Transcriptomic analysis uncovers novel synergistic mechanisms in combination therapy for lupus nephritis

Inhibition of receptor interacting protein kinase-1 (RIPK1) in the treatment of murine lupus

OBJECTIVE

Systemic lupus erythematosus (SLE) is a type of autoimmune disease that involves multiple organs involved as well as cytokine dysregulation. The treatment of SLE is still challenging due to the side effects of the different drugs used. Receptor-interacting protein kinase 1 (RIPK1) is a kinase involved in T cell homeostasis and autoinflammation. Although clinical trials have shown that RIPK1 inhibition exhibits significant efficacy in different autoimmune diseases, its role in SLE remains unclear.

METHODS

MRL/lpr lupus-prone mice received RIPK1 inhibitor ZJU37 or vehicle intraperitoneally for 10 weeks. A BM12-induced chronic graft-versus-host-disease (cGVHD) lupus-like model was introduced in RIPK1 D138N mice or C57BL/6 mice. Nephritis, serum autoantibody levels, dysregulation of adaptive immune response and cytokines were compared in treated and untreated mice.

RESULTS

ZJU37 alleviated the clinical features of the MRL/lpr mice including nephritis and anti-dsDNA antibody production. In addition, ZJU37 treatment reduced the proportion of double-negative T cells in the spleen and the cytokines of TNFα, IFN-γ, IL-6, IL-17 and IL-1β in the serum. Moreover, RIPK1 D138N mice were able to prevent the cGVHD lupus-like model from SLE attack, manifesting as anti-dsDNA antibody production, the proliferation of germinal centre B cells, plasma cells, and T follicular helper cells as well as IgG and C3 deposits in kidneys.

CONCLUSION

RIPK1 inhibition has a protective effect in the mouse model of SLE and can potentially become a new therapeutic target for SLE in humans.

Research trends and frontiers in lupus nephritis: a bibliometric analysis from 2012 to 2022

OBJECTIVES

Lupus nephritis is a prevalent renal manifestation of systemic lupus erythematosus (SLE) and represents a significant cause of morbidity and mortality associated with the disease. This study endeavors to undertake a meticulous bibliometric analysis of LN publications to comprehend the research hotspots and future directions.

METHODS

The literature on LN was acquired from the Web of Science Core Collection (WoSCC). Co-occurrence and cooperative relationship analysis of authors, institutions, countries, journals, references and keywords in the publication was performed through CiteSpace, VOSviewer and a bibliometric online analysis platform. The knowledge graphs were created, and clustering and emergence analyses were performed.

RESULTS

According to the search strategy, a total of 2077 publications related to lupus nephritis (LN) have been identified, with China being the largest contributor globally. The Ohio State University emerged as the most prolific institution. Lupus is the most cited and published journal. Jan J Weening and Brad Rovin were the most prolific and cocited authors. The current research focus revolved around the "nirp3 inflammasome," "biomarker," and "voclosporin". "international society," "thrombotic microangiopathy (TMA)," and "pathway" were identified to be future research hotpots by keyword burst analysis.

CONCLUSIONS

This bibliometric analysis summarizes for the first time the progress of LN research (2012-2022), and qualitatively and quantitatively evaluates the bibliometric information of LN research. There has been a steady increase in the scientific literature on LN over the past 11 years, with an average growth rate of 7.27%. In this field, researchers are primarily based in China and the United States. The pathogenic mechanisms, management strategies and prognostic outcomes of LN are acknowledged as prospective research hotspots. Bibliometrically, the research status and trends of LN publications may greatly assist and be a significant reference for future research in the area.

