Structural Analysis Reveals that the Cytokine IL-17F Forms a Homodimeric Complex with Receptor IL-17RC to Drive IL-17RA-Independent Signaling.

Interleukin-17A (IL-17A), IL-17F, and IL-17A/F heterodimers are key cytokines of the innate and adaptive immune response. Dysregulation of the IL-17 pathway contributes to immune pathology, and it is therefore important to elucidate the molecular mechanisms that govern IL-17 recognition and signaling. The receptor IL-17RC is thought to act in concert with IL-17RA to transduce IL-17A-, IL-17F-, and IL-17A/F-mediated signals. We report the crystal structure of the extracellular domain of human IL-17RC in complex with IL-17F. In contrast to the expected model, we found that IL-17RC formed a symmetrical 2:1 complex with IL-17F, thus competing with IL-17RA for cytokine binding. Using biophysical techniques, we showed that IL-17A and IL-17A/F also form 2:1 complexes with IL-17RC, suggesting the possibility of IL-17RA-independent IL-17 signaling pathways. The crystal structure of the IL-17RC:IL-17F complex provides a structural basis for IL-17F signaling through IL-17RC, with potential therapeutic applications for respiratory allergy and inflammatory bowel diseases.

Rare genetic variants of NLRP12 in Admixed Latino-American Children with SARS-CoV-2-related Multisystem Inflammatory Syndrome.

Multisystem Inflammatory Syndrome in Children (MIS-C) is a rare, potentially fatal complication of SARS-CoV-2 infection. Genetic defects in inflammation-related pathways have been linked to MIS-C, but additional research is needed, especially in diverse ethnic groups. The present study aimed to identify genetic variants underlying MIS-C in Brazilian patients. Whole-exome sequencing was performed, focusing on genes involved in the host immune response to SARS-CoV-2. Functional assays assessed the impact of selected variants on NF-κB signaling. Nine rare, potentially deleterious variants were found in eight of 21 patients, located in IL17RC, IFNA10, or NLRP12 genes. Unlike the wild-type NLRP12 protein, which inhibits NF-κB activation in HEK 293T cells, the mutant NLRP12 proteins have significantly reduced inhibitory properties. In conclusion, our results indicate that rare autosomal variants in immune-related genes may underlie MIS-C, highlighting the potential role of NLRP12 in its predisposition. These findings provide new insights for the appropriate management of MIS-C.

Isolated Chronic Mucocutaneous Candidiasis due to a Novel Duplication Variant of IL17RC.

PURPOSE: Inborn errors of the IL-17A/F-responsive pathway lead to chronic mucocutaneous candidiasis (CMC) as a predominant clinical phenotype, without other significant clinical manifestations apart from mucocutaneous staphylococcal diseases. Among inborn errors affecting IL-17-dependent immunity, autosomal recessive (AR) IL-17RC deficiency is a rare disease with only three kindreds described to date. The lack of an in vitro functional evaluation system of IL17RC variants renders its diagnosis difficult. We sought to characterize a 7-year-old Japanese girl with CMC carrying a novel homozygous duplication variant of IL17RC and establish a simple in vitro system to evaluate the impact of this variant. METHODS: Flow cytometry, qPCR, RNA-sequencing, and immunoblotting were conducted, and an IL17RC-knockout cell line was established for functional evaluation. RESULTS: The patient presented with oral and mucocutaneous candidiasis without staphylococcal diseases since the age of 3 months. Genetic analysis showed that the novel duplication variant (Chr3: 9,971,476-9,971,606 dup (+131bp)) involving exon 13 of IL17RC results in a premature stop codon (p.D457Afs*16 or p.D457Afs*17). Our functional evaluation system revealed this duplication to be loss-of-function and enabled discrimination between loss-of-function and neutral IL17RC variants. The lack of response to IL-17A by the patient's SV40-immortalized fibroblasts was restored by introducing WT-IL17RC, suggesting that the genotype identified is responsible for her clinical phenotype. CONCLUSIONS: The clinical and cellular phenotype of the current case of AR IL-17RC deficiency supports a previous report on this rare disorder. Our newly established evaluation system will be useful for the diagnosis of AR IL-17RC deficiency, providing accurate validation of unknown IL17RC variants.

