IL-9 and its receptor are predominantly involved in the pathogenesis of UC

Decreased placental IL9 and IL9R in preeclampsia impair trophoblast cell proliferation, invasion, and angiogenesis

OBJECTIVE

Our study aimed to investigate IL9 and IL9R expression in preeclampsia and assess their effects on trophoblast biological behaviors.

METHODS

IL9 and IL9R expression of placenta tissue were evaluated by immunochemistry and q-PCR. Using transwell, CCK-8, and tubule formation assays measured invasion, proliferation and angiogenesis of trophoblast with adding IL9 or anti-IL9R antibody.

RESULTS

IL9 and IL9R levels were significantly decreased in preeclampsia. IL9 improved trophoblast activities. Blocking IL9/IL9R resulted in decreased proliferation, invasion, and tube-formation capability of trophoblast.

CONCLUSIONS

IL9 and IL9R contribute to the pathogenesis of preeclampsia. IL9/IL9R signaling provides a new potential therapeutic target for preventing preeclampsia.

Higher Prevalence of Nickel and Palladium Hypersensitivity in Patients with Ulcerative Colitis

BACKGROUND

The etiology of ulcerative colitis (UC) remains elusive even though many genetic and environmental pathogenic factors have been reported. Aberrant inflammatory responses mediated by specific subsets of T cells have been observed in ulcerative lesions of UC patients.

OBJECTIVES

To elucidate the involvement of a delayed-type hypersensitivity reaction in UC, we focused on dental metal hypersensitivity, a T cell-mediated, delayed-type allergic reaction that causes oral contact mucositis and systemic cutaneous inflammation.

METHOD

We recruited 65 Japanese UC patients and 22 healthy controls (HC) and used the in vitro lymphocyte stimulation test to quantify their sensitivity to zinc, gold, nickel, and palladium - the metals that have been widely used in dentistry. All subjects were users of metallic dental implants and/or prostheses containing zinc, gold, nickel, and/or palladium as major constituents.

RESULTS

Sixty percent of the UC patients were hypersensitive to at least one metal species, whereas 32% of the HC were hypersensitive to only a single metal species. The overall incidence of metal hypersensitivity was significantly higher for UC patients than for HC. Furthermore, a significantly greater proportion of UC patients were hypersensitive to nickel or palladium. The severity of the sensitivity to nickel and palladium was also significantly greater for UC patients than for HC.

CONCLUSIONS

This pilot study demonstrates that UC patients have a significantly higher incidence of hypersensitivity to nickel and palladium, suggesting the possible involvement of dental metal hypersensitivity in UC pathogenesis.

Advances in the role of helper T cells in autoimmune diseases

Autoimmune diseases are primary immune diseases in which autoreactive antibodies or sensitized lymphocytes destroy and damage tissue and cellular components, resulting in tissue damage and organ dysfunction. Helper T cells may be involved in the pathogenesis of autoimmune diseases under certain conditions. This review summarizes recent research on the role of helper T cells in autoimmune diseases from two aspects, helper T cell-mediated production of autoantibodies by B cells and helper T cell-induced activation of abnormal lymphocytes, and provides ideas for the treatment of autoimmune diseases. The abnormal expression of helper T cells promotes the differentiation of B cells that produce autoantibodies, which leads to the development of different diseases. Among them, abnormal expression of Th2 cells and T follicular helper cells is more likely to cause antibody-mediated autoimmune diseases. In addition, abnormal activation of helper T cells also mediates autoimmune diseases through the production of abnormal cytokines and chemokines. Helper T cells play an essential role in the pathogenesis of autoimmune diseases, and a full understanding of their role in autoimmune diseases is helpful for providing ideas for the treatment of autoimmune diseases.

A new target for the treatment of inflammatory bowel disease: Interleukin-37

Interleukin (IL)-37 belongs to the IL-1 cytokine family. It has anti-inflammatory effects on numerous autoimmune diseases such as asthma, psoriasis, inflammatory bowel disease (IBD), systemic lupus erythematosus (SLE), multiple sclerosis (MS) and rheumatoid arthritis (RA). Mechanistically, IL-37 plays an anti-inflammatory role by regulating the expression of inflammatory factors in two ways: binding extracellular receptors IL-18R or transferring into the nucleus with Smad3. IBD is a kind of idiopathic intestinal inflammatory disease with unknown etiology and pathogenesis. Recent researches had proved that IL-37 is negatively involved in the pathogenesis and development of IBD. Among various inflammatory diseases, IL-37 has been shown to regulate inflammatory development by acting on various immune cells such as neutrophils, macrophages (Mϕ), dendritic cells (DCs), T cells and intestinal epithelial cells. This review summarizes the biological role of IL-37, and its immunoregulatory effects on the immune cells, especially anti-inflammatory function in both human and experimental models of IBD.

IL-9 exerts biological function on antigen-experienced murine T cells and exacerbates colitis induced by adoptive transfer

IL-9 is involved in various T cell-dependent inflammatory models including colitis, encepahlitis, and asthma. However, the regulation and specificity of IL-9 responsiveness by T cells during immune responses remains poorly understood. Here, we addressed this question using two different models: experimental colitis induced by transfer of naive CD4⁺ CD45RB^high T cells into immunodeficient mice, and OVA-specific T cell activation. In the colitis model, constitutive IL-9 expression exacerbated inflammation upon transfer of CD4⁺ CD45RB^high T cells from WT but not from Il9r^-/- mice, indicating that IL-9 acts directly on T cells. Suprisingly, such naïve CD4⁺ CD45RB^high T cells failed to express the Il9r or respond to IL-9 in vitro, in contrast with CD4⁺ CD45RB^low T cells. By using OVA-specific T cells, we observed that T cells acquired the capacity to respond to IL-9 along with CD44 upregulation, after long-lasting (5 to 12 days) in vivo antigenic stimulation. Il9r expression was associated with Th2 and Th17 phenotypes. Interestingly, in contrast to the IL-2 response, antigen restimulation downregulated IL-9 responsiveness. Taken together, our results demonstrate that IL-9 does not act on naïve T cells but that IL-9 responsiveness is acquired by CD4⁺ T cells after in vivo activation and acquisition of memory markers such as CD44.

IL-13 mRNA Tissue Content Identifies Two Subsets of Adult Ulcerative Colitis Patients With Different Clinical and Mucosa-Associated Microbiota Profiles

BACKGROUND AND AIMS

A personalized approach to therapy hold great promise to improve disease outcomes. To this end, the identification of different subsets of patients according to the prevalent pathogenic process might guide the choice of therapeutic strategy. We hypothesize that ulcerative colitis [UC] patients might be stratified according to distinctive cytokine profiles and/or to a specific mucosa-associated microbiota.

METHODS

In a cohort of clinically and endoscopic active UC patients and controls, we used quantitative PCR to analyse the mucosal cytokine mRNA content and 16S rRNA gene sequencing to assess the mucosa-associated microbiota composition.

RESULTS

We demonstrate, by means of data-driven approach, the existence of a specific UC patient subgroup characterized by elevated IL-13 mRNA tissue content separate from patients with low IL-13 mRNA tissue content. The two subsets differ in clinical-pathological characteristics. High IL-13 mRNA patients are younger at diagnosis and have a higher prevalence of extensive colitis than low IL-13 mRNA patients. They also show more frequent use of steroid/immunosuppressant/anti-tumour necrosis factor α therapy during 1 year of follow-up. The two subgroups show differential enrichment of mucosa-associated microbiota genera with a prevalence of Prevotella in patients with high IL-13 mRNA tissue content and Sutterella and Acidaminococcus in patients with low IL-13 mRNA tissue content.

