A77 1726, the active metabolite of leflunomide, attenuates lupus nephritis by promoting the development of regulatory T cells and inhibiting IL-17-producing double negative T cells

Double-Negative T (DNT) Cells in Patients with Systemic Lupus Erythematosus

Double-negative T (DNT) cells are a rare and unconventional T-lymphocyte subpopulation lacking both CD4 and CD8 markers. Their immunopathological roles and clinical relevance have yet to be elucidated. Beyond autoimmune lymphoproliferative syndrome (ALPS), these cells may also play a role in rheumatic disorders, including systemic lupus erythematosus (SLE); indeed, these two diseases share several autoimmune manifestations (including nephritis). Moreover, one of the main experimental murine models used to investigate lupus, namely the MRL/lpr mouse, is characterized by an expansion of DNT cells, which can support the production of pathogenic autoantibodies and/or modulate the immune response in this context. However, lupus murine models are not completely consistent with their human SLE counterpart, of course. In this mini review, we summarize and analyze the most relevant clinical studies investigating the DNT cell population in SLE patients. Overall, based on the present literature review and analysis, DNT cell homeostasis seems to be altered in patients with SLE. Indeed, most of the available clinical studies (which include both adults and children) reported an increased DNT cell percentage in SLE patients, especially during the active phases, even though no clear correlation with disease activity and/or inflammatory parameters has been clearly established. Well-designed, standardized, and longitudinal clinical studies focused on DNT cell population are needed, in order to further elucidate the actual contribution of these cells in SLE pathogenesis and their interactions with other immune cells (also implicated and/or altered in SLE, such as basophils), and clarify whether their expansion and/or immunophenotypic aspects may have any immunopathological relevance (and, then, represent potential disease markers and, in perspective, even therapeutic targets) or are just an unspecific epiphenomenon of autoimmunity.

TCRαβ+ CD4-/CD8- "double negative" T cells in health and disease-implications for the kidney

Double negative (DN) T cells, one of the least studied T lymphocyte subgroups, express T cell receptor αβ but lack CD4 and CD8 coreceptors. DN T cells are found in multiple organs including kidney, lung, heart, gastrointestinal tract, liver, genital tract, and central nervous system. DN T cells suppress inflammatory responses in different disease models including experimental acute kidney injury, and significant evidence supports an important role in the pathogenesis of systemic lupus erythematosus. However, little is known about these cells in other kidney diseases. Therefore, it is important to better understand different functions of DN T cells and their signaling pathways as promising therapeutic targets, particularly with the increasing application of T cell-directed therapy in humans. In this review, we aim to summarize studies performed on DN T cells in normal and diseased organs in the setting of different disease models with a focus on kidney.

CD3+CD4-CD8- (Double-Negative) T Cells in Inflammation, Immune Disorders and Cancer

The crucial role of CD4⁺ and CD8⁺ T cells in shaping and controlling immune responses during immune disease and cancer development has been well established and used to achieve marked clinical benefits. CD3⁺CD4^-CD8^- double-negative (DN) T cells, although constituting a rare subset of peripheral T cells, are gaining interest for their roles in inflammation, immune disease and cancer. Herein, we comprehensively review the origin, distribution and functions of this unique T cell subgroup. First, we focused on characterizing multifunctional DN T cells in various immune responses. DN regulatory T cells have the capacity to prevent graft-versus-host disease and have therapeutic value for autoimmune disease. T helper-like DN T cells protect against or promote inflammation and virus infection depending on the specific settings and promote certain autoimmune disease. Notably, we clarified the role of DN tumor-infiltrating lymphocytes and outlined the potential for malignant proliferation of DN T cells. Finally, we reviewed the recent advances in the applications of DN T cell-based therapy for cancer. In conclusion, a better understanding of the heterogeneity and functions of DN T cells may help to develop DN T cells as a potential therapeutic tool for inflammation, immune disorders and cancer.

