Interleukin-17 augments tumor necrosis factor-alpha-induced granulocyte and granulocyte/macrophage colony-stimulating factor release from human colonic myofibroblasts

Recruited bone marrow derived cells, local stromal cells and IL-17 at the front line of resistance development to anti-VEGF targeted therapies

Although anti-angiogenic agents targeting VEGF have shown affordable beneficial outcomes in several human cancer types, in most pre-clinical and clinical studies, these effects are transient and followed by rapid relapse and tumor regrowth. Recently, it has been suggested that recruited bone marrow derived cells (BMDCs) to the tumor-microenvironment together with stromal cells play an important role in development of resistance to anti-VEGF therapies. Additionally, acquired resistance to anti-VEGF therapies has shown to be mediated partly through overexpression of different pro-angiogenic cytokines and growth factors including G-CSF, IL-6, IL-8, VEGF and FGF by these cells. Alongside, IL-17, a pro-inflammatory cytokine, mostly secreted by infiltrated CD4⁺ T helper cells, has shown to mediate resistance to anti-VEGF therapies, through recruiting BMDCs and modulating stromal cells activities including endothelial cells, tumor associated macrophages and cancer associated fibroblasts. Here, we examined the role of BMDCs, tumor stromal cells, IL-17 and their negotiation in development of resistance to anti-VEGF targeted therapies.

Paraneoplastic hyperleucocytosis in a melanoma patient after initiation of ipilimumab and nivolumab combination therapy

Background

Paraneoplastic hyperleucocytosis (PH) is sporadically seen in patients with advanced solid tumors.

Case presentation

We report a female patient with disseminated melanoma metastases. Two days after the first dosage of combined immunotherapy using the cytotoxic T lymphocyte antigen-4 (CTLA-4) blocker ipilimumab and the programmed death receptor-1 (PD-1) blocker nivolumab the patient developed asymptomatic hyperleucocytosis (over 120.000 leucocytes per μl) associated with elevated granulocyte colony-stimulating factor blood levels. Hematological and infectious disorders could be ruled out. Although paraneoplastic hyperleucocytosis spontaneously resolved she died from progressive disease about 60 days after start of treatment.

Conclusions

PH is extremely rare in malignant melanoma, however, most patients who developed this complication had preceding immunotherapies such as interleukin-2. The latter observation and the fact that our patient developed PH rapidly after initiation of ipilimumab and nivolumab immunotherapy indicate an immune-mediated mechanism which may trigger PH under unknown circumstances. The development of paraneoplastic hyperleucocytosis indicates a very poor prognosis.

Interleukin-17 augments tumor necrosis factor α-mediated increase of hypoxia-inducible factor-1α and inhibits vasodilator-stimulated phosphoprotein expression to reduce the adhesion of breast cancer cells

Interleukin-17 (IL-17) and tumor necrosis factor (TNF)-α are able to cooperatively alter the expression levels of a number of genes. In the present study, the mRNA expression levels of hypoxia-inducible factor (HIF)-1α were analyzed in MDA-MB-231 breast cancer cells following treatment with IL-17, TNF-α or the combination of IL-17 and TNF-α. The protein expression levels of HIF-1α and vasodilator-stimulated phosphoprotein (VASP) were evaluated using western blot analysis. The adhesive ability of the cells was determined using an MTT assay following treatment with HIF-1α-small interfering RNA and short hairpin RNA-VASP that were used to suppress the expression levels of HIF-1α and VASP protein, respectively. These results demonstrated that IL-17 augmented TNF-α-induced gene expression of HIF-1α. The combination of IL-17 and TNF-α promoted an increase in HIF-1α expression and a decrease in VASP expression and a reduction in the adhesive ability of cells. These results demonstrated that IL-17 effectively enhanced the TNF-α-induced increase in HIF-1α and inhibited VASP expression, thus reducing the adhesion of MDA-MB-231 cells.

IL-17A synergistically stimulates TNF-α-induced IL-8 production in human airway epithelial cells: A potential role in amplifying airway inflammation

BACKGROUND

Recent reports have suggested an involvement of neutrophilic inflammation driven by interleukin (IL)-17 from Th17 cells, especially in severe, refractory asthma. It remains unknown about the possible interactions of this cytokine and other proinflammatory cytokines to direct neutrophilic airway inflammation.