CONCLUSION

Assessment of mucosal IL-13 mRNA might help in the identification of a patient subgroup that might benefit from a therapeutic approach modulating IL-13.

PODCAST

This article has an associated podcast which can be accessed at https://academic.oup.com/ecco-jcc/pages/podcast.

Different cytokine patterns induced by Helicobacter pylori and Lactobacillus acidophilus extracts in PBMCs of patients with abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a degenerative inflammatory disease with unknown etiology. AAA is characterized by abdominal aortic dilatation more than 3 cm and is often asymptomatic, but the rupture of aneurysm can lead to death. Age, smoking and male sex are major predisposing factors of AAA. This study compares the effect of Helicobacter (H.) pylori and Lactobacillus (L.) acidophilus on the cytokine profile of PBMCs of 5 men with abdominal aortic aneurysm (AAA) and 5 men with normal/insignificant angiography, CT-Scan and ultrasonography results in the single-culture and in the co-culture with HUVECs. IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17A, IL-17 F, IL-21, IL-22, IFN-γ and TNF-α were measured in culture supernatants using a commercial fluorescent-labeled-bead assay. In general, CagA+ H. pylori-extract induced higher production of IFN-γ, IL-13 and IL-21 by PBMCs. Treatment of patients' PBMCs with CagA⁺H. pylori-extract induced Th2 cytokines while treatment of controls' PBMCs with CagA⁺H. pylori-extract increased Th1 cytokines. In the co-culture, however, patients' PBMCs produced Th1 cytokines irrespective of extract treatment, while controls' PBMCs produced Th2 cytokines and decreased IL-10. CagA+ H. pylori- as well as L. acidophilus-extract induced higher levels of IL-9 by controls' PBMCs in co-culture with HUVECs than patients (P = 0.05 and P = 0.01). The cytokine pattern of PBMCs induced by CagA+ H. pylori- and L. acidophilus-extracts in the co-culture with HUVECs shows differences in AAA patients and in comparison to controls. Decreased secretion of IL-9, IL-21 and IL-22 by PBMCs of patients treated with CagA+ H. pylori extract in co-culture, as opposed to non-AAA controls may indicate the active role ECs play in AAA. Simultaneous production of IL-10 and Th1 cytokines in patients and pronounced Th2 cytokines in controls in response to both bacteria may point to the inherent differences between patients and controls, which need further investigation.

Inhibition of Histone H3K27 Acetylation Orchestrates Interleukin-9-Mediated and Plays an Anti-Inflammatory Role in Cisplatin-Induced Acute Kidney Injury

Nephrotoxicity is a major side effect of cisplatin (CP)- and platinum-related chemotherapy, and inflammation contributes to disease pathogenesis. Interleukin-9 (IL-9) is a pleiotropic cytokine associated with inflammation. Here, we investigated the key role of IL-9 as a regulator of protective mechanisms in CP-induced acute kidney injury (AKI). We observed that IL-9 was decreased not only in a CP-induced AKI mouse model but also in THP-1 and RAW264.7 cell lines. Seventy-two hours post-CP injection, renal dysfunction and tubule injury were significantly attenuated in IL-9 overexpression adeno-associated virus 9 (AAV9)-treated mice. The levels of serum urea, serum creatinine, kidney injury molecule-1 (KIM-1), and histological damage were partially diminished following treatment with IL-9. The renoprotective effects of IL-9 may be attributed to the regulation of cytokines, and we found that IL-9 acted on macrophages in a regulatory manner, promoting an anti-inflammatory phenotype. Furthermore, IL-9 enhanced the suppression of macrophage-driven renal inflammation. Inhibition of H3K27 acetylation orchestrated IL-9-mediated renoprotection in CP-induced AKI. Thus, our findings indicate novel and potent anti-inflammatory properties of IL-9 that confer preservation of kidney function and structure in CP-induced AKI, which may counteract kidney disease procession.

The effect of nitrogen dioxide on low birth weight in women with inflammatory bowel disease: a Norwegian pregnancy cohort study (MoBa)

Background: Adverse birth outcomes are more frequent among mothers with inflammatory bowel diseases (IBDs) than non-IBD mothers. In recent studies, air pollution, such as high concentrations of nitrogen dioxide (NO₂), is reckoned as a risk factor for preterm birth in the general population. In this study, we investigated whether IBD mothers are at higher risk of preterm birth when exposed to NO₂ compared to non-IBD mothers.Methods: We used information from the Norwegian Mother, Father and Child Cohort Study (MoBa). The pregnancy cohort was linked to the Norwegian Medical Birth Registry and air-pollution exposure data available from a subset of the study cohort. The relevant outcome in this study was preterm birth. A total of 16,170 non-IBD and 92 IBD mothers were included in the study.Results: The mean exposure of NO₂ during the pregnancy was similar for IBD and non-IBD mothers, 13.7 (6.9) μg/m³ and 13.6 (4.2) μg/m³, respectively.IBD mothers with higher exposure of NO₂ in the second and third trimester were at significant risk of preterm birth compared to non-IBD mothers [OR = 1.28 (CI 95%: 1.04-1.59) and OR = 1.23 (95% CI: 1.06-1.43), respectively]. The mean NO₂ exposure was significantly higher in IBD mothers with preterm birth than in IBD mothers who delivered at term, at 19.58 (1.57) μg/m³ and 12.89 (6.37) μg/m³, respectively.Conclusions: NO₂ exposure influenced the risk of preterm birth in IBD mothers. Higher risk of preterm birth in IBD was associated with higher exposure of NO₂, suggesting vulnerability of preterm birth in IBD when exposed to NO₂.

Indirect Regulation and Equilibrium of p35 and p40 Subunits of Interleukin (IL)-12/23 by Ustekinumab in Psoriasis Treatment

BACKGROUND Ustekinumab, a human-derived monoclonal antibody that targets the p40 subunit of interleukin (IL)-12 and IL-23, has excellent clinical efficacy and safety in treating psoriasis, with a long half-life. However, no reports have described the use of human skin/serum samples to elucidate its molecular mechanisms. MATERIAL AND METHODS Twenty-four psoriasis patients were enrolled in our double-blind study and randomly divided into placebo and ustekinumab-administered groups. Dynamic changes in psoriasis area-severity index scores, and mRNA and protein levels of p35 and p40 were analyzed at 3 time points (before treatment and during the 12th and 24th weeks of treatment). RESULTS Ustekinumab initially increased and then decreased p35 mRNA expression, but increased p40 mRNA levels throughout the study. The p35 protein levels were not significantly altered, while p40 protein levels were increased after the first 2 injections but decreased after the third injection. CONCLUSIONS We concluded that 2 equilibria influence the efficacy of ustekinumab against psoriasis. First, because of the dual roles of p35 in psoriasis pathogenesis, homeostasis occurs between p35 and p40 expression levels. The second balance lies between the upregulation of p40 mRNA levels and the ability of ustekinumab to neutralize the function of the elevated p40 protein.

