Receptor IL-4Rα Research Articles

Interleukin-17: A pleiotropic cytokine implicated in inflammatory, infectious, and malignant disorders.

IL-17A, referred to as IL-17, is the founding member of a family of pro-inflammatory cytokines, including IL-17B, IL-17C, IL-17D, IL-17E (or IL-25), and IL-17F, which act via receptors IL-17RA to IL-17RE, and elicit potent cellular responses that impact diverse diseases. IL-17's interactions with various cytokines include forming a heterodimer with IL-17F and being stimulated by IL-23's activation of Th17 cells, which can lead to inflammation and autoimmunity. IL-17 is implicated in infectious diseases and inflammatory disorders such as rheumatoid arthritis and psoriasis, promoting neutrophil recruitment and anti-bacterial immunity, but potentially exacerbating fungal and viral infections, revealing its dual role as protective and pathologic. IL-17 is also involved in various cancers, including breast, colon, cervical, prostate, and skin cancer, contributing to proliferation, immune invasion, and metastases, but also playing a protective role in certain instances. Four FDA-approved drugs-secukinumab (for ankylosing spondylitis, enthesitis-related arthritis, hidradenitis suppurativa, non-radiographic axial spondyloarthritis, plaque psoriasis, and psoriatic arthritis), ixekizumab (for ankylosing spondylitis, non-radiographic axial spondyloarthritis, plaque psoriasis, and psoriatic arthritis), brodalumab (for plaque psoriasis), and bimekizumab (for plaque psoriasis)-suppress the IL-17 pathway, with more in development, including netakimab, sonelokimab, izokibep, and CJM112. These agents and others are being studied across a spectrum of disorders. Understanding the complicated interplay between IL-17 and other immune mediators may yield new treatments for inflammatory/autoimmune conditions and malignancies.

Cell-Specific Contribution of IL-4 Receptor α Signaling Shapes the Overall Manifestation of Allergic Airway Disease.

IL-4 and IL-13 play a critical role in allergic asthma pathogenesis via their common receptor IL-4Rα. However, the cell-specific role of IL-4Rα in mixed allergen (MA)-induced allergic asthma has remained unclear. Therefore, we aimed to identify the cell-specific contribution of IL-4Rα signaling in the manifestation of various pathological outcomes in mice with allergic airway disease. We compared MA-induced pathological outcomes between hematopoietic progenitor cell (HPC)- or non-HPC-specific IL-4Rα-deficient chimera, myeloid cell-specific IL-4Rα-deficient (LysMcre+/+IL-4Rαfl/fl), and airway epithelial cell-specific IL-4Rα-deficient (CCSP-Cre+/IL-4Rαfl/fl) mice. Chimeric mice with systemic IL-4Rα sufficiency displayed hallmark features of allergic asthma, including eosinophilic and lymphocytic infiltration, type 2 (T-helper type 2) cytokine/chemokine production, IgE production, and lung pathology. These features were markedly reduced in chimeric mice with systemic IL-4Rα deficiency. Non-HPC-specific IL-4Rα-deficient mice displayed typical inflammatory features of allergic asthma but with markedly reduced mucous cell metaplasia (MCM). Deletion of IL-4Rα signaling on airway epithelial cells, a subpopulation within the non-HPC lineage, resulted in almost complete absence of MCM. In contrast, all features of allergic asthma except for MCM and mucin production were mitigated in HPC-specific IL-4Rα-deficient chimeric mice. Deleting IL-4Rα signaling in myeloid cells, a subpopulation within the HPC lineage, significantly alleviated MA-induced allergic airway inflammatory responses, but, similar to the HPC-specific IL-4Rα-deficient chimeric mice, these mice showed significant MCM and mucin production. Our findings demonstrate that the differential allergen responsiveness seen in mice with HPC-specific and non-HPC-specific IL-4Rα deficiency is predominantly driven by the absence of IL-4Rα in myeloid cells and airway epithelial cells, respectively. Our findings also highlight distinct and mutually exclusive roles of IL-4Rα signaling in mediating pathological outcomes within the myeloid and airway epithelial cell compartments.

