Increased expression of Bruton’s tyrosine kinase in peripheral blood is associated with lupus nephritis

Bruton's tyrosine kinase: A promising target for treating systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disorder involving multiple organs and systems. There is growing evidence that autoreactive B cells occupy a central role in the occurrence and progression of SLE due to their ability to generate pathogenic autoantibodies. Small molecule inhibitors targeting Bruton's tyrosine kinase (BTK), a crucial intracellular kinase regulating B cell development and function, emerge as a new strategy to treat SLE in recent years and are superior to biologic agents depleting B cells in many aspects. Supportive data obtained from lupus-prone mice preliminarily demonstrated the promising therapeutic potential of BTK inhibition. However, these BTK inhibitors, including elsubrutinib, evobrutinib, etc., mostly face with unsatisfactory efficacy and certain safety issues during clinical use, driving the quest for new-generation inhibitors with improved potency and higher selectivity. This paper elaborates the importance of BTK involvement in SLE pathogenesis, reviews the clinical research progress of BTK inhibitors for SLE and discusses limitations and challenges the drugs met in development, in order to contribute to a deeper understanding of disease mechanism and provide a reference for new-generation BTK inhibitor research.

The conneXion between sex and immune responses

There are notable sex-based differences in immune responses to pathogens and self-antigens, with female individuals exhibiting increased susceptibility to various autoimmune diseases, and male individuals displaying preferential susceptibility to some viral, bacterial, parasitic and fungal infections. Although sex hormones clearly contribute to sex differences in immune cell composition and function, the presence of two X chromosomes in female individuals suggests that differential gene expression of numerous X chromosome-linked immune-related genes may also influence sex-biased innate and adaptive immune cell function in health and disease. Here, we review the sex differences in immune system composition and function, examining how hormones and genetics influence the immune system. We focus on the genetic and epigenetic contributions responsible for altered X chromosome-linked gene expression, and how this impacts sex-biased immune responses in the context of pathogen infection and systemic autoimmunity.

Xist Deletion in B Cells Results in Systemic Lupus Erythematosus Phenotypes

Systemic lupus erythematosus (SLE) is an autoimmune disease preferentially observed in females. X-linked gene expression in XX females is normalized to that of XY males by X-Chromosome Inactivation (XCI). However, B cells from female SLE patients and mouse models of SLE exhibit mislocalization of Xist RNA, a critical regulator of XCI, and aberrant expression of X-linked genes, suggesting that impairment of XCI may contribute to disease. Here, we find that a subset of female mice harboring a conditional deletion of Xis t in B cells ("Xist cKO") spontaneously develop SLE phenotypes, including expanded activated B cell subsets, disease-specific autoantibodies, and glomerulonephritis. Moreover, pristane-induced SLE-like disease is more severe in Xist cKO mice. Activated B cells from Xist cKO mice with SLE phenotypes have increased expression of proinflammatory X-linked genes implicated in SLE. Together, this work indicates that impaired XCI maintenance in B cells directly contributes to the female-bias of SLE.

Inhibitors of Bruton's tyrosine kinase as emerging therapeutic strategy in autoimmune diseases

Bruton's tyrosine kinase (BTK) is a cytoplasmic, non-receptor signal transducer, initially identified as an essential signaling molecule for B cells, with genetic mutations resulting in a disorder characterized by disturbed B cell and antibody development. Subsequent research revealed the critical role of BTK in the functionality of monocytes, macrophages and neutrophils. Various immune cells, among which B cells and neutrophils, rely on BTK activity for diverse signaling pathways downstream of multiple receptors, which makes this kinase an ideal target to treat hematological malignancies and autoimmune diseases. First-generation BTK inhibitors are already on the market to treat hematological disorders. It has been demonstrated that B cells and myeloid cells play a significant role in the pathogenesis of different autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus and primary Sjögren's syndrome. Consequently, second-generation BTK inhibitors are currently being developed to treat these disorders. Despite the acknowledged involvement of BTK in various cell types, the focus on B cells often overshadows its impact on innate immune cells. Among these cell types, neutrophils are often underestimated in the pathogenesis of autoimmune diseases. In this narrative review, the function of BTK in different immune cell subsets is discussed, after which an overview is provided of different upcoming BTK inhibitors tested for treatment of autoimmune diseases. Special attention is paid to BTK inhibition and its effect on neutrophil biology.