Dissecting the Heterogeneity in T-Cell Mediated Inflammation in IBD

Infiltration of the lamina propria by inflammatory CD4+ T-cell populations is a key characteristic of chronic intestinal inflammation. Memory-phenotype CD4+ T-cell frequencies are increased in inflamed intestinal tissue of IBD patients compared to tissue of healthy controls and are associated with disease flares and a more complicated disease course. Therefore, a tightly controlled balance between regulatory and inflammatory CD4+ T-cell populations is crucial to prevent uncontrolled CD4+ T-cell responses and subsequent intestinal tissue damage. While at steady state, T-cells display mainly a regulatory phenotype, increased in Th1, Th2, Th9, Th17, and Th17.1 responses, and reduced Treg and Tr1 responses have all been suggested to play a role in IBD pathophysiology. However, it is highly unlikely that all these responses are altered in each individual patient. With the rapidly expanding plethora of therapeutic options to inhibit inflammatory T-cell responses and stimulate regulatory T-cell responses, a crucial need is emerging for a robust set of immunological assays to predict and monitor therapeutic success at an individual level. Consequently, it is crucial to differentiate dominant inflammatory and regulatory CD4+ T helper responses in patients and relate these to disease course and therapy response. In this review, we provide an overview of how intestinal CD4+ T-cell responses arise, discuss the main phenotypes of CD4+ T helper responses, and review how they are implicated in IBD.

IL-9 Exerts Antitumor Effects in Colon Cancer and Transforms the Tumor Microenvironment In Vivo

As a newly discovered cytokine, interleukin 9 was initially considered a T-lymphocyte growth factor. Interleukin 9 affects target cells by binding to a member of the γc-family of receptors and is involved in inflammation, autoimmune diseases, and other ailments. In recent years, mounting evidence reveals that interleukin 9 exerts antitumor effects, which has attracted considerable attention. Many previous studies were performed in vivo by establishing a mouse model of melanoma. Here, interleukin 9 protein and messenger RNA expression levels were both low in colon carcinoma tissue specimens, as assessed by immunohistochemistry and quantitative real-time polymerase chain reaction. In addition, interleukin 9 expression in these samples was correlated with TNM staging, Dukes staging, lymph node metastasis, and good prognosis, but not with gender, age, tumor size, tumor differentiation, and hepatic metastasis. In vivo, by establishing a mouse subcutaneous allograft model, we found that interleukin 9 overexpression inhibited tumor growth and resulted in longer survival time. Then, antitumor immune responses were increased by interleukin 9 as demonstrated by flow cytometry. Furthermore, interleukin 9 was shown to exert antitumor effects by regulating T-cell function and killing tumor cells in the tumor microenvironment. Overall, this study revealed that interleukin 9 exerts robust antitumor effects in colon cancer and transforms the tumor microenvironment in vivo.

IL-9 and Mast Cells Are Key Players of Candida albicans Commensalism and Pathogenesis in the Gut

Candida albicans is implicated in intestinal diseases. Identifying host signatures that discriminate between the pathogenic versus commensal nature of this human commensal is clinically relevant. In the present study, we identify IL-9 and mast cells (MCs) as key players of Candida commensalism and pathogenicity. By inducing TGF-β in stromal MCs, IL-9 pivotally contributes to mucosal immune tolerance via the indoleamine 2,3-dioxygenase enzyme. However, Candida-driven IL-9 and mucosal MCs also contribute to barrier function loss, dissemination, and inflammation in experimental leaky gut models and are upregulated in patients with celiac disease. Inflammatory dysbiosis occurs with IL-9 and MC deficiency, indicating that the activity of IL-9 and MCs may go beyond host immunity to include regulation of the microbiota. Thus, the output of the IL-9/MC axis is highly contextual during Candida colonization and reveals how host immunity and the microbiota finely tune Candida behavior in the gut.

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IL-9/IL-9R signaling affects MC function in mucosal candidiasis

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IL-9 and mucosal MCs contribute to barrier function loss in leaky gut models

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IL-9 and stromal MCs induce local protective tolerance in infection via IDO1

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IL-9 and mucosal MCs expand and IDO1 decreases in human celiac disease

A Comprehensive Review and Update on the Pathogenesis of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic and life-threating inflammatory disease of gastroenteric tissue characterized by episodes of intestinal inflammation. The pathogenesis of IBD is complex. Recent studies have greatly improved our knowledge of the pathophysiology of IBD, leading to great advances in the treatment as well as diagnosis of IBD. In this review, we have systemically reviewed the pathogenesis of IBD and highlighted recent advances in host genetic factors, gut microbiota, and environmental factors and, especially, in abnormal innate and adaptive immune responses and their interactions, which may hold the keys to identify novel predictive or prognostic biomarkers and develop new therapies.

T-Cell Differentiation to T Helper 9 Phenotype is Elevated by Extremely Low-Frequency Electromagnetic Fields Via Induction of IL-2 Signaling

Owing to the development of information technology and the electronics industry, and the increase in the use of electronic products, an increasing number of people are exposed to electromagnetic fields (EMFs) in daily life. There has been concern about the effects of EMFs on the human body. Th9 cells, which are characterized by the generation of interleukin-(IL-9), are a recently defined subset of T helper (Th) cells. In this study, we investigated the effect of extremely low-frequency (60 Hz) EMFs, such as those generated by household power sources, at 0.8 mT intensity on CD4⁺ T cells. The exposure of CD4⁺ T cells to such EMFs under Th9-polarizing conditions increased IL-9 secretion and gene expression of transcription factors that are important for Th9 development. The expression of GATA3 increased in the early stage, and the phosphorylation of STAT5 and STAT6, which regulate the expression of GATA3, increased. In addition, EMFs increased the expression of IL-2 by the T cells. In conclusion, the differentiation of CD4⁺ T cells to the Th9 phenotype was increased by exposure to extremely low-frequency EMFs, and this appeared to be dependent on the IL-2 signaling pathway. Furthermore, co-cultures of EMF-exposed Th9 cells and mast cells showed an increased expression of mast cell proteases, FcεR1α, and mast cell-derived inflammatory cytokines compared with co-cultures of non-EMF-exposed Th9 cells and mast cells. Our results suggest that EMFs enhance the differentiation of CD4⁺ T cells to the Th9 phenotype, resulting in mast cell activation and inflammation. Bioelectromagnetics. 2019;40:588-601. © 2019 Bioelectromagnetics Society.

The γc Family of Cytokines: Basic Biology to Therapeutic Ramifications

The common cytokine receptor γ chain, γ_c, is a component of the receptors for interleukin-2 (IL-2), IL-4, IL-7, IL-9, IL-15, and IL-21. Mutation of the gene encoding γ_c results in X-linked severe combined immunodeficiency in humans, and γ_c family cytokines collectively regulate development, proliferation, survival, and differentiation of immune cells. Here, we review the basic biology of these cytokines, highlighting mechanisms of signaling and gene regulation that have provided insights for immunodeficiency, autoimmunity, allergic diseases, and cancer. Moreover, we discuss how studies of this family stimulated the development of JAK3 inhibitors and present an overview of current strategies targeting these pathways in the clinic, including novel antibodies, antagonists, and partial agonists. The diverse roles of these cytokines on a range of immune cells have important therapeutic implications.