Plasma IL-1 and IL-6 Family Cytokines with Soluble Receptor Levels at Diagnosis in Head and Neck Squamous Cell Carcinoma: High Levels Predict Decreased Five-Year Disease-Specific and Overall Survival.

Activation of the acute-phase cascade (APC) has been correlated with outcomes in various cancers, including head and neck squamous cell carcinoma (HNSCC). Primary drivers of the APC are the cytokines within the interleukin-6 (IL-6) and IL-1 families. Plasma levels of IL-6 family cytokines/soluble receptors (IL-6, IL-27, IL-31, OSM, CNTF, soluble (s-)gp130, s-IL-6Rα) and IL-1 family members (IL-1RA, s-IL-33Rα) were determined at diagnosis for 87 human papillomavirus (HPV)-negative (-) HNSCC patients. We then studied the 5-year Disease-Specific Survival (DSS) and Overall Survival (OS). Increased plasma levels of IL-6 (p < 0.001/p < 0.001) (DSS/OS), IL-31 (p = 0.044/p = 0.07), IL-1RA (p = 0.004/p = 0.035), soluble (s)-IL-6Rα p = 0.022/p = 0.035), and s-gp130 (p = 0.007/p = 0.003) at diagnosis were predictors of both OS and DSS from HPV(-) HNSCC patients. The cytokine DSS/OS predictions were associated with TNM stage and smoking history, whereas the soluble receptors IL-6Rα, gp130, and IL33Rα more uniquely predicted DSS/OS. Clinically, IL-6 levels above 2.5 pg/mL yielded 75% specificity and 70% sensitivity for DSS. In conclusion, high plasma levels of IL-6, IL-31, and IL-1RA, as well as the soluble receptors IL-6Rα, gp130, and IL33Rα, predicted clinical outcome. This shows their potential as candidates for both general therapy and immune therapy stratification, as well as being future platforms for the development of new immunotherapy.

Expression of IL-17RA in Innate Cells of Patients with Common Variable Immunodeficiency (CVID) and its Clinical Implications.

Background. Common Variable Immunodeficiency (CVID) is a primary immunodeficiency disorder characterized by B-cell dysfunction and immunoglobulin production deficiency. Dysregulation of interleukin-17 (IL-17) and its receptor IL-17RA have been reported in various immune disorders. This study aimed to investigate the expression of IL-17RA in innate immune cells of CVID patients and its correlation with clinical manifestations. Methods. A cross-sectional study included 22 CVID patients and 14 age- and sex-matched healthy controls. IL-17RA expression was assessed in various immune cell subsets using flow cytometry. Demographic and clinical data were collected, and statistical analysis was performed. Results. CVID patients had elevated IL-17RA expression in neutrophils, non-classical monocytes, and dendritic cells compared to healthy controls. Patients with a history of intestinal microbial colonization, particularly with Campylobacter jejuni and Giardia intestinalis, showed significantly higher IL-17RA expression in innate cells. Elevated IL-17RA expression in monocytes and dendritic cells also correlated with higher fecal calprotectin levels in CVID patients, regardless of microbial colonization. Conclusions. The study suggests that despite previous reports of reduced circulating Th17 cells and IL-17 levels in CVID patients, IL-17RA expression in innate cells may be elevated, potentially indicating altered IL-17 signaling. This heightened IL-17RA expression could contribute to a persistent pro-inflammatory state, possibly due to microbial translocation or other inflammatory factors. The association of IL-17RA expression with gastrointestinal microbial colonization and its correlation with fecal calprotectin underscores the complexity of IL-17RA's role in CVID pathophysiology. Further research in larger cohorts could elucidate the implications of IL-17RA expression in both infectious and non-infectious inflammatory aspects of CVID.

