A reverse translational study on the effect of rituximab, rituximab plus belimumab, or bortezomib on the humoral autoimmune response in SLE

New and emerging therapies for systemic lupus erythematosus

Systemic Lupus Erythematosus (SLE) and lupus nephritis treatment is still based on non-specific immune suppression despite the first biological therapy for the disease having been approved more than a decade ago. Intense basic and translational research has uncovered a multitude of pathways that are actively being evaluated as treatment targets in SLE and lupus nephritis, with two new medications receiving FDA approval in the last 3 years. Herein we provide an overview of targeted therapies for SLE including medications targeting the B lymphocyte compartment, intracellular signaling, co-stimulation, and finally the interferons and other cytokines.

A variety of death modes of neutrophils and their role in the etiology of autoimmune diseases

Neutrophils are important in the context of innate immunity and actively contribute to the progression of diverse autoimmune disorders. Distinct death mechanisms of neutrophils may exhibit specific and pivotal roles in autoimmune diseases and disease pathogenesis through the orchestration of immune homeostasis, the facilitation of autoantibody production, the induction of tissue and organ damage, and the incitement of pathological alterations. In recent years, more studies have provided in-depth examination of various neutrophil death modes, revealing nuances that challenge conventional understanding and underscoring their potential clinical utility in diagnosis and treatment. This review explores the multifaceted processes and characteristics of neutrophil death, with a focus on tailored investigations within various autoimmune diseases. It also highlights the potential interplay between neutrophil death and the landscape of autoimmune disorders. The review encapsulates the pertinent pathways implicated in various neutrophil death mechanisms across diverse autoimmune diseases while also charts possible avenues for future research.

Lupus Nephritis Risk Factors and Biomarkers: An Update

Lupus nephritis (LN) represents the most severe organ manifestation of systemic lupus erythematosus (SLE) in terms of morbidity and mortality. To reduce these risks, tremendous efforts have been made in the last decade to characterize the different steps of the disease and to develop biomarkers in order to better (i) unravel the pre-SLE stage (e.g., anti-nuclear antibodies and interferon signature); (ii) more timely initiation of therapy by improving early and accurate LN diagnosis (e.g., pathologic classification was revised); (iii) monitor disease activity and therapeutic response (e.g., recommendation to re-biopsy, new urinary biomarkers); (iv) prevent disease flares (e.g., serologic and urinary biomarkers); (v) mitigate the deterioration in the renal function; and (vi) reduce side effects with new therapeutic guidelines and novel therapies. However, progress is poor in terms of improvement with early death attributed to active SLE or infections, while later deaths are related to the chronicity of the disease and the use of toxic therapies. Consequently, an individualized treat-to-target strategy is mandatory, and for that, there is an unmet need to develop a set of accurate biomarkers to be used as the standard of care and adapted to each stage of the disease.

Rituximab induces a flare-up of activated neutrophil extracellular traps under in vitro conditions

Purpose: During neutrophil extracellular traps (NET) formation granulocytes release a decondensed chromatin web that is studded with antimicrobial proteins. These NET engulf and kill pathogens like bacteria and fungi. NET formation is part of the innate immune response but can also contribute to the aggravation of autoimmune diseases, thrombosis, and cancer metastasis. Anti-NET therapeutics to prevent potentially harmful consequences of excessive NET formation are warranted.Materials and methods: Therefore, we stimulated NET formation with ionomycin in the peripheral blood of 25 healthy individuals and quantified NET with flow cytometry and fluorescence microscopy after exposure to five different anti-inflammatory and cytostatic drugs. NET were identified by their expression of myeloperoxidase, citrullinated histone H3, and (extracellular) DNA release.Results: The preliminary in vitro drug screening indicated that acetylsalicylic acid (ASA) might suppress (-3.82%), and rituximab might enhance (+10.52%) NET formation. To consolidate the screening results, we quantified NET after exposure to rituximab and ASA in the blood of nine additional healthy subjects. Rituximab showed a significant increased NET formation compared to the neutrophils treated with ASA (a mean of differences 3.96%; 95% CI 1.90-6.03%; p < .01) or compared to neutrophils without treatment (a mean of differences 4.39%; 95% CI 1.17-7.61%; p = .01). Contrary to the screening results ASA showed no significant suppression of NET formation in the consolidation experiments (a mean of differences 0.43%; 95% CI -1.27 to 2.12%; p = .58).Conclusions: We conclude that rituximab therapy might further trigger activated NET formation and should be applied with caution in patients with pro-inflammatory state and underlying autoimmune disease, thrombosis, or cancer.