TL1A modulates the severity of colitis by promoting Th9 differentiation and IL-9 secretion

AIMS

TL1A was reported to contribute to the susceptibility to ulcerative colitis (UC). However, the molecular mechanisms of TL1A in UC development are poorly understood. We aimed to investigate the role of TL1A in colitis, and reveal the regulatory mechanism of TL1A in chronic colitis development.

MAIN METHODS

Wild-type mice and transgenic mice with overexpressing TL1A in lymphocytes were used to construct chronic DSS colitis models. To investigate the molecular mechanism in vitro, CD4+ T cells were sorted from spleens and mesenteric lymph node cells to induce Th9 cells. Biopsy specimens from ulcerative colitis patients were collected for in vivo validation.

KEY FINDINGS

The elevated TL1A expression in chronic DSS colitis models exacerbated intestinal inflammation. The differentiation of Th9 cells, IL-9 secretion and production of TGF-β, IL-4 and PU.1 was significantly enhanced in transgenic mice with TL1A overexpression. In vitro results showed that TL1A enhanced the Th9 cells, IL-9 and PU.1 production, while TL1A antibodies inhibited their production. In human translational studies, patients with ulcerative colitis with elevated TL1A expression also exhibited more serious inflammation with higher levels of Th9 cells, IL-9 and PU.1 expression.

SIGNIFICANCE

We presented a possible mechanism of TL1A in UC development that TL1A may promote the differentiation of Th9 cells and enhanced IL-9 secretion by up-regulating the expression of TGF-β, IL-4 and PU.1, which provided a novel perspective to study the UC pathogenesis, and indicated that targeting of TL1A signal pathway may by a likely strategy for the treatment of chronic colitis.

Inflammatory cytokines: from discoveries to therapies in IBD

Introduction: Although the etiology of inflammatory bowel diseases (IBD) remains unknown, accumulating evidence suggests that the intestinal tissue damage in these disorders is due to a dynamic interplay between immune cells and non-immune cells, which is mediated by cytokines produced within the inflammatory microenvironment. Areas covered: We review the available data about the role of inflammatory cytokines in IBD pathophysiology and provide an overview of the therapeutic options to block the function of such molecules. Expert opinion: Genome studies, in vitro experiments with patients' samples and animal models of colitis, have largely advanced our understanding of how cytokines modulate the ongoing mucosal inflammation in IBD. However, not all the cytokines produced within the damaged gut seem to play a major role in the amplification and perpetuation of the IBD-associated inflammatory cascade. Indeed, while some of the anti-cytokine compounds are effective in some subgroups of IBD patients, others have no benefit. In this complex scenario, a major unmet need is the identification of biomarkers that can predict response to therapy and facilitate a personalized therapeutic approach, which maximizes the benefits and limits the adverse events.

Fas signaling-mediated TH9 cell differentiation favors bowel inflammation and antitumor functions

Fas induces apoptosis in activated T cell to maintain immune homeostasis, but the effects of non-apoptotic Fas signaling on T cells remain unclear. Here we show that Fas promotes TH9 cell differentiation by activating NF-κB via Ca2+-dependent PKC-β activation. In addition, PKC-β also phosphorylates p38 to inactivate NFAT1 and reduce NFAT1-NF-κB synergy to promote the Fas-induced TH9 transcription program. Fas ligation exacerbates inflammatory bowel disease by increasing TH9 cell differentiation, and promotes antitumor activity in p38 inhibitor-treated TH9 cells. Furthermore, low-dose p38 inhibitor suppresses tumor growth without inducing systemic adverse effects. In patients with tumor, relatively high TH9 cell numbers are associated with good prognosis. Our study thus implicates Fas in CD4+ T cells as a target for inflammatory bowel disease therapy. Furthermore, simultaneous Fas ligation and low-dose p38 inhibition may be an effective approach for TH9 cell induction and cancer therapy.

Claudin Family Participates in the Pathogenesis of Inflammatory Bowel Diseases and Colitis-Associated Colorectal Cancer

Claudins are a multigene transmembrane protein family comprising at least 27 members. In gastrointestinal tract, claudins are mainly located in the intestinal epithelia; many types of claudins form a network of strands in tight junction plaques within the intercellular space of neighboring epithelial cells and build paracellular selective channels, while others act as signaling proteins and mediates cell behaviors. Claudin dysfunction may contribute to epithelial permeation disorder and multiple intestinal diseases. Over recent years, the importance of claudins in the pathogenesis of inflammatory bowel diseases (IBD) has gained focus and is being investigated. This review analyzes the expression pattern and regulatory mechanism of claudins based on existing evidence and elucidates the fact that claudin dysregulation correlates with increased intestinal permeability, sustained activation of inflammation, epithelial-to-mesenchymal transition (EMT), and tumor progression in IBD as well as consequent colitis-associated colorectal cancer (CAC), possibly shedding new light on further etiologic research and clinical treatments.

Targeting immune cell circuits and trafficking in inflammatory bowel disease

Inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis are characterized by uncontrolled activation of intestinal immune cells in a genetically susceptible host. Due to the progressive and destructive nature of the inflammatory process in IBD, complications such as fibrosis, stenosis or cancer are frequently observed, which highlights the need for effective anti-inflammatory therapy. Studies have identified altered trafficking of immune cells and pathogenic immune cell circuits as crucial drivers of mucosal inflammation and tissue destruction in IBD. A defective gut barrier and microbial dysbiosis induce such accumulation and local activation of immune cells, which results in a pro-inflammatory cytokine loop that overrides anti-inflammatory signals and causes chronic intestinal inflammation. This Review discusses pathogenic cytokine responses of immune cells as well as immune cell trafficking as a rational basis for new translational therapies in IBD.

Differential Pathogenic Th17 Profile in Mesenteric Lymph Nodes of Crohn's Disease and Ulcerative Colitis Patients

The drug targets IL23 and IL12 regulate pathogenicity and plasticity of intestinal Th17 cells in Crohn's disease (CD) and ulcerative colitis (UC), the two most common inflammatory bowel diseases (IBD). However, studies examining Th17 dysregulation in mesenteric lymph nodes (mLNs) of these patients are rare. We showed that in mLNs, CD could be distinguished from UC by increased frequencies of CCR6⁺CXCR3⁻RORγ⁺Tbet⁻CD4⁺ (Th17) memory T cells enriched in CD62L^low effector memory T cells (T_EM), and their differentially expressed molecular profile. Th17 T_EM cells (expressing IL17A, IL17F, RORC, and STAT3) displayed a higher pathogenic/cytotoxic (IL23R, IL18RAP, and GZMB, CD160, PRF1) gene signature in CD relative to UC, while non-pathogenic/regulatory genes (IL9, FOXP3, CTLA4) were more elevated in UC. In both CD and UC, IL12 but not IL23, augmented IFNγ expression in Th17 T_EM and switched their molecular profile toward an ex-Th17 (Th1^*)-biased transcriptomic signature (increased IFNG, and decreased TCF7, IL17A), suggesting that Th17 plasticity occurs in mLNs before their recruitment to inflamed colon. We propose that differences observed between Th17 cell frequencies and their molecular profile in CD and UC might have implications in understanding disease pathogenesis, and thus, therapeutic management of patients with IBD.

