Activation of mammalian target of rapamycin controls the loss of TCRzeta in lupus T cells through HRES-1/Rab4-regulated lysosomal degradation

Beneficial effects of rapamycin on endothelial function in systemic lupus erythematosus

Introduction

Endothelial function is significantly impaired in patients with SLE compared to healthy controls. Elevated activation of the mammalian target of rapamycin complex 1 (mTORC1) is reported in humans and mice with SLE. However, it is unclear if elevated mTORC1 in SLE contributes to impaired mitophagy and endothelial dysfunction. Therefore, we tested the hypothesis that inhibiting mTORC1 with rapamycin would increase mitophagy and attenuate endothelial dysfunction and inflammatory responses in SLE.

Methods

Nine-week-old female lupus-prone (MRL/lpr) and healthy control (MRL/MpJ) mice were randomly assigned into rapamycin treatment (lpr_Rapamycin and MpJ_Rapamycin) or control (lpr_Control and MpJ_Control) groups. Rapamycin was injected i.p. 3 days per week for 8 weeks. After 8 weeks, endothelium-dependent vasorelaxation to acetylcholine (ACh) and endothelium-independent vasorelaxation to sodium nitroprusside (SNP) were measured in thoracic aortas using a wire myograph.

Results

MTORC1 activity was increased in aorta from lpr mice as demonstrated by increased phosphorylation of s6rp and p70s6k and significantly inhibited by rapamycin (s6rp, p < 0.0001, p70s6k, p = 0.04, respectively). Maximal responses to Ach were significantly impaired in lpr_Control (51.7% ± 6.6%) compared to MpJ_Control (86.7% ± 3.6%) (p < 0.0001). Rapamycin prevented endothelial dysfunction in the thoracic aorta from lupus mice (lpr_Rapamycin) (79.6% ± 4.2%) compared to lpr_Control (p = 0.002). Maximal responses to SNP were not different across groups. Phosphorylation of endothelial nitric oxide synthase also was 42% lower in lpr_Control than MpJ_Control and 46% higher in lpr_Rapamycin than lpr_Control. The inflammatory marker, vascular cell adhesion protein 1 (Vcam 1), was elevated in aorta from lupus mice compared with healthy mice (p = 0.001), and significantly reduced with Rapamycin treatment (p = 0.0021). Mitophagy markers were higher in lupus mice and reduced by rapamycin treatment, suggesting altered mitophagy in lpr mice.

Conclusion

Collectively, these results demonstrate the beneficial effects of inhibiting mTORC1 on endothelial function in SLE mice and suggest inflammation and altered mitophagy contribute to endothelial dysfunction in SLE.

The immunology of systemic lupus erythematosus

Understanding the pathogenesis and clinical manifestations of systemic lupus erythematosus (SLE) has been a great challenge. Reductionist approaches to understand the nature of the disease have identified many pathogenetic contributors that parallel clinical heterogeneity. This Review outlines the immunological control of SLE and looks to experimental tools and approaches that are improving our understanding of the complex contribution of interacting genetics, environment, sex and immunoregulatory factors and their interface with processes inherent to tissue parenchymal cells. Efforts to advance precision medicine in the care of patients with SLE along with treatment strategies to correct the immune system hold hope and are also examined.

Mitochondrial Dysfunction and Fatigue in Sjögren's Disease

Objectives

Sjögren's disease (SjD) is a common exocrine disorder typified by chronic inflammation and dryness, but also profound fatigue, suggesting a pathological basis in cellular bioenergetics. In healthy states, damaged or dysfunctional mitochondrial components are broken down and recycled by mitophagy, a specialized form of autophagy. In many autoimmune disorders, however, evidence suggests that dysfunctional mitophagy allows poorly functioning mitochondria to persist and contribute to a cellular milieu with elevated reactive oxygen species. We hypothesized that mitophagic processes are dysregulated in SjD and that dysfunctional mitochondria contribute to overall fatigue. We sought to link fatigue with mitochondrial dysfunction directly in SjD, heretofore unexamined, and further sought to assess the pathogenic extent and implications of dysregulated mitophagy in SjD.

Methods

We isolated pan T cells via negative selection from the peripheral blood mononuclear cells of 17 SjD and 8 age-matched healthy subjects, all of whom completed fatigue questionnaires prior to phlebotomy. Isolated T cells were analyzed for mitochondrial oxygen consumption rate (OCR) and glycolysis using Seahorse, and linear correlations with fatigue measures were assessed. A mitophagy transcriptional signature in SjD was identified by reanalysis of whole-blood microarray data from 190 SjD and 32 healthy subjects. Differential expression analyses were performed by case/control and subgroup analyses comparing SjD patients by mitophagy transcriptional cluster against healthy subjects followed by bioinformatic interpretation using gene set enrichment analysis.

Results

Basal OCR, ATP-linked respiration, maximal respiration, and reserve capacity were significantly lower in SjD compared to healthy subjects with no observed differences in non-mitochondrial respiration, basal glycolysis, or glycolytic stress. SjD lymphocytic mitochondria show structural alterations compared to healthy subjects. Fatigue scores related to pain/discomfort in SjD correlated with the altered OCR. Results from subgroup analyses by mitophagic SjD clusters revealed highly variable inter-cluster differentially expressed genes (DEGs) and expanded the number of SjD-associated gene targets by tenfold within the same dataset.

Conclusion

Mitochondrial dysfunction, associated with fatigue, is a significant problem in SjD and warrants further investigation.

Redox Pathogenesis in Rheumatic Diseases

Despite being some of the most anecdotally well-known roads to pathogenesis, the mechanisms governing autoimmune rheumatic diseases are not yet fully understood. The overactivation of the cellular immune system and the characteristic development of autoantibodies have been linked to oxidative stress. Typical clinical manifestations, such as joint swelling and deformities and inflammation of the skin and internal organs, have also been connected directly or indirectly to redox mechanisms. The differences in generation and restraint of oxidative stress provide compelling evidence for the broad variety in pathology among rheumatic diseases and explain some of the common triggers and discordant manifestations in these diseases. Growing evidence of redox mechanisms in pathogenesis has provided a broad array of new potential therapeutic targets. Here, we explore the mechanisms by which oxidative stress is generated, explore its roles in autoimmunity and end-organ damage, and discuss how individual rheumatic diseases exhibit unique features that offer targets for therapeutic interventions.

Immmunometabolism of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a potentially fatal chronic autoimmune disease which is underlain by complex dysfunction of the innate and adaptive immune systems. Although a series of well-defined genetic and environmental factors have been implicated in disease etiology, neither the development nor the persistence of SLE is well understood. Given that several disease susceptibility genes and environmental factors interact and influence inflammatory lineage specification through metabolism, the field of immunometabolism has become a forefront of cutting edge research. Along these lines, metabolic checkpoints of pathogenesis have been identified as targets of effective therapeutic interventions in mouse models and validated in clinical trials. Ongoing studies focus on mitochondrial oxidative stress, activation of the mechanistic target of rapamycin, calcium signaling, glucose utilization, tryptophan degradation, and metabolic cross-talk between gut microbiota and the host immune system.