BTK signaling-a crucial link in the pathophysiology of chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is an inflammatory skin disorder that manifests with itchy wheals, angioedema, or both for more than 6 weeks. Mast cells and basophils are the key pathogenic drivers of CSU; their activation results in histamine and cytokine release with subsequent dermal inflammation. Two overlapping mechanisms of mast cell and basophil activation have been proposed in CSU: type I autoimmunity, also called autoallergy, which is mediated via IgE against various autoallergens, and type IIb autoimmunity, which is mediated predominantly via IgG directed against the IgE receptor FcεRI or FcεRI-bound IgE. Both mechanisms involve cross-linking of FcεRI and activation of downstream signaling pathways, and they may co-occur in the same patient. In addition, B-cell receptor signaling has been postulated to play a key role in CSU by generating autoreactive B cells and autoantibody production. A cornerstone of FcεRI and B-cell receptor signaling is Bruton tyrosine kinase (BTK), making BTK inhibition a clear therapeutic target in CSU. The potential application of early-generation BTK inhibitors, including ibrutinib, in allergic and autoimmune diseases is limited owing to their unfavorable benefit-risk profile. However, novel BTK inhibitors with improved selectivity and safety profiles have been developed and are under clinical investigation in autoimmune diseases, including CSU. In phase 2 trials, the BTK inhibitors remibrutinib and fenebrutinib have demonstrated rapid and sustained improvements in CSU disease activity. With phase 3 studies of remibrutinib ongoing, it is hoped that BTK inhibitors will present an effective, well-tolerated option for patients with antihistamine-refractory CSU, a phenotype that presents a considerable clinical challenge.

Promising Experimental Treatments for Lupus Nephritis: Key Talking Points and Potential Opportunities

Lupus nephritis (LN) is a frequent and serious complication of systemic lupus erythematosus (SLE), impairing patients' quality of life and significantly increasing mortality. Despite optimizing the use of conventional immunosuppressants and other biological drugs, its management remains unsatisfactory. This is mainly due to the heterogeneity of SLE, but also to insufficiently effective treatment regimens and clinical trial limitations (strict criteria, low number of patients included, and side effects). Most clinical trials of new biological therapies have failed to meet their primary endpoints in both general SLE and LN, with only two biological drugs (belimumab and anifrolumab) being approved by the Food and Drug Administration (FDA) for the treatment of SLE. Recently, several Phase II randomized controlled trials have evaluated the efficacy and safety of new biologics in LN, and some of them have demonstrated an improvement in clinical and laboratory measures. Multi-target therapies are also being successfully developed and encourage a belief that there will be an improvement in LN outcomes.

Targeted Small Molecules for Systemic Lupus Erythematosus: Drugs in the Pipeline

Despite the uncertainty of the pathogenesis of systemic lupus erythematosus, novel small molecules targeting specific intracellular mechanisms of immune cells are being developed to reverse the pathophysiological processes. These targeted molecules have the advantages of convenient administration, lower production costs, and the lack of immunogenicity. The Janus kinases, Bruton's tyrosine kinases, and spleen tyrosine kinases are important enzymes for activating downstream signals from various receptors on immune cells that include cytokines, growth factor, hormones, Fc, CD40, and B-cell receptors. Suppression of these kinases impairs cellular activation, differentiation, and survival, leading to diminished cytokine actions and autoantibody secretion. Intracellular protein degradation by immunoproteasomes, levered by the cereblon E3 ubiquitin ligase complex, is an essential process for the regulation of cellular functions and survival. Modulation of the immunoproteasomes and cereblon leads to depletion of long-lived plasma cells, reduced plasmablast differentiation, and production of autoantibodies and interferon-α. The sphingosine 1-phosphate/sphingosine 1-phosphate receptor-1 pathway is responsible for lymphocyte trafficking, regulatory T-cell/Th17 cell homeostasis, and vascular permeability. Sphingosine 1-phosphate receptor-1 modulators limit the trafficking of autoreactive lymphocytes across the blood-brain barrier, increase regulatory T-cell function, and decrease production of autoantibodies and type I interferons. This article summarizes the development of these targeted small molecules in the treatment of systemic lupus erythematosus, and the future prospect for precision medicine.

Targeting B cells and plasma cells in autoimmune diseases: From established treatments to novel therapeutic approaches

Autoimmune diseases are characterized by the recognition of self-antigens by the immune system, which leads to inflammation and tissue damage. B cells are directly and indirectly involved in the pathophysiology of autoimmunity, both via antigen-presentation to T cells and production of proinflammatory cytokines and/or autoantibodies. Consequently, B lineage cells have been identified as therapeutic targets in autoimmune diseases. B cell depleting strategies have proven beneficial in the treatment of rheumatoid arthritis (RA), systemic lupus erythematous (SLE), ANCA-associated vasculitis (AAV), multiple sclerosis (MS), and a wide range of other immune-mediated inflammatory diseases (IMIDs). However, not all patients respond to treatment or may not reach (drug-free) remission. Moreover, B cell depleting therapies do not always target all B cell subsets, such as short-lived and long-lived plasma cells. These cells play an active role in autoimmunity and in certain diseases their depletion would be beneficial to achieve disease remission. In the current review article, we provide an overview of novel strategies to target B lineage cells in autoimmune diseases, with the focus on rheumatic diseases. Both advanced therapies that have recently become available and more experimental treatments that may reach the clinic in the near future are discussed.