The effect of mycophenolate mofetil on podocytes in nephrotoxic serum nephritis

Mycophenolate mofetil (MMF) is applied in proteinuric kidney diseases, but the exact mechanism of its effect on podocytes is still unknown. Our previous in vitro experiments suggested that MMF can ameliorate podocyte damage via restoration of the Ca2+-actin cytoskeleton axis. The goal of this study was to characterize podocyte biology during MMF treatment in nephrotoxic serum (NTS) nephritis (NTN). NTN was induced in three-week old wild-type mice. On day 3, half of the mice were treated with MMF (100 mg/kgBW/d p.o.) for one week. On day 10, we performed proteomic analysis of glomeruli as well as super-resolution imaging of the slit diaphragm. For multiphoton imaging of Ca2+ concentration ([Ca2+]i), the experimental design was repeated in mice expressing podocyte-specific Ca2+ sensor. MMF ameliorated the proteinuria and crescent formation induced by NTS. We identified significant changes in the abundance of proteins involved in Ca2+ signaling and actin cytoskeleton regulation, which was further confirmed by direct [Ca2+]i imaging in podocytes showing decreased Ca2+ levels after MMF treatment. This was associated with a tendency to restoration of podocyte foot process structure. Here, we provide evidence that MPA has a substantial direct effect on podocytes. MMF contributes to improvement of [Ca2+]i and amelioration of the disorganized actin cytoskeleton in podocytes. These data extend the knowledge of direct effects of immunosuppressants on podocytes that may contribute to a more effective treatment of proteinuric glomerulopathies with the least possible side effects.

Fasudil compensates podocyte injury via CaMK4/Rho GTPases signal and actin cytoskeleton-dependent activation of YAP in MRL/lpr mice

Deposition of immune complexes in the glomerulus leads to irreversible renal damage in lupus nephritis (LN), of which podocyte malfunction arises earlier. Fasudil, the only Rho GTPases inhibitor approved in clinical settings, possesses well-established renoprotective actions; yet, no studies addressed the amelioration derived from fasudil in LN. To clarify, we investigated whether fasudil exerted renal remission in lupus-prone mice. In this study, fasudil (20 mg/kg) was intraperitoneally administered to female MRL/lpr mice for 10 weeks. We report that fasudil administration swept antibodies (anti-dsDNA) and attenuated systemic inflammatory response in MRL/lpr mice, accompanied by preserving podocyte ultrastructure and averting immune complex deposition. Mechanistically, it repressed the expression of CaMK4 in glomerulopathy by preserving nephrin and synaptopodin expression. And fasudil further blocked cytoskeletal breakage in the Rho GTPases-dependent action. Further analyses showed that beneficial actions of fasudil on the podocytes required intra-nuclear YAP activation underlying actin dynamics. In addition, in vitro assays revealed that fasudil normalized the motile imbalance by suppressing intracellular calcium enrichment, thereby contributing to the resistance of apoptosis in podocytes. Altogether, our findings suggest that the precise manners of crosstalks between cytoskeletal assembly and YAP activation underlying the upstream CaMK4/Rho GTPases signal in podocytes is a reliable target for podocytopathies treatment, and fasudil might serve as a promising therapeutic agent to compensate for the podocyte injury in LN.

Mycophenolic acid directly protects podocytes by preserving the actin cytoskeleton and increasing cell survival

Mycophenolate Mofetil (MMF) has an established role as a therapeutic agent in childhood nephrotic syndrome. While other immunosuppressants have been shown to positively affect podocytes, direct effects of MMF on podocytes remain largely unknown. The present study examines the effects of MMF's active component Mycophenolic Acid (MPA) on the transcriptome of podocytes and investigates its biological significance. We performed transcriptomics in cultured murine podocytes exposed to MPA to generate hypotheses on podocyte-specific effects of MPA. Accordingly, we further analyzed biological MPA effects on actin cytoskeleton morphology after treatment with bovine serum albumin (BSA) by immunofluorescence staining, as well as on cell survival following exposure to TNF-α and cycloheximide by neutral red assay. MPA treatment significantly (adjusted p < 0.05) affected expression of 351 genes in podocytes. Gene Ontology term enrichment analysis particularly clustered terms related to actin and inflammation-related cell death. Indeed, quantification of the actin cytoskeleton of BSA treated podocytes revealed a significant increase of thickness and number of actin filaments after treatment with MPA. Further, MPA significantly reduced TNFα and cycloheximide induced cell death. MPA has a substantial effect on the transcriptome of podocytes in vitro, particularly including functional clusters related to non-immune cell dependent mechanisms. This may provide a molecular basis for direct beneficial effects of MPA on the structural integrity and survival of podocytes under pro-inflammatory conditions.