Rab4A-directed endosome traffic shapes pro-inflammatory mitochondrial metabolism in T cells via mitophagy, CD98 expression, and kynurenine-sensitive mTOR activation

Activation of the mechanistic target of rapamycin (mTOR) is a key metabolic checkpoint of pro-inflammatory T-cell development that contributes to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE), however, the underlying mechanisms remain poorly understood. Here, we identify a functional role for Rab4A-directed endosome traffic in CD98 receptor recycling, mTOR activation, and accumulation of mitochondria that connect metabolic pathways with immune cell lineage development and lupus pathogenesis. Based on integrated analyses of gene expression, receptor traffic, and stable isotope tracing of metabolic pathways, constitutively active Rab4AQ72L exerts cell type-specific control over metabolic networks, dominantly impacting CD98-dependent kynurenine production, mTOR activation, mitochondrial electron transport and flux through the tricarboxylic acid cycle and thus expands CD4+ and CD3+CD4-CD8- double-negative T cells over CD8+ T cells, enhancing B cell activation, plasma cell development, antinuclear and antiphospholipid autoantibody production, and glomerulonephritis in lupus-prone mice. Rab4A deletion in T cells and pharmacological mTOR blockade restrain CD98 expression, mitochondrial metabolism and lineage skewing and attenuate glomerulonephritis. This study identifies Rab4A-directed endosome traffic as a multilevel regulator of T cell lineage specification during lupus pathogenesis.

α-Ketoglutarate-Dependent KDM6 Histone Demethylases and Interferon-Stimulated Gene Expression in Lupus

OBJECTIVE

We aimed to investigate the hypothesis that interferon (IFN)-stimulated gene (ISG) expression in systemic lupus erythematosus (SLE) monocytes is linked to changes in metabolic reprogramming and epigenetic regulation of ISG expression.

METHODS

Monocytes from healthy volunteers and patients with SLE at baseline or following IFNα treatment were analyzed by extracellular flux analysis, proteomics, metabolomics, chromatin immunoprecipitation, and gene expression. The histone demethylases KDM6A/B were inhibited using glycogen synthase kinase J4 (GSK-J4). GSK-J4 was tested in pristane and resiquimod (R848) models of IFN-driven SLE.

RESULTS

SLE monocytes had enhanced rates of glycolysis and oxidative phosphorylation compared to healthy control monocytes, as well as increased levels of isocitrate dehydrogenase and its product, α-ketoglutarate (α-KG). Because α-KG is a required cofactor for histone demethylases KDM6A and KDM6B, we hypothesized that IFNα may be driving "trained immune" responses through altering histone methylation. IFNα priming (day 1) resulted in a sustained increase in the expression of ISGs in primed cells (day 5) and enhanced expression on restimulation with IFNα. Importantly, decreased H3K27 trimethylation was observed at the promoters of ISGs following IFNα priming. Finally, GSK-J4 (KDM6A/B inhibitor) resulted in decreased ISG expression in SLE patient monocytes, as well as reduced autoantibody production, ISG expression, and kidney pathology in R848-treated BALB/c mice.

CONCLUSION

Our study suggests long-term IFNα exposure alters the epigenetic regulation of ISG expression in SLE monocytes via changes in immunometabolism, a mechanism reflecting trained immunity to type I IFN. Importantly, it opens the possibility that targeting histone-modifying enzymes, such as KDM6A/B, may reduce IFN responses in SLE.

Add-on sirolimus for the treatment of mild or moderate systemic lupus erythematosus via T lymphocyte subsets balance

OBJECTIVE

The efficacy of sirolimus in treating severe or refractory systemic lupus erythematosus (SLE) has been confirmed by small-scale clinical trials. However, few studies focused on mild or moderate SLE. Therefore, in this study we elucidated clinical efficacy of add-on sirolimus in patients with mild or moderate SLE.

METHODS

Data of 17 consecutive patients with SLE were retrospectively collected. SLE Disease Activity Index-2000 (SLEDAI-2K), clinical manifestation, laboratory data and peripheral T lymphocyte subsets with cytokines were collected before and 6 months after sirolimus add-on treatment. T cell subsets were detected by flow cytometry and cytokines were determined by multiplex bead-based flow fluorescent immunoassay simultaneously. Twenty healthy controls matched with age and sex were also included in our study.

RESULTS

(1) The numbers of peripheral blood lymphocytes, T cells, T helper (Th) cells, regulatory T (Treg) cells, Th1 cells, Th2 cells and Treg/Th17 ratios in patients with SLE were significantly lower, while the numbers of Th17 cells were evidently higher than those of healthy control (p<0.05). (2) After 6 months of sirolimus add-on treatment, urinary protein, pancytopenia, immunological indicators and SLEDAI-2K in patients with SLE were distinctively improved compared with those before sirolimus treatment (p<0.05). (3) The numbers of peripheral blood lymphocytes, T cells, Th cells, Treg cells, Th2 cells and the ratios of Treg/Th17 in patients with SLE after treatment were clearly higher than those before (p<0.05). (4) The levels of plasma interleukin (IL)-5, IL-6 and IL-10 in patients with SLE decreased notably, conversely the IL-4 levels increased remarkably compared with pretreatment (p<0.05).

CONCLUSIONS

(1) Patients with SLE presented imbalanced T cell subsets, especially the decreased ratio of Treg/Th17. (2) Sirolimus add-on treatment ameliorated clinical involvement, serological abnormalities and disease activity without adverse reactions in patients with SLE. (3) The multi-target therapy facilitates the enhanced numbers of Treg cells, Treg/Th17 imbalance and anti-inflammatory cytokines, simultaneously, reducing inflammatory cytokines.

Signalling mechanisms driving homeostatic and inflammatory effects of interleukin-15 on tissue lymphocytes

There is an intriguing dichotomy in the function of cytokine interleukin-15-at low levels, it is required for the homeostasis of the immune system, yet when it is upregulated in response to pathogenic infections or in autoimmunity, IL-15 drives inflammation. IL-15 associates with the IL-15Rα within both myeloid and non-haematopoietic cells, where IL-15Rα trans-presents IL-15 in a membrane-bound form to neighboring cells. Alongside homeostatic maintenance of select lymphocyte populations such as NK cells and tissue-resident T cells, when upregulated, IL-15 also promotes inflammatory outcomes by driving effector function and cytotoxicity in NK cells and T cells. As chronic over-expression of IL-15 can lead to autoimmunity, IL-15 expression is tightly regulated. Thus, blocking dysregulated IL-15 and its downstream signalling pathways are avenues for immunotherapy. In this review we discuss the molecular pathways involved in IL-15 signalling and how these pathways contribute to both homeostatic and inflammatory functions in IL-15-dependent mature lymphoid populations, focusing on innate, and innate-like lymphocytes in tissues.

Mechanistic target of rapamycin (mTOR): a potential new therapeutic target for rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by systemic synovitis and bone destruction. Proinflammatory cytokines activate pathways of immune-mediated inflammation, which aggravates RA. The mechanistic target of rapamycin (mTOR) signaling pathway associated with RA connects immune and metabolic signals, which regulates immune cell proliferation and differentiation, macrophage polarization and migration, antigen presentation, and synovial cell activation. Therefore, therapy strategies targeting mTOR have become an important direction of current RA treatment research. In the current review, we summarize the biological functions of mTOR, its regulatory effects on inflammation, and the curative effects of mTOR inhibitors in RA, thus providing references for the development of RA therapeutic targets and new drugs.

Hidradenitis suppurativa presents a methylome dysregulation capable to explain the pro-inflammatory microenvironment: Are these DNA methylations potential therapeutic targets?

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic, systemic, inflammatory skin condition with elusive pathogenesis that affects therapeutic intervention directly.

OBJECTIVE

To characterize epigenetic variations in cytokines genes contributing to HS.

METHODS

Epigenome-wide DNA methylation profiling with the Illumina Epic array was performed on blood DNA samples from 24 HS patients and 24 age- and sex-matched controls to explore DNA methylation changes in cytokine genes.

