function of IL-37.

Conclusions

The results show that IL-37 was able to promote the polarization of macrophages to the M2 phenotype, thereby inhibiting the development of schistosomiasis. In comparison to the rIL-37 protein, the CPP-IgG₂Fc-IL-37 protein has the advantages of being effective in small doses and having fewer side effects and a better efficacy.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05420-6.

Pregnancy-related complications in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune inflammatory disease that predominantly affects women of childbearing age and results in various adverse pregnancy outcomes (APOs). Pregnancy was formerly discouraged in patients with SLE because of unstable disease activity during the gestation period, increased thrombosis risk, severe organ damage, and inevitable side effects of immunosuppressive agents. Currently, most patients with SLE have successful pregnancies due to preconception counselling, strict monitoring, and improved therapy with minimised complications for both the mother and foetus. Hydroxychloroquine (HCQ) is extensively used and is beneficial for improving pregnancy outcomes. However, pregnant women with SLE have a high-risk of APOs, such as disease flare, preterm birth, intrauterine growth restriction (IUGR), preeclampsia, and pregnancy loss. Better understanding of the changes in maternal immunity and serum biomarkers, as well as their relationships with SLE-related APOs progression, would facilitate the investigation of molecular mechanisms for triggering and ameliorating APOs. Furthermore, it would enable us to explore and develop novel and effective therapeutic strategies to prevent disease activation. Therefore, this review briefly introduces the interaction between pregnancy outcomes and SLE, elucidates pathophysiological and immunological changes during SLE pregnancy. Furthermore, this review systematically expounds on the effective predictors of APOs and the molecular mechanisms underlying the SLE-related APOs to provide a solid foundation for the advanced management of lupus pregnancy.

Mechanistic insight into premature atherosclerosis and cardiovascular complications in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is associated with a significant risk of cardiovascular disease (CVD), which substantially increases disease mortality and morbidity. The overall mechanisms associated with the development of premature atherosclerosis and CVD in SLE remain unclear, but has been considered as a result of an intricate interplay between the profound immune dysregulation and traditional CVD risk factors. Aberrant systemic inflammation in SLE may lead to an abnormal lipid profile and dysfunction, which can further fuel the pro-atherosclerotic environment. The existence of a strong imbalance between endothelial damage and vascular repair/angiogenesis promotes vascular injury, which is the early step in the progression of atherosclerotic CVD. Profound innate and adaptive immune dysregulation, characterized by excessive type I interferon burden, aberrant macrophage, platelet and complements activation, neutrophil dysregulation and neutrophil extracellular traps formation, uncontrolled T cell activation, and excessive autoantibody production and immune complex formation, have been proposed to promote accelerated CVD in SLE. While designing targeted therapies to correct the dysregulated immune activation may be beneficial in the treatment of SLE-related CVD, much additional work is needed to determine how to translate these findings into clinical practice. Additionally, a number of biomarkers display diagnostic potentials in improving CVD risk stratification in SLE, further prospective studies will help understand which biomarker(s) will be the most impactful one(s) in assessing SLE-linked CVD. Continued efforts to identify novel mechanisms and to establish criteria for assessing CVD risk as well as predicting CVD progression are in great need to improve CVD outcomes in SLE.