The Behaviour of Serum Survivin in Patients With Lupus Nephritis

Background:

Systemic lupus erythematosus (SLE) is a chronic, multi phenotypic, autoimmune inflammatory disease and renal involvement significantly worsens its prognosis. Apoptosis dysregulation plays a key pathogenic role. Survivin, a protein from the apoptosis inhibitors family, has been considered a promising strategy in cancer therapy and evaluated as one of the regulatory pathways in the scenario of immune-mediated disorders.

Objective:

This study aims to explore survivin behaviour in SLE patients with lupus nephritis (LN), assessing its potential as a therapeutic and prognostic biomarker.

Methods:

297 SLE patients were classified based on the American College of Rheumatology (ACR) 1997 criteria, from 2000 to 2015. In a cross-sectional study, the serum level of survivin was measured by an ELISA test and compared between 200 SLE individuals and healthy controls. In a longitudinal cohort, 97 patients with active LN had the concentration of survinin measured, before and after treatment with cyclophosphamide pulse therapy.

Results:

The serum concentration of survivin was significantly lower in the SLE group than in healthy controls, regardless of concomitant NL or disease activity. The longitudinal evaluation revealed a significant reduction in survivin serum level after treatment. However, survivin rates were not able to discriminate groups that achieved remission from those that maintained nephritis activity.

Conclusion:

Our study suggests that survivin levels in SLE patients are lower than in the general population. Even so, its use as a biomarker in SLE seems limited, not reflecting disease activity or response to LN treatment, as in other contexts.

Novel Effects of Combination Therapy Through Inhibition of Caspase-1/Gasdermin D Induced-Pyroptosis in Lupus Nephritis

Objectives

Combination therapy with mycophenolate mofetil, tacrolimus and steroids are effective in achieving complete remission in lupus nephritis (LN). Combination therapy uniquely downregulated caspase-1 compared with monotherapies, which can cleave gasdermin D (GSDMD) and was recently identified as the pyroptosis executioner. We therefore investigated whether combination therapy enabled the suppression of caspase-1/GSDMD-mediated pyroptosis in LN.

Methods

Expression and activation of GSDMD were detected in kidney specimens of the human and mouse with LN using immunohistochemical staining and immunoblotting. Primary podocytes isolated from MRL/lpr mice were incubated with LPS+ATP, and pretreated with monotherapy or combination therapy. Inhibition of caspase-1/GSDMD-induced pyroptosis by combination therapy were assessed in MRL/lpr mice and human specimens. Pyroptosis was examined using a FAM caspase-1 kit and flow cytometry. The correlation between pyroptosis in peripheral blood and the systemic lupus erythematosus disease activity index (SLEDAI) was analyzed.

Results

Kidney tissue specimens from LN patients and mice exhibited greatly increased expression levels and cleavage of GSDMD. In cultured podocytes, combination treatment significantly suppressed the activation of NLRP3 and caspase-1 and reduced GSDMD N-terminal levels. Combination therapy repressed disease progression through inhibition of caspase-1/GSDMD-mediated pyroptosis in both humans and MRL/lpr mice. Caspase-1/PI positive cell numbers in peripheral blood were positively correlated with SLE-DAI. LN patients with complete remission and partial remission had remarkably reduced caspase-1/PI positive cell numbers compared to baseline. Ac-FLTD-CMK, a GSDMD-derived inhibitor, prevented the development of LN.

Conclusion

Combination therapy suppressed caspase-1/GSDMD-mediated pyroptosis in vitro and in vivo and reduced disease progression.