RESULTS

We identified 170 cytokine genes including 27 hypermethylated CpG sites and 143 genes with hypomethylated sites respectively. Hypermethylated genes, including LIF, HLA-DRB1, HLA-G, MTOR, FADD, TGFB3, MALAT1 and CCL28; hypomethylated genes, including NCSTN, SMAD3, IGF1R, IL1F9, NOD2, NOD1, YY1, DLL1 and BCL2 may contribute to the pathogenesis of HS. These genes were enriched in the 117 different pathways (FDR p-values ≤ 0.05), including IL-4/IL-13 pathways and Wnt/β-catenin signalling.

CONCLUSIONS

The lack of wound healing, microbiome dysbiosis and increased tumour susceptibility are all sustained by these dysfunctional methylomes, hopefully, capable to be targeted in the next future. Since methylome describes and summarizes genetic and environmental contributions, these data may represent a further step towards a feasible precision medicine also for HS patients.

Refractory systemic lupus erythematosus with chylous effusion successfully treated with sirolimus: a case report and literature review

Chylous effusion is a rare manifestation of systemic lupus erythematosus (SLE). When it does occur in SLE, it is generally well treated with standard pharmacologic or surgical measures. We present a decade of management in a case of SLE with lung affliction and development of refractory bilateral chylous effusion and pulmonary arterial hypertension (PAH). In the first years, the patient was treated under a Sjogren syndrome diagnose. After few years, her respiratory condition worsened due to chylous effusion and PAH. Immunosuppression therapy (methylprednisolone) was reintroduced, and vasodilator therapy commenced. With this, her cardiac function remained stable, but respiratory function continuously worsened despite several therapy trials with different combinations of immunosuppressant (glucocorticoids, resochin, cyclophosphamide and mycophenolate mofetil). On top of pleural effusion worsening, the patient developed ascites and severe hypoalbuminaemia. Even though albumin loss was stabilized with monthly octreotide applications, the patient remained respiratory insufficient and in need of continuous oxygen therapy. At that point, we decided to introduce sirolimus on top of glucocorticoids and mycophenolate mofetil therapy. Her clinical status, radiological finding, and lung function gradually improved and she became respiratory sufficient at rest. The patient remains in our follow-up and has been stable on given therapy for over 3 years despite overcoming a severe COVID-19 pneumonia in 2021. This case adds to the body of evidence of sirolimus effectiveness in patients with refractory systemic lupus and is, to our best knowledge, the first case to report its successful application in a patient with SLE and refractory chylous effusion.

Lactate-induced mtDNA Accumulation Activates cGAS-STING Signaling and the Inflammatory Response in Sjögren's Syndrome

Acinar epithelial cell atrophy in secretory glands is a hallmark of primary Sjögren's syndrome (pSS), the cause of which is far from elucidated. We examined the role of acinar atrophy by focusing on the metabolism of glandular epithelial cells and mitochondria in the pSS environment. After confirming the presence of a high-lactate environment in the labial glands of human pSS patients, we used the A253 cell line and NOD/Ltj mice as models to investigate the metabolic changes in salivary gland epithelial cells in a high-lactate environment in vitro and in vivo. We found that epithelial cells produced high levels of IL-6, IL-8, IFN-α, IFN-β and TNF-α and exhibited significant NF-κB and type I IFN-related pathway activation. The results confirmed that lactate damaged mitochondrial DNA (mtDNA) and led to its leakage, which subsequently activated the cGAS-STING pathway. Inflammatory cytokine production and pathway activation were inhibited in vivo and in vitro by the lactate scavenger sodium dichloroacetate (DCA). Our study provides new insights into the etiology and treatment of pSS from the perspective of cell metabolism.

Signaling Pathways Leading to mTOR Activation Downstream Cytokine Receptors in Lymphocytes in Health and Disease

CD8+ T cells and Natural Killer (NK) cells are cytotoxic lymphocytes important in the response to intracellular pathogens and cancer. Their activity depends on the integration of a large set of intracellular and environmental cues, including antigenic signals, cytokine stimulation and nutrient availability. This integration is achieved by signaling hubs, such as the mechanistic target of rapamycin (mTOR). mTOR is a conserved protein kinase that controls cellular growth and metabolism in eukaryotic cells and, therefore, is essential for lymphocyte development and maturation. However, our current understanding of mTOR signaling comes mostly from studies performed in transformed cell lines, which constitute a poor model for comprehending metabolic pathway regulation. Therefore, it is only quite recently that the regulation of mTOR in primary cells has been assessed. Here, we review the signaling pathways leading to mTOR activation in CD8+ T and NK cells, focusing on activation by cytokines. We also discuss how this knowledge can contribute to immunotherapy development, particularly for cancer treatment.

Endosome Traffic Modulates Pro-Inflammatory Signal Transduction in CD4+ T Cells-Implications for the Pathogenesis of Systemic Lupus Erythematosus

Endocytic recycling regulates the cell surface receptor composition of the plasma membrane. The surface expression levels of the T cell receptor (TCR), in concert with signal transducing co-receptors, regulate T cell responses, such as proliferation, differentiation, and cytokine production. Altered TCR expression contributes to pro-inflammatory skewing, which is a hallmark of autoimmune diseases, such as systemic lupus erythematosus (SLE), defined by a reduced function of regulatory T cells (Tregs) and the expansion of CD4⁺ helper T (Th) cells. The ensuing secretion of inflammatory cytokines, such as interferon-γ and interleukin (IL)-4, IL-17, IL-21, and IL-23, trigger autoantibody production and tissue infiltration by cells of the adaptive and innate immune system that induce organ damage. Endocytic recycling influences immunological synapse formation by CD4⁺ T lymphocytes, signal transduction from crosslinked surface receptors through recruitment of adaptor molecules, intracellular traffic of organelles, and the generation of metabolites to support growth, cytokine production, and epigenetic control of DNA replication and gene expression in the cell nucleus. This review will delineate checkpoints of endosome traffic that can be targeted for therapeutic interventions in autoimmune and other disease conditions.

Cordyceps proteins alleviate lupus nephritis through modulation of the STAT3/mTOR/NF-кB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps is a parasitic edible fungus, which is a unique Chinese medicinal material. It has been reported to have immunomodulatory effects and use in kidney disease. Especially, Cordyceps has been used in the treatment of lupus nephritis (LN).

AIM OF STUDY

Cordyceps proteins (CP) have a favorable bidirectional immunomodulatory functions and may have therapeutic potential for LN. However, the underlying molecular mechanism remains unknown. So this study aimed to examine the activities of CP in LN and possible mechanism.

MATERIALS AND METHODS

So proteomics was performed to detect proteins components of Cordyceps, and analysis it. In addition, MRL/lpr mice were used to study the progression of LN. The MRL/lpr mice were fed either CP (i.g, 0.5, 1.0, 1.5 g/kg/d), prednisolone acetate (PA, i.g, 6 mg/kg/d), or Bailing capsule (BC, i.g, 0.75 g/kg/d) for 8 weeks. Hematoxylin-eosin (H&E), Periodic Acid Schif (PAS) and Masson's stainings, Immunofluorescence, and Immunohistochemistry were performed to verify the therapeutic effect of CP on MRL/lpr mice. The mechanism by CP alimerated LN was uncovered by Western blotting (WB) and Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) methods.

RESULTS

Our results revealed that CP blocked proteinuria production and renal inflammatory infiltratation in MRL/lpr mice to reduce the renal fibrosis. In addition, CP worked better than BC which is artificial Cordyceps fungus powder in regulating proteinuria to urine creatinine ratio and interleukin-4(IL-4) protein amount. Especially, CP modulated the STAT3/mTOR/NF-кB signaling pathway in LN mice and brought a more pronounced lowering effect on the contents of IL-6 and IL-1β than the PA.

CONCLUSION

CP could be a potential anti-inflammatory immune product with strong regulatory effects and potency than BC and PA in nephritis therapeutics.