Efficacy and Safety of the Bruton's Tyrosine Kinase Inhibitor Evobrutinib in Systemic Lupus Erythematosus: Results of a Phase II, Randomized, Double-Blind, Placebo-Controlled Dose-Ranging Trial

OBJECTIVE

Evobrutinib is a highly selective, orally administered Bruton's tyrosine kinase (BTK) inhibitor. The objective of this phase II, multicenter, randomized, double-blind, placebo-controlled trial was to evaluate the efficacy and safety of evobrutinib in patients with active autoantibody-positive systemic lupus erythematosus (SLE).

METHODS

Patients were diagnosed with SLE by either the Systemic Lupus International Collaborating Clinics criteria or at least four American College of Rheumatology criteria 6 months or more prior to screening, had an SLE Disease Activity Index-2000 score of 6 or more, were autoantibody-positive and on standard-of-care therapy. Randomization was 1:1:1:1 to oral evobrutinib 25 mg once daily (QD), 75 mg QD, 50 mg twice daily, or placebo. Primary efficacy endpoints were SLE responder index (SRI)-4 response at week 52 and SRI-6 response at week 52 in the high disease activity subpopulation. Safety endpoints included treatment-emergent adverse events (TEAEs).

RESULTS

A total of 469 patients were randomized and received at least one dose of evobrutinib or placebo at the time of primary analysis. Mean (SD) age at baseline was 40.7 (±12.3) years; 94.9% of patients were female. Neither primary efficacy endpoint was met. All doses of evobrutinib were well tolerated, and there was no clear dose effect on the incidence of reported TEAEs, or serious TEAEs, including severe infections.

CONCLUSION

This phase II, dose-ranging trial in SLE failed to show a treatment effect of evobrutinib versus placebo at any dose. Evobrutinib was generally well tolerated, with no dose effect observed for TEAEs. These results suggest that BTK inhibition does not appear to be an effective therapeutic intervention for patients with SLE.

Therapeutic effect of ibrutinib, a selective Bruton's tyrosine kinase inhibitor, in orbital fibroblasts from patients with Graves' orbitopathy

PURPOSE

Bruton's tyrosine kinase (BTK) is an essential protein in B-cell antigen receptor (BCR) signaling pathway and is known to be related to pathogenetic effect on B-cell related malignancies and various autoimmune diseases. In this study, we investigated the therapeutic effect of ibrutinib, an orally bioavailable BTK inhibitor in the pathogenesis of Graves' orbitopathy (GO) in in vitro model.

METHODS

Expression of BTK in orbital tissues from GO and normal control subjects were evaluated by real-time polymerase chain reaction (PCR). Primary cultured orbital fibroblasts from each subject were exposed to ibrutinib and stimulated with interleukin (IL)-1β or insulin like growth factor (IGF)-1. Production of inflammatory cytokines was evaluated by real time PCR and enzyme-linked immunosorbent assays (ELISA). The downstream transcription factors were also determined by western blot assays.

RESULTS

The expression of BTK in GO tissues were significantly higher than in healthy controls. After stimulation of GO orbital fibroblasts with IL-1β or IGF-1, BTK mRNA and phosphorylated (p)- BTK protein expression was also enhanced. Ibrutinib reduced the expression of BTK mRNA and proteins of p-BTK, and inhibited the IL-1β- and IGF-1-induced production of proinflammatory cytokines including IL-6, IL-8 and COX-2 in both GO and normal cells. Ibrutinib also significantly attenuated phosphorylation of Akt, p38, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) in IL-1β stimulated GO cells and Akt, JNK, and NF-κB in IL-1ß stimulated normal cells.

CONCLUSIONS

BTK expression is enhanced in GO tissue and orbital fibroblasts. Ibrutinib, a BTK inhibitor suppresses proinflammatory cytokine production as well as phosphorylation of Akt and NF-κB protein. Our results suggest the potential role of BTK in GO inflammatory pathogenesis and possibility of a novel therapeutic target of GO.

B cell-targeted therapies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology that primarily affects women of childbearing age. There is no disease more heterogeneous than SLE as patients experience a myriad of manifestations and unpredictable periods of heightened disease activity. This heterogeneity not only makes it difficult for treatment decisions and prognostication, but has made drug development quite challenging. Despite these challenges, belimumab, voclosporin, and anifromulab, approved by the United States Food and Drug Administration (FDA) to treat SLE or lupus nephritis (LN), enhanced our armamentarium of traditional therapies, such as hydroxychloroquine, corticosteroids, and immunosuppressives. However, there remains a dire need to develop therapies that offer greater efficacy and safety. Patients with SLE produce excessive amounts of autoantibodies and cytokines that result in inflammation and organ damage. While a considerable number of potential drug development targets exist, there has been much attention focused on B cells. Strategies have included direct B cell killing, modulation of B cell function, inhibition of molecules essential to B cell growth and survival, and acceleration of autoantibody clearance, to name just a few. In this article, we review SLE clinical trials evaluating experimental agents that target B cells or plasma cells.

