Lupus nephritis. How latest insights into its pathogenesis promote novel therapies

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.

Dan Bai Xiao Formula combined with glucocorticoids and cyclophosphamide for pediatric lupus nephritis: A pilot prospective study

BACKGROUND

Patients with lupus nephritis (LN) typically undergo long-term treatment with glucocorticoids (GCs) and immunosuppressants. There is a growing demand for optimal therapy with better remission results and fewer side effects. Sustained traditional Chinese medicine (TCM) might be quite valuable for multitarget therapy, reducing the total dosage of GCs and minimizing the side effects of immunosuppressants.

AIM

To evaluate whether Dan Bai Xiao Formula (DBXF) can reduce the exposure to GCs and cyclophosphamide (CYC) and to assess the efficacy and safety of DBXF for the resolution of proteinuria and hematuria in children with LN.

METHODS

A 24-wk pilot study was conducted at Beijing Children’s Hospital. Children with active LN were divided into either a TCM group or a control group. Children in the TCM group received DBXF combined with GCs and CYC, and the ones in the control group received GCs and CYC every 4 wk for 24 wk. The primary endpoints of this trial were urinary protein excretion of < 150 mg/d and normal serum albumin concentration and renal function.

RESULTS

The trial included 78 children, of whom 38 received GCs and CYC treatment (control group) and the remaining 40 received DBXF combined with GCs and CYC treatment (TCM group). At week 24, the TCM group showed a better rate of complete remission (42.5%); however, there was no significant difference compared with the control group (31.5%, P > 0.05). The urine red blood cell count and urine protein level were significantly lower in the TCM group than in the control group at weeks 4, 12, and 24 (P < 0.05). Furthermore, patients in the TCM group had a lower proportion of methylprednisolone pulses than those in the control group (1.30 ± 1.41 vs 3.05 ± 2.02, P < 0.0001). The ending GC dose was significantly lower in the TCM group than in the control group (P < 0.001). Moreover, more hepatic function damage, gastrointestinal adverse effects, and hypertension were observed in the control group than in the TCM group (P < 0.05).

CONCLUSION

The findings suggest that DBXF treatment is effective and safe as a supplementary therapy for LN and is superior to routine GC and CYC therapy. DBXF containing combination treatment possibly results in a faster resolution of proteinuria and hematuria, smoother GC reduction, fewer methylprednisolone pulses, and fewer adverse events.

Heme-Oxygenase-1 Is Decreased in Circulating Monocytes and Is Associated With Impaired Phagocytosis and ROS Production in Lupus Nephritis

Lupus nephritis (LN) is one of the most serious manifestations of systemic lupus erythematosus (SLE). Based on studies showing the potential role of heme oxygenase-1 (HO-1), an enzyme that catalyzes the degradation of heme and has anti-inflammatory properties in SLE development, we decided to explore HO-1 in LN. Accordingly, we evaluated HO-1 levels and function in circulating and infiltrating monocytes and neutrophils of LN patients. HO-1 levels were assessed in peripheral monocytes of LN patients and controls by flow cytometry and immunofluorescence microscopy. Phagocytosis and the production of reactive oxygen species (ROS) were evaluated to determine the effect of HO-1 in monocyte function. In addition, renal biopsies with proliferative LN were used to identify HO-1 in infiltrating cells and renal tissue by immunofluorescence and immunohistochemistry. Biopsies of healthy controls (HC) and patients who underwent nephrectomy were included as controls. Circulating pro-inflammatory monocytes and activated neutrophils were increased in LN patients. HO-1 levels were decreased in all subsets of monocytes and in activated neutrophils. LN monocytes showed increased phagocytosis and higher production of ROS than those of HC. When HO-1 was induced, phagocytosis and ROS levels became similar to those of HC. HO-1 was mostly expressed in renal tubular epithelial cells (RTEC). Renal tissue of LN patients showed lower levels of HO-1 than HC, whereas infiltrating immune cells of LN showed lower levels of HO-1 than biopsies of patients who had renal surgery. HO-1 is decreased in circulating monocytes and activated neutrophils of LN patients. HO-1 levels modulate the phagocytosis of LN monocytes and ROS production. HO-1 expression in RTEC might be an attempt of self-protection from inflammation.