A cellular overview of immunometabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease, characterized by a breakdown of immune tolerance and the development of autoantibodies against nucleic self-antigens. Immunometabolism is a rapidly expanding scientific field investigating the metabolic programming of cells of the immune system. During the normal immune response, extensive reprogramming of cellular metabolism occurs, both to generate adenosine triphosphate and facilitate protein synthesis, and also to manage cellular stress. Major pathways upregulated include glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle and the pentose phosphate pathway, among others. Metabolic reprogramming also occurs to aid resolution of inflammation. Immune cells of both patients with SLE and lupus-prone mice are characterized by metabolic abnormalities resulting in an altered functional and inflammatory state. Recent studies have described how metabolic reprogramming occurs in many cell populations in SLE, particularly CD4+ T cells, e.g. favouring a glycolytic profile by overactivation of the mechanistic target of rapamycin pathway. These advances have led to an increased understanding of the metabolic changes affecting the inflammatory profile of T and B cells, monocytes, dendritic cells and neutrophils, and how they contribute to autoimmunity and SLE pathogenesis. In the current review, we aim to summarize recent advances in the field of immunometabolism involved in SLE and how these could potentially lead to new therapeutic strategies in the future.

Serum proteome and metabolome uncover novel biomarkers for the assessment of disease activity and diagnosing of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease affecting thousands of people. There are still no effective biomarkers for SLE diagnosis and disease activity assessment. We performed proteomics and metabolomics analyses of serum from 121 SLE patients and 106 healthy individuals, and identified 90 proteins and 76 metabolites significantly changed. Several apolipoproteins and the metabolite arachidonic acid were significantly associated with disease activity. Apolipoprotein A-IV (APOA4), LysoPC(16:0), punicic acid and stearidonic acid were correlated with renal function. Random forest model using the significantly changed molecules identified 3 proteins including ATRN, THBS1 and SERPINC1, and 5 metabolites including cholesterol, palmitoleoylethanolamide, octadecanamide, palmitamide and linoleoylethanolamide, as potential biomarkers for SLE diagnosis. Those biomarkers were further validated in an independent cohort with high accuracy (AUC = 0.862 and 0.898 for protein and metabolite biomarkers respectively). This unbiased screening has led to the discovery of novel molecules for SLE disease activity assessment and SLE classification.

Autophagy pathways in autoimmune diseases

Autophagy comprises a growing range of cellular pathways, which occupy central roles in response to energy deprivation, organelle turnover and proteostasis. Over the years, autophagy has been increasingly linked to governing several aspects of immunity, including host defence against various pathogens, unconventional secretion of cytokines and antigen presentation. While canonical autophagy-mediated antigen processing in thymic epithelial cells supports the generation of a self-tolerant CD4+ T cell repertoire, mounting evidence suggests that deregulated autophagy pathways contribute to or sustain autoimmune responses. In animal models of multiple sclerosis (MS), non-canonical autophagy pathways such as microtubule-associated protein 1 A/1 B-light chain 3 (LC3)-associated phagocytosis can contribute to major histocompatibility complex (MHC) class II presentation of autoantigen, thereby amplifying autoreactive CD4+ T cell responses. In systemic lupus erythematosus (SLE), increased type 1 interferon production is linked to excessive autophagy in plasmacytoid dendritic cells (DCs). In rheumatoid arthritis (RA), autophagy proteins contribute to pathological citrullination of autoantigen. Immunotherapies effective in autoimmune diseases modulate autophagy functions, and strategies harnessing autophagy pathways to restrain autoimmune responses have been developed. This review illustrates recent insights in how autophagy, distinct autophagy pathways and autophagy protein functions intersect with the evolution and progression of autoimmune diseases, focusing on MS, SLE and RA.

Association between glomerular mTORC1 activation and crescents formation in lupus nephritis patients

OBJECTIVE

This study aims to explore the association between glomerular mammalian target of rapamycin complex 1 (mTORC1) pathway activation and crescents' degree in lupus nephritis (LN) patients.

METHODS

A total of 159 biopsy-proven LN patients were enrolled in this retrospective study. The clinical and pathological data of them were collected at the time of renal biopsy. mTORC1 pathway activation was measured by immunohistochemistry, expressed by the mean optical density (MOD) of p-RPS6 (ser235/236), and multiplexed immunofluorescence. The association of mTORC1 pathway activation with clinico-pathological features especially renal crescentic lesions, and the composite outcomes in LN patients was further analyzed.

RESULTS

mTORC1 pathway activation could be detected in the crescentic lesions and was positively correlated with the percentage of crescents (r = 0.479, P < 0.001) in LN patients. Subgroup analysis showed mTORC1 pathway was more activated in patients with cellular or fibrocellular crescentic lesions (P < 0.001), but not fibrous crescentic lesions (P = 0.270). The optimal cutoff value of the MOD of p-RPS6 (ser235/236) was 0.0111299 for predicting the presence of cellular-fibrocellular crescents in >7.39% of the glomeruli by the receiver operating characteristic curve. Cox regression survival analysis showed that mTORC1 pathway activation was an independent risk factor for the worse outcome (defined by composite endpoints of death, end-stage renal disease and a decrease of >30% in eGFR from baseline).

CONCLUSION

Activation of mTORC1 pathway was closely associated with the cellular-fibrocellular crescentic lesions and could be a prognostic marker in LN patients.

mTOR Signaling Network in Cell Biology and Human Disease

The mechanistic target of rapamycin (mTOR) is a serine/threonine protein kinase that regulates multiple processes, including gene transcription, protein synthesis, ribosome biogenesis, autophagy, cell metabolism, and cell growth [...].

Conditional knockout of oestrogen receptor alpha in CD11c+ cells impacts female survival and inflammatory cytokine profile in murine lupus

Oestrogen and oestrogen receptor alpha (ERα) have been implicated in systemic lupus erythematosus pathogenesis. ERα signalling influences dendritic cell (DC) development and function, as well as inflammation and downstream immune responses. We previously reported that ERα modulates multiple Toll-like receptor-stimulated pathways in both conventional and plasmacytoid DCs in lupus-prone mice. For example, CD11chi MHCII+ cell numbers are reduced in mice with global ERα deficiency or when expressing a short variant of ERα. Herein, RNA-seq analysis of CD11chi cells from bone marrow of NZM2410 mice expressing WT ERα versus ERα short versus ERα null revealed differentially expressed complement genes, interferon-related genes and cytokine signalling (e.g., IL-17 and Th17 pathways). To better understand the role of ERα in CD11c+ cells, lupus prone NZM2410 mice with selective deletion of the Esr1 gene in CD11c+ cells were generated. Phenotype and survival of these mice were similar with the exception of Cre positive (CrePos) female mice. CrePos females, but not males, all died unexpectedly prior to 35 weeks. DC subsets were not significantly different between groups. Since ERα is necessary for robust development of DCs, this result suggests that DC fate was determined prior to CD11c expression and subsequent ERα deletion (i.e., proximally in DC ontogeny). Overall, findings point to a clear functional role for ERα in regulating cytokine signalling and inflammation, suggesting that further study into ERα-mediated regulatory mechanisms in DCs and other immune cell types is warranted.

PRDX6AS1 gene polymorphisms and SLE susceptibility in Chinese populations

Background

Systemic lupus erythematosus (SLE) is a complex, multisystem autoimmune disease that is characterized by the production of autoantibodies. Although accumulated evidence suggests that the dysregulation of long non-coding RNAs (lncRNAs) is involved in the pathogenesis of SLE, the genetic contributions of lncRNA coding genes to SLE susceptibility remain largely unknown. Here, we aimed to provide more evidence for the role of lncRNA coding genes to SLE susceptibility.