A role for BATF3 in TH9 differentiation and T-cell-driven mucosal pathologies

T helper 9 (T_H9) cells are important for the development of inflammatory and allergic diseases. The T_H9 transcriptional network converges signals from cytokines and antigen presentation but is incompletely understood. Here, we identified TL1A, a member of the TNF superfamily, as a strong inducer of mouse and human T_H9 differentiation. Mechanistically, TL1A induced the expression of the transcription factors BATF and BATF3 and facilitated their binding to the Il9 promoter leading to enhanced secretion of IL-9. BATF- and BATF3-deficiencies impaired IL-9 secretion under T_H9 and T_H9-TL1A-polarizing conditions. In vivo, using a T-cell transfer model, we demonstrated that TL1A promoted IL-9-dependent, T_H9 cell-induced intestinal and lung inflammation. Neutralizing IL-9 antibodies attenuated TL1A-driven mucosal inflammation. Batf3^-/- T_H9-TL1A cells induced reduced inflammation and cytokine expression in vivo compared to WT cells. Our results demonstrate that TL1A promotes T_H9 cell differentiation and function and define a role for BATF3 in T-cell-driven mucosal inflammation.

An Update on Interleukin-9: From Its Cellular Source and Signal Transduction to Its Role in Immunopathogenesis

Interleukin-9 (IL-9) is a pleiotropic cytokine and was primarily studied in the context of T helper 2 (TH2)-associated immuno-pathological conditions such as asthma and parasitic infections. There was a paradigm shift in the biology of IL-9 after the recent discovery of TH9 cells, a new subtype of TH cells which secrete IL-9 in copious amounts. This has resulted in renewed interest in this cytokine, which was neglected since discovery because it was considered it to be just another TH2 cytokine. Recent studies have shown that it has multiple cellular sources and is critically involved in the immune-pathogenesis of inflammatory diseases and in guarding immune tolerance. In this review, we will discuss its discovery, gene organization, cellular sources, and signaling pathways. Especially, we will give an update on the recent development regarding its relevance in the immune pathogenesis of human diseases.

Oligonucleotides-A Novel Promising Therapeutic Option for IBD

Inflammatory Bowel Diseases (IBD), whose denomination comprehends Crohn's Disease (CD) and Ulcerative Colitis (UC), are intestinal chronic diseases that often require lifelong medical therapy. In the last two decades monoclonal antibodies against the cytokine TNF have become integral parts in the treatment of IBD patients, however there are unwanted side-effects and one third of patients show primary non-response while another subgroup loses response over time. Finding novel drugs which could act as therapies against precise pro-inflammatory molecular targets to avoid unwanted systemic side effects and additionally the process of immunization, represents an important aim for subsequent therapeutic approaches. Oligonucleotide based therapies represent a promising novel concept for the treatment of IBD. The molecular action of oligonucleotides ranges from inhibition of the translational process of mRNA transcripts of pro-inflammatory molecules, to mimicking bacterial DNA which can activate cellular targets for immunomodulation. Alicaforsen, selectively targets ICAM-1 mRNA. ICAM-1 is an adhesion molecule which is upregulated on endothelial cells during IBD, thereby mediating the adhesion and migration of leucocytes from blood to sites of active inflammation. In CD parenteral application of alicaforsen did not show therapeutic efficacy in phase II trials, but it demonstrated an improved efficacy as a topical enema in distal UC. Topical application of alicaforsen might represent a therapeutic perspective for refractory pouchitis as well. SMAD7 is a protein that inhibits the signaling of TGFβ, which is the mainstay of a regulatory counterpart in cellular immune responses. An antisense oligonucleotide against SMAD7 mRNA (mongersen) demonstrated pre-clinical and phase II efficacy in CD, but a phase III clinical trial was stopped due to lack of efficacy. Cobitolimod is a single strand oligonucleotide, which mimics bacterial DNA as its CpG dinucleotide sequences can be recognized by the Toll-like receptor 9 on different immune cells thereby causing induction of different cytokines, for example IL10 and IFNα. Topical application of cobitolimod was studied in UC patients. We will also discuss two other novel oligonucleotides which act on the GATA3 transcription factor (SB012) and on carbohydrate sulfotransferase 15 (STNM01), which could both represent novel promising therapeutic options for the treatment of UC.

Stimulation of histamine H4 receptors increases the production of IL-9 in Th9 polarized cells

BACKGROUND AND PURPOSE

Th9 cells represent a recently defined subset of CD4⁺ T-helper cells, characterized by a high production of IL-9. They are found at increased frequency in lesions of atopic dermatitis, where IL-9 is also elevated. As histamine is up-regulated in lesions of inflammatory skin diseases, we investigated the expression profile of histamine receptors and their functional role on Th9 cells.

EXPERIMENTAL APPROACH

Naïve CD4⁺ T-cells were purified from human peripheral blood mononuclear cells, using magnetic beads and further differentiated into Th9 cells. During differentiation, cells were additionally stimulated with histamine receptor agonists or left untreated. Histamine receptor expression as well as IL-9 production was measured.

KEY RESULTS

As proof of a successful differentiation, IL-9 production was measured at mRNA and protein level. Expression of mRNA for histamine H₁ , H₂ and H₄ receptors were up-regulated in differentiated Th9 cells compared to Th0 cells, while no mRNA for the H₃ receptor was detectable. Stimulation of Th9 cells with histamine significantly up-regulated expression of mRNA and protein for IL-9 . Experiments with specific histamine receptor agonists and antagonists revealed that this up-regulation was mediated by H₄ receptors.

CONCLUSIONS AND IMPLICATIONS

In summary, our study demonstrates a functional role for histamine H₄ receptors on Th9 cells, which might amplify the pro-inflammatory potency of these cells. Together with earlier studies on Th2 and Th17 cells, this study underlines the promising approach for the use of H₄ receptor antagonists in inflammatory and allergic diseases such as atopic dermatitis.

LINKED ARTICLES

This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc.

The capability and potential of new forms of personalized colon cancer treatment: Immunotherapy and Photodynamic Therapy

INTRODUCTION

PDT can interfere with cytokine-mediated responses that play an important role in the processes of cancer progression, tumor angiogenesis and metastasis. Therefore, based on the identification of these cancer biomarkers, the therapy of combining various forms of treatment, including immunotherapy and PDT, may be a justified strategy for colorectal cancer treatment that focuses on individualized comprehensive therapy.

METHOD

We reviewed the major approaches on the use of immunotherapy in colorectal cancer, with the special regard to photodynamic therapy, its immunological effect and new oncological treatment directions, connected with adjuvant immunotherapy including use of nanoparticles. Databases such as PubMed, ScienceDirect and Springer were utilized to search the literature for relevant articles.

PURPOSE

To review studies of the immunotherapy in colon cancer and immune response to PDT.

CONCLUSION

Based on the identification of immunological cancer biomarkers, the therapy of combining various forms of treatment, including immunotherapy and PDT, may be a justified strategy for colorectal cancer treatment that focuses on individualized comprehensive therapy.

Vitamin A and inflammatory bowel diseases: from cellular studies and animal models to human disease

Vitamin A (VA) and metabolites such as Retinoic Acid (RA) and all-trans-RA (at-RA) are crucial in the modulation of the immune system and may be determinative in the balance of the immune responses. Inflammatory bowel diseases (IBD) consist of chronic relapsing and heterogeneous disorders with not well-known etiology. Due to its role in inflammatory processes, VA may be helpful in the treatment of IBD. Area covered: As VA plays a significant role in the inflammatory processes, this review aims to show the potential role of this vitamin in IBD, searching for cellular studies, animal models, and studies with humans. Expert commentary: Many studies have described the importance of alternative therapeutic approaches for IBD. Due to its role in the immune system, VA may also exert an indispensable role in the IBD. Nevertheless, some authors have shown that these compounds could stimulate the release of pro-inflammatory cytokines. For these reasons, more studies should be performed to establish the precise mechanisms of VA and its metabolites in systemic and intestinal inflammation.