Belimumab for systemic lupus erythematosus - Focus on lupus nephritis

In recent years, advances in the treatment and management of patients with systemic lupus erythematosus (SLE) have improved their life expectancy and quality of life. However, lupus nephritis (LN) still represents a major life-threatening complication of the disease. Belimumab (BEL), a fully human monoclonal IgG1λ antibody neutralizing soluble B cell activating factor, was approved more than ten years ago as add-on therapy in adults and pediatric patients with a highly active, autoantibody-positive disease despite standard of care (SoC). Recently, the superiority of the addition of BEL to SoC was also demonstrated in LN. In this review, we provide a comprehensive overview of the study landscape, available therapeutic options for SLE (focusing on BEL in renal and non-renal SLE), and new perspectives in the treatment field of this disease. A personalized treatment approach will likely become available with the advent of novel therapeutic agents for SLE and LN.

Efficacy of belimumab combined with rituximab in severe systemic lupus erythematosus: study protocol for the phase 3, multicenter, randomized, open-label Synbiose 2 trial

Background

Belimumab, an anti-B-cell activating factor antibody, is approved for the treatment of auto-antibody positive systemic lupus erythematosus with a high degree of disease activity. Anti-CD20 B cell depletion with rituximab is used in refractory SLE as well, although with variable responses. We hypothesized that incomplete B cell depletion, related to a surge in BAFF levels following rituximab treatment, can cause ongoing disease activity and flares. The Synbiose 1 study primarily focused on immunological effects and shows the preliminary clinical benefit of combined rituximab and belimumab in SLE. The Synbiose 2 study will evaluate the clinical efficacy of combining belimumab with rituximab in patients with severe SLE, allowing the tapering of prednisolone and mycophenolate.

Methods

Synbiose 2 is a phase 3, multicenter, randomized, controlled, open-label 2-year clinical trial. Seventy adults with severe SLE including lupus nephritis will be randomized 1:1 to receive either standard of care consisting of prednisolone and mycophenolate as induction and maintenance treatment, or belimumab and rituximab combined with standard of care as induction treatment, followed by prednisolone and belimumab as maintenance treatment. The primary objective is to assess whether combined B cell therapy will lead to a reduction of treatment failure. Secondary endpoints are complete and partial clinical and renal response and the improvement of SLE-specific autoimmune phenomena. Safety endpoints include the incidence of adverse events, with a special interest in infections.

Discussion

The Synbiose 2 trial is the first multicenter phase 3 clinical trial investigating combined B cell targeted therapy in SLE, including lupus nephritis. The outcome of this study will provide further evidence for the clinical efficacy of this new treatment strategy in severe SLE.

Trial registration

ClinicalTrials.gov NCT03747159. Registered on 20 November 2018.

B cells in systemic lupus erythematosus

PURPOSE OF REVIEW

New insight into altered B cell distribution including newly identified subsets and abnormalities in systemic lupus erythematosus (SLE) as well as their role in immune protection are summarized in this review.

RECENT FINDINGS

SLE carries characteristic B cell abnormalities, which offer new insights into B cell differentiation and their disturbances including discoveries of pathogenic B cell subsets and intrinsic B cell abnormalities. A recent study in SLE found that antigen-experienced B cell subsets lacking expression of CD27 and IgD defined by their lack of CXCR5 and CD19low expression are expanded in SLE and represent plasmablasts likely escaping proper selection. In terms of therapeutic targeting with broader coverage than rituximab, second-generation anti-CD20, anti-CD38 and CD19-CART treatment experiences have advanced our understanding recently. However, the key role of qualitative and quantitative B cell requirements in connection with T cells became apparent during SARS-Cov2 infection and vaccination, especially in patients with gradual B cell impairments by rituximab, mycophenolate mofetil and cyclophosphamide.

SUMMARY

Identification and characterization relevant B cell subsets together with altered regulatory mechanisms in SLE facilitates new approaches in targeting pathogenic B cells but require consideration of preservation of protection.