IL-17 in Renal Immunity and Autoimmunity

The kidney is an organ particularly susceptible to damage caused by infections and autoimmune conditions. Renal inflammation confers protection against microbial infections. However, if unchecked, unresolved inflammation may lead to kidney damage. Although proinflammatory cytokine IL-17 is required for immunity against extracellular pathogens, dysregulated IL-17 response is also linked to autoimmunity. In this review, we will discuss the current knowledge of IL-17 activity in the kidney in context to renal immunity and autoimmunity and raise the intriguing question to what extent neutralization of IL-17 is beneficial or harmful to renal inflammation.

Corticosteroids combined with doublet or single-agent immunosuppressive therapy for active proliferative lupus nephritis

OBJECTIVES

We performed a meta-analysis to assess whether corticosteroids (C) plus (+) doublet immunosuppressive therapy (IT) is superior to the classical combination of C with single-agent IT in active proliferative lupus nephritis (LN).

METHOD

Randomized trials evaluating the benefits and risks of C+doublet versus single-agent IT in active proliferative LN were obtained by searching PubMed, EMBASE, and Cochrane Central Register. The primary outcome was overall response rate (ORR). The secondary outcomes were the change from baseline in Systemic Lupus Erythematosus Disease Activity Index (SLE-DAI) score, negative conversion ratio of anti-double-stranded DNA (anti-dsDNA), and adverse events. The PROSPERO registry number is CRD42017068491.

RESULTS

Eleven trials with 1855 patients were included. Compared with C+single-agent IT, C+doublet IT had a significantly higher ORR (relative risk [RR], 1.22; 95% confidence interval [CI], 1.09 to 1.35; P < 0.01). In a subgroup analysis, C+doublet IT without biologics had a significantly higher ORR than C+single-agent IT (RR, 1.30; 95% CI, 1.13 to 1.50; P < 0.01), while C+doublet IT including biologics improved ORR only for refractory severe LN (RR, 1.46; 95% CI, 1.09 to 1.96; P = 0.012). A larger change from baseline in SLE-DAI scores (standardized mean difference, - 0.49; 95% CI, - 0.68 to - 0.30; P < 0.01) and a higher negative conversion ratio of anti-dsDNA (RR, 1.34; 95% CI, 1.06 to 1.69; P = 0.014) were observed with C+doublet IT than with C+single-agent IT. The rates of adverse events were similar between the two regimens.

CONCLUSIONS

Compared with single-agent IT, the combination of C and doublet IT without biologics improved clinical outcomes in active proliferative LN. Key Points • Compared with corticosteroids + single-agent immunosuppressive therapy, corticosteroids + doublet immunosuppressive therapy without biologics had a significantly higher overall response rate in active proliferative lupus nephritis. • Compared with corticosteroids + single-agent immunosuppressive therapy, corticosteroids + doublet immunosuppressive therapy including biologics improved overall response rate only for refractory severe lupus nephritis. • A larger change from baseline in SLE-DAI scores and a higher negative conversion ratio of anti-dsDNA were observed with corticosteroids + doublet immunosuppressive therapy than with corticosteroids + single-agent immunosuppressive therapy.

Pharmacodynamic Monitoring of RO5459072, a Small Molecule Inhibitor of Cathepsin S

Major histocompatibility complex class II (MHCII)-restricted antigen priming of CD4⁺ T cells is both involved in adaptive immune responses and the pathogenesis of autoimmune diseases. Degradation of invariant chain Ii, a protein that prevents premature peptide loading, is a prerequisite for nascent MHCII–peptide complex formation. A key proteolytic step in this process is mediated by cathepsin S. Inhibition of this cysteine protease is known to result in the intracellular accumulation of Lip10 in B cells. Here, we describe the development and application of a neoepitope-based flow cytometry assay measuring accumulation of Lip10. This novel method enabled the investigation of cathepsin S-dependent MHCII maturation in professional antigen-presenting cell (APC) subsets. Inhibition of cathepsin S by a specific inhibitor, RO5459072, in human PBMC ex vivo resulted in accumulation of Lip10 in B cells and myeloid dendritic cells, but not in plasmacytoid dendritic cells and only to a minor degree in monocytes. We qualified Lip10 as a pharmacodynamic biomarker by showing the cathepsin S inhibitor-dependent accumulation of Lip10 in vivo in cynomolgus monkeys treated with RO5459072. Finally, dosing of RO5459072 in a first-in-human clinical study (www.ClinicalTrials.gov, identifier NCT02295332) exhibited a dose-dependent increase in Lip10, confirming target engagement and demonstrating desired pharmacologic inhibition in vivo. The degree of cathepsin S antagonist-induced maximum Lip10 accumulation in APCs varied significantly between individuals both in vitro and in vivo. This finding has not been reported previously using alternative, less sensitive methods and demands further investigation as to the potential of this biomarker to predict response to treatment. These results will help guide subsequent clinical studies investigating the pharmacokinetic and pharmacodynamic relationship of cathepsin S inhibitor RO5459072 after multiple dosing.