IL-17A promotes Helicobacter pylori-induced gastric carcinogenesis via interactions with IL-17RC.

BACKGROUND: Gastric cancer (GC) is a common malignancy worldwide, with a major attribution to Helicobacter pylori. Interleukin (IL)-17A has been reported to be up-regulated in serum and tumor of GC patients, but the precise mechanisms underlying its involvement in gastric tumorigenesis are yet to be established. Here, we investigated the roles of IL-17A in the pathogenesis of H. pylori-induced GC. METHODS: GC was induced in IL-17A knockout (KO) and wild-type (WT) mice via N-methyl-N-nitrosourea (MNU) treatment and H. pylori infection. At 50 weeks after treatment, gastric tissues were examined by histopathology, immunohistochemistry, and immunoblot analyses. In vitro experiments on the human GC cell lines were additionally performed to elucidate the underlying mechanisms. RESULTS: Deletion of IL-17A suppressed MNU and H. pylori-induced gastric tumor development accompanied by a decrease in gastric epithelial cell growth, oxidative stress, and expression of gastric epithelial stem cells markers. In AGS cells, recombinant human IL-17A (rhIL-17A) inhibited apoptosis and G1/S phase transition arrest while promoting reactive oxygen species production, sphere formation ability of cancer stem cells (CSC), and expression of stemness-related genes. In addition, rhIL-17A induced expression of IL-17RC, leading to NF-κB activation and increased NADPH oxidase 1 (NOX1) levels. Inhibition of NOX1 with GKT136901 attenuated rhIL-17A-mediated elevation of GC cell growth, ROS generation, and CSC stemness. Clinically, IL-17RC expressions were significantly upregulated in human GC compared with normal gastric tissues. CONCLUSION: Our results suggest that IL-17A promotes gastric carcinogenesis, in part, by regulating IL-17RC/NF-κB/NOX1 pathway, supporting its potential as a target in human GC therapy.

Neutrophils from F508del cystic fibrosis patients produce IL-17A and express IL-23 - dependent IL-17RC.

Cystic fibrosis (CF) is a chronic pulmonary disease that is associated with persistent microbial infection and chronic neutrophil infiltration, and also with elevated production of the pro-inflammatory cytokine IL-17A (IL-17). In the current study, we examined IL-17 and the inducible IL-17RC receptor subunit in neutrophils from Pseudomonas aeruginosa infected F508del CF patients at the time of pulmonary exacerbation, and again following intravenous antibiotic treatment. Neutrophils expressed Il17a and Il17rc transcripts and protein at the time of pulmonary exacerbation, which were absent following antibiotic treatment. Further, CF sputum induced IL-23 - dependent Il17rc expression in neutrophils from healthy individuals. Similarly, IL-17 producing neutrophils were detected in F508del and Cftr(-/-) mice infected intranasally with P. aeruginosa. In the sputum of CF subjects, the percentage IL-17 producing neutrophils correlated with elastase and MMP9 activity; therefore, this population of neutrophils may be an important contributor to the severity of pulmonary disease in CF patients.

Biomass-related PM2.5 induced inflammatory microenvironment via IL-17F/IL-17RC axis.

Biomass exposure is a significant environmental risk factor for COPD, but the underlying mechanisms have not yet been fully elucidated. Inflammatory microenvironment has been shown to drive the development of many chronic diseases. Pollution exposure can cause increased levels of inflammatory factors in the lungs, leading to an inflammatory microenvironment which is prevalent in COPD. Our findings revealed that IL-17F was elevated in COPD, while exposure to biomass led to increased expression of IL-17F in both alveolar epithelial and macrophage cells in mice. Blocking IL-17F could alleviate the lung inflammation induced by seven days of biomass exposure in mice. We employed a transwell co-culture system to simulate the microenvironment and investigate the interactions between MLE-12 and MH-S cells. We demonstrated that anti-IL-17F antibody attenuated the inflammatory responses induced by BRPM2.5 in MLE-12 and MH-S co-cultured with BRPM2.5-MLE-12, which reduced inflammatory changes in microenvironment. We found that IL-17RC, an important receptor for IL-17F, played a key role in the interactions. Knockout of IL-17RC in MH-S resulted in inhibited IL-17F signaling and attenuated inflammatory response after MH-S co-culture with BRPM2.5-MLE-12. Our investigation suggests that BRPM2.5 induces lung epithelial-macrophage interactions via IL-17F/IL-17RC axis regulating the inflammatory response. These results may provide a novel strategy for effective prevention and treatment of biomass-related COPD.