Autoreactive T cells and their role in atopic dermatitis

Atopic dermatitis (AD) is an itchy, non-contagious relapsing and chronic inflammatory skin disease that usually develops in early childhood. This pathology is associated with food allergy, allergic asthma, allergic rhinitis and anaphylaxis which may persist in adulthood. The underlying mechanisms of AD (endotypes) are just beginning to be discovered and show a complex interaction of various pathways including skin barrier function and immune deviation. Immune reactions to self-proteins (autoantigens) of the skin have been identified in patients with inflammatory skin diseases, such as chronic spontaneous urticaria, connective tissue disease, pemphigus vulgaris and bullous pemphigoid. IgE antibodies and T cells directed against epitopes of the skin were observed in adult patients with severe and chronic AD as well. This was associated with disease severity and suggests a progression from allergic inflammation to severe autoimmune processes against the skin. IgE-mediated autoimmunity and self-reactive T cells might accelerate the ongoing skin inflammation or might contribute to the relapsing course of the disease. However, to date, the exact mechanisms of IgE-mediated autoimmunity and self-reactive T cells in the pathophysiology of AD are still unclear. The aim of this review is to evaluate the development of (autoreactive) T cells and their response to (auto)antigens, as well as the role of the peripheral tolerance in autoimmunity in the pathophysiology of AD, including the unmet needs and gaps.

Leflunomide ameliorates experimental autoimmune myasthenia gravis by regulating humoral and cellular immune responses

Leflunomide, an immunosuppressive disease-modifying anti-rheumatic drug (DMARD), is widely used in the treatment of rheumatoid arthritis (RA), psoriatic arthritis (PA) as well as multiple sclerosis. However, its role in myasthenia gravis (MG) has not yet been clearly explored. Here, we investigated the effect of leflunomide on experimental autoimmune myasthenia gravis (EAMG) in vivo and in vitro. The results demonstrated that leflunomide alleviated the severity of EAMG associated with reduced serum total anti-acetylcholine receptor (AChR) IgG levels. During the development of EAMG, the increase of follicular helper T cells (Tfh) 1, Tfh 17 cells and decrease of follicular regulatory T cells (Tfr) were reversely altered after leflunomide administration. Our work further found that leflunomide might inhibit Tfh cells through the IL-21/STAT3 pathway to reduce the secretion of antibodies by B cells. In addition, leflunomide rebuilt the balance of Th1/Th2/Th17/Treg subsets. These results suggested that leflunomide ameliorated EAMG severity by regulating humoral immune responses and Th cell profiles thereby providing a novel effective treatment strategy for MG.

Angiotensin II Type 2 Receptor Modulates Synovial Macrophage Polarization by Inhibiting GRK2 Membrane Translocation in a Rat Model of Collagen-Induced Arthritis

The chronic inflammatory autoimmune disease rheumatoid arthritis (RA) is characterized by an infiltration of activated proinflammatory immune cells into the joint that is accompanied by an overproduction of various mediators, leading to destruction of cartilage and bone erosion. Angiotensin II type 2 receptor (AT2R) is involved in antioxidative, anti-inflammatory, and antifibrotic responses. Synovial macrophages (SMs) are a type of tissue macrophages that are derived from bone marrow cells. SMs plays a central role in synovial regional immunization, which is significantly increased in both collagen-induced mice with arthritis mice and RA patients. AT2R activation caused a reversal of the polarization of SMs in the joint from the proinflammatory M1 SM to the tolerogenic, benign M2 SM. In consequence, this switch resulted in an attenuated form of the joint pathology in a rat model of collagen-induced arthritis. These results were mechanistically linked to the observation that GRK2 was translocated into cytoplasm, and ERK1/2 and NF-κB activation were inhibited. These findings open the way to a new therapeutic approach using an activation of AT2R to subvert joint inflammation in RA.

Efficacy of leflunomide combined with prednisone for the treatment of PLA2R-associated primary membranous nephropathy

Objective

To evaluate the clinical efficacy and safety of leflunomide (LEF) combined with prednisone for the treatment of PLA2R-associated primary membranous nephropathy (PMN) and changes in anti-PLA2R antibody titers after treatment.

Methods

Sixty patients with nephrotic syndrome, biopsy-proven MN and anti-PLA2R antibody positivity were included in this study conducted from December 2017 to February 2019. The patients were randomly divided into an experimental group (n = 30) and a control group (n = 30). The patients in the experimental group were treated with LEF combined with prednisone, whereas the patients in the control group were treated with cyclophosphamide (CTX) combined with prednisone. We assessed 24-h urinary protein and serum albumin levels, kidney function markers, blood lipid levels and anti-PLA2R antibody titers before and after treatment. Adverse reactions during treatment were recorded.