Low-Density Granulocytes in Immune-Mediated Inflammatory Diseases

Low-density granulocytes (LDGs), a distinct subset of neutrophils that colocalize with peripheral blood mononuclear cells after density gradient centrifugation, have been observed in many immune-mediated diseases. LDGs are considered highly proinflammatory because of enhanced spontaneous formation of neutrophil extracellular traps, endothelial toxicity, and cytokine production. Concomitantly, increased numbers of LDGs are associated with the severity of many immune-mediated inflammatory diseases. Recent studies, with the help of advanced transcriptomic technologies, demonstrated that LDGs were a mixed cell population composed of immature subset and mature subset, and these two subsets showed different pathogenic features. In this review, we summarize the current knowledge on the composition, origin, and pathogenic properties of LDGs in several immune-mediated inflammatory diseases and discuss potential medical interventions targeting LDGs.

Inhibition of NETosis for treatment purposes: friend or foe?

Active neutrophils participate in innate and adaptive immune responses through various mechanisms, one of the most important of which is the formation and release of neutrophil extracellular traps (NETs). The NETs are composed of network-like structures made of histone proteins, DNA and other released antibacterial proteins by activated neutrophils, and evidence suggests that in addition to the innate defense against infections, NETosis plays an important role in the pathogenesis of several other non-infectious pathological states, such as autoimmune diseases and even cancer. Therefore, targeting NET has become one of the important therapeutic approaches and has been considered by researchers. NET inhibitors or other molecules involved in the NET formation, such as the protein arginine deiminase 4 (PAD4) enzyme, an arginine-to-citrulline converter, participate in chromatin condensation and NET formation, is the basis of this therapeutic approach. The important point is whether complete inhibition of NETosis can be helpful because by inhibiting this mechanism, the activity of neutrophils is suppressed. In this review, the biology of NETosis and its role in the pathogenesis of some important diseases have been summarized, and the consequences of treatment based on inhibition of NET formation have been discussed.

Clinical Experience of Proteasome Inhibitor Bortezomib Regarding Efficacy and Safety in Severe Systemic Lupus Erythematosus: A Nationwide Study

As treatment options in advanced systematic lupus erythematosus (SLE) are limited, there is an urgent need for new and effective therapeutic alternatives for selected cases with severe disease. Bortezomib (BTZ) is a specific, reversible, inhibitor of the 20S subunit of the proteasome. Herein, we report clinical experience regarding efficacy and safety from all patients receiving BTZ as therapy for SLE in Sweden during the years 2014−2020. 8 females and 4 males were included with a mean disease duration at BTZ initiation of 8.8 years (range 0.7–20 years). Renal involvement was the main target for BTZ. Reduction of global disease activity was recorded by decreasing SLEDAI-2K scores over time and remained significantly reduced at the 6-month (p=0.007) and the 12-month (p=0.008) follow-up visits. From BTZ initiation, complement protein 3 (C3) levels increased significantly after the 2^nd treatment cycle (p=0.05), the 6-month (p=0.03) and the 12-month (p=0.04) follow-up visits. The urine albumin/creatinine ratio declined over time and reached significance at the 6-month (p=0.008) and the 12-month follow-up visits (p=0.004). Seroconversion of anti-dsDNA (27%), anti-C1q (50%) and anti-Sm (67%) was observed. 6 of 12 patients experienced at least one side-effect during follow-up, whereof the most common adverse events were infections. Safety parameters (C-reactive protein, blood cell counts) mainly remained stable over time. To conclude, we report favorable therapeutic effects of BTZ used in combination with corticosteroids in a majority of patients with severe SLE manifestations irresponsive to conventional immunosuppressive agents. Reduction of proteinuria was observed over time as well as seroconversion of some autoantibody specificities. In most patients, tolerance was acceptable but mild adverse events was not uncommon. Special attention should be paid to infections and hypogammaglobinemia.