Multitarget therapy for induction treatment of lupus nephritis: a randomized trial

BACKGROUND

Treatment of lupus nephritis (LN) remains challenging.

OBJECTIVE

To assess the efficacy and safety of a multitarget therapy consisting of tacrolimus, mycophenolate mofetil, and steroid compared with intravenous cyclophosphamide and steroid as induction therapy for LN.

DESIGN

24-week randomized, open-label, multicenter study. (ClinicalTrials.gov: NCT00876616).

SETTING

26 renal centers in China.

PATIENTS

Adults (aged 18 to 65 years) with biopsy-proven LN.

INTERVENTION

Tacrolimus, 4 mg/d, and mycophenolate mofetil, 1.0 g/d, versus intravenous cyclophosphamide with a starting dose of 0.75 (adjusted to 0.5 to 1.0) g/m2 of body surface area every 4 weeks for 6 months. Both groups received 3 days of pulse methylprednisolone followed by a tapering course of oral prednisone therapy.

MEASUREMENTS

The primary end point was complete remission at 24 weeks. Secondary end points included overall response (complete and partial remission), time to overall response, and adverse events.

RESULTS

After 24 weeks of therapy, more patients in the multitarget group (45.9%) than in the intravenous cyclophosphamide group (25.6%) showed complete remission (difference, 20.3 percentage points [95% CI, 10.0 to 30.6 percentage points]; P < 0.001). The overall response incidence was higher in the multitarget group than in the intravenous cyclophosphamide group (83.5% vs. 63.0%; difference, 20.4 percentage points [CI, 10.3 to 30.6 percentage points]; P < 0.001), and the median time to overall response was shorter in the multitarget group (difference, -4.1 weeks [CI, -7.9 to -2.1 weeks]). Incidence of adverse events did not differ between the multitarget and intravenous cyclophosphamide groups (50.3% [91 of 181] vs. 52.5% [95 of 181]).

LIMITATION

The study was limited to 24 weeks of follow-up.

CONCLUSION

Multitarget therapy provides superior efficacy compared with intravenous cyclophosphamide as induction therapy for LN.

PRIMARY FUNDING SOURCE

National Basic Research Program of China, National Key Technology R&D Program.

Piperlongumine alleviates lupus nephritis in MRL-Fas(lpr) mice by regulating the frequency of Th17 and regulatory T cells

Recent data have shown that piperlongumine (PL), an important component of Piper longum fruits, is known to possess anti-inflammatory and vascular-protective activities. This study aimed to examine the therapeutic effects and underlying mechanisms of PL on lupus-prone MRL-Fas(lpr) mice. Female MRL-Fas(lpr) mice were intraperitoneally treated with PL (2.4 mg kg(-1) d(-1)) for 10 weeks, and the proteinuria level was biweekly monitored. After the mice were euthanized, serum biochemical parameters and renal damage were determined. Splenocytes of MRL-Fas(lpr) mice were isolated for in vitro study. Treatment of the mice with PL significantly attenuated the progression of proteinuria and glomerulonephritis. The improvement was accompanied by decreased serum levels of nephritogenic anti-dsDNA antibodies, IL-6, IL-17, IL-23 and TNF-α. Treatment of the mice with PL suppressed the frequency of Th17 cells and increased the regulatory T cells (Tregs). In vitro, the levels of IL-6, IL-17, IL-23 and TNF-α were significantly decreased in the cultures of splenocytes from PL-treated mice compared with those from vehicle-treated mice. In addition, PL treatment impeded activation of the JAK/STAT3 signaling in splenocytes. Of great important, the survival of MRL-Fas(lpr) mice were improved by PL treatment. In summary, PL effectively ameliorates lupus syndrome in MRL-Fas(lpr) mice by suppressing the pathogenic Th17 cells and increasing the Tregs as well as inhibiting activation of the JAK/STAT3 signaling pathway. This study sheds new light on the immune-modulatory role of PL.