Features and roles of T helper 9 cells and interleukin 9 in immunological diseases

T helper 9 (TH9) cells are considered as newly classified helper T cells that have an important role in the regulation of immune responses. Since these cells preferentially produce IL-9, these cells are termed TH9 cells. Recently, the role of TH9 and its signature cytokine (IL-9) has been investigated in a wide range of diseases, including autoimmunity, allergy, infections, cancer and immunodeficiency. Herein, we review the most recent data concerning TH9 cells and IL-9 as well as their roles in disease. These insights suggest that TH9 cells are a future target for therapeutic intervention.

Immune response and inflammatory pathway of ulcerative colitis

Ulcerative colitis (UC) is an idiopathic relapsing inflammatory disease. Although the etiology of UC remains unclear, it could be characterized by inflammation of the intestinal mucosa, starting from the rectum and potentially involving the entire colon. The immune response and inflammatory pathway of UC have shown that tissue damage is driven by dynamic and complexes of cells and cytokines. Various types of cells, including antigen-presenting cells (dendritic cells and macrophages), T helper cells, regulatory T cells, and natural killer T cells, play a crucial role in UC pathogenesis by regulation, suppression, and maintenance of inflammation. Moreover, cytokine networks become an important part due to their signaling function, which is indispensable for cell communication. Pro-inflammatory cytokines [tumor necrosis factor-α, interleukin (IL)-1, IL-6, IL-9, IL-13, and IL-33] play significant roles in upregulation, while anti-inflammatory cytokines (transforming growth factor-β, IL-10, and IL-37) play significant roles in downregulation of disease progression. The pathogenesis of UC consists of immuno-inflammatory pathways related to the multiple components of the intestine, including the epithelial barrier, commensal microflora, antigen recognition, dysregulation of immunological responses, leukocyte recruitment, and genetic factors. The understanding of immuno-inflammatory pathways of UC might lead to the development of a specific therapy and/or a novel treatment that could be more efficient.

IL-9 promotes the pathogenesis of ulcerative colitis through STAT3/SOCS3 signaling

Ulcerative colitis (UC) is a chronic condition in which the overreacting immune system may play an important role. It has been confirmed that the interleukin (IL) 9 (IL-9) participates in the pathogenesis of UC but the molecular mechanism is not fully illustrated. Here, we show that levels of peripheral blood cytokines IL-9, IL-8, IL-10, IL-6, IL-1β, IL-12, and tumor necrosis factor (TNF) were higher in patients with UC than normal control, and serum and local IL-9 levels were positively correlated with the disease activity grade. Moreover, IL-9 stimulation inhibited suppressor of cytokine signaling 3 (SOCS3) expression and wound healing ability in colonic epithelial cells and promoted the phosphorylation level of signal transducers and activators of transcription 3 (STAT3). And IL-9 stimulation promoted claudin-2 expression while inhibited claudin-3 and occludin expression. Furthermore, SOCS3 overexpression rescued the IL-9-induced effects. Altogether, IL-9 participates in the pathogenesis of UC through STAT3/SOCS3 signaling pathway and has the potential to serve as a possible therapeutic candidate in patients with UC.

TGF-β enhances the cytotoxic activity of Vδ2 T cells

TGF-β is a pleiotropic cytokine with multiple roles in immunity. Apart from its suppressive activity, TGF-β is a driving cytokine in the differentiation of induced regulatory T cells (iTreg) but also in the polarization of interleukin-9 (IL-9) producing T helper 9 (Th9) T cells. Human Vδ2 expressing γδ T cells exert potent cytotoxicity towards a variety of solid tumor and leukemia/lymphoma target cells and thus are in the focus of current strategies to develop cell-based immunotherapies. Here we report that TGF-β unexpectedly augments the cytotoxic effector activity of short-term expanded Vδ2 T cells when purified γδ T cells are activated with specific pyrophosphate antigens and IL-2 or IL-15 in the presence of TGF-β. TGF-β up-regulates the expression of CD54, CD103, interferon-γ, IL-9 and granzyme B in γδ T cells while CD56 and CD11a/CD18 are down-regulated. Moreover, we show that CD103 (αE/β7 integrin) is recruited to the immunological synapse in γδ T cells. Increased cytotoxic activity of TGF-β-exposed γδ T cells is reduced by anti-CD103 and further diminished upon additional anti-CD11a antibody treatment, pointing to a role of cellular adhesion in the enhanced cytolytic activity. Furthermore, magnetically sorted CD103-positive Vδ2 T cells exhibit superior cytolytic activity. In view of the importance of CD103 for tissue homing of lymphocytes, our results suggest that adoptive transfer of CD103-expressing Vδ2 T cells might favor their homing to solid tumors.

Th9 lymphocytes and functions of interleukin 9 with the focus on IBD pathology

The work presents the newest knowledge on a new phenotype of T helper lymphocytes (Th9) and on Interleukin 9 (IL-9). Processes leading to transformation of naïve T lymphocyte into Th9 lymphocytes are presented, including the role of IL-4 and TGFβ signaling. Involvement of transcription factor network in production of IL-9 is described. Other cells capable of expressing IL-9 and secreting IL-9 are portrayed. Diversity of IL-9 effects caused by activation of IL-9 receptors on various types of cells is presented. Principal effects of the activation of IL-9 receptor on T-cells seem to be antiapoptotic and stimulatory which leads to enhanced defense against parasitic infection and cancer development but, from the other side, it perpetuate chronic inflammation in autoimmune diseases and allergic processes. In the last years the role of IL-9 in autoimmune diseases such as rheumatic diseases and inflammatory bowel disease gained importance since the increased expression of this cytokine has been observed in animal models of intestinal inflammation and in groups of patients with ulcerative colitis. It was also noted that neutralization of IL-9 in animal models of ulcerative colitis leads to amelioration of inflammatory process, what could have significance in the treatment of this disease in humans in the future.

Advances in understanding the role of cytokines in inflammatory bowel disease

Cytokines represent the key pathophysiologic elements that govern the initiation, progression, and, in some circumstances, the resolution of the inflammation occurring in inflammatory bowel disease (IBD). Areas covered: In this review, we will focus on the main effector and anti-inflammatory cytokines produced in IBD and discuss the results of recent trials in which cytokine-based therapy has been used for treating IBD patients. Expert commentary: The possibility to sample mucosal biopsies from IBD patients and analyze which molecular pathways are prominent during the active phases of the disease and the easy access to various models of experimental colitis has largely advanced our understanding about the role of cytokines in IBD. These progresses have facilitated the development of several therapeutic compounds, which either target inflammatory cytokines or enhance the regulatory function of immunosuppressive cytokines. While some of such drugs are effective in the induction and maintenance of remission of the disease, other compounds are not useful for attenuating the ongoing mucosal inflammation, thus establishing a hierarchical scale of the relevance of cytokines in IBD. Further work is needed to identify biomarkers, which could help personalize cytokine-targeted therapy and minimize potential side effects.

