Infection of keratinocytes with Trichophytum rubrum induces epidermal growth factor-dependent RNase 7 and human beta-defensin-3 expression

Human keratinocytes are able to express various antimicrobial peptides (AMP) to protect the skin from exaggerated microbial colonization and infection. Recently, in vitro growth-inhibiting activity of the skin-derived AMP psoriasin, RNase 7 and human beta-defensin (hBD)-2 against dermatophytes such as Trichophyton (T.) rubrum have been reported. To evaluate whether keratinocytes are able to respond to T. rubrum infection by an induced expression of AMP we exposed primary keratinocytes to living conidia of T. rubrum. This led to conidia germination and mycelial growth which was paralleled by a strong gene induction of the skin-derived AMP RNase 7 and hBD-3. Gene expression of the AMP psoriasin (S100A7) and hBD-2 were only slightly induced. The T. rubrum-mediated RNase 7 gene induction was accompanied by increased secretion of RNase 7. Parallel treatment of the keratinocytes with T. rubrum and the cytokine combination IL-17A/IFN-γ resulted in synergistic induction of RNase 7 and hBD-3 expression. Since patients receiving therapy by inhibition of the epidermal growth factor receptor (EGFR) more often suffer from dermatophytoses we investigated whether EGFR may be involved in the T. rubrum-mediated RNase 7 and hBD-3 induction. Primary keratinocytes incubated with an EGFR blocking antibody as well as with the EGFR antagonist AG1478 showed a significantly diminished RNase 7 and hBD-3 induction upon exposure of the keratinocytes to T. rubrum indicating that EGFR is involved in the T. rubrum-mediated induction of RNase 7 and hBD-3. The growth of T. rubrum in vitro was inhibited by hBD-3 in a dose-dependent manner suggesting that hBD-3 may contribute to cutaneous innate defense against T. rubrum. Taken together our data indicate that keratinocytes are able to initiate a fast defense response towards T. rubrum by the increased expression of AMP active against T. rubrum. A dysregulation of AMP may contribute to chronic and recurring dermatophytoses.

IL-17 induces an expanded range of downstream genes in reconstituted human epidermis model

Background

IL-17 is the defining cytokine of the Th17, Tc17, and γδ T cell populations that plays a critical role in mediating inflammation and autoimmunity. Psoriasis vulgaris is an inflammatory skin disease mediated by Th1 and Th17 cytokines with relevant contributions of IFN-γ, TNF-α, and IL-17. Despite the pivotal role IL-17 plays in psoriasis, and in contrast to the other key mediators involved in the psoriasis cytokine cascade that are capable of inducing broad effects on keratinocytes, IL-17 was demonstrated to regulate the expression of a limited number of genes in monolayer keratinocytes cultured in vitro.

Methodology/Principal Findings

Given the clinical efficacy of anti-IL-17 agents is associated with an impressive reduction in a large set of inflammatory genes, we sought a full-thickness skin model that more closely resemble in vivo epidermal architecture. Using a reconstructed human epidermis (RHE), IL-17 was able to upregulate 419 gene probes and downregulate 216 gene probes. As possible explanation for the increased gene induction in the RHE model is that C/CAAT-enhancer-binding proteins (C/EBP) -β, the transcription factor regulating IL-17-responsive genes, is expressed preferentially in differentiated keratinocytes.

Conclusions/Significance

The genes identified in IL-17-treated RHE are likely relevant to the IL-17 effects in psoriasis, since ixekizumab (anti-IL-17A agent) strongly suppressed the “RHE” genes in psoriasis patients treated in vivo with this IL-17 antagonist.

Interleukin-17A promotes MUC5AC expression and goblet cell hyperplasia in nasal polyps via the Act1-mediated pathway

BACKGROUND

Recent studies demonstrated that nasal polyps (NP) patients in China and other Asian regions possessed distinct Th17-dominant inflammation and enhanced tissue remodeling. However, the mechanism underlying these observations is not fully understood. This study sought to evaluate the association of interleukin (IL)-17A with MUC5AC expression and goblet cell hyperplasia in Chinese NP patients and to characterize the signaling pathway underlying IL-17A-induced MUC5AC expression in vitro.

METHOD

We enrolled 25 NP patients and 22 normal controls and examined the expression of IL-17A, MUC5AC and act1 in polyp tissues by immunohistochemical (IHC) staining, quantitative polymerase chain reaction (qPCR) and western blot. Moreover, by using an in vitro culture system of polyp epithelial cells (PECs), IL-17A-induced gene expression was screened in cultured PECs by DNA microarray. The expression of IL-17RA, IL-17RC, act1 and MUC5AC and the activation of the MAPK pathway (ERK, p38 and JNK), were further examined in cultured PECs and NCI-H292 cells by qPCR and western blotting, respectively.

RESULTS

We found that increased IL-17A production was significantly correlated with MUC5AC and act1 expression and goblet cell hyperplasia in polyp tissues (p<0.05). IL-17A significantly stimulated the expression of IL-17RA, IL-17RC, act1 and MUC5AC, and the activation of the MAPK pathway in cultured PECs and NCI-H292 cells (p<0.05). In addition, IL-17RA, IL-17RC and act1 siRNA significantly blocked IL-17A-induced MUC5AC production in vitro (p<0.05).