Altered expression of genes controlling metabolism characterizes the tissue response to immune injury in lupus

To compare lupus pathogenesis in disparate tissues, we analyzed gene expression profiles of human discoid lupus erythematosus (DLE) and lupus nephritis (LN). We found common increases in myeloid cell-defining gene sets and decreases in genes controlling glucose and lipid metabolism in lupus-affected skin and kidney. Regression models in DLE indicated increased glycolysis was correlated with keratinocyte, endothelial, and inflammatory cell transcripts, and decreased tricarboxylic (TCA) cycle genes were correlated with the keratinocyte signature. In LN, regression models demonstrated decreased glycolysis and TCA cycle genes were correlated with increased endothelial or decreased kidney cell transcripts, respectively. Less severe glomerular LN exhibited similar alterations in metabolism and tissue cell transcripts before monocyte/myeloid cell infiltration in some patients. Additionally, changes to mitochondrial and peroxisomal transcripts were associated with specific cells rather than global signal changes. Examination of murine LN gene expression demonstrated metabolic changes were not driven by acute exposure to type I interferon and could be restored after immunosuppression. Finally, expression of HAVCR1, a tubule damage marker, was negatively correlated with the TCA cycle signature in LN models. These results indicate that altered metabolic dysfunction is a common, reversible change in lupus-affected tissues and appears to reflect damage downstream of immunologic processes.

Glucocorticoid receptor wields chromatin interactions to tune transcription for cytoskeleton stabilization in podocytes

Elucidating transcription mediated by the glucocorticoid receptor (GR) is crucial for understanding the role of glucocorticoids (GCs) in the treatment of diseases. Podocyte is a useful model for studying GR regulation because GCs are the primary medication for podocytopathy. In this study, we integrated data from transcriptome, transcription factor binding, histone modification, and genome topology. Our data reveals that the GR binds and activates selective regulatory elements in podocyte. The 3D interactome captured by HiChIP facilitates the identification of remote targets of GR. We found that GR in podocyte is enriched at transcriptional interaction hubs and super-enhancers. We further demonstrate that the target gene of the top GR-associated super-enhancer is indispensable to the effective functioning of GC in podocyte. Our findings provided insights into the mechanisms underlying the protective effect of GCs on podocyte, and demonstrate the importance of considering transcriptional interactions in order to fine-map regulatory networks of GR.

Glycol chitosan-based tacrolimus-loaded nanomicelle therapy ameliorates lupus nephritis

Background

Recently, we developed hydrophobically modified glycol chitosan (HGC) nanomicelles loaded with tacrolimus (TAC) (HGC-TAC) for the targeted renal delivery of TAC. Herein, we determined whether the administration of the HGC-TAC nanomicelles decreases kidney injury in a model of lupus nephritis. Lupus-prone female MRL/lpr mice were randomly assigned into three groups that received intravenous administration of either vehicle control, an equivalent dose of TAC, or HGC-TAC (0.5 mg/kg TAC) weekly for 8 weeks. Age-matched MRL/MpJ mice without Fas^lpr mutation were also treated with HGC vehicle and used as healthy controls.

Results

Weekly intravenous treatment with HGC-TAC significantly reduced genetically attributable lupus activity in lupus nephritis-positive mice. In addition, HGC-TAC treatment mitigated renal dysfunction, proteinuria, and histological injury, including glomerular proliferative lesions and tubulointerstitial infiltration. Furthermore, HGC-TAC treatment reduced renal inflammation and inflammatory gene expression and ameliorated increased apoptosis and glomerular fibrosis. Moreover, HGC-TAC administration regulated renal injury via the TGF-β1/MAPK/NF-κB signaling pathway. These renoprotective effects of HGC-TAC treatment were more potent in lupus mice compared to those of TAC treatment alone.

Conclusion

Our study indicates that weekly treatment with the HGC-TAC nanomicelles reduces kidney injury resulting from lupus nephritis by preventing inflammation, fibrosis, and apoptosis. This advantage of a new therapeutic modality using kidney-targeted HGC-TAC nanocarriers may improve drug adherence and provide treatment efficacy in lupus nephritis mice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00857-w.