Methods

The genetic association analysis was first adopted from the previous genome-wide association studies (GWAS) and was then validated in an independent cohort. PRDX6-AS1 is located at chr1:173204199-173446294. It spans a region of approximately 240 kb, and 297 single nucleotide polymorphisms (SNPs) were covered by the previous GWAS. Differential expression at the mRNA level was analyzed based on the ArrayExpress Archive database.

Results

A total of 33 SNPs were associated with SLE susceptibility, with a P<1.68×10^-4. The strongest association signal was detected at rs844649 (P=2.12×10^-6), according to the previous GWAS. Combining the results from the GWAS Chinese cohort and our replication cohort, we pursued a meta-analysis approach and found a pronounced genetic association between PRDX6-AS1 rs844649 and SLE susceptibility (p_meta=1.24×10^-13, OR 1.50, 95% CI: 1.34–1.67). The mRNA expression of PRDX6 was elevated in peripheral blood cells, peripheral blood mononuclear cells (PBMCs), and multiple cell subpopulations, such as B cells, CD4⁺ T cells, CD3⁺ cells, and monocytes in patients with SLE. The PRDX6 protein expression level was also increased in patients with SLE compared with healthy donors.

Conclusion

Our study provides new evidence that variants located in lncRNA coding genes are associated with SLE susceptibility.

The key player in the pathogenesis of environmental influence of systemic lupus erythematosus: Aryl hydrocarbon receptor

The aryl hydrocarbon receptor was previously known as an environmental receptor that modulates the cellular response to external environmental changes. In essence, the aryl hydrocarbon receptor is a cytoplasmic receptor and transcription factor that is activated by binding to the corresponding ligands, and they transmit relevant information by binding to DNA, thereby activating the transcription of various genes. Therefore, we can understand the development of certain diseases and discover new therapeutic targets by studying the regulation and function of AhR. Several autoimmune diseases, including systemic lupus erythematosus (SLE), have been connected to AhR in previous studies. SLE is a classic autoimmune disease characterized by multi-organ damage and disruption of immune tolerance. We discuss here the homeostatic regulation of AhR and its ligands among various types of immune cells, pathophysiological roles, in addition to the roles of various related cytokines and signaling pathways in the occurrence and development of SLE.

mTORC1 activation induced proximal tubular damage via the pentose phosphate pathway in lupus nephritis

More recent studies suggested that metabolic disorders could contribute to the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis (LN). The present work aimed at identifying metabolic reprogramming in the kidney of lupus nephritis via proteomics and investigating the potential regulatory mechanism. The proteomic studies on the renal biopsies revealed that the pentose phosphate pathway (PPP) was significantly enriched in the kidneys of LN patients compared with normal controls (NCs). Immunohistochemical stanning of glucose-6-phosphate dehydrogenase (G6PD), the key rate-limiting enzyme of PPP, verify the results of proteomics. We found that G6PD was highly expressed in the kidneys of LN patients and correlated with several clinicopathological indices. The univariate Cox regression analysis (HR, 95%CI, 1.877 (1.059-3.328), P = 0.031) and Kaplan-Meier (KM) analysis (P = 0.028) suggested that high G6PD expression in the tubulointerstitial area was a risk factor for worse prognosis. Moreover, the Gene set enrichment analysis (GSEA) demonstrated that the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway ranked first in the kidneys of LN patients with high G6PD expression and G6PD was co-localized with mTORC1 activation in the tubule. Immunoglobulin G (IgG) isolated from LN patients significantly activated the mTORC1 pathway and increased G6PD expression, G6PD activity, NADPH production, NADPH oxidase 2 (NOX2) expression, reactive oxygen species (ROS) production, and cell apoptosis in tubule cells in vitro. The above phenotypes were partially rescued after the addition of rapamycin or knock-down of G6PD. Overall, our study suggested that renal G6PD expression was associated with the overall enhanced disease activity and worse renal prognosis. mTORC1 activation might be involved in IgG-LN-induced tubular damage via PPP.

Mitochondria as a key player in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous, multisystemic autoimmune disease with a broad clinical spectrum. Loss of self-tolerance and chronic inflammation are critical markers of SLE pathogenesis. Although alterations in adaptive immunity are widely recognized, increasing reports indicate the role of mitochondrial dysfunction in activating pathogenic pathways involving the innate immune system. Among these, disarrangements in mitochondrial DNA copy number and heteroplasmy percentage are related to SLE activity. Furthermore, increased oxidative stress contributes to post-translational changes in different molecules (proteins, nucleic acids, and lipids), release of oxidized mitochondrial DNA through a pore of voltage-dependent anion channel oligomers, and spontaneous mitochondrial antiviral signaling protein oligomerization. Finally, a reduction in mitophagy, apoptosis induction, and NETosis has been reported in SLE. Most of these pathways lead to persistent and inappropriate exposure to oxidized mitochondrial DNA, which can stimulate plasmacytoid dendritic cells, enhance autoreactive lymphocyte activation, and release increased amounts of interferons through stimulation of toll-like receptors and cytosolic DNA sensors. Likewise, abnormal T-cell receptor activation, decreased regulatory T cells, enhanced Th17 phenotypes, and increased monocyte maturation to dendritic cells have also been observed in SLE. Targeting the players involved in mitochondrial damage can ultimately help.

Analyzing biomarker discovery: Estimating the reproducibility of biomarker sets

Many researchers try to understand a biological condition by identifying biomarkers. This is typically done using univariate hypothesis testing over a labeled dataset, declaring a feature to be a biomarker if there is a significant statistical difference between its values for the subjects with different outcomes. However, such sets of proposed biomarkers are often not reproducible – subsequent studies often fail to identify the same sets. Indeed, there is often only a very small overlap between the biomarkers proposed in pairs of related studies that explore the same phenotypes over the same distribution of subjects. This paper first defines the Reproducibility Score for a labeled dataset as a measure (taking values between 0 and 1) of the reproducibility of the results produced by a specified fixed biomarker discovery process for a given distribution of subjects. We then provide ways to reliably estimate this score by defining algorithms that produce an over-bound and an under-bound for this score for a given dataset and biomarker discovery process, for the case of univariate hypothesis testing on dichotomous groups. We confirm that these approximations are meaningful by providing empirical results on a large number of datasets and show that these predictions match known reproducibility results. To encourage others to apply this technique to analyze their biomarker sets, we have also created a publicly available website, https://biomarker.shinyapps.io/BiomarkerReprod/, that produces these Reproducibility Score approximations for any given dataset (with continuous or discrete features and binary class labels).

AIM2-inflammasome role in systemic lupus erythematous and rheumatoid arthritis

The inflammasome AIM2 regulates multiple aspects of innate immune functions and serves as a critical mediator of inflammatory responses. AIM2 inflammasome activation leads to the production of pro-inflammatory cytokines, IL-1β and IL-18 and participates triggering a pyroptosis response needed to counteract excessive cell proliferation. In addition, AIM2 expression and activation is wide regulated since alteration in its activity may derived in pathological consequences. Consequently, deregulated AIM2 activation contributes to the pathogenic processes of various inflammatory diseases. In this review, we will discuss the activation and function of AIM2 inflammasome, as well as its contribution in rheumatoid arthritis and systemic lupus erythematous pathology. Finally, we highlight the participation of the AIM2-inflammasome at the level of joint in rheumatoid arthritis and at kidney in systemic lupus erythematous. The development of therapeutic strategies based on modulation of AIM2-inflammasome activity should have a tissue-specific focus.