MATERIALS AND METHODS

We evaluated the effects of IL-17A, IL-17E, and IL-17F in combination with other stimuli such as tumor necrosis factor (TNF) -α on the production and expression of IL-8 in human bronchial epithelial cells. We also studied their effects on other cytokine production. The possible role of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways was evaluated by specific inhibitors. We examined the effects of anti-asthma drugs, such as steroids or salmeterol.

RESULTS

IL-17A alone induced only a minimal effect on IL-8 expression. IL-17A, but not IL-17E or IL-17F, in combination with TNF-α showed a synergistic effect on IL-8 expression. Similar findings were found when combination with IL-1β and IL-17A were used, but such was not the case with lipopolysaccharide (LPS). In addition, we further found such synergy on GM-CSF production. The synergy with TNF-α and IL-17A was significantly inhibited by MAPKs inhibitors. Corticosteroids such as fluticasone propionate and dexamethasone, but not salmeterol, partially suppressed the IL-17A and TNF-α-induced IL-8 production.

CONCLUSIONS

IL-17A in the combination with TNF-α or IL-1β showed a synergistic augmenting effect on IL-8 and GM-CSF production in human airway epithelial cells.

Granulocyte macrophage colony-stimulating factor and the intestinal innate immune cell homeostasis in Crohn's disease

Current literature consolidates the view of Crohn's disease (CD) as a form of immunodeficiency highlighting dysregulation of intestinal innate immunity in the pathogenesis of CD. Intestinal macrophages derived from blood monocytes play a key role in sustaining the innate immune homeostasis in the intestine, suggesting that the monocyte/macrophage compartment might be an attractive therapeutic target for the management of CD. Granulocyte macrophage colony-stimulating factor (GM-CSF) is a hematopoietic growth factor that also promotes myeloid cell activation, proliferation, and differentiation. GM-CSF has a protective effect in human CD and mouse models of colitis. However, the role of GM-CSF in immune and inflammatory reactions in the intestine is not well defined. Beneficial effects exerted by GM-CSF during intestinal inflammation could relate to modulation of the mucosal barrier function in the intestine, including epithelial cell proliferation, survival, restitution, and immunomodulatory actions. The aim of this review is to summarize potential mechanistic roles of GM-CSF in intestinal innate immune cell homeostasis and to highlight its central role in maintenance of the intestinal immune barrier in the context of immunodeficiency in CD.

Intestinal stromal cells in mucosal immunity and homeostasis

A growing body of evidence suggests that non-hematopoietic stromal cells of the intestine have multiple roles in immune responses and inflammation at this mucosal site. Despite this, many still consider gut stromal cells as passive structural entities, with past research focused heavily on their roles in fibrosis, tumor progression, and wound healing, rather than their contributions to immune function. In this review, we discuss our current knowledge of stromal cells in intestinal immunity, highlighting the many immunological axes in which stromal cells have a functional role. We also consider emerging data that broaden the potential scope of their contribution to immunity in the gut and argue that these so-called "non-immune" cells are reclassified in light of their diverse contributions to intestinal innate immunity and the maintenance of mucosal homeostasis.

T(H)17 cells in asthma and inflammation

BACKGROUND

The chronic airway disease asthma causes significant burden to patients as well as the healthcare system with limited options for prevention or cure. Inadequate treatment strategies are most likely due to the complex heterogeneous nature of asthma. Furthermore, the severe asthma phenotype is characterized by the lack of a response to standard medication, namely, corticosteroids.

SCOPE OF REVIEW

In the last several years it has been shown that the eosinophilic/atopic phenotype of asthma driven by T(H)2 mechanisms is not the only immunologic pathway contributing to disease. In fact, there has been evidence revealing that severe asthmatics in particular have neutrophilic inflammation, and this is associated with corticosteroid resistance. T(H)17 cells, a recently discovered lineage of T helper cells, play an important role in lung host defense against multiple pathogens via production of the cytokine IL-17. IL-17 promotes neutrophil production and chemotaxis via multiple factors.