TMT-based quantitative proteomics analysis and potential serum protein biomarkers for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) was not only a typical systemic autoimmune disease, but also one of the most challenging heterogeneous diseases for physicians. Currently, the pathogenesis of SLE was unclear, and there were no accurate, universal or easy-to-use diagnostic criteria for assessing SLE activity and predicting SLE severity. Proteins were direct effectors of biological mechanisms, and were closer to clinical phenotypes than the other discovered biomarkers. Moreover, proteins were widely used as biomarkers for clinical diagnosis and mechanism research of many diseases. Herein, we compared the proteins profiles of healthy individuals (HCs) and SLE patients to reveal the pathogenesis and provide evidence for diagnosis and management of persons with SLE. Serum samples were collected from 28 SLE patients and 30 HCs. Tandem mass tag (TMT)-based quantitative proteomics method was used to identify, screen and detect differentially expressed proteins (DEPs) in the collected serum samples. A total of 744 proteins were identified, and 84 of them were considered as DEPs with 71 upregulated and 13 downregulated. Bioinformatics analysis suggested that these DEPs were mainly involved in many biological processes, including immune response, signal transduction, inflammatory response, proteolysis, innate immune response and apoptosis, which were closely related to the pathogenesis of SLE. After comprehensive analysis, serum amyloid A1 (SAA1) and endothelin (CD248) were identified as specific biomarkers for the diagnosis of SLE, and were confirmed by subsequent enzyme-linked immunosorbent assays (ELISA), indicating a high reliability of TMT-based quantitative proteomics results. Areas under the ROC curve (AUC) results confirmed that SAA1 and CD248 combination as early immune diagnosis biomarkers of SLE presented excellent sensitivity and specificity.

Glycolysis in Innate Immune Cells Contributes to Autoimmunity

Autoimmune diseases (AIDs) refer to connective tissue inflammation caused by aberrant autoantibodies resulting from dysfunctional immune surveillance. Most of the current treatments for AIDs use non-selective immunosuppressive agents. Although these therapies successfully control the disease process, patients experience significant side effects, particularly an increased risk of infection. There is a great need to study the pathogenesis of AIDs to facilitate the development of selective inhibitors for inflammatory signaling to overcome the limitations of traditional therapies. Immune cells alter their predominant metabolic profile from mitochondrial respiration to glycolysis in AIDs. This metabolic reprogramming, known to occur in adaptive immune cells, i.e., B and T lymphocytes, is critical to the pathogenesis of connective tissue inflammation. At the cellular level, this metabolic switch involves multiple signaling molecules, including serine–threonine protein kinase, mammalian target of rapamycin, and phosphoinositide 3-kinase. Although glycolysis is less efficient than mitochondrial respiration in terms of ATP production, immune cells can promote disease progression by enhancing glycolysis to satisfy cellular functions. Recent studies have shown that active glycolytic metabolism may also account for the cellular physiology of innate immune cells in AIDs. However, the mechanism by which glycolysis affects innate immunity and participates in the pathogenesis of AIDs remains to be elucidated. Therefore, we reviewed the molecular mechanisms, including key enzymes, signaling pathways, and inflammatory factors, that could explain the relationship between glycolysis and the pro-inflammatory phenotype of innate immune cells such as neutrophils, macrophages, and dendritic cells. Additionally, we summarize the impact of glycolysis on the pathophysiological processes of AIDs, including systemic lupus erythematosus, rheumatoid arthritis, vasculitis, and ankylosing spondylitis, and discuss potential therapeutic targets. The discovery that immune cell metabolism characterized by glycolysis may regulate inflammation broadens the avenues for treating AIDs by modulating immune cell metabolism.

FABP4 secreted by M1-polarized macrophages promotes synovitis and angiogenesis to exacerbate rheumatoid arthritis

Increasing evidence shows that adipokines play a vital role in the development of rheumatoid arthritis (RA). Fatty acid-binding protein 4 (FABP4), a novel adipokine that regulates inflammation and angiogenesis, has been extensively studied in a variety of organs and diseases. However, the effect of FABP4 on RA remains unclear. Here, we found that FABP4 expression was upregulated in synovial M1-polarized macrophages in RA. The increase in FABP4 promoted synovitis, angiogenesis, and cartilage degradation to exacerbate RA progression in vivo and in vitro, whereas BMS309403 (a FABP4 inhibitor) and anagliptin (dipeptidyl peptidase 4 inhibitor) inhibited FABP4 expression in serum and synovial M1-polarized macrophages in mice to alleviate RA progression. Further studies showed that constitutive activation of mammalian target of rapamycin complex 1 (mTORC1) by TSC1 deletion specifically in the myeloid lineage regulated FABP4 expression in macrophages to exacerbate RA progression in mice. In contrast, inhibition of mTORC1 by ras homolog enriched in brain (Rheb1) disruption specifically in the myeloid lineage reduced FABP4 expression in macrophages to attenuate RA development in mice. Our findings established an essential role of FABP4 that is secreted by M1-polarized macrophages in synovitis, angiogenesis, and cartilage degradation in RA. BMS309403 and anagliptin inhibited FABP4 expression in synovial M1-polarized macrophages to alleviate RA development. Hence, FABP4 may represent a potential target for RA therapy.