CONCLUSION

Our results suggest that IL-17A plays a crucial role in stimulating the production of MUC5AC and goblet cell hyperplasia through the act1-mediated signaling pathway and may suggest a promising strategy for the management of Th17-dominant NP patients.

Interleukin-23 deficiency leads to impaired wound healing and adverse prognosis after myocardial infarction

BACKGROUND

CD4+ cells are implicated in the healing process after myocardial infarction (MI). We sought to investigate the role of interleukin-23 (IL-23) deficiency, a cytokine important in differentiation of CD4+ cells, in scar formation of the ischemic heart.

METHODS AND RESULTS

MI was performed in wild-type and IL23p19-/- mice. Thirty-day mortality, hemodynamic function 4 days after MI and myocardial inflammation, and remodeling 4 and 30 days after MI were examined. Differentiation of fibroblasts from infarcted and noninfarcted hearts into myofibroblasts was examined under basal conditions and after stimulation with interferon-γ, IL-17α and IL-23. Interleukin-23p19-/- mice showed higher expression of proinflammatory cytokines and immune cell infiltration in the scar early after MI compared with wild-type mice. A stronger interferon-γ/Th1 reaction seemed to be responsible for the increased inflammation under IL-23 deficiency. Expression of α-smooth muscle actin (α-SMA), collagen I and III was significantly higher in the heart tissue and isolated cardiac fibroblasts 4 days after MI in the wild-type mice. Interleukin-23p19-/- mice showed impaired healing compared with wild-type mice, as seen by significantly higher mortality because of ventricular rupture (40% higher after 30 days) and stronger left ventricular dilation early after MI. Stimulation of cardiac fibroblasts with interferon-γ, the main Th1 cytokine, but not with IL-23 or IL-17α, led to a significant downregulation of α-smooth muscle actin, collagen I and III and decreased migration and differentiation to myofibroblasts.

CONCLUSIONS

IL-23 deficiency leads to increased myocardial inflammation and decreased cardiac fibroblast activation, associated with impaired scar formation and adverse remodeling after MI.

IL-17 inhibits chondrogenic differentiation of human mesenchymal stem cells

OBJECTIVE

Mesenchymal stem cells (MSCs) can differentiate into cells of mesenchymal lineages, such as osteoblasts and chondrocytes. Here we investigated the effects of IL-17, a key cytokine in chronic inflammation, on chondrogenic differentiation of human MSCs.

METHODS

Human bone marrow MSCs were pellet cultured in chondrogenic induction medium containing TGF-β3. Chondrogenic differentiation was detected by cartilage matrix accumulation and chondrogenic marker gene expression.

RESULTS

Over-expression of cartilage matrix and chondrogenic marker genes was noted in chondrogenic cultures, but was inhibited by IL-17 in a dose-dependent manner. Expression and phosphorylation of SOX9, the master transcription factor for chondrogenesis, were induced within 2 days and phosphorylated SOX9 was stably maintained until day 21. IL-17 did not alter total SOX9 expression, but significantly suppressed SOX9 phosphorylation in a dose-dependent manner. At day 7, IL-17 also suppressed the activity of cAMP-dependent protein kinase A (PKA), which is known to phosphorylate SOX9. H89, a selective PKA inhibitor, also suppressed SOX9 phosphorylation, expression of chondrogenic markers and cartilage matrix, and also decreased chondrogenesis.

CONCLUSIONS

IL-17 inhibited chondrogenesis of human MSCs through the suppression of PKA activity and SOX9 phosphorylation. These results suggest that chondrogenic differentiation of MSCs can be inhibited by a mechanism triggered by IL-17 under chronic inflammation.

A role for interleukin-17A in modulating intracellular survival of Mycobacterium bovis bacillus Calmette-Guérin in murine macrophages

Interleukin 17A IL-17A is a crucial immunomodulator in various chronic immunological diseases including rheumatoid arthritis and inflammatory bowel disease. The cytokine has also been demonstrated to control the pathogenesis of the Mycobacterium tuberculosis by dysregulating production of cytokines and chemokines and promoting granuloma formation. Whether IL-17A regulates innate defence mechanisms of macrophages in response to mycobacterial infection remains to be elucidated. In the current report, we investigated the effects of IL-17A on modulating the intracellular survival of Mycobacterium bovis bacillus Calmette-Guérin (BCG) in RAW264.7 murine macrophages. We observed that IL-17A pre-treatment for 24 hr was able to synergistically enhance BCG-induced nitric oxide (NO) production and inducible nitric oxide synthase expression in dose- and time-dependent manners. We further delineated the mechanisms involved in this synergistic reaction. IL-17A was found to specifically enhanced BCG-induced phosphorylation of Jun N-terminal kinase (JNK), but not of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase. By using a specific JNK inhibitor (SP600125), we found that the production of NO in BCG-infected macrophages was significantly suppressed. Taken together, we confirmed the involvement of the JNK pathway in IL-17A-enhanced NO production in BCG-infected macrophages. We further demonstrated that IL-17A significantly enhanced the clearance of intracellular BCG by macrophages through an NO-dependent killing mechanism. In conclusion, our study revealed an anti-mycobacterial role of IL-17A through priming the macrophages to produce NO in response to mycobacterial infection.

