Genetics and pathogenesis of systemic lupus erythematosus and lupus nephritis

A Comprehensive Review of Biological Agents for Lupus: Beyond Single Target

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves multiple immune cells. Due to its complex pathogenesis, the effectiveness of traditional treatment methods is limited. Many patients have developed resistance to conventional treatment or are not sensitive to steroid and immunosuppressant therapy, and so emerging therapeutic antibodies have become an alternative and have been shown to work well in many patients with moderate and severe SLE. This review summarizes the biological agents that are in the preclinical and clinical trial study of SLE. In addition to the various monoclonal antibodies that have been studied for a long time, such as belimumab and rituximab, we focused on another treatment for SLE, bispecific antibodies (BsAbs) such as tibulizumab, which simultaneously targets multiple pathogenic cytokines or pathways. Although the application of BsAbs in cancer has been intensively studied, their application in autoimmune diseases is still in the infant stage. This unique combined mechanism of action may provide a novel therapeutic strategy for SLE.

Regulatory T Cell Plasticity and Stability and Autoimmune Diseases

CD4⁺CD25⁺ regulatory T cells (Tregs) are a class of CD4⁺ T cells with immunosuppressive functions that play a critical role in maintaining immune homeostasis. However, in certain disease settings, Tregs demonstrate plastic differentiation, and the stability of these Tregs, which is characterized by the stable expression or protective epigenetic modifications of the transcription factor Foxp3, becomes abnormal. Plastic Tregs have some features of helper T (Th) cells, such as the secretion of Th-related cytokines and the expression of specific transcription factors in Th cells, but also still retain the expression of Foxp3, a feature of Tregs. Although such Th-like Tregs can secrete pro-inflammatory cytokines, they still possess a strong ability to inhibit specific Th cell responses. Therefore, the plastic differentiation of Tregs not only increases the complexity of the immune circumstances under pathological conditions, especially autoimmune diseases, but also shows an association with changes in the stability of Tregs. The plastic differentiation and stability change of Tregs play vital roles in the progression of diseases. This review focuses on the phenotypic characteristics, functions, and formation conditions of several plastic Tregs and also summarizes the changes of Treg stability and their effects on inhibitory function. Additionally, the effects of Treg plasticity and stability on disease prognosis for several autoimmune diseases were also investigated in order to better understand the relationship between Tregs and autoimmune diseases.

Dexamethasone prodrug nanomedicine (ZSJ-0228) treatment significantly reduces lupus nephritis in mice without measurable side effects - A 5-month study

Lupus nephritis (LN) is a major cause of morbidity and mortality among systemic lupus erythematosus patients. Glucocorticoids (GCs) are uniformly used in clinical LN management. Their notorious toxicities, however, have hampered the long-term clinical application. To circumvent GC side effects while maintaining their potent therapeutic efficacy, we have developed a macromolecular prodrug nanomedicine based on dexamethasone (ZSJ-0228). The focus of this study was to investigate its long-term efficacy and, most importantly, safety in the lupus-prone NZB/W F1 mouse. Monthly ZSJ-0228 treatment for five months significantly reduced the incidence of nephritis in NZB/W F1 mice with an improved survival rate. In contrast to treatment with dose equivalent daily free dexamethasone, long-term monthly ZSJ-0228 did not result in any measurable GC-associated side effects. With its outstanding efficacy and exceptional safety, it is anticipated that ZSJ-0228 may be a novel therapy for long-term clinical management of LN.

Kidney Tertiary Lymphoid Structures in Lupus Nephritis Develop into Large Interconnected Networks and Resemble Lymph Nodes in Gene Signature

Immune aggregates organized as tertiary lymphoid structures (TLS) are observed within the kidneys of patients with systemic lupus erythematosus and lupus nephritis (LN). Renal TLS was characterized in lupus-prone New Zealand black × New Zealand white F1 mice analyzing cell composition and vessel formation. RNA sequencing was performed on transcriptomes isolated from lymph nodes, macrodissected TLS from kidneys, and total kidneys of mice at different disease stages by using a personal genome machine and RNA sequencing. Formation of TLS was found in anti-double-stranded DNA antibody-positive mice, and the structures were organized as interconnected large networks with distinct T/B cell zones with adjacent dendritic cells, macrophages, plasma cells, high endothelial venules, supporting follicular dendritic cells network, and functional germinal centers. Comparison of gene profiles of whole kidney, renal TLS, and lymph nodes revealed a similar gene signature of TLS and lymph nodes. The up-regulated genes within the kidneys of lupus-prone mice during LN development reflected TLS formation, whereas the down-regulated genes were involved in metabolic processes of the kidney cells. A comparison with human LN gene expression revealed similar up-regulated genes as observed during the development of murine LN and TLS. In conclusion, kidney TLS have a similar cell composition, structure, and gene signature as lymph nodes and therefore may function as a kidney-specific type of lymph node.

A review of advances in the understanding of lupus nephritis pathogenesis as a basis for emerging therapies

Lupus nephritis is an important cause of both acute kidney injury and chronic kidney disease that can result in end-stage renal disease. Its pathogenic mechanisms are characterized by aberrant activation of both innate and adaptive immune responses, dysregulation of inflammatory signaling pathways, and increased cytokine production. Treatment of lupus nephritis remains a challenging issue in the management of systemic lupus erythematosus since the clinical presentation, response to treatment, and prognosis all vary considerably between patients and are influenced by ethnicity, gender, the degree of chronic kidney damage, pharmacogenomics, and non-immunological modulating factors. Elucidation of the various immunopathogenic pathways in lupus nephritis has resulted in the development of novel therapies, including biologics that target specific antigens on B lymphocytes to achieve B cell depletion, agents that modulate B cell proliferation and development, drugs that block co-stimulatory pathways, drugs that target T lymphocytes primarily, and therapies that target complement activation, signaling pathways, pro-inflammatory cytokines, and neutrophil extracellular traps. This review will discuss recent advances in the understanding of disease pathogenesis in lupus nephritis in the context of potential emerging therapies.

Regulating the Polarization of Macrophages: A Promising Approach to Vascular Dermatosis

Macrophages, a kind of innate immune cells, derive from monocytes in circulation and play a crucial role in the innate and adaptive immunity. Under the stimulation of the signals from local microenvironment, macrophages generally tend to differentiate into two main functional phenotypes depending on their high plasticity and heterogeneity, namely, classically activated macrophage (M1) and alternatively activated macrophage (M2). This phenomenon is often called macrophage polarization. In pathological conditions, chronic persistent inflammation could induce an aberrant response of macrophage and cause a shift in their phenotypes. Moreover, this shift would result in the alteration of macrophage polarization in some vascular dermatoses; e.g., an increase in proinflammatory M1 emerges from Behcet's disease (BD), psoriasis, and systemic lupus erythematosus (SLE), whereas an enhancement in anti-inflammatory M2 appears in infantile hemangioma (IH). Individual polarized phenotypes and their complicated cytokine networks may crucially mediate in the pathological processes of some vascular diseases (vascular dermatosis in particular) by activation of T cell subsets (such as Th1, Th2, Th17, and Treg cells), deterioration of oxidative stress damage, and induction of angiogenesis, but the specific mechanism remains ambiguous. Therefore, in this review, we discuss the possible role of macrophage polarization in the pathological processes of vascular skin diseases. In addition, it is proposed that regulation of macrophage polarization may become a potential strategy for controlling these disorders.

Independent Replication on Genome-Wide Association Study Signals Identifies IRF3 as a Novel Locus for Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a genetically complex autoimmune disease. Despite the significant progress made in identifying susceptibility genes for SLE, the genetic architecture of the disease is far from being understood. In this study, we set to replicate a number of suggestive association signals found in genome-wide association studies (GWASs) in additional independent cohorts. Replication studies were performed on Han Chinese cohorts from Hong Kong and Anhui, involving a total of 2,269 cases and 5,073 controls. We identified a missense variant in IRF3 (rs7251) reaching genome-wide significance through a joint analysis of GWAS and replication data (OR = 0.876, P = 4.40E-08). A significant correlation was observed between rs7251 and lupus nephritis (LN) by subphenotype stratification (OR = 0.785, P = 0.0128). IRF3 is a key molecule in type I interferon production upon nucleic acid antigen stimulations and may inhibit regulatory T cell differentiation. Further elucidation of the mechanism of this association could help us better understand the pathogenesis of SLE.