Mitochondrial impairment and repair in the pathogenesis of systemic lupus erythematosus

Nucleic acid autoantibodies, increase type I interferon (IFN-α) levels, and immune cell hyperactivation are hallmarks of systemic lupus erythematosus (SLE). Notably, immune cell activation requires high level of cellular energy that is predominately generated by the mitochondria. Mitochondrial reactive oxygen species (mROS), the byproduct of mitochondrial energy generation, serves as an essential mediator to control the activation and differentiation of cells and regulate the antigenicity of oxidized nucleoids within the mitochondria. Recently, clinical trials on normalization of mitochondrial redox imbalance by mROS scavengers and those investigating the recovery of defective mitophagy have provided novel insights into SLE prophylaxis and therapy. However, the precise mechanism underlying the role of oxidative stress-related mitochondrial molecules in skewing the cell fate at the molecular level remains unclear. This review outlines distinctive mitochondrial functions and pathways that are involved in immune responses and systematically delineates how mitochondrial dysfunction contributes to SLE pathogenesis. In addition, we provide a comprehensive overview of damaged mitochondrial function and impaired metabolic pathways in adaptive and innate immune cells and lupus-induced organ tissues. Furthermore, we summarize the potential of current mitochondria-targeting drugs for SLE treatment. Developing novel therapeutic approaches to regulate mitochondrial oxidative stress is a promising endeavor in the search for effective treatments for systemic autoimmune diseases, particularly SLE.

Cell type-specific mechanistic target of rapamycin-dependent distortion of autophagy pathways in lupus nephritis

Pro-inflammatory immune system development, metabolomic defects, and deregulation of autophagy play interconnected roles in driving the pathogenesis of systemic lupus erythematosus (SLE). Lupus nephritis (LN) is a leading cause of morbidity and mortality in SLE. While the causes of SLE have not been clearly delineated, skewing of T and B cell differentiation, activation of antigen-presenting cells, production of antinuclear autoantibodies and pro-inflammatory cytokines are known to contribute to disease development. Underlying this process are defects in autophagy and mitophagy that cause the accumulation of oxidative stress-generating mitochondria which promote necrotic cell death. Autophagy is generally inhibited by the activation of the mammalian target of rapamycin (mTOR), a large protein kinase that underlies abnormal immune cell lineage specification in SLE. Importantly, several autophagy-regulating genes, including ATG5 and ATG7, as well as mitophagy-regulating HRES-1/Rab4A have been linked to lupus susceptibility and molecular pathogenesis. Moreover, genetically-driven mTOR activation has been associated with fulminant lupus nephritis. mTOR activation and diminished autophagy promote the expansion of pro-inflammatory Th17, Tfh and CD3⁺CD4^-CD8^- double-negative (DN) T cells at the expense of CD8⁺ effector memory T cells and CD4⁺ regulatory T cells (Tregs). mTOR activation and aberrant autophagy also involve renal podocytes, mesangial cells, endothelial cells, and tubular epithelial cells that may compromise end-organ resistance in LN. Activation of mTOR complexes 1 (mTORC1) and 2 (mTORC2) has been identified as biomarkers of disease activation and predictors of disease flares and prognosis in SLE patients with and without LN. This review highlights recent advances in molecular pathogenesis of LN with a focus on immuno-metabolic checkpoints of autophagy and their roles in pathogenesis, prognosis and selection of targets for treatment in SLE.

T Cell Help in the Autoreactive Germinal Center

The germinal center serves as a site of B cell selection and affinity maturation, critical processes for productive adaptive immunity. In autoimmune disease tolerance is broken in the germinal center reaction, leading to production of autoreactive B cells that may propagate disease. Follicular T cells are crucial regulators of this process, providing signals necessary for B cell survival in the germinal center. Here we review the emerging roles of follicular T cells in the autoreactive germinal center. Recent advances in immunological techniques have allowed study of the gene expression profiles and repertoire of follicular T cells at unprecedented resolution. These studies provide insight into the potential role follicular T cells play in preventing or facilitating germinal center loss of tolerance. Improved understanding of the mechanisms of T cell help in autoreactive germinal centers provides novel therapeutic targets for diseases of germinal center dysfunction.

A Deep Insight Into Regulatory T Cell Metabolism in Renal Disease: Facts and Perspectives

Kidney disease encompasses a complex set of diseases that can aggravate or start systemic pathophysiological processes through their complex metabolic mechanisms and effects on body homoeostasis. The prevalence of kidney disease has increased dramatically over the last two decades. CD4⁺CD25⁺ regulatory T (Treg) cells that express the transcription factor forkhead box protein 3 (Foxp3) are critical for maintaining immune homeostasis and preventing autoimmune disease and tissue damage caused by excessive or unnecessary immune activation, including autoimmune kidney diseases. Recent studies have highlighted the critical role of metabolic reprogramming in controlling the plasticity, stability, and function of Treg cells. They are also likely to play a vital role in limiting kidney transplant rejection and potentially promoting transplant tolerance. Metabolic pathways, such as mitochondrial function, glycolysis, lipid synthesis, glutaminolysis, and mammalian target of rapamycin (mTOR) activation, are involved in the development of renal diseases by modulating the function and proliferation of Treg cells. Targeting metabolic pathways to alter Treg cells can offer a promising method for renal disease therapy. In this review, we provide a new perspective on the role of Treg cell metabolism in renal diseases by presenting the renal microenvironment、relevant metabolites of Treg cell metabolism, and the role of Treg cell metabolism in various kidney diseases.

Advances in CD247

CD247, which is also known as CD3ζ, CD3H, CD3Q, CD3Z, IMD25, T3Z, and TCRZ, encodes CD3ζ protein, which is expressed primarily in natural killer (NK) and T cells. Since the discovery of the ζ peptide in 1986, it has been continuously investigated. In this paper, we review the composition, molecular mechanisms and regulatory factors of CD247 expression in T cells; and review the autoimmune diseases, tumors and inflammatory diseases associated with CD247, providing a detailed and comprehensive reference for further research on the mechanism of CD247 and related diseases.

T cell metabolism and possible therapeutic targets in systemic lupus erythematosus: a narrative review

In the immunopathogenesis of systemic lupus erythematosus (SLE), there is a dysregulation of specific immune cells, including T cells. The metabolic reprogramming in T cells causes different effects. Metabolic programs are critical checkpoints in immune responses and are involved in the etiology of autoimmune disease. For instance, resting lymphocytes generate energy through oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO), whereas activated lymphocytes rapidly shift to the glycolytic pathway. Specifically, mitochondrial dysfunction, oxidative stress, abnormal metabolism (including glucose, lipid, and amino acid metabolism), and mTOR signaling are hallmarks of T lymphocyte metabolic dysfunction in SLE. Herein it is summarized how metabolic defects contribute to T cell responses in SLE, and some epigenetic alterations involved in the disease. Finally, it is shown how metabolic defects could be modified therapeutically.

Long Non-Coding RNAs in Systemic Lupus Erythematosus: New Insights into Disease Pathogenesis and Diagnosis

Systemic lupus erythematosus (SLE) is a remarkable heterogeneous autoimmune disease that is sometimes hard to diagnose at the early stage and can lead to premature mortality. Long non-coding RNAs (lncRNAs) are a class of non-protein-coding RNAs greater than 200 nucleotides in length that can regulate gene expression in various human diseases, including SLE. Peripheral blood samples and renal tissue samples from SLE patients were used for study. Abnormally expressed lncRNAs in SLE have been shown to influence several signaling pathways, including the IFN-I, MAPK and WNT pathways. This can affect cellular phenotypes like cell activation, differentiation skewing, cytokine production, and cell apoptosis. Many of the reported lncRNAs may be useful for diagnosing, evaluating progression, and predicting potential organ damage in SLE patients. While numerous lncRNAs play important roles in SLE, more basic and clinical studies are warranted to clarify the function of these regulatory molecules and determine their diagnostic value.