The role of Act1, a NF-κB-activating protein, in IL-6 and IL-8 levels induced by IL-17 stimulation in SW982 cells

CONTEXT

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation in the synovial membrane of affected joints. It has been shown that several kinds of cytokine were increased in synovial fluid, while the underlying mechanism remains poorly understood.

OBJECTIVES

NF-κB activator 1 (Act1) is a recently identified protein binding to the IκB kinase complex. Our study aimed to investigate the expression of Act1 induced by cytokine IL-17 stimulation in SW982 cells.

MATERIALS AND METHODS

The human synovial sarcoma cell line SW982 and primary cultured RA fibroblast-like synovial cells were used. RT-PCR and Western blot assays were selected to investigate the genetic and protein expression of Act1. Additionally, four independent Act1 small interfering RNA (siRNA) oligonucleotides were designed and obtained according to the GenBank cDNA, the sequence of Act1 (Traf3ip2). Finally, enzyme-linked immunosorbent assay (ELISA) double antibody sandwich was used to assay supernatant IL-6 and IL-8 concentrations.

RESULTS

The Act1 mRNA expression level increased significantly after stimulation with IL-17 (5-100 ng/ml) in SW982 cells. Additionally, the level of Act1 mRNA expression correlated positively with the concentration of IL-17 (p < 0.01). IL-17 induced IL-6 and IL-8 in SW982 cells was in a concentration- and time-dependent way. Furthermore, ELISA assay revealed that IL-17 (20 ng/ml) significantly increased IL-6 (1927.4 ± 288.77 versus 786.5 ± 172.42 ng/ml, p < 0.01) and IL-8 levels (984.8 ± 95.09 ng/ml versus 307.1 ± 90.83 ng/ml, p < 0.01) compared with control group after stimulation for 24 h. However, transfection of Traf3ip2 siRNA markedly decreased IL-6 (995.9 ± 115.30 ng/ml versus 1816.1 ± 273.27 ng/ml, p < 0.01) and IL-8 levels (575.6 ± 65.96 ng/ml versus 929.4 ± 124.39 ng/ml, p < 0.01) compared to transfection negative control. These findings suggested that IL-6 and IL-8 level induced by IL-17 in SW982 cells could be reversed by down-regulation of Act1 expression level with Traf3ip2 siRNA.

CONCLUSION

Our results suggested that Act1 might play a key role in the pathophysiology and the treatment of RA.

Multiplex analyses of cytokine and chemokine release from the cultured fibroblast of nasal polyps: the effect of IL-17A

CONCLUSION

Our results demonstrate for the first time a potentially enhanced basal secretion of monocyte chemoattractant protein-1 (MCP-1) and interleukin (IL)-17A-stimulated secretion of IL-6 from nasal polyp fibroblasts, enhanced basal secretion of IL-6 from eosinophilic nasal polyp fibroblasts, and a remarkable up-regulation of IL-9 and granulocyte colony-stimulating factor (G-CSF) from nasal fibroblasts by IL-17A stimulation.

OBJECTIVES

The fibroblast, one of the main cell types making up nasal polyps, is thought to be a target cell of various cytokines.

METHODS

Subcultured fibroblasts were established from human polyp biopsy tissues. Simultaneous quantification of 27 kinds of cytokines and chemokines in culture supernatants in unstimulated and IL-17A-stimulated conditions was performed with a human multiplex cytokine assay system.

RESULTS

The IL-17A receptor was expressed at similar levels in all three groups. In the eosinophilic group, basal secretion levels of IL-6 were significantly higher than those in the control and non-eosinophilic groups. Basal secretion of MCP-1 in both the non-eosinophilic and eosinophilic groups was also higher than that of the control group. Both IL-9 and G-CSF secretion were remarkably enhanced by IL-17A stimulation in all three groups. The receptor-mediated response by IL-17A significantly up-regulated IL-6 release alone in the non-eosinophilic and eosinophilic groups as compared with the control group.

Extension of the germinal center stage of B cell development promotes autoantibodies in BXD2 mice

OBJECTIVE

Regulator of G protein signaling (RGS) proteins inhibit chemokine signaling by desensitizing G protein-coupled receptor signals. This study was undertaken to determine the mechanisms by which RGS13 promotes the generation of pathogenic autoantibodies in germinal centers (GCs), using BXD2-Rgs13-/- mice.

METHODS

Confocal and light microscopy imaging techniques were used to determine the location of cells that express RGS13 and activation-induced cytidine deaminase (AID) in the mouse spleen, and the number of plasmablasts. The levels of GC and plasma cell program transcripts in GC B cells were determined by real-time quantitative polymerase chain reaction (qPCR). Differential interleukin-17 (IL-17)-mediated expression of RGS13 in GC versus non-GC B cells was analyzed using A20 and 70Z/3 B cells.