An integrated analysis of lncRNA and mRNA expression profiles in the kidneys of mice with lupus nephritis

Long noncoding RNAs (lncRNAs) are persistently expressed and have been described as potential biomarkers and therapeutic targets in various diseases. However, there is limited information regarding lncRNA expression in the tissue of kidney exhibiting lupus nephritis (LN)a serious complication of systemic lupus erythematosus (SLE). In this study, RNA sequencing (RNA-seq) was performed to characterize the lncRNA and mRNA expression in kidney tissues from LN (MRL/lpr) and control mice. We identified 12,979 novel lncRNAs in mouse. The expression profiles of both mRNAs and lncRNAs were differed significantly between LN and control mice. In particular, there were more upregulated lncRNAs and mRNAs than downregulated ones in the kidney tissues of LN mice. However, GO analysis showed that more downregulated genes were enriched in immune and inflammatory response-associated pathways. KEGG analysis showed that both downregulated and upregulated genes were enriched in a number of pathways, including the SLE pathway, and approximately half of these SLE-associated genes encoded inflammatory factors. Moreover, we observed that 2,181 DElncRNAs may have targeted and regulated the expression of 778 mRNAs in LN kidney tissues. The results of this study showed that 11 DElncRNAs targeted and were co-expressed with six immune and SLE-associated genes. qPCR analysis confirmed that lncRNA Gm20513 positively regulated the expression of the SLE-associated gene H2-Aa. In conclusion, the results of our study demonstrates that lncRNAs influence the progression of LN and provide some cues for further study of lncRNAs in LN. These results regarding the lncRNA-mRNAregulatory network may have important value in LN diagnosis and therapy.

Soluble urokinase-type plasminogen activator receptor (suPAR) is a risk indicator for eGFR loss in kidney transplant recipients

The prognostic significance of suPAR in various kidney diseases has recently been demonstrated. Its role in transplantation-specific outcomes is still largely unknown. Therefore, we prospectively investigated the prognostic relevance of suPAR in patients before and one year after kidney transplantation (KTx). We included 100 patients who had received a kidney transplantation between 2013 and 2015. The plasma concentration of suPAR was measured by ELISA assay. In recipients of living donations (LD), pre-transplant suPAR levels were significantly lower than those of recipients of deceased donations (DD). After KTx, suPAR levels significantly declined in LD and DD recipients, without a detectable difference between both groups any more. Higher suPAR levels in recipients one year after KTx were associated with a more severe eGFR loss in the following three years in multivariable cox-regression (n = 82, p = 0.021). suPAR-levels above 6212 pg/ml one year after KTx are associated with eGFR loss > 30%, which occurred almost twice as fast as in patients with suPAR ≤ 6212 pg/ml (p < 0.001). Hence, suPAR level at one year mark might be a risk indicator of increased eGFR loss.

The podocyte as a direct target of glucocorticoids in nephrotic syndrome

Nephrotic syndrome (NS) is characterized by massive proteinuria; podocyte loss or altered function is a central event in its pathophysiology. Treatment with glucocorticoids is the mainstay of therapy. However, many patients experience one or multiple relapses and prolonged use may be associated with severe adverse effects. Recently, the beneficial effects of glucocorticoids have been attributed to a direct effect on podocytes in addition to the well-known immunosuppressive effects. The molecular effects of glucocorticoid action have been studied using animal and cell models of NS. This review provides a comprehensive overview of different molecular mediators regulated by glucocorticoids including an overview of the model systems that were used to study them. Glucocorticoids are described to stimulate podocyte recovery by restoring pro-survival signaling of slit diaphragm related proteins and limiting inflammatory responses. Of special interest is the effect of glucocorticoids on stabilizing the cytoskeleton of podocytes, since these effects are also described for other therapeutic agents used in NS, such as cyclosporin. Current models provide much insight, but do not fully recapitulate the human condition since the pathophysiology underlying NS is poorly understood. New and promising models include the glomerulus-on-a-chip and kidney organoids, which have the potential to be further developed into functional NS models in the future.