MAJOR CONCLUSIONS

Mouse and human studies provide robust evidence that T(H)17 cells and IL-17 play a role in severe asthma and may contribute to corticosteroid resistance.

GENERAL SIGNIFICANCE

As we learn more about T(H)17 cells in severe asthma, the goal is to potentially target this pathway for treatment in the hope of significantly improving the quality of life for those children and adults affected with this disease. This article is part of a Special Issue entitled: Biochemistry of Asthma.

IL-17A increases ADP-induced platelet aggregation

The increased risk of thromboembolism and higher incidence of cardiovascular disorders are among the most common causes of morbidity in patients suffering from autoimmune diseases. In this study we tested the hypothesis that IL-17A, a key pro-inflammatory cytokine involved in the development of autoimmune diseases, exerts pro-aggregant effects on both human and mouse platelets. Human or murine platelets were incubated with IL-17A for 2 min at 37°C prior the addition of the stimuli. Aggregation was monitored in a light transmission aggregometer measuring changes in turbidity with continuous observation over a 5-min interval after the addition of the stimuli. IL-17RA, CD42b and CD62P expression as well as fibrinogen bindings were measured by FACS while Erk-2 phosphorylation was analyzed by western blot using phospho-specific antibodies. Pre-incubation with IL-17A increased ADP-, but not collagen-induced platelet aggregation and accelerated CD62P expression and exposure of fibrinogen binding sites. These effects were associated with a faster kinetic of ADP-induced Erk-2 phosphorylation and were lost in platelets deficient in the IL-17 receptor. Together these results unveil a novel aspect of the inflammatory nature of IL-17A suggesting, at the same time, that therapeutic strategies targeting this cytokine might provide further benefit for the treatment of autoimmune diseases by reducing the risk of cardiovascular-related pathologies.

Lactobacillus rhamnosus GR-1 stimulates colony-stimulating factor 3 (granulocyte) (CSF3) output in placental trophoblast cells in a fetal sex-dependent manner

Bacterial vaginosis is associated with a 1.4-fold increased risk of preterm birth. We have shown previously that Lactobacillus rhamnosus GR-1 supernatant up-regulates interleukin 10 and down-regulates tumor necrosis factor-alpha output in lipopolysaccharide (LPS)-treated human primary placenta cultures in a fetal sex-dependent manner. We hypothesize that lactobacilli also exert their anti-inflammatory effect by up-regulation of colony-stimulating factor 3 (granulocyte) (CSF3), which is secreted from both immune and placental trophoblast cells, and that this activity is dependent on the sex of the fetus. Placental trophoblast cells were isolated from term elective cesarean section placentae using a Percoll gradient and separated from CD45(+) cells using magnetic purification. Cells were treated with LPS in the presence or absence of pretreatments with L. rhamnosus GR-1 supernatant or chemical inhibitors of the intracellular signaling pathways. Phosphorylations of mitogen-activated protein kinase 14 (MAPK14, previously known as p38) and signal transducer and activator of transcription (STAT) 3 were measured by Western blot analysis, and levels of CSF3 were determined by ELISA. CSF3 output was increased only in the placental trophoblast cells of female fetuses treated with LPS, GR-1 supernatant, and a combination of both treatments. The GR-1 supernatant up-regulated the phosphorylation of STAT3 and MAPK14. CSF3 output was inhibited by both Janus kinases (JAK) and MAPK14 inhibitors. None of the treatments was able to increase CSF3 output in either the pure trophoblast or the CD45(+) cell preparations alone. These results suggest an underlying mechanism for the sex difference in incidence of preterm birth and provide potential evidence for a therapeutic benefit of lactobacilli in reducing the risk of preterm labor.

The multifaceted effects of granulocyte colony-stimulating factor in immunomodulation and potential roles in intestinal immune homeostasis

The three colony-stimulating factors, granulocyte/macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), and granulocyte colony-stimulating factor (G-CSF), have been regarded as immunostimulators because of their role in granulocyte and myeloid hematopoiesis and immune function. However, unlike GM-CSF and M-CSF, G-CSF possesses immunosuppressive effects on other immune cells including monocytes/macrophages, dendritic cells, and T lymphocytes when exogenously administered. Given the immunomodulatory effects of exogenous G-CSF, endogenous G-CSF may also play an important role in maintaining local immune homeostasis in tissue in which it is highly and constitutively produced. This review highlights the potential role of G-CSF in immunomodulation and intestinal immune homeostasis.