Cmtm4 deficiency exacerbates colitis by inducing gut dysbiosis and S100a8/9 expression.

The dysfunction of innate immunity components is one of the major drivers for ulcerative colitis (UC), and increasing reports indicate that the gut microbiome serves as an intermediate between genetic mutations and UC development. Here, we find that the IL-17 receptor subunit, CMTM4, is reduced in UC patients and dextran sulfate sodium (DSS)-induced colitis. The deletion of CMTM4 (Cmtm4-/-) in mice leads to a higher susceptibility to DSS-induced colitis than in wild-type, and the gut microbiome significantly changes in composition. The causal role of the gut microbiome is confirmed with a cohousing experiment. We further identify that S100a8/9 is significantly up-regulated in Cmtm4-/- colitis, with the block of its receptor RAGE that reverses the phenotype associated with the CMTM4 deficiency. CMTM4 deficiency rather suppresses S100a8/9 expression in vitro via the IL17 pathway, further supporting that the elevation of S100a8/9 in vivo is most likely a result of microbial dysbiosis. Taken together, the results suggest that CMTM4 is involved in the maintenance of intestinal homeostasis, suppression of S100a8/9, and prevention of colitis development. Our study further shows CMTM4 as a crucial innate immunity component, confirming its important role in UC development and providing insights into potential targets for the development of future therapies.

Interleukin-17 signaling influences CD8+ T cell immunity and tumor progression according to the IL-17 receptor subunit expression pattern in cancer cells.

IL-17 immune responses in cancer are controversial, with both tumor-promoting and tumor-repressing effects observed. To clarify the role of IL-17 signaling in cancer progression, we used syngeneic tumor models from different tissue origins. We found that deficiencies in host IL-17RA or IL-17A/F expression had varying effects on the in vivo growth of different solid tumors including melanoma, sarcoma, lymphoma, and leukemia. In each tumor type, the absence of IL-17 led to changes in the expression of mediators associated with inflammation and metastasis in the tumor microenvironment. Furthermore, IL-17 signaling deficiencies in the hosts resulted in decreased anti-tumor CD8+ T cell immunity and caused tumor-specific changes in several lymphoid cell populations. Our findings were associated with distinct patterns of IL-17A/F cytokine and receptor subunit expression in the injected tumor cell lines. These patterns affected tumor cell responsiveness to IL-17 and downstream intracellular signaling, leading to divergent effects on cancer progression. Additionally, we identified IL-17RC as a critical determinant of the IL-17-mediated response in tumor cells and a potential biomarker for IL-17 signaling effects in tumor progression. Our study offers insight into the molecular mechanisms underlying IL-17 activities in cancer and lays the groundwork for developing personalized immunotherapies.

Isolated chronic mucocutaneous candidiasis due to a novel duplication variant of IL17RC.