Human T-bet+ B cell development is associated with BTK activity and suppressed by evobrutinib

Recent clinical trials have shown promising results for the next-generation Bruton’s tyrosine kinase (BTK) inhibitor evobrutinib in the treatment of multiple sclerosis (MS). BTK has a central role in signaling pathways that govern the development of B cells. Whether and how BTK activity shapes B cells as key drivers of MS is currently unclear. Compared with levels of BTK protein, we found higher levels of phospho-BTK in ex vivo blood memory B cells from patients with relapsing-remitting MS and secondary progressive MS compared with controls. In these MS groups, BTK activity was induced to a lesser extent after anti-IgM stimulation. BTK positively correlated with CXCR3 expression, both of which were increased in blood B cells from clinical responders to natalizumab (anti–VLA-4 antibody) treatment. Under in vitro T follicular helper–like conditions, BTK phosphorylation was enhanced by T-bet–inducing stimuli, IFN-γ and CpG-ODN, while the expression of T-bet and T-bet–associated molecules CXCR3, CD21, and CD11c was affected by evobrutinib. Furthermore, evobrutinib interfered with in vitro class switching, as well as memory recall responses, and disturbed CXCL10-mediated migration of CXCR3⁺ switched B cells through human brain endothelial monolayers. These findings demonstrate a functional link between BTK activity and disease-relevant B cells and offer valuable insights into how next-generation BTK inhibitors could modulate the clinical course of patients with MS.

Integrated bioinformatics analysis reveals novel key biomarkers in diabetic nephropathy

Objectives:

The underlying molecular mechanisms of diabetic nephropathy have yet not been investigated clearly. In this investigation, we aimed to identify key genes involved in the pathogenesis and prognosis of diabetic nephropathy.

Methods:

We downloaded next-generation sequencing data set GSE142025 from Gene Expression Omnibus database having 28 diabetic nephropathy samples and nine normal control samples. The differentially expressed genes between diabetic nephropathy and normal control samples were analyzed. Biological function analysis of the differentially expressed genes was enriched by Gene Ontology and REACTOME pathways. Then, we established the protein–protein interaction network, modules, miRNA-differentially expressed gene regulatory network and transcription factor-differentially expressed gene regulatory network. Hub genes were validated by using receiver operating characteristic curve analysis.

Results:

A total of 549 differentially expressed genes were detected including 275 upregulated and 274 downregulated genes. The biological process analysis of functional enrichment showed that these differentially expressed genes were mainly enriched in cell activation, integral component of plasma membrane, lipid binding, and biological oxidations. Analyzing the protein–protein interaction network, miRNA-differentially expressed gene regulatory network and transcription factor-differentially expressed gene regulatory network, we screened hub genes MDFI, LCK, BTK, IRF4, PRKCB, EGR1, JUN, FOS, ALB, and NR4A1 by the Cytoscape software. The receiver operating characteristic curve analysis confirmed that hub genes were of diagnostic value.

Conclusions:

Taken above, using integrated bioinformatics analysis, we have identified key genes and pathways in diabetic nephropathy, which could improve our understanding of the cause and underlying molecular events, and these key genes and pathways might be therapeutic targets for diabetic nephropathy.

Bruton's tyrosine kinase regulates macrophage‑induced inflammation in the diabetic kidney via NLRP3 inflammasome activation

It has been previously reported that macrophages may be involved in diabetic nephropathy (DN) development. Furthermore, Bruton's tyrosine kinase (BTK) may participate in macrophage activation and lead to the release of inflammatory mediators. The main aim of the present study was to analyze the association between renal BTK expression and clinical indicators. Moreover, BTK knockout mice were used to establish a diabetic model for further research. The results demonstrated that BTK was activated in the kidneys of patients with DN and was associated with the progression of proteinuria, creatinine levels, estimated glomerular filtration rate and pathological changes in the kidneys of patients with DN. Furthermore, BTK knockout was observed to reduce urinary protein excretion, alleviate renal injury and decrease renal inflammation in diabetic mice. This protection may be attributed to BTK‑induced suppression of the activation of the Nod‑like receptor (NLR) family pyrin domain containing 3 inflammasome. Collectively, it has been demonstrated in the present study that BTK may be a potential target for DN treatment.