RESULTS

In the spleens of BXD2 mice, RGS13 was mainly expressed by GC B cells and was stimulated by IL-17 but not IL-21. IL-17 up-regulated RGS13 in A20 GC cells but not 70Z/3 non-GC B cells. BXD2- Rgs13-/- mice exhibited smaller GCs and lower AID levels, suggesting lower somatic hypermutation and affinity maturation. However, GC B cells from BXD2- Rgs13-/- mice showed increased levels of IgMbright plasmablasts, up-regulation of the genes encoding plasma program, including interferon regulatory factor 4, B lymphocyte-induced maturation protein 1, and X-box binding protein 1 and the p-CREB target genes Fosb and Obf1, and down-regulation of the GC program genes Aid, Pax5, and Bach2 compared to BXD2 mice. BXD2-Rgs13-/- mice had lower titers of IgG autoantibodies and IgG deposits in the glomeruli, suggesting reduced autoantibody pathogenicity.

CONCLUSION

RGS13 deficiency is associated with a reduction in GC program genes and the exit of fewer pathogenic IgM plasmablasts in BXD2 mice. Our findings indicate that prolonged GC program, mediated by up-regulation of RGS13, enhances AID expression and enables the generation of pathogenic autoantibodies in autoreactive GCs.

IL-17A potentiates TNFα-induced secretion from human endothelial cells and alters barrier functions controlling neutrophils rights of passage

Interleukin-17A (IL-17A) is an important pro-inflammatory cytokine that regulates leukocyte mobilization and recruitment. To better understand how IL-17A controls leukocyte trafficking across capillaries in the peripheral blood circulation, we used primary human dermal microvascular endothelial cells (HDMEC) to investigate their secretory potential and barrier function when activated with IL-17A and TNFα. Activation by TNFα and IL-17A causes phosphorylation of p38 as well as IκBα whereby NFκB subsequently becomes phosphorylated, a mechanism that initiates transcription of adhesion molecules such as E-selectin. Members of the neutrophil-specific GRO-family chemokines were significantly up-regulated upon IL-17A stimulation on the mRNA and protein level, whereas all tested non-neutrophil-specific chemokines remained unchanged in comparison. Moreover, a striking synergistic effect in the induction of granulocyte colony-stimulating factors (G-CSF) was elicited when IL-17A was used in combination with TNFα, and IL-17A was able to significantly augment the levels of TNFα-induced E-selectin and ICAM-1. In accordance with this observation, IL-17A was able to markedly increase TNFα-induced neutrophil adherence to HDMEC monolayers in an in vitro adhesion assay. Using a trans-well migration assay with an HDMEC monolayer as a barrier, we here show that pre-stimulating the endothelial cells with TNFα and IL-17A together enhances the rate of neutrophil transmigration compared to TNFα or IL-17A alone. These results show that IL-17A and TNFα act in cooperation to facilitate neutrophil migration across the endothelial cell barrier. In addition, the synergistic actions of IL-17A with TNFα to secrete G-CSF appear to be important for mobilizing neutrophils from the bone marrow to the blood stream.

Association between specific adipose tissue CD4+ T-cell populations and insulin resistance in obese individuals

BACKGROUND & AIMS

An increased number of macrophages in adipose tissue is associated with insulin resistance and metabolic dysfunction in obese people. However, little is known about other immune cells in adipose tissue from obese people, and whether they contribute to insulin resistance. We investigated the characteristics of T cells in adipose tissue from metabolically abnormal insulin-resistant obese (MAO) subjects, metabolically normal insulin-sensitive obese (MNO) subjects, and lean subjects. Insulin sensitivity was determined by using the hyperinsulinemic euglycemic clamp procedure.

METHODS

We assessed plasma cytokine concentrations and subcutaneous adipose tissue CD4(+) T-cell populations in 9 lean, 12 MNO, and 13 MAO subjects. Skeletal muscle and liver samples were collected from 19 additional obese patients undergoing bariatric surgery to determine the presence of selected cytokine receptors.

RESULTS

Adipose tissue from MAO subjects had 3- to 10-fold increases in numbers of CD4(+) T cells that produce interleukin (IL)-22 and IL-17 (a T-helper [Th] 17 and Th22 phenotype) compared with MNO and lean subjects. MAO subjects also had increased plasma concentrations of IL-22 and IL-6. Receptors for IL-17 and IL-22 were expressed in human liver and skeletal muscle samples. IL-17 and IL-22 inhibited uptake of glucose in skeletal muscle isolated from rats and reduced insulin sensitivity in cultured human hepatocytes.

CONCLUSIONS

Adipose tissue from MAO individuals contains increased numbers of Th17 and Th22 cells, which produce cytokines that cause metabolic dysfunction in liver and muscle in vitro. Additional studies are needed to determine whether these alterations in adipose tissue T cells contribute to the pathogenesis of insulin resistance in obese people.