TH17 cells in asthma and COPD

Asthma and chronic obstructive pulmonary disease (COPD) represent two classes of chronic obstructive lung disorders that may share some similar immunologic mechanisms of disease. Asthma is a complex human disease characterized by airway hyperresponsiveness (AHR) and inflammation, whereas COPD is marked by progressive emphysematic changes in the lung. Recently it has been shown that advanced COPD is characterized by lymphoid follicles, drawing attention to immunological mechanisms in COPD. Despite numerous studies in mice to elucidate the immunologic mechanisms of asthma, sufficient current treatment options are limited. Clinically, many asthma patients fail to satisfactorily respond to standard steroid therapy, and this type of steroid-resistant, severe asthma has been linked to the presence of neutrophilic inflammation in the lung. The role of neutrophils, macrophages, and their secreted proteases in COPD needs to be better defined. Recently, the T lymphocyte subset T(H)17 was shown to play a role in regulating neutrophilic and macrophage inflammation in the lung, suggesting a potential role for T(H)17 cells in severe, steroid-insensitive asthma and COPD.

The increased mucosal mRNA expressions of complement C3 and interleukin-17 in inflammatory bowel disease

Recent studies have demonstrated that the complement system participates in the regulation of T cell functions. To address the local biosynthesis of complement components in inflammatory bowel disease (IBD) mucosa, we investigated C3 and interleukin (IL)-17 mRNA expression in mucosal samples obtained from patients with IBD. The molecular mechanisms underlying C3 induction were investigated in human colonic subepithelial myofibroblasts (SEMFs). IL-17 and C3 mRNA expressions in the IBD mucosa were evaluated by real-time polymerase chain reaction. The C3 levels in the supernatant were determined by enzyme-linked immunosorbent assay. IL-17 and C3 mRNA expressions were elevated significantly in the active lesions from ulcerative colitis (UC) and Crohn's disease (CD) patients. There was a significant positive correlation between IL-17 and C3 mRNA expression in the IBD mucosa. IL-17 stimulated a dose- and time-dependent increase in C3 mRNA expression and C3 secretion in colonic SEMFs. The C3 molecules secreted by colonic SEMFs were a 115-kDa alpha-chain linked to a 70-kDa beta-chain by disulphide bonds, which was identical to serum C3. The IL-17-induced C3 mRNA expression was blocked by p42/44 mitogen-activated protein kinase (MAPK) inhibitors (PD98059 and U0216) and a p38 MAPK inhibitor (SB203580). Furthermore, IL-17-induced C3 mRNA expression was inhibited by an adenovirus containing a stable mutant form of I kappaB alpha. C3 and IL-17 mRNA expressions are enhanced, with a strong correlation, in the inflamed mucosa of IBD patients. Part of these clinical findings was considered to be mediated by the colonic SEMF response to IL-17.

The receptor SIGIRR suppresses Th17 cell proliferation via inhibition of the interleukin-1 receptor pathway and mTOR kinase activation

Interleukin-1 (IL-1)-mediated signaling in T cells is essential for T helper 17 (Th17) cell differentiation. We showed here that SIGIRR, a negative regulator of IL-1 receptor and Toll-like receptor signaling, was induced during Th17 cell lineage commitment and governed Th17 cell differentiation and expansion through its inhibitory effects on IL-1 signaling. The absence of SIGIRR in T cells resulted in increased Th17 cell polarization in vivo upon myelin oligodendrocyte glycoprotein (MOG(35-55)) peptide immunization. Recombinant IL-1 promoted a marked increase in the proliferation of SIGIRR-deficient T cells under an in vitro Th17 cell-polarization condition. Importantly, we detected increased IL-1-induced phosphorylation of JNK and mTOR kinase in SIGIRR-deficient Th17 cells compared to wild-type Th17 cells. IL-1-induced proliferation was abolished in mTOR-deficient Th17 cells, indicating the essential role of mTOR activation. Our results demonstrate an important mechanism by which SIGIRR controls Th17 cell expansion and effector function through the IL-1-induced mTOR signaling pathway.