Purpose: Inborn errors of the IL-17A/F-responsive pathway lead to chronic mucocutaneous candidiasis (CMC) as a predominant clinical phenotype, without other significant clinical manifestations apart from mucocutaneous staphylococcal diseases. Amongst inborn errors affecting IL-17-dependent immunity, autosomal recessive (AR) IL-17RC deficiency is a rare disease with only three kindreds described to date. The lack of an in vitro functional evaluation system of IL17RC variants renders its diagnosis difficult. We sought to characterize a seven-year-old Japanese girl with CMC carrying a novel homozygous duplication variant of IL17RC and establish a simple in vitro system to evaluate the impact of this variant. Methods: Flow cytometry, qPCR, RNA-sequencing, and immunoblotting were conducted, and an IL17RC-knockout cell line was established for functional evaluation. Results: The patient presented with oral and mucocutaneous candidiasis without staphylococcal diseases since the age of three months. Genetic analysis showed that the novel duplication variant (Chr3: 9,971,476-9,971,606 dup (+ 131bp)) involving exon 13 of IL17RC results in a premature stop codon (p.D457Afs*16 or p.D457Afs*17). Our functional evaluation system revealed this duplication to be loss-of-function and enabled discrimination between loss-of-function and neutral IL17RC variants. The lack of response to IL-17A by the patient's SV40-immortalized fibroblasts was restored by introducing WT-IL17RC, suggesting that the genotype identified is responsible for her clinical phenotype. Conclusions: The clinical and cellular phenotype of the current case of AR IL-17RC deficiency supports a previous report on this rare disorder. Our newly established evaluation system will be useful for diagnosis of AR IL-17RC deficiency, providing accurate validation of unknown IL17RC variants.

IL-17A expression by both T cells and non-T cells contribute to HSV-IL-2-induced CNS demyelination.

Previously we reported that a recombinant HSV-1 expressing murine IL-2 (HSV-IL-2) causes CNS demyelination in different strains of mice and in a T cell-dependent manner. Since TH17 cells have been implicated in CNS pathology, in the present study, we looked into the effects of IL-17A-/- and three of its receptors on HSV-IL-2-induced CNS demyelination. IL-17A-/- mice did not develop CNS demyelination, while IL-17RA-/-, IL-17RC-/-, IL-17RD-/- and IL-17RA-/-RC-/- mice developed CNS demyelination. Adoptive transfer of T cells from wild-type (WT) mice to IL-17A-/- mice or T cells from IL-17A-/- mice to Rag-/- mice induced CNS demyelination in infected mice. Adoptive T cell experiments suggest that both T cells and non-T cells expressing IL-17A contribute to HSV-IL-2-induced CNS demyelination with no difference in the severity of demyelination between the two groups of IL-17A producing cells. IL-6, IL-10, or TGFß did not contribute to CNS demyelination in infected mice. Transcriptome analysis between IL-17A-/- brain and spinal cord of infected mice with and without T cell transfer from WT mice revealed that "neuron projection extension involved in neuron projection guidance" and "ensheathment of neurons" pathways were associated with CNS demyelination. Collectively, the results indicate the importance of IL-17A in CNS demyelination and the possible involvement of more than three of IL-17 receptors in CNS demyelination.

IL-17-induced dimerization of IL-17RA drives the formation of the IL-17 signalosome to potentiate signaling.

Signaling through innate immune receptors such as the Toll-like receptor (TLR)/interleukin-1 receptor (IL-1R) superfamily proceeds via the assembly of large membrane-proximal complexes or "signalosomes." Although structurally distinct, the IL-17 receptor family triggers cellular responses that are typical of innate immune receptors. The IL-17RA receptor subunit is shared by several members of the IL-17 family. Using a combination of crystallographic, biophysical, and mutational studies, we show that IL-17A, IL-17F, and IL-17A/F induce IL-17RA dimerization. X-ray analysis of the heteromeric IL-17A complex with the extracellular domains of the IL-17RA and IL-17RC receptors reveals that cytokine-induced IL-17RA dimerization leads to the formation of a 2:2:2 hexameric signaling assembly. Furthermore, we demonstrate that the formation of the IL-17 signalosome potentiates IL-17-induced IL-36γ and CXCL1 mRNA expression in human keratinocytes, compared with a dimerization-defective IL-17RA variant.

Defect of IL17 Signaling, but Not Centrinone, Inhibits the Development of Psoriasis and Skin Papilloma in Mouse Models.