Results

After 16 weeks of treatment, there were 2 cases of complete remission and 6 cases of partial remission in the experimental group, with a total effective rate of 26.67%. In the control group, there were 4 cases of complete remission and 8 cases of partial remission, with a total effective rate of 40% (p > .05). After 24 weeks of treatment, the total effective rates of the experimental and control groups were 66.67% and 76.67%, respectively (p > .05). There were no significant differences in 24-h urinary protein, serum albumin, kidney function marker or blood lipid levels between the two groups after treatment (p > .05). However, there were fewer adverse reactions in the experimental group than in the control group (p < .05). After treatment, serum anti-PLA2R antibody titers were clearly decreased in patients with complete remission and partial remission (p < .05), but these levels remained relatively high in patients without remission (p > .05).

Conclusion

LEF combined with prednisone has a certain efficacy for the treatment of PLA2R-associated PMN and provokes few adverse reactions. A large-sample randomized double-blind controlled study with a long follow-up period is needed to verify the efficacy of LEF combined with prednisone.

Tris DBA Ameliorates Accelerated and Severe Lupus Nephritis in Mice by Activating Regulatory T Cells and Autophagy and Inhibiting the NLRP3 Inflammasome

Tris (dibenzylideneacetone) dipalladium (Tris DBA), a small-molecule palladium complex, has been shown to inhibit cell growth and proliferation in pancreatic cancer, lymphocytic leukemia, and multiple myeloma. In the current study, we examined the therapeutic effects of Tris DBA on glomerular cell proliferation, renal inflammation, and immune cells. Treatment of accelerated and severe lupus nephritis (ASLN) mice with Tris DBA resulted in improved renal function, albuminuria, and pathology, including measurements of glomerular cell proliferation, cellular crescents, neutrophils, fibrinoid necrosis, and tubulointerstitial inflammation in the kidneys as well as scoring for glomerulonephritis activity. The treated ASLN mice also showed significantly decreased glomerular IgG, IgM, and C3 deposits. Furthermore, the compound was able to 1) inhibit bone marrow-derived dendritic cell-mediated T cell functions and reduce serum anti-dsDNA autoantibody levels; 2) differentially regulate autophagy and both the priming and activation signals of the NLRP3 inflammasome; and 3) suppress the phosphorylation of JNK, ERK, and p38 MAPK signaling pathways. Tris DBA improved ASLN in mice through immunoregulation by blunting the MAPK (ERK, JNK)-mediated priming signal of the NLRP3 inflammasome and by regulating the autophagy/NLRP3 inflammasome axis. These results suggest that the pure compound may be a drug candidate for treating the accelerated and deteriorated type of lupus nephritis.

Analysis of interleukin-17 and interleukin-23 for estimating disease activity and predicting the response to treatment in active lupus nephritis patients

Renal biopsy is a "gold standard" for establishing the diagnosis and assessing prognosis and monitoring therapy in lupus nephritis (LN) patients, but it is an invasive and inconvenient procedure. Evidences showed that interleukin-17(IL-17) and interleukin-23(IL-23) may be as alternative biomarkers for diagnosing LN, monitoring LN activity and predicting the response to treatment of LN. To analyze the roles of IL-17 and IL-23 in evaluation activity of LN and predicting active LN response to immunosuppressive treatment, by comparison between IL-17, IL-23 and clinical data of LN. Eighty patients with LN and 20 healthy volunteers were enrolled in this study. Plasma levels of IL-17 and IL-23 were detected by ELISA and clinical data were collected in patients with LN. Thirty-seven patients with active LN accepted immunosuppressive therapy and followed up to 6 months. The roles of IL-17 and IL-23 in evaluation the activity of LN and the predictability for active LN response to immunosuppressive treatment were analyzed. The ages or gender rations between LN patients and healthy controls were not significant difference at baseline. Baseline levels of IL-17 and IL-23 were higher in patients with active LN compare to them in patients with inactive LN or controls (P<0.001) and IL-23 in patients with inactive LN was higher than its in controls (P=0.004). IL-17 and IL-23 decreased significantly in active LN patients after 6 months therapy (P<0.001). The baseline level of IL-23 was significantly different in subgroups response to the immunosuppressive treatment in patients with active LN (P=0.0014). Baseline level of IL-23 in complete response group was lower than its in partial response group (P=0.0015) or nonresponse group (P=0.013). IL-17 was negative correlation with C3 (r=-0.44, P<0.001). IL-17 and IL-23 correlated with systemic lupus erythematosus (SLE) disease activity index (P<0.001). The correlation between IL-17 and LN pathological acute index (AI) was higher than the correlation between IL-23 and AI. (r=0.52, P<0.001 vs. r=0.41, P<0.001). Receiver Operation Characteristics (ROC) showed that IL-17 and IL-23 could be used to evaluate SLE disease activity index. IL-17 could be used as biomarker to evaluate pathological AI. IL-23 could be used as a predictor for predicting response to immunosuppressive treatment in patients with active LN. IL-17 and IL-23 may involve and contribute to LN. IL-17 could be used as a biomarker for LN clinical and pathological AI. IL-23 could be used as a predictor for predicting response to immunosuppressive treatment in patients with active LN.