In vitro effects of IL-17 on angiogenic properties of endothelial cells in relation to oxygen levels

The aim of this study has been to elucidate how different oxygen levels impact the effects of Interleukin-17 (IL-17) on angiogenic properties of endothelial cells. Two endothelial cell lines, mouse MS-1 and human EA.hy 926, were grown in 20% and 3% O2 and their angiogenic abilities analyzed after IL-17 treatment: proliferation, apoptosis, migration and tubulogenesis. Expression of endothelial nitric oxide synthase (eNOS) and cyclooxygenase-2 (Cox-2) was also measured. Considering EA.hy 926 cell line, hypoxia alone reduced proliferation, survival and migration, but not their ability to form tubules. When cultured at 20% O2 , IL-17 stimulated proliferation, migration and tubulogenesis, whereas a hypoxic environment did not affect their migration and proliferation, but increased their survival and tubulogenic properties. Expression of eNOS and Cox-2 increased by both IL-17 and hypoxia, as well as with their combination. With the MS-1 cell line hypoxia did not affect proliferation, survival, migration and tubule formation. At 20% O2 , IL-17 did not alter their proliferation,but inhibited migration and stimulated tubule formation. At 3% O2 , only the stimulating effect of IL-17 on tubulogenesis was evident. The constitutive expression of eNOS was unaffected by oxygen concentrations or IL-17 supplementation, whereas both IL-17 and hypoxia upregulated Cox-2 expression. Thus the effects of IL-17 on the angiogenic properties of endothelial cells depend on both the cell line used and the oxygen concentration.

Involvement of interleukin-17A in pancreatic damage in rat experimental acute necrotizing pancreatitis

Interleukin (IL)-17A is a proinflammatory cytokine, which has recently attracted much interest due to its pathogenic role in various inflammatory conditions such as ischemia/reperfusion injury, chronic inflammation, and autoimmune diseases, but the role of IL-17A in acute pancreatitis remains unclear. This study aimed to investigate the role of IL-17A in experimental acute necrotizing pancreatitis (ANP). We analyzed the expression of IL-17A during the pathogenesis of ANP in vivo induced by 3 % sodium taurocholate (NaTc), by microarray test, quantitative real-time PCR, Western blotting, enzyme-linked immunosorbent assay, and immunohistochemistry. The effects of IL-17A on pancreatic acinar cells and pancreatic stellate cells (PSCs) were further investigated in vitro using recombinant rat IL-17A (rIL-17A). Expression of IL-17A was significantly increased following experimental acute pancreatitis. In addition, rIL-17A induced rat pancreatic acinar cell necrosis and promoted expression of several target genes, including IL-6, IL-1β, CXCL1, CXCL2, and CXCL5, in acinar cells and PSCs. These findings suggest that IL-17A may be involved in pancreatic damage by regulating the expression of inflammatory cytokines and chemokines during experimental acute pancreatitis.

TGF-β enhanced IL-21-induced differentiation of human IL-21-producing CD4+ T cells via Smad3

IL-21 has pleiotropic effects on innate and adaptive immune response, and plays an important role in the development of autoimmune disease and antitumor activity. It has been reported that IL-21 is produced by CD4(+) T cells and NKT cells. However, the differentiation of IL-21-producing CD4(+) T cells in humans remains largely unclear. In the present study, we showed that cytokines of IL-1β, IL-6 or IL-21 induced differentiation of human IL-21-producing CD4(+) T cells, and TGF-β enhanced the effect of inflammatory cytokines on the development of IL-21-producing CD4(+) T cells. Furthermore, we found that the majority of IL-21-producing cells were distinct from Th17 cells and Th1 cells since they did not co-express IL-17 and IFN-γ. TGF-β significantly inhibited the production of IFN-γ and enhanced the effect of IL-21 on the development of IL-21-producing CD4(+) T cells. In addition, we found that IL-21 inhibited the differentiation of CD4(+) Foxp3(+) T cells induced by TGF-β. Further study indicated that IL-21 induced phosphorylation of transcriptional factors of STAT1, STAT3 and STAT5, and TGF-β induced phosphorylation of Smad3 in CD4(+) T cells. Taken together, our data indicated that TGF-β enhanced IL-21-induced differentiation of IL-21-producing CD4(+) T cells, and the majority of IL-21-producing cells were different from Th17 and Th1 cells. Our results provide a new sight regarding the differentiation of human CD4(+) T cells.

Anti-CD40 Ab- or 8-oxo-dG-enhanced Treg cells reduce development of experimental autoimmune encephalomyelitis via down-regulating migration and activation of mast cells

This study investigated whether anti-CD40 Ab and 8-oxo-dG attenuate mast cell migration and EAE development. Anti-CD40 Ab and 8-oxo-dG reduced EAE scores, mast cell numbers, expression of adhesion molecules, OX40L and Act1, levels of TNF-α, LTs, expression of cytokines, and co-localization of Treg cells and mast cells, all of which are increased in EAE-brain tissues. Each treatment enhanced Treg cells, expression of OX40, and cytokines related to suppressive function of Treg cells in EAE brain tissues. Act-BMMCs with Treg cells reduced expression of OX40L and CCL2/CCR2, VCAM-1, PECAM-1, [Ca²⁺]i levels, release of mediators, various signaling molecules, Act1 related to IL-17a signals versus those in act-BMMCs without Treg cells. The data suggest that IL-10- and IL-35-producing Foxp3⁺-Treg cells, enhanced by anti-CD40 Ab or 8-oxo-dG, suppress migration of mast cells through down-regulating the expression of adhesion molecules, and suppress mast cell activation through cell-to-cell cross-talk via OX40/OX40L in EAE development.