The dynamic epigenetic regulation of the inactive X chromosome in healthy human B cells is dysregulated in lupus patients

Systemic lupus erythematous (SLE) is a female-predominant disease characterized by autoimmune B cells and pathogenic autoantibody production. Individuals with two or more X chromosomes are at increased risk for SLE, suggesting that X-linked genes contribute to the observed sex bias of this disease. To normalize X-linked gene expression between sexes, one X in female cells is randomly selected for transcriptional silencing through X-chromosome inactivation (XCI), resulting in allele-specific enrichment of epigenetic modifications, including histone methylation and the long noncoding RNA XIST/Xist on the inactive X (Xi). As we have previously shown that epigenetic regulation of the Xi in female lymphocytes from mice is unexpectedly dynamic, we used RNA fluorescence in situ hybridization and immunofluorescence to profile epigenetic features of the Xi at the single-cell level in human B cell subsets from pediatric and adult SLE patients and healthy controls. Our data reveal that abnormal XCI maintenance in B cells is a feature of SLE. Using single-cell and bulk-cell RNA sequencing datasets, we found that X-linked immunity genes escape XCI in specific healthy human B cell subsets and that human SLE B cells exhibit aberrant expression of X-linked genes and XIST RNA interactome genes. Our data reveal that mislocalized XIST RNA, coupled with a dramatic reduction in heterochromatic modifications at the Xi in SLE, predispose for aberrant X-linked gene expression from the Xi, thus defining a genetic and epigenetic pathway that affects X-linked gene expression in human SLE B cells and likely contributes to the female bias in SLE.

Targeting Bruton's Tyrosine Kinase in Inflammatory and Autoimmune Pathologies

Bruton's tyrosine kinase (BTK) was discovered due to its importance in B cell development, and it has a critical role in signal transduction downstream of the B cell receptor (BCR). Targeting of BTK with small molecule inhibitors has proven to be efficacious in several B cell malignancies. Interestingly, recent studies reveal increased BTK protein expression in circulating resting B cells of patients with systemic autoimmune disease (AID) compared with healthy controls. Moreover, BTK phosphorylation following BCR stimulation in vitro was enhanced. In addition to its role in BCR signaling, BTK is involved in many other pathways, including pattern recognition, Fc, and chemokine receptor signaling in B cells and myeloid cells. This broad involvement in several immunological pathways provides a rationale for the targeting of BTK in the context of inflammatory and systemic AID. Accordingly, numerous in vitro and in vivo preclinical studies support the potential of BTK targeting in these conditions. Efficacy of BTK inhibitors in various inflammatory and AID has been demonstrated or is currently evaluated in clinical trials. In addition, very recent reports suggest that BTK inhibition may be effective as immunosuppressive therapy to diminish pulmonary hyperinflammation in coronavirus disease 2019 (COVID-19). Here, we review BTK's function in key signaling pathways in B cells and myeloid cells. Further, we discuss recent advances in targeting BTK in inflammatory and autoimmune pathologies.

Enhanced Bruton's tyrosine kinase activity in the kidney of patients with IgA nephropathy

Purpose

Bruton’s tyrosine kinase (BTK) is a vital biological molecule that contributes to immune regulation. Previous studies have showed that BTK can be detected in patients with lupus nephritis and rheumatoid arthritis. However, the role of BTK in IgA nephropathy (IgAN) has not yet been elucidated. The purpose of this research was to investigate the role of BTK activation in macrophages in IgAN.

Methods

Peripheral blood and renal tissue samples were collected from 63 patients with IgAN, and peritumoral normal tissues were collected from 20 patients after surgical resection of renal tumor for use as control. Additionally, 20 healthy volunteers were recruited as control. The levels of BTK, CD68, phosphorylated BTK (pBTK), phosphorylated NF-κB (p-NF-κB p65), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and monocyte chemotactic protein (MCP)-1 were measured by immunohistochemistry (IHC), real-time polymerase chain reaction (RT-PCR), western blotting, and enzyme-linked immunosorbent assay (ELISA).

Results

Compared to peritumoral normal tissues, the expression levels of CD68 and BTK were significantly increased in IgAN group (p < 0.001) and the differences between M0 and M1, E0 and E1, S0 and S1, T0 and T1-2, C0 and C1-2 were statistically significant in the updated Oxford Classification (p < 0.05). Also, CD68 and BTK were positively correlated with Katafuchi semi-quantitative glomerular and tubulointerstitial scores (r = 0.580, 0.637 and 0.442, 0.489, respectively, p < 0.05). The expression of BTK was significantly higher in C3b- and C4d-positive renal tissues of patients with IgAN (p < 0.05). In addition, BTK was positively correlated with 24-h urine protein, serum creatinine levels (r = 0.456 and 0.453, respectively, p < 0.001), and negatively correlated with serum albumin (r = 0.357, p < 0.05). The intensity of expression of pBTK and p-NF-κB p65 was observably increased in renal tissues and monocytes of patients with IgAN compared to the control group. The results of IHC, RT-PCR, and ELISA indicated that the levels of TNF-ɑ, IL-1β, and MCP-1 were markedly increased in the IgAN group (p < 0.05).