The IL-17-IL-17RA axis is required to promote osteosarcoma progression in mice

Osteosarcoma is rare but is the most common bone tumor. Diagnostic tools such as magnetic resonance imaging development of chemotherapeutic agents have increased the survival rate in osteosarcoma patients, although 5-year survival has plateaued at 70%. Thus, development of new treatment approaches is needed. Here, we report that IL-17, a proinflammatory cytokine, increases osteosarcoma mortality in a mouse model with AX osteosarcoma cells. AX cell transplantation into wild-type mice resulted in 100% mortality due to ectopic ossification and multi-organ metastasis. However, AX cell transplantation into IL-17-deficient mice significantly prolonged survival relative to controls. CD4-positive cells adjacent to osteosarcoma cells express IL-17, while osteosarcoma cells express the IL-17 receptor IL-17RA. Although AX cells can undergo osteoblast differentiation, as can patient osteosarcoma cells, IL-17 significantly inhibited that differentiation, indicating that IL-17 maintains AX cells in the undifferentiated state seen in malignant tumors. By contrast, IL-17RA-deficient mice transplanted with AX cells showed survival comparable to wild-type mice transplanted with AX cells. Biopsy specimens collected from osteosarcoma patients showed higher expression of IL-17RA compared to IL-17. These findings suggest that IL-17 is essential to maintain osteosarcoma cells in an undifferentiated state and could be a therapeutic target for suppressing tumorigenesis.

The mechanism of IL-13 targeting IL-13Rα2 in regulating oral mucosal FBs through PI3K/AKT/mTOR.

The objective of this investigation was to examine the presence of interleukin (IL)-13 and its receptor IL-13Rα2 in the tissues of oral submucous fibrosis (OSF), investigate their biological functions, and explore the underlying mechanisms involved in the development of OSF. The expression of IL-13 and IL-13Rα2 in the oral mucosa of patients with OSF and normal individuals was determined through immunohistochemistry and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Primary fibroblasts (FBs) were extracted through enzymatic digestion and then cultured. Immunofluorescence was employed to identify the FB cultures and the location of IL-13Rα2. The effects of IL-13/IL-13Rα2/PI3K/AKT/mTOR on the migration, proliferation, and secretion of fiber-related proteins of FBs were explored via the wound healing assay, CCK-8 assay, EDU assay, and RT-qPCR. The impact of IL-13Rα2 silencing and PI3K/AKT inhibition on the effect of IL-13 on FBs was analyzed by RT-qPCR and Western blotting. IL-13 and IL-13Rα2 were highly expressed in OSF. Primary FBs were successfully extracted and cultured. IL-13Rα2 was found to be localized in myofibroblasts. IL-13 promoted the proliferation, migration, and secretion of fibril-associated proteins in FBs. The proliferation, migration, and secretion of fibril-associated proteins of FBs were decreased following IL-13Rα2 silencing and inhibition of the PI3K/AKT/mTOR pathway. IL-13 may promote the proliferation, migration, and secretion of fiber-related proteins of FBs through the PI3K/AKT/mTOR pathway by targeting IL-13Rα2.

Role of IL-17A and IL-17RA in Prostate Cancer with Lymph Nodes Metastasis: Expression Patterns and Clinical Significance.

Prostate cancer (PCa) is the second most frequently diagnosed cancer among men. The use of IL-17A and its receptor IL-17RA as prognostic markers for PCa has shown promising results. We analyzed the clinical data of 77 patients with PCa after radical prostatectomy with lymphadenectomy and lymph node metastasis (LN+). We assessed the expression levels of IL-17A and IL-17RA in cancer cells in prostate and, for the first time, also in LN+. Prostate IL-17A expression positively correlated with BMI (p = 0.028). In LN+, the expression of IL-17A was positively correlated with the percentage of affected lymph nodes (p = 0.006) and EAU risk groups (p = 0.001). Additionally, in the group with high IL-17A expression in LN+, the extracapsular extension (ECE) of the prostate was significantly more frequent (p = 0.033). Also, significant correlations with the level of IL-17RA expression was found-expression was higher in prostate than in LN+ (p = 0.009); in LN+, expression positively correlated with the EAU risk group (p = 0.045), and in the group of high expression in LN+ ECE of lymph nodes was detected significantly more often (p = 0.009). Our findings support the potential role of IL-17A and IL-17RA as PCa markers; however, further studies are needed to determine their roles and potential clinical applications.