Patients with psoriasis tend to develop skin cancer, and the hyperproliferation of the epidermis is a histopathological hallmark of both psoriasis and cutaneous squamous cell carcinoma (SCC), indicating that they may share pathogenic mechanisms. Interleukin-17 (IL17) stimulates the proliferation of the epidermis, leading to psoriasis. Overexpression of Polo-like kinase 4 (PLK4), which controls centriole duplication, has been identified in SCC, which also shows the hyperproliferation of keratinocytes. To investigate the cooperation between IL17 signaling and centriole duplication in epidermal proliferation, we established psoriasis and skin papilloma models in wild type (WT), IL17 receptor A (T779A) knockin (Il17ra(T779A)-KI), and IL17 receptor C knockout (Il17rc-KO) mouse strains. Bioinformatics, Western blot, immunohistochemical staining, colony formation, and real-time PCR were used to determine the effect of IL17 signaling and centrinone on epithelial proliferation. In the psoriasis model, compared to WT and Il17ra(T779A)-KI, Il17rc-KO dramatically suppressed epidermal thickening. The proliferation of keratinocytes significantly decreased in this order from WT to Il17ra(T779A)-KI and Il17rc-KO mice. In the skin papilloma model, Il17ra(T779A)-KI significantly decreased tumor burden compared to the WT, while Il17rc-KO abolished papilloma development. However, centrinone, a selective inhibitor of PLK4, did not affect skin lesion formation in either model. Our data demonstrated that Il17ra(T779A)-KI and Il17rc-KO prevent the development of psoriasis and tumorigenesis in the skin, while the topical administration of centrinone does not have any effect.

Self-assembled chitosan nanoparticles for intranasal delivery of recombinant protein interleukin-17 receptor C (IL-17RC): preparation and evaluation in asthma mice.

Asthma is mentioned as a chronic airway inflammatory disease, whose pathogenesis is complicated. The promotion of inflammation in asthma by IL-17A and IL-17F has been confirmed. In addition to covalent homodimers, both cytokines are also able to form heterodimers, further inducing downstream pathways via binding to the IL-17RA and IL-17RC receptor complex. In recent years, IL-17RA and its signal transduction pathway have been extensively researched. IL-17RC, however, remains relatively unexplored. In the present study, we self-assembled chitosan (CS) nanoparticles for intranasal delivery of recombinant protein IL-17RC (rIL-17RC) and preliminarily investigated its effect on a murine model of allergic asthma induced by ovalbumin (OVA). rIL-17RC was produced by the prokaryotic expression system and encapsulated into the CS nanoparticles via ionic cross-linking technique. The results showed that CS-RC nanoparticles via intranasal intervention significantly caused inhibition of mucus secretion and airway inflammatory cell infiltration, and reduced IL-4, IL-17, IL-17F levels in BALF. Hence, delivering receptor proteins such as IL-17RC, through CS nanoparticles as a carrier, could be an attractive therapeutic intervention for asthma.

Identification of two interleukin 17 receptor C (IL-17RC) genes and their binding activities to three IL-17A/F ligands in the Japanese medaka, Oryzias latipes.

In mammals, interleukin (IL)-17 receptor C (IL-17RC) and IL-17RA mediate IL-17A and IL-17F signaling to produce mucin, antimicrobial peptides, and maintain healthy intestinal flora. However, IL-17RC signaling in fish remains unclear. In this study, three il17rc transcripts (il17rca1, il17rca2, and il17rcb) from the Japanese medaka (Oryzias latipes) were cloned; il17rca1 and il17rca2 mRNAs were alternatively spliced from il17rca pre-mRNA as transcript variants. The il17rca and il17rcb genes were located on chromosomes 7 and 5, respectively. Teleost clades containing medaka il17rca and il17rcb clustered separately from the tetrapod clade. In adult tissues, il17rca1 expression was significantly higher than il17rca2 and il17rcb. Conversely, il17rcb expression was significantly higher in embryos and larvae. These expression patterns changed following infection with Edwardsiella piscicida and Aeromonas hydrophila. Furthermore, an immunoprecipitation assay using recombinant IL-17RCs and rIL-17A/Fs suggested that, in teleosts, three ligands could function in signaling through two IL-17RCs.

Interleukin-17 receptor C gene polymorphism reduces treatment effect and promotes poor prognosis of ischemic stroke.