Conclusion

The results of this study indicate that activation of BTK in macrophages may play an important role in promoting the progression of renal inflammation in IgAN.

Bruton's Tyrosine Kinase Inhibitors: A New Therapeutic Target for the Treatment of SLE?

Systemic lupus erythematosus (SLE) is an autoimmune disease with a complex pathogenesis, which presents a great variability in its presentation and can affect almost all organs and systems. Multiple therapeutic targets have been discovered recently, but there also have been failed attempts to treat SLE using biologic agents. Bruton’s tyrosine kinase (BTK) is a cytoplasmic tyrosine kinase expressed in several types of cells of hematopoietic origin which participate in both innate and adaptive immunity. Ibrutinib, a BTK inhibitor, is approved for the treatment of several B cell malignancies, including some types of lymphoma and leukemia. As BTK is expressed on several immune cell types, the mechanism of action of BTK also suggests the use of BTK inhibitors in the treatment of autoimmune diseases. In this review, we will summarize what is known and what has been published so far about the treatment of mouse models of SLE and the human disease, using BTK inhibitors.

Safety, pharmacokinetics and pharmacodynamics of branebrutinib (BMS-986195), a covalent, irreversible inhibitor of Bruton's tyrosine kinase: Randomised phase I, placebo-controlled trial in healthy participants

Aims

Branebrutinib (BMS‐986195) is a potent, highly selective, oral, small‐molecule, covalent inhibitor of Bruton's tyrosine kinase (BTK). This study evaluated safety, pharmacokinetics and pharmacodynamics of branebrutinib in healthy participants.

Methods

This double‐blind, placebo‐controlled, single‐ and multiple‐ascending dose (SAD; MAD) Phase I study (NCT02705989) enrolled participants into 3 parts: SAD, MAD and JMAD (MAD in first‐generation Japanese participants). In each part, participants were randomised 3:1 to receive branebrutinib (SAD: 0.3–30 mg; [J]MAD: 0.3–10 mg) or placebo. Participants in the MAD parts received branebrutinib daily for 14 days and were followed for 14 days postdosing. Safety was assessed by monitoring, laboratory and physical examinations, vital signs, and recording adverse events (AEs). Pharmacodynamics were assessed with a mass spectrometry assay that measured drug‐occupied and free BTK.

Results

The SAD, MAD and JMAD parts of the study included 40, 32 and 24 participants. Branebrutinib was well tolerated and AEs were mild/moderate, except for 1 serious AE that led to discontinuation. Branebrutinib was rapidly absorbed, with maximum plasma concentration occurring within 1 hour and a half‐life of 1.2—1.7 hours, dropping to undetectable levels within 24 hours. BTK occupancy was rapid, with 100% occupancy reached after a single 10‐mg dose. BTK occupancy decayed predictably over time (mean half‐life in MAD panels: 115–154 hours), such that pharmacodynamic effects were maintained after branebrutinib plasma levels fell below the lower limit of quantification.

Conclusion

Rapid and high occupancy of BTK and the lack of notable safety findings support further clinical development of branebrutinib.

Loss of epigenetic modifications on the inactive X chromosome and sex-biased gene expression profiles in B cells from NZB/W F1 mice with lupus-like disease

The mechanisms underlying the female-bias in autoimmunity are poorly understood. The contribution of genetic and epigenetic factors from the inactive X chromosome (Xi) are beginning to emerge as critical mediators of autoimmunity in females. Here, we ask how epigenetic features of the Xi change during disease development in B cells from the NZB/W F1 spontaneous mouse model of lupus, which is female-biased. We find that Xist RNA becomes increasingly mislocalized from the Xi with disease onset. While NZB/W F1 naïve B cells have H3K27me3 foci on the Xi, which are missing from healthy C57BL/6 and BALB/c mice, these foci are progressively lost in stimulated B cells during disease. Using single-molecule RNA FISH, we show that the X-linked gene Tlr7 is biallelically expressed in ~20% of NZB/W F1 B cells, and that the amount of biallelic expression does not change with disease. We also present sex-specific gene expression profiles for diseased NZB/W F1 B cells, and find female-specific upregulation of 20 genes, including the autoimmunity-related genes Cxcl13, Msr1, Igj, and Prdm1. Together, these studies provide important insight into the loss of epigenetic modifications from the Xi and changes with gene expression in a mouse model of female-biased SLE.

Immune cell infiltration characteristics and related core genes in lupus nephritis: results from bioinformatic analysis

BACKGROUND

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus that presents a high risk of end-stage renal disease. In the present study, we used CIBERSORT and gene set enrichment analysis (GSEA) of gene expression profiles to identify immune cell infiltration characteristics and related core genes in LN.