Binding, Neutralization and Internalization of the Interleukin-13 Antibody, Lebrikizumab.

IL-13 is the primary upregulated cytokine in atopic dermatitis (AD) skin and is the pathogenic mediator driving AD pathophysiology. Lebrikizumab, tralokinumab and cendakimab are therapeutic monoclonal antibodies (mAb) that target IL-13. We undertook studies to compare in vitro binding affinities and cell-based functional activities of lebrikizumab, tralokinumab and cendakimab. Lebrikizumab bound IL-13 with higher affinity (as determined using surface plasma resonance) and slower off-rate. It was more potent in neutralizing IL-13-induced effects in STAT6 reporter and primary dermal fibroblast periostin secretion assays than either tralokinumab or cendakimab. Live imaging confocal microscopy was employed to determine the mAb effects on IL-13 internalization into cells via the decoy receptor IL-13Rα2, using A375 and HaCaT cells. The results showed that only the IL-13/lebrikizumab complex was internalized and co-localized with lysosomes, whereas IL-13/tralokinumab or IL-13/cendakimab complexes did not internalize. Lebrikizumab is a potent, neutralizing high-affinity antibody with a slow disassociation rate from IL-13. Additionally, lebrikizumab does not interfere with IL-13 clearance. Lebrikizumab has a different mode of action to both tralokinumab and cendakimab, possibly contributing to the clinical efficacy observed by lebrikizumab in Ph2b/3 AD studies.

TRLS-05. PRELIMINARY RESULTS FROM A PHASE I TRIAL TO EVALUATE INTRAVENTRICULAR DELIVERY OF IL13RΑ2-TARGETING CAR T CELLS AFTER LYMPHODEPLETION IN PEDIATRIC BRAIN TUMORS PATIENTS

Abstract Brain tumors are the leading cause of cancer death in children, and outcomes for patients with recurrent or aggressive disease remain poor. We have previously shown that locoregionally-delivered chimeric antigen receptor (CAR) T cells targeting the high-affinity IL13 receptor IL13Rα2 are safe and well-tolerated in adults, and that they can mediate a remarkable clinical response. This antigen is also expressed on roughly half of pediatric neuromalignancies. Here, we present the clinical experience from the first patients treated with IL13BBζ-CAR T cells on our trial. Patients received four doses of CAR T cells, delivered weekly through an indwelling CNS catheter; the first dose was 1e7 CAR T cells and subsequent doses were 5e7 cells. The first three patients received CAR T cells alone; the rest received lymphodepletion with cyclophosphamide and fludarabine before CAR T cell infusion. After follow-up imaging at the end of the dose-limiting toxicity (DLT) period, patients were given the option to continue therapy. Six patients have been treated without DLTs; one patient on the lymphodepletion arm did not complete the four infusions due to a Grade 3 catheter-related infection. Other patients experienced occasional Grade 3 AEs that were not attributed to CAR T therapy, with the exception of headache, muscle weakness, and ALT elevation. Otherwise, AEs were Grade 1-2. Five patients completed four infusions and were evaluable at the end of the DLT period. Of those, three experienced radiographic and/or clinical benefit, although none met protocol criteria for a partial response. Specific cytokines were increased in the cerebrospinal fluid (CSF) of patients during radiographic response periods. Additionally, single-cell transcriptomic analysis paired with TCR sequencing of CSF cells demonstrated characteristic immune signatures correlated with response. These preliminary results support combining lymphodepletion and repeated intraventricular CAR T cell delivery as a promising therapy in children with brain tumors.