Formalin-fixed paraffin-embedded renal biopsy tissues: an underexploited biospecimen resource for gene expression profiling in IgA nephropathy

Primary IgA nephropathy (IgAN) diagnosis is based on IgA-dominant glomerular deposits and histological scoring is done on formalin-fixed paraffin embedded tissue (FFPE) sections using the Oxford classification. Our aim was to use this underexploited resource to extract RNA and identify genes that characterize active (endocapillary–extracapillary proliferations) and chronic (tubulo-interstitial) renal lesions in total renal cortex. RNA was extracted from archival FFPE renal biopsies of 52 IgAN patients, 22 non-IgAN and normal renal tissue of 7 kidney living donors (KLD) as controls. Genome-wide gene expression profiles were obtained and biomarker identification was carried out comparing gene expression signatures a subset of IgAN patients with active (N = 8), and chronic (N = 12) renal lesions versus non-IgAN and KLD. Bioinformatic analysis identified transcripts for active (DEFA4,TNFAIP6,FAR2) and chronic (LTB,CXCL6, ITGAX) renal lesions that were validated by RT-PCR and IHC. Finally, two of them (TNFAIP6 for active and CXCL6 for chronic) were confirmed in the urine of an independent cohort of IgAN patients compared with non-IgAN patients and controls. We have integrated transcriptomics with histomorphological scores, identified specific gene expression changes using the invaluable repository of archival renal biopsies and discovered two urinary biomarkers that may be used for specific clinical decision making.

Evaluation of the inhibitory effect of tacrolimus combined with mycophenolate mofetil on mesangial cell proliferation based on the cell cycle

The inhibition of mesangial cell proliferation has become an important therapy for the prevention of glomerular proliferation‑associated diseases. The combined application of immunosuppressants with multiple targets presents a novel direction in the treatment of kidney diseases. The present study was designed to explore the inhibitory effects of tacrolimus (TAC) combined with mycophenolate mofetil (MMF) on the proliferation of mesangial cells based on the cell cycle. In vitro, the levels of the proliferation index markers, Ki67 and cyclin D1, in human mesangial cells (HMCs) were determined by immunofluorescence staining and western blot analysis, respectively. In mice with lupus nephritis (LN), the proliferation of mesangial cells was determined using PAS and Masson's trichrome staining, while immunohistochemistry was used to detect Ki67 and western blot analysis was employed for the evaluation of cyclin D1 levels. The expression of platelet‑derived growth factor (PDGF), a proliferation‑associated protein, was estimated using immunohistochemistry and western blot analysis. In patients with LN, Ki67, cyclin D1 and PDGF expression was estimated by immunohistochemistry. The transforming growth factor‑β1/Smad pathway influenced by TAC and the p38 pathway influenced by MMF were also examined by western blot analysis. The results suggested that the combination of TAC and MMF at half the concentration based on the cell cycle was more effective than monotherapy in inhibiting mesangial cell proliferation in vitro and in vivo. TAC inhibited HMC proliferation by affecting the Smad2 signaling pathway. MMF inhibited HMC proliferation by affecting the p38 signaling pathway. Combined treatment with TAC and MMF significantly improved the clinical indexes of patients with LN without severe adverse effects. On the whole, the findings of the present study validate and reinforce the potential use of the combination of TAC and MMF for the treatment of mesangial proliferative diseases.

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.

Update on the cellular and molecular aspects of lupus nephritis

Recent progress has highlighted the involvement of a variety of innate and adaptive immune cells in lupus nephritis. These include activated neutrophils producing extracellular chromatin traps that induce type I interferon production and endothelial injury, metabolically-rewired IL-17-producing T-cells causing tissue inflammation, follicular and extra-follicular helper T-cells promoting the maturation of autoantibody-producing B-cells that may also sustain the formation of germinal centers, and alternatively activated monocytes/macrophages participating in tissue repair and remodeling. The role of resident cells such as podocytes and tubular epithelial cells is increasingly recognized in regulating the local immune responses and determining the kidney function and integrity. These findings are corroborated by advanced, high-throughput genomic studies, which have revealed an unprecedented amount of data highlighting the molecular heterogeneity of immune and non-immune cells implicated in lupus kidney disease. Importantly, this research has led to the discovery of putative pathogenic pathways, enabling the rationale design of novel treatments.