Review: transcriptome and trans-omics analysis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE), which was recognized as a defined clinical entity more than 100 years ago, is an archetype for systemic autoimmune diseases. The 10-year survival of SLE patients has shown dramatic improvement during the last half-century. However, SLE patients receiving long-term prednisone therapy are at high risk of morbidity due to organ damage. Identification of key immune pathways is mandatory to develop a suitable therapy and to stratify patients based on their responses to therapy. Recently developed transcriptome and omic analyses have revealed a number of immune pathways associated with systemic autoimmunity. In addition to type I interferon, plasmablast and neutrophil signatures demonstrate associations with the SLE phenotype. Systematic investigations of these findings enable us to understand and stratify SLE according to the clinical and immunological features.

Associations of FKBP4 and FKBP5 gene polymorphisms with disease susceptibility, glucocorticoid efficacy, anxiety, depression, and health-related quality of life in systemic lupus erythematosus patients

OBJECTIVES

To explore the associations of FKBP4 and FKBP5 gene polymorphisms with disease susceptibility, glucocorticoid (GC) efficacy, anxiety, depression, and health-related quality of life (HRQOL) in systemic lupus erythematosus (SLE) patients.

METHODS

All subjects were collected from the First and the Second Affiliated Hospital of Anhui Medical University in Hefei, China, during 2011 to 2015. In the case-control study, 541 SLE patients and 543 controls were recruited. In the follow-up study, 466 patients completed the 12-week follow-up and then were divided into GC-sensitive and GC-insensitive groups. Genotyping was determined using Multiplex SNaPshot technique. Data were analyzed using chi-square test and univariate and multivariate logistic regression analyses.

RESULTS

rs4713904, rs9368878, and rs7757037 of FKBP5 were associated with depression in SLE patients (rs4713904, P_BH = 0.037; rs9368878, P_BH = 0.001; rs7757037, P_BH = 0.003). Moreover, rs4713904 was associated with GC efficacy in males with SLE (P_BH = 0.011). The rs755658 of FKBP5 was associated with improvement in social function (P_BH = 0.022) and mental component summary (P_BH = 0.028). The rs4713907 of FKBP5 was related to improvement in total score of SF-36, bodily pain, and mental component summary score (all P_BH = 0.018). Furthermore, the rs12582595 of FKBP4 was correlated with general health improvement (P_BH = 0.033). No associations were seen between FKBP4/FKBP5 gene polymorphisms and SLE susceptibility and anxiety.

CONCLUSIONS

FKBP5 gene polymorphisms may be associated with depression and GC efficacy of SLE patients. Meanwhile, the genetic polymorphisms of FKBP4 and FKBP5 genes may be associated with HRQOL improvement in SLE patients. Key Points • FKBP5 gene polymorphisms were associated with depression of SLE patients. • FKBP5 gene polymorphisms were associated with GC efficacy of SLE patients. • FKBP5 gene polymorphisms were associated with HRQOL improvement in SLE patients. • FKBP4 gene polymorphisms were associated with HRQOL improvement in SLE patients.

Are lupus animal models useful for understanding and developing new therapies for human SLE?

Systemic lupus erythematosus is a systemic autoimmune disease driven by a complex combination of genetic, environmental, and other immunoregulatory factors. The development of targeted therapies is complicated by heterogeneous clinical manifestations, varying organ involvement, and toxicity. Despite advances in understanding the mechanisms contributing to SLE, only one biologic drug, belimumab, is FDA-approved. The identification and development of potential therapies have largely been driven by studies in lupus animal models. Therefore, direct comparison of both the therapeutic and immunological findings in human and murine SLE studies is critical and can reveal important insights into indeed how useful and relevant are murine studies in SLE drug development. Studies involving belimumab, mycophenolate mofetil, abatacept, rituximab, and anti-interferon strategies generally demonstrated analogous findings in the attenuation of SLE manifestations and modulation of select immune cell populations in human and murine SLE. While further basic and translational studies are needed to identify SLE patient subsets likely to respond to particular therapeutic modalities and in dissecting complex mechanisms, we believe that despite some inherent weaknesses SLE mouse models will continue to be integral in developing targeted SLE therapies.

A highly potent lymphatic system-targeting nanoparticle cyclosporine prevents glomerulonephritis in mouse model of lupus

Cyclosporine A (CsA) is a powerful immunosuppressant, but it is an ineffective stand-alone treatment for systemic lupus erythematosus (SLE) due to poor target tissue distribution and renal toxicity. We hypothesized that CD71 (transferrin receptor 1)-directed delivery of CsA to the lymphatic system would improve SLE outcomes in a murine model. We synthesized biodegradable, ligand-conjugated nanoparticles [P2Ns-gambogic acid (GA)] targeting CD71. GA conjugation substantially increased nanoparticle association with CD3⁺ or CD20⁺ lymphocytes and with intestinal lymphoid tissues. In orally dosed MRL-lpr mice, P2Ns-GA-encapsulated CsA increased lymphatic drug delivery 4- to 18-fold over the ligand-free formulation and a commercial CsA capsule, respectively. Improved lymphatic bioavailability of CsA was paralleled by normalization of anti-double-stranded DNA immunoglobulin G titer, plasma cytokines, and glomerulonephritis. Thus, this study demonstrates the translational potential of nanoparticles that enhance the targeting of lymphatic tissues, transforming CsA into a potent single therapeutic for SLE.

Urinary activated leukocyte cell adhesion molecule as a novel biomarker of lupus nephritis histology

Background

Lupus nephritis (LN) is one of the most severe complications of SLE patients. We aim to validate urinary ALCAM as a biomarker in predicting renal disease histpathology in a Chinese lupus cohort.

Methods

In this cross-sectional study, a total of 256 patients and controls were recruited. Urinary levels of ALCAM were determined by ELISA. Renal histopathology was reviewed by an experienced renal pathologist.

Results

Urinary ALCAM levels were significantly increased in active LN patients when compared to active SLE patients without renal involvement (p < 0.001), inactive LN patients (p = 0.023), inactive SLE patients without renal involvement (p < 0.001), and healthy controls (p < 0.001). Correlation analysis revealed a positive correlation between urinary ALCAM and general disease activity—SLEDAI score (r = 0.487, p < 0.001), as well as renal disease activity—rSLEDAI (r = 0.552, p < 0.001) and SLICC RAS (r = 0.584, p < 0.001). Urinary ALCAM also correlated with lab parameters including 24-h urine protein, hemoglobin, and complement 3. Moreover, urinary ALCAM levels were significantly increased in class III and IV (proliferative) LN as compared to those in class V (membranous) LN. It outperformed conventional biomarkers (anti-dsDNA antibody, C3, C4, proteinuria) in discriminating the two groups of LN. On renal histopathology, urinary ALCAM levels correlated positively with activity index (r = 0.405, p < 0.001) but not chronicity index (r = 0.079, p = 0.448).

Conclusion

Urinary ALCAM is a potential biomarker for predicting renal pathology activity in LN and may serve as a valuable surrogate marker of renal histopathology.

Comprehensive bioinformatics analysis of mRNA expression profiles and identification of a miRNA-mRNA network associated with lupus nephritis

OBJECTIVE

Lupus nephritis (LN) is one of the serious complications of systemic lupus erythematosus. The aim of this study was to identify core genes and pathways involved in the pathogenesis of LN.

METHODS

We screened differentially expressed genes (DEGs) in LN patients using mRNA expression profile data from the Gene Expression Omnibus. The functional and pathway enrichment analysis of DEGs was performed utilizing the Database for annotation, Visualization and Integrated Discovery. Target genes with differentially expressed miRNAs (DEMIs) were predicted using the miRTarBase database, and the intersection between these target genes and DEGs was selected to be studied further.