Potential role of interleukin-17 in the pathogenesis of bullous pemphigoid

Bullous pemphigoid is an autoimmune blistering disease of the skin caused by autoantibodies directed against basement membrane zone adhesion molecules. Autoantibodies cannot fully explain several important features of the disease such as the difficulty transferring with the pathogenic autoantibodies, or the presence of heavy lesional infiltration of eosinophils and neutrophils that is necessary for disease production. There is increasing evidence that Th17 cells and the cytokines they release such as interleukin-17 are important regulators of innate and adaptive immune responses in many Th1 and/or Th2 mediated autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and allergic asthma. There is also evidence that Th17 cells have a role in pathogenesis of blistering skin diseases. Interleukin-17 is important in initiation and maintenance of many autoimmune reactions and it is involved in production of pro-inflammatory cytokines, matrix metalloproteinases, neutrophils, and eosinophils, all of which are important pathogenic factors in bullous pemphigoid. The hypothesis is that interleukin-17 has an important pathogenic role in BP and can describe features of the disease not explained by the autoantibody theory. This cytokine can be assessed in the blister fluid and sera of patients, and can be used as a marker of disease activity and response to therapy. The information obtained could also lead to the development of novel therapeutic strategies for this and other autoimmune blistering diseases.

Translational mini-review series on Th17 cells: function and regulation of human T helper 17 cells in health and disease

T helper (Th) cell have a central role in modulating immune responses. While Th1 and Th2 cells have long been known to regulate cellular and humoral immunity, Th17 cells have been identified only recently as a Th lineage that regulates inflammation via production of distinct cytokines such as interleukin (IL)-17. There is growing evidence that Th17 cells are pathological in many human diseases, leading to intense interest in defining their origins, functions and developing strategies to block their pathological effects. The cytokines that regulate Th17 differentiation have been the focus of much debate, due primarily to inconsistent findings from studies in humans. Evidence from human disease suggests that their in vivo development is driven by specialized antigen-presenting cells. Knowledge of how Th17 cells interact with other immune cells is limited, but recent data suggest that Th17 cells may not be subject to strict cellular regulation by T regulatory cells. Notably, Th17 cells and T regulatory cells appear to share common developmental pathways and both cell types retain significant plasticity. Herein, we will discuss the molecular and cellular regulation of Th17 cells with an emphasis on studies in humans.

[Role of myofibroblast in inflammatory bowel disease and tumor genesis]

Stroma cells with the microenvironment around them have primary role in the regulation of inflammation processes, conformation of tumors and development of metastasis. Myofibroblasts have essential role in inflammation processes and in the regeneration of encompassed tissue. Molecules produced by them operate the cells of the immune system and effect the proliferation of epithelium. Tumors can activate myofibroblasts which can lead to uncontrolled epithelium proliferation across production of changed and increased regulation ligands (such as cytokines, chemokines, chemotactic and other growth factors) and activation of stem cell. This process could lead piling of uncontrolled epithelial cells and can impact later on conformation of tumors. In this study we present an overview about of myofibroblasts and their roles in inflammation and neoplastic processes.

Mucosal cytokine network in inflammatory bowel disease

Inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohn’s disease (CD) are characterized by ongoing mucosal inflammation in which dysfunction of the host immunologic response against dietary factors and commensal bacteria is involved. The chronic inflammatory process leads to disruption of the epithelial barrier, and the formation of epithelial ulceration. This permits easy access for the luminal microbiota and dietary antigens to cells resident in the lamina propria, and stimulates further pathological immune cell responses. Cytokines are essential mediators of the interactions between activated immune cells and non-immune cells, including epithelial and mesenchymal cells. The clinical efficacy of targeting TNF-α clearly indicates that cytokines are the therapeutic targets in IBD patients. In this manuscript, we focus on the biological activities of recently-reported cytokines [Interleukin (IL)-17 cytokine family, IL-31 and IL-32], which might play a role through interaction with TNF-α in the pathophysiology of IBD.