Redox Control of Integrin-Mediated Hepatic Inflammation in Systemic Autoimmunity

Significance: Systemic autoimmunity affects 3%-5% of the population worldwide. Systemic lupus erythematosus (SLE) is a prototypical form of such condition, which affects 20-150 of 100,000 people globally. Liver dysfunction, defined by increased immune cell infiltration into the hepatic parenchyma, is an understudied manifestation that affects up to 20% of SLE patients. Autoimmunity in SLE involves proinflammatory lineage specification in the immune system that occurs with oxidative stress and profound changes in cellular metabolism. As the primary metabolic organ of the body, the liver is uniquely capable to encounter oxidative stress through first-pass derivatization and filtering of waste products. Recent Advances: The traffic of immune cells from their development through recirculation in the liver is guided by cell adhesion molecules (CAMs) and integrins, cell surface proteins that tightly anchor cells together. The surface expression of CAMs and integrins is regulated via endocytic traffic that is sensitive to oxidative stress. Reactive oxygen species (ROS) that elicit oxidative stress in the liver may originate from the mitochondria, the cytosol, or the cell membrane. Critical Issues: While hepatic ROS production is a source of vulnerability, it also modulates the development and function of the immune system. In turn, the liver employs antioxidant defense mechanisms to protect itself from damage that can be harnessed to serve as therapeutic mechanisms against autoimmunity, inflammation, and development of hepatocellular carcinoma. Future Directions: This review is aimed at delineating redox control of integrin signaling in the liver and checkpoints of regulatory impact that can be targeted for treatment of inflammation in systemic autoimmunity. Antioxid. Redox Signal. 36, 367-388.

The Role of Oxidative Stress in Epigenetic Changes Underlying Autoimmunity

Significance: Epigenetic dysregulation plays an important role in the pathogenesis and development of autoimmune diseases. Oxidative stress is associated with autoimmunity and is also known to alter epigenetic mechanisms. Understanding the interplay between oxidative stress and epigenetics will provide insights into the role of environmental triggers in the development of autoimmunity in genetically susceptible individuals. Recent Advances: Abnormal DNA and histone methylation patterns in genes and pathways involved in interferon and tumor necrosis factor signaling, cellular survival, proliferation, metabolism, organ development, and autoantibody production have been described in autoimmunity. Inhibitors of DNA and histone methyltransferases showed potential therapeutic effects in animal models of autoimmune diseases. Oxidative stress can regulate epigenetic mechanisms via effects on DNA damage repair mechanisms, cellular metabolism and the local redox environment, and redox-sensitive transcription factors and pathways. Critical Issues: Studies looking into oxidative stress and epigenetics in autoimmunity are relatively limited. The number of available longitudinal studies to explore the role of DNA methylation in the development of autoimmune diseases is small. Future Directions: Exploring the relationship between oxidative stress and epigenetics in autoimmunity will provide clues for potential preventative measures and treatment strategies. Inception cohorts with longitudinal follow-up would help to evaluate epigenetic marks as potential biomarkers for disease development, progression, and treatment response in autoimmunity. Antioxid. Redox Signal. 36, 423-440.

Redox Homeostasis Involvement in the Pharmacological Effects of Metformin in Systemic Lupus Erythematosus

Significance: Metformin has been proposed as a treatment for systemic lupus erythematosus (SLE). The primary target of metformin, the electron transport chain complex I in the mitochondria, is associated with redox homeostasis in immune cells, which plays a critical role in the pathogenesis of autoimmune diseases. This review addresses the evidence and knowledge gaps on whether a beneficial effect of metformin in lupus may be due to a restoration of a balanced redox state. Recent Advances: Clinical trials in SLE patients with mild-to-moderate disease activity and preclinical studies in mice have provided encouraging results for metformin. The mechanism by which this therapeutic effect was achieved is largely unknown. Metformin regulates redox homeostasis in a context-specific manner. Multiple cell types contribute to SLE, with evidence of increased mitochondrial oxidative stress in T cells and neutrophils. Critical Issues: The major knowledge gaps are whether the efficacy of metformin is linked to a restored redox homeostasis in the immune system, and if it does, in which cell types it occurs? We also need to know which patients may have a better response to metformin, and whether it corresponds to a specific mechanism? Finally, the identification of biomarkers to predict treatment outcomes would be of great value. Future Directions: Mechanistic studies must address the context-dependent pharmacological effects of metformin. Multiple cell types as well as a complex disease etiology should be considered. These studies must integrate the rapid advances made in understanding how metabolic programs direct the effector functions of immune cells. Antioxid. Redox Signal. 36, 462-479.

The Role of Immunometabolism in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder in which pathogenic abnormalities within both the innate and adaptive immune response have been described. In order to activated, proliferate and maintain this immunological response a drastic upregulation in energy metabolism is required. Recently, a greater understanding of these changes in cellular bioenergetics have provided new insight into the links between immune response and the pathogenesis of a number of diseases, ranging from cancer to diabetes and multiple sclerosis. In this review, we highlight the latest understanding of the role of immunometabolism in SLE with particular focus on the role of abnormal mitochondrial function, lipid metabolism, and mTOR signaling in the immunological phenomenon observed in the SLE. We also consider what implications this has for future therapeutic options in the management of the disease in future.

Association of Viral Infection With the Development and Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that causes multiple organ damage in women of childbearing age and has a relapsing-remitting course. SLE is caused by the interaction between genetic and environmental factors, however, its underlying triggers remain unknown. Among the environmental factors, the involvement of infections as a trigger for SLE, especially those of viral etiology, has been widely reported. Human endogenous retroviruses (HERVs) may put patients at a genetic predisposition to SLE, while the Epstein-Barr virus (EBV) may play a role as an environmental factor that triggers the development of SLE. It has been suggested that EBV-infected B-cells may become resistant to apoptosis, resulting in the activation, proliferation, and antibody production of autoreactive B-cells, which cause tissue damage in SLE. However, the interaction between the virus and immune cells, as well as the impact of the virus on the differentiation and dysfunction of immune cells, remain unclear. In this review, we focus on the relationship between the development and pathogenesis of SLE and viral infections, as well as the mechanism of SLE exacerbation via activation of immune cells, such as B-cells, based on the latest findings.

Identification and Validation of Pathogenic Genes in Sepsis and Associated Diseases by Integrated Bioinformatics Approach

Sepsis is a clinical syndrome with high mortality and morbidity rates. In sepsis, the abrupt release of cytokines by the innate immune system may cause multiorgan failure, leading to septic shock and associated complications. In the presence of a number of systemic disorders, such as sepsis, infections, diabetes, and systemic lupus erythematosus (SLE), cardiorenal syndrome (CRS) type 5 is defined by concomitant cardiac and renal dysfunctions Thus, our study suggests that certain mRNAs and unexplored pathways may pave a way to unravel critical therapeutic targets in three debilitating and interrelated illnesses, namely, sepsis, SLE, and CRS. Sepsis, SLE, and CRS are closely interrelated complex diseases likely sharing an overlapping pathogenesis caused by erroneous gene network activities. We sought to identify the shared gene networks and the key genes for sepsis, SLE, and CRS by completing an integrative analysis. Initially, 868 DEGs were identified in 16 GSE datasets. Based on degree centrality, 27 hub genes were revealed. The gProfiler webtool was used to perform functional annotations and enriched molecular pathway analyses. Finally, core hub genes (EGR1, MMP9, and CD44) were validated using RT-PCR analysis. Our comprehensive multiplex network approach to hub gene discovery is effective, as evidenced by the findings. This work provides a novel research path for a new research direction in multi-omics biological data analysis.