The efficacy of novel B cell biologics as the future of SLE treatment: a review

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease with wide ranging multi-systemic effects. Current understanding centralises B cells in SLE pathogenesis with clinical features resulting from autoantibody formation, immune complex deposition, antigen presentation and cytokine activation. Existing standard of care therapies generates adverse side effects; secondary to corticosteroid use and untargeted immunosuppression. The inability to uphold remission and abolish the disease process, in addition to the increasing numbers of patients seen with refractory disease with these therapies, has provoked the development of novel B cell biologics targeting specific pathogenic pathways fundamental to the SLE disease process. Current evidence highlighting the efficacy of Rituximab, Ocrelizumab and Epratuzumab in inducing B cell depletion and achieving disease amelioration through specific B cell surface receptor antagonism is discussed. We review the efficacy of Atacicept, Briobacept and Belimumab in antagonising B lymphocyte stimulator (BLyS) and A proliferation inducing ligand (APRIL), two stimulatory cytokines crucial to B cell survival, growth and function. Two large multicentre randomised controlled trials, BLISS-52 and BLISS-76, have led to FDA approval of Belimumab. Following this breakthrough, other anti-BLyS therapies, Blisibimod and Tabalumab, are currently under Phase III evaluation. Similarly, murine models and Phase I/II trials have demonstrated significant efficacy of Rituximab, Epratuzumab, Briobacept and Atacicept as potential future therapies and we now eagerly await results from Phase III trials. Future research must compare the efficacy of different biologics amongst different patient subpopulations and SLE manifestations, in order to develop clinically and cost effective therapies.

NLRP3 and ASC suppress lupus-like autoimmunity by driving the immunosuppressive effects of TGF-β receptor signalling

OBJECTIVES

The NLRP3/ASC inflammasome drives host defence and autoinflammatory disorders by activating caspase-1 to trigger the secretion of mature interleukin (IL)-1β/IL-18, but its potential role in autoimmunity is speculative.

METHODS

We generated and phenotyped Nlrp3-deficient, Asc-deficient, Il-1r-deficient and Il-18-deficient C57BL/6-lpr/lpr mice, the latter being a mild model of spontaneous lupus-like autoimmunity.

RESULTS

While lack of IL-1R or IL-18 did not affect the C57BL/6-lpr/lpr phenotype, lack of NLRP3 or ASC triggered massive lymphoproliferation, lung T cell infiltrates and severe proliferative lupus nephritis within 6 months, which were all absent in age-matched C57BL/6-lpr/lpr controls. Lack of NLRP3 or ASC increased dendritic cell and macrophage activation, the expression of numerous proinflammatory mediators, lymphocyte necrosis and the expansion of most T cell and B cell subsets. In contrast, plasma cells and autoantibody production were hardly affected. This unexpected immunosuppressive effect of NLRP3 and ASC may relate to their known role in SMAD2/3 phosphorylation during tumour growth factor (TGF)-β receptor signalling, for example, Nlrp3-deficiency and Asc-deficiency significantly suppressed the expression of numerous TGF-β target genes in C57BL/6-lpr/lpr mice and partially recapitulated the known autoimmune phenotype of Tgf-β1-deficient mice.

CONCLUSIONS

These data identify a novel non-canonical immunoregulatory function of NLRP3 and ASC in autoimmunity.

An essential role of interleukin-17 receptor signaling in the development of autoimmune glomerulonephritis

In recent years, proinflammatory cytokines in the nephritic kidney appear to contribute to the pathogenesis of AGN. The complex inflammatory cytokine network that drives renal pathology is poorly understood. IL-17, the signature cytokine of Th17 cells, which promotes autoimmune pathology in a variety of settings, is beginning to be identified in acute and chronic kidney diseases as well. However, the role of IL-17-mediated renal damage in the nephritic kidney has not been elucidated. Here, with the use of a murine model of experimental AGN, we showed that IL-17RA signaling is critical for the development of renal pathology. Despite normal systemic autoantibody response and glomerular immune-complex deposition, IL-17RA(-/-) mice exhibit a diminished influx of inflammatory cells and kidney-specific expression of IL-17 target genes correlating with disease resistance in AGN. IL-17 enhanced the production of proinflammatory cytokines and chemokines from tECs. Finally, we were able to show that neutralization of IL-17A ameliorated renal pathology in WT mice following AGN. These results clearly demonstrated that IL-17RA signaling significantly contributes to renal tissue injury in experimental AGN and suggest that blocking IL-17RA may be a promising therapeutic strategy for the treatment of proliferative and crescentic glomerulonephritis.