The role of B cell metabolism in autoimmune diseases

B cells are major players in immune responses being the source of protective antibodies and antigen presenting cells. When self-tolerance fails, auto reactive B cells produce autoantibodies and pro-inflammatory cytokines leading to the development of autoimmune diseases. Many recent studies have assessed importance of metabolic pathways in B cells, demonstrating their role in controlling autoimmunity and maintaining immune homeostasis. Alterations in B cell functions in autoimmune diseases are closely associated with abnormal metabolic shifts, allowing auto reactive B cells to escape tolerogenic checkpoints. Understanding the metabolic changes in B cells, opens up new possibilities for targeting metabolic pathways and manipulating metabolic avenues as a therapeutic strategy for the treatment of autoimmune diseases.

Role of Butylphthalide in Immunity and Inflammation: Butylphthalide May Be a Potential Therapy for Anti-Inflammation and Immunoregulation

Inflammation and immunity play an essential role in disease pathogenesis. 3-N-Butylphthalide (NBP), a group of compounds extracted from seeds of Apium graveolens (Chinese celery), has been demonstrated as an efficient and effective therapy for ischemic stroke. The amount of research on NBP protective effect is increasing at pace, such as microcircular reconstruction, alleviating inflammation, ameliorating brain edema and blood-brain barrier (BBB) damage, mitochondrial function protection, antiplatelet aggregation, antithrombosis, decreasing oxidative damage, and reducing neural cell apoptosis. There has been increasing research emphasizing the association between NBP and immunity and inflammation in the past few years. Hence, it is aimed at reviewing the related literature and summarizing the underlying anti-inflammatory and immunoregulatory function of NBP in various disorders.

The naturally-occurring flavonoid nobiletin reverses methotrexate resistance via inhibition of P-glycoprotein synthesis

Methotrexate (MTX) is the first-line treatment for rheumatoid arthritis (RA). However, after long-term treatment, some patients develop resistance. P-glycoprotein (P-gp), as an indispensable drug transporter, is essential for mediating this MTX resistance. In addition, nobiletin (NOB), a naturally occurring polymethoxylated flavonoid, has also been shown to reverse P-gp–mediated MTX resistance in RA groups; however, the precise role of NOB in this process is still unclear. Here, we administered MTX and NOB alone or in combination to collagen II-induced arthritic (CIA) mice and evaluated disease severity using the arthritis index, synovial histopathological changes, immunohistochemistry, and P-gp expression. In addition, we used conventional RNA-seq to identify targets and possible pathways through which NOB reverses MTX-induced drug resistance. We found that NOB in combination with MTX could enhance its performance in synovial tissue and decrease P-gp expression in CIA mice compared to MTX treatment alone. In vitro, in MTX-resistant fibroblast-like synoviocytes from CIA cells (CIA-FLS/MTX), we show that NOB treatment downregulated the PI3K/AKT/HIF-1α pathway, thereby reducing the synthesis of the P-gp protein. In addition, NOB significantly inhibited glycolysis and metabolic activity of CIA-FLS/MTX cells, which could reduce the production of ATP and block P-gp, ultimately decreasing the efflux of MTX and maintaining its anti-RA effects. In conclusion, this study shows that NOB overcomes MTX resistance in CIA-FLS/MTX cells through the PI3K/AKT/HIF-1α pathway, simultaneously influencing metabolic processes and inhibiting P-gp–induced drug efflux.