OBJECTIVE: To study the relationship between Interleukin-17 receptor C (IL-17RC) gene polymorphism and ischemic stroke (IS). METHODS: Three hundred cases of IS patients and 300 cases of the healthy controls were selected. Serum of IS patients and the controls was collected. The relative mRNA levels of IL-17, IL-17RC, IL-6, IL-8, G-CSF and granulocyte-macrophage colony stimulating factor (GM-CSF) by qRT-PCR. The protein expression of IL-17 and IL-17RC was determined by Western blotting. IL-17RC genotype was identified by PCR amplification. The proportion of IL-17RC, SNP and re37511 in IS and control group was determined. The treatment effect on IS and prognosis of patients with IL-17RC, SNP and re37511 was compared. RESULTS: The relative mRNA levels of IL-17, IL-17RC, IL-6, IL-8, G-CSF and GM-CSF in IS group were significantly higher than the control group. The protein expression of IL-17 and IL-17RC in IS group was also markedly higher than the control group. The proportion of IL-17RC re37511 in IS group was much larger than control group and proportion of IL-17RC much less. The percent of poor treatment effect in re37511 was much larger than IL-17RC. The percent of death and recrudescence in patients with IL-17RC re37511 was the highest. CONCLUSION: IS up-regulates the expression of IL-17 and IL-17RC. IL-17RC re37511 indicates the patients have a poorer treatment effect and prognosis.

IL17RC affects the predisposition to thoracic ossification of the posterior longitudinal ligament.

BACKGROUND: Thoracic ossification of the posterior longitudinal ligament (T-OPLL) can cause thoracic spinal stenosis, which results in intractable myelopathy and radiculopathy. The etiology of T-OPLL is unknown and the condition is difficult to treat surgically. Whole-genome sequencing identified a genetic variant at rs199772854 of the interleukin 17 receptor C (IL17RC) gene as a potentially pathogenic locus associated with T-OPLL. We aimed to determine whether the rs199772854A site mutation causes abnormal expression of the IL17RC in Han Chinese patients with T-OPLL and predict the possible pathogenic mechanisms of T-OPLL. Analyses were performed to determine whether IL17RC is involved in the pathogenicity of T-OPLL. METHODS: Peripheral blood and OPLL tissue were collected from a total of 72 patients with T-OPLL disease (36 patients carrying the rs199772854A site mutation in IL17RC and 36 wild-type patients). The expression of IL17RC was analyzed by enzyme-linked immunosorbent assay, reverse transcription-quantitative polymerase chain reaction, immunohistochemistry, and Western blotting. RESULTS: rs199772854A mutation resulted in markedly increased IL17RC gene expression levels in peripheral blood samples and the OPLL tissue obtained following clinical surgery (P < 0.05). CONCLUSIONS: The results suggest that the rs199772854A site mutation of IL17RC can significantly increase the expression of IL17RC. The IL17RC gene rs199772854A site polymorphism is a potential pathogenic mutation in T-OPLL disease, which may be associated with the occurrence of T-OPLL.

Association of IL17RC and COL6A1 genetic polymorphisms with susceptibility to ossification of the thoracic posterior longitudinal ligament in Chinese patients.

BACKGROUND: In our previous whole-genome sequencing study of 30 unrelated northern Chinese Han patients, we identified six single nucleotide polymorphisms (SNPs) in the interleukin 17 receptor C (IL17RC) and collagen type VI α1 chain (COL6A1) genes that were potentially associated with thoracic ossification of the posterior longitudinal ligament (T-OPLL). To determine whether these six SNPs are associated with susceptibility to T-OPLL in the northern Chinese Han population, we performed a case-control association study to confirm specific susceptible loci in the expanded samples. METHODS: The six SNPs in the IL17RC and COL6A1 genes were analyzed in 200 northern Chinese individuals (100 patients and 100 control subjects) using the Sequenom system. RESULTS: The genotype distributions and allele frequencies of each SNP in the control and patient groups were compared. rs201153092, rs13051496, rs199772854, rs76999397, and rs189013166 showed potential pathogenic loci for T-OPLL in the northern Chinese Han population, whereas rs151158105 did not. At the genotype level, the differences in the genotype frequencies of rs201153092, rs13051496, rs199772854, rs76999397, and rs189013166 between T-OPLL cases and controls reached statistical significance. CONCLUSIONS: To the best of our knowledge, this is the first association study of susceptibility genes in Han Chinese patients with T-OPLL. The results revealed five SNPs in the IL17RC and COL6A1 genes that represented potentially pathogenic mutations in patients with T-OPLL.