Genomic control of inflammation in experimental atopic dermatitis

Atopic Dermatitis (AD) or eczema, a recurrent allergic inflammation of the skin, afflicts 10–20% of children and 5% adults of all racial and ethnic groups globally. We report a new topical treatment of AD by a Nuclear Transport Checkpoint Inhibitor (NTCI), which targets two nuclear transport shuttles, importin α5 and importin β1. In the preclinical model of AD, induced by the active vitamin D3 analog MC903 (calcipotriol), NTCI suppressed the expression of keratinocyte-derived cytokine, Thymic Stromal Lymphopoietin (TSLP), the key gene in AD development. Moreover, the genes encoding mediators of TH2 response, IL-4 and its receptor IL-4Rα were also silenced together with the genes encoding cytokines IL-1β, IL-6, IL-13, IL-23α, IL-33, IFN-γ, GM-CSF, VEGF A, the chemokines RANTES and IL-8, and intracellular signal transducers COX-2 and iNOS. Consequently, NTCI suppressed skin infiltration by inflammatory cells (eosinophils, macrophages, and CD4 + T lymphocytes), and reduced MC903-evoked proliferation of Ki-67-positive cells. Thus, we highlight the mechanism of action and the potential utility of topical NTCI for treatment of AD undergoing Phase 1/2 clinical trial (AMTX-100 CF, NCT04313400).

Brain Interleukin-17A contributes to neuroinflammation and cardiac dysfunction in rats with myocardial infarction.

Proinflammatory cytokines produced outside the central nervous system can act in the brain to promote sympathetic activation that contributes to the progression of heart failure (HF). Interleukin (IL)-17A, a key inflammatory regulator which orchestrates immune responses to promote chronic inflammation, has been implicated in the pathophysiology of HF. We previously reported that IL-17A acts within the brain, particularly in the hypothalamic paraventricular nucleus (PVN), to increase expression of inflammatory mediators and, consequently, sympathetic outflow. The present study sought to determine whether IL-17A levels are elevated in a rat model of HF induced by myocardial infarction and, if so, whether increased expression of IL-17A in the brain itself contributes to neuroinflammation and cardiac dysfunction in this disease setting. Male SD rats underwent coronary artery ligation (CL) to induce HF or sham operation (SHAM). Compared with SHAM rats, HF rats exhibited significantly increased IL-17A levels in plasma, beginning within 1 week with a peak increase at 4 weeks after CL. IL-17A levels in cerebrospinal fluid (CSF) were also increased in HF rats and correlated with IL-17A levels in the plasma. The mRNA expression of IL-17A and its receptor IL-17RA, but not IL-17RC, was markedly upregulated in the PVN of HF when compared with SHAM rats. Genetic knockdown of IL-17RA by bilateral PVN microinjections of an IL-17RA siRNA AAV virus attenuated mRNA expression of proinflammatory cytokines and chemokines, and ameliorated sympathetic activation and cardiac function in HF rats. These data indicate that elevated expression of IL-17A in the brain in HF contributes to the excessive central inflammatory state and cardiac dysfunction in HF. Interventions to suppress IL-17A/IL-17RA axis in the brain have the potential for treating HF.

IL-15/IL-15Rα in SJS/TEN: Relevant Expression of IL15 and IL15RA in Affected Skin.

Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a life-threatening hypersensitivity reaction to medications characterized by keratinocyte apoptosis and skin detachment. IL-15 serum levels have been associated with severity and prognosis of SJS/TEN. We have measured IL-15 concentrations in serum and blister fluid (BF) from patients with SJS/TEN by ELISA and used quantitative RT-PCR to analyze the expression of IL15 and IL15RA (encoding for IL-15 Receptor-α chain) genes in peripheral blood and BF cells, including isolated monocytes, and in affected skin. A positive correlation was found between IL-15 serum levels and a percent of detached skin. BF concentrations were higher, but no correlation was found. Higher IL15 and IL15RA gene expression levels were found in skin-infiltrating blister fluid cells compared to peripheral mononuclear cells. Moreover, IL15RA transcripts were barely detected in healthy skin, being the highest expression levels found in samples from two SJS/TEN patients who did not survive. The cutaneous expression of IL-15Rα in SJS/TEN may provide an explanation to the tissue-specific immune cytotoxic response in this clinical entity, and the results suggest that the effects of IL-15 in SJS/TEN patients may be dependent on the expression of its private receptor IL-15Rα in affected skin.