RESULTS

Datasets from the Gene Expression Omnibus, GSE32591 and GSE113342, were downloaded for further analysis. The GSE32591 dataset, which included 32 LN glomerular biopsy tissues and 14 glomerular tissues from living donors, was analyzed by CIBERSORT. Different immune cell types in LN were analyzed by the Limma software. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis based on GSEA were performed by clusterProfiler software. Lists of core genes were derived from Spearman correlation between the most significant GO term and differentially expressed immune cell gene from CIBERSORT. GSE113342 was employed to validate the association between selected core genes and clinical manifestation. Five types of immune cells revealed important associations with LN, and monocytes emerged as having the most prominent differences. GO and KEGG analyses indicated that immune response pathways are significantly enriched in LN. The Spearman correlation indicated that 15 genes, including FCER1G, CLEC7A, MARCO, CLEC7A, PSMB9, and PSMB8, were closely related to clinical features.

CONCLUSIONS

This study is the first to identify immune cell infiltration with microarray data of glomeruli in LN by using CIBERSORT analysis and provides novel evidence and clues for further research of the molecular mechanisms of LN.

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.

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.

Management strategies and future directions for systemic lupus erythematosus in adults

Systemic lupus erythematosus (SLE) is an autoimmune disease characterised by the loss of self-tolerance and formation of nuclear autoantigens and immune complexes resulting in inflammation of multiple organs. The clinical presentation of SLE is heterogeneous, can involve one or more organs, including the skin, kidneys, joints, and nervous system, and take a chronic or relapsing and remitting disease course. SLE is most common in women and in those of non-white ethnicity. Because of the multitude of presentations, manifestations, and serological abnormalities in patients with SLE, diagnosis can be challenging. Therapeutic approaches predominantly involve immunomodulation and immunosuppression and are targeted to the specific organ manifestation, with the aim of achieving low disease activity. Despite many treatment advances and improved diagnostics, SLE continues to cause substantial morbidity and premature mortality. Current management strategies, although helpful, are limited by high failure rates and toxicity. An overreliance on corticosteroid therapy contributes to much of the long-term organ damage. In this Seminar, we outline the classification criteria for SLE, current treatment strategies and medications, the evidence supporting their use, and explore potential future therapies.

Non-receptor tyrosine kinase signaling in autoimmunity and therapeutic implications

Autoimmune diseases are characterized by impaired immune tolerance towards self-antigens, leading to enhanced immunity to self by dysfunctional B cells and/or T cells. The activation of these cells is controlled by non-receptor tyrosine kinases (NRTKs), which are critical mediators of antigen receptor and cytokine receptor signaling pathways. NRTKs transduce, amplify and sustain activating signals that contribute to autoimmunity, and are counter-regulated by protein tyrosine phosphatases (PTPs). The function of and interaction between NRTKs and PTPs during the development of autoimmunity could be key points of therapeutic interference against autoimmune diseases. In this review, we summarize the current state of knowledge of the functions of NRTKs and PTPs involved in B cell receptor (BCR), T cell receptor (TCR), and cytokine receptor signaling pathways that contribute to autoimmunity, and discuss their targeting for therapeutic approaches against autoimmune diseases.

Emerging targets for the treatment of lupus erythematosus: There is no royal road to treating lupus

Systemic lupus erythematosus (SLE) is a highly heterogeneous autoimmune disease that preferentially affects women of child-bearing age. Most current treatments for SLE with the exception of belimumab are not target-specific. Nontargeted therapy such as corticosteroids, cyclophosphamide, and other immunosuppressive drugs results in unwanted adverse effects. Although progress in treatment, including supportive therapy, has dramatically improved the prognosis of patients with SLE, better treatment drugs and protocols with fewer adverse effects and higher efficacy for the most severe form of SLE are needed. Advancements in genomics, immunology, and pathophysiology in the field of systemic autoimmunity have provided physicians with increasing knowledge, but the most appropriate treatment for each patient with SLE remains to be established. Therefore, the search for novel treatment targets in patients with SLE is ongoing. This review focuses on recent findings in the genetics of lupus and the abnormalities in cellular interactions, cytokine profiles, and intracellular signaling in patients with SLE. Novel molecular targets for lupus, mostly introduced through clinical trials, are then discussed based on these findings.