IL-17A and IFN-γ synergistically induce RNase 7 expression via STAT3 in primary keratinocytes

Human keratinocytes produce several antimicrobial peptides and proteins (AMP) which contribute to the protection of human skin against infection. RNase 7 is a major AMP involved in cutaneous defense with a high expression in keratinocytes and a broad spectrum of antimicrobial activity. The cytokine IL-17A has been recently identified as a potent inducer of several AMP in keratinocytes. Since the role of IL-17A to induce RNase 7 expression is unknown we analyzed IL-17A alone and in combination with other cytokines to induce RNase 7 expression in keratinocytes. Whereas IL-17A alone only weakly induced RNase 7 expression, the synergistic combination of IL-17A and IFN-γ (IL-17A/IFN-γ) was identified as a potent inducer of RNase 7 expression. This combination was more effective in inducing RNase 7 than the combination of IL-17A/TNF-α, a combination previously identified as a strong inducer of psoriasis-related immune response genes including several AMP. IFN-γ and IL-17A both have been reported to activate the transcription factor STAT3 (Signal transducer and activator of transcription 3). Therefore we investigated the influence of STAT3 on the IL-17A/IFN-γ -mediated RNase 7 induction. The use of a STAT3 inhibitor as well as siRNA-mediated downregulation of STAT3 resulted in a diminished IL-17A/IFN-γ -mediated RNase 7 induction in keratinocytes indicating that STAT3 is involved in this process. Similarly as seen with RNase 7, treatment of keratinocytes with IL-17A/IFN-γ revealed also a synergistic induction of gene expression of the AMP human beta-defensin (hBD)-2 and -3 as well as the S100 protein psoriasin (S100A7) indicating that the combination of IL-17A/IFN-γ is a potent inducer of various AMP classes in general. This was also reflected by an increase of the Staphylococcus aureus-killing activity of IL-17A/IFN-γ -treated keratinocytes.

Interleukin-17 induces AP-1 activity and cellular transformation via upregulation of tumor progression locus 2 activity

Inflammatory conditions elicited by extrinsic environmental factors promote malignant transformation, tumor growth and metastasis. Although the role of T cells in cancer promotion has been examined, little is known about the underlying molecular mechanisms of interleukin-17 A (IL-17A), a proinflammatory cytokine produced by activated CD4(+) memory T cells, in carcinogenesis. Here, we report that IL-17A induces neoplastic transformation of JB6 Cl41 cells through activation of tumor progression locus 2 (TPL2). IL-17A dose- and time-dependently increases TPL2 phosphorylation in JB6 Cl41 cells through IL-17A receptor. IL-17A activates mitogen-activated protein kinase/extracellular signal-regulated kinase kinases, c-jun N-terminal kinases and STAT3 signaling pathways, which are inhibited by a TPL2 kinase inhibitor (TKI). Furthermore, IL-17A activates c-fos and c-jun promoter activity, resulting in increased activator protein-1 (AP-1) activity. When small interfering RNA of IL-17A receptor (IL-17R), IL-17A and TPL2 were introduced into JB6 Cl41 cells, respectively, IL-17A-induced AP-1 activity was significantly decreased compared with control cells. Similarly, TPL2 inhibition suppressed AP-1 activity induced by IL-17A. The knockdown of IL-17R and TKI treatment in JB6 Cl41 cells resulted in decreased IL-17A-induced cell transformation. The in vivo chorioallantoic membrane assay also showed that IL-17A increased tumor formation of JB6 Cl41 cells, whereas TKI inhibited the tumorigenesis promoted by IL-17A. Consistent with these observations, knockdown of IL-17A and/or inhibition of TPL2 attenuated tumorigenicity of human breast cancer MCF7 cells. Together, our findings point to a critical role for the IL-17A-induced TPL2 signaling pathway in supporting cancer-associated inflammation in the tumor microenvironment. Therapeutic approaches that target this pathway may, therefore, effectively inhibit carcinogenesis.