Transcriptional regulation of CD4+ TH cells that mediate tissue inflammation

Acquired and genetic immunodeficiencies have revealed an indispensable role for CD4⁺ T cells in the induction of protective host immune responses against a myriad of microbial pathogens. Influenced by the cytokines present in the microenvironment, activated CD4⁺ T cells may differentiate into several highly-specialized helper subsets defined by the production of distinct signature cytokines tailored to combat diverse classes of pathogens. The process of specification and differentiation is controlled by networks of core, master, and accessory transcription factors, which ensure that CD4⁺ T helper (T_H ) cell responses mounted against an invading microbe are of the correct specificity and type. However, aberrant activation or inactivation of transcription factors can result in sustained and elevated expression of immune-related genes, leading to chronic activation of CD4⁺ T_H  cells and organ-specific autoimmunity. In this review, we provide an overview of the molecular basis of CD4⁺ T_H  cell differentiation and examine how combinatorial expression of transcription factors, which promotes genetic plasticity of CD4⁺ T_H  cells, can contribute to immunological dysfunction of CD4⁺ T_H responses. We also discuss recent studies which highlight the potential of exploiting the genetic plasticity of CD4⁺ T_H  cells in the treatment of autoimmune and other immune-mediated disorders.

[Expression of interleukin-9 in colon cancer tissues and its clinical significance]

OBJECTIVE

To investigate the expression of interleukin-9 (IL-9) in colon cancer tissues and its clinical significance.

METHODS

Immunohistochenmistry and qRT-PCR were used to detect the expressions of IL-9 protein and mRNA in 92 colon cancer tissues and paired adjacent normal tissues. The correlation of IL-9 expressions with the clinicopathological features and prognosis of the patients was analyzed.

RESULTS

IL-9 protein and mRNA expressions were significantly higher in adjacent normal tissues than in the colon cancer tissues (P < 0.001). In colon cancer patients, IL-9 expression was significantly correlated with TNM stage (P=0.013), Ducks stage (P=0.025) and lymph node metastasis (P=0.004) but not with gender, age, tumor size, differentiation or hepatic metastasis (P > 0.05). The survival time of colon cancer patients with positive IL-9 expression was significantly longer than that of patients negative for IL-9 expression (P=0.015).

CONCLUSIONS

IL-9 expression is lowered in colon cancer tissues compoved with in the adjacent normal tissues. IL-9 expression is negatively correlated with TNM staging, Ducks staging and lymph node metastasis but positively with good prognosis, suggesting its important role in the tumor microenvironment of colon cancer.

Effector T Helper Cell Subsets in Inflammatory Bowel Diseases

The gastrointestinal tract is a site of high immune challenge, as it must maintain a delicate balance between tolerating luminal contents and generating an immune response toward pathogens. CD4⁺ T cells are key in mediating the host protective and homeostatic responses. Yet, CD4⁺ T cells are also known to be the main drivers of inflammatory bowel disease (IBD) when this balance is perturbed. Many subsets of CD4⁺ T cells have been identified as players in perpetuating chronic intestinal inflammation. Over the last few decades, understanding of how each subset of Th cells plays a role has dramatically increased. Simultaneously, this has allowed development of therapeutic innovation targeting specific molecules rather than broad immunosuppressive agents. Here, we review the emerging evidence of how each subset functions in promoting and sustaining the chronic inflammation that characterizes IBD.

A Decade of Th9 Cells: Role of Th9 Cells in Inflammatory Bowel Disease

T helper cell subsets play a critical role in providing protection against offending pathogens by secreting specific cytokines. However, unrestrained T helper cell responses can promote chronic inflammation-mediated inflammatory diseases. Dysregulated T helper cell responses have been suggested to be involved in the pathogenesis of multiple inflammatory diseases, including allergic airway inflammation, rheumatoid arthritis, and inflammatory bowel disease (IBD) among others. Aberrant pro-inflammatory responses induced by Th1, Th2, and Th17 subsets are known to trigger IBD. IBD is a chronic inflammatory disease characterized by weight loss, diarrhea, pain, fever, and rectal bleeding. It poses a major health burden worldwide owing to the increased risk of colorectal cancer development. Despite numerous therapeutic advancements, IBD still remains a major health burden due to the inefficiency of the conventional therapies. Recently, IL-9-secreting Th9 cells are known to be involved in the pathogenesis of IBD. However, the role of Th9 cells and their secretory cytokine IL-9 in IBD is unclear. The functional relevance of Th9 cells is also relatively understudied in IBD. Thus, investigating the actual role of various T helper cell subsets including Th9 cells in IBD is essential to develop novel therapies to treat IBD. Here, we highlight the role of Th9 cells in promoting IBD. We discuss the mechanisms that might be employed by Th9 cells and IL-9 in promoting IBD and thereby propose potential targets for the treatment of Th9 cell-mediated IBD.

Cell-Intrinsic Roles for Autophagy in Modulating CD4 T Cell Functions

The catabolic process of autophagy plays important functions in inflammatory and immune responses by modulating innate immunity and adaptive immunity. Over the last decade, a cell-intrinsic role for autophagy in modulating CD4 T cell functions and differentiation was revealed. After the initial observation of autophagosomes in effector CD4 T cells, further work has shown that not only autophagy levels are modulated in CD4 T cells in response to environmental signals but also that autophagy critically affects the biology of these cells. Mouse models of autophagy deletion in CD4 T cells have indeed shown that autophagy is essential for CD4 T cell survival and homeostasis in peripheral lymphoid organs. Furthermore, autophagy is required for CD4 T cell proliferation and cytokine production in response to T cell receptor activation. Recent developments have uncovered that autophagy controls CD4 T cell differentiation and functions. While autophagy is required for the maintenance of immunosuppressive functions of regulatory T cells, it restrains the differentiation of T_H9 effector cells, thus limiting their antitumor and pro-inflammatory properties. We will here discuss these findings that collectively suggest that therapeutic strategies targeting autophagy could be exploited for the treatment of cancer and inflammatory diseases.

Transcriptional Control of Th9 Cells: Role of Foxo1 in Interleukin-9 Induction

Interleukin (IL) 9-producing helper T (Th) 9 cells play a major role in contributing immunity against extracellular pathogens. In addition, the role of Th9 cells was demonstrated in the pathogenesis of allergic, skin, and intestinal inflammation. The functions of Th9 cells were further extended in antitumor immune response, as Th9 cells were suggested to be potent antitumor Th cells. Given the pleotropic functions of IL-9 in various pathophysiological conditions, it is essential to understand the differentiation and stability of Th9 cells and other IL-9-producing T cells. In addition to Th9 cells, Th2 and Th17 cells as well as induced Foxp3+ regulatory T cells (iTregs) cells also produce IL-9, but how IL-9 production is regulated in these cell types is not yet clearly defined. Although Th2, Th9 and Th17 cells as well as iTregs develop in the presence of distinct differentiating factors, yet they all express IL-9 together with their own lineage specific cytokines. Here, in this review, we summarize the current understanding of signaling pathways that lead to the promotion of differentiation of Th9 cells and IL-9 induction in Th2 and Th17 cells, as well as in iTregs. We further discuss the transcriptional regulation of Th9 cells in context of Foxo1, as an essential transcription factor required for the development and functions of Th9 and other IL-9-producing T cells.