Renal mTORC1 activation is associated with disease activity and prognosis in lupus nephritis

OBJECTIVE

This study was initiated to evaluate mammalian target of rapamycin (mTOR) activation in renal tissue of lupus nephritis (LN) patients.

METHODS

This retrospective study included 187 LN patients, 20 diabetic nephropathy (DN) patients, 10 minimal change disease (MCD) patients, and 10 normal controls (NCs). 7 of 187 LN patients had repeated renal biopsies. mTORC1/2 activation was evaluated by immunohistochemistry and multiplexed immunofluorescence. The association of mTORC1/2 activation with the clinicopathologic indices and prognostic outcomes was analysed among 187 LN patients. Proteomics was performed in renal biopsies of 20 LN patients. Proteomics was employed to comprehensively evaluate the impact of mTOR activation on intrarenal gene expression.

RESULTS

mTORC1/2 was significantly activated in podocytes, mesangial cells, endothelial cells and tubular epithelial cells of LN patients as compared with those with MCD or NC. The glomerular mTORC1 activation was higher in LN patients compared with DN patients. mTORC1, but not mTORC2, activation strongly correlated with serum albumin, complement C3, proteinuria, and the following pathological biomarkers of LN: crescent formation, interstitial inflammation and fibrosis. Moreover, mTORC1 activation was identified as a prognostic marker in LN patients. Bioinformatic analyses of proteomics and immunohistochemical data unveiled increased complement activation, antigen presentation, and phagocytosis in LN patients with mTORC1 activation.

CONCLUSION

Renal mTORC1 activation could be a biomarker to reveal disease activity and predict clinical prognosis in LN patients.

Cytoplasmic RNA quality control failure engages mTORC1-mediated autoinflammatory disease

Inborn errors of nucleic acid metabolism often cause aberrant activation of nucleic acid sensing pathways, leading to autoimmune or autoinflammatory diseases. The SKIV2L RNA exosome is cytoplasmic RNA degradation machinery that was thought to be essential for preventing the self-RNA-mediated interferon (IFN) response. Here, we demonstrate the physiological function of SKIV2L in mammals. We found that Skiv2l deficiency in mice disrupted epidermal and T cell homeostasis in a cell-intrinsic manner independently of IFN. Skiv2l-deficient mice developed skin inflammation and hair abnormality, which were also observed in a SKIV2L-deficient patient. Epidermis-specific deletion of Skiv2l caused hyperproliferation of keratinocytes and disrupted epidermal stratification, leading to impaired skin barrier with no appreciable IFN activation. Moreover, Skiv2l-deficient T cells were chronically hyperactivated and these T cells attacked lesional skin as well as hair follicles. Mechanistically, SKIV2L loss activated the mTORC1 pathway in both keratinocytes and T cells. Both systemic and topical rapamycin treatment of Skiv2l-deficient mice ameliorated epidermal hyperplasia and skin inflammation. Together, we demonstrate that mTORC1, a classical nutrient sensor, also senses cytoplasmic RNA quality control failure and drives autoinflammatory disease. We also propose SKIV2L-associated trichohepatoenteric syndrome (THES) as a new mTORopathy for which sirolimus may be a promising therapy.

Rapamycin relieves lupus nephritis by regulating TIM-3 and CD4+CD25+Foxp3+ Treg cells in an MRL/lpr mouse model

Lupus nephritis (LN) is a severe consequence of systemic lupus erythematosus (SLE) and is an important driver of morbidity and mortality in SLE. Treg cells and TIM-3 play an important role in the pathogenesis of LN. The beneficial effect of rapamycin on LN has been confirmed in both mouse models and patients, but the effect of rapamycin on Treg cells and TIM-3 is not yet completely understood. In this study, rapamycin treatment attenuated proteinuria, histological damage, and renal deposition of C3, and improved renal function. Spleen and renal draining lymph node weight and serum levels of anti-dsDNA antibodies were also improved by rapamycin. Furthermore, the frequency of Treg cells and Treg functional molecules, such as cytotoxic T cell antigen 4 (CTLA-4), interleukin 10 (IL-10), and transforming growth factor β1 (TGF-β1), increased significantly after treatment with rapamycin in MRL/lpr mice. We also found that expression of TIM-3 was significantly decreased in CD4+ T cells and Treg cells in mice treated with rapamycin. In summary, the study demonstrated that rapamycin treatment induced preferential expansion of CD4+CD25+Foxp3+ Tregs with increased expression of CTLA-4, IL-10, and TGF-β1, and decreased TIM-3 expression, thereby ameliorating lupus nephritis in the MRL/lpr mouse model.

Pharmacological insights into autophagy modulation in autoimmune diseases

As a cellular bulk degradation and survival mechanism, autophagy is implicated in diverse biological processes. Genome-wide association studies have revealed the link between autophagy gene polymorphisms and susceptibility of autoimmune diseases including systemic lupus erythematosus (SLE) and inflammatory bowel disease (IBD), indicating that autophagy dysregulation may be involved in the development of autoimmune diseases. A series of autophagy modulators have displayed protective effects on autoimmune disease models, highlighting the emerging role of autophagy modulators in treating autoimmune diseases. This review explores the roles of autophagy in the autoimmune diseases, with emphasis on four major autoimmune diseases [SLE, rheumatoid arthritis (RA), IBD, and experimental autoimmune encephalomyelitis (EAE)]. More importantly, the therapeutic potentials of small molecular autophagy modulators (including autophagy inducers and inhibitors) on autoimmune diseases are comprehensively analyzed.

Exploring the role of the multiple sclerosis susceptibility gene CLEC16A in T cells

C-type lectin-like domain family 16 member A (CLEC16A) is associated with autoimmune disorders, including multiple sclerosis (MS), but its functional relevance is not completely understood. CLEC16A is expressed in several immune cells, where it affects autophagic processes and receptor expression. Recently, we reported that the risk genotype of an MS-associated single nucleotide polymorphism in CLEC16A intron 19 is associated with higher expression of CLEC16A in CD4⁺ T cells. Here, we show that CLEC16A expression is induced in CD4⁺ T cells upon T cell activation. By the use of imaging flow cytometry and confocal microscopy, we demonstrate that CLEC16A is located in Rab4a-positive recycling endosomes in Jurkat TAg T cells. CLEC16A knock-down in Jurkat cells resulted in lower cell surface expression of the T cell receptor, however, this did not have a major impact on T cell activation response in vitro in Jurkat nor in human, primary CD4⁺ T cells.

Metabolic preconditioning in CD4+ T cells restores inducible immune tolerance in lupus-prone mice

Autoimmune disease has presented an insurmountable barrier to restoration of durable immune tolerance. Previous studies indicate that chronic therapy with metabolic inhibitors can reduce autoimmune inflammation, but it remains unknown whether acute metabolic modulation enables permanent immune tolerance to be established. In an animal model of lupus, we determined that targeting glucose metabolism with 2-deoxyglucose (2DG) and mitochondrial metabolism with metformin enables endogenous immune tolerance mechanisms to respond to tolerance induction. A 2-week course of 2DG and metformin, when combined with tolerance-inducing therapy anti-CD45RB, prevented renal deposition of autoantibodies for 6 months after initial treatment and restored tolerance induction to allografts in lupus-prone mice. The restoration of durable immune tolerance was linked to changes in T cell surface glycosylation patterns, illustrating a role for glycoregulation in immune tolerance. These findings indicate that metabolic therapy may be applied as a powerful preconditioning to reinvigorate tolerance mechanisms in autoimmune and transplant settings that resist current immune therapies.