Jagged-1-HES-1 signaling inhibits the differentiation of TH17 cells via ROR gammat

Notch signaling plays an important role in differentiation of T cells. However, little is known as to action of it in differentiation of Th17 cell subset. In this study, a soluble Jagged-1/Fc chimera protein (Jagged-1) was directly used to activate Jagged-1-Notch signaling, while Hes-1-targeting siRNA was used to knock down Hes-1 gene to investigate effect of Jagged-1-Hes-1 signaling on the differentiation of CD4+ T cells into Th17 cells. The results showed that Jagged-1 could promote the expression of Hes-1 and Deltex-1 mRNAs and the expression of NICD, Hes-1 and Deltex-1 proteins, which might be significantly blocked by DAPT, a specific inhibitor of Notch signaling. Jagged-1-Hes-1 signaling resulted in the markedly decreased in situ expression of RORgammat in the CD4+ T cells induced by IL-6 plus TGF-ß. Flow cytometric analysis showed the reduction of IL-17 production in CD4+ T cells by Jagged-1, but the enhancement of it by Hes-1-targeting siRNA. The level of IL-10 produced by the treated cells was also enhanced, whereas the expression of IL-17 was prominently attenuated, which could be offset by anti-Jagged-1 antibody or DAPT. The results indicate that Jagged-1-Hes-1 signaling can suppress the skewing of CD4+ T cells toward Th17 cells via RORgammat, for which Hes-1 may be crucial.

Th17-associated cytokines promote human airway smooth muscle cell proliferation

Increased airway smooth muscle (ASM) mass is a hallmark of airway remodeling in severe asthma. Th17-associated cytokines, particularly IL-17A, IL-17F, and IL-22, have been postulated to play a role in the pathogenesis of asthma. To investigate the in vitro effect of Th17 cytokines on the proliferation and survival of airway smooth muscle cells (ASMCs), human ASMCs from asthmatic and nonasthmatic subjects were incubated with IL-17A, IL-17F, or IL-22. The aforementioned cytokines demonstrated an ability to promote proliferation and survival of ASMCs from asthmatic and nonasthmatic subjects, which were mediated by selective activation of their corresponding receptors on ASMCs, including IL-17RA, IL-17RC, or IL-22R1, respectively. IL-17A and IL-17F-induced proliferation of ASMCs was dependent on ERK1/2 MAPK pathway, while IL-22-induced proliferation involved both ERK1/2 MAPK and NF-κB pathways. The involvement of signaling pathways was further confirmed by the inhibition of proliferation by knockdown of ERK1/2 MAPK or NF-κB p65 expression with pathway-specific siRNA. Together, our results show that Th17-associated cytokines promote proliferation and reduce the apoptotic rate of human ASMCs, raising the possibility that Th17 cytokines may contribute to increasing airway smooth muscle mass and airway remodeling in asthma.

Interleukin-17 (IL-17) expression is reduced during acute myocardial infarction: role on chemokine receptor expression in monocytes and their in vitro chemotaxis towards chemokines

The roles of immune cells and their soluble products during myocardial infarction (MI) are not completely understood. Here, we observed that the percentages of IL-17, but not IL-22, producing cells are reduced in mice splenocytes after developing MI. To correlate this finding with the functional activity of IL-17, we sought to determine its effect on monocytes. In particular, we presumed that this cytokine might affect the chemotaxis of monocytes important for cardiac inflammation and remodeling. We observed that IL-17 tends to reduce the expression of two major chemokine receptors involved in monocyte chemotaxis, namely CCR2 and CXCR4. Further analysis showed that monocytes pretreated with IL-17 have reduced in vitro chemotaxis towards the ligand for CCR2, i.e., MCP-1/CCL2, and the ligand for CXCR4, i.e., SDF-1α/CXCL12. Our results support the possibility that IL-17 may be beneficial in MI, and this could be due to its ability to inhibit the migration of monocytes.

Hypomethylation of the IL17RC promoter associates with age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly population worldwide. Although recent studies have demonstrated strong genetic associations between AMD and SNPs in a number of genes, other modes of regulation are also likely to play a role in the etiology of this disease. We identified a significantly decreased level of methylation on the IL17RC promoter in AMD patients. Furthermore, we showed that hypomethylation of the IL17RC promoter in AMD patients led to an elevated expression of its protein and messenger RNA in peripheral blood as well as in the affected retina and choroid, suggesting that the DNA methylation pattern and expression of IL17RC may potentially serve as a biomarker for the diagnosis of AMD and likely plays a role in disease pathogenesis.

Interleukin-25 promotes basic fibroblast growth factor expression by human endothelial cells through interaction with IL-17RB, but not IL-17RA

BACKGROUND

Unlike other IL-17 family members, the Th2-derived cytokine IL-25 (IL-17E) induces (promotes) Th2 responses. One or both of the two receptors for IL-25 (IL-17RA, IL-17RB) is expressed on inflammatory cells and tissue structural cells, suggesting that in addition to promoting Th2-type inflammation IL-25 may also act on structural cells at sites of Th2-type inflammation such as in the asthmatic bronchial mucosa to promote remodelling changes.

OBJECTIVE

Our previous studies showed elevated expression of IL-25 and IL-17RB immunoreactivity in asthmatic airways with co-localization of the latter to endothelial cells. We therefore hypothesized that IL-25 acts on endothelial cells through this receptor to induce production of the key angiogenic and remodelling cytokine basic fibroblast growth factor (bFGF).