RESULTS

In total, 107 common DEGs (CDEGs) were identified from the Tub_LN group and Glom_LN group, and 66 DEMIs were identified. Fifty-three hub genes and two significant modules were identified from the protein-protein interaction (PPI) network, and a miRNA-mRNA network was constructed. The CDEGs, module genes in the PPI network and genes intersecting with the CDEGs and target genes of DEMIs were all associated with the PI3K-Akt signalling pathway.

CONCLUSION

In summary, this study reveals some crucial genes and pathways potentially involving in the pathogenesis of LN. These findings provide a new insight for the research and treatment of LN.

Complement Deficiencies Result in Surrogate Pathways of Complement Activation in Novel Polygenic Lupus-like Models of Kidney Injury

Lupus nephritis (LN) is a major contributor to morbidity and mortality in lupus patients, but the mechanisms of kidney damage remain unclear. In this study, we introduce, to our knowledge, novel models of LN designed to resemble the polygenic nature of human lupus by embodying three key genetic alterations: the Sle1 interval leading to anti-chromatin autoantibodies; Mfge8-/- , leading to defective clearance of apoptotic cells; and either C1q-/- or C3-/- , leading to low complement levels. We report that proliferative glomerulonephritis arose only in the presence of all three abnormalities (i.e., in Sle1.Mfge8 -/- C1q -/- and Sle1.Mfge8 -/- C3 -/- triple-mutant [TM] strains [C1q -/-TM and C3-/- TM, respectively]), with structural kidney changes resembling those in LN patients. Unexpectedly, both TM strains had significant increases in autoantibody titers, Ag spread, and IgG deposition in the kidneys. Despite the early complement component deficiencies, we observed assembly of the pathogenic terminal complement membrane attack complex in both TM strains. In C1q-/- TM mice, colocalization of MASP-2 and C3 in both the glomeruli and tubules indicated that the lectin pathway likely contributed to complement activation and tissue injury in this strain. Interestingly, enhanced thrombin activation in C3-/- TM mice and reduction of kidney injury following attenuation of thrombin generation by argatroban in a serum-transfer nephrotoxic model identified thrombin as a surrogate pathway for complement activation in C3-deficient mice. These novel mouse models of human lupus inform the requirements for nephritis and provide targets for intervention.

Application of principal component analysis and logistic regression model in lupus nephritis patients with clinical hypothyroidism

Background

Previous studies indicate that the prevalence of hypothyroidism is much higher in patients with lupus nephritis (LN) than in the general population, and is associated with LN’s activity. Principal component analysis (PCA) and logistic regression can help determine relevant risk factors and identify LN patients at high risk of hypothyroidism; as such, these tools may prove useful in managing this disease.

Methods

We carried out a cross-sectional study of 143 LN patients diagnosed by renal biopsy, all of whom had been admitted to Xiangya Hospital of Central South University in Changsha, China, between June 2012 and December 2016. The PCA–logistic regression model was used to determine the influential principal components for LN patients who have hypothyroidism.

Results

Our PCA–logistic regression analysis results demonstrated that serum creatinine, blood urea nitrogen, blood uric acid, total protein, albumin, and anti-ribonucleoprotein antibody were important clinical variables for LN patients with hypothyroidism. The area under the curve of this model was 0.855.

Conclusion

The PCA–logistic regression model performed well in identifying important risk factors for certain clinical outcomes, and promoting clinical research on other diseases will be beneficial. Using this model, clinicians can identify at-risk subjects and either implement preventative strategies or manage current treatments.

A unique thymus-derived regulatory T cell subset associated with systemic lupus erythematosus

Background

Foxp3 is a marker for regulatory T cells (Treg cells), but recent studies have shown the plasticity and heterogeneity of CD4⁺Foxp3⁺ T cells. This study aimed to examine the phenotype and function of circulating CD4⁺Foxp3⁺ T cells in patients with systemic lupus erythematosus (SLE).

Methods

We enrolled 47 patients with SLE, 31 with organ-specific autoimmune diseases (15 with multiple sclerosis and 16 with primary immune thrombocytopenia), and 19 healthy subjects. Peripheral blood mononuclear cells were used to evaluate the proportion and phenotype of CD4⁺Foxp3⁺ cells using multicolor flow cytometry, the status of the Treg-specific demethylated region (TSDR) of the foxp3 gene by methylation-specific polymerase chain reaction, and the immunoregulatory function of CD4⁺CD25⁺ cells by allogeneic mixed lymphocyte reaction. Immunohistochemistry of renal biopsy specimens obtained from 6 patients with lupus nephritis and 5 with IgA nephropathy was conducted to detect IL-17A-expressing CD4⁺Foxp3⁺ cells.

Results

CD4⁺Foxp3⁺ T cells were increased in SLE patients compared with organ-specific autoimmune disease controls or healthy controls. Circulating CD4⁺Foxp3⁺ T cells were correlated with the disease activity of SLE. The increased CD4⁺Foxp3⁺ T cells in active SLE patients were mainly derived from thymus-derived Treg (tTreg) cells, as determined by a demethylated TSDR status, and represented a unique phenotype, upregulated expression of CD49d, CD161, and IL-17A, with immunosuppressive ability comparable to that of healthy controls. Finally, CD4⁺Foxp3⁺IL-17A⁺ cells were infiltrated into the renal biopsy specimens of patients with active lupus nephritis.

Conclusions

A unique tTreg subset with dichotomic immunoregulatory and T helper 17 phenotypes is increased in the circulation of SLE patients and may be involved in the pathogenic process of SLE.

Association of Urine sCD163 With Proliferative Lupus Nephritis, Fibrinoid Necrosis, Cellular Crescents and Intrarenal M2 Macrophages

CD163 is a marker for alternatively activated macrophages, which have been implicated in the pathogenesis of lupus nephritis (LN). In our preliminary screening of urine proteins in LN, urine soluble CD163 (sCD163) was significantly elevated in patients with active LN. To evaluate the potential of sCD163 as a biomarker in LN, urine sCD163 was assayed in patients with active LN, active non-renal lupus patients (ANR), inactive SLE and healthy controls (HC), using ELISA and normalized to urine creatinine. The correlation of urine sCD163 with clinical parameters and renal pathological attributes was further investigated in LN patients with concurrent renal biopsies. A total of 228 SLE patients and 56 HC were included from three cohorts. Results demonstrated that urine sCD163 was significantly elevated in active LN when compared with HC, inactive SLE, or ANR in African-American, Caucasian and Asian subjects (all P < 0.001). In LN patients with concurrent renal biopsies, urine sCD163 was significantly increased in patients with proliferative LN when compared with non-proliferative LN (P < 0.001). Urine sCD163 strongly correlated with SLEDAI, rSLEDAI, activity index (AI) of renal pathology, fibrinoid necrosis, cellular crescents, and interstitial inflammation on biopsies (all P < 0.01). Macrophages, particularly M2 macrophages, the predominant cells expressing CD163 within LN kidneys, represented a potential source of elevated urine sCD163, based on single-cell RNA sequencing analysis. To conclude, urine sCD163 discriminated patients with active LN from other SLE patients and was significantly elevated in proliferative LN. It strongly correlated with concurrent AI and several specific pathological attributes, demonstrating its potential in predicting renal pathology.

Promises of Big Data and Artificial Intelligence in Nephrology and Transplantation

Kidney diseases form part of the major health burdens experienced all over the world. Kidney diseases are linked to high economic burden, deaths, and morbidity rates. The great importance of collecting a large quantity of health-related data among human cohorts, what scholars refer to as “big data”, has increasingly been identified, with the establishment of a large group of cohorts and the usage of electronic health records (EHRs) in nephrology and transplantation. These data are valuable, and can potentially be utilized by researchers to advance knowledge in the field. Furthermore, progress in big data is stimulating the flourishing of artificial intelligence (AI), which is an excellent tool for handling, and subsequently processing, a great amount of data and may be applied to highlight more information on the effectiveness of medicine in kidney-related complications for the purpose of more precise phenotype and outcome prediction. In this article, we discuss the advances and challenges in big data, the use of EHRs and AI, with great emphasis on the usage of nephrology and transplantation.