BTK inhibition ameliorates kidney disease in spontaneous lupus nephritis

Lupus nephritis is a common disease manifestation of SLE, in which immune complex deposition and macrophage activation are important contributors to disease pathogenesis. Bruton's tyrosine kinase (BTK) plays an important role in both B cell and FcgammaR mediated myeloid cell activation. In the current study, we examined the efficacy of BI-BTK-1, a recently described irreversible BTK inhibitor, in the classical NZB × NZW F1 (NZB/W) and MRL/lpr spontaneous mouse models of SLE. NZB/W mice were randomly assigned to a treatment (0.3 mg/kg, 1 mg/kg, 3 mg/kg and 10 mg/kg) or control group and began treatment at 22 weeks of age. The experimental setup was similar in MRL/lpr mice, but with a single treated (10 mg/kg, beginning at 8-9 weeks of age) and control group. A separate experiment was performed in the MRL/lpr strain to assess the ability of BI-BTK-1 to reverse established kidney disease. Early treatment with BI-BTK-1 significantly protected NZB/W and MRL/lpr mice from the development of proteinuria, correlating with significant renal histological protection, decreased anti-DNA titers, and increased survival in both strains. BI-BTK-1 treated mice displayed a significant decrease in nephritis-associated inflammatory mediators (e.g. LCN2 and IL-6) in the kidney, combined with a significant inhibition of immune cell infiltration and accumulation. Importantly, BI-BTK-1 treatment resulted in the reversal of established kidney disease. BTK inhibition significantly reduced total B cell numbers and all B cell subsets (immature, transitional, follicular, marginal zone, and class switched) in the spleen of NZB/W mice. Overall, the significant efficacy of BI-BTK-1 in ameliorating multiple pathological endpoints associated with kidney disease in two distinct murine models of spontaneous lupus nephritis provides a strong rationale for BTK inhibition as a promising treatment approach for lupus nephritis.

CircIBTK inhibits DNA demethylation and activation of AKT signaling pathway via miR-29b in peripheral blood mononuclear cells in systemic lupus erythematosus

Background

Systemic lupus erythematosus (SLE) is a chronic and incurable autoimmune disease involving the dysfunction of lymphocytes. Circular RNAs (circRNAs) are noncoding RNAs (ncRNAs) with a covalently closed loop structure, with abnormal expression in various human diseases may participate in the pathogenesis, while further study is needed in SLE. In this study, we aimed to find the circRNAs abnormally expressed in SLE and explore the function of circRNAs in SLE.

Methods

CircRNA sequencing was used to find the abnormally expressed circRNA and qRT-PCR was used to detect the expression. Correlation analysis was used to analyze the correlation between circIBTK or miR-29b and clinicopathological variables in patients with SLE. Cell culture, nuclear-cytoplasmic fractionation, qRT-PCR, transfection, luciferase reporter assay, western blot analysis, DNA extraction and global methylation analysis were used to explain the function of circIBTK and miR-29b in the progression of SLE. SPSS 18.0 software was used to perform statistics.

Results

We found that the expression of circIBTK was downregulated in SLE and correlated with Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score, anti-double-stranded (ds)DNA and complement C3 level in patients with SLE. Then miR-29b expression was upregulated in SLE and correlated with SLEDAI score, anti-dsDNA and complement C3 level in patients with SLE. Mechanistic investigations indicated that miR-29b could induce DNA demethylation and activate the AKT signaling pathway and circIBTK might reverse the DNA demethylation and activation of the AKT signaling pathway induced by miR-29b via binding to miR-29b in SLE.

Conclusions

CircIBTK was downregulated in SLE and might regulate DNA demethylation and the AKT signaling pathway via binding to miR-29b in SLE. CircIBTK and miR-29 could also act as biomarkers and therapeutic targets for SLE.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1618-8) contains supplementary material, which is available to authorized users.

Bruton's Tyrosine Kinase, a Component of B Cell Signaling Pathways, Has Multiple Roles in the Pathogenesis of Lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the loss of adaptive immune tolerance to nucleic acid-containing antigens. The resulting autoantibodies form immune complexes that promote inflammation and tissue damage. Defining the signals that drive pathogenic autoantibody production is an important step in the development of more targeted therapeutic approaches for lupus, which is currently treated primarily with non-specific immunosuppression. Here, we review the contribution of Bruton’s tyrosine kinase (Btk), a component of B and myeloid cell signaling pathways, to disease in murine lupus models. Both gain- and loss-of-function genetic studies have revealed that Btk plays multiple roles in the production of autoantibodies. These include promoting the activation, plasma cell differentiation, and class switching of autoreactive B cells. Small molecule inhibitors of Btk are effective at reducing autoantibody levels, B cell activation, and kidney damage in several lupus models. These studies suggest that Btk may promote end-organ damage both by facilitating the production of autoantibodies and by mediating the inflammatory response of myeloid cells to these immune complexes. While Btk has not been associated with SLE in GWAS studies, SLE B cells display signaling defects in components both upstream and downstream of Btk consistent with enhanced activation of Btk signaling pathways. Taken together, these observations indicate that limiting Btk activity is critical for maintaining B cell tolerance and preventing the development of autoimmune disease. Btk inhibitors, generally well-tolerated and approved to treat B cell malignancy, may thus be a useful therapeutic approach for SLE.