Use of Dupilumab in Bullous Pemphigoid: Where Are We Now?

Bullous pemphigoid (BP) is the most frequent autoimmune subepidermal bullous disease. At present, the main treatment options are represented by corticosteroids and immunosuppressant drugs. Steroids often need to be administered in high doses, with subsequent adverse events and safety issues, as BP mainly affects elderly people. As dupilumab, a recombinant fully human IgG4 monoclonal antibody with binding specificity to human interleukin-4 receptor IL-4Rα has become paramount in the treatment of atopic dermatitis, its use in autoimmune bullous diseases has been theorized and it has been used to treat patients with BP. Dupilumab seems to be an effective and safe option to treat recalcitrant BP. Here, we report the results of a literature review on the use of dupilumab in BP, including a total of 30 treated patients in 9 papers.

Structure-based 3D-Pharmacophore modeling to discover novel interleukin 6 inhibitors: An in silico screening, molecular dynamics simulations and binding free energy calculations.

Interleukin 6 (IL-6) is a cytokine with various biological functions in immune regulation, hematopoiesis, and inflammation. Elevated IL-6 levels have been identified in several severe disorders such as sepsis, acute respiratory distress syndrome (ARDS), and most recently, COVID-19. The biological activity of IL-6 relies on interactions with its specific receptor, IL-6Rα, including the membrane-bound IL-6 receptor (mIL-6R) and the soluble IL-6 receptor (sIL-6R). Thus, inhibition of the interaction between these two proteins would be a potential treatment for IL-6 related diseases. To date, no orally available small-molecule drug has been approved. This study focuses on finding potential small molecules that can inhibit protein-protein interactions between IL-6 and its receptor IL-6Rα using its crystal structure (PDB ID: 5FUC). First, two pharmacophore models were constructed based on the interactions between key residues of IL-6 (Phe74, Phe78, Leu178, Arg179, Arg182) and IL-6Rα (Phe229, Tyr230, Glu277, Glu278, Phe279). A database of approximately 22 million compounds was screened using 3D-pharmacophore models, molecular docking models, and ADMET properties. By analyzing the interactive capability of successfully docked compounds with important amino acids, 12 potential ligands were selected for further analysis via molecular dynamics simulations. Based on the stability of the complexes, the high interactions rate of each ligand with the key residues of IL-6/IL-6Rα, and the low binding free energy calculation, two compounds ZINC83804241 and ZINC02997430, were identified as the most potential IL-6 inhibitor candidates. These results will pave the way for the design and optimization of more specific compounds to combat cytokine storm in severe coronavirus patients.

Deletion of IL-17ra in osteoclast precursors increases bone mass by decreasing osteoclast precursor abundance.

Metabolic bone diseases, such as osteoporosis, typically reflect an increase in the number and activity of bone-resorbing osteoclasts that result in a loss of bone mass. Inflammatory mediators have been identified as drivers of both osteoclast formation and activity. The IL-17 family of inflammatory cytokines has gained attention as important contributors to both bone formation and resorption. The majority of IL-17 cytokines signal through receptor complexes containing IL-17a receptor (IL-17ra); however, the role of IL-17ra signaling in osteoclasts remains elusive. In this study, we conditionally deleted Il17ra in osteoclast precursors using LysM-Cre and evaluated the phenotypes of skeletally mature male and female conditional knockout and control mice. The conditional knockout mice displayed an increase in trabecular bone microarchitecture in both the appendicular and axial skeleton. Assessment of osteoclast formation in vitro revealed that deletion of Il17ra decreased osteoclast number, which was confirmed in vivo using histomorphometry. This phenotype was likely driven by a lower abundance of osteoclast precursors in IL-17ra conditional knockout mice. This study suggests that IL-17ra signaling in preosteoclasts can contribute to osteoclast formation and subsequent bone loss.