Th9 Cells: Probable players in ulcerative colitis pathogenesis

T lymphocytes represent an important part of adaptive immune system undertaking different functions to regulate immune responses. CD4+ T cells are the most important activator cells in inflammatory conditions. Depending on the type of induced cells and inflamed sites, expression and activity of different subtypes of helper T cells are changed. Recent studies have confirmed the existence of a new subset of helper T lymphocytes called Th9. Naive T cells can differentiate into Th9 subtypes if they are exposed simultaneously by interleukin (IL) 4 and transforming growth factor β and also secondary activation of a complicated network of transcription factors such as interferon regulatory factor 4 (IRF4) and Smads which are essential for adequate induction of this phenotype. Th9 cells specifically produce interleukin 9 and their probable roles in promoting intestinal inflammation are being investigated in human subjects and experimental models of ulcerative colitis (UC). Recently, infiltration of Th9 cells, overexpression of IL-9, and certain genes associated with Th9 differentiation have been demonstrated in inflammatory microenvironment of UC. Intestinal oversecretion of IL-9 protein is likely to break down epithelial barriers and compromise tolerance to certain commensal microorganisms which leads to inflammation. Th9 pathogenicity has not yet been adequately explored in UC and they are far from being considered as inflammatory cells in this milieu, therefore precise understanding the role of these newly identified cells in particular their potential role in gut pathogenesis may enable us to develop novel therapeutic approaches for inflammatory bowel disease. So, this article tries to discuss the latest knowledge on the above-mentioned field.

Immunopathogenesis of inflammatory bowel disease and mechanisms of biological therapies

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract with a multifactorial pathophysiology. Full comprehension of IBD pathology is still out of reach and, therefore, treatment is far from ideal. Nevertheless, components involved in IBD pathogenesis including environmental, genetic, microbial, and immunological factors are continuously being investigated and the improved knowledge contributes to the development of new therapies. In this article we review the aspects of the immunopathogenesis of IBD, with focus on mucosal immunity, and discuss mechanisms of action for current and emerging biological therapies.

CD96 expression determines the inflammatory potential of IL-9-producing Th9 cells

T helper type (Th) 9 cells demonstrate both pro- and antiinflammatory properties, pointing to a functional heterogeneity not examined so far. Applying single cell gene expression analysis of alloreactive Th9 cells, we revealed the existence of two major subsets, CD96^high and CD96^low Th9 cells, with strongly opposing inflammatory and, especially, colitis-inducing potential. Mechanistically, we found that CD96 controls cytokine and colitis-inducing potential of Th9 cells, providing strong evidence for an inhibitory role of CD96 in controlling CD4⁺ T-cell effector functions. Thus, interfering with CD96-mediated immune inhibition would be a promising approach in preventing Th9-mediated diseases, such as ulcerative colitis, or reinforcement of Th9-mediated immune control of tumors and infections.

Recent findings demonstrated proinflammatory functions of interleukin (IL)-9–producing T helper type (Th) 9 cells in the pathogenesis of intestinal bowel diseases (IBDs). However, also antiinflammatory properties have been ascribed to Th9 cells, pointing to a functional heterogeneity. To dissect the specific expression pattern and, especially, diversity of murine antigen-specific Th9 cells, we applied single cell transcription profiling. Th9 cells displayed reduced expression of typical activation markers, such as Cd40 ligand and Cd96, whereas expression of Cd25 and Cd83 was increased compared with other Th subsets. Importantly, we identified two subsets of Th9 cells differing above all in their CD96 expression. The heterogeneous CD96 expression was specific for Th9 cells and not observed for other Th subtypes, such as Th1 cells. Lower CD96 expression was also observed in human IL-9⁺ compared with IFN-γ⁺ T cells. Although Il9 was highly transcribed by all Th9 cells, IL-9 mRNA and protein expression was increased in CD96^low cells. Transfer of CD96^low Th9 cells into recombination activating gene 1-deficient (Rag1^−/−) mice caused severe weight loss, intestinal and colonic inflammation, and destruction of allogeneic skin grafts and thus showed high inflammatory potential. This was associated with their expansion and tissue accumulation. Contrastingly, CD96^high Th9 cells did not cause colitis and showed reduced expansion and migratory potential. Blockade of CD96 completely restored the expansion and inflammatory properties of CD96^high Th9 cells. Collectively, our data suggest an inhibitory role for the cosignaling receptor CD96 in Th9 cells, raising new opportunities in the treatment of IL-9–associated inflammations such as IBD.

TH9 cell differentiation, transcriptional control and function in inflammation, autoimmune diseases and cancer

Naïve CD4⁺T cells differentiate into various T cell subsets depending on the specific cytokine environment. T_H9 cells are less well-characterized than other T cell subsets, and factors that control their development and function have only recently been identified. It is now clear that T_H9 cells play critical roles in immune-mediated diseases, including allergic airway, autoimmune and inflammatory bowel diseases, and cancer. Thus, the promotion or suppression of T_H9 cell differentiation, transcriptional control and function may provide novel treatments for clinical inflammation, autoimmune diseases and tumors.

Neutralization of IL-15 abrogates experimental immune-mediated cholangitis in diet-induced obese mice

Obesity is a global epidemic affecting chronic inflammatory diseases. Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease that can occur as an extraintestinal manifestation of inflammatory bowel disease (IBD). Previously we reported that patients with PSC who are obese have a higher risk of advanced liver disease. Currently it is unknown how obesity accelerates or worsens PSC. We evaluated the progression of PSC in an antigen-driven cholangitis mouse model of diet-induced obesity. Obesity was induced in our murine model of immune-mediated cholangitis (OVAbil). OVAbil mice were fed standard chow or high-fat/sucrose diet for twelve weeks followed by induction of biliary inflammation by OVA-specific T cell transfer. Histopathological damage in portal tracts was scored and serum collected. Neutralizing antibodies against IL-15 were administered daily until study termination. Obese mice developed exacerbated liver inflammation and damage. Immune cell phenotyping in liver revealed greater numbers of neutrophils and CD8+ T cells in obese mice. Higher levels of cytokines and chemokines were found in obese mice with cholangitis. Immuno-neutralizing antibodies against IL-15 greatly attenuated cholangitis in obese mice. Obesity exacerbated experimental PSC in part by overproduction of IL-15. Timely targeting of IL-15 may slow the progression of PSC.

Old and New Lymphocyte Players in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, is a chronic intestinal inflammatory disorder characterized by diffuse accumulation of lymphocytes in the gut mucosa as a consequence of over-expression of endothelial adhesion molecules. The infiltrating lymphocytes have been identified as subsets of T cells, including T helper (Th)1 cells, Th17 cells, and regulatory T cells. The function of these lymphocyte subpopulations in the development of IBD is well-known, since they produce a number of pro-inflammatory cytokines, such as interferon-γ and interleukin-17A, which in turn activate mucosal proteases, thus leading to the development of intestinal lesions, i.e., ulcers, fistulas, abscesses, and strictures. However, the immune mechanisms underlying IBD are not yet fully understood, and knowledge about the function of newly discovered lymphocytes, including Th9 cells, innate lymphoid cells, mucosal-associated invariant T cells, and natural killer T cells, might add new pieces to the complex puzzle of IBD pathogenesis. This review summarizes the recent advances in the understanding of the role of mucosal lymphocytes in chronic intestinal inflammation and deals with the therapeutic potential of lymphocyte-targeting drugs in IBD patients.