METHODS

Polymerase chain reaction (PCR) immunocytochemistry/immunohistochemistry and ELISA were employed to detect expression of IL-17RB, IL-17RA and bFGF by human vascular endothelial cells (HUVEC) and immunoreactivity for IL-25 and bFGF in asthmatic bronchial biopsies. Receptor-blocking antibodies, PCR and an in vitro angiogenesis assay were used to investigate whether IL-25 acts on IL-17RB or IL-17RA to induce bFGF expression and angiogenesis. PCR was also employed to investigate the signalling pathways involved in IL-25-mediated bFGF expression.

RESULTS

HUVEC constitutively expressed IL-17RB, IL-17RA and bFGF. Production of the latter was further increased by IL-25, but attenuated after blockade of the IL-17RB, but not the IL-17RA receptor. Neutralization of endogenous VEGF and bFGF completely abrogated IL-25-induced angiogenesis which was also inhibited by blocking IL-17RB, but not IL-17RA. The PI3K-specific inhibitor LY294002 also completely attenuated IL-25-induced bFGF expression. Immunoreactivity for IL-25 and bFGF was elevated in the asthmatic bronchial mucosa and the expression of each correlated with the other.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data support the hypothesis that IL-25 contributes to elevated bFGF in asthmatic airways by acting on the endothelial cell IL-17RB receptor through PI3K-signalling pathways. Targeting the pathways might benefit therapy of airways remodelling.

Effects of IL-17 on erythroid progenitors growth: involvement of MAPKs and GATA transcription factors

Interleukin-17 is Th17 cell cytokine implicated in regulation of hematopoiesis and inflammation. Besides promoting granulopoiesis, we have previously shown that IL-17 also affects erythropoiesis stimulating the development of early erythroid progenitors, BFU-E, but suppressing, at least partly via p38 MAPK, the growth of late stage erythroid progenitors, CFU-E. The aim of the present study was to investigate the involvement of other MAPKs, JNK and ERK1/2, as well as GATA transcription factors, in IL-17-mediated effects on murine bone marrow erythroid progenitors. Data obtained by use of specific MAPKs inhibitors indicated that MEK1/2-ERK1/2 MAPK signaling mediates IL-17-induced CFU-E inhibition, as well as that JNK and/or MEK1/2-ERK1/2 MAPKs activation underlies IL-17-induced stimulation of BFU-E growth. Furthermore, Western blot analyses demonstrated no effect on early hematopoiesis transcription factor, GATA-2, and enhanced expression level of erythroid-specific factor GATA-1 in murine bone marrow cells after IL-17 stimulation, which in light of previous reports that GATA-1 overexpression inhibits erythroid differentiation, could be related to IL-17-mediated inhibition of CFU-E growth. Although, no contribution for p38, JNK and ERK MAPKs in IL-17-induced GATA-1 expression was shown, data obtained using specific inhibitors pointed to the role of JNK and MEK1/2-ERK1/2 in GATA-1 downregulation. Overall, obtained data gave an insight into the mechanisms by which IL-17 exerts its effects on erythropoiesis, implying the involvement of JNK and ERK MAPKs, as well as GATA-1, in IL-17-regulated growth of erythroid progentors.

The cytokines interleukin 27 and interferon-γ promote distinct Treg cell populations required to limit infection-induced pathology

Interferon-γ (IFN-γ) promotes a population of T-bet(+) CXCR3(+) regulatory T (Treg) cells that limit T helper 1 (Th1) cell-mediated pathology. Our studies demonstrate that interleukin-27 (IL-27) also promoted expression of T-bet and CXCR3 in Treg cells. During infection with Toxoplasma gondii, a similar population emerged that limited T cell responses and was dependent on IFN-γ in the periphery but on IL-27 at mucosal sites. Transfer of Treg cells ameliorated the infection-induced pathology observed in Il27(-/-) mice, and this was dependent on their ability to produce IL-10. Microarray analysis revealed that Treg cells exposed to either IFN-γ or IL-27 have distinct transcriptional profiles. Thus, IFN-γ and IL-27 have different roles in Treg cell biology and IL-27 is a key cytokine that promotes the development of Treg cells specialized to control Th1 cell-mediated immunity at local sites of inflammation.

[Effect of IL-17 on collagen I/III expression in cardiac fibroblasts isolated from BALB/c mice]

AIM

To investigate the effect of IL-17 on the expression of collagen I/III in cardiac fibroblasts and analyze its molecular mechanism.

METHODS

Cardiac fibroblasts were isolated from 7-14-day-old BALB/c mice and cultured in DMEM with 10% fetal bovine serum (FBS). The cells were collected after IL-17 treatment for 0, 24, 48, 72 h. IL-17 receptors on cardiac fibroblasts were detected by PCR; the collagen I/III expression was analyzed by immunofluorescence; the PKCβ, Erk1/2, NF-κB phosphorylation were investigated by Western blotting.

RESULTS

IL-17RA/C was expressed on cardiac fibroblasts; after 24 h of IL-17 stimulation, the collagen I/III expression obviously increased; Western blotting showed that PKCβ, Erk1/2 and NF-κB were phosphorylated on 30, 45, 45 min, respectively.

CONCLUSION

IL-17 could induce the expression of collagen I/III in cardiac fibroblasts, which might be related with PKCβ-ERK1/2-NF-κB phosphorylation.