Low expression of TCP1 (T-Complex 1) and PSMC1 (Proteasome 26S subunit, ATPase 1) in heterotopic ossification during ankylosing spondylitis

Heterotopic ossification (HO) is frequently seen in patients with spinal injuries. Therefore, this study aimed to characterize the association of HO with ankylosing spondylitis (AS) through gene expression profiling. The human transcriptomic datasets (GSE73754 and GSE94683) were obtained from the Gene Expression Omnibus database for analysis. Overlapping differentially expressed genes (DEGs) were identified between AS and HO disease states. Subsequently, weighted gene co-expression network analysis (WGCNA) was performed for constructing and identifying hub genes for each condition. Finally, a consensus of the overlapping DEGs and the hub genes in AS and HO was taken for determining the key genes involved in AS-induced HO. Quantitative real-time polymerase chain reaction and western blotting were used to detect the mRNA and protein expression levels in mesenchymal stem cells of AS patients and controls. Additionally, immunohistochemistry was performed on interspinous ligament samples for experimental validation of genes. DEG analysis identified 355 overlapping genes between HO and AS. WGCNA indicated that the salmon module of the 22 modules constructed, was most significantly correlated with AS-induced HO. Subsequently, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of the salmon module indicated the presence of genes enriched in proteasome regulatory particle and proteasome pathways. mRNA expression analysis identified TCP1 and PSMC1 as the key genes in AS-induced HO. Further validation of these genes could help elucidate their role in the complex association of AS and HO.

Bortezomib: a proteasome inhibitor for the treatment of autoimmune diseases

Autoimmune diseases (ADs) are conditions in which the immune system cannot distinguish self from non-self and, as a result, tissue injury occurs primarily due to the action of various inflammatory mediators. Different immunosuppressive agents are used for the treatment of patients with ADs, but some clinical cases develop resistance to currently available therapies. The proteasome inhibitor bortezomib (BTZ) is an approved agent for first-line therapy of people with multiple myeloma. BTZ has been shown to improve the symptoms of different ADs in animal models and ameliorated symptoms in patients with systemic lupus erythematous, rheumatoid arthritis, myasthenia gravis, neuromyelitis optica spectrum disorder, Chronic inflammatory demyelinating polyneuropathy, and autoimmune hematologic diseases that were nonresponsive to conventional therapies. Proteasome inhibition provides a potent strategy for treating ADs. BTZ represents a proteasome inhibitor that can potentially be used to treat AD patients resistant to conventional therapies.

Role of Proteasomes in Inflammation

The ubiquitin–proteasome system (UPS) is involved in multiple cellular functions including the regulation of protein homeostasis, major histocompatibility (MHC) class I antigen processing, cell cycle proliferation and signaling. In humans, proteasome loss-of-function mutations result in autoinflammation dominated by a prominent type I interferon (IFN) gene signature. These genomic alterations typically cause the development of proteasome-associated autoinflammatory syndromes (PRAAS) by impairing proteasome activity and perturbing protein homeostasis. However, an abnormal increased proteasomal activity can also be found in other human inflammatory diseases. In this review, we cast a light on the different clinical aspects of proteasomal activity in human disease and summarize the currently studied therapeutic approaches.

Neutrophils in the Pathogenesis of Rheumatoid Arthritis and Systemic Lupus Erythematosus: Same Foe Different M.O

Dysregulated neutrophil activation contributes to the pathogenesis of autoimmune diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Neutrophil-derived reactive oxygen species (ROS) and granule proteases are implicated in damage to and destruction of host tissues in both conditions (cartilage in RA, vascular tissue in SLE) and also in the pathogenic post-translational modification of DNA and proteins. Neutrophil-derived cytokines and chemokines regulate both the innate and adaptive immune responses in RA and SLE, and neutrophil extracellular traps (NETs) expose nuclear neoepitopes (citrullinated proteins in RA, double-stranded DNA and nuclear proteins in SLE) to the immune system, initiating the production of auto-antibodies (ACPA in RA, anti-dsDNA and anti-acetylated/methylated histones in SLE). Neutrophil apoptosis is dysregulated in both conditions: in RA, delayed apoptosis within synovial joints contributes to chronic inflammation, immune cell recruitment and prolonged release of proteolytic enzymes, whereas in SLE enhanced apoptosis leads to increased apoptotic burden associated with development of anti-nuclear auto-antibodies. An unbalanced energy metabolism in SLE and RA neutrophils contributes to the pathology of both diseases; increased hypoxia and glycolysis in RA drives neutrophil activation and NET production, whereas decreased redox capacity increases ROS-mediated damage in SLE. Neutrophil low-density granulocytes (LDGs), present in high numbers in the blood of both RA and SLE patients, have opposing phenotypes contributing to clinical manifestations of each disease. In this review we will describe the complex and contrasting phenotype of neutrophils and LDGs in RA and SLE and discuss their discrete roles in the pathogenesis of each condition. We will also review our current understanding of transcriptomic and metabolomic regulation of neutrophil phenotype in RA and SLE and discuss opportunities for therapeutic targeting of neutrophil activation in inflammatory auto-immune disease.