Associations of four common VDR polymorphisms with rheumatoid arthritis and systemic lupus erythematosus: evidence from a meta-analysis

Associations of polymorphisms in vitamin D receptor ( VDR) with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) have already been explored by many studies. The aim of this meta-analysis was to better clarify associations between polymorphisms in VDR and RA/SLE by combing the results of all relevant studies. Eligible studies were searched from Pubmed, Embase, WOS and CNKI. We used Review Manager to combine the results of eligible studies. Thirty-seven studies were included in this meta-analysis. VDR rs1544410 (recessive comparison: odds ratio (OR) = 1.36, 95% confidence interval (CI) 1.06–1.76; over-dominant comparison: OR = 0.81, 95% CI 0.71–0.93) and rs731236 (over-dominant comparison: OR = 0.77, 95% CI 0.63–0.94) polymorphisms were found to be significantly associated with RA in overall combined analyses. Besides, VDR rs1544410 (dominant comparison: OR = 0.61, 95% CI 0.46–0.82; over-dominant comparison: OR = 1.45, 95% CI 1.16–1.81; allele comparison: OR = 0.75, 95% CI 0.62–0.92), rs2228570 (dominant comparison: OR = 0.58, 95% CI 0.50–0.67; recessive comparison: OR = 1.57, 95% CI 1.21–2.03; allele comparison: OR = 0.69, 95% CI 0.60–0.80) and rs731236 (dominant comparison: OR = 0.69, 95% CI 0.50–0.96; allele comparison: OR = 0.80, 95% CI 0.70–0.90) polymorphisms were also found to be significantly associated with SLE in overall combined analyses. Subgroup analyses revealed that significant associations for VDR polymorphisms and RA/SLE were mainly driven by Asians. Collectively, this meta-analysis proved that VDR rs7975232, rs1544410, rs2228570 and rs731236 polymorphisms may confer susceptibility to RA and SLE, especially for Asians.

The presence of IFL3/4 rs12979860 C allele influences the in vitro IP-10 production by mononuclear cells from patients with systemic lupus erythematosus

OBJECTIVE

To explore whether the IFNL3/4 rs12979860 genotype may influence serum levels or production of interferon-inducible protein-10 (IP-10) by peripheral blood mononuclear cells from patients with systemic lupus erythematosus (SLE).

METHODS

Sixty-six patients with SLE and 22 healthy blood donors (controls) were included. The IFNL3/4 rs12979860 polymorphism was genotyped by real-time polymerase chain reaction. IP-10 levels in sera supernatants of IFNα stimulated peripheral blood mononuclear cells were measured by enzime-linked immunosorbent assay.

RESULTS

Allelic frequencies were CC (29%), CT (52%) and TT (20%) in SLE, and CC (32%), CT (41%) and TT (27%) in healthy controls. Median serum IP-10 levels were higher in SLE patients than in controls (190.8 versus 118.1 pg/ml; p < 0.001), particularly in those with high disease activity (278.5 versus 177.2 pg/ml; p = 0.037). However, serum IP-10 levels were not influenced by IFNL3/4 genotypes. Higher IP-10 production by peripheral blood mononuclear cells was found in both SLE patients (median 519.3 versus 207.6 pg/ml; p = 0.012) and controls (median 454.0 versus 201.7 pg/ml; p = 0.034) carrying the IFNL3/4 C allele compared with carriers of the T allele.

CONCLUSIONS

Although IFNL3/4 rs12979860 allele C does not appear to influence serum IP-10 levels in SLE, it plays an important role in the production of IP-10 by peripheral blood mononuclear cells after IFNα stimulation.

Long-term Safety and Effectiveness of Tacrolimus in Patients With Lupus Nephritis: 5-year Interim Postmarketing Surveillance Study in Japan (TRUST)

OBJECTIVE

To assess the long-term safety and effectiveness of tacrolimus for treating lupus nephritis (LN) in the real-world clinical setting.

METHODS

This is an ongoing, open-label, noncomparative, observational, postmarketing surveillance study conducted across 275 sites in Japan. Registered patients with LN were followed for 10 years. Here we report data relating to 5 years of tacrolimus maintenance therapy at the interim data cutoff in August 2016.

RESULTS

Of 1395 registered patients, 1355 received tacrolimus maintenance therapy for LN and provided safety data. The most common serious adverse drug reactions (ADR) included pneumonia (1.1%), herpes zoster (1.0%), cellulitis (1.0%), and diabetes mellitus (1.0%). ADR occurred mainly within the first 28 weeks of tacrolimus treatment, and no marked increase was observed during the follow-up period. Subgroup analyses suggested that risk factors for commonly observed ADR associated with tacrolimus included inpatient management, LN disease severity, increasing age, abnormal renal or hepatic function, and comorbid or previous disease. The cumulative rate of progression to renal failure (based on the attending physician's assessment) was 0.8% at Year 1 and 6.6% at Year 5. Cumulative relapse rates were 7.8% and 30.6%, respectively. Urine protein:creatinine ratio, serum anti-dsDNA antibody levels, complement C3 levels, and steroid-sparing effects were all significantly improved from 4 weeks after tacrolimus treatment initiation (P < 0.001) and were sustained over 5 years.

CONCLUSION

Long-term tacrolimus maintenance treatment over 5 years in the real-world clinical setting was well tolerated and effective in a large population of patients with LN (www.ClinicalTrials.gov: NCT01410747).

Serum GlycA Level is Elevated in Active Systemic Lupus Erythematosus and Correlates to Disease Activity and Lupus Nephritis Severity

Objective: Reliable non-invasive biomarkers are needed to assess disease activity and prognosis in patients with systemic lupus erythematosus (SLE). Glycoprotein acetylation (GlycA), a novel biomarker for chronic inflammation, has been reported to be increased in several inflammatory diseases. We investigated the relevance of serum GlycA in SLE patients exhibiting various levels of activity and severity, especially with regards to renal involvement. Methods: Serum GlycA was measured by nuclear magnetic resonance spectroscopy in samples from well characterized SLE patients and from both healthy controls and patients with other kidney diseases (KD). Disease activity was evaluated using the Systemic Lupus Erythematosus Activity Index 2000 (SLEDAI-2K). Renal severity was assessed by kidney biopsy. Results: Serum GlycA was elevated in active (n = 105) compared to quiescent SLE patients (n = 39, p < 10⁻⁶), healthy controls (n = 20, p = 0.009) and KD controls (n = 21, p = 0.04), despite a more severely altered renal function in the latter. GlycA level was correlated to disease activity (SLEDAI-2K, ρ = 0.37, p < 10⁻⁴), C-reactive protein, neutrophil count, triglyceride levels, proteinuria and inversely to serum albumin. In patients with biopsy-proven lupus nephritis (LN), GlycA levels were higher in proliferative (n = 26) than non-proliferative LN (n = 10) in univariate analysis (p = 0.04), and was shown to predict proliferative LN independently of renal parameters, immunological activity, neutrophil count and daily corticosteroid dosage by multivariate analysis (p < 5 × 10⁻³ for all models). In LN patients with repeated longitudinal GlycA measurement (n = 11), GlycA varied over time and seemed to peak at the time of the flare. Conclusions: GlycA, as a summary measure for different inflammatory processes, could be a valuable biomarker of disease activity in patients with SLE, and a non-invasive biomarker of pathological severity in the context of LN.