Expression and activity of IL-17 receptor subunits in human cutaneous cells as targets for anti-IL-17 therapeutic antibodies

The key players in different chronic inflammatory skin diseases are cytokines belonging to the IL-17 group, IL-17 receptors and a T helper cell population, Th17 cells. Successful therapeutic strategies that target either IL-17 or the major IL-17 receptor IL-17RA have confirmed the immune-pathogenic pathway. To study the IL-17-ligand – receptor axis at the molecular level, a number of cutaneous cell types from healthy human subjects has been cultured and analyzed for the expression of IL-17 receptors. IL-17RA was the most abundantly expressed receptor type in keratinocytes, epidermal stem cells, fibroblasts, mesenchymal stem cells, hemo- and lymphovascular endothelial cells. IL-17RC and IL-17RD showed moderate expression, while the genes for IL-17RB and IL-17RE were poorly expressed. In none of the investigated cell types, IL-17 ligands caused an increased expression level of the five receptor types in time- and dose-dependent experiments. No evidence for IL-17A, -C, -E or -F induced signal transduction cascades could be obtained by a qRT-PCR and western blot analyses. Further studies are necessary to identify relevant co-stimulating factors from IL-17 subtypes under physiological and pathophysiological conditions.

Interleukin-17 Cytokines and Receptors: Potential Amplifiers of Tendon Inflammation.

Interleukin (IL)-17A, a pro-inflammatory cytokine that is linked to the pathology of several inflammatory diseases, has been shown to be upregulated in early human tendinopathy and to mediate inflammatory and tissue remodelling events. However, it remains unclear which cells in tendons can respond to IL-17A, and how IL-17A, and its family members IL-17F and IL-17AF, can affect intracellular signalling activation and mRNA expression in healthy and diseased tendon-derived fibroblasts. Using well-phenotyped human tendon samples, we show that IL-17A and its receptors IL-17RA and IL-17RC are present in healthy hamstring, and tendinopathic and torn supraspinatus tendon tissue. Next, we investigated the effects of IL-17A, IL-17F, or IL-17AF on cultured patient-derived healthy and diseased tendon-derived fibroblasts. In these experiments, IL-17A treatment significantly upregulated IL6, MMP3, and PDPN mRNA expression in diseased tendon-derived fibroblasts. IL-17AF treatment induced moderate increases in these target genes, while little change was observed with IL-17F. These trends were reflected in the activation of intracellular signalling proteins p38 and NF-B p65, which were significantly increased by IL-17A, modestly increased by IL-17AF, and not increased by IL-17F. In combination with TNF-α, all three IL-17 cytokines induced IL6 and MMP3 mRNA expression to similar levels. Therefore, this study confirms that healthy and diseased tendon-derived fibroblasts are responsive to IL-17 cytokines and that IL-17A induces the most profound intracellular signalling activation and mRNA expression of inflammatory genes, followed by IL-17AF, and finally IL-17F. The ability of IL-17 cytokines to induce a direct response and activate diverse pro-inflammatory signalling pathways through synergy with other inflammatory mediators suggests a role for IL-17 family members as amplifiers of tendon inflammation and as potential therapeutic targets in tendinopathy.

TICAM-1/TRIF associates with Act1 and suppresses IL-17 receptor-mediated inflammatory responses.