Interleukin 17A promotes diabetic kidney injury

The role of the pro-inflammatory cytokine IL-17 in the pathogenesis of numerous inflammatory disorders is well-documented, but conflicting results are reported for its role in diabetic nephropathy. Here we examined the role of IL-17 signalling in a model of streptozotocin-induced diabetic nephropathy through IL-17 knockout mice, administration of neutralising monoclonal anti-IL-17 antibody and in vitro examination of gene expression of renal tubular cells and podocytes under high glucose conditions with or without recombinant IL-17. IL-17 deficient mice were protected against progression of diabetic nephropathy, exhibiting reduced albuminuria, glomerular damage, macrophage accumulation and renal fibrosis at 12 weeks and 24 weeks. Administration of anti-IL-17 monoclonal antibody to diabetic wild-type mice was similarly protective. IL-17 deficiency also attenuated up-regulation of pro-inflammatory and pro-fibrotic genes including IL-6, TNF-α, CCL2, CXCL10 and TGF-β in diabetic kidneys. In vitro co-stimulation with recombinant IL-17 and high glucose were synergistic in increasing the expression of pro-inflammatory genes in both cultured renal tubular cells and podocytes. We conclude that absence of IL-17 signalling is protective against streptozotocin-induced diabetic nephropathy, thus implying a pro-inflammatory role of IL-17 in its pathogenesis. Targeting the IL-17 axis may represent a novel therapeutic approach in the treatment of this disorder.

Restoring self-tolerance in autoimmune diseases by enhancing regulatory T-cells

Self-tolerance, the state of unresponsiveness to self-tissues/antigens, is maintained through central and peripheral tolerance mechanisms, and a breach of these mechanisms leads to autoimmune diseases. Foxp3 + T-regulatory cells (Tregs) play an essential role in suppressing autoimmune response directed against self-antigens and thereby regulate self-tolerance. Natural Tregs are differentiated in the thymus on the basis of their higher TCR-affinity to self-antigens and migrate to the periphery where they maintain peripheral tolerance. In addition, extra-thymic differentiation of induced Tregs can occur in the periphery which can control abrupt immune responses under inflammatory conditions. A defect in Treg cell numbers and/or function is found to be associated with the development of autoimmune disease in several experimental models and human autoimmune diseases. Moreover, augmentation of Tregs has been shown to be beneficial in treating autoimmunity in preclinical models, and Treg based cellular therapy has shown initial promise in clinical trials. However, emerging studies have identified an unstable subpopulation of Tregs which expresses pro-inflammatory cytokines under both homeostatic and autoimmune conditions, as well as in ex vivo cultures. In addition, clinical translation of Treg cellular therapy is impeded by limitations such as lack of easier methods for selective expansion of Tregs and higher cost associated with GMP-facilities required for cell sorting, ex vivo expansion and infusion of ex vivo expanded Tregs. Here, we discuss the recent advances in molecular mechanisms regulating Treg differentiation, Foxp3 expression and lineage stability, the role of Tregs in the prevention of various autoimmune diseases, and critically review their clinical utility for treating human autoimmune diseases.