Orofacial manifestations and dental management of systemic lupus erythematosus: A review

Systemic lupus erythematosus (SLE) is an autoimmune multisystem disease with numerous clinical manifestations. There is no consensus about the ideal oral management for this group of patients to date. This review aimed to describe the broad spectrum of orofacial and clinical manifestations and their therapeutic approaches. Studies concerning orofacial manifestations of SLE and dental treatment modalities were selected by a literature search (1978-2019) using Google Scholar, PubMed/MEDLINE electronic databases. The initial search strategy provided a total of 129 articles, and of these, 30 were included for qualitative synthesis. The reviewed studies revealed that SLE patients are more at risk of compromised oral and dental health exhibiting increased risk of periodontal diseases and temporomandibular joint disorders. The use of systemic drugs especially immunosuppressive and anticoagulants in SLE patients may also influence their oral management. Results emphasize the need to carry out, at an early stage of the disease, an appropriate oral management of these patients to improve oral health-related quality of life and to prevent the need of more invasive therapeutics. A multidisciplinary approach is needed for dental and medical management of such patients.

B Cell Endosomal RAB7 Promotes TRAF6 K63 Polyubiquitination and NF-κB Activation for Antibody Class-Switching

Upon activation by CD40 or TLR signaling, B lymphocytes activate NF-κB to induce activation-induced cytidine deaminase and, therefore, Ig class switch DNA recombination, as central to the maturation of the Ab and autoantibody responses. In this study, we show that NF-κB activation is boosted by colocalization of engaged immune receptors, such as CD40, with RAB7 small GTPase on mature endosomes, in addition to signals emanating from the receptors localized on the plasma membrane, in mouse B cells. In mature endosomes, RAB7 directly interacts with TRAF6 E3 ubiquitin ligase, which catalyzes K63 polyubiquitination for NF-κB activation. RAB7 overexpression in Cd19+/creRosa26fl-STOP-fl-Rab7 mouse B cells upregulates K63 polyubiquitination activity of TRAF6, enhances NF-κB activation and activation-induced cytidine deaminase induction, and boosts IgG Ab and autoantibody levels. This, together with the extensive intracellular localization of CD40 and the strong correlation of RAB7 expression with NF-κB activation in mouse lupus B cells, shows that RAB7 is an integral component of the B cell NF-κB activation machinery, likely through interaction with TRAF6 for the assembly of "intracellular membrane signalosomes."

Modulation of iron homeostasis with hepcidin ameliorates spontaneous murine lupus nephritis

Lupus nephritis is the end organ manifestation of systemic lupus erythematosus. Iron metabolism and its master regulator, hepcidin, are known to regulate cell proliferation and inflammation, but their direct role in the pathophysiology of lupus nephritis remains under-investigated. Exogenous hepcidin reduced the severity of lupus nephritis in MRL/lpr mice, a preclinical model of spontaneous systemic lupus erythematosus without worsening anemia of inflammation. Hepcidin treatment reduced renal iron accumulation, systemic and intrarenal cytokines, and renal immune cell infiltration, independent of glomerular immune complex deposits and circulating autoantibodies. Hepcidin increased renal H-ferritin (a ferroxidase), reduced expression of free iron dependent DNA synthesis enzymes, Ribonucleotide Reductase 1 and 2, and intra-renal macrophage proliferation. These findings were recapitulated in vitro upon treatment of macrophages with hepcidin and murine colony stimulation factor-1. Furthermore, hepcidin-treated macrophages secreted less IL-1β and IL-6 upon stimulation with the TLR3 agonist polyinosine-polycytidylic acid. Of clinical relevance, hepcidin reduced progression and severity of nephritis in old mice with established systemic autoimmunity and overt proteinuria, highlighting its therapeutic potential. Thus, our findings provide a proof-of-concept that targeting cellular iron metabolism with hepcidin represents a promising therapeutic strategy in lupus nephritis.

CTLA-4: From mechanism to autoimmune therapy

CD28 and CTLA-4 are both important stimulatory receptors for the regulation of T cell activation. Because receptors share common ligands, B7.1 and B7.2, the expression and biological function of CTLA-4 is important for the negative regulation of T cell responses. Therefore, elimination of CTLA-4 can result in the breakdown of immune tolerance and the development of several diseases such as autoimmunity. Inhibitory signals of CTLA-4 suppress T cell responses and protect against autoimmune diseases in many ways. In this review, we summarize the structure, expression and signaling pathway of CTLA-4. We also highlight how CTLA-4 defends against potentially self-reactive T cells. Finally, we discuss how the CTLA-4 regulates a number of autoimmune diseases that indicate manipulation of this inhibitory molecule is a promise as a strategy for the immunotherapy of autoimmune diseases.

Lupus nephritis

Lupus nephritis (LN) is a form of glomerulonephritis that constitutes one of the most severe organ manifestations of the autoimmune disease systemic lupus erythematosus (SLE). Most patients with SLE who develop LN do so within 5 years of an SLE diagnosis and, in many cases, LN is the presenting manifestation resulting in the diagnosis of SLE. Understanding of the genetic and pathogenetic basis of LN has improved substantially over the past few decades. Treatment of LN usually involves immunosuppressive therapy, typically with mycophenolate mofetil or cyclophosphamide and with glucocorticoids, although these treatments are not uniformly effective. Despite increased knowledge of disease pathogenesis and improved treatment options, LN remains a substantial cause of morbidity and death among patients with SLE. Within 10 years of an initial SLE diagnosis, 5-20% of patients with LN develop end-stage kidney disease, and the multiple comorbidities associated with immunosuppressive treatment, including infections, osteoporosis and cardiovascular and reproductive effects, remain a concern. Clearly, early and accurate diagnosis of LN and prompt initiation of therapy are of vital importance to improve outcomes in patients with SLE.

Type II but Not Type I IFN Signaling Is Indispensable for TLR7-Promoted Development of Autoreactive B Cells and Systemic Autoimmunity

TLR7 is associated with development of systemic lupus erythematosus (SLE), but the underlying mechanisms are incompletely understood. Although TLRs are known to activate type I IFN (T1IFN) signaling, the role of T1IFN and IFN-γ signaling in differential regulation of TLR7-mediated Ab-forming cell (AFC) and germinal center (GC) responses, and SLE development has never been directly investigated. Using TLR7-induced and TLR7 overexpression models of SLE, we report in this study a previously unrecognized indispensable role of TLR7-induced IFN-γ signaling in promoting AFC and GC responses, leading to autoreactive B cell and SLE development. T1IFN signaling in contrast, only modestly contributed to autoimmune responses and the disease process in these mice. TLR7 ligand imiquimod treated IFN-γ reporter mice show that CD4⁺ effector T cells including follicular helper T (Tfh) cells are the major producers of TLR7-induced IFN-γ. Transcriptomic analysis of splenic tissues from imiquimod-treated autoimmune-prone B6.Sle1b mice sufficient and deficient for IFN-γR indicates that TLR7-induced IFN-γ activates multiple signaling pathways to regulate TLR7-promoted SLE. Conditional deletion of Ifngr1 gene in peripheral B cells further demonstrates that TLR7-driven autoimmune AFC, GC and Tfh responses and SLE development are dependent on IFN-γ signaling in B cells. Finally, we show crucial B cell-intrinsic roles of STAT1 and T-bet in TLR7-driven GC, Tfh and plasma cell differentiation. Altogether, we uncover a nonredundant role for IFN-γ and its downstream signaling molecules STAT1 and T-bet in B cells in promoting TLR7-driven AFC, GC, and SLE development whereas T1IFN signaling moderately contributes to these processes.