An overview of IL-17 function and signaling

Since the discovery of interferons over 50 years ago, efforts to understand the biochemistry, molecular biology and biological activities of cytokines have been intense and rewarding. Although there are several hundred cytokines and receptors currently recognized, they in fact fall into a fairly limited set of subfamilies (reviewed in [Ozaki K, Leonard WJ. Cytokine and cytokine receptor pleiotropy and redundancy. J Biol Chem 2002;277:29355-58 [1]; Shen F, Gaffen SL. Structure-function relationships in the IL-17 receptor: implications for signal transduction and therapy. Cytokine 2008;41:92-104 [2]). Within these families (and in some cases even outside them), cytokines share many structural and functional features that have provided a framework for understanding their biological activities and signal transduction mechanisms. This review will focus on interleukin (IL)-17, the founding member of the newest subclass of cytokines, which has received considerable attention in the last several years due to its central role in the Th17 system.

Structure-function relationships in the IL-17 receptor: implications for signal transduction and therapy

IL-17 is the defining cytokine of a newly-described "Th17" population that plays critical roles in mediating inflammation and autoimmunity. The IL-17/IL-17 receptor superfamily is the most recent class of cytokines and receptors to be described, and until recently very little was known about its function or molecular biology. However, in the last year important new insights into the composition and dynamics of the receptor complex and mechanisms of downstream signal transduction have been made, which will be reviewed here.

Inflammatory responses induced by interleukin-17 family members in human colonic subepithelial myofibroblasts

BACKGROUND

We investigated the potential role of interleukin (IL)-17 family members (IL-17A to IL-17F) in the induction of inflammatory responses in human colonic subepithelial myofibroblasts (SEMFs).

METHODS

The expression of the inflammatory cytokines IL-6, IL-8, leukemia inhibitory factor (LIF), and matrix metalloproteinases (MMP)-1 and MMP-3 were evaluated by enzyme-linked immunosorbent assay and Northern blotting. Activation of mitogen-activated protein kinase (MAPK) was assessed by immunoblotting.

RESULTS

IL-17A and IL-17F significantly enhanced IL-6, IL-8, LIF, MMP-1, and MMP-3 secretion. The effects of IL-17A were relatively stronger than those induced by IL-17F. The effects of IL-17B, IL-17C, IL-17D, and IL-17E were modest as compared with those induced by IL-17A and IL-17F. Both IL-17A and IL-17F augmented IL-1beta-induced secretion of IL-6, IL-8, LIF, MMP-1, and MMP-3. A similar augmentation was also observed in tumor necrosis factor (TNF)-alpha-induced cytokine and MMP secretion. IL-17A and IL-17F rapidly induced phosphorylation of extracellular signal-regulated kinases (ERK) 1/2, p38 MAPKs, and c-Jun-NH(2)-terminal kinase (JNK) as early as 15 min after stimulation. Inhibitors for ERK (PD98059 and U0216) and p38 MAPK (SB203580) significantly reduced the IL-17F-induced IL-6, IL-8, LIF, MMP-1, and MMP-3 secretion.

CONCLUSIONS

Among IL-17 family members, IL-17A and IL-17F strongly stimulate human colonic SEMFs, inducing inflammatory responses.

Role of intestinal subepithelial myofibroblasts in inflammation and regenerative response in the gut

Inflammatory bowel disease (IBD) is characterized by an ongoing mucosal inflammation caused by a dysfunctional host immune response to commensal microbiota and dietary factors. In the pathophysiology of IBD, mesenchymal cells such as intestinal subepithelial myofibroblasts (ISEMF) affect the recruitment, retention and activation of immune cells. Mesenchymal cells also promote resolution of inflammatory activity accompanied with balanced repair processes. The transient appearance of mesenchymal cells is a feature of normal wound healing, but the persistence of these cells is associated with tissue fibrosis. Recent studies suggest that mesenchymal cells derived from bone marrow (BM) stem cells play a crucial role in intestinal repair and fibrosis. This article focuses on recent knowledge about ISEMF in the field of immune response inflammation and repair. Two major topics were documented: interaction between interleukin (IL)-17-secreting CD4+ cells (Th-17 cells) and about role of BM-derived stem cells in mucosal regenerative response via differentiation to ISEMF. Recent therapeutic strategies targeting BM stem cells for IBD patients were also documented.