Akt Signaling Pathway Is Activated in the Minor Salivary Glands of Patients with Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune exocrinopathy of mainly the salivary and lacrimal glands associated with high prevalence of lymphoma. Akt is a phosphoinositide-dependent serine/threonine kinase, controlling numerous pathological processes, including oncogenesis and autoimmunity. Herein, we sought to examine its implication in pSS pathogenesis and related lymphomagenesis. The expression of the entire and activated forms of Akt (partially and fully activated: phosphorylated at threonine-308 (T308) and serine-473 (S473), respectively), and two of its substrates, the proline-rich Akt-substrate of 40 kDa (PRAS40) and FoxO1 transcription factor has been immunohistochemically examined in minor salivary glands (MSG) of pSS patients (n = 29; including 9 with pSS-associated lymphoma) and sicca-complaining controls (sicca-controls; n = 10). The entire and phosphorylated Akt, PRAS40, and FoxO1 molecules were strongly, uniformly expressed in the MSG epithelia and infiltrating mononuclear cells of pSS patients, but not sicca-controls. Morphometric analysis revealed that the staining intensity of the fully activated phospho-Akt-S473 in pSS patients (with or without lymphoma) was significantly higher than sicca-controls. Akt pathway activation was independent from the extent or proximity of infiltrates, as well as other disease features, including lymphoma. Our findings support that the Akt pathway is specifically activated in MSGs of pSS patients, revealing novel therapeutic targets.

Glycolysis Rate-Limiting Enzymes: Novel Potential Regulators of Rheumatoid Arthritis Pathogenesis

Rheumatoid arthritis (RA) is a classic autoimmune disease characterized by uncontrolled synovial proliferation, pannus formation, cartilage injury, and bone destruction. The specific pathogenesis of RA, a chronic inflammatory disease, remains unclear. However, both key glycolysis rate-limiting enzymes, hexokinase-II (HK-II), phosphofructokinase-1 (PFK-1), and pyruvate kinase M2 (PKM2), as well as indirect rate-limiting enzymes, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), are thought to participate in the pathogenesis of RA. In here, we review the latest literature on the pathogenesis of RA, introduce the pathophysiological characteristics of HK-II, PFK-1/PFKFB3, and PKM2 and their expression characteristics in this autoimmune disease, and systematically assess the association between the glycolytic rate-limiting enzymes and RA from a molecular level. Moreover, we highlight HK-II, PFK-1/PFKFB3, and PKM2 as potential targets for the clinical treatment of RA. There is great potential to develop new anti-rheumatic therapies through safe inhibition or overexpression of glycolysis rate-limiting enzymes.

UPLC-MS/MS-based plasma lipidomics reveal a distinctive signature in systemic lupus erythematosus patients

Global lipidomics is of considerable utility for exploring altered lipid profiles and unique diagnostic biomarkers in diseases. We aim to apply ultra-performance liquid chromatography-tandem mass spectrometry to characterize the lipidomics profile in systemic lupus erythematosus (SLE) patients and explore the underlying pathogenic pathways using the lipidomics approach. Plasma samples from 18 SLE patients, 20 rheumatoid arthritis (RA) patients, and 20 healthy controls (HC) were collected. A total of 467 lipids molecular features were annotated from each sample. Orthogonal partial least square-discriminant analysis, K-mean clustering analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated disrupted lipid metabolism in SLE patients, especially in phospholipid, glycerol, and sphingolipid metabolism. The area under curve (AUC) of lipid metabolism biomarkers was better than SLE inflammation markers that ordinarily used in the clinic. Proposed model of monoglyceride (MG) (16:0), MG (18:0), phosphatidylethanolamine (PE) (18:3-16:0), PE (16:0-20:4), and phosphatidylcholine (PC) (O-16:2-18:3) yielded AUC 1.000 (95% CI, 1.000-1.000), specificity 100% and sensitivity 100% in the diagnosis of SLE from HC. A panel of three lipids molecular PC (18:3-18:1), PE (20:3-18:0), PE (16:0-20:4) permitted to accurately diagnosis of SLE from RA, with AUC 0.921 (95% CI, 0.828-1.000), 70% specificity, and 100% sensitivity. The plasma lipidomics signatures could serve as an efficient and accurate tool for early diagnosis and provide unprecedented insight into the pathogenesis of SLE.