Dysregulated Fcγ receptor IIa-induced cytokine production in dendritic cells of lupus nephritis patients

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown etiology. One of the key factors associated with SLE pathogenesis is excessive production of type I interferons (IFNs). This could result from increased activation of type I IFN-stimulating pathways, but also from decreased activation of type I IFN-inhibitory pathways. Recently, we have identified that immunoglobulin (Ig)G immune complexes strongly inhibit type I IFN production in healthy individuals by inhibitory signaling through Fcγ receptor IIa (FcγRIIa) on dendritic cells (DCs). Because, in SLE patients, immune complexes are characteristically present, we assessed whether FcγR-induced suppression of type I IFN is functional in DCs of SLE patients. We divided the SLE patients into one group without, and one group with, previous major organ involvement, for which we chose nephritis as a prototypical example. We show that DCs of lupus nephritis patients displayed impaired FcγR-mediated type I IFN inhibition compared to SLE patients without major organ involvement or healthy controls. We verified that this impaired type I IFN inhibition was not related to differences in disease activity, medication, FcγRIIa expression or expression of IFN regulatory transcription factors (IRF)1 and IRF5. In addition, we identified that DCs of lupus nephritis patients show increased FcγR-induced interleukin (IL)-1β production, which is another important cytokine that promotes kidney inflammation. Taken together, these data indicate that DCs of lupus nephritis patients display altered FcγR-mediated regulation of cytokine production, resulting in elevated levels of type I IFN and IL-1β. This dysregulation may contribute to the development of nephritis in SLE patients.

Population-Specific Patterns of Epigenetic Defects in the B Cell Lineage in Patients With Systemic Lupus Erythematosus

OBJECTIVE

To determine the stage of B cell development at which a systemic lupus erythematosus (SLE)-associated DNA methylation signature originates in African American (AA) and European American (EA) subjects, and to assess whether epigenetic defects in B cell development patterns could be predictive of SLE status in individual and mixed immune cell populations.

METHODS

B cells from AA patients (n = 31) and EA patients (n = 49) with or without SLE were sorted using fluorescence-activated cell sorting into 5 B cell subsets. DNA methylation, measured at ~460,000 CpG sites, was interrogated in each subset. Enrichment analysis of transcription factor interaction at SLE-associated methylation sites was performed. A random forests algorithm was used to identify an epigenetic signature of SLE in the B cell subsets, which was then validated in an independent cohort of AA and EA patients and healthy controls.

RESULTS

Regression analysis across all B cell stages resulted in identification of 60 CpGs that reached genome-wide significance for SLE-associated methylation differences (P ≤ 1.07 × 10^-7 ). Interrogation of ethnicity-specific CpGs associated with SLE revealed a hypomethylated pattern that was enriched for interferon (IFN)-regulated genes and binding of EBF1 in AA patients (each P < 0.001). AA patients with SLE could be distinguished from healthy controls when the predictive model developed with the transitional B cell subset was applied to other B cell subsets (mean receiver operating characteristic [ROC] area under the curve [AUC] 0.98), and when applied to CD19+ pan-B cells (mean ROC AUC 0.95) and CD4+ pan-T cells (mean ROC AUC 0.97) from the independent validation cohort.

CONCLUSION

These results indicate that SLE-specific methylation patterns are ethnicity dependent. A pattern of epigenetic changes near IFN-regulated genes early in B cell development is a hallmark of SLE in AA female subjects. EBF1 binding sites are highly enriched for significant methylation changes, implying that this may be a potential regulator of SLE-associated epigenetic changes.

Sex differences in clinical presentation of systemic lupus erythematosus

Objective

Systemic lupus erythematosus (SLE) predominantly affects women, but previous studies suggest that men with SLE present a more severe disease phenotype. In this study, we investigated a large and well-characterized patient group with the aim of identifying sex differences in disease manifestations, with a special focus on renal involvement.

Methods

We studied a Swedish multi-center SLE cohort including 1226 patients (1060 women and 166 men) with a mean follow-up time of 15.8 ± 13.4 years. Demographic data, disease manifestations including ACR criteria, serology and renal histopathology were investigated. Renal outcome and mortality were analyzed in subcohorts.

Results

Female SLE patients presented more often with malar rash (p < 0.0001), photosensitivity (p < 0.0001), oral ulcers (p = 0.01), and arthritis (p = 0.007). Male patients on the other hand presented more often with serositis (p = 0.0003), renal disorder (p < 0.0001), and immunologic disorder (p = 0.04) by the ACR definitions. With regard to renal involvement, women were diagnosed with nephritis at an earlier age (p = 0.006), while men with SLE had an overall higher risk for progression into end-stage renal disease (ESRD) with a hazard ratio (HR) of 5.1 (95% CI, 2.1–12.5). The mortality rate among men with SLE and nephritis compared with women was HR 1.7 (95% CI, 0.8–3.8).

Conclusion

SLE shows significant sex-specific features, whereby men are affected by a more severe disease with regard to both renal and extra-renal manifestations. Additionally, men are at a higher risk of developing ESRD which may require an increased awareness and monitoring in clinical practice.

An Overview of the Intrinsic Role of Citrullination in Autoimmune Disorders

A protein undergoes many types of posttranslation modification. Citrullination is one of these modifications, where an arginine amino acid is converted to a citrulline amino acid. This process depends on catalytic enzymes such as peptidylarginine deiminase enzymes (PADs). This modification leads to a charge shift, which affects the protein structure, protein-protein interactions, and hydrogen bond formation, and it may cause protein denaturation. The irreversible citrullination reaction is not limited to a specific protein, cell, or tissue. It can target a wide range of proteins in the cell membrane, cytoplasm, nucleus, and mitochondria. Citrullination is a normal reaction during cell death. Apoptosis is normally accompanied with a clearance process via scavenger cells. A defect in the clearance system either in terms of efficiency or capacity may occur due to massive cell death, which may result in the accumulation and leakage of PAD enzymes and the citrullinated peptide from the necrotized cell which could be recognized by the immune system, where the immunological tolerance will be avoided and the autoimmune disorders will be subsequently triggered. The induction of autoimmune responses, autoantibody production, and cytokines involved in the major autoimmune diseases will be discussed.

Potential protein biomarkers for systemic lupus erythematosus determined by bioinformatics analysis

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disorder, and its pathogenesis in males and in cases without accompanying lupus nephritis (LN^-) is not fully understood. In this study, we identified 90 (82 up- and 8 downregulated) differentially expressed genes (DEGs) common to female LN^-, female LN⁺ and male LN⁺ using the GSE65391 and GSE49454 gene expression datasets from Gene Expression Omnibus database (GEO). The protein-protein interaction (PPI) network of 70 DEGs was constructed using STRING and cytoscape, and the Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the PPI network was significantly enriched in defense response to virus, cytosol, protein binding and measles. Sixteen hubgenes were identified from this PPI network, and Literature Mining Gene Networks molecular of GenCLiP 2.0 showed strong interaction between STAT1, DDX58 and IFIT1. Enrichment analysis of hubgenes in published literature showed the involvement of immune response and interferon-related genes in the pathogenesis of SLE. In addition, the transcription factors STAT1 & 2 and IRF6 & 9 had high Normalized Enrichment Score (NES). The 70 DEGs with PPI network and 16 hubgenes are potential biomarkers of SLE, and can help improve diagnosis and develop individualized therapies.

Differential Treatments Based on Drug-induced Gene Expression Signatures and Longitudinal Systemic Lupus Erythematosus Stratification

Systemic lupus erythematosus (SLE) is a heterogeneous disease with unpredictable patterns of activity. Patients with similar activity levels may have different prognosis and molecular abnormalities. In this study, we aimed to measure the main differences in drug-induced gene expression signatures across SLE patients and to evaluate the potential for clinical data to build a machine learning classifier able to predict the SLE subset for individual patients. SLE transcriptomic data from two cohorts were compared with drug-induced gene signatures from the CLUE database to compute a connectivity score that reflects the capability of a drug to revert the patient signatures. Patient stratification based on drug connectivity scores revealed robust clusters of SLE patients identical to the clusters previously obtained through longitudinal gene expression data, implying that differential treatment depends on the cluster to which patients belongs. The best drug candidates found, mTOR inhibitors or those reducing oxidative stress, showed stronger cluster specificity. We report that drug patterns for reverting disease gene expression follow the cell-specificity of the disease clusters. We used 2 cohorts to train and test a logistic regression model that we employed to classify patients from 3 independent cohorts into the SLE subsets and provide a clinically useful model to predict subset assignment and drug efficacy.