The IL-17F/IL-17RC Axis Promotes Respiratory Allergy in the Proximal Airways.

The interleukin 17 (IL-17) cytokine and receptor family is central to antimicrobial resistance and inflammation in the lung. Mice lacking IL-17A, IL-17F, or the IL-17RA subunit were compared with wild-type mice for susceptibility to airway inflammation in models of infection and allergy. Signaling through IL-17RA was required for efficient microbial clearance and prevention of allergy; in the absence of IL-17RA, signaling through IL-17RC on epithelial cells, predominantly by IL-17F, significantly exacerbated lower airway Aspergillus or Pseudomonas infection and allergic airway inflammation. In contrast, following infection with the upper respiratory pathogen Staphylococcus aureus, the IL-17F/IL-17RC axis mediated protection. Thus, IL-17A and IL-17F exert distinct biological effects during pulmonary infection; the IL-17F/IL-17RC signaling axis has the potential to significantly worsen pathogen-associated inflammation of the lower respiratory tract in particular, and should be investigated further as a therapeutic target for treating pathological inflammation in the lung.

A Truncated IL-17RC Peptide Ameliorates Synovitis and Bone Destruction of Arthritic Mice.

Peptide-based therapy, such as modified peptides, has attracted increased attention. IL-17 is a promising therapeutic target for autoimmune diseases, and levels of circulating bioactive IL-17 are associated with rheumatoid arthritis severity. In this study, a modified truncated IL-17RC is generated to ameliorate inflammation and bone destruction in arthritis. The truncated IL-17RC binds to both IL-17A and IL-17F with higher binding capacity compared to nonmodified IL-17RC. In addition, the truncated IL-17RC reduces the secretion of inflammatory and osteoclastogenic factors induced by IL-17A/F in vitro. Moreover, the administration of truncated IL-17RC dramatically improves symptoms of inflammation and inhibited bone destruction in collagen-induced arthritis mice. Collectively, these data demonstrate that modified truncated IL-17RC peptide may be a more effective treatment strategy in the simultaneous inhibition of both IL-17A and IL-17F signaling, whereas the existing agents neutralize IL-17A or IL-17F alone. These suggest that the truncated IL-17RC may be a potential candidate in the treatment of inflammatory associated bone diseases.

Probable Chemical Hypoxia Effects on Progress of CNV Through Induction of Promoter CpG Demethylation and Overexpression of IL17RC in Human RPE Cells.

PURPOSE: To survey the changes of promoter CpG methylation status and mRNA expression of IL17RC (interleukin 17 receptor C) gene in retinal pigment epithelium (RPE) cells under chemical hypoxia condition for choroidal neovascularization (CNV) modeling in vitro. MATERIALS AND METHODS: RPE cells were cultured in both untreated as a control group and treated by cobalt chloride media as a hypoxia group for various concentrations (100-150µM) and times (24-36 hrs.) To confirm chemical hypoxia condition, mRNA expression of HIF (Hypoxia Inducible Factor) -1α, -2α, and Vascular Endothelial Growth Factor (VEGF) was compared between two groups by Real-time PCR. Also, in normoxia and hypoxia conditions, IL17RC expression changes and promoter CpG methylation status were evaluated by Real-time PCR and methylation-specific PCR (MSP) techniques, respectively. RESULTS: Overexpression of HIF-1α, HIF-2α, and VEGF was significant in hypoxia versus normoxia conditions. Our data showed overexpression of IL17RC (2.1- to 6.3-fold) and decreasing of its promoter methylation in comparison with hypoxia and normoxia conditions. It was found that there are significant association between promoter methylation status and expression of IL17RC in chemical hypoxia condition. CONCLUSION: Therefore, methylation of IL17RC could play as a marker in CNV and degeneration of RPE cells in vitro. Additionally, HIF-α and methylation phenomena may be considered as critical targets for blocking in angiogenesis of age-related degeneration in future studies.