Complexities in the relationship between infection and autoimmunity

The possible role of infections in driving autoimmune disease (AD) has long been debated. Many theories have emerged including release of hidden antigens, epitope spread, anti-idiotypes, molecular mimicry, the adjuvant effect, antigenic complementarity, or simply that AD could be a direct consequence of activation or subversion of the immune response by microbes. A number of issues are not adequately addressed by current theories, including why animal models of AD require adjuvants containing microbial peptides in addition to self tissue to induce disease, and why ADs occur more often in one sex than the other. Reviews published in the past 3 years have focused on the role of the innate immune response in driving AD and the possible role of persistent infections in altering immune responses. Overall, recent evidence suggests that microbes activating specific innate immune responses are critical, while antigenic cross-reactivity may perpetuate immune responses leading to chronic autoinflammatory disease.

Cathepsin S inhibition suppresses systemic lupus erythematosus and lupus nephritis because cathepsin S is essential for MHC class II-mediated CD4 T cell and B cell priming

OBJECTIVES

Major histocompatibility complex (MHC) class II-mediated priming of T and B lymphocytes is a central element of autoimmunity in systemic lupus erythematosus (SLE) and lupus nephritis. The cysteine protease cathepsin S degrades the invariant peptide chain during MHC II assembly with antigenic peptide in antigen-presenting cells; therefore, we hypothesised that cathepsin S inhibition would be therapeutic in SLE.

METHODS

We developed a highly specific small molecule, orally available, cathepsin S antagonist, RO5461111, with suitable pharmacodynamic and pharmacokinetic properties that efficiently suppressed antigen-specific T cell and B cell priming in vitro and in vivo.

RESULTS

When given to MRL-Fas(lpr) mice with SLE and lupus nephritis, RO5461111 significantly reduced the activation of spleen dendritic cells and the subsequent expansion and activation of CD4 T cells and CD4/CD8 double-negative T cells. Cathepsin S inhibition impaired the spatial organisation of germinal centres, suppressed follicular B cell maturation to plasma cells and Ig class switch. This reversed hypergammaglobulinemia and significantly suppressed the plasma levels of numerous IgG (but not IgM) autoantibodies below baseline, including anti-dsDNA. This effect was associated with less glomerular IgG deposits, which protected kidneys from lupus nephritis.

CONCLUSIONS

Together, cathepsin S promotes SLE by driving MHC class II-mediated T and B cell priming, germinal centre formation and B cell maturation towards plasma cells. These afferent immune pathways can be specifically reversed with the cathepsin S antagonist RO5461111, which prevents lupus nephritis progression even when given after disease onset. This novel therapeutic strategy could correct a common pathomechanism of SLE and other immune complex-related autoimmune diseases.

Toll-like receptor and accessory molecule mRNA expression in humans and mice as well as in murine autoimmunity, transient inflammation, and progressive fibrosis

The cell type-, organ-, and species-specific expression of the Toll-like receptors (TLRs) are well described, but little is known about the respective expression profiles of their accessory molecules. We therefore determined the mRNA expression levels of LBP, MD2, CD36, CD14, granulin, HMGB1, LL37, GRP94, UNC93b1, TRIL, PRAT4A, AP3B1, AEP and the respective TLRs in human and mouse solid organs. Humans and mice displayed significant differences between their respective mRNA expression patterns of these factors. In addition, the expression profiles in transient tissue inflammation upon renal ischemia-reperfusion injury, in spleens and kidneys from mice with lupus-like systemic autoimmunity, and in progressive tissue fibrosis upon unilateral ureteral obstruction were studied. Several TLR co-factors were specifically regulated during the different phases of these disease entities, suggesting a functional involvement in the disease process. Thus, the organ- and species-specific expression patterns need to be considered in the design and interpretation of studies related to TLR-mediated innate immunity, which seems to be involved in the tissue injury phase, in the phase of tissue regeneration, and in progressive tissue remodelling.