Nucleosomal dsDNA Stimulates APOL1 Expression in Human Cultured Podocytes by Activating the cGAS/IFI16-STING Signaling Pathway

APOL1 alleles G1 and G2 are associated with faster progression to lupus nephritis (LN)-associated end-stage renal disease (LN-ESRD) in African Americans. Increased levels of type I interferons (IFNs) and nucleosome-associated double-stranded DNA (dsDNA) fragments (nsDNA) are the hallmark of this disease. Here, we identify cyclic GMP-AMP synthase (cGAS) and interferon-inducible protein 16 (IFI16) as the major DNA sensors in human immortalized podocytes. We also show that nsDNA triggers the expression of APOL1 and IFNβ via IRF3 activation through the cGAS/IFI16-STING pathway. We demonstrate that maximal APOL1 expression also requires the activation of type I IFN receptor (IFNAR) and STAT1 signaling triggered by IFNβ produced in response to nsDNA, or by exogenous IFNβ. Finally, we show that STAT1 activation is sufficient to upregulate IFI16, subsequently boosting APOL1 expression through a positive feedback mechanism. Collectively, we find that nsDNA-induced APOL1 expression is mediated by both IFNβ-independent and dependent signaling pathways triggered by activation of the cGAS/IFI16-STING pathway. We propose that simultaneous inhibition of STING and the IFNAR-STAT1 pathway may attenuate IFI16 expression, reduce IFI16-cGAS cross-talk, and prevent excessive APOL1 expression in human podocytes in response to nsDNA.

When the balance is broken: X-linked gene dosage from two X chromosomes and female-biased autoimmunity

Women and men exhibit differences in innate and adaptive immunity, and women are more susceptible to numerous autoimmune disorders. Two or more X chromosomes increases the risk for some autoimmune diseases, and increased expression of some X-linked immune genes is frequently observed in female lymphocytes from autoimmune patients. Evidence from mouse models of autoimmunity also supports the idea that increased expression of X-linked genes is a feature of female-biased autoimmunity. Recent studies have begun to elucidate the correlation between abnormal X-chromosome inactivation (XCI), an essential mechanism female somatic cells use to equalize X-linked gene dosage between the sexes, and autoimmunity in lymphocytes. In this review, we highlight research describing overexpression of X-linked immunity-related genes and female-biased autoimmunity in both humans and mouse models, and make connections with our recent work elucidating lymphocyte-specific mechanisms of XCI maintenance that become altered in lupus patients.

Regulation and role of the transcription factor IRF5 in innate immune responses and systemic lupus erythematosus

The transcription factor interferon regulatory factor-5 (IRF5) plays an important role in innate immune responses via the TLR-MyD88 (Toll-like receptor - myeloid differentiation primary response 88) pathway. IRF5 is also involved in the pathogenesis of the autoimmune disease systemic lupus erythematosus (SLE). Recent studies have identified new regulators, both positive and negative, which act on IRF5 activation events in the TLR-MyD88 pathway such as post-translational modifications, dimerization and nuclear translocation. A model of the causal relationship between IRF5 activation and SLE pathogenesis proposes that a loss of the negative regulation of IRF5 causes its hyperactivation, resulting in hyperproduction of type I interferons and other cytokines, and ultimately in the development of SLE. Importantly, to our knowledge, all murine models of SLE studied thus far have shown that IRF5 is required for the pathogenesis of SLE-like diseases. During the development of SLE-like diseases, IRF5 plays key roles in various cell types, including dendritic cells and B cells. It is noteworthy that the onset of SLE-like diseases can be inhibited by reducing the activity or amount of IRF5 by half. Therefore, IRF5 is an important therapeutic target of SLE, and selective suppression of its activity and expression may potentially lead to the development of new therapies.

A phenotypic and genomics approach in a multi-ethnic cohort to subtype systemic lupus erythematosus

Systemic lupus erythematous (SLE) is a heterogeneous autoimmune disease in which outcomes vary among different racial groups. Here, we aim to identify SLE subgroups within a multiethnic cohort using an unsupervised clustering approach based on the American College of Rheumatology (ACR) classification criteria. We identify three patient clusters that vary according to disease severity. Methylation association analysis identifies a set of 256 differentially methylated CpGs across clusters, including 101 CpGs in genes in the Type I Interferon pathway, and we validate these associations in an external cohort. A cis-methylation quantitative trait loci analysis identifies 744 significant CpG-SNP pairs. The methylation signature is enriched for ethnic-associated CpGs suggesting that genetic and non-genetic factors may drive outcomes and ethnic-associated methylation differences. Our computational approach highlights molecular differences associated with clusters rather than single outcome measures. This work demonstrates the utility of applying integrative methods to address clinical heterogeneity in multifactorial multi-ethnic disease settings.

Novel functions of inactive rhomboid proteins in immunity and disease

iRhoms are related to a family of intramembrane serine proteinases called rhomboids but lack proteolytic activity. In mammals, there are two iRhoms, iRhom1 and iRhom2, which have similar domain structures and overlapping specificities as well as distinctive functions. These catalytically inactive rhomboids are essential regulators for the maturation and trafficking of the disintegrin metalloprotease ADAM17 from the endoplasmic reticulum to the cell surface, and are required for the cleavage and release of a variety of membrane-associated proteins, including the IL-6 receptor, l-selectin, TNF, and EGFR ligands. iRhom2-dependent regulation of ADAM17 function has been recently implicated in the development and progression of several autoimmune diseases including rheumatoid arthritis, lupus nephritis, as well as hemophilic arthropathy. In this review, we discuss our current understanding of iRhom biology, their implications in autoimmune pathologies, and their potential as therapeutic targets.

IL-6/p-BTK/p-ERK signaling mediates calcium phosphate-induced pruritus

Uremic pruritus with elevated levels of calcium phosphate (CaP) in skin is a common symptom in patients with chronic kidney disease (CKD). In this study, we demonstrate that intradermal injection of CaP into mice triggered scratching by up-regulating the IL-6 in skin and phosphorylation of ERKs in dorsal root ganglion (DRG) in a dose-dependent manner. IL-6 is essential because the CaP-induced up-regulation of phosphorylated (p)-ERK in DRG was considerably reduced in the IL-6 knockout mice. Microarray analysis in conjunction with real-time PCR revealed a higher mRNA expression of Bruton's tyrosine kinase (BTK) gene in DRG after CaP injection. The inhibition of BTK by ibrutinib noticeably diminish the CaP-induced up-regulation of IL-6 and p-ERK in mice. A high amount of IL-6 was detected in itchy skin and blood of patients with CKD. The expressions of p-BTK and p-ERK in DRG primary cells reached maximum levels at 1 and 10 min, respectively, after treatment of recombinant IL-6 and were significantly reduced by treatment of IL-6 along with ibrutinib. The mechanism by which the CaP-induced pruritus mediated by the IL-6/p-BTK/p-ERK signaling was revealed.-Keshari, S., Sipayung, A. D., Hsieh, C.-C., Su, L.-J., Chiang, Y.-R., Chang, H.-C., Yang, W.-C., Chuang, T.-H., Chen, C.-L., Huang, C.-M. IL-6/p-BTK/p-ERK signaling mediates calcium phosphate-induced pruritus.

Evaluation of genetic susceptibility between systemic lupus erythematosus and GRB2 gene

Multiple lines of evidence have shown that systemic lupus erythematosus (SLE) is attributable to both genetic and environmental factors. The product of GRB2 is a key factor in the activation of B cells and has been reported to be significantly associated with SLE in European populations. In the study, we aimed to investigate the relationship between GRB2 and SLE. A total of 1,710 Han Chinese women comprising 567 SLE patients and 1,143 controls were recruited to genotype 20 selected tagging SNPs. We tested the potential association between 13 clinical variables of SLE and the significant polymorphisms related to SLE. The eQTL data were extracted from the GTEx database to examine the functional consequences of the targeted SNPs. A significant association signal was identified between rs36023980 and SLE in both genotypic and allelic analyses (OR = 0.61, P = 0.0003). Complement inhibition was shown to be significantly associated with the genotypes of SNP rs36023980 in SLE patients (P_genotype = 0.003). Further stratification analyses showed that the genetic association signal of SNP rs36023980 on SLE could only be identified in cases with complement inhibition. SNP rs36023980 was also identified to be significantly associated with the expression of GRB2 in whole blood and sun-exposed skin. In conclusion, our findings confirm the results from the previous GWAS and are the first to report the association of GRB2 with SLE in Han Chinese population.