SMAD-specific E3 ubiquitin ligase 2 promotes angiogenesis by facilitating PTX3 degradation in MSCs from patients with ankylosing spondylitis

Dysregulated angiogenesis of mesenchymal stem cells (MSCs) is closely related to inflammation and disrupted bone metabolism in patients with various autoimmune diseases. However, the role of MSCs in the development of abnormal angiogenesis in patients with ankylosing spondylitis (AS) remains unclear. In this study, we cultured human umbilical vein endothelial cells (HUVECs) with bone marrow-derived MSCs from patients with AS (ASMSCs) or healthy donors (HDMSCs) in vitro. Then, the cocultured HUVECs were assayed using a cell counting kit-8 (CCK-8) to evaluate the cell proliferation. A wound healing assay was performed to investigate cell migration, and a tube formation assay was conducted to determine the angiogenesis efficiency. ASMSCs exhibited increased angiogenesis, and increased expression of SMAD-specific E3 ubiquitin ligase 2 (Smurf2) in MSCs was the main cause of abnormal angiogenesis in patients with AS. Downregulation of Smurf2 in ASMSCs blocked angiogenesis, whereas overexpression of Smurf2 in HDMSCs promoted angiogenesis. The pro-angiogenic effect of Smurf2 was confirmed by the results of a Matrigel plug assay in vivo. By functioning as an E3 ubiquitin ligase in MSCs, Smurf2 regulated the levels of pentraxin 3 (PTX3), which has been shown to suppress angiogenesis through the PTX3-fibroblast growth factor 2 pathway. Moreover, Smurf2 transcription was regulated by activating transcription factor 4-induced endoplasmic reticulum stress. In conclusion, these results identify novel roles of Smurf2 in negatively regulating PTX3 stability and promoting angiogenesis in ASMSCs.

Insights into the Procoagulant Profile of Patients with Systemic Lupus Erythematosus without Antiphospholipid Antibodies

We aimed to identify the key players in the prothrombotic profile of patients with systemic lupus erythematosus (SLE) not mediated by antiphospholipid antibodies, as well as the potential utility of global coagulation tests to characterize hemostasis in these patients. Patients with SLE without antiphospholipid antibodies and without signs of thrombosis were included. The kinetics of clot formation were determined by ROTEM^®. Platelet activation markers were determined by flow cytometry. Thrombin generation associated with Neutrophil Extracellular Traps (NETs) and microparticles (MPs) was measured by calibrated automated thrombogram (CAT). The plasma levels of PAI-1 were also determined. ROTEM^® showed a procoagulant profile in SLE patients. SLE patients had activated platelets and more leukocyte/platelet aggregates at basal conditions. The plasma PAI-1 and platelet aggregates correlated with several ROTEM^® parameters. The thrombin generation associated withthe tissue factor (TF) content of MPs and with NETs was increased. Our results suggest the utility of global tests for studying hemostasis in SLE patients because they detect their procoagulant profile, despite having had neither antiphospholipid antibodies nor any previous thrombotic event. A global appraisal of hemostasis should, if possible, be incorporated into clinical practice to detect the risk of a thrombotic event in patients with SLE and to consequently act to prevent its occurrence.

Recent insights how combined inhibition of immuno/proteasome subunits enables therapeutic efficacy

The proteasome is a multicatalytic protease in the cytosol and nucleus of all eukaryotic cells that controls numerous cellular processes through regulated protein degradation. Proteasome inhibitors have significantly improved the survival of multiple myeloma patients. However, clinically approved proteasome inhibitors have failed to show efficacy against solid tumors, neither alone nor in combination with other therapies. Targeting the immunoproteasome with selective inhibitors has been therapeutically effective in preclinical models for several autoimmune diseases and colon cancer. Moreover, immunoproteasome inhibitors prevented the chronic rejection of allogeneic organ transplants. In recent years, it has become apparent that inhibition of one single active center of the proteasome is insufficient to achieve therapeutic benefits. In this review we summarize the latest insights how targeting multiple catalytically active proteasome subunits can interfere with disease progression in autoimmunity, growth of solid tumors, and allograft rejection.