Role of mesothelial cell-derived granulocyte colony-stimulating factor in interleukin-17-induced neutrophil accumulation in the peritoneum

Recent studies suggest that peritoneal CD4(+) T lymphocytes may control recruitment of polymorphonuclear leukocytes (PMN) during peritonitis by an interleukin-17 (IL-17)-dependent mechanism. IL-17 and granulocyte colony-stimulating factor (G-CSF) have been proposed to form an axis that regulates PMN transmigration. Here we report on the role of G-CSF released by human peritoneal mesothelial cells (HPMCs) in IL-17A-mediated peritoneal PMN accumulation. In vitro exposure of HPMCs to IL-17A resulted in a time- and dose-dependent release of G-CSF. This effect was related to the induction of G-CSF mRNA and mediated through the nuclear factor-kappaB (NF-kappaB) pathway. The novel observation was that IL-17A-stimulated NF-kappaB activation in HPMCs followed a biphasic profile, with an early induction (45 min), followed by the return to basal levels (90 min), and a delayed induction (3 h). Tumor necrosis factor alpha synergistically amplified IL-17A-induced G-CSF production by enhanced NF-kappaB activation and through stabilization of G-CSF mRNA. Intraperitoneal (i.p.) administration of IL-17A in Balb/c mice resulted in increased local levels of G-CSF and selective PMN accumulation. Administration of anti-G-CSF blocking antibody before IL-17A injection significantly reduced the IL-17A-triggered PMN infiltration. This effect occurred despite increased i.p. levels of PMN-specific chemokines KC and macrophage inflammatory protein-2 seen in animals treated with anti-G-CSF antibody. These data demonstrate that the mesothelium-derived G-CSF plays an important role in IL-17A-induced PMN recruitment into the peritoneum.

Interaction between interleukin-17-producing CD4+ T cells and colonic subepithelial myofibroblasts: what are they doing in mucosal inflammation?

Recent studies have shown alterations and activations in the mucosal immune system in patients with irritable bowel syndrome (IBS) as well as in those with inflammatory bowel disease (IBD). As one of effectors of mucosal inflammation, a new lineage of effector CD4+ T cells characterized by production of interleukin (IL)-17, the T-helper (Th)-17 lineage, was recently described. Th-17 cells are developmentally and functionally distinct from Th1 and Th2 cells. Here, we discuss the recent concept of low-grade inflammation as a factor associated with the pathophysiology of IBS. Furthermore, based on the data from our laboratory, interaction between Th-17 cells and colonic subepithelial myofibroblasts may play an important role in the pathophysiology of IBS and IBD.

TNF-alpha and IFN-gamma inversely modulate expression of the IL-17E receptor in airway smooth muscle cells

The interleukin-17B receptor (IL-17BR) is expressed in a variety of tissues and is upregulated under inflammatory conditions. This receptor binds both its cognate ligand IL-17B and IL-17E/IL-25, a novel cytokine known to promote Th2 responses. The present study shows that airway smooth muscle cells express IL-17BR in vitro and that its expression is upregulated by TNF-alpha and downregulated by IFN-gamma. Our data indicate that TNF-alpha upregulates IL-17BR mainly through nuclear factor-kappaB as assessed with the IkappaB kinase 2 inhibitor AS-602868. In addition, both IFN-gamma and dexamethasone are able to antagonize a TNF-alpha-induced IL-17BR increase in mRNA expression. The mitogen-activated protein kinase kinase inhibitor U0126 totally reversed the inhibition observed with IFN-gamma, suggesting the involvement of the extracellular signal-regulated kinase pathway in this effect. In addition, on stimulation with IL-17E, airway smooth muscle cells increase their expression of ECM components, namely procollagen-alphaI and lumican mRNA. Furthermore, immunohistochemical analysis of biopsies from asthmatic subjects reveals that this receptor is abundant in smooth muscle layers. This is the first report showing IL-17BR receptor in structural cells of the airways. Our results suggest a potential proremodeling effect of IL-17E on airway smooth muscle cells through the induction of ECM and that its receptor is upregulated by proinflammatory conditions.