The Kidney Biopsy in Systemic Lupus Erythematosus: A View of the Past and a Vision of the Future

The kidney biopsy advanced our understanding of kidney disease in systemic lupus erythematosus. It allowed for better recognition and classification of lupus nephritis (LN). Several LN classifications have been devised in an effort to inform treatment decision and predict prognosis, and these are being further updated. In this review, we will examine the role of diagnostic as well as repeat kidney biopsy in the management of LN, including the potential role of molecular interrogation as a step forward beyond conventional histology to guide the discovery of novel biomarkers and a precision medicine approach to the management of LN.

Individualizing Therapy in Lupus Nephritis

The ideal therapeutic approach for lupus nephritis (LN) is to quickly achieve a complete remission and maintain that response long-term while minimizing drug toxicity, and prevent tissue damage and death. The combination therapy consisting of multiple medications is aimed at incorporating drugs with complementary actions at reduced doses to achieve additive or synergistic therapeutic effects while minimizing toxicity. Here, we review the available evidence using combination therapies (triple therapy) and how such strategies can improve therapeutic efficacy in LN, which will mainly focus on the combination of high-dose corticosteroids with mycophenolate mofetil (MMF) and a calcineurin inhibitor (CNI) at low dose. We discuss the rationale, efficacy, and safety of the therapy, as well as its molecular mechanisms. We also discuss the questions raised from the trials and briefly describe emerging approaches developed on the basis of combination therapy, and these advances that promise to improve on the standard-of-care treatments and toward individual therapy in LN.

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.

Transcriptomics analysis of sirolimus treatment in lupus nephritis

Lupus nephritis (LN) is one of the principal causes of mortality and disability in patients with systemic lupus erythematosus. Sirolimus has been used to treat patients with LN; however, the effects and mechanism of sirolimus in these patients remains unclear. The present study aimed to elucidate the therapeutic effects and mechanisms of sirolimus in LN mice using low, medium and high doses of sirolimus (0.1, 0.3 and 1 mg/kg, respectively). The survival probability and kidney index were calculated, and renal fibrosis was determined using Masson's Trichrome staining. The expression levels of E-cadherin, α-smooth muscle actin (α-SMA) and vimentin were assessed via immunofluorescence analysis. Transcriptome analysis of control and sirolimus-treated LN mice was performed using RNA-sequencing, differentially expressed gene (DEG) identification and annotation, and Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. The results suggested that a medium dose of sirolimus alleviated renal fibrosis and increased the survival rates of mice with LN (P<0.05). Furthermore, transcriptome analysis revealed 334 DEGs associated with LN, 176 of which were upregulated and 158 were downregulated. Following GO functional enrichment, ‘biological process’, ‘molecular function’ and ‘cellular component’ terms were identified. A total of 10 KEGG pathways were enriched, with ‘cytokine-cytokine receptor interaction’ and ‘interleukin-17 signaling pathway’ being significantly enriched (P<0.05). To the best of our knowledge, the present study is the first to conduct transcriptome analysis of LN mice treated with sirolimus, and demonstrated that a dose of 0.3 mg/kg exerted the greatest therapeutic effects.