SNP rs4937333 in the miRNA-5003-Binding Site of the ETS1 3'-UTR Decreases ETS1 Expression

Mutations in and reduced expression of the ETS1 gene may be associated with systemic lupus erythematosus (SLE). Here, we report a replication study to investigate associations of eight ETS1 single-nucleotide polymorphisms in the 3′-untranslated region (3′-UTR) with SLE and their regulation of ETS1 expression in a study population. We found that the rs4937333 T allele was associated with a significantly increased risk of SLE (odds ratio: 1.800, 95% confidence interval: 1.02–3.157, P = 0.040) and with dramatically reduced levels of ETS1 in B cells from SLE subjects. Functionally, the rs4937333 T allele alters the binding affinity between miR-5003 and its ETS1 3′-UTR target, thus enhancing suppression of ETS1 expression. Furthermore, immunoglobulin M-secreting plasmacytes were significantly reduced among B cells with the rs4937333 C allele versus the T allele according to FACS and ELISA. Additionally, miR-5003 expression was higher in B cells than in T cells from SLE patients, and a negative correlation between miR-5003 and ETS1 was found, especially in B cells with the T allele. These findings suggest that the rs4937333 T allele is a risk factor for susceptibility to SLE in the studied population. The rs4937333 T allele may enhance the binding of miR-5003 to ETS1, which probably promotes the involvement of ETS1 in the differentiation of B cells into plasmacytes.

Single-cell RNA sequencing for the study of lupus nephritis

Single-cell RNA sequencing (scRNA-seq) has recently undergone rapid advances in the development of this technology, leading to high throughput and accelerating discovery in many biological systems and diseases. The single-cell resolution of the technique allows for the investigation of heterogeneity in cell populations, and the pinpointing of pathological populations contributing to disease. Here we review the development of scRNA-seq technology and the analysis that has evolved with the ever-increasing throughput. Finally, we highlight recent applications of scRNA-seq to understand the molecular pathogenesis of lupus and lupus nephritis.

Treatment with a CD40 Antagonist Antibody Reverses Severe Proteinuria and Loss of Saliva Production and Restores Glomerular Morphology in Murine Systemic Lupus Erythematosus

CD40 is a costimulatory receptor on APCs that is critical for the induction and maintenance of humoral and cell-mediated immunity. Accordingly, CD40 and its ligand, CD40L, have long been considered targets for the treatment of autoimmune diseases. We developed a rat/mouse chimeric anti-mouse CD40 antagonist mAb, 201A3, and evaluated its ability to alleviate murine lupus. Treatment of NZB/W-F₁ mice with 201A3 after the onset of severe proteinuria rapidly reversed established severe proteinuria and nephritis and largely restored normal glomerular and tubular morphology. This coincided with a normalization of the expression of genes associated with proteinuria and injury by kidney parenchymal cells. Anti-CD40 treatment also prevented and reversed loss of saliva production and sialadenitis. These effects on kidney and salivary gland function were confirmed using mice of a second strain, MRL/Mp-lpr/lpr, and extended to alleviating joint inflammation. Immunologically, anti-CD40 treatment disrupted multiple processes that contribute to the pathogenesis of systemic lupus erythematosus (SLE), including autoreactive B cell activation, T effector cell function in target tissues, and type I IFN production. This ability to disrupt disease-critical immunological mechanisms, to reverse glomerular and tubular injury at the cellular and gene expression levels, and to confer exceptional therapeutic efficacy suggests that CD40 is a central disease pathway in murine SLE. Thus, a CD40 antagonist Ab could be an effective therapeutic in the treatment of SLE.

Tubular cell and keratinocyte single-cell transcriptomics applied to lupus nephritis reveal type I IFN and fibrosis relevant pathways

The molecular and cellular processes that lead to renal damage and to the heterogeneity of lupus nephritis (LN) are not well understood. We applied single-cell RNA sequencing (scRNA-seq) to renal biopsies from patients with LN and evaluated skin biopsies as a potential source of diagnostic and prognostic markers of renal disease. Type I interferon (IFN) response signatures in tubular cells and in keratinocytes distinguished patients with LN from healthy control subjects. Moreover, a high IFN response signature and fibrotic signature in tubular cells were each associated with failure to respond to treatment. Analysis of tubular cells from patients with proliferative, membranous, and mixed LN indicated pathways relevant to inflammation and fibrosis, which offer insight into their histological differences. In summary, we applied scRNA-seq to LN to deconstruct its heterogeneity and identify novel targets for personalized approaches to therapy.

Patrolling monocytes promote the pathogenesis of early lupus-like glomerulonephritis

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with genetic and environmental contributions. Hallmarks of the disease are the appearance of immune complexes (IC) containing autoreactive Abs and TLR-activating nucleic acids, whose deposition in kidney glomeruli is suspected to promote tissue injury and glomerulonephritis (GN). Here, using a mouse model based on the human SLE susceptibility locus TNFAIP3-interacting protein 1 (TNIP1, also known as ABIN1), we investigated the pathogenesis of GN. We found that GN was driven by TLRs but, remarkably, proceeded independently of ICs. Rather, disease in 3 different mouse models and patients with SLE was characterized by glomerular accumulation of patrolling monocytes (PMos), a cell type with an emerging key function in vascular inflammation. Consistent with such function in GN, monocyte-specific deletion of ABIN1 promoted kidney disease, whereas selective elimination of PMos provided protection. In contrast to GN, PMo elimination did not protect from reduced survival or disease symptoms such as IC generation and splenomegaly, suggesting that GN and other inflammatory processes are governed by distinct pathogenic mechanisms. These data identify TLR-activated PMos as the principal component of an intravascular process that contributes to glomerular inflammation and kidney injury.

RNA-seq of circular RNAs identified circPTPN22 as a potential new activity indicator in systemic lupus erythematosus

Background

Circular RNAs (circRNAs) are possible biomarkers for many diseases, but the knowledge of circRNAs in the peripheral blood mononuclear cells (PBMCs) of patients with systemic lupus erythematosus (SLE) remains limited. This study aimed to assess the expression of circRNAs in PBMCs from patients with SLE and healthy individuals by RNA sequencing (RNA-seq).

Methods

In total, 128 circRNAs were significantly differentially expressed including 39 upregulated and 89 downregulated circRNAs in four new-onset SLE patients compared with three healthy controls. After verification of the four candidate circRNAs in 49 patients with SLE and 37 controls using quantitative real-time polymerase chain reaction (qRT-PCR) assays, a previously undescribed circRNA with potential translation activity, circPTPN22, was selected to confirm its clinical significance.

Results

Bioinformatics analysis demonstrated that the parent gene of circPTPN22 was protein tyrosine phosphatase non-receptor type 22 (PTPN22), a potent regulator of T cell activation. The downregulation of circPTPN22 in patients with SLE was strongly negatively correlated with their Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores. circRNA-miRNA-mRNA co-expression network analysis indicated a correlation between circPTPN22 and the miRNAs and mRNAs related to immunological regulation including the development of SLE. Patients with higher SLEDAI scores had lower circPTPN22 expression levels, and long-term hormone treatment significantly increased circPTPN22 levels. Receiver operating characteristic curve analysis indicated that circPTPN22 has good diagnostic value for SLE.

Conclusion

Our data demonstrated the aberrant expression of circRNAs in patients with SLE compared with healthy controls; circPTPN22 might function as a diagnostic and disease severity indicator in SLE.