Recent Advances in Understanding the Pathogenesis of Rheumatoid Arthritis: New Treatment Strategies

Rheumatoid arthritis (RA) is considered a chronic systemic, multi-factorial, inflammatory, and progressive autoimmune disease affecting many people worldwide. While patients show very individual courses of disease, with RA focusing on the musculoskeletal system, joints are often severely affected, leading to local inflammation, cartilage destruction, and bone erosion. To prevent joint damage and physical disability as one of many symptoms of RA, early diagnosis is critical. Auto-antibodies play a pivotal clinical role in patients with systemic RA. As biomarkers, they could help to make a more efficient diagnosis, prognosis, and treatment decision. Besides auto-antibodies, several other factors are involved in the progression of RA, such as epigenetic alterations, post-translational modifications, glycosylation, autophagy, and T-cells. Understanding the interplay between these factors would contribute to a deeper insight into the causes, mechanisms, progression, and treatment of the disease. In this review, the latest RA research findings are discussed to better understand the pathogenesis, and finally, treatment strategies for RA therapy are presented, including both conventional approaches and new methods that have been developed in recent years or are currently under investigation.

Enhanced cGAS-STING-dependent interferon signaling associated with mutations in ATAD3A

Mitochondrial DNA (mtDNA) has been suggested to drive immune system activation, but the induction of interferon signaling by mtDNA has not been demonstrated in a Mendelian mitochondrial disease. We initially ascertained two patients, one with a purely neurological phenotype and one with features suggestive of systemic sclerosis in a syndromic context, and found them both to demonstrate enhanced interferon-stimulated gene (ISG) expression in blood. We determined each to harbor a previously described de novo dominant-negative heterozygous mutation in ATAD3A, encoding ATPase family AAA domain-containing protein 3A (ATAD3A). We identified five further patients with mutations in ATAD3A and recorded up-regulated ISG expression and interferon α protein in four of them. Knockdown of ATAD3A in THP-1 cells resulted in increased interferon signaling, mediated by cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). Enhanced interferon signaling was abrogated in THP-1 cells and patient fibroblasts depleted of mtDNA. Thus, mutations in the mitochondrial membrane protein ATAD3A define a novel type I interferonopathy.

Immunometabolism in systemic lupus erythematosus: Relevant pathogenetic mechanisms and potential clinical applications

Systemic lupus erythematosus (SLE) is a complex, heterogeneous, systemic autoimmune disease involving a wide array of aberrant innate and adaptive immune responses. The immune microenvironment of SLE promotes the metabolic reprogramming of immune cells, leading to immune dyshomeostasis and triggering autoimmune inflammation. Different immune subsets switch from a resting state to a highly metabolic active state by alternating the redox-sensitive signaling pathway and the involved metabolic intermediates to amplify the inflammatory response, which is critical in SLE pathogenesis. In this review, we discuss abnormal metabolic changes in glucose metabolism, tricarboxylic acid cycle, and lipid and amino acid metabolism as well as mitochondrial dysfunction in immune cells in SLE. We also review studies focused on the potential targets for key molecules of metabolic pathways in SLE, such as hypoxia-inducible factor-1α, mammalian target of rapamycin, and AMP-activated protein kinase. We highlight the therapeutic rationale for targeting these pathways in treating SLE and summarize their recent clinical applications in SLE.