Leflunomide counter akt s cardiac hypertrophy

Cardiac hypertrophy (CH) is a major independent risk factor for heart failure and mortality. However, therapeutic interventions that target hypertrophy signaling in a load-independent way are unavailable. In a recent issue of Clinical Science (vol. 132, issue 6, 685-699), Ma et al. describe that the anti-inflammatory drug leflunomide markedly antagonized CH, dysfunction, and fibrosis induced by aortic banding or angiotensin-II in mice or by agonists in cultured cells. Unexpectedly, this occurred not via anti-inflammatory mechanisms but rather via inhibtion of Akt (protein kinase B, PKB) signaling. We further discuss the mechanisms underlying Akt activation and its effects on CH and review possible mechanisms of leflunomide effects. Despite some caveats, the availability of such a newly repurposed compound to treat CH can be a relevant advance.

A77 1726 (leflunomide) blocks and reverses cardiac hypertrophy and fibrosis in mice

T-cell infiltration and the subsequent increased intracardial chronic inflammation play crucial roles in the development of cardiac hypertrophy and heart failure (HF). A77 1726, the active metabolite of leflunomide, has been reported to have powerful anti-inflammatory and T cell-inhibiting properties. However, the effect of A77 1726 on cardiac hypertrophy remains completely unknown. Herein, we found that A77 1726 treatment attenuated pressure overload or angiotensin II (Ang II)-induced cardiac hypertrophy in vivo, as well as agonist-induced hypertrophic response of cardiomyocytes in vitro In addition, we showed that A77 1726 administration prevented induction of cardiac fibrosis by inhibiting cardiac fibroblast (CF) transformation into myofibroblast. Surprisingly, we found that the protective effect of A77 1726 was not dependent on its T lymphocyte-inhibiting property. A77 1726 suppressed the activation of protein kinase B (AKT) signaling pathway, and overexpression of constitutively active AKT completely abolished A77 1726-mediated cardioprotective effects in vivo and in vitro Pretreatment with siRNA targetting Fyn (si Fyn) blunted the protective effect elicited by A77 1726 in vitro More importantly, A77 1726 was capable of blocking pre-established cardiac hypertrophy in mice. In conclusion, A77 1726 attenuated cardiac hypertrophy and cardiac fibrosis via inhibiting FYN/AKT signaling pathway.

Leflunomide prevents ROS-induced systemic fibrosis in mice

Systemic sclerosis (SSc) is a connective tissue disorder characterized by fibrosis of the skin and inner organs, vasculopathy and immunological abnormalities. Recent insights into the polarization of macrophages in scleroderma and into the implication of STAT6 and KLF4 in this process have prompted us to investigate the effects of the inhibition of STAT6 signaling pathway by leflunomide in mice. SSc was induced in BALB/c mice by daily subcutaneous injections of hypochlorous acid (HOCl) or bleomycin. Mice were treated (or not) every other day, for 4 or 6 weeks, by leflunomide. Skin and lung fibrosis as well as immunological features were studied. Mice exposed to HOCl developed a diffuse cutaneous SSc with pulmonary fibrosis and anti-DNA topoisomerase 1 auto-antibodies. STAT6 pathway was hyperactivated and KLF4 was overexpressed in the skin and the lungs of diseased mice. Their inhibition by leflunomide prevented skin and lung fibrosis. Moreover, the hyperproliferative and pro-oxidative phenotype of skin and lung fibroblasts was reversed by leflunomide. Beneficial immunological effects of leflunomide were associated with decreased activation of CD4+ and CD8+ T cells, B cell activation, decreased auto-antibodies production and restored polarization of macrophages in the spleen. The improvement provided by leflunomide in both mouse models of SSc provides a rationale for the evaluation of this immunomodulating drug in the management of patients affected by this disease.

The role of icaritin in regulating Foxp3/IL17a balance in systemic lupus erythematosus and its effects on the treatment of MRL/lpr mice

Systemic lupus erythematosus (SLE) is a female predominant autoimmune disease characterized by multi-organ dysfunctions. However, current available therapies control the disease at the cost of many potential adverse effects. The development of safer and more effective therapies for SLE is a critical unmet need. Icaritin (ICT) is an active monomer extracted from Chinese herbals named the Epimedium genus. In this study, we found that ICT exhibited the capacity of regulating Foxp3/IL17a balance, enhancing Treg cell suppressive activities, and inhibiting over-activation of CD4(+)T cells from SLE. We also observed that ICT regulated Foxp3/IL17a balance by increasing STAT5b expression and histone methylation modification. Subsequent experiments further confirmed that ICT-treated mice exhibited amelioration of renal damages and suggested that ICT may be a potential new drug for the treatment of SLE.