TICAM-1 (also called TRIF) is the sole adaptor of TLR3 that recognizes double-stranded RNA. Here, we report that TICAM-1 is involved not only in TLR3 signaling but also in the cytokine receptor IL-17RA signaling. We found that TICAM-1 bound to IL-17R adaptor Act1 to inhibit the interaction between IL-17RA and Act1. Interestingly, TICAM-1 knockout promoted IL-17RA/Act1 interaction and increased IL-17A-mediated activation of NF-κB and MAP kinases, leading to enhanced expression of inflammatory cytokines and chemokines upon IL-17A stimulation. Moreover, Ticam-1 knockout augmented IL-17A-mediated CXCL1 and CXCL2 expression in vivo, resulting in accumulation of myeloid cells. Furthermore, Ticam-1 knockout enhanced delayed type hypersensitivity and exacerbated experimental autoimmune encephalomyelitis. Ticam-1 knockout promoted accumulation of myeloid and lymphoid cells in the spinal cord of EAE-induced mice. Collectively, these data indicate that TICAM-1 inhibits the interaction between IL-17RA and Act1 and functions as a negative regulator in IL-17A-mediated inflammatory responses.

Resolvin D1 reduces inflammation in co-cultures of primary human macrophages and adipocytes by triggering macrophages

Obesity leads to chronic inflammation of the adipose tissue which is tightly associated with the metabolic syndrome, type 2 diabetes and cardiovascular disease. Inflammation of the adipose tissue is mainly characterized by the presence of crown-like structures composed of inflammatory macrophages in the neighborhood of adipocytes. Resolvin D1 (RvD1), a potent anti-inflammatory and pro-resolving lipid mediator derived from the omega-3 fatty acid docosahexaenoic acid, has been shown to reduce the inflammatory tone of adipose tissue in animal models but the underlying mechanism is not clear. We investigated the effect of RvD1 on the inflammatory state of a human co-culture system of adipocytes and macrophages. For this, human mesenchymal stem cells were differentiated into mature adipocytes and overlaid with human primary macrophages. In this co-culture, 10–500 nM RvD1 dose-dependently reduced the secretion of the pro-inflammatory cytokine IL-6 (-21%) and its soluble receptor IL-6Rα (-22%), of the chemokine MCP-1 (-13%), and of the adipokine leptin (-22%). Similarly, we observed a reduction in secretion of the soluble receptor IL-6Rα (-20%), and TNF-α (-11%) when macrophages alone were treated with RvD1, while no change of cytokine secretion was observed when adipocytes were treated with RvD1. We conclude that RvD1 polarizes macrophages to an anti-inflammatory phenotype, which in turn modulates inflammation in adipocytes.

IL-15 Prevents Renal Fibrosis by Inhibiting Collagen Synthesis: A New Pathway in Chronic Kidney Disease?

Chronic kidney disease (CKD), secondary to renal fibrogenesis, is a public health burden. The activation of interstitial myofibroblasts and excessive production of extracellular matrix (ECM) proteins are major events leading to end-stage kidney disease. Recently, interleukin-15 (IL-15) has been implicated in fibrosis protection in several organs, with little evidence in the kidney. Since endogenous IL-15 expression decreased in nephrectomized human allografts evolving toward fibrosis and kidneys in the unilateral ureteral obstruction (UUO) model, we explored IL-15’s renoprotective role by pharmologically delivering IL-15 coupled or not with its soluble receptor IL-15Rα. Despite the lack of effects on myofibroblast accumulation, both IL-15 treatments prevented tubulointerstitial fibrosis (TIF) in UUO as characterized by reduced collagen and fibronectin deposition. Moreover, IL-15 treatments inhibited collagen and fibronectin secretion by transforming growth factor-β (TGF-β)-treated primary myofibroblast cultures, demonstrating that the antifibrotic effect of IL-15 in UUO acts, in part, through a direct inhibition of ECM synthesis by myofibroblasts. In addition, IL-15 treatments resulted in decreased expression of monocyte chemoattractant protein 1 (MCP-1) and subsequent macrophage infiltration in UUO. Taken together, our study highlights a major role of IL-15 on myofibroblasts and macrophages, two main effector cells in renal fibrosis, demonstrating that IL-15 may represent a new therapeutic option for CKD.