Roles of Natural Killer T Cells and Natural Killer Cells in Kidney Injury

Mouse natural killer T (NKT) cells and natural killer (NK) cells are innate immune cells that are highly abundant in the liver. In addition to their already-known antitumor and antimicrobial functions, their pathophysiological roles in the kidney have recently become evident. Under normal circumstances, the proportion of activated NKT cells in the kidney increases with age. Administration of a synthetic sphingoglycolipid ligand (alpha-galactosylceramide) further activates NKT cells, resulting in injury to renal vascular endothelial cells via the perforin-mediated pathway and tubular epithelial cells via the TNF-α/Fas ligand pathway, causing acute kidney injury (AKI) with hematuria. Activation of NKT cells by common bacterial DNA (CpG-ODN) also causes AKI. In addition, NKT cells together with B cells play significant roles in experimental lupus nephritis in NZB/NZW F1 mice through their Th2 immune responses. Mouse NK cells are also assumed to be involved in various renal diseases, and there may be complementary roles shared between NKT and NK cells. Human CD56⁺ T cells, a functional counterpart of mouse NKT cells, also damage renal cells through a mechanism similar to that of mice. A subpopulation of human CD56⁺ NK cells also exert strong cytotoxicity against renal cells and contribute to the progression of renal fibrosis.

Emerging areas for therapeutic discovery in SLE

Recent advances in the field of autoimmunity have identified numerous dysfunctional pathways in Systemic Lupus Erythematosus (SLE), including aberrant clearance of nucleic-acid-containing debris and immune complexes, excessive innate immune activation leading to overactive type I IFN signalling, and abnormal B and T cell activation. On the background of genetic polymorphisms that reset thresholds for immune responses, multiple immune cells contribute to inflammatory amplification circuits. Neutrophils activated by immune complexes are a rich source of immunogenic nucleic acids. Identification of new B subsets suggests several mechanisms for induction of autoantibody producing effector cells. Disordered T cell regulation involves both CD4 and CD8 cells. An imbalance in immunometabolism in immune cells amplifies autoimmunity and inflammation. These new advances in understanding of disease pathogenesis provide fertile ground for therapeutic development.

Induction Therapy for Lupus Nephritis: the Highlights

PURPOSE OF REVIEW

Lupus nephritis is a frequent complication of systemic lupus erythematosus and is more common and severe in children. This is a disease of the immune system characterized by T cell, B cell, and complement activation, as well as immune complex formation and deposition. The introduction of steroids and later cyclophosphamide transformed lupus nephritis from a fatal to a treatable condition. However, the standard therapies currently used for treatment carry significant toxicity and chronic kidney disease still remains a far too frequent outcome. To address these issues, we will review current and emerging induction therapies in LN.

RECENT FINDINGS

Several clinical trials have been undertaken to test more effective and safer drugs, often targeting mechanistic disease pathways. At present, it is difficult to identify an induction regimen that is more effective and less toxic than the standard of care; however, we believe continuing efforts in drug development will bring breakthrough agents to clinics.

Repeated administration of alpha-galactosylceramide ameliorates experimental lupus nephritis in mice

Lupus nephritis is a crucial complication of systemic lupus erythematosus. In this study, we investigated the roles of mouse natural killer T (NKT) cells in lupus nephritis. From 24 weeks of age, NZB/NZW F1 mice were injected with alpha-galactosylceramide (α-GalCer) or vehicle once a week for four weeks. In the α-GalCer group, the levels of proteinuria and blood urea nitrogen were significantly lower than those in the vehicle group. The histological evaluation showed a decrease in glomerular immune complex deposits and an alleviation of podocyte injury. The proportion of NKT cells in the mononuclear cell (MNC) fraction in the α-GalCer group was significantly decreased in the liver, kidney, and spleen. The proliferation and cytokine production in α-GalCer-stimulated liver MNCs were markedly diminished in the α-GalCer group (anergy). The IFN-γ production in liver MNCs stimulated by concanavalin A or an anti-CD3 antibody did not differ between the two groups, whereas the IL-4 production was significantly lower in the α-GalCer group. In addition, the IgM production in CpG-oligodeoxynucleotide-stimulated spleen MNCs was significantly lower in the α-GalCer group. These results suggest that α-GalCer suppressed Th2 immune responses in NKT cells and B cell function, thereby slowing